In IPS mode or VA mode liquid crystal display, polarizers are arranged on front and rear surfaces of a liquid crystal cell so that absorption axes (vibrating directions of light to cause absorption) become perpendicular to each other. A long polarizing film prepared by dyeing a polyvinyl alcohol film or the like with a dichroic substance has been heretofore formed in such a manner that the long film is uniaxially stretched in the lengthwise direction of the long film. In this case, the absorption axis of the polarizing film appears in the lengthwise direction.
In use of the conventional long polarizing film, the long film is cut into film pieces by a predetermined size. The film pieces are used in combination so that the lengthwise direction based on the long film, which is the direction of flow of the film at the time of production of the film (MD direction: Machine Direction), corresponds to a direction perpendicular to the lengthwise direction (TD direction: Transverse Direction). Thus, the orthogonal relation between the absorption axes thereof on the front and rear surfaces of the liquid crystal cell can be achieved. Incidentally, hereinafter, the MD direction is referred to as “lengthwise direction” and the TD direction is referred to as “widthwise direction”, simply.
Accordingly, in the aforementioned method, the polarizing film pieces are used to have the relation in which the polarizing film pieces are rotated by 90 degrees on the basis of the absorption axes. Therefore, when polarizing film pieces of the same size are prepared to be applied to the front and rear surfaces of the liquid crystal cell, the width (widthwise length) of the long film is a limit size thereof. In this case, a sufficient widthwise length could not be obtained in the conventional polarizing film since shrinkage occurred in the widthwise direction in a uniaxial stretching step or the like. Then, there was a problem that it was difficult to increase the screen size of liquid crystal display and particularly to obtain a sufficient transverse length. There is a limitation in enlarging of the conventional long film in the widthwise direction because of accuracy in processing into the polarizing film such as the accuracy of orientation, the degree of polarization, etc.
On the other hand, for optical compensation of the retardation due to the liquid crystal cell, particularly for compensation of the viewing angle, the polarizing film and the retardation film are needed so that the slow axis of the retardation film (the direction of the maximum in-plane refractive index) becomes perpendicular to the absorption axis of the polarizing film. In this case, it is advantageous that the polarizing film and the retardation film each provided in the form of rolls can be laminated each other as long films from the point of view of efficiency in production of a laminated film comprising the laminate thereof.
The above can be achieved by stretching a long film in the widthwise direction to form a retardation film having a slow axis in the widthwise direction. In this case, there was a drawback that the direction of the slow axis was apt to vary because of a boing phenomenon that the center portion of the film progressed compared with the case where the long film is stretched in the lengthwise direction to provide a retardation film having a slow axis in the lengthwise direction.
[Reference 1] JP 3-24502
[Reference 2] JP 3-33719
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