Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-05-03
2003-08-26
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C427S201000, C427S222000, C427S226000, C427S447000, C428S407000
Reexamination Certificate
active
06610405
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to (i) a light-diffusing agent for use in, for example, a mold article having light-diffusing properties such as a light-diffusing film and a light-diffusing panel for a backlight or illuminating device of a liquid crystal display, (ii) a grain aggregate which can preferably be adopted as various surf ace treatment agents such as a matte agent and a coating material, a catalyst carrier, an additive of a resin molded material and the like, and (iii) a producing method of the grain aggregate.
BACKGROUND OF THE INVENTION
A grain aggregate is widely used in a coating material, various surface treatment agents, a catalyst carrier, an additive of a resin mold material and others. What has been highly called for in recent years is a grain aggregate of cross-linking polymeric grains having higher heat resistance, higher strength, and higher solvent resistance. The grain aggregate can be produced by, for example, a method disclosed in the Publication of Japanese Patent No. 2559833 (Date of patent: Sep. 5, 1996). According to this publication, grains are fused by adding a solvent after aggregating a polymer latex. However, this method employs an organic solvent, thereby requiring processing of the organic solvent. Further, when producing the grain aggregate of the cross-linking polymeric grains by this method, there arises such a problem that the fusion of the cross-linking polymeric grains can hardly occur by an application of heat, thereby preventing an easy formation of an aggregate.
The grain aggregate of the cross-linking polymeric grains can be produced by, for example, a method disclosed in Japanese Unexamined Patent Publication No. 70741/1990 (Tokukaihei 2-70741 published on Mar. 9, 1990). In this publication, a polymer including a carboxylic unsaturated acid is neutrally swollen so that it can be used as a seed grain, and as a second step, an emulsion-polymerization of a polymer having a composition different from that of the polymer of the seed grain is carried out so as to obtain a grain aggregate of the cross-linking polymeric grains.
However, by this method, in the emulsion-polymerization at the second step, a condition to avoid generation of a new grain should be selected. Thus, there arises a problem of limitation in composition of a polymer and/or a polymerization condition. A further problem is that the resultant grain aggregate is poor in strength and easily destroyed.
As explained, neither methods for easily producing a grain aggregate of the cross-linking polymeric grains nor a grain aggregate with the high strength have conventionally been known.
Further, the inventors of the present invention have formerly discovered that a cross-linking polymeric grain can efficiently be obtained by adopting a spray drying method to dry cross-linking polymeric grains obtained from polymerization of a mixture of vinyl-family monomers including monomers having cross-linking characteristics such as divinylbenzene and trimethylolpropane tri(meth)acrylate (Japanese Unexamined Patent Publication No. 53720/2000 [Tokukai 2000-53720 published on Feb. 22, 2000]). By this method can be obtained such a grain aggregate that has high heat resistance and high strength, maintains the shape of a cross-linking polymeric grain, and has a large specific surface area. However, recently, a demand for a further improvement in the heat resistance and the solvent resistance of the grain aggregate has been increasing.
Meanwhile, conventionally, a variety of liquid crystal display devices have been adopting a backlight to project light from a rear side of a liquid crystal. Particularly, devices such as a laptop PC which has been required to further reduce a volume and a size adopts a method for propagating light by means of a sidelit surface light source device so that the light is uniformly diffused by a light-diffusing film and the like. The light-diffusing film is commonly produced by a method for coating a surface of a transparent film which is a base material with a mixture of inorganic or organic grains and binders. Further, a light-diffusing panel is produced by a method for coating a surface of a transparent panel of glass, plastic or like with a mixture of inorganic or organic grains and binders, or a method for molding the panel by blending a resin such as a polyester resin or epoxy resin with grains.
However, the conventional light-diffusing film and light-diffusing panel have a problem such that a distribution of brightness fluctuates in accordance with a difference in angle with respect to a light projecting surface. Therefore, an improvement has been made to propagate the light by uniformly diffusing it while enhancing light transmissivity. More specifically, methods for such an improvement includes, for example, a method adopting a grain made of an organic substance, which is completely spherical in shape, for improving a ratio of grains to binders when blending the grains and the binders so as to coat the surface of the film or panel (Japanese Unexamined Patent Publication No. 35124/1993 [Tokukaihei 5-35124 published on Feb. 12, 1993]; Japanese Unexamined Patent Publication No. 16732/1996 [Tokukaihei 8-16732 published on Jan. 19, 1996]), a method for improving the shape of a surface to be coated (Japanese Unexamined Patent Publication No. 118830/1996 [Tokukaihei 8-118830 published on May 14, 1996]; Japanese Unexamined Patent Publication No. 121878/1996 [Tokukaihei 8-121878 published on May 17, 1996]), and a method for improving a burial state of grains under a surface to be coated (Japanese Unexamined Patent Publication No. 229202/1997 [Tokukaihei 9-229202 published on Sep. 5, 1997]), where particularly a coating method has been examined in various forms. A method for improving a grain itself, however, has not been taken into consideration. Accordingly, a current problem of the light-diffusing film and the light-diffusing panel is that they have not attained a sufficient distribution of brightness and light transmissivity.
SUMMARY OF THE INVENTION
It is a first object of the present invention to provide a grain aggregate having higher heat resistance, higher solvent resistance, higher strength, higher light-diffusing properties, and a large specified surface area, and a method for readily producing the grain aggregate.
In order to attain the foregoing object, the grain aggregate according to the present invention is made up of a plurality of cross-linking polymeric grains bonding together via a substance having a reactive functional group.
With this arrangement, a grain aggregate having strong bonding among the cross-linking polymeric grains can be obtained, thereby making it possible to provide a grain aggregate having the greatly improved heat resistance, solvent resistance, strength and light-diffusing properties, and the large specific surface area.
Further, in order to attain the foregoing object, the grain aggregate according to the present invention is made up of a plurality of differently composed grains of at least two types bonding together.
With this arrangement, a grain aggregate provided with the respective properties of the plurality of the differently composed grains bonding together can be obtained, thereby making it possible to provide a grain aggregate having the further improved heat resistance, solvent resistance, strength and light-diffusing properties. In addition, the grain aggregate is effective when used in, for example, various surface treatment agents such as a coating material, a matte agent and a light-diffusing agent, a catalyst carrier, an additive of a resin mold material, and others.
In order to attain the foregoing object, a producing method of the grain aggregate according to the present invention includes the step of drying by spraying a dispersion liquid containing the cross-linking polymeric grains and a substance having a reactive functional group.
The spraying is performed under no particularly limited conditions, insofar as the shape and d
Inoue Masafumi
Iriguchi Jiro
Oishi Hideki
Shimizu Shuji
Yamamoto Yasuhiro
Le H. Thi
Nippon Shokubai Co. , Ltd.
Nixon & Vanderhye P.C.
Presta Frank P.
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