Title: Radiation image storage panel
Abstract: A radiation image storage panel comprises a stimulable phosphor layer, which contains a stimulable phosphor, and a transparent protective layer overlaid on the stimulable phosphor layer. The transparent protective layer has a layer thickness of at most 50 μm and comprises at least four layers formed on a transparent protective layer support for supporting the transparent protective layer, the at least four layers comprising transparent inorganic layers and organic layers, which are located alternately. Each of the transparent inorganic layers contains a compound selected from the group consisting of a metal oxide, a metal nitride, and a metal oxynitride, and is formed with a vacuum deposition technique. Each of the organic layers is formed with a coating technique or a vacuum deposition technique.
Patent Number: 6,992,304 Issued on 01/31/2006 to Fukui
| Inventors:
|
Fukui; Shinichiro (Kaisei-machi, JP)
|
| Assignee:
|
Fuji Photo Film Co., Ltd. (Kanagawa-ken, JP)
|
| Appl. No.:
|
358355 |
| Filed:
|
February 5, 2003 |
Foreign Application Priority Data
| Feb 05, 2002[JP] | 2002-028368 |
| Current U.S. Class: |
250/484.4 |
| Current Intern'l Class: |
G03B 42/08 (20060101) |
| Field of Search: |
250/4844
|
References Cited [Referenced By]
U.S. Patent Documents
| 4239968 | Dec., 1980 | Kotera et al.
| |
| 4645721 | Feb., 1987 | Arakawa et al.
| |
| 4741993 | May., 1988 | Kano et al.
| |
| 5023461 | Jun., 1991 | Nakazawa et al.
| |
| Foreign Patent Documents |
| 1-131496 | May., 1989 | JP.
| |
| 10-12376 | Jan., 1998 | JP.
| |
| 11-344698 | Dec., 1999 | JP.
| |
Primary Examiner: Porta; David
Assistant Examiner: Lee; Shun
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A radiation image storage panel, comprising a stimulable phosphor layer, which
contains a stimulable phosphor, and a transparent protective layer overlaid on
the stimulable phosphor layer,
wherein the transparent protective layer has a layer thickness of at most 25
μm and comprises at least four layers formed on a transparent protective
layer support for supporting the transparent protective layer, the at least four
layers comprising transparent inorganic layers and organic layers, which are located alternately.
2. A radiation image storage panel as defined in claim 1 wherein each of the
transparent inorganic layers contains a compound selected from the group consisting
of a metal oxide, a metal nitride, and a metal oxynitride, and is formed with a
vacuum deposition technique.
3. A radiation image storage panel as defined in claim 1 wherein each of the
organic layers is formed with a technique selected from the group consisting of
a coating technique and a vacuum deposition technique.
4. A radiation image storage panel as defined in claim 2 wherein each of the
organic layers is formed with a technique selected from the group consisting of
a coating technique and a vacuum deposition technique.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation image storage panel for use in radiation
image recording and reproducing techniques, in which stimulable phosphors are utilized.
2. Description of the Related Art
In lieu of conventional radiography, radiation image recording and reproducing
techniques utilizing stimulable phosphors have heretofore been used in practice.
The radiation image recording and reproducing techniques are described in, for
example, U.S. Pat. No. 4,239,968. The radiation image recording and reproducing
techniques utilize a radiation image storage panel (referred to also as the stimulable
phosphor sheet) provided with a stimulable phosphor. With the radiation image recording
and reproducing techniques, the stimulable phosphor of the radiation image storage
panel is caused to absorb radiation, which carries image information of an object
or which has been radiated out from a sample, and thereafter the stimulable phosphor
is exposed to an electromagnetic wave (stimulating rays), such as visible light
or infrared rays, which causes the stimulable phosphor to produce the fluorescence
(i.e., to emit light) in proportion to the amount of energy stored thereon during
its exposure to the radiation. The produced fluorescence (i.e., the emitted light)
is photoelectrically detected to obtain an electric signal. The electric signal
is then processed, and the processed electric signal is utilized for reproducing
a visible image of the object or the sample. The radiation image storage panel,
from which the electric signal has been obtained, is subjected to an erasing operation
for erasing energy remaining on the radiation image storage panel, and the erased
radiation image storage panel is utilized again for the image recording. Specifically,
the radiation image storage panel is used repeatedly.
The radiation image recording and reproducing techniques have the advantages
in that a radiation image containing a large amount of information is capable of
being obtained with a markedly lower dose of radiation than in the conventional
radiography utilizing a radiation film and an intensifying screen. Also, with the
conventional radiography, the radiation film is capable of being used only for
one recording operation. However, with the radiation image recording and reproducing
techniques, the radiation image storage panel is used repeatedly. Therefore, the
radiation image recording and reproducing techniques are advantageous also from
the view point of resource protection and economic efficiency.
As described above, the radiation image recording and reproducing techniques
are
advantageous techniques for forming images. As in the cases of the intensifying
screens utilized in the conventional radiography, it is desired that the radiation
image storage panels utilized in the radiation image recording and reproducing
techniques have the performance, such that the radiation image storage panels have
a high sensitivity, yield good image quality, and endure a long period of use without
the image quality of the radiation images becoming bad.
However, the stimulable phosphors utilized for the production of the radiation
image storage panels ordinarily have high levels of water vapor absorbing characteristics
and absorb moisture contained in air when being left within a room under ordinary
weather conditions. Therefore, the stimulable phosphors have the problems in that
the sensitivity of the stimulable phosphors with respect to the radiation becomes
low as the amount of moisture absorbed by the stimulable phosphors becomes large,
and the characteristics of the stimulable phosphors deteriorate markedly-with the
passage of time.
Also, ordinarily, latent images of the radiation images having been recorded
on the stimulable phosphors have the properties such that the latent images fade
with the passage of time after the stimulable phosphors have been exposed to the
radiation. Therefore, as the time occurring between when the stimulable phosphors
are exposed to the radiation and when the stimulable phosphors are exposed to the
stimulating rays becomes long, the intensities of the radiation image signals detected
from the stimulable phosphors become low. In cases where the stimulable phosphors
absorb water vapor, the rate of the fading of the latent images having been recorded
on the stimulable phosphors becomes high. Therefore, in cases where the radiation
image storage panels, whose stimulable phosphors have absorbed water vapor, are
used, there has arisen a tendency toward low reproducibility of the image signals
at the time of the readout of the radiation images.
