JPH08184937A - Production of stimulable phosphor plate - Google Patents

Abstract

PURPOSE: To provide a process for producing a stimulable phosphor (accumulable phosphor) of a cell structural body having an excellent function in a process for producing the stimulable phosphor to be used as a radiation sensor for obtaining a radiation digital image. CONSTITUTION: Many through-holes (cells) are formed in the respective positions corresponding to each other of plural sheets of metallic sheets. The reflectivity of light of the inside walls of the through-holes of these metallic sheets is improved. Plural sheets of the metallic sheets are superposed on each other in such a manner that the through-holes formed in the positions corresponding to each other communicate with each other. A protective sheet closing the one-side openings of the through-holes of the laminated metallic sheets is adhered to one surface of the laminated metallic sheet and the stimulable phosphors are filled into the cells. A light transparent sheet to allow the passage of the light is adhered to another one surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a photostimulable phosphor (storable phosphor) plate used as a radiation sensor for obtaining a digital radiation image.

[0002]

2. Description of the Related Art In recent years, a radiographic image is recorded on an X-ray film or the like, and the film on which the radiographic image is recorded is used as it is for observing, diagnosing, etc.
A sheet or panel-shaped photostimulable phosphor plate (including a panel and a sheet) is irradiated with radiation that has passed through an object to accumulate and record a radiographic image on the photostimulable phosphor plate. 2. Description of the Related Art A system has been used in which an image signal is read by reading, an image signal is subjected to appropriate image processing, and then a reproduced image is obtained. The basic method of the system using this stimulable phosphor plate is described in detail in US Pat. No. 3,859,527. Here, the stimulable phosphor means that, when irradiated with radiation such as X-rays, α-rays, β-rays, and γ-rays, a part of the energy of the radiation is accumulated inside for a while, and infrared light, visible light Light, a phosphor that emits accumulated energy as stimulated emission light when irradiated with excitation light such as ultraviolet light. Depending on the type of the phosphor, the type of radiation that easily accumulates energy and the stimulated emission light The wavelength of the excitation light that is easily emitted, the wavelength of the emitted stimulated emission light, and the like are different.

In the system using this stimulable phosphor plate, the energy of the radiation applied to this stimulable phosphor plate and the amount of the stimulated emission light emitted by the irradiation of excitation light over a wide energy range. Is proportional to
Also, this ratio can be changed by the amount of excitation light,
Therefore, it is possible to obtain a radiation image that is not affected by variations in radiation exposure. Further, in a system for obtaining an X-ray image of a human body, it is possible to reduce the exposure dose of the human body in X-ray photography.

FIG. 1 is a diagram showing an example of the configuration of a system using a photostimulable phosphor plate. FIG. 1 shows a standing type imaging device 2
6 is shown, and X is displayed on the subject 12 standing in front of the photographing unit.
The X-rays 13 generated by the line generator 11 are irradiated, the X-rays 13 transmitted through the subject 12 are irradiated on the photostimulable phosphor plate 15, and the X-ray image of the subject is accumulated on the photostimulable phosphor plate 15. Will be recorded.

After the photographing is performed in this manner, the photostimulable phosphor plate 15 is conveyed to the reading section 19 along the conveying path 18 and is read. That is, in the reading unit 19, the conveyed photostimulable phosphor plate is scanned by the excitation light beam, and the stimulated emission light emitted from the photostimulable phosphor plate 15 is photoelectrically received by this scanning, and an image signal is obtained. Is generated. The image signal generated by the reading unit 19 is input to the image processing unit 23 via the signal transmission path 22, the image processing unit 23 performs appropriate image processing such as frequency enhancement processing, and further the signal transmission. The image is input to the image display unit 25 via the path 24, and the X-ray image of the subject 12 is displayed on the CRT display screen, for example. An image recording device such as a laser printer (not shown) is provided instead of or together with the image display unit 25 for displaying an image, and an X-ray image is reproduced and recorded on a silver salt film, for example. You may make it obtain the X-ray image as a visible image by developing.

The photostimulable phosphor plate 15 read by the reading unit 19 is conveyed to the erasing unit 20 along the conveying path 18. In the erasing section 20, the stimulable phosphor plate 15 is irradiated with erasing light, so that the energy (remaining image) remaining in the stimulable phosphor plate 15 is erased. The photostimulable phosphor plate 15 from which the afterimage has been erased is further transported, placed again in the imaging section, and reused for the next imaging.

FIG. 2 is a diagram showing an example of the configuration of another system using a photostimulable phosphor plate. In this figure, the components corresponding to the components of the system shown in FIG.
The same numbers as those shown in FIG. 1 are given and shown, and only different points will be described. In the system shown in FIG. 2, the photostimulable phosphor plate 15 is fixed, and the reading unit 19 and the erasing unit 20 are provided.
However, it is configured to move up and down along the back surface side of the stimulated phosphor plate 15 when the X-ray irradiation side is the front surface for reading and erasing.

In the radiation imaging system as described above, stimulable phosphors having various compositions can be used. As a typical example thereof, europium-activated barium chloride bromide (BaClBr: Eu) is used. be able to. In addition to this, for example, Li, Na, K, Rb,
Group IA alkali metals such as Cs and Fr, and Be, Mg, C
a, Sr, Ba, Ra and other alkaline earth metals, and F, C
A compound of a halogen element such as l, Br, or I or a chalcogen element such as O, S, or Se is used as a base, and La or C
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
A phosphor containing a lanthanide element such as y, Ho, Er, Tm, Yb, or Lu, a transition metal element such as Mo, or an emission center such as Tl or Bi can also be used.

In order to use this stimulable phosphor as a radiation sensor, a stimulable phosphor plate formed into a sheet or panel as described above is used. To manufacture this stimulable phosphor plate, Generally, a photostimulable phosphor layer is formed on a substrate by mixing a photostimulable phosphor powder with an organic solvent, a resin or the like, coating the mixture on the substrate, and curing the mixture. However, if the photostimulable phosphor layer is formed to have a large film thickness, the sensitivity to radiation increases, but the spatial resolution decreases. On the other hand, if the film thickness is reduced to improve the spatial resolution, the sensitivity decreases. . The cause is that, as shown in FIG. 3 (A), excitation light and stimulated emission light generated by irradiation of the excitation light are largely scattered in the stimulated phosphor layer. Therefore, suppressing this scattering or keeping this scattering locally is effective in improving both sensitivity and spatial resolution.

Various measures have been taken to keep the scattering local, but as one of them, it is proposed to form a minute hole (cell) on the substrate and embed the stimulable phosphor in the cell. Has been done. In that case, the excitation light applied to the cell and the stimulated emission light emitted in the cell stop on the wall surface of the cell as shown in FIG. Guaranteed by the value determined by the cell diameter and cell arrangement. Further, since the scattering is stopped, the thickness of the photostimulable phosphor plate may be increased, so that it is easy to increase the sensitivity to some extent. As described above, since the cell structure stimulated phosphor plate can be an ideal radiation sensor, some proposals regarding its shape and the like have been made, but not realized. For example, in the method of embedding a phosphor in a glass cell structure (micro channel plate), it is technically difficult and costly to make a large area, for example, a half-cut size (about 14 inches × 17 inches). Is. Further, the method of forming cells in gelatin by lithography (etching) does not withstand use in terms of strength and life even if a cell structure is formed.

The most practical method is disclosed in JP-A-59-202100 in which cell production is applied to a stimulated phosphor, or JP-A-60-171500 in which a phosphor plate for a silver salt film is applied. Japanese Patent Laid-Open No. 60-1735
JP-A-00-00 (since the contents of these three publications are almost the same, Japanese Patent Laid-Open No. 59-
This is one of several methods described in Japanese Patent Publication No. 202100 (hereinafter, this may be simply referred to as "publication"), and its outline will be described below.

The nickel plate 51 is etched to produce a substrate as shown in FIG. According to the above publication, the cell size of this substrate was d = 120 μm and h = 190 μm, and the partition wall thickness was w = 35 μm at the minimum. Next, the stimulable phosphor and the binder are mixed and dispersed using a solvent to prepare a coating solution, which is uniformly coated on the substrate, filled in each cell, and dried to produce a stimulable phosphor plate. Is to do.

