CN114545531A

CN114545531A - Protective film for polarizer, method for producing protective film for polarizer, and apparatus for producing protective film for polarizer

Info

Publication number: CN114545531A
Application number: CN202210137602.6A
Authority: CN
Inventors: 品川雅; 秦纪明; 高山侃也; 中田美惠
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2017-01-20
Filing date: 2018-01-19
Publication date: 2022-05-27
Also published as: JP2018116244A; KR20180086137A; TWI772355B; TW201831326A; KR102453707B1; CN108363124A; JP6987429B2

Abstract

The invention provides a protective film for a polarizer, a method for manufacturing the protective film for a polarizer, and an apparatus for manufacturing the protective film for a polarizer, wherein the protective film for a polarizer is formed by using a protective film for a polarizer, in which a base material layer and an antistatic layer are melt-fixed without being mixed, and the base material layer and the antistatic layer have orientation properties together, and the antistatic layer has a specific thickness, whereby the cohesion and adhesion between the base material layer and the antistatic layer are excellent, and the antistatic property are provided without reducing the optical characteristics. The protective film for a polarizer of the present invention comprises a base material and an antistatic layer formed on one surface of the base material and comprising an antistatic agent composition containing a conductive polymer, wherein the base material and the antistatic layer are melt-fixed without being mixed and have orientation properties, and the thickness of the antistatic layer is 100nm or less.

Description

Protective film for polarizer, method for producing protective film for polarizer, and apparatus for producing protective film for polarizer

The application is a divisional application of Chinese patent application with application date of 2018, 1, 19 and application number of 201810054157.0.

Technical Field

The present invention relates to a protective film for a polarizer, a method for manufacturing the protective film for a polarizer, and an apparatus for manufacturing the protective film for a polarizer. In particular, a polarizing plate obtained by laminating the above protective film for a polarizer is useful for forming an image display device such as a Liquid Crystal Display (LCD), an organic Electroluminescence (EL) display device, a Cathode Ray Tube (CRT), or a Plasma Display Panel (PDP) as a single or an optical film obtained by laminating the polarizing plate.

Background

In a liquid crystal display device, an organic EL display device, or the like, depending on the image forming system, for example, in the liquid crystal display device, it is essential to dispose a polarizer on a liquid crystal cell, and a polarizing plate is generally attached.

For example, in the manufacture of a liquid crystal display panel, a polarizing plate bonded to a liquid crystal cell is attached to the surface of the polarizing plate via an adhesive layer constituting a surface protective film for the polarizing plate in order to prevent the occurrence of scratches, stains, and the like during processing, transportation, and other steps. However, the surface protective film is peeled off and removed at a stage where the surface protective film is no longer necessary, but there is a problem that static electricity is generated at the time of peeling, defective alignment of liquid crystal of the liquid crystal panel occurs, whitening (white unevenness) occurs, and panel inspection cannot be performed until the unevenness naturally disappears.

In order to suppress such generation of static electricity, for example, it is conceivable to use a pressure-sensitive adhesive layer, which is provided with antistatic properties by blending an antistatic agent such as an alkali metal salt as disclosed in patent document 1, as a pressure-sensitive adhesive layer constituting a surface protective film.

However, as in patent document 1, there is a problem that the adhesive force by the pressure-sensitive adhesive layer becomes insufficient by blending an antistatic agent in the pressure-sensitive adhesive layer.

In addition, an attempt has been made to provide antistatic properties by forming an antistatic layer on the surface of a transparent protective film for a polarizer laminated on a polarizer constituting a polarizing plate (for example, patent document 2).

Documents of the prior art

Patent literature

Patent document 1: japanese laid-open patent publication No. 2009-251281

Patent document 2: japanese patent laid-open publication No. 2016-535321

Disclosure of Invention

Problems to be solved by the invention

However, even when an antistatic layer (conductive layer) is formed by directly applying a solution for an antistatic layer (conductive layer) on the surface of a transparent protective film for a polarizer and heating (drying), the cohesive force and adhesion between the transparent protective film and the antistatic layer are weak, and problems such as peeling between layers occur in a working process.

Further, when the antistatic property is provided by increasing the thickness of the antistatic layer, there are problems that deterioration of optical characteristics such as haze and transmittance of a film such as a polarizing plate including the antistatic layer is remarkable, or that the antistatic layer is broken when the surface protective film is peeled off from the polarizing plate.

Accordingly, the present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a protective film for a polarizer, which is melt-fixed without being mixed by using a base material and an antistatic layer, has orientation properties together with the base material layer and the antistatic layer, and has an antistatic layer having a specific thickness, and thus has excellent cohesion and adhesion between the base material and the antistatic layer, and also has antistatic properties and antistatic properties without lowering optical characteristics, a method for producing the protective film for a polarizer, and an apparatus for producing the protective film for a polarizer.

Means for solving the problems

That is, the polarizer protective film of the present invention is a polarizer protective film including a base material and an antistatic layer formed of an antistatic agent composition containing a conductive polymer on one surface of the base material, wherein the base material and the antistatic layer are melt-fixed without being mixed and have orientation, and the thickness of the antistatic layer is 100nm or less.

In the protective film for a polarizer of the present invention, the base material is preferably formed mainly of a (meth) acrylic resin.

In the protective film for a polarizer of the present invention, the antistatic agent composition preferably contains poly (3, 4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT/PSS) as the conductive polymer.

In the protective film for a polarizer according to the present invention, the antistatic layer preferably has a surface resistance value of 1.0 × 10⁸Omega/□ or less.

The method for producing a protective film for a polarizer according to the present invention is a method for producing the protective film for a polarizer, and preferably includes: the antistatic agent composition is applied to one surface of the substrate to form a coating film, and the substrate and the coating film are heated and stretched together at a temperature of not less than the glass transition temperature Tg +20 ℃ of the substrate.

The method for producing the protective film for a polarizer of the present invention preferably includes: the step of heating and stretching is a step of simultaneously or sequentially biaxially stretching in the width direction and the longitudinal direction using a tenter type stretching machine.

The method for producing the protective film for a polarizer of the present invention preferably includes: the stretching ratio of the simultaneous or sequential biaxial stretching is 1.5 times or more and 3.0 times or less in each of the width direction and the longitudinal direction.

The apparatus for manufacturing a protective film for a polarizer according to the present invention is preferably an apparatus for manufacturing the protective film for a polarizer, including: a coating film forming means for forming a coating film by applying the antistatic agent composition to one surface of the substrate, and a heating and stretching means for heating and stretching the substrate together with the coating film at a temperature of not less than the glass transition temperature Tg +20 ℃ of the substrate.

In the apparatus for manufacturing a protective film for a polarizer according to the present invention, it is preferable that the heating and stretching unit is a tenter type stretching machine.

Effects of the invention

The protective film for a polarizer of the present invention is useful because it is a protective film for a polarizer in which a base material layer and an antistatic layer are melt-fixed without being mixed, the base material layer and the antistatic layer have orientation properties together, and the antistatic layer having a specific thickness is formed, and thus it is possible to obtain a protective film for a polarizer which has excellent cohesion and adhesion between the base material layer and the antistatic layer, and also has excellent antistatic properties and antistatic properties. Further, it is useful to provide a method and an apparatus for manufacturing the protective film for a polarizer, in which the thickness accuracy is improved by heating and stretching at a specific temperature or stretching at a specific stretching ratio. In addition, in a state where the polarizer (polarizing plate) on which the protective film for polarizer is laminated on a Liquid Crystal Display (LCD) or the like, when a surface protective film directly attached to protect the polarizing plate is peeled off, generation of static electricity can be suppressed, whitening (white unevenness) of a panel of the liquid crystal display or the like can be prevented, and further, a defect in panel inspection can be prevented, and peeling electrification preventing properties are excellent, which is a preferable embodiment.

Drawings

Fig. 1 is a schematic cross-sectional view showing one configuration example of a polarizer in which a protective film for a polarizer of the present invention is laminated.

Reference numerals

1: polarizer (polarizing plate) with protective film for polarizer

2: protective film for polarizer

10: antistatic layer

11: base material

12: polarizer

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

< integral Structure of polarizer laminated with protective film for polarizer >

The polarizer laminated with the protective film for a polarizer (polarizer with a protective film for a polarizer) disclosed herein includes, for example, a polarizer laminated with a protective film for a polarizer, which is configured such that an antistatic layer 10 is laminated on one surface of a base material 11 in a surface protective film 2 for a polarizer and a polarizer 12 is laminated on the other surface, as shown in fig. 1. The polarizer (polarizing plate) with a protective film for a polarizer disclosed herein may be in a roll shape or a sheet shape (e.g., a Ye shape).

