JP2008230036A - Protective film, method for producing the same, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective film which reduces troubles due to the fact that dust is easily attached by peeling charge or the like, its manufacturing method, a polarizing plate using the protective film, and a liquid crystal display device using the polarizing plate. <P>SOLUTION: The protective film is characterized in that a covering layer containing at least either a resin containing a repeating unit derived from a chlorine-containing vinyl monomer and fluorine-containing resin is deposited on at least one surface of a transparent base material film, and in that moisture content is 1.4 mass% to 4.0 mass%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a protective film, a manufacturing method thereof, a polarizing plate provided with the protective film, and a liquid crystal display device provided with the polarizing plate.

A protective film for protecting a polarizer is provided on a polarizing plate provided in a liquid crystal display device (hereinafter also referred to as LCD). As a material for the protective film, a plastic film is used. For example, a roll-shaped plastic film having a single layer structure such as a cellulose acylate film is mainly exemplified.
In recent years, functional layers such as an optical compensation layer, an antireflection layer, and a low moisture-permeable layer (hereinafter sometimes referred to as a coating layer) are laminated on a base film such as a cellulose acylate film. A multi-layered roll-shaped protective film to which various functions are added is used.

  The roll-shaped protective film on which the coating layer is laminated is a single-layer roll-shaped base film that is continuously fed out, coated with a coating liquid composition containing a solvent on the roll-shaped base film, and heated in a drying step. It is preferable from the viewpoint of productivity that the solvent is evaporated, and if necessary, the coating layer after drying is polymerized, the coating layer is laminated, and wound as a bulk roll.

The roll-shaped protective film having a multi-layer structure thus produced is sent out again from the bulk roll when the polarizing plate is produced.
Here, the roll-shaped protective film having a multi-layer structure is a laminated film composed of at least two layers of a base film and a coating layer, and is formed of a material having a different surface and back surface. When the protective film is fed out from the bulk roll, it may cause a large peeling charge.
The charged roll-shaped protective film easily attracts the surrounding dust due to static electricity, so that dust adheres to the polarizing plate when it is made, and the polarizing plate is directly bonded to the liquid crystal display device. Could cause problems.

In recent years, the quality requirements of the market for minute defects such as defects with dust in liquid crystal display devices have become very strict, so even if such dust is minute, liquid crystal display with dust attached The device cannot be shipped as is.
Therefore, in order not to reduce the productivity of the liquid crystal display device, there has been a demand for a technique for minimizing such dust adhesion as much as possible.

  On the other hand, the adhesion of dust due to charging is not only due to peeling charging as described above. For example, a hard coat layer or an antireflection layer may be further laminated as a second coating layer on the roll-shaped protective film laminated with the low moisture-permeable layer as described above. When such a hard coat layer or antireflection layer is laminated on a protective film that has not been removed, there may be a problem of uneven charging.

  In order to solve such a problem of charging of the protective film, a method has been disclosed in which a charge remover is installed to neutralize charges generated by charging with ions having a counter charge. (See Patent Document 1)

However, it is difficult to remove the charge generated by the peeling charge, and the charge removal on the protective film by the charge remover is no exception.
The reason is that the static eliminator generates ions with the opposite polarity to the charge of the charged body, and these ions are attracted to the charged body to neutralize the charge. As a result of the inventor's examination, it was found that it was very difficult to remove the charge from the protective film charged with the charge of the sign different from that of the protective film charged with the charge of the sign different on both sides.
That is, when both surfaces of the protective film are charged with different signs of charge, the electric lines of force are generated in the thickness direction of the film and are closed at the thickness portion, and the electric lines of force do not point out of the film. Even if there is a charge on the surface of the film, the electric field on the surface is weak, the force to attract ions generated by the static eliminator is weak, and it is considered that the charge cannot be removed efficiently.

  Further, Patent Document 2 discloses a method for preventing charging by laminating an antistatic layer, but a new antistatic layer must be laminated, resulting in an increase in cost.

  By the way, we realize that in winter there is little absolute moisture content in the air, and static electricity is likely to occur in such an atmosphere. As described above, the ease of occurrence of peeling electrification has a large correlation with the humidity of the atmosphere, and it becomes easy to charge rapidly in a low humidity atmosphere.

Here, the plastic film generally has a low water content, and the plastic film is easily charged in this respect.
On the other hand, among such plastic films, the cellulose acylate film is exceptionally a plastic film having relatively high water content.

However, in the conventional method, even if a cellulose acylate film having a high water content is used, the substrate film is heated in the drying step in order to evaporate the organic solvent in the coating liquid after coating in the step of laminating the coating layer. The water inside was also evaporated. Therefore, it was wound up in a state where the moisture content was significantly reduced unintentionally.
Therefore, even when a cellulose acylate film that should be advantageous in terms of antistatic properties is used, the characteristics cannot be fully utilized, and charging problems have occurred.

  In particular, the cellulose acylate film is a plastic film having a high moisture content and a plastic film having a high moisture permeability. Therefore, even if it is wound in a high moisture content state, if it is stored in a low-humidity storage, it has a problem that it gradually loses moisture and becomes easily peeled and charged again.

JP 2003-103224 A JP 2006-82241 A

  An object of the present invention is to provide a protective film that reduces problems caused by dust being easily attached due to peeling charging, a manufacturing method thereof, a polarizing plate using the protective film, and a liquid crystal display device using the polarizing plate. It is to provide.

  As a result of intensive studies, the present inventors have confirmed that the peeling charge that occurs when the difference in charge column between the transparent substrate film and the material forming the coating layer is large is protected when the coating layer is laminated and wound up. The front and back surfaces that are greatly affected by the moisture content of the film and that are highly charged when the moisture content is low, and conversely when the moisture content is high, are less charged. It has been found that the above problems can be solved by increasing the moisture content of the protective film, even though they have a large difference in charge train.

This invention is based on the said knowledge by the present inventors, and the means for solving the said subject are as follows. That is,
<1> A coating layer containing at least one of a resin containing a repeating unit derived from a chlorine-containing vinyl monomer and a fluorine-containing resin is formed on at least one surface of the transparent substrate film, and the moisture content is 1 It is a protective film characterized by being 4 mass% to 4.0 mass%.
<2> The protective film according to <1>, which is long and wound in a roll shape.
<3> The absolute value of the surface potential is 10 kV or less when the film is drawn out at a speed of 5 m / min for 5 m or more from a rolled state in an environment of 25 ° C. and 50% RH. It is a protective film.
<4> The protective film according to any one of <1> to <3>, wherein the width is 0.2 m to 3 m and the length is 20 to 10,000 m.
<5> The covering layer is the protective film according to any one of <1> to <4>, including a material in which the charged column is more negative than polyethylene.
<6> The protective film according to any one of <1> to <5>, wherein the chlorine-containing vinyl monomer is vinylidene chloride.
<7> The protective film according to any one of <1> to <6>, wherein the transparent base film contains cellulose acylate.
<8> The protective film according to any one of <1> to <7>, wherein moisture permeability at 60 ° C. and 95% RH is 500 g / m ² · day or less.
<9> The protection according to any one of <1> to <8>, wherein the centerline average roughness Ra of the surface of the coating layer and the centerline average roughness Ra of the opposite surface are 0.08 μm or less. It is a film.
<10> The surface electrical resistance value of the surface of the coating layer and the surface electrical resistance value of the opposite surface are 1.0 × 10 ¹² Ω / □ or more, and any one of <1> to <9> It is a protective film of description.
<11> A coating layer forming step of forming one or more coating layers on the transparent substrate film, and a moisture content of the protective film forming the laminate by forming the coating layer on the transparent substrate film is 1. In the manufacturing method of the protective film characterized by including the moisture content adjustment process which adjusts a moisture content so that it may become 0.5 mass%-4.0 mass%, and the winding-up process which winds up the said transparent base film. is there.
<12> The method for producing a protective film according to <11>, wherein the moisture content adjusting step includes a step of adjusting the humidity for 10 seconds or more in an atmosphere of 25 ° C. and 55% RH or more while conveying the protective film.
<13> The method for producing a protective film according to any one of <11> to <12>, wherein the coating layer forming step includes a drying step of exposing the protective film to a temperature of 50 ° C. or higher for 20 seconds or longer.
<14> The method for producing a protective film according to any one of <11> to <13>, wherein the coating layer forming step continuously forms the coating layer on the transparent substrate film at a conveyance speed of 10 m / min or more. It is.
<15> The method for producing a protective film according to any one of <11> to <14>, further including a transporting step of transporting the protective film while removing static electricity after the coating layer forming step.
<16> A protective film produced by the method for producing a protective film according to any one of <11> to <15>.
<17> A polarizing plate comprising a polarizer and the protective film according to any one of <1> to <10> and <16> provided on at least one surface of the polarizer. It is.
<18> A liquid crystal display device comprising the polarizing plate according to <17>.

