JP2009047800A - Optical film, polarization plate using the same and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film capable of enlarging a viewing angle when being used as a protective film for a polarization plate for a display of an image display device such as a large screen VA type liquid crystal panel, to provide a polarization plate using the optical film, and to provide a display device using the polarization plate. <P>SOLUTION: The optical film is formed of a transparent resin film having holes of 1.5 to 10 pieces on the average per 100 μm<SP>3</SP>, wherein the content volume of the holes is 0.002 to 0.6 μm<SP>3</SP>on the average. Further, it is preferable that the major side of the holes is 0.2 to 3 μm on the average, the minor side of the holes is 0.05 to 0.2 μm on the average, the holes exist on the inner part of 20% or more of the total thickness from the surface of the optical film, and the major side of the holes intersects the slow axis of the optical film at an angle of 75 to 115°. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to various functional films such as a protective film for polarizing plates used for liquid crystal display devices (LCDs), retardation films, viewing angle widening films, antireflection films used for plasma displays, and organic EL (electroluminescence) displays. It is related with the optical film which can be utilized also for various functional films etc. which are used by etc., a polarizing plate using the same, and a display apparatus.

  In general, the basic configuration of a liquid crystal display device is one in which polarizing plates are provided on both sides of a liquid crystal cell. Since the polarizing plate allows only light with a polarization plane in a certain direction to pass, it plays an important role in visualizing changes in the orientation of the liquid crystal due to the electric field in the liquid crystal display device. The performance of the liquid crystal display device depends on the performance of the polarizing plate. Is greatly affected.

  In recent years, demand for display quality of thin-film liquid crystal display devices has increased, and various liquid crystal display methods such as VA (vertical alignment mode), OCB, and IPS have been proposed. In a liquid crystal display device with a wide viewing angle, it is common to use a retardation correction film. The quality required for optical films has become stricter due to the larger screen and higher definition, and the uniformity of the film retardation value in the width direction and the longitudinal direction is required.

  Conventionally, a polarizing plate used for a VA mode liquid crystal panel is bonded to a liquid crystal cell so as to have a polarization axis in the vertical and horizontal directions of the screen. The polarizer of the elements constituting the polarizing plate used here is manufactured by greatly stretching the PVA film. A polarizing film of a polarizing plate used in a liquid crystal display device is laminated on one or both sides of a polarizer made of a stretched polyvinyl alcohol film with an optical film made of a cellulose ester film as a protective film. The retardation film is used for the purpose of widening the viewing angle and improving the contrast. The retardation film is provided by stretching a film of polycarbonate, polymer having an alicyclic structure, cellulose ester, or the like. Or a liquid crystal layer coated on a transparent film substrate. Sometimes called an optical compensation film. When the slow axis of the retardation film is in the width direction, it is possible to perform roll-to-roll bonding with a polarizing plate, so that production efficiency can be significantly improved from conventional batch bonding.

  These optical films are required to have no optical defect and uniform retardation. In particular, the required quality is becoming stricter as monitors and TVs are becoming larger and higher definition.

  In particular, there has been a strong demand for the appearance of an optical film that can expand the viewing angle of a display of an image display device such as the large screen VA liquid crystal panel.

Conventionally, there are the following patent documents regarding optical films used in liquid crystal display devices.
JP-A-2006-99076 discloses a technique of a polarizer having high transmittance and high degree of polarization. This technique can achieve a high transmittance and a high degree of polarization by using a film in which a minute region is dispersed in a resin matrix. Japanese Patent Application Laid-Open No. 2006-126313 discloses a technique of a polarizer having no appearance defect due to cracks and the like, and having a high transmittance and a high degree of polarization. This technique can achieve high transmittance and high degree of polarization by a film having a structure in which a gap between two kinds of fibers is embedded with a transparent resin without a gap.

  However, in the technique described in Patent Document 1, the microregion is formed of an oriented birefringent material, and no technique is described regarding an optical film having pores in the film. In the technique described in Patent Document 2, a transparent resin is embedded without a gap between the resins, and nothing is described about an optical film having pores in the film.

  Therefore, the techniques described in Patent Documents 1 and 2 have a problem that it is insufficient to obtain an optical film that expands the viewing angle in the large-screen VA liquid crystal panel.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and to increase the viewing angle when used as a protective film for a polarizing plate in a display of an image display device such as a large-screen VA liquid crystal panel. An object is to provide a film, a polarizing plate using the film, and a display device.

  As a result of intensive studies to solve the above-mentioned problems of the prior art, the present inventor has made specific holes in the optical film to improve the viewing angle widening effect in the large screen VA liquid crystal panel. It became clear that is effective. In particular, when the holes are present in the optical film and the long side of the holes is perpendicular to the slow axis in the film plane, the effect is remarkable and the present invention is completed. It is a thing.

In order to achieve the above object, the invention of the optical film of claim 1 comprises a transparent resin film having 1.5 to 10 pores on an average per 100 μm ³ , and the pore internal volume is , 0.002 .mu.m ³ or an average value, is characterized in that at 0.6 .mu.m ³ or less.

  The invention according to claim 2 is the optical film according to claim 1, characterized in that the long side of the holes is an average value of 0.2 μm or more and 3 μm or less.

  The invention according to claim 3 is the optical film according to claim 1 or 2, characterized in that the short sides of the holes are 0.05 μm or more and 0.2 μm or less on average.

  Invention of Claim 4 is an optical film as described in any one of Claims 1-3, Comprising: A void | hole exists in 20% or more of total thickness from the surface of an optical film, It is characterized by the above-mentioned. It is said.

  Invention of Claim 5 is an optical film as described in any one of Claims 1-4, Comprising: The long side of a void | hole is 75 degree | times or more and 115 with respect to the slow axis of an optical film. It is characterized by being less than or equal to degrees.

  Invention of Claim 6 is an optical film as described in any one of Claims 1-5, Comprising: A transparent resin film is a cellulose-ester-type resin film, It is characterized by the above-mentioned.

  Invention of Claim 7 is an optical film as described in any one of Claims 1-5, Comprising: A transparent resin film is a resin film containing 80% or more of cyclic olefin type addition polymers, It is characterized by the above-mentioned. It is said.

  The invention of a polarizing plate according to an eighth aspect is characterized in that the optical film according to any one of the first to seventh aspects is used on one surface.

  The invention of a display device according to claim 9 is characterized in that the polarizing plate according to claim 8 is used.

The invention of the optical film of claim 1 comprises a transparent resin film having 1.5 to 10 pores on an average per 100 μm ³ , and the pore internal volume is 0.002 μm ³ or more on average. , but it is 0.6 .mu.m ³ or less, according to the first aspect of the invention, an effect that it is possible to widen the viewing angle in a large screen VA liquid crystal panel.

  In the optical film according to claim 1, the long side of the holes is preferably 0.2 μm or more and 3 μm or less on average, and the short side of the holes is 0.05 μm or more on average. The thickness is preferably 0.2 μm or less.

  In the optical film according to the first aspect, it is preferable that the long side of the hole is 75 degrees or more and 115 degrees or less with respect to the slow axis of the optical film.

  Invention of Claim 4 is an optical film as described in any one of Claims 1-3, Comprising: A void | hole exists in 20% or more of total thickness from the surface of an optical film, According to invention of Claim 4, in addition to the effect that the viewing angle in a large screen VA type liquid crystal panel can be expanded, there exists an effect that the haze of an optical film can be made low.

  In the optical film of the present invention, the transparent resin film is preferably a cellulose ester resin film.

  In the optical film of the present invention, the transparent resin film is preferably a resin film containing 80% or more of a cyclic olefin addition polymer.

  The polarizing plate of the present invention uses the optical film according to any one of claims 1 to 7 on one side, and according to the invention of claim 8, in a large screen VA type liquid crystal panel. There is an effect that the viewing angle can be enlarged.

  The display device of the present invention uses the above polarizing plate. According to the invention of claim 9, there is an effect that the viewing angle in the large screen VA type liquid crystal panel can be enlarged.

  Next, embodiments of the present invention will be described, but the present invention is not limited thereto.

  The present invention particularly relates to an optical film that can be used as a protective film for a polarizing plate of a liquid crystal display (LCD).

The optical film according to the present invention is made of a transparent resin film having 1.5 to 10 holes on an average per 100 μm ³ , and the inner volume of the holes is 0.002 μm ³ or more on the average and 0.005 μm. 6 μm ³ or less.

The average number of pores per 100 μm ³ is preferably 1.5 to 10 in order to obtain the effect of the present invention. Here, if the average number of holes in the optical film is less than 1.5 per 100 μm ³ , the effect of expanding the viewing angle of the present invention is reduced, which is not preferable. Moreover, since the transparency of an optical film will be impaired when the void | hole exceeds 10 on an average per 100 micrometers ³ , it is unpreferable.

The internal volume of the pores of the optical film according to the present invention, 0.002 .mu.m ³ or the average value is 0.6 .mu.m ³ or less. Here, if the internal volume of the pores is less than 0.002 μm ^{3 on} average, the effect of enlarging the viewing angle is reduced, which is not preferable. Moreover, since the transparency of an optical film will be impaired when the internal volume of a void | hole exceeds 0.6 micrometer ³ by an average value, it is unpreferable. Internal volume of the pores of the optical film, the average value at 0.01 [mu] m ³ or more, preferably 0.55 .mu.m ³ or less.

  In the optical film according to the present invention, the long side of the pores is 0.2 μm or more and 3 μm or less on average. The long sides of the holes are preferably 0.5 μm or more and 2.5 μm or less on average.

  Here, if the long side of the holes is less than 0.2 μm on average, the effect of enlarging the viewing angle becomes small, which is not preferable. Moreover, since the transparency of an optical film will be impaired when the long side of a void | hole exceeds 3 micrometers by an average value, it is unpreferable.

  The short side of the optical film according to the present invention and the pores has an average value of 0.05 μm or more and 0.2 μm or less. The short side of the pores is preferably 0.06 μm or more and 0.12 μm or less on average.

  Here, if the short side of the holes is less than 0.05 μm on average, the effect of enlarging the viewing angle becomes small, which is not preferable. Moreover, since the transparency of an optical film will be impaired when the short side of a void | hole exceeds 0.2 micrometer on an average value, it is unpreferable.

  In the optical film according to the present invention, pores are present inside 20% or more of the total thickness from the surface of the optical film.

  Here, if the presence of pores is within a range of less than 20% of the total thickness from the surface of the optical film, the adhesive enters the pores on the surface of the optical film during polarizing plate processing, and the viewing angle is expanded. Since the effect cannot be expected and the transparency of the optical film is impaired, it is not preferable.

  In the optical film according to the present invention, the long side of the pores is 75 degrees or more and 115 degrees or less with respect to the slow axis of the optical film.

  Here, if the long side of the hole is less than 75 degrees with respect to the slow axis of the optical film, the effect of enlarging the viewing angle cannot be obtained sufficiently, which is not preferable. Further, if the long side of the hole exceeds 115 degrees with respect to the slow axis of the optical film, the effect of widening the viewing angle cannot be obtained sufficiently, which is not preferable.

  According to the optical film of the present invention, it is possible to improve the enlargement of the viewing angle in the large screen VA type liquid crystal panel.

  These will be described in detail below.

  The optical film according to the present invention includes preferable requirements such as easy production, good adhesion to the polarizing film, and optical transparency, among which a polymer film is preferable.

  The term “transparent” as used in the present invention means that the visible light transmittance is 60% or more, preferably 80% or more, and particularly preferably 90% or more.

