US3894871A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Photographic products and processes for forming silver and additive color transparencies
Assignee: Polaroid Corp
•
Filing: 1973-07-27
•
Granted: 1975-07-15
•
Expires: 1993-07-27
Abstract
Abstract Diffusion transfer photographic products and processes are disclosed for forming transparencies wherein a positive silver transfer image is maintained together with a negative silver image in a separate layer, said images being viewed together as a positive transparency. The invention is particularly applicable to forming additive color transfer images. The sum of the projected areas of the silver halide grains in the silver halide emulsion layer does not exceed about 50% of the surface area of the silver halide emulsion layer. Development of the exposed silver halide grains results in little, if any, increase in the projected area whereby the maximum negative silver density is kept low. Predominantly homogeneous grain size silver halide emulsions, preferably of particular mean diameter and grain size distribution, are utilized to obtain good sensitometry in addition to desired minimum and maximum image densities.
Inventors
- 👤 Edwin H Land
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:46
CPC Classifications
G; G03; G03C; G03C8/00; G03C8/02; G03C8/04; G03C8/06; G03C8/30
Claims Analysis
Total Claims: 74
Claim 1
Independent Claim
140 words
A PHOTOSENSITIVE ELEMENT FOR FORMING A COLOR TRANSPARENCY BY DIFFUSION TRANSFER PROCESSING TO PROVIDE A DEVELOPED NEGATIVE SILVER IMAGE AND A POSITVE SILVER TRANSFER IMAGE, AND NEGATIVE SILVER IMAGE AND SAID POSITIVE SILVER TRANSFER IMAGE BEING VIEWABLE AS A POSITIVE IMAGE WITHOUT SEPARATION, SAID PHOTOSENSITIVE ELEMENT COMPRISING (A) A TRANSPARENT SUPPORT CARRYING A LIGHT-TRANSMITTING SCREEN COMPOSED OF MNUTE OPTICAL ELEMENTS, (B) A LAYER CONTAINING A PHOTOSENSITIVE SILVER HALIDE EMULSION AND (C) A SILVER RECEPTIVE LAYER INCLUDING A SILVER PRECIPITATING AGENT, SAID SILVER RECEPTIVE LAYER BEING POSITIONED BETWEEN SAID LIGHT-TRANSMITING SCREEN AND SAID SILVER HALIDE EMULSION LAYER: THE SILVER HALIDE GRAINS OF SAID SILVER HALIDE EMULSION BEING PREDOMINANTLY HOMOGENEOUS IN CRYSTAL DIAMETER AND HABIT, THE SUM OF THE PROJECTED AREAS OF SAID SILVER HALIDE GRANS BEING NOT MORE THAN ABOUT 50% OF THE SURFACE AREA OF SAID SILVER HALIDE EMULSION LAYER.
Claim 2
Dependent Claim
140 words
A PHOTOSENSITIVE ELEMENT FOR FORMING A COLOR TRANSPARENCY BY DIFFUSION TRANSFER PROCESSING TO PROVIDE A DEVELOPED NEGATIVE SILVER IMAGE AND A POSITVE SILVER TRANSFER IMAGE, AND NEGATIVE SILVER IMAGE AND SAID POSITIVE SILVER TRANSFER IMAGE BEING VIEWABLE AS A POSITIVE IMAGE WITHOUT SEPARATION, SAID PHOTOSENSITIVE ELEMENT COMPRISING (A) A TRANSPARENT SUPPORT CARRYING A LIGHT-TRANSMITTING SCREEN COMPOSED OF MNUTE OPTICAL ELEMENTS, (B) A LAYER CONTAINING A PHOTOSENSITIVE SILVER HALIDE EMULSION AND (C) A SILVER RECEPTIVE LAYER INCLUDING A SILVER PRECIPITATING AGENT, SAID SILVER RECEPTIVE LAYER BEING POSITIONED BETWEEN SAID LIGHT-TRANSMITING SCREEN AND SAID SILVER HALIDE EMULSION LAYER: THE SILVER HALIDE GRAINS OF SAID SILVER HALIDE EMULSION BEING PREDOMINANTLY HOMOGENEOUS IN CRYSTAL DIAMETER AND HABIT, THE SUM OF THE PROJECTED AREAS OF SAID SILVER HALIDE GRANS BEING NOT MORE THAN ABOUT 50% OF THE SURFACE AREA OF SAID SILVER HALIDE EMULSION LAYER.
