JPH09106764A - Manufacture of electronic tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize excellent vacuum, decrease residual gas in an electron tube, and significantly reduce noise caused by remaining gas. SOLUTION: In a vacuum atmosphere, an incident window 1 having a photoelectric face 2, an indium ring 22 to which a SUS ring 22 is concentrically fitted outside, a side tube 6 holding the photoelectric face 2 in vacuum are coaxially disposed successively. The incident window 1 and side tube 6 are relatively made closer so as to block the opening end of the side tube by the incident window 1, and to push deform the indium ring 2 to vacuum seal an electron tube. The indium ring 20 is made thinner toward the center side and is formed tapered in a cross section, and a slit 21 which can communicate the outside and the inside of the electron tube until just before sealing completion is formed in the indium ring 20 so that gas inside the tube is exhausted from the slit 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electron tube, and more particularly to a method of manufacturing an electron tube in which a low melting point metal is used to vacuum-seal an entrance window and a side tube.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for collecting biological information in a dark field. Under such circumstances, electron tubes such as phototubes, photomultiplier tubes, and image intensifier tubes are widely used because they can detect weak optical image information as electric signals or images with high sensitivity.

A proximity type image intensifying tube is shown in FIG. 15 as an example of the electron tube for such application. In this image intensifying tube, a photocathode 2 for converting an optical image received by the incident window 1 into a photoelectron image according to its brightness is provided inside an incident window 1 made of a glass face plate (face plate). It is formed of a metal or a compound semiconductor. An exit window 3 composed of a fiber optic plate (FOP) made up of a large number of glass fibers is arranged at a position facing the entrance window 1, and the inside of the exit window 3 corresponds to the incident electrons. A fluorescent surface 4 that emits light (fluorescence) is formed. Further, between the entrance window 1 and the exit window 3, an MCP (microchannel plate) which multiplies the photoelectrons emitted from the photocathode 2 and emits electrons (secondary electrons).
Electrons accelerated and multiplied by the interposition of 5 collide and enter the phosphor screen 4. The entrance window 1 and the exit window 3 are
They are connected by a side tube 6 made of ceramic, and the inside of the tubes is kept in a high vacuum. The side tube 6 is also provided with electrodes 7, 8 and 9 as connecting means for ensuring electrical continuity while maintaining vacuum tightness.

In manufacturing the image intensifying tube having such a structure, the entrance window 1 and the side tube 6 are hermetically connected to each other by forming the photocathode 2 in the entrance window 1, while the side tube 6 and the exit window 3 and the MCP are formed.
After the connection with 5 and the like is completed and only one end of the side tube 6 is opened, it is performed in the vacuum sealing stage of the final assembly. In addition, the connection between the entrance window 1 and the side tube 6 is generally made of indium 10 which is a low melting point metal in consideration of the thermal expansion coefficient of both members.
Is used.

Conventionally, as a sealing method using indium,
As described in JP-A-62-262353,
A method using a sealing member in which a hard metal ring is provided on an indium ring is known. The method using this sealing member is shown in FIG.
As shown in FIG. 6, in a vacuum atmosphere, an entrance window 1 having a photocathode 2, an indium ring 12 provided with a hard metal ring 11 on the outer periphery, and a side tube 6 for holding the photocathode 2 in vacuum are provided.
After coaxially arranging and, the incident window 1 and the side tube 6 are relatively brought close to each other, the opening end of the side tube 6 is closed by the incident window 1, and the indium ring 12 is pressed and deformed. Vacuum sealing is performed.

[0006]

Generally, the quality of vacuum airtightness largely depends on the manner of contact between the end face of the entrance window 1 and the side tube 6 and the surface of the indium ring 12, and the wettability of this contact portion is poor. Therefore, good vacuum tightness cannot be maintained. However, before vacuum sealing, a heat treatment for degassing is usually performed in advance in vacuum. As a result, an oxide film may be formed on the surface of the indium ring 12. Since the metal oxide film deteriorates the wettability, it causes poor airtightness.

Therefore, it is conceivable to use a large amount of indium to increase the amount of deformation thereof and destroy the oxide film on the surface. However, in the above-described conventional manufacturing method, the thickness of the indium ring 12 used is uniform, and first, the surface of the indium ring 12 comes into surface contact with each end face of the entrance window 1 and the side tube 6. Therefore, the oxide film existing on the surface of the indium ring 12 does not easily collapse even if a large amount of indium is used, and the oxide film remains at the interface between the indium ring 12 and the incident window 1 or the side tube 6, which may cause poor airtightness. was there.
Further, if the thickness of the indium ring 12 is uniform, the incident window 1 and the side tube 6 may be misaligned (center misalignment) when pressed, which is also a factor that impedes vacuum airtightness.

