Liquid crystal device having LEDs of a wide polar lighting angle, the polar angle determining the LEDs spacing

• US 5,499,120 A
• Filed: 12/22/1994
• Issued: 03/12/1996
• Est. Priority Date: 06/26/1992
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hansen, Ingolf G.
• Primary Examiner(s): Gross, Anita Pellman
• Assistant Examiner(s): Ton, Toan
• Application Number:
  US08/362,587
• Time in Patent Office: 446 Days
• Field of Search: 359/48, 359/83, 359/49, 359/50
• US Class Current: 349/62
• CPC Class Codes: G02F 1/133385 with cooling means, e.g. fans
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: G02F 1/1397 the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells
• CPC Class Codes: G02F 2203/01 transmissive
• CPC Class Codes: G02F 2203/09 transflective

Abstract

A display is provided comprising a semi-transparent display element (16, 17, 18, 19), such as double super twisted nematic (DSTN) liquid crystal display (LCD) cell, a sub-assembly having backlight elements (11, 12, 13) mounted thereon, and mounting means (20) mounting the display element over the sub-assembly with the display element adjacent to the back light elements, with no diffuser between the backlight elements and the display element. The backlight elements are an array of light emitting diodes of sufficiently wide angle and spaced sufficiently close together that, when viewed from the front of the display element, the display has substantially evenly dispersed brightness across the array.

Claims

1. A display comprising:

a semi-transparent display element;

a backlight sub-assembly; and

mounting means mounting the display element over and directly adjacent to the backlight sub-assembly wherein the backlight sub-assembly comprises a two-dimensional array of light emitting diodes mounted on a circuit board, characterized in that;

there is no diffuser between the light emitting diodes and the display element,

the light emitting diodes have a wide polar lighting angle, and the spacing between the light emitting diodes is determined by the polar lighting angle such that overlapping of light from one light emitting diode to another provides the display, when viewed from the front of the display element, with substantially evenly dispersed brightness across the array.

2. A display according to claim 1, wherein the display element has a layer of reflective material on the back side thereof, making it a transflective display element.

3. A display according to claim 1, wherein the display element comprises double super twisted nematic liquid crystal cell.

4. A display according to claim 1, wherein the display element is a negative transmissive or transflective mode liquid crystal assembly.

5. A display according to claim 1, wherein the display element is a transmissive or transflective mode liquid crystal assembly having a front polarizer, a back polarizer and a display cell element and a compensation cell element sandwiched between the front and back polarizers.

6. A display according to claim 5, wherein the display element has a layer of reflective material on the back side thereof, making it a transflective display element.

7. A display according to claim 5, wherein the display element comprises double super twisted nematic liquid crystal cell.

8. A display according to claim 5, wherein the display element has a layer of reflective material on the back side thereof, making it a transflective display element.

9. A display according to claim 5, wherein the display element is a negative transmissive or transflective mode liquid crystal assembly.

10. A display according to claim 9, wherein the display element has a layer of reflective material on the back side thereof, making it a transflective display element.

11. A display according to claim 9, wherein the display element comprises double super twisted nematic liquid crystal cell.

12. A display according to claim 11, wherein the display element has a layer of reflective material on the back side thereof, making it a transflective display element.

13. A display comprising:

a liquid crystal display element;

a backlight sub-assembly; and

mounting means mounting the display element over and directly adjacent to the backlight sub-assembly, wherein the backlight sub-assembly comprises a two-dimensional array of light emitting diodes mounted on a circuit board, the circuit board and other surfaces behind and around the light emitting diodes forming a reflective surface, characterized in that;

the liquid crystal display element is of the double super twisted nematic type,

there is no diffuser between the light emitting diodes and the display element,

the light emitting diodes have a wide polar lighting angle, and the spacing between the light emitting diodes is determined by the polar lighting angle such that overlapping of light from one light emitting diode to another provides the display, when viewed from the front of the display element, with substantially evenly dispersed brightness across the array.

14. A display according to claim 13, wherein the light emitting diodes are surface-mounted on the circuit board.

15. A display according to claim 13, comprising temperature measuring means, supply current means and means for controlling the supply current to the backlight sub-assembly to reduce the current when the temperature exceeds a threshold.

16. A display according to claim 13, wherein holes are provided in the mounting means for circulation of air.

17. A display according to claim 16, wherein the light emitting diodes are surface-mounted on the circuit board.

18. A display according to claim 16, comprising temperature measuring means, supply current means and means for controlling the supply current to the backlight sub-assembly to reduce the current when the temperature exceeds a threshold.

19. A display according to claim 18, wherein the light emitting diodes are surface-mounted on the circuit board.