The above is one mode relating to the production of the cell structure phosphor plate described in the publication. As a result of additional tests by the present inventor, the cell structure board is produced according to the above publication for several reasons. could not. The biggest technical difficulty in the additional test is that the cell structure having the shape as described cannot be obtained because the cell diameter d and the cell pitch p = d + w are smaller than the cell depth, that is, the plate thickness h. That is.
In the case of etching from both sides of a thin metal plate as described in the official gazette, in the usual etching technique, the cell diameter d is 1.6 times or more of h and uniform etching is desired, although it depends on the plate thickness h. In this case, it is required to be 2.0 times or more, and below that, the cells may not penetrate, or cells may stick at the same time as the cells penetrate, and in some cases the entire cell may fall out. In order to avoid these defects, the cell pitch p must be increased, resulting in a cell having a large size, which lowers the spatial resolution. For example, when h = 190 μm described in the publication, d
≧ 304 μm, or d ≧ 380 μm in order to obtain stable etching. Therefore, the cell pitch p becomes 420 μm or more, and the spatial resolution decreases. The required spatial resolution is limited to a width of 14 inches (about 356 mm) with a size of one pixel that is a large-angle size or half-cut size used for chest and abdominal imaging.
It is considered to be a value when divided into four pixels, that is, about 350 μm. For breast, a cell size of 40 μm or less is required because a resolution of 40 μm is required.
For example, it is necessary to make it 10 μm or 20 μm.

On the contrary, d = 120 μm, p described in the publication
= 155 μm, h cannot be created unless it is 75 μm or less. As a result, usually 150 to 400 μm
The thickness is too thin as compared with the conventional photostimulable phosphor plate made to have a layer thickness, the absolute amount of the photostimulable phosphor is small, and the sensitivity is remarkably lowered. Therefore, the function of the stimulated phosphor plate cannot be fulfilled.

Therefore, the inventors of the present invention have formed a cell structure having a small pitch as compared with the plate thickness, which is formed by opening a large number of through holes (cells) in a plurality of thin metal sheets and stacking the plurality of metal sheets. Proposed body (JP-A-2-129)
See Japanese Patent Publication No. 600). However, how to actually manufacture such a laminated substrate, and how to prepare a photostimulable phosphor plate as a radiation sensor using such a laminated substrate. Is a problem.

In view of the above circumstances, it is an object of the present invention to provide a method for producing a photostimulated phosphor plate capable of producing a photostimulated phosphor plate having a cell structure having an excellent function.

[0017]

The method for manufacturing a stimulable phosphor plate of the present invention which achieves the above object is as follows: (1) Through holes for forming a large number of through holes at positions corresponding to each other on a plurality of metal sheets. Forming step (2) A reflectance improving step for improving the reflectance of light on the inner wall of the through hole of the metal sheet (3) A metal sheet on which metal sheets are overlaid so that the through holes formed at corresponding positions communicate with each other Sheet laminating step (4) Protective sheet adhering step of adhering a protective sheet closing one opening of the through hole of the laminated metal sheet to one surface of the laminated metal sheet (5) Laminating with a protective sheet adhered The stimulable phosphor filling step of filling the stimulable phosphor into the through-holes of the formed metal sheet. (6) Opposite to the one side of the laminated metal sheet in which the stimulable phosphor is filled into the through-holes. The other on the side On the surface,
A light-transmitting sheet bonding step of bonding a light-transmitting sheet that transmits light is provided.

Here, in the method for producing a photostimulable phosphor plate of the present invention, the peripheral portion of the metal sheet having the improved reflectance of light on the inner wall of the through hole in the reflectance improving step (7) is cut and removed. It is preferable to include a frame cutting step. Further, in the method for producing a stimulated phosphor plate of the present invention, the protective sheet and the light transmissive sheet are sheets having an area larger than the area of the laminated metal sheets, and the protective sheet according to (4) above. The step of adhering and the step (6) of adhering a light-transmissive sheet, which adheres the protective sheet and the light-transmissive sheet to the metal sheet such that the peripheral edges of the protective sheet and the light-transmissive sheet protrude from the peripheral edge of the metal sheet, respectively. In addition, (8) between the peripheral portion of the protective sheet and the spacer, with the spacer sandwiched between the peripheral portions of the protective sheet and the light-transmissive sheet that protrude from the metal sheet, And a photostimulable phosphor sealing step of sealing the photostimulable phosphor filled in the through holes of the metal sheet by adhering the spacer and the light transmissive sheet. It is also preferable to obtain.

In the method for producing a photostimulable phosphor plate of the present invention, the metal sheet has a thickness of 10 μm or more and 150 μm or more.
m or less, and the metal sheet is used for the positioning of the through hole formation in the through hole formation step of (1) and the superposition of the metal sheets in the metal sheet laminating step of (3) above. It is preferable to have a positioning hole for positioning.

In the method for producing a stimulable phosphor plate of the present invention, it is preferable that the through hole forming step (1) is a step of forming through holes by etching. Further, in the through hole forming step (1) above, at least for the metal sheet laminated on the first layer on the light transmissive sheet side,
It is preferable to form the through holes so that the surface of the partition wall between the through holes adjacent to each other of the metal sheet on the light transmitting sheet side is formed in a substantially semicircular cross-sectional shape.

Further, in the method for producing a stimulated phosphor plate of the present invention, the step (2) of improving reflectance is electrolytic polishing,
It is preferable that the process is to improve the light reflectance of the inner wall of the through hole by using at least one method selected from the group consisting of chemical polishing, electroless plating, and electrolytic plating. Further, among them, it is particularly preferable that the reflectance improving step (2) is a step of improving the reflectance of light on the inner wall of the through hole by using electrolytic polishing or chemical polishing.
In that case, the reflectance improving step of (2) above is further performed.
The above-mentioned metal sheet is used as one electrode plate, and the other electrode plate is arranged in parallel with the metal sheet. Further, between the two electrode plates, the central portion is larger, and the central portion is larger than the peripheral portion. It is preferable that a current control plate in which holes having smaller diameters are formed is arranged as it goes, and electrolytic polishing is performed. Further, when the reflectance improving step (2) is a step of improving the reflectance of light on the inner wall of the through hole by using electrolytic polishing or chemical polishing,
It is preferable that the step of performing electrolytic polishing is such that the amount of polishing is within a range in which the partition walls remain between the through holes that are 1.5 μm or more and are adjacent to each other.

Further, the reflectance improving step (2) is
In the step of improving the reflectance of light on the inner wall of the through hole by setting the thickness of the partition wall between the through holes adjacent to each other to be 20% or less of the pitch of the through holes after the completion of the reflectance improving step. Preferably there is. Further, regarding the metal sheet laminating step of (3) above, the metal sheet laminating step is
It is preferable that the metal sheet is a step of stacking the adhesive sheet on the peripheral portion with the adhesive sheet sandwiched therebetween.

Further, in the step (4) of adhering the protective sheet, the protective sheet is a metal sheet having at least one surface polished or plated, and the step of adhering the protective sheet includes polishing or plating the metal sheet. The step of adhering the metal sheet as a protective sheet to the laminated metal sheet with the surface of the laminated side facing the laminated metal sheet side is preferable. Alternatively, the protective sheet is a resin or glass sheet having a light-reflecting film formed on one surface, and the protective sheet bonding step (4) is performed on the side of the protective sheet on which the light-reflecting film is formed. The step of adhering the protective sheet to the laminated metal sheets may be performed with the surface thereof facing the laminated metal sheets.

Further, in the method for producing a stimulable phosphor plate of the present invention, in the stimulable phosphor filling step (5), the resin is placed in the through holes of the laminated metal sheets to which the protective sheet is adhered. One of the preferred embodiments is a step of filling the stimulated phosphor powder in which the powder is mixed, spraying an organic solvent on the filled stimulated phosphor powder, and volatilizing the organic solvent. In that case, the amount of the resin powder mixed with the stimulable phosphor powder is 0.5% by volume or more with respect to the stimulable phosphor powder.
It is preferably 0% by volume or less, and the resin powder mixed with the stimulable phosphor is preferably a powder of polymethylmethacrylate having a particle size distribution peak of 5 μm or less. Further, it is preferable that the stimulable phosphor powder filled in the through holes is a mixture of white inorganic powder having a particle size distribution peak of 0.2 μm or less. The white inorganic powder to be mixed with the stimulable phosphor powder is preferably one or more kinds of powder selected from the group consisting of silicon oxide, calcium carbonate and titanium oxide.

