JP2002341038A - Method for producing radiation imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems in the sticking of a sensor panel, a phosphor sheet and a reflector, or peeling of a phosphor and deterioration of the sensor panel by generation of bubbles from pinholes of a phosphor protective PET by the moisture in the phosphor sheet. SOLUTION: The phosphor sheet is heat-treated and then stuck to a sensor substrate. Otherwise, after the reflector is heat-treated, the reflector and the phosphor sheet are stuck to the sensor substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a radiation imaging apparatus used for a medical diagnostic apparatus, a nondestructive inspection apparatus, and the like.

[0002]

2. Description of the Related Art Conventionally, when manufacturing an indirect X-ray area sensor using a phosphor, there are two methods for forming the phosphor. One is a method of directly depositing a phosphor on a sensor, and the other is a method of forming a phosphor on a substrate different from the sensor and bonding the substrate to the sensor via an adhesive. A conventional method for manufacturing an indirect X-ray area sensor by the latter bonding will be described.

FIG. 6 is a configuration diagram of an indirect X-ray area sensor using a conventional bonding method. GOS fluorescent plate 106
Is composed of a phosphor protection PET 105 / GOS phosphor 103 / phosphor base PET 104, and a phosphor protection PE
T105 and phosphor base PET104 are biaxially stretched PE
T (polyethylene terephthalate), GOS phosphor 10
3, Gd ₂ O ₂ S: Tb ³⁺ is used. Stretched P on phosphor protection PET 105 and phosphor base PET 104
The reasons why ET is used include X-ray transmission, solvent resistance,
It is inexpensive. The solvent resistance must be good when bonding together with a solvent (IPA, acetone)
This is to prevent dust from being caught between the sensor panel 101 and the GOS fluorescent plate 106.

[0004] The GOS phosphor plate 106 having such a configuration is bonded onto the sensor panel 101 via the acrylic adhesive 102, and the acrylic adhesive 1 used in this case is used.
The thermosetting type 02 is used from the viewpoint of reliability (temperature and humidity durability) and restrictions in the manufacturing process. In the case of the UV curable resin, the UV light does not pass through the phosphor and the white substrate, so that the adhesive is not cured. The reason for using an acrylic resin is to alleviate the stress caused by bonding and to reduce the light absorption even slightly, and a colorless resin is selected and used.

The reflecting plate 111 is formed to efficiently transmit light to the sensor panel 101 without leaking light generated by the GOS phosphor 103 to the outside, and to protect the GOS phosphor 103 and the sensor panel 101 from moisture. Have been. The reflection plate 111 is made of aluminum 1 similarly to the GOS fluorescent plate 106.
08 is sandwiched between a reflective layer base PET109 and a reflective layer protective PET110 of biaxially stretched PET. The reflection plate 111 having such a configuration is connected to the sensor panel 101 / GOS fluorescent plate 10 via the thermosetting acrylic adhesive 107.
6 are pasted together. Such an indirect X-ray area sensor converts incident X-rays into light by the GOS phosphor 103 and detects the light converted by the sensor panel 101.

[0006]

FIG. 7 shows a state after the GOS fluorescent plate 106 and the reflecting plate 111 of FIG. GOS fluorescent screen 10
6 and the reflection plate 111 are a stretched PET, the sensor panel 101
Are made of glass, and have different thermal contraction rates and thermal expansion rates. Therefore, when bonding is performed with a thermosetting adhesive, warping may occur as shown in FIG. 7A, or peeling may occur at a place where the adhesive strength is weak as shown in FIG. 7B. In the case of multi-layer bonding, peeling occurs at a portion where the adhesive strength is weakest as shown in FIG. 7 (b), but when peeling occurs in the GOS phosphor in the indirect X-ray area sensor using the GOS phosphor. There is.

FIG. 8 is an enlarged sectional view of the GOS fluorescent plate 106. As shown in FIG. 8, it can be seen that the fluorescent plate 106 is partially peeled off. As the GOS phosphor, two types of a large particle phosphor 113 having a large particle diameter and a small particle phosphor 112 having a small particle diameter are used in layers. This is to increase the light emission intensity. However, in the case of a layered structure, the adhesion strength between the layers of the large particle phosphor 113 and the small particle phosphor 112 is weak, and peeling occurs between them.

Since the GOS phosphor is powdery as it is, the adhesion strength of particles is increased by mixing the binder 114. FIG. 9 is a diagram showing the relationship between the amount of binder contained in the phosphor and the amount of light emitted from the phosphor. The abscissa indicates the amount of the binder added in mass percent, and the ordinate indicates the luminescence amount as a ratio when the amount of the binder when no binder is added is 1. As can be seen from FIG. 9, if the amount of the binder added is increased, the binder absorbs the emitted light, so that the amount of emitted light is reduced.

