Scanning head and printer Number:7,522,810 from the United States Patent and Trademark Office (PTO) owispatent A scanning head includes a surface emitting part array panel which has an array of surface emitting parts to emit light A plurality of light guide parts are respectively opposite to the surface emitting parts. Each of light guide parts has an entrance plane to receive the light from the surface emitting part, a reflection plane to reflect the light from the entrance plane, and an exit plane to emit the light from the reflection plane.<H Scanning, printer, Scanning, head, a, 7522810.html, Patent, pto, 7522810

Title: Scanning head and printer

Abstract: A scanning head includes a surface emitting part array panel which has an array of surface emitting parts to emit light A plurality of light guide parts are respectively opposite to the surface emitting parts. Each of light guide parts has an entrance plane to receive the light from the surface emitting part, a reflection plane to reflect the light from the entrance plane, and an exit plane to emit the light from the reflection plane.

Patent Number: 7,522,810 Issued on 04/21/2009 to Ogura, et al.

Inventors: Ogura; Jun (Fussa, JP), Daiku; Yasuhiro (Iruma, JP), Shirasaki; Tomoyuki (Higashiyamato, JP), Kusuno; Tetsuya (Iruma, JP)
Assignee: Casio Computer Co., Ltd. (Tokyo, JP)

Appl. No.: 11/350,985

Filed: February 9, 2006

Foreign Application Priority Data


Feb 14, 2005 [JP]			2005-036219
Nov 18, 2005 [JP]			2005-334583
Jan 27, 2006 [JP]			2006-019193

Current U.S. Class: 385/146 ; 385/129; 385/147

Current International Class: G02B 6/10 (20060101)

Field of Search: 385/129-133,146,147

References Cited [Referenced By]

U.S. Patent Documents


2001/0046365	November 2001	Bohle et al.

Foreign Patent Documents


06-130878	May., 1994	JP
9-226172	Sep., 1997	JP
2002-289019	Oct., 2002	JP
WO 2004/039595	May., 2004	WO

Other References

Chinese Office Action (and English translation thereof) dated Jul. 4, 2008, issued in a counterpart Chinese Application. cited by other.

Primary Examiner: Wood; Kevin S
Attorney, Agent or Firm: Frishauf, Holtz, Goodman & Chick, P.C.

Claims

What is claimed is:

1. A scanning head comprising: a surface emitting part array panel which comprises an array of surface emitting parts to emit light; and a plurality of light guide parts which are positioned opposite to the surface emitting parts, respectively, each of the light guide parts including: (i) an entrance plane to receive the light from the surface emitting part opposite to the light guide part, (ii) at least one reflection plane to reflect the light received through the entrance plane, and (iii) an exit plane to emit the light reflected by the reflection plane; wherein each of the surface emitting parts comprises an organic electroluminescent element which is opposite to the entrance plane of one of the light guide parts.

2. The scanning head according to claim 1, wherein the at least one reflection plane of each of the light guide parts comprises a pair of reflection planes positioned opposite to each other, each of the light guide parts comprises a light adjusting part which is positioned between the opposite reflection planes and which has a width extending between the opposite reflection planes, and the width of the light adjusting part gradually increases toward the exit plane.

3. The scanning head according to claim 1, wherein the at least one reflection plane of each of the light guide parts comprises an opposite reflection plane positioned opposite to the entrance plane, each of the light guide parts comprises a light adjusting part which is positioned between the entrance plane and the opposite reflection plane and which has a height extending between the entrance plane and the opposite reflection plane, and the height of the light adjusting part gradually increases toward the exit plane.

4. The scanning head according to claim 1, wherein each of the surface emitting parts expands in width toward the exit plane.

5. The scanning head according to claim 1, wherein the at least one reflection plane comprises a plurality of reflection planes.

6. The scanning head according to claim 1, wherein the exit plane has a convex surface.

7. The scanning head according to claim 1, wherein the light guide part has a hollow body.

8. The scanning head according to claim 1, further comprising a substrate for supporting the organic electroluminescent elements, wherein each of the organic electroluminescent elements comprises a lower electrode, an organic electroluminescent layer and an upper electrode, and the entrance plane of each of the light guide parts is opposite to the upper electrode of one of the electroluminescent elements.

9. The scanning head according to claim 1, wherein an area of the exit plane is smaller than an area of the entrance plane.

10. A printer comprising: (i) a scanning head which comprises: a surface emitting part array panel which comprises an array of surface emitting parts to emit light; and a plurality of light guide parts which are positioned opposite to the surface emitting parts, respectively, each of the light guide parts including: (i) an entrance plane to receive the light from the surface emitting part opposite to the light guide part, (ii) at least one reflection plane to reflect the light received through the entrance plane, and (iii) an exit plane to emit the light reflected by the reflection plane; and (ii) a photoconductive drum to which the light from the exit planes is emitted.

11. The printer according to claim 10, wherein the at least one reflection plane of each of the light guide parts comprises a pair of reflection planes positioned opposite to each other, each of the light guide parts comprises a light adjusting part which is positioned between the opposite reflection planes and which has a width extending between the opposite reflection planes, and the width of the light adjusting part gradually increases toward the exit plane.

12. The printer according to claim 10, wherein the at least one reflection plane of each of the light guide parts comprises an opposite reflection plane positioned opposite to the entrance plane, each of the light guide parts comprises a light adjusting part which is positioned between the entrance plane and the opposite reflection plane and which has a height extending between the entrance plane and the opposite reflection plane, and height of the light adjusting part gradually increases toward the exit plane.

13. The printer according to claim 10, wherein each of the surface emitting parts expands in width toward the exit plane.

14. The printer according to claim 10, wherein the exit plane has a projected surface.

15. The printer according to claim 10, wherein each of the light guide parts has a hollow body.

16. The printer according to claim 10, wherein the exit plane has an area that is smaller than an area of the entrance plane.

17. The scanning head according to claim 1, wherein the at least one reflection plane of each of the light guide parts comprises an opposite reflection plane positioned opposite to the entrance plane.

18. The scanning head according to claim 17, wherein each of the light guide parts comprises a light adjusting part which is positioned between the entrance plane and the opposite reflection plane.

19. The printer according to claim 10, wherein the at least one reflection plane of each of the light guide parts comprises an opposite reflection plane positioned opposite to the entrance plane.

