JP2009208358A - Optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film, wherein an emboss having a desired height can be secured even at a high speed hot embossing at both ends of a film, winding property of a film can be stabilized, winding ability of a film can be secured without sprouting failure, a high speed film formation becomes possible and production efficiency can be increased by making film surface soft in a solution-flowing film forming method. <P>SOLUTION: A web (flowing film) peeled off from a metallic supporter by a solution flowing film forming method is drown in a horizontal direction and then wound in a role state after drying to give an optical film, wherein a ratio H<SB>V2</SB>/H<SB>V1</SB>of a Vicars hardness (H<SB>V1</SB>) on a most outer surface of a film to one (H<SB>V2</SB>) when impacting until 10% of a film thickness is conducted is adjusted to 1.0 to 1.5. It is preferable that the drawing rate of the web is 20 to 60% and an effective knurl of a film wound in a role state is 2.5 to 7.0 μm (effective knurl=(a cross section surface of a role in an embossing part-a core cross section surface)/a wound length-an average film thickness). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention can be used for various functional films such as a protective film for a polarizing plate used for a liquid crystal display (LCD), a retardation film, a viewing angle widening film, and an antireflection film used for a plasma display. The present invention relates to an optical film as a film.

  The production amount of optical films for liquid crystal display devices is increasing year by year due to the increase in size and spread of liquid crystal display devices, and improvement in productivity is demanded as demand for optical films for liquid crystal display devices grows. Optical films for liquid crystal displays, especially polarizing plate protective films and retardation films, are formed by the solution casting film forming method and the melt film forming method. However, in order to improve productivity, the film forming speed has been studied to be increased. ing. These films are wound into a roll after film formation and used by a processing manufacturer. In order to stabilize the winding shape, both ends of the film are embossed.

  Although embossing is processed by heating / pressurization, the heating / pressurization time cannot be sufficient due to the high speed of film formation, so ensure the embossing of the height necessary to stabilize the rollability of the film. Is getting harder.

  That is, in embossing, if the embossing temperature is raised too much, fibrous foreign matter is generated around the embossing called the whisker shape, and if the embossing pressure is raised too much, the end of the film is deformed into a wave shape or wound. There was a problem that ears were formed in the shape.

In the following Patent Document 1, in the method for producing an optical film by a solution casting film forming method, the surface hardness is adjusted to 200 to 900 MPa (megapascal) or the like by a resin or an additive, thereby causing foreign matters in the film production process. A technique is disclosed in which the surface is hardened by laminating in a thickness direction that can be pressed to suppress failure.
JP 2005-206721 A

  As in the prior art described in Patent Document 1 above, there has been a technique for hardening the surface of the optical film, but the technique for softening the surface is conventionally known as an optical film. There wasn't.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and is an optical film manufactured by a solution casting film forming method. By softening the film surface, unevenness by embossing is formed on both ends of the film. Because it is easy to be attached, it is possible to secure embossing of the height required to stabilize the winding property of the film with hot embossing even at high speed, and there is no beard-like failure, and the winding property of the film can be ensured. Therefore, an object of the present invention is to provide an optical film that can meet the recent demand for higher film formation speed for improving productivity.

  As a result of intensive studies in view of the above points, the present inventor has found that the surface of the film becomes soft by increasing the stretch ratio, and in particular, in order to obtain a film having a width of 1.8 m or more. An embossing of a height required to stabilize the rollability of the film by embossing even when the film forming speed is increased by specifying a Vickers hardness ratio of the film is required. It has been found that the unevenness can be secured, and the present invention has been completed.

In order to achieve the above object, the invention of claim 1 forms a casting film (web) by casting a thermoplastic resin solution (dope) on a metal support by a solution casting film forming method, After evaporating a part of the solvent, the web is peeled from the metal support, the peeled web is stretched in the width direction at a stretch ratio of 20% or more, dried after stretching, and further knurled (embossed) on both ends of the film. Is an optical film manufactured by winding the film into a roll shape, and when the film is pressed to the Vickers hardness (H _V1 ) of the outermost surface of the film and 10% of the film thickness Ratio to Vickers hardness (H _V2 ): H _V2 / H _V1 is 1.0 to 1.5.

  The invention according to claim 2 is the optical film according to claim 1, characterized in that the stretch ratio is 20 to 60%.

  Invention of Claim 3 is an optical film of Claim 1 or 2, Comprising: The effective nar defined by the following formula of a roll-shaped optical film is 2.5-7.0 micrometers, It is characterized by the above-mentioned. Yes.

Effective knurl = (embossed portion roll cross-sectional area−core cross-sectional area) / winding length−average film thickness The invention of claim 4 is the optical film according to claim 1, The thermoplastic resin is characterized by being a cellulose ester.

In the first aspect of the present invention, a thermoplastic resin solution (dope) is cast on a metal support by a solution casting film forming method to form a casting film (web), and a part of the solvent is evaporated. The web is peeled from the metal support, the peeled web is stretched in the width direction at a stretch ratio of 20% or more, dried after stretching, and further subjected to knurling (embossing) at both ends of the film. The ratio of the Vickers hardness (H _V1 ) on the outermost surface of the film to the Vickers hardness (H _V2 ) when pressed to 10% of the film thickness. : H _V2 / H _V1 is 1.0 to 1.5, and according to the invention of claim 1, unevenness due to embossing is easily attached to both ends of the film by softening the film surface. Because even at high speed With hot embossing, it is possible to ensure the height of embossing necessary to stabilize the film winding property, there is no whisker-like failure, and the film winding property can be secured, improving productivity in recent years. Therefore, there is an effect that it is possible to meet the demand for higher film forming speed.

  Invention of Claim 2 is an optical film of Claim 1, Comprising: A draw ratio is 20 to 60%, According to invention of Claim 2, a film surface can be made soft, Since both the end portions of the film are likely to be uneven due to embossing, the embossing at a height necessary for stabilizing the rollability of the film can be ensured by hot embossing even at high speed.

