EP0246696A2
Expired / Lapsed
EP
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A method of manufacturing a cathode ray tube and a cathode ray tube made by the method
Assignee: Koninklijke Philips NV
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Filing: 1987-05-12
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Granted: —
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Expires: 2007-05-12
Abstract
Abstract A cathode ray tube, particularly, but not exclusively, a projection cathode ray tube having a multilayer interference filter (22) disposed between the cathodoluminescent screen (23) and the interior side of the faceplate (12). The interference filter (22) comprises alternate layers having high (H) and low (L) refractive indices. Known filters suffer from crazing after the tube processing is completed, as cathode ray tubes having them are heated up to between 4OO°C and 46O°C during the normal processing of the cathode ray tubes. It has been found that crazing is eliminated substantially if the high refractive index material is niobium pentoxide and the low refractive index material is either silicon oxide or magnesium fluoride. Deposition of the layers can be done by sputtering or evaporation onto a substrate which is cool relative known substrate temperatures used for other materials.
Inventors
- 👤 Henricusm. De Vrieze
- 👤 Johannesh. J. Roosen
- 👤 Leendert Vriens
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 10:01
CPC Classifications
H; H01; H01J; H01J29/00; H01J29/02; H01J29/10; H01J29/18; H01J29/20; H01J29/185; H01J29/24; H01J29/28
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
63 words
A method of making a cathode ray tube having a multilayer interference filter provided on an internally facing surface of a faceplate, the method including the step of depositing alternate layers of a material having a relatively high refractive index and a material having a relatively low refractive index on the faceplate, the material having a relatively high refractive index comprising niobium pentoxide.
Claim 2
Independent Claim
63 words
A method of making a cathode ray tube having a multilayer interference filter provided on an internally facing surface of a faceplate, the method including the step of depositing alternate layers of a material having a relatively high refractive index and a material having a relatively low refractive index on the faceplate, the material having a relatively high refractive index comprising niobium pentoxide.
Claim 3
Dependent Claim
102 words
A method as claimed in claim 1, characterised in that at least 9 alternate layers are deposited, the layers having an optical thickness nd , where n is the refractive index of the materials and d is the thickness, the optical thickness nd of the individual layers being between O.2λ f and O.3λ f , with an average optical thickness of the layers being O.25λ f , where λ f is equal to p × λ, where λ is the desired central wavelength selected from the spectrum emitted by the cathodoluminescent screen material and p is a number between 1.2O and 1.33.
Claim 4
Dependent Claim
38 words
A method as claimed in claim 1 or 2, characterised in that the low refractive index material comprises silicon dioxide, and the alternate layers are deposited at a temperature in the range of substantially 8O°C to substantially 3OO°C.
Claim 5
Dependent Claim
38 words
A method as claimed in claim 1 or 2, characterised in that the low refractive index material comprises magnesium fluoride, and the alternate layers are deposited at a temperature in the range of substantially 2OO°C to substantially 3OO°C.
Claim 6
Independent Claim
30 words
A method as claimed in any one of claims 1 to 4, characterised in that the multilayer interference filter is annealed whilst the faceplate is still at above ambient temperature.
Claim 7
Independent Claim
27 words
A method as claimed in any one of claims 1 to 5, characterised in that the faceplate comprises a mixed-alkali glass substantially free of lead oxide (PbO).
Claim 8
Dependent Claim
36 words
A method as claimed in claim 6, characterised in that the faceplate has a coefficient of expansion in the range 85 × 1O⁻⁷ to 1O5 × 1O⁻⁷ per degree centigrade for temperatures between O and 4OO°C.
Claim 9
Dependent Claim
52 words
A method as claimed in claim 6 or 7, characterised in that the glass composition in weight per cent comprises as main components: with the restrictions that (1) BaO and SrO together lie between 16 to 24, and (2) the combination formed by Li₂O, Na₂O and K₂O lie between 14 and 17.
Claim 10
Independent Claim
24 words
A method as claimed in any one of claims 1 to 8, characterised in that a cathodoluminescent screen is provided on the interference filter.
Claim 11
Dependent Claim
92 words
1O. A method as claimed in claim 2 or any one of claims 3 to 8 when appended to claim 2, characterised in that the last layer of average optical thickness of O.25λ f of the filter comprises a material having a high refractive index, a terminating layer is provided on the last layer, the terminating layer having a lower refractive index than the last layer and a thickness of substantially less than an average optical thickness of O.25λ f and in which a cathodoluminescent screen is provided on the terminating layer.
Claim 12
Dependent Claim
61 words
A cathode ray tube having a faceplate, a cathodoluminescent screen and a multilayer interference filter disposed between the faceplate and the screen, the filter comprising alternate layers of a material having a relatively high refractive index and a material having a relatively low refractive index deposited on the faceplate, wherein the material having a relatively high refractive index comprises niobium pentoxide.
