JP2002333525A - Protective film for polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film for a polarizing plate, with which dust hardly sticks onto a viscous layer and which has excellent adhesion property a supporting body is obtained. SOLUTION: The protective film for the polarizing plate has at least one layer having conductivity on at least one surface of the film and the layer has <=10<11> Ω/cm surface resistivity (at 25 deg.C and 20%RH). The conductive material in the conductive layer is at least one kind of metal oxide containing Sn, Ti, In, Zn, Al, Si, Mg, Ba, Mo, W or V as the main component and having 10<7> Ω/cm (at 25 deg.C and 20%RH) volume resistivity. The electric conductive material in the layer having the conductive layer essentially consists of an ionic polymer. The electric conductive material in the layer having the conductive layer is an alumina sol containing an electrolyte. The primary particle size of the metal oxide is <=0.2 μm. The protective film for a polarizing plate is a cellulose ester film and has a layer containing a hydrophilic binder on the opposite surface of the protective film for a polarizing plate to the surface where the layer having conductivity is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a polarizing plate, and more particularly to a cellulose ester film widely used for applications requiring optical performance, for example, a protective film for a polarizing plate of a liquid crystal display device. The present invention relates to a polarizing plate protective film provided with a conductive layer.

[0002]

BACKGROUND OF THE INVENTION A polarizing plate composed of a polarizing film is composed of a combination of sunglasses, an anti-reflection plate, and a liquid crystal, and is used as a calculator, a clock, an OA.
2. Description of the Related Art In recent years, the range of applications as devices and display devices for automobiles has been expanding.

[0003] A polarizing plate is usually formed by adsorbing and dyeing iodine or dichroic dyes on a polyvinyl alcohol-based film and stretching them in a certain direction to form a polarizing film. When this polarizing plate is attached to a liquid crystal display device or the like, an adhesive layer is provided, and the adhesive layer is usually covered and protected by a separator or the like until it is used for bonding.

On the other hand, in a process of assembling a liquid crystal display device and the like and a process of distributing a polarizing plate, a protective film is provided on the surface of the polarizing plate to protect the surface of the polarizing plate.

In the use of the polarizing plate, strong adhesion is required between the polarizing plate and the protective film in order to exhibit high reliability and durability under various environments. As a method of improving this adhesiveness, in the case of a cellulose triacetate film most widely used as a protective film, the surface is saponified in advance with an alkali solution, and then laminated with a polyvinyl alcohol-based adhesive or the like to form a polarizing film. I have.

However, the above-mentioned alkali treatment uses a high concentration alkaline solution, which is not preferable in terms of work safety and environmental protection. In addition, the alkali treatment increases the quality such as bleed out of the plasticizer and increase in haze. There is a risk of dropping.

[0007] Further, if a process for imparting functionality such as antistatic treatment or hard coating is performed before the alkali treatment, the effect is reduced by the alkali treatment. Therefore, the functional assignment of the protective film is limited after the alkali treatment. Problem.

Heretofore, as the polarizing plate used as described above, a polarizing plate provided with a transparent protective layer made of a resin film on one or both sides of the polarizing plate is known. However,
Dirt and the like adhere and contaminate before the separator and the like are peeled off from the adhesive layer attached to the polarizing plate and used for bonding.
There is a problem that induces poor appearance.

Further, when the polarizing plate is adhered to the liquid crystal display device through the adhesive layer and then the surface protective film is peeled off, an abnormal display occurs and a normal liquid crystal display cannot be realized, or the liquid crystal display device malfunctions during operation. Problems. As a method of improving the above disadvantages, for example, JP-A-4-124601,
It is disclosed in JP-A-62-89907.

In any of these methods, it is necessary to provide a plastic film provided with a conductive layer by vapor deposition or sputtering and to provide a new protective film using an adhesive or an adhesive. Optical properties such as transparency are not sufficient, and adhesion to a film is poor.

Further, when the above film is bonded to a polarizing film via an adhesive 1) Air bubbles easily enter the interface and the workability is poor 2) Providing a new pressure-sensitive adhesive has a problem in that its performance is affected by temperature and humidity. Deterioration, foaming phenomenon, or peeling phenomenon of the polarizing plate occurs. 3) There is a problem that the polarizing plate is curled and lifted up, and it is not enough.

