JPH0637353A - Solid image conversion element - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To form an opaque layer between the EL layer and the PC layer, unlike the conventional X-ray image conversion element, which is composed of a dispersion type laminate. The present invention newly provides a solid-state image conversion element that converts near-infrared rays into a visible image by injecting near-infrared rays from the EL layer side with a simple dispersed structure. The solid-state image conversion device of the present invention is a dispersion type laminated body, and is a transparent electrode layer 4, an electroluminescent layer 6, a dielectric layer 8, a photoconductor layer 10 and a back electrode 12 on a transparent substrate 2. The photoconductor layer has a spectral sensitivity in the infrared region on the wavelength side longer than visible light in the emission distribution of the electroluminescent layer, and the infrared rays incident from the transparent substrate cause a photoconductive effect. It is characterized by

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 is, for example, as shown in Japanese Patent Publication No. Sho 49-3037, after an EL layer, a dielectric layer, an opaque layer, and a PC layer are sequentially laminated on a glass substrate having a transparent electrode layer, It has a structure in which a metal vapor deposition electrode and a moisture-proof coating layer are 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 the X layer is applied from the PC layer side. X-ray image is P
Converted to impedance image at C layer and E at EL layer
It is converted into a visible image by L emission. In this case, the opaque layer is made of carbon powder and an epoxy resin-based binder, and the film thickness is such that the opaque layer is a PC produced by light emission in the EL layer.
A minimum thickness of about 10 μm is necessary to prevent the return to 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. Further, for example, as disclosed in Japanese Patent Laid-Open No. 1-238100, a thin film type X-ray image conversion element in which each layer excluding electrodes is formed by sputtering or the like has been proposed. In addition, as such a thin film type, a light emitting element having a memory function, which is currently proposed, includes, for example, a transparent electrode, a first insulating layer, an EL layer, and a second insulating layer on a glass substrate. , The PC layer and the back electrode are sequentially laminated in a thin film by vapor deposition or the like. In this operating principle, a sustain voltage is applied between both electrodes. In this case, the EL layer is in a dark state, Either increase the voltage applied between the electrodes to increase the distribution voltage to the EL layer to start EL emission, or irradiate the PC layer with sufficient light from the EL layer side to lower the impedance of the PC layer. , The EL layer starts to emit light. Once the EL layer is in a light emitting state, the PC layer is excited by the EL light emission and continues to have a low impedance, so that the light emission of the EL layer is maintained even if the applied voltage is reduced or the external light irradiation is stopped. . In this case, since it functions as a memory function and the PC layer must be continuously excited by EL light emission, there is no opaque layer in the configuration, and the emission distribution of the EL layer and the spectral distribution of the PC layer must match. .

However, in the above-mentioned X-ray solid-state image conversion device in which the PC layer and the EL layer are combined, the X-ray image irradiated from the PC layer side is converted into visible light regardless of whether it is a dispersion type or a thin film type. The incident light source is an X-ray and does not utilize light having a wavelength longer than visible light such as infrared rays, and an X-ray image is obtained from the transparent substrate on the EL layer side instead of the PC layer. It does not let in light. Moreover, EL layer and PC
An opaque layer is required between the layers to prevent the return of light that excites the PC layer by EL emission. Also,
Since the X-ray having a large penetrating power is targeted, the PC layer is thick, and the opaque layer or the current diffusion layer is laminated on the dielectric layer on the EL layer, so that the entire film thickness is inevitably large. Therefore, there is a drawback that high applied power is required and dielectric breakdown easily occurs.

Therefore, the conventional solid-state image conversion element for converting an X-ray image into visible light is used as it is to convert a near-infrared image into visible light in the case of inputting near-infrared light from the PC layer side. , Near-infrared rays cannot be transmitted due to the presence of a back electrode made of a moisture-proof coating or metal vapor deposition, and in the case of light incident from the EL layer side, the near-infrared rays can hardly be transmitted or can be transmitted due to the presence of an opaque layer. However, the sensitivity of the PC layer is poor because it reaches only the vicinity of the surface of the PC layer and most of the thick PC layer becomes insensitive. Furthermore, a non-translucent layer or a current diffusion layer is laminated on the dielectric layer on the EL layer,
Further, since the PC layer has to be thickened due to the X-ray having a large penetrating power and the high applied voltage caused by the X-ray, it is inevitable that the entire film thickness is remarkably increased, and that a high applied voltage is involved. There is inconvenience.

