JP3070940B2 - Manufacturing method of radiation image conversion panel - Google Patents

Description

The present invention relates to a method for manufacturing a radiation image conversion panel,
More specifically, the present invention relates to a method for manufacturing a radiation image conversion panel characterized in that the temperature of a substrate is lowered with time when a stimulable phosphor layer is formed by a vapor deposition method.

[Conventional technology]

For example, in the medical field, radiation images such as X-ray images are often used for diagnosing diseases.

Conventionally, as a method of forming a radiation image, X-rays transmitted through a subject are irradiated on a phosphor layer (fluorescent screen), thereby generating visible light and taking a picture of passing the visible light in the same manner. A 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 taking out an image directly from the phosphor layer without using a film coated with a silver salt, the radiation transmitted through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or heat energy. Then, a method has been proposed in which radiation energy absorbed and accumulated in the phosphor is emitted as fluorescence, and the fluorescence is detected and imaged.

For example, U.S. Pat.No. 3,859,527, JP-A-55-121
No. 44 discloses a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulating excitation light. In this method, a radiation image conversion panel having a stimulable phosphor layer formed on a substrate is used. Forming a latent image by accumulating radiation energy corresponding to the radiation transmittance of each part of
Thereafter, by scanning this stimulable phosphor layer with stimulating excitation light, radiation energy accumulated in each part is emitted as stimulating luminescence, and an optical signal depending on the intensity of this light is photoelectrically converted, for example, and an image reproducing apparatus is used. The image is formed by This final image is played as a hard copy or on a CRT.

A radiation image conversion panel having a stimulable phosphor layer used in such a radiation image conversion method has a radiation absorption rate and a light conversion rate (both of which are the same as in the case of the radiography method using a fluorescent screen described above). (Hereinafter referred to as “radiation sensitivity”), and the image must have good graininess and high sharpness.

However, the sharpness of the image tends to be higher as the thickness of the stimulable phosphor layer of the radiation image conversion panel is thinner. To improve the sharpness, the stimulable phosphor layer needs to be thinner. Was needed.

On the other hand, the granularity of an image is determined by the spatial fluctuation of the radiation quantum number (quantum mottle) or the structural disorder of the stimulable phosphor layer of the radiation image conversion panel (structural mottle). When the thickness of the body layer is reduced, the quantum number of radiation absorbed by the stimulable phosphor layer is decreased, the quantum mottle is increased, and the image quality is reduced. Therefore, in order to improve the granularity of an image, it is necessary to increase the thickness of the stimulable phosphor layer. A thicker layer is also advantageous from the viewpoint of increasing the radiation sensitivity and contributing to the improvement of the graininess.

As described above, in the conventional radiation image conversion panel, the sensitivity to radiation and the granularity of the image, and the sharpness of the image show a completely opposite tendency to the layer thickness of the stimulable phosphor layer. Radiation image conversion panels have been manufactured with some compromise between sensitivity and granularity to radiation and sharpness.

By the way, it is well known that the sharpness of an image in the conventional radiographic method is determined by the spread of instantaneous light emission (light emission at the time of irradiation) of a phosphor in a fluorescent screen. The sharpness of an image in a radiation image conversion method using a stimulable phosphor is not determined by the spread of stimulable luminescence of the stimulable phosphor in the radiation image conversion panel, that is, as in radiography. Rather than being determined by the spread of the emission of the phosphor, it is determined by the spread of the stimulating excitation light within the panel. More specifically, in this radiation image conversion method, the radiation image information accumulated in the radiation image conversion panel is chronologically extracted and taken out, so that the stimulus by the stimulating excitation light irradiated at a certain time (t _i ) The luminescence is preferably recorded as an output from a pixel (x _i , y _i ) on the panel to which all light was collected and to which the stimulating excitation light was irradiated at that time. When the stimulable phosphor existing outside the illuminated pixel (x _i , y _i ) also spreads due to scattering or the like in the inside and is excited, the pixel is output as the output from the illuminated pixel (x _i , y _y ) Output from a wider area is recorded. Therefore, the stimulating light emitted by the stimulating excitation light irradiated at a certain time (t _i ) is changed to the pixel (x _i , y) on the panel to which the stimulating excitation light is truly irradiated at the time (t _i ). The light emission from _i ) alone has no effect on the sharpness of the obtained image, regardless of the extent of the light emission.

