US2384598A

US2384598A - Photographic material

Info

Publication number: US2384598A
Application number: US383379A
Authority: US
Inventors: Burt H Carroll
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1941-03-14
Filing date: 1941-03-14
Publication date: 1945-09-11
Anticipated expiration: 1962-09-11

Description

Sept 11, 1945.

DENSITY DE/YS/ TY B. H. CARROLL 2,384,598

PHOTOGRAPHIC MATERIAL I Filed March 14, 1941 Fla.

Lbs EXPOSURE L06 EXPOSURE BURT/7. CARROLL NV T ATTORNEYS Patented Sept. El, 1945 UNITED STATES PATENT orrics amass PHOTOGBAPHIO MATERIAL Burt H. Carroll, Rochester, N. Y., mlgnor to Eastman Kodak Companmliochester, N. Y., a corporation of New Jersey Application March 14, 1941, Serial No. 383,379

. 12 Claims. (01495-7) This invention relates to photographic material and more particularly to photographic material which gives images of diilerent contrast under the same conditions of development.

It has been proposed to prepare photographic materials which give images of different contrast under the same conditions of development, by utilizing two independently prepared emulsions of different contrasts (either mixed together or coated in layers, one upon the other) and sensitizing one or both of the emulsions with sensitizing dyes, so that the composite emulsion re-' sponded difierently to light of different wavelengths. As an example of this prior proposal, an emulsion which works hard (contrasty) and is sensitive to blue, such as a silver chloride emulsion, is mixed with an emulsion which works soft and is sensitized to green, such as a spectrally sensitized silver bromide emulsion. Wh' n such a composite emulsion is exposed with light passed through a filter permeable only to green, the light which acts on the contrasty emulsion is cut oil, and normal images can be made from objects of high contrast. Likewise, when such a composite emulsion is exposed with light passed through a filter permeable only to blue. the light which acts on the "soft emulsion is cut 011, and;-

normal images can be made from objects of low contrast.

A variation of this prior proposal comprises spectrally sensitizing the contrasty chloride emulsion to the green and leaving the "soft bromide emulsion free from spectral sensitizers, so that the contrasty emulsion, and not the soft" emulsion is afiected by light passed through a filter permeable only to green.

I have now found that a' photographic material which responds differently to light of different wavelengths and which gives images of different contrast under the same conditions of development, can m prepared with a single emulsion, instead of a composite of two or more different emulsions. Thus, I have been able to avoid the undesirable features of such a composite. By using a. single emulsion instead of a composite of two difierent emulsions, the time of develop ment is more constant over the whole range oi contrasts, and a wider latitude in choice of developers obtains. Moreover, if any addition (e. g. potassium bromide) is made to the developing solution, the eflect thereof will be morenearly the same over the whole range than when two difierent emulsions are involved.

It is accordingly an object of my invention to provide a photographic material which gives images of different contrast under the same conditions of development. A further object is to provide a process for preparing such materials. Other objects will become apparent hereinafter.

In accordance with one embodiment of my invention, I take a silver halide emulsion which may be of the chloride, chloriodide, chlorobromide, bromide or bromiodide type. of this emulsion, I take a portlonwhich is less than half and spectrally sensitize the portion (for example, to the green) with -a sensitizing dye which does not wander or difiuse in emulsions. I then thoroughly mix the spectrally sensitized portion with the larger portion of the emulsion. If the so prepared emulsion is exposed through a blue filter, i. e., a filter permeable only to blue light; it will be found to work hard, 1. e., to give normal images of low contrast objects, while if it is exposed through aminus blue filter (Wratten N0. 12) it will be found to workisoft, i. e., to give normal images of high contrast objects. Advantageously the portion of the emulsion which I spectrally sensitize in practicing my invention is equal to from about A; to about 5 of the volume of the total emulsion. In practice, I have attained especially useful results by spectrally' sensitizingv about A of the silver halide particles.