For this reason, the amount of the binder 114 must be suppressed as much as possible, and peeling must be prevented. Further, a phosphor protective PET 105 is used on the bonding surface side of the GOS fluorescent plate 106. Since the protective PET 105 is located between the GOS fluorescent substance 103 and the sensor panel 101 at the time of bonding, it is thinned even slightly. Absorption must be reduced. Therefore, the pinhole 115 is easily generated, and it is difficult to eliminate it.

FIG. 10 shows a case where the GOS fluorescent plate 106 is bonded to the sensor panel 101. At this time, when the acrylic adhesive 102 is heated after the two are bonded together, if the pinhole 115 is vacant in the phosphor protective PET 105, the moisture 117 contained in the GOS phosphor is vaporized. Then, air bubbles 116 are generated between the phosphor protection PET 105 and the acrylic adhesive 102. When air bubbles 116 are mixed between the GOS phosphor 103 and the sensor panel 101, refraction of light occurs, which affects an X-ray image.

The GOS phosphor 103 contains water 117
Remaining will not only cause air bubbles 116,
After bonding, the moisture 117 in the GOS phosphor 103 becomes
In order to penetrate the sensor panel 101 and deteriorate the sensor panel 101, it is necessary to eliminate moisture in the GOS phosphor 103. Thus, conventionally, the sensor panel 10
When manufacturing by bonding the 1 / GOS phosphor plate 106 / reflection plate 111, the GOS phosphor is peeled off, and further, the phosphor protection PE due to the moisture in the GOS phosphor.
Since bubbles are generated from the T pinhole, there is a problem that the sensor panel is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described conventional problems, and has as its object to provide a method of manufacturing a radiation imaging apparatus capable of reliably preventing a sensor panel from being deteriorated due to peeling of a phosphor or a pinhole. It is in.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a phosphor sheet having a particulate phosphor, a base resin for supporting the phosphor, and a protective resin for protecting the phosphor, using a thermosetting adhesive. In the method for manufacturing a radiation imaging device bonded to a sensor substrate having a photoelectric conversion element using the method, the heat treatment of the phosphor sheet is performed, and then the phosphor sheet is bonded to the sensor substrate. This is achieved by a manufacturing method.

Another object of the present invention is to provide a reflector having a reflective layer, a base resin for supporting the reflective layer, a protective resin for protecting the reflective layer, a phosphor sheet having particulate phosphor, In a method for manufacturing a radiation imaging apparatus in which a sensor substrate having a conversion element is bonded to a sensor substrate using a thermosetting adhesive, after the reflective plate is heat-treated, the reflective plate, the phosphor sheet, and the sensor substrate are bonded to each other. This is achieved by a method of manufacturing a radiation imaging apparatus characterized by the following.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, FIG.
With reference to (d), the cause of warpage and peeling when two materials are bonded together using a thermosetting adhesive will be described. As shown in FIG. 1A, the material A121 and the material B122 are bonded using a thermosetting adhesive 123.

At this time, the coefficient of thermal expansion of material A121 <material B
The coefficient of thermal expansion of 122 The coefficient of thermal contraction of material A121 <the coefficient of thermal contraction of material B122.

Next, as shown in FIG.
In order to cure 23, material A121 / adhesive 123 /
Put material B122 into the oven and apply heat. On this occasion,
Thermal expansion is performed according to each coefficient of thermal expansion. Adhesive 12
No. 3 cures at this time. Further, after the adhesive 123 is cured as shown in FIG.
/ Remove material B122 from oven and cool. At this time, the heat-expanded state is returned to the state before heat is applied, and further, heat shrinkage is performed according to the heat shrinkage rate.

FIG. 1D shows a change in the state where the temperature is returned from high to low. As is clear from FIG.
Is larger in thermal expansion rate and thermal shrinkage rate than material A,
Large heat shrinkage when returning from high temperature to low temperature. Therefore, at the time of curing (high temperature), the point b of the material B122 and the material A121
Assuming that point a is bonded at a distance t, when the temperature is returned to normal temperature, a difference occurs by a distance 1 from a difference between a coefficient of thermal expansion and a coefficient of thermal shrinkage. Distance √ (l ²
+ T ² ). Therefore, the corresponding stress is applied to the material A121, the adhesive 123, and the material B122, and as a result, warpage or peeling occurs. in short,
The cause of the occurrence of warpage or peeling is a difference between the coefficient of thermal expansion and the coefficient of thermal contraction of the two bonded materials.