In order for the deterioration phenomenon of the stimulable phosphors due to
water
vapor absorption to be eliminated, for example, there has heretofore been employed
a technique, wherein a stimulable phosphor is covered with a film of a polytrifluorochloroethylene,
or the like, acting as a water vapor proof protective layer having a low water
vapor transmission rate, and the amount of moisture reaching the stimulable phosphor
layer is thus reduced. However, the aforesaid technique for eliminating the deterioration
phenomenon of the stimulable phosphors due to moisture absorption has the problems
in that the cost of the aforesaid film of the polytrifluorochloroethylene, or the
like, is high, and the thickness of the film is large. The aforesaid technique
for eliminating the deterioration phenomenon of the stimulable phosphors due to
moisture absorption also has the problems in that the film of the polytrifluorochloroethylene,
or the like, is produced by use of FREON chlorofluorocarbons as a raw material,
and therefore causes environmental pollution to occur.
Also, a constitution comprising two kinds of protective layers having different
levels of water vapor absorbing characteristics, wherein one protective layer having
a higher level of water vapor absorbing characteristics than the water vapor absorbing
characteristics of the other protective layer is located on the side of a phosphor
layer, is described in, for example, U.S. Pat. No. 4,741,993. Further, a constitution,
wherein a protective layer contains a silicon compound containing nitrogen and
oxygen, is described in, for example, Japanese Unexamined Patent Publication No.
1 (1989)-131496. However, water vapor proof characteristics, which are achieved
by each of the constitutions described above, are not necessarily of a satisfactory
level. Furthermore, a technique for utilizing a laminated film for an electric
field fluorescent lamp, where in the laminated film is formed by laminating two
to eight films, each of which has been prepared by forming a thin layer of a metal
oxide, silicon nitride, or the like, on a polyethylene terephthalate (PET) film
with vacuum evaporation, is described in, for example, Japanese Unexamined Patent
Publication No. 10(1998)-12376. However, with the laminated film described above,
the problems with regard to image defects due to the water vapor proof protective
film, image defects due to a condition of adhesion between the water vapor proof
protective film and a phosphor surface, and the like, occur. Therefore, the laminated
film described above cannot be employed as a water vapor proof protective film
for the radiation image storage panels, which are exclusively used for obtaining
medical images for making a diagnosis of an illness.
Also, as a constitution for used in a radiation image storage panel, a constitution,
wherein a laminated film comprising a plurality of resin films, which contain at
least one metal oxide evaporated resin film and have been adhered to one another
in a layer form, is located on the side of a phosphor layer surface, is proposed
in, for example, Japanese Unexamined Patent Publication No. 11(1999)-344698. However,
with the proposed constitution, wherein the laminated film is adhered by an adhesive
layer to the phosphor layer surface, the problems occur in that nonuniformity occurs
with images, depending upon the condition of the adhesion of the laminated film.
Also, with the proposed constitution, the problems occur in that the thickness
of the entire water vapor proof layer becomes large, and the image quality becomes bad.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a radiation image storage
panel, which has good water vapor proof characteristics and a high durability,
which is capable of being used in good conditions for a long period of time, and
which has a high sensitivity and is capable of yielding good image quality.
The present invention provides a radiation image storage panel, comprising a
stimulable phosphor layer, which contains a stimulable phosphor, and a transparent
protective layer overlaid on the stimulable phosphor layer,
wherein the transparent protective layer has a layer thickness of at most
50 μm and comprises at least four layers formed on a transparent protective
layer support for supporting the transparent protective layer, the at least four
layers comprising transparent inorganic layers and organic layers, which are located alternately.
In the radiation image storage panel in accordance with the present invention,
the at least four layers comprising the transparent inorganic layers and the organic
layers, which are located alternately, are formed on the transparent protective
layer support. Specifically, the layer, which is formed directly on the transparent
protective layer support, may be one of the transparent inorganic layers. Alternatively,
the layer, which is formed directly on the transparent protective layer support,
may be one of the organic layers. Also, the layer, which is formed at the position
remotest from the transparent protective layer support, may be one of the transparent
inorganic layers. Alternatively, the layer, which is formed at the position remotest
from the transparent protective layer support, may be one of the organic layers.
The transparent protective layer has a layer thickness of at most 50 μm.
The transparent protective layer should preferably have a layer thickness of at
most 25 μm.
The radiation image storage panel in accordance with the present invention should
preferably be modified such that each of the transparent inorganic layers contains
a compound selected from the group consisting of a metal oxide, a metal nitride,
and a metal oxynitride, and is formed with a vacuum deposition technique.
Also, the radiation image storage panel in accordance with the present invention
should preferably be modified such that each of the organic layers is formed with
a technique selected from the group consisting of a coating technique and a vacuum
deposition technique.
The present invention also provides a radiation image storage panel, comprising
a stimulable phosphor layer, which contains a stimulable phosphor, and a transparent
protective layer overlaid on the stimulable phosphor layer,
wherein the transparent protective layer has an air transmission rate at
25° C. of at most 0.5 cc/m
2/24 h and a water vapor transmission
rate of at most 0.5 g/m
2/24 h.
The radiation image storage panel in accordance with the present invention comprises
the stimulable phosphor layer, which contains the stimulable phosphor, and the
transparent protective layer overlaid on the stimulable phosphor layer. The transparent
protective layer comprises at least four layers formed on the transparent protective
layer support for supporting the transparent protective layer, the at least four
layers comprising the transparent inorganic layers and the organic layers, which
are located alternately. Therefore, the radiation image storage panel in accordance
with the present invention has markedly good water vapor proof characteristics
and a markedly high durability. Also, the radiation image storage panel in accordance
with the present invention, wherein the transparent protective layer has a layer
thickness of at most 50 μm, has a high sensitivity and is capable of yielding
good image quality.