Further, in the method for producing a stimulable phosphor plate of the present invention, the stimulable phosphor filling step (5) above is performed by applying a resin to an organic solvent on a laminated metal sheet to which a protective sheet is adhered. Is filled with the stimulable phosphor powder by coating a solution of the stimulable phosphor mixed with the resin solution, and the air in the through-hole is replaced by the resin solution by depressurizing the organic solvent. It is also one of the preferable embodiments to be a step of volatilizing.

In the present invention, the "sheet" typically refers to a thin plate or the like having a certain degree of flexibility, but is not limited to such a flexible plate, and is not flexible or It is a concept that includes a panel or plate having poor flexibility.

[0027]

The present invention is provided with the steps (1) to (6) described above, and in particular, since metal sheets are laminated on each other, the photocatalyst having a cell (through hole) structure of a necessary fine pitch is provided. A phosphor plate is manufactured. In addition, the present invention has the reflectance improving step (2) described above, so that excitation light can be sent to the back of the cell, and stimulated emission light in the cell can be efficiently emitted. Thus, according to the present invention,
A stimulated phosphor plate having a cell structure having an excellent function is manufactured.

By the way, depending on the through hole forming step (1) and the reflectance improving step (2), the thickness of the metal sheet may be changed through the steps. For example, when electrolytic polishing is performed in the reflectance improving step, the diameter of the through hole is expanded and the thickness of the metal sheet is reduced by electrolytic polishing. However, in electropolishing, the electrode is attached to the peripheral edge of the metal sheet, the portion to which the electrode is attached is not polished, and after electropolishing, the electropolished central portion of the metal sheet and the peripheral edge to which the electrode is attached are The thickness will be different. Therefore, when a plurality of such metal sheets are stacked, a gap is created between the metal sheets.

Therefore, in the present invention, if the frame cutting step (7) is provided, even if there is a step of changing the thickness between the central portion and the peripheral portion as described above, the metal sheets are overlapped with each other without a gap. be able to. Further, some of the stimulable phosphors have hygroscopicity. In the present invention, the photostimulable phosphor is filled in the cell, the opening of the cell is closed by the protective sheet and the light-transmissive sheet, and the inside of the cell is temporarily sealed. When the photostimulable phosphor sealing step is provided, the photostimulable phosphor is further surely sealed, and moisture absorption and the like are further reliably prevented.

The metal sheet used in the present invention is
It is preferably 10 μm or more and 150 μm or less. 1
50 μm is a constraint that comes from the cell diameter and cell pitch,
If this thickness is exceeded, it is difficult to form a cell structure having a small diameter and a fine pitch, which is necessary for a radiation sensor. On the other hand, if the thickness is 10 μm or less, the sheet is too thin to be handled, and the number of metal sheets when stacking to a required thickness is too large. Errors such as alignment increase and the lamination process is difficult.

Further, when the metal sheet used in the present invention has the above-mentioned positioning holes, the positioning of the through holes when forming the through holes and the positioning when the metal sheets are superposed are facilitated. Further, in the present invention, when the through hole forming step (1) is to form the through holes by etching, the through holes having high positional accuracy and dimensional accuracy are formed in the metal sheet. Further, this through-hole forming step, the surface of the partition wall of the metal sheet laminated on the first layer on the light-transmissive sheet side, on the light-transmissive sheet side,
When the through hole is formed so as to have a substantially semicircular cross-sectional shape, the apparent opening of each cell spreads and the reflection of excitation light on the partition wall surface decreases, and the excitation light efficiently enters the cell. As a result, it is possible to improve the luminous efficiency and reduce the variation in the emitted light amount depending on the location.

In the reflectance improving step of the present invention, as described above, at least one selected from electrolytic polishing, chemical polishing, electroless plating, and electrolytic plating.
Two methods can be adopted, and in each case, the inside of the cell can be made light-reflecting. In the case of electroless plating or electrolytic plating, there is an advantage that the cell inner wall can be made light-reflective with inexpensive equipment, but the plating reduces the cell diameter. In the case of electropolishing and chemical polishing, the cell diameter is widened in order to make the inside of the cell light-reflective, and therefore improvement in sensitivity is expected to be more than improvement in sensitivity due to improvement in light-reflecting property.

When electropolishing is performed, by disposing the above-mentioned current control plate between the electrode plates, uniform electropolishing can be performed irrespective of the cell position of the metal sheet. 1.5 μm for electrolytic or chemical polishing
In the following electrolytic polishing or chemical polishing, the reflectance increases as the polishing progresses, and the reflectance is almost saturated at 1.5 μm. Therefore, in order to improve the reflectance as much as possible, 1.5
It is preferable to perform polishing to a size of μm or more. On the other hand, if the polishing progresses too much, the partition walls between the cells will collapse and connect to the adjacent cell, in which case fluorescence or excitation light in one cell will enter into the adjacent cell, and the spatial resolution will decrease. Become. Therefore, the upper limit of polishing is the range in which the partition walls remain between the cells. Further, although it may be entangled with the above-mentioned through hole forming step (1), the cell diameter is too small compared to the cell pitch, and the partition wall after the reflectance improving step has a thickness of 20% or more of the cell pitch. In this case, the aperture ratio is too small, the ratio of excitation light entering the cell is reduced, and the luminous efficiency is reduced, which is not preferable. Therefore, the thickness of the partition wall after the reflectance improving step is preferably 20% or less of the cell pitch.

In addition, in the metal sheet laminating step, if a plurality of metal sheets are laminated without any positional deviation, they need not be adhered to each other, but they are lightly adhered so as not to cause positional deviation in the subsequent steps. Is preferred. In the case of adhering, any adhering method may be adopted as long as it does not adversely affect the stimulated phosphor and the like, but, for example, as described above, in a state where the adhesive sheet is sandwiched in the peripheral portion of the metal sheet. It is possible to employ a method in which they are stacked and pressurized and heated.

The cell-side surface of the protective sheet forms the bottom surface of each cell. The inside of the cell is preferably as light-reflecting as possible. Therefore, it is preferable that the bottom surface thereof, that is, the cell-side surface of the protective sheet is also light-reflecting. Therefore, the protective sheet is a metal sheet having at least one side polished or plated, and the surface of the polished or plated side of the metal sheet faces the laminated metal sheet side. When a metal sheet as a protective sheet is adhered, or when the protective sheet is a resin or glass sheet having a light reflecting film formed on one surface, the side of the protective sheet on which the light reflecting film is formed When the protective sheet is adhered to the laminated metal sheet with the surface thereof facing the laminated metal sheet side, the reflectance as a whole in the cell is further increased in any case.

In the photostimulable phosphor filling step (5), the photostimulable phosphor powder mixed with the resin powder is filled in the through holes of the laminated metal sheets to which the protective sheet is adhered, Disperse an organic solvent on the filled phosphor powder,
In the case of the step of volatilizing the organic solvent, the photostimulable phosphor powder is easily filled in the cell, and the sensitivity is improved. In this case, the amount of the resin mixed with the stimulable phosphor powder is preferably 0.5% by volume or more and 10% by volume or less. 0.5
If it is less than 10% by volume, the amount of the resin is too small and it becomes difficult for the stimulable phosphor powders to be fixed to each other by the resin. On the other hand, if it exceeds 10% by volume, the filling rate of the stimulable phosphor is lowered and the sensitivity is lowered. is there.

Polymethylmethacrylate (MMA) is preferable as the resin mixed with the photostimulable phosphor, and the peak of the particle size distribution is preferably 5 μm or less. If it exceeds 5 μm, the MMA powder prevents dense filling of the stimulable phosphor powder, and the filling rate of the stimulable phosphor powder is reduced. When a white inorganic powder having a particle size distribution peak of 0.2 μm or less is mixed with the stimulable phosphor powder, the fluidity of the stimulable phosphor powder having a relatively large diameter is caused by the white inorganic powder having such a small diameter. It is improved and the filling of the stimulated phosphor powder becomes easier. The request that the inorganic powder is white is to prevent absorption of light in the cell, and the limitation of 0.2 μm or less is poor in improving the fluidity of the stimulated phosphor powder when the diameter exceeds this, Further, it is because the filling rate of the photostimulable phosphor powder is lowered unless the size is such that the photostimulable phosphor powder is allowed to enter the gap between the powders.