Next, when PET (polyethylene terephthalate) is bonded to glass in a radiation imaging apparatus, the thermal expansion coefficient and the thermal contraction rate are as follows. In this embodiment, it is assumed that the layer configuration of the X-ray area sensor is the same as that of the related art in FIG. 6, and PET is the phosphor protection PET 105 of the GOS phosphor 106, the phosphor base PET 104, and the reflection layer base of the reflection plate 111. Stand PET109, Reflective layer protection PET1
Refers to 10. Further, glass refers to a glass substrate of the sensor panel 101.

Thermal expansion coefficient PET = 1.6 × 10 ⁻⁵ (cm / cm / ° C.) Glass = 10 ⁻⁷ (cm / cm / ° C.) Thermal shrinkage rate (at 70 ° C.) PET = 0.06 (%) Glass = 0 (%) As is clear from the above results, glass and substrate resin (PE
The thermal expansion coefficient and thermal shrinkage coefficient of T) are large for PET.
By minimizing the thermal expansion and contraction of T, warpage and peeling can be prevented.

Next, a method of reducing the difference between the coefficient of thermal expansion and the rate of contraction using the shape change of PET according to the present embodiment will be described. FIG. 2 is a diagram showing a change in length of PET depending on temperature. The horizontal axis is temperature, and the vertical axis is PET length.

(A) 200 (m) length at normal temperature (20 ° C.)
m) When 70 ° C. heat is applied to the material, expansion begins according to the coefficient of thermal expansion. If the coefficient of thermal expansion is 1.6 × 10 ^-5 (c
m / cm / ° C.), the length is increased by 1.6 × 10 ⁻³ (mm). Therefore, the length is 200 (mm) +1.
It becomes 6 × 10 ⁻³ (mm).

(B) Next, the thermally expanded PET is returned to normal temperature (70 ° C. → 20 ° C.). Then, 1.6 × 10 ⁻³ (mm) of the expanded portion does not return to the original state, and further contracts according to the heat shrinkage rate. If the heat shrinkage is 0.06
(%), 200 (mm) × 0.06 (%) =
Shrink by 0.12 (mm). Therefore, the length is 2 (m
m) -0.12 (mm).

(C) Next, 7
When the heat of 0 ° C is added again (20 ° C → 70 ° C), the heat
The expansion is performed for the expansion rate. That is, (200 mm−0.12
mm) × (70 ° C.-20 ° C.) × 1.6 × 10^-Five(Cm /
cm / ° C) = 1.6 × 10^-3(Mm) expanded length
Is 200 (mm) −0.12 (mm) + 1.6 × 10 ^-3
(Mm).

(D) When the expanded PET is returned to room temperature again, future shrinkage will be reduced only by the amount expanded in (C). For this reason, only the length of the contracted length multiplied by the coefficient of thermal expansion expands. Therefore, the length is 200 (mm) −0.12
(Mm). Therefore, comparing the difference between the thermal expansion and thermal contraction of the first (A, B) and the second (C, D), the length of the first thermal expansion−the length of thermal contraction = (200 mm)
+ 1.6 × 10 ⁻³ mm) − (200 mm−0.12 m)
m) = 1.6 × 10 ⁻³ (mm) +0.12 (mm) Second time thermal expansion length−heat contraction length = (200 mm)
−0.12 mm) + (1.6 × 10 ⁻³ mm) − (200
mm−0.12 mm) = 1.6 × 10 ⁻³ (mm), and the difference is smaller at the second time. That is, once P
By performing the ET heat treatment, the difference in shrinkage becomes smaller when heating is performed again using a thermosetting adhesive, so that warpage and peeling can be prevented.

FIG. 3 shows the relationship between the annealing time and the heat shrinkage when PET is annealed at 70.degree. In FIG. 3, MDs of ○ and TDs of X indicate the stretching directions when PET is manufactured, MDs of ○ are stretched in the vertical direction, and TDs of X are manufactured by stretching in the horizontal direction. As can be seen from FIG. 3, the heat shrinkage rate is saturated when the annealing time is 6 (Hr) for both MD and TD. Therefore, it can be seen that the heat shrinkage is eliminated by performing the annealing for 6 (Hr). Also, 0.
Even with annealing of 5 (Hr), the shrinkage rate can be reduced to about half.

FIG. 4 shows the relationship between the annealing time of the GOS fluorescent plate 106 and the amount of water evaporation. It can be seen that the moisture evaporates by annealing. It takes more than ten hours for the water evaporation to saturate. FIG. 5 shows the relationship between the standing time of the GOS phosphor plate 106 after annealing and moisture absorption. Even if annealed, if the standing time before bonding is long, moisture is absorbed, and as a result, the generation of bubbles due to pinholes and the deterioration of the sensor panel are caused.