20. The printer according to claim 19, wherein each of the light guide parts comprises a light adjusting part which is positioned between the entrance plane and the opposite reflection plane.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2005-036219, filed Feb. 14, 2005; No. 2005-334583, filed Nov. 18, 2005; and No. 2006-019193, filed Jan. 27, 2006, the entire contents of all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scanning head having a structure suitable for a printer, scanner, copier or other image input and/or output apparatus, and a printer having such a scanning head.

2. Description of the Related Art

Page printers have been vigorously developed in recent years, because they can print on ordinary paper as well as specific paper. A page printer uses a laser scanning head composed of a laser diode and a polygon lens. In a laser scanning head, a laser emitting point is moved by a polygon lens, and printing at high-speed is difficult.

For high-speed printing, an LED scanning head using two or more LEDs has been developed. Two or more LEDs are aligned in an LED scanning head. These LEDs simultaneously emit light of different intensity, thereby scanning a photoconductor. As high picture quality is demanded, very high accuracy is demanded for packaging of LEDS with high density. This causes a problem of increased number of components.

To solve the above problems, Jpn. Pat. Appln. KOKAI Publication No. 9-226172 proposed a scanning head using an organic electroluminescent element as an LED.

However, at present, an organic electroluminescent element has a problem in luminous intensity and life. Namely, a light-emitting element requires sufficient amount of light to expose a photoconductor, and if the luminous intensity per dot of an organic electroluminescent element is weak, the exposing time per a dot must be set long. To set the exposing time long, the printing speed must be delayed. Conversely, if the luminous intensity per a dot of an organic electroluminescent element is increased, the exposing time per dot is reduced and the printing time is reduced, but the life of an organic electroluminescent element is reduced.

The luminous flux of an LED such as an organic electroluminescent element spreads from a light-emitting point, and it is preferable to provide an optical system between LED and photoconductor, which gives directivity to incident light from a dot of an LED to be emitted only to a specified part of a photoconductor. However, the efficiency of using such an optical system depends on an angle of taking in light (angular aperture), and the efficiency of using light is not high in a source like an LED which causes a light diffusion.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a scanning head and a printer, which can efficiently emit light without increasing the luminous intensity of a surface emitting part.

According to a first aspect of the invention, there is provided a scanning head comprising:

a surface emitting part array panel which has an array of surface emitting parts to emit light; and

a plurality of light guide parts which are respectively opposite to the surface emitting parts, each of light guide parts having an entrance plane to receive the light from the surface emitting part, a reflection plane to reflect the light from the entrance plane, and an exit plane to emit the light from the reflection plane.

According to a second aspect of the invention, there is provided a printer comprising:

a surface emitting part array panel which has an array of surface emitting parts to emit light; and

a plurality of light guide parts each of which is opposite to the surface emitting part, and has an entrance plane to receive the light from the surface emitting part, a reflection plane to reflect the light from the entrance plane, and an exit plane to emit the light from the reflection plane.

In the above scanning head and printer, the light emitted from the surface emitting part enters the entrance plane of the light guide part, the entered light is reflected on the reflection plane, and the reflected light is emitted from the exit plane. As the exit plane of the light guide part is a plane different from the entrance plane, and the exit plane is not increased even if the entrance plane is increased. If the entrance plane is increased and the light-emitting area of the surface emitting part is increased, the intensity per unit area of the exit plane is increased without increasing the light emission intensity per a unit area of the surface emitting part. Therefore, the exposing time can be reduced. Further, since the light emission intensity per unit area of the surface emitting part is not increased, the life of the surface emitting part can be made long.

According to a third aspect of the invention, there is provided a scanning head comprising:

a surface emitting part array panel which has an array of surface emitting parts to emit a light beam; and

a plurality of light guide parts each of which has an entrance plane opposite to the surface emitting part, a first opposite reflection plane opposite to the entrance plane in the state inclined to the entrance plane, a second opposite reflection plane provided along the first opposite reflection plane and inclined to the entrance plane to have an included angle larger than an included angle between the entrance plane and first opposite reflection plane, and an exit plane to emit the light from the surface emitting part.

According to a fourth aspect of the invention, there is provided a printer comprising:

a surface emitting part array panel which has an array of surface emitting parts to emit light; and

a plurality of light guide parts each of which has an entrance plane opposite to the surface emitting part, a first opposite reflection plane opposite to the entrance plane in the state inclined to the entrance plane, a second opposite reflection plane provided along the first opposite reflection plane and inclined to the entrance plane to have an included angle larger than an included angle between the entrance plane and first opposite reflection plane, and an exit plane to emit the light from the surface emitting part.

In the above scanning head and printer, the light emitted from the surface emitting part enters the entrance plane of the light guide part, the entered light is reflected on the first opposite reflection plane and second opposite reflection plane, and the reflected light is emitted from the exit plane. The second opposite reflection plane is provided in the inclined state to have an included angle larger than the included angle between the first opposite reflection plane and entrance plane, by transmitting light in the light guide part, and the directivity of light in the direction vertical to the exit plane can be improved.

According to the present invention, the intensity per unit area of the exit plane can be increased, without increasing the light emission intensity per unit area of the surface emitting part. As a result, the life of the surface emitting part can be made long.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

FIG. 1 is a perspective view of an image output apparatus;

FIG. 2 is a perspective view showing the configuration of three dots of a scanning head;

FIG. 3 is a plane view of the emitting plane of a surface emitting part array panel for four dots;

FIG. 4 is an arrow indicated cross section of the plane taken along lines IV-IV of FIG. 3;

FIG. 5 is an arrow indicated cross section of the plane along the cutting lines V-V of FIG. 3;

FIG. 6A is a plane view showing a dot radiation element in a modification, and FIG. 6B is a sectional view along the cutting lines 6B-6B of FIG. 6A;

FIG. 7A is a plane view showing a dot radiation element in another modification, and FIG. 7B is a sectional view along the cutting lines 7B-7B of FIG. 7A;

FIG. 8A is a plane view showing a dot radiation element in another modification, and FIG. 8B is a sectional view along the cutting lines 8B-8B of FIG. 8A;

FIG. 9 is a perspective view showing the configuration of three dots of a scanning head in another modification;

FIG. 10 is a perspective view showing the configuration of three dots of a scanning head in another modification;

FIG. 11 is a sectional view of a longitudinal section for one dot of a scanning head;