  According to the present invention, there is provided a protective film that reduces defects due to dust being easily attached due to peeling electrification and the like, a manufacturing method thereof, a polarizing plate using the protective film, and a liquid crystal display device using the polarizing plate. Can be provided.

  Hereinafter, the protective film of the present invention, the manufacturing method thereof, the polarizing plate, and the liquid crystal display device will be described in detail.

(Protective film)
The protective film of this invention has a transparent base film and the coating layer laminated | stacked on this transparent base film at least one or more layers.

<Physical properties of protective film>
<< moisture content >>
The moisture content of the protective film of the present invention is preferably 1.4 to 4.0 mass%, more preferably 1.7 to 3.6 mass%, and more preferably 1.9 to 3.3 mass%. Further preferred is 2.1 to 3.0% by mass. By controlling the water content of the protective film within the above range, charging and curling can be made within a preferable range. The moisture content of the protective film can be measured by the Karl Fischer method or the like.
Here, when the transparent substrate film is a cellulose acylate film, the protective film of the present invention has a moisture content of approximately 4.0% by mass when equilibrated at 25 ° C. and 100% RH. The upper limit of the rate is determined here.

<< Surface potential >>
The protective film of the present invention needs to have an absolute value of the surface potential of the roll of 10 kV or less after the film is drawn 5 m from the roll form in an atmosphere of 50% RH at 25 ° C. The absolute value of the surface potential of the roll is preferably 5 kV or less, and more preferably 3 kV or less.
At this time, the surface potential of the roll can be measured by a commercially available surface potential meter. The method for measuring the surface potential is described in, for example, p173 to p178 in “Static Fundamentals and Antistatic Technology” (Murata Yuji: Nikkan Kogyo Shimbun: 1998).

  The protective film on which the coating layer of the present invention is laminated is preferably in the form of a roll. In that case, the width of the film is preferably 0.2 to 3 m, and more preferably 0.5 to 2.5 m. 1 to 2 m is more preferable. The length of the film is preferably 20 to 10,000 m, more preferably 50 to 7,000 m, and still more preferably 200 to 5000 m.

<< Moisture permeability >>
The protective film of the present invention preferably has low moisture permeability so as not to allow moisture to escape from the bulk roll after winding it after containing sufficient moisture for preventing peeling electrification, The water vapor transmission rate at 95 ° C. and 95% RH is preferably 500 g / m ² · day or less, more preferably 300 g / m ² · day or less, and particularly preferably 200 g / m ² · day or less.
The moisture permeability of the protective film is 70 mm ² of the film sample, conditioned according to JIS Z-0208, using a moisture permeable cup containing a moisture absorbent at 60 ° C. and 95% RH for 24 hours. It can obtain | require by calculating the moisture content per unit area from mass difference of this. At this time, correction of moisture permeability in a blank cup without a hygroscopic agent is not performed.
In the above measuring method, a commercially available cellulose acylate film shows a value of about 800 to 1,500 g / m ² · day.

<< Surface roughness >>
When the surface (back surface) of the protective film has an uneven shape, peeling charge on the surface and back surface of the protective film, or peeling charge between the protective film and the surface of the metal pass roll hardly occurs.
However, the uneven shape causes problems such as a decrease in transmittance.
For these reasons, it is preferable that the front and back surfaces of the protective film of the present invention are substantially smooth. Specifically, as a measure of the smoothness of the surface of the protective film, the center line average roughness Ra of the surface of the protective film is preferably 0.08 μm or less, more preferably 0.07 μm or less, 0 More preferably, it is 0.06 μm or less.
Here, the center line average roughness Ra is measured by a method according to JIS-K-7194.

<< Surface resistance value >>
If the surface resistance of the protective film is low and the surface conductivity is high, the charge leakage rate is fast, so that even if it is charged once, the charge is likely to be dispersed and the influence of charging is less likely to occur.
Therefore, a method of preventing charging by reducing the surface resistance by adding an antistatic agent such as conductive fine particles to the coating layer is conceivable.
However, when the coating layer is a low moisture permeable layer, the inclusion of conductive fine particles causes problems such as an increase in moisture permeability. The present invention preferably does not contain an antistatic agent in order to remove the adverse effects of such an antistatic agent.
Therefore, the protective film of the present invention preferably has a surface electrical resistance value (hereinafter sometimes referred to as a surface resistance value) of 1.0 × 10 ¹² Ω / □ or more on both sides, and 1.0 × 10 6. It is more preferably ¹³ Ω / □ or more, and particularly preferably 1.0 × 10 ¹⁴ Ω / □ or more.

<Configuration of protective film>
<< Transparent substrate film >>
The light transmittance of the transparent substrate film is preferably 80% or more, and more preferably 86% or more. The haze of the transparent substrate film is preferably 2.0% or less, and more preferably 1.0% or less. The refractive index of the transparent plastic substrate is preferably 1.4 to 1.7.

  Examples of the material of the transparent substrate film include cellulose ester, polyamide, polycarbonate, polyester (for example, polyethylene terephthalate, polyethylene naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, polyethylene-1,2-diphenoxyethane- 4,4′-dicarboxylate, polybutylene terephthalate, etc.), polystyrene (eg, syndiotactic polystyrene), polyolefin (eg, polypropylene, polyethylene, polymethylpentene, etc.), polysulfone, polyethersulfone, polyarylate, polyetherimide , Polymethyl methacrylate and polyether ketone. Cellulose ester, polycarbonate, polyethylene terephthalate and polyethylene naphthalate are preferred.

[Cellulose acylate film]
The transparent substrate film of the present invention preferably has a high water content, and a cellulose acylate film is preferred. Cellulose acylate is produced by esterifying cellulose. As the cellulose before esterification, linter, kenaf and pulp are used after purification.

-Cellulose acylate-
In the present invention, cellulose acylate means a fatty acid ester of cellulose, preferably a lower fatty acid ester, and more preferably a fatty acid ester film of cellulose.

  The lower fatty acid means a fatty acid having 6 or less carbon atoms. A cellulose acylate having 2 to 4 carbon atoms is preferred, and cellulose acetate is particularly preferred. It is also preferable to use a mixed fatty acid ester such as cellulose acetate propionate or cellulose acetate butyrate.

The viscosity average degree of polymerization (Dp) of cellulose acylate is preferably 250 or more, and more preferably 290 or more.
In addition, the cellulose acylate preferably has a narrow molecular weight distribution based on Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and particularly preferably 1.0 to 2.0. preferable.

As the transparent substrate film, it is preferable to use cellulose acylate having an acetylation degree of 55.0 to 62.5%. The acetylation degree is more preferably 57.0 to 62.0%, and particularly preferably 59.0 to 61.5%.
Here, the degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation is determined by measurement and calculation of the degree of acylation in ASTM: D-817-91 (testing method for cellulose acylate, etc.).

  In cellulose acylate, the hydroxyl groups at the 2-position, 3-position and 6-position of cellulose are not evenly substituted, but the substitution degree at the 6-position tends to be small. In the cellulose acylate used in the present invention, it is preferable that the degree of substitution at the 6-position of cellulose is the same or greater than that at the 2- and 3-positions. The ratio of the substitution degree at the 6-position to the total substitution degree at the 2-position, the 3-position, and the 6-position is preferably 30 to 40%, more preferably 31 to 40%, and more preferably 32 to 40%. It is particularly preferred.

Various additions to the transparent base film to adjust the mechanical properties (film strength, curl, dimensional stability, slipperiness, etc.) and durability (wet heat resistance, weather resistance, etc.) of the film An agent may be used. For example, plasticizers (phosphoric acid esters, phthalic acid esters, esters of polyols and fatty acids, etc.), UV inhibitors (eg, hydroxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, cyanoacrylate compounds) Etc.), deterioration inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines, etc.), fine particles (eg, SiO ₂ , Al ₂ O ₃ , TiO _2). , BaSO ₄ , CaCO ₃ , MgCO ₃ , talc, kaolin, etc.), release agents, antistatic agents, infrared absorbers, and the like.

  These details are disclosed in the Invention Association Public Technique No. 2001-1745 (issued March 15, 2001, Invention Association), p. Materials described in detail in 17-22 are preferably used.

  Moreover, it is preferable that it is 0.01-20 mass% with respect to a transparent support body, and, as for the usage-amount of the said additive, it is still more preferable that it is 0.05-10 mass%.