Claim 3
Dependent Claim
22 words
A photosensitive element as defined in claim 1 wherein said silver halide emulsion layer is substantially free of overlapping silver halide grains.
Claim 4
Dependent Claim
42 words
A photosensitive element as defined in claim 1 wherein said light-transmitting screen is an additive color screen composed of sets of interspersed minute color filter elements, the color filter elements of each set transmitting the same predetermined wavelength range of visible light.
Claim 5
Dependent Claim
22 words
A photosensitive element as defined in claim 3 wherein said additive color screen is composed of red, green and blue filter elements.
Claim 6
Dependent Claim
49 words
A photosensitive element as defined in claim 3 wherein said silver halide grains have a mean diameter of about one-fifth to one-tenth the width of said color filter elements, at least 90% of said silver halide grains having a diameter within + or -30% of the mean grain diameter.
Claim 7
Dependent Claim
26 words
A photosensitive element as defined in claim 1 wherein said silver halide grains have a mean diameter within the range of about 0.70 to 1.5 micron.
Claim 8
Dependent Claim
21 words
A photosensitive element as defined in claim 1 wherein said silver halide grains have a mean diameter of about 0.9 micron.
Claim 9
Dependent Claim
22 words
A photosensitive element as defined in claim 1 wherein said silver halide emulsion layer contains about 90 to 125 mg./ft.2 of silver.
Claim 10
Dependent Claim
15 words
A photosensitive element as defined in claim 1 wherein said minute optical elements are lenticules.
Claim 11
Dependent Claim
31 words
A photosensitive element as defined in claim 4 wherein said red, green and blue filter elements are in the form of lines, and said additive color screen contains approximately 550 lines/color/inch.
Claim 12
Dependent Claim
31 words
A photosensitive element as defined in claim 4 wherein said red, green and blue filter elements are in the form of lines, and said additive color screen contains approximately 750 lines/color/inch.
Claim 13
Dependent Claim
31 words
A photosensitive element as defined in claim 4 wherein said red, green and blue filter elements are in the form of lines, and said additive color screen contains approximately 1000 lines/color/inch.
Claim 14
Dependent Claim
41 words
A photosensitive element as defined in claim 1 wherein said silver halide emulsion is a substituted-halide silver halide emulsion prepared by replacing part of the chloride anions of a silver chloride emulsion with bromide anions or with bromide and iodide anions.
Claim 15
Dependent Claim
19 words
A photosensitive element as defined in claim 13 wherein said substituted-halide silver halide emulsion is a silver iodochlorobromide emulsion.
Claim 16
Dependent Claim
19 words
A photosensitive element as defined in claim 13 wherein said substituted-halide silver halide emulsion is a silver chlorobromide emulsion.
Claim 17
Dependent Claim
18 words
A photosensitive element as defined in claim 1 wherein said silver halide emulsion is a silver iodobromide emulsion.
Claim 18
Dependent Claim
23 words
A photosensitive element as defined in claim 1 wherein said silver halide grains have a mean projected area of about 0.6 square micron.
Claim 19
Dependent Claim
30 words
A photosensitive element as defined in claim 17 wherein at least 90% of said silver halide grains have a projected area between 0.5 and 1.5 times said mean projected area.
Claim 20
Dependent Claim
114 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive sIlver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 21
Dependent Claim
114 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive sIlver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 22
Dependent Claim
25 words
A photosensitive element as defined in claim 19 wherein said silver receptive layer is positioned between said transparent support and said silver halide emulsion layer.
