Patent ID: 7939002
Filing Date: 2011-05-10
Classification: B29C,B29K,C09K

Abstract:
1. A method of producing a long roll retardation film comprising the sequential steps of: (a) casting a film forming material on an endless support to form a long roll film; (b) stretching the long roll film in a lateral direction of the long roll film while both edges of the long roll film are held employing a plurality of clips for each of the edges in a tenter, the step (b) being designated as First Process; (c) reducing distances in the lateral direction between the clips holding the both edges of the long roll film while the edges of the long roll film are held continuously from First Process with the clips, the step (c) being designated as Second Process; and (d) enlarging the distances in the lateral direction between the clips holding the both edges of the long roll film while the edges of the long roll film are held continuously from Second Process with the clips, the step (d) being designated as Third Process, wherein (i) a stretching ratio of the long roll film in First Process is 1.01 to 1.10; (ii) a stretching ratio of the long roll film in Second Process is 0.90 to 0.99 based on a width of the long roll film stretched in First Process; (iii) a stretching ratio of the long roll film in Third Process is 1.15 to 2.0 based on a width of the long roll film stretched in Second Process; (iv) distances in the lateral direction between the clips are reduced while the edges of the long roll film are continuously held after Third Process is over, wherein the long roll retardation film has a thickness of 20 to 200 μm and an in-plane retardation Ro of 100 nm or less, wherein the long roll film is one of a cellulose ester type film, a cycoolefin polymer film, a polycarbonate type film, and a polysulfon type film, and wherein the long roll retardation film has a front contrast of 900 or more.