US3846135A - Light-sensitive photographic material with increased sensitivity to light - Google Patents

Light-sensitive photographic material with increased sensitivity to light Download PDF

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US3846135A
US3846135A US00130617A US13061771A US3846135A US 3846135 A US3846135 A US 3846135A US 00130617 A US00130617 A US 00130617A US 13061771 A US13061771 A US 13061771A US 3846135 A US3846135 A US 3846135A
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emulsion
sensitivity
silver
layer
silver halide
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US00130617A
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E Hellmig
W Saleck
F Moll
A Randolph
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Agfa Gevaert AG
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
    • G03C1/46—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein having more than one photosensitive layer

Definitions

  • the invention relates to a photographic black-white material with increased sensitivity.
  • the more sensitive silver halide emulsion layer which is arranged on the top, contains per unit of surface at most 60% of silver halide based on the silver halide content of the less sensitive lower silver halide emulsion layer.
  • the silver halide content of the more sensitive layer should be that suflicient to provide a maximum density of not more than 0.90 preferably between 0.50 and 0.70, while that of the lower provides a density of at least 1.5 with a straight characteristic.
  • the difference of sensitivity between the more sensitive silver halide emulsion layer and the less sensitive silver halide emulsion layer is preferably 0.1 to 0.4 log 1.)? units.
  • the sensitivity curves are those of a density-log exposure graph for photographic emulsions.
  • the coordinates on which such curves are customarily plotted are the density which is indicated along the ordinate.
  • the threshold is the log I.t value on the abscissa at which the plotted photosensitivity emulsion becomes responsive to light.
  • the shoulder is the log I.t unit value where the emulsion approaches saturation.
  • the more sensitive silver halide emulsion layer is thinner than the less sensitive layer underneath it.
  • the thickness of the more sensitive silver halide emulsion layer lies between 2 and 7,u, while the less sensitive layer has a thickness of between 5 and 15,u.
  • the sensitivity of the double layered element is not equal to the sensitivity of the more sensitive top layer but considerably higher.
  • the double layer element of the invention is used a synergistic effect appears and a very high light-sensitive photographic material results.
  • silver halide emulsions can be used for production of the double layered element of the invention; it is preferred, however, to use silver bromide gelatin emulsions that have a minor silver iodide content of up to about 10 mols percent. If required, however, silver chloride emulsions may also be used, if desired in admixture with the above mentioned silver halides.
  • the light-sensitive emulsion to be used according to the invention may contain the usual additives such as chemical or optical sensitizers, stabilizers, wetting agents, hardeners, etc.
  • Photographic materials prepared according to the invention can be used in all fields of photography. They are of special importance for reproduction work where there is a demand for panchromatic half-tone films of maximum sensitivity which are commonly used for the production of color separation records.
  • EXAMPLE 1 A panchromatically sensitized silver halide gelatin emulsion containing per kg. g. of gelatin, 0.55 mol silver halide (silver bromide plus 4% silver iodide) which has been after-ripened as described by Glafkides Photographic Chemistry Vol. 1, 2nd Edition, page 319, in the presence of 15 mg. of thiosulfate and 1.6 mg. of gold in the form of ammonium aurothiocyanate per liter and which further contains 50 ml. of 1% methanolic solution of -methyl-7-oxy-1,3,4-triazaindolizine, ml. of a 10% aqueous solution of formaldehyde and ml. of a 7.5% aqueous solution of saponine is applied onto a support of polyethylene glycol terephthalate.
  • silver halide silver bromide plus 4% silver iodide
  • a second layer of a panchromatically sensitized silver bromide emulsion containing 2 mol percent of silver iodide Onto that layer is applied a second layer of a panchromatically sensitized silver bromide emulsion containing 2 mol percent of silver iodide.
  • the emulsion is an ammonia emulsion containing the additives referred to above and is further chemically sensitized by addition of a pentaerythritol phosphoric acid ester as described in British Pat. No. 1,045,184.
  • second silver halide emulsion layer is applied an antistatic gelatin layer (0.5,u in thickness) which protects the silver halide layers against mechanical damage
  • the thickness of the lower layer is 7.6 its silver content in the form of silver halide is 4.50 g./m.
  • the upper layer has a thickness of 4.7,u and a sliver content in the form of silver halide 2.43 g./m.
  • the finished material is exposed behind a test wedge in a sensitometer customarily employed in the art.
  • the sensitivity of the more sensitive top layer, measured at a density of 0.10 over fogging is only 0.25 log 1.1 units higher than that of the less sensitive layer.
  • the double layer element has a sensitivity of 0.46 log I.t units above that of the less sensitive layer.
  • An additional increase in sensitivity of 0.21 has thus been obtained by the greater than additive effect of the inventive double layer element. This increase amount to the factor 1.62 or 62%.
  • the sensitivity increase of 0.46 log units amounts to 188% (factor 2.88) without any coarsening of the silver grain.
  • the emulsion B has sensitivity of about 0.1 to 0.4 log 1.: units less than the sensitivity of the upper emulsion.
  • the upper emulsion A has a maximum density of not more than 0.9 and the emulsion B has a maximum density of at least 1.5.
  • the sensitivity of the combination of the emulsions is substantially higher in sensitivity than the emulsions A and B and the difference between the sensitivity of the combination and emulsion B is greater than the difference between the sensitivities of emulsions A and B.
  • the sensitivity of the combined emulsions is substantially different from the sensitivity of the upper emulsion, which is the one with the higher sensitivity.
  • a light sensitive photographic material of improved speed and granularity essentially consisting of a support and in superposed relationship a first silver halide emulsion of silver bromide or silver bromo-iodide closer to the support and a second silver halide emulsion of silver bromide or silver bromo-iodide superposed over the first emulsion wherein the improvement comprises the second emulsion is in a layer having a thickness of at least 2 1.
  • the first emulsion has a sensitivity about 0.1 to 0.4 log I.t units less than the sensitivity of the second emulsion as measured by the points on the characteristic curves which are above the exposure required to produce visible density, and which improvement results in the first emulsion giving a density of at least 1.5, the second emulsion giving a density of not over 0.9 and the slower emulsion having the threshold of its characteristic curve coinciding in log 1.1 units with the shoulder of the characteristic curve of the faster emulsion and whereby the overall sensitivity in log I.t units of said light sensitive material is greater than the sensitivity of the more sensitive second emulsion measured by the points on the characteristic curve above the exposure required to produce visible density.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)

