JP2809657B2 - X-ray image tube and method of manufacturing the same - Google Patents

Description

The present invention relates to an X-ray image tube and a manufacturing method thereof.
In particular, it relates to improvement of the input surface.

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

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

That is, the input surface has an input substrate 101 having a smooth surface, a first fluorescent layer 102 formed on the input substrate 101 by a vapor deposition method under a low vacuum and activated by Na and CsI, and A second fluorescent layer 103 formed on the first fluorescent layer 102 by a vapor deposition method under a high vacuum, and the first fluorescent layer 102 and the second fluorescent layer 103
And an annular metal thin film 104 formed to cover each peripheral portion of the input substrate 101, and a photoelectric surface (not shown) formed directly on the second fluorescent layer 103 or indirectly via another thin layer. ).

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

The ring-shaped metal thin film 104 has a function for electrically connecting the photocathode on the second fluorescent layer 103 to, for example, a thin metal plate electrode holding the input surface. Also, the annular metal thin film 104
Is set to a value substantially equal to the effective diameter of the input surface. As another function of the annular metal thin film 104, it also has a function of blocking electron emission due to fluorescence from a portion of the input fluorescent layer 105 outside the effective diameter.

The first fluorescent layer 102 is an aggregate of columnar crystals of CsI having an average diameter of 5 μm to 50 μm and grown almost perpendicular to the input substrate 101, and has a typical thickness of about 400 μm. As described above, since the adjacent columnar crystals of CsI are separated from each other by fine gaps, when the photoelectric surface is directly formed on the half surface having high resolution characteristics, the photoelectric surface is also similar. Therefore, electrical conduction in a direction parallel to the surface of the photocathode cannot be obtained.

As a result, as the number of photoelectrons emitted from the photocathode increases, the potential of the photocathode cannot be kept constant,
The electron-optical uniformity of the X-ray image tube is significantly impaired, resulting in distortion of an output image and deterioration of resolution characteristics.

Therefore, the surface of the first fluorescent layer 102 has a thickness of 10 μm to 30 μm.
A second fluorescent layer 103 having a thickness of m is formed. Since the second fluorescent layer 103 has a relatively continuous surface, electrical conduction in a direction parallel to the surface of the photoelectric surface formed on this surface can be ensured.

Conventionally, a first fluorescent layer 102 and a second fluorescent layer
In order to deposit 103, a deposition apparatus as shown in FIG. 12 is used, and the input substrate 101 is fixed to a rotatable substrate holder 106 in a deposition tank 109. Then, the phosphor is evaporated from the evaporation source 108 under a low degree of vacuum while rotating the input substrate 101 to form the first fluorescent layer 102 on the input substrate 101.
The inner diameter of the opening of the portion of the substrate holder 106 where the input substrate 101 directly rests (hereinafter, referred to as the opening diameter) is set to a value slightly larger than the effective diameter of the input surface of the X-ray image tube.

In forming the second fluorescent layer 103 following the first fluorescent layer 102, the deposition tank 109 is not returned to the atmospheric pressure and the input substrate 101
It is possible, in principle, to restart the deposition in a high vacuum state without removing the substrate from the substrate holder 106 without any problem.

However, when the second phosphor layer 103 is continuously deposited on the same substrate holder 106, the annular metal thin film 104
Was partially discontinuous and could not be put to practical use.

Hereinafter, a detailed description 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.

That is, the region indicated by A in FIG. 11 is a portion masked by the substrate holder 106, and the region indicated by B is a portion not masked by the substrate holder 106, that is, a portion corresponding to the opening of the substrate holder 106. is there. Since the first fluorescent layer 102 is deposited in a low vacuum, the first fluorescent layer 102 is formed so as to partially reach the region A. On the other hand, since the second fluorescent layer 103 is deposited under a high vacuum, it is hardly formed in the region A. Therefore,
The continuity of the surface of the first fluorescent layer 102 is increased by the second fluorescent layer 103 in the region B, but the columnar crystal is formed in the region A.
The gap 112 between 111 is not filled with the second fluorescent layer 103, and has a discontinuous surface state.

The annular metal thin film 104 formed on the surface of the fluorescent layer is
For example, Al is used as a material and is formed to a thickness of 0.1 μm to 10 μm. On the fluorescent layer formed around the region A, a film is formed in an island shape on the surface of the columnar crystal 111 and substantially formed. Into a non-conductive state.

