JP2008088531A - Method for forming phosphor layer - Google Patents

Abstract

The growth of a phosphor layer during vapor deposition can be improved, that is, a highly accurate and stable phosphor layer can be formed from the initial stage of vapor deposition. It is an object of the present invention to provide a method for forming a phosphor layer that makes it possible to emit emitted light uniformly from a reading surface.
When forming a phosphor layer of FPD by vacuum vapor deposition, the temperature of the molten vapor deposition material is within ± 5 ° C with respect to a preset temperature, and the temperature distribution of the vapor deposition material is ± 5 ° C. A first condition that is within the range, a second condition in which the temperature of the container containing the vapor deposition material is within ± 3 ° C. with respect to a preset temperature, and the temperature distribution of the container is within ± 3 ° C., And after satisfy | filling at least 1 condition of the 3rd conditions whose fluctuation width of a vapor deposition rate is less than +/- 7% with respect to the preset vapor deposition rate, vapor deposition of a fluorescent substance layer is started to a support body. This solves the problem.
[Selection] Figure 2

Description

  The present invention relates to a method for forming a phosphor layer, and more particularly to a method for forming a phosphor layer used in a planar radiation image detector.

  Conventionally, a radiological image detector is used for medical or industrial nondestructive inspection and the like, and is a plane that extracts radiation (X-ray, α-ray, β-ray, γ-ray, electron beam, ultraviolet ray, etc.) as an electrical image signal. There are a radiation image detector (flat panel display, hereinafter referred to as FDP), an X-ray image tube that extracts a radiation image as a visible image, and the like.

  For FPD, for example, a direct method in which electron-hole pairs (e-h pairs) emitted from a photoconductive film are collected by an electric field when X-rays are incident and read out as an electric signal, and similar to an X-ray image tube In addition, there are two methods, an indirect method in which X-rays are converted into visible light by a phosphor layer formed of a fluorescent material that emits light by radiation and read by a photoelectric conversion element such as a photodiode.

  The indirect type FPD as described above photoelectrically converts radiation onto a photodetector panel composed of a photoelectric conversion element portion in which a plurality of photosensors and elements such as TFTs (Thin Film Transistors) are two-dimensionally arranged. A phosphor layer for converting light into light detectable by the element is directly formed.

  When manufacturing the FPD as described above, it is common to deposit a phosphor to a predetermined thickness on the surface of the photodetector panel. Compared with the layer by the coating method, a coating material is prepared by dispersing phosphor powder in a solvent containing a binder, etc., and this coating material is applied to the surface of the photodetector panel and dried. Since the phosphor layer is formed in a vacuum, there are few impurities, and since there are almost no components other than the phosphor such as a binder, there is little variation in performance, and the luminous efficiency is very good. This is because it has excellent characteristics.

In recent years, especially in the field of use related to medical diagnostic devices, there has been a demand for devices capable of recording with much higher sensitivity and sharpness than in the past, as a technology developed for this purpose. There is a method in which the phosphor layer is composed of a large number of independent columnar crystals whose growth state is uniform.
Therefore, when manufacturing the FPD as described above, it is preferable to apply a method of forming a phosphor layer composed of a large number of independent columnar crystals.
For example, Patent Document 1 has at least a columnar crystal scintillator layer (a phosphor layer made of a phosphor material that emits light by radiation), the scintillator layer has a thickness of 500 μm or more, and the columnar crystal in the scintillator layer. A radiation scintillator characterized by a filling rate of 70 to 85% is disclosed.

Here, in the FPD in which the phosphor layer is directly formed on the photodetector panel as described above, light (fluorescence) emitted by the radiation irradiated from the upper surface of the phosphor layer is converted into the phosphor by the photodetector. Read from the bottom side of the layer. Therefore, it is essential that a large number of independent columnar crystals constituting the phosphor layer have a uniform growth state, particularly in the vicinity of the bottom surface of the phosphor layer, that is, there is no growth in a non-uniform shape. is there.
Therefore, for example, when the phosphor layer is formed by vapor deposition, the evaporation at the initial stage of vapor deposition is not constant, and fluctuations in the evaporation cause hillocks on the bottom surface of the phosphor layer. The phosphor layer is generally composed of a non-columnar layer that is not a columnar crystal. However, if fluctuations in evaporation occur at the initial stage of the deposition of the phosphor layer, the density of the non-columnar layer becomes non-uniform. Although the film thickness distribution of the non-columnar layer may be non-uniform, it is necessary to prevent these phenomena from occurring.

JP 2006-58099 A

  The present invention is to solve the problems of the prior art, and when forming a phosphor layer used in a planar radiation image detector by vacuum deposition, the temperature of the molten deposition material, a container for storing the deposition material, and , After strictly controlling any one of the deposition rates, by starting the deposition of the phosphor layer, it is possible to improve the growth of the phosphor layer during the deposition, that is, from the beginning of the deposition To provide a method for forming a phosphor layer that can form a highly accurate and stable phosphor layer and enables emission light to be uniformly emitted from a reading surface of a radiation image in a planar radiation image detector. It is in.

  In order to solve the above-described problems, the present invention provides a flat radiation image detector for taking a radiation image by measuring light of a phosphor layer that emits light upon incidence of radiation with a photoelectric conversion element, and vacuuming the phosphor layer. When forming by vapor deposition, the support on which the photoelectric conversion element is formed is used as a substrate, and the temperature of the molten vapor deposition material is within ± 5 ° C. with respect to a preset temperature, and the vapor deposition material The temperature distribution of the container is within ± 3 ° C. with respect to a preset temperature, and the temperature distribution of the container is ± 3. After the second condition is within ± 5 ° C. and the fluctuation range of the deposition rate satisfies at least one of the third conditions within ± 7% of the preset deposition rate, the support The phosphor layer is deposited on the body A method for forming a phosphor layer is provided.

