JPH06135054A - Optical printer head - Google Patents

Abstract

PURPOSE:To provide an optical printer head employing a highly precise and reliable edge emission EL element array. CONSTITUTION:In the optical printer head employing an edge emission EL element array, a lower electrode layer 2, a lower dielectric layer 3, an EL light emission layer 4, and an upper dielectric layer 5 are formed integrally on a substrate 1. An upper electrode layer 6 is formed to correspond with a light emitting pixel 7 and the edge of laminate is shaped such that the light is collected at the edge emission part 8 of pixel while scattered at the other edge part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical printer head, and more particularly, to an edge emitting electroluminescent element array (hereinafter referred to as edge emitting EL element array) which has a high performance and excellent reliability by a simple manufacturing method. ) Is used for the optical printer head.

[0002]

2. Description of the Related Art Markets of information processing equipment such as copying machines, facsimiles, computers, etc. are rapidly expanding, and devices used therefor are required to be inexpensive, high quality and highly functional. There is. The optical printer head is a device used for irradiating light on the photoconductor in the above-mentioned copying machine, facsimile, computer and the like.

In recent years, an optical printer head using an edge emitting EL element array in which a plurality of edge emitting EL elements are arranged in an array has attracted attention. For example, such an optical printer head is disclosed in Japanese Patent Laid-Open No. 2-162687. It is disclosed.

The structure of a conventional optical printer head using an edge emitting EL element will be described with reference to FIG. FIG. 3 shows a perspective view of a schematic structure of a conventional optical printer head.

A lower electrode layer 2, a lower dielectric layer 3, an EL light emitting layer 4, an upper dielectric layer 5, and an upper electrode layer 6 are formed on an insulating substrate 1.
A plurality of edge emitting EL elements, which are sequentially stacked, are arranged at a predetermined interval to form an array having a light emitting pixel portion 7. In such an edge-emitting EL device, the lower and upper electrode layers are usually made of Cr--Au, Al, etc.
2μm~0.4 formed in the layer thickness of [mu] m by sputtering, the lower and upper dielectric layers, such as SiON or SiO ₂ is formed by again sputtering the layer thickness of the 0.2μm~0.4 μm. ZnS: Mn, etc. is 1.0 μm in the EL emission layer
It is formed by vapor deposition or sputtering to a layer thickness of up to 2.0 μm. After that, a pixel including an EL light emitting layer is formed by a photolithography method.

The edge emitting EL element array obtained by arranging such pixels has a depth of several hundreds of μm, and the light emitted in this area is condensed at the edge, so that extremely strong light is obtained. A sufficient amount of light can be obtained as a printer head.

[0007]

However, the optical printer head using the edge emitting EL element array has the following problems to be solved. The edge emitting EL element array, which has rectangular pixels with a width of about 80 μm and a length of 400 to 500 μm corresponding to the printed dots, tends to deteriorate due to moisture. Long-term reliability is ensured by covering the entire surface with a protective film. However, it is difficult to completely cover the side wall portion having a length of about 400 to 500 μm, and there is a problem that the moisture resistance cannot be secured.

Further, the edge emitting EL element array used in the conventional optical printer head usually forms pixels having a roughness of about 12 dots / mm. In this case, the pixel width is about 80 μm and the pixel spacing is about 5 μm.
It is possible to form an EL layer approximately 2 μm thick by etching. However, the edge emitting EL element array used in recent high-definition optical printer heads requires pixels with a roughness of about 32 dots / mm. In this case, the pixel width is about 30 μm and the pixel interval is about 3 μm, making it extremely difficult to form an EL layer with a thickness of about 2 μm by etching, and a high-definition optical printer head cannot be obtained. There was a problem.

The present invention has been made to address such a problem, and has a high-definition and reliable edge emitting EL.
An object is to provide an optical printer head using an element array.

[0010]

An optical printer head according to the present invention comprises a substrate and a lower electrode layer, a lower dielectric layer, an EL light emitting layer, an upper dielectric layer and an upper electrode layer which are sequentially laminated on the substrate. In an optical printer head using an edge emitting EL element array having a plurality of pixels with the edge surface of the laminate as a light emitting portion at a predetermined interval, a lower electrode layer, a lower dielectric layer, and EL light emitting which constitute the edge emitting EL element array. Each of the layers, the upper dielectric layer, is integrally formed on the substrate, the upper electrode layer is formed corresponding to the pixel that emits light, and the end surface of the stacked body collects light at the end light emitting portion of the pixel and the other end surface portion. It is characterized in that it has a shape that is scattered light.

