JP2006292834A - Protection film for polarizing plate, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protection film for a polarizing plate having low moisture permeability, to provide a polarizing plate showing little change in the transmittance and the polarization degree due to heat or humidity, and to provide a liquid crystal display device having high display quality without causing problems such as light leakage. <P>SOLUTION: The protection film for a polarizing plate comprises a low moisture permeable curing layer formed directly or via another layer on a cellulose acylate film, and at least one layer containing a metal oxide and/or a metal nitride on the low moisture permeable curing layer. The protection film shows ≤200 g/m<SP>2</SP>day moisture permeability measured in an atmosphere at 60°C and 95% relative humidity according to JIS-Z-0208. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a protective film for a polarizing plate, a polarizing plate, and a liquid crystal display device.

Liquid crystal display devices are increasingly used year by year as space-saving image display devices with low power consumption. Conventionally, the large viewing angle dependence of images has been a major drawback of liquid crystal display devices, but in recent years, high viewing angle liquid crystal modes such as VA mode and IPS mode have been put into practical use. The demand for liquid crystal display devices is rapidly expanding even in markets where viewing angles are required.
Along with this, higher performance has begun to be required for retardation films and polarizing plates used in liquid crystal display devices. In particular, improvement of durability against temperature and humidity is a big problem for polarizing plates.

In the durability test of a polarizing plate, the problem is a decrease in the degree of polarization. This is because iodine adsorbed on the polarizer is decomposed by the action of water. It is known that it is effective to reduce the moisture permeability of the protective film. Since cellulose acylate, which is widely used as a protective film for polarizing plates, is a hydrophilic polymer and has high moisture permeability, a method for reducing moisture permeability by adding various hydrophobizing agents has been proposed. Patent Document 1 added rosin derivatives, Patent Document 2 added polyhydric alcohol esters having an aromatic ring or cycloalkyl ring in the molecule and glycolates having an aromatic ring or cycloalkyl ring in the molecule. A method for reducing humidity is disclosed.
However, in these methods, the moisture permeability can be reduced by adding a hydrophobizing agent up to a certain addition amount. However, even if the addition amount is further increased, there is a problem that the change reaches its peak and a sufficient improvement effect cannot be obtained.

  Patent Document 3 discloses a polarizing film in which a vapor deposition film is formed on at least one surface of a polarizing plate, but there is a problem that the adhesion of the vapor deposition film is not sufficient. Patent Document 4 discloses an optical film excellent in durability at high temperature and high humidity, but does not mention the durability of a polarizing plate such as a decrease in the degree of polarization. Patent Document 5 discloses a hard-coated acetyl cellulose resin article, but does not mention the durability of the polarizing plate such as a decrease in the degree of polarization.

JP 2002-146044 A JP 2003-232920 A JP-A-6-289227 JP 2003-232920 A JP 2004-2508 A

The objective of this invention is providing the protective film for polarizing plates with low moisture permeability, and the polarizing plate with a small change of the transmittance | permeability and polarization degree by heat and humidity.
Another object of the present invention is to use a polarizing plate in which a polarizing plate protective film having a low moisture permeability is disposed on at least one side of a polarizer for a liquid crystal display device, so that display quality can be improved without causing problems such as light leakage. It is to provide a high liquid crystal display device.
A further object of the present invention is to use a polarizing plate in which a retardation film having excellent viewing angle compensation ability and a polarizing plate protective film with low moisture permeability are arranged on both sides of a polarizer, for light leakage, etc. It is an object of the present invention to provide a liquid crystal display device having a wide viewing angle and high display quality without causing the above problem.

The above object of the present invention is achieved by the following means.
That is,
(1) A low moisture permeability cured layer is provided directly on the cellulose acylate film or via another layer, and at least one layer containing a metal oxide and / or metal nitride is provided on the low moisture permeability cured layer. A protective film for a polarizing plate, wherein the moisture permeability measured in an atmosphere of 60 ° C. and 95% relative humidity is 200 g / m ² · day or less according to JIS-Z-0208 the film.
(2) The protective film for polarizing plate according to (1), wherein the moisture permeability is 150 g / m ² · day or less.
(3) The protective film for polarizing plate according to (1), wherein the moisture permeability is 100 g / m ² · day or less.
(4) The low moisture-permeable cured layer is applied and dried by curing and curing a curable composition containing a compound having an I / O value (inorganic value / organic value) of 0.8 or less in the organic conceptual diagram. The protective film for a polarizing plate according to any one of (1) to (3), wherein the protective film is a polarizing plate.
(5) The low moisture-permeable cured layer is coated with a curable composition containing at least one compound selected from a compound represented by the following general formula (A) and a compound represented by the following general formula (B). -The protective film for polarizing plates in any one of said (1)-(4) characterized by drying and hardening this.

(In the formula, R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 represents an alkylene group or alkylene oxide group having 1 to 5 carbon atoms, and R3 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. And n represents an integer of 1 or 2.)
General formula (B)

(Wherein R1, R3 and n represent the same meaning as in the general formula (A)).
(6) The protective film for a polarizing plate according to any one of the above (1) to (5), wherein the cellulose acylate film has a thickness of 30 to 100 μm.
(7) In the polarizing plate in which a protective film is bonded to both sides of the polarizer, at least one of the protective films is the protective film for a polarizing plate according to any one of the above (1) to (6). A characteristic polarizing plate.
(8) A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein at least one polarizing plate is the polarizing plate described in (7) above.

  According to the present invention, it is possible to provide a polarizing plate protective film having a low moisture permeability and a polarizing plate having a small change in transmittance and degree of polarization due to heat and humidity. Furthermore, by using a polarizing plate in which the polarizing plate protective film of the present invention is disposed on at least one surface of a polarizer for a liquid crystal display device, a liquid crystal display device with high display quality is provided without causing problems such as light leakage. be able to. Furthermore, by using a polarizing plate in which a retardation film having excellent viewing angle compensation ability and a polarizing plate protective film of the present invention are disposed in a polarizer, a wide viewing field can be obtained without causing problems such as light leakage. A liquid crystal display device with high display quality at corners can be provided.

  In the present specification, the description “(meth) acryloyl” represents the meaning of “at least one of acryloyl and methacryloyl”. The same applies to “(meth) acrylate”, “(meth) acrylic acid” and the like. In addition, when a numerical value represents a physical property value, a characteristic value, or the like, the description “(numerical value 1) to (numerical value 2)” means “(numerical value 1) or more and (numerical value 2) or less”.

  In the present specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. Re (λ) is measured in KOBRA 21ADH (manufactured by Oji Scientific Instruments) by making light having a wavelength of λ nm incident in the normal direction of the film. Rth (λ) is the light of wavelength λnm from the direction inclined by + 40 ° with respect to the normal direction of the film, with Re (λ) and the in-plane slow axis (determined by KOBRA 21ADH) as the tilt axis (rotary axis). And a retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). KOBRA 21ADH calculates based on the retardation value measured in a total of three directions, the assumed value of the average refractive index, and the input film thickness value. Here, as an assumed value of the average refractive index, values of catalogs of various optical films such as a polymer handbook (John Wiley & Sons, Inc.) can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). The KOBRA 21ADH calculates nx, ny, and nz by inputting the assumed value of the average refractive index and the film thickness. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

Hereinafter, embodiments of a protective film for a polarizing plate, a polarizing plate and a liquid crystal display device according to the present invention will be described.
1. Protective film for polarizing plate The protective film for polarizing plate of the present invention has a low moisture-permeable cured layer provided directly on the cellulose acylate film or through another layer, and further a metal on the low moisture-permeable cured layer. At least one layer containing an oxide and / or a metal nitride is provided. Hereinafter, each layer which comprises the protective film for polarizing plates is demonstrated.

[Low moisture permeability cured layer]
In the present invention, the low moisture-permeable cured layer refers to a layer that can reduce moisture permeability by providing the layer as compared to the case without the layer. As an index of moisture permeability, moisture permeability specified in JIS-Z-0208 can be used.
The low moisture-permeable cured layer is formed on the cellulose acylate film by the following polymerizable compound (for example, a compound having an I / O value of 0.8 or less), a polymerization initiator, a solvent, and inorganic fine particles as necessary. The curable composition containing the additive is applied directly or through another layer and then dried, and then cured by a method such as heat curing, redox room temperature curing, anaerobic curing or ultraviolet curing. Can do.

(Polymerizable compound)
It is preferable that the low moisture-permeable cured layer includes a polymer unit derived from at least one compound selected from the group of compounds having an I / O value of 0.8 or less. When the I / O value is 0.8 or less, the adhesion with the layer containing metal oxide and / or metal nitride is improved. It preferably contains a polymer unit derived from at least one compound selected from the group of compounds having an I / O value of 0.7 or less, more preferably an I / O value of 0.6 or less. These compounds are preferably curable by ultraviolet rays.
The I / O value is a value known as (inorganic value / organic value) in an organic conceptual diagram, and is described in “Organic conceptual diagram-basics and application-” (by Yoshio Koda, Sankyo Publishing). There is a description.

  The polymer unit derived from the compound having an I / O value of 0.8 or less in the low moisture permeable cured layer is preferably 30 to 99% by mass with respect to the total mass of the mortality cured layer, and is preferably 50 to 99. More preferably, it is mass%.

  Particularly preferred as a compound having an I / O value of 0.8 or less is at least one compound selected from the group of compounds represented by the following general formula (A) and the following general formula (B). A compound. By including at least one of these compounds, the moisture permeability of the polarizing plate protective film can be further reduced. The mechanism of action is not necessarily clear, but it is presumed that the alicyclic structure contained in the structure of the polymerized unit shows the effect of reducing moisture permeability.

  In general formula (A) and general formula (B), R1 represents a hydrogen atom or a C1-C3 alkyl group, Preferably, a hydrogen atom, a methyl group, and an ethyl group are represented. R2 represents an alkylene group having 1 to 5 carbon atoms or an alkylene oxide group, preferably a methylene group, an ethylene group, a methylene oxide group, or an ethylene oxide group. R3 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and preferably represents a hydrogen atom, a methyl group, or an ethyl group. n represents an integer of 1 or 2.

  Although the preferable specific example of a compound represented by general formula (A) below is shown, this invention is not limited to these.

  Moreover, although the preferable specific example of a compound represented by general formula (B) is shown, this invention is not limited to these.

  As the compound represented by the general formula (A) and the compound represented by the general formula (B), compounds described in JP-A-60-152515 can also be used.

In addition to the compounds represented by the general formulas (A) and (B), the curable composition used for forming the low moisture-permeable cured layer may contain, for example, the following polymerizable compound.
For example, as a compound having two or more ethylenically unsaturated groups, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane polyethoxytri (meta) ) Acrylate, ditrimethylolpropane tetra (meth) acrylate, glycene polypropoxytri (meth) acrylate, di (meth) acrylate of ε-caprolactone adduct of hydroxypenic acid neopenglycol (eg Nippon Kayaku Co., Ltd.) KAYARAD HX-220, HX-620, etc.), pentaerythritol tetra (meth) acrylate, poly (meth) acrylate of dipentaerythritol and ε-caprolactone reaction product, dipentaerythritol Hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate, tripentaerythritol hepta (meth) acrylate, polyglycidyl compounds (polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1 , 6-hexanediol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, glycerin polyglycidyl ether, glycerin polyethoxyglycidyl ether, trimethylolpropane polyglycidyl ether, trimethylolpropane polyethoxypolyglycidyl ether, etc.) and (meth) Epoxy (meth) acrylate, which is a reaction product of acrylic acid, and polyfunctional (meth) acrylate containing hydroxyl group And polyisocyanate compounds (tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate) , P-phenylene diisocyanate, etc.) and a polyfunctional urethane acrylate. You may use these individually or in mixture of 2 or more types.

  Furthermore, as vinyl monomers, esters derived from acrylic acid or α-alkylacrylic acid (for example, methacrylic acid), or amides (for example, Ni-propylacrylamide, Nn-butylacrylamide, N- t-butylacrylamide, N, N-dimethylacrylamide, N-methylmethacrylamide, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylamidopropyltrimethylammonium chloride, methacrylamide, diacetone acrylamide, acryloylmorpholine, N-methylol Acrylamide, N-methylol methacrylamide, methyl acrylate, ethyl acrylate, hydroxyethyl acrylate, n-propyl acrylate, i-propyl acrylate 2-hydroxypropyl acrylate, 2-methyl-2-nitropropyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, t-pentyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-methoxymethoxyethyl acrylate, 2,2,2-trifluoroethyl acrylate, 2,2-dimethylbutyl acrylate, 3-methoxybutyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, n-pentyl acrylate, 3-pentyl acrylate , Octafluoropentyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, cyclopentyl acrylate, cetyl acrylate, benzyl acrylate Benzyl methacrylate, methoxypolyethylene glycol methacrylate, n-octyl acrylate, 2-ethylhexyl acrylate, 4-methyl-2-propylpentyl acrylate, heptadecafluorodecyl acrylate, n-octadecyl acrylate, methyl methacrylate, 2,2,2 -Trifluoroethyl methacrylate, tetrafluoropropyl methacrylate, hexafluoropropyl methacrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate , 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate Benzyl methacrylate, heptadecafluorodecyl methacrylate, n-octadecyl methacrylate, 2-isobornyl methacrylate, 2-norbornylmethyl methacrylate, 5-norbornen-2-ylmethyl methacrylate, 3-methyl-2-norbol Nylmethyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate, dicyclopentenyloxyethyl methacrylate, dicyclopentanyl methacrylate, pentamethylpiperidyl methacrylate, tetramethylpiperidyl methacrylate, dimethylaminoethyl methacrylate, etc. ), Acrylic acid or α-alkyl acrylic acid (acrylic acid, methacrylic acid, itaconic acid, etc.),

  Vinyl esters (eg, vinyl acetate), esters derived from maleic acid or fumaric acid (dimethyl maleate, dibutyl maleate, diethyl fumarate, etc.), maleimides (N-phenylmaleimide, etc.), maleic acid, fumaric acid , Sodium salt of p-styrenesulfonic acid, acrylonitrile, methacrylonitrile, dienes (eg butadiene, cyclopentadiene, isoprene), aromatic vinyl compounds (eg styrene, p-chlorostyrene, t-butylstyrene, α-methyl) Styrene, sodium styrenesulfonate), N-vinylpyrrolidone, N-vinyloxazolidone, N-vinylsuccinimide, N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methyl Cetamide, 1-vinylimidazole, 4-vinylpyridine, vinyl sulfonic acid, sodium vinyl sulfonate, sodium allyl sulfonate, sodium methallyl sulfonate, vinylidene chloride, vinyl alkyl ethers (eg methyl vinyl ether), ethylene, propylene, 1 -Butene, isobutene, etc. are mentioned. Two or more of these vinyl monomers may be used in combination. Vinyl monomers other than these are listed in Research Disclosure No. 1955 (1980, July), JP-A-63-243108, high performance liquid polymer material (Maruzen Co., Ltd., issued on May 20, 1990) Chapter 14 may be used. it can. In the present invention, esters derived from acrylic acid or methacrylic acid, amides, and aromatic vinyl curable resins are particularly preferably used vinyl monomers.

