KR20160028316A - Adhesive composition and polarizing plate using the same - Google Patents

Abstract

The present invention relates to an adhesive composition for a polarizing plate and, more particularly, to an adhesive composition for a polarizing plate, which comprises: an aceto acetyl group-modified polyvinylaochol-based resin (A); a cross-linker (B) including at least two functional groups of a hydroxyl group or a carboxylic group in the molecule; and a water-soluble chelate compound (C). The adhesive composition of the present invention has improved adhesive strength and water resistance while maintaining excellent degree of polarization. Therefore, a polarizing plate prepared by using the adhesive composition of the present invention has remarkably improved durability.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a polarizing plate,

The present invention relates to an adhesive composition, and more particularly, to an adhesive composition having improved adhesive strength and water resistance while maintaining an excellent degree of polarization, and a polarizing plate produced using the same.

Polarizing plates used in various image display devices such as a liquid crystal display (LCD), an electroluminescence (EL) display, a plasma display (PDP), a field emission display (FED) and an OLED are generally made of polyvinyl alcohol alcohol, PVA) film comprises a polarizer in which an iodine compound or a dichroic polarizing material is adsorbed and oriented, a polarizer protective film is laminated on one side of the polarizer, and a polarizer protective film, a liquid crystal cell Layer structure in which a pressure-sensitive adhesive layer and a release film are laminated in this order.

A polarizing plate having a structure in which a protective film such as triacetyl cellulose (TAC) is bonded to at least one side of the polarizer through an adhesive layer formed using an aqueous solution of a polyvinyl alcohol-based resin (polyvinyl alcohol-based adhesive) , The polarizing plate having such a constitution has a problem that the cross section of the protective film and the polarizer is liable to be peeled off when the polarizing plate is used for a long time under the condition of humid heat.

Thus, a polarizing plate in which a polarizer (polarizing film) and a protective film are bonded using a polyvinyl alcohol-based adhesive and then heated and dried at a temperature of 90 to 100 ° C to improve the heat and humidity resistance has been proposed. However, The problem that the cross section of the protective film and the polarizer is easily peeled is not solved.

In order to solve such a problem, JP-A-1995-134212 discloses a resin composition comprising an acetoacetyl group-modified polyvinyl alcohol resin, a polyvinyl alcohol resin (crosslinking regulator), glyoxal (crosslinking agent), and zinc chloride And the like. However, even in the case of the above composition, since the curing rate is slow due to the presence of the crosslinking control agent, there is a problem that the polarization degree is deteriorated due to the deterioration of the heat and moisture.

Japanese Laid-Open Publication No. 1995-134212

It is an object of the present invention to provide an adhesive composition for a polarizing plate that does not contain a crosslinking regulator.

An object of the present invention is to provide an adhesive composition having improved adhesive force and water resistance while maintaining an excellent degree of polarization.

It is another object of the present invention to provide a polarizing plate bonded with the above adhesive composition.

1. Acetoacetyl group-modified polyvinyl alcohol-based resin (A);

A crosslinking agent (B) containing a hydroxyl group or a carboxyl group having two or more functional groups in the molecule; And

A water-soluble chelate compound (C)

Wherein the acetoacetyl group-modified polyvinyl alcohol-based resin (A) has a degree of polymerization of 1,000 or less.

2. The adhesive composition for a polarizing plate according to 1 above, wherein the acetoacetyl group-modified polyvinyl alcohol resin (A) is contained in an amount of 3 to 9% by weight based on the solid content in the adhesive composition.

3. The crosslinking agent (B) as described in 1 above, wherein the crosslinking agent (B) containing a bifunctional or more functional hydroxyl group in the molecule is 3-methoxy-1,2-propanediol, Wherein the adhesive composition is at least one selected from the group consisting of 3-ethoxy-1,2-propanediol, di-ethylene glycol, and glycerol.

