JP2003043259A - Optical film, polarizing plate and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film, a polarizing plate and a display device having excellent color reproducibility and durability against irradiation of UV rays. SOLUTION: The optical film has a spectral transmittance of >=50% and <=95% at 390 nm and <=5% spectral transmittance at 350 nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film used for optical applications, and particularly to a protective film for a polarizing plate, a retardation film, a viewing angle widening film, a plasma display used for a liquid crystal display device or the like. Various functional films such as anti-reflection film used,
The present invention relates to an optical film that can be used for various functional films used in organic EL displays and the like, a polarizing plate using the same, and a display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have come to be used in notebook personal computers, mobile type portable terminals, mobile phones and the like. It is desired that the portable liquid crystal display device can be used for a long time with one charge, and power saving is an important point. Reflective and semi-transmissive liquid crystals have been developed as liquid crystal display devices suitable for power saving. Recently, colorized products have also been developed. Since reflective or semi-transmissive liquid crystal uses a reflector instead of a backlight, it has a structure in which light passes through the liquid crystal panel twice. The spectral transmittance characteristics of the color filter have been significantly changed to match this structure, and the overall transmittance is designed to increase. However, it was found that the color reproducibility was poor because the same polarizing plate as the liquid crystal display device used so far was used. As a result of our research, it is found that the cause is the spectral transmittance characteristic of the optical film. The optical film also has a role of blocking ultraviolet rays and protecting the liquid crystal and the polarizing element. This characteristic is important for mobile terminals that are often used outdoors.

Optical films containing an ultraviolet absorber have been proposed in JP 2001-72782 A, JP 2001-154017 A and the like. However, in these proposals, the compatibility between the color reproducibility of the reflective type or semi-transmissive type liquid crystal and the protection of the liquid crystal or the polarizing element was insufficient. As a result of diligent research, we have found a spectral transmittance characteristic capable of achieving both color reproducibility and protection of a liquid crystal and a polarizing element, and have accomplished the present invention. Further, the inventors have found a constitution of a polarizing plate capable of achieving both color reproducibility and protection of a liquid crystal and a polarizing element, and arrived at the present invention.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is an optical film, a polarizing plate and a display which are excellent in color reproducibility and ultraviolet light durability. To provide a device.

[0005]

That is, the above object of the present invention is achieved by the following means.

The spectral transmittance at 1.390 nm is 50.
% Or more and 95% or less, and the spectral transmittance in 350 nm is 5% or less, The optical film characterized by the above-mentioned.

2. 2. The optical film as described in 1 above, which contains at least one ultraviolet absorber selected from benzophenone type and benzotriazole type ultraviolet absorbers.

3. 3. The optical film as described in 1 or 2 above, which contains substantially no phosphate ester.

4. The optical element as described in any one of 1 to 3 above, which contains silicon dioxide fine particles having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more. the film.

5. Secondary average particle size of 0.3 or more, 1.5
5. The optical film as described in any one of 1 to 4 above, which contains fine particles of silicon dioxide having a size of not more than μm.

6. 6. The optical film as described in any one of 1 to 5 above, which contains a cellulose ester as a main component.

7. 7. The optical film as described in any one of 1 to 6 above, which has a film thickness of 20 to 65 μm.

8. In a polarizing plate in which an optical film is arranged such that a polarizing element is sandwiched from both sides, the amount of the ultraviolet absorber contained in the optical film arranged on one side is 0.3 g or more and 3.0 g or less per 1 m ² . The polarizing plate characterized in that the optical film arranged on the other side contains substantially no ultraviolet absorber.

9. In a polarizing plate in which an optical film is arranged so as to sandwich a polarizing element from both sides, the optical film described in any one of 1 to 7 is arranged on at least one side. .

10. A display device using the optical film according to any one of 1 to 7 above.

11. A display device using the polarizing plate described in 8 or 9 above. 12. 12. The display device according to 10 or 11 above, which is a reflective or transflective display device.

The present invention will be described in more detail below. A polarizing plate used in a transmissive liquid crystal display device generally has a structure in which a polarizer is sandwiched between two optical films. This optical film is ideally 380
It absorbs all ultraviolet rays having a wavelength of less than nm and does not absorb visible light having a wavelength of 380 nm or more. However, since this is practically difficult, an optical film having an excellent ultraviolet absorbing performance of 370 nm or less is practically used. Has been used. However, this optical film had a low transmittance of about 30% in the visible region of 390 nm. It has been found that in the case of a reflective or semi-transmissive liquid crystal, the low transmittance at 390 nm makes it look yellowish and deteriorates the color balance. This is a structure in which a reflection type or semi-transmission type liquid crystal panel reflects light by a reflection plate, and therefore the light is emphasized by passing through the polarizing plate twice.

On the other hand, in order to increase the transmittance in the visible region,
If the ultraviolet absorber is removed from the optical film, the polarizer and the liquid crystal element will be deteriorated by the ultraviolet rays.

As a result of our research, instead of the conventional optical film, the spectral transmittance at 390 nm is set to 50% or more and 95% or less, and the spectral transmittance at 350 nm is 5%.
It has been found that an optical film with good color balance and excellent color reproducibility can be obtained without deterioration of the polarizer and the liquid crystal element by the following. The spectral transmittance at 390 nm is more preferably 70% or more and 95% or less, and 80% or more 9
It is most preferably 5% or less. The transmittance at 350 nm is more preferably 4% or less, most preferably 3% or less. Compared with conventional optical films, the cut performance in the near-ultraviolet region near 360 to 370 nm is slightly lower when viewed from the spectral transmittance curve, but it is colored yellow when used as a reflective or semi-transmissive liquid crystal panel, It has been found that the optical film of the present invention is very effective for the problem of imbalance, and can sufficiently prevent the deterioration of the polarizer, the liquid crystal element and the like. The higher the spectral transmittance at 390 nm, the better the color reproducibility, and the lower the spectral transmittance at 350 nm, the more the deterioration of the polarizer and the liquid crystal element can be prevented.

The spectral transmittance of the optical film can be controlled within the above range by adjusting the type and the amount of the ultraviolet absorber contained in the optical film.

Further, we pay attention to the reflective type or semi-transmissive type liquid crystal panel structure, and the optical film 2 disposed inside the polarizer of the polarizing plate shown in FIG.
It has been found that by substantially not including the ultraviolet absorber, the color reproducibility is good and at the same time, the deterioration of the polarizer and the liquid crystal element can be prevented.

FIG. 1 is a schematic cross-sectional view of a reflective TFT color liquid crystal panel, which includes an optical film 1 and an optical film 2.
2 shows an example of the configuration of a reflective liquid crystal panel including a polarizing plate having a configuration in which a polarizer is sandwiched between and a glass serving as a substrate, a color filter, a liquid crystal layer, a reflection plate, and a substrate glass.