Under such circumstances, several methods for improving the sharpness of a radiographic image have been proposed. For example, a method in which white powder is mixed into a stimulable phosphor layer of a radiation image conversion panel (see Japanese Patent Application Laid-Open No. 55-146447). A method of coloring such that the reflectance is smaller than the average reflectance in the stimulating emission wavelength region of the stimulable phosphor (Japanese Patent Laid-Open No.
-163500). However, in these methods, the sharpness is improved, but as a result, there is a problem that the sensitivity is necessarily significantly reduced.

On the other hand, as a technique for improving the conventional disadvantages in a radiation image conversion panel using a stimulable phosphor by the applicant of the present application, a radiation image conversion panel in which a stimulable phosphor layer does not contain a binder and a method of manufacturing the same Has been proposed (see JP-A-61-73100). According to this technique, since the stimulable phosphor layer of the radiation image conversion panel does not contain a binder, the filling rate of the stimulable phosphor is significantly improved, and the stimulable phosphor layer in the stimulable phosphor layer is improved. Since the directivity of stimulated excitation light and stimulated emission is improved, the sensitivity of the radiation image conversion panel to radiation and the granularity of the image are improved, and the sharpness of the image is also improved.

Further, the applicant of the present application has proposed a radiation image conversion panel in which the stimulable phosphor layer is composed of fine columnar crystals and a method for producing the same (Japanese Patent Application Laid-Open Nos. 61-142497 to 142500).
Nos., 62-105098). According to this technique, the stimulating excitation light reaches the bottom of the columnar crystal without dissipating outside the columnar crystal while repeating reflection within the columnar crystal due to the light guiding effect of the fine columnar crystal, so that the stimulating light emission , The sharpness of the image can be further increased.

[Problems to be solved by the invention]

However, even in the above-mentioned conventional technology, there is a problem that the sharpness of an image is still insufficient.

That is, when producing a stimulable phosphor layer using a vapor phase deposition method, even under the condition where the columnar crystal grows, the columnar crystal becomes thicker as the layer thickness increases under the same conditions, As a result, the voids separating the columnar crystals become narrower and eventually disappear, so that the effect of the columnar crystals is not sufficiently exhibited, and the sharpness of the image becomes insufficient.

Accordingly, an object of the present invention is to provide a method of manufacturing a radiation image conversion panel capable of forming a radiation image that satisfies the conditions of radiation sensitivity and granularity of an image while also sufficiently satisfying the sharpness of an image. Is to do.

[Means for solving the problem]

In order to achieve the above object, the present inventors have conducted intensive studies, and as a result, when forming a stimulable phosphor layer by a vapor deposition method, it is extremely simple to lower the temperature of the substrate over time. Columnar crystals do not become thicker,
It has been found that the voids reach the surface, and that the present invention can produce a radiation image conversion panel capable of forming a radiation image sufficiently satisfying not only the radiation sensitivity and the granularity of the image but also the sharpness of the image. It has been completed.

Therefore, a method of manufacturing a radiation image conversion panel according to the present invention includes a method of manufacturing a radiation image conversion panel in which at least one stimulable phosphor layer is formed on a substrate by a vapor deposition method. In the formation by a vapor deposition method, the temperature of the substrate is lowered over time.

 Hereinafter, the present invention will be described specifically.

FIG. 1 shows one example of a manufacturing apparatus that can be used for forming a stimulable phosphor layer in a method for manufacturing a radiation image conversion panel (hereinafter, abbreviated as “conversion panel” as appropriate) of the present invention.
It is the schematic of an example of the electron beam evaporation apparatus which is a seed.

In the vapor deposition apparatus shown in FIG. 1, 1 is a vacuum tank, 2 is a vacuum tank substrate, 3 is an evaporation source container, 4 is an evaporation source, 5 is an electron beam generator, 6 is a substrate, and 7 is a heater for heating the substrate. , 8 is an exhaust port, 9 is a gas introduction pipe, 10 is a probe for controlling the layer thickness, 11
Is a vacuum gauge, 12 is a viable leak valve capable of controlling a small amount of gas flow, and 13 is a main valve.

The evaporation source 4 filled in the evaporation source container 3 is for forming a stimulable phosphor layer on the surface of the substrate 6 and is made of a stimulable phosphor or a material constituting the stimulable phosphor. Become.

