WO2014175040A1 - Polarizing plate, method for producing same and liquid crystal display device - Google Patents

Abstract

The objective of the present invention is to provide a polarizing plate which uses an acrylic film and a cellulose ester film as protective films of a polarizer, and which is free from deterioration in adhesion to the polarizer such as waving and separation of a film and display unevenness of a liquid crystal panel even if temperature/humidity conditions in the environment of usage have changed in cases where the polarizing plate is provided in a liquid crystal display device. A polarizing plate of the present invention, in which a polarizer is sandwiched between a film A and a film B, respectively with an active ray-curable adhesive layer interposed therebetween, is characterized in that: the film A is an acrylic film that contains an acrylic resin, has a film thickness within the range of 20-60 μm, and has a dimensional change characteristic within a specific range; and the film B is an cellulose acetate film which has a film thickness within the range of 20-60 μm, contains a cellulose acetate having an average acetyl group substitution degree within the range of 2.0-2.5, and has a dimensional change characteristic within the above-described specific range.

Description

Polarizing plate, manufacturing method thereof, and liquid crystal display device

The present invention relates to a polarizing plate, a manufacturing method thereof, and a liquid crystal display device. More specifically, when a polarizing plate using an acrylic film and a cellulose acetate film as a protective film for a polarizer is provided in a liquid crystal display device, even if the temperature and humidity atmosphere of the usage environment changes, the display unevenness and polarization of the liquid crystal panel The present invention relates to a polarizing plate in which no deterioration of the child adhesion is observed, a manufacturing method thereof, and a liquid crystal display device including the polarizing plate.

In recent years, there has been a demand for an increase in size and thickness of a polarizing plate provided in a liquid crystal display device because of an increase in size and thickness of the liquid crystal display device. Specifically, there is a demand for thinning a polarizer constituting the polarizing plate and a polarizing plate protective film used as a protective film. However, from the viewpoint of thinning the polarizing plate, there is a problem that when the cellulose ester film (for example, a triacetylcellulose (TAC) film) that is usually used as a protective film is thinned, the film strength and flatness are lowered. In particular, a thin film having a thickness of 50 μm or less is a hindrance to the realization of a thin polarizing plate because it causes a decrease in film properties.

In order to improve the strength of the polarizing plate having the thin film protective film as described above, attempts have been made to increase the strength of the protective film for the polarizing plate and to improve the adhesion between the polarizer and the protective film. For example, for the purpose of increasing the strength of a protective film for a polarizing plate, an acrylic film using an acrylic resin which is excellent in transparency and dimensional stability and is a low hygroscopic resin has been proposed (for example, Patent Document 1). reference.). However, since such an acrylic film has a property that a retardation is difficult to occur, it is not suitable for a retardation film for the purpose of expanding a viewing angle of a VA mode liquid crystal display device or the like.

Therefore, for example, as a film disposed on the liquid crystal cell side of the VA mode type liquid crystal display device, conventional cellulose is used from the viewpoints of easy expression of retardation, productivity (handleability, reworkability, etc.) and cost. It is preferable to use a retardation film containing an ester resin. As a polarizing plate, a retardation film containing an acrylic film / polarizer / cellulose ester resin from the viewing side (in the present invention, a cellulose ester film or a cellulose acetate). It is preferable to take the form of a film).

On the other hand, as an improvement in the adhesion between the polarizer and the protective film, for example, a method of bonding the polarizer and the cellulose ester film through an actinic radiation curable adhesive is disclosed (for example, see Patent Document 2). ). According to this method, it is said that a polarizer (polarizing film) is not easily decolorized even under severe environmental conditions such as high temperature and high humidity, and a polarizing plate having high durability with respect to adhesion or the like can be obtained. .

However, according to a detailed study by the present inventors, a liquid crystal display device having a thin film polarizing plate having the above-mentioned acrylic film / polarizer / cellulose ester film structure is changed from a high temperature and high humidity atmosphere to a low temperature and low humidity atmosphere. When the screen was moved and the display screen was observed, it was found that display irregularities peculiar to the liquid crystal panel occurred. Moreover, when the actinic radiation curable adhesive is used for bonding, the range of the display unevenness is enlarged. This is particularly true when the temperature and humidity atmosphere of the use environment changes rapidly. The speed of dimensional change of the protective film was different, and it was presumed to be due to optical unevenness caused by the distortion of the two films and the adhesive part across the polarizer.

In addition, due to the distortion, the adhesion between the polarizer and the protective film is reduced, and when the temperature and humidity atmosphere changes in a harsher environment than before, the problem is that the protective film is likely to wavy or peel off. is there.

JP 2012-237818 A JP 2010-230806 A

The present invention has been made in view of the above-mentioned problems and situations, and the problem to be solved is that a polarizer is bonded to a protective film via an actinic radiation curable adhesive layer, and the protective film is an acrylic film. A polarizing plate using a cellulose acetate film, and when the polarizing plate is provided in a liquid crystal display device, even if the temperature and humidity atmosphere of the usage environment changes, the display unevenness of the liquid crystal panel, the undulation of the protective film, and the film An object of the present invention is to provide a polarizing plate in which deterioration of polarizer adhesion such as peeling is not observed. Moreover, it is providing the liquid crystal display device excellent in the visibility which comprised the manufacturing method of the said polarizing plate, and the said polarizing plate.

In order to solve the above problems, the present inventor is a polarizing plate in which a polarizer is sandwiched between films A and B through an active ray curable adhesive layer in the process of examining the cause of the above problems. The film A is an acrylic film that is a thin film and has a dimensional change within a specific range, and the film B contains cellulose acetate having a low degree of substitution. Similarly, the polarizing plate is a cellulose acetate film within a specific range, and even if the temperature and humidity atmosphere of the usage environment changes, display unevenness of the liquid crystal panel and deterioration of the polarizer adhesion are not seen. The inventors have found that a polarizing plate can be obtained and have reached the present invention.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. The polarizer is a polarizing plate sandwiched between the film A and the film B through an active ray curable adhesive layer,
The film A is an acrylic film containing an acrylic resin having a thickness in the range of 20 to 60 μm and satisfying the following formulas (1) to (4):
The film B contains cellulose acetate having a film thickness in the range of 20 to 60 μm and an average substitution degree of acetyl groups in the range of 2.0 to 2.5, and the following formulas (1) to ( A polarizing plate characterized by being a cellulose acetate film satisfying 4).

(1) 0.03 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.30 (%)
(2) 0.03 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.30 (%)
(3) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.10 (%)
(4) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.10 (%)
In the above formula, L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD are determined by the following formulas (a) to (f) after 1 minute, 5 minutes, And the dimensional change rate of the film after 30 minutes. In the following formulas (a) to (f), the film A and the film B are sampled in a rectangular shape so that one side is parallel to the TD direction or the MD direction, and this is obtained under a temperature and humidity condition of 23 ° C. and 55% RH. The specified dimensions of the film left over are measured in the MD and TD directions and are designated as L ₀ MD and L ₀ TD, respectively. This film is left in a constant temperature and humidity chamber at 80 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment at 23 ° C./55% RH, the dimensions after 1 minute, the dimensions after 5 minutes, and 30 minutes. The subsequent dimensions are measured in the MD direction and TD direction, respectively, and are defined as L ₁ MD ′, L ₁ TD ′, L ₅ MD ′, L ₅ TD ′, L ₃₀ MD ′, and L ₃₀ TD ′, respectively. Substituting into (a) to (f), the dimensional change rate is obtained.
Dimensional change rate after 1 minute (formula a) L ₁ MD (%) = (L ₁ MD′−L ₀ MD) / L ₀ MD × 100
(Formula b) L ₁ TD (%) = (L ₁ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 5 minutes (formula c) L ₅ MD (%) = (L ₅ MD′−L ₀ MD) / L ₀ MD × 100
(Formula d) L ₅ TD (%) = (L ₅ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 30 minutes (formula e) L ₃₀ MD (%) = (L ₃₀ MD′−L ₀ MD) / L ₀ MD × 100
(Formula f) L ₃₀ TD (%) = (L ₃₀ TD′−L ₀ TD) / L ₀ TD × 100
2. 2. The polarizing plate according to item 1, wherein the film A and the film B satisfy the following formulas (5) to (8), respectively.

(5) 0.05 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.15 (%)
(6) 0.05 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.15 (%)
(7) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.05 (%)
(8) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.05 (%)
In the above formula, L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD are synonymous with the first term.

3. 3. The polarizing plate according to item 1 or 2, wherein L ₃₀ TD and L ₃₀ MD of the film A and the film B are in the range of −0.10 to 0.10%, respectively. .

4. The polarizing plate according to any one of Items 1 to 3, wherein the film A contains a sugar ester or a polycondensed ester having a structure represented by the following general formula (1). .

General formula (1)
B _3- (G ₂ -A) _n -G ₂ -B ₄
(In the above general formula, B ₃ and B ₄ each independently represents an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, Represents an aryl glycol residue having 6 to 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms, wherein A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. N represents an integer of 1 or more.)
5. The film A has a configuration of at least three layers having skin layers on both sides of the core layer, the core layer contains an acrylic resin, and the skin layer contains a cellulose ester. The polarizing plate as described in any one to 4th term | claim.

6. 6. The film A according to any one of claims 1 to 5, wherein the film A is stretched within a range of 1.05 to 1.5 times the original width in the TD direction. Polarizer.

7. In the film B, the in-plane retardation value Ro defined by the following formulas (i) and (ii) is in the range of 40 to 60 nm, and the retardation value Rt in the thickness direction is in the range of 100 to 140 nm. The polarizing plate as described in any one of 1st term | claim to 6th term | claim characterized by being in.

Formula (i): Ro = (n _x −n _y ) × d (nm)
Formula (ii): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In [Equation (i) and Formula (ii), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. The measurement is performed at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH. ]
8). Item 8. The film B according to any one of items 1 to 7, wherein the film B contains cellulose acetate having an average degree of substitution of acetyl groups within a range of 2.1 to 2.4. Polarizer.

9. The polarizing plate according to any one of Items 1 to 8, wherein the film B contains a sugar ester or a polycondensed ester having a structure represented by the following general formula (1): .

General formula (1)
B _3- (G ₂ -A) _n -G ₂ -B ₄
(In the above formula, B ₃ and B ₄ each independently represents an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, 6 carbon atoms. Represents an aryl glycol residue having 12 to 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms, and A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. N represents an integer of 1 or more.)
10. The film B has a structure of at least three layers having skin layers on both sides of the core layer, and the core layer contains cellulose acetate having an acetyl group substitution degree in the range of 2.0 to 2.45, Item 10. The polarizing plate according to any one of Items 1 to 9, wherein the skin layer contains cellulose acetate having an acetyl group substitution degree in the range of 2.6 to 2.95.

11. The polarizing plate according to any one of items 1 to 10, wherein the polarizer has a thickness in a range of 2 to 15 μm.

12 A method for producing a polarizing plate in which films A and B are bonded to both surfaces of a polarizer via an active ray curable adhesive layer,
As the film A, an acrylic film containing an acrylic resin having a thickness in the range of 20 to 60 μm and satisfying the following formulas (1) to (4) is used.
The film B contains cellulose acetate having a film thickness in the range of 20 to 60 μm and an average substitution degree of acetyl groups in the range of 2.0 to 2.5, and the following formulas (1) to ( A method for producing a polarizing plate, comprising using a cellulose acetate film satisfying 4).

(1) 0.03 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.30 (%)
(2) 0.03 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.30 (%)
(3) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.10 (%)
(4) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.10 (%)
In the above formula, L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD are determined by the following formulas (a) to (f) after 1 minute, 5 minutes, And the dimensional change rate of the film after 30 minutes. In the following formulas (a) to (f), the film A and the film B are sampled in a rectangular shape so that one side is parallel to the TD direction or the MD direction, and this is obtained under a temperature and humidity environment of 23 ° C. and 55% RH. Measure the specified dimensions of the film left over in the MD and TD directions, which are L ₀ MD and LoTD, respectively. This film is left in a constant temperature and humidity chamber at 80 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment at 23 ° C./55% RH, the dimensions after 1 minute, the dimensions after 5 minutes, and 30 minutes. The subsequent dimensions are measured in the MD direction and TD direction, respectively, and are defined as L ₁ MD ′, L ₁ TD ′, L ₅ MD ′, L ₅ TD ′, L ₃₀ MD ′, and L ₃₀ TD ′, respectively. Substituting into (a) to (f), the dimensional change rate is obtained.
Dimensional change rate after 1 minute (formula a) L ₁ MD (%) = (L ₁ MD′−L ₀ MD) / L ₀ MD × 100
(Formula b) L ₁ TD (%) = (L ₁ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 5 minutes (formula c) L ₅ MD (%) = (L ₅ MD′−L ₀ MD) / L ₀ MD × 100
(Formula d) L ₅ TD (%) = (L ₅ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 30 minutes (formula e) L ₃₀ MD (%) = (L ₃₀ MD′−L ₀ MD) / L ₀ MD × 100
(Formula f) L ₃₀ TD (%) = (L ₃₀ TD′−L ₀ TD) / L ₀ TD × 100
13. The film A is
Casting a dope containing at least an acrylic resin and an organic solvent to form a web on a metal support;
Drying and peeling the formed web from the metal support;
Stretching the peeled web;
Drying the stretched web in a dryer zone;
A cooling step of cooling the web at a rate in the range of 50-100 ° C./second after the web exits the dryer zone;
13. The method for producing a polarizing plate according to item 12, wherein the polarizing plate is formed by:

14 The film B is
Casting a dope containing at least cellulose acetate and an organic solvent to form a web on a metal support;
Drying and peeling the formed web from the metal support;
Stretching the peeled web;
Drying the stretched web in a dryer zone;
The step of drying the web in the dryer zone is formed at a temperature in the range of 130 to 150 ° C., and the B side facing the A side of the web is alternately turned inside by the conveying roller. has a bending step of bending manner, the bending step, when the radius when bending the web was a (mm), the range value of the 1 / a is 0.035 mm ^-1 ~ 0.050 mm ^-1 The method for producing a polarizing plate according to Item 12 or 13, wherein the bending is performed while repeating bending 50 times or more and less than 120 times.

15. Forming a polyvinyl alcohol resin layer on one surface of a base film in which a rubber component is dispersed in a thermoplastic resin to obtain a laminated film;
Uniaxially stretching the laminated film to obtain a stretched film;
Dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to obtain a dyed film;
Immersing the polyvinyl alcohol-based resin layer of the dyed film in a solution containing a crosslinking agent to form a polarizer layer, and obtaining a crosslinked film;
Drying the crosslinked film;
After forming a polarizing laminated film by
Any one of Items 12 to 14, wherein the polyvinyl alcohol-based resin layer is used as the polarizer by peeling the polyvinyl alcohol-based resin layer of the polarizing laminated film from the base film. The manufacturing method of the polarizing plate of one term.

16. A liquid crystal display device comprising the polarizing plate according to any one of items 1 to 11.

17. 17. The liquid crystal display device according to item 16, wherein the liquid crystal display device is a VA mode type liquid crystal display device.

By the above means of the present invention, a polarizer is bonded to a protective film via an active ray curable adhesive layer, and a polarizing plate using an acrylic film and a cellulose acetate film as the protective film, When a plate is provided in a liquid crystal display device, it is possible to provide a polarizing plate that does not show deterioration in polarizer adhesion such as uneven display of the liquid crystal panel, undulation, film peeling, etc. even if the temperature and humidity atmosphere of the usage environment changes. . Moreover, the manufacturing method of the said polarizing plate and the liquid crystal display device excellent in visibility which comprised the said polarizing plate can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

A polarizer is bonded to a protective film through an actinic radiation curable adhesive layer, and a thin film polarizing plate having a structure of acrylic film / polarizer / cellulose acetate film is changed from a high temperature and high humidity atmosphere to a low temperature and low humidity atmosphere. When the liquid crystal display device is moved and the display screen is observed, there is a problem that display unevenness peculiar to the liquid crystal panel appears. This is because, particularly when the temperature and humidity atmosphere of the environment is suddenly changed, the dimensional change speed of the two protective films is different, so that there is a strain between the two protective films and the adhesive part across the polarizer. It was estimated that it was caused by the optical non-uniformity that occurred.

In the process of examining the speed of dimensional change of the protective film, the present inventor can adjust the dimensional change of the film after being left for a relatively long time such as one day in a specific environment as in the past. As a result of obtaining knowledge that the improvement effect is not sufficient and studying in more detail, focusing on the speed of dimensional change in a relatively short time immediately after suddenly changing the temperature and humidity atmosphere of the environment, acrylic The film and various cellulose ester films were found to follow a specific history of dimensional change within the short time, and it was estimated that the problem of the present invention could be improved by adjusting the difference in the behavior of the dimensional change. It was done.

FIG. 1 shows the above formula (a) after 1 minute, 5 minutes, 30 minutes and 60 minutes immediately after the environmental change of the acrylic film (under an environment of 80 ° C./90% RH to 23 ° C./55% RH). FIG. 6 is a schematic diagram showing dimensional change rates (%) in the MD direction and the TD direction represented by () to (f).

It can be seen that the acrylic film changes (shrinks) in dimension from 1 minute to 5 minutes, and thereafter exhibits a stable behavior with little dimensional change.

FIG. 2 is a schematic view showing a similar dimensional change of a triacetyl cellulose film (TAC film).

The triacetyl cellulose film is greatly different from the acrylic film, and when it is moved from a high temperature and high humidity to a low temperature and low humidity environment, the film slightly expands and then continues to fluctuate (shrink).

FIG. 3 is a schematic view showing a similar dimensional change of a cellulose acetate propionate film (CAP film).

Cellulose acetate propionate film, unlike an acrylic film, greatly varies (shrinks) in dimensions from 1 minute to 5 minutes, and continues to vary (shrink) thereafter.

FIG. 4 is a schematic diagram showing a similar dimensional change of a diacetylcellulose film (DAC film).

The diacetyl cellulose film shows a slightly larger dimensional change (shrinkage) than that of the acrylic film from 1 minute to 5 minutes later, but thereafter exhibits a stable behavior with almost no dimensional change similar to the acrylic film. I understand that.

From the above examination results, if the dimensional change from 1 minute to 5 minutes after the environmental change of the diacetyl cellulose film is adjusted by some means and can be approximated with the behavior of the acrylic film, the two dimensional change behavior matches. It was estimated that the strain between the polarizer and the adhesive portion could be reduced.

Therefore, the technical characteristics of the polarizing plate of the present invention are the use of an acrylic film as the two protective films and a film containing diacetyl cellulose as the cellulose acetate film, and the dimensional change during each short time is specified. By making adjustments so that they fall within the range, the distortion in the protective film and the adhesive part can be suppressed, and even when the temperature and humidity atmosphere of the usage environment changes, the display unevenness that appears on the liquid crystal panel can be reduced. It is presumed that a polarizing plate can be obtained in which the adhesiveness with the polarizer is not deteriorated even in a harsh environment.

