Compensators for liquid crystal displays and the use and manufacture of the compensators

#Twisted nematic (TN) liquid crystal displays have inherently narrow and non-uniform viewing angle characteristics. Such viewing angle characteristics can describe, at least in part, the optical performance of a display. Characteristics such as contrast, color, and gray scale intensity profile can vary substantially in uncompensated displays for different viewing angles. There is a desire to modify these characteristics from those of an uncompensated display to provide a desired set of characteristics as a viewer changes positions horizontally, vertically, or both and for viewers at different horizontal and vertical positions. For example, in some applications there may be a desire to make the viewing characteristics more uniform over a range of horizontal or vertical positions.

#The range of viewing angles that are important can depend on the application of the liquid crystal display. For example, in some applications, a broad range of horizontal positions may be desired, but a relatively narrow range of vertical positions may be sufficient. In other applications, viewing from a narrow range of horizontal or vertical angles (or both) may be desirable. Accordingly, the desired optical compensation for non-uniform viewing angle characteristics can depend on the desired range of viewing positions.

#One important viewing angle characteristic is the contrast ratio between the bright state and the dark state of the liquid crystal display. The contrast ratio can be affected by a variety of factors including, for example, leakage of light at different viewing angles.

#The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:

#FIG. 1 is a schematic illustration of a coordinate system with an optical element;

#FIG. 2 is a further schematic illustration of the coordinate system;

#While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

#The present invention is believed to be applicable to optical compensators for displays, such as liquid crystal displays, as well as the displays and other devices containing the optical compensators and methods of making and using the optical compensators, displays, and other devices. While the present invention is not so limited, an appreciation of various aspects of the invention will be gained through a discussion of the examples provided below.

#The optical compensators can be formed using a variety of different optical elements. Among these optical elements are o-plates, c-plates, a-plates, biaxial retarders, twisted retarders, and other retarders. Information regarding o-plates, c-plates, and a-plates can be found, for example, in Yeh et al., Optics of Liquid Crystal Displays, John Wiley & Sons, New York (1999), U.S. Pat. Nos. 5,504,603, 5,557,434, 5,612,801, 5,619,352, 5,638,197, 5,986,733, and 5,986,734, and PCT Patent Applications Publication Nos. WO 01/20393 and WO 01/20394, all of which are incorporated herein by reference.