JP3269857B2 - Manufacturing method of radiation image conversion panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a radiation image conversion panel having a stimulable phosphor layer.

[0002]

2. Description of the Related Art In the medical field, for example, radiation images such as X-ray images are often used for diagnosing diseases. As a method of forming such a radiation image, conventionally, X-rays transmitted through a subject are irradiated on a phosphor layer (fluorescent screen) to generate visible light, and this visible light is used in the same manner as when a normal photograph is taken. The so-called radiographic method of irradiating and developing a film using a silver salt has been generally used.

However, in recent years, as a method of directly taking out an image from a phosphor layer without using a film coated with a silver salt, radiation that has passed through a subject is absorbed by the phosphor, and then the phosphor is irradiated with light or heat, for example. A method has been proposed in which, by excitation with energy, radiation energy absorbed and accumulated in the phosphor is emitted as fluorescence, and the fluorescence is detected and imaged.

For example, US Pat. No. 3,859,527 and JP-A-55-12144 show a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulating excitation light. ing. In this method, a radiation image conversion panel having a stimulable phosphor layer formed on a substrate is used. A latent image is formed by accumulating radiation energy corresponding to the radiation transmittance of each part, and then the radiation energy accumulated in each part is stimulated by scanning the stimulable phosphor layer with stimulating excitation light. The light is emitted as light emission, and an optical signal based on the intensity of the light is photoelectrically converted, for example, and is imaged by an image reproducing apparatus. This final image is reproduced as a hard copy or on a CRT.

[0005] However, the stimulable phosphor generally exhibits the phenomenon of so-called "afterglow" in which the phosphor continues to emit fluorescence even after the excitation is stopped. Therefore, afterglow mixes with the fluorescence to be detected in the radiation image conversion panel, and when the amount of residual light is large, there is a problem that the SN ratio of the radiation image is reduced. Conventionally, a technique using an oxygen-containing alkali halide phosphor has been proposed to reduce the residual light amount of the stimulable phosphor (Japanese Patent Application No. 60-2975).
No. 16).

[0006]

However, in the above prior art, since an oxygen compound is added during the formation of the stimulable phosphor layer, the stimulable phosphor layer is formed by a preferable vapor deposition method. In this case, the vapor deposition apparatus is liable to be contaminated, and the difference in vapor pressure is likely to cause a non-uniform concentration in the film thickness direction. Further, the oxygen compound is separated by a subsequent heat treatment to sufficiently reduce the residual light amount. There is a problem that can not be. Further, after forming a stimulable phosphor layer or a base layer thereof on a substrate, a method of adding an oxygen compound by heat treatment in an atmosphere containing an oxygen compound may be considered. The particles of the oxygen compound do not sufficiently enter the gaps between the phosphors, and the crystals of the phosphor are fused to each other during the heat treatment, so that the area constituting the light-emitting unit becomes large. Decrease.

Accordingly, an object of the present invention is to provide a method capable of manufacturing a radiation image conversion panel having high image sharpness.

[0008]

According to the present invention, there is provided a method for producing a radiation image conversion panel having a stimulable phosphor layer, the method comprising: forming a stimulable phosphor layer formed on a substrate by a vapor deposition method; Alternatively, the method includes a step of applying a coating liquid for forming a coating made of an oxide or a fluoride by heat treatment to the base layer, drying the coating liquid , and then performing a heat treatment .

[0009]

In such a method, in the stimulable phosphor layer or its base layer, the coating liquid for forming a film enters into the gaps between the phosphor crystals, so that the phosphor crystals are mutually separated during the heat treatment. Fusing is prevented, and a radiation image conversion panel with high image sharpness is obtained. In addition, a radiation image conversion panel with a small amount of residual light can be obtained depending on the type of the film formed by the heat treatment.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a coating solution for forming a film made of an oxide or a fluoride by heat-treating a plate having a stimulable phosphor layer or its base layer formed on a substrate is subjected to heat treatment. Apply and dry , then
Heat treatment .

The coating solution for forming a film is composed of a film-forming substance for forming an oxide or fluoride film by heat treatment, and a medium for dissolving the film-forming substance or a medium for dispersing the film-forming substance.

As a medium of the coating solution for forming a film, a medium which does not easily dissolve the stimulable phosphor layer or the phosphor constituting the base layer thereof is preferable. For example, an organic solvent such as xylene, ethanol, methanol, isopropyl alcohol or acetone is preferable. A system medium or a mixture thereof is preferred.

Specific examples of the film-forming substance include metal oxides, metal fluorides, silicon oxides, organosilicon compounds, and organometallic compounds such as metal alkoxides. In particular, it is preferable that the formed film has heat resistance and does not cause oxidation or reaction with the phosphor during the heat treatment, and specifically, the film is formed of Al ₂ O ₃ ,
It is preferable to be made of TiO ₂ , ZrO ₂ , SiO ₂ , MgF, a compound containing them, or a mixture thereof.