As the white inorganic powder which can be used for the above purpose, as mentioned above, there may be mentioned silicon oxide, calcium carbonate, titanium oxide, etc. Among them, silicon oxide is preferable. The step (5) of filling the stimulated phosphor is
The protective phosphor is adhered to the through holes of the laminated metal sheets, and the photostimulable phosphor powder mixed with a resin solution in which a resin is dissolved in an organic solvent is applied to the through holes to form the photostimulable phosphor in the through holes. It may be a step of filling the powder and replacing the air in the through-holes with the resin liquid by depressurizing, and volatilizing the organic solvent. In the case of a paint-type stimulated phosphor, by adopting this method, the stimulated phosphor can be densely packed in the cell.

[0039]

Embodiments of the present invention will be described below. FIG. 5 is a process diagram showing an embodiment of the method for producing a stimulated phosphor plate of the present invention, and FIG. 6 is a photostimulated fluorescence produced by an embodiment of the method for producing a stimulated phosphor plate of the present invention. It is the top view (A) which shows the structure of a body board, and sectional drawing (B) along arrow XX shown in FIG. 6 (A). However, in FIG. 6, the size of the cell is greatly enlarged for convenience of illustration.

(Cell Arrangement Structure) Here, prior to the explanation of the process chart of FIG. 5, the cell arrangement structure which has a great influence on both the reading sensitivity and the spatial resolution will be described. The advantage of the cell structure stimulated phosphor plate is that it can guarantee the inter-resolution. However, the presence of cells necessarily results in the presence of partition walls. Radiation that is applied to the partition wall and absorbed or transmitted does not contribute to the signal output at all. Further, the excitation light (laser light) applied to the wall portion does not contribute at all if it is absorbed or reflected by the partition wall surface. Further, since the photostimulable phosphor does not exist in the partition wall portion, the amount of photostimulable fluorescent light emitted is correspondingly reduced, resulting in a decrease in sensitivity. Therefore, it is preferable to make the surface areas of the front and back of the partition wall as small as possible. In conclusion, the cell arrangement that minimizes the surface area of partition walls is honeycomb. Japanese Unexamined Patent Publication No. 59-202100 discloses a matrix type cell structure as shown in FIG. 7 (A) in detail. FIG. 7 described in Japanese Patent No. 202100.
The finely arranged structure of circles as shown in (B), that is, the honeycomb structure is the best.

Originally, even if the structure is not a honeycomb structure, it is disclosed in
A matrix-type structure should be used if the square cells described in Japanese Patent Publication No. 9-202100 are made and the walls can be made thin. However, it was not possible in the additional test by the inventors. Even if the cell mask pattern is square, the cell pitch and cell size, and the plate thickness are 100
When the value is around μm, the cell shape after etching becomes a circle instead of a square. If you try to force it into a square, the partition between adjacent cells will be lost. As a result, when d = 120 μm and p = 155 μm, the cell volume ratio is reduced to about 47% as compared with the uniform coating type which is not the cell type. On the other hand, when the honeycomb cell structure is used, the volume ratio of the cells can be reduced to about 85%.

Regarding the spatial resolution, the honeycomb cell structure gives a spatial resolution of up to 50% of the pitch, depending on the diameter of the excitation light beam. On the other hand, the matrix structure guarantees only a spatial resolution equivalent to the pitch. (Material of Honeycomb Cell Structure) In this example, first, 1
The process of forming cells with thin walls as much as possible on a thin sheet is performed. As a result, the mechanical strength of the portion where a large number of cells are opened (hereinafter referred to as “cell region”) is significantly reduced. Therefore, as a material for the honeycomb cell structure, a thin but strong stainless sheet is preferable. Especially, the plate thickness is 30μ
m, 50 μm, and 100 μm stainless sheets are mass-produced products, and the prices are low, so they are easy to use. Other plate thicknesses can also be custom made or polished by means such as electrolytic polishing.

(Etching) Stainless sheet (SUS
304), a cell diameter of 160% or more of the cell depth (plate thickness) h can be obtained by double-sided etching. When a cell having a cell pitch as small as possible and a cell diameter as large as possible is formed on a stainless steel sheet by etching, the cell diameter on the back side becomes very small in single-sided etching, so double-sided etching is performed. Since the stainless steel sheet is opaque, it is easy to shift the position of the center of the cell when patterning the resist applied on both sides.Therefore, even if the center of the cell is slightly shifted by slightly changing the size of the cell pattern on the front and back sides (Cell) to be formed. As a result, the cell diameters on the front and back sides are slightly different, though not as much as in single-sided etching.

When the cell diameters on the front and back sides are different, the stimulated fluorescent light or the excited light from the stimulated phosphor powder filled in the cells of the stimulated phosphor plate in which a plurality of cell-structured stainless sheets are stacked has the same cell diameter. The performance inconvenience that it reflects at different parts, and when plating explained later, the plating thickness on the front and back partition walls will be different, causing distortion, and the stainless sheet will be distorted and alignment will be This causes a manufacturing inconvenience that it becomes difficult.

Therefore, the cell diameters on the front and back sides are made as equal as possible by a method such as overetching only the surface on the side of the small cell diameter. In the resist patterning of the honeycomb cell structure, the cell shape was hexagonal. The shape of the cell after etching is almost a circle, but the penetration is slightly better than in the case where a circular pattern is used, and a large cell can be made.

(Electrolytic polishing) A honeycomb cell structure can be formed by double-sided etching of a stainless steel sheet, but the surface of partition walls inside the cell becomes a satin finish as a result of etching, and the light reflectivity is very poor. The low reflectance of the partition walls inside the cell means that the photostimulable phosphor powder filled in the cells is absorbed by the partition walls when it emits light, and the amount of light emitted to the cell surface decreases. In particular, an ordinary stimulable phosphor plate shows a strong light scattering property, and even if the air between the stimulable phosphor powders is covered with a transparent resin or the like, it is not completely transparent, and some light scattering property is exhibited. Show. Due to such strong light scattering properties, the emitted light collides with the partition walls many times, and the amount of emitted light emitted from the cell is only from the very surface inside the cell, depending on the depth of the cell. It is estimated that only 1/5 to 1/100 of the total amount of emitted light comes out of the cell. Therefore, JP-A-59-20
As described in Japanese Patent No. 2100, "The excitation light absorption layer or the excitation light reflection layer may be formed on the inner wall of the chamber by a method such as coating or vapor deposition." It is necessary to improve the light reflectance. However, in the vapor phase growth method such as vapor deposition, it is necessary to install the stainless sheet at an angle to form the light reflection layer on the partition walls inside the cell, and to perform it while rotating it. However, there is the inconvenience of requiring large-scale equipment such as a very large vapor deposition kettle.

The present inventor has tried several methods such as chemical polishing, ultrasonic polishing and electroless plating in order to improve the light reflectivity of the partition wall surface inside the cell, but no method has obtained excellent results. Electrolytic plating, electrolytic plating, chemical polishing, and electrolytic polishing. In particular, performing only chemical polishing or electrolytic polishing, or performing electroless plating after the polishing gives the best results with less distortion.

It has been found that not only the light reflectivity of the partition wall surface inside the cell is significantly improved but also the cell diameter is increased by performing electrolytic polishing with a phosphate-based liquid composition. However, since the thickness of the stainless steel sheet also becomes thin, it is necessary to select an electrolytic polishing amount in an appropriate range and perform uniform polishing over the entire surface. As for the equipment, a stainless sheet and a tank for the electrodes are enough.

The amount of electrolytic polishing is 1.5 μm, which is sufficient to improve the light reflectivity. In performing electrolytic polishing, as shown in FIG. 8 (A), the stainless sheet having the cell holes formed therein is used as a positive electrode, and another stainless sheet is prepared and arranged in parallel to serve as a negative electrode.
A plastic current control plate was placed between the stainless sheets. This current control plate is shown in FIG.
As shown in (B), large holes are formed in the central portion, and small holes are sparsely formed toward the peripheral portion.

If only two electrode plates (stainless steel sheets) are used, the current concentrates only on the peripheral portion, and the electrolytic polishing proceeds more strongly toward the peripheral portion. However, by arranging such a current control plate, the cell position can be improved. Uniform electrolytic polishing.
In electrolytic polishing, the peripheral edge of the stainless steel sheet is covered with the electrode frame, and therefore the peripheral edge is not polished. Therefore, it is necessary to form an effective cell region inside the peripheral edge.

FIG. 9 shows a stainless sheet having a cell structure,
It is explanatory drawing of the measuring method of reflectance. Light is emitted to one surface (front surface) of the stainless steel sheet from a direction inclined by about 10 ° with respect to the plane on which the stainless steel sheet spreads, and an optical sensor with a hood is arranged on the back surface of the stainless steel sheet. Only relative evaluation was made to reach the back side. Table 1 shows the evaluation results.