Abstract

1. A LIGHT SENSITIVE PHOTOGRAPHIC MATERIAL OF IMPROVED SPEED AND GRANURALITY ESSENTIALLY CONSISTING OF A SUPPORT AND IN SUPERPOSED RELATIONSHIP A FIRST SILVER HALIDE EMULSION OF SILVER BROMIDE OR SILVER BROMO-IODIDE CLOSER TO THE SUPPORT AND A SECOND SILVER HALIDE EMULSION OF SILVER BROMIDE OR SILVER BROMO-IODIDE SUPERPOSED OVER THE FIRST EMULSION WHEREIN THE IMPROVEMENT COMPRISES THE SECOND EMULSION IS IN A LAYER HAVING A THICKNESS OF AT LAST 2$ AND THE FIRST EMULSION IS IN A LAYER HAVING A THICKNESS OF BETWEEN 5 AND 15U AND IS GREATER IN THICKNESS, THE FIRST EMULSION HAS A SENSITIVITY ABOUT 0.1 TO 0.4 LOG 1.T UNITS LESS THAN THE SENSITIVITY OF THE SECOND EMULSION AS MEASURED BY THE POINTS ON THE CHARACTERISTIC CURVES WHICH

ARE ABOVE THE EXPOSURE REQUIRED TO PRODUCE VISIBLE DENSITY, AND WHICH IMPROVEMENT RESULTS IN THE FIRST EMULSION GIVING A DENSITY OF AT LEAST 1.5, THE SECOND EMULSION GIVIMG A DENSITY OF NOT OVER 0.9 AND THE SLOWER EMULSION HAVING THE THRESHOLD OF ITS CHARACTERISTIC CURVE COINCIDING IN LOG 1.T UNITS WITH THE SHOULDER OF THE CHARACTERISTIC CURVE OF THE FASTER EMULSION AND WHEREBY OVERALL SENSITIVITY IN LOG 1.T UNITS OF SAID LIGHT SENSITIVE MATERIAL IS GREATER THEN THE SENSITIVITY OF THE MORE SENSITIVE SECOND EMULSION MEASURED BY THE POINTS ON THE CHARATERISTIC CURVE ABOVE THE EXPOSURE REQUIRED TO PRODUCE VISHIBLE DENSITY.

