JP2000353590A - Organic el light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end face light-emitting type organic EL light-emitting device with a compact size, a light weight, a long life, and an optimal exposure. SOLUTION: An organic EL light-emitting device 1 has an organic layer including a board 3, a signal electrode/reflective film 2, a hole injection electrode 4, and a light- emitting layer 8, an electron injection electrode 9, a protective film 10 and a reflective film 11. The light-emitting layer 8 comprises light-emitting dots arranged in a sub scanning direction, and combining three colors of R, G, and B as a set, and the individual colors are arranged in a main scanning direction. Light from the individual light- emitting layers are reflected on the signal electrode/reflective film 2 and the reflective layer 11, and is projected forward in the sub scanning direction from one end face of an element on a red light-emitting layer side. One exposure enables a full color high speed reproduction, thereby reducing an impressing time of an input power on a phosphor per exposure, resulting in increasing the life of the device. A switching mechanism for a color filter is dispensed with and so reduction in size and weight can be attained. Light-emitting intensities of the individual colors are properly set/ corrected with a impressed voltage, a pulse width, a light-emitting area and the like, thereby enabling a exposure under an optimal condition matching a photosensitive characteristic of a recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic EL light emitting device having an organic layer laminated on a substrate and emitting light from the organic layer from an end face of the layer.

[0002]

2. Description of the Related Art An organic EL device has a structure in which a thin organic layer containing a fluorescent organic compound is sandwiched between a cathode serving as an electron injection electrode and an anode serving as a hole injection electrode. A display element that generates excitons (excitons) by injecting and recombining holes and injects light to emit light (fluorescence / phosphorescence) when the excitons are deactivated.

In recent years, there has been proposed an optical printer using the organic EL element as a light source. An example in which an organic EL element is used in an optical print head is disclosed in JP-A-9-22.
No. 6,171. In these, the direction in which light emitted from the light emitting layer is extracted is set to the end face of the stacked organic layers. The light-emitting section has monochrome light-emitting dots arranged on one line at predetermined intervals.

FIG. 5 is a sectional view of such a conventional organic EL device. This organic EL light emitting device is
And the signal electrode 101 formed thereon and the signal electrode 1
01, a hole injection electrode 102, an insulating layer 103 having a window (opening) 104 formed thereon, and a hole transport layer formed on the insulating layer 103 so as to cover the window 104. 105, a light emitting layer 106 formed thereon, and an electron injection electrode 107 formed thereon.

A voltage is applied to the signal electrode 101 and the electron injection electrode 107. Light emitted from the light-emitting layer 106 passes through the light-transmitting insulating layer 103 from the end face of the light-emitting layer 106 and is emitted to the outside of the element as light emitted by an arrow in FIG.

[0006]

When the above-described edge-emitting type organic EL light emitting device is used as a print head, there are the following problems.

[0007] In order to form a full-color image in a print head using the organic EL element as a light source,
The following two types of configurations are conceivable.

[0008] First, R (red), G (green) are placed outside one organic EL light emitting element having one line of light emitting dots.
This is an organic EL light emitting element provided with three color filters of (green) and B (blue) switchable.

Light emitted from a light emitting dot of one organic EL element passes through a color filter, passes through a lens element of equal magnification, and forms an image on a recording medium. In this head, 1
A full-color image can be formed by exposing light of each color three times to one recording medium.

However, in this case, it is necessary to reciprocate the head at least three times, and there is a problem that the exposure time becomes long. In addition, since three multiple exposures are performed in the same light emitting portion, there is a problem that the life of the element is short.

Further, in this head, in order to form a full-color image, color filters outside the organic EL element are switched in the predetermined order of R, G, and B to perform multiple exposures three times. To take R,
The correction is performed by changing the input power for each of the colors G and B. Therefore, a power source is required for each of R, G, and B, and the driving circuit becomes complicated. Also, three power supplies are required, which is disadvantageous in reducing the size and weight of the print head including the drive circuit.

Further, in this head, the color filters outside the organic EL element are switched to R, G, and B in a predetermined order to perform a multiple exposure three times in order to form a full-color image. A color filter switching mechanism is required, which hinders the reduction in size and weight of the print head including the housing.

Next, a method for forming a full-color image in a print head using an organic EL light emitting element as a light source is described.
The following configuration can be considered as the second configuration.

That is, three organic EL light emitting elements are used, R, G, and B fixed color filters are provided for each element, and an equal magnification lens element is provided for each element.