That is, the harmful ultraviolet rays contained in the external light are
The optical film 1 arranged on the outside of the polarizer of the polarizing plate absorbs the light, and the optical film 2 arranged on the inside of the polarizer uses a film having a high transmittance in the visible region to separate the functions of the optical film. You can do it. Therefore, the color reproducibility of the display device using the polarizing plate is good, and the deterioration of the polarizer and the liquid crystal element can be prevented.

The amount of UV absorber included in the optical film disposed on the outside of the polarizer is preferably from 0.3g or more per 1 m ² 2.0 g, more preferably more than 1.5g or less 0.5 g, 0. Most preferably 7 g or more and 1.2 g or less. It is preferable that the optical film disposed inside the polarizer is substantially free of an ultraviolet absorber. The term “substantially free of” means that the amount of the ultraviolet absorber contained per 1 m ² is 0.2 g or less, more preferably 0.1 g or less, and most preferably none.

The optical film of the present invention is preferably a film containing cellulose ester as a main component, and the fact that it contains cellulose ester as a main component means that the cellulose ester is at least 50% or more of all components constituting the film. And is a cellulose ester film as described below.

The method for producing a cellulose ester film, which is a preferred embodiment of the present invention, will be described below.

The preferred film forming process used in the method for producing a cellulose ester film of the present invention comprises the following dissolution process, casting process, solvent evaporation process, peeling process, drying process and winding process. Each step will be described below. << Dissolution Step >> In the present invention, the cellulose ester solution is referred to as a cellulose ester dope or simply dope. The dissolution step is a step of dissolving the flakes of the cellulose ester in an organic solvent mainly composed of a good solvent described later in a dissolution vessel while stirring the flakes to form a dope.

In the present invention, the solid content concentration in the dope is 15
It is preferable to adjust the content to be not less than mass%, particularly 18 to 35
Mass% is preferably used.

If the solid content concentration in the dope is too high, the viscosity of the dope becomes too high, and sharkskin or the like may occur during casting to deteriorate the flatness of the film.
It is desirable that the content is not more than mass%.

The dope viscosity is preferably adjusted within the range of 10 to 50 Pa · s. For the dissolution, a method performed at normal pressure, a method performed at a boiling point of a preferred organic solvent (that is, a good solvent) or lower, a method performed by pressurizing at a boiling point of the good solvent or higher,
There are various dissolution methods such as a cooling dissolution method and a high pressure method. As a method of dissolving at a temperature not lower than the boiling point of a good solvent and applying a pressure that does not boil, 40.4 to 12
By pressurizing at 0.11 to 1.50 MPa at 0 ° C., foaming can be suppressed and dissolution can be performed in a short time.

As the cellulose ester used in the present invention, a lower fatty acid ester of cellulose is preferably used.

The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms, for example, cellulose acetate, cellulose propionate, cellulose butyrate, and the like.
Examples of lower fatty acid esters of cellulose include mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in 0-45804, 8-231761, and US Pat. No. 2,319,052. As.

Among the above fatty acids, cellulose acetate and cellulose acetate propionate are preferably used. In the case of the cellulose ester film of the present invention, the degree of polymerization is preferably 250 to 250 from the viewpoint of film strength.
Those of 400 are preferably used.

A method for measuring the substitution degree of the acyl group of the cellulose ester can be carried out according to ASTM-D-817-96.

The cellulose ester film of the present invention is preferably a cellulose ester having a total degree of substitution of 2.5 to 3.0, and particularly preferably a cellulose ester having a total degree of substitution of 2.55 to 2.85. When the total substitution degree is 2.55 or more, the mechanical strength of the film increases,
When it is 2.85 or less, the solubility of the cellulose ester is improved and the generation of foreign matter is reduced, which is more preferable.

In the case of cellulose acetate propionate, the acetyl group substitution degree is X and the propionyl group substitution degree is Y.
Then, those in the range of 2.55 ≦ X + Y ≦ 2.85 1.5 ≦ X ≦ 2.4 are preferably used.

As the cellulose ester, a cellulose ester synthesized from cotton linter, a cellulose ester synthesized from wood pulp, and a cellulose ester synthesized from other raw materials can be used alone or in combination.

The solvent used for preparing the dope is not particularly limited as long as it is a solvent capable of dissolving the cellulose ester, but even a solvent which cannot be dissolved alone is mixed with another solvent, Any substance that can be dissolved can be used. Generally, a mixed solvent composed of a good solvent, methylene chloride, and a poor solvent of cellulose ester is used, and the poor solvent is 4 to 4 times in the mixed solvent.
Those containing 30% by mass are preferably used.

Other good solvents that can be used include methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2. , 2-trifluoroethanol, 2,
2,3,3-tetrafluoro-1-propanol, 1,
3-difluoro-2-propanol, 1,1,1,3
3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1
-Propanol, nitroethane and the like can be mentioned, but organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like can be mentioned as preferable organic solvents (that is, good solvents). The use of methyl acetate is particularly preferable because the resulting film has less curl.

As the poor solvent for cellulose ester, for example, methanol, ethanol, n-propanol, is
alcohols having 1 to 8 carbon atoms such as o-propanol, n-butanol, sec-butanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, monochlorobenzene,
Examples thereof include benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. These poor solvents may be used alone or in combination of two or more kinds.

In the production of the cellulose ester film of the present invention, it is also preferable to use a cooling dissolution method when dissolving the cellulose ester. As a cooling dissolution method,
For example, JP-A-9-95538 and 9-95544,
The method described in No. 9-95557 can be used. Further, the high pressure dissolution method described in JP-A-11-21379 can also be preferably used.

Cellulose ester solution (dope) after dissolution
Is preferably filtered with a filter material, defoamed, and sent to the next step by a pump. At that time, a plasticizer, an antioxidant, an ultraviolet absorber, a dye, fine particles and the like are preferably added to the dope. .

These additives may be added together with the cellulose ester and the solvent during the preparation of the cellulose ester solution, or during or after the solution preparation.

The cellulose ester film of the present invention preferably contains, as a plasticizer, a polymer or oligomer having a weight average molecular weight of Mw 300 to 1000, more preferably Mw 300 to 500.

Mw is GPC (Gel Permeati)
on Chromatography).

The amount of the polymer used as the plasticizer is not particularly limited, but it is 1 with respect to the cellulose ester.
The content is preferably 0 to 50% by mass, more preferably 15 to 45% by mass, still more preferably 15 to 30% by mass.

The type of polymer used as the plasticizer used in the present invention is not particularly limited, but polyesters, polyester ethers, polyester urethanes, polyurethanes, vinyl polymers, acrylic acid polymers, methacrylic acid polymers, copolymers thereof, and the like. Can be given. Among these polymers, polyester,
Polyester ether and vinyl polymer are particularly preferable.

