JP5447374B2 - Acrylic film manufacturing method and acrylic film produced by the manufacturing method - Google Patents

Description

  The present invention relates to a method for producing an optical acrylic film having excellent flexibility and surface properties.

  An acrylic film typified by a polymethyl methacrylate film has been expected as an optical film because of its high transmittance in the visible light region, low intrinsic birefringence, and a small photoelastic coefficient.

  However, acrylic films are prone to cracking, and their inferior handleability has hindered their use.

  As a countermeasure against cracking, a method of stretching an acrylic film has been proposed (Patent Document 1).

  In addition, there is also known a method of imparting flexibility by adding elastic particles to a specific acrylic film and further heat-treating (Patent Document 2).

A technique of mixing a flexible resin having a glass transition temperature of 10 ° C. or lower instead of elastic particles has also been proposed (Patent Document 3).
Since the method of Patent Document 1 is originally applied to an acrylic film that is easily cracked, it is difficult to establish production conditions and lacks versatility.

  The method of Patent Document 2 has a problem that the time required for the heat treatment is very long, and the surface properties of the manufactured acrylic film are inferior. In addition, the heat resistance is remarkably lowered, and when such an acrylic film is used for, for example, a liquid crystal display device, the film is deformed by continuous use for a long time, and a clear image cannot be displayed. There was a thing.

  The method of Patent Document 3 is effective for a specific acrylic resin having a lactone ring structure, and since it is premised on melt casting, the surface property does not exceed the level of Patent Document 2. It was. Further, as in Patent Document 2, there is a problem that the heat resistance is remarkably lowered.

JP 2005-162835 A International Publication No. 2005/105918 JP 2007-100044 A

  The present invention provides a method for producing an acrylic film having excellent flexibility and surface properties with good productivity and an acrylic film produced by the method.

  The above-described problems of the present invention are solved by the following means.

  1. A method for producing an acrylic film containing an acrylic resin (A) and less than 5% by mass of acrylic particles (C) by a solution casting method, wherein the solvent satisfies the following relationships (1) and (2) Using a mixed solution of A and B and drying until the residual solvent is 5 to 50% by mass, and in a state where the residual solvent is 5 to 50% by mass, the acrylic film is applied to the glass transition temperature (hereinafter, apparent Tg) And a step of heat-treating in the range of + 10 ° C. to apparent Tg + 90 ° C.

(1) Boiling point of solvent A + 35 ° C. <boiling point of solvent B (2) Mass ratio of solvent A to solvent B in the mixed solution A: B = 98: 2 to 70:30
2. The production according to 1 above, wherein no ductile fracture occurs in an atmosphere of 23 ° C. and 55% RH, the tension softening point is 105 to 145 ° C., and the haze value is less than 1.0%. Acrylic film produced by the method.

  3. The acrylic film is a resin film containing an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70 and in a compatible state, the acrylic resin (A) 2. The weight average molecular weight Mw is 80000 or more and 1000000 or less, the weight average molecular weight Mw of the cellulose ester resin (B) is 75000 or more and 280000 or less, and the total substitution degree (T) of acyl group is 2.0 or more. 3. The acrylic film as described in 2 above, wherein the substitution degree of the acyl group having 0 or less and 3 to 7 carbon atoms is 1.2 or more and 3.0 or less.

  According to the present invention, an acrylic film having excellent flexibility and surface properties can be produced with high productivity.

Schematic diagram showing the dope preparation process, casting process and drying process of the solution casting film forming method

  The present invention is a method for producing an acrylic film containing an acrylic resin (A) and less than 5% by mass of acrylic particles (C) by a solution casting method, wherein the following (1) and (2) are used as a solvent: Using a mixed solvent of solvents A and B satisfying the relationship, drying until the residual solvent becomes 5 to 50% by mass, and in the state where the residual solvent is 5 to 50% by mass, the acrylic film is applied to Tg + 10 ° C. to Tg + 90 It has the process of heat-processing in the range of ° C.

(1) Boiling point of solvent A + 35 ° C. <boiling point of solvent B (2) Mass ratio of solvent A to solvent B in the mixed solution A: B = 98: 2 to 70:30
That is, in the present invention, when the acrylic film is cast by solution casting, the solvent to be used is a mixed solution that satisfies the relations (1) and (2), so that the time for heat treatment can be greatly reduced. The acrylic film can be shortened and the surface properties of the finished acrylic film are also excellent.

The acrylic film of the present invention is produced by dissolving at least an acrylic resin (A) and less than 5% by mass of acrylic particles (C) in a mixed solvent of a solvent A and a solvent B, and casting on a support such as a belt or a drum. It is what is filmed.
<Mixed solvent of solvent A and solvent B>
The mixed solvent of the solvent A and the solvent B in the present invention is a mixed solvent composed of at least the solvent A and the solvent B, and the combined amount of the solvents A and B is 70% by mass or more of the entire mixed solvent.

  The solvent A and the solvent B satisfy the following relationship.

(1) Boiling point of solvent A +++ 35 ° C. <Boiling point of solvent B (2) Mass ratio of solvent A to solvent B in the mixed solution A: B = 98: 2 to 70:30
The boiling point of the solvent A is 40 to 95 ° C, preferably 50 to 90 ° C. The boiling point of the solvent B is 70 to 155 ° C, preferably 75 to 150 ° C.

  Solvents A include methanol (MeOH, 64 ° C.), ethanol (EtOH, 77 ° C.), methyl acetate (MeAc, 55 ° C.), ethyl acetate (EtAc, 75 ° C.), methylene chloride (MC 40 ° C.), acetone (AC, 55 ° C.) and methyl ethyl ketone (MEK, 77 ° C.). In addition, () represents an abbreviation and a boiling point (abbreviation, boiling point).

  As the solvent B, ethanol (EtOH, 77 ° C.), toluene (TOL, 111 ° C.) n-butyl alcohol (nBuOH, 118 ° C.), isoamyl alcohol (iAmOH, 126 ° C.), cyclohexanol (CHOH, 152 ° C.), ethylene Examples include glycol monomethyl ether (EGMME, 124 ° C.), ethylene glycol monoethyl ether (EGMEE, 132 ° C.), cyclohexanone (CHNO, 150 ° C.), and the like.

  Two or more solvents A and B may be used.

Solvent A alone has a solubility of 10% by mass or more with respect to the acrylic resin (A). Moreover, you may mix a solvent other than solvent A and B in the mixed solvent in the range of less than 30 mass% of a mixed solvent.
<The process of heat-processing in the range of Tg + 10 degreeC-Tg + 90 degreeC of an acrylic film in a state whose residual solvent is 5-50 mass%>
In this invention, it is characterized by heat-processing in the range of Tg + 10 degreeC-Tg + 90 degreeC over the acrylic film only in the state whose residual solvent is 5-50 mass% of an acrylic film. Therefore, in a drying process, it adjusts so that a residual solvent may be 5-50 mass%.