< base Material for protective film for polarizer >

The protective film for a polarizer of the present invention is a protective film for a polarizer, which has a base material and an antistatic layer formed of an antistatic agent composition containing a conductive polymer on one surface of the base material, wherein the base material and the antistatic layer are melt-fixed without being mixed, and the base material layer and the antistatic layer have orientation properties together. Preferably, the substrate and the antistatic layer are fused and fixed to each other and firmly adhered to each other, thereby ensuring adhesion between the substrate and the antistatic layer. In addition, the base material has orientation, and the optical characteristics of the laminated polarizing plate can be appropriately maintained by controlling the degree of orientation. As the orientation, for example, the orientation can be confirmed by three-dimensional IR polarization measurement using a fourier transform infrared spectrophotometer manufactured by shimadzu corporation. The degree of orientation (dimensionless) was determined by analyzing the difference in the in-plane orientation (ND) direction in addition to the length (MD) direction and the width (TD) direction and using the ND value. The ND value is-0.1 or less, preferably-0.1 to-0.01, more preferably-0.06 to-0.02. If the degree of orientation is too large, it is suggested that, for example, the substrate and the antistatic layer cannot be formed uniformly in the plane, and thus, the appearance of the protective film for a polarizer may be uneven, or the protective film for a polarizer may be cracked. On the other hand, when the degree of orientation is too small, it means that the polarizing plate cannot be stretched to a predetermined magnification, and therefore, the properties (optical properties, dimensional stability due to thickness distribution, and the like) of the polarizing plate on which the protective film for a polarizer is laminated may be affected.

The material of the base material constituting the polarizer protective film is not particularly limited, and a polymer (resin) excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, ultraviolet absorptivity, and the like is preferable. Examples thereof include: polyester polymers (polyester resins) such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as diacetylcellulose and triacetylcellulose; (meth) acrylic polymers ((meth) acrylic resins) such as polymethyl methacrylate; styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin); polycarbonate-series polymers (polycarbonate-series resins), and the like. Further, there may be mentioned: examples of the polymer forming the base material include polyethylene, polypropylene, polyolefin having a cyclic or norbornene structure (cyclic olefin resin), polyolefin polymers such as ethylene-propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers, polyethersulfone polymers, polyetherether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, aromatic ester polymers, polyoxymethylene polymers, epoxy polymers, and blends of the above polymers, and among these, the polymer is preferably formed using a (meth) acrylic resin as a main component. The "main component" means that the content of the polymer in the base material is 50 to 100% by weight, preferably 50 to 99% by weight, more preferably 60 to 98% by weight, and still more preferably 70 to 97% by weight. When the content of the polymer in the base material is 50% by weight or less, high transparency and the like inherent in the polymer may not be sufficiently expressed.

The base material is generally used as a polarizing plate by being bonded to a polarizer with an adhesive layer.

The base material of the protective film for a polarizer may contain one or more optional appropriate additives. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like.

The thickness of the base material of the polarizer protective film may be appropriately determined, and is usually preferably 5 μm to 50 μm, more preferably 5 μm to 45 μm, from the viewpoints of workability such as strength and workability, and thin layer property.

The base material of the protective film for a polarizer may be provided with a functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer, or an antiglare layer on the surface to which the polarizer is not adhered. The functional layers such as the hard coat layer, antireflection layer, release layer, diffusion layer, and antiglare layer may be provided separately from the substrate, in addition to the substrate itself.

When the polarizer is laminated on the base material, an easy-adhesion layer may be provided between the base material and the adhesive layer.

< antistatic layer of protective film for polarizer >

The polarizer protective film of the present invention is a polarizer protective film comprising a base material and an antistatic layer formed of an antistatic agent composition containing a conductive polymer on one surface of the base material, wherein the base material and the antistatic layer are melt-fixed without being (substantially) mixed, the base material layer and the antistatic layer have an orientation together, and the thickness of the antistatic layer is 100nm or less. The antistatic layer is preferably formed from an antistatic agent composition containing a conductive polymer, and thus can suppress an increase in surface resistance even in a high-temperature and low-humidity environment, and can provide an antistatic layer having excellent antistatic properties, flexibility, and durability. Further, by providing the antistatic layer on the surface of the protective film for a polarizer, it is not necessary to impart antistatic properties to the pressure-sensitive adhesive layer constituting the surface protective film, which is directly laminated (bonded) to the above antistatic layer of the polarizing plate (polarizer with protective film for a polarizer), in other words, it is not necessary to add an antistatic component, and workability is excellent. The phrase "not mixed" means that the mixture layer is not substantially mixed, and means that the thickness of the mixture layer at the interface between the substrate and the antistatic layer is less than 10 nm.

In particular, the reason why the antistatic stability in a high-temperature environment is improved by blending the polyaniline sulfonic acid and the polythiophene doped with a polyanion (ポリアニオン syn) in the above range is presumed to be as follows, as compared with the case where the polyaniline sulfonic acid is blended alone or the polythiophene doped with a polyanion is blended alone. As for the polythiophene doped with the polyanion, the conduction mechanism of the polythiophene forming a complex by coordinating with an anionic group of the polyanion is known as intramolecular conduction of the polythiophene generated in the complex, intermolecular conduction of the polythiophene, and conduction between complex structures. Here, the conduction between the composite structures is a rate-dependent process because the intermolecular distance is long. It is presumed that by using a combination of a polyaniline sulfonic acid having a higher molecular weight than that of a polythiophene, the polyaniline sulfonic acid connects the complexes including the polythiophene and the polyanion and has conductivity itself, and thus the conductivity between the complexes is improved, the antistatic property is improved, and the stability under a high temperature environment is increased, and thus the polyaniline-sulfonic acid is useful as a protective film for a polarizer.

In addition, when the polyaniline sulfonic acid is used alone as a conductive polymer, the initial conductivity is low, and therefore, the peeling electrification voltage, the surface resistance value, and the like are likely to increase with time.

In addition, when the polythiophene doped with the polyanion is used alone, although the initial conductivity is high, the polyanion (corresponding to the dopant) is more easily released than the polythiophene with the passage of time, and thus the peeling electrification voltage, the surface resistance value, and the like are easily increased with the passage of time, which is not preferable.

< conductive Polymer >

The antistatic layer is preferably formed of an antistatic agent composition containing polyaniline sulfonic acid and polythiophene doped with polyanion as a conductive polymer component. In the case where the above-mentioned conductive polymers are combined, polyaniline sulfonic acid is responsible for electric conduction between core-shell structures of polythiophene and polyanion, and therefore, the conductivity is improved, and the antistatic property by the antistatic layer and the antistatic property in a high-temperature environment can be stabilized, which is useful.

The content of the conductive polymer is preferably 1 to 90 wt%, more preferably 5 to 80 wt%, further preferably 10 to 70 wt%, and most preferably 20 to 50 wt% with respect to the total components contained in the antistatic layer. When the content of the conductive polymer is too small, the antistatic effect may be reduced, and when the content of the conductive polymer is too large, the adhesion of the antistatic layer to the substrate may be reduced or the transparency may be reduced, which is not preferable.

The polyaniline sulfonic acid used as the conductive polymer component preferably has a weight average molecular weight (Mw) of 5 × 10 in terms of standard polystyrene as measured by Gel Permeation Chromatography (GPC)⁵Hereinafter, more preferably 3 × 10⁵The following. In addition, the weight average molecular weight of these conductive polymers is preferably 1 × 10 in general³Above, more preferably 5 × 10³As described above.

Examples of the commercially available polyaniline sulfonic acid include "aqua-PASS" manufactured by Mitsubishi Rayon.

The polythiophene used as the conductive polymer component includes, for example: polythiophene, poly (3-methylthiophene), poly (3-ethylthiophene), poly (3-propylthiophene), poly (3-butylthiophene), poly (3-hexylthiophene), poly (3-heptylthiophene), poly (3-octylthiophene), poly (3-decylthiophene), poly (3-dodecylthiophene), poly (3-octadecylthiophene), poly (3-bromothiophene), poly (3-chlorothiophene), poly (3-iodothiophene), poly (3-cyanothiophene), poly (3-phenylthiophene), poly (3, 4-dimethylthiophene), poly (3, 4-dibutylthiophene), poly (3-hydroxythiophene), poly (3-methoxythiophene), poly (3-ethoxythiophene), poly (3-butoxythiophene), Poly (3-hexyloxythiophene), poly (3-heptyloxythiophene), poly (3-octyloxythiophene), poly (3-decyloxythiophene), poly (3-dodecyloxythiophene), poly (3-octadecyloxythiophene), poly (3, 4-dihydroxythiophene), poly (3, 4-dimethoxythiophene), poly (3, 4-diethoxythiophene), poly (3, 4-dipropoxythiophene), poly (3, 4-dibutoxythiophene), poly (3, 4-dihexylooxythiophene), poly (3, 4-diheptyloxythiophene), poly (3, 4-dioctyloxythiophene), poly (3, 4-didecyloxythiophene), poly [3, 4-di (dodecyloxy) thiophene ], poly (3, 4-ethylenedioxythiophene), Poly (3, 4-propylenedioxythiophene), poly (3, 4-butylenedioxythiophene), poly (3-methyl-4-methoxythiophene), poly (3-methyl-4-ethoxythiophene), poly (3-carboxythiophene), poly (3-methyl-4-carboxyethylthiophene), poly (3-methyl-4-carboxybutylthiophene). Among them, poly (3, 4-ethylenedioxythiophene) is preferable from the viewpoint of conductivity. These may be used alone or in combination of two or more. Among them, poly (3, 4-ethylenedioxythiophene) (PEDOT) is preferable from the viewpoint of conductivity.

