US2665220A - Method of manufacturing luminescent screens - Google Patents

Method of manufacturing luminescent screens Download PDF

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US2665220A
US2665220A US78507A US7850749A US2665220A US 2665220 A US2665220 A US 2665220A US 78507 A US78507 A US 78507A US 7850749 A US7850749 A US 7850749A US 2665220 A US2665220 A US 2665220A
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layer
metal
luminescent
light
intermediate layer
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US78507A
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Gier Johannes De
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Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/18—Luminescent screens
    • H01J29/28—Luminescent screens with protective, conductive or reflective layers

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  • the invention relates to a method of manufacturing a luminescent screen for a cathode-ray tube, which screen, on the side facing the electron source, is coated with a light-reflecting metal layer.
  • the invention furthermore relates to a luminescent screen manufactured by this method and to a cathode-ray tube comprising such a screen.
  • the layer of luminescent material and the reflecting metal layer are separated temporarily by an intermediate layer which seals the granular surface of the luminescent substance.
  • a substance particularly suitable for this layer being, for example, nitrocellulose.
  • the light-reflecting metal layer must naturally be of such thinness that it substantially does not hamper the electrons of the electron beam, since these are required to be able to strike the luminescent material to bring it to luminescence.
  • a metal atom of this layer may catch an electron and become a metal ion.
  • This metal ion may travel to the luminescent layer and bring about a reduction of the luminescent substance.
  • coloured metal may be released from the luminescent sub- Stance.
  • a temporary intermediate layer made of material removable by heat, the temporary intermediate layer has applied to it a thin second intermediate layer made primarily of one or more metal oxides.
  • the temporary intermediate layer is removed, and the lightreiiecting metal layer is then applied to the second intermediate layer.
  • the use of the method according to the invention has the advantage that the light-reflecting metal layer is separated by the intermediate layer of metal oxide from the luminescent layer. Metal atoms or ions of the mirror layer are thus prevented from affecting the grains of the luminescent material.
  • One of the possible above causes for fogging of the luminescent, screen is thus obviated.
  • the intermediate layer made of metal oxides also largely obviates the second cause for fogging as set out hereinbefore, since owing to the second intermediate layer being thin, volatilisation and oxidation of the temporary intermediate layer becomes almost complete so that substantially no material thereof is left.
  • any reduction of luminescent material which may be due, for example, to materials by which the purity of the luminescent material is afiected, is prevented by the presence of the intermediate layer which is rich in oxygen, since the reduction may be looked upon as a balanced reaction with a large quantity of a substance liable to be produced by the reaction previously available.
  • the use of the temporary intermediate layer is required in order that the oxide layer applied may be smooth in appearance on the side facing the electron source, a light-reflecting metal layer being thus enabled to be readily applied to the said oxide layer.
  • a luminescent screen comprising a glass support to which the luminescent material is applied.
  • a sealing layer of boron-trioxide of such thickness as to be pervious to light and electrons.
  • the layer of boron trioxide is coated also on the side facing the cathode with a reflecting metal layer which is pervious to electrons.
  • the intermediate layer of boron trioxide serves to seal smoothly the granular luminescent layer so as to enable it to be coated with a satisfactory reflecting metal layer. It is not obvious how the intermediate layer of boron trioxide gets a smooth surface on the side facing the cathode.
  • this layer will exhibit all irregularities of the granular luminescent layer. Only if this intermediate layer were made very thick, asubstantially smooth surface could probably be produced but this is inconvenient in that the output :of the screen is reduced, since an excessive quantity of electrons is retained by the intermediate layer.
  • the oxide layer may be applied in a very simple manner by applying a thin metal layer to the temporary intermediate layer and by carrying out the heating operation required to remove the temporary intermediate layer in such manner that the thin metal layer applied is substantially oxidised. Subsequent to this heating operation the reflecting metal layer is applied to the side facing the electron source.
  • Heating is preferably eifected in an oxidising atmosphere, for example air.
  • the intermediate layer constituted by oxides may be made of alumina, silica or boron trioxide.
  • the reflecting metal layer it is not necessary for the reflecting metal layer to be constituted by the same metal as that the oxide of which is used as the intermediate layer.
  • the thickness of the intermediate oxide layer is preferably chosen to be less than one quarter of that of the light reflecting metal layer.
  • the thickness of the oxide layer is preferably chosen to be lower than 0.69 ,u..
  • the method according to the invention presents the following additional advantage.
  • the method heretofore employed has the disadvantage that during the heating operation for removing the intermediate layer the contact between the metal layer on the screen and the metal layer on the bulb wall is weakened.
  • the method according to the invention according to which the application of the reflecting metal layer is not followed by heating the said contact is quite sure and reliable.
  • a method of manufacturing a luminescent screen assembly for a cathode ray tube which comprises depositing a layer of luminescent particles on a light-transparent base, applying a temporary layer of heat volatilizable film-forming organic coating material over said luminescent layer to form a smooth surface thereover,
  • a method of manufacturing a luminescent screen assembly for a cathode ray tube which comprises depositing a layer of luminescent particles on a light-transparent base, applying a temporary layer of nitrocellulose over said luminascent layer to form a smooth surface thereover, applying an electron and light-pervious layer of aluminum over said layer ofvheat-removable material, heating the aluminum layer in an oxidizing atmosphere to convert the same to a layer of an oxide of said metal, while removing the temporary intermediate layer, and thereafter applying a thin light reflecting electron permeable metal layer over said metal oxide layer, said metal layer having a thickness which is substantially four times greater than said oxide layer.