<< Coating layer >>
The thickness of the coating layer is preferably 0.01 to 10 μm. By controlling the thickness of the coating layer within this range, the function of the coating layer can be sufficiently exerted, while the problem of curling hardly occurs. In addition, since the appropriate thickness of a coating layer changes with kinds of coating layer, it demonstrates with a raw material sequentially.

[Charged column]
The material contained in the coating layer is largely different from the base film in the charge train, and is preferably biased to the negative side with respect to the base film (easily charged negatively). More preferably, the charged column is biased to the negative side.
As for the charged column, many types of materials have been reported. For example, “Plastic antistatic” p30-p31 Tachibana Takashige, Nikkan Kogyo Shimbun, May 31, 1967, first edition issued ” it can.
In addition, as a method for measuring the charge train, for example, the charge sequence of two materials from the sign of charge when different materials are contact-charged at room temperature in a low humidity atmosphere (for example, 25 ° C. and 10% RH). (Charged column) can be known. The sign of charging at this time can be measured by using a commercially available potential measuring device (for example, STATIRON DX, manufactured by Shishido electrostatic Co., Ltd.).

[Function of coating layer]
The function of the coating layer is not particularly limited as long as it is a layer that can add a new function by being laminated on a transparent substrate film or can enhance a conventional function, and is appropriately selected according to the purpose. Is done.
When the protective film is used as a protective film for a polarizing plate, the coating layer is preferably an optically anisotropic layer, an antireflection layer, or a low moisture permeable layer. More preferably, it is a low moisture-permeable layer. In the case of a low moisture permeable layer, once moisture is contained in the roll film laminated with the coating layer as described above, even if the protective film is stored under low humidity conditions, it is difficult for moisture to escape to the outside of the roll. Preventive properties can be maintained.

[Coating layer forming material]
As a specific material for forming the coating layer, a chlorine-containing compound or a fluorine-containing compound is preferable from the viewpoint of the charge train and usefulness. Such a material has a negatively charged column and easily causes a problem of peeling electrification with the plastic base film, and thus has a better effect.

[Low moisture permeability layer]
The coating layer formed from a chlorine-containing compound is preferably used as a low moisture-permeable layer that is a coating layer aimed at low moisture permeability. In this case, the coating layer is preferably a resin containing a repeating unit derived from a chlorine-containing vinyl monomer. Examples of the chlorine-containing monomer generally include vinyl chloride and vinylidene chloride. Among these, vinylidene chloride is particularly preferable. The chlorine-containing monomer can be obtained by copolymerizing these vinyl chloride or vinylidene chloride monomers with a monomer copolymerizable therewith.

-Monomer copolymerizable with chlorine-containing vinyl monomer-
Examples of the copolymerizable monomer include olefins, styrenes, acrylic acid esters, methacrylic acid esters, acrylamides, methacrylamides, itaconic acid diesters, maleic acid esters, fumaric acid diesters, N -Monomers selected from alkylmaleimides, maleic anhydride, acrylonitrile, vinyl ethers, vinyl esters, vinyl ketones, vinyl heterocycles, glycidyl esters, unsaturated nitriles, unsaturated carboxylic acids, etc. .

Examples of the olefins include dicyclopentadiene, ethylene, propylene, 1-butene, 1-pentene, isoprene, chloroprene, butadiene, and 2,3-dimethylbutadiene.
Examples of styrenes include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, isopropyl styrene, chloromethyl styrene, methoxy styrene, acetoxy styrene, chloro styrene, dichloro styrene, bromo styrene, trifluoromethyl styrene, vinyl. And benzoic acid methyl ester.

Specific examples of the acrylic esters and methacrylic esters include the following.
Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, t-octyl acrylate, 2-methoxyethyl acrylate, 2-butoxyethyl acrylate, 2-phenoxyethyl acrylate, chloroethyl acrylate, Cyanoethyl acrylate, dimethylaminoethyl acrylate, benzyl acrylate, methoxybenzyl acrylate, furfuryl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, oct Methacrylate, benzyl methacrylate, cyanoacetoxyethyl methacrylate, chlorobenzyl methacrylate, sulfopropyl methacrylate, N-ethyl-N-phenylaminoethyl methacrylate, 2-methoxyethyl methacrylate, 2- (3-phenylpropyloxy) ethyl methacrylate, dimethylamino Phenoxyethyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, phenyl methacrylate, cresyl methacrylate, naphthyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, 3 -Chloro-2-hydro Cypropyl methacrylate, 2,2-dimethylhydroxypropyl acrylate, 5-hydroxypentyl acrylate, diethylene glycol monoacrylate, trimethylolpropane monoacrylate, pentaerythritol monoacrylate, 2,2-dimethyl-3-hydroxypropyl methacrylate, 5-hydroxypropyl Methacrylate, diethylene glycol monomethacrylate, trimethylolpropane monomethacrylate, pentaerythritol monomethacrylate.

Specific examples of vinyl ethers include the following.
Methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, ethyl hexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl ether, dimethylaminoethyl Vinyl ether, diethylaminoethyl vinyl ether, butylaminoethyl vinyl ether, benzyl vinyl ether, tetrahydrofurfuryl vinyl ether, vinyl phenyl ether, vinyl tolyl ether, vinyl chlorophenyl ether, vinyl-2,4-dichlorophenyl ether, vinyl naphthyl ether, vinyl anthranyl ether .

  Specific examples of the vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl dimethyl propionate, vinyl ethyl butyrate, vinyl valerate, vinyl caproate, vinyl chloroacetate. , Vinyl dichloroacetate, vinyl methoxyacetate, vinyl butoxy acetoacetate, vinyl phenyl acetate, vinyl acetoacetate, vinyl lactate, vinyl-β-phenyl butyrate, vinyl cyclohexyl carboxylate, vinyl benzoate, vinyl salicylate, vinyl chlorobenzoate , Vinyl tetrachlorobenzoate, and vinyl naphthoate.

  Examples of the acrylamides include acrylamide, methyl acrylamide, ethyl acrylamide, propyl acrylamide, butyl acrylamide, t-butyl acrylamide, cyclohexyl acrylamide, benzyl acrylamide, hydroxymethyl acrylamide, methoxyethyl acrylamide, dimethylaminoethyl acrylamide, phenyl acrylamide, dimethyl acrylamide, Examples include diethyl acrylamide, β-cyanoethyl acrylamide, and N- (2-acetoacetoxyethyl) acrylamide.

  Examples of the methacrylamides include methacrylamide, methyl methacrylamide, ethyl methacrylamide, propyl methacrylamide, butyl methacrylamide, t-butyl methacrylamide, cyclohexyl methacrylamide, benzyl methacrylamide, hydroxymethyl methacrylamide, methoxyethyl methacrylamide. Examples include amide, dimethylaminoethyl methacrylamide, phenyl methacrylamide, dimethyl methacrylamide, diethyl methacrylamide, β-cyanoethyl methacrylamide, N- (2-acetoacetoxyethyl) methacrylamide.

  Further, acrylamides having a hydroxyl group can also be used, and examples thereof include N-hydroxymethyl-N- (1,1-dimethyl-3-oxo-butyl) acrylamide, N-methylolacrylamide, and N-methylol. Examples include methacrylamide, N-ethyl-N-methylol acrylamide, N, N-dimethylol acrylamide, N-ethanol acrylamide, N-propanol acrylamide, N-methylol acrylamide, and the like.

  Examples of the itaconic acid diesters include dimethyl itaconate, diethyl itaconate, and dibutyl itaconate. Examples of maleic acid diesters include diethyl maleate, dimethyl maleate, and dibutyl maleate. Examples of the fumaric acid diesters include diethyl fumarate, dimethyl fumarate, dibutyl fumarate, and the like.

  Examples of the vinyl ketones include methyl vinyl ketone, phenyl vinyl ketone, and methoxyethyl vinyl ketone. Examples of the vinyl heterocyclic compound include vinyl pyridine, N-vinyl imidazole, N-vinyl oxazolidone, N-vinyl triazole, and N-vinyl pyrrolidone. Examples of glycidyl esters include glycidyl acrylate and glycidyl methacrylate. Examples of unsaturated nitriles include acrylonitrile and methacrylonitrile. Examples of N-alkylmaleimides include N-ethylmaleimide and N-butylmaleimide.

  Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and the like, and further anhydrides such as fumaric acid, itaconic acid and maleic acid. Two or more kinds of these copolymerizable monomers may be used.

  Examples of the chlorine-containing polymer in the present invention include JP-A-53-58553, JP-A-55-43185, JP-A-57-139109, JP-A-57-139136, JP-A-60. -235818, JP-A 61-108650, JP-A 62-256871, JP-A 62-280207, JP-A 63-256665, and the like.

