WO2009119268A1 - Acrylic resin-containing film, process for producing acrylic resin-containing film, and polarizing plate and liquid crystal display device using the acrylic resin-containing film - Google Patents

Abstract

Disclosed is an acrylic resin-containing film that has excellent transparency and high heat resistance and has significantly improved brittleness. Also disclosed is a liquid crystal display device that has realized an improved yield in works such as stamping of a polarizing plate and panel lamination, has reduced color shifting, which occurs depending upon a viewing angle, and has realized a significantly improved contrast by using the acrylic resin-containing film. The acrylic resin-containing film comprises 50 to 90 parts by mass of an acrylic resin (A) and 10 to 50 parts by mass of a cellulose ester resin (B). The acrylic resin-containing film is characterized in that, when one side of the acrylic resin-containing film is superimposed on another side of the acrylic resin-containing film, the coefficient of static friction is 0.3 to 0.8; and the acrylic resin-containing film has a tension softening point of 105 to 145°C and does not cause a ductile fracture when the haze value is less than 1%.

Description

Acrylic resin-containing film, acrylic resin-containing film manufacturing method, polarizing plate and liquid crystal display device using the same

The present invention relates to an acrylic resin-containing film mainly composed of an acrylic resin, a polarizing plate and a display device using the same, and more specifically, by using an acrylic resin-containing film obtained by blending an acrylic resin and a cellulose ester resin. The present invention relates to a liquid crystal display device that improves the yield in operations such as punching and panel bonding, reduces the color shift that occurs depending on the viewing angle, and remarkably improves the contrast.

Polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of conventional acrylic resins, has been suitably used for optical films from the viewpoint of its excellent transparency, dimensional stability, low hygroscopicity, and the like.

However, the PMMA film has poor heat resistance and has a problem that its shape changes when used at high temperatures or for long-term use.

In order to solve this problem, a method of using a film in which an acrylic resin and a cellulose ester resin are blended is disclosed (for example, see Patent Document 1). However, in the example of this document, from the viewpoint of compatibility between the acrylic resin and the cellulose resin, since the low molecular weight cellulose resin was used, there was a problem that the film was brittle and easily broken.

On the other hand, an invention has been disclosed in which silicone fine particles are added to a cellulose ester film to improve light transmission and light resistance (see, for example, Patent Document 2). However, the added fine particles are aggregated to cause haze, and there is a problem of compatibility with the UV agent, which makes it difficult to use.

Further, an invention has been disclosed in which a heat transferable protective layer is provided on at least a part of one surface of a cellulose ester film so as to improve heat resistance (see, for example, Patent Document 3). It takes too much. Furthermore, an invention is disclosed in which a matting agent is added to suppress the occurrence of scratch failure during winding of the cellulose ester film without reducing the transmittance of the cellulose ester film (see, for example, Patent Document 4). In this case, if too much matting agent is added, haze is generated, so the amount of addition is limited, and the above object cannot be achieved sufficiently.

In addition, surface physical properties associated with the thinning of the cellulose ester film, to improve the pressing and failure when rolled up, the surface roughness of the cellulose ester film, the amount of matting agent, the amount of plasticizer, An invention that defines a moisture content and the like within a specific range is disclosed (for example, see Patent Document 5). However, this method has problems such as curling, dimensional change, surface and internal refractive indexes are different, and front contrast (hereinafter also referred to as CR) is lowered.
Japanese Patent Laid-Open No. 5-119217 Japanese Unexamined Patent Publication No. 7-11056 JP 2001-105749 A JP 2002-317059 A JP 2004-168981 A

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide an acrylic resin-containing film that is extremely excellent in transparency, high heat resistance, and markedly improved in brittleness. Furthermore, by using the acrylic resin-containing film, the yield in operations such as polarizing plate punching and panel bonding is improved, color shifts that occur depending on the viewing angle are reduced, and contrast is remarkably increased. An object is to provide an improved liquid crystal display device.

The above object of the present invention can be achieved by the following configuration.

1. An acrylic resin-containing film containing 10 to 50 parts by mass of a cellulose ester resin (B) with respect to 50 to 90 parts by mass of the acrylic resin (A), the one side of the acrylic resin-containing film and the other side The coefficient of static friction when superposed on a surface is 0.3 to 0.8, the softening point of tension is 105 to 145 ° C., the haze value is less than 1%, and no ductile fracture occurs. Acrylic resin-containing film.

2. The acrylic resin-containing film has an acrylic resin (A) having a weight average molecular weight (Mw) of 80000 to 1000000, and a total substitution degree (T) of acyl groups of the cellulose ester resin (B) of 2.00 to 3.00. The acetyl group substitution degree (ac) is 0.10 to 1.90, and the portion other than the acetyl group is substituted with an acyl group composed of 3 to 7 carbon atoms. r) is 1.10 to 2.90, the weight average molecular weight (Mw) is 75000 to 280000, and the film contains 0.05 to 45% by mass of acrylic fine particles (C) based on the total mass of the film. 2. The acrylic fine particles as described in 1 above, wherein 40-60% of the total abundance is present in a region within 25% of the total thickness of the film from both surfaces of the film. A Lil resin-containing film.

3. 3. A method for producing an acrylic resin-containing film, wherein the acrylic resin-containing film according to 1 or 2 is produced by being stretched by 5% to 40% in at least one direction.

4. A polarizing plate using the acrylic resin-containing film as described in 1 or 2 above.

5. 5. A liquid crystal display device using the polarizing plate described in 4 above.

6. 4. A polarizing plate using a film produced by the method for producing an acrylic resin-containing film as described in 3 above.

7. 7. A liquid crystal display device using the polarizing plate described in 6 above.

According to the present invention, it was possible to provide an acrylic resin-containing film that is transparent, has high heat resistance, and has markedly improved brittleness, and can provide a liquid crystal display device that has reduced color shift and further improved contrast.

It is the figure which showed typically the dope preparation process, casting process, and drying process of the solution casting film forming method used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter Stretching Device 35 Roll Drying Device 41 Fine Particle Charger 42 Stock Tank 43 Pump 44 Filter

Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

The present invention is a drawback of the conventional acrylic resin-containing film, which has improved properties such as poor heat resistance, high temperature use, long-term use, etc. As a result of blending (A) and cellulose ester resin (B), it was found that an acrylic resin-containing film having transparency, high heat resistance, and markedly improved brittleness can be obtained. It is.

