Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1992-08-14
1995-04-25
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526301, 4284244, 4284246, 359742, C08F 1800, C08F 2000, G02B 308
Patent
active
054100062
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a composition for forming a lens and to a Fresnel lens and a transmission screen of rear projection type using said composition, and in particular to a transmission screen having a Fresnel lens of short focal length.
BACKGROUND ART
For a transmission screen to be used in microfilm reader, projection television, etc., attempts are made to increase light diffusion property of the screen. For this purpose, a lenticular lens, Fresnel lens, etc. are provided on light source side, and a light shielding layer is furnished on observer side to enhance screen contrast, and a light diffusion substance is added on the screen to increase light diffusion property of the screen.
Conventionally, to form such transmission screen, a synthetic resin sheet is produced by extrusion molding method, press molding method or casting method, and this is laminated with film of base material, and a lenticular lens or a Fresnel lens is formed directly on the film.
In the transmission screen, a Fresnel lens is arranged between various types of light sources such as cathode ray tube, liquid crystal filter type projection system on one side and a lenticular lens sheet on the other side, and light beam from the light source entering at high angle toward the surrounding region of the screen is converged slightly inwardly to prevent the darkening of the surrounding regions of the screen due to divergence of light from the light source.
When light beam enters Fresnel lens, refractive angle of the beam is determined according to the material of the Fresnel lens. The higher refractive index the material has, the less the light beam is lost even when the beam is refracted at high angle. Thus, if a material with higher refractive index is used for Fresnel lens, it is possible to refract light beam entering at high incident angle with less reflecting loss. As the result, it is possible to bring the position of the light source much closer to the screen and to shorten the distance between the light source of projection television and the screen. This contributes to designing of the projection television in smaller size.
Then, it is necessary to use a lens of short focal length as the Fresnel lens in order to shorten the distance between the light source of an image and the transmission screen. For this purpose, instead of methyl metacrylate resin with high transparency (refractive index n=1.49), a material of higher refractive index such as styrene is copolymerized with methyl metacrylate, and a sheet of the resultant material (e.g. having refractive index n=1.57) is used for the purpose by molding through thermal pressing.
However, the productivity of such Fresnel lens is not very high because it is produced by a series of processes including heating, pressurizing and cooling. In particular, to mold a Fresnel lens having fine lens shape over a large area by thermal pressing, it is necessary to heat under strict temperature condition and to perform pressurizing and cooling for long time, and this leads to very low production efficiency.
Under such circumstances, it has been proposed to utilize a UV-setting resin, which is cured by ionizing radiation such as ultraviolet ray within short time, instead of thermosetting resin as conventionally used in order to improve production efficiency and to form lenses with fine shape.
The UV-setting resin has a prepolymer of UV-setting resin as its material. The prepolymer of UV-setting resin is a macromolecular substance with low polymerization degree and high viscosity, and it is not possible to coat it on or to fill into a die. For this reason, it is necessary to use a diluent to dissolve the prepolymer. If an organic solvent is used as the diluent, the molded object is deformed due to evaporation of the organic solvent, and it is practiced to use a monomer as the diluent to polymerize with the prepolymer.
For a composition of UV-setting resin to be used in Fresnel lens or transmission screen using such lens must have, along with transparency of cur
REFERENCES:
patent: 4487904 (1984-12-01), Fukuda et al.
Tachibana Kazuhiro
Takahashi Katsunori
Dai Nippon Printing Co. Ltd.
DeWitt LaVonda
Michl Paul R.
LandOfFree
Composition for forming lens, and Fresnel lens and transmission does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composition for forming lens, and Fresnel lens and transmission , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composition for forming lens, and Fresnel lens and transmission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1568456