  The proportion of the chlorine-containing vinyl monomer in the chlorine-containing polymer is preferably from 50 to 99 mass%, more preferably from 60 to 98 mass%, still more preferably from 70 to 97 mass%. If the ratio of the chlorine-containing vinyl monomer is 50% or more, problems such as deterioration of moisture permeability will not occur, and if it is 99% or less, solubility in various solvents is obtained, which is preferable. .

Examples of the chlorine-containing polymer include “Saran Resin R241C”, “Saran Resin F216”, “Saran Resin R204”, “Saran Latex L502”, “Saran Latex L529B”, “Saran Latex L536B”, “Saran Latex L544D”, “ Saran Latex L549B, Saran Latex L551B, Saran Latex L557, Saran Latex L561A, Saran Latex L116A, Saran Latex L411A, Saran Latex L120, Saran Latex L123D, Saran Latex L106C "," Saran Latex L131A "," Saran Latex L111 "," Saran Latex L232A "," Saran Latex L321B "(above, Asahi Kasei Made Karuzu Co., Ltd.) and the like.
Among these, Saran Resin F216 is more preferably used because it is soluble in ketone solvents (such as methyl ethyl ketone and cyclohexanone).
In addition, since Saran Resin R204 has high crystallinity, the moisture permeability of the coating layer can be lowered, and it is difficult to dissolve in a solvent when a layer having a hard coat property described later is applied, and a layer having a hard coat property. It is more preferably used because it is difficult to make a mixed region with.

When the coating layer is a low moisture permeable layer, the thickness is preferably 1 to 10 μm, more preferably 1.2 to 7 μm, and still more preferably 1.5 to 5 μm. If the thickness of the coating layer is less than or equal to the upper limit value, it is preferable because it has excellent low moisture permeability and does not cause adverse effects such as an increase in curling and deterioration of the brittleness of the coating layer. If the curl becomes too large, it will hinder subsequent processes for producing a polarizing plate, for example, a bonding process with a polarizing film and handling. Further, it is not preferable that the curl remains not only in the manufacturing process but also as the polarizing plate, which causes display unevenness in the LCD.
Accordingly, the upper limit of the thickness of the coating layer is preferably within the above range in order to reduce the curl to such an extent that it does not occur or is practically unproblematic.
Moreover, it is preferable if the thickness of the coating layer is equal to or less than the above upper limit value because there are no adverse effects such as formation of a brittle film or easy coloring. On the other hand, the lower limit of the thickness of the coating layer is defined as a range that is more preferable than moisture resistance, and the effect of the present invention can be sufficiently exhibited by setting the above range. The coating layer is composed of at least one layer, and may be laminated in two or more layers.

  When the coating layer is a low moisture-permeable layer, the haze is preferably 5% or less, more preferably 3% or less, and still more preferably 1% or less. The ratio between the surface haze and the internal haze may be arbitrary, but the surface haze is particularly preferably 1% or less.

The coating layer formed from the fluorine-containing compound is preferably a low refractive index layer formed from a fluorine-containing binder compound and used as an antireflection layer.
The low refractive index layer may be directly laminated on the base film, but is preferably laminated via a hard coat layer. Further, the antireflection layer may have a multilayer structure. In this case, a medium refractive index layer, a high refractive index layer, and the like are laminated. Furthermore, it is also a preferable aspect to provide a low moisture permeability layer between the hard coat layer and the base film.

Examples of preferred layer configurations are listed below, but are not limited to the following layer configurations.
Base film / Low refractive index layer Base film / Hard coat layer / Low refractive index layer Base film / Hard coat layer / High refractive index layer / Low refractive index layer Base film / Hard coat layer / Medium refractive index layer / High Refractive Index Layer / Low Refractive Index Layer In addition, providing a low moisture permeable layer between the base film and the hard coat layer is one of the preferred embodiments because the antistatic property can be maintained.

[Low refractive index layer]

When the coating layer is a low refractive index layer, the thickness of the coating layer is preferably 0.03 to 1 μm, more preferably 0.05 to 0.5 μm, and 0.07 to 0.2 μm. More preferably. By controlling within this range, moisture permeability and reflectance can be appropriately controlled.
When the coating layer is a low refractive index layer, the refractive index is preferably 1.20 to 1.49, more preferably 1.30 to 1.44. Furthermore, the low refractive index layer preferably satisfies the following formula (A) from the viewpoint of reducing the reflectance.

( _M / 4) λ × 0.7 <n _L d _L <(m / 4) × 1.3... Formula (A)

In the above formula (A), m is a positive odd number, n _L is the refractive index of the low refractive index layer, and d _L is the film thickness (nm) of the low refractive index layer. Further, λ is a wavelength, which is a value in the range of 500 to 550 nm.

The low refractive index layer is preferably a fluorine-containing resin that is crosslinked by heat or ionizing radiation (hereinafter sometimes referred to as “fluorine-containing resin before crosslinking”).
The material for forming the fluorine-containing resin that is cross-linked by heat or ionizing radiation will be described below.
The low refractive index layer is, for example, a cured film formed by applying, drying and curing a curable composition containing a fluorine-containing polymer as a main component.

-Fluoropolymer for low refractive index layer-
The fluorine-containing polymer used in the low refractive index layer preferably contains fluorine atoms in the range of 30 to 80% by mass, and is preferably a fluorine-containing polymer containing a crosslinkable or polymerizable functional group. .
For example, in addition to hydrolysates and dehydration condensates of perfluoroalkyl group-containing silane compounds [for example, (heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane], crosslink reactivity with fluorine-containing monomer units Examples thereof include fluorine-containing copolymers having units as constituent units. In the case of a fluorinated copolymer, the main chain preferably consists of only carbon atoms. That is, it is preferable that the main chain skeleton does not have an oxygen atom or a nitrogen atom.

  Specific examples of the fluorine-containing monomer unit include, for example, fluoroolefins (for example, fluoroethylene, vinylidene fluoride, tetrafluoroethylene, perfluorooctylethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3- Dioxoles, etc.), (meth) acrylic acid partial or fully fluorinated alkyl ester derivatives (for example, Biscoat 6FM (Osaka Organic Chemical) or M-2020 (Daikin)), fully or partially fluorinated vinyl ethers, etc. However, perfluoroolefins are preferred, and hexafluoropropylene is particularly preferred from the viewpoints of refractive index, solubility, transparency, availability, and the like.

  The curable composition preferably contains (A) the fluoropolymer, (B) inorganic fine particles, and (C) an organosilane compound described later.

-Other substances contained in the curable composition for the low refractive index layer-
The curable composition contains the above-mentioned (A) fluorine-containing polymer, (B) inorganic fine particles, and (C) an organosilane compound, if necessary, various additives and a radical polymerization initiator and a cationic polymerization initiator described later. It is prepared by adding them and further dissolving them in a suitable solvent. At this time, the concentration of the solid content is appropriately selected according to the use, but is generally about 0.01 to 60% by mass, preferably 0.5 to 50% by mass, particularly preferably 1% to 20% by mass. %.

--- Coating layer forming coating composition--
The coating layer is preferably formed from a coating solution composition containing an organic solvent. A drying step for evaporating the organic solvent is required, and at the same time, moisture is evaporated to easily cause a charging problem, and the present invention is effective.

(Method for producing protective film)
Next, the manufacturing method of the protective film of this invention is demonstrated.
The method for producing a protective film of the present invention includes a coating layer forming step of forming a coating layer on the transparent substrate film, and a winding step of winding up the transparent substrate film on which the coating layer is formed. The forming step includes a moisture content adjusting step for increasing the moisture content of the protective film that has been lowered by the drying step of drying the coating layer. In addition, you may perform the said winding-up process and the said moisture content adjustment process simultaneously.

<Coating layer forming step>
The coating layer forming step is a step of forming a coating layer on the transparent substrate film. For example, the cellulose acylate film is formed by a coating method such as a direct gravure method, a reverse gravure method, a die coating method, or a comma coating method. It is the process of apply | coating the coating liquid for coating layers on transparent substrate films, such as forming into a film.
At the time of film formation, in order to optimize the viscosity characteristics of the liquid with respect to the coating apparatus, a method of adjusting the liquid viscosity of the coating liquid by adding a viscosity modifier such as a thickener to the coating liquid is used. May be.

<< Drying process >>
In the coating layer forming step, in order to evaporate the organic solvent in the coating layer coating solution and further improve the moisture resistance and water resistance of the coating layer, the coating layer coating solution is formed on the transparent substrate film. After coating, it is preferable to provide a drying step of heat-treating the coating layer coating solution.
This heat treatment is preferably exposed to a temperature atmosphere of 50 ° C. or higher for 20 seconds or longer.
The heat treatment temperature is more preferably 70 ° C. or higher, and still more preferably 90 ° C. or higher. The heat treatment time is more preferably 25 seconds or more and 3 minutes or less, and further preferably 30 seconds or more and 2 minutes or less from the viewpoint of productivity and water resistance.