  As long as the polymer film has the above properties, the polymer film is not particularly limited. For example, cellulose ester films such as cellulose diacetate film, cellulose triacetate film, cellulose acetate butyrate film, and cellulose acetate propionate film. , Polyester film, polycarbonate film, polyarylate film, polysulfone (including polyethersulfone) film, polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, polyvinylidene chloride film, polyvinyl Alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, poly -Bonate film, cycloolefin polymer film (Arton (manufactured by JSR), ZEONEX, ZEONOR (manufactured by ZEON CORPORATION), polymethylpentene film, polyetherketone film, polyetherketoneimide film, polyamide film, fluororesin Examples thereof include a film, a nylon film, a polymethyl methacrylate film, an acrylic film, a glass plate, etc. Among them, a cellulose ester film, a cycloolefin polymer film, a polycarbonate film, and a polysulfone (including polyether sulfone) film are preferable. In the present invention, in particular, the transparent resin film contains a cellulose ester resin film or a resin film containing 80% or more of a cyclic olefin addition polymer. In the range of Lum is the manufacturing, cost, transparency, are preferably used from the viewpoint of adhesiveness.

  These films may be films produced by melt casting film formation or films produced by solution casting film formation.

[Cellulose ester film]
Preferred cellulose esters as the main component of the optical film according to the present invention are cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, and cellulose acetate propionate. Among them, cellulose acetate, cellulose acetate butyrate, Cellulose acetate propionate is preferably used.

  In particular, the main component of the resin contained in the film is a cellulose ester, and the cellulose ester preferably contains at least one selected from cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. .

  As described above, in the present invention, by using the above cellulose ester as the resin constituting the film, corner unevenness in the large-screen VA liquid crystal panel can be improved while maintaining the transparency of the film. .

  Here, the ester group substitution degree of the cellulose ester is preferably 2.42 to 2.60. By using the cellulose ester whose ester group substitution degree is defined in this way, an optical film having good adhesion to the polarizing film can be obtained while maintaining the transparency of the film. These cellulose esters can be synthesized by a known method.

  When a cellulose ester is used as the optical film according to the present invention, the cellulose as a raw material for the cellulose ester is not particularly limited, and examples thereof include cotton linters, wood pulp (derived from coniferous trees, derived from hardwoods), kenaf and the like. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively. When the acylating agent is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), these cellulose esters use an organic solvent such as acetic acid or an organic solvent such as methylene chloride, and It can be obtained by reacting with a cellulose raw material using a protic catalyst.

When the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804. In addition, the cellulose ester used in the present invention is obtained by mixing and reacting the amount of the acylating agent in accordance with the degree of substitution. In the cellulose ester, these acylating agents react with hydroxyl groups of cellulose molecules. Cellulose molecules are composed of many glucose units linked together, and the glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution (mol%). For example, cellulose triacetate has acetyl groups bonded to all three hydroxyl groups of the glucose unit (actually 2.6 to 3.0).

  As the cellulose ester used in the present invention, as described above, cellulose having propionate group or butyrate group in addition to acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate butyrate is used. The mixed fatty acid ester is particularly preferably used. Cellulose acetate propionate containing a propionate group as a substituent has excellent water resistance and is useful as a film for a liquid crystal image display device.

  The measuring method of the substitution degree of an acyl group can be measured according to the rule of ASTM-D817-96.

  The number average molecular weight of the cellulose ester is preferably 40,000 to 200,000, and the mechanical strength when molded is strong, and an appropriate dope viscosity is preferable in the case of the solution casting method, and more preferably 50,000 to 150,000. The weight average molecular weight (Mw) / number average molecular weight (Mn) is preferably in the range of 1.4 to 4.5.

  Here, since the average molecular weight of the cellulose ester can be measured using gel permeation chromatography, the number average molecular weight (Mn) and the weight average molecular weight (Mw) can be calculated using this.

  The weight average molecular weight (Mw) and number average molecular weight (Mn) of the cellulose ester were measured by the gel permeation chromatography method using the apparatus and materials shown below. The measurement conditions for the average molecular weight are as follows.

Gel permeation chromatography Solvent (eluent): Dichloromethane Column name: GPCk806-GPCk805-GPCk803 (3) manufactured by Showa Denko
Sample concentration: 0.1 (mass%)
Flow rate: 1.0 (ml / min)
Sample injection volume: 100 (μl)
Standard sample: polystyrene (Mw: 5 to 6.7 million)
Temperature: 25 ° C
Detection: RI (Suggested refractometer)
These cellulose esters are pressurized by applying a cellulose ester solution (dope), generally called a solution casting film forming method, onto, for example, an endless metal belt that moves indefinitely or a support for casting a rotating metal drum. It is preferable to manufacture the dope from a die by casting (casting).

  As the organic solvent used for preparing these dopes, it is preferable that the cellulose ester can be dissolved and has an appropriate boiling point. For example, methylene chloride, methyl acetate, ethyl acetate, amyl acetate, methyl acetoacetate, acetone, tetrahydrofuran 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, 1,3-difluoro-2 -Propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3 , 3,3-pentafluoro-1-propanol, nitroethane, 1,3-dimethyl-2-imidazolidinone, etc. Can, organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone, methyl acetoacetate, and the like are preferable organic solvents (i.e., good solvent), and as.

  Moreover, as shown in the following film forming process, it is used from the viewpoint of preventing foaming in the web when the solvent is dried from the web (dope film) formed on the casting support in the solvent evaporation process. The boiling point of the organic solvent is preferably 30 to 80 ° C. For example, the boiling point of the good solvent is methylene chloride (boiling point 40.4 ° C), methyl acetate (boiling point 56.32 ° C), acetone (boiling point 56.3). ° C), ethyl acetate (boiling point 76.82 ° C), and the like.

  Among the above good solvents, methylene chloride or methyl acetate having excellent solubility is preferably used.

  It is preferable to contain 0.1 mass%-40 mass% of C1-C4 alcohol other than the said organic solvent. It is particularly preferable that the alcohol is contained at 5 to 30% by mass. After casting the above dope onto the casting support, the solvent starts to evaporate and the alcohol ratio increases and the web (dope film) gels, making the web strong and peeling from the casting support. When it is used as a gelling solvent for facilitating or the ratio of these is small, it also has a role of promoting the dissolution of the cellulose ester of the non-chlorine organic solvent.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like.

  Of these solvents, ethanol is preferred because the dope has good stability, the boiling point is relatively low, and the drying property is good. It is preferable to use a solvent containing 5% by mass to 30% by mass of ethanol with respect to 70% by mass to 95% by mass of methylene chloride. Methyl acetate can be used in place of methylene chloride. At this time, the dope may be prepared by a cooling dissolution method.

  As the plasticizer used in the present invention, a phosphate ester plasticizer and a non-phosphate ester plasticizer are preferably used.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  Non-phosphate ester plasticizers include phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol plasticizers, glycolate plasticizers, and citrate ester plasticizers. Agents, fatty acid ester plasticizers, polyester plasticizers, polycarboxylic acid ester plasticizers and the like can be preferably used. Particularly, in order to obtain the effects of the present invention, polyhydric alcohol plasticizers, polyesters are preferable. It is preferable to use a plasticizer and a polycarboxylic acid plasticizer.

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

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

R _1- (OH) n (1)
In the formula, R ₁ represents an n-valent organic group, and n represents a positive integer of 2 or more.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, pentaerythritol, dipentaerythritol and the like. Of these, trimethylolpropane and pentaerythritol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid. Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof. Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. In particular, benzoic acid is preferred.

  The molecular weight of the polyhydric alcohol ester is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester. The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  In the present invention, the content of the polyhydric alcohol ester is preferably 1 to 15% by mass, particularly preferably 3 to 10% by mass in the cellulose ester film.

(Polyester plasticizer)
The polyester plasticizer is not particularly limited, but a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. Although it does not specifically limit as a preferable polyester plasticizer, For example, the aromatic terminal ester plasticizer represented by following General formula (2) is preferable.

B- (GA) n-GB (2)
In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A Represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

  In the general formula (2), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the polyester plasticizer used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer used in the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol) ), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3 -Methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol , 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. It is used as one kind or a mixture of two or more kinds. In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester used in the present invention include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Glycols can be used as one or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester used in the present invention include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are each used as one or a mixture of two or more. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The polyester plasticizer used in the present invention has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  The polyvalent carboxylic acid plasticizer useful in the present invention comprises a divalent or higher, preferably a divalent to valent 20 polyvalent carboxylic acid and an alcohol ester. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid used in the present invention is represented by the following general formula (3).

R ₅ (COOH) m (OH) n (3)
In the formula, R ₅ is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxyl group, and an OH group is an alcoholic or phenolic hydroxyl group.

  Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these. Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving the retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound used for this invention, Well-known alcohol and phenol can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10. In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

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

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

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. And aromatic monocarboxylic acids possessed by them, or derivatives thereof. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  Although there is no restriction | limiting in particular in the molecular weight of a polyhydric carboxylic acid ester compound, It is preferable that it is the range of molecular weight 300-1000, and it is more preferable that it is the range of 350-750. The larger one is preferable in terms of improving the retention, and the smaller one is preferable in terms of moisture permeability and compatibility with the cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto. For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  These plasticizers can be used alone or in combination of two or more. If the amount of the plasticizer used is less than 1% by mass relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, which is not preferable. If the amount exceeds 20% by mass, the plasticizer bleeds out from the film and the physical properties of the film are reduced. Since it deteriorates, 1-20 mass% is preferable. 6-16 mass% is further more preferable, Most preferably, it is 8-13 mass%.

  An ultraviolet absorber is preferably used for the optical film of the present invention.

  As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties.

  Specific examples of the ultraviolet absorber preferably used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. However, it is not limited to these.

  Specific examples of the benzotriazole-based ultraviolet absorbers include the following ultraviolet absorbers, but the present invention is not limited thereto.

UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole UV-3 : 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-Chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2- (2H-benzotriazol-2-yl) -6 (Linear and side chain dodecyl) -4-methylphenol (TINUVIN171, manufactured by Ciba)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- 4-Hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN109, manufactured by Ciba)
Moreover, although the following specific example is shown as a benzophenone series ultraviolet absorber, this invention is not limited to these.

UV-10: 2,4-dihydroxybenzophenone UV-11: 2,2'-dihydroxy-4-methoxybenzophenone UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13: Bis (2-methoxy -4-hydroxy-5-benzoylphenylmethane)
As the ultraviolet absorber preferably used in the present invention, a benzotriazole-based ultraviolet absorber and a benzophenone-based ultraviolet absorber that are highly transparent and excellent in preventing the deterioration of the polarizing plate and the liquid crystal are preferable, and unnecessary coloring is less. A benzotriazole-based ultraviolet absorber is particularly preferably used.

  Moreover, the ultraviolet absorber whose distribution coefficient described in Unexamined-Japanese-Patent No. 2001-187825 is 9.2 or more improves the surface quality of a long film, and is excellent also in applicability | paintability. In particular, it is preferable to use an ultraviolet absorber having a distribution coefficient of 10.1 or more.

  Further, the polymer ultraviolet absorbers described in the general formula (1) or general formula (2) described in JP-A-6-148430 and the general formulas (3), (6), and (7) described in JP-A-2002-47357 ( Or UV-absorbing polymers) or UV-absorbing copolymer polymers described in paragraphs [0027] to [0055] of JP-A No. 2002-169020 are also preferably used. As a polymer ultraviolet absorber, PUVA-30M (manufactured by Otsuka Chemical Co., Ltd.) and the like are commercially available.

