JPH07105884A - X-ray image tube and its manufacture - Google Patents

Abstract

PURPOSE:To provide an X-ray image tube reduced the luminance difference between the central part and peripheral part and a method for manufacturing it. CONSTITUTION:A metal film 7 is formed between the input base 6 and input phosphor screen 8 of an input face, so that the reflectance of the metal film is gradually increased from the center part to the peripheral part. The metal film is formed by use of sputtering method and a sputtering shielding plate having a selective hole conformed to the selection of the film thickness and the size and curved face form of the input base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray image tube and a manufacturing method thereof, and more particularly to an input surface thereof.

[0002]

2. Description of the Related Art An X-ray image tube is an electron tube that converts radiation such as X-rays into a visible light image, and its structure is constructed as shown in FIG. That is, the vacuum envelope 1 having a cylindrical central axis as a whole is configured such that the input window on one end side and the output window on the multi-end side are coaxially opposed to each other.

An input surface 2 is arranged inside the tube of the input window so as to closely face the input window. The input surface 2 has a curved surface shape that bulges toward the input window side, and an input phosphor screen is formed on the side surface of the output window of the input substrate such as Al having a high X-ray transmittance.
The protective film and the photocathode are sequentially stacked. On the other hand, the output surface 4 is arranged inside the tube of the output window, and the output fluorescent surface is formed on the side surface of the input window of the output surface 4. A focusing electrode 5 and an anode electrode 3 are arranged between the input surface 2 and the output surface 4.

The X-ray image tube having such a structure operates as follows. That is, a normal ground potential is applied to the input surface 2, and a potential of -30 KV is applied to the output surface 4 and the anode electrode 3 in the 6 to 16 inch class of the input surface. A potential between the input surface 2 and the output surface 4 is applied to the focusing electrode 5. Then, for medical use, the X-rays that have been transmitted through a subject such as a human body and modulated are transmitted through the input substrate of the input surface 2, and the energy of the X-rays is converted into light within the layer of the input fluorescent surface. The converted light reaches the photocathode, converts the energy of the light into electrons,
The converted electrons become photoelectrons and are emitted to the output surface side in the tube vacuum. These photoelectron groups are subjected to a focusing action by the electric fields of the focusing electrode and the anode electrode, accelerated by the anode potential, projecting and emitting light on the output fluorescent surface, and observed as an output optical image from the outside of the tube on the output surface.

As a matter of course, an output optical image of such an X-ray image tube is required to have high brightness and high resolution. However, the X-ray image tube has an X-ray image tube because of its structure.
The non-uniformity of the incident angle to the curved surface bulge shape of the input surface with respect to the incident X-rays from the radiation source along the radial direction or the axial direction, and further, the photoelectron group has Due to the effect of an axially symmetric electric field, the nonuniformity of the luminance distribution in the peripheral part with respect to the central part and the deterioration of the resolution,
It is also usually affected by pincushion distortion and the like due to the action of an electric field.

[0006]

[Problems to be Solved by the Invention]
For example, Japanese Patent Application Laid-Open No. 4-154031 proposes the following. That is, a metal film is formed between the input substrate of the input surface and the input phosphor screen, and the reflectance of light incident perpendicularly to the substrate surface is r ₁ and the reflectance of light obliquely incident is r ₁ by this metal film. _When it is set to ₂ , r ₁ > r ₂ . This focuses on the light that is reflected back to the input substrate side among the light generated on the input phosphor screen, absorbs the light that spreads in the lateral direction, reflects the light that has little spread, and does not contribute to the output image. The light is erased to improve the resolution. However, in this proposal, 1 / of the light generated at the input phosphor screen is
Since it utilizes interference of four wavelengths, it is necessary to control the film thickness of the metal film on the order of angstroms, which makes process control difficult. Further, there is a problem that it is impossible to deal with the nonuniformity of brightness.

Further, it is proposed to form a black metal film between the input substrate and the input phosphor screen and change the blackness, that is, the light absorptance from the axial center to the peripheral portion to reduce the unevenness of the brightness. Has also been done. However, although the metal as the blackening material is formed on the input substrate by the vapor deposition method,
The metal film formed by the vapor deposition method has a problem that the blackening degree is likely to be uneven and the adhesion strength to the input substrate is weak, which causes the peeling of the input fluorescent screen and the generation of foreign substances in the tube.

