US4059450A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Direct positive silver halide elements
Assignee: Agfa Gevaert NV
•
Filing: 1973-11-20
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Granted: 1977-11-22
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Expires: 1993-11-20
Abstract
Abstract Direct positive silver halide emulsions are provided which contain fogged silver halide grains with a layered grain structure wherein the external shell of the silver halide grains comprise up to 20 mole % of silver iodide based on the silver halide of the shell. The emulsions show improved sensitivity and produce images of improved maximum density.
Inventors
- 👤 Willy Joseph Vanassche
- 👤 Herman Alberik Pattyn
- 👤 Erik Moisar
- 👤 Sieghart Klotzer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 23:16
CPC Classifications
G; G03; G03C; G03C1/00; G03C1/005; G03C1/485; G03C1/48515; Y; Y10; Y10S; Y10S430/00; Y10S430/141
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
179 words
Photographic material containing at least one direct-positive silver halide emulsion layer containing surface fogged silver halide grains selected from the group consisting of: a. silver halide grains that are free of internal centers promoting the deposition of photolytic silver and have adsorbed to the surface of the grains an electron-accepting compound having an anodic polarographic half-wave potential and a cathodic polarographic half-wave potential which when added together give a positive sum, and b. silver halide grains having a central silver halide core containing centers promoting the deposition of photolytic silver and a silver halide shell coated thereover, wherein the silver halide grains have been precipitated so as to form in the silver halide grains (a) or in the silver halide shell of grains (b) an external shell of silver halide containing silver iodide in an amount up to 20 mole percent based on the silver halide of the external shell sufficient to provide an emulsion having improved sensitivity and which produces images of improved maximum density, the remainder of the silver halide grains being substantially free of silver iodide.
Claim 2
Dependent Claim
179 words
Photographic material containing at least one direct-positive silver halide emulsion layer containing surface fogged silver halide grains selected from the group consisting of: a. silver halide grains that are free of internal centers promoting the deposition of photolytic silver and have adsorbed to the surface of the grains an electron-accepting compound having an anodic polarographic half-wave potential and a cathodic polarographic half-wave potential which when added together give a positive sum, and b. silver halide grains having a central silver halide core containing centers promoting the deposition of photolytic silver and a silver halide shell coated thereover, wherein the silver halide grains have been precipitated so as to form in the silver halide grains (a) or in the silver halide shell of grains (b) an external shell of silver halide containing silver iodide in an amount up to 20 mole percent based on the silver halide of the external shell sufficient to provide an emulsion having improved sensitivity and which produces images of improved maximum density, the remainder of the silver halide grains being substantially free of silver iodide.
Claim 3
Dependent Claim
130 words
Process for the preparation of a direct-positive silver halide emulsion comprising fogged silver halide grains having adsorbed to their surface an electron-accepting compound which comprises the steps of: 1. precipitating silver halide cores that are substantially free of silver iodide and free of centers promoting the deposition of photolytic silver, 2. precipitating on the silver halide cores a shell of silver halide containing silver iodide in an amount up to 20 mole percent based on the silver halide of the shell sufficient to provide an emulsion having improved sensitivity and which produces images of improved maximum density, 3. chemically fogging the silver halide grains, and 4. adding an electron-accepting compound having an anodic polarographic half-wave potential and a cathodic polarographic half-wave potential which when added together give a positive sum.
Claim 4
Dependent Claim
130 words
Process for the preparation of a direct-positive silver halide emulsion comprising fogged silver halide grains having adsorbed to their surface an electron-accepting compound which comprises the steps of: 1. precipitating silver halide cores that are substantially free of silver iodide and free of centers promoting the deposition of photolytic silver, 2. precipitating on the silver halide cores a shell of silver halide containing silver iodide in an amount up to 20 mole percent based on the silver halide of the shell sufficient to provide an emulsion having improved sensitivity and which produces images of improved maximum density, 3. chemically fogging the silver halide grains, and 4. adding an electron-accepting compound having an anodic polarographic half-wave potential and a cathodic polarographic half-wave potential which when added together give a positive sum.
Claim 5
Dependent Claim
148 words
Process for the preparation of a direct-positive silver halide emulsion comprising fogged silver halide grains having in their interior centers promoting the deposition of photolytic silver, which comprises the steps of: 1. precipitating silver halide cores that are substantially free of silver iodide, 2. during or after formation of the silver halide cores chemically or physically treating the cores so as to form centers promoting the deposition of photolytic silver, 3. precipitating on the silver halide cores a shell of silver halide that is substantially free of silver iodide, 4. precipitating on the shell of silver halide an external shell of silver halide containing silver iodide in an amount up to 20 mole percent based on the silver halide of the external shell sufficient to provide an emulsion having improved sensitivity and which produces images of improved maximum density, and 5. chemically fogging the silver halide grains formed.