Claim 23
Dependent Claim
22 words
A photosensitive element as defined in claim 19 wherein said silver halide emulsion layer is substantially free of overlapping silver halide grains.
Claim 24
Dependent Claim
29 words
A photosensitive element as defined in claim 19 wherein at least 90% of said silver halide grains have a diameter within + or - 30% of the mean diameter.
Claim 25
Dependent Claim
43 words
A photosensitive element as defined in claim 19 wherein said silver halide grains have a mean diameter of about 0.70 to 1.5 micron, at least 90% of said silver halide grains having a diameter within + or - 30% of said mean diameter.
Claim 26
Dependent Claim
21 words
A photosensitive element as defined in claim 19 wherein said silver halide grains have a mean diameter of about 0.9 micron.
Claim 27
Dependent Claim
22 words
A photosensitive element as defined in claim 19 wherein said silver halide emulsion layer contains about 90 to 125 mg./ft.2 of silver.
Claim 28
Dependent Claim
41 words
A photosensitive element as defined in claim 19 wherein said silver halide emulsion is a substitutedhalide silver halide emulsion prepared by replacing part of the chloride anions of a silver chloride emulsion with bromide anions or with bromide and iodide anions.
Claim 29
Dependent Claim
19 words
A photosensitive element as defined in claim 26 wherein said substituted-halide silver halide emulsion is a silver iodochlorobromide emulsion.
Claim 30
Dependent Claim
19 words
A photosensitive element as defined in claim 26 wherein said substituted-halide silver halide emulsion is a silver chlorobromide emulsion.
Claim 31
Dependent Claim
18 words
A photosensitive element as defined in claim 19 wherein said silver halide emulsion is a silver iodobromide emulsion.
Claim 32
Dependent Claim
23 words
A photosensitive element as defined in claim 19 wherein said silver halide gains have a mean projected area of about 0.6 square micron.
Claim 33
Dependent Claim
30 words
A photosensitive element as defined in claim 30 wherein at least 90% of said silver halide grains have a projected area between 0.5 and 1.5 times said mean projected area.
Claim 34
Dependent Claim
16 words
A photosensitive element as defined in claim 19 wherein said silver halide grains are generally spherical.
Claim 35
Dependent Claim
16 words
A photosensitive element as defined in claim 19 wherein said silver halide grains are generally cubic.
Claim 36
Dependent Claim
122 words
A photosensitive element for forming a color transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive silver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying a light-transmitting screen composed of minute optical elements, (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent, the silver halide gains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 37
Dependent Claim
122 words
A photosensitive element for forming a color transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive silver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying a light-transmitting screen composed of minute optical elements, (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent, the silver halide gains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 38
Dependent Claim
42 words
A photosensitive element as defined in claim 34 wherein said light-transmitting screen is an additive color screen composed of sets of interspersed minute color filter elements, the color filter elements of each set transmitting the same predetermined wavelength range of visible light.
Claim 39
Dependent Claim
22 words
A photosensitive element as Defined in claim 35 wherein said additive color screen is composed of red, green and blue filter elements.
Claim 40
Dependent Claim
48 words
A photosensitive element as defined in claim 35 wherein said silver grains have a mean diameter of about one-fifth to one-tenth the width of said color filter elements, at least 90% of said silver halide grains having a diameter within + or - 30% of said mean diameter.
Claim 41
Dependent Claim
26 words
A photosensitive element as defined in claim 34 wherein said silver halide grains have a mean diameter within the range of about 0.70 to 1.5 micron.
Claim 42
Dependent Claim
127 words
A photosensitive element for forming a transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive silver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support, (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent, said silver receptive layer being positioned between said support and said silver halide emulsion layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 43
Dependent Claim
127 words
A photosensitive element for forming a transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive silver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support, (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent, said silver receptive layer being positioned between said support and said silver halide emulsion layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 44
Dependent Claim
22 words
A photosensitive element as defined in claim 39 wherein said silver halide emulsion layer is substantially free of overlapping silver halide grains.