FIG. 12 is a sectional view of a cross section orthogonal to the cross section of FIG. 11;

FIG. 13 is a perspective view showing the configuration of three dots of a scanning head in another modification;

FIG. 14 is a plane view of the emitting plane of a surface emitting part array panel in another modification;

FIG. 15 is an arrow indicated cross section of a plane in another modification taken along lines XV-XV of FIG. 14;

FIG. 16 is a perspective view showing the configuration of three dots of a scanning head in another modification;

FIGS. 17A and 17B are views for explaining the relation of an included angle .gamma. between an entrance plane and an opposite reflection plane, to an emission intensity/luminous intensity, wherein FIG. 17A shows light guide parts of this invention and reference example, and FIG. 17B is a graph showing the result of the relation of an angle .theta. to an emission intensity/luminous intensity;

FIGS. 18A to 18C are graphs showing the relation between the radiation angle and luminous intensity of light emitted from an exit plane of a light guide part;

FIG. 19 is a perspective view of an image output apparatus 1;

FIG. 20 is a perspective view showing the configuration of three dots of a scanning head;

FIG. 21 is a plane view of an emitting plane of a surface emitting part array panel for four dots;

FIG. 22 is an arrow indicated cross section of the surface taken along lines XXII-XXII of FIG. 21;

FIG. 23 is an arrow indicated cross section of the surface taken along lines XXIII-XXIII of FIG. 21;

FIG. 24 is a perspective view showing the configuration of three dots of a scanning head in a comparing example;

FIG. 25 is a sectional view of a scanning head cut in the direction of a principal axis;

FIG. 26 is a perspective view showing the configuration of three dots of a scanning head;

FIG. 27 is a plane view of an emitting plane of a surface emitting part array panel for four dots;

FIG. 28 is a plane view of an emitting plane of a surface emitting part array panel for four dots; and

FIG. 29 is a conceptual illustration of a printer using the scanning head shown in any one of FIGS. 1 to 28.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be explained hereinafter with reference to the accompanying drawings. In the embodiments, technically preferably various limitations are given to embody the invention, but the scope of the invention is not to be limited to the embodiments and drawings.

FIG. 1 is a perspective view of an image output apparatus 1. As shown in FIG. 1, in the image output apparatus 1, a scanning head 2 is placed with the light-emitting part opposed to a generating line of a photoconductive drum 3 and the longish side mode parallel to the rotary shaft of the roller-shaped photoconductive drum 3. A SELFOC lens array 4 is provided between the light-emitting part of the scanning head 2 and the generating line of the photoconductive drum 3. The SELFOC lens array 4 is composed of a plurality of CELFOC lens arranged in one or more lines along the light-emitting part of the scanning head 2, each of which takes a radial straight line of the photoconductive drum 3 as an optical axis. The CELFOC lens array 4 focuses a light beam from the light-emitting part of the scanning head 2 on the generating line of the photoconductive drum 3. The photoconductive drum 3 forms an electrostatic latent image on the peripheral surface when exposed by the scanning head 2.

FIG. 2 is a perspective view showing the configuration of three dots of the scanning head 2. The scanning head 2 has a surface emitting part array panel 20, and a plurality of light guide parts 60 arranged in a line on the emission plane 21 of the surface emitting part array panel 20.

FIG. 3 is a plane view showing the emission plane 21 (FIG. 4) of the surface emitting part array panel 20. FIG. 4 is an arrow indicated cross section of the plane along the thickness of an insulating substrate 30 passing lines IV-IV of FIG. 3. FIG. 5 is an arrow indicated cross section of the plane along the thickness of an insulating substrate 30 passing lines V-V of FIG. 3. As shown in FIG. 3 to FIG. 5, the surface emitting part array panel 20 is composed of more than one surface emitting part 22 shaped like substantially a wedge or triangle in a plane view, arranged in a line on the insulating substrate 30. The light emitted from the surface emitting part 22 is emitted to the plane (the emission plane 21) opposite to the insulating substrate 30.

Each surface emitting part 22 has an organic electroluminescent element 27. Namely, the surface emitting part 22 has a lower electrode 23 formed on the insulating substrate 30, an organic electroluminescent layer stacked on the lower electrode 23, and an upper electrode 26.

The organic electroluminescent layer has a two-layer structure consisting of a positive hole carrying layer 24 and a light-emitting layer 25, for example, as shown in FIG. 4. The positive hole carrying layer 24 includes polythiophene (PEDOT) as a conductive high polymer, and polystyrene sulfonic acid (PSS) as dopant. The light-emitting layer 25 is made of polyfluorene based light-emitting material, for example. If the surface emitting part 22 emits light as an organic electroluminescent element 27, the organic electroluminescent layer between the lower electrode 23 and upper electrode 26 may not have the two-layer structure consisting of the positive hole carrying layer 24 and light-emitting layer 25. For example, the layer between the lower electrode 23 and upper electrode 26 may have a three-layer structure consisting of a positive hole carrying layer, a light-emitting layer and an electron carrying layer stacked sequentially on the lower electrode 23, or may have one-layer structure consisting of a light-emitting layer only, or may have a light-emitting layer and an electron carrying layer. It may also be a laminated structure having an electron or positive hole carrying layer interposed between appropriate layers in these layer structures, or may be another laminated structure. If the lower electrode 23 is used as a cathode and the upper electrode 26 is used as an anode, the lower electrode 23 shall have an electric charge carrying layer with an electron carrying property, and the upper electrode 26 shall have an electric charge carrying layer with a positive hole carrying property.

The lower electrode 23 preferably has a reflective property for the light of the organic electroluminescent layer, and is preferably made of material easy to carry a positive hole for the positive hole carrying layer 24, including metal such as aluminum, chromium or titanium, when used as an anode. The lower electrode 23 may be a layered product, which has such a reflective conductive layer as a lower layer, and has a transparent conductive layer containing at least one of tin doped indium oxide (ITO), zinc doped indium oxide, indium oxide (In.sub.2O.sub.3), tin oxide (SnO.sub.2), zinc oxide (ZnO) and cadmium tin oxide (CdSnO.sub.4), as an upper layer just like contacting the positive hole carrying layer 24.

