WO2010035564A1

WO2010035564A1 - Optical film and polarizing plate

Info

Publication number: WO2010035564A1
Application number: PCT/JP2009/062284
Authority: WO
Inventors: 笠原　健三
Original assignee: コニカミノルタオプト株式会社
Priority date: 2008-09-25
Filing date: 2009-07-06
Publication date: 2010-04-01
Also published as: JPWO2010035564A1

Abstract

Disclosed is an optical film having high meltability and excellent strength. Also disclosed is a polarizing plate comprising the optical film. The optical film is produced by melting and casting a resin mixture comprising a cellulose ester resin and an acrylic resin, wherein the acrylic resin is a mixture of at least two acrylic resins having different weight average molecular weights.

Description

Optical film and polarizing plate

The present invention relates to an optical film having high melt suitability and excellent strength, and a polarizing plate using the optical film.

Generally, a liquid crystal display device has a basic configuration including a liquid crystal cell that controls a light transmission path by applying an electric field, and two polarizing plates that sandwich the liquid crystal cell.

This polarizing plate has a structure in which a polarizer is sandwiched between two optical films called a polarizing plate protective film. This optical film is required to have high transparency and low birefringence.

Patent Document 1 discloses a film that is a resin composition and a molded body that can produce an optical film or the like that has advantages such as transparency and heat resistance and that can ensure small birefringence even by an extrusion molding method.

With this disclosed technology, haze and birefringence as an optical film are reduced, but when this optical film is used to produce a polarizing plate and further assembled into a liquid crystal display device, the screen unevenness is always at a sufficient level. I couldn't say that.

This unevenness of screen involves the uniformity of adhesive surface, stress uniformity, elastic modulus uniformity, photoelastic modulus, etc. when making a polarizing plate or affixing to a liquid crystal cell, and can be solved using single physical properties as an index. It was a difficult and complex task.

On the other hand, in general, in order to obtain a uniform optical film by melt casting, it is necessary to design the resin to have a low melt viscosity. Even in Patent Document 1, an acrylic resin having a relatively low molecular weight, that is, a low melt viscosity (polymethyl methacrylate) is required. , Hereinafter abbreviated as PMMA).

The surface of the liquid crystal display device may be physically damaged, and in order to increase the physical strength of the optical film used on the outermost surface, the produced optical film is subjected to a hard coat treatment by coating to the outermost surface. Reinforce the hardness of.

By the way, when applying and drying this hard coat coating solution, if a low molecular weight resin is used as the resin constituting the optical film, a part of the resin is slightly dissolved by the coating solution, and the strength of the outermost surface of the optical film is increased. Reduce.

At the same time, a part of the resin component is eluted in the hard coat coating solution, and the effect of the hard coat treatment is reduced.

As described above, since the strength reinforcing effect by the hard coat treatment is not sufficient, it is desired to satisfy both the melt suitability of the resin for producing the optical film and the outermost surface strength.

JP 2008-88417 A

In the optical film containing cellulose ester resin and acrylic resin, the present invention increases the hardness of a hard coat applied on the obtained film while casting a resin having a relatively low melt viscosity, and the resin. The purpose is to improve deterioration and brittleness.

Also, a second object is to provide a polarizing plate that does not have screen unevenness when a liquid crystal display device is assembled, and thus an optical film for producing the polarizing plate.

1. In an optical film obtained by melt casting a resin mixture containing a cellulose ester resin and an acrylic resin, the acrylic resin is a mixture of two or more acrylic resins having different weight average molecular weights. Optical film.

2. The weight average molecular weight and molecular weight distribution dispersity (weight average molecular weight / number average molecular weight) of the cellulose ester resin are Mwc and Vc, respectively, and the weight average molecular weight and molecular weight distribution dispersity of the acrylic resin are Mwa and Va, respectively. 2. The optical film as described in 1 above, wherein Mwa <Mwc and Va> Vc is satisfied.

3. 3. The optical film as described in any one of 1 to 2 above, which contains elastic resin particles.

4. A polarizing plate comprising the optical film as described in any one of 1 to 3 above.

With the configuration of the present invention, it was possible to obtain an optical film in which the hardness of the applied hard coat was increased while casting a resin having a relatively low melt viscosity, and to improve resin degradation and brittleness.

Further, when a polarizing plate was produced using the optical film of the present invention and a liquid crystal display device was assembled, an image having no screen unevenness could be obtained.

It is a general | schematic flow sheet of the apparatus which enforces the manufacturing method of the cellulose-ester film of this invention.

The optical film of the present invention is an optical film obtained by melt casting a resin mixture containing a cellulose ester resin and an acrylic resin, and the acrylic resin is a mixture of two or more types of acrylic resins having different weight average molecular weights. It is characterized by that.
<Cellulose ester resin>
The cellulose ester resin of the present invention (hereinafter, also simply referred to as cellulose ester) is the above-mentioned single or mixed acid ester of cellulose containing at least one of a fatty acyl group and a substituted or unsubstituted aromatic acyl group. It is.

The cellulose ester is preferably at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate.

Among these, particularly preferable cellulose esters include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

As the substitution degree of the mixed fatty acid ester, more preferable cellulose acetate propionate and lower fatty acid ester of cellulose acetate butyrate have an acyl group having 2 to 4 carbon atoms as a substituent, and the substitution degree of the acetyl group is X. When the substitution degree of propionyl group or butyryl group is Y, it is a cellulose resin containing a cellulose ester which simultaneously satisfies the following formulas (I) and (II).

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Among these, cellulose acetate propionate is particularly preferably used, and among them, 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 are preferable. The portion not substituted with the acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

[Raw material cellulose]
The raw material cellulose of the cellulose ester may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of releasability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.
<Acrylic resin>
The acrylic resin of the present invention includes a methacrylic resin. The resin is preferably composed of 50 to 100% by mass of methyl methacrylate units and 1 to 50% by mass of other monomer units copolymerizable therewith.

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

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

The production method of the acrylic resin is not particularly limited, and any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used.

Here, as the polymerization initiator, a normal peroxide type or azo type can be used, and a redox type can also be used. The polymerization temperature may be 30 to 100 ° C. for suspension or emulsion polymerization, and 80 to 160 ° C. for bulk or solution polymerization.

Furthermore, in order to control the reduced viscosity of the produced copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent. With this molecular weight, both heat resistance and brittleness can be achieved.

Commercially available acrylic resins can also be used. For example, Delpet 60N, 80N (manufactured by Asahi Kasei Chemicals Corporation), Dynal BR52, BR80, BR83, BR85, BR88, Metabrene P series (manufactured by Mitsubishi Rayon Co., Ltd.), KT75 (manufactured by Denki Chemical Co., Ltd.) Etc.

The acrylic resin of the present invention is obtained by mixing two or more types of acrylic resins having different weight average molecular weights. In this case, it is preferable that the compositions of the two types of acrylic resins are the same. If the characteristics are sufficiently approximate, the difference in composition can be ignored.

The number of types to be mixed is not particularly limited in order to achieve the object of the present invention, but is preferably within 10 types as an executable range.

For example, acrylic resins having different monomer compositions within a range of 20% by mass or less can be handled as the same acrylic resin in the present invention.
<Dispersion degree of weight average molecular weight and molecular weight distribution of cellulose ester resin and acrylic resin>
(Weight average molecular weight)
The weight average molecular weight Mwc of the cellulose ester resin of the present invention is preferably 50,000 to 400,000, and more preferably 70000 to 200,000.

Further, those having a weight average molecular weight Mwc / number average molecular weight Mnc ratio of 1.5 to 5.5 are preferably used, particularly preferably 2.0 to 5.0, and further preferably 2.5 to 5.0. More preferably, a cellulose ester of 3.0 to 5.0 is preferably used.

Since the average molecular weight and molecular weight distribution of the cellulose ester resin can be measured using gel permeation chromatography (hereinafter abbreviated as GPC), the number average molecular weight (Mnc) and the weight average molecular weight (Mwc) are calculated using this, The ratio can be calculated.