Claim 45
Dependent Claim
136 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive silver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent, said silver receptive layer being about 0.1 to 0.3 micron thick and positioned between said silver halide emulsion layer and said support; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 46
Dependent Claim
136 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive silver transfer image, said negative silver image and said positive silver transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer including a silver precipitating agent, said silver receptive layer being about 0.1 to 0.3 micron thick and positioned between said silver halide emulsion layer and said support; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 47
Dependent Claim
31 words
A photosensitive element as defined in claim 41 wherein said silver halide emulsion layer is substantially free of overlapping silver halide grains and contains about 90 to 125 mg./ft.2 of silver.
Claim 48
Dependent Claim
31 words
A photosensitive element as defined in claim 42 including an additive color screen of alternating red, green and blue lines, said color screen containing approximately 1000 lines per color per inch.
Claim 49
Dependent Claim
48 words
A photosensitive element as defined in claim 43 wherein the mean diameter of the silver halide grains is within the range of about 0.70 to 1.0 micron, and at least 90% of the silver halide grains have a diameter within + or - 30% of said mean diameter.
Claim 50
Dependent Claim
27 words
A photosensitive element as defined in claim 42 wherein the dispersion number of the grain size-frequency distribution curve for said silver halide emulsion is 0.40 or less.
Claim 51
Dependent Claim
38 words
A photosensitive element as defined in claim 45 wherein said photosensitive element includes an additive color screen of red, green and blue filter lines, said color screen containing about 550 to about 750 lines per color per inch.
Claim 52
Dependent Claim
26 words
A photosensitive element as defined in claim 43 wherein the mean diameter of said silver halide grains is within the range of 1.2 to 1.4 microns.
Claim 53
Dependent Claim
114 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive transfer image, said negative silver image and said posItive transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying, (b) a layer containing a photosensitive silver halide emulsion and (c) an image-receiving layer for forming a positive transfer image; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter and habit, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 54
Dependent Claim
114 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive transfer image, said negative silver image and said posItive transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carrying, (b) a layer containing a photosensitive silver halide emulsion and (c) an image-receiving layer for forming a positive transfer image; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter and habit, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 55
Dependent Claim
29 words
A photosensitive element as defined in claim 1 wherein said silver halide emulsion layer contains about 100 mg./ft.2 of silver and is substantially free of overlapping silver halide grains.
Claim 56
Dependent Claim
20 words
A photosensitive element as defined in claim 48 including a permeable polymer layer coated over said silver halide emulsion layer.
Claim 57
Dependent Claim
17 words
A photosensitive element as defined in claim 50 wherein said permeable polymer layer is a gelatin layer.
Claim 58
Dependent Claim
21 words
A photosensitive element as defined in claim 51 wherein said permeable polymer layer contains about 80 to 250 mg./ft.2 of gelatin.
Claim 59
Dependent Claim
107 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive transfer image, said negative silver image and said positive transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carring (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 60
Dependent Claim
107 words
A photosensitive element for forming a positive transparency by diffusion transfer processing to provide a developed negative silver image and a positive transfer image, said negative silver image and said positive transfer image being viewable as a positive image without separation, said photosensitive element comprising (a) a transparent support carring (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer.
Claim 61
Dependent Claim
26 words
A photosensitive element as defined in claim 53 wherein said silver halide grains have a mean diameter within the range of about 0.7 to 1.5 microns.
Claim 62
Dependent Claim
41 words
A photosensitive element as defined in claim 54 wherein said silver halide grains have a mean diameter of about 0.9 micron, at least 90% of said silver halide grains having a diameter within + or - 30% of said mean diameter.
Claim 63
Dependent Claim
20 words
A photosensitive element as defined in claim 55 wherein said silver halide emulsion layer contains about 100 mg./ft.2 of silver.
Claim 64
Dependent Claim
23 words
A photosensitive element as defined in claim 53 wherein said silver halide grains have a mean projected area of about 0.6 square micron.