Therefore, when the GOS fluorescent plates are bonded together, the following effects can be obtained by annealing before bonding. (1) Shrinkage can be reduced and the phosphor can be prevented from warping or peeling. (2) The moisture in the GOS phosphor is vaporized, and the phosphor protection P
Bubbles generated from the pinhole of the ET can be prevented. (3) Moisture in the GOS phosphor is vaporized, and deterioration of the sensor panel due to residual moisture can be prevented.

The annealing time and the temperature limit are determined as follows. (1) The thermosetting temperature of the adhesive is 70 ° C to vaporize the water
As described above, the temperature is preferably 130 ° C. or lower, which is 20 ° C. lower than the thermal deformation temperature (150 ° C.) of PET. (2) Annealing time = Yield (factors: peeling, bubbles,
Degradation) and manufacturing cost. (3) Leaving time = Depending on the annealing temperature, the PET is left at room temperature (20 ° C.) until it is once cooled. The upper limit is G
It is before the moisture of the OS phosphor is saturated.

[0030]

Next, a method for manufacturing a radiation imaging apparatus according to the present invention will be described in more detail with reference to examples.

(Embodiment 1) The configuration of the radiation imaging apparatus of this embodiment is the same as that of FIG. 6, but in this embodiment, as a manufacturing procedure, annealing was performed before bonding the GOS fluorescent plate 106 and the reflecting plate 111, respectively. At this time, the number of samples was 200. The annealing conditions for the GOS fluorescent plate and the reflection plate are as follows. The curing temperature of the adhesive is 70 ° C. Annealing temperature = 80 ° C., annealing time = 1 hour, leaving time = 2
The condition of 70 minutes at 0 minutes is the curing temperature of the acrylic adhesive used for bonding. When annealing is performed for 3 hours, 10 (mg) of water in the GOS phosphor disappears as shown in FIG. The saturation amount (initial amount) is 11 (m) as shown in FIG.
g), about 90% has been vaporized. The leaving time was 20 minutes, and at this time, as shown in FIG.
g) moisture absorption. Therefore, the amount of water in the GOS phosphor becomes about 1.8 (mg). In the case of bonding with this amount of water, generation of air bubbles was not observed in the bonding of 200 sheets. Assuming that the incidence of pinholes is about 10%, 20 of the bonded substrates have pinholes,
Since no bubbles are generated in 200 sheets, it is understood that the number of bubbles is 0 out of 20 sheets. The effect on the sensor panel was confirmed by X-ray radiographic images, but was not recognized.

Example 2 As in Example 1, as a manufacturing procedure of the radiation imaging apparatus shown in FIG. 6, annealing was performed before bonding the GOS fluorescent plate 106 and the reflecting plate 111, respectively. The annealing conditions for the GOS fluorescent plate and the reflection plate are as follows. Annealing temperature = 70 ° C, annealing time = 30
Minute, leaving time = 1 hour When the annealing is performed for 30 minutes, the water content of the GOS phosphor becomes 3
(Mg) is gone. Saturation amount (initial amount) is 11 (mg)
Therefore, about 30% has vaporized. Leave time is 1
Time, at which time there is about 2 (mg) of water absorption. Therefore, the amount of water in the GOS phosphor becomes about 10 (mg). In the case of bonding with this amount of water, the generation of bubbles is 7 sheets and the generation rate of pinholes is 10% in the bonding of 200 sheets.
Therefore, 20 of the laminated pieces have pinholes. Therefore, it can be seen that the generation of bubbles is 7 out of 20 sheets. Regarding the influence on the sensor panel, the influence of the deterioration of the sensor panel was observed in the output of two out of 200 images from the X-ray photographed image.

Example 3 As in Example 1, as a manufacturing procedure of the radiation imaging apparatus of FIG. 6, annealing was performed before bonding the GOS fluorescent plate 106 and the reflecting plate 111, respectively. The annealing conditions for the GOS fluorescent plate and the reflection plate are as follows. Annealing temperature = 70 ° C, annealing time = 1 hour, leaving time = 1 hour When annealing is performed for 1 hour, the moisture in the GOS phosphor becomes 6%.
(Mg) is gone. Saturation amount (initial amount) is 11 (mg)
Therefore, about 55% has vaporized. Leave time is 1
Time, in this case about 2 (mg) of water absorption.
Therefore, the amount of water in the GOS phosphor becomes about 7 (mg). In the case of laminating with this amount of water, generation of one bubble and lamination of pinholes are 10% in lamination of 200 sheets.
Therefore, 20 of the laminated pieces have pinholes. Therefore, it can be seen that one out of twenty bubbles is generated. The effect on the sensor panel was not recognized from the X-ray photographed image among 200 sheets.

