TWI690574B - Adhesive composition and polarizing plate comprising same - Google Patents

Abstract

Adhesive composition for polarizing plate of this invention includes an acetoacetyl group modified polyvinyl alcohol resin, a dialdehyde, and a water-soluble chelating compound, excluding crosslinking modifier, wherein, the average of polymerization degree of the polyvinyl alcohol resin with modified acetoacetyl group is 1500 or less.

Description

Adhesive composition and polarizing plate containing the adhesive composition

The present invention relates to an adhesive composition and a polarizing plate formed by bonding a polarizer and a polarizer protective film using the adhesive composition.

The polarizing plate can be used as one of the optical elements constituting the liquid crystal display device. The polarizing plate usually has a structure in which protective films are laminated on both sides of the polarizing plate, and is inserted into the liquid crystal display device. It is known that a protective film is provided only on one side of the polarizer. However, in most cases, the other side is not a simple protective film but a protective film in which, for example, a layer having an optical function as another function is bonded.

At present, the following polarizing plates are generally used: a iodine film made by aligning iodine with polyvinyl alcohol and a dye film made by aligning dichroic dye with polyvinyl alcohol are used as polarizers, and at least in One side of the film is formed by bonding a protective film such as cellulose triacetate (TAC) through an adhesive layer formed using an aqueous solution of a polyvinyl alcohol-based resin (polyvinyl alcohol-based adhesive); When used for a long time under humid heat, there will be easy to peel off the protective film and the end face of the polarizer Question.

Therefore, a polarizing plate is proposed, which uses a polyvinyl alcohol-based adhesive to bond a polarizer (polarizing film) and a protective film, and heat and dry at a temperature of 90 to 100°C to improve the heat and humidity resistance. When it is used for a long time, it still has not solved the problem that the end surfaces of the protective film and the polarizer are easy to peel off.

In order to improve this problem, Japanese Patent Laid-Open No. 07-134212 discloses an adhesive composition containing a polyvinyl alcohol-based resin, glyoxal, and zinc chloride.

(Prior technical literature) (Patent Literature)

[Patent Document 1] Japanese Patent Laid-Open No. 07-134212

However, in the case of the above-mentioned adhesive composition, it is known that the degree of polarization may decrease due to deterioration of damp heat.

The present invention provides an adhesive composition for polarizing plates that does not decrease the adhesion and polarization degree and improves the water resistance.

The present invention provides an adhesive composition for polarizing plates, which contains acetyl acetyl modified polyvinyl alcohol-based resins, dialdehydes, and water-soluble chelate compounds, does not contain crosslinking regulators, and acetyl acetyl The average degree of polymerization of the acetyl group-modified polyvinyl alcohol-based resin is 1500 or less.

Another specific example is based on the total weight of the adhesive composition, and may contain 3 to 9% by weight of acetylacetyl-modified polyvinyl alcohol-based resin.

Yet another specific example is that it can contain 20 to 50 parts by weight of dialdehydes and 2 to 10 parts by weight of a water-soluble chelate compound with respect to 100 parts by weight of the acetylacetonyl modified polyvinyl alcohol-based resin.

In yet another specific example, the dialdehyde can be glyoxal.

In yet another specific example, the water-soluble chelate compound may be one or more selected from the group consisting of zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate, and zinc sulfate.

Furthermore, the present invention provides a polarizing plate comprising: a polyvinyl alcohol-based polarizer; an adhesive layer which is laminated on one or both sides of the polarizer and contains the adhesive composition; and a polarizer protective film, It is laminated on one or both sides of the adhesive layer.

The adhesive composition for polarizing plates of the present invention has the effect of improving the water resistance without reducing the adhesive force and the degree of polarization.

1‧‧‧ Polaroid sample

1a‧‧‧End

2‧‧‧ Polarizer protective film

3‧‧‧Decolorized part

4‧‧‧ Polarizer

5‧‧‧ Holder

Fig. 1 is a diagram schematically showing an evaluation test method of water resistance by an experimental example.

(Form for carrying out the invention)

Hereinafter, the present invention will be described in detail.