In the conventional solid-state image conversion device for converting an X-ray image into visible light, the opaque layer or the current diffusion layer is a PC.
Since it is a layer that functions as a connection layer between the layer and the EL layer and has both capacitance and resistance components, it is a solid-state image conversion element that reduces efficiency, image quality and brightness, and converts a near-infrared image into visible light. It cannot be applied.

[0097]

SUMMARY OF THE INVENTION Therefore, the present invention has been made in view of the above circumstances, and its object is to be composed of a dispersion type laminated body, which is different from the conventional X-ray image conversion element. A solid-state image conversion element for converting near-infrared rays into a visible image by making near-infrared rays incident from the EL layer side with a simple dispersion type structure without forming an opaque layer between the EL layer and the PC layer. It is to newly provide.

[0085]

The inventors of the present invention have found that even if the EL layer having ZnS as a matrix transmits near-infrared rays, and even if it is a dispersed type that diffuses light more easily than a thin-film type, an electroluminescent body. When the layers (EL layer) and the dielectric layer are set to have appropriate thicknesses, they have found that near infrared rays can pass without significant attenuation, and as a result of earnest research,
The near-infrared rays are mixed as incident light from the EL layer side to complete the solid-state image conversion device of the present invention for converting the near-infrared rays into a visible image.

That is, the above-mentioned object is a dispersion type laminate, which is formed by sequentially laminating a transparent electrode layer, an electroluminescent layer, a dielectric layer, a photoconductor layer and a back electrode on a transparent substrate. The conductor layer has a spectral sensitivity in the infrared region on the longer wavelength side of visible light in the emission distribution of the electroluminescent layer, and is characterized by being a substance that produces a photoconductive effect by infrared rays incident from the transparent substrate. It is solved by the image conversion element.

In the solid-state image conversion device of the present invention, 1) the EL layer is ZnS: Cu, Al or ZnS: Cu, X from the viewpoint of conversion of near infrared rays to visible light.
Alternatively, it comprises ZnS: Cu, Mn, X particles (X is a halogen element), while the PC layer is CdSe: C.
u, Cl particles are included. 2) The thickness of the EL layer is 15 to 35 μm, the dielectric layer contains barium titanate particles, the thickness of the dielectric layer is 3 to 15 μm, and the thickness of the PC layer is 70. ~
It should be 240 μm. 3) The average particle size of CdSe: Cu, Cl particles in the PC layer is 5
~ 15 μm. These are preferred.

[0111]

In the solid-state image conversion device of the present invention, an AC voltage is applied between the transparent electrode and the back electrode, and when near infrared rays are incident from the transparent substrate on the EL layer side, the incident near infrared rays are electroluminescent. It passes through the body layer and the dielectric layer and excites the PC layer, whereby the incident portion of near infrared rays in the PC layer lowers the impedance, and then the portion in the EL layer emits light. The light emission of the EL layer can be viewed as a visible image from the transparent substrate side.

That is, most notably, in the conventional dispersion type solid-state image conversion element, the PC required to prevent the feedback of light from exciting the PC layer by EL emission.
An opaque layer between the layer and the EL layer can be eliminated. This is because the PC layer of the present invention has its light emission sensitivity in the infrared region on the longer wavelength side of the visible light in the light emission distribution of the electroluminescent layer.

For example, as the electroluminescent phosphor phosphor particles in the EL layer, ZnS: Cu, Al, ZnS: Cu, C
1, ZnS: Cu, Br, ZnS: Cu, Mn, Cl, etc. are selected, while CdSe: Cu, Cl particles are selected as the PC layer, the influence of light feedback from the EL layer to the PC layer is reduced. You can almost avoid it. FIG. 2 shows the light emission distribution in the EL layer using ZnS: Cu, Al phosphor particles, while FIG. 3 shows the spectral sensitivity in the PC layer using CdSe: Cu, Cl particles. As shown in FIG. 2 and FIG.
The emission distribution of the EL layer using ZnS: Cu, Al phosphor particles having a main wavelength of 530 nm is CdSe: Cu, Cl.
It can be seen that there is almost no effect on the spectral sensitivity of the PC layer using particles and there is no need to provide an opaque layer.

Further, in the conventional solid-state image conversion element provided with the light opaque layer, a current diffusion having a small resistance value is provided between the PC layer which is a semiconductor and the dielectric layer and the opaque layer which are insulators. A layer (the opaque layer may also serve as the current diffusion layer) is provided, and the current diffusion layer facilitates the flow of current between the PC layer, the dielectric layer and the opaque layer, and makes the EL layer emit light. Although it is necessary to increase the brightness, the solid-state image conversion device of the present invention does not require a current diffusion layer.