  An antioxidant can be used in the optical film of the present invention. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the polarizing plate protective film may be deteriorated. The antioxidant has a role of delaying or preventing the polarizing plate protective film from being decomposed by, for example, halogen in the residual solvent in the polarizing plate protective film or phosphoric acid of the phosphoric acid plasticizer. It is preferable to make it contain in a polarizing plate protective film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose derivative.

  Moreover, it is preferable to use fine particles in order to impart slipperiness to the optical film according to the present invention.

  The primary average particle diameter of the fine particles added to the optical film according to the present invention is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm. These fine particles preferably form secondary particles having a particle size of 0.1 to 5 μm and are contained in the optical film, and the preferable average particle size is 0.1 to 2 μm, more preferably 0.2 to 0. .6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high can be formed in the film surface, and, thereby, appropriate slipperiness can be given to the film surface.

  The primary average particle diameter of the fine particles used in the present invention is measured by observing the particles with a transmission electron microscope (magnification of 500,000 to 2,000,000 times), observing 100 particles, measuring the particle diameter, and measuring the average. The value was taken as the primary average particle size.

  The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, and particularly preferably 100 to 200 g / liter. A larger apparent specific gravity makes it possible to make a high-concentration dispersion, which improves haze and agglomerates, and is preferable when preparing a dope having a high solid content concentration as in the present invention. Are particularly preferably used.

  Silicon dioxide fine particles having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more are, for example, a mixture of vaporized silicon tetrachloride and hydrogen burned in air at 1000 to 1200 ° C. Can be obtained. For example, it is marketed with the brand name of Aerosil 200V and Aerosil R972V (above, Nippon Aerosil Co., Ltd.), and can use them.

  The apparent specific gravity is calculated by the following equation by taking a certain amount of silicon dioxide fine particles in a graduated cylinder, measuring the weight at this time.

Apparent specific gravity (g / liter) = silicon dioxide mass (g) / volume of silicon dioxide (liter)
Examples of the method for preparing the fine particle dispersion used in the present invention include the following three types.

(Preparation method A)
After stirring and mixing the solvent and the fine particles, the dispersion is performed with a disperser. This is a fine particle dispersion. The fine particle dispersion is added to the dope solution and stirred.

(Preparation method B)
After stirring and mixing the solvent and the fine particles, the dispersion is performed with a disperser. This is a fine particle dispersion. Separately, a small amount of cellulose triacetate is added to the solvent and dissolved by stirring. The fine particle dispersion is added to this and stirred. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

(Preparation method C)
Add a small amount of cellulose triacetate to the solvent and dissolve with stirring. Fine particles are added to this and dispersed by a disperser. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

  Preparation method A is excellent in dispersibility of silicon dioxide fine particles, and preparation method C is excellent in that silicon dioxide fine particles are difficult to re-aggregate. Above all, the above-mentioned preparation method B is a preferable preparation method which is excellent in both dispersibility of silicon dioxide fine particles and difficulty in reaggregation of silicon dioxide fine particles.

(Distribution method)
The concentration of silicon dioxide when the silicon dioxide fine particles are mixed with a solvent and dispersed is preferably 5% by mass to 30% by mass, more preferably 10% by mass to 25% by mass, and most preferably 15% by mass to 20% by mass. A higher dispersion concentration is preferable because liquid turbidity with respect to the added amount tends to be low, and haze and aggregates are improved.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

  The addition amount of silicon dioxide fine particles relative to cellulose ester is preferably 0.01 parts by mass to 5.0 parts by mass, and more preferably 0.05 parts by mass to 1.0 part by mass with respect to 100 parts by mass of cellulose ester. Preferably, 0.1 mass part-0.5 mass part is the most preferable. The larger the added amount, the better the dynamic friction coefficient, and the smaller the added amount, the less aggregates.

  As the disperser, a normal disperser can be used. Dispersers can be broadly divided into media dispersers and medialess dispersers. For dispersing silicon dioxide fine particles, a medialess disperser is preferred because of its low haze. Examples of the media disperser include a ball mill, a sand mill, and a dyno mill. Examples of the medialess disperser include an ultrasonic type, a centrifugal type, and a high pressure type. In the present invention, a high pressure disperser is preferable. The high pressure dispersion device is a device that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

  When processing with a high-pressure dispersion apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.807 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm. More preferably, it is 19.613 MPa or more. Further, at that time, those having a maximum reaching speed of 100 m / second or more and those having a heat transfer speed of 420 kJ / hour or more are preferable.

  The high-pressure dispersion apparatus as described above includes an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer. UHN-01 manufactured by Sanwa Machinery Co., Ltd.

  In addition, casting a dope containing fine particles so as to be in direct contact with the casting support is preferable because a film having high slip properties and low haze can be obtained.

  Moreover, after peeling and drying after casting and winding up in a roll shape, functional thin films such as a hard coat layer and an antireflection layer are provided. Until processing or shipment, packaging is usually performed in order to protect the product from dirt, static electricity, and the like. The packaging material is not particularly limited as long as the above purpose can be achieved, but a material that does not hinder volatilization of the residual solvent from the film is preferable. Specific examples include polyethylene, polyester, polypropylene, nylon, polystyrene, paper, various non-woven fabrics, and the like. A fiber having a mesh cloth shape is more preferably used.

  The optical film of the present invention preferably contains a retardation control agent to adjust the retardation.

  The optical film of the present invention preferably contains a rod-shaped compound having a maximum absorption wavelength (λmax) of the ultraviolet absorption spectrum of the solution shorter than 250 nm as a retardation control agent.

  From the viewpoint of the function of the retardation control agent, the rod-like compound preferably has at least one aromatic ring, and more preferably has at least two aromatic rings. The rod-like compound preferably has a linear molecular structure. The linear molecular structure means that the molecular structure of the rod-like compound is linear in the most thermodynamically stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation.

  For example, molecular orbital calculation is performed using molecular orbital calculation software (eg, WinMOPAC2000, manufactured by Fujitsu Limited), and a molecular structure that minimizes the heat of formation of a compound can be obtained. The molecular structure being linear means that the angle of the molecular structure is 140 degrees or more in the thermodynamically most stable structure obtained by calculation as described above. The rod-shaped compound preferably exhibits liquid crystallinity. More preferably, the rod-like compound exhibits liquid crystallinity upon heating (has thermotropic liquid crystallinity). The liquid crystal phase is preferably a nematic phase or a smectic phase.

  The optical film according to the present invention is produced by any one of a solution casting method and a melt casting method.

  Here, the production of the optical film by the solution casting film forming method will be described in detail. For example, a step of preparing a dope by dissolving a resin such as cellulose ester and an additive such as the plasticizer in a solvent, a step of casting the dope on a belt-shaped or drum-shaped metal support, a cast dope Is carried out by a step of drying as a web, a step of peeling from the metal support, a step of stretching, a step of further drying, a step of further heat-treating the obtained film, and a step of winding after cooling.

  The optical film of the present invention preferably contains 70 to 95% by mass of cellulose ester in the solid content.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy increases. Becomes worse. The concentration for achieving both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass.

  The solvent used in the dope of the present invention may be used alone or in combination of two or more. However, it is preferable from the viewpoint of production efficiency that a good solvent and a poor solvent of cellulose ester are mixed and used. The more solvent is preferable from the viewpoint of solubility of the cellulose ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, depending on the acyl group substitution degree of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4) and cellulose acetate propionate are good. As a solvent, cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope.

  As a method for dissolving the cellulose ester when preparing the dope, a general method can be used. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and does not boil under pressure, in order to prevent the formation of massive undissolved material called gel or mamako. A method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  The pressure is more preferably Pa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface, and as the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is set to −50 ° C. to a temperature at which the solvent boils and does not foam.

  A higher temperature is preferable because the web can be dried faster, but if it is too high, the web may foam or the flatness may deteriorate. A preferable support temperature is appropriately determined at 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use hot water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%. The temperature at the peeling position on the metal support is preferably −50 to 40 ° C., more preferably 10 to 40 ° C., and most preferably 15 to 30 ° C.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Moreover, in the drying process of the cellulose ester film, the web is peeled from the metal support, further dried, and dried until the residual solvent amount is 0.5% by mass or less.

  In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a method of drying while transporting the web by a tenter method is adopted.

  When peeling from the metal support, the web is stretched in the longitudinal direction due to the peeling tension and the subsequent conveying tension. Therefore, in the present invention, when peeling the web from the casting support, the peeling and conveying tension is lowered as much as possible. It is preferable to carry out in the state. Specifically, for example, it is effective to set it to 50 to 170 N / m or less. At that time, it is preferable to apply a cold air of 20 ° C. or less to fix the web rapidly.

  In the production of the optical film of the present invention, in the stretching step, as a film for a liquid crystal display device, a tenter method in which both side edges of a transport web (or film) are fixed with a clip or the like is stretched. It is preferable for improving the stability.

As described above, the optical film according to the present invention is made of a transparent resin film having 1.5 to 10 holes on average per 100 μm ³ , and the inner volume of the holes is 0.002 μm on average. ³ or more and 0.6μm ³ below. The internal volume of the pores has an average value in the 0.01 [mu] m ³ or more, preferably 0.55 .mu.m ³ or less.

  In the optical film according to the present invention, the long side of the pores is an average value of 0.2 μm or more and 3 μm or less. The long sides of the holes are preferably 0.5 μm or more and 2.5 μm or less on average.

  In the optical film according to the present invention, the short side of the holes has an average value of 0.05 μm or more and 0.2 μm or less. The short sides of the holes are preferably 0.06 μm or more and 0.12 μm or less on average.

  In order to manufacture an optical film by adjusting the number of holes of the optical film, the internal volume of the holes, the long side of the hole, and the short side of the hole, It can be carried out by appropriately setting the residual solvent amount of the web (film), the stretch ratio of the web (film) in the tenter in the stretching step, and the stretching temperature in the tenter.

  That is, in the production of the optical film of the present invention, the residual solvent amount of the web (film) immediately before entering the tenter of the stretching process is 0.6 to 10.0% by mass, and 0.6 to 5.0% by mass. It is preferable that it is 0.8-2.0 mass%.

  Moreover, in this invention, the draw ratio of the web (film) in the tenter of an extending process is 1.1 to 1.5 times, and it is preferable that it is 1.2 to 1.4 times.

  Furthermore, the temperature of the hot air blown from the hot air blowing slit port in the tenter is 95 to 200 ° C, and preferably 100 to 150 ° C.

  In the most preferable embodiment of the method for producing an optical film according to the present invention, a resin solution (dope) containing a polymer is cast on a metal support to form a cast film, and a solvent in the cast film is cast. By drying until it is in a peelable state and peeling from the metal support, followed by a stretching process in which both ends of the peeled web are gripped and stretched in the width direction, and the solvent is dried and wound up A method for producing an optical film by a solution casting film forming method for obtaining an optical film, wherein a residual solvent amount of a web (film) immediately before entering a tenter in a stretching step is 0.8 to 2.0% by mass, The stretch ratio of the web (film) in the tenter in the stretching step is 1.2 to 1.3 times, and the temperature of the warm air (stretching temperature) blown from the hot air blowing slit port in the tenter is 100 to 110 ° C. As a feature There.

  In the optical film according to the present invention, pores are present in the interior of 20% or more of the total thickness from the surface of the optical film.