Furthermore, it was found that the tension softening point is 105 to 145 ° C. and that no ductile fracture occurs satisfies the heat resistance required for an optical film used in a liquid crystal display device or the like.

<Acrylic resin-containing film>
The acrylic resin-containing film of the present invention has a haze value of less than 1%, a tension softening point of 105 to 145 ° C., and a static friction coefficient when one surface and the other surface are overlapped. It is 0.3 to 0.8.

The static friction coefficient when one surface of the acrylic resin-containing film in the present invention is overlapped with the other surface is 0.3 to 0.8. If it is within this range, when the formed film is wound around the core core and stored for a long period of time, the films will not stick to each other, and the smoothness and appearance will not be impaired. Can be sent out. Moreover, if it is this range, it will be very easy to slip | slide between films, and when it winds up, it will not jump out in what is called a bamboo shoot shape, and there is no possibility of impairing quality. It is also possible to obtain a long film of 4000 to 6000 m by controlling the static friction coefficient to 0.3 to 0.8.

The acrylic resin-containing film according to the present invention has a low haze, considering the use in a high-temperature environment such as a high temperature device such as a projector or an in-vehicle display device, the tension softening point is 105 ° C to 145 ° C. More preferably, the temperature is controlled at 110 to 130 ° C. By controlling the tension softening point within the above range, a clear image can be continuously displayed when the liquid crystal display device using the film is used for a long time. Within this range, although depending on the use environment, there is generally no fear that the image quality, color, etc. of the display device will be impaired in long-term use, and it is not necessary to use an extremely high heat-resistant acrylic resin.

As a specific method for measuring the tension softening point temperature of an acrylic resin-containing film, for example, using a Tensilon tester (ORIENTEC Co., RTC-1225A), the acrylic resin-containing film is 120 mm (length) × 10 mm (width). The temperature is increased at a rate of temperature increase of 30 ° C./min while pulling at a tension of 10 N, and the temperature at the time of 9 N is measured three times, and the average value can be obtained.

Further, the acrylic resin-containing film of the present invention is characterized by being an acrylic resin film that does not cause ductile fracture.

In the present invention, the ductile fracture is caused by a stress that is greater than the strength of a certain material, and is defined as a fracture accompanied by significant elongation or squeezing of the material before the final fracture. The fracture surface is characterized by numerous indentations called dimples. Therefore, “an acrylic resin film that does not cause ductile fracture” is characterized in that, for example, fracture such as fracture is not observed even when a large stress is applied such that the film is folded in two.

The demand for the brittleness of optical films is increasing from the viewpoint of reworkability and productivity as optical films become larger and thinner with the recent increase in liquid crystal display devices, and the above ductile fracture does not occur. Is required.

Forming an acrylic resin film that does not cause ductile fracture is achieved by appropriately selecting the material configuration of the acrylic resin, cellulose ester, acrylic fine particles, and other additives used.

The acrylic resin-containing film of the present invention preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a heating rate of 20 ° C./min. Point glass transition temperature (Tmg).

The acrylic resin-containing film of the present invention has a defect of 5 μm or more in diameter in the film plane of 1 piece / 10 cm square. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

Here, the diameter of the defect indicates the diameter when the defect is circular, and when it is not circular, the range of the defect is determined by observing with a microscope according to the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

In addition, when observing with reflected light, if the size of the defect is not clear, aluminum or platinum is vapor-deposited on the surface for observation.

In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

When the number of defects is more than 1/10 cm square, for example, when a tension is applied to the film during processing in a later process, the film breaks with the defect as a starting point, and the productivity may be significantly reduced. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

Also, even when visual confirmation is not possible, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in defects (coating defects). Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to the foreign matter (foreign matter defect) in the film.

The acrylic resin-containing film of the present invention preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more, as measured in accordance with JIS-K7127-1999.

The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

The thickness of the acrylic resin-containing film of the present invention is preferably 20 μm or more. More preferably, it is 30 μm or more.

The upper limit of the thickness is not particularly limited, but in the case of forming a film by a solution casting method, the upper limit is about 250 μm from the viewpoint of applicability, foaming, solvent drying, and the like. The thickness of the film can be appropriately selected depending on the application.

The acrylic resin-containing film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. The practical upper limit is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the acrylic resin.

The acrylic resin-containing film of the present invention is characterized in that the haze value (turbidity), which is one of the indices indicating transparency, is 1.0% or less, but the luminance when incorporated in a liquid crystal display device, From the viewpoint of contrast, it is preferably 0.5% or less.

In order to achieve such a haze value, it is effective to remove foreign substances in the polymer by high-precision filtration and reduce the diffusion of light inside the film.

When acrylic fine particles are used, it is also effective to reduce the refractive index difference between the acrylic resin (A) and the acrylic fine particles (C).

In addition, since the surface roughness also affects the haze value as surface haze, the particle diameter and addition amount of the acrylic fine particles (C) should be kept within the above ranges, or the surface roughness of the film contact portion during film formation should be reduced. Is also effective.

The total light transmittance and haze value of the acrylic resin-containing film are values measured according to JIS-K7361-1-1997 and JIS-K7136-2000.

The acrylic resin-containing film of the present invention can be preferably used as an optical acrylic resin-containing film as long as it satisfies the physical properties as described above, but is excellent in workability and heat resistance by having the following composition. Film can be obtained.

That is, from the viewpoint of achieving both workability and heat resistance, the acrylic resin-containing film contains the acrylic resin (A) and the cellulose ester resin (B) in a mass ratio of 90:10 to 50:50, and the cellulose ester Resin (B) has a total acyl group substitution degree (T) of 2.00 to 3.00, an acetyl group substitution degree (ac) of 0.10 to 1.90, and an acyl group other than the acetyl group has 3 carbon atoms. The acrylic resin-containing film having the substitution degree (r) of 1.10 to 2.90 and the weight average molecular weight (Mw) of 75,000 to 280000 is excellent. An effect is obtained.

In the acrylic resin-containing film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 90:10 to 50:50, preferably 70% by mass of the acrylic resin (A). That's it.

When the acrylic resin component is increased, for example, the dimensional change under high temperature and high humidity is suppressed, and curling of the polarizing plate and warping of the panel when used as a polarizing plate can be remarkably reduced. Further, in a composition having an acrylic resin component of 70% by mass or more, the above physical properties can be maintained for a longer time.

The acrylic resin-containing film of the present invention may contain a resin other than the acrylic resin (A) and the cellulose ester resin (B).

