JPS5814754B2 - photoconductive target - Google Patents

Description

[Detailed description of the invention] The present invention relates to photoconductive targets.

It is known to apply photoconductive targets, such as photoconductive targets, with layers of cadmium selenide or cadmium sulfoselenide or mixtures of cadmium sulphide and cadmium selenide to image pickup tubes, such as vidicons.

For example, a photoconductive target using cadmium selenide has the following structure.

That is, as shown in FIG. 1, a signal electrode 12 made of a transparent conductive film is provided on one side of a face plate 11 made of light-transmitting glass, and a cadmium selenide layer 13 is provided on this signal electrode 12.
(CdSe), and on this layer 13, as an insulator, Sb2S3 or Sb2Se3 or As2S3 or As2Se3 or Zn. An insulator layer 14 made of S or the like is provided.

Further, FIG. 2 shows a target in which, among the CdSe layer 13 and the insulator 14, the insulator 14 is further provided with a selenium oxysalt layer or a mixture layer 15 of selenium oxysalt and cadmium oxide.

An example of a selenium oxyacid salt is cadmium selenite (CdSeO3).

Further, FIG. 3 shows a target which is already under application and has a selenium oxysalt layer or a mixture layer 16 of selenium oxysalt and cadmium oxide provided in an island shape on the insulating layer 14.

All of the targets obtained in this way have extremely high photoelectric sensitivity, which is more than 20 times that of the commonly used antimony trisulfide photoconductor, and is no problem when compared with the sensitivity of targets using lead monoxide. The less the better.

This evaluation has been recognized by broadcast station engineers, and the characteristics are particularly good, with almost no burn-in or dark current observed.

However, even in such conventional targets, there are still some deficiencies, particularly in the afterimage characteristics, and improvement thereof has been desired.

The present invention was made in view of the above points, and an object of the present invention is to provide a photoconductive target that can reduce afterimages.

That is, in a target having a photoconductor layer having a photoelectric conversion effect on incident light, and an insulator layer having no photoelectric conversion effect on the incident light, a rice grain layer is formed on the insulator layer. This is to reduce afterimages.

The insulator layer in the present invention may be a rice grain layer alone, a rice grain layer and a normal solid layer, or a rice grain layer and a porous layer.

Embodiments of the target of the present invention will be described below with reference to the drawings.

As shown in FIG. 4, a cadmium selenide photoconductor layer 13 is provided on a transparent conductive film 12 provided on one side of a face plate 11 made of light-transmitting glass.

Further, a cadmium selenite layer 16 is provided on the cadmium selenide layer 13.

The cadmium selenite layer 16 shows an example of an island-shaped layer.

Furthermore, in a vacuum higher than 2 x 10-3 Torr (for example, in a high vacuum of 2 x 10-5 Torr), the thickness is, for example, 0.5
Arsenic triselenide (As2Se3; hereinafter As
A solid layer 21 (described as 40←Se60) is vapor-deposited and further
A porous layer 22 of arsenic triselenide is deposited in a low vacuum argon atmosphere at a pressure of, for example, 0.2 Torr, and then a porous layer 22 of arsenic triselenide is deposited on the layer 22 to a thickness of, for example, 1.5 μm in a high vacuum of, for example, 2×10 −5 Torr. A second solid layer of arsenic triselenide before and after 2
3 is evaporated to form a photoconductive target.

A rice grain-like layer is formed in the insulator layer consisting of the cadmium selenite layer 16, the solid layer 21, the porous layer 22, and the solid layer 23 of the photoconductive target obtained through such a manufacturing process.

This state is shown in FIGS. 5 and 6.

That is, this rice grain layer is seen in the region of the porous layer 22 and the solid layer 23, and FIGS. 5 and 6 show the state of this rice grain layer.

The photograph in FIG. 5 shows a rice grain-like layer when the porous layer 22 is formed relatively thin.

A of this photo is a cross-sectional photo, and it seems that a small amount of porous layer 22 remains at the base of the rice grain layer, but it is not clear.

Mouth is a photograph of the surface of the rice grain layer viewed from an oblique angle, and C is a photograph of the surface from above.

FIG. 6 shows a case where the porous layer 22 is formed relatively thick.

FIG. 6 is a photograph of the rice grain layer in this case, and A is a cross-sectional view, in which the existence of the porous layer 22 can be clearly confirmed at the base.

B is a surface photograph of the rice grain layer viewed from an oblique angle, and C is a surface photograph of the rice grain layer viewed from above.

As described above, the afterimage characteristics of the photoconductive target having the rice grain layer in the insulating layer are improved as shown in FIG.