  The compound having two or more ethylenically unsaturated groups and the vinyl monomer are from Nippon Kayaku Co., Ltd. under the trade name of KAYARAD, and from Daiichi Kogyo Seiyaku Co., Ltd. under the trade name of New Frontier. It can be obtained under the trade name of Aronix from Co., Ltd. and under the trade name of Funkrill from Hitachi Chemical Co., Ltd.

  The amount of the compound having two or more ethylenically unsaturated groups or the vinyl monomer added to the compound represented by the general formulas (A) and (B) is the required moisture permeability, pencil hardness, refractive index, and transparency. Although it can choose arbitrarily by property etc., it is two or more with respect to the total mass of the compound and vinyl monomer which have a compound represented by general formula (A) and (B), two or more ethylenically unsaturated groups, and vinyl monomer The mass of the compound having an ethylenically unsaturated group and / or the vinyl monomer is preferably 70% by mass or less, more preferably 50% by mass or less, and most preferably 30% by mass or less.

(Polymerization initiator)
In order to obtain a low moisture-permeable cured layer, the curable composition preferably contains a polymerization initiator.
(I) When heat-curing, benzoyl peroxide, dicumyl peroxide, etc. can be added.
(Ii) In the case of carrying out redox room temperature curing, benzoyl peroxide / dimethylaniline, cumene hydroperoxide / vanadium accelerator, etc. can be added.
(Iii) In the case of anaerobic curing, hydroperoxide / tertiary amine / sulfimide can be added.
(Iv) In the present invention, ultraviolet curing is most preferred and will be described in detail.

Examples of polymerization initiators that generate radicals by ultraviolet rays include known radical generators such as acetophenones, benzophenones, Michler's ketone, benzoylbenzoate, benzoins, α-acyloxime esters, tetramethylthiuram monosulfide, and thioxanthone. Can be used. In general, sulfonium salts and iodonium salts used as photoacid generators also act as radical generators upon irradiation with ultraviolet rays, and these may be used alone in the present invention. In addition to a polymerization initiator, a sensitizer may be used for the purpose of increasing sensitivity. Examples of the sensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, and thioxanthone derivatives.
For ultraviolet curing, various methods described in “Latest UV Curing Technology” (Information Technology Association, Inc., issued on September 29, 1991) can be preferably used.

  The addition amount of the polymerization initiator is preferably 0.1 to 15% by mass, preferably 1 to 10% by mass, based on the total mass of the polymerizable compound contained in the curable composition. More preferably it is used.

(solvent)
Examples of the solvent include alcohols, ketones, esters, amides, ethers, ether esters, hydrocarbons, halogenated hydrocarbons and the like. Specifically, alcohol (for example, methanol, ethanol, propanol, butanol, benzyl alcohol, ethylene glycol, propylene glycol, ethylene glycol monoacetate, etc.), ketone (for example, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, etc.), ester ( For example, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl formate, propyl formate, butyl formate, ethyl lactate, etc.), aliphatic hydrocarbons (eg, hexane, cyclohexane), halogenated hydrocarbons (eg, methyl chloroform), aromatic Group hydrocarbons (eg, benzene, toluene, xylene, etc.), amides (eg, dimethylformamide, dimethylacetamide, n-methylpyrrolidone, etc.), ethers (eg, dioxane) Emissions, tetrahydrofuran, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, etc.), ether alcohols (such as 1-methoxy-2-propanol, ethyl cellosolve, methyl carbinol and the like). Two or more kinds may be mixed and used. As a preferable solvent, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, butanol and the like can be used.

(Inorganic fine particles)
In order to improve the adhesiveness with the layer containing a metal oxide and / or metal nitride, the low moisture permeability cured layer preferably contains inorganic fine particles. As inorganic fine particles, silica, alumina, zirconium oxide, titanium oxide and the like are preferably used. The primary particle size is preferably 5 to 200 nm, more preferably 7 to 150 nm, and most preferably 10 to 100 nm. Preferred inorganic particles include methanol silica sol, MA-ST-MS, IPA-ST, IPA-ST-MS, IPA-ST-L, IPA-ST-ZL, IPA-ST-UP, EG-ST, NPC-ST- 30, MEK-ST, MEK-ST-MS, MIBK-ST, XBA-ST, PMA-ST, DMAC-ST manufactured by Nissan Chemical Industries, Ltd.
Although content of an inorganic particle is suitably selected from adhesiveness with the layer containing a metal oxide and / or a metal nitride, 10-70 mass% is preferable with respect to a low moisture-permeable cured layer, and 20-60 mass. % Is more preferable, and 30 to 50% by mass is most preferable.

(Film thickness)
The preferable film thickness of the low moisture-permeable cured layer is 0.5 to 20.0 μm, more preferably 1.0 to 15.0 μm, and still more preferably 2.0 to 10.0 μm. 0.5 μm or more is preferable in terms of sufficient moisture-proof curing, and 20.0 μm or less is preferable in terms of curling being small and suitable for handling.

[Layer containing metal oxide and / or metal nitride]
In the layer containing a metal oxide and / or metal nitride in the present invention, water penetrates into the polarizer and the degree of polarization decreases, and the polarizer expands and contracts due to the penetrated water, and stress is applied to the cellulose acylate film. This is a layer having a function of preventing light leakage when a liquid crystal display device is formed.

(Metal oxide / metal nitride)
Preferred specific examples of the metal oxide include aluminum oxide, zinc oxide, antimony oxide, indium oxide, calcium oxide, cadmium oxide, silver oxide, gold oxide, chromium oxide, silicon oxide, cobalt oxide, zirconium oxide, tin oxide, Examples include titanium oxide, iron oxide, copper oxide, nickel oxide, platinum oxide, palladium oxide, bismuth oxide, magnesium oxide, manganese oxide, molybdenum oxide, vanadium oxide, and barium oxide. It is particularly preferable since it has both barrier properties, water vapor barrier properties and transparency and is industrially inexpensive.
Silicon nitride is preferably used as the metal nitride.

The silicon oxide in the present invention, SiO, refers to oxides and are compounds represented by SiOx of Si, such as SiO _2. Among them, metal oxides mainly composed of silicon oxide having a ratio of the number of oxygen atoms to the number of silicon atoms of 1.5 to 2.0 from the viewpoint of moisture permeability, transparency, surface smoothness, flexibility and the like are good. . The ratio of the number of oxygen atoms to silicon oxide is analyzed and determined by X-ray electron spectroscopy, X-ray microspectroscopy, Auger electron spectroscopy, Rutherford backscattering method, and the like. Since this ratio is 1.5 or more and transparency is good, 1.5 to 2.0 is preferable.

  Such metal oxides and / or metal nitrides such as silicon oxide, aluminum oxide and silicon nitride may be used alone or as a mixture. The metal oxide may contain trace amounts of metals, non-metals, sub-metals or their hydroxides, and carbon, fluorine, or magnesium fluoride as appropriate in order to improve plasticity.

(Film thickness)
The thickness of the layer containing metal oxide and / or metal nitride is preferably in the range of 5 to 200 nm. A thickness of 5 nm or more is preferable because it is easy to form a film uniformly and an increase in moisture permeability due to permeation of water vapor from a portion where the film is not formed can be prevented. Moreover, since it is excellent in transparency and it becomes difficult to generate | occur | produce a crack, 200 nm or less is preferable.

(Formation method)
As a method for forming a layer containing a metal oxide and / or metal nitride, a CVD method (PE-CVD, atmospheric pressure CVD) or a PVD method (evaporation, ion plating, sputtering) can be mainly used. . Regarding the CVD method, “HANDBOOK OF CHEMICAL VAPOR DEPOSITION PRINCIPLES, Technology and Applications” Hugh O. A method described in NOYES PUBLICATIONS by Pierson is preferably used. As for PVD, the method described in “Basics of Spattering Phenomenon and Application to Thin Film / Coating Technology” (Akira Kanehara, University of Tokyo Press) is preferably used. As an example, sputtering will be described in detail.

  For example, in a sputtering method for forming a layer containing silicon oxide SiOx, a sintered body mainly composed of silicon and silicon oxide can be used as a target. The former performs reactive sputtering by introducing an inert gas such as argon and a reactive gas such as oxygen gas into the vacuum chamber. In the latter, sputtering is performed using an inert gas such as argon mixed with a reactive gas such as a slight amount of oxygen gas. As a sputtering method, a known method such as direct current or high frequency bipolar sputtering, direct current or high frequency magnetron sputtering, or ion beam sputtering can be applied. Among these, the magnetron method is preferable because it has less plasma impact on the substrate and enables high-speed film formation. In the present invention, it is particularly preferable to perform film formation by direct current pulse magnetron sputtering using a Si metal target in order to increase the film formation speed. Although an Si oxide target may be used, the deposition rate is extremely slow and the discharge stability is poor, which is not preferable from the viewpoint of productivity. As the sputtering apparatus, a roll-to-roll system is desirable from the viewpoint of productivity, but a batch system can also be used.

In reactive sputtering, there are a mass flow control method and an impedance control method for controlling the amount of introduced oxygen, but the impedance control method is preferred because the film formation rate is high.
The total pressure during sputtering is preferably 0.005 Pa to 0.5 Pa. More preferably, it is 0.01-0.3Pa, More preferably, it is 0.01-0.2Pa. If it is 0.005 Pa or more, stable discharge is possible, and if it is 0.5 Pa or less, the water vapor transmission rate is reduced.

  It is also preferable to perform plasma treatment before film formation by CVD or PVD. By performing the plasma treatment, the adhesion of the layer containing metal oxide and / or metal nitride can be improved. For the plasma treatment, argon plasma, argon / oxygen plasma, or argon / nitrogen plasma is preferably used.

[Cellulose acylate film]
(Cellulose acylate)
As cellulose of the raw material of the cellulose acylate film used for the protective film for polarizing plate, there are cotton linter, kenaf, wood pulp (hardwood pulp, softwood pulp), etc., and any cellulose ester obtained from any raw material cellulose can be used, You may mix and use depending on the case.
In the present invention, cellulose acylate is produced by esterification from cellulose. However, the above-mentioned cellulose is not usable as it is, and linter, kenaf, and pulp are purified and used.

In the present invention, cellulose acylate is a carboxylic acid ester having 2 to 22 carbon atoms in total.
Examples of carboxylic acid esters include cellulose alkylcarbonyl esters, alkenylcarbonyl esters, cycloalkylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. .

  The acyl group having 2 to 22 carbon atoms in cellulose acylate may be either an aliphatic acyl group or an aromatic acyl group, and is not particularly limited. Examples of these preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, cyclohexanecarbonyl, adamantanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, (meth) acryloyl, and cinnamoyl groups. Among these, more preferred acyl groups are acetyl, propionyl, butanoyl, pentanoyl, hexanoyl, cyclohexanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, and the like.

  A method for synthesizing cellulose acylate is disclosed in JIII Journal of Technical Disclosure No. 2001-1745 (issued March 15, 2001, Japan Institute of Invention) p. 9 is described in detail.

The cellulose acylate preferably used in the present invention preferably has a degree of substitution with a hydroxyl group of cellulose satisfying the following mathematical formulas (1) and (2).
Formula (1): 2.3 ≦ SA ′ + SB ′ ≦ 3.0
Formula (2): 0 ≦ SA ′ ≦ 3.0

  Here, SA ′ is the substitution degree of the acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB ′ is the substitution degree of the acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose. Represents. SA represents an acetyl group substituting a hydrogen atom of a hydroxyl group of cellulose, and SB represents an acyl group having 3 to 22 carbon atoms substituting a hydrogen atom of a hydroxyl group of cellulose.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification at each position is substitution degree 1). In the present invention, the total sum of substitution degrees of SA and SB (SA ′ + SB ′) is more preferably 2.6 to 3.0, and particularly preferably 2.80 to 3.00. Further, the substitution degree (SA ′) of SA is more preferably 1.4 to 3.0, and particularly 2.3 to 2.9.

It is preferable that the cellulose acylate further satisfies the following formula (3).
Formula (3): 0 ≦ SB ”≦ 1.2
Here, SB ″ represents an acyl group having 3 or 4 carbon atoms replacing a hydrogen atom of a hydroxyl group of cellulose.

  Further, SB ″ is preferably 28% or more of the substituent at the 6-position hydroxyl group, more preferably 30% or more is the substituent at the 6-position hydroxyl group, more preferably 31% or more, and particularly preferably 32% or more. It is also preferred that the substituent is a hydroxyl group at the 6-position. Furthermore, the sum of the substitution degrees of SA ′ and SB ″ at the 6-position of the cellulose acylate is 0.8 or more, more preferably 0.85 or more, A cellulose acylate film having a value of 0.90 or more can also be mentioned as a preferable example. These cellulose acylate films can produce a solution having a preferable solubility, and in particular, a non-chlorine organic solvent can produce a good solution.

The degree of substitution can be obtained by calculating the degree of binding of the fatty acid bound to the hydroxyl group in cellulose. As a measuring method, it can measure based on ASTM-D817-91 and ASTM-D817-96. The state of substitution of the acyl group with the hydroxyl group is measured by ¹³ C NMR method.

  The cellulose acylate film is preferably composed of a cellulose acylate in which the polymer component constituting the film substantially satisfies the above mathematical expressions (1) and (2). “Substantially” means 55% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of the total polymer components. The cellulose acylate may be used alone or in combination of two or more.