  Invention of Claim 3 is an optical film of Claim 1 or 2, Comprising: The effective nar defined by the following formula of a roll-shaped optical film is 2.5-7.0 micrometers.

Effective knurl = (embossed portion roll cross-sectional area−core cross-sectional area) / winding length−average film thickness According to the invention of claim 3, the effective knurl of the roll-shaped optical film is in the range of 2.5 to 7.0 μm. As the film surface becomes soft, both ends of the film are prone to unevenness due to embossing, so hot embossing is necessary even at high speeds to ensure the height of embossing necessary to stabilize the rollability of the film. Thus, there is no beard-like failure, the film winding property can be secured, and it is possible to reliably cope with the increase in speed and length in the production of optical films.

  Invention of Claim 4 is an optical film as described in any one of Claims 1-3, Comprising: Thermoplastic resin is a cellulose ester, According to invention of Claim 4, contact | adherence When the coating layer is provided, the wettability of the solvent can be ensured and the coating layer can be easily provided.

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

The optical film according to the present invention is obtained by casting a thermoplastic resin solution (dope) on a metal support by a solution casting film forming method to form a casting film (web) and evaporating a part of the solvent. The web is peeled from the metal support, the peeled web is stretched in the width direction at a stretch ratio of 20 to 60%, and further, both ends of the film are knurled (embossed), and then the film is rolled. An optical film produced by winding, the ratio of the Vickers hardness (H _V1 ) on the outermost surface of the film to the Vickers hardness (H _V2 ) when pressed to 10% of the film thickness: H _V2 / H _V1 is, it is characterized in that 1.0 to 1.5.

  In the above, the stretching ratio is preferably 20 to 60%. This is because a stretch ratio of 20 to 60% is generally required to obtain an optical film having a width of 1800 mm or more. And a film becomes soft by extending | stretching at a high extending | stretching rate in this way.

In the optical film of the present invention, the ratio of the Vickers hardness (H _V1 ) on the outermost surface of the film to the Vickers hardness (H _V2 ) when pressed to 10% of the film thickness: H _V2 / H _V1 is 1. It is characterized by being 0-1.5.

Here, the ratio of the Vickers hardness (H _V1 ) on the outermost surface of the film to the Vickers hardness (H _V2 ) when the film is pushed down to 10% of the film thickness: when the _{V V2} / H _V1 increases, the film becomes softer. . Here, if the ratio of Vickers hardness: H _V2 / H _V1 is less than 1.0, the film surface is hard, and therefore, processing at high temperature and high pressure is required for embossing by temperature and pressure. This is not preferable because a whisker-like failure or wave-like deformation occurs. In addition, when the ratio of Vickers hardness: H _V2 / H _V1 exceeds 1.5, the surface becomes too soft, which is not preferable because it causes a failure due to a foreign matter on the roll surface in the conveying process. .

  Moreover, it is preferable that the effective nar defined by the following formula of a roll-shaped optical film is 2.5-7.0 micrometers for the optical film by this invention. Here, the effective knurl is a so-called rolling value.

Effective knurl = (embossed portion roll cross-sectional area−core cross-sectional area) / winding length−average film thickness Here, if the effective knurl of the roll-shaped optical film is less than 2.5 μm, a sticking failure between films occurs. Or convex local deformation occurs, and the flatness as an optical film is not satisfied. On the other hand, if the effective nar exceeds 7.0 μm, the center of the winding is recessed in a shape like the back of a horse and the flatness as an optical film cannot be maintained, which is not preferable.

In the optical film of the present invention, it is preferable that the number of whisker-like foreign matters adhering around the embossed portion of the roll-shaped optical film is 0 to 14 / cm ² .

In the above, the number of the beard-like foreign matters adhering to the periphery of the embossed portion of the optical film is preferably as small as possible. When the number of the beard-like foreign matters exceeds 15 / cm ² , the cleaning apparatus for processing as a polarizing plate If it cannot be completely removed and enters a liquid crystal display device as a foreign substance between the polarizer and the film, it becomes an image defect. The same applies to the case where application processing such as antireflection treatment or antiglare treatment is applied to the surface.

  In the optical film of the present invention, the roll length of the roll film is preferably 3900 m or more and 9100 m or less.

  Here, if the winding length of the roll film is less than 3900 m, it is not preferable because the time for switching the rolled-up roll becomes insufficient when the production speed is increased. Moreover, since the frequency of the film switching operation increases during the polarizing plate processing, the productivity is lowered. On the other hand, when the roll length of the roll film exceeds 9100 m, the load of the core increases due to the weight of the film, and even if the emboss is increased, the effective knurl cannot be maintained and sticking occurs.

  Hereinafter, the present invention will be described in detail.

  The optical film of the present invention is produced by a solution casting method. In the method for producing an optical film, various resins can be used as the film material, and cellulose ester is particularly preferable.

  A cellulose ester is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, cellulose acetate, cellulose acetate propionate, and cellulose acetate having an aliphatic polyester graft side chain are preferable. Other substituents may be included as long as the effects of the present invention are not impaired.

  As an example of cellulose triacetate, the substitution degree of acetyl groups is preferably 2.0 or more and 3.0 or less. By setting the degree of substitution within this range, good moldability can be obtained, and desired in-plane retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as a retardation film, particularly the dimensional stability under wet heat may be inferior, and if the substitution degree is too large, the necessary retardation characteristics will not be exhibited. There is a case.

  The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  In the present invention, the number average molecular weight of the cellulose ester is preferably in the range of 60000 to 300000, since the mechanical strength of the resulting film is strong. Furthermore, 70000-200000 are preferable. The cellulose ester used in the present invention preferably has an Mw / Mn ratio of 1.4 to 3.0, more preferably 1.4 to 2.3.

  Since the average molecular weight and molecular weight distribution of the cellulose ester can be measured using high performance liquid chromatography, the number average molecular weight (Mn) and the weight average molecular weight (Mw) can be calculated using this, and the ratio can be calculated.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G
(Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by weight
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 1,000,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  The total acyl group substitution degree of the cellulose ester is 2.3 to 2.9, and 2.6 to 2.9 is preferably used. The total acyl group substitution degree can be measured according to ASTM-D817-96.