  In order to manufacture such an optical film, for example, after stretching the web (film) in the width direction with a tenter, the tension in the width direction is relaxed to release the width, followed by the following: Surface treatment with a solvent is performed. That is, a vapor of a solvent such as methylene chloride is sprayed on both surfaces of the stretched and tensioned web (film) to form an atmosphere containing the solvent in the vicinity of the web (film) surface. The web (film) is passed between a pair of rolls, whereby the optical film according to the present invention in which pores are present in the interior of 20% or more of the total thickness from the surface of the optical film is obtained.

  It is preferable that the surface-treated web (film) thus obtained is further transported for a required time in a drying zone set at a predetermined temperature to be dried to disperse the solvent and the like.

  Thus, a drying apparatus is usually provided before and after the tenter in the stretching step. In the drying apparatus, the web (film) is meandered by a plurality of transport rolls arranged in a staggered manner as viewed from the side, and the web is dried during the meandering. The film transport tension in the drying apparatus is affected by the physical properties of the dope, the amount of residual solvent in the peeling and film transport process, the drying temperature, etc., but the film transport tension during drying is 30 to 300 N / width m. 40 to 270 N / width m is more preferable.

  The means for drying the web (film) is not particularly limited, and is generally performed with hot air, infrared rays, a heating roll, a microwave, or the like. It is preferable to dry with hot air from the viewpoint of simplicity, for example, it is dried by the hot air blown from the warm air inlet at the front portion of the bottom of the drying device, and the exhaust air is discharged from the outlet at the rear portion of the ceiling of the drying device. It is dried by being discharged. The temperature of the drying air is preferably 40 to 160 ° C, and more preferably 50 to 160 ° C in order to improve the flatness and dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  For example, a cellulose ester film that has finished the transport drying process is generally processed to form an emboss on the film by an embossing apparatus before the introduction to the winding process.

  Here, the height h (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. . Embossing may be formed on both sides of the film. In this case, the height h1 + h2 (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. For example, when the film thickness is 40 μm, the emboss height h 1 + h 2 (μm) is set to 2 to 12 μm. The emboss width is set to 5 to 30 mm.

  The film after drying is taken up by a take-up device to obtain the original roll of the optical film. A film having good dimensional stability can be obtained by setting the residual solvent amount of the film to be dried to 0.5% by mass or less, preferably 0.1% by mass or less.

  The winding method of the film may be a generally used winder, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc. Use it properly.

  The film may be bonded to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

  In the optical film according to the present invention, the width of the film after winding is preferably 1200 to 2500 mm.

  In this invention, the film thickness after drying of a cellulose-ester film has the preferable range of 20-150 micrometers as a finished film from a viewpoint of thickness reduction of a liquid crystal display device. Here, the film thickness after drying refers to a film in which the amount of residual solvent in the film is 0.5% by mass or less.

  Here, when the film thickness of the cellulose ester film after winding is too thin, for example, the required strength as a protective film for a polarizing plate may not be obtained. If the film thickness is too thick, the advantage of thinning the film becomes less than the conventional cellulose ester film. In order to adjust the film thickness, the dope concentration, the pumping amount, the slit gap in the die of the casting die, the extrusion pressure of the casting die, the speed of the metal support, etc. are controlled so as to obtain the desired thickness. It is good. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  In the process from immediately after casting through the solution casting film-forming method to drying, the atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . However, of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be considered.

  In the present invention, the cellulose ester film preferably has a moisture content of 0.1 to 5%, more preferably 0.3 to 4%, and even more preferably 0.5 to 2%.

  In the present invention, the cellulose ester film desirably has a transmittance of 90% or more, more preferably 92% or more, and further preferably 93% or more.

  The optical film of the present invention has a haze of 0.3 to 2.0 when three sheets are stacked. According to the optical film of the present invention, the haze of the film is very low. It has optical properties with excellent transparency and flatness.

  Here, the haze measurement method of the optical film is performed according to JIS K 7105-1981, using “Nippon Denshoku Kogyo Co., Ltd .: Turbidimeter, model name: NDH2000”, the surface unevenness of the transparent resin film. What is necessary is just to measure so that the surface of the structure faces the light source.

  When the haze of the transparent resin film is 3% or less, the string-proof property is not obtained. When the transparent resin film is 70% or more, when the transparent resin film is pasted on the monitor of the liquid crystal display panel, sufficient visibility of the image (ease of viewing) ) Is not obtained.

  Further, the tensile modulus of elasticity in the machine direction (MD direction) of the cellulose ester film constituting the optical film according to the present invention is 1500 MPa to 3500 MPa, and the tensile modulus of elasticity in the direction perpendicular to the machine direction (TD direction) is 3000 MPa to 4500 MPa. It is preferable that the ratio of the elastic modulus in the TD direction / elastic modulus in the MD direction is 1.40 to 1.90.

  Here, if the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the optical film is less than 1.40, the winding of the film having a width exceeding 1650 mm increases the sag of the central portion, and the winding core film Since sticking increases, it is not preferable. Further, if the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction exceeds 1.90, warpage after overheating on the deflecting plate occurs, or the backlight is heated by the heat of the backlight when incorporated in the liquid crystal panel. Since the dimensional change behavior of the polarizing plate on the side and the surface side is greatly different, unevenness occurs in the corner, which is not preferable.

  As a specific method for measuring the tensile modulus of elasticity in the MD direction and TD direction of the film, for example, the method of JIS K7217 can be mentioned.

  That is, using a tensile tester (TG-2KN, manufactured by Minebea Co., Ltd.), a sample was set at a chucking pressure: 0.25 MPa, a distance between marked lines: 100 ± 10 mm, and a pulling speed: 100 ± 10 mm / min. Pull on. As a result, from the obtained tensile stress-strain curve, the elastic modulus calculation start point is 10N, the end point is 30N, and the tangent line drawn between them is extrapolated to calculate the elastic modulus.

  In the optical film of the present invention, the in-plane retardation (Ro) defined by the following formula is 30 to 300 nm under the conditions of a temperature of 23 ° C. and a humidity of 55% RH, and the thickness direction retardation (Rt) is a temperature of 23 ° C. and humidity. It is preferably 70 to 400 nm under the condition of 55% RH.

Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is the film. The refractive index in the thickness direction (refractive index measured at a wavelength of 590 nm), d represents the thickness (nm) of the film.

  The retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, using KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), the wavelength can be obtained at 590 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH.

[Cycloolefin polymer film]
The cycloolefin polymer film preferably used in the present invention will be described.

  The cycloolefin polymer used in the present invention is composed of a polymer resin containing an alicyclic structure.

  A preferred cycloolefin polymer is a resin obtained by polymerizing or copolymerizing a cyclic olefin. Examples of the cyclic olefin include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, tetracyclo [7.4.0.110, 13.02,7] trideca-2,4. Unsaturated hydrocarbons of polycyclic structures such as 6,11-tetraene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- (2-methylbutyl) -1-cyclohexene, cyclo Examples thereof include monocyclic unsaturated hydrocarbons such as octene, 3a, 5,6,7a-tetrahydro-4,7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene, and derivatives thereof. These cyclic olefins may have a polar group as a substituent. Examples of the polar group include a hydroxyl group, a carboxyl group, an alkoxyl group, an epoxy group, a glycidyl group, an oxycarbonyl group, a carbonyl group, an amino group, an ester group, and a carboxylic acid anhydride group. Or a carboxylic anhydride group is preferred.

  Preferred cycloolefin polymers may be those obtained by addition copolymerization of monomers other than cyclic olefins. Addition copolymerizable monomers include ethylene, propylene, 1-butene, 1-pentene and other ethylene or α-olefins; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl- Examples include dienes such as 1,4-hexadiene and 1,7-octadiene.

The cyclic olefin is obtained by an addition polymerization reaction or a metathesis ring-opening polymerization reaction. The polymerization is carried out in the presence of a catalyst. Examples of the addition polymerization catalyst include a polymerization catalyst composed of a vanadium compound and an organoaluminum compound. As a catalyst for ring-opening polymerization, a polymerization catalyst comprising a metal halide such as ruthenium, rhodium, palladium, osmium, iridium, platinum, nitrate or acetylacetone compound, and a reducing agent; or titanium, vanadium, zirconium, tungsten, molybdenum And a polymerization catalyst comprising a metal halide such as acetylacetone compound and an organoaluminum compound. The polymerization temperature, pressure and the like are not particularly limited, but the polymerization is usually carried out at a polymerization temperature of −50 ° C. to 100 ° C. and a polymerization pressure of 0 to 490 N / cm ² .

  The cycloolefin polymer used in the present invention is preferably a polymer obtained by polymerizing or copolymerizing a cyclic olefin, followed by a hydrogenation reaction to change the unsaturated bond in the molecule to a saturated bond. The hydrogenation reaction is performed by blowing hydrogen in the presence of a known hydrogenation catalyst. Examples of hydrogenation catalysts include cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, transition metal compounds such as titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, tetrabutoxytitanate / dimethylmagnesium / alkyl. Homogeneous catalyst consisting of a combination of metal compounds; heterogeneous metal catalyst such as nickel, palladium, platinum; nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / diatomaceous earth And a heterogeneous solid-supported catalyst in which a metal catalyst such as palladium / alumina is supported on a carrier.

  Or the following norbornene-type polymer is also mentioned as a cycloolefin polymer. The norbornene-based polymer preferably has a norbornene skeleton as a repeating unit. Specific examples thereof include JP-A-62-252406, JP-A-62-2252407, and JP-A-2-133413. JP-A-63-145324, JP-A-63-264626, JP-A-1-240517, JP-B-57-8815, JP-A-5-39403, JP-A-5-43663 JP-A-5-43834, JP-A-5-70655, JP-A-5-279554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411, Although what was described in the Kaihei 9-241484 gazette etc. can be utilized preferably, it is not limited to these. Moreover, these may be used individually by 1 type and may use 2 or more types together.

  Examples of other monomers copolymerizable with the norbornene-based monomer include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, C2-C20 alpha olefins, such as 1-hexadecene, 1-octadecene, 1-eicocene, and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, cyclooctene, 3a, 5,6,7a-tetrahydro-4,7 -Cycloolefins such as methano-1H-indene, and derivatives thereof; non 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadiene, etc. Conjugated dienes; and the like are used. Among these, an α-olefin, particularly ethylene is preferable.

  These other monomers copolymerizable with the norbornene-based monomer can be used alone or in combination of two or more. In the case of addition copolymerization of a norbornene monomer and another monomer copolymerizable therewith, the ratio of the structural unit derived from the norbornene monomer and the structural unit derived from the other monomer copolymerizable in the addition copolymer However, it is appropriately selected so that the mass ratio is usually 30:70 to 99: 1, preferably 50:50 to 97: 3, more preferably 70:30 to 95: 5.

  When the unsaturated bond remaining in the molecular chain of the synthesized polymer is saturated by a hydrogenation reaction, the hydrogenation rate is 90% or more, preferably 95% or more, particularly from the viewpoint of light resistance deterioration, weather resistance deterioration, etc. Preferably it is 99% or more.

  In addition, examples of the cycloolefin polymer used in the present invention include thermoplastic saturated norbornene resins described in paragraph Nos. [0014] to [0019] of JP-A No. 5-2108, paragraph No. [0015] of JP-A No. 2001-277430. ] To [0031] thermoplastic norbornene polymers, JP 2003-14901 paragraph Nos. [0008] to [0045] thermoplastic norbornene resins, JP 2003-139950 paragraph Nos. [0014] to [0028] Norbornene-based resin composition, paragraph Nos. [0029] to [0037] described in JP-A No. 2003-161832, paragraph Nos. [0027] to [0036] described in JP-A No. 2003-195268 Norbornene-based resin, JP2003-21158 Paragraph Nos. [0009] to [0023] alicyclic structure-containing polymer resin, norbornene polymer resin or vinyl alicyclic hydrocarbon described in JP-A-2003-212588, paragraph Nos. [0008] to [0024] Polymer resin etc. are mentioned.