  The heat treatment is performed in the range of Tg + 10 ° C. to Tg + 90 ° C. over the acrylic film. Preferably, it is Tg + 50-Tg + 90 degreeC.

  The heat treatment time is 15 to 90 seconds, preferably 30 to 60 seconds.

  In the present invention, by using the mixed solvent, rapid volatilization of the solvent at the initial stage of drying in the drying step can be prevented, and as a result, the surface shape of the film can be kept good.

  Moreover, since the boiling point of the solvent B is relatively high, the content ratio of the solvent B is higher than the initial solvent ratio when the residual solvent amount is 5 to 50% by mass, and the solvent B has an absolute boiling point. Since it is high, the solvent can remain even during the heat treatment, that is, where the residual solvent is as large as 5 to 50% by mass, the Tg of the acrylic film is apparently lowered, and the effect of the heat treatment is amplified and the heating is performed. It is thought that the effect of the treatment was expressed efficiently.

  Note that the apparent Tg of the acrylic film in the present invention indicates a state in which a phenomenon such as softening occurs at a temperature lower than the actual glass transition temperature by including a solvent. Specifically, it can be measured by the following procedure.

  In the fully dried acrylic film (less than 1% residual solution) of the present invention, a differential scanning calorimeter (DSC-7 manufactured by Perkin Elmer) was used in advance under an atmosphere of 23 ° C. and 55% RH. The time-conditioned sample is measured in a nitrogen stream at a heating rate of 20 ° C./min, and the glass transition temperature (Tg) is determined according to JIS K7121 (1987).

  Next, the elastic modulus of the film is measured at a temperature of 5 points or more from 30 ° C. to 100 ° C. (with an interval of 10 ° C. or more) to create an approximate curve (calibration curve). Furthermore, the elastic modulus of the acrylic film containing the residual solvent is measured at 30 ° C., and the value at this time is defined as Ea (GPa). A temperature corresponding to Ea (GPa) is calculated from a calibration curve prepared in advance, and this value is defined as Ta (° C.).

Finally, apparent Tg is apparent Tg (° C.) = Tg−Ta (° C.) − 30 (° C.)
Can be obtained as
<Configuration of acrylic film>
The acrylic film of the present invention comprises at least an acrylic resin (A) and less than 5% by mass of acrylic particles (C), and contains other additives.

  And, in an atmosphere of 23 ° C. and 55% RH, ductile fracture does not occur, the tension softening point is 105 to 145 ° C., and the haze value is less than 1.0%.

  Furthermore, the acrylic film is a resin film containing an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70 and in a compatible state, and the acrylic resin (A ) Has a weight average molecular weight Mw of 80000 or more and 1000000 or less, the weight average molecular weight Mw of the cellulose ester resin (B) is 75000 or more and 280000 or less, and the total substitution degree (T) of the acyl group is 2.0 or more, The substitution degree of the acyl group having 3.0 or less and 3 to 7 carbon atoms is 1.2 or more and 3.0 or less.

In this invention, it is preferable that it is an aspect containing 0.1 to less than 5 mass% acrylic particle (C) with respect to the total mass of resin which comprises the said acrylic film.
<Acrylic resin (A)>
The acrylic resin (A) used in the present invention includes a methacrylic resin. As resin, what consists of 50-100 mass% of methyl methacrylate units and 0-50 mass% of other monomer units copolymerizable with this is preferable.

  Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Saturated acids, maleic acids, fumaric acids, unsaturated divalent carboxylic acids 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, glutaric anhydride, and the like. These may 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 film of the present invention has a weight average molecular weight (Mw) of 80,000 to 1,000,000, preferably 150,000 from the viewpoint of mechanical strength as a film and fluidity when producing the film. ~ 400,000.

  The weight average molecular weight of the acrylic resin (A) 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.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin (A) in this invention, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide can be used, an azo type can be used, and a redox type can also be used.

  Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. 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.

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

A commercially available thing can also be used as an acrylic resin (A) of this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Denki Kagaku Kogyo Co., Ltd.) and the like can be mentioned. .
<Acrylic particles (C)>
The acrylic particles (C) of the present invention are characterized by existing in the form of particles in the acrylic film containing the acrylic resin (A).

  Here, for example, a PTFE membrane having a pore diameter smaller than the average particle diameter of the acrylic particles (C) when a predetermined amount of the prepared acrylic film is collected, dissolved in a solvent, stirred, and sufficiently dissolved and dispersed. It is preferable that the weight of the insoluble matter filtered and collected using a filter is 90% by mass or more of the acrylic particles (C) added to the acrylic film.

  The acrylic particles (C) used in the present invention are preferably acrylic particles (C) having a layer structure of two or more layers, and particularly preferably the following multilayer structure acrylic granular composite.

  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.

  The following are mentioned as a preferable aspect of the multilayer structure acrylic type granular composite used for the acrylic resin composition of this invention. (A) Monomer composed of 80 to 98.9% by mass of methyl methacrylate, 1 to 20% by mass of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group, and 0.01 to 0.3% by mass of polyfunctional grafting agent An innermost hard layer polymer obtained by polymerizing the body mixture, (b) in the presence of the innermost hard layer polymer, 75 to 98.5% by mass of an alkyl acrylate having an alkyl group with 4 to 8 carbon atoms, A crosslinked soft layer polymer obtained by polymerizing a monomer mixture comprising a multifunctional crosslinking agent of 0.01 to 5% by mass and a multifunctional grafting agent of 0.5 to 5% by mass; (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 The outermost hard layer polymer (c) is composed of 20 to 50% by mass, has 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 size of each layer of the multilayer structure acrylic granular composite are defined, but also the multilayer structure acrylic granular composite. By setting the tensile modulus of the body and the swelling degree 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 multi-layer structure acrylic granular composite is 80 to 98.9% by mass of methyl methacrylate and 1 to 20% of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. % And a polyfunctional grafting agent obtained by polymerizing a monomer mixture consisting of 0.01 to 0.3% by mass.

  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 75-98.5 having 1 to 8 carbon atoms in the presence of the innermost hard layer polymer (a). What is obtained by polymerizing a monomer mixture consisting of mass%, polyfunctional crosslinking agent 0.01 to 5 mass% and polyfunctional grafting agent 0.5 to 5 mass% is preferable.

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

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

  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 (A), and the ratio between the two 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 item 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. 0.5-5 mass% is preferable from a viewpoint of the property provision effect.

  As the polyfunctional crosslinking agent, generally known crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, and dimethacrylic compounds can be used, and 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 at the time of polymerization of the soft layer (b) and develop an 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 mass from the viewpoint of imparting impact resistance.

