| 摘要 |
PURPOSE:To continuously obtain a polyester film of 0.1% or less in its thermal contraction by contracting a non-heat treatment film gradually in a heating oven while keeping it run in a specified temperature range. CONSTITUTION:Upon heat treatment, the film is in a state of being hung or sagged and the decision of the contraction rate or excessive supplying rate is made in such a manner that the film is pre-heated at T+10 deg.C and it is confirmed wherein the contraction rate is S%, and then on heat treatment, a stably slackened heat treatment is given while adjusting the excessive supplying rate in the range of maximum S+0.3% in accordance with its heat treating temperature. By performing the slackening heat treatment of a biaxially oriented polyester film in the temperature proximity T+5-T+15 of about 10 deg.C higher than a predetermined temperature, an effect is realized that the maintaining condition of plane becomes the most. The term selection of the heat treatment temperature or excessive supplying rate for restraining the thermal contraction of a film into 0.1% or less is a wide range, whereas condition not damaging the plane or flatness of the film is the condition restricted herein extremely narrow. |