The inventors of the present invention have found that the ease with which a current flows between the PC layer and the dielectric layer, that is, the electrical adhesion, determines the particle size of the particles forming the PC layer and the dielectric layer, particularly the PC layer. The present invention has been completed as a result of earnest research that was found to be affected by. That is, the particle diameter of the barium titanate particles constituting the dielectric layer is 0.5 to 2 μm, whereas PC
The particle diameter of the photoconductor particles forming the layer was 20 μm or more, and voids were generated at the joint between the PC layer and the dielectric layer, which hindered the electrical adhesion. In the solid-state image conversion device of the present invention, the particle size of the CdSe: Cu, Cl particles is selected to be 5 to 12 μm, more preferably 7 to 9 μm, so that the PC layer and the dielectric layer can be formed without impairing the photosensitivity of the PC layer. The state of bonding with the layer is good, and it is not necessary to provide a current spreading layer.

Next, the film thicknesses of the EL layer and the dielectric layer that allow near infrared rays incident on the PC layer from the transparent substrate side to pass through will be described.

By selecting the film thickness of the dielectric layer to 3 to 15 μm, and more preferably 6 to 8 μm, from the viewpoint of the reflection action of electroluminescence to the transparent electrode side, the prevention of leakage current, etc. High efficiency can be achieved and near-infrared rays can pass through.

On the other hand, the film thickness of the EL layer greatly affects the transmittance of near infrared rays. Further, the film thickness of the EL layer is related to the light emission start voltage of electroluminescence and the rise of luminance, and therefore the film thickness must be determined in consideration of these things. FIG. 4 shows the relationship between the thickness of the EL layer and the transmittance of near infrared rays. FIG. 5 shows the relationship between the thickness of the EL layer and the light emission starting voltage under the application of an alternating voltage having a sinusoidal waveform of 1 kHz. FIG. 6 shows the relationship between the film thickness of the EL layer in the state where the dielectric layer having a film thickness of 7 μm is laminated on the EL layer and the light emission luminance at the rise when the light emission start voltage is set to 25V. 4 through As apparent from FIG. 6, well in terms of power supply designs as light emission start voltage is low, but better EL layer film thickness is thin in terms of near-infrared transmittance, 10 Cd / m ² or more as the element Therefore, the thickness of the EL layer is 15 to 35 μm in consideration of the rising luminance.
Is preferable, and about 30 μm is particularly desirable.

Next, P which absorbs near infrared rays and exhibits photoconductivity
The film thickness of the C layer will be described. In Figure 7, the particle size distribution is 5
To 25 μm and an average particle size of 8 μm
The relationship between the absorption rate of near infrared rays and the film thickness in the PC layer made of Se: Cu, Cl particles is shown. As is clear from FIG. 7, when the film thickness is 240 μm or more, the absorption rate is 1
Since it will be saturated with 00%, P will increase at a film thickness of 240 μm or more.
Since a dead part is generated in the C layer, 240 μm
The above film thickness is inappropriate. On the other hand, the minimum film thickness is determined in terms of applied voltage. That is, from FIG. 6, from the viewpoint of the emission brightness of the EL layer that the device requires a brightness of 10 Cd / m ² or more, for example, the thickness of the EL layer is 30 μm.
Then, it is necessary from FIG. 5 to have a light emission start voltage of about 30V, and normally, about half of the applied voltage of the PC layer is distributed to the EL layer due to the incidence of near infrared rays. Normally, 7V per 10μm thickness of PC layer
Since it is necessary to distribute the voltage to some extent, the thickness of the PC layer is 70
μm. Therefore, the desirable thickness of the PC layer is 70 to 2
40 μm, more preferably 100 to 150 μm.

Further, it should be noted that the conventional solid-state image conversion device for converting an X-ray image into a visible image requires an applied voltage of about 400 V, whereas the solid-state image conversion device of the present invention. Then, it can be reduced to 80 to 120V, which is one-third to one-quarter of the conventional value.

[0211]

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

FIG. 1 shows a sectional view of the solid-state image conversion device of the present invention. This solid-state image conversion device comprises a transparent substrate 2, a transparent electrode layer 4, an EL layer 6, a dielectric layer 8, PC layer 1
0 and the back electrode layer 12 are sequentially laminated.