The type of polyester is not particularly limited, but for example, the following can be preferably used. Preferred polybasic acids include adipic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, 1,4-cyclohexanedicarboxylic acid, and combinations thereof. . Examples of preferable polyhydric alcohols include ethylene glycol, diethylene glycol, 1,
2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,4 −
Examples thereof include cyclohexanediol, 1,4-cyclohexanedimethanol, and a combination thereof. The end of the polymer may be modified with a monovalent acid or a monovalent alcohol.

The type of polyester ether is not particularly limited, but for example, a combination of the above polyester and an ether unit or a polyester ether obtained by polymerizing the above dibasic acid and an ether unit can be preferably used. The ether unit is not particularly limited,
For example, polytetramethylene ether glycol, polyethylene ether glycol, or a combination thereof can be used. The end of the polymer is 1
It may be modified with a divalent acid or a monohydric alcohol.

In the present invention, a low molecular weight plasticizer may be added in addition to the polymer. The low molecular weight plasticizer that can be used in the present invention is not particularly limited, but for example, a phthalate ester plasticizer, a glycolate plasticizer, etc. can be preferably used. Phthalate ester plasticizers include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butylbenzyl phthalate, dibenzyl phthalate, and glycolate plasticizers include butyl phthalyl butyl glycol. Rate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be preferably used. These plasticizers can be used alone or in combination of two or more.

In the present invention, it is preferable that the phosphoric acid ester is not substantially contained. Substantially not included
It is preferably 3% by mass or less, more preferably 1% by mass or less, and most preferably not contained at all, based on the solid content. The one that does not contain a phosphoric acid ester is superior in decomposition durability of the film under high temperature and high humidity.

As the compound containing a phosphoric acid ester. Examples of the phosphate plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

The amount of the low molecular plasticizer used depends on the film performance,
0 to 20 relative to cellulose ester in terms of processability
Mass% is preferred. From the viewpoint of dimensional stability, 1 to 15 mass% is more preferable for a liquid crystal display member, and particularly preferably 2 to 12 mass%.

The workability is the ease of processing when slitting or punching a base film or a liquid crystal display member. If the workability is poor, the cut surface becomes sawtooth and chips are generated. It is not preferable because it adheres to the surface and causes foreign matter failure.

Examples of UV absorbers generally used in the film include oxybenzophenone compounds,
Examples thereof include benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex salt compounds and the like.

In the present invention, benzophenone compounds and benzotriazole compounds as ultraviolet absorbers are particularly preferable because they have excellent durability when irradiated with ultraviolet rays.
Most preferred are benzotriazole compounds that have no unwanted coloration.

As the benzotriazole type ultraviolet absorber, a compound represented by the following general formula [1] is preferably used.

[0058]

[Chemical 1]

In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different and each is a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group or an alkoxy group. Represents a group, an acyloxy group, an aryloxy group, an alkylthio group, an arylthio group, a mono- or dialkylamino group, an acylamino group or a 5- or 6-membered heterocyclic group, and R ₄ and R ₅ are ring-closed to form a 5- or 6-membered carbon. You may form a ring.

Specific examples of the ultraviolet absorber used in the present invention will be given below, but the present invention is not limited thereto. UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-
tert-Butylphenyl) benzotriazole UV-3: 2- (2'-hydroxy-3'-tert-
Butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-
tert-Butylphenyl) -5-chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ",
4 ", 5", 6 "-tetrahydrophthalimidomethyl)
-5'-Methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3)
3-Tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) Further, a polymer having a benzotriazole structure can also be preferably used. For example, polymeric UV absorber PUVA-30M commercially available from Otsuka Chemical can be preferably used.

Further, as the benzophenone type ultraviolet absorber which is one of the ultraviolet absorbers used in the present invention, a compound represented by the following general formula [2] is preferably used.

[0062]

[Chemical 2]

In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxy group, and a phenyl group, and these alkyl group, alkenyl group and phenyl group may have a substituent. A is a hydrogen atom,
An alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group or a -CO (NH) _n-1 -D group, where D is an alkyl group,
It represents an alkenyl group or a phenyl group which may have a substituent. m and n represent 1 or 2.

In the above, the alkyl group represents, for example, a straight chain or branched aliphatic group having up to 24 carbon atoms, the alkoxy group has, for example, an alkoxy group having 18 carbon atoms, and the alkenyl group has, for example, carbon atoms. Number 1
Up to 6 alkenyl groups represent, for example, an allyl group and a 2-butenyl group. Further, as a substituent for an alkyl group, an alkenyl group, or a phenyl group, a halogen atom, for example, a chlorine atom, a bromine atom, a fluorine atom, etc., a hydroxyl group, a phenyl group, (this phenyl group is substituted with an alkyl group or a halogen atom, etc. You may have) etc.

Specific examples of the benzophenone compound represented by the general formula [2] are shown below, but the invention is not limited thereto. UV-7: 2,4-dihydroxybenzophenone UV-8: 2,2'-dihydroxy-4-methoxybenzophenone UV-9: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-10: bis (2-methoxy) -4-hydroxy-5
-Benzoylphenylmethane) In the present invention, for example, a blue dye or the like may be used as an additive in order to adjust the tint of the film. Anthraquinone dyes are preferred dyes.
Anthraquinone dyes are from the 1st position of anthraquinone to 8
It can have any substituents up to the position. Preferred substituents include an anilino group, a hydroxyl group, an amino group, a nitro group, or a hydrogen atom which may be substituted. The amount of these dyes added to the film is 0.1 to 1000 μg / in order to maintain the transparency of the film.
m ² , preferably 10 to 100 μg / m ² .

Fine particles are preferably added as a matting agent to the optical film used in the present invention. Examples of the fine particles used in the present invention include inorganic compounds such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, Mention may be made of aluminum silicate, magnesium silicate and calcium phosphate. It is preferable that the fine particles contain silicon because the turbidity is low, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide have a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70.
It is preferably g / liter or more. The average diameter of the primary particles is more preferably 5 to 16 nm, further preferably 5 to 12 nm. The smaller the average diameter of the primary particles, the lower the haze, which is preferable. The apparent specific gravity is preferably 90 to 200 g / liter or more, more preferably 100 to 200 g / liter or more. The larger the apparent specific gravity is, the higher the concentration of the dispersion liquid can be made, and the haze and the aggregate are improved, which is preferable.

These fine particles usually have an average particle size of 0.
Secondary particles having a size of 1 to 3.0 μm are formed, and these fine particles are present in the film as an agglomerate of primary particles to form unevenness of 0.1 to 3.0 μm on the surface of the film. Two
The average secondary particle size is preferably 0.3 μm or more and 1.5 μm or less, more preferably 0.5 μm or more and 1.2 μm or less,
Most preferably, it is 0.8 μm or more and 1.1 μm or less.

The particle diameter in the present invention is defined as the diameter of a circle circumscribing the particle by observing the particle in the film with a scanning electron microscope. Also, change the place and particle 1
00 particles were observed, and the average value was defined as the average particle size.