  In the present invention, it is preferable to use a plurality of containers containing the vapor deposition material.

  In the present invention, the heating of the vapor deposition material is feedback-controlled so as to satisfy at least one of the first condition, the second condition, and the third condition until the vapor deposition is completed. Is preferred.

  Further, in the present invention, the heating of the vapor deposition material is feedback controlled until at least one of the first condition, the second condition, and the third condition is satisfied, and the first condition, After satisfying at least one of the second condition and the third condition, it is preferable to heat the vapor deposition material at a predetermined heating timing at a predetermined heating condition.

  In the present invention, when forming a phosphor layer used in a planar radiation image detector by vacuum vapor deposition, any one of the temperature of the molten vapor deposition material, the container for accommodating the vapor deposition material, and the vapor deposition rate is strictly determined. After controlling, by starting the deposition of the phosphor layer, it is possible to improve the growth of the phosphor layer during the deposition, that is, to form a highly accurate and stable phosphor layer from the initial stage of the deposition. Thus, it is possible to provide a planar radiographic image detector that makes it possible to emit emitted light uniformly from the radiographic image reading surface.

  Hereinafter, a method for forming a phosphor layer according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view showing a phosphor layer forming apparatus for carrying out the present invention.
A phosphor layer forming apparatus 10 (hereinafter simply referred to as a forming apparatus 10) shown in FIG. 1 includes CsI (cesium iodide) as an example of a material that becomes a phosphor (matrix) and an activator (activator: activator: A support (in this case, 2 on the upper surface) that is rotated and held by single vapor deposition in which a raw material mixed with TlI (thallium iodide) as an example in a predetermined mixing ratio is accommodated in one evaporation source and heated and evaporated. This is a device for forming a phosphor layer on the surface of a support (S) having photoelectric conversion means arranged in a dimension.

  Such a forming apparatus 10 basically includes a vacuum chamber 12, a support rotation holding mechanism P of the support S disposed in the vacuum chamber 12, a heating evaporation unit 14, a vacuum pump (vacuum exhaust). Means) 16 and a gas introduction nozzle 18. In addition, of course, the formation apparatus 10 may satisfy various components included in a known vacuum vapor deposition apparatus. For example, an RF matching box for cleaning the deposition object, a vacuum gauge (measuring means) for measuring the degree of vacuum in the vacuum chamber 12, or the like may be provided.

  The support S having the photoelectric conversion means arranged two-dimensionally on the upper surface used here is not particularly limited, and an element that photoelectrically converts and detects the light emitted from the phosphor layer upon incidence of radiation. Various plate-like objects such as an FPD (flat panel detector, hereinafter referred to as FPD) and a scintillator panel arranged in a two-dimensional direction can be used. As a specific example, JP-A-60-240285 is disclosed. A suitable example is a two-dimensional arrangement of independent photoconductive layers for each pixel, as disclosed in JP-A-8-116044.

Moreover, there is no limitation in particular also in the material used as the base material of the support body S, Various sheets utilized by radiation detectors, such as glass, ceramics, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), and polyimide. All of the substrates are available.
In the support S, the deposition surface of the layer is not limited, and examples thereof include glass, ceramics, PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polyimide, and the like, and directly on the surface of the photoelectric conversion element. A layer may be formed.

  Further, the forming apparatus 10 having the gas introduction nozzle 18 for introducing the inert gas during film formation preferably introduces the gas while evacuating the vacuum chamber 12 to a high vacuum once. An inert gas is introduced by a nozzle (gas introduction pipe) 18 to make the inside of the vacuum chamber 12 have a degree of vacuum (medium vacuum) of about 0.1 Pa to 10 Pa, and vapor deposition is performed by resistance heating in the heating evaporation unit 14 under this medium vacuum. The materials (thallium iodide and cesium iodide) are evaporated by heating, and the phosphor layer is formed on the support S by vacuum deposition while rotating the support S by the support rotation holding mechanism P.

In the present invention, the phosphor that forms the phosphor layer is not particularly limited, and a phosphor that emits light in a wavelength range of 300 to 800 nm when irradiated with radiation is preferably used, in addition to CsI: Tl mentioned as an example. Various types are also available.
As another example, the basic composition formula (I):
M ^I X · aM ^II X ′ ₂ · bM ^III X ″ ₃ : zA
An alkali metal halide phosphor represented by the formula is preferably exemplified.
In the above formula, M ^I represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, and M ^II represents Be, Mg, Ca, Sr, Ba, Ni, Cu, Zn and at least one rare earth element or trivalent metal selected from the group consisting cd, M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho Represents at least one rare earth element or trivalent metal selected from the group consisting of Er, Tm, Yb, Lu, Al, Ga and In. X, X ′ and X ″ each represent at least one halogen selected from the group consisting of F, Cl, Br and I, and A represents Y, Ce, Pr, Nd, Sm, Eu, Gd, Represents at least one rare earth element or metal selected from the group consisting of Tb, Dy, Ho, Er, Tm, Yb, Lu, Na, Mg, Cu, Ag, Tl, and Bi, and a, b, and z represent Respective numerical values are in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <z <1.0.
In the basic composition formula (I), M ^I preferably includes at least Cs, X preferably includes at least I, and A is particularly preferably Tl or Na. . z is preferably a numerical value within the range of 1 × 10 ⁻⁴ ≦ z ≦ 0.1.