  The degree of polymerization of the cellulose acylate preferably used in the present invention is a viscosity average degree of polymerization of 200 to 700, preferably 230 to 550, more preferably 230 to 350, and particularly preferably a viscosity average degree of polymerization of 240 to 320. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.

The number average molecular weight Mn of the cellulose acylate is preferably in the range of 7 to 25 × 10 ⁴ , more preferably in the range of 8 to 15 × 10 ⁴ . The ratio of the cellulose acylate to the mass average molecular weight Mw, Mw / Mn, is preferably 1.0 to 5.0, more preferably 1.0 to 3.0. In addition, the average molecular weight and molecular weight distribution of a cellulose ester can be measured using a high performance liquid chromatography, Mn and Mw can be calculated using this, and Mw / Mn can be calculated.

  The cellulose acylate film used in the present invention has a cellulose acylate and a plasticizer in a range satisfying the above mathematical formulas (1) and (2) [particularly preferably an octanol / water partition coefficient (log P value) described later]. 0 to 10 plasticizers] and a film containing at least one kind of fine particles (particularly preferably, fine particles having an average primary particle size of 3 to 100 nm described later) are preferably used.

(Plasticizer)
It is preferable to use a plasticizer as a component added to impart flexibility to the cellulose acylate film, improve dimensional stability, and improve moisture resistance. The preferred plasticizer is preferably a solid having a boiling point of 200 ° C. or higher and a liquid at 25 ° C. or a melting point of 25 to 250 ° C. More preferred are plasticizers having a boiling point of 250 ° C. or higher and a liquid at 25 ° C. or a solid having a melting point of 25 to 200 ° C. When the plasticizer is a liquid, purification is usually carried out by distillation under reduced pressure, and higher vacuum is preferred. In the present invention, it is particularly preferable to use a plasticizer having a vapor pressure at 200 ° C. of 1333 Pa or less, more preferably steam. A compound having a pressure of 667 Pa or less, more preferably 133 to 1 Pa is preferred.

  As these plasticizers that are preferably added, phosphate esters, carboxylic acid esters, polyol esters and the like within the above-mentioned physical properties are used. Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.

  Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diphenyl phthalate, diethyl hexyl phthalate and the like. Examples of the citrate ester include O-acetyl triethyl citrate, O-acetyl tributyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate. These preferred plasticizers are liquid except for TPP (melting point: about 50 ° C.) at 25 ° C., and the boiling point is 250 ° C. or higher.

  Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, methyl phthalyl methyl glycolate, propyl phthalyl Examples include propyl glycolate, butyl phthalyl butyl glycolate, and octyl phthalyl octyl glycolate.

  JP-A-5-194788, JP-A-60-250053, JP-A-4-227941, JP-A-6-16869, JP-A-5-271471, JP-A-7-286068, JP-A-5-5047. No. 11, JP-A-11-80381, JP-A-7-20317, JP-A-8-57879, JP-A-10-152568, JP-A-10-120824, etc. are also preferably used. It is done. According to these publications, there are many preferable descriptions regarding not only examples of plasticizers but also their usage or characteristics, and they are preferably used in the present invention.

  Other plasticizers include (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, diglycerol esters described in JP-A No. 2000-63560, Citric acid esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946, ester compounds containing an aromatic ring and a cyclohexane ring described in JP-A No. 2003-165868 are preferably used. .

  Furthermore, in the present invention, a plasticizer having an octanol / water partition coefficient (log P value) of 0 to 10 is particularly preferably used. If the log P value of the compound is 10 or less, the compatibility with the cellulose acylate is good, there is no problem such as cloudiness or powder blowing of the film, and if the log P value is greater than 0, the hydrophilicity is high. Since it does not become too high, adverse effects such as deterioration of the water resistance of the cellulose acylate film are unlikely to occur. As the logP value, a more preferable range is 1 to 8, and a particularly preferable range is 2 to 7.

  The octanol / water partition coefficient (log P value) can be measured by a flask immersion method described in JIS Japanese Industrial Standard Z7260-107 (2000). Further, the octanol / water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement. As a calculation method, the Crippen's fragmentation method [J. Chem. Inf. Comput. Sci. 27, 21 (1987)], Viswanadhan's fragmentation method [J. Chem. Inf. Comput. Sci. , 29, 163 (1989)], Broto's fragmentation method [Eur. J. et al. Med. Chem. -Chim. Theor. 19 (71) (1984)] is preferably used, and the Crippen's fragmentation method is more preferable. When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the scope of the present invention by the Crippen's fragmentation method.

  A polymer plasticizer having a resin component having a molecular weight of 1,000 to 100,000 is also preferably used. For example, polyesters and / or polyethers described in JP-A No. 2002-22956, polyester ethers, polyester urethanes or polyesters described in JP-A No. 5-97073, copolyester ethers described in JP-A No. 2-292342, Examples thereof include an epoxy resin or a novolac resin described in JP-A No. 2002-146044.

  These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 2 to 30 parts by mass, particularly 5 to 20 parts by mass with respect to 100 parts by mass of the cellulose acylate.

(Fine particles)
It is preferable to add fine particles to the cellulose acylate film for forming a protective film for a polarizing plate for the purpose of improving the mechanical strength and dimensional stability of the film and improving the slipperiness. The fine particles are preferably hydrophobic.

  The primary average particle size of the fine particles is preferably 1 to 100 nm, more preferably 3 to 100 nm, still more preferably 3 to 80 nm, and particularly preferably 5 to 100 nm, from the viewpoint of keeping haze low. 60 nm, most preferably 5-50 nm. The primary average particle diameter of the fine particles can be measured by measuring the particles with a transmission electron microscope and determining the average particle diameter.

  The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, and particularly preferably 100 to 200 g / liter.

  The addition amount of the fine particles is preferably 0.005 to 2 parts by mass, particularly 0.01 to 1.0 part by mass with respect to 100 parts by mass of the cellulose acylate.

  Preferred specific examples of the fine particles include inorganic compounds such as silicon-containing compounds, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin oxide / antimony carbonate, Calcium, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate are preferred, more preferably silicon-containing inorganic compounds and zirconium oxide, cellulose acylate Since the haze increase of the film can be suppressed, silicon dioxide is particularly preferably used.

  The fine particles suitably used for the cellulose acylate film in the present invention are surface-treated for the reason that aggregation in the film after dope and after film formation is suppressed and the fine particles are stably dispersed as fine particles. Is preferred. The surface treatment is performed by treating the surface of fine particles with an organic compound. Examples of organic compounds that can be used in this case include surface modification of conventionally known inorganic fillers such as metal oxides and inorganic pigments. Examples are described in, for example, “Pigment Dispersion Stabilization and Surface Treatment Technology / Evaluation”, Chapter 1 (Technical Information Association, 2001). Specifically, an organic compound having a polar group having an affinity for the fine particle surface and a coupling compound can be mentioned.

  Examples of the polar group having an affinity for the fine particle surface include a carboxy group, a phosphono group, a hydroxy group, a mercapto group, a cyclic acid anhydride group, an amino group, and the like, and a compound containing at least one kind in the molecule is preferable. For example, long-chain aliphatic carboxylic acids (eg, stearic acid, lauric acid, oleic acid, linoleic acid, linolenic acid, etc.), polyol compounds (eg, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, ECH-modified glycerol, etc.), phosphono groups Examples thereof include compounds [for example, EO (ethylene oxide) -modified phosphoric acid and the like], alkanolamines [ethylene diamine adduct (5 mol) and the like] and the like.

As a coupling compound, a conventionally well-known organometallic compound is mentioned, A silane coupling agent, a titanate coupling agent, an aluminate coupling agent, etc. are contained. Silane coupling agents are most preferred. Specific examples include coupling compounds described by Fuzo Yamashita and Tosuke Kaneko “Crosslinking Agent Handbook” (Taiseisha, published in 1981).
In the surface treatment, two or more kinds of the above-mentioned compounds can be used in combination.

  As the organic compound, for example, polymers such as a silicone resin, a fluorine resin, and an acrylic resin are preferable, and among these, a silicone resin is preferably used. Among the silicone resins, those having a three-dimensional network structure are particularly preferable. For example, a commercial product having a trade name of Tospearl marketed by Toshiba Silicone Co., Ltd. can be used.

  The shape of the fine particles is not particularly limited, but is preferably a rice grain shape, a spherical shape, a cubic shape, a spindle shape, or an indefinite shape. The fine particles may be used alone or in combination of two or more.

The fine particles are preferably uniformly dispersed in the film after film formation. Therefore, the fine particles are preferably introduced into the dope solution after preparing a fine particle dispersion in the following manner or the like.
(1) After stirring and mixing the solvent and the fine particles, a fine particle dispersion is prepared with a disperser, and added to the dope solution and stirred.
(2) After stirring and mixing the solvent and the fine particles, the dispersion is made into a fine particle dispersion, and a small amount of cellulose acylate is added to the solvent and dissolved by stirring. The fine particle dispersion obtained by adding the fine particle dispersion and stirring to this is sufficiently mixed with the dope solution using an in-line mixer.
(3) A small amount of cellulose acylate is added to a solvent and dissolved by stirring. Fine particles are added to the solvent and dispersed with a disperser to obtain a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

  The mass average diameter of the primary particles of the fine particles in the dispersion is preferably 3 to 200 nm, more preferably 3 to 150 nm, still more preferably 3 to 100 nm, and particularly preferably 5 to 80 nm. In particular, it is preferable that the dispersed fine particles in the wet dispersion are substantially maintained at a primary particle size or larger so as not to excessively increase the specific surface area of the fine particles during dispersion. Furthermore, the dispersed fine particles in the wet dispersion preferably do not contain large particles having an average particle diameter of 500 nm or more, and particularly preferably do not contain large particles having an average particle diameter of 300 nm or more. This makes it possible to form a specific fine concavo-convex shape to be described later, which has no optical defects, has a small haze value and good transparency, and has no rough undulations on the surface.

(UV protection agent)
In order to improve the light resistance of the film itself or to prevent deterioration of image display members such as a polarizing plate and a liquid crystal compound of a liquid crystal display device, it is preferable to add an ultraviolet ray inhibitor to the cellulose acylate film.

  As the ultraviolet absorber, one having an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal and having as little absorption of visible light having a wavelength of 400 nm or more as possible from the viewpoint of good image display properties is used. It is preferable. In particular, the transmittance at a wavelength of 370 nm is desirably 20% or less, preferably 10% or less, and more preferably 5% or less. Examples of such ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and ultraviolet absorbing groups as described above. Examples thereof include, but are not limited to, polymer ultraviolet absorbing compounds. Two or more kinds of ultraviolet absorbers may be used.

  As a method of adding the ultraviolet absorber to the dope, it may be added after being dissolved in an organic solvent such as alcohol, methylene chloride, dioxolane, or may be added directly into the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  In this invention, the usage-amount of a ultraviolet absorber is 0.1-5.0 mass parts normally with respect to 100 mass parts of cellulose acylates, Preferably it is 0.5-2.0 mass parts, More preferably, it is 0.8-2. 0.0 part by mass.

(Other additives)
Furthermore, the cellulose acylate composition has various other additives (for example, deterioration inhibitors (for example, antioxidants, peroxide decomposers, radical inhibitors, metal inertness) depending on applications in each preparation step. Agents, acid scavengers, amines, etc.), optical anisotropy control agents, release agents, antistatic agents, infrared absorbers, etc.), which may be solid or oily. That is, the melting point and boiling point are not particularly limited. Furthermore, as an infrared absorber, the thing as described in Unexamined-Japanese-Patent No. 2001-194522 can be used, for example.

  These additives may be added at any time in the dope preparation step, but may be added in the final preparation step of the dope preparation step by adding a preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a cellulose acylate film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902, and these are conventionally known techniques. These details including the ultraviolet absorbers described above are the materials described in detail on pages 16 to 22 of the Japan Society for Invention and Innovation Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Japan Institute of Invention). Preferably used.

  The amount of these additives used is preferably used in the range of 0.001 to 20% by mass in the entire cellulose acylate composition.

(solvent)
As a solvent for cellulose acylate, an organic solvent is preferably used. As an organic solvent, a conventionally well-known organic solvent is mentioned, For example, the thing of the range of 17-22 is preferable by a solubility parameter. Solubility parameters are described in, for example, J. The content described in “Polymer Handbook (4th.edition)” by Brandrup, EH, etc., VII / 671 to VII / 714. Lower aliphatic hydrocarbon chloride, lower aliphatic alcohol, ketone having 3 to 12 carbon atoms, ester having 3 to 12 carbon atoms, ether having 3 to 12 carbon atoms, fat having 5 to 8 carbon atoms Group hydrocarbons, aromatic hydrocarbons having 6 to 12 carbon atoms, fluoroalcohols (for example, described in paragraph No. [0020] of JP-A-8-143709, paragraph No. [0037] of JP-A-11-60807) Compound) and the like.

  The cellulose acylate is preferably a solution in which 10 to 30% by mass is dissolved in an organic solvent, more preferably 13 to 27% by mass, and particularly 15 to 25% by mass of cellulose acylate. A solution is preferred. The method for preparing cellulose acylate at these concentrations may be prepared so as to be a predetermined concentration at the stage of dissolution, or it is prepared in advance as a low concentration solution (for example, 9 to 14% by mass) and then concentrated later. You may adjust to a predetermined high concentration solution by a process. Furthermore, a cellulose acylate solution having a high concentration may be added to the cellulose acylate solution at a predetermined low concentration by adding various additives, and the cellulose acylate solution concentration of the present invention is obtained by any method. If implemented, there is no particular problem.

(Preparation of dope)
Regarding the preparation of the cellulose acylate solution (dope), the dissolution method is not particularly limited as described above, and it is carried out by a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, and further a combination thereof. Is done. Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, JP JP-A Nos. 2000-273184, 11-323017, and 11-302388 describe methods for preparing cellulose acylate solutions. These techniques for dissolving cellulose acylate in an organic solvent can apply these techniques as appropriate in the present invention. About these details, especially a non-chlorine type | system | group solvent system, it implements by the method described in detail on the 22-25th pages of the above-mentioned technical numbers 2001-1745. Further, the cellulose acylate dope solution of the present invention is usually subjected to solution concentration and filtration, and is also described in detail on page 25 of the above-mentioned official technical number 2001-1745. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.