  In the present invention, various additives can be added to the cellulose ester.

  In the method for producing an optical film according to the present invention, an organic solvent having good solubility with respect to the cellulose derivative is referred to as a good solvent, and has a main effect on dissolution, and an organic solvent used in a large amount among them is mainly used. It is called (organic) solvent or main (organic) solvent.

  Examples of good solvents include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, formic acid Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by weight of an alcohol having 1 to 4 carbon atoms. After casting the dope on the metal support, the solvent starts to evaporate and the alcohol ratio increases, so the web (name of the dope film after casting the cellulose derivative dope on the metal support) Is used as a gelling solvent that makes the web strong and makes it easy to peel off from the metal support, or when these ratios are small, cellulose derivatives of non-chlorine organic solvents There is also a role to promote the dissolution of.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose derivatives and are called poor solvents.

  The most preferable solvent for dissolving a cellulose derivative, which is a preferable polymer compound satisfying such conditions, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethyl alcohol of 95: 5 to 80:20. Alternatively, a mixed solvent of methyl acetate: ethyl alcohol 60:40 to 95: 5 is also preferably used.

  The film according to the present invention includes a plasticizer that imparts processability, flexibility, and moisture resistance to the film, fine particles that impart slipperiness to the film (matting agent), an ultraviolet absorber that imparts an ultraviolet absorbing function, and deterioration of the film. You may contain the antioxidant etc. which prevent.

  The plasticizer used in the present invention is not particularly limited. However, a cellulose derivative or a reactive metal compound capable of hydrolytic polycondensation can be used so as not to cause haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting with the condensate by hydrogen bonding or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

  Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol ester plasticizers, glycolate plasticizers. Agents, citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, etc. can be preferably used, but polyhydric alcohol ester plasticizers, glycolate plasticizers are particularly preferred. And non-phosphate ester plasticizers such as polycarboxylic acid ester plasticizers.

  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).

Formula _{(1) R 1 - (OH} ) n
(Wherein 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.

  Examples of preferred polyhydric alcohols include 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, gallium Examples include lactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred 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 side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose derivative is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Examples of 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, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, laccellic acid, etc., undecylen Examples thereof include unsaturated fatty acids such as acid, 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. Examples thereof include aromatic monocarboxylic acids and derivatives thereof, and benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 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 derivatives.

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

  The glycolate plasticizer is not particularly limited, but a glycolate plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. As preferred glycolate plasticizers, for example, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be used.

  For phosphate ester plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, and the like can be used, but in the present invention, it is preferable that a phosphate ester plasticizer is not substantially contained.

  Here, “substantially does not contain” means that the content of the phosphoric ester plasticizer is less than 1% by weight, preferably 0.1% by weight, and particularly preferably not added.

  These plasticizers can be used alone or in combination of two or more.

  The amount of the plasticizer used is preferably 1 to 20% by weight. 6 to 16% by weight is further preferable, and 8 to 13% by weight is particularly preferable. If the amount of the plasticizer used is less than 1% by weight relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, so this is not preferred. If it exceeds 20% by weight, the plasticizer bleeds out from the film, and the film Since the physical properties of the material deteriorate, it is not preferable.

  In order to impart slipperiness to the cellulose derivative in the present invention, it is preferable to add fine particles such as a matting agent. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound.

  Examples of the fine particles of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide and the like. Of these, fine particles of a compound containing a silicon atom are preferred, and fine silicon dioxide particles are particularly preferred. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  Examples of the organic compound fine particles include fine particles such as acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  The primary particle size of the fine particles is not particularly limited, but the average particle size in the film is preferably about 0.05 to 5.0 μm. More preferably, it is 0.1-1.0 micrometer.

  When the cellulose ester film is observed with an electron microscope or an optical microscope, the average particle diameter of the fine particles indicates an average value of the lengths in the major axis direction of the particles at the observation position of the film. As long as the particles are observed in the film, they may be primary particles or secondary particles in which the primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

As an example of the measurement method, 10 vertical cross-sectional photographs are taken at random for each film, and the number of particles in 100 μm ² whose major axis length is in the range of 0.05 to 5 μm for each cross-sectional photograph. Count. The average value of the major axis lengths of the particles counted at this time is obtained, and a value obtained by averaging the average values of 10 locations is defined as the average particle size.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size added to the film often change, and it is important that the fine particles are finally combined with the cellulose ester in the film. It is to control the particle size formed by aggregation.

  Here, if the average particle size of the fine particles exceeds 5 μm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. Moreover, when the average particle diameter of fine particles is less than 0.05 μm, it becomes difficult to impart slipperiness to the film.

  The fine particles are used by adding 0.04 to 0.5% by weight to the cellulose ester. Preferably, 0.05 to 0.3% by weight, more preferably 0.05 to 0.25% by weight is added. When the amount of fine particles added is 0.04% by weight or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.5% by weight, the coefficient of friction on the film surface will be too low, causing winding misalignment during winding, and the transparency of the film will be low and haze will be high. The above range is essential because it has no value as a film.

  For the dispersion of the fine particles, it is preferable to treat the composition in which the fine particles and the solvent are mixed with a high-pressure dispersion apparatus. The high-pressure dispersion apparatus used in the present invention is an apparatus 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.

It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, the maximum pressure condition inside the apparatus is 1960 N / cm ² or more. Further, at that time, those having a maximum reaching speed of 100 m / sec or more and those having a heat transfer speed of 100 kcal / hr or more are preferable.

  Examples of the high-pressure dispersing device as described above include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation, or a nanomizer manufactured by Nanomizer, and also a Manton Gorin type high-pressure dispersing device such as Izumi Food Machinery. A homogenizer etc. are mentioned.

  In the present invention, the fine particles are dispersed in a solvent containing 25 to 100% by weight of a lower alcohol, and then mixed with a dope in which a cellulose ester (cellulose derivative) is dissolved in a solvent, and the mixed solution is placed on a metal support. A cellulose ester film is obtained which is cast and dried to form a film.