The basic composition formula (II):
M ^II FX: zLn
Also preferred are rare earth activated alkaline earth metal fluoride halide phosphors.
In the above formulas, M ^II is Ba, at least one rare earth metal selected from the group consisting of Sr and Ca, Ln is Ce, Pr, Sm, Eu, Tb, Dy, Ho, Nd, Er, Tm And at least one rare earth element selected from the group consisting of Yb. X represents at least one halogen selected from the group consisting of Cl, Br and I. Z represents a numerical value within a range of 0 <z ≦ 0.2.
As M ^II in the above formula, Ba preferably accounts for more than half. Ln is particularly preferably Eu or Ce.
In addition, LnTaO ₄ : (Nb, Gd), Ln ₂ SiO ₅ : Ce, LnOX: Tm (Ln is a rare earth element), Gd ₂ O ₂ S: Tb, Gd ₂ O ₂ S: Examples thereof include Pr, Ce, ZnWO ₄ , LuAlO ₃ : Ce, Gd ₃ Ga ₅ O ₁₂ : Cr, Ce, HfO _{2 and the} like.

The vacuum chamber 12 is a known vacuum chamber (bell jar, vacuum tank) that is formed of iron, stainless steel, or the like and is used in a vacuum deposition apparatus.
A vacuum pump 16 is connected to the side surface of the vacuum chamber 12 via a diffuser 16a. For example, an oil diffusion pump is used as the vacuum pump 16. In addition, the vacuum pump 16 is not specifically limited, The various pumps utilized with the vacuum evaporation system can be utilized if the required ultimate vacuum degree can be achieved. As an example, a cryopump or a turbomolecular pump can be used, and a cryocoil or the like may be used in combination as an auxiliary. In the forming apparatus 10 for forming the phosphor layer described above, the ultimate vacuum in the vacuum chamber 12 is preferably 8.0 × 10 ⁻⁴ Pa or less.

The gas introduction nozzle 18 is connected to a cylinder through an appropriate pipe, and has a gas flow rate adjusting means or the like (or connected thereto) and is used in a vacuum vapor deposition apparatus or a sputtering apparatus. An inert gas such as argon gas (Ar gas) or nitrogen gas is introduced into the vacuum chamber 12 in order to form a phosphor layer by vacuum deposition under medium vacuum. This inert gas is a gas that does not react with the support S and the phosphor layer during vacuum deposition.
An inert gas is introduced into the vacuum chamber 12 through the gas introduction nozzle 18. The gas introduction nozzle 18 is provided on the bottom surface 12a of the vacuum chamber 12 in the illustrated example.

  The support rotation holding mechanism P rotates and holds the support S, and a known one used in a vacuum vapor deposition apparatus or a sputtering apparatus can be used as appropriate.

A heating evaporation unit 14 is disposed below the vacuum chamber 12.
The heating evaporation unit 14 is a part that evaporates cesium iodide and thallium iodide, which are vapor deposition materials, by resistance heating. In addition, a shutter 40 that shields vapor of the vapor deposition material from the heating evaporation unit 14 (the crucible 50 and the crucible 52) is disposed on the heating evaporation unit 14.

  As described above, the forming apparatus 10 includes CsI (cesium iodide) as an example of a material to be a phosphor (matrix) and TlI (iodide) as an example of a material to be an activator (activator). Thallium) is housed in one evaporation source and is evaporated by heating.

  As shown in FIG. 1, in the illustrated forming apparatus 10, two crucibles 50 having the same shape are arranged below the rotation center of the support S. Note that the crucibles are insulated from each other due to separation, insertion of an insulating material, or the like.

  In the present embodiment, the crucible 50 is a large drum type (cylindrical) crucible.

FIG. 2 shows a schematic diagram of the crucible 50. 2A is a top view, FIG. 2B is a partially cutaway front view, and FIG. 2C is a side view.
The crucible 50 has a slit-like steam outlet extending in the axial direction of the drum on the side surface of the drum. In addition, a square cylindrical chimney 50a having an upper and lower opening surface having the same shape is fixed to the vapor outlet, and similarly, vapor of the vapor deposition material is discharged from the chimney 50a.

  By having such a chimney (chimney-shaped steam discharge part), it is possible to prevent the vapor deposition material from being unexpectedly ejected from the crucible when local boiling or abnormal heating occurs in the crucible. Contamination of the body S can be prevented. In particular, in the above-described medium vacuum deposition, it is necessary to bring the support S and the crucible 50 close to each other as described above.

  As described above, the crucible 50 is a drum-type crucible, and a slit-like steam discharge port 50b that coincides with the axial direction is formed on the side surface of the drum. The steam discharge port 50b has a rectangular tube whose upper and lower surfaces are open. A shaped chimney 50a is fixed. In the chimney 50a, a substantially Z-shaped rib 50c is disposed in order to support from the inside and improve the strength.

  Further, a shielding member 62 for preventing the bumped vapor deposition material from being ejected is fixed in the crucible 50. The shielding member 62 is formed by folding a long rectangular plate material in the short direction to form a substantially T shape, and the attachment portion 62a is formed by vertically folding both longitudinal ends of the T-shaped upper portion upward. When viewed from above, the shielding member 62 is disposed in the crucible 50 (drum) so as to close the steam discharge port 50b on the T-shaped upper surface, and the mounting portion 62a is fixed to the drum end surface from the inside.

