DE1764682A1 - Photoconductive target or photoconductive screen - Google Patents

Description

Case 43 951-5

TOKYO SHIBlTTEA EI ₁ ECSRIO COMPMTIE LTD., Kawasaki-ski, JAPABT

Photoconductive a Sargst or photoconductive screen

The invention relates to a photoconductive coffin or on a photoconductive screen formed by forming a layer of photoconductive material on a Layer of electrically conductive material is formed *

According to the invention, such a photo-sensitive target should be made highly sensitive and have a high photoconductive resistance, the target being a photoelectric multiplier or a photoconductive semiconductor * image recording tube belongs to, ale bale television and * uf used in other areas. The structure can be the same

109910 / 077S

like the commercially available VIDICON, PLUMBICON etc. ■

The usual photoconductive target is a photoconductive one Image pickup tube is fabricated by depositing a photoconductive layer on a clear pinned support attached to one end of a vacuum vessel is arranged and forms a light input plane with a transparent signal electrode interposed therebetween. When an image pickup tube is in operation, which is provided, for example, with such a photoconductive target, the signal electrode has a positive one Voltage (for example 30 ToIt) applied and the The surface of the photoconductive layer is scanned with low speed electron beams which by an electron gun, which is similarly contained in the vacuum vessel opposite the target. The electrical resistance of the photoconductive Layer varies with the intensity of the penetration into the image pickup tube from outside through the faceplate Light, so that when the electron beam is scanned, a signal current is generated by a load resistor which is proportional to the intensity of the incident light on the transparent electrode connected 1st

109810/0775

BATH

It has often been found that the properties of the pliotole it ends image pickup tube are influenced by those of a photoconductive element forming a photoconductive target. Generally speaking, the photoconductive layer is made of a p-type porous material such as antimony trisulfide, lead monoxide, etc. However, these materials have not been able to provide a fully satisfactory effect as a photoconductive layer To ensure photoconductive targets, attempts have already been made in the case of. Antimony trisulfide, for example, can be used to manufacture the target from these three layers of sulfide, namely a so-called continuous solid layer - a so-called porous layer and a continuous layer of plague formed in the order mentioned in the direction of the thickness of the photoconductive layer thus formed . "Porous layer" is a loose aggregate of relatively large particles from the vapor of the photoconductive material to understand, that under low Va- ^; kuum, for example 1CT ^ Torr is deposited; the expression "continuous solid layer ¹ * stands for a compact or vitreous layer of extremely finely comminuted particles of the material vapor, which under high yakuum,

"for example ΙΟ" "* Torr deposited. General it can be said that a place where the same material is used becomes, a porous layer made from it has a relatively high apparent resistance to the introduced Electrons are released, while a continuous layer of fuel produced from them has a relative effect forms low apparent resistance to this. Indeed, the quality of one is therefore increased by an image pickup tube Using such material, the regenerated image is bsstisast by a combination of the in the direction of the Thickness of the photoconductive donor layer measured specific Resistance and that in one direction perpendicular to this cast resistivity, namely one direction parallel to the surface of the layer.

In addition to the aforementioned photoconductive layer Antimony trisulfide, a lead monoxide photoconductive target, has been proposed as a type of higher sensitivity.

PLUMBICON using this target is in Practically used in ear TV camoras recently been. Compared to the image-orthicon-type image pickup tube however, "this" photoconductive still has one lower PhotoempflLÄdlicakei ^ v Just because of that were

1 0 9 8 1 Π / Π 7 7 5 BAD ORIGINAL

consistently considerable efforts. - but without success - made to develop a far more sensitive photoconductive target «-

The applicant in has already succeeded in using a photoconductive target using cadmium selenide as the photoleltendo layer; an image pickup tube with this target had a photosensitivity which was more than ten times that of an image pickup tube consisting of a conventional photoconductive target. This photoconductive target differed from the one used at that time not only in the use of a different material for the photoconductive layer but also in the fact that the cadranium solids used for this layer had an electronic conductivity of the η-type. The difference in operation between this η-type photoconductive target and the previously known p-type target resides in the fact that with η-type conductivity, electron beam scanning is free . a photoconductive layer can be made »to reach the signal electrode. This high iFhotosensitivity for the n-type target is based on the fact that the photoexcited holes in the layer are immediately started in the hecombination centers within the layer and that a secondary photo atom

