Electroluminescent lamp with controlled field intensity for displaying graphics

• US 5,660,573 A
• Filed: 08/16/1995
• Issued: 08/26/1997
• Est. Priority Date: 09/08/1994
• Status: Expired due to Term

• Current Assignee: World Properties Incorporated
• Original Assignee: James H. Butt
• Inventors: Butt, James H.
• Primary Examiner(s): Ramsey, Kenneth J.
• Application Number:
  US08/515,873
• Time in Patent Office: 741 Days
• Field of Search: 445/24, 427/66, 40/544
• US Class Current: 445/24
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/12 Light sources with substantially two-dimensional radiating surfaces
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers

Abstract

An EL lamp includes a transparent electrode, an electroluminescent dielectric layer overlying the transparent electrode, a patterned insulating layer overlies selected portions of the dielectric layer for reducing the electric field across the selected portions of the electroluminescent dielectric layer, and a rear electrode overlying the insulating layer and the electroluminescent dielectric layer. The insulating layer is preferably a low dielectric constant material and can overlie the electroluminescent dielectric layer or can be located between a separate dielectric layer and a phosphor layer. A gray scale is produced by depositing or printing more than one thickness of insulating layer.

Claims

1. A method for making an electroluminescent lamp capable of displaying graphics when lit and appearing plain when unlit, said method comprising the steps of:

depositing a conductive layer on a substrate;

depositing an electroluminescent layer on said conductive layer;

deposition a dielectric layer on said electroluminescent layer;

depositing an insulating layer either before or after depositing said dielectric layer, wherein said insulating layer is patterned in accordance with said graphics; and

depositing a conductive layer.

2. The method as set forth in claim 1 wherein said step of depositing an insulating layer comprises the step of printing said insulating layer in a pattern corresponding to said graphics.

3. The method as set forth in claim 1 wherein said step of depositing an insulating layer comprises the step of printing said insulating layer in a pattern corresponding to the reverse of said graphics.

5. The method as set forth in claim 1 wherein said insulating layer is deposited after the dielectric layer and said step of depositing said insulating layer comprises the steps of:

printing a first insulating layer in a first pattern;

printing a second insulating layer in a second pattern on said first insulating layer to produce an insulation layer of non-uniform thickness.

6. The method as set forth in claim 5 wherein the first printing step is followed by the step of partially curing said first insulating layer before printing the second insulating layer.

4. A method for displaying graphics in an electroluminescent lamp by controlling the electric field within said lamp, said method comprising the steps of:

depositing a continuous, transparent, conductive layer on a substrate;

depositing an electroluminescent layer on said transparent, conductive layer;

depositing on said electroluminescent layer a dielectric layer having increased thickness portions patterned in accordance with said graphics for reducing the electric field in said electroluminescent layer; and

depositing a conductive layer on said dielectric layer.