[0052]

[Table 1]

The reflectance after etching (before electrolytic polishing) is 1
When set to 00, the reflectance is improved to 150 when electrolytic polishing is performed by 1 μm (cell diameter is increased by 2 μm), and the reflectance is improved to 400 when electrolytic polishing is performed by 1.5 μm (cell diameter is increased by 3 μm). did. However, there was no noticeable increase in reflectance even if electrolytic polishing was further performed. (Chemical Polishing) In this example, each step described below was carried out for the electrolytically polished stainless steel sheet. Here, the result of the chemical polishing will be described.

Here, an austenitic stainless steel chemical polishing agent (Sanbit 50 manufactured by Sanshin Chemical Industry Co., Ltd.) is used.
7 ') after etching the stainless steel sheet (SU
S304) was chemically polished, and the reflectance was relatively evaluated in the same manner as described above (see FIG. 9). Table 2 shows the evaluation results.

[0055]

[Table 2]

As in the case of Table 1, assuming that the reflectance after etching (before electrolytic polishing) is 100, the reflectance is 20 when chemical polishing is performed by 1 μm (cell diameter increase is 2 μm).
0, chemical polishing 1.5μm (cell diameter increase is 3
μm), the reflectance improved to 450. Even after chemical polishing was performed at 2.5 μm (increase in cell diameter was 5 μm), the reflectance remained 450.

(Electrolytic Plating) Although the light reflectivity of the partition wall surface inside the cell could be improved by electrolytic polishing (or chemical polishing), metal plating may be further performed to further improve the light reflectivity. There are many kinds of metals to be plated. For example, gold or copper plating has a light reflectivity of 400 nm which is the wavelength of stimulated fluorescent light, although light of laser wavelength 600 nm to 800 nm which is excitation light is well reflected. It can't be used because it absorbs much light in the vicinity. Aluminum has drawbacks such as difficulty in plating. After all, silver or nickel plating is preferable from the viewpoint of light reflectivity, and electrolytic nickel plating or electroless nickel plating may be optimal considering the change over time. Do you get it. Direct plating on stainless steel is difficult, and 0.1
Strike nickel plating of about μm is preferably applied.

Moreover, the electrolytic nickel plating is 400 nm.
In addition to high reflectance of light of 800 nm to 800 nm, under certain special conditions, the front and back partition wall surfaces are rounded and plated as shown in FIG. It has been found that the plating is performed so as to form a linear shape, and a point shape in which only a flat portion remains. Usually, the plating is devised so as to be uniformly adhered to the object to be plated, but the electrolytic nickel plating in the present invention, conversely, selects the condition that the adhesion is poor.

As described above, the fact that the front and back partition walls have almost no flat portions means that the laser beam as the excitation light is placed on the honeycomb cell structure plate by installing it on the surface of the honeycomb cell structure. This means that the reflected light is reduced when scanning, and most of the excitation light is incident on the cell. As a result, not only the luminous efficiency is improved, but also the variation in the amount of emitted light depending on the place is reduced. Note that the meaning of "depending on location" means that when the center of the excitation light scanning beam deviates from the center line of the cell, the amount of reflection at the partition wall varies depending on the deviation, and thus the amount of light emission changes periodically.

By such special plating, the thickness of the sheet is 0% to 80% of that of the stainless sheet before electrolytic polishing.
It will increase by as much as%. However, since the partition wall surface inside the cell is also plated and the cell diameter becomes smaller, 0% to 50%
It is preferable that the minimum wall thickness between the cells after plating is 1/5 or less of the pitch. The 0% increase in thickness means the extent to compensate for the thinning due to electrolytic polishing.

If another plating condition is selected, the front and back surfaces can be plated relatively flat, and the partition surface in the cell can be plated thinner than the front and back surfaces.
Therefore, a combination is possible in which the above two types of plating are selectively performed, the former is used for the surface of the honeycomb cell structure, and the latter is used for the other parts. The light reflectivity of the cell wall surface of the honeycomb cell structure used in this example is electrolytically polished, and by electrolytic plating or electroless plating,
Although the quantitative reflectance is not measurable due to its structure, the reflectance is extremely excellent. The estimate is vertical (90
°) It is 80% or more at incidence, and it is more than that if the incidence angle is small.

Table 3 shows the evaluation results of the reflectance improvement by plating.

[0063]

[Table 3]

In Table 3, as in Tables 1 and 2, FIG.
The relative value is shown when the reflectance of the stainless steel sheet after etching by the measurement method shown in (1) is 100. Nickel electroplating without polishing 5
Even when only μm or nickel electroless plating of 5 μm is performed, the reflectance is considerably improved. However, in the case of electrolytic plating, caution is required because distortion tends to occur in the plated stainless steel sheet. In addition, regardless of whether electroplating or electroless plating is used, care must be taken not to make the partition wall too thick when plating.

In this example, electrolytic polishing was applied to a thickness of 1.5 μm (cell diameter increase of 3 μm), and then nickel electroless plating was applied to a thickness of 2.0 μm. As a result, the reflectance showed 460 (relative value). (Lamination / Alignment / Adhesion) The stainless sheets having a honeycomb cell structure obtained in the above steps are laminated by the following method. Several methods are possible, but some embodiments are described.

Two methods were used to apply the adhesive before the lamination. In any case, it is necessary that the adhesive does not adhere to the inner surface of the partition wall, and the adhesive layer is formed only on the partition surface on one side of the stainless sheet. One of the methods that satisfies the conditions is a method by electrostatic coating, and the other is a method by screen printing. Electrostatic coating is performed by fixing a cell-structured stainless steel sheet after electropolishing to a jig with the side with the larger cell diameter facing up, and then installing electrodes above and below the electrode and between the electrodes. Disperse the liquid. The sprayed resin liquid is drawn by the lower electrode, passes through the cell wall without wetting, and adheres only to the cell surface. As a result, it becomes possible to apply the resin only to the surface without causing the cells to be clogged. The resin used is
For example, a fine powder for imparting thixotropy, for example, silica having a particle size of 0.1 μm or less, so that the resin liquid adhered to the surface of the cell structure plate with a mixed resin mainly composed of an epoxy system does not easily flow before drying. It is advisable to mix powder such as or calcium carbonate. After coating, the solvent is completely dried, the uppermost layer honeycomb cell structure sheet is arranged in the uppermost layer, and a plurality of sheets are stacked and aligned, and then a weight such as a Teflon plate is placed thereon to cure.

Also in the case of screen printing, a thixotropic viscous resin liquid in which fine powder is dispersed is used. The coating thickness is the film thickness after drying and is about 5 μm in each case. The application place is a triangular portion between three adjacent cells in the honeycomb structure (see FIG. 7B). It is applied and laminated with the solvent dried. Stacked vertical and horizontal 480mm
The observation was performed while observing the cell position with a stereoscopic microscope equipped with a movable sample setting table with a scroll function. The original stainless steel sheet has several holes for alignment around the cell area (see FIG. 6A). If the positions of at least two alignment holes at the farthest positions are aligned, the positions of all the cells match. A plurality of stainless steel sheets are aligned with the positioning holes, and a resin is applied in advance. In some cases, a weight plate is placed and placed in a thermostatic chamber to cure and fix. When the resin is not applied in advance, the frame portion is fixed with an adhesive in the aligned state. Especially when electrolytic nickel plating is applied,
When a resin is applied to the cell partition wall, the resin easily flows into the cell, so that only the peripheral portion outside the cell region was bonded. At this time, what is important is to control the coating amount so that the adhesive does not flow into the cells.

Next, another embodiment will be described. Here, a stainless sheet is used in which the cell region is made slightly larger than the reading region and only electrolytic polishing is performed. At the time of electrolytic polishing, the cell region is thinner than the frame because the portion that is in contact with the electrode plate is not polished. For example, a stainless steel sheet having a thickness of 50 μm, a length of 480 mm, and a width of 400 mm has a pitch of 125 μm and a diameter of about 100 μm in a size range (cell area) of a central length of 460 mm and a width of 370 mm, as shown in FIG. With a honeycomb cell arrangement that has a 15 degree inclination with the outer periphery of the sheet,
When the honeycomb cell structure stainless sheet having about 12 million cells is electrolytically polished to increase the cell diameter by 20 μm, the thickness of the cell region is reduced by about 12 μm to about 38 μm. On the other hand, the frame portion outside the cell region remains 50 μm because it is covered with the electrode.

