METHOD FOR MANUFACTURING POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE

• Main Authors: TSUCHIMOTO KAZUYOSHI, YOSHIKAWA SENRI, SUGINO YOICHIRO, HAMAMOTO EIJI, KUSUMOTO SEIICHI
• Format: Patent
• Language: English
• Published: 26.10.2001
• Edition: 7
• Subjects: 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; NON-LINEAR OPTICS; OPTICAL ANALOGUE/DIGITAL CONVERTERS; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICAL LOGIC ELEMENTS; OPTICS; PHYSICS; TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate making high transmittance and high polarization degree compatible with each other and a liquid crystal display device. SOLUTION: The method for manufacturing the polarizing plate comprises a step for dyeing a polyvinyl alcohol(PVA) film with iodine or a dye having dichroism, a step for cross-linking the PVA film with a cross-linking agent and a step for stretching the PVA film with rolls in either of the steps. In cross-linking the PVA film in a bath containing the cross-linking agent after dyeing it in a dyeing bath, the stretch ratio is kept in the range of 1.01-4.5 times the length of a PVA film raw sheet for the film raw sheet to dyeing treatment finish. Immersion treatment at least in a bath containing 4-20 wt.% iodide is carried out after the cross-linking treatment in the bath containing the cross-linking agent, and at the same time and stretch ratio after the cross- linking treatment in the bath is kept in the range of <=3 times the previous length. Furthermore, the total stretch ratio from the PVA film raw sheet to the final product is kept in the range of 4.5-8 times the initial length.