  Here, the content ratio of the lower alcohol is preferably 50 to 100% by weight, more preferably 75 to 100% by weight.

  Examples of lower alcohols preferably include 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 formation of a cellulose ester.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by weight. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by weight, more preferably 10 to 20% by weight.

  The ultraviolet absorbing function of the film is preferably imparted to various optical films such as a polarizing plate protective film, a retardation film, and an optical compensation film from the viewpoint of preventing deterioration of the liquid crystal. For such an ultraviolet absorbing function, a material that absorbs ultraviolet rays may be included in the cellulose derivative, and a layer having an ultraviolet absorbing function may be provided on a film made of the cellulose derivative.

  Examples of ultraviolet absorbers that can be used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloring is preferable. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used.

  As the ultraviolet absorber, those having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal and those having little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. preferable.

  Specific examples of useful UV absorbers in the present invention include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-). Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2- Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, 2- (2'-hydroxy) 3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl -3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5 A mixture of-(5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as commercially available products of ultraviolet absorbers, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

  Specific examples of the benzophenone-based compound that is an ultraviolet absorber that can be used in the present invention include 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5- Examples thereof include, but are not limited to, sulfobenzophenone and bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane).

  In this invention, the compounding quantity of these ultraviolet absorbers has the preferable range of 0.01 to 10 weight% with respect to a cellulose ester (cellulose derivative), and also 0.1 to 5 weight% is preferable. If the amount of the ultraviolet absorber used is too small, the ultraviolet absorbing effect may be insufficient. If the amount of the ultraviolet absorber is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

  Further, as the ultraviolet absorber that can be used in the optical film of the present invention, the polymer ultraviolet absorber (or ultraviolet absorbing polymer) described in JP-A-6-148430 and JP-A-2002-47357 is preferably used. be able to. In particular, the general formula (1) described in JP-A-6-148430, the general formula (2), or the general formulas (3), (6), and (7) described in JP-A-2002-47357. Molecular ultraviolet absorbers are preferably used.

  In general, the antioxidant is also referred to as a deterioration inhibitor, but is preferably contained in a cellulose ester film as an optical film. That is, when a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film as an optical film may be deteriorated. The antioxidant has a role of delaying or preventing the film from being decomposed by, for example, halogen in the residual solvent in the film or phosphoric acid of the phosphoric acid plasticizer, so that it is preferably contained in the 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-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0% by weight, more preferably 10 to 1000 ppm by weight with respect to the cellulose derivative.

  Hereinafter, the method for producing the optical film according to the present invention will be described in detail. The optical film can be produced by a solution casting method.

  FIG. 1 is a flow sheet showing a specific example of an apparatus for carrying out a method for producing an optical film of the present invention by a solution casting film forming method. Note that the implementation of the present invention is not limited to the process of FIG.

  In the method for producing an optical film by the solution casting film forming method of the present invention, a thermoplastic resin solution (dope) is cast on a metal support (1) to form a casting film (web). After evaporating the part, the step of peeling the web (10) from the metal support (1), the step of stretching the peeled web (10) in the width direction by the tenter (4), and the stretched film And a winding process for winding.

  First, in a melting pot (not shown), a thermoplastic resin, for example, a cellulose ester resin is dissolved in a mixed solvent of a good solvent and a poor solvent, and an additive such as the above plasticizer or ultraviolet absorber is added to the resin. A solution (dope) is prepared.

  Next, the dope adjusted in the melting pot is fed to the casting die (2) by a conduit through, for example, a pressurized metering gear pump, and is made of a metal made of a rotationally driven stainless steel endless belt as shown in FIG. The dope is cast from the casting die (2) to the casting position on the support (1).

  Although not shown in the drawings, for example, a dope fed to the casting die (2) through, for example, a pressurized metering gear pump is rotated by a stainless steel having a surface mirror-treated by hard chrome plating from the casting die (2). It may be cast on a cooling drum.

  In order to cast the dope by the casting die (2), there is a doctor blade method in which the film thickness of the cast dope film (web) is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. However, a pressure die that can adjust the slit shape of the die portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

  In addition, as a casting die (2), the pressure die which can adjust the slit shape of a nozzle | cap | die part and is easy to make a film thickness uniform is preferable.

  Here, it is preferable that the solid content concentration of the cellulose ester solution (dope) is 20 to 30% by weight.

  Here, if the solid content concentration of the cellulose ester solution (dope) is less than 20% by weight, sufficient drying cannot be performed on the metal support (1), and a part of the dope film is removed from the metal support (at the time of peeling). 1) Since it remains on top and leads to drum contamination, it is not preferable. If the solid content concentration exceeds 30%, the dope viscosity increases, filter clogging becomes faster in the dope adjustment process, or the pressure increases during casting on the metal support (1), and cannot be extruded. It is not preferable.

  In the illustrated film forming apparatus provided with a rotationally driven endless belt as the metal support (1), the belt metal support (1) is disposed between a pair of drums and the endless belt metal support (1 ), A plurality of rolls (not shown) that respectively support the upper transition portion and the lower transition portion from the back side.

  One or both of the drums at both ends of the rotary drive endless belt metal support (1) is provided with a drive device for applying tension to the belt metal support (1), thereby supporting the belt metal support. The body (1) is used in a tensioned state.

  The width of the metal support is 1800 to 2200 mm, the casting width of the cellulose ester solution is 1600 to 2150 mm, and the width of the film after winding is 1490 to 3000 mm. Thereby, the wide cellulose-ester film for liquid crystal display devices can be manufactured by a metal support body system.

  Here, when the width of the metal support (1), the casting width of the cellulose ester solution, and the width of the film after winding are less than the above lower limit values, respectively, it is possible to cope with the recent enlargement of liquid crystal display devices. If the width of the metal support (1), the casting width of the cellulose ester solution, and the width of the film after winding exceed the upper limit values, the residual solvent amount of the film after peeling In a state where there is a large amount of film, the film hangs down at the entrance of a tenter in the stretching process described later, unevenness in width is generated, and dispersion of retardation is increased, which is not preferable. In addition, the sagging film may hit the guide of the tenter, and the film may break and stop production.