In this head, an equal magnification lens element is provided for each of the three organic EL light emitting elements, and the optical characteristics of the respective equal magnification lens elements are not completely the same due to manufacturing variations. It was difficult to expose the dot-shaped light from the two organic EL light emitting elements so as to completely coincide with the same position on the recording medium. There are other causes of this difficulty. For example, it is difficult to completely overlap the dot-like lights from the three organic EL light emitting elements at the same position on the recording medium due to the uneven feeding of the head. Further, according to this head having three organic EL light emitting elements, there is a problem that the size and weight of the entire device cannot be avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems. In an edge-emitting type organic EL light-emitting device, it is compact and lightweight, has a simple structure, and can effectively extract light from the edge. It is an object of the present invention to provide a color organic EL light emitting element that can be used.

[0017]

According to the present invention, there is provided an organic EL light emitting device (1) comprising a substrate (3) and a first electrode (hole injection electrode 4) formed on the substrate. An organic layer including a light emitting layer (8) and formed on the first electrode;
Second electrode (electron injection electrode) formed on the organic layer
Wherein the light from the light emitting layer is output in a direction parallel to the organic layer, wherein the light emitting layer (8) is arranged so that the light overlaps and is output in the same direction. And a plurality of light emitting layers.

According to a second aspect of the present invention, there is provided an organic EL light emitting device (1), comprising a substrate (3), a first electrode (hole injection electrode 4) formed on the substrate, and a light emitting layer (8). And an organic layer formed on the first electrode and a second electrode (electron injection electrode) formed on the organic layer, wherein light from the light emitting layer is parallel to the organic layer. Organic E output in the direction
In the L light-emitting element, the light-emitting layer (8) is characterized in that the light-emitting layers (8) are composed of a plurality of light-emitting layers arranged to emit light of different colors and to output light in the same direction.

According to a third aspect of the present invention, there is provided the organic EL light emitting device according to the second aspect.
The luminous intensities of the plurality of luminous layers (8) are different from each other, a luminous layer having a relatively low luminous intensity is disposed outside the element, and a luminous layer having a relatively high luminous intensity is disposed inside the element. It is characterized by:

The organic EL device according to the fourth aspect is the organic EL device according to the second aspect, wherein
It is characterized in that the areas of the plurality of light emitting layers (8) are different depending on the emission color.

According to a fifth aspect of the present invention, there is provided the organic EL light emitting element according to the second aspect, wherein
It is characterized in that the current applied to the plurality of light emitting layers (8) differs depending on the emission color.

According to a sixth aspect of the present invention, there is provided the organic EL device according to the second aspect, wherein
It is characterized in that the light emission time of the plurality of light emitting layers (8) differs depending on the emission color.

According to a seventh aspect of the present invention, in the organic EL light emitting device according to the first or second aspect, the light emitting layer (the electron injection electrode 9) is provided on the second electrode (the electron injection electrode 9). The reflective film (11) for reflecting the light from 8) is continuously provided via an insulating layer (protective film 10).

According to an eighth aspect of the present invention, there is provided the organic EL light emitting device according to the first or second aspect, wherein the first electrode (the hole injection electrode 4) and the substrate (3) are connected to each other. A reflection film (signal electrode / reflection film 2) for reflecting the light from the light emitting layer (8) is provided between them.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An organic EL light-emitting device as an example of an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic plan view of an organic EL light emitting device according to the present invention, and FIG.
1 is a cross-sectional view taken along the line AA in FIG. 1, and FIG.
It is sectional drawing in the -B cutting line.

First, the structure of the organic EL device 1 of this embodiment will be described along with its manufacturing steps. As shown in FIG. 1, in this organic EL device 1, R (red), B
Light emitting dots that emit light of each color (blue) and G (green) are arranged in the main scanning direction for each color. Here, the longitudinal direction of the transparent substrate 3 is hereinafter referred to as a main scanning direction, and the lateral direction thereof is referred to as a sub-scanning direction. The light emitting dots that emit light of each color of R (red), B (blue), and G (green) are arranged in groups of three in the sub-scanning direction. R (red), B (blue), G
Light-emitting dots that emit light of each color (green) have different areas.

(1) A signal electrode / reflection film 2 is formed on a transparent substrate 3 using a material such as Al having a high reflectance and a low resistance. The signal electrode / reflection film 2 is a rectangular short band-shaped electrode whose longitudinal direction is in the sub-scanning direction, and is arranged in parallel with each other along the main scanning direction. Above each signal electrode / reflection film 2, a set of light emitting dots of each color is formed. Above a plurality of signal electrode / reflection films 2 arranged in the main scanning direction,
Light-emitting dots of the same color are formed so as to be arranged in a line along the main scanning direction. If a material having a surface work function of 4.0 eV or more is used, the signal electrode / reflection film 2 also has the function of a hole injection electrode, which is more preferable.