Japanese Patent Application Laid-Open No. 1-238602 discloses a method in which a specific surfactant is coated on a thermoplastic resin film such as a polyethylene film. Is not sufficient.

[0013]

An object of the present invention is to provide a protective film for a polarizing plate having the following characteristics.

1. 1. Adhesion layer is contaminated by dust and the like, and has no appearance defect. 2. Less problem of abnormal display of liquid crystal and malfunction of liquid crystal display device. 3. It is not necessary to attach a film provided with a new conductive layer with an adhesive, and it is not necessary to perform a saponification treatment, and the operation steps can be omitted. Excellent optical properties such as transparency and excellent adhesion to the support film

[0015]

The object of the present invention is to provide a polarizing plate protective film having at least one conductive layer on at least one side thereof and having a surface resistivity of 10 ¹¹ Ω / cm (25 ° C., 20% R
H) It is achieved by a protective film for a polarizing plate characterized by the following.

Preferred embodiments of the present invention include the following.

1. 1. The protective film for a polarizing plate is a cellulose ester film. 2. Having a layer containing a hydrophilic binder on the opposite side of the conductive layer of the polarizing plate protective film. When the conductive material of the conductive layer is Sn, Ti, In, Z
at least one metal oxide selected from the group consisting of n, Al, Si, Mg, Ba, Mo, W and V as main components and having a volume resistivity of 10 ⁷ Ω / cm (25 ° C., 20% RH); 3. 4. The electrically conductive material of the layer having the conductive layer mainly contains an ionic polymer. 5. The primary particle size of the metal oxide is 0.2 μm or less. The electrically conductive material of the layer having the conductive layer is an alumina sol containing an electrolyte. Hereinafter, the present invention will be specifically described.

As a protective film for a polarizing plate, a transparent and flexible thermoplastic plastic film, especially a plastic such as polyethylene has been used.
In the present invention, it is preferable to use a cellulose ester film because there is no orientation and the transparency is good.

Examples of the cellulose ester film used in the present invention include cellulose ester films made of materials such as diacetyl cellulose, triacetyl cellulose, cellulose propionate, cellulose acetate butyrate, and nitrocellulose. For use as a protective film such as a polarizing film, a thickness of 10 μm or more is necessary due to the strength, and in particular, a 20 to 500 μm triacetyl cellulose film or diacetyl cellulose film is transparent, has a moisture absorption dimensional stability, a strong property and It is preferable in terms of weather resistance and the like. For the purpose of improving the light resistance of the cellulose ester film, a benzophenone-based or benzotriazole-based ultraviolet absorber can be added, and if necessary, other additives such as a slipping agent plasticizer can be added.

In the constitution of the protective film for a polarizing plate of the present invention, an antistatic layer is provided on one side of triacetyl cellulose, and a hydrophilic binder for bonding to a polarizer is provided on the other side.

As the hydrophilic binder according to the present invention, for example, a vinyl acetate-maleic acid copolymer compound containing -COOM group or a hydrophilic cellulose derivative (for example, methylcellulose, carboxymethylcellulose, hydroxyalkylcellulose, etc.), a polyvinyl alcohol derivative (for example, Vinyl acetate-vinyl alcohol copolymer, polyvinyl acetal, polyvinyl formal, polyvinyl benzal, etc.) natural polymer compounds (eg, gelatin, casein gum arabic, etc.), and hydrophilic group-containing polyester derivatives (eg, sulfone group-containing polyester copolymer). No.

The specific -COOM group-containing copolymer compound used in the present invention is represented by the following general formula.

[0023]