4. The crosslinking agent (B) as set forth in the above 1, wherein the crosslinking agent (B) containing two or more functional carboxyl groups in the molecule is selected from the group consisting of oxalic acid, malonic acid, dimethylmalonic acid, succinic acid wherein the adhesive composition is at least one selected from the group consisting of succinic acid and glutaric acid.

5. The polarizing plate according to item 1, wherein the cross-linking agent (B) having a bifunctional or more functional hydroxyl group or carboxyl group in the molecule is contained in an amount of 20 to 50 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol- / RTI >

6. The adhesive composition for a polarizing plate according to 1 above, wherein the water-soluble chelate compound (C) is at least one selected from the group consisting of zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate and zinc sulfate.

7. The adhesive composition for a polarizing plate according to 1 above, wherein the water-soluble chelate compound (C) is contained in an amount of 2 to 10 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol resin (A).

8. The adhesive composition for a polarizing plate according to item 1 above, which does not contain a crosslinking controlling agent.

9. The polarizing plate according to any one of the above 1 to 8, wherein the protective film is bonded to at least one surface of the polarizer with an adhesive composition for a polarizing plate.

10. An image display device comprising the polarizing plate of claim 9.

The adhesive composition for a polarizing plate of the present invention exhibits excellent polarization degree even when it does not contain a crosslinking regulator, and is excellent in adhesive strength and water resistance. Accordingly, the durability of the polarizing plate can be remarkably improved.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram schematically showing an evaluation test method for water resistance according to an experimental example.

The present invention relates to an acetoacetyl group-modified polyvinyl alcohol-based resin (A); A crosslinking agent (B) containing a hydroxyl group or a carboxyl group having two or more functional groups in the molecule; And an aqueous chelate compound (C), wherein the acetoacetyl group-modified polyvinyl alcohol-based resin (A) has a degree of polymerization of 1,000 or less, thereby improving adhesive strength and water resistance while maintaining an excellent degree of polarization .

Hereinafter, the present invention will be described in detail.

< For polarizer  Adhesive composition>

The adhesive composition for a polarizing plate of the present invention comprises an acetoacetyl group-modified polyvinyl alcohol-based resin (A); A crosslinking agent (B) containing a hydroxyl group or a carboxyl group having two or more functional groups in the molecule; And a water-soluble chelate compound (C).

Aceto Acetyl group  denaturalization Polyvinyl alcohol system  Resin (A)

The acetoacetyl group-modified polyvinyl alcohol (PVA) based resin contains functional groups having higher reactivity than modified polyvinyl alcohol resins such as carboxyl group denaturation, methylol group denaturation or amino group denaturation, and is excellent in durability.

The acetoacetyl group-modified polyvinyl alcohol-based resin (A) can be obtained by reacting a polyvinyl alcohol-based resin with diketene by a known method. Specifically, a method of dispersing a polyvinyl alcohol-based resin in a solvent such as acetic acid and adding diketene thereto, a method of previously dissolving a polyvinyl alcohol-based resin in a solvent such as dimethylformamide or dioxane, Or a method in which a diketene gas or liquid diketene is directly contacted with a polyvinyl alcohol-based resin, or the like. The acetoacetyl group-modified polyvinyl alcohol-based resin (A) is not particularly limited so long as the acetoacetyl group modification degree is 0.1 mol% or more, preferably 0.1 to 40 mol%, more preferably 1 to 20 mol% Is preferably 2 to 7 mol%. When the degree of modification of the acetoacetyl group is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient, which is unsuitable. When the degree of modification of the acetoacetyl group exceeds 40 mol%, the effect of improving the water resistance may be insignificant.

The degree of saponification of the acetoacetyl group-modified polyvinyl alcohol-based resin (A) is not particularly limited, but is preferably 80 mol% or more, more preferably 85 mol% or more. When the degree of saponification of the polyvinyl alcohol-based resin contained in the adhesive composition is low, the sufficient water-solubility is difficult to manifest, and thus the adhesiveness tends to become insufficient.