. In accordance with a further embodiment of my invention, I take a .silver halide emulsion which can be any ofthe usual types indicated above. I take a portion of the' emulsion which is less than half and spectrally sensitize the portion- (for example to the red) with a sensitizing dye which does not wander or difiuse in emulsions. I then take the larger portion of the emulsion-and spectrally sensitize it to light of a diiferent wavelength (for example, to the green) with a sensitizing dye which does not wander or dlfiuse in emulsion. I then thoroughly mix together the two portions of emulsion. If the soprepared emulsion is exposed through a filterpermeable only to green light it will be found to work hard, 1. e., to give normal images of low contrast objects, while if it is exposed through a filter permeable only to red light, it will work soft, i. e., give normal images of high contrast objects. Advantageously, the portion of the emulsion which I spectrally sensitize to light of one wavelength is equal to from about to A, of the total volume of the emulsion, so that the portion of the emulsion which is spectrally sensitized to light of another wavelength is from three to seven times as large. In practice, I have found that an emulsion, M 01' the particles of which are spectrally sensitized to light of one wavelength, and the remainder of the particles geously practiced with sensitizing dyes which are inherently non-diffusing. I have found that irreversibility of adsorption ofthe sensitizing dyes to the silver halide grains or -particles, i. e., lack of diffusion, can'be enh ced by digesting the emulsion for some time th the sensitizing dye. Normally, sensitizing dyes arev incorporated in emulsion while the emulsions are in a liquid state, at about 30 to 35 C. I have found that irreversibility of adsorption is enhanced by digesting at 40 C. or above for several minutes; for example, for about 15 minutes at 40 C. or for from into minutes at 50 C. In practicing my invention, it is very important not to use excessive quantities of the sensitizing dyes, 1. e for the particles of silver halide, which it is intended should be dyed, the adsorptive capacity of the particles for dye should not be exceeded. Otherwise the unadsorbed excess dye will be adsorbed by the grains of silver halide which were intended to be free from dye, thereby ruining the effects obtained according to my'invention. Ordinarily, I have found it advisable to employ concentrations of sensitizing dyes somewhat less than required to produce-optimum sensitization, i. e., within the range from /2 of the optimum concentration up to the optimum. However, it should be borne in mind that the best results are obtained in accordance with my invention when all of the dyed silver halide particles have rather high sensitivity. Accordingly, I have found it advantageous to incorporate in those portions of the emulsion which I spectrally sensitize, substances which have a supersensitizing effect upon the sensitizing dyes.

The foregoing embodiments of my invention are not to be confused with the so-cailed mixed grain color photographic emulsions where equal. instead of unequal, parts of an emulsion are treated to confer a different color sensitivity on each part.

'Non-diflusing sensitizing dyes which sensitize to the green are to be found in the thia-2'- cyanine, the benzothia-2'-cyanine, the selena-2'- cyanine, the 2,2'-cyanine, the thiazolo-2'-cyanine and the dibenzoxacarbocyanine classes of dyes. Non-diifusing dyes which sensitize to longer wavelengths are to be found in the dibensothiacarbocyanine, the 5,5'- dichlorothiacarbocyanine, the 5 chlorothiacarbocyauine, the 5 chlorothiaselenacarbocyanine, the fi -chlorothiabenzothiacarbocyanine, the 5,5 dichloroselenacarbo cyanine,-th 5-chloroselenacarbocyanine, the 5- chloroselenathiacarbocyanine and the 5-chloroselenabenzothiacarbocyanine classes of dyes. Non-diffusing sensitizing dyes are also to be found among the simple merocyanines, the merocarbocyanines and the merodicarbocyanines containing on the one hand a 3-alkylrhqdanine, a 3-arylrhodanine or a 2-diarylamino-4(5) -thiazolone nucleus and on the other hand a benzoxazole, a benzothiazole, a benzoselenazole, a napthoxazole, anaphthothiazole, or a simple thiazole nucleus (1. e. a thiazole nucleus devoid of a fused-on aromatic ring, e. g. i-methyl-thiazole and 4- phenylthiazole). Merocyanine dyes which contain a long chain organic group (e. g. a 3-heptyl-'- l-phenyl- 2-thiohydantoin nucleus) and which are especially resistant to diffusion are described in the copending application of Leslie G. 8.