The upper electrode 26 has a transmissible property for the light of the organic electroluminescent layer, and is a layered product composed of an electron carrying film with a thickness of 1-20 nm, preferably 5-12 nm, which is made of material with a work function lower than an anode made of a single substance or alloy containing at least one of indium, magnesium, calcium, lithium, barium and rare earth metal, and provided on the surface contacting a charge carrying layer with an electron carrying property, when used as a cathode; and a transparent conductive layer containing at least one of tin doped indium oxide (ITO), zinc doped indium oxide, indium oxide (In.sub.2O.sub.3), tin oxide (SnO.sub.2), zinc oxide (ZnO) and cadmium tin oxide (CdSnO.sub.4) with a thickness of 30-200 nm, to decrease a sheet resistance as a cathode, when used as an anode. The upper electrode 26 is composed of a transparent conductive layer containing at least one of tin doped indium oxide (ITO), zinc doped indium oxide, indium oxide (In.sub.2O.sub.3), tin oxide (SnO.sub.2), zinc oxide (ZnO) and cadmium tin oxide (CdSnO.sub.4) on the surface contacting the charge carrying layer with a positive hole carrying property, when used as an anode electrode.

The upper electrode 26 and lower electrode 23 are spaced, so that at least one of these electrodes is electrically insulated from the surface emitting part 22 and the two or more surface emitting parts 22 separately emit light. As shown in FIG. 5, in this embodiment, the lower electrode 23 is formed separately for each surface emitting part 22, and the upper electrode 26 is formed evenly as a film common to all surface emitting parts 22.

The positive hole carrying layer 24 may be formed separately for each surface emitting part 22, and may be formed evenly as a film common to all surface emitting parts 22. The light-emitting layer 25 may also be formed separately for each surface emitting part 22, and may be formed evenly as a film common to all surface emitting parts 22. The positive hole carrying layer 24 may be formed evenly as a film common to all surface emitting parts 22, and the light-emitting layer 25 may be formed separately for each surface emitting part 22, as a light-emitting layer to emit light with a different color. In this embodiment, the positive hole carrying layer 24 and light-emitting layer 25 are both formed separately for each surface emitting part 22.

In this embodiment, the lower electrode 23, positive hole carrying layer 24 and light-emitting layer 25 are formed separately and parted for each surface emitting part 22, and the lower electrode 23, positive hole carrying layer 24 and light-emitting layer 25 are enclosed by an insulating film 28. The insulating film 28 is made of inorganic substance such as silicon nitride and silicon dioxide, or made of photoconductive resin such as polyimide. The insulating film 28 is preferably lightproof to prevent propagation of the light emitted from the light-emitting layer 25 of each surface emitting part 22 to the light-emitting layer 25 of the adjacent surface emitting part 22.

The exposed surfaces of the insulating film 28 and upper electrode 26 (the outside surface of the insulating film 28 and the upper surfaces of the insulating film 28 and upper electrode 26, as shown in FIGS. 4 and 5) are covered by a smooth transparent sealing film 29. As a result, the lower electrode 23, positive hole carrying layer 24, light-emitting layer 25 and insulating film 28 are sealed by the sealing film 29. As the surface emitting part 22 is a top emission type organic electroluminescent element 27, the surface (upper surface) of the sealing film 29 becomes an emission plane of the surface emitting part 22.

A light guide part 60 is provided oppositely to the surface emitting part 22. A dot radiation element is composed of the surface emitting part 22 and the opposite light guide part 60. The light guide part 60 will be explained hereinafter.

The light guide part 60 is made of transparent material, such as polymethyl, methacrylate, polydimethylsiloxane, polycarbonate, cyclic olefin polymer, and has transmissivity. The light guide part 60 is a quadrangular pyramid, as shown in FIGS. 1-5.

One of the four sides of the light guide part 60 (the lower side in FIGS. 4 and 5) is an entrance plane 63 to receive the light from the surface emitting part 22, and the bottom (the left side in FIG. 4) is an exit plane 61. The sides other than the exit plane 61 and entrance plane 63 are reflection planes to reflect the light in the surface emitting part 22, and composed of an opposite reflection plane 64 opposite to the entrance plane 63, and side reflection planes 65 and 66 between the peripheral edge of the entrance plane 63 and the peripheral edge of the opposite reflection plane 64. The opposite reflection plane 64 is opposite to the entrance plane 63 in the state inclined in one direction toward the entrance plane 63. The exit plane or surface 61 is a flat plane opposite to the apex angle 62 that is an included angle between the opposite reflection plane 64 and entrance plane 63. The included angle formed by the exit plane 61 and entrance plane 63 is substantially a right angle. The side reflection planes 65 and 66 are rectangular to the entrance plane 63, and the side contacting the opposite reflection plane 64 is substantially wedge-shaped having a predetermined elevation angle .theta. (.theta.=0.degree.) from the apex angle 62 to the exit plane 61. At the same time, the side reflection planes 65 and 66 are crossed forming an included angle .gamma. (.gamma.=0.degree.). As a result, the light guide part 60 is shaped like a pyramid with the rectangular sectional area cut parallel to the exit plane 61 or the bottom gradually increased as approaching from the part of the apex angle 62 to the exit plane 61, or as approaching the exit plane 61. The area of the entrance plane 63 of the light guide part 60 is set larger than the area of the exit plane 61.

On these reflection planes, a reflection film 70 made of material with high reflectivity to the light from the surface emitting part 22 (e.g., metal and alloy) is substantially entirely formed. The reflection film 70 is formed separately for each light guide part 60. Therefore, the parts covering the opposite reflection plane 64 and side reflection planes 65 and 66 are substantially wedge-shaped.

The exit plane of the surface emitting part 22 is shaped similar to the entrance plane 63 of the light guide part 60 with substantially the same dimensions (a little smaller in this embodiment), as shown in FIG. 3, and emits a light beam like a wedge expanding in width from one end 31 to the other end 32, or as approaching the exit plane 61. The area of the exit plane of the surface emitting part 22 is 80-110%, preferably 85-99% of the area of the entrance plane 63 of the light guide part 60. For the emission of sedge-shaped light of the surface emitting part 22, the electrode formed separately for each surface emitting part 22 out of the upper and lower electrodes 26 and 23, the lower electrode 23 in this embodiment, is formed like a wedge. In the surface emitting part 22, the whole exit plane preferably overlaps the entrance plane 63 of the corresponding light guide part 60, so that light is not emitted to the light guide part 60 corresponding to the adjacent surface emitting part 22.

