JPH0645639A - Solid-state image conversion element - Google Patents

Abstract

PURPOSE:To newly provide a dispersion-type solid-state image conversion element wherein the element does not cause a so-called 'umbrella of light' that the element is affected by the diffused reflection of near-infrared rays due to an EL layer and the element converts the near-infrared rays into a visible image. CONSTITUTION:In a solid-state image conversion element, a transparent electrode layer 4, a PC layer 6, a dielectric layer 8, an EL layer 10 and a back electrode layer 12 are laminated sequentially on a transparent substrate 2, an organic binder is dispersed to the PC layer 6, the dielectric layer 8 and the EL layer 10, the PC layer 6 is formed as an infrared region in which its luminous sensitivity is situated on the longer wavelength side than visible light of the luminuous distribution of the EL layer 10, and the back electrode layer 12 is light-transmitting.

Description

Detailed Description of the Invention

[001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image conversion element for converting infrared rays, particularly near-infrared rays into visible light, and more particularly to a solid-state image conversion element in which an electroluminescent layer and a photoconductor layer are laminated in a dispersed form. Related to the improvement of.

[002]

2. Description of the Related Art The principle of an optical amplifier in which an electroluminescent layer (hereinafter referred to as an EL layer) and a photoconductor layer (hereinafter referred to as a PC layer) are combined has been known for a long time. The applied X-ray image conversion element has also been studied by many researchers and partially put to practical use. Compared to X-ray photography, these X-ray image conversion elements are inexpensive and easy to see as a visible image directly without the need for development, so expensive equipment such as an image intensifier is used. It is widely used for obvious purposes. This kind of X
The line image conversion element, for example, as shown in Japanese Patent Publication No. Sho 49-3037, has an EL layer, a dielectric layer, an opaque layer, and a PC layer sequentially laminated on a glass substrate having a transparent electrode, and then the The structure has a metal vapor deposition electrode and a moisture-proof coating layer formed on it. From this structure, an AC voltage is applied between these electrodes, the subject is placed on the moisture-proof coating layer, and X-rays are applied from the PC layer side. , The X-ray image is P
The impedance changes in the C layer depending on the intensity of X-rays, and the EL layer converts the impedance into a visible image. In this case, the opaque layer is composed of carbon powder and an epoxy resin-based binder, and the thickness of the opaque layer is EL.
The minimum is necessary to prevent the return of light to the PC layer by light emission in the layer.

By the way, in the above-mentioned Japanese Patent Publication No. 49-3037, a so-called dispersion formed by dispersing a powdery material for each layer excluding electrodes in an organic binder and applying the material by screen printing or the like. X-ray image conversion element. For each layer excluding the electrodes, dimethylformamide, diethylene glycol monoethyl ether or the like is used as an organic solvent, and cyanoethylated pullulan, cyanoethylated cellulose or the like is used as a binder.

However, in such a dispersive solid-state image conversion element in which the PC layer and the EL layer are combined, the light source that enters is X-rays, and light having a wavelength longer than visible light, such as infrared rays, is used. E, between the EL layer and the PC layer
Since the PC layer is excited by L emission, a light opaque layer is required to prevent light from returning.

Therefore, when the near-infrared image is converted into visible light by using the conventional combination of the PC layer and the EL layer as it is, the opaque layer or the current diffusion layer is formed on the dielectric layer on the EL layer. In addition, since the PC layer must be thickened by laminating X-rays having a large penetrating power and a high applied voltage resulting from the X-rays, it is inevitable that the entire film thickness becomes remarkably thick. It was

In order to convert near infrared rays into a visible image, a transparent electrode layer, an EL layer, a dielectric layer, a PC layer and a back electrode layer are sequentially formed on a glass substrate by omitting the opaque layer or the current diffusion layer. Even if it is formed, even if near-infrared rays incident from the glass substrate are transmitted to the EL layer through the transparent electrode layer, and the near-infrared rays are transmitted as a whole in the EL layer with a certain transmittance, the particles of the EL layer may The near infrared rays are diffusely reflected, and a part of the diffused reflected light is totally reflected by the transparent substrate and again passes through the EL layer and the dielectric layer through the transparent electrode layer to reach the PC layer. If the cross-sectional shape of the incidence constraint is circular, there is a problem that "light umbrellas" are generated concentrically. This "light umbrella" phenomenon is inevitable if the transparent substrate and the EL layer are in contact with each other.