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 Co., Ltd.) Mw = 1,000,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

On the other hand, the weight average molecular weight Mwa of the acrylic resin of the present invention is preferably 10,000 to 500,000. The weight average molecular weight can be measured by the method described above.

The acrylic resin of the present invention is obtained by mixing two or more kinds of acrylic resins having different weight average molecular weights. For example, any combination such as mixing an acrylic resin having a weight average molecular weight of 10,000 and an acrylic resin having a weight of 5,000,000 may be used. Conceivable. Mwa represents the weight average molecular weight of the acrylic resin after mixing.

The relationship between the weight average molecular weights of the cellulose ester resin and the acrylic resin is preferably Mwc> Mwa.

As the weight average molecular weight of the acrylic resin increases, the melt viscosity increases and the extrusion suitability decreases. If the melting temperature is increased to lower the melt viscosity, the resin degradation of the cellulose ester to be mixed proceeds.

Conversely, when the molecular weight of the cellulose ester resin is lowered, the brittleness specific to the acrylic resin increases, and the film becomes brittle, so that the workability when producing a polarizing plate is lowered.

By making the weight average molecular weight Mwc of the cellulose ester resin larger than the weight average molecular weight Mwa of the acrylic resin, a balanced design can be achieved.
(Dispersion of molecular weight distribution)
The degree of dispersion of the molecular weight distribution is defined by the calculation “weight average molecular weight ÷ number average molecular weight”.

The dispersion degree Vc of the average molecular weight distribution of the cellulose ester resin is controlled today as disclosed in Japanese Patent Application Laid-Open No. 8-337601 as Vc = 1.0 to 1.7 as cellulose acetate having high moldability. It is possible.

The dispersion degree Vc of the molecular weight distribution of the cellulose ester of the present invention is preferably 1.0 to 4.0, more preferably 2.0 to 3.5.

On the other hand, the dispersion degree Va of the molecular weight distribution of the acrylic resin of the present invention is preferably 2.3 to 6.0, and more preferably 2.5 to 4.5.

In general, with an acrylic resin, the degree of dispersion increases as the average molecular weight increases. However, by mixing at least two types of polymers, a resin with a high molecular weight and a resin with a low molecular weight, the degree of dispersion before mixing can be increased. It is possible to obtain a large degree of dispersion.

In addition, according to a known polymer synthesis method, the average molecular weight and the degree of dispersion can be designed independently.

In the acrylic resin of the present invention, two or more types of acrylic resins having different weight average molecular weights are mixed for the purpose of increasing the degree of dispersion.

In the present invention, Va> Vc is preferable as the relationship between the cellulose swell resin and the acrylic resin.

When Va is reduced, the hard coat strength is lowered. Further, when Vc is increased, resin deterioration at the time of melting is promoted. That is, it is preferable that Va> Vc from the balance of both. <Elastic resin particles>
The optical film of the present invention preferably contains, for example, acrylic particles as elastic resin particles. Acrylic particles, for example, a PTFE membrane having a pore diameter less than the average particle diameter of acrylic particles when a predetermined amount of the prepared acrylic resin-containing film is collected, dissolved in a solvent, stirred, and sufficiently dissolved and dispersed. It is preferable that the weight of the insoluble matter filtered and collected using a filter is 90% by mass or more of the acrylic particles added to the acrylic resin-containing film.

The acrylic particles are not particularly limited, but are preferably acrylic particles having a layer structure of two or more layers, and more preferably the following multilayer structure acrylic granular composite.

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

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

The acrylic particles preferably contain 0.5 to 45% by mass of acrylic particles based on the total mass of the cellulose ester resin and the acrylic resin.

Further, a film made of cellulose ester resin and acrylic resin (hereinafter also referred to as cellulose ester resin / acrylic resin film) is preferably a film having a tension softening point of 105 to 145 ° C. and not causing ductile fracture.

Ductile fracture is caused by a stress that is greater than the strength of a certain material, and is defined as a fracture that involves significant elongation or drawing of the material before final fracture.

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

In addition, the film made of cellulose ester resin and acrylic resin preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

The glass transition temperature is determined by using a differential scanning calorimeter (DSC-7, manufactured by Perkin Elmer) at a heating rate of 20 ° C./min, and determined in accordance with JIS K7121 (1987). Tmg).

The film composed of a cellulose ester resin and an acrylic resin preferably has a breaking elongation of at least one direction of 10% or more, more preferably 20% or more, as measured in accordance with JIS-K7127-1999.

The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming. The thickness of the film made of cellulose ester resin and acrylic resin is preferably 20 μm or more.

More preferably, it is 30 μm or more. The upper limit of the thickness is not particularly limited, but is about 250 μm. The thickness of the film can be appropriately selected depending on the application.

The film comprising a cellulose ester resin and an acrylic resin preferably contains the acrylic resin and the cellulose ester resin in a mass ratio of 95: 5 to 30:70 from the viewpoint of both workability and heat resistance. The acyl group has a total substitution degree (T) of 2.00 to 3.00, an acetyl group substitution degree (ac) of 0 to 1.89, and an acyl group other than the acetyl group has 3 to 7 carbon atoms, and the weight The average molecular weight (Mw) is preferably 75,000 to 280000. The total mass of the acrylic resin and the cellulose ester resin is 55 to 100% by mass, preferably 60 to 99% by mass of the acrylic resin-containing film.

The film made of a cellulose ester resin and an acrylic resin may contain other acrylic resins.

The length of the optical film of the present invention is preferably 100 m to 5000 m, and the width is preferably 1.2 m or more, more preferably 1.4 to 4 m. A transparent support having a light transmittance of 90% or more, more preferably 93% or more is preferable.

The optical film of the present invention includes a plasticizer, an antioxidant, an acid scavenger, a light stabilizer, a peroxide decomposer, a radical scavenger, a metal deactivator, an ultraviolet absorber, a matting agent, a dye, and a pigment. These additives may be added.
<Additives>
(Plasticizer)
It is preferable to add a compound known as a plasticizer from the viewpoint of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability.

As the plasticizer, for example, phosphate ester derivatives and carboxylic acid ester derivatives are preferably used.

Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 or more and 10,000 or less described in JP-A-2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or cyclohexyl An acrylic polymer having a group in the side chain is also preferably used.

Specific plasticizers include phosphate ester plasticizers, ethylene glycol ester plasticizers, glycerin ester plasticizers, diglycerin ester plasticizers (fatty acid esters), polyhydric alcohol ester plasticizers, dicarboxylic acid esters. System plasticizers, polycarboxylic acid ester plasticizers, polymer plasticizers, and the like.

Of these, polyhydric alcohol ester plasticizers, dicarboxylic acid ester plasticizers and polycarboxylic acid ester plasticizers are preferred. Further, the plasticizer may be a liquid or a solid, and is preferably colorless due to restrictions on the composition.

Thermally, it is preferably stable at a higher temperature, and the decomposition start temperature is preferably 150 ° C. or higher, more preferably 200 ° C. or higher. The addition amount may be as long as the optical properties and mechanical properties are not adversely affected, and the blending amount is appropriately selected within the range not impairing the object of the present invention, and is preferably set to 0.1 parts by weight with respect to 100 parts by mass of the cellulose ester used in the present invention. The amount is 001 to 50 parts by mass, more preferably 0.01 to 30 parts by mass. In particular, 0.1 to 15% by mass is preferable.

Hereinafter, specific examples of the plasticizer will be given below, but the invention is not limited thereto.

Phosphate ester plasticizers: specifically, 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 And phosphoric acid aryl esters such as cresylphenyl 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 phosphate) ), Arylene bis (dialkyl phosphate) such as biphenylene bis (dioctyl phosphate), phosphate esters such as arylene bis (diaryl phosphate) such as phenylene bis (diphenyl phosphate) and naphthylene bis (ditoluyl phosphate).

Furthermore, the partial structure of phosphate ester may be part of the polymer, or may be regularly pendant, and also introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. 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.

Ethylene glycol ester plasticizer: Specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropyl carboxylate, ethylene glycol dicyclohexyl carboxylate and the like Examples include ethylene glycol cycloalkyl ester plasticizers 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. Moreover, the mix of an alkylate group, a cycloalkylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond.

