KR20090107496A - Method of producing optical film, optical film, polarizing plate and image display device - Google Patents

Abstract

It is intended to provide a method of producing an optical film which is widely usable for improving contrast. This object can be achieved by providing a method of producing an optical film which contains a resin and an additive, characterized by comprising heat melting and kneading the resin with the additive to form a hot molten matter, and casting a resin solution having been prepared by dissolving this hot molten matter in a solvent to thereby give an optical film.

Description

Manufacturing method of optical film, optical film, polarizing plate and image display device {METHOD OF PRODUCING OPTICAL FILM, OPTICAL FILM, POLARIZING PLATE AND IMAGE DISPLAY DEVICE}

TECHNICAL FIELD This invention relates to the manufacturing method of an optical film. Specifically, It is related with the manufacturing method of the optical film which improved contrast performance.

In recent years, the spread of large-size liquid crystal televisions has been promoted as home televisions. As the performance of large-sized liquid crystal televisions, contrast has attracted attention, which is a factor in product differentiation. Various methods for improving contrast have been proposed.

The improvement method by an optical film is recognized as an important technique because the improvement effect is large and the method is easy, but the contrast improvement effect is inadequate and cannot be said to be a versatility technique (Patent Documents 1 to 3). ).

Patent Document 1: Japanese Patent Application Laid-Open No. 2005-164957

Patent Document 2: Japanese Patent Laid-Open No. 2005-173588

Patent Document 3: Japanese Patent Application Laid-Open No. 2005-202101

<Start of invention>

Problems to be Solved by the Invention

An object of the present invention is to provide a method for producing a general purpose optical film for improving contrast.

Means for solving the problem

An object of the present invention is a method for producing an optical film containing a resin and an additive, wherein the resin and the additive are heated and melted and kneaded to adjust the heated melt, and the solution is cast by solution casting of the resin solution in which the heated melt is dissolved in a solvent. It was achieved by the manufacturing method of the optical film characterized by setting it as a film.

Effect of the Invention

According to the present invention, it is possible to stably supply an optical film having general purpose for improving contrast.

The present invention is capable of producing an optical film capable of improving contrast by heating and kneading a resin and an additive, particularly a plasticizer, as raw materials for forming an optical film, and then adjusting the heating melt by dissolving it in a solvent to soften the solution. I found that.

In a conventional solution casting film, a solution casting film is formed by dissolving a resin and an additive in a solvent, stirring and mixing to produce a resin solution (hereinafter also referred to as dope), and casting the dope on a support such as a belt.

The dope by this method seemed to have the additives uniformly mixed in the resin at first glance, but in the microscopic observation, the additives existed in the form of a sea island in the resin.

MEANS TO SOLVE THE PROBLEM When this additive exists in resin form even if it exists in resin, the microscopic nonuniformity of extending | stretching will generate | occur | produce in the extending process which is a part of solution casting film forming process after that, and this nonuniformity of extending | stretching will generate the light leakage of polarized light, It discovered that it was a cause of the contrast fall of the optical film which is a manufactured product.

On the other hand, when the present inventor adjusts a heating melt by heat-kneading resin and an additive which are raw materials for forming an optical film, an additive will disperse | distribute uniformly in resin and the additive once uniformly disperse | maintains uniformity after that. Also found.

That is, even if the raw material adjusted as a heating melt is melt | dissolved in a solvent and solution casting, the nonuniformity of extending | stretching does not generate | occur | produce and the contrast fall resulting from an optical film is also improved.

Since the melt casting and solution casting which are the film forming processes of an optical film are performed consistently from the mixing process of a raw material to the film forming process normally, the characteristic of the individual intermediate process like this invention was not observed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram which shows the manufacture of the heating melt of this invention, pellet, and dope.

<Brief description of symbols describing the main parts of the drawing>

1: hopper

2: melt extruder

3: Pelletizer pellet storage

4: dope kiln

Best Mode for Carrying Out the Invention

The optical film of this invention contains resin for forming an optical film, and the additive added to this resin. These materials should be materials capable of both melt casting and solution casting.

As resin for forming the optical film of this invention, although the cellulose resin, polycarbonate resin, cycloolefin resin, etc. which are represented by cellulose ester are mentioned, It is preferable that it is a cellulose resin.

<Cellulose resin>

The cellulose resin used in the present invention is preferably a cellulose ester, and the cellulose ester is not particularly limited, but is a carboxylic acid ester having about 2 to 22 carbon atoms, and may be an ester of an aromatic carboxylic acid, in particular, a lower fatty acid ester of cellulose. It is preferable.

Lower fatty acids in lower fatty acid esters of cellulose mean fatty acids having 6 or less carbon atoms. The acyl group which couple | bonds with a hydroxyl group may be linear, branched, and may form a ring. Another substituent may substitute.

In the case of the same degree of substitution, since the birefringence decreases when the carbon number is large, it is preferable to select among the acyl groups having 2 to 6 carbon atoms as the carbon number.

As a preferable cellulose ester for this invention, it is preferable to satisfy following formula (1) and (2) simultaneously.

2.0≤X + Y≤3.0

0≤Y≤1.5

In formula, X is substitution degree of an acetyl group, Y is substitution degree of a propionyl group or butyryl group.

Among them, triacetyl cellulose and cellulose acetate propionate are particularly preferably used. As cellulose acetate propionate, it is preferable that it is 1.0 <= <= <= 2.5, 0.1 <= <= <========= ++ <= + <=>. The measuring method of substitution degree of an acyl group can be measured according to ASTM-D817-96.

The number average molecular weight of the cellulose ester used for this invention is preferable because the mechanical strength of the film from which the range of 60000-300000 is obtained is strong. Moreover, the thing of 70000-200000 is used preferably.

Although there is no limitation in particular as a cellulose which is a raw material of the cellulose ester used for this invention, Cotton linter, wood pulp, kenaf, etc. are mentioned. In addition, the cellulose ester obtained from these can be mixed and used in arbitrary ratios, respectively.

In the cellulose ester according to the present invention, when the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), an organic acid such as acetic acid or an organic solvent such as methylene chloride is used to form a positive acetic acid such as sulfuric acid. The reaction is carried out using a magnetic catalyst.

When the acylating agent is an acid chloride, the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can synthesize | combine with reference to the method of Unexamined-Japanese-Patent No. 10-45804.

In the sixth position of the glucose unit constituting the cellulose ester, there is a highly reactive primary hydroxyl group unlike the 2nd and 3rd positions, and the primary hydroxyl group is sulfuric acid in the process of producing cellulose ester using sulfuric acid as a catalyst. The ester is preferentially formed.

For this reason, in the esterification reaction of cellulose, by increasing the amount of catalytic sulfuric acid, the average substitution degree in the 2-position and 3-position can be made higher than the 6-position of glucose unit compared with normal cellulose ester.

In addition, if tritylated cellulose can be selectively protected as needed, the 6-position hydroxyl group of the glucose unit can be selectively protected. Thus, the trityl group is protected after esterification by protecting the 6-position hydroxyl group by tritylation. By leaving (protecting group), the average substitution degree of 2nd-position and 3-position can be made higher than the 6th position of a glucose unit.

Specifically, the cellulose ester manufactured by the method of Unexamined-Japanese-Patent No. 2005-281645 can also be used preferably.

In addition, the synthesized cellulose ester is preferably purified to remove low molecular weight components or to remove components of microacetization or low acetization degree by filtration.

In addition, in the case of a mixed acid cellulose ester, it can obtain by the method of Unexamined-Japanese-Patent No. 10-45804.

