JPH02170331A - X-ray image tube - Google Patents

Abstract

PURPOSE:To make it possible to obtain the electric connection of a photoelectric surface and an electrode securely even though a metal membrane is thin by spreading the circular conductive membrane continued electrically to the photoelectric surface on the part of the pillarform crystal surface positioned outside the effective diameter of the input surface, which is made into a plain and continued surface by a mechanical deformation process. CONSTITUTION:A part 210 of the surface outside the effective diameter R of an input phosphor layer is moved to be rubbed while squeezing it with a block made of a material with a relatively small friction coefficient such as a cloth of gauze or the like or Teflon. The part applied with such a grinding process is made as a conductive membrane 204 and Al is vacuum-evaporated in a specific membranous thickness. And the surface of the first phosphor layer 202 which is formed around the A area in such a grinding process is deformed plastically only at the tip part of the pillar-form crystals, and the neighboring parts are connected each other making plain and continued. As a result, the conductive membrane 204 formed thereover is also continued, and a sufficiently low surface resistance value is secured. Consequently, the electric connection of the photoelectric surface at the periphery of the phosphor layers 202 and 203, and the electrode can be obtained securely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) This invention relates to an X-ray image tube, and particularly to improvements in its human power.

(Prior Art) Generally, an X-ray image tube is provided with an input surface on the input side within a vacuum envelope, and an anode and an output surface on the output side. Further, a focusing electrode is disposed along the side wall inside the vacuum envelope from the input side to the output side.

By the way, the conventional input surface is constructed as shown in FIGS. 10 and 11, and FIG. 11 is an enlarged schematic diagram of the peripheral portion 110 of the human input surface in FIG. 10.

That is, the input surface is formed by an input substrate 101 with a smooth surface and an evaporation method on this human-powered substrate 101 under a low degree of vacuum.
A first fluorescent layer 102 whose base material is Csl activated by a.
A second fluorescent layer 103 is formed on the first fluorescent layer 102 by vapor deposition under a high degree of vacuum, and these first fluorescent layers 10
2. An annular metal thin film 104 formed to cover each peripheral edge of the second fluorescent layer 103 and the human-powered board 101;
It consists of a photocathode (not shown) formed directly on the second fluorescent layer 103 or indirectly through another thin layer.

The first fluorescent layer 102 and the second fluorescent layer 103 constitute a so-called input fluorescent layer 105.

The annular metal thin film 104 has a function of electrically connecting the photocathode on the second fluorescent layer 103 and, for example, a metal thin plate electrode holding the input surface. Further, the inner diameter of the annular metal thin film 104 is set to the value of the effective diameter of the input surface. As another function of the annular metal thin film 104, the input fluorescent layer 1
It also has the function of blocking electron emission due to fluorescence from a portion outside the effective diameter of 05.

The first fluorescent layer 102 is an aggregate of Csl columnar crystals having an average diameter of 5 μm to 50 μm and grown almost perpendicular to the input substrate 101, and has a typical film thickness of about 400 μm.
It is. In this way, adjacent columnar crystals of Csl are separated from each other by minute gaps, so they have high resolution characteristics, but if a photocathode is formed directly on the surface, the photocathode will also be similar. The photocathode is divided into micro-islands, and electrical continuity in the direction parallel to the photocathode cannot be obtained.

As a result, as the number of photoelectrons emitted from the photocathode increases, it becomes impossible to keep the potential of the photocathode constant, and
The electron-optical uniformity of the line image tube is significantly impaired,
This causes distortion of the output image and deterioration of resolution characteristics.

Therefore, the surface of the first fluorescent layer 102 has a thickness of 10 μm to 3 μm.
A second fluorescent layer 103 with a thickness of 0 μm is formed. Since this second fluorescent layer 103 has a relatively continuous surface, it is possible to ensure electrical continuity in a direction parallel to the plane of the photocathode formed on this surface.

Conventionally, in order to deposit a first fluorescent layer 102 and a second fluorescent layer 103 on an input substrate 101, a vapor deposition apparatus as shown in FIG.
It is fixed to a rotatable substrate holder 106 inside. Then, while rotating the input substrate 10, the phosphor is evaporated from the evaporation source 108 under a low degree of vacuum, and the first phosphor layer 102 is formed on the manual substrate 101. The inner diameter of the opening of the substrate holder 106 on which the input substrate 101 is directly placed (hereinafter referred to as the opening diameter) is set to a value slightly larger than the manual effective diameter of the X-ray image tube.