A method for increasing the amount of deformation by filling a large amount of indium in an indium reservoir with an inner groove is disclosed in Japanese Patent Laid-Open No. 6-318439, but this method also uses baking for degassing. Since the excessively filled indium sometimes flows out from the indium reservoir into the inner groove, its effect could not be expected.

Further, in the conventional manufacturing method, when the indium ring 12 is pressed and deformed, the gas generated by the deformation of indium is confined inside the image intensifying tube. In the case of a vidicon, which has a large electron tube capacity, a gas generated from indium does not cause a problem in sensitivity, but when a very small PMT (photomultiplier tube) is used to detect extremely weak light with high sensitivity. However, the gas generated from indium remains in the electron tube having a small capacity, so that noise is generated and the performance of the electron tube is significantly deteriorated.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to obtain good vacuum tightness, reduce the gas remaining in the electron tube, and significantly reduce the noise due to the residual gas. An object of the present invention is to provide a method of manufacturing an electron tube that can be manufactured.

[0011]

In order to solve the above problems, the invention according to claim 1 provides an entrance window having a photocathode and a hard metal ring on the outer peripheral surface of the low melting point metal ring in a vacuum atmosphere. The sealing ring provided and the side tube for holding the photocathode in vacuum are sequentially arranged coaxially, and the entrance window and the side tube are relatively brought close to each other with the sealing ring sandwiched between them. In the method of manufacturing an electron tube in which the opening end of is closed by the entrance window and the low melting metal ring is pressed and deformed to vacuum seal the electron tube, the low melting metal ring is tapered toward the center side to have a tapered cross-section. It was decided to form a groove in the low melting point metal ring that allows communication between the inside and outside of the electron tube until just before the completion of sealing.

In the invention according to claim 2, the low melting point metal is indium or an alloy containing indium as a main component, and the groove is formed from the inner peripheral surface to the outer peripheral surface of the low melting point metal ring.

Further, in the invention according to claim 3, the electron tube to be manufactured further comprises electron multiplying means for multiplying photoelectrons photoelectrically converted in the photocathode and emitted into a vacuum to emit secondary electrons. It is characterized by

Further, the invention according to claim 4 is characterized in that the manufactured electron tube further comprises a light emitting display means which emits light in response to incident electrons.

In the manufacturing method of the present invention, since the low-melting-point metal ring is formed in a tapered cross-section so that the thickness gradually decreases toward the center, the low-melting-point metal ring is first pressed at the time of pressing in vacuum sealing. The entrance window and the peripheral portions of the end faces of the side tubes start contacting the surface of the ring so as to cut into the low melting point metal ring, and the low melting point metal ring is deformed. Therefore, even if an oxide film is present on the surface of the low melting point metal ring, the oxide film is broken and the end face of the entrance window or the side tube comes into contact with the non-oxidizing low melting point metal inside the low melting point metal ring. This makes it possible to maintain vacuum tightness with good reproducibility.

Further, since the low-melting-point metal ring has a tapered cross-section, the entrance window, the low-melting-point metal ring and the side tube can be easily aligned with each other, and the low-melting point metal ring is pressed without displacement. be able to. Therefore, good vacuum tightness can be obtained.

Further, according to the present invention, an exhaust groove is formed in the low melting point metal ring so that the inside and outside of the electron tube can communicate with each other until just before the completion of sealing. For example, the low-melting-point metal ring has a diameter larger than the diameter of the entrance window and the side tube, and the groove extending in the radial direction is formed.
As a result, the gas generated by the deformation of the low melting point metal ring and entering the inside of the tube is exhausted to the outside of the tube through the groove until the groove is crushed by the incident window and the side tube and sealing is completed. be able to. Therefore, the gas remaining in the electron tube can be reduced, and the noise due to the residual gas can be significantly reduced.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIGS.
The manufacturing method according to the present invention will be described.

FIGS. 1 and 2 are partially fragmented front views showing the state before and after vacuum sealing of the image intensifying tube according to this embodiment, and FIG. 1 is composed of an indium ring 20 and a SUS ring 22. A state in which the entrance window 1 having the photocathode 2 formed on the inner surface and the side tube 6 are arranged coaxially with each other with the sealing ring sandwiched therebetween, FIG. 2 shows the inner peripheral portion of the entrance window 1 and the open end of the side tube 6. The state is shown in which the indium ring 20 is pressed and deformed in between to complete vacuum sealing.

