KR20080046574A - Polarizing plate and production method thereof - Google Patents

Abstract

A polarization plate, and a method for preparing the polarization plate are provided to improve the adhesion between a polarizer and a protection layer and to obtain a very thin plate. A polarization plate comprises a polarizer made of a poly(vinyl alcohol)-based resin; an undercoat layer which is laminated on the one or both surfaces of the polarizer; and a cured layer of an ionization radiation resin which is formed on the undercoat layer, wherein the undercoat layer comprises poly(vinyl alcohol)-based resin and a water-soluble epoxy compound. Preferably the water-soluble epoxy compound is a polyamide epoxy resin.

Description

POLARIZING PLATE AND PRODUCTION METHOD THEREOF}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a polarizing plate which is suitably used for an optical display device such as a liquid crystal display device and the like and a method of manufacturing the same. More specifically, a polarizing plate which does not use a triacetyl cellulose protective film conventionally used and its production It is about a method.

Currently, the polarizing plate for liquid crystal display devices uses the iodine type film which adsorbed and oriented iodine to polyvinyl alcohol, or the dye type film which adsorbed and oriented the dichroic dye to polyvinyl alcohol as a polarizer, and at least one side of the polarizer. The thing of the structure which affixed protective film, such as a triacetyl cellulose (TAC), through the adhesive bond layer which consists of aqueous solution of polyvinyl alcohol-type resin in is common. However, in such a structure, there exists a problem that the wide polarizing plate which has width more than the width | variety, such as TAC which is a protective film, cannot be manufactured. Therefore, with the recent enlargement of the liquid crystal panel, while the wide polarizing plate is calculated | required, there was a limit to the manufacturing method of the polarizing plate which attaches previously formed protective film, such as TAC, to a polarizer. In addition, the TAC film used for the protective film of a polarizing plate is normally formed into the film by the casting method from a solvent solution, and the thickness is 80 micrometers in general, In addition, in recent years, the thing of 40 micrometers thick is used in some, As long as the TAC film was used, there was a limit to thinning the entire polarizing plate.

In order to solve such a problem, the method of forming a protective film directly on a polarizer has been examined in the past, and this method is examined again in recent years. For example, Patent Literatures 1 to 3 apply a polarizer to a composition comprising a compound having two or more isocyanate groups in a molecule and a compound having active hydrogen and a polymerizable unsaturated group reacting with an isocyanate group in one molecule. The manufacturing method of the polarizing plate characterized by irradiating and hardening an active energy ray, and the polarizing plate which has the said hardened coating film are disclosed.

In addition, Patent Document 4 has (1) a photoinitiator and (2) at least one group selected from the group consisting of amide bond groups, imide bond groups, urethane bond groups, urea bond groups, triazine groups, and isocyanurum groups. In addition to the functional (meth) acrylate, (3) a polyene compound or a polyfunctional maleic acid derivative having one or more groups selected from the group consisting of amide bond groups, imide bond groups, urethane bond groups, urea bond groups, triazine groups, and isocyanurum groups And / or (4) A polarizing material is coated with a photocurable resin composition composed of a polythiol compound and photocured.

However, the polarizing plate obtained by apply | coating these ionizing radiation curable resins directly to a polarizer is not enough adhesiveness with the protective layer which consists of a hardened | cured material layer of an ionizing radiation curable resin, and a polarizer. This is considered to be due to the specificity that the contact angle with respect to water shows the high value of 50 degrees, although the surface of the polyvinyl alcohol-type resin film which is a polarizer is hydrophilic.

On the other hand, it is also known to apply the curable resin composition which mixed the hydrolyzate of a silane coupling agent to the curable compound on the surface of a polarizer, harden | cure, and to make it a protective layer (for example, patent document 5). Moreover, forming the undercoat layer containing a silane coupling agent, and apply | coating curable resin composition on it and hardening are also considered. However, even if a silane coupling agent is used as the undercoat layer, the adhesion between the polarizer and the protective film cannot be said to be sufficient.

[Patent Document 1] Japanese Patent Laid-Open No. 55-12930

[Patent Document 2] Japanese Patent Laid-Open No. 55-36862

[Patent Document 3] Japanese Unexamined Patent Publication No. 56-80001

[Patent Document 4] Japanese Patent Laid-Open No. 62-218904

[Patent Document 5] Japanese Unexamined Patent Publication No. 2005-107238

This invention is made | formed in order to solve the said subject, The objective is to provide the polarizing plate which is thin and wide, and whose adhesiveness of a polarizer and a protective layer is very favorable, and its manufacturing method.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching in order to achieve the said objective, the inventors found that the undercoat layer containing a polyvinyl alcohol-type resin and a water-soluble epoxy compound is interposed between a polarizer and a protective layer, and adhesiveness with a polarizer and a protective layer is carried out. It was found that a very good polarizing plate was obtained. Based on these findings, the present invention has been completed with further studies.