(2) The hole injection electrode 4 is formed on the signal electrode / reflection film 2. The hole injection electrode 4 is a rectangular short-strip electrode whose longitudinal direction is in the sub-scanning direction, but the length in the sub-scanning direction is slightly shorter than that of the signal electrode / reflection film 2. The hole injection electrodes 4 are arranged parallel to each other along the main scanning direction. The hole injection electrode 4 has a surface work function of 4.0 eV or more, such as ITO (composite oxide of indium oxide and tin) and IDIXO (composite oxide of indium oxide and zinc oxide, a trademark of Idemitsu Kosan). Made of a transparent conductive material. The hole injection electrode 4 does not necessarily have to be transparent. If the hole injection electrode 4 is made of a material that reflects light in the visible region well, the hole injection electrode 4 has the function of both the signal electrode and the reflection film 2, which is more preferable.

(3) An insulating layer 5 is formed on the hole injection electrode 4 so that the light emitting dots are formed in a predetermined pattern on the hole injection electrode 4 to form a window opening pattern (opening 6). To form

(4) The insulating layer 5 is made of a material that is transparent to the emission wavelength of the organic EL device 1 and is formed on the hole injection electrode 4 by spin coating, vapor deposition, sputtering, or the like. Form.

(5) Materials suitable for the insulating layer 5 include, for example, SiO _x and SiN _x .

(6) A part of the insulating layer 5 on the hole injection electrode 4 is removed by photolithography and patterned. On each of the hole injection electrodes 4, a set of three window openings (openings 6) having different opening areas and arranged in the sub-scanning direction is formed. The three openings 6 define light emitting dots of each color of RBG.

(7) A hole injection layer and a transport layer (HTL) 7 are formed to cover the opening 6 of the insulating layer 5 by a resistance heating evaporation method. This film forming operation is performed by bringing a metal mask having an opening corresponding to the light emitting area into close contact with the substrate 3.

(8) The hole injection layer and the transport layer 7 are preferably made of a material transparent to the visible region. Such materials suitable for the hole injection layer include 4,4 ', 4 "-tris (3-methylphenyph
enylamino) triphenylamine, ie m-MTDATA. Such materials suitable for the hole transport layer include N, N'-diphe
nyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-di
amine, i.e., TPD or N, N'-bis (N- (1-naphtyl) -Np
henyl) benzidine, that is, α-NPD and the like.

(9) The light emitting layer 8 is formed on the HTL by the resistance heating evaporation method. In this example, light-emitting dots of the same color are arranged at predetermined intervals along the main scanning direction, and light-emitting dots of different colors of RGB are arranged in a predetermined order in the sub-scanning direction. In order to form such an array of luminescent dots, the luminescent layer 8 is formed by bringing a corresponding metal mask into close contact with the substrate 3 for each luminescent dot row of different luminescent colors arranged in the main scanning direction.

(10) The arrangement of the light emitting layer 8 is determined by the light emission spectrum, light emission efficiency, sensitivity of the recording medium to light, etc. of the phosphor used for the light emitting layer 8. Preferably, a phosphor of a luminescent color having the least intensity when white balance is obtained is disposed on the light output side of the end face.

That is, as shown in FIG. 1, in this example, three R, B, and G light emitting layers 8 having different emission colors are arranged in the same plane along the sub-scanning direction. 3 in a row
Light from each of the RGB light emitting layers 8 is output in the same direction from the end face side of the upper light emitting layer 8 in the drawing. In such a configuration, the red (R) light-emitting layer 8 having the lowest intensity is arranged on the light emission side. Next, the blue (B) light emitting layer 8 having insufficient intensity is placed next to the red light emitting layer 8 (red light emitting layer 8).
Next to the light emission side). The green light-emitting layer 8 having a relatively high intensity was disposed at a position farthest from the end face on the light emission side.

In this way, the effect of light absorption can be reduced as much as possible in the device of the present embodiment in which light is extracted through the insulating layer 5 and the organic layer.

(11) Shape of light emitting dot of each color (insulating layer 5
The opening 6) has the same width in the main scanning direction, and its area can be freely set by changing the length in the sub-scanning direction.

(12) The amount of light that can be extracted from the end face side of the organic EL light emitting device 1 having a multilayer laminated structure depends on the light emitting layer 8
Is proportional to the light-emitting area. Therefore, the light intensity of each color can be arbitrarily set according to the light emitting area. From this point of view, as described above, it may not be particularly necessary to determine whether the light emitting dots are arranged at a position close to the end surface of the layer structure or at a position far from the end surface of the layer structure depending on the color.