The radiation image storage panel in accordance with the present invention may
be modified such that each of the transparent inorganic layers contains the compound
selected from the group consisting of the metal oxide, the metal nitride, and the
metal oxynitride, and is formed with the vacuum deposition technique. Also, the
radiation image storage panel in accordance with the present invention may be modified
such that each of the organic layers is formed with the technique selected from
the group consisting of the coating technique and the vacuum deposition technique.
With each of the modifications described above, the water vapor proof characteristics
of the radiation image storage panel are capable of being enhanced even further.
Also, with each of the modifications described above, since each of the transparent
inorganic layers and each of the organic layers need not be adhered with an adhesive
agent to each other, the problems are capable of being prevented from occurring
in that nonuniformity occurs with images due to the condition of the adhesion of
layers. Further, with each of the modifications described above, the thickness
of the entire transparent protective layer is capable of being set at a small value,
and therefore good image quality is capable of being obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic sectional view showing a first embodiment of the radiation
image storage panel in accordance with the present invention, and
FIG. 2 is a schematic sectional view showing a second embodiment of the radiation
image storage panel in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will hereinbelow be described in further detail with reference
to the accompanying drawings.
FIG. 1 is a schematic sectional view showing a first embodiment of the radiation
image storage panel in accordance with the present invention. FIG. 2 is a schematic
sectional view showing a second embodiment of the radiation image storage panel
in accordance with the present invention.
As illustrated in FIG. 1, a radiation image storage panel
1, which is
the
first embodiment of the radiation image storage panel in accordance with the present
invention, comprises a substrate
2. The radiation image storage panel
1
also comprises a stimulable phosphor layer
3 and a transparent protective
layer
4, which are overlaid on the substrate
2. The transparent protective
layer
4 comprises a transparent protective layer support
5 for supporting
the transparent protective layer
4. The transparent protective layer
4
also comprises a first transparent inorganic layer
6a, a first organic
layer
7a, a second transparent inorganic layer
6b,
and a second organic layer
7b, which are overlaid in this order on
the transparent protective layer support
5. In the first embodiment of FIG.
1, the first transparent inorganic layer
6a is formed directly on
the transparent protective layer support
5. Alternatively, an organic layer
may be formed directly on the transparent protective layer support
5. In
such cases, if four layers comprising the transparent inorganic layers and the
organic layers, which are located alternately, are formed on the transparent protective
layer support
5, a top layer, which is remotest from the transparent protective
layer support
5 among the layers constituting the radiation image storage
panel
1, will be constituted of a transparent inorganic layer. In this manner,
the radiation image storage panel
1 may be modified such that the top layer,
which is remotest from the transparent protective layer support
5 among
the layers constituting the radiation image storage panel
1, is constituted
of the transparent inorganic layer. Also, in such cases, if it is necessary, for
reasons of a process for producing the radiation image storage panel or for special
use of the radiation image storage panel, that the top surface of the radiation
image storage panel
1 is constituted of an organic layer, the organic layer
may be overlaid even further on the transparent inorganic layer. Further, in the
first embodiment of FIG. 1, by way of example, the four layers comprising the transparent
inorganic layers and the organic layers, which are located alternately, are formed
on the transparent protective layer support
5. Alternatively, an odd number
of layers, e.g. five layers, may be formed on the transparent protective layer
support
5, such that the layer thickness of the entire transparent protective
layer is at most 50 μm. As another alternative, at least six layers may be
formed on the transparent protective layer support
5, such that the layer
thickness of the entire transparent protective layer is at most 50 μm. Furthermore,
each of the organic layers or each of the transparent inorganic layers may be formed
in a plurality of steps and may thus be constituted of a plurality of sublayers.
The layer thickness of each of the first transparent inorganic layer
6a
and the second transparent inorganic layer
6b may take one of
various values, depending upon the number of the transparent inorganic layers and
the organic layers, which are located alternately. The layer thickness of each
of the first transparent inorganic layer
6a and the second transparent
inorganic layer
6b may ordinarily fall within the range of 10 nm
to 1,000 nm. The layer thickness of each of the first transparent inorganic layer
6a and the second transparent inorganic layer
6b should
preferably fall within the range of 15 nm to 700 nm, and should more preferably
fall within the range of 20 nm to 500 nm. If the layer thickness of each of the
first transparent inorganic layer
6a and the second transparent inorganic
layer
6b is smaller than 10 nm, for example, holes will occur through
the transparent inorganic layer, and a uniform and smooth transparent inorganic
layer cannot always be formed. Also, in such cases, a sufficient water vapor proof
effect cannot be obtained. If the layer thickness of each of the first transparent
inorganic layer
6a and the second transparent inorganic layer
6b
is larger than 1,000 nm, the formed transparent inorganic layer will be apt
to suffer from peeling and cracking.
The layer thickness of each of the first organic layer
7a and the
second organic layer
7b may take one of various values, depending
upon the number of the transparent inorganic layers and the organic layers, which
are located alternately. The layer thickness of each of the first organic layer
7a and the second organic layer
7b may ordinarily fall
within the range of 0.25 μm to 10 μm. The layer thickness of each of
the first organic layer
7a and the second organic layer
7b
should preferably fall within the range of 0.3 μm to 7 μm, and
should more preferably fall within the range of 0.5 μm to 5 μm. If
the layer thickness of each of the first organic layer
7a and the
second organic layer
7b is smaller than 0.25 μm, for example,
holes will occur through the organic layer, and a uniform and smooth organic layer
cannot always be formed. Also, in such cases, a sufficient water vapor proof effect
cannot be obtained. If the layer thickness of each of the first organic layer
7a
and the second organic layer
7b is larger than 10 μm, good
image quality cannot always be obtained.
The layer thickness of the entire transparent protective layer
4 is at
most 50 μm. The layer thickness of the entire transparent protective layer
4 should preferably be at most 25 μm. If the layer thickness of the
entire transparent protective layer
4 is larger than 50 μm, good image
quality cannot always be obtained.
