WO2009123160A1 - Drawn film, drawn film manufacturing method, and polarizer - Google Patents

Abstract

Disclosed is drawn film in which a film, formed by solution casting and with retardation in the thickness direction having an initial value of 30 nm or larger, is drawn at temperature T to satisfy the following formula I), and of which the weight reduction percentage, as measured by TG-DTA, after 60 min, at said temperature T is 5% or less. In formula (I), Rth(T) is the retardation value in the thickness direction of said film measured at ? = 590 nm after 3 min at temperature T when at least two sides of said film are held, and Rth(I) is the initial value of the retardation in the thickness direction of said film measured at ? =590 nm. Also, said weight reduction percentage is found with weight reduction percentage (%) = [{(Initial film weight) - (film weight after being kept at temperature T for 60 min)}/(initial film weight)] x 100.

Description

Stretched film, stretched film manufacturing method, and polarizing plate

The present invention relates to a stretched film, a method for producing the stretched film, and a polarizing plate.

The polarizing plate is usually produced by bonding a protective film mainly composed of cellulose triacetate on both sides of a polarizing film in which iodine or a dichroic dye is oriented and adsorbed on polyvinyl alcohol. Cellulose triacetate is widely used as the above-mentioned protective film for polarizing plate because of its characteristics such as toughness, flame retardancy, and high optical isotropy (low retardation value). The liquid crystal display device includes a polarizing plate and a liquid crystal cell. Currently, as described in Patent Document 1, a liquid crystal display device with high display quality is realized by inserting an optical compensation sheet (also referred to as an optical compensation film) between a polarizing plate and a liquid crystal cell.

In addition to the cellulose triacetate, a cyclic olefin resin film has been proposed as a material for the protective film.
As a method for producing these protective films, a solution casting method in which a dope in which a resin or other additive is used as a solution is cast on a support is known. However, in the solution casting method, when the solvent volatilizes, the solvent volatilizes from the upper surface of the film, resulting in superposition of molecular chains, forming a state as if the molecules are stacked. For this reason, unlike the melt film formation, there is a problem that the retardation (Rth) in the thickness direction tends to be high.
On the other hand, the invention specifying the stretching conditions for producing the functional film is disclosed in, for example, Patent Documents 2 and 3, but the temperature conditions for actively reducing the Rth of the film formed by the solution casting method are as follows. There is no mention of a technique for searching or setting an optimum temperature including film additives to obtain a functional film having desired optical properties.

JP-A-8-50206 JP 2006-235085 A Japanese Patent Laid-Open No. 5-150115

As described above, generally, in the solution casting method, molecular chains are superposed due to the molecular chain stacking effect when the solvent volatilizes, and Rth tends to increase. This is the most different point from melt film formation, and the film obtained by melt film formation has an initial value of Rth close to zero. In general, the polymer is often stretched in the vicinity of the glass transition temperature (Tg) because of its efficient optical property development. However, a crystalline polymer may sometimes increase Rth even if it is stretched in the vicinity of Tg.
By increasing the stretching temperature, the polymer approaches a molten state and may reduce Rth, but depending on the stretching temperature, crystallization proceeds and Rth increases. If the temperature is further increased so as not to crystallize, the thermal decomposition point of the polymer is exceeded and the decomposition of the polymer starts. If the polymer is decomposed, free acid is generated or the film color changes, so it is very important to stretch at a temperature below the decomposition point.
Moreover, when an additive is used, depending on the volatility of the additive, the volatility of the additive increases with respect to the film temperature, and the intended optical properties may not be obtained.
Thus, the expression of optical characteristics varies depending on the type, structure, and additives of the polymer, and the optimum temperature range cannot be determined only by Tg and the crystallization temperature.

Therefore, in the present invention, there is nothing to do with the Tg or crystallinity of the polymer, and the temperature at which the Rth that is initially expressed by the solution casting method is lowered to the intended Rth and the weight reduction of the film. It has been found that by arbitrarily selecting a temperature having a low rate and low volatility, the film can be arbitrarily stretched to exhibit arbitrary optical properties.
That is, the present invention provides a stretched film obtained by stretching a film formed by a solution casting method, wherein the stretched Rth value is lower than the initial Rth value and the weight reduction rate is small. The purpose is to provide.

The above problem was solved by the following configuration.

1. A film formed by a solution casting method having an initial retardation of 30 nm or more in the thickness direction is stretched at a temperature T satisfying the following formula I), and measured by TG-DTA at the temperature T The stretched film is characterized in that the weight loss rate for 60 minutes is 5% or less.
Formula I) 0.2 ≦ (Rth (T) / Rth (I)) ≦ 0.9
In Formula I), Rth (T) is a retardation value in the thickness direction measured at λ = 590 nm of the film after being placed at a temperature T for 3 minutes while holding at least two sides of the film. , Rth (I) is an initial value of retardation in the thickness direction measured at λ = 590 nm of the film. The weight reduction rate is obtained by weight reduction rate (%) = [{(initial film weight) − (film weight after holding at temperature T for 60 minutes)} / (initial film weight)] × 100. It is what
2. 2. The stretched film according to 1 above, wherein the optical properties after stretching satisfy the following conditions.
1.75 ≦ Rth / Re + 0.5 ≦ 5 (where Rth is the retardation value in the thickness direction measured at λ = 590 nm, and Re is the in-plane retardation value measured at λ = 590 nm) is there.)
3. 3. The stretched film according to 1 or 2 above, wherein the film is a cyclic olefin resin film.
4). 3. The stretched film as described in 1 or 2 above, wherein the film comprises a cellulose resin having an acyl substituent having 2 to 4 carbon atoms and an acyl group substitution degree of 2.1 to 2.7.
5). 5. The stretched film as described in 4 above, wherein the film comprises a cellulose resin having an acyl substituent having 2 to 4 carbon atoms and an acyl group substitution degree of 2.3 to 2.6.
6). 6. The stretched film according to any one of 1 to 5 above, wherein the optical characteristics satisfy 25 nm ≦ Re ≦ 100 nm and 50 nm ≦ Rth ≦ 300 nm. (Re is an in-plane retardation value measured at λ = 590 nm, and Rth is a thickness direction retardation value measured at λ = 590 nm.)
7). 6. The stretched film according to any one of 1 to 5 above, wherein the optical characteristics satisfy 50 nm ≦ Re ≦ 70 nm and 90 nm ≦ Rth ≦ 120 nm. (Re is an in-plane retardation value measured at λ = 590 nm, and Rth is a thickness direction retardation value measured at λ = 590 nm.)
8). 8. The stretched film according to any one of 1 to 7 above, wherein the film contains a retardation adjusting agent.
9. A polarizing plate having a polarizer and two protective films on both sides of the polarizer, wherein at least one of the two protective films is a stretched film according to any one of 1 to 8 above .
10. A step of stretching a film formed by a solution casting method having an initial value of 30 nm or more in the thickness direction at a temperature T satisfying the following formula I), and TG-DTA at the temperature T A method for producing a stretched film, wherein the weight loss rate measured for 60 minutes is 5% or less.
Formula I) 0.2 ≦ (Rth (T) / Rth (I)) ≦ 0.9
In Formula I), Rth (T) is a retardation value in the thickness direction measured at λ = 590 nm of the film after being placed at a temperature T for 3 minutes while holding at least two sides of the film. , Rth (I) is an initial value of retardation in the thickness direction measured at λ = 590 nm of the film. The weight reduction rate is obtained by weight reduction rate (%) = [{(initial film weight) − (film weight after holding at temperature T for 60 minutes)} / (initial film weight)] × 100. It is what

According to the present invention, there is provided a stretched film obtained by stretching a film formed by a solution casting method, wherein the stretched Rth value is lower than the initial Rth value and the weight reduction rate is small. Can be provided.
The stretched film has optical properties useful as each functional film. Moreover, the polarizing plate which was rich in durability using this stretched film can be provided.

Hereinafter, the present invention will be described in detail.
In this specification, “(numerical value 1) to (numerical value 2)” and “(numerical value 1) to (numerical value 2)” mean “(numerical value 1) to (numerical value 2)”.

The stretched film of the present invention is obtained by stretching a film formed by a solution casting method having an initial value of 30 nm or more in the thickness direction at a temperature T satisfying the following formula I). The weight loss rate for 60 minutes measured by TG-DTA at T is 5% or less.
Formula I) 0.2 ≦ (Rth (T) / Rth (I)) ≦ 0.9
In Formula I), Rth (T) is a retardation value in the thickness direction measured at λ = 590 nm of the film after being placed at a temperature T for 3 minutes while holding at least two sides of the film. , Rth (I) is an initial value of retardation in the thickness direction measured at λ = 590 nm of the film. The weight reduction rate is obtained by weight reduction rate (%) = [{(initial film weight) − (film weight after holding at temperature T for 60 minutes)} / (initial film weight)] × 100. It is what

In the present invention, any film formed by a solution casting method can be used, but a cyclic olefin resin film (also referred to as a cyclic polyolefin film) or a cellulose resin film is preferable.
The cyclic polyolefin film contains at least a cyclic olefin resin (also referred to as a cyclic polyolefin resin or a cyclic polyolefin). The cellulose resin film contains at least a cellulose resin. The cyclic olefin resin and the cellulose resin will be described below.

(Cyclic polyolefin resin)
In the present invention, the cyclic polyolefin resin represents a polymer resin having a cyclic polyolefin structure.
Examples of the polymer resin having a cyclic olefin structure that can be used in the present invention include (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, (4) Vinyl alicyclic hydrocarbon polymers and hydrides of (1) to (4). The polymer resin preferably used in the present invention is an addition (co) polymer cyclic polyolefin containing at least one repeating unit represented by the following general formula (7) and, if necessary, the general formula (6). An addition (co) polymer cyclic polyolefin further comprising at least one or more repeating units. A ring-opening (co) polymer containing at least one cyclic repeating unit represented by the general formula (8) can also be suitably used.

In the formula, m represents an integer of 0 to 4. R ¹ to R ⁶ are a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, X ¹ to X ³ , Y ¹ to Y ³ are hydrogen atoms, a hydrocarbon group having 1 to 10 carbon atoms, a halogen atom, or a halogen atom. A substituted hydrocarbon group having 1 to 10 carbon atoms, — (CH ₂ ) _n COOR ¹¹ , — (CH ₂ ) _n OCOR ¹² , — (CH ₂ ) _n NCO, — (CH ₂ ) _n NO ₂ , — ( CH ₂ ) _n CN, — (CH ₂ ) _n CONR ¹³ R ¹⁴ , — (CH ₂ ) _n NR ¹³ R ¹⁴ , — (CH ₂ ) _n OZ, — (CH ₂ ) _n W, or X ¹ and Y ¹ Alternatively, (—CO) ₂ O and (—CO) ₂ NR ¹⁵ composed of X ² and Y ² or X ³ and Y ³ are shown. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are hydrogen atoms, hydrocarbon groups having 1 to 20 carbon atoms, Z is a hydrocarbon group or a hydrocarbon group substituted with halogen, and W is SiR ¹⁶ _p D _3-p (R ¹⁶ is a hydrocarbon group having 1 to 10 carbon atoms, D is a halogen atom, —OCOR ¹⁵ or —OR ¹⁶ , p is an integer of 0 to 3), n is an integer of 0 to 10 Show.

By introducing a highly polarizable functional group into the substituents X ¹ to X ³ and Y ¹ to Y ³ , the thickness direction retardation (Rth) of the film is increased and the in-plane retardation (Re) is expressed. The sex can be increased. A film having a high Re developability can increase the Re value by stretching in the film forming process.

As the norbornene-based addition (co) polymer, those disclosed in JP-A-10-7732, JP-T 2002-504184, US2004229157A1 or International Publication No. 2004 / 070463A1 may be used. it can. It can be obtained by addition polymerization of norbornene-based polycyclic unsaturated compounds. If necessary, norbornene-based polycyclic unsaturated compounds and conjugated dienes such as ethylene, propylene, butene, butadiene and isoprene; non-conjugated dienes such as ethylidene norbornene; acrylonitrile, acrylic acid, methacrylic acid, maleic anhydride It is also possible to carry out addition polymerization with linear diene compounds such as acid, acrylic acid ester, methacrylic acid ester, maleimide, vinyl acetate and vinyl chloride. As this norbornene type addition (co) polymer, a commercial item can also be used. Specifically, grades such as APL8008T (Tg70 ° C), APL6013T (Tg125 ° C), or APL6015T (Tg145 ° C), which are sold under the trade name of Apel from Mitsui Chemicals, Inc. and have different glass transition temperatures (Tg), are used. There is. Pellets such as TOPAS 8007, 6013, and 6015 are sold by Polyplastics Co., Ltd. Further, Appear 3000 is sold by Ferrania.

