TWI483845B - Process for producing polarizing layered film and two-sides polarizing layered film - Google Patents

Description

Method for producing polarizing laminated film and double-sided polarizing laminated film

The present invention relates to a method for producing a polarizing laminate, a polarizing plate or a substrate-containing polarizing plate, and a two-layer film, a double-sided polarizing laminate film, a double-sided bonding film, and a single-sided bonding film.

A polarizing plate has been widely used as a polarizing supply element or the like in a display device such as a liquid crystal display device. Such a polarizing plate has been conventionally used as a protective film formed of triethyl fluorene cellulose by a polarizing film (polarizing layer) formed of a polyvinyl alcohol-based resin, but in recent years, a liquid crystal display device is attached to a notebook personally. The development of mobile technology devices such as computers and mobile phones requires thin and light weight.

Conventionally, a film formed of a polyvinyl alcohol-based resin is separately stretched or stretched, and then subjected to a dyeing treatment and a cross-linking treatment to form a polarizing film, which is then laminated on a protective film to form a polarizing plate, but it is thin. It can only reach the critical thickness when it is a polarizing film alone. Therefore, it is known that after the polyvinyl alcohol-based resin layer provided with the polarizer layer on the surface of the base film, the polyvinyl alcohol-based resin layer in each base film is stretched and dyed. The step of crosslinking and the drying step thereafter, the polyvinyl alcohol-based resin layer is formed into a polarizer layer, so that the total thickness of the base film and the polarizer layer is thin to its critical value, and the polarizing layer can be used as a polarizing layer (polarized light) The thickness of the film) is thinner than the former (refer to, for example, JP2000-338329-A).

However, in the method described in JP 2000-338329-A, in the drying step immediately after the completion of the crosslinking step, the crosslinking reaction proceeds remarkably, and the polyvinyl alcohol-based resin layer shrinks in the width direction of the film. The situation When the film is to be continuously produced, since the laminated film composed of the base film and the polyvinyl alcohol-based resin layer has only the polyvinyl alcohol-based resin layer shrinks in the width direction, the polyvinyl alcohol-based resin in each base film may be caused. The end of the layer forms a problem of a collapsed state. Further, when the laminated film after stretching is placed, the single-sided polyvinyl alcohol-based resin layer spreads due to water absorption, so that the film curls.

In view of the above problems, an object of the present invention is to produce a thin polarizing plate having a high polarizing property, wherein film curling which occurs during the stretching step, the drying step after dyeing, or the storage of the stretched film can be suppressed. .

That is, the present invention encompasses the following items.

[1] A method for producing a double-sided polarizing laminate film comprising: a base film; and a polarizer layer formed on both surfaces of the base film, wherein the manufacturing method comprises: a resin layer forming step of forming a polyvinyl alcohol-based resin layer on both sides of the material film to obtain a two-area layer film; an extending step of extending the two-area layer film; and the polyvinyl alcohol-based resin on both sides of the extended two-area layer film The layer is dyed with a dichroic dye and subjected to a crosslinking treatment to form a dyeing step of the polarizer layer.

[2] The method according to [1], wherein the material of the polyvinyl alcohol-based resin layer constituting both surfaces of the two-area layer film is the same material.

[3] The method according to the above [1], wherein the difference in thickness of the polyvinyl alcohol-based resin layer on both surfaces of the extended two-layer film is 3 μm or less.

[4] The method according to any one of [1] to [3], wherein in the above step, the stretching is performed at a stretching ratio higher than 5 times.

[5] The method according to any one of [1] to [4] wherein the thickness of each of the polarizing plate layers on both surfaces of the double-sided polarizing laminated film is 10 μm or less.

[6] A method of producing a polarizing plate comprising: a polarizing plate layer; and a protective film formed on one surface of the polarizing plate layer, wherein the manufacturing method comprises: the method according to [1] A protective film bonding step of obtaining a double-sided bonding film on both surfaces of the obtained double-sided polarizing laminated film, and a peeling step of peeling at least one of the polarizing plates from the double-sided bonding film.

[7] The method according to [6], wherein in the peeling step, two polarizing plates on both sides of the double-sided bonding film are simultaneously peeled off.

[8] The method according to [6], wherein in the peeling step, the polarizing plate on one surface of the double-sided bonding film is peeled off, and then the polarizing plate on the other surface is peeled off.

[9] A method of producing a polarizing plate with a base film, comprising: a polarizing plate layer; a protective film formed on one surface of the polarizer layer; and a polarizing film attached thereto a substrate film on one side of the layer, and the production method comprises the step of: bonding a protective film on both surfaces of the double-sided polarizing laminate film obtained by the method described in [1] to obtain a protective film of the double-sided bonding film. And a peeling step of peeling off the polarizing plate with the base film attached from the double-sided bonding film.

[10] A method of producing a polarizing plate comprising: a polarizing sheet layer; and a protective film formed on one surface of the polarizing sheet layer, wherein the manufacturing method comprises: the method according to [1] Obtaining a two-sided polarizing laminated film A protective film bonding step of obtaining a single-sided bonding film with a protective film attached thereto, and a peeling step of peeling off the polarizing plate from the single-sided bonding film.

[11] A method for producing a single-sided polarizing laminated film, comprising: a base film; and a polarizer layer formed on one surface of the base film, wherein the manufacturing method comprises: A protective film bonding step of obtaining a single-sided bonding film on one surface of a double-sided polarizing laminated film obtained by the method described in the above [1], and peeling off the single-sided polarization from the single-sided bonding film The peeling step of the laminated film.

[12] A two-area film comprising a base film and a polyvinyl alcohol-based resin layer formed on both surfaces of the base film.

[13] A two-area film comprising a base film and a polyvinyl alcohol-based resin layer formed on the both surfaces of the base film.

[14] A double-sided polarizing laminate film comprising a base film and a polyvinyl alcohol-based resin layer formed on both surfaces of the base film and having a dichroic dye adsorbed thereto.

[15] A double-sided adhesive film comprising: a base film and a double-sided polarizing laminate film formed on both surfaces of the base film, and bonded to both sides of the double-sided polarizing laminate film Protective film.

[16] A single-sided adhesive film comprising: a base material film; and a double-sided polarizing laminate film formed on both surfaces of the base film; and a film bonded to the double-sided polarizing laminate film Protective film on one side.

In the present invention, since the treatment such as stretching, dyeing, and drying is performed in a state where the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film, it is possible to suppress film curling which occurs in the manufacturing process of the polarizing plate or the like. can Stable production.

At the same time, in the stretching step, the dyeing step, and the drying step, the double-layer (two-sided) polyvinyl alcohol-based resin layer can be treated once, so that the production efficiency of the polarizing plate can be improved. Further, when drying is performed in each manufacturing step, it is not necessary to use a special drying furnace, so the cost of equipment can be reduced.

In the present specification, a laminate having a polyvinyl alcohol-based resin layer (a layer composed of a polyvinyl alcohol-based resin) on one surface of the base film is referred to as a "single-area film", and both sides of the base film are provided with polyethylene. The layered body of the alcohol resin layer is referred to as a "two-area layer film".