The entrance plane 63 of the light guide part 60 entirely contacts just like facing the exit plane of the surface emitting part 22, the shape of the entrance plane 63 of the light guide part 60 overlaps the emission form of the surface emitting part 22, the apex angle 62 of the light guide part 60 is located at the vertex or close to the vertex of one end 31 of the surface emitting part 22, and the entrance plane 61 of the light guide part 60 is parallel to the bottom side of the other end 32 of the surface emitting part 22. The direction of a principal axis passing through one end 31 of the surface emitting part 22 and orthogonal to the other end face 32 is identical to the direction of a principal axis Ax (FIG. 4) of the light guide part 60 viewed from the normal of the surface emitting part 22.

As explained above, the opposite reflection plane 64 of the light guide part 60, or the width W (FIG. 3) of the light guide part 60, is set to be gradually prolonged from the apex 62 to the exit plane 61, or as approaching the exit plane 61. The side reflection planes 65 and 66 of the light guide part 60, or the height H (FIG. 4) of the light guide part 60 are set to be gradually prolonged from the apex angle 62 to the exit plane 61, or as approaching the exit plane 61.

The light guide part 60 can be formed by using nano-inprint technology, that is, flowing polydimethylsiloxane resin, a kind of silicon rubber, in a resist pattern, and solidifying it as a mold.

As shown in FIG. 1, the exit plane 61 of the light guide part 60 is opposite to the entrance plane of the SELFOC lens array 4, so that the exit plane 61 of the light guide parts 60 becomes a light-emitting part of the scanning head 2, and the principal axis Ax of the light guide part 60 coincides with the optical axis of the CELFOC lens array 4.

A driving circuit 80 is provided on one side of the surface emitting part array panel 20, a wiring 33 connected electrically to the lower electrode 23 of the surface emitting part 22 is also electrically connected to the driving circuit 80. The driving circuit 80 applies a light emission voltage to the lower electrode 23 through the wiring 33. The upper electrode 26 is held at a constant voltage, and for example, the upper electrode 26 is grounded.

For driving the scanning head 2, the driving circuit 80 applies a light emission voltage to the lower electrode 23 of each surface emitting part 22, based on an image signal. Each surface emitting part 22 emits a light beam onto the light-emitting layer 25 with the intensity according to the potential difference between the lower electrode 23 and upper electrode 26. In this time, since the light-emitting layer overlapping the lower electrode 23 and upper electrode 26 is wedge-shaped, the surface emitting part 22 emits light like a wedge. The wedge pattern light emitted from the surface emitting part 22 enters the entrance plane 63 of the light guide part 60. Since the light guide part 60 is set to have an included angle .gamma. and elevation angle .theta., the entered light is given directivity to advance toward the exit plane 61, and propagated in the light guide part 60, while repeating reflection on the entrance plane 63, opposite reflection plane 54 and side reflection planes 65 and 66, and by the reflection member, such as the lower electrode 23 of the surface emitting part 22, and finally output from the exit plane 61 of the light guide part 60 substantially along the principal axis Ax of the light guide part 60. In this way, the light guide part 60 itself functions as a light adjusting part to adjust the directivity of an incident light beam. Therefore, the light entered the entrance plane 63 of the light guide part 60 is efficiently emitted from the exit plane 61. The light beam emitted from the exit plane 61 of the light guide part 60 is focused at the generating line of the photoconductive drum 3 by the CELFOC lens array 4, forming an image on the side of the photoconductive drum 3.

As explained above, according to this embodiment, since the area of the exit plane 61 of the light guide part 60 is smaller than the area of the entrance plane 63, the light emitted from the surface emitting part 22 into the entrance plane 63 of the light guide part 60 is outputted from the exit plane 61 in being converged. As a result, the light beam is emitted with a high intensity from the exit plane 61 of the light guide part 60, even if the emission intensity per a unit area of the surface emitting part 22 is low. Therefore, the photoconductive drum 3 is exposed in a short time without increasing the sensitivity of the photoconductive drum, and the photoconductive drum 3 can be rotated at high speed. As a result, the printing time can be reduced.

It can be considered to increase the emission intensity of the surface emitting part 22 to increase the intensity of the light beam output from the exit plane 61 of the light guide part 60. But, if the emission intensity of the surface emitting part 22 is increased, the life of the surface emitting part 22 will be reduced. However, in this embodiment, the light emitted from the surface emitting part 22 to the entrance plane 63 of the light guide part 60 is outputted from the exit plane 61 in the converged state, and the intensity of the light output from the exit plane 61 of the light guide part 60 can be increased also by increasing the light-emitting area of the surface emitting part 22. Even if the light-emitting area of the surface emitting part 22 is increased, the light intensity on the exit plane 61 of the light guide part 60 is increased without increasing the area of the exit plane 61 of the light guide part 60, by expanding the area of the entrance plane 63 of the light guide part 60 to meet the expanded light-emitting area of the surface emitting part 22. Therefore, an image can be formed with high resolution without increasing a dot diameter.

Further, the shape of the light guide part 60 is set so that the light entered into the light guide part 60 easily advances to the exit plane 61 of the light guide part 60, and the light taken in from the entrance plane of the light guide part 60 can be efficiently emitted. Directivity is given to increase the light intensity in the direction of the principal axis Ax of the light guide part 60, and the light beam can be efficiently applied to the CELFOC lens array 4. The light use efficiency is increased, and the photoconductive drum 3 can be exposed in short time and rotated at high speed without increasing the sensitivity, and the printing time can be increased.

The invention is not limited to the above embodiments. Various improvements and design changes are permitted without departing from the spirit or essential characteristics of the invention. Examples of modification will be explained hereinafter.

[Modification 1]

FIG. 6A to FIG. 8B show modifications of the invention, in which the emission form of the surface emitting part 22 and the shape of the light guide part 60 are modified. FIG. 6A, FIG. 7A, and FIG. 8A are plane views showing the emission form of the surface emitting part 22 together with the light guide part 60. FIG. 6B, FIG. 7B and FIG. 8B are arrow indicated cross sections of the planes along the thickness direction of the insulating substrate 30, passing the cutting lines 6B-6B, 7B-7B and 8B-8B of FIG. 6A, FIG. 7A and FIG. 8A, respectively. To simplify the figures, the layers of the surface emitting part 22 are omitted.

