JP5073728B2 - Protective film for polarizing plate, method for producing the same, and polarizing plate - Google Patents

Description

The present invention relates to a polymer film having a conductive polymer attached to the surface. Specifically, the conductive polymer is polythiophene or a derivative thereof, and the polymer film is made of an acetylcellulose-based or norbornene-based material. The present invention relates to a polymer film having a thickness of 3 μm or less, a visible light transmittance of 78% or more, and a surface resistivity of 10 ³ to 10 ¹² Ω / mouth, such as a liquid crystal display (LCD). The present invention relates to a highly transparent conductive polymer film having an antistatic or electromagnetic wave shielding function, which is used for display, and particularly useful for a protective film of a polarizing plate.

  The polarizing plate is made by stretching a polyvinyl alcohol (PVA) film and adhering and fixing iodine or dye to the both sides of a polarizing film, and attaching a film made of triacetyl cellulose (TAC) to both sides of the PVA. It has a structure that prevents changes in properties due to reinforcement of strength and water absorption. TAC has been used as a protective film for such a polarizing film because it is excellent in transparency, has low birefringence, and is easy to adhere to PVA. In recent years, along with the increase in size of liquid crystal displays, the size change due to water absorption may become a problem even in TAC films. For this reason, the norbornene system has excellent transparency, low birefringence, and low water absorption. Films made of materials are being considered as TAC alternatives.

  On the other hand, in displays such as LCDs, CRTs, ELs, PDPs and the like, electromagnetic waves generated from them have an adverse effect on the human body. In addition, when installing a film with such a function of blocking electromagnetic waves inside or outside the display, it must have excellent transparency, low birefringence, high strength, high heat resistance, and low water absorption. In addition to satisfying these characteristics, it was necessary to find a film having an electromagnetic wave shielding function.

  In order to block electromagnetic waves, a conductive material may be placed on the front surface of the display. Generally, as a highly transparent conductive material, ITO or the like is used by sputtering or vapor deposition. The one attached to the molecular film is used, but these methods have poor productivity and the material itself is expensive, so there is a problem that the film imparted with conductivity becomes very expensive. . In addition, ITO tends to be colored yellow, and this coloration also becomes a problem with the colorization of LCDs.

  In addition, when it is arranged on a display such as an LCD, EL, or PDP, the adhesion of dust due to static electricity is a big problem, and it has been desired to have an antistatic function.

  As the polymer material having conductivity, polyaniline derivatives, polypyrrole derivatives and polythiophene derivatives are well known. However, when high resistance is obtained, polyaniline is colored green, and polypyrrole is There was a problem of coloring in gray.

  The object of the present invention is to solve such problems of the prior art, and to protect a conductive polarizing plate that has transparency without any problems even when placed on a display such as an LCD, and has an antistatic function and an electromagnetic wave shielding function. It is to provide a protective film for a polarizing plate that is a film and inexpensive.

That is, the protective film for polarizing plate of the present invention is a polymer film having a conductive polymer attached to the surface, and has a visible light transmittance of 78% or more and a surface resistivity of 10 ³ to 10 ¹² Ω / mouth. The conductive polymer film is a polythiophene material as the conductive polymer, the thickness of the conductive polymer layer is controlled to 3 μm or less, and the polymer film material is an acetylcellulose material or a norbornene material. This is easily achieved by using materials.

  Hereinafter, the present invention will be described in detail. The conductive polymer used in the present invention is a homopolymer or copolymer obtained by polymerizing thiophene and / or a thiophene derivative. This conductive polymer is a homopolymer or copolymer having as a main component a unit represented by the following formula (I), formula (II), formula (III) and / or formula (IV) as a polymerization unit. A copolymer containing a small amount of other polymer units as a copolymer component may also be used.

In the above formula (I) and formula (II), R ¹ and R ² are each a hydrogen atom, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group or an aromatic hydrocarbon group, a hydroxyl group, a terminal A group having a hydroxyl group, an alkoxy group, a group having an alkoxy group at the end, a carboxy group, a carboxyl base, a group having a carboxyl group at the end, a group having a carboxyl base at the end, an ester group, a group having an ester group at the end, Sulfonic acid group, group having sulfonic acid group at the terminal, sulfonyl group, group having sulfonyl group at the terminal, sulfinyl group, group having sulfinyl group at the terminal, acyl group, group having acyl group at the terminal, amino group, terminal Group having an amino group, a group in which part or all of the hydrogen atoms of the amino group are substituted, or a group in which part or all of the hydrogen atoms of the amino group are substituted. A group having a carbamoyl group at the terminal, a group in which part or all of the hydrogen atoms of the carbamoyl group are substituted, a group having a group having all or part of the hydrogen atoms in the carbamoyl group substituted, halogen groups A phosphate group, a group having a phosphate group at the terminal, an oxirane group or a group having an oxirane group at the terminal.