With the radiation image storage panel in accordance with the present invention,
the transparent protective layer comprises at least four layers formed on the transparent
protective layer support for supporting the transparent protective layer, the at
least four layers comprising the transparent inorganic layers and the organic layers,
which are located alternately. Therefore, with the radiation image storage panel
in accordance with the present invention, good water vapor proof performance is
capable of being obtained. In such cases, basically, it is sufficient for the transparent
protective layer to be overlaid on the stimulable phosphor layer. Specifically,
as in the first embodiment described above, the transparent protective layer
4
may be overlaid on the stimulable phosphor layer
3 such that the transparent
protective layer support
5 is in contact with the stimulable phosphor layer
3. Alternatively, the radiation image storage panel in accordance with the
present invention may be constituted as a radiation image storage panel
10
shown in FIG. 2, which constitutes a second embodiment of the radiation image storage
panel in accordance with the present invention. The radiation image storage panel
10 comprises a substrate
12. The radiation image storage panel
10
also comprises a stimulable phosphor layer
13, which contains a stimulable
phosphor, and a transparent protective layer
14, which are overlaid on the
substrate
12. Also, the transparent protective layer
14 comprises
a transparent protective layer support
15 for supporting the transparent
protective layer
14. The transparent protective layer
14 also comprises
a first transparent inorganic layer
16a, a first organic layer
17a,
a second transparent inorganic layer
16b, and a second organic layer
17b, which are overlaid in this order on the transparent protective
layer support
15. The transparent protective layer
14 is located
on the stimulable phosphor layer
13 such that the second organic layer
17b
is in contact with the stimulable phosphor layer
13. The radiation image
storage panel
10 may be modified such that a third transparent inorganic
layer is formed even further on the second organic layer
17b, and
the transparent protective layer
14 may be located on the stimulable phosphor
layer
13 such that the third transparent inorganic layer is in contact with
the stimulable phosphor layer
13.
The transparent protective layer of the radiation image storage panel in accordance
with the present invention may be formed in the manner described below. Specifically,
the transparent protective layer support is firstly formed on the stimulable phosphor
layer with an adhesion technique using an adhesive agent, or the like, or with
a reduced pressure lamination technique. The first transparent inorganic layer
is then formed on the transparent protective layer support with a vacuum deposition
technique, and the first organic layer is thereafter formed on the first transparent
inorganic layer with a coating technique or the vacuum deposition technique. Thereafter,
in the same manner as that described above, the second transparent inorganic layer
and the second organic layer are formed successively.
Alternatively, the transparent protective layer of the radiation image
storage panel in accordance with the present invention may be formed in the manner
described below. Specifically, after the transparent protective layer has been
prepared, the transparent protective layer is overlaid on the stimulable phosphor
layer. More specifically, the first transparent inorganic layer is formed on the
transparent protective layer support with the vacuum deposition technique, and
the first organic layer is then formed on the first transparent inorganic layer
with the coating technique or the vacuum deposition technique. Thereafter, in the
same manner as that described above, the second transparent inorganic layer and
the second organic layer are formed successively. In this manner, the transparent
protective layer is prepared. Thereafter, the transparent protective layer support
of the thus prepared transparent protective layer is adhered to the stimulable
phosphor layer by use of an adhesive agent, or the like. Alternatively, the organic
layer or the transparent inorganic layer, which constitutes the layer remotest
from the transparent protective layer support among the layers constituting the
transparent protective layer, may be combined with the stimulable phosphor layer
with the adhesion technique using an adhesive agent, or the like, or with the reduced
pressure lamination technique.
Each of the transparent inorganic layers may be a transparent evaporated layer
formed with a vacuum evaporation technique utilizing an inorganic material, which
exhibits no light absorption with respect to light having wavelengths falling within
the range of 300 nm to 1,000 nm and has gas barrier characteristics. Examples of
the inorganic materials, which exhibit no light absorption with respect to the
light having wavelengths falling within the range of 300 nm to 1,000 nm, include
silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, zirconium oxide,
tin oxide, silicon oxynitride, and aluminum oxynitride. Aluminum oxide and silicon
oxide may be subjected alone to the vacuum evaporation technique. However, in cases
where aluminum oxide and silicon oxide are subjected together to the vacuum evaporation
technique, the gas barrier characteristics are capable of being enhanced. Therefore,
in cases where aluminum oxide and silicon oxide are utilized for the formation
of the transparent inorganic layer, aluminum oxide and silicon oxide should preferably
be subjected together to the vacuum evaporation technique. Among the above-enumerated
inorganic materials, silicon oxynitride and aluminum oxynitride have a high light
transmittance and good gas barrier characteristics. Specifically, with silicon
oxynitride or aluminum oxynitride, a dense film free from cracks and micro-pores
is capable of being formed. Therefore, silicon oxynitride and aluminum oxynitride
are more preferable as the inorganic materials.
As described above, the transparent inorganic layer is formed directly on the
transparent protective layer support or the organic layer with the vacuum deposition
technique. In such cases, the transparent protective layer support or the organic
layer should preferably be free from fillers of at least 50 nm or having an aspect
ratio of at most 10. The vacuum deposition technique may be a sputtering technique,
a physical vapor deposition technique (i.e., the PVD technique), a chemical vapor
deposition technique (i.e., the CVD technique), or the like. With any of the above-enumerated
techniques, the transparency and the barrier characteristics of the obtained transparent
inorganic layer do not vary largely. Therefore, the vacuum deposition technique
may be selected appropriately from the above-enumerated techniques. However, from
the view point of easiness and simplicity of layer formation, the CVD technique
is preferable as the vacuum deposition technique. Particularly, a plasma enhanced
CVD technique (i.e., the PE-CVD technique), an ECR-PE-CVD technique, and the like,
are preferable.
The organic layer may be constituted of a transparent high-molecular weight material.
Examples of the transparent high-molecular weight materials include cellulose derivatives,
such as cellulose acetate and nitrocellulose; and synthetic high-molecular weight
materials, such as a polymethyl methacrylate, a polyvinyl butyral, a polyvinyl
formal, a polycarbonate, a polyvinyl acetate, a vinyl chloride-vinyl acetate copolymer,
a fluorine type of resin, a polyethylene, a polypropylene, a polyester, an acrylic
resin, a poly-para-xylene, a polyethylene terephthalate (PET), hydrochlorinated
rubber, and a vinylidene chloride copolymer. The above-enumerated synthetic high-molecular
weight materials for the formation of the organic layer may be utilized in the
form of the polymers. Alternatively, monomers for forming the above-enumerated
synthetic high-molecular weight materials may be utilized in order to form the
organic layer.