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.

Glycerin ester plasticizers: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, glycerol cycloalkyl esters such as glycerol tricyclopropyl carboxylate, glycerol tricyclohexyl carboxylate Glycerol aryl esters such as glycerol tribenzoate and glycerol 4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol alkyl ester such as diglycerol tetralaurate, di Diglycerides such as glycerin tetracyclobutylcarboxylate and diglycerin tetracyclopentylcarboxylate Phosphorus cycloalkyl esters, 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 mix 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, and the partial structure of the glycerin ester and diglycerin ester may be part of the polymer or regularly pendant, and may be an antioxidant or an acid scavenger. Or may be introduced into a part of the molecular structure of an additive such as an ultraviolet absorber.

Polyhydric alcohol ester plasticizer: Specific examples 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. Moreover, the mix of alkylate group, a cycloalkyl carboxylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the 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.

Dicarboxylic acid ester plasticizers: Specifically, alkyldocarboxylic acid alkyl ester plasticizers such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), dicyclopentyl succinate, Alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, dihexyl-1,4-cyclohexanedicarboxylate, Cycloalkyldicarboxylic acid alkyl ester plasticizers such as didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicyclopropyl-1, Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as cyclohexyl dicarboxylate, cycloalkyldicarboxylic acids such as diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate Aryl ester plasticizers, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate, and aryl dicarboxylic acid cyclohexanes such as dicyclopropyl phthalate and dicyclohexyl phthalate Examples include alkyl ester plasticizers and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di4-methylphenyl phthalate.

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, or 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.

Polycarboxylic acid ester plasticizers: Specifically, alkyl polycarboxylic acid alkyl ester plastics such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate Agents, alkyl polyvalent carboxylic acid cycloalkyl ester plasticizers such as tricyclohexyl tricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy-1,2 Alkyl polyvalent carboxylic acid aryl ester plasticizers such as 1,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2,3,4 -Cyclobutane tetracarboxylate, tetrabutyl-1,2 Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as 3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl-1,3,5- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2,3,4,5, Cycloalkyl polycarboxylic acid aryl ester plasticizers such as 6-cyclohexylhexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4,5-tetracarboxylate Aryl polycarboxylic acids such as Kill ester plasticizers, aryl polycarboxylic acid cycloalkyl ester plasticizers such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polycarboxylic acid aryl ester based plasticizers such as triphenylbenzene-1,3,5-tetracartoxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Is mentioned.

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, or 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.

Polymer plasticizer: Specifically, aliphatic hydrocarbon polymers, alicyclic hydrocarbon polymers, vinyl polymers such as polyvinyl isobutyl ether and poly N-vinyl pyrrolidone, styrene resins such as polystyrene and poly 4-hydroxystyrene Examples thereof include polymers, polybutylene succinates, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes and polyureas.

The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5,000 to 200,000.

If it is 1,000 or less, a problem occurs in volatility, and if it exceeds 500,000, the plasticizing ability is lowered, and the mechanical properties of the cellulose ester derivative composition 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, and other plasticizers, antioxidants, acid scavengers, ultraviolet absorbers, slip agents, matting agents, and the like may be included.

The amount of these compounds added is preferably in the range of 0.5% by weight to less than 50% by weight, more preferably 1% by weight to 30% by weight with respect to the resin constituting the film of the plasticizer. %, More preferably in the range of 1% by weight to less than 15% by weight.

Among the above plasticizers, it is preferable that no volatile components are generated during heat melting.

Specific examples include non-volatile phosphate esters described in JP-A-6-501040. For example, among arylene bis (diaryl phosphate) esters and the above exemplified compounds, trimethylolpropane tribenzoate is preferable. It is not limited to.

(Antioxidant)
Next, the antioxidant will be described.

Antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, heat-resistant processing stabilizers, oxygen scavengers, etc. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic compounds Antioxidants are preferred.

By blending these antioxidants, coloring and strength reduction of the molded product due to heat and oxidative degradation during molding can be prevented without lowering transparency, heat resistance and the like. These antioxidants can be used singly or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the purpose, but is preferably based on 100 parts by mass of the cellulose ester. The amount is 0.001 to 5 parts by mass, more preferably 0.01 to 1 part by mass.

The hindered phenolic antioxidant compound is a known compound, and is described in, for example, columns 12 to 14 of US Pat. No. 4,839,405, and includes a 2,6-dialkylphenol derivative compound. It is.

Specific examples of the hindered 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 = β (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate, ethyl = α- (4-hydroxy-3,5-di-t-butylphenyl) isobut Tyrate, 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-octadecylthio) ethyl = 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl = 3,5-di-t-butyl-4-hydroxy -Benzoate, 2- (2-hydroxyethylthio) ethyl = 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol = Bis- (3,5-di-tert-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl = 3- (3,5-di-tert-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-tert-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl = 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyl) Oxyethylthio) ethyl = 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol = bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], ethylene glycol = bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], neo Pentyl glycol = bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol = bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), Glycerin-ln-octadecanoate-2,3-bis- (3,5-di-t-butyl-4-hydroxyphenylacetate), pentaerythritol-tetrakis- [3- (3 ', 5'- Di-t-butyl-4'-hydroxyphenyl) propionate], 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-t -Butyl-4-hydroxyphenyl) propionate, 2-stearoyloxyethyl = 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ′ , 5'-di-tert-butyl-4-hydroxyphenyl) propionate], pentaerythritol-tetrakis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate).

The above-mentioned type of hindered phenol antioxidant is commercially available from Ciba Japan Co., Ltd. under the trade names “Irganox 1076” and “Irganox 1010”.

Specific examples of the other antioxidants include phosphorus antioxidants such as trisnonylphenyl phosphite, triphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, and dilauryl-3. , 3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythrityl tetrakis (3-laurylthiopropionate), etc. Series antioxidants, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5- Di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate Agent, 3,4-dihydro-2H-1-benzopyran compound, 3,3′-spirodichroman compound, 1,1-spiroindane compound, morpholine, thiomorpholine, thiomorpholine described in JP-B-08-27508 Examples thereof include oxides, thiomorpholine dioxide, compounds having a piperazine skeleton in the partial structure, and oxygen scavengers such as dialkoxybenzene compounds described in JP-A-3-174150.

These partial structures of the antioxidant may be pendant to a part of the polymer or regularly to the polymer.

(Acid scavenger)
Next, the acid scavenger will be described.

Any useful acid scavenger can be used without limitation as long as it is a compound that reacts with an acid to inactivate the acid. Among them, the epoxy group described in US Pat. No. 4,137,201 is particularly useful. A compound having is preferred.

Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of diglycidyl ethers of various polyglycols, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ethers of glycerol, 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 alkyl of about 2 to 2 carbon atoms of fatty acids of 2 to 22 carbon atoms such as butyl Epoxy steer And the like, and epoxidized vegetable oils and other unsaturated natural oils, which are sometimes epoxidized, which may be represented and exemplified by compositions of various epoxidized long chain fatty acid triglycerides such as epoxidized soybean oil These are referred to as natural glycerides or unsaturated fatty acids, which generally contain 12 to 22 carbon atoms). Moreover, EPON 815C can also be preferably used as a commercially available epoxy group-containing epoxide resin compound.

In addition to the above, acid scavengers that can be used include oxetane compounds, oxazoline compounds, alkaline earth metal organic acid salts and acetylacetonate complexes, and paragraphs 68 to 105 of JP-A-5-194788. Is included.

The acid scavenger may be referred to as an acid scavenger, an acid scavenger, an acid catcher or the like, but can be used in the present invention without any difference due to their names.

(Light stabilizer)
The substrate film includes a hindered amine light stabilizer (HALS) compound as a stabilizer against external light and light from the backlight of a liquid crystal display, which is a known compound, for example, US Pat. 2,2,6,6-tetraalkylpiperidine compounds as described in columns 5-11 of US Pat. No. 619,956 and columns 3-5 of US Pat. No. 4,839,405. Or their acid addition salts or complexes of them with metal compounds.

Specific examples of hindered amine light stabilizer compounds include 4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-benzyl -4-hydroxy-2,2,6,6-tetramethylpiperidine, 1- (4-tert-butyl-2-butenyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-stearoyl Oxy-2,2,6,6-tetramethylpiperidine, 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6 6-pentamethylpiperidine, 1,2,2,6,6-pentamethylpiperidin-4-yl-β (3,5-di-t-butyl-4-hydroxyphenyl) -propionate 1-benzyl-2,2,6,6-tetramethyl-4-piperidinyl maleate, (di-2,2,6,6-tetramethylpiperidin-4-yl) -adipate, -2,2,6,6-tetramethylpiperidin-4-yl) -sebacate, (di-1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl) -sebacate, Di-1-allyl-2,2,6,6-tetramethyl-piperidin-4-yl) -phthalate, 1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl-acetate, trimellitic acid -Tri- (2,2,6,6-tetramethylpiperidin-4-yl) ester, 1-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperidine, dibutyl-malonic acid- Di- (1,2,2,6,6-pentamethyl-piperidin-4-yl) -ester, dibenzyl-malonic acid-di- (1,2,3,6-tetramethyl-2,6-diethyl-piperidine -4-yl) -ester, dimethyl-bis- (2,2,6,6-tetramethylpiperidine-4-oxy) -silane, tris- (1-propyl-2,2,6,6-tetramethylpiperidine -4-yl) -phosphite, tris- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -phosphate, N, N'-bis- (2,2,6,6 -Tetramethylpiperidin-4-yl) -hexamethylene-1,6-diamine, N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -hexamethylene-1,6 -Diacetamide, 1-acetate 4- (N-cyclohexylacetamide) -2,2,6,6-tetramethyl-piperidine, 4-benzylamino-2,2,6,6-tetramethylpiperidine, N, N'-bis- (2 , 2,6,6-tetramethylpiperidin-4-yl) -N, N'-dibutyl-adipamide, N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl)- N, N'-dicyclohexyl- (2-hydroxypropylene), N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -p-xylylene-diamine, 4- (bis- 2-hydroxyethyl) -amino-1,2,2,6,6-pentamethylpiperidine, 4-methacrylamide-1,2,2,6,6-pentamethylpiperidine, α-cyano-β-methyl-β -[N- (2, , 6,6-tetramethyl-piperidin-4-yl)] - amino - and methyl acrylate and the like.

At least one or more stabilizers in the film-forming material can be selected, and the amount added is preferably 0.001% by mass to 5% by mass with respect to the mass of the cellulose ester. More preferably, it is 0.005 mass% or more and 3 mass% or less, More preferably, it is 0.01 mass% or more and 0.8 mass% or less.

(UV absorber)
When the optical film is used as a polarizer protective film used on the viewing side with respect to the liquid crystal cell, it is preferable to further contain an ultraviolet absorber. The ultraviolet absorber is a material having an effect of preventing the material constituting the film from being decomposed by ultraviolet rays in an environment used after production.

Cellulose ester itself is a material that is relatively resistant to ultraviolet rays, but other additives may be compounds that are weak against ultraviolet rays, and polarizers and liquid crystal cells are also vulnerable to ultraviolet rays. In addition, it is preferable that at least the polarizer protective film on the side exposed to external light and the polarizer protective film on the side on which the backlight of the liquid crystal display is incident contain an ultraviolet absorber.

As such an ultraviolet absorber, from the viewpoint of preventing deterioration of a polarizer and a display device with respect to ultraviolet rays, the ultraviolet absorber has an excellent 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. Those that absorb less are preferred.

Examples include oxybenzophenone compounds, benzotriazole compounds, triazine compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Triazole compounds are preferable, and benzotriazole compounds are particularly preferable.

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

Specific examples of useful benzotriazole ultraviolet absorbers include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) Benzotriazole, 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′-hydride) Xy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 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 Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate.

As commercially available products, TINUVIN 109, TINUVIN 171, TINUVIN 234, TINUVIN 360, TINUVIN 928 (all manufactured by Ciba Japan Co., Ltd.) may be used. it can.

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-benzoylphenyl) methane and the like can be mentioned, but not limited thereto.

The ultraviolet absorber is preferably added in an amount of 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and further preferably 1 to 5% by mass. Two or more of these may be used in combination.

(Matting agent)
In order to impart slipperiness, fine particles such as a matting agent may be added. Examples of the fine particles include inorganic compound fine particles and organic compound fine particles. The matting agent is preferably as fine as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include inorganic fine particles such as magnesium silicate and calcium phosphate, and crosslinked polymer fine particles.

Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because it can reduce the haze of the film.

Preferred organic materials for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and 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 particle size of the secondary particles of the fine particles is in the range of 0.05 to 1.0 μm. The average particle size of secondary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used in the cellulose ester film in order to produce irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film.

The content of fine particles in the cellulose ester is preferably 0.005 to 0.3% by mass with respect to the cellulose ester.

Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972. , R972V, R974, R202, R812.

These fine particles may be used in combination of two or more. When using 2 or more types together, it can mix and use in arbitrary ratios.

In this case, 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.

The presence of fine particles in the film used as the matting agent can be used for another purpose to improve the strength of the film.
<Method for producing optical film>
(Film formation)
The optical film of the present invention is preferably produced by a melt casting method.

<Melt casting method>
The cellulose ester film and the cellulose ester resin / acrylic resin film are preferably formed by a melt casting film forming method. In the melt casting film forming method, a composition containing cellulose ester, cellulose ester resin / acrylic resin, and an additive such as a plasticizer is heated and melted to a temperature showing fluidity, and then contains fluid cellulose ester. It refers to casting a melt.

The molding method for heating and melting can be further 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 cellulose ester film excellent in mechanical strength and surface accuracy, and a cellulose ester resin / acrylic resin film, the melt extrusion method is excellent.

It is preferable that a plurality of raw materials used for melt extrusion are usually kneaded and pelletized in advance.

Pelletization may be performed by a known method. For example, dry cellulose ester, plasticizer, and other additives are fed to an extruder with a feeder and kneaded using a single-screw or twin-screw extruder, and formed into a strand from a die. It can be done by extrusion, water cooling or air cooling and cutting.

Additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of additives such as particles and antioxidants are preferably mixed in advance in order to mix uniformly.

The extruder is preferably processed at as low a temperature as possible so that it can be pelletized so as to suppress the shearing force and prevent the resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

Film formation is performed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.

Using a single-screw or twin-screw type extruder, the melting temperature at the time of extrusion is about 200 to 300 ° C, filtered through a leaf disk type filter, etc. to remove foreign matter, and then formed into a film from the T die. And solidified on a cooling roll.

When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum or reduced pressure or in an inert gas atmosphere.

The extrusion flow rate is preferably carried out stably by introducing a gear pump. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances.

The stainless steel fiber sintered filter is a united stainless steel fiber body that is intricately intertwined and compressed, and the contact points are sintered and integrated. The density of the fiber is changed depending on the thickness of the fiber and the amount of compression, and the filtration accuracy is improved. Can be adjusted.

Additives such as plasticizers and particles may be mixed with the resin in advance, or 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.

The film temperature on the touch roll side when the film is nipped by the cooling roll and the elastic touch roll is preferably Tg or more and Tg + 110 ° C. or less of the film. A well-known roll can be used for the roll which has the elastic body surface used for such a purpose. The elastic touch roll is also called a pinching rotator.

As the elastic touch roll, a touch roll disclosed in Japanese Patent No. 3194904, Japanese Patent No. 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.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

Moreover, it is preferable that the film obtained as described above is stretched by the stretching operation after passing through the step of contacting the cooling roll.

As the stretching method, a known roll stretching machine or tenter can be preferably used. The stretching temperature is usually preferably in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

Before winding, the end may be slit and cut to the product width, and knurled (embossed) may be applied to both ends to prevent sticking or scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing.

In addition, since the film is deformed and cannot be used as a product, the clip holding portions at both ends of the film are usually cut out and reused.

The film thickness of the cellulose ester film is not particularly limited, but a film in the range of 10 to 200 μm is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20 to 80 μm.

Since the optical film of the present invention is melt cast, it does not contain a solvent after production, and the amount of residual solvent is 0.1% by mass or less of the entire optical film mass.
<Hard coat>
The optical film of the present invention is preferably provided with a hard coat layer by a hard coat treatment. It is preferable to use the following materials together with the solvent for the hard coat layer.

(Polyfunctional acrylate)
The hard coat layer is generally composed of an active energy ray curable resin such as ultraviolet rays. As such an active energy ray curable resin, a polyfunctional acrylate is preferable.

The polyfunctional acrylate is preferably selected from the group consisting of pentaerythritol polyfunctional acrylate, dipentaerythritol polyfunctional acrylate, pentaerythritol polyfunctional methacrylate, and dipentaerythritol polyfunctional methacrylate. Here, the polyfunctional acrylate is a compound having two or more acryloyloxy groups and / or methacryloyloxy groups in the molecule.

Examples of the polyfunctional acrylate monomer include ethylene glycol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, and tetramethylolmethane triacrylate. , Tetramethylolmethane tetraacrylate, pentaglycerol triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, glycerin triacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaeth Thritol hexaacrylate, tris (acryloyloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, Tetramethylol methane trimethacrylate, tetramethylol methane tetramethacrylate, pentaglycerol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerin trimethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol tetra Methacrylate, dipentaerythritol penta methacrylate, dipentaerythritol hexa methacrylate, isobornyl acrylate and the like preferably.

These compounds can be used alone or in admixture of two or more. Moreover, oligomers, such as a dimer and a trimer of the said monomer, may be sufficient.

Commercially available polyfunctional acrylates include Adekaoptomer KR / BY series: KR-400, KR-410, KR-550, KR-566, KR-567, BY-320B (Asahi Denka Co., Ltd.); Hard A-101-KK, A-101-WS, C-302, C-401-N, C-501, M-101, M-102, T-102, D-102, NS-101, FT-102Q8 MAG-1-P20, AG-106, M-101-C (manufactured by Guangei Chemical Co., Ltd.); Seika Beam PHC2210 (S), PHC X-9 (K-3), PHC2213, DP-10, DP-20 DP-30, P1000, P1100, P1200, P1300, P1400, P1500, P1600, SCR900 (manufactured by Dainichi Seika Kogyo Co., Ltd.); KRM7033 KRM 7039, KRM 7130, KRM 7131, UVECRYL 29201, UVECRYL 29202 (manufactured by Daicel UCB); RC-5015, RC-5016, RC-5020, RC-5031, RC-5100, RC-5102, RC-5120, RC- 5122, RC-5152, RC-5171, RC-5180, RC-5181 (Dainippon Ink Chemical Co., Ltd.); 340 clear (manufactured by China Paint Co., Ltd.); Sunrad H-601, RC-750, RC-700, RC-600, RC-500, RC-611, RC-612 (manufactured by Sanyo Chemical Industries); SP -1509, SP-1507 (manufactured by Showa High Polymer Co., Ltd.); RCC-15C (manufactured by Grace Japan Co., Ltd.), Aronix M-6100, M-8030, M-8060 (manufactured by Toagosei Co., Ltd.); B420 (manufactured by Shin-Nakamura Chemical Co., Ltd.) or the like can be appropriately selected and used.

The addition amount of the active energy ray-curable resin is preferably 15% by mass or more and less than 70% by mass in the solid content in the hard coat layer forming composition.

In addition, the hard coat layer preferably contains a photopolymerization initiator in order to accelerate the curing of the active energy ray-curable resin.

The amount of the photopolymerization initiator is preferably contained in a mass ratio of photopolymerization initiator; active energy ray-curable resin = 20: 100 to 0.01: 100.

Specific examples of the photopolymerization initiator include acetophenone, benzophenone, hydroxybenzophenone, Michler ketone, α-amyloxime ester, thioxanthone, and derivatives thereof, but are not particularly limited thereto.

In the hard coat layer, a binder such as a thermoplastic resin, a thermosetting resin, or a hydrophilic resin such as gelatin can be mixed with the active energy ray-curable resin and used. Further, the hard coat layer may contain fine particles of an inorganic compound or an organic compound in order to adjust the scratch resistance, slipperiness and refractive index.

Inorganic fine particles include silicon oxide, titanium oxide, aluminum oxide, tin oxide, indium oxide, ITO, zinc oxide, zirconium oxide, magnesium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, water Mention may be made of Japanese calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. In particular, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide and the like are preferably used.

Organic particles include polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, and melamine resin. An ultraviolet curable resin composition such as powder, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, or polyfluoroethylene resin powder can be added. Particularly preferred are cross-linked polystyrene particles (for example, SX-130H, SX-200H, SX-350H manufactured by Soken Chemical), polymethyl methacrylate particles (for example, MX150, MX300 manufactured by Soken Chemical), and fluorine-containing acrylic resin fine particles. .

Examples of the fluorine-containing acrylic resin fine particles include commercially available products such as FS-701 manufactured by Nippon Paint. Examples of the acrylic particles include Nippon Paint: S-4000, and examples of the acrylic-styrene particles include Nippon Paint: S-1200, MG-251.

The average particle size of these fine particle powders is preferably 0.01 to 5 μm, more preferably 0.1 to 5.0 μm, and particularly preferably 0.1 to 4.0 μm.

Moreover, it is preferable to contain two or more kinds of fine particles having different particle diameters. It is desirable that the ratio of the curable resin composition to the fine particles is 0.1 to 30 parts by mass with respect to 100 parts by mass of the curable resin composition.

The hard coat layer has a center line average roughness (Ra) defined by JIS B 0601 of 0.001 to 0.1 μm, or a fine layer or the like is added to adjust Ra to 0.1 to 1 μm. An antiglare hard coat layer may also be used.

The center line average roughness (Ra) is preferably measured with an optical interference type surface roughness measuring instrument, and can be measured using, for example, a non-contact surface fine shape measuring device WYKO NT-2000 manufactured by WYKO.

In order to increase the heat resistance of the hard coat layer, an antioxidant that does not inhibit the photocuring reaction can be selected and used.

Examples include hindered phenol derivatives, thiopropionic acid derivatives, phosphite derivatives, and the like. Specifically, for example, 4,4′-thiobis (6-tert-3-methylphenol), 4,4′-butylidenebis (6-tert-butyl-3-methylphenol), 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) mesitylene, di-octadecyl-4- Examples include hydroxy-3,5-di-tert-butylbenzyl phosphate.

Furthermore, the hard coat layer preferably contains a silicone surfactant or a polyoxyether compound.

The silicone-based surfactant is preferably a polyether-modified silicone. Specifically, BYK-UV3500, BYK-UV3510, BYK-333, BYK-331, BYK-337 (manufactured by BYK-Chemical Japan), TSF4440, TSF4445 , TSF4446, TSF4452, TSF4460 (manufactured by GE Toshiba Silicone), KF-351, KF-351A, KF-352, KF-353, KF-354, KF-355, KF-615, KF-618, KF-945, KF -6004 (polyether-modified silicone oil; manufactured by Shin-Etsu Chemical Co., Ltd.) and the like, but are not limited thereto.

Of the polyoxyether compounds, polyoxyethylene oleyl ether compounds are preferred, and are generally compounds represented by general formula (α).

Formula (α) C ₁₈ H ₃₅ —O (C ₂ H ₄ O) nH
In the formula, n represents 2 to 40.

The average number (n) of ethylene oxide added to the oleyl moiety is 2 to 40, preferably 2 to 10, more preferably 2 to 9, and further preferably 2 to 8. The compound of the general formula (α) can be obtained by reacting ethylene oxide with oleyl alcohol.

Specific products include Emulgen 404 (polyoxyethylene (4) oleyl ether), Emulgen 408 (polyoxyethylene (8) oleyl ether), Emulgen 409P (polyoxyethylene (9) oleyl ether), Emulgen 420 (polyoxy) Ethylene (13) oleyl ether), Emulgen 430 (polyoxyethylene (30) oleyl ether) or more, Kao Corporation, NOFLEEAO-9905 (polyoxyethylene (5) oleyl ether) manufactured by NOF Corporation.

In addition, () represents the number n. Nonionic polyoxyether compounds may be used alone or in combination of two or more.

These enhance the coatability, and these components are preferably added in the range of 0.01 to 3% by mass with respect to the solid component in the coating solution.

Further, the hard coat layer may contain a fluorine-siloxane graft polymer.

The fluorine-siloxane graft polymer is a copolymer polymer obtained by combining at least a fluorine resin with a polysiloxane containing siloxane and / or organosiloxane alone and / or an organopolysiloxane by grafting.

Examples of commercially available products include ZX-022H, ZX-007C, ZX-049, and ZX-047-D manufactured by Fuji Chemical Industry Co., Ltd.

These compounds may be used in combination. The composition for forming a hard coat layer is such that the content ratio of the fluorine-siloxane graft polymer to the active energy ray-curable resin is fluorine-siloxane graft polymer: active energy ray-curable resin = 0.05: 100 to 5.00: 100 It is preferable from the viewpoint of stability in the product.

Further, the hard coat layer may have a multilayer structure of two or more layers. One of the layers may be a so-called conductive layer containing, for example, conductive fine particles, a π-conjugated conductive polymer, or an ionic polymer.

Examples of π-conjugated conductive polymers include polythiophene, poly (3-methylthiophene), poly (3-ethylthiophene), poly (3-propylthiophene), poly (3-butylthiophene), and poly (3-hexylthiophene). , Poly (3-octylthiophene), poly (3-decylthiophene), poly (3-dodecylthiophene), poly (3-bromothiophene), poly (3-chlorothiophene), poly (3-cyanothiophene), poly (3-phenylthiophene), poly (3,4-dimethylthiophene), poly (3,4-dibutylthiophene), poly (3-hydroxythiophene), poly (3-methoxythiophene), poly (3-ethoxythiophene) , Poly (3-butoxythiophene), poly (3-hexyloxythiophene), poly ( -Octyloxythiophene), poly (3-decyloxythiophene), poly (3-dodecyloxythiophene), poly (3,4-dihydroxythiophene), poly (3,4-dimethoxythiophene), poly (3,4 Diethoxythiophene), poly (3,4-dipropoxythiophene), poly (3,4-dibutoxythiophene), poly (3,4-dihexyloxythiophene), poly (3,4-dioctyloxythiophene), poly (3,4-didecyloxythiophene), poly (3,4-didodecyloxythiophene), poly (3,4-ethylenedioxythiophene), poly (3,4-propylenedioxythiophene), poly (3 , 4-butenedioxythiophene), poly (3-methyl-4-methoxythiophene), poly (3-methyl- 4-ethoxythiophene), poly (3-carboxythiophene), poly (3-methyl-4-carboxythiophene), poly (3-methyl-4-carboxyethylthiophene), poly (3-methyl-4-carboxybutylthiophene) ), Polypyrrole, poly (N-methylpyrrole), poly (3-methylpyrrole), poly (3-ethylpyrrole), poly (3-N-propylpyrrole), poly (3-butylpyrrole), poly (3- Octylpyrrole), poly (3-decylpyrrole), poly (3-dodecylpyrrole), poly (3,4-dimethylpyrrole), poly (3,4-dibutylpyrrole), poly (3-carboxypyrrole), poly ( 3-methyl-4-carboxypyrrole), poly (3-methyl-4-carboxyethylpyrrole), poly (3-methyl) -4-carboxybutylpyrrole), poly (3-hydroxypyrrole), poly (3-methoxypyrrole), poly (3-ethoxypyrrole), poly (3-butoxypyrrole), poly (3-hexyloxypyrrole), poly (3-methyl-4-hexyloxypyrrole), polyaniline, poly (2-methylaniline), poly (3-isobutylaniline), poly (2-anilinesulfonic acid), poly (3-anilinesulfonic acid), etc. It is done. Each of these may be used alone or two types of copolymers can be suitably used.

Further, the ionic polymer may contain a color tone adjusting agent (dye or pigment) having a color tone adjusting function as a color correction filter for various display elements, or may contain an electromagnetic wave blocking agent or an infrared absorber. It is preferable to have each function.

As a coating method of the hard coat layer coating solution, it can be applied by a known method such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, and an ink jet method. After application, it is heat-dried and UV-cured.

The coating amount is suitably 0.1 to 40 μm, preferably 0.5 to 30 μm, as the wet film thickness. The dry film thickness is an average film thickness of 0.1 to 30 μm, preferably 1 to 20 μm.

The hard coat layer should be irradiated with ultraviolet rays after coating and drying, and the irradiation time for obtaining the necessary irradiation amount of active energy rays is preferably about 0.1 second to 1 minute, and the curing efficiency of the ultraviolet curable resin Or, from the viewpoint of work efficiency, 0.1 to 10 seconds is more preferable.

Further, the illuminance of these active energy ray irradiated portions is preferably 0.05 to 0.2 W / m ² .

The refractive index of the hard coat layer is preferably 1.5 to 2.0, more preferably 1.5 to 1.6 as measured at 23 ° C. and a wavelength of 550 nm.

If the refractive index of the hard coat layer is too large, the color of the reflected light of the optical film becomes strong, which is not preferable. The refractive index of the hard coat layer used in the present invention is particularly preferably in the range of 1.5 to 1.6 from the viewpoint of optical design for obtaining a low reflective film. The refractive index of the hard coat layer can be adjusted by the refractive index and content of the fine particles to be added.

(Coating process)
The hard coat layer preferably has a step of heat-treating after light irradiation after coating and drying since the objective effect of the present invention is more easily exhibited. The heat treatment step needs to be performed in a place where the temperature and humidity can be adjusted, and is preferably performed in a clean room without dust.

The preferable temperature of the heat treatment is 80 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint that the target effect is better exhibited. Further, the heat treatment time is preferably 20 minutes or less. Even if the heat treatment is carried out for a time longer than 20 minutes, the objective effect obtained better is not changed, and the film tends to be deteriorated in appearance such as discoloration or deformation due to heat.

Here, the heat treatment time means a time during which the temperature is kept constant at a desired temperature, and does not include the time when the temperature is raised and the time when the temperature is lowered.

The temperature to be maintained is preferably in the range of ± 5 ° C of the set temperature. There may be a plurality of heat treatment steps. In that case, it may be designed so that each temperature can be changed.

As examples of the light irradiation lamp, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used.

These light sources are preferably air-cooled or water-cooled. Irradiation conditions vary depending on each lamp, but the irradiation amount of actinic rays is preferably 50 mJ / cm ² to 1 J / cm ² , particularly preferably 50 to 500 mJ / cm ² .

Also, it is preferable to reduce the oxygen concentration to 0.01% to 5% by nitrogen purge in the irradiated part.

Next, after light irradiation, heat treatment is performed in a heating zone. In the heating zone, the long film is subjected to heat treatment at a predetermined temperature for a predetermined time by transport rollers arranged above and below.

In the heat treatment step, it is preferably performed while applying a tension in the film conveying direction or the width direction, and the applied tension is preferably 50 to 500 N / m, and more preferably 250 to 500 N / m. At 250 to 500 N / m, after the more severe durability test, the object effect of the present invention is better exhibited.

If it exceeds 500 N / m, it becomes difficult to maintain the flatness of the film. The width tension applying method is not particularly limited, and may be a free span, a back roll or the like. In addition, a method of applying tension using a width regulating device in the width direction is also effective, and is preferably achieved by stretching at 3.0% or less, more preferably 0.05% to 1.0%. Is more effective. Thereby, a film excellent in blocking resistance can be obtained.

The long film subjected to the heat treatment is taken up as a take-up roll in the take-up chamber. In that case, it is also preferable to carry out while blowing hot air of a predetermined temperature from the hot air outlet.

As a measure against antistatic and dust adhesion, the hot air is preferably adjusted to a relative humidity in the range of 10 to 70% RH, preferably 20 to 70% RH, particularly 40 to 60% RH. Moreover, it is preferable that warm air is an ion wind, and it is preferable to install a static elimination apparatus and an air cleaner in the vicinity of the winding part.

The heat treatment may be a method in which, after coating, drying, and light irradiation, the wound hard coat film roll is placed on a movable carriage and heat-treated in a heat treatment chamber.

In the heat treatment, it is preferable to gradually increase or decrease the temperature in order to prevent the temperature difference between the inside and outside of the roll of the roll due to a rapid temperature increase and avoid wrinkles entering near the core. Specifically, the rate of temperature increase and the rate of temperature decrease are preferably 0.3 to 5 ° C./hour.

Also, it is preferable to apply a knurling process in order to prevent blocking and to maintain a good winding shape. The knurling process should just be formed in the at least one surface of the film, and may be formed in both surfaces.

The thickness of the knurling portion is preferably larger than the thickness of the hard coat layer, and the thickness of the knurling portion is preferably in the range of 5 to 30 μm. The range is preferably 10 to 25 μm.

In addition, as the winding core when the optical film provided with the hard coat layer is wound into a roll shape, any material may be used as long as it is a cylindrical core, but a hollow plastic core is preferable. The plastic material may be any heat-resistant plastic that can withstand the heat treatment temperature, and examples thereof include resins such as phenol resin, xylene resin, melamine resin, polyester resin, and epoxy resin.

Further, a thermosetting resin reinforced with a filler such as glass fiber is preferable. The number of windings on these winding cores is preferably 100 windings or more, more preferably 500 windings or more, and the winding thickness is preferably 5 cm or more.

Further, when the heat treatment is performed in a state where the hard coat film wound in a roll shape is wound, the roll may be rotated.

Rotation is preferably performed at a speed of 1 rotation or less per minute, and may be continuous or intermittent. Moreover, it is also preferable to perform the roll rewinding once or more during the heating period.

In order to rotate the long hard coat film wound around the core during the heat treatment, it is preferable to provide a dedicated turntable in the heat treatment chamber. More preferably, the hard coat film is set on a dedicated carriage having a heat-resistant rotation function and rotated during the heat treatment in the heating chamber.

It is also preferable that the optical film roll after the heat treatment is carried, for example, to a rewinding step (not shown) and cooled to room temperature while rewinding the hard coat film to obtain a rewinding roll.

Furthermore, in the rewinding step, it is preferable to pass through an atmosphere having a relative humidity of 10 to 70% RH or to wind in the atmosphere. When the relative humidity is preferably 20 to 70% RH, particularly 40 to 60% RH, a good hard coat film roll can be obtained without static electricity failure or collapse of the winding shape.

The film rewinding speed is 1 to 200 m / min, preferably 10 to 100 m / min. At the time of rewinding, it is preferable that the film is drawn out and brought into contact with at least one roller in order to lower the film temperature.

When rotating or rewinding these rolls, there is a possibility that static electricity failure or scratches may occur on the film. It is preferable to install a static eliminator or in a clean room. The surface of the contact roller during rewinding is smooth. It is preferable to use one having a high value.

As the heating means in the heat treatment step, hot air blowing, contact heat transfer using a heating roll, induction heating using a microwave, radiant heat heating using an infrared heater, or the like can be used. As the infrared heater, an electric, gas, oil or steam far infrared ceramic heater can be used.

Commercially available infrared heaters (for example, manufactured by Noritake Company Limited) may be used. An oil-type or steam-type infrared heater using oil or steam as the heat medium is preferable from the viewpoint of explosion prevention in an atmosphere in which an organic solvent coexists.

Also, the film temperature and heating temperature during heating can be measured with a commercially available non-contact infrared thermometer. Further, feedback control may be performed on the heating means in order to control the temperature range.

The optical film with a hard coat layer in the present invention is a film having a pencil hardness of H to 9H. Particularly preferred is 2H to 6H.

The pencil hardness is evaluated by pencil hardness evaluation specified by JIS K 5400 using a test pencil specified by JIS S 6006 after the prepared hard coat film is conditioned for 2 hours at a temperature of 25 ° C. and a relative humidity of 55%. It is the value measured according to the method.
<Polarizing plate>
<Polarizing plate protective film>
The optical film of the present invention is preferably used for a polarizing plate protective film. When using as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method.

The obtained optical film is alkali-treated, and a polarizer protective film is bonded to both sides of the polarizer using a completely saponified polyvinyl alcohol aqueous solution on both sides of the polarizer prepared by immersing and stretching the polyvinyl alcohol film in an iodine solution. There is a method, and it is preferable that the optical film of the present invention is directly bonded to a polarizer on at least one side.

The optical film of the present invention preferably has a surface roughness Ra of 1 μm or less. When Ra is larger than 1 μm, when the above-described various functional layers are provided, the surface may become uneven or remain as convex defects, and smoothness and gloss may be impaired.

In order to reduce Ra to 1 μm or less, the surface of the take-up roll and the drawing roll immediately after melt extrusion is made into a mirror surface, immediately after being taken up by the roll, nipped between the mirror-like rolls, the temperature of the vertical and / or horizontal drawing, This is achieved by appropriately selecting the magnification and the stretching speed.

It is also effective to reduce Ra by sharpening the lip edge of the melt-extrusion die or mirroring the surface in contact with the molten resin inside the die.

The thickness of the optical film of the present invention is preferably 10 to 350 μm. In particular, it is preferably 20 μm or more, and more preferably 35 μm or more. Moreover, 150 micrometers or less, Furthermore 120 micrometers or less are preferable. Particularly preferred is 25 to 90 μm.

"Polarizer"
A polarizing plate using the optical film of the present invention will be described.

The polarizing plate can be produced by a general method. The back side of the optical film of the present invention is subjected to alkali saponification treatment, and the treated optical film is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. It is preferable.

If it has a hard coat layer, the surface without the hard coat layer is alkali saponified.

Another polarizing plate protective film may be used on the other side. The polarizing plate protective film used for the other surface is an optical compensation film (retardation film) having an in-plane retardation Ro of 590 nm, a retardation of 20 to 70 nm, and a thickness direction retardation Rt of 100 to 400 nm. Is preferred.

These can be produced, for example, by the methods described in JP-A-2002-71957 and Japanese Patent Application No. 2002-155395. Alternatively, it is preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optically anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal.

For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348. Alternatively, a non-oriented film having a retardation Ro of 590 nm at 0 to 5 nm and an Rt of −20 to +20 nm described in JP-A No. 2003-12859 is also preferably used.

When used in combination with the optical film of the present invention, a polarizing plate having excellent flatness and a stable viewing angle expansion effect can be obtained.

In addition, as the polarizing plate protective film used for the other side, as commercially available cellulose ester films, KC8UX2MW, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC4UEW, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR -1, KC4FR-2, KC8UE, KC4UE (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

Furthermore, it is also preferable to use the optical film of the present invention on both sides.

A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are ones in which iodine is dyed on a system film and ones in which a dichroic dye is dyed, but it is not limited to this.

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

A polarizer having a thickness of 5 to 30 μm, preferably 8 to 15 μm is preferably used. On the surface of the polarizer, one surface of the optical film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.
<Liquid crystal display device>
The optical film of the present invention is preferably used for various image display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and electronic paper.

The optical film of the present invention is incorporated in the polarizing plate, and is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type. It is preferably used in liquid crystal display devices of various driving systems such as OCB type.

As the cellulose ester resin, the following was used. All are manufactured by Eastman Chemical Co., Ltd.

C-1: CAP482-20, weight average molecular weight 221,000, dispersity 3.5
C-2: CAP482-0.5, weight average molecular weight 70000, dispersity 2.4
As the acrylic resin, acrylic resins 1 to 4 having poly (methyl methacrylate-methyl acrylate) = 97: 3 shown in Table 1 were mixed as shown in Table 2, and Mwa and Va were adjusted. 9 was obtained.

