JPS6277959A - Light-writing head for electrostatic recording - Google Patents

Abstract

PURPOSE:To enable realization of a seamless emitter array requiring no separate light source, by a method wherein first and second electrodes, formed across an emitter layer on a single substrate, selectively apply the voltage on emitting elements to allow the emitting elements to emit lights. CONSTITUTION:On a single substrate 2, a first electrode 4 and a second electrode 14 are formed opposedly to each other across an emitter layer 10 made of fluorescent material. At least one of the electrodes 4, 14 has light transmission properties to take the light from the emitter layer 10. Both the electrodes 4, 14 are so disposed that emitting elements which are formed on the laid portion of the opposed electrodes 4, 14 in the emitter layer 10 can be arranged in array. The electrodes 4, 14 selectively apply the voltage on the emitting elements to allow the emitting elements to emit lights. As the substrate 2, a glass substrate or a ceramic substrate is used. In this manner, a small dispersion of pitch between the adjacent emitting elements and the emitter array requiring no separate light source can be realized.

Description

TECHNICAL FIELD The present invention relates to an optical writing head used in electrostatic recording equipment such as printers and facsimiles.

(Prior Art) As optical writing heads for electrostatic recording, those using an LED array and those using a liquid crystal shutter array are known.

The LED array head has a light emitting array formed by forming 7 PN junctions on a GaAs substrate, and then
A large number of aAs chips are arranged on a substrate to form an optical writing head.

However, this LED array head has the following drawbacks.

(1) Since it is inevitable that the light emitting array section will have a joint between GaAs chips, the pitch of the light emitting dots will vary in that part.

(2) Since the GaAs substrate on which the light emitting diode is formed is expensive, the cost is high.

A liquid crystal shutter array head is an optical writing head in which liquid crystals are arranged in a row on a substrate and used as a light shutter by placing them between a fluorescent lamp and a photoreceptor.

However, this liquid crystal shutter array head has the following drawbacks.

(1) Since the liquid crystal itself does not emit light, a separate fluorescent lamp is required as a light source.

(2) Since the printing speed of a printer or the like is determined by the liquid crystal response speed, it is not suitable for high-speed printing.

(Purpose) The purpose of the present invention is to realize a light emitter array that has no seams and does not require a separate light source by forming an optical writing head used for electrostatic recording using thin film light emitting elements. It is something to do.

(Structure) In the optical writing head of the present invention, a first electrode and a second electrode are provided on a single substrate and are opposed to each other with a light-emitting layer made of a fluorescent material in between, and at least one of the The electrodes are light-transmissive in order to take out light from the light-emitting layer, and the electrodes are arranged so that light-emitting elements formed in opposing overlapping portions of the two electrodes are arranged in a row in the light-emitting layer region. is formed, and a voltage is selectively applied to the light emitting element using both electrodes to cause it to emit light.

The fluorescent substance used in the light emitting layer, the light-transmitting electrode, and the dielectric material provided between the light emitting layer and the electrode are all E.
You can use the one used in the L display. Examples of these are as follows.

As the fluorescent material, dielectric materials such as sulfides such as zinc sulfide, cadmium sulfide, and magnesium sulfide, and oxides such as zinc silicate and zinc oxide can be used singly or in the form of a mixture. Furthermore, the light emitting layer may be a single layer or a laminate.

In terms of brightness, ZnS:Mn, ZnS:TbF, etc. are preferred.

ITO1Sn○2 is used as a material for the electrode with optical transparency.
Alternatively, ITO with a trace amount of Sn added can be used.

Moreover, between the light emitter layer and the first electrode or the second electrode,
Alternatively, the dielectric material provided between the light emitting layer and both electrodes includes, for example, nitrides such as silicon nitride, boron nitride, and aluminum nitride, silicon oxide, tantalum oxide, titanium oxide, tungsten oxide, yttrium oxide, and zirconium oxide. , oxides such as niobium oxide, strontium oxide, and samarium oxide, perovskite oxides such as lead titanate, strontium titanate, barium titanate, and zirconium titanate, and carbides such as silicon carbide and boron carbide. These dielectrics are single;
Or it can be used in the form of a mixture. Further, this dielectric layer may be a single layer or a laminate. This dielectric layer is for preserving the light emitting layer.

A glass substrate, a ceramic substrate, or the like is used as the substrate. Light from the light emitter layer is extracted from the substrate side or the side opposite to the substrate, but when the light is extracted from the substrate side, a transparent glass substrate is used as the substrate.

Examples will be specifically described below.

FIG. 1 is a partially cutaway view of one embodiment, and FIG. 2 is a cross-sectional view of FIG. 1 along the line A--B.

2 is a ceramic substrate, which has an elongated shape extending in the Y direction. A glass layer 3 with a thickness of about 50 μm is formed on the surface of the ceramic substrate 2.

On the surface of the ceramic substrate 2 on the side where the glass layer 3 is formed, an aluminum electrode 4 having a thickness of approximately 2000 mm is formed. The aluminum electrodes 4 extend in the X direction (perpendicular to the Y direction) and are patterned into slits with a pitch of 84.7 μm, and are arranged in large numbers in the Y direction.

Each aluminum electrode 4 is connected to the drive circuit IC 6 by wire bonding using a gold wire. The IC 6 may be mounted on the ceramic substrate 2 or may be separate from the ceramic substrate 2.

A 5isN4 layer 8 with a thickness of about 2000 to 4000 layers, preferably about 3000 layers, is formed on the aluminum electrode 4 as a lower dielectric protective layer, excluding the connection part with the IC 6, and on the Si3N4 layer 8. A light emitting layer 10 having a thickness of approximately 3000 mm is formed to extend in the Y direction. ZnS:Mn (the amount of Mn added is about 0.5% by weight) is used as the fluorescent material for the light emitting layer 10.

A T a =Os layer 12 having a thickness of approximately 3000 nm is formed as an upper dielectric protective layer covering the top of the light emitting layer 10 .

On the T a =05 layer 12, Y
A common electrode 14 extending in the direction is formed.

This common electrode 14 is a light-transmissive electrode made of an ITo layer with a thickness of about 1000 layers, and is patterned into a band shape with a width of about 60 μm. The common electrode 14 is connected to a connector (not shown) that is connected to an external power source.

In this way, the aluminum electrode 4 and the common electrode 14 are arranged perpendicularly to each other, and a light emitting element is formed at the intersection of both electrodes 4 and 14. The light-emitting layer in the light-emitting element portion emits light by selectively applying a voltage.

In this embodiment, light from the light emitter layer 10 is extracted through a light-transmissive common electrode 14.

The resolution can be arbitrarily set by the arrangement pitch of the aluminum electrodes 4 and the width of the common electrode 14. In this embodiment, an optical writing head for a printer having a resolution of about 12 dots/mm is obtained.

Further, in this embodiment, since both the upper and lower portions of the light emitting layer 10 are protected by the dielectric protective layers 8 and 12, the brightness can be increased by applying a high voltage. In addition, reliability is also increased.

Next, a method for manufacturing the optical writing head of this embodiment will be explained.

-Explain an example.

After forming an aluminum layer with a thickness of about 2,000 mm on the glass layer 3 on the substrate 2 by vapor deposition or sputtering, an aluminum layer with a thickness of about 84 mm is formed by photolithography, etching, and etching.
．． The aluminum electrode 4 is formed by patterning it into a slit shape with a pitch of 7 μm.

A 513N-+ layer 8 of approximately 3000 layers is formed on the aluminum electrode 4 by mask sputtering.

The phosphor layer 1O is formed by forming ZnS:Mn to a thickness of about 3000 nm by mask electron beam evaporation, and then annealing in vacuum at 400° C. for 60 minutes. After the annealing is completed, the substrate is cooled in a vacuum, and then a film with a thickness of about 30 mm is coated by mask sputtering or mask evaporation.
A Ta-205 layer 12 of 0.00 is formed.

The common electrode 14 is formed by forming an ITO layer of about 1,000 layers by sputtering the entire surface, and then patterning it into a strip of about 60 μm by photolithography and etching.

