JP5217913B2 - Optical film, polarizing plate using the same, and liquid crystal display device - Google Patents

Description

  The present invention relates to an optical film, and more specifically, by combining a specific additive with a resin obtained by blending an acrylic resin and a cellulose ester resin, the optical film has good haze and does not cause breakage failure even when productivity is increased. It relates to the manufacturing method.

  The demand for liquid crystal display devices is expanding in applications such as liquid crystal televisions and personal computer liquid crystal displays. In general, a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter, etc. are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. The optical element (polarizing plate protective film) is sandwiched between a child (also referred to as a polarizing film or a polarizing film). As this polarizing plate protective film, a cellulose triacetate film is usually used.

  On the other hand, with the recent advancement of technology, the enlargement of the liquid crystal display device is accelerated, and the use of the liquid crystal display device is diversified. For example, it can be used as a large display installed in a street or a store, or used as an advertising display in a public place using a display device called digital signage.

  In such an application, since it is assumed to be used outdoors, degradation due to moisture absorption of the polarizing film becomes a problem, and higher moisture resistance is required for the polarizing plate protective film. However, it has been difficult to obtain sufficient moisture resistance with cellulose ester films such as cellulose triacetate films that have been used in the past, and there has been a problem that the optical effect increases when the film thickness is increased to obtain moisture resistance. . Furthermore, in recent years, there has been a demand for thinning of the apparatus, so that the thickness of the polarizing plate itself has also become a problem.

  On the other hand, polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of acrylic resin, as an optical film material with low hygroscopicity, exhibits excellent transparency and dimensional stability in addition to low hygroscopicity. It was used suitably for.

  However, as described above, the liquid crystal display device is increased in size, the width of the film original is wide, and the winding length is required to be long. Therefore, although the film original is wide, workability is poor due to insufficient improvement in brittleness, and handling properties are not sufficient for producing an optical film used for a large liquid crystal display device.

  As a technique for improving moisture resistance and workability, a resin in which an acrylic resin is combined with an impact-resistant acrylic rubber-methyl methacrylate copolymer or butyl-modified acetyl cellulose has been proposed (for example, see Patent Document 1).

  However, even in this method, improvement in brittleness is insufficient, so that there is a problem in workability, and handling properties are not sufficient for manufacturing an optical film used for a large-sized liquid crystal display device.

  In addition, a technique for producing a mixed composition of a cellulose derivative and a polymer having negative intrinsic birefringence by an extrusion method has been proposed (see, for example, Patent Document 2). However, when various two resins were mixed by the extrusion molding method proposed in this method and melt film formation was performed, there was a case where the compatibility was estimated to be insufficient depending on the mixed resin components. When used as an optical film, there is a problem that the contrast of the image is lowered due to high haze and insufficient transparency.

  Furthermore, the problem that the film broke during melt film formation frequently occurred.

  Rupture in the film manufacturing process by normal melt film formation is mainly caused by non-uniform film thickness, non-uniform conveying stress, and the presence of foreign matter, but these are not always the case in a system in which cellulose ester resin and acrylic resin are mixed. Even if it cannot be said that the cause is, the breakage during the production may occur, and the cause and the response of the cause have been demanded.

Under the above circumstances, with the recent expansion of applications of liquid crystal display devices, optical films are strongly required to improve productivity while maintaining high performance.
Japanese Patent Laid-Open No. 5-119217 JP 2008-88417 A

  Accordingly, the present invention has been made in view of the above problems, and its purpose is to provide an optical film that has a low haze and does not cause breakage failure during production, a method for producing the optical film, a polarizing plate using the same, and the subject matter It is to provide a liquid crystal display device using a polarizing plate. In particular, an object of the present invention is to provide an optical film suitably used as a polarizing plate protective film in a large-sized liquid crystal display device or a liquid crystal display device for outdoor use.

The above object of the present invention is achieved by the following configurations.
1. The acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 50:50, and the weight average molecular weight Mw of the acrylic resin (A) is 110,000 to 1000000, and the cellulose ester The total substitution degree (T) of the acyl group of the resin (B) is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 or more and 7 or less carbon atoms is 1.2 or more and 3.0 or less. An optical film comprising a resin composition, and (1) a carbon radical scavenger, (2) a primary antioxidant having hydrogen radical donating ability for peroxy radicals, and (3) a reducing action on peroxides An optical film comprising a secondary antioxidant having
2. 2. The optical film as described in 1 above, wherein the carbon radical scavenger is a compound represented by the following general formula (1).

(In General Formula (1), R ₁₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ₁₂ and R ₁₃ each independently represents an alkyl group having 1 to 8 carbon atoms.)
3. 3. The optical film as described in 1 or 2 above, wherein the primary antioxidant is a phenol compound or a hindered amine compound.
4). 4. The optical film as described in any one of 1 to 3, wherein the secondary antioxidant is a phosphorus compound.
5. The optical film according to any one of 1 to 4, wherein the optical film contains acrylic particles (C).
6). A polarizing plate using the optical film according to any one of 1 to 5 above.
7. 7. A liquid crystal display device using the polarizing plate described in 6 above.

  According to the present invention, it is possible to provide an optical film that has good haze and does not cause fracture failure during production, a method for producing the optical film, a polarizing plate using the optical film, and a liquid crystal display device using the polarizing plate.

  In particular, it is possible to provide an optical film that is suitably used as a polarizing plate protective film used in a large-sized liquid crystal display device or a digital signage liquid crystal display device.

  The reason why the above problem can be solved by the configuration of the present invention is estimated as follows.

  In general, melt film formation is a method in which a molten resin is extruded from a die and then wound around a cooling roll to form a film, but at the mass production stage, the film thickness is increased in order to increase the film productivity. In order to adjust, the cooling roll is formed by increasing the roll rotation speed with respect to the die extrusion speed. At this time, it is considered that the film is stretched between the die and the cooling roll. Such film stretching occurs throughout the conveying process of the process.

  With respect to the production conditions, the present inventors have found that the cellulose ester resin and the acrylic resin melted in the extruder have a weak physical interaction due to their molecular structure (6-membered cyclic ether structure). When the film is stretched while being cooled between a die and a cooling roll, for example, the film is formed with little entanglement between the cellulose ester resin and the acrylic resin, and the resulting film is subjected to a conveyance stress, resulting in a film. It was considered that the breakage of the steel was likely to occur.

  The above properties are particularly remarkable around the cooling roll by increasing the production speed. When cooling in this part becomes insufficient, the cooling rate of the resin becomes slow, and the cellulose ester resin and the acrylic resin, which are the resin composition of the present invention, each form a stable state, so different resin components Phase separation is facilitated. And it can be estimated that this phase-separated portion is ruptured by tension.

  Here, melt mixing two or more kinds of polymers is widely known as a polymer blend or a polymer alloy, and is widely used as a method for modifying the defects of individual polymers. However, in many cases where two or more kinds of polymers are melt-mixed, they are often separated into individual phases due to differences in viscosity, molecular weight, molecular structure, etc., and have a coarse dispersion structure.

  As a method for improving such phase separation, means for incorporating a compatibilizer has been tried, but it is very difficult to select an optimal compatibilizer for the resin to be mixed without adversely affecting the performance of the film. It has become difficult.

  That is, the three types of additives of the present invention promote the interaction between the cellulose ester resin melted in the extruder and the acrylic resin, and as a result, the physical entanglement is increased, so that the film can be applied even if it is subjected to conveyance stress. This is because it is less likely to break.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

<Optical film>
In the present invention, the “optical film” is a functional film used for various display devices such as a liquid crystal display, a plasma display, and an organic EL display, and more specifically, a polarizing plate protective film and a retardation film for a liquid crystal display device. , An antireflection film, a brightness enhancement film, a hard coat film, an antiglare film, an antistatic film, an optical compensation film for expanding the viewing angle, and the like.

  The optical film of the present invention is preferably used for a polarizing plate protective film (including a polarizing plate protective film provided with a functional layer) and a retardation film.

  The optical film of the present invention contains the acrylic resin (A) and the cellulose ester resin (B) in a mass ratio of 95: 5 to 50:50, and the weight average molecular weight Mw of the acrylic resin (A) is 110,000 or more and 1000000. The total substitution degree (T) of the acyl group of the cellulose ester resin (B) is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 or more and 7 or less carbon atoms is 1.2. An optical film comprising a resin composition of 3.0 or less, and an additive (1) a carbon radical scavenger and (2) a primary antioxidant having a hydrogen radical donating ability for peroxy radicals And (3) containing a secondary antioxidant having a reducing action on peroxide.

  In some cases, adding acrylic particles (C) produces favorable results.

<Acrylic resin (A)>
The acrylic resin used in the present invention includes a methacrylic resin. Although it does not restrict | limit especially as resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 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. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned, and these can be used alone or in combination of two or more monomers.

  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 optical film of the present invention has a weight average molecular weight (Mw) particularly from the viewpoint of improving brittleness as an optical film and improving transparency when it is compatible with the cellulose ester resin (B). Is 110,000 or more and 1000000 or less.

  When the weight average molecular weight (Mw) of the acrylic resin (A) is less than 110,000, sufficient brittleness improvement may not be obtained, and the compatibility with the cellulose ester resin (B) is likely to deteriorate. The weight average molecular weight (Mw) of the acrylic resin (A) is more preferably in the range of 110000 to 600000, and particularly preferably in the range of 110000 to 400000.

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

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

  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 type and an azo type can be used, and a redox type can also be used.

  Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  A commercially available thing can also be used as an acrylic resin which concerns on this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more acrylic resins can be used in combination.

<Cellulose ester resin (B)>
The cellulose ester resin (B) of the present invention has a total acyl group substitution degree (T) of 2.0 to 3.3 from the viewpoint of transparency, particularly when it is improved in brittleness and is compatible with the acrylic resin (A). The substitution degree of 0 and the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0. That is, the cellulose ester resin of the present invention 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 When the resin (A) and the acrylic resin (B) are not sufficiently compatible and used as an optical film, haze may be a problem.

  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 may be reduced. 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. If it is less than 2, the compatibility may decrease and haze may increase.

  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, the brittleness deteriorates and desired characteristics are obtained. It may not be possible.

  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. It is preferable that the total substitution degree of acyl groups other than 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms is 1.3 or less.

  The total substitution degree (T) of the acyl group of the cellulose ester resin (B) is more preferably in the range of 2.5 to 3.0.

  In the present invention, the acyl group may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The number of carbon atoms of the acyl group in the present invention includes an acyl group substituent.

  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 benzoyl group has 7 carbon atoms, when it has a substituent containing carbon, the benzoyl 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 cellulose ester resin (B) as described above, having a structure having at least one kind of an aliphatic acyl group having 3 to 7 carbon atoms is used as a structure used for the cellulose ester resin (B) of the present invention. .

  The cellulose ester resin (B) according to the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate. Among these, cellulose ester resins that are particularly preferred are cellulose acetate propionate and cellulose propionate.

  The portion that is 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) according to the present invention is preferably in the range of 75,000 to 300,000, particularly from the viewpoint of improving compatibility with the acrylic resin (A) and brittleness, and 100,000 to 250,000. Is more preferably within the range of 150,000 to 250,000.

  When the important average molecular weight (Mw) of the cellulose ester resin is less than 75,000, the effect of improving heat resistance and brittleness may not be sufficient, and the effect of the present invention may not be obtained. In the present invention, two or more kinds of cellulose resins can be mixed and used.

  In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 50:50 and in a compatible state, preferably 90:10 to 60. : 40.

  If the mass ratio of the acrylic resin (A) and the cellulose ester resin (B) is more than 95: 5, the effect of the cellulose ester resin (B) cannot be sufficiently obtained, and the mass ratio is When the acrylic resin is less than 50:50, the moisture resistance is insufficient.

  In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) must be contained in a compatible state. The physical properties and quality required for an optical 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 can be determined by, for example, the glass transition temperature Tg.

  For example, when the two resins have different glass transition temperatures, when the two resins are mixed, there are two or more glass transition temperatures for each resin because there is a glass transition temperature for each resin. When they are compatible, the glass transition temperature specific to each resin disappears and becomes one glass transition temperature, which is the glass transition temperature of the compatible resin.

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

  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.

  In the optical film of the present invention, the weight average molecular weight (Mw) of the acrylic resin (A), the weight average molecular weight (Mw) of the cellulose ester resin (B), and the degree of substitution are different in solubility in the solvent of both resins. It is obtained by measuring each after use. When fractionating the resin, it is possible to extract and separate the soluble resin by adding a compatible resin in a solvent that is soluble only in either one. At this time, heating operation or reflux is performed. May be. A combination of these solvents may be combined in two or more steps to separate the resin.

  The dissolved resin and the resin remaining as an insoluble matter are filtered off, and the solution containing the extract can be separated by an operation of evaporating the solvent and drying. These fractionated resins can be identified by general structural analysis of polymers. When the optical film of the present invention contains a resin other than the acrylic resin (A) and the cellulose ester resin (B), it can be separated by the same method.

  If the weight average molecular weights (Mw) of the compatible resins are different, the high molecular weight substances are eluted earlier by gel permeation chromatography (GPC), and the lower molecular weight substances are eluted after a longer time. Therefore, it can be easily fractionated and the molecular weight can be measured.

  In addition, the molecular weight of the compatible resin is measured by GPC, and at the same time, the resin solution eluted every time is separated, the solvent is distilled off, and the dried resin is different by quantitatively analyzing the structure. By detecting the resin composition for each molecular weight fraction, it is possible to identify each compatible resin. By measuring the molecular weight distribution of each of the resins separated in advance based on the difference in solubility in a solvent by GPC, it is possible to detect each of the compatible resins.

  In the present invention, “containing acrylic resin (A) and cellulose ester resin (B) in a compatible state” means mixing each resin (polymer), resulting in a compatible state. This means that a state in which a precursor of acrylic resin such as monomer, dimer or oligomer is mixed with cellulose ester resin (B) and then polymerized by polymerization is not included. .

  For example, the process of obtaining a mixed resin by mixing a precursor of an acrylic resin such as a monomer, dimer or oligomer with the cellulose ester resin (B) and then polymerizing it is complicated by the polymerization reaction. The resin is difficult to control the reaction, and it is difficult to adjust the molecular weight. In addition, when a resin is synthesized by such a method, graft polymerization, cross-linking reaction or cyclization reaction often occurs. In many cases, the resin is soluble in a solvent or cannot be melted by heating. Since it is difficult to elute the resin and measure the weight average molecular weight (Mw), it is difficult to control the physical properties and it cannot be used as a resin for stably producing an optical film.

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

<Acrylic particles (C)>
The optical film of the present invention preferably contains acrylic particles (C).

  The acrylic particles (C) according to the present invention are present in the state of particles (also referred to as incompatible state) in the optical film containing the acrylic resin (A) and the cellulose ester resin (B) in a compatible state. Represents an acrylic component.

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

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

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

  That is, the multilayer structure acrylic granular composite is a multilayer structure acrylic granular composite comprising an innermost hard layer, a crosslinked soft layer, and an outermost hard layer from the central portion toward the outer peripheral portion. This three-layer core-shell multilayer acrylic granular composite is preferably used.

  Preferred embodiments of the multilayer structure acrylic granular composite used in the acrylic resin composition according to the present invention include the following. (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 a mixture of the body, (b) in the presence of the innermost hard layer polymer, an alkyl acrylate having an alkyl group of 4 to 8 carbon atoms of 75 to 98.5% by mass. A crosslinked soft layer polymer obtained by polymerizing a mixture of monomers comprising 0.01 to 5% by mass of a polyfunctional crosslinking agent and 0.5 to 5% by mass of a multifunctional grafting agent, (c) In the presence of a polymer comprising an inner hard layer and a crosslinked soft layer, a mixture of monomers 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. Outermost obtained by polymerizing The layered polymer has a three-layer structure, and the obtained three-layered polymer is the innermost hard layer polymer (a) 5 to 40% by mass, the soft layer polymer (b) 30 to 60% by mass. And the outermost hard layer polymer (c) 20 to 50% by mass, having an insoluble part when fractionated with acetone, and an insoluble granular part having a methyl ethyl ketone swelling degree of 1.5 to 4.0 Complex.

  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 degree of swelling of methyl ethyl ketone in the acetone-insoluble part within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

  Here, the innermost hard layer polymer (a) constituting the 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 mixture of monomers consisting of 0.01 to 0.3% by mass of a polyfunctional grafting agent is preferred.

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

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

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

  The crosslinked soft layer polymer (b) constituting the acrylic granular composite is an alkyl acrylate 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 preferred.

  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 for the ratio of the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group and styrene, the glass transition temperature of the polymer (b) decreases as the former increases, that is, the ratio can be softened.

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

  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 mixture of monomers consisting of 1 to 20% by mass of an alkyl acrylate having 1 to 8 carbon atoms in the alkyl group is preferred.

  Here, as the acrylic alkylate, those described above are used, 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. Specifically, the outermost hard layer is divided into two or more monomer mixtures for forming the outermost hard layer, and the amount of chain transfer agent to be added each time is increased sequentially. It is possible to decrease the molecular weight of the polymer forming the layer from the inside to the outside of the multilayer structure acrylic granular composite.

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

  The particle diameter of the acrylic particles (C) preferably used in the present invention is not particularly limited, but is preferably 10 nm or more and 1000 nm or less, and more preferably 20 nm or more and 500 nm or less. In particular, the thickness is most preferably from 50 nm to 400 nm.

  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, the core layer here is an innermost hard layer.

  Specific examples of the acrylic particles (C) which are graft copolymers suitably used as the acrylic particles (C) preferably used in the present invention include unsaturated carboxylic acid ester-based monomers in the presence of a rubbery polymer. A mixture of a monomer, an unsaturated carboxylic acid monomer, an aromatic vinyl monomer, and, if necessary, other vinyl monomers copolymerizable therewith were copolymerized. A graft copolymer 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-methyl acrylate copolymer A polymer etc. are mentioned. These rubbery polymers can be used alone or in a mixture of two or more.

  Moreover, when adding an acrylic particle (C) to the optical film of this invention, the refractive index of the mixture of an acrylic resin (A) and a cellulose-ester resin (B) and the refractive index of an acrylic particle (C) must be near. From the viewpoint of obtaining a film with high transparency. 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) and / or a rubbery polymer or monomer used for the acrylic particles (C) The refractive index difference can be reduced by a method of adjusting the composition ratio, and an optical film excellent in transparency can be obtained.

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

  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 melt-kneading with a single-screw or twin-screw extruder while adding acrylic particles (C) is preferably used.

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

  A commercially available thing can also be used as an acrylic particle concerning this invention. For example, Metabrene W-341 (C1) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C2), MS-300X (manufactured by Soken Chemical Co., Ltd.), Kane Ace (manufactured by Kaneka Chemical Co., Ltd.), Paraloid (manufactured by Kureha Chemical Industry Co., Ltd.), Acryloid (manufactured by Rohm and Haas Co., Ltd.), Staphyloid (manufactured by Ganz Kasei Kogyo Co., Ltd.), Parapet SA (manufactured by Kuraray Co., Ltd.) and the like can be mentioned.

  In the optical film of the present invention, it is preferable to contain 0.5 to 30% by mass of acrylic particles (C) with respect to the total mass of the resin constituting the film, and in the range of 1.0 to 15% by mass. It is more preferable to contain.

<Additives>
In the optical film of the present invention, the following additives are added for the purpose of reducing breakage failure in the production process.
Three types of additives: (1) carbon radical scavenger, (2) primary antioxidant having hydrogen radical donating ability for peroxy radical, and (3) secondary antioxidant having a reducing action on peroxide. Combined.

(1) Carbon radical scavenger The optical film of the present invention contains at least one carbon radical scavenger.

  In the present invention, the “carbon radical scavenger” has a group (for example, an unsaturated group such as a double bond or a triple bond) that allows a carbon radical to rapidly undergo an addition reaction, and is followed by polymerization or the like after the addition of the carbon radical. It is a compound that gives a stable product in which no reaction takes place.

  Examples of the carbon radical scavenger include compounds having a radical polymerization inhibitory ability such as a group (unsaturated group such as (meth) acryloyl group and aryl group) that reacts quickly with a carbon radical in the molecule, and a phenolic or lactone based compound. The compound represented by the following general formula (1) or general formula (2) is particularly preferable.

In the general formula (1), R ₁₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, particularly preferably a hydrogen atom or a methyl group. .

R ₁₂ and R ₁₃ each independently represent an alkyl group having 1 to 8 carbon atoms, and may be linear or have a branched structure or a ring structure.

R ₁₂ and R ₁₃ are preferably a structure represented by “* —C (CH ₃ ) ₂ —R ′” containing a quaternary carbon (* represents a linking site to an aromatic ring, and R ′ has 1 carbon atom. Represents an alkyl group of ˜5).

R ₁₂ is more preferably a tert-butyl group, a tert-amyl group or a tert-octyl group. R ₁₃ is more preferably a tert-butyl group or a tert-amyl group. As the compound represented by the general formula (1), commercially available products include “Sumilizer GM, Sumilizer GS” (both trade names, manufactured by Sumitomo Chemical Co., Ltd.) and the like.

  Specific examples (I-1 to I-18) of the compound represented by the general formula (1) are illustrated below, but the present invention is not limited thereto.

In the general formula (2), R _{22 to} R ₂₅ each independently represent a hydrogen atom or a substituent, and the substituent represented by R _{22 to} R ₂₅ is not particularly limited. (For example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), cycloalkyl group (for example, cyclopentyl group, cyclohexyl group) Etc.), aryl groups (eg phenyl group, naphthyl group etc.), acylamino groups (eg acetylamino group, benzoylamino group etc.), alkylthio groups (eg methylthio group, ethylthio group etc.), arylthio groups (eg phenylthio) Group, naphthylthio group, etc.), alkenyl group (for example, vinyl group, 2-propenyl group, 3- Tenenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, etc.), halogen atom (for example, fluorine atom, chlorine atom, bromine atom) , Iodine atoms, etc.), alkynyl groups (eg, propargyl group, etc.), heterocyclic groups (eg, pyridyl group, thiazolyl group, oxazolyl group, imidazolyl group, etc.), alkylsulfonyl groups (eg, methylsulfonyl group, ethylsulfonyl group, etc.) ), Arylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group, etc.), alkylsulfinyl group (eg, methylsulfinyl group, etc.), arylsulfinyl group (eg, phenylsulfinyl group, etc.), phosphono group, acyl group (eg, Acetyl group, pivaloyl group, benzoyl group, etc.), potassium Vamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group) , Methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group Group), sulfonamide group (for example, methanesulfonamide group, benzenesulfonamide group, etc.), cyano group, alkoxy group (for example, Methoxy group, ethoxy group, propoxy group etc.), aryloxy group (eg phenoxy group, naphthyloxy group etc.), heterocyclic oxy group, siloxy group, acyloxy group (eg acetyloxy group, benzoyloxy group etc.), sulfone Acid group, salt of sulfonic acid, aminocarbonyloxy group, amino group (for example, amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino Groups (for example, phenylamino group, chlorophenylamino group, toluidino group, anisidino group, naphthylamino group, 2-pyridylamino group, etc.), imide group, ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexyl) Ureido group, octyl urei Group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), alkoxycarbonylamino group (eg methoxycarbonylamino group, phenoxycarbonylamino group etc.), alkoxycarbonyl group (eg methoxycarbonyl group) Ethoxycarbonyl group, phenoxycarbonyl, etc.), aryloxycarbonyl group (eg, phenoxycarbonyl group, etc.), heterocyclic thio group, thioureido group, carboxyl group, carboxylic acid salt, hydroxyl group, mercapto group, nitro group, etc. Groups. These substituents may be further substituted with the same substituent.

In the general formula (2), R ₂₆ represents a hydrogen atom or a substituent, and examples of the substituent represented by R ₂₆ include the same groups as the substituents represented by R _{22 to} R _25. .

  In the general formula (2), n represents 1 or 2.

In the general formula (2), when n is 1, R ₂₁ represents a substituent, and when n is 2, R ₂₁ represents a divalent linking group. When R ₂₁ represents a substituent, examples of the substituent include the same groups as the substituents represented by R _{22 to} R ₂₅ .

When R ₂₁ represents a divalent linking group, examples of the divalent linking group include an alkylene group that may have a substituent, an arylene group that may have a substituent, an oxygen atom, a nitrogen atom, and a sulfur atom. Or a combination of these linking groups.

  In the general formula (2), n is preferably 1.

  Next, although the specific example of a compound represented by the said General formula (2) in this invention is shown, this invention is not limited by the following specific examples.

  The carbon radical scavengers can be used alone or in combination of two or more, and the amount of the carbon radical scavenger is appropriately selected within a range that does not impair the object of the present invention, but resin (acrylic resin (A) and cellulose The ester resin (B)) is usually 0.001 to 10.0 parts by mass, preferably 0.01 to 5.0 parts by mass, and more preferably 0.1 to 1.0 parts by mass with respect to 100 parts by mass. is there.

(2) Primary antioxidant The optical film of the present invention contains at least one primary antioxidant having hydrogen radical donating ability for peroxy radicals.

  In the present invention, the “primary antioxidant having the ability to donate a hydrogen radical to a peroxy radical” means that the molecule has at least one hydrogen atom that is rapidly extracted by the peroxy radical, and the peroxide is removed from the peroxy radical. The compound to be formed is preferably an aromatic compound substituted with a hydroxyl group or a primary or secondary amino group or a heterocyclic compound having a sterically hindered group, and more preferably has an alkyl group at the ortho position. It is a phenol compound or a hindered amine compound.

(Phenolic compounds)
The phenolic compounds preferably used in the present invention include 2,6-dialkylphenol derivative compounds such as those described in US Pat. No. 4,839,405, columns 12-14. Such a compound includes a compound represented by the following general formula (3).

  In formula, R31-R36 represents a hydrogen atom or a substituent. Examples of the substituent include a halogen atom (eg, fluorine atom, chlorine atom), an alkyl group (eg, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group, etc.), A cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), an aralkyl group (eg, benzyl group, 2-phenethyl group, etc.), an aryl group (eg, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, etc.), alkoxy Groups (eg methoxy, ethoxy, isopropoxy, butoxy), aryloxy (eg phenoxy), cyano, acylamino (eg acetylamino, propionylamino), alkylthio (eg methylthio) Group, ethylthio group, butylthio group, etc.), aryl O group (for example, phenylthio group), sulfonylamino group (for example, methanesulfonylamino group, benzenesulfonylamino group, etc.), ureido group (for example, 3-methylureido group, 3,3-dimethylureido group, 1,3-dimethylureido) Group), sulfamoylamino group (dimethylsulfamoylamino group etc.), carbamoyl group (eg methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group etc.), sulfamoyl group (eg ethylsulfamoyl group, dimethylsulfamoyl group) Moyl group etc.), alkoxycarbonyl group (eg methoxycarbonyl group, ethoxycarbonyl group etc.), aryloxycarbonyl group (eg phenoxycarbonyl group etc.), sulfonyl group (eg methanesulfonyl group, butanesulfonyl group, phenylsulfonyl group) Group), acyl group (eg, acetyl group, propanoyl group, butyroyl group, etc.), amino group (methylamino group, ethylamino group, dimethylamino group, etc.), cyano group, hydroxy group, nitro group, nitroso group, amine oxide Group (for example, pyridine-oxide group), imide group (for example, phthalimide group, etc.), disulfide group (for example, benzene disulfide group, benzothiazolyl-2-disulfide group, etc.), carboxyl group, sulfo group, heterocyclic group (for example, pyrrole group, Pyrrolidyl group, pyrazolyl group, imidazolyl group, pyridyl group, benzimidazolyl group, benzthiazolyl group, benzoxazolyl group, etc.). These substituents may be further substituted.

  A compound in which R31 is a hydrogen atom and R32 and R36 are t-butyl groups is preferable. Specific examples of the phenol compound include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl 3- (3,5-di-t-butyl-4 -Hydroxyphenyl) -acetate, n-octadecyl 3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl 3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3,5 -Di-t-butyl-4-hydroxyphenylbenzoate, neo-dodecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl beta (3,5-di-t-butyl-4 -Hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n- Octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (n-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-phenylacetate, 2- (n-octadecyl) Thio) ethyl 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (2-hydroxy Ethylthio) ethyl 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5-di-t-butyl-4- Droxy-phenyl) propionate, 2- (n-octadecylthio) ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide N, N-bis- [ethylene 3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino N, N-bis- [ethylene 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2- ( 2-stearoyloxyethylthio) ethyl 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl 7- (3-methyl-5-tert-butyl-4-hydroxy) Phenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxypheny ) Propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3,5-di-t-butyl-4) -Hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenylacetate), glycerin-ln-octadecanoate-2,3-bis- (3,5 -Di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol tetrakis- [3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], 3,9-bis- { 2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl -2,4,8,10-tetraoxaspiro [5.5] undecane, 1,1,1-trimethylolethane-tris- [3- (3,5-di-t-butyl-4-hydroxyphenyl) Propionate], sorbitol hexa- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- (3-methyl-5-tbutyl-4-hydroxyphenyl) propionate 2-stearoyloxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ', 5'-di-t-butyl- 4-hydroxyphenyl) propionate], pentaerythritol tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate) Be turned. The phenol compound of the above type is commercially available from Ciba Japan Co., Ltd. under the trade names “Irganox 1076” and “Irganox 1010”, for example.

  The above-mentioned phenol compounds can be used alone or in combination of two or more, and the blending amount is appropriately selected within the range not impairing the object of the present invention, but resin (acrylic resin (A) and cellulose ester resin) (B)) It is 0.001-10.0 mass parts normally with respect to 100 mass parts, Preferably it is 0.05-5.0 mass parts, More preferably, it is 0.1-2.0 mass parts.

(Hindered amine compounds)
The hindered amine compound preferably used in the present invention is preferably a hindered amine compound represented by the following general formula (4).

  In formula, R41-R47 represents a substituent. As a substituent, it is synonymous with the substituent represented by R31-R36 of the said General formula (3). R44 is preferably a hydrogen atom and a methyl group, R47 is preferably a hydrogen atom, and R42, R43, R45 and R46 are preferably a methyl group. Specific examples of hindered amine compounds include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) succinate, bis (1 , 2,2,6,6-pentamethyl-4-piperidyl) sebacate, bis (N-octoxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-benzyloxy-2,2) , 6,6-tetramethyl-4-piperidyl) sebacate, bis (N-cyclohexyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6- Pentamethyl-4-piperidyl) 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1-acryloyl-2,2,6,6- Tramethyl-4-piperidyl) 2,2-bis (3,5-di-tert-butyl-4-hydroxybenzyl) -2-butylmalonate, bis (1,2,2,6,6-pentamethyl-4- Piperidyl) decanedioate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] -1- [ 2- (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy) ethyl] -2,2,6,6-tetramethylpiperidine, 2-methyl-2- (2,2, 6,6-tetramethyl-4-piperidyl) amino-N- (2,2,6,6-tetramethyl-4-piperidyl) propionamide, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, and the like.

  Further, it may be a polymer type compound. As specific examples, N, N ′, N ″, N ″ ′-tetrakis- [4,6-bis- [butyl- (N-methyl-2,2,6, 6-tetramethylpiperidin-4-yl) amino] -triazin-2-yl] -4,7-diazadecane-1,10-diamine, dibutylamine and 1,3,5-triazine-N, N′-bis ( 2,2,6,6-tetramethyl-4-piperidyl) -1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine polycondensate, di Polycondensate of butylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1,1,3,3 -Tetramethylbutyl) amino-1,3,5-tri Gin-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], Between 1,6-hexanediamine-N, N'-bis (2,2,6,6-tetramethyl-4-piperidyl) and morpholine-2,4,6-trichloro-1,3,5-triazine Polycondensate, poly [(6-morpholino-s-triazine-2,4-diyl) [(2,2,6,6-tetramethyl-4-piperidyl) imino] -hexamethylene [(2,2,6 , 6-tetramethyl-4-piperidyl) imino]], etc., high molecular weight HALS in which a plurality of piperidine rings are bonded via a triazine skeleton; dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl- 1-piperidine ester Polymer with diol, 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and 3,9-bis (2-hydroxy-1,1-dimethyl) (Ethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane and the like, and the like are exemplified by compounds in which a piperidine ring is bonded through an ester bond, but the present invention is not limited thereto. It is not a thing.

  Among these, polycondensates of dibutylamine, 1,3,5-triazine and N, N′-bis (2,2,6,6-tetramethyl-4-piperidyl) butylamine, poly [{(1, 1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2 , 2,6,6-tetramethyl-4-piperidyl) imino}], a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, etc. Those having a molecular weight (Mn) of 2,000 to 5,000 are preferred.

  The hindered amine compound of the above type is commercially available from Ciba Japan Co., Ltd. under the trade names “Tinuvin 144” and “Tinuvin 770” and from ADEKA Co., Ltd. under the name “ADK STAB LA-52”.

  The above-mentioned hindered amine compounds can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within the range not impairing the object of the present invention, but resin (acrylic resin (A) and cellulose ester resin) (B)) It is 0.001-10.0 mass parts normally with respect to 100 mass parts, Preferably it is 0.05-5.0 mass parts, More preferably, it is 0.1-2.0 mass parts.

(3) Secondary antioxidant The optical film of the present invention contains at least one secondary antioxidant having a reducing action on peroxide.

  In the present invention, the “secondary antioxidant having a reducing action on peroxide” is a reducing compound that rapidly reduces peroxide to convert it to a hydroxyl group.

  The secondary antioxidant having a reducing ability for peroxide is preferably a phosphorus compound or a sulfur compound.

(Phosphorus compounds)
The phosphorus compound preferably used in the present invention is preferably a phosphorus compound selected from the group consisting of phosphite, phosphonite, phosphinite, or tertiary phosphane. Is preferably a compound having a partial structure represented by the following general formulas (5-1), (5-2), (5-3), (5-4), and (C-5) in the molecule.

In the formula, Ph ₁ and Ph ′ ₁ represent a substituent. As a substituent, it is synonymous with the substituent represented by R31-R36 of the said General formula (3). More preferably, Ph ₁ and Ph ′ ₁ represent a phenylene group, and the hydrogen atom of the phenylene group is a phenyl group, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or 6 to 12 carbon atoms. Or an alkyl cycloalkyl group or an aralkyl group having 7 to 12 carbon atoms. Ph ₁ and Ph ′ ₁ may be the same as or different from each other. X represents a single bond, a sulfur atom or a —CHR— group. R represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. These may be substituted with a substituent having the same meaning as the substituents represented by R31 to R36 in the general formula (3).

Wherein, Ph ₂ and Ph _'2 each represent a substituent. As a substituent, it is synonymous with the substituent represented by R31-R36 of the said General formula (3). More preferably, Ph ₂ and Ph ′ ₂ represent a phenyl group or a biphenyl group, and the hydrogen atom of the phenyl group or biphenyl group is an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or a carbon number. It may be substituted with a 6-12 alkylcycloalkyl group or an aralkyl group having 7-12 carbon atoms. Ph ₂ and Ph ′ ₂ may be the same as or different from each other. These may be substituted with a substituent having the same meaning as the substituents represented by R31 to R36 in the general formula (3).

In the formula, Ph ₃ represents a substituent. As a substituent, it is synonymous with the substituent represented by R31-R36 of the said General formula (3). More preferably, Ph ₃ represents a phenyl group or a biphenyl group, and the hydrogen atom of the phenyl group or biphenyl group is an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or a 6 to 12 carbon atom. It may be substituted with an alkylcycloalkyl group or an aralkyl group having 7 to 12 carbon atoms. These may be substituted with a substituent having the same meaning as the substituents represented by R31 to R36 in the general formula (3).

In the formula, Ph ₄ represents a substituent. As a substituent, it is synonymous with the substituent represented by R31-R36 of the said General formula (3). More preferably, Ph ₄ represents an alkyl group having 1 to 20 carbon atoms or a phenyl group, and the alkyl group or phenyl group is a substituent having the same meaning as the substituent represented by R31 to R36 in the general formula (3). May be substituted.

In the formula, Ph ₅ , Ph ′ ₅ and Ph ″ ₅ represent substituents. The substituents have the same meaning as the substituents represented by R 31 to R 36 in the general formula (3). More preferably, Ph ₅ , Ph ′ ₅ and Ph ″ ₅ represent an alkyl group or phenyl group having 1 to 20 carbon atoms, and the alkyl group or phenyl group is a substituent having the same meaning as the substituent represented by R31 to R36 in the general formula (3). It may be substituted by a group.

  Specific examples of phosphorus compounds include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris (2,4-di-). t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 6- [ 3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-tert-butyldibenz [d, f] [1,3,2] dioxaphosphine Monophosphite compounds such as pin and tridecyl phosphite; 4,4'-butylidene-bis (3-methyl-6-t-butyl) Diphosphite compounds such as phenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis (phenyl-di-alkyl (C12-C15) phosphite); triphenylphosphonite, tetrakis (2,4- Di-tert-butylphenyl) [1,1-biphenyl] -4,4'-diylbisphosphonite, tetrakis (2,4-di-tert-butyl-5-methylphenyl) [1,1-biphenyl]- Phosphonite compounds such as 4,4'-diylbisphosphonite; phosphinite compounds such as triphenylphosphinite and 2,6-dimethylphenyldiphenylphosphinite; triphenylphosphine and tris (2,6-dimethoxyphenyl) Phosphine compounds such as phosphine; and the like.

  Phosphorus compounds of the above type are, for example, from Sumitomo Chemical Co., Ltd. “Sumilizer GP”, from ADEKA Co., Ltd. “Adekastab PEP-24G”, “Adekastab PEP-36” and “Adekastab 3010”, from Ciba Japan “IRGAFOS P-EPQ”, commercially available from Sakai Chemical Industry Co., Ltd. under the trade name “GSY-P101”.

  The above phosphorus compounds can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within the range not impairing the object of the present invention. Resin (acrylic resin (A) and cellulose ester Resin (B)) is usually 0.001 to 10.0 parts by mass, preferably 0.05 to 5.0 parts by mass, and more preferably 0.05 to 2.0 parts by mass with respect to 100 parts by mass. .

(Sulfur compounds)
The sulfur compound preferably used in the present invention is preferably a sulfur compound represented by the following general formula (6).

General formula (6)
R61-S-R62
In the formula, R61 and R62 each represent a substituent. As a substituent, it is synonymous with the substituent represented by R31-R36 of the said General formula (3).

  Specific examples of the sulfur compound include dilauryl 3,3-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3-thiodipropionate, lauryl stearyl 3,3-thiodipropioate. And pentaerythritol-tetrakis (β-lauryl-thio-propionate), 3,9-bis (2-dodecylthioethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane and the like. .

  The above-mentioned types of sulfur compounds are commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer TPL-R” and “Sumilizer TP-D”, for example.

  The above sulfur-based compounds can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within the range not impairing the object of the present invention, but resin (acrylic resin (A) and cellulose ester Resin (B)) is usually 0.001 to 10.0 parts by mass, preferably 0.05 to 5.0 parts by mass, and more preferably 0.05 to 2.0 parts by mass with respect to 100 parts by mass. .

<Other additives>
In the optical film of the present invention, additives such as an acid scavenger, an ultraviolet absorber, a plasticizer, a mat agent, an optical anisotropy control agent and an antistatic agent may be used in combination as other additives.

(Acid scavenger)
Since decomposition is accelerated by an acid in a high temperature environment where melt film formation is performed, the optical film of the present invention preferably contains an acid scavenger as a stabilizer. Any acid scavenger useful in the present invention can be used without limitation as long as it is a compound that reacts with an acid to inactivate the acid, and is described in U.S. Pat. No. 4,137,201. A compound having an epoxy group is preferred.

  Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of various polyglycol diglycidyl ethers, particularly about 8 to 40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ethers of glycerol, etc., metal epoxy compounds (such as those conventionally used in and with vinyl chloride polymer compositions), epoxidized ether condensation products, diphenols of bisphenol A Glycidyl ether (ie, 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 4 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (for example, Butyl epoxy stearate) ), And epoxidized vegetable oils and other unsaturated natural oils (sometimes these may be represented and exemplified by compositions of various epoxidized long chain fatty acid triglycerides and the like (eg, epoxidized soybean oil, epoxidized linseed oil, etc.) Epoxidized natural glycerides or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms).

  In addition, as a commercially available epoxy group-containing epoxide resin compound, EPON 815C and other epoxidized ether oligomer condensation products of the following general formula (7) can also be preferably used.

  In formula, n is an integer of 0-12. Other acid scavengers that can be used include those described in paragraphs 87 to 105 of JP-A-5-194788.

  Each of the acid scavengers can be used alone or in combination of two or more, and the amount of the acid scavenger is appropriately selected within the range not impairing the object of the present invention. Resin (acrylic resin (A) and cellulose ester resin (B )) It is 0.001-10.0 mass parts normally with respect to 100 mass parts, Preferably it is 0.05-5.0 mass parts, More preferably, it is 0.05-2.0 mass parts.

  In addition, although an acid scavenger may be called an acid scavenger, an acid capture agent, an acid catcher etc. with respect to resin, in this invention, it can use without a difference by these names.

(UV absorber)
In the optical film of the present invention, from the viewpoint of preventing deterioration of the polarizer and the display device with respect to ultraviolet rays, the optical film is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, visible light having a wavelength of 400 nm or more is used. It is preferable to contain an ultraviolet absorber that absorbs little.

  Examples of the ultraviolet absorber used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. However, benzophenone compounds, less colored benzotriazole compounds, and triazine compounds are preferable.

  Further, ultraviolet absorbers described in JP-A Nos. 10-182621 and 8-337574, and polymer ultraviolet absorbers described in JP-A Nos. 6-148430 and 2003-113317 may be used.

  Specific examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzo Triazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5 Chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy- '-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-(2-octyloxycarbonylethyl) -phenyl) -5 -Chlorobenzotriazole, 2- (2'-hydroxy-3 '-(1-methyl-1-phenylethyl) -5'-(1,1,3,3-tetramethylbutyl) -phenyl) benzotriazole, 2 -(2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H- Benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro- H- benzotriazol-2-yl) can be mentioned mixtures of phenyl] propionate, and the like.

  As commercially available products, TINUVIN 171, TINUVIN 900, TINUVIN 928, TINUVIN 360 (all manufactured by Ciba Japan), LA31 (manufactured by ADEKA Corporation), RUVA- 100 (manufactured by Otsuka Chemical).

  Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but are not limited thereto.

  In this invention, it is preferable to add 0.1-5 mass% of ultraviolet absorbers with respect to resin (Acrylic resin (A) and cellulose-ester resin (B)), Furthermore, 0.2-3 mass% is added. It is preferable to add 0.5 to 2% by mass. Two or more of these may be used in combination.

  The benzotriazole structure or triazine structure may be part of the polymer, or may be regularly pendant to the polymer, and part of the molecular structure of other additives such as plasticizers, antioxidants, and acid scavengers. May be introduced.

  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. Furthermore, the polymer etc. which are described in Unexamined-Japanese-Patent No. 2003-113317 are mentioned.

(Plasticizer)
In the optical film of the present invention, at least one plasticizer may be added to the film.

  A plasticizer is generally an additive that has the effect of improving brittleness or imparting flexibility by being added to a polymer. In this case, a plasticizer is added in order to lower the melting temperature than the melting temperature alone, and to lower the melt viscosity of the film constituent material containing the plasticizer than the resin alone at the same heating temperature. Moreover, since it adds also in order to improve the hydrophilic property of a cellulose ester and to improve the water vapor transmission rate of an optical film, it has a function as a moisture permeation preventive agent.

  Here, the melting temperature of the film constituent material means a temperature at which the material is heated and fluidity is developed. In order to melt and flow the resin according to the present invention, it is necessary to heat at least a temperature higher than the glass transition temperature. Above the glass transition temperature, the elastic modulus or viscosity decreases due to heat absorption, and fluidity is exhibited.

  However, in the resin according to the present invention, the molecular weight of the cellulose ester is reduced due to thermal decomposition at the same time as melting at a high temperature, which may adversely affect the mechanical properties of the resulting film. Therefore, the resin is melted at a temperature as low as possible. There is a need.

  In order to lower the melting temperature of the film constituting material, it can be achieved by adding a plasticizer having a melting point or glass transition temperature lower than the glass transition temperature of the resin according to the present invention.

  In the optical film of the present invention, it is preferable to add a plasticizer in an amount of 0.1 to 20% by mass, and further 0.2 to 10% by mass with respect to the resin (acrylic resin (A) and cellulose ester resin (B)). It is preferable to do. Two or more of these may be used in combination.

  In the present invention, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol are preferred.

  Examples of polyhydric alcohols that are raw materials for ester plasticizers include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, glycerin, diglycerin, 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-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, ditrimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, xyl Mention may be made of the toll and the like. In particular, ethylene glycol, glycerin, and trimethylolpropane are preferable.

  Specific examples of ethylene glycol ester plasticizers that are one of the polyhydric alcohol esters include ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, and ethylene glycol dicyclopropyl. Examples thereof include ethylene glycol cycloalkyl ester plasticizers such as carboxylate and ethylene glycol dicyclohexylcarboxylate, and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di4-methylbenzoate.

  These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mix of alkylate group, cycloalkylate group and arylate group, and these substituents may be covalently bonded.

  Further, the ethylene glycol part may be substituted, and the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It may be introduced into a part of the molecular structure of the additive.

  Specific examples of the glycerin ester plasticizer that is one of the polyhydric alcohol esters include glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, and glycerol tricyclopropylcarboxylate. Glycerol glycerol esters such as glycerol tricyclohexyl carboxylate, glycerol aryl esters such as glycerol tribenzoate and glycerol 4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol Tetralaurate, diglycerin alkyl ester, diglycerin tetracyclobutylcarboxylate, diglycerin tet Diglycerol cycloalkyl esters such as cyclopentyl carboxylate diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond.

  Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

  Specific examples of other polyhydric alcohol ester plasticizers include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A No. 2003-12823.

  These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond.

  Furthermore, the polyhydric alcohol part may be substituted, and the partial structure of the polyhydric alcohol may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber. May be introduced into a part of the molecular structure of the additive.

  Among the ester plasticizers composed of the polyhydric alcohol and the monovalent carboxylic acid, alkyl polyhydric alcohol aryl esters are preferable. Specifically, the ethylene glycol dibenzoate, glycerin tribenzoate, diglycerin tetrabenzoate, penta Examples include erythritol tetrabenzoate and exemplified compound 16 described in paragraph 31 of JP-A No. 2003-12823.

  Specific examples of the dicarboxylic acid ester plasticizer that is one of the polyvalent carboxylic acid esters include alkyl dicarboxylic acid alkyl ester plasticizers such as didodecyl malonate, dioctyl adipate, and dibutyl sebacate. Alkyl dicarboxylic acid cycloalkyl ester type plasticizers such as cyclopentyl succinate and dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester type plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, dihexyl-1,4-cyclohexane Cycloalkyl dicarboxylic acid alkyl ester plasticizers such as dicarboxylate and didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicis Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as ropropyl-1,2-cyclohexyldicarboxylate, diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate, etc. Cycloalkyldicarboxylic acid aryl ester plasticizer, diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate and other aryl dicarboxylic acid alkyl ester plasticizers, dicyclopropyl phthalate, dicyclohexyl phthalate, etc. Aryl dicarboxylic acid cycloalkyl ester plasticizers, and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di-4-methylphenyl phthalate And the like. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted.

  The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used.

  Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and it may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  Examples of other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizers, alkylpolycarboxylic acid cycloalkyl ester plasticizers such as tricyclohexyltricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy- Alkyl polyvalent carboxylic acid aryl ester plasticizers such as 1,2,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2, 3,4-cyclobutanetetracarboxylate, tetrabu Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as ru-1,2,3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as 1,3,5-cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2, Cycloalkyl polycarboxylic acid aryl ester plasticizers such as 3,4,5,6-cyclohexylhexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4 , 5-tetracarboxylate and other aryl polyvalent Rubinoic acid alkyl ester plasticizers, tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate and other aryl polyvalent carboxylic acid cycloalkyl esters Plasticizers of aryl polyvalent carboxylic acid aryl esters such as plasticizers triphenylbenzene-1,3,5-tetracarboxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Agents.

  These alkoxy groups and cycloalkoxy groups may be the same or different, and may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond.

  Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant into the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Among the ester plasticizers composed of the polyvalent carboxylic acid and the monohydric alcohol, alkyl dicarboxylic acid alkyl esters are preferable, and specific examples include the dioctyl adipate.

  Examples of other plasticizers used in the present invention include phosphate ester plasticizers, carbohydrate ester plasticizers, and polymer plasticizers.

  Specific examples of the phosphoric acid ester plasticizer include phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate, Examples thereof include phosphoric acid aryl esters such as cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted.

  Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Also, alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl) And phosphate esters such as arylene bis (diaryl phosphate) such as arylene bis (dialkyl phosphate), phenylene bis (diphenyl phosphate), naphthylene bis (ditoluyl phosphate) such as biphenylene bis (dioctyl phosphate). These substituents may be the same or different, and may be further substituted.

  Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Furthermore, the partial structure of the phosphate ester may be part of the polymer or may be regularly pendant, and may be introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

  Next, the carbohydrate ester plasticizer will be described. The carbohydrate means a monosaccharide, disaccharide or trisaccharide in which the saccharide is present in the form of pyranose or furanose (6-membered ring or 5-membered ring). Non-limiting examples of carbohydrates include glucose, saccharose, lactose, cellobiose, mannose, xylose, ribose, galactose, arabinose, fructose, sorbose, cellotriose and raffinose.

  The carbohydrate ester refers to an ester compound formed by dehydration condensation of a carbohydrate hydroxyl group and a carboxylic acid, and specifically means an aliphatic carboxylic acid ester or an aromatic carboxylic acid ester of a carbohydrate.

  Examples of the aliphatic carboxylic acid include acetic acid and propionic acid, and examples of the aromatic carboxylic acid include benzoic acid, toluic acid, and anisic acid.

  Carbohydrates have a number of hydroxyl groups depending on the type, but even if a part of the hydroxyl group reacts with the carboxylic acid to form an ester compound, the whole hydroxyl group reacts with the carboxylic acid to form an ester compound. Also good. In the present invention, it is preferable that all of the hydroxyl groups react with the carboxylic acid to form an ester compound.

  Specific examples of the carbohydrate ester plasticizer include glucose pentaacetate, glucose pentapropionate, glucose pentabylate, saccharose octaacetate, saccharose octabenzoate and the like. Among these, saccharose octaacetate, saccharose Octabenzoate is more preferred, and sucrose octabenzoate is particularly preferred.

  Examples of these compounds are listed below, but the present invention is not limited thereto.

Monopet SB: manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Monopet SOA: manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Specific examples of the polymer plasticizer include aliphatic hydrocarbon polymers, alicyclic hydrocarbon polymers, and ethyl polyacrylate. , Acrylic polymers such as polymethyl methacrylate, copolymers of methyl methacrylate and 2-hydroxyethyl methacrylate (eg, any ratio between 1:99 and 99: 1), polyvinyl isobutyl Ethers, vinyl polymers such as poly N-vinyl pyrrolidone, styrene polymers such as polystyrene and poly 4-hydroxystyrene, polybutylene succinates, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide , Polyamide, polyureta , And a polyurea or the like.

  The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5,000 to 200,000. If it is 1000 or less, a problem arises in volatility, and if it exceeds 500000, the plasticizing ability is lowered, and the mechanical properties of the optical film are adversely affected. These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination.

(Matting agent)
In the optical film according to the present invention, a matting agent can be added in order to impart slipperiness, optical and mechanical functions. Examples of the matting agent include inorganic compound fine particles and organic compound fine particles.

  The shape of the matting agent is preferably a spherical shape, a rod shape, a needle shape, a layer shape, a flat shape or the like. Examples of the matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Examples thereof include inorganic fine particles such as oxides, phosphates, silicates, and carbonates, and crosslinked polymer fine particles.

  Among these, silicon dioxide is preferable because it can reduce the haze of the film. These fine particles are preferably surface-treated with an organic substance because the haze of the film can be reduced.

  The surface treatment is preferably performed with halosilanes, alkoxysilanes, silazane, siloxane, or the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average primary particle size of the fine particles is in the range of 0.01 to 1.0 μm. The average particle size of the primary particles of preferable fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used for generating irregularities of 0.01 to 1.0 μm on the optical film surface.

  As the fine particles of silicon dioxide, Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, NAX50, etc. manufactured by Nippon Aerosil Co., Ltd. P10, KE-P30, KE-P100, KE-P150 and the like can be mentioned, and Aerosil 200V, R972V, NAX50, KE-P30 and KE-P100 are preferable. Two or more kinds of these fine particles may be used in combination.

  When using 2 or more types together, it can mix and use in arbitrary ratios. Fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

  These matting agents are preferably added by kneading. Further, as another form, after mixing and dispersing a matting agent dispersed in a solvent in advance with a resin and / or a plasticizer and / or an antioxidant and / or an ultraviolet absorber, a solid material obtained by volatilizing or precipitating the solvent is obtained. It is preferable to use this in the process of producing the resin melt from the viewpoint that the matting agent can be uniformly dispersed in the resin.

  The matting agent can also be added to improve the mechanical, electrical and optical properties of the film.

  In addition, although the slipperiness of the film obtained improves, so that these microparticles | fine-particles are added, since haze will raise so that it adds, content is preferably (acrylic resin (A) and cellulose-ester resin (B)). 0.001-5 mass% is preferable with respect to this, More preferably, it is 0.005-1 mass%, More preferably, it is 0.01-0.5 mass%.

(Optical anisotropy control agent)
A retardation increasing agent for controlling optical anisotropy is optionally added. Since these adjust the retardation of an optical film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation increasing agent.

  An aromatic compound is used in 0.01-20 mass parts with respect to 100 mass parts (acrylic-type resin (A) and cellulose-ester resin (B)). And it is preferable to use in 0.05-15 mass parts, and it is still more preferable to use in 0.1-10 mass parts. Two or more aromatic compounds may be used in combination.

  The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring.

  Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.

  Details of these are described in JP-A No. 2004-109410, JP-A No. 2003-344655, JP-A No. 2000-275434, JP-A No. 2000-1111914, JP-A No. 12-275434, and the like.

<Method for producing optical film>
The example of the manufacturing method of the optical film of this invention is demonstrated.

(Melt casting method)
In detail, the optical film of the present invention can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these, in order to obtain a polarizing plate protective film excellent in mechanical strength, surface accuracy, etc., the melt extrusion method is excellent.

  Hereinafter, the manufacturing method of the optical film of the present invention will be described by taking the melt extrusion method as an example.

  FIG. 1 is a schematic flow sheet showing the overall configuration of an apparatus for carrying out the method for producing an optical film according to the present invention, and FIG. 2 is an enlarged view of a cooling roll portion from a casting die.

  1 and 2, the method for producing an optical film according to the present invention is performed by mixing film materials such as cellulose ester resin and acrylic resin and then using an extruder 1 on a first cooling roll 5 from a casting die 4. The film is melted and extruded to be circumscribed to the first cooling roll 5, and is further circumscribed in turn to a total of three cooling rolls of the second cooling roll 7 and the third cooling roll 8, and is cooled and solidified to form a film 10. Next, after the film 10 peeled off by the peeling roll 9 is stretched in the width direction by holding both ends of the film by the stretching device 12, the film 10 is wound up by the winding device 16.

  In addition, a touch roll 6 is provided that clamps the molten film on the surface of the first cooling roll 5 in order to correct the flatness. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5. Details of the touch roll 6 will be described later.

  In the method for producing an optical film according to the present invention, the conditions for melt extrusion can be carried out in the same manner as the conditions used for other thermoplastic resins such as polyester. The material is preferably dried beforehand. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less by using a vacuum or reduced pressure drier or a dehumidifying hot air drier.

  For example, resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using the extruder 1, filtered through a leaf disk type filter 2, and the like to remove foreign matters.

  When introducing into the extruder 1 from a supply hopper (not shown), it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer 3.

  In the present invention, the resin and other additives that are added as necessary are preferably mixed before melting, and more preferably the resin and the additive are mixed before heating. Mixing may be performed by a mixer or the like, or may be performed in the resin preparation process as described above. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, a Henschel mixer, or a ribbon mixer can be used.

  After the film constituent materials are mixed as described above, the mixture may be directly melted using the extruder 1 to form a film. Once the film constituent materials are pelletized, the pellets are extruded. The film may be melted by the machine 1 to form a film. When the film constituent material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only the material having a low melting point is melted, and the semi-melt is supplied to the extruder 1. It is also possible to form a film by introducing it. If the film component contains a material that is easily pyrolyzed, in order to reduce the number of times of melting, a method of directly forming a film without producing pellets, or after making a paste-like semi-molten material as described above A method of forming a film is preferred.

  As the extruder 1, various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used. When forming a film directly without producing pellets from film constituent materials, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is necessary, but even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used. When a pellet or braided semi-melt is once used as a film constituent material, it can be used in either a single screw extruder or a twin screw extruder.

  In the extruder 1 and the cooling step after the extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

  The preferable conditions for the melting temperature of the film constituent material in the extruder 1 vary depending on the viscosity and discharge amount of the film constituent material, the thickness of the sheet to be manufactured, etc., but generally the glass transition temperature Tg of the film Tg to Tg + 100 ° C., preferably Tg + 10 ° C. to Tg + 90 ° C. The melt viscosity at the time of extrusion is 1 to 10000 Pa · s, preferably 10 to 1000 Pa · s. Further, the residence time of the film constituting material in the extruder 1 is preferably short, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes.

  The residence time depends on the type of the extruder 1 and the extrusion conditions, but can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, and the like. is there.

  The shape, rotation speed, and the like of the screw of the extruder 1 are appropriately selected depending on the viscosity, the discharge amount, and the like of the film constituent material. In the present invention, the shear rate in the extruder 1 is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second.

  The extruder 1 that can be used in the present invention is generally available as a plastic molding machine.

  The film constituent material extruded from the extruder 1 is sent to the casting die 4 and extruded from the slit of the casting die 4 into a film shape. The casting die 4 is not particularly limited as long as it is used for producing a sheet or a film.

  The material of the casting die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Processing such as buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And the like. A preferred material for the lip portion of the casting die 4 is the same as that of the casting die 4. The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

  The slit of the casting die 4 is configured so that the gap can be adjusted. This is shown in FIG. Of the pair of lips forming the slit 32 of the casting die 4, one is a flexible lip 33 having low rigidity and easily deformed, and the other is a fixed lip 34. A large number of heat bolts 35 are arranged at a constant pitch in the width direction of the casting die 4, that is, in the length direction of the slits 32.

  Each heat bolt 5 is provided with a block 36 having an embedded electric heater 37 and a cooling medium passage, and each heat bolt 35 penetrates each block 36 vertically. The base of the heat bolt 35 is fixed to the die body 31, and the tip is in contact with the outer surface of the flexible lip 33.

  While constantly cooling the block 36, the input to the embedded electric heater 37 is increased or decreased to increase or decrease the temperature of the block 36, thereby causing the heat bolt 35 to thermally expand and contract, thereby displacing the flexible lip 33 and thereby increasing the film thickness. adjust.

  Thickness gauges are installed at the required locations in the wake of the die, and the web thickness information detected by this is fed back to the control device. This thickness information is compared with the set thickness information by the control device, and corrections coming from the device It is also possible to control the power or ON rate of the heat bolt heating element by a control amount signal. The heat bolt preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged at a pitch of 20 to 40 mm. Instead of the heat bolt, a gap adjusting member mainly composed of a bolt for adjusting the slit gap by manually moving back and forth in the axial direction may be provided. The slit gap adjusted by the gap adjusting member is usually 200 to 1000 μm, preferably 300 to 800 μm, more preferably 400 to 600 μm.

  The first to third cooling rolls are made of seamless steel pipe having a wall thickness of about 20 to 30 mm, and the surface is finished to a mirror surface. Inside, a pipe for flowing a coolant is arranged so that heat can be absorbed from the film on the roll by the coolant flowing through the pipe. Of the first to third cooling rolls, the first cooling roll 5 corresponds to the rotary support according to the present invention.

  On the other hand, the touch roll 6 in contact with the first cooling roll 5 has an elastic surface and is deformed along the surface of the first cooling roll 5 by the pressing force to the first cooling roll 5. A nip is formed between the two. The touch roll 6 is also called a pinching rotary body. As the touch roll 6, a touch roll disclosed in registered patent 3194904, registered patent 3422798, Japanese Patent Application Laid-Open No. 2002-36332, Japanese Patent Application Laid-Open No. 2002-36333, or the like can be preferably used. These can also use what is marketed.

  These will be described in more detail below.

  FIG. 4 is a cross-sectional view showing an example of the pinching rotator. (The 1st example of touch roll 6 (henceforth, outline section of touch roll A)) is shown. As shown in the drawing, the touch roll A has an elastic roller 42 disposed inside a flexible metal sleeve 41.

  The metal sleeve 41 is made of stainless steel having a thickness of 0.3 mm and has flexibility. If the metal sleeve 41 is too thin, the strength is insufficient, whereas if it is too thick, the elasticity is insufficient. For these reasons, the thickness of the metal sleeve 41 is preferably 0.1 to 1.5 mm. The elastic roller 42 is formed in a roll shape by providing a rubber 44 on the surface of a metal inner cylinder 43 that is rotatable via a bearing. When the touch roll A is pressed toward the first cooling roll 5, the elastic roller 42 presses the metal sleeve 41 against the first cooling roll 5, and the metal sleep 41 and the elastic roller 42 have the shape of the first cooling roll 5. It deforms corresponding to the familiar shape, and forms a nip with the first cooling roll. Cooling water 45 flows in a space formed between the metal sleeve 41 and the elastic roller 42.

  FIG. 5 is a cross-sectional view taken along a plane perpendicular to the rotation axis, showing a second example (hereinafter referred to as touch roll B) of the pinching rotator.

  FIG. 6 is a cross-sectional view showing an example of a plane including the rotation axis of the second example (touch roll B) of the pinching rotator.

  5 and 6 show a touch roll B which is another embodiment of the pinching rotator. The touch roll B includes a flexible, seamless stainless steel pipe (thickness 4 mm) outer cylinder 51, and a highly rigid metal inner cylinder 52 arranged on the same axis as the inner side of the outer cylinder 51. It is roughly composed. A coolant 54 flows in the space 53 between the outer cylinder 51 and the inner cylinder 52. Specifically, in the touch roll B, outer cylinder support flanges 56a and 56b are attached to the rotation shafts 55a and 55b at both ends, and a thin metal outer cylinder 51 is attached between the outer peripheral portions of the both outer cylinder support flanges 56a and 56b. Yes.

  A fluid supply pipe 59 is disposed in the same axial center in a fluid discharge hole 58 formed in the axial center portion of one rotary shaft 55a and forming a fluid return passage 57. The fluid supply pipe 59 is thin-walled. It is connected and fixed to a fluid shaft cylinder 60 arranged at the axial center in the metal outer cylinder 51. Inner cylinder support flanges 61a and 61b are attached to both ends of the fluid shaft cylinder 60, respectively, and a thickness of about 15 to 20 mm between the outer periphery of the inner cylinder support flanges 61a and 61b and the other outer cylinder support flange 56b. A metal inner cylinder 52 having a thickness is attached.

  A cooling liquid flow space 53 of, for example, about 10 mm is formed between the metal inner cylinder 52 and the thin metal outer cylinder 51, and the metal inner cylinder 52 has a flow space 53 and an inner space near both ends. An outlet 52a and an inlet 52b are formed to communicate with the intermediate passages 62a and 62b outside the cylinder support flanges 61a and 61b, respectively.

  Further, the outer cylinder 51 is thinned within a range in which the thin cylinder theory of elastic mechanics can be applied in order to have flexibility, flexibility, and resilience close to rubber elasticity. The flexibility evaluated by the thin-walled cylinder theory is expressed by the thickness t / roll radius r, and the flexibility increases as t / r decreases.

  In this touch roll B, the flexibility is the optimum condition when t / r ≦ 0.03. Usually, the touch roll generally used has a roll diameter R = 200 to 500 mm (roll radius r = R / 2), a roll effective width L = 500 to 1600 mm, and a horizontally long shape with r / L <1. is there.

  As shown in FIG. 6, for example, when the roll diameter R = 300 mm and the roll effective width L = 1200 mm, the appropriate range of the wall thickness t is 150 × 0.03 = 4.5 mm or less, but the molten sheet width is 1300 mm. On the other hand, when the average linear pressure is clamped at 98 N / cm, the equivalent spring constant is equal by setting the wall thickness of the outer cylinder 51 to 3 mm compared to the rubber roll of the same shape. The nip width k in the roll rotation direction of the nip is also about 9 mm, which is almost the same as the nip width of this rubber roll of about 12 mm. The deflection amount at the nip width k is about 0.05 to 0.1 mm.

  Here, t / r ≦ 0.03. However, in the case of a general roll diameter R = 200 to 500 mm, flexibility is sufficiently obtained especially in the range of 2 mm ≦ t ≦ 5 mm. Thinning by processing can be easily performed, and it is an extremely practical range. If the wall thickness is 2 mm or less, high-precision processing cannot be performed due to elastic deformation during processing.

  The converted value of 2 mm ≦ t ≦ 5 mm is 0.008 ≦ t / r ≦ 0.05 with respect to a general roll diameter, but in practical use, the roll diameter under the condition of t / r≈0.03. The wall thickness should be increased in proportion to For example, when roll diameter: R = 200, t = 2 to 3 mm, and when roll diameter: R = 500, t = 4 to 5 mm.

  The touch rolls A and B are urged toward the first cooling roll by urging means (not shown). The urging force of the urging means is F, and the value F / W (linear pressure) obtained by dividing the width of the film in the nip in the direction along the rotation axis of the first cooling roll 5 is 9.8 to 147 N / cm. Set to

  According to the present embodiment, a nip is formed between the touch rolls A and B and the first cooling roll 5, and the flatness may be corrected while the film passes through the nip. Accordingly, since the film is sandwiched over a long time with a small linear pressure compared to the case where the touch roll is formed of a rigid body and no nip is formed between the first cooling roll and the flatness is more reliably corrected. Can do.

  That is, when the linear pressure is smaller than 9.8 N / cm, the die line cannot be sufficiently eliminated. On the other hand, if the linear pressure is greater than 147 N / cm, the film is difficult to pass through the nip, resulting in unevenness in place of the film thickness.

  Moreover, since the surface of the touch rolls A and B can be made smoother than the case where the surface of the touch rolls is made of rubber, the surface of the touch rolls A and B can be made smoother. Can be obtained. In addition, as a material of the elastic body 44 of the elastic roller 42, ethylene propylene rubber, neoprene rubber, silicon rubber, or the like can be used.

  Now, in order to satisfactorily eliminate the die line by the touch roll 6, it is important that the viscosity of the film when the touch roll 6 clamps the film is in an appropriate range. Cellulose esters are known to have a relatively large change in viscosity with temperature.

  Therefore, in order to set the viscosity when the touch roll 6 clamps the optical film to an appropriate range, it is important to set the temperature of the film when the touch roll 6 clamps the film to an appropriate range. . When the glass transition temperature of the optical film is Tg, it is preferable to set the temperature T of the film immediately before the film is sandwiched between the touch rolls 6 so as to satisfy Tg <T <Tg + 110 ° C.

  Preferably, Tg + 10 ° C. <T2 <Tg + 90 ° C., more preferably Tg + 20 ° C. <T2 <Tg + 70 ° C. In order to set the temperature of the film when the touch roll 6 clamps the optical film to an appropriate range, the first cooling roll starts from the position P1 at which the melt extruded from the casting die 4 contacts the first cooling roll 5. What is necessary is just to adjust the length L along the rotation direction of the 1st cooling roll 5 of the nip of 5 and the touch roll 6. FIG.

  In the present invention, preferred materials for the first roll 5 and the second roll 6 include carbon steel, stainless steel, resin, and the like. The surface accuracy is preferably increased, and the surface roughness is set to 0.3 S or less, more preferably 0.01 S or less. In the present invention, it was discovered that the die line correction effect is more greatly manifested by reducing the pressure from the opening (lip) of the casting die 4 to the first roll 5 to 70 kPa or less. The reduced pressure is preferably 50 to 70 kPa.

  Although there is no restriction | limiting in particular as a method of keeping the pressure of the part from the opening part (lip | rip) of the casting die 4 to the 1st roll 5 below 70 kPa, Cover the roll periphery from the casting die 4 with a pressure | voltage resistant member, and reduce pressure. There are methods. At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where the sublimate is attached. In the present invention, if the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure to an appropriate value.

  In the present invention, a molten film-like resin from the T die 4 is cooled and solidified while being conveyed in close contact with the first roll (first cooling roll) 5, the second cooling roll 7, and the third cooling roll 8. The unstretched resin film 10 is obtained.

  In the embodiment of the present invention shown in FIG. 1, the cooled and solidified unstretched film 10 peeled from the third cooling roll 8 by the peeling roll 9 is guided to a stretching machine 12 via a dancer roll (film tension adjusting roll) 11. Therefore, the film 10 is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

  As a method for stretching the film in the width direction, a known tenter or the like can be preferably used. In particular, it is preferable to set the stretching direction to the width direction because lamination with a polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the optical film becomes the width direction.

  On the other hand, the transmission axis of the polarizing film is also usually in the width direction. By incorporating a polarizing plate in which the transmission axis of the polarizing film and the slow axis of the optical film are parallel to each other into the liquid crystal display device, the display contrast of the liquid crystal display device can be increased and a good viewing angle can be obtained. Is obtained.

  The glass transition temperature Tg of the film constituting material can be controlled by varying the material type constituting the film and the ratio of the constituting material. When a retardation film is produced as an optical film, Tg is preferably 120 ° C. or higher, preferably 135 ° C. or higher. In the liquid crystal display device, in the image display state, the temperature environment of the film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source.

  At this time, if the Tg of the film is lower than the use environment temperature of the film, the retardation value derived from the orientation state of the molecules fixed inside the film by stretching and the dimensional shape as the film are greatly changed.

  If the Tg of the film is too high, the temperature is increased when the film constituent material is made into a film, so that the energy consumption for heating is increased, and the material itself may be decomposed when it is made into a film, resulting in coloring. Therefore, Tg is preferably 250 ° C. or lower.

  The stretching step may be performed by known heat setting conditions, cooling, and relaxation treatment, and may be appropriately adjusted so as to have the characteristics required for the target optical film.

  For example, in order to provide the physical properties of the retardation film and the functionality of the retardation film for expanding the viewing angle of the liquid crystal display device, the stretching step and the heat setting treatment are appropriately selected and performed. When such a stretching step and heat setting treatment are included, the heating and pressurizing step is performed before the stretching step and heat setting treatment.

  When the optical film of the present invention is manufactured as a retardation film, and further as a retardation film in which the functions of a polarizing plate protective film are combined, it is necessary to perform refractive index control, and the refractive index control may be performed by a stretching operation. preferable. Hereinafter, the stretching method will be described.

  In the retardation film stretching step, the required retardation is obtained by stretching 1.0 to 2.0 times in one direction of the film and 1.01 to 2.5 times in the direction perpendicular to the film plane. Ro and Rt can be controlled. Here, Ro indicates in-plane retardation, and Rt indicates thickness direction retardation.

  Retardation Ro and Rt are calculated | required by a following formula.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film (refractive index is 23 ° C., 55 (Measured at a wavelength of 590 nm in an environment of% RH), d represents the thickness (nm) of the film.)
The refractive index of the optical film is an Abbe refractometer (4T), the thickness of the film is a commercially available micrometer, and the retardation value is an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Etc.) can be used for measurement.

  Stretching can be performed, for example, sequentially or simultaneously in the longitudinal direction of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction. At this time, if the stretching ratio in at least one direction is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and film breakage may occur.

  For example, when stretching in the melt casting direction (longitudinal direction), if the shrinkage in the width direction is too large, the value of nz becomes too large. In this case, it can be improved by suppressing the width shrinkage of the film or stretching in the width direction. When stretching in the width direction, the refractive index may be distributed in the width direction. This distribution may appear when the tenter method is used. By stretching the film in the width direction, a shrinkage force is generated at the center of the film, and the phenomenon is caused by the end being fixed. It is thought to be called the Boeing phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed and the distribution of the phase difference in the width direction can be reduced.

  By stretching in the biaxial directions perpendicular to each other, the film thickness variation of the obtained film can be reduced. When the film thickness variation of the retardation film is too large, the retardation becomes uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

  The film thickness variation of the optical film is preferably in the range of ± 3%, and more preferably ± 1%. For the purposes as described above, the method of stretching in the biaxial directions perpendicular to each other is effective, and the stretching ratio in the biaxial directions perpendicular to each other is finally 1.0 to 2.0 times in the casting direction. The width direction is preferably 1.01 to 2.5 times, the casting direction is 1.01 to 1.5 times, and the width direction is 1.05 to 2.0 times. It is more preferred to obtain the required retardation value.

  When the absorption axis of the polarizer exists in the longitudinal direction, the transmission axis of the polarizer coincides with the width direction. In order to obtain a long polarizing plate by roll-to-roll bonding, the retardation film is preferably stretched so as to obtain a slow axis in the width direction.

  For example, when a cellulose ester that obtains positive birefringence with respect to stress is used, the slow axis of the retardation film can be provided in the width direction by stretching in the width direction from the above-described configuration.

In this case, in order to improve the display quality, the slow axis of the retardation film is preferably in the width direction, and in order to obtain the desired retardation value,
Formula (Stretch ratio in the width direction)> (Stretch ratio in the casting direction)
It is necessary to satisfy the following conditions.

  After stretching, after slitting the edge of the film to a product width by the slitter 13, the film is subjected to knurling (embossing) on both ends of the film by a knurling device comprising an embossing ring 14 and a back roll 15. By winding with the winder 16, sticking in the optical film (original winding) F and generation of scratches are prevented. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  Next, in the film winding process, the film is wound on the take-up roll while keeping the shortest distance between the outer peripheral face of the cylindrical roll film and the outer peripheral face of the mobile transport roll immediately before this constant. It is. In front of the take-up roll, a means such as a static elimination blower for removing or reducing the surface potential of the film is provided.

  The winding machine related to the production of the optical film according to the present invention may be a commonly used winding method such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, etc. Can be rolled up. In addition, it is preferable that the initial winding tension at the time of winding of a polarizing plate protective film is 90.2-300.8 N / m.

  In the film winding step in the method according to the present invention, the film is preferably wound under environmental conditions of a temperature of 20 to 30 ° C. and a humidity of 20 to 60% RH. In this way, by defining the temperature and humidity in the film winding process, the resistance to change in humidity of the thickness direction retardation (Rt) is improved.

  If the temperature in the winding process is less than 20 ° C., wrinkles are generated and the film winding quality is deteriorated, which is unpractical. If the temperature in the film winding process exceeds 30 ° C., wrinkles are also generated, and the film winding quality is deteriorated, so that it cannot be put into practical use.

  Moreover, if the humidity in the film winding process is less than 20% RH, it is not preferable because it is easily charged and cannot be put into practical use due to deterioration in film winding quality. If the humidity in the film winding process exceeds 60% RH, the winding quality, sticking failure, and transportability deteriorate, which is not preferable.

  When winding the polarizing plate protective film in a roll shape, the winding core may be any material as long as it is a cylindrical core, but is preferably a hollow plastic core, as a plastic material May be any heat-resistant plastic that can withstand the heat treatment temperature, and examples thereof include phenol resins, xylene resins, melamine resins, polyester resins, and epoxy resins. A thermosetting resin reinforced with a filler such as glass fiber is preferred. For example, a hollow plastic core: a wound core made of FRP and having an outer diameter of 6 inches (hereinafter, inch represents 2.54 cm) and an inner diameter of 5 inches is used.

  The number of windings to these winding cores is preferably 100 windings or more, more preferably 500 windings or more, the winding thickness is preferably 5 cm or more, and the width of the film substrate is 80 cm or more. It is preferably 1 m or more.

  Although the film thickness of the optical film according to the present invention varies depending on the purpose of use, the finished film is preferably 10 to 500 μm. In particular, the lower limit is 20 μm or more, preferably 35 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less. A particularly preferable range is 25 to 90 μm. When the retardation film also serves as a polarizing plate protective film, if the film is thick, the polarizing plate after polarizing plate processing becomes too thick. Not suitable. On the other hand, if the film is thin, it is difficult to develop retardation as a retardation film. In addition, the moisture permeability of the film increases, and the ability to protect the polarizer from humidity decreases, which is not preferable.

  The slow axis or the fast axis of the retardation film exists in the film plane, and θ1 is −1 to + 1 °, preferably −0.5 to + 0.5 °, where θ1 is an angle formed with the film forming direction. To be.

  This θ1 can be defined as an orientation angle, and the measurement of θ1 can be performed using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments).

  When each θ1 satisfies the above relationship, it contributes to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to faithful color reproduction in a color liquid crystal display device.

  When the retardation film is used for the multi-domain VA mode, the retardation film is arranged in the above region with the fast axis of the retardation film being θ1, which contributes to the improvement of display image quality. When the plate and the liquid crystal display device are in the MVA mode, for example, the configuration shown in FIG. 7 can be adopted.

  In FIG. 7, 21a and 21b are protective films, 22a and 22b are retardation films, 25a and 25b are polarizers, 23a and 23b are slow axis directions of the film, 24a and 24b are transmission axis directions of the polarizer, 26a, Reference numeral 26b denotes a polarizing plate, 27 denotes a liquid crystal cell, and 29 denotes a liquid crystal display device.

  The retardation Ro distribution in the in-plane direction of the optical film is preferably adjusted to 5% or less, more preferably 2% or less, and particularly preferably 1.5% or less. Further, the retardation Rt distribution in the thickness direction of the film is preferably adjusted to 10% or less, more preferably 2% or less, and particularly preferably 1.5% or less.

  In the retardation film, the retardation value distribution variation is preferably small. When a polarizing plate including a retardation film is used in a liquid crystal display device, the retardation distribution variation is preferably small from the viewpoint of preventing color unevenness and the like. .

  The retardation film is adjusted to have a retardation value suitable for improving the display quality of the VA mode or TN mode liquid crystal cell, and is preferably used for the MVA mode by dividing the retardation film into the above multi-domain as the VA mode. In order to achieve this, it is required to adjust the in-plane retardation Ro to a value greater than 30 nm and 95 nm or less, and the thickness direction retardation Rt to a value greater than 70 nm and 400 nm or less.

  The in-plane retardation Ro was observed obliquely from the normal line of the display surface when the two polarizing plates were arranged in crossed Nicols and the liquid crystal cell was arranged between the polarizing plates, for example, as shown in FIG. It mainly compensates for light leakage due to the deviation of the polarizing plate from the crossed Nicols state. The retardation Rt in the thickness direction mainly compensates for the birefringence of the liquid crystal cell similarly observed when viewed from an oblique direction when the liquid crystal cell is in the black display state in the TN mode or VA mode, particularly in the MVA mode. To contribute.

  As shown in FIG. 7, in the liquid crystal display device, when two polarizing plates are arranged above and below the liquid crystal cell, 22a and 22b in the figure select the distribution of the thickness direction retardation Rt. It is preferable that the total value of both of the above-mentioned ranges and the thickness direction retardation Rt be larger than 140 nm and 500 nm or less. In this case, in-plane retardation Ro and thickness direction retardation Rt of 22a and 22b are preferably the same for improving productivity of an industrial polarizing plate. Particularly preferably, the in-plane retardation Ro is larger than 35 nm and not larger than 65 nm, and the thickness direction retardation Rt is larger than 90 nm and not larger than 180 nm, and is applied to the MVA mode liquid crystal cell in the configuration of FIG. is there.

  In the liquid crystal display device, for example, a TAC film having an in-plane retardation Ro = 0 to 4 nm and a thickness direction retardation Rt = 20 to 50 nm and a thickness of 35 to 85 μm as one commercially available polarizing plate protective film, for example, When used at the position 22b in FIG. 7, the polarizing film disposed on the other polarizing plate, for example, the retardation film disposed on 22a in FIG. 7, has an in-plane retardation Ro of greater than 30 nm and 95 nm. It is preferable to use a film having a thickness direction retardation Rt of greater than 140 nm and less than or equal to 400 nm. The display quality is improved and the production of the film is preferred.

  The production effect obtained by the present invention becomes more remarkable particularly in a long roll of 100 m or more, and the longer the length is 1500 m, 2500 m, or 5000 m, the more the production effect of polarizing plate production is obtained.

  For example, in the production of a polarizing plate protective film, the roll length is 10 to 5000 m, preferably 50 to 4500 m in consideration of productivity and transportability. At this time, the width of the film is the width of the polarizer or the production line. A suitable width can be selected. A film with a width of 0.5 to 4.0 m, preferably 0.6 to 3.0 m, may be wound into a roll shape and used for polarizing plate processing. After being manufactured and wound on a roll, it may be cut to obtain a roll having a desired width, and such a roll may be used for polarizing plate processing.

  In producing the polarizing plate protective film, functional layers such as an antistatic layer, a hard coat layer, a slippery layer, an adhesive layer, an antiglare layer, and a barrier layer may be coated before and / or after stretching. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

  In the film forming process, the clip holding portions at both ends of the cut film are pulverized as described above, or after granulating as necessary, and then used as film raw materials of the same type or of different types. It can be reused as a raw material for film.

  Moreover, the optical film of a laminated structure can also be produced by coextruding compositions having different additive concentrations such as the above-mentioned plasticizer, ultraviolet absorber and matting agent.

  For example, an optical film having a structure of skin layer / core layer / skin layer can be produced. For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. In addition, the type of plasticizer and UV absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or UV absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption.

  The glass transition temperature of the skin layer and the core layer may be different, and the glass transition temperature of the core layer is preferably lower than the glass transition temperature of the skin layer. At this time, the glass transition temperatures of both the skin and the core can be measured, and an average value calculated from these volume fractions can be defined as the glass transition temperature Tg and similarly handled. Moreover, the viscosity of the melt at the time of melt casting may be different between the skin layer and the core layer, and the viscosity of the skin layer> the viscosity of the core layer or the viscosity of the core layer ≧ the viscosity of the skin layer may be used.

  The optical film according to the present invention has a dimensional stability of ± 2.0 when measured at 80 ° C. and 90% RH, based on the dimensions of the film left at 23 ° C. and 55% RH for 24 hours. %, Preferably less than 1.0%, more preferably less than 0.5%.

  When the optical film according to the present invention is used for a polarizing plate protective film as a retardation film, the retardation film itself has a variation within the above range, and the retardation has an absolute value and an orientation angle as the initial values. This is preferable because it does not deviate from the setting and does not cause deterioration in display quality.

<Polarizing plate>
When using the optical film of this invention as a protective film for polarizing plates, a polarizing plate can be produced by a general method. It is preferable that an adhesive layer is provided on the back side of the optical 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.

  On the other surface, the optical film of the present invention may be used, or another polarizing plate protective film may be used. For example, a commercially available cellulose ester film (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4R-4, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, -1, KC8UY-HA, KC8UX-RHA, manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

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

  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 optical film of the present invention into a liquid crystal display device, it is possible to produce various liquid crystal display devices with excellent visibility, but particularly outdoors such as large liquid crystal display devices and digital signage. It is preferably used for a liquid crystal display device for use. The polarizing plate according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

  The polarizing plate according to the present invention includes a reflective type, a transmissive type, a transflective type LCD or a TN type, an STN type, an OCB type, a HAN type, a VA type (PVA type, MVA type), an IPS type (including an FFS type), and the like. It is preferably used in LCDs of various driving methods. In particular, in a large-screen display device having a screen size of 30 or more, especially 30 to 54, there is no white spot at the periphery of the screen, and the effect is maintained for a long time.

  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
<Production of optical film>
(Preparation of acrylic resin (A))
The following acrylic resins A1 to A5 were prepared by a known method.

A1: Monomer mass ratio (MMA: MA = 97: 3), Mw95000
A2: monomer mass ratio (MMA: MA = 97: 3), Mw110000
A3: monomer mass ratio (MMA: MA = 97: 3), Mw550,000
A4: monomer mass ratio (MMA: MA = 97: 3), Mw 950,000
A5: monomer mass ratio (MMA: MA = 94: 6), Mw1100000
In addition, the following commercially available acrylic resins were used.

Dianar BR85 (manufactured by Mitsubishi Rayon Co., Ltd.), Mw 280000
Dianar BR88 (Mitsubishi Rayon Co., Ltd.), Mw 480000
Acrypet V (Mitsubishi Rayon Co., Ltd.), Mw105000
Acrypet VH4 (Mitsubishi Rayon Co., Ltd.), Mw 140000
The ratio of the MMA unit in the molecule in the commercially available acrylic resin was 90% by mass or more and 99% by mass or less.