Norbornene-based polymer hydrides are disclosed in JP-A-1-240517, JP-A-7-196736, JP-A-60-26024, JP-A-62-19807, JP-A-2003-1159767, or As disclosed in Japanese Patent Application Laid-Open No. 2004-309979 and the like, those prepared by hydrogenation after polycyclic unsaturated compounds are subjected to addition polymerization or metathesis ring-opening polymerization can be used. In the norbornene-based polymer used in the present invention, R ⁵ to R ⁶ are preferably a hydrogen atom or —CH ₃ , X ³ and Y ³ are preferably a hydrogen atom, Cl, —COOCH ₃ , and other groups are appropriately selected. The This norbornene-based resin may be a commercially available product. Specifically, JSR Co., Ltd. is sold under the trade name of Arton G or Arton F, and ZEONOR from Nippon Zeon Co., Ltd. ) ZF14, ZF16, Zeonex 250 or ZEONEX 280 are commercially available and can be used.

The cyclic polyolefin resin that can be used in the present invention has a mass average molecular weight (Mw) measured by gel permeation chromatography (GPC) of 5,000 to 1,000,000 in terms of polystyrene molecular weight. It is preferably 10,000 to 500,000, more preferably 50,000 to 300,000. Moreover, it is preferable that molecular weight distribution (Mw / Mn; Mn is the number average molecular weight measured by GPC) is 10 or less, More preferably, it is 5.0 or less, More preferably, it is 3.0 or less. The glass transition temperature (Tg; measured by DSC) is preferably 50 to 350 ° C., more preferably 80 to 330 ° C., still more preferably 100 to 300 ° C.

(Cellulosic resin)
The cellulose resin that can be used in the present invention is not particularly limited as long as the substitution degree of all acyl groups is 2.0 to 2.95. The cellulose resin is preferably a cellulose ester, and more preferably cellulose acylate. Examples of the raw material cellulose for the cellulose resin include cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose resins obtained from any raw material cellulose can be used, and in some cases, they may be mixed and used. Detailed descriptions of these raw material celluloses can be found in, for example, Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970), and the Japan Institute of Invention and Innovation Technical Bulletin No. 2001. The cellulose described in No.-1745 (pages 7 to 8) can be used.

(Cellulose ester)
The cellulose ester that can be preferably used in the present invention will be described in detail. The β-1,4-bonded glucose unit constituting cellulose has free hydroxyl groups at the 2nd, 3rd and 6th positions. The cellulose ester is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio in which the hydroxyl groups of cellulose located at the 2-position, 3-position and 6-position are esterified (100% esterification has a substitution degree of 1).
The total acyl substitution degree, that is, DS2 + DS3 + DS6 is preferably 2.1 to 2.9, more preferably 2.1 to 2.7, and particularly preferably 2.3 to 2.6. DS6 / (DS2 + DS3 + DS6) is preferably 0.08 to 0.66, more preferably 0.15 to 0.60, and still more preferably 0.20 to 0.45. Here, DS2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS3 is the degree of substitution of the hydroxyl group at the 3-position with an acyl group (hereinafter, referred to as “acyl group”). DS6 is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”). DS6 / (DS2 + DS3 + DS6) is the ratio of the acyl substitution degree at the 6-position to the total acyl substitution degree, and is hereinafter also referred to as “acyl substitution rate at the 6-position”.

Only one type of acyl group may be substituted, or two or more types of acyl groups may be substituted. The cellulose resin preferably has an acyl group having 2 to 4 carbon atoms as a substituent. The acyl group having 2 to 4 carbon atoms is preferably a propionyl group or a butyryl group. When two or more types of acyl groups are used, one of them is preferably an acetyl group. DSA is the sum of the substitution degrees of the hydroxyl groups at the 2nd, 3rd and 6th positions by the acetyl group, and DSB is the sum of the substitution degrees of the 2nd, 3rd and 6th hydroxyl groups by the propionyl group or butyryl group. The value is preferably from 2.0 to 2.9. More preferably, the DSA + DSB value is 2.3 to 2.8, and the DSB value is 0.10 to 1.70. More preferably, the value of DSA + DSB is 2.40 to 2.50, and the value of DSB is 0.5 to 1.2. It is preferable that the DSA and DSB values be in the above ranges because a film having a small change in Re value and Rth value due to environmental humidity can be obtained.
Further, 28% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 30% or more is a substituent at the 6-position hydroxyl group, and 31% or more is a substituent at the 6-position hydroxyl group. More preferably, 32% or more is particularly preferably a substituent of the hydroxyl group at the 6-position. These cellulose esters can produce a solution having preferable solubility, and in particular, a non-chlorine organic solvent can be used to produce a good solution. Furthermore, it becomes possible to produce a solution having a low viscosity and good filterability.

The acyl group having 2 or more carbon atoms of the cellulose ester may be an aliphatic group or an aryl group and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples thereof include propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, isobutanoyl, tert -Butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable. is there.

In the acylation of cellulose, when an acid anhydride or acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent.

As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), Basic compounds are used.

The most common industrial synthesis method of cellulose mixed fatty acid ester is to use cellulose corresponding to fatty acid corresponding to acetyl group and other acyl groups (acetic acid, propionic acid, valeric acid, etc.) or their acid anhydrides. This is a method of acylating with a mixed organic acid component.

The cellulose ester that can be used in the present invention can be synthesized, for example, by the method described in JP-A-10-45804.

(Additive)
The film of the present invention may contain an additive. The additive will be described below.
As the additive, for example, known low molecular weight additives and high molecular weight additives can be widely employed as additives for cellulose acylate films and cyclic polyolefin films.

(Low molecular weight additive)
The film of the present invention preferably contains at least one additive represented by the following general formulas (1) to (5) as an additive.

First, the additives of the general formulas (1) and (2) will be described.
In the general formula (1), R ¹ represents an alkyl group or an aryl group, and R ² and R ³ each independently represent a hydrogen atom, an alkyl group, or an aryl group. Moreover, it is particularly preferable that the total number of carbon atoms of R ¹ , R ² and R ³ is 10 or more. In the general formula (2), R ⁴ and R ⁵ each independently represents an alkyl group or an aryl group. The total number of carbon atoms of R ⁴ and R ⁵ is 10 or more, and each of the alkyl group and aryl group may have a substituent. As the substituent, a fluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfone group, and a sulfonamide group are preferable, and an alkyl group, an aryl group, an alkoxy group, a sulfone group, and a sulfonamide group are particularly preferable. Further, the alkyl group may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 6 to 25, and more preferably 6 to 20 (Eg, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, heptyl, octyl, bicyclooctyl, nonyl, adamantyl, decyl, t-octyl, undecyl, Dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, didecyl) are particularly preferred. As the aryl group, those having 6 to 30 carbon atoms are preferable, and those having 6 to 24 carbon atoms (for example, phenyl, biphenyl, terphenyl, naphthyl, binaphthyl, triphenylphenyl) are particularly preferable.
Details of these additives are described in JP-A-2005-139304, [0016] to [0022].

Next, the additive of General formula (3), (4), (5) is demonstrated.
In formula (3), R ¹¹ represents an aryl group. R ¹² and R ¹³ each independently represents an alkyl group or an aryl group, and at least one of them is an aryl group. Moreover, the alkyl group and the aryl group may each have a substituent.
In formula (4), R ²¹ , R ²² and R ²³ each independently represents an alkyl group. Moreover, each alkyl group may have a substituent.
In formula (5), R ³¹ , R ³² , R ³³ and R ³⁴ each represent a hydrogen atom, a substituted or unsubstituted aliphatic group, or a substituted or unsubstituted aromatic group. X ³¹ , X ³² , X ³³ and X ³⁴ are each a single bond, —CO— and NR ³⁵ — (R ³⁵ represents a substituted or unsubstituted aliphatic group or a substituted or unsubstituted aromatic group) Represents a divalent linking group formed from one or more groups selected from the group consisting of: a, b, c and d are integers of 0 or more, and a + b + c + d is 2 or more. Z ³¹ represents an (a + b + c + d) -valent organic group (excluding a cyclic group).
Details of these additives are described in JP-A-2007-272177, [0075] to [0085].

(Retardation adjuster)
The stretched film of the present invention may contain a retardation adjusting agent. From the viewpoint of increasing the (Rth / Re) value, a compound having one or more aromatic rings is preferable, a compound having 2 to 15 aromatic rings is more preferable, and a compound having 3 to 10 aromatic rings is more preferable. The atoms other than the aromatic ring in the compound are preferably arranged in the same plane as the aromatic ring, and when there are a plurality of aromatic rings, the aromatic rings are also arranged in the same plane. Is preferred. Further, in order to selectively increase the Rth value, the presence state of the additive in the film is preferably such that the aromatic ring plane is in a direction parallel to the film surface. Specific examples of such compounds are described, for example, as “retardation increasing agents” on pages 6 to 38 of JP-A No. 2006-235483, and these can be used as appropriate. Particularly preferred.

(High molecular weight additive)
The polymer additive is selected from polyester polymers, styrene polymers, acrylic polymers, and copolymers thereof, and aliphatic polyesters, aromatic polyesters, acrylic polymers, and styrene polymers are preferable. In addition, it is preferable to include at least one polymer having negative intrinsic birefringence, such as a styrene polymer and an acrylic polymer.

(Polyester polymer)
The polyester polymer used in the present invention comprises a mixture of an aliphatic dicarboxylic acid having 2 to 20 carbon atoms and an aromatic dicarboxylic acid having 8 to 20 carbon atoms, an aliphatic diol having 2 to 12 carbon atoms, and 4 to 20 carbon atoms. Those obtained by reaction with at least one diol selected from alkyl ether diols and aromatic diols having 6 to 20 carbon atoms are preferred. Although both ends of the reaction product may remain as the reaction product, so-called end-capping may be carried out by further reacting monocarboxylic acids, monoalcohols or phenols. It is effective in terms of preservability that the end capping is performed in order not to contain free carboxylic acids. The dicarboxylic acid used in the polyester polymer is preferably an aliphatic dicarboxylic acid residue having 4 to 20 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 20 carbon atoms.

Examples of the aliphatic dicarboxylic acid having 2 to 20 carbon atoms preferably used in the present invention include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, and azelaic acid. , Sebacic acid, dodecanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid.
Examples of the aromatic dicarboxylic acid having 8 to 20 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8 -Naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid.

Among these, preferred aliphatic dicarboxylic acids are malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and 1,4-cyclohexanedicarboxylic acid. As the aromatic dicarboxylic acid, phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, and 1,4-naphthalenedicarboxylic acid are preferable. Particularly preferably, the aliphatic dicarboxylic acid component is succinic acid, glutaric acid, and adipic acid, and the aromatic dicarboxylic acid is phthalic acid, terephthalic acid, and isophthalic acid.

The aforementioned aliphatic dicarboxylic acid and aromatic dicarboxylic acid are used in combination of at least one of them, but the combination is not particularly limited, and there is no problem even if several kinds of each component are combined.

Diols or aromatic ring-containing diols used for high molecular weight additives include, for example, aliphatic diols having 2 to 20 carbon atoms, alkyl ether diols having 4 to 20 carbon atoms, and aromatic ring-containing diols having 6 to 20 carbon atoms. It is chosen from.

Examples of the aliphatic diol having 2 to 20 carbon atoms include alkyl diols and alicyclic diols such as ethane diol, 1,2-propane diol, 1,3-propane diol, 1,2-butane. Diol, 1,3-butanediol, 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-1,3propanediol (3,3-dimethylolheptane), 3 -Methyl-1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. Or it is used as a mixture of two or more.

Preferred aliphatic diols include ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1 , 4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, particularly preferred Is ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- Hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol.