The polymerization degree of the acetoacetyl group-modified polyvinyl alcohol-based resin (A) may be 1,000 or less, and if the degree of polymerization is 1,000 or less, the reaction rate is delayed and the stability of the solution is improved.

Commercially available products include, but are not limited to, Z-100, Z-200, Z-200H, Z-210, Z-220, and Z-320 (Gohsefymer, These may be used alone or in combination of two or more.

The acetoacetyl group-modified polyvinyl alcohol resin (A) may be contained in an amount of 3 to 9% by weight based on the solid content in the adhesive composition. If it is less than 3% by weight based on the weight of the solid content in the adhesive composition, there is a problem that water hardness is lowered due to insufficient curing. If it exceeds 9% by weight, viscosity may increase and bubbles may be mixed in the bonding process.

Within the molecule Bifunctionality  The above hydroxy group or Carboxy group  Included Cross-linking agent (B)

The cross-linking agent (B) comprising a hydroxyl group or a carboxyl group having two or more functional groups in the molecule of the present invention is obtained by reacting an acetoacetyl group-modified polyvinyl alcohol resin (A) with a polyvinyl alcohol (PVA) polarizer and a cellulose- Thereby improving the adhesion to the protective film and the water resistance.

The crosslinking agent according to the present invention contains a hydroxyl group or a carboxyl group having two or more functional groups in the molecule, so that a condensation reaction occurs between the hydroxy group or the carboxyl group and the hydroxyl group contained in the polyvinyl alcohol resin, thereby improving the adhesion and water resistance.

Therefore, the adhesive composition for a polarizing plate according to the present invention is excellent in adhesion and water resistance, and exhibits excellent polarization even without a crosslinking control agent.

Specific examples of the cross-linking agent (B) containing a bifunctional or more hydroxyl group in the molecule according to the present invention include 3-methoxy-1,2-propanediol, 3-ethoxy- 3-ethoxy-1,2-propanediol, di-ethylene glycol, glycerol and the like. These may be used alone or in combination of two or more. .

Specific examples of the cross-linking agent (B) containing a bifunctional or more carboxyl group in the molecule according to the present invention include oxalic acid, malonic acid, dimethylmalonic acid, succinic acid succinic acid, and glutaric acid). These may be used alone or in combination of two or more.

The content of the crosslinking agent (B) containing a bifunctional or more functional hydroxyl group or a carboxyl group in the molecule of the present invention is not particularly limited, but is preferably 20 to 50 parts by weight per 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol resin (A) . When the amount of the cross-linking agent is less than 20 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol-based resin (A), the water resistance of the adhesive layer is not sufficiently manifested, and when the amount is more than 50 parts by weight, .

receptivity Chelate  The compound (C)

The water-soluble chelate compound (C) contained in the adhesive composition of the present invention enhances the degree of crosslinking between the adhesive layer and a protective film such as a polyvinyl alcohol (PVA) -based polarizer, a cellulose-based film or an olefin-based film to improve adhesion and water resistance And to improve optical durability.

Further, the water-soluble chelate compound (C) of the present invention accelerates the curing of the crosslinking agent (B) containing a hydroxyl group or a carboxyl group having two or more functional groups in the molecule.

The water-soluble chelate compound (C) can be used in the art without any particular limitation, and specific examples thereof include zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate and zinc sulfate. Preferably, zinc chloride, zinc nitrate and aluminum nitrate are preferable from the viewpoint of excellent crosslinking catalyst function. These may be used alone or in combination of two or more.

The content of the water-soluble chelate compound (C) is not particularly limited, and is, for example, 2 to 10 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol resin (A). When the amount of the water-soluble chelate compound (C) is less than 2 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol-based resin (A), the water resistance of the adhesive layer is hardly manifested sufficiently. There is a problem of deterioration.

additive

If necessary, the adhesive composition for a polarizing plate of the present invention may further comprise an additive.