The volume concentration of the film forming substance in the coating solution for forming a film is preferably 10% or less. When the volume concentration of the film-forming substance exceeds 10%, the film formed on the stimulable phosphor layer or the base layer thereof becomes too thick due to the heat treatment, and the light transmittance of the film is lowered. Radiation sensitivity decreases. Further, the coating liquid for forming a coating film preferably has a viscosity of less than 50 cP at 20 ° C. When the viscosity is 50 cP or more, the coating liquid for forming a film does not sufficiently enter the gaps between the phosphor crystals during coating. Further, in the coating liquid for forming a film, the degree of dispersion of the film forming substance (the ratio of aggregated particles to all particles) is preferably 30% or less, and the size of the particles of the film forming substance (unaggregated particles) is preferably Preferably, the size of the aggregated particles is 100 nm or less and the size of the aggregated particles is 500 nm or less.

Examples of the method of applying the coating solution include an impregnating pull-coating method, a spin coating method, a spray coating method, and a doctor blade coating method. In particular, when the phosphor is a columnar crystal, the impregnating pull-coating method is used. Alternatively, it is preferable to use a spin coating method.

In the case of coating by the impregnation pull-up coating method, bubbles are generated immediately after the coating liquid is impregnated into the phosphor layer. It is preferable to raise after confirming. The pulling is preferably performed in a range where the pulling speed is 1 cm / min to 50 cm / min. When the pulling speed is less than 1 cm / min, the film formed by the heat treatment becomes too thick or the film thickness becomes non-uniform. When the pulling speed exceeds 50 cm / min, the coating liquid does not sufficiently enter the gaps between the phosphor crystals. In addition, it may be effective to apply ultrasonic waves to the coating liquid in order to sufficiently allow the coating liquid to enter the gaps between the phosphor crystals. Furthermore, when the stimulable phosphor layer or its base layer is formed by oblique deposition, the columnar crystals of the phosphor are inclined with respect to the normal direction of the substrate, so that the crystals are applied in a state of facing upward. It is preferable that the coating liquid is immersed in the liquid, so that the coating liquid can sufficiently enter the gaps between the phosphor crystals.

FIG. 6 is an explanatory view showing a state in which a coating liquid for forming a film is applied to a stimulable phosphor layer formed by an oblique vapor deposition method. The stimulable phosphor layer 19 formed on the substrate 18 is composed of columnar crystals 41 inclined with respect to the normal direction of the substrate 18, and the surface 4 of the stimulable phosphor layer 19 is formed.
A coating liquid 44 for forming a film is applied to the gap 43 between the second crystal 41 and the columnar crystal 41.

In the case of coating by spin coating, the rotation speed of the spinner is preferably, for example, 100 rpm to 3000 rpm. Further, when the stimulable phosphor layer or its base layer is formed by an oblique deposition method, since the phosphor crystals have an inclination with respect to the normal direction of the substrate, the crystals are oriented in the rotation axis direction. It is preferable that the coating liquid be sufficiently introduced into the gaps between the phosphor crystals. Furthermore, by applying under reduced pressure, gas in the gap between the crystals is evacuated, and the coating liquid can be made to penetrate deeper.

In order for the coating liquid for forming a film to sufficiently enter the gaps between the phosphor crystals, dust applied to the fluorescent layer by nitrogen blow or the like before applying the coating liquid for forming a film must be removed. It is preferable to perform a treatment for removing dust and the like or a treatment for removing organic substances and moisture adsorbed on the crystal surface of the phosphor by a heat treatment at a temperature of 100 ° C. or more. It is preferable to work in a clean room so that foreign matter does not adhere to the phosphor layer. For the same reason, it is preferable that the application is performed in several steps, and after the application, a defoaming treatment (such as a reduced pressure heat treatment at 100 ° C. or more) is performed. Furthermore, after the application, in order to obtain a panel having high radiation sensitivity, it is preferable to remove the coating solution applied on the surface of the stimulable phosphor layer or the base layer thereof by blasting or the like. FIG. 7 is an explanatory diagram showing a state in which the coating liquid for forming a film on the surface of the stimulable phosphor layer has been removed. As shown in this figure, the gap 4 between the columnar crystals 41
In 3, the coating liquid 44 for forming a film is left as applied.

It is preferable that the formed film has a light transmittance of 90% or more. If the light transmittance of the coating is less than 90%, the transmittance of stimulated emission decreases, and the radiation sensitivity of the obtained panel decreases. For the same reason, the thickness of the coating is preferably, for example, 3 μm or less.

The drying treatment of the plate after the application of the coating solution for forming a film is a process of evaporating the medium of the coating solution for forming a film, which causes an abnormality in the stimulable phosphor layer and the like by a subsequent heat treatment. Can be prevented.
Therefore, the drying treatment is preferably performed at a drying temperature of 150 ° C. or lower.