  In the presence of the innermost hard layer polymer (a) and the soft layer polymer (b), the outermost hard layer polymer (c) constituting the multilayer structure acrylic granular composite is 80 to 99 masses of methyl methacrylate. % And a monomer mixture obtained by polymerizing a monomer mixture consisting of 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is preferable.

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

  Further, for the purpose of improving the compatibility with the acrylic resin (A) during the polymerization of the outermost hard layer (c), it is also possible to use an alkyl mercaptan or the like as a chain transfer agent in order to adjust the molecular weight.

  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 to the outside by a method of sequentially increasing the amount of chain transfer agent to be added each time. It is possible to make it smaller.

  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 (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. , More preferably 500 nm or less, and 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.

  In addition, specific examples of acrylic particles that are graft copolymers preferably used as acrylic particles (C) preferably used in the present invention include unsaturated carboxylic acid ester-based monomers in the presence of a rubbery polymer. A graft copolymer obtained by copolymerizing a monomer mixture of a polymer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith. A polymer is mentioned.

  The rubbery polymer used for the acrylic particles (C) that are the 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.

  Moreover, since the transparency of the acrylic film of this invention can be obtained when each refractive index of an acrylic resin (A) and an acrylic particle (C) is approximated, it is preferable.

  Specifically, the refractive index difference between the acrylic 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), or the composition of the rubbery polymer or monomer used in the acrylic particles (C) The difference in refractive index can be reduced by a method of adjusting the ratio, and an acrylic film having excellent transparency can be obtained.

  In addition, the refractive index difference here means that the acrylic film of the present invention is sufficiently dissolved in a solvent in which the acrylic resin (A) is soluble to obtain a cloudy solution, and this is subjected to an operation such as centrifugation. After separating the solvent-soluble part and the insoluble part and purifying the soluble part (acrylic resin (A)) and the insoluble part (acrylic particles), the difference in the measured refractive index (23 ° C., measurement wavelength: 550 nm) Indicates.

  There is no restriction | limiting in particular in the method of mix | blending an acrylic particle (C) with an acrylic resin (A) in this invention, After blending an acrylic resin (A) and another arbitrary component previously, Usually at 200-350 degreeC, A method of uniformly kneading with a single screw or twin screw extruder while adding acrylic particles is preferably used.

  In addition, a solution in which acrylic particles are dispersed in advance is added to and mixed with a solution (dope solution) in which acrylic resin (A) is dissolved, and acrylic particles (C) and other optional additives are dissolved and mixed. A method such as adding the solution in-line can be used.

  As the acrylic particles (C) of the present invention, commercially available ones can also be used. For example, Metablene W-341 (C2), Chemisnow MR-2G (C3), MS-300X (C4) (manufactured by Mitsubishi Rayon Co., Ltd.) "Kane Ace" manufactured by Kaneken Chemical Co., Ltd., "Paraloid" manufactured by Kureha Chemical Industry Co., Ltd., "Acryloid" manufactured by Rohm and Haas, "Staffroid" manufactured by Gantz Kasei Kogyo Co., Ltd., and "Kuraray Co." Parapet SA ″ and the like can be mentioned, and these can be used alone or in combination of two or more.

In the acrylic film of this invention, it is preferable to contain 0.1-5 mass% acrylic particle (C) with respect to the gross mass of resin which comprises this film.
<Cellulose ester resin (B)>
The acrylic film of the present invention preferably contains a cellulose ester resin (B) from the viewpoint of transparency, particularly when improved with brittleness and heat resistance, and when mixed with the acrylic resin (A). The cellulose ester resin (B) has a total substitution degree (T) of acyl groups of 2.0 to 3.0 and a substitution degree of acyl groups of 3 to 7 carbon atoms of 1.2 to 3.0. Is preferred. That is, the cellulose ester resin (B) is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used, but a propionyl group is particularly preferably used. .

  When the total substitution degree of the acyl group of the cellulose ester resin (B) is less than 2.0, that is, when the residual degree of the hydroxyl groups at the 2, 3, and 6 positions of the cellulose ester molecule is more than 1.0, the acrylic ester The resin (A) is not sufficiently compatible with the haze.

  Moreover, even if the total substitution degree of the acyl group is 2.0 or more, if the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2, still sufficient compatibility cannot be obtained, Brittleness will decrease. For example, even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1. When it is less than 2, the compatibility is lowered and the haze is increased. Even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 8 or more carbon atoms is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2. In such a case, the brittleness is lowered and desired characteristics cannot be obtained.

As for the acyl substitution degree of the cellulose ester resin (B) of the present invention, the total substitution degree (T) is 2.0 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3. .0 is fine,
It is preferable that the total substitution degree of acyl groups having 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms is 1.3 or less.

  In the present application, the “acyl group” is meant to include those further having a substituent. However, the carbon number of the acyl group includes a substituent of the acyl group.

  When the said cellulose ester resin (B) has an aromatic acyl group as a substituent, it is preferable that the number of the substituents X substituted to an aromatic ring is 0-5. Also in this case, it is necessary to pay attention so that the substitution degree of the acyl group having 3 to 7 carbon atoms including the substituent is 1.2 to 3.0. For example, since the benzyl group has 7 carbon atoms, when it has a substituent containing carbon, the benzyl group has 8 or more carbon atoms and is not included in the acyl group having 3 to 7 carbon atoms. Become.

  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 said cellulose ester resin (B), having a structure which has at least 1 sort (s) of a substituted or unsubstituted C3-C7 aliphatic acyl group is used as a structure used for the cellulose resin of this invention.

  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, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3 .0.

  Moreover, it is a preferable structure that the sum total of the substitution degree of other than an acyl group having 3 to 7 carbon atoms, that is, an acetyl group and an acyl group having 8 or more carbon atoms is 1.3 or less.

  The cellulose ester resin (B) of the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate, particularly cellulose acetate. Propionate and cellulose propionate are more preferable.

  Among these, particularly preferable cellulose ester resins (B) are cellulose acetate propionate and cellulose acetate butyrate, and those having an acyl group having 3 or 4 carbon atoms as a substituent are preferable.

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

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin (B) of the present invention is 75000 or more, particularly from the viewpoint of improvement in compatibility with the acrylic resin (A) and brittleness, and is preferably in the range of 75,000 to 300,000. More preferably, it is within the range of 100,000 to 240,000, particularly preferably 160000 to 240,000.
<Compatible state>
In the acrylic film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably contained in a compatible state at a mass ratio of 100: 0 to 30:70.

  Preferably it is 95: 5-50: 50, More preferably, it is 90: 10-60: 40.

  In the acrylic film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) need to be contained in a compatible state. The physical properties and quality required for an acrylic film are achieved by supplementing each other by dissolving different resins.