In addition, a cellulose ester is also influenced by the trace metal component in a cellulose ester. These are considered to be related to water used in the manufacturing process, but a smaller number of components that can become insoluble nuclei is preferable, and metal ions such as iron, calcium, and magnesium may contain organic acidic groups. Insoluble matters may be formed by salt formation with decomposition products and the like, and few are preferable.

<Additive>

The present invention is characterized in that the melt containing the resin is molded into a film, but the melt contains an additive other than the resin.

Examples of the additive include plasticizers, sugar ester compounds, acrylic polymers, antioxidants, thermal deterioration inhibitors, particles, and the like. Here, the additive suitable for a cellulose-ester film is mentioned later.

<< plasticizer >>

In manufacture of the optical film which concerns on this invention, 1-30 mass% of 1 or more types of plasticizers are contained in a film formation material.

A plasticizer is an additive which generally has the effect of improving fragility or imparting flexibility by adding it to a polymer. However, in the present invention, the plasticizer lowers the melting temperature rather than the melting temperature of the cellulose ester alone. A plasticizer is added in order to reduce the melt viscosity of the film component material containing a plasticizer rather than a cellulose resin alone.

Moreover, since hydrophilicity of a cellulose ester is improved and it is added also for the improvement of the moisture permeability of a cellulose ester film, it has a function as a moisture permeation prevention agent.

The melting temperature of a film component material means the temperature of the state in which the said material was heated and the fluidity | liquidity was expressed here. In order to melt-flow a cellulose ester, it is necessary to heat at least higher than glass transition temperature.

Above the glass transition temperature, the elastic modulus or the viscosity decreases due to the absorption of heat, and the fluidity is expressed. However, the cellulose ester may be melted under high temperature and thermally decomposed at the same time, thereby degrading the molecular weight of the cellulose ester and adversely affecting the mechanical properties of the resulting film. Therefore, it is necessary to melt the cellulose ester at a low temperature if possible. have.

In order to reduce the melting temperature of a film component material, it can achieve by adding the plasticizer which has melting | fusing point or glass transition temperature lower than the glass transition temperature of a cellulose ester.

It is preferable that the cellulose-ester film of this invention contains 1-25 mass% of ester compounds of the molecular weight 350-1500 which have a structure which the organic acid and the trivalent or more alcohol condensed, Preferably 400-1000. The effect of planarity improvement is recognized by addition of 1 mass% or more, and when it is less than 25 mass%, it becomes difficult to bleed out, and since it is excellent in the aging stability of a film, it is preferable.

The ester compound which has a structure which the organic acid and trivalent or more alcohol condensation of this invention is represented by following General formula (1).

In the formula, R ₁ to R ₅ represent a hydrogen atom or a cycloalkyl group, aralkyl group, alkoxy group, cycloalkoxy group, aryloxy group, aralkyloxy group, acyl group, carbonyloxy group, oxycarbonyl group, oxycarbonyloxy group , They may further have a substituent. L represents a linking group, and represents a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond.

As a cycloalkyl group represented by R <_1> -R <_5> , a C3-C8 cycloalkyl group is preferable, Specifically, they are groups, such as cyclopropyl, cyclopentyl, cyclohexyl. These groups may be substituted, and as a preferable substituent, a halogen atom, for example, a chlorine atom, a bromine atom, a fluorine atom, a hydroxyl group, an alkyl group, an alkoxy group, a cycloalkoxy group, an aralkyl group (in this phenyl group, an alkyl group or a halogen atom) It may be further substituted by, etc.), alkenyl groups such as vinyl group, allyl group, phenyl group (this phenyl group may be further substituted by alkyl group or halogen atom, etc.), phenoxy group (this phenyl group may be further substituted by alkyl group or halogen atom, etc.) And unsubstituted carbonyloxy groups having 2 to 8 carbon atoms, such as acetyl group and propionyl group, and C2-C8 acyl groups such as acetyl group and propionyloxy group.

The aralkyl group represented by R ₁ to R ₅ represents a group such as a benzyl group, a phenethyl group, a γ-phenylpropyl group, and these groups may be substituted, and as a preferred substituent, a group which may be substituted with the cycloalkyl group is likewise Can be mentioned.

Examples of the alkoxy group represented by R ₁ to R ₅ include an alkoxy group having 1 to 8 carbon atoms, specifically, methoxy, ethoxy, n-propoxy, n-butoxy, n-octyloxy, isopropoxy, Each alkoxy group such as isobutoxy, 2-ethylhexyloxy, or t-butoxy.

In addition, these groups may be substituted, and as a preferable substituent, a halogen atom, for example, a chlorine atom, a bromine atom, a fluorine atom, a hydroxyl group, an alkoxy group, a cycloalkoxy group, an aralkyl group (in this phenyl group, an alkyl group or a halogen atom) Etc. may be substituted), alkenyl group, phenyl group (which may be further substituted by alkyl group or halogen atom, etc.), aryloxy group (for example, phenoxy group (more substituted by alkyl group or halogen atom, etc. in this phenyl group) Acyl groups such as acetyl group, propionyl group, and arylcarbonyloxy groups such as unsubstituted acyloxy group having 2 to 8 carbon atoms such as acetyloxy group and propionyloxy group, and benzoyloxy group Can be mentioned.

As a cycloalkoxy group represented by R <_1> -R <_5> , a C1-C8 cycloalkoxy group is mentioned as an unsubstituted cycloalkoxy group, Specifically, groups, such as cyclopropyloxy, cyclopentyloxy, cyclohexyloxy, are mentioned. Can be.

Moreover, these groups may be substituted and the group which may be substituted by the said cycloalkyl group as a preferable substituent is mentioned similarly.

Although phenoxy group is mentioned as an aryloxy group represented by R <_1> -R <_5> , As this phenyl group, it may be substituted by the substituent mentioned as a group which may be substituted by the said cycloalkyl group, such as an alkyl group or a halogen atom.

Examples of the aralkyloxy group represented by R ₁ to R ₅ include a benzyloxy group, a phenethyloxy group, and the like, and these substituents may be further substituted, and as the preferred substituents, groups which may be substituted with the cycloalkyl group are similarly mentioned. Can be.

Examples of the acyl group represented by R ₁ to R ₅ include an unsubstituted acyl group having 2 to 8 carbon atoms such as an acetyl group and a propionyl group (hydrocarbon groups of the acyl group include alkyl, alkenyl and alkynyl groups), These substituents may be further substituted, and the group which may be substituted by the said cycloalkyl group as a preferable substituent is mentioned similarly.

The carbonyloxy group represented by R ₁ to R ₅ includes an unsubstituted acyloxy group having 2 to 8 carbon atoms such as an acetyloxy group and propionyloxy group (the hydrocarbon group of the acyl group includes alkyl, alkenyl, alkynyl groups). And arylcarbonyloxy groups, such as a benzoyloxy group, although these groups may be further substituted by the same group as the group which may further be substituted with the said cycloalkyl group.

The oxycarbonyl group represented by R ₁ to R ₅ represents an alkoxycarbonyl group such as methoxycarbonyl group, ethoxycarbonyl group or propyloxycarbonyl group, and aryloxycarbonyl group such as phenoxycarbonyl group.

These substituents may further be substituted and the group which may be substituted by the said cycloalkyl group as a preferable substituent is mentioned similarly.

The oxycarbonyloxy group represented by R ₁ to R ₅ represents a C 1-8 alkoxycarbonyloxy group such as a methoxycarbonyloxy group, and these substituents may be further substituted, and the preferred substituents are the cycloalkyl group. The group which may be substituted by is mentioned similarly.