In this example, as shown in FIG. 1, the red (R) light-emitting layer 8 having the least strength was formed in the widest area. Next, the area is reduced in the order of the blue (B) light emitting layer 8 and the green light emitting layer 8.

(13) FIG. 4 shows an example of sensitivity characteristics of a photosensitive material used for a film as an example of a recording medium.
R, G, B having sensitivity corresponding to light of each color of R, G, B
Tables 1 to 3 show examples of organic materials which have respective emulsions for use and emit light having a wavelength corresponding to each emulsion.

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

(14) Each organic material constituting the light emitting layer 8 has an optimum film forming condition determined for each material. Each of them may be used as a single layer film or may be used after being doped into an appropriate host material.

(15) After forming the light emitting layer 8, an electron transporting layer is formed thereon if necessary. This is also determined according to the characteristics of the material of the light emitting layer 8 to be used. In this example,
Since the light emitting layer 8 also serves as an electron transport layer, a single electron transport layer is not required.

(16) The electron injection electrode 9 is formed on the light emitting layer 8. The electron injection electrodes 9 are formed electrically independently of each other for each row of light-emitting dots of the same color arranged in the main scanning direction. Therefore, in this example, three electron injection electrodes 9 parallel to the main scanning direction are formed in parallel with each other for each light emitting layer 8 of each color of RGB. Each electron injection electrode 9 is individually controlled for each luminescent dot row of a different luminescent color.

(17) The electron injection electrode 9 is made of a material having a small work function so that electrons can be easily injected at the interface with the light emitting layer 8 or the electron transport layer. Good characteristics can be obtained by using simple substances such as Li, Na, Mg, and Ca, and compounds thereof, or Al: Li, Mg: In, and Mg: A.
Various alloys such as g can be used.

(18) After the formation of the electron injecting electrode 9, a protective film 10 for suppressing moisture absorption between the electron injecting electrode 9 and the organic layer is made of SiO 2 so as to cover the entire electron injecting cathode and the organic layer.
_X , a film such as SiN _X is formed.

(19) Finally, the reflective film 11 is formed on the protective film 10.
To form The reflective film 11 is formed so as to cover the entire stacked structure of the element except for the front end face from which light from the light emitting layer 8 is extracted. The reflection film 11 is made of a material having a high reflectance such as Al, reflects the light from the light emitting layer 8 without escaping in an invalid direction, efficiently guides the light to the front side in the sub-scanning direction,
Light is emitted from the end face of the layer structure.

According to this embodiment, even if the reflective film 11 made of Al is provided, there is no possibility of conduction since the protective film 10 exists between the reflective film 11 and the electron injection electrode 9. That is, the protective film 1
0 functions as an insulating layer between the reflection film 11 and the electron injection electrode 9.

(20) Organic EL device 1 having the above structure
Will be described. The electron injection electrode 9 is scanned in a predetermined order, and in synchronization with the scanning, a signal is applied to the signal electrode / reflection film 2 to select and emit a light emitting layer 8 (light emitting dot) of a desired color. Light from each light emitting layer 8 exits from the front end face in the sub-scanning direction.

In synchronization with the driving of the organic EL element 1, the print head including the organic EL element 1 or the recording medium facing the print head moves in the sub-scanning direction. As a result, light of each color of R, G, and B is multiple-exposed to the same portion of the recording medium, and a high-quality full-color image can be formed by one movement.

In the example described above, the organic EL light emitting element having three kinds of light emitting layers that emit light of each color of RGB has been described. However, two or more kinds of colors may be used. When the number of colors is two or three or more than the three primary colors, full color cannot be obtained, but multicolor display or optical recording of three or more colors is possible.

In the example of the organic EL device 1 described above, a plurality of types of light emitting layers 8 having different emission colors are formed with substantially the same light emitting area, and the amount of light irradiated on the recording medium is adjusted to the sensitivity of the recording medium. Light emission driving may be performed by changing the input power so as to obtain an optimum color balance.

In the example of the organic EL device 1 described above, the luminescent dots of each luminescent color are respectively interpolated so as to cover one line region in the main scanning direction of the recording medium by interpolating the gap in the main scanning direction. They may be arranged in a staggered manner. Here, the light emitting dots are changed in width in the main scanning direction and / or width in the sub-scanning direction so that the amount of light irradiated on the recording medium has an optimal color balance in conformity with the sensitivity of the recording medium. It is formed with a light emitting area according to the ratio.

