Laminate sheet and manufacturing method therefor
A method for manufacturing a laminate sheet including a fluororesin film and a silicone rubber sheet that are adhered to one another, where the fluororesin film has a reactive functional group as a result of a surface treatment, the side with the reactive functional group is overlapped with an organic peroxide-containing millable-type silicone rubber composition, where the silicone rubber composition is sheet-shaped and the organic peroxide has a one-minute half-life temperature in the range of 100−150° C., and the silicone rubber composition is cured by being heated under pressure at 90-135° C. The laminate sheet has a peel adhesion strength of 3N or more. The four corners of a 120 mm square test sample of the laminate sheet do not curve into one end of a semicircular arc shape or one end of a C shape, and the average warpage value of the four corners is 35 mm or less.
1. A method of manufacturing a laminate sheet, the method comprising the steps of:
(1) providing a fluororesin film with a thickness of 10-1000 μm, wherein a surface of the fluororesin film has a reactive functional group as a result of a surface treatment, wherein the reactive functional group is selected from the group consisting of an unsaturated aliphatic hydrocarbon group, an alkenyl group, an epoxy group, an acryloxy group, a methacryloxy group, an amide group, a glycidyl group, a combination of a carbonyl group and an epoxy group, and a combination of a carbonyl group and a glycidyl group,
(2) providing a millable silicone rubber composition sheet with a thickness of 0.2-5.0 mm, wherein the millable silicone rubber composition sheet comprises a millable silicone rubber composition containing (a1) a hydrophobized reinforcing silica filler or (a2) a reinforcing silica filler and a hydrophobizing agent, and (b) an organic peroxide having a one-minute half-life temperature in a temperature range of 100−150° C.;
(3) overlapping the fluororesin film and the millable silicone rubber composition sheet so that a side of the fluororesin film having the reactive functional group as a result of the surface treatment contacts the silicone rubber composition sheet; and
(4) curing the millable silicone rubber composition sheet by heating under pressure at 90-135° C. to produce the laminate sheet, which is characterized in that the fluororesin film and a silicone rubber sheet formed by curing the millable silicone rubber composition sheet adhere to one another, the laminate sheet has a peel adhesion strength of 5N/25 mm or more as measured on a test strip of the laminate sheet in accordance with JIS K6854-2, and an average warpage value of the four corners of a 120 mm square test sample of the laminate sheet is 35 mm or less.
2. The method of manufacturing the laminate sheet according to claim 1 , wherein the organic peroxide is selected from the group consisting of diacylperoxides and peroxyesters.
3. The method of manufacturing the laminate sheet according to claim 1 , wherein, after curing the millable silicone rubber composition sheet by heating under pressure at 90-135° C., the laminate sheet is placed in hot wind to remove decomposed products of the organic peroxide.
4. A laminate sheet, manufactured according to the method of claim 1 , wherein:
(a) the fluororesin film has the reactive functional group on at least one side of the film as a result of the surface treatment; and
(b) the silicone rubber sheet has a thickness of 0.2-5.0 mm.
5. The laminate sheet according to claim 4 , wherein the fluororesin film is selected from the group consisting of a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) film, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) film, and a polytetrafluoroethylene (PTFE) film.