Table 1 summarizes the probability of peeling of the GOS phosphor, generation of bubbles due to pinholes, and deterioration of the sensor panel with respect to the annealing time, annealing temperature, and standing time in Examples 1 to 3.

[0035]

[Table 1]

As is apparent from Table 1, in the case of no annealing (conventional case), peeling of the GOS fluorescent plate, generation of bubbles due to pinholes, and deterioration of the sensor panel were observed. I was not able to admit. As described above, in Example 2, seven out of 200 bubbles were generated due to pinholes, and deterioration of the sensor panel was recognized in two out of 200 sheets. In Embodiment 3, bubbles were generated out of 200 sheets due to pinholes. One was recognized.

[0037]

As described above, according to the present invention, the phosphor sheet and the reflector are heat-treated and then bonded to the sensor substrate, so that the phosphor can be prevented from warping or peeling off, and the generation of air bubbles can be prevented. Therefore, deterioration of the sensor substrate can be prevented, and deterioration of the radiation image can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the cause of occurrence of warpage or peeling when two materials are bonded together using a thermosetting adhesive.

FIG. 2 is a diagram illustrating a method for reducing a difference in coefficient of thermal expansion and contraction when a PET and a sensor panel are bonded.

FIG. 3 is a diagram showing a relationship between an annealing time and a heat shrinkage rate when PET (polyethylene terephthalate) is annealed.

FIG. 4 is a diagram showing the relationship between the annealing time of a GOS fluorescent plate and the amount of water evaporation.

FIG. 5 is a diagram showing a relationship between a standing time of a GOS fluorescent plate after annealing and a water absorption amount.

FIG. 6 is a diagram showing a layer configuration of an indirect X-ray area sensor.

FIG. 7 is a view showing warpage and peeling that occur when the GOS fluorescent plate and the reflection plate of FIG. 6 are bonded to a sensor panel.

FIG. 8 is an enlarged view showing a part of the GOS fluorescent plate.

FIG. 9 is a diagram showing the relationship between the amount of binder added to the phosphor and the amount of light emitted by the phosphor.

FIG. 10 is a diagram illustrating generation of bubbles due to a pinhole of a GOS fluorescent plate.

[Explanation of symbols]

 Reference Signs List 101 sensor panel 102, 107 acrylic adhesive 103 GOS phosphor 104 phosphor base PET 105 phosphor protection 106 GOS phosphor plate 108 aluminum 109 reflection layer base PET 110 reflection layer protection PET 111 reflection plate 115 pinhole 116 bubbles

Continued on the front page F-term (reference) 2G088 EE01 EE30 FF02 GG16 GG19 GG20 JJ05 JJ09 JJ10 JJ37 LL12 4M118 AA08 AB01 CB11 GA10 GD15 HA23 HA24

Claims (5)

[Claims] 1. A phosphor sheet having a particulate phosphor, a base resin for supporting the phosphor, and a protective resin for protecting the phosphor is formed on a sensor substrate having a photoelectric conversion element by using a thermosetting adhesive. In the method for manufacturing a radiation imaging apparatus to be bonded, a method for manufacturing a radiation imaging apparatus, comprising: after heat treating the phosphor sheet, bonding the phosphor sheet to the sensor substrate. 2. The radiation imaging apparatus according to claim 1, wherein a temperature of the heat treatment is equal to or higher than a curing temperature of the thermosetting adhesive and lower than a thermal deformation temperature of the phosphor sheet by 20 ° C. or more. Manufacturing method. 3. The method according to claim 1, wherein the amount of water contained in the phosphor sheet immediately after the heat treatment is 200 ppm or less. 4. A reflector having a reflective layer, a base resin for supporting the reflective layer, and a protective resin for protecting the reflective layer,
In a method for manufacturing a radiation imaging apparatus in which a phosphor sheet having particulate phosphor and a sensor substrate having a photoelectric conversion element are bonded using a thermosetting adhesive, after the reflection plate is heat-treated, the reflection plate and the A method for manufacturing a radiation imaging apparatus, comprising: bonding a phosphor sheet to the sensor substrate. 5. The method according to claim 4, wherein the temperature of the heat treatment is equal to or higher than the curing temperature of the thermosetting adhesive and lower than the thermal deformation temperature of the phosphor sheet or the reflection plate by 20 ° C. or more. A method for manufacturing a radiation imaging apparatus.