JP2001160922A - Image detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image detector, where line electrodes for strip electrodes and sub line electrodes for sub electrodes are alternately arranged and both the line electrodes are not short-circuited. SOLUTION: An insulation layer 28 transparent to a read light L2 is provided to the outside of a 2nd electrode layer 25 provided with an element 26 for a stripe electrode 26. An element 27a for the sub electrode 27 is placed, with the elements 26a, 27a being placed alternately at the outside of the insulation layer 28. The thickness of the insulation layer 28 is selected as thin as possible, in a range where the elements 26a, 27a are not short-circuited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical reading type image detector in which a large number of linear electrodes for obtaining an electric signal corresponding to the amount of latent image charges are arranged in stripes.

[0002]

2. Description of the Related Art Conventionally, apparatuses using an image detector, such as a facsimile, a copying machine, and a radiation imaging apparatus, are known.

For example, in radiation imaging for medical diagnosis or the like, electric charges obtained by detecting radiation are temporarily stored in a power storage unit as latent image charges, and the stored latent image charges are stored in an electric signal representing radiation image information. Various methods and apparatuses have been proposed and put to practical use, which use a radiation solid state detector (electrostatic recording medium) that converts and outputs the image as an image detector. Various types of solid-state radiation detectors have been proposed for use in this method and apparatus. However, the surface of the charge readout process for detecting a signal having a magnitude corresponding to the amount of accumulated latent image charge has been proposed. There is an optical reading type that irradiates a detector with reading light (electromagnetic wave for reading).

The applicant of the present application has disclosed a solid-state radiation detector of the optical readout type capable of achieving both high-speed readout response and efficient signal charge extraction, as disclosed in Japanese Patent Application No. 10-271.
No. 374, No. 11-87922, No. 11-89553
No. 11-207283 and the like, a first electrode layer (conductive layer) having transparency to recording radiation carrying image information or light emitted by excitation of radiation (hereinafter collectively referred to as recording light) ), The photoconductive layer for recording, which exhibits conductivity when irradiated with recording light, acts substantially as an insulator with respect to charges of the same polarity as the charges charged on the first electrode layer, and has the same polarity. A charge transport layer that acts as a substantially conductive material for charges having a polarity opposite to that of the photoconductive layer, a reading photoconductive layer that exhibits conductivity when irradiated with reading light (reading electromagnetic waves), and a reading light A second electrode layer (conductor layer) having transparency is laminated in this order, and a signal charge carrying image information is stored in a power storage unit formed at an interface between the recording photoconductive layer and the charge transport layer. A detector that accumulates latent image charges) There.

[0005] Japanese Patent Application No. 11-87922,
In JP-A-11-89553 and JP-A-11-207283, in particular, a large number of linear electrodes (light irradiation electrodes) of a second electrode layer having transparency to reading light are arranged in stripes. A large number of sub-linear electrodes for outputting an electric signal at a level corresponding to the amount of latent image charges stored in the power storage unit,
There has been proposed a detector in which the linear electrodes forming the stripe electrodes are arranged in the second electrode layer in parallel and alternately with each other.

As described above, by providing the sub-electrodes (electrodes for extracting electric charges) composed of the sub-linear electrodes in the second electrode layer, a new capacitor is formed between the power storage unit and each of the sub-linear electrodes. The sub-linear electrodes can be charged with transport charges having a polarity opposite to that of the latent image charges stored in the power storage unit by recording by charge rearrangement at the time of reading.
Thereby, the amount of the transport charge distributed to the capacitor formed between the linear electrode forming the stripe electrode and the power storage unit via the reading photoconductive layer is reduced as compared with the case where the sub-linear electrode is not provided. As a result, the readout efficiency is improved by increasing the amount of signal charges that can be extracted from the detector to the outside, and at the same time, high-speed readout response and efficient signal charge extraction can be achieved at the same time. Can also be planned.

