Electroluminescence device

• US 4,945,009 A
• Filed: 03/11/1988
• Issued: 07/31/1990
• Est. Priority Date: 03/12/1987
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hashimoto, Kenichi, Abe, Yoshio, Sato, Akira, Nakayama, Takahiro, Tamura, Katsumi, Taguchi, Kazuo, Onisawa, Kenichi, Ono, Yoshimasa, Fuyama, Moriaki
• Primary Examiner(s): Seidleck, James
• Application Number:
  US07/166,986
• Time in Patent Office: 872 Days
• Field of Search: 428/690, 428/691, 428/917, 313/506, 313/503, 313/509
• US Class Current: 428/690
• CPC Class Codes: G09F 9/33 being semiconductor devices, e.g. diodes
• CPC Class Codes: H05B 33/145 Arrangements of the electroluminescent material
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

In an electroluminescence element including light emitting layers emitting light by applying AC voltages thereto the light emitting layer consists of a light emitting layer emitting red light and a light emitting layer emitting bluish green light and a blue filter transmitting blue light and a green filter transmitting green light are disposed on the light emitting surface side of the bluish green light emitting layer. In this way it is possible to take out red, blue and green lights at an approximately equal brightness level and to realize full color.

Claims

1. An electroluminescence element comprising:

a structure, in which a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are superposed one after another on a substrate; and

AC power sources connected between said first electrode and said second electrode;

wherein said light emitting layer comprises a bluish green light emitting sub-layer made of SrS as base material doped with Ce as activation material and a red light emitting sub-layer made of one selected from the group consisting of CaS as base material doped with Eu as activation material, ZnS as base material doped with Sm as activation material, and SrS as base material doped with Eu as activation material, said bluish green light emitting sub-layer being provided with a blue filter transmitting only blue light and a green filter transmitting only green light in the light emitted by said bluish green light emitting sub-layer, the brightness of the red, blue and green lights being substantially uniform, whereby three separate colors are transmitted from the red and bluish green light emitting sub-layers, and one of said AC power sources is for exciting said red light emitting layer and the other of said AC power sources is for exciting said bluish green light emitting layer.

2. An electroluminescence element according to claim 1, wherein the area of light emitting pixels in said red light emitting sub-layer is greater than each of the area of blue light emitting pixels and the area of green light emitting pixels in said bluish green light emitting layer so that the brightness level is approximately equal for the red, the blue and the green light emissions.

3. An electroluminescence element according to claim 1, wherein a blue filter transmitting only blue light and a green filter transmitting only green light are disposed at an arbitrary position between the light emitting layer on the light emitting surface side of said bluish green light emitting sub-layer and the surface of said electroluminescence element.

4. An electroluminescence element according to claim 1, wherein one of the first and second electrodes is divided into electrode elements for providing blue light and green light, and the blue and green filters respectively corresponding to the electrode elements for providing blue light and green light are larger than the respective electrode elements.

5. An electroluminescence element according to claim 1, wherein the red light emitting sub-layer is not provided with a filter.

10. An electroluminescence element according to claim 3, wherein the area of light emitting pixels in the red light emitting layer is greater than either of the areas of blue light and green light emitting pixels.

11. An electroluminescence element according to claim 10, wherein the area of light emitting pixels in the red light emitting layer is approximately equal to the sum of the areas of blue light and green light emitting pixels.

6. An electroluminescence element comprising:

a first electroluminescence element including a first electrode, a first insulating layer, a red light emitting layer, a second insulating layer and a second electrode superposed one after another on a substrate, and an AC power source applying an AC voltage between said first electrode and said second electrode, said red light emitting layer being made of one selected from the group consisting of CaS as base material doped with Eu as activation material, ZnS as base material doped with Sm as activation material, and SrS as base material doped with Eu as activation material, and

a second electroluminescence element superposed on said first electroluminescence element including a first electrode, a first insulating layer, a bluish green light emitting layer, a second insulating layer and a second electrode superposed one after another on a substrate, said bluish green light emitting layer being provided with a blue filter transmitting only blue light and a green filter transmitting only green light in the light emitted by said bluish green light emitting layer, the brightness of the red, blue and green lights being substantially uniform, whereby three separate colors are transmitted from the first and second electro-luminescence elements, and an AC power source applying an AC voltage between said first electrode and said second electrode for exciting said bluish green light emitting layer, said bluish green light emitting layer being made of SrS as base material doped with Ce as activation material.