FIG. 3 shows an example of an image intensifying tube manufactured by the manufacturing method according to the present invention. In FIG. 3, the same components as those of the image intensifying tube shown in FIG. 15 are designated by the same reference numerals. Unlike the image intensifying tube shown in FIG. 15, the image intensifying tube shown in FIG. 3 is not provided with MCP which is a means for multiplying photoelectrons emitted from the photocathode 2 into a vacuum. Further, the sealing ring shown in FIGS. 4 to 6 is used for connecting the entrance window 1 and the side tube 6.

FIG. 4 is a perspective view showing the sealing ring used in the present embodiment, and FIGS. 5 and 6 are sectional views taken along the line VV and VI-VI in FIG. 4, respectively. is there. The indium ring 20 having an outer diameter larger than that of the entrance window 1 and the side tube 6 is formed with a width such that the inner diameter is larger than the inner diameter of the side tube 6. Moreover, the indium ring 20 is formed in a tapered cross-section that becomes thinner toward the center side. Then, U-shaped grooves 21 are formed on the tapered surfaces on both sides of the indium ring 20 so as to extend in the radial direction at intervals that divide the circumferential direction into eight equal parts and extend along the tapered surfaces. The groove 21 on one surface and the groove 21 on the other surface
Means that the groove 21 on one surface is formed at an intermediate position between the adjacent grooves 21 on the other surface without overlapping in the axial direction.

Further, a stainless steel SUS ring 22 is concentrically attached to the indium ring 20, and the indium ring 20 is held by the SUS ring 22. The height of the SUS ring 22 is the same as the outer peripheral thickness of the indium ring 20.

An image intensifying tube is manufactured in the following manner using the sealing ring having such a structure. FIG. 7 shows an evacuation device used in this embodiment. In the first vacuum container 23 shown in FIG. 7, the support rods 2 are arranged so as to face each other on the axis thereof.
4, 25 are provided to be able to approach and separate from each other while maintaining an airtight state via a bellows or the like. Further, a second vacuum container 27 is connected to the first vacuum container 23 via a gate valve 26.

First, the entrance window 1 having the photocathode 2 formed therein is provided at the inner end of one of the supporting rods 25, and the side tube 6 to which the exit window 3 having the phosphor screen 4 is airtightly connected in advance is connected to the other side. The support rod 24 is provided at the inner end portion thereof, and further, the indium ring 20 having the SUS ring 22 fitted therein is provided between the incident window 1 and the side tube 6. After evacuating the inside of the first vacuum container 23 to a predetermined vacuum degree, open the gate valve 26,
The entrance window 1 is carried into the second vacuum container 27 by a carrying device (not shown). Thereafter, in the second vacuum container 27, the photocathode 2 formed in the entrance window 1 is heated to about 600 ° C. to clean the surface of the photocathode 2 by heating.

Next, the temperature of the photocathode 2 is lowered to near room temperature,
An activation treatment for lowering the work function of the surface is performed by applying Cs and O ₂ . During this period, the SUS ring 22 in the first vacuum container 23, the fluorescent screen 4 of the emission window 3 and the like are degassed. Then, the entrance window 1 supporting the photocathode 2 that has been subjected to the activation treatment is conveyed again into the first vacuum container 23.
At this stage, the entrance window 1, the indium ring 20, and the side tube 6 are coaxially located.

Next, the support rods 24 and 25 are brought close to each other (in the direction of the arrow in FIG. 7), the indium ring 20 is pressed and deformed by the entrance window 1 and the side tube 6, and the groove 21 provided in the indium ring 20 is formed. Press until it is crushed to complete vacuum sealing. FIG.
FIG. 2 shows the positional relationship of each member immediately before the start of pressing, and FIG. 2 shows the state where the vacuum sealing is completed.

In such a manufacturing method, when the vacuum sealing is pressed, first, on the surface of the indium ring 20, the peripheral edge portions of the end faces of the entrance window 1 and the side tube 6 are formed.
To make contact with each other so that the indium ring 20 is deformed. At this time, the indium ring 20 tends to deform inward and outward in the radial direction, but the outward deformation is suppressed by the SUS ring 22, and most of it deforms inward. As a result, even if an oxide film is present on the surface of the indium ring 20, the oxide film is broken and the indium ring 20 is largely deformed, so that the end faces of the entrance window 1 and the side tube 6 are not oxidized inside the indium ring 20. Contact indium in the state. FIG. 8 shows a cross section of a main part at the start of pressing, and FIG. 9 shows a cross section of the main part at the time of completion of vacuum sealing.

