JP2955317B2 - Evaporation source, its manufacturing method and image tube - Google Patents

Description

The present invention relates to an evaporation source suitable for forming a photocathode of an image tube, a method for manufacturing the same, and an image tube.

2. Description of the Related Art An evaporation source used for forming a photocathode of an image tube has been disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 51-36821. This evaporation source is configured as shown in FIG. 3, and the platinum clad wire 16 has antimony (hereinafter referred to as Sb).
Are welded in places and become granular, and Sb granular portions 17 are formed.

The temperature of such an evaporation source rises due to electric heating, and the Sb of the Sb granular portion 17 evaporates in a vacuum to become an Sb thin film of a material for forming a photocathode of an image tube. The Sb thin film forms a compound with an alkali metal or the like to form a photocathode, and is used for forming a photocathode such as an image tube, an imaging tube, a phototube, and the like.

(Problems to be Solved by the Invention) When the above-mentioned conventional evaporation source is used, a large number of fragments of the Sb granular portion 17 made of Sb deposited on the platinum clad wire 16 at the time of forming the photocathode are dropped, and the imaging tube is removed. There is a disadvantage that the quality of the photocathode deteriorates.

Further, when the area for forming the photocathode is large, if the amount of granular Sb is used, a film required for forming the photocathode cannot be obtained, and there is a disadvantage that good sensitivity cannot be obtained. In addition, since this is a local point evaporation source, there is a problem that unevenness in adhesion of the Sb thin film occurs, which is inconvenient.

SUMMARY OF THE INVENTION The present invention solves the above problems, and further provides an evaporation source capable of improving sensitivity uniformity by forming a uniform photocathode over the entire surface when a photocathode is formed in a large area, and a method of manufacturing the same. And an image tube.

[Constitution of the Invention] (Means for Solving the Problems) The present invention comprises a refractory metal wire, and one or more kinds of white metal elements coated on the refractory metal wire combined with Sb. An evaporation source comprising a compound layer and an Sb layer coated on the compound layer.

Further, according to the present invention, a step of coating one or more kinds of white metal elements on a high melting point metal wire, and then, one or more kinds of the above white metal elements are coated in a non-reactive atmosphere or vacuum. The step of continuously immersing the high-melting metal wire in the Sb melt to cover the compound layer on the high-melting metal wire, and then covering the compound layer with the Sb layer. This is a method for producing an evaporation source.

Further, the present invention is an image tube having a photocathode formed using the above-mentioned evaporation source.

(Operation) According to the present invention, the linearly heated Sb evaporation source is
The heating of the refractory metal wire decomposes the platinum-Sb compound, and only Sb evaporates in vacuum due to low vapor pressure. And the Sb evaporation site extends over all of the linear Sb evaporation sources,
The evaporated SB is formed as a thin film on the surface to be photocathode-formed, and moves so that the photocathode can be easily formed.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

First, the evaporation source will be described. The evaporation source according to the present invention is constructed as shown in FIG. 1 and has a platinum clad wire 1 in which platinum is plated on a core wire made of a high melting point metal wire, for example, molybdenum (hereinafter referred to as Mo). A Pt—Sb compound layer 2 combined with platinum (Pt) is coated thereon. Further, an Sb layer 3 is coated on the Pt—Sb compound layer 2 to form a linear Sb evaporation source 4.

In this case, the diameter of the platinum clad wire 1 is set in the range of 0.2 to 0.7 mm, and the thickness of the Pt—Sb compound layer 2 is 50 to 150 μm.
And the thickness of the Sb layer 3 is set in the range of 10 to 50 μm.

Note that both the thickness of the Pt—Sb compound layer 2 and the thickness of the Sb layer 3 are the same over a linear shape. Further, the atomic ratio of Pt to Sb is preferably from 1: 1 to 2: 1.

When the linear Sb evaporation source 4 is used, for example, for forming a photocathode in an image tube described later, the linear Sb evaporation source 4 is arranged, for example, in an annular shape so as to face a large-area input surface. When forming a uniform photocathode such as an image tube, the linear Sb evaporation source 4 can be arranged so as to satisfy the geometrical arrangement.

Next, a method for manufacturing the linear Sb evaporation source 4 will be described.

First, a Pt clad wire 1 is formed by coating a Mo core wire having a diameter of 0.3 mm with Pt.

Next, the platinum clad wire 1 is placed in a non-oxidizing atmosphere, for example, a nitrogen gas atmosphere, and a Sb melting crucible, for example, 500 ° C.
Continuous immersion in a solution at ~ 650 ° C.

After the immersion, the platinum clad wire 1 has Mo as a core wire, a Pt—Sb compound layer 2 and an Sb layer 3 sequentially formed, and is wound up and stored.

In the above case, the temperature of the Sb melt can be kept substantially constant by using a high melting point metal such as Mo or Ta or a ceramic as the Sb melt crucible.

In addition, the wire is transported by adjusting the rotation speed of the spool around which the wire is wound, and the composition of the Pt-Sb compound, its thickness, and the surface.
The thickness of the Sb layer 3 can be selected.

