JPH06151952A - Infrared-visible ray conversion element - Google Patents

Abstract

PURPOSE:To improve the contrast and sensitivity by specifying the dielectric constant of organic binder of electric field light emitting layer (EL layer) and the dielectric constant of organic binder of photo conductive layer (PC layer). CONSTITUTION:A clear glass substrate 2, a clear electrode layer 4, an EL layer 6, a dielectric layer 8, a PC layer 10 and a rear electrode layer 12 are sequentially laminated. The relative dielectric constant of organic binder of EL layer 6 is made larger than 12 and, on the other hand, the relative dielectric constant of organic binder of the PC layer 10 is made smaller than 7. For a better case, the dielectric constant of organic binder of EL layer 6 is made larger than 15 and, on the other hand, the dielectric constant of organic binder of the PC layer 10 is made smaller than 5. As organic binders with a high dielectric constant, cyanoethylcellulose and cyanoethylpullulan, etc., can be considered. On the other hand, acrylic resin, ethylcellulose, etc., can be considered as the organic binder with a low dielectric constant. By doing this, both the contrast and sensitivity can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a photoconductor layer (hereinafter referred to as P
An infrared-visible conversion element for converting a radiation image of infrared rays, particularly near-infrared rays into a visible image by a combined structure of a C layer) and an electroluminescent layer (hereinafter referred to as an EL layer), particularly the EL layer. And an infrared-visible conversion device having an improved organic binder for the PC layer.

[0002]

2. Description of the Related Art An infrared-visible conversion element that combines an EL layer and a PC layer to convert infrared rays into a visible image is useful for aligning the optical axis of infrared laser light. , In addition to the advantages of continuous use and high durability compared to infrared detection cards that use stimulated phosphors, the brightness is extremely high and it can be used not only in dark rooms but also in bright rooms. It has been particularly noticeable.

However, with regard to this infrared-visible conversion element, further improvement in contrast and sensitivity is desired in a bright room.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an infrared-visible conversion element with improved contrast and sensitivity.

[Means for Solving the Problems]

In order to improve the contrast and sensitivity, the inventors of the present invention have conducted intensive studies and as a result, lowered the relative permittivity in the PC layer, which has been conventionally considered to have a high relative permittivity, to improve the contrast and sensitivity. I found that I could improve.

[0006] That is, the above-mentioned object is to provide between a pair of electrode layers,
In an infrared-visible conversion element for converting an infrared image into a visible image by combining a PC layer and an EL layer coated with photoconductive particles and electroluminescent particles with an organic binder, an organic binder for the EL layer. Relative permittivity of 12
On the other hand, the relative dielectric constant of the organic binder of the PC layer is 7
By the infrared-visible conversion element characterized by the following,
Will be resolved.

Preferably, the relative dielectric constant of the organic binder of the EL layer is 15 or more, while the relative dielectric constant of the organic binder of the PC layer is 5 or less. As an organic binder with high dielectric constant,
Examples thereof include cyanoethyl cellulose and cyanoethyl pullulan, while examples of the organic binder having a low dielectric constant include acrylic resin and ethyl cellulose.

[0008]

By setting the organic binder in the PC layer to 7 or less, more preferably 5 or less, the brightness of the EL layer at the same frequency and at the same applied voltage at the time of non-excitation can be suppressed as low as possible, and further, at the time of excitation. The brightness of the EL layer is almost unchanged. That is, when infrared rays are not incident, if an organic binder having a high relative dielectric constant is used in addition to the resistance of the PC layer, the capacitance C as a capacitor cannot be ignored in addition to the high resistance Z of the PC layer. While the current due to the organic binder becomes dominant and the brightness at the time of non-incident increases, when the relative dielectric constant of the organic binder is low, the capacitance C as a capacitor can be ignored, and the resistance of the PC layer is mainly used. Since the impedance is only Z, it is preferable for contrast and sensitivity when not incident.

[0009]

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

(Example 1) FIG. 1 shows a sectional view of an infrared-visible conversion element of the present invention. This infrared-visible conversion element basically comprises a transparent glass substrate 2 and a transparent electrode layer. 4, E
The L layer 6, the dielectric layer 8, the PC layer 10, and the back electrode layer 12 are sequentially laminated.

This infrared-visible conversion element will be described based on a specific manufacturing method. ITO is formed on the transparent glass substrate 2.
(Indium oxide / tin) A transparent conductive film is formed by a sputtering method or the like to form a transparent electrode layer 4, and an average particle is formed on the transparent electrode 4 with an organic binder made of cyanoethyl cellulose (relative permittivity: 16, room temperature). Zn with a diameter of 13 μm
An EL layer 6 having a film thickness of 30 μm formed by dispersing S: Cu and Al powders, and a dielectric layer 8 having a film thickness of 7 μm formed by dispersing barium titanate particles having an average particle diameter of 1.4 μm are formed. Next, an acrylic resin (Paraloid A-11 manufactured by Rohm and Haas Co., a relative dielectric constant of 3) was used as an organic binder in a butyl carbitoacetate solution, and the particle size was 6 to 8 μm.
The PC layer 10 made of CdSe: Cu, Cl having a film thickness of 160 μm is laminated by screen printing. This PC
A paste of ITO fine powder is laminated on the layer 10 by a screen printing method to form a back electrode layer 1 which is a translucent electrode.
Form 2. Although not shown, the back electrode layer 12 is covered with a sealing glass at a predetermined interval, and the transparent glass substrate 2 and the transparent electrode layer 2 cover the back electrode layer 1 at the peripheral edge thereof.
Seal up to 2 stacks. Suitable connecting means, eg
The transparent electrode layer 2 and the back electrode layer 12 are connected to a suitable AC power source by an electrode lead or the like penetrating the sealing portion.