The total mass of the acrylic resin (A) and the cellulose ester resin (B) is 55 to 100% by mass, preferably 60 to 99% by mass of the acrylic resin-containing film.

<Acrylic resin (A)>
The acrylic resin used in the present invention includes a methacrylic resin. The resin is not particularly limited, but a resin comprising 50 to 99% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith is preferable.

Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 alkyl carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, alkyl acrylates such as acrylic acid and methacrylic acid. Saturated acids, maleic acids, fumaric acids, divalent carboxylic acids containing unsaturated groups such as itaconic acid, aromatic vinyl compounds such as styrene, α-methylstyrene, and nucleus-substituted styrene, α, β- such as acrylonitrile, methacrylonitrile, etc. Examples thereof include unsaturated nitrile, maleic anhydride, maleimide, N-substituted maleimide, and glutaric anhydride, and these can be used alone or in combination of two or more.

Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used.

The acrylic resin (A) used in the acrylic resin-containing film of the present invention preferably has a weight average molecular weight (Mw) of 80,000 to 1,000,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film. .

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

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

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

By using this molecular weight, both heat resistance and brittleness can be achieved.

Commercially available acrylic resins can be used as the acrylic resin of the present invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dialal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. .

<Cellulose ester resin (B)>
The cellulose ester resin (B) of the present invention may be substituted with either an aliphatic acyl group or an aromatic acyl group, but is preferably substituted with an acetyl group.

When the cellulose ester resin (B) of the present invention is an ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, isobutyryl, valeryl, pivaloyl , Hexanoyl, octanoyl, lauroyl, stearoyl and the like.

In the present invention, the aliphatic acyl group is meant to include those further having a substituent. When the aromatic ring is a benzene ring in the above-described aromatic acyl group, the substituent of the benzene ring Are exemplified.

When the cellulose ester resin (B) is an ester with an aromatic acyl group, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, 1 or 2 is preferred.

Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

In the cellulose resin of the present invention, the cellulose ester resin (B) has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group. Used as the structure used, these may be single or mixed acid esters of cellulose.

The substitution degree of the cellulose ester resin (B) of the present invention is such that the total substitution degree (T) of the acyl group is 2.00 to 3.00, the acetyl group is not necessarily required, and the substitution degree of acetyl group (ac) is It is preferably 0.10 to 1.90. More preferably, the substitution degree (r) of acyl group other than acetyl group is 1.10 to 2.90.

The acyl group other than the acetyl group preferably has 3 to 7 carbon atoms.

In the cellulose ester resin (B) of the present invention, those having an acyl group having 3 to 7 carbon atoms as a substituent, that is, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, It is preferably at least one selected from cellulose acetate benzoate and cellulose benzoate.

Among these, particularly preferable cellulose ester resins (B) include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

More preferably, the mixed fatty acid is a lower fatty acid ester of cellulose acetate propionate or cellulose acetate butyrate having an acyl group having 3 to 4 carbon atoms as a substituent.

The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

Incidentally, the substitution degree of the acetyl group and the substitution degree of other acyl groups were determined by the method prescribed in ASTM-D817-96.

If the weight average molecular weight (Mw) of the cellulose ester resin (B) of the present invention is 75,000 or more, the object of the present invention can be achieved even if the weight average molecular weight (Mw) is about 1,000,000. Is preferably ˜280,000, more preferably 100,000 to 240,000.

<Acrylic fine particles (C)>
In the present invention, the acrylic resin-containing film may contain acrylic fine particles.

The acrylic fine particles (C) according to the present invention are characterized by being present in the state of particles in the acrylic resin (A) and the cellulose ester resin (B) and the acrylic resin-containing film (also referred to as incompatible state). .

The acrylic fine particles (C) are obtained, for example, by collecting a predetermined amount of the prepared acrylic resin-containing film, dissolving in a solvent, stirring, and sufficiently dissolving / dispersing the acrylic fine particles (C) less than the average particle size of the acrylic fine particles (C). It is preferable that the weight of the insoluble matter filtered and collected using a PTFE membrane filter having a pore size is 90% by mass or more of the acrylic fine particles (C) added to the acrylic resin-containing film.

The acrylic fine particles (C) used in the present invention are not particularly limited, but are preferably acrylic fine particles (C) having a layer structure of two or more layers, particularly the following multilayer structure acrylic granular composite. It is preferable.

The multilayer structure acrylic granular composite is formed by laminating an innermost hard layer polymer, a cross-linked soft layer polymer exhibiting rubber elasticity, and an outermost hard layer polymer from the center to the outer periphery. This refers to a particulate acrylic polymer having a structure.

Preferred embodiments of the multilayer structure acrylic granular composite used in the acrylic resin composition of the present invention include the following. (A) Monomer comprising 80 to 98.9% by weight of methyl methacrylate, 1 to 20% by weight of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by weight of polyfunctional grafting agent (B) 75 to 98.5% by mass of an alkyl acrylate having 4 to 8 carbon atoms in the presence of the innermost hard layer polymer in the presence of the innermost hard layer polymer, A crosslinked soft layer polymer obtained by polymerizing a monomer mixture comprising 0.01 to 5% by mass of a multifunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent; (c) the innermost hard In the presence of a polymer comprising a layer and a crosslinked soft layer, a monomer mixture comprising 80 to 99% by mass of methyl methacrylate and 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is polymerized. Outermost hard layer weight And the obtained three-layer structure polymer is an innermost hard layer polymer (a) 5 to 40% by mass, a soft layer polymer (b) 30 to 60% by mass, and An outermost hard layer polymer (c) comprising 20 to 50% by mass, having an insoluble part when fractionated with acetone, and an acrylic granular composite having a methyl ethyl ketone swelling degree of 1.5 to 4.0 at the insoluble part .

As disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, not only the composition and particle diameter of each layer of the multilayered acrylic granular composite are defined, but also the multilayered acrylic granular composite. By setting the tensile modulus of the body and the degree of swelling of methyl ethyl ketone in the acetone-insoluble part within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

Here, the innermost hard layer polymer (a) constituting the multilayer structure acrylic granular composite is 80 to 98.9% by mass of methyl methacrylate and 1 to 20 mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. % And a monomer mixture consisting of 0.01 to 0.3% by mass of a polyfunctional grafting agent is preferred.

Here, examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like. And n-butyl acrylate are preferably used.