Electrodes 60 are fixed to both end faces of the crucible 50 (drum).
The electrode 60 is connected to a resistance heating power source 20 (hereinafter simply referred to as a power source 20). The power source 20 is not particularly limited, and various types of power sources that are used for heat generation of a crucible serving as a resistance heating source in vacuum deposition by resistance heating can be used.

  In the illustrated example, thermocouples 58a and 58b (measurement portions) serving as temperature measuring means are provided at the center portion of the bottom surface of the crucible 50 and the vicinity of the end portion of the bottom surface farthest from the center portion. It is inserted from 50b and arranged in contact with the bottom surface in the crucible.

The heating control means 22 is connected to the thermocouples 58a and 58b.
The heating control means 22 controls (feedback control) the power supplied from the power source 20 to the crucible 50 so that the molten deposition material temperature becomes a predetermined temperature according to the temperature measurement results by the thermocouples 58a and 58b. It is. Details of this control operation will be described later.

  Hereinafter, the method of forming the phosphor layer of the present invention will be described in more detail by explaining the operation of the phosphor layer forming apparatus 10.

  First, the vacuum chamber 12 is opened, the support S is held by the support rotation holding mechanism P, and all the crucibles 50 are mixed with a raw material in which thallium iodide and cesium iodide are mixed at a predetermined mixing ratio. After filling up to a fixed amount, the shutter 40 is closed, and the vacuum chamber 12 is further closed.

Next, the vacuum exhaust means 16 is driven to exhaust the inside of the vacuum chamber 12. When the inside of the vacuum chamber 12 reaches 8 × 10 ⁻⁴ Pa, for example, the vacuum chamber 12 is continued by the gas introduction nozzle 18 while continuing the exhaust. Argon gas is introduced therein, the pressure in the vacuum chamber 12 is adjusted to, for example, 1 Pa, and the resistance heating power source 20 is driven to energize all the crucibles 50 to heat the deposition material. At this point, the shutter 40 is closed.

  When the heating of the vapor deposition material is started, the heating control means 22 determines the power source according to the measurement result by the thermocouple 58a arranged at the center of the crucible 50 and the thermocouple 58b arranged at a position farthest from the center. The heating of the crucible 50 by 20 is controlled. The heating control by the heating control means 22 may be performed according to the temperature measurement result of one of the thermocouple 58a and the thermocouple 58b. The heating control may be current control, voltage control, or power control.

Here, in the method for forming the phosphor layer of the present invention, after the heating of the vapor deposition material, the temperature of the molten vapor deposition material is within ± 5 ° C. with respect to a preset temperature, and the vapor deposition is performed. The first condition that the temperature distribution of the material is within ± 5 ° C., the temperature of the container containing the vapor deposition material is within ± 3 ° C. with respect to the preset temperature, and the temperature distribution of the container is ± 3 After satisfying at least one of the second condition that is within ° C. and the third condition that the fluctuation range of the deposition rate is within ± 7% with respect to the preset deposition rate, the support S Start vapor deposition.
The forming apparatus 10 in the illustrated example arranges thermocouples 58a and 58b at the bottom of the crucible 50, measures the temperature of the molten vapor deposition material, and the temperature of the molten vapor deposition material is ± After satisfying the first condition that is within 5 ° C. and the temperature distribution of the vapor deposition material is within ± 5 ° C., the shutter 40 is opened and vapor deposition is started.

As described above, in FPD, radiation is incident from the front end (opposite side of the substrate) of the phosphor layer, and light emission from the phosphor layer is received by the photoelectric conversion element such as a photodiode on the base end side. / Measure to obtain a radiographic image.
Therefore, when forming the phosphor layer of the FPD by vacuum deposition, unlike a radiation image conversion panel (so-called IP) using a stimulable phosphor that obtains a radiation image by stimulating light emitted by incidence of excitation light, It is important that the properties of the base end side of the phosphor layer are appropriate.

In the present invention, the evaporation of the vapor deposition material, that is, the vapor deposition is started by starting the vapor deposition after starting the heating of the vapor deposition material and satisfying at least one of the first to third conditions. After very high stability, the deposition of the support S is started. In other words, in the present invention, prior to the start of vapor deposition, the vapor deposition material is vaporized, i.e., the vapor deposition rate is initially set, and the initial vapor deposition state is matched according to the preferred phosphor layer vapor deposition, and then vapor deposition is performed. Start.
Thereby, it can vapor-deposit by the vapor deposition material vapor | steam of a very appropriate and stable state from the initial stage of vapor deposition, and a suitable fluorescent substance layer can be formed stably from the start time of vapor deposition.

As described above, in the forming apparatus 10 shown in FIG. 1, the temperature of the melted vapor deposition material is within ± 5 ° C., preferably within ± 1 ° C. with respect to the preset temperature, and the temperature distribution of the vapor deposition material. Is within ± 5 ° C., and preferably after ± 1 ° C.
Specifically, after the measured temperature of the vapor deposition material by the thermocouples 58a and 58b is within ± 5 ° C. of the set temperature and the difference between the measured temperatures by the thermocouples 58a and 58b is within ± 5 ° C., the shutter 40 Vapor deposition is performed. According to the inventor's study, if the temperature of the vapor deposition material is measured at two points in the crucible 50, the temperature distribution of the vapor deposition material can be found, that is, the temperature difference of the vapor deposition material measured at the two points is ± 5 ° C. Therefore, it can be considered that the temperature distribution of the vapor deposition material is within ± 5 ° C.