The kind of the additive is not particularly limited and includes, for example, silane coupling agents, fine particles, alcohols for improving spreadability, sensitizers, adhesion promoters, leveling agents, ultraviolet absorbers, antioxidants, dyes, processing aids, , A tackifier, a filler, a plasticizer, a foam inhibitor, an antistatic agent, and a fragrance. These may be used alone or in combination of two or more.

The content of the additive is not particularly limited and can be, for example, 0.01 to 3% by weight, preferably 0.5 to 1% by weight, based on the total weight of the adhesive composition.

The viscosity of the adhesive composition according to the present invention at 20 캜 is preferably in the range of 3 to 25 mPa · sec. When the viscosity of the adhesive composition is less than 3 mPa · sec, the water resistance of the polarizing plate can not be sufficiently exhibited. When the viscosity is 25 mPa · sec or more, the optical characteristics of the polarizing plate deteriorate.

The form of the adhesive composition is not particularly limited, but it is preferably a liquid form in order to form a uniform adhesive layer on the surface of the polarizer or the protective film as the adhesive. A solution type or a dispersed liquid type of various solvents can be used for such a liquid type adhesive, and a solution type is preferable in view of the coated surface of the substrate, and a solution type or a dispersed liquid type in which water is used as a solvent is suitable from the viewpoint of stability.

<Polarizing plate and image display device including the same>

The present invention relates to a polarizing plate in which a protective film is bonded to at least one surface of a polarizer with an adhesive composition for a polarizing plate of the present invention.

A polarizer is one in which a dichroic dye is adsorbed and oriented on a stretched polyvinyl alcohol-based resin film.

The polyvinyl alcohol-based resin constituting the polarizer can be obtained by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include acrylamide monomers having an unsaturated carboxylic acid type, an unsaturated sulfonic acid type, an olefin type, a vinyl ether type, and an ammonium group. The polyvinyl alcohol resin may also be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The saponification degree of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polymerization degree of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

Such a polyvinyl alcohol-based resin film is used as the original film of the polarizer. The method of forming the film of the polyvinyl alcohol-based resin is not particularly limited, and a known method can be used. The thickness of the original film is not particularly limited, and may be, for example, 10 to 150 mu m.

The polarizer of the present invention is produced by continuously uniaxially stretching a polyvinyl alcohol-based film in an aqueous solution, staining with a dichroic dye and adsorbing, treating with an aqueous solution of boric acid, and washing and drying.

The uniaxial stretching of the polyvinyl alcohol film may be performed before dyeing, concurrently with dyeing, or may be performed after dyeing. If uniaxial stretching is carried out after dyeing, it may be carried out before the boric acid treatment, or may be carried out during the boric acid treatment. Of course, it is also possible to perform uniaxial stretching in a plurality of such steps. For uniaxial stretching, other rolls or rolls of different circumferences may be used. The uniaxial stretching may be either dry stretching in air or wet stretching in the state of being swollen with a solvent. The stretching ratio is usually 3 to 8 times.

As a step of dyeing a stretched polyvinyl alcohol film with a dichroic dye, for example, a method of immersing a polyvinyl alcohol film in an aqueous solution containing a dichroic dye can be used. As the dichroic dye, iodine or a dichroic dye is used. It is preferable that the polyvinyl alcohol film is pre-immersed in water before dyeing to swell.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based film is dipped in an aqueous solution for dyeing usually containing iodine and potassium iodide may be used. Usually, the content of iodine in an aqueous solution for dyeing is 0.01 to 1 part by weight with respect to 100 parts by weight of water (distilled water), and the content of potassium iodide is 0.5 to 20 parts by weight with respect to 100 parts by weight of water. The temperature of the aqueous solution for dyeing is usually 20 to 40 占 폚, and the immersion time (dyeing time) is usually 20 to 1,800 seconds.

When a dichroic dye is used as the dichroic dye, a method of dying and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is generally employed. The content of the dichroic dye in this aqueous solution is usually 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The dye aqueous solution used for dyeing usually has a temperature of 20 to 80 DEG C, and the immersion time for this aqueous solution is usually 10 to 1,800 seconds.