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Wherein A is a vinyl monomer, B is a hydrogen atom,
-CO-OM or-(CO) -R, wherein when Z = 0, B is a hydrogen atom, when R is an alkyl group, B is a hydrogen atom, M is hydrogen or a cation, and R is -O-R '. Or -N (R ") (R ') wherein R' is an alkyl group, an aralkyl group, an aryl group, a heterocyclic ring residue or a nonmetal atom required for forming an heterocyclic ring in cooperation with R", R ″ is a hydrogen atom,
R1 and R2 are a hydrogen atom or a lower alkyl group, and X is-(CO) -O- or -O- (CO).
-, R3 is a halogenoalkyl or halogenoalkyloxyalkyl group, m, p, q, r, x, y, and z are values each representing a mol% of each monomer, m is 0 to 60,
p is 0 to 100, q is 0 to 100, r is 0 to 100, x is 0 to 6
0, y is 0 to 100, z is 0 to 100, and m + p + q + r
= 100, x + y + z = 100. In the above general formula, as the vinyl monomer, for example, styrene, nitro group, fluorine, chlorine, bromine, chloromethyl group, styrene substituted with lower alkyl group, etc., vinyl methyl ether, vinyl ethyl ether, vinyl chloroethyl ether, vinyl acetate , Vinyl chloroacetate, vinyl propionate, acrylic acid, unsaturated acids such as methacrylic acid or itaconic acid, alkyl acrylates or alkyl methacrylates having 1 to 5 carbon atoms and unsubstituted or substituted with chlorine, phenyl group and the like, Phenyl acrylate or phenyl methacrylate, acrylonitrile, vinyl chloride,
Vinylidene chloride, ethylene, acrylamide, carbon number 1
And acrylamide, vinyl alcohol, chrysidyl acrylate, acrolein, etc. substituted with an alkyl group or chlorine, phenyl group, etc., preferably styrene, styrene having a substituent, vinyl acetate, vinyl methyl ether, alkyl acrylate, acrylonitrile, etc. It is.

The alkyl group represented by R 'in the above formula is preferably an alkyl group having 1 to 24 carbon atoms.
Any of alkyl groups such as a branched alkyl group and a cycloalkyl group may be used, and the alkyl group may have a substituent. Examples of the substituent include a hydroxy group, a hydroxycarbonyl group, and a cationic oxycarbonyl group. Particularly, a halogenoalkyl group or a halogenoalkyloxyalkyl group in which a halogen such as fluorine is substituted can obtain a desirable result. In this case, a halogenoalkyl group having 2 to 18 carbon atoms, a halogenoalkyloxyalkyl group or a halogenocycloalkyl group is obtained. Thus, the halogen number is desirably from 1 to 37. The halogenoalkyl group and the halogenoalkyloxyalkyl group and the halogenoalkyl group and the halogenoalkyloxyalkyl group of R3 in the above formula are
It is preferably represented by the following general formula [A].

[0026]

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(Where R4, R5, R6, R7, R8 are hydrogen or fluorine, n2 is 0 or 1, n1 is 0 when n2 is 0, and n1 is 2 or 3 when n2 is 1. And n3 is an integer of 1 to 17, provided that n1 + n3 is 1 to 17. However, when R4 is two or more in the structural formula, one is hydrogen and the other is fluorine. May be
Similarly, when there are a plurality of R5, R6, and R7 in the structural formula, they may be different groups. In addition, when R ′ in the general formulas [I] and [II] is a halogenoalkyl group or a halogenoalkyloxyalkyl group as described above, preferably, the general formulas [I] and [II] R in the formula is -O-R '. An aryl group such as a phenyl group or an aralkyl group such as a benzyl group for R ′ may have a substituent, such as a halogen lower alkyl group such as fluorine, chlorine, or bromine; -A hydroxycarbonyl group, an oxycarbonyl group of a cation, a nitrile group, a nitro group and the like. The heterocyclic ring of R 'or the heterocyclic ring formed by R' and R "in the formula is a saturated or unsaturated heterocyclic ring containing oxygen, sulfur, or nitrogen, such as aziridine / pyrrole. A heterocycle selected from heterocycles such as pyrrolidine, pyrazole, imidazole, imidazoline, triazole, piperidine, piperazine, oxazine, morpholine, thiazine, etc. The cation of M in the formula is, for example, ammonium ion, sodium ion And cations such as potassium ion and lithium ion.

The -COOM group-containing copolymer compound represented by the above general formula is used singly or in combination of two or more, and those having an average molecular weight of about 500 to 500,000 are preferably used.

The following are typical examples of the above-mentioned copolymer compound.

However, the present invention is not limited to these.

[0031]

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The -COOM group-containing copolymer compound represented by the above general formula used in the present invention is synthesized by a known method. That is, it is well known that a maleic anhydride copolymer is a very general polymer, and these derivatives can also be obtained by reacting an alcohol or an amine compatible with them with the maleic anhydride copolymer. It can be obtained easily, or can be obtained by copolymerizing a product obtained by reacting and purifying an alcohol or an amine compatible with a maleic anhydride monomer with another vinyl monomer. Acrylates such as halogenoalkyl and halogenoalkyloxyalkyl are available from the Journal of Polymer Science (Journal of Polymer Science).
Science.15 515-574 (1955) or British Patent 1,121,
It can be easily synthesized by the method of synthesizing monomers and polymers described in the specification of Japanese Patent No. 357. The amount of the copolymer compound according to the present invention to be used is preferably 10 to 1000 mg / m ² , more preferably ²⁰ to 300 mg / m ² .