The heat treatment includes forming a film, sensitizing the crystal of the stimulable phosphor to heat, modifying the film with an activator and an oxygen compound, and annealing the crystal for disturbing the formation of the stimulable phosphor. Is what you do. These can be performed simultaneously in one heat treatment depending on the atmosphere containing the activator and the oxygen compound, or can be performed under different conditions by several heat treatment steps. In the case where the layer formed on the substrate is a stimulable phosphor layer and the film formed by the heat treatment is an oxide, the heat treatment can be performed in an atmosphere containing no activator and oxygen compound. .

FIG. 1 shows a heat treatment apparatus which can be used for heat treatment. Reference numeral 1 denotes a plate, on which a stimulable phosphor layer 1B is formed on a substrate 1A. The phosphor crystals constituting the stimulable phosphor layer 1B are covered with the film-forming substance. 2 is a heat treatment vessel, 3 is a heat treatment vessel heater, 4 is a heat treatment furnace, 5 is an evaporation vessel heater, 6
Denotes an evaporation container, 7 denotes atmosphere powder, and 8 denotes a gas amount adjusting valve. Here, the atmosphere powder refers to a powder containing an activator and an oxygen compound.

At the time of heat treatment, the plate 1 to be heat-treated is placed in the heat treatment vessel 2 and the atmosphere powder 7 is placed in the evaporation vessel 6. Thereafter, the heat treatment container 2 and the evaporation container 6 are heated to a predetermined temperature by the heat treatment container heater 3 and the evaporation container heater 5, and then the gas amount adjusting valve 8 is gradually opened to release the activator and the oxygen compound gas. It diffuses into the heat treatment container 2. The gas diffusion amount of the activator and the oxygen compound is determined by the heating temperature of the evaporation container 6, the temperature difference between the heat treatment container 2 and the evaporation container 6, the degree of opening of the gas amount adjusting valve 8, and the like. The heat treatment temperature T of the plate 1 is
Although it depends on the type of the stimulable phosphor, it is preferably lower than the melting point Tm [° C.] of the stimulable phosphor matrix, and 0.25 T
The range of m <T <Tm is preferable. After the heat treatment,
Plate 1 is cooled to room temperature at a predetermined rate. According to the above-described method, a film is formed, and at the same time, thermal sensitization to the crystal of the stimulable phosphor, modification with an activator and an oxygen compound, and Annealing for crystal disorder is performed. Before the heating, the inside of the heat treatment container 2 and the inside of the evaporation container 6 may be evacuated by evacuating the inside of the heat treatment container 2 and the inside of the evaporation container 6.

FIG. 2 shows another example of a heat treatment apparatus that can be used for the heat treatment. Reference numeral 9 denotes an atmosphere powder of an activator and an oxygen compound, and reference numeral 10 denotes a heat treatment container. In this heat treatment apparatus, a plate 1 to be thermally sensitized and an atmosphere powder 9 of an activator and an oxygen compound coexist in a heat treatment container 10. By using the atmosphere powder 9, the concentrations of the activator and the oxygen compound in the plate 1 can be easily adjusted.

The concentrations of the activator and the oxygen compound in the atmosphere powder 9 differ depending on the conditions of the heat treatment, but are preferably substantially equal to or higher than the concentration of the activator in the stimulable phosphor of the plate 1. However, in the case where the layer formed on the substrate is a stimulable phosphor layer and the film formed by the heat treatment is an oxide, the heat treatment can be performed in an atmosphere containing no activator and oxygen compound. . Further, the heat treatment temperature T of the plate 1 is set to the melting point Tm [° C.] of the stimulable phosphor matrix as in the case of using the apparatus of FIG.
It is preferably lower, and more preferably in the range of 0.25 Tm <T <Tm.

FIG. 3 shows still another example of a heat treatment apparatus which can be used for heat treatment, in which heat treatment is performed by an ion implantation method. In the ion source section 11,
The required activator and oxygen compound ions are generated from the activator and oxygen compound solid or a gas such as chloride or hydride thereof. The generated ions are extracted by the extraction electrode 12, and the acceleration section selects and accelerates energy according to the setting of the average projection range and the distribution of the activator and the oxygen compound. The mass analyzer 13 takes out ions having the required energy and mass, and further deflects x
The plate 16 which has been uniformly heat-treated by the heater 17 attached to the sample chamber 15 by sweeping the ion beam uniformly in the −y direction.
Irradiate uniformly on top. At this time, it is important to incline the surface of the plate 16 by about 7 to 8 degrees with respect to the beam direction in order to avoid ion penetration into the tunnel called channeling. The vacuum degree of the heat treatment apparatus is generally about 1 × 10 ^-8 Torr in the ion source unit 11 is set to 10 ^-7 Torr table in the specimen chamber 15.

The activator for heat treatment includes Eu compounds, Tb compounds, Ce compounds, Tm compounds, D
y compound group, Pr compound group, Ho compound group, Nd compound group, Yb compound group, Er compound group, Gd compound group, Lu
Compound group, Sm compound group, Y compound group, Tl compound group,
At least one of a Na compound group, an Ag compound group, a Cu compound group, an In compound group, and a Mg compound group is used.