At the same time, a polyvinyl alcohol-based resin layer having a function as a polarizer is referred to as a "polarized sheet layer", and a laminate having a polarizer layer on one surface of a base film is referred to as a "single-sided polarizing laminated film". A laminate having a polarizer layer on both sides of the film is referred to as a "two-sided polarizing laminate film". Further, a laminate having a protective film on one surface of the polarizer layer is referred to as a "polarizing plate".

Hereinafter, each component will be described in more detail.

[Substrate film]

As the resin to be used for the substrate film, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation can be used, and an appropriate resin can be selected from Tg or Tm. Specific examples of the thermoplastic resin include a polyolefin resin, a polyester resin, a cyclic polyolefin resin (norbornene resin), a (meth)acrylic resin, a cellulose ester resin, and a polycarbonate. Ester resin, polyvinyl alcohol resin, vinyl acetate resin, A polyarylate resin, a polystyrene resin, a polyether oxime resin, a polyfluorene-based resin, a polyamine-based resin, a polyimide-based resin, a mixture or the like, and the like.

The base film may be a film composed of one type of the above-mentioned resin, or a film formed by mixing two or more types of resins. The substrate film may be a single layer film or a multilayer film.

Examples of the polyolefin-based resin, such as polyethylene, polypropylene, etc., are preferably those which can be easily stably stabilized at a high magnification. Further, an ethylene-polypropylene copolymer obtained by copolymerizing propylene with ethylene or the like can also be used. For the copolymerization, other kinds of monomers may be used, and examples of other kinds of monomers copolymerizable with propylene may, for example, be ethylene or an α-olefin. Among them, the α-olefin is preferably an α-olefin having 4 or more carbon atoms, and the α-olefin having 4 to 10 carbon atoms is more preferable. Specific examples of the α-olefin having 4 to 10 carbon atoms include a linear chain such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene. a monoolefin; a branched monoolefin such as 3-methyl-1-butene, 3-methyl-1-pentene or 4-methyl-1-pentene; ethylene cyclohexane or the like. Copolymers of other monomers copolymerizable with propylene may form random copolymers or block copolymers. The content of the constituent unit derived from the other monomer in the copolymer can be infrared (IR) spectroscopy according to the method described in the "Handbook of Polymer Analysis" (1995, issued by Kiyoshi Shoya, Japan) on page 616. The measurement was performed and obtained.

In the above, the propylene-based resin constituting the propylene-based resin film is a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and propylene-ethylene- A 1-butene random copolymer is suitable.

The stereoregularity of the propylene-based resin constituting the propylene-based resin film is preferably substantially the same-row polymer or the counter-polymer. The propylene-based resin film which is substantially composed of a propylene-based resin having a stereoregularity of the same-row polymer or the alignment polymer has good workability and mechanical strength in a high-temperature environment.

The polyester resin is a polymer having an ester bond, and is mainly a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. Among the polycarboxylic acids, a divalent dicarboxylic acid is mainly used, and examples thereof include isophthalic acid, terephthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylate. Meanwhile, the polyol used therein mainly uses a divalent diol, and examples thereof include propylene glycol, butylene glycol, neopentyl glycol, and cyclohexane dimethanol. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and trimethylene terephthalate. , polytrimethylene naphthalate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate, and the like. The resin and copolymer which are mixed as such can be applied.

In terms of the cyclic polyolefin resin, a norbornene-based resin is preferably used. The cyclic polyolefin resin is a general term for a resin which is polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include those described in JPH01-240517-A, JPH03-14882-A, and JPH03-122137-A. Resin. Specific examples thereof include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, an α-olefin such as a cyclic olefin and ethylene, propylene, and a copolymer thereof (representatively random) Copolymers), and graft polymers which have been modified with unsaturated carboxylic acids and their derivatives, and such hydrides. Specific examples of the cyclic olefin include a norbornene-based monomer.

Cylindrical polyolefin resins are also sold in various products. Specific examples thereof include Topas (registered trademark) (manufactured by Ticona, Japan), ARTON (registered trademark) (manufactured by JSR Corporation of Japan), ZEONOR (registered trademark) (manufactured by Japan ZEON Co., Ltd.), and ZEONEX (registered trademark) (Japan) Manufactured by ZEON Co., Ltd., APEL (registered trademark) (manufactured by Mitsui Chemicals, Japan).

As the (meth)acrylic resin, any appropriate (meth)acrylic resin can be used. For example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, methyl group Methyl acrylate-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), alicyclic hydrocarbon-containing polymer (eg methyl methacrylate-A) A cyclohexyl acrylate copolymer, a methyl methacrylate-(meth)acrylic acid norbornyl ester copolymer, etc.).

Among them, poly(meth)acrylic acid C1 to 6 alkyl ester such as poly(methyl) acrylate is preferred. As the (meth)acrylic resin, a methyl methacrylate-based resin containing methyl methacrylate as a main component (preferably 50 to 100% by weight, preferably 70 to 100% by weight) is preferably used.

A cellulose ester resin is an ester composed of cellulose and a fatty acid. Specific examples of such a cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate.

Other examples thereof include a copolymer of such a copolymer, and a species in which a part of a hydroxyl group is modified by a substituent or the like. Among them, cellulose triacetate is particularly preferred. Cellulose triacetate has been sold in a variety of products with advantages in terms of ease of availability and cost. Examples of cellulose triacetate vending products For example, FUJITAC (registered trademark) TD80 (manufactured by Fujifilm Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by Fujifilm Japan Co., Ltd.), FUJITAC (registered trademark) TD80UZ (manufactured by Fujifilm Japan Co., Ltd.), FUJITAC (registered trademark) TD40UZ (manufactured by Fujifilm Japan Co., Ltd.), KC8UX2M (manufactured by Konica-Minolta Opto., Japan), KC4UY (manufactured by Konica-Minolta Opto., Japan), and the like.

The polycarbonate resin is an engineering plastic composed of a polymer having a monomer unit bonded to a carbonate group, and is a resin having high impact resistance, heat resistance, and flame retardancy. Moreover, due to its high transparency, it is also suitable for use in optical applications. Further, in terms of optical use, a resin which is modified to reduce the photoelasticity coefficient and which is called a modified polycarbonate, and a polycarbonate which has been improved in wavelength dependence, has been sold. Suitable for use. Such a polycarbonate resin is widely sold, and examples thereof include Panlite (registered trademark) (manufactured by Teijin Chemical Co., Ltd.), Iupilon (registered trademark) (manufactured by Mitsubishi Engineering Plastics Co., Ltd.), and SD POLYCA (registered trademark). (manufactured by Sumitomo-Dow Japan Co., Ltd.), CALIBRE (registered trademark) (manufactured by Dow Chemical Co., Ltd.), etc.

In addition to the above thermoplastic resin, any suitable additive may be added to the base film. Examples of such an additive include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color preventive agents, flame retardants, nucleating agents, antistatic agents, pigments, and color formers. The content of the above-exemplified thermoplastic resin in the substrate film is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, particularly preferably from 70 to 97% by weight. good. The content of the thermoplastic resin in the substrate film is lower than At 50% by weight, it is feared that the high transparency and the like which the thermoplastic resin originally has cannot be fully exhibited.

The thickness of the base film before stretching can be appropriately determined, but it is preferably 1 to 500 μm, more preferably 1 to 300 μm, and even more preferably 5 to 200 μm, in terms of workability such as strength and workability. 5 to 150 μm is the best.

