US4647812A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Display tube having a display window with an interference filter
Assignee: US Philips Corp
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Filing: 1985-06-10
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Granted: 1987-03-03
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Expires: 2005-06-10
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 compises 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 optical thickness nd, wherein n is the refractive index of the material and d is the thickness, which optical thickness is between 0.2 λ f and 0.3 λ f and preferably between 0.23 λ f and 0.27 λ f , wherein λ f is equal to p x λ, 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. Color improvement and gain in contrast also occur.
Inventors
- 👤 Leendert Vriens
- 👤 Johannes H. M. Spruit
- 👤 Johannes C. N. Rijpers
- 👤 Titus E. C. Brandsma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 12:25
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: 16
Claim 1
Independent Claim
150 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 0.2λ f and 0.3λ f , in which λ f is equal to p xλ, 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
150 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 0.2λ f and 0.3λ f , in which λ f is equal to p xλ, 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 claim 1, 2, or 3, characterized in that the layers of the filter having a high refractive index consist of titanium oxide (TiO 2 ) or tantalum oxide (Ta 2 O 5 ) and the layers having a low refractive index consist of silicon oxide (SiO 2 ) or magnesium fluoride (MgF 2 ).
Claim 6
Dependent Claim
20 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
43 words
A display tube as claimed in claim 1, 2, or 3, 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 TiO 2 --SiO 2 filter.
Claim 8
Dependent Claim
42 words
A display tube as claimed in claim 1, 2, or 3, 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 TiO 2 --SiO 2 filter.
Claim 9
Dependent Claim
44 words
A display tube as claimed in claim 1 or 2, characterized in that the luminescing material is europium-activated yttrium oxide (Y 2 O 3 :Eu) and λ=612 nm and p is a number between 1.22 and 1.27 for a TiO 2 --SiO 2 filter.
Claim 10
Dependent Claim
43 words
A display tube as claimed in claim 1, 2, or 3, 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
43 words
A display tube as claimed in claim 1, 2, or 3, 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 O 5 --SiO 2 filter.
Claim 12
Dependent Claim
47 words
A display tube as claimed in claim 1, 2, or 3, characterized in that the luminescent material is europium-activated yttrium oxid (Y 2 O 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
77 words
A display tube as claimed in claim 1, 2 or 3, characterized in that the layer of the filter closest to the luminescent material has a thickness of approximately 0.25λ f , consists essentially of a material having a high refractive index, and is coated with a terminating layer having an optical thickness of approximately 0.125λ f and consisting essentially of a material having a lower refractive index, the luminescent material being provided on said terminating layer.
Claim 14
Dependent Claim
68 words
A display tube as claimed in claim 1, 2 or 3, characterized in that the layer of the filter closest to the display window has a thickness of approximately 0.25λ f , consists essentially of a material having a high refractive index, and is coated with an intermediate layer having an optical thickness of approximately 0.125λ f and consisting essentially of a material having a lower refractive index.
Claim 15
Dependent Claim
75 words
A display tube as claimed in claim 1, 2 or 3, characterized in that the layer of the filter closest to the luminescent material has a thickness of approximately 0.25λ f , comprises a mixture of metal oxides including titanium oxide (TiO 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
21 words
A display tube as claimed in claim 1, 2, or 3, characterized in that it is a projection television display tube.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-03-02 | 1990-09-01 | 1991-03-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-03-02 | 1994-09-01 | 1995-03-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-03-02 | 1998-09-01 | 1999-03-03 | $7700.00 | Window Closed / Lapsed |