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US005307188A
United States Patent m tm Patent Number: 5,307,188
Dingwall et al. [45] Date of Patent: Apr. 26,1994
[54] COLOR LIQUID CRYSTAL DISPLAY WITH DEAD FRONT APPEARANCE HAVING OPAQUE MASK FORMED ON THE PRIMARY DISPLAY
[75] Inventors: Richard B. Dingwall, Rochester;
Lowell W. Knapp, Victor; John H.
Steele, Spencerport; James S. Celebi,
Holcomb; Virgil J. Hull, Fairport, all
ofN.Y.
[73] Assignee: Xerox Corporation, Stamford, Conn.
[21] Appl. No.: 12,491
[22] Filed: Feb. 2,1993
Related U.S. Application Data
[62] Division of Ser. No. 755,967, Sep. 6, 1991, Pat. No. 5,220,442.
[51] Int. C1.5 G02F 1/133; G02F 1/137
[52] U.S. CI 359/53; 359/67;
359/66; 359/68; 359/87
[58] Field of Search 359/53, 67, 68, 63,
359/62, 87, 89, 66; 340/765, 784; 345/38, 50,
75, 87, 88
[56] References Cited
U.S. PATENT DOCUMENTS
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4,475,806 10/1984 Daughton et al 355/14 R
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4,527,864 7/1985 Dir 359/63
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FOREIGN PATENT DOCUMENTS
0209439A1 1/1987 European Pat. Off. 359/53
3340468A1 5/1985 Fed. Rep. of Germany 359/53
1- 161220 6/1989 Japan 359/53
2- 137818 5/1990 Japan 359/63
Primary Examiner—William L. Sikes
Assistant Examiner—Tai V. Duong
Attorney, Agent, or Firm—Oliff & Berridge
[57] ABSTRACT
A liquid crystal display unit is provided which includes a primary, image-defining display and a secondary display, arranged in series with the primary display. The primary and secondary displays have equal numbers of light shutters, similarly sized and located on each display, so that when the corresponding light shutters on the primary and secondary displays are closed, substantially no light passes through the viewing side of the primary display. An opaque mask is formed on the input side of the primary display to define the shape of the image elements to be displayed. This mask covers the edges of the primary display light shutters to define the image elements display. This mask permits the primary and secondary displays to be easily aligned with each other. Color patches can be located on the light input side of the primary display light shutters so that the viewed images are in color. The use of the opaque mask to form the image elements eliminates the need to form precisely shaped color patches. Since and the mask blocks all light between light shutters, a display is provided having a true dead front. The true dead front display permits colored text displays using mimic-type electrodes to be produced. Since the secondary displays need not perform as well as the primary displays, displays which are not suitable for use as primary displays can be used as the secondary displays.
17 Claims, 6 Drawing Sheets