Each of the lower electrode layer, the lower dielectric layer, the EL light emitting layer, and the upper dielectric layer forming the edge emitting EL element array according to the present invention is integrally formed on the substrate.
It means that each of these layers is sequentially formed on an insulating substrate such as glass by a sputtering method or the like, and is formed integrally by a subsequent photolithography method without being separated into each pixel. Thereby, the moisture resistance is significantly improved.

A plurality of upper electrode layers are formed at a predetermined interval at the uppermost part of each layer integrally formed as described above, and each EL light emitting layer located under the upper electrode layer emits light. It becomes a pixel.

In the present invention, the end face of the laminated body forming each pixel is convex so as to have a shape for condensing at the end face light emitting portion, and each end face has a shape in which scattered light is provided at the other end face portion. The end faces of the stacked body between the pixels to be formed are formed to be uneven.

The convex shape of the end surface of the laminated body is such that when the light generated in the light emitting layer is emitted into the atmosphere, it is condensed from the end surface portion,
Alternatively, it may be a shape that is emitted almost vertically.

Further, the unevenness of the end surface of the laminated body between the adjacent pixels may be an uneven shape having an interval and height capable of scattering the wavelength of light generated in the light emitting layer. Specifically, in the case of a light emitting layer containing ZnS as a main component, the wavelength of the emitted light is about 0.5 μm, so the interval and height of the irregularities are preferably 0.2 to 1.0 μm. The irregular shape may be triangular or semicircular. This uneven shape has a space and height in the vicinity of the wavelength of emitted light.
It is recognized that if the thickness is in the range of 0.2 to 1.0 μm, the emitted light is sufficiently scattered even if the shape is broken.

The convex shape and the uneven shape of the end surface of the laminate can be formed by using a known photolithography method.

Edge emitting EL manufactured as described above
An optical printer head of the present invention can be obtained by providing an exterior assembly such as a drive circuit on the element array.

[0018]

In order to extract emitted light from a desired pixel using the optical printer head of the present invention, a predetermined voltage is applied between the lower common electrode and the upper electrode formed separately corresponding to this pixel. To do. As a result, light energy is generated in the light emitting layer sandwiched between these electrodes, and this light energy propagates in the light emitting layer and is emitted as radiated light from the end face portion sandwiched between the electrodes. Although the light generated in the light emitting layer propagates in various directions, the optical printer head of the present invention changes the shape of the end face portion between the pixel portion and the other portion. Therefore, the light is emitted from the pixel portion for the following reason. To be done. The relationship between the light propagating in the light emitting layer and the shape of the end face will be described with reference to FIG. 2 which is a plan view of the end face light emitting EL element array.

The refractive index of a light-emitting layer containing ZnS as a main component is usually
Over 2.0. Therefore, the critical angle (= sin ^-1 (1 / refractive index)) when the light generated in the light emitting layer is emitted into the atmosphere is 3
At 0 ° or more, only light that is substantially perpendicular to the end face is emitted at the end face of the pixel having a convex shape. On the other hand, regarding the possibility that the light generated in this pixel is emitted from an adjacent pixel, as shown in FIG. 2, there is a partial emission area and an emission area in the adjacent pixel. However, the radiated light from the partially radiable area becomes almost totally reflected light in the adjacent pixels, and the light generated in the radiable area several tens of μm deeper than the end face of the pixel has a relatively long distance in the light emitting layer. The intensity is weakened due to scattering and the like.
The relationship between the voltage of the photosensitive drum and the amount of light is shown in FIG. 4. As shown in FIG. 4, since the photosensitive drum has a steep sensitivity characteristic, the amount from adjacent pixels is small and the intensity is attenuated. The leaked light does not form a latent image on the photosensitive drum.

Next, the emitted light from the end face portion between the adjacent pixels is scattered at the end face portion between the adjacent pixels and its intensity is greatly attenuated. Therefore, in combination with the sensitivity characteristic shown in FIG. It does not form a latent image on it.

As a result of the above, the optical printer head of the present invention can take out the emitted light only from the desired pixel and does not emit the emitted light at the end face portion between the adjacent pixels. It is possible to perform high-quality printing with extremely good sharpness without forming a latent image that is larger than the pixel.