Examples of the alkyl ether diol having 4 to 20 carbon atoms preferably include polytetramethylene ether glycol, polyethylene ether glycol, polypropylene ether glycol, and combinations thereof. The average degree of polymerization is not particularly limited, but is preferably 2 to 20, more preferably 2 to 10, further 2 to 5, and particularly preferably 2 to 4. Examples of these typically commercially available polyether glycols include Carbowax resin, Pluronics® resin and Niax resin.

Examples of the aromatic diol having 6 to 20 carbon atoms include, but are not limited to, bisphenol A, 1,2-hydroxybenzene, 1,3-hydroxybenzene, 1,4-hydroxybenzene, and 1,4-benzenedimethanol. Of these, bisphenol A, 1,4-hydroxybenzene, and 1,4-benzenedimethanol are preferred.

In particular, a high molecular weight additive having a terminal sealed with an alkyl group or an aromatic group is preferred. This is because the terminal is protected with a hydrophobic functional group, which is effective against deterioration with time at high temperature and high humidity, and is due to the role of delaying hydrolysis of the ester group.
It is preferable to protect with a monoalcohol residue or a monocarboxylic acid residue so that both ends of the polyester additive do not become carboxylic acid or OH group.
In this case, the monoalcohol is preferably a substituted or unsubstituted monoalcohol having 1 to 30 carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol. , Octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, aliphatic alcohols such as dodecaoctanol, allyl alcohol, oleyl alcohol, benzyl alcohol, 3-phenyl Examples include substituted alcohols such as propanol.

End-capping alcohols that can be preferably used are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, isononyl alcohol, oleyl alcohol Benzyl alcohol, in particular methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, benzyl alcohol.

In the case of sealing with a monocarboxylic acid residue, the monocarboxylic acid used as the monocarboxylic acid residue is preferably a substituted or unsubstituted monocarboxylic acid having 1 to 30 carbon atoms. These may be aliphatic monocarboxylic acids or aromatic ring-containing carboxylic acids. Preferred aliphatic monocarboxylic acids are described, for example, acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, oleic acid, and examples of the aromatic ring-containing monocarboxylic acid include Benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc. Yes, these can be used alone or in combination of two or more.

Such additives may be synthesized by a conventional method, a hot melt condensation method using a polyesterification reaction or a transesterification reaction between the dicarboxylic acid and a diol and / or a monocarboxylic acid or monoalcohol for end-capping, or by using these acids. It can be easily synthesized by any of the interfacial condensation methods of acid chloride and glycols. These polyester-based additives are described in detail in Koichi Murai, “Additives, Theory and Application” (Kokaibo Co., Ltd., first edition published on March 1, 1973). Also, JP-A Nos. 05-155809, 05-155810, JP-A-5-97073, JP-A-2006-259494, JP-A-07-330670, JP-A-2006-342227, JP-A-2007-003679. The materials described in each publication can also be used.
Although the specific example of the polyester-type polymer which can be used by this invention is described below, it is not limited to these.

In Table 1, PA is phthalic acid, TPA is terephthalic acid, IPA is isophthalic acid, AA is adipic acid, SA is succinic acid, 2,6-NPA is 2,6-naphthalenedicarboxylic acid, 2 , 8-NPA is 2,8-naphthalenedicarboxylic acid, 1,5-NPA is 1,5-naphthalenedicarboxylic acid, 1,4-NPA is 1,4-naphthalenedicarboxylic acid, 1,8-NPA is 1,8-naphthalenedicarboxylic acid is shown respectively.

The polyester-based polymer preferably has a number average molecular weight of 700 to 10,000, more preferably a number average molecular weight of 800 to 8000, still more preferably a number average molecular weight of 800 to 5000, and particularly preferably a number average molecular weight of 1,000 to 5,000. is there. By setting it as such a range, it is more excellent in compatibility.

(Styrene polymers and acrylic polymers)
As the additive, a compound having a structure represented by the following general formula (9) (styrene polymer) or a compound having a structure represented by the following general formula (10) (acrylic polymer) is also preferable.

{In the general formulas (9) and (10), R ⁴¹ to R ⁴⁸ may each independently have a hydrogen atom; a halogen atom; an oxygen atom, a sulfur atom, a nitrogen atom or a silicon atom-containing linking group. A substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms; or a polar group, and R ⁴⁴ are all bonded to each other whether they are the same atom or group, or different atoms or groups. Then, a carbocycle or a heterocycle (these carbocycles and heterocycles may have a monocyclic structure or other rings may be condensed to form a polycyclic structure) may be formed. }

The general formula (9) is a structural unit obtained from an aromatic vinyl monomer. Specific examples of the aromatic vinyl monomers include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen substitution such as 4-chlorostyrene and 4-bromostyrene. Styrenes; hydroxystyrenes such as p-hydroxystyrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, 3,4-dihydroxystyrene; vinyl benzyl alcohols; p-methoxystyrene, p- alkoxy-substituted styrenes such as t-butoxystyrene and mt-butoxystyrene; vinyl benzoic acids such as 3-vinylbenzoic acid and 4-vinylbenzoic acid; methyl-4-vinylbenzoate, ethyl-4-vinylbenzoate, and the like Vinyl benzoates; 4-vinyl benzyl ester Tate; 4-acetoxystyrene; amide styrenes such as 2-butylamidostyrene, 4-methylamidostyrene, p-sulfonamidostyrene; 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline, vinylbenzyldimethylamine Aminostyrenes such as 3-nitrostyrene, nitrostyrenes such as 4-nitrostyrene; cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; arylstyrenes such as phenylstyrene, indenes However, the present invention is not limited to these specific examples. Two or more of these monomers may be used as a copolymerization component. Of these, styrene and α-methylstyrene are preferable because they are easily available industrially and are inexpensive.

General formula (10) is a structural unit obtained from an acrylate monomer. Examples of the acrylate monomer include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-) Pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), acrylic acid Nonyl (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2- Hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid (2-methoxyethyl), acrylic acid Phosphoric acid (2-ethoxyethyl) phenyl acrylate, phenyl methacrylate, acrylic acid (2 or 4-chlorophenyl), methacrylic acid (2 or 4-chlorophenyl), acrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), Methacrylic acid (2 or 3 or 4-ethoxycarbonylphenyl), acrylic acid (o or m or p-tolyl), methacrylic acid (o or m or p-tolyl), benzyl acrylate, benzyl methacrylate, phenethyl acrylate, Phenethyl methacrylate, acrylic acid (2-naphthyl), cyclohexyl acrylate, cyclohexyl methacrylate, acrylic acid (4-methylcyclohexyl), methacrylic acid (4-methylcyclohexyl), acrylic acid (4-ethylcyclohexyl), methacrylate Examples thereof include luric acid (4-ethylcyclohexyl) and the like, or those obtained by replacing the above acrylic ester with a methacrylic ester, but the present invention is not limited to these specific examples. Two or more of these monomers may be used as a copolymerization component. Of these, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), or a methacrylic ester instead of the acrylate is preferred.

The additive may be a copolymer including both the structure represented by the general formula (9) and the structure represented by the general formula (10). Moreover, it is preferable that it is a thing excellent in the said monomer and copolymerization as another structure which comprises a copolymer composition. Examples include maleic anhydride, citraconic anhydride, cis-1-cyclohexene-1,2-dicarboxylic anhydride, 3-methyl-cis-1-cyclohexene-1,2-dicarboxylic anhydride, 4-methyl-cis-1 -Acid anhydrides such as cyclohexene-1,2-dicarboxylic anhydride, nitrile group-containing radical polymerizable monomers such as acrylonitrile, methacrylonitrile; amides such as acrylamide, methacrylamide, trifluoromethanesulfonylaminoethyl (meth) acrylate Bond-containing radical polymerizable monomers; Fatty acid vinyls such as vinyl acetate; Chlorine-containing radical polymerizable monomers such as vinyl chloride and vinylidene chloride; Conjugates such as 1,3-butadiene, isoprene and 1,4-dimethylbutadiene Diolefins can be mentioned but are not limited to these Not to.

When using the copolymer as described above, it is preferable to contain at least 30 mol% of the structure represented by the general formula (9) in the copolymer composition. Moreover, it is preferable that the structure shown by General formula (10) is included at least 20 mol% or more. Moreover, it is preferable that the ratio of another copolymerization component is 50 mol% or less.

The weight average molecular weight of the compound having the structure represented by the general formula (9) or (10) is preferably 500 or more and 300,000 or less, and is excellent in compatibility with the binder and transparency of the film after film formation. In order to obtain a film exhibiting good expression of characteristics, it is more preferably 500 or more and 15000 or less, and particularly preferably 500 or more and 5000 or less. The weight average molecular weight of the compound is a value measured by GPC (developing solvent: tetrahydrofuran, polystyrene conversion method).

(Additive synthesis method)
The additives preferably used in the present invention described above can also be synthesized.
For example, the additive of the general formula (1) can be obtained by a condensation reaction between a sulfonyl chloride derivative and an amine derivative. The compound of the general formula (2) can be obtained by oxidation reaction of sulfide or Friedel-Crafts reaction of aromatic compound and sulfonic acid chloride.

(Addition amount of additive)
The additive amount represented by the general formulas (1) to (5) preferably used in the present invention is, for example, 5% by mass or more with respect to the resin constituting the film. The content is preferably 5 to 40% by mass, and more preferably 20 to 30% by mass. If the amount added is less than 5% by mass, the moisture content * oxygen permeability value is (1) low: poor polarizing plate bonding suitability and easy to peel off after polarizing plate processing (2) high: wet heat durability test The problem of poor durability may occur.
Moreover, the said additive may be used 1 type, or may use 2 or more types. When two or more types are used, the addition amount of two or more types of additives is preferably 5 to 40% by mass, more preferably 20 to 30% by mass of the resin constituting the film. Is more preferable.

The compound having the structure represented by the general formula (9) or (10) preferably used in the present invention described above is preferably 5 to 40% by mass of the resin constituting the film, and the transparency after film formation In order to obtain a film that is excellent in optical properties and exhibits good optical properties, it is more preferably 20 to 30% by mass.

These compounds having the structure represented by the general formula (9) or (10) may be used alone or in combination of two or more compounds at an arbitrary ratio.

The total content of the compounds having a structure represented by two or more types of the general formula (9) or (10) is preferably 5 to 40% by mass of the resin constituting the film. In order to obtain a film that is excellent and exhibits good optical properties, it is more preferably 20 to 30% by mass.

(Method of adding additives)
Moreover, these additives may be used independently or may mix and use 2 or more types of additives by arbitrary ratios.
Furthermore, the timing for adding these additives may be any of the steps for preparing a solution (dope) of the resin constituting the film, or may be performed at the end of the dope preparation step.
The amount is preferably 5 to 40% by mass, more preferably 8 to 35% by mass, and still more preferably 10 to 30% by mass with respect to the polymer contained in the film.

(Fine particles)
By adding fine particles to the film of the present invention, the film formation stability and processability of the film can be further improved, and the optical unevenness of the film due to winding crease can be reduced. As fine particles that can be used in the present invention, fine particles of organic or inorganic compounds can be used.

Inorganic compounds include silicon-containing compounds, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, barium oxide, zirconium oxide, strongtium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, clay, Preferred are calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate, and more preferred are inorganic compounds and metal oxides containing silicon. That is, in the present invention, a metal oxide or an inorganic silicon compound is preferably used as the fine particles. In the present invention, since the turbidity of the film can be reduced, silicon dioxide is particularly preferably used. As the silicon dioxide fine particles, for example, commercially available products having a trade name such as Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) can be used. As the fine particles of zirconium oxide, for example, those commercially available under trade names such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.

Examples of the organic compound include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, starch and the like, and pulverized and classified products thereof. Alternatively, a polymer compound synthesized by a suspension polymerization method, a polymer compound made spherical by a spray drying method, a dispersion method, or the like can be used.