Further, since the indium ring 20 has a tapered cross-section and the grooves 21 are provided at equal intervals, the entrance window 1, the indium ring 20 and the side tube 6 can be easily aligned with each other, and the indium ring 20 can be easily aligned. The pressing of 20 is also performed without displacement, and good vacuum tightness is secured.

On the other hand, until the groove 21 is crushed by the entrance window 1 and the side tube 6 and sealing is completed, the gas generated by the deformation of the indium ring 20 and entering the inside of the tube passes through the groove 21. Exhausted outside the pipe. Therefore, the gas remaining in the image intensifier tube is reduced, and the noise due to the residual gas is significantly reduced.

(Embodiment 2) FIG. 10 shows an example of a photomultiplier tube with a built-in microchannel plate manufactured by the manufacturing method according to the present invention. In FIG. 10, the same structure as the image intensifier tube shown in FIG. 15 is shown. Parts are denoted by the same reference numerals.

Unlike the image intensifier tube shown in FIG. 15, the microchannel plate photomultiplier tube of FIG. 10 is provided with an anode 28 for collecting photoelectrons multiplied by MCP5 instead of the emission window having a fluorescent screen. ing. Reference numeral 29 is
The electrodes are shown. Further, the same sealing member as that of the first embodiment is used for connecting the entrance window 1 and the side tube 6.

As shown in FIG. 11, the microchannel plate photomultiplier of this embodiment is manufactured by the same vacuum exhaust device as in the first embodiment. The method is the same as that of the first embodiment, such as starting the vacuum sealing operation after previously connecting the MCP 5 and the anode 28 to the side tube 6. However,
When degassing the SUS ring 22 and the like during the activation process of the photocathode 2, the MCP 5 and the anode 28 are also degassed. At this time, depending on the case, MCP5 is changed to Cs.
May be treated with alkali. In addition, the operation and effect at the time of vacuum sealing are similar to those of the first embodiment.

(Embodiment 3) FIG. 12 shows an example of an image intensifying tube manufactured by the manufacturing method according to the present invention. This image intensifying tube has substantially the same structure as the image intensifying tube shown in FIG. Only the sealing part is different. In the image intensifying tube of FIG. 12, the same sealing member as that of the first embodiment is used for connecting the entrance window 1 and the side tube 6.

The manufacture of the image intensifying tube according to this embodiment is as shown in FIG.
As shown in FIG. 3, the same vacuum exhaust device as that of the first embodiment is used. The method is such that the vacuum sealing work is started after the MCP 5 and the emission window 3 are connected to the side tube 6 in advance.
Is the same as However, when degassing the SUS ring 22 and the like during the activation process of the photocathode 2, the MCP 5 is also degassed. At this time, depending on the case, MCP5
May be alkali-treated with Cs. In addition, the operation and effect at the time of vacuum sealing are similar to those of the first embodiment.

In each of the above-mentioned embodiments, the sealing member having the same structure is used, but the present invention is not limited to this embodiment, and as shown in FIGS. 14 (a) and 14 (b), for example. You may use the sealing member of various structures.
The indium ring 30 of the sealing member of (a) is provided with the grooves 31 continuous on both sides. On the other hand, in the indium ring 32 of the sealing member of (b), grooves 33 having a triangular cross section which do not follow the tapered surface are formed on both sides. The cross-sectional shape of the groove may be U-shaped, V-shaped, triangular, or the like,
The surface on which the groove is provided may be only one surface or both surfaces. Further, the relationship between the thickness of the indium ring and the height of the SUS ring is not limited to the above embodiment. That is, it suffices that an exhaust groove is formed in the low-melting-point metal ring so that the inside and outside of the electron tube can communicate with each other just before the completion of sealing.

Although the case where the side tube 6 is made of ceramic is used as an example, the present invention can be applied to glass or metal, and the material is not limited. Furthermore, it is possible to apply a thin film to the joining portion of the members to be vacuum-sealed to facilitate the joining.

The present invention can also be applied to an electron tube that operates as a phototube by replacing the fluorescent surface of the image intensifying tube in Embodiment 1 with a metal electrode and using it as an anode. Similarly, the fluorescent surface has a semiconductor element such as a photodiode or CCD. It can also be applied to an electron implantation type electron tube. The present invention is not limited to the photomultiplier tube having the MCP according to the second embodiment, but can be widely applied to other general photomultiplier tubes having a second-order multiplication function. In the third embodiment, a so-called proximity type image intensifying tube is taken as an example, but the same applies to, for example, an electrostatic focusing type image intensifying tube.