The substrate 6 is a substrate constituting the conversion panel, and is disposed immediately above the evaporation source 4. Behind this substrate 6,
A heater 7 for heating the substrate 6 is provided. The operation of the heater 7 is controlled by a control unit (not shown), and the temperature of the substrate 6 is adjusted.

The electron beam generator 5 is mounted separately from the vacuum chamber 1.

In the present invention, a stimulable phosphor layer is formed using this evaporator, for example, as follows.

First, after arranging the substrate 6 in the vacuum chamber 1, the inside of the apparatus is evacuated, and the surface of the substrate 6 is cleaned by heating the substrate 6 with the heater 7.

Next, the temperature of the substrate 6 is set to a predetermined temperature by the heater 7. If necessary, the variable leak valve 12 is opened, an atmospheric gas is introduced from the gas introduction pipe 9 into the vacuum chamber 1, and the pressure is set to a predetermined degree of vacuum. The atmosphere gas preferably contains at least one of N ₂ , Ar, Ne, and He.

Next, the evaporation source 4 is irradiated with an electron beam from the electron beam generator 5 to evaporate the evaporation source 4, that is, the stimulable phosphor or its constituent material. By this evaporation, the evaporating substance adheres and deposits on the substrate 6, and at the same time,
The crystal grows to form a stimulable phosphor layer. Depending on the conditions of the vapor deposition step, the crystal becomes a columnar crystal whose growth direction extends almost perpendicular to the surface of the substrate 6.

However, in the present invention, this deposition step is performed on the substrate 6
Is performed under the condition that the temperature is lowered over time. Here, the term “reducing the temperature of the substrate over time” is a concept that includes not only a case where the temperature of the substrate is gradually and gradually reduced, but also a case where the temperature of the substrate is gradually decreased.

The temperature of the substrate 6 can be adjusted by the heater 7.

Further, the temperature of the substrate at the start of the deposition was T _1, when the temperature of the substrate during the deposition and end T _2, it is preferable to satisfy the _{T 1 -T 2 ≧ 100 (℃} ), in particular, T ₁ -T It is preferable to satisfy ₂ ≧ 150 (° C.).

Further, the temperature T ₂ of the substrate at the end of vapor deposition is determined by the evaporation source 4
Is preferably Tm × 0.35 ≦ T ₂ ≦ Tm × 0.6 (K).

In this vapor deposition step, there are crystal faces where crystal growth is promoted and faces where crystal growth is suppressed. The surface where crystal growth is promoted grows more and more in the direction in which evaporated molecules or atoms adhere. The surface on which crystal growth is suppressed forms many fine cavities or voids in the stimulable phosphor layer.
The shape of the cavity or void is often elongated in a direction substantially perpendicular to the surface of the substrate 6.

However, in the present invention, the deposition rate is increased with time, so that the columnar crystals do not become thick and the voids surely reach the surface. In this way, a stimulable phosphor layer composed of columnar crystals having a large number of voids is formed on the substrate 6, and each columnar crystal is partitioned by the voids to form an optically independent columnar block. The columnar crystal may be in a state in which, for example, several to several tens of thin elongated needle-like crystals are bundled, or may have fine voids in the columnar crystal.

In the present invention, the stimulable phosphor layer is formed by a vapor deposition method, and the vapor deposition method is preferably a vapor deposition method,
In addition to the electron beam evaporation method described above, a resistance heating evaporation method or the like may be used.

Further, co-evaporation may be performed using a plurality of electron beam generators or resistance heaters. That is, the constituent materials of the stimulable phosphor are co-evaporated using a plurality of resistance heaters or electron beams to synthesize the desired stimulable phosphor on the substrate 6 and at the same time, the stimulable phosphor layer is formed. It is also possible to form.

In the present invention, a protective layer may be provided on the surface of the stimulable phosphor layer on the substrate 6 if necessary after the end of the vapor deposition step.

FIG. 2 shows a specific configuration example of the conversion panel manufactured by the manufacturing method of the present invention. Reference numeral 6 denotes a substrate, 14 denotes a stimulable phosphor layer composed of fine columnar crystals extending in a direction substantially perpendicular to the surface of the substrate 6, and 14a denotes each fine columnar crystal.
4b represents a minute gap separating 14a.