  In the above formulas (II) and (IV), Y- is an element or compound having an anion, and examples thereof include a halogen ion, a sulfonate ion, a carboxylate ion, and the like. Show.

To such a thiophene conductive polymer, a doping agent can be added in an amount of 0.1 to 500 parts by weight, for example, with respect to 100 parts by weight of the conductive polymer in order to further increase the conductivity. As this doping agent, LiCl, R ³ COOLi (R ³ : saturated hydrocarbon group having 1 to 30 carbon atoms), R ³ SO ₃ Li, R ³ COONa, R ³ SO ₃ Na, R ³ COOK, R ³ SO ₃ K, _{tetraethylammonium, I 2, BF 3 Na,} BF 4 Na, HClO 4, CF 3 SO 3 H, FeCl 3, tetra cyano _quinoline, Na ₂ B _{10 Cl 10,} phthalocyanines, porphyrins, glutamic acid, alkyl sulfonate Polystyrene sulfonic acid alkali salt copolymer, polystyrene sulfonic acid anion, styrene sulfonic acid and styrene sulfonic acid anion copolymer, and the like can be used, and two or more of these can be used in combination.

  In the present invention, a binder resin can be blended in order to improve the adhesion between the polymer film and the conductive polymer. The binder resin may be appropriately selected from those having excellent adhesion to the type of polymer film, and is not particularly limited, but is not limited to polyester resin, acrylic resin, acrylic modified polyester resin, urethane resin, It can be selected from vinyl acetate, vinyl chloride, polyvinyl alcohol, polyethylene vinyl acetate, organic silicate, and the like. Of course, two or more kinds of binders can be mixed and used.

In the present invention, the conductive polymer layer is formed by applying an aqueous coating liquid containing a conductive polymer obtained by polymerizing thiophene and / or a thiophene derivative onto a polymer film, and drying and curing the surface resistivity. Is a coating film of 10 ³ to 10 ¹² Ω / mouth. Particularly preferably, it is 10 ⁴ to 10 ⁸ Ω / mouth. When the surface resistivity is less than 10 ³ Omega / mouth, or it is necessary to increase the thickness of the coating layer, the coating film becomes brittle due to the lack of amount of binder to be described later, when it exceeds 10 ¹² Omega / mouth electrostatic Electricity prevention effect and electromagnetic wave shielding effect are insufficient.

  The conductive polymer layer formed by the coating method has a composition of 1 to 95% by weight, preferably 2 to 70% by weight of the conductive polymer, and 5 to 99% by weight, preferably 30 to 98% by weight of the binder resin. An aqueous coating liquid containing a product is preferably applied to a polymer film, dried and cured.

  When the ratio of the conductive polymer and the binder resin is in the above range, the adhesion between the polymer film and the conductive polymer is good, the antistatic effect is excellent, and the adhesiveness and abrasion resistance are good. Therefore, it is preferable.

  The composition of the conductive polymer and the binder resin can be obtained by a commonly used mixing method, but the method of coating the surface of the fine particle binder resin with the conductive polymer or the functional group in the conductive polymer. It is also possible to apply a method of chemically binding the functional group present in the binder resin.

  As a component of the conductive polymer layer, an epoxy resin, a vinyl resin, a polyether resin, a water-soluble resin, or the like can be arbitrarily blended for the purpose of adjusting adhesiveness, solvent resistance, water resistance and the like. In addition, in order to improve the slipperiness and blocking resistance of the coating film, inorganic or organic fine particles having an average particle diameter of about 0.01 to 20 μm are used as a lubricant in a proportion of 0.001 to 5% by weight. It can be included.

  As such fine particles, inorganic fine particles such as silica, alumina, titanium oxide, carbon black, kaolin, calcium carbonate, polystyrene resin, cross-linked polystyrene resin, acrylic resin, cross-linked acrylic resin, melamine resin, silicon resin, fluorine resin, urea resin, Examples include organic fine particles such as benzoguanamine resin. The organic fine particle may be a thermoplastic resin or a thermosetting resin as long as it is a resin that can maintain the fine particle state to some extent in the coating film. Moreover, in order to improve electroconductivity, an electroconductive filler, for example, a tin oxide type fine particle, an oxide oxide type fine particle, etc. can also be mixed.