The present invention provides an adhesive composition for polarizing plates and a polarizing plate formed by bonding a polarizer and a polarizer protective film using the adhesive composition, wherein the adhesive composition for polarizing plates contains acetylene Acetyl-modified polyvinyl alcohol-based resins, dialdehydes, and water-soluble chelates do not contain cross-linking regulators, and the average degree of polymerization of the acetoyl-modified polyvinyl alcohol-based resin is 1500 or less.

The adhesive composition of the present invention improves the input process of the adhesive and solves the problem of the stability of the liquid adjustment. Even if the crosslinking regulator that reduces the polarization degree due to the deterioration of moisture and heat is not added, it also has the effect of adhesion and durability. . That is, the present invention is characterized by increasing the content of the acetyl-acetyl-modified polyvinyl alcohol-based resin, dialdehydes, and water-soluble chelate compound of the composition in which the adhesive of the cross-linking modifier is removed, polarizing The degree does not decrease and can improve the water resistance.

Hereinafter, the structure of the adhesive composition will be described in more detail.

Acetyl Acetyl Modified Polyvinyl Alcohol Resin

Compared with modified polyvinyl alcohol resins such as carboxyl modification, hydroxymethyl modification, amine modification, etc., acetoxyethylene modified polyvinyl alcohol (PVA) resins contain higher reactivity The functional group is excellent in improving durability.

The acetoacetyl modified polyvinyl alcohol-based resin can be obtained by reacting the polyvinyl alcohol-based resin with diketene using a known method. Specifically, it can be obtained by dispersing the polyvinyl alcohol-based resin in a solvent such as acetic acid, and then adding two The method of ketene; the method of adding divinyl ketone to the polyvinyl alcohol resin before dissolving it in a solvent such as dimethylformamide or dioxane; or directly contacting the polyvinyl alcohol resin with diethylene The method of ketone gas or liquid diketene, etc. Acetyl ethene-modified polyvinyl alcohol-based resin is not particularly limited as long as the degree of modification of the acetyl ethyl group is 0.1 mol% or more, preferably 0.1 to 40 mol%, preferably 1 To 20 mol%, more preferably 2 to 7 mol%. When the degree of modification of the acetylacetate group is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient and unsuitable. When the degree of modification of the acetylacetate group is greater than 40 mol%, the effect of improving the water resistance is not significant.

The degree of saponification of the ethoxylated polyvinyl alcohol-based resin is also not particularly limited. It is preferably 80 mol% or more, and more preferably 85 mol% or more. When the degree of saponification of the polyvinyl alcohol-based resin contained in the adhesive composition is low, sufficient water solubility is not easily developed, so the adhesiveness tends to be insufficient.

The average degree of polymerization of the above-mentioned ethoxylate-modified polyvinyl alcohol-based resin is 1500 or less, preferably 1400 or less, and more preferably 1300 or less. With an average polymerization degree of 1500 or less, the reaction rate is slowed down and the stability of liquid adjustment is improved.

Examples of products include Z-100, Z-200, Z-200H, Z-210, Z-220, and Z-320 (Japan Synthetic Chemical Industry Corporation).

The above-mentioned acetoacetyl-modified polyvinyl alcohol-based resin may contain 3 to 9% by weight based on the total weight of the adhesive composition. If it is less than 3% by weight based on the above standard, there will be insufficient hardening and the water resistance will be reduced The problem is that when it is more than 9% by weight, the viscosity becomes high and bubbles are mixed in the joining step.

Dialdehydes:

The dialdehydes contained in the adhesive composition are used to make acetoacetyl-based modified polyvinyl alcohol (PVA)-based resins such as polyvinyl alcohol (PVA)-based polarizers and cellulose-based films , Adhesive strength and water resistance of protective films such as olefin films.

Examples of the dialdehydes include glyoxal, malondialdehyde, and succinaldehyde. Especially preferred is glyoxal with a simple structure and rich in reactivity.

Hereinafter, glyoxal will be described, but as the dialdehydes, those previously known as above can be used, and not limited to glyoxal.

The aldehyde portion of the glyoxal-based glyoxal undergoes a condensation reaction with the acetoacetyl group of the polyvinyl alcohol-based resin, and it is assumed that it functions as a crosslinking agent.