The average diameter of the fine columnar crystals 14a is preferably 1 to 50 μm,
Particularly, 2 to 20 μm is preferable. Also, fine columnar crystals 14a, 14a
The space 14b between them is not particularly limited as long as the fine columnar crystals 14a are optically independent from each other, but the average width is preferably 20 μm or less, and particularly preferably 5 μm or less.

The layer thickness of the stimulable phosphor layer 14 is preferably 50 to 1000 μm,
In particular, 100 to 600 μm is preferable. If this layer thickness is too thick, the sharpness of the image tends to decrease.

Reference numeral 15 denotes a protective layer provided as needed, which is provided on the stimulable phosphor layer 14.

An adhesive layer may be provided between the substrate 6 and the stimulable phosphor layer 14 to improve the adhesion between the respective layers, if necessary, or the stimulable excitation light and / or the stimulable phosphor layer may be provided. A reflective layer or an absorbing layer for emitting light may be provided.

The production apparatus that can be used in the production method of the present invention is not limited to the one shown in FIG. 1, and any other apparatus that can form a stimulable phosphor layer on a substrate may be used. An apparatus can also be used.

In the present invention, the stimulable phosphor is, after being irradiated with the first light or high-energy radiation, optically, thermally,
A phosphor that emits photostimulated light corresponding to the amount of initial light or high-energy radiation by mechanical, chemical, or electrical stimulation (stimulated excitation). Is a phosphor that shows stimulated emission by stimulated excitation light of 500 nm or more.

The following can be used as the stimulable phosphor constituting the stimulable phosphor layer.

(1) SrS: Ce, S described in US Pat. No. 3,859,527
m, SrS: Eu, Sm, La ₂ O ₂ S: Eu, Sm, (Zn, Cd) S: Mn, X (where X represents a halogen).

(2) Barium aluminate fluorescence represented by the general formula of BaO.xAl ₂ O ₃ : Eu (where x represents a number satisfying 0.8 ≦ x ≦ 10) described in JP-A-55-12142. body.

(3) The general formula described in JP- _A -55-12142 is M _A O · xSiO ₂ : A (where M _A represents Mg, Ca, Sr, Zn, Cd, Ba, and A is Ce,
Represents at least one of Tb, Eu, Tm, Pb, Tl, Bi, and Mn, and x is 0.5
Represents a number satisfying ≦ x <2.5. An alkaline earth metal silicate-based phosphor represented by:

(4) When the general formula described in JP-A-55-12143 is (Ba _1-xy Mg _x Ca _y ) FX: eEu ²⁺ (where X represents at least one of Br and Cl, x, y, e
Represents a number satisfying 0 <x + y ≦ 0.6, xy ≠ 0, 10 ⁻⁶ ≦ e ≦ 5 × 10 ⁻² . ) A phosphor represented by.

(5) The general formula described in JP-A-55-12144 is represented by LnOX: xA (where Ln represents at least one of La, Y, Gd and Lu;
X represents at least one kind of Cl and Br, A represents at least one kind of Ce and Tb, and x represents a number satisfying 0 <x <0.1. ) A phosphor represented by.

(6) When the general formula described in JP-A-55-12145 is (Ba _1-x (M _A ) _x ) FX: yA (where M _A is at least one of Mg, Ca, Sr, Zn, and Cd) Represents a species, X represents at least one of Cl, Br, I, and A represents Eu,
Represents at least one of Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er,
x and y represent numbers satisfying 0 ≦ x ≦ 0.6 and 0 ≦ y ≦ 0.2. ) A phosphor represented by.

(7) The general formula described in JP- _A- 55-160078 is M _A FX · xA: yLn (where M _A represents at least one of Mg, Ca, Ba, Sr, Zn, and Cd; Is BeO, MgO, CaO, SrO, BaO, ZnO, Al ₂ O ₃ , Y ₂ O ₃ , L
a ₂ O ₃ , In ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , Th
Represents at least one kind of O ₂ , wherein Ln is Eu, Tb, Ce, Tm, Dy, Pr,
Represents at least one of Ho, Nd, Yb, Er, Sm, and Gd, and X represents Cl,
Represents at least one of Br and I, and x and y are 5 × 10 ⁻⁵ ≦ x ≦
0.5, a number satisfying 0 <y ≦ 0.2. A rare earth element-activated divalent metal fluorohalide phosphor represented by the formula:

(8) General formula [I] xM ₃ (PO ₄ ) ₂ · NX ₂ : yA described in JP-A-59-38278. General formula [II] M ₃ (PO ₄ ) ₂ · yA (where M , N represents at least one of Mg, Ca, Sr, Ba, Zn, and Cd, X represents at least one of F, Cl, Br, and I, and A represents Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sb, Tl, M
represents at least one of n and Sn, and x and y are 0 <x ≦ 6, 0
Represents a number satisfying ≦ y ≦ 1. ) A phosphor represented by.