  In addition to the fine particles, surfactants, antioxidants, colorants, pigments, fluorescent brighteners, plasticizers, crosslinking agents, organic slip agents, ultraviolet absorbers, antistatic agents, and the like may be added as necessary. it can.

  In the present invention, the conductive polymer layer is formed using the aqueous coating liquid containing the composition. The solid content concentration of the aqueous coating liquid is usually 0.1% to 30% by weight, and 1 to 20%. % By weight is preferred. When the solid content concentration is in such a range, the viscosity of the aqueous coating liquid becomes suitable for coating. The aqueous coating liquid can be used in any form such as an aqueous solution, aqueous dispersion, emulsion, etc., and in the aqueous coating liquid, alcohols such as methanol, ethanol, isopropyl alcohol, and ethylene glycol, and ketones such as acetone and methyl ethyl ketone are used. The evaporation rate of the solvent can be increased by adding a water-soluble solvent such as a liquid. In particular, alcohols are preferably used because they have high miscibility with water and improve smoothness. Further, other solvents may be contained in a small amount as long as they do not become inconvenient.

  In the present invention, the conductive polymer layer is formed by applying the coating liquid to a transparent polymer film. Since the polymer film coated with the conductive polymer layer is used as an optical film, it is particularly used as a protective film for a polarizing plate. Refraction is an important characteristic. The higher the visible light transmittance, the better, and it is 78% or more, preferably 82% or more, particularly preferably 85% or more. The smaller the birefringence, the better. The thickness is preferably 100 nm or less, preferably 50 nm or less, and a polymer film having these characteristics at the same time is suitably used.

  As such a polymer film, an acetylcellulose-based film and a norbornene-based film are used because of properties such as visible light transmittance, birefringence, and yellow colorability.

  Examples of the acetylcellulose-based film include cellulose triacetate film (TAC film), cellulose diacetate film, and modified films thereof made of cellulose fiber as a raw material. This film is usually obtained by applying a solution obtained by dissolving cellulose fibers in a suitable solvent such as methylene chloride onto, for example, a stainless steel belt or a suitable polymer film, and then removing the solvent and drying.

  The norbornene-based film suitably used in the present invention is not particularly limited as long as it is a polymer obtained from one or more polymerizable monomers having a norbornene structure. For example, a polymer can be obtained by ring-opening polymerization of monomers containing a norbornene structure and then hydrogenating part or all of the remaining double bonds with a hydrogenation catalyst. Specific examples include ZEONEX and ZEONOR of Nippon Zeon Co., Ltd., and JP-A-5-97978 as trade names produced by the methods disclosed in JP-A-63-218726, JP-A-5-25220, JP-A-9-183832, and the like. And Arton of JSR Corporation manufactured by the method exemplified in JP-A-1-240517 and the like.

  In addition, there are also polymers obtained by addition polymerization of a monomer group in which a monomer having a norbornene structure and several other monomers having a double bond are combined by a known method, such as JP-A-6-107735 and JP-A-62-2. 252406, Japanese Patent Application Laid-Open No. 8-259629, etc., and Mitsui Chemicals Co., Ltd.'s trade name Appel, Topas commercialized by Hoechst, and the like are included.

  As a method for producing a film from the polymer thus obtained, known methods can be applied. For example, a polymer that dissolves the polymer well, specifically, a halogen-based solvent such as methylene chloride or an aromatic or alicyclic organic solvent, a metal belt such as stainless steel, polyester, etc. It can be produced by a so-called casting method obtained by applying a polymer solution on the polymer film, removing the solvent and drying. It can also be produced by a so-called extrusion method in which a polymer is melted by heat and discharged onto a metal belt and then cooled.

  In addition, when producing acetylcellulose-based films and norbornene-based films, antioxidants, ultraviolet absorbers, ultraviolet stabilizers, colorants, lubricants, antistatic agents, various pigments are included in these polymers as necessary. A film can be produced by adding various additives such as dyes, fibers, and dispersants. When used as a protective film for a polarizing plate, a film containing an antioxidant, an ultraviolet absorber, and an ultraviolet stabilizer is preferably used.