In the base film, in order to improve the adhesion to the polyvinyl alcohol-based resin layer, corona treatment, plasma treatment, flame treatment, or the like can be applied to the surface on the side where at least the polyvinyl alcohol-based resin layer is formed. Moreover, in order to improve the adhesiveness, a thin layer such as a primer layer or an adhesive layer may be formed on the surface on the side where the polyvinyl alcohol-based resin layer of the base film is formed.

(primer coating)

When the undercoat layer is formed on the surface on the side where the polarizer layer of the base film is formed, the undercoat layer may be a material which can exhibit a certain strength in the base film and the polyvinyl alcohol-based resin layer. Yes, there is no particular limitation. For example, a thermoplastic resin excellent in transparency, heat stability, and elongation can be used. Specific examples thereof include a polyacrylic resin and a polyvinyl alcohol resin, but are not limited thereto. Among them, a polyvinyl alcohol-based resin having a good adhesion is preferred.

Examples of the polyvinyl alcohol-based resin used as the undercoat layer include polyvinyl alcohol resins and derivatives thereof. Examples of the polyvinyl alcohol resin derivative include polyethylene formaldehyde, polyvinyl acetal, and the like, and polyvinyl alcohol resin, such as ethyl, propyl, and the like; acrylic acid, methacrylic acid, crotonic acid, etc. Unsaturated carboxylic acid; alkyl ester of unsaturated carboxylic acid, acrylamide, etc. Species. Among the above polyvinyl alcohol-based resin materials, a polyvinyl alcohol resin is preferably used.

In order to increase the strength of the undercoat layer, a crosslinking agent may be further added to the above thermoplastic resin. As the crosslinking agent to be added to the thermoplastic resin, a conventional species such as an organic system or an inorganic system can be used. It is possible to appropriately select a suitable species for use in accordance with the thermoplastic resin to be used. Examples thereof include a low molecular crosslinking agent such as an epoxy crosslinking agent, an isocyanate crosslinking agent, a dialdehyde crosslinking agent, and a metal chelating agent crosslinking agent, and a methylolated melamine resin or a polyglycol. A polymer crosslinking agent such as a guanamine epoxy resin. When a polyvinyl alcohol-based resin is used as the thermoplastic resin, the crosslinking agent is preferably a polyamine epoxy resin, a methylolated melamine, a dialdehyde, a metal chelating agent crosslinking agent or the like.

The thickness of the undercoat layer is preferably 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. When the thickness is too thin, the adhesion between the base film and the polyvinyl alcohol layer is lowered. When the thickness is too thick, the polarizing plate becomes thick.

[Polarized film layer]

The polarizer layer is specifically a layer in which a dichroic dye is adsorbed and aligned on the stretched polyvinyl alcohol-based resin layer.

As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin layer, a saponified species of a polyvinyl acetate-based resin can be used. The polyvinyl acetate-based resin may, for example, be a polyvinyl acetate of a monomer of vinyl acetate, or a copolymer of another monomer copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The polyvinyl alcohol-based resin constituting the polarizer layer (polyvinyl alcohol-based resin layer) is preferably a fully saponified product. The degree of saponification is preferably in the range of 80 mol% to 100 mol%, more preferably in the range of 90 mol% to 99.5 mol%, and most preferably in the range of 94 mol% to 99 mol%.

When the degree of saponification is less than 80 mol%, there will be water resistance after forming the polarizing plate. The disadvantage of poor heat and humidity resistance. In addition, when a polyvinyl alcohol-based resin having a degree of saponification of more than 99.5 mol% is used, there is a case where a dyeing speed is slow and a polarizing laminated film having sufficient polarizing performance is obtained, which is required to be several times longer than a general one. .

The degree of saponification referred to herein is a unit ratio (% by mole) of the ratio of the acetic acid group contained in the polyvinyl acetate-based resin of the raw material of the polyvinyl alcohol-based resin to the hydroxyl group via the saponification step, that is, The values defined by the following formula. This can be obtained by the method specified in JIS K 6726 (1994).

Degree of saponification (% by mole) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100

The higher the degree of saponification, the higher the ratio of the hydroxyl group, that is, the lower the proportion of the acetate group which inhibits crystallization.

Further, the polyvinyl alcohol-based resin used in the present invention may be a partially modified modified polyvinyl alcohol. Examples thereof include an olefin such as a stretched ethyl group and a propyl group of a polyvinyl alcohol-based resin; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid; an alkyl ester of an unsaturated carboxylic acid; and a modification of acrylamide and the like. Species, etc. The proportion of the modification is preferably less than 30 mol%, more preferably less than 10 mol%. When the modification is higher than 30 mol%, there is a case where the dichroic dye is hard to adsorb and the polarizing performance is lowered.

The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but 100 to 10,000 is preferred, and 1500 to 8000 is preferred. The best from 2000 to 5000. The average degree of polymerization can also be determined by the method specified in JIS K 6726 (1994).

Examples of the polyvinyl alcohol-based resin having such a property include PVA124 (saponification degree: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd., PVA117 (saponification degree: 98.0 to 99.0 mol%), and PVA624 (saponification). Degree: 95.0 to 96.0 mol%) and PVA617 (saponification degree: 94.5 to 95.5 mol%); for example, AH-26 (saponification degree: 97.0 to 98.8 mol%) manufactured by Nippon Chemical Industry Co., Ltd., AH-22 ( Saponification degree: 97.5 to 98.5 mol%), NH-18 (saponification degree: 98.0 to 99.0 mol%), and N-300 (saponification degree: 98.0 to 99.0 mol%); for example, manufactured by VAM & POVAL Co., Japan JC-33 (saponification degree: 99.0 mol% or more), JM-33 (saponification degree: 93.5 to 95.5 mol%), JM-26 (saponification degree: 95.5 to 97.5 mol%), JP-45 (saponification degree) : 86.5 to 89.5 mol%), JF-17 (saponification degree: 98.0 to 99.0 mol%), JF-17L (saponification degree: 98.0 to 99.0 mol%), and JF-20 (saponification degree: 98.0 to 99.0) Mole%), etc., are all suitable for use in the present invention.

A polyvinyl alcohol-based resin layer can be formed by forming a film of the polyvinyl alcohol-based resin. The film forming method of the polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a conventional method. However, a solution of a polyvinyl alcohol-based resin is used in the substrate film at a point where a polarizing layer of a desired thickness can be easily obtained. The upper coating film is preferred.

The polyvinyl alcohol-based resin layer is formed by simultaneously extending and aligning with the base film, and then displacing the dichroic dye to form a polarizer layer. The stretching ratio is preferably more than 5 times, more than 5 times and more preferably 17 times or less.

The thickness of the polarizing layer (thickness of the polyvinyl alcohol-based resin layer after stretching) is preferably 10 μm or less, more preferably 7 μm or less. When the thickness of the polarizer layer is 10 μm or less, a thin polarizing plate can be formed.

The dichroic dye used in the polarizing layer may, for example, be iodine or an organic dye. Examples of organic dyes include red BR, red LR, red R, pink LB, deep pink BL, wine red GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy blue. RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Fresh Purple BK, S Supra Blue G, Sprague Blue GL, Supra orange GL, direct sky blue, direct light orange S, light fast black, etc. These dichroic substances may be used alone or in combination of two or more.