In this state, the stainless sheet is cut into a cell region and a frame region to obtain a stainless sheet having only the cell region. Positioning holes are formed in the outer peripheral portion of the cell region, and the cells are placed on a press provided with position adjusting pins. After alignment, a thinly cut adhesive sheet is placed on the outer peripheral portion of the cell region, and 10 or more stainless sheets are stacked in the same procedure. The adhesive sheet used is a thermoplastic or thermosetting double-sided adhesive sheet having a thickness of 35 μm or less, and exhibits fluidity at a temperature of 100 ° C. or more, although it varies depending on the type.

When the upper plate of the press is put on and heated under pressure, the adhesive sheet flows into the cells, and the stainless sheets only in the cell region are adhered to each other. Examples of usable adhesive sheets include Kurashiki Spinning Co., Ltd. Clan Better H-1760. In this last method, since the frame is removed and the layers are laminated, there is an advantage that the size of the photostimulable phosphor plate to be finally finished does not become unnecessarily large.

In this way, the honeycomb cell structure plate having a plurality of stainless steel sheets as a matrix is lifted. The number of sheets to be laminated was tried to be 5 to 15. (Protective sheet) The structure of the photostimulable phosphor plate is slightly different depending on the reading method, and the present invention can be applied to any structure. However, the structure described here is the same as that described with reference to FIG. Exhaust phosphor plate is a honeycomb cell structure plate to be applied to a fixed type device, and the method of using the finally prepared phosphor-stimulated phosphor plate is as follows. Radiation is radiated from the photocatalyst to be absorbed by the photostimulable phosphor powder to form a latent image, which is read from the back surface side. Also,
The back surface of the cover must be light-transmissive so that the excitation light can be scanned to emit stimulated fluorescence from the latent image and the fluorescence can be collected.

The cover on the surface on the subject side will be called a protective sheet. The physical properties required for the protective sheet are (a) waterproofness for avoiding deterioration of the photostimulable phosphor, (b) mechanical strength,
(C) Light reflectivity on the cell bottom surface for reflecting excitation light and stimulated fluorescence, and (d) radiation transparency. Regarding the light reflectivity, at least one surface of the protective sheet facing the cell structure plate side is provided with a layer having a high light reflectivity. Alternatively, a material having a good light reflectance is used. For example, it may be a thin stainless steel plate, or a stainless steel plate plated with Ni, or a glass plate coated with a white paint containing a highly reflective powder such as titanium oxide. . The light emitted from the phosphor may be considered as a point light source, and in order to direct the light toward the cell bottom to the light extraction side,
It is necessary to put the protective sheet in a state with good light reflectance. It should be noted that the light reflectance of this protective sheet is rather low in the case of a uniform coating type phosphor plate because it lowers the spatial resolution even though it has the effect of increasing the sensitivity, but in the case of the cell type, the spatial resolution is low. Higher light reflectance is better as it is guaranteed.

In order to satisfy these conditions to some extent and also to consider the price, here, as the protective sheet, a thickness of 50 μm is used.
It was decided to use a stainless steel sheet of m. However,
The light reflectance of the surface of a commercially available stainless steel sheet has an incident angle of 80.
It is about 70% when measured at a reflection angle of 60 degrees, which is not very good. By electropolishing about 10 μm on one surface, the thickness became about 40 μm, and not only the radiation transmission amount increased but also the light reflectance increased to about 88%. The wavelength dependence of the light reflectance of stainless steel is 400 nm to 800 nm.
It can be said that there is almost no in the range of nm.

In the case of a stainless sheet, it is necessary to carry out an oxidation treatment in order to improve the adhesiveness. (Spacer) The stimulated phosphor used in this example is BaBr.
₂ : Eu. This phosphor is very easy to absorb moisture, and if it absorbs moisture, the sensitivity is significantly lowered. It may not be necessary if BaFBr: Eu or the like is used, but it is preferable to firmly waterproof the outside of the frame portion around the honeycomb cell structure plate. For this reason, a water-resistant resin such as epoxy resin or acrylic resin is used as the spacer, but if the resin is filled between the thin stainless sheet of the protective sheet and the surface cover, the shape becomes unstable. Was filled with a spacer, and the gap was bonded with an epoxy resin.

Spacers having various thicknesses are prepared by oxidizing stainless steel made of the same material as the stainless steel sheet, and on the other hand, an adhesive which is liquid at room temperature and has a thickness of about 3 μm is formed on the entire surface of the protective sheet or the surface cover. Was applied, a spacer slightly thicker than the thickness of the honeycomb cell structure plate was placed on the outside, the honeycomb cell structure plate was placed in the central portion, and a weight plate was placed and cured.

(Particle Size Distribution of Stimulated Phosphor Powder) When the powder is packed into a fine cell as used in this example, at least a powder having a size larger than the cell diameter cannot be packed. Also, the stimulated phosphor powder has a particle size distribution rather than monodispersion.
As a result of examination, it was found that unless the peak of the particle size distribution is 1/3 or less of the cell diameter and the maximum diameter is not 1/2 or less of the cell diameter, clogging easily occurs and filling is difficult. From the viewpoint of sensitivity, the larger the particle size, the better. Therefore, the particle size distribution of the stimulable phosphor powder should be such that the peak is 1/3 to 1/20 of the cell diameter and the width of the distribution is as small as possible.

(Filling of stimulable phosphor powder) The step of filling the cell with the stimulable phosphor powder will be described below. It was not possible to sufficiently fill the cell having the structure disclosed in JP-A-59-202100 by simply coating the resin solution in which the phosphor powder was dispersed. The reason is that the resin solution cannot be entered inside the cell because the resin under the phosphor layer substrate completely seals the air surrounded by the cell and the cell. It is thought to be in.

The filling method carried out by the inventor is basically 2
There is a street way. One is to scatter only the stimulated phosphor powder on the honeycomb cell structure plate adhered on the protective sheet and shake the whole. Add the stimulated phosphor powder little by little and shake to add a little excess. By doing so, the air in the cell can be filled with the stimulable phosphor powder without any obstruction. Excess photostimulable phosphor powder that could not fit in the cell is attached to an adhesive tape and removed.
As it is, the powder filled in the cell is unstable, so resin is applied to the surface cover, and the resin is gently laminated and cured. Alternatively, a resin dissolved in a solvent is applied by spraying, and after decompressing in a decompression box, the pressure is returned to normal pressure, followed by heating to completely volatilize the solvent and fix the resin to fix the powder in the cell. be able to.

Another method for filling the stimulated phosphor powder as it is will be described. This is a method in which resin powder is mixed with stimulated phosphor powder and filled. The physical properties of the resin powder to be used are (a) at least a swellable hydrophilic solvent is present or capable of melting at a high temperature, and (b) the powder has a size of about 0.1 μm or about 5 μm, If possible, it is in the form of beads, and (c) has a good transmittance for light of 400 nm. A non-crosslinking type polymethylmethacrylate in the form of beads having a particle size of 0.1 μm to 5 μm, which satisfies these conditions, is available from, for example, Matsumoto Yushi Kagaku Co., Ltd. However, this resin powder does not melt.

The ease of filling the stimulated phosphor powder into the cell is also affected by its fluidity. Since the peak of the particle size distribution of the photostimulated phosphor powder used here is 20 μm rather than 5 μm, the fluidity is originally good, but it was found that the fluidity is further improved by adding a fine inorganic powder. The inorganic powder that can be used is a white powder that does not absorb light in the vicinity of 400 nm, needs to have a size that blocks the stimulable phosphor powder, and the particle size is preferably 0.2 μm or less.
Such inorganic powders include silicon oxide, calcium carbonate, titanium oxide and the like. The fluidity is greatly improved by adding 0.1% to 2% by volume of these powders.

After filling the mixed powder in the cell, the excess powder is removed. Next, acetone or toluene, which is the parent solvent, and isopropyl alcohol, which is the poor solvent, are mixed at a ratio of 1:10, sprinkled on the cell region with a spray, and after leaving for a while, put in a vacuum box to volatilize most of the solvent,
Finally, it is heated to about 80 ° C. to completely evaporate the residual solvent.

By these operations, the stimulable phosphor powder is fixed in the cell, but most of the surface of the stimulable phosphor powder is in contact with air. As a result, the excitation light laser entering the stimulable phosphor powder has a small total reflection angle,
It is reflected on the surface of the stimulated phosphor powder and is hard to go out, so that stimulated fluorescence is emitted many times. If the resin entirely covers the surface of the stimulable phosphor powder, the angle of total reflection becomes large and the utilization efficiency of the excitation light decreases.