The proportion of the alkyl acrylate unit in the innermost hard layer polymer (a) is 1 to 20% by mass. When the unit is less than 1% by mass, the thermal decomposability of the polymer is increased, while the unit is 20% by mass. If it exceeds 50%, the glass transition temperature of the innermost hard layer polymer (c) is lowered, and the impact resistance imparting effect of the three-layer structure acrylic granular composite is lowered.

Examples of the polyfunctional grafting agent include polyfunctional monomers having different polymerizable functional groups, such as allyl esters of acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and allyl methacrylate is preferably used. . The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the soft layer polymer, and the ratio used during the innermost hard layer polymerization is 0.01 to 0.3% by mass. .

The crosslinked soft layer polymer (b) constituting the acrylic granular composite is an alkyl acrylate having from 9 to 8 carbon atoms having an alkyl group of 1 to 8 in the presence of the innermost hard layer polymer (a). What is obtained by polymerizing a monomer mixture consisting of 10% by mass, 0.01 to 5% by mass of a multifunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent is preferred.

Here, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used as the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group.

In addition to these polymerizable monomers, it is possible to copolymerize 25% by mass or less of other monofunctional monomers capable of copolymerization.

Examples of other monofunctional monomers that can be copolymerized include styrene and substituted styrene derivatives. As the ratio of the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group and styrene increases, the glass transition temperature of the produced polymer (b) decreases as the former increases, that is, it can be softened.

On the other hand, from the viewpoint of the transparency of the resin assembly, the refractive index of the soft layer polymer (b) at room temperature is set to the innermost hard layer polymer (a), the outermost hard layer polymer (c), and the hard heat. It is more advantageous to make it closer to the plastic acrylic resin, and the ratio between them is selected in consideration of these.

For example, in applications where the coating layer thickness is small, it is not always necessary to copolymerize styrene.

As the polyfunctional grafting agent, those mentioned in the section of the innermost layer hard polymer (a) can be used. The polyfunctional grafting agent used here is used to chemically bond the soft layer polymer (b) and the outermost hard layer polymer (c), and the proportion used during the innermost hard layer polymerization is impact resistance. From the viewpoint of the effect of imparting properties, 0.5 to 5% by mass is preferable.

As the polyfunctional crosslinking agent, generally known crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, dimethacrylic compounds and the like can be used, but polyethylene glycol diacrylate (molecular weight 200 to 600) is preferably used.

The polyfunctional cross-linking agent used here is used to generate a cross-linked structure during the polymerization of the soft layer (b) and to exhibit the effect of imparting impact resistance. However, if the above-mentioned polyfunctional grafting agent is used during the polymerization of the soft layer, the polyfunctional crosslinking agent is not an essential component because the crosslinked structure of the soft layer (b) is generated to some extent. Is preferably 0.01 to 5% by weight from the viewpoint of imparting impact resistance.

The outermost hard layer polymer (c) constituting the multi-layer structure acrylic granular composite has a methyl methacrylate of 80 to 99 mass in the presence of the innermost hard layer polymer (a) and the soft layer polymer (b). % And a monomer mixture comprising 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is preferred.

Here, as the acrylic alkylate, those described above are used, but methyl acrylate and ethyl acrylate are preferably used. The proportion of the alkyl acrylate unit in the outermost hard layer (c) is preferably 1 to 20% by mass.

Also, when the outermost hard layer (c) is polymerized, an alkyl mercaptan or the like can be used as a chain transfer agent to adjust the molecular weight for the purpose of improving the compatibility with the acrylic resin (A).

In particular, it is preferable to provide the outermost hard layer with a gradient such that the molecular weight gradually decreases from the inside toward the outside in order to improve the balance between elongation and impact resistance. As a specific method, the monomer mixture for forming the outermost hard layer is divided into two or more, and the molecular weight is increased from the inside by a method of sequentially increasing the amount of chain transfer agent added each time. It is possible to make it smaller toward the outside.

The molecular weight formed at this time can also be examined by polymerizing the monomer mixture used each time under the same conditions, and measuring the molecular weight of the obtained polymer.

The particle diameter of the acrylic granular composite which is a multilayer structure polymer preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, and more preferably 20 nm or more and 500 nm or less. More preferably, it is most preferably 50 nm or more and 400 nm or less.

In the acrylic granular composite that is a multilayer structure polymer preferably used in the present invention, the mass ratio of the core and the shell is not particularly limited, but when the entire multilayer structure polymer is 100 parts by mass, The core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and more preferably 60 parts by mass or more and 80 parts by mass or less.

Examples of such commercially available multilayered acrylic granular composites include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., “Kane Ace” manufactured by Kaneka Chemical Co., Ltd., “Paralloid” manufactured by Kureha Chemical Co., Ltd., Rohm and Haas “Acryloid” manufactured by KK, “Staffyroid” manufactured by Ganz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd., and the like can be used alone or in combination.

Further, specific examples of the acrylic fine particles (c-1), which are graft copolymers preferably used as the acrylic fine particles (C) preferably used in the present invention, include unsaturated carboxylic acids in the presence of a rubbery polymer. A monomer mixture comprising an acid ester monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith A polymerized graft copolymer may be mentioned.

The rubbery polymer used for the acrylic fine particles (c-1), which is a graft copolymer, is not particularly limited, but diene rubber, acrylic rubber, ethylene rubber, and the like can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. , Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic acid Examples thereof include a methyl copolymer. These rubbery polymers can be used alone or in a mixture of two or more.

Further, it is preferable that the refractive index of each of the acrylic resin (A) and the acrylic fine particles (C) is approximate because the transparency of the acrylic resin-containing film of the present invention can be obtained. Specifically, the refractive index difference between the acrylic fine particles (C) and the acrylic resin (A) is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

In order to satisfy such a refractive index condition, a method of adjusting the monomer unit composition ratio of the acrylic resin (A) and / or a rubbery polymer or monomer used for the acrylic fine particles (C) The difference in refractive index can be reduced by a method of adjusting the composition ratio, and an acrylic resin-containing film excellent in transparency can be obtained.

The difference in refractive index referred to here is a solution in which the acrylic resin-containing film of the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble to obtain a cloudy solution, which is subjected to an operation such as centrifugation. By separating the solvent-soluble part and the insoluble part, and purifying the soluble part (acrylic resin (A)) and the insoluble part (acrylic fine particles (C)), respectively, the measured refractive index (23 ° C., measurement wavelength) : 550 nm).

