Multilayer heat-conductive sheet, and manufacturing method for multilayer heat-conductive sheet
Peeling due to interfacial fracture between a tack-free layer 11 and a heat-conductive layer is prevented. In the tack-free layer, an inorganic filler having a median diameter of 0.5 μM or more is contained in a thermoplastic resin having a glass transition temperature of 60° C. or higher to form concaves and convexes on an adhesive surface. Then, the heat-conductive layer being in contact with the adhesive surface is disposed. The adhesion between the tack-free layer and the heat-conductive layer is strengthened by an anchor effect caused by the concaves and convexes of the adhesive surface, without strengthening the adhesion of the surface opposite to the adhesive surface.
1. A method of manufacturing a multilayer heat-conductive sheet of which a tack-free layer and a heat-conductive layer are in contact with each other, the method comprising the steps of:
a tack-free layer formation step for forming the tack-free layer having an adhesive surface having a Bekk smoothness within a range of at least 20 seconds and at most 300 seconds by including a thermoplastic resin having a glass transition temperature of 60° C. or higher with an inorganic filler having a median diameter of at least 0.5 μm in a manner such that a part of the inorganic filler is projected from a layer of the thermoplastic resin; and
a heat-conductive layer disposition step for bringing the heat-conductive layer including a binder resin in contact with the adhesive surface of the tack-free layer.
2. The method of manufacturing a multilayer heat-conductive sheet according to claim 1 ,
wherein the binder resin includes an acrylic-based resin having a glass transition temperature within a temperature range of −80° C. or higher and 15° C. or lower, and
wherein a resin having a glass transition temperature within a range of 60° C. or higher and 110° C. or lower is used for the thermoplastic resin.
3. The method of manufacturing a multilayer heat-conductive sheet according to claim 2 , wherein a resin that forms the tack-free layer is a polyvinyl butyral resin, a polyester resin, or a urethane resin.
4. The method of manufacturing a multilayer heat-conductive sheet according to claim 1 , wherein a resin that is incompatible with the binder resin is used as the thermoplastic resin.
5. The method of manufacturing a multilayer heat-conductive sheet according to claim 1 , wherein a value of a ratio of the inorganic filler relative to the thermoplastic resin in the tack-free layer is 5:95 or more in terms of weight ratio.