| 摘要 |
PURPOSE: To give excellent deep-drawing nature, flatness and heat resistance, and very few coarse particles included in a base film for transfer as well by limiting second order transition temperature, mean refractive index, degree of plane orientation and heat of dissolution, respectively, of the film. CONSTITUTION: Second order transition temperature (Tg) must be at least 70 deg.C in the state of film, for instance, what is cheaply obtained with industrial means is copolymerized polyester having polyethylene terephthalate as the base and added with neopenthyl glycol and 1,4-cyclohexane dimethanol as diol components. It is also necessary that degree of plane orientationΔP expressed withΔP=(nγ+nβ)/2-nαis from 0.05 to 0.14, where the largest refractive index in the film plane is denoted as nγ, refractive index in the direction normal to it as nβ, that in the direction of thickness as nα; also that average value of mean refractive index n of the film expressed as (nα+nβ+nγ)/3 is 1.598 or smaller; and it is further an important condition that heat of melting of the filter is 8 cal/G or smaller. |