[0007]

However, if the linear electrodes forming the stripe electrodes and the sub-linear electrodes forming the sub-electrodes are alternately arranged in the second electrode layer, the linear electrodes and the sub-linear electrodes are formed. The space between the electrodes is very narrow,
There is a possibility that both linear electrodes may be short-circuited due to a manufacturing defect or the like. When both linear electrodes are short-circuited, the sub-linear electrodes do not function as electrodes for improving the reading efficiency. When only some of the two linear electrodes are short-circuited, the reading efficiency is improved because the sub-linear electrodes are provided as a whole, but the reading efficiency of the short-circuited part is lower than that of the surroundings, so that the image is not displayed. In the above, the short part appears as streak noise.

The present invention has been made in view of the above circumstances, and has as its object to provide an image detector in which there is no risk of short-circuit between the linear electrode and the sub-linear electrode.

[0009]

In the image detector according to the present invention, an insulating layer is provided outside the second electrode layer, and the light irradiation electrode (inside the second electrode layer) and charge extraction are interposed between the insulating layers. In this case, an electrode is provided.

That is, an image detector according to the present invention comprises a first electrode layer having transparency to recording light carrying image information, and a recording photoconductive material exhibiting conductivity when irradiated with the recording light. A layer, a reading photoconductive layer that exhibits conductivity by being irradiated with the reading light, and a second electrode layer in which a large number of linear electrodes that are transparent to the reading light are arranged in stripes. An optical detector in which a power storage unit is formed between the recording photoconductive layer and the reading photoconductive layer, wherein the reading is performed outside the second electrode layer. An insulating layer having a light-transmitting property is laminated, and a number of sub-linear electrodes for outputting an electric signal at a level corresponding to the amount of the latent image charges stored in the power storage unit outside the insulating layer. Are striped so that they are located between many linear electrodes and each other And it is characterized in that it is the column. The electrode composed of the sub-linear electrodes is the above-described sub-electrode (charge extraction electrode).

"Outside the second electrode layer" means the side of the second electrode layer opposite to the reading photoconductive layer, and "outside the insulating layer".
Means the side of the insulating layer opposite to the second electrode layer.

"Located between each other" means that the linear electrodes and the sub-linear electrodes in the second electrode layer are alternately arranged with the insulating layer interposed therebetween. In this case, the two linear electrodes may partially overlap each other in the arrangement direction.

"Insulating layer having transparency to reading light"
However, at least in the arrangement direction of the linear electrodes,
It is sufficient that the portion corresponding to the linear electrode in the second electrode layer has transparency to the reading light, and the entire insulating layer does not necessarily have to have transparency.

In order to make the insulating layer transparent to the reading light, it is preferable to use, for example, SiO ₂ , SiC, SiN or the like.

[0015]

According to the image detector of the present invention, the second
An insulating layer having transparency to reading light is provided outside the electrode layer, and a linear electrode for light irradiation and a sub-linear electrode for charge extraction are provided with the insulating layer interposed therebetween. The thickness of the layer can be set arbitrarily to some extent. Thereby, the insulating layer can be formed to a thickness that does not cause a short circuit between the two linear electrodes, and the electrode short circuit can be reliably prevented.

Further, since the insulating layer may be formed to have an appropriate thickness so that the two linear electrodes do not short-circuit, the distance between the two linear electrodes can be kept small to some extent. It is possible to maintain the same reading efficiency as in the case where the linear electrodes are alternately arranged.

Further, since the sub-linear electrodes are provided outside the insulating layer, problems such as erasing of an electrostatic latent image due to charge injection from the sub-linear electrodes can be eliminated.

[0018]

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

FIG. 1 is a diagram showing a schematic configuration of an embodiment of an image detector according to the present invention. FIG. 1 (A) is a perspective view of a solid-state radiation detector as an image detector, and FIG. 1 (B). 1A is an XZ cross-sectional view of the arrow Q finger part of FIG. 1A, and FIG.
It is XY sectional drawing of the arrow P part of (A).