As the oxygen compound, SiO 2_Two, MgO,
Al_TwoO_Three, TiO_Two, ZrO_TwoCeramics, glass, etc.
Acids, carbonic acids or their compounds are preferred. these
Oxygen compounds may be used in appropriate combination. Nitric acid compound
As RbNO_Three, TlNO_Three, Pb (NO
_Three )_Two, CsNO _ThreeAre used. As carbonate compound
Is Na_TwoCO_Three, BaCO_Three, SrCO_Three, Pb_TwoC
O_Three, Cs_TwoCO_ThreeAre used.

When ceramics is used as the oxygen compound, the amount of the powder used is 0.
It is preferably at least 01% by weight, particularly preferably at least 0.2% by weight.

When a compound such as nitric acid is used as the oxygen compound, the amount of the compound is preferably 0.5 mol or less, more preferably 10 ^{-6 to} 0.2 mol, per mol of the atmosphere powder. In particular, nitric acid or a compound thereof is excellent in the effect of reducing afterglow, and can sufficiently reduce afterglow with a small amount of addition. In addition, since it is less hygroscopic than carbonic acid or its compound, it is easy to handle.

As a method of forming the stimulable phosphor layer or its base layer to be subjected to the heat treatment, a stimulable phosphor layer and an activator layer are separately provided on a substrate by a vapor deposition method, and thereafter, A method in which a heat treatment is applied to thermally diffuse an activator into a stimulable phosphor layer. A base layer is formed on a substrate by a vapor deposition method, and then an activator separately prepared for the base layer is diffused. And a method of obtaining a stimulable phosphor layer by adding the stimulable phosphor layer by ion implantation or the like. Here, the “base layer” refers to a stimulable phosphor layer containing no activator. Examples of the vapor deposition method include a vapor deposition method, a sputtering method, a CVD method, and an ion plating method.

In one example in which the stimulable phosphor layer is formed by a vapor deposition method, after the substrate is placed in a vapor deposition apparatus,
The inside of the vapor deposition apparatus is evacuated to a vacuum degree of, for example, about 10 ^-6 Torr. Next, the evaporation source provided with the stimulable phosphor material is arranged at a predetermined position, and the stimulable phosphor material is heated and evaporated using a resistance heater or an electron beam, and the vapor flow is applied to the substrate. The stimulable phosphor is deposited to a predetermined thickness on the deposition surface. In the vapor deposition step, the stimulable phosphor layer can be formed in a plurality of times. Further, at the time of vapor deposition, the substrate may be cooled or heated as necessary.

In an example in which a stimulable phosphor layer is formed by a sputtering method, a substrate is placed in a sputtering apparatus in the same manner as in a vapor deposition method, and then the apparatus is once evacuated to about 10 ^-6 Torr. The degree of vacuum is set, and then, an inert gas such as Ar or Ne is introduced as a gas for sputtering to a gas pressure of, for example, about 10 ^-3 Torr. Next, the stimulable phosphor is deposited to a predetermined thickness on the surface of the substrate by sputtering using the plurality of stimulable phosphors as targets. Also in this sputtering process,
It is also possible to form the stimulable phosphor layer a plurality of times in the same manner as in the vapor deposition method. At the time of sputtering, the substrate may be cooled or heated as necessary.

In the step of forming the stimulable phosphor layer by the vapor deposition method, the deposition rate of the stimulable phosphor layer is 0.1 to 50 μm.
/ Min is preferred. If the deposition rate is too low, the productivity will be low, and if the deposition rate is too high, it will be difficult to control the deposition rate. Further, in the step of forming the stimulable phosphor layer by the vapor deposition method, the temperature of the substrate is preferably 400 ° C. or lower from the viewpoint of preventing the sharpness of the image from being lowered due to the progress of crystallization. The thickness of the stimulable phosphor layer depends on the radiation sensitivity of the intended radiation image conversion panel, the type of the stimulable phosphor, etc., but from the viewpoint of preventing a decrease in radiation sensitivity due to a decrease in radiation absorption, It is preferably from 30 to 1000 μm, particularly preferably from 50 to 500 μm.

In the present invention, it is preferable that the stimulable phosphor layer or its host layer is composed of columnar crystals. Radiation image conversion panels having a stimulable phosphor layer composed of columnar crystals originally have high sharpness, but columnar crystals are easily fused to each other by heat treatment, so that the effect of the present invention on sharpness is large. .

FIG. 4 shows a specific configuration example of a radiation image conversion panel manufactured by the manufacturing method of the present invention, wherein 18 is a substrate, 19 is a stimulable phosphor layer, 20 is a protective layer, 21 is a spacer,
22 is a low refractive index layer.

As a material of the substrate 18, glass, ceramics, metal or the like is used. Specifically, quartz glass,
Examples include glass such as chemically strengthened glass, crystallized glass, ceramics such as a sintered plate of alumina or zirconia, and metal sheets such as aluminum, aluminum-magnesium alloy, iron, stainless steel, copper, chromium, and lead. The thickness of the substrate 18 varies depending on its material and the like, but is generally preferably 100 μm to 5 mm, and particularly preferably 200 μm to 2 mm for convenience of handling.