Description

Jan. 5, 1954 DE GIER 2,665,220
METHOD OF MANUFACTURING LUMINESCENT SCREENS Filed Feb. 26. 1949 HEAT DECOMPOSABLE METAL OXIDE LAYER RTEFLECTING LAYER BEAM PRODUCING ELEMENTS INVENTOR JOHANNES DE GIER AGENT Patented Jan. 5, 1954 METHOD OF MANUFACTURING LUMINESCENT SCREENS Johannes de Gier, Eindhoven, Netherlands, as-
signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application February 26, 1949, Serial No. 78,507
Claims priority, application Netherlands March 5, 1948 2 Claims.
The invention relates to a method of manufacturing a luminescent screen for a cathode-ray tube, which screen, on the side facing the electron source, is coated with a light-reflecting metal layer. The invention furthermore relates to a luminescent screen manufactured by this method and to a cathode-ray tube comprising such a screen.
It is known to coat the luminescent screen of a cathode-ray tube on the side facing the electron source with a light-reflecting metal layer. This layer must have satisfactory mirror properties on the side remote from the electron source and to attain this object, a variety of methods have been suggested. According to a method which gives quite satisfactory results, the layer of luminescent material and the reflecting metal layer are separated temporarily by an intermediate layer which seals the granular surface of the luminescent substance. A substance particularly suitable for this layer being, for example, nitrocellulose. After the reflecting metal layer has been applied, the said intermediate layer has served its purpose and is therefore removed. This may be eiiected quite simply by heating the whole screen in an oxidizing atmosphere, for example air, the intermediate layer thus volatilizing and being burnt. The gases thus evolved can partly escape at the sides of the screen and Partly through the thin metal layer.
The light-reflecting metal layer must naturally be of such thinness that it substantially does not hamper the electrons of the electron beam, since these are required to be able to strike the luminescent material to bring it to luminescence.
It has now been found that screens manufactured in the above manner exhibit the unpleasant property of fogging during operation of the tube in which they are housed, this being obviously due to the electron bombardment. After operation for some hours, the luminescent layer presents a grey or brown appearance. Exhaustive experiments on which this invention is based showed that this fogging is related on the one hand to the method of manufacturing the screen, particularly to the temporary provision of the intermediate layer, and on the other hand to the light-reflecting meta1 layer. Although it is not yet quite clear to what the fogging of the screen is due, there are indications that the fogging is produced in the following manner.
Due to the electron bombardment of the lightreflecting metal layer a metal atom of this layer may catch an electron and become a metal ion. This metal ion may travel to the luminescent layer and bring about a reduction of the luminescent substance. Thus, for example, coloured metal may be released from the luminescent sub- Stance.
An alternative explanation is that the material of the temporary intermediate layer is not completely removed in spite of the heating operation and, during operation of the tube, possibly also due to the electrons arriving at a high speed, reacts with the luminescent material and also releases metal from the luminescent substance.
In a method according to the invention, for use in manufacturing a luminescent screen coated on the side facing the electron source with a lightreiiecting metal layer, according to which a layer of luminescent material applied to a support has applied to it, prior to the application of the lightreiiecting metal layer, a temporary intermediate layer made of material removable by heat, the temporary intermediate layer has applied to it a thin second intermediate layer made primarily of one or more metal oxides. Next the temporary intermediate layer is removed, and the lightreiiecting metal layer is then applied to the second intermediate layer.
The use of the method according to the invention has the advantage that the light-reflecting metal layer is separated by the intermediate layer of metal oxide from the luminescent layer. Metal atoms or ions of the mirror layer are thus prevented from affecting the grains of the luminescent material. One of the possible above causes for fogging of the luminescent, screen is thus obviated. The intermediate layer made of metal oxides also largely obviates the second cause for fogging as set out hereinbefore, since owing to the second intermediate layer being thin, volatilisation and oxidation of the temporary intermediate layer becomes almost complete so that substantially no material thereof is left. it is furthermore probable that owing to the presence of the oxide layer any reduction of luminescent material which may be due, for example, to materials by which the purity of the luminescent material is afiected, is prevented by the presence of the intermediate layer which is rich in oxygen, since the reduction may be looked upon as a balanced reaction with a large quantity of a substance liable to be produced by the reaction previously available.
