| Compensators for liquid crystal displays -> Monitor Keywords |
|
|
  Compensators for liquid crystal displaysThe Patent Description & Claims data below is from USPTO Patent Application 20060238682. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE [0001] This application is a continuation of U.S. patent application Ser. No. 10/767,708, filed Jan. 29, 2004; which is a continuation-in-part of U.S. patent application Ser. No. 10/365,332 filed Feb. 12, 2003, which is incorporated by reference herein. BACKGROUND OF THE INVENTION [0002] Liquid crystal displays, such as for example, twisted nematic (TN), single domain vertically aligned (VA), optically compensated birefringent (OCB) liquid crystal displays and the like, 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. [0003] 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. [0004] One 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. [0005] Another viewing angle characteristic is the color shift of the display with changes in viewing angle. Color shift refers to the change in the color coordinates (e.g., the color coordinates based on the CIE 1931 standard) of the light from the display as viewing angle is altered. Color shift can be measured by taking the difference in the chromaticity color coordinates (e.g., .DELTA.x or .DELTA.y) at an angle normal to the plane containing the screen and at any non-normal viewing angle or set of viewing angles. The definition of acceptable color shift is determined by the application, but can be defined as when the absolute value of .DELTA.x or .DELTA.y exceeds some defined value, for example, exceeds 0.05 or 0.10. For example, it can be determined whether the color shift is acceptable for a desired set of viewing angles. Because the color shift may depend upon the voltage to any pixel or set of pixels, color shift is ideally measured at one or more pixel driving voltages. [0006] Yet another viewing angle characteristic that can be observed is substantial non-uniform behavior of gray scale changes and even the occurrence of gray scale inversion. The non-uniform behavior occurs when the angular dependent transmission of the liquid crystal layer does not monotonically follow the voltage applied to the layer. Gray scale inversion occurs when the ratio of intensities of any two adjacent gray levels approaches a value of one, where the gray levels become indistinguishable or even invert. Typically, gray scale inversion occurs only at some viewing angles. [0007] Compensators have been proposed to address these issues. One concept includes a compensator film made of discotic molecules. One drawback of current discotic compensators is the typical occurrence of comparatively large color shifts. Other concepts include specific combinations of birefringent layers. There is a need for new compensator structures to provide improved or desired viewing angle characteristics. SUMMARY OF THE INVENTION [0008] Generally, the present invention relates to optical compensators for displays, such as liquid crystal displays, as well as the displays and other devices containing the optical compensators. [0009] In one embodiment, an optical stack includes a first liquid crystal layer and a j-retarder disposed on the liquid crystal layer. The j-retarder includes a simultaneous biaxially stretched polymeric film being substantially non-absorbing and non-scattering for at least one polarization state of visible light. The j-retarder has x, y, and z orthogonal indices of refraction where at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an absolute value of an out-of-plane retardance being 55 nm or greater. [0010] In a further embodiment, an optical stack includes a polarizer layer and a j-retarder disposed on the polarizer layer. The j-retarder includes a simultaneous biaxially stretched polymeric film being substantially non-absorbing and non-scattering for at least one polarization state of visible light. The j-retarder has x, y, and z orthogonal indices of refraction where at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an absolute value of an out-of-plane retardance being 55 nm or greater. [0011] In another embodiment, a liquid crystal display includes a first liquid crystal layer, a light modulating device, and a j-retarder disposed disposed between the first liquid crystal layer and the light modulating device. The j-retarder includes a simultaneous biaxially stretched polymeric film being substantially non-absorbing and non-scattering for at least one polarization state of visible light. The j-retarder has x, y, and z orthogonal indices of refraction where at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an absolute value of an out-of-plane retardance being 55 nm or greater. [0012] In a further embodiment, a liquid crystal display includes a polarizer layer, a light modulating device, and a j-retarder disposed between the polarizer layer and the light modulating device. The j-retarder includes a simultaneous biaxially stretched polyolefin film being substantially non-absorbing and non-scattering for at least one polarization state of visible light. The j-retarder has x, y, and z orthogonal indices of refraction where at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an absolute value of an out-of-plane retardance being 55 nm or greater. [0013] The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures, Detailed Description and Examples which follow more particularly exemplify these embodiments. BRIEF DESCRIPTION OF THE DRAWINGS [0014] 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: [0015] FIG. 1 is a is a schematic illustration of a coordinate system with an optical film element; [0016] FIG. 2 is a top schematic view of a tenter apparatus for use to form the optical film element; [0017] FIG. 3 is a schematic cross-sectional view of an optical compensator stack according to the present invention; [0018] FIG. 4 is a schematic cross-sectional view of an optical compensator stack according to the present invention; [0019] FIG. 5 is a schematic cross-sectional view of a liquid crystal display according to the present invention; and [0020] FIG. 6 is a schematic cross-sectional view of a liquid crystal display according to the present invention. Continue reading... Full patent description for Compensators for liquid crystal displays Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Compensators for liquid crystal displays patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Compensators for liquid crystal displays or other areas of interest. ### Previous Patent Application: Transflective liquid crystal display with vertical alignment Next Patent Application: Display device Industry Class: Liquid crystal cells, elements and systems ### FreshPatents.com Support Thank you for viewing the Compensators for liquid crystal displays patent info. IP-related news and info Results in 5.51252 seconds Other interesting Feshpatents.com categories: Software: Finance , AI , Databases , Development , Document , Navigation , Error |
||