One of R ₁ to R ₅ may be linked to each other to form a ring structure.

In addition, the connecting group represented by L is only represent a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond, an alkylene group include a methylene group, an ethylene group, a group, such as a propylene group, these groups are added to the R ₁ to It may be substituted by the group mentioned as a group which may be substituted by the group represented by R <_5> .

Especially, as a coupling group represented by L, what is especially preferable is a direct bond and aromatic carboxylic acid.

In the present invention, the organic acid represented by the general formula (1) constituting the ester compound to be a plasticizer includes at least R ₁ or R ₂ in the alkoxy group, acyl group, oxycarbonyl group, carbonyloxy group, and oxycarbonyl. It is preferable to have an oxy group. Moreover, the compound which has several substituent is also preferable.

In addition, in this invention, the organic acid which substitutes the hydroxyl group of a trivalent or more alcohol may be single type, or multiple types may be sufficient as it.

In the present invention, the trihydric or higher alcohol compound which reacts with the organic acid represented by the formula (1) to form a polyhydric alcohol ester compound is preferably a trivalent to 20-valent aliphatic polyhydric alcohol. It is preferable that it is represented by following formula (3).

R '-(OH) m

In formula, R 'is a m-valent organic group, m is a positive integer of 3 or more, and an OH group represents an alcoholic hydroxyl group. Especially preferable thing is 3 or 4 polyhydric alcohol as m.

As an example of a preferable polyhydric alcohol, the following are mentioned, for example, However, this invention is not limited to this.

Adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, di Pentaerythritol, tripentaerythritol, galactitol, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

In particular, glycerin, trimethylol ethane, trimethylol propane and pentaerythritol are preferable.

Esters of the organic acid represented by the formula (1) and the trihydric or higher polyhydric alcohol can be synthesized by a known method. Although the typical synthesis example was shown in the Example, the method of condensation of the organic acid represented by the said Formula (1) with a polyhydric alcohol, for example in presence of an acid, and also the organic acid beforehand as an acid chloride or an acid anhydride, There is a method of reacting with an alcohol, a method of reacting a phenyl ester of an organic acid with a polyhydric alcohol, and the like, and it is preferable to select a method having a good yield appropriately according to the target ester compound.

As a plasticizer which consists of ester of the organic acid represented by General formula (1) and a trivalent or more polyhydric alcohol, the compound represented by following General formula (2) is preferable.

In the formula, R ₆ to R ₂₀ represent a hydrogen atom or a cycloalkyl group, aralkyl group, alkoxy group, cycloalkoxy group, aryloxy group, aralkyloxy group, acyl group, carbonyloxy group, oxycarbonyl group, oxycarbonyloxy group These may further have a substituent. R ₂₁ represents a hydrogen atom or an alkyl group.

For the cycloalkyl group, aralkyl group, alkoxy group, cycloalkoxy group, aryloxy group, aralkyloxy group, acyl group, carbonyloxy group, oxycarbonyl group, and oxycarbonyloxy group of R ₆ to R ₂₀ , R in the general formula (1) _The same group as ₁ to R ₅ can be mentioned.

Below, the specific compound of the polyhydric alcohol ester which concerns on this invention is illustrated.

Although it does not specifically limit as other plasticizer which can be used for this invention, Preferably it is a polyhydric carboxylic acid ester plasticizer, a glycolate plasticizer, a phthalic acid ester plasticizer, a fatty acid ester plasticizer, a polyester plasticizer, and an acrylic type Plasticizer and the like.

Among them, when using two or more plasticizers, it is preferable that one or more of them is a polyhydric alcohol ester plasticizer having a molecular weight of 350 to 1500 having a structure in which an organic acid and a trivalent or higher alcohol are condensed.

<< sugar ester compound >>

It is preferable that the optical film of this invention melt-film-forms the molten composition containing the sugar ester compound which esterified the hydroxyl group of the sugar compound which 1-1 or more types of structures chosen from the furanose structure and the pyranose structure couple | bonded 1-12. Do.

Examples of the sugar compound of the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellulose trios, maltotriose, raffinose, and the like. It is preferable to have both a noose structure and a pyranose structure. An example is sucrose.

The sugar ester compound of this invention is the thing in which one part or all part of the hydroxyl group which a sugar compound has are esterified, or its mixture.

<< acrylic polymer >>

In this invention, it is preferable to melt-film-form the melt composition containing the acryl-type polymer whose weight average molecular weights are 500 or more and 30000 or less.

As an acrylic polymer of this invention, the weight average molecular weights 5000-500000 obtained by copolymerizing the ethylenically unsaturated monomer Xa which does not have an aromatic ring and a hydrophilic group in a molecule | numerator, and the ethylenically unsaturated monomer Xb which does not have an aromatic ring in a molecule | numerator and have a hydrophilic group The polymer X of these is mentioned.

And more preferably, it is preferable to use together the polymer Y of the weight average molecular weights 500 or more and 3000 or less obtained by superposing | polymerizing the ethylenically unsaturated monomer Ya which does not have an aromatic ring.

Polymer X of the present invention is a polymer having a weight average molecular weight of 5000 to 30000, obtained by copolymerizing an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in a molecule and an ethylenically unsaturated monomer Xb having a hydrophilic group without an aromatic ring in a molecule. .

Preferably, Xa is an acrylic or methacrylic monomer which does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer which does not have an aromatic ring in the molecule and has a hydrophilic group.

In addition, the measurement of the number average molecular weight and weight average molecular weight of resin and the additive in this invention was measured using the gel permeation chromatography. Measurement conditions are as follows.

Solvent: Methylene Chloride

Column: Shodex K806, K805, K803G (using three manufactured by Showa Denko Co., Ltd.)

Column temperature: 25 ℃

Sample concentration: 0.1% by mass

Detector: RI Model 504 (made by GL Science)

Pump: L6000 (manufactured by Hitachi Seisakusho Co., Ltd.)

Flow rate: 1.0 ml / min

Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 1000000 to 500 was used as a calibration curve by 13 samples. 13 samples are used at approximately equal intervals.

<< antioxidant, thermal deterioration agent >>

In this invention, what is normally known can be used as antioxidant and a thermal deterioration inhibitor. In particular, those of a lactone-based, sulfur-based, phenol-based, double-bond-based, hindered amine-based and phosphorus-based compounds can be preferably used.

For example, it is preferable to include what is marketed under the brand names "Irgafos XP40" and "Irgafoss XP60" by Ciba Specialty Chemicals.

As said phenol type compound, what has a structure of 2, 6- dialkyl phenol is preferable, for example, Ciba Specialty Chemicals, Inc., "Irganox 1076", and "Irganox 1010" It is preferable that it is marketed by.

The phosphorus compound is, for example, "Sumilizer GP" at Sumitomo Kagaku Kogyo Co., Ltd., "ADK STAB PEP-24G", "ADK STAB PEP-36" and "ADK from Asahi Denka High School Co., Ltd.". STAB 3010 ", Shiva Specialty Chemicals Co., Ltd.," Irgafoss P-EPQ ", API Corporation Corp., and Sakai Kagaku Kogyo Co., Ltd. are sold under the brand name" GSY-P101 ". .

The hindered amine-based compound is, for example, "ADK STAB LA-52" in Shiva Specialty Chemicals Co., Ltd., "Tinuvin 144" and "Tinubin 770", Asahi Denka Kogyo Co., Ltd. It is preferable that it is marketed by a brand name.

It is preferable that the said sulfur type compound is marketed under the brand names "Smallizer TPL-R" and "Smallizer TP-D", for example by Sumitomo Chemical Co., Ltd ..

