Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Polymerizing – cross-linking – or curing
Reexamination Certificate
2002-03-26
2003-07-15
Seidleck, James J. (Department: 1711)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Polymerizing, cross-linking, or curing
C264S446000, C264S447000, C264S448000, C264S494000, C264S495000, C264S212000, C264S213000, C264S216000, C427S487000, C427S508000
Reexamination Certificate
active
06592802
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for efficiently producing a polymer sheet superior in surface smoothness and small in retardation, as well as to an optical polymer sheet produced by the process.
BACKGROUND ART
Glass substrates have been used as a transparent electrode substrate for liquid crystal display device. Liquid crystal display devices using a glass substrate have had problems in that the large thickness of glass substrate makes it difficult to produce a liquid crystal display device of small thickness and light weight and the use of glass incurs insufficient impact resistance.
To alleviate these drawbacks of liquid crystal display devices using a glass substrate, it has been investigated to use an optical polymer sheet for production of a liquid crystal display device of lighter weight and improved impact resistance.
For example, in JP-A-53-68099 and JP-A-54-126559, it is disclosed to continuously produce a liquid crystal display device using, in place of a glass substrate, a long polyester film having a conductive metal oxide vapor-deposited thereon. However, the polyester film (polymer sheet) has no sufficient surface smoothness, unlike a glass substrate having a very good surface smoothness as a result of polishing. When, in particular, a STN (super twisted nematic) type liquid crystal display device is produced in order to obtain a very fine display, the surface smoothness of the above polymer sheet becomes a very serious problem because in the liquid crystal display device, display is made utilizing the birefringence of the liquid crystal present between substrates having a substrate-to-substrate distance controlled at a 0.1 &mgr;m accuracy.
To improve the surface smoothness of polymer sheet, a method was proposed which comprises casting, on a polished glass or the like, an ultraviolet-curing resin composition or a thermosetting resin composition, both of which are liquid, and curing the composition to obtain a sheet. This method, however, has a problem in that the sheet obtained is fragile and causes cracking or chipping during its handling; therefore, there is no clear advantage by use of the polymer sheet over use of a glass substrate. Further, the method is low in productivity, resulting in a substrate of high cost.
DISCLOSURE OF THE INVENTION
The present invention aims at providing a process for continuously and efficiently producing a polymer sheet superior in surface smoothness and showing excellent properties when used as an optical polymer sheet for a substrate of a liquid crystal display device or the like; and an optical polymer sheet superior in the above properties, produced using a resin suitable for the above process.
The present invention provides the followings.
(1) A process for producing a polymer sheet, which comprises coating or laminating, on a polymer base sheet, an ultraviolet-curing resin composition, adhering the coated or laminated polymer base sheet to a member having a smooth surface whose maximum surface roughness (Rmax) satisfies Rmax≦0.1 &mgr;m, in a state that the ultraviolet-curing resin composition is soft, and applying an ultraviolet light to transfer smoothness of the smooth surface of the member onto the polymer base sheet.
(2) A process according to the above (1), wherein the member having a smooth surface can transmit an ultraviolet light of a particular wavelength and, after the ultraviolet light has been applied to the ultraviolet-curing resin composition from a side of the member not adhering to the polymer base sheet and the composition has been cured, can be peeled from the polymer base sheet.
(3) A process according to the above (1), wherein the polymer base sheet is transparent and can transmit an ultraviolet light and, after the ultraviolet light has been applied to the ultraviolet-curing resin composition from a side of the polymer base sheet not adhering to the member having a smooth surface and the composition has been cured, can be peeled from the member.
(4) A process according to any of the above (1) to (3), wherein a releasing agent is continuously fed to the member having a smooth surface.
(5) A process according to the above (4), which comprises, after application of an ultraviolet light, a step of removing the releasing agent transferred onto the surface of the polymer base sheet.
(6) A process according to the above (4) or (5), wherein the releasing agent contains at least a fluorine compound or a silicon compound.
(7) A process according to any of the above (1) to (6), wherein the member having a smooth surface is a roll.
(8) A process according to any of the above (1) to (6), wherein the member having a smooth surface is an endless belt having a flat area of 30 cm or more extending in the movement direction.
(9) A process according to any of the above (1) to (6), wherein the member having a smooth surface is a plastic film having a smooth surface.
(10) A process according to the above (9), wherein the plastic film is subjected to a slidability-imparting treatment at a side opposite to the smooth surface.
(11) An apparatus for producing a polymer sheets comprising:
a hollow transparent roll which has a smooth surface whose maximum surface roughness (Rmax) satisfies Rmax≦0.1 &mgr;m and which can transmit an ultraviolet light, and
an ultraviolet source placed in the hollow portion of the roll.
(12) An optical polymer sheet produced by a process set forth in any of the above (1) to (10).
(13) An optical polymer sheet according to the above (12), wherein the polymer is a polyethersulfone.
REFERENCES:
patent: 4414275 (1983-11-01), Woods
patent: 0 623 440 (1994-11-01), None
patent: 0 916 474 (1999-05-01), None
patent: 53-68099 (1978-06-01), None
patent: 54-126559 (1979-10-01), None
patent: 5-162229 (1993-06-01), None
patent: WO 95/00876 (1995-01-01), None
Official Action of the Japanese Patent Office dated Dec. 16, 2002, 4 pages.
Eguchi Toshimasa
Goto Hideki
Ohno Shinji
Takenaka Tsuyoshi
Tanaka Junji
Ribar Travis B
Seidleck James J.
Smith , Gambrell & Russell, LLP
Sumitomo Bakelite Company Limited
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