As described above, since the above-described problem occurs, conventionally, after the first fluorescent layer 102 is formed, the input substrate 101 is temporarily removed from the evaporation apparatus.
Substrate holder 106 having a larger opening diameter
After re-fixing, the vapor deposition process had to be restarted.
Here, the substrate holder 1 when forming the first fluorescent layer 102 is formed.
The opening diameter of 06 is D ₁ , the opening diameter of the substrate holder 106 for forming the second fluorescent layer 103 is D ₂ , and the length of the first fluorescent layer 102 formed around the area A is 1. When D ₁ , D ₂ , l
, The relationship of D ₂ ≧ D ₁ +1 needs to be satisfied. The first phosphor layer 102 and the second phosphor layer 1 are formed through the two-step phosphor layer deposition process as described above.
FIG. 13 is an enlarged schematic view of the periphery of the input surface obtained by depositing the 03 and then depositing the annular metal thin film 104.

Since the surface of the portion of the first fluorescent layer 102 that goes around the region A is also continuous by the second fluorescent layer 103, the annular metal thin film 104
Was not present at all.

The problem described with reference to FIG. 11 could not be improved at all even when a conductive intermediate layer, for example, an indium oxide film or an indium tin oxide film was used as a base of the photocathode.

Further, in order to solve the problem described in FIG. 11, an attempt was made to increase the thickness of the annular metal thin film 104.
In order to obtain a continuous film on the surface of the first fluorescent layer 102 which goes around the region A in FIG. 1, a film thickness of several tens μm or more is required. In this case, the annular metal thin film 104 is easily peeled off. , This attempt could not be adopted.

(Problems to be Solved by the Invention) In the conventional technique, it takes too much time to form the input fluorescent layer in order to secure the continuity of the surface in the peripheral portion of the input fluorescent layer, and a high-resolution X-ray image This was a major hindrance to making tubes cheap.

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray image tube which has a high resolution and is relatively easy to manufacture, and a method of manufacturing the same.

[Constitution of the Invention] (Means for Solving the Problems) According to the present invention, among the columnar crystals in the input fluorescent layer, the surface of the columnar crystal located outside the effective diameter of the input surface is flattened / continuous by mechanical deformation processing. An X-ray image tube in which a conductive thin film electrically connected to the photocathode is deposited on the flattened and continuous portion, and a method of manufacturing the same.

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

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

It should be noted that the present invention is an improvement of the input fluorescent layer on the input surface in order to solve the above-mentioned problem, and only the input fluorescent layer will be described in terms of a manufacturing method.

Example 1 First, FIGS. 1 (a) and (b) and FIGS. 2 (a) and 2 (a)
The input substrate 201 shown in (b) is fixed, the CsI phosphor is evaporated under a low degree of vacuum while rotating, and the first phosphor layer 202 is formed on the input substrate 201 to a thickness of about 400 μm.

After that, the CsI phosphor was evaporated under a high vacuum without returning the vapor deposition tank 109 to the atmospheric pressure, and 5 to 20 μm was deposited on the first phosphor layer 202.
The second fluorescent layer 203 is formed with a thickness of. As already described in the conventional example, even if the ring-shaped conductive thin film 204 is formed as it is, conduction failure partially occurs as shown in FIG. 11 and cannot be put to practical use.

Therefore, a part 210 of the surface outside the effective diameter of the input fluorescent layer, which is hatched in FIG. 1 (b), is pressed by a cloth made of gauze or the like or a block made of a material having a relatively small coefficient of friction such as Teflon. While rubbing. The pressing force is 2 to 20 gf / cm
^The rubbing speed is about ² to 4 cm / sec.

The portion subjected to such a polishing step is replaced with a conductive thin film 20.
Al was deposited to a thickness of 0.1 μm as 4. FIG. 2 is an enlarged schematic view of the cross section.

By the above-mentioned polishing step, only the tip of the columnar crystal is plastically deformed on the surface of the first fluorescent layer 202 formed around the region A (see FIG. 11), and the adjacent surfaces are connected and flattened.・ Continuous. As a result, the conductive thin film 204 formed thereon is also continuous, and a sufficiently low surface resistance value can be secured.