Another method is to disperse the stimulable phosphor powder in a low-concentration resin solution from the beginning and reduce the pressure in a pressure reducing box to replace the air inside the cell with the resin solution in the powder dispersion system. Then, it is a method of volatilizing the solvent and curing. In the case of this method, it is preferable that the resin solution of the powder dispersion system be added once again to complete the filling after the replacement, and the surface is wiped to remove the excess powder when the solvent has evaporated to some extent.

(Light-Transmissive Sheet) When the light-transmissive sheet is covered on the honeycomb cell structure filled with the photostimulable phosphor powder prepared as described above, the photostimulable phosphor is protected. At the same time, the excitation light and the stimulated emission light can be transmitted. Although any sheet can be used as long as it fulfills the purpose, a glass plate having a thickness of 1 mm was used in this example.

A room temperature-curable two-component epoxy resin was applied onto the spacer, a glass plate cut into the same size as the protective sheet was placed on the spacer, and left overnight to cure. This completes the honeycomb cell structure stimulated phosphor plate. (Evaluation Results of Photostimulated Phosphor Plate) FIG. 11 shows the MTF of the honeycomb cell structure photostimulated phosphor plate manufactured as described above.
It is a figure shown with a comparative example.

In FIG. 11, A is the theoretical MTF of the honeycomb cell structure stimulated phosphor plate, and B is the stainless steel sheet.
The MTF and C of the honeycomb cell structure stimulated phosphor plate having a cell thickness of 0.4 mm with 0 layers stacked are 1 stainless steel sheet.
It is an MTF of a honeycomb-stimulated phosphor plate having a cell thickness of 0.6 mm in which five layers are stacked. Both have fairly good spatial resolution. G is MT of the conventional uniform coating type stimulable phosphor plate (thickness of the stimulable phosphor layer is 0.3 mm).
F measurement results, D to F, H are MT of the conventional silver salt film.
It is an F measurement result. As shown in this figure, according to this example, the spatial resolution was significantly improved.

Table 4 shows the results of sensitivity comparison.

[0088]

[Table 4]

A conventional uniform coating type photostimulable phosphor plate (see FIG. 11)
(Corresponding to G in FIG. 11) and an example of the present invention (B and C in FIG.
(Corresponding to), the average pixel value when the X-ray is irradiated under the same condition and the reading is performed under the same condition is shown. As shown in Table 4, the same level of sensitivity as in the prior art could be maintained in this example. That is,
According to this example, the spatial resolution was significantly improved while the sensitivity was kept at the same level as the conventional one.

The following is a deviation from the embodiments of the present invention.
An outline of a reading method and an image processing method using the photostimulable phosphor plate manufactured as described above will be described. (Reading Method of Honeycomb Cell Structure Stimulated Phosphor Plate) (Laser Beam Diameter) Each cell of the honeycomb cell structure stimulated phosphor plate is a radiation sensor, and as shown in FIG. 11, it has excellent spatial resolution and concentration resolution. ing. The spatial resolution of the honeycomb-stimulated phosphor plate is up to 0.5 times the cell pitch. Therefore, when a radiation image is read using the honeycomb cell structure stimulated phosphor plate as a radiation sensor, the beam diameter of the laser beam scanned by the laser scanner on the surface of the stimulated phosphor plate is 0.
It is meaningless even if it is 5 times or less.

FIG. 11 shows the results obtained by compensating for some of the drawbacks of the honeycomb cell structure stimulated phosphor plate.
The drawbacks and how to compensate for them are described below. (Sampling Interval) One of the drawbacks is that, unlike the conventional coating type photostimulable phosphor plate having a relatively uniform layer, it is nonuniform. That is, there are partition walls, and one cell does not necessarily correspond to one pixel. Depending on the size of one pixel, two or more cells may correspond to one pixel, and the number of corresponding cells may differ, and the change has periodicity. Therefore, even if the uniform radiation is applied, the sensitivity changes with periodicity.

There are several possible methods for reducing this periodic output change. (A) Electrolytic nickel plating is applied to the uppermost metal mask of the honeycomb cell structure so that the partition wall surface is not flat. , (B) making the cell diameter as close as possible to the cell pitch, (c) making the cell pitch small, (d) making the beam diameter large,
(E) increasing the size of one pixel, and
(E) Increasing the number of samplings in one pixel.

(A) to (c) relate to a method for manufacturing a honeycomb-cell-structured photostimulable phosphor plate, and (d) and (e) indicate the purpose of use (what kind of disease is to be diagnosed).
It is decided by. And, the technique (e) is applicable to any case. As a result of the examination, compared to the case where the number of samplings in one pixel is 1, the number of samplings is set to 2 and the average value is set to 1 pixel. It was found that the output change was further improved, although it was smaller than the change of the two output changes.

(Correction of all pixels-correction of variation in filling rate)
Each cell of the honeycomb-cell-structured photostimulable phosphor plate is a radiation sensor, and as shown in FIG. 11, it has excellent spatial resolution and concentration resolution, but has the drawback of a conventional coating type phosphor having a relatively uniform layer. Unlike the exhaust phosphor plate, the filling amount of the stimulated phosphor powder may vary from cell to cell depending on the method of making. As a result, variations in sensitivity of 5% to 20% occur even if uniform radiation is applied.

To correct this variation in sensitivity, the following all-pixel correction is performed. As shown in FIG. 2, the photostimulable phosphor plate is fixed to the photographing unit in the reading device, and the laser scanner unit, the light-collecting and light-receiving unit, and the erasing unit are moved so that the photostimulable phosphor plate becomes After the stimulated emission light proportional to the formed latent image is converted into an electric signal by the photoelectric converter, or as shown in FIG. 1, the laser scanner unit, the condensing light receiving unit, and the erasing unit are fixed. , The photostimulable phosphor plate after being photographed is moved, and the photostimulable fluorescence proportional to the latent image is converted into a digital image signal by an analog-digital converter, after which the photostimulable phosphor is converted into a digital image signal. The fluctuation of the image signal due to the variation of the filling rate of the phosphor powder which is different for each cell of the phosphor plate is corrected.

A concrete correction method is as follows. First, the photostimulable phosphor plate is irradiated with radiation in the absence of an object to read the pixel values of all the pixels of the photostimulable phosphor plate, and the maximum of those pixel values is read. All pixels that store the correction values of all pixels obtained by dividing all pixel values by the value or the minimum value, and then correct the pixel values of all pixels obtained through the subject with the correction values of the corresponding pixels Use the correction method.

This correction method may bring about a great improvement in the Wiener spectrum as a method for correcting uneven coating even in the case of the conventional coating type photostimulable phosphor plate, but it is not always necessary. However, in the case of the honeycomb-stimulated stimulable phosphor plate, this all-pixel correction eliminates not only the variation of the filling rate for each cell but also the above-mentioned periodical output fluctuation, which is an essential correction.

(Spatial frequency treatment) When a honeycomb cell structure stimulable phosphor plate is used as a radiation sensor, a very high concentration resolution can be obtained, so that it can be obtained by a conventional coating type stimulable phosphor plate or a silver salt film. The image is different from the image. Therefore, it may not meet the diagnostic criteria of a doctor who has made a diagnosis while observing a conventional image.
For example, taking a chest image as an example, if thin blood vessels in the peripheral part of the lung field are visible too much, it is suspected that some disease such as interstitial disease will be suspected according to the conventional diagnostic criteria, despite being normal .

In order to avoid such a situation, the spatial frequency processing which has been carried out for increasing the sharpness in the case of the conventional digital radiation image is reversed in the case of the honeycomb cell structure stimulated phosphor plate. There are cases where it is better to use it for lowering. That is, when the pixel value of the processed pixel is S, the average value of surrounding pixels is Sm, the pixel value after the process is P, and the weighting coefficient is k, the spatial frequency processing using P = S + k (S-Sm) is performed. , K is negative.

However, it is preferable that the value of k can be changed according to the wishes of a doctor who makes a diagnosis, and it is not necessary to lower the sharpness in the mediastinum, the heart, the diaphragm, etc., where density resolution is required. Therefore, it is also preferable to be able to select k for each anatomical region so as to reduce the sharpness of only the lung field. The anatomical region can be easily discriminated by a known method for obtaining the corresponding pixel value range by analyzing the histogram of pixel values.

