BASIC COMPOSITE FILM HAVING GOOD UV CUT-OFF AND SEE-THROUGH PROPERTIES, PRACTICAL COMPOSITE FILM USING THE SAME, AND MANUFACTURE OF THEM

摘要

PROBLEM TO BE SOLVED: To obtain a thin, soft film which cuts off near UV rays well, and is bloomingless. SOLUTION: A basic composite film consists of an UV cut-off layer and a migration obstructing layer which are laminated on both side of the UV cut-off layer. The UV cut-off layer contains an UV absorbing agent which absorbs near ultraviolet rays well, and the amount of the agent corresponds at least to the solubility at room temperature. The migration obstructing layers are formed from an oxygen-containing resin, and at least one of them is laminated by coextrusion with the UV cut-off layer. Moreover, in a practical composite film, on one side of the basic composite film, for example, polyolefin inner skin layer and/or on the other side, for example, a nylon outer skin layer are laminated. The adjacent two layers of one of the two composite films are coextruded or lamination-bonded with an adhesive polymer placed between them. Therefore, the following is made possible: ultraviolet transmittance 20% or less, visible light transmittance 80% or more, no blooming of UV absorbing agent, no deterioration of packaged contents after a long period, and durable transparency and oxygen barrier properties.