(9) The general formula M _A X ₂ · a M _A X ' ₂ : xEu ²⁺ described in JP- _A- 60-84381 (where M _A is at least one alkaline earth element of Ba, Sr, Ca) X represents a metal, X and X ′ represent at least one halogen of Cl, Br, I, and X ≠ X ′, and a is
X represents a number satisfying 0.1 ≦ a ≦ 10.0, and x represents a number satisfying 0 <x ≦ 0.2. A divalent europium-activated alkaline earth metal halide phosphor represented by the formula:

(10) JP-63-27588 Patent formula MX ₂ · AMX described in JP _'2: bEu ²⁺ (although, M represents Ca, Sr, at least one alkaline earth metal Ba, X And X ′ represent at least one halogen of Cu, Br, I, a represents a number satisfying 0.5 ≦ a ≦ 1.8, and b represents a number satisfying 10 ⁻⁴ ≦ b ≦ 10 ⁻² . A divalent europium-activated alkaline earth metal halide phosphor represented by the formula:

(11) Proceedings of the 51st JSAP Symposium (19
(Autumn 1990) A divalent europium-activated barium halide phosphor represented by the general formula BaX ₂ : Eu (X is a halogen) described on page 1086.

(12) JP formula described in JP _{61-72088 M A X · aM B X} '2 · bM CX "3: cA ( However, M _A is, Li, Na, K, Rb , at least Cs represents one alkali metal, M _B is, Be, Mg, Ca, Sr , Ba, Zn, Cd, Cu, Ni
Of represents at least one divalent metal, M _C is, Sc, Y, La,
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In
X, X ′, X ″ represents at least one trivalent metal of
Represents at least one halogen of F, Cl, Br, I;
u, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, C
u, Mg represents at least one metal, a, b, c is 0 <a
<0.5, 0 ≦ b <0.5, and 0 <c ≦ 0.2. ) An alkali halide phosphor represented by the formula:

In the present invention, an alkali halide phosphor is particularly preferable because a stimulable phosphor layer is easily formed by a vapor deposition method such as vapor deposition.

However, in the present invention, the phosphor is not limited to the above, and other phosphors may be used as long as the phosphor exhibits stimulable fluorescence when irradiated with radiation and then irradiated with stimulating excitation light. it can.

In the present invention, a plurality of stimulable phosphor layers may be used to form a stimulable phosphor layer group including two or more stimulable phosphor layers. In this case, the stimulable phosphor contained in each stimulable phosphor layer may be the same or different.

In the present invention, as the substrate, for example, a ceramic plate such as alumina, a glass plate such as chemically strengthened glass, a metal plate such as aluminum, iron, copper, and chromium, or a metal plate having a coating layer of the metal oxide is preferable. And a plastic film such as a cellulose acetate film, a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, and a polycarbonate film.

The layer thickness of these substrates varies depending on the material of the substrate to be used and the like, but is generally 80 to 3000 μm.

The surface of these substrates may be a smooth surface, or may be a mat surface for the purpose of improving the adhesion to the stimulable phosphor layer. Further, the surface of the substrate may be an uneven surface as described in JP-A-61-142497, or may be
As described in Japanese Patent Publication No. 142498, a structure in which isolated tile plates are spread may be used. Further, a light reflection layer, a light absorption layer, an adhesive layer, and the like may be provided on these substrates as needed.

In the present invention, it is preferable to provide a protective layer on the surface of the stimulable phosphor layer for physically or chemically protecting the stimulable phosphor layer. It may be formed by directly applying on the stimulable phosphor layer, or a protective layer separately formed in advance may be adhered on the stimulable phosphor layer. Further, a resin which is cured by radiation and / or heat as proposed in JP-A-61-176900 may be used. Materials for the protective layer include cellulose acetate, nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polypropylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, and polytrifluoride. Ethylene monochloride, ethylene tetrafluoride / propylene hexafluoride copolymer, vinylidene chloride / vinyl chloride copolymer,
A vinylidene chloride / acrylonitrile copolymer and the like can be mentioned.