When forming the i2 phosphor layer 103 following the first phosphor layer 102, the deposition tank 109 is not returned to atmospheric pressure, and the input substrate 101 is not removed from the substrate holder 106.
In principle, it is possible to restart vapor deposition in a high vacuum state without any problem.

However, it has been found that when the second fluorescent layer 103 is successively deposited using the same substrate holder 106, the annular metal thin film 104 becomes partially discontinuous, making it impossible to put it into practical use.

Hereinafter, a detailed explanation will be given with reference to FIG. 11, which is an enlarged schematic diagram of the peripheral portion 110 of the input surface shown in FIG. 10.

That is, the area marked A in FIG.
The area marked B is the part that is not masked by the substrate holder 106, that is, the part corresponding to the opening of the substrate holder 106. First fluorescent layer 10
Since the film No. 2 is deposited in a low vacuum, the film partially wraps around the A region as well. On the other hand, since the second fluorescent layer 103 is deposited under high vacuum, almost no film is formed in the A region.

Therefore, the surface of the first fluorescent layer 102 is
Continuity is enhanced by the fluorescent layer 103, but in area A, the gaps 112 between the columnar crystals 111 are connected to the second fluorescent layer 10.
3, which results in a discontinuous surface condition.

The annular metal thin film 104 formed on the surface of this fluorescent layer is
For example, the phosphor layer is made of AN and has a thickness of 0.1 μm to 10 μm. On the fluorescent layer that is formed around the A region, the film is formed in an island shape on the surface of the columnar crystal 111, and is substantially electrical conduction becomes impossible.

Because of the problems explained above, conventionally, the first
After forming the fluorescent layer 102, -U, the manual substrate 1 is removed from the vapor deposition apparatus.
After removing 01 and fixing it again in the substrate holder 106 with a larger opening diameter, it was necessary to restart the deposition process. Here, the opening diameter of the substrate holder 106 when forming the first fluorescent layer 102 is DI, the opening diameter of the substrate holder 106 when forming the second fluorescent layer 103 is D2, and the opening diameter of the substrate holder 106 when forming the second fluorescent layer 103 is set as D2. The length of the first fluorescent layer 102 is g
Then, between Dl, D2, and g, D2≧D, -I
The relationship J needs to be satisfied. After forming the first fluorescent layer 102 and the second fluorescent layer 103 through the two-step fluorescent layer deposition process described above, an enlarged schematic view of the peripheral area of the input surface obtained by depositing the annular metal thin film 104 is shown. The one that became the 13th
It is a diagram.

Since the surface of the portion of the first fluorescent layer 102 that wrapped around the A region was also made continuous by the second fluorescent layer 103, there was no discontinuous portion of the annular metal thin film 104.

Incidentally, the problem explained in FIG. 11 could not be improved at all even when a conductive intermediate layer, such as an indium oxide film or an indium tin oxide film, was used as a base for the photocathode.

Furthermore, in order to solve the problem explained in FIG. 11, an attempt was made to increase the thickness of the annular metal thin layer 111104, but it was not continuous on the surface of the first fluorescent layer 102 that wrapped around the area A in FIG. In order to obtain a film, a film thickness of several tens of μm or more is required, and in that case, peeling of the annular metal thin film 104 is likely to occur, so this attempt could not be adopted.

(Issue [1] to be solved by the invention) In the conventional technology, it takes too much time to form the input phosphor layer in order to ensure the continuity of the surface in the peripheral area of the input phosphor layer. This has been a major hindrance to manufacturing line image tubes at low cost.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide an X-ray image tube that has high resolution and is relatively easy to manufacture.

[Structure of the Invention] (Means for Solving the Problems) This invention provides a method in which the surfaces of the columnar crystals located outside the effective diameter of the input surface, among the columnar crystals in the input fluorescent layer, are flattened and made continuous by mechanical deformation processing. This is an X-ray image tube in which a conductive thin film electrically connected to the photocathode is deposited on the flattened and continuous portion.

(Function) According to the present invention, electrical connection between the photocathode and the electrode at the peripheral portion of the fluorescent layer outside the effective diameter can be reliably obtained.

(Examples) Hereinafter, embodiments (seven examples) of the present invention will be described in detail with reference to the drawings.

In order to solve the above problems, this invention improves the input fluorescent layer on the input surface, and only the input fluorescent layer has the following features:
I will explain the manufacturing method.

[Example-1] First, in a vapor deposition apparatus as shown in FIG. 12, the substrate holder 106 was coated with the materials shown in FIGS. 1(a), (b) and 2(a).
, the human-powered board 201 shown in (b) is fixed, and the Csl phosphor is evaporated under low vacuum while rotating.
A first fluorescent layer 202 is formed on 01 to a thickness of about 400 μm.