In order to compare the luminosity sensitivities of the thus constructed infrared-visible conversion elements, the organic binder of the PC layer 10 was dimethyl with cyanoethylpullulan having a high relative dielectric constant of 18 (room temperature) as a binder. The same conventional product as in the above-described example was prepared except that formamide was used as the solvent. For this conventional product and this embodiment product, 1 kHz, 15
By applying an AC voltage of 0 V and changing the amount of near-infrared light having a wavelength of 780 nm, irradiation is performed from the transparent glass substrate 2 side,
The result of comparing the relative luminance with respect to the amount of incident light is shown in FIG. As shown by the dotted line in FIG. 2, when the incident light amount is 0.01 mW / cm ² which is the vicinity of the incident area of the conventional product, the luminance is increased when the incident light amount becomes 100 times or more as the incident light amount increases. Shows 30 Cd / m ² and is saturated. On the other hand, as shown by the solid line in FIG. 2, in the product of this example, the gradient is steep in the region where the incident light amount is 0.7 mW / cm ² or less, that is, the contrast is high and the light amount is 0.7.
At mW / cm ² or more, the brightness is the same as the conventional product.
In other words, in the present embodiment, the brightness can be suppressed as low as possible during non-excitation, and there is no decrease in brightness during excitation.

This will be described with reference to FIG. 3, which shows an equivalent circuit modeling the photoconductive particles of the PC layer 10 and the organic binder. In the infrared-visible conversion element in which the PC layer 10 and the EL layer 6 are combined, the PC layer 10 can be operated by direct current or alternating current, but generally, the EL layer can be efficiently operated only by alternating current and the transparent electrode layer 4 And back electrode layer 1
An alternating voltage of 100 Hz to several kHz is applied between the two. When infrared rays are not incident, the resistance R of the PC layer 10
₁ is high, the capacitance C ₁ of the PC layer 10 is small, and R ₁ and C ₁
The total impedance Z ₁ obtained by combining the above becomes a large value. In this state, the organic binder of the PC layer 10 has a size that cannot be ignored as the capacitor C ₂ , and particularly when the relative dielectric constant is increased to 12 or more as in the conventional case, the current caused by the organic binder is It becomes dominant, and unfortunately, this current contributes to the light emission of the EL layer 6, and the brightness at the time of non-incidence increases,
Although the sensitivity and the contrast are deteriorated, on the other hand, when the relative dielectric constant of the organic binder of the PC layer 10 is reduced as in the present embodiment, the capacitance component of the capacitor C ₂ can be reduced to a negligible level, and the EL layer 6 In, the brightness at the time of non-incident can be lowered, and the sensitivity and the contrast can be improved.

When the organic binder of the PC layer 10 is considered as the capacitor C ₂ , the capacitance component can be neglected by reducing the frequency as much as possible, and it is considered that the contrast is improved. In this case, the EL layer Since the light emission luminance of 6 also decreases substantially in proportion to the frequency, practical luminance cannot be obtained. Further, it is conceivable to reduce the capacitance component of the capacitor C ₂ of the organic binder by generating bubbles in the organic binder of the PC layer 10, but in this case, since the applied voltage is relatively high, sparks or the like occur. It is not preferable because it may cause

Example 2 Example 1 was repeated except that Hercules ethyl cellulose N-14 (dielectric constant 3.1) manufactured by Daicel Chemical Industries, Ltd. was used as a butyl cellosolve solution as the organic binder of the PC layer 10 of Example 1. As in Example 1, the brightness was kept as low as possible during non-excitation, and there was no decrease in brightness during excitation.

In the above-mentioned embodiment, the PC layer 6, the dielectric layer 8 and the EL layer 10 are sequentially formed on the transparent electrode 4 on the transparent glass substrate 2, but the present invention is not limited to this.
It can be applied to an element that converts infrared rays into visible light in combination with the EL layer 10 and, for example, a transparent electrode on a glass substrate, E
A transmissive element in which an L layer, a dielectric layer and a PC layer are sequentially formed,
Alternatively, it goes without saying that the invention can also be applied to a double-sided symmetric element in which a PC layer and an EL layer are formed on both sides of a dielectric layer.

[0017]

As described above, according to the present invention,
A simple structure in which an organic binder having a high relative dielectric constant is used for the electroluminescent layer (EL layer) and an organic binder having a low relative dielectric constant is used for the photoconductor layer (PC layer) improves contrast and sensitivity. An infrared-visible conversion device could be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a part of an infrared-visible conversion element according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the amount of incident light and the brightness in the infrared-visible conversion element according to FIG.

FIG. 3 is a schematic diagram schematically showing an equivalent circuit of a photoconductor layer (PC layer) according to FIG.

[Explanation of symbols]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshifumi Tominaga 491, Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Nichia Kagaku Kogyo Co., Ltd.

Claims (2)

[Claims] 1. An infrared image is formed as a visible image by combining a pair of electrode layers with a photoconductive layer and an electroluminescent layer coated with photoconductive particles and electroluminescent particles with an organic binder, respectively. In the infrared-visible conversion element, the relative dielectric constant of the organic binder of the electroluminescent layer is 12 or more, and the relative dielectric constant of the organic binder of the photoconductor layer is 7 or less. Infrared-visible conversion element. 2. The organic binder of the electroluminescent layer has a relative permittivity of 15 or more, while the organic binder of the photoconductor layer has a relative permittivity of 5 or less. Solid-state image conversion device.