■ 10 9810/0775

BATH

further due to the incidence of electron beams can be maintained until the trapped hole is recombined with a free electron. Like one made of the usual photoconductive material Target, however, still had the sarget with the photoconductive layer made of cadmium elenide, since it was impossible was to receive a signal stream, unless a screen voltage Considerable value was applied, ala another requirement being a limitation of the width in which the sarget worked, was added *

The photoconductive target according to the invention consists of a first photoconductive layer, which is composed solely or mainly of caduia alenide and the like on one transparent electrode was formed to a thickness of at least 0.5 Ilicron and a second layer of one High resistance semiconductor material superimposed on the first layer to a thickness of 0.6 microns marimal so that the potential gradient in the part of the second layer which is opposite to the first layer, is broadened and the electron influx from the second Layer is facilitated. Thus, the invention produces photoconductive target generates a signal current at low screen voltage and operates over a wide voltage range.

10 9810/0775

BATH ORIGINAL

·. "7 -

The invention should now be further based on the enclosed Drawing explained trerden in the

Mgur 1 schematically shows a section through an image pickup tube shows that with a photoconductive target after, the invention is equipped;

Figure 2 shows schematically !! a section through an embodiment of the photoconductive! target according to the invention; and ■, ■

Figure 3 is a Diagr..2üi in which a comparison of the known photoconductive target, aait only a photoconductive Layer provided \ rar, which consisted of Cadiumiumsolenid, and vorgenoiamen the photoconductive target according to the invention which is provided with a photoconductive layer produced in the Vieisa shown in FIG Target illumination "and / or illumination strength as a parameter took place

FIG. 1 symbolizes the structure of the image pickup tube using fles targets according to the invention, ate construction, is the same as in other normal VIDIKON tubes, except for the target, for which a brief description follows. The illustrated tube 10 consists of a vacuum vessel 11 which has an electron gun section 12

10.9 8 10/0775 BAD

and a photoconductive target assembly 15 includes. The electron gun assembly 12 includes a heater H, a cathode 15 surrounding the heater and a control grid electrode 16 as an accelerator electrode 17 ″ these are both arranged coaxially to the cathode 15. An electrode 18 is arranged coaxially to the accelerator electrode 17 and a mesh electrode 19 is provided so that they meet the cathode at one end of the electrode 18 opposite to accelerator electrode 17 opposite D © rphötpleitende target section 13 consists from a transparent glass substrate 20, a transparent one conductive layer 21 deposited on substrate 20 and a photoconductive target 22 according to the invention, the target 22 being deposited on the conductive layer 21 opposite the cup electrode 19,

As FIG. 2 shows, the photoconductive target according to the invention consists of a first layer 23, mainly of cadmium selenide, which is formed on a transparent electrode 21 and a second semiconductor material layer 24, for example antimony sulfide, which is superimposed on the first layer 23 Figure indicates the arrow C ^ the direction in which the light

109810/0775 _gA D ORIGINAL

is projected and the arrow (h indicates the direction in which the electron beams are introduced » ^;

In the following, an example of the method for producing a photoconductive target according to the invention will be given. A cadmium selenide layer about 1 micron thick is deposited on a transparent electrode 21 on a transparent substrate in the form of vapor under a vacuum of 1 odor 2 2 10 "'mm of mercury. 05 percent by weight of copper (I) chloride was added. The laminated so by vapor deposition layer is further sintered, for example, with 15 minute long heating at a temperature of 600 ⁰ O in a nitrogen atmosphere. The Hasse is then subjected to heat treatment in a Selenatnosphäre ", for example, for 30 minutes at exposed to a temperature of 500 ⁰ O, in order to obtain a photoconductive layer of high resistivity. For the sake of convenience, this layer is referred to as the first layer 23. On the first layer 23 an antirontist foil 24 is vapor-deposited under the above-mentioned high vacuum of 10 * "* mm Hg, the thickness of which is 0.4 microns, which causes the photoconductive target to follow the

• 1 0 981 Π / 077 5 _BAD original

• Inventing is formed. The addition of E-apfer (I) chloride In this process, the iliotoconductivity is said to be obtained Increase shift. An inclusion of caesium chloride in the Väriiebelianülun;?; after dar Aufdaaipfuzigiot on this accelerates3 the growth of the cadmium ulenide crystals directed. In this! Fall full of this purpose. ”Furthermore Can the Oa & QiuiriselenicLkoiaporienta s; ua c-insr solid solution or ancii a lliGcliimc »^ iG a suitable proportion of CadaiumEulfid without bloom, order (for example v / eiae can do that Weight ratio of cadmium sulfide to cadmium selenide be equal to 1: 2). lax-uberhinaua irönnon put the suges Impurities BUDadditionally suin copper one or more the substances silver, gold, tiallium, indium, gallium, aluminum, Halogens, tellurium, antimony, viourafc, lead, tin, Contain alkali metals and alkaline earth metals.