  Whether the acrylic resin (A) and the cellulose ester resin (B) are in a compatible state is determined by the glass transition temperature Tg.

  When both resins are simply mixed, there are two glass transition temperatures for each resin because there is a glass transition temperature for each resin. However, when both resins are compatible, each glass has its own glass transition temperature. The temperature disappears and becomes one glass transition temperature, which becomes the glass transition temperature of the compatible resin.

The glass transition temperature Tg1, 2 of the mixture in this compatible state is _approximated by the Gordon-Taylor equation (M. Gordon and JS Taylor, 2 J. of Applied Chem. 493-500 (1952)). It is known that it can be done.

T _g1,2 = (w ₁ T _g1 + Kw ₂ T _g2 ) / (w ₁ + Kw ₂ )
[Where w ₁ and w ₂ are mass fractions of component 1 (acrylic resin (A)) and 2 (cellulose ester resin (B)); T _g1 and T _g2 are component 1 _{And Tg1,2} is the glass transition temperature of the mixture of components 1 and 2; K is a constant for the free volume of the two resins. ]
The acrylic resin (A) and the cellulose ester resin (B) are each preferably an amorphous resin, and either one may be a crystalline polymer or a partially crystalline polymer. In the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably compatible with each other to become an amorphous resin.

  The mixed resin obtained by polymerizing the precursor of acrylic resin (A) such as monomer, dimer or oligomer with cellulose ester resin (B) undergoes graft polymerization, crosslinking reaction or cyclization reaction. In many cases, it does not dissolve in a solvent or cannot be melted by heating, and does not correspond to the resin contained in the compatible state of the present invention.

  The total mass of the acrylic resin (A) and the cellulose ester resin (B) in the acrylic film of the present invention is preferably 55% by mass or more of the acrylic film, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

  When using a resin other than the acrylic resin (A), the cellulose ester resin (B), and the acrylic particles (C), it is preferable to adjust the addition amount within a range that does not impair the function of the acrylic film of the present invention.

Examples of resins other than the acrylic resin (A), the cellulose ester resin (B), and the acrylic particles (C) include polystyrene, polyvinyl acetate, polyolefin, and polycarbonate.
<Other additives>
The acrylic film of the present invention can contain an ultraviolet absorber, a retardation control agent, a matting agent, and an antioxidant as other additives.

<Ultraviolet absorber>
Moreover, in this invention, a ultraviolet absorber can also be used individually or in combination.

  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.

  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.

  In the present invention, a conventionally known ultraviolet absorbing polymer can also be used. Although it does not specifically limit as a conventionally well-known ultraviolet absorptive polymer, For example, the polymer which homopolymerized RUVA-93 (made by Otsuka Chemical), the polymer which copolymerized RUVA-93, and another monomer, etc. are mentioned. .

Specific examples include PUVA-30M obtained by copolymerization of RUVA-93 and methyl methacrylate at a ratio (mass ratio) of 3: 7, and PUVA-50M obtained by copolymerization at a ratio of 5: 5 (mass ratio). It is done.
(Phase difference control agent)
In the present invention, as the retardation control agent, compounds described in JP-A No. 2002-296421 and various ester plasticizers can be used. Hereinafter, preferred ester compounds will be described in detail.

  In the present invention, among various compounds described below, a compound having a structure in which aromatic rings are arranged in a plane when added and stretched as an additive is preferable.

  For this reason, a compound in which an aromatic ring is contained as a block in the main chain or at the terminal is preferable.

<Polyester polyol>
The polyester polyol used in the present invention includes a dehydration condensation reaction between a glycol having an average carbon number of 2 to 3.5 and a dibasic acid having an average carbon number of 4 to 5.5, or the glycol. It is preferable that it is manufactured by a conventional method by addition of an anhydrous dibasic acid having an average carbon number of 4 to 5.5 and a dehydration condensation reaction.

  As the glycol and the dibasic acid constituting the polyester polyol used in the present invention, a combination in which the total of the average carbon number of the glycol and the average carbon number of the dibasic acid is 6 to 7.5 is preferable.

  The polyester polyol obtained from the glycol and the dibasic acid may have a number average molecular weight in the range of 1,000 to 200,000, more preferably 1000 to 5,000 basically hydroxyl-terminated polyester, and a number average molecular weight of 1200. Those having ˜4000 are particularly preferably used.

  By using a polyester polyol having a number average molecular weight in such a range, a retardation control agent (cellulose ester modifier) excellent in compatibility with the cellulose ester can be obtained by solid phase reaction.

  In obtaining the effect of the present invention, the polyester polyol having a number average molecular weight of 1000 or more is preferably contained in the film in an amount of 2 to 30% by mass from the viewpoint of retardation development, compatibility, moisture permeability, and the like. More preferably, it is 10-20 mass%.

  Actually, the content of the polymer in the film depends on the type of polymer and the weight average molecular weight, and the performance such as dimensional stability, retentivity, and transmittance is within the range where dope, web, and phase separation does not occur after film formation. It is decided accordingly.

  On the other hand, the content of the carboxyl group terminal in the polyester polyol used in the present invention is preferably 1/20 or less of the number of hydroxyl groups from the viewpoint of the effect of the present invention. It is more preferable to stop at 40 or less.

<Aromatic terminal ester plasticizer>
As the retardation control agent of the present invention, an aromatic terminal ester plasticizer represented by the following general formula (I) can be used.

General formula (I) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (I), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the aromatic terminal ester plasticizer of the present invention include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, and normal propyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Although the specific compound of the aromatic terminal ester plasticizer of this invention is shown below, this invention is not limited to this.

  The content of the aromatic terminal ester plasticizer of the present invention is preferably 1 to 20% by mass, particularly preferably 3 to 11% by mass in the cellulose ester film.

<Polyhydric alcohol ester>
In the present invention, a polyhydric alcohol ester plasticizer can be further used as the retardation control agent.

  The polyhydric alcohol ester used in the present invention is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in the present invention is represented by the following general formula (1).

General formula (1) R1- (OH) _n
In the formula, R1 represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic or phenolic hydroxyl group.

  Examples of preferable polyhydric alcohols include the following.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol.

  Of these, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used.

  Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used.

  It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. In particular, benzoic acid is preferred.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric alcohol ester, It is preferable that it is the range of molecular weight 300-1500, and it is further more preferable that it is the range of 350-750.

  A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The specific compound of a polyhydric alcohol ester is shown below.

<Sugar ester compound>
The retardation control agent of the present invention is preferably an acrylic film containing a sugar ester compound obtained by esterifying a hydroxyl group of a sugar compound in which 1 to 12 at least one structure selected from a furanose structure and a pyranose structure is bonded.

  Examples of the sugar compound of the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, etc., particularly those having both a furanose structure and a pyranose structure. preferable.