Schematic showing the dimensional change of acrylic film in a short time Schematic showing the dimensional change of triacetyl cellulose film in a short time Schematic showing the dimensional change of cellulose acetate propionate film in a short time Schematic showing the dimensional change of diacetylcellulose film in a short time Schematic diagram showing dimensional change of film B (improved diacetylcellulose film) according to the present invention in a short time Schematic diagram when measuring dimensional change of film The schematic diagram which shows an example of the dope preparation process of the preferable solution casting film forming method of the cellulose-ester film based on this invention, a casting process, and a drying process. Schematic diagram showing a co-casting die and casting to form a multilayer web. Schematic diagram of a bending processing apparatus preferably applicable to the present invention

The polarizing plate of the present invention is a polarizing plate in which a polarizer is sandwiched between a film A and a film B via an actinic radiation curable adhesive layer, and the film A is a thin film and has dimensions under specific conditions. It is an acrylic film whose change is within a specific range, the film B is a cellulose acetate film containing a low-substituted cellulose acetate, a thin film, and the above dimensional change is also within a specific range. A feature of the present invention is to provide a polarizing plate in which when such a polarizing plate is provided in a liquid crystal display device, even if the temperature and humidity atmosphere of the usage environment changes, the display unevenness of the liquid crystal panel and the deterioration of the polarizer adhesion are not observed. is there. This feature is a technical feature common to the inventions according to claims 1 to 17.

In the present invention, MD is an abbreviation for “Machineach Direction”, and the MD direction is a direction in which a film generally called a casting direction or a longitudinal direction is conveyed during film formation. TD is an abbreviation for Transverse Direction, and the TD direction is a direction perpendicular to the transport direction generally called the width direction and the lateral direction.

In this specification, the film A and the film B may be simply referred to as a protective film.

As an embodiment of the present invention, the film A and the film B are polarizing plates satisfying the range of dimensional change represented by the formulas (5) to (8) from the viewpoint of manifesting the effects of the present invention. It is preferable that the L ₃₀ TD and the L ₃₀ MD of the film A and the film B are in the range of −0.10 to 0.10%, respectively, even when the temperature and humidity atmosphere of the use environment changes rapidly. This is a preferred embodiment from the viewpoint of suppressing the occurrence of display unevenness of the liquid crystal panel and further improving the durability against the deterioration of the adhesion to the polarizer.

In addition, the film A preferably contains a sugar ester or a polycondensed ester having a structure represented by the general formula (1) from the viewpoint of reducing the dimensional change due to its plastic effect. A is a structure of at least three layers having a skin layer on both sides of the core layer, the core layer contains an acrylic resin, and the skin layer contains a cellulose ester. It is easier to control by adjusting within the range of dimensional change represented by the formulas (1) to (4), which is preferable. Further, the film A is stretched within a range of 1.05 to 1.5 times the original width in the TD direction, thereby improving the orientation of the molecular chain of the acrylic resin, thereby increasing the dimension due to the entry and exit of moisture. The change can be reduced, and the effect of improving the display unevenness of the liquid crystal panel and the adhesiveness of the polarizer can be easily expressed, which is preferable.

In the film B, the in-plane retardation value Ro defined by the above formulas (i) and (ii) is in the range of 40 to 60 nm, and the retardation value Rt in the thickness direction is in the range of 100 to 140 nm. It is preferable from the viewpoint of enlarging the viewing angle of the liquid crystal display device and improving the visibility. In order to express the retardation value, it is preferable to contain cellulose acetate having an average degree of substitution of acetyl groups in the range of 2.1 to 2.4.

In order to stabilize the dimensional change, the film B preferably contains a sugar ester or a polycondensation ester having a structure represented by the general formula (1) because the plastic effect is exhibited, Further, the film B has at least three layers having skin layers on both sides of the core layer, and the core layer contains cellulose acetate having an acetyl group substitution degree in the range of 2.0 to 2.45, and the skin The fact that the layer contains cellulose acetate having an acetyl group substitution degree in the range of 2.6 to 2.95 means that the dimensional change represented by the above formulas (1) to (4) can be achieved by stacking different types of resins. The relationship can be more easily controlled, and the influence of environmental humidity fluctuations on the film can be reduced.

It is preferable that the polarizer has a thickness in the range of 2 to 15 μm from the viewpoint of reducing the thickness of the entire polarizing plate. Further, the flexibility of the polarizer increases, and it becomes easier to follow the dimensional change of the protective film. When an actinic radiation curable adhesive is used, the adhesion between the polarizer and the protective film can be further improved, and there is also an effect of reducing display unevenness, which is preferable.

The manufacturing method of the polarizing plate of this invention is a manufacturing method of the polarizing plate which bonds the film A and the film B to both surfaces of a polarizer through an active ray curable adhesive layer, Comprising: As the said film A, the said acrylic resin When manufacturing the polarizing plate which expresses the effect of this invention, it is preferable that it is a manufacturing method using the said cellulose acetate film as the said film B using the acrylic film containing this.

The film A is formed by adding a cooling step of cooling the web at a speed in the range of 50 to 100 ° C./second after the step of drying the stretched web in the dryer zone in the forming step. It is preferable that the molecular chain can be made dense to adjust the amount of water that can be contained in the film, and the shrinkage ratio of the film containing moisture can be effectively controlled.

In addition, in the forming process of the film B, the step of drying the web is performed in the dryer zone held within a specific temperature range, and the B surface facing the A surface of the web is alternately turned inward by the conveying roller. A bending process that bends as follows, and the bending process is performed by repeating the bending within a specific range of the radius when the web is bent, and by repeating the bending within a specific number of times, By adjusting the amount of moisture that can be contained in the film by making the molecular chain state of the film dense, it is possible to effectively control the shrinkage ratio of the moisture-containing film.

Further, as the polarizer, a polarizing property is formed by forming a polyvinyl alcohol-based resin layer on one surface of a base film in which a rubber component is dispersed in a thermoplastic resin, and then uniaxially stretching, dyeing, crosslinking, and drying. After forming the laminated film, it is preferable to peel off the polyvinyl alcohol-based resin layer of the polarizing laminated film from the base film to form the polarizer, so that a thin film and a high-quality polarizing plate can be obtained. .

The polarizing plate of the present invention is suitably provided in a liquid crystal display device, and particularly suitable for a VA mode liquid crystal display device.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

<< Outline of Polarizing Plate of the Present Invention >>
The polarizing plate of the present invention is a polarizing plate in which a polarizer is sandwiched between a film A and a film B via an active ray curable adhesive layer,
The film A is an acrylic film containing an acrylic resin having a thickness in the range of 20 to 60 μm and satisfying the following formulas (1) to (4):
The film B contains cellulose acetate having a film thickness in the range of 20 to 60 μm and an average substitution degree of acetyl groups in the range of 2.0 to 2.5, and the following formulas (1) to ( It is a cellulose acetate film satisfying 4).

(1) 0.03 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.30 (%)
(2) 0.03 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.30 (%)
(3) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.10 (%)
(4) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.10 (%)
In the above formula, L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD are determined by the following formulas (a) to (f) after 1 minute, 5 minutes, And the dimensional change rate of the film after 30 minutes. In the following formulas (a) to (f), the film A and the film B are sampled in a rectangular shape so that one side is parallel to the TD direction or the MD direction, and this is obtained under a temperature and humidity environment of 23 ° C. and 55% RH. The specified dimensions of the film left over are measured in the MD and TD directions and are designated as L ₀ MD and L ₀ TD, respectively. This film is left in a constant temperature and humidity chamber at 80 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment at 23 ° C./55% RH, the dimensions after 1 minute, the dimensions after 5 minutes, and 30 minutes. The subsequent dimensions are measured in the MD direction and TD direction, respectively, and are defined as L ₁ MD ′, L ₁ TD ′, L ₅ MD ′, L ₅ TD ′, L ₃₀ MD ′, and L ₃₀ TD ′, respectively. Substituting into (a) to (f), the dimensional change rate is obtained.
Dimensional change rate after 1 minute (formula a) L ₁ MD (%) = (L ₁ MD′−L ₀ MD) / L ₀ MD × 100
(Formula b) L ₁ TD (%) = (L ₁ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 5 minutes (formula c) L ₅ MD (%) = (L ₅ MD′−L ₀ MD) / L ₀ MD × 100
(Formula d) L ₅ TD (%) = (L ₅ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 30 minutes (formula e) L ₃₀ MD (%) = (L ₃₀ MD′−L ₀ MD) / L ₀ MD × 100
(Formula f) L ₃₀ TD (%) = (L ₃₀ TD′−L ₀ TD) / L ₀ TD × 100
In order to improve the strength of the polarizing plate in the thinning of the polarizing plate, the present inventor has an acrylic film using an acrylic resin that is excellent in transparency and dimensional stability and has a low hygroscopic property on one surface of the polarizer. The other side of the polarizer contains a conventional cellulose ester resin as a retardation film from the viewpoint of ease of retardation development, productivity (handleability, reworkability, etc.) and cost. A configuration using a retardation film, that is, a configuration of a retardation film containing an acrylic film / polarizer / cellulose ester resin was examined from the viewing side.

In addition, in order to improve the adhesion between the polarizer of the thin film polarizing plate and the protective film and increase the strength of the polarizing plate, a method of bonding the polarizer and the protective film through an actinic radiation curable adhesive is also combined. investigated.

However, from the viewing side of the polarizing plate, the thin film polarizing plate, which is composed of the above acrylic film / polarizer / cellulose ester film, transfers the liquid crystal display device from a high temperature / high humidity atmosphere to a low temperature / low humidity atmosphere and observes the display screen. Then, it became clear that there was a problem that display unevenness peculiar to a liquid crystal panel appeared. This is particularly because the two protective films and the adhesive part are sandwiched by sandwiching the polarizer because the dimensional change speeds of the two protective films are different immediately after a rapid change in the temperature and humidity environment of the environment. It was presumed to be caused by optical non-uniformity due to distortion.

Therefore, the present invention does not use a protective film in which a dimensional change after being left for a relatively long time such as one day or night in a specific environment as in the prior art, but immediately after a rapid change in the temperature and humidity atmosphere of the environment. By using as a protective film for a thin film polarizing plate a specific film that has been adjusted to match the speed of dimensional change in a relatively short time within a specific range, even if the temperature and humidity atmosphere of the usage environment changes The present inventors have found that a polarizing plate can be obtained in which display unevenness of the panel and deterioration of polarizer adhesion are not observed.

[Measurement of dimensional change rate of film]
The dimensional change rate of the film A and the film B according to the present invention after a rapid change in the temperature and humidity atmosphere of the environment is measured by the following method.

[1] FIG. 6 shows a schematic diagram of a film when measuring specific L ₀ MD and L ₀ TD.

Two films A and B are sampled in 10 cm square so that one side is parallel to the TD direction or the MD direction, and used for measuring the dimensional change in the MD direction or the TD direction, respectively. The film is scratched with a razor so that the distance is 8 cm, and then placed in a thermostatic oven at 23 ° C. and 55% RH and left for 24 hours.

The humidity-controlled film is placed on a microscope stage, a glass plate is placed on the film, and the specified dimension (8 cm) is precisely measured with a microscope in the MD direction and the TD direction. L ₀ MD and L ₀ TD, respectively. And

The microscope was Nikon MEASURESCOPE MM-11 (eyepiece: x10, objective lens: x3) manufactured by Nikon, and the data measuring machine was directly connected to the microscope using Nikon DP-302 DATA PROCESSOR. Output to spreadsheet software.

[2] After leaving this film in a constant temperature and humidity chamber of 80 ° C./90% RH for 1 hour, it moved to a temperature / humidity environment of 23 ° C./55% RH, and immediately after 1 minute, after 5 minutes. The dimension and the dimension after 30 minutes are measured in the MD direction and the TD direction by the microscope and the data measuring device, respectively, and L ₁ MD ′, L ₁ TD ′, L ₅ MD ′, L ₅ TD ′, and L _{30 respectively.} Let MD ′ and L ₃₀ TD ′.

[3] Substituting the respective dimensions obtained in [1] and [2] into the following (formula a) to (formula f), and calculating the dimensional change rate of the film after 1 minute, 5 minutes, and 30 minutes. Obtained as L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD.
Dimensional change rate after 1 minute (formula a) L ₁ MD (%) = (L ₁ MD′−L ₀ MD) / L ₀ MD × 100
(Formula b) L ₁ TD (%) = (L ₁ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 5 minutes (formula c) L ₅ MD (%) = (L ₅ MD′−L ₀ MD) / L ₀ MD × 100
(Formula d) L ₅ TD (%) = (L ₅ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 30 minutes (formula e) L ₃₀ MD (%) = (L ₃₀ MD′−L ₀ MD) / L ₀ MD × 100
(Formula f) L ₃₀ TD (%) = (L ₃₀ TD′−L ₀ TD) / L ₀ TD × 100
The film A and the film B according to the present invention are an acrylic film and a cellulose acetate film that satisfy the following (1) to (4). That is, by satisfying (1) and (2), the dimensional variation in the MD direction and the TD direction, which fluctuate relatively greatly after 5 minutes from immediately after (1 minute) when the temperature / humidity atmosphere of the environment changes rapidly, is reduced. By adjusting the film A and the film B so as to fall within the following specific range, the distortion between the protective film and the adhesive part due to the difference in dimensional variation between the two can be suppressed, and (3) and ( By satisfying 4), the effect over time is further stabilized.

(1) 0.03 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.30 (%)
(2) 0.03 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.30 (%)
(3) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.10 (%)
(4) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.10 (%)
Further, the film A and the film B according to the present invention are preferably an acrylic film and a cellulose acetate film satisfying the following (5) to (8).

(5) 0.05 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.15 (%)
(6) 0.05 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.15 (%)
(7) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.05 (%)
(8) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.05 (%)
In addition, the L ₃₀ TD and L ₃₀ MD of the film A and the film B are in the range of −0.10 to 0.10%, respectively, even when the temperature and humidity atmosphere of the environment changes rapidly. From the standpoint of further improving durability against display unevenness of the liquid crystal panel and deterioration of adhesion to the polarizer, this is a preferred embodiment.

Means for adjusting the initial dimensional change rate of the film A and the film B according to the present invention to be within the range indicated by the above (1) to (8) is not particularly limited, but the following means are appropriately selected. It is possible to adjust by adopting.

The means for adjusting the dimensional change rate of the film A according to the present invention within the range indicated by the above (1) to (8) is not limited to the following, but the type of acrylic resin and the weight average molecular weight In addition to selection, adjustment of the type and amount of plasticizer, adjustment of the stretching direction and stretching ratio, and adjustment of the film thickness, details will be described later. It is preferable to form a film by adding a cooling step of cooling the web at a speed in the range of 50 to 100 ° C./second after the above.

Further, the film A has a structure of at least three layers having skin layers on both sides of the core layer, the core layer contains an acrylic resin, and the skin layer has a laminated structure containing a cellulose ester. However, it is preferable to stack different types of resins because the film A can be more easily controlled within the range of dimensional change represented by the above formulas (1) to (8).

Furthermore, the acrylic resin and cellulose ester can be mixed and used as a thermoplastic resin, or the film A can be represented by the above formulas (1) to (8) by utilizing the characteristics of different resins synergistically. This is preferable because it can be controlled more easily within the range of dimensional change.

Means for adjusting the dimensional change rate of the film B according to the present invention within the range represented by the above (1) to (8) is not limited to the following, but the degree of acetyl group substitution and the weight of cellulose acetate. In addition to selecting the average molecular weight, adjusting the type and amount of the plasticizer, adjusting the stretching direction and the stretching ratio, and adjusting the film thickness, details will be described later. The dryer zone within the range has a bending process in which the B surface facing the A surface of the web is alternately turned inside by the conveying roller, and the bending process determines the radius when the web is bent. when the a (mm), 1 / the value of a is set within a range of 0.035 mm ^-1 ~ 0.050 mm ^-1, and, while repeating the bending less than 120 times more than 50 times the line , That film formation, the state of the molecular chains of the film in close, by adjusting the amount of water that can be contained in the film, because it can effectively control the shrinkage percentage of the film containing the moisture, preferred.

Further, the film B has a structure of at least three layers having skin layers on both sides of the core layer, and the core layer contains cellulose acetate having an acetyl group substitution degree in the range of 2.0 to 2.45. The skin layer is a film having a laminated structure containing cellulose acetate having an acetyl group substitution degree in the range of 2.6 to 2.95. By stacking different types of resins, the above-described formula (1) to It can be easily adjusted within the range of the dimensional change represented by (4), which is preferable.

FIG. 5 is a schematic view showing a dimensional change of film B (improved diacetylcellulose film) according to the present invention.

By adding the above adjusting means, it became possible to approximate the behavior of dimensional change in a short time immediately after the environmental change of the diacetyl cellulose film to the behavior of dimensional change of the acrylic film shown in FIG. Further, from comparison with the example, it was found that not the absolute value of the dimensional change itself but the behavior of the speed of the dimensional change is a factor affecting the display unevenness.

Hereinafter, the contents of the film A and the film B and the manufacturing method will be sequentially described.

≪Film A: Acrylic film≫
The film A according to the present invention is characterized in that it is an acrylic film having a total film thickness within a range of 20 to 60 μm. By making the film thickness within the range, the effects of the present invention are exhibited, A thin-film polarizing plate having sufficient rigidity and excellent handleability can be provided. More preferably, it is in the range of 20 to 40 μm.

〔acrylic resin〕
The film A according to the present invention is a film containing an acrylic resin, and in the present invention, the acrylic resin is a polymer of an acrylate ester or a methacrylate ester, and includes a copolymer with another monomer. It is.

Therefore, the acrylic resin used in the present invention includes a methacrylic resin. The resin is not particularly limited, but a resin having a methyl methacrylate unit content in the range of 50 to 99% by mass and other monomer units copolymerizable therewith is preferably in the range of 1 to 50% by mass. .

Other units constituting the acrylic resin formed by copolymerization include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, isobornyl methacrylate, 2-hydroxy Hydroxyalkyl acrylates such as ethyl acrylate, α, β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acryloylmorpholine, Nhydroxyphenyl methacrylamide, N-vinylpyrrolidone, maleic acid, fumaric acid, itaconic acid, etc. Unsaturated divalent carboxylic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutarimide , Glutaric anhydride Etc.

Examples of the copolymerizable monomer that forms a unit excluding glutarimide and glutaric anhydride from the above units include monomers corresponding to the above units. That is, alkyl methacrylate having 2 to 18 carbon atoms, alkyl acrylate having 1 to 18 carbon atoms, hydroxyalkyl acrylate such as isobornyl methacrylate and 2-hydroxyethyl acrylate, acrylic acid, methacrylic acid, etc. α, β-Unsaturated acids, acrylamides such as acryloylmorpholine, N-hydroxyphenylmethacrylamide, divalent carboxylic acids containing unsaturated groups such as N-vinylpyrrolidone, maleic acid, fumaric acid, itaconic acid, styrene, α-methylstyrene And monomers such as α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, and N-substituted maleimide.

Further, the glutarimide unit can be formed, for example, by reacting a primary amine (imidizing agent) with an intermediate polymer having a (meth) acrylic acid ester unit (see JP 2011-26563 A). ).

The glutaric anhydride unit can be formed, for example, by heating an intermediate polymer having a (meth) acrylic ester unit (see Japanese Patent No. 496164).

In the acrylic resin used in the present invention, among the above structural units, from the mechanical properties, isobornyl methacrylate, acryloylmorpholine, N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, styrene, hydroxyethyl methacrylate, maleic anhydride , Maleimide, N-substituted maleimide, glutaric anhydride or glutarimide are particularly preferred.