[protective film]

In terms of the protective film, it may be a protective film which is not a separate optical function, or a protective film having a retardation film and a brightness improving film.

The protective film is not particularly limited, and examples thereof include a cyclic polyolefin resin film; a cellulose acetate resin film composed of a resin such as cellulose triacetate or cellulose diacetate; Polyester resin film composed of a resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate; polycarbonate resin film; polyacrylic resin film A polypropylene resin film or the like is a film conventionally used in the field.

Suitable commercial products of the cyclic polyolefin resin can be exemplified by, for example: Topas (registered trademark) (manufactured by Ticona, Japan), ARTON (registered trademark) (manufactured by JSR Corporation of Japan), ZEONOR (registered trademark) (manufactured by Zeon, Japan), ZEONEX (registered trademark) (manufactured by Zeon, Japan), APEL ( Registered trademark) (manufactured by Mitsui Chemicals, Inc.) are suitable for use. When a film is formed by forming a film of such a cyclic polyolefin resin, it is suitable for use in a conventional method such as a solution casting method or a melt extrusion method. In addition, ESSINA (registered trademark) (manufactured by Japan Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Japan Sekisui Chemical Co., Ltd.), ZEONOR (registered trademark) film (manufactured by Japan OPTES Co., Ltd.), etc. Commercial products of the film can also be used.

The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. After stretching, an arbitrary phase difference value can be imparted to the cyclic polyolefin resin film. In terms of elongation, it is generally carried out continuously by extrusion rolls, and in the heating furnace, it extends in the direction in which the rolls are moved, in the direction perpendicular to the direction in which they are formed, or in both directions. The temperature of the heating furnace is generally preferably in the range of a glass transition temperature close to the cyclic polyolefin resin to a glass transition temperature of +100 °C. The magnification of the extension is preferably 1.1 to 6 times in a single direction, and more preferably 1.1 to 3.5 times.

Since the cyclic polyolefin-based resin film generally has a poor surface activity, it is preferable to perform surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment on the surface of the polarizing film. Among them, plasma treatment and corona treatment which are easy to implement are preferred.

For the suitable product of the cellulose acetate-based resin film, for example, FUJITAC (registered trademark) TD80 (manufactured by Fujifilm Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by Fujifilm Japan Co., Ltd.), FUJITAC (registered trademark) TD80UZ (manufactured by Fujifilm Japan), FUJITAC (registered trademark) TD40UZ (manufactured by Fujifilm Japan), KC8UX2M (registered trademark) KC8UX2M (manufactured by Konica-Minolta Opto., Japan), KC4UY (manufactured by Konica-Minolta Opto., Japan) ) are suitable for use.

The surface of the cellulose acetate-based resin film can be further formed into a liquid crystal layer or the like in order to improve the viewing angle characteristics. Further, the cellulose acetate-based resin film can be stretched in order to impart a phase difference therebetween. The cellulose acetate-based resin film can be further subjected to a saponification treatment in order to increase its adhesion to the polarizing film. Among them, the saponification treatment may be carried out by immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

As the surface of the protective film described above, an optical layer such as a cured film layer, an anti-glare layer, an anti-reflection layer or the like may be further formed. The method of forming these optical layers on the surface of the protective film is not particularly limited, and a conventional method can be used.

The thickness of the protective film is required to be as thin as possible due to the demand for thinning, and is preferably 90 μm or less, more preferably 50 μm or less. When it is too thin, the strength is lowered and the workability is deteriorated, so it is preferably 5 μm or more.

<Method of Manufacturing Polarizing Plate>

Fig. 1 is a flow chart showing an outline of a method of manufacturing a polarizing plate of the present invention. A method for producing a double-sided polarizing laminate film according to the present invention, comprising: a resin layer forming step of forming a two-area layer film on both surfaces of the base film to obtain a two-layer film; (S10); a step of extending the extension (S20); and a step of dyeing the polyvinyl alcohol-based resin layer on both sides of the extended two-layer film by dyeing with a dichroic dye and performing a crosslinking treatment to form a polarizer layer (S30) .

At the same time, in order to make a polarizing plate, etc., it is carried out in sequence: the above two polarizing laminated films are washed. a drying and drying step (S40); a protective film bonding step of the double-sided bonding film or the single-sided bonding film on both sides or one surface of the double-sided polarizing laminated film to obtain a protective film bonding step (S50); a drying step of drying the laminated film or the single-sided bonding film (S60); and peeling off the polarizing plate, the polarizing plate containing the substrate film, or the single-sided polarizing laminated film by the double-sided bonding film or the single-sided bonding film Step (S70).

The method for producing a double-sided polarizing laminate film of the present invention is characterized in that a polyvinyl alcohol-based resin layer is formed not only on one side of the base film but also on both surfaces. According to this manufacturing method, film curl which occurs in the manufacturing steps of a polarizing plate or the like can be suppressed, and therefore, it can be stably produced.

<Production steps>

Hereinafter, each step of S10 to S70 in Fig. 1 will be described in detail.

[Resin layer forming step (S10)]

Here, by forming a polyvinyl alcohol-based resin layer on both surfaces of the base film, a two-layer film composed of a base film and a polyvinyl alcohol-based resin layer can be obtained.

Among them, suitable as the material of the base film can be as described in the description of the configuration of the above-mentioned polarizing laminated film. At the same time, the substrate film is preferably extended in an appropriate temperature range for use in the extension of the polyvinyl alcohol-based resin.

The two constituent materials of the polyvinyl alcohol-based resin layer formed on both surfaces of the base film are preferably the same material. When the materials are different, the effect of suppressing curl will be reduced.

Since the effect of suppressing curling is reduced when there is a significant difference in the thickness of the resin layer formed on both sides, it is preferable to form the thickness of the polyvinyl alcohol-based resin layer on both sides of the film of the two-area layer as much as possible. In particular, the difference between the thicknesses of the two resin layers is preferably 3 μm or less. On the other hand, the specific thickness of the resin layer formed in the resin layer forming step (S10) is preferably 3 to 50 μm, more preferably 5 to 40 μm. When it is thinner than 3 μm, it may become thinner after stretching and the dyeability may be lowered. On the other hand, when it is higher than 50 μm, the thickness of the finally obtained polarizing plate layer exceeds 10 μm.

The polyvinyl alcohol-based resin layer is preferably formed by coating a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent on one surface of a substrate film, and evaporating and drying the solvent. By forming the polyvinyl alcohol-based resin layer in this manner, the polyvinyl alcohol-based resin can be made thin. The method of applying the polyvinyl alcohol-based resin solution to the base film may be a roll coating method such as a wire bar coating method, a reverse coating method or a gravure coating method, a die casting method, or a comma. Conventional methods such as a coating method, a lip coating method, a spin coating method, a screen printing method, a spray coating method, a dipping method, and a spray coating method are appropriately selected and used. The drying temperature is, for example, 50 to 200 ° C, and preferably 60 to 150 ° C. The drying time is, for example, 2 to 20 minutes.

The coating of the polyvinyl alcohol-based resin layer on both surfaces of the substrate film can be carried out sequentially from one side by the above method, or can be simultaneously performed on both sides of the substrate film by using a dipping method, a spraying method, or the like. Coating of a vinyl alcohol-based resin layer.