Thereafter, the Csl phosphor is evaporated under high vacuum without returning the vapor deposition tank 109 to atmospheric pressure, and the Csl phosphor is deposited on the first phosphor layer 202.
A second fluorescent layer 203 is formed to have a thickness of 20 μm. As already explained in the conventional example, even if the annular conductive thin film 204 is formed as it is, as shown in FIG. 11, there will be a partial conduction failure and it cannot be put to practical use.

Therefore, a part 210 of the surface outside the effective diameter of the input phosphor layer shown by diagonal lines in FIG. Rub it while doing so. The pressing force is about 2 to 20 g/cm 2 and the rubbing speed is about 2 to 4 cm/sec.

A conductive thin film 20 is formed on the area where such polishing process has been performed.
As No. 4, AfI was deposited to a film thickness of 0.1 μm. FIG. 2 is an enlarged and schematic cross-sectional view.

Through the above-mentioned polishing process, the surface of the first fluorescent layer 202 that is formed around the A area (see FIG. 11) is plastically deformed only at the tips of the columnar crystals, and the adjacent ones are connected to each other to make the surface flat. It becomes continuous. As a result, the conductive thin film 204 formed thereon is also made continuous, and a sufficiently low surface resistance value can be ensured.

In FIG. 2, 211 is a columnar crystal, and 212 is a gap.

[Example 2] First, as shown in FIGS. 3(a) and 3(b), a portion 311 is formed by partially protruding two parts of the peripheral portion of the fluorescent layer, and the protruding portion 311 is Polish the edges. Therefore, in the method of Example-2, there is less possibility that the inside of the effective diameter will be undesirably polished in the polishing step.

In order to form the protruding portion 311 in the peripheral portion of the fluorescent layer, a substrate holder 106 as shown in FIG.
This can be easily achieved by cutting out a part of the circumference of the opening diameter.

In addition, 301 in the figure is an input board, 302 is a first fluorescent layer, and 3
03 is a second fluorescent layer, and 304 is a conductive thin film.

[Example-3] In the above-mentioned Examples-1 and -2, the cases were described in which the protective layer serving as the base of the photocathode was not formed, but as shown in FIG. 4, the protective layer 405 was formed immediately after the polishing process. After forming,
Similar effects can be obtained by forming an annular conductive thin film 404.

In particular, when the protective layer 405 is electrically conductive, it is also possible to use an annular thin film made of an opaque non-metallic material in place of the electrically conductive thin film 404.

In addition, 401 in the figure is a manual board, 402 is a first fluorescent layer, 4
03 is a second fluorescent layer.

[Example 4] In the above Example 3, the protective layer 405 was formed immediately after the polishing process, but as shown in FIG. 5, the protective layer 505 may be formed immediately before the polishing process.

By the polishing process, not only the first fluorescent layer 502 but also the protective layer 5
05 also undergoes mechanical deformation. When the protective layer 505 is made of an oxide such as silicon oxide, indium oxide, or indium tin oxide, the protective layer 505 may develop cracks 506 or be partially peeled off due to the above polishing (507).
is the peeled part), but the thickness of the protective layer 505 is generally 0.01
Since it is as thin as ~0.5 μm, the continuity of the annular conductive thin film 504 formed thereon with a thickness of 0.1 to 10 μm is not impaired, and the same effects as in the above embodiment can be obtained.

Note that 501 in the figure is a human-powered board, and 503 is a second fluorescent layer.

[Example 5] When a protective layer is used as the underlayer of the photocathode, especially when the protective layer has conductivity, after forming the annular conductive thin film 604 as shown in FIG. Even if the protective layer 605 is formed, the same effects as in the above embodiment can be obtained.

In addition, 601 in the figure is an input board, 602 is a first fluorescent layer, and 6
03 is a second fluorescent layer.

[Example 6] Above, an example in which the surface of the input fluorescent layer is polished before the formation of the annular thin film has been described. Next, an example in which the surface is polished after the formation of the thin film will be described.

First, a manual fluorescent layer similar to that shown in FIG. 11 is formed.

As already explained, the artificial fluorescent layer shown in FIG. 11 cannot be realized because a part of the annular conductive thin film is not electrically conductive.

In FIG. 7, a part of the surface of the non-electrically conductive region of the annular metal thin film 11i704 is pressed and rubbed with a block made of a relatively hard material such as AI, and the annular metal thin film 704 is plastically deformed. Demonstrates a highly developed human resource side.