Such that the coating characteristics of the organic layer composition, the
vacuum evaporation characteristics of the organic layer composition, and the physical
properties of the thin film after being hardened may be enhanced, and such that
photosensitive properties may be imparted to the coating film, various additives
may be contained in the organic layer in accordance with the purposes. Examples
of the additives include various kinds of polymers and monomers having a hydroxyl
group; coloring agents, such as pigments and dyes; stabilizing agents, such as
anti-yellowing agents, age resistors, and ultraviolet light absorbers; thermal
acid generating agents; photosensitive acid generating agents; surface active agents;
solvents; crosslinking agents; hardening agents; and polymerization inhibitors.
The organic layer may be formed in the manner described below. Specifically,
a coating composition for the formation of the organic layer is prepared by mixing
together a polymer acting as a raw material or monomers acting raw materials, various
additives, and a solvent. The thus prepared coating composition for the formation
of the organic layer is applied onto the inorganic layer by use of coating means,
such as a doctor blade, a dip coater, a slide coater, or an extrusion coater. The
applied coating composition for the formation of the organic layer is then dried
and hardened. Alternatively, the organic layer may be formed with the vacuum deposition
technique as in the case of the organic layer.
The transparent protective layer support may be constituted of a plastic sheet
made from a PET, a polyurethane, a polyethylene naphthalate, a polyethylene, a
polypropylene, a polyvinylidene chloride, or a polyamide. The transparent protective
layer support may be prepared with the thin film formation using the raw material,
which is employed for the formation of the organic layer described above.
Such that the durability may be enhanced, and nonuniformity may be prevented
from occurring, the organic layer and the transparent protective layer support
of the radiation image storage panel in accordance with the present invention may
contain organic powder or inorganic powder. In such cases, the organic powder or
the inorganic powder may be contained in a proportion falling within the range
of 0.5% by weight to 60% by weight with respect to the weight of the organic layer,
and should preferably be contained in a proportion falling within the range of
approximately 5% by weight to approximately 50% by weight with respect to the weight
of the organic layer. The powder may exhibit light absorption with respect to the
light having wavelengths of a specific wavelength range and may be, for example,
ultramarine blue, or the like. However, ordinarily, white powder, which does not
exhibit specific light absorption with respect to the light having wavelengths
of 300 nm to 900 nm, is preferable. The mean particle diameter of the powder should
preferably fall within the range of approximately 0.01 μm to approximately
10 μm, and should more preferably fall within the range of approximately
0.3 μm to approximately 3 μm. Ordinarily, the particles have a certain
distribution of the particle size. The distribution of the particle size should
preferably be as narrow as possible.
In order for the transparent protective layer to be overlaid on the stimulable
phosphor layer, the side of the transparent protective layer support, the side
of the organic layer, or the side of the transparent inorganic layer of the transparent
protective layer may be combined with the stimulable phosphor layer in a dry atmosphere
by use of the adhesion technique using an adhesive agent or by use of the reduced
pressure lamination technique. In such cases, the transparent protective layer
should preferably be overlaid on the stimulable phosphor layer with reduced pressure
sealing. In cases where the reduced pressure sealing is utilized, peeling of the
transparent protective layer support, the organic layer, or the transparent inorganic
layer from the stimulable phosphor layer, particularly under a low atmospheric
pressure condition, is capable of being suppressed.
The adhesive agent for adhering the transparent protective layer support to the
stimulable phosphor layer or for adhering the organic layer to the stimulable phosphor
layer may be selected from a wide variety of adhesive agents. Examples of the adhesive
agents include a vinyl type of adhesive agent, an acrylic type of adhesive agent,
a polyamide type of adhesive agent, an epoxy type of adhesive agent, a rubber type
of adhesive agent, and a urethane type of adhesive agent.
Also, in order for water vapor absorption from side faces of the stimulable
phosphor layer to be prevented sufficiently, the side faces of the radiation image
storage panel should preferably be sealed with glass, an epoxy resin, a UV curing
resin, or a metal (a solder). Further, in order for deterioration of performance
due to water vapor absorption of the stimulable phosphor layer to be prevented
from occurring, the operations ranging from the taking of the radiation image storage
panel out of a vacuum evaporation tank (i.e., a vacuum evaporation machine) to
the sealing of the end faces of the radiation image storage panel should preferably
be performed in a vacuum, dry air, an inert gas, or a hydrophobic inert gas.
The stimulable phosphor, which constitutes the stimulable phosphor layer in the
radiation image storage panel in accordance with the present invention, should
preferably be, for example, a stimulable phosphor represented by Formula (I) shown
below, as described in Japanese Patent Publication No. 7(1995)-84588.
(M
1-f.M
If)X.bM
IIIX"
3:cA (I)
From the view point of the luminance of the light emitted by the stimulable
phosphor, in Formula (I) shown above, M
I should preferably be at least
one kind of alkali metal selected from the group consisting of Rb, Cs, Cs-containing
Na, and Cs-containing K, particularly at least one kind of alkali metal selected
from the group consisting of Rb and Cs. Also, M
III should preferably
be at least one kind of trivalent metal selected from the group consisting of Y,
La, Lu, Al, Ga, and In. Further, X" should preferably be at least one kind of halogen
selected from the group consisting of F, Cl, and Br. The value of b representing
the content of M
IIIX"
3 should preferably be selected from
the range of 0≦b≦10
-2.
Furthermore, in Formula (I) shown above, A acting as the activator should
preferably be at least one kind of metal selected from the group consisting of
Eu, Tb, Ce, Tm, Dy, Ho, Gd, Sm, Tl, and Na, particularly at least one kind of metal
selected from the group consisting of Eu, Ce, Sm, Tl, and Na. Also, from the view
point of the luminance of the light emitted by the stimulable phosphor, the value
of c representing the quantity of the activator should preferably be selected from
the range of 10
-6<c<0.1.