The amount of the matting agent added is 0.01 per 1 m ^2.
Is preferably 1.0 to 1.0 g, more preferably 0.03 to 0.3 g, most preferably 0.08 to 0.16 g.

The fine particles of silicon dioxide are, for example, Aerosil R972, R972V, R974, R812, 20.
0, 200V, 300, R202, OX50, TT60
It is commercially available under the trade name of 0 (manufactured by Nippon Aerosil Co., Ltd.) and can be used. The fine particles of zirconium oxide are commercially available under the trade names of Aerosil R976 and R811 (all manufactured by Nippon Aerosil Co., Ltd.) and can be used.

Other fine particles used in the present invention include, for example, polymers such as silicone resin, fluorine resin and acrylic resin. A silicone resin is preferable, and one having a three-dimensional network structure is particularly preferable. For example, Tospearl 103, 105,
Ibid 108, ibid 120, ibid 145, ibid 3120 and ibid 24
It is commercially available under the trade name of 0 (all manufactured by Toshiba Silicone Co., Ltd.) and can be used.

Among these, Aerosil 200V and Aerosil R972V have a primary average particle diameter of 20 nm or less,
In addition, it is fine particles of silicon dioxide having an apparent specific gravity of 70 g / liter or more, and it is particularly preferable because it has a great effect of reducing the friction coefficient while keeping the turbidity of the optical film low.

As a method for preparing a dispersion liquid of fine particles in order to obtain the cellulose ester film of the present invention, there are, for example, the following three kinds.

<< Preparation Method A >> A solvent and fine particles are mixed by stirring and then dispersed by a disperser. This is referred to as a fine particle dispersion liquid. The fine particle dispersion liquid is added to the dope liquid and stirred.

<< Preparation Method B >> The solvent and the fine particles are mixed by stirring and then dispersed by a disperser. This is referred to as a fine particle dispersion liquid. Separately, a small amount of cellulose ester is added to the solvent and dissolved by stirring. The fine particle dispersion is added to this and stirred.
This is used as a fine particle addition liquid. The fine particle added liquid is thoroughly mixed with the dope liquid by an in-line mixer.

<< Preparation Method C >> A small amount of cellulose ester is added to a solvent and dissolved by stirring. Fine particles are added to this and dispersed by a disperser. This is used as a fine particle addition liquid. The fine particle added liquid is thoroughly mixed with the dope liquid by an in-line mixer.

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

<< Dispersion Method >> When the silicon dioxide fine particles are mixed with a solvent or the like and dispersed, the concentration of silicon dioxide is 5 to 30.
Mass% is preferable, 10-25 mass% is more preferable,
Most preferably, it is 15 to 20% by mass. The higher the dispersion concentration, the more the liquid turbidity with respect to the added amount tends to be low, and the haze and the aggregates are improved, which is preferable.

The solvent used is a lower alcohol, preferably methyl alcohol, ethyl alcohol,
Propyl alcohol, isopropyl alcohol, butyl alcohol and the like can be mentioned. The solvent other than the lower alcohol is not particularly limited, but it is preferable to use the solvent used when forming the cellulose ester film.

Using the dope thus obtained, a cellulose ester film can be obtained through the casting process described below.

<Casting Step> The dope is sent to a pressure die through a pressure-type metering gear pump and infinitely transferred at a casting position. An endless metal belt or a rotating metal drum is used as a casting support (hereinafter referred to as a casting support). (It may be simply a support)
In this step, the dope is cast from the pressure die. The surface of the casting support is a mirror surface.

Other casting methods include a doctor blade method in which the film thickness of the cast dope film is adjusted with a blade, a method using a reverse roll coater in which the film is adjusted with a counter-rotating roll, and the like. A pressure die that can adjust the shape and facilitates uniform film thickness is preferable. The pressure die includes a coat hanger die and a T die, and any of them is preferably used.

In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the dope amount may be divided to form multiple layers. Alternatively, the inside of the die is divided by slits, and multiple dope solutions with different compositions are cast simultaneously (also called co-casting).
Then, a cellulose ester film having a laminated structure can be obtained.

Thus, the obtained dope is cast on a support such as a belt or a drum to form a film, and the present invention is particularly effective in a solution casting film forming method using a belt. This is because it is easy to finely adjust the drying conditions on the support as described later.

<Solvent Evaporation Step> A web (in the present invention, a dope is cast on a casting support and the formed dope film is called a web) is heated on the casting support to remove the solvent. This is the step of evaporating. 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 support by a liquid, a method of transferring heat from the front and back sides by radiant heat, and the like. Drying efficiency is preferred. A method of combining them is also preferable. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air of this temperature to the upper surface of the web or heat it by means such as infrared rays.

In particular, the cellulose ester film of the present invention is desirably peeled from the support within 30 to 90 seconds after casting. If it is peeled off in less than 30 seconds, not only the surface quality of the film is deteriorated, but also the moisture permeability is not preferable. Drying for more than 90 seconds is not preferable because the surface quality is deteriorated due to deterioration of peelability and strong curling occurs in the film.

<< Peeling Step >> In this step, the web having the solvent evaporated on the support is peeled from the support at the peeling position. The peeled web is sent to the next step. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, peeling may be difficult, or conversely, if the web is sufficiently dried on the support and then peeled off, a part of the web may peel off.

The temperature at the peeling position on the support is preferably 10 to 40 ° C., more preferably 11 to 30.
℃. The residual solvent amount of the web at the peeling position is 2
5 to 120 mass% is preferable, and 40 to 1 is more preferable.
It is 00 mass%.

The residual solvent amount of the web according to the present invention is defined by the following formula. Residual solvent amount = (mass before heat treatment of web−mass after heat treatment of web) / (mass after heat treatment of web) × 100% The heat treatment for measuring the amount of residual solvent is 115 ° C.
Represents that heat treatment is performed for 1 hour.

In order to adjust the residual solvent amount at the time of peeling as described above, the surface temperature of the casting support after casting is controlled so that the organic solvent can be efficiently evaporated from the web. It is preferable to set the temperature at the peeling position on the casting support in the above temperature range. To control the temperature of the support, it is preferable to use a heat transfer method having high heat transfer efficiency, and for example, a back surface heat transfer method using a liquid is preferable.

The heat transfer method using radiant heat or hot air is not a preferable method because it is difficult to control the temperature of the support, but in a belt (support) machine, it is possible to control the temperature when the belt to be transferred comes to the lower side. The belt temperature can be adjusted by gentle wind.

The temperature of the support can be partially changed by dividing the heating means, and the temperature of the casting support should be different, such as the casting position, drying section, and peeling position. Can be done.

As a method for increasing the film-forming speed (the film-forming speed can be increased by peeling while the amount of residual solvent is as large as possible), there is a gel casting method (gel casting) in which the amount of residual solvent can be separated. .