Description

Nov. 5, 1974 E. HELLMIG E AL 3,846,135
LIGHT-SENSITIVE PHOTOGRAPHIC MATERIAL WITH INCREASED SENSITIVITY TO LIGHT Filed April 8. 1971 INVENTORS:
EHRHARB HELLMIG, FRANZ EvICiJL, AUGUST RANDOLPH, WILHELM SALECK.
United States Patent ()flice 3,846,135 Patented Nov. 5, 1974 1m. 01. G03c 1/02, 1/08, N46
US. Cl. 96-68 3 Claims ABSTRACT OF THE DISCLOSURE Synergistic increase in light sensitivity of combination of two superposed silver halide emulsion layers is obtained where lower layer is less sensitive than upper layer, has a density of at least 1.5 as against a maximum density of 0.9 for the upper layer, the characteristic curve of the upper layer is no steeper than that of the lower layer, the lower layer is about 5 to 15/L thick and thicker than the upper layer. Both emulsions are preferably iodobromide emulsions, and can be panchromatically sensitized.
This application is a continuation-in-part of our copending US. Application Ser. No. 634,507 filed Apr. 28, 1967, entitled Light Sensitive Photographic Material With Increased Sensitivity to Light, now abandoned.
The invention relates to a photographic black-white material with increased sensitivity.
It is well known that the greater the sensitivity of a light-sensitive photographic silver halide emulsion, the coarser will be the silver grain after development of the exposed material. The production of photographic layers of high light sensitivity is therefore limited by the coarseness of the grain. This applies equally to black and white films and to color photographic elements, because of the degree of granularity of the silver halide grain of the emulsion used.
Since the graininess of the color image interferes particularly strongly with the overall impression of the image, epecially on projection, and since photographic practice demands highly sensitive and therefore coarse-grained emulsions, there has been a search for means for increasing the sensitivity of color photographic layers without concomitant increases in grain. It is known to apply over a fine-grained silver halide emulsion of medium sensitivity a second silver halide emulsion of higher sensitivity and hence also coarser grain, which has the same silver content but a lower color coupler content so that after color development, the second layer assumes only a limited maximum color density, e.g., of 0.20 to 0.60, even at maximum exposure. Although the desired increased sensitivity is thus provided by the second layer, the influence of the coarser grain on the total grain of the double layer remains relatively slight.
It is among the objects of the present invention to produce a black and white photographic material with increased sesitivity without concomitant increases in granularity of the grain.
We now have found that the sensitivity of black and white photographic materials can be considerably increased by the use of double silver halide emulsion layers if certain conditions are observed as regards the proportions of the silver halide contents in the two silver halide emulsion layers and the density of the more sensitive layer. In the arrangement of layers of the invention, the more sensitive silver halide emulsion layer, which is arranged on the top, contains per unit of surface at most 60% of silver halide based on the silver halide content of the less sensitive lower silver halide emulsion layer. The silver halide content of the more sensitive layer should be that suflicient to provide a maximum density of not more than 0.90 preferably between 0.50 and 0.70, while that of the lower provides a density of at least 1.5 with a straight characteristic.
The difference of sensitivity between the more sensitive silver halide emulsion layer and the less sensitive silver halide emulsion layer is preferably 0.1 to 0.4 log 1.)? units.
With the threshold of the characteristic curve of the less sensitive emulsion coinciding with the shoulder of the characteristic curve of the more sensitive emulsion flatter, very good results are obtained. The sensitivity curves are those of a density-log exposure graph for photographic emulsions. The coordinates on which such curves are customarily plotted are the density which is indicated along the ordinate. The threshold is the log I.t value on the abscissa at which the plotted photosensitivity emulsion becomes responsive to light. The shoulder is the log I.t unit value where the emulsion approaches saturation.