The polymer solution according to the present invention may be a gravure coater, a dip coater, a reverse roll coater,
It can be applied by a known method such as an extrusion coater. Amount with the polymer according to the present invention is in the range of 10 to 1000 mg / m ^2,
Especially stable adhesive strength and finish after application are 20-30
0 mg / m ² is preferred. The method of drying after applying the coating solution is not particularly limited, but the amount of residual solvent after drying is 5 wt%.
It is preferable to set the following. If the amount of the residual solvent is large, air bubbles may be generated at the bonding interface during the drying process after lamination with the polarizer, which is not preferable.

The polymer solution according to the present invention may optionally contain an ultraviolet absorber, a slipping agent, a matting agent, an antistatic agent, a crosslinking agent, an activator, and the like.

In particular, a cross-linking agent is preferable for promoting the adhesion of the polarizer to the polyvinyl alcohol film. Examples of such a cross-linking agent include a polyvalent epoxy compound, an aziridine compound, an isocyanate compound, a bright vane, and a boron compound.

Examples of the adhesive used for bonding the treated surface of the protective film according to the present invention to the polarizer include polyvinyl alcohol-based adhesives such as polyvinyl alcohol and polyvinyl butyral, and vinyl-based latex such as butyl acrylate. Is raised.

Next, the conductive metal oxide powder of the present invention will be described.

Examples of metal oxides include ZnO, Ti
O ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , Mg
O, BaO, MoO ₂ , V ₂ O _{5, and the} like or a composite oxide thereof are preferable, and ZnO, TiO _2, and SnO ₂ are particularly preferable. Examples of including heteroatoms include, for example, addition of Al, In or the like for ZnO, and N for TiO ₂ .
b, Ta, etc., and for SnO ₂ , Sb, N
The addition of b, a halogen element or the like is effective. The addition amount of these different atoms is preferably in the range of 0.01 mol% to 25 mol%, and particularly preferably in the range of 0.1 mol% to 15 mol%.

The volume resistivity of these conductive metal oxide powders is 10 ⁷ Ωcm, especially 10 ⁵ Ωcm or less,
The conductive layer contains a powder having a specific structure in which the primary particle size is 100 mm or more and 0.2 μm or less and the major axis of the high-order structure is 300 mm or more and 6 μm or less in the conductive layer in a volume fraction of 0.01% or more and 20% or less. preferable.

As for the particle diameter having a higher-order structure, it is preferable to use the average particle diameter determined by the measurement of a particle size distribution analyzer by a sedimentation method, a laser diffraction method, etc. More particle size must be determined. However, when using only an electron microscope to measure both, the longest diameter of the particles that exist independently in the field of view is used as the particle diameter of the higher-order structure, and there is clearly a grain boundary The diameter of the particles is adopted as the primary particle diameter.

Here, the higher order structure of the particles will be described in detail. The connection of the particles may be branched, linearly arranged, or helical. It is better to arrange on top.
The number of connections should be 3 or more and 100 or less,
Preferably less than 500, more preferably 3 or more and less than 100 is suitably selected in consideration of dispersion and the like. However, usually synthesized powders vary not only in particle size distribution but also in particle formation, and it may be economically disadvantageous to separate only these connected particles. Even if particles other than the connected particles described above, that is, particles having a connected number of 2 or less are included, the number is not limited as long as the object of the present invention can be achieved. However, if such a powder is present in the connected particles in an amount of 40% or more, the object of the present invention cannot be achieved unless an amount exceeding 20% in volume fraction is added.

The conductivity of the present invention can be obtained by dispersing conductive fine particles in a binder and providing the support in a support layer, or by subjecting the support to a subbing treatment and adhering the conductive fine particles thereon. Good.

In addition, a heat-resistant agent, a weather-resistant agent, inorganic particles, a water-soluble resin, an emulsion, etc. are added to the layer made of the metal oxide of the present invention so as not to impair the effect of the present invention, to form a mat and improve the film quality. You may.