The step of treating the dyed polyvinyl alcohol film with boric acid can be carried out by immersing it in an aqueous solution containing boric acid. The content of boric acid in an aqueous solution containing boric acid is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight based on 100 parts by weight of water. When iodine is used as the dichroic dye, it is preferable that the aqueous solution containing boric acid contains potassium iodide. The content thereof is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., and more preferably 60 to 80 ° C. The immersing time is usually 60 to 1,200 seconds, preferably 150 to 600 seconds, Preferably 200 to 400 seconds.

After the boric acid treatment, the polyvinyl alcohol film is usually washed with water and dried. The washing treatment can be carried out by immersing the boric acid-treated polyvinyl alcohol-based film in water. The water temperature of the water treatment is usually 5 to 40 占 폚, and the immersion time is usually 1 to 120 seconds. After washing with water, the polarizer can be obtained. The drying treatment can be usually carried out using a hot air dryer or a far infrared ray heater. The drying treatment temperature is usually 30 to 100 占 폚, preferably 50 to 80 占 폚, and the drying time is usually 60 to 600 seconds, preferably 120 to 600 seconds.

The thickness of the polarizer according to the present invention is not particularly limited, but may be, for example, 5 to 40 탆.

The kind of the protective film is not particularly limited as long as it is excellent in transparency, mechanical strength, thermal stability, moisture shielding property, isotropy, and the like. For example, the protective film is made of an acrylic resin film, a cellulose resin film, a polyolefin resin film and a polyester resin film Various transparent resin films containing at least one kind selected from the group consisting of

Specific examples of the protective film include acrylic resin films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Polyester based resin films such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and polybutylene terephthalate; Cellulose-based resin films such as diacetylcellulose and triacetylcellulose; Polyolefin-based resin films such as polyethylene, polypropylene, cyclo-based or norbornene structures, polyolefin-based or ethylene-propylene copolymer; , But are not limited thereto.

The thickness of the protective film is not particularly limited, but may be 10 to 200 占 퐉, preferably 10 to 150 占 퐉. When the thickness of the protective film is 10 to 200 탆, when the polarizer protective film is laminated on both sides of the polarizer, the respective protective films may have the same or different thicknesses.

The adhesive composition for a polarizing plate according to the present invention may be applied to at least one surface of the polarizer to form an adhesive layer, and the polarizer and the protective film or adhesive layer may be bonded to each other via the adhesive layer.

The thickness of the adhesive layer formed by applying the adhesive composition of the present invention is not particularly limited, but it may be usually 0.01 to 10 탆, and preferably 0.1 to 5 탆. When the thickness of the adhesive layer is 0.5 탆 or less, there is a high possibility that air bubbles are mixed at the time of bonding, and when the thickness of the adhesive layer is 5 탆 or more, the price increases.

In order to improve the adhesion, the surface of the polarizer and / or the protective film may be suitably subjected to a surface treatment such as a chemical treatment such as a primer treatment, a plasma treatment, a corona treatment, or a dry treatment or a saponification (alkali) treatment . Examples of the saponification (alkali) treatment include a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

The other side of the polarizer to which the protective film is bonded on one side may be suitably subjected to surface treatment such as hard coat treatment, antireflection treatment, anti-stick treatment, diffusion or anti-glare treatment as required.

In addition to the above-described surface treatment, the other surface of the polarizer to which the protective film is bonded on one surface may further be laminated with a surface treatment layer such as a hard coating layer, an antireflection layer, an antiglare layer and an antistatic layer, An optical functional film may be further laminated.

The type of the optically functional film is not particularly limited. For example, an optically compensatory film in which a liquid crystalline compound or a polymer compound thereof is oriented on the surface of a base material, an optically compensatory film which transmits polarized light of any kind, A retardation film including a polycarbonate resin, a retardation film including a cyclic polyolefin resin, an anti-glare function film having a concavo-convex shape on its surface, an additional film having a surface antireflection treatment, A transflective film having both a reflective function and a transmissive function, and the like.

