JPH09258023A - Polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate having excellent adhesiveness between polarizing film and a protective film and wet heat resistance. SOLUTION: The adhesive layer of the polarizing plate formed by sticking the protective film on at least one surface of the polyvinyl alcohol (PVA) polarizing film via the PVA adhesive layer consists of a PVA adhesive contg. a water- soluble epoxy compd. The ratio of the water-soluble epoxy compd. and PVA resin in the adhesive is specified to (5 to 50)/100 (by the weight of the solid content), thereby, the polarizing plate having the excellent adhesiveness of the polarizing film and the protective film and the wet heat resistance is obtd.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polarizing plate. More specifically, the present invention relates to a polarizing plate having excellent adhesiveness between a polarizing film and a protective film and excellent heat and moisture resistance.

[0002]

2. Description of the Related Art At present, polyvinyl alcohol (hereinafter referred to as PVA) is generally used as a polarizer by using an iodine film in which iodine is adsorbed and oriented, or a dye film in which PVA is adsorbed and oriented by a dichroic dye as a polarizer. Of PVA-based resin on at least one side of PVA (PVA-based adhesive)
A polarizing plate having a structure in which a protective film such as triacetyl cellulose (TAC) is attached via an adhesive layer formed using The polarizing plate with such a configuration,
When used for a long time under moist heat, there is a problem that the protective film and the end surface of the polarizer are easily peeled off.

In order to solve this, a polarizer and a protective film are pasted together with a PVA-based adhesive, and then 90 to 110.
A polarizing plate having improved wet heat resistance by heating and drying at a temperature of ℃ has been proposed. Also, JP-A-56-50
No. 301 discloses a method of saponifying the surface of the protective film to strengthen the adhesive force and improve the wet heat resistance. Japanese Unexamined Patent Publication No. 61-245107 proposes a method of improving adhesive strength by treating a polarizing film once with an adhesive and then adhering a protective film again via the adhesive. Further, Japanese Patent Laid-Open No. 7-1
Japanese Patent Publication No. 98945 discloses that a resin solution containing an acetoacetyl group-containing PVA-based resin and a crosslinking agent is used as an adhesive to form a polarizing plate excellent in durability and wet heat resistance.

[0004]

However, it is difficult to say that the conventional polarizing plate has sufficient resistance to moist heat and durability. The inventors of the present invention have diligently studied to improve the adhesiveness between the polarizing film and the protective film, and the heat and moisture resistance, and as a result, by using a PVA-based adhesive containing a specific amount of a water-soluble epoxy compound as an adhesive, The inventors have found that a polarizing plate having excellent adhesiveness between a film and a protective film and resistance to moist heat can be obtained, and arrived at the present invention.

[0005]

Means for Solving the Problems That is, the present invention provides a polarizing plate in which a protective film is laminated on at least one surface of a polyvinyl alcohol-based polarizing film via a polyvinyl alcohol-based adhesive layer, and the adhesive layer is a water-soluble epoxy. A polarizing plate comprising a polyvinyl alcohol-based adhesive containing a compound, wherein the ratio of the water-soluble epoxy compound and the polyvinyl alcohol-based resin in the adhesive is (5 to 50) / 100 (solid content weight ratio). Is. Hereinafter, the present invention will be described in detail.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As a PVA type polarizing film,
A conventionally known PVA type polarizing film is used. For example, an iodine-based polarizing film in which iodine is adsorbed and oriented on a PVA-based film, a dye-based polarizing film in which a dichroic dye is adsorbed and oriented on a PVA-based film, and a polyene-based polarizing film in which these films are partially dehydrated Can be mentioned. The thickness of the PVA type polarizing film is, for example, about 10 to 50 μm. Examples of the PVA film include a PVA film, a polyvinyl butyral film, a polyvinyl acetal film, a polyvinyl formal film, a poly (ethylene-vinyl acetate) copolymer saponified film, and the like.

Examples of the protective film include acetylcellulose-based films having excellent optical transparency such as triacetylcellulose (TAC) and diacetylcellulose (DAC) whose surfaces are saponified. The thickness is, for example, about 10 to 200 μm.