At the same time, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, An undercoat layer may be further provided between the substrate film and the polyvinyl alcohol-based resin layer. The undercoat layer is preferably formed from a composition containing a composition such as a polyvinyl alcohol-based resin or a crosslinking agent from the viewpoint of adhesion. Suitable materials for the undercoat layer and the like are as described in the constitutional description of the above polarizing plate.

When the undercoat layer is provided, the order of application on the substrate film is not particularly limited, and after the undercoat layer is formed on both surfaces of the substrate film, a polyvinyl alcohol-based resin layer may be formed on both surfaces thereof, or may be on the substrate. After the undercoat layer and the polyvinyl alcohol-based resin layer are sequentially formed on one surface of the film, an undercoat layer and a resin layer are sequentially formed on the other surface of the substrate film.

[Extension step (S20)]

Here, the two-area layer film obtained in the resin layer forming step (S10) is stretched. It is preferred to carry out uniaxial stretching at a stretching ratio of more than 5 times and less than 17 times. It is more preferable to perform uniaxial stretching at a stretching ratio of more than 5 times and less than 8 times. When the stretching ratio is 5 times or less, the polyvinyl alcohol-based resin layer cannot be sufficiently aligned, and as a result, the degree of polarization of the polarizing sheet layer cannot be sufficiently improved. On the other hand, when the stretching ratio is higher than 17 times, the fracture of the laminated film is liable to occur during stretching, and at the same time, the thickness of the laminated film after stretching exceeds the necessary thinness, that is, the workability is obtained in the subsequent step. The operability is reduced. The extension process in the extension step (S20) does not limit an extension, and may also perform multi-segment extension. When the multi-segment extension is performed, all the segments of the collective extension process are extended at a stretching ratio higher than 5 times.

In the extending step (S20) of the present embodiment, the longitudinal stretching treatment for the longitudinal direction of the laminated film, the lateral stretching treatment for extending the width direction, and the like can be performed.

Examples of the longitudinal stretching method include a roll stretching method and a compression stretching method, and examples of the lateral stretching method include a tenter method.

The extension treatment in the present invention is preferably carried out using a dry stretching method. When the polyvinyl alcohol-based resin layer is subjected to dry stretching before the dyeing step of each base material film, a polyvinyl alcohol-based resin film (polarized sheet layer) which is thinner than the conventional one can be obtained without being broken, and high-rate extension can be performed. Therefore, the polarizing plate obtained can be made thinner.

[Staining step (S30)]

Here, the polyvinyl alcohol-based resin layer on both surfaces of the two-layer film is dyed with a dichroic dye. The dichroic dye may, for example, be iodine or an organic dye. Examples of organic dyes include red BR, red LR, red R, pink LB, deep pink BL, wine red GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy blue RY , Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Fresh Purple BK, SP Pull blue G, Sprague blue GL, emerald orange GL, direct sky blue, direct light orange S, fast black. These dichroic substances may be used alone or in combination of two or more.

The dyeing step can be carried out, for example, by immersing the entire stretched film in a solution (dyeing solution) containing the above dichroic dye. As the dyeing solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. As the solvent of the dyeing solution, water can be generally used, and an organic solvent which is miscible with water can be further added. The concentration of the dichroic dye is preferably 0.01 to 10% by weight, and 0.02 to 7% by weight More preferably, it is particularly preferably from 0.025 to 5% by weight.

When the dichroic dye uses iodine, the dyeing efficiency can be further improved, so that it is preferable to add an iodide. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and iodide. Titanium, etc. The proportion of such iodide added is preferably from 0.01 to 20% by weight in the dyeing solution. Among the iodides, potassium iodide is preferably added. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100 by weight, more preferably in the range of 1:6 to 1:80, particularly in the range of 1:7 to 1:70. Better yet.

The immersion time of the stretched film in the dyeing solution is not particularly limited, and is generally preferably in the range of 15 seconds to 15 minutes, and more preferably in the range of 1 minute to 3 minutes. The temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably in the range of 20 to 40 ° C.

In the dyeing step, a cross-linking treatment may be carried out after the dyeing thereof. The crosslinking treatment is carried out, for example, by immersing a laminated film in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, conventionally known materials can be used. Examples thereof include boron compounds such as boric acid and borax; glyoxal and glutaraldehyde. These species may be used alone or in combination of two or more.

As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. Among the solvents, for example, water may be used, but it may also contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is not limited, but is preferably in the range of 1 to 20% by weight, more preferably in the range of 6 to 15% by weight.

In the cross-linking solution, an iodide may be further added. Addition via iodide In addition, the polarizing characteristics in the surface of the resin layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. . The content of the iodide is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight.

The immersion time of the stretched film in the crosslinking solution is preferably from 15 seconds to 20 minutes, more preferably from 30 seconds to 15 minutes. The temperature of the cross-linking solution is preferably in the range of 10 to 80 °C.

From the above dyeing step (S30), the polyvinyl alcohol-based resin layer can have a function as a polarizing plate layer, and a double-sided polarizing laminated film can be obtained.

[Washing and drying step (S40)]

Next, the washing step of washing the double-sided polarizing laminated film is not essential, but it is preferably carried out. The water washing step can be performed by washing with water. The water washing treatment can be generally carried out by immersing the stretched film in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually from 3 to 50 ° C, preferably from 4 to 20 ° C. The immersion time is generally from 2 to 300 seconds, preferably from 3 seconds to 240 seconds.

In the washing step, the iodide solution may be combined with a washing treatment and a water washing treatment, and a solution in which a liquid alcohol such as methanol, ethanol, isopropanol, butanol or propanol is blended may be suitably used. After the washing step, a water-repellent step using a roll, an air knife or the like can also be designed.

After the washing step, the double-sided polarizing laminate film is preferably dried. The drying operation is preferably carried out by a drying step comprising a temperature of 60 ° C or higher, and a drying step comprising a temperature of 70 ° C or higher is more preferable. Of course, A drying step comprising multiple stages of different temperatures. In this case, in the multi-stage drying step, any drying step may be carried out at 60 ° C or higher.

In addition to the temperature, in order to further enhance the drying force, it is possible to optimize the circulation method of the hot air such as the air volume and the wind direction, or to provide an IR heater which can be locally heated. These subsidized operations can make drying more efficient and affect productivity improvement.

The upper limit of the drying temperature is preferably a temperature lower than the boiling point of water, that is, preferably lower than 100 °C. Further, it is more preferably 95 ° C or less, and is preferably 90 ° C or less.

[Protective film bonding step (S50)]

Here, the protective film is bonded to one surface or both surfaces of the two-layer film which has passed through the above steps. A method of bonding the polarizer layer and the protective film, for example, a method of bonding the polarizer layer and the protective film via an adhesive layer or an adhesive layer. Suitable materials for the protective film are as described in the description of the constitution of the above polarizing plate.

(adhesive layer)

As the adhesive constituting the pressure-sensitive adhesive layer, a polyacrylic resin, a polystyrene resin, a ruthenium-based resin or the like can be generally used as a base polymer, and an isocyanate compound, an epoxy compound, an anthracycline compound or the like can be added thereto. The composition of the agent. At the same time, fine particles may be formulated in the adhesive to form an adhesive layer exhibiting light scattering properties.