Examples of the other stimulable phosphors, which may also be employed in
the radiation image storage panel in accordance with the present invention, include
the following:
a phosphor represented by the formula SrS:Ce, Sm; SrS:Eu, Sm; ThO
2:Er;
or La
2O
2S:Eu, Sm, as described in U.S. Pat. No. 3,859,527,
a phosphor represented by the formula ZnS:Cu, Pb; BaO.xAl
2O
3:Eu
wherein 0.8≦x≦10; M
IIO.xSiO
2:A wherein M
II
is Mg, Ca, Sr, Zn, Cd, or Ba, A is Ce, Tb, Eu, Tm, Pb, Tl, Bi, or Mn, and
x is a number satisfying 0.5≦x≦2.5; or LnOX:xA wherein Ln is at least
one of La, Y, Gd, and Lu, X is at least one of Cl and Br, A is at least one of
Ce and Tb, x is a number satisfying 0<x<0.1, as disclosed in U.S. Pat.
No. 4,236,078,
a phosphor represented by the formula (Ba
1-x-y,Mg
x,Ca
y)FX:aEu
2+
wherein X is at least one of Cl and Br, x and y are numbers satisfying 0<x+y≦0.6
and xy≠0, and a is a number satisfying 10
-6≦a≦5×10
-2,
as disclosed in DE-OS No. 2,928,245,
a phosphor represented by the formula (Ba
1-x,M
2+x)FX:yA
wherein M
2+ is at least one of Mg, Ca, Sr, Zn, and Cd, X is at least
one of Cl, Br, and I, A is at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb,
and Er, x is a number satisfying 0≦x≦0.6, and y is a number satisfying
0≦y≦0.2, as disclosed in U.S. Pat. No. 4,239,968,
a phosphor represented by the formula M
IIFX.xA:yLn wherein M
II
is at least one of Ba, Ca, Sr, Mg, Zn, and Cd, A is at least one of BeO,
MgO, CaO, SrO, BaO, ZnO, Al
2O
3, Y
2O
3,
La
2O
3, In
2O
3, SiO
2, TiO
2,
ZrO
2, GeO
2, SnO
2, Nb
2O
5,
Ta
2O
5, and ThO
2, Ln is at least one of Eu, Tb,
Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sm, and Gd, X is at least one of Cl, Br, and I,
x is a number satisfying 5×10
-5≦x≦0.5, and y is a
number satisfying 0<y≦0.2, as described in Japanese Unexamined Patent
Publication No. 55(1980)-160078,
a phosphor represented by the formula (Ba
1-xM
IIx)F
2.aBaX
2:yEu,zA
wherein M
II is at least one of beryllium, magnesium, calcium, strontium,
zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, A is at
least one of zirconium and scandium, a is a number satisfying 0.5≦a≦1.25,
x is a number satisfying 0≦x≦1, y is a number satisfying 10
-6≦y≦2×10
-1,
and z is a number satisfying 0<z≦10
-2, as described in Japanese
Unexamined Patent Publication No. 56(1981)-116777,
a phosphor represented by the formula (Ba
1-x,M
IIx)F
2.aBaX
2:yEu,
zB wherein M
II is at least one of beryllium, magnesium, calcium, strontium,
zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, A is a number
satisfying 0.5≦a≦1.25, x is a number satisfying 0≦x≦1,
y is a number satisfying 10
-6≦y≦2×10
-1,
and z is a number satisfying 0<z≦10
-2, as described in Japanese
Unexamined Patent Publication No. 57(1982)-23673,
a phosphor represented by the formula (Ba
1-x,M
IIx)F
2.aBaX
2:yEu,zA
wherein M
II is at least one of beryllium, magnesium, calcium, strontium,
zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, A is at
least one of arsenic and silicon, a is a number satisfying 0.5≦a≦1.25,
x is a number satisfying 0≦x≦1, y is a number satisfying 10
-6≦y≦2×10
-1,
and z is a number satisfying 0<z≦5×10
-1, as described
in Japanese Unexamined Patent Publication No. 57(1982)-23675,
a phosphor represented by the formula M
IIIOX:xCe wherein M
III
is
at least one trivalent metal selected from the group consisting of Pr, Nd, Pm,
Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Bi, X is either one or both of Cl and Br, and
x is a number satisfying 0<x<0.1, as described in Japanese Unexamined
Patent Publication No. 58(1983)-69281,
a phosphor represented by the formula Ba
1-xM
x/2L
x/2FX:yEu
2+
wherein M is at least one alkaline metal selected from the group consisting of
Li, Na, K, Rb, and Cs, L is at least one trivalent metal selected from the group
consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al,
Ga, In, and Tl, X is at least one halogen selected from the group consisting of
Cl, Br, and I, x is a number satisfying 10
-2≦x≦0.5, and
y is a number satisfying 0<y≦0.1, as described in Japanese Unexamined
Patent Publication No. 58(1983)-206678,
a phosphor represented by the formula BaFX.xA:yEu
2+ wherein X is at
least one halogen selected from the group consisting of Cl, Br, and I, A is a calcination
product of a tetrafluoro boric acid compound, x is a number satisfying 10
-6≦x≦0.1,
and y is a number satisfying 0<y≦0.1, as described in Japanese Unexamined
Patent Publication No. 59(1984)-27980,
a phosphor represented by the formula BaFX.xA:yEu
2+ wherein X is at
least one halogen selected from the group consisting of Cl, Br, and I, A is a calcination
product of at least one compound selected from the hexafluoro compound group consisting
of salts of hexafluoro silicic acid, hexafluoro titanic acid, and hexafluoro zirconic
acid with monovalent or bivalent metals, x is a number satisfying 10
-6≦x≦0.1,
and y is a number satisfying 0<y≦0.1, as described in Japanese Unexamined
Patent Publication No. 59(1984)-47289,
a phosphor represented by the formula BaFX.xNaX′:aEu
2+ wherein
each of X and X′ is at least one of Cl, Br, and I, x is a number satisfying
0<x≦2, and a is a number satisfying 0<a≦0.2, as described
in Japanese Unexamined Patent Publication No. 59(1984)-56479,
a phosphor represented by the formula M
IIFX.xNaX′:yEu
2+:zA
wherein M
II is at least one alkaline earth metal selected from the group
consisting of Ba, Sr, and Ca, each of X and X′ is at least one halogen selected