The film thus obtained may be coated on the surface for various purposes. For example, to prevent scratches on the surface, acrylic, urethane, urethane acrylic UV curable or thermosetting hard coating agents, epoxy hard coating agents, silicon hard coating agents, etc. are applied. Can also be used. In addition, a so-called antiglare hard-coated material in which the hard coat agent is coated by containing fine particles such as SiO ₂ and alumina to reduce gloss can be used. As the protective film for polarizing plate of the present invention, a film coated with the above hard coat or antiglare hard coat agent is more preferably used.

  As a method for applying the coating liquid to the polymer film, any known coating method can be applied. For example, roll coating method, gravure coating method, screen printing method, offset printing method, micro gravure coating method, reverse coating method, roll brush method, spray coating method, air knife coating method, impregnation method and curtain coating method alone Or they can be applied in combination.

  In the present invention, the conductive polymer layer has a thickness of 0.005 to 3 μm, preferably 0.01 to 1 μm, more preferably 0.02 to 0.5 μm. If the thickness is too thin, a sufficient antistatic effect may not be obtained. If the thickness is too thick, the coating film may be cracked or the blocking resistance may be reduced. It goes without saying that the conductive polymer layer may be applied on both sides of the polymer film or on one side.

  The hard coat agent and antiglare hard coat described above can also be performed on the polymer film having the conductive polymer layer formed in this manner. Various known coatings such as antireflection coating, antifouling coating, and pressure-sensitive adhesive layer coating can also be applied according to the purpose. In addition, when the conductive polymer layer is formed on one side, a hard coat, an antiglare hard coat, an antireflection coat, an antifouling coat, a pressure-sensitive adhesive layer, etc. are applied to the opposite side according to the purpose. be able to. These coats can be combined in various ways according to the purpose.

  Two polarizing plates are usually arranged before and after the liquid crystal of the LCD, but the film of the present invention can be used as all four protective films of the two polarizing plates. It can also be used as a sheet, and can also be used as two or one sheet. When using two or more, each resistance value does not need to be the same, and the kind of polymer film can also be suitably selected according to the objective. From the viewpoint of the electromagnetic wave shielding function, it is preferable to use it for the protective film of the outermost layer from the viewpoint of effect and cost.

  The following examples further illustrate the present invention.

Dioxyethylene polythiophene (Baytron PH from BAYER) 16 parts by weight of conductive polymer 20 g doped with polystyrene sulfonate ion and polystyrene sulfonate at a 1: 1 molar ratio and acrylic resin as binder 100 g of urethane resin and polyvinyl alcohol mixed at a weight ratio of 1: 1: 1, and 5 g of polyoxyethylene nonylphenyl ether which is a nonionic surfactant are dissolved in 1 kg of water containing 20% by weight of isopropyl alcohol. An aqueous coating solution 1 was obtained. This was applied to a triacetyl cellulose film (TAC film) having a thickness of 80 μm with a gravure coater and dried at 100 ° C. The thickness of the conductive polymer layer was 0.11 μm. The properties of this film are shown in Table 1. Compared with Comparative Example 1 which showed the difference that the conductive polymer described later was not applied, the surface resistivity was 10 ¹⁴ Ω / mouth or more, and the resistance value reached 8 × 10 ⁵ Ω / mouth by coating. It can be seen that the total light transmittance and the birefringence are hardly deteriorated even though the conductivity is lowered and the conductivity is increased, and the yellowness is decreased. Even if it is placed inside the LCD, especially when it is used as a protective film for polarizing plates, it does not adversely affect the optical properties, but rather the chromaticity is improved in yellowness, electromagnetic wave shielding function and antistatic function It is shown that can be added.

Comparative Example 1

  In Example 1, the characteristic value of the TAC film not coated with the conductive polymer was measured and shown in Table 1.

The aqueous coating liquid 1 used in Example 1 was used, and this was applied to a TAC film having a thickness of 80 μm, in which fine silica was previously dispersed in an ultraviolet curable acrylic hard coating agent, followed by curing to obtain a haze value of 27. A conductive polymer was applied to the surface in the same manner as in Example 1 using a film that was antiglare-treated so that the gloss at 60 ° angle was 34.3% at 1%. The thickness of the conductive polymer layer was 0.12 μm. The properties of this film are shown in Table 2. Comparative Example 2 to be described later shows the characteristic value when the conductive polymer is not applied. Compared with this, the resistance value decreases from 10 ¹⁴ Ω / port or more to 7 × 10 ⁵ Ω / port and is thus conductive. It can be seen that although the light transmittance is increased, the total light transmittance and birefringence are hardly changed, while the yellowness is rather improved. It can also be seen that the haze value and glossiness hardly change even when applied on the antiglare treatment layer. From this result, even when the anti-glare-treated TAC film coated with the conductive polymer of the present invention is placed inside the LCD, the anti-glare treatment effect can be maintained and there is no adverse effect on the optical characteristics. It can be seen that an electromagnetic wave blocking and antistatic function can be imparted without giving, and the yellowness can be improved.

