JPH04254803A - Adhesion type polarizing plate or adhesion type phase difference plate - Google Patents

Abstract

PURPOSE:To prevent hydrolysis of an acetylcellulose film even in the case of long time exposure under a condition of high temperature and high humidity to remarkably enhance durability of a polarizing plate and a phase difference plate. CONSTITUTION:In the case of providing an acryl adhesive agent layer on each of both sides or one side of a polarizing plate or a phase difference plate having an acetylcellulose film as a carrier, 2,4,6-tris (N,N-dimethylaminomethyl) phenol is contained in the adhesive layer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate and a retardation plate. More specifically, the present invention relates to an adhesive polarizing plate and an adhesive retardation plate that have excellent durability under high temperature and high humidity conditions.

0002

BACKGROUND OF THE INVENTION With the spread of liquid crystal displays, polarizing plates have come to be industrially produced and used in large quantities. Liquid crystal displays, which started out as displays for small items such as watches and calculators, are also used in high-priced and highly durable equipment such as office automation equipment such as computers and word processors, LCD televisions, LCD projectors, in-vehicle instrument panels, and in-vehicle navigation systems. As the technology has come to be applied to more and more applications, higher reliability has come to be required.

[0003] Among the reliability of liquid crystal displays, one of the parts for which improvement has been most desired is the polarizing plate. In addition to improving the durability of the polarizer itself, the most important thing for practical use is
The key is to improve the durability of the adhesive layer.

Most liquid crystal polarizing plates are adhesive type polarizing plates with an adhesive layer in order to simplify assembly and reduce reflection loss on the surface. This has become the most important practical technical issue that cannot be avoided.

Generally, adhesive type polarizing plates are made by laminating and adhering a stretched polyvinyl alcohol (hereinafter abbreviated as PVA) film with triacetyl cellulose (hereinafter abbreviated as TAC) film on both sides of a stretched polyvinyl alcohol (hereinafter abbreviated as PVA) film in which iodine or dichroic dye is oriented as a polarizer. It is manufactured by further providing an acrylic adhesive layer on the TAC surface.

In actual use, this adhesive polarizing plate is bonded to the surface of a glass plate of a liquid crystal cell via an adhesive layer. If a general liquid crystal cell with a polarizing plate made in this way is exposed to high temperature and high humidity conditions for a long time, the polarizing plate will deteriorate to cloudiness, discoloration, and physical destruction, and eventually the polarizing plate will not be polarized at all. This may lead to the board losing its function.

On the other hand, as one of the black and white display methods using an STN type liquid crystal display, a method of providing a retardation plate between a liquid crystal cell and a polarizing plate has become popular. A PVA-based retardation plate, which is a type of retardation plate, is manufactured by supporting a stretched PVA film on one or both sides with a TAC film, and providing an acrylic adhesive layer on the surface thereof.

[0008] A liquid crystal display is constructed by laminating one or more layers of retardation plates to an STN cell via an adhesive layer, and laminating a polarizing plate to the outermost layer.
In this case as well, as in the case of laminating a single layer of polarizing plate, high temperature,
If exposed to high humidity conditions for a long period of time, it may become cloudy and may completely lose its function in a short period of time, leading to physical destruction.

[0009] After intensive investigation into the cause of these problems, we found that the acidity of acrylic acid, which is one of the copolymerized components of acrylic adhesives, causes the acetyl groups of TAC that come into contact with it to be hydrolyzed under high temperature and high humidity conditions. It was discovered that acetic acid is generated, and that acetic acid successively hydrolyzes other acetyl groups, rapidly destroying and degrading them.

0010

Problems to be Solved by the Invention It is desired to develop a method for manufacturing highly durable adhesive polarizing plates or adhesive retardation plates that do not deteriorate even when exposed to high temperature and high humidity conditions for a long time.

[0011]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have made extensive studies and found that when forming an adhesive layer, the acidic components such as acrylic acid in the acrylic adhesive are neutralized. Therefore, the inventors have discovered that the above-mentioned problems can be solved by adding a specific amino compound, leading to the present invention.

That is, the present invention provides a laminate in which an acetyl cellulose film is provided on one or both sides of a polarizing film or a retardation film, and an acrylic adhesive layer is further provided on one or both sides of the film. 4,6
The present invention relates to an adhesive polarizing plate or an adhesive retardation plate characterized by containing tris(N,N-dimethylaminomethyl)phenol.

The polarizing film used in the present invention is not particularly limited, but for example, a polyvinyl alcohol film is dyed with iodine or a dichroic dye, and while esterified in an aqueous boric acid solution, it is dyed in a uniaxial direction for about 30 minutes. It can be obtained by uniaxially stretching the film to ~5 times and drying it by heating, and the retardation film can be obtained by, for example, polyvinyl alcohol-based film being stretched in an aqueous solution of boric acid at a stretching ratio of 2 times or less to obtain a specific retardation value. It can be manufactured by stretching in a uniaxial direction.