The PVA adhesive is prepared, for example, by dissolving the PVA resin in water and then dissolving the water-soluble epoxy compound in the aqueous solution. The ratio of PVA-based resin to water is not particularly limited, but is, for example, (1-10) / 10.
It is about 0 (weight ratio), preferably (1 to 5) / 100 (weight ratio). As the PVA-based resin, for example, a resin modified with a carboxyl group, an acetoacetyl group, a methylol group, an amino group or the like is used, but a carboxyl group-modified PVA is particularly preferable. Moreover, as the PVA-based resin, it is preferable to use a PVA-based resin having a molecular weight of 40,000 to 120,000.

Examples of water-soluble epoxy compounds include reaction products of polyamide and epichlorohydrin.
A reaction product of a polyamide and epichlorohydrin is a reaction product obtained by reacting a polyamide obtained by a reaction of an alkylpolyamine compound such as diethylenetriamine and hexamethylenediamine with an alkyldicarboxylic acid such as adipic acid with epichlorohydrin. As this water-soluble epoxy compound, for example, a polyamide epoxy-based additive (Sumitomo Chemical Co., Ltd.
Resin 650, Sumireze resin 675), polyamide epichlorohydrin (WS-52 manufactured by Japan PMC)
5) and the like are commercially available.

The ratio of the water-soluble epoxy compound and the PVA resin in the PVA adhesive is (5-100) / 100 (solid content weight ratio), preferably (5-50) / 100 (solid content weight ratio). ). If the amount of the water-soluble epoxy compound is less than this range, the effect of preventing peeling of the protective film is reduced, and if it is too large, the adhesive layer becomes brittle, which is not preferable.

Zinc chloride, tin chloride, zinc borofluoride, a tertiary amine, a quaternary ammonium salt, an imidazole compound, etc. are added to a PVA adhesive containing a water-soluble epoxy compound in order to accelerate the curing of the adhesive. You may.

As a method for laminating the PVA-based polarizing film and the protective film, for example, a PVA-based adhesive is uniformly applied to the surface of the PVA-based polarizing film or the protective film, and the protective film or the PVA-based polarizing film is applied to the coated surface. Examples of the method include stacking and laminating them with a roll or the like, and drying. PVA-based adhesives are usually prepared at 15 ° C to 40 ° C after preparation.
The coating temperature is usually in the range of 15 to 30 ° C. The drying temperature is usually in the range of 30 to 85 ° C, preferably in the range of 40 to 80 ° C.

Thus, a protective film is provided on at least one surface of the polarizing film via an adhesive layer made of a PVA adhesive having a ratio of the water-soluble epoxy compound to the PVA resin of (5 to 50) / 100 (solid content weight ratio). The laminated polarizing plate of the present invention can be obtained.

[0014]

EFFECT OF THE INVENTION The polarizing plate of the present invention is excellent in durability without the problem of peeling of the end faces of the polarizing film and the protective film under the conditions of wet heat. Therefore, it can be used even under a wet heat condition which cannot be used in the conventional polarizing plate.

[0015]

Hereinafter, the present invention will be described in detail with reference to Examples.
The present invention is not limited to this. Example 1 A PVA film having a thickness of 75 μm (average degree of polymerization: 1700,
An aqueous solution containing iodine and potassium iodide (iodine / potassium iodide / water =) was uniaxially stretched to a saponification degree of 99.9% or more) (stretching ratio: 5 times) and kept in a tension state.
It was immersed in 0.05 / 5/100 (weight ratio) for 60 seconds. Next, an aqueous solution containing potassium iodide and boric acid at 65 ° C. (potassium iodide / boric acid / water = 2.5 / 7.5 /
100 (weight ratio)) for 300 seconds. It was washed with pure water at 25 ° C. for 20 seconds and then dried at 50 ° C. to obtain a PVA type polarizing film.

PVA resin (KL-3 manufactured by Kuraray Co., Ltd.)
18, a 25 wt% aqueous solution of polyamide epichlorohydrin (WS-525 manufactured by Japan PMC Co., Ltd.), which is a water-soluble epoxy compound, was added to a 5 wt% aqueous solution having a saponification degree of 87.8% and a molecular weight of 85,000) to obtain a PVA adhesive (KL). -31
8 / WS-525 = 100/10 (solid content weight ratio)). In a 28 ° C atmosphere, this PVA-based adhesive is applied to both surfaces of the polarizing film, and a protective film (a surface-saponified triacetylcellulose film having a thickness of 50 μm (Fujitac SH-50)) is applied to both surfaces. Pasted
Then, it was dried at 80 ° C. for 6 minutes to obtain a polarizing plate (thickness of the adhesive layer was about 0.1 μm). The appearance of this polarizing plate was good.