Further, as shown in FIG. 1, the optical printer head of the present invention has a highly reliable structure because the area of the exposed end surface, which is the etched portion of the EL layer, is extremely narrow and a protective film is easily formed. In addition, since the etching process for forming the pixel only needs the upper electrode, the manufacturing process becomes simpler than ever.

[0023]

Embodiments of the present invention will be described below with reference to the perspective view of the optical printer head shown in FIG.

A lower electrode 2, a lower dielectric layer 3, an EL light emitting layer 4, an upper dielectric layer 5 and an upper electrode 6 were sequentially laminated on a glass substrate 1. The lower electrode 2 has two layers of Cr-Au, and each film thickness is
Each film was formed to a thickness of 0.2 μm by a sputtering method. The lower dielectric layer 3 and the upper dielectric layer 5 were each formed of SiON to a thickness of 0.2 μm by a sputtering method. The EL emission layer 4 is Zn
S: Mn was formed into a film having a thickness of 1.2 μm by the EB vapor deposition method.
The upper electrode 6 was formed by sputtering Al with a thickness of 0.5 μm.

Thereafter, only the upper electrode 6 was separately formed corresponding to the light emitting pixel by dry etching by the RIE method. The electrode width was 28 μm, the electrode length was 500 μm, and the electrode interval was 3 μm.

Finally, a photoresist film was used to form the EL end face portion by dry etching by the RIE method. At this time, the light emitting pixel portion 7 was formed in a convex shape, and the end face portion 8 between the light emitting pixels was formed in an uneven shape at the same time during the dry etching.

An optical printer head was manufactured by providing an exterior assembly such as a driving circuit on the edge emitting EL element array.

Using the optical printer head thus obtained, a predetermined voltage was applied to the upper and lower electrodes of the desired pixel portion to examine the latent image on the photosensitive drum. As a result, it was confirmed that although the light was emitted from the adjacent pixels, its intensity was weak and there was no interference. The emitted light between pixels was also reduced in the amount of emitted light due to the scattering effect of the EL end face portion, and the sharpness of the pixel shape was not significantly impaired.

[0029]

The optical printer head using the edge emitting EL element array of the present invention has a lower electrode layer, a lower dielectric layer, and an E layer.
Each layer of the L light emitting layer and the upper dielectric layer is integrally formed on the substrate,
In addition, since the upper electrode layer is formed corresponding to the pixel, and the light is condensed at the edge emitting portion of the pixel and scattered light is generated at the other edge, the light with high definition and high reliability is obtained. The printer head can be obtained.

Further, since the etching process for forming the pixel only requires the upper electrode, the manufacturing process becomes simpler than ever.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of an edge emitting EL element array according to the present invention.

FIG. 2 is a plan view of an edge emitting EL element array showing the relationship between light propagating in the light emitting layer of the optical printer head of the present invention and the shape of the edge surface.

FIG. 3 is a perspective view of a conventional edge emitting EL element array.

FIG. 4 is a diagram showing a relationship between a voltage of a photosensitive drum and a light amount.

[Explanation of symbols]

1 ... Glass substrate, 2 ... lower electrode, 3 ... lower dielectric layer, 4 ... EL emission layer, 5 ... upper dielectric layer, 6 ... upper electrode, 7 ... … Emitting pixel part, 8…
...... End face part between light emitting pixels.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H01L 33/00 N 7376-4M H04N 1/036 A 8721-5C

Claims (1)

[Claims] 1. A predetermined pixel having a substrate and a laminated body including a lower electrode layer, a lower dielectric layer, an EL light emitting layer, an upper dielectric layer, and an upper electrode layer, which are sequentially laminated on the substrate, with an end face of a light emitting portion as a light emitting portion. In an optical printer head using an edge-emitting electroluminescent device array having a plurality of edge-emitting electroluminescent device arrays, the lower electrode layer, the lower dielectric layer, the EL light-emitting layer, and the upper dielectric layer constituting the edge-emitting electroluminescent device array. Layers are integrally formed on the substrate, the upper electrode layer is formed corresponding to the pixel that emits light, and the end surface of the stacked body collects light at the end light emitting portion of the pixel and scatters at the other end surface portion. An optical printer head characterized by having a shape of light.