  Specifically, ZEONEX, ZEONOR manufactured by Nippon Zeon Co., Ltd., Arton manufactured by JSR Corporation, APPEL manufactured by Mitsui Chemicals, Inc. (APL8008T, APL6509T, APL6013T, APL5014DP, APL6015T) and the like are preferably used.

  The molecular weight of the cycloolefin polymer used in the present invention is appropriately selected according to the purpose of use, but was measured by gel permeation chromatography method of cyclohexane solution (toluene solution when the polymer resin is not dissolved). When the polyisoprene or polystyrene-equivalent weight average molecular weight is usually in the range of 5,000 to 500,000, preferably 8,000 to 200,000, more preferably 10,000 to 100,000, the mechanical strength and molding processability of the molded body are high. It is preferable to be balanced.

  The cycloolefin polymer film may contain an additive that can be generally blended into a plastic film, if necessary. Examples of such additives include heat stabilizers, light stabilizers, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, and fillers, and the content thereof is within a range that does not impair the purpose of the present invention. You can choose.

  There is no particular limitation on the method for forming the cycloolefin polymer film, and either a hot melt molding method or a solution casting method can be used. The heat-melt molding method can be further classified into an extrusion molding method, a press molding method, an inflation molding method, an injection molding method, a blow molding method, a stretch molding method, etc. Among these methods, mechanical strength, surface accuracy are included. In order to obtain an excellent film, an extrusion molding method, an inflation molding method, and a press molding method are preferable, and an extrusion molding method is most preferable. The molding conditions are appropriately selected depending on the purpose of use and the molding method. In the case of the hot melt molding method, the cylinder temperature is usually in the range of 150 to 400 ° C, preferably 200 to 350 ° C, more preferably 230 to 330 ° C. Is set as appropriate. If the resin temperature is too low, fluidity will deteriorate, causing shrinkage and distortion in the film. If the resin temperature is too high, voids and silver streaks will occur due to thermal decomposition of the resin, and the film will turn yellow. Defects may occur. The thickness of the film is usually in the range of 5 to 300 μm, preferably 10 to 200 μm, more preferably 20 to 100 μm. When the thickness is too thin, handling at the time of lamination becomes difficult, and when it is too thick, the drying time after the lamination becomes long and the productivity is lowered.

  The cycloolefin polymer film has a surface wetting tension of preferably 40 mN / m or more, more preferably 50 mN / m or more, and even more preferably 55 mN / m or more. When the surface wetting tension is in the above range, the adhesive strength between the film and the polarizing film is improved. In order to adjust the surface wetting tension, for example, corona discharge treatment, ozone spraying, ultraviolet irradiation, flame treatment, chemical treatment, and other known surface treatments can be performed.

  The sheet before stretching needs to have a thickness of about 50 to 500 μm, and the thickness unevenness is preferably as small as possible. The entire surface is within ± 8%, preferably within ± 6%, more preferably within ± 4%. is there.

  In order to make the said cycloolefin polymer film into the optical film of this invention, it can obtain by the manufacturing method similar to the cellulose-ester film mentioned above. Moreover, it is obtained by extending | stretching a sheet | seat at least to a uniaxial direction. In addition, it may be substantially uniaxial stretching, for example, biaxial stretching in which uniaxial stretching is performed in order to orient the molecules after stretching in a range that does not affect the molecular orientation. For stretching, it is preferable to use the tenter device or the like.

  In the film thus obtained, the molecules are oriented by stretching, and can have a retardation having a desired size. In the present invention, the in-plane retardation value Ro at 589 nm is 30 to 100 nm, and more preferably 40 to 70 nm. Further, the thickness direction retardation value Rt is 70 to 300 nm, and more preferably 100 to 250 nm.

  Retardation can be controlled by the retardation of the sheet before stretching, the stretching ratio, the stretching temperature, and the thickness of the stretched oriented film. When the sheet before stretching has a constant thickness, the absolute value of retardation tends to increase as the stretching ratio of the film increases. Therefore, a stretched oriented film having a desired retardation can be obtained by changing the stretching ratio.

  The retardation variation is preferably as small as possible, and the cycloolefin polymer film of the present invention has a retardation variation within a wavelength of 589 nm usually within ± 50 nm, preferably within ± 30 nm, more preferably within ± 20 nm.

  The variation and thickness unevenness in the retardation plane can be reduced by using such a small pre-stretched sheet and by applying a uniform stress to the sheet during stretching. For that purpose, it is desirable to stretch in a controlled temperature environment under a uniform temperature distribution, preferably within ± 5 ° C., more preferably within ± 2 ° C., particularly preferably within ± 0.5 ° C.

[Polycarbonate film]
There are various types of polycarbonate resins used for producing polycarbonate films, and aromatic polycarbonates are preferable from the viewpoint of chemical properties and physical properties, and bisphenol A polycarbonates are particularly preferable. Among them, more preferred is a bisphenol A derivative in which a benzene ring, a cyclohexane ring, or an aliphatic hydrocarbon group is introduced into bisphenol A, but these groups are introduced asymmetrically with respect to the central carbon. A polycarbonate having a structure in which the anisotropy in the unit molecule is reduced, obtained by using the obtained derivative is preferable. For example, one in which two methyl groups on the central carbon of bisphenol A are replaced with benzene rings, and one hydrogen on each benzene ring in bisphenol A is replaced asymmetrically with respect to the central carbon by methyl groups or phenyl groups The polycarbonate obtained is preferred.

  Specifically, 4,4′-dihydroxydiphenylalkane or a halogen-substituted product thereof is obtained by a phosgene method or a transesterification method. For example, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenylethane 4,4'-dihydroxydiphenylbutane and the like.

  The optical film made of the polycarbonate resin used in the present invention may be used by mixing with a transparent resin such as polystyrene resin, methyl methacrylate resin or cellulose acetate resin, or at least one of the cellulose acetate films. A polycarbonate resin may be laminated on the surface.

  The production method of the polycarbonate film that can be used in the present invention is not particularly limited. That is, any of a film by an extrusion method, a film by a solvent casting method, a film by a calendar method, and the like may be used.

  In the present invention, a polycarbonate film having a glass transition point (Tg) of 110 ° C. or more and a water absorption (measured under conditions of 23 ° C. water for 24 hours) of 0.3% or less is used. It is good. More preferably, Tg is 120 ° C. or higher and water absorption is 0.2% or less.

  Next, the case where the optical film according to the present invention is produced by the melt casting method will be described.

  In order to produce the optical film according to the present invention by the melt casting film forming method, the same resin as in the case of the above solution casting film forming method can be used.

  For example, cellulose ester films such as cellulose diacetate film, cellulose triacetate film, cellulose acetate butyrate film, cellulose acetate propionate film, polyester film, polycarbonate film, polyarylate film, polysulfone (including polyethersulfone) ) Film, polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, polycarbonate film, cycloolefin film Polymer film (Arton ( SR Inc.), ZEONEX, ZEONOR (manufactured by ZEON CORPORATION), polymethylpentene film, polyetherketone film, polyetherketoneimide film, polyamide film, fluororesin film, nylon film, polymethylmethacrylate film, acrylic film Or a glass plate etc. Among them, a cellulose ester film, a cycloolefin polymer film, a polycarbonate film, and a polysulfone (including polyethersulfone) film are preferable.

  In the present invention, in particular, the transparent resin film is a cellulose ester-based resin film or a resin film containing 80% or more of a cyclic olefin-based addition polymer, in terms of production, cost, transparency, adhesiveness, etc. From the viewpoint of, it is preferably used.

  As the cellulose ester resin, at least one resin selected from the group consisting of cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate It is preferable that

  The degree of substitution of the acetyl group of the cellulose ester resin is preferably at least 1.5 or more because the resulting film has excellent dimensional stability. The method for measuring the substitution degree of the acyl group of the cellulose ester resin can be carried out in accordance with ASTM D-817-91. The molecular weight of the cellulose ester resin is preferably 50,000 to 300,000, particularly 60,000 to 200,000 as the number average molecular weight because the mechanical strength of the resulting film can be increased.

  In the cellulose ester resin of the present invention, a plasticizer, an ultraviolet absorber, an antioxidant, a matting agent, an antistatic agent, a flame retardant, for various purposes, as in the case of the solution casting film forming method described above. Additives such as dyes and oils can be included.

  In order to manufacture the optical film according to the present invention by the melt casting film forming method, for example, after mixing the materials of the cellulose ester resin film, using an extruder, the material is melt extruded from the casting die onto the cooling drum, and the first The two cooling drums of the cooling drum and the second cooling drum are sequentially circumscribed, cooled and solidified to form an unstretched film (web), and the unstretched film (web) peeled off by a peeling roll is then transferred to a film ( The both ends of the web) are gripped and stretched in the width direction.

  In this case, the uniformity of retardation of the film after stretching can be improved by adjusting the surface temperature of the two cooling drums and the rotational speed (circumferential speed) of the cooling drum.

  Here, a method in which a cellulose ester resin is melt-extruded from a casting die onto a cooling drum and cooled and solidified on the cooling drum is called a melt-casting film forming method.

  As the melt casting film forming method, there are a melt extrusion method such as a method using a casting die and an inflation method, a calendar method, a heat press method, an injection molding method, etc., but in the present invention, the thickness unevenness is small, A method using a casting die that can be easily processed to a thickness of about 50 to 500 μm and that can reduce film thickness unevenness and retardation unevenness is employed.

  The material of the cellulose ester resin film is preferably dried in advance. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less, using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

  Cellulose ester resins and stabilizers are preferably mixed with a mixer before melting, but plasticizers, UV absorbers, and matting agents are also mixed with a mixer before melting. You can also keep it. As the mixer, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, or the like can be used.

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

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

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

  In the present invention, in addition to the method of directly forming a film using an extruder after mixing the materials, it is also possible to form a film by once pelletizing and then melting the pellet with an extruder. In a system in which a plurality of materials having different melting points are mixed, a so-called braided semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is introduced into an extruder. It is also possible to film. When using resins and additives that are susceptible to thermal decomposition, in order to reduce the number of times the resin is melted, a method of directly forming a film without producing pellets, A method of forming a film from is preferred.

  In the present invention, the extruder used for film formation may be a single screw extruder or a twin screw extruder. In the case of forming a film directly without forming pellets from the material, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is necessary. However, even with a single-screw extruder, the screw shape is a Maddock type, Unimelt type. By changing to a kneading type screw such as a mold or a dull mage, moderate kneading can be obtained and film formation becomes possible. In both the single screw extruder and the twin screw extruder, it is desirable to provide a vent port and remove gas from the vent port using a vacuum pump or the like. Once a pellet or braided semi-melt is produced, it may be a single screw extruder or a twin screw extruder.

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

  Although the preferable conditions for the melting temperature of the resin in the extruder vary depending on the viscosity and discharge amount of the resin, the thickness of the sheet to be manufactured, etc., in general, the glass transition temperature relative to the glass transition temperature (Tg) of the molding material. The glass transition temperature (Tg) is preferably in the range of (Tg) to 100 ° C. or higher. More preferably, the melting temperature is glass transition temperature (Tg) + 10 ° C. or higher and glass transition temperature (Tg) + 90 ° C. or lower. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. The residence time of the resin in the extruder is preferably short, and is within 5 minutes, more preferably within 3 minutes, and most preferably within 2 minutes. The residence time depends on the type of extruder and the extrusion conditions, but can be shortened by adjusting the material supply rate, L / D, screw rotation speed, screw groove depth, etc. It is.