It is preferable that the said double bond type compound is marketed by Sumitomo Chemical Co., Ltd. under the brand names "Smallizer GM" and "Smallizer GS".

It is also possible to contain a compound having an epoxy group described in US Pat. No. 4,137,201 as an acid trapping agent.

Although these antioxidants etc. are suitably determined according to the process at the time of regeneration use, they are generally added in 0.05-20 mass% with respect to resin which is a main raw material of a film.

These antioxidants and thermal deterioration inhibitors can obtain a synergistic effect by using several kinds of different types of compounds together than using only one type. For example, combination of lactone type, phosphorus type, phenol type and double bond type compound is preferable.

<< reduction adjustment agent >>

In the cellulose-ester film of this invention, you may contain the compound for adjusting retardation.

As the compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings described in European Patent No. 911,656 A2 may be used.

Moreover, you may use together 2 or more types of aromatic compounds. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. It is especially preferable that it is an aromatic hetero ring, and an aromatic hetero ring is generally an unsaturated hetero ring. Especially, the compound which has a 1,3,5-triazine ring is especially preferable.

In the cellulose-ester film which concerns on this invention, since a haze value exceeds 1.0%, it affects as an optical material, Preferably, haze value is less than 1.0%, More preferably, it is less than 0.5%. The haze value can be measured based on JIS-K7136.

<< coloring agent >>

In this invention, it is preferable to use a coloring agent. The colorant means a dye or a pigment, but the present invention refers to an effect of making the color tone of the liquid crystal display blue, or adjusting the yellow index and reducing haze.

Although various dyes and pigments can be used as a coloring agent, anthraquinone dye, an azo dye, a phthalocyanine pigment, etc. are effective. Although the specific example of a preferable coloring agent is given to the following, it is not limited to these.

<< other additive >>

The cellulose ester film of this invention can be made to contain the additive which can be added to a normal cellulose ester film other than the said compound.

These additives include plasticizers, ultraviolet absorbers, fine particles and the like.

Although the ultraviolet absorber used for this invention is not specifically limited, For example, an oxybenzophenone type compound, a benzotriazole type compound, a salicylic acid ester type compound, a benzophenone type compound, the cyanoacrylate type compound, a triazine type compound, nickel complex salt A system compound, an inorganic powder, etc. are mentioned. It may be a polymer ultraviolet absorber.

As a commercial item, Tinuvin 171, Tinuvin 234, Tinuvin 360, Tinuvin 928 (both manufactured by Shiba Specialty Chemicals Co., Ltd.), "Sumisorb 250" (manufactured by Sumitomo Chemical Co., Ltd.), LA31 (manufactured by Asahi Denka Co., Ltd.) ), And the like.

As the fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, calcium silicate hydrate, aluminum silicate, Magnesium silicate and calcium phosphate.

It is preferable that microparticles | fine-particles contain silicon from a low turbidity, and especially silicon dioxide is preferable.

As for the average particle diameter of the primary particle of microparticles | fine-particles, 5-50 nm is preferable, More preferably, it is 7-20 nm. It is preferable to contain these mainly as a secondary aggregate of particle size 0.05-0.3 micrometer.

It is preferable that content of these microparticles | fine-particles in a cellulose ester film is 0.05-1 mass%, and 0.1-0.5 mass% is especially preferable. In the case of the cellulose-ester film of the multilayered constitution by a covalent smoke method, it is preferable to contain the particle | grains of this addition amount on the surface.

The fine particles of silicon dioxide are commercially available under the trade names of, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, and NAX50 (produced by Nippon Aerosil Co., Ltd.). have.

The fine particles of zirconium oxide are commercially available under the trade names of Aerosil R976 and R811 (above manufactured by Nippon Aerosil Co., Ltd.), for example.

Examples of the polymer include silicone resins, fluororesins and acrylic resins. A silicone resin is preferable and it is preferable to have a three-dimensional mesh-like structure especially, for example, Tospal 103, 105, 108, 120, 145, 3120, and 240 (above Toshiba Silicone Co., Ltd. make). It is marketed under a brand name of) and can use it.

Among them, aerosil 200V and aerosil R972V are particularly preferably used because the effect of lowering the coefficient of friction is great while keeping the turbidity of the cellulose ester film low.

<Flexible film forming of a cellulose-ester film>

<< adjustment of heating melt >>

The method of adjusting a heating melt by heat-melting and kneading the resin of this invention and an additive is demonstrated.

(1) preheat

The dried resin is thrown into the hopper of the melt extruder. The hopper is made into Tg-50 degreeC or more and Tg or less of resin at this time. This removes moisture adsorbed in the hopper.

(2) addition of additives

The additive is generally added while the resin is conveyed to the kneader. The additive may be powder or may be in the form of a slurry dispersed at a concentration of 5 to 20% by mass in a suitable dispersion medium such as water.

However, when it contains water or an organic solvent, it is necessary to remove in a polymer rapidly during kneading. For this reason, it is preferable to provide a vacuum degassing pump in the middle of a kneader.

In the case of powder, it is quantitatively supplied by an injector such as a screw injector or an electron injector using a hopper separate from the resin. In addition, in the case of a slurry form, it can quantitatively add using high-viscosity metering pumps, such as a mono pump and a tube pump.

(3) melting and kneading extrusion

The resin and the additive are kneaded at a melting temperature of Tg + 30 ° C. to 80 ° C. At this time, the melting temperature may be performed at a constant temperature, or may be divided into several and controlled. More preferably, the temperature on the upstream side (hopper side) is 1 ° C. or more and 50 ° C. or less, more preferably 2 ° C. or more and 30 ° C. or less, more preferably 3 ° C. or more 20 than the temperature on the downstream side (T-die side). It is preferable to make it higher in degrees C or less since it can suppress decomposition of resin more.

Since the melting point of the material in which the resin and the plasticizer are used decreases, it is preferable to make the upstream portion governing this higher temperature in order to promote melting, and to lower the temperature in order to suppress decomposition after melting.

Preferable kneading time is 2 minutes or more and 60 minutes or less, More preferably, they are 3 minutes or more and 40 minutes or less, More preferably, they are 4 minutes or more and 30 minutes or less. Moreover, it is also preferable to carry out the inside of a melt extruder in inert (nitrogen etc.) airflow.

The additive may be mixed with the resin before kneading, may be added during melting of the resin, or may be added after the resin is completely melted. In this invention, making a heat-kneaded material pelletized in this process is also a preferable method from a viewpoint of storage stability.

It is preferable to use a pelletizer for pelletizing, and to adjust the temperature, the discharge amount, the viscosity of the material, etc. using a pelletizer such as a strand cutting method, a hot cutting method, a watering cutting method, an underwater cutting method, etc. Pellets are prepared.

Although the size of a pellet does not have a restriction | limiting in particular, It is preferable from the viewpoint of solubility to a solvent, storage stability, etc. in the range of the cube of 1 mm x 1 mm x 1 mm-20 mm x 20 mm x 20 mm.

Although the additive which concerns on this invention may add a whole part at the time of manufacture of dope after a heating and kneading | mixing, the addition at the time of preparation of dope is 50 mass% or less, Preferably it is 20 mass% or less.

In addition, the measuring method of glass transition temperature (Tg) was performed using Seiko Denshi Kogyo Co., Ltd. differential scanning calorimeter DSC220 according to JISK7121.