The polythiophene preferably has a polymerization degree of 2 to 1000, more preferably 5 to 100. When the polymerization degree is within the above range, the conductivity is excellent, and therefore, the polymerization degree is preferable.

The polyanion is a polymer having a structural unit of an anionic group, and functions as a dopant in the polythiophene. Examples of the polyanion include: polystyrenesulfonic acid, polyvinylsulfonic acid, polyallylsulfonic acid, polyacrylylsulfonic acid (ポリアクリルスルホン acid), polymethacrylenesulfonic acid (ポリメタクリルスルホン acid), poly (2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, sulfoethyl polymethacrylate, poly (4-sulfobutyl methacrylate), polymethacryloxybenzenesulfonic acid, polyvinylcarboxylic acid (ポリビニルカルボン acid), polystyrenecarboxylic acid (ポリスチレンカルボン acid), polyallylcarboxylic acid (ポリアリルカルボン acid), polyacryloylcarboxylic acid (ポリアクリルカルボン acid), polymethacryloylcarboxylic acid (ポリメタクリルカルボン acid), poly (2-acrylamido-2-methylpropanecarboxylic acid) (ポリ (2- アクリルアミド -2- メチルプロパ acid) ンカルボン acid), polyisoprene carboxylic acid (ポリイソプレンカルボン acid), polyacrylic acid, polysulfonated phenylacetylene, and the like. These may be homopolymers or copolymers of two or more kinds. Among them, polystyrene sulfonic acid (PSS) is preferable.

The weight average molecular weight (Mw) of the polyanion is preferably 1000 to 100 ten thousand, more preferably 2000 to 50 ten thousand. When the Mw is within the above range, doping and dispersibility in the polythiophene are excellent, and therefore, it is preferable.

Examples of commercially available products of the polythiophene doped with the polyanion include: the poly (3, 4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT/PSS) is available under the trade name "Bytron P" from Bayer corporation, under the trade name "Seplegyda" from shin-transiter Polymer corporation, under the trade name "VERAZOL" from Soken chemical corporation, under the trade name "Dentron P-502 RG" from Rex chemical Co. Among these, when PEDOT/PSS is used in the antistatic layer constituting the protective film for a polarizer, since PEDOT/PSS is a conductive polymer even after the heating and stretching step, an antistatic layer having excellent flexibility and durability and maintaining antistatic property and peeling electrification preventing property can be obtained, which is a preferable embodiment. When a coating film obtained by applying an antistatic component as a nonconductive polymer to a substrate is heated and stretched together with the substrate, there is a problem that cracks, or the like are introduced into the coating film (antistatic layer), and therefore, the coating film cannot be put into practical use, which is not preferable.

In the antistatic agent composition, the mixing ratio (weight ratio) of the polyaniline sulfonic acid to the polythiophene doped with a polyanion (the polyaniline sulfonic acid: the polythiophene doped with a polyanion) is preferably 90:10 to 10:90, more preferably 85:15 to 15:85, and further preferably 80:20 to 20: 80. When the blending ratio is within the above range, the surface resistance value can be suppressed to be low, and particularly, the stability of the surface resistance value in a high-temperature environment is excellent, which is a preferable embodiment. When the content of the polyaniline sulfonic acid is small or the content of the polythiophene doped with the polyanion is small, the surface resistance value in a high-temperature environment tends to increase, which is not preferable.

< Binder >

The antistatic layer may contain a binder component, may be used without particular limitation, and is preferably formed of an antistatic agent composition containing a polyester resin as a binder in order to impart solvent resistance, mechanical strength, charging characteristics, and thermal stability. The polyester resin is preferably a resin material containing a polyester as a main component (typically, a component accounting for more than 50% by weight, preferably 75% by weight or more, for example, 90% by weight or more). The polyester typically preferably has a structure obtained by condensing one or more compounds (polycarboxylic acid component) selected from polycarboxylic acids (typically dicarboxylic acids) having two or more carboxyl groups in one molecule and derivatives thereof (anhydrides, esters, halides, and the like of the polycarboxylic acids) with one or more compounds (polyol component) selected from polyhydric alcohols (typically glycols) having two or more hydroxyl groups in one molecule.

Examples of compounds that can be used as the polycarboxylic acid component include: aliphatic dicarboxylic acids such as oxalic acid, malonic acid, difluoromalonic acid, alkylmalonic acid, succinic acid, tetrafluorosuccinic acid, alkylsuccinic acid, (±) -malic acid, meso-tartaric acid, itaconic acid, maleic acid, methylmaleic acid, fumaric acid, methylfumaric acid, acetylenedicarboxylic acid, glutaric acid, hexafluoroglutaric acid, methylglutaric acid, glutaconic acid, adipic acid, dithioadipic acid, methyladipic acid, dimethyladipic acid, tetramethyladipic acid, methyleneadipic acid, muconic acid, galactaric acid, pimelic acid, suberic acid, perfluorosuberic acid, 3,6, 6-tetramethylsuberic acid, azelaic acid, sebacic acid, perfluorosebacic acid, brassylic acid, dodecanedicarboxylic acid, tridecanedicarboxylic acid, and tetradecanedicarboxylic acid; alicyclic dicarboxylic acids such as cycloalkyldicarboxylic acids (e.g., 1, 4-cyclohexanedicarboxylic acid, 1, 2-cyclohexanedicarboxylic acid), 1,4- (2-norbornene) dicarboxylic acid, 5-norbornene-2, 3-dicarboxylic acid (nadic acid), adamantanedicarboxylic acid, and spiroheptanedioic acid; phthalic acid, isophthalic acid, dithioisophthalic acid, methylisophthalic acid, dimethylisophthalic acid, chloromisophthalic acid, dichloroisophthalic acid, terephthalic acid, methylterephthalic acid, dimethylterephthalic acid, chloroterephthalic acid, bromoterephthalic acid, naphthalenedicarboxylic acid, oxofluorenyldicarboxylic acid, anthracenedicarboxylic acid, biphenyldicarboxylic acid, biphenylenedicarboxylic acid (ビフェニレンジカルボン acid), dimethylbiphenylenedicarboxylic acid (ジメチルビフェニレンジカルボン acid), 4 ' -p-terphenylenedicarboxylic acid, 4 ' -p-quaterphenyldicarboxylic acid, bibenzyldicarboxylic acid, azobenzenedicarboxylic acid, homophthalic acid, phenylenediacetic acid, phenylenedipropionic acid, naphthalenedicarboxylic acid, naphthalenedipropionic acid, biphenyldiacetic acid, biphenyldipropionic acid, 3' - [ 4], aromatic dicarboxylic acids such as 4 '- (methylenedi-p-biphenylene) dipropionic acid, 4' -bibenzyldiacetic acid, 3'- (4, 4' -bibenzyl) dipropionic acid, and oxydi-p-phenylenediacetic acid; anhydrides of any of the above polycarboxylic acids; esters (e.g., alkyl esters, which may be monoesters, diesters, etc.) of any of the foregoing polycarboxylic acids; acid halides corresponding to any of the above-mentioned polycarboxylic acids (e.g., diformylchloride); and so on.

Preferable examples of the compound that can be used as the polycarboxylic acid component include: aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid, and anhydrides thereof; aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, succinic acid, fumaric acid, maleic acid, nadic acid, and 1, 4-cyclohexanedicarboxylic acid, and anhydrides thereof; and lower alkyl esters of the above dicarboxylic acids (for example, esters with monohydric alcohols having 1 to 3 carbon atoms).

On the other hand, as examples of the compounds which can be used as the above-mentioned polyol component, there can be mentioned: glycols such as ethylene glycol, propylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, neopentyl glycol, 1, 5-pentanediol, 1, 6-hexanediol, 3-methylpentanediol, diethylene glycol, 1, 4-cyclohexanedimethanol, 3-methyl-1, 5-pentanediol, 2-methyl-1, 3-propanediol, 2-diethyl-1, 3-propanediol, 2-butyl-2-ethyl-1, 3-propanediol, benzenedimethanol, hydrogenated bisphenol A, and bisphenol A. Other examples thereof include alkylene oxide adducts (e.g., ethylene oxide adducts, propylene oxide adducts, etc.) of these compounds.