There are a method in which a poor solvent for cellulose ester is added to the dope, the solution is cast and then gelled, and a method in which the temperature of the support is lowered to gel.
There is also a method of adding a metal salt to the dope.

By making the film stronger by gelling it on the support, peeling can be accelerated and the film forming speed can be increased.

When peeling at a time when the amount of residual solvent is large, if the web is too soft, the flatness is deteriorated at the time of peeling, and cracks and vertical lines due to peeling tension are likely to occur, and peeling remains due to a balance between economic speed and quality. The amount of solvent can be determined.
The peeling tension when peeling the support from the film is usually 19
Peeling is performed at 6 to 245 N / m, but if wrinkles are easily formed at the time of peeling, it is preferable to peel at 190 N / m or less, and further, the lowest tensile force at which peeling is possible to 166.6 N / m.
m, and then peeling at a minimum tension of -137.2 N / m is preferable, but a minimum tension of 100 N is particularly preferable.
/ M. The lower the peeling tension, the more preferable the in-plane retardation Ro can be kept low. The in-plane retardation Ro is preferably less than 20 nm, more preferably less than 10 nm and then less than 5 nm, but most preferably 0 to 1 nm.

In the present invention, the in-plane retardation R
o is an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) at a wavelength of 590 nm,
Three-dimensional refractive index measurement is performed, and the obtained refractive indices nx, ny,
It can be calculated from nz. Further, a retardation value Rt in the film thickness direction of 0 to 300 nm is obtained, further preferably 0 to 150 nm, more preferably 0 to 70 nm.
Those of nm are preferably obtained depending on the application.

Ro = (nx-ny) × d Rt = ((nx-ny) / 2-nz) × d The cellulose ester film of the present invention has an angle θ (radian) between the slow axis direction and the film forming direction. ) And the retardation Ro in the in-plane direction have the following relationship, and are particularly preferably used as optical films such as protective films for polarizing plates.

P ≦ 1-sin ² (2θ) × sin ² (πRo / λ) P = 0.9999 nx is the refractive index in the slow axis direction in the film plane, and ny is the fast axis direction in the film plane. Refractive index, nz is the refractive index in the thickness direction of the film, and d is the film thickness (nm) of the film. θ is the angle (radian) formed by the slow axis direction in the plane of the film and the film forming direction (direct direction of the film), and λ is the above n.
The wavelength of light at the time of three-dimensional refractive index measurement for determining x, ny, nz, and θ is 590 nm, and π is the circular constant. << Drying Step >> Drying the web while holding the width using a drying device that alternately conveys the web through staggered rolls and / or a tenter device that holds and holds both ends of the web with clips or pins. It is a process to do. It is preferable to keep the conveying tension in the drying step as low as possible so that Ro can be kept low, and it is preferably 190 N / m or less. More preferably 170 N / m
It is preferably below, and more preferably 140 N /
It is preferably m or less, and particularly preferably 100 to 130 N / m. In particular, it is effective to maintain the transport tension below the above value until the amount of residual solvent in the film becomes at least 5% by mass or less.

As a drying means, hot air is generally blown to both sides of the web, but a microwave may be applied instead of the air to heat the web. Drying too rapidly tends to impair the flatness of the finished film. Drying at a high temperature is preferably carried out when the residual solvent is about 8% by mass or less. Throughout the whole, the drying temperature is approximately 40 to 250 ° C.
It is particularly preferable to dry at 40 to 160 ° C.

In the drying step after peeling from the surface of the casting support, the web tends to shrink in the width direction due to the evaporation of the solvent. Shrinkage increases with rapid drying at high temperature.

Drying while suppressing this shrinkage as much as possible is preferable in order to improve the flatness of the finished film.

From this point of view, for example, JP-A-62-46.
No. 625, a method of drying all or a part of the drying step while holding the width ends of the web with clips or pins in the width direction (called a tenter method), among which a tenter using a clip The method and the pin tenter method using a pin are preferably used.

At this time, the stretching ratio in the width direction is 0% to 10%.
It is preferably 0%, more preferably 5% to 20% when used as a polarizing plate protective film, and 8% to 15%.
% Is most preferable, and when used as a retardation film, 10% to 40% is more preferable, and 20% to 30% is most preferable. R0 can be controlled by the draw ratio, and a higher draw ratio is preferable because the flatness of the finished film is excellent.

When performing the tenter, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and the web is dried while the tenter is applied until the residual solvent amount becomes 10% by mass or less. It is preferably carried out, and more preferably 5% by mass or less.

When the tenter is used, the drying temperature is from 30 to
150 degreeC is preferable, 50-120 degreeC is more preferable,
The most preferable range is 70 to 100 ° C. The lower the drying temperature is, the less evaporation of the ultraviolet absorber, the plasticizer, etc., and the better the process contamination, and the higher the drying temperature, the better the flatness of the film. The ultraviolet absorber represented by the general formula (1) does not easily evaporate even when the drying temperature is high, and therefore the tenter drying temperature is high,
The effect is remarkably exhibited under the manufacturing conditions in which the draw ratio is high.

In the film drying step, the film peeled from the support is further dried so that the residual solvent amount is 0.5% by mass or less, more preferably 0.1% by mass or less. , And more preferably 0 to 0.0
It is to be 1 mass% or less.

In the film drying step, generally, a roll suspension method or a method of drying while conveying the film by the above-mentioned pin tenter method is adopted. The means for drying the film is not particularly limited, and generally, hot air, infrared rays, heating rolls, microwaves or the like is used. It is preferable to use hot air for the sake of simplicity. Drying temperature is 3-5 in the range of 40-150 ° C.
It is preferable to gradually increase the temperature depending on the temperature of the steps, and it is more preferable to perform it in the range of 80 to 140 ° C. in order to improve the dimensional stability.

In the steps from immediately after the casting through the solution casting film forming method to the drying, the atmosphere in the drying device may be air, but in an atmosphere of an inert gas such as nitrogen gas, carbon dioxide gas or argon. You can go.

However, it goes without saying that the danger of the explosion limit of the evaporating solvent in a dry atmosphere must always be taken into consideration. << Winding process >> This is a process of winding the cellulose ester film after the amount of residual solvent in the web is 2% by mass or less. By adjusting the amount of residual solvent to 0.4% by mass or less, good dimensional stability can be obtained. You can get a film.

As the winding method, those generally used may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like, and these may be used properly. .

The film thickness can be adjusted by controlling the dope concentration, the amount of liquid pumped, the slit gap of the die die, the extrusion pressure of the die, the speed of the casting support, etc. so as to obtain a desired thickness. Good to do.

Further, as means for making the film thickness uniform, it is preferable to use the film thickness detecting means to feed back the programmed feedback information to the above-mentioned respective devices for adjustment.

