LIGHT-EMITTING DEVICE AND METHOD FOR THE PRODUCTION OF LIGHT-EMITTING DEVICE

Abstract

The invention concerns a light-emitting device comprising an electroluminescent element as a light source and a light-detecting element disposed superimposed on the electroluminescent element for detecting the quantity of light emitted by the electroluminescent element to generate an electric signal for use in the correction of the quantity of light emitted, wherein the light-detecting element has a semiconductor island region AR formed larger than a light-projecting region ALE and the thickness of the light-emitting layer in the light-projecting region ALE is uniform.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view illustrating the configuration of a light head employing the light-emitting device according to Embodiment 1, particularly the peripheral configuration of an electroluminescent element which is a light-emitting element provided in the light head.

FIG. 2 is a plan view of the electroluminescent element according to Embodiment 1.

FIG. 3 is a circuit diagram of a light quantity detecting circuit incorporated in the light head according to Embodiment 1.

FIG. 4 is a diagram illustrating the relationship between the gate voltage Vg and the drain current ID of a light-detecting element according to Embodiment 1.

FIG. 5 is a timing chart illustrating the timing of detection of quantity of light according to Embodiment 1.

FIG. 6 is a sectional view illustrating a modification of the peripheral configuration of the electroluminescent element according to Embodiment 1.

FIG. 7 is a sectional view of a light head according to Embodiment 2 in the form of a top emission structure.

FIG. 8 is a sectional view illustrating a modification of the peripheral configuration of an electroluminescent element according to Embodiment 2.

FIG. 9 is a configurational diagram of an image forming device comprising a light-emitting device according to Embodiment 3 as a light head.

FIG. 10 is a configurational diagram illustrating the periphery of a development station in an image forming device according to Embodiment 3.

FIG. 11 is a sectional view illustrating a light-emitting device according to Embodiment 4.

FIG. 12 is a sectional view illustrating a light-emitting device according to Embodiment 5.

FIG. 13 is a configurational diagram of a display device employing a light-emitting device according to Embodiment 6.

FIG. 14 is a diagram illustrating the pixel arrangement of a display device according to Embodiment 6.

FIG. 15A is a plan view of a light-detecting element according to Embodiment 7 and FIG. 15B is a sectional view of the light-detecting element taken on the line A-A of FIG. 15A.

FIGS. 16A and 16B each are a diagram illustrating another configuration of the light-detecting element according to Embodiment 7.

FIG. 17A is a plan view of a light detecting element according to Embodiment 8 and FIG. 17B is a sectional view of the light-detecting element taken on the line B-B of FIG. 17A.

FIG. 18A is a plan view of a light-detecting element according to Embodiment 9, FIG. 18B is a sectional view of the light-detecting element taken on the line C-C of FIG. 18A and FIG. 18C is a sectional view of the light-detecting element taken on the lines D-D and E-E of FIG. 18A.

FIG. 19A is a plan view of a light-detecting element according to Embodiment 10, FIG. 19B is a sectional view of the light-detecting element taken on the line C-C of FIG. 19A and FIG. 19C is a sectional view of the light-detecting element taken on the line G-G of FIG. 19A.

FIG. 20 is a configurational diagram illustrating the configuration of a part of a light head having a light-detecting element according to Embodiment 11 in the vicinity of the light-detecting element.

FIG. 21 is a configurational diagram illustrating the configuration of a part of a light head having a light-detecting element according to Embodiment 12 in the vicinity of the light-detecting element.

FIG. 22 is a sectional view illustrating the configuration of a related art light head, particularly the peripheral configuration of a light-emitting element provided in the light head.

Claims

1. A light-emitting device, comprising: a light-emitting element; anda light-detecting element for detecting light emitted by the light-emitting element laminated on a substrate;wherein the light-emitting element has a light-projecting region provided on a flat surface thereof.

2. The light-emitting device as defined in claim 1, wherein the light-detecting element and the light-emitting element are formed in this order on the substrate and the flat surface is formed by the light-detecting element.

3. The light-emitting device as defined in claim 1, wherein the light-emitting element is formed laminated on the top of the light-detecting element formed on the substrate and the element region of the light-detecting element is formed larger than the light-projecting region so as to cover the light-projecting region of the light-emitting element.

4. The light-emitting device as defined in claim 3, wherein the light-detecting element is formed in an island-shaped semiconductor region formed on the substrate, the light-projecting region of the light-emitting element is formed in the semiconductor region and the lower side electrode of the light-emitting element is formed covering the semiconductor region.