 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 projecting two portions of a peripheral portion of the fluorescent layer. Polish the edges. Thus, in the method of the embodiment-2, there is little possibility that the polishing is performed undesirably within the effective diameter in the polishing step.

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

In the figure, 301 is an input substrate, 302 is a first fluorescent layer, 303 is a second fluorescent layer, and 304 is a conductive thin film.

Example 3 In Examples 1 and 2 described above, the case where the protective layer serving as the underlayer of the photocathode is not formed is described. However, as shown in FIG. After forming
Similar effects can be obtained even if the annular conductive thin film 404 is formed.

In particular, when the protective layer 405 has conductivity, an annular thin film using an opaque non-metallic material can be used instead of the conductive thin film 404.

In the figure, reference numeral 401 denotes an input substrate, 402 denotes a first fluorescent layer, and 403 denotes a second fluorescent layer.

Example 4 In Example 3, the protective layer 405 was formed immediately after the polishing step. However, as shown in FIG. 5, the protective layer 505 may be formed immediately before the polishing step.

By the polishing process, not only the first fluorescent layer 502 but also the protective layer 505 is formed.
Also undergo mechanical deformation. In the case where an oxide such as silicon oxide, indium oxide, or indium tin oxide is used as the protective layer 505, the protective layer 505 is cracked by the above polishing.
06 enters or peels off partly (507 is peeling part)
However, since the thickness of the protective layer 505 is generally as thin as 0.01 to 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. A similar effect can be obtained.

 In the drawing, reference numeral 501 denotes an input substrate, and 503 denotes a second fluorescent layer.

[Example-5] In the case where a protective layer is used as an underlayer of the photocathode, and particularly when the protective layer has conductivity, after the formation of the annular conductive thin film 604 as shown in FIG. Even if the protective layer 605 is formed, the same operation and effect as the above embodiment can be obtained.

In the figure, 601 is an input substrate, 602 is a first fluorescent layer, and 603 is a third fluorescent layer.

[Embodiment-6] The embodiment in which the surface of the input fluorescent layer is polished before the formation of the annular thin film has been described above. Next, an example in which the surface is polished after the thin film is formed will be described.

First, an input fluorescent layer similar to that shown in FIG. 11 is formed. As described above, the input fluorescent layer shown in FIG. 11 cannot be realized because part of the annular conductive thin film cannot electrically conduct.

FIG. 7 is a diagram showing a continuous process of plastically deforming the annular metal thin film 704 by rubbing while partially pressing the surface of the electrically non-conductive region of the annular metal thin film 704 with a block made of a relatively hard material such as Al. The input surface with enhanced characteristics is shown. It has been confirmed that the electrically non-conductive region of the annular metal thin film 704 can secure electrical conduction by the above-mentioned polishing step. As a material of the annular metal thin film 704, Al or Sr or In or Tl which is relatively easily plastically deformed is used. It is desirable to use a carrier metal such as, or another alloy.

When an Al film having a thickness of about 5 μm was used as the annular metal thin film 704, good results were obtained under the above polishing conditions with a pressing force of about 50 / cm ² and a rubbing speed of about 4 cm / sec.

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

In the figure, 701 is an input substrate, 702 is a first fluorescent layer, and 703 is a second fluorescent layer.

[Embodiment-7] In the above embodiment, the case where the annular metal thin film or the annular nonmetal thin film is used has been described. However, it has a function of blocking the fluorescence from the fluorescent layer outside the effective diameter from reaching the photoelectric surface. An embodiment in which no membrane is used will be described.

FIG. 8 shows the first fluorescent layer 802 in the same manner as in Example 3 described above.
FIG. 4 is a partial cross-sectional view of an input fluorescent layer on which a conductive protective layer 805 is formed after polishing the surface of FIG. When a photocathode is formed on the input fluorescent layer, electrical connection between the external electrode and the photocathode is ensured by the conductive protective layer 805. In the above case, the manufacturing method will be described in more detail. When the surface of the columnar fluorescent layer in the outer peripheral area of the effective diameter of the input surface is pressed and flattened, the input substrate is further planarized from the entire area of the effective diameter. A light-transmitting conductive protective layer 805 is formed so as to cover up to the surface, and then a photoelectric surface is formed on the conductive protective layer 805.

 In the figure, reference numeral 801 denotes an input substrate, and 803 denotes a second fluorescent layer.