This solid-state image conversion element will be described based on a specific manufacturing method. The transparent substrate 2 having the transparent electrode layer 4 will be described.
On a (Corning glass substrate 7059), an EL layer 6 of ZnS: Cu, Al powder having an average particle diameter of 13 μm and a film thickness of 30 μm, and a barium titanate having an average particle diameter of 1.4 μm and having a film thickness of 7 μm. Dielectric layer 6, grain size 6-8
Thickness of CdSe: Cu, Cl of 120 μm
The PC layer 8 of m was laminated by screen printing, and aluminum was vapor-deposited thereon to form the back electrode layer 12. The transparent electrode layer 2 and the back electrode layer 1 are sealed while sealing the peripheral portion.
2 is connected to a suitable AC power source.

In the solid-state image conversion device having such a structure, when an alternating voltage of 1 kHz and 100 V is applied, when a near infrared ray having a wavelength of 780 nm and 100 μW / cm ² is radiated from the transparent substrate 2 side, the irradiated region EL layer 6
Emission was 10 Cd / m ² .

[025]

As described above, according to the present invention, the dispersion type laminated body is used, but unlike the conventional X-ray image conversion element, the electroluminescent layer (EL layer) and the photoconductor layer ( PC layer)
A new solid-state image converter that converts near-infrared light into a visible image by making near-infrared light incident from the electroluminescent layer (EL layer) side with a simple dispersive structure without forming an opaque layer between An element can be provided.

Further, in the solid-state image conversion device of the present invention, the total thickness can be made extremely thin, and it is possible to reduce failures and dielectric breakdown due to high applied voltage due to the large number of laminated layers, which are conventional defects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a solid-state image conversion device of one embodiment of the present invention.

FIG. 2 is a graph showing a light emission distribution of an electroluminescent layer according to the present invention.

FIG. 3 is a graph showing the spectral sensitivity of the photoconductor layer according to the present invention.

FIG. 4 is a graph showing the relationship between the film thickness of the electroluminescent layer according to the present invention and the transmittance of near infrared rays.

FIG. 5 is a graph showing the relationship between the film thickness of the electroluminescent layer and the light emission starting voltage according to the present invention.

FIG. 6 is a graph showing the relationship between the film thickness of the electroluminescent layer and the emission luminance according to the present invention.

FIG. 7 is a graph showing the relationship between the film thickness of the photoconductor layer according to the present invention and the absorption rate of near infrared rays.

[Explanation of symbols]

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

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 21, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 004

[Correction method] Change

[Correction content]

However, in the above-mentioned X-ray solid-state image conversion device in which the PC layer and the EL layer are combined, the X-ray image irradiated from the PC layer side is converted into visible light regardless of whether it is a dispersion type or a thin film type. The incident light source is an X-ray and does not utilize light having a wavelength longer than visible light such as infrared rays, and an X-ray image is obtained from the transparent substrate on the EL layer side instead of the PC layer. It does not let in light. Moreover, EL layer and PC
An opaque layer is required between the layers to prevent the return of light that excites the PC layer by EL emission. Also,
Since the X-ray having a large penetrating power is targeted, the PC layer is thick, and the opaque layer or the current diffusion layer is laminated on the dielectric layer on the EL layer, so that the entire film thickness is inevitably large. Therefore, a required high applied voltage, there is a disadvantage that tends to breakdown.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 010

[Correction method] Change

[Correction content]

In the solid-state image conversion device of the present invention, 1) the EL layer is ZnS: Cu, Al or ZnS: Cu, X from the viewpoint of conversion of near infrared rays to visible light.
Alternatively, it comprises ZnS: Cu, Mn, X particles (X is a halogen element), while the PC layer is CdSe: C.
u, Cl particles are included. 2) The thickness of the EL layer is 15 to 35 μm, the dielectric layer contains barium titanate particles, the thickness of this dielectric layer is 3 to 30 μm, and the thickness of the PC layer is 70-
It should be 240 μm. 3) The average particle size of CdSe: Cu, Cl particles in the PC layer is 5
~ 15 μm. These are preferred.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 012

[Correction method] Change

[Correction content]

That is, most notably, in the conventional dispersion type solid-state image conversion element, the PC required to prevent the feedback of light from exciting the PC layer by EL emission.
An opaque layer between the layer and the EL layer can be eliminated. This is because the PC layer of the present invention has its spectral sensitivity in the infrared region of the emission distribution of the electroluminescent layer, which is on the longer wavelength side than visible light.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 013

[Correction method] Change

[Correction content]