Moreover, as an acrylic resin used for this invention, the acrylic resin which has a lactone ring structure in a structure from viewpoints of high heat resistance, high transparency, etc. is used preferably. Examples of acrylic resins having a lactone ring structure include, for example, JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005-146084. And (meth) acrylic copolymers having a lactone ring structure described in JP-A-2009-157352 and the like. Specifically, a (meth) acrylic resin having a lactone ring structure in which R ¹ is a hydrogen atom, and R ² and R ³ are methyl groups in the general formula (1) described in JP2009-157352A [ The mass ratio of the copolymerization monomer: methyl methacrylate / 2- (hydroxymethyl) methyl acrylate = 8/2; lactone cyclization rate of about 100%] can be preferably used.

The acrylic resin used for the film A according to the present invention has a viewpoint of controlling a dimensional change with respect to a change in the temperature and humidity atmosphere of the use environment, peelability from a metal support during film production, drying property of an organic solvent, and heat resistance. From the viewpoint of improving mechanical properties, the weight average molecular weight (Mw) is preferably in the range of 80,000 to 2,000,000, more preferably in the range of 90,000 to 1,000,000. It is particularly preferable that it is within the range of 10,000.

If it is 80,000 or more, the heat resistance and mechanical properties are excellent, and if it is 2 million or less, the peelability from the metal support and the drying property of the organic solvent are excellent. If it is 80,000 or more, the heat resistance and mechanical properties are further excellent, and if it is 500,000 or less, the peelability from the metal support and the drying property of the organic solvent are further excellent.

The weight average molecular weight of the acrylic resin used in the present invention can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve with 13 samples within the range of Mw = 500 to 2800000 was used. The 13 samples are preferably used at approximately equal intervals.

The production method of the acrylic resin used in the present invention is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension or emulsion polymerization may be carried out within a range of 30 to 100 ° C., and bulk or solution polymerization may be carried out within a range of 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

Commercially available acrylic resins can be used as the acrylic resin used in the present invention. For example, Delpet 60N, 80N, 980N, SR8200 (above, manufactured by Asahi Kasei Chemicals Corporation), Dianal BR52, BR80, BR83, BR85, BR88, EMB-143, EMB-159, EMB-160, EMB-161, EMB-218, EMB-229, EMB-270, EMB-273 (above, manufactured by Mitsubishi Rayon Co., Ltd.), KT75, TX400S, IPX012 (above, manufactured by Denki Kagaku Kogyo Co., Ltd.) and the like. Two or more acrylic resins can be used in combination.

The acrylic resin is a polymer obtained by polymerizing one or more kinds of monomers containing an acrylic ester monomer, and is preferably a copolymer of plural kinds of monomers from the viewpoint of optical properties, heat resistance and mechanical properties. . In addition, the film A according to the present invention can contain additives other than acrylic resin, but the acrylic resin is contained within the range of 80 to 100% by mass with respect to the film. It is preferable from the viewpoints of heat resistance, mechanical properties and cost.

As an example of the additive, acrylic particles (D) described in International Publication No. 2010/001668 may be included to adjust the mechanical strength of the film in order to adjust the dimensional change rate. Examples of commercially available products of such a multilayer structure acrylic granular composite include, for example, “Metablen W-341” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Co., “Paraloid” manufactured by Kureha Co., Ltd., Rohm and "Acryloid" manufactured by Haas, "Staffyroid" manufactured by Gantz Kasei Kogyo Co., Ltd., Chemisnow MR-2G, MS-300X (manufactured by Soken Chemical Co., Ltd.) and "Parapet SA" manufactured by Kuraray These can be used alone or in combination of two or more.

Further, as other additives, it is also preferable to contain additives such as a plasticizer, an ultraviolet absorber, an antioxidant, a deterioration inhibitor, a peeling aid, a surfactant, a dye, and fine particles, which will be described later.

In particular, the following sugar ester or polycondensation ester is preferably contained.

[Sugar ester]
In the acrylic film which is the film A according to the present invention, it is preferable to contain a sugar ester other than the cellulose ester from the viewpoint of controlling the behavior of dimensional change.

The sugar ester according to the present invention is preferably a sugar ester obtained by esterifying at least one pyranose ring or furanose ring and having one or more and twelve or less OH groups in the structure.

The sugar ester according to the present invention is a compound containing at least one of a furanose ring and a pyranose ring, and may be a monosaccharide or a polysaccharide having 2 to 12 sugar structures linked together. The sugar ester is preferably a compound in which at least one OH group of the sugar structure is esterified. In the sugar ester according to the present invention, the average ester substitution degree is preferably within the range of 4.0 to 8.0, and more preferably within the range of 5.0 to 7.5.

The sugar ester applicable to the present invention is not particularly limited, and examples thereof include sugar esters represented by the following general formula (A).

Formula (A)
(HO) _m -G- (OC (= O) -R ² ) _n
In the general formula (A), G represents a monosaccharide or disaccharide residue, R ² represents an aliphatic group or an aromatic group, and m is directly bonded to the monosaccharide or disaccharide residue. N is the total number of — (O—C (═O) —R ² ) groups directly bonded to the monosaccharide or disaccharide residue, 3 ≦ m + n ≦ 8, and n ≠ 0.

The sugar ester having the structure represented by the general formula (A) is a single kind of hydroxy group (m) and-(O—C (═O) —R ² ) groups in which the number (n) is fixed. It is difficult to isolate as a compound, and it is known that a compound in which several components different in m and n in the formula are mixed is obtained. Accordingly, the performance as a mixture in which the number of hydroxy groups (m) and the number of — (O—C (═O) —R ² ) groups (n) are changed is important. In the case of the protective film according to the present invention, A sugar ester having an average degree of ester substitution within the range of 5.0 to 7.5 is preferred.

In the above general formula (A), G represents a monosaccharide or disaccharide residue. Specific examples of monosaccharides include allose, altrose, glucose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose, lyxose, and the like.

Specific examples of the compound having a monosaccharide residue of the sugar ester represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

 

 

Specific examples of the disaccharide residue include trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and isotrehalose.

Specific examples of the compound having a disaccharide residue of the sugar ester represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

 

 

In the general formula (A), R ² represents an aliphatic group or an aromatic group. Here, the aliphatic group and the aromatic group may each independently have a substituent.

In general formula (A), m is the total number of hydroxy groups directly bonded to the monosaccharide or disaccharide residue, and n is directly bonded to the monosaccharide or disaccharide residue. And the total number of — (O—C (═O) —R ² ) groups. Further, it is necessary that 3 ≦ m + n ≦ 8, and it is preferable that 4 ≦ m + n ≦ 8. Further, n ≠ 0. When n is 2 or more, the — (O—C (═O) —R ² ) groups may be the same as or different from each other.

The aliphatic group in the definition of R ² may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 1 to 20 carbon atoms. Those of ˜15 are particularly preferred. Specific examples of the aliphatic group include, for example, methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, tert-butyl, amyl, iso-amyl, tert-amyl, n- Examples include hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl, didecyl and the like.

The aromatic group in the definition of R ² may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, more preferably 6 to 12 carbon atoms. Specific examples of the aromatic hydrocarbon group include rings such as benzene, naphthalene, anthracene, biphenyl, and terphenyl. As the aromatic hydrocarbon group, a benzene ring, a naphthalene ring, and a biphenyl ring are particularly preferable. As the aromatic heterocyclic group, a ring containing at least one of an oxygen atom, a nitrogen atom or a sulfur atom is preferable. Specific examples of the heterocyclic ring include, for example, furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, Examples of each ring include isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzthiazole, benzotriazole, and tetrazaindene. As the aromatic heterocyclic group, a pyridine ring, a triazine ring, and a quinoline ring are particularly preferable.

Next, preferred examples of the sugar ester represented by the general formula (A) are shown below, but the present invention is not limited to these exemplified compounds.

A sugar ester may contain two or more different substituents in one molecule, contains an aromatic substituent and an aliphatic substituent in one molecule, and contains two or more different aromatic substituents. Two or more different aliphatic substituents contained in one molecule can be contained in one molecule.

It is also preferable to contain a mixture of two or more sugar esters. It is also preferable to simultaneously contain a sugar ester containing an aromatic substituent and a sugar ester containing an aliphatic substituent.

 

 

 

 

<Synthesis Example: Synthesis Example of Sugar Ester Represented by Formula (A)>
Below, an example of the synthesis | combination of the sugar ester which can be used suitably for this invention is shown.

 

 

Four-headed Kolben equipped with a stirrer, reflux condenser, thermometer and nitrogen gas inlet tube, 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, pyridine 379.7 g (4.8 mol) of each were charged, and the temperature was raised while bubbling nitrogen gas from a nitrogen gas inlet tube under stirring, and esterification was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass sodium carbonate aqueous solution were added, and the mixture was stirred at 50 ° C. for 30 minutes, and then allowed to stand to separate a toluene layer. Finally, 100 g of water was added to the separated toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer was separated, and toluene was distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of compounds A-1, A-2, A-3, A-4 and A-5 was obtained. Analysis of the resulting mixture by HPLC and LC-MASS revealed that A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5 Was 3% by mass, and the average ester substitution degree of the sugar ester was 6.57. A part of the obtained mixture was purified by silica gel column chromatography to obtain 100% pure A-1, A-2, A-3, A-4 and A-5, respectively.

The addition amount of the sugar ester is preferably within a range of 0.1 to 20% by mass, and more preferably within a range of 1 to 15% by mass with respect to the acrylic resin.

The film A according to the present invention preferably contains the following ester (polycondensation ester).

[Polycondensed ester]
In the film A according to the present invention, it is preferable to use an ester other than a sugar ester as one of the plasticizers.

The ester other than the sugar ester applicable to the present invention is not particularly limited, but it is preferable to use a polycondensed ester having a structure represented by the following general formula (1).

Due to its plastic effect, the polycondensed ester is preferably contained in the range of 1 to 20% by mass, more preferably in the range of 2 to 15% by mass in the film A according to the present invention. preferable.

General formula (1)
B _3- (G ₂ -A) _n -G ₂ -B ₄
In the general formula (1), B ₃ and B ₄ each independently represent an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. n represents an integer of 1 or more.

In the present invention, the polycondensed ester is a polycondensed ester containing a repeating unit obtained by reacting a dicarboxylic acid and a diol, A represents a carboxylic acid residue in the polycondensed ester, and G ₂ represents an alcohol residue. To express.

The dicarboxylic acid constituting the polycondensed ester is an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid or an alicyclic dicarboxylic acid, preferably an aromatic dicarboxylic acid. The dicarboxylic acid may be one type or a mixture of two or more types. In particular, it is preferable to mix aromatic and aliphatic.

The diol constituting the polycondensed ester is an aromatic diol, an aliphatic diol or an alicyclic diol, preferably an aliphatic diol, more preferably a diol having 1 to 8 carbon atoms. The diol may be one type or a mixture of two or more types.

Among these, it is preferable to include a repeating unit obtained by reacting at least a dicarboxylic acid containing an aromatic dicarboxylic acid and a diol having 1 to 8 carbon atoms, and a dicarboxylic acid containing an aromatic dicarboxylic acid and an aliphatic dicarboxylic acid. And a repeating unit obtained by reacting a diol having 1 to 8 carbon atoms.

Both ends of the polycondensed ester molecule may or may not be sealed.

Specific examples of the alkylene dicarboxylic acid constituting A in the general formula (1) include 1,2-ethanedicarboxylic acid (succinic acid), 1,3-propanedicarboxylic acid (glutaric acid), 1,4-butanedicarboxylic acid. Divalent groups derived from (adipic acid), 1,5-pentanedicarboxylic acid (pimelic acid), 1,8-octanedicarboxylic acid (sebacic acid) and the like are included. Specific examples of the alkenylene dicarboxylic acid constituting A include maleic acid and fumaric acid. Specific examples of the aryl dicarboxylic acid constituting A include 1,2-benzenedicarboxylic acid (phthalic acid), 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and the like. Can be mentioned.

A may be one type or two or more types may be combined. Among them, A is preferably a combination of an alkylene dicarboxylic acid having 4 to 12 carbon atoms and an aryl dicarboxylic acid having 8 to 12 carbon atoms.

G ₂ in the general formula (1) is a divalent group derived from an alkylene glycol having 2 to 12 carbon atoms, a divalent group derived from an aryl glycol having 6 to 12 carbon atoms, or a carbon atom. It represents a divalent group derived from oxyalkylene glycol of 4 to 12.

Examples of the divalent group derived from an alkylene glycol having 2 to 12 carbon atoms in G ₂ include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, , 3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (Neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-di-) Methylol heptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanedio , 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. Divalent groups are included.

Examples of divalent groups derived from aryl glycols having 6 to 12 carbon atoms in G ₂ include 1,2-dihydroxybenzene (catechol), 1,3-dihydroxybenzene (resorcinol), 1,4-dihydroxy Divalent groups derived from benzene (hydroquinone) and the like are included. Examples of the divalent group derived from oxyalkylene glycol having 4 to 12 carbon atoms in G are derived from diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like. Divalent groups are included.

G ₂ may be a single type or a combination of two or more types. Among these, G ₂ is preferably a divalent group derived from an alkylene glycol having 2 to 12 carbon atoms, more preferably 2 to 5, and most preferably 2 to 4.

B ₃ and B ₄ in the general formula (1) are each a monovalent group derived from an aromatic ring-containing monocarboxylic acid or an aliphatic monocarboxylic acid, or a hydroxy group.

The aromatic ring-containing monocarboxylic acid in the monovalent group derived from the aromatic ring-containing monocarboxylic acid is a carboxylic acid containing an aromatic ring in the molecule, and not only those in which the aromatic ring is directly bonded to a carboxy group, Also included are those in which an aromatic ring is bonded to a carboxy group via an alkylene group or the like. Examples of monovalent groups derived from aromatic ring-containing monocarboxylic acids include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, and normal propyl benzoic acid. , Monovalent groups derived from aminobenzoic acid, acetoxybenzoic acid, phenylacetic acid, 3-phenylpropionic acid and the like. Of these, benzoic acid and p-toluic acid are preferable.

Examples of monovalent groups derived from aliphatic monocarboxylic acids include monovalent groups derived from acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid and the like. Is included. Among these, a monovalent group derived from an alkyl monocarboxylic acid having 1 to 3 carbon atoms in the alkyl portion is preferable, and an acetyl group (a monovalent group derived from acetic acid) is more preferable.

The weight average molecular weight of the polycondensed ester according to the present invention is preferably in the range of 500 to 3000, and more preferably in the range of 600 to 2000. The weight average molecular weight can be measured by the gel permeation chromatography (GPC).

Hereinafter, although the specific example of the polycondensation ester which has a structure represented by General formula (1) is shown, it is not limited to this.

 

 

 

 

 

 

Hereinafter, a specific synthesis example of the polycondensation ester described above will be described.

<Polycondensed ester P1>
180 g of ethylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a slow cooling tube. The temperature is gradually raised with stirring until reaching 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted ethylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P1. The acid value was 0.20 and the number average molecular weight was 450.

<Polycondensed ester P2>
251 g of 1,2-propylene glycol, 244 g of phthalic anhydride, 103 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L four-neck equipped with thermometer, stirrer, and quick cooling tube The flask is charged and gradually heated with stirring until it reaches 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P2. The acid value was 0.10 and the number average molecular weight was 450.

<Polycondensed ester P3>
1,4-butanediol (330 g), phthalic anhydride (244 g), adipic acid (103 g), benzoic acid (610 g), tetraisopropyl titanate (0.191 g) as an esterification catalyst, 2 L four-neck equipped with a thermometer, stirrer, and slow cooling tube The flask is charged and gradually heated with stirring until it reaches 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,4-butanediol was distilled off at 200 ° C. under reduced pressure to obtain a polycondensed ester P3. The acid value was 0.50 and the number average molecular weight was 2000.

<Polycondensed ester P4>
251 g of 1,2-propylene glycol, 354 g of terephthalic acid, 610 g of benzoic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a quick cooling tube. The temperature is gradually raised with stirring until it reaches 230 ° C. in an air stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off at 200 ° C. under reduced pressure to obtain a polycondensed ester P4. The acid value was 0.10 and the number average molecular weight was 400.

<Polycondensed ester P5>
251 g of 1,2-propylene glycol, 354 g of terephthalic acid, 680 g of p-troyl acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst are charged into a 2 L four-necked flask equipped with a thermometer, stirrer, and slow cooling tube. The temperature is gradually raised with stirring until it reaches 230 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P5. The acid value was 0.30 and the number average molecular weight was 400.

<Polycondensed ester P6>
180 g of 1,2-propylene glycol, 292 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a slow cooling tube, in a nitrogen stream. The temperature is gradually raised while stirring until 200 ° C is reached. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P6. The acid value was 0.10 and the number average molecular weight was 400.

<Polycondensed ester P7>
180 g of 1,2-propylene glycol, 244 g of phthalic anhydride, 103 g of adipic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, stirrer, and quick cooling tube. The temperature is gradually raised with stirring until it reaches 200 ° C. in a nitrogen stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P7. The acid value was 0.10 and the number average molecular weight was 320.

<Polycondensed ester P8>
251 g of ethylene glycol, 244 g of phthalic anhydride, 120 g of succinic acid, 150 g of acetic acid, and 0.191 g of tetraisopropyl titanate as an esterification catalyst were charged into a 2 L four-necked flask equipped with a thermometer, a stirrer, and a slow cooling tube, and nitrogen The temperature is gradually raised with stirring until it reaches 200 ° C. in an air stream. The dehydration condensation reaction was carried out while observing the degree of polymerization. After completion of the reaction, unreacted ethylene glycol was distilled off under reduced pressure at 200 ° C. to obtain a polycondensed ester P8. The acid value was 0.50 and the number average molecular weight was 1200.

[Laminated film: (TAC / acrylic / TAC) film]
Film A according to the present invention has a structure of at least three layers having skin layers on both sides of a core layer, the core layer containing an acrylic resin, and the skin layer containing a cellulose ester. It is preferable to stack different types of resins because the dimensional change rate represented by the formulas (1) to (4) can be easily controlled within a desired range.

In this specification, “core layer” refers to the thickest layer among the layers of the film, and “skin layer” refers to a layer that is thinner than the “core layer”. Say. Further, in the present invention, there is a “skin layer” on the “core layer” side of the film having a laminated structure of “core layer” and “skin layer”. In this case, the film is disposed on both sides of the “core layer”. The “skin layer” may have the same or different film thickness.

As the acrylic resin contained in the core layer, the above-mentioned acrylic resin and additives can be used as appropriate.

The cellulose ester contained in the skin layer is not particularly limited, but specific cellulose esters include cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose It is preferably at least one selected from acetate butyrate, cellulose acetate phthalate, and cellulose phthalate, and cellulose triacetate having an average substitution degree of acetyl groups in the range of 2.6 to 2.95 It is particularly preferable from the viewpoint of excellent adhesion to the child and reducing the occurrence of distortion of the film and the adhesive part due to dimensional change.

The core layer and skin layer preferably contain additives such as a plasticizer, an ultraviolet absorber, an antioxidant, a deterioration inhibitor, a peeling aid, a surfactant, a dye, and fine particles, which will be described later.

As a method for producing the film A according to the present invention, it is preferable that the film formation is simultaneous multilayer casting film formation, and co-casting described later is preferable.

In the case of co-casting, the thickness of each layer is not particularly limited as long as the skin layer is thinner than the core layer, but preferably the skin layer is 0.2 to 50% of the total thickness of the film A. The thickness is preferably 2 to 30%. Since the total film thickness of the film A is in the range of 20 to 60 μm, it is preferable to adjust the film thickness of the core layer and the film thickness of the skin layer within the above ranges.

