Anti-fogging sheets and trays using thereof

Abstract

An anti-fogging tray is obtained by coating a base styrenic resin sheet having a projection with a height of 0.2 to 2 μm, in which an average density of the projection is 5 to 50 per square millimeter, with an anti-fogging agent to mold the sheet into a tray. The anti-fogging agent comprises 1 to 100 parts by weight of a hydrophilic polymer (e.g., a polysaccharide, a polyvinylpyrrolidone), and 0 to 100 parts by weight of a silicone oil, relative to 100 parts by weight of a polyhydric alcohol fatty acid ester (e.g., a sucrose fatty acid ester, a polyglycerin fatty acid ester). In the base resin sheet, a coating layer of the anti-fogging agent may be formed on one side of the base resin sheet and a release layer having a wetting index of 30 to 55 dyn/cm may be formed on the other side of the base resin sheet. The projection with a height of 0.2 to 2 μm may be formed on the other side at an average density of about 5 to 50 per square millimeter. The present invention provides a resin sheet and a tray which have high anti-fogging property and mold-releasing property (or antiblocking property).

What is claimed is:  
     
         1 . A coated resin sheet comprising a base resin sheet and a coating layer formed on at least one side of the base resin sheet, wherein the coating layer comprises a polyhydric alcohol fatty acid ester and a hydrophilic polymer, a projection with a height of 0.2 to 2 μm is formed on the surface of the coating layer, and an average density of the projection is 5 to 50 per square millimeter.  
     
     
         2 . A sheet according to  claim 1 , wherein the polyhydric alcohol fatty acid ester comprises at least one member selected from the group consisting of a sucrose fatty acid ester and a polyglycerin fatty acid ester.  
     
     
         3 . A sheet according to  claim 1 , wherein the hydrophilic polymer comprises at least one member selected from the group consisting of anon-ether-series hydrophilic polymer and an ether-series hydrophilic polymer.  
     
     
         4 . A sheet according to  claim 3 , wherein the non-ether-series hydrophilic polymer comprises at least one member selected from the group consisting of a polysaccharide, an acrylic acid-series polymer or a salt thereof, and a homo- or copolymer of vinylpyrrolidone; and the ether-series hydrophilic polymer comprises at least one member selected from the group consisting of a polyoxyethylene-polyoxypropylene block copolymer, and a nonionic surfactant having an oxyethylene unit.  
     
     
         5 . A sheet according to  claim 1 , wherein the coating layer comprises 1 to 100 parts by weight of the hydrophilic polymer and 0 to 100 parts by weight of a silicone oil relative to 100 parts by weight of the polyhydric alcohol fatty acid ester.  
     
     
         6 . A sheet according to  claim 1 , wherein the coating layer comprises 0 to 50 parts by weight of a silicone oil relative to 100 parts by weight of the polyhydric alcohol fatty acid ester.  
     
     
         7 . A sheet according to  claim 1 , wherein the coating layer is formed on one side of the base resin sheet, and a wetting index of the other side of the base resin sheet is 30 to 55 dyn/cm.  
     
     
         8 . A sheet according to  claim 7 , wherein a projection with a height of 0.2 to 2 μm is formed on the other side of the base resin sheet, and an average density of the projection is 5 to 50 per square millimeter.  
     
     
         9 . A sheet according to  claim 8 , wherein a release layer comprising a silicone oil is formed on the other side of the base resin sheet.  
     
     
         10 . A sheet according to  claim 1 , wherein the base resin sheet comprises a styrenic resin.  
     
     
         11 . A sheet according to  claim 10 , wherein the base styrenic resin sheet comprises 100 parts by weight of a styrenic resin, and 0.001 to 5 parts by weight of a crosslinked organic particle.  
     
     
         12 . A sheet according to  claim 10 , wherein the base styrenic resin sheet comprises 100 parts by weight of a styrenic resin, 0.2 to 1.5 parts by weight of a rubber-reinforced styrenic resin, and 0.003 to 0.05 parts by weight of a crosslinked styrenic resin particle.  
     
     
         13 . A coated resin sheet comprising a base resin sheet, a coating layer formed on one side of the base resin sheet, and a release layer formed on the other side of the base resin sheet, wherein the coating layer comprises a polyhydric alcohol fatty acid ester, a hydrophilic polymer, and a silicone emulsion; the release layer comprises a silicone emulsion; in the coating layer, the proportion of the silicone emulsion as a solid matter is 0 to 30 parts by weight relative to 100 parts by weight of the polyhydric alcohol fatty acid ester; a projection with a height of 0.2 to 2 μm is formed on the surfaces of the coating layer and the release layer; and an average density of the projection is 5 to 30 per square millimeter.  
     
     
         14 . A process for producing a sheet, which comprises forming a coating layer on at least one side of a base resin sheet having a projection with a height of 0.2 to 2 μm to give a sheet recited in  claim 1 , wherein an average density of the projection is 5 to 50 per square millimeter.  
     
     
         15 . A tray formed with a sheet recited in  claim 1.