The weight ratio of glyoxal contained in the adhesive composition is preferably in the range of 20 to 50 parts by weight with respect to 100 parts by weight of the acetoacetyl modified polyvinyl alcohol-based resin. When the weight ratio of glyoxal is less than 20 parts by weight based on the above standard, the water resistance of the adhesive layer cannot be sufficiently exhibited when it becomes a polarizing plate, and when the weight ratio of glyoxal is more than 50 parts by weight, the liquid is adjusted Stability is reduced.

Water-soluble chelate:

The water-soluble chelate contained in the adhesive composition can act as a crosslinking agent between the adhesive layer and protective films such as polyvinyl alcohol (PVA) polarizers, cellulose films, and olefin films. The degree of increase increases the adhesion and water resistance, and can also play a role in adding no optical durability. The role of additives.

Water-soluble chelate is added to promote the hardening of glyoxal. The type of chelate compound can be added zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate, zinc sulfate, and the like. In particular, zinc chloride, zinc nitrate, and aluminum nitrate, which are excellent in crosslinking catalysts, are preferred.

The weight ratio of the water-soluble chelate compound contained in the adhesive composition is preferably in the range of 2 to 10 parts by weight with respect to 100 parts by weight of the acetylacetone-modified polyvinyl alcohol-based resin. Based on the above criteria, when the weight ratio of the water-soluble chelate is less than 2 parts by weight, the water resistance of the adhesive layer cannot be sufficiently exhibited when it becomes a polarizing plate, and when the weight ratio is more than 10 parts by weight, the optical characteristics are degraded.

Crosslinking regulator:

The adhesive composition for polarizing plates of this embodiment does not contain a crosslinking regulator. The cross-linking regulator is a polyvinyl alcohol-based resin that does not have an acetoacetyl group, and examples thereof include polyvinyl alcohol resins and carboxylic acid-modified polyvinyl alcohol resins.

The viscosity of the adhesive composition at 20°C 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 cannot be sufficiently exhibited when it becomes a polarizing plate, and when the viscosity is greater than 25 mPa‧sec, the optical characteristics of the polarizing plate deteriorate.

The adhesive composition of the present invention can use a plasticizer, a silane coupling agent, an antistatic agent, fine particles, an alcohol with good diffusibility, a leveling agent, etc. within a range that does not hinder the effect of the present invention It is formed by conventional additives.

The form of the adhesive composition is not particularly limited, and in order to form a uniform adhesive layer on the surface of the polarizer or protective film of the adherend, a liquid type is preferable. This type of liquid adhesive is a solution type or a dispersion type which can use various solvents. When considering the coating properties of the substrate, the solution type is preferred, and when considering the stability, water is used as the solvent. Solution type or dispersion type are suitable.

Hereinafter, the configuration of the polarizing plate will be described in detail.

Polarizer (polarizing film):

The polyvinyl alcohol-based resin used to form the polarizer can be obtained by saponifying the polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable therewith can also be exemplified. Examples of other monomers capable of copolymerizing with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and acrylamides having an ammonium group. The saponification degree of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin can be further modified, and for example, polyvinyl polymers modified with aldehydes, polyvinyl acetals, and the like can be used. The average degree of polymerization of the polyvinyl alcohol-based resin constituting the polarizer is usually 1,000 to 10,000, preferably 1,500 to 5,000.

If such a polyvinyl alcohol-based resin is formed into a film shape (polyvinyl alcohol-based resin film), a embryonic film as a polarizer (polarizing film) can be used. The method of forming the polyvinyl alcohol-based resin film is not particularly limited, and a conventional film-forming method can be used. The polyvinyl alcohol resin film used as the embryo membrane The film thickness system is not particularly limited, and is, for example, 10 to 150 μm.

A polarizer (polarizing film) can usually be manufactured by a method including the following steps: a step of uniaxially extending such a polyvinyl alcohol-based resin film as a embryo membrane; using a dichroic pigment to convert the polyvinyl alcohol The step of dyeing the resin film to adsorb the dichroic pigment; the step of treating the polyvinyl alcohol resin film adsorbed with the dichroic pigment with an aqueous solution of boric acid; and the step of washing with the aqueous solution of boric acid.

