METHOD FOR PRODUCING BIREFRINGENT FILM, OPTICAL FILM AND IMAGE DISPLAY DEVICE USING THE SAME

• Main Authors: TSUCHIMOTO, KAZUKI, YOSHIMI, HIROYUKI, ISHIBASHI, KUNIAKI
• Format: Patent
• Language: English; French; Japanese
• Published: 30.06.2005
• Edition: 7
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; DEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH ISMODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THEDEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY,COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g.SWITCHING, GATING, MODULATING OR DEMODULATING; FREQUENCY-CHANGING; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULARARTICLES; NON-LINEAR OPTICS; OPTICAL ANALOGUE/DIGITAL CONVERTERS; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICAL LOGIC ELEMENTS; OPTICS; PERFORMING OPERATIONS; PHYSICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION; TECHNICAL SUBJECTS COVERED BY FORMER USPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

A method for producing a birefringent film involving a step of stretching a polymer film, which comprises stretching the polymer film in its width direction and simultaneously allowing it to shrink in its longitudinal direction, in such a manner that the change ratio of the length in the width direction (STD) by the above stretching and the change ratio of the length in the longitudinal direction (SMD) by the above shrinkage, with the proviso that the lengths of the film in the width and longitudinal directions before the stretching or shrinkage are taken as 1, respectively, satisfy the following formula (1): (1/STD)<1/2> <= SMD < 1 (1). The birefringent film exhibits excellent uniformity in the in-plane phase contrast, the thickness direction phase contrast and the orientation axis. L'invention concerne un procédé qui permet de produire un film biréfringent, qui comprend une étape d'étirement d'un film polymère lors de laquelle on étire le film polymère dans le sens de la largeur et, simultanément, on le laisse rétrécir dans le sens de la longueur, de manière que le rapport de changement de longueur dans le sens de la largeur (STD) sous l'effet de l'étirement précité et le rapport de changement de longueur dans le sens de la longueur (SMD) sous l'effet du rétrécissement précité, pour autant que les longueurs du film dans le sens de la largeur et de la longueur avant l'étirement ou le rétrécissement soit considérées comme 1, respectivement, satisfont la formule (1) suivante : (1/STD)<1/2> </= SMD < 1 (1). Le film biréfringent de l'invention présente une excellente uniformité dans le contraste de phase dans le plan, dans le contraste de phase dans le sens de l'épaisseur et dans l'axe d'orientation.