The protective layer 20 is provided to protect the stimulable phosphor layer 19 physically or chemically.
This protective layer 20 may be provided so as to face the stimulable phosphor layer 19 via the low refractive index layer 22 as shown in FIG. It may be formed by directly applying on the upper surface. Further, a protective layer separately formed in advance may be bonded onto the stimulable phosphor layer.

When the protective layer 20 is provided with the low refractive index layer 22 interposed therebetween, the constituent material of the protective layer 20 has good translucency,
What can be formed into a sheet is used. In order for the protective layer 20 to efficiently transmit stimulated excitation light and stimulated emission, it is desirable that the protective layer 20 exhibit high light transmittance in a wide wavelength range, and the light transmittance is preferably 80% or more. Such materials include
Examples include sheet glass such as quartz, borosilicate glass, and chemically strengthened glass, and organic polymer compounds such as PET, drawn polypropylene, and polyvinyl chloride. Borosilicate glass
It shows a light transmittance of 80% or more in the wavelength range of 330 nm to 2.6 μm, and quartz glass shows a high light transmittance even at a shorter wavelength. Further, it is preferable to provide an anti-reflection layer such as MgF _{2 on} the surface of the protective layer 20 because it has the effects of efficiently transmitting the stimulating light and the stimulating light and reducing the decrease in sharpness.

When the protective layer 20 is provided directly on the stimulable phosphor layer 19, the constituent materials of the protective layer 20 include cellulose acetate, nitrocellulose, polymethyl methacrylate, and the like.
Polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, vinylidene chloride, nylon, polyethylene sulfonate and the like can be used. The protective layer 20 is formed by vapor deposition, sputtering, or the like.
An inorganic material such as iC, SiO ₂ , Si ₃ N ₄ , and Al ₂ O ₃ may be stacked. In this case, when the protective layer 20 is provided directly on the stimulable phosphor layer 19,
The thickness is preferably from 0.1 to 100 μm, and in the case where it is provided via the low refractive index layer 22, the thickness is from 50 μm to 5 mm, preferably from 100 μm to 3 mm. The thickness of the protective layer 20 is usually 50 μm to 5 mm, and is preferably 100 μm to 3 mm in order to obtain good moisture proofness.

The low refractive index layer 22 is provided as needed from the viewpoint of further improving the sharpness of a radiation image. Specifically, CaF ₂ (refractive index: 1.23 to 1.26), N
a ₃ AlF ₆ (refractive index 1.35), MgF ₂ (refractive index 1.38)
, SiO ₂ (refractive index 1.46) etc. layer; ethanol
(Refractive index 1.36), layer composed of liquid such as methanol (refractive index 1.33), diethyl ether (refractive index 1.35); layer composed of gas such as air, nitrogen, argon, etc .; Selected from the group consisting of: In particular,
A gas or vacuum layer is preferred. In this case, the low refractive index layer
The thickness of 22 is usually 0.05-3 mm.

The low-refractive-index layer 22 is preferably in close contact with the stimulable phosphor layer 19. Therefore, when the low-refractive-index layer 22 is a liquid layer, a gas layer, or a vacuum layer, it may be left as it is. However, the low-refractive-index layer 22 is made of CaF ₂ , Na ₃ AlF ₆ , MgF ₂ , S
When the protective layer 20 is provided on the inner surface of the protective layer 20 using iO ₂ or the like, the stimulable phosphor layer 19 and the low refractive index layer 22 may be brought into close contact with each other by, for example, an adhesive.

When the protective layer 20 is disposed at a distance from the stimulable phosphor layer 19, a spacer surrounding the stimulable phosphor layer 19 is provided between the substrate 18 and the protective layer 20. 21 is provided. The spacer 21 is not particularly limited as long as it can hold the stimulable phosphor layer 19 in a state of being shielded from the external atmosphere, and glass, ceramics, metal, plastic, or the like is used.

In the present invention, the term "stimulable phosphor" refers to a stimulus such as optical, thermal, mechanical, chemical or electrical after the first irradiation of light or high-energy radiation. ) Means a phosphor that exhibits stimulated emission corresponding to the amount of initial light or high-energy radiation, but from a practical point of view, a phosphor that exhibits stimulated emission by a stimulated excitation light having a wavelength of 500 nm or more. The body is preferred.

The stimulable phosphor constituting the stimulable phosphor layer is preferably an alkali halide phosphor represented by the following general formula (1). Formula _{(1) M I X · aM} II X '2 · bM III X''3 · cA: in dB formula, M _I represents Li, Na, K, Rb, at least one alkali metal Cs . M _II is Be, Mg, C
a, Sr, Ba, Zn, Cd, Cu, and Ni represent at least one divalent metal. M _III is Sc, Y, La,
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Yb, Lu, Al, Ga, In
Represents at least one trivalent metal. X, X ', X''
Represents at least one halogen of F, Cl, Br, I. A is an oxygen-containing compound composition, and preferably represents at least one of the compounds constituting the above-mentioned M _I , M _II , M _III and activator B described later. B is an activator composition, which is Eu, Tb, Ce, Tm, Dy, Pr,
Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, T
1, at least one metal of Na, Ag, Cu, In, and Mg. a, b, c, d are 0 ≦ a <0.5, 0 ≦ b
<0.5, 0 <c ≦ 0.5, preferably 10 ⁻⁶ <c ≦ 0.2, 0
<D ≦ 0.2. However, when A is an oxygen compound of the activator constituting B, d may be 0.