As shown in FIG. 6A, the included angle at one end 31 is set to .gamma. (.gamma.>0.degree.), and the surface emitting part 22 is pentagonal with both sides 34 of the other end 32 made parallel to each other, so that the width is increased to the substantial halfway and becomes constant from the halfway, as approaching the exit plane 61. The shape of the entrance plane 63 of the light guide part 60 is similar to the emission form of the surface emitting part 22, and the area of the surface emitting part 22 is 80-110%, preferably 85-99% of the area of the entrance plane or light receiving surface 63 of the light guide part 60. The whole surface of the surface emitting part 22 preferably overlaps the entrance plane 63 of the corresponding light guide part 60, so that light is not emitted into the light guide part 60 corresponding to the adjacent surface emitting part 22. Similarly, the light guide part 60 has an included angle of .gamma.. As shown in FIG. 6B, the opposite reflection plane 64 of the light guide part 60 is divided into an inclined reflection flat plane 64a which is inclined with a predetermined elevation angle .theta. from the apex 62 to the exit plane 61, and a parallel reflection flat plane 64b which corresponds to the side 34 and is parallel to the entrance plane 63. Therefore, the sectional area parallel to the exit plane 61 is gradually expanded from the apex angle 62 to both side sides 34, but the sectional area of the parts corresponding to both sides of the other end 32 is even. The part surrounded by the inclined reflection plane 64a, side reflection planes 65/66 and the entrance plane 63 functions as a light adjusting part to adjust the directivity of incident light.

As shown in FIG. 7A, the emission form or plane of the surface emitting part 22 is trapezoidal with the width increased from one end 31 to the other end 32, or as approaching the exit plane 61. The one end 31 is short, and the other end 32 is long. In the surface emitting part 22, the inclination angle between the sides is set to .gamma. (.gamma.>0.degree.). In this case, the shape and dimensions of the entrance plane 63 of the light guide part 60 is substantially similar to those of the surface emitting part 22. In the light guide part 60, a flat top plane 64c is formed at the position opposite to the exit plane 61. One side of the top 64c is identical to one side of the inclined reflection plane 64d that is opposite to the entrance plane 63 and has the elevation angle .theta. to the entrance plane 63. The area of the emission surface of the surface emitting part 22 is 80-110%, preferably 85-99% of the area of the entrance plane 63 of the light guide part 60. The whole surface of the surface emitting part 22 is preferably overlaps the entrance plane 63 of the corresponding light guide part 60, so that light is not emitted to the light guide part 60 corresponding to the adjacent surface emitting part 22. In the surface emitting part 22 having such an emission form, the light guide part 60 is a quadrangular pyramid, as shown in FIG. 7A and FIG. 7B. Namely, as the width and height of the light guide part 60 are increased, as approaching the exit plane 61, the area of the section parallel to the exit plane 61 is expanded from the included angle between the entrance plane 63 and opposite reflection plane 64, to the exit plane 61. Therefore, the light guide 60 itself functions as a light adjusting part to adjust the directivity of incident light.

In the surface emitting part 22 shown in FIG. 8A, the emission form of the surface emitting part 22 is hexagonal with the width increased from one end 31 to the halfway of the other end 32, that is, to the substantial halfway of the exit plane 61, as approaching the exit plane 61, and becomes the same thereafter. The one end 31 has a short width, and the other end 32 is opposite to the short lateral side and has a long width. In the surface emitting part 22, the inclination angle between the inclined side plane portions close to the one end 31 is set to .gamma. (.gamma.>0.degree.). Both side plane portions 34 adjacent to the long end 32 are parallel to each other. In this case, also, the shape of the entrance plane 63 of the light guide part 60 is substantially similar to the emission pattern of the surface emitting part 22. The area of the emission plane of the surface emitting part 22 is 80-110%, preferably 85-99% of the area of the entrance plane of the light guide part 60. The whole surface of the surface emitting part 22 preferably overlaps the entrance plane 63 of the corresponding light guide part 60, so that light is not emitted to the other light guide part 60 corresponding to the adjacent surface emitting part 22. In the surface emitting part 22 having such an emission form, the oppositing reflection plane 64 of the light guide part 60 is divided into an inclined reflection plane or part 64a which is inclined with a predetermined elevation angle .theta. to the entrance plane 63, a parallel reflection plane or part 64b which corresponds to the side 34 and is parallel to the entrance plane 63, and an upper bottom surface or part 64c which is provided at the position opposite to the exit plane 61, as shown in FIG. 8B. Namely, though the sectional area parallel to the exit plane 61 is expanded over the inclined reflection plane 64a, the sectional area of the parts corresponding to both sides 34 of the other end 32 is even. As a result, the part surrounded by the inclined reflection plane 64a, side reflection planes 65, 66 and entrance plane 63 functions as a light adjusting part to adjust the directivity of incident light.

The surface emitting part 22 can be lit in the form shown in FIG. 8A, by changing appropriately the shape of the light-emitting layer 24 of the part which overlaps the lower electrode 23 and upper electrode 26, or the shape of the lower electrode 23 with the whole surface covered by the upper electrode 26 and light-emitting layer 25.

In either FIG. 6A or FIG. 8A, the area of the entrance plane or light receiving surface 63 of the light guide part 60 is preferably larger than the area of the exit plane or light emitting surface 61. Even if the emission intensity per unit area of the surface emitting part 22 is low, the exit plane 61 of the light guide part 60 emits a light beam with a high intensity. The light guide 60 is expanded from the included angle side between the entrance plane 63 and opposite reflection plane 64, to the exit plane 61, and the directivity of light in the direction vertical to the exit plane 61 is improved.

[Modification 2]

In the embodiment and modification explained above, the exit plane 61 of the light guide part 60 is flat. The exit plane 61 may be configured to function as a lens surface. For example, as shown in FIG. 9, the exit plane light emitting surface 61 may function as a condenser lens surface if the surface is formed as a convex surface. In this case, an the exit plane 61 functions as a lens surface, and thus emitted light beam can be condensed on the generating line of the photoconductive drum 3 without the CELFOC lens array 4 shown in FIG. 1.

