US4657805A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dust cover superior in transparency for photomask reticle use and process for producing the same
Assignee: Asahi Kasei Corp
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Filing: 1984-10-12
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Granted: 1987-04-14
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Expires: 2004-10-12
Abstract
Abstract In a dust cover for photomask reticle purposes which consists essentially of a supporting frame and a thin film bonded to a surface of the frame, the dust cover is improved in transparency by constructing at least the outermost layers of the thin film with thin films of a fluoropolymer which exhibits an average transmittance of at least 90% for rays of wavelengths from 240 to 290 nm and an average transmittance of at least 93.5% for rays of wavelengths from 290 to 500 nm, when having a thickness of 10 μm, and has a refractive index of up to 1.42.
Inventors
- 👤 Yasunori Fukumitsu
- 👤 Mitsuo Kohno
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 21:50
CPC Classifications
B; B32; B32B; B32B27/00; B32B27/30; B32B27/304; B32B23/00; B32B23/04; B32B23/08; B32B27/06; B32B27/08; G; G03; G03F; G03F1/00; G03F1/62; B32B2307/00; B32B2307/40; B32B2307/412; B32B2559/00; Y; Y10; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/2495; Y10T428/24967; Y10T428/31504; Y10T428/3154; Y10T428/31544
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
105 words
A dust cover superior in transparency for photomask reticle purposes, which consists essentially of a supporting frame and a thin film bonded to edge areas thereof, said thin film consisting of either a single layer of a fluoropolymer which exhibits an average transmittance at least 90% for rays of wavelengths from 240 to 290 nm and an average transmittance of at least 93.5% for rays of wavelengths from 290 to 500 nm, when having a thickness of 10 μm, and has a refractive index of up to 1:42 or three or more multilayers both the outermost layers of which are formed of the above-defined fluoropolymer.
Claim 2
Dependent Claim
105 words
A dust cover superior in transparency for photomask reticle purposes, which consists essentially of a supporting frame and a thin film bonded to edge areas thereof, said thin film consisting of either a single layer of a fluoropolymer which exhibits an average transmittance at least 90% for rays of wavelengths from 240 to 290 nm and an average transmittance of at least 93.5% for rays of wavelengths from 290 to 500 nm, when having a thickness of 10 μm, and has a refractive index of up to 1:42 or three or more multilayers both the outermost layers of which are formed of the above-defined fluoropolymer.
Claim 3
Dependent Claim
24 words
The dust cover of claim 1, wherein said thin film is of a single layer structure having a thickness of 1 to 15 μm.
Claim 4
Dependent Claim
31 words
The dust cover of claim 1, wherein said thin film has a three-layer structure and the core layer thereof is a nitrocellulose film having a thickness of 0.5 to 15 μm.
Claim 5
Dependent Claim
26 words
The dust cover of claim 3, wherein both the outermost layers has an optical thickness corresponding to 1/4±10% of the wavelength of the light to use.
Claim 6
Dependent Claim
135 words
The dust cover of claim 1, wherein said thin film has the five-layer structure consisting of a core layer, two intermediate layers bonded separately onto both sides of the core layer, and two outermost layers, the core layer is a thin film of fluoropolymer exhibiting an average transmittance of at least 90% for rays of wavelengths from 240 to 290 nm and an average transmittance of at least 93.5% for rays of wavelengths from 290 to 500 nm, when having a thickness of 10 μm, and having a refractive index of up to 1.42, the intermediate layers are thin films of a transparent polymer having a refractive index of at least 1.45, and the outermost layers are thin films of the above-defined fluoropolymer having a refractive index not higher than that of the core film.
Claim 7
Dependent Claim
30 words
The dust cover of claim 5, wherein the intermediate layers and the outermost layers have each an optical thickness corresponding to 1/4±10% of the wavelength of the light to use.
Claim 8
Dependent Claim
66 words
The dust cover of claim 1, wherein said thin film has the five-layer structure consisting of a core layer, two intermediate layers bonded separately onto both sides of the core layer, and two outermost layers, the core layer is a nitrocellulose film having a thickness of 0.5 to 1.5 μm, and the intermediate layers are transparent polymer film having a refractive index of at least 1.57.
Claim 9
Dependent Claim
30 words
The dust cover of claim 7, wherein the intermediate layers and the outermost layers have each an optical thickness corresponding to 1/4±10% of the wavelength of the light to use.
Claim 10
Dependent Claim
31 words
The dust cover of claim 2, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethylene copolymer having a vinylidene fluoride content of at least 50 mole %.
Claim 11
Dependent Claim
38 words
The dust cover of claim 1, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TEF content of 35 to 65 mole % and an HFP: VdF molar ratio of from 1:1 to 1:2.3.
Claim 12
Dependent Claim
31 words
The dust cover of claim 2, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethylene copolymer having a vinylidene fluoride contect of at least 50 mole %.
Claim 13
Dependent Claim
31 words
The dust cover of claim 3, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethylene copolymer having a vinylidene fluoride content of at least 50 mole %.
Claim 14
Dependent Claim
31 words
The dust cover of claim 4, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethlene copolymer having a vinylidene fluoride content of at least 50 mole %.
Claim 15
Dependent Claim
31 words
The dust cover of claim 5, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethylene copolymer having a vinylidene fluoride content of at least 50 mole %.
Claim 16
Dependent Claim
31 words
The dust cover of claim 6, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethylene copolymer having a vinylidene fluoride content of at least 50 mole %.
Claim 17
Dependent Claim
31 words
The dust cover of claim 7, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethylene copolymer having a vinylidene fluoride content of at least 50 mole %.
Claim 18
Dependent Claim
31 words
The dust cover of claim 8, wherein said fluoropolymer is a homopolymer of vinylidene fluoride or a vinylidene fluoride-tetrafluoroethylene copolymer having a vinylidene fluoride content of at least 50 mole %.
Claim 19
Dependent Claim
38 words
The dust cover of claim 2, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TEF content of 35 to 65 mole % and an HFP: VdF molar ratio of from 1:1 to 1:2.3.
Claim 20
Dependent Claim
38 words
The dust cover of claim 3, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TEF content of 35 to 65 mole % and an HFP: VdF molar ratio of from 1:1 to 1:2.3.
Claim 21
Dependent Claim
37 words
The dust cover of claim 4, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TEF content of 35 to 65 mole % and an HFP:VdF molar ratio of from 1:1 to 1:2.3.
Claim 22
Dependent Claim
37 words
The dust cover of claim 5, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TEF content of 35 to 65 mole % and an HFP:VdF molar ratio of from 1:1 to 1:2.3.
Claim 23
Dependent Claim
37 words
The dust cover of claim 6, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TEF content of 35 to 65 mole % and an HFP:VdF molar ratio of from 1:1 to 1:2.3.
Claim 24
Dependent Claim
37 words
The dust cover of claim 7, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TEF content of 35 to 65 mole % and an HFP:VdF molar ratio of from 1:1 to 1:2.3.
Claim 25
Dependent Claim
37 words
The dust cover of claim 7, wherein said fluoropolymer is a tetrafluoroethylene (TFE)-hexafluoropropylene (HFP)-vinylidene fluoride (VdF) terpolymer having a TFE content of 35 to 65 mole % and an HFP:VdF molar ratio of from 1:1 to 1:2.3.
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) | 1990-04-13 | 1990-10-13 | 1991-04-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-04-13 | 1994-10-13 | 1995-04-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-04-13 | 1998-10-13 | 1999-04-14 | $7700.00 | Window Closed / Lapsed |