Electroluminescent element and display

• US 20040207577A1
• Filed: 10/16/2003
• Published: 10/21/2004
• Est. Priority Date: 10/17/2002
• Status: Active Grant

• Current Assignee: Dai Nippon Printing Company Limited
• Original Assignee: Dai Nippon Printing Company Limited
• Inventors: Ito, Norihito, Ito, Nobuyuki
• Granted Patent: US 7,215,305 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2320/046 Dealing with screen burn-in prevention or compensation of the effects thereof
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/122 Pixel-defining structures or layers, e.g. banks
• CPC Class Codes: H10K 71/135 using ink-jet printing

Abstract

The present invention relates to an electroluminescent (EL) element comprising at least a substrate, an electrode formed on the substrate and an electric light emitting layer and to a display using this element as pixel unit. The object of the present invention is to provide a display without property deterioration due to heating of the EL layer or remaining of the solvent, and is practical though the thickness of the film is uneven. A display comprising the electroluminescent element, wherein the light emitting region is changed by the applied voltage, as a pixel unit wherein the display is driven by a digital gradation driving method in which a low voltage value at which the pixel dose not emit light is a non-selected state, and a high voltage value at which the light emitting region within the pixel is saturated is a selected state. By using the present invention, though the film thickness is not even, a practical display with excellent gradation control property can be provided.

Claims

1. An electroluminescent element comprising at least a substrate, an electrode formed on the substrate and an electric light emitting layer wherein an area of a light emitting region changes in an element region where an electric field is applied to a pair of facing electrodes.

2. The electroluminescent element according to claim 1 wherein the light emitting region changes with a change of brightness per unit area.

3. The electroluminescent element according to claim 1 wherein, in the element region where an electric field is applied to a pair of facing electrodes, a thickness of the thickest part of the light emitting layer is within 300% of the thickness of the thinnest part.

4. The electroluminescent element according to claim 2 wherein, in the element region where an electric field is applied to a pair of facing electrodes, a thickness of the thickest part of the light emitting layer is within 300% of the thickness of the thinnest part.

5. The electroluminescent element according to claim 3 wherein the thickness of the thickest part of the light emitting layer is within 220% of the thickness of the thinnest part.

6. The electroluminescent element according to claim 4 wherein the thickness of the thickest part of the light emitting layer is within 220% of the thickness of the thinnest part.

7. The electroluminescent element according to claim 3 wherein the thickness of the thinnest part of the light emitting layer is not less than 10 nm and not more than 500 nm.

8. The electroluminescent element according to claim 4 wherein the thickness of the thinnest part of the light emitting layer is not less than 10 nm and not more than 500 nm.

9. A display comprising the electroluminescent element according to claim 1 as a pixel unit wherein the display is driven by a digital gradation driving method in which a low voltage value at which the pixel dose not emit light is a non-selected state, and a high voltage value at which the light emitting region within the pixel is saturated is a selected state.

10. A display comprising the electroluminescent element according to claim 2 as a pixel unit wherein the display is driven by a digital gradation driving method in which a low voltage value at which the pixel dose not emit light is a non-selected state, and a high voltage value at which the light emitting region within the pixel is saturated is a selected state.

11. The electroluminescent display according to claim 1 wherein the digital gradation driving method is a time divisional gradation driving method, an area divisional gradation driving method or a combination of the time divisional gradation driving method and area divisional gradation driving method.

12. The electroluminescent display according to claim 2 wherein the digital gradation driving method is a time divisional gradation driving method, an area divisional gradation driving method or a combination of the time divisional gradation driving method and area divisional gradation driving method.

13. The electroluminescent display according to claim 1 wherein at least the light emitting layer of the electroluminescent element is formed by a wet process of an ink jet method, a printing method, a casting method, a layer-by-layer self-assembling method, a spin coating method, a dipping method or dispenser method.

14. The electroluminescent display according to claim 2 wherein at least the light emitting layer of the electroluminescent element is formed by a wet process of an ink jet method, a printing method, a casting method, a layer-by-layer self-assembling method, a spin coating method, a dipping method or dispenser method.

15. An electronic device using a display according to claim 1 as a displaying part.

16. An electronic device using a display according to claim 2 as a displaying part.