Although the thickness of the cellulose ester film varies depending on the purpose of use, it is usually in the range of 5 to 500 μm as a finished film, and further 10 to 250 μm.
Is preferable, and a range of 10 to 120 μm is particularly used for a liquid crystal image display device film. The cellulose ester film of the present invention is a thin film having a thickness of 10 to 60 μm, but is excellent in moisture permeability and dimensional stability.

The water vapor permeability in the present invention means JIS Z
It is defined by the value measured by the method described in 0208. Moisture permeability is preferably 20~250g / m ² · 24 hours, but is preferably in particular 20~200g / m ² · 24 hours. When the moisture permeability exceeds 250 g / m ² · 24 hours, the durability of the polarizing plate is remarkably reduced, and conversely 2
If it is less than 0 g / m ² · 24 hours, it is difficult to dry the solvent such as water used in the adhesive during the production of the polarizing plate and the drying time becomes long, which is not preferable. More preferably 25-
It is 200 g / m ² · 24 hours.

In the cellulose ester film of the present invention, the dimensional stability can be further improved by reducing the mass change at 80 ° C. and 90% RH.

In the cellulose ester film of the present invention, it is more preferable that the mass change rate before and after the heat treatment at 80 ° C. and 90% RH for 48 hours is within ± 2%, whereby the thin film having improved moisture permeability. Although it is a film, a cellulose ester film having an excellent dimensional change rate can be obtained.

The cellulose ester film of the present invention comprises
The dimensional change rate when heat-treated for 48 hours at 80 ° C. and 90% RH was MD direction (film forming direction), TD
The direction (width direction of the film) is preferably within ± 0.5%, more preferably within ± 0.3%, further preferably within ± 0.1%, and further ± 0. It is preferably within 0.05%.

The dimensional change rate in the present invention is a characteristic value representing the dimensional change in the longitudinal and lateral directions of the film under severe conditions of temperature and humidity. Specifically, the film is placed under heating conditions, humidification conditions, and hot humidity conditions to force deterioration,
Measure vertical and horizontal dimensional changes. For example, a film sample to be measured is cut into a size of 150 mm in the width direction × 120 mm in the length direction, and the film surface is cut in two positions at 100 mm intervals in the width direction and the length direction, respectively.
Make a cross-shaped mark with a sharp blade such as a razor. The film is conditioned under the environment of 23 ° C. and 55% RH for 24 hours or more, and the distances L1 between the marks in the width direction and the length direction before processing are measured with a factory microscope. Next, the sample was subjected to high temperature and high humidity treatment in an electric constant temperature bath (conditions: 80 ° C., 90% RH).
Left in the environment for 48 hours). Again, the sample is conditioned for 24 hours in an environment of 23 ° C. and 55% RH, and the width L2 of each mark in the width direction and the length direction after treatment is measured with a factory microscope. The rate of change before and after this process is calculated by the following equation.

Dimensional change rate (%) = (L ₂ −L ₁ ) / L ₁ × 100 In the formula, L ₁ is the distance between marks before treatment, and L ₂ is the distance between marks after treatment.

That is, a desired dimensional change rate can be measured by arranging marks to be attached in the longitudinal direction and the width direction of the film.

The rate of dimensional change when treated at 105 ° C. for 5 hours is preferably within ± 0.5% in both MD and TD directions, more preferably within ± 0.3%, and further within ± 0.3%. It is preferably within 0.1%, and further ±
It is preferably within 0.05%.

The cellulose ester film of the present invention has a tensile strength of 90 to 170 N / mm ² in both MD and TD.
Is preferable, and particularly 120 to 160 N / mm ²
Is preferred.

The water content is preferably 0.1 to 5%,
0.3 to 4% is more preferable, and 0.5 to 2% is even more preferable.

The cellulose ester film of the present invention comprises
The transmittance is preferably 90% or more, more preferably 92% or more, further preferably 93% or more. Further, the haze is preferably 0.5% or less,
In particular, it is preferably 0.1% or less, more preferably 0%.

In the cellulose ester film of the present invention, the curl value preferably has a small absolute value, and the deformation direction may be the + direction or the-direction. The absolute curl value is preferably 30 or less, more preferably 2
It is 0 or less, and particularly preferably 10 or less.
The curl value is represented by the radius of curvature (1 / m).

The method for producing the cellulose ester film of the present invention by the solution casting method will be described in more detail with reference to the drawings.

FIG. 2 is a schematic view showing a preferred example of a solution casting film forming method for a film. FIG. 2A is a schematic diagram in the case of drying in a roll conveying / drying process after casting. Figure 2
(B) is a schematic diagram in the case where after casting, it is dried in a roll conveying / drying step and then dried in a tenter conveying / drying step. FIG. 2C is a schematic diagram in the case where after casting, it is dried in a tenter conveying / drying step and then dried in a roll conveying / drying step. FIG. 2D is a schematic diagram in the case where after casting, it is dried in a roll carrying / drying process, then dried in a tenter carrying / drying process, and then dried in a roll carrying / drying process.

In the present invention, the step including the tenter transporting / drying step and the roll transporting / drying step means that the film peeled from the support is dried and wound at any point. A process having a tenter conveyance / drying step and a roll conveyance / drying step for adjusting the expansion / contraction rate. The tenter transport / drying process is a process of simultaneously drying while transporting with a tenter transport device and adjusting the drying expansion / contraction rate.The roll transport / drying process is simultaneous drying while transporting with a roll transport device, and drying expansion / contraction. The process of adjusting the rate.

In FIG. 2, reference numeral 1 denotes a support which runs endlessly. Mirror-like metal strips are used as the support. Reference numeral 2 denotes a die for casting a dope prepared by dissolving a cellulose ester resin in a solvent on the support 1. Reference numeral 3 denotes a peeling point for peeling the film on which the dope solidified on the support 1 is solidified, and 4 denotes the peeled film. 5 indicates a tenter conveying / drying process, 51 indicates an exhaust port, 5
2 shows a dry air intake. The exhaust port 51 and the dry air intake port 52 may be reversed. Reference numeral 6 indicates a tension cutting means. Examples of the tension cutting means include a nip roll and a suction roll. The tension cutting means may be provided between the steps.

Reference numeral 8 indicates a roll conveying / drying step, 81 indicates a drying box, 82 indicates an exhaust port, and 83 indicates a dry air intake port. The exhaust port 82 and the dry air intake port 83
May be reversed. 84 indicates an upper conveyance roll,
Reference numeral 85 denotes a lower conveyance roll. The transport roll 84,
The upper and lower parts 85 are one set, and are composed of a plurality of sets. Reference numeral 7 represents a rolled film.

In the step shown in FIG. 2D, the roll transfer / drying step before the tenter transfer / drying step 5 is called the first roll transfer / drying step, and the roll transfer / rolling step after the tenter transfer / drying step 5 is called. -The drying process is called the second roll conveyance / drying process. A cooling step not shown in FIGS. 2A to 2D may be provided as necessary before winding.