That is, the polarizing plate of this invention contains the polarizer which consists of polyvinyl alcohol-type resin, and the undercoat layer and the hardened | cured material layer of ionizing radiation curable resin laminated | stacked on one side or both sides of the said polarizer in this order, The said undercoat The layer is characterized by containing a polyvinyl alcohol-based resin and a water-soluble epoxy compound.

Here, it is preferable that the undercoat layer contains a carboxyl group-modified polyvinyl alcohol and a water-soluble epoxy compound. Moreover, it is preferable that the said water-soluble epoxy compound is a polyamide epoxy resin.

Moreover, this invention is a method of manufacturing any one of said polarizing plates, (a) Applying the aqueous solution containing a polyvinyl alcohol-type resin and a water-soluble epoxy compound to one side or both sides of a polarizer, and then drying under An undercoat layer forming step of forming a coat layer, and (b) a cured product layer forming step of applying a resin composition containing an ionizing radiation curable resin onto the undercoat layer and then irradiating and curing the ionizing radiation. It provides a method for producing a polarizing plate, characterized in that.

Since the polarizing plate of this invention uses said specific undercoat layer, adhesiveness with a polarizer and the hardened | cured material layer of ionizing radiation curable resin is very favorable. In addition, in the conventional polarizing plate, in order to impart mechanical strength, it was common to laminate a hard coat layer on the protective film. In the polarizing plate of the present invention, the cured product layer of the ionizing radiation curable resin can also function as the hard coat layer. In addition, since it is not necessary to adhere a previously formed film like TAC, it can be made thin compared with the past.

Moreover, according to the manufacturing method of the polarizing plate of this invention, unlike the method of attaching protective films, such as TAC, to a polarizer, the wide polarizing plate which can respond to the enlargement of a liquid crystal display device can be manufactured satisfactorily.

<Polarizing plate>

The polarizing plate of this invention contains the polarizer which consists of polyvinyl alcohol-type resin, and the hardened | cured material layer of the undercoat layer and ionizing radiation curable resin laminated | stacked on one side or both sides of a polarizer in this order. EMBODIMENT OF THE INVENTION Hereinafter, the polarizing plate of this invention is demonstrated concretely.

(Polarizer)

As a polarizer used for the polarizing plate of this invention, the polarizing film which consists of conventionally well-known polyvinyl alcohol-type resin can be used, For example, the iodine type polarizing film and polyvinyl alcohol which adsorbed and oriented iodine to the polyvinyl alcohol-type resin film The dye type polarizing film which adsorbed and oriented a dichroic dye to the type resin film, the polyene type polarizing film which partially dehydrated polyvinyl alcohol-type resin, etc. are mentioned.

Polyvinyl alcohol-type resin which comprises a polarizer (polarizing film) is obtained by saponifying polyvinyl acetate type resin. As polyvinyl acetate type resin, besides polyvinyl acetate which is a homopolymer of vinyl acetate, the copolymer of vinyl acetate and the other monomer copolymerizable with it, for example, ethylene, etc. are illustrated. The saponification degree of polyvinyl alcohol-type resin is about 80 mol%-100 mol%, Preferably it is about 98 mol%-100 mol%. The degree of polymerization of the polyvinyl alcohol-based resin is, for example, about 1,000 to 10,000, preferably about 1,700 to 5,000. The polyvinyl alcohol-based resin may also be modified. For example, butyl aldehyde-modified polyvinyl butyral, acetaldehyde-modified polyvinyl acetal, formaldehyde-modified polyvinyl formal and the like can also be used. Among these, the film of polyvinyl alcohol which is a saponified polyvinyl acetate is used suitably as a disk of a polarizer.

Here, the method of manufacturing a polarizer (polarizing film) using a polyvinyl alcohol-type resin film is described. The method of producing a polarizer (polarizing film) using a polyvinyl alcohol-type resin film is not specifically limited, A conventionally well-known method can be used suitably. For example, the film which consists of polyvinyl alcohol-type resin as mentioned above is made into a disk, and the process which performs uniaxial stretching, dyes with the dichroic dye which consists of iodine or a dichroic dye, and adsorb | sucks the dichroic dye is carried out. It is manufactured through the process of making it, the process of processing the polyvinyl alcohol-type resin film which the dichroic dye adsorbed by the boric acid containing aqueous solution, and the process of washing with water after the process by this boric acid containing aqueous solution. Although the thickness of a raw film is not specifically limited, For example, what is about 50 micrometers-150 micrometers is used. Moreover, the thickness of the polarizer (polarizing film) obtained by giving uniaxial stretching etc. to a raw film is not specifically limited, either, About 10 micrometers-about 50 micrometers, for example.