The primary average particle diameter of the fine particles is preferably 0.001 μm to 20 μm, more preferably 0.001 μm to 10 μm, and still more preferably 0.002 μm to 1 μm, from the viewpoint of keeping the haze low. Particularly preferably, the thickness is 0.005 μm to 0.5 μm. The measurement of the primary average particle diameter of the fine particles is obtained by the average particle diameter of the particles with a transmission electron microscope. The purchased fine particles are often agglomerated and are preferably dispersed by a known method before use. The secondary particle diameter is preferably 0.2 μm to 1.5 μm by dispersion, and more preferably 0.3 μm to 1 μm. The addition amount of fine particles is preferably 0.01 to 0.3 parts by mass, more preferably 0.05 to 0.2 parts by mass, and 0.08 parts by mass with respect to 100 parts by mass of the resin constituting the film. Most preferred is 0.12 parts by mass.

When the particles are dispersed, the haze increases and the transparency is reduced. Therefore, the average particle diameter is preferably 0.001 μm to 100 μm, more preferably 0.01 μm to 10 μm, and still more preferably 0.01 μm. ~ 5 μm.
Further, the content is preferably 0.0001% by mass to 10% by mass in the whole film regardless of the case where it is dispersed in the form of particles such as spheres and irregular shapes, or in the form of molecules. Is 0.001% by mass to 5% by mass, more preferably 0.01% by mass to 3% by mass.

The preferable light transmittance range of the film of the present invention is 88.0% or more, more preferably 89.0% or more, and particularly preferably 90.0% or more. The transmittance was measured at a measurement wavelength of 550 nm with a spectrophotometer (U-3210, Hitachi, Ltd.) at 25 ° C. and 60% RH for a 13 mm × 40 mm sample.

The method of incorporating the above compound into the film is not particularly limited, but a method of casting a solution containing the resin constituting the film and the above compound to form a film, and the resin constituting the film into the film after casting. Examples thereof include a method of applying a coating solution containing the above compound or a method of casting in multiple layers. In this invention, it is preferable to manufacture a film by either of the following two manufacturing methods.
1. A method for producing a film comprising a resin constituting a film and a step of dissolving or dispersing at least one compound in a solvent, a step of casting, a step of drying, and a step of winding.
2. A method for producing a film comprising a step of dissolving a resin constituting a film in a solvent, a step of casting, a step of drying, and a step of winding, wherein at least one surface of the film after casting A method for producing a film comprising a step of applying a coating liquid containing at least one compound on the top.
It is more preferable that the film is produced by one of the above two methods, and a film suitable as an optical film having excellent flatness and uniformity can be produced.

In the above method 1, a solution containing the resin constituting the film and the above compound is cast to form a film. In the case of this method, the compound may be dissolved or dispersed when preparing the resin solution constituting the film, or the compound solution or dispersion may be added immediately before casting the resin solution constituting the film. It may be added. In preparing the dispersion, known methods such as a normal stirrer, a soft high-speed stirrer for a homogenizer, a dispersion using a medium such as a ball mill, a paint shaker, and a dyno mill, and an ultrasonic disperser can be used. When the above compound is dispersed in the resin solution constituting the film, a small amount of a surfactant or polymer usually used as a dispersion aid may be added.

In the above method 2, the “coating liquid” may contain the above compound as a main component. Simply apply a solution or dispersion obtained by dissolving or dispersing the above compound in a suitable solvent onto the surface of a layer (ie, a film after casting) containing a resin as a main component (ie, a film after casting). A liquid may be applied. Moreover, the coating liquid may contain the binder, and the layer containing the said compound may be formed by coating this coating liquid.
The coating liquid can be applied to one side or both sides of a layer mainly composed of a resin constituting the film.

The binder for forming the compound layer is not particularly limited, and may be a lipophilic binder or a hydrophilic binder. As the oleophilic binder, known thermoplastic resins, thermosetting resins, radiation curable resins, reactive resins, and mixtures thereof can be used.
The Tg of the resin is preferably 80 ° C. to 400 ° C., more preferably 120 ° C. to 350 ° C. The mass average molecular weight of the resin is preferably 10,000 to 1,000,000, more preferably 10,000 to 500,000. When the above compound is dispersed in the coating solution, the same dispersion method as the above-mentioned method 1 can be used, and a small amount of a surfactant or polymer usually used as a dispersion aid may be added.

Examples of the thermoplastic resin include vinyl chloride / vinyl acetate copolymers, vinyl chloride, copolymers of vinyl acetate and vinyl alcohol, maleic acid and / or acrylic acid, vinyl chloride / vinylidene chloride copolymers, vinyl chloride / Acrylonitrile copolymer, vinyl copolymer such as ethylene / vinyl acetate copolymer, cellulose derivatives such as nitrocellulose, cellulose acetate propionate, cellulose acetate butyrate resin, cyclic polyolefin resin, acrylic resin, polyvinyl acetal resin, Polyvinyl butyral resin, polyester polyurethane resin, polyether polyurethane, polycarbonate polyurethane resin, polyester resin, polyether resin, polyamide resin, amino resin, styrene butadiene resin, butadiene resin Rubber-based resins such as Rironitoriru resins, silicone resins, and fluorine resins.
The thickness of the layer containing the compound is preferably 0.0001 to 10 μm, more preferably 0.001 to 5 μm, and still more preferably 0.01 to 1 μm.
Further details of the film manufacturing method will be described later.

(Other additives)
In the film of the present invention, various additives (for example, deterioration inhibitors, UV inhibitors, peeling accelerators, plasticizers, infrared absorbers, etc.) depending on the use may be added in each production process of the film. They can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of an ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and a mixture of deterioration preventing agents are also possible. Furthermore, infrared absorbing dyes are described in, for example, JP-A-2001-194522. Moreover, the addition time may be added at any time in the resin solution (dope) production process of the resin constituting the film, but it is performed by adding an additive to the final preparation process of the dope preparation process. Also good. Furthermore, the amount of each material added is not particularly limited as long as the function is exhibited. Moreover, when a film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ.

(Deterioration inhibitor)
A known deterioration (oxidation) inhibitor such as 2,6-di-t-butyl, 4-methylphenol, 4,4′-thiobis- (6-t-butyl-3-) is added to the resin solution constituting the film. Methylphenol), 1,1′-bis (4-hydroxyphenyl) cyclohexane, 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, pentaerythrityl A phenolic or hydroquinone antioxidant such as tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] can be added. Further, tris (4-methoxy-3,5-diphenyl) phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, bis (2,6-di-t It is preferable to add a phosphorus-based antioxidant such as -butyl-4-methylphenyl) pentaerythritol diphosphite and bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite. The antioxidant is added in an amount of 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the resin constituting the film.

(UV absorber)
From the viewpoint of preventing the deterioration of the polarizing plate or the liquid crystal, an ultraviolet absorber can be added to the resin solution constituting the film. As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having a small absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specific examples of ultraviolet absorbers preferably used in the present invention include, for example, hindered phenol compounds, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds Etc. Examples of hindered phenol compounds include 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]. N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert) -Butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate and the like. Examples of benzotriazole compounds include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5- Triazine, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-tert-butyl-4- Hydroxy-hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5 -Chlorobenzotriazole, 2,6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and the like. The addition amount of these ultraviolet light inhibitors is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm by mass in the whole film.

(Plasticizer)
A plasticizer can be added to the film of the present invention. Specifically, phthalate ester, trimellitic ester, aliphatic dibasic ester, orthophosphate ester, acetate ester, polyester / epoxidized ester, ricinoleate ester, polyolefin, polyethylene A glycol type compound can be mentioned.

The plasticizer that can be used is preferably selected from a compound having a normal temperature, normal pressure, liquid, and a boiling point of 200 ° C. or higher. As specific compound names, the following can be exemplified.
Examples of the aliphatic dibasic acid ester system include dioctyl adipate (230 ° C./760 mmHg), dibutyl adipate (145 ° C./4 mmHg), di-2-ethylhexyl adipate (335 ° C./760 mmHg), dibutyl diglycol adipate (230-240). ° C / 2mmHg), di-2-ethylhexyl azelate (220-245 ° C / 4mmHg), di-2-ethylhexyl sebacate (377 ° C / 760mmHg), etc .; as the phthalate ester system, for example, diethyl phthalate (298 ° C / 760 mmHg), diheptyl phthalate (235 to 245 ° C./10 mm Hg), di-n-octyl phthalate (210 ° C./760 mm Hg), diisodecyl phthalate (420 ° C./760 mm Hg), etc .; Paraffin waxes (average molecular weight 330-600, melting point 45-80 ° C), liquid paraffins (JIS standard K2231 ISOVG8, VG15, VG32, VG68, VG100, etc.), paraffin pellets (Melting point 56-58 ° C., 58-60 ° C., 60-62 ° C., etc.), chlorinated paraffin, low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight polyisobutene, hydrogenated polybutadiene, hydrogenated polyisoprene, squalane and the like. it can.

The amount of the plasticizer added is 0.5 to 40.0 parts by mass, preferably 1.0 to 30.0 parts by mass, and more preferably 3.0 to 100 parts by mass of the resin constituting the film. To 20.0 parts by mass. If the added amount of the plasticizer is less than this, the plastic effect is insufficient and the processability is not improved. On the other hand, the plasticizer may be separated and eluted over time for a long time, which is not preferable because optical unevenness and contamination of other parts occur.

Hereafter, the manufacturing method of the film of this invention is demonstrated in detail. As a solution casting method, a film can be manufactured by either of the following two manufacturing methods.
1. A method for producing a film comprising a resin constituting a film, and optionally a step of dissolving or dispersing at least one compound in a solvent, a step of casting, a step of drying, and a step of winding.
2. A method for producing a film, comprising a step of dissolving a resin constituting a film in a solvent, a step of casting, a step of drying, and a step of winding, wherein, if desired, at least the film after casting The manufacturing method of the film including the process of coating the coating liquid containing an at least 1 sort (s) of compound on one surface.
Moreover, it extends | stretches after the said casting process.

Note that the two production methods 1 and 2 differ in how the compound is incorporated into the film. In the method 1 described above, the compound is dissolved or dispersed in the same layer with respect to the layer containing the resin constituting the film as the main component, whereas in the method 2 the layer containing the resin constituting the film as the main component. However, it differs in that a coating solution containing a compound is applied.
Hereinafter, the steps from (dissolving step, dope preparation) to (winding step after drying) will be described in detail for each step. The manufacturing method of 1 described above is dissolved or dispersed in (dissolving step, dope preparation). , Except for the addition, is the same as the production method of 2 above.

(Dissolution process, dope preparation)
First, each material component is dissolved in a solvent described later to prepare a resin solution (dope) constituting the film. As for the preparation of the dope, a method by stirring and dissolving at room temperature, a method of cooling and dissolving by stirring at room temperature to swell the resin constituting the film, cooling from -20 to -100 ° C., and heating again to 20 to 100 ° C. And a high-temperature dissolution method that dissolves at a temperature equal to or higher than the boiling point of the main solvent in a closed container, and a method that dissolves at a high temperature and high pressure up to the critical point of the solvent. Resins having good solubility are preferably dissolved at room temperature, but resins having poor solubility are dissolved by heating in a sealed container. If the solubility is not so bad, it is more efficient to select a temperature as low as possible.

In the present invention, the viscosity of the dope is preferably in the range of 1 to 500 Pa · s at 25 ° C. More preferably, it is in the range of 5 to 200 Pa · s. Viscosity can be measured by using 1 mL of a sample solution in a rheometer (CLS 500) using a Steel Cone (both manufactured by TA Instruments) with a diameter of 4 cm / 2 °. Measurement is started after the sample solution is kept warm at the measurement start temperature until the liquid temperature becomes constant.

Describe the solvent used to prepare the dope. In the present invention, the solvent that can be used is not particularly limited as long as the object can be achieved as long as the resin or the like constituting the film can be dissolved and cast and formed. The solvent used in the present invention is, for example, a solvent selected from chlorinated solvents such as dichloromethane and chloroform, chain hydrocarbons having 3 to 12 carbon atoms, cyclic hydrocarbons, aromatic hydrocarbons, esters, ketones and ethers. preferable. The ester, ketone and ether may have a cyclic structure. Examples of chain hydrocarbons having 3 to 12 carbon atoms include hexane, octane, isooctane and decane. Examples of cyclic hydrocarbons having 3 to 12 carbon atoms include cyclopentane, cyclohexane and derivatives thereof. Examples of the aromatic hydrocarbon having 3 to 12 carbon atoms include benzene, toluene, xylene and the like. Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The preferable boiling point of the organic solvent is 35 ° C. or more and 150 ° C. or less. The solvent used in the present invention can be used by mixing two or more kinds of solvents in order to adjust solution properties such as drying property and viscosity, and further, as long as the resin constituting the film is dissolved in the mixed solvent. It is also possible to add a poor solvent.