The following stimulable phosphor raw materials constituting the alkali halide stimulable phosphor are used. (1) LiF, LiCl, LiBr, LiI, NaF,
NaCl, NaBr, NaI, KF, KCl, KBr,
KI, RbF, RbCl, RbBr, RbI, CsF,
At least one of CsCl, CsBr and CsI. (2) BeF ₂ , BeCl ₂ , BeBr ₂ , BeI ₂ ,
MgF ₂ , MgCl ₂ , MgBr ₂ , MgI ₂ , CaF
₂ , CaCl ₂ , CaBr ₂ , CaI ₂ , SrF ₂ , S
rCl ₂ , SrBr ₂ , SrI ₂ , BaF ₂ , BaCl
₂ , BaBr ₂ , BaBr ₂ .2H ₂ O, BaI ₂ , Z
nF ₂ , ZnCl ₂ , ZnBr ₂ , ZnI ₂ , Cd
F ₂ , CdCl ₂ , CdBr ₂ , CdI ₂ , CuF ₂ ,
CuCl ₂ , CuBr ₂ , CuI ₂ , NiF ₂ , NiC
at least one of l ₂ , NiBr ₂ and NiI ₂ . (3) ScF ₃ , ScCl ₃ , ScBr ₃ , ScI ₃ ,
YF ₃ , YCl ₃ , YBr ₃ , YI ₃ , LaF ₃ , La
Cl ₃ , LaBr ₃ , LaI ₃ , CeF ₃ , CeC
_{l 3, CeBr 3, CeI 3} , PrI 3, PrF 3, P
rCl ₃ , PrBr ₃ , PrI ₃ , NdF ₃ , NdCl
_{3, NdBr 3, NdI 3,} PmF 3, PmCl 3, P
mBr ₃ , PmI ₃ , SmF ₃ , SmCl ₃ , SmBr
₃ , SmI ₃ , EuF ₃ , EuCl ₃ , EuBr ₃ , E
uI ₃ , GdF ₃ , GdCl ₃ , GdBr ₃ , Gd
I ₃ , TbF ₃ , TbCl ₃ , TbBr ₃ , TbI ₃ ,
_{DyF 3, DyCl 3, DyBr 3} , DyI 3, HoF
₃ , HoCl ₃ , HoBr ₃ , HoI ₃ , ErF ₃ , E
rCl ₃ , ErBr ₃ , ErI ₃ , TmF ₃ , TmCl
_{3, TmBr 3, TmI 3,} YbF 3, YbCl 3, Y
bBr ₃ , YbI ₃ , LuF ₃ , LuCl ₃ , LuBr
₃ , LuI ₃ , AlF ₃ , AlCl ₃ , AlBr ₃ , A
11 ₃ , GaF ₃ , GaCl ₃ , GaBr ₃ , Ga
At least one of I ₃ , InF ₃ , InCl ₃ , InBr ₃ , and InI ₃ . (4) Eu compound group, Tb compound group, Ce compound group, T
m compound group, Dy compound group, Pr compound group, Ho compound group, Nd compound group, Yb compound group, Er compound group, Gd
Compound group, Lu compound group, Sm compound group, Y compound group,
At least one activator raw material of a Tl compound group, a Na compound group, an Ag compound group, a Cu compound group, an In compound group, and a Mg compound group.

In order to form a stimulable phosphor layer or its base layer on a substrate, an alkali halide phosphor is particularly preferably used because it is suitable for a vapor deposition method. That is, since the columnar shape is easily formed by the vapor deposition method, the oxygen compound can be added uniformly along the columnar shape by the subsequent application of the coating liquid for forming a film and heat treatment. However, in the present invention, it is not limited to the above phosphors, and other phosphors may be used as long as the phosphors show stimulated emission when irradiated with radiation and then irradiated with stimulated excitation light. Can be.

FIG. 5 schematically shows a radiation image conversion apparatus constituted by using a radiation image conversion panel manufactured by the method of the present invention.
Is a radiation image conversion panel, 26 is a stimulating excitation light source, 27 is a photoelectric conversion device that detects stimulable luminescence emitted from the radiation image conversion panel 25, and 28 is a signal reproduced by the photoelectric conversion device 27 as an image. A reproducing device, 29 is a display device for displaying an image reproduced by the reproducing device, and 30 is a filter that separates stimulated excitation light and stimulated emission and transmits only stimulated emission.