It is preferable that the viscosity and dynamic storage elastic modulus of the cellulose acylate solution are in a specific range. 1 mL of the sample solution was used in a rheometer (CLS 500) with Steel Cone (both manufactured by TA Instruments) with a diameter of 4 cm / 2 °, and the measurement conditions were Oscillation Step / Temperature Ramp in the range of 40 ° C. to −10 ° C. within a range of 2 ° C./-10° C. Measured by varying the minute, the static non-Newtonian viscosity n ^* (Pa · sec) at 40 ° C. and the storage modulus G ′ (Pa) at 5 ° C. are determined. The sample solution is kept warm until the liquid temperature becomes constant at the measurement start temperature, and then the measurement is started. In the present invention, the viscosity at 40 ° C. is preferably 1 to 300 Pa · sec, and the dynamic storage elastic modulus at −5 ° C. is preferably 10,000 to 1,000,000 Pa. More preferably, the viscosity at 40 ° C. is 1 to 200 Pa · sec, and the dynamic storage elastic modulus at −5 ° C. is 30,000 to 500,000 Pa.

(Method for producing cellulose acylate film)
Next, a method for producing a cellulose acylate film using the cellulose acylate solution will be described. As the method and equipment for producing the cellulose acylate film, a conventionally known solution casting film forming method and solution casting film forming apparatus called a drum method or a band method used for producing a cellulose triacetate film can be used. .

  The metal support used in the casting step preferably has an arithmetic average roughness (Ra) of 0.015 μm or less and a ten-point average roughness (Rz) of 0.05 μm or less. More preferably, the arithmetic average roughness (Ra) is 0.001 to 0.01 μm, and the ten-point average roughness (Rz) is 0.001 to 0.02 μm. More preferably, the (Ra) / (Rz) ratio is 0.15 or more. Thus, the surface shape of the film after film formation can be controlled within a preferable range described later by setting the surface roughness of the metal support within a predetermined range.

Hereinafter, the film forming process will be described using the band method as an example.
The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations, and the dope is run endlessly from the die (slit) of the pressure die. The dry-dried dope film (also referred to as web) is peeled off from the metal support at a peeling point that is uniformly cast on the metal support and substantially rounds the metal support. Both ends of the obtained web are sandwiched between clips, transported by a tenter while keeping the width, dried, then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. Each of these manufacturing processes is described in detail in the above-mentioned official technical numbers 2001-1745, pages 25-30, and is classified into casting (including co-casting), metal support, drying, peeling, stretching, etc. The

  In the casting step, one type of cellulose acylate solution may be cast as a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially.

(Thickness of cellulose acylate film)
The film thickness of the cellulose acylate film is preferably 30 to 100 μm, more preferably 30 to 90 μm, still more preferably 35 to 85 μm, and most preferably 40 to 80 μm.

(Width of cellulose acylate film)
The width of the cellulose acylate film is arbitrary, and is determined in consideration of the convenience in polarizing plate processing. Usually 1000 mm to 2000 mm.

(Characteristics of cellulose acylate film)
The cellulose acylate film suitably used as the protective film for polarizing plate of the present invention has the following characteristics.

(A) Properties of film surface The cellulose acylate film used as a protective film for a polarizing plate preferably has a specific surface shape. Hereinafter, the surface shape of the cellulose acylate film will be described.

  The surface of the cellulose acylate film on the side where the low moisture-permeable cured layer is provided has an arithmetic average roughness (Ra) of surface irregularities of the film based on JIS B-0601-1994 of 0.0001 to 0.1 μm, a 10-point average. The roughness (Rz) is preferably 0.0001 to 0.3 μm and the maximum height (Ry) is preferably 0.5 μm or less, and the arithmetic average roughness (Ra) is 0.0001 to 0.08 μm, ten points. More preferably, the average roughness (Rz) is 0.0001 to 0.1 μm, and the maximum height (Ry) is 0.5 μm or less, and the arithmetic average roughness (Ra) is 0.0002 to 0.015 μm, It is more preferable that the ten-point average roughness (Rz) is 0.002 to 0.05 μm and the maximum height (Ry) is 0.05 μm or less, and the arithmetic average roughness (Ra) is 0.001 to 0.00. 010 μm, 10-point average roughness ( It is particularly preferable that Rz) is 0.002 to 0.025 μm and the maximum height (Ry) is 0.04 μm or less. Within these ranges, a uniform coated surface with no coating unevenness, a low moisture permeability cured layer with good adhesion to the cellulose acylate film is provided, and bonded to a polarizer as a protective film for a polarizing plate In this case, the adhesiveness is good.

  The concave and convex shapes on the surface can be evaluated by a transmission electron microscope (TEM), an atomic force microscope (AFM), or the like.

In addition, the number of optical defects having a visual size of 100 μm or more in the cellulose acylate film is preferably 1 or less per 1 m ² , from the viewpoint that a uniform and clear film can be obtained with high yield. . This optical defect can be observed using a polarizing microscope with the slow axis of the film parallel to the absorption axis of the polarizing film under crossed Nicols. The defects that appear as bright spots are approximated in a circular area, and those having a diameter of 100 μm or more are counted. Bright spots of 100 μm or more can be easily observed with the naked eye.

That is, the surface of the cellulose acylate film has an arithmetic average roughness (Ra) of surface irregularities based on JIS B-0601-1994 of 0.0001 to 0.1 μm, and a ten-point average roughness (Rz) of 0. It is preferable that the number of optical defects having a size of 0.0001 to 0.3 μm and a visual size of 100 μm or more is 1 or less per 1 m ² . The film having the surface shape as described above is preferable because nonuniformity of a display image such as optical defects and unevenness in brightness is remarkably reduced.

(B) Mechanical properties of film The curl value in the width direction of the cellulose acylate film used in the present invention is preferably -7 / m to + 7 / m. When handling a long and wide cellulose acylate film, if the curl value in the width direction of the film is within the above-mentioned range, the handling of the film and the film will not be cut, and the film At the edge and center, the dust generated from the film coming into strong contact with the transport roll and the adhesion of foreign matter on the film are reduced, and the frequency of point defects and coating stripes of the polarizing plate of the present invention exceeds the allowable value. This is preferable. Further, it is preferable because bubbles can be prevented from entering when the polarizing film is bonded.

  The curl value can be measured according to a measurement method (ANSI / ASCPH1.29-1985) defined by the American National Standards Institute.

  The residual solvent amount of the cellulose acylate film used in the present invention is preferably 1.5% by mass or less because curling can be suppressed. Furthermore, it is more preferable that it is 0.01-1.0 mass% or less. This is presumably because the reduction of the free volume by reducing the amount of residual solvent during film formation by the above-mentioned solution casting film forming method becomes the main effect factor.

  The tear strength of the cellulose acylate film is 2 g or more based on the tear test method (Elmendorf tear method) of JIS K-7128-2: 1998. It is preferable at the point which can fully hold | maintain. More preferably, it is 5-25g, More preferably, it is 6-25g. Further, in terms of 60 μm, 8 g or more is preferable, and more preferably 8 to 15 g. Specifically, it can be measured using a light load tear strength tester after conditioning a sample piece of 50 mm × 64 mm under the conditions of 25 ° C. and 65% RH for 2 hours.

  The scratch strength is preferably 2 g or more, more preferably 5 g or more, and particularly preferably 10 g or more. By setting it as this range, the scratch resistance and handling property of the film surface can be maintained without any problem. The scratch strength can be evaluated with a load (g) by which the surface of the transparent protective film is scratched using a sapphire needle having a cone apex angle of 90 ° and a tip radius of 0.25 m, and the scratch mark can be visually confirmed.

(C) Hygroscopic expansion coefficient of film The hygroscopic expansion coefficient of the cellulose acylate film is preferably 30 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is more preferably 15 × 10 ⁻⁵ /% RH or less, and further preferably 10 × 10 ⁻⁵ /% RH or less. The hygroscopic expansion coefficient is preferably small, but usually it is 1.0 × 10 ⁻⁵ /% RH or more. The hygroscopic expansion coefficient indicates the amount of change in the length of the sample when the relative humidity is changed at a constant temperature. By adjusting the coefficient of hygroscopic expansion, the durability of the protective film for polarizing plate is improved, or in the case of a polarizing plate combined with an optical compensation film, the frame-shaped transmittance increases while maintaining the optical compensation function, that is, Light leakage can be prevented.

The method for measuring the hygroscopic expansion coefficient is shown below. A sample having a width of 5 mm and a length of 20 mm is cut out from the produced cellulose acylate film, and one end is fixed and hung in an atmosphere of 25 ° C. and 20% RH (R0). A weight of 0.5 g was hung from the other end and left for 10 minutes to measure the length (H0). Next, the length (H1) is measured after leaving the temperature at 25 ° C. and leaving the humidity at 80% RH (R1) for 24 hours. The hygroscopic expansion coefficient is calculated by the following mathematical formula (4). The measurement is performed 10 samples for the same sample, and the average value is adopted.
Formula (4): Hygroscopic expansion coefficient (/% RH) = {(H1-H0) / H0} / (R1-R0)

  In order to reduce the dimensional change due to moisture absorption of the produced cellulose acylate film, it is possible to add the plasticizer or fine particles. A plasticizer having a polycyclic alicyclic structure having a bulky and hydrophobic property in the molecule seems to work effectively. Another effective means is to reduce the amount of residual solvent in the cellulose acylate film to reduce the free volume. Specifically, it is preferable that the residual solvent amount with respect to the cellulose acylate film is dried under the condition of 0.001 to 1.5% by mass. More preferably, it is 0.01-1.0 mass%.

(D) Equilibrium moisture content of film When the cellulose acylate film used in the present invention is used as a protective film for a polarizing plate, the equilibrium moisture content of the film is such that it does not impair adhesiveness with a water-soluble polymer such as polyvinyl alcohol. Regardless of the thickness, the equilibrium moisture content at 25 ° C. and 80% RH is preferably 0 to 4% by mass. The content is more preferably 0.1 to 3.5% by mass, and particularly preferably 1 to 3% by mass. If the equilibrium moisture content is less than or equal to the upper limit value, it is preferable that the dependency of retardation due to a change in humidity does not become too large when the cellulose acylate film is used as a protective film for a polarizing plate.

  The moisture content was measured using a cellulose acylate film sample 7 mm × 35 mm used in the present invention with a moisture measuring device “CA-03” and a sample drying apparatus “VA-05” (both manufactured by Mitsubishi Chemical Corporation). Measured by the Karl Fischer method. The moisture content is calculated by dividing the moisture content (g) by the sample mass (g).

(E) Photoelastic coefficient The photoelastic coefficient of the cellulose acylate used in the present invention is preferably 60 × 10 ⁻⁸ cm ² / N or less, and more preferably 20 × 10 ⁻⁸ cm ² / N or less. The photoelastic coefficient can be obtained by an ellipsometer.

(F) Glass transition temperature The glass transition temperature of the cellulose acylate used in the present invention is preferably 120 ° C. or higher, more preferably 140 ° C. or higher. The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). Is obtained as an average value of.

(Surface treatment of cellulose acylate film)
The cellulose acylate film is preferably subjected to a surface treatment. Specific examples include corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet irradiation treatment. It is also preferable to provide an undercoat layer as described in JP-A-7-333433.
From the viewpoint of maintaining the flatness of the film, in these treatments, the temperature of the cellulose acylate film is preferably Tg (glass transition temperature) or lower, specifically 150 ° C. or lower.
In the protective film for polarizing plate of the present invention, the cellulose acylate surface is particularly preferably subjected to acid treatment or alkali treatment, that is, saponification treatment to cellulose acylate, from the viewpoint of adhesiveness with a polarizer.

The surface energy of the cellulose acylate surface of the protective film for polarizing plate is preferably 55 mN / m or more, and more preferably 60 mN / m or more and 75 mN / m or less. The surface energy of a solid can be determined by a contact angle method, a wet heat method, and an adsorption method as described in “Basics and Applications of Wetting” (issued by Realize 1989.12.10). In the case of the protective film for polarizing plate of the present invention, it is preferable to use a contact angle method.
Specifically, two types of solutions having known surface energies are dropped on the cellulose acylate film surface, and at the intersection between the surface of the droplet and the film surface, the angle formed between the tangent line drawn on the droplet and the film surface. The surface angle of the film can be calculated by defining the angle containing the droplet as the contact angle.

Hereinafter, the alkali saponification treatment will be specifically described as an example.
The alkali saponification treatment of the cellulose acylate surface is preferably performed in a cycle in which the film surface is immersed in an alkali solution, neutralized with an acidic solution, washed with water and dried.
Examples of the alkaline solution include potassium hydroxide solution and sodium hydroxide solution, and the prescribed concentration of hydroxide ions is preferably in the range of 0.1 to 3.0N, and in the range of 0.5 to 2.0N. More preferably it is. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C.
When an alkali saponification treatment is performed after providing a layer containing metal oxide and / or metal nitride, a PET film is used so that the layer containing metal oxide and / or metal nitride is not damaged by an alkali solution. It is preferable to protect with such as.

[Moisture permeability]
Moisture permeability is measured according to JIS-Z-0208 at 60 ° C and 95% relative humidity in accordance with the moisture permeability measurement method. The moisture permeability of each sample is measured and the amount of moisture that permeates in 24 hours per 1 m ² area. Calculate as (g). Since the moisture permeability shows different values depending on the layer configuration and the number of layers, the moisture permeability of the protective film for polarizing plate of the present invention is provided with a low moisture permeability cured layer directly on the cellulose acylate film or through another layer, Furthermore, it is measured in a state in which at least one layer containing a metal oxide and / or metal nitride is provided thereon.
The moisture permeability is a film property closely related to the durability of the polarizing plate, and the durability of the polarizing plate can be improved by reducing the moisture permeability. In the protective film for polarizing plates of this invention, the water vapor permeability in a 60 degreeC95% RH environment is 200 g / m < ² > * day or less. More preferably, it is 150 g / m ² · day or less, and particularly preferably 100 g / m ² · day or less. If the water vapor transmission rate is 200 g / m ² · day or less, the infiltration of water from the outside can be prevented, and the durability of the polarizing plate and the light leakage in the case of a liquid crystal display device are improved.