A preferred poor solvent can be appropriately selected depending on the polymer type to be used. When a chlorinated organic solvent is used as the good solvent, alcohols can be preferably used. The alcohols may preferably be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbons are preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, and the like. Among the poor solvents, monohydric alcohols have a peeling resistance reducing effect and can be preferably used. Particularly preferred alcohols vary depending on the good solvent selected, but considering the drying load, alcohols having a boiling point of 120 ° C. or lower are preferred, monohydric alcohols having 1 to 6 carbon atoms are more preferred, and those having 1 to 4 carbon atoms are preferred. Alcohols can be used particularly preferably. A particularly preferred mixed solvent is a combination in which dichloromethane is the main solvent and one or more alcohols selected from methanol, ethanol, propanol, isopropanol, or butanol are poor solvents.

The cyclic polyolefin solution is characterized in that a high concentration dope can be obtained by appropriately selecting a solvent to be used, and a cyclic polyolefin solution having a high concentration and excellent stability can be obtained without relying on a means of concentration. . Furthermore, in order to make it easy to melt | dissolve, you may melt | dissolve at a low density | concentration and may concentrate using a concentration means. The concentration method is not particularly limited. For example, the low concentration solution is guided between the cylinder and the rotation trajectory of the outer periphery of the rotating blade rotating in the circumferential direction, and the temperature between the solution and the solution is determined. A method of obtaining a high-concentration solution while evaporating the solvent by giving a difference (for example, Japanese Patent Laid-Open No. 4-259511), blowing a heated low-concentration solution into the container from the nozzle, In which the solvent is flash evaporated and the solvent vapor is withdrawn from the container and the concentrated solution is withdrawn from the bottom of the container (eg, US Pat. No. 2,541,012, US Pat. No. 2,858,229, US Pat. No. 4,414,341, U.S. Pat. No. 4,504,355, etc.).

Prior to casting, it is preferable to filter off foreign matters such as undissolved matter, dust, and impurities using a suitable filter medium such as a wire mesh or flannel. For the filtration of the resin solution constituting the film, a filter having an absolute filtration accuracy of 0.1 μm to 100 μm is preferably used, and a filter having an absolute filtration accuracy of 0.5 μm to 25 μm is more preferable. The thickness of the filter is preferably 0.1 μm to 10 mm, more preferably 0.2 mm to 2 mm. In that case, the filtration pressure is preferably 1.6 MPa or less, more preferably 1.3 MPa or less, further 1.0 MPa or less, and particularly preferably 0.6 MPa or less. As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, and fluororesins such as tetrafluoroethylene resin can be preferably used, and ceramics and metals are also preferably used.

The viscosity of the dope just before film formation may be within a range that allows casting, and is usually adjusted to a range of 5 Pa · s to 1000 Pa · s, preferably 15 Pa · s to 500 Pa · s. More preferred is 30 Pa · s to 200 Pa · s. The temperature at this time is not particularly limited as long as it is a temperature at the time of casting, but is preferably −5 to 70 ° C., more preferably −5 to 35 ° C.

For the method and equipment for producing the film of the present invention, the same solution casting film forming method and solution casting film forming apparatus as those used for producing a film made of conventional cellulose triacetate are used. The dope prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations, and the dope is run endlessly from the die (slit) of the pressure die. The dry-dried dope film (also referred to as web) is peeled off from the metal support at a peeling point that is uniformly cast on the metal support and substantially rounds the metal support. Both ends of the obtained web are sandwiched between clips, transported with a tenter and dried, then transported with a roll group of a drying device, dried, and wound up to a predetermined length with a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. In the solution casting film forming method used for the functional protective film for electronic displays, in addition to the solution casting film forming apparatus, surface processing on films such as an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. Therefore, a coating device is often added. Although each manufacturing process is described briefly below, it is not limited to these.

The dope is preferably cast on an endless metal support, such as a metal drum or metal support (band or belt), and the solvent is evaporated to form a film. The dope before casting is preferably adjusted in concentration so that the amount of resin constituting the film is 10 to 35% by mass. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 30 ° C. or less, and particularly preferably at a metal support temperature of −50 to 20 ° C.
Further, JP 2000-301555, JP 2000-301558, JP 7-032391, JP 3-193316, JP 5-086212, JP 62-037113, JP 2-276607. The cellulose acylate film-forming techniques described in JP-A-55-014201, JP-A-2-111511, and JP-A-2-208650 can be applied in the present invention.

(Casting, multistory casting)
The dope may be cast as a single layer liquid on a smooth band or a drum as a metal support, or a plurality of dopes of two or more layers may be cast.
When casting a plurality of dopes, a film may be produced by casting and laminating the dopes from a plurality of casting openings provided at intervals in the traveling direction of the metal support. The methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be applied.
The film can also be formed by casting a dope from two casting ports. For example, Japanese Patent Publication No. 60-27562, Japanese Patent Laid-Open No. 61-94724, Japanese Patent Laid-Open No. 61-947245, Japanese Patent Laid-Open No. It can be carried out by the methods described in JP-A Nos. 61-104813, 61-158413, and 6-134933. Alternatively, a film casting method described in Japanese Patent Application Laid-Open No. 56-162617 may be a film casting method in which a flow of a high viscosity dope is wrapped with a low viscosity dope and the high and low viscosity dopes are extruded simultaneously. Furthermore, it is also a preferred embodiment that the outer solution described in JP-A-61-94724 and JP-A-61-94725 contains a larger amount of an alcohol component which is a poor solvent than the inner solution. Alternatively, the film is formed by peeling the film formed on the metal support by the first casting port using the two casting ports, and performing the second casting on the side in contact with the metal support surface. For example, it is a method described in Japanese Patent Publication No. 44-20235. The cast dope may be the same solution or different dope, and is not particularly limited. In order to give a function to a plurality of resin layers, a dope corresponding to the function may be extruded from each casting port. Further, the dope may be cast by simultaneously casting other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a matting agent layer, a UV absorbing layer, a polarizing layer).

In order to achieve the required film thickness with a single layer solution, it is necessary to extrude a high-concentration and high-viscosity dope. The flatness is poor, and it tends to be a problem. As a solution to this, by casting a plurality of dopes from a casting port, a highly viscous solution can be extruded onto a metal support at the same time, and the planarity is improved and an excellent planar film can be produced. In addition, by using a thick dope, a reduction in drying load can be achieved, and the production speed of the film can be increased.
In the case of co-casting, the inner and outer thicknesses are not particularly limited, but the outer side is preferably 1 to 50% of the total film thickness, more preferably 2 to 30%. Here, in the case of co-casting with three or more layers, the total thickness of the layer in contact with the metal support and the layer in contact with the air side is defined as the outer thickness. In the case of co-casting, a film having a laminated structure can be produced by co-casting the above-mentioned dopes having different additive concentrations. For example, a film having a structure of skin layer / core layer / skin layer can be produced. The deterioration inhibitor and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. It is also possible to change the type of deterioration inhibitor and ultraviolet absorber between the core layer and the skin layer. For example, the skin layer may contain a low volatility deterioration inhibitor and / or an ultraviolet absorber so that the core layer is plastic. It is also possible to add an excellent plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. Moreover, it is also a preferable aspect to contain a peeling accelerator only in the skin layer on the metal support side. It is also preferable to add more alcohol, which is a poor solvent, to the skin layer than the core layer in order to cool the metal support by the cooling drum method to gel the solution. The Tg of the skin layer and the core layer may be different, and the Tg of the core layer is preferably lower than the Tg of the skin layer. Further, the viscosity of the dope at the time of casting may be different between the skin layer and the core layer, and the viscosity of the skin layer is preferably smaller than the viscosity of the core layer, but the viscosity of the core layer is smaller than the viscosity of the skin layer. Also good.

(Casting)
As a dope casting method, a method of uniformly extruding the prepared dope from a pressure die onto a metal support, a method using a doctor blade for adjusting the film thickness of the dope once cast on the metal support with a blade Alternatively, there is a method using a reverse roll coater that adjusts with a reverse rotating roll, but a method using a pressure die is preferable. The pressure die includes a coat hanger type and a T die type, and any of them can be preferably used. In addition to the methods listed here, it can be carried out by various methods of casting a cellulose triacetate solution known in the art, and by setting each condition in consideration of differences in the boiling point of the solvent used, etc. The same effects as described in the above publication can be obtained. The endlessly running metal support used for producing the film of the present invention includes a drum whose surface is mirror-finished by chrome plating and a stainless steel belt whose surface is mirror-finished by surface polishing (may be called a band) Is used. One or two or more pressure dies used for producing the film of the present invention may be installed above the metal support. Preferably 1 or 2 groups. When two or more units are installed, the amount of dope to be cast may be divided into various ratios for each die, or the dope may be fed to the dies from each of a plurality of precision quantitative gear pumps. The temperature of the dope used for casting is preferably −10 to 55 ° C., more preferably 25 to 50 ° C. In that case, all of the processes may be the same, or may be different at various points in the process. If they are different, the temperature may be a desired temperature just before casting.

(Dry)
The drying of the dope on the metal support involved in the production of the film is generally performed by applying hot air from the surface side of the metal support (for example, drum or band), that is, the surface of the web on the metal support, Method of applying hot air from the back side of the band, contacting the temperature controlled liquid from the back side opposite to the band or drum dope casting surface, and heating the drum or band by heat transfer to control the surface temperature Although there are methods, the back surface liquid heat transfer method is preferable. The surface temperature of the metal support before casting may be any number as long as it is not higher than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the metal support, the temperature should be set to 1 to 10 degrees below the boiling point of the lowest boiling solvent used. Is preferred. This is not the case when the casting dope is cooled and peeled off without drying.

(Peeling)
When peeling a raw dry film from a metal support, if the peeling resistance (peeling load) is large, the film is irregularly stretched in the film forming direction, resulting in uneven optical anisotropy. In particular, when the peeling load is large, a portion stretched stepwise in the film forming direction and a portion unstretched are alternately generated, resulting in a distribution in retardation. When loaded in a liquid crystal display device, the line or strip becomes uneven. In order not to cause such a problem, it is preferable to set the peeling load of the film to 0.25 N or less per 1 cm of the film peeling width. The peeling load is more preferably 0.2 N / cm or less, further preferably 0.15 N or less, and particularly preferably 0.10 N or less. When the peeling load is 0.2 N / cm or less, even in a liquid crystal display device in which unevenness is likely to appear, no unevenness due to peeling is observed, which is particularly preferable. As a method for reducing the peeling load, there are a method of adding a release agent as described above and a method of selecting a solvent composition to be used.
The peel load is measured as follows. The dope is dropped on a metal plate having the same material and surface roughness as the metal support of the film forming apparatus, spread to a uniform thickness using a doctor blade, and dried. Cut the film with a cutter knife with a uniform width, peel off the tip of the film by hand and sandwich it with a clip connected to the strain gauge, and measure the load change while pulling up the strain gauge in an oblique 45 degree direction. The volatile content in the peeled film is also measured. The same measurement is performed several times by changing the drying time, and the peeling load at the same time as the residual volatile content at the peeling in the actual film forming process is determined. As the peeling speed increases, the peeling load tends to increase, and it is preferable to measure at a peeling speed close to the actual peeling speed.
A preferable residual volatile content at the time of peeling is 5% by mass to 60% by mass. 10% by mass to 50% by mass is more preferable, and 20% by mass to 40% by mass is particularly preferable. Peeling with a high volatile content is preferable because the drying rate can be increased and the productivity is improved. On the other hand, when the volatile content is high, the strength and elasticity of the film are small, and the film is cut or stretched against the peeling force. Further, the self-holding force after peeling is poor, and deformation, wrinkles and nicks are likely to occur. It also causes distribution in the retardation.