In addition, the present invention provides an image display device including the polarizing plate.

The image display apparatus of the present invention may further include a configuration known in the art in addition to the polarizing plate.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Manufacturing example  One. Polarizer  Produce

A polyvinyl alcohol film having a thickness of 75 탆 and an average degree of polymerization of 2,400 and a saponification degree of 99.9 mol% or more was uniaxially stretched by a dry method about 5 times and immersed in water (distilled water) at 60 캜 for 1 minute while maintaining the stretched state And immersed for 60 seconds in an aqueous solution at 28 DEG C in which the weight ratio of after-iodine / potassium iodide / distilled water was 0.05 / 5/100. Thereafter, the substrate was immersed in an aqueous 72 ° C aqueous solution having a weight ratio of potassium iodide / boric acid / distilled water of 8.5 / 8.5 / 100 for 300 seconds, washed with distilled water at 26 ° C for 20 seconds and dried at 65 ° C to remove iodine Adsorbed polarizers were prepared.

Manufacturing example  2. Preparation of protective film

A triacetyl cellulose-based film, KC8UX (Konica Corp., T), was used by saponification

Example  And Comparative Example

Example  One

(1) Preparation of adhesive composition

Acetoacetyl modified polyvinyl alcohol resin (Kosenol Z200, Nippon Synthetic Chemical Industry Co., Ltd., average degree of polymerization of 1000 or less) having a degree of saponification of 99.2 mol% was dissolved in water (distilled water) to prepare a 6 wt% Of acetoacetyl-modified polyvinyl alcohol was added.

The aqueous solution of the acetoacetyl group-modified polyvinyl alcohol resin and the 3-methoxy-1,2-propanediol as a crosslinking agent were dissolved in 100 parts by weight of an acetoacetyl group-modified polyvinyl alcohol resin 20 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol resin, and 2 parts by weight of the water-soluble chelate compound zinc chloride (purified gold) was added to 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol resin to prepare an adhesive composition.

(2) Bonding of polarizer to protective film (Polarizing plate production)

The adhesive composition was coated on both sides of the polarizer prepared in Preparation Example 1 to a dry film thickness of 0.1 mu m, and then a cellulose protective film (Konica Corp., KC8UX (trade name), triacetyl cellulose film) Respectively. The bonded polarizing plate was dried in a hot air drier at 80 캜 for 5 minutes to prepare a polarizing plate.

Example  2 to 9 and Comparative Example  1 to 5

An adhesive composition having the composition and the content (parts by weight) shown in the following Table 1 was prepared in the same manner as in Example 1 above.

Example  10

An adhesive composition was prepared under the same conditions as in Example 1 except that acetoacetyl group-modified polyvinyl alcohol was contained in an amount of 3% by weight based on the solid content in the adhesive composition.

Example  11

An adhesive composition was prepared under the same conditions as in Example 1 except that acetoacetyl group-modified polyvinyl alcohol was contained in an amount of 9% by weight based on the solid content in the adhesive composition.

Example  12

An adhesive composition was prepared under the same conditions as in Example 1 except that acetoacetyl group-modified polyvinyl alcohol was contained in an amount of 2% by weight based on the solid content in the adhesive composition.