The use of the temporary intermediate layer is required in order that the oxide layer applied may be smooth in appearance on the side facing the electron source, a light-reflecting metal layer being thus enabled to be readily applied to the said oxide layer.
In U. S. Patent No. 2,233,786 a luminescent screen is described comprising a glass support to which the luminescent material is applied. On the side facing the cathode this is coated with a sealing layer of boron-trioxide of such thickness as to be pervious to light and electrons. The layer of boron trioxide is coated also on the side facing the cathode with a reflecting metal layer which is pervious to electrons. The intermediate layer of boron trioxide serves to seal smoothly the granular luminescent layer so as to enable it to be coated with a satisfactory reflecting metal layer. It is not obvious how the intermediate layer of boron trioxide gets a smooth surface on the side facing the cathode. It is to be expected that this layer will exhibit all irregularities of the granular luminescent layer. Only if this intermediate layer were made very thick, asubstantially smooth surface could probably be produced but this is inconvenient in that the output :of the screen is reduced, since an excessive quantity of electrons is retained by the intermediate layer.
Inoneembodiment of the invention the oxide layer may be applied in a very simple manner by applying a thin metal layer to the temporary intermediate layer and by carrying out the heating operation required to remove the temporary intermediate layer in such manner that the thin metal layer applied is substantially oxidised. Subsequent to this heating operation the reflecting metal layer is applied to the side facing the electron source. Such a method can be readily carried out for example with the metal aluminum. Heating is preferably eifected in an oxidising atmosphere, for example air.
In an alternative embodiment of the invention, the intermediate layer constituted by oxides may be made of alumina, silica or boron trioxide.
Obviously it is not necessary for the reflecting metal layer to be constituted by the same metal as that the oxide of which is used as the intermediate layer.
The thickness of the intermediate oxide layer is preferably chosen to be less than one quarter of that of the light reflecting metal layer. Thus, for example, if the latter layer is 0.35 micron in thickness, the thickness of the oxide layer is preferably chosen to be lower than 0.69 ,u..
The method according to the invention presents the following additional advantage.
If that part of the bulb wall which adjoins the luminescent screen must be coated with a metal layer, the method heretofore employed has the disadvantage that during the heating operation for removing the intermediate layer the contact between the metal layer on the screen and the metal layer on the bulb wall is weakened. With the method according to the invention, according to which the application of the reflecting metal layer is not followed by heating the said contact is quite sure and reliable.
What I claim is:
1. A method of manufacturing a luminescent screen assembly for a cathode ray tube which comprises depositing a layer of luminescent particles on a light-transparent base, applying a temporary layer of heat volatilizable film-forming organic coating material over said luminescent layer to form a smooth surface thereover,
applying an electron and light-pervious layer of aluminum over said layer of heat-removable material, heating the aluminum layer in an oxidizing atmosphere to convert the same to a layer of an oxide of said metal, while removing the temporary intermediate layer, and thereafter applying a thin light reflecting electron permeable metal layer over said metal oxide layer, said metal layer having a thickness which is substantially greater than said oxide layer.
2. A method of manufacturing a luminescent screen assembly for a cathode ray tube which comprises depositing a layer of luminescent particles on a light-transparent base, applying a temporary layer of nitrocellulose over said luminascent layer to form a smooth surface thereover, applying an electron and light-pervious layer of aluminum over said layer ofvheat-removable material, heating the aluminum layer in an oxidizing atmosphere to convert the same to a layer of an oxide of said metal, while removing the temporary intermediate layer, and thereafter applying a thin light reflecting electron permeable metal layer over said metal oxide layer, said metal layer having a thickness which is substantially four times greater than said oxide layer.
JOHANNES DE GIER.
References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,197,625 Teves et al Apr. 16, 1940 2,233,786 Law Mar. 4, 1941 2,374,310 Shaefer Apr. 24, 1945 2,374,311 Shaefer Apr. 24, 1945 2,378,875 Vansant June 19, 1945

Claims (1)