The ester compound is a monosaccharide (α-glucose, β-fructose) benzoate or a monosaccharide represented by the following general formula (A): —OR ₁₂ , —OR ₁₅ , —OR ₂₂ , —OR ₂₅ It is preferable that the benzoic acid ester of the polysaccharide of m + n = 2-12 produced | generated by dehydration condensation of arbitrary two or more places.

  The sugar ester compound of the present invention is one in which part or all of the hydroxyl groups of the sugar compound are esterified or a mixture thereof.

  The benzoic acid in the above general formula may further have a substituent, for example, an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group have a substituent. You may have.

  The acrylic film of the present invention preferably contains 1 to 30% by mass of the total amount of the resin constituting the acrylic film in order to suppress the fluctuation of the retardation value and stabilize the display quality.

  The sugar ester compound of the present invention is commercially available as Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.).

<Other phase difference control agents>
As the phase difference controlling agent of the present invention, those containing bisphenol A in the molecule are also preferred. A compound in which ethylene oxide or propylene oxide is added to both ends of bisphenol A can be used.

  For example, BP series such as New Pole BP-2P, BP-3P, BP-23P, BP-5P, BPE-20 (F), BPE-20NK, BPE-20T, BPE-40, BPE-60, BPE-100, There are BPE series (manufactured by Sanyo Chemical Co., Ltd.) such as BPE-180, and BPX series (manufactured by Adeka Co., Ltd.) such as Adeka polyether BPX-11, BPX-33, BPX-55.

  Diallyl bisphenol A, dimethallyl bisphenol A, tetrabromobisphenol A with bisphenol A substituted with bromine, oligomers and polymers obtained by polymerizing this, bisphenol A bis (diphenyl phosphate) substituted with diphenyl phosphate, etc. Can be used.

  Polycarbonate obtained by polymerizing bisphenol A, polyarylate obtained by polymerizing bisphenol A with a dibasic acid such as terephthalic acid, and an epoxy oligomer or polymer polymerized with an epoxy-containing monomer can also be used.

  Modiper CL130D or L440-G obtained by graft polymerization of bisphenol A and styrene, styrene acrylic, or the like can also be used.

  The acrylic film of the present invention can also contain two or more retardation control agents. In this case, by optimizing the combination, elution of the phase difference controlling agent can be reduced.

  The reason is not clear, but the amount of addition per one type can be reduced and elution is suppressed by the interaction between the two phase difference control agents and the acrylic resin (A) -containing composition. Seem.

<Antioxidant>
In this invention, what is generally known can be used as an antioxidant.

  In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, the thing containing what is marketed by the brand name "IrgafosXP40" and "IrgafosXP60" from Ciba Japan KK is preferable.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, Ciba Japan Co., Ltd., “Irganox 1076”, “Irganox 1010”, and ADEKA “ADEKA STAB AO-50” are trade names. And those commercially available.

  Examples of the phosphorous compounds are Sumitomo Chemical Co., Ltd., “Sumilizer GP”, ADEKA Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, Ciba Japan Co., Ltd. “IRGAFOS P-EPQ”, commercially available from Sakai Chemical Industry Co., Ltd. under the trade name “GSY-P101” is preferable.

  As the hindered amine compound, for example, those commercially available from Ciba Japan Co., Ltd. under the trade names “Tinuvin 144” and “Tinvin 770”, and from ADEKA Co., Ltd. as “ADK STAB LA-52” are preferable.

  The sulfur compound is preferably commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer TPL-R” and “Sumilizer TP-D”.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”.

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling and use. Is added in the range of 0.1 to 1% by mass.

  These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Matting agent>
The acrylic film of the present invention preferably contains fine particles as a matting agent.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. Further, fine particles of an organic compound can also be preferably used.

  Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine resin Also, pulverized and classified products of organic polymer compounds such as polyolefin-based powders, polyester-based resins, polyamide-based resins, polyimide-based resins, polyfluorinated ethylene-based resins, and starches.

  Alternatively, a polymer compound synthesized by a suspension polymerization method, a polymer compound made spherical by a spray dry method or a dispersion method, or an inorganic compound can be used.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle size of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

  These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable.

  The content of these fine particles in the film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used.

  Examples of the polymer include silicone resin, fluororesin and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

  Various additives may be batch-added to the dope, which is a solution before film formation, or an additive solution may be separately prepared and added in-line.

  In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

  In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

<Other additives>
In the acrylic film of this invention, in order to improve the fluidity | liquidity and softness | flexibility of a composition, it is also possible to use a plasticizer together. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

  For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate and the like can be used.

  Of these, polyester and phthalate 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.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 mPa · s (25 ° C.) in view 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. These plasticizers may be used alone or in combination of two or more.

  Furthermore, various antioxidants can also be added to the acrylic resin (A) used in the acrylic film of the present invention in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to impart antistatic performance to the acrylic film.

  As the acrylic resin (A) 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.
<Film formation of acrylic film>
The preferable example of the manufacturing method by the solution casting film forming method of the acrylic film of this invention is demonstrated.

(Organic solvent)
An organic solvent useful for forming a dope when the acrylic film of the present invention is produced by a solution casting method is a mixed solvent containing solvents A and B.

  A dope composition is prepared by dissolving at least 15 to 45% by mass in total of three types of acrylic resin (A), acrylic particles (C), and optionally cellulose ester resin (B) in this mixed solvent.

1) Dissolution Step Dissolution is a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9-95557, Alternatively, various dissolution methods such as a cooling method as described in JP-A-9-95538 and a high-pressure method as described in JP-A-11-21379 can be used. A method in which pressure is applied at a boiling point or higher is preferred.

  After the additive is added to the dope during or after dissolution, the dope is dissolved and dispersed, filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Filtration is preferably performed using a filter medium having a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  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 agglomerates are removed from the acrylic particle charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, the acrylic particle additive solution is added from the stock kettle 42 to the main dope dissolving kettle 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 mass of the recycled material. The return material may contain acrylic particles. In that case, it is preferable to control the addition amount of the acrylic particle addition liquid in accordance with the addition amount of the return material.

  Recycled material is a finely pulverized acrylic film, which is generated when the acrylic film is formed, and is cut off on both sides of the film, or the original acrylic film that has been speculated out of scratches is used. .

  Moreover, what knead | mixed and pelletized acrylic resin (A), acrylic particle (C), and the cellulose-ester resin (B) depending on the case can be used preferably.

2) Casting process An endless metal belt 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 the dope from the pressure die slit to the casting position on the support.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface.

  In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. 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 process A web (dope is cast on a casting support, and the formed dope film is called a web) is heated on the casting support to evaporate the solvent to produce a film shape. It is a process.

