US3607255A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Surfacing nonimage areas of lithographic master with hydrophilic desensitizing composition
Assignee: Fort James Corp
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Filing: 1968-01-22
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Granted: 1971-09-21
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Expires: 1988-01-22
Abstract
Abstract A convertible plate adapted for conversion into a lithographic offset master comprising a paper web, and a dielectric film extending over the paper web with finely divided silica distributed therein. In preparing an offset master, an imagedefining electrostatic charge is laid down on the film and developed with toner to form an image, and nonimage areas are rendered hydrophilic to prepare the plate for lithographic printing by coating the nonimage areas with a desensitizing composition comprising an aqueous solution of polyvinyl alcohol which mechanically fixed to the dielectric film through adhesion promoted by the divided silica.
Inventors
- 👤 Sangho E Back
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:33
CPC Classifications
G; G03; G03G; G03G13/00; G03G13/26; G03G13/28
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
18 words
The offset master of claim 1, where the dielectric film further comprises up to 50 parts zinc oxide.
Claim 2
Dependent Claim
22 words
The offset master of claim 1, wherein the silica is silica aerogel, with a surface area exceeding 50 square meters per gram.
Claim 3
Independent Claim
174 words
A method of preparing a lithographic offset master from a convertible plate comprising a sheet base and a dielectric film extending over the sheet base where the sheet base is relatively conductive in comparison with said film, said dielectric film having a resistance above about 1010 ohms per square and being adapted to receive an image-defining electrostatic image charge, said dielectric film further including finely divided silica distributed in the film, comprising 100 parts resin binder and from 10 to 50 parts finely divided silica, the method comprising depositing an image-defining electrostatic charge on the dielectric film to produce image charge areas thereon distributed with nonimage areas, developing the image charge areas with a developer material whiCh covers and fixes to the dielectric film in said image charge areas while leaving nonimage areas free of developer material, and coating the dielectric film in such nonimage areas with a film of polyvinyl alcohol, such film of polyvinyl alcohol serving to render such nonimage areas hydrophilic and capable of being wetted with an aqueous fountain solution.
Claim 4
Dependent Claim
36 words
The method of claim 4, wherein the film of polyvinyl alcohol is prepared by distributing over the dielectric film in nonimage areas a desensitizing solution comprising water and up to 1.5 percent by weight polyvinyl alcohol.
Claim 5
Dependent Claim
46 words
The method of claim 4, wherein the film of polyvinyl alcohol is prepared by distributing over the nonimage areas in the dielectric film a desensitizing composition comprising water, up to about 1.5 percent by weight polyvinyl alcohol, and up to about 15 percent by weight glycerin.
Claim 6
Dependent Claim
125 words
An offset master for lithographic printing comprising a plate including a sheet base and a dielectric film extending over said sheet base, said sheet base in comparison with said film being relatively conductive, said dielectric film having a resistance greater than about 1010 ohms per square and comprising 100 parts resin binder and from 10 to 50 parts finely divided silica distributed in the resin binder, a fixed toner deposit on the surface of the dielectric film extending over image areas in the master, and a film of polyvinyl alcohol extending over nonimage areas of said dielectric film, said polyvinyl alcohol adhering to the silica distributed in the resin binder of the dielectric film and rendering the nonimage areas wettable with an aqueous fountain solution.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-20 | 1975-03-22 | 1975-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-20 | 1979-03-22 | 1979-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-20 | 1983-03-22 | 1983-09-21 | $7700.00 | Window Closed / Lapsed |