JPH0482066B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a photoelectric conversion film suitable for use in a reading section of a facsimile machine, etc., and particularly to a method for improving the image signal output characteristics of a photoelectric conversion film. At the same time, the photoresponse characteristics are also improved.
The present invention relates to a method for manufacturing a photoelectric conversion film that makes it possible to employ a real-time image readout method.

<Prior Art> Conventionally, optical sensors formed using IC technology, such as CCD and MOS type sensors, have been used in reading units of facsimile machines and the like.

However, since such sensors are created using IC technology, they can only be created with a length of several tens of millimeters.
For actual use, it is necessary to reduce and image the original. When performing reduced imaging, the optical path length of the lens is required, and generally a distance of 20 cm to 30 cm is required from the document to the sensor. Such an optical path length poses a very big problem in reducing the size and weight of the reading unit.

In recent years, in contrast to the above-mentioned reduced-size sensor, a contact image sensor has been proposed that uses a fiber optic lens array to form an image of a document on a one-to-one basis on a sensor having the same width as the document.

The photoelectric conversion section of this image sensor _{contains CdS}
- _X mixed crystal evaporated film, a-Si film, etc. are used, but
Since both use a vacuum process, there are problems with productivity and yield, resulting in high costs.

On the other hand, as a relatively inexpensive method for producing photoelectric conversion films, cadmium sulfide, cadmium selenide, or sulfur/cadmium selenide powder is mixed with a small amount of activated impurities, a flux, and an organic binder. A method is known in which the material is coated onto a substrate and the coated substrate is fired in a nitrogen gas atmosphere or a nitrogen gas atmosphere containing a trace amount (0.8%) of oxygen gas (for example, −
Publication No. 25305).

<Problems to be solved by the invention> However, although photoelectric conversion films can be produced relatively inexpensively and with good reproducibility using the above-mentioned thick film forming method, it is difficult to use a real-time image readout method. It was not possible to produce a photoelectric conversion film with excellent image signal output characteristics and photoresponse characteristics, and it was difficult to apply the method to a high-density, high-pixel reading section such as a facsimile machine.

The present invention was devised in view of the above-mentioned problems, and aims to provide a method for producing a highly sensitive and inexpensive photoelectric conversion film that enables the adoption of a real-time image readout method. be.

<Means for solving the problems> In order to achieve the above object, the present invention provides at least CdS, CdSe, CdS _X Se ₁ - _X , CdS _X Te ₁ - _X ,
In a method for producing _a photoelectric _conversion film, which has one or more types of photoconductor materials of _CdSe
The above heat treatment reduces the oxygen partial pressure to inert gas to 1/
4 to 1/20, and is configured to be carried out in an inert gas containing at least oxygen and flowing at a constant flow rate.

<Function> With the above configuration, a photoelectric conversion film in which particle growth and surface roughness are suitably controlled is formed, and a photoelectric conversion film with stable high output is obtained.

<Example> Next, an example using CdSe will be described in detail as an example of the present invention.

FIG. 1 is a diagram showing an example of the structure of a photoelectric conversion element equipped with a photoelectric conversion film produced according to the present invention, where 1 is an insulating substrate and 2 is a photoconductive film produced according to the present invention. , 3 are electrodes.

CdSe as the photoconductive material of the photoconductive film 2 is prepared using a chemical precipitation method, and a fine powder is used which has been activated in advance by baking treatment. A low-melting glass and a halide are added to the above CdSe powder, and an organic solvent is further added to form a paste, which is applied onto a substrate using a screen printing method to form a predetermined film.
Specifically, an insulating substrate 1 made of ceramic, glass, etc.
CdSe microcrystalline powder on top with low melting point glass and 3mol%
CdCl ₂ is added thereto, and a photoconductive paste 2 made into a paste with an organic solvent is applied to a predetermined width. In this example, screen printing was used to determine the film thickness.
It was applied to 10μ to 20μ. Next, after the organic solvent of the film 2 coated on the substrate 1 is evaporated, re-baking is performed in a furnace. The firing temperature is between 450°C and 550°C. Further, during firing, a gas containing a mixture of oxygen and nitrogen is flowed at a constant flow rate. That is, after the organic solvent is evaporated at 100° C., the activation treatment is performed. Activation process is 450
The experiments were carried out in a mixed atmosphere of nitrogen and oxygen at temperatures ranging from 0.degree. C. to 550.degree. C., with a mixed gas flow rate of 1 to 10 times per minute.

At this time, if the oxygen partial pressure is lowered, particle growth is suppressed and the photocurrent is reduced. Furthermore, when the oxygen partial pressure is increased, grain growth progresses, but the surface roughness deteriorates and the yield in electrode formation etc. decreases.

FIG. 2 shows the dependence of grain growth and surface roughness on the firing atmosphere due to activation treatment.

As is clear from FIG. 2, when the oxygen partial pressure is increased, the grain growth becomes remarkable and grows to about 5 μm, but on the other hand, the surface roughness worsens, causing defects etc. when forming the upper electrode portion. Furthermore, if the oxygen partial pressure is lowered, particle growth will be suppressed, making it impossible to obtain the required minimum output (1.0 μA). Therefore, in the present invention, the device was manufactured by setting the oxygen partial pressure to 1/20 to 1/4.

As a result of forming planar electrodes 3 of 8 electrodes/mm on the photoconductive film 2 prepared as described above using a lift-off process and measuring the output characteristics, as shown in FIG. 3, the oxygen partial pressure 1/ At 20 or more, an output of about 5 μA or more was obtained, which is more than the required minimum output of 1.0 μA. Especially when the oxygen partial pressure is 1/10 or more, the output is 10 μA.
As described above, satisfactory results were obtained with a photoresponse speed of 5 msec or less.

Although the above embodiments have been described using nitrogen as the inert gas, the present invention is not limited to this, and can be similarly carried out using other inert gases such as argon and helium. It goes without saying that it is possible.

<Effects of the Invention> As described above, according to the present invention, a photoelectric conversion film with high output stability can be produced by controlling the oxygen partial pressure during heat treatment. Furthermore, when manufacturing an element, the yield during electrode formation can be improved and an inexpensive element can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the structure of a photoelectric conversion element equipped with a photoelectric conversion film produced according to the present invention, and FIG.
The figure shows the particle size and surface roughness with respect to oxygen and nitrogen partial pressures during heat treatment, and FIG. 3 shows the output with respect to oxygen and nitrogen partial pressures. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Photoconductive film, 3... Electrode.

Claims (1)

[Claims] 1 At least CdS, CdSe, CdTe, CdS _X Se ₁ −
A method for producing _a photoelectric conversion film comprising as _a main component one or more photoconductor materials of _X , _{CdS X} Te ₁ - _X , CdSe In the above heat treatment, the oxygen partial pressure relative to the inert gas is
A method for producing a photoelectric conversion film, characterized in that the process is carried out in an inert gas containing at least oxygen and flowing at a constant flow rate of 1/4 to 1/20.