Brooker, Serial No.,321,730, filed March 1, 1940' aseaeoe The following examples will serveto illustrate my invention.

Emmple 1 One liter of a cine positive gelatino-silveb bromiodide emulsion was divided into two portions of approximately 250 cc. and 750 cc. "The 250 cc. portion was sensitized with,3.75 mg. of 2- methyl-l'-ethyl thia-2'-cyanine iodide by adding to the portion sufficient of a concentrated methyl alcoholic solutionof the dye to give 3.75 mg.

After the dye was added to the portion, it was held at 50 C. for ten minutes. This spectrally sensitized portion was then thoroughly mixed with the other portion of emulsion to which was added 1 mg. of 1-(p-diethylaminostyryl) benzothiazole. The styryl compound, being a diffusing substance, passes from the silver halide grains which'are not spectraliy sensitized and superson- 250 cc. portion sitizes the sensitizing dye thereby increasing the speed of thosesilver halide particles containing the sensitizing dye. Such supersensitization is described in the copending application of B. 8. Carroll and J. A.'Leermakers, Serial No. 278,572, filed June 10. 1939 (-now U. 8. Patent 2,313,922, dated March 16, 1943). When an emulsion prepared as shown above was coated on a suitable support and allowed to dry and then exposed through a blue filter which was found to have a speed of 7.25 and a gamma of 1.97. On the other hand, when the emulsion was exposed through a minus blue filter (Wratten No. 12), it was found to have a speed of 5.35 and a gamma of 0.97, under the same conditions of development. In Figure 1 of the accompanying drawing, the char! acteristic curve for the exposure through the blue filter is shown by curve A, and the characteristic curve for the exposure through the minus blue filter isshown by curve B. a If instead of adding 3.75 mg. of '2-methyi-1'- ethyl thia-2'-cyanine iodideto the 250 cc. portion only, the dye had been mixed with the whole liter of emulsion, the result would have been low speed and relatively high contrast in the green-sensitive region, with the poor gradation characteristic of undersensitized emulsions as illustrated by the characteristic curve in Figure 2 of the accompanying drawing. In Figure 2, curve C is the characteristic curve of such an emulsion exposed through a blue filter and curve B is the characteristic curve of such an emulsion exposed through a minus blue fil v Emmple 2 One liter of a medium speed gelatino-silverbromiodide emulsion, such as can be used for reversal processing in color photography, was divided into portions of 250 cc. and 750 cc. The

was sensitized with 2.5 mg. of 2,2- dimethyl 8 ethyl 3',4,3',4' dibenzothiacarbocyanine bromide and the 750 cc. portion was sensitized with 20 mg. of 2,l'-diethyl-3,4-benzothia-2'-cyanine bromide. In each case, the dye was incorporated in the portion in the form of a concentrated methyl alcoholic solution. In each (now U. S. patent 2,282,116, dated May 5, 1M2). 0! my invention,Ispectrally sensitizean emulsion.

emulsion was held for ten minutes at 50 C. after the addition of the sen- 4.7 and a gamma of 2.12.

ass-1,598

which can be any of the usual types indicated above, with a sensitizing dye which produces two sensitization maxima in the emulsion, one of which tends to disappear as the concentration of the dye is increased. With such dyes, at some low concentration (considerably less than that required for the normal optimum sensitization), maximum sensitization will btain at some wavelength, say in the green and if exposed with light of about the wavelength of the region of maximum sensitivity, the emulsion will work hard. On the other hand, with such dyes at some higher concentration (but still substantially less than that required for normal optimum sensitization) a second sensitization maximum will obtain at some longer wavelength, say in the red, and if exposed with light of about the wavelength of the region of such a second maximum, the emulsion will work soft. At this second concentration, then, the emulsion has two regions of maximum sensitivity, the one region giving high contrast and the other low. It is believed that the second maximum of sensitivity is caused by a new state of aggregation of-the dye on the surface of the silver halide grains, and that an increasing number of grains are covered by the dye in this new state, as the concentration in creases.