FIG. 9 shows an X-ray image tube using the input surface of this embodiment-7. That is, since the light emission from the fluorescent layer outside the effective diameter of the input surface 901 is not blocked at all, the photoelectrons 906 also accelerate to the output surface 902 from the photoelectric surface formed on the fluorescent layer surface outside the effective diameter of the input surface 901. Focused. Therefore, by disposing a mask 903 that does not allow the photoelectrons 906 from the fluorescent layer outside the effective diameter of the input surface to be incident on the output surface 902 in the vicinity of the output surface 902, the photoelectrons 906 incident on the output surface 902 can be moved to the effective diameter of the input surface. It is possible to limit to only photoelectrons 907 from inside.
In the figure, 904 is an anode, and 905 is a focusing electrode.

Note that, instead of the mask 903, an optical mask that blocks transmission of light emitted from the output surface may be disposed on the light emission side of the output surface 902.

As described above, in the seventh embodiment, the same effects as those of the other embodiments can be obtained. Furthermore, in Example-7
In this case, the electrical connection between the photocathode and the input substrate 801 can be reliably obtained without the need for an extra conductor such as an aluminum film, and the peripheral portion of the output image is difficult to see due to the generation of photoelectrons from the peripheral portion of the input surface. Is eliminated.

[Effects of the Invention] According to the present invention, of the columnar crystals in the input fluorescent layer, the surface of the columnar crystal located outside the effective diameter of the input surface is flattened and made continuous by mechanical deformation processing. 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, electrical connection with the photocathode can be reliably obtained and the metal thin film is hardly peeled off.

In addition, as a known example of flattening the tip of the CsI columnar crystal of the effective screen by cutting, there is a known example described in JP-A-63-88732, which takes into account the peripheral portion. Not admitted. Further, even if cutting is performed, a gap remains, so that the effect of the present invention cannot be obtained.

[Brief description of the drawings]

1 (a) and 1 (b) are a sectional view and a bottom view showing an input surface of an X-ray image tube according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a main part A of FIG. 1 (a). 3 (a) and 3 (b) are a sectional view and a bottom view showing an input surface according to another embodiment of the present invention, and FIGS. 4 to 8 are other alternative views of the present invention. FIG. 9 is an enlarged cross-sectional view showing a main part of an input surface according to the embodiment of FIG. 9. FIG. 9 is a cross-sectional view showing an entire X-ray image tube using the input surface according to another embodiment of FIG. FIG. 11 is a cross-sectional view showing an input surface of a conventional X-ray image tube, FIG. 11 is a cross-sectional view showing an enlarged part of FIG. 10, FIG. 12 is a cross-sectional view showing a vapor deposition apparatus, and FIG. FIG. 11 is a cross-sectional view showing an input surface of another X-ray image tube. 201: input substrate, 202: first fluorescent layer, 203: second fluorescent layer, 204: annular metal thin film.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 9/233 H01J 29/18-29/38 H01J 31/49-31/50

Claims (2)

(57) [Claims] An input substrate is provided on an input substrate disposed on an X-ray input side of a vacuum envelope. An input surface is provided by stacking at least a phosphor layer made of columnar crystals and a photocathode, and an anode and an output surface are provided on an output side. Wherein the surface of the columnar fluorescent layer in the outer peripheral area of the effective diameter of the input surface is flattened, and the flattened area from the entire inner area of the effective diameter is provided. A light-transmitting conductive protective layer covers the phosphor substrate from the fluorescent layer to the input substrate surface. The photoelectric surface is formed on the conductive protective layer. A mask for limiting the incidence of photoelectrons to the output surface or a mask for limiting emission of emitted light from the periphery of the output surface.
Line image tube. 2. An input substrate disposed on an X-ray input side of a vacuum envelope, at least a phosphor layer and a photocathode made of columnar crystals are laminated to provide an input surface, and an anode and an output surface are provided on an output side. In the method for manufacturing an X-ray image tube, the surface of the columnar fluorescent layer in the outer peripheral area of the effective diameter of the input surface is pressed and flattened, and the flattened area is further removed from the entire area of the effective diameter. A method for manufacturing an X-ray image tube, comprising: forming a light-transmitting conductive protective layer covering the input substrate surface through the above-described process; and forming the photocathode on the conductive protective layer.