In other words, when applied to an 18 mm vidicon tube, in the conventional method, when the signal current is 50 nA, the third field of attenuation is 15 to 20%, and the third field of rise is 15%.
~25%, whereas the target of the present invention has a third
The field is improved to 8-2%, and the rising third field is improved to 50-75%.

The improvement is particularly remarkable in the afterimage at the beginning of the image.

A rice grain layer having such an effect is formed in the vertical direction when the solid layer is deposited when the porous layer and the solid layer are formed in this order.

Although it is not clear, this seems to be based on a part of the porous layer.

During manufacturing, if a relatively thin porous layer is formed and then a solid layer is formed, the porous layer may disappear in the actually completed photoconductive target and may even disappear.

In addition, the porous layer is extremely thick, and a rice grain layer is formed on top of it to obtain the vision target! The pressure must be extremely high (for example, 100 cm or more), which is not practical.

If there is a small amount of remaining porous layer and a grain-like layer is formed by depositing a solid layer on top of it, the target voltage will be within the practical range of 50V or less, and an image pickup tube with optimal afterimages will be obtained. .

Conventionally, it has been known that the afterimage characteristics of a vidicon target using antimony trisulfide (Sb2S3) are improved by combining a porous layer and a solid layer, and the target of the present invention also has a similar effect due to the porous layer. Conceivable.

However, the photoconductive target obtained in the manufacturing process of the porous layer of arsenic triselenide described above and the solid layer and porous layer made of other arsenic-selenium materials described later has the following points in contrast to the antimono trisulfide example. It's different.

In other words, in the case of a target mainly made of normal antimony trisulfide, if a solid layer-porous layer-solid layer is formed on a Nesa film (Sn02 film) that becomes a transparent signal electrode on one side of a glass substrate, a solid layer is formed. As is well known, the afterimage characteristics are improved compared to a single target.

However, in this example of antimono trisulfide, the porous layer is used as a layer having a photoelectric conversion function for incident light.

In contrast, in the present invention, the layer that performs photoelectric conversion on incident light is only cadmium selenide, and the rice grain-like layer is provided on the insulator layer that does not play a role in photoelectric conversion.

In the conventional example of antimony trisulfide, the photoelectric conversion layer, which is sensitive to light, is a porous layer, which not only improves the afterimage characteristics but also changes the spectral characteristics.

The solid layer of antimono trisulfide is usually sensitive to the long wavelength side of red, and the porous layer is usually more sensitive to the shorter wavelength side than the solid layer, and by using both together, it is possible to obtain spectral characteristics over the entire visible light range. There is.

In the case of the present invention, the rice grain-like layer is not provided in a layer having a photoelectric conversion function, but is applied to a portion that performs a so-called accumulation function, and only the afterimage can be improved without changing the spectral characteristics.

The following fact was also found to be different from the antimony trisulfide vision example.

When arsenic triselenide is deposited as a solid layer on a SnO2 film,
As one of the inventors has already reported, it becomes an accumulative vision (Japanese Journal of A
pplied Pbysics Volume 6, No. 7 875~
882 pages 1967).

Instead of the solid layer of arsenic triselenide, a layer excluding the cadmium selenide layer 13 and the cadmium selenite layer 16 shown in FIG. 4, that is, a solid layer of arsenic triselenide, a porous layer, and a solid layer is used. A target formed on a glass substrate-NESA film does not exhibit normal vidicon operation, but exhibits the characteristics of a storage type vidicon as shown by the dotted line in FIG.

When light is irradiated at time t-to, the signal current increases with the irradiation time, and when the light is cut off at t=to+T after an appropriate time, the signal current does not return to its original value but follows a slow attenuation curve over a long period of time. draw.

Even if a porous layer is used in combination, the afterimage characteristics will not be improved as in the case of ordinary antimony trisulfide vidicon.

However, in the target with the configuration shown in Figure 4, when light irradiation is started at t=to, a constant signal current is reached in an extremely short time, and when the light is cut off at t=to+T, the signal current returns to normal within an extremely short time. Return to dark current value.

This is observed in more detail in Figure 7 above.
Afterimage improvement is realized by the rice grain layer.

As described above, when an insulating layer is formed on a photoelectric conversion layer mainly made of cadmium selenide, the afterimage characteristics can be improved by providing a rice grain-like layer on the insulating layer.

Materials that can make this effect possible are not limited to arsenic triselenide (As40Se60), which has been mentioned so far, but also As60se40, As50Se50, As30S.
It is effective for materials with an appropriate molar ratio of As and Se, such as e70, AS20Se30.

