Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Utilizing plasma – electric – electromagnetic – particulate – or...
Patent
1998-07-15
2000-06-06
Vargot, Mathieu D.
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Utilizing plasma, electric, electromagnetic, particulate, or...
264 138, 264 16, 264 17, 427162, B29D 1100
Patent
active
060714433
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing a lens sheet such as a circular Fresnel lens sheet, and to a projection screen for a rear-projection-type or front-projection-type television, utilizing a lens sheet produced by the production process.
BACKGROUND ART
In general, lens sheets for use in projection screens, especially circular Fresnel lens sheets are formed by a pressing or casting method. However, these two production methods are long in production time, so that they have had the problems of low productivity and high production cost.
Japanese Patent Laid-Open Publication No. 9301/1991 describes, as a means for solving the aforementioned problems, a process for producing a lens sheet, comprising the steps of coating a first ionizing radiation curable resin onto the entire surface of a forming die in the shape of a flat plate; forming a resin bank of a second ionizing radiation curable resin on the first ionizing radiation curable resin; and superposing a laminating base material on the second ionizing radiation curable resin, and uniformly laying the second ionizing radiation curable resin over the first ionizing radiation curable resin with forcing out, by the use of a pressure roll, those air bubbles that enter between the base material and the forming die.
In the process described in the above Japanese Patent Laid-Open Publication No. 9301/1991, it is necessary to use, as the first ionizing radiation curable resin, a resin having a decreased viscosity prepared by diluting the second ionizing radiation curable resin; a resin having a decreased viscosity prepared by heating the second ionizing radiation curable resin to a high temperature; another resin having a low viscosity; or the like, in order to promote deaeration in the step that comes after the step of coating the first ionizing radiation curable resin.
However, if a solvent is used for diluting the second ionizing radiation curable resin, the problem of safety occurs, and it becomes necessary to add the drying step. Further, in the case where the second ionizing radiation curable resin is heated to a high temperature, it is necessary to install a heater or the like; and, in addition, such a problem occurs that resin components are changed as a result of the evaporation of monomer components contained in the resin. Furthermore, when another resin having a low viscosity, containing excessive monomers is used, a lens in the desired shape cannot be obtained due to cure shrinkage; and such a problem occurs that adjustment of refractive index is required between the first and second ionizing radiation curable resins.
DISCLOSURE OF THE INVENTION
We found that, when a resin composition for a lens sheet is coated onto a forming die by the use of a multiple nozzle in which a plurality of nozzles are arranged at intervals along a forming die for a lens sheet in a direction substantially rectangular to a direction in which the resin composition for a lens sheet will be coated, the resin composition for a lens sheet can readily spread over the entire surface of the forming die, so that a lens sheet containing no air bubbles in the lens area thereof can be obtained without using a solvent.
The present invention was accomplished on the basis of this finding. An object of the present invention is to provide a process for producing a lens sheet, which is safe, which can cut the material cost and the facility cost, which can continuously produce, by the use of a forming die, a formed lens sheet that contains no air bubbles in the lens area thereof and which can attain higher productivity, and reduction of costs by using a decreased number of forming dies or the like; and a projection screen.
A first aspect of the present invention is a process for producing a lens sheet, comprising the steps of coating a resin composition for a lens sheet onto a forming die for a lens sheet by the use of a multiple nozzle in which a plurality of nozzles are arranged at intervals along the forming die in a direction substantially rectangul
REFERENCES:
patent: 3689346 (1972-09-01), Rowland
patent: 5410006 (1995-04-01), Tachibana et al.
Patent Abstracts of Japan; vol. 015, No. 333 (M-1150); Aug. 23, 1991 & JP 03 128212 A (Mitsubishi Rayon Co Ltd); May 31, 1991 *abstract*.
Goto Masahiro
Osawa Futoshi
Dai Nippon Printing Co. Ltd.
Vargot Mathieu D.
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