(Averaging Process) There is another adverse effect when the density resolution is too high, and when the amount of radiation applied is small, a quantum mottle which has not been a problem in the past appears. . In order to reduce the effect of this, local averaging processing is required. That is, for the obtained image, for example, the surrounding pixels including the processing pixels, such as 9 to 25 pixels,
An averaging process is performed using the average value of pixels or the median value as the pixel value. The shape of the pixels to be averaged may be square or rectangular.

[0102]

As described above, according to the method for producing a photostimulable phosphor plate of the present invention, both sensitivity and spatial resolution are high.
A stimulable phosphor plate having an excellent function is produced.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a system using a stimulated phosphor plate.

FIG. 2 is a diagram showing a configuration example of another system using a stimulated phosphor plate.

FIG. 3 is a diagram showing how the excitation light is scattered in the stimulated phosphor layer.

FIG. 4 is a schematic view of a conventional cell structure manufactured by etching.

FIG. 5 is a process drawing showing an example of a method for producing a stimulated phosphor plate of the present invention.

FIG. 6 is a plan view (A) showing a structure of a stimulable phosphor plate manufactured by an embodiment of the method for manufacturing a stimulable phosphor plate of the present invention, and an arrow shown in FIG. It is sectional drawing (B) along X.

FIG. 7 is a schematic diagram showing a cell pattern.

FIG. 8 is a schematic view showing a state of electrolytic polishing.

FIG. 9 is an explanatory diagram of a method for measuring the reflectance of a stainless sheet having a cell structure.

FIG. 10 is a sectional view of a partition wall.

FIG. 11: MTF of stimulated phosphor plate with honeycomb cell structure
It is a figure which shows with a comparative example.

[Explanation of symbols]

 11 X-ray generation section 15 Photostimulated phosphor plate 19 Reading section 20 Erasing section 23 Image processing section 25 Image display section

Claims (21)

[Claims] 1. A through hole forming step of forming a large number of through holes at positions corresponding to each other on a plurality of metal sheets, and a reflectance improving step of improving the light reflectance of the inner wall of the through hole of the metal sheet. A metal sheet stacking step of stacking the metal sheets on each other so that through holes formed at corresponding positions communicate with each other, and one of the through holes of the stacked metal sheets on one side of the stacked metal sheets. A protective sheet bonding step of bonding a protective sheet that closes the opening of the protective sheet, and a protective fluorescent material filling step of filling a stimulated fluorescent material into the through holes of the laminated metal sheets to which the protective sheet is bonded, The stimulated phosphor is filled in the holes, the laminated metal sheets, on the other side opposite to the one side, a light transmitting sheet bonding step of bonding a light transmitting sheet that transmits light, and To Manufacturing method of the accelerated phosphorescence fluorescent plate, characterized in that there was e. 2. A frame cutting step of cutting and removing a peripheral edge portion of the metal sheet whose reflectance of light on the inner wall of the through hole is improved by the reflectance improving step. A method for manufacturing a stimulated phosphor plate. 3. The protective sheet and the light transmissive sheet are sheets having a larger area than the area of the laminated metal sheets, and the protective sheet adhering step and the light transmissive sheet adhering step respectively include The protective sheet and the light-transmitting sheet are adhered to the metal sheet so that the peripheral edge portions of the protective sheet and the light-transmitting sheet protrude from the peripheral edge of the metal sheet. Of the conductive sheet, with a spacer sandwiched between the peripheral portions protruding from the metal sheet,
By bonding the peripheral portion of the protective sheet and the spacer, and the spacer and the light-transmissive sheet, the bright phosphor for sealing the photostimulable phosphor filled in the through hole of the metal sheet is adhered. The method for producing a stimulated phosphor according to claim 1, further comprising a step of sealing the exhausted phosphor. 4. The metal sheet has a thickness of 10 μm or more 1
The method for producing a stimulable phosphor plate according to claim 1, which has a thickness of 50 μm or less. 5. The metal sheet has a positioning hole for positioning through hole formation in the through hole forming step and positioning for overlapping the metal sheets in the metal sheet laminating step. The method for producing a stimulated phosphor plate according to claim 1. 6. The method of manufacturing a stimulable phosphor plate according to claim 1, wherein the through hole forming step is a step of forming the through hole by etching. 7. The through-hole forming step, at least for the metal sheet laminated on the first layer on the light-transmissive sheet side, of partition walls between adjacent through-holes of the metal sheet, The method for producing a photostimulable phosphor plate according to claim 1, wherein the through hole is formed so that the surface of the light transmitting sheet side is formed into a substantially semicircular cross-sectional shape. 8. The light reflectance of the inner wall of the through hole is formed by using at least one method selected from the group consisting of electrolytic polishing, chemical polishing, electroless plating, and electrolytic plating in the reflectance improving step. The method for producing a photostimulable phosphor plate according to claim 1, which is a step of improving 9. The stimulated phosphor plate according to claim 1, wherein the reflectance improving step is a step of improving the reflectance of light on the inner wall of the through hole by using electrolytic polishing or chemical polishing. Manufacturing method. 10. The reflectance improving step uses the metal sheet as one of the electrode plates and arranges the other electrode plate in parallel with the metal sheet, and further, between the two electrode plates. 9. The brightening according to claim 8, wherein the electropolishing is performed by arranging a current control plate having a hole that is larger toward the central portion and smaller in diameter from the central portion toward the peripheral portion. Exhaust phosphor plate manufacturing method. 11. The step of improving the reflectance is a step of performing electrolytic polishing or chemical polishing so that the polishing amount is within a range in which the partition walls remain between the through holes that are 1.5 μm or more and are adjacent to each other. 9. The method for producing a photostimulable phosphor plate according to claim 8, wherein. 12. The reflectance improving step is performed so that the partition wall thickness between the through holes adjacent to each other after the reflectance improving step is 20% or less of the pitch of the through holes. 2. The method for manufacturing a stimulable phosphor plate according to claim 1, which is a step of improving the light reflectance of the inner wall of the through hole. 13. The method for producing a photostimulable phosphor plate according to claim 1, wherein the metal sheet laminating step is a step of superposing the adhesive sheet on a peripheral portion of the metal sheet so as to sandwich the adhesive sheet. . 14. The protective sheet is a metal sheet having at least one surface polished or plated, and the protective sheet adhering step has a metal sheet side on which a polished or plated surface of the metal sheet is laminated. 2. The method for producing a photostimulable phosphor plate according to claim 1, which is a step of adhering a metal sheet as the protective sheet to the laminated metal sheet toward the above. 15. The protective sheet is a resin or glass sheet having a light reflecting film formed on one surface,
In the protective sheet bonding step, the surface of the protective sheet on which the light reflecting film is formed is directed toward the laminated metal sheet side,
The method for producing a photostimulable phosphor plate according to claim 1, which is a step of adhering the protective sheet to the laminated metal sheets. 16. The stimulable phosphor powder filling step comprises filling a stimulable phosphor powder mixed with resin powder into the through-holes of the laminated metal sheets to which the protective sheet is adhered The method for producing a stimulable phosphor plate according to claim 1, which is a step of spraying an organic solvent on the stimulable phosphor powder and volatilizing the organic solvent. 17. The amount of the resin powder mixed with the stimulable phosphor powder is 0.5% by volume or more and 10% by volume or less with respect to the stimulable phosphor powder. A method for manufacturing a stimulated phosphor plate. 18. The stimulable phosphor plate according to claim 16, wherein the resin powder mixed with the stimulable phosphor is a powder of polymethylmethacrylate having a particle size distribution peak of 5 μm or less. Production method. 19. The stimulable phosphor powder to be filled in the through hole is a mixture of white inorganic powder having a particle size distribution peak of 0.2 μm or less.
6. The method for producing a stimulated phosphor plate according to item 6. 20. The white inorganic powder mixed with the stimulable phosphor powder is a powder composed of one kind or a plurality of kinds selected from the group consisting of silicon oxide, calcium carbonate and titanium oxide. 20. The method for producing a stimulated phosphor plate according to claim 19. 21. The stimulable phosphor filling step applies a stimulable phosphor powder prepared by mixing a resin solution in which a resin is dissolved in an organic solvent, onto the laminated metal sheet to which the protective sheet is adhered. By filling the stimulable phosphor powder into the through hole by the above, and depressurizing, the air in the through hole is replaced with the resin liquid, and the organic solvent is volatilized. Item 2. A method for producing a stimulated phosphor plate according to Item 1.