7. An electroluminescence element according to claim 6, wherein the area of light emitting pixels in said red light emitting layer is greater than each of the area of blue light emitting pixels and the area of green light emitting pixels in said bluish green light emitting layer so that the brightness level is approximately equal for the red, the blue and the green light emissions.

8. An electroluminescence element according to claim 6, wherein a blue filter transmitting only blue light and a green filter transmitting only green light are disposed at an arbitrary position between the light emitting layer on the light emitting surface side of said bluish green light emitting layer and the surface of said electroluminescence element.

9. An electroluminescence element according to claim 6, wherein one of the first and second electrodes is divided into electrode elements for providing blue light and green light, and the blue and green filters respectively corresponding to the electrode elements for providing blue light and green light are larger than the respective electrode elements.

12. An electroluminescence element according to claim 6, wherein the red light emitting layer is not provided with a filter.

13. An electroluminescence element comprising:

a structure, in which a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are superposed one after another on a substrate; and

AC power sources applying AC voltages between said first electrode and said second electrode;

wherein said light emitting layer comprises red light emitting elements made of one selected from the group consisting of CaS as base material doped with Eu as activation material, ZnS as base material doped with Sm as activation material, and SrS as base material doped with Eu as activation material and bluish green light emitting elements made of SrS as base material doped with Ce as activation material, said red and said bluish green light emitting elements being disposed alternately on a same plane, each of said bluish green light emitting elements being provided with a blue filter transmitting only blue light and a green filter transmitting only green light in the light emitted by each of said bluish green light emitting elements, the brightness of the red, blue and green lights being substantially uniform, whereby three separate colors are transmitted from the red and bluish green light emitting elements, and one of said AC power sources is for exciting said red light emitting elements and the other of said AC power sources is for exciting said bluish green light emitting elements.

14. An electroluminescence element according to claim 13, wherein the area of light emitting pixels in said red light emitting elements is greater than each of the area of blue light emitting pixels and the area of green light emitting pixels in said bluish green light emitting elements so that the brightness level is approximately equal for the red, the blue and the green light emissions.

15. An electroluminescence element according to claim 13, wherein a blue filter transmitting only blue light and a green filter transmitting only green light are disposed at an arbitrary position between the light emitting layer on the light emitting surface side of said bluish green light emitting elements and the surface of said electroluminescence element.

16. An electroluminescence element according to claim 13, wherein one of the first and second electrodes is divided into electrode elements for providing blue light and green light, and the blue and green filters respectively corresponding to the electrode elements for providing blue light and green light are larger than the respective electrode elements.

17. An electroluminescence element according to claim 13, wherein the red light elements are not provided with a filter.

18. An electroluminescence element having a light emitting layer emitting light by applying an AC voltage thereto, comprising:

a red light emitting layer made of calcium sulfide doped with europium and a bluish green light emitting layer made of strontium sulfide doped with cerium constituting said light emitting layer; and

blue filters transmitting only blue light and green filters transmitting only green light in the light emitted by said bluish green light emitting layer, whereby three colors can be transmitted from the red light and bluish green light emitting layers;

wherein the area of light emitting pixels in said red light emitting layer is greater than each of the area of blue light emitting pixels and the area of green light emitting pixels in said bluish green light emitting layer so that the brightness level is approximately equal for the red light emitted by said red light emitting layer, the blue and the green lights emitted by said bluish green light emitting layer through said blue and said green filters, respectively.