(Preparation of cellulose ester resin (B))
The following cellulose ester resins B1-B4 were prepared by known methods.

B1: Cellulose acetate propionate (acyl group total substitution degree 1.9, acetyl group substitution degree 0.2, propionyl group substitution degree 1.7, molecular weight Mw = 200000)
B2: cellulose acetate propionate (acyl group total substitution degree 2.5, acetyl group substitution degree 1.4, propionyl group substitution degree 1.1, molecular weight Mw = 200000)
B3: cellulose acetate propionate (acyl group total substitution degree 2.75, acetyl group substitution degree 0.2, propionyl group substitution degree 2.55, molecular weight Mw = 200000)
B4: cellulose acetate propionate (acyl group total substitution degree 2.0, acetyl group substitution degree 0.2, propionyl group substitution degree 1.8, molecular weight Mw = 200000)
B5: cellulose acetate propionate (acyl group total substitution degree 2.5, acetyl group substitution degree 1.3, propionyl group substitution degree 1.2, molecular weight Mw = 200000)
B6: cellulose acetate propionate (acyl group total substitution degree 3.0, acetyl group substitution degree 0.1, propionyl group substitution degree 2.9, molecular weight Mw = 200000)
(Preparation of optical film 1)
As described below, an optical film 1 was produced by a melt casting method using an acrylic resin (A), a cellulose ester resin (B), and various additives.

Acrylic resin Dianal BR85 (Mitsubishi Rayon Co., Ltd.) 70 parts by weight Cellulose ester resin B3 30 parts by weight As a carbon radical scavenger used in the present invention,
1-A: Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.25 parts by mass As a primary antioxidant used in the present invention,
3-A: IRGANOX 1010 (manufactured by Ciba Japan Co., Ltd.) 0.5 part by mass As a secondary antioxidant used in the present invention,
5-A: GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.) 0.25 parts by mass The acrylic resin and cellulose ester resin were dried at 70 ° C. under reduced pressure for 3 hours and cooled to room temperature, and then the above additives were added. Mixed.

  The above mixture was melt-mixed at 230 ° C. using a twin-screw extruder and pelletized.

  Using this pellet, it was melted at 250 ° C. in a nitrogen atmosphere, extruded from the casting die 4 onto the first cooling roll 5, and formed by pressing the film between the first cooling roll 5 and the touch roll 6. .

  The heat bolt was adjusted so that the gap width of the casting die 4 was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other locations. The touch roll A was used as the touch roll, and 80 ° C. water was poured as cooling water therein.

  From the position P1 at which the resin extruded from the casting die 4 contacts the first cooling roll 5 to the position P2 at the upstream end in the rotation direction of the first cooling roll 5 in the nip between the first cooling roll 5 and the touch roll 6. 1 The length L along the peripheral surface of the cooling roller 5 was set to 20 mm. Thereafter, the touch roll 6 was separated from the first cooling roll 5, and the temperature T of the melted part immediately before being sandwiched between the first cooling roll 5 and the touch roll 6 was measured.

  In the present embodiment, the temperature T of the melted part immediately before being sandwiched between the nips of the first cooling roll 5 and the touch roll 6 is 1 mm upstream from the nip upstream end P2, and a thermometer (an independent meter). It was measured by HA-200E manufactured by Co., Ltd. As a result of the measurement in this example, the temperature T was 141 ° C.

  The linear pressure of the touch roll 6 against the first cooling roll 5 was 14.7 N / cm. Furthermore, after being introduced into a tenter and stretched 1.3 times at 160 ° C in the width direction, it was cooled to 30 ° C while relaxing 3% in the width direction, then released from the clip, the clip gripping part was cut off, and both ends of the film Was subjected to a knurling process with a width of 10 mm and a height of 5 μm, and wound on a winding core with a winding tension of 220 N / m and a taper of 40%.

  The extrusion amount and the take-up speed were adjusted so that the film had a thickness of 80 μm, and the finished film width was slit and wound up so as to have a width of 1430 mm. The winding core had an inner diameter of 152 mm, an outer diameter of 165 to 180 mm, and a length of 1550 mm.

  A prepreg resin obtained by impregnating glass fibers and carbon fibers with an epoxy resin was used as the core material for the core. The surface of the core was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 μm. The winding length was 2500 m. This film original fabric sample of the present invention is designated as an optical film 1.

  There were no breaks or breaks during film formation, transportation, winding, or film handling.

  Moreover, when the glass transition temperature of the produced optical film 1 was measured using a differential scanning calorimeter (DSC-7 type manufactured by Perkin Elmer), a peak was observed only at one location of Tg: 126 ° C., and acrylic It was found that the resin (A) and the cellulose ester resin (B) exist in a compatible state.

(Preparation of optical films 2-31)
Optical films 2 to 31 were prepared in the same manner as in the production of the optical film 1 except that the resin type, composition ratio, additive type, and addition amount were changed as shown in Table 1.

  The following was used as an additive.

1-B: Sumilizer GM (manufactured by Sumitomo Chemical Co., Ltd.)
3-B: IRGANOX1076 (Ciba Japan Co., Ltd.)
3-C: IRGANOX245 (Ciba Japan Co., Ltd.)
4-A: ADK STAB LA-52 (manufactured by ADEKA Corporation)
4-B: TINUVIN 144 (Ciba Japan Co., Ltd.)
5-B: ADK STAB 2112 (manufactured by ADEKA Corporation)
5-C: ADK STAB HP-10 (manufactured by ADEKA Corporation)
6-A: ADK STAB AO-412S (manufactured by ADEKA Corporation)
6-B: Sumilizer TPS (manufactured by Sumitomo Chemical Co., Ltd.)

  In the acyl group of the cellulose ester resin, Ac represents an acetyl group, and Pr represents a propionyl group.

<Evaluation method>
The following evaluation was implemented about the obtained optical films 1-31.

(Haze: Transparency evaluation that greatly affects contrast)
About each produced said film sample, 23 degreeC55% RH atmosphere WHEREIN: One film sample was measured using the haze meter (NDH2000 type | mold, Nippon Denshoku Industries Co., Ltd.) according to JISK-7136. .

(Ductile fracture: brittleness evaluation)
In an atmosphere of 23 ° C. and 55% RH, the optical film was cut out at 100 mm (vertical) × 10 mm (width), folded at the center in the vertical direction once into a mountain fold and a valley fold, and this evaluation was evaluated as 3 The measurement was repeated and evaluated according to the following criteria. In addition, the evaluation break here means that it broke and separated into two or more pieces, and when a break is made, it means that the crack is broken and the two or more pieces are not separated, but a cut is made halfway. Represent.

○: Cannot be broken 3 times △: At least 1 out of 3 breaks ×: At least 1 out of 3 breaks (breaking failure)
Evaluation was made according to the following criteria.

◎: No breakage occurred in 10 film formation tests ○: One break occurred in 10 film formation tests Δ: Break occurred twice in 10 film formation tests ×: In 10 film formation tests Break occurred 3 times or more.

<Characteristic evaluation as a liquid crystal display device>
<Preparation of polarizing plate>
A polarizing plate using each optical 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 in the transport direction 5 times at 50 ° C. to prepare a polarizing film.

  Next, the optical film 1 produced in Example 1 was subjected to corona treatment using an acrylic adhesive on one side of the polarizing film, 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 polarizing film and dried to prepare a polarizing plate P1. Similarly, polarizing plates P2 to P31 were produced using the optical films 2 to 31.

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

<Production of liquid crystal display device>
Each of the produced polarizing plates was used to evaluate the display characteristics of the optical film.

  Remove the polarizing plates on both sides of the 32-inch TV AQ-32AD5 previously manufactured by Sharp Corporation so that the KC8UCR-5 is 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 12 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, a sample obtained by treating the polarizing plate at 60 ° C. and 90% RH for 1000 hours was measured in the same manner, and evaluated 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 51, 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 1000 hours was observed in the same manner, and the color change was evaluated according to the following criteria.

○: No color change Δ: Color change is slightly recognized ×: Color change is large Table 2 shows the results of the above evaluation.

  As shown in Table 2, the optical film of the present invention was transparent and exhibited the characteristics of excellent improvement in brittleness, and could be produced without causing breakage failure. Moreover, the polarizing plate and liquid crystal display device produced using the optical film of the present invention exhibited excellent properties in visibility and color shift.

Example 2
As shown in Table 3 below, resin types, composition ratios, additive types, addition amounts, acrylic particles, and ultraviolet absorbers were added, and optical films 32 to 36 were produced in the same manner as in Example 1. A liquid crystal display device was produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 4.

  The following were used as acrylic particles.

C1: Metabrene W-341 (Mitsubishi Rayon Co., Ltd.)
C2: Chemisnow MR-2G (manufactured by Soken Chemical Co., Ltd.)
The following was used as the ultraviolet absorber.

UV1: TINUVIN928 (Ciba Japan Co., Ltd.)
UV2: ADK STAB LA-31 (manufactured by ADEKA Corporation)

  In the acyl group of the cellulose ester resin, Ac represents an acetyl group, and Pr represents a propionyl group.

  The optical film of the present invention exhibited the characteristics of excellent improvement in brittleness although transparency (haze) slightly decreased, and could be produced without causing breakage failure. Moreover, the polarizing plate and the liquid crystal display device produced using the optical film of the present invention were able to further improve visibility and color shift.

Schematic flow sheet showing one embodiment of an apparatus for carrying out the method for producing an optical film (cellulose ester film) according to the present invention 1 is an enlarged flow sheet of the main part of the manufacturing apparatus of FIG. (A) is the external view of the principal part of a casting die, (b) is sectional drawing of the principal part of a casting die. Sectional drawing of 1st Embodiment of a pinching rotary body Sectional drawing in the plane perpendicular | vertical to the rotating shaft of 2nd Embodiment of a pinching rotary body Sectional drawing in the plane containing the rotating shaft of 2nd Embodiment of a pinching rotary body (cited from patent 319404 specification) Exploded perspective view schematically showing the configuration of a liquid crystal display device The figure which shows the state of storage of an optical film (cellulose ester film) original fabric

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Cellulose acylate film 12 Stretcher 16 Winding device 21a, 21b Protective film 22a, 22b Retardation film 23a, 23b Film slow axis direction 24a, 24b Transmission of polarizer Axial direction 25a, 25b Polarizers 26a, 26b Polarizer 27 Liquid crystal cell 29 Liquid crystal display device 31 Die body 32 Slit 41 Metal sleeve 42 Elastic roller 43 Metal inner cylinder 44 Rubber 45 Cooling water 51 Outer cylinder 52 Inner cylinder 53 Space 54 Coolant 55a, 55b Rotating shaft 56a, 56b Outer cylinder support flange 60 Fluid shaft cylinder 61a, 61b Inner cylinder support flange 62a, 62b Intermediate passage 110 Winding core body 117 Support plate 118 Base 120 Cellulose ester film original fabric

Claims (7)

  The acrylic resin (A) and the cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 50:50, and the weight average molecular weight Mw of the acrylic resin (A) is 110,000 to 1000000, and the cellulose ester The total substitution degree (T) of the acyl group of the resin (B) is 2.0 or more and 3.0 or less, and the substitution degree of the acyl group having 3 or more and 7 or less carbon atoms is 1.2 or more and 3.0 or less. An optical film comprising a resin composition, and (1) a carbon radical scavenger, (2) a primary antioxidant having hydrogen radical donating ability for peroxy radicals, and (3) a reducing action on peroxides An optical film comprising a secondary antioxidant having The optical film according to claim 1, wherein the carbon radical scavenger is a compound represented by the following general formula (1).

(In General Formula (1), R ₁₁ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ₁₂ and R ₁₃ each independently represents an alkyl group having 1 to 8 carbon atoms.)   The optical film according to claim 1 or 2, wherein the primary antioxidant is a phenol compound or a hindered amine compound.   The optical film according to claim 1, wherein the secondary antioxidant is a phosphorus compound.   The said optical film contains an acrylic particle (C), The optical film of any one of Claims 1-4 characterized by the above-mentioned.   A polarizing plate using the optical film according to claim 1.   A liquid crystal display device using the polarizing plate according to claim 6.

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