(Extension process)
The stretched film of the present invention is a film formed by the above-mentioned solution casting method, and has a temperature T satisfying the following formula I), where Rth (measured at λ = 590 nm) is 30 nm or more. It is a film formed by stretching.
Formula I) 0.2 ≦ (Rth (T) / Rth (I)) ≦ 0.9
In the formula, Rth (T) is Rth (measured at λ = 590 nm) of the film after being held at temperature T for 3 minutes while holding at least two sides of the film, and Rth (I) is This is the initial value of Rth of the film.
The temperature T can be determined by measuring the Tg of the film and then actually processing the film at each temperature of Tg / Tg + 30 ° C./Tg+60° C./Tg+90° C. and then evaluating each optical characteristic.

There is no particular limitation on the method of stretching the web. For example, a method in which a circumferential speed difference is applied to a plurality of rolls, and the roll circumferential speed difference is used to stretch the rolls in the longitudinal direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, or a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions. Of course, these methods may be used in combination. More specifically, when the clip portion is driven by the linear drive method, smooth stretching can be performed and the risk of breakage or the like can be reduced, so the tenter method is more preferable.

Any general stretching machine may be used. For example, stretching can be performed by a one-side five-chuck stretching method using a film biaxial stretching apparatus 11A9 manufactured by Imoto Seisakusho. In the method for producing an unstretched film, the temperature of the biaxial stretching apparatus is raised to the temperature T, and the film is grasped as quickly as possible by opening the lid in a stable state. Immediately close the lid and wait until the temperature reaches temperature T again. When the temperature reaches, leave it in that state for 3 minutes. When the incubation period is over, open the lid, remove the sample, and cool immediately.
Next, with respect to the stretched film, the temperature of the biaxial stretching apparatus is raised to the temperature T, and in a stable state, the lid is opened and the film is gripped as quickly as possible. Immediately close the lid and wait until the temperature reaches temperature T again. When the temperature reaches, it is left in that state for 1 min and stretching is started. Then open the lid, remove the sample and cool immediately.
In the formula I), it is more preferable that 0.5 ≦ (Rth (T) / Rth (I)) ≦ 0.8.

When the film is stretched, it is preferably carried out in a state where the solvent still remains in the film immediately after peeling. The purpose of stretching is (1) to obtain a film having excellent flatness without wrinkles and deformation, and (2) to increase the in-plane retardation of the film. When stretching is performed for the purpose of (1), stretching is performed at a relatively high temperature, and stretching is performed at a low magnification from 1% to 10% at most. A stretch of 2% to 5% is particularly preferred. When stretching for the purposes of both (1) and (2) or only for the purpose of (2), stretching is performed at a relatively low temperature and a stretching ratio of 5% to 150%.

The stretching of the film may be uniaxial stretching only in the longitudinal or lateral direction, or simultaneous or sequential biaxial stretching. The birefringence of the optical compensation film for a VA liquid crystal cell or OCB liquid crystal cell is preferably such that the refractive index in the width direction is larger than the refractive index in the length direction. Therefore, it is preferable to stretch more in the width direction.

The film of the present invention has a weight loss rate of 60% or less as measured by TG-DTA at a temperature T satisfying the formula I). If the weight loss rate is greater than 5%, it is not preferable because of thermal decomposition of molecules and volatilization substances contaminating the stretching process.
The weight reduction rate is preferably 4% or less, and more preferably 3% or less.
The weight reduction rate is obtained by weight reduction rate (%) = [{(initial film weight) − (film weight after holding at temperature T for 60 minutes)} / (initial film weight)] × 100. is there.

(Post-drying and winding process)
The film is further dried after stretching, and wound up with a residual volatile content of 2% or less.
The thickness of the finished stretched film (after drying) of the present invention varies depending on the purpose of use, but is usually in the range of 20 μm to 500 μm, preferably in the range of 30 μm to 150 μm, and in particular for liquid crystal display devices, it is 40 μm to 110 μm. Preferably there is.
The stretched film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like so as to obtain a desired thickness. The width of the stretched film obtained as described above is preferably 0.5 m to 3 m, more preferably 0.6 m to 2.5 m, and still more preferably 0.8 m to 2.2 m. If the width of the film is 0.5 m or more, the productivity is not reduced, and if it is 3 m or less, the web handling property is not deteriorated or the optical uniformity of the film is not reduced. This is preferable because undesirable phenomena such as streaks do not occur. The length is preferably 100 m to 10,000 m per roll, more preferably 500 m to 7000 m, and still more preferably 1000 m to 6000 m. If the film length is 100 m or more, there is no reduction in productivity due to an increase in the frequency of roll exchange, and if it is 10000 m or less, the web handling property is not deteriorated, and the optical uniformity of the film is further reduced. Is preferable because no undesirable phenomenon such as twisting or streaking occurs in the film. When winding, knurling is preferably applied to at least one end, the width is 3 mm to 50 mm, more preferably 5 m to 30 mm, and the height is 0.5 to 500 μm, more preferably 1 to 200 μm. This may be a single push or a double push. The variation in the Re value over the entire width is preferably ± 5 nm, and more preferably ± 3 nm. Further, the variation of the Rth value is preferably ± 10 nm, and more preferably ± 5 nm. Further, it is preferable that the variation in the Re value and the Rth value in the length direction is also within the range of the variation in the width direction. In order to maintain transparency, the haze is preferably 0.01 to 2%.

(Optical properties of stretched film)
The preferred optical properties of the stretched film of the present invention vary depending on the application of the film, but in the present invention, the stretched optical properties preferably satisfy 25 nm ≦ Re ≦ 100 nm and 50 nm ≦ Rth ≦ 300 nm. Moreover, it is more preferable to satisfy 50 nm ≦ Re ≦ 70 nm and 90 nm ≦ Rth ≦ 120 nm. Here, Re is an in-plane retardation value measured at λ = 590 nm, and Rth is a thickness direction retardation value measured at λ = 590 nm.
Moreover, it is preferable that the stretched film of the present invention satisfies the following conditions from the use of an optical film for a liquid crystal display device, particularly a retardation film for a VA panel.
The stretched film of the present invention preferably satisfies 1.75 ≦ Rth / Re + 0.5 ≦ 5 (Rth is a retardation value in the thickness direction measured at λ = 590 nm, and Re is at λ = 590 nm. It is the measured in-plane retardation value). By satisfying this range, it is preferable in terms of optically compensating the VA liquid crystal display device.

The stretched film of the present invention preferably has a haze of 3% or less. The haze is measured on a film sample of 40 mm × 80 mm at 25 ° C. and 60% RH with a haze meter “HGM-2DP” (manufactured by Suga Test Instruments Co., Ltd.) according to JIS K-6714.

The stretched film of the present invention can realize desired optical characteristics by appropriately adjusting the process conditions such as the structure of the resin used, the type and amount of additives, the stretch ratio, the residual volatile content during peeling, and the like. .
In this specification, Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments). In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measured value can be converted by a program or the like. When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method. Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotary axis) (in the absence of the slow axis, any direction in the film plane) Is measured in 6 points from the inclined direction in 10 degree steps from the normal direction to 50 degrees on one side with respect to the normal direction of the film. KOBRA 21ADH is calculated based on the retardation value, the assumed average refractive index, and the input film thickness value. The retardation value is measured from any two directions with the slow axis as the tilt axis (rotary axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotational axis), and the value Rth can also be calculated from the following formulas (1) and (2) based on the assumed average refractive index and the input film thickness value. Here, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

Here, the above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.

Rth = ((nx + ny) / 2−nz) × d −−− Formula (2)
At this time, an average refractive index n is required as a parameter, and a value measured by an Abbe refractometer (“Abbe refractometer 2-T” manufactured by Atago Co., Ltd.) was used.

Next, a polarizing plate having the above-described stretched film of the present invention, a polarizing plate protective film and an optical compensation film, and the polarizing plate having the polarizing plate protective film will be described.

(Retardation film-optical compensation film)
When a stretched film is used as a retardation film, the range of Re and Rth varies depending on the type of retardation film, and there are various needs. It is preferable to use it as an optical compensation film. The optical compensation film of the present invention may be the stretched film itself of the present invention or may have other constituent layers described below. Moreover, it is desirable to contain a substituent having a large polarizability at an appropriate ratio in the molecule.

(Protective film for polarizing plate)
When the stretched film of the present invention is used as a protective film for a polarizing plate, the in-plane retardation (Re) is preferably 5 nm or less, and more preferably 3 nm or less. The thickness direction retardation (Rth) is preferably 50 nm or less, more preferably 35 nm or less, and particularly preferably 10 nm or less.
The protective film for polarizing plates of the present invention may be the stretched film itself of the present invention or may have other constituent layers described below.

(Polarizer)
The polarizing plate usually has a polarizer and two transparent protective films disposed on both sides thereof. And the polarizing plate of this invention uses the protective film for polarizing plates of this invention as both or one protective film. When the protective film for polarizing plates of the present invention is used only on one side, a normal cellulose acetate film or the like may be used for the other protective film. Examples of the polarizer include an iodine polarizer, a dye polarizer using a dichroic dye, and a polyene polarizer. The iodine-based polarizer and the dye-based polarizer are generally produced using a polyvinyl alcohol (PVA) film. PVA is a polymer material obtained by saponifying polyvinyl acetate, but may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. . In addition, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, or the like can also be used.
The degree of saponification of PVA is not particularly limited, but is preferably from 80 to 100 mol%, particularly preferably from 90 to 100 mol%, from the viewpoint of solubility and the like. The polymerization degree of PVA is not particularly limited, but is preferably 1000 to 10,000, and particularly preferably 1500 to 5000.
The syndiotacticity of PVA is preferably 55% or more for improving durability as described in Japanese Patent No. 2978219, but 45 to 52.5% described in Japanese Patent No. 3317494 is also preferably used. Can do.

When the stretched film of the present invention is used as a protective film for a polarizing plate and a retardation film, the film is subjected to a surface treatment as described later, and then the film treated surface and a polarizer are bonded together using an adhesive. preferable. The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and is further constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.

The method of bonding the polarizing plate protective film of the present invention to the polarizer is preferably bonded so that the transmission axis of the polarizer matches the slow axis of the polarizing plate protective film of the present invention. In addition, when the polarizing plate produced under polarizing plate crossed Nicols was evaluated, the orthogonality accuracy between the slow axis of the protective film for polarizing plate of the present invention and the absorption axis of the polarizer (axis orthogonal to the transmission axis) is It was found that when the angle was larger than 1 °, the polarization degree performance under the polarizing plate crossed Nicols was reduced and light leakage occurred. In this case, when combined with a liquid crystal cell, sufficient black level and contrast cannot be obtained. Therefore, the deviation between the direction of the main refractive index nx of the protective film for polarizing plate of the present invention and the direction of the transmission axis of the polarizing plate is preferably within 1 °, preferably within 0.5 °.
UV3100PC (manufactured by Shimadzu Corporation) can be used to measure the single plate transmittance TT, parallel transmittance PT, and orthogonal transmittance CT of the polarizing plate. In the measurement, measurement is performed in the range of 380 nm to 780 nm, and the average value of 10 measurements can be used for the single plate, parallel, and orthogonal transmittance.

In the polarizing plate durability test, it is preferable that the amount of change before and after the test is small. For example, with respect to the degree of polarization of a polarizing plate, two polarizing plates are placed in crossed Nicols at 60 ° C. and 90% RH, and the light transmittance after 500 hours has been compared with the transmittance before the test. Can evaluate sex.
Change rate of transmittance, that is, {(light transmittance at crossed Nicols after polarizing plate durability test) − (light transmittance at crossed Nicols before polarizing plate durability test)} / (before polarizing plate durability test) The light transmittance at the time of crossed Nicols) × 100 (%) is preferably as small as possible, and is preferably 0.5% or less.

(Surface treatment of stretched film)
The protective film for polarizing plate of the present invention is preferably subjected to a surface treatment on the surface of the stretched film in order to improve the adhesion with the polarizer. As for the surface treatment, any method may be used as long as the adhesiveness can be improved. Preferred examples of the surface treatment include glow discharge treatment, ultraviolet irradiation treatment, corona treatment, and flame treatment. The glow discharge treatment here refers to so-called low temperature plasma that occurs under low pressure gas. In the present invention, plasma treatment under atmospheric pressure is also preferable. The details of the glow discharge treatment are described in US Pat. No. 3,462,335, US Pat. No. 3,761,299, US Pat. No. 4,072,769, and British Patent No. 891469. A method described in JP-A-59-556430 in which the gas composition of the discharge atmosphere is changed to only the gas species generated in the container by the discharge treatment of the polyester support itself after the start of discharge is also used. Also, the method described in Japanese Patent Publication No. 60-16614, in which the surface temperature of the film is set to 80 ° C. or higher and 180 ° C. or lower when the vacuum glow discharge treatment is performed, can be applied.