19. An electroluminescence display device comprising:

a first electroluminescence element including a first substrate, a first electrode formed on said first substrate, a first insulating layer covering said first electrode, a first light emitting layer for emitting light of first and second colors, formed on said first insulating layer, a second transparent insulating layer covering said first light emitting layer and a second transparent electrode formed on said second insulating layer;

a second electroluminescence element including a second transparent substrate, a third transparent electrode formed on said second substrate, a third transparent insulating layer covering said third electrode, a second transparent light emitting layer for emitting light of a third color, formed on said third transparent insulating layer, a fourth transparent insulating layer covering said second light emitting layer, a fourth transparent electrode formed on said fourth transparent insulating layer;

a first filter for transmitting light of the first color, of the light of the first and second colors emitted from the first light emitting layer;

a second filter for transmitting light of the second color, of the light of the first and second colors emitted from the first light emitting layer, said first and second filters being arranged side by side, whereby three separate colors are transmitted from the first and second light emitting layers; and

an AC power source for applying AC power to said electrodes;

wherein said second and third electrodes face each other through said first and second filters;

20. An electroluminescence display device according to claim 19, wherein the light of first and second colors is bluish green light, wherein said first filter is for transmitting blue light, and wherein said second filter is for transmitting green light.

21. An electroluminescence display device according to claim 19, wherein said first light emitting layer is made of SrS as base material doped with Ce as activation material, and said second light emitting layer is made of one selected from the group consisting of CaS as base material doped with Eu as activation material, ZnS as base material doped with Sm as activation material, and SrS as base material doped with Eu as activation material.

22. An electroluminescence display device comprising:

a structure, in which a first electrode, a first insulating layer, a light emitting layer, a second insulating layer and a second electrode are superposed one after another on a substrate; and

AC power sources applying AC voltages between said first electrode and said second electrode;

wherein said light emitting layer comprises first light emitting elements emitting light of a first color, and second light emitting elements emitting light of second and third colors, disposed on a same plane; and

wherein said structure further includes a first filter for transmitting light of the second color, of the light of the second and third colors emitted from the second light emitting elements, and a second filter for transmitting light of the third color, of the third of the second and third colors emitted from the second light emitting elements, whereby three separate colors are transmitted from the first and second light emitting elements.

23. An electroluminescence display device according to claim 22, wherein the light of the second and third colors is bluish green light, wherein said first filter is for transmitting blue light, and wherein said second filter is for transmitting green light.

24. An electroluminescence display device according to claim 22, wherein said first light emitting elements and said second light emitting elements are disposed alternately on the same plane.

25. An electroluminescence display device according to claim 24, wherein the first and second filters are disposed on a surface of said substrate opposed to a surface of the substrate on which the first electrode is disposed.

26. An electroluminescence display device according to claim 22, wherein the first and second filters are disposed on a surface of said substrate opposed to a surface of the substrate on which the first electrode is disposed.

27. An electroluminescence display device comprising:

a structure, including a first electrode, a first insulating layer, a light emitting structure, a second insulating layer and a second electrode;

at least one AC power source, connected between said first electrode and said second electrode;

wherein said light emitting structure comprises first light emitting elements emitting at least first and second colors, and second light emitting elements emitting a third color; and

wherein the structure further includes a first filter for transmitting said first color from said first light emitting elements, and a second filter for transmitting said second color from said first light emitting elements, whereby three separate colors are transmitted from the first and second light emitting elements.

28. An electroluminescence display device according to claim 27, wherein said first color is blue and said second color is green, and wherein said third color is red.

29. An electroluminescence display device according to claim 27, wherein the first and second light emitting elements are disposed in the same plane, between the first and second insulating layers which are between the first and second electrodes.

30. An electroluminescence display device according to claim 27, wherein the first electrode, first insulating layer, first light emitting elements, second insulating layer and second electrode, stacked one on the other, form a first display element, and wherein the device further comprises:

a third electrode, a third insulating layer, a fourth insulating layer and a fourth electrode, with at least one further AC source, connected between the third and fourth electrodes; and

wherein said third electrode, said third insulating film, said second light emitting elements, said fourth insulating layer and said fourth electrode, stacked one on the other, form a second display element.

31. An electroluminescence display device according to claim 30, wherein said first and second filters are disposed between the first and second display elements.