Uniaxial stretching may be performed before dyeing, may be performed simultaneously with dyeing, or may be performed after dyeing. When performing uniaxial stretching after dyeing, this uniaxial stretching may be performed before boric acid treatment, or may be performed during boric acid treatment. Of course, it is also possible to uniaxially stretch in these several steps. As uniaxial stretching, the method etc. which extend | stretch uniaxially between the rolls from which a circumferential speed differs, for example can be employ | adopted. Moreover, dry stretching, such as extending | stretching uniaxially using the heat roll, extending | stretching in air | atmosphere, may be sufficient, and wet extending | stretching extending | stretching in the state swollen with a solvent may be sufficient. The draw ratio is usually about 3 to 8 times. In the case of dry stretching, it is preferable to extend | stretch in the temperature range of glass transition temperature-160 degreeC of a polyvinyl alcohol-type resin film.

In order to dye a polyvinyl alcohol-type resin film with a dichroic dye, what is necessary is just to immerse a polyvinyl alcohol-type resin film in the aqueous solution containing a dichroic dye, for example. Specifically as an dichroic dye, iodine or a dichroic dye is used. In addition, it is preferable that the polyvinyl alcohol-based resin film be immersed in water before the dyeing treatment.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing iodine and potassium iodide is employ | adopted normally.

The content of iodine and potassium iodide in this aqueous solution is, for example, about 0.01 parts by mass to 0.5 parts by mass and about 0.5 parts by mass to 10 parts by mass of potassium iodide relative to 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is about 20 degreeC-40 degreeC normally, and the immersion time (dyeing time) in this aqueous solution is about 20 second-1,800 second normally.

On the other hand, when using a dichroic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing water-soluble dichroic dye is employ | adopted normally. The content of the dichroic dye in this aqueous solution is, for example, 1 × 10 ⁻⁴ parts by mass to 10 parts by mass, preferably 1 × 10 ⁻³ parts by mass to 1 parts by mass with respect to 100 parts by mass of water. This aqueous solution may contain inorganic salts, such as sodium sulfate, as a dyeing adjuvant. The temperature of the dye aqueous solution used for dyeing is about 20 degreeC-80 degreeC normally, and the immersion time (dyeing time) in this aqueous solution is about 10 second-1,800 second normally.

After adsorb | sucking a dichroic dye, it processes with boric acid containing aqueous solution. The treatment method is not particularly limited, but a method of immersion in an aqueous solution containing boric acid is preferably used. The quantity of boric acid is not specifically limited, For example, about 2 mass parts-15 mass parts of boric acid with respect to 100 mass parts of water, Preferably about 5 mass parts-12 mass parts of boric acid with respect to 100 mass parts of water. to be. When iodine is used as a dichroic dye, it is preferable to contain potassium iodide in this boric acid containing aqueous solution, and the quantity is about 2 mass parts-about 20 mass parts with respect to 100 mass parts of water, More preferably, Is about 5 mass parts-15 mass parts with respect to 100 mass parts of water. Immersion time in boric acid containing aqueous solution is about 60 to 1,200 second normally, Preferably it is 150 to 600 second, More preferably, it is 200 to 400 second. The temperature of the boric acid containing aqueous solution is 50 degreeC or more normally, Preferably it is 50 degreeC-85 degreeC, More preferably, it is 60 degreeC-80 degreeC.

The polyvinyl alcohol-based resin film after boric acid treatment is usually washed with water. The water washing process is performed by immersing the polyvinyl alcohol-type resin film processed by boric acid in water, for example. The temperature of water in a water washing process is about 5 to 40 degreeC normally, and immersion time is about 1 to 120 second normally. After water washing, a drying process is performed and a polarizing film is obtained. The drying treatment is usually performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 ° C to 100 ° C, preferably 50 ° C to 80 ° C. The drying treatment time is usually about 60 seconds to 600 seconds, and preferably about 120 seconds to 600 seconds.