In the present invention, the cellulose ester film may be produced by any of the above solution casting film forming methods.

The cellulose ester film of the present invention comprises
From the viewpoint of good moisture permeability, dimensional stability, etc., it is preferably used for a liquid crystal display member, specifically, a protective film for a polarizing plate.
In particular, the cellulose ester film of the present invention is preferably used in a protective film for a polarizing plate, which has severe requirements for both moisture permeability and dimensional stability.

The polarizing plate according to the present invention can be manufactured by a general method. For example, a method in which an optical film or a cellulose ester film is subjected to an alkali saponification treatment, a polyvinyl alcohol film is immersed in an iodine solution, and stretched on both surfaces of a polarizing film produced using a fully saponified polyvinyl alcohol aqueous solution is used. is there. The alkali saponification treatment refers to a treatment in which the cellulose ester film is immersed in a high temperature strong alkaline solution in order to improve the wettability of the water-based adhesive and improve the adhesiveness.

The polarizing plate thus obtained is provided on one side or both sides of a liquid crystal cell, and the liquid crystal display device of the present invention is obtained by using the polarizing plate.

By using the protective film for a polarizing plate comprising the cellulose ester film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability and optical isotropy as well as thinning. Furthermore, by using a polarizing plate or a retardation film using the optical film of the present invention in a liquid crystal display device, stable display performance can be maintained for a long period of time.

In the cellulose ester film of the present invention, a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optically anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer,
Various functional layers such as an adhesive layer and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, atmospheric pressure plasma treatment and the like. The cellulose ester film of the present invention can also be used as a base material for an antireflection film or an optical compensation film.

[0139]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 <Production of Film Samples 1 to 15> (Silicon Oxide Dispersion) Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 10 parts by mass (average diameter of primary particles: 12 nm, apparent specific gravity: 100 g / liter) Ethanol 90 After stirring and mixing more than 1 part by mass with a dissolver for 30 minutes, dispersion was performed with manton-goulin. Liquid turbidity after dispersion is 93 pp
It was m.

(Preparation of Additive Liquid A) UV Absorber shown in Table 1 10 parts by mass Cellulose triacetate synthesized from linter cotton 4 parts by mass Methylene chloride 100 parts by mass or more are charged into a closed container, heated and stirred. , Completely dissolved and filtered.

12 parts by mass of the silicon oxide dispersion liquid was added to this while stirring, and the mixture was further stirred for 30 minutes, and then filtered with a polypropylene wind cartridge filter TCW-PPS-20N manufactured by Advantech Toyo Co., Ltd. to obtain an addition liquid A. Prepared.

(Preparation of Dope Liquid A) Cellulose triacetate synthesized from linter cotton 85 parts by weight Cellulose triacetate synthesized from wood pulp 15 parts by weight Adipic acid-1,3 butylene glycol polyester (Mw = 600) 15 parts by weight Methylene chloride 475 parts by mass Ethanol 50 parts by mass or more was put into a closed container, completely dissolved while heating and stirring, and Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. was used. A dope solution A was prepared by filtration using 244.

The dope liquid A was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film forming line. Finemet NF manufactured by Nippon Seisen Co., Ltd. in the in-line additive liquid line
Solution A was filtered with. The filtered additive liquid A was added to 100 parts by mass of the filtered dope liquid A so that the amount of the ultraviolet absorber described in Table 1 was obtained, and sufficiently mixed with an in-line mixer (Toray static type in-tube mixer Hi-Mixer, SWJ). Then, using a belt casting device, the temperature is 33 ° C., 1
It was evenly cast on a stainless band support with a width of 500 mm. With a stainless steel band support, the solvent is evaporated until the residual solvent amount reaches 80%, and the peeling tension is 127 Newton.
It was peeled from the stainless band support at a rate of / m. The peeled cellulose triacetate film is slit into a width of 1550 mm, and then dried at a drying temperature of 70 ° C. while being stretched by 10% in the width direction with a tenter, and then 1
Drying was completed while transporting the drying zone of 20 ° C. and 135 ° C. with a large number of rolls, slitting to a width of 1330 mm, and knurling of 10 mm in width and 5 μm in height at both ends of the film to obtain a cellulose triacetate film sample 1. It was At this time, the film thickness of the cellulose triacetate film was 40 μm, and the winding number was 2000 m.

By the same manufacturing method as in Sample 1, the dope solution A,
Film samples 2 to 15 were prepared in the same manner except that the additive liquid A was changed to the one described in Table 1.

(Preparation of Dope Liquid B) Cellulose triacetate synthesized from linter cotton 85 parts by weight Cellulose triacetate synthesized from wood pulp 15 parts by weight Adipic acid-1,3 butylene glycol polyester (Mw = 600) 14 parts by weight Triphenyl phosphate 1 part by mass Methylene chloride 475 parts by mass Ethanol 50 parts by mass or more is charged into a closed container, and is completely dissolved while heating and stirring, and Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. A dope solution B was prepared by filtration using 244.

(Preparation of Dope Solution C) Cellulose triacetate synthesized from linter cotton 85 parts by weight Cellulose triacetate synthesized from wood pulp 15 parts by weight Adipic acid-1,3 butylene glycol polyester (Mw = 600) 13 parts by weight Triphenyl phosphate 2 parts by mass Methylene chloride 475 parts by mass Ethanol 50 parts by mass or more is charged into a closed container, completely dissolved while heating and stirring, and Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. A dope solution C was prepared by filtration using 244.

(Preparation of Additive Solution B) 20 parts by mass of the ultraviolet absorbent described in Table 1 100 parts by mass or more of methylene chloride were placed in a closed container, heated, stirred, and completely dissolved and filtered.

To this, 12 parts by mass of the silicon oxide dispersion liquid was added with stirring, and the mixture was further stirred for 30 minutes and then filtered with a polypropylene wind cartridge filter TCW-PPS-20N manufactured by Advantech Toyo Co., Ltd. to obtain an addition liquid B.
Was prepared.

The obtained film sample is shown below, and the results of measuring the spectral transmittance according to the following measuring method are also shown.

<< Measurement Method >> (Spectral Transmittance) Spectrophotometer
The spectral absorption spectrum of the film was measured using U-3200 (manufactured by Hitachi, Ltd.), and the transmittances at 350 nm and 390 nm were obtained.

[0152]

[Table 1]

[0153]

[Chemical 3]

For the inventive film sample 4 and the comparative film sample 13, between 255 nm and 800 nm,
Table 2 shows the values obtained by measuring the transmittance of each film sample by 5 nm.