For example, inorganic fine particles may be added to the layer comprising the metal oxide of the present invention. Examples of the inorganic fine particles to be added include silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate and the like. Fine particles have an average particle size of 0.01 to
The thickness is preferably 10 μm, more preferably 0.01 to 5 μm, and preferably 0.05 to 10 parts by weight, and particularly preferably 0.1 to 5 parts by weight, based on the solid content of the coating composition.

The binder used in the present invention is not particularly limited as long as it has a film forming ability. Examples of the binder include proteins such as gelatin and casein, carboxymethylcellulose, hydroxyethylcellulose, and the like.
Cellulose compounds such as acetylcellulose, diacetylcellulose and triacetylcellulose, dextran,
Agar, sodium alginate, sugars such as starch derivatives, polyvinyl alcohol, polyvinyl acetate, polyacrylate, polymethacrylate, polystyrene,
Examples include synthetic polymers such as polyacrylamide, poly-N-vinylpyrrolidone, polyester, polyvinyl chloride, and polyacrylic acid.

In particular, gelatin (lime-treated gelatin, acid-treated gelatin, oxygen-decomposed gelatin, phthalated gelatin, acetylated gelatin, etc.), acetylcellulose, diacetylcellulose, triacetylcellulose, polyvinyl acetate, polyvinyl alcohol, polybutyl acrylate , Polyacrylamide, dextran and the like.

In the present invention, the layer provided on one surface of the support contains an ion conductive substance and conductive fine particles.

The ionic conductive substance used in the present invention is a substance which exhibits electrical conductivity and contains ions which are carriers for selecting electricity. An example of this is a metal oxide sol containing an ionic polymer compound and an electrolyte.

The ionic polymer compound is disclosed in
-23828, 49-23827, 47-28937, anionic polymer compounds as disclosed in JP-B-55-734, JP-A-Showa 50
-54672, JP-B-59-14735, JP-B-57-18175, JP-B-57-181
No. 76, No. 57-56059, etc., an ionene-type polymer having a dissociation group in the main chain;
No. 57-15376, No. 53-45231, No. 55-145783, No. 5
5-65950, 55-67746, 57-11342, 57-19735
And pendant cationic polymers having a cationic dissociating group in the side chain, as shown in JP-B-58-56858, JP-A-61-27853 and JP-A-62-9346.

Particularly preferred ionic polymer compounds include polymers having units of the following general formulas [1], [2a] and [2b].

[0051]

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[0052]

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In the formula, R 3, R 4, R 5 and R 6 represent a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, or R 3 and R 4
And / or R5 and R6 may combine to form a nitrogen-containing heterocycle such as piperazine. A and B each represent a substituted or unsubstituted alkylene group having 2 to 10 carbon atoms, an arylene group, an alkenylene group, an arylene alkylene group,
-R1COR8-, -R9COOR10OCOR11-, -R12OCR13COOR14
-, -R15- (OR16) -m, -R17CONHR18NHCOR19, -R20OC
ONHR21NHCOR22 or -R25NHCONHR24NHCONHR25 group,
CR7, R8, R9, R11, R12, R14, R15, R16, R1
7, R19, R20, R22, R23 and R25 are alkylene groups, and R10, R13, R18, R21 and R24 are each selected from a substituted or unsubstituted alkylene group, alkenylene group, arylene group, arylenealkylene group and alkylenearylene group. A linking group, m is a linking group selected from positive integers of 1 to 4, and X- is an anion.

However, when A is an alkylene group, a hydroxyalkylene group or an arylenealkylene group, it is preferred that B is not an alkylene group, a hydroxylalkylene group or an arylenealkylene.

E represents a mere bond, -NHCOR26CONH- or a group selected from D. R26 is a substituted or unsubstituted alkylene group, alkenylene group, arylene group,
Represents an arylene alkylene group or an alkylene arylene group.

Z 1 and Z 2 each have a —N ＝ C— group of 5 members or 6 members;
Group of non-metal atoms necessary to form a membered ring (≡N + [X-]
-May be linked to E in the form of a quaternary salt.

N represents an integer of 5 to 300.

Next, specific examples of preferred ionic polymer compounds having units of the structures represented by the general formulas [1], [2a] and [2b] will be described.

These specific compounds are described, for example, in JP-A-62-2
64046 (5) to (8), Ip1 to Ip36.