  In addition, the step of exposing a sample such as a protective film to a high temperature as in this drying step is not limited to the purpose of evaporating the organic solvent in the coating layer coating solution, for example, in order to align the liquid crystal compound. It is also used in the process of aging.

<Winding process>
The protective film of the present invention is preferably wound up at a moisture content of 1.4 to 4.0% by mass or more from the viewpoint of antistatic. The moisture content of the protective film can be measured by the Karl Fischer method or the like.

<Moisture content adjustment process>
In order to wind up the roll-shaped protective film with a moisture content of 1% by mass or more as described above, the atmosphere of the portion where the roll-shaped protective film is wound is preferably an absolute moisture content of 25 ° C. and 55% RH, It is more preferable to wind in an atmosphere having an absolute moisture content of 25 ° C. and 60% RH or more, and it is more preferable to wind in an atmosphere having an absolute moisture content of 25 ° C. and 65% RH or more.
The absolute moisture content referred to here means the amount of water (g / liter) contained in a unit volume of air, and the atmosphere of a winding portion is not less than a specific temperature and humidity (for example, 25 ° C. and 55% RH). The absolute water content means that the amount of water contained in the unit volume of air is larger than the amount of water contained in a unit volume contained in a specific temperature and humidity (for example, 25 ° C. and 55% RH).

  In order to obtain a moisture content of 1.4% by mass or more by short-term humidity conditioning, it is preferable to condition the humidity under the condition that the equilibrium moisture content is 1.7% by mass or more. The condition for the equilibrium moisture content of the cellulose acylate film at room temperature to be 1.7% by mass is approximately 55% RH at 25 ° C., and the equilibrium moisture content increases with increasing humidity. Therefore, the atmosphere during winding is preferably as described above.

In order to wind up the roll-shaped protective film with a moisture content of 1% by mass or more, after drying the organic solvent in the coating solution, the humidity is adjusted for 10 seconds or more in an atmosphere having an absolute moisture content of 25 ° C. and 55% RH or more. It is more preferable to adjust the humidity in an atmosphere having an absolute moisture content of 25 ° C. and 60% RH or more, and it is more preferable to adjust the humidity in an atmosphere having an absolute moisture content of 25 ° C. and 65% RH.
The humidity control time is more preferably 20 seconds or longer, and further preferably 30 seconds or longer.

  Humidity adjustment in a high-humidity atmosphere as described above may be performed by winding the coating liquid once after drying, feeding it again, and adjusting and winding the humidity. Then, winding is preferable from the viewpoint of productivity.

In order to suppress the absolute value of the surface potential of the roll-shaped protective film when the roll-shaped protective film of the present invention is pulled out by 5 m, the absolute value of the surface potential of the roll-shaped protective film at the time of winding is suppressed to a low value preferable.
The absolute value of the surface potential of the roll-shaped protective film during winding is preferably 5 kV or less, more preferably 3 kV or less, and even more preferably 2 kV or less.

  In order to keep the absolute value of the surface potential of the roll-shaped protective film low during winding, in addition to winding after increasing the water content of the roll-shaped protective film, It is also a preferable aspect to install it near the picking device.

<Static elimination process>
As an antistatic measure for the roll-shaped protective film, in addition to the above-described method for increasing the water content of the roll-shaped protective film, it is also preferable to use static elimination from the roll-shaped protective film being conveyed at the time of coating layer formation. is there.
In this case, it is preferable to remove static electricity during transportation by installing a static eliminating device. In particular, when the charge train of the coating layer is biased to the negative side, peeling charge may occur when the coating layer comes into contact with the metal pass roll, and the charge removal for such charging is performed by laminating the coating layer, After the coating layer comes into contact with the metal pass roll, it is preferable to carry out static elimination on both the coating layer surface and the back surface in this order.
Charging of the protective film of the present invention occurs on the surface of the coating layer, but if it is attempted to remove electricity using an ionizer first from the back surface, the back surface may be newly charged.

The static eliminator for removing static electricity from the protective film being transported may be any device that can remove or reduce static electricity from the protective film, and examples thereof include a static eliminator bar, static eliminating yarn, or an ion blow type static eliminator.
Among these, an ion blowing type static eliminator is preferable. The ion blow type static eliminator is an apparatus having a structure in which a gas is ionized by corona discharge, flame plasma, ultraviolet rays, a heated metal body, a radioisotope, and the like to generate ions, and the generated ions are sprayed on an object.
The static eliminator using corona discharge is composed of an electrode unit with a built-in high-voltage transformer, a blowing unit, a gas supply unit, a controller, and the like. The electrode unit generates corona discharge, ionizes the gas, and blows out the unit. The ionized gas is sprayed onto the object.
Usually, air is used as the gas to be supplied. However, by introducing an inert gas and setting the oxygen concentration in the gas to 10% by volume or less, an effect of improving safety against dangerous substances can be obtained. preferable.
The type of the inert gas is not particularly limited, but may be a gas such as nitrogen, carbon dioxide, or argon. Nitrogen and carbon dioxide are preferable from the viewpoint of cost. It can be implemented by providing a flow meter in the gas supply unit and supplying these gases.

(Polarizer)
The polarizing plate is composed of a polarizer (hereinafter sometimes referred to as a polarizing film) and two protective films disposed on both sides of the polarizer. At least one protective film of the protective film is the protective film of the present invention described above. Note that a normal cellulose acetate film may be used as the other protective film.
Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film.

(Liquid crystal display device)
The liquid crystal display device of the present invention includes at least a liquid crystal cell and the polarizing plate provided in at least one of the liquid crystal cells. The liquid crystal display device of the present invention may be any of a reflection type, a semi-transmission type, a transmission type liquid crystal display device and the like.
Further, the liquid crystal display device of the present invention may be provided with members such as a retardation plate, a reflective layer, a light diffusion layer, a backlight, a front light, a light control film, a light guide plate, a prism sheet, and a color filter as necessary. Good.
The liquid crystal cell used in the liquid crystal display device of the present invention is not particularly limited, and is a general liquid crystal cell such as one appropriately selected according to the purpose and having a liquid crystal layer sandwiched between a pair of transparent substrates having electrodes. Can be used.
In addition, the transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate having the property of aligning the liquid crystal itself, a substrate itself lacking alignment ability, but a transparent substrate provided with an alignment film having the property of aligning liquid crystal, etc. Can also be used.
Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. Usually, it can be provided on the surface of the transparent substrate in contact with the liquid crystal layer, and when a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.
The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystalline compounds, high-molecular liquid crystalline compounds, and mixtures thereof that can constitute various liquid crystal cells.
Moreover, you may add a pigment | dye, a chiral agent, a non-liquid crystalline compound, etc. in the range which does not impair liquid crystallinity to these.

In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later.
As the liquid crystal cell system, a TN (Twisted Nematic) system, a STN (Super Twisted Nematic) system, an ECB (Electrically Controlled Birefringence) system, an IPS (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, a VA (In-Plane Switching) system, Alignment), PVA (Patterned Vertical Alignment), OCB (Optically Compensated Birefringence), HAN (Hybrid Aligned Nematic Asymmetric), ASM l) method, a halftone gray scale method, the domain division method or a ferroelectric liquid crystal, various methods such as a display system using an antiferroelectric liquid crystal and the like.
The driving method of the liquid crystal cell is not particularly limited, and a passive matrix method used for STN-LCD and the like, and an active matrix method using an active electrode such as a TFT (Thin Film Transistor) electrode and a TFD (Thin Film Diode) electrode, Any driving method such as a plasma addressing method may be used. Further, a field sequential method that does not use a color filter may be used.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the embodiments of the present invention are not limited to these examples.

(Example 1)
A protective film in which the transparent substrate film is a cellulose acylate film and the coating layer is a low moisture-permeable layer containing vinylidene chloride is shown as Example 1 of the present invention.

<Preparation of coating solution for low moisture permeable layer>
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a coating solution for a coating layer.

[Coating solution composition for coating layer (low moisture-permeable layer)]
-Chlorine-containing polymer: R204
{"Saran Resin R204" manufactured by Asahi Kasei Life & Living Co., Ltd.} 12 parts by mass, tetrahydrofuran 62 parts by mass, toluene 13 parts by mass
・ Methyl ethyl ketone 13 parts by mass

<Coating of coating layer (low moisture permeability layer)>
A commercially available cellulose acylate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd., width 1,340 mm, thickness 80 μm) is drawn out in the form of a roll as a transparent protective film, and the coating layer under the conditions of a conveyance speed of 30 m / min The coating solution for (low moisture permeable layer) was applied using a bar coater, dried at 100 ° C. for 1 minute, passed through a zone of 25% 65% atmosphere for 1 minute while being conveyed, and then 3,000 m Rolled up. The film thickness of the coating layer (low moisture permeability layer) at this time was 2.0 μm.