[0155]

[Table 2]

FIG. 3 is a graph of this.
It is a figure which shows the transmittance | permeability characteristic of the film of this invention and the conventional film. (A) shows the respective transmittance characteristics in the wavelength range of 250 nm to 750 nm,
(B) shows the wavelength range from 250 to 450 nm. It can be seen that the transmittance characteristics of the film of the present invention and the conventional film are significantly different in the range of 350 nm to 410 nm.

Each of the obtained film samples was subjected to the alkali saponification treatment shown below, and polarizing plate samples 1 to 21 were produced in the combinations shown in Table 3 according to the following production method. The optical film 1 shown in Table 3 is an optical film arranged outside the polarizer (on the side opposite to the liquid crystal panel), and is arranged in the same manner as the optical film 1 of the polarizing plate shown in FIG. The optical film 2 is an optical film arranged inside the polarizer, and is arranged in the same manner as the optical film 2 of the polarizing plate shown in FIG.

<Alkali Saponification Treatment> Saponification step 2 mol / l-NaOH 50 ° C. 90 seconds Water washing step Water 30 ° C. 45 seconds Intermediate step 10 mass% HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds Film sample under the above conditions Are sequentially saponified, washed with water, neutralized and washed with water, and then dried at 80 ° C.

(Production of Polarizing Plate) Using a polyvinyl alcohol film having a thickness of 120 μm, 1 kg of iodine and 4 kg of boric acid were used.
Was dipped in 100 kg of an aqueous solution containing and was stretched 6 times at 50 ° C. to form a polarizing film. Cellulose ester film samples that had been subjected to alkali saponification treatment on both sides of this polarizing film were attached to each other using a fully saponified polyvinyl alcohol 5% aqueous solution as an adhesive to prepare a polarizing plate.

Evaluation was carried out by the following measuring methods. The results are shown in Table 3. << Measurement Method >> (Light resistance) First, the parallel transmittance and the orthogonal transmittance of the produced polarizing plate were measured, and the degree of polarization was calculated according to the following formula. After that, a reflection plate was attached to the optical film 2 side of each polarizing plate, and after sunshine weather meter 300 hours, without UV cut filter, light was applied from the direction of the optical film 1 of the polarizing plate to forcibly deteriorate the polarizing plate. After removal, the parallel transmittance and the orthogonal transmittance were measured again, and the polarization degree was calculated according to the following formula. The amount of change in the degree of polarization was determined by the following formula.

Degree of polarization P = ((H ₀ −H ₉₀ ) / (H ₀ +
H ₉₀ )) ^1/2 × 100 Polarization degree change = P ₀ −P ₅₀₀ H ₀ : Parallel transmittance H ₉₀ : Cross transmittance P ₀ : Polarization degree before forced deterioration P ₅₀₀ : Polarization after 500 hours of forced deterioration Degree ◎: Polarization degree change rate less than 10% ◯: Polarization degree change rate 10% or more and less than 25% ×: Polarization degree change rate 25% or more.

(Color Reproducibility) A commercially available portable device equipped with a reflective TFT color liquid crystal display device (Personal mobile tool Zaurus model name MI-L1 manufactured by Sharp)
The polarizing plate of 2 was carefully peeled off, the polarizing plate prepared as described above was aligned with the polarizing direction, and the liquid crystal display panel was attached to the optical film 2 side. Polarizing plate sample 21 (comparative sample) for each liquid crystal display panel
The color reproduction was evaluated in comparison with the liquid crystal display panel to which was attached, and ranked as follows.

[0163] ⊚: Excellent color reproducibility equivalent to comparison ○: A slight deterioration in color reproducibility can be seen Δ: Deterioration of color reproducibility can be seen X: Clear deterioration of color reproducibility

[0164]

[Table 3]

It can be seen that the polarizing plate sample using the optical film sample of the present invention has excellent light resistance and excellent color reproducibility even when used as a liquid crystal display device.

[0166]

EFFECT OF THE INVENTION An optical film which can be used as a protective film for a polarizing plate used in a liquid crystal display device and various functional films such as a retardation film, a viewing angle widening film and an antireflection film was obtained. .

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a reflective TFT color liquid crystal panel.

FIG. 2 is a schematic view showing a preferred example of a solution casting film forming method of a film.

FIG. 3 is a diagram showing transmittance characteristics of an optical film of the present invention and a conventional optical film.

[Explanation of symbols]

1 Mirror-like strip metal casting support 2 dice 4 Cellulose ester film 5 Tenter transfer and drying process 6 Tension cutting means 8-roll transfer / drying process 84 Upper transport roll 85 Lower transport roll

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 1/10 C08L 1/10 5G435 101/00 101/00 G02B 5/22 G02B 5/22 G02F 1/1335 G02F 1 / 1335 G09F 9/00 313 G09F 9/00 313 F-term (reference) 2H048 CA01 CA04 CA05 CA09 CA13 CA17 CA24 CA27 CA29 2H049 BA02 BB13 BB22 BB33 BC09 BC10 2H091 FA07X FA11X FA37X FD06 GA16 LA03 4F071 AA09 AB26 AC07 AC12 AE05 AF30Y AH16 BB06 BC01 BC12 4J002 AB021 DE097 DE137 DE147 DE237 DH047 DJ007 DJ017 DJ037 DJ047 EE036 EU176 FD020 FD056 GP00 5G435 AA04 AA14 CC12 GG12 GG16 GG43 LL07 LL08

Claims (12)

[Claims] 1. The spectral transmittance at 390 nm is 50%.
95% or more and a spectral transmittance at 350 nm of 5% or less. 2. The optical film according to claim 1, which contains at least one ultraviolet absorber selected from benzophenone-based and benzotriazole-based ultraviolet absorbers. 3. The optical film according to claim 1, which is substantially free of a phosphoric acid ester. 4. The primary average particle diameter is 20 nm or less,
The optical film according to any one of claims 1 to 3, further comprising silicon dioxide fine particles having an apparent specific gravity of 70 g / liter or more. 5. The secondary average particle diameter is 0.3 or more and 1.5 μm.
The optical film according to any one of claims 1 to 4, comprising silicon dioxide fine particles having a particle size of m or less. 6. The optical film according to claim 1, which comprises a cellulose ester as a main component. 7. The optical film according to claim 1, wherein the film thickness is 20 to 65 μm. 8. A polarizing plate in which an optical film is arranged such that a polarizing element is sandwiched from both sides, and the amount of the ultraviolet absorber contained in the optical film arranged on one side is 0.3 g or more per 1 m ^2. A polarizing plate having a weight of 0.0 g or less, and the optical film arranged on the other side is substantially free of an ultraviolet absorber. 9. A polarizing plate in which an optical film is arranged so as to sandwich a polarizing element from both sides, wherein the optical film according to any one of claims 1 to 7 is arranged on at least one side. Polarizing plate characterized by. 10. A display device using the optical film according to any one of claims 1 to 7. 11. A display device using the polarizing plate according to claim 8. 12. The display device according to claim 10, which is a reflective or transflective display device.