The thickness of the adhesive layer is preferably from 1 to 40 μm, and it is preferably from 3 to 25 μm insofar as it does not impair the properties such as workability and durability. It has excellent processability at 3 to 25 μm and a suitable thickness in suppressing dimensional change of the polarizing film. Adhesive layer at When it is thinner than 1 μm, the adhesiveness is lowered, and when it is higher than 40 μm, there is a disadvantage that the adhesive overflows easily.

The method of forming the adhesive layer on the protective film and the polarizer is not particularly limited, and it may be applied to the surface of the protective film or the surface of the polarizer layer by a solution containing the base polymer to each component, and dried to form an adhesive. After the agent layer is applied to the separator layer or a film thereof, after the adhesive layer is formed on the separator layer, the surface of the protective film or the surface of the polarizer layer may be attached to laminate. Meanwhile, when the adhesive layer is formed on the surface of the protective film or the polarizer layer, it may be subjected to, for example, corona treatment on one or both sides of the protective film or the polarizer layer or the adhesive layer as needed. Close connection processing.

(adhesive layer)

Examples of the adhesive constituting the adhesive layer include a water-based adhesive such as a polyvinyl alcohol-based resin aqueous solution or an aqueous two-liquid polyurethane emulsion adhesive. Among them, an aqueous solution of a polyvinyl alcohol-based resin is preferably used. In the polyvinyl alcohol-based resin used as the adhesive, in addition to the vinyl alcohol homopolymer obtained by subjecting the polyvinyl acetate of the monomeric polymer of vinyl acetate to saponification, vinyl acetate and the like may be used. The copolymer of the other monomer copolymerized is further subjected to a saponification treatment to obtain a vinyl alcohol-based copolymer, and the modified polyvinyl alcohol-based polymer obtained by partially modifying the hydroxyl group. Further, an additive such as a polyvalent aldehyde, a water-soluble epoxide, a melamine-based compound, a zirconia compound, or a zinc compound may be added to the aqueous binder. When such a water-based adhesive is used, the thickness of each of the obtained adhesive layers is generally thinner than 1 μm, and the adhesive layer is not actually observed even when the cross section is observed by a general optical microscope.

The method of bonding using a film of a water-based adhesive is not particularly limited, and for example, an adhesive is uniformly applied to the surface of the film, or a flow is injected first, and a film is laminated on the other film of the coated surface to form a roll or the like. A method of bonding, drying, and the like. In general, the adhesive is applied at a temperature of 15 to 40 ° C after its preparation, and the bonding temperature is generally in the range of 15 to 30 ° C.

When a water-based adhesive is used, it is necessary to dry the water contained in the water-based adhesive after the film is bonded. The temperature of the drying furnace is preferably from 30 ° C to 90 ° C. The adhesive surface tends to be easily peeled off at a lower temperature than 30 ° C. When the temperature is higher than 90 ° C, there is a concern that the optical properties of the polarizer or the like are deteriorated by heat. The drying time can generally be set to 10 to 1000 seconds.

After drying, it can be maintained at room temperature or slightly above room temperature, such as at a temperature of about 20 to 45 ° C for about 12 to 600 hours. In the case of the temperature during the maintenance, the temperature can be set lower than the temperature used in the drying.

Meanwhile, as the non-aqueous adhesive, a photocurable adhesive can be used. The photocurable adhesive may, for example, be a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

The method of laminating the film on the photocurable adhesive can be carried out by a conventional method, and examples thereof include a flow casting method, a meyer bar coating method, a gravure coating method, a notch wheel coating method, and a doctor blade. A doctor blade coating method, a die casting method, a dip coating method, a spray method, or the like, a method in which an adhesive is applied to the subsequent surface of the film, and two films are laminated. The casting method is applied to the two films of the object to be coated, approximately perpendicular to the horizontal direction. A method of moving obliquely toward, or between, the two, while allowing the adhesive to flow downward from its surface.

After the adhesive is applied to the surface of the film, the film may be bonded by a roll or the like and then bonded. A method in which the laminate is further pressed by a roller or the like to be uniformly pressed is also suitable. In this case, the material used for the roller may be metal or rubber. Further, a method in which the laminated body is passed between a roll and a roll and pressurized to be pressed may be employed. In this case, the same material can be used for these rolls, and different materials can be used. The thickness of the contact agent layer after bonding with the above-mentioned rolls or the like is preferably 5 μm or less and 0.01 μm or more before drying or curing.

The surface of the film may be subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment or the like in order to improve the adhesion.

Among them, the saponification treatment may, for example, be a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

When a photocurable resin is used as the adhesive, the photocurable adhesive can be cured by irradiation with an active energy ray after the film is laminated. The light source of the active energy line is not particularly limited, but an active energy line having a light-emitting distribution of 400 nm or less is preferred, and specifically applicable: a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, and an ultra-high pressure mercury lamp. , chemical lamp, black light lamp, microwave excited mercury lamp, metal halide lamp, etc.

The light irradiation intensity of the photocurable adhesive can be appropriately determined depending on the composition of the photocurable adhesive, and is not particularly limited, but the irradiation intensity in the wavelength range in which activation of the polymerization initiator is effective is 0.1 to 6000. mW/cm ^{2 is} preferred. When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time is not excessively long, and when it is 6000 mW/cm ² or less, the heat generated by the light source and the heat generated by the curing of the photocurable adhesive are yellow. The fear of deterioration and deterioration of the polarizing film will be reduced. The light irradiation time of the photocurable adhesive is not particularly limited as long as it is applied to the photocurable adhesive which is cured, but the integrated light amount indicated by the product of the above-described irradiation intensity and irradiation time is set to 10 It is preferably 10,000 mJ/cm ² . When the integrated light amount of the photocurable adhesive is 10 mJ/cm ² or more, the amount of the active species derived from the polymerization initiator is sufficient, so that the hardening reaction can be more reliably performed; when it is 10000 mJ/cm ² or less The irradiation time is not too long, so good productivity can be maintained. Meanwhile, the thickness of the adhesive layer after the active energy ray irradiation is generally about 0.001 to 5 μm, more preferably 0.01 μm or more and more preferably 2 μm or less, and more preferably 0.01 μm or more and more preferably 1 μm or less.

When the photocurable adhesive containing the film of the polarizer layer and the protective film is cured by irradiation with an active energy ray, the degree of polarization, transmittance, and color tone of the polarizer layer, and transparency of the protective film are used in the polarizing plate. It is preferable to perform hardening under the condition that the respective functions are not lowered.

[Drying step (S60)]

In the protective film bonding step (S50) described above, in order to form a solvent-containing solution for forming the adhesive layer or the adhesive layer, it is necessary to further dry the double-sided bonding film or the single-sided bonding film. The main purpose of the drying step is to carry out drying of the adhesive layer or the adhesive layer, and the drying conditions and the like are the same as the above-described washing and drying step (S40). In particular, in order to form an adhesive layer, when a polyvinyl alcohol-based resin aqueous solution or the like is used, it is carried out at a temperature of 60 ° C or higher. Drying is preferred.

[Peeling step (S70)]

After the drying step (S60), a peeling step (S70) of peeling off the polarizing plate, the base film-containing polarizing plate, or the single-sided polarizing laminated film from the double-sided bonding film or the single-sided bonding film is further performed. The peeling method of the polarizing plate, the polarizing plate including the base film, or the single-sided polarizing laminated film is not particularly limited, and the same method as the peeling step of the release film which is generally performed in the polarizing plate containing the adhesive can be employed. After the drying step (S60), it may be directly peeled off immediately, or after another roll is formed, another peeling step is designed to perform the peeling.