<Measurement of moisture content>
A protective film sample of 20 mm × 35 mm was measured by a Karl Fischer method using a moisture measuring device (CA-03, manufactured by Mitsubishi Chemical Corporation) and a sample drying apparatus (VA-05, manufactured by Mitsubishi Chemical Corporation).
Here, the moisture content of the bulk roll is determined by immediately sampling the outer circumference of the bulk roll after three rounds are discarded, enclosing it in a sample bottle, and the total water content contained in the sample bottle (water contained in the film and air) Amount) was measured by the Karl Fischer method to obtain a water content A.
Subsequently, the amount of water contained in the air enclosed in the sample bottle in the sampling environment is similarly measured to obtain the amount of water B, and the value obtained by subtracting the amount of water B from the amount of water A and dividing by the sample mass The moisture content of the bulk was used.
It was 2.0 mass% when the sample was extract | collected from the roll (bulk roll) after winding, and the moisture content of the protective film was measured. Table 3 shows the measurement results.

<Measurement of surface potential>
The wound roll (bulk roll) is conveyed to a room at 25 ° C. and 50%, and the surface potential at the center of the roll (bulk roll) after the film is pulled out by 5 m is measured with an electric potential meter (STATIRON DX, It was -0.5 kV. That is, the protective film of this example was substantially not charged at ± 0.5 kV or less. Table 3 shows the measurement results.

<Comparison of charged column with polyester>
The triboelectric charge with the polyester fabric was measured in accordance with the frictional band voltage measurement method specified in JIS L 1094 “Testing method for charging properties of woven fabrics and knitted fabrics”. At this time, as a friction cloth, polyester 8-2 specified in JIS L 0803 “attached white cloth for dyeing fastness test” is used as a friction cloth, the protective film of the present invention is used as a test piece, and the surface of the coating layer is triboelectrically charged. The sign was measured.
Since the coating layer of Example 1 was negatively charged, the charged column is on the negative side with respect to the polyester.

<Dust evaluation>
Film 5m drawn from the bulk roll 25 ° C. 50% condition, after 1 hour standing the bulk roll after measuring the surface potential is measured by visual observation the number of dust adhered to the roll, the number per 1 m ² The number of dust.

<Measurement of surface roughness>
When the surface roughness (centerline average roughness (Ra)) of the obtained protective film was measured according to JIS-B0601-2001, the centerline average roughness (Ra ) Was 0.03 μm, and the center line average roughness (Ra) of the opposite surface was 0.04 μm. That is, the center line average roughness (Ra) of Example 1 was 0.05 μm or less on both the surface of the protective film on the coating layer side and the surface on the opposite side.

<Measurement of surface electrical resistance>
About the said protective film, when the surface electrical resistance value was measured in the environment of 25 degreeC and 60% RH using the method according to JIS-K-7194, the surface electrical resistance value of the surface by the side of the coating layer in the said protective film Was 1.3 × 10 ¹⁴ Ω / □, and the surface electrical resistance value of the opposite surface was 6.3 × 10 ¹⁴ Ω / □. That is, the surface electrical resistance of the protective films of Examples 6 to 9 was 1.0 × 10 ¹⁴ Ω / □ or more on the surface on which the coating layer was laminated and the back surface on the opposite side.

(Examples 2 to 5)
In Example 1, the protective film of Examples 2-5 was produced like Example 1 except having changed the process conditions as shown in Table 2. About the produced protective films of Examples 2 to 5, as in Example 1, the surface potential, the moisture content, the surface roughness, and the surface electrical resistance value were measured, and in addition, dust was evaluated. Table 3 shows the measurement results and the evaluation results. In Table 3, “<−20 kV” described in the column “Surface potential (kV)” means that the sign of the surface potential is negative and the absolute value is greater than 20 kV.

(Comparative Examples 1-3)
In Example 1, as shown in Table 2, protective films of Comparative Examples 1 to 3 were produced in the same manner as in Example 1 except that the process conditions were changed so as to eliminate the humidity control process. About the produced protective film of Comparative Examples 1-3, it measured about surface potential, moisture content, surface roughness, and surface electrical resistance value similarly to Example 1, and also evaluated dust. Table 3 shows the measurement results and the evaluation results.

(Examples 6 to 9)
In Example 1, the moisture permeability was controlled in the same manner as in Example 1 except that the thickness (film thickness) of the coating layer (low moisture permeability layer) was changed as shown in Table 2. A protective film was prepared.
The protective films of Example 1 and Examples 6 to 9 produced above were subjected to surface potential measurement and dust evaluation immediately after production, and kept in a roll state in an environment of 25 ° C. and 30% RH. After storing for 1 month, the film was again pulled out in an atmosphere of 25 ° C. and 50% RH for 5 m, and the surface potential of the roll-shaped protective film was measured. Table 3 shows the measurement results.

<Measurement of moisture permeability>
Also, 70 mm ² of the protective film sample was conditioned and stored at 60 ° C. and 95% RH for 24 hours in accordance with JIS Z-0208 using a moisture permeable cup containing a hygroscopic agent. From this, the water content per unit area was calculated.

Using the same method as in Example 1, the surface of the coating layer side of the protective films of Examples 6 to 9 was compared with polyester, and the surface of the coating layer was negatively charged. The surface charge train was negative with respect to the polyester.
Moreover, when the centerline surface roughness Ra of the protective films of Examples 6 to 9 was measured in the same manner as in Example 1, the centerline average roughness (Ra) of the surface on the coating layer side in the protective film was The center line average roughness (Ra) of the opposite surface was 0.04 μm. That is, the centerline surface roughness Ra of the protective films of Examples 6 to 9 was 0.05 μm or less on both the surface on which the coating layer was laminated and the back surface on the opposite side.
On the other hand, when the surface electrical resistance values of the protective films of Examples 6 to 9 were measured in the same manner as in Example 1, the surface electrical resistance value of the surface on the coating layer side in the protective film was as described in Table 2. Met. That is, the surface electrical resistance of the protective films of Examples 6 to 9 was 1.0 × 10 ¹⁴ Ω / □ or more on the surface on which the coating layer was laminated and the back surface on the opposite side.

(Example 10)
<Preparation of protective film>
A protective film in which the transparent substrate film is a cellulose acylate film and the coating layer is a low refractive index layer formed of a fluorine-based binder is shown as Example 10 of the present invention.

<< Preparation of hard coat layer coating solution H >>
306 parts by mass of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (DPHA, manufactured by Nippon Kayaku Co., Ltd.) was dissolved in a mixed solvent of 16 parts by mass of methyl ethyl ketone and 220 parts by mass of cyclohexanone. After adding 7.5 parts by mass of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy) to the obtained solution and stirring until dissolved, 450 parts by mass of MEK-ST (average particle size of 10 to 20 nm, solid content) 30 wt% SiO ₂ sol methyl ethyl ketone dispersion (manufactured by Nissan Chemical Co., Ltd.) was added and stirred to obtain a mixture, which was filtered through a polypropylene filter (PPE-03) with a pore size of 3 μm for the hard coat layer. A coating solution H was prepared.

<< Synthesis of Perfluoroolefin Copolymer (1) >>
In an autoclave with a stirrer made of stainless steel having an internal volume of 100 ml, 40 ml of ethyl acetate, 14.7 g of hydroxyethyl vinyl ether, and 0.55 g of dilauroyl peroxide were charged, and the inside of the system was deaerated and replaced with nitrogen gas.
Furthermore, 25 g of hexafluoropropylene (HFP) was introduced into the autoclave and the temperature was raised to 65 ° C. The pressure when the temperature in the autoclave reached 65 ° C. was 0.53 Mpa (5.4 kg / cm ² ). The reaction was continued for 8 hours while maintaining the temperature, and when the pressure reached 0.31 MPa (3.2 kg / cm ² ), the heating was stopped and the mixture was allowed to cool.
Next, when the internal temperature decreased to room temperature, unreacted monomers were driven out, the autoclave was opened, and the reaction solution was taken out. The obtained reaction solution was poured into a large excess of hexane, and the polymer was precipitated by removing the solvent by decantation.
Further, this polymer was dissolved in a small amount of ethyl acetate and reprecipitated twice from hexane to completely remove the residual monomer. After drying, 28 g of polymer was obtained.
Next, 20 g of the polymer was dissolved in 100 ml of N, N-dimethylacetamide, and 11.4 g of acrylic acid chloride was added dropwise under ice cooling, followed by stirring at room temperature for 10 hours.
Thereafter, ethyl acetate was added to the reaction solution, washed with water, the organic layer was extracted and concentrated, and the resulting polymer was reprecipitated with hexane to obtain 19 g of a perfluoroolefin copolymer (1) represented by the following structural formula. It was. The resulting polymer had a refractive index of 1.421.