The following are representative examples.

[0061]

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[0062]

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[0063]

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The ionic polymer compound may be used alone or in combination of several kinds of ionic conductive substances. And such ionic polymer compound is preferably used in a range of 0.005g~2.0g / m ^2, preferably used in particular in the range of 0.01g~1.0g / m ^2.

On the other hand, alumina sols having an electrolyte are disclosed in JP-A-54-59926, JP-A-55-126238, and 55-126239.
No. 55-140834, etc. can be used. This alumina sol contains colloidal particles mainly composed of aluminum oxide and an electrolyte, and can be obtained by a known method, for example, a method described in JP-B-39-20150. For example, it can be produced by adding a metal aluminum powder to an aqueous hydrochloric acid solution and heating to react. In addition, it can be produced from an aqueous solution of acetic acid or nitric acid in a similar manner.

Examples of the electrolyte contained in the alumina sol include inorganic acids (eg, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, etc.), fatty acid carboxylic acids (eg, formic acid, acetic acid, propionic acid), aromatic carboxylic acids (eg, silica film), etc. Organic acids, alkali metal hydroxides and salts (e.g., sodium chloride, sodium acetate, sodium silicate). The anion moiety preferably has a small molecular weight, and inorganic acids are particularly desirable. The amount of the electrolyte is preferably 10 ^-4 to 10 ^-2 mol per gram of aluminum. The size of the colloidal particles of alumina sol is approximately 0.1 to 0.02 μm.
However, since the hydrate is adsorbed on the surface and has a property of being easily connected continuously, it is suitably used in the present invention.

The above-mentioned ionic conductive substance may be dissolved in water and a water-miscible organic solvent and applied on a support, or added to a hydrophobic polymer such as polystyrene or cellulose diacetate and mixed. May be set.

Further, it is more preferable that a layer made of a hydrophobic polymer is further provided as an upper layer on the coated layer. In this case, the hydrophobic polymer for forming the upper layer may be applied in the form of a solution or an aqueous latex dissolved in an organic solvent, and the coating amount may be 0.05% by dry weight.
g / m ² ~1g / m ² about is good. Examples of the hydrophobic polymer include cellulose esters (for example, nitrocellulose, cellulose acetate), vinyl polymers including vinyl chloride, vinylidene chloride, and vinyl acrylate, and polymers such as polyamides and polyesters soluble in organic solvents.

The conductive material-containing layer of the present invention may contain a matting agent, a lubricant, a plasticizer (eg, triphenyl phosphate, biphenyl diphenyl phosphate, dimethyl ethyl phosphate), a defoaming agent, and a surfactant if necessary. Agents or other auxiliaries can be used.

Examples of the matting agent include silicon oxide, aluminum oxide, magnesium oxide and other metal oxides having a particle size of 0.1 to 5 μm, and high molecular compounds such as polymethyl methacrylate and methyl methacrylate-methacrylic acid copolymer. Polymer beads can be used.

The conductive fine particles used in the layer containing the conductive substance of the present invention are preferably crystalline metal oxide particles, but those containing oxygen vacancies and the metal oxide used are preferred. Contains a small amount of heteroatoms forming a donor.

The conductive fine particles comprising a crystalline metal oxide used in the present invention are produced mainly by the following method. First, a method of preparing metal oxide particles by firing and performing a heat treatment in the presence of a heteroatom for improving conductivity, and second, a method for improving conductivity when manufacturing metal oxide fine particles by firing. Coexisting heterogeneous atoms, 3rd
When the metal oxide particles are manufactured by firing, the oxygen concentration in the atmosphere is reduced to introduce oxygen defects.

The average particle size of the conductive fine particles is preferably 0.5 μm or less, more preferably 0.2 μm or less.

In providing a layer containing these conductive metal oxide particles, binders that can be used include:
For example, gelatin, gelatin derivatives, polyvinylpyrrolidone, polyacrylic acid, carboxymethylcellulose, water-soluble polymers such as hydroxyethylcellulose, cellulose diacetate, cellulose triacetate, cellulose nitrate, cellulose acetate propionate, cellulose acetate phthalate, etc. , Vinyl chloride, vinylidene chloride, polystyrene, alkyl (alkyl group having 1 to 4 carbon atoms) acrylate, alkyl (alkyl group having 1 to 4 carbon atoms) methacrylate, vinyl acetate, ethylene, propylene, butadiene, hydroxyethyl acrylate, Examples include homopolymers or copolymers such as acrylamide, and maleic anhydride-containing copolymers. When a layer containing the conductive metal oxide particles of the present invention is provided, the thickness of the layer is preferably 0.05 μm to 5 μm, and more preferably 0.1 μm to 3 μm.
μ.