(Film formation)
30 parts by mass of cellulose ester C-1 dried at 80 ° C. for 6 hours (water content 200 ppm), 70 parts by mass of A-1, 1.1 parts by mass of Tinuvin 928 (manufactured by Ciba Japan Co., Ltd.), as a phosphorus compound 0.25 parts by mass of GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.), 0.5 parts by mass of Irganox 1010 (manufactured by Ciba Japan Co., Ltd.), 0.24 parts by mass of Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.), Aerosil NAX50 (Japan) 0.2 parts by weight of Aerosil Co., Ltd. and 0.02 parts by weight of Sea Hoster KEP-30 (manufactured by Nippon Shokubai Co., Ltd.) were further dried by mixing with a vacuum nauter mixer at 80 ° C. and 1 Torr for 3 hours.

The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized.

The production of the optical film was performed with the production apparatus shown in FIG.

The pellets (moisture content 50 ppm) were melt-extruded from a T-die onto a first cooling roll having a surface temperature of 90 ° C. using a single-screw extruder to obtain a 120 μm cast film. At this time, the film was pressed on the first cooling roll with an elastic touch roll having a 2 mm thick metal surface.

First, the obtained film was stretched 60% in the transport direction at 175 ° C. by a stretching machine using a difference in peripheral speed of the roll. Next, it is introduced into a tenter having a preheating zone, a stretching zone, a holding zone, and a cooling zone (there is also a neutral zone for ensuring thermal insulation between the zones), and is 70 ° C. at 175 ° C. in the width direction. The film was cooled to 30 ° C., then released from the clip, and the clip holding part was cut off to obtain an optical film 1 having a film thickness of 40 μm and a film width of 2500 mm.

In the same manner, cellulose ester resin and acrylic resin were mixed as shown in Table 3 to prepare optical film samples 2 to 10.

In Sample 9, 10 parts by mass of 70 parts by mass of acrylic resin were replaced with acrylic resin particle Methbrene W-341 (Mitsubishi Rayon Co., Ltd.). Sample 8 was severely deteriorated in resin and could not proceed to the subsequent evaluation.

The melting temperature was set for each resin mixture as a temperature at which the melt viscosity becomes 1000 Pa · s.

The evaluation results for the obtained optical film samples are shown in Table 3 below.

(Melt viscosity)
The pellets prepared before being made into an optical film were measured for viscosity at a shear rate of 100 sec ^{−1 at} a temperature using a rotational rheometer rheostress 600 manufactured by Thermo Haake. The time required for the measurement is about 7 minutes.
(Resin degradation)
The YI value of the optical film sample was measured to evaluate the degree of deterioration. Further, the melt viscosity of the finished film was measured, and the ratio of the melt viscosity to the raw material resin mixture was calculated.
○: YI value is 1.5 or less and the ratio of melt viscosity is 90% or more Δ: YI value is 2.0 or less and the ratio of melt viscosity is 80% or more ×: Not applicable to ○ or Δ (brittleness)
The obtained optical film sample was stored in a room at a temperature of 25 ° C. and a humidity of 55% RH for 12 hours, and then a circular hole was formed by a punching punch and the shape of the cut surface was observed. Judgment was made based on the following criteria.
○: The hole is neatly rounded.
Δ: There is a slight crack at the cut end.
X: A crack with a length of more than half the diameter of the hole occurs.

As can be seen from Table 3, the optical film in which the acrylic resin of the present invention is mixed has little resin deterioration at the time of melting, has an appropriate melt viscosity, and has excellent melt suitability. In addition, the brittleness is good and the optical film has strength.
<Hard coat layer application>
On the optical film sample 1, the following hard coat layer composition 1 is filtered through a polypropylene filter having a pore size of 0.4 μm to prepare a hard coat layer coating solution, which is applied to the surface using an extrusion coater. After drying at a temperature of 80 ° C. for 1 minute, a hard coat layer having a dry film thickness of 10 μm is cured by using an ultraviolet lamp and curing the coating layer with an irradiance of 100 mW / cm ² and an irradiation amount of 0.2 J / cm ^2. To prepare an optical film sample 1 with a hard coat.

(Hard coat layer composition 1)
90 parts by mass of dipentaerythritol hexaacrylate (NK ester A-DPH, manufactured by Shin-Nakamura Chemical Co., Ltd.)
Pentaerythritol triacrylate 20 parts by mass Pentaerythritol tetraacrylate 60 parts by mass Urethane acrylate (trade name U-4HA, manufactured by Shin-Nakamura Chemical Co., Ltd.)
10 parts by mass Irgacure 184 (manufactured by Ciba Japan) 8 parts by mass Irgacure 907 (manufactured by Ciba Japan) 10 parts by mass 9 parts by mass of a polyether-modified silicone compound (trade name; KF-355A, Shin-Etsu Chemical Co., Ltd.) (Made by Co., Ltd.)
Propylene glycol monomethyl ether 162 parts by mass Ethyl acetate 4 parts by mass Methyl ethyl ketone 14 parts by mass As with the optical film sample 1 with hard coat, a hard coat layer was provided on the optical film samples 2 to 10, and the optical film samples 2 to 10 with hard coat were prepared. Obtained.

About these samples, pencil hardness was measured. The results are shown in Table 4.
(Pencil hardness during application)
The prepared optical film with hard coat is conditioned for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 55%, and then, using a test pencil specified by JIS S 6006, according to the pencil hardness evaluation method specified by JIS K 5400. It was measured. Evaluation was made according to the following criteria.
◎: 4H or more ○: 3H ~
Δ: 2H ~
×: 1H or less

It can be seen from Table 4 that the hard coat layer provided on the optical film of the present invention is sufficiently strong.
<Preparation of polarizing plate>
Using the optical film samples 1 to 9 prepared as described above, the alkali saponification treatment described below was performed to prepare a polarizing plate.

<Alkali saponification treatment>
Saponification process 2M-NaOH 50 ° C. 90 seconds Water washing process Water 30 ° C. 45 seconds Neutralization 10% HCl 30 ° C. 45 seconds Water washing process Water 30 ° C. 45 seconds After saponification treatment, water washing, neutralization and water washing Subsequently, it dried at 80 degreeC.

<Production of polarizer>
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 6 times at 50 ° C. in the conveying direction to produce a polarizer.

5% of completely saponified polyvinyl alcohol in the constitution of the optical film of the present invention having the alkali saponification treatment applied to one side of the polarizer and the optical film with a hard coat of the invention having the alkali saponification treatment applied to the other surface. Each of the aqueous solutions was bonded as an adhesive and dried to prepare polarizing plates 1 to 10.
<Production of liquid crystal display device>
The obtained polarizing plate was carefully peeled off from the viewing side polarizing plate previously bonded to the Hitachi liquid crystal display device Woo W32L-H90, which is an IPS type liquid crystal display device, and aligned with the transmission axis of the polarizing plate originally applied. Then, a polarizing plate was attached so that the optical film of the present invention produced through the pressure-sensitive adhesive was on the viewing side, and a liquid crystal display device was produced. Thereafter, in an environment of a temperature of 23 ° C. and a humidity of 55% RH, the backlight was lit continuously for 5 hours, the entire black display state was visually observed in a dark room, and the screen unevenness was visually sensory evaluated. The results are shown in Table 5.
(Screen unevenness)
○: Unevenness is not observed.
Δ: Not mindful in a bright room, but unevenness is observed in a dark room.
X: Unevenness is observed even in a bright room.

As is clear from Table 5, the liquid crystal display device using the optical film of the present invention has improved screen unevenness.

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 ester film 16 Winding device

Claims

In an optical film obtained by melt casting a resin mixture containing a cellulose ester resin and an acrylic resin, the acrylic resin is a mixture of two or more acrylic resins having different weight average molecular weights. Optical film.
The weight average molecular weight and molecular weight distribution dispersity (weight average molecular weight / number average molecular weight) of the cellulose ester resin are Mwc and Vc, respectively, and the weight average molecular weight and molecular weight distribution dispersity of the acrylic resin are Mwa and Va, respectively. 2. The optical film according to claim 1, wherein Mwa <Mwc and Va> Vc are satisfied.
3. The optical film according to claim 1, comprising elastic resin particles.
A polarizing plate using the optical film according to any one of claims 1 to 3.