Comparative Example 2

  Table 2 shows the characteristic values of the anti-glare-treated TAC film in which only the conductive polymer was not applied in Example 2.

  In Example 1, a coated film was obtained in exactly the same manner except that the amount of the conductive polymer was changed to 10 g. The thickness of the conductive polymer layer was 0.12 μm. The properties of this film are shown in Table 1.

  A coated film was obtained in the same manner as in Example 1 except that the thickness of the conductive polymer layer was 1.2 μm. The properties of this film are shown in Table 1.

  The same aqueous coating solution 1 as in Example 1 was applied to a 100 μm-thick film (trade name Arton) made of JSR Corporation's norbornene material. The thickness of the conductive polymer layer was 0.10 μm. The properties of this film are shown in Table 1.

Comparative Example 3

  In Example 5, the characteristic values of the film not coated with the aqueous coating solution are shown in Table 1.

  In the same manner as in Example 2, coating was carried out in the same manner as in Example 5 except that an Arton film having a thickness of 100 μm, which had been antiglareed, was used. The thickness of the conductive polymer layer was 0.11 μm. The properties of this film are shown in Table 2.

Comparative Example 4

  In Example 6, the characteristic values of the film not coated with the conductive polymer are shown in Table 2.

  Coating was performed in exactly the same manner as in Example 6 except that a 100 μm thick film (trade name: ZEONOR) made of ZEON Corporation's norbornene material and anti-glare-treated was used. A film was obtained. The thickness of the conductive polymer layer was 0.12 μm, and the properties of this film are shown in Table 2.

Comparative Example 5

  In Example 7, the characteristic values of the film not coated with the conductive polymer are shown in Table 2.

Claims (9)

A conductive polymer film having a conductive polymer layer having a conductive polymer attached to the surface of the polymer film,
The conductive polymer is polythiophene or a derivative thereof;
The polymer film is an acetylcellulose film or a norbornene film,
The conductive polymer layer is obtained by copolymerizing polystyrene sulfonate ion and polystyrene sulfonate in a molar ratio of 1: 1 as a doping agent with respect to 100 parts by weight of polythiophene or a derivative thereof, which is a conductive polymer. 0.1 to 500 parts by weight added,
It has a conductive polymer film having a conductive polymer layer thickness of 3 μm or less, a visible light transmittance of 78% or more, and a surface resistivity of 10 ³ to 10 ¹² Ω / mouth. A protective film for polarizing plate.   The protective film for a polarizing plate according to claim 1, wherein the conductive polymer layer contains 1 to 95% by weight of the conductive polymer and 5 to 99% by weight of the binder resin.   3. The protective film for polarizing plate according to claim 1, wherein the conductive polymer film is hard-coated or anti-glare hard-coated. It is a manufacturing method of the protective film for polarizing plates in any one of Claims 1-3,
On the surface of the acetylcellulose film or norbornene film,
As a doping agent, 0.1 to 500 parts by weight of a copolymer of polystyrene sulfonate ion and polystyrene sulfonic acid in a molar ratio of 1: 1 is included with respect to 100 parts by weight of polythiophene or a derivative thereof, which is a conductive polymer. A method for producing a protective film for a polarizing plate, comprising a step of forming a conductive polymer layer with an aqueous coating liquid.   The method for producing a protective film for a polarizing plate according to claim 4, wherein the aqueous coating liquid contains 1 to 95% by weight of a conductive polymer and 5 to 99% by weight of a binder resin.   The method for producing a protective film for a polarizing plate according to claim 4 or 5, wherein the aqueous coating liquid has a solid concentration of 0.1 to 30% by weight.   The method for producing a protective film for a polarizing plate according to any one of claims 4 to 6, wherein the aqueous coating liquid contains a water-soluble solvent. By forming a conductive polymer layer,
Than the yellowness of acetylcellulose film or norbornene film,
The method for producing a protective film for a polarizing plate according to any one of claims 4 to 7, wherein the yellowness of the conductive polymer film is reduced.   The polarizing plate in which the protective film for polarizing plates in any one of Claims 1-3 was used as at least one protective film of a polarizing film.