The uniaxial extension system can be carried out before dyeing, can be carried out simultaneously with dyeing, or can be carried out after dyeing. When uniaxial stretching is performed after dyeing, the uniaxial stretching system may be performed before boric acid treatment, may also be performed during boric acid treatment, or may be performed after boric acid treatment. Of course, these can also be uniaxially extended through a plurality of stages. In uniaxial stretching, the embryo film can also be uniaxially stretched between different rollers, or hot rollers can also be used for uniaxial stretching. In addition, dry stretching such as stretching in the atmosphere may be used, or wet stretching may be performed in a state of being swelled with a solvent. The extension magnification is usually 3 to 8 times.

In order to dye a polyvinyl alcohol-based resin film using a dichroic dye, for example, the polyvinyl alcohol-based resin film can be immersed in an aqueous solution containing a dichroic dye. As the dichroic dye, specifically, iodine or a dichroic dye can be used. In addition, it is preferable that the polyvinyl alcohol-based resin film is immersed in water before dyeing.

When iodine is used as a dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide and dyeing is generally used. The content of iodine in the aqueous solution is usually per 100 weight The water content is 0.01 to 1 part by weight, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually 20 to 40°C, and the immersion time in the aqueous solution is usually 20 to 1800 seconds.

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

The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. The amount of boric acid in the aqueous solution containing boric acid is generally 2 to 15 parts by weight per 100 parts by weight of water, preferably 5 to 12 parts by weight. When iodine is used as a dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide. The amount of potassium iodide in the aqueous solution containing boric acid is usually 0.1 to 15 parts by weight per 100 parts by weight of water, preferably 5 to 12 parts by weight. The immersion time in the aqueous solution containing boric acid is usually 60 to 1,200 seconds, preferably 150 to 600 seconds, more preferably 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually above 50°C, preferably 50 to 85°C, more preferably 60 to 80°C.

PVA resin film after boric acid treatment, usually It is washed with water. The water washing treatment is performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water in the water washing treatment is usually 5 to 40°C, and the dipping time is usually 1 to 120 seconds. After washing with water, a drying process is performed to obtain a polarizer (polarizing film). The drying process can usually be performed using a hot air dryer and a far-infrared heater. The drying temperature is usually 30 to 100°C, preferably 50 to 80°C. The drying time is usually 60 to 600 seconds, preferably 120 to 600 seconds.

In this way, the polyvinyl alcohol-based resin film was uniaxially stretched, and dyed with a dichroic dye and subjected to boric acid treatment to obtain a polarizer (polarizing film). The thickness of the polarizer (polarizing film) is usually in the range of 5 to 40 μm, preferably in the range of 10 to 35 μm.

Protective film:

As the polarizing plate of the present invention, a protective film is laminated on at least one surface of a polarizer (polarizing film) through the adhesive layer. As the protective film, for example, various transparent resin films such as a cellulose resin film, a cycloolefin resin film, an acrylic resin film, and a polyester resin film can be used.

When a cellulose-based resin film is used as a protective film, it is preferably a cellulose acetate-based resin obtained by esterifying at least a part of cellulose. For example, cellulose triacetate, cellulose diacetate, cellulose acetate propionate, etc. may be mentioned.

Cycloolefin-based resins, for example, thermoplastic resins having cycloolefin monomer units such as norbornene and polycyclic norbornene-based monomers, not only ring-opening polymers of the aforementioned cycloolefins or the use of two or more types of cycloolefins Open Hydride of cyclic copolymer; can also be addition copolymer of cyclic olefin and chain olefin or aromatic compound with vinyl group. In addition, a polar group may be introduced into the cycloolefin-based resin.

The bonding of the polarizer (polarizing film) and the protective film using the adhesive composition can be performed by an appropriate method, and examples thereof include casting, wire rod coating, gravure coating, and die coating. A method such as a method, a dip coating method, a spray method, and the like is to apply an adhesive composition to the polarizing film (polarizing film) and/or the adhering surface of the protective film and superimpose the two. The so-called casting method refers to applying the adhesive composition on the surface of the coated object while moving the polarizer (polarizing film) or protective film in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two. Method.