[other optical layers]

In the polarizing plate obtained in the present invention, a polarizing plate laminated with other optical layers may be used in practical use. At the same time, the above protective film may also have the function of such optical layers.

Examples of the other optical layer include a reflective polarizing film that reflects light of a polarized light having opposite properties by some kinds of polarized light, an anti-glare film having a concave-convex shape on the surface, and an anti-reflection surface. Functional film; reflective film with reflective function on the surface; semi-transparent reflective film with both reflection function and light transmission function; viewing angle compensation film.

A commercially available product in which a reflective polarizing film exhibiting polarized light of the opposite nature is reflected by some types of polarized light, and may be, for example, DBEF (manufactured by 3M Company, available from Sumitomo 3M Co., Ltd.). APF (manufactured by 3M Company, available from Sumitomo 3M). The viewing angle compensation film is an optical compensation film in which a liquid crystal compound is applied to the surface of the substrate to be aligned, and examples thereof include a retardation film made of a polycarbonate resin and a cyclic polyolefin. A retardation film made of a resin. For example, a WV film (manufactured by Fujifilm Japan Co., Ltd.), an NH film (manufactured by Nippon Oil & Steel Co., Ltd.), and an NR film are available as a commercial product in which the liquid crystal compound is coated on the surface of the substrate. (manufactured by Nippon Oil Corporation of Japan) and the like. For the sales of the retardation film made of the cyclic polyolefin resin, for example, ARTON (registered trademark) film (manufactured by JSR Japan), ESSINA (registered trademark) (manufactured by Japan Sekisui Chemical Co., Ltd.), ZEONOR (registered trademark) film (manufactured by Japan OPTES Co., Ltd.).

[Examples] Example 1

The fabrication of the double-sided polarizing laminate film 302 is carried out in accordance with the flow chart shown in FIG.

(substrate film)

Homopolymerization of propylene on both sides of a resin layer composed of a random copolymer of propylene/ethylene (Sumitomo Noblen W151, manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 138 ° C) of about 5% by weight of ethylene-containing unit A homogenous polypropylene ("Sumitomo Noblen FLX80E4" manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 °C) is used as a base material film 1 having a three-layer structure, and a co-pressure of a multi-lamination molding machine is used. It is made by molding. The obtained substrate film 1 had a total thickness of 90 μm, and the thickness ratio of each layer (FLX80E4/W151/FLX80E4) was 3/4/3.

(undercoat layer forming step)

Polyvinyl alcohol powder (trade name: Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) The solution was dissolved in hot water at 95 ° C to prepare an aqueous solution having a concentration of 3% by weight. Further, the obtained aqueous solution was mixed with 5 parts by weight of a crosslinking agent (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMIREZ (registered trademark) resin 650) in an amount of 6 parts by weight based on the polyvinyl alcohol powder to obtain a base film solution. Thereafter, one side of the substrate film 1 was subjected to corona treatment, and the under film solution was applied by a micro gravure coater and dried at 80 ° C for 10 minutes to form an undercoat layer having a thickness of 0.2 μm.

Further, a corona treatment is applied to the other surface of the substrate film, and a coating treatment is applied to the same primer solution to form a film having an undercoat layer formed on both surfaces of the substrate film 1.

(Resin layer forming step)

First, polyvinyl alcohol powder (trade name: PVA124, manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol having a concentration of 8 wt%. Aqueous solution. Further, the obtained aqueous solution was coated on the surface on which one of the base film 1 had been formed with a lip coater, and continuously dried at 80 ° C for 2 minutes, at 70 ° C for 2 minutes, and at 60 ° C for 4 minutes. A single-layer film 201 of two layers composed of the base film 1 and the polyvinyl alcohol-based resin layer 21 was produced.

Further, the surface of the undercoat layer formed on the other surface of the base film 1 is subjected to the same coating treatment to form a polyvinyl alcohol-based resin layer 21, a base film 1 and a polyvinyl alcohol-based resin layer 22. Two-layer film 202. The thickness of the polyvinyl alcohol-based resin layers 21 and 22 (before stretching) at this time was 10.5 μm and 10.2 μm, respectively.

(extension step)

Applying the two-layer film 202 to the longitudinal stretching machine between rolls at 160 ° C It is uniaxially extended by 5.8 times from the free end. The thickness of the two layers of the polyvinyl alcohol-based resin layer of the two-layer film after stretching was 5.1 μm and 4.9 μm each. The extended two-layer film 202 can be observed to be almost curl-free and flat, and the workability in the stretching step is also very good.

Further, the small piece cut out from the stretched two-layer film was allowed to stand for 5 days in an environment of 23 ° C and 50% RH, and it was observed that the curl was hardly formed and the shape was maintained good.

(staining step)

The stretched two-layer film is immersed in a 60 ° C warm bath for 60 seconds, and then immersed in a dyeing solution of a mixed aqueous solution of iodine and potassium iodide at 30 ° C for about 150 seconds for dyeing, followed by pure water at 10 ° C. Rinse excess iodine solution. Next, it was further immersed in a crosslinking solution of a mixed aqueous solution of boric acid and potassium iodide at 76 ° C for 600 seconds.

(washing and drying step)

Thereafter, the two-layer film was further washed with pure water of 10 ° C for 4 seconds, and finally dried at 80 ° C for 300 seconds. Through the above steps, the double-sided polarizing laminated film 302 in which the polarizing plate layers 31 and 32 of the polyvinyl alcohol-based resin layers 21 and 22 are formed on both surfaces of the base film 1 can be obtained. When drying is carried out, it is observed that almost no curling occurs, and a double-sided polarizing laminated film can be continuously produced in a good state.

Moreover, the mixing ratio of the dyeing solution and the crosslinking solution is:

<dyeing solution>

Water: 100 parts by weight

Iodine: 0.6 parts by weight

Potassium iodide: 10 parts by weight

<cross-linking solution>

Water: 100 parts by weight

Boric acid: 9.5 parts by weight

Potassium iodide: 5 parts by weight.

Example 2

The production of the double-sided polarizing laminate film 302 to the polarizing plates 501a and 501b is carried out in accordance with the flow chart shown in Fig. 2 .

(Protective film bonding step)

Polyvinyl alcohol powder (manufactured by Kuraray Co., Ltd., average polymerization degree 1800, trade name: KL-318) was dissolved in hot water of 95 ° C to prepare an aqueous solution having a concentration of 3% by weight. In the obtained aqueous solution, a crosslinking agent (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMIREZ (registered trademark) resin 650) was mixed as an adhesive solution in an amount of 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder. Further, both surfaces of the double-sided polarizing laminate film 302 obtained in Example 1 were coated with the above-mentioned polyvinyl alcohol-based adhesive, and then the protective films 41 and 42 (TAC: KC4UY, manufactured by Konica-Minolta Opto., Japan) were attached. After drying at 80 ° C for 5 minutes, a double-sided bonding film 402 composed of five layers of the protective film 41, the polarizing plate layer 31, the substrate film 1, the polarizing plate layer 32, and the protective film 42 can be obtained.