  To evaporate the solvent, there are a method in which air is blown from the web side, a method in which heat is transferred from the back surface of the support by a liquid, a method in which heat is transferred from the front and back by radiant heat, and the like. Well preferred. 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 to 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.

  In addition, it is preferable that the residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is 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 residual solvent amount of the web which is the residual solvent of the present invention 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 140 ° C. for 2 hours.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m. However, when 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 that can be peeled to 166.6 N / m, and then peel at a minimum tension to 137.2 N / m, and particularly preferably peel at a minimum tension to 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 step After peeling, using the drying device 35 that alternately conveys the web through a plurality of rolls arranged in the drying device, and / or the tenter stretching device 34 that clips and conveys both ends of the web with a clip, Dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film.

  It is preferable to dry at 40-160 degreeC through the whole, and a residual solvent is adjusted to 5-50 mass% by this process.

6) Heat treatment process It is preferable to heat-treat the film in which the residual solvent is adjusted to 5 to 50% by mass in the drying step at an apparent Tg + 10 to 90 ° C., and further to treat at an apparent Tg + 40 to 90 ° C. preferable. Specifically, it is 80-160 degreeC.

  As a method of the treatment, the treatment may be performed in stages, such as treatment at about 120 ° C. at the beginning and heating at 140 ° C. at the end.

  As heat processing time, 15 to 60 minutes are preferable, and 20 to 40 minutes are especially preferable.

  In this heat treatment step, drying is also performed at the same time, and it is preferable that the residual solvent amount of the acrylic film exiting from this step is less than 1.0% by mass.

7) Stretching step In the present invention, a stretching step may be provided after the heat treatment.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right 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 the zones do not interfere with each other.

  In addition, extending | stretching operation may be divided | segmented and implemented in multiple steps, and it is also preferable to implement biaxial stretching in a casting direction and a 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 preferable draw ratio of simultaneous biaxial stretching can be taken in the range of x1.01 to x1.5 times in both the width direction and the longitudinal direction.

  As a temperature condition at the time of stretching, it is preferable to carry out at an acrylic film over Tg + 10-50 ° C. Specifically, it is good to carry out at 80-160 degreeC.

  In the tenter process, 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. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C is most preferable.

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

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

  The acrylic film of the present invention is preferably a long film. Specifically, the acrylic film has a thickness of about 100 m to 5000 m and is usually provided in a roll shape. Moreover, it is preferable that the width | variety of a film is 1.3-4m, and it is more preferable that it is 1.4-2m.

Although there is no restriction | limiting in particular in the film thickness of the acrylic film of this invention, when using for the polarizing plate protective film mentioned later, it is preferable that it is 20-200 micrometers, it is more preferable that it is 25-100 micrometers, and it is 30-80 micrometers. It is particularly preferred.
<Physical properties of acrylic film>
Hereafter, the characteristic about the physical property etc. of the acrylic film of this invention is demonstrated.

<Photoelastic coefficient>
The acrylic film of the present invention is preferably adjusted so that the photoelastic coefficient is −6.0 × 10 ^{−12 to} 6.0 × 10 ⁻¹² / Pa, and −2.0 × 10 ⁻¹² to 2. It is particularly preferable to control within the range of 0 × 10 ⁻¹² / Pa.

  In the present invention, in order to adjust the photoelastic coefficient within the above range, the ratio of the acrylic resin (A) to the cellulose ester resin (B) and other resins is adjusted, and the phase difference control agent is adjusted according to this resin ratio. This is done by adjusting the combination and the amount of addition to optimize the composition of the acrylic film.

  Even if stress is applied to the retardation film when the liquid crystal display device is turned on for a long time by adjusting the photoelastic coefficient to such a range and the panel becomes high temperature or the surrounding atmosphere becomes high temperature and high humidity. The phase difference is less likely to occur and image unevenness can be reduced. Furthermore, image unevenness that occurs when used for a long time can also be reduced.

<Moisture permeability>
The acrylic film of the present invention is measured under conditions of a temperature of 40 ° C. and a humidity of 90% RH based on JIS Z 0208, and the moisture permeability value converted to a film thickness proportional to a film thickness of 60 μm is 50 to 600 g / m ² · 24 h. 200 to 450 g / m ² · 24 h is particularly preferable.

  When the acrylic film of the present invention is used for at least one of the polarizing plates, by setting the moisture permeability to the above range, even if the liquid crystal display device is used in a high humidity environment, light leakage and image quality due to deterioration of the polarizer are prevented. Polarizer with vapor that does not deteriorate, and is generated even when the liquid crystal display device is placed in a high temperature environment and used outdoors with high illuminance and exposed to high heat by increasing the brightness of the backlight. Deterioration and deformation can be suppressed.

<Others>
The acrylic 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 or less. 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 the defect is not circular, the range of the defect is determined by observing with a microscope by 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 unclear, aluminum or platinum is 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.

  If the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a later step, the film may break with the defects as a starting point, and 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.

  Moreover, even when it cannot be visually confirmed, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in a defect (missing coating). 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 foreign matter (foreign matter defect) in the film.

  The acrylic film of the present invention preferably has a breaking elongation in at least one direction of 10% or more, more preferably 20% or more, in the measurement based on 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 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 film of the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more.

  Moreover, as a realistic upper limit, it 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 (A).

  The acrylic film of the present invention is characterized by having a haze value (turbidity), which is one of the indices indicating transparency, of 1.0% or less. However, the luminance and contrast when incorporated in a liquid crystal display device are characteristic. From the point, 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 to reduce the diffusion of light inside the film.

  It is also effective to express the smoothness of the surface as surface haze, and to suppress the particle diameter and addition amount of acrylic particles within the above ranges, or to reduce the surface roughness of the film contact portion during film formation.

  In addition, the total light transmittance and haze value of the acrylic film are values measured in accordance with JIS-K7361-1-1997 and JIS-K7136-2000.

  The acrylic film of the present invention can be preferably used as an optical acrylic film as long as the above physical properties are satisfied.

(Polarizer)
The acrylic film of the present invention can be used as a polarizing plate protective film. The polarizing plate can be produced by a general method.

  It is preferable that an adhesive layer is provided on the back side of the acrylic film of the present invention, and is bonded to at least one surface of a polarizer produced by immersion 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, OP Etc.) are preferably used.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to 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 pressure-sensitive adhesive may be a one-component type or a type that is used by mixing two or more components 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 density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.