Note that the measurement point of the vapor deposition material in the crucible 50 is not particularly limited, and one point or three or more points may be measured, and the convection of the vapor deposition material in the crucible according to the shape of the crucible or the like. It may be set appropriately according to the above.
Here, according to the study of the present inventor, as shown in the illustrated example, by measuring the temperature of the vapor deposition material at two points of the center part and the position farthest from the center part on the bottom surface of the crucible, In the crucible 50, the temperature distribution of the vapor deposition material can be found appropriately. Further, by measuring the temperature at the bottom of the crucible 50, the temperature of the vapor deposition material can be properly measured regardless of the amount of the vapor deposition material.

As described above, in the forming apparatus 10, after energization of the crucible 50 is started (heating of the vapor deposition material), the measurement temperature of the vapor deposition material by the thermocouples 58a and 58b is within ± 5 ° C. of the set temperature, and After the difference in temperature measured by the thermocouples 58a and 58b is within ± 5 ° C., the shutter 40 is opened and deposition is started.
After the vapor deposition is started, when vapor deposition is performed for a predetermined time set in accordance with the thickness of the phosphor layer to be formed, the shutter 40 is closed, the energization of the crucible 50 by the power source 20 is stopped, and the support S The rotation is stopped and the deposition is finished. When vapor deposition is completed, the inside of the vacuum chamber 12 is opened to the atmosphere, and after the support S is sufficiently cooled, the support S on which the phosphor layer is formed is taken out.

Here, the heating control (heating feedback control) according to the temperature measurement results by the thermocouples 58a and 58b may be performed until the deposition is completed.
However, it is preferable that feedback control (that is, monitoring of the deposition rate by temperature measurement) is stopped at an appropriately set timing after the deposition is started, and heating is controlled at a constant output thereafter.

As a matter of course, the vapor deposition material in the crucible 50 decreases as the vapor deposition proceeds. As a result, the last zero in the vapor deposition often loses a sufficient amount of vapor deposition material in the crucible 50 to measure the temperature. In such a state, there are many cases where the temperature of the vapor deposition material cannot be accurately measured, and in that case, accurate monitoring of the vapor deposition rate, that is, proper feedback control cannot be performed. In some cases, the deposition rate becomes unstable, and the characteristics of the phosphor layer deteriorate.
On the other hand, after starting vapor deposition, the feedback control is stopped at a predetermined timing, and heating is performed as a constant output control, and vapor deposition is performed as it is to the end, thereby avoiding the inconvenience due to a decrease in vapor deposition material in the crucible. Thus, stable heating, that is, vapor deposition is maintained, and proper vapor deposition can be performed to the end.

The constant output control is performed, for example, when the vapor deposition start condition is satisfied, or when a predetermined time elapses after the vapor deposition start condition is satisfied, or when a predetermined time elapses after the vapor deposition start. 20 outputs may be calculated, and heating may be performed at a constant output according to the result.
The constant output control may be current control, pressure control, or power control.

The timing for switching the heating from the feedback control to the constant output control is not particularly limited, and may be appropriately determined according to the amount of vapor deposition, the amount of vapor deposition material filled in the crucible, the shape of the crucible, etc. The control of heating by output is preferably 80% or less of the total deposition time of the phosphor layer.
As a result, an appropriate film can be formed initially by feedback control, and finally, an appropriate phosphor layer can be formed over the entire region in the thickness direction by performing film formation that avoids the above-described disadvantages by constant output control. .

Alternatively, when the first condition is satisfied, the heating may be switched to constant output control at a set timing as appropriate, and then the shutter 40 may be opened to start vapor deposition.
Also by this, the same effect as before can be obtained.

  In addition, regarding switching of the deposition control of such a phosphor layer, a case where deposition is started according to second and third conditions described later, or a plurality of first to third conditions are satisfied. The same applies to the case where vapor deposition is started later.

As described above, the second condition is that the temperature of the container (crucible 50) containing the vapor deposition material is within ± 3 ° C. with respect to the preset temperature, and the temperature distribution of the container is within ± 3 ° C. It is to be.
FIG. 3 shows a schematic diagram of the crucible 50 and the heating control system used in the apparatus for starting the deposition of the phosphor layer according to the second condition.
The crucible 50 shown in FIG. 3 is the same as the crucible 50 shown in FIG. 2 described above, and only the measurement position by the thermocouple 58 is different. That is, in the example shown in FIG. 2, the thermocouples 58 a and 58 b are inserted into the crucible 50 from the chimney 50 a and the temperature of the vapor deposition material is measured at the bottom of the crucible 50. In contrast, in the example shown in FIG. 3, the two thermocouples 58 c and 58 d measure the temperature of the crucible 50, that is, the container for the vapor deposition material, on the bottom outer wall of the crucible 50.
Moreover, the heating control means 22 controls the power supply 20 according to the temperature measurement result of this crucible 50, and controls the heating of vapor deposition material.

As described above, under the second condition, after the heating is started, the temperature of the crucible 50 (container for the vapor deposition material) is within ± 3 ° C., preferably within ± 1 ° C. of the preset temperature, Deposition is started after the temperature distribution of the crucible 50 is within ± 3 ° C., preferably within ± 1 ° C.
Specifically, after the heating is started, the estimated temperature of the vapor deposition material by the thermocouples 58c and 58d is within ± 3 ° C. of the set temperature, and the difference between the measured temperatures by the thermocouples 58c and 58d is within ± 3 ° C. After that, the shutter 40 is opened and vapor deposition is started.