[0038]

As described above, according to the method of manufacturing the electron tube of the present invention, since the low melting point metal ring formed in the tapered shape in cross section which becomes thinner toward the center side is used, the vacuum sealing pressing is performed. At this time, the contact state between the low-melting point metal ring and the end face of the side window becomes good, and the centering of the low-melting point metal ring with the side window is easy, and the pressure of the low-melting point metal ring is misaligned. It is possible to improve the probability of obtaining a good vacuum airtightness, which was 50% or less in the past, to almost 100%.

Furthermore, since a groove for exhaust which can communicate the inside and outside of the electron tube is formed in the low melting point metal ring until just before the sealing is completed, the groove is crushed by the incident window and the side tube, and the sealing is completed. Up to the first, the gas generated by the deformation of the low melting point metal ring and entering the inside of the tube can be exhausted outside the tube, reducing the gas remaining in the electron tube and reducing the noise due to the residual gas to 1 /
It can be significantly reduced to 10 or less.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view showing one manufacturing process of the first embodiment.

FIG. 2 is a partially cutaway front view showing a vacuum sealing completion state of the first embodiment.

FIG. 3 is a schematic configuration diagram showing an image intensifying tube manufactured in the first embodiment.

FIG. 4 is a perspective view showing a sealing member used in the first embodiment.

5 is a cross-sectional view taken along the line VV in FIG.

6 is a sectional view taken along line VI-VI in FIG.

FIG. 7 is a schematic configuration diagram showing a vacuum exhaust device used in the first embodiment.

FIG. 8 is a longitudinal sectional view of an essential part showing the manufacturing process of the first embodiment.

FIG. 9 is a vertical cross-sectional view of essential parts showing a vacuum-sealed completed state of the first embodiment.

10 is a schematic configuration diagram showing a photomultiplier tube manufactured in Embodiment 2. FIG.

FIG. 11 is a schematic configuration diagram showing a vacuum exhaust device used in a second embodiment.

FIG. 12 is a schematic configuration diagram showing an image intensifying tube manufactured in a third embodiment.

FIG. 13 is a schematic configuration diagram showing a vacuum exhaust device used in a third embodiment.

FIG. 14 is a vertical cross-sectional view showing a modified example of the sealing member that can be used in the present invention.

FIG. 15 is a schematic configuration diagram showing an image intensifying tube.

FIG. 16 is a longitudinal sectional view of an essential part showing a conventional method for manufacturing an image intensifying tube.

[Explanation of symbols]

1 ... Incident window, 2 ... Photocathode, 3 ... Exit window, 4 ... Phosphor screen,
5 ... MCP, 6 ... Side tube, 10 ... Indium, 11 ... Hard metal ring, 12, 20, 30, 32 ... Indium ring, 2
1, 31, 33 ... Groove, 22 ... SUS ring, 28 ... Anode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Kifuna 1126-1 Nonomachi, Hamamatsu City, Shizuoka Prefecture 1 Hamamatsu Photonics Co., Ltd.

Claims (4)

[Claims] 1. An entrance window having a photocathode, a sealing ring provided with a hard metal ring on an outer peripheral surface of a low melting point metal ring, and a side tube for holding the photocathode in vacuum in a vacuum atmosphere. Are sequentially arranged on the same axis, and the entrance window and the side tube are relatively brought close to each other with the sealing ring sandwiched therebetween to close the opening end of the side tube with the entrance window and the low melting point. In a method of manufacturing an electron tube in which a metal ring is pressed and deformed to perform vacuum sealing of an electron tube, the low melting point metal ring is formed into a tapered cross-section that becomes thin toward the center side, and the low melting point metal ring is sealed. A method of manufacturing an electron tube, characterized in that a groove capable of communicating the inside and outside of the electron tube was formed until just before the completion. 2. The electron tube according to claim 1, wherein the low melting point metal is indium or an alloy containing indium as a main component, and the groove is formed from an inner peripheral surface to an outer peripheral surface of the low melting point metal ring. Manufacturing method. 3. The electron tube comprises electron multiplying means for multiplying photoelectrons photoelectrically converted in a photocathode and emitted in a vacuum to emit secondary electrons. A method of manufacturing the electron tube described. 4. The electron tube includes a light emitting display unit that emits light in accordance with incident electrons.
Or the method of manufacturing the electron tube according to item 2.