The ratio of As and Se is As55Se45, AS52Se
Of course, a value such as 48 would also be acceptable.

However, if As exceeds Se, As will not react sufficiently with Se, and As alone may become liberated and cause harm.
It is practical.

When the molar ratio of Se increases, the release of As alone is not a problem, but rather the problem is deterioration of image quality due to crystallization of selenium after forming a thin film.

Therefore, As has a molar ratio of 2 to prevent Se crystallization.
It may be around %.

In addition, it is not limited to AsSe, but also As-S, As-Te, As-SSe, As-S-Te, As-Se-
Formation of a grain-like layer is also effective for Te material.

Note that the characteristics shown in FIG. 8 often occur with materials mainly composed of As-Se.

Although arsenic triselenide was mainly used as the insulating layer in the explanation of the manufacturing process shown in FIG. 4, the solid layer and the porous layer may be made of different materials.

For example, arsenic triselenide (As) is used to form the first solid layer.
40Se60), arsenic diselenide (
A8!5oSe50), arsenic triselenide (As40Se60) may be used again to form the second solid layer.

Arsenic diselenide allows easier control of formation of a porous layer than arsenic triselenide, and has many manufacturing advantages.

Furthermore, the materials may be combined in any manner, such as in the case where an As-S solid layer is formed on an As-Se solid layer-porous layer.

In the above embodiment shown in FIG. 4, after forming the solid layer S,
Abbreviation S- in which a porous layer P is provided and a solid layer S is provided on the layer.
P-S, however, as shown in FIG. 9, a porous layer 22 may be provided on the island-like cadmium selenite layer 16, and a solid layer 23 may be provided on the layer 22.

The rice grain layer in this case is shown in FIGS. 10 and 11.

That is, FIG. 10 is a photograph of a rice grain layer when the porous layer 22 is relatively thin.

A is a cross-sectional photograph, and it can be seen that it is difficult to confirm the porous layer at the base of the rice grain layer.

Mouth is a photograph of the surface of the rice granule layer viewed from an oblique angle, and C is a photograph of the surface of the rice granule layer viewed from above.

The rice grain layer when the porous layer 22 is made relatively thick is the 11th layer.
As shown in the figure.

The photo in A is a cross-sectional photo, and it can be seen that there is a porous layer at the base of the rice grain layer.

Mouth is a photograph of the surface of the rice granule layer viewed from an oblique angle, and C is a photograph of the surface of the rice granule layer viewed from above.

Both have the effect of reducing the afterimage characteristics as in the case of FIG. 4.

FIG. 12 shows an example of a PSP structure in which a porous layer 22 is further provided on the surface of the solid layer 23 shown in FIG.

In addition, when the rice grain layer is exposed on the scanning surface, a porous layer may be provided on the scanning side surface in order to improve the landing characteristics of the electron beam.

The thickness of the porous layer in this case may be thin, and may be formed only slightly on the scanning surface.

In the above explanation, as shown in Fig. 4, a photoelectric conversion layer mainly made of cadmium selenide and an island-shaped cadmium selenite layer formed thereon were used as an example. It is clear that this method can be applied both to the case of only a layer mainly composed of cadmium selenide, and also to the case where a cadmium selenite layer is formed on a layer mainly composed of cadmium selenide, as shown in Fig. 2. .

Examples are shown in FIGS. 13 and 14.

This is an example in which the insulating layer is a solid layer, a porous layer, and a solid layer.

In the embodiment of the composite target according to the present invention, an example was described in which cadmium selenide was used in the first layer.
It may be a solid solution (cadmium sulfoselenide) containing 1/2 of cadmium selenide or a mixture.

Alternatively, layers of cadmium sulfide and cadmium selenide may be superimposed.

Further, it may be a solid solution or a mixture containing cadmium telluride and cadmium selenide.

Alternatively, each layer of cadmium telluride and cadmium selenide may be superimposed.

Further, it may be a solid solution or a mixture containing zinc selenide and cadmium selenide, or it may be a layer in which zinc selenide and cadmium selenide are superimposed.

Further, any other material may be used as long as it forms a solid solution with cadmium selenide, or can be mixed with or superimposed with cadmium selenide.

For example, 99.999% high purity cadmium selenide can be used as is for these composite targets.

Alternatively, in addition to thallium, impurities include well-known copper, gold, indium, gallium, aluminum, halogens, tellurium, antimony, bismuth, lead, tin, alkali metals, alkaline earth metals, etc. Or it may contain several types.

The role of the first layer, which is mainly made of cadmium selenide, is to obtain photosensitivity, similar to the conventional target structure, and light absorption takes place in this first layer.