  Moreover, in the manufacturing method of the optical film of this invention, it is preferable that the peripheral speed of a metal support body (1) is 80-200 m / min.

  That is, since the amount of solvent to be dried is small in a thin film, the production speed of the film can be increased by making the peripheral speed of the metal support (1) faster than the conventional drum peripheral speed. Productivity can be increased.

  When an endless belt is used as the metal support (1), the belt temperature during film formation is a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, and the mixed solvent is lower than the boiling point of the lowest boiling solvent. The temperature is more preferably in the range of 5 ° C to the boiling point of the solvent-5 ° C. At this time, it is necessary to control the ambient atmospheric humidity above the dew point.

  The dope cast on the surface of the metal support (1) as described above increases the gel film strength (film strength) due to cooling gelation, and further promotes drying until stripping. This also increases the strength (film strength) of the gel film.

  Further, in order to increase the film forming speed, two or more pressure casting dies (2) may be provided on the casting metal support (1), and the dope amount may be divided to form a multilayer film.

  In the system using an endless belt as the metal support (1), the film strength on which the web (10) can be peeled from the metal support (1) by the peeling roll (3) on the metal support (1). In order to dry and solidify until it becomes, it is preferable to dry to 150 weight% or less of the residual solvent amount in a web (10), and 80 to 120 weight% is more preferable. Moreover, as for web temperature when peeling a web (10) from metal support bodies (1), 0-30 degreeC is preferable. Further, immediately after the web (10) is peeled off from the metal support (1), the temperature rapidly decreases once due to the solvent evaporation from the metal support (1) adhesion surface side, and water vapor or solvent vapor in the atmosphere. For example, the web temperature at the time of peeling is more preferably 5 to 30 ° C. because volatile components are easily condensed.

  Here, the residual solvent amount can be expressed by the following equation.

Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M represents the weight of the film at an arbitrary time point, and N represents the weight after drying a film having a weight of M at 110 ° C. for 3 hours.

  The dope film (web) formed by the dope cast on the endless belt metal support (1) is heated on the metal support (1), and the release roll ( The solvent is evaporated until the web is peelable by 3).

  In order to evaporate the solvent, there are a method of blowing air from the web side, and / or a method of transferring heat from the back surface of the metal support (1) by a liquid, a method of transferring heat from the front and back by radiant heat, and the like.

  In the system using an endless belt for the metal support (1), the peeling tension when the metal support (1) and the web (10) are peeled by the peeling roll (3) is usually 100 N / m to 200 N / In the optical film produced by the present invention, which is made thinner than in the past, the amount of residual solvent of the web (10) is large at the time of peeling, and it is easy to stretch in the conveying direction. The film is easy to shrink in the hand direction, and when drying and shrinkage overlap, the end curls and folds, so that wrinkles are likely to occur. Therefore, it is preferable to peel at a minimum tension that can be peeled off to 170 N / m, more preferably , Peeling at a minimum tension of 140 N / m.

  After drying and solidifying until the web (10) has a peelable film strength on the metal support (1), the web (10) is peeled off by the peeling roll (3).

  Next, the peeled web (10) is introduced into a tenter (4) in the stretching process. In the method of the present invention, as the tenter (4) in the stretching step, a pin tenter and a clip tenter can be used. Among them, as a film for a liquid crystal display device, a web (or film) (10) A clip tenter is preferred in which both side edges are fixed with a clip and stretched, and is preferred in order to improve the flatness and dimensional stability of the film.

  The residual solvent amount of the web (film) (10) immediately before entering the tenter (4) in the stretching step is preferably 10 to 50% by weight.

  In the stretching process, warm air is blown from the warm air blowing means at the front portion of the bottom of the tenter (4), that is, the warm air blowing slit port, and exhaust air is blown from the discharge port at the rear portion of the ceiling of the tenter (4). By being discharged, the web (10) is stretched and dried.

  In the present invention, the stretch ratio of the web (10) in the tenter (4) is preferably 20 to 60%. This is because a stretch ratio of 20 to 60% is generally required to obtain an optical film having a width of 1800 mm or more. And a film becomes soft by extending | stretching by a high extending | stretching rate in this way.

  In addition, the hot air blowing means in the stretching step specifically refers to the hot air blowing slit port of the tenter (4) in the stretching step, but any shape that efficiently heats the film by blowing hot air. There is no particular limitation. The temperature of the warm air is preferably 165 to 190 ° C, and more preferably 170 to 185 ° C.

  Next, the stretched film (web) (10) is introduced into the roll conveyance drying device (5) and dried while being conveyed by the conveyance roll (7) composed of a non-driven free roll in the drying device (5). .

  In this drying device (5), the web (10) is meandered by the conveying rolls (7) arranged in a staggered manner as viewed from the side of 50 to 1000, and the web (10) is dried in the meantime. is there. Moreover, although the film conveyance tension | tensile_strength in drying apparatus (5) is influenced by the physical property of dope, the amount of residual solvents at the time of peeling and a film conveyance process, the temperature in drying apparatus (5), etc., it is 30-250 N / m. Is preferable, and 60 to 150 N / m is more preferable. 80 to 120 N / m is most preferable.

  The means for drying the web (or film) (10) is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air from the viewpoint of simplicity. For example, it is dried by the drying air blown from the warm air inlet at the front portion of the bottom of the drying device (5), and the rear portion of the ceiling of the drying device (5). It is dried by exhausting the exhaust air from the outlet. 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.

  The process from casting to final post-drying may be performed in an air atmosphere or 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.

  After drying by the roll conveyance drying device (5), both ends of the film were slit into a product width by a pair of upper and lower slitters (11) and (12), cut and cut, and a base film was formed according to the product width. Then, a roll-shaped optical film is manufactured by giving an embossed part by giving a knurling process to the width direction Shiro of this base film, and winding up.