Similar to the first condition, according to the study by the present inventor, if the temperature of the crucible 50 is measured at two points, the temperature distribution of the crucible 50 can be found, that is, the temperature difference of the crucible 50 measured at two points. Is within ± 3 ° C, it can be considered that the temperature distribution of the crucible is within ± 3 ° C.
The temperature measurement point of the crucible 50 is not particularly limited, and one point or three or more points may be measured. In addition, the convection of the vapor deposition material in the crucible 50 according to the shape of the crucible 50 or the like. Accordingly, it may be set appropriately. According to the study of the present inventor, as shown in the example of the figure, by measuring the temperature of the crucible 50 at the two points of the central portion and the position farthest from the central portion on the bottom outer wall of the crucible 50, In this crucible 50, the temperature distribution of the crucible can be found appropriately.

Furthermore, in the present invention, the third condition for starting the vapor deposition is that the fluctuation range of the vapor deposition rate is within ± 7% with respect to the vapor deposition rate set in advance.
FIG. 4 shows a schematic view of the vicinity of the crucible and the heating control system used in the apparatus for starting the deposition of the phosphor layer according to the third condition.

The crucible 50 shown in FIG. 4 has the same configuration as the crucible 50 shown in FIG.
However, in this example, the temperature measurement by the thermocouple 58 is not performed, but the evaporation amount of the vapor deposition material is measured using the evaporation amount sensor 56 using a crystal resonator, and the measurement result is sent to the heating control means 22. .
The heating control means 22 detects the vapor deposition rate (vapor deposition rate) at that time from the evaporation amount, and controls the power source 20 to control the heating of the vapor deposition material so that the vapor deposition rate becomes a predetermined set value. To do. Of course, the heating control may be performed in accordance with the detected evaporation amount by knowing the relationship between the evaporation amount and the evaporation rate in advance without calculating the evaporation rate.

As described above, under the third condition, after starting heating, the fluctuation range of the deposition rate (the amount of variation in the deposition rate) is within ± 7%, preferably ± 3%, with respect to the preset deposition rate. After that, the shutter 40 is opened and vapor deposition is started. That is, after [variation width of deposition rate / set deposition rate] × 100 ≦ 7, deposition of the phosphor layer on the support S is started.
Although there is no limitation in particular in a vapor deposition rate, 1-50 micrometers / min are preferable.

In the present invention, the method for detecting the vapor deposition rate is not limited to the evaporation amount sensor 56 using the crystal resonator of the illustrated example, and various methods used in vacuum vapor deposition can be used.
As an example, the position of the surface of the shutter 40 may be measured using a laser displacement meter, and the deposition rate may be detected from the change. As a matter of course, when the shutter 40 is closed, a phosphor layer is deposited on the surface (lower surface) of the shutter 40. Therefore, the deposition rate can be determined from the change in the surface of the shutter 40, that is, the height of the phosphor layer.

  In the above example, after satisfying any one of the first condition to the third condition, the shutter 40 is opened and the phosphor deposition on the support S is started. However, the present invention is not limited to this, and vapor deposition may be started after satisfying any two of the first condition to the third condition, or the first condition to the third condition. After satisfying all of the above, vapor deposition may be started.

In the illustrated example, the two crucibles 50 are filled with the vapor deposition material to perform the vapor deposition, but the present invention is not limited to this, and the phosphor layer is vapor deposited using only one crucible 50. Alternatively, the phosphor layer may be deposited using three or more crucibles 50.
In the present invention, the phosphor layer is vapor-deposited by using a plurality of crucibles 50 in that the effect of the present invention is more suitably expressed and the properties of the phosphor layer at the start of vapor deposition can be improved. Is preferred.

Furthermore, in the illustrated example, a mixture of a phosphor (matrix) and an activator (activator [activator]) is used as the vapor deposition material, but the present invention is not limited to this, and the phosphor Binary (or more multi-component) vacuum deposition may be performed, in which vapor deposition is performed by filling different crucibles and activators.
Since the amount of activator in the phosphor layer is extremely small, when performing binary vacuum vapor deposition, only the vapor deposition material that becomes the phosphor, temperature measurement of the vapor deposition material or the crucible, You may make it start vapor deposition, after performing a measurement etc. and satisfy | filling 1st condition-3rd condition. Alternatively, the vapor deposition may be started after these measurements are performed on both the phosphor and the activator and the first to third conditions are satisfied. is there.

  As mentioned above, although the vacuum evaporation method concerning one embodiment of the present invention was explained in detail, the present invention is not limited to the above-mentioned embodiment, and in the range which does not deviate from the gist of the present invention, various improvement and change are performed. It goes without saying.

  Moreover, although the apparatus of the illustrated example is an apparatus that performs film formation while rotating and supporting the support S, the present invention is not limited to this, and a so-called straight line that performs film formation while conveying the support linearly. A conveyance type vacuum forming apparatus may be used.

  Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

[Example 1]
First, the vacuum chamber 12 is opened, a glass plate (hereinafter referred to as substrate Z) is held by the support rotation holding mechanism P, and thallium iodide and cesium iodide are added to all the crucibles 50 by 0.001. After filling the raw materials mixed at a mixing ratio of 99.999, the shutter 40 was closed and the vacuum chamber 12 was further closed.