The molecular weight of the polyester resin may be, for example, about 5 × 10 in terms of number average molecular weight (Mn) in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC)³About 1.5X 10⁵(preferably about 1X 10)⁴About 6X 10⁴). The glass transition temperature (Tg) of the polyester resin may be, for example, 0 to 120 ℃ (preferably 10 to 80 ℃).

Examples of the commercially available polyester resin include: trade names VYLONAL MD-1100, MD-1200, MD-1245, MD-1335, MD-1480, MD-1500, MD-1930, MD-1985, MD-2000, trade names Plascoat Z-221, Z-446, Z-561, Z-565, Z-880, Z-3310, RZ-105, RZ-570, Z-730, Z-760, Z-592, Z-687, Z-690, PESRESIN A-110, A-120, A-124GP, A-125S, A-160P, A-520, A-613D, A-615GE, A-640, A-645GH, A-647GEX, A-680, A-684G, A-561G, and the like, all available from Toyobo Co Ltd, WAC-14, WAC-17XC, etc.

The antistatic layer may be formed by using a resin other than a polyester resin (for example, one or two or more resins selected from an acrylic resin, an acrylic-urethane resin, an acrylic-styrene resin, an acrylic-polysiloxane resin, a polysilazane resin, a fluororesin, a styrene resin, an alkyd resin, a polyurethane resin, an amide resin, a polyolefin resin, and the like) as a binder, as long as the performance (for example, antistatic performance and the like) of the protective film disclosed herein is not significantly impaired. When the above resins are used in combination, the antistatic layer preferably contains the polyester resin in an amount of 51 to 100 wt% based on the binder. The proportion of the binder in the entire antistatic layer may be set to, for example, 50 to 95% by weight, and is preferably set to 60 to 90% by weight.

< Lubricant >

The antistatic agent composition used for forming the antistatic layer in the technology disclosed herein is preferably: at least one selected from the group consisting of fatty acid amides, fatty acid esters, silicone-based lubricants, fluorine-containing lubricants, and wax-based lubricants is used as the lubricant. By using the above lubricant, an antistatic layer having both sufficient lubricity and print adhesion can be obtained even in a mode in which a further peeling treatment (for example, a treatment of applying a known peeling treatment agent such as a silicone-based peeling agent or a long chain alkyl-based peeling agent and drying) is not performed on the surface of the antistatic layer, and therefore, a preferable mode can be obtained. As described above, the mode in which no further peeling treatment is performed on the surface of the antistatic layer is preferable in terms of being able to prevent whitening (for example, whitening due to storage under heated and humidified conditions) and the like caused by the peeling treatment agent in advance. In addition, it is also advantageous from the viewpoint of solvent resistance.

Specific examples of the fatty acid amide include: lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, oleic acid amide, erucic acid amide, N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, methylol stearic acid amide, methylene bis stearic acid amide, ethylene bis capric acid amide, ethylene bis lauric acid amide, ethylene bis stearic acid amide, ethylene bis hydroxystearic acid amide, ethylene bis behenic acid amide, hexamethylene bis stearic acid amide, hexamethylene bis behenic acid amide, hexamethylene hydroxystearic acid amide, N '-distearyl adipic acid amide, N' -distearyl sebacic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, Hexamethylene bis-oleamide, N ' -dioleyl adipic acid amide, N ' -dioleyl sebacic acid amide, m-xylylene bis-stearic acid amide, m-xylylene bis-hydroxystearic acid amide, N ' -stearyl isophthalic acid amide, and the like. These lubricants may be used alone or in combination of two or more.

Specific examples of the fatty acid ester include: polyoxyethylene bisphenol a laurate, butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, glyceryl monobehenate, cetyl 2-ethylhexanoate, isopropyl myristate, isopropyl palmitate, cholesterol isostearate, lauryl methacrylate, methyl cocoate, methyl laurate, methyl oleate, methyl stearate, myristyl myristate, octyldodecyl myristate, pentaerythritol monooleate, pentaerythritol monostearate, pentaerythritol tetrapalmitate, stearyl stearate, isotridecyl stearate, tri-2-ethylhexanoate, butyl laurate, octyl oleate, and the like. These lubricants may be used alone or in combination of two or more.

Specific examples of the silicone-based lubricant include: polydimethylsiloxane, polyether-modified polydimethylsiloxane, amino-modified polydimethylsiloxane, epoxy-modified polydimethylsiloxane, carbinol-modified polydimethylsiloxane, mercapto-modified polydimethylsiloxane, carboxyl-modified polydimethylsiloxane, methylhydrogenpolysiloxane, methacrylic-modified polydimethylsiloxane, phenol-modified polydimethylsiloxane, silanol-modified polydimethylsiloxane, aralkyl-modified polydimethylsiloxane, fluoroalkyl-modified polydimethylsiloxane, long-chain alkyl-modified polydimethylsiloxane, higher fatty acid-modified ester-modified polydimethylsiloxane, higher fatty acid amide-modified polydimethylsiloxane, phenyl-modified polydimethylsiloxane, and the like. These lubricants may be used alone or in combination of two or more.

Specific examples of the fluorine-containing lubricant include: perfluoroalkanes, perfluorocarboxylic acid esters, fluorine-containing block copolymers, polyether polymers having fluoroalkyl groups, and the like. These lubricants may be used alone or in combination of two or more.

Specific examples of the wax-based lubricant include: various waxes such as petroleum waxes (paraffin wax, etc.), plant waxes (carnauba wax, etc.), mineral waxes (montan wax, etc.), higher fatty acids (cerotic acid, etc.), neutral fats (tripalmitate, etc.), and the like. These lubricants may be used alone or in combination of two or more.

The proportion of the lubricant in the entire antistatic layer may be set to 1 to 50 wt%, and is preferably set to 5 to 40 wt%. When the content of the lubricant is too small, the lubricity tends to be easily lowered. If the content ratio of the lubricant is too high, the print adhesion and the back peel force (adhesive force) may be reduced.

The antistatic agent composition for forming the antistatic layer preferably contains at least one selected from the group consisting of a silane coupling agent, an epoxy crosslinking agent, a melamine crosslinking agent and an isocyanate crosslinking agent as a crosslinking agent, and among these, it is more preferable to use the melamine crosslinking agent and/or the isocyanate crosslinking agent. In the formation of the antistatic layer, a conductive polymer component (for example, polyaniline sulfonic acid or polythiophene doped with polyanion) can be fixed in a binder, and the antistatic layer is excellent in water resistance and solvent resistance and can achieve effects such as improvement in print adhesion. In particular, it is useful to use a melamine-based crosslinking agent to improve water resistance and solvent resistance, to use an isocyanate-based crosslinking agent to improve water resistance and print adhesion, and to use these crosslinking agents in combination to improve water resistance, solvent resistance and print adhesion.

As the melamine-based crosslinking agent, melamine, alkylated melamine, methylolmelamine, alkoxylated methyl melamine, and the like can be used.

In addition, as the isocyanate-based crosslinking agent, a blocked isocyanate-based crosslinking agent which is stable even in an aqueous solution is preferably used. Specific examples of the blocked isocyanate crosslinking agent include those obtained by blocking an isocyanate crosslinking agent (for example, an isocyanate compound used in the pressure-sensitive adhesive layer described later) which can be used for producing a general pressure-sensitive adhesive layer or antistatic layer with an alcohol, a phenol, a thiophenol, an amine, an imide, an oxime, a lactam, an active methylene compound, a thiol, an imine, a urea, a diaryl compound, sodium hydrogen sulfite, or the like.

The antistatic layer in the technology disclosed herein may contain additives such as antistatic agents, antioxidants, colorants (pigments, dyes, etc.), fluidity modifiers (thixotropic agents, thickeners, etc.), film-forming aids, surfactants (defoaming agents, etc.), preservatives, and the like, as necessary. In addition, a glycidyl compound, a polar solvent, a polyhydric aliphatic alcohol, a lactam compound, or the like may be contained as the conductivity improver.