[Modification 3]

In the embodiment and modifications explained above, the light guide part is made of transparent solid material such as resin or glass. A part 167 corresponding to the body of the light guide part 60 may be hollow, and the hollow light guide part 167 may be made of gaseous matter such as air, as shown in FIG. 10 to FIG. 12. To form the hollow light guide part 167, a plurality of hollow light guide parts 167 are depressed or grooved on one side of an opposite substrate 190 made of such as glass, a reflection film 168 is formed on the inside wall surface (opposite surface 164) of these hollow light guide parts 167, one hollow light guide part 167 is related to one surface emitting part 22, and the side with the hollow light guide part 167 formed is stuck to the emission plane 21 of the surface emitting part array panel 20. The hollow light guide part 167 is extended to the side end face of the opposite substrate 190, and the extended one end of the hollow light guide part 167 is opened as an opening 161 which becomes an exit plane or light emitting part. The shape of the hollow light guide part 167 is preferably the same as the light guide part 60, and the hollow light guide part 167 is formed as a pyramid with the opening area reduced in the part from the opening 161 to the end 162. The part 163 of the hollow light guide part 167, facing the surface emitting part 22 serves as an entrance plane, the opposite side surface 164 serves as an opposite reflection plane, and the opening 161 serves as an exit plane. Reflection film 168 are formed also on the side reflection planes 165 and 166, thus, the side reflection planes 165 and 166 serve as a reflection plane. Even if the area of the opening 161 of the hollow light guide part 167 is smaller than the light emitting area of the surface emitting part 22 and the emission intensity per a unit area of the surface emitting part 22 is low, as in the case shown in FIG. 10, the rectangular opening 161 of the hollow light guide part 167 emits light with a high intensity. The opening area of the hollow light guide part 167 is reduced in the part from the opening 161 to the end 162, and the directivity of light is improved.

[Modification 4]

In the embodiment and modifications explained above, the light guide parts 60 and 167 are formed to have wedge-shaped entrance plane 63 and opposite reflection plane 64, and the area of the cross section parallel to the exit planes 61 and 161 are pyramidal expanding in the part from the apex angle 62 (the end 162) to the exit planes 61 and 161. The light guide part 60 may be formed to have rectangular entrance plane 63 and opposite reflection plane 64, as shown in FIG. 13. A reflection film is formed on the surface of its light guide part 60 except the entrance plane 63 and exit plane 61 facing the surface emitting part array panel 20. In this case, it is recommendable to make the emission form or pattern of the surface emitting part 22 the same as the shape of the entrance panel 63 of the light guide part 60. Since the light guide part 60 has such a shape that the light in the light guide part 60 may easily advance to the exit plane 61 of the light guide part 60, the light taken in from the entrance plane of the light guide part 60 can be efficiently emit and given directivity to increase the light intensity in the principal axis Ax of the light guide part 60.

[Modification 5]

In the embodiment and modifications explained above, the reflection films 70 and 170 are formed separately for the light guide parts 60 and 167. The reflection films may be one continuous film covering all light guide parts 60, as shown in FIG. 14 and FIG. 15. The reflection film 70 is a part hatched by slanted lines in FIG. 14. The reflection film covers not only the outside surface of the surface emitting part 22, but also the whole upper surface of the surface emitting part array panel 20, and prevents leakage of light from the upper surface of the surface emitting part array panel 20.

[Modification 6]

In the embodiment and modifications explained above, the scanning head 2 is used as a printer head. The scanning head 2 may be used as an output head to emit a light beam linearly, by combining with a linear image pickup element (line sensor) in an image input apparatus.

[Modification 7]

In the embodiment and modifications explained above, the light guide parts 60 and 167 are formed to have the height gradually increased based on the elevation angle .theta.(.theta.>0.degree.) of the opposite reflection planes 64 and 164, as approaching the exit planes 61 and 161. The invention is not limited to this. Even if the opposite reflection plane 64 is placed parallel to the entrance plane, directivity is given to increase the light intensity in the principal axis Ax of the light guide part 60 as long as the sides 65 and 66 are inclined with an inclination angle of .gamma. (.gamma.>0.degree.), as shown in FIG. 16.

[Modification 8]

In the embodiment and modifications explained above, the surface emitting part 22 is composed of the top emission type organic electroluminescent element 27, which is formed on the side provided with the light guide part of the insulating substrate 30. The surface emitting part 22 may be composed of an organic electroluminescent element of a so-called bottom emission type, which is formed on the opposite side of the light guide part of the insulating substrate 30. Namely, an organic electroluminescent element is provided on one side of the insulating substrate 30, and the light guide parts 60 and 167 are provided on the opposite side. In this case, the light from the surface emitting part 22 is diffused in the insulating substrate 30 according to the thickness of the insulating substrate 30, before reaching the entrance planes of the light guide parts 60 and 167. To compensate the light-diffusion, it is preferable to set the area of the entrance planes of the light guide parts 60 and 167 sufficiently wide with respect to the area of the exit plane of the organic electroluminescence element.

[Modification 9]

In the embodiment and modifications explained above, an organic electroluminescent element is used for the surface emitting part 22. An inorganic electroluminescent element may be used for the surface emitting part 22.

EMBODIMENT 1

The invention will be explained more concretely hereinafter by taking examples of embodiment.

In FIG. 17B, X is an example to be compared to X in FIG. 17A, and is a simulation value of the ratio of the emission intensity (unit: W/sr m.sup.2) of the exit plane 61 of the light guide part 60 to the emission intensity (unit: W/sr m.sup.2) of the surface emitting part 22 of the rectangular parallelepiped light guide part, assuming that the elevation angle .theta. is 0.degree., the inclination angle .gamma. is 0.degree. (the opposite reflection plane 64 is rectangular), the exit plane width W is 10 .mu.m, the exit plane height H is 10 .mu.m, and the length L from the exit plane to the opposite side of the light guide part 60 is 200 .mu.m. Here, the refractive index of the light guide part 60 is 1.0, and the surface emitting part 22 is set to the same shape and size as those of the lower side of the light guide part 60.

In FIG. 17B, Y is an example to be compared to Y in FIG. 17A, and is a simulation value of the ratio of the emission intensity (unit: W/sr m.sup.2) of the exit plane 61 of the light guide part 60 to the emission intensity (unit: W/sr m.sup.2) of the surface emitting part 22 of the rectangular parallelepiped light guide part, assuming that the elevation angle .theta. is 2.86.degree., the inclination angle .gamma. is 0.degree. (the opposite reflection plane 64 is rectangular), the exit plane width W is 10 .mu.m, the exit plane height H is 10 .mu.m, and the length L from the exit plane to the opposite side of the light guide part 60 is 200 .mu.m. Here, the refractive index of the light guide part 60 is 1.0, and the surface emitting part 22 is set to the same shape and size as those of the lower side of the light guide part 60.