For example, as the electroluminescent phosphor particles in the EL layer, ZnS: Cu, Al, ZnS: Cu, Cl, Z
By selecting nS: Cu , Br, ZnS: Cu, Mn, Cl, etc., while selecting CdSe: Cu, Cl particles as the PC layer, the influence of light feedback from the EL layer to the PC layer is almost eliminated. It can be lost. FIG. 2 shows the light emission distribution in the EL layer using ZnS: Cu, Al phosphor particles, while FIG. 3 shows C.
The spectral sensitivity of the PC layer using dSe: Cu, Cl particles is shown. Referring to FIGS. 2 and 3, the EL layer of ZnS: Cu, Al phosphor particles having a dominant wavelength of 530 nm is shown. It can be seen that the light emission distribution has almost no effect on the spectral sensitivity of the PC layer using the CdSe: Cu, Cl particles, and there is no need to provide a light opaque layer.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 017

[Correction method] Change

[Correction content]

The thickness of the dielectric layer is 3 to 30 μm, preferably
Is 3 to 15 μm, and more preferably 6 to 8 μm, to thereby reflect the electroluminescence to the transparent electrode side,
From the viewpoint of preventing leakage current, the efficiency of electroluminescence can be improved, and near-infrared rays can be transmitted.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 018

[Correction method] Change

[Correction content]

On the other hand, the film thickness of the EL layer greatly affects the transmittance of near infrared rays. Further, the film thickness of the EL layer is related to the light emission start voltage of electroluminescence and the rise of luminance, and therefore the film thickness must be determined in consideration of these things. FIG. 4 shows the relationship between the thickness of the EL layer and the transmittance of near infrared rays. In Fig. 5, a dielectric layer with a thickness of 7 μm is stacked on the EL layer .
The relationship between the thickness of the EL layer in the layered state and the light emission start voltage is shown under the application of an alternating voltage of sinusoidal waveform of 1 kHz. In FIG. 6, 25 V is added to the film thickness of the EL layer in the state where the dielectric layer having a film thickness of 7 μm is laminated on the EL layer and the light emission start voltage.
Relationship of the luminous intensity is shown at the rising time was. 4 through As apparent from FIG. 6, well in terms of power supply designs as light emission start voltage is low, but better EL layer film thickness is thin in terms of near-infrared transmittance, 10 Cd / m ² or more as the element Therefore, the thickness of the EL layer is preferably 15 to 35 μm, and particularly preferably about 30 μm in consideration of rising luminance.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 023

[Correction method] Change

[Correction content]

This solid-state image conversion element will be described based on a specific manufacturing method. The transparent substrate 2 having the transparent electrode layer 4 will be described.
On a (Corning glass substrate 7059), an EL layer 6 of ZnS: Cu, Al powder having an average particle diameter of 13 μm and a film thickness of 30 μm, and a barium titanate having an average particle diameter of 1.4 μm and having a film thickness of 7 μm. Dielectric layer 8 , grain size 6-8
Thickness of CdSe: Cu, Cl of 120 μm
The PC layer 10 of m was laminated by screen printing, and aluminum was vapor-deposited thereon to form the back electrode layer 12.
The transparent electrode layer 4 and the back electrode layer 12 are connected to a suitable AC power source while sealing the peripheral portion.

[Procedure Amendment 9]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (4)

[Claims] 1. A dispersion type laminate, comprising a transparent electrode layer, an electroluminescent layer having ZnS as a matrix, a dielectric layer, a photoconductor layer, and a back electrode, which are sequentially laminated on a transparent substrate. The photoconductor layer has a spectral sensitivity in the infrared region on the wavelength side longer than visible light in the light emission distribution of the electroluminescent layer, and is characterized in that the infrared light incident from the transparent substrate causes a photoconductive effect. A solid-state image conversion element. 2. The electroluminescent layer is ZnS: Cu, Al
Or ZnS: Cu, X or ZnS: Cu, Mn, X
The solid-state image conversion device according to claim 1, wherein (X is a halogen element) is contained, while the photoconductor layer contains CdSe: Cu, Cl particles. 3. The film thickness of the electroluminescent layer is 15 to 35 μm.
m, the dielectric layer comprises barium titanate particles, the dielectric layer has a thickness of 3 to 15 μm, and the photoconductor layer has a thickness of 70 to 240 μm. The solid-state image conversion element according to claim 1, wherein the solid-state image conversion element is a solid-state image conversion element. 4. The CdSe: Cu, Cl of the photoconductor layer
The solid-state image conversion device according to claim 3, wherein the particles have an average particle size of 5 to 15 μm.