EP0170320A1
Expired / Lapsed
EP
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Display tube
Assignee: Koninklijke Philips NV
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Filing: 1985-07-08
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Granted: —
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Expires: 2005-07-08
Abstract
Abstract A display tube comprising in an evacuated envelope (1) a display screen (7) provided on the inside of a display window (2) in the wall of the envelope (1), which display screen (7) comprises luminescent material (13), and a multilayer interference filter (12) is provided between this material and the display window and comprises a number of layers (HL) which alternately are manufactured from a material having a high (H) and a material having a low (L) refractive index. If the filter is composed substantially of 14 to 30 layers, each having an opical thickness nd, wherein n is the refractive index of the material and d is the thickness, which optical thickness is between 0.2λ f and 0.3λ f and preferably between 0.23λ f and 0.27λ f , wherein λ f is equal top xx, wherein λ is the desired central wavelength which is selected from the spectrum emitted by the luminescent material (13) and p is a number between 1.18 and 1.36, a display tube is obtained in which the luminous efficiency in the forward direction and at small angles for the central wavelength of the phosphor is at least 40% larger than in a tube without such a filter. Colour improvement and gain in contrast also occur.
Inventors
- 👤 Leendert Vriens
- 👤 Johannes Hendrikus Maria Spruit
- 👤 Johannes Cornelis Norbertus Rijpers
- 👤 Titus Emile Christiaan Brandsma
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 22:59
CPC Classifications
H; H01; H01J; H01J29/00; H01J29/02; H01J29/10; G; G02; G02B; G02B5/00; G02B5/20; G02B5/28; G02B5/285; H01J29/18; H01J29/185; H01J29/28; H04; H04N; H04N5/00; H04N5/64; H04N5/65
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
152 words
A display tube comprising in an evacuated envelope a display screen of a luminescent material provided on the inside of a display window in the wall of the envelope, and a multilayer interference filter disposed between said material and the display window, said filter comprising a plurality of layers manufactured alternately from a material having a high refractive index and a material having a low refractive index, characterized in that the filter is composed substantially of 14 to 30 layers each having an optical thickness nd, wherein n is the refractive index of the material of the layer and d is the thickness, said optical thickness nd being between 0.2 λ f and 0.3λ f , in which λ f is equal to p x λ, in which λ is the desired central wavelength selected from the spectrum emitted by the luminescent material and p is a number between 1.18 and 1.36.
Claim 2
Dependent Claim
152 words
A display tube comprising in an evacuated envelope a display screen of a luminescent material provided on the inside of a display window in the wall of the envelope, and a multilayer interference filter disposed between said material and the display window, said filter comprising a plurality of layers manufactured alternately from a material having a high refractive index and a material having a low refractive index, characterized in that the filter is composed substantially of 14 to 30 layers each having an optical thickness nd, wherein n is the refractive index of the material of the layer and d is the thickness, said optical thickness nd being between 0.2 λ f and 0.3λ f , in which λ f is equal to p x λ, in which λ is the desired central wavelength selected from the spectrum emitted by the luminescent material and p is a number between 1.18 and 1.36.
Claim 3
Dependent Claim
21 words
A display tube as claimed in Claim 1, characterized in that the filter is composed substantially of 18 to 22 layers.
Claim 4
Dependent Claim
23 words
A display tube as claimed in Claim 1, characterized in that the optical thickness nd is between 0.23λ f and 0.27λ f .
Claim 5
Dependent Claim
60 words
A display tube as claimed in any of the preceding Claims, characterized in that the layers of the filter having a high refractive index consist of titanium oxide (Ti0 2 ) or tantalum oxide (Ta 2 0 5 ) and the layers having a low refractive index consist of silicon oxide (Si0 2 ) or magnesium fluoride (MgF 2 ).
Claim 6
Dependent Claim
19 words
A display tube as claimed in Claim 4, characterized in that the magnesium fluoride is provided at approximately 300°C.
Claim 7
Dependent Claim
47 words
A display tube as claimed in any of the Claims 1 to 4, characterized in that the luminescent material comprises a terbium-activated, substantially green luminescing phosphor and λ = 545 nm and p is a number between 1.22 and 1.27 for a Ti0 2 -Si0 2 filter.
Claim 8
Dependent Claim
46 words
A display tube as claimed in any of the Claims 1 to 4, characterized in that the luminescent material comprises a terbium-activated blue luminescing phosphor and λ = 490 nm and p is a number between 1.22 and 1.27 for a Ti0 2 -Si0 2 filter.
Claim 9
Dependent Claim
46 words
A display tube as claimed in Claim 1 or 2, characterized in that the luminescing material is europium-activated yttrium oxide (Y 2 0 3 :Eu) and A = 612 nm and p is a number between 1.22 and 1.27 for a TiO 2 -SiO 2 filter.
Claim 10
Dependent Claim
46 words
A display tube as claimed in any-of the Claims 1 to 4, characterized in that the luminescent material comprises terbium-activated, substantially green-luminescing phosphor and λ = 545 nm and p is a number between 1.18 and 1.23 for a Ta 2 O 5 -SiO 2 filter.
Claim 11
Dependent Claim
47 words
A display tube as claimed in any of the Claims 1 to 4, characterized in that the luminescent material comprises a terbium-activated, blue-luminescing phosphor and λ = 490 nm and p is a number between 1.18 and 1.23 for a Ta 2 0 5 -Si0 2 filter.
Claim 12
Dependent Claim
51 words
A display tube as claimed in any of the Claims 1 to 4, characterized in that the luminescent material is europium-activated yttrium oxid (Y 2 0 3 :Eu) and λ = 612 nm and p is a number between 1.18 and 1.23 for a Ta 2 O 5 -SiO 2 filter.
Claim 13
Dependent Claim
73 words
A display tube as claimed in any of the preceding Claims, characterized in that the outermost approximately 0.25 λ f thick layer of the filter which faces the luminescent material consists of a material having a high refractive index and is coated with a terminating layer having an optical thickness of approximately 0.125 λ f of a material having a lower refractive index, the luminescent material being provided on the said terminating layer.
Claim 14
Dependent Claim
62 words
A display tube as claimed in any one of Claims 1 to 12, characterized in that the outermost approximately 0.25λ f thick layer of the filter facing the display window consists of a material having a high refractive index and is coated with an intermediate layer having an optical thickness of approximately 0.125λ f of a material having a lower refractive index.
Claim 15
Dependent Claim
81 words
A display tube as claimed in any one of Claims 1 to 8, and 12 and 13, characterized in that the outermost approximately 0.25λ f thick layer of the filter facing the luminescent material is composed of a mixture of metal oxides, which mixture comprises titanium oxide (Ti0 2 ) and a metal oxide from the group beryllium oxide (BeO), magnesium oxide (MgO) and calcium oxide (CaO), in which mixture the quantity of titanium oxide is 70 to 99% by weight.
Claim 16
Dependent Claim
22 words
A display tube as claimed in any one of the preceding Claims, characterized in that it is a projection television display tube.
Claim 17
Dependent Claim
18 words
A projection television device comprising at least a display tube as claimed in any of the preceding Claims.
Claim 18
Dependent Claim
45 words
A projection television device as claimed in Claim 16, characterized in that it comprises a display tube as claimed in Claim 6 or 9, a display tube as claimed in Claim 7 or 10, and a display tube as claimed in Claim 8 or 11.
Claim 19
Dependent Claim
27 words
A display window having a multilayer interference filter and a display screen for use in a display tube as claimed in any one of the preceding Claims.
References Cited (Backward Citations)
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