JPH05335605A - Organic image sensor - Google Patents

Abstract

PURPOSE:To obtain an organic image sensor which has a small size and can be manufactured easily by using phthalocyanine for its photoconductive layer so as to eliminate the need of such a vacuum process as vapor deposition, sputtering, etc. CONSTITUTION:When a photoconductive film 15 is irradiated with light from a transparent insulating substrate 13 side while an electric field is applied across a transparent electrode 12 and metallic electrode 11, electron-hole pairs are generated in the film 15 and the resistance of the film 15 drops. As a result, the electron-hole pairs are separated from each other and an electric current is generated. Although a dark current flows when the electric field is applied even when the film 15 is not irradiated with light, it is considered that the dark current is generated due to the injection of holes from the electrode 12. Accordingly, the generation of the electric current can be prevented when a low-resistance insulating film 14 is inserted on the positive electrode (transparent electrode 12) side. Therefore, the need of such a vacuum process as vapor deposition, sputtering, etc., can be eliminated and a large-size film can be formed. In addition, a simple, inexpensive, and small-sized contact type image sensor can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic image sensor as an image reading element for reading an image in an information processing apparatus such as a facsimile or a printer.

[0002]

2. Description of the Related Art Conventionally, a semiconductor image sensor such as a CCD photodiode array, for example, a MOS photodiode array has been widely used as a reading device used in a facsimile, a printer and the like. In these image sensors, it is customary to use a reduction optical system, which requires a lens and the like, resulting in a long optical path length.
This was a big problem in downsizing the device.

FIG. 4 shows the structure of a conventional reader using an image sensor. 1 is a light source such as an LED, 2 is an image sensor, 5 is a document, 6 is a reading (advancing) direction of the document 5, and 8 is optical. System size (optical path length), 300 to 5
It is about 00 mm. 9 is a mirror and 10 is a lens.

Next, the operation of the above device will be described. Light source 1
The light from is reflected by the document 5 and the mirror 9, is condensed by the lens 10, and is incident on the image sensor 2. For example,
The light reflectance differs between the black and white parts of the original 5,
The image sensor 2 photoelectrically converts this and reads it.

On the other hand, recently, a contact type thin film reading device having the same size as the document width has been proposed. This device is called a planar type, and a photosensitive layer is provided on a substrate and electrodes are provided on the photosensitive layer to form an element corresponding to 1 bit. Then, a plurality of these elements are formed in a row, and the photocurrent corresponding to the light irradiation of the element portion is sequentially measured and read.

In addition, as a solar cell application, there have been many proposals of a sandwich type structure in which amorphous silicon is used for a photoelectric conversion layer and electrodes are provided above and below the photoelectric conversion layer. Here, in the case where the amorphous silicon is of the pin type, the specific resistance of the n-type amorphous silicon layer is 10 ⁴ to
Since it is as low as 10 ⁶ Ω · cm, complete separation between bits divided by using a lithography technique such as photoresist coating and etching has become a big problem. Also, recently, many proposals have been made and manufactured using a high resistance amorphous silicon layer, but the current leakage between the adjacent bits has not been solved.

Further, since the conventional image sensors have used the inorganic photoconductive substance, they have a vacuum process such as vapor deposition or sputtering for film formation. Therefore, a large-scale device was needed to make a large quantity at a time. Further, it has been difficult to uniformly and inexpensively manufacture a large-area element.

[0008]

As described above, the conventional image sensor must use the reduction optical system,
It was impossible to make a perfect contact type, and there was a limit to miniaturization. Further, since the manufacturing process includes a vacuum process, a large-scale device is required, and it is difficult to mass-produce uniformly, and the element size is limited.

The present invention has been made to solve the above problems, and an object thereof is to obtain an organic image sensor which is small in size and easy to manufacture.

[0010]

An organic image sensor according to the present invention is a transparent or semi-transparent electrode, a low resistance insulating film formed on the electrode, and a low resistance insulating film formed on a metal-free or A photoconductive layer made of an organic photoelectric conversion material containing a metal phthalocyanine and a binder polymer, and a metal electrode formed on the photoconductive layer are provided.

[0011]

In the present invention, phthalocyanine is used for the photoconductive layer, which eliminates the need for vacuum processes such as vapor deposition and sputtering, and enables production by a simple method such as dipping. Further, since it is a perfect contact type, no lens is required in the optical system.