Next, the vacuum exhaust means 16 is driven to exhaust the interior of the vacuum chamber 12. When the interior of the vacuum chamber 12 reaches 8 × 10 ⁻⁴ Pa, the exhaust is continued and the interior of the vacuum chamber 12 is performed by the gas introduction nozzle 18. Argon gas was introduced to adjust the pressure in the vacuum chamber 12 to 1 Pa, and the resistance heating power source 20 was driven to energize all the crucibles 50 to heat the vapor deposition material.

Here, using the thermocouples 58a and 58b as shown in FIG. 2, the temperature of the vapor deposition material was measured in the center of the bottom surface in the crucible 50 and in the vicinity of the end of the bottom surface farthest from the center. .
At this time, the heating control means 22 feedback-controlled the heat generation of the crucible 50 according to the results of the measured temperatures of the thermocouples 58a and 58b.

  After that, in all the crucibles 50, after the measured temperature at two points is within ± 4.0 ° C with respect to the set temperature (650 ° C) and the difference between the two is within ± 4.0 ° C, The shutter 40 was opened, and then the rotation of the substrate Z was started, and the deposition of the phosphor layer on the surface of the substrate Z was started.

After the start of vapor deposition, when the phosphor layer thickness reaches 600 μm according to a preset vapor deposition rate, the vapor deposition of the phosphor layer is terminated, the rotational drive of the substrate Z is stopped, and the shutter 40 is closed. The power source for resistance heating was turned off, the amount of Ar gas introduced by the gas introduction nozzle 18 was increased, the inside of the vacuum chamber 12 was brought to atmospheric pressure, and then the vacuum chamber was opened.
In this example, feedback control of heating was performed until the end of vapor deposition.

[Example 2]
In all the crucibles 50, the two measured temperatures are both within ± 1.7 ° C. with respect to the preset temperature (650 ° C.), and the difference between the two is within 1.7 ° C. A phosphor layer was formed in the same manner as in Example 1 except that the evaporation was performed with the shutter 40 opened.

[Example 3]
In all the crucibles 50, the two measured temperatures are both within ± 0.9 ° C. with respect to the preset temperature (650 ° C.) and the difference between the two is within 0.9 ° C. A phosphor layer was formed in the same manner as in Example 1 except that the evaporation was performed with the shutter 40 opened.

[Example 4]
The temperature of the crucible 50 is measured at the center of the bottom surface of the outer wall of the crucible 50 and not at the temperature of the deposition material, and the heating of the deposition material is controlled by the thermocouples 58c and 58d. The temperature measurement result is within ± 3.0 ° C with respect to a preset temperature (650 ° C), and after the difference between the two is within ± 3.0 ° C, the shutter 40 is opened and vapor deposition is performed. A phosphor layer was formed in exactly the same manner as in Example 1.

[Example 5]
In all the crucibles 50, the two measured temperatures are both within 1.0 ° C. with respect to the preset temperature (650 ° C.) and the difference between the two is within ± 1.0 ° C. A phosphor layer was formed in exactly the same manner as in Example 4 except that the deposition was performed with the shutter 40 opened.

[Example 6]
Instead of the temperature of the vapor deposition material, the evaporation amount of the vapor deposition material is detected using an evaporation amount sensor 56 using a crystal resonator, and the heating of the crucible 50 is controlled according to the detection result, and the measured evaporation amount is obtained. The phosphor layer is formed in the same manner as in the example except that the deposition is started after the fluctuation range of the corresponding evaporation rate is within ± 6.8% of the preset evaporation rate (5 μm / min). did.

[Example 7]
Example in which vapor deposition was performed by opening the shutter 40 after the fluctuation range of the evaporation rate corresponding to the measured evaporation amount was within ± 3.0% of the preset evaporation rate (5 μm / min). A phosphor layer was formed in exactly the same manner as in FIG.

[Example 8]
As a method for detecting the deposition rate, instead of using the evaporation sensor 56 using a crystal resonator, the position of the surface of the shutter 40 is measured using a laser displacement meter, and the deposition rate is detected from the change. A phosphor layer was formed in exactly the same manner as in Example 6.

[Example 9]
Example in which vapor deposition was performed by opening the shutter 40 after the fluctuation range of the evaporation rate corresponding to the measured evaporation amount was within ± 2.0% of the preset evaporation rate (5 μm / min). A phosphor layer was formed in exactly the same manner as in FIG.

[Example 10]
In all the crucibles 50, after the measured temperatures at the two points are both within ± 4.0 ° C with respect to the preset temperature and the difference between the two is within 4.0 ° C, the power supply at that time A phosphor layer was formed in exactly the same manner as in Example 1 except that 20 outputs were detected, feedback control was switched to the constant current output mode in accordance with the current value, and deposition was started. The constant current value at this time was the current value immediately before switching.

[Example 11]
The substrate is exactly the same as in Example 1 except that the output of the power source 20 at that time is detected 30 minutes before the end of vapor deposition, and the feedback control is switched to the constant current output mode according to the current value at that time. A phosphor layer was formed on Z. At this time, the constant current value was the current value immediately before switching.

[Example 12]
30 minutes before the end of vapor deposition, the output of the power source 20 at that time is detected, and the substrate is exactly the same as in Example 1 except that the feedback control is switched to the constant power output mode according to the power value at that time. A phosphor layer was formed on Z. In this case, the constant power value is the power value immediately before switching.