The electrically non-conductive region of the annular metal thin film 704 is made of 11% annular metal thin film 704, which has been confirmed to be able to ensure electrical conduction through the polishing process described above. It is desirable to use single metals such as or TJ or other alloys.

The annular metal thin film 704 has a thickness of about 5 μm l! 1 thickness of Ag
When using a membrane, the above polishing conditions are a pressing force of approximately 50/c
Good results were obtained at a rubbing speed of 4 cm/see.

When the input surface shown in FIG. 7 was applied to an X-ray image tube, it was confirmed that electrical continuity between the photocathode and the external electrode could be ensured.

In the figure, 701 is an input board, 702 is a first fluorescent layer, and 702 is a first fluorescent layer.
03 is a second fluorescent layer.

[Example-7] In the above example, a case was described in which an annular metal thin film or an annular non-metal thin film was used, but these have the function of blocking fluorescence from the fluorescent layer outside the effective diameter from reaching the photocathode. An example will be described in which no membrane is used at all.

FIG. 8 shows a first fluorescent layer 802 similar to Example-3 above.
FIG. 3 is a partial cross-sectional view of the input fluorescent layer in which a conductive protective layer 805 is formed after polishing the surface of the input fluorescent layer. When forming a photocathode on this input fluorescent layer, electrical connection between the external electrode and the photocathode is ensured by the conductive protective layer 805.

Note that 801 in the figure is a human-powered board, and 803 is a second fluorescent layer.

FIG. 9 shows an X-ray image tube using the input surface of Example 7. That is, since the human power surface 901 does not block light emission from the fluorescent layer outside the effective diameter of the human power surface 901 at all, photoelectrons 9 are also emitted from the photocathode formed on the surface of the fluorescent layer outside the effective diameter.
06 is accelerated and focused onto the output surface 902. Therefore, a mask 903 is installed near the output surface 902 to prevent photoelectrons 906 from the fluorescent layer outside the effective diameter of the input surface from entering the output surface 902.
By arranging this, it is possible to limit the photoelectrons 906 incident on the output surface 902 to only the photoelectrons 907 from within the effective diameter of the input surface.

In the figure, 904 is an anode, and 905 is a focusing electrode.

Note that instead of the mask 903, an optical mask may be placed on the light output side of the output surface 902 to block transmission of light emitted from the output surface.

As described above, the same effects as in the other embodiments can be obtained in this embodiment-7 as well.

[Effects of the Invention] According to the present invention, among the columnar crystals in the human-powered fluorescent layer, the surfaces of the columnar crystals located outside the effective diameter of the human-powered surface are flattened and made continuous by mechanical deformation processing, and this flattening and Since the annular conductive thin film electrically connected to the photocathode is deposited on the continuous portion, even if the metal thin film is thin, the electrical connection with the photocathode is reliably obtained and it is difficult to peel off.

A known example of flattening the tips of the Csl columnar crystals of the effective screen by cutting is described in Japanese Patent Application Laid-Open No. 63-88732, but this method does not take the surrounding areas into consideration. It is recognized that there is no Also, even if you cut it,
Since a gap remains, the effects of the present invention cannot be obtained.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are a sectional view and a bottom view showing the input surface of an X-ray image tube according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the main part A of FIG. 1(a). 3 (a)
) and (b) are cross-sectional views and bottom views showing an input surface according to another embodiment of the present invention, and FIGS. 4 to 8 show the main parts of the human power surface according to another embodiment of the present invention. FIG. 9 is an enlarged cross-sectional view showing the entire X-ray image tube using the input surface according to another embodiment of FIG. 8, and FIG. 1O is the input surface of the conventional X-ray image tube. FIG. 11 is an enlarged cross-sectional view of the main part of FIG. 10, FIG. 12 is a cross-sectional view of the vapor deposition apparatus, and FIG. 13 is an input surface of another conventional X-ray image tube. FIG. 201... Input substrate, 202... First fluorescent layer, 20
3... Second fluorescent layer, 204... Annular metal thin film. Applicant's agent Patent attorney Takehiko Suzue Figure 6 Figure 10

Claims (1)

[Scope of Claim] An X-ray image tube comprising an input surface in which at least a fluorescent layer made of columnar crystals and a photocathode are laminated on an input substrate, wherein the columnar crystals are located outside the effective diameter of the input surface. The surface of the columnar crystal is made flat and continuous by mechanical deformation processing,
An X-ray image tube characterized in that a conductive thin film electrically connected to the photocathode is deposited on the flattened and continuous portion.