Further, the distance between the centers in the sub-scanning direction of the light emitting dots arranged in a staggered manner in the main scanning direction is the same between the light emitting dot rows of different light emission colors, and at least the width in the sub scanning direction is changed to be the same. May be obtained.

According to the organic EL device 1 of each example described above, the organic EL device is controlled so that the image of each color overlaps the same position on the recording medium in accordance with the image signal of each color, and the multiple exposure is performed. A color image can be formed on a recording medium.

In the example described above, the organic EL light-emitting element used as the light source of the print head has been described. In addition, for example, a plurality of light-emitting dots are arranged at predetermined pitches in a row direction parallel to the rotation axis. A light source provided, rotation driving means for rotating the light source with its light emitting side facing the front about a rotation axis, and control means for emitting light emitting dots of the light source in synchronization with driving of the rotation driving means. It can also be used as a light source or the like for a rotary display device that performs display using the afterglow when the light source is rotated.

[0061]

According to the organic EL light-emitting device of the present invention, light from light-emitting layers having different emission colors is output in the same direction from the end face side perpendicular to the laminating direction of the organic layers. A plurality of effects as described below, or a composite effect in which these effects are synergistically obtained.

A single exposure makes it possible to reproduce full-color or multi-color at high speed, thereby shortening the application time of the input power applied to the phosphor in one exposure and prolonging the life of the device.

The need for a color filter switching mechanism is eliminated, and the size and weight of the print head including the housing can be reduced.

The light emission intensity of each color can be appropriately set and corrected by an applied voltage, a pulse width, a light emission area, and the like, so that exposure can be performed under optimum conditions suitable for the photosensitive sensitivity characteristics of the recording medium.

Further, when the intensity of each color is adjusted by the light emitting area, the light amount can be corrected while the input power per unit area is kept constant, so that the operating voltage or the current density can be made common and the driving circuit can be used. The print head, including the print head, can be reduced in size and weight.

Since the input power per unit area can be made constant, the deterioration mode does not change, and therefore the white balance does not change, so that a high-quality print can be stably reproduced.

Since the full-color light-emitting dots are arranged in one line, they can be used where the MTF of the SLA is optimal.

[Brief description of the drawings]

FIG. 1 is a plan view of an organic EL light emitting device which is an example of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a diagram illustrating an example of sensitivity characteristics of a photosensitive material used for a film as an example of a recording medium.

FIG. 5 is a cross-sectional view of a conventional organic EL device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 organic EL light emitting element 3 substrate 4 hole injection electrode as first electrode 7 hole injection layer and transport layer as organic layer 8 light emitting layer as organic layer 9 electron injection electrode as second electrode 10 protective film 11 reflective film

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Tatsuo Fukuda 629 Oshiba, Mobara-shi, Chiba Futaba Electronics Co., Ltd. F-term (reference) 3K007 AB00 AB04 BA04 CB01 DA00 DB03 EB00 FA01 GA04

Claims (8)

[Claims] A first substrate formed on the substrate; and a first substrate formed on the substrate.
An electrode, an organic layer including a light emitting layer, formed on the first electrode, and a second electrode formed on the organic layer, wherein light of the light emitting layer is parallel to the organic layer. In the organic EL light emitting device that outputs light in a direction, the light emitting layer is composed of a plurality of light emitting layers arranged so that light overlaps and is output in the same direction. 2. A substrate, and a first substrate formed on the substrate.
An electrode, an organic layer including a light emitting layer, formed on the first electrode, and a second electrode formed on the organic layer, wherein light of the light emitting layer is parallel to the organic layer. An organic EL light-emitting element that outputs light in a direction, wherein the light-emitting layer comprises a plurality of light-emitting layers arranged to emit light in different colors and to output light in the same direction. EL light emitting element. 3. A plurality of light emitting layers having different light emitting intensities, a light emitting layer having a relatively low light emitting intensity is disposed outside the element, and a light emitting layer having a relatively strong light emitting intensity is disposed inside the element. 3. The organic EL device according to claim 2, wherein the organic EL device is arranged.
Light emitting element. 4. The organic EL device according to claim 2, wherein the areas of the plurality of light emitting layers are different depending on the emission color. 5. The organic EL light emitting device according to claim 2, wherein currents applied to the plurality of light emitting layers differ depending on emission colors. 6. The organic EL light-emitting device according to claim 2, wherein the times at which the plurality of light-emitting layers emit light differ depending on the emission color. 7. The organic EL light emitting device according to claim 1, wherein a reflection film for reflecting light from the light emitting layer is provided continuously on the second electrode via an insulating layer. 8. A reflection film for reflecting light from the light emitting layer between the first electrode and the substrate.
The organic EL light-emitting device according to the above.