from the group consisting of Cl, Br, and I, A is at least one transition metal
selected from the group consisting of V, Cr, Mn, Fe, Co, and Ni, x is a number
satisfying 0<x ≦2, y is a number satisfying 0<y≦0.2, and
z is a number satisfying 0<z≦10
-2, as described in Japanese
Unexamined Patent Publication No. 59(1984)-56480,
a phosphor represented by the formula M
IIFX.aM
IX′.bM′
IIX"
2.cM
IIIX"′
3.xA:yEu
2+
wherein M
II is at least one alkaline earth metal selected from the group
consisting of Ba, Sr, and Ca, M
I is at least one alkali metal selected
from the group consisting of Li, Na, K, Rb, and Cs, M′
II is at
least one bivalent metal selected from the group consisting of Be and Mg, M
III
is at least one trivalent metal selected from the group consisting of Al,
Ga, In, and Tl, A is a metal oxide, X is at least one halogen selected from the
group consisting of Cl, Br, and I, each of X′, X", and X"′ is at
least one halogen selected from the group consisting of F, Cl, Br, and I, a is
a number satisfying 0≦a≦2, b is a number satisfying 0≦b≦10
-2,
c is a number satisfying 0≦c≦10
-2, and a+b+c≧10
-6,
x is a number satisfying 0<x≦0.5, and y is a number satisfying 0<y≦0.2,
as described in Japanese Unexamined Patent Publication No. 59(1984)-75200,
a stimulable phosphor represented by the formula M
IIX
2.aM
IIX′
2:xEu
2+
wherein M
II is at least one alkaline earth metal selected from the group
consisting of Ba, Sr, and Ca, each of X and X′ is at least one halogen selected
from the group consisting of Cl, Br, and I, and X≠X′, a is a number
satisfying 0.1≦a≦10.0, and x is a number satisfying 0<x≦0.2,
as described in Japanese Unexamined Patent Publication No. 60(1985)-84381,
a stimulable phosphor represented by the formula M
IIFX.aM
IX′:xEu
2+
wherein M
II is at least one alkaline earth metal selected from the group
consisting of Ba, Sr, and Ca, M
I is at least one alkali metal selected
from the group consisting of Rb and Cs, X is at least one halogen selected from
the group consisting of Cl, Br, and I, X′ is at least one halogen selected
from the group consisting of F, Cl, Br, and I, a is a number satisfying 0≦a≦4.0,
and x is a number satisfying 0<x≦0.2, as described in Japanese Unexamined
Patent Publication No. 60(1985)-101173,
a stimulable phosphor represented by the formula M
IX:xBi wherein M
I
is at least one alkali metal selected from the group consisting of Rb and
Cs, X is at least one halogen selected from the group consisting of Cl, Br, and
I, and x is a number falling within the range of 0<x≦0.2, as described
in Japanese Unexamined Patent Publication No. 62(1987)-25189, and
a cerium activated rare earth element oxyhalide phosphor represented by the formula
LnOX:xCe wherein Ln is at least one of La, Y, Gd, and Lu, X is at least one of
Cl, Br, and I, x is a number satisfying 0<x≦0.2, the ratio of X to
Ln, expressed in terms of the atomic ratio, falls within the range of 0.500<X/Ln≦0.998,
and a maximum wavelength λ of the stimulation spectrum falls within the range
of 550 nm<λ<700 nm, as described in Japanese Unexamined Patent
Publication No. 2(1990)-229882.
The stimulable phosphor represented by the formula M
IIX
2.aM
IIX′
2:xEu
2+,
which is described in Japanese Unexamined Patent Publication No. 60(1985)-84381,
may contain the additives described below in the below-mentioned proportions per
mol of M
IIX
2.aM
IIX′
2:
bM
IX" wherein M
I is at least one alkali metal
selected from the group consisting of Rb and Cs, X" is at least one halogen selected
from the group consisting of F, Cl, Br, and I, and b is a number satisfying 0<b≦10.0,
as described in Japanese Unexamined Patent Publication No. 60(1985)-166379,
bKX".cMgX
2.dM
IIIX′
3
wherein M
III is at least one trivalent metal selected from the group
consisting of Sc, Y, La, Gd, and Lu, each of X", X, and X′ is at least one
halogen selected from the group consisting of F, Cl, Br, and I, b is a number satisfying
0≦b≦2.0, c is a number satisfying 0≦c≦2.0, d is a number
satisfying 0≦d≦2.0, and 2×10
-5≦b+c+d, as described
in Japanese Unexamined Patent Publication No. 60(1985)-221483,
yB wherein y is a number satisfying 2×10
-4≦y≦2×10
-1,
as described in Japanese Unexamined Patent Publication No. 60(1985)-228592,
bA wherein A is at least one oxide selected from the group consisting of SiO
2
and P
2O
5, and b is a number satisfying 10
-4≦b≦2×10
-1,
as described in Japanese Unexamined Patent Publication No. 60(1985)-228593,
bSiO wherein b is a number satisfying 0<b≦3×10
-2,
as described in Japanese Unexamined Patent Publication No. 61(1986)-120883,
bSnX"
2 wherein X" is at least one halogen selected from
the group consisting of F, Cl, Br, and I, and b is a number satisfying 0<b≦10
-3,
as described in Japanese Unexamined Patent Publication No. 61(1986)-120885,
bCsX".cSnX
2 wherein each of X" and X is at least
one halogen selected from the group consisting of F, Cl, Br, and I, b is a number
satisfying 0<b≦10.0, and c is a number satisfying 10
-6≦c≦2×10
-2,
as described in Japanese Unexamined Patent Publication No. 61(1986)-235486, and
bCsX".yLn
3+ wherein X" is at least one halogen
selected from the group consisting of F, Cl, Br, and I, Ln is at least one rare
earth element selected from the group consisting of Sc, Y, Ce, Pr, Nd, Sm, Gd,
Tb, Dy, Ho, Er, Tm, Yb, and Lu, b is a number satisfying 0<b≦10.0,
and y is a number satisfying 10
-6≦y≦1.8×10
-1,
as described in Japanese Unexamined Patent Publication No. 61(1986)-235487.