The antistatic layer can be formed by a method including applying a liquid composition (antistatic agent composition) obtained by dissolving or dispersing an additive used according to the conductive polymer component or the like in an appropriate solvent (water or the like) on a substrate. In the present invention, the following method can be preferably employed: the antistatic agent composition is applied to one surface of a substrate, heated (dried) and stretched together with the substrate, and if necessary, cured (heat treatment, ultraviolet treatment, and the like). The NV (nonvolatile component) of the antistatic agent composition material can be set to, for example, 5 wt% or less (typically 0.05 wt% to 5 wt%), and is preferably set to 1 wt% or less (typically 0.10 wt% to 1 wt%). In the case of forming an antistatic layer having a small thickness, the NV of the antistatic agent composition is preferably set to, for example, 0.05 wt% to 0.50 wt% (e.g., 0.10 wt% to 0.40 wt%). By using such a low NV antistatic agent composition, a more uniform antistatic layer can be formed.

As the solvent constituting the antistatic agent composition, a solvent capable of stably dissolving or dispersing the components forming the antistatic layer is preferable. The solvent may be an organic solvent, water, or a mixed solvent thereof. Examples of the organic solvent include esters such as ethyl acetate; ketones such as methyl ethyl ketone, acetone, and cyclohexanone; tetrahydrofuran (THF), bis

Cyclic ethers such as alkanes; aliphatic or alicyclic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; aliphatic or alicyclic alcohols such as methanol, ethanol, n-propanol, isopropanol and cyclohexanol; one or more kinds of glycol ethers such as alkylene glycol monoalkyl ether (e.g., ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) and dialkylene glycol monoalkyl ether. In a preferred embodiment, the solvent of the antistatic agent composition is water or a mixed solvent mainly containing water (for example, a mixed solvent of water and ethanol).

In addition, in order to improve dispersion stability in a solvent, a basic organic compound capable of coordinating or bonding with an anionic group of the polyanion in the form of an ion pair may be contained. Examples of the basic organic compound include: known amine compounds, hydrochloride salts of amine compounds, cationic emulsifiers, basic resins, and the like.

Specific examples of the basic organic compound include: amine compounds such as methyloctylamine, methylbenzylamine, N-methylaniline, dimethylamine, diethylamine, diethanolamine, N-methylethanolamine, di-N-propylamine, diisopropylamine, methyl-isopropanolamine, dibutylamine, di-2-ethylhexylamine, aminoethylethanolamine, 3-amino-1-propanol, isopropylamine, monoethylamine, 2-ethylhexylamine, tert-butylamine, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane, amine compounds such as N-octylamine, methylbenzylamine, N-methylaniline, dimethylamine, diethylamine, diethanolamine, N-methylethanolamine, di-N-propylamine, diisopropylamine, methyl-isopropanolamine, dibutylamine, di-2-ethylhexylamine, aminoethylethanolamine, 3-1-propanol, isopropylamine, monoethylamine, 2-ethylethanolamine, tert-3-aminopropyltrimethoxysilane, and the like, Hydrochloride of primary amine such as monomethylamine, monoethylamine, or stearylamine, hydrochloride of secondary amine such as dimethylamine, diethylamine, or distearylamine, hydrochloride of tertiary amine such as trimethylamine, triethylamine, or stearyldimethylamine, quaternary ammonium salt such as stearyltrimethylammonium chloride, distearyldimethylammonium chloride, or stearyldimethylbenzylammonium chloride, hydrochloride of ethanolamine such as monoethanolamine, diethanolamine, or triethanolamine, and hydrochloride of polyethylene polyamine such as ethylenediamine, diethylenetriamine, or the like.

Specific examples of the cationic emulsifier include: alkyl ammonium salts, alkyl amide betaines, alkyl dimethyl amine oxides, and the like.

Specific examples of the basic resin include: a basic resin having a weight average molecular weight (Mw) of 1000 to 100 ten thousand, which contains a high molecular weight copolymer such as polyester, acrylic, or polyurethane. When the weight average molecular weight of the basic resin is less than 1000, sufficient steric hindrance may not be obtained, and the dispersing effect may be reduced, whereas when the weight average molecular weight is more than 100 ten thousand, the coagulation may be caused.

The amine value of the basic resin is preferably 5mgKOH/g to 200 mgKOH/g. When the amount is less than 5mgKOH/g, the interaction with the polyanion doped with the polythiophene is liable to become insufficient, and a sufficient dispersion effect may not be obtained. On the other hand, when the amine value of the basic resin exceeds 200mgKOH/g, the steric hindrance layer is reduced as compared with the portion having affinity for the polyanion doped with the polythiophene, and the dispersing effect may be insufficient.

Examples of the basic resin include: solsperse 17000, Solsperse20000, Solsperse 24000, Solsperse 32000 (manufactured by Zeneca K.K.), Disperbyk-160, Disperbyk-161, Disperbyk-162, Disperbyk-163, Disperbyk-170, Disperbyk-2000, Disperbyk-2001 (manufactured by Bikk chemical Co., Ltd.), AJISPER PB711, AJISPER PB821, AJISPER PB822, AJIR PB824 (manufactured by Meizhi Co., Ltd.), EPOMIN 012, 006 MIN 018 (manufactured by Nippon catalyst Co., Ltd.), EFKA 4046, EFKA 4300, EFKA 4330, EFKA4510 (manufactured by EF45K Co., Ltd.), DISPARLON DA-400N (manufactured by Nanbo chemical Co., Ltd.), and the like, and can be used alone or in combination. In particular, AJISPER PB821, AJISPER PB822, and AJISPER PB824 are preferable from the viewpoints of dispersibility and conductivity during use.

The content of the basic compound is not limited, and may be added in the range of preferably 1 to 10 ten thousand parts by weight, more preferably 10 to 1 ten thousand parts by weight, based on 100 parts by weight of the total of the polythiophene and the polyanion.

The antistatic layer in the present invention is characterized by having orientation. The antistatic layer has orientation, and the optical characteristics of the laminated polarizing plate can be appropriately maintained by controlling the degree of orientation, which is a preferred embodiment. The orientation can be confirmed in the same manner as the orientation of the base material.

The thickness of the antistatic layer (after heating and stretching) is 100nm or less, preferably 3nm to 100nm, and more preferably 20nm to 80 nm. If the thickness of the antistatic layer is too small, it is difficult to form the antistatic layer uniformly (for example, the thickness of the antistatic layer varies greatly depending on the position (バラツキ)), and thus there is a possibility that unevenness is likely to occur in the appearance of the polarizer protective film. On the other hand, when the antistatic layer is too thick, the properties (optical properties, dimensional stability due to thickness distribution, etc.) of the polarizing plate on which the protective film for a polarizer is laminated may be affected. In the case where a surface protective film is attached to the surface of a polarizing plate obtained by laminating protective films for polarizers to protect the polarizing plate, if the antistatic layer is too thick when the surface protective film is peeled off and removed, damage occurs between the base material and the antistatic layer, which is not preferable.

The surface resistance value (Ω/□) measured on the surface of the antistatic layer is preferably 1.0 × 10⁸The following, more preferably 1.0X 10⁴～1.0×10⁸More preferably 1.0X 10⁶～1.0×10⁷. The protective film for polarizer having the surface resistance value within the above range can suppress triboelectric charging generated in the processing step and the conveying stepThe protective film is preferably used because electrification of the protective film can prevent suction of dust or deterioration of workability. The surface resistance value can be calculated from a surface resistance value measured by a commercially available insulation resistance measuring apparatus in an atmosphere of 23 ℃ and 50% RH.

< method for producing protective film for polarizer >

The method for producing a protective film for a polarizer of the present invention preferably includes: the antistatic agent composition is applied to one surface of the substrate to form a coating film, and the substrate and the coating film are heated and stretched together at a temperature of not less than the glass transition temperature Tg +20 ℃ of the substrate. By heating and stretching at a temperature 20 ℃ or higher than Tg of the substrate, the substrate and the coating film (antistatic layer) are (substantially) melt-fixed without being mixed, and the interface between the substrate and the antistatic layer can be confirmed, whereby the adhesion between the substrate and the antistatic layer can be improved, which is a preferable mode. Further, stretching is preferable because the base material and the antistatic layer have orientation properties, and the degree of orientation is controlled, whereby the optical properties of the laminated polarizing plate can be appropriately maintained. In the present invention, the obtained substrate and antistatic layer are melt-fixed by heating and stretching the substrate and coating film, but generally, an antistatic layer is formed on the substrate by solvent penetration (for example, a method of adding a solvent capable of melting the substrate such as dimethyl ketone) without using such melt-fixing, and improvement of interlayer adhesion can be expected. On the other hand, a permeation layer formed by solvent permeation (a permeation portion, an interface between a base material and an antistatic layer is not present, and a mixed layer (permeation layer) obtained by mixing a base material, an antistatic layer and a solvent component may be formed in the order of several tens of nm or more) tends to have a reduced cohesive force (becomes a fragile layer), and the thickness of the permeation layer is likely to vary depending on production conditions, and therefore, it is difficult to control in practice, which is not preferable. The temperature in the heating and stretching step is more preferably 30 ℃ or more higher than the Tg of the base material, and still more preferably 40 ℃ or more higher than the Tg of the base material. Heating and stretching at a temperature higher than Tg of the base material are preferable because the base material and the antistatic layer are melt-fixed and firmly adhered to each other, and the base material and the antistatic layer can be formed while securing adhesion.