(Liquid crystal display device)
By incorporating the polarizing plate bonded with the acrylic film of the present invention into a liquid crystal display device using at least one surface of the liquid crystal cell, liquid crystal display devices having various durability can be manufactured. The polarizing plate of the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

  The polarizing plate of the present invention is preferably a reflective, transmissive, transflective LCD or LCD of various drive systems such as TN, STN, OCB, HAN, VA (PVA, MVA) and IPS. Used.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
(Acrylic resin (A))
The following acrylic resins A1-A7 and MS1, 2 were prepared by a known method.
A1: Monomer mass ratio (MMA: MA = 98: 2) Tg 103 ° C., Mw 70000
A2: monomer mass ratio (MMA: MA = 97: 3) Tg 102 ° C., Mw 160000
A3: monomer mass ratio (MMA: MA = 97: 3) Tg 102 ° C., Mw 350,000
A4: monomer mass ratio (MMA: MA = 97: 3) Tg 102 ° C., Mw 550000
A5: monomer mass ratio (MMA: MA = 97: 3) Tg 102 ° C., Mw 800000
A6: monomer mass ratio (MMA: MA = 97: 3) Tg 102 ° C., Mw 930,000
A7: monomer mass ratio (MMA: MA = 94: 6) Tg 99 ° C., Mw 1100000
MS1: Monomer mass ratio (MMA: ST = 60: 40) Tg 103 ° C., Mw 100000 MS2: Monomer mass ratio (MMA: ST = 40: 60) Tg 102 ° C., Mw 100000
The following commercially available products were used.
Dianal BR50 (Mitsubishi Rayon Co., Ltd.) Tg100 ° C. Mw100,000
Dianar BR52 (Mitsubishi Rayon Co., Ltd.) Tg105 ° C Mw85000
Dianar BR80 (Mitsubishi Rayon Co., Ltd.) Tg105 ° C Mw95000
Dianar BR83 (Mitsubishi Rayon Co., Ltd.) Tg105 ° C Mw40000
Dianar BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) Tg 105 ° C. Mw 280000
Dianal BR88 (manufactured by Mitsubishi Rayon Co., Ltd.) Tg 105 ° C. Mw 480000
80N (manufactured by Asahi Kasei Chemicals Corporation) Tg110 ° C Mw100,000
The ratio of the MMA unit in the molecule of the above-mentioned commercially available acrylic resin (A) is about 30% by mass for Dialal BR50, about 70% by mass for Dialal BR52, and 90% to 99% by mass for all of Dialal BR80 to 80N. It was the following.

(Synthesis of A8)
First, a methyl methacrylate / acrylamide copolymer suspension was prepared as follows.

Methyl methacrylate 20 parts by weight Acrylamide 80 parts by weight Potassium persulfate 0.3 part by weight Ion-exchanged water 1500 parts by weight The above is charged into the reactor and the reactor is replaced with nitrogen gas. The reaction was allowed to proceed at 70 ° C. until converted to. The obtained aqueous solution was used as a suspending agent. A solution in which 0.05 part by mass of the above suspending agent is dissolved in 165 parts by mass of ion-exchanged water is supplied to a stainless steel autoclave having a capacity of 5 liters and equipped with a baffle and a foudra-type stirring blade, and the system is filled with nitrogen gas. It stirred at 400 rpm, replacing.

  Next, a mixed substance having the following charge composition was added while stirring the reaction system.

Methacrylic acid 27 parts by weight Methyl methacrylate 73 parts by weight t-dodecyl mercaptan 1.2 parts by weight 2,2′-azobisisobutyronitrile 0.4 part by weight The mixture was heated to 70 ° C. and the internal temperature was 70 ° C. The time at which the polymerization was reached was set as the polymerization start time, and the polymerization was continued for 180 minutes.

  Thereafter, the reaction system was cooled, the polymer was separated, washed and dried in accordance with a normal method to obtain a bead-shaped copolymer. The polymerization rate of this copolymer was 97%, and the weight average molecular weight was 130,000.

0.2% by mass of an additive (NaOCH ₃ ) is blended in this copolymer, and nitrogen is added at 10 L / L from the hopper using a twin-screw extruder (TEX30, Nippon Steel Co., Ltd., L / D = 44.5). While purging with a minute amount, an intramolecular cyclization reaction was performed at a screw rotation speed of 100 rpm, a raw material supply rate of 5 kg / hour, and a cylinder temperature of 290 ° C. Got. The weight average molecular weight (Mw) of the acrylic resin A8 was 130,000, and Tg was 140 ° C.

<Preparation of acrylic 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. 0.36 g of APS was added, and after stirring for 5 minutes, a monomer mixture consisting of 1657 g of MMA, 21.6 g of BA, and 1.68 g of ALMA was added all at once. Completed.

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

  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. The polymerization of 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. 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 average particle size was determined by the absorbance method. As a result, it was 0.10 μm and 100 nm. 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 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 <Preparation of acrylic film 1>
(Dope solution composition 1)
Acrylic resin (A) Dianal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) 70 parts by weight Cellulose ester resin (B) CE1 30 parts by weight Acrylic particles (C) C2 3 parts by weight Ultraviolet absorber (D) Tinuvin 928 (Ciba Japan ( Made by Co., Ltd.)
2 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

(Formation of acrylic film 1)
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 residual solvent amount reached 100%, and the film was peeled from the stainless steel band support with a peeling tension of 162 N / m.

  The peeled acrylic resin web was slit to 1.6 m width, then transported to a drying step having a tenter function, and dried at 135 ° C. while being stretched 1.1 times in the width direction.

  At this time, the residual solvent amount when starting stretching with a tenter was 30% by mass.

  The amount of residual solvent after stretching with a tenter was 20% by mass. In this state, the solvent was transported to a heat treatment step, and heat treatment was performed at 120 ° C. for 15 minutes and then at 140 ° C. for 15 minutes.

  After that, slitting to 1.5 m width, 10 mm width and 5 μm knurling were applied to both ends of the film, and wound on a core with an initial tension of 220 N / m and a final tension of 110 N / m to an inner diameter of 15.24 cm to obtain an acrylic film 1 It was.

  The MD draw ratio calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.1 times.

  The residual solvent amount of the acrylic film 1 described in Table 2 was 0.1% by mass, the film thickness was 60 μm, and the winding length was 4000 m.

<Preparation of acrylic films 2-17 and 15-1 to 15-47>
In the production of the acrylic film 1, the types and composition ratios of the acrylic resin (A), the acrylic particles (C), and in some cases, the cellulose ester resin (B) were changed as described in Tables 2 and 3 in the same manner. Then, acrylic films 2-17 and 15-1 to 15-47 were produced.

  In addition, 15-2 to 15-47 were produced by the same solvent composition and amount as 15-1 (88 parts by mass of methylene chloride, 6 parts by mass of n-butanol, 6 parts by mass of ethanol).

  In the cellulose ester resin (B) in Table 1, ac represents an acetyl group, pr represents a propionyl group, bu represents a butyryl group, pen represents a pentanoyl group, bz represents a benzoyl group, hep represents a heptanoyl group, oct represents an octanoyl group, ph represents a phthalyl group. “Amount” described in Table 2 represents parts by mass.