An image pickup tube containing a target in which the first and second layers entsprechenl of the measure according to the invention are present, beaitzt, as shown in Figure 3, wherein weiteai hera.uaragender3 Eigenachaf * th than the known target, on the second layer of Antimontriaulfide is missing. 9 shows a comparison iki zwiochen the invention and known targets been made, wherein the Signalatroewert (logarithmic

10 9810/0775 bad original

Scale) through the ordinate and the BlldschlrmBpannungsvert (logarithmic scale) is denoted by the abscissa, where the earget lighting is at a level (0.8 lux, 0.3 lux and without lighting) were used as parameters *. the The solid curves in FIG. 3 indicate the properties of the known target and the dashed lashings of the target according to the invention.

As can be seen from this figure, the inventive • according to target with a lower voltage than in the known case, 12a achieve the same signal current eu. This is of particular importance, if only a tiny one Signal flow required is also affected the application of such a low carget voltage does not affect the dark current. Da3 photoconductive sarget according to the Invention makes it possible that the larget voltage over a wider range than in the known device can be selected. For example, if you are a The illuminance of 0.8 lux is based on the screen voltage the known device between about and about 25 volts, whereas according to the invention this between about 45 and about 8 toIt lies.

The measure according to the invention does not only bring that

1 0 98 1 Π / Π775

~ 12 -

Favorable from Pigur 3 readable! Progress with si cn, it also provides the additional advantage that the picture reduces vircU Ea coil dor case enganonnGii v / erden that atopielauoißö a phoUoloitcnclo E5.1äauinabia3rl> hre is put into operation? ersucli £ reinster 1 minute long illuminated thereon and diones after removal of the pattern to the light treißen cusgeoetat% IIRD · the Auagangsbesucliisaiuster remains Cg ^ o in the known back Sarget _t ία wherein only a first layer cxl3 Cadiaiumselenid is used. A photoleitends, SSAS Sargot according to the invention Bilßaufiiaiiuaröhr containing © However seigt substantially 2cein JJachbild »i / SiSn oiö the same conditions is subjected to" The Bildaufnahiaeröhre namely beeitßt not only high sensitivity and Panohrotaatismus the known image pickup tube _t simply with Gadmiumsäenid first Layer is spared, condom is compared to this bszüglioli voroclaiedonGr unorwUnschtor transition properties Törbeesert, which arrange a generated image, and thus offers greater practical usability. .

The decisive importance of the assembled target according to the invention is to be seen in the fact that the first layer consists of cadtaium selenium "which itself has sufficient photosensitivity. It has a first layer

■■■■■■■ - ■■ 10981 (1/0775 BADOR ₁ Q ₁ NA ₁ .

a bad light eapfincH-ichlceit, so offers a to- ■ s target » \ ϊβώλ es euoli corresponding to the

Measure © was produced, none Gate part. Selbstvöretyjaiiliah lot äü3 Verjfahröa to the manuf This first layer does not apply to the above-described level Execution fcria. limited- For example, it is Gate of heat treatment in a selenium atmosphere possible »^ the damping of the mixed layer in an inert Atmosphere under a Valnmgijöas sp deep vle 10 * "camouflage is to be carried out instead of 10 "^ around Hg vie before described

Be! For the first layer ölo vollö Photoeapfindlichlceit £ ieitigen lcann, soil bevorEUst the first Sohioht Ö »5 microns minimum thickness" Dar reason is the fact that _r au eohön diarin, VQTm. the first layer is thin, this on a Vemninä-

■ ·. ■■■■: ■

. tion of the highly sensible ^ Git and on the rise of the dark streaks and - to the impossibility - high quality television pictures you can see.