5. The light-emitting device as defined in claim 1, wherein the light-emitting element is laminated on the top of the light-detecting element formed on the substrate and the outer edge of the element region of the light-detecting element is formed disposed outside the light-projecting region of the light-emitting element.

6. The light-emitting device as defined in claim 1, wherein the light-emitting element is formed in a semiconductor layer formed integrally on the substrate, the light-projecting region of the light-emitting element is formed in the semiconductor layer, the lower side electrode of the light-emitting element is formed on a part of the top of the semiconductor layer and the light-projecting region is defined smaller than the lower side electrode.

7. The light-emitting device as defined in claim 4, wherein the substrate is a light-transmitting substrate having insulating properties, the light-detecting element is a semiconductor element having a semiconductor layer formed on the light-transmitting substrate as an active region, the light-emitting element comprises a first electrode formed by a light-transmitting electrically-conductive film formed covering the semiconductor layer, a light-emitting layer formed on the first electrode and a second electrode formed on the light-emitting layer and the light-emitting layer is allowed to emit light when an electric field is applied between the light-emitting element and the first electrode.

8. The light-emitting device as defined in claim 4, wherein the substrate is a substrate having insulating properties and a reflective surface, the light-detecting element is a semiconductor element having a semiconductor layer formed on the substrate as an active region, the light-emitting element comprises a first electrode formed by a light-transmitting electrically-conductive film formed covering the semiconductor layer, a light-emitting layer formed on the first electrode and a second electrode formed on the light-emitting layer and the light-emitting layer is allowed to emit light when an electric field is applied between the light-emitting element and the first electrode.

9. The light-emitting device as defined in claim 7, wherein the semiconductor element is a diode.

10. The light-emitting device as defined in claim 7, wherein the semiconductor element is a transistor which is formed by the first electrode of the light-emitting element as a gate electrode.

11. The light-emitting device as defined in claim 10, wherein the semiconductor element is a thin film transistor formed by a polycrystalline silicon or amorphous silicon, the first electrode is formed with the interposition of an insulating film covering the semiconductor layer, the thin film transistor forms an electric field effect transistor having the first electrode of the light-emitting element as a gate electrode and the insulating film as a gate insulating film and the gate insulating film is arranged having a thickness such that a voltage drop occurs to an extent such that the dispersion of potential of the first electrode can be neglected.

12. The light-emitting device as defined in claim 1, wherein the light-projecting region is defined by an opening formed in an insulating film provided interposed between the first electrode or second electrode and the light-emitting layer.

13. The light-emitting device as defined in claim 1, wherein the light-projecting region is defined by an opening formed in a light-screening film provided closer to the light emission side than the light-projecting region of the light-emitting element.

14. The light-emitting device as defined in claim 1, wherein the light-emitting element is disposed in a number of one every the light-projecting region.

15. The light-emitting device as defined in claim 1, wherein the light-emitting element is an organic electroluminescent element comprising an organic semiconductor layer as a light-emitting layer or an inorganic electroluminescent element comprising an inorganic semiconductor layer as a light-emitting layer.

16. The light-emitting device as defined in claim 1, comprising a shading correction portion for correcting the quantity of light from the light-emitting element according to the output of the light-detecting element.

17. The light-emitting device as defined in claim 1, wherein the light-detecting element is formed by a photoconductor and a good conductor provided adjacent to a plurality of sides of the photoconductor and the joint area of the photoconductor with the good conductor is arranged larger than the section of the photoconductor taken on the line parallel to the good conductor.

18. The light-emitting device as defined in claim 17, wherein the joint area is formed by a surface oblique to the width direction, length direction and thickness direction of the light-detecting element.

19. The light-emitting device as defined in claim 18, wherein the oblique surface is formed by a curved surface.

20. A method for the production of a light-emitting element comprising at least the following steps: i) A step of forming a light-detecting element having an island-shaped semiconductor region on a substrate; andii) A step of forming a light-emitting element superimposed on the semiconductor region on the top of a flat portion of the semiconductor region, wherein the step ii) comprises the following steps:a) A step of forming a driving electrode of the light-emitting element covering the entire part of the island-shaped semiconductor region;b) A step of covering a part of the driving electrode by an insulating film and forming an opening at least inside the flat portion to define a light-emitting region;c) A step of spreading a luminescent material over a portion including at least the opening to form a light-emitting layer; andd) A step of forming other electrode made of a metal as a main material on the spread of the luminescent material such that the light-emitting layer is interposed between the other electrode and the driving electrode to form the light-emitting element.