The polyvinyl alcohol-based resin film may be adsorbed and oriented in a dichroic dye, subjected to boric acid treatment, and further washed with water if necessary, and then the film may be subjected to high temperature and humidification under tension to prevent thermal relaxation. The tension in the tensioned state is about 3 kg / cm 2 to 30 kg / cm 2, preferably about 8 kg / cm 2 to 20 kg / cm 2. Typically, the high temperature humidification treatment is performed under such a tension state, for example, using a constant temperature humidifier or the like, for about 1 minute to 24 hours in an atmosphere having a temperature of about 40 ° C to 90 ° C and a relative humidity of about 50% to 95%. Is done. Preferably it is about 10 minutes to 10 hours in an atmosphere having a temperature of about 60 ° C to 80 ° C and a relative humidity of about 60% to 90%. In addition, when uniaxial stretching is performed before dyeing, adsorption orientation of the dichroic dye, boric acid treatment, water washing and high temperature humidification treatment are performed while maintaining the tension state when uniaxially stretching the polyvinyl alcohol-based resin film. It is usual to make, but it is not particularly limited.

(Undercoat layer)

In the polarizing plate of this invention, a specific undercoat layer is formed between the said polarizer and hardened | cured material layer of ionizing radiation curable resin. Thereby, adhesiveness of a polarizer and the hardened | cured material layer of ionizing radiation curable resin can be improved. The undercoat layer is formed on one side or both sides of the polarizer depending on whether the cured product layer of the ionizing radiation curable resin is formed on one side or both sides of the polarizer.

Here, the undercoat layer which concerns on this invention contains a polyvinyl alcohol-type resin and a water-soluble epoxy compound. As the polyvinyl alcohol-based resin, for example, polyvinyl alcohol modified with a carboxyl group, acetacetyl group, methylol group, amino group, etc. can be used in addition to polyvinyl alcohol which is a saponified product of polyvinyl acetate, but especially carboxyl group-modified polyvinyl alcohol This is preferred. Such modified polyvinyl alcohol is obtained by copolymerizing an unsaturated monomer having such a group with vinyl acetate and saponifying it. In the case of using a carboxyl group-modified polyvinyl alcohol, the degree of modification is not particularly limited, but for example, those having a degree of about 0.1 mol% to 30 mol% can be used. Moreover, as polyvinyl alcohol-type resin, it is preferable to use polyvinyl alcohol-type resin of the number average molecular weights 40,000-120,000.

As a water-soluble epoxy compound, the polyamide epoxy resin etc. which are reaction products of polyamide and epichlorohydrin can be used suitably, for example. Here, polyamide epoxy resin is epichloro to the polyamide obtained by reaction of alkylene polyamine compounds, such as diethylene triamine, triethylene tetramine, and hexamethylene diamine, and dicarboxylic acid, such as adipic acid, for example. It is a reaction product obtained by making hydrin react. As a commercial item of such a water-soluble polyamide epoxy resin, for example, "Sumirez resin 650" sold by Sumika Chemtex Co., Ltd. "Sumirez resin 675", "WS-" sold by Japan PMC Corporation 525 ”and the like.

It is preferable that ratios of the water-soluble epoxy compound and polyvinyl alcohol-type resin in a undercoat layer, and water-soluble epoxy compound / polyvinyl alcohol-type resin (solid content mass ratio) are 5 / 100-100 / 100, and 5 / 100-50 / 100 More preferably. When the said ratio is less than 5/100, adhesiveness between a polarizer and the hardened | cured material layer of ionizing radiation curable resin may not be enough, and when the said ratio is larger than 100/100, there exists a tendency for an undercoat layer to become easy to be broken.

In addition, the undercoat layer may contain other components other than polyvinyl alcohol-type resin and a water-soluble epoxy compound. Examples of other components include zinc chloride, tin chloride, zinc borofluoride, tertiary amines, quaternary ammonium salts, and imidazole compounds for promoting the curing of epoxy components.

The thickness of the undercoat layer is not particularly limited as long as adhesion between the polarizer and the cured product layer of the ionizing radiation curable resin is secured, but may be, for example, about 50 nm to 500 nm. As described later, the undercoat layer can be formed by applying an aqueous solution containing the polyvinyl alcohol-based resin and a water-soluble epoxy compound to the polarizer, followed by drying to remove the solvent.