'Sun to the second layer of sailed did targets are described invention! "Said Antimontrlsul" fid is geiiählt as an example. In the previous embodiment, the antimony sulfide forms a continuous one

109810/0775 .. _BAD0RialN At

Plague layer of 0.4 Mliroa thickness · If the thickness increases .. over 0.6 microns, Dan only illuminates a laomontcaee regenerated image at the moment of recording This can be deduced from the above-mentioned working principle of this layer, and it is due to the fact that such a thick second layer hinders the inflow of electron beams and thus interrupts a secondary phototroia. In other words, the second layer formed on the first layer should not be so thick that it significantly prevents the inflow of scanning electron beams. The materials of the second layer may comprise cusätslich sua unknown Antiaontrißulfld other Halbloiterjiaterialien high resistance, for example AntimontrißclGixid, ArsentrlsuXfld, Arsentrleelenid _# Wismuttrisulfid, Wismuttriselenld, Cadniumtellurid, lead monoxide, selenium "Sirucoulfid and zinc selenide. If the second layer consists of one of the above-mentioned materials, the same results are obtained as in the case of the above-mentioned description continuous plague «etoffacbicht or designed as a porous layer»

10 9 810/0775

BATH ORIGINAL

1764882

l3eIspIelsvjelG0 Irscatrisulfid with a relatively high negative tfidGretaad da wide layer »eo doesn’t form a pre-difeioe as a continuous solid ocliicTic with regard to a simple control of the layer thickness during the absorption. In the case of a material with relatively low resistance as cpesifischen Antimontriselenid it is viinochensisrert, this in a porous layer also äarua su f ο risen vm, to prevent the degradation of the so Aufioaefähigköit liergedtolltan layer. While the wide layer or one or more layers apply Icaan, cpllte free seed thickness 0 _r 6 microns in Pedell lall not exceed.

The spelrtrookopiehe photo-ability of the first layer, which consists mainly of cedaium selenide prevails over the entire visible radiation range from blue to red in front · Anders Gucgedrüclct, the layer has one large subscriptions across the entire area de3 visible in the light. The light that passed through the first Shift was transferred »is conit in Sea assets that second layer to excite, daily reduced; According to the invention also used the second layer of vira Vapor deposition produced »a further © special treatment not necessary.

10 9810 / η 775

■ - 16

Since the above materials argue öar laminates tog p-Syp nafcsaGa, tennn imagine that "■ · a pn Übergan ^ cit in barrier gopolter Vorspsx ^ ang ■

Syrian first layer (layer of the E-vieitea layer (layer of the p ~ type) formed virö · V7ie cos Pigar 3, however, see below, the properties of flea eucscaccgoeetatca targets after the dew- finding are such that it, while there is geeeiate area der Arheitsspaunimg dos! üargeta ßioh rather against the low *

moves »the! Target Stroiaspaiinungaei-

gsnschaftea ± m vssantlichen analogous to those of a largets shows that only oit a first layer is provided.

The assembled target has no current saturation state due to the existence of a p-n junction3, as ellgomein assumed * The fact shows that the photoelectric UniforaierGiger.schaften dos Targets according to the invention completely independent of the particular problem Kontc & tes evrischen the c »reten and. second layers are. The svoita layer is supposed to flow in Elelctronotrohlen or lighten, indea Qrtlloh a ucharfer Potential gradient on the cibgetaototen surface of the first layer is caused. In other words, the second layer is used for a large number of levels

109810/0775 BATH ORIGINAL

- ■ 17 -

the on the? Obörflaoha dar Cretan layer exist Bind, au redcaiQisnj corpse uio "trcpo" opposite the üa-

ssi- v © s? h2lton. Bio ^ or. 33if ©! Et ctcssit from the,. ö & Q- dta liT3o ^ c. ^ a ^ £: Qig <saschaft © n of the target,

ica the uassütbiacihte UachMlt! you EiBfaKgca (trapping) of a leöuagotragerö '.atafch this surface * level ■ originates from * ·. - ■ w

Eat entaits

109810 / O77S

Claims (2)

PAI ¹ EJiMlTSPRAGEB f 1 «) JPhotoleitenüGo target in which a layer of photcleitencicn Katorielo on a layer of electrically conductive mater-islc? formed iot »characterized in that the layer of photoconductive material (22) is formed from a first layer (23) of i / snstena Gaflniuisoelenid, the eüf a layer of electrically conductive limaterials (21) with a thickness of 0.5 micron minimal and one second layer (24) is constructed, which contains at least a semiconductor material of high resistance and the first layer (23) with a thickness of 0.6 microns. is maximally superimposed 2.) Photoconductive serget according to claim 1, characterized in that the Eweita layer consists of antimony trisulfide. 109810/0775 bad original