[Retardation of protective film for polarizing plate]
The protective film for polarizing plates of the present invention is used as a protective film for polarizing plates and is exclusively used on the outermost surface of the liquid crystal cell. Moreover, it can use preferably also as a retardation film corresponding to various liquid crystal modes as another usage.
When using the protective film for polarizing plates of the present invention as a retardation film, preferred optical properties of the cellulose acylate film vary depending on the liquid crystal mode.
For the OCB mode, Re at a wavelength of 589 nm is preferably 10 to 100 nm, more preferably 20 to 70 nm. Rth at a wavelength of 589 nm is preferably 50 to 300 nm, more preferably 100 to 250 nm.
For VA mode, Re at a wavelength of 589 nm is preferably 20 to 100 nm, more preferably 30 to 70 nm. Rth at a wavelength of 589 nm is preferably 50 to 250 nm, more preferably 80 to 180 nm.
For TN mode, Re at a wavelength of 589 nm is preferably 0 to 50 nm, more preferably 2 to 30 nm. Rth at a wavelength of 589 nm is preferably 10 to 200 nm, more preferably 30 to 150 nm.
In the OCB mode and the TN mode, a low moisture-permeable cured layer / optically anisotropic layer is coated on the cellulose acylate film having the retardation value, or an optically anisotropic layer is formed on the cellulose acylate film. / Can be used as an optical compensation film by applying a low moisture-permeable cured layer.

2. Polarizing plate [Configuration of polarizing plate]
First, a protective film and a polarizer constituting the polarizing plate of the present invention will be described.
The polarizing plate of this invention may have an adhesive layer, a separate film, etc. as a component other than a polarizer and a protective film.

(1) Protective film The polarizing plate of the present invention has two protective films, one on each side of the polarizer, and at least one is the polarizing plate protective film of the present invention. Moreover, it is preferable that at least one of the two protective films has a function as a retardation film. When using the polarizing plate of this invention for a liquid crystal display device, it is preferable that at least one of the two polarizing plates arrange | positioned at the both sides of a liquid crystal cell is a polarizing plate of this invention.
The protective film used in the present invention is preferably a polymer film produced from norbornene resin, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyarylate, polysulfone, cellulose acylate, etc., and is a cellulose acylate film. Most preferred.

(2) Polarizer The polarizer of the present invention is preferably composed of polyvinyl alcohol (PVA) and a dichroic molecule. However, as described in JP-A-11-248937, PVA or polyvinyl chloride is used. A polyvinylene polarizer in which a polyene structure is generated by dehydration and dehydrochlorination and oriented is also usable.

PVA is a polymer material obtained by saponifying polyvinyl acetate, but may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. . In addition, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, or the like can also be used.
The saponification degree of PVA is not particularly limited, but is preferably 80 to 100 mol%, particularly preferably 90 to 100 mol% from the viewpoint of solubility and the like. The degree of polymerization of PVA is not particularly limited, but is preferably 1000 to 10,000, and particularly preferably 1500 to 5000.
The syndiotacticity of PVA is preferably 55% or more for improving durability as described in Japanese Patent No. 2978219, but 45 to 52.5% described in Japanese Patent No. 3317494 is also preferably used. it can.

After PVA is formed into a film, it is preferable to introduce a dichroic molecule to constitute a polarizer. As a method for producing a PVA film, a method of forming a film by casting a stock solution in which a PVA resin is dissolved in water or an organic solvent is generally preferably used. The concentration of the polyvinyl alcohol-based resin in the stock solution is usually 5 to 20% by mass, and a PVA film having a thickness of 10 to 200 μm can be produced by forming this stock solution by casting. The PVA film can be produced with reference to Japanese Patent No. 3342516, Japanese Patent Application Laid-Open No. 09-328593, Japanese Patent Application Laid-Open No. 2001-302817, and Japanese Patent Application Laid-Open No. 2002-144401.
The degree of crystallinity of the PVA film is not particularly limited. However, in order to reduce the average crystallinity (Xc) of 50 to 75% by mass described in Japanese Patent No. 3251073 and the in-plane hue variation, Japanese Patent Application Laid-Open No. 2002-2005 A PVA film having a crystallinity of 38% or less described in Japanese Patent No. 236214 can be used.

The birefringence (Δn) of the PVA film is preferably small, and a PVA film having a birefringence of 1.0 × 10 ⁻³ or less described in Japanese Patent No. 3342516 can be preferably used. However, as described in JP-A No. 2002-228835, in order to obtain a high degree of polarization while avoiding cutting during stretching of the PVA film, the birefringence of the PVA film may be set to 0.002 or more and 0.01 or less. Alternatively, as described in JP-A-2002-060505, the value of (nx + ny) / 2-nz may be 0.0003 or more and 0.01 or less.
The Re of the PVA film is preferably 0 nm or more and 100 nm or less, and more preferably 0 nm or more and 50 nm or less in the wavelength range of 589 nm. The Rth of the PVA film is preferably 0 nm or more and 500 nm or less, and more preferably 0 nm or more and 300 nm or less in the wavelength range of 589 nm.

In addition, the polarizing plate of the present invention includes a PVA film having a 1,2-glycol bond amount of 1.5 mol% or less described in Japanese Patent No. 3021494, 5 μm or more described in JP-A No. 2001-316492. PVA film having 500 or less optical foreign matter per 100 cm ² , PVA film having a hot water cutting temperature spot of 1.5 ° C. or less in the TD direction of the film described in JP-A-2002-030163, and glycerin Preferred is a PVA film formed from a solution in which 1 to 100 parts by mass of a trivalent to hexavalent polyhydric alcohol such as 1 to 100 parts by mass or a plasticizer described in JP-A 06-289225 is mixed in an amount of 15% by mass or more. Can be used.

  Although the film thickness before extending | stretching of a PVA film is not specifically limited, 1 micrometer-1 mm are preferable and 20-200 micrometers is especially preferable from a viewpoint of stability of film holding | maintenance and the uniformity of extending | stretching. As described in JP-A-2002-236212, a thin PVA film in which the stress generated when stretching 4 to 6 times in water is 10 N or less may be used.

Dichroic molecule I ₃ ^- or I ₅ ^- can be preferably used an iodine ion or a dichroic dye higher such. In the present invention, higher-order iodine ions are particularly preferably used. Higher-order iodine ions are described in “Applications of Polarizing Plates” by Nagata Ryo, CMC Publishing and Industrial Materials, Vol. 28, No. 7, p. 39-p. As described in 45, PVA can be produced by immersing PVA in a solution obtained by dissolving iodine in an aqueous potassium iodide solution and / or an aqueous boric acid solution and adsorbing and orienting the PVA.

  When a dichroic dye is used as the dichroic molecule, an azo dye is preferable, and a bisazo dye and a trisazo dye are particularly preferable. The dichroic dye is preferably a water-soluble dye. For this reason, a hydrophilic substituent such as a sulfonic acid group, an amino group or a hydroxyl group is introduced into the dichroic molecule, so that a free acid, an alkali metal salt, an ammonium salt or an amine is introduced. It is preferably used as a salt.

Specific examples of such dichroic dyes include, for example, CIDirect Red 37, Congo Red (CI Direct Red 28), CIDirect Violet 12, CIDirect Blue 90, CIDirect Blue 22, CIDirect Blue 1, CIDirect Blue 151, CIDirect Green 1
Benzidine series such as CIDirect Yellow 44, CIDirect Red 23, CIDirect Red 79 and other diphenylurea series, CIDirect Yellow 12 and other stilbene series, CIDirect Red
Examples thereof include dinaphthylamine series such as 31 and J acid series such as CIDirect Red 81, CIDirect Violet 9 and CIDirect Blue 78.
Besides this, CIDirect Yellow 8, CIDirect Yellow 28, CIDirect Yellow 86, CIDirect Yellow 87, CIDirect Yellow 142, CIDirect Orange 26, CIDirect Orange 39, CIDirect Orange 72, CIDirect Orange 106, CIDirect Orange 107, CIDirect Red 2, CIDirect Red Red 39, CIDirect Red 83
CIDirect Red 89, CIDirect Red 240, CIDirect Red 242, CIDirect Red 247, CIDirect Violet 48, CIDirect Violet 51, CIDirect Violet 98, CIDirect Blue 15, CIDirect Blue 67, CIDirect Blue 71, CIDirect
Blue 98, CIDirect Blue 168, CIDirect Blue 202, CIDirect Blue 236, CIDirect Blue 249, CIDirect Blue 270, CIDirect Green 59, CIDirect Green 85, CIDirect Brown 44, CIDirect Brown 106, CIDirect Brown 195, CIDirect Brown 210, CIDirect Brown 223 CIDirect Brown 224, CIDirect Black 1, CIDirect Black 17, CIDirect Black 19, CIDirect Black 54, and the like are further disclosed in Japanese Patent Laid-Open Nos. 62-70802, 1-161202, 1-172906, and 1-. The dichroic dyes described in JP-A Nos. 172907, 1-183602, 1-248105, 1-265205, and 7-261024 can also be preferably used. In order to produce dichroic molecules having various hues, two or more of these dichroic dyes may be blended. When a dichroic dye is used, the adsorption thickness may be 4 μm or more as described in JP-A No. 2002-082222.

If the content of the dichroic molecule in the film is too small, the degree of polarization is low, and if it is too large, the single-plate transmittance is lowered. Therefore, the polyvinyl alcohol polymer constituting the film matrix is usually used. On the other hand, it is adjusted in the range of 0.01% by mass to 5% by mass.
A preferable film thickness of the polarizer is preferably 5 μm to 40 μm, more preferably 10 μm to 30 μm. The ratio between the thickness of the polarizer and the thickness of the protective film described later is 0.01 ≦ A (polarizer film thickness) / B (protective film thickness) ≦ 0.16 described in JP-A No. 2002-174727. A range is also preferable.
The crossing angle between the slow axis of the protective film and the absorption axis of the polarizer may be any value, but is preferably parallel or an azimuth angle of 45 ± 20 °.

(3) Adhesive layer As the adhesive used for the adhesive layer, an adhesive using a base polymer such as acrylic acid, methacrylic acid, butyl rubber, or silicone can be used. Although not particularly limited, (meth) acrylate base polymers such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, A copolymer base polymer using two or more of these (meth) acrylic acid esters is preferably used. In the pressure-sensitive adhesive, a polar monomer is usually copolymerized in these base polymers. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, Examples thereof include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as glycidyl (meth) acrylate.

  The pressure-sensitive adhesive usually contains a crosslinking agent. Crosslinking agents include those that generate divalent or polyvalent metal ions and carboxylate metal salts, those that form amide bonds with polyamine compounds, those that form ester bonds with polyepoxy compounds and polyols, polyisocyanate compounds and amides. Examples of these compounds include one that forms a bond, and these compounds are used as a cross-linking agent in one or more kinds and mixed with a base polymer.

  As for the thickness of an adhesive layer, 2-50 micrometers is preferable. It is a normal form that a separate film is bonded to the surface of the pressure-sensitive adhesive layer opposite to the polarizing plate in order to protect the pressure-sensitive adhesive layer. As the separate film, a polyester film that has been subjected to a release treatment with a silicone resin or the like is used. This separate film is peeled and removed at the time of bonding with a liquid crystal cell or another optical functional film.

[Polarizing plate manufacturing process]
Next, the manufacturing process of the polarizing plate of this invention is demonstrated.
The production process of the polarizing plate in the present invention is preferably composed of a swelling process, a dyeing process, a hardening process, a stretching process, a drying process, a protective film bonding process, and a post-bonding drying process. The order of the dyeing step, the hardening step, and the stretching step may be arbitrarily changed, or several steps may be combined and performed simultaneously. In addition, as described in Japanese Patent No. 3331615, washing with water after the hardening step can be preferably performed.

  In the present invention, it is particularly preferable to sequentially perform the swelling process, the dyeing process, the hardening process, the stretching process, the drying process, the protective film bonding process, and the drying process after bonding in the order described. An on-line surface inspection step may be provided during or after the above-described steps.

The swelling step is preferably performed only with water, but as described in JP-A-10-153709, for the purpose of stabilizing optical performance and avoiding wrinkling of the polarizing plate substrate in the production line. It is also possible to manage the degree of swelling of the polarizing plate substrate by swelling the polarizing plate substrate with an aqueous boric acid solution.
Moreover, although the temperature and time of a swelling process can be defined arbitrarily, 10 to 60 degreeC and 5 to 2000 second are preferable.
For the dyeing step, the method described in JP-A-2002-86554 can be used. Further, as a dyeing method, not only immersion but any means such as application or spraying of iodine or a dye solution can be used. Further, as described in JP-A-2002-290025, a method of dyeing while stirring the iodine concentration, the dyeing bath temperature, the draw ratio in the bath, and the bath liquid in the bath may be used.

When higher-order iodine ions are used as the dichroic molecule, in order to obtain a high-contrast polarizing plate, it is preferable to use a solution obtained by dissolving iodine in an aqueous potassium iodide solution in the dyeing step. In this case, iodine in the iodine-potassium iodide aqueous solution is preferably 0.05 to 20 g / l, potassium iodide is 3 to 200 g / l, and the mass ratio of iodine and potassium iodide is preferably 1 to 2000. The dyeing time is preferably 10 to 1200 seconds, and the liquid temperature is preferably 10 to 60 ° C. More preferably, iodine is 0.5 to 2 g / l, potassium iodide is 30 to 120 g / l, the mass ratio of iodine and potassium iodide is 30 to 120, dyeing time is 30 to 600 seconds, and liquid temperature is 20-50 degreeC is good.
Further, as described in Japanese Patent No. 3145747, boron compounds such as boric acid and borax may be added to the dyeing solution.

  In the hardening step, it is preferable to immerse in the crosslinking agent solution or apply the solution to contain the crosslinking agent. Further, as described in JP-A-11-52130, the hardening process can be performed in several steps.

  As the cross-linking agent, those described in US Reissue Patent No. 232897 can be used, and as described in Japanese Patent No. 3357109, a polyhydric aldehyde may be used as a cross-linking agent in order to improve dimensional stability. However, boric acids are most preferably used. When boric acid is used as a crosslinking agent used in the hardening step, metal ions may be added to the boric acid-potassium iodide aqueous solution. Zinc chloride is preferred as the metal ion, but as described in JP 2000-35512 A, zinc halides such as zinc iodide, zinc sulfates, zinc acetates and the like are used instead of zinc chloride. You can also.

