JPH03108244A - Contact device for photocathode of phototube and its manufacture - Google Patents

Abstract

PURPOSE: To provide a high quantum efficiency and a low resistance value per unit area by forming a contact device with a narrow conductive contact, accumulated in an effective area on a substrate. CONSTITUTION: A contact device 10 is formed with a narrow conductive contact 20, accumulated in an effective area on a substrate 12 as a glass window. In manufacture, a photopolymerized resin layer 30 is accumulated on the substrate 12, and the resin layer is exposed to light and developed to form a track 31 for the narrow conductive contact 20. A metal layer 32 is accumulated in an effective area on the substrate 12. The residual resin area and the metal layer area located outside the track 31 are removed with a known treatment as 'lift-off' method using ultrasonic wave and acetone, so that only the narrow conductive contact 20 can remain on the surface of the substrate 12. In the final treatment, a photoelectric cathode 11 is accumulated on the surface of the substrate 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a contact device for a photocathode of a phototube, which comprises a metal coating provided on a substrate supporting the photocathode.

The invention also relates to a method of manufacturing such a contact device.

The invention is particularly useful in the fields of high speed image intensifiers and ultra high speed slot scanning imager tubes.

BACKGROUND OF THE INVENTION A technical problem to be solved for photocathode contact devices for photocells and especially for high-speed and ultra-fast photocells is the time constant RC associated with the photocathode (R is the resistance per unit area of the photocathode).
The goal is to obtain a high-speed supply of electrons from the tube power supply to the photocathode in order to reduce the

During operation, the photocathode depletes its electrons practically rapidly, so if the tube needs to operate at high switching speeds, it is necessary to regenerate the photocathode electrons within a very short time. A fast supply of electrons is absolutely necessary. A known solution to this technical problem consists in forming a metallization on the substrate supporting the photocathode, for example comprising a translucent conductive sublayer of nickel, nickel-chromium, aluminum or platinum. be.

The quantum efficiency of this known contact device is limited on the one hand by the sensitivity of the photocathode itself and on the other hand by the light transmission of the conductive sub-N/substrate assembly.

The thickness of this sublayer is therefore chosen to obtain the right trade-off between the resistivity of the two N (metal and photocathode) assembly and the light transmission of the sublayer and photocathode. In other words, the thickness of the conductive sublayer needs to be thick enough so that its resistance per unit area is fairly low (typically 100-500), but this is too thick. This results in an unacceptably reduced quantum efficiency of the device.

In practice, the need to achieve this trade-off makes it impossible to obtain a contact device that is completely satisfactory, especially for ultrafast phototubes. Furthermore, this known type of contact device has the disadvantage that the electrically conductive sublayer has a relatively high resistivity and that electrons can only be efficiently injected at the periphery of the photocathode.

The object of the present invention is to solve the above-mentioned technical problem and to provide a high quantum efficiency and a low resistance per unit area, which makes it possible to inject electrons into the photocathode substantially uniformly over the entire effective area of the photocathode. It is an object of the present invention to provide a contact device for a photocathode of a phototube, which can obtain the following values. In certain instances where the substrate is the end face of a bundle of optical fibers having a transparent core glass portion and an opaque edge glass portion, it is desired that the light transmittance is already reduced by the opaque edge glass portion and not further reduced. .

SUMMARY OF THE INVENTION The means of the invention to solve the above-mentioned technical problem consists in forming the contact device with narrow electrically conductive contacts deposited on the active area of the substrate. In this case, a desired overall light transmittance can be obtained by adjusting the width of the narrow conductive contacts, and a desired overall resistance value can be obtained by giving these contacts a sufficient thickness. . Furthermore, the injection of electrons does not occur preferentially at the periphery of the photocathode, but occurs uniformly over the entire effective area, which further improves the response time. The reason is that the time required for electrons to travel to different parts of the photocathode is reduced. In a particular embodiment, the narrow conductive contact is deposited on an edge glass portion of an end face of a bundle of optical fibers. In this case, the initial light transmission associated with the core glass portion and the edge glass portion is not affected by the presence of the narrow conductive contacts.

The method of manufacturing the contact device of the present invention includes performing a technique known as "lift-of" to deposit a layer of photopolymerizable resin on a substrate, which is then exposed and developed to form a narrow conductive contact. forming tracks, then depositing a metal layer over the entire effective area of the substrate, then removing the remaining photopolymerizable resin layer and the metal layer portion located outside said tracks by ultrasonication, and then Advantageously, a photocathode is deposited on top.

(Example) The invention will be explained in detail with reference to the drawings.