In addition, this protective layer may be formed by laminating inorganic substances such as SiC, SiO ₂ , SiN, and Al ₂ O ₃ by a vacuum deposition method, a sputtering method, or the like.

In addition, a protective layer can be formed by adhering a material that can be formed into a sheet having excellent translucency onto the stimulable phosphor layer or disposing it at a distance from the stimulable phosphor layer.

The protective layer desirably exhibits high light transmittance over a wide wavelength range in order to efficiently transmit stimulated excitation light and stimulated emission, and the light transmittance is preferably 80% or more.

Examples of such a material include plate glass such as quartz, borosilicate glass, and chemically strengthened glass, and organic polymer compounds such as PET, drawn polypropylene, and polyvinyl chloride. Borosilicate glass shows a light transmittance of 80% or more in a wavelength range of 330 nm to 2.5 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, because it has an effect of efficiently transmitting stimulated excitation light and stimulated emission and reducing a decrease in sharpness.

The thickness of the protective layer is 50 μm to 5 mm, and 100 μm
~ 3 mm is preferred.

When the protective layer is disposed at a distance from the stimulable phosphor layer, a spacer is preferably provided between the substrate and the protective layer so as to surround the phosphor layer. Is not particularly limited as long as it can maintain the stimulable phosphor layer in a state of being shielded from the external atmosphere,
Glass, ceramics, metal, plastic, and the like can be used, and the thickness is preferably equal to or more than the thickness of the stimulable phosphor layer.

As described above, in the manufacturing method of the present invention, when the stimulable phosphor layer is formed by the vapor deposition method, the temperature of the substrate is lowered with time, so that the stimulable phosphor layer is formed. The columnar crystals do not become thick, and the voids reach the surface of the stimulable phosphor layer. As a result, the radiation sufficiently satisfies not only the radiation sensitivity and the granularity of the image but also the sharpness of the image. A conversion panel on which an image can be formed can be easily manufactured.

〔Example〕

Hereinafter, examples of the present invention will be described together with comparative examples, but the present invention is not limited to these embodiments.

Example 1 A substrate made of an aluminum plate having a thickness of 0.5 mm and a smooth surface was placed in a vapor deposition apparatus.

The evaporation source container was filled with RbBr: 0.002 TlBr (a material of a stimulable phosphor), and the evaporation source container was disposed in a vapor deposition apparatus.

The inside of the vapor deposition apparatus was evacuated, and the substrate was heated to clean the substrate surface.

The temperature T ₁ of the substrate at the start of deposition by adjusting the heater 400 ° C.
, Ar gas is introduced into the vapor deposition apparatus, the atmospheric pressure in the vapor deposition apparatus is set to a constant value of 1 × 10 ⁻³ Torr, and the electron beam generator is adjusted to maintain a constant deposition rate of 15 μm / min. Set to a value.

While the temperature of the substrate was gradually lowered as shown by the curve (a) in FIG. 3, the evaporation source container was subjected to electron beam evaporation under the condition that the temperature T ₂ of the substrate at the end of vapor deposition was 200 ° C. The stimulable phosphor in the inside was evaporated and deposited on a substrate to form a stimulable phosphor layer having a thickness of 200 μm, thereby producing the conversion panel A of the present invention. FIG. 4 (a) schematically shows a part of the structure of the stimulable phosphor layer.

After attaching the CTF chart to this conversion panel A, X-rays with a tube voltage of 80 kV _pp are applied to 10 mR (distance from the tube to the panel:
1.5m) after irradiation, semiconductor laser light (oscillation wavelength: 780nm,
(Beam diameter: 100 μmφ) to scan and stimulate the excitation, read the CTF chart image as stimulated emission emitted from the stimulable phosphor layer, photoelectrically convert it with a photodetector (photomultiplier tube), and image signal I got

Based on the signal value, the modulation transfer function (MTF) of the image was examined, and the sharpness of the image was evaluated. The modulation transfer function (MTF) is a value when the spatial frequency is 3 cycles / mm.

Example 2 The substrate temperature was set to a third value so that the substrate temperature T ₁ at the start of vapor deposition was 360 ° C. and the substrate temperature T ₂ at the end of vapor deposition was 240 ° C.
A conversion panel B having a stimulable phosphor layer was manufactured in the same manner as in Example 1, except that the temperature was gradually lowered as shown by the curve (b) in the figure. FIG. 4 (b) schematically shows a part of the structure of the stimulable phosphor layer.