Of the above-enumerated stimulable phosphors, the bivalent europium activated
alkaline earth metal fluorohalide phosphor (e.g., BaFI:Eu), the europium activated
alkali metal halide phosphor (e.g., CsBr:Eu), the bivalent europium activated alkaline
earth metal halide phosphor containing iodine, the rare earth element-activated
rare earth element oxyhalide phosphor containing iodine, and the bismuth activated
alkali metal halide phosphor containing iodine exhibit light emission with a high
luminance and therefore are preferable. The phosphors described above are capable
of taking one the form of an acicular crystal and therefore are apt to have the
problems with regard to the water vapor absorption. Accordingly, in cases where
the transparent protective layer of the radiation image storage panel in accordance
with the present invention is employed, the water vapor proof characteristics are
capable of being efficiently imparted with respect to the phosphor described above.
The stimulable phosphor layer may be overlaid on the substrate with a known technique,
such as the vacuum evaporation technique, the sputtering technique, or the coating technique.
With the vacuum evaporation technique, the substrate is located within a vacuum
evaporation apparatus, and the vacuum evaporation apparatus is then evacuated to
a degree of vacuum of approximately 10
-4 Pa. Thereafter, at least one
kind of stimulable phosphor is heated and evaporated with a resistance heating
technique, an electron beam technique, or the like, and a layer of the stimulable
phosphor is deposited to a desired thickness on the surface of the substrate. In
this manner, the stimulable phosphor layer containing no binder is capable of being
formed on the substrate. The vacuum evaporation process may be performed in a plurality
of stages in order to form the stimulable phosphor layer. Also, in the vacuum evaporation
process, a plurality of constituents for a desired stimulable phosphor may be co-evaporated
by use of a plurality of resistance heaters or a plurality of electron beams. In
this manner, the desired stimulable phosphor may be synthesized on the substrate,
and the stimulable phosphor layer may thereby be formed on the substrate. After
the vacuum evaporation process has been finished, the formed stimulable phosphor
layer may be subjected to heat treatment.
With the sputtering technique, in the same manner as that in the vacuum evaporation
technique, the substrate is located within a sputtering apparatus, and the sputtering
apparatus is then evacuated to a degree of vacuum of approximately 10
-4 Pa.
Thereafter, an inert gas, such as an Ar gas or a Ne gas, acting as the gas for
the sputtering is introduced into the sputtering apparatus, and the gas pressure
in the sputtering apparatus is set at approximately 10
-1 Pa. Thereafter,
sputtering is performed with the stimulable phosphor being set as a target, and
the stimulable phosphor is thereby deposited to a desired thickness on the surface
of the substrate. As in the cases of the vacuum evaporation process, the sputtering
process may be performed in a plurality of stages in order to form the stimulable
phosphor layer on the substrate. Also, a plurality of targets constituted of different
stimulable phosphors may be utilized and simultaneously or successively subjected
to the sputtering in order to form the stimulable phosphor layer. Further, in the
sputtering technique, when necessary, a gas, such as an O
2 gas, an H
2
gas, or a halogen gas, may be introduced into the sputtering apparatus, and
a reactive sputtering process may thereby be performed. After the sputtering process
has been finished, the formed stimulable phosphor layer may be subjected to heat treatment.
With the coating technique, the stimulable phosphor, a binder, and a solvent
are intimately mixed together. In this manner, a coating composition, in which
the stimulable phosphor has been dispersed uniformly in the binder solution, is
prepared. Thereafter, the coating composition is uniformly applied onto the surface
of the substrate. In this manner, a coating film is formed on the surface of the
substrate. The operation for applying the coating composition onto the substrate
may be performed by utilizing ordinary coating means, such as a doctor blade coater,
a roll coater, or a knife coater.
As the binder utilized in the stimulable phosphor layer of the radiation image
storage panel in accordance with the present invention, a thermoplastic elastomer,
which has elasticity at normal temperatures and which exhibits fluidity when being
heated, should preferably be employed. Examples of the thermoplastic elastomers
include a polystyrene, a polyolefin, a polyurethane, a polyester, a polyamide,
a polybutadiene, an ethylene-vinyl acetate copolymer, a polyvinyl chloride, natural
rubber, fluorine rubber, a polyisoprene, a chlorinated polyethylene, a styrene-butadiene
rubber, and silicone rubber. As the elastomer, ordinarily, an elastomer having
a softening temperature or a melting temperature falling within the range of 30°
C. to 300° C. is ordinarily employed. An elastomer having a softening temperature
or a melting temperature falling within the range of 30° C. to 200° C.
is more preferable. An elastomer having a softening temperature or a melting temperature
falling within the range of 30° C. to 150° C. is most preferable.
Examples of the solvents include lower alcohols, such as methyl alcohol,
ethyl alcohol, n-propyl alcohol, n-butyl alcohol, and diacetone alcohol; ketones,
such as acetone, methyl ethyl ketone, methyl isopropyl ketone, and cyclohexanone;
esters of lower fatty acids with lower alcohols, such as methyl acetate, ethyl
acetate, and butyl acetate; ethers, such as ethylene glycol monopropyl ether; hydrocarbons,
such as toluene, xylene, and cyclohexane; and mixtures of two or more of the above-enumerated solvents.
The mixing ratio of the binder to the stimulable phosphor in the coating composition
varies for different characteristics desired for the radiation image storage panel,
different kinds of the phosphors, and the like. Ordinarily, the mixing ratio of
the binder to the stimulable phosphor is selected from the range between 1:1 and
1:100 (weight ratio). The mixing ratio of the binder to the stimulable phosphor
should preferably be selected from the range between 1:8 and 1:40 (weight ratio).
The substrate may be constituted of a material selected from various kinds of
materials known as substrates for conventional radiation image storage panels.
In the conventiona