Figures 1a and 1b show a contact device 1 for a photocathode of a phototube, which comprises a metal coating on a substrate 12 supporting a photocathode 11.
00 is a sectional view and a plan view showing a first embodiment of the present invention. As shown in Figures 1a and 1b, in a first embodiment the contact device 10 is a narrow conductive contact deposited on the active area of a substrate 12, which in the case of Figures 18 and Ib is a glass window. Consists of 20. These narrow conductive contacts 20 are connected to the power source of the phototube comprising the contact device 10. While reducing the electrical resistance value of the contact device 10, the photocathode 1
In order to increase the rate of electron exchange with 1, the narrow conductive contact 20 is provided with a thickness that is significantly greater, e.g. Sufficient light transmittance can be maintained. In this case, the light transmittance of the narrow conductive contacts 20 is practically zero, so that the light transmittance of the contact device is determined by the effective area of the substrate 12 occupied by the narrow conductive contacts 20 and the effective area of the substrate 12. It is determined by the ratio to the area of the area. When the narrow conductive contacts 20 are equally spaced parallel conductive wires, as shown in Figures 1a and Ib, the light transmission of the device is determined by the ratio of the width of these conductors to the spacing of these conductors. Because of this, the width is 1
If there are 0 people and the distance is 100 people, the light transmittance of the device is 9
It is 0χ. In contrast, in the case of known translucent sublayers, the light transmission is limited to around 60-70x, and these values are obtained for example for a palladium layer of about 50 people.

Figures 2a and 2b show a second embodiment of the contact device 10, in which the base Fi 12 is the end face of a bundle of optical fibers having a transparent core glass portion 12 and an opaque edge glass portion 23. In this particular embodiment, the narrow conductive contact 20
Let be the metal conductive wire deposited on the edge glass portion 22.

In this case, the contact device 10 does not cause any reduction in light transmission.

FIG. 3 shows the various steps for manufacturing the contact device described in connection with FIGS. 1a, Ib, 2a and 2b. The manufacture of this device involves (a) depositing a photopolymerizable resin layer 30 on the substrate 12, and then ω) exposing and developing the resin layer to form tracks 31 for the narrow conductive contacts 20. Form. In the example of FIG. 3 in which the substrate 12 is a glass window, a positive photopolymerizable resin 30 is used and exposed through a mask having the tracks 31 described above. On the other hand, if the substrate is the end face of a bundle of optical fibers (FIGS. 2a and 2b), a negative photopolymerizable resin is used and is exposed through the bundle of optical fibers itself without the use of a mask. Next, (C) a metal layer 32 is deposited over the entire effective area of the substrate 12. This metal layer can be several hundred angstroms thick. next,
(d) residual resin and said track 3 by a process known as the "lift-off" method using ultrasound and acetone;
1 is removed, leaving only narrow conductive contacts 20 on the surface of substrate 12. metal layer 3
The metals used to form 2 are metals that can adhere well to glass and do not contaminate the photocathode: gold, palladium, nickel-chromium mixtures. Final processing (e)
In , a photocathode 11 is deposited on the surface of a substrate 12 .

[Brief explanation of drawings]

FIG. 1a is a sectional view of a first embodiment of the contact device of the present invention, FIG. 1b is a plan view of the contact device of FIG. 1a, and FIG. 2a is a sectional view of a second embodiment of the contact device of the present invention. FIG. 2b is a plan view of the contact device shown in FIG. 2a, and FIG. 3 is a sectional view showing the sequential manufacturing steps of the method for manufacturing the contact device of the present invention.

Claims (1)

[Claims] 1. A contact device (10) for a photocathode of a phototube, comprising a metal coating on a substrate (12) that supports a photocathode (11).
Contact device (10), characterized in that the contact device (10) is formed by a narrow conductive contact (20) deposited on an active area (21) of a substrate (12). 2. The contact device according to claim 1, wherein the substrate (12) is a glass window, wherein the narrow conductive contact (20
) is a contact device characterized by being equally spaced parallel metal conductive wires. 3. The substrate (12) is a transparent core glass portion (22)
A contact device according to claim 1, wherein the narrow conductive contact (20) is deposited on the edge glass portion (23). A contact device characterized in that it is a metal conducting wire. 4. In manufacturing the contact device according to any one of claims 1 to 3, a photopolymerizable resin layer (3) is provided on the substrate (12).
0), which is then exposed and developed to form tracks (31) for forming narrow conductive contacts (20), and then deposits a metal layer (32) over the entire active area (21) of the substrate.
), then the remaining photopolymerizable resin layer and the metal layer portion located outside the tracks (31) are removed by ultrasonication, and then a photocathode (1) is deposited on the surface of the substrate.
1) A method for manufacturing a contact device, comprising depositing the following: 5. In the method according to claim 4 for manufacturing the contact device according to claim 3, the photopolymerizable resin layer (30) is exposed to light through the transparent core glass portion (22). A method for manufacturing a featured contact device.