  The shape, rotation speed, and the like of the screw of the extruder are appropriately selected depending on the viscosity and discharge amount of the resin. In the present invention, the shear rate in the extruder is preferably 1 / second to 10000 / second, more preferably 5 / second to 1000 / second, and most preferably 10 / second to 100 / second. In order to prevent biting of the gear pump and reduce the main filter load, it is preferable to provide a prefilter on the exit side of the extruder.

  For example, a 50/80/100 mesh screen or a metal fiber sintered filter is preferably provided as necessary. It is preferable to use a type that can be changed online.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Moreover, it is preferable to provide a filter downstream of the prefilter. A stainless fiber sintered filter is preferably used. Stainless steel fiber sintered filter is made by compressing the stainless fiber body after creating a complex intertwined state, and sintering and integrating the contact points. The density is changed according to the thickness and compression amount of the fiber, and the filtration accuracy Can be adjusted. It is preferable to use a multilayer body in which the filtration accuracy is repeated coarsely and densely multiple times. Further, it is preferable to adopt a configuration in which the filtration accuracy is sequentially increased or a method in which coarse and dense filtration accuracy is repeated, so that the filtration life of the filter can be extended and the accuracy of capturing foreign matters and gels can be improved. The filtration accuracy is preferably 0.5 μm or more and 50 μm or less.

  In the present invention, the material of the cellulose ester-based resin film is melt-extruded from the casting T die using an extruder, and sequentially circumscribed on the two cooling drums of the first cooling drum and the second cooling drum. Straighten and cool and solidify into an unstretched film.

  When the cooling drum with which the material extruded from the casting die first comes into contact is the first cooling drum, the time until the material contacts the first cooling drum from the casting die is preferably shorter, preferably within 10 seconds. Is within 5 seconds, most preferably within 2 seconds. Further, the distance from the casting die to the first cooling drum is preferably 10 mm or more and 100 mm or less.

  In the present invention, at this time, the surface temperatures of the first cooling drum and the second cooling drum are set to a glass transition temperature (Tg) of −100 degrees or more and a glass transition temperature (Tg) of −20 degrees or less.

  By setting the surface temperatures of the first cooling drum and the second cooling drum within this range, it is possible to suppress the occurrence of slight retardation unevenness due to conveyance tension or the like.

  In the present invention, when the peripheral speed of the first cooling drum is V1 and the peripheral speed of the second cooling drum is V2, the ratio between the peripheral speed of the second cooling drum and the peripheral speed of the first cooling drum: V2 / V1 is set to 0.950 or more and 0.999 or less.

  By setting the ratio of the peripheral speed of the second cooling drum to the peripheral speed of the first cooling drum: V2 / V1 within this range, the occurrence of slight retardation unevenness due to the transport tension or the like can be suppressed.

  In order to improve smoothness with respect to both surfaces of the film, it is preferable that a third cooling drum is disposed subsequent to the second cooling drum. For example, the surface temperature of the third cooling drum may be the second cooling drum. The surface temperature is preferably the same.

  If the peripheral speed of the third cooling drum is V3, the peripheral speed of the third cooling drum V3 and the second cooling are in the relationship between the peripheral speed V2 of the second cooling drum and the peripheral speed V1 of the first cooling drum. Ratio to the peripheral speed V2 of the drum: It is preferable that V3 / V2 = V2 / V1.

  In the melt casting film forming method, when flaws or foreign matters adhere to the casting die, streak-like defects may occur. Such a defect is called a die line, but in order to reduce surface defects such as the die line, the piping from the extruder to the casting die should have a structure that minimizes the resin retention. Is preferred. It is preferable to use a casting die that has as few scratches as possible inside the lip. Since the volatile component is deposited from the resin around the casting die and may cause a die line, it is preferable to suck the atmosphere containing the volatile component. Moreover, since it may precipitate also in apparatuses, such as an electrostatic application, it is preferable to apply alternating current or to prevent precipitation with another heating means.

  The casting die is not particularly limited as long as it is used for producing a sheet or a film, but a coat hanger die is preferable. The lip portion gap t is preferably 0.1 mm or more and 2 mm or less, and the land portion length L is preferably 5 mm or more and 50 mm or less. L / t is preferably 10 or more.

  Thickness adjustment mechanisms include a heater type that adjusts the temperature by dividing in the width direction, a manual bolt type that adjusts the lip opening mechanically, or a lip opening adjustment that uses expansion and contraction of the bolts with a heater. It is preferable to use a heat bolt system or the like.

  Casting die materials are hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. Stuff.

  A preferred material for the die lip is the same as that of the casting die. The surface accuracy of the lip portion is preferably 0.5S or less, and more preferably 0.2S or less.

  Here, the cellulose ester resin is melt-extruded from the casting die onto the cooling drum. The temperature of the cooling drum is preferably adjusted by flowing a heat medium such as water or oil into the cooling drum.

  In the present invention, when the cellulose ester resin flows out from the casting die, it is preferable to attach a suction device in the vicinity of the casting die in order to prevent contamination of the casting die and the cooling drum with sublimates. The suction device needs to be treated such as heating with a heater so that the device itself does not become a place where the sublimate is attached. On the other hand, if the suction pressure is too large, film quality such as unevenness is affected. Conversely, if the suction pressure is too small, the sublimate cannot be sucked effectively.

  In the present invention, the film and the cooling drum are preferably in close contact. As a method for bringing the film and the cooling drum into close contact, pressing using a touch roll, an electrostatic contact method, an air knife, a decompression chamber, or the like can be used.

  It is preferable that two or more cooling drums are provided in order to improve smoothness on both sides of the film, and that both sides are brought into contact with the cooling drum. Further, the cooling drum can be provided with cleaning equipment such as a cleaning roll.

  The temperature unevenness of the cooling drum is preferably 0.5 ° C. or less. The speed unevenness is preferably 0.5% or less. The surface of the cooling drum can use hard chrome plating, but is not limited thereto. The surface roughness is preferably 0.1 s or less. As the material of the touch roll, a metal or a material obtained by winding a resin, rubber or the like around a metal roll can be used.

  In the present invention, a film-like cellulose ester resin in a molten state from a T-die is brought into close contact with the first cooling drum, the second cooling drum, and the third cooling drum in order to be cooled and solidified, and unstretched cellulose. An ester resin film (web) is obtained. The cooled and solidified film (web) peeled from the third cooling drum by the peeling roll is guided to a stretching machine through a dancer roll (film tension adjusting roll), where the film is stretched in the width direction.

As described above, the optical film according to the present invention is made of a transparent resin film having 1.5 to 10 holes on average per 100 μm ³ , and the inner volume of the holes is 0.002 μm on average. ³ or more and 0.6μm ³ below. The internal volume of the pores has an average value in the 0.01 [mu] m ³ or more, preferably 0.55 .mu.m ³ or less.

  In the optical film according to the present invention, the long side of the pores is an average value of 0.2 μm or more and 3 μm or less. The long sides of the holes are preferably 0.5 μm or more and 2.5 μm or less on average.

  In the optical film according to the present invention, the short side of the holes has an average value of 0.05 μm or more and 0.2 μm or less. The short sides of the holes are preferably 0.06 μm or more and 0.12 μm or less on average.

  Further, in the optical film according to the present invention, the long side of the hole is 75 degrees or more and 115 degrees or less with respect to the slow axis of the optical film, preferably 85 degrees or more and 95 degrees or less, Most preferably, it is 88 degrees or more and 91 degrees or less.

  In order to manufacture an optical film by adjusting the number of holes of the optical film, the internal volume of the holes, the long side of the hole, and the short side of the hole, It can be carried out by appropriately setting the residual solvent amount of the web (film), the stretching ratio of the film in the tenter in the stretching step, and the stretching temperature in the tenter.

  In the production of the optical film of the present invention, for example, for a film after extrusion molding, before stretching with a tenter, methylene chloride vapor is sprayed in advance from both sides of the film so that the entire film contains methylene chloride. The film is stretched with a tenter.

  That is, the residual solvent amount of the film immediately before entering the tenter of the stretching process is 0.6 to 10.0% by mass, preferably 0.6 to 5.0% by mass, and further 0.8 to 2%. Most preferably, it is 0.0 mass%.

  Moreover, in this invention, the draw ratio of the film in the tenter of a extending process is 1.1 to 1.5 times, and it is preferable that it is 1.2 to 1.4 times.

  Furthermore, the temperature of the hot air blown from the hot air blowing slit port in the tenter is 95 to 200 ° C, and preferably 100 to 150 ° C.

  In the most preferable embodiment of the method for producing an optical film according to the present invention, a melt of a resin mixture containing a polymer and an additive other than the polymer is extruded into a film form from a casting die and then sandwiched by a cooling rotator. In the method for producing an optical film by a melt casting film forming method, the optical film is obtained by winding through a stretching process in which both ends of the cooling film are gripped and stretched in the width direction, and then cooled. The amount of residual solvent in the film immediately before entering the tenter in the stretching process is 0.8 to 2.0 mass%, the stretching ratio of the film in the tenter in the stretching process is 1.2 to 1.3 times, and the temperature in the tenter The temperature (stretching temperature) of the hot air blown out from the air blowing slit port is 100 to 110 ° C.

  Further, in the optical film according to the present invention, the long side of the hole is 75 degrees or more and 115 degrees or less with respect to the slow axis of the optical film, preferably 85 degrees or more and 95 degrees or less, Most preferably, it is 88 degrees or more and 91 degrees or less.

  Further, in this way, in the optical film according to the present invention manufactured by the melt casting film forming method, it is preferable that the pores exist within 20% or more of the total thickness from the surface of the optical film.

  In order to manufacture such an optical film, for example, after stretching the film in the width direction by a tenter, the tension in the width direction is relaxed to release the width retention, followed by the surface by the following solvent. Perform the process. That is, a vapor of a solvent such as methylene chloride is sprayed on both surfaces of the stretched and tension-reduced film to form an atmosphere containing the solvent near the film surface, and then the surface-treated film is placed between a pair of rolls. Thus, the optical film according to the present invention in which the pores are present in the interior of 20% or more of the total thickness from the surface of the optical film is obtained.

  It is preferable that the surface-treated film thus obtained is further transported for a required time in a drying zone set at a predetermined temperature to be dried to disperse the solvent and the like.

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

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

  The film thickness of the optical film varies depending on the purpose of use, but as a finished film, the film thickness range used in the present invention is 30 to 200 μm, and the recent thin tendency is preferably 40 to 120 μm, particularly 40 to A range of 100 μm is preferred. The average film thickness of the film can be adjusted by controlling the extrusion flow rate, the gap of the casting port of the casting die, the speed of the cooling drum, and the like so as to obtain a desired thickness.

  After slitting the edge of the film to a product width with a slitter and cutting it off, the film is subjected to knurling (embossing) on both ends of the film by a knurling device consisting of an embossing ring and a back roll, and wound by a winder. This prevents sticking in the optical film (winding) and generation of scratches. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  Thus, unlike the resin film molded by the solution casting film forming method, the cellulose ester-based resin film molded by the method for producing an optical film by the melt casting film forming method of the present invention has a thickness direction retardation ( Rt) is small, and by stretching such a cellulose ester resin film, in-plane retardation (Ro) can be easily expressed. In addition, since there is no need to increase the draw ratio, the risk of breakage is small and stable production can be achieved.