1. A METHOD OF MANUFACTURING A LUMINESCENT SCREEN ASSEMBLY FOR A CATHODE RAY TUBE WHICH COMPRISES DEPOSITING A LAYER OF LUMINESCENT PARTICLES ON A LIGHT-TRANSPARENT BASE, APPLYING A TEMPORARY LAYER OF HEAT VOLATILIZABLE FILM-FORMING ORGANIC COATING MATERIAL OVER SAID LUMI NESCENT LAYER TO FROM A SMOOTH SURFACE THEREOVER, APPLYING AN ELECTRON AND LIGHT-PERVIOUS LAYER OF ALUMINUM OVER SAID LAYER OF HEAT-REMOVABLE MATERIAL, HEATING THE ALUMINUM LAYER IN AN OXIDIZING ATMOSPHERE TO CONVERT THE SAME TO A LAYER OF AN OXIDE OF SAID METAL, WHILE REMOVING THE TEMPORARY INTERMEDIATE LAYER, AND THEREAFTER APPLYING A THIN LIGHT REFLECTING ELECTRON PERMEABLE METAL LAYER OVER SAID METAL OXIDE LAYER, SAID
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2734013A (en) * 1956-02-07 myers
US2758942A (en) * 1952-04-04 1956-08-14 Hartford Nat Bank & Trust Co Cathode-ray tube of the kind comprising a luminescent screen
US2836754A (en) * 1942-09-14 1958-05-27 Nat Union Electric Corp Dark trace cathode-ray tube and method of manufacture
US2836753A (en) * 1942-09-14 1958-05-27 Nat Union Electric Corp Dark trace cathode-ray tubes and screens therefor
US3195199A (en) * 1961-09-01 1965-07-20 Rca Corp Method of making targets for pickup tubes
US3980888A (en) * 1972-09-28 1976-09-14 Siemens Aktiengesellschaft Self-supporting luminescent screens
US4160187A (en) * 1975-11-05 1979-07-03 Gte Sylvania Incorporated Post-deflection acceleration crt system
US4626739A (en) * 1984-05-10 1986-12-02 At&T Bell Laboratories Electron beam pumped mosaic array of light emitters
WO1988001824A1 (en) * 1986-08-26 1988-03-10 Tds Patent Management, Inc. Cathode ray tube with integral mirror optics for three-tube projection television systems having increased light output

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2197625A (en) * 1937-06-17 1940-04-16 Rca Corp Cathode ray tube
US2233786A (en) * 1939-11-29 1941-03-04 Rca Corp Fluorescent screen assembly and method of manufacture
US2374310A (en) * 1941-06-27 1945-04-24 Gen Electric Method of producing solids of desired configuration
US2374311A (en) * 1944-06-21 1945-04-24 Gen Electric Cathode ray tube
US2378875A (en) * 1942-03-30 1945-06-19 Philco Radio & Television Corp Cathode ray television tube

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2197625A (en) * 1937-06-17 1940-04-16 Rca Corp Cathode ray tube
US2233786A (en) * 1939-11-29 1941-03-04 Rca Corp Fluorescent screen assembly and method of manufacture
US2374310A (en) * 1941-06-27 1945-04-24 Gen Electric Method of producing solids of desired configuration
US2378875A (en) * 1942-03-30 1945-06-19 Philco Radio & Television Corp Cathode ray television tube
US2374311A (en) * 1944-06-21 1945-04-24 Gen Electric Cathode ray tube

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2734013A (en) * 1956-02-07 myers
US2836754A (en) * 1942-09-14 1958-05-27 Nat Union Electric Corp Dark trace cathode-ray tube and method of manufacture
US2836753A (en) * 1942-09-14 1958-05-27 Nat Union Electric Corp Dark trace cathode-ray tubes and screens therefor
US2758942A (en) * 1952-04-04 1956-08-14 Hartford Nat Bank & Trust Co Cathode-ray tube of the kind comprising a luminescent screen
US3195199A (en) * 1961-09-01 1965-07-20 Rca Corp Method of making targets for pickup tubes
US3980888A (en) * 1972-09-28 1976-09-14 Siemens Aktiengesellschaft Self-supporting luminescent screens
US4160187A (en) * 1975-11-05 1979-07-03 Gte Sylvania Incorporated Post-deflection acceleration crt system
US4626739A (en) * 1984-05-10 1986-12-02 At&T Bell Laboratories Electron beam pumped mosaic array of light emitters
WO1988001824A1 (en) * 1986-08-26 1988-03-10 Tds Patent Management, Inc. Cathode ray tube with integral mirror optics for three-tube projection television systems having increased light output

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