After the adhesive composition is applied, the polarizer (polarizing film) and the protective film are sandwiched and joined using a nip roller.

In addition, in order to improve the adhesiveness, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, etc. may be appropriately performed on the surface of the polarizer (polarizing film) and/or the protective film. As the saponification treatment, a method of immersing in an aqueous solution of alkali such as sodium hydroxide and potassium hydroxide can be mentioned.

After the polarizing film (polarizing film) and the protective film are laminated, a drying process is performed. The drying treatment system can be performed, for example, by spraying hot air, and the temperature at this time is appropriately selected in the range of 50 to 100°C. The drying time is usually 30 to 1,000 seconds.

Hereinafter, the present invention will be described in more detail using Examples, Comparative Examples, and Experimental Examples. However, the following examples, comparative examples and experiments Examples are intended to illustrate the present inventors. The present invention is not limited to the following examples, comparative examples, and experimental examples, but can be modified and changed in various ways.

Manufacturing Example 1. Manufacturing of Polarizer

A 75 μm-thick polyvinyl alcohol film with an average degree of polymerization of 2,400 and a degree of saponification of 99.9 mol% or more was uniaxially stretched by dry method to approximately 5 times, and maintained in stretched state in 60°C water (distilled water) After immersing for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/distilled water of 28°C of 0.05/5/100 for 60 seconds. Subsequently, it was immersed in an aqueous solution of 72° C. with 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 then dried at 65° C. to produce a PVA system. Polarizing film made by absorbing iodine on film.

Manufacturing Example 2. Manufacturing of protective film

KC8UX (KONICA, T) of cellulose triacetate film was saponified and used.

Example 1

(1) Manufacture of adhesive composition

Dissolve in water (distilled water) 99.2 mol% saponification acetyl acetyl modified polyvinyl alcohol-based resin (Z200, Japan Synthetic Chemical Industry Co., Ltd., average degree of polymerization 1200) and add it with an adhesive composition The total weight basis of the substance was 6% by weight of acetoacetoxy-modified polyvinyl alcohol-based resin, thereby obtaining an acetoacetoxy-modified polyvinyl alcohol-based resin aqueous solution.

The above-mentioned aqueous solution of acetoacetoxy-modified polyvinyl alcohol-based resin and glyoxal (40% aqueous solution, Daejung chemical gold) are 20 parts by weight with respect to 100 parts by weight of acetoacetoxy-modified polyvinyl alcohol-based resin Serving Formula, and the water-soluble chelate zinc chloride (Daejung gold) is mixed in such a way that it is 2 parts by weight with respect to 100 parts by weight of the acetylacetone-modified polyvinyl alcohol-based resin to prepare an adhesive composition. .

(2) Bonding of polarizer and protective film (manufacturing of polarizer):

After applying the adhesive composition on both sides of the polarizer produced in Production Example 1 so that the dry film thickness becomes 0.1 μm, the cellulose-based protective film (KONICA, KC8UX (trade name), Cellulose triacetate film). The polarized plate after joining was dried for 5 minutes using a hot air dryer at 80°C to prepare a polarized plate.

Examples 2 to 6 and Comparative Examples 1 to 7

An adhesive composition (unit: parts by weight, see Table 1) was prepared using the same method as in Example 1 above except that the ratio was different.

Example 7

It is the same as Example 1 except that the water-soluble chelate zinc sulfate (Daejung's gold) is mixed with 5 parts by weight with respect to 100 parts by weight of the acetyl modified vinyl alcohol-based resin. The adhesive composition was prepared under the conditions (refer to Table 1).

Example 8

The water-soluble chelate aluminum sulfate (ALDRICH) was mixed at 5 parts by weight with respect to 100 parts by weight of the acetyl modified polyvinyl alcohol-based resin, under the same conditions as in Example 1. The adhesive composition was prepared (refer to Table 1).