Claim 13
Dependent Claim
61 words
A cathode ray tube having a faceplate, a cathodoluminescent screen and a multilayer interference filter disposed between the faceplate and the screen, the filter comprising alternate layers of a material having a relatively high refractive index and a material having a relatively low refractive index deposited on the faceplate, wherein the material having a relatively high refractive index comprises niobium pentoxide.
Claim 14
Dependent Claim
102 words
A tube as claimed in claim 11, characterised in that the filter comprises at least 9 layers, the layers having an optical thickness nd , where n is the refractive index of the materials and d is the thickness, the optical thickness nd of the individual layers being between O.2λ f and O.3λ f , with an average optical thickness of the layers being O.25λ f , where λ f is equal to p × λ, where λ is the desired central wavelength selected from the spectrum emitted by the cathodoluminescent screen material and p is a number between 1.2O and 1.33.
Claim 15
Dependent Claim
18 words
A tube as claimed in claim 12, characterised in that the filter has between 14 to 3O layers.
Claim 16
Dependent Claim
21 words
A tube as claimed in claim 12 or 13, characterised in that nd is between O.23λ f and O.27λ f .
Claim 17
Dependent Claim
23 words
A tube as claimed in any one of claims 11 to 14, characterised in that the low refractive index material comprises silicon dioxide.
Claim 18
Dependent Claim
23 words
A tube as claimed in any one of claims 11 to 14, characterised in that the low refractive index material comprises magnesium fluoride.
Claim 19
Dependent Claim
28 words
A tube as claimed in any one of claims 11 to 16, characterised in that the filter has been annealed substantially immediately after the layers have been deposited.
Claim 20
Dependent Claim
27 words
A tube as claimed in any one of claims 11 to 17, characterised in that the faceplate comprises a mixed-alkali glass substantially free of lead oxide (PbO).
Claim 21
Dependent Claim
36 words
A tube as claimed in claim 18, characterised in that the faceplate has a coefficient of expansion in the range 85 × 1O⁻⁷ to 1O5 × 1O⁻⁷ per degree centigrade for temperatures between O and 4OO°C.
Claim 22
Dependent Claim
53 words
2O. A tube as claimed in claim 18 or 19, characterised in that the glass composition in weight per cent comprises as main components: with the restrictions that (1) BaO and SrO together lie between 16 to 24, and (2) the combination formed by Li₂O, Na₂O and K₂O lie between 14 and 17.
Claim 23
Dependent Claim
57 words
A tube as claimed in any one of claims 11 to 2O, characterised in that the inside of the faceplate is convex with a maximum angle of curvature φ = 18°, where φ is the angle between the optical axis and a normal to the convex surface at a point furthest from the centre of the screen.
Claim 24
Dependent Claim
28 words
A tube as claimed in claim 21, characterised in that the convex faceplate is substantially spherical and has a radius of curvature between 15O mm and 73O mm.
Claim 25
Dependent Claim
37 words
A tube as claimed in claim 15 or 16, characterised in that the cathodoluminescent screen comprises a terbium activated substantially green luminescing phosphor having λ = 545 nm and p is a number between 1.2O and 1.26.
Claim 26
Dependent Claim
36 words
A tube as claimed in claim 15 or 16, characterised in that the cathodoluminescent screen comprises a europium-activated yttrium oxide phosphor (Y₂O₃:Eu) having λ = 612 nm and p is a number between 1.2O and 1.26.
Claim 27
Dependent Claim
34 words
A tube as claimed in claim 15 or 16, characterised in that the cathodoluminescent screen comprises a zinc sulphide-silver (ZnS:Ag) having λ = 46O nm and p is a number between 1.24 and 1.33.
Claim 28
Dependent Claim
70 words
A tube as claimed in claim 12 or any one of claims 13 to 25, when appended to claim 12, characterised in that the average optical thickness of the layers is O.25λ f , the layer furthest from the faceplate having a thickness of substantially O.25λ f comprises a material having a high refractive index, and in that the layer furthest from the faceplate is covered by the cathodoluminescent material.
Claim 29
Dependent Claim
62 words
A tube as claimed in claim 26, characterised in that a terminating layer is disposed between the layer of high refractive index material furthest from the faceplate and the layer of cathodoluminescent screen material, the terminating layer having an optical thickness of substantially O.125λ f and being of a material having a lower refractive index than that of the adjacent filter layer.
Claim 30
Dependent Claim
37 words
A projection television system comprising three cathode ray tubes having cathodoluminescent screens luminescing in different colours, characterised in that at least one of said cathode ray tubes comprises a cathode ray tube as claimed in claim 23.
Claim 31
Dependent Claim
37 words
A projection television system comprising three cathode ray tubes having cathodoluminescent screens luminescing in different colours, characterised in that at least one of said cathode ray tubes comprises a cathode ray tube as claimed in claim 24.
Claim 32
Dependent Claim
38 words
3O. A projection television system comprising three cathode ray tubes having cathodoluminescent screens luminescing in different colours, characterised in that at least one of said cathode ray tubes comprises a cathode ray tube as claimed in claim 25.
References Cited (Backward Citations)
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