  Moreover, in the manufacturing method of the optical film by this invention, it is preferable to apply 10-20 degreeC cold air to the film discharge side of an embossing stamping roll in the case of a knurling process. Here, during the knurling process, 10-20 ° C cold air is applied to the film discharge side of the embossing stamping roll because the resin part melted by heat is cooled and solidified by cooling the film and the ring part immediately after the embossing process. For this reason, the generation of thread-like foreign matters (beard-like foreign matters) can be suppressed, and a sufficiently high embossing height can be obtained.

The optical film according to the present invention, the Vickers hardness of the outermost surface of the film _{(H V1),} the ratio of the Vickers hardness when pushed up to 10% of the film thickness _{(H V2): H V2 /} H V1 is 1. According to the invention of claim 1, since the film surface is softened, unevenness due to embossing is easily attached to both ends of the film. The embossing of the height required to stabilize the winding property can be secured, there is no beard-like failure, the winding property of the film can be secured, and the film forming speed for improving productivity in recent years It can meet the demand for higher speeds.

  Moreover, it is preferable that the effective nar defined by the following formula of a roll-shaped optical film is 2.5-7.0 micrometers in the optical film of this invention.

Effective nar = (embossed part roll cross-sectional area−core cross-sectional area) / winding length−average film thickness In the above, if the effective nar is less than 2.5 μm, a sticking failure between films may occur or a convex Since local deformation occurs and flatness as an optical film is not satisfied, it is not preferable. On the other hand, if the effective nar exceeds 7.0 μm, the center of the winding is recessed in a shape like the back of a horse and the flatness as an optical film cannot be maintained, which is not preferable.

In the optical film produced by the method for producing an optical film of the present invention, the number of whisker-like foreign substances adhering around the embossed portion of the roll-shaped optical film is preferably 0-14 / cm ² , More preferably, it is 0-10 pieces / cm ² .

In the above, the number of beard-like foreign matters adhering to the periphery of the embossed portion of the optical film is preferably as small as possible. When the number of beard-like foreign matters exceeds 14 / cm ² , the cleaning apparatus for processing as a polarizing plate If it cannot be completely removed and enters a liquid crystal display device as a foreign substance between the polarizer and the film, it becomes an image defect. The same applies to the case where application processing such as antireflection treatment or antiglare treatment is applied to the surface.

  Here, the height h (μm) of the embossed portion is set in a range of 0.05 to 0.3 times the film thickness H, and the width W is set in a range of 0.005 to 0.02 times the film width L. To do. You may form an embossing part in both surfaces of a film. In this case, the height h1 + h2 (μm) of the embossed portion is set in the range of 0.05 to 0.3 times the film thickness H, 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 height h1 + h2 (μm) of the embossed portion is set to 2 to 12 μm. The embossed portion width is preferably set to 5 to 30 mm.

  The lower limit of the height of the embossed part is from the height necessary to prevent partial adhesion unevenness between the films. On the other hand, the upper limit is too high for the embossed part to be too high. This is because it deforms into a polygonal shape and induces a failure.

  Regarding the width of the embossed part, the embossed part will eventually become a loss part, but it is desirable to reduce it. However, for example, it is a minimum for suppressing slippage of a film at a high speed of 50 m / min or more with a thin film within 50 μm. Required embossed part width.

  However, it is also linked to the height of the embossed portion described above, and it is necessary to set the height of the embossed portion × the width of the embossed portion that clears all the convex shape, pyramid shape, horse back, polygonal shape, and winding failure.

  The roll length of the roll film in the optical film produced by the method of the present invention is preferably 3900 m or more and 9100 m or less.

  Here, if the winding length of the roll film is less than 3900 m, it is not preferable because the time for switching the rolled-up roll becomes insufficient when the production speed is increased. Moreover, since the frequency of the film switching operation increases during the polarizing plate processing, the productivity is lowered.

  On the other hand, when the roll length of the roll film exceeds 9100 m, the load of the core increases due to the weight of the film, and even if the emboss is increased, the effective knurl cannot be maintained and sticking occurs.

  In addition, a film with good dimensional stability can be obtained by setting the residual solvent amount of the film taken up by the take-up device (15) to 0.5% by weight or less, preferably 0.1% by weight or less.

(Polarizer)
Next, a polarizing plate using the hard coat film of the present invention will be described.

  The polarizing plate can be produced by a general method. The back side of the hard coat film of the present invention is subjected to alkali saponification treatment, and the treated film is attached to at least one surface of a polarizing film produced by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. It is preferable to match. The film may be used for the other surface, or another polarizing plate protective film may be used. With respect to the hard coat film of the present invention, the polarizing plate protective film used on the other surface has an in-plane retardation (Ro) of 590 nm, a retardation of 20 to 70 nm, and a thickness direction retardation (Rt) of 100 to 400 nm. It is preferable that it is an optical compensation film (retardation film). These can be prepared, for example, by the methods described in JP-A No. 2002-71957 and Japanese Patent Application No. 2002-155395. Further, it is preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optically anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348. Alternatively, a non-oriented film having an in-plane retardation (Ro) of 590 nm to 0 to 5 nm and a thickness direction retardation (Rt) of -20 to +20 nm is preferably used, and has excellent planarity and a stable viewing angle widening effect. Can be obtained.

  As a polarizing plate protective film used on the back side, as a commercially available cellulose ester film, KC8UX2MW, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC4UEW, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1, KC4F-1, -2 (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

  The polarizing film, which is the main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are ones in which iodine is dyed on a system film and ones in which a dichroic dye is dyed, but it is not limited to this. As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. A polarizing film having a thickness of 5 to 30 μm, preferably 8 to 15 μm, is preferably used. On the surface of the polarizing film, one side of the hard coat film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

(Image display device)
By incorporating a polarizing plate using the hard coat film of the present invention on the viewing surface side of the image display device, various image display devices with excellent visibility can be produced. The hard coat film of the present invention is a reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS type, etc. Preferably used. Moreover, it is excellent in flatness and is preferably used for various display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and electronic paper. In particular, a large-screen image display device having a screen size of 30 or more has the effect of good visibility and prevents eyes from being tired even during long-time viewing.