(Cured product layer of ionizing radiation curable resin)

Next, the hardened | cured material layer of the ionizing radiation curable resin which concerns on the polarizing plate of this invention is demonstrated. The said hardened | cured material layer is made by hardening resin hardened | cured by ionizing radiation, and plays a role as a protective layer which protects a polarizer. Typically, it is formed by apply | coating the resin composition containing an ionizing radiation curable resin and a polymerization initiator and a solvent added as needed on an undercoat layer, and irradiating and hardening this to ionizing radiation, such as an ultraviolet-ray or an electron beam. As an ionizing radiation curable resin, although the compound which has one or more acryloyloxy group in a molecule | numerator is used preferably, in order to improve the mechanical strength at the time of setting it as a protective layer, or the extent which can function also as a hard-coat layer, In order to further provide, trifunctional or higher acrylate, that is, a compound having three or more acryloyloxy groups in the molecule is more preferably used. Specifically, trimethylol propane triacrylate, trimethylol ethane triacrylate, glycerin triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate and the like are exemplified.

Moreover, in order to provide flexibility to a hardened | cured material layer of an ionizing radiation curable resin, and to make it hard to be broken, the acrylate compound which has a urethane bond in a molecule | numerator is also used preferably. Specifically, two molecules of a compound having at least one hydroxyl group together with an acryloyloxy group in a molecule, such as trimethylolpropanediacrylate or pentaerythritol triacrylate, are diisocyanates such as hexamethylene diisocyanate and tolylene diisocyanate. Urethane acrylates of structures added to compounds are exemplified. In addition, other acrylic resins, such as ether acrylates and ester acrylates, which initiate radical polymerization by ionizing radiation and cure can also be used. 1 type of said acrylic resin may be used and may be used in combination of 2 or more type.

In the case of curing the above-mentioned acrylic ionizing radiation curable resin by ultraviolet irradiation, it is known to a resin composition to be applied on the undercoat layer in order to generate radicals when the ultraviolet irradiation is received and to initiate a polymerization / curing reaction. Ultraviolet radical initiators are added.

Examples of the ultraviolet radical initiators include 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one, and 2-hydroxy-2-methyl-. 1-phenylpropan-1-one, bis (2,4,6-trimethylbenzoyl) phenylphosphineoxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphineoxide, 2, Optical radical initiators, such as 4, 6- trimethyl benzoyl diphenyl phosphine oxide, are illustrated.

Moreover, you may use cationically polymerizable ionizing radiation curable resins, such as an epoxy type and an oxetane type, as resin for protective layer formation. In this case, for example, cationically polymerizable polyfunctional jade such as 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene or bis (3-ethyl-3-oxetanylmethyl) ether Cetane compounds and photocationic initiators, such as (4-methylphenyl) [4- (2-methylpropyl) phenyl] iodonium and hexafluorophosphate, are used together.

It is preferable that the thickness of the hardened | cured material layer of ionizing radiation curable resin exists in the range of 5 micrometers-50 micrometers. In particular, even if it is a thin thickness of 30 micrometers or less, it fully functions as a protective layer of a polarizer. When the thickness of the said hardened | cured material layer is less than 5 micrometers, there exists a possibility that sufficient hardness and mechanical strength may not be obtained as a protective layer. Moreover, when the thickness of the said hardened | cured material layer exceeds 50 micrometers, since hardness becomes too high and it becomes easy to be broken, the thickness as a polarizing plate also becomes thick, and it is unpreferable.

<Method of manufacturing polarizing plate>

Next, the manufacturing method of the polarizing plate of this invention is demonstrated. The manufacturing method of the polarizing plate of this invention basically includes the process (a) and (b) shown below.

(a) an undercoat layer forming step of forming an undercoat layer by applying an aqueous solution containing a polyvinyl alcohol-based resin and a water-soluble epoxy compound to one or both surfaces of the polarizer, followed by drying;

(b) After apply | coating the resin composition containing an ionizing radiation curable resin on an undercoat layer, the hardened | cured material layer formation process of irradiating and hardening an ionizing radiation.

(a) Undercoat layer forming process

In this step, first, an aqueous solution containing polyvinyl alcohol-based resin and a water-soluble epoxy compound is applied to one or both surfaces of the polarizer. Herein, the polyvinyl alcohol-based resin and the water-soluble epoxy compound are as described above, and the polarizer can be suitably used as described above by using a conventionally known method. The solvent used for the aqueous solution containing the polyvinyl alcohol-based resin and the water-soluble epoxy compound is mainly water, and is not particularly limited as long as it dissolves the polyvinyl alcohol-based resin and the water-soluble epoxy compound. Although hydrophilic organic solvents, such as these, may be contained, it is more preferable to comprise only water generally.