[0012]

EXAMPLES Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 shows a structure of an organic image sensor according to the first embodiment, 13 is an insulating substrate, 12 is a lower transparent electrode formed on the insulating substrate 13, and 14 is a low resistance formed on the transparent electrode 12 by dipping. An insulating film 15 is a photoconductive film made of phthalocyanine and a polymer binder formed on the low resistance insulating film 14. The low resistance insulating film 14 is formed on the photoconductive film 15 and a metal film is formed on the low conductive insulating film 14 by vapor deposition. The electrode 11 is formed. Note that, as shown in FIG. 2, the low resistance insulating film 14 on the upper side may be omitted.

Here, the insulating substrate 13 may be made of ceramic, glass, plastic, or the like, as long as it has high mechanical strength and is transparent and has a high insulating property, and may have a laminated structure of two or more kinds. .. The plurality of transparent electrodes 12 can have any shape, but here, they are rectangular. The material of the metal electrode 11 is Au, Cr, P
t, Ni, Tl and the like are good, and two or more kinds may be used in combination. The method for forming the low resistance insulating film 14 and the photoconductive film 15 is as follows.
In addition to the dipping method, an ordinary solvent casting method (including spinner coat, spray coat, etc.) may be used. In order to prevent the internal impedance from becoming too large, the low resistance insulating film 14 has a thickness of 0.5 to 4 μm.
The thickness of the photoconductive film 15 is preferably 5 to 30 μm.

Next, the operation of the organic image sensor having the above structure will be described. The details of the principle are unknown, but it is considered as follows. Insulating substrate 13 which is transparent to light under an electric field applied between transparent electrode 12 and metal electrode 11
When irradiated from the side, electron-hole pairs are generated in the photoconductive film 15 to reduce the resistance, the electron-hole pairs are separated, and a current is generated. Note that when an electric field is applied, a dark current flows even if light is not applied. This is considered to occur because holes are injected from the transparent electrode 12, and the positive electrode (transparent electrode 1
This can be prevented by inserting the low resistance insulating film 14 on the 2) side. The specific resistance of the low resistance insulating film 14 is 10 ⁹ to 10
^{It is 13} Ω · cm. Further, the low-resistance insulating film 14 can effectively perform electrical isolation from an adjacent element, and it is easy to increase the screen size. The electrode 12 may be semitransparent.

Next, a method of manufacturing the image sensor will be described. A solution of 1 part by weight of polyamide (CM-8000; manufactured by Toray Industries, Inc.) and 9 parts by weight of methanol was prepared, and then this solution was dried on a glass plate having an ITO electrode pattern to have a thickness of 2 μm. Thus, it was applied by the dipping method. Then, in a constant temperature bath at 100 ° C, 30
Min dried.

Next, 7 parts by weight of a vinyl chloride / vinyl acetate / maleic acid copolymer (S-REC M; manufactured by Sekisui Chemical Co., Ltd.) and 3 parts by weight of a metal-free phthalocyanine pigment are dissolved in 50 parts by weight of a toluene / methyl ethyl ketone 1: 1 solution. Then, it was sufficiently dispersed by a planetary type crusher (manufactured by Fritsch Japan).
Next, this dispersion mixture is taken out to obtain a photoelectric conversion layer forming liquid. Then, about 20 μm when dried by the dipping method on the substrate on which the polyamide layer having a thickness of 2 μm is formed.
The photoelectric conversion layer forming liquid is applied so that a film thickness of m can be obtained,
Then, it was dried at 100 ° C. for 1 hour, and the metal electrode was vacuum-deposited to obtain a photoelectric conversion element.

Next, with respect to the photoelectric conversion element thus obtained, a method of measuring photoelectric conversion characteristics and a result of measurement, in which Au side is negative and transparent electrode side is positive, will be described. Three
Approximately 50 at the light-receiving surface after passing a 00W xenon lamp light through a 570nm bandpass filter and a 1/20 neutral density filter.
μW / cm ² This light was irradiated from the transparent electrode side, and a voltage of 50 V was applied between the electrodes. At that time, the dark current was 160 nA / cm ² , the photocurrent was 370 nA / cm ² , and the response speed was rising (20 to 80%) 4 msec and falling (20 to 80%) 9 msec.