In the method for producing a protective film for a polarizer of the present invention, the step of heating and stretching is preferably a step of simultaneously or sequentially performing biaxial stretching (simultaneous biaxial stretching or sequential biaxial stretching) in the width direction and the longitudinal direction using a tenter type stretching machine. By carrying out simultaneous biaxial stretching or sequential biaxial stretching, the thickness distribution of the substrate and the antistatic layer formed of the coating film can be uniformly adjusted, and a protective film for a polarizer with little variation in adhesiveness and antistatic property can be obtained, which is a preferable embodiment. The method of simultaneous biaxial stretching or sequential biaxial stretching is not particularly limited, and any method may be used as long as simultaneous biaxial stretching or sequential biaxial stretching can be performed in the width direction and the longitudinal direction.

In the method for producing a protective film for a polarizer according to the present invention, the biaxial stretching is preferably performed simultaneously or sequentially at a stretching ratio of 1.5 times or more and 3.0 times or less (in both the longitudinal direction (MD) and the width direction (TD)). When the stretching ratio is within the above range, the thickness distribution of the polarizer protective film in the width direction is narrow, the distribution of the thickness accuracy is improved, the retardation by the base material is less likely to occur, and the optical characteristics are excellent, which is a preferable embodiment. On the other hand, if the stretch ratio is increased, the film itself may be easily cracked or embrittled, and the distribution of thickness accuracy may be decreased, and if the film is wound, the appearance is poor, and a retardation may be generated by the substrate, which is not preferable. The stretch ratio is more preferably 1.5 times or more and 2.5 times or less, still more preferably 1.5 times or more and 2.3 times or less, and particularly preferably 1.5 times or more and 2.1 times or less.

< apparatus for producing protective film for polarizer >

The apparatus for manufacturing a protective film for a polarizer of the present invention preferably includes: a coating film forming means for forming a coating film by applying the antistatic agent composition to one surface of the substrate, and a heating and stretching means for heating and stretching the substrate together with the coating film at a temperature of not less than the glass transition temperature Tg +20 ℃ of the substrate. In addition, as the heating stretching unit, a tenter type stretching machine is preferably used. The apparatus for producing the protective film for a polarizer includes the coating film forming means and the heating and stretching means, whereby the base material and the coating film (antistatic layer) are melt-fixed without being (substantially) mixed, and the interface between the base material and the antistatic layer can be confirmed, and a protective film for a polarizer excellent in adhesion between the obtained base material and the antistatic layer can be obtained, which is a preferable embodiment. In addition, by including a tenter type stretching machine as the heating and stretching unit, the thickness distribution in the width direction of the polarizer protective film is narrowed, the distribution of the thickness accuracy is improved, the retardation by the base material is not easily generated, and the optical characteristics are excellent, which is a preferable embodiment. Further, since the coating film formation (coating) and the stretching can be continuously performed, man-hours can be reduced, which is preferable.

< polarizer >

As the polarizer constituting the polarizing plate and to which the protective film for a polarizer of the present invention is to be laminated, a polarizer using a polyvinyl alcohol-based resin is used. Examples of the polarizer include: and polyene alignment films such as films obtained by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formylated polyvinyl alcohol films, and ethylene-vinyl acetate copolymer partially saponified films, polyvinyl alcohol dehydrated products, and polyvinyl chloride dehydrochlorinated products, to which dichroic substances such as iodine and dichroic dyes are adsorbed. Among them, a polarizer containing a polyvinyl alcohol film and a dichroic substance such as iodine is preferable.

The polarizer obtained by dyeing the polyvinyl alcohol film with iodine and uniaxially stretching the film can be produced, for example, by: the polyvinyl alcohol is dyed by immersing in an aqueous iodine solution and stretched to 3 to 7 times the original length. Boric acid, zinc sulfate, zinc chloride, etc. may be contained as necessary, or the sheet may be immersed in an aqueous solution of potassium iodide, etc. If necessary, the polyvinyl alcohol film may be washed with water by immersing it in water before dyeing. By washing the polyvinyl alcohol film with water, stains and an anti-blocking agent on the surface of the polyvinyl alcohol film can be washed, and the polyvinyl alcohol film is swollen to prevent unevenness such as uneven dyeing. The stretching may be performed after the dyeing with iodine, may be performed simultaneously with the dyeing, or may be performed after the stretching with iodine. Stretching may be performed in an aqueous solution or water bath of boric acid, potassium iodide, or the like.

From the viewpoint of thinning, the thickness of the polarizer is preferably 20 μm or less, more preferably 10 μm or less, and still more preferably 5 μm or less. On the other hand, the thickness of the polarizer is preferably 1 μm or more. Such a thin polarizer has excellent durability against thermal shock because of its small thickness unevenness, excellent visibility, and small dimensional change. Typical examples of the thin polarizer include: a thin polarizer described in japanese patent No. 4751486, japanese patent No. 4751481, japanese patent No. 4815544, japanese patent No. 5048120, international publication No. 2014/077599, international publication No. 2014/077636, and the like, or a thin polarizer obtained by the manufacturing method described in the above documents.

The above polarizer is preferably such that optical characteristics represented by a single sheet transmittance ( body transmittance) T and a degree of polarization P satisfy the following expression P>- (100.929T-42.4-1). times.100 (wherein, T)<42.3) or P.gtoreq.99.9 (wherein T.gtoreq.42.3). A polarizer configured to satisfy the above conditions has a unique property required for a display for a liquid crystal television using a large-sized display element. Specifically, the contrast ratio is 1000:1 or more and the maximum luminance is 500cd/m²The above. For another application, for example, the organic EL element is bonded to a viewing side of an organic EL unit.

As the thin polarizer, from the viewpoint that the polarizer can be stretched at a high magnification and the polarization performance can be improved even in a production method including a step of stretching a laminate and a step of dyeing, a polarizer obtained by a production method including a step of stretching in an aqueous boric acid solution as described in japanese patent No. 4751486, japanese patent No. 4751481, and japanese patent No. 4815544 is preferable, and particularly a polarizer obtained by a production method including a step of auxiliarily stretching in air before stretching in an aqueous boric acid solution as described in japanese patent No. 4751481 and japanese patent No. 4815544 is preferable. These thin polarizers can be obtained by a production method including a step of stretching a polyvinyl alcohol resin (hereinafter, also referred to as PVA-based resin) layer and a stretching resin base material in a state of a laminate and a step of dyeing. In this production method, even if the PVA-based resin layer is thin, the PVA-based resin layer can be supported by the stretching resin base material and can be stretched without causing troubles such as breakage due to stretching.

< polarizing plate >

As the polarizing plate comprising a polarizer laminated with the protective film for a polarizer of the present invention, a polarizing plate having a protective film for a polarizer provided with an antistatic layer on at least one surface of a polarizer can be used. In addition, a polarizing plate having a structure in which an adhesive layer is laminated on at least one surface of the polarizing plate may be used, and another optical member (for example, a retardation film, a liquid crystal display device, or the like) may be laminated on a surface of the adhesive layer opposite to a surface thereof in contact with the polarizing plate. The polarizing plate may be configured such that the antistatic layer located on the surface layer of the polarizing plate and the adhesive layer constituting the surface protective film for the polarizing plate are directly laminated (in contact) with each other.

The thickness of the polarizing plate is preferably 100 μm or less, more preferably 75 μm or less, and still more preferably 50 μm or less. The thickness of the polarizing plate is 100 μm or less, which can meet the demand for reduction in thickness, and is useful in design, portability, and weight reduction.

< first adhesive layer >

A polarizing plate having a structure in which a first pressure-sensitive adhesive layer is laminated on at least one surface of the polarizing plate may be used, and another optical member (for example, a retardation film, a liquid crystal display device, or the like) may be laminated on a surface of the first pressure-sensitive adhesive layer opposite to a surface thereof in contact with the polarizing plate. An appropriate adhesive (adhesive composition) may be used in the first adhesive layer, and the kind thereof is not particularly limited. As the binder, there may be mentioned: rubber-based adhesives, acrylic adhesives, silicone-based adhesives, polyurethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinyl pyrrolidone-based adhesives, polyacrylamide-based adhesives, cellulose-based adhesives, and the like. Among these pressure-sensitive adhesives (pressure-sensitive adhesive compositions), those excellent in optical transparency, exhibiting appropriate adhesive properties such as wettability, cohesiveness and adhesiveness, and excellent in weather resistance, heat resistance and the like are preferably used. As the adhesive exhibiting such characteristics, an acrylic adhesive is preferably used.