[0097]

SUMMARY OF THE INVENTION Therefore, the present invention has been made in view of the above circumstances, and its object is to be influenced by diffuse reflection of near infrared rays by an EL layer in a dispersion type solid-state image conversion device. It is to newly provide a solid-state image conversion element that converts a near infrared ray into a visible image without generating a so-called “light umbrella”.

[0085]

The above-mentioned object is to form a transparent electrode layer, a PC layer, a dielectric layer, an EL layer and a back electrode layer in this order on a transparent substrate, and to provide a PC layer, a dielectric layer and The EL layer is dispersed in the organic binder, and the PC layer is
This is solved by a solid-state image conversion element characterized in that its light emission sensitivity is in the infrared region on the longer wavelength side than visible light in the light emission distribution of the EL layer, and the back electrode layer is translucent.

Preferably, the solid-state image conversion device of the present invention is P
A resin layer is further formed between the C layer and the dielectric layer.

[0101]

In the solid-state image conversion device of the present invention, when an AC voltage is applied between the transparent electrode layer and the back electrode layer and near infrared rays enter from either the transparent substrate or the back electrode layer,
This incident near-infrared ray excites the PC layer, whereby
The impedance of the near-infrared incident portion of the PC layer is lowered, and this portion of the EL layer emits light.
A visible image due to this light emission can be seen from the transparent back electrode layer side.

In this case, the most remarkable thing is that the transparent electrode layer, the PC layer, the dielectric layer, the EL layer and the back electrode layer are sequentially laminated on the transparent substrate on which the near infrared rays are incident, and Transparent electrode layer, EL on transparent substrate
In comparison with a structure in which a layer, a dielectric layer, a PC layer, and a back electrode layer are sequentially laminated, for example, when the cross-sectional shape of the constraint of near infrared rays is circular, conventionally, a so-called "light umbrella" is formed on concentric circles. Does not occur.

Further, by forming a resin layer between the PC layer and the dielectric layer, the dielectric particles of the dielectric layer are several times larger than the dielectric particles, and the photoconductivity of the PC layer is increased. Since the particles do not enter between the body particles, the light emitting surface becomes clean and the luminous efficiency improves.

[0113]

Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) FIG. 1 is a sectional view of a solid-state image conversion device of the present invention. This solid-state image conversion device includes a transparent substrate 2, a transparent electrode layer 4, a PC layer 6 and a dielectric layer. The body layer 8, the EL layer 10, and the translucent back electrode layer 12 are sequentially laminated.

This solid-state image conversion element will be described based on a concrete manufacturing method. ITO (tin oxide / indium) is formed on the transparent substrate 2 (glass substrate 7059 manufactured by Corning Incorporated).
A transparent electrode layer 4 made of cyanoethylated pullulan as a binder and dimethylformamide as a solvent in the organic binder.
CdSe: Cu, Cl particles are applied by a screen printing method to form a PC layer 6 having a film thickness of 120 μm, and then cyanoethylated pullulan is used as a binder and dimethylformamide is used as a solvent to obtain an average particle size of 1 A dielectric layer 8 made of barium titanate and having a thickness of 7 μm and an EL layer 10 having a thickness of 30 μm and made of ZnS: Cu, Al powder having an average particle diameter of 13 μm are respectively formed.
On the L layer 10, an ITO paste (Catalyst Kasei Kogyo ELC
OM p1210) was applied to form a back electrode layer 12 having a thickness of 5 μm. The transparent electrode layer 2 and the back electrode layer 12 are connected to a suitable AC power source while sealing the peripheral portion.