FIG. 3 shows the construction of a reading apparatus using the organic image sensor 16 according to this embodiment, 3 is a support base for supporting the organic image sensor 16, 4 is a rod lens array, and 7 is a size of an optical system ( Optical path length), 20 to 20
It is about 50 mm. As described above, in Example 1, the size of the optical system can be reduced because it is a perfect contact type.

Example 2. Next, another manufacturing method is described in Example 2.
Will be explained. First, a polyamide resin solution prepared in the same manner as in Example 1 was formed on the transparent electrode by dipping to form a film, which was dried in a constant temperature bath at 100 ° C. for 30 minutes. Next, PVC
8 parts by weight of a vinyl acetate / maleic acid copolymer (Eslec M) and 2 parts by weight of a metal-free phthalocyanine pigment were dissolved in 80 parts by weight of a 1: 1 solution of toluene and methyl ethyl ketone, and sufficiently dispersed by a planetary crusher. This mixed solution was taken out, a few drops of it were dropped on the transparent electrode substrate, and the photoelectric conversion layer was coated with a spinner (film thickness when dry 5 μm).
Then, it was dried in a constant temperature bath at 100 ° C. for 1 hour. Furthermore, the polyamide resin solution prepared at the beginning was dipped, dried in a constant temperature bath at 100 ° C. for 30 minutes, and a metal electrode was vacuum-deposited to obtain a photoelectric conversion element.

Next, for the sample thus obtained, A
The measurement method and the measurement results of the photoelectric conversion characteristics performed with the u side being negative and the transparent electrode side being positive are shown below. 300W xenon lamp light with 570nm bandpass filter and 1 /
After passing through a 20 neutral density filter, the light receiving surface is set to about 50 μW / cm ² . This light is emitted from the transparent electrode side, and 5 V is applied between the electrodes.
Was applied. The dark current at this time is 30 nA / cm ²
Below, photocurrent is 60 nA / cm ² , response speed is rising (20-80%) 4 msec, falling (20-80%)
It was 8 msec.

[0021]

As described above, according to the present invention, a vacuum process such as vapor deposition or sputtering is unnecessary, large-scale film formation is possible, and a contact image sensor can be manufactured easily and inexpensively. The size can be reduced. or,
A low-resistance insulating film is provided between the photoconductive layer and the electrode, and sensitivity, response speed and SN (photocurrent / dark current) can be obtained by applying a low voltage.
An organic photoelectric conversion element having excellent characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an organic image sensor according to the present invention.

FIG. 2 is a perspective view of another organic image sensor according to the present invention.

FIG. 3 is a configuration diagram of a reading device using an organic image sensor according to the present invention.

FIG. 4 is a configuration diagram of a reading device using a conventional image sensor.

[Explanation of symbols]

 11 metal electrode 12 transparent electrode 13 insulating substrate 14 low resistance insulating film 15 photoconductive film 16 organic image sensor

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[Procedure amendment]

[Submission date] December 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Next, 7 parts by weight of a vinyl chloride / vinyl acetate / maleic acid copolymer (S-REC M; Sekisui Chemical Co., Ltd.) and X-type metal
3 parts by weight of the free phthalocyanine pigment was dissolved in 50 parts by weight of a 1: 1 solution of toluene and methyl ethyl ketone, and sufficiently dispersed by a planetary type crusher (manufactured by Fritsch Japan). Next, this dispersion mixture is taken out to obtain a photoelectric conversion layer forming liquid. After that, about 2 μm when dried by the dipping method on the substrate on which the polyamide layer having a thickness of 2 μm is formed.
A photoelectric conversion layer forming liquid was applied so as to obtain a film thickness of 0 μm, and then dried at 100 ° C. for 1 hour, and a metal electrode was vacuum-deposited to obtain a photoelectric conversion element.

Claims (1)

[Claims] 1. An organic photoelectric conversion material containing a transparent or semitransparent electrode, a low resistance insulating film formed on the electrode, and at least one of a metal-free phthalocyanine and a metal phthalocyanine formed on the low resistance insulating film. An organic image sensor comprising a photoconductive layer made of a binder polymer and a metal electrode formed on the photoconductive layer.