JPH06208836A - Image pickup tube - Google Patents

Abstract

PURPOSE:To improve the surface plate of an image pickup tube for providing high sensitivity by using a photoconductive film at high voltage. CONSTITUTION:A glass surface plate 1 in which a signal drawing pin 4 is embedded, is polished, and adhesive foreign matters are removed. An indium oxide film 2 is deposited so that the thickness of the film becomes 800OAngstrom -16000Angstrom without intervention by gold and chromium, on the glass surface plate, and high frequency ion etching is carried out to stop the thickness of the surface of the indium oxide film at no thinner than 1500Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a face plate of an image pickup tube which obtains high sensitivity by using a photoconductive film mainly composed of amorphous selenium at a high voltage.

[0002]

2. Description of the Related Art There is a system in which a film mainly composed of amorphous selenium is used as a photoconductive film of an image pickup tube and a high voltage is used to obtain high sensitivity. The biggest problem of this image pickup tube is a white defect screen defect resulting from the use of a high voltage.
The occurrence of the white flaws is often due to the irregularities on the surface of the glass face plate, which will be the substrate for forming the photoconductive film, and the surface of the indium oxide film (hereinafter referred to as "nesa film"). In the conventional image pickup tube used at a low voltage (20 to 75 V), the size of the unevenness defect of the substrate could be up to about 3 μm. However, in an image pickup tube used at a high voltage (250 V or more), even a defect having a size of 0.5 micron causes white marks. The number of irregularities on the glass substrate increases as the number of glass substrate processing steps increases. Further, it is a very difficult task to completely remove the defects of 0.5 microns or less. It is an object of the present invention to reduce the number of processing steps that increase this defect and to alleviate fine defects with a Nesa film to reduce the occurrence of white flaw screen defects in the image pickup tube. Next, details of the conventional technique will be described with reference to the drawings. A photoconductive type image pickup tube having a photoconductive layer usually has a structure as shown in FIG. In the figure, 1 is a translucent glass substrate, 2 is a nesa film which serves as a signal electrode, 3 is a photoconductor layer, and 4 is a metal pin for taking out a signal current. Here, the metal pin 4 is embedded in the glass substrate, and the height of the pin is made to coincide with the glass surface by optical polishing of the glass substrate. Conventionally, chromium and gold 5 were vacuum-deposited before forming the nesa film 2, as shown in FIG. The purpose is to ensure the electrical connection between the signal extraction pin 4 and the signal electrode (nesa film) 2. The signal extraction pin 4 is as thin as 0.5 to 0.7 mm. Also,
A minute step is likely to form between the glass and the periphery of the pin. Therefore, since the Nesa film formed on this is usually thin at about 800Å, the Nesa film may be broken around the pins. In order to prevent this, a vapor deposition film of chromium and gold was needed under the Nesa film.

[0003]

The chromium and gold film is formed by vacuum heating vapor deposition. However, because of this processing step, even if the adhered foreign matter is removed from the glass surface by super-optical polishing and washing, the foreign matter adheres again. For this reason, it is necessary to perform cleaning for removing foreign matters again after vapor deposition processing of chromium and gold. However, this cleaning is different from the glass substrate alone,
Due to the presence of the vapor deposition film, it is not possible to sufficiently remove the foreign matter due to the output limitation of the ultrasonic cleaner and the generation of foreign matter around the vapor deposition film. As a result, a white defect screen defect occurs and it is difficult to reduce the defect. Then, this invention aims at eliminating the vapor deposition process of chromium and gold in order to eliminate this defect.

[0004]

According to the present invention, the thickness of the nesa film is increased according to the conventional image pickup tube condition to eliminate the vapor deposition process of chromium and gold, and the nesa film and the signal take-out pin are directly bonded. Further, the Nesa film is formed to a desired thickness by etching after vapor deposition to a thickness 12 to 20 times that of a conventional film.

[0005]

By increasing the thickness of the Nesa film, the electrical connection around the signal extraction pin, which is a problem in the prior art, can be sufficiently made, and the vapor deposition film of chromium and gold becomes unnecessary. As a result, the processing of the glass substrate is reduced by one step, so that the adhesion of foreign matter to the glass surface is reduced and the occurrence of white marks is prevented. Further, in order to make the Nesa film thick, fine unevenness defects on the glass surface are
There is also the effect of being covered with a Nesa film.