Example 9

It is the same as Example 1 except that the water-soluble chelate magnesium sulfate (Daejung's gold) is mixed with 5 parts by weight with respect to 100 parts by weight of the acetoacetyl-modified polyvinyl alcohol-based resin. The adhesive composition was prepared under the conditions (refer to Table 1).

Example 10

The adhesive composition was prepared under the same conditions as in Example 1 except that it contained 3% by weight of acetylacetonyl modified polyvinyl alcohol-based resin based on the total weight of the adhesive composition (refer to Table 1).

Example 11

The adhesive composition was prepared under the same conditions as in Example 1 except that it contained 9% by weight of the acetylacetonyl modified polyvinyl alcohol-based resin based on the total weight of the adhesive composition (see Table 1).

Example 12

The adhesive composition was prepared under the same conditions as in Example 1 except that it contained 2% by weight of an acetylacetonyl-modified polyvinyl alcohol-based resin based on the total weight of the adhesive composition (see Table 1).

Example 13

The adhesive composition was prepared under the same conditions as in Example 1 except that it contained 10% by weight of the acetylacetonyl modified polyvinyl alcohol-based resin based on the total weight of the adhesive composition (refer to Table 1).

Example 14

The conditions were the same as in Example 1, except that the acetyl-acetyl-modified polyvinyl alcohol-based resin in the adhesive composition was changed from Z200 to Z100 (Japan Synthetic Chemical Industry Co., Ltd., average polymerization degree 650). The adhesive composition was prepared as follows (see Table 1).

Comparative Example 8

An adhesive composition was prepared under the same conditions as in Example 1 except that sodium glyoxylate (Sigma Aldrich) was used instead of glyoxal and mixed with acetoacetyl modified polyvinyl alcohol resin. Table 1).

*PVA-117H (KURARAY (share), polymerization degree 1700)

Experimental example

(1) Adhesive force (cutter evaluation)

After placing the produced polarizing plate at room temperature for 1 hour, the cutting edge of the cutter is placed between the films of the polarizing plate (between the polarizer and the polarizer protective film), and the evaluation is performed according to the following criteria. The way in which the blade enters is shown in Table 2 below.

◎: The blade of the cutter did not enter between any films.

○: When advancing the blade, the blade system stops when it enters at least one of the films between 1 and 2 mm.

△: When advancing the blade, the blade system stopped when it entered 3 to 5 mm between at least one of the films.

×: When advancing the blade, the blade is inserted between at least one of the films.

(2) Water resistance:

For each polarizing plate after being left in an environment of 23° C. and a relative humidity of 55% for 24 hours, the following temperature and water resistance test was performed and the water resistance was evaluated. The absorption axis of the polarizing plate was taken as the long side, and the polarizing plate was cut into a strip shape of 5 cm×2 cm as a sample, and the dimension in the long side direction was accurately measured. Among them, the sample is due to the iodine adsorbed by the polarizer (polarizing film) and uniformly displays a unique color throughout the entire surface. FIG. 1 is a diagram schematically showing the evaluation test method of water resistance, (A) is a sample (1) before warm water immersion, and (B) is a sample (1) after warm water immersion. As shown in (A) of Figure 1, use the holder (5) to hold a short side of the sample, and About 80% is immersed in a 60°C water tank and maintained for 4 hours. Subsequently, the sample (1) was taken out of the water tank and the water was wiped off.

The polarizer (polarizing film) (4) of the polarizing plate shrinks due to immersion in warm water. By measuring the distance from the end (1a) (the end of the protective film (2)) of the center of the short side of the sample (1) to the end of the polarizer (polarizing film) (4) after contraction, To evaluate the degree of shrinkage of the polarizer (polarizing film) (4). Also, as shown in (B) of FIG. 1, the polarizer (polarizing film) (4) located in the center of the polarizing plate shrinks due to warm water immersion, so that between the protective films, iodine is removed from the polarizing film (polarizing film) ) The peripheral part of (4) is eluted and a discolored part (3) is generated in the peripheral part of the sample (1). The degree of discoloration was evaluated by measuring the distance from the end of the polarizer (polarizing film) (4) after shrinking of the sample (1) at the center of the short side to the area where the color unique to the polarizing plate remained Set to the length of iodine detachment. Let the total of the shrinkage length and the iodine detachment length be the total erosion length X. The total erosion length X refers to the distance from the end (1a) of the sample (1) in the center of the short side of the sample (1) to the area where the color unique to the polarizing plate remains. The smaller the shrinkage length, the iodine detachment length, and the total erosion length X, the higher the adhesion in the presence of water can be judged. In addition, the following four stages were used to evaluate the total erosion length X, and the results are shown in Table 2.