The solid-state radiation detector 20 includes a first electrode layer 21 having transparency with respect to recording light L1 such as visible light or X-ray carrying image information, and a recording light transmitted through the first electrode layer 21. The recording photoconductive layer 22, which exhibits conductivity when irradiated with L1, acts substantially as an insulator against latent image charges (eg, negative charges), and has transport charges (of opposite polarity to the latent image charges). In the above-described example, the charge transport layer 23 which functions as a substantially conductive material for the positive charge, the reading photoconductive layer 24 which exhibits conductivity by being irradiated with the reading light (electromagnetic wave for reading) L2, and the reading. The second light-transmitting second light L2
An electrode layer 25, an insulating layer 28, and a sub-electrode (charge extraction electrode) 27 are arranged in this order. At the interface between the recording photoconductive layer 2 and the charge transport layer 3, a power storage unit 29 for storing the latent image polarity charge generated in the recording photoconductive layer 22 is formed.

In manufacturing the solid-state radiation detector 20, the sub-array is usually placed on a support such as a glass or an organic polymer material (not shown) which is transparent to the reading light L2 in a manner opposite to the above-described arrangement order. The electrode 27 is formed (laminated), and then the insulating layer 28, the second electrode layer 25, and the reading photoconductive layer 2 are sequentially formed.
4. The charge transport layer 23, the recording photoconductive layer 22, and the first electrode layer 21 are formed (laminated).

The material of the recording photoconductive layer 22 is a-
Lead (II) such as Se (amorphous selenium), PbO, PbI ₂ , lead (II) iodide, Bi ₁₂ (Ge, Si)
A photoconductive substance mainly containing at least one of O ₂₀ , Bi ₂ I ₃ / organic polymer nanocomposite, etc. is suitable.

As the substance of the charge transport layer 23, for example, the larger the difference between the mobility of the negative charge charged in the first electrode layer 21 and the mobility of the positive charge having the opposite polarity, the better (for example, 1 to 1).
0 ² or more, preferably 10 ³ or more) poly N-vinylcarbazole (PVK), N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1′-biphenyl] -4, Four'
An organic compound such as diamine (TPD) or discotic liquid crystal, or a polymer (polycarbonate, polystyrene, PUK) dispersion of TPD;
A semiconductor material such as a-Se doped with 0 ppm is suitable. In particular, organic compounds (PVK, TPD, discotic liquid crystal, etc.) are preferable since they have photosensitivity,
In addition, since the dielectric constant is generally small, the capacity of the charge transport layer 23 and the reading photoconductive layer 24 is reduced, and the signal extraction efficiency at the time of reading can be increased. Note that “having light insensitivity” means that the film hardly exhibits conductivity even when irradiated with the recording light L1 or the reading light L2.

The material of the reading photoconductive layer 24 is a-
Se, Se-Te, Se-As-Te, metal-free phthalocyanine, metal phthalocyanine, MgPc (Magnesium ph
talocyanine), VoPc (phase II of Vanadyl phthal)
Preferred is a photoconductive material containing at least one of ocyanine), CuPc (Cupper phtalocyanine) and the like as a main component.

The thickness of the recording photoconductive layer 22 should be 50 μm or more and 100 μm or more in order to sufficiently absorb the recording light L1.
0 μm or less, and in this example, about 50 μm.
It is 0 μm. The charge transport layer 23 and the photoconductive layer 24
Is preferably not more than の of the thickness of the recording photoconductive layer 22, and the thinner the better, the better the response at the time of reading. Is preferably 1/20 or less.

As the first electrode layer 21, for example, a transparent conductive film such as ITO (Indium Tin Oxide) is suitable when the recording light is visible light, and a metal film such as gold or aluminum is suitable when the recording light is radiation such as X-rays. .

The light irradiation electrode of the second electrode layer 25 is formed as a stripe electrode 26 in which a number of elements (linear electrodes) 26a are arranged in a stripe shape. here,
As the material and thickness of the electrode material forming each element 26a of the stripe electrode 26, specifically, ITO having a thickness of 100 nm and IDIXO (Idemitsu Indiu having a thickness of 100 nm) are used.
m X-metal Oxide; Idemitsu Kosan Co., Ltd .; 10 nm-thick aluminum; 10 nm-thick molybdenum; By using these, both, the transmittance P _b with respect to the reading light L2 may be 50% or more. The space 25a between the elements 26a may be filled with a non-conductive polymer material such as polyethylene in which a small amount of pigment such as carbon black is dispersed, and may have a light-shielding property with respect to the reading light L2. .