About 10 mg of the sample was set, and the temperature was raised from room temperature to 250 ° C. at 20 ° C./min for 10 minutes under the condition of nitrogen flow rate 50 ml / min (first scan), and then 30 ° C. at a rate of 20 ° C./min. The temperature was lowered to 10 minutes (secondary scan), and further heated to 250 ° C at 20 ° C / min (third scan) to obtain a DSC curve. The glass transition temperature was calculated | required from the DSC curve of the obtained 3rd scan.

<< solution flexibility >>

The manufacture of the optical film of this invention is a process of manufacturing the dope by melt | dissolving the pellet obtained by kneading and extruding resin and an additive as a heating melt in a solvent, the process of casting on the endless metal support body which transfers dope infinitely, and the flexible dope It is carried out by the process of drying as a web, the process of peeling from a metal support body, the process of extending | stretching or holding width, the process of further drying, and the process of winding up the finished film.

The process of manufacturing dope is described.

BRIEF DESCRIPTION OF THE DRAWINGS The conceptual diagram which shows the manufacture of the heating melt of this invention, pellet, and dope.

The resin and the additive are introduced into the melt extruder 2 from the hopper 1, kneaded and heated and melted, and then the heated melt is pelletized and stored in the pelletizer pellet storage 3.

The pellets of the heated melt are dissolved and mixed in a solvent in the dope kiln 4 to be dope.

As described above, in the present invention, all of the film forming materials may be supplied by the heating melt, and additives such as resins, particles, plasticizers, and stabilizers may be further added and dissolved apart from the heating melt. In that case, the additive may be the same kind or different kinds.

The concentration of the resin in the dope is preferable because a thick one can reduce the dry load after being pliable to the metal support, but when the concentration of the cellulose ester is too high, the load during filtration increases and the filtration accuracy deteriorates. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%. These concentrations can be adjusted by the addition amount of a pellet and the addition amount of resin to add.

Although the solvent used by the dope of this invention may be used independently or may use 2 or more types together, For example, when using cellulose ester as resin, it is more efficient to mix and use the good solvent of a cellulose ester, and a nonsolvent. It is preferable from the viewpoint of, and the one with many good solvents is preferred from the viewpoint of solubility of the cellulose ester.

As for the preferable range of the mixing ratio of a good solvent and a nonsolvent, a good solvent is 70-98 mass%, and a nonsolvent is 2-30 mass%. A good solvent and a nonsolvent are defined as a nonsolvent which dissolves the cellulose ester to be used independently and does not swell or melt | dissolve alone with a good solvent.

For this reason, a good solvent and a nonsolvent change with the average degree of aceticization (acetyl group substitution degree) of a cellulose ester, For example, when using acetone as a solvent, the acetate ester of a cellulose ester (acetyl group substitution degree 2.4), cellulose acetate In propionate, it becomes a good solvent, and in cellulose acetate ester (acetyl group substitution degree 2.8), it becomes a nonsolvent.

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

In addition, although the nonsolvent 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 is contained in dope.

In addition, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying in a film forming process, and reuses and uses it.

As a dissolution method of the cellulose ester at the time of manufacturing the dope described above, a general method can be used. When heating and pressurization are combined, it can heat above the boiling point in normal pressure. It is preferable to melt and dissolve above the boiling point at the atmospheric pressure of the solvent while heating to a temperature in a range in which the solvent does not boil under pressure, because it prevents the generation of bulky debris called gels or lumps.

In addition, a method in which the resin is mixed with a non-solvent to wet or swell, followed by addition of a good solvent to dissolve is also preferably used.

Pressurization can also be performed by the method of press-fitting inert gas, such as nitrogen gas, or the method of raising the vapor pressure of a solvent by heating. It is preferable to perform heating externally, for example, a jacket type thing is preferable because temperature control is easy.

The higher the heating temperature after the addition of the solvent is preferable from the viewpoint of the solubility of the resin, but if the heating temperature is too high, the required pressure becomes large and productivity is deteriorated. Preferable heating temperature is 45-120 degreeC, 60-110 degreeC is more preferable, and 70 degreeC-105 degreeC is still more preferable. In addition, the pressure is adjusted so that the solvent does not boil at the set temperature.

Alternatively, a cooling dissolution method is also preferably used, whereby the resin can be dissolved in a solvent such as methyl acetate.

Next, this dope is filtered using a suitable filter medium, such as a filter paper. As a filter medium, although absolute absolute filtration precision is preferable in order to remove an insoluble matter etc., when the absolute filtration precision is too small, there exists a problem that clogging of a filter medium is easy to generate | occur | produce.

For this reason, the filter medium of 0.008 mm or less of absolute filtration accuracies is preferable, A 0.001-0.008 mm filter medium is more preferable, A 0.003-0.006 mm filter medium is still more preferable.

There is no restriction | limiting in particular in the material of a filter medium, Although a normal filter medium can be used, The filter medium made from plastics, such as a polypropylene and Teflon (trademark), and the metal filter material, such as stainless steel, are preferable because there is no fallout of a fiber. It is preferable to remove and reduce the impurities contained in the raw material, particularly the bright point foreign matter, by filtration.

Although dope can be filtered by a conventional method, the method of filtering while heating at the temperature of the range which the solvent does not boil above the boiling point in normal pressure of a solvent and under pressure is the difference of the filtration pressure before and behind filtration (pressure difference Rise is small, which is preferable. Preferable temperature is 45-120 degreeC, 45-70 degreeC is more preferable, and it is still more preferable that it is 45-55 degreeC.

It is preferable that the filtration pressure is small. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and even more preferably 1.0 MPa or less.

Next, the softness of dope is demonstrated.

The dope is passed through a liquid feed pump (e.g., a pressurized metering gear pump) to be fed to the press die, and the flexible position on a metal support such as an endless metal belt, for example, a stainless steel belt, or a rotating metal drum, which is transported indefinitely. It is a process to cast dope from a pressurized die slit.

The pressurization die which can adjust the slit shape of the die part of die | dye and is easy to make film thickness uniform is preferable. There exist a coat hanger die, a T die, etc. in pressurization die | dye, and all are used preferably. The surface of the metal support is mirror surface.

In order to raise a film forming speed | rate, two or more press dies may be provided on a metal support body, and dope amount may be divided | stacked and layered. Or it is also preferable to obtain the film of a laminated structure by the co-combustion method which casts a plurality of dope simultaneously.

The metal support in the casting (casting) step is preferably mirror-finished with a surface, and as the metal support, a stainless steel belt or a drum plated with a casting is preferably used. The width of the casting can be 1 to 4 m.

The surface temperature of the metal support of the casting process is preferably at a temperature below -50 ° C. to a boiling point of the solvent, because a higher temperature can speed up the drying speed of the web, but if it is too high, the web may foam or planarity. It may deteriorate.

Preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is more preferable. Or it is also a preferable method to gelatinize a web by cooling and peeling from a drum in the state containing many residual solvents.

The method of controlling the temperature of the metal support is not particularly limited, but there is a method of blowing hot or cold air or a method of bringing hot water into contact with the back surface of the metal support. Since the transfer of heat is efficiently performed by using hot water, the time until the temperature of the metal support becomes constant is preferable. When using warm air, the wind of temperature higher than the target temperature may be used.

In order for an optical film to show favorable planarity, the residual solvent amount at the time of peeling a web from a metal support body is preferably 10 to 150 mass%, more preferably 20 to 40 mass% or 60 to 130 mass%, particularly Preferably it is 20-30 mass% or 70-120 mass%.

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

Residual solvent amount (mass%) = {(M-N) / N} × 100

In addition, M is the mass of the sample taken at the arbitrary time during manufacture or after a web or film, N is the mass after heating M at 115 degreeC for 1 hour.