The accompanying Figure shows the characteristic curves of the individual emulsions and the curve which results from the combination of the emulsions according to this invention.
According to a preferred embodiment of the invention, the more sensitive silver halide emulsion layer is thinner than the less sensitive layer underneath it.
The thickness of the more sensitive silver halide emulsion layer lies between 2 and 7,u, while the less sensitive layer has a thickness of between 5 and 15,u.
It is unexpected that in the black and white photographic element according to the invention the sensitivity of the double layered element is not equal to the sensitivity of the more sensitive top layer but considerably higher. Thus, when the double layer element of the invention is used a synergistic effect appears and a very high light-sensitive photographic material results.
The usual silver halide emulsions can be used for production of the double layered element of the invention; it is preferred, however, to use silver bromide gelatin emulsions that have a minor silver iodide content of up to about 10 mols percent. If required, however, silver chloride emulsions may also be used, if desired in admixture with the above mentioned silver halides.
The light-sensitive emulsion to be used according to the invention may contain the usual additives such as chemical or optical sensitizers, stabilizers, wetting agents, hardeners, etc.
Photographic materials prepared according to the invention can be used in all fields of photography. They are of special importance for reproduction work where there is a demand for panchromatic half-tone films of maximum sensitivity which are commonly used for the production of color separation records. The use of narrow band color separation filters which absorb a considerable amount of light as well as the combination of the original with a masking image and in many cases the necessity of producing an enlargement of the original or a portion of it diminish the amount of light available to such an extent that the exposure time for the separation records is in many cases increased to an unacceptable degree.
EXAMPLE 1 A panchromatically sensitized silver halide gelatin emulsion containing per kg. g. of gelatin, 0.55 mol silver halide (silver bromide plus 4% silver iodide) which has been after-ripened as described by Glafkides Photographic Chemistry Vol. 1, 2nd Edition, page 319, in the presence of 15 mg. of thiosulfate and 1.6 mg. of gold in the form of ammonium aurothiocyanate per liter and which further contains 50 ml. of 1% methanolic solution of -methyl-7-oxy-1,3,4-triazaindolizine, ml. of a 10% aqueous solution of formaldehyde and ml. of a 7.5% aqueous solution of saponine is applied onto a support of polyethylene glycol terephthalate.
Onto that layer is applied a second layer of a panchromatically sensitized silver bromide emulsion containing 2 mol percent of silver iodide. The emulsion is an ammonia emulsion containing the additives referred to above and is further chemically sensitized by addition of a pentaerythritol phosphoric acid ester as described in British Pat. No. 1,045,184.
Onto that second silver halide emulsion layer is applied an antistatic gelatin layer (0.5,u in thickness) which protects the silver halide layers against mechanical damage The thickness of the lower layer is 7.6 its silver content in the form of silver halide is 4.50 g./m. the upper layer has a thickness of 4.7,u and a sliver content in the form of silver halide 2.43 g./m.
The finished material is exposed behind a test wedge in a sensitometer customarily employed in the art. The sensitivity of the more sensitive top layer, measured at a density of 0.10 over fogging is only 0.25 log 1.1 units higher than that of the less sensitive layer. The double layer element, however, has a sensitivity of 0.46 log I.t units above that of the less sensitive layer. An additional increase in sensitivity of 0.21 has thus been obtained by the greater than additive effect of the inventive double layer element. This increase amount to the factor 1.62 or 62%. Compared with the less sensitive lower layer, the sensitivity increase of 0.46 log units amounts to 188% (factor 2.88) without any coarsening of the silver grain.
The results are set forth in the Figure. The Figure shows curves that are based on the description of Example 1:
1. The emulsion B has sensitivity of about 0.1 to 0.4 log 1.: units less than the sensitivity of the upper emulsion.
2. The shoulder of the curve of the upper emulsion A coincides with the threshold of the curve of the emulsion B.
3. The curves of emulsions A and B have substantially the same shape.
4. The upper emulsion A has a maximum density of not more than 0.9 and the emulsion B has a maximum density of at least 1.5.
5. The sensitivity of the combination of the emulsions is substantially higher in sensitivity than the emulsions A and B and the difference between the sensitivity of the combination and emulsion B is greater than the difference between the sensitivities of emulsions A and B. The sensitivity of the combined emulsions is substantially different from the sensitivity of the upper emulsion, which is the one with the higher sensitivity.
EXAMPLE 2 A maximum sensitivity emulsion containing 5 mols percent of silver iodide is substituted for the less sensitive layer described in Example 1. The same additives as listed in Example 1 are added to the final after-ripened emulsion. Thickness of lower layer: 7.6,u/upper layer: 4.6 Silver content of lower layer: 4.5g./m.-/upper layer: 1.77 g./m. in the form of silver halide Sensitivity upper/lower layer=0.1 log I .t
0.1 over Sensitivity total/lower layer=0.3 log I .t foggmg' This example shows that the synergistic effect has led to a sensitivity increase of 0.2 log. 1.! units, in other Words to a 58% higher sensitivity.
It is thus possible to produce light-sensitive photographic materials with an unexpectedly high sensitivity without concomitant coarsening of the silver halide grain.
If this sensitivity increase in panchromatic films is to be obtained for light of all three-thirds of the visible spectrum, that is blue, green and red light, then it is of course necessary for both the upper layer and the lower layer to be panchromatically sensitized and the sensitvity of the upper layer must be higher by the same amount than that of the lower layer for each of the said regions of the spectrum.
I claim:
1. A light sensitive photographic material of improved speed and granularity essentially consisting of a support and in superposed relationship a first silver halide emulsion of silver bromide or silver bromo-iodide closer to the support and a second silver halide emulsion of silver bromide or silver bromo-iodide superposed over the first emulsion wherein the improvement comprises the second emulsion is in a layer having a thickness of at least 2 1. and the first emulsion is in a layer having a thickness of between 5 and 15a and is greater in thickness, the first emulsion has a sensitivity about 0.1 to 0.4 log I.t units less than the sensitivity of the second emulsion as measured by the points on the characteristic curves which are above the exposure required to produce visible density, and which improvement results in the first emulsion giving a density of at least 1.5, the second emulsion giving a density of not over 0.9 and the slower emulsion having the threshold of its characteristic curve coinciding in log 1.1 units with the shoulder of the characteristic curve of the faster emulsion and whereby the overall sensitivity in log I.t units of said light sensitive material is greater than the sensitivity of the more sensitive second emulsion measured by the points on the characteristic curve above the exposure required to produce visible density.
2. The photographic material claimed in claim 1, wherein the more sensitive silver halide emulsion has a density between 0.5 and 0.7.
3. The photographic material claimed in claim 1, wherein both silver halide emulsion layers are panchromatically sensitized and the sensitivities of the two layers for blue, green and red light are different by a ratio in the range of 0.1 to 0.4 log 1.1 units which is the ratio of the sensitivity of the lower emulsion to the sensitivity of the upper emulsion.
References Cited UNITED STATES PATENTS 2,996,382 8/1961 Luckey 9668 3,050,391 8/1962 Thompson 9668 3,140,179 7/1964 Russell 9668 3,141,773 7/1964 Hellmig 96-68 3,353,957 11/1967 Blake 9668 3,402,046 9/ 1968 Zwick 9674 3,418,123 12/1968 Haugh 9668 3,450,536 6/1969 Wyckoff 9668 3,505,068 4/1970 Beckett 9668 3,591,382 7/1971 Millikan 9668 RONALD H. SMITH, Primary Examiner A. T. S. PIC-O, Assistant Examiner US. Cl. X.R. 96107