[0006]

Embodiments of the present invention will be described below. First, the glass face plate 1 in which the signal extraction pins 4 are embedded is super-optically polished. This glass face plate is cleaned using a cleaning chemical, pure water, and an ultrasonic cleaner to remove adhered foreign substances. The cleaned glass face plate with signal extraction pins is set in a high-frequency sputtering device, and a nesa film is sputter-deposited. The thickness of the Nesa film is based on the conventional image pickup tube conditions (about 800
Evaporation is carried out under the condition that the thickness is 12 to 20 times that of Å). On the surface of the vapor-deposited nesa film, foreign matter generated by high frequency sputtering is often attached. In order to remove the foreign matter, ultrasonic cleaning is performed again using detergent and pure water. With this wash,
Large foreign matter on the surface of the Nesa film is greatly reduced. However, in this state, if it is used for an image pickup tube that is used at a high voltage, white defects and screen defects often occur, and it cannot be used. For this purpose, the cleaned nesa film surface is subjected to high frequency ion etching using nitrogen gas. About 2/3 to 4/5 of the Nesa film deposited by this high-frequency ion etching will be scraped off. This high-frequency ion etching is stopped under the condition that the thickness of the nesa film is 1500 Å or more, which is, for example, about 4 times or more the thickness used in the conventional image pickup tube. Next, this face plate is taken out into the atmosphere, immediately set in the vacuum vapor deposition apparatus in the next step, and kept in vacuum. Then, a photoconductive film mainly composed of amorphous selenium is formed. The above is the implementation process of the present invention. As this step shows, there is no conventional chromium and gold deposition step after cleaning the glass face plate. Therefore, it is possible to reduce the foreign matters attached to the surface of the glass face plate. Moreover, since the thickness of the Nesa film is four times or more than the conventional one,
No breakage of the Nesa film around the signal extraction pins on the glass plate. Also, fine flaws and foreign matter on the glass face plate are covered with the Nesa film to be smooth. Here, it is conceivable that the transmittance of light is deteriorated and the sensitivity of the image pickup tube is lowered by making the Nesa film four times or more the thickness of the conventional image pickup tube. However, in the actual research, it was found that this deterioration was hardly caused in the visible light range. In this embodiment, the case where the Nesa film is formed by the sputtering method has been described, but the same applies to the Nesa film in which indium is heated and vapor-deposited in oxygen. Further, the cleaning of the nesa film is not necessary when the foreign matter adheres little.

[0007]

When the method of the present invention is used, glass surface plate processing for removing fine irregularity defects on the glass surface plate can be sufficiently carried out, and the Nesa film can be immediately vapor-deposited, so that the defects on the glass surface can be reduced. . As a result, the yield of the image pickup tube can be improved. Further, the processing steps are shortened, the processing time can be shortened, and the processing cost is reduced. From the above, it is possible to reduce the cost of the image pickup tube.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of vapor deposition of signal electrodes according to the present invention.

FIG. 2 is a structural explanatory view of the present invention.

FIG. 3 is a diagram illustrating a conventional vapor deposition of chromium and gold.

[Explanation of symbols]

 1 glass substrate 2 signal electrode (nesa film) 3 photoconductive layer 4 signal extraction pin 5 vapor-deposited film of chromium and gold.

Claims (4)

[Claims] 1. An image pickup tube, wherein an indium oxide film forming a signal electrode is directly vapor-deposited on an end face of a signal extraction pin. 2. The image pickup tube, wherein the indium oxide film has a thickness of 1500 Å or more. 3. A step of depositing an indium oxide film on a glass face plate having signal extraction pins embedded therein under a condition of a thickness of 8000Å to 16000Å, and high frequency ion etching for stopping the surface of the indium oxide film at a thickness of 1500Å or more. An image pickup tube characterized in that the manufacturing process includes the process. 4. A step of polishing a glass face plate having signal extraction pins embedded therein, a process of removing adhering foreign substances, and an indium oxide film of 8,000 to 1600 on the glass face plate.
An image pickup tube characterized in that the manufacturing process includes a step of vapor deposition under conditions of a thickness of 0Å and a step of high frequency ion etching for stopping the surface of the indium oxide film at a thickness of 1500Å or more.