An aqueous solution containing a polyvinyl alcohol-based resin and a water-soluble epoxy compound is prepared by dissolving the polyvinyl alcohol-based resin in water and then dissolving the water-soluble epoxy compound in the aqueous solution. Although the ratio of polyvinyl alcohol-type resin and water is not specifically limited, For example, polyvinyl alcohol-type resin / water is about 1 / 100-10 / 100 by mass ratio, Preferably it is about 1 / 100-5 / 100. Moreover, it is preferable that ratio of the water-soluble epoxy compound and polyvinyl alcohol-type resin in the said aqueous solution, and water-soluble epoxy compound / polyvinyl alcohol-type resin (solid content mass ratio) are 5 / 100-100 / 100, and it is 5 / 100-50 More preferably, it is / 100. When the said ratio is less than 5/100, adhesiveness between a polarizer and the hardened | cured material layer of ionizing radiation curable resin may not be enough, and when the said ratio is larger than 100/100, there exists a tendency for an undercoat layer to become easy to be broken.

In addition, as mentioned above, the said aqueous solution may contain other components other than polyvinyl alcohol-type resin and a water-soluble epoxy compound. As another component, a zinc chloride, tin chloride, zinc borofluoride, a tertiary amine, a quaternary ammonium salt, an imidazole compound, etc. for accelerating hardening of an epoxy component are mentioned, for example.

In this step, an aqueous solution containing the polyvinyl alcohol-based resin and a water-soluble epoxy compound is applied to one side or both sides of the polarizer, but the coating method is not particularly limited, and for example, the dipping method and the microgravure coating method Known coating methods such as gravure coating, roll coating, die coating and bar coating are used. There is no restriction | limiting in particular also about the coating thickness of an aqueous solution.

Next, the solvent is removed by drying to form an undercoat layer. There is no restriction | limiting in particular about a drying method, A conventionally well-known method can be used suitably.

(b) hardened | cured material layer formation process

Next, after apply | coating the resin composition containing an ionizing radiation curable resin on the undercoat layer formed in process (a), ionizing radiation is irradiated and hardened. The resin composition containing an ionizing radiation curable resin contains the solvent as a polymerization initiator or a diluent other than an ionizing radiation curable resin as needed. As the coating method, for example, a known coating method such as a dipping method, a microgravure coating method, a gravure coating method, a roll coating method, a die coating method or a bar coating method is used. When the resin composition containing an ionizing radiation curable resin contains a solvent, a solvent is dried after application | coating. There is no restriction | limiting in particular about the drying method of a solvent, A conventionally well-known method can be used.

It is preferable that the ionizing radiation curable resin layer has a thickness after curing within the range of 5 µm to 50 µm. When the thickness of the said resin layer is less than 5 micrometers, it becomes difficult to obtain sufficient hardness and mechanical strength as a protective layer. Moreover, when the thickness of the said resin layer exceeds 50 micrometers, since hardness becomes too high and it becomes easy to be cracked, since the thickness as a polarizing plate becomes thick, it is not preferable.

Next, the ionizing radiation curable resin layer is irradiated with an ionizing radiation to be cured to obtain a cured product layer. The cured product layer of the ionizing radiation curable resin serves as a protective layer for protecting the polarizer. The ionizing radiation may be ultraviolet rays or electron beams, but from the viewpoint of ease of handling and safety, ultraviolet rays are preferably used. As a light source of an ultraviolet-ray, the high pressure mercury lamp which has an electrode, a metal halide lamp, etc., "V-bulb", "D-bulb" (all brand names) etc. which are fusion products of an electrode are also used suitably. The irradiation dose may be any dose sufficient to impart desired hardness, for example, pencil hardness of about 2H or more, to the ultraviolet curable resin, and is not particularly limited. In order to further improve the surface hardness, a plurality of irradiations may be performed.

The polarizing plate of this invention can be obtained as mentioned above. In the polarizing plate of the present invention thus obtained, the cured product layer of the ionizing radiation curable resin plays a role of protecting the polarizer, and in general, it also plays a role as a hard coat layer. (I) It is not necessary to make the protective film adhere, and it becomes thin compared with the conventional polarizing plate. Moreover, according to the manufacturing method of the polarizing plate of this invention, since the width | variety of the polarizing plate does not limit to the width | variety of the triacetyl cellulose type film which has been used as a protective film, it mass-produces the wide polarizing plate which can respond to the enlargement of the recent panel. I can produce it well.

<Example>

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples,% and parts indicating the content to the amount of use are based on mass unless otherwise specified.