Further, measures such as changing the distribution of the thickness of the input phosphor screen and the input window have been considered, and although they have some effects on the problem of non-uniformity of brightness, they are still insufficient. It is something. The present invention has been made in view of the above problems, and an object of the present invention is to provide an X-ray image tube and a manufacturing method thereof in which the difference in brightness between the central portion and the peripheral portion is reduced.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to an input window at one end of a vacuum envelope, and an input fluorescent screen and a photocathode which are arranged in close proximity and facing each other inside the tube of the input window. An input surface having, an output window arranged at a multi-end portion of the vacuum envelope and facing the input window coaxially, an output surface arranged inside a tube of the output window, and the input surface. In an X-ray image tube including at least a plurality of electrodes arranged between the input surface and an output surface, an input phosphor screen of the input surface is formed between the input substrate and a metal thin film, The X-ray image tube is formed so that the light reflectance gradually increases from the central portion of the tube axis to the peripheral portion,
An X-ray image including at least an input window at one end of the vacuum envelope and at least an input surface which is disposed in close proximity to the inside of the tube of the input window and has an input fluorescent surface and a photoelectric surface on at least an input substrate. In the method of manufacturing a tube, in the step of forming the input surface, before the step of forming the input phosphor screen, the metal thin film is exposed to light through a shield plate having an opening while rotating the input substrate along an axis. It is a method of manufacturing an X-ray image tube, including a step of depositing such that the reflectance gradually increases from the axial center portion to the peripheral portion.

[0010]

In the X-ray image tube of the present invention, a metal film is formed between the input substrate of the input surface and the input fluorescent screen, and the reflectance of this metal film is gradually increased from the central portion to the peripheral portion. To be done. Of the light generated by the X-rays incident on the layer of the input phosphor screen, part of the light proceeds to the photocathode side as it is, and part of it goes to the input substrate side. The light that has traveled to the input substrate side is reflected by the metal film and travels to the photocathode side again, but the reflectance of the metal film is formed to gradually increase from the central portion to the peripheral portion. Therefore, the total amount of light that reaches the photocathode and generates photoelectrons is relatively larger in the peripheral part than in the central part, and the difference in brightness between the central part and the peripheral part is more effective than the conventional one. Can be reduced to

For the metal film, a material having good adhesion to the input substrate can be selected. In addition, the sputtering method and the film thickness selection, and the sputtering having a selective opening corresponding to the size and the curved surface shape of the input substrate. By using the shielding plate, it is possible to easily form a metal film having a desired reflectance change with good reproducibility, which is suitable for mass production.

[0012]

EXAMPLES Examples of the X-ray image tube of the present invention will be described in detail below, including the manufacturing method thereof. The X-ray image tube of the present invention is the same as the X-ray image tube shown in FIG. 8 except for the configuration of the input surface thereof, and the description of the overall configuration of the X-ray image tube is omitted in the following examples. , The structure of the input surface will be mainly described. FIG. 1 shows a sectional structure of an input surface of an embodiment of the present invention.

In FIG. 1, an input surface 2 is an input substrate 6, a metal sputtered film 7, an input fluorescent screen 8, a protective film 9 and a photocathode.
It is organized in order of 10. Since the input substrate 6 has a high X-ray transmittance and can be formed into a curved surface, a material such as Al is generally used. The metal sputtered film 7 is Al, Ni, Cr, A
A material such as u, Ag, an alloy thereof, or a multilayer film that can be easily formed and has good adhesion to the input substrate 6 can be appropriately selected.

The metal sputtered film 7 is formed so that the reflectance of the light is gradually higher in the peripheral portion than in the central portion. In order to provide the metal sputtered film 7 with such a reflectance characteristic, for example, as shown in FIG. 2, the metal sputtered film 7 is formed so that the peripheral portion thereof is gradually thinner than the central portion thereof. To do. Alternatively, as shown in FIG. 2, the metal sputtered film 7 is formed such that the concentration of the sputtered metal film 7 is gradually thinner in the peripheral portion than in the central portion.

To form such a metal sputtered film 7,
A vacuum sputtering apparatus as shown in FIG. 4 is used. That is, a support tool 15 for supporting an object to be sputtered is disposed above the bell jar 11, and the support tool 15 is rotatably connected by a motor 14. Further, a sputter source 13 is provided below the bell jar 11 so as to face the support tool 15, and a sputter shield plate 12 is disposed between the sputter source 13 and the support tool 15. When the metal sputtered film 7 is formed by using such a vacuum sputter device, the input substrate 6
Is supported by a support 15, and the motor 14 rotates the input substrate 6 to perform sputtering. By rotating the input substrate 6, the deposited metal sputtered film 7 becomes axially symmetric, and it is possible to easily prevent film deposition unevenness due to at least the angle from the axial center.