As the acetyl cellulose film, T
In addition to AC film, diacetyl cellulose film, acetyl butyl cellulose film, etc. can be used as long as they are highly transparent and optically isotropic.

[0015] Usually, a polarizing plate or a phase plate is manufactured by laminating and adhering an acetylose film on both or one side of a polarizing film or a retardation film using a polyvinyl alcohol adhesive or a UV curable adhesive.

[0016] The acrylic adhesive used is one obtained by copolymerizing the main component (meth)acrylic acid ester and a carboxyl group-containing compound that can be copolymerized with this. Then, just before coating, add a polyisocyanate hardener or epoxy hardener,
It is also possible to form a crosslinked structure.

One component of the copolymer adhesive (meth)
Examples of acrylic esters include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (
isooctyl (meth)acrylate, isononyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, benzyl (meth)acrylate, (meth)
Examples include 2-hydroxyethyl acrylate, which is adjusted to account for 60 to 99% by weight of the total copolymerization component.

[0018] As another component, a carboxyl group-containing compound, acrylic acid, methacrylic acid,
Itaconic acid, crotonic acid, maleic acid, etc. can be mentioned, and the proportion of these as copolymerization components is 1 to 20%. Furthermore, if necessary, it is also possible to add, for example, 0 to 20% by weight of a copolymerizable vinyl compound.

The adhesive layer is formed on the polarizing plate or retardation plate produced by the method described above to form an adhesive polarizing plate or an adhesive retardation plate. When these adhesive polarizing plates or a laminate of an adhesive retardation plate and an adhesive polarizing plate were attached to a glass cell and exposed for a long time under the conditions of 80°C x 95% RH or 80°C x 90% RH, it became cloudy. , polarizer discoloration, TA
Due to hydrolysis of C, the shape was destroyed and the function completely disappeared.

On the other hand, 2,4,6-tris (
Adhesive polarizing plates and adhesive retardation plates were formed in the same way using a material to which N,N-dimethylaminomethyl)phenol was added, and their durability was confirmed in the same manner. It has durability of more than 1000 hours under the condition of 95% RH and 15 hours under the condition of 80℃ x 90% RH.
It was confirmed that the device still had this function even after 00 hours had passed.

In the present invention, 2,4,6-tris (N,
The amount of N-dimethylaminomethyl)phenol added to the adhesive is usually 0.3 to 20 parts per 100 parts of the solid content of the adhesive.
Department.

The adhesive polarizing plate or adhesive phase plate of the present invention is excellent in the following points.

(2) Under conditions of high temperature and high humidity, the adhesive layer does not peel off from the glass plate, has no foaming, has no surface irregularities, and does not cause yellowing or browning due to the added amino compound. ■ Does not foam under high temperature (dry heat) conditions and does not cause cracks in the adhesive layer. ■ There is no adhesive residue when removing the polarizing plate after pasting it on the glass plate.

[0024] In the present invention, the adhesive layer may be provided on one side of the polarizing plate or retardation plate, or in the production of a polarizing plate with a reflective plate, a polarizing plate with an anti-glare PET film, a polarizing plate-retardation plate laminate, etc. It is also possible to use the adhesive layer provided on both sides.

[0025]

[Example] Next, the present invention will be explained with reference to an example. In the examples, parts represent parts by weight. Example 1 A 75 μm PVA film was swollen in hot water, dyed in a dye solution consisting of orange, red, blue, and green dichroic dyes and Glauber's salt, and stretched 4 times in a boric acid bath.
A 30 μm polarizing film was prepared by washing with water and drying, and an 80 μm TAC film was laminated and bonded on both sides of the film using a PVA adhesive to produce a dye-based polarizing plate.

On the other hand, an acrylic adhesive was prepared by dissolving 25 parts of a copolymer composition consisting of 69% butyl acrylate, 10% methyl acrylate, 10% methyl methacrylate, and 11% acrylic acid (all by weight) in 75 parts of ethyl acetate. 2,4,6-tris (N,
After adding 0.8 parts of N-dimethylaminomethyl) phenol, 0.06 parts of an epoxy curing agent, and 40 parts of methyl ethyl ketone for viscosity adjustment and defoaming, 38 μP was subjected to silicone mold release treatment.
The ET film was coated with a solid layer of 23μ. After removing the solvent, the dye-based polarizing plate described above was laminated and aged at room temperature for one week or more to obtain an adhesive polarizing plate.