In this radiation image conversion apparatus, the radiation from the radiation generation apparatus 23 enters the radiation image conversion panel 25 through the subject 24. The incident radiation is absorbed by the stimulable phosphor layer of the radiation image conversion panel 25, and its energy is accumulated, so that an accumulated radiation transmission image is formed. Next, the accumulated image is excited by stimulating light from the stimulating light source 26 and emitted as stimulating light. Since the intensity of the radiated stimulated emission is proportional to the amount of accumulated radiation energy, the optical signal is photoelectrically converted by a photoelectric conversion device 27 such as a photomultiplier tube, and reproduced as an image by a reproduction device 28. By displaying the image on the display device 29, a radiographic image of the subject 24 can be observed.

Hereinafter, more specific examples will be described, but the present invention is not limited to these examples. Example 1 A base (RbI) of an alkali halide phosphor was deposited to a thickness of 300 μm on a substrate made of a crystallized glass plate of about 400 mm × 500 mm × 1 mm by an electron beam evaporation method. The width of the gap between the columnar crystals of the phosphor base was about 2 μm. This plate is coated with a film-forming substance, TiSiO ₄ (GLASS- manufactured by FUJI-TOK) in an amount of 3% in volume concentration in a xylene medium.
TS-100) was immersed in a coating solution (viscosity at 20 ° C. of 12 cp) in which it was dispersed, and then pulled up at a rate of 10 cm / min. Thereafter, drying was performed at 120 ° C. for 1 hour.
The thickness of the coating was 1 μm. This plate and RbI:
1 kg of 5 × 10 ⁻⁴ TlI (base material: activator) powder and 0.2% by weight of SiO ₂ with respect to the atmosphere powder were placed in the heat treatment vessel shown in FIG. 1 and heat-treated at a temperature of 500 ° C. for 2 hours. went. A radiation image conversion panel was produced using the heat-treated plate.

Example 2 In Example 1, the coating liquid for forming a film was prepared in such a manner that the volume concentration of the film-forming substance MgF in a xylene medium was 5%.
_{2 A} radiation image conversion panel was prepared in the same manner as above except that a coating liquid (viscosity at 20 ° C. 2 cp) in which (ARG401 manufactured by Sumitomo Cement) was dispersed was used.

Example 3 The same procedure as in Example 1 was carried out except that the coating liquid was applied at a rotational speed using a spinner.
A radiation image conversion panel was produced in the same manner except that the coating was performed under the conditions of 2000 rpm and a coating solution amount of 2 ml.

Example 4 In Example 1, as a coating solution for forming a film, an amount of a film forming material TiSiO ₄ (GLASS-TS- manufactured by FUJI SPECIAL CO., LTD.) Having a volume concentration of 3% in an isopropyl alcohol medium was used.
A radiation image conversion panel was prepared in the same manner except that a coating liquid for forming a film (viscosity at 20 ° C. of 12 cp) in which 100) was dispersed was used.

Example 5 In Example 1, the amount of the film-forming substance TiS in the xylene medium was 12% by volume as the coating liquid for forming the film.
A radiation image conversion panel was produced in the same manner except that a coating liquid (viscosity at 20 ° C. 50 cp) in which iO ₄ (GLASS-TS-100 manufactured by Fujitok) was dispersed was used.

Example 6 An alkali halide phosphor (RbI: 5 × 10 ^-4 TlI) was vapor-deposited to a thickness of 300 μm on a substrate made of a crystallized glass plate of about 400 mm × 500 mm × 1 mm by an electron beam vapor deposition method. The width of the gap between the columnar crystals of the phosphor was about 2 μm. This plate is prepared by adding 3% by volume in xylene medium.
Amount of the film-forming substance TiSiO ₄ (Fujitoku GL
ASS-TS-100) was immersed in a coating solution (viscosity 12 cp at 20 ° C.) in which 10 cm /
Raised in minutes. Thereafter, drying was performed at 120 ° C. for 1 hour. The thickness of the coating was 1 μm. This plate and powder of RbI: 5 × 10 ^-4 TlI (base material: activator) 1 k
g and 0.2% by weight of SiO ₂ with respect to the atmosphere powder were placed in the heat treatment container of FIG. 1 and heat-treated at a temperature of 500 ° C. for 2 hours. A radiation image conversion panel was produced using the heat-treated plate.

Example 7 An alkali halide phosphor (RbI; 5 × 10 ^-4 TlI) was vapor-deposited to a thickness of 300 μm on a substrate made of a crystallized glass plate of about 400 mm × 500 mm × 1 mm by an electron beam vapor deposition method. The width of the gap between the columnar crystals of the phosphor was about 2 μm. This plate is prepared by adding 3% by volume in xylene medium.
Amount of the film-forming substance TiSiO ₄ (Fujitoku GL
ASS-TS-100) was immersed in a coating solution (viscosity 12 cp at 20 ° C.) in which 10 cm /
Raised in minutes. Thereafter, drying was performed at 120 ° C. for 1 hour. The thickness of the coating was 1 μm. This plate was placed in the heat treatment container of FIG. 1 and heat treated at a temperature of 500 ° C. for 2 hours. A radiation image conversion panel was produced using the heat-treated plate.