◎: The total erosion length X is less than 2mm

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

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

×: Total erosion length X is more than 5mm

(3) Transmittance and polarization (%)

The produced polarizing plate was cut into a size of 4 cm×4 cm to produce a test piece, and after attaching the test piece to the measurement holder, measurement was carried out using an ultraviolet-visible light spectrometer (V-7100, manufactured by JASCO), and The results are shown in Table 2.

As shown in Table 2, compared with Comparative Examples 1 to 8, Examples 1 to 14 showed superior adhesion, water resistance, and light characteristics.

1‧‧‧ Polaroid sample

1a‧‧‧End

2‧‧‧ Polarizer protective film

3‧‧‧Decolorized part

4‧‧‧ Polarizer

5‧‧‧ Holder

Claims (8)

Adhesive composition for polarizing plate, which contains acetyl acetyl modified polyvinyl alcohol resin, dialdehydes, and water-soluble chelate, does not contain polyvinyl alcohol resin and carboxylic acid modified polyvinyl alcohol resin ; Among them, the average degree of polymerization of the ethoxylated polyvinyl alcohol-based resin is 1500 or less; based on the total weight of the adhesive composition as a reference, containing 3 to 9% by weight of the aforementioned ethoxylated ethylenic modified polymer Vinyl alcohol resin. The adhesive composition for polarizing plates as described in item 1 of the patent application scope, which contains 20 to 50 parts by weight of dialdehydes relative to 100 parts by weight of the acetylacetyl-modified polyvinyl alcohol-based resin, 2 Up to 10 parts by weight of the aforementioned water-soluble chelate compound. The adhesive composition for polarizing plates as described in item 1 or 2 of the patent application, wherein the dialdehydes are glyoxal. The adhesive composition for polarizing plates as described in item 1 or 2 of the patent application, wherein the water-soluble chelate compound is selected from the group consisting of zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate, and More than one species in the group formed by zinc sulfate. The adhesive composition for polarizing plates as described in item 3 of the patent application, wherein the water-soluble chelate compound is selected from the group consisting of zinc chloride, cobalt chloride, magnesium chloride, magnesium acetate, aluminum nitrate, zinc nitrate, and zinc sulfate More than one type in the group. An adhesive composition for polarizing plates, which contains acetoxyethyl modified vinyl alcohol resin, dialdehydes, and water-soluble chelate, Does not contain polyvinyl alcohol resin and carboxylic acid-modified polyvinyl alcohol resin; wherein, based on the total weight of the adhesive composition, it contains 3 to 9% by weight of the aforementioned acetylacetate-modified polyvinyl alcohol-based resin; The average degree of polymerization of the above-mentioned acetoacetyl-modified polyvinyl alcohol-based resin is 1500 or less, and the degree of modification of acetoacetyl-based resin is 4.6 mol% to 40 mol%. A polarizing plate comprising: a polyvinyl alcohol-based polarizer; an adhesive layer laminated on one or both sides of the polarizer and containing the adhesive composition according to any one of claims 1 to 6 And the polarizer protective film, which is laminated on one or both sides of the adhesive layer. A polarizing plate is one in which a protective film is laminated on at least one side of a polarizer through an adhesive layer; wherein the adhesive layer is composed of an ethoxylated polyvinyl alcohol modified with an average polymerization degree of 1500 or less The polarizing plate of resin, dialdehydes and water-soluble chelate is formed with an adhesive composition; based on the total weight of the adhesive composition, it contains 3 to 9% by weight of the above-mentioned acetyl-acetyl modified polyethylene Alcohol-based resin; the total length of the shrinkage length and iodine detachment length of the polarizing plate after being immersed in 60°C warm water for 4 hours is less than 2 mm.

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