The optical film according to the present invention is made of a transparent resin film having 1.5 to 10 holes on an average per 100 μm ³ , and the inner volume of the holes is 0.002 μm ³ or more on the average and 0.005 μm. 6 μm ³ or less.

The average number of pores per 100 μm ³ is preferably 1.5 to 10 in order to obtain the effect of the present invention. Here, if the average number of holes in the optical film is less than 1.5 per 100 μm ³ , the effect of expanding the viewing angle of the present invention is reduced, which is not preferable. Moreover, since the transparency of an optical film will be impaired when the void | hole exceeds 10 on an average per 100 micrometers ³ , it is unpreferable.

The internal volume of the pores of the optical film according to the present invention, 0.002 .mu.m ³ or the average value is 0.6 .mu.m ³ or less. Here, if the internal volume of the pores is less than 0.002 μm ^{3 on} average, the effect of enlarging the viewing angle is reduced, which is not preferable. Moreover, since the transparency of an optical film will be impaired when the internal volume of a void | hole exceeds 0.6 micrometer ³ by an average value, it is unpreferable. Internal volume of the pores of the optical film, the average value at 0.01 [mu] m ³ or more, preferably 0.55 .mu.m ³ or less.

  In the optical film according to the present invention, the long side of the holes has an average value of 0.2 μm or more and 3 μm or less. The long sides of the holes are preferably 0.5 μm or more and 2.5 μm or less on average. Here, if the long side of the holes is less than 0.2 μm on average, the effect of enlarging the viewing angle is reduced, and if the long side of the holes exceeds 3 μm on average, the optical film The transparency of the glass is impaired.

  In the optical film according to the present invention, the short side of the pores has an average value of 0.05 μm or more and 0.2 μm or less. Here, if the short side of the hole is less than 0.05 μm on average, the effect of expanding the viewing angle is reduced, and if the short side of the hole exceeds 0.2 μm on average, The transparency of the optical film is impaired.

  In the optical film according to the present invention, pores are present in the interior of 20% or more of the total thickness from the surface of the optical film. Here, if the presence of pores is within the range of less than 20% of the total thickness from the surface of the optical film, the effect of expanding the viewing angle into the adhesive during the polarizing plate processing cannot be expected, and the optical film is transparent. Sexuality is impaired.

  In the optical film according to the present invention, the long side of the pore is 75 degrees or more and 115 degrees or less with respect to the slow axis of the optical film. Here, if the long side of the hole is less than 75 degrees with respect to the slow axis of the optical film, the effect of widening the viewing angle cannot be obtained sufficiently. If the long side of the hole exceeds 115 degrees with respect to the slow axis of the optical film, the effect of widening the viewing angle cannot be obtained sufficiently.

  And the liquid crystal display device which has a favorable viewing angle characteristic can be provided by using the above optical films of this invention for a liquid crystal display device.

  The optical film obtained by the present invention can be made into a polarizing plate by bonding to at least one surface of a polarizing film.

  The polarizing film is a film that has been conventionally stretched, such as a polyvinyl alcohol film that can be stretched and oriented, treated with a dichroic dye such as iodine. Since the polarizing film itself does not have sufficient strength and durability, a polarizing plate is generally obtained by adhering a cellulose triacetate film having no anisotropy as a protective film to both sides thereof. The optical film obtained by the present invention may be prepared by bonding to the polarizing plate with the protective film, or may also be prepared by directly bonding to the polarizing film also serving as the protective film.

  In particular, since the optical film obtained according to the present invention has a slow axis in the width direction, it can be bonded between the polarizing film and long rolls without cutting, and the productivity of the polarizing plate is dramatically increased. Improve.

  The polarizing plate is a sticking type in which a peelable sheet is laminated on one or both sides thereof via a pressure sensitive adhesive layer (for example, an acrylic pressure sensitive adhesive layer). Or the like can be easily attached).

  Thus, the obtained polarizing plate is provided in the one or both surfaces of a liquid crystal cell, and a liquid crystal display device is obtained using this.

  An image display device capable of realizing an easy-to-view display having a high contrast ratio over a wide range, particularly a liquid crystal display device operating in an IPS mode, includes a liquid crystal cell driven in an IPS mode comprising a pair of substrates sandwiching a liquid crystal layer, A liquid crystal display device having a pair of polarizing plates disposed in an orthogonal state on both sides of a liquid crystal cell, wherein the optical film of the present invention is provided on the liquid crystal cell side of at least one polarizing plate.

  A liquid crystal display device composed of a polarizing plate using the optical film of the present invention is used to develop a higher display quality than a normal polarizing plate.

  The polarizing plate of the present invention has an MVA (Multi-domestic Vertical Alignment) mode typified by a vertical alignment mode, in particular, an MVA mode divided into four, a known PVA (Patterned Vertical Alignment) mode multi-domained by electrode arrangement, an electrode It can be effectively used in a CPA (Continuous Pinwheel Alignment) mode in which arrangement and chiral ability are fused. In addition, a proposal of an optically biaxial film in conformity with the OCB (Optical Compensated Bend) mode is disclosed, and “T.Miyashita, T.Uchida: J.SID, 3 (1), 29 ( 1995) ”, the polarizing plate of the present invention can also exhibit the effect of the present invention in display quality. If the effect of this invention can be expressed by using the polarizing plate of this invention, arrangement | positioning of a liquid crystal mode and a polarizing plate will not be limited. In particular, the optical film of the present invention is preferably used in a vertical alignment mode liquid crystal display device, and particularly preferably used in a liquid crystal display device of MVA (Multi-domestic Vertical Alignment) mode.

  The display quality of the display cell is preferably symmetrical with respect to human observation. Therefore, when the display cell is a liquid crystal display cell, it is possible to multiplex domains by giving priority to the symmetry on the observation side. A known method can be used to divide the domain, and can be determined in consideration of the properties of a known liquid crystal mode by a two-part dividing method, more preferably a four-part dividing method.

  Liquid crystal display devices are being applied to color display and moving image display devices, and the display quality in the present invention is less fatigued and more faithful to display moving images due to improved contrast and resistance to polarizing plates. It becomes.

  In the liquid crystal display device of the present invention, a polarizing plate using the optical film of the present invention is disposed only on one surface of the liquid crystal cell or on both surfaces. At this time, by using the optical film of the present invention contained in the polarizing plate so as to be on the liquid crystal cell side, the display quality can be improved.

  Examples of the present invention and comparative examples will be described below, but the present invention is not limited to these examples.

Example 1
(Preparation of dope)
100 parts by mass of cellulose acetate propionate (total substitution degree 2.50, number average molecular weight 70000, weight average molecular weight 180000, intrinsic viscosity (IV) 1.4: referred to as cellulose ester A)
Aromatic terminal ester plasticizer (example of compound (1)) 6 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole (ultraviolet absorber) 1 part by mass Ruethyl glycolate 4 parts by weight Dichloromethane 450 parts by weight Ethyl alcohol 50 parts by weight A dope solution having the above composition was prepared. First, methylene chloride and ethyl alcohol were added to the pressure dissolution tank. Cellulose acetate propionate was added to a pressurized dissolution tank containing a solvent while stirring. This was heated and stirred to dissolve completely, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. A dope solution was prepared by filtration using 244.

(Preparation of fine particle dispersion)
Fine particles (Aerosil R972V (produced by Nippon Aerosil Co., Ltd.)) 11 parts by mass (average diameter of primary particles 16 nm, apparent specific gravity 90 g / liter)
89 parts by mass of ethyl alcohol The above materials were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to prepare a fine particle dispersion.

(Preparation of fine particle additive solution)
Methylene chloride 99 parts by weight Cellulose acetate propionate 4 parts by weight Fine particle dispersion 11 parts by weight Cellulose acetate propionate was added to a dissolution tank containing methylene chloride, heated to completely dissolve, Azumi filter paper No. Filtered using 244. While finely stirring the filtered cellulose ester solution, the fine particle dispersion was slowly added thereto. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

  Next, 100 parts by mass of the dope solution and 5 parts by mass of the fine particle additive solution are added and mixed thoroughly with an in-line mixer (Toray static type in-pipe mixer, Hi-Mixer, SWJ), and then a belt casting apparatus is used. And uniformly cast on a stainless steel band support having a width of 2 m. Peeling was performed on a stainless steel band support under conditions of a peeling tension of 130 N / m, a residual solvent amount of 100% by mass, and a cold air temperature of 20 ° C.

  Next, a drying device was provided before the tenter of the stretching process, and the web (film) was dried with a drying air at a temperature of 100 ° C.

  Thereafter, both ends of the width direction of the web (film) were held with a tenter, and the amount of residual solvent at the start of stretching, the stretching temperature, and the stretching ratio were performed under the conditions described in Table 1 below. Then, after the tension in the width direction of the web (film) was relaxed, the width retention was released.

  Following this, surface treatment with the following solvents was performed. That is, after stretching, methylene chloride vapor is sprayed on both sides of the web (film) whose tension has been relaxed to form an atmosphere containing a solvent near the surface of the web (film), and then the surface-treated web ( Film) is passed between a pair of rolls, whereby an optical film according to the present invention in which pores are present in the interior of 20% or more of the total thickness from the surface of the optical film is obtained.

  The surface-treated web (film) thus obtained is further conveyed for 30 minutes in a third drying zone set at 125 ° C. for drying and generally embossed before being introduced into the winding process. From the cellulose acetate propionate with a film thickness of 45μm that has a knurling (unevenness due to embossing) with a width of 1.4m and a width of 1cm and a height of 6μm. An optical film was produced.

When the pores of the obtained optical film were measured by performing cross-sectional observation with an SEM (electron microscope), the average number of pores in the transparent resin film made of cellulose acetate propionate was ³ per 100 μm ^3. there were. And the internal volume of the void | hole was 0.50 micrometer ³ by the average value.

  Moreover, the long side of the hole of the transparent resin film was an average value of 2.0 μm, and the short side of the hole was an average value of 0.08 μm.

  Furthermore, the void | hole of the obtained resin film existed inside 22 to 78% of the total thickness from the surface of the resin film.

  Moreover, the long side of the void | hole of the resin film had an angle of 90 degree | times with respect to the slow axis of an optical film.

  In Table 2 below, for the transparent resin film made of cellulose acetate propionate obtained in Example 1, the number of holes, the inner volume of the holes, the length of the long side and the short side of the hole (both The average value), the positions of the holes from the surface of the resin film, and the angles of the long sides of the holes to the slow axis of the optical film are collectively shown.

Examples 2-8
In these Examples 2-8, it carries out similarly to the case of the said Example 1, but in each Example, the width direction of a web (film) is hold | gripped both ends with a tenter, and the residual solvent at the time of an extending | stretching start The amount, stretching temperature, and stretching ratio were determined according to the conditions shown in Table 1 below. Further, after stretching, methylene chloride vapor is sprayed on both sides of the web (film) whose tension has been relaxed to form an atmosphere containing a solvent near the surface of the web (film), and then the surface-treated web ( The film was passed through a pair of rolls, thereby producing an optical film according to the present invention in which pores existed in the interior of 20% or more of the total thickness from the surface of the optical film.

  In the following Table 2, the transparent resin film made of cellulose acetate propionate obtained in these Examples 2-8, the number of holes, the internal volume of the holes, the long side of the holes and the length of the short side (Both average values), the positions of the holes from the surface of the resin film, and the angles of the long sides of the holes to the slow axis of the optical film are also shown.