When the sharpness of this conversion panel B was evaluated in the same manner as in Example 1, a high value of 62% was shown.

Example 3 The substrate temperature was set to a third temperature such that the substrate temperature T ₁ at the start of vapor deposition was 330 ° C. and the substrate temperature T ₂ at the end of vapor deposition was 270 ° C.
A conversion panel C provided with a stimulable phosphor layer was manufactured in the same manner as in Example 1 except that the temperature was gradually lowered as shown by the curve (c) in the figure. FIG. 4 (c) schematically shows a part of the structure of the stimulable phosphor layer.

When the sharpness of this conversion panel C was evaluated in the same manner as in Example 1, a high value of 58% was shown.

Example 4 The substrate temperature was set to a third value so that the substrate temperature T ₁ at the start of vapor deposition was 400 ° C. and the substrate temperature T ₂ at the end of vapor deposition was 200 ° C.
As shown by the curve (d) in the figure,
A conversion panel D provided with a stimulable phosphor layer was manufactured in the same manner as in Example 1. FIG. 4 (d) schematically shows a part of the structure of the stimulable phosphor layer.

When the sharpness of this conversion panel D was evaluated in the same manner as in Example 1, it was as high as 58%.

Example 5 The substrate temperature was set to a third temperature so that the substrate temperature T ₁ at the start of vapor deposition was 550 ° C. and the substrate temperature T ₂ at the end of vapor deposition was 350 ° C.
A conversion panel E provided with a stimulable phosphor layer was manufactured in the same manner as in Example 1 except that the temperature was gradually lowered as shown by the curve (e) in the figure. FIG. 4 (e) schematically shows a part of the structure of the stimulable phosphor layer.

When the sharpness of this conversion panel E was evaluated in the same manner as in Example 1, the value was as high as 55%.

Example 6 The temperature of the substrate is shown by the curve (f) in FIG. 3 such that the temperature T ₁ of the substrate at the start of vapor deposition is 240 ° C. and the temperature T ₂ of the substrate at the end of vapor deposition is 40 ° C. Conversion panel F provided with a stimulable phosphor layer in the same manner as in Example 1 except that the temperature was gradually lowered.
Was manufactured. FIG. 4 (f) schematically shows a part of the structure of the stimulable phosphor layer.

When the sharpness of this conversion panel F was evaluated in the same manner as in Example 1, a high value of 56% was shown.

Example 7 In Example 1, the material of the stimulable phosphor was changed to CsI: 0.002.
Change in NaI, at a temperature T ₁ is 360 ° C. of the substrate at the start of deposition, so that the temperature T ₂ of the substrate during deposition termination becomes 610 ° C., indicating the temperature of the substrate in the curve of FIG. 5 (a) A conversion panel G having a stimulable phosphor layer similar to that shown in FIG. 4 (a) was manufactured in the same manner except that the temperature was gradually lowered.

When the sharpness of this conversion panel G was evaluated in the same manner as in Example 1, a high value of 63% was shown.

Example 8 In Example 2, the material of the stimulable phosphor was CsI: 0.002.
The temperature of the substrate is shown by the curve (b) in FIG. 5 so that the temperature T ₁ of the substrate at the start of vapor deposition is 320 ° C. and the temperature T ₂ of the substrate at the end of vapor deposition is 200 ° C. A conversion panel H having a stimulable phosphor layer similar to that shown in FIG. 4B was manufactured in the same manner except that the temperature was gradually lowered.

When the sharpness of this conversion panel H was evaluated in the same manner as in Example 1, a high value of 61% was shown.

Example 9 In Example 3, the material of the stimulable phosphor was CsI: 0.002.
Change in NaI, at a temperature T ₁ is 290 ° C. of the substrate at the start of deposition, so that the temperature T ₂ of the substrate during deposition termination becomes 230 ° C., indicating the temperature of the substrate in the curve of FIG. 5 (c) A conversion panel I having the same stimulable phosphor layer as in FIG. 4 (c) was produced in the same manner except that the temperature was gradually lowered.

When the sharpness of this conversion panel I was evaluated in the same manner as in Example 1, the value was as high as 59%.