The first pressure-sensitive adhesive layer can be formed, for example, by the following method: a method in which the pressure-sensitive adhesive (pressure-sensitive adhesive composition) is applied to a separator after a release treatment, and a polymerization solvent or the like is dried and removed to form a pressure-sensitive adhesive layer, followed by transfer to a polarizing plate; or a method in which the adhesive is applied to a polarizing plate and the polymerization solvent or the like is dried and removed to form an adhesive layer on the polarizer. In the case of applying the adhesive, one or more solvents other than the polymerization solvent may be added newly as appropriate. As the separator after the release treatment, a silicone separator is preferably used.

In the step of forming the pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive (pressure-sensitive adhesive composition) to such a separator and drying the pressure-sensitive adhesive, a suitable method can be appropriately employed as a method for drying the pressure-sensitive adhesive according to the purpose. A method of drying the coating film by heating is preferably used. The heating and drying temperature is preferably 40 to 200 ℃, more preferably 50 to 180 ℃, and particularly preferably 70 to 170 ℃. By setting the heating temperature to the above range, an adhesive layer having excellent adhesive properties can be obtained.

As a method for forming the adhesive layer, various methods can be used. Specifically, for example, there may be mentioned: roll coating, roll and lick coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, and the like.

The thickness of the first pressure-sensitive adhesive layer is preferably 2 to 50 μm, more preferably 2 to 40 μm, and still more preferably 5 to 35 μm.

The spacer may protect the first adhesive layer until ready for use. Examples of the material constituting the separator include: plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; porous materials such as paper, cloth, and nonwoven fabric; a plastic film is preferably used from the viewpoint of excellent surface smoothness, for example, a thin paper-like material (a "Yeye"), such as a web, a foam sheet, a metal foil, and a laminate thereof. The plastic film is not particularly limited as long as it is a film capable of protecting the pressure-sensitive adhesive layer, and examples thereof include: polyethylene films, polypropylene films, polybutylene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, ethylene-vinyl acetate copolymer films, and the like.

The separator may be subjected to release and anti-fouling treatment with a release agent of silicone type, fluorine type, long chain alkyl group or fatty acid amide type, silica powder or the like, or antistatic treatment such as coating type, kneading type, vapor deposition type or the like, as required. In particular, by appropriately subjecting the surface of the release film to a release treatment such as a polysiloxane treatment, a long-chain alkyl treatment, or a fluorine treatment, the releasability from the first pressure-sensitive adhesive layer can be further improved.

The thickness of the spacer is preferably 5 μm to 50 μm, and more preferably 20 μm to 40 μm.

The polarizing plate disclosed herein may be implemented to include other layers in addition to the polarizer protective film including the antistatic layer and the base material, the polarizer, and the intermediate layer (the body frame body interposed therebetween) (the adhesive layer, the first adhesive layer, and the like).

Examples

The present invention will be described below with reference to some examples, but the present invention is not intended to be limited to the specific examples. Unless otherwise specified, "part" and "%" in the following description are based on weight. The amounts (amounts added) in the table are shown.

The characteristics in the following description were measured or evaluated as described below. The following methods for producing the protective film for a polarizer were prepared according to the configurations shown in table 1.

< measurement of thickness and thickness distribution >

The thickness distribution (thickness) in the width direction was measured using a digital thickness gauge manufactured by toyoyo seiki co. The thickness distribution of the protective film for a polarizer in the present invention is preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm. Within the above range, the mechanical properties of the protective film for a polarizer can be maintained and the optical properties are not impaired, which is preferable.

< measurement of cohesion force (nanoindenter) >

The antistatic layer of the protective film for a polarizer was subjected to indentation test under the following conditions, and the cohesive force (GPa) between the base material and the antistatic layer was determined from the results.

(measurement apparatus and measurement conditions)

Measurement device: tribo Inder (manufactured by Hysitron Inc.)

The pressure head used: berkovich (triangular cone type)

The determination method comprises the following steps: single indentation measurement

Measuring temperature: 80 deg.C

And (3) indentation depth setting: about 70nm

Pressing-in speed: about 10 nm/sec

And (3) measuring the atmosphere: in the air

(measurement method)

Using the above apparatus, the temperature was raised from room temperature to 80 ℃ and held for 1 hour, and then a shape image was measured using a Berkovich type diamond indenter. The polarizer protective film was vertically pressed from the surface to a depth of 70nm by the indenter on the antistatic layer surface. The area in the load-displacement curve obtained when the indenter was pressed was defined as the cohesive force (GPa) using the analytical software "Triboscan Ver.9.2.12.0".

The cohesive force of the polarizer protective film in the present invention is preferably 0.1GPa or more, and more preferably 0.2 GPa. When the amount is within the above range, the adhesion between the substrate and the antistatic layer is excellent, and it is preferable.

< measurement of adhesion >

An adhesive tape ("No. 31B" manufactured by Nindon electric Co., Ltd.) was pressure-bonded to the surface of the antistatic layer of the protective film for polarizer under conditions of a linear pressure of 8Kg/m and a pressure-bonding speed of 0.3 m/min, and after the pressure-bonding, the film was stored at 50 ℃ for 48 hours. After storage, the mixture was passed through a 180-degree stretch hood at a stretching speed of 30 m/min^°Peeling test for peeling was performed (according to JIS-Z-0237).

In the evaluation in table 1, the peeling of the antistatic layer, the destruction of the antistatic layer (aggregation destruction, interfacial peeling) and the like at the time of peeling were confirmed while measuring the adhesive force, and the comprehensive evaluation was performed. The evaluation was made according to the following criteria.

O: the peel force was not measurable (non-peelable, strong), no detachment was visible to the naked eye, and no destruction of the antistatic layer.

X: the peeling force was 1.0N/18mm or less (easily peeled and weak), or the peeling-off and the breakage of the antistatic layer were visible to the naked eye.

In the evaluation in table 2, the adhesion was evaluated by changing the stretching temperature while the glass transition temperature (Tg) was 120 ℃ and the thickness of the antistatic layer was fixed at 100 nm. In the evaluation in table 3, the glass transition temperature (Tg) was 120 ℃, and the thickness of the antistatic layer was varied to evaluate the adhesion.

< measurement of surface resistance value on surface of antistatic layer >

The surface resistance value (omega/□) of the antistatic layer surface of the polarizer protective film was measured by a resistance measuring instrument (Hiresta, Mitsubishi chemical Analyticech, Ltd.) according to JIS-K-6911-1995 under an atmosphere of a temperature of 23 ℃ and a humidity of 50% RH. The applied voltage was set to 10V using Registration table UFL Teflon (registered trademark) electrodes, and the surface resistance value was read 10 seconds after the start of measurement.

The surface resistance value (Ω/□) measured on the antistatic layer surface of the polarizer protective film of the present invention is preferably 1.0 × 10¹²Hereinafter, more preferably 1.0X 10¹⁰The following, more preferably 1.0X 10⁴～1.0×10⁹Particularly preferably 1.0X 10⁴～1.0×10⁹. The protective film for a polarizer having an antistatic layer exhibiting a surface resistance value in the above range can be suitably used, for example, as a polarizer (polarizing plate) with a protective film for a polarizer used in processing or transporting of an article such as a liquid crystal cell, a semiconductor device, or the like, which is resistant to static electricity. The polarizer protective film exhibiting the surface resistance value within the above range is useful in that the operation can be confirmed even when a polarizing plate is mounted on the touch panel sensor and the surface protective film is attached to the polarizing plate.

< measurement of peeling electrification Voltage >

The sample laminated with the protective film for polarizer was subjected to 180-degree peeling at a peeling rate of 10 m/min in an atmosphere of 23 ℃ and a humidity of 50% RH from a position of 10cm in height using an electrostatic potential measuring instrument KSD-0103 manufactured by Chunshi electric motors K.K.^°Peeling electrification voltage generated at the time of peeling.

The peeling electrification voltage is mainly derived from the electrification preventing layer constituting the protective film for a polarizer of the present invention, and contributes to the peeling electrification preventing property.

The peeling electrification voltage (absolute value) of the surface protective film for a polarizing plate of the present invention is preferably 0.4kV or less, and more preferably 0.3kV or less. When the peeling electrification voltage exceeds 0.4kV, the polarizer array in the polarizing plate is disturbed, which is not preferable.