In the solid-state image conversion element having such a structure, when an alternating voltage of 1 kHz and 100 V is applied, near infrared rays having a wavelength of 780 nm and 100 μW / cm ² are irradiated from the back electrode layer 12 (reference A in FIG. 1). And the emission of the EL layer 6 in the irradiated region is 10 Cd / m ² ,
A visible image can be seen from the back electrode 12 side (reference numeral X in FIG. 1), and even if near-infrared rays having a circular cross section are irradiated from the back electrode 12, a visible image due to the light emission of the EL layer 10 is obtained. The so-called "light umbrella" did not occur. Further, even when the near infrared rays were made incident from the transparent substrate 2 side (reference numeral B in FIG. 1), the “light umbrella” did not occur, and the light emission of the EL layer 6 was the same as described above.

By coating the back electrode layer 12 with an ITO paste on the EL layer, a near infrared image incident from either the back electrode layer 12 side or the transparent substrate 2 side can be applied from the back electrode layer 12 side. You can see the image. Of course, the back electrode layer 12 made of ITO paste is formed in contact with the EL layer 10, but since the EL layer and the transparent substrate are not in contact with each other as in the conventional case, the problem of so-called "light umbrella" Does not happen.

Example 2 As shown in FIG. 2, a resin layer 7 was formed between the PC layer 6 and the dielectric layer 8 using cyanoethylated cellulose as a binder and diethylene glycol monoethyl ether as a solvent. A solid-state image conversion device was produced in the same manner as in Example 1 except that the thickness was 3 μm.

The solid-state image conversion element obtained had an emission luminance of 10.5 Cd / m, as compared with the element obtained in Example 1.
^It was slightly increased to ^2, and the resolution on the entire light emitting surface became more uniform.

The CdSe: Cu, Cl particles of the PC layer 6 are 6 to
Since it is 8 μm, which is larger than the barium titanate particles of 1.4 μm of the dielectric layer 8, the barium titanate particles permeate between the CdSe: Cu, Cl particles of the PC layer 6 without the resin layer 7. , The PC layer 6 is disturbed, and the dielectric layer 8 becomes thin, which may deteriorate the light emitting surface. However, in this embodiment, the resin layer 7 solves this problem. For this reason, it is preferable that the thickness of the resin layer 7 is as thin as possible.
m, especially 0.1 to 5 μm is preferable.

Although the same organic binder as that for the PC layer 6 may be used as the resin layer 7, an organic solvent in which the binder used for the PC layer 6 is difficult to dissolve and a high dielectric constant resin which dissolves in the organic solvent are used. Since it does not melt the PC layer 6, it must be a desirable and transparent material for transmitting near infrared rays. Further, in view of the luminous efficiency of the EL layer 10, it is desirable that the resin layer 7 has a high dielectric constant. As an example, usually a PC
Examples include cyanoethylated saccharose used as a binder for the layer 6, the dielectric layer 8, and the EL layer 10. If cyanoethylated pullulan is not used for the PC layer 6, cyanoethylated pullulan may be used.

[0222]

As described above, according to the present invention, in a dispersion type solid-state image conversion device, a so-called "light umbrella" which is affected by diffuse reflection of near infrared rays by an EL layer does not generate a near infrared ray from a glass substrate. It is possible to provide a solid-state image conversion device that converts the near-infrared rays into a visible image by irradiating with.

[Brief description of drawings]

FIG. 1 is a sectional view showing a solid-state image conversion device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a solid-state image conversion device according to another embodiment of the present invention.

[Explanation of symbols]

 2 transparent substrate 4 transparent electrode layer 6 photoconductor layer (PC layer) 7 resin layer 8 dielectric layer 10 electroluminescent layer (EL layer) 12 back electrode layer

Claims (2)

[Claims] 1. A transparent electrode layer, a photoconductor layer, and a transparent substrate on a transparent substrate.
The dielectric layer, the electroluminescent layer and the back electrode layer are sequentially laminated, and the photoconductor layer, the dielectric layer and the electroluminescent layer are dispersed in an organic binder, and the photoconductive layer is A solid-state image conversion device having a spectral sensitivity in an infrared region on the longer wavelength side than visible light in the light emission distribution of the electroluminescent layer, and the back electrode being translucent. 2. The solid-state image conversion device according to claim 1, further comprising a resin layer formed between the photoconductor layer and the dielectric layer.