In the present invention, the method of blending the acrylic fine particles (C) with the acrylic resin (A) is not particularly limited, and after blending the acrylic resin (A) and other optional components in advance, usually at 200 to 350 ° C. A method of uniformly kneading with a single screw or twin screw extruder while adding the acrylic fine particles (C) is preferably used.

In addition, a solution in which acrylic fine particles (C) are dispersed in advance is added to and mixed with a solution (dope solution) in which acrylic resin (A) and cellulose ester resin (B) are dissolved, acrylic fine particles (C) and A method such as in-line addition of a solution obtained by dissolving or mixing other optional additives can be used.

Commercially available acrylic fine particles (C) of the present invention can also be used. For example, metabrene W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C3), MS-300X (C4) (manufactured by Soken Chemical Co., Ltd.) and the like can be mentioned.

The acrylic resin-containing film of the present invention preferably contains 0.5 to 45 mass% of acrylic fine particles (C) with respect to the total mass of the resin constituting the film.

Further, it is preferable that 40-60% of the total amount of the acrylic fine particles (C) is present in a region within 25% of the thickness of the entire film from both surfaces of the acrylic resin-containing film. . Such distribution of the acrylic fine particles (C) is achieved by a preferable method for forming an acrylic resin-containing film, which will be described later as an example.

This is because when the abundance is less than 40%, the film does not have sufficient slipperiness, and the films stick to each other when wound, making handling difficult. On the other hand, if it exceeds 60%, the tension softening point may decrease or the haze value may increase.

The ratio of the acrylic fine particles is determined by taking a cross section of the acrylic resin-containing film with a high resolution scanning electron microscope (SEM) at a magnification of about 10,000 to 50,000 times, analyzing the obtained SEM photograph, It is calculated as the existence ratio with respect to the thickness direction.

<Other additives>
In the acrylic resin-containing film of the present invention, a plasticizer can be used in combination in order to improve the fluidity and flexibility of the composition. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

Of these, polyester-based and phthalate-based plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

In particular, when adipic acid, phthalic acid, or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

Also, the viscosity of the plasticizer has a correlation with the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, the range of 200 to 5000 mPa · s (25 ° C.) is preferable because of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing the acrylic resin (A). If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

The composition containing the acrylic resin (A) of the present invention preferably contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole, 2-hydroxybenzophenone, and salicylic acid phenyl ester. Can be mentioned. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone And benzophenones.

Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

In addition, since the transition from the thin coating layer to the substrate layer is particularly small and hardly precipitates on the surface of the laminate, the amount of contained UV absorber is maintained for a long time, and the durability of the weather resistance improvement effect is excellent. From the point of view, it is preferable.

Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] Such as til] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

Furthermore, various antioxidants can be added to the acrylic resin (A) used in the acrylic resin-containing film of the present invention in order to improve the thermal decomposability and thermal colorability during molding. In addition, an antistatic agent can be added to impart antistatic performance to the acrylic resin-containing film.

As the acrylic resin composition of the present invention, a flame retardant acrylic resin composition containing a phosphorus flame retardant may be used.

Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

<Formation of acrylic resin-containing film>
Although the example of the film forming method of an acrylic resin containing film is demonstrated, this invention is not limited to this.

As a method for producing the acrylic resin-containing film of the present invention, production methods such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. From the viewpoints of suppressing foreign matter defects and optical defects such as die lines, solution casting by casting is preferred.

(Organic solvent)
The organic solvent useful for forming the dope when the acrylic resin-containing film of the present invention is produced by the solution casting method dissolves the acrylic resin (A), the cellulose ester resin (B), and other additives at the same time. Anything can be used without limitation.

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

In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the ratio of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the ratio of alcohol is small, acrylic resin (A) and cellulose ester in non-chlorine organic solvent system. There is also a role of promoting dissolution of the resin (B).

In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, acrylic resin (A), cellulose ester resin (B), and acrylic fine particles (C) 3 A dope composition in which at least 15 to 45% by mass of the seed is dissolved is preferable.

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

Hereinafter, a preferable method for forming the acrylic resin-containing film of the present invention will be described.

1) Dissolution Step In an organic solution mainly composed of a good solvent for the acrylic resin (A) and the cellulose ester resin (B), the acrylic resin (A), the cellulose ester resin (B), and, in some cases, acrylic fine particles ( C), a step of dissolving other additives while stirring to form a dope, or the acrylic resin (A) or cellulose ester resin (B) solution, optionally with acrylic fine particle (C) solution or other additive solution Are mixed to form a dope which is a main solution.

For dissolving the acrylic resin (A) and the cellulose ester resin (B), a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544 Various dissolution methods such as a method of performing a cooling dissolution method as described in JP-A-9-95557 or JP-A-9-95538, a method of performing at a high pressure as described in JP-A-11-21379, and the like. Although it can be used, a method in which pressure is applied at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

The acrylic resin (A) and cellulose ester resin (B) in the dope are preferably in the range of 15 to 45% by mass in total. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

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

In this method, agglomerates remaining at the time of particle dispersion and agglomerates generated upon addition of the main dope are only aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

FIG. 1 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

If necessary, large aggregates are removed from the acrylic fine particle charging vessel 41 with a filter 44 and fed to the stock tank 42. Thereafter, the acrylic fine particle additive solution is added from the stock tank 42 to the main dope dissolving pot 1.

Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

In many cases, the main dope may contain about 10 to 50% by weight of recycled material. The return material may contain acrylic fine particles. In that case, it is preferable to control the addition amount of the acrylic fine particle addition liquid in accordance with the addition amount of the return material.

The additive liquid containing acrylic fine particles preferably contains 0.5 to 10% by mass of acrylic fine particles, more preferably 1 to 10% by mass, and more preferably 1 to 5% by mass. Most preferably.

The above range is preferable because the smaller the content of the acrylic fine particles, the lower the viscosity and the easier the handling, and the higher the content of the acrylic fine particles, the smaller the addition amount and the easier the addition to the main dope.

Recycled material is a finely pulverized acrylic resin-containing film that is generated when an acrylic resin-containing film is formed. The original fabric is used.

In addition, an acrylic resin, a cellulose ester resin, and in some cases, an acrylic fine particle kneaded into pellets can be preferably used.

2) Casting process An endless metal support 31, such as a stainless steel belt or a rotating metal drum, which feeds the dope through a liquid feed pump (for example, a pressurized metering gear pump) to the pressure die 30 and transfers it indefinitely. This is a step of casting a dope from a pressure die slit to a casting position on a metal support.