Moreover, in the drying process of an optical film, it is preferable to peel a web from a metal support body, and to further dry and to make residual solvent quantity 1 mass% or less, More preferably, it is 0.1 mass% or less, Especially preferably, it is 0-. It is 0.01 mass% or less.

In the film drying process, generally, the method of drying while conveying a web is employ | adopted by the roll drying method (the method of drying the web by passing a plurality of rolls arranged up and down alternately) and a tenter system.

In order to manufacture the optical film of this invention, it extends in the conveyance direction (vertical direction) in the place where the amount of residual solvent of a web immediately after peeling from a metal support body is wide, and also the width | variety by the tenter system which grips both ends of a web with a clip etc. It is especially preferable to extend | stretch in a direction (horizontal direction).

In order to stretch in a longitudinal direction immediately after peeling, it is preferable to peel peeling tension at 210 N / m or more, Especially preferably, it is 220-300 N / m.

For example, it can extend | stretch sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of a film, and the direction orthogonal in it and a film surface, ie, the width direction.

The stretching ratio in the biaxial direction perpendicular to each other is preferably in the range of 1.0 to 2.0 times in the casting direction and 1.01 to 2.5 times in the width direction, respectively, and is 1.01 to 1.5 times in the casting direction and 1.05 in the width direction, respectively. It is preferable to carry out in the range of -2.0 times.

There is no restriction | limiting in particular in the method of extending a web. For example, a method in which a circumferential speed difference is applied to a plurality of rolls and stretched in the longitudinal direction using a roll circumferential speed therebetween, both ends of the web are fixed with clips or pins, and the distance between the clips and pins is extended in the advancing direction. The method of extending | stretching in a longitudinal direction, the method of extending | stretching in a horizontal direction, extending | stretching in a horizontal direction, or the method of extending | stretching simultaneously in a longitudinal direction, and extending | stretching in both directions later and later etc. are mentioned.

Of course, these methods can also be used in combination. In addition, in the so-called tenter method, it is preferable to drive the clip portion by a linear drive method because smooth stretching can be performed and the risk of breaking or the like can be reduced.

It is preferable to perform these width maintenance or extending | stretching of the lateral direction of a film forming process with a tenter, and a pin tenter or a clip tenter may be sufficient as it.

The means for drying the web is not particularly limited and generally can be carried out by hot air, infrared rays, heating rolls, microwaves or the like.

It is preferable to make drying temperature in the drying process of a web step by step high at 40-200 degreeC, and performing in the range of 50-140 degreeC is more preferable, since dimensional stability is favorable.

Although the film thickness of an optical film is not specifically limited, The range of 10-200 micrometers is used. In particular, the film thickness is particularly preferably in the range of 20 to 100 m. More preferably, it is the range of 30-90 micrometers. Most preferably, it is the range of 40-80 micrometers.

As for the optical film of this invention, the thing of width 1-4m is used. Especially the thing of width 1.4-4 m is used preferably, Especially preferably, it is 1.6-3 m.

<Optical characteristics of the optical film>

In the optical film of the present invention, the retardation value Ro defined by the following formula (i) is preferably 0 to 300 nm, and the retardation value Rt defined by the following formula (ii) is preferably in the range of -600 to 600 nm. Do.

Moreover, the more preferable range is the range of 0-80 nm of Ro value, -400-400 nm of Rt value, The range of 0-40 nm of Ro value and -200-200 nm of Rt value is especially preferable range.

When using the optical film of this invention as retardation film, it is preferable that retardation value Ro is 20 nm or more and 300 nm or less, and retardation value Rt is 70 nm or more and 400 nm or less.

Equation i

Ro = (nx-ny) × d

<Equation ii>

Rt = ((nx + ny) / 2-nz) × d

(In the formula, Ro is the film surface retardation value, Rt is the film thickness direction retardation value, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the film thickness direction Refractive index, d represents the thickness (nm) of the film)

The said refractive index can be calculated | required at the wavelength of 590 nm in the film left for 24 hours in 23 degreeC and 55% RH environment using KOBRA-21ADH (Oji Keisoku Kiki Co., Ltd.), for example.

In order to obtain said retardation values Ro and Rt, it is preferable that an optical film takes the structure of this invention, and performs refractive index control by an extending | stretching operation further.

When the slow axis or fastening axis of the optical film of the present invention exists in the film plane, and the angle formed with the film forming direction is θ1, θ1 is preferably -1 ° or more and + 1 ° or less, and preferably -0.5 ° or more and + 0.5 ° or less. More preferred.

This (theta) 1 can be defined as an orientation angle, and measurement of (theta) 1 can be performed using automatic birefringence system KOBRA-21ADH (Oji Keisokukiki). θ1 satisfying the above relationship can contribute to obtaining high luminance in the display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in the color liquid crystal display device.

<Optical film>

The optical film which concerns on this invention can be used as a polarizing plate protective film, retardation film, etc. in a liquid crystal display device.

<< polarizing plate protective film >>

As for the thickness of the polarizing plate protective film of this invention, 10-500 micrometers is preferable. 20-150 micrometers is especially preferable, and a preferable range is 25-90 micrometers. When the polarizing plate protective film is thick, the polarizing plate after polarizing plate processing becomes too thick, and is particularly unsuitable for the purpose of thin and light in liquid crystal display used in notebook computers and mobile electronic devices.

On the other hand, when a polarizing plate protective film is thin, expression of retardation becomes difficult, and also the moisture permeability of a film becomes high and the ability to protect a polarizer from humidity may fall.

When the slow axis or fast axis of a polarizing plate protective film exists in a film surface, and makes the angle formed with the film forming direction into (theta) 1, it is preferable to make (theta) 1 become -1 to +1 degree, Preferably it is -0.5 to +0.5 degree. . It is preferable that it is -0.1 to +0.1 degrees especially when providing a phase difference function.

This (theta) 1 can be defined as an orientation angle, and measurement of (theta) 1 can be performed using automatic birefringence system KOBRA-21ADH (made by Oji Keisoku Kiki Co., Ltd.).

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

When using the cellulose-ester film which concerns on this invention as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method, for example, a roll to roll.

There exists a method of bonding a polarizing plate protective film to both surfaces of a polarizer using the fully saponified polyvinyl alcohol aqueous solution on both surfaces of the polarizer which alkali-processed the obtained cellulose-ester film, and immersed and stretched a polyvinyl alcohol film in the iodine solution, The polarizing plate protective film of this invention directly bonds to a polarizer on at least one surface.

The polarizing plate protective film of this invention can also be used for the other side. Alternatively, commercially available cellulose ester films prepared by the solution casting method (Konica Minolta Tak KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4CR, KC4UE, KC8UE, KC8UE, HA, KC8UX-RHA (above, manufactured by Konita Minolta Opto Co., Ltd.), or a polyester film, a cycloolefin-based resin film (Zeonor film (manufactured by Nihon Zeon), an aton film (manufactured by JSR)) A film having a film thickness of 10 to 150 µm may be used.

Instead of the alkali treatment, an easy-adhesion process described in Japanese Patent Application Laid-Open Nos. Hei 6-94915 and 6-118232 can be carried out to perform polarizing plate treatment, or a corona discharge treatment or a plasma treatment can be performed. It may be.

A polarizing plate is comprised from the polarizer and the protective film which protects both surfaces, and can further comprise the protective film on one side of the said polarizing plate, and the independent film was bonded to the opposite side. A protective film and an independent film are used for the purpose of protecting a polarizing plate at the time of a polarizing plate shipment, a product inspection, etc.

