Light-absorption film for rear electrodes of electroluminescent display panel

• US 4,287,449 A
• Filed: 01/31/1979
• Issued: 09/01/1981
• Est. Priority Date: 02/03/1978
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kishishita, Hiroshi, Isaka, Kinichi, Kawabata, Hiroyuki, Takeda, Mikio
• Primary Examiner(s): DEMEO, PALMER
• Application Number:
  US06/008,186
• Time in Patent Office: 944 Days
• Field of Search: 313/506, 313/509, 313/510
• US Class Current: 313/509
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers

Abstract

At least one light-absorption layer is disposed between a thin electroluminescent film and a counter electrode for absorbing light applied through a transparent electrode. According to the light-absorption layer, less light is reflected by the counter electrode, thereby preventing a visual contrast provided by electroluminescence from lowering owing to the reflected light. A plurality of light-absorption layers may be formed in the same arrangement. Materials useful for the light-absorption layers are Al₂ O₃, Al₂ O_3-x, Mo, Zr, Ti, Y, Ta, Ni, Al or the like with a thickness of about 10-300 A.

Claims

1. A display divice comprising:

a front electrode;

a counter electrode having reflective properties;

a light emission layer interposed between said front electrode and said counter electrode for providing light emission in response to a voltage applied across the front and counter electrodes;

light-absorption layer means positioned between the light emission layer and the counter electrode, said light-absorption layer means having light-absorption properties for absorbing light applied through the front electrode, said light-absorption layer means including a first thin film and a second thin film formed over said first thin film, said first thin film being selected from the group consisting of Al₂ O₃ or Al₂ O₃ -x, said second thin film formed over said first thin film selected from the group consisting of Mo, Zr, Ti, Y, Ta, or Ni.

2. The display device according to claim 1, wherein said light emission layer comprises a thin electroluminescent film including a luminescent center and wherein said display device further comprises first and second dielectric layers for sandwiching the thin electroluminescent film therebetween.

3. The display device according to claim 1, wherein each of the thin films of said light-absorption layer means has a thickness lying in a range from 10 A to 300 A.

4. A display device comprising:

a front electrode;

a counter electrode having reflective properties;

a light emission layer means interposed between said front electrode and said counter electrode for providing light emission in response to a voltage applied across the front and counter electrodes;

light-absorption layer means positioned between the light emission layer and the counter electrode for absorbing light applied thereto via said front electrode, said light-absorption layer means including a first light-absorption layer and a second light-absorption layer formed thereover, the first and second light-absorption layers including a metallic layer and a layer containing a metal common to the metallic layer and an oxidation material of said metal, respectively.

5. A display device in accordance with claim 4 wherein said first and second light-absorption layers contain a material selected from a group consisting of Al₂ O₃, Al₂ O_3-x, or Al, each of the first and second light-absorption layers having a thickness lying in a range from 10 A to 300 A.

6. A thin film electroluminescent display device comprising:

a front electrode;

a counter electrode having reflective properties;

first and second dielectric layers disposed between said front electrode and said counter electrode;

a thin film electroluminescent layer disposed between the first and second dielectric layers, said thin electroluminescent layer including a luminescent center; and

light-absorption layer means positioned between one of the dielectric layers and the counter electrode, said light-absorption layer means having light absorption properties for absorbing light applied thereto via said front electrode, said light-absorption layer means including a first light-absorption layer and a second light-absorption layer formed thereover, said first and second light-absorption layers including a metallic layer and a layer containing a metal common to said metallic layer and an oxidation material of said metal, respectively.

7. A thin film electroluminescent display device in accordance with claim 6 wherein said first and second light-absorption layers contain a material selected from a group consisting of Al₂ O₃, Al₂ O_3-x, or Al, each of the first and second light-absorption layers having a thickness lying in a range from 10 A to 300 A.

8. A display device having a display side and a rear side, comprising:

front electrode means positioned at said display side of said display device, said front electrode capable of permitting ambient light to pass therethrough;

counter electrode means positioned at said rear side of said display device;

light emission layer means interposed between said front electrode means and said counter electrode means for providing light emission in response to a voltage applied across the front and counter electrode means;

light-absorption layer means interposed between said front electrode means and said counter electrode means for absorbing the ambient light passing through said front electrode means thereby preventing the reflection of said ambient light off said counter electrode, said light-absorption layer means including at least a first thin film layer and a second thin film layer disposed over said first thin film layer, the first thin film layer is comprised of a material selected from the group consisting of Al₂ O₃ or Al₂ O_3-x, the second thin film layer is comprised of a material selected from the group consisting of Mo, Zr, Ti, Y, Ta, or Ni.

9. A display device in accordance with claim 8 wherein the thickness of each said thin film layer includes a thickness value lying in a range from 10 A to 300 A.