Comparative Examples 1-5
For comparison, it is carried out in the same manner as in the case of Example 1 described above. The difference from Example 1 is that, as shown in Table 1 below, in Comparative Example 1, the web (film) is stretched at the start of stretching. Both the residual solvent amount and the stretching temperature were set high. In Comparative Example 2, both the residual solvent amount at the start of stretching of the web (film) and the stretching temperature were set low. In Comparative Example 3, only the stretching temperature of the web (film) was set high, and the film was not surface-treated with the solvent after stretching. In Comparative Example 4, only the stretch ratio of the web (film) was set low. In Comparative Example 5, the residual solvent amount at the start of web (film) stretching was set low, while the stretching temperature was set high. Further, the film was not surface-treated with the solvent after stretching.

  In Table 2 below, for the transparent resin film made of cellulose acetate propionate obtained in Comparative Examples 1 to 5, the number of pores, the internal volume of the pores, the long side of the pore and the length of the short side (Both average values), the positions of the holes from the surface of the resin film, and the angles of the long sides of the holes to the slow axis of the optical film are also shown.

Example 9
Preparation of cycloolefin polymer film by melt casting film formation method In a nitrogen atmosphere, dehydrated cyclohexane 500 parts by mass, 1.2 parts by mass of 1-hexene, 0.15 parts by mass of dibutyl ether, 0.30 parts by mass of triisobutylaluminum After mixing the parts in a reactor at room temperature, while maintaining at 45 ° C., tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP) 20 mass Parts, 1,4-methano-1,4,4a, 9a-tetrahydrofluorene (hereinafter abbreviated as MTF) 140 parts by mass, and 8-methyl-tetracyclo [4.4.0.12,5.17,10] -Norbornene monomer mixture comprising 40 parts by weight of dodec-3-ene (hereinafter abbreviated as MTD) and tungsten hexachloride (0.7% toluene solution) 40 Part by mass was continuously added over 2 hours for polymerization. To the polymerization solution, 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to deactivate the polymerization catalyst and stop the polymerization reaction.

  Next, 270 parts by mass of cyclohexane is added to 100 parts by mass of the reaction solution containing the obtained ring-opening polymer, and 5 parts by mass of a nickel-alumina catalyst (manufactured by JGC Chemical) is added as a hydrogenation catalyst. The mixture was heated to 200 ° C. with stirring under pressure of 5 MPa and then reacted for 4 hours to obtain a reaction solution containing 20% of a DCP / MTF / MTD ring-opening polymer hydrogenated polymer.

  After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray; Septon 2002) and an antioxidant (manufactured by Ciba Specialty Chemicals; Irganox 1010) are added and dissolved in the resulting solutions. (Both 0.1 parts by mass per 100 parts by mass of the polymer).

  Next, cyclohexane and other volatile components, which are solvents, are removed from the solution using a cylindrical concentrating dryer (manufactured by Hitachi, Ltd.), the hydrogenated polymer is extruded in a strand form from an extruder in a molten state, and pellets are cooled. And recovered.

  When the copolymerization ratio of each norbornene monomer in the polymer was calculated from the composition of residual norbornenes in the solution after polymerization (by gas chromatography method), it was almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition.

  This hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 31,000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9%, and a Tg of 134 ° C.

  The obtained pellets of the ring-opened polymer hydrogenated product were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture.

  Next, the pellets were made into a single-screw extruder having a coat hanger type T die with a lip width of 1.5 m (Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T die lip material is tungsten carbide, peel strength 44N from molten resin) ) To produce a cyclic olefin resin film having a length of 2500 m and a thickness of 60 μm. Extrusion molding was performed in a clean room of class 10000 or less under molding conditions of a molten resin temperature of 240 ° C. and a T die temperature of 240 ° C.

  About the film after this extrusion molding, after extending | stretching the vapor | steam of a methylene chloride from the both surfaces of a film in advance before extending | stretching by a tenter and making the whole film contain a methylene chloride, on the conditions shown in Table 2, Stretched. That is, the residual solvent amount of the web (film) immediately before entering the tenter in the stretching process is 1.0 mass%, the stretching ratio of the web (film) in the tenter in the stretching process is 1.3 times, and the stretching temperature in the tenter is 110. The stretching step was performed by setting the temperature to ° C.

  Then, after stretching with a tenter, surface treatment with a solvent was performed. That is, after stretching in the width direction of the film by the tenter, the tension in the width direction is relaxed to release the width, and subsequently, the following surface treatment with a solvent is performed. That is, the vapor of methylene chloride solvent is sprayed on both sides of the stretched and tension-reduced film to form an atmosphere containing the solvent near the film surface, and then the surface-treated film is placed between a pair of rolls. A cellulose acetate propionate film according to the present invention was obtained, which was allowed to pass through, and the pores were present within 22 to 78% of the total thickness from the surface of the optical film.

  The cyclic olefin resin film thus obtained was slit at both ears and processed to a width of 1.4 m to obtain an optical film having a thickness of 80 μm. Moreover, the polyester film was wound up together as a protective film when winding up.

The pores of the obtained film were measured by cross-sectional observation with an SEM (electron microscope), and as a result, the average number of pores in the transparent resin film made of cellulose acetate propionate was ³ per 100 μm ^3. It was. And the internal volume of the void | hole was 0.36 micrometer ³ by the average value.

  The long side of the pores of the transparent cellulose acetate propionate film was 1.5 μm on average, and the short side of the pores was 0.08 μm on average.

  Furthermore, the pores of the obtained cellulose acetate propionate film were present within 22 to 78% of the total thickness from the surface of the resin film.

  Further, the long side of the pores of the cellulose acetate propionate film had an angle of 90 degrees with respect to the slow axis of the optical film.

  In the following Table 2, with respect to the transparent cellulose acetate propionate film of Example 9, the number of holes, the internal volume of the holes, the lengths of the long and short sides of the holes (both are average values), the holes The angle from the surface of the resin film and the angle of the long side of the hole to the slow axis of the optical film are also shown.

Comparative Example 6
For comparison, it is carried out in the same manner as in Example 9, but as shown in Table 1 below, the points different from Example 9 are different from those in Example 9 in Table 1 below. As shown, in Comparative Example 6, only the stretch ratio of the web (film) was set low.

  In Table 2 below, for the transparent resin film made of cellulose acetate propionate obtained in Comparative Example 6, the number of pores, the internal volume of the pores, the length of the long side and the short side of the pore (both The average value), the positions of the holes from the surface of the resin film, and the angles of the long sides of the holes to the slow axis of the optical film are also shown.

(Evaluation test)
About the optical film by this invention obtained in the said Examples 1-9, and the optical film for the comparison obtained in Comparative Examples 1-6, evaluation regarding the following optical characteristics was performed.

Evaluation of Haze (Transparency) of Optical Film Haze values were measured for the transparent resin films obtained in Examples 1 to 9 and Comparative Examples 1 to 6. The measuring method is performed according to JIS K 7105-1981, and the surface of the surface uneven structure of each transparent resin film faces the light source by using “Nippon Denshoku Industries Co., Ltd .: Turbidimeter, model name: NDH2000”. The measurement was performed as described above. The obtained results were evaluated in the following four stages. The evaluation rank is as follows, and the obtained results are summarized in Table 2 below.

Evaluation rank ◎: Transparent ○: Transparent but slightly white △: Some of the transparent part is cloudy white ×: Example 10 and Comparative Example 7 are cloudy white
(Preparation of polarizing plate)
Then, using each sample of the optical film obtained in Examples 1 to 9 and Comparative Examples 1 to 6, a polarizing plate was prepared in the following manner, and the following evaluation was performed.

  A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizing film.

  Then, according to the following steps 1 to 5, Konica as a polarizing film, a front side film made of each sample of the optical film obtained in Examples 1 to 9 and Comparative Examples 1 to 6, and a cellulose ester film on the back side. A polarizing plate was produced by laminating a Minolta-tack KC8UX-RHA film (manufactured by Konica Minolta Opto).

  Step 1: The optical film samples obtained in Examples 1 to 9 and Comparative Examples 1 to 6 were immersed in a 1 mol / L sodium hydroxide solution at a temperature of 50 ° C. for 60 seconds, then washed with water and dried. Thus, a saponified cellulose ester film was obtained on the side to be bonded to the polarizing film.

  Step 2: The polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Gently wipe off excess adhesive adhering to the polarizing film in Step 2, place it on each sample of the optical film treated in Step 1, and laminate so that the antireflection layer is on the outside And arranged.

Step 4: The optical film, the polarizing film, and the cellulose ester film sample laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Process 5: Each sample of the optical films obtained in Examples 4 to 9 and Comparative Examples 1 to 6 prepared in Process 4 in a dryer at 80 ° C., a polarizing film, and a cellulose ester film were bonded together. The laminated film was dried for 2 minutes to produce a polarizing film.

(Production of liquid crystal display device)
The polarizing film produced by using the optical films obtained in Examples 1 to 9 and Comparative Examples 1 to 6 above was peeled off from the polarizing plate of a commercially available liquid crystal TV (Aquos 32AD5 manufactured by Sharp Corporation). Bonded to the surface.

  At that time, the direction of bonding of the polarizing plate is such that the surface of each optical film is on the liquid crystal cell side, and the absorption axis is directed in the same direction as the polarizing plate previously bonded, Each liquid crystal display device was produced.

(Evaluation of viewing angle expansion)
About each liquid crystal display device using the polarizing film produced using the optical film obtained in the said Examples 1-9 and Comparative Examples 1-6, viewing angle expansion was evaluated in the following four steps. The evaluation rank is as follows. The front luminance at the center of the screen of the liquid crystal display device was set to 1. The obtained results are summarized in Table 2 below.

Evaluation rank ◎: No image inversion / whiteness when viewed from top / bottom / left / right ○: Image inversion / whiteness when viewed from top / bottom / left / right, but no sense of incongruity △: Inverted and whitish, with a sense of incongruity ×: Seen from the top, bottom, left, or right, the image is inverted or whitish, clearly different from the original image

  As is clear from the results in Table 2 above, in the liquid crystal panel using the polarizing film produced by using the optical film obtained in Examples 1 to 9 according to the present invention, the evaluation of the viewing angle expansion is ranked “「 ”. Or it was "(circle)" and the viewing angle of the liquid crystal panel was able to be expanded. On the other hand, in the liquid crystal panel using the polarizing film produced using the optical film obtained in Comparative Examples 1 to 6, the evaluation of the viewing angle expansion is rank “Δ” or “×”, and the liquid crystal panel There was a problem with display quality.

Claims (9)

On average per 100 [mu] m ^3, that becomes a transparent resin film having a 1.5 to 10 pieces of holes, and the internal volume of the pores, 0.002 .mu.m ³ or an average value, is 0.6 .mu.m ³ or less An optical film characterized.   2. The optical film according to claim 1, wherein the long side of the pores has an average value of 0.2 μm or more and 3 μm or less.   3. The optical film according to claim 1, wherein the short side of the pores has an average value of 0.05 μm or more and 0.2 μm or less.   The optical film according to any one of claims 1 to 3, wherein pores are present in the inside of 20% or more of the total thickness from the surface of the film.   5. The optical film according to claim 1, wherein the long side of the pore is 75 degrees or more and 115 degrees or less with respect to the slow axis of the film.   The optical film according to claim 1, wherein the transparent resin film is a cellulose ester resin film.   The optical film according to any one of claims 1 to 5, wherein the transparent resin film is a resin film containing 80% or more of a cyclic olefin-based addition polymer.   A polarizing plate using the optical film according to claim 1 on one surface.   A display device comprising the polarizing plate according to claim 8.