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

Example 1
An optical film made of the cellulose triacetate film of the present invention was produced by the solution casting film forming method as follows.

(Dope composition 1)
100 parts by weight of cellulose triacetate (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight Tinuvin 171 (Ciba Specialty Chemicals) 0.5 parts by weight Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by weight The material of the above dope composition 1 was put into a sealed container, heated, stirred and completely dissolved and filtered. . The filtration was performed through a sintered metal filter (capture particle size = 10 microns) after filtration by a filter press. Subsequently, the dope was uniformly cast to a width of 1950 mm on a stainless steel band support (1) having a width of 2050 mm at a temperature of 35 ° C. using the belt casting apparatus shown in FIG.

  On the stainless steel band support (1), the solvent was evaporated until the residual solvent amount reached 100% by weight, and the web (film) (10) was peeled from the stainless steel band support (1). Next, both ends of the web (10) in the width direction (TD direction) were held by the tenter (4), and the web (10) was stretched at a stretch ratio of 20% in the width direction. In addition, the residual solvent amount of the web (film) (10) immediately before entering the tenter (4) in the stretching process was 30% by weight.

  In the stretching step, warm air is blown at a temperature of 180 ° C. from the warm air blowing means at the front part of the bottom of the tenter (4), that is, the warm air blowing slit port, and the outlet of the rear part of the ceiling of the tenter (4). The web (10) was stretched and dried by the exhaust air being discharged from.

  Next, the stretched film (web) (10) is introduced into a roll transport dryer (5), and this film is mirror transported with a surface roughness (Rmax) of 0.8 μm in the roll transport dryer (5). It dried, conveying with the conveyance roll (7) comprised by 500 non-driving free rolls which consist of a roll (surface length 2500mm, diameter 110mm). The film conveyance tension in the drying device (5) was 80 N / m. In the drying device (5), drying was performed by a drying air having a temperature of 120 ° C. blown from a hot air inlet at a front portion of the bottom of the drying device.

  After drying with the drying device (5), both ends of the film were slit into a product width by a pair of upper and lower slitters (11) and (12) and cut and cut.

  Subsequently, the left and right ends of the slit film (10) were knurled by an embossing ring (13) and a back roll (14) to give an embossed portion (not shown) having a width of 10 mm to the film end. In the knurling process, cold air having a temperature of 20 ° C. was applied to the embossing ring, that is, the film discharge side of the embossing stamp roll (13).

  Thereafter, the cellulose triacetate film (F) having an end product width of 1800 mm and a film thickness of 80 μm having an embossed portion was wound up by a winding device (15). The wound length of the rolled cellulose triacetate film (F) was 3900 m.

The roll-shaped cellulose triacetate film produced in Example 1 has a ratio between the Vickers hardness (H _V1 ) on the outermost surface of the film and the Vickers hardness (H _V2 ) when pressed to 10% of the film thickness: H _V2 / H _V1 was 1.24.

Here, the Vickers hardness (H _V ) was measured by an ultrafine hardness meter DUH-211S manufactured by Shimadzu Corporation.

The Vickers hardness is measured by measuring the Vickers hardness (H _V1 ) on the outermost surface of the film, and for Vickers hardness when pressed to 10% of the film thickness, that is, for a cellulose triacetate film having a thickness of 80 μm, Vickers hardness (H _V2 ) when pressed to a thickness of 10% of 8 μm was measured, and these ratios were calculated.

  Moreover, when the roll-like cellulose triacetate film produced in Example 1 calculated the effective nar defined by the following formula, it was 3.5 μm.

  Here, the effective nal is a so-called roll-up value of the rolled cellulose triacetate film.

Effective knurl = (embossed portion roll cross-sectional area−core cross-sectional area) / winding length−average film thickness The results obtained are shown in Table 1 below.

Examples 2-4
A cellulose triacetate film is prepared in the same manner as in Example 1 above. However, the stretching rate is 30% in Example 2, 40% in Example 3, and in Example 4 as in Example 1 above. Cellulose triacetate film was produced under various conditions of 50%. The cast widths of the dopes on the stainless steel band support (1) are the same at 1900 mm, respectively. However, since the stretch ratios are different, the final product widths having the embossed portions are different from each other. The results are shown in Table 1 below.

And about the obtained roll-shaped cellulose triacetate film, ratio of Vickers hardness (H _V1 ) of the film outermost surface and Vickers hardness (H _V2 ) when pressed to 10% of the film thickness: H _V2 / H While measuring _V1 , effective nar (μm) was calculated, and the obtained results are shown in Table 1 below.

Comparative Examples 1-3
For comparison, a cellulose triacetate film is prepared in the same manner as in Example 1 above, but the difference from the case of Example 1 is that in Comparative Examples 1 and 2, the stretch ratio is less than 20%. In the comparative example 3, it is in the point made out of the scope of the present invention as exceeding 60%.

And the final product width of the obtained roll-shaped cellulose triacetate film, the Vickers hardness (H _V1 ) of the outermost surface of each film, and the Vickers hardness (H _V2 ) when pressed to 10% of the film thickness The ratio: H _V2 / H _V1 was measured, the effective nar (μm) was calculated, and the obtained results are shown in Table 1 below.

Examples 5-8
A cellulose ester film is produced in the same manner as in Example 1, but the difference from Example 1 is that cellulose acetate propionate was produced using the following dope composition 2. .

(Dope composition 2)
Cellulose acetate propionate 100 parts by weight (acetyl group substitution degree + propionyl group substitution degree = 2.45,
Mn = 60000, Mw = 18000, Mw / Mn = 3.00)
Triphenyl phosphate 8 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Methylene chloride 360 parts by weight Ethanol 60 parts by weight Tinuvin 109 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight Tinuvin 171 (Ciba Specialty Chemicals) 0.5 parts by weight Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by weight And the stretch ratio is 20% in Example 5, 30% in Example 6, 40% in Example 7, and Example In Example 8, a cellulose acetate propionate film was produced under various conditions of 60%.