According to this manufacturing method, the composition and thickness of the Pt—Sb compound layer 2 of the linear Sb evaporation source 4 are continuously uniform, and the thickness and adhesion strength of the Sb layer 3 are also uniform. In addition, since no oxidation or contamination occurs, the quality of the linear Sb evaporation source 4 is improved.

The material of the high melting point metal wire is Ta, W
Etc. are suitable.

Next, an image tube having a photocathode formed by using the linear Sb evaporation source 4 of the present invention will be described.

That is, the image tube of the present invention is constructed as shown in FIG. 2, in which an input surface 6 is provided on the input side in a vacuum envelope 5 mainly made of glass, and an anode 7 and an output surface are provided on the output side.
8 are provided. A focusing electrode 9 is provided along the inner surface of the side wall of the vacuum envelope 5.

The input surface 6 is configured by sequentially forming an input fluorescent film 11 and a photoelectric surface 12 on a spherical substrate 10. The output surface 8 is formed by sequentially forming an output fluorescent film 14 on a substrate 13.

Further, in the present invention, an annular electrode 15 is disposed on the output side in the vacuum envelope 5 so as to face the input surface 6 , and the linear Sb evaporation source 4 of the present invention is disposed on the electrode 15.

In this case, the arrangement shape of the linear Sb evaporation source 4 is selected according to the area of the input surface 6 and the distance between the linear Sb evaporation source 4 and the photocathode 12. It is the easiest to place.

In forming the photocathode 12, the temperature of the linear Sb evaporation source 4 rises due to electric heating, and evaporation of Sb due to thermal decomposition of the Pt-Sb compound layer 2 and evaporation of the Sb layer 3 on the surface occur. At this time, when the linear Sb evaporation source 4 is heated, all of the energized portions have the same temperature, and the decomposition and evaporation of the Pt—Sb compound layer 2 become uniform on the line.

For this reason, Sb of the linear Sb evaporation source 4 is uniformly evaporated,
The Sb thin film which becomes the photocathode 12 is obtained. The film pressure distribution of this Sb thin film became uniform over the entire photocathode, and corresponded to the point evaporation source.
The thickness unevenness of the Sb thin film is eliminated. As a result, the sensitivity characteristics of the photocathode 12 are uniform over the entire surface, so that the image luminance of the image tube can be uniform.

The linear Sb evaporation source 4 of the present invention is a surface layer thereof.
The Sb layer 3 is formed densely, so that there is no damage of the linear Sb evaporation source 4 during evaporation of Sb due to thermal decomposition of the Pt-Sb compound layer 2 and evaporation of the Sb layer 3 and does not fall off as foreign matter. Therefore, the image quality is not reduced.

In the above case, since the linear Sb evaporation source 4 is uniform as a resistor, the temperature of any part on the thin wire is almost the same, the heat generated as a heating element is small, and the heat generation gas source is used. Is small because there is no other connection lead wire.

In addition, such a linear Sb evaporation source 4 has a plurality of point evaporation sources arranged or is linearly integrated. Since the structure is simple, it can be easily fixed on the electrode 15. As a result, the assembling time is shortened, and the number of fixing parts involved in the assembling is reduced.

[Effects of the Invention] According to the present invention, the evaporation source is formed by continuously and uniformly forming two types of layers coated on the high melting point metal wire.
When Sb is uniformly deposited over a large area, the Sb film thickness distribution has no local variation in film thickness and has uniform characteristics.

As a result, the sensitivity of the photocathode obtained by using the evaporation source of the present invention becomes uniform, and uneven brightness of an image is prevented.

Further, since the evaporation source of the present invention has a laminated structure of the Pt—Sb compound layer and the Sb layer, it is very strong, no fragments are dropped off from the core wire, and the surface quality is not deteriorated.

Further, according to the method for forming a photocathode using the evaporation source of the present invention, stable quality can be obtained and continuous production can be performed, which is extremely efficient.

[Brief description of the drawings]

FIG. 1 is a transverse sectional view showing an evaporation source according to one embodiment of the present invention, FIG. 2 is a longitudinal sectional view schematically showing an image tube according to one embodiment of the present invention, and FIG. It is a perspective view which shows a source. 1 ... Platinum clad wire (high melting point metal wire) 2 ... Pt-Sb
Compound layer, 3 ... Sb layer, 4 ... Linear Sb evaporation source, 12 ... Photocathode.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 9/12 H01J 29/38 H01J 31/50 H01J 29/45 H01J 9/233

Claims (3)

(57) [Claims] 1. A high melting point metal wire, a compound layer formed by combining one or more kinds of white metal elements coated on the high melting point metal wire with Sb, and a Sb coated on the compound layer And an evaporation source. 2. A step of coating one or more kinds of white metal elements on a refractory metal wire; and a step of coating one or more kinds of white metal elements in a non-reactive atmosphere or vacuum. A step of continuously immersing the melting point metal wire in the Sb melt to coat a compound layer on the high melting point metal wire, and then a step of coating the compound layer with an Sb layer. A method for producing an evaporation source. 3. An image tube having a photocathode formed by using the evaporation source according to claim 1.