JPH08244272A - Optical printer head - Google Patents

Abstract

PURPOSE: To provide an optical printer head having a light element array which has all advantages of an optical head such as high speed, high resolution, low noise, compactness, plain paper printing, low voltage driving, etc., at a low driving voltage, and indicates uniform light emission brightness over a large area. CONSTITUTION: At least an electro-conductive film being a first electrode 11, a hole transportable inorganic thin film layer 12, an organic thin film layer 13 containing a light emittable organic material, and an electroconductive film being a second electrode 14 are laminated in this order on a substrate 10. By impressing voltage between two electroconductive films, light is emitted from the organic thin film layer 13.

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 used in an electrophotographic printer device.

[0002]

2. Description of the Related Art In recent years, demands for printers such as high speed, high resolution, low noise, compact size, and plain paper printing are increasing. It is becoming popular. Further, the optical printer can be applied to an output device such as a facsimile and a copying machine, and a great demand is expected also in this field.

FIG. 3 is a schematic configuration diagram showing the overall configuration of a conventional optical printer. In this figure, 1 is a device for storing print data, 2 is an optical print head, 3 is a converging rod lens array, 4 is a photosensitive drum, 5 is a charger, 6 is a developing device, 7 is a transfer device, and 8 is a sheet. Is. Generally, printing by an optical printer includes steps of charging, exposing, developing, transferring, fixing, removing charge and cleaning.

First, the surface of the photosensitive member formed on the photosensitive drum 4 (or belt) is uniformly charged by the charger 5 (charging). Then, the charged photosensitive drum 4
When the light corresponding to the image pattern is radiated from the optical print head 2, the portion exposed to the light is neutralized, and a latent image by electrostatic charge is written on the photosensitive drum 4 (exposure). Next, by dispersing colored particles called electrostatically charged toner on the photosensitive drum 4 by the developing device 6,
The latent image due to electrostatic charge is made visible in the image due to toner (development).

Then, the paper 8 is pressed onto the photosensitive drum 4, and for example, an electric field is applied to transfer the toner to the paper 8 (transfer), and the transfer device 7 applies heat, for example. The toner is fused to the paper 8 (fixing). Electric charges are erased (charge elimination) from the surface of the photosensitive drum 4 after transfer by applying, for example, an AC voltage or whole-surface light irradiation. Then, the toner remaining after the transfer is removed (cleaning).

Such an electrophotographic optical printer is
In particular, it is classified into several types according to the type of the optical printer head used for writing an image on the photoconductor in the exposure process. Commercialized products include a laser beam (LB) scan method, a light emitting diode (LED) array method, and a liquid crystal shutter (LCS) array method. In addition, an electroluminescence (EL) array system has recently been studied at the level of research and development.

[0007]

However, the above-mentioned LB scan type optical head of the conventional optical printer has the following problems.
There are problems that it is difficult to reduce the cost of the scanning mechanism mainly composed of a rotating polyhedron, etc., and to make it ultra-high-speed and miniaturize. The LED array type optical head uses an expensive semiconductor single crystal substrate of GaAs or the like, and uses an expensive vacuum epitaxial device when growing layers such as AlGaAs and GaAsP. Also, L
Since an ED array cannot be made on a single substrate,
The process becomes complicated and an LED chip arrangement error occurs.

The LCS array type optical head has a slower printing speed than other heads. Moreover, since a fluorescent lamp is used as the light source, the size of the head is large. The conventional EL array type optical head is of an electric field excitation type using ZnS: Mn or the like as a light emitting layer, and has a problem that it is necessary to apply a high AC voltage of about 100 to 200V.

As described above, each type of optical head has advantages and disadvantages. The present invention eliminates the above problems and has the advantages of all optical heads such as high speed, high resolution, low noise, compact size, plain paper printing, low voltage drive, low drive voltage, and uniform emission brightness over a large area. It is an object of the present invention to provide an optical printer head having a light emitting element array shown in FIG.

[0010]

In order to achieve the above-mentioned object, the present invention provides: (1) In an optical printer head, at least a conductive film serving as a first electrode, a hole-transporting inorganic thin film layer, on a substrate, An organic thin film layer containing a light-emitting organic substance and a conductive film to be a second electrode are laminated in this order, and a voltage is applied between the two conductive films so that the organic thin film layer emits light. .

(2) In the optical printer head described in (1) above, amorphous silicon carbide is used as the hole transporting inorganic thin film layer. (3) In the optical printer head described in (1) above, amorphous silicon is used as the hole transporting inorganic thin film layer. (4) In the optical printer head described in (1) above, a metal complex material such as a quinolinol complex such as Alq3 or a porphyrin complex is used as the organic thin film layer.

(5) In the optical printer head described in (1) above, a quinolinol complex such as Alq3 doped with a dye molecule such as DCM is used as the organic thin film layer.

[0013]

The optical printer head of the present invention is made by arranging EL elements in an array, and each EL element includes a thin film layer made of an inorganic material having a hole transporting property and an organic material having a light emitting property. It is characterized by being laminated with a thin film layer made of. The EL element is basically injection-type electroluminescence (EL) based on light emission resulting from double injection of electrons and holes and their recombination, and the emission brightness basically changes to the film thickness. Do not depend. In addition, a large-area, high-quality thin film can be obtained by the vacuum deposition method or the like.

Therefore, it is possible to manufacture a light emitting element array which has a low driving voltage and exhibits uniform emission luminance over a large area.

[0015]

Embodiments of the present invention will be described in detail below with reference to the drawings. Note that the materials used, the film forming method, the film thickness, and other conditions described below are merely examples. Therefore, the present invention is not limited to only these conditions.

Now, the following several terms will be described to describe the embodiment. The “electron transport layer” means that when an electron injection electrode having a small work function is used, a large amount of electrons can be injected and the injected electrons can move in the film, while holes cannot be injected. It is a thin film layer that has the property that it is difficult, or that injection is possible but it is difficult to move in the film.

On the other hand, the "hole transport layer" is capable of injecting a large amount of holes when a hole injection electrode having a large work function is used, and the injected holes can move in the film. But,
On the other hand, it is a thin film layer having a property that it is difficult to inject electrons, or it is difficult to move in the film even though it can be injected. First, the structure of an EL element showing an example of the present invention will be described.

FIG. 1 is a perspective view of an EL device showing an embodiment of the present invention. As shown in this figure, this EL device has a conductive film layer as a transparent or semitransparent first electrode 11 (anode) and an inorganic thin film layer 12 (having a film thickness of 0. 01 to 1 μm), and an organic thin film layer 13 (film thickness 0.01 to 1 μm) containing a luminescent organic substance as an electron transport layer.
m), a conductive film layer as the patterned second electrode 14 (cathode) (line width and pitch are each 10 to 500 μm), and a patterned third electrode 15 (line width and pitch is each 10 to 500 μm). It is composed of a conductive film layer.

Here, as the material of the inorganic thin film layer 12,
P-type amorphous silicon carbide (a-SiC),
The material of the organic thin film layer 13 is an aluminum quinolinol complex, the material of the conductive film layer of the first electrode 11, the material of the conductive film layer of the second electrode 14, and the material of the conductive film layer of the third electrode 15, Indium-tin oxide (IT
O), magnesium-silver alloy (MgAg), and aluminum (Al) were used.

Next, a method of manufacturing an EL element array showing an embodiment of the present invention will be described. 2A to 2C are cross-sectional views of manufacturing steps of the EL element array showing the embodiment of the present invention, and are cross-sectional views of each step viewed from the direction A in FIG. (1) First, as shown in FIG. 2A, the glass substrate 10
To wash. (2) Next, as shown in FIG. 2B, an ITO transparent thin film layer is formed as a first electrode 11 to a thickness of 100 nm by a sputtering method, and processed into a desired shape by a photolithographic etching method, and thereafter, Perform cleaning.

(3) Next, as shown in FIG.
The inorganic thin film layer 12 made of type a-SiC was produced by a high frequency plasma CVD method. SiH ₄ : CH ₄ : B ₂ H ₆
= 50: 50: 0.2 mixed gas was used to form a film having a thickness of 50 nm. The substrate was heated to 180 ° C. during the film formation. (4) Next, as shown in FIG. 2D, the substrate was transferred to a vacuum deposition apparatus for forming an organic film, and sublimation-purified aluminum quinolinol complex [Tris (8-h
ydroxyquinolinol) aluminu
m] [hereinafter abbreviated as Alq3] was formed to a thickness of 50 nm. The evaporation was performed by placing the sample in a quartz crucible and heating the crucible with a resistance wire to sublimate the sample. The deposition rate is 0.3n by controlling the heating to a constant temperature.
The temperature of the crucible was controlled so as to obtain m / sec. The degree of vacuum during vapor deposition was 10 ⁻³ Pa or less, and the substrate temperature was room temperature.

(5) Next, as shown in FIG. 2E, the substrate is transferred to a vacuum deposition apparatus for metal deposition, covered with a metal mask having a line / pitch of 100 μm / 200 μm, and magnesium (Mg) is added. The deposition rate ratio of silver (Ag) is 1
Co-deposited so that the ratio becomes 0: 1, and the second electrode 1 of 150 nm
A conductive film as No. 4 was formed. (6) Further, as shown in FIG. 2F, aluminum (Al) as the third electrode 15 is overlapped on the second electrode 14 through the metal mask of the same line / pitch to form 500.
It was formed to a thickness of nm to form an anode lead pad.

In the device thus constructed, the electrons injected from the cathode and the holes injected from the anode are
It moves in a thin film by an applied electric field. The electrons and holes that have moved in the thin film are recombined, and the energy released at that time excites the fluorescent molecule (in this case, the material of the electron transport layer), fluorescence (EL emission) occurs, and it is emitted to the outside through the transparent electrode. Is emitted. In this device using Alq3 for the organic thin film layer, green light emission having a peak at a wavelength of 520 nm was obtained at a luminance of 1000 cd / m ² or more when a direct current of 10 V was applied.

As the hole injecting electrode material used for the first electrode 11, a metal having a large work function (approximately 4 eV or more) or an electrically conductive material can be used. In the first electrode 11, in addition to the above-mentioned ITO, Sn
Transparent oxide conductive materials such as O ₂ and ZnO, and gold (A
Metals such as u) can be used. When Au is used, the film thickness is 20 to 4 in order to improve the transmission of EL light.
It is desirable that the thickness is 0 nm and the film is a semitransparent thin film.

As the electron injection electrode material used for the second electrode 14, a metal, an alloy, or the like having a small work function (approximately 4 eV or less) can be used. In the second electrode 14, in addition to MgAg, Mg, In, A
Metals such as 1 and alloys such as MgIn and AlLi can be used. For the third electrode 15, a stable metal such as Au other than Al that has high conductivity and has little change in characteristics over time can be used.

As the inorganic thin film layer 12 to be produced by hole transport, in addition to a-SiC, a thin film of hydrogenated amorphous silicon (a-Si: H), polycrystalline silicon or the like can be used. The organic thin film layer 13 used as the light-emitting electron transport layer is not limited to Alq3, but other quinolinol complexes such as beryllium benzoquinolinol complex, or metal complexes such as porphyrin-based complex, cyclopentadiene derivative, Perylene derivative,
Alternatively, a known material as an organic EL light emitting material such as a doped material obtained by doping Alq3 with a fluorescent dye can be used. However, from the viewpoint of preventing deterioration due to Joule heat etc. generated when driven as an optical printer head,
It is desirable to use a material having a melting point of 300 ° C. or higher and excellent thermal stability.

Furthermore, regarding the substrate on which the element is formed,
The material is not limited to glass, and transparent plastic, film-shaped transparent resin, or the like can be used. Further, although not shown in the process, in order to prevent the element from being deteriorated by contact with an atmosphere containing humidity, or by the oxygen in the air, the electron injecting electrode or the like is prevented from deteriorating.
It is desirable to seal the element with a protective layer having a moisture-proof and deoxidizing function. A resin such as polyimide or epoxy can be used as the moisture-proof material, and a getter material such as GeO or BaO can be used as the deoxidizing material.

The procedure for producing each thin film is not limited to the embodiment, and for example, in the case of metal, a resistance wire heating method, an electron beam vapor deposition method, a sputtering method or the like can be appropriately used. Further, in the production of the hole transporting inorganic film,
Other than the plasma CVD method, a photo CVD method, a thermal CVD method, a metal organic decomposition method (MOCVD) or the like can be used.

Further, in addition to the vacuum vapor deposition method described in the embodiment as a method for forming the organic thin film layer, as a dry method,
As the wet methods such as the organic molecular beam deposition method and the plasma polymerization method, the dip coating method, the spin coating method, the Langmuir-Blodgett (LB) method, the micelle electrolysis method and the like can be applied. In this example, the patterned electrode was formed by vapor deposition through a metal mask. However, when the pattern is narrower than 100 μm, the pattern is formed by a microfabrication process using a photolithography technique. Is desirable.

The completed EL array type optical head is connected to a circuit composed of a plurality of driving driver LSIs by a method such as wire bonding to form an electrophotographic printer light source. By using an imaging system such as a condensing rod lens array, the output light from the EL array type head can be imaged on the surface of the photosensitive drum. In the same process as in the first embodiment,
Hydrogenated amorphous silicon (a-Si: H) is used as the hole-transporting inorganic thin film, and 4-dicyanom is used as the organic thin film layer by a high frequency plasma CVD method to a thickness of 50 nm.
Ethylene-6- (p-dimethylami
nostyryl) -2-methyl-4H-pyr
50% of Alq3 doped with 0.3% an (DCM)
It was formed to a thickness of m by a vacuum vapor deposition method. This vacuum vapor deposition was performed while controlling the vapor deposition rates of DCM and Alq3 so that the doping amount was constant.

From the device thus formed, 580 nm
An orange EL emission having a peak at was obtained. The completed EL array type optical head is similar to the first embodiment.
An EL array type optical printer head unit was manufactured by combining a driving driver, a condensing rod lens array and the like.

This optical head can be widely used in optical printers, facsimiles, output devices of copying machines, and the like. The present invention is not limited to the above-mentioned embodiments, and various modifications can be made based on the spirit of the present invention, and these modifications are not excluded from the scope of the present invention.

[0033]

As described in detail above, according to the present invention, the following effects can be achieved. Since the optical printer head of the present invention is made by arraying EL elements on a substrate, it does not have a scanning mechanism mainly composed of a rotating polygon mirror and is ultra-high speed as compared with an LB scan type optical head of an optical printer. It can be miniaturized and miniaturized.

Further, compared to the LED array type optical head, an expensive GaAs semiconductor single crystal substrate or an expensive vacuum epitaxial device is not used. In addition, one optical head can be made from one substrate, the number of substrate breaks and the time required for positioning (mounting, inspection) are reduced, the process is simplified, and the cost can be reduced. , At the same time, no array error occurs.

The printing speed is faster than that of the LCS array type optical head. Also, because the fluorescent light source is not used,
The head size can also be reduced. The driving voltage is lower (for example, about 10 V) than that of the conventional optical head of the electric field excitation type inorganic EL array system using ZnS: Mn as a light emitting layer,
High brightness (for example, 10 ⁵ cd / m ² or more at maximum).

Therefore, the optical printer head of the present invention has all the advantages of the optical head such as high speed, low cost, high resolution, low noise, compact size, plain paper printing, and low voltage drive.
Further, as the effect obtained by using the hole transporting material made of an inorganic material, the following can be mentioned.
First, in semiconductor-based inorganic materials such as amorphous silicon and amorphous silicon carbide, the energy levels of the valence band and conduction band can be changed by modulating the composition, and high hole injection efficiency can be obtained. The
Therefore, it is possible to optimize the composition so that high luminous efficiency is obtained.

The optimization of the composition is not limited to the relationship with the hole injecting electrode, but is also adjusted with respect to the material of the organic thin film layer, and the optimization is performed for each individual material. Is desirable. Further, in terms of thermal stability, characteristic deterioration is not observed at a temperature of 200 to 300 ° C., and is generally higher than that when a hole transport material made of an organic material having poor thermal stability is used. It is possible to manufacture an element having durability.

By using the hole transporting thin film made of an inorganic material as described above, an element having high luminous efficiency and high durability can be obtained, and a high performance and highly reliable optical printer head is manufactured. Became possible.

[Brief description of drawings]

FIG. 1 is a perspective view of an EL device showing an embodiment of the present invention.

FIG. 2 is a sectional view of a manufacturing process of an EL element array showing an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing an overall configuration of a conventional optical printer.

[Explanation of symbols]

 10 Glass Substrate 11 First Electrode (Anode) 12 Inorganic Thin Film Layer 13 Organic Thin Film Layer 14 Second Electrode (Cathode) 15 Third Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Jicho Ichigo 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (5)

[Claims] 1. A conductive film to be a first electrode, a hole transporting inorganic thin film layer, an organic thin film layer containing a light emitting organic substance, and a conductive film to be a second electrode are laminated in this order on a substrate, An optical printer head having an EL element array, characterized in that light is emitted from the organic thin film layer by applying a voltage between two conductive films. 2. The optical printer head according to claim 1, wherein amorphous silicon carbide is used as the hole transporting inorganic thin film layer. 3. The optical printer head according to claim 1, wherein amorphous silicon is used as the hole transporting inorganic thin film layer. 4. The optical printer head according to claim 1, wherein a quinolinol complex or metal complex material is used as the organic thin film layer. 5. The optical printer head according to claim 1, wherein a quinolinol complex doped with a dye molecule is used as the organic thin film layer.