Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-07-09
2004-04-20
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S560000, C524S321000, C524S230000, C524S577000, C428S514000
Reexamination Certificate
active
06723772
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a resin composition having a light diffusing property. More specifically, the present invention relates to a resin composition comprising a light diffusing agent, an ultraviolet absorber and a phosphor. Further, the present invention relates to a molded article obtained by molding this resin composition.
2. Description of Related Art
Resin compositions such as a methyl methacrylate resin containing a light diffusing agent and the like are widely used as materials of light diffusible members such as a lighting cover, illumination sign board and light diffusing plate for transmission-type display. Recently, in the fields of illumination and transmission-type display, energy saving has progressed, and those providing excellent diffusion and transmittance of light are required as the above-mentioned light diffusible member. On the other hand, high brilliance of a light source lamp has also progressed, and those showing excellent durability are required as the above-mentioned light diffusible member.
Conventionally, there are many proposals regarding resin compositions such as a methyl methacrylate resin containing a light diffusing agent and the like, however, any of them is not necessarily satisfactory in light diffusion and transmittance and durability, and a problem of yellowing of transmitted light occurs in some cases.
Though there are technologies of adding benzotriazole-based or benzophenone-based ultraviolet absorbers to improving durability, when added in large amount for enhancing durability, transmitted light or reflected light is resultantly yellowed, and when a phosphor is further added for improving the yellow color, the above-mentioned ultraviolet absorber absorbs ultraviolet ray around 370 nm necessary for light excitation of the phosphor and an effect cannot be manifested.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems and to provide a resin composition used as a material of a light diffusible member, showing excellent in light diffusion and transmission, having excellent durability and suppressing yellowing of transmitted light.
The present inventors have intensively studied, and resultantly found that a resin composition comprising a light diffusing agent, ultraviolet absorber as described herein and phosphor in the amounts respectively as described herein can attain the above-mentioned object, leading to completion of the present invention.
Namely, the present invention provides a resin composition comprising 100 parts by weight of a methyl methacrylate resin or styrene resin, about 0.1 to about 20 parts by weight of a light diffusing agent, about 0.0005 to about 0.1 parts by weight of an ultraviolet absorber selected from the group consisting of 2-(1-arylalkylidene) malonates and oxalanilides, and about 0.0001 to about 0.01 parts by weight of a phosphor.
Also, the present invention provides a molded article made of this resin composition, having a thickness of about 0.8 to about 5 mm and having a content of the light diffusing agent of about 1 to about 500 g/m
2
, a content of the ultraviolet absorber selected from the group consisting of 2-(1-arylalkylidene) malonates and oxalanilides of about 0.02 to about 3 g/m
2
and a content of the phosphor of about 0.001 to about 0.3 g/m
2
.
Further, the present invention provides a laminated plate obtained by integrally laminating a resin layer (B) made of a resin composition comprising 100 parts by weight of a methyl methacrylate resin or styrene resin and about 0.01 to about 3 parts by weight of an ultraviolet absorber selected from the group consisting of 2-(1-arylalkylidene) malonates and oxalanilides, on at least one surface of a resin layer (A) made of the above-mentioned resin composition.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the methyl methacrylate resin is a polymer containing 50% by weight or more of methyl methacrylate as a monomer constituting the resin, and mentioned are polymethyl methacrylate which is substantially a homopolymer of methyl methacrylate, and copolymers comprising 50% by weight or more of methyl methacrylate and less than 50% by weight of an unsaturated monomer copolymerizable therewith.
As the unsaturated monomer copolymerizable with methyl methacrylate, there are mentioned, for example, methacrylates such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate and 2-hydroxyethyl methacrylate; acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate; unsaturated acids such as methacrylic acid and acrylic acid; styrene, &agr;-methylstyrene, acrylonitrile, methacrylonitrile, maleic anhydride, phenylmaleimide, cyclohexylmaleimide and the like, and if necessary, two or more of them can be used. Further, the above-mentioned copolymer may have glutaric anhydride unit and glutarimide unit.
The styrene resin is a polymer containing 50% by weight or more of styrene as a monomer constituting the resin, and mentioned are polystyrene which is substantially a homopolymer of styrene, and copolymers comprising 50% by weight or more of styrene and less than 50% by weight of an unsaturated monomer copolymerizable therewith.
As the unsaturated monomer copolymerizable with styrene, the above-mentioned monomers excepting styrene are listed in addition to methyl methacrylate.
The resin composition of the present invention comprises about 0.1 to about 20 parts by weight, preferably about 0.3 to about 15 parts by weight, further preferably about 1 to about 10 parts by weight of a light diffusing agent based on 100 parts by weight of a methyl methacrylate resin or styrene resin. When the content is less than about 0.1 parts by weight, a light diffusing property is not sufficient, and when over about 20 parts by weight, strength is not sufficient.
The particle size of the light diffusing agent, in terms of the weight-average particle size, is preferably about 1 &mgr;m or more from the standpoint of a hiding property, and about 30 &mgr;m or less, preferably about 20 &mgr;m or less from the standpoints of strength and appearance.
As the light diffusing agent, there are usually used inorganic or organic transparent fine particles having a different refractive index from that of the methyl methacrylate resin or styrene resin which is a base material. Regarding the difference between the refractive index of the light diffusing agent and the refractive index of the base material, the absolute value thereof is preferably about 0.02 or more from the standpoint of a light diffusing property, and preferably about 0.13 or less from the standpoint of light transmission. In the present invention, by making a difference in refractive index between the light diffusing agent and base material, a so-called internal diffusible property can be imparted, and a so-called external diffusible property can also be imparted by forming surface unevenness by allowing the light diffusing agent to extrude on the surface of the base material.
As the inorganic light diffusing agent, there are listed, for example, calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talk, mica, white carbon, magnesium oxide, zinc oxide and the like, and these may be surface-treated by a fatty acid and the like. As the organic light diffusing agent, there are listed, for example, styrene polymer par
Lee Rip A
Sughrue & Mion, PLLC
Sumitomo Chemical Company Limited
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