JPS6184957A - Color photoconductive element - Google Patents

Abstract

PURPOSE:To heighten reliability in durability and to obtain a small color photoelectric element of high reading speed by forming two or more kinds of thin semiconductor films for color filter at a fixed pitch in the direction of main scanning on a transparent substrate and forming thin light sensor films on the thin films. CONSTITUTION:Two or more kinds of thin semiconductor films 2-4 for color filter having different absorption edge wavelength periodically are formed at a fixed pitch in the direction of main scanning on a transparent substrate. Thin filmy light sensors 6-8 are formed on the thin semiconductor films 2-4 through a transparent and insulating film 5. One kind of absorption edge wavelength of the thin semiconductor films 2-4 is made to 480-500nm and that of another kind is made to 580-600nm. The thin film of light sensors 6-8 is mainly made of CdS, SdSe or CdS-CdSe solid solution. Thus, reliability in durability of the color photoelectric element is heightened, its reading speed is made high and the size is made small.

Description

[Detailed description of the invention] Industrial applications The present invention relates to the structure of a color photoconductive element.

Conventional structure and its problems A photoconductive element in which an optical sensor is formed on a transparent substrate in one-to-one correspondence with the original A method for making it possible to read color originals with a so-called contact image sensor uses gelatin as the main agent. and then red and green.

A color filter patterned by periodically dyeing blue is formed on a thin glass plate and is pasted on a line of sensors.The signal obtained from the sensor by the light incident from the filter side is colored red, The color was detected by reading the green color separately on the back. The organic color filter produced by this method suffers from deterioration due to reflected light from the original or due to the thermal component of the light, and has low reliability in terms of durability.

Another method is to prepare light sources with emission peaks in the red, green, and blue regions and turn them on sequentially, and then read the signals when the red, green, and blue light sources are turned on to determine the color. was detected. This method requires extra space for the light source, which increases the size of the apparatus, and has the drawback that it takes time to read the original because each light source must read the original.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a color photoconductive element that eliminates the above-mentioned drawbacks, has high durability and reliability, is small in size, and has a high reading speed.

Structure of the Invention In order to achieve the above object, the present invention forms two or more types of color filter semiconductor thin films having different absorption edge wavelengths arranged periodically at a constant pitch in the main scanning direction on a transparent substrate. By creating a structure in which an optical sensor thin film is formed on top with a light-transmitting and insulating thin film, the reliability of the final photoconductive element is increased, the reading speed is increased, and it is also made smaller. It is characterized by

Description of Examples When a semiconductor is formed into a thin film, light with energy greater than the forbidden band width is absorbed due to the forbidden band width peculiar to the semiconductor.
It is well known that light with energy smaller than the forbidden band width is transmitted without being absorbed. The wavelength of light corresponding to the bandgap energy is called the absorption edge wavelength, and this wavelength is determined by the material, and the half-value wavelength, that is, the light transmittance is 5.
The variation in wavelengths that have a coefficient of 0 is small. Therefore, by using materials with different forbidden band widths, it is possible to make various types of capto filters on the short wavelength side.

By placing such a semiconductor thin film on the light incident side of the optical sensor, it is possible to detect the presence or absence of the signal from the optical sensor and determine whether the wavelength of the incident light is longer or shorter than the absorption edge. Furthermore, by combining several types of semiconductors with different absorption edge wavelengths, it is possible to determine the color of incident light from the signal of the optical sensor.

FIG. 1 shows the structure of a photoconductive element according to the present invention using three types of photoconductive filters.

In FIG. 1, 1 is a transparent substrate, 2 is a first semiconductor thin film for a color filter, 3 is a second semiconductor thin film, and 4 is a third semiconductor thin film, each of which has an absorption edge wavelength of λ1. λ2.
The materials are selected so that the relationship λ1, λ2, λ3 holds true for λ3. Further, on the top thereof, an optical sensor 6 (sensor a') whose photosensitive wavelength range is from λ to λ4 (however, λ3 to λ4) is connected via an optically transparent insulating thin film 6.
, 7 (sensor b).

8 (sensor C) is formed separately and a voltage is applied in a direction perpendicular to the plane of the paper. Consider the case where light ('hv) is incident on such a photoconductive element from the glass substrate 1 side. Table 1 shows the wavelength range of incident light and the signals of each optical sensor. The output signal when photocurrent flows is "1".

The output signal when there is no flow is assumed to be "o", and the signals are added as the wavelength range expands.

