1
POLARIZING PLATE WITH OPTICAL
COMPENSATION LAYER, METHOD OF
PRODUCING THE SAME, AND LIQUID
CRYSTAL PANEL, LIQUID CRYSTAL
DISPLAY, AND IMAGE DISPLAY INCLUDING 5
THE SAME
CROSS-REFERENCE TO RELATED
APPLICATION
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The present patent application claims priority based on prior-filed Japanese Patent Application No. 2006-191246 (filing date: Jul. 12, 2006).
BACKGROUND OF THE INVENTION 15
1. Field of the Invention
The present invention relates generally to a polarizing plate with optical compensation layers, a method of producing the same, and a liquid crystal panel, a liquid crystal display, and 20 an image display, each of which includes the same.
2. Description of the Related Art
A semitransparent-reflective liquid crystal display has been proposed as a vertical alignment (VA) mode liquid crystal display in addition to a transmission liquid crystal display 25 and a reflective liquid crystal display (see, for example, JP11 (1999)-242226AandJP 2001-209065 A). The semitransparent-reflective liquid crystal display allows displays to be visible by using outside light in bright places as in the reflective liquid crystal display and an internal light source such as a 30 backlight in dark places. In other words, the semitransparentreflective liquid crystal display employs a display system of combination of the reflective and transmission types. It switches the display mode into either a reflective mode or a transmission mode according to the brightness of the sur- 35 rounding. Accordingly, the semitransparent-reflective liquid crystal display can provide a clear display even when the surrounding is dark, while reducing consumption power. Therefore, it is used suitably for display parts of mobile devices. 40
An example of such a semitransparent-reflective liquid crystal display is a liquid crystal display that includes an upper substrate, a lower substrate, a liquid crystal layer, and a reflective film that is allowed to function as a semitransparentreflective plate. The liquid crystal layer is sandwiched 45 between the upper substrate and the lower substrate. The reflective film is provided on the inner side of the lower substrate and is formed of a metal thin film such as aluminum that is provided with a window formed for light transmission. In this type of liquid crystal display, in the case of the reflec- 50 tive mode, outside light incident from the upper substrate side is transmitted through the liquid crystal layer, is then reflected by the reflective film disposed on the inner side of the lower substrate, is transmitted through the liquid crystal layer again, and is then emitted from the upper substrate side to contribute 55 to the display. On the other hand, in the case of the transmission mode, light emitted from a backlight that has entered from the lower substrate side passes through the window of the reflective film to pass through the liquid crystal layer and is then emitted from the upper substrate side to contribute to 60 the display. Accordingly, in the region where the reflective film is formed, the region where the window is formed serves as a transmissive display region and the other region serves as a reflective display region. However, in these VA mode liquid crystal displays, especially liquid crystal displays of a reflec- 65 tion type, a semitransparent type, and a semitransparent-reflective type, there is a problem in that light leakage is caused
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in a black display which reduces the contrast. Accordingly, there is a demand for the solution conventionally.
On the other hand, the liquid crystal display requires a polarizing plate. An elliptically polarizing plate including a retardation film stacked on a polarizing plate as an optical compensation layer is used increasingly. The elliptically polarizing plate is also referred to as a "polarizing plate with optical compensation layers". It is used for supplying polarized light to the liquid crystal display while providing wide viewing angle properties at the same time. The polarizing plate with optical compensation layers is required to have not only the wide viewing angle properties but also a function that allows circularly polarized light to be obtained over a wide range of light wavelengths and contrast to be improved by preventing the above-mentioned light leakage from occurring in a black display. Moreover, in order to improve the brightness and to reduce the weight and thickness of the liquid crystal display, it is also required to improve the brightness and to reduce the weight and thickness of the polarizing plate with optical compensation layers. In addition, the polarizing plate with optical compensation layers has a problem of "thermal irregularity", that is, optical functions become uneven due to heat. This problem occurs because the thickness thereof is too thick.
SUMMARY OF THE INVENTION
Therefore, it is an obj ect of the present invention to provide a polarizing plate with optical compensation layers that compensates the viewing angle with respect to a liquid crystal cell, allows circularly polarized light to be obtained over a wide wavelength range, contributes to an improve in brightness and a reduction in thickness, prevents thermal irregularity from occurring, and can effectively prevent light leakage from occurring in a black display. Other embodiments of the present invention are a liquid crystal panel, a liquid crystal display, and an image display, each of which includes the polarizing plate of the present invention.
A polarizing plate with optical compensation layers of the present invention includes a polarizer, a first optical compensation layer, and a second optical compensation layer that are stacked together in this order. The first optical compensation layer is formed of a liquid crystal compound and has a relationship of nx>ny=nz and an in-plane retardation Re1 in the range of 100 to 170 nm. The second optical compensation layer has a relationship of nx=ny>nz and a thickness-direction retardation Rth2 in the range of 30 to 400 nm. The angle formed between an absorption axis of the polarizer and a slow axis of the first optical compensation layer is in the range of 25 to 65 degrees in the clockwise direction (-) or in the counterclockwise direction (+) with respect to the absorption axis of the polarizer.
The liquid crystal panel of the present invention includes a polarizing plate with optical compensation layers of the present invention and a liquid crystal cell. The second optical compensation layer is disposed on the side that is close to the liquid crystal cell, and the second optical compensation layer is disposed on the visible side of the liquid crystal cell.
The liquid crystal display of the present invention is a liquid crystal display including a liquid crystal panel of the present invention.
The image display of the present invention is an image display including a polarizing plate with optical compensation layers of the present invention.
