Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2001-09-21
2004-10-26
Acquah, Sam A. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S424200, C428S001100, C428S001310, C428S001550
Reexamination Certificate
active
06808811
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polarizing plate protection film and a polarizing plate. The polarizing plate protection film of the present invention is excellent in terms of adhesive strength with the polarizer. The polarizing plate of the present invention is excellent in terms of durability under high temperature and humidity conditions. The polarizing plate is used for liquid crystal displays and such.
BACKGROUND ART
A polarizing plate is composed of a polarizer on either side of which a protection film is laminated.
Conventionally, a drawn polyvinyl alcohol film on which a dichroism dye or iodine is adsorbed is used for the polarizer. For the protection film, a triacetylcellulose film is used.
However, there is the following problem in this conventional technology:
1. There is not sufficient heat resistance and moisture resistance in the triacetylcellulose film which is the protection film.
Therefore, the triacetylcellulose film peels off from the polarizer at high temperatures or under high humidity.
2. The transparency of the triacetylcellulose film, the protection film, lowers due to hydrolysis. As a result, the polarizing plate performance deteriorates due to a reduction in the degree of polarization.
3. When stress arises due to the orientation relaxation of the polyvinyl alcohol (hereafter referred to as “PVA”) of the protection film at high temperatures, the triacetylcellulose (hereafter referred to as “TAC”) of the protection film will have a large birefringence.
Display nonuniformity and a contrast reduction in the LCD result due to a reduction in the degree of polarization.
The use of a thermoplastic saturated norbornene-type resin is proposed instead of the TAC in a polarizing plate protection film in order to solve the aforesaid problem.
However, though a PVA type adhesive is used for the adhesion between the TAC and the PVA, in the adhesion between a thermoplastic saturated norbornene-type resin and PVA, the adhesive strength of the PVA type adhesive is insufficient.
Because of this, a bonding method between the thermoplastic saturated norbornene-type resin and the PVA is proposed in Tokkai Hei 5-212828 and such. This method is a method for bonding a thermoplastic saturated norbornene-type resin film with an acrylic pressure sensitive adhesive layer to PVA by means of heat pressurization.
However, there are the following problems in this method:
1. The polarizing function of the polarizing plate is lost through discoloration and color fading of the PVA of the polarizer because heat clamping is necessary and the heating time is long.
2. The degree of polarization of the polarizing plate is reduced due to deformation contraction or degradation of the PVA, even if the polarizing function does not disappear.
3. Since heat clamping for a fixed amount of time is necessary, the production efficiency is low.
4. The manufacturing facility becomes expensive because heating and pressurization are necessary for the whole film.
5. The durability of the polarizing plate is low because adhesive strength nonuniformity arises due to uneven heating temperatures and pressurization of the whole film, resulting in poor quality.
6. The conventional bonding method of wet-lamination using a PVA type adhesive cannot be adopted as is.
The objects of the present invention are as follows.
1. To provide a polarizing plate protection film and a polarizing plate which solve the aforesaid problem in the technical field of a polarizing plate protection film using the thermoplastic saturated norbornene-type resin film.
2. (Regarding the bonding method between the polarizer and the polarizing plate protection film) to provide a polarizing plate with sufficient adhesive strength to allow the use of a conventional bonding method by wet lamination of the PVA type adhesive as is.
3. To provide a polarizing plate which solves the aforesaid problem by bonding the polarizing plate protection film made of the thermoplastic saturated norbornene-type resin and the PVA polarizer by means of a polyurethane adhesive.
DISCLOSURE OF INVENTION
1. The present invention is a polarizing plate protection film consisting of a thermoplastic saturated norbornene-type resin film on which a polyurethane resin layer is formed.
2. The present invention is a polarizing plate protection film wherein a polyurethane resin layer and a polyvinyl alcohol layer are formed in this order on a thermoplastic saturated norbornene-type resin film.
3. The present invention is said polarizing plate protection film wherein said polyurethane resin layer consists of a polyurethane adhesive which contains modified polyisocyanate.
4. The present invention is said polarizing plate protection film wherein said polyurethane resin layer consists of a water-type polyurethane adhesive.
5. The present invention is a polarizing plate wherein said polarizing plate protection film is bonded onto at least one side of the polarizer by wet lamination using a polyvinyl alcohol-type adhesive.
6. The present invention is a polarizing plate wherein a polyvinyl alcohol polarizer and a protection film which consists of the thermoplastic saturated norbornene-type resin are bonded together with a polyurethane adhesive.
7. The present invention is said polarizing plate wherein said polyurethane adhesive is a two-component type and the main agent consists of a polyester resin.
8. The present invention is said polarizing plate in which said polyurethane adhesive consists of a water-type polyurethane adhesive.
The advantages of the invention are the following:
1. The polarizing plate protection film of the present invention can provide a polarizing plate which is excellent in terms of durability.
2. It is possible to wet-laminate the polarizing plate protection film of the present invention onto the polarizer. Therefore, the polarizing plate can be manufactured without changing the protection film bonding process from the conventional method.
3. The polarizing plate of the present invention has excellent optical characteristics. In addition, the optical characteristics and appearance characteristics do not deteriorate under high temperature and humidity conditions and the polarizing plate has the excellent durability.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is described in detail below.
“Thermoplastic Saturated Norbornene-Type Resin for the Present Invention”
It is possible to use a prior art thermoplastic saturated norbornene-type resin.
The thermoplastic saturated norbornene-type resin is a resin whose polymerization unit has the norbornane skeleton. The norbornane skeleton may have substitutional groups such as an alkyl group, carboxyl group, or phenyl group.
Prior art resins have been described in Japanese unexamined patent publication Tokkai Hei 1-240517, Tokkai-Sho 62-252406, Tokkai-Sho 62-252407, Tokkai-Hei 2-133413, Tokkai-Sho 63-145324, Tokkai-Sho 63-264626, Tokkai-Sho 57-8815, etc. Examples follow:
A hydrogenated product of the ring-opened polymer of the norbornene-type monomer, a hydrogenated product of a copolymer of two or more types of norbornene-type monomers, a hydrogenated product of a copolymer of a norbornene-type monomer and an olefin-type monomer (ethylene, &agr;-olefin, etc.), a hydrogenated product of a copolymer of a norbornene-type monomer and a cyclic olefin-type monomer (cyclopentene, cyclooctene, 5,6-dihydro dicyclopentadiene, etc.), and modified products of the aforesaid resins.
Examples of the monomers used for the thermoplastic saturated norbornene-type resin are as follows: norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5-phenyl-5-methyl-2-norbornene, ethylene-tetracyclo dodecen copolymer, 6-methyl-1,4:5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a and 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-ethylidene-1,4,4a and 5,6,7,8,8a-octahydronaphthal
Kobayashi Hitoshi
Okada Yasumasa
Sawada Takahiko
Acquah Sam A.
Bissett Melanie
Sekisui Chemical Co. Ltd.
Townsend & Banta
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