Further outside the insulating layer 28, an electric signal of a level corresponding to the amount of the latent image charge stored in the power storage unit 29 formed substantially at the interface between the recording photoconductive layer 22 and the charge transport layer 23. Is provided with a sub-electrode 27 which is a conductive member for outputting an output. The sub-electrode 27 is formed by arranging a large number of elements (sub-linear electrodes) 27a in a stripe shape.
a and the element 26a of the stripe electrode 26 are arranged so as to be located between each other. Sub electrode 27
Specifically, the material and thickness of the electrode material forming each element 27a may be 100 nm thick aluminum,
Molybdenum having a thickness of 00 nm, chromium having a thickness of 100 nm, or the like can be used. By using these, the transmittance _Pc for the reading light L2 can be reduced to 10% or less, and the charge pair for signal extraction is formed in the reading photoconductive layer 24 corresponding to the element 27a. It can be prevented from occurring.

Each element 26a and each element 27a
Are electrically insulated because they are arranged with the insulating layer 28 interposed therebetween.

FIG. 2 is a diagram showing an arrangement relationship between the two elements 26a and 27a. Here, both elements 26a,
When the elements 27a are arranged so as to be located between them, as shown in FIG.
7a, both elements 26a, 27a
Spaces d1 and d2 are provided between the two elements 26.
a, 27a may be arranged so as not to have a portion overlapping in the laminating direction. Also, as shown in FIG.
In the arrangement direction of the two elements 26a and 27a, the two elements 26a and 27a may be arranged so that a part thereof has a width d3 and d4 and overlaps in the stacking direction.

The insulating layer 28 is made of a material having transparency to the reading light L2. For example, SiO ₂ , SiC, Si
N or the like may be used. Further, a resin such as PET (polyethylene terephthalate) or polycarbonate can also be used.

It is sufficient that the portion corresponding to the position where the element 26a forming the stripe electrode 26 is disposed has transparency to the reading light L2, and transmissive portions and non-transmissive portions are formed alternately. It is also possible to be composed. The thickness of the insulating layer 28 is determined by the element 26a and the element 27a.
It is preferable to make the thickness as thin as possible within the range where the short circuit does not occur.

In this detector 20, the element 2
7a width W_cIs the width W of the element 26a._bWider than
And the transmission of the element 26a to the reading light L2.
Rate P _b, The transmittance P of the element 27a for the reading light L2
_cIs a conditional expression (W_b× P_b) / (W_c× P_c) ≧ 1 (Article
(Referred to as conditional expression (1)).

The above conditional expression (1) satisfies element 26a,
Regardless of the width and transmittance of each electrode 27a and the light amount of the reading light L2, the total light amount (transmission light amount) of the reading light L2 incident on the reading photoconductive layer 24 via the light irradiation element 26a regardless of the light amount of the reading light L2. Means that the total light amount (transmitted light amount) of the reading light L2 incident on the reading photoconductive layer 24 via the charge extracting element 27a is always larger.

[0035] The total amount of light ratio _{(W b × P b) /} (W c ×
Since the greater the value of P _c ), the greater the degree of improvement in the reading efficiency, the right side of the conditional expression (1) is preferably 5 or more, for example, 8, more preferably 12, or the like.

[0036] In using the detector 20, in accordance with the fact that wider than the width W _b of the element 26a of the width W _c of the elements 27a, at the time of recording an electrostatic latent image, the stripe electrode 26 and the sub-electrode 27 And the sub-electrode 27 is positively used for forming an electric field distribution.

When recording is performed by connecting the stripe electrode 26 and the sub-electrode 27 in this way, the latent image charges are not only stored at the position corresponding to the element 26a but also at the element 27a
Is stored at the position corresponding to
When the reading light L2 is irradiated on the reading photoconductive layer 24 through the element a, the latent image charges in the sky portions of the two elements 27a sandwiching the element 26a are sequentially read out via the two elements 27a. Therefore, in this case, the position corresponding to the element 26a is the pixel center, and up to each half of the element 27a on both sides of the element 26a is one pixel in the arrangement direction of the elements 26a, 27a.