In FIG. 17B, Z is an example to be compared to Z in FIG. 17A, and is a simulation value of the ratio of the emission intensity (unit: W/sr m.sup.2) of the exit plane 61 of the light guide part 60 to the emission intensity (unit: W/sr m.sup.2) of the surface emitting part 22 of the rectangular parallelepiped light guide part, assuming that the elevation angle .theta. is 5.72.degree., the inclination angle .gamma. is 0.degree. (the opposite reflection plane 64 is rectangular), the exit plane width W is 10 .mu.m, the exit plane height H is 10 .mu.m, and the length L from the exit plane to the opposite side of the light guide part 60 is 200 .mu.m. Here, the refractive index of the light guide part 60 is 1.0, and the surface emitting part 22 is set to the same shape and size as those of the lower side of the light guide part 60.

As described above, as the elevation angle is increased from 0.degree., the emission intensity per unit area is increased. In other words, as the elevation angle is increased, the directivity of the emergent light from the exit plane 61 is improved, and the intensity of the emergent light is amplified. The emission efficiency of whole emission energy is 30-50%, and this efficiency is increased when the angle .theta. is optimized. For example, assuming that the area of the entrance plane 63 (the light-emitting area of the surface emitting part 22) is 10 times of the area of the exit plane 61, when the emission efficiency is 50%, a current density can be increased to 5 times.

EMBODIMENT 2

In a rectangular parallelepiped light guide part with an elevation angle .theta.=0.degree. and an inclination angle .gamma.=0.degree., the relation between the emission angle and luminous intensity of the light emitted from the exit plane of the light guide part is simulated as a comparing example. The exit plane width W of the light guide part is 10, the exit plane height H is 10 .mu.m, the length L from the exit plane to the opposite side is 200 .mu.m, and the refractive index is 1.0. The result is shown in the pola graph of FIG. 18A. A maximum radiation luminous intensity is approximately 1740.

In a light guide part with the same structure as the light guide part of FIG. 10, the relation between the emission angle and luminous intensity of the light emitted from the exit plane is simulated. The width W of the exit plane 161 in FIG. 10 is 10 .mu.m, the exit plane height H is 10 .mu.m, the length L from the apex angle 162 of the light guide part to the exit plane 161 is 200 .mu.m, and the refractive index of the light guide part 60 is 1.0. The result is shown in FIG. 18B. In FIGS. 10 to 12, the reflection planes 165 and 166 are right triangles. In this embodiment, the side reflection planes corresponding to the reflection planes 165 and 166 are set to an isosceles triangle with the same shape and size as the opposite reflection plane 164. A maximum radiation luminous intensity is approximately 3100.

In another light guide part with the same structure as the light guide part of FIG. 10, the relation between the emission angle and luminous intensity of the light emitted from the exit plane is simulated. The width W of the exit plane 161 in FIG. 10 is 20 .mu.m, the exit plane height H is 20 .mu.m, the length L from the apex 162 of the light guide part to the exit plane 161 is 200 .mu.m, and the refractive index of the light guide part 60 is 1.0. The result is shown in FIG. 18C. In FIG. 10, the reflection planes 165 and 166 are right triangles. In this embodiment, the side reflection planes corresponding to the reflection planes 165 and 166 are set to an isosceles triangle with the same shape and size as the opposite reflection plane 164. A maximum radiation luminous intensity is approximately 3690.

In either FIG. 18A or FIG. 18C, the radius of the graph indicates a luminous intensity, and the central angle indicates a radiation angle. As the elevation angle .theta. and inclination angle .gamma. are increased, a maximum radiation luminous intensity can be increased.

Other embodiments to implement the invention will be explained hereinafter with reference to the figures. These embodiments are given various technically preferable limitations to implement the invention, but the scope of the invention is not limited to these embodiments and illustrated examples.

FIG. 19 is a perspective view of an image output apparatus 1. As shown in FIG. 19, in the image output apparatus 1, a scanning head 2 having two or more light-emitting elements is placed with the light-emitting part opposed to a generating line of a photoconductive drum 3 and the longish side paralleled to the rotary shaft of the roller-shaped photoconductive drum 3. A SELFOC lens array 4 is provided between the light-emitting part of the scanning head 2 and the generating line of the photoconductive drum 3, with two or more CELFOC lenses arranged in a line or two or more lines along the light-emitting part of the scanning head 2, each of which takes a radial straight line of the photoconductive drum 3 as an optical axis. The light beam from the light-emitting part of the scanning head 2 is focused onto the generating line of the photoconductive drum 3 by the CELFOC lens.

FIG. 20 is a perspective view showing the configuration of three dots of the scanning head 2. The scanning head 2 has a surface emitting part array panel 20, and a plurality of light guide parts 60 aligned arranged on the emission plane 21 of the surface emitting part array panel 20.

FIG. 21 is a plane view of the emission plane 21 of the surface emitting part array panel 20. FIG. 22 is an arrow indicated cross section of the plane along the thickness of an insulating substrate 30, passing lines XXII-XXII of FIG. 21. FIG. 23 is an arrow indicated cross section of the plane along the thickness of an insulating substrate 30, passing lines XXIII-XXIII of FIG. 21.

As shown in FIGS. 21 to 23, the surface emitting part array panel 20 is composed of an insulating substrate 30 and a plurality of surface emitting parts 22 shaped like substantially a rectangle (quadrilateral) in a plane view, and aligned on the insulating substrate 30 to be placed underside of the light guide part 60.

Each of the surface emitting parts 22 has an organic electroluminescent element 27. Namely, the surface emitting part 22 has a light reflective lower electrode 23 formed on the insulating substrate 30, an organic EL layer stacked on the lower electrode 23, and a transparent upper electrode 26.

The organic electroluminescent layer has a positive hole carrying layer 24 and a light-emitting layer 25, for example, as shown in FIG. 22. The positive hole carrying layer 24 contains polythiophene (PEDOT) as a conductive high polymer, and polystyrene sulfonic acid (PSS) as dopants. The light-emitting layer 25 contains a conjugated double-bond polymer such as polyphenylene vin