[Example 13]
After the fluctuation range of the evaporation rate corresponding to the measured evaporation amount is within ± 6.9% of the preset evaporation rate (5 μm / min), the output of the power source 20 at that time is detected, The phosphor layer was formed in exactly the same manner as in Example 6 except that the feedback control was switched to the constant current output mode according to the current value, and the shutter 40 was opened to perform the vapor deposition. At this time, the constant current value was the current value immediately before switching.

[Example 14]
After the fluctuation range of the evaporation rate corresponding to the measured evaporation amount is within ± 6.9% of the preset evaporation rate (5 μm / min), the shutter 40 is opened and vapor deposition is performed. Before detecting the output of the power source 20 at that time and switching from the feedback control to the constant current output mode according to the current value at that time, the phosphor layer was formed in exactly the same manner as in Example 6. . At this time, the constant current value was the current value immediately before switching.

[Comparative Example 1]
The heating control means 22 supplies a constant current (200 A) to the crucible 50 from the time when the vapor deposition material is heated until the vapor deposition is completed, and the fluorescence is performed in the same manner as in the first embodiment except that the crucible 50 is heated. A body layer was formed.

[Comparative Example 2]
A phosphor layer was formed in exactly the same manner as in Comparative Example 1 except that constant power (300 W) was supplied from the time when the vapor deposition material was heated by the heating control means 22 until the vapor deposition was completed.

[Comparative Example 3]
In all the crucibles 50, after the measured temperatures at the two points are both within ± 6.0 ° C. with respect to the preset temperature (650 ° C.), and the difference between the two is within ± 6.0 ° C. A phosphor layer was formed in exactly the same manner as in Example 1 except that the shutter 40 was opened and vapor deposition was started.

[Comparative Example 4]
In all the crucibles 50, after the measured temperatures at the two points are both within ± 4.0 ° C with respect to the preset temperature (650 ° C), and the difference between the two is within ± 4.0 ° C. A phosphor layer was formed in exactly the same manner as in Example 4 except that the shutter 40 was opened and vapor deposition was started.

[Comparative Example 5]
This was performed except that the evaporation range corresponding to the measured evaporation amount was within ± 8.0% of the preset evaporation rate (5 μm / min) and then the shutter 40 was opened to perform evaporation. A phosphor layer was formed in exactly the same manner as in Example 6.

[Comparative Example 6]
This was performed except that the evaporation range corresponding to the measured evaporation amount was within ± 8.0% of the preset evaporation rate (5 μm / min) and then the shutter 40 was opened to perform evaporation. A phosphor layer was formed in exactly the same manner as in Example 8.

  About the obtained various fluorescent substance layers, the number of point defects of the fluorescent substance layer after vapor deposition was investigated as follows. A summary of these results is shown in Table 1.

[Measurement method of point defects]
After forming the phosphor layer on the substrate Z as described above, an AgBr film is attached to the surface of the substrate Z on which the phosphor layer is not formed, and then X-rays are irradiated from the phosphor layer side, The latent image is printed on an AgBr film and developed.
Ten locations were selected at random from the image obtained at this time, and 100 cm ² per location was observed to determine the average number of point defects per location.
If the average number of point defects is within 30, a high-quality planar radiation image detector can be manufactured using this phosphor layer.

From the above results, the effects of the present invention are clear.
The above-described embodiments and examples are merely examples of the present invention, and the present invention is not limited thereto, and appropriate modifications and improvements can be made without departing from the scope of the present invention. Needless to say, it may be performed.

1 is a schematic perspective view of a phosphor layer forming apparatus for carrying out the phosphor layer forming method of the present invention. (A) is a top view of a crucible of the phosphor layer forming apparatus shown in FIG. 1, (B) is the same schematic front view, and (C) is a schematic side view of the inside. FIG. 2 is a schematic perspective view of another crucible. FIG. 2 is a schematic perspective view of another crucible.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Phosphor layer formation apparatus 12 Vacuum chamber 16 Vacuum pump 18 Gas introduction nozzle 20 (Resistance heating) Power source 22 Heating control means 40 Shutter 50 Crucible 56 Evaporation amount sensor 58 Thermocouple 62 Shielding member P Holding and conveying means

Claims (4)

When forming the phosphor layer by vacuum deposition of a planar radiation image detector that captures a radiation image by measuring light of the phosphor layer that emits light upon incidence of radiation with a photoelectric conversion element,
While using a support formed with the photoelectric conversion element as a substrate,
A first condition in which a temperature of the molten deposition material is within ± 5 ° C. with respect to a preset temperature, and a temperature distribution of the deposition material is within ± 5 ° C .;
A second condition in which the temperature of the container containing the vapor deposition material is within ± 3 ° C. with respect to a preset temperature, and the temperature distribution of the container is within ± 3 ° C .;
And after satisfying at least one of the third conditions in which the fluctuation range of the deposition rate is within ± 7% with respect to the preset deposition rate,
A method of forming a phosphor layer, characterized by starting vapor deposition of the phosphor layer on the support.   The method for forming a phosphor layer according to claim 1, wherein a plurality of containers containing the vapor deposition material are used.   The heating of the vapor deposition material is feedback controlled so as to satisfy at least one of the first condition, the second condition, and the third condition until the vapor deposition is completed. Method for forming phosphor layer.   Until at least one of the first condition, the second condition, and the third condition is satisfied, the heating of the vapor deposition material is feedback-controlled, and the first condition, the second condition, and the second condition are controlled. 3. The method for forming a phosphor layer according to claim 1, wherein, after satisfying at least one of the three conditions, the deposition material is heated at a predetermined timing at a predetermined timing.

Images