In this detector 20, _a capacitor C _{* a} is formed between the first electrode layer 21 and the power storage unit 29 with the recording photoconductive layer 22 interposed therebetween, and the charge transport layer 23 and the reading photoconductive layer 24, the power storage unit 29 and the stripe electrode 26
Capacitor C _{* b} between the (element 26a) is formed, a capacitor C _{* c} between the electric storage unit 29 via the reading photoconductive layer 24 and charge transport layer 23 sub-electrode 27 (the element 27a) It is formed. During charge rearrangement at the time of reading, the amount of positive charge Q _{+ a} , Q _{+ b} , Q _{+ c} distributed to each of the capacitors C _{* a} , C _{* b} , C _{* c} is represented by a total of Q ₊ the amount of charge Q _- the same as the capacitance of each capacitor C _a, C _b, C
_The amount is proportional to _c . This can be represented by the following equation.

[0039] _{Q - = Q + = Q +} a + Q + b + Q + c Q + a = Q + × C a / (C a + C b + C c) Q + b = Q + × C b / (C a + C _b + _Cc ) Q _{+ c} = Q ₊ * _Cc / ( _Ca + _Cb + _Cc ) The signal charge amount that can be taken out of the detector 20 is equal to the positive charge distributed to the capacitors C _{* a} and C _{* c} . Q _{+ a} , Q _{+ c}
(Q _{+ a} + Q _{+ c} ), and the positive charges distributed to the capacitor C _{* b} cannot be taken out as signal charges (for details, refer to Japanese Patent Application No. 11-87922).

Here, the stripe electrode 26 and the sub electrode
Capacitor C with pole 27_{* b}, C_{* c}Think about the capacity of
The capacity ratio C_b: C_cRepresents each element 26a,
27a width ratio W_b: W_cBecomes On the other hand, the capacitor C
_{* a}Capacity C_aAnd capacitor C _{* b}Capacity C_bIs the sub electrode
Even if 27 is provided, substantially no significant effect appears.

As a result, during charge rearrangement at the time of reading, the amount of positive charge Q _{+ b} distributed to the capacitor C _{* b} can be made relatively smaller than when the sub-electrode 27 is not provided. By that amount, the detector 20 is connected via the sub-electrode 27.
The amount of signal charges that can be extracted from the sub-electrode 27 can be made relatively large as compared with the case where the sub-electrode 27 is not provided, so that reading efficiency and S / N of an image can be improved.

Further, the width W _b of the element 26a, the transmittance P _b with respect to the reading light L2 of the elements 26a, the width W _c of the elements 27a, the transmittance P _c for reading light L2 of the element 27a is, the conditional expression (1 ) Is satisfied, the amount of signal charge that can be taken out can be reliably increased, and reading efficiency and S / N of an image can be reliably improved.

In order to extract more signal charges, the capacitance ratio between the capacitors C _{* b} and C _{* c} is defined by the width ratio between the elements 26a and 27a forming the electrodes.
Width W _b of the element 26a of the width W _c of the elements 27a
It is better to make it as wide as possible. At this time, each of the elements 26a and 27a is set so as to satisfy the conditional expression (1).
transmittance P _b with respect to the reading light L2 in a, set the P _c.

When the charge remaining in the detector 20 is to be erased, it is preferable that the sub-electrode 27 also be transparent to the reading light L2, but even in this case, the above conditional expression is satisfied. By doing so, the residual charges can be erased without deteriorating the reading efficiency or the S / N of the image.

The stripe electrode 26 and the sub electrode 27
Since the insulating layer 28 having an appropriate thickness is provided between them, there is less possibility that both elements 26a and 27a are short-circuited, and the reading efficiency is reliably improved over the entire surface of the detector 20. The problem that a streak-like noise appears in an image due to a short circuit does not occur.

Further, the insulating layer 28 may be formed to have an appropriate thickness such that the two elements 26a and 27a are not short-circuited, so that the distance between the two elements 26a and 27a can be kept small to some extent. The same reading efficiency as in the case where the two elements 26a and 27a are alternately arranged in the layer 25 can be maintained.