[Film mixed with acrylic resin and cellulose ester]
The film A according to the present invention may be used by mixing an acrylic resin and a cellulose ester. In the case of mixing, the mixing mass ratio of the acrylic resin and the cellulose ester is preferably in the range of acrylic resin: cellulose ester = 95: 5 to 50:50, and preferably in the range of 90:10 to 70:30. From the viewpoint of controlling the behavior of dimensional changes due to environmental fluctuations, it is more preferable.

The acrylic resin can be appropriately selected from the aforementioned acrylic resins. As the cellulose ester, a resin contained in the skin layer can be used. Cellulose triacetate having an average substitution degree of acetyl groups in the range of 2.6 to 2.95, or a total substitution degree of total acyl groups of 2 Cellulose acetate propio, which is in the range of 0.0 to 2.9, has an acetyl group substitution degree of 0.1 to 1.9, and a propionyl group substitution degree of 1.1 to 2.8 It is more preferable to use an acrylate, and it is particularly preferable to use the cellulose acetate propionate.

≪Film B: Cellulose acetate film≫
The film B according to the present invention is characterized in that it contains a cellulose acetate having a thickness of 20 to 60 μm and an average acetyl group substitution degree of 2.0 to 2.5. The film thickness is more preferably in the range of 20 to 40 μm. If it is in this range, it is possible to obtain a property having sufficient rigidity and excellent handleability, and it becomes easy to produce a thin film polarizing plate.

[Cellulose acetate]
The film B according to the present invention is characterized in that the main component is cellulose acetate having an average degree of substitution of acetyl groups in the range of 2.0 to 2.5. In the present invention, the main component means that the cellulose acetate constituting the cellulose acetate film has a ratio of 60% by mass or more of cellulose acetate having an average degree of substitution of acetyl groups in the range of 2.0 to 2.5. Yes, preferably 80% by mass or more, more preferably 95% by mass or more. The average degree of substitution of the acetyl group is in the range of 2.1 to 2.4, it is easy to control the behavior of dimensional change, and in addition, the development of retardation is high, and it can be used as a retardation film. preferable.

The average degree of substitution of acetyl groups in cellulose acetate can be determined by measurement according to ASTM-D817-96.

In the present invention, if the average substitution degree of the acetyl group of cellulose acetate to be applied is within the above range, the effect of the present invention is exhibited, the castability at the time of film formation is high, and the handleability is excellent as a film. It is possible to realize characteristics such as being.

In addition, the number average molecular weight (Mn) of the cellulose acetate is preferably in the range of 80000 to 155000, and more preferably in the range of 90000 to 152000. The weight average molecular weight (Mw) is preferably in the range of 120,000 to 310000. The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is preferably in the range of 1.4 to 2.5, more preferably in the range of 1.5 to 2.0. preferable.

The average molecular weight (Mn, Mw) of the cellulose acetate can be measured by gel permeation chromatography. The measurement conditions are as described above.

The cellulose acetate according to the present invention can be produced by a conventional method such as a sulfuric acid catalyst method, an acetic acid method, a methylene chloride method, and the raw materials are not particularly limited. ), Kenaf and the like. Moreover, the cellulose acetate obtained from them can be mixed and used in arbitrary ratios, respectively. The cellulose acetate according to the present invention can be synthesized with reference to the methods described in JP-A Nos. 10-45804 and 2005-281645, for example.

[Sugar ester and polycondensation ester having the structure represented by the general formula (1)]
From the viewpoint of adjusting the rate of dimensional change, the film B according to the present invention contains the aforementioned sugar ester or the polycondensed ester having the structure represented by the above general formula (1) in the same manner as the film A. ,preferable.

The content of the sugar ester and the polycondensed ester in the film B is preferably in the range of 1 to 20% by mass, more preferably in the range of 2 to 15% by mass.

[Other additives]
Film A and film B according to the present invention preferably contain additives such as a plasticizer, an ultraviolet absorber, an antioxidant, a deterioration inhibitor, a peeling aid, a surfactant, a dye, and fine particles. Hereinafter, although these additives are demonstrated, it is preferable to adjust suitably the kind and addition amount of an additive with the film A and the film B suitably. Hereinafter, the film A and the film B are referred to as a protective film for explanation.

(Polyhydric alcohol ester)
In the protective film which concerns on this invention, it is also preferable to contain the polyhydric alcohol ester represented by following General formula (2).

General formula (2)
B ₁ -GB ₂
In the general formula (2), B ₁ and B ₂ each independently represent an aliphatic or aromatic monocarboxylic acid residue. G represents an alkylene glycol residue having a straight chain or branched structure having 2 to 12 carbon atoms.

In the general formula (2), G represents a divalent group derived from an alkylene glycol having a linear or branched structure having 2 to 12 carbon atoms.

Examples of the divalent group derived from an alkylene glycol having 2 to 12 carbon atoms in G include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1, 3-butanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol ( Neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylol) Heptane), 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanedio , 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc. A divalent group can be mentioned. Two or more types of alkylene glycol can be preferably used in combination.

In the general formula (2), B ₁ and B ₂ are each independently a monovalent group derived from an aromatic ring-containing monocarboxylic acid or an aliphatic monocarboxylic acid.

The aromatic ring-containing monocarboxylic acid in the monovalent group derived from the aromatic ring-containing monocarboxylic acid is a carboxylic acid containing an aromatic ring in the molecule, and not only those in which the aromatic ring is directly bonded to a carboxy group, Also included are those in which an aromatic ring is bonded to a carboxy group via an alkylene group or the like. Examples of monovalent groups derived from aromatic ring-containing monocarboxylic acids include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, and normal propyl benzoic acid. , Monovalent groups derived from aminobenzoic acid, acetoxybenzoic acid, phenylacetic acid, 3-phenylpropionic acid and the like. Of these, benzoic acid and p-toluic acid are preferable.

Examples of monovalent groups derived from aliphatic monocarboxylic acids include monovalent groups derived from acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid and the like. Is included. Of these, a monovalent group derived from an alkyl monocarboxylic acid having 1 to 10 carbon atoms in the alkyl moiety is preferable, and an acetyl group (a monovalent group derived from acetic acid) is more preferable.

Specific examples of polyhydric alcohol esters applicable to the present invention are shown below, but the present invention is not limited to these exemplified compounds.

 

 

 

 

 

 

The polyhydric alcohol ester having the structure represented by the general formula (2) according to the present invention is preferably contained in the range of 0.5 to 5% by mass with respect to the protective film. The content is more preferably within the range, and particularly preferably within the range of 1 to 2% by mass.

The polyhydric alcohol ester having the structure represented by the general formula (2) according to the present invention can be synthesized according to a conventionally known general synthesis method.

(Phosphate ester)
A phosphoric acid ester can be used for the protective film according to the present invention. As phosphoric acid esters, triaryl phosphoric acid esters, diaryl phosphoric acid esters, monoaryl phosphoric acid esters, aryl phosphonic acid compounds, aryl phosphine oxide compounds, condensed aryl phosphoric acid esters, halogenated alkyl phosphoric acid esters, halogen-containing condensed phosphoric acid Examples thereof include esters, halogen-containing condensed phosphonic acid esters, and halogen-containing phosphorous acid esters.

Specific phosphoric acid esters include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloro) Propyl) phosphate, tris (tribromoneopentyl) phosphate, and the like.

(Esters of glycolic acid)
In the present invention, glycolic acid esters (glycolate compounds) can be used as one kind of polyhydric alcohol esters.

The glycolate compound applicable to the present invention is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl Ethyl glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl Glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl Lil ethyl glycolate and the like, preferably ethyl phthalyl ethyl glycolate.

(UV absorber)
The protective film according to the present invention preferably contains an ultraviolet absorber from the viewpoint of improving light resistance. The ultraviolet absorber is intended to improve light resistance by absorbing ultraviolet rays of 400 nm or less, and the transmittance at a wavelength of 370 nm is preferably in the range of 2 to 30%, more preferably. It is within the range of 4 to 20%, more preferably within the range of 5 to 10%.

The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, and particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers.

For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, There are tinuvins such as tinuvin 928, and these are all commercially available products from BASF Japan and can be preferably used. Of these, halogen-free ones are preferred.

In addition, a discotic compound such as a compound having a 1,3,5-triazine ring is also preferably used as the ultraviolet absorber.

The protective film according to the present invention preferably contains two or more kinds of ultraviolet absorbers.

Also, as the ultraviolet absorber, a polymeric ultraviolet absorber can also be preferably used, and in particular, a polymer type ultraviolet absorber described in JP-A-6-148430 is preferably used. Moreover, it is preferable that the ultraviolet absorber does not have a halogen group.

The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

For inorganic powders that do not dissolve in organic solvents, use a dissolver or sand mill in the organic solvent and cellulose ester (cellulose acetate) to disperse them before adding them to the dope.

The amount of UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but when the dry film thickness of the protective film is in the range of 15 to 50 μm, it is 0.5 to It is preferably in the range of 10% by mass, and more preferably in the range of 0.6-4% by mass.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When an organic electroluminescence display device or the like is placed in a high humidity and high temperature state, the protective film may be deteriorated.

The antioxidant has a role of delaying or preventing the protective film from being decomposed by, for example, the residual solvent amount of halogen in the protective film or phosphoric acid of the phosphoric acid plasticizer. It is preferable to make it contain in a film.

As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], oct Decyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

The amount of these compounds added is preferably in the range of 1 ppm to 1.0% by weight with respect to the protective film, more preferably in the range of 10 to 1000 ppm.

(Fine particles (matting agent))
The protective film may further contain fine particles (matting agent) as necessary in order to improve the slipperiness of the surface.

The fine particles may be inorganic fine particles or organic fine particles. Examples of inorganic fine particles include silicon dioxide (silica), titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples include magnesium silicate and calcium phosphate. Among these, silicon dioxide and zirconium oxide are preferable, and silicon dioxide is more preferable in order to reduce the increase in haze of the obtained film.

Examples of the fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Seahoster KE-P10, KE-P30, KE-P50, KE-P100 (manufactured by Nippon Shokubai Co., Ltd.) and the like are included. Among them, Aerosil R972V, NAX50, Seahoster KE-P30 and the like are particularly preferable because they reduce the coefficient of friction while keeping the turbidity of the resulting film low.

The primary particle diameter of the fine particles is preferably in the range of 5 to 50 nm, and more preferably in the range of 7 to 20 nm. A larger primary particle size has a larger effect of increasing the slipperiness of the resulting film, but the transparency tends to decrease. Therefore, the fine particles may be contained as secondary aggregates having a particle diameter of 0.05 to 0.3 μm. The size of primary particles or secondary aggregates of the fine particles is determined by observing the primary particles or secondary aggregates with a transmission electron microscope in the range of magnification of 500 to 2 million times. It can obtain | require as an average value of an individual particle diameter.

The content of the fine particles is preferably in the range of 0.05 to 1.0% by mass, more preferably in the range of 0.1 to 0.8% by mass with respect to the resin forming the protective film. preferable.

[Laminated film: (TAC / DAC / TAC) film]
Similarly to the film A, the film B according to the present invention has a structure of at least three layers having skin layers on both sides of the core layer, and the core layer has a degree of acetyl group substitution within the range of 2.0 to 2.45. It is a heterogeneous film containing a certain diacetyl cellulose (DAC), and the skin layer is a laminated structure film containing triacetyl cellulose (TAC) having a degree of acetyl group substitution in the range of 2.60 to 2.95. By overlapping the resins, the dimensional change rate represented by the above formulas (1) to (4) can be easily controlled within a desired range, which is preferable.

When the average degree of substitution of acetyl groups of triacetylcellulose contained in the skin layer is 2.6 or more, the adhesiveness to the polarizer is excellent, and the viewpoint of reducing the occurrence of distortion between the film and the adhesive portion due to dimensional change. Are particularly preferred.

Further, it is preferable that the core layer and the skin layer appropriately contain additives such as the plasticizer, ultraviolet absorber, antioxidant, deterioration inhibitor, peeling aid, surfactant, dye, and fine particles.

The cellulose acetate film according to the present invention is not particularly limited as long as the skin layer is thinner than the core layer, but preferably the skin layer is in the range of 0.2 to 50% of the total thickness of the film B. The thickness is preferably in the range of 2 to 30%. Since the total film thickness of the film B is in the range of 20 to 60 μm, it is preferable to adjust the film thickness of the core layer and the film thickness of the skin layer within the above ranges.

<< Production Method of Film A and Film B >>
Examples of the method for producing the acrylic film as the film A and the cellulose acetate film as the film B according to the present invention include a normal inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method. However, from the viewpoint of suppression of coloring, suppression of foreign matter defects, suppression of optical defects such as die lines, etc., a solution casting film forming method and a melt casting film forming method can be selected. The solution casting film forming method is particularly preferable from the viewpoint of obtaining a uniform and smooth surface.

[Solution casting film forming method]
Hereinafter, the manufacture example which manufactures the protective film which concerns on this invention by the solution casting method is demonstrated.

As a method for producing a protective film according to the present invention, production methods such as a normal inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. From the viewpoint of suppressing foreign matter defects and suppressing optical defects such as die lines, a film casting method can be selected from a solution casting film forming method and a melt casting film forming method, and the solution casting method is particularly preferable.

The production of the protective film according to the present invention comprises the steps of preparing a dope by dissolving an additive such as an acrylic resin, cellulose ester and the plasticizer in a solvent, and casting the dope on a belt-like or drum-like metal support. It is carried out by a step of drying, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching, a step of further drying, and a step of winding after cooling. The protective film of the present invention preferably contains acrylic resin or cellulose acetate in the solid content in the range of 60 to 95% by mass.

Here, although the film forming method of the cellulose acetate film which is the film B will be described as an example, it can be similarly applied to the manufacturing method of the acrylic film which is the film A. Further, in the following description, portions relating to the manufacturing method related to the acrylic film will be appropriately described as an acrylic film.

(1) Dissolution process In a dissolution vessel, the cellulose acetate, in some cases, a sugar ester, a polycondensation ester, a polyhydric alcohol ester, or other compound is added to an organic solvent mainly composed of a good solvent for cellulose acetate. The step of dissolving with stirring to form a dope, or mixing the sugar ester, polycondensation ester, polyhydric alcohol ester, or other compound solution according to the present invention into the cellulose acetate solution, It is a process of forming.

When the cellulose acetate film according to the present invention is produced by the solution casting method, an organic solvent useful for forming a dope can be used without limitation as long as it dissolves cellulose acetate and other compounds at the same time.

For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used.

In addition to the organic solvent, the dope preferably contains a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in the range of 1 to 40% by mass. When the proportion of alcohol in the dope increases, the web gels, and peeling from the metal support becomes easy. When the proportion of alcohol is small, cellulose acetate and other compounds dissolve in non-chlorine organic solvents. There is also a role to promote. In the film formation of the cellulose acetate film according to the present invention, the film is formed using a dope having an alcohol concentration in the range of 0.5 to 15.0% by mass in order to improve the flatness of the obtained cellulose acetate film. The method can be applied.

In particular, a dope in which cellulose acetate and other compounds are dissolved in a total amount of 15 to 45 mass% in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. A composition is preferred.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Methanol and ethanol are preferred because of the stability, boiling point of these inner dopes, and good drying properties.

Cellulose acetate and sugar ester, polycondensation ester, polyhydric alcohol ester, or other compounds are dissolved at atmospheric pressure, below the boiling point of the main solvent, or pressurized above the boiling point of the main solvent. A method using a cooling dissolution method as described in JP-A-9-95544, JP-A-9-95557, or JP-A-9-95538, and a high pressure described in JP-A-11-21379. Various dissolution methods such as a method of performing can be used, and a method of performing pressurization at a pressure equal to or higher than the boiling point of the main solvent is particularly preferable.

The concentration of cellulose acetate in the dope is preferably in the range of 10 to 40% by mass. After the compound is added to the dope during or after dissolution and dissolved and dispersed, it is filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

For the filtration, it is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a filtering time of 10 to 25 sec / 100 ml.

In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are within the range of the collected particle diameter of 0.5 to 5 μm and the filtering time is within the range of 10 to 25 sec / 100 ml. Only the aggregates can be removed by using. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

FIG. 7 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

大 き な Remove large agglomerates from the charging vessel 41 with the filter 44 and feed the solution to the stock vessel 42. Thereafter, various additive solutions are added from the stock kettle 42 to the main dope dissolving kettle 1.

Thereafter, the main dope is filtered by the main filter 3, and an ultraviolet absorber additive solution is added inline to the main dope 16.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material.

Recycled material is a finely pulverized cellulose acetate film, which is generated when the cellulose acetate film is formed, and is obtained by cutting both sides of the film, or cellulose acetate that exceeds the specified value of the film due to scratches, etc. Film stock is used.

Also, as the raw material of the resin used for the dope preparation, those obtained by pelletizing cellulose acetate and other compounds in advance can be preferably used.

(2) Casting step (2-1) Dope casting An endless metal support 31 that feeds the dope to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it infinitely, For example, a dope is cast from a pressure die slit at a casting position on a metal support such as a stainless steel belt or a rotating metal drum.

The metal support in the casting process is preferably a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support. The cast width can be in the range of 1 to 4 m, preferably in the range of 1.5 to 3 m, more preferably in the range of 2 to 2.8 m. The surface temperature of the metal support in the casting step is set in the range of −50 ° C. to the temperature at which the solvent boils and does not foam, more preferably in the range of −30 to 100 ° C. A higher temperature is preferable because the web can be dried faster, but if it is too high, the web may foam or the flatness may deteriorate. The preferred support temperature is appropriately determined within the range of 0 to 100 ° C, and more preferably within the range of 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked.

(2-2) Co-casting A film having a laminated structure such as a (TAC / acrylic / TAC) film and a (TAC / DAC / TAC) film according to the present invention contains a dope containing an acrylic resin and a cellulose ester. Each dope can be used to form a film by casting two or more kinds of dopes on a smooth band or drum as a support.

Two or more kinds of dopes may be cast on the support at the same time or separately on the support. In the case of the sequential casting method in which casting is performed separately, the dope on the support side can be cast first and dried to some extent on the support, and then overlaid on the support. When three or more kinds of dopes are used, a film having a laminated structure can be produced by appropriately combining simultaneous casting (also called co-casting) and sequential casting. These methods, which are formed by co-casting or sequential casting, differ from the method of coating on a dried film, and the boundary of each layer of the laminated structure becomes unclear, and the laminated structure is clear by observing the cross section. There is a feature that there is a case where there is no separation, there is an effect of improving the adhesion between each layer.

The production method in the case where the film A and the film B according to the present invention are formed into the above laminated structure is preferably performed by co-casting from the viewpoint of productivity, and a known co-casting method can be used. For example, in the case of film A, a film is produced while casting and laminating a solution containing an acrylic resin and a solution containing a cellulose ester from a plurality of casting openings provided at intervals in the traveling direction of the metal support. For example, the methods described in JP-A-61-158414, JP-A-1-122419, JP-A-11-198285 and the like can be applied. Further, a film may be formed by casting a solution containing an acrylic resin and a solution containing a cellulose ester from two casting ports, for example, Japanese Patent Publication No. 60-27562 and Japanese Patent Laid-Open No. 61-94724. It can be carried out by the methods described in JP-A 61-947245, JP-A 61-104413, JP-A 61-158413, JP-A 6-134933, and the like.

FIG. 8 is a schematic view showing a co-casting die and a multi-layered web formed by casting.