Example  13

An adhesive composition was prepared under the same conditions as in Example 1, except that acetoacetyl group-modified polyvinyl alcohol was contained in an amount of 10% by weight based on the solid content in the adhesive composition.

division
(Parts by weight) Polyvinyl
Alcohol resin (A) The crosslinking agent (B) Water-soluble chelate
The compound (C) A-1 A-2 B-1 B-2 B-3 B-4 B-5 C-1 C-2 C-3 C-4 Example 1 100 - 20 - - - - 2 - - - Example 2 100 - 20 - - - - 5 - - - Example 3 100 - 20 - - - - 12 - - - Example 4 100 - 30 - - - - 5 - - - Example 5 100 - 40 - - - - 5 - - - Example 6 100 - 16 - - - - 5 - - - Example 7 100 - - 30 - - - - 5 - - Example 8 100 - - - 30 - - - - 5 - Example 9 100 - - - 30 - - - - 5 Example 10 100 - 20 - - - - 2 - - - Example 11 100 - 20 - - - - 2 - - - Example 12 100 - 20 - - - - 2 - - - Example 13 100 - 20 - - - - 2 - - - Comparative Example 1 - 100 30 - - - - 5 - - - Comparative Example 2 100 100 30 - - - - 5 - - - Comparative Example 3 50 50 30 - - - - 5 - - - Comparative Example 4 100 - - - - - 20 5 - - - Comparative Example 5 100 - 30 - - - - - - - - A-1: Acetoacetyl group-modified polyvinyl alcohol (Z200)
A-2: Polyvinyl alcohol resin (crosslinking regulator) (PVA-117H, Kuraray)
B-1: 3-methoxy-1,2-propanediol
B-2: Glycerol
B-3: Malonic Acid
B-4: 3-Ethoxy-1,2-propanediol
B-5: Methylol melamine
C-1: Zinc chloride (antiseptic)
C-2: Zinc nitrate (purified gold)
C-3: Aluminum nitrate (Aldrich)
C-4: Magnesium acetate (purified gold)

Experimental Example

(1) Adhesive strength evaluation (cutter evaluation)

The polarizing plates prepared in the above Examples and Comparative Examples were allowed to stand at room temperature for 1 hour, and a cutter blade was inserted between each film of the polarizing plate (between the polarizer and the polarizer protective film), and a blade was inserted Were evaluated according to the following criteria, and the results are shown in Table 2 below.

◎: The cutter blade does not enter any film.

○: When pushing the blade, it stops when the blade enters 1 to 2 mm between at least one of the films

△: When pushing the blade, it stops when the blade enters 3 to 5 mm between at least one of the films

X: When pushing the blade, the blade enters the gap between at least one of the films

(2) Water resistance evaluation

After the polarizing plates prepared in the above Examples and Comparative Examples were allowed to stand at 23 DEG C and 55% relative humidity for 24 hours, a sample of 5 cm x 2 cm was produced with the absorption axis (stretching direction) as the long side. Thereafter, the dimensions of the long side were measured accurately. Here, the sample exhibits uniform color uniformly over the entire surface due to the iodine adsorbed on the polarizer (polarizing film).

Fig. 1 is a diagram schematically showing an evaluation test method for water resistance. Fig. 1 (A) shows samples 1 before immersion in hot water, and Fig. 1 (B) shows sample 1 after immersion in hot water. As shown in Fig. 1 (A), one short side of the sample was held by the waveguide 5, about 80% in the longitudinal direction was immersed in a 60 degree water bath, and held for 4 hours. Thereafter, the sample (1) was taken out of the water tank and wiped off the water.

The polarizer (polarizing film) 4 of the polarizing plate shrinks due to immersion in hot water. The degree of shrinkage of the polarizer (polarizing film) 4 is set so that the distance from the end 1a of the short side of the sample 1 (the end of the protective film) to the end of the polarizer (polarizing film) And the shrinkage length was determined.

As shown in Fig. 1 (B), the polarizer (polarizing film) 4 located at the center of the polarizing plate is shrunk by immersion in hot water so that the polarizing film (polarizing film) Iodine is eluted and a portion (3) in which a color is missing is formed in the periphery of the sample (1). The degree of discoloration was evaluated by measuring the distance from the end of the shrunk polarizer (polarizing film) 4 at the center of the short side of the sample 1 to the area where the peculiar color of the polarizing plate remained, . The total length of the shrinkage length and the length without iodine was taken as the total erosion length. The total erosion length is the distance from the end 1a of the sample 1 to the region where the color unique to the polarizer remains, at the center of the short side of the sample 1. The shorter the length of contraction, the length of iodine missing, and the total length of erosion, the higher the adhesion in the presence of water. The results are shown in Table 2, according to the total erosion length.