In this sense, this layer can be called a photoelectric conversion layer.

Although cadmium selenite was used in the above embodiments, cadmium oxide may also be mixed therein.

In addition, complex intermediate compounds consisting of cadmium, selenium, and oxygen, such as Cd3Se4O11 (3CdSeO3.
SeO2) may be mixed with cadmium selenite.

In addition to arsenic-selenides such as arsenic triselenide and arsenic monosulfides such as arsenic trisulfide mentioned in the examples, the materials for the porous layer include germanium sulfide, germanium selenide, thallium sulfide, thallium selenide, Bismuth trisulfide, bismuth triselenide, zinc selenide, zinc sulfide, cadmium telluride, antimony trisulfide, antimony triselenide,
Materials used include calcium fluoride, magnesium fluoride, aluminum fluoride, sodium fluoride, cryolite, and lead oxide.

In addition, to form a porous layer, vapor deposition in an argon atmosphere as described in the examples is effective, but not only argon but also nitrogen or other inert gases may be used, and even oxygen may be included. .

As described above, by applying a porous layer to the layer that is not responsible for photoelectric conversion, an image pickup tube with excellent afterimage characteristics can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view for explaining a conventional photoconductive target using cadmium selenide, Fig. 2 is a cross-sectional view showing another structure of Fig. 1, and Fig. 3 is another structure of Fig. 1. FIG. 4 is a cross-sectional view for explaining the manufacturing method of one embodiment of the photoconductive target according to the present invention, FIGS. 5 and 6 are photographs of the rice grain layer of the target in FIG. 4, Figure 7 is a characteristic curve diagram showing a comparison of afterimage characteristics when a conventional photoconductive target and the photoconductive target of the present invention are built into a vidicon, and Figure 8 is a photoelectric conversion mainly using cadmium selenide in the target of the present invention. A characteristic curve diagram showing a comparison of the photoresponse characteristics of a photoconductive target consisting of a layer and arsenic selenide and a photoconductive target consisting only of arsenic selenide, FIG. 9 is a manufacturing method explanatory diagram of another example of FIG. 4, Figures 10 and 11 are photographs of the rice grain layer of the target in Figure 9, Figure 12 is an explanatory diagram of the manufacturing method of another example of Figure 9, and Figures 13 and 14 are the same as Figure 4. It is a manufacturing method explanatory diagram of an example. 11...Face, plate, 12...
・Transparent conductive film, 13...CdSe layer, 14...
... Insulator layer, 16 ... Cadmium selenite layer, 21, 23 ... Solid layer, 22 ...
...Porous layer.

Claims (1)

[Scope of Claims] 1. A photoconductor layer that performs photoelectric conversion of incident light, and an insulator layer provided on the photoconductor layer that does not have a photoelectric conversion function of incident light, the insulator layer 1. A photoconductive target comprising a porous layer formed by low-vacuum vapor deposition as a core, and a rice grain-like layer formed by vapor deposition on the porous layer. 2. The photoconductive target according to claim 1, wherein the rice grain layer has a longitudinal direction of the rice grains oriented substantially perpendicular to the target surface. 3. The photoconductive target according to claim 1, wherein the rice grain layer is arsenic selenide. 4 As the rice grain layer, arsenic-selenide, arsenic-sulfide, arsenic-telluride, arsenic-sulfur-selenium compound, arsenic-sulfur tellurium compound, arsenic-selenium-tellurium compound, germanium sulfide, germanium selenide, sulfide Thallium, thallium selenide, bismuth trisulfide, bismuth triselenide, zinc selenide, zinc sulfide, cadmium telluride, antimony trisulfide, anotimony triselenide,
The photoconductive target according to claim 1, which uses calcium fluoride, magnesium fluoride, aluminum fluoride, sodium fluoride, cryolite or lead oxide. 5. The photoelectric conversion layer is cadmium selenide, cadmium sulfoselenide, a mixture layer of cadmium sulfide and cadmium selenide, a solid solution layer or mixture layer of cadmium telluride and cadmium selenide, or a solid solution layer of zinc selenide and cadmium selenide. or a mixed material layer, the photoconductive target according to claim 1. 6. The light according to claim 1, wherein the insulating layer has a laminated structure of a solid layer formed by high vacuum evaporation and the rice grain-like layer formed on this solid layer. conductive target. 7. Claims characterized in that the insulator layer has a laminated structure of a porous layer formed by low vacuum evaporation and the rice grain-like layer formed on this porous layer by high vacuum evaporation. The photoconductive target according to item 1. 8. The photoconductive target according to claim 1, wherein the insulator layer has the rice grain layer formed on the photoconductor layer.