|Publication number||US3729342 A|
|Publication date||Apr 24, 1973|
|Filing date||Apr 1, 1970|
|Priority date||Apr 16, 1969|
|Also published as||DE2016211A1, DE2016211B2, DE2016211C3|
|Publication number||US 3729342 A, US 3729342A, US-A-3729342, US3729342 A, US3729342A|
|Inventors||Velde T Te|
|Original Assignee||Philips Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (10), Classifications (16)|
|External Links: USPTO, USPTO Assignment, Espacenet|
April 24, 1973 T, s, TE VELDE 3,729,342
METHOD OF MANUFACTURING A RADIATION-SENSITIVE ELECRONIC DEVICE Filed April 1, 1970 INVENTOR.
TIES S.TE VELDE E@ Awe@ United States Patent Office 3,729,342 Patented Apr. 24, 1973 3,729,342 METHOD F MANUFACTURING A RADIATION- SENSITIVE ELECTRGNIC DEVICE Ties Siebolt te Velde, Emmasingel, Eindhoven, Netherlands, assignor to U.S. Philips Corporation, New York,
Filed Apr. 1, 1970, Ser. No. 24,556 Claims priority, application Netherlands, Apr. 16, 1969, 6905835 Int. Cl. B44d 1/16 U.S. Cl. 117-217 6 Claims ABSTRACT 0F THE DISCLOSURE The invention relates to a method of manufacturing a radiation-sensitive or electroluminescent electronic device which comprises a foil consisting of radiation-sensitive or electroluminescent grains, for example, semiconductor grains which are incorporated in an insulating binder surface portions of said grains being free from the binder on at least one side of the foil, said foil being covered at least on said side with a contact layer which electrically interconnects said grains, the contact layer being permeable to radiation to which the grains are sensitive or which can be emitted by the grains.
The invention furthermore relates to a device manufactured by using the method according to the invention.
Devices as described above are known, and may be used, for example, in radiation detectors, photoresstors, solar batteries and electroluminescent panels. Ihe said radiation may be of an electromagnetic or corpuscular nature.
In manufacturing such a device, on the one hand the grains must be fixed upon forming the foil while on the other hand the radiation-permeable contact layer must be provided on the foil in such manner that a good electric contact with the grains is obtained.
In known methods a rather large number of more or less complicated operations are used for that purpose, in which first the grains are embedded in the binder, parts of grains being then liberated from the binder on at least one side and finally a radiation-permeable contact layer is provided on said side usually in several operation steps.
One of the objects of the invention is to provide a very simple method in which the desirable result is obtained with a minimum number of operation steps.
The invention is based inter alia on the discovery that by using a comparatively low-melting-point metal layer and making use of capillary forces, the fixing of the grains and the provision of a radiation-permeable contact layer in good electric contact with the grains can be carried out in one operation step.
.According to the invention, a method of the type mentioned in the preamble is therefore characterized in that on a first electrically conductive layer which is permeable to the said radiation a second layer is provided of a metal which, in the melted condition, Wets the first layer less readily than the grains, the grains are spread on the second layer, the metal of the second layer is then melted and contracts between the grains and the first layer due to the occurring capillary forces and is substantially removed from the parts of the first layer situated between the grains, that after cooling the non-adhered grains are removed and that a binder permeable to said radiation is then provided in the spaces between the grains. Of course the thickness of the metal layer must be chosen to be so that the grainscannot entire sink away in the metal.
Metals for fixing and contacting the grains are those metals and alloys having a lower melting-point than the grains and the first radiation-permeable conductive layer. Particularly useful are metals those having a melting point below 1000 C., for example, Zn, Cd, Ga, In, Tl, Sn, Pb, Sb, Bi and Te.
With a given grain material the metals chosen are those which readily wet the grains and therefore can give a good adhesion and a good electric contact with the grains. Of course, low melting-point metals which have an undesired reaction with the materials with which they are contacted, cannot be used.
As is known from semiconductor technology, the possibility is available by the choice of the metals and possible additions to said metals, to form both ohmic and rectifying contacts on the grains in so far as these are active as semiconductors.
Light-permeable conductive oxide layers can be used for the said first radiation-permeable conductive layer. For example, layers of tin oxide and/or indium oxide, which can be realized by spraying with a solution of tin chloride and indium chloride, respectively, or by vapour deposition in known manner. The electric conductivity is effected by additions, such as antimony or boron, or as a result of deviations from the stoichiometric composition caused during the provision. Furthermore, thin light-permeable metal layers, for example, gold layers, may be used in many cases.
In general the first radiation-permeable conductive layer will be provided on a support during the manufacture. If this support is at best sparingly permeable to the said radiation, it will have t0 be removed at the end of the operation. According to an important preferred embodiment, however, the first layer is provided on a support which is permeable to the said radiation and need therefore not be removed from the foil.