<Example 1>

(i) fabrication of polarizer

A polyvinyl alcohol film ("Kurerevinyllon # 7500" sold by Kuraray Co., Ltd.) having a thickness of 75 µm was immersed in pure water at 30 ° C. for about 130 seconds while maintaining a tension state so that the film does not come loose. The film was swelled sufficiently. Next, uniaxial stretching was carried out while iodine / potassium iodide / water was immersed in an aqueous solution having a mass ratio of 0.02 / 1.5 / 100 and dyed. Then, uniaxial stretching was performed until the integrated draw ratio from the master became 5.9 times while potassium iodide / boric acid / water was immersed in a 60 ° C. aqueous solution having a mass ratio of 10/5/100 and subjected to boric acid treatment. Subsequently, the film was shrunk by about 3% in the stretching direction while the second boric acid treatment was performed by immersing the aqueous solution of potassium iodide / boric acid / water in a mass ratio of 10/3/100 for about 30 seconds at 40 ° C. (thus, final stretching Magnification is 5.9 × 0.97 = 5.72 times). Furthermore, after washing with water for 10 seconds with 10 degreeC pure water, it dried at 60 degreeC for 2 minutes, and obtained the polarizer. The thickness of the obtained polarizer was 31 micrometers.

(ii) Preparation of Aqueous Solution for Undercoat Layer

To 100 parts of water, 3 parts of carboxyl group-modified polyvinyl alcohol "Kurarefobal KL318" (modification degree 2 mol%) sold by Kuraray Co., Ltd. is dissolved, and there is a water-soluble polyamide epoxy resin. 1.5 parts of "Sumirez resin 650" (solid solution of 30% of solid content) sold by Sumika Chemtex Co., Ltd. was added, and it melt | dissolved, and obtained the aqueous solution for undercoat layers.

(iii) Preparation of ionizing radiation curable resin composition

60 parts of pentaerythritol triacrylate and 40 parts of polyfunctional urethane acrylate which are a reaction product of hexamethylene diisocyanate and pentaerythritol triacrylate are melt | dissolved in ethyl acetate so that solid content concentration may be 60%, and per 100 parts of solid content, photopolymerization 5 parts of "Lucirin TPO" (BASF company make, chemical name: 2,4,6-trimethylbenzoyldiphenylphosphine oxide) which is an initiator was added and mixed in solid amount, and it was set as the ionizing radiation curable resin composition.

(iv) Preparation of Polarizer

On one surface of the polarizer obtained in the above (i), the aqueous solution for the undercoat layer obtained in the above (ii) was coated with a wire bar of # 4, put in an oven at 80 ° C, and dried for 3 minutes to form an undercoat. Next, the ionizing radiation curable resin composition of the above (iii) was coated with a wire bar of # 8. The hardened | cured material layer was formed by irradiating an ultraviolet-ray with the cumulative light quantity of 550mJ / cm <2> as a light source using the "V bulb" lamp (maximum light emission wavelength 420nm) which is a fusion company product, and hardening an ionizing radiation curable resin.

The thickness of the hardened | cured material layer was 7 micrometers. On the other side of the polarizer, the cured product layer of the ionizing radiation curable resin was formed to a thickness of 7 μm via the undercoat layer in the same order. In this way, the polarizing plate in which the hardened | cured material layer of ionizing radiation curable resin was formed through the undercoat layer on both surfaces of the polarizer.

<Example 2>

As an ionizing radiation curable resin composition, 5 parts per 100 parts of dipentaerythritol hexaacrylate which is a resin component are made the same photoinitiator "Lucirine TPO" used in Example 1 in the 50% ethyl acetate solution of dipentaerythritol hexaacrylate. A polarizing plate was produced in the same manner as in Example 1 except that the added composition was used.

<Example 3>

In the preparation of the aqueous solution for the undercoat layer, except that 5 parts of carboxyl group-modified polyvinyl alcohol "Kurarefobal KL318" and 1.5 parts of "Sumirez resin 650" (water content of 30% of solid content) which are water-soluble polyamide epoxy resins were used. Was the same as in Example 1 to produce a polarizing plate.

<Example 4>

In the preparation of the aqueous solution for the undercoat layer, 1 part of carboxyl group-modified polyvinyl alcohol "Kurarefobal KL318" and 0.5 part of "Sumirez resin 650" (30% of solid content) which are water-soluble polyamide epoxy resins were used. Was the same as in Example 1 to produce a polarizing plate.

<Example 5>

In preparation of the aqueous solution for undercoat layers, except having used 3 parts of polyvinyl alcohol "163-03045" obtained from Wako Pure Chemical Co., Ltd. instead of carboxyl group-modified polyvinyl alcohol "kurarefobal KL318", A polarizing plate was produced in the same manner as in Example 1.

