JPH0217081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive adhesive polarizing plate having heat resistance and heat and humidity resistance.

Traditionally, pressure-sensitive adhesive polarizing plates have been used in liquid crystal display devices for digital watches and liquid crystal display devices for electronic calculations, but recently their use has been expanded further and they are now being used in digital meters for cars, digital meters for industrial use, etc. Development is also progressing into liquid crystal display devices. However, in these applications, heat resistance, heat and humidity resistance, weather resistance, etc. are more strictly required than in the conventional case. In other words, meters placed in cars or outdoors are exposed to high temperature and humidity conditions for long periods of time, so conventional pressure-sensitive adhesive polarizing plates deteriorate severely and cannot withstand use. Polarizing films are generally constructed by laminating triacetylcellulose films on both sides of a PVA film that has iodine or dichroic dye adsorbed and oriented. Then, either a pressure-sensitive adhesive layer such as acrylic adhesive is provided on one side to make a transmissive polarizing plate, or a pressure-sensitive adhesive layer is provided on both sides and a reflective layer is provided on one side to make a reflective polarizing plate. These are attached to the upper and lower glass plate surfaces of a liquid crystal cell of a liquid crystal display device via pressure-sensitive adhesive layers, respectively. The above-mentioned deterioration phenomenon is that the polarizing film portion of the liquid crystal display device constructed in this way is destroyed to pieces. The causes of deterioration of the polarizing film under high humidity and heat are the acid contained in the pressure sensitive adhesive and the hydrolysis of the triacetyl cellulose film.

The present invention was made for the purpose of preventing the above-mentioned polarizing film from deteriorating or suppressing the occurrence of deterioration to increase the usable time as a liquid crystal display device. The present invention was developed based on the finding that the inclusion of diphenylguanidine neutralizes acidic substances generated under high humidity and heat, thereby preventing deterioration of the polarizing film.

In other words, the present invention provides a polarizing film in which an acrylic pressure-sensitive adhesive layer is provided on one or both sides of a polarizing film made by laminating a triacetyl cellulose film on both sides of a polyvinyl alcohol film on which iodine or dichroic dye is adsorbed and oriented. On the board,
This is a pressure-sensitive adhesive polarizing plate characterized in that the adhesive layer contains dibutylamine or diphenylguanidine.

As described above, the present invention contains dibutylamine or diphenylguanidine in the acrylic pressure-sensitive adhesive layer, which significantly doubles or more the time it takes for a polarizing film to deteriorate under high humidity and heat conditions. Can be extended.

The appropriate amount of dibutylamine or diphenylguanidine is in the range of 1 to 30 parts by weight based on 100 parts by weight of the solid content of the pressure sensitive adhesive. That is, 1
When the amount is less than parts by weight, the effect is not clear. On the other hand, if the amount is more than 30 parts by weight, bubbles may occur or the polarizing film may peel off if the pressure-sensitive adhesive polarizing plate is bonded to a liquid crystal cell and left in high temperature or high temperature and humidity conditions.

The structure and effects of the present invention will be specifically explained below using Examples and Comparative Examples. Hereinafter, parts represent parts by weight.

Example 1 Acrylic pressure-sensitive adhesive with the following composition (solid concentration
40%) 100 parts (solid content) Butyl alcohol 100〃 Methyl methacrylate 20〃 Acrylic acid 5〃 Coronate 0.2〃 Ethyl acetate 120〃 Toluene 68〃 Dibutylamine 10 parts Use the dibutylamine-containing acrylic pressure-sensitive adhesive of the above composition. Use a polarizing film with a thickness of 30 mm on one side.
A micron adhesive layer was formed. This is the thickness
When bonded to a 0.9 mm glass plate and left in an atmosphere of 80°C and 95% RH, no abnormalities were observed even after 1500 hours.

Example 2 Acrylic pressure sensitive adhesive with the following composition (solid content 35%)
100 parts (solid content) 2-ethylhexyl acrylate
100 parts Ethyl acrylate 80〃 Ethyl methacrylate 15〃 Acrylic acid 15〃 Ethyl acetate 300〃 Toluene 90〃 Diphenylguanidine 8 parts Methyl ethyl ketone 40 parts Using an acrylic pressure-sensitive adhesive containing diphenylguanidine in the above formulation, polarizing film was produced. An adhesive layer with a thickness of 30 microns was formed on both sides, and a reflector-type polarizing plate was created on one side. Example 1
When left in the same manner and under the same conditions, no abnormalities were observed even after 800 hours.

Comparative Example 1 After forming an adhesive layer under exactly the same conditions as in Example 1 using only the acrylic pressure-sensitive adhesive of Example 1, this was left to stand in the same manner and under the same conditions, and after 900 hours. A phenomenon of deterioration of the polarizing film occurred.

Comparative Example 2 A reflector-type polarizing plate was prepared under exactly the same conditions as in Example 2 using only the acrylic pressure-sensitive adhesive of Example 2, and left in the same manner and under the same conditions. A phenomenon of deterioration of the polarizing film occurred.

Claims (1)

[Claims] 1 In a polarizing plate in which an acrylic pressure-sensitive adhesive layer is provided on one or both sides of a polarizing film made by laminating a triacetyl cellulose film on both sides of a polyvinyl alcohol film on which iodine or dichroic dye has been adsorbed, the adhesive A pressure-sensitive adhesive polarizing plate characterized in that the agent layer contains dibutylamine or diphenylguanidine.