Claims (1)

1. A LIGHT SENSITIVE PHOTOGRAPHIC MATERIAL OF IMPROVED SPEED AND GRANURALITY ESSENTIALLY CONSISTING OF A SUPPORT AND IN SUPERPOSED RELATIONSHIP A FIRST SILVER HALIDE EMULSION OF SILVER BROMIDE OR SILVER BROMO-IODIDE CLOSER TO THE SUPPORT AND A SECOND SILVER HALIDE EMULSION OF SILVER BROMIDE OR SILVER BROMO-IODIDE SUPERPOSED OVER THE FIRST EMULSION WHEREIN THE IMPROVEMENT COMPRISES THE SECOND EMULSION IS IN A LAYER HAVING A THICKNESS OF AT LAST 2$ AND THE FIRST EMULSION IS IN A LAYER HAVING A THICKNESS OF BETWEEN 5 AND 15U AND IS GREATER IN THICKNESS, THE FIRST EMULSION HAS A SENSITIVITY ABOUT 0.1 TO 0.4 LOG 1.T UNITS LESS THAN THE SENSITIVITY OF THE SECOND EMULSION AS MEASURED BY THE POINTS ON THE CHARACTERISTIC CURVES WHICH
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1979001020A1 (en) * 1978-05-02 1979-11-29 Polaroid Corp Photosensitive elements
US4209329A (en) * 1977-05-02 1980-06-24 E. I. Du Pont De Nemours And Company Low silver coating weight, high speed films having two similar emulsion layers
US4444874A (en) * 1982-09-15 1984-04-24 Eastman Kodak Company Photographic elements containing direct-positive emulsions and processes for their use
USRE32149E (en) * 1982-09-15 1986-05-20 Eastman Kodak Company Photographic elements containing direct-positive emulsions and processes for their use
US4654297A (en) * 1984-09-14 1987-03-31 Fuji Photo Film Co., Ltd. Silver salt diffusion transfer element comprising two silver halide layers
US5314794A (en) * 1992-06-26 1994-05-24 Eastman Kodak Company Elements and processes for producing superior photographic records

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4209329A (en) * 1977-05-02 1980-06-24 E. I. Du Pont De Nemours And Company Low silver coating weight, high speed films having two similar emulsion layers
WO1979001020A1 (en) * 1978-05-02 1979-11-29 Polaroid Corp Photosensitive elements
US4444874A (en) * 1982-09-15 1984-04-24 Eastman Kodak Company Photographic elements containing direct-positive emulsions and processes for their use
USRE32149E (en) * 1982-09-15 1986-05-20 Eastman Kodak Company Photographic elements containing direct-positive emulsions and processes for their use
US4654297A (en) * 1984-09-14 1987-03-31 Fuji Photo Film Co., Ltd. Silver salt diffusion transfer element comprising two silver halide layers
US5314794A (en) * 1992-06-26 1994-05-24 Eastman Kodak Company Elements and processes for producing superior photographic records
US5389506A (en) * 1992-06-26 1995-02-14 Eastman Kodak Company Elements and processes for producing superior photographic records

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