Note that the structure in which the sub-electrode 27 is provided outside the insulating layer 28 has an additional effect of eliminating problems such as erasure of an electrostatic latent image due to charge injection from the sub-electrode 27. You can also get.

Although the preferred embodiment of the image detector according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes can be made without changing the gist of the invention. It is possible.

For example, the basic image detector to which the present invention is applied is not limited to the solid-state radiation detector serving as the above-described image detector, but includes a first electrode layer having transparency with respect to reading light, and a reading light. , A recording photoconductive layer that exhibits electrical conductivity when irradiated with reading light, a reading photoconductive layer that exhibits electrical conductivity when irradiated with reading light, and a plurality of linear shapes that are transparent to the reading light. Any structure may be used as long as the structure has a second electrode layer in which electrodes are arranged in a stripe shape in this order. For example, the present invention is applicable to an image detector (radiation solid state detector) proposed by the present applicant in Japanese Patent Application No. 11-87922.

In the image detector according to the above-described embodiment, the recording photoconductive layer exhibits conductivity when irradiated with recording radiation. The recording photoconductive layer of the image detector according to the present invention is used. Is not necessarily limited to this, and the recording photoconductive layer may exhibit conductivity by irradiation with light emitted by exciting recording radiation (see Japanese Patent Application No. 10-271374). In this case, a wavelength conversion layer called a so-called X-ray scintillator that converts the radiation for recording into light of another wavelength region, such as blue light, may be laminated on the surface of the first electrode layer. As the wavelength conversion layer, for example, cesium iodide (CsI) or the like is preferably used. Also, the first
The electrode layer is permeable to light emitted from the wavelength conversion layer by excitation of recording radiation.

Further, a recording photoconductive layer which exhibits conductivity by irradiating visible light carrying image information without laminating the wavelength conversion layer may be provided.

Further, the image detector 2 according to the above embodiment is used.
0, a charge transport layer is provided between the recording photoconductive layer and the read photoconductive layer, and a power storage unit is formed at the interface between the recording photoconductive layer and the charge transport layer. The charge transport layer may be replaced with a trap layer. When a trap layer is used, the latent image charges are captured by the trap layer, and the latent image charges are accumulated in the trap layer or at the interface between the trap layer and the recording photoconductive layer. Further, a microplate may be particularly provided for each pixel at the interface between the trap layer and the recording photoconductive layer. Further, a microplate may be provided at the interface between the recording photoconductive layer and the reading photoconductive layer without providing the charge transport layer or the trap layer.

[Brief description of the drawings]

FIG. 1 is a perspective view of a solid-state radiation detector according to an embodiment of the present invention (A), an XZ sectional view of a Q arrow finger part (B), and an XY sectional view of a P arrow finger part (C).

FIG. 2A is a diagram for explaining the arrangement relationship of elements.
(B)

[Explanation of symbols]

 Reference Signs List 20 solid-state radiation detector (image detector) 21 first electrode layer 22 photoconductive layer for recording 23 charge transport layer 24 photoconductive layer for reading 25 second electrode layer 26 stripe electrode 26a element (linear electrode) 27 sub-electrode 27a Element (sub-linear electrode) 28 Insulating layer 29 Power storage unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // G21K 4/00 H01L 31/00 A

Claims (2)

[Claims] A first electrode layer having a transmitting property with respect to a recording light carrying image information; a recording photoconductive layer exhibiting conductivity by being irradiated with the recording light; A reading photoconductive layer exhibiting conductivity by receiving, and a second electrode layer in which a large number of linear electrodes having transparency to the reading light are arranged in a stripe shape, in this order, In an optical reading type image detector in which a power storage unit is formed between the recording photoconductive layer and the reading photoconductive layer, the photodetector has transparency to the reading light outside the second electrode layer. An insulating layer is laminated, and a number of sub-linear electrodes for outputting an electric signal at a level corresponding to the amount of latent image charges stored in the power storage unit are provided outside the insulating layer. Are arranged in stripes so as to be located between each other Image detector, wherein the door. 2. The method according to claim 1, wherein the insulating layer is made of SiO ₂ , SiC, S
The image detector according to claim 1, wherein the image detector is made of any one of iN.