In the figure, the co-casting die 50, the die part 51, the layer B, the slits 53 and 55 for the layer C, the slit 54 for the layer A, the metal support 56, the layer B, the dopes 57 and 59 for the layer C, and the dope for the layer A 58, a multilayer web 60, a layer C61, a layer A62, and a layer B63, respectively.

(3) Solvent evaporation step The web (the dope is cast on the casting support and the formed dope film is referred to as a web) is heated on the casting support to evaporate the solvent.

To evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back side of the support, a method of transferring heat from the front and back by radiant heat, etc. Is preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

(4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

The temperature at the peeling position on the metal support is preferably in the range of 10 to 40 ° C, more preferably in the range of 11 to 30 ° C.

The amount of residual solvent at the time of peeling of the web on the metal support at the time of peeling is preferably peeled within a range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. However, when peeling off at a time when the amount of residual solvent is larger, if the web is too soft, flatness at the time of peeling is impaired, and slippage and vertical stripes due to peeling tension are likely to occur.Therefore, the balance between economic speed and quality The amount of residual solvent is determined.

The residual solvent amount of the web is defined by the following formula (Z).

Formula (Z)
Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

The peeling tension when peeling the metal support from the film is usually in the range of 196 to 245 N / m. However, when wrinkles are likely to occur during peeling, peeling with a tension of 190 N / m or less is preferable. .

In the present invention, the temperature at the peeling position on the metal support is preferably in the range of −50 to 40 ° C., more preferably in the range of 10 to 40 ° C., and in the range of 15 to 30 ° C. Is most preferred.

(5) Drying and stretching step The drying step can be divided into a preliminary drying step and a main drying step.

(Preliminary drying process)
The web obtained by peeling from the metal support is dried. The web may be dried while being conveyed by a large number of rollers arranged above and below, or may be dried while being conveyed while fixing both ends of the web with clips like a tenter dryer. .

The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roller, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

The drying temperature in the web drying step is preferably a glass transition temperature of the film of −5 ° C. or lower, and it is effective to perform heat treatment at 100 ° C. or higher and 10 minutes or longer and 60 minutes or shorter. Drying is performed at a drying temperature in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

(Stretching process)
The cellulose acetate film according to the present invention is preferably stretched in the MD direction and / or TD direction, and is preferably produced by stretching in the TD direction by at least a tenter stretching apparatus.

The stretching may be uniaxial stretching or biaxial stretching, and biaxial stretching includes a mode in which stretching is performed in one direction and the tension in the other direction is relaxed and contracted.

The acrylic film according to the present invention is oriented in the MD direction and / or so that the film thickness after stretching is in the range of 20-60 μm, and the cellulose acetate film is in the range of 20-60 μm after stretching. Alternatively, the film is preferably stretched in the temperature range of (Tg + 15) to (Tg + 50) ° C., where Tg is the glass transition temperature of the film in the TD direction, preferably in the TD direction. When it is stretched within the above temperature range, the retardation can be easily adjusted, and the stretching stress can be lowered, so that the haze is lowered. Moreover, the generation | occurrence | production of a fracture | rupture is suppressed and the polarizing plate protective film excellent in planarity and the coloring property of the film itself is obtained. The stretching temperature is preferably within the range of (Tg + 20) to (Tg + 40) ° C.

The glass transition temperature Tg referred to here is a midpoint glass transition temperature (Tmg) measured at a rate of temperature increase of 20 ° C./min using a commercially available differential scanning calorimeter and determined according to JIS K7121 (1987). It is.

A specific method for measuring the glass transition temperature Tg of the optical film is measured using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. according to JIS K7121 (1987).

The acrylic film according to the present invention is preferably stretched within a range of 1.05 to 1.5 times the original width in the TD direction. By stretching within the above range, the flatness can be improved and the behavior of dimensional change can be controlled within a desired range.

Further, the cellulose acetate film according to the present invention preferably stretches the web at least 1.1 times in the TD direction. The stretching range is preferably in the range of 1.1 to 1.5 times the original width, and more preferably in the range of 1.05 to 1.3 times. Within the above range, the movement of molecules in the film is large, and not only a desired retardation value can be obtained, but also the behavior of the dimensional change of the film can be controlled within the desired range.

Furthermore, it is preferable to start stretching the film in the MD direction when the residual solvent amount is 40% by mass or more after film formation, and in the TD direction when the residual solvent amount is less than 40% by mass. It is preferable to stretch.

In order to stretch in the MD direction, peeling is preferably performed at a peeling tension of 130 N / m or more, and particularly preferably in the range of 150 to 170 N / m. Since the web after peeling is in a high residual solvent state, stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the web dries and the residual solvent amount decreases, the draw ratio in the MD direction decreases.

The draw ratio in the MD direction can be calculated from the rotation speed of the belt support and the tenter operation speed.

In order to stretch in the TD direction, for example, the entire drying process or a part of the process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 can be performed while holding the width ends of the web with clips or pins in the width direction. A drying method (referred to as a tenter method), among them, a tenter method using clips and a pin tenter method using pins are preferably used.

The cellulose acetate film according to the present invention inevitably has a retardation by stretching, but the in-plane retardation value Ro and the retardation value Rt in the thickness direction are determined by an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix). Polarimeter: manufactured by Axometrics Co., Ltd.) can be calculated from the obtained refractive indexes nx, ny, and nz by performing a three-dimensional refractive index measurement at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH. .

In the cellulose acetate film according to the present invention, the retardation value Ro in the in-plane direction defined by the following formulas (i) and (ii) is in the range of 40 to 60 nm, and the retardation value Rt in the thickness direction is 100. The range of ˜140 nm is preferable from the viewpoint of improving the visibility of the VA mode liquid crystal display device. The cellulose acetate film can be adjusted within the above retardation value by stretching at least while adjusting the stretching ratio in the TD direction.

Formula (i): Ro = (n _x −n _y ) × d (nm)
Formula (ii): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In [Equation (i) and Formula (ii), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
<Bending process>
The cellulose acetate film according to the present invention is a step in which a web is stretched and then dried in a dryer zone in order to adjust the speed of dimensional change immediately after changing the ambient temperature and humidity atmosphere. A bending step in which the temperature is maintained within a range of 130 to 150 ° C. and the bending zone has a bending step in which a B-side facing the A-side of the web is alternately turned inside by a conveying roller in the dryer zone; but when the radius when bending the web was a (mm), the value of 1 / a is in the range of 0.035 mm ^-1 ~ 0.050 mm ^-1, and the bending 50 times or more 120 times It is preferable to dry by carrying out while repeating less than.

The above bending process preferable for the present invention will be described with reference to the drawings. However, it is not limited to this.

FIG. 9 is a schematic diagram of a bending processing apparatus that can be preferably applied to the present invention.

A dope solution is cast from a die 101 onto a metal support 102 and continuously dried on the metal support by a driving roller 103 to obtain a web (referred to as a dope film after casting on the metal support. Form). The web is dried so that the residual solvent amount becomes a desired value, peeled into a film at the peeling point 104, subjected to preliminary drying and stretching treatment (not shown), conveyed to the bending zone 106, The transport roller 105 continuously conveys the A surface (the surface opposite to the surface where the web contacts the metal support) and the B surface (the surface where the web contacts the metal support) alternately inside the transport roller 105. The bending process is repeated. The bending process is performed in a bending zone 106 having an intake port 107 and an exhaust port 108, and is adjusted so that the film is bent at a desired atmospheric temperature.

The diameter of the conveying roller is preferably in the range of 90 to 108 mm, and the distance between the rollers is preferably about 1800 mm. The radius when bending the film may be determined roller diameter as the value of 1 / a when the a (mm) is in the range of 0.035mm ^-1 ~ 0.050mm ^-1.

In the bending zone 106, hot air whose temperature has been adjusted is introduced from the intake port 107, and the inside of the bending zone 106 is maintained at a constant atmospheric temperature and is exhausted from the exhaust port 108. In order to adjust the atmospheric temperature in the bending zone 106, it may be performed by infrared rays, a heating roller, or the like, but it is preferably performed by hot air in terms of simplicity. The atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas, carbon dioxide gas, or argon.

The atmospheric temperature during the bending treatment of the cellulose acetate film according to the present invention is preferably within the range of 130 to 150 ° C., and more preferably within the range of 135 to 150 ° C. in order to obtain the effects of the present invention.

The number of times of bending the cellulose acetate film according to the present invention is preferably 50 times or more and less than 120 times, and more preferably 70 times or more and 100 times or less. The film folding interval is preferably within a range of 1 second to 1 minute, and more preferably within a range of 2 to 30 seconds.

The conveyance speed of the cellulose acetate film according to the present invention is preferably 10 to 150 m / min, more preferably 15 to 100 m / min in terms of productivity and breakage.

<Cooling process>
The acrylic film according to the present invention further includes a step of drying the web in the dryer zone in order to adjust the speed of dimensional change immediately after changing the ambient temperature and humidity atmosphere. It is preferably formed later by a cooling step in which the web is cooled at a rate in the range of 50-100 ° C./second.

After the step of drying the stretched web in the dryer zone, a film is formed by adding a cooling step of cooling the web at a speed in the range of 50 to 100 ° C./second, thereby densifying the molecular chains of the film. The amount of water that can be contained in the film is adjusted, and the shrinkage ratio of the film containing water can be effectively controlled, which is preferable. The cooling rate is more preferably in the range of 70 to 90 ° C./second.

In order to cool the web, for example, it is preferable to connect the cooling zone 109 in FIG. 9 after the bending zone 106 which is the drying step.

The means for cooling the web is not particularly limited, and can be generally performed by using a cold air nozzle, a cooling roller, etc., but in terms of simplicity, while conveying the web in the cooling zone, It is preferable to carry out by blowing from a cold air nozzle. At that time, it is preferable to blow cold air on both sides of the web because the web can be cooled with high accuracy.

<Knurling>
After a predetermined heat treatment or cooling treatment, it is preferable to provide a slitter and cut off the end portion before winding to obtain a good winding shape. Furthermore, it is preferable to knurling both ends of the width.

The knurling process can be formed by pressing a heated embossing roller. Fine embossing is formed on the embossing roller, and by pressing the embossing roller, unevenness can be formed on the film and the end can be made bulky.

The height of the knurling at both ends of the width of the retardation film of the present invention is preferably in the range of 4 to 20 μm and in the range of 5 to 20 mm.

In the present invention, the knurling process is preferably provided after the drying in the film forming process and before winding.

(6) Winding step This is a step of winding as a film after the residual solvent amount in the web is 2% by mass or less, and the film having good dimensional stability by making the residual solvent amount 0.4% by mass or less. Can be obtained.

As a winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

[Physical properties of protective film]
(Haze)
The protective film according to the present invention preferably has a haze of less than 1%, more preferably less than 0.5%. By setting the haze to less than 1%, there is an advantage that the transparency of the film becomes higher and it becomes easier to use as an optical film.

(Equilibrium moisture content)
In the protective film according to the present invention, the equilibrium water content at 25 ° C. and a relative humidity of 60% is preferably 4% or less, and more preferably 3% or less. By setting the equilibrium moisture content to 4% or less, it is preferable to easily cope with a change in humidity and to hardly change the optical characteristics and dimensions.

(Film length, width)
The protective film of the present invention is preferably long, and specifically, preferably has a length of about 100 to 10,000 m, and is wound into a roll. The width of the protective film of the present invention is preferably 1 m or more, more preferably 1.4 m or more, and particularly preferably 1.4 to 4 m.

≪Polarizing plate≫
The polarizing plate of the present invention is characterized in that the polarizer is a polarizing plate sandwiched between the film A and the film B according to the present invention via an active ray curable adhesive layer.

When the polarizing plate of the present invention is used as a polarizing plate on the viewing side, it is preferable to provide an antiglare layer or a clear hard coat layer, an antireflection layer, an antistatic layer, an antifouling layer, etc. on the viewing side of the film A. .

[Polarizer]
The polarizer, which is the main component of the polarizing plate according to the present invention, is an element that passes only light having a polarization plane in a certain direction, and a typical polarizer currently known is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

As the polarizer, a polarizer obtained by forming a polyvinyl alcohol aqueous solution into a film and dyeing it by uniaxial stretching or dyeing and then uniaxially stretching and then preferably performing a durability treatment with a boron compound may be used. The thickness of the polarizer is preferably in the range of 2 to 30 μm, particularly preferably in the range of 2 to 15 μm.

Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. The ethylene-modified polyvinyl alcohol is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability performance and has little color mottle, and is particularly preferably used for a large liquid crystal display device.

[Laminated film type polarizer]
In addition, since the polarizing plate of the present invention is a thin film, the thickness of the polarizer is particularly preferably in the range of 2 to 15 μm from the viewpoint of achieving both the strength of the polarizing plate and the thinning.

As such a thin film polarizer, a laminated film type polarizer can be produced by the method described in JP 2011-1000016 A, JP 4691205 A, JP 4751481 A, and JP 4804589 A. Is preferred.

As an example, it is particularly preferable to use a thin film-type polarizer (polarizing laminate film) produced by the following steps, which can improve display unevenness and adhesion, which are the effects of the present invention.

(Production method of polarizing laminated film)
The manufacturing method of the light-polarizing laminated film which concerns on this invention includes the following process.
(A) a laminating step of obtaining a laminated film by forming a polyvinyl alcohol-based resin layer on one surface of a base film in which a rubber component is dispersed in a thermoplastic resin;
(B) A stretching process for uniaxially stretching the laminated film to obtain a stretched film;
(C) a dyeing process of obtaining a dyed film by dyeing a polyvinyl alcohol resin layer of a stretched film with a dichroic dye;
(D) The polyvinyl alcohol resin layer of the dyed film is immersed in a solution containing a crosslinking agent to form a polarizer layer, and a crosslinking step for obtaining a crosslinked film; and (e) a drying step for drying the crosslinked film. Explaining the process,
(A) Laminating step In this step, a film obtained by dispersing (blending) a rubber component in a thermoplastic resin is used as a base film, and a polyvinyl alcohol-based resin layer is formed on one surface thereof to obtain a laminated film.

(Base film)
The thermoplastic resin used as the base of the base film is preferably a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such a thermoplastic resin include, for example, a chain polyolefin resin; a cyclic polyolefin resin; a (meth) acrylic resin; a polyester resin; a cellulose ester resin; a polycarbonate resin; and a polyvinyl alcohol resin. A vinyl acetate resin; a polyarylate resin; a polystyrene resin; a polyethersulfone resin; a polysulfone resin; a polyamide resin; a polyimide resin; and a mixture or copolymer thereof.

The rubber component dispersed in the thermoplastic resin is a resin component having rubber elasticity, and is usually uniformly dispersed in the thermoplastic resin as rubber particles. By mixing and dispersing the rubber component, it is possible to improve the tear strength of the base film and thus the stretched film. The rubber component is not particularly limited as long as it is a resin having rubber elasticity. However, from the viewpoint of compatibility with the thermoplastic resin, the rubber component is preferably composed of the same or similar resin as the thermoplastic resin to be used.

For example, when the thermoplastic resin is a chain polyolefin resin, the rubber component can be a copolymer of two or more monomers selected from ethylene and α-olefin. In this case, the content (polymerization ratio) of each monomer constituting the copolymer is preferably less than 90% by mass, and more preferably less than 80% by mass.

When the thermoplastic resin is a (meth) acrylic resin, it is preferable to contain an acrylic polymer having rubber elasticity as a rubber component from the viewpoint of compatibility. The acrylic polymer is preferably a polymer mainly composed of alkyl acrylate, and may be a homopolymer of alkyl acrylate, or 50% by mass or more of alkyl acrylate and 50% by mass or less of other monomers. And a copolymer thereof.

The compounding amount of the rubber component is preferably 5 to 50% by mass of the thermoplastic resin, more preferably 10 to 45% by mass. If the blending amount of the rubber component is too small, a sufficient tear strength improving effect tends to be difficult to obtain, and if the blending amount of the rubber component is too large, the handleability of the base film tends to be lowered.

The method for dispersing the rubber component in the thermoplastic resin is not particularly limited. For example, the thermoplastic resin and rubber component (rubber particles) produced separately are kneaded and dispersed with a plastmill or the like, or the same reaction when preparing the thermoplastic resin. Examples thereof include a reactor blend method in which a rubber component is also prepared in a container to obtain a thermoplastic resin in which the rubber component is dispersed. The reactor blending method is advantageous in improving the degree of dispersion of the rubber component.

(Polyvinyl alcohol resin layer)
As a polyvinyl alcohol-type resin which forms a polyvinyl alcohol-type resin layer, polyvinyl alcohol resin and its derivative (s) are mentioned, for example. Derivatives of polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, etc., olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters of unsaturated carboxylic acids. And those modified with acrylamide or the like. Among these, it is preferable to use a polyvinyl alcohol resin.

The polyvinyl alcohol resin is preferably a completely saponified product. The range of the degree of saponification is preferably within the range of 80.0 to 100.0 mol%, more preferably within the range of 90.0 to 99.5 mol%, and even more preferably 94.0 to 99. Within the range of 0.0 mol%.

In the above-described polyvinyl alcohol resin, additives such as a plasticizer and a surfactant may be added as necessary. As the plasticizer, polyols and condensates thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. Although the compounding quantity of an additive is not restrict | limited in particular, It is suitable to set it as 20 mass% or less of a polyvinyl alcohol-type resin.

As a method for coating a polyvinyl alcohol resin solution on a base film, a wire bar coating method, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method, or a spray method. It can select suitably from well-known methods, such as. The drying temperature is, for example, in the range of 50 to 200 ° C., and preferably in the range of 60 to 150 ° C. The drying time is, for example, in the range of 2 to 20 minutes.

The thickness of the polyvinyl alcohol resin layer in the laminated film is preferably 3 μm or more and 50 μm or less, and more preferably 5 μm or more and 45 μm or less. If it is 3 μm or less, it becomes too thin after stretching and the dyeability is significantly deteriorated. If it exceeds 50 μm, the resulting polarizing laminate film becomes thick.

The thickness of the polyvinyl alcohol-based resin layer as the polarizer used in the present invention is within the range of 2 to 15 μm as the film thickness after the following stretching treatment from the viewpoint of thinning, strength and flexibility as the polarizer. Is preferred.

(B) Stretching step This step is a step of obtaining a stretched film by uniaxially stretching a laminated film including a base film and a polyvinyl alcohol-based resin layer. The stretching ratio of the laminated film can be appropriately selected according to the desired polarization characteristics, but is preferably more than 5 times and 17 times or less, more preferably more than 5 times and 8 times or less with respect to the original length of the laminated film. It is.

Stretching is preferably longitudinal stretching in which stretching is performed in the longitudinal direction (film transport direction) of the laminated film. Examples of the longitudinal stretching method include an inter-roller stretching method, a compression stretching method, and a stretching method using a tenter. The uniaxial stretching is not limited to the longitudinal stretching process, and may be oblique stretching or the like.

(C) Dyeing step This step is a step of obtaining a dyed film by dyeing the polyvinyl alcohol resin layer of the stretched film with a dichroic dye. Examples of the dichroic dye include iodine and organic dyes. Examples of organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. These dichroic substances may be used alone or in combination of two or more.

When iodine is used as the dichroic dye, it is preferable to further add iodide to the dyeing solution containing iodine because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium.

(D) Crosslinking step In this step, the polyvinyl alcohol resin layer of the dyed film obtained by dyeing with a dichroic dye is subjected to a crosslinking treatment, and a crosslinked film using the polyvinyl alcohol resin layer as a polarizer layer is obtained. It is a process to obtain. The crosslinking step can be performed, for example, by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be used alone or in combination of two or more.