The degree of vacuum during the glow discharge treatment is preferably 0.5 Pa to 3000 Pa, more preferably 2 Pa to 300 Pa. The voltage is preferably between 500V and 5000V, more preferably between 500V and 3000V. The discharge frequency to be used is from direct current to several thousand MHz, more preferably 50 Hz to 20 MHz, and further preferably 1 KHz to 1 MHz. The discharge treatment intensity is preferably 0.01 KV · A · min / m ² to 5 KV · A · min / m ² , more preferably 0.15 KV · A · min / m ² to 1 KV · A · min / m ² . is there.

In the present invention, it is also preferable to perform an ultraviolet irradiation method as the surface treatment. For example, it can be carried out by the processing methods described in JP-B 43-2603, JP-B 43-2604, and JP-B 45-3828. The mercury lamp is a high-pressure mercury lamp made of a quartz tube and preferably has an ultraviolet wavelength of 180 to 380 nm. As for the method of ultraviolet irradiation, a high pressure mercury lamp with a dominant wavelength of 365 nm can be used as long as the surface temperature of the protective film rises to around 150 ° C. in terms of the performance of the support. When low-temperature treatment is required, a low-pressure mercury lamp having a dominant wavelength of 254 nm is preferable. It is also possible to use an ozone-less high-pressure mercury lamp and a low-pressure mercury lamp. Regarding the amount of processed light, the greater the amount of processed light, the better the adhesive force between the film and the polarizer. Accordingly, a high pressure mercury lamp for a 365nm main wavelength, irradiation dose ^{20mJ / cm 2 ~ 10000mJ / cm} 2 C., more preferably ^{50mJ / cm 2 ~ 2000mJ / cm} 2. If the low-pressure mercury lamp for a 254nm main wavelength, the irradiation light intensity ^{100mJ / cm 2 ~ 10000mJ / cm} 2 C., more preferably ^{300mJ / cm 2 ~ 1500mJ / cm} 2.

Furthermore, in the present invention, it is also preferable to perform a corona discharge treatment as the surface treatment. For example, it can be carried out by the processing methods described in JP-B-39-12838, JP-A-47-19824, JP-A-48-28067, and JP-A-52-42114. As the corona discharge treatment apparatus, a solid state corona treatment machine manufactured by Pillar, a LEPEL type surface treatment machine, a VETAPHON type treatment machine, or the like can be used. The treatment can be performed at normal pressure in air. The discharge frequency during the treatment is 5 KV to 40 KV, more preferably 10 KV to 30 KV, and the waveform is preferably an AC sine wave. The gap transparent lance between the electrode and the dielectric roll is 0.1 mm to 10 mm, more preferably 1.0 mm to 2.0 mm. The discharge is processed above a dielectric support roller provided in the discharge zone, and the treatment amount is 0.34 KV · A · min / m ² to 0.4 KV · A · min / m ² , more preferably 0.344 KV. A · min / m ² to 0.38 KV · A · min / m ²

In the present invention, it is also preferable to perform a flame treatment as the surface treatment. The gas used may be natural gas, liquefied propane gas, or city gas, but the mixing ratio with air is important. This is because the effect of surface treatment by flame treatment is considered to be brought about by plasma containing active oxygen, and the point is how much plasma activity (temperature) and oxygen are important properties of flame. is there. The governing factor of this point is the gas / oxygen ratio. When the reaction is carried out without excess or deficiency, the energy density is the highest and the plasma activity is increased. Specifically, a preferable mixing ratio of natural gas / air is 1/6 to 1/10, preferably 1/7 to 1/9 by volume. In the case of liquefied propane gas / air, 1/14 to 1/22, preferably 1/16 to 1/19, and in the case of city gas / air, 1/2 to 1/8, preferably 1/3 to 1. / 7. The amount of flame treatment is 1 Kcal / m ² to 50 Kcal / m ² , more preferably 3 Kcal / m ² to 20 Kcal / m ² . The distance between the tip of the burner's internal flame and the film is preferably 3 cm to 7 cm, more preferably 4 cm to 6 cm. The burner nozzle shapes are: Flynburner (US) ribbon type, Wise (US) multi-hole type, Aerogen (UK) ribbon type, Kasuga Electric (Japan) staggered multi-hole type, Koike Oxygen ( Japan) is preferred. The backup roll that supports the film for the flame treatment is a hollow roll, and is preferably cooled at a constant temperature of 20 ° C. to 50 ° C. by cooling with cooling water.

As for the degree of surface treatment, the preferred range varies depending on the type of surface treatment and the type of resin used, but as a result of the surface treatment, the contact angle of the surface of the protective film subjected to the surface treatment with pure water is 50 °. It is preferable that it becomes less than. The contact angle is more preferably 25 ° or more and less than 45 °. When the contact angle with the pure water on the surface of the protective film is in the above range, the adhesive strength between the protective film and the polarizing film becomes good.

(adhesive)
When laminating a polarizer made of a polyvinyl alcohol film and a surface-treated stretched film as a polarizing plate protective film, an adhesive containing a water-soluble polymer is preferably used. Water-soluble polymers preferably used for the adhesive include N-vinylpyrrolidone, acrylic acid, methacrylic acid, maleic acid, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, vinyl alcohol, methyl vinyl ether, vinyl acetate. , Acrylamide, methacrylamide, diacetone acrylamide, vinyl imidazole and other homopolymers or copolymers having ethylenically unsaturated monomers as constituents, polyoxyethylene, polyoxypropylene, poly-2-methyloxazoline, methylcellulose, hydroxy Examples include ethyl cellulose, hydroxypropyl cellulose, gelatin, and the like. Of these, PVA and gelatin are preferred in the present invention.

Preferred PVA characteristics when PVA is used for the adhesive are the same as the preferred characteristics of PVA used for the polarizer described above. In the present invention, it is preferable to use a crosslinking agent in combination. Examples of the cross-linking agent preferably used in combination with PVA as an adhesive include boric acid, polyvalent aldehyde, polyfunctional isocyanate compound, polyfunctional epoxy compound, and the like, but boric acid is particularly preferred in the present invention. When gelatin is used for the adhesive, so-called lime-processed gelatin, acid-processed gelatin, enzyme-processed gelatin, gelatin derivatives and modified gelatin can be used. Of these gelatins, lime-processed gelatin and acid-processed gelatin are preferably used. When gelatin is used for the adhesive, the crosslinking agent preferably used in combination is an active halogen compound (2,4-dichloro-6-hydroxy-1,3,5-triazine and its sodium salt) and an active vinyl compound ( 1,3-bisvinylsulfonyl-2-propanol, 1,2-bisvinylsulfonylacetamido) ethane, bis (vinylsulfonylmethyl) ether or vinyl polymers having a vinylsulfonyl group in the side chain), N-carbamoylpyridinium salts (Such as (1-morpholinocarbonyl-3-pyridinio) methanesulfonate) and haloamidinium salts (such as 1- (1-chloro-1-pyridinomethylene) pyrrolidinium 2-naphthalenesulfonate). In the present invention, an active halogen compound and an active vinyl compound are particularly preferably used.

When the above-mentioned crosslinking agent is used in combination, the preferred addition amount of the crosslinking agent is 0.1 parts by mass or more and less than 40 parts by mass with respect to 100 parts by mass of the water-soluble polymer in the adhesive. 5 parts by mass or more and less than 30 parts by mass. It is preferable to apply an adhesive to at least one surface of the protective film or the polarizer, form an adhesive layer, and bond the adhesive film, and apply the adhesive to the surface-treated surface of the protective film to form an adhesive layer. Is preferably bonded to the surface of the polarizer. The thickness of the adhesive layer is preferably 0.01 μm to 5 μm, and particularly preferably 0.05 μm to 3 μm after drying.

(Antireflection layer)
It is preferable to provide a functional layer such as an antireflection layer on the transparent protective film disposed on the opposite side of the polarizing plate from the liquid crystal cell. In particular, in the present invention, at least a light scattering layer and a low refractive index layer are laminated in this order on a transparent protective film, or a medium refractive index layer, a high refractive index layer, and a low refractive index layer are formed on this transparent protective film. An antireflection layer laminated in order is preferably used. These details are described in the published technical bulletin 2001-1745 (issued 2001.1.35).

(Other layers of antireflection layer)
Further, a hard coat layer, a forward scattering layer, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

(Hard coat layer)
The hard coat layer is provided on the surface of the transparent support in order to impart physical strength to the transparent protective film provided with the antireflection layer. In particular, it is preferably provided between the transparent support and the high refractive index layer. The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound. As the curable functional group, a photopolymerizable functional group is preferable, and the organometallic compound containing a hydrolyzable functional group is preferably an organic alkoxysilyl compound.
Specific examples of these compounds are the same as those exemplified for the high refractive index layer. Specific examples of the composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO 00/46617.
The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.

The hard coat layer can also serve as an antiglare layer containing particles having an average particle size of 0.2 μm to 10 μm and imparting an antiglare function (antiglare function).
The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 μm to 10 μm, more preferably 0.5 μm to 7 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

(Antistatic layer)
When an antistatic layer is provided, it is preferable to impart conductivity with a volume resistivity of 10 ⁻⁸ Ωcm ⁻³ or less. Volume resistivity of 10 ⁻⁸ Ωcm ⁻³ can be given by using hygroscopic substances, water-soluble inorganic salts, certain surfactants, cationic polymers, anionic polymers, colloidal silica, etc. However, there is a problem that sufficient conductivity cannot be secured at low humidity. Therefore, a metal oxide is preferable as the antistatic layer material. Some metal oxides are colored, but if these metal oxides are used as the antistatic layer material, the entire film is colored, which is not preferable. Zn, Ti, Al, In, Si, Mg, Ba, Mo, W, or V can be given as the metal that forms the metal oxide without coloring, and a metal oxide containing this as a main component should be used. preferable. Specific examples include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₃ , MgO, BaO, MoO ₃ , V ₂ O ₅ , or a composite oxide thereof. In particular, ZnO, TiO ₂ and SnO ₂ are preferable. Examples of containing different atoms include, for example, additives such as Al and In for ZnO, addition of Sb, Nb and halogen elements for SnO ₂ , and Nb and TA for TiO ₂ . Addition is effective. Furthermore, as described in Japanese Examined Patent Publication No. 59-6235, a material obtained by adhering the above metal oxide to other crystalline metal particles or fibrous materials (for example, titanium oxide) may be used. Although the volume resistance value and the surface resistance value are different physical values and cannot be simply compared, in order to ensure the conductivity of 10 ⁻⁸ Ωcm ⁻³ or less in the volume resistance value, the antistatic layer ^May have a surface resistance value of about 10 ⁻¹⁰ Ω / □ or less, more preferably 10 ⁻⁸ Ω / □. The surface resistance value of the antistatic layer needs to be measured as a value when the antistatic layer is the outermost layer, and can be measured in the middle of forming the laminated film described in this specification.

Next, the liquid crystal display device of the present invention having at least one of the stretched film, the polarizing plate protective film, the optical compensation film, and the polarizing plate will be described.

(Liquid crystal display device)
The stretched film of the present invention, the optical compensation film having the film, and the polarizing plate using the film can be used for liquid crystal cells and liquid crystal display devices in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Nyst) Various display modes such as HAN (Hybrid Aligned Nematic) and ECB (Electrically Controlled Birefringence) have been proposed. Of these, the IPS mode, ECB mode, OCB mode or VA mode can be preferably used.

(IPS liquid crystal display device and ECB liquid crystal display device)
The stretched film of the present invention is particularly advantageously used as a support for an optical compensation sheet of an IPS liquid crystal display device and an ECB liquid crystal display device having IPS mode and ECB mode liquid crystal cells, or as a protective film for a polarizing plate. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules in parallel with the substrate surface in the absence of applied voltage. In these embodiments, the polarizing plate using the stretched film of the present invention contributes to widening the viewing angle and improving the contrast.