Next, the film thickness distribution and the concentration distribution in the radial direction from the axial center of the metal sputtered film 7 are greatly influenced by the sputter time and the shape of the sputter shield plate 12, and are important factors. First, the basic design of the reflectance distribution is performed corresponding to the luminance distribution of the X-ray image tube to be applied as shown in FIG. 5, for example.

As a design factor, the sputtering time at the time of film formation and the reflectance of the metal sputtered film 7 to be formed are different depending on the material, but do not change linearly as shown in FIG. 6, for example. , The reflectance shows the lowest peak in a certain period of time. Therefore, it is necessary to select the sputtering time corresponding to the desired reflectance. Furthermore, spatter shield plate
The 12 aperture shapes directly affect the film thickness and concentration distribution. For example, in the example shown in FIG. 7, the sputter shield plate 12 is provided with a heart-shaped opening 12a. The distribution change from the central part to the peripheral part can be appropriately changed by selecting such an opening 12a.

[0018]

As described above, according to the present invention, a metal film is formed between the input substrate of the input surface and the input fluorescent screen, and the reflectance of this metal film gradually increases from the central portion to the peripheral portion. By making the total amount of light reaching the photocathode and generating photoelectrons relatively larger in the peripheral part than in the central part, the difference in brightness between the central part and the peripheral part is Can be more effectively reduced.

For the metal film, a material having good adhesion to the input substrate can be selected. In addition, the sputtering method and the film thickness selection, and the sputtering having selective openings corresponding to the size and the curved surface shape of the input substrate. By using the shielding plate, it is possible to easily form a metal film having a desired reflectance change with good reproducibility, which is suitable for mass production.

[Brief description of drawings]

FIG. 1 is a schematic sectional configuration diagram showing a sectional configuration of an input surface according to an embodiment of the present invention.

FIG. 2 is a schematic sectional configuration diagram showing a sectional configuration of a main part of an input surface according to the embodiment of the present invention.

FIG. 3 is a schematic sectional configuration diagram showing a sectional configuration of a main part of an input surface according to the embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a vacuum sputtering apparatus for forming an input surface according to the embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a luminance distribution of an input substrate in a radial direction.

FIG. 6 is a characteristic diagram showing the relationship between the sputtering time and the reflectance of a metal film.

7 is a schematic view showing an example of a sputtering shield plate of the sputtering apparatus of FIG.

FIG. 8 is a schematic configuration diagram showing a configuration of an X-ray image tube.

[Explanation of symbols]

 1 ... Vacuum envelope 2 ... Input surface 3 ... Anode 4 ... Output surface 5 ... Focusing electrode 6 ... Input substrate 7 ... Metal film 8 ... Input fluorescent surface 9 ... Protective film 10 ... Photoelectric surface

Claims (2)

[Claims] 1. An input window at one end of a vacuum envelope, an input surface disposed in close proximity to the inside of the tube of the input window and having an input fluorescent surface and a photoelectric surface on at least an input substrate, and the vacuum. An output window arranged at the multi-end portion of the envelope and coaxially opposed to the input window, an output surface arranged inside the tube of the output window, and arranged between the input surface and the output surface. In the X-ray image tube having at least a plurality of electrodes, the input phosphor screen of the input surface is formed with a metal thin film between the input substrate and the input substrate, and the light reflectance of the metal thin film is at the center of the tube axis. An X-ray image tube characterized in that the X-ray image tube is formed so that the height gradually increases from the periphery to the periphery. 2. A vacuum envelope having at least one input window and at least an input surface disposed inside and confronting the inside of the vacuum tube and having at least an input fluorescent surface and a photoelectric surface on an input substrate. In the method of manufacturing an X-ray image tube, in the step of forming the input surface, before the step of forming the input phosphor screen, a metal thin film is inserted through a shield plate having an opening while rotating the input substrate along an axial center. A method for manufacturing an X-ray image tube, comprising the step of depositing so that the light reflectance thereof gradually increases from the axial center portion to the peripheral portion.