Example 10 In Example 4, the material of the stimulable phosphor was CsI: 0.002 Na
The temperature of the substrate is indicated by curve (d) in FIG. 5 so that the temperature T ₁ of the substrate at the start of vapor deposition is 360 ° C. and the temperature T ₂ of the substrate at the end of vapor deposition is 160 ° C. A conversion panel J having the same stimulable phosphor layer as in FIG. 4 (d) was produced in the same manner except that the temperature was lowered stepwise.

When the sharpness of this conversion panel J was evaluated in the same manner as in Example 1, the value was as high as 60%.

Example 11 In Example 5, the material of the stimulable phosphor was CsI: 0.002.
The temperature of the substrate is shown by the curve (e) in FIG. 5 so that the temperature T ₁ of the substrate at the start of the deposition is 500 ° C. and the temperature T ₂ of the substrate at the end of the deposition is 300 ° C. A conversion panel K having a stimulable phosphor layer similar to that shown in FIG. 4E was manufactured in the same manner except that the temperature was gradually lowered.

When the sharpness of this conversion panel K was evaluated in the same manner as in Example 1, a high value of 55% was shown.

Example 12 In Example 6, the material of the stimulable phosphor was CsI: 0.002.
The temperature of the substrate is shown by a curve (f) in FIG. 5 so that the temperature T ₁ of the substrate at the start of vapor deposition is 220 ° C. and the temperature T ₂ of the substrate at the end of vapor deposition is 20 ° C. A conversion panel L having a stimulable phosphor layer similar to that shown in FIG. 4 (f) was manufactured in the same manner except that the temperature was gradually lowered.

When the sharpness of this conversion panel L was evaluated in the same manner as in Example 1, the value was as high as 56%.

Example 1 A conversion panel a provided with a stimulable phosphor layer was manufactured in the same manner as in Example 1 except that the temperature of the substrate was kept at a constant value of 300 ° C. FIG. 4 (g) schematically shows a part of the structure of the stimulable phosphor layer.

The sharpness of this conversion panel a was evaluated in the same manner as in Example 1, and it was as low as 51%.

Comparative Example 2 A conversion panel b having the same stimulable phosphor layer as in FIG. 4 (g) was manufactured in the same manner as in Example 7, except that the substrate temperature was kept at a constant value of 260 ° C. did.

When the sharpness of this conversion panel b was evaluated in the same manner as in Example 1, it was as low as 50%.

The contents of the above Examples and Comparative Examples are summarized in Table 1 below.

As is clear from the above Table 1, the conversion panels A to L obtained in the examples are the conversion panels a and b obtained in the comparative example.
The sharpness is much better than that of

Further, regarding the conversion panels A to L obtained in the examples,
Radiation sensitivity and granularity were also evaluated, and all were satisfactory.

〔The invention's effect〕

As described in detail above, according to the manufacturing method of the present invention, when the stimulable phosphor layer is formed by the vapor deposition method, the temperature of the substrate is lowered with time,
The columnar crystals are not thickened, and the voids reach the surface of the stimulable phosphor layer. As a result, the radiation sufficiently satisfies not only the radiation sensitivity and the granularity of the image but also the sharpness of the image. A radiation image conversion panel capable of forming an image can be manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a manufacturing apparatus that can be used in the manufacturing method of the present invention, and FIG. 2 is a cross-sectional view showing a specific configuration example of a radiation image conversion panel manufactured by the manufacturing method of the present invention. FIGS. 3 and 5 are curve diagrams showing the change in deposition rate in each embodiment, and FIGS. 4 (a) to 4 (g) show the state of the stimulable phosphor layer formed in the embodiment. It is sectional drawing which shows a part typically. DESCRIPTION OF SYMBOLS 1 ... Vacuum tank, 2 ... Vacuum tank substrate 3 ... Evaporation source container 4, ... Evaporation source 5 ... Electron beam generator, 6 ... Substrate 7 ... Heater, 8 ... Exhaust port 9 ... Gas Introduction tube, 10 Probe 11 Vacuum gauge 12 Variable leak valve 13 Main valve 14 Photostimulable phosphor layer 14a Fine columnar crystal 14b Void 15 Protective layer

Continuation of 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, wherein at least one stimulable phosphor layer is formed on a substrate by a vapor deposition method, wherein the stimulable phosphor layer is formed by a vapor deposition method. A method for manufacturing a radiation image conversion panel, comprising lowering the temperature of a substrate over time.