Provision of a releasing layer transfer film which can form, in a simple manner, a releasing layer on a COF flexible printed wiring board, the releasing layer preventing melt adhesion of an insulating layer to a heating tool, thereby enhancing productivity and reliability of semiconductor devices produced by use of a semiconductor chip mounting line.The releasing layer transfer film 1 for forming a releasing layer onto an insulating layer serving as a component layer of a COF flexible printed wiring board, the releasing layer transfer film includes a transfer film substrate 2 and a transferable releasing layer 3 provided on a surface of the transfer film substrate 2, wherein the transferable releasing layer 3 is formed from a releasing agent and can be transferred onto the insulating layer.

The present invention provides a COF flexible printed wiring board whose insulating layer is not melt-adhered to a heating tool, to thereby enhance reliability and productivity of a semiconductor chip mounting line, and also provides a method of producing the COF flexible printed wiring board. The COF flexible printed wiring board contains an insulating layer, a wiring pattern, on which a semiconductor chip being mounted, formed of a conductor layer provided on at least one side of the insulating layer and a releasing layer, wherein the releasing layer is formed from a releasing agent containing at least one species selected from a silane compound and silica sol and is provided on a surface of the insulating layer, which is opposite to the mounting side of the semiconductor chip.