(drying step and stripping step)

The polarizing plate 501a composed of the polarizing plate layer 31 and the protective film 41 is peeled off by the double-sided bonding film 402. After the remaining film (by the substrate film 1, partial The polarizing plate 501b composed of the polarizer layer 32 and the protective film 42 can be obtained by peeling off the base film by the film layer 32 and the film formed by the protective film 42.

The base film 1 can be easily peeled off from the polarizing plates 501a and 501b formed on both sides thereof. The thicknesses of the polarizing plate layers 31 and 32 of the obtained two polarizing plates 501a and 501b were both 5.0 μm.

Example 3

In the same manner as in Example 1, a two-layer film was obtained. The thickness of the polyvinyl alcohol-based resin layers 21 and 22 (before stretching) at this time was 25.2 μm and 28.7 μm, respectively. The two-layer film was further stretched by a lenticular extension device at 160 ° C at 158 times to obtain a stretch film by laterally uniaxial stretching from the fixed end. The thickness of the stretched polyvinyl alcohol-based resin layer was 4.6 μm and 4.9 μm each. The extended two-layer film 202 can be observed to be almost curl-free and flat, so that the workability in the stretching step is very good.

Further, the small piece cut out from the stretched two-layer film was allowed to stand for 5 days in an environment of 23 ° C and 50% RH, and it was observed that almost no curl occurred, and a good shape was maintained.

Thereafter, the same operation as in Example 1 was carried out, and the stretched two-layer film was dyed, and after the dyeing, almost no curling occurred during drying, and a double-sided polarizing laminate film was continuously formed in a good shape.

Example 4

As shown in the flow chart shown in Fig. 3, a double-sided polarizing laminated film was obtained in the same manner as in Example 1. Thereafter, in the same manner as in the second embodiment, the protective film 41 is bonded to only one surface of the double-sided polarizing laminate film 302, and dried to obtain a protective film 41/polarizing sheet 31/substrate film. 1/ partial A single-sided bonding film 401 composed of four layers of the photo sheet layer 32.

Thereafter, the polarizing plate 501 (the polarizer layer 31 and the protective film 41) is peeled off by the film. The other base film 1 and the polarizer layer 32 become the polarizing laminated film 601. According to this manufacturing method, the polarizing plate 501 and the single-sided polarizing laminated film 601 can be obtained at the same time.

Comparative example 1

A stretched film was produced in the same manner as in Example 1 except that the undercoat layer and the resin layer were tightly provided on one side of the substrate film. Among them, since only the resin layer is formed on one side, the obtained film is liable to be curled, and the handleability is poor. At the same time, when the obtained film is placed in an environment of 23 ° C and 50% RH, the curl is more enlarged. Further, the film produced by the conventional method can be used without any problem if it is placed on a production line and in a state where a tensile force is applied, but when it is subjected to a winding step or the like, its workability is deteriorated and it is not easy to use, therefore, If it is necessary to enter the winding step according to the convenience of the production line, there may be an unfavorable situation.

Next, the stretched film was dyed in the same dyeing step as in Example 1 to obtain a polarizing laminated film. However, when drying, the film caused a significant curl which was almost impossible to transport, and the end portion of the film was folded inward. The shortcomings. Therefore, the polarizing laminated film cannot be obtained continuously and stably.

1‧‧‧Base film

21, 22‧‧‧ polyvinyl alcohol resin layer

201‧‧‧Single-layer film

202‧‧‧Two-layer film

31, 32‧‧‧ polarized film

302‧‧‧Two-sided polarizing laminated film

41, 42‧‧‧ protective film

401‧‧‧Single-sided film

402‧‧‧Two-sided film

501, 501a, 501b‧‧‧ polarizing plate

601‧‧‧Single-sided polarizing laminated film

Fig. 1 is a flow chart showing an outline of a method of manufacturing a polarizing plate of the present invention.

Fig. 2 is a flow chart for explaining the method for producing the double-sided polarizing laminate film of the first embodiment and the method for producing the polarizing plate of the second embodiment.

Fig. 3 is a flow chart for explaining the method of manufacturing the polarizing plate of the third embodiment.

Claims (8)

A method for producing a double-sided polarizing laminate film comprising a base film and a polarizer layer formed on both surfaces of the base film, wherein the manufacturing method includes a resin layer forming step, Applying a polyvinyl alcohol-based resin solution to both surfaces of the base film and drying to form a polyvinyl alcohol-based resin layer to obtain a two-area layer film; an extending step of extending the two-area layer film; and a dyeing step The polyvinyl alcohol-based resin layer on both sides of the extended two-layer film is dyed with a dichroic dye and subjected to a crosslinking treatment to form a polarizer layer; wherein, in the resin layer forming step, the drying temperature is 50 The drying time is 2 to 20 minutes at 200 ° C; the material of the polyvinyl alcohol-based resin layer constituting both sides of the two-area film is the same material; and the polyvinyl alcohol-based resin layer on both sides of the two-layer film after the stretching The difference in thickness is 3 μm or less; in the aforementioned stretching step, the stretching is performed at a stretching ratio higher than 5 times. The method for producing a double-sided polarizing laminate film according to the first aspect of the invention, wherein the thickness of each of the polarizing layer on both surfaces of the double-sided polarizing laminate film is 10 μm or less. A method of manufacturing a polarizing plate comprising a polarizing plate layer and a protective film formed on one side of the polarizing plate layer, and the manufacturing method is sequentially packaged And a protective film bonding step of obtaining a double-sided bonding film by bonding a protective film to both surfaces of the double-sided polarizing laminated film obtained by the method for producing a double-sided polarizing laminated film according to the first aspect of the invention; The peeling step of peeling off at least one of the polarizing plates by the double-sided bonding film. In the method for producing a polarizing plate according to claim 3, in the peeling step, two polarizing plates on both sides of the double-sided bonding film are simultaneously peeled off. In the method for producing a polarizing plate according to claim 3, in the peeling step, the polarizing plate on one surface of the double-sided bonding film is peeled off, and then the polarizing plate on the other surface is peeled off. A method for producing a polarizing plate with a base film, comprising: a polarizing plate layer; a protective film formed on one surface of the polarizer layer; and another layer attached to the polarizer layer The base film of one surface, and the manufacturing method includes the two sides of the double-sided polarizing laminated film obtained by the method for producing a two-sided polarizing laminated film according to the first aspect of the invention, and the two sides are bonded to each other to obtain two sides. a protective film bonding step of the bonding film; and a peeling step of peeling off the polarizing plate with the substrate film from the double-sided bonding film. A method of manufacturing a polarizing plate comprising: a polarizing plate layer; and a protective film formed on one side of the polarizing plate layer, wherein the manufacturing method comprises: a protective film bonding step of obtaining a single-sided bonding film by laminating a protective film on one surface of a double-sided polarizing laminated film obtained by the method for producing a double-sided polarizing laminated film according to the first aspect of the invention; The single-sided bonding film peels off the peeling step of the above polarizing plate. A method for producing a single-sided polarizing laminated film, comprising: a base film; and a polarizer layer formed on one surface of the base film, wherein the manufacturing method comprises: The protective film bonding step of obtaining a single-sided bonding film on one surface of the double-sided polarizing laminated film obtained by the method for producing a double-sided polarizing laminated film according to the first aspect of the invention, and the single-sided bonding from the single-sided bonding The film is peeled off from the single-sided polarizing laminated film.