Comparative Example 1

A polarizing plate was produced in the same manner as in Example 1 except that a cured product layer of ionizing radiation curable resin was formed directly on both surfaces of the polarizer without forming an undercoat layer.

Comparative Example 2

1% toluene of the silane coupling agent "KBM-303" (chemical name: 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane) sold by Shin-Etsu Chemical Co., Ltd. instead of the aqueous solution for undercoat layers. Except having formed the undercoat layer using the solution, it carried out similarly to Example 1, and produced the polarizing plate.

The polarizing plates of the said Examples 1-5 and Comparative Examples 1 and 2 were evaluated with the following method. The results are shown in Table 1.

(1) Pencil hardness test: Pencil hardness of the hardened | cured material layer of the ionizing radiation curable resin of the polarizing plate surface was measured based on JISK5600-5-4 (scratch hardness (pencil method)).

(2) Adhesion test: 100 pieces of square checkerboard eyes having a side of 1 mm with a cutter knife were carved on the cured product layer of the ionizing radiation curable resin on the surface of the polarizing plate, and a test was carried out after attaching the cellophane tape thereto. The number of checkerboard eyes remaining in the dog's checkerboard eyes was evaluated.

(3) Scratch resistance test: After the steel wool # 0000 was reciprocated ten times with a load of 250 g / cm 2 to the cured product layer of the ionizing radiation curable resin on the surface of the polarizing plate, the degree of scratch on the surface was visually evaluated based on the following criteria. It was.

A: No wound observed

A ': Little scarring observed

B: Several wounds observed

C: Dozens of wounds observed

D: Dozens of wounds observed

E: Multiple wounds observed

Thickness of polarizer Evaluation results Pencil hardness Adhesion Scratch resistance Example 1 45㎛ 5H 100/100 A Example 2 45㎛ 2H 100/100 C Example 3 45㎛ 5H 100/100 A Example 4 45㎛ 5H 95/100 A Example 5 45㎛ 5H 80/100 A Comparative Example 1 45㎛ 5H 0/100 A Comparative Example 2 45㎛ 5H 0/100 A

As shown in Table 1, the polarizing plates of Examples 1-5 showed sufficient mechanical characteristics and favorable adhesiveness. In addition, although the polarizing plates of Examples 1-5 are all 45 micrometers in thickness, they have sufficient mechanical characteristics. And since the surface hardness is also high, it is not necessary to form a hard coat layer thereon. Therefore, it is thinner as a whole compared with the conventional polarizing plate. On the other hand, the polarizing plates of Comparative Examples 1 and 2 were inferior in adhesion between the polarizer and the protective layer, and it was found that the laminated cured product layer could not function as a protective layer.

The embodiments and examples disclosed herein are to be considered in all respects only as illustrative and not restrictive. The scope of the present invention is shown by above-described not description but Claim, and it is intended that the meaning of a claim and equality and all the changes within a range are included.

The polarizing plate of this invention can be used suitably for a liquid crystal display device. Specifically, a pair of substrates, a pair of electrodes provided on opposing inner surfaces (in the case of TN or VA) of the substrates or inner surfaces of the one substrate (in the case of IPS), and a liquid crystal filled between the substrates About the liquid crystal cell of the structure containing a layer at least, the polarizing plate which concerns on this invention can be arrange | positioned on one side or both sides of the outer side, and it can be set as a liquid crystal display device.

Claims (4)

A polarizer made of a polyvinyl alcohol-based resin, and a cured product layer of an undercoat layer and an ionizing radiation curable resin laminated on one or both surfaces of the polarizer, in this order, The undercoat layer comprises a polyvinyl alcohol-based resin and a water-soluble epoxy compound. The polarizing plate according to claim 1, wherein the undercoat layer contains a carboxyl group-modified polyvinyl alcohol and a water-soluble epoxy compound. The polarizing plate according to claim 1 or 2, wherein the water-soluble epoxy compound is a polyamide epoxy resin. As a method of manufacturing the polarizing plate of claim 1, (a) an undercoat layer forming step of forming an undercoat layer by applying an aqueous solution containing a polyvinyl alcohol-based resin and a water-soluble epoxy compound to one or both surfaces of the polarizer, followed by drying; (b) After apply | coating the resin composition containing an ionizing radiation curable resin on the said undercoat layer, the hardened | cured material layer formation process of irradiating and hardening an ionizing radiation is included, The manufacturing method of the polarizing plate characterized by the above-mentioned.