And about the obtained roll-shaped cellulose acetate propionate film of Examples 4-8, it pushes to the film final product width, the Vickers hardness ( _HV1 ) of the outermost surface of each film, and 10% of a film film thickness. The ratio to the Vickers hardness (H _V2 ) at the time: H _V2 / H _V1 was measured, the effective nar (μm) was calculated, and the obtained results are shown in Table 1 below.

And the ratio of the Vickers hardness (H _V1 ) on the outermost surface of the obtained roll-shaped cellulose triacetate film to the Vickers hardness (H _V2 ) when pressed to 10% of the film thickness: H _V2 / H _V1 While measuring, the effective nar (μm) was calculated, and the obtained results are shown in Table 1 below.

Comparative Examples 4-6
For comparison, a cellulose acetate propionate film is prepared using the dope composition 2 in the same manner as in Example 5 above. The difference from Example 5 is as shown in Table 1. In Comparative Examples 4 and 5, the stretch ratio is less than 20%, and in Comparative Example 6 it exceeds 60%, which is outside the scope of the present invention.

And about the roll-shaped cellulose acetate propionate film of the comparative examples 4-6 obtained, the film final product width | variety, the Vickers hardness ( _HV1 ) of the outermost surface of each film, and 10% of film thickness were pushed in The ratio to the Vickers hardness (H _V2 ) at the time: H _V2 / H _V1 was measured, the effective nar (μm) was calculated, and the obtained results are shown in Table 1 below.

  Next, in order to evaluate the performance of the roll-shaped cellulose ester films obtained in Examples 1 to 8 and Comparative Examples 1 to 6, the following tests were performed.

(Number of bearded foreign matter)
About the roll-shaped cellulose-ester film manufactured in the said Examples 1-8 and Comparative Examples 1-6, the embossed part was observed with the 30 time optical microscope. Then, the number of whisker-like foreign matters having a length of 200 μm or more attached around the embossed portion of the film was counted and converted to the number per lcm ² . The results of the number of bearded foreign matters (pieces / cm ² ) for each of the obtained cellulose ester films are shown in Table 1 below.

(Evaluation of winding quality)
As a method for evaluating the winding quality, the roll-like wound films of the cellulose ester films obtained in Examples 1 to 8 and Comparative Examples 1 to 6 were observed and evaluated for the appearance, and the protrusions were observed on the outer periphery of the winding. The following four stages of grading were performed according to the number of convex portions appearing. The obtained results are shown in Table 1 below.

A: 0 to 5 O: 6 to 10 Δ: 11 to 20 ×: 21 or more (evaluation of winding deformation and occurrence of film sticking failure)
After storing the roll-like rolls of the cellulose ester films obtained in Examples 1 to 8 and Comparative Examples 1 to 6 at a temperature of 40 ° C. and a humidity of 80% RH for 2 weeks, the appearance was confirmed, and the horse-back rolls The presence or absence of deformation was confirmed and evaluated as winding deformation.

  Next, the roll-shaped wound films obtained in Examples 1 to 8 and Comparative Examples 1 to 6 were respectively fed out to inspect whether the films were adhered to each other. Then, the following four grades were applied according to the state of film sticking.

◎: Not attached at all ○: Slightly attached, but easily peeled △: Sticked but easily peeled ×: Many sticking and difficult to peel off The results are shown in Table 1.

  As is clear from the results in Table 1 above, according to the cellulose ester films prepared in Examples 1 to 8 of the present invention, the evaluation of winding quality, the evaluation of winding deformation, and the evaluation of occurrence of sticking failure of the film are anyway. There was little generation of thread-like foreign matter (bottle-like foreign matter) in which the resin was dissolved around the embossed portion of the obtained optical film, and the quality of the film could be improved. Thus, according to the cellulose-ester film produced in Examples 1-8 of this invention, with the speeding-up of manufacture of an optical film, ensuring the embossed part height after winding up a film in roll shape. Thus, it was possible to reliably cope with the increase in speed and length in the production of optical films.

  On the other hand, in the cellulose ester films of Comparative Examples 1 to 6, all the number of bearded foreign matters was generated, and in particular, in the cellulose ester films of Comparative Examples 3 and 6, the horse-like spine deformation occurred. It was. In any of the cellulose ester films of Comparative Examples 1 to 6, the evaluation of occurrence of film sticking failure is Δ or ×, and at such an evaluation level of Δ, a coating defect occurs in coating processing on the film surface. Therefore, it cannot be used for coating, and at the evaluation level of x, it breaks when the film is fed out, so that it cannot be used for a polarizing plate.

It is a schematic sectional drawing of the apparatus which enforces the method to manufacture the optical film of this invention.

Explanation of symbols

1: Endless belt support 2: Casting die 3: Peeling roll 4: Tenter 5: Roll transporting and drying device 7: Transporting roll 10: Web 11: Upper slitter roll 12: Lower slitter roll 13: Embossing ring 14: Back roll 15: Winding device F: Cellulose ester film (optical film)

Claims (4)

A thermoplastic resin solution (dope) is cast on a metal support by a solution casting film forming method to form a cast film (web), a part of the solvent is evaporated, and then the web is removed from the metal support. The peeled web is stretched in the width direction at a stretch ratio of 20% or more, dried after stretching, and further subjected to knurling (embossing) at both ends of the film, and then the film is wound into a roll. Thus, an optical film manufactured, and the ratio of the Vickers hardness (H _V1 ) on the outermost surface of the film to the Vickers hardness (H _V2 ) when pressed to 10% of the film thickness: H _V2 / H _V1 is 1.0 to 1.5, an optical film.   The optical film according to claim 1, wherein a stretching ratio is 20 to 60%. 3. The optical film according to claim 1, wherein an effective nar defined by the following formula of the roll-shaped optical film is 2.5 to 7.0 μm.
Effective knurl = (embossed roll cross-sectional area−core cross-sectional area) / winding length−average film thickness   The optical film according to claim 1, wherein the thermoplastic resin is a cellulose ester.

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