The sensitizing dyes which are employed in practicing this third embodiment of my invention need not be dyes which are resistant to diffusion. Moreover, the dyes may be added to the whole of the emulsion. The most useful concentration of dye will, of course, depend upon the nature of the dye and the nature of the emulsion. However, the most useful concentration of dye can readily be determined by sensitizing a given emulsion with a series of concentrations of dye, beginning with a rather low concentration, and

determining the sensitivity and contrast (gamma) of the emulsion in the usual manner. The following example will serve to illustrate the manner of practicing this third embodiment of my invention.

Example 3 A cine positive gelatino-silver-bromiodide emulsion was sensitized with various concentrations 2,2 dimethyl 8-ethyl-thiacarbocyanine iodide, using small test portions of the emulsion for each concentration. At the lowest concentrations, (0.2 to 1.0 mg. of dye per liter of emulsion), the emulsion was sensitized only for the green with a maximum at 560 mu. As the concentration of the dye was increased, red sensitization appeared with a maximum at630 mu. At a concentration of to 10 mg. of dye per liter of emulsion, the emulsion when exposed through a red (Wratten No. 25) filter had a speed of the same order as through a blue (Wratten No. 47) filter, with a red light" nine dyes, especially those derived from 5-chlorobenzoselenazole, and the meso alkyl substituted 5,5-dichloro-oxacarbocyanine dyes.

Practiced in accordance with any of the embodiments, my invention is primarily directed to the customarily employed gelatino-silver-halide developing-out emulsions. However, my inven-'' tions of development-it is possible to print sound.

and picture images at different and appropriate contrasts in cine positive film. -What I claim as my invention and desire to be secured by Letters Patent of the United States is:

1. A process for preparing a photographic printing material for the production of images of diflerent contrast under the same conditions of development comprising dividing a batch of one photographic silver halide emulsion into two portions of unequal volume, one portion constituting from about $4; to about $4; of the total volume of 7 the batch, sensitizing the smaller portion with a sensitizing dye which does not wander from the silver halide grains so that the two portions oi emulsion are sensitized to diflerent spectral regions, and then mixing the two portions of emulsion together.

2. A process for preparing a photographicprinting material for the production of images of diflerent contrast under the same conditions of development comprising dividing a batch of gamma varying from M to of that of the blue light gamma. The main body of the emul ployed in practicing this third embodiment of my invention are the meso alkyl "substituted thiacarbocyanine dyes, especially those derived from 5- chloro-benzothiazole and dialkylaminobenzothiazoles, the meso alkyl substituted selenacarbocyaone photographic silver halide emulsion into two portions of unequal volume. one portion constituting about A of the total volume of the batch. sensitizing the smaller portion with a sensitizing dye which does not wander from the silver halide grains so that the twoportions of emulsion are sensitized to diii'er'ent spectral regions, and then mixing the two portions of emulsion together.

3. A process for preparing a photographic printing material for the production of images oi dinerent contrast under the same conditions of development comprising dividing a batch of 'one photographic silver halide emulsion intotwo portions of unequal volume, one portion constituting from about V8 to about M; 01' the total volume of the batch, sensitizing the smaller portion to the green with a sensitizing dye which does not wander from the silver halide grains, and then mixing the two portions of emulsion together.

4. A process for preparing a photographic printing material for the production of images of different contrast under the same conditions of development comprising dividing a batch of one photographic silver halide emulsion into two portions 01' unequal volume, one portion constituting about 01' the total volume of the batch, sensitizing the smaller portion to the green with a sensitizing dye which does not wander from the silver halide grains, and then mixing the two portions of emulsion together.