The ratio of the conductive oxide to the binder to be used varies depending on the kind of the oxide, the particle size and the like, but the volume ratio is preferably about 2 for the former 1 and about 1 for the former 2.

The conductive fine particles used in the present invention may be used in combination with the ionic conductive compound. The amount of the conductive fine particles to be used is preferably 0.01 to 5.0 g / m ² , particularly
0.005 to 1 g / m ² is preferred.

[0077]

EXAMPLES The effects of the present invention will now be specifically illustrated by examples.

Example 1 A coating composition according to the present invention shown below was applied on one surface of a cellulose triacetate film having a thickness of 80 μm to a coating thickness of 20 ml / m 2.
And dried at 80 ° C. for 5 minutes. (Coating composition for first layer of antistatic layer) Conductive fine particle dispersion composition Conductive SnO2 antimony composite fine particles 200 parts by weight (Primary particle diameter 0.015 nm, manufactured by Mitsubishi Materials Corporation) Nitrocellulose 5 parts by weight Acetone 150 parts by weight The mixture was dispersed using a sand mill for 2 hours.

Using the conductive fine particle dispersion composition thus prepared, a coating composition was prepared as follows.

Coating Composition Conductive Fine Particle Dispersion Composition 70 parts by weight Nitrocellulose 10 parts by weight Acetone 700 ml Methanol 300 ml Further, the following composition was coated on the first antistatic layer to a coating thickness of 16 ml / m 2.
^It was applied so as to be ² and dried.

(Coating composition for the second layer of antistatic layer) Diacetyl cellulose 10 parts by weight Pentaerythritol tetrapalmitate 1.5 parts by weight Acetone 500 ml Ethyl acetate 400 ml Toluene 100 ml / M2 and dried at 90 ° C.

(Adhesive Layer Coating Composition 1) Exemplified Compound (1) 10 parts by weight Water 20 parts by weight Methanol 400 ml Acetone 600 ml Example 2 The following composition was used in place of the first antistatic layer composition used in Example 1. Was further applied as an adhesive layer coating composition, and dried to obtain a cellulose triacetate film having both the conductive layer and the adhesive layer having the same constitution as in Example 1.

(Coating Composition for Antistatic First Layer) Ionene-type polymer Ip-3 3.5 parts by weight Ethylene glycol 270 ml Acetone 400 ml Methanol 600 ml (Adhesive layer coating composition 2) Exemplified compound (3) 5 parts by weight Ethyl acetate 500 ml Acetone 500 ml Example 3 The following composition was applied in the same manner as in Example 1 and dried at 80 ° C. for 5 minutes. Further, the same antistatic second layer coating composition as in Example 1 was applied at 20 ml / m ² and dried.

(Coating composition for antistatic first layer) Alumina sol AS-100 4 parts by weight (manufactured by Nissan Chemical Industries, Ltd.) Acetone 500 ml Methanol 400 ml Dimethylformamide 100 ml Example 4 Prepare the dispersion,
Using this dispersion, a coating solution of the following formulation was adjusted to a film thickness of 50
25m coating amount on μm cellulose triacetate film
1 / m ² and dried at 120 ° C. for 3 minutes.

(Coating Composition for Antistatic First Layer) Conductive Dispersion 100 parts by weight Saran (Saran F-310 manufactured by Asahi Dow Co., Ltd.) 10 parts by weight Methyl ethyl ketone 700 ml Methanol 300 ml Cyclohexanone 200 ml Example 5 Ip of Example 3 A sample was prepared in exactly the same manner except that Ip-10 was used instead of -3.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that the conductivity-imparting material was removed from the coating composition of Example 1. Further, the film was immersed in an aqueous solution of sodium hydroxide having a temperature of 60 ° C. and a concentration of 8 wt% for 5 minutes and washed with water to form a saponified layer.

Comparative Example 2 In place of the alumina sol AS-100 of Example 3, JP-A-1-238
A solution was prepared by adding 2 parts by weight of Chemistat 1100 described in 602 (manufactured by Sanyo Chemical Co., Ltd.), and was applied and dried under the same conditions as in Example 3.