Comparative Example 1 A base (RbI) of an alkali halide phosphor was vapor-deposited to a thickness of 300 μm on a substrate made of a crystallized glass plate of about 400 mm × 500 mm × 1 mm by an electron beam vapor deposition method. The width of the gap between the columnar crystals of the phosphor base was about 2 μm. This plate and RbI: 5 × 10 ^-4 TlI (Base: activator)
1 kg of powder and 0.2% by weight of SiO
₂ was placed in the heat treatment container of FIG. 1 and heat treated at a temperature of 500 ° C. for 2 hours. A radiation image conversion panel was produced using the heat-treated plate.

Evaluation 1 The radiation image conversion panels obtained in Examples 1 to 7 and Comparative Example 1 were evaluated for radiation sensitivity and
Sharpness and afterglow were evaluated. The evaluation results are shown in Table 1 below.

Radiation Sensitivity After X-ray exposure, the amount of light emitted when excited by a semiconductor laser beam was measured. The relative value was set to 100 with the case of the radiation image conversion panel obtained in Example 1.

Sharpness After attaching the CTF chart to the radiation image conversion panel,
After irradiating X-rays with a tube voltage of 80 kV _PP at 10 mR (distance from the bulb to the panel: 1.5 m), the semiconductor laser light (oscillation wavelength: 780 nm, beam diameter: 100 μm) is used to perform stimulating excitation, and CTF The chart image was read as stimulated emission emitted from the stimulable phosphor layer, and photoelectrically converted by a photodetector (photomultiplier) to obtain an image signal. Based on this signal value, the modulation transfer function (MTF) of the image is examined, and the sharpness of the radiation image is determined by using the radiation image conversion panel obtained in the first embodiment.
The relative value was set to 100. The MTF is a value when the spatial frequency is 1 cycle / mm.

Afterglow The ratio S ₁ / S ₂ of the signal S ₁ immediately before the stop of the excitation and the signal value S ₂ 200 μsec after the stop of the excitation was measured.
In the case of the radiation image conversion panel obtained in the above, the values are shown as relative values with 100 as the values.

[0063]

[Table 1]

As is clear from Table 1, according to the manufacturing method of the present invention, a radiation image conversion panel having high image sharpness can be obtained. In particular, by using an oxide as a film-forming substance, a radiation image conversion panel having a small amount of residual light can be obtained.

[0065]

As described above in detail, according to the present invention, in the stimulable phosphor layer or its base layer, the coating liquid for forming a film enters the gap between the phosphor crystals.
The fusion of the phosphor crystals to each other during the heat treatment is prevented, so that a radiation image conversion panel with high image sharpness can be obtained. In addition, when the film formed by the heat treatment is an oxide, a radiation image conversion panel with a small residual light amount can be obtained even when the heat treatment is not performed in an atmosphere containing an activator and an oxygen compound.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a heat treatment apparatus.

FIG. 2 is a sectional view showing another example of the heat treatment apparatus.

FIG. 3 is a sectional view showing still another example of the heat treatment apparatus.

FIG. 4 is a sectional view showing an example of a radiation image conversion panel.

FIG. 5 is an explanatory view schematically showing a radiation image conversion apparatus.

FIG. 6 is an explanatory view showing a state in which a coating liquid for forming a film is applied to a stimulable phosphor layer formed by an oblique vapor deposition method.

FIG. 7 is an explanatory view showing a state in which a coating liquid for forming a film on the surface of a stimulable phosphor layer is removed.

[Explanation of symbols]

Reference Signs List 1 plate 1A substrate 1B stimulable phosphor layer 2 heat treatment container 3 heater for heat treatment container 4 heat treatment furnace 5 heater for evaporation container 6 evaporation container 7 atmosphere powder (powder containing activator and oxygen compound) 8 gas amount adjustment valve REFERENCE SIGNS LIST 9 atmosphere powder 10 heat treatment container 11 ion source unit 12 extraction electrode 13 mass analysis unit 14 deflection unit 15 sample chamber 16 plate 17 heater 18 substrate 19 stimulable phosphor layer 20 protective layer 21 spacer 22 low refractive index layer 23 radiation generator Reference Signs List 24 subject 25 radiation image conversion panel 26 photostimulated excitation light source 27 photoelectric conversion device 28 reproducing device 29 display device 30 filter 41 columnar crystal 42 surface of photostimulable phosphor layer 43 gap between columnar crystals 44 coating liquid for forming film

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G21K 4/00

Claims (1)

(57) [Claims] 1. A method of manufacturing a radiation image conversion panel having a stimulable phosphor layer, comprising: oxidizing a stimulable phosphor layer formed on a substrate by a vapor phase deposition method or a base layer thereof by heat treatment; A method for producing a radiation image conversion panel, comprising a step of applying a coating liquid for forming a coating made of a substance or a fluoride, drying the coating liquid , and then performing a heat treatment .