◎: total erosion length less than 2mm

○: total erosion length is 2 mm or more and less than 3 mm

△: total erosion length is 3 mm or more and less than 5 mm

X: Total erosion length is 5mm or more

(3) Evaluation of polarization degree (%)

The polarizing plate prepared in the above Examples and Comparative Examples was cut into a size of 4 cm x 4 cm to prepare a specimen. The specimen was attached to a measurement holder, and then the specimen was irradiated with an ultraviolet ray spectrophotometer (V-7100, manufactured by JASCO) And the results are shown in Table 2.

division Adhesion Water resistance Polarization degree Example 1 ◎ ◎ 99.995 Example 2 ◎ ◎ 99.996 Example 3 ◎ ◎ 99.992 Example 4 ◎ ◎ 99.997 Example 5 ◎ ◎ 99.996 Example 6 ◎ ○ 99.994 Example 7 ◎ ◎ 99.996 Example 8 ◎ ◎ 99.996 Example 9 ◎ ○ 99.996 Example 10 ◎ ◎ 99.995 Example 11 ◎ ◎ 99.995 Example 12 ◎ ○ 99.995 Example 13 ◎ ◎ 99.993 Comparative Example 1 ○ X 99.989 Comparative Example 2 ◎ △ 99.986 Comparative Example 3 ◎ △ 99.987 Comparative Example 4 ○ X 99.985 Comparative Example 5 ○ △ 99.983

Referring to Table 2, it was confirmed that the adhesive composition according to the present invention has excellent adhesive strength and water resistance while maintaining an excellent degree of polarization.

Claims (10)

Acetoacetyl group-modified polyvinyl alcohol-based resin (A);
A crosslinking agent (B) containing a hydroxyl group or a carboxyl group having two or more functional groups in the molecule; And
A water-soluble chelate compound (C)
Wherein the acetoacetyl group-modified polyvinyl alcohol-based resin (A) has a degree of polymerization of 1,000 or less.
The adhesive composition for a polarizing plate according to claim 1, wherein the acetoacetyl group-modified polyvinyl alcohol resin (A) is contained in an amount of 3 to 9% by weight based on the solid content in the adhesive composition.
2. The positive resist composition according to claim 1, wherein the cross-linking agent (B) containing a bifunctional or more hydroxyl group in the molecule is 3-methoxy-1,2-propanediol, 3-ethoxy- Wherein the adhesive composition is at least one selected from the group consisting of 3-ethoxy-1,2-propanediol, di-ethylene glycol, and glycerol.
The crosslinking agent (B) according to claim 1, wherein the cross-linking agent (B) containing two or more functional carboxyl groups in the molecule is selected from the group consisting of oxalic acid, malonic acid, dimethylmalonic acid, succinic acid wherein the adhesive composition is at least one selected from the group consisting of acrylic acid and glutaric acid.
The crosslinking agent (B) comprising a bifunctional or more hydroxyl group or a carboxyl group in the molecule is contained in an amount of 20 to 50 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol resin (A) Composition.
The adhesive composition for a polarizing plate according to claim 1, wherein the water-soluble chelate compound (C) is at least one selected from the group consisting of zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate and zinc sulfate.
The adhesive composition for a polarizing plate according to claim 1, wherein the water-soluble chelate compound (C) is contained in an amount of 2 to 10 parts by weight based on 100 parts by weight of the acetoacetyl group-modified polyvinyl alcohol resin (A).
The adhesive composition for a polarizing plate according to claim 1, which does not comprise a crosslinking regulator.
Wherein a protective film is bonded to at least one surface of the polarizer with an adhesive composition for a polarizing plate of any one of the above 1 to 8.
An image display apparatus comprising the polarizer of claim 9.

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