US1482613A - Potassium iodide composition of matter for photographic processes - Google Patents

Description

time tea. 5, i924.

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ROBERT JOHN, OF NEW YORK, N. Y., ASSIGNOR TO DAYL IGH'I' FILM CORPORATION,

CORPORATION OF NEW YORK.

v POTASSIUM IODIDE COMIlPOS ITION OF MATTERFOR PHOTOG-BAPHIC PROOESSF5.

Ho Drawing. i

To all whom/it may concern:

Be it'known that I, ROBERT JOHN, a citizen of the United States, residing at New York, in the county of New York and State of New York, haveinvented a certain new and useful Potassium Iodide Composition of Matter for Photographic Processes, of which the following is a specification.

My invention relates to a potassium iodide composition of matter for photographic processes and has for its object the production of a-photographic record of lights and shades in which the gradation between the recorded light-s and shades may be controlled.

A further object of my invention is to produce a series of pictures taken under different lighting and other conditions in which the evenness of gradation in each picture shall be approximately the same. If desired, hard pictures can be made soft and soft pictures can be made hard.

A further object of my invention is to obtain, in one embodiment thereof, a printing surface which is mounted on a suitable carrier and which represents photographic lights and shades in such a manner that copies may be made therefrom by a dye or inktransfer contact process.

For the purposes of illustration, my invention will be described in connection with the formation of aprinting surface obtained by exposing to the action of light modified by the lights" and shades of a completed negative which it is desired to reproduce a sensitized emulsion mounted on a transparent carrier through which it preferably is exposed, which then is treated to form a hardened printingv surface.

Itis considered desirable in producing a printing surface to expose the sensitized emulsion through its transparent carrier rather than onits outside surface in order that the printing surface may be as close as possible to the carrier. exposed on its outside surface, it is necessary to strip the emulsion from its carrier in order' to remove the unhardened portions which will lie adjacent the carrier. Stripping the emulsion is a delicate operation which can be performed only by those skilled in the art and is likely to lnjure the image.

When an emulsion is exposed throughits transparent carrier, however, certain. dlfi.

If the emulsion is Application tied October 2, 1919. Serial no. 327,891. 4

portionsadjacent the transparent carrier.

This usually is accomplished by the use of an excess of alkali, such, for example, as sodium carbonate, which opens the pores of the emulsion and carries the solution through.

The objection to this is that the excess of alkali has a tendency to affect the image unfavorably, destroy the delicate intermediate shades, and make it too contrasting. In the second -place, an ordinary sensitized emulsion usually is in excess of one-thousandth of an inch in thickness, while the preferable printing surface adjacent the carrier should be very thin. substantially one ten-thousandth of an inch or less. As this ordinary thick emulsion will be penetrated deepl by the light to which it is exposed, particu arly that portion of the light coming through clear spaces or light shadows in the negative which is being reproduced, the resultant printing surface after treatment will give a relatively too thick printing surface in those portions. This undesirable thickness is in creased by the use of an alkali as referred to above. It is very difiicult, therefore, to t the darker ,portions of the negative recorfe d properly without having the lighter portions of the negative registered too heavy and deep.

One manner of overcoming the above difiiculties has been to incorporate'in