<< Preparation of Sol Solution a >>
A stirrer, a reactor equipped with a reflux condenser, 120 parts of methyl ethyl ketone, 100 parts of acryloyloxypropyltrimethoxysilane (KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.), 3 parts of diisopropoxyaluminum ethyl acetoacetate were added and mixed. Thereafter, 30 parts of ion-exchanged water was added and reacted at 60 ° C. for 4 hours, and then cooled to room temperature to obtain sol solution a.
The obtained sol liquid a had a mass average molecular weight of 1,600, and among the components higher than the oligomer component, the component of the compound having a molecular weight of 1,000 to 20,000 was 100%. Further, from the gas chromatography analysis, the raw material acryloyloxypropyltrimethoxysilane did not remain at all.

<< Preparation of coating liquid L for low refractive index layer >>
Perfluoroolefin copolymer (1) 15.2 g, hollow silica sol (refractive index 1.31, average particle size 60 nm, solid content concentration 20%) 2.1 g, sol liquid a 7.3 g, photopolymerization initiator (Irgacure 907 (trade name), Ciba Specialty Chemicals Co., Ltd. (0.76 g), methyl ethyl ketone (301 g), cyclohexanone (9.0 g) were added. After stirring, the mixture was filtered through a polypropylene filter with a pore size of 5 μm for a low refractive index layer. A coating liquid L was prepared. The refractive index of the layer formed by this coating solution was 1.40.

<< Coating of hard coat layer >>
A cellulose acylate film (Fujitac TD80UF, manufactured by FUJIFILM Corporation) with a thickness of 80 μm wound in a roll form is pulled out, and the die coat shown by the apparatus configuration described in JP-A-2003-211052 and the following coating conditions The coating liquid H for hard coat layer is applied by the method, dried at 30 ° C. for 15 seconds and 90 ° C. for 20 seconds, and further air-cooled metal halide lamp (made by Eye Graphics Co., Ltd.) of 160 W / cm under nitrogen purge. Then, the coating layer was cured by irradiating ultraviolet rays with an irradiation amount of 90 mJ / cm ² to form a 6 μm thick hard coat layer and wound up.

<< Coating of low refractive index layer >>
The cellulose acylate film coated with the hard coat layer is drawn out again, and the coating liquid L for the low refractive index layer is applied, dried at 120 ° C. for 150 seconds, and further dried at 140 ° C. for 8 minutes. Using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) of 240 W / cm in an atmosphere with an oxygen concentration of 0.1% by nitrogen purge, ultraviolet rays with an irradiation amount of 300 mJ / cm ² were irradiated, and a low thickness of 100 nm A refractive index layer was formed and passed through a zone having an atmosphere of 25 ° C. and 65% for 2 minutes while being conveyed, and then 3,000 m was wound up.

  A sample was taken from the roll after winding and the moisture content was measured by the method described later, and it was 2.0% by mass. Thereafter, the wound roll was conveyed to a room at 25 ° C. and 50%, and when the surface potential of the roll after the film was pulled out by 5 m was measured, it was ± 0.5 kV or less and there was no charge.

<Measurement of surface roughness>
When the center line average surface roughness Ra on the surface of the coating layer of the roll-shaped protective film of Example 10 and the back surface on the opposite side was measured in the same manner as in Example 1, the center line average surface roughness of the surface was measured. Ra was 0.02 μm, and the center line average surface roughness Ra of the back surface was 0.04 μm. Table 3 shows the measurement results.

<Measurement of surface electrical resistance>
When the surface of the coating layer (low refractive index layer) of the protective film of Example 10 was compared with the polyester and the charged column in the same manner as in Example 1, the coating layer was negatively charged and the surface of the coating layer was charged. The row was confirmed to be negative with respect to the polyester.
Moreover, the surface electrical resistance in the surface of the coating layer of the roll-shaped protective film of Example 10 and the back surface on the opposite side was measured in the same manner as in Example 1. Table 3 shows the measurement results.

<Evaluation of spots on hard coat layer>
In the step of producing the roll-shaped protective film of Example 10, a hard coat layer was laminated, a sample having a length of 50 cm was sampled from the wound film, and the side on which the hard coat layer was not laminated was black magic. After coating, the substrate was placed on a table so that the surface on which the hard coat layer was laminated, and illuminated from above with a three-wavelength fluorescent lamp, and interference spots were evaluated based on the following evaluation criteria. The evaluation results are shown in Table 3.

[Evaluation criteria]
○: Spots cannot be confirmed.
X: Spots can be confirmed.

<Change in surface potential over time>
About the roll-shaped protective film of Example 10, after evaluating surface potential and dust, after storing for 1 month in an environment of 25 ° C. and 30% RH, the protective film is again used in an atmosphere of 25 ° C. and 50% RH. Was pulled out for 5 m, and the surface potential of the roll-shaped protective film was measured. The results are shown in Table 3.

(Example 11)
<Preparation of protective film>
In the protective film of Example 10, the roll-shaped protective film of Example 11 was prepared in the same manner as in Example 10 except that the transparent substrate film was a roll-shaped protective film prepared in Example 1 instead of TD80UF. Produced. In addition, the hard-coat layer was laminated | stacked on the surface which laminated | stacked the coating layer of the protective film of Example 1. FIG.

<Measurement of surface roughness>
In the same manner as in Example 10, the centerline average surface roughness Ra on the surface of the coating layer of the roll-shaped protective film of Example 11 and the back surface on the opposite side was measured. Table 3 shows the measurement results.

<Measurement of surface electrical resistance>
In the same manner as in Example 10, when the surface of the protective film covering layer (low refractive index layer) of Example 11 was compared with a charged column, the surface of the covering layer was found to be negatively charged. It was confirmed that the charged column of the negative electrode was negative with respect to the polyester.
Moreover, it carried out similarly to Example 10, and measured the surface electrical resistance in the surface of the coating layer of the roll-shaped protective film of Example 11, and the back surface on the opposite side. Table 3 shows the measurement results.

<Evaluation of spots on hard coat layer>
In the same manner as in Example 10, interference spots on the hard coat layer of the roll-shaped protective film of Example 11 were evaluated. The evaluation results are shown in Table 3.

<Change in surface potential over time>
In the same manner as in Example 10, the roll-shaped protective film of Example 11 was stored for 1 month in an environment of 25 ° C. and 30% RH, and then the surface potential in an atmosphere of 25 ° C. and 50% RH was measured. The results are shown in Table 3.

(Comparative Example 4)
In the manufacturing method of the protective film of Example 10, the roll-shaped protective film of Comparative Example 4 was carried out in the same manner as in Example 10 except that the step of passing the zone at 25 ° C. and 65% atmosphere for 1 minute was eliminated while being conveyed. Was made.

<Measurement of surface roughness>
In the same manner as in Example 10, the centerline average surface roughness Ra on the surface of the coating layer of the roll-shaped protective film of Comparative Example 4 and the back surface on the opposite side was measured. Table 3 shows the measurement results.

<Measurement of surface electrical resistance>
In the same manner as in Example 10, the surface of the coating layer (low refractive index layer) of the protective film of Comparative Example 4 was contact-charged with polyester and measured using the surface potentiometer. The coating layer was negatively charged. It was confirmed that the charge train on the surface of the coating layer was negative with respect to the polyester.
Moreover, it carried out similarly to Example 10, and measured the surface electrical resistance in the surface of the coating layer of the roll-shaped protective film of the comparative example 4, and the back surface on the opposite side. Table 3 shows the measurement results.

<Evaluation of spots on hard coat layer>
In the same manner as in Example 10, interference spots on the hard coat layer of the roll-shaped protective film of Comparative Example 4 were evaluated. The evaluation results are shown in Table 3.

<Change in surface potential over time>
In the same manner as in Example 10, the roll-shaped protective film of Comparative Example 4 was stored for 1 month in an environment of 25 ° C. and 30% RH, and then the surface potential in an atmosphere of 25 ° C. and 50% RH was measured. The results are shown in Table 3.