(E) Drying step The obtained crosslinked film is usually dried after washing. Thereby, a light-polarizing laminated film is obtained. Washing can be performed by immersing the crosslinked film in pure water such as ion exchange water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C., preferably in the range of 4 to 20 ° C. The immersion time is usually in the range of 2 to 300 seconds, preferably in the range of 5 to 240 seconds. The washing may be a combination of a washing treatment with an iodide solution and a water washing treatment, and a solution in which a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like is appropriately blended may be used.

Any appropriate method (for example, natural drying, air drying, heat drying) can be adopted as the drying method. For example, the drying temperature in the case of heat drying is usually in the range of 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes.

The polarizing laminated film includes a polarizer layer composed of a polyvinyl alcohol-based resin layer in which a dichroic dye is adsorbed and oriented, and can be used as a polarizing plate itself. As a preferred embodiment of the present invention, after the polarizing laminated film is formed by the above-mentioned process, the polyvinyl alcohol layer of the polarizing laminated film is peeled from the substrate film, whereby the polyvinyl alcohol layer is related to the present invention. It is to be used as a polarizer. According to the method of the present invention, since the thickness of the polarizer layer can be 15 μm or less, a thin polarizer can be obtained. Moreover, the polarizer used in the present invention is excellent in polarization performance and durability.

[Actinic radiation curable adhesive]
In the polarizing plate according to the present invention, the above-described protective film, which is an acrylic film and a polarizer, and a cellulose acetate film and a polarizer are bonded with an actinic radiation curable adhesive. .

Further, it is preferable to use the following ultraviolet curable adhesive as the active ray curable adhesive.

In the present invention, by applying an ultraviolet curable adhesive to the bonding between the protective film and the polarizer, it is possible to obtain polarizing plate characteristics having high strength and excellent flatness even in a thin film.

[Composition of UV curable adhesive]
As the UV curable adhesive composition for polarizing plates, a photo radical polymerization composition using photo radical polymerization, a photo cation polymerization composition using photo cation polymerization, and photo radical polymerization and photo cation polymerization are used in combination. Hybrid type compositions are known.

The radical photopolymerizable composition includes a radically polymerizable compound containing a polar group such as a hydroxy group and a carboxy group described in JP-A-2008-009329 and a radically polymerizable compound not containing a polar group at a specific ratio. Composition) and the like are known. In particular, the radical polymerizable compound is preferably a compound having a radical polymerizable ethylenically unsaturated bond. Preferable examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include an N-substituted (meth) acrylamide compound and a (meth) acrylate compound. (Meth) acrylamide means acrylamide or methacrylamide.

In addition, as the cationic photopolymerization type composition, as disclosed in JP2011-08234A, (α) a cationic polymerizable compound, (β) a cationic photopolymerization initiator, and (γ) a wavelength longer than 380 nm. And an ultraviolet curable adhesive composition containing each component of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other ultraviolet curable adhesives may be used.

(Pretreatment process)
A pre-processing process is a process of performing an easily bonding process on the adhesive surface of a protective film with a polarizer. When the film A and the film B, which are protective films, are adhered to both surfaces of the polarizer, easy adhesion treatment is performed on the adhesive surfaces of the respective protective films with the polarizer. Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(Application process of UV curable adhesive)
In the step of applying the ultraviolet curable adhesive, the ultraviolet curable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the protective film. When the ultraviolet curable adhesive is applied directly to the surface of the polarizer or the protective film, the application method is not particularly limited. For example, various wet coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting an ultraviolet curable adhesive between a polarizer and a protective film, it is also possible to use a method of pressurizing with a roller or the like and spreading it uniformly.

(Bonding process)
After apply | coating a ultraviolet curable adhesive by said method, it processes by a bonding process. In this bonding step, for example, when an ultraviolet curable adhesive is applied to the surface of the polarizer in the previous application step, a protective film is superimposed thereon. In the case of a method in which an ultraviolet curable adhesive is first applied to the surface of the protective film, a polarizer is superimposed thereon. Moreover, when an ultraviolet curable adhesive is cast between the polarizer and the protective film, the polarizer and the protective film are superposed in that state. In this state, the pressure is usually sandwiched between a pressure roller and the like from both protective film sides. Metal, rubber, or the like can be used as the material of the pressure roller. The pressure rollers arranged on both sides may be made of the same material or different materials.

(Curing process)
In the curing step, an uncured ultraviolet curable adhesive is irradiated with ultraviolet rays, and a cationic polymerizable compound (for example, epoxy compound or oxetane compound) or a radical polymerizable compound (for example, acrylate compound, acrylamide compound, etc.) The ultraviolet curable adhesive layer that is included is cured, and the polarizer and the protective film, or the polarizer and the retardation film that are superposed via the ultraviolet curable adhesive are bonded. When bonding a protective film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or a protective film side. In addition, when a protective film and a retardation film are bonded to both sides of a polarizer, ultraviolet rays are irradiated in a state where the protective film and the retardation film are superposed on both sides of the polarizer via an ultraviolet curable adhesive, respectively. It is advantageous to cure the UV curable adhesive on both sides simultaneously.

Any appropriate conditions can be adopted as the ultraviolet irradiation conditions as long as the ultraviolet curable adhesive applied to the present invention can be cured. Preferably the dose of ultraviolet rays in the range of 50 ~ 1500mJ / cm ² in accumulated light amount, and even more preferably in the range of within the range of 100 ~ 500mJ / cm ^2.

When the polarizing plate production process is performed in a continuous line, the line speed depends on the curing time of the adhesive, but is preferably in the range of 1 to 500 m / min, more preferably in the range of 5 to 300 m / min, and still more preferably. It is within the range of 10 to 100 m / min. If the line speed is 1 m / min or more, productivity can be ensured, or damage to the protective film A can be suppressed, and a polarizing plate having excellent durability can be produced. If the line speed is 500 m / min or less, the ultraviolet curable adhesive is sufficiently cured, and an ultraviolet curable adhesive layer having a desired hardness and excellent adhesiveness can be formed.

≪Liquid crystal display device≫
By using the polarizing plate on which the protective film according to the present invention is bonded to a liquid crystal display device, the liquid crystal display device of the present invention having various visibility can be manufactured.

The polarizing plate of the present invention can be used for liquid crystal display devices of various driving systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB. A VA (MVA, PVA) type liquid crystal display device is preferable.

In the liquid crystal display device, usually two polarizing plates, a polarizing plate on the viewing side and a polarizing plate on the backlight side, are used, but it is also preferable to use the polarizing plate of the present invention as both polarizing plates. It is also preferable to use as. In particular, the polarizing plate of the present invention is preferably used as a polarizing plate on the viewing side that directly touches the external environment. In this case, the acrylic film according to the present invention is arranged on the viewing side, and the cellulose acetate film according to the present invention is positioned. The phase difference film is preferably disposed on the liquid crystal cell side.

Further, as the polarizing plate on the backlight side, a polarizing plate other than the present invention can also be used. In that case, for example, a commercially available cellulose ester film (e.g. KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UAKC, 2UAH, KU T60UZ, Fujitac T80UZ, Fujitac TD80UL, Fujitac TD60UL, Fujitac TD40UL, Fujitac R02, Fujitac R06, Fujifilm Polarizing plate stuck to manufacturing, etc.) are preferably used.

Moreover, as the polarizing plate on the backlight side, the cellulose acetate film according to the present invention is used on the liquid crystal cell side of the polarizer, and the above-mentioned commercially available cellulose ester film, polycarbonate film, or cycloolefin polymer film is bonded to the opposite surface. The polarizing plate made can also be used preferably.

By using the polarizing plate of the present invention, it is possible to obtain a liquid crystal display device excellent in visibility such as display unevenness and front contrast even in the case of a large screen liquid crystal display device having a screen of 30 type or more.

Further, the polarizing plate of the present invention can be preferably used for an organic electroluminescence display device as well as a liquid crystal display device.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Production of Film A and Film B>
[Production of Film A-101]
Film A-101, which is a film containing an acrylic resin, was produced according to the following method.

(Preparation of fine particle dispersion)
10 parts by mass of Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 16 nm, apparent specific gravity of 90 g / L) and 90 parts by mass of ethanol were stirred and mixed with a dissolver for 30 minutes, and then high pressure disperser Manton Gorin Was used to prepare a fine particle dispersion.

Into the obtained fine particle dispersion, 88 parts by mass of dichloromethane was added with stirring, and the mixture was diluted by stirring and mixing with a dissolver for 30 minutes. The obtained solution was filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to obtain a fine particle dispersion dilution.

(Preparation of inline additive solution)
15 parts by weight of Tinuvin 928 (manufactured by BASF Japan) and 100 parts by weight of dichloromethane as an ultraviolet absorber and 100 parts by weight of dichloromethane were put into a sealed container, and heated and stirred to completely dissolve, followed by filtration. To the obtained solution, 36 parts by mass of the fine particle dispersion diluted liquid was added with stirring, and further stirred for 30 minutes, and then 6 parts by mass of acrylic resin: Dianal BR85 (Mitsubishi Rayon, Mw: 280000) was added. The mixture was further stirred for 60 minutes with stirring, and the resulting solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to obtain an in-line additive solution. It was.

(Preparation of dope 1)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. The main dope 1 was obtained by filtering at 24.

<Composition of main dope 1>
Acrylic resin 1: Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd., acrylic resin Mw: 280000) 85 parts by mass Sugar ester: BzSc (benzyl saccharose: Compound g-
1 to g-4), average ester substitution degree = 6.0 10 parts by mass Polycondensed ester: Polycondensed ester P1 represented by the general formula (1)
5 parts by mass Methylene chloride 360 parts by mass Ethanol 15 parts by mass 100 parts by mass of main dope 1 and 2.5 parts by mass of in-line additive solution are sufficient with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ) To obtain a dope 1.

(Film forming process)
The obtained dope 1 is uniformly cast on a stainless steel band support using a belt casting apparatus under the conditions that the liquid temperature of the dope 1 is 35 ° C. and the width is 1.7 m, and the final film thickness is 40 μm. I let you. On the stainless steel band support, the organic solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% by mass to form a web, and then the web was peeled from the stainless steel band support. The obtained web was further pre-dried at 110 ° C. for 10 minutes, and then the web was stretched 1.5 times with respect to the original width in the TD direction at 160 ° C. with a tenter. The residual solvent amount of the web at the start of stretching was 2.0% by mass. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then the film was conveyed for 15 minutes at 130 ° C. by the dryer (bending zone 106) shown in FIG. Cooled to ° C. The obtained film was slit to 2.0 m width, 10 mm wide and 5 μm knurled at both ends of the film, wound on a core of 15.24 cm in inner diameter with an initial tension of 220 N / m and a final tension of 110 N / m. A film A-101 containing a long acrylic resin having a thickness of 4000 m and a film thickness of 40 μm was obtained.

[Production of Films A-102 to A-138]
A film containing the long acrylic resin described in Tables 1 and 2 except that in the production of the film A-101, the presence or absence of a cooling step, the cooling rate in the cooling zone, and the film thickness were changed. A-102 to A-138 were obtained.

[Production of Film B-101]
(Preparation of fine particle dispersion)
10 parts by weight Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L) and 90 parts by weight of ethanol were stirred and mixed with a dissolver for 30 minutes, and then high pressure disperser Manton Gorin Was used to prepare a fine particle dispersion.

Into the obtained fine particle dispersion, 88 parts by mass of dichloromethane was added with stirring, and the mixture was diluted by stirring and mixing with a dissolver for 30 minutes. The obtained solution was filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to obtain a fine particle dispersion dilution.

(Preparation of inline additive solution)
To 100 parts by mass of dichloromethane, 36 parts by mass of the prepared fine particle dispersion diluted liquid was added with stirring and further stirred for 30 minutes, and then 6 parts by mass of diacetylcellulose (acetyl group substitution degree 2.3, Mn = 90000, Mw = 152000, Mw / Mn = 1.7) was added with stirring, and the mixture was further stirred for 60 minutes. The obtained solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to obtain an in-line additive solution. The filter medium having a nominal filtration accuracy of 20 μm was used.

(Preparation of dope 2)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. The main dope 2 was obtained by filtering through 24.

<Composition of main dope 2>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 81 parts by mass Polyhydric alcohol ester (compound represented by formula (2)): Exemplified compound 2-10 2 parts by mass Sugar ester; BzSc (benzyl saccharose: Compound a- according to Chemical formula 3
1 to a-4), average ester substitution degree = 5.5 7 parts by mass Polycondensation ester: Polycondensation ester represented by formula (1): P8
5 parts by mass Retardation adjusting agent 1: 3 parts by mass of the following compound Additive A: 2 parts by mass of the following compound Dichloromethane 430 parts by mass Methanol 11 parts by mass 100 parts by mass of the main dope 1 and 2.5 parts by mass of the in-line additive solution Was mixed well with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ) to obtain a dope 2.

(Film forming process)
The obtained dope 2 is uniformly cast on a stainless steel band support using a belt casting apparatus under the conditions that the liquid temperature of the dope 2 is 35 ° C. and the width is 1.95 m, and the final film thickness is 40 μm. I let you. On the stainless steel band support, the organic solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% by mass to form a web, and then the web was peeled from the stainless steel band support. The obtained web was further pre-dried at 110 ° C. for another 10 minutes, and then the web was stretched 1.2 times with respect to the original width in the TD direction at 160 ° C. with a tenter. The residual solvent amount of the web at the start of stretching was 2.0% by mass. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then the temperature was maintained at 140 ° C. by a dryer (bending zone 106) shown in FIG. The diameter and arrangement of the transport rollers so that the value of 1 / a is 0.040 mm ⁻¹ when the radius when the B surface facing the A surface is alternately bent inward is a (mm). The web was conveyed at a conveyance speed of 20 m / min by repeating 80 times of bending.

The obtained film was slit to 2.0 m width, 10 mm wide and 5 μm knurled at both ends of the film, wound on a core of 15.24 cm in inner diameter with an initial tension of 220 N / m and a final tension of 110 N / m. A film B-101 containing a long diacetyl cellulose having a thickness of 4000 m and a film thickness of 40 μm was obtained.

[Production of Films B-102 to B-138]
In the production of the film B-101, the same except that the acetyl group substitution degree of diacetyl cellulose (referred to as DAC substitution degree in the table), the value of 1 / a in the bending zone, the number of bendings, and the film thickness were changed. Thus, long films B-102 to B-132 shown in Tables 1 and 2 were obtained.

B-133 to B138 were prepared in the same manner as B-132 using the following main dopes 3 to 8, respectively.

  <Composition of main dope 3>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 85 parts by mass Sugar ester; BzSc (benzyl saccharose: Compound a-
1 to a-4)), average ester substitution degree = 5.5 10 parts by mass Polycondensation ester: polycondensation ester represented by formula (1): P7
2.5 parts by mass Retardation adjusting agent 1: the following compound 2.5 parts by mass dichloromethane 430 parts by mass ethanol 11 parts by mass <composition of main dope 4>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 86 parts by mass Polyhydric alcohol ester (compound represented by general formula (2)): Exemplified compound 2-1 1 part by mass Sugar ester; BzSc (benzyl saccharose: Compound a- according to Chemical formula 3
1 to a-4)), average ester substitution degree = 5.5 10 parts by mass Polycondensation ester: Polycondensation ester represented by formula (1): P2
2 parts by mass Retardation adjusting agent 1: Compound shown below 2.2 parts by mass Dichloromethane 430 parts by mass Ethanol 11 parts by mass <Composition of main dope 5>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 85 parts by mass Polyhydric alcohol ester (compound represented by formula (2)): Exemplified compound 2-1 1 part by mass Sugar ester; BzSc (benzyl saccharose: Compound a- according to Chemical formula 3
1 to a-4)), average ester substitution degree = 5.5 10 parts by mass Polycondensation ester: Polycondensation ester represented by formula (1): P2
2 parts by mass Retardation adjusting agent 1: the following compound 2.5 parts by mass dichloromethane 430 parts by mass ethanol 11 parts by mass <composition of main dope 6>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 85 parts by mass Polyhydric alcohol ester (compound represented by formula (2)): Exemplified compound 2-9 1 part by mass Sugar ester; BzSc (benzyl saccharose: Compound a- according to Chemical formula 3
1 to a-4)), average ester substitution degree = 5.5 10 parts by mass Polycondensation ester: Polycondensation ester represented by formula (1): P2
2 mass parts Retardation adjusting agent 2: The following compound 2.5 mass parts Dichloromethane 430 mass parts Ethanol 11 mass parts <Composition of main dope 7>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 87 parts by mass Polyhydric alcohol ester (compound represented by formula (2)): Exemplified compound 2-9 1 part by mass Sugar ester; BzSc (benzyl saccharose: Compound a- according to Chemical formula 3
1 to a-4), average ester substitution degree = 5.5 10 parts by mass Polycondensation ester: Polycondensation ester represented by the general formula (1): P1
2 parts by mass Dichloromethane 430 parts by mass Ethanol 11 parts by mass <Composition of main dope 8>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 86 parts by mass Sugar ester; BzSc (benzyl saccharose: Compound a-
1 to a-4)), average ester substitution degree = 5.5 10 parts by mass Polycondensation ester: Polycondensation ester represented by formula (1): P2
2 parts by mass Dichloromethane 430 parts by mass Ethanol 11 parts by mass

<Preparation of polarizing plate>
[Production of Polarizer 1]
In order to form a thin film polarizer by the following steps, a polarizing laminated film was prepared, and the base film was peeled from the polarizing laminated film to obtain a thin film polarizer.

(1) Production of base film A thermoplastic resin and a rubber component were sequentially prepared in the same reaction vessel by a reactor blend method. Specifically, propylene monomer was fed in the gas phase as a first step using a Ziegler-Natta type catalyst to produce a propylene homopolymer as a thermoplastic resin. After stopping the reaction by stopping the propylene monomer feed, the ethylene monomer and the propylene monomer are fed into the reaction vessel as they are in the gas phase as the second step, and the ethylene-propylene copolymer as the rubber component is fed. Thus, a propylene homopolymer in which an ethylene-propylene copolymer as a rubber component was dispersed in a particulate form was obtained. The ethylene unit content in the copolymer was determined from the material balance during polymerization and found to be 35% by mass. Further, the content of ethylene units in the entire resin (total of thermoplastic resin and rubber component) is determined according to the method described on page 616 of the Polymer Handbook (published by Kinokuniya Shoten in 1995), and the resin is determined from this value. When the content of the ethylene-propylene copolymer in the whole was calculated, it was 29% by mass (that is, the content of the ethylene-propylene copolymer was 40.8% by mass of the thermoplastic resin).

The obtained mixed resin was melt-kneaded at 250 ° C. and then melt-extruded with a T-die at a temperature of 280 ° C. to obtain a base film having a thickness of 100 μm.

(2) Formation of primer layer Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in 95 ° C. hot water, A polyvinyl alcohol aqueous solution having a concentration of 3% by mass was prepared. The resulting aqueous solution was mixed with 5 parts by mass of a crosslinking agent (“SUMIREZ RESIN 650” manufactured by Sumitomo Chemical Co., Ltd.) with respect to 6 parts by mass of the polyvinyl alcohol powder. The obtained mixed aqueous solution was applied onto the corona-treated surface of the base film subjected to the corona treatment using a micro gravure coater, and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm. Formed.