(OCB type liquid crystal display device)
The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. OCB mode liquid crystal cells are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are aligned symmetrically between the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. For this reason, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.

(VA type liquid crystal display device)
In a VA mode liquid crystal cell, rod-like liquid crystal molecules are aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes: (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech.Papers 28 (1997) 845 in which the VA mode is converted into a multi-domain (in MVA mode) for widening the viewing angle ), (3) A liquid crystal cell (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary collections 58-59 of the Japan Liquid Crystal Society) (1998)) and (4) SURVAIVAL mode liquid crystal cells (announced at LCD International 98).
The VA mode liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates. In one aspect of the transmissive liquid crystal display device of the present invention, the optical compensation film of the present invention is disposed between the liquid crystal cell and one polarizing plate, or between the liquid crystal cell and both polarizing plates. Place two in between.
In another aspect of the transmissive liquid crystal display device of the present invention, an optical compensation film having the stretched film of the present invention is used as a transparent protective film of a polarizing plate disposed between a liquid crystal cell and a polarizer. That is, the transparent protective film of the polarizing plate can also serve as an optical compensation film. The above optical compensation film may be used only for the transparent protective film (between the liquid crystal cell and the polarizer) of one polarizing plate, or between the polarizing plates (between the liquid crystal cell and the polarizer). The above optical compensation film may be used for the two transparent protective films. When the optical compensation film is used only for one polarizing plate, it is particularly preferable to use it as a protective film for the liquid crystal cell side of the backlight side polarizing plate of the liquid crystal cell. For bonding to the liquid crystal cell, the stretched film of the present invention is preferably on the VA cell side. The other protective film may be a commonly used cellulose acylate film. For example, 40 μm to 80 μm are preferable, and examples include, but are not limited to, commercially available KC4UX2M (40 μm manufactured by Konica Capto), KC5UX (60 μm manufactured by Konica Capto), TD80 (80 μm manufactured by Fuji Photo Film), and the like. .

In an OCB mode liquid crystal display device or a TN liquid crystal display device, an optical compensation film is used to expand the viewing angle. As the optical compensation film for OCB cell, a film provided with an optically anisotropic layer in which a discotic liquid crystal is hybrid-aligned and fixed on an optically uniaxial or biaxial film is used. As the optical compensation film for TN cell, a film in which an optical anisotropic layer in which a discotic liquid crystal is fixed in a hybrid orientation is fixed on a film having optical isotropy or an optical axis in the thickness direction. The stretched film of the present invention is also useful for producing the optical compensation film for OCB cell and TN cell.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited thereto.

<Synthesis of Cyclic Polyolefin Polymer K-1>
100 parts by mass of purified toluene and 100 parts by mass of norbornene carboxylic acid methyl ester were charged into a reaction kettle. Next, ethylhexanoate-Ni 25 mmol% (based on monomer weight) dissolved in toluene, tri (pentafluorophenyl) boron 0.225 mol% (based on monomer weight), and triethylaluminum 0.25 mol% (based on monomer weight) dissolved in toluene ) Was charged into the reaction kettle. The reaction was allowed to proceed for 18 hours at room temperature with stirring. After completion of the reaction, the reaction mixture was put into excess ethanol to produce a polymer precipitate. The cyclic polyolefin polymer K-1 obtained by purifying the precipitate was vacuum dried at 65 ° C. for 24 hours.

When the obtained polymer was dissolved in tetrahydrofuran and the molecular weight was measured by GPC, the polystyrene-equivalent number average molecular weight was 79,000, and the weight average molecular weight was 205,000. The refractive index of the obtained polymer measured by Abbe refractometer was 1.52.

Example 1
The following composition was put into a mixing tank and stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope for film formation.

Cyclic polyolefin polymer K-1 100 parts by mass Dichloromethane 325 parts by mass Methanol 28.5 parts by mass The following additive A 20 parts by mass The following additive B 10 parts by mass The following additive E 0.3 parts by mass

The above dope was cast with a band casting machine. The film peeled off from the band with a residual solvent amount of about 30% by mass was dried by applying hot air at 140 ° C. while being held by a tenter. Thereafter, the tenter transport was shifted to the roll transport, and further dried at 120 to 140 ° C. to obtain a 1440 mm wide cyclic olefin resin film. The film thickness was 25 μm.

[Production of film]
As a solution casting method, the prepared dope was cast with a band casting machine.

Stretching was performed by the tenter method, but the film once wound may be stretched again. In that case, (1) the wound film is sent out, and (2) the film is placed in a stretching zone adjusted to the temperature T. , (3) stretching, and (4) rewinding.

The production conditions for the stretched film A thus obtained are shown in Table 2. Further, the following optical properties of the stretched film A were examined. The results are shown in Table 2. Re and Rth were measured by the above method at λ = 590 nm.
(1) Initial values of Re and Rth (Re (I), Rth (I))
(2) Re, Rth (Re (T), Rth (T)) after holding at temperature T for 3 minutes while holding at least two sides of the film
(3) Value of (Rth (T) / Rth (I)) (4) Weight reduction rate (%)
Weight reduction rate is measured by differential thermothermal gravimetric simultaneous measurement device (TG / DTA): Model II EXSTAR6000 TG / DTA manufactured by SII, heated to temperature T at a rate of 20 ° C./min, and held at temperature T for 60 minutes. The weight loss was calculated by measuring the weight loss. Weight reduction rate (%) = [{(initial film weight) − (film weight after holding at temperature T for 60 minutes)} / (initial film weight)] × 100
(5) Initial value of film haze (%) The haze is JIS K-6714 using a haze meter “HGM-2DP” (manufactured by Suga Test Instruments Co., Ltd.) at 25 ° C. and 60% RH for a film sample of 40 mm × 80 mm. Measured according to
(6) Haze (%) after standing at temperature T for 3 minutes while holding at least two sides of the film (haze after heat treatment)
(7) Optical properties of stretched film A (Re, Rth)
(8) NZ was calculated by measuring Re and Rth of the produced film.

(9) Change in optical properties after treatment at 60 ° C. and 90% RH for 24 hours The stretched film was conditioned at 25 ° C. and 60% RH for 24 hours, and Re and Rth were measured (Re-Before and Rth−, respectively). Before).
Further, the stretched film was conditioned at 60 ° C. and 90% RH for 24 hours, then removed from the thermo condition, conditioned at 25 ° C. and 60% RH for 24 hours, and Re and Rth were measured (re-after, Re-After, Rth-After). ΔRe (60w) and ΔRth (60w) were calculated by the following equations.
ΔRe (60w) = (Re−After) − (Re−Before)
ΔRth (60w) = (Rth−After) − (Rth−Before)
Evaluation was performed according to the following criteria.
A: | ΔRe (60w) | ≦ 5 nm and | ΔRth (60w) | ≦ 5 nm
○: 5 nm <| ΔRe (60w) | ≦ 10 nm and 5 nm <| ΔRth (60w) | ≦ 10 nm
Δ: 10 nm <| ΔRe (60w) | and 10 nm <| ΔRth (60w) |

(10) Film wavelength dispersibility Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH (manufactured by Oji Scientific Instruments).
The film wavelength dispersibility (ΔRe) was determined by Re (440) −Re (630).

(11) Suitability for polarizing plate for VA The obtained film is mounted on a VA mode liquid crystal display device as a protective film for polarizing plate, and measured at 25 ° C. and 60% using a measuring instrument (EZ-contrast 160D, manufactured by ELDIM). The black luminance (oblique black luminance) at a polar angle of 60 ° at an azimuth angle of 45 ° was measured in a black display state under an environment of RH. The measured oblique black luminance was evaluated according to the following evaluation criteria.
An oblique black luminance of 0.4 cd / m ² or less was determined to be suitable for a VA polarizing plate (◯). Since the film was not suitable for VA, the test was not performed (-).

Examples 2 to 57 and Comparative Examples 1 to 8
A stretched film was produced and evaluated in the same manner as in Example 1 except that the polymers and additives shown in Tables 2 to 5 were used and the production conditions shown in Tables 2 to 5 were changed. The results are shown in Tables 6-9.

Additives A to G, X, and Y are as follows.
Additive A: Toagosei Co., Ltd., trade name UH2041
Additive B: manufactured by Toagosei Co., Ltd., trade name UH2180

Additive E: Product name IRG1010, manufactured by Ciba
Additive F: Triphenyl phosphate Additive G: Biphenyl diphenyl phosphate Additive X: Polyester polymer P-64
Additive Y: Polyester polymer P-6

In Tables 2 to 5, the additive amount is the part by mass of the additive with respect to 100 parts by mass of the polymer.

The stretched film produced by the production method of the present invention has optical characteristics useful as each functional film, and can be suitably used, for example, as a protective film for a polarizing plate.
This application is based on a Japanese patent application filed on March 31, 2008 (Japanese Patent Application No. 2008-94235), the contents of which are incorporated herein by reference.

Claims (10)

A film formed by a solution casting method having an initial retardation of 30 nm or more in the thickness direction is stretched at a temperature T satisfying the following formula I), and measured by TG-DTA at the temperature T The stretched film is characterized in that the weight loss rate for 60 minutes is 5% or less.
Formula I) 0.2 ≦ (Rth (T) / Rth (I)) ≦ 0.9
In Formula I), Rth (T) is a retardation value in the thickness direction measured at λ = 590 nm of the film after being placed at a temperature T for 3 minutes while holding at least two sides of the film. , Rth (I) is an initial value of retardation in the thickness direction measured at λ = 590 nm of the film. The weight reduction rate is obtained by weight reduction rate (%) = [{(initial film weight) − (film weight after holding at temperature T for 60 minutes)} / (initial film weight)] × 100. It is what The stretched film according to claim 1, wherein optical properties after stretching satisfy the following conditions.
1.75 ≦ Rth / Re + 0.5 ≦ 5 (where Rth is the retardation value in the thickness direction measured at λ = 590 nm, and Re is the in-plane retardation value measured at λ = 590 nm) is there.) The stretched film according to claim 1 or 2, wherein the film is a cyclic olefin resin film. The stretched film according to claim 1 or 2, wherein the film comprises a cellulose resin having an acyl substituent having 2 to 4 carbon atoms and a substitution degree of the acyl group of 2.1 to 2.7. The stretched film according to claim 4, wherein the film comprises a cellulose resin having an acyl substituent having 2 to 4 carbon atoms and a substitution degree of the acyl group of 2.3 to 2.6. 6. The stretched film according to claim 1, wherein the optical characteristics satisfy 25 nm ≦ Re ≦ 100 nm and 50 nm ≦ Rth ≦ 300 nm. (Re is an in-plane retardation value measured at λ = 590 nm, and Rth is a thickness direction retardation value measured at λ = 590 nm.) 6. The stretched film according to claim 1, wherein the optical characteristics satisfy 50 nm ≦ Re ≦ 70 nm and 90 nm ≦ Rth ≦ 120 nm. (Re is an in-plane retardation value measured at λ = 590 nm, and Rth is a thickness direction retardation value measured at λ = 590 nm.) The stretched film according to any one of claims 1 to 7, wherein the film contains a retardation adjusting agent. A polarizing plate having a polarizer and two protective films on both sides of the polarizer, wherein at least one of the two protective films is a stretched film according to any one of claims 1 to 8. Board. A step of stretching a film formed by a solution casting method having an initial value of 30 nm or more in the thickness direction at a temperature T satisfying the following formula I), and TG-DTA at the temperature T A method for producing a stretched film, wherein the weight loss rate measured for 60 minutes is 5% or less.
Formula I) 0.2 ≦ (Rth (T) / Rth (I)) ≦ 0.9
In Formula I), Rth (T) is a retardation value in the thickness direction measured at λ = 590 nm of the film after being placed at a temperature T for 3 minutes while holding at least two sides of the film. , Rth (I) is an initial value of retardation in the thickness direction measured at λ = 590 nm of the film. The weight reduction rate is obtained by weight reduction rate (%) = [{(initial film weight) − (film weight after holding at temperature T for 60 minutes)} / (initial film weight)] × 100. It is what