In this case, a protective film is bonded for the purpose of protecting the surface of a polarizing plate, and is used for the opposite surface side of the surface which bonds a polarizing plate to a liquid crystal plate. In addition, an independent film is used for the purpose of covering the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

In addition, the polarizer which is a main component of a polarizing plate is an element which passes only the light of the polarization plane of a fixed direction, and the typical polarizer currently known is a polyvinyl alcohol-type polarizing film, and is used preferably. This is dyed with iodine or dichroic dye on polyvinyl alcohol-based films such as ethylene-modified polyvinyl alcohol having 1 to 4 mol% of polyvinyl alcohol or ethylene units, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%. have.

The polarizer is preferably uniaxially stretched or dyed a polyvinyl alcohol-based film, or after uniaxially stretched after dyeing, preferably a durable treatment with a boron compound is preferably used.

On the surface of the said polarizer, one side of the polarizing plate protective film of this invention is bonded together, and a polarizing plate is formed. Preferably, it joins by the water-based adhesive which has a fully saponified polyvinyl alcohol etc. as a main component. As film thickness of a polarizer, the thing of 5-30 micrometers is used preferably.

<< phase difference film >>

The optical film of this invention can be used suitably also as retardation film.

It is preferable to adjust the retardation Ro distribution of the in-plane direction of the optical film of this invention to 5% or less, More preferably, it is 2% or less, Especially preferably, it is 1.5% or less. Moreover, although it is preferable to adjust the retardation Rth distribution of the thickness direction of a film to 10% or less, More preferably, it is 2% or less, Especially preferably, it is 1.5% or less.

In the retardation film, the smaller the variation in distribution of the retardation value is preferable, and when the polarization plate containing the retardation film is used in the liquid crystal display device, the smaller variation in the retardation distribution is preferable from the viewpoint of preventing color unevenness. .

In-plane retardation is used to adjust the retardation film so as to have a retardation value suitable for improving display quality of the liquid crystal cell in VA mode or TN mode, and in particular, to divide it into the above-mentioned multi-domain as VA mode so that it is preferably used in MVA mode. It is required to adjust Ro to greater than 30 nm, to 95 nm or less, and to adjust the thickness direction retardation Rth to greater than 70 nm and 400 nm or less.

The above-mentioned in-plane retardation Ro is the display surface when the two polarizing plates are arranged in cross nicol and the liquid crystal cell is arranged between the polarizing plates and is in the cross nicol state on the basis of the observation from the normal direction of the display surface. When observed obliquely from the normal line, a deviation from the cross nicol state of the polarizing plate occurs, and mainly compensates for light leakage, which is a factor.

The retardation in the thickness direction contributes mainly to compensating for the birefringence of the liquid crystal cell which is recognized when viewed in an oblique manner when the liquid crystal cell is in the black display state in the TN mode or the VA mode, particularly the MVA mode.

In the liquid crystal display device, a TAC film having an in-plane retardation Ro = 0 to 4 nm and a thickness direction retardation Rth = 20 to 50 nm and a thickness of 35 to 85 μm is used as a polarizing plate protective film commercially available on one polarizing plate, for example. If present, the polarizing film disposed on the other polarizing plate and the in-plane retardation Ro are larger than 30 nm and 95 nm or less, and the thickness direction retardation Rth is larger than 140 nm and 400 nm or less.

Generally, as a retardation film, what has little fluctuation | variation of Ro or Rth as said retardation value is calculated | required in order to acquire stable optical characteristic. In the liquid crystal display device of the birefringence mode in particular, these fluctuations may be the cause of image nonuniformity.

The manufacturing effect obtained by this invention becomes more remarkable especially in the long winding of 100 m or more, and when it becomes longer in 1500 m, 2500 m, 5000 m, and 10000 m, the manufacturing effect of polarizing plate manufacture is acquired.

<Liquid crystal display device>

The polarizing plate including the optical film of the present invention (which also serves as a phase difference film) can express high display quality as compared with a normal polarizing plate, and in particular, a multi-domain type liquid crystal display device, more preferably a multi-refraction mode It is suitable for use in a domain type liquid crystal display device.

The polarizer of the present invention can be used in a multi-domein vertical alignment (MVA) mode, a patterned vertical alignment (PVA) mode, a continuous pinwheel alignment (CPA) mode, an optically compensated bend (OCB) mode, an IPS mode, and the like. It is not limited to arrangement | positioning of a polarizing plate.

The liquid crystal display device is also applied as a device for colorization and moving picture display, and the display quality is improved by the present invention, and the improvement of contrast and durability of the polarizing plate are improved, so that eyes are not tired easily and faithful moving picture display is possible.

In the liquid crystal display device containing at least the polarizing plate containing retardation film, one polarizing plate containing the polarizing plate protective film of this invention is arrange | positioned with respect to a liquid crystal cell, or two sheets are arrange | positioned at both sides of a liquid crystal cell.

At this time, it can contribute to the improvement of display quality by using so that the polarizing plate protective film side of this invention contained in a polarizing plate may face the liquid crystal cell of a liquid crystal display device.

In such a configuration, the polarizing plate protective film of the present invention can optically compensate the liquid crystal cell.

When using the polarizing plate of this invention for a liquid crystal display device, what is necessary is just to make at least one polarizing plate of the polarizing plates of a liquid crystal display device as the polarizing plate of this invention. By using the polarizing plate of this invention, display quality improves and the liquid crystal display device excellent in viewing angle characteristic can be provided.

Although an Example is given to the following and this invention is concretely demonstrated to it, this invention is not limited to this.

(Material to use)

<Resin>

(Cellulose acetate propionate)

C-1 (total acyl group substitution degree 2.5, acetyl group substitution degree: 1.6, propionyl group substitution degree: 0.9, Tg: 170 ° C, number average molecular weight 80000)

C-2 (total acyl group substitution degree 2.4, acetyl group substitution degree: 1.5, propionyl group substitution degree: 0.9, Tg: 175 ° C, number average molecular weight 80000)

C-3 (total acyl group substitution degree 2.4, acetyl group substitution degree: 1.3, propionyl group substitution degree: 1.1, Tg: 160 ° C, number average molecular weight 70000)

In addition, the measuring method of substitution degree of acyl groups, such as an acetyl group and a propionyl group, was measured according to the prescription | regulation of ASTM-D 817-96.

<Plasticizer>

P-1 Polyhydric Alcohol Ester Compound 62

P-2 Polyhydric Alcohol Ester Compound 48

P-3 Polyhydric Alcohol Ester Compound 64

P-4 Polyhydric Alcohol Ester Compound 63

P-5 Polymethyl methacrylate polymer (number average molecular weight 7000)

P-6 ethylphthalyl ethyl glycolate

P-7 triphenylphosphate

<Production of Optical Film (Retardation Film) V-101>

(Preparation of Heating Melt 1)

Resin: 100 parts by mass of cellulose acetate propionate C-1

Additive 1: 10 parts by mass of plasticizer P-1

Additive 2: 0.3 parts by mass of GSY-P101 (manufactured by Sakai Chemical Industries, Ltd.)

Additive 3: 0.3 parts by weight of smearizer GS (manufactured by Sumitomo Chemical Industries, Ltd.)

Additive 4: Irganox-1010 (Ciba Specialty Chemicals) 0.5 parts by mass

The material is mixed with a Henschel mixer, the material is melted and kneaded at an temperature shown in Table 1 below using an extruder, and the pellets are combined into pellets at an outlet temperature of Tg-5 ° C of the heated melt to form a heated melt. 1 was obtained. The size of the pellets was a cube of 10 mm x 10 mm x 10 mm.