(3) Formation of polyvinyl alcohol resin layer Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0 to 99.0 mol%) is dissolved in hot water at 95 ° C. An aqueous polyvinyl alcohol solution having a concentration of 8% by mass was prepared. The obtained aqueous solution was coated on the primer layer using a lip coater, and dried under conditions of 80 ° C. for 2 minutes, 70 ° C. for 2 minutes, and then 60 ° C. for 4 minutes, whereby a base film A laminated film having a polyvinyl alcohol resin layer laminated thereon with a primer layer interposed therebetween was produced. The thickness of the polyvinyl alcohol-based resin layer was 9.8 μm.

(4) Production of stretched film The laminated film was uniaxially stretched 5.8 times at a stretching temperature of 160 ° C. to obtain a stretched film. The obtained stretched film had a thickness of 28.5 μm, and the polyvinyl alcohol-based resin layer had a thickness of 5.0 μm.

(5) Preparation of polarizing laminated film The stretched film was immersed in a 60 ° C warm bath for 60 seconds, and then immersed in a dyeing solution at 30 ° C, which is an aqueous solution containing iodine and potassium iodide, for about 150 seconds to obtain polyvinyl alcohol. The system resin layer was dyed, and then the excess iodine solution was washed away with pure water at 10 ° C. Next, it was immersed for 600 seconds in the 76 degreeC bridge | crosslinking solution which is the aqueous solution containing a boric acid and potassium iodide. Thereafter, the film was washed with pure water at 10 ° C. for 4 seconds, and finally dried at 50 ° C. for 300 seconds to obtain a polarizing laminated film. The polyvinyl alcohol-type resin layer of this polarizing laminated film was peeled from the base film, and the polyvinyl alcohol-type resin layer was used as a polarizer.

[Preparation of UV curable adhesive solution 1]
After mixing the following components, defoaming was performed to prepare an ultraviolet curable adhesive liquid 1. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries)
40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass [Production of Polarizing Plate 101]
A polarizing plate 101 was produced according to the following method.

First, the above-prepared film B-101 was used as a retardation film, and its surface was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the prepared UV curable adhesive liquid 1 is applied to the corona discharge-treated surface of the film B-101 with a bar coater so that the film thickness after curing is about 3 μm, and the UV curable adhesive layer is applied. Formed. The polarizer (thickness 5 μm) side of the produced polarizing laminated film was bonded to the obtained ultraviolet curable adhesive layer, and then the base film was peeled off.

Next, the produced film A-101 was subjected to corona discharge treatment. The conditions of the corona discharge treatment were a corona output intensity of 2.0 kW and a speed of 18 m / min.

Next, the UV curable adhesive liquid 1 prepared above is applied to the corona discharge treated surface of the film A-101 with a bar coater so that the film thickness after curing is about 3 μm, and the UV curable adhesive layer is applied. Formed.

A polarizer bonded to one side of the film B-101 is bonded to this UV curable adhesive layer, and the film A-101 / UV curable adhesive layer / polarizer / UV curable adhesive layer / A laminate in which film B-101 was laminated was obtained. At that time, the films A-101 and B-101 were bonded so that the slow axis of the film and the absorption axis of the polarizer were orthogonal to each other.

From both sides of this laminate, using a UV irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), UV light was applied so that the integrated light amount was 750 mJ / cm ^2. The UV curable adhesive layer was cured to produce a polarizing plate 101 having a total film thickness of 91 μm.

[Preparation of Polarizing Plate 102 to Polarizing Plate 138]
In the same manner as the polarizing plate 101, films A-102 to A-138 and films B-102 to B-138 are used, respectively, and have the structures shown in Table 1 and Table 2, respectively. The polarizing plate 102 to the polarizing plate 138 which are the child / ultraviolet curable adhesive layer / film B were produced.

≪Evaluation 1≫
The film A-101 to film A-138 and the film B-101 to film B-138 are respectively L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD were measured. From the measurement results, the respective values (%) of (L ₁ MD-L ₅ MD), (L ₁ TD-L ₅ TD), (L ₅ MD-L ₃₀ MD), and (L ₅ TD-L ₃₀ TD) ) Was calculated.

≪Evaluation 2≫
(Production of liquid crystal display device)
Using a commercially available VA type liquid crystal display device (40 type display KLV-40J3000 manufactured by SONY), the polarizing plate bonded to the viewing side of the liquid crystal cell was peeled off, and the above prepared polarizing plates 101 to 138 were placed on the liquid crystal cell side. The liquid crystal display devices 101 to 138 were produced by bonding so that the film B was placed on the surface of the liquid crystal display device. A liquid crystal display device was prepared by bonding so that the absorption axis of the prepared polarizing plate was in the same direction as the absorption axis of the polarizing plate bonded in advance, and display unevenness was evaluated by the following method.

(Evaluation of display unevenness)
The obtained liquid crystal display device was left in a constant temperature and humidity chamber of 50 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment of 23 ° C./55% RH to display the liquid crystal display device in black at room temperature. In the state, the difference (display unevenness) between the luminance near the four vertices of the display screen and the luminance near the center of the display screen was visually observed. Display unevenness was evaluated according to the following criteria. In the following evaluation, ○ or ◎ is preferable.

◎: No display unevenness. ○: Slight display unevenness is observed with very careful attention. △: Display unevenness is observed at one of the four vertices. X: Display unevenness occurs at three or more of the four vertices. Recognized (Evaluation of polarizer adhesion)
The obtained liquid crystal display device was left in a constant temperature and humidity chamber at 80 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment at 23 ° C./55% RH for 1 hour. The cycle was repeated to observe the undulation and film peeling on the panel surface, and the adhesion between the film A and the film B and the polarizer was evaluated.

◎: There is no undulation or film peeling on the panel surface ○: Slight undulation is observed on the panel surface when very careful, △: Clear undulation is observed on the panel surface, but there is no film peeling ×: On the panel surface Table 1 and Table 2 summarize the configurations of Film A and Film B, the configuration of the polarizing plate, and the evaluation results described above.

 

 

 

 

From Tables 1 and 2, film A is a web drying step in addition to the selection of the type of acrylic resin and the weight average molecular weight, the use of a plasticizer such as sugar ester or polycondensation ester, and the adjustment of the film thickness. Then, after the web exits the drying step (dryer zone), a film is formed by adding a cooling step of cooling the web at a speed in the range of 50 to 100 ° C./sec. It can be seen that it is possible to adjust within the range.

In addition, in addition to adjusting the degree of acetyl group substitution and weight average molecular weight of cellulose acetate, the use of a plasticizer such as a sugar ester or a polycondensed ester, and adjusting the film thickness, the film B is a step of drying the web. In a dryer zone in the range of 130 to 150 ° C., bending is performed by repeating 50 times or more and less than 120 times in a bending process in which the B surface facing the A surface of the web is alternately turned inside by the conveying roller. Thus, it can be seen that adjustment within the range of the dimensional change rate of the present invention is possible.

From Table 1, the polarizing plate using the film A and the film B adjusted within the range of the dimensional change rate according to the present invention is the display unevenness of the liquid crystal panel, the undulation, the film even when the temperature and humidity atmosphere of the usage environment is changed. It is apparent that a polarizing plate can be obtained in which deterioration of the adhesiveness of the polarizer such as peeling is not observed. In particular, it has been found that even when a cycle test is performed under harsh temperature and humidity conditions that have never been seen before, a polarizing plate can be obtained in which deterioration of polarizer adhesion such as undulation and film peeling is not observed.

In addition, the polarizing plate using B-137 and B-138 in which the dope of film B is changed to dope 7 and dope 8 not containing a retardation adjusting agent is used for B-132 to B using dope 2 to dope 6. Compared with the polarizing plate using -136, there was no problem in practical use, but the visibility (contrast) was slightly lowered.

Example 2
In the preparation of the film A-104 and the film B-104 in Example 1, by changing the cooling rate in the film A, by changing the drying temperature and times when bending the film B, L _{30 MD} described in Table 3, Film A-201 to film A-204 and film B-201 to film B-204 having a value of L ₃₀ TD were prepared, and a polarizing plate was prepared in the same manner as in Example 1. Display unevenness and polarizer adhesion Was evaluated.

The results are shown in Table 3.

 

 

From Table 3, when L ₃₀ TD and L ₃₀ MD of film A and film B are in the range of −0.10 to 0.10%, respectively, the liquid crystal panel can be used even if the temperature and humidity atmosphere of the usage environment changes It can be seen that a more excellent polarizing plate can be obtained in which no deterioration of the polarizer adhesion such as display unevenness, wavy, and film peeling is observed.

Example 3
[Film A-301: (TAC / acrylic resin 2 / TAC) film and film A-302: (TAC / acrylic resin 3 / TAC) film production]
Using the co-casting die shown in FIG. 8, according to the following procedure, a film A-301 having a three-layer structure of (TAC / acrylic resin 2 / TAC) and a three-layer simultaneous casting method (co-casting method) and ( A film A-302 having a three-layer structure of (TAC / acrylic resin 3 / TAC) was produced.

(Preparation of dope 9)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24, and the main dope 9 was obtained.

<Composition of main dope 9>
Acrylic resin 2: Dianal BR88 (manufactured by Mitsubishi Rayon Co., Ltd., acrylic resin Mw: 1,500,000) 90 parts by mass Sugar ester: BzSc benzyl saccharose: Compound a-1 described in Chemical formula 3
A-4)), average ester substitution degree = 5.5 10 parts by mass Methylene chloride 360 parts by mass Ethanol 15 parts by mass 100 parts by mass of main dope 9 and in-line additive solution prepared for film A in Example 1 2.5 parts by mass were sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ) to obtain a dope 9.

(Preparation of dope 10)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24, and the main dope 10 was obtained.

<Composition of main dope 10>
Acrylic resin 3: General formula (1) described in JP2009-157352A
) A (meth) acrylic resin having a lactone ring structure in which R ¹ is a hydrogen atom and R ² and R ³ are methyl groups [mass ratio of copolymerization monomer: methyl methacrylate / 2- (hydroxymethyl) methyl acrylate = 8/2; mixture of 90 parts by mass of lactone cyclization rate of about 100%] and 10 parts by mass of acrylonitrile-styrene (AS) resin (Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.)
90 parts by mass Sugar ester: BzSc benzyl saccharose: Compound a-1 described in Chemical formula 3
Mixture of a-4), average ester substitution degree = 5.5 10 parts by mass Methylene chloride 360 parts by mass Ethanol 15 parts by mass 100 parts by mass of main dope 10 and in-line additive solution prepared for film A in Example 1 2.5 parts by mass were sufficiently mixed with an in-line mixer (Toray static in-tube mixer Hi-Mixer, SWJ) to obtain a dope 10.

(Preparation of dope 11)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24, and the main dope 11 was obtained.

<Composition of main dope 11>
Triacetyl cellulose (TAC: Degree of substitution of acetyl group 2.80, Mn = 9
0000, Mw = 152000, Mw / Mn = 1.7) 86 parts by mass Polyhydric alcohol ester (compound represented by general formula (2)): Exemplified compound 2-10 2 parts by mass Sugar ester; BzSc (benzyl saccharose: Compound a- according to Chemical formula 3
1 to a-4), average ester substitution degree = 5.5 7 parts by mass Polycondensation ester: Polycondensation ester represented by the general formula (1): P1
5 parts by mass Dichloromethane 430 parts by mass Ethanol 11 parts by mass 100 parts by mass of the main dope 11 and 2.5 parts by mass of the inline additive liquid prepared for the film B in Example 1 were combined with an inline mixer (Toray static type in-tube mixer) The dope 11 was obtained by thoroughly mixing with Hi-Mixer, SWJ.

(Film forming process)
Using the dope 9 and the dope 11, the dope 11 is used as the skin layer (B surface), the dope 9 is used as the core layer, and the skin layer (from the surface of the endless belt 16 which is the metal support for casting shown in FIG. The dope 11 is simultaneously supplied to the co-casting die 10 as the A-side), and the flow is a laminate composed of the skin layer (B-side) / core layer / skin layer (A-side) by one casting operation. The casting film 20 was supplied onto the endless belt 16. The supply amount of each dope was such that the film thickness of each layer after the drying was finally completed was skin layer (B surface) / core layer / skin layer (A surface) = 3 μm / 30 μm / 3 μm.

On the metal support for casting, the organic solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% by mass to form a web, and then the web was peeled from the stainless steel band support. . The obtained web was further pre-dried at 110 ° C. for 10 minutes, and then the web was stretched 1.3 times with respect to the original width in the TD direction at 160 ° C. with a tenter. The residual solvent amount of the web at the start of stretching was 2.0% by mass. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then the film was conveyed for 15 minutes at 130 ° C. by the dryer (bending zone 106) shown in FIG. 9 and then 23 ° C. in the cooling zone 109 at a rate of 80 ° C./min. Cooled to ° C. The obtained film was slit to 2.0 m width, 10 mm wide and 5 μm knurled at both ends of the film, wound on a core of 15.24 cm in inner diameter with an initial tension of 220 N / m and a final tension of 110 N / m. A film A-301 having a long three-layer structure having a thickness of 4000 m and a film thickness of 36 μm was obtained. Similarly, a film A-302 having a three-layer structure was obtained using the dope 10 as the core layer and the dope 11 as the skin layer.

[Film A-303: Production of (Acrylic Resin 1 / Cellulose Ester) Film]
(Preparation of dope 12)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24 to obtain the main dope 12.

Acrylic resin 1: Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd., acrylic resin Mw: 280000) 70 parts by weight Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution) Degree 2.5
6, Mw = 200000, described as CAP in the table) 30 parts by mass Acrylic fine particles (C1) 2 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass <Preparation of acrylic fine particles (C1)>
A reactor with a reflux condenser with an internal volume of 60 liters was charged with 38.2 liters of ion-exchanged water and 111.6 g of sodium dioctylsulfosuccinate, and the temperature was raised to 75 ° C. under a nitrogen atmosphere while stirring at a rotational speed of 250 rpm. The effect of oxygen was virtually eliminated. A single unit consisting of 0.36 g of ammonium persulfate (APS) and stirring for 5 minutes, consisting of 1657 g of methyl methacrylate (MMA), 21.6 g of n-butyl acrylate (BA), and 1.68 g of allyl methacrylate (ALMA) The body mixture was added all at once and held for an additional 20 minutes after detection of the exothermic peak to complete the polymerization of the innermost hard layer.

Next, 3.48 g of APS was added, and after stirring for 5 minutes, a monomer mixture consisting of 8105 g of BA, 31.9 g of polyethylene glycol diacrylate (PEGDA: molecular weight 200), and 264.0 g of ALMA was applied for 120 minutes. The mixture was continuously added and held for an additional 120 minutes after completion of the addition to complete the polymerization of the soft layer.

Next, 1.32 g of APS was added, and after stirring for 5 minutes, a monomer mixture consisting of 2106 g of MMA and 201.6 g of BA was continuously added over 20 minutes, and held for another 20 minutes after the addition was completed. Polymerization of the outermost hard layer 1 was completed.

Next, 1.32 g of APS was added, and after 5 minutes, a monomer mixture consisting of 3148 g of MMA, 201.6 g of BA, and 10.1 g of n-OM was continuously added over 20 minutes. Later held for another 20 minutes. Next, the temperature was raised to 95 ° C. and held for 60 minutes to complete the polymerization of the outermost hard layer 2.

A small amount of the polymer latex thus obtained was collected, and the flat particle size was determined by the absorbance method, which was 0.10 μm. The remaining latex was put into a 3% by mass sodium sulfate warm aqueous solution, salted out and coagulated, and then dried after repeated dehydration and washing to obtain acrylic fine particles (C1) having a three-layer structure.

100 parts by mass of the main dope 12 and 2.5 parts by mass of the inline additive solution prepared for the film A in Example 1 were sufficiently mixed with an inline mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ). Thus, dope 12 was obtained.

(Film forming process)
In the same manner as in the production of the film A-101 of Example 1, the obtained dope 12 was used on a stainless band support using a belt casting apparatus, and the liquid temperature of the dope 12 was 35 ° C. and the width was 1.7 m. Then, the film was uniformly cast under the condition that the final film thickness was 40 μm. On the stainless steel band support, the organic solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% by mass to form a web, and then the web was peeled from the stainless steel band support. The obtained web was further pre-dried at 110 ° C. for 10 minutes, and then the web was stretched 1.5 times with respect to the original width in the TD direction at 160 ° C. with a tenter. The residual solvent amount of the web at the start of stretching was 2.0% by mass. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then the film was conveyed for 15 minutes at 130 ° C. by the dryer (bending zone 106) shown in FIG. Cooled to ° C. The obtained film was slit to 2.0 m width, 10 mm wide and 5 μm knurled at both ends of the film, wound on a core of 15.24 cm in inner diameter with an initial tension of 220 N / m and a final tension of 110 N / m. A film A-303 containing a long acrylic resin having a thickness of 4000 m and a film thickness of 40 μm was obtained.

For the film B facing the produced films A-301, A-302 and A-303, polarizing plates 301, 302 and 303 were produced using the film B-111.

Using the produced polarizing plates 301, 302, and 303, the evaluation conditions of Example 1 were changed to the following evaluation conditions.

(Evaluation of display unevenness)
The obtained liquid crystal display device was left in a constant temperature and humidity chamber of 50 ° C./90% RH for 1 hour and then placed in a temperature / humidity environment of 23 ° C./55% RH for 1 hour. After repeating the cycle, the difference (display unevenness) between the luminance near the four vertices of the display screen and the luminance near the center of the display screen was visually observed in a state where the liquid crystal display device was black-displayed at room temperature. Display unevenness was evaluated according to the following criteria. In the following evaluation, ○ or ◎ is preferable.

◎: No display unevenness. ○: Slight display unevenness is observed with very careful attention. △: Display unevenness is observed at one of the four vertices. X: Display unevenness occurs at three or more of the four vertices. Recognized (Evaluation of polarizer adhesion)
The obtained liquid crystal display device was left in a constant temperature and humidity chamber at 80 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment at 23 ° C./55% RH for 1 hour. The cycle was repeated to observe the undulation and film peeling on the panel surface, and the adhesion between the film A and the film B and the polarizer was evaluated.

◎: There is no undulation or film peeling on the panel surface ○: Slight undulation is observed on the panel surface when very careful, △: Clear undulation is observed on the panel surface, but there is no film peeling ×: On the panel surface Table 4 shows the results of waving and film peeling.

 

 

From Table 4, the temperature and humidity atmosphere of the usage environment changes under more severe conditions by making the film A a three-layer film using TAC for the skin layer, such as a (TAC / acrylic resin / TAC) film. Even so, it can be seen that a more excellent polarizing plate can be obtained in which no deterioration of the polarizer adhesion such as display unevenness of the liquid crystal panel, undulation, and film peeling occurs. In addition, the liquid crystal panel using the three-layer film improved the warpage of the panel. In addition, a film having a configuration such as A-303 in which an acrylic resin and a cellulose ester are mixed also has excellent polarizer adhesion such as display unevenness of a liquid crystal panel, undulation, and film peeling.

Example 4
In the production of the film A-104 of Example 1, the film A-401 to the film A-404 were produced by changing the stretching ratio in the TD direction as shown in Table 5, and the film B-104 was formed as the opposing film B. Thus, polarizing plates 401 to 404 were produced, and display unevenness and polarizer adhesion were evaluated in the same manner as in Example 1.

The results are shown in Table 5.