  In the present invention, it is preferable to prepare a boric acid-potassium iodide aqueous solution to which zinc chloride has been added, and perform dura- tion by immersing the PVA film. Boric acid is preferably 1 to 100 g / l, potassium iodide is 1 to 120 g / l, zinc chloride is preferably 0.01 to 10 g / l, hardening time is preferably 10 to 1200 seconds, and liquid temperature is preferably 10 to 60 ° C. . More preferably, boric acid is 10 to 80 g / l, potassium iodide is 5 to 100 g / l, zinc chloride is 0.02 to 8 g / l, hardening time is 30 to 600 seconds, and liquid temperature is 20 to 50 ° C is preferable.

For the stretching step, a longitudinal uniaxial stretching method as described in US Pat. No. 2,454,515, or a tenter method as described in JP-A-2002-86554 can be preferably used. A preferable draw ratio is 2 times or more and 12 times or less, and more preferably 3 times or more and 10 times or less. Moreover, the relationship between the draw ratio, the thickness of the original fabric and the thickness of the polarizer is described in JP-A No. 2002-040256 (polarizer film thickness / raw film thickness after bonding of the protective film) × (total draw ratio) > 0.17 or the relationship between the width of the polarizer when leaving the final bath and the width of the polarizer when bonding the protective film is 0.80 ≦ (protective film pasting) described in JP-A-2002-040247 It is also preferable to satisfy the following condition: polarizer width at time / width of polarizer when leaving the final bath) ≦ 0.95.

  As the drying step, a method known in JP-A-2002-86554 can be used, but a preferable temperature range is 30 ° C. to 100 ° C., and a preferable drying time is 30 seconds to 60 minutes. Further, as described in Japanese Patent No. 3148513, heat treatment is performed so that the fading temperature in water is 50 ° C. or higher, or described in JP-A-07-325215 and JP-A-07-325218. Aging in an atmosphere in which the temperature and humidity are controlled as described above can also be preferably performed.

  A protective film bonding process is a process of bonding the both surfaces of the above-mentioned polarizer which went out of the drying process with two protective films. A method of bonding with a pair of rolls is preferably used so that the adhesive liquid is supplied immediately before bonding and the polarizer and the protective film are overlapped. Further, as described in JP-A-2001-296426 and JP-A-2002-86554, in order to suppress the groove-like unevenness of the record due to the stretching of the polarizer, It is preferable to adjust the moisture content. In the present invention, a moisture content of 0.1% to 30% is preferably used.

  The adhesive between the polarizer and the protective film is not particularly limited, and examples thereof include PVA resin (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 5 μm, and particularly preferably 0.05 to 3 μm after drying.

Moreover, in order to improve the adhesive force of a polarizer and a protective film, it is preferable to perform adhesion after surface-treating the protective film to make it hydrophilic. The surface treatment method is not particularly limited, and a known method such as a saponification method using an alkaline solution or a corona treatment method can be used. Further, an easy-adhesion layer such as a gelatin undercoat layer may be provided after the surface treatment. As described in JP-A-2002-267839, the contact angle of the protective film surface with water is preferably 50 ° or less.
The drying conditions after bonding are in accordance with the method described in JP-A-2002-86554, but the preferred temperature range is 30 ° C. to 100 ° C., and the preferred drying time is 30 seconds to 60 minutes. It is also preferable to perform aging in an atmosphere with temperature and humidity control as described in JP-A-07-325220.

Element content in the polarizer, iodine 0.1 to 3.0 g / m ^2, boron 0.1 to 5.0 g / m ^2, potassium 0.1~2.00g / m ^2, zinc 0-2. It is preferably 00 g / m ² . Further, the potassium content may be 0.2% by mass or less as described in JP-A No. 2001-166143, and the zinc content in the polarizer is described in JP-A No. 2000-035512. It is good also as 0.04 mass%-0.5 mass%.

  As described in Japanese Patent No. 3323255, in order to increase the dimensional stability of the polarizing plate, an organic titanium compound and / or an organic zirconium compound is added and used in any of the dyeing process, stretching process and hardening process And at least 1 type of compound chosen from the organic titanium compound and the organic zirconium compound can also be contained. A dichroic dye may be added to adjust the hue of the polarizing plate.

[Characteristics of polarizing plate]
(1) Transmittance and degree of polarization The preferred single plate transmittance of the polarizing plate of the present invention is 40.0 to 49.5%, more preferably 41.0 to 49.5%. Further, the iodine concentration and the single plate transmittance may be in the ranges described in JP-A No. 14-258051. Furthermore, the preferable range of the transmittance (parallel transmittance) when two polarizing plates of the same type are overlapped with the absorption axes being coincident is 36 to 42%, and the transmission when the absorption axes are overlapped is orthogonal. A preferable range of the rate (orthogonal transmittance) is 0.001 to 0.05%. These transmittances are defined by the following formula (5) based on JIS Z-8701.

Formula (5):

  Here, K, S (λ), y (λ), and τ (λ) are as follows.

S (λ): spectral distribution of standard light used for color display y (λ): color matching function in XYZ system τ (λ): spectral transmittance λ: measurement wavelength [nm]

  Moreover, the preferable range of the polarization degree in the polarizing plate of this invention is 99.900% or more and 99.999% or less based on the definition by following formula (6), More preferably, it is 99.940% or more and 99.99. 995% or less.

Formula (6):

  Further, the preferable range of the dichroic ratio defined by the following formula (7) is 48 or more and 1215 or less, and more preferably 53 or more and 525 or less.

Formula (7):

The iodine concentration and the single plate transmittance may be within the ranges described in JP-A No. 2002-258051.
The parallel transmittance may be small in wavelength dependency as described in Japanese Patent Application Laid-Open Nos. 2001-083328 and 2002-022950. The optical characteristics when the polarizing plates are arranged in crossed Nicols may be in the range described in Japanese Patent Application Laid-Open No. 2001-091736, and the relationship between parallel transmittance and orthogonal transmittance is disclosed in Japanese Patent Application Laid-Open No. 2002-174728. It may be within the range described.

  As described in Japanese Patent Application Laid-Open No. 2002-221618, the standard deviation of the parallel transmittance every 10 nm when the light wavelength is between 420 and 700 nm is 3 or less, and the light wavelength is between 420 and 700 nm. The minimum value of (parallel transmittance / orthogonal transmittance) every 10 nm may be 300 or more.

  The parallel transmittance and the orthogonal transmittance at a wavelength of 440 nm of the polarizing plate, the parallel transmittance, the parallel transmittance and the orthogonal transmittance at a wavelength of 550 nm, and the parallel transmittance and the orthogonal transmittance at a wavelength of 610 nm are disclosed in JP-A No. 2002-258042 and JP-A No. 2002-80442. The range described in 2002-258043 can also be preferably performed.

(2) Hue The hue of the polarizing plate of the present invention is preferably evaluated using the lightness index L ^* and the chromaticness index a ^* and b ^* in the L ^* a ^* b ^* color system recommended as the CIE uniform perceptual space. Is done.
L ^* , a ^* , and b ^* are defined by Equation (8) using the above-described X, Y, and Z.

Formula (8):

Here, X ₀ , Y ₀ , and Z ₀ represent tristimulus values of the illumination light source. In the case of standard light C, X ₀ = 98.072, Y ₀ = 100, Z ₀ = 118.225, and standard light D _In the case of ₆₅ , X ₀ = 95.045, Y ₀ = 100, and Z ₀ = 108.892.

A preferable range of a ^* of the single polarizing plate is −2.5 or more and 0.2 or less, and more preferably −2.0 or more and 0 or less. A preferable range of b ^* of the single polarizing plate is 1.5 or more and 5 or less, and more preferably 2 or more and 4.5 or less. The preferable range of a ^* of the parallel transmitted light of the two polarizing plates is −4.0 to 0, and more preferably −3.5 to −0.5. A preferable range of b ^* of parallel transmitted light of the two polarizing plates is 2.0 or more and 8 or less, and more preferably 2.5 or more and 7 or less. The preferred range of a ^* of the orthogonally transmitted light of the two polarizing plates is from −0.5 to 1.0, and more preferably from 0 to 2. The preferable range of b ^* of the orthogonally transmitted light of the two polarizing plates is −2.0 or more and 2 or less, and more preferably −1.5 or more and 0.5 or less.

The hue may be evaluated by the chromaticity coordinates (x, y) calculated from the aforementioned X, Y, and Z. For example, the chromaticity (x _p , y _p ) of the parallel transmitted light of the two polarizing plates. And the chromaticity (x _c , y _c ) of the orthogonal transmitted light are within the ranges described in JP-A-2002-214436, JP-A-2001-166136, and JP-A-2002-169024, or the relationship between the hue and the absorbance. It can also be preferably performed within the range described in JP-A-2001-311827.

(3) Viewing angle characteristics When a polarizing plate is arranged in crossed Nicol and light with a wavelength of 550 nm is incident, when vertical light is incident, from a azimuth of 45 degrees with respect to the polarization axis, 40 degrees with respect to the normal line It is also preferable that the transmittance ratio and the xy chromaticity difference when the light is incident at an angle of within the range described in Japanese Patent Application Laid-Open Nos. 2001-166135 and 2001-166137. Further, as described in JP-A-10-068817, the light transmittance (T ₀ ) in the vertical direction of the polarizing plate laminate having the crossed Nicols arrangement and the light transmission in the direction inclined by 60 ° from the normal line of the laminate. The ratio (T ₆₀ / T ₀ ) to the rate (T ₆₀ ) is 10000 or less, or as described in JP-A No. 2002-139625, the polarizing plate is at an arbitrary angle from the normal to an elevation angle of 80 degrees. When natural light is incident, the transmittance difference of transmitted light within a wavelength range of 20 nm within the wavelength range of 520 to 640 nm of the transmission spectrum is set to 6% or less, or a film described in JP-A-08-248201 It is also preferable that the brightness difference of the transmitted light at an arbitrary place 1 cm above is within 30%.

(4) Durability (4-1) Wet heat durability As described in JP-A-2001-116922, light transmittance and polarization degree before and after standing in an atmosphere of 60 ° C. and 90% RH for 500 hours. It is preferable that the change rate of is 3% or less based on the absolute value. In particular, the change rate of the light transmittance is 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value. Further, as described in JP-A-07-0777608, it is also preferred that the degree of polarization after standing at 80 ° C. and 90% RH for 500 hours is 95% or more and the single transmittance is 38% or more.

(4-2) Dry durability It is preferable that the light transmittance and the rate of change of the degree of polarization before and after standing in a dry atmosphere at 80 ° C. for 500 hours are also 3% or less based on absolute values. In particular, the change rate of the light transmittance is preferably 2% or less, and the change rate of the polarization degree is preferably 1.0% or less, more preferably 0.1% or less based on the absolute value.

(4-3) Other durability Further, as described in JP-A-06-167611, the shrinkage after standing at 80 ° C. for 2 hours is 0.5% or less, or the both sides of the glass plate are crossed. The x and y values after leaving the Nicol-arranged polarizing plate laminate in an atmosphere of 69 ° C. for 750 hours are within the ranges described in JP-A-10-068818, or an atmosphere of 80 ° C. and 90% RH. the change in spectral intensity ratio of the 105 cm ^-1 and 157cm ^-1 after 200 hours standing processing by Raman spectroscopy at medium, it is also preferable to fall within the range as described in JP-a-08-094834 and JP-a-09-197127 It can be carried out.

(5) Orientation degree The higher the degree of orientation of PVA, the better the polarization performance, but the range of 0.2 to 1.0 is preferable as the order parameter value calculated by means such as polarization Raman scattering or polarization FT-IR. It is. Further, as described in JP-A-59-133509, the difference between the orientation coefficient of the polymer segment in the entire amorphous region of the polarizer and the orientation coefficient of the occupied molecule (0.75 or more) is at least 0.7. 15, the orientation coefficient of the amorphous region of the polarizer is 0.65 to 0.85 as described in JP-A No. 04-204907, and the higher order iodine ions of I ₃ ⁻ and I ₅ — It is also preferable to set the degree of orientation to 0.8 to 1.0 as an order parameter value.

(6) Other properties As described in JP-A-2002-006133, the contraction force in the absorption axis direction per unit width when heated at 80 ° C. for 30 minutes is 4.0 N / cm or less, As described in 2002-236213, when the polarizing plate was placed under heating conditions of 70 ° C. for 120 hours, both the dimensional change rate in the absorption axis direction and the dimensional change rate in the polarization axis direction of the polarizing plate were It can be preferably carried out within ± 0.6%, or the moisture content of the polarizing plate can be 3% by mass or less as described in JP-A-2002-090546. Further, as described in JP-A No. 2000-249832, the surface roughness in the direction perpendicular to the stretching axis is set to 0.04 μm or less based on the center line average roughness, or described in JP-A No. 10-268294. The refractive index n ₀ in the transmission axis direction is preferably made larger than 1.6, or the relationship between the thickness of the polarizing plate and the thickness of the protective film is preferably within the range described in JP-A-10-111411. be able to.

[Functionalization of polarizing plate]
The polarizing plate of the present invention includes an LCD viewing angle widening film, a retardation film such as a λ / 4 plate for application to a reflective LCD, an antireflection film for improving display visibility, a brightness enhancement film, It is preferably used as a functionalized polarizing plate combined with an optical film having functional layers such as a coat layer, a forward scattering layer, and an antiglare (antiglare) layer.
The structural example which combined the polarizing plate using the protective film for polarizing plates of this invention and the below-mentioned functional optical film was shown in FIG. As the protective film for the polarizing plate 5, the polarizing plate protective film 1 and the functional optical film 3 may be bonded to the polarizer 2 through an adhesive (FIG. 1A) or the polarizer 2. The functional optical film 3 may be bonded to the polarizing plate 5 provided with the protective film 1a for polarizing plate of the present invention on one side thereof through the pressure-sensitive adhesive layer 4 (FIG. 1B). The functional optical film can be arranged on the liquid crystal cell side according to the intended function, or can be arranged on the side opposite to the liquid crystal cell, that is, on the display side or the backlight side. In addition, the other protective film 1b for polarizing plates may use the same thing as the protective film 1a for polarizing plates of this invention, and may use things other than the protective film of this invention.

The functional optical film used in combination with the polarizing plate of the present invention will be described below.
(1) Viewing Angle Enlargement Film The polarizing plate of the present invention includes TN (Twisted Nematic), IPS (In-Plane Switching), OCB (Optically Compensatory).
Bend), VA (Vertically Aligned), and ECB (Electrically Controlled Birefringence) can be used in combination with a viewing angle widening film proposed for display modes.

As a viewing angle widening film for the TN mode, the Japan Printing Society Vol. 36, No. 3 (1999) p. 40-44, monthly display August issue (2002) p. No. 20-24, JP-A-4-229828, JP-A-6-75115, JP-A-6-214116, JP-A-8-50206, etc. are preferably used in combination. The
A preferred configuration of the viewing angle widening film for the TN mode has an alignment layer and an optically anisotropic layer (viewing angle compensation layer) in this order on a transparent polymer film. The viewing angle widening film may be used by being bonded to a polarizing plate via an adhesive, but SID'00 Dig., P. As described in 551 (2000), it is particularly preferable from the viewpoint of thinning that one of the protective films of the polarizer is also used.

  The alignment layer can be provided by means such as a rubbing treatment of an organic compound (preferably a polymer), oblique vapor deposition of an inorganic compound, or formation of a layer having microgrooves. Furthermore, an alignment layer in which an alignment function is generated by application of an electric field, application of a magnetic field or light irradiation is also known, but an alignment layer formed by a rubbing treatment of a polymer is particularly preferable. The rubbing treatment is preferably performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. It is preferable that the absorption axis direction and the rubbing direction of the polarizer are substantially parallel. As the polymer used for the alignment layer, polyimide, polyvinyl alcohol, a polymer having a polymerizable group described in JP-A-9-152509, and the like can be preferably used. The thickness of the alignment layer is preferably 0.01 to 5 μm, and more preferably 0.05 to 2 μm.

  The optically anisotropic layer preferably contains a liquid crystalline compound. It is particularly preferable that the liquid crystal compound has a discotic compound (discotic liquid crystal). The discotic liquid crystal molecule has a disk-like core portion like the following triphenylene derivative, and has a structure in which side chains extend radially therefrom. In order to impart stability over time, it is also preferable to further introduce a group that reacts with heat, light or the like. Preferred examples of the discotic liquid crystal are described in JP-A-8-50206.

  The discotic liquid crystal molecules are aligned almost parallel to the film plane with a pretilt angle in the rubbing direction in the vicinity of the alignment layer, and the discotic liquid crystal molecules are oriented so that they are perpendicular to the plane on the opposite air side. is doing. The discotic liquid crystal layer as a whole has a hybrid alignment, and this layer structure can realize a wide viewing angle of a TN mode TFT-LCD.

  The optically anisotropic layer is generally a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) dissolved in a solvent, coated on the alignment layer, dried, and then discotic nematic. After heating to the phase formation temperature, it is obtained by polymerization by irradiation with UV light or the like and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, particularly preferably 70 to 170 ° C.

In addition to the discotic compound added to the optically anisotropic layer, the compound has compatibility with the discotic compound and can give a preferable change in tilt angle to the liquid crystalline discotic compound or inhibit the alignment. Any compound can be used as long as it is not. Among these, additives for controlling the orientation on the air interface side such as polymerizable monomers (eg, compounds having vinyl group, vinyloxy group, acryloyl group and methacryloyl group), fluorine-containing triazine compounds, cellulose acetate, cellulose acetate Mention may be made of polymers such as pionate, hydroxypropylcellulose and cellulose acetate butyrate. These compounds are generally used in an amount of 0.1 to 50% by mass, preferably 0.1 to 30% by mass, based on the discotic compound.
The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm.

  A preferred embodiment of the viewing angle widening film is composed of a cellulose acylate film as a transparent substrate film, an alignment layer provided thereon, and an optically anisotropic layer comprising a discotic liquid crystal formed on the alignment layer And the optically anisotropic layer is crosslinked by UV light irradiation.

  The viewing angle widening film for an IPS mode liquid crystal cell is used for optical compensation of liquid crystal molecules aligned in parallel to the substrate surface and improvement of viewing angle characteristics of the orthogonal transmittance of the polarizing plate during black display in the absence of an applied electric field. In the IPS mode, black is displayed when no electric field is applied, and the transmission axes of the pair of upper and lower polarizing plates are orthogonal. However, when observed from an oblique direction, the crossing angle of the transmission axes is not 90 °, and leakage light is generated, resulting in a decrease in contrast. When the polarizing plate of the present invention is used in an IPS mode liquid crystal cell, the in-plane retardation as described in JP-A-10-54982 is close to 0 and the thickness direction is reduced in order to reduce leakage light. It is preferably used in combination with a viewing angle widening film having a phase difference.

  The OCB mode viewing angle widening film for liquid crystal cells is intended to improve the viewing angle characteristics of black display by optically compensating the liquid crystal layer that is vertically aligned at the center of the liquid crystal layer by applying an electric field and tilted near the substrate interface. used. When the polarizing plate of the present invention is used in an OCB mode liquid crystal cell, it is preferably used in combination with a viewing angle widening film in which a discotic liquid crystalline compound as described in US Pat. No. 5,805,253 is hybrid-aligned.

The viewing angle widening film for liquid crystal cells in the VA mode improves the viewing angle characteristics of black display in a state where liquid crystal molecules are vertically aligned with respect to the substrate surface in a state where no electric field is applied. As such a viewing angle widening film, a film having an in-plane retardation close to 0 and having a retardation in the thickness direction as described in Japanese Patent No. 2866372, and a discotic compound are used. Films arranged in parallel to the substrate, stretched films with the same in-plane retardation value laminated so that the slow axes are orthogonal, and liquid crystals to prevent the deterioration of orthogonal transmittance in the oblique direction of the polarizing plate It is preferably used in combination with a laminate of films made of rod-like compounds such as molecules.
Moreover, what gave phase difference by extending | stretching norbornene-type resin film and polycarbonate resin can also be used preferably as a viewing angle expansion film or its part.

(2) Retardation film The polarizing plate of the present invention may have a retardation layer. The retardation layer in the present invention is preferably a λ / 4 plate, and can be used as a circularly polarizing plate by laminating the polarizing plate of the present invention and the λ / 4 plate. The circularly polarizing plate has a function of converting incident light into circularly polarized light, and is preferably used for a reflective liquid crystal display device, a transflective liquid crystal display device such as an ECB mode, or an organic EL element.

  The λ / 4 plate used in the present invention is a retardation film having a retardation (Re) of approximately ¼ of the wavelength in the visible light wavelength range in order to obtain almost perfect circularly polarized light in the visible light wavelength range. It is preferable that “Retardation of approximately ¼ in the wavelength range of visible light” means that the longer the wavelength is from 400 to 700 nm, the larger the retardation, and the retardation value (Re450) measured at a wavelength of 450 nm is 80 to 125 nm. And the range which satisfies the relationship whose retardation value (Re590) measured by wavelength 590nm is 120-160 nm is shown. It is more preferable that Re590-Re450 ≧ 5 nm, and it is particularly preferable that Re590-Re450 ≧ 10 nm.

  The λ / 4 plate used in the present invention is not particularly limited as long as the above conditions are satisfied, but for example, described in JP-A-5-27118, JP-A-10-68816, and JP-A-10-90521. A λ / 4 plate obtained by laminating a plurality of polymer films, a λ / 4 plate obtained by stretching a single polymer film described in WO00 / 65384, WO00 / 26705, JP 2000-284126 A, A known λ / 4 plate such as a λ / 4 plate in which at least one optically anisotropic layer is provided on a polymer film described in JP-A-2002-31717 can be used. Moreover, the direction of the slow axis of the polymer film and the orientation direction of the optically anisotropic layer can be arranged in any direction according to the liquid crystal cell.

  In the circularly polarizing plate, the slow axis of the λ / 4 plate and the transmission axis of the polarizer can intersect at an arbitrary angle, but preferably intersect within a range of 45 ° ± 20 °. However, the slow axis of the λ / 4 plate and the transmission axis of the polarizer may intersect within a range other than the above.

  When the λ / 4 plate is formed by laminating the λ / 4 plate and the λ / 2 plate, as described in Japanese Patent No. 3236304 and Japanese Patent Laid-Open No. 10-68816, the λ / 4 plate and The λ / 2 plate is preferably bonded so that the angle formed between the slow axis in the plane of the λ / 2 plate and the transmission axis of the polarizing plate is substantially 75 ° and 15 °.

(3) Antireflection film The polarizing plate of the present invention can be used in combination with an antireflection film. Specifically, an antireflection film is provided on 1 and 1a in FIG. For the anti-reflection film, either a film having a reflectance of about 1.5% only by applying a single layer of a low refractive index material such as a fluorine-based polymer, or a film having a reflectance of 1% or less using multilayer interference of a thin film is used. it can. A structure in which a medium refractive index layer, a high refractive index layer and a low refractive index layer are laminated on a support is preferably used. In addition, Nitto Technical Report, vol. 38, no. 1, may, 2000, pages 26 to 28 and JP-A No. 2002-301783 can also be preferably used.

(4) Brightness improving film The polarizing plate of this invention can be used in combination with a brightness improving film. The brightness enhancement film has a function of separating circularly polarized light or linearly polarized light, and is disposed between the polarizing plate and the backlight, and reflects or scatters one circularly polarized light or linearly polarized light back to the backlight side. Re-reflected light from the backlight part partially changes the polarization state and partially transmits when re-entering the brightness enhancement film and the polarizing plate, so the light utilization rate is improved by repeating this process. The front luminance is improved to about 1.4 times. As the brightness enhancement film, an anisotropic reflection system and an anisotropic scattering system are known, and both can be combined with the polarizing plate of the present invention.

  In the anisotropic reflection system, a brightness enhancement film having anisotropy in reflectance and transmittance is known by laminating a uniaxially stretched film and an unstretched film in multiple layers and increasing the refractive index difference in the stretching direction. Multilayer film systems using the principle of dielectric mirrors (described in the specifications of WO95 / 17691, WO95 / 17692, WO95 / 17699) and cholesteric liquid crystal systems (European Patent No. 606940A2, Japanese Patent Laid-Open No. Hei 8- No. 271731) is known. DBEF-E, DBEF-D, and DBEF-M (all manufactured by 3M) are used as multi-layer brightness enhancement films using the principle of dielectric mirrors, and NIPOCS (Nitto Denko Corporation) as a cholesteric liquid crystal brightness enhancement film. )) Is preferably used in the present invention. For NIPOCS, see Nitto Giho, vol. 38, no. 1, may, 2000, pages 19 to 21 and the like.

Further, in the present invention, positive numbers described in the specifications of WO97 / 32223, WO97 / 32224, WO97 / 32225, WO97 / 32226 and JP-A-9-274108 and 11-174231 are described. It is also preferable to use in combination with an anisotropic scattering type brightness enhancement film obtained by uniaxially stretching by blending an intrinsic birefringent polymer and a negative intrinsic birefringent polymer. As the anisotropic scattering system brightness enhancement film, DRPF-H (manufactured by 3M) is preferable.
The polarizing plate and the brightness enhancement film of the present invention may be used as an integrated type in which one of the polarizing film and the protective film of the polarizing plate (for example, 1b in FIG. 1) is used as a brightness enhancement film. preferable.

(5) Other Functional Optical Film The polarizing plate of the present invention is also preferably used in combination with a forward scattering layer and an antiglare (antiglare) layer.

(5-1) Forward scattering layer The forward scattering layer is used to improve the viewing angle characteristics (hue and luminance distribution) in the vertical and horizontal directions when the polarizing plate of the present invention is applied to a liquid crystal display device. In the present invention, a configuration in which fine particles having different refractive indexes are dispersed in a binder is preferable. The construction of JP-A No. 199809, JP-A No. 2002-107512 or the like which defines the haze value as 40% or more can be used. In addition, in order to control the viewing angle characteristics of haze, the polarizing plate of the present invention is also preferably used in combination with “Lumisty” described in Sumitomo Chemical's technical report “Photofunctional Films” on pages 31-39. be able to.

(5-2) Antiglare layer The antiglare (antiglare) layer is used to scatter reflected light and prevent reflection. The antiglare function is obtained by forming irregularities on the outermost surface (display side) of the liquid crystal display device. The haze of the optical film having an antiglare function is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.
The method for forming irregularities on the film surface is, for example, a method of forming irregularities on the film surface by adding fine particles (for example, JP-A No. 2000-271878), relatively large particles (particle size 0.05-2 μm). ) Is added in a small amount (0.1 to 50% by mass) (for example, Japanese Patent Application Laid-Open Nos. 2000-281410, 2000-95893, 2001-100004, and 2001). No. 281407, etc.), a method of physically transferring the uneven shape onto the film surface (for example, as an embossing method, JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401) Etc.) can be preferably used.

3. Next, a liquid crystal display device in which the polarizing plate of the present invention is used will be described.
FIG. 2 is an example of a liquid crystal display device in which the polarizing plate of the present invention is used. The liquid crystal display device shown in FIG. 2 includes a liquid crystal cell (15 to 19) and an upper polarizing plate 11 and a lower polarizing plate 22 that are disposed with the liquid crystal cell (15 to 19) interposed therebetween. The polarizing plate is sandwiched between a polarizer and a pair of protective films, but is shown as an integrated polarizing plate in FIG. The liquid crystal cell includes a liquid crystal layer formed of an upper substrate 15 and a lower substrate 18 and liquid crystal molecules 17 sandwiched therebetween. The liquid crystal cell is different in the alignment state of liquid crystal molecules that perform ON / OFF display. However, the polarizing plate of the present invention can be used in any display mode regardless of the transmissive and reflective types.

  An alignment film (not shown) is formed on the surface of the substrates 15 and 18 in contact with the liquid crystal molecules 17 (hereinafter also referred to as “inner surface”), and by rubbing treatment or the like applied on the alignment film, The orientation of the liquid crystal molecules 17 in the state where no electric field is applied or in the state where a low voltage is applied is controlled. Further, on the inner surfaces of the substrates 15 and 18, a transparent electrode (not shown) capable of applying an electric field to the liquid crystal layer made of the liquid crystal molecules 17 is formed.

The rubbing direction of the TN mode is applied in directions perpendicular to each other on the upper and lower substrates, and the magnitude of the tilt angle can be controlled by the strength and the number of rubbing times. The alignment film is formed by applying and baking a polyimide film. The magnitude of the twist angle (twist angle) of the liquid crystal layer is determined by the crossing angle of the upper and lower substrates in the rubbing direction and the chiral agent added to the liquid crystal material. Here, a chiral agent having a pitch of about 60 μm is added so that the twist angle becomes 90 °.
The twist angle is in the vicinity of 90 ° (85 to 95 °) in the case of a notebook computer, a personal computer monitor, and a liquid crystal display device for a television, and is 0 to 70 ° in the case of use as a reflective display device such as a mobile phone. Set. In the IPS mode and the ECB mode, the twist angle is 0 °. In the IPS mode, electrodes are disposed only on the lower substrate 8 and an electric field parallel to the substrate surface is applied. In the OCB mode, there is no twist angle, and in the VA mode, the liquid crystal molecules 17 are aligned perpendicular to the upper and lower substrates.

Here, the magnitude of the product Δnd of the thickness d of the liquid crystal layer and the refractive index anisotropy Δn changes the brightness during white display. Therefore, in order to obtain the maximum brightness, the range is set for each display mode.
The crossing angle of the absorption axis 12 of the upper polarizing plate 11 and the absorption axis 23 of the lower polarizing plate 22 is generally laminated substantially orthogonally to obtain a high contrast. The crossing angle between the absorption axis 12 of the upper polarizing plate 11 of the liquid crystal cell and the rubbing direction of the upper substrate 15 varies depending on the liquid crystal display mode, but is generally set to be parallel or vertical in the TN and IPS modes. In OCB and ECB modes, it is often set to 45 °. However, the optimum value differs in each display mode for adjusting the color tone and viewing angle of the display color, and the present invention is not limited to this range.

  The liquid crystal display device in which the polarizing plate of the present invention is used is not limited to the configuration of FIG. 2, and may include other members. For example, a color filter may be disposed between the liquid crystal cell and the polarizer. In addition, the above-described viewing angle widening films 13 and 20 may be separately disposed between the liquid crystal cell and the polarizing plate. The polarizing plates 11 and 22 and the viewing angle widening films 13 and 20 may be arranged in a laminated form bonded with an adhesive, or a so-called integrated elliptical polarization using one of the liquid crystal cell side protective films for widening the viewing angle. It may be arranged as a plate.

  When the liquid crystal display device using the polarizing plate of the present invention is used as a transmission type, a backlight using a cold cathode or a hot cathode fluorescent tube, or a light emitting diode, a field emission element, or an electroluminescent element as a light source. Can be placed on the back. Further, the liquid crystal display device in which the polarizing plate of the present invention is used may be of a reflective type. In such a case, only one polarizing plate may be disposed on the observation side, and the back of the liquid crystal cell or under the liquid crystal cell. A reflective film is installed on the inner surface of the side substrate. Of course, a front light using the light source may be provided on the liquid crystal cell observation side.

[Example 1]
(Production of cellulose acetate film)
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose acetate solution A was prepared.

―――――――――――――――――――――――――――――――――
<Composition of cellulose acetate solution A>
Cellulose acetate with 61.2% acetylation 50 parts by mass Cellulose acetate with 60.6% acetylation 50 parts by mass Triphenyl phosphate (hydrophobizing agent 1) 7.8 parts by mass Biphenyl diphenyl phosphate (hydrophobizing agent 2) 3 .9 parts by weight Methylene chloride (first solvent) 300 parts by weight Methanol (second solvent) 54 parts by weight 1-butanol 11 parts by weight ――――――――――――――――――――― ――――――――――――

  The following composition was charged into another mixing tank, stirred while heating to dissolve each component, and an additive solution B-1 was prepared.

―――――――――――――――――――――――――――――――――
<Additive solution B-1 composition>
Methylene chloride 80 parts by weight Methanol 20 parts by weight UV absorber (A) 2 parts by weight UV absorber (B) 4 parts by weight ――――――――――――――――――――――― ――――――――――

  A dope was prepared by adding 474 parts by mass of cellulose acetate solution A and 40 parts by mass of additive solution B-1 and stirring sufficiently. The dope was cast from a casting port onto a drum cooled to 0 ° C. The film is peeled off at a solvent content of 70% by mass, both ends in the width direction of the film are fixed with a pin tenter (the pin tenter described in FIG. 3 of JP-A-4-1009), and stretched in the lateral direction (direction perpendicular to the machine direction). Drying was performed at 115 ° C. until the solvent content became 5% by mass while keeping the rate of 4% (drying step 1). Then, by conveying between the rolls of the heat treatment apparatus, it was further dried at 140 ° C. to produce cellulose acetate films having thicknesses of 80 μm and 40 μm.

(Preparation of coating solution A for forming a low moisture-permeable cured layer)
Dipentaerythritol hexaacrylate (I / O value: 0.70) 14.25 parts by mass Cyclohexanone 2.50 parts by mass MEK-ST (Colloidal silica manufactured by Nissan Chemical Industries, Ltd.) 33.33 parts by mass Photoradical polymerization initiator 0.73 parts by mass (Irgacure 907, manufactured by Ciba Geigy)
Were mixed and stirred to obtain a coating solution A for forming a low moisture permeability cured layer.

(Preparation of coating solution B for forming a low moisture permeability cured layer)
Compound K-5 (I / O value: 0.43) 14.25 parts by mass (Kyarad R-684, manufactured by Nippon Kayaku Co., Ltd.)
Cyclohexanone 2.50 parts by mass MEK-ST (Colloidal silica manufactured by Nissan Chemical Industries, Ltd.) 33.33 parts by mass Photoradical polymerization initiator 0.73 parts by mass (Irgacure 907, manufactured by Ciba-Geigy Corporation)
Were mixed and stirred to obtain a coating solution B for forming a low moisture permeability cured layer.

(Preparation of cured layer forming coating solution C)
PE-300 (I / O value: 1.37, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 14.25 parts by mass Cyclohexanone 2.50 parts by mass MEK-ST (Colloidal silica manufactured by Nissan Chemical Industries, Ltd.) 33.33 Parts by mass 0.73 parts by mass of photo radical polymerization initiator (Irgacure 907, manufactured by Ciba Geigy)
Were mixed and stirred to obtain a coating liquid C for forming a low moisture permeability cured layer.

(Formation of a low moisture-permeable cured layer)
Using a microgravure roll with a diameter of 50 mm having a gravure pattern of 135 lines / inch and a depth of 60 μm, and a doctor blade, a coating solution for forming a low moisture permeability cured layer or a coating solution for forming a cured layer on the cellulose acetate film, The coating layer was applied at a conveyance speed of 10 m / min, dried at 60 ° C. for 150 seconds, and further irradiated with ultraviolet rays having an irradiation amount of 300 mJ / cm ² under a nitrogen purge to cure the coating layer. The rotation speed of the gravure roll was adjusted so that the thickness of the layer after curing was 5.0 μm.
Table 1 shows the combinations of sample numbers and hardened layer coating solutions.

(Formation of metal oxide layer or metal nitride layer)
A metal oxide layer made of the following silica or a metal nitride layer made of silicon nitride was formed on the low moisture-permeable cured layer or cured layer.
<Formation conditions of metal oxide layer (silica)>
Film formation was performed under the following conditions using a DC pulse magnetron sputtering apparatus.
Target material: Metallic silicon Electric power: 8KW
Film width: 1500mm
Film tension: 250N / 1500mm
Line speed: 0.2 m / min Reactive gas: Oxygen Discharge gas: Argon Discharge pressure: 0.03 Pa
The thickness of the silica film was 50 nm. When forming a 100 nm silica film, the line speed was 0.1 m / min.

<Formation of metal nitride layer (silicon nitride)>
Film formation was performed using a PE-CVD apparatus (manufactured by Cellvac Co., Ltd.).
Gas flow ratio: SiH4: N2 = 5: 95
Mixed gas flow rate: 400SCCM
Power: 1KW (13.56MHz)
The film formation time was adjusted to obtain a silicon nitride film having a thickness of 50 nm.

(Measurement of moisture permeability)
According to the method described in JIS-Z-0208 (however, the temperature and humidity were 60 ° C. and 95% RH), the moisture permeability was measured for each sample described in Table 1. The results are shown in Table 1.
In Samples 4 and 8, generation of cracks was observed after the formation of the silica layer.

[Example 2]
(Saponification treatment)
Each sample obtained in Example 1 was immersed in a 1.5 N aqueous sodium hydroxide solution at 55 ° C. for 2 minutes. It wash | cleaned in the room temperature water-washing tub, and neutralized using 0.1 N sulfuric acid at 30 degreeC. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. In this way, the surface of the cellulose acetate film was saponified.
However, for the sample on which the silica and silicon nitride layers were formed, the silica and silicon nitride layers were prevented from being damaged by alkali by sticking the PET adhesive film to the surface.
Furthermore, the Fuji Photo Film WV film was saponified under the same conditions and used for the following sample preparation.

(Preparation of polarizing plate)
Iodine was adsorbed on the stretched polyvinyl alcohol film to produce a polarizer, and the above-mentioned various saponified protective films were attached to one side of the polarizer using a polyvinyl alcohol-based adhesive. The transmission axis of the polarizer and the slow axis of the cellulose acetate film were arranged in parallel.
Further, the saponified WV film was attached to the opposite side of the polarizer using a polyvinyl alcohol adhesive. In this way, a polarizing plate was produced.

(Evaluation)
The polarizing plate produced in this manner is attached to a glass plate so that the WV film is on the glass side, the parallel transmittance and the orthogonal transmittance are measured with a Shimadzu UV2200 spectrophotometer, and the degree of polarization is calculated by the above (Formula 6). did. Further, after the polarizing plate was aged at 60 ° C. and 95% RH for 1000 hours, the parallel transmittance and the orthogonal transmittance were measured again, and the change in the polarization degree before and after the aging was calculated. The results are shown in Table 1.
From the results in Table 1, it can be seen that the polarizing plate of the present invention has a small change in the degree of polarization with respect to heat and humidity and is excellent in durability.

[Example 3]
A pair of polarizing plates provided on a 20-inch liquid crystal display device (LC-20V1, manufactured by Sharp Corporation) using a TN type liquid crystal cell is peeled off, and the polarizing plate produced in Example 2 is replaced with WV. A film was attached to the viewer side and the backlight side one by one through an adhesive so that the film would be on the liquid crystal cell side. The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged so as to be orthogonal. After processing for 48 hours in an environment with a temperature of 60 ° C and a relative humidity of 90%, the backlight is lit continuously for 24 hours under the environmental conditions of a temperature of 25 ° C and a relative humidity of 60%. Then, light leakage was evaluated.

(Evaluation criteria)
○: No light leakage is observed.
(Triangle | delta): Light leakage is observed a little, but it is not a problem practically.
X: There is a light leakage, which may cause a practical problem.
As shown in Table 1, frame-like light leakage was observed on the display screen of the liquid crystal display device in the polarizing plate of the comparative example, whereas it was not observed or very slight in the polarizing plate of the present invention.

It is explanatory drawing which shows the structural example which compounded the polarizing plate of this invention, and a functional optical film, and used the protective film for polarizing plates of this invention and a functional optical film as a protective film of a polarizing plate through an adhesive agent to a polarizer. Example (A), and a functional optical film adhered to a polarizing plate provided with a protective film for a polarizing plate of the present invention on one side of the polarizer and a protective film on the back side (B) through an adhesive layer Each is shown. It is explanatory drawing which shows an example of the liquid crystal display device in which the polarizing plate of this invention is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Protective film for polarizing plates 1a Protective film for polarizing plates 1b Protective film 2 Polarizer 3 Functional optical film 4 Adhesive layer 5 Polarizing plate 11 Upper polarizing plate 12 Upper polarizing plate absorption axis 13 Upper viewing angle widening film 14 Upper viewing angle widening Film orientation control direction 15 Liquid crystal cell upper electrode substrate 16 Upper substrate orientation control direction 17 Liquid crystal layer 18 Liquid crystal cell lower electrode substrate 19 Lower substrate orientation control direction 20 Lower viewing angle widening film 21 Lower viewing angle widening film orientation control direction 22 Lower polarizing plate 23 Lower polarizing plate absorption axis

Claims (8)

A polarizing plate in which a low moisture-permeable cured layer is provided on a cellulose acylate film directly or via another layer, and at least one layer containing a metal oxide and / or metal nitride is provided on the low moisture-permeable cured layer A protective film for a polarizing plate, which is a protective film and has a moisture permeability of 200 g / m ² · day or less measured in an atmosphere of 60 ° C. and 95% relative humidity in accordance with JIS-Z-0208. The said moisture permeability is 150 g / m < ² > * day or less, The protective film for polarizing plates of Claim 1 characterized by the above-mentioned. The said water vapor permeability is 100 g / m < ² > * day or less, The protective film for polarizing plates of Claim 1 characterized by the above-mentioned.   The low moisture-permeable cured layer is obtained by applying and drying a curable composition containing a compound having an I / O value (inorganic value / organic value) of 0.8 or less in an organic conceptual diagram, and curing it. The protective film for polarizing plates according to claim 1, wherein the protective film is a polarizing plate. The low moisture-permeable cured layer is applied and dried with a curable composition containing at least one compound selected from the compound represented by the following general formula (A) and the compound represented by the following general formula (B). The protective film for polarizing plates according to claim 1, wherein the protective film is a cured product of the polarizing plate.

(In the formula, R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 represents an alkylene group or alkylene oxide group having 1 to 5 carbon atoms, and R3 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. And n represents an integer of 1 or 2.)

(Wherein R1, R3 and n represent the same meaning as in the general formula (A)).   The film thickness of the said cellulose acylate film is 30-100 micrometers, The protective film for polarizing plates in any one of Claims 1-5 characterized by the above-mentioned.   A polarizing plate in which a protective film is bonded to both sides of a polarizer, wherein at least one of the protective films is the polarizing plate protective film according to claim 1.   A liquid crystal display device comprising a liquid crystal cell and two polarizing plates disposed on both sides thereof, wherein at least one polarizing plate of the polarizing plate is the polarizing plate according to claim 7.

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