Subsequently, heated melts 2 to 12 were prepared as shown in Table 1 in the same manner as heated melt 1. In addition, the heating melt 13 was manufactured similarly to the heating melt 1 with the structure of Table 1 except not having added the additives 1-4.

(Particulate dispersion diluent)

12 parts by mass of aerosil 972 V (manufactured by Nippon Aerosil Co., Ltd.)

(Average particle size 16 nm, apparent specific gravity 90 g / liter of primary particles)

Ethanol 88 parts by mass

The above was stirred and mixed for 30 minutes with a dissolver, and then dispersed with mantongorin. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion with stirring, followed by stirring and mixing for 30 minutes with a dissolver to prepare a fine particle dispersion dilution.

(Dope D-1)

Heated melt 1 111 parts by mass

Methylene chloride 430 parts by mass

40 parts by mass of ethanol

The above was put into an airtight container, completely dissolved while heating and stirring, and slowly added while stirring 4 parts by mass of the fine particle dispersion dilution liquid, and further heated and stirred for 30 minutes. Then, it filtered using Azumi filter paper No.24 of Azumi-Roshi Corporation make, and dope D-1 was manufactured.

Next, in the structure shown in Table 2, dope D-2 to 12 were produced in the same manner as dope D-1. Dopes D-13 to 14 were prepared in the same manner as dope D-1 by the following prescription.

(Dope D-13)

Heated melt 13 100 parts by mass

Additive 1: 10 parts by mass of plasticizer P-1

Additive 2: 0.3 parts by mass of GSY-P101 (manufactured by Sakai Chemical Industries, Ltd.)

Additive 3: 0.3 parts by weight of smearizer GS (manufactured by Sumitomo Chemical Industries, Ltd.)

Additive 4: Irganox-1010 (Ciba Specialty Chemicals) 0.5 parts by mass

Methylene chloride 430 parts by mass

40 parts by mass of ethanol

(Dope D-14)

Resin: 100 parts by mass of cellulose acetate propionate C-1

Additive 1: 10 parts by mass of plasticizer P-1

Additive 2: 0.3 parts by mass of GSY-P101 (manufactured by Sakai Chemical Industries, Ltd.)

Additive 3: 0.3 parts by weight of smearizer GS (manufactured by Sumitomo Chemical Industries, Ltd.)

Additive 4: Irganox-1010 (Ciba Specialty Chemicals) 0.5 parts by mass

Methylene chloride 430 parts by mass

40 parts by mass of ethanol

The dope D-1 was filtered by the fine met NF by Nihon Seisen Corporation in a film forming line. Subsequently, using a belt casting apparatus, it was cast uniformly on the stainless steel band support body at the temperature of 35 degreeC, and 2 m width.

Then, after drying to the peelable range, dope was peeled off on the stainless steel band support body. The amount of residual solvent of dope at this time was 80%. The time required from dope casting to peeling was 3 minutes.

After peeling from a stainless steel band support body, after drying at 30 degreeC to 70 degreeC, conveying with many rolls, it extended | stretched 1.3 times in the width direction with the tenter, drying at 120 degreeC.

Subsequently, the width was released and further dried at 120 ° C. while being conveyed with a large number of rolls, and then drying was further terminated in a drying zone at 130 ° C., and knurled processing having a width of 10 mm and a height of 7 μm was applied to both ends of the film. And retardation film V-101 having a thickness of 40 μm was produced.

The film width was 1.5 m and the winding length was 3900 m. The winding tension was made into the initial tension of 150 N / 1.5 m and the final winding tension of 100 N / 1.5 m.

Then, in the same manner, the doped retardation films V-102 to V-114 described in Table 3 below were prepared.

<Light leakage rate of single film>

Retardation films V-101 to V-114 were sandwiched between two polarizing plates, and light was irradiated with Endo Kagaku Co., Ltd. flat illuminator. The luminance of the irradiation light was 880 cd / m 2.

About each case where two polarizing plates were arrange | positioned by cross nicol and the case where it was arrange | positioned by para nicol, brightness was measured by SPECTRO radiometer SR-3 by TOPON Corporation. The light leakage rate was defined as follows.

Light leakage rate (%) = (luminance when the film was inserted into two polarizing plates arranged in cross nicol) / (luminance when the film was inserted into the two polarizing plates arranged in paranicols) x 100

(Manufacture of Polarizing Plate)

<Manufacture of polarizer>

A 120 micrometers polyvinyl alcohol film was immersed in 100 mass parts of aqueous solution containing 1 mass part of iodine and 4 mass parts of boric acid, and it extended | stretched 4 times at 50 degreeC, and manufactured the polarizer of width 1.4m. The film thickness was 25 micrometers.

<Production of Polarizing Plate>

The saponification process was performed on alkali saponification conditions shown below which manufactured retardation film and Konica Minolta tag KC8UX (Konica Minolta Opto Corporation make, film thickness of 80 micrometers) which are commercially available polarizing plate protective films.

Subsequently, using the polarizer manufactured above, using a 5% aqueous saponification polyvinyl alcohol solution, it laminated | stacked in the order of KC8UX, a polarizer, and the said retardation film manufactured, and used the polarizing plate which used the retardation film of Table 3 as a polarizing plate protective film. Prepared.

<Alkaline saponification treatment>

Saponification process 2N-NaOH 50 ℃ 90 seconds

Water washing process 30 ℃ 45 seconds

Neutralization process 10 mass% HCl 30 ℃ 45 seconds

Water washing process 30 ℃ 45 seconds

Under the above conditions, the film sample was performed in the order of saponification, washing with water, neutralization, and washing with water, followed by drying at 80 ° C.

(Polarization)

The parallel transmittance and the linear transmittance were measured with respect to the polarizing plate, and the polarization degree was computed according to the following formula.

Polarization degree P = ((H0-H90) / (H0 + H90)) 1/2 × 100

Polarization degree change amount = P0-P500

H0: parallel transmittance

H90: through transmission

◎: less than 10% change in polarization degree

○: polarization degree change rate of 10% or more but less than 25%

X: 25% or more of polarization degree change rate.

(Contrast of the liquid crystal panel)

The polarizing plate of this invention obtained by the above and the comparative example peels off the optical compensation film and polarizing plate which were previously bonded by 32 type liquid crystal television KDL-32V2000 made by SONY, and absorbed the polarizing plate which previously bonded the absorption axis of the polarizing plate of this invention and a comparative example. It bonded together so that the phase difference film side of this invention might become a glass cell side so that it might become the same direction as an axis | shaft, the display apparatus was manufactured, and the contrast was evaluated.

For evaluation, the amount of transmitted light at the time of black display and white display was measured using EZ-contrast manufactured by ELDIM. Contrast = (transmitted light amount in white display: cd / cm <2>) / (transmitted light amount in black display: cd / cm <2>) was computed and evaluated. The results are shown in Table 3.

As can be seen from Table 3, the optical film of the present invention has little light leakage and is excellent in contrast.

Claims (4)

A method for producing an optical film containing a resin and an additive, wherein the heating melt is adjusted by heat melting and kneading the resin and the additive, and the resin solution obtained by dissolving the heated melt in a solvent is used as an optical film by solution casting. The manufacturing method of the optical film. It was manufactured by the manufacturing method of Claim 1, The optical film characterized by the above-mentioned. The optical film of Claim 2 was used, The polarizing plate characterized by the above-mentioned. The optical film of Claim 2 was used, The image display apparatus characterized by the above-mentioned.

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