Of course, the composition of the first transparent layer must be chosen to be such as not to dissolve in an undesired manner in the metal to be used. However, the possibility of choice is so wide than in this respect no difficulties need to occur.
The invention will now be described with reference to the accompanying drawing, in which FIG. 1 is a diagrammatic cross-sectional view of a stage of the method according to the invention, and
FIG. 2 is a diagrammatic cross-sectional view of a device manufactured by using the method according to the invention.
A layer of indium oxide 2 is vapour-deposited on a glass support as shown in FIG. 1. This is carried out by evaporating indium oxide at C. in an atmosphere which contains oxygen at a pressure of 5.10-4 mm. mercury. The support 1 is kept at a temperature of 300 C. Thus a layer 2 is obtained which is light-permeable and electrically conductive.
On this layer a layer of cadmium 3, 500 A. thick, is then provided by vapour deposition in a vacuum at 500 C. Zinc selenide 4 in powder form having an average grain size of 30 um. is scattered on said layer.
After heating for 30 minutes at 450 C. in hydrogen of atmospheric pressure, the grains contacting the metal 3 adhere to the support as is shown in FIG. 2, as a result of which a mono-grain layer is formed after removing the non-adhering grains.
The cadmium 3 which forms an ohmic contact with the grains is drawn away from the iridium oxide between the grains by the occurring capillary forces, and interruptions are formed in the metal layer 3. As a result of this, transmission of radiation from and to the grains 4 can take place.
The layer of grains 4 is then impregnated with a mixture of components which form a polyurethane 6. After partial hardening of the polyurethane the grain surfaces are cleaned by etching with an alcoholic lye solution and entirely hardened.
Finally a copper layer 7 is vapour-deposited which forms rectifying contacts with the grains `4 of zinc selenide.
The resulting assembly may be used, for example, as an electroluminescent panel.
It will be obvious that the invention is not restricted to the examples described, but that many variations are possible to those skilled in the art by choosing other combinations of materials without departing from the scope of this invention. For example, by a suitable choice of the metal 3 and the grain material 4 in FIG. 2, a photosensitive or radiating rectifying contact instead of an ohmic contact can be obtained between the metal 3 and the grains 4, an ohmic contact being preferably e'iected between the metal 7 and the grains 4. The contact layer 7 may be omitted, if desirable, for example, if in the operating condition on this side of the foil charge transport from or to the grains takes place in a diierent manner, for example, by an electron or iron beam, an electrolyte or analogous charge-transporting means.
What is claimed is:
1. A method of manufacturing a radiation-sensitive electronic device having electrically responsive grains of a radiation-sensitive material incorporated in an insulating binder comprising the steps of depositing on a support a iirst electrically-conductive radiation permeable layer,
depositing a second layerof a metal, depositing -radiationsensitive grains on said metal layer, melting the metal layer whereby those portions of the metal layer not in contact with at least one of the grain are drawn by capillary action to substantially accumulate between those grains which are in contact with the metal layer substantially removing the metal between those grains in contact with the metal layer to form separate metal layers for each 0f those grains, cooling the metal layers to solidify the same, removing the remaining grains not contacting said metal layers, and thereafter impregnating the spaces between those grains with an insulating binder.
2. A method as claimed in claim 1 wherein the rst layer is provided on a support which is permeable to the said radiation.
3. A method as claimed in claim 1 wherein the metal of the second layer has a melting point lower than 1000 C.
4. A method as claimed in claim 1 wherein the grains are electroluminescent.
5. A method as claimed in claim 1 wherein the grains are photosensitive.
6. A method as claimed in claim S wherein the radiation permeable layer is indium oxide and the metal iS cadmium.
References Cited UNITED STATES PATENTS 2,881,344 4/1959 Michlin 313-108 A 3,108,202 10/ 1963 Farnsworth 313-65 A 3,408,223 10/ 1968 Shortes 117-100 B ALFRED L. LEAVITT, Primary Examiner C. K. WEIFFENBACH, Assistant Examiner U.S. Cl. X.R.
UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3172923142 Dated April 2,4-, 1973 Inventor(s) Ties T6 Velde It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 2, line l1, "useful are metals those" should read --useful are those metals".
Column 3,V line 2, "iridium oxide" should read --indium oxide-"H Signed land seald this 25th day of June 19714.
EUNARD M.FLETCH.`ER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents ORM PO-1050 (1D-69) USCOMMDC 60376P69 U.S. GOVERNMENT PRINTING OFFICE 199 O-SGG-SB,
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|U.S. Classification||427/64, 427/70, 427/66, 427/69, 427/71, 148/DIG.107, 428/917, 427/74|
|International Classification||H05B33/10, H05B33/26|
|Cooperative Classification||H05B33/10, H05B33/26, Y10S148/107, Y10S428/917|
|European Classification||H05B33/26, H05B33/10|