Various characteristics of each of the above examples were evaluated by the following evaluation methods.

[Measurement method of surface electric resistance]
After leaving for 1 hour or more under the condition of RH, the surface resistance value to the coated surface was measured with an insulation resistance measuring instrument (VE-30 type, manufactured by Kawaguchi Electric Co., Ltd.).

<Charge Amount, Dust Adhesion Test, Abnormal Display Test of Liquid Crystal> Two layers of polyethylene / ethylene / vinyl acetate copolymer were formed on the outer surfaces of the layers on which the conductive layers were arranged in the polarizing plates obtained in Examples and Comparative Examples. A surface protective film made of an extruded film is attached, an acrylic adhesive layer having a thickness of 20 μm is attached to the other surface of the polarizing plate, and the surface is covered and protected with a separator made of a polyester film treated with a silicone release agent. The following test was performed.

A charge-type potential meter (trade name: KS-471 type,
Using a Kasuga Electric Co., Ltd.), the amount of static electricity on the surface of the polarizing plate after the separator and the surface protective film were peeled and removed under the conditions of 25 ° C. and 20% RH was measured.

Further, the amount of adhesion on the adhesive layer after the separator was peeled off and removed, and the adhesive layer on the liquid crystal display device via the adhesive layer,
The above display of the liquid crystal after adhesion and removal of the surface protective film was also examined.

Ash adhesion test on cigarettes ・ ・ ・: No dust was observed at all △: 少 し Slightly observed ×: Slightly observed ま た Further, the above cellulose triacetate film was used as a protective film, and A polarizing plate was made by adhering to both sides of the polarizing film produced by the method with an acrylic adhesive.

How to make a polarizing plate film A polyvinyl alcohol film having a thickness of 120 μm was immersed in an aqueous solution containing 1 part by weight of iodine and 2 parts by weight of potassium iodide and 4 parts by weight of boric acid, and stretched 4 times at 50 ° C. A polarizing film was obtained.

Using the protective films obtained in each of the examples and comparative examples, a polarizing plate was prepared by the following method so that the adhesive layer became an adhesive surface, and each polarizing plate was cut into a size of 5 cm × 7 cm. did. Each of the obtained cut pieces was temporarily adhered to the center of a 6 cm × 8 cm glass plate with an acrylic adhesive, and then pressed to cut each cut so as to completely remove bubbles between each piece and the glass plate. Adhered to glass plate.

The test pieces prepared in this manner were placed vertically in a constant temperature and humidity oven set at 80 ° C. and 95% RH so as not to overlap each other, and fixed to a support frame for 1000 hours. The adhesion of the film was measured.

Evaluation of adhesion between polarizing film and protective film: After the high-temperature and high-humidity treatment, the film was visually observed to evaluate the peeling state between the polarizing film and the protective film.

・ ・ ・: The rising portion of the film is 1 mm or less at the periphery Δ ・ ・ ・: The rising portion of the film is in the range of 1 to 5 at the periphery ×: The result is that the rising portion of the film is 5 mm or more at the periphery It is shown in FIG.

[0099]

[Table 1]

From the results shown in Table 1, it can be seen that the examples according to the present invention have a small amount of electricity after peeling off the conductive and surface protective film, have a small amount of dust adhered to the adhesive layer, and have no abnormal display of the liquid amount.

[0101]

According to the present invention, a protective film for a polarizing plate having the following characteristics can be provided.

1. 1. Adhesion layer is contaminated by dust and the like, and there is no appearance defect. 2. Less problem of abnormal display of liquid crystal and malfunction of liquid crystal display device. 3. It is not necessary to attach a film provided with a new conductive layer with an adhesive, and it is not necessary to perform a saponification treatment and the operation steps can be omitted. Excellent optical properties such as transparency and excellent adhesion to the support film

Continued on front page F term (reference) 2H049 BA02 BA27 BB33 BB43 BB51 BB67 BC14 BC22 2H091 FA08X FA08Z FB02 GA16 LA07 LA12 2K009 BB28 CC09 CC25 CC38 DD02 EE03

Claims (1)

[Claims] 1. A protective film for a polarizing plate, comprising a layer containing a hydrophilic binder on the surface opposite to the conductive layer of the protective film for a polarizing plate.