  As a comparative example, a film according to 1-A described in Example 1 of JP 2007-10044 A and a film described in Example 1 of WO 2005/105918 was prepared.

"Evaluation method"
(All haze: Transparency evaluation)
For each of the prepared film samples, a haze meter (NDH2000 type, manufactured by Nippon Denshoku Industries Co., Ltd.) was prepared according to JIS K-7136 for one sample that was conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH. Measured using.

(Surface haze%: Surface property evaluation)
The surface haze of the acrylic film of the present invention was measured by the following procedure.
(1) The total haze (H) is measured as described above.
(2) A polyethylene terephthalate film with an adhesive having an acrylic adhesive applied on one side is attached to the surface of the acrylic film of the present invention, and the total haze value H0 is measured for the whole attached film.
(3) Separately, the total haze value Ht of only the polyethylene terephthalate film with pressure-sensitive adhesive to which the acrylic pressure-sensitive adhesive was applied was measured, and the value obtained by subtracting Ht from the previously measured H0 was defined as the internal haze value Hi. (Hi = H0-Ht)
(4) A value obtained by subtracting the internal haze (Hi) calculated in (3) from the total haze (H) measured in (1) above is calculated as the surface haze (Hs) of the film. (Hs = H-Hi)
(Tension softening point: heat resistance evaluation)
A sample conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH was cut out at 120 mm (vertical) × 10 mm (width) under the same conditions, and 10N using a Tensilon tester (ORIENTEC, RTC-1225A). The temperature was continuously increased at a rate of temperature increase of 30 ° C./min while pulling at a tension of 10 ° C., and the temperature (° C.) at 9 N was measured three times, and the average was obtained.

(Ductile fracture: brittleness evaluation)
A sample conditioned for 24 hours in an air-conditioned room at 23 ° C. and 55% RH was 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 of 180 ° at the center in the vertical direction. Then, the film was folded once in a mountain fold and a valley fold so that the films were exactly overlapped, and this evaluation was measured 5 times and evaluated as follows. In addition, breaking of evaluation here represents having broken into two or more pieces.

○: Folded 5 times △: Folded 1 time out of 5 times ×: Folded at least 2 times out of 5 times (Cutting property: Manufacturing suitability evaluation)
Each acrylic film was torn using a light load tear tester (manufactured by Toyo Seiki Co., Ltd.) under the same conditions for a sample conditioned for 24 hours in an air-conditioned room at 23 ° C. and 60% RH, and evaluated as follows.

○: The tear surface is very smooth and is torn straight. Δ: The tear surface has some burrs, but is torn straight.

×: There are considerable burrs on the tear surface, and it is not broken straight (characteristic evaluation as a liquid crystal display device)
<Preparation of polarizing plate>
A polarizing plate using each acrylic film as a polarizing plate protective film was prepared as follows.

  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 5 times in the transport direction at 50 ° C. to prepare a polarizer.

  Next, the acrylic film 1 produced in Example 1 was subjected to corona treatment using an acrylic adhesive on one side of the polarizer, and then bonded.

  Furthermore, KC8UCR-5 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 polarizer and dried to prepare a polarizing plate P1. Similarly, polarizing plates P2 to P-17 and 15-1 to 15-47 were prepared using acrylic films 2 to 17 and 15-1 to 15-47.

  The polarizing plate using the acrylic film of the present invention was excellent in film cutting property and easy to process.

<Production of liquid crystal display device>
The display characteristic evaluation of the acrylic film was performed using each produced said polarizing plate.

  Remove the polarizing plates on both sides of the 32-inch TV AQ-32AD5 manufactured by Sharp Corporation in advance, and make the KC8UCR-5 on the glass surface side of the liquid crystal cell. The liquid crystal display devices were each fabricated by pasting so that the absorption axis was directed in the same direction as the polarizing plate that had been pasted in advance.

(Variation of viewing angle: Evaluation of heat and moisture resistance as a polarizing plate protective film)
The following evaluation was performed using the liquid crystal display devices 1 to 17 and 15-1 to 15-47 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 above polarizing plate treated at 60 ° C. and 90% RH for 500 hours was measured in the same manner, and evaluated in three stages according to the following criteria.

○: No change in viewing angle △: A little change in viewing angle is observed ×: Large viewing angle change (Color shift: Evaluation of heat and moisture resistance as a polarizing plate protective film)
Regarding the produced liquid crystal display devices 1 to 1, the display was displayed in black in an environment of 23 ° C. and 55% RH and observed from an oblique angle of 45 °. Subsequently, the polarizing plate treated at 60 ° C. and 90% RH for 500 hours was similarly observed, and the color change was evaluated according to the following criteria.

◯: No color change Δ: Slight color change X: Large color change The results of the above evaluation are shown in Tables 4 and 5.

  As described in Tables 4 and 5, the acrylic film of the present invention exhibited low hygroscopic properties, transparency, high heat resistance, and excellent brittleness improvement. Moreover, the polarizing plate and the liquid crystal display device produced using the acrylic film of the present invention exhibited excellent properties in visibility and color shift.

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 device 35 Roll dryer 41 Particle charging vessel 42 Stock tank 43 Pump 44 Filter

Claims (4)

It is a manufacturing method by the solution casting film-forming method of the acrylic film containing 0.1-5 mass % acrylic particle (C) with respect to the total mass of the resin which comprises an acrylic resin (A) and a film, Comprising: Using a mixed solution of solvents A and B satisfying the relationship of (1) and (2) below, and drying until the residual solvent is 5 to 50% by mass, and the state of the residual solvent being 5 to 50% by mass And a step of heat treatment in the range of the apparent glass transition temperature + 10 ° C. to the apparent glass transition temperature + 90 ° C. of the acrylic film.
(1) Boiling point of solvent A + 35 ° C. <boiling point of solvent B (2) Mass ratio of solvent A to solvent B in the mixed solution A: B = 98: 2 to 70:30 The manufacturing method of the acrylic film of Claim 1 whose said acrylic particle (C) resin is 2-5 mass% with respect to the total mass of resin which comprises a film. Under an atmosphere of 23 ° C. 55% RH, without causing ductile fracture, a tension softening point one hundred and five to one hundred and forty-five ° C., according to claim 1 or 2, wherein the haze value is less than 1.0% Acrylic film produced by the manufacturing method. The acrylic film is a resin film containing an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 30:70 and in a compatible state, the acrylic resin (A) 2. The weight average molecular weight Mw is 80000 or more and 1000000 or less, the weight average molecular weight Mw of the cellulose ester resin (B) is 75000 or more and 280000 or less, and the total substitution degree (T) of acyl group is 2.0 or more. The acrylic film according to claim 3 , wherein the substitution degree of the acyl group having 0 or less and 3 to 7 carbon atoms is 1.2 or more and 3.0 or less.