5. A process for preparing a photographic printing material for the production of images oi diiierent contrast under the same conditions of development comprising dividing a-batch of one photographic silver halide emulsion into two portions 01' unequal volume, one. portionconstituting from about it to about A oi the total volume oi the batch, sensitizing the smaller portion to the red with a sensitizing dye which does not wander from the silver halide grains, sensitizing the larger portion to the green with a sensitizing dye Y which does not wander from the silver halide printing material for the production of images of diiterent contrast under the same conditions of development comprising dividing a batch of one photographic silver halide emulsion into two po tions of unequal volume. one portion constituting about V of thetotal volume of. the batch, sensitiling the smaller portion to the red with a sensitiling dye which does not wander from the silver halide grains, sensitizing the larger portion to the green with a sensitizing dye which does not wander from the silver halide grains, and then mixing the two portions of the .emulsion together.

7. A photographic printing material (or 'the production oi images or diflerent contrast in the same emulsion layer under the same conditions of development comprising a photographic silver halide emulsion layer which comprises a mixture of two portionsot unequal volume of the same batch of photographic silver halide emulsion, one portion constituting from about it to about V or the total volume of the batch. the smaller portion having been sensitised before mixing the portions with a sensitizing dye which does not wander from the silver halide grains so that the two portions of emulsion are sensitized to diii'erent spectralregions.

8. A photographic printing material for the production of images of diii'erent contrast in the same emulsion layer under the same conditions of development comprising a photographic silver halide emulsion layer which comprises a mixture of'two portions of unequal volume of the same batch of photographic silver halide emulsion, one portion constituting about V4 oi the total volume of the batch, the smaller portion having been sensitized before mixing the portions with a sensitizing dye which dom not wander from the silver halide grains so that the two portions ofemulsion are sensitized to diflerent spectral regions.

9. A photographic Printing material for the .production of images of diil'erent contrast in the same emulsion layer under the same conditions of development comprising a photographic silver halide emulsion layer which comprises a mixture or two portions of unequal volume of-the same batch of photographic silver halide emulsion, one

assesses v portion constituting from about it to about V4 01' the total volume of the batch. the smaller portion having been sensitized before mixing the portions with a sensitizing dye which doesnot wander from the silver halide grains so that the two portions of emulsion are sensitized to diflerent spectral regions.

10. A photographic printing material for the production of'images of diiierent contrast in the same emulsion layer under the same conditions I of development comprising a photographic silver halide'emulsion layer which comprises a mixture or two portions of unequal volume 01' the same batch of photographic silver halide emulsion, one Portion constituting about V4 oi the total volume of the batch, the smaller portion having been sensitized to the green before mixing the portions with a sensitizing .dye which does not wander groin the silver halide grains so that the two por- 20 ions of emulsion are sensitized to difl'erent spectral regions.

11. A photographic printing material for the production of images of different contrast in the same emulsion layer under the same conditions of development comprising a photographic silver halide emulsion'layer which comprises a mixture of two portions of unequal .volume 01' the same batch of photographic silver halide emulsion, one portion constituting from about V to about V oi the total volume of the batch, the smaller portion having been sensitized to the red'before mixing the portions with a sensitizing dye which does not wander from the silver halide grains and the larger portion having been sensitized to the green before mixing the portions with a sensitizing dye which does not wander from the silver halide stains.

12. A photographic printing material for the production of images of diiierent contrast in the same emulsion layer under the same conditions of development comprising a photographic silver halide emulsion layer which comprises a mixture of two portions of unequal volume of the same batch of photographic silver halide emulsions, one portion constituting about V4 of the total volume of the batch, the smaller portion having been sensitized to the red before mixing the portions with a sensitizing dye which does not wander from the silver halide grains and the larger portion having been sensitized to the green before BURT-H. CARROLL.