Claim 65
Dependent Claim
30 words
A photosensitive element s defined in claim 57 wherein at least 90% of said silver halide grains have a projected area between 0.5 and 1.5 times said means projected area.
Claim 66
Dependent Claim
165 words
A diffusion transfer process comprising the steps of exposing a photosensitive element comprising (a) a transparent support carrying (b) a layer containing a photosensitive silver halide emulsion and (c) an image-receiving layer for forming a positive transfer image, said image-receiving layer being positioned between said support and said silver halide emulsion layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter and habit, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer, developing the exposed silver halide emulsion to a negative silver image having a maximum density of no more than about 0.3, said development being effected in the presence of a silver halide solvent to form a positive silver transfer image in said image-receiving layer, and maintaining the layers containing said negative and said positive images together as a permanent laminate, said images being viewed together as a positive image.
Claim 67
Dependent Claim
165 words
A diffusion transfer process comprising the steps of exposing a photosensitive element comprising (a) a transparent support carrying (b) a layer containing a photosensitive silver halide emulsion and (c) an image-receiving layer for forming a positive transfer image, said image-receiving layer being positioned between said support and said silver halide emulsion layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter and habit, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer, developing the exposed silver halide emulsion to a negative silver image having a maximum density of no more than about 0.3, said development being effected in the presence of a silver halide solvent to form a positive silver transfer image in said image-receiving layer, and maintaining the layers containing said negative and said positive images together as a permanent laminate, said images being viewed together as a positive image.
Claim 68
Dependent Claim
140 words
A diffusion transfer process comprising the steps of exposing a photosensitive element comprising (a) transparent support caRrying (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer, developing said exposed silver halide emulsion in the presence of a quaternary ammonium compound to form a negative silver image having a maximum density of no more than about 0.3, forming a positive silver transfer image in said silver receptive layer, and maintaining the layers containing said negative and positive silver images together as a permanent laminate, said images being viewed together as a positive transparency.
Claim 69
Dependent Claim
140 words
A diffusion transfer process comprising the steps of exposing a photosensitive element comprising (a) transparent support caRrying (b) a layer containing a photosensitive silver halide emulsion and (c) a silver receptive layer; the silver halide grains of said silver halide emulsion being predominantly homogeneous in crystal diameter, the sum of the projected areas of said silver halide grains being not more than about 50% of the surface area of said silver halide emulsion layer, developing said exposed silver halide emulsion in the presence of a quaternary ammonium compound to form a negative silver image having a maximum density of no more than about 0.3, forming a positive silver transfer image in said silver receptive layer, and maintaining the layers containing said negative and positive silver images together as a permanent laminate, said images being viewed together as a positive transparency.
Claim 70
Dependent Claim
23 words
A diffusion transfer process as defined in claim 60 wherein said silver halide emulsion layer contains about 90 to 125 mg./ft.2 of silver.
Claim 71
Dependent Claim
49 words
A diffusion transfer process as defined in claim 60 wherein the silver halide grains of said silver halide emulsion have a mean diameter of about 0.70 to 1.5 microns, at least 90% of said silver halide grains having a diameter within + or - 30% of said mean diameter.
Claim 72
Dependent Claim
29 words
A diffusion transfer process as defined in claim 62 wherein said mean diameter is about 0.90 micron and said silver halide emulsion layer contains about 100 mg./ft.2 of silver.
Claim 73
Dependent Claim
19 words
A diffusion transfer process as defined in claim 62 wherein said quaternary ammonium compound is N-benzyl- Alpha -picolinium bromide.
Claim 74
Dependent Claim
17 words
A diffusion transfer process as defined in claim 64 wherein development is effected using tetramethyl reductic acid.
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) | 1978-07-14 | 1979-01-13 | 1979-07-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-14 | 1983-01-13 | 1983-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-14 | 1987-01-13 | 1987-07-15 | $7700.00 | Window Closed / Lapsed |