Thereafter, wire bonding is performed between the aluminum electrode 4 and the drive circuit IC 6, and between the common electrode 14 and the connector.

FIG. 3 represents another embodiment.

This embodiment has a structure in which light is extracted from the substrate side, and the lower dielectric protective layer is omitted. As the substrate 20, a transparent glass substrate is used.

Approximately 100 IT○ is applied as a transparent electrode 22 on the substrate 20.
The film is formed to have a thickness of 0.05 mm, and patterned into a slit shape using photolithography and etching. The pitch of this slit pattern is, for example, 84.7 μm.
Thereon, as in the embodiment shown in FIG. 1, a ZnS:Mn layer having a thickness of about 3000 nm is formed as a light-emitting layer 10 by mask electron beam evaporation. In this case as well, annealing is performed in vacuum.

Covering the phosphor layer 10, a 5isNi film with a thickness of about 5000
The layer 12 is formed as a dielectric protective layer and its 5i
An aluminum common electrode 24 extending in the longitudinal direction (Y direction) of the substrate 20 is formed on the aN4 layer 12. The width of this common electrode 24 is, for example, about 60 μm.

In this example, the light emitting layer IO is formed on glass substrates 2° and 5is.
It is protected by being sandwiched between N4 layers 12.

Compared to the embodiment shown in FIG. 1, the number of dielectric protective layers is reduced by one layer, so the manufacturing process is simplified accordingly.

FIG. 4 shows yet another embodiment.

In the embodiment shown in FIG. 1, there is one common electrode 14, that is, one row of light emitting elements, whereas in this embodiment, there are two common electrodes 14 in parallel to each other extending in the longitudinal direction (Y direction) of the substrate 2.
The difference is that 1.14-2 is provided and the five light emitting element rows are made into two rows.

Light emitted from the light emitting elements via each common electrode 14-1.14-2 is transmitted through a SELFOC lens array (trade name) 26 of optical fibers arranged along each common electrode 14-1.14-2. -1.26-2, photosensitive drum 2
The light is focused on a straight line on 8.

According to this embodiment, the irradiation energy on the photosensitive drum 28 is twice that in the case where there is one row of light emitting elements.

As a result, if there is one row of light emitting elements, a printing speed of 4 sheets/min for A4 size paper, for example, can be obtained.

In this embodiment, the printing speed is doubled, and 8 sheets/minute of A4 size can be obtained.

(Effects) In the optical writing head of the present invention, by forming a thin light emitting layer on a single substrate, variations in pitch between adjacent light emitting elements are reduced, and expensive materials such as GaAs can be used. Since it is not used, cost reduction can be achieved.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line A-B in FIG. 1. FIG. 3 is a sectional view showing another embodiment, and FIG. 4 is a sectional view showing still another embodiment. 2.20... Board, 4.14.14-1.14-2.22.24...
- Electrode, 8.12...Dielectric layer, 10... Luminescent layer. Agent B I' Physician Field 1] Shiteo Figure 1 Δ Figure 2 Figure 9 No. 44

Claims (4)

[Claims] (1) A first electrode and a second electrode are provided on a single substrate and face each other with a light-emitting layer made of a fluorescent material in between, and at least one electrode is provided with a light-emitting layer made of a fluorescent material. Both electrodes are light-transmissive to extract light, and are formed such that light-emitting elements formed in opposing overlapping portions of both electrodes in the light-emitting layer region are arranged in a row; An optical writing head for electrostatic recording, characterized in that a voltage is selectively applied to a light emitting element by an electrode to cause it to emit light. (2) The optical writing head for electrostatic recording according to claim 1, wherein the light emitting elements are provided in a plurality of rows. (3) An optical writing head for electrostatic recording according to claim 1 or 2, wherein a light-transmitting dielectric layer is formed between the light-emitting layer and the light-extracting electrode. . (4) The electrostatic recording light according to claim 1 or 2, wherein a dielectric layer is formed between the light emitting layer and the electrode on the side opposite to the side from which the light is taken out. write head.