Claim 6
Dependent Claim
148 words
Process for the preparation of a direct-positive silver halide emulsion comprising fogged silver halide grains having in their interior centers promoting the deposition of photolytic silver, which comprises the steps of: 1. precipitating silver halide cores that are substantially free of silver iodide, 2. during or after formation of the silver halide cores chemically or physically treating the cores so as to form centers promoting the deposition of photolytic silver, 3. precipitating on the silver halide cores a shell of silver halide that is substantially free of silver iodide, 4. precipitating on the shell of silver halide an external shell of silver halide containing silver iodide in an amount up to 20 mole percent based on the silver halide of the external shell sufficient to provide an emulsion having improved sensitivity and which produces images of improved maximum density, and 5. chemically fogging the silver halide grains formed.
Claim 7
Dependent Claim
28 words
Process according to claim 3, wherein the volume of the external shell containing silver iodide is up to 75 volume percent of the total volume of the grain.
Claim 8
Dependent Claim
28 words
Process according to claim 3, wherein the volume of the external shell containing silver iodide is 5 to 50 volume percent of the total volume of the grain.
Claim 9
Dependent Claim
28 words
Process according to claim 3, wherein the volume of the external shell containing silver iodide is 5 to 15 volume percent of the total volume of the grain.
Claim 10
Dependent Claim
31 words
Process according to claim 3, wherein the external shell containing silver iodide contains from 10 to 20 mole percent of the silver iodide, based on the silver halide of the shell.
Claim 11
Dependent Claim
27 words
Photographic material according to claim 1, wherein the volume of the external shell containing silver iodide is up to 75% of the volume of the total grain.
Claim 12
Dependent Claim
26 words
Photographic material according to claim 1, wherein the volume of the external shell containing silver iodide is 5 to 50vol. % of the total grain volume.
Claim 13
Dependent Claim
27 words
Photographic material according to claim 1, wherein the volume of the external shell containing silver iodide is 5 to 15 mole % of the total grain volume.
Claim 14
Dependent Claim
30 words
Photographic material according to claim 1, wherein the silver iodide content of the external shell is 10 to 20 mole % based on the total silver halide of the shell.
Claim 15
Dependent Claim
17 words
Photographic material according to claim 1, wherein said silver halide grains have been fogged by reduction sensitization.
Claim 16
Dependent Claim
26 words
Photographic material according to claim 12, wherein the said silver halide grains have been fogged by treatment of the silver halide grains with a reducing agent.
Claim 17
Dependent Claim
15 words
Photographic material according to claim 13, wherein said reducing agent is thiourea dioxide or tin(II)chloride.
Claim 18
Dependent Claim
26 words
Photographic material according to claim 8, wherein the silver halide grains have been fogged by low pAg and/or high pH silver halide precipitating or digestion conditions.
Claim 19
Dependent Claim
23 words
Photographic material according to claim 12, wherein fogging also occurs in the presence of a compound of a metal more electropositive than silver.
Claim 20
Dependent Claim
14 words
Photographic material according to claim 16, wherein said metal compound is a gold compound.
Claim 21
Dependent Claim
13 words
Photographic material according to claim 1, wherein the emulsion has been spectrally sensitized.
Claim 22
Dependent Claim
19 words
Photographic material according to claim 1, wherein the silver halide emulsion layer is homodisperse and consists of regular crystals.
Claim 23
Dependent Claim
27 words
Process according to claim 2, wherein the volume of the shell containing silver iodide is up to 75 vol. % of the total volume of the grain.
Claim 24
Dependent Claim
27 words
Process according to claim 2, wherein the volume of the shell containing silver iodide is 5 to 50 vol. % of the total volume of the grain.
Claim 25
Dependent Claim
27 words
Process according to claim 2, wherein the volume of the shell containing silver iodide is 5 to 15 vol. % of the total volume of the grain.
Claim 26
Dependent Claim
28 words
Process according to claim 2, wherein the shell containing silver iodide contains 10 to 20 mole % of silver iodide, based on the silver halide of the shell.
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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) | 1980-11-21 | 1981-05-23 | 1981-11-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-11-21 | 1985-05-23 | 1985-11-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-11-21 | 1989-05-23 | 1989-11-22 | $7700.00 | Window Closed / Lapsed |