(Comparative Example 5)
In the protective film of Example 10, the transparent substrate film was used in the same manner as in Example 10 except that the roll-shaped protective film prepared in Comparative Example 1 was used instead of TD80UF, and the low refractive index layer was not laminated. The roll-shaped protective film of Comparative Example 5 was produced. In addition, the hard-coat layer was laminated | stacked on the surface which laminated | stacked the coating layer of the protective film of the comparative example 1. FIG.

<Evaluation of spots on hard coat layer>
In the same manner as in Example 10, interference spots on the hard coat layer of the roll-shaped protective film of Comparative Example 5 were evaluated. The evaluation results are shown in Table 3.

<Change in surface potential over time>
In the same manner as in Example 10, the roll-shaped protective film of Comparative Example 5 was stored for 1 month in an environment of 25 ° C. and 30% RH, and then the surface potential in an atmosphere of 25 ° C. and 50% RH was measured. The results are shown in Table 3.

  Here, the structures of the protective films of Examples 1 to 11 and Comparative Examples 1 to 5 are shown in Table 1.

As shown in Table 3, it is recognized that the surface of the coating layer containing vinylidene chloride, which is a chlorine-containing compound, is negatively charged with respect to the polyester, and peeling charge tends to occur between the transparent substrate film and the surface. It was.
Even in such an environment, the protective films of Examples 1 to 5 that have undergone the moisture content adjustment step after the coating layer is laminated on the transparent base film have the absolute value of the surface potential suppressed to 5 kV or less. It was confirmed that Moreover, in Examples 1-5, it was recognized that the number of dust is increasing with the increase in the absolute value of surface potential.
On the other hand, in Comparative Example 1 in which the moisture content adjustment step was not performed and in Comparative Example 2 in which the humidity control humidity was set to 10% RH, the moisture content in the coating layer was remarkably small, and the presence of dust appeared remarkably.

Moreover, according to Table 3, the protective film of Example 10 provided with a coating layer having a moisture permeability of about 1,000 g / m ² · day greatly increases the surface potential after being sent out after one month. However, in the protective films of Examples 1 to 7 and Example 11 in which the coating layer having a moisture permeability of 500 g / m ² · day or less was provided, the increase in surface potential was small and the antistatic property was highly durable. It was confirmed.

In addition, according to Table 3, as in Examples 10 to 11, the protective film in which the low refractive index layer using the fluorine-based binder was formed had a negatively charged column, and the protective film Peeling electrification tends to occur between them.
However, even such a protective film can be prevented from being charged because it has undergone a moisture content adjusting step of making the moisture content 1.4% by mass or more. In particular, the antistatic effect can be maintained by setting the moisture permeability of the protective film to 500 g / m ² · day or less.

  Furthermore, since the protective film of Example 11 uses the roll-shaped protective film of Example 1 that is hardly charged as a transparent base film, it is excellent in dust resistance and prevents the occurrence of interference spots on the hard coat layer. It was confirmed. On the other hand, it was confirmed that Comparative Example 4 using the roll-shaped protective film of Comparative Example 1 having a large charge as a transparent substrate film cannot prevent the occurrence of interference spots on the hard coat layer.

(Example 12)
<Preparation of polarizing plate>
A polarizing film is manufactured by adsorbing iodine to a stretched polyvinyl alcohol film, a polarizing film is manufactured, and a commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd.) is saponified to form a polyvinyl alcohol adhesive. Was attached to one surface of the polarizing film.
Further, the roll-shaped protective film produced in Example 1 was saponified while performing dust removal treatment, and the surface on which the coating layer was not formed was coated with a polyvinyl alcohol-based adhesive. Affixed to the other surface to produce the polarizing plate of Example 12.

(Example 13)
<Preparation of polarizing plate>
In Example 12, a viewing angle widening film (Wide View Film SA 12B, manufactured by Fuji Film Co., Ltd.) was used instead of the commercially available cellulose acetate film (Fujitac TD80UF, manufactured by Fuji Film Co., Ltd.). In the same manner as described above, a polarizing plate of Example 13 was produced. In addition, the said viewing angle expansion film was bonded together so that the surface by which the liquid crystal layer was not laminated | stacked might become a polarizer side.

(Comparative Example 6)
<Preparation of polarizing plate>
In Example 12, a polarizing plate of Comparative Example 6 was produced in the same manner as Example 12 except that the roll-like protective film produced in Comparative Example 1 was used instead of the roll-like protective film produced in Example 1. did.

<Evaluation of point defects>
The obtained polarizing plates of Examples 12 to 13 and the polarizing plate of Comparative Example 6 were subjected to a surface inspection in a transmission mode by 10 m each, and existed between the protective film and the polarizing film, and dust of 20 μm or more The resulting point defects were investigated.
In the polarizing plates of Examples 12 to 13, since the roll-shaped protective film of Example 1 having almost no charge was used, no point defect due to dust was confirmed.
On the other hand, in the polarizing plate of Comparative Example 6, since the roll-shaped protective film of Comparative Example 1 having a large charge was used even though the dust removal treatment was performed at the time of saponification treatment and bonding with the polarizing film, Five point defects due to the above were confirmed.
Therefore, it can be seen that by using the protective film of the present invention, a polarizing plate free from point defects caused by dust can be obtained.

(Example 14)
<Production of liquid crystal display device>
The polarizing plate of a notebook personal computer (Satellite J11, manufactured by Toshiba) equipped with a transmission type TN liquid crystal display device is peeled off, and the polarizing plate of Example 12 is used instead of the polarizing plate so that the viewing angle widening film faces the liquid crystal cell. The liquid crystal display device of Example 14 was produced.

<Evaluation of bright spots>
The liquid crystal display device produced above was turned on to display black, and the number of bright spots was visually evaluated. No bright spots were seen.

(Comparative Example 7)
<Production of liquid crystal display device>
A liquid crystal display device of Comparative Example 7 was produced in the same manner as in Example 14 except that the polarizing plate of Example 12 was replaced with the polarizing plate of Comparative Example 6 in Example 14.

<Evaluation of bright spots>
When the number of bright spots was evaluated in the same manner as in Example 14, the portion corresponding to the dust adhering portion of the polarizing plate was a bright spot, and two bright spots were observed.

As described above, since the protective film of the present invention has reduced peeling electrification, it is possible to reduce the adhesion of dust due to the peeling electrification and the occurrence of spots on the hard coat layer.
Further, by using such a protective film, it is possible to provide a polarizing plate in which the occurrence of point defects is reduced and a liquid crystal display device free from white spots (bright spots) during black display.

Since the protective film of the present invention has reduced peeling electrification, it can reduce the adhesion of dust due to the peeling electrification and the occurrence of spots on the hard coat layer, etc., so that the polarizing plate and the liquid crystal using the same It can be suitably used for a display device.
The polarizing plate and the liquid crystal display device of the present invention have excellent performance with reduced occurrence of point defects, and are suitably used for mobile phones, personal computer monitors, televisions, liquid crystal projectors, and the like.

Claims (12)

  A coating layer containing at least one of a resin containing a repeating unit derived from a chlorine-containing vinyl monomer and a fluorine-containing resin is formed on at least one surface of the transparent substrate film, and the moisture content is 1.4 mass. % To 4.0% by mass of a protective film.   A protective film having an absolute value of a surface potential of 10 kV or less when drawn 5 m or more at a speed of 5 m / min from a rolled state in an environment of 25 ° C. and 50% RH.   The protective film according to claim 1, wherein the coating layer includes a material in which the charged column is more negative than polyethylene.   The protective film according to claim 1, wherein the chlorine-containing vinyl monomer is vinylidene chloride.   The protective film according to claim 1, wherein the transparent base film contains cellulose acylate. The protective film according to any one of claims 1 to 5, wherein moisture permeability at 60 ° C and 95% RH is 500 g / m ² · day or less.   The coating layer forming step of forming one or more coating layers on the transparent substrate film, and the moisture content of the protective film forming the laminate by forming the coating layer on the transparent substrate film is 1.5 mass The manufacturing method of the protective film characterized by including the moisture content adjustment process which adjusts a moisture content so that it may become% -4.0 mass%, and the winding-up process which winds up the said transparent base film.   The manufacturing method of the protective film of Claim 7 in which a moisture content adjustment process includes the process of humidity-controlling for 10 second or more in 25 degreeC and 55% RH or more atmosphere, conveying a protective film.   The manufacturing method of the protective film in any one of Claim 7 to 8 in which a coating layer formation process includes the drying process which exposes a protective film to the temperature of 50 degreeC or more for 20 second or more.   A protective film produced by the method for producing a protective film according to claim 7.   A polarizing plate comprising a polarizer and the protective film according to claim 1 provided on at least one surface of the polarizer.   A liquid crystal display device comprising the polarizing plate according to claim 11.