¡Pressure dies that can adjust the slit shape of the die base and make the film thickness uniform are preferred. The pressure die includes a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

To evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. High efficiency and preferable. A method of combining them is also preferably used.

The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

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

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

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

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

The amount of residual solvent in the web is defined by the following formula.

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

The peeling tension at the time of peeling the metal support from the film is usually 196 to 245 N / m. However, if wrinkles easily occur at the time of peeling, it is preferable to peel with a tension of 190 N / m or less. It is preferable to peel at a minimum tension of ˜166.6 N / m, and then peel at a minimum tension of ˜137.2 N / m, and particularly preferable to peel at a minimum tension of ˜100 N / m.

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

5) Drying and stretching step After peeling, a drying device 35 that alternately conveys the web through a plurality of rolls arranged in the drying device and / or a tenter stretching device 34 that clips and conveys both ends of the web with a clip are used. And dry the web.

The drying means is generally to blow hot air on both sides of the web, but there is also a means to heat by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, drying is generally performed at 40-250 ° C. In particular, drying at 40 to 160 ° C. is preferable.

When using a tenter stretching apparatus, it is preferable to use an apparatus capable of independently controlling the film gripping length (distance from the start of gripping to the end of gripping) by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

It is also preferable to provide a neutral zone between different temperature zones so that each zone does not cause interference.

The stretching operation may be performed in multiple stages, and it is also preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise.

In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction-Stretch in the width direction-Stretch in the width direction-Stretch in the casting direction-Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferred draw ratio for simultaneous biaxial stretching can be in the range of x1.01 to x1.5 in both the width direction and the longitudinal direction.

When the tenter stretching is performed, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and drying is performed while applying a tenter until the residual solvent amount of the web becomes 10% by mass or less. Preferably, it is 5 mass% or less more preferably.

The drying temperature in the case of tenter stretching is preferably 30 to 150 ° C, more preferably 50 to 120 ° C, and most preferably 70 to 100 ° C.

In the tenter stretching step, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film, and the temperature distribution in the width direction in the tenter stretching step is preferably within ± 5 ° C., and ± 2 It is more preferably within 1 ° C, and most preferably within 1 ° C.

6) Winding step This is a step of winding up the acrylic resin-containing film by the winder 37 after the residual solvent amount in the web is 2% by mass or less, and by setting the residual solvent amount to 0.4% by mass or less. A film having good dimensional stability can be obtained.

As a winding method, a generally used one may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc., and these may be used properly.

The acrylic resin-containing film of the present invention is preferably a long film. Specifically, the acrylic resin-containing film is about 100 m to 5000 m, and is usually in the form of a roll. The width of the film is preferably 1.3 to 4 m, and more preferably 1.4 to 3 m.

The film thickness of the acrylic resin-containing film of the present invention is not particularly limited, but when used for a polarizing plate protective film described later, it is preferably 20 to 200 μm, more preferably 25 to 100 μm, and 30 to 80 μm. It is particularly preferred that

<Polarizing plate>
The polarizing plate used in the present invention can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the acrylic resin-containing film of the present invention, and is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution.

The film may be used on the other surface, or another polarizing plate protective film may be used. For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KV8UY-HA, KV8UX-RHA, KV8UX-RHA Etc.) are preferably used.

A polarizer, which is a main component of a polarizing plate, is an element that transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing or uniaxially stretching, and then performing a durability treatment with a boron compound.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. It is preferable to use a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded.

Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

The above-mentioned pressure-sensitive adhesive may be a one-component type or a type in which two or more components are mixed before use.

The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the film thickness after adhesion, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.

<Liquid crystal display device>
By incorporating the polarizing plate bonded with the acrylic resin-containing film of the present invention into a liquid crystal display device, various liquid crystal display devices with excellent visibility can be produced. The polarizing plate according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

The polarizing plate according to the present invention is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. Preferably used. In particular, in a large-screen display device having a screen of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen and the effect is maintained for a long time.

In addition, there was little color unevenness, glare and wavy unevenness, and the eyes were not tired even after long hours of viewing.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Production of acrylic resin-containing film>
(Preparation of acrylic resin-containing film 1)
(Preparation of dope solution)
BR85 (acrylic resin manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by mass Cellulose ester (cellulose acetate propionate acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 200000)
30 parts by mass Acrylic fine particles (C1) 2 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass <Preparation of acrylic fine particles (C1)>
A reactor with a reflux condenser with an internal volume of 60 liters was charged with 38.2 liters of ion-exchanged water and 111.6 g of sodium dioctylsulfosuccinate, and the temperature was raised to 75 ° C. under a nitrogen atmosphere while stirring at a rotational speed of 250 rpm. The effect of oxygen was virtually eliminated. Add 0.36 g of APS, and after stirring for 5 minutes, add a monomer mixture consisting of 1657 g of MMA, 21.6 g of BA, and 1.68 g of ALMA, and hold for another 20 minutes after detecting the exothermic peak. Polymerization of the innermost hard layer was completed.

Next, 3.48 g of APS was added, and after stirring for 5 minutes, a monomer mixture consisting of 8105 g of BA, 31.9 g of PEGDA (200), and 264.0 g of ALMA was continuously added over 120 minutes. After completion of the addition, the mixture was further maintained for 120 minutes to complete the polymerization of the soft layer.

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

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

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

The above abbreviations are the following materials.

MMA; methyl methacrylate MA; methyl acrylate BA; n-butyl acrylate ALMA; allyl methacrylate PEGDA; polyethylene glycol diacrylate (molecular weight 200)
n-OM; n-octyl mercaptan APS; ammonium persulfate (film formation of acrylic resin-containing film)
The produced dope solution was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. The peeled acrylic resin web was evaporated at 35 ° C., slit to 1.6 m width, and then dried at a drying temperature of 135 ° C. while being stretched 1.1 times in the width direction by a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter and relaxing at 130 ° C for 5 minutes, drying was completed while transporting the drying zone at 120 ° C and 130 ° C with a number of rolls, slitting to a width of 1.5 m, and 10 mm wide at both ends of the film. A knurling process having a thickness of 5 μm was performed, and the film was wound around a 6-inch inner diameter core with an initial tension of 220 N / m and a final tension of 110 N / m to obtain an acrylic resin-containing film 1. The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.10 times, and the TD direction was 1.01 times. The residual solvent amount of the acrylic resin-containing film film 1 described in Tables 2 and 3 was 0.1%, the film thickness was 60 μm, and the number of turns was 5000 m.