[ examples 1 to 4]

< preparation of protective film for polarizer (Using conductive Polymer + Hot-melt) >

A transparent protective film (Tg: 120 ℃, same transparent protective film used in the following examples and comparative examples) comprising a (meth) acrylic resin having a lactone ring structure as a base material was coated with a wire rod #6 with Denatron P-502RG (containing PEDOT/PSS) manufactured by garrulite inc, and then the transparent protective film (base material) and the coating film (antistatic layer) were preheated at 150 ℃ for 30 seconds and stretched at 150 ℃ at a strain rate of 6%/second with a KARO IV film batch stretcher manufactured by BRUCKNER, to prepare a sample. As for the stretching magnification, as shown in table 1, the same magnification was used in both the width direction (TD) and the longitudinal direction (MD) in the magnification in each example. As shown in Table 1, the thickness of the antistatic layer in each example was 20nm, 50nm, and 100 nm.

Comparative example 1

< production of protective film for polarizer (Using conductive Polymer + heating (drying) alone) >

A transparent protective film comprising a (meth) acrylic resin having a lactone ring structure as a base material was stretched 2 times in both the width direction (TD) and the length direction (MD), and then Denatron P-502RG manufactured by garlines chemical company was applied to the film by a wire bar #6, followed by drying at 150 ℃ for 60 seconds, thereby preparing a sample.

Comparative example 2

< preparation of protective film for polarizer (conductive Polymer use + solvent infiltration) >

On a transparent protective film comprising a (meth) acrylic resin having a lactone ring structure as a base material, a liquid obtained by adding 10% by weight of dimethyl ketone to Denatron P-502RG manufactured by gargariner was prepared and coated with a wire bar #6, and then preheated at 150 ℃ for 30 seconds and stretched at 150 ℃ at a strain rate of 6%/second 2 times in each of both the width direction (TD) and the length direction (MD) by a KARO IV film batch stretcher manufactured by BRUCKNER, to prepare a sample. Since dimethyl ketone was used as a solvent, the solvent permeated, and it was confirmed that a permeation layer (mixed layer) was formed at the interface between the substrate and the antistatic layer.

Comparative example 3

< preparation of protective film for polarizer (Using Metal oxide + Hot melting) >

A tin oxide S-1 produced by mitsubishi Material electronics corporation was coated on a transparent protective film comprising a (meth) acrylic resin having a lactone ring structure by a wire rod #6, and then the transparent protective film (substrate) and a coating film (antistatic layer) were preheated at 150 ℃ for 30 seconds by a KARO IV film batch stretcher produced by BRUCKNER corporation and stretched at 150 ℃ at a strain rate of 6%/second to prepare a sample.

Comparative example 4

< preparation of protective film for polarizer (Using Ionic liquid + Heat fusion) >

A transparent protective film comprising a (meth) acrylic resin having a lactone ring structure was coated with a Saftomer ST-1000 manufactured by mitsubishi chemical corporation using a wire rod #6, and then the transparent protective film (substrate) and the coating film (antistatic layer) were preheated at 150 ℃ for 30 seconds and stretched at 150 ℃ at a strain rate of 6%/second using a KARO IV film batch stretcher manufactured by BRUCKNER corporation, to produce a sample.

Comparative example 5

< preparation of protective film for polarizer (Using Metal salt/inorganic salt + Hot melting) >

A transparent protective film comprising a (meth) acrylic resin having a lactone ring structure was coated with 1SX-1055, manufactured by Fine Chemical corporation, by using a wire rod #6, and then the transparent protective film (base material) and the coating film (antistatic layer) were preheated at 150 ℃ for 30 seconds and stretched at 150 ℃ at a strain rate of 6%/second by using a KARO IV film batch stretcher manufactured by BRUCKNER corporation, to prepare a sample.

Examples 5-1 to 5-3 and comparative examples 6-1 to 6-3

On a transparent protective film comprising a (meth) acrylic resin having a lactone ring structure, samples were produced by the same method as in example 1 and the like using Denatron P-502RG manufactured by chancron chemical company at various stretching temperatures (heating and stretching temperatures) so that the thickness of the antistatic layer after stretching was 100 nm. In table 2, the stretching ratios are 2 times in the width direction (TD) and 2 times in the length direction (MD).

Examples 6-1 to 6-3 and comparative examples 7-1 to 7-2

A transparent protective film comprising a (meth) acrylic resin having a lactone ring structure was coated with Denatron P-502RG manufactured by gargaritifer using a wire rod #6, and then the transparent protective film (base material) and the coating film (antistatic layer) were preheated at 140 ℃ for 30 seconds by a KARO IV film batch stretcher manufactured by BRUCKNER and stretched at a strain rate of 6%/second at 140 ℃ to prepare a sample (the temperature was fixed at 140 ℃). Further, the thickness of the antistatic layer after stretching was adjusted as shown in table 3 by controlling the stretching ratio, and samples were produced by the same method as in example 1 and the like. In table 3, the stretching ratios are 2 times in the width direction (TD) and 2 times in the length direction (MD).

The contents of the above-described components, the preparation conditions, and the results of various measurements and evaluations of the protective films for polarizers of examples and comparative examples are shown in tables 1 to 3.

TABLE 2

TABLE 3

As confirmed from table 1: in the examples, the adhesion form of the base material and the antistatic layer was a hot-melted state (melt-fixed) after heating and stretching, and therefore, the cohesion and adhesion between the base material and the antistatic layer were excellent, and the antistatic property were also excellent. In particular, in the case of examples prepared by setting the stretching ratio to 1.5 times or more and 3.0 times or less, it was confirmed that: a protective film for a polarizer, which has a very narrow thickness distribution in the width direction and is uniform without variation in thickness, can be obtained.

On the other hand, in comparative example 1, it was confirmed that: since only heating (drying) was performed without stretching, uniform thermal fusion between the base material and the antistatic layer did not occur, and the adhesive force was poor, as confirmed in comparative example 2: since the solvent penetration is utilized, the cohesion between the base material and the antistatic layer is poor. In addition, in comparative examples 3 to 5, it was confirmed that: since a metal oxide or the like is used for the antistatic layer instead of the conductive polymer, antistatic property and anti-peeling electrification property cannot be maintained by heat fusion by heating and stretching.

According to Table 2, it was confirmed that, when the substrate and the antistatic layer constituting the protective film for a polarizer had a glass transition temperature of 120 ℃ and the thickness of the antistatic layer was fixed at 100nm and only the stretching temperature was changed, the stretching temperature was lower than the substrate Tg +20 ℃ (comparative examples 6-1 to 6-3): no thermal fusion between the substrate and the antistatic layer occurs, and the adhesion is poor. On the other hand, when the stretching temperature was not less than Tg +20 ℃ of the base material (examples 5-1 to 5-3), it was confirmed that the base material was in a hot-melt (melt-fixed) state and was firmly adhered to such an extent that the adhesion could not be measured.

According to Table 3, it was confirmed that, when the thickness of the antistatic layer was changed only by fixing the stretching temperature of 140 ℃ to 120 ℃ as the base material and the antistatic layer constituting the protective film for polarizer, the glass transition temperature of the base material was 120 ℃ and the thickness of the antistatic layer was 100nm or less (examples 6-1 to 6-3): the adhesion between the substrate and the antistatic layer was good and no damage occurred. On the other hand, when the thickness of the antistatic layer exceeded 100nm (comparative examples 7-1 to 7-2), the adhesion was reduced, and it was confirmed that a crack occurred between the substrate and the antistatic layer.

Industrial applicability

The protective film for a polarizer disclosed herein is used as a polarizing plate by laminating the protective film to a polarizer, and can be suitably used as a component of a liquid crystal display panel, a Plasma Display Panel (PDP), an organic Electroluminescence (EL) display, or the like.

Claims

1. A method for producing a protective film for a polarizer, the protective film comprising a base material and an antistatic layer formed of an antistatic agent composition containing a conductive polymer on one surface of the base material,

the substrate and the antistatic layer are melt-fixed without being mixed and have orientation,

the thickness of the antistatic layer is less than 100nm,

the base material is formed with a (meth) acrylic resin as a main component,

the antistatic agent composition contains poly (3, 4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT/PSS) as the conductive polymer, and contains a polyester resin as a binder component,

the method for manufacturing the protective film for the polarizer comprises the following steps:

a step of applying the antistatic agent composition to one surface of the substrate to form a coating film, and a step of heating and stretching the substrate together with the coating film at a temperature of not less than the glass transition temperature Tg +20 ℃ of the substrate, wherein

The step of heating and stretching is a step of simultaneously or sequentially biaxially stretching in the width direction and the longitudinal direction using a tenter type stretching machine.

2. The method for producing a protective film for a polarizer according to claim 1, wherein the antistatic layer has a surface resistance value of 1.0 x 10¹²Omega/□ or less.

3. The method for producing a protective film for a polarizer according to claim 1 or 2, wherein the simultaneous or sequential biaxial stretching is performed at a stretch ratio of 1.5 times or more and 3.0 times or less in each of a width direction and a length direction.