Transflective mode liquid crystal display with phosphor illumination

• US 5,146,355 A
• Filed: 03/18/1991
• Issued: 09/08/1992
• Est. Priority Date: 10/23/1986
• Status: Expired due to Fees

• Current Assignee: 1294339 Ontario, Inc.
• Original Assignee: Litton Systems Canada Limited (L3Harris Technologies, Inc.)
• Inventors: Farrell, James F., Prince, John C.
• Primary Examiner(s): Howell, Janice A.
• Assistant Examiner(s): TRICE, RONALD
• Application Number:
  US07/671,024
• Time in Patent Office: 540 Days
• Field of Search: 359/50, 359/71, 359/68, 359/48
• US Class Current: 349/71
• CPC Class Codes: G02F 1/133617 Illumination with ultraviolet light; Luminescent elements or materials associated to the cell
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night
• CPC Class Codes: G09F 9/35 being liquid crystals G09F9/302 takes precedence; liquid crystal materials C09K19/00; liquid crystal panels comprising a number of electrodes in a single cell per se G02F1/13

Abstract

A transflective liquid crystal display provides a high quality color image and efficient energy utilization. A layer of liquid cyrstal material is controlled by a transparent electrode matrix. A matrix of (primary color emitting) phosphors is aligned with a matrix of transparent electrodes for controlling the shuttering of the liquid crystal layer. A source of fluorescent energy excites the phosphors. A first dichroic filter and a second dichroic filter are located behind the liquid crystal layer. The first filter reflects untraviolet light and transmits visible light while the second filter transmits ultraviolet light and reflects visible light. The two filters are arrayed so that the phosphors are efficiently energized by the ultraviolet light source while ambient illumination is utilized, the display thereby providing both transmissive and reflective modes of operation. The phosphor matrix is separated from the liquid crystal shutter layer by substantially less than the dot pitch of the phosphor matrix layer to maintain the requisite registration and minimize cross-contamination of colors.

Claims

1. A transflective mode liquid crystal display comprising in combination:

(a) a layer of liquid crystal material;

(b) an active planar array of transparent control electrodes on a first side of said layer of liquid crystal material for forming a corresponding array of adjacent, modulated light-conducting cells within said layer of liquid crystal material;

(c) a planar matrix layer of discrete phosphor elements of predetermined dot pitch, said layer being located on the opposed, second side of said layer of liquid crystal material;

(d) an ultraviolet light source located behind said second side of said layer of liquid crystal material and behind said planar matrix of discrete phosphor elements for irradiating said phosphor elements with ultraviolet light;

(e) a dilute color filter comprising a planar matrix of light-absorbing, wide-passband dye elements, each of said dye elements being in alignment with a like color emitting one of said phosphor elements located between said phosphor layer and said layer of liquid crystal material and adjacent a transparent counterelectrode; and

(f) the spacing between said layer of discrete phosphor elements and said planar array of transparent control electrodes does not exceed one-tenth of said dot pitch.

2. A display as defined in claim 1 wherein said planar array of transparent control electrodes is formed upon an absorptive bus mask.

3. A display as defined in claim 2 further including:

(a) a first dichroic filter behind said planar matrix of discrete phosphor elements and in front of said ultraviolet light source for transmitting ultraviolet light to said phosphor layer and for reflecting incident visible ambient light;

(b) a second dichroic filter means in front of said planar matrix for transmitting visible ambient light to said matrix and for reflecting incident ultraviolet light incident thereupon; and

(c) a planarizing layer on the front of said phosphor matrix.

4. A display as defined in claim 3 wherein said planarizing layer is fabricated of silica-dioxide.

5. A display as defined in claim 3 wherein said planarizing layer is fabricated of polyimide.

6. A display as defined in claim 3 further including a transparent counterelectrode layer located adjacent said second side of said layer of liquid crystal material.

7. A display as defined in claim 6 further characterized in that said transparent counterelectrode layer is located between said phosphor layer and said layer of liquid crystal material.