Chapter 1 Table As shown in Table 1, sensor a and sensor b.

Since the combinations of signals from sensor C are all different, it is possible to determine the color of the incident light.

Similarly, by increasing the number of filters with different absorption edge wavelengths, it becomes possible to read a wide variety of colors.

Any material may be used for the semiconductor thin film 2, 3.4 for color filters as long as its absorption edge is in the wavelength range of visible light, but materials made of ■-■ group compounds or solid solutions thereof are particularly suitable for visible light. It is particularly preferred because it is easy to control the absorption edge in the optical range, has excellent absorption characteristics, and is easy to form a thin film. For example, CdS is a material that cuts wavelengths shorter than 520 nm, and solid solution CdS Se is available as a material that cuts wavelengths shorter than 620 nm.

0.6 0+4 The material for the photosensor thin films 6 and 7.8 may be any material as long as it has sensitivity in the visible light range, but it may include ■-■ group compounds whose sensitive wavelength range can be easily controlled, or their Solid solutions, especially CdS, which has a large photocurrent,
Preferably, the material is mainly composed of CdSe or a solid solution thereof, Cd5-CdSe. Usually, a small amount of Ct and Cu are added to the film to increase sensitization and brightness ratio.

Specific examples will be described below.

Specific Examples When using a photoconductive element in a color image sensor, etc.
Usually, red (hereinafter referred to as R), green (hereinafter referred to as G), blue (hereinafter referred to as B), and their complementary colors cyan (hereinafter referred to as C), magenta (hereinafter referred to as M), and yellow (hereinafter referred to as Y).

If the eight colors of white (hereinafter referred to as W) and black (hereinafter referred to as Bt) can be distinguished, a color original can be read.

In this case, the above 1. Second. The wavelength of the absorption edge of the third color filter semiconductor thin film 2, 3.4 is λ = 38
0 nm, λ2 = 49 On! n, λ3=
The wavelength should be around 590 nm.

Further, if the sensor photosensitive wavelength range is around 380 to 700 nm, as in the case of a Cd5-CdSe solid solution, the first semiconductor thin film is not necessary, and the second semiconductor thin film is not necessary. Third semiconductor thin film 3'.

4' only, R, G from the signals of three types of optical sensors.

Eight types of colors can be identified: B, Y, C, M, W, and Bt. A schematic diagram of the cross section of the photoconductive element in this case is shown in FIG. 2, and Table 2 shows the magnitude of the signal obtained from each sensor on an arbitrary scale. It can be seen that eight types of electrical signals can be clearly distinguished.

Table 2 In Figure 2, 3' is a semiconductor thin film for color filters whose absorption edge wavelength is around 490 nm, and 4' is a semiconductor thin film whose absorption edge is around 590 nm.
Nearby semiconductor thin films, 6' and 7'.

Reference numeral 81 denotes an optical sensor made of a Cd5-CdSe solid solution; sensor a/, sensor b', and sensor C', respectively.

Effects of the invention The optical sensor with this structure has a small variation in the half-value wavelength of the semiconductor filter, so it has good color separation, and has high temperature resistance, so it can have a long life, and it can still use a large number of light sources. Because it does not, the reading speed is fast.

As described above, the photoconductive element according to the present invention provides a color photoconductive element with high reliability and a fast reading speed, and is of great industrial value.

[Brief explanation of drawings]

1 and 2 are schematic cross-sectional views of photoconductive elements according to embodiments of the present invention. 1...Transparent substrate, 2,3.4...Semiconductor thin film. 5...Transparent insulating film, 6,7.8... Optical sensor, 2'. 3/, 4/...-semiconductor thin film, 6', 7
', 8'... Light sensor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (3)

[Claims] (1) On a transparent substrate, two or more types of semiconductor thin films for color filters with different absorption edge wavelengths are formed periodically at a constant pitch in the main scanning direction, and on this semiconductor film, a transparent and insulating film is formed. A color photoconductive element characterized in that a photosensor thin film is formed through a thin film of. (2) At least one of the semiconductor thin films for color filters
The absorption edge wavelength of various semiconductor thin films is 480 to 500 nm.
The absorption edge wavelength of another type of semiconductor thin film is 5.
The color photoconductive element according to claim 1, characterized in that the wavelength range is from 80 to 600 nm. (3) The optical sensor thin film is CdS, CdSe, or Cd
A color photoconductive element according to claim 1 or 2, characterized in that the color photoconductive element is mainly composed of an S-CdSe solid solution.