[0027] The adhesive polarizing plate was attached to a glass plate to prepare a test piece. The initial characteristics of this polarizing plate are:
Single transmittance 40.01% Parallel transmittance 31.34%, Orthogonal transmittance 0.08%, Luminous correction average polarization rate ρ99.7
6%, the hue was neutral gray in both the single position, parallel position, and orthogonal position, and had excellent performance. (Here, the transmittance Y represents the Y value of the tristimulus value, and the luminous sensation correction average polarization ratio ρ is represented by the following formula.

[0028]

[0029] The test piece for testing was heated to 80°C x 90%RH.
The optical properties after being exposed to the atmosphere for 1000 hours were carrier transmittance 36.71%, parallel transmittance 28.19%, orthogonal transmittance 0.05%, and ρ99.82%, although the transmittance decreased slightly. The polarization rate did not decrease at all, the hue only slightly changed to bluish color, and almost no deterioration in appearance was observed. In addition, as a durability test, 85℃
Dry heat (heat resistance) 63℃ carbon arc (weather resistance) condition 10
Even after 00 hours of exposure, almost no decrease in optical properties or deterioration in appearance was observed.

Example 2 In Example 1, a transparent film made of acrylic polyol as the main ingredient and Coronate EH (isocyanate curing agent, manufactured by Nippon Polyurethane) as the hardening agent was placed on one side of the dye-based polarizing plate manufactured before adhesive processing. Paint is applied and the solid content is 30
A top coat layer with a thickness of μ was formed to obtain a top coated polarizing plate. An adhesive having the same composition as in Example 1 was applied to the surface of the other polarizing plate on which the top coat layer was not formed, in the same manner as in Example 1, to create a highly durable adhesive polarizing plate. A test piece was prepared in the same manner as in Example 1, and heated at 80°C x 9
Changes in optical properties and appearance after exposure for 1000 hours under high temperature and high humidity conditions of 5% RH were as follows.

Single transmittance 40.5%
40.35% ρ
99.72% 99
．． 74% Hue Neutral Gray Neutral Gray It was possible to obtain an extremely durable polarizing plate that has even more durability against high temperatures and high humidity than in Example 1.

Comparative Example 1 An adhesive polarizing plate was prepared in the same manner as in Example 1 except that 2,4,6-tris(N,N-dimethylaminomethyl)phenol was not added to the acrylic adhesive. A test piece was prepared and subjected to a moisture and heat resistance test. 80℃×90
Under %RH conditions, it becomes cloudy from 800 hours to 80°C x 95% RH conditions, and from 600 hours onwards, it begins to become cloudy and rapidly changes color to reddish brown, loses its degree of polarization, and eventually cracks on the TAC surface and physically destroys it. It's arrived.

Comparative Example 2 A dye-based polarizing plate having a commercially available 2,4,6-tris(N,N'-dimethylaminomethyl)phenol-free acrylic adhesive layer was subjected to a moist heat resistance test under the same conditions as Comparative Example 1. As a result, the initial neutral gray color was 80℃ x 9
From about 500 hours under 0%RH condition, 80℃ x 95%
Under RH conditions, the filter began to change color to reddish-brown after 400 hours, and eventually lost its polarizing plate function and became a mere dirty reddish-brown filter.

Example 3 An ethyl acetate/toluene (6:3) solution containing a copolymer of 80% butyl acrylate, 16% methyl methacrylate, and 4% acrylic acid in terms of solids concentration by weight. An acrylic adhesive was prepared. 0.5 parts of triisocyanate curing agent and 2,4,6 parts for 200 parts of the adhesive.
- Prepare an adhesive coating solution by adding 2.5 parts of tris(N,N-dimethylaminomethyl)phenol, and apply it to a retardation plate consisting of a laminate of TAC film, stretched PVA film, and TAC film. I got a type retardation plate.

The adhesive polarizing plate produced in Example 1 was laminated and adhered on the adhesive retardation plate to produce an integrated polarizing plate-retardation plate. The adhesive retardation plate and the integrated product were each attached to a glass plate via their adhesive layers to prepare a test piece, which was exposed to conditions of 80° C. and 90% RH. Even after 1000 hours had passed, no deterioration of TAC due to hydrolysis occurred.

[0036]

[Effect of the invention] Hydrolysis of acetyl cellulose film can be prevented even when exposed to harsh conditions of high temperature and high humidity for a long time, greatly improving the durability of polarizing plates and retardation plates. I was able to do it.

Claims (1)

[Claims] Claim 1: An acetyl cellulose film layer is provided on one or both sides of a polarizing film or a retardation film,
Further, in a laminate plate having an acrylic adhesive layer on one or both sides, the adhesive layer is coated with 2,4,6-tris (N
, N-dimethylaminomethyl) phenol.