An adhesive is applied to one side of the obtained polarizing plate,
A polarizing plate was attached to a glass plate via this pressure-sensitive adhesive to obtain a test sample for peeling the end surface of the polarizing plate. After leaving the polarizing plate attached to a glass plate at 60 ° C. and 90% RH for 240 hours, the end face was observed.
No peeling of the end surface of the polarizing film was observed.

Example 2 A 60 ° C. aqueous solution containing a dichroic dye and Glauber's salt instead of an aqueous solution containing iodine and potassium iodide (dichroic dye / Glauber's salt / water = 0.5 / 40/10000 (weight ratio)) ) Was immersed for 5 minutes, and a PVA-based polarizing film was prepared in the same manner as in Example 1 except that an aqueous solution of boric acid (boric acid / water = 150/2000 (weight ratio)) was used instead of the aqueous solution containing potassium iodide and boric acid. Obtained. A polarizing plate was obtained in the same manner as in Example 1 except that a triacetyl cellulose film having a thickness of 80 μm (Fujitac UV-80) was used instead of the triacetyl cellulose film having a thickness of 50 μm (Fujitac SH-50). Further, in the same manner as in Example 1, a test sample for peeling the end surface was prepared. A polarizing plate attached to a glass plate is 60
After leaving it for 240 hours under humid heat of 90 ° C. and 90% RH, the end face was observed, and no peeling of the end face between the protective film and the PVA-based polarizing film was observed.

Example 3 Composition ratio of PVA adhesive (KL-318 / WS-52
A polarizing plate was obtained in the same manner as in Example 2 except that 5) was changed to 100 / 5.5 (solid content weight ratio), and used as a sample for a peel test. Polarizing plate attached to a glass plate at 60 ℃, 90
After standing for 240 hours under the heat of humidity of% RH, the end faces were observed, and no peeling of the end face between the protective film and the PVA-based polarizing film was observed.

Comparative Example 1 Polyamide epichlorohydrin (WS manufactured by Japan PMC Co., Ltd.
-525) without adding PVA resin (manufactured by Kuraray Co., Ltd.)
A polarizing plate was obtained in the same manner as in Example 2 except that a 5 wt% aqueous solution of KL-318) was used alone as a PVA-based adhesive, and a test sample for end face peeling was obtained. After the polarizing plate attached to a glass plate was left for 240 hours under the heat of humidity of 60 ° C. and 90% RH, the end face was observed.
Edge peeling of the A-based polarizing film was observed.

Comparative Example 2 Composition ratio of PVA adhesive (KL-318 / WS-52
A polarizing plate was obtained in the same manner as in Example 2 except that 5) was changed to 100 / 2.8 (solid content weight ratio), and used as a sample for a peel test. Polarizing plate attached to a glass plate at 60 ℃, 90
After standing for 240 hours under the humidity heat of% RH, the end faces were observed, and the end face peeling between the protective film and the PVA type polarizing film was observed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C09J 163: 00)

Claims (4)

[Claims] 1. A polarizing plate in which a protective film is laminated on at least one surface of a polyvinyl alcohol-based polarizing film via a polyvinyl alcohol-based adhesive layer, wherein the adhesive layer contains a water-soluble epoxy compound. The ratio of the water-soluble epoxy compound to the polyvinyl alcohol-based resin in the adhesive is (5 to 50) /
A polarizing plate having a weight ratio of 100 (solid content weight ratio). 2. The polarizing plate according to claim 1, wherein the polyvinyl alcohol resin of the polyvinyl alcohol adhesive is a carboxyl group-modified polyvinyl alcohol. 3. The polarizing plate according to claim 1, wherein the water-soluble epoxy compound is a reaction product of polyamide and epichlorohydrin. 4. The polarizing plate according to claim 1, wherein the protective film is triacetyl cellulose whose surface is saponified.