Hereinafter, the amount, type and composition ratio of the acrylic resin (A), the cellulose ester resin (B), and the acrylic fine particles (C) are changed as shown in Table 2 and Table 3, and in the same manner as the acrylic resin-containing film 1, Acrylic resin-containing films 2 to 34 were produced.

The acrylic resins used for the acrylic resin-containing films 1 to 28, 33, and 34 are Delpet 80N (Asahi Kasei Chemicals), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon). Is shown in Table 1.

The acrylic resins A1 to A4 used for the acrylic resin-containing films 29 to 32 were prepared by a known method.
A1: Poly (MMA-MA) mass ratio 98: 2 Mw 70000
A2: Poly (MMA-MA) mass ratio 97: 3 Mw 800000
A3: Poly (MMA-MA) mass ratio 97: 3 Mw930000
A4: Poly (MMA-MA) mass ratio 94: 6 Mw1100000
MMA; methyl methacrylate MA; methyl acrylate In addition, the column abbreviation of the substitution degree of the cellulose ester resin (B) shown in Tables 2 and 3 is as follows:
ac: acetyl group p: propionyl group b: butyryl group bz: benzoyl group oc: octanoyl group ph: phthalyl group In addition, the following ultraviolet absorbers were added to the acrylic resin-containing films 6 and 11 to prepare dopes.

Acrylic resin-containing film 6
Tinuvin 109 (Ciba Japan Co., Ltd.) 1.5 parts by mass Tinuvin 171 (Ciba Japan Co., Ltd.) 0.7 parts by mass Acrylic resin-containing film 11
LA-31 (made by ADEKA) 1.5 parts by mass

The comparative cellulose triacetate films 1 to 3 were prepared by the following method.

(Preparation of comparative cellulose triacetate film 1)
100 parts by mass of cellulose triacetate (degree of acetylation: 61%), 12 parts by mass of TPP (triphenyl phosphate), 320 parts by mass of methylene chloride, 50 parts by mass of methanol and 10 parts by mass of 1-butanol were put into a mixing tank for dope, By heating and stirring, cellulose triacetate was dissolved to prepare a dope. Separately, 15 parts by mass of UV absorber of UV-1 below, 80 parts by mass of methylene chloride and 20 parts by mass of methanol are put into another mixing tank, heated and stirred to dissolve the UV absorber, and an ultraviolet absorber-containing solution is prepared. Prepared. Furthermore, 0.5 parts by mass of silicon dioxide fine particles (trade name: Aerosil R972D, average particle size of primary particles: 0.016 μm; manufactured by Nippon Aerosil Co., Ltd.) are charged and mixed. Dispersion was prepared by dispersing so that the average particle size in the solution was 0.3 μm, and a solution containing an ultraviolet absorber was prepared. An ultraviolet absorber-containing solution was added at a ratio of 2 parts by mass with respect to 100 parts by mass of the dope prepared above and mixed well in a mixing tank, and then cast as a 50 ° C. dope on a casting band. Casting was performed so that the thickness of the dried film was 80 μm. After drying from the casting band, it was peeled off and further dried in a drying zone at 145 ° C. for 15 minutes, and then a comparative cellulose triacetate film 1 (shown as Comparative 1 in Table 5) having a thickness of 80 μm was produced.

(Preparation of comparative cellulose triacetate film 2)
As a matting agent solution, 0.7% by mass of silicon dioxide (secondary average particle size of 0.5 μm, primary particle size of 16 nm is used), cellulose triacetate (average degree of acetylation 61%), 3.3% by mass, methylene chloride 88 It prepared so that it might become mass% and methanol 8 mass%. Next, a dope having a mixed composition of cellulose triacetate (average acetylation degree 61%) mass 17%, plasticizer 2% by mass, methylene chloride 71% by mass, methanol 6% by mass and the matting agent solution 4% by mass was prepared in advance. . After the dope was swollen, it was cooled to -70 ° C. Further, the dope was introduced into the autoclave replaced under a nitrogen atmosphere and dissolved at 160 ° C. and 0.98 MPa for 10 minutes. The solution was filtered and cast on a casting band as a 50 ° C. dope. Casting was performed so that the thickness of the dried film was 80 μm. After drying from the casting band, it was peeled off, and further dried at 145 ° C. for 15 minutes in a drying zone to obtain a comparative cellulose triacetate film 2 having a thickness of 80 μm (shown as Comparative 2 in Table 5). Moreover, the mat agent content of the obtained film was 0.15% by mass.

(Preparation of comparative cellulose triacetate film 3)
A dope solution of cellulose triacetate was prepared as follows.
Cellulose triacetate (TAC): 100kg
Tinuvin 326 (Ciba Japan): 0.3kg
Tinuvin 171 (Ciba Japan): 0.5kg
Tinuvin 109 (Ciba Japan): 0.5kg
Ethyl phthalyl ethyl glycolate: 2kg
Triphenyl phosphate (TPP): 9.7 kg
Aerosil 200V (Nippon Aerosil Co., Ltd.): 0.09kg
Methylene chloride: 320kg
Ethanol: 20kg
These were put into an airtight container and completely dissolved while maintaining agitation at 80 ° C. under pressure.

After the dope solution was filtered, it was cast as a 33 ° C. dope on a casting band. Casting was performed so that the thickness of the dried film was 80 μm. After drying from the casting band, it was peeled off, and further dried at 145 ° C. for 15 minutes in a drying zone to obtain a comparative cellulose triacetate film 3 (shown as Comparative 3 in Table 5) having a thickness of 80 μm.

"Evaluation methods"
The following evaluations were carried out on the obtained acrylic resin-containing films 1 to 34 and comparative cellulose triacetate films 1 to 3, and the results are shown in Tables 4 and 5.

(Calculation of particle abundance)
The cross-sectional SEM images of the prepared acrylic resin-containing films 1 to 33, comparative cellulose triacetate films 1 to 3 and comparative acrylic resin-containing film 34 were analyzed, and the existence ratio of acrylic fine particles and silicon dioxide in the film thickness direction was calculated.

(Haze)
Each of the film samples prepared above was conditioned in an air-conditioned room at 23 ° C. and 55% RH for 24 hours, and then one film sample was subjected to the same conditions under JIS K-7136 as a haze meter (NDH2000 type, Nippon Denshoku). Measured by Kogyo Co., Ltd.).

