Electroluminescent lamp for liquid crystal display

• US 4,500,173 A
• Filed: 05/02/1983
• Issued: 02/19/1985
• Est. Priority Date: 05/02/1983
• Status: Expired due to Fees

• Current Assignee: Timex Corporation (Tanager Group BV)
• Original Assignee: Timex Corporation (Tanager Group BV)
• Inventors: George, Douglas A., Leibowitz, Marshall
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Lewis, David
• Application Number:
  US06/490,621
• Time in Patent Office: 659 Days
• Field of Search: 350/338, 350/345, 365/110, 365/111, 315/169.3, 430/917
• US Class Current: 349/69
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

A backlighted liquid crystal display is disclosed which includes an electroluminescent backlight having a reduced amount of phosphor acting as both a source of light for viewing the display during nighttime hours and as a light diffuser for viewing the display during daytime hours. The electroluminescent backlight is made thinner while the phosphor content is optimally reduced to provide a backlight that improves the viewability of the display especially during daytime hours without the need of a transflector. Wherein the minimal amount of phosphor is dispersed in a binder in the electroluminescent layer is substantially 1 volume unit of phosphor for every 4 to 5 volume units of binder.

Claims

1. An improved combination electroluminescent backlight and incident light reflector for a liquid crystal display for nighttime and daytime viewing, respectively, the improvement comprising:

a liquid crystal display

a light-reflective electrode in said electroluminescent backlight arranged to reflect incident light entering and passing through said liquid crystal display, and

a thin electroluminescent layer in said electroluminescent backlight between said light-reflective electrode and said liquid crystal display having a minimal amount of phosphor selected to provide for light diffusion for improving daytime viewability of said liquid crystal display as well as to provide a light source for improving nighttime viewability of said crystal display, in which said minimal amount of phosphor is dispersed in a binder in said electroluminescent layer in substantially one volume unit of phosphor for every four to five volume units of binder.

2. The improved combination electroluminescent backlight and incident light reflector of claim 1 in which said minimal amount of phosphor is dispersed in a binder in said electroluminescent layer in substantially the volume to volume ratio of 1 to 4.

3. The improved combination electroluminescent backlight and incident light reflector to claim 2 in which said phosphor in said electroluminescent layer is selectively activated by an applied voltage produced by an electronic circuit means, and also selectively serves as a diffuser for light reflected from said light-reflective electrode when the electroluminescent layer is not activated.

4. The improved combination electroluminescent backlight and incident light reflector of claim 1 in which said light-reflective electrode is metal.

5. The improved combination electroluminescent backlight and incident light reflector of claim 4 in which said metal is aluminum.

6. The improved combination backlight and incident light reflector of claim 1, in which said binder is transparent epoxy resin.