 

 

From Table 5, the film A is stretched within the range of 1.05 to 1.5 times the original width in the TD direction, so that even if the temperature and humidity atmosphere of the usage environment changes, the display unevenness of the liquid crystal panel In addition, it can be seen that a more excellent polarizing plate can be obtained in which deterioration of the adhesiveness of the polarizer such as waving and film peeling is not observed.

Example 5
In the production of the film B-104 of Example 1, the stretching ratio in the TD direction was changed within the range of 1.05 to 1.4 times, and the films B-501 to B having the retardation values shown in Table 6 were obtained. -505 was produced, polarizing films 501 to 505 were produced using the film A-104 as the opposing film A, and display unevenness and polarizer adhesion were evaluated in the same manner as in Example 1. The retardation was measured by the method described above.

The results are shown in Table 6.

 

 

From Table 6, by stretching the film B in the TD direction, the retardation values Ro and Rt can be adjusted within the preferred range of the present invention, and even if the temperature and humidity atmosphere of the use environment changes, It can be seen that a more excellent polarizing plate can be obtained in which no deterioration of the polarizer adhesion such as display unevenness of the liquid crystal panel, undulation, and film peeling is observed.

Example 6
[Film B-601: Production of (TAC / DAC2 / TAC) Film and Film B-602: (TAC / DAC3 / TAC) Film]
Using the co-casting die shown in FIG. 8, according to the following procedure, the three-layer simultaneous casting method (co-casting method) (TAC / DAC2 / TAC) three-layer film B-601 and (TAC / A three-layer film B-602 (DAC3 / TAC) was produced.

(Preparation of dope 13)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24, and the main dope 13 was obtained.

<Composition of main dope 13>
Diacetyl cellulose 2 (acetyl group substitution degree: 2.40, Mn = 8000)
0, Mw = 136000, Mw / Mn = 1.7) 86 parts by mass Compound E-104 described in JP 2012-215817 A 2 parts by mass Sugar ester; BzSc (benzyl saccharose: Compound a- described in Chemical formula 3
1 to a-4), average ester substitution degree = 5.5 7 parts by mass Polycondensation ester: Polycondensation ester represented by the general formula (1): P1
5 parts by mass Dichloromethane 30 parts by mass Ethanol 11 parts by mass 100 parts by mass of the main dope 13 and 2.5 parts by mass of the inline additive solution prepared for the film B in Example 1 were combined with an inline mixer (Toray static type in-tube mixer) The dope 13 was obtained by thoroughly mixing with Hi-Mixer, SWJ.

(Preparation of dope 14)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24 to obtain the main dope 14.

<Composition of main dope 14>
Diacetylcellulose 3 (acetyl group substitution degree: 2.20, Mn = 1000
00, Mw = 1700, Mw / Mn = 1.7) 86 parts by mass Compound E-203 described by JP 2012-215817 A 2 parts by mass Sugar ester; BzSc (benzyl saccharose: Compound a- described in Chemical formula 3
1 to a-4), average ester substitution degree = 5.5 7 parts by mass Polycondensation ester: Polycondensation ester represented by formula (1): P8
5 parts by mass Dichloromethane 430 parts by mass Ethanol 11 parts by mass 100 parts by mass of the main dope 14 and 2.5 parts by mass of the inline additive solution prepared for the film B in Example 1 were combined with an inline mixer (Toray static type in-tube mixer) Mix well with Hi-Mixer, SWJ) to obtain Dope 14.

(Film forming process)
Using the dope 13 and the dope 11 produced in Example 3, the dope 11 is doped as the skin layer (B surface) and the core layer is doped from the surface of the endless belt 16 which is the metal support for casting shown in FIG. The dope 11 is supplied to the co-casting die 10 at the same time as a skin layer (A surface) 13 and is composed of skin layer (B surface) / core layer / skin layer (A surface) by a single casting operation. A cast film 20 as a laminated body was supplied onto the endless belt 16. The supply amount of each dope was such that the film thickness of each layer after the drying was finally completed was skin layer (B surface) / core layer / skin layer (A surface) = 3 μm / 30 μm / 3 μm.

On the metal support for casting, the organic solvent in the obtained dope film was evaporated until the residual solvent amount reached 100% by mass to form a web, and then the web was peeled from the stainless steel band support. . The obtained web was further pre-dried at 110 ° C. for 10 minutes, and then the web was stretched 1.3 times with respect to the original width in the TD direction at 160 ° C. with a tenter. The residual solvent amount of the web at the start of stretching was 2.0% by mass. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then the temperature was maintained at 135 ° C. by the dryer (bending zone 106) shown in FIG. The diameter and arrangement of the transport rollers so that the value of 1 / a is 0.040 mm ⁻¹ when the radius when the B surface facing the A surface is alternately bent inward is a (mm). The web was conveyed at a conveyance speed of 20 m / min by repeating 80 times of bending.

The obtained film was slit to 2.0 m width, 10 mm wide and 5 μm knurled at both ends of the film, wound on a core of 15.24 cm in inner diameter with an initial tension of 220 N / m and a final tension of 110 N / m. A film B-601 having a long three-layer structure having a thickness of 4000 m and a film thickness of 40 μm was obtained. Similarly, a film B-602 having a three-layer structure was obtained using the dope 14 as the core layer and the dope 11 as the skin layer.

Further, a single-layer film B-603 containing diacetylcellulose was produced in the same manner as the film B-116 of Example 1 using the following dope 15.

(Preparation of dope 15)
The following components were put into a sealed container and completely dissolved with heating and stirring. The obtained solution was prepared as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. 24 to obtain the main dope 15.

<Composition of main dope 15>
Diacetylcellulose 1 (acetyl group substitution degree: 2.35, Mn = 9000)
0, Mw = 152000, Mw / Mn = 1.7) 83 parts by mass Sugar ester; BzSc (benzyl saccharose: Compound a-
1 to a-4), average ester substitution degree = 5.5 7 parts by mass Polycondensed ester: polycondensed ester P8 represented by the general formula (1) 5 parts by mass Retardation adjusting agent 1 3 parts by mass Additive A 2 parts by mass Dichloromethane 430 parts by mass Ethanol 11 parts by mass 100 parts by mass of the main dope 15 and 2.5 parts by mass of the inline additive solution prepared for the film B in Example 1 were mixed with an inline mixer (Toray static type in-tube mixing) The dope 15 was obtained by thoroughly mixing with a machine Hi-Mixer, SWJ).

For the films A facing the produced films B-601, B-602, and B-603, polarizing plates 601 to 603 were produced using the film A-116.

Using the produced polarizing plates 601 to 603, display unevenness and polarizer adhesion were evaluated under the evaluation conditions of Example 3.

The results are shown in Table 7.

 

 

From Table 7, film B is a three-layer film using TAC for the skin layer, such as a (TAC / DAC / TAC) film, so that the conditions are more severe than those of a single layer film. It can be seen that even when the temperature and humidity atmosphere of the usage environment changes, an excellent polarizing plate can be obtained in which the display unevenness of the liquid crystal panel, the deterioration of the adhesiveness of the polarizer such as waving and film peeling are not observed.

Example 7
In the production of the polarizing laminate film used in Example 1, the polarizer was produced by changing the film thickness of the polarizer as shown in Table 7, and the polarizing plate 117 having the configuration of the polarizing plate 117 produced in Example 1 was used. 705 was produced.

Further, in order to see the difference in the polarizer, a conventional polyvinyl alcohol (PVA) film shown below was stretched to produce a polarizer, and a polarizing plate 706 was produced in the same manner.

(Preparation of polarizer 2)
A 45 μm thick polyvinyl alcohol (PVA) film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. composed of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. This uniaxially stretched film was washed with water and dried to obtain a 9 μm thick polarizer.

Using the produced polarizing plates 701 to 706, display unevenness and polarizer adhesion were evaluated under the evaluation conditions of Example 1.

The results are shown in Table 8.

 

 

According to Table 8, by using a polarizing laminated film type polarizer and having a film thickness in the range of 2 to 15 μm, even if the temperature and humidity atmosphere of the usage environment changes, the display unevenness of the liquid crystal panel It can be seen that a more excellent polarizing plate can be obtained in which deterioration of polarizer adhesion such as undulation and film peeling is not observed. In addition, compared with a polarizer obtained by stretching a conventional polyvinyl alcohol (PVA) film, it is possible to obtain a polarizing plate that is superior in terms of display unevenness of a liquid crystal panel, polarizer adhesion such as waving and film peeling. I understand.

Industrial applicability

The polarizing plate of the present invention is a liquid crystal panel display even when the temperature and humidity atmosphere of the usage environment changes when a polarizing plate using an acrylic film and a cellulose ester film as a protective film for a polarizer is provided in a liquid crystal display device. Since deterioration of polarizer adhesion such as unevenness, undulation, and film peeling is not observed, it is suitably used for liquid crystal display elements and the like, and particularly suitable for VA mode liquid crystal display devices.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock pot 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber preparation pot 20 Merge pipe 21 Mixer 30 Pressure die 31 Metal belt 32 Web 33 Peeling Position 34 Tenter stretching device 35 Drying device 41 Stock kettle 42 Stock kettle 43 Pump 44 Filter 50 Co-casting die 51 Base part 53, 55 Layer B, Layer C slit 54 Layer A slit 56 Metal support 57, 59 layer B, dope for layer C 58 dope for layer A 60 multilayer web 61 layer C (skin layer)
62 Layer A (core layer)
63 Layer B (skin layer)
DESCRIPTION OF SYMBOLS 100 Dies 102 Metal support body 103 Driving roller 104 Peeling point 105 Conveyance roller 106 Bending zone 107 Inlet 108 Outlet 109 Cooling zone

Claims (17)

The polarizer is a polarizing plate sandwiched between the film A and the film B through an active ray curable adhesive layer,
The film A is an acrylic film containing an acrylic resin having a thickness in the range of 20 to 60 μm and satisfying the following formulas (1) to (4):
The film B contains cellulose acetate having a film thickness in the range of 20 to 60 μm and an average substitution degree of acetyl groups in the range of 2.0 to 2.5, and the following formulas (1) to ( A polarizing plate characterized by being a cellulose acetate film satisfying 4).
(1) 0.03 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.30 (%)
(2) 0.03 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.30 (%)
(3) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.10 (%)
(4) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.10 (%)
In the above formula, L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD are determined by the following formulas (a) to (f) after 1 minute, 5 minutes, And the dimensional change rate of the film after 30 minutes. In the following formulas (a) to (f), the film A and the film B are sampled in a rectangular shape so that one side is parallel to the TD direction or the MD direction, and this is obtained under a temperature and humidity environment of 23 ° C. and 55% RH. The specified dimensions of the film left over are measured in the MD and TD directions and are designated as L ₀ MD and L ₀ TD, respectively. This film is left in a constant temperature and humidity chamber at 80 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment at 23 ° C./55% RH, the dimensions after 1 minute, the dimensions after 5 minutes, and 30 minutes. The subsequent dimensions are measured in the MD direction and TD direction, respectively, and are defined as L ₁ MD ′, L ₁ TD ′, L ₅ MD ′, L ₅ TD ′, L ₃₀ MD ′, and L ₃₀ TD ′, respectively. Substituting into (a) to (f), the dimensional change rate is obtained.
Dimensional change rate after 1 minute (formula a) L ₁ MD (%) = (L ₁ MD′−L ₀ MD) / L ₀ MD × 100
(Formula b) L ₁ TD (%) = (L ₁ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 5 minutes (formula c) L ₅ MD (%) = (L ₅ MD′−L ₀ MD) / L ₀ MD × 100
(Formula d) L ₅ TD (%) = (L ₅ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 30 minutes (formula e) L ₃₀ MD (%) = (L ₃₀ MD′−L ₀ MD) / L ₀ MD × 100
(Formula f) L ₃₀ TD (%) = (L ₃₀ TD′−L ₀ TD) / L ₀ TD × 100 The polarizing plate according to claim 1, wherein the film A and the film B satisfy the following formulas (5) to (8), respectively.
(5) 0.05 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.15 (%)
(6) 0.05 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.15 (%)
(7) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.05 (%)
(8) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.05 (%)
In the above formula, L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD are synonymous with the first term. 3. The polarizing plate according to claim 1, wherein L ₃₀ TD and L ₃₀ MD of the film A and the film B are in the range of −0.10 to 0.10%, respectively. . The said film A contains sugar ester or the polycondensation ester which has a structure represented by following General formula (1), The polarizing plate as described in any one of Claim 1- Claim 3 characterized by the above-mentioned. .
General formula (1)
B _3- (G ₂ -A) _n -G ₂ -B ₄
(In the above general formula, B ₃ and B ₄ each independently represents an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, Represents an aryl glycol residue having 6 to 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms, wherein A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. N represents an integer of 1 or more.) The film A has a structure of at least three layers having skin layers on both sides of a core layer, the core layer contains an acrylic resin, and the skin layer contains a cellulose ester. The polarizing plate as described in any one of Claim 4. The film A according to any one of claims 1 to 5, wherein the film A is stretched within a range of 1.05 to 1.5 times the original width in the TD direction. Polarizer. In the film B, the in-plane retardation value Ro defined by the following formulas (i) and (ii) is in the range of 40 to 60 nm, and the retardation value Rt in the thickness direction is in the range of 100 to 140 nm. It is inside, The polarizing plate as described in any one of Claim 1- Claim 6 characterized by the above-mentioned.
Formula (i): Ro = (n _x −n _y ) × d (nm)
Formula (ii): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In [Equation (i) and Formula (ii), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the direction y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. The measurement is performed at a measurement wavelength of 590 nm in an environment of 23 ° C. and 55% RH. ] 8. The film B according to any one of claims 1 to 7, wherein the film B contains cellulose acetate having an average degree of substitution of acetyl groups within a range of 2.1 to 2.4. Polarizer. The polarizing plate according to any one of claims 1 to 8, wherein the film B contains a sugar ester or a polycondensed ester having a structure represented by the following general formula (1). .
General formula (1)
B _3- (G ₂ -A) _n -G ₂ -B ₄
(In the above formula, B ₃ and B ₄ each independently represents an aliphatic or aromatic monocarboxylic acid residue or a hydroxy group. G ₂ represents an alkylene glycol residue having 2 to 12 carbon atoms, 6 carbon atoms. Represents an aryl glycol residue having 12 to 12 carbon atoms or an oxyalkylene glycol residue having 4 to 12 carbon atoms, and A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms. N represents an integer of 1 or more.) The film B has a structure of at least three layers having skin layers on both sides of the core layer, and the core layer contains cellulose acetate having an acyl group substitution degree in the range of 2.0 to 2.45, The polarizing plate according to any one of claims 1 to 9, wherein the skin layer contains cellulose acetate having an acyl group substitution degree in the range of 2.6 to 2.95. The polarizing plate according to any one of claims 1 to 10, wherein the polarizer has a thickness of 2 to 15 µm. A method for producing a polarizing plate in which films A and B are bonded to both surfaces of a polarizer via an active ray curable adhesive layer,
As the film A, an acrylic film containing an acrylic resin having a thickness in the range of 20 to 60 μm and satisfying the following formulas (1) to (4) is used.
The film B contains cellulose acetate having a film thickness in the range of 20 to 60 μm and an average substitution degree of acetyl groups in the range of 2.0 to 2.5, and the following formulas (1) to ( A method for producing a polarizing plate, comprising using a cellulose acetate film satisfying 4).
(1) 0.03 (%) ≦ L ₁ MD-L ₅ MD ≦ 0.30 (%)
(2) 0.03 (%) ≦ L ₁ TD-L ₅ TD ≦ 0.30 (%)
(3) 0 (%) ≦ L ₅ MD-L ₃₀ MD ≦ 0.10 (%)
(4) 0 (%) ≦ L ₅ TD-L ₃₀ TD ≦ 0.10 (%)
In the above formula, L ₁ MD, L ₁ TD, L ₅ MD, L ₅ TD, L ₃₀ MD, and L ₃₀ TD are determined by the following formulas (a) to (f) after 1 minute, 5 minutes, And the dimensional change rate of the film after 30 minutes. In the following formulas (a) to (f), the film A and the film B are sampled in a rectangular shape so that one side is parallel to the TD direction or the MD direction, and this is obtained under a temperature and humidity environment of 23 ° C. and 55% RH. The specified dimensions of the film left over are measured in the MD and TD directions and are designated as L ₀ MD and L ₀ TD, respectively. This film is left in a constant temperature and humidity chamber at 80 ° C./90% RH for 1 hour, and then placed in a temperature / humidity environment at 23 ° C./55% RH, the dimensions after 1 minute, the dimensions after 5 minutes, and 30 minutes. The subsequent dimensions are measured in the MD direction and TD direction, respectively, and are defined as L ₁ MD ′, L ₁ TD ′, L ₅ MD ′, L ₅ TD ′, L ₃₀ MD ′, and L ₃₀ TD ′, respectively. Substituting into (a) to (f), the dimensional change rate is obtained.
Dimensional change rate after 1 minute (formula a) L ₁ MD (%) = (L ₁ MD′−L ₀ MD) / L ₀ MD × 100
(Formula b) L ₁ TD (%) = (L ₁ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 5 minutes (formula c) L ₅ MD (%) = (L ₅ MD′−L ₀ MD) / L ₀ MD × 100
(Formula d) L ₅ TD (%) = (L ₅ TD′−L ₀ TD) / L ₀ TD × 100
Dimensional change rate after 30 minutes (formula e) L ₃₀ MD (%) = (L ₃₀ MD′−L ₀ MD) / L ₀ MD × 100
(Formula f) L ₃₀ TD (%) = (L ₃₀ TD′−L ₀ TD) / L ₀ TD × 100 The film A is
Casting a dope containing at least an acrylic resin and an organic solvent to form a web on a metal support;
Drying and peeling the formed web from the metal support;
Stretching the peeled web;
Drying the stretched web in a dryer zone;
A cooling step of cooling the web at a rate in the range of 50-100 ° C./second after the web exits the dryer zone;
13. The method for producing a polarizing plate according to item 12, wherein the polarizing plate is formed by: The film B is
Casting a dope containing at least cellulose acetate and an organic solvent to form a web on a metal support;
Drying and peeling the formed web from the metal support;
Stretching the peeled web;
Drying the stretched web in a dryer zone;
The step of drying the web in the dryer zone is formed at a temperature in the range of 130 to 150 ° C., and the B side facing the A side of the web is alternately turned inside by the conveying roller. has a bending step of bending manner, the bending step, when the radius when bending the web was a (mm), the range value of the 1 / a is 0.035 mm ^-1 ~ 0.050 mm ^-1 14. The method for producing a polarizing plate according to claim 12, wherein the bending is performed while repeating bending 50 times or more and less than 120 times. Forming a polyvinyl alcohol resin layer on one surface of a base film in which a rubber component is dispersed in a thermoplastic resin to obtain a laminated film;
Uniaxially stretching the laminated film to obtain a stretched film;
Dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to obtain a dyed film;
Immersing the polyvinyl alcohol-based resin layer of the dyed film in a solution containing a crosslinking agent to form a polarizer layer, and obtaining a crosslinked film;
Drying the crosslinked film;
After forming a polarizing laminated film by
The polyvinyl alcohol-based resin layer is used as the polarizer by peeling off the polyvinyl alcohol-based resin layer of the polarizing laminated film from the base film. 15. The manufacturing method of the polarizing plate of one term. A liquid crystal display device comprising the polarizing plate according to any one of claims 1 to 11. The liquid crystal display device according to claim 16, wherein the liquid crystal display device is a VA mode type liquid crystal display device.

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