(Tension softening point)
The following evaluation was performed using a Tensilon tester (ORIENTEC, RTC-1225A).

An acrylic resin-containing film conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH is cut out at 120 mm (length) × 10 mm (width) under the same conditions, and heated at 30 ° C./min while pulling with a tension of 10 N The temperature was continuously increased at a speed, and the temperature at 9 N was measured three times, and the average was obtained.

(Ductile fracture)
An acrylic resin-containing film conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH is cut out at 100 mm (length) × 10 mm (width) under the same conditions, with a radius of curvature of 0 mm and a bending angle at the center in the vertical direction. Was folded in a mountain fold and a valley fold one time each so that the films were exactly overlapped at 180 °, and this evaluation was measured three times and evaluated as follows. In addition, breaking of evaluation here represents having broken and isolate | separated into two or more pieces.

○ ・ ・ ・ Cannot be folded 3 times × ・ ・ ・ Can be folded at least 1 out of 3 times (Static friction coefficient)
Each of the produced film samples was conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH, and then measured using a friction measuring device TR-2 (manufactured by Toyo Seiki Co., Ltd.).

(Film deformation)
Each of the produced film samples was allowed to stand for 1000 hours in an atmosphere of 90 ° C. and DRY (relative humidity of 5% RH or less), and the degree of film deformation was visually observed under the conditions of 23 ° C. and 55% RH.

○: No film deformation Δ: Film deformation is observed ×: Significant film deformation is recognized (cutting property)
A sample conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH is torn using a light load tear (Elmendorf) tester (manufactured by Toyo Seiki Co., Ltd.) under the same conditions, and evaluated as follows. did.

◯: The tear surface is very smooth and is torn straight.

△: There is a slight burr on the tear surface, but it is torn straight.

X: There are considerable burrs on the tearing surface, and it is not torn straight.

(Film appearance)
Regarding the produced film, the appearance of the film conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH was visually evaluated and evaluated as follows.

○: Very smooth flatness △: Slightly creased, wrinkled, and step can be confirmed ×: Clearly creased, wrinkled, and step can be confirmed (Preparation of polarizing plate)
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 5 times at 50 ° C. to form a polarizing film. Next, the acrylic resin-containing film 1 produced in Example 1 was subjected to corona treatment on one side of the polarizing film and then bonded. Furthermore, KC4UY manufactured by Konica Minolta Opto Co., Ltd., which is a retardation film subjected to alkali saponification treatment, was bonded to the other surface of the polarizing film and dried to prepare a polarizing plate P1. Similarly, polarizing plates P2 to P37 (corresponding film numbers are shown in Tables 4 and 5 respectively) were prepared using acrylic resin-containing films 2 to 34 and comparative cellulose triacetate films 1 to 3. The polarizing plate using the acrylic resin-containing film of the present invention was excellent in film cutting properties and easy to process.

(Characteristic evaluation as a liquid crystal display device)
<Production of liquid crystal display device>
Using the Hitachi liquid crystal television Woo32 H-90, which is an IPS mode type liquid crystal display device, the polarizing plate on the viewing side previously bonded is peeled off, and the polarizing plates P1 to P37 thus prepared are contained in the acrylic resin of the present invention. Bonding was performed so that the film became the glass surface of the liquid crystal cell. In that case, it bonded together so that an absorption axis might face in the same direction as the polarizing plate previously bonded.
As described above, liquid crystal display devices 1 to 37 were produced.

(Viewing angle fluctuation)
The following evaluation was performed using the liquid crystal display devices 1 to 37 produced as described above.

The viewing angle of the liquid crystal display device was measured using EZ-Contrast 160D manufactured by ELDIM in an environment of 23 ° C. and 55% RH. Subsequently, the polarizing plate treated at 60 ° C. and 90% RH for 1000 hours was measured in the same manner, and evaluated according to the following criteria in four stages.

○: No viewing angle variation △: Viewing angle variation is observed ×: Viewing angle variation is very large (color shift)
Liquid crystal display devices 1 to 37 were prepared by attaching a polarizing plate in the same manner as the viewing angle evaluation described above. Next, the display was made black and the color change when observed from an angle of 45 ° with the front was evaluated according to the following criteria.

○: No color change Δ: Color change is recognized ×: Color change is very large Tables 4 and 5 show the results of the above evaluation.

From Table 4 and Table 5, the acrylic resin-containing film of the present invention has excellent transparency, high heat resistance, and markedly improved brittleness. By using the acrylic resin-containing film, the polarizing plate is punched out. Improves the yield in work such as work and panel pasting, makes it possible to increase the length of film winding, and improves work efficiency. Furthermore, color generated depending on the viewing angle when used in a liquid crystal display device It can be seen that a liquid crystal display device in which the shift is reduced and the contrast is remarkably improved can be obtained.

Claims (7)

An acrylic resin-containing film containing 10 to 50 parts by mass of a cellulose ester resin (B) with respect to 50 to 90 parts by mass of the acrylic resin (A), the one side of the acrylic resin-containing film and the other side The coefficient of static friction when superposed on a surface is 0.3 to 0.8, the softening point of tension is 105 to 145 ° C., the haze value is less than 1%, and no ductile fracture occurs. Acrylic resin-containing film. The acrylic resin-containing film has an acrylic resin (A) having a weight average molecular weight (Mw) of 80000 to 1000000, and a total substitution degree (T) of acyl groups of the cellulose ester resin (B) of 2.00 to 3.00. The acetyl group substitution degree (ac) is 0.10 to 1.90, and the portion other than the acetyl group is substituted with an acyl group composed of 3 to 7 carbon atoms. r) is 1.10 to 2.90, the weight average molecular weight (Mw) is 75000 to 280000, and the film contains 0.05 to 45% by mass of acrylic fine particles (C) based on the total mass of the film. The acrylic fine particles are present in an amount of 40 to 60% of the total abundance in a region within 25% of the total thickness of the film from both surfaces of the film. Term Acrylic resin-containing film according. A method for producing an acrylic resin-containing film, wherein the acrylic resin-containing film according to claim 1 or 2 is produced by being stretched by 5% to 40% in at least one direction. A polarizing plate using the acrylic resin-containing film according to claim 1 or 2. A liquid crystal display device using the polarizing plate according to claim 4. A polarizing plate using a film produced by the method for producing an acrylic resin-containing film according to claim 3. A liquid crystal display device using the polarizing plate according to claim 6.

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