JPS5828696B2 - Manufacturing method of fluorescent surface for image tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phosphor surface for an image tube, and more particularly to a method for manufacturing an output phosphor surface for an X-ray fluorophore multiplier tube.

Generally, the output phosphor surface of an image tube, for example an It is formed by covering the surface of the body layer with a thin film of metal or the like.

Fluorescent surfaces are closely related to improvements in luminance, resolution, and contrast among tube characteristics.

Hereinafter, a conventional output fluorescent surface will be explained using an X-ray fluorescent multiplier tube as an example with reference to the drawings.

As shown in FIG. 1, the X-ray fluorescence multiplier tube has an envelope 1 mainly made of glass and an input surface 2 disposed on the input side of the envelope 1.

On the input surface 2, a substrate 3 having a certain curvature is fixed to the envelope 1 with the convex surface facing the input side, and on the concave side of the substrate 3 is a phosphor 4 made of cesium iodide added with sodium as an activator. is deposited to a thickness of 100 to 250 microns, and is superimposed on the four phosphor layers to form a photocathode 5.

A focusing electrode 6 is formed on the inner surface of the side surface of the envelope 1 .

An accelerating electrode 7 and an output fluorescent surface 8 (described later) are attached to the output side of the envelope 1.

When the input surface 2 is irradiated with X-rays 9, the phosphor layer 4 emits light and is converted into light, and the photocathode 5 further converts the light into electrons.
Emit photoelectrons.

The photoelectrons are accelerated and focused by the accelerating electrode 7 and the focusing electrode 6,
The output fluorescent surface 8 is caused to emit light, and the X-ray image irradiated onto the input surface is reproduced as a light image on the output surface.

During this time, the X-ray image is reduced to 1/10 in terms of the input-to-output image diameter ratio, and the brightness is several thousand times smaller than that obtained at the input surface by accelerating photoelectrons and emitting light from the output fluorescent surface.
It is reproduced on the output surface as a double-bright 0 image.

On the other hand, as shown in FIG. 2, the output fluorescent surface of the X-ray fluorescence multiplier tube consists of phosphor particles 11 having a particle diameter of 0.2 to 3 microns and approximately 5 to 15 microns on a transparent substrate 10. is deposited to a thickness of .

The surface of the deposited phosphor layer 12 is covered with a continuous aluminum film 13.

The aluminum film 13 is formed by forming a thin film of nitrocellulose (not shown) on the surface of the phosphor layer 12, and then depositing aluminum on this surface to a thickness of 3000 to 4000× under a pressure of about 10 5 Torr. It is formed by heating in the atmosphere to remove the nitrocellulose film.

The aluminum film 13 has irregular irregularities and metallic luster because it is formed on the nitrocellulose film formed on the surface layer of the phosphor particles 12 with a packing density of about 40%, and after the film is formed, the nitrocellulose film is Since it is removed by burning, it initially has no bonding force with the phosphor particles 12 in the uppermost layer.

The photoelectrons emitted from the human power surface 2 are accelerated and focused, and transmitted through the anohenium film 13 to cause the phosphor particles 12 to emit light. We are observing through.

However, in order to obtain a clearer output image and the manufacturing process, the conventional output fluorescent surface has the following drawbacks.

(1) Since the anohenium film 13 has a high reflectance, the light emitted by the phosphor particles 11 is reflected and scattered by the aluminum film 13, reducing the contrast.

(2) Since the anohenium film 13 is formed by vapor deposition on the nitrocellulose film formed on the surface of the phosphor layer 12, which has many gaps and lacks flatness, a thin part is formed in the aluminum film 13, and the fluorescein is emitted from this part. The light from the light body layer 12 is transmitted and photoelectrons are emitted from the photocathode again, resulting in a decrease in contrast.

(3) If the aluminum film 13 is made thicker in order to avoid contrast deterioration due to the above reasons, the aluminum film 13 will be easily peeled off from the phosphor layer 12 and photoelectrons will not pass through easily, resulting in a reduction in brightness.

This invention is also applicable to the fluorescent surface of an image tube, such as the output fluorescent surface of the X-ray fluorescent multiplier tube, and by having a phosphor layer, the layer made of aluminum can be separated from the phosphor layer. This eliminates peeling and improves image quality and brightness.

An embodiment of the present invention will be described below with reference to FIG.

First, phosphor particles having a particle size of 0.2□ to 0.3□ are deposited on a transparent glass substrate 20 to form a phosphor layer 22.

An organic film, such as a nitrocellulose film, is then formed on the phosphor layer 22 by known methods.

On this nitrocellulose membrane, 2×102 to 2×1O−
Aluminum is deposited under a pressure of 3 Torr to form an aluminum porous layer 23.

On this porous layer 23, aluminum is deposited under a pressure of 10-5 Torr to form a dense aluminum layer 24.

Among the multiple layers thus formed, the nitrocellulose membrane is heated to about 300° C. to burn and disappear.

The output fluorescent surface obtained through the above steps is as shown in FIG.

FIG. 3 is a schematic diagram showing a cross section of the output fluorescent surface of an X-ray fluorescence multiplier tube, in which phosphor particles 21 with a particle size of 0.2□ to 3 microns are deposited on the surface of a transparent substrate 20. to form a phosphor layer 22 having an average thickness of 10 microns.

The phosphor layer 22 is deposited in a circular shape with a diameter of 40 mm on a circular substrate 20 with a diameter of 55 m, and the surface layer is covered with an aluminum porous layer 23.

The periphery of the porous layer 23 also covers the surface of the substrate 20.

The surface of the porous layer 23 is a dense layer 24 made of aluminum.
is formed.

The thickness of the conductive film 25 including the porous layer 23 and the dense layer 24 is 2000 to 300X.

When observed under a microscope, the porous layer 23 shows granularity; for example, in the case of aluminum ram, it is deposited under a pressure higher than 2×10 3 Torr, that is, at a degree of vacuum P≧2×10 3 Torr.

However, this porous layer 23 has a pressure of 2×10 2 Torr.
If the temperature is higher than that, the evaporated aluminum will not adhere uniformly, and
Shading may occur.

Even when observed under a microscope, the dense layer 23 is a uniform film with no graininess observed.

In the case of aluminum, this corresponds to the case where it is deposited under a pressure on the order of 10' Torr.

With the output phosphor surface having the configuration shown in FIG. 3, an image with good contrast can be obtained because the light is not reflected or diffused by the conductive film 25 on the surface of the phosphor layer 22.

Another advantage is that the larger the proportion of the porous layer 23 in the thickness of the conductive film 25 becomes, the more difficult it becomes for the conductive film 25 to peel off from the phosphor layer 22.

In addition, the porous layer 23 is prepared in a low vacuum using, for example, 2×10 3TO
If it is formed by vapor deposition using rr, the evaporated atoms will collide with the residual gas and be scattered, so it is suitable for completely covering the uneven surface of the phosphor layer 220 and preventing light from leaking backward.

For example, normal vacuum evaporation, for example, 300 at 10 5 Torr.
In vacuum evaporation, the same low shielding effect as when deposited with a thickness of 0 arrow can be obtained at 15ooX, and when evaporated with 20ooX under 2X10"l'orr, a shielding effect superior to that of normal vacuum evaporation can be obtained. The amount of light leaking from the tube 23 is reduced, the amount of scattered light inside the tube is reduced, and the contrast is improved.

Another advantage of obtaining a light shielding effect with a thin film thickness is that the photoelectron accelerating voltage is relatively low.For example, the output fluorescent surface of a close focusing image tube has a low brightness that occurs due to the small electron transmission ability. Particularly effective in improving contrast without reducing brightness.

Furthermore, the dense layer 24 is provided in consideration of preventing the phosphor from being poisoned by alkali metal vapor when forming a photocathode within the tube.

However, in the case of a small image tube, since the ability to transmit electrons is small, it is possible to obtain a substantially satisfactory image quality and other aspects without forming a dense layer.

Furthermore, since both the porous layer and the dense layer are made of aluminum, both layers can be formed continuously during vapor deposition by changing the degree of vacuum, which is advantageous in manufacturing.

In addition, similar effects can be obtained by repeatedly forming a porous layer and a dense layer.

As mentioned above, 2X102 to 2X1 on the surface of the phosphor layer
By having an aluminum porous layer deposited under a pressure of 0.3 Torr, a high-quality fluorescent surface with almost no peeling from the phosphor layer can be obtained. A photomultiplier tube can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an X-ray fluorescence multiplier tube used to explain the present invention, and FIG. 2 is a cross-sectional view showing the output fluorescent surface of the conventional X-ray fluorescence multiplier tube shown in FIG. 3 are cross-sectional views showing the fluorescent surface of the present invention. 20: Substrate, 22: Fluorescent layer, 25: Conductive film, 23: Porous layer.

Claims (1)

[Claims] 1. A step of depositing a phosphor layer on a transparent substrate, a step of depositing an organic film on the phosphor layer, and a step of depositing 2 on the organic film.
A step of forming a porous aluminum layer by vapor deposition under pressure of ×10 −2 to 2×10 Torr, a step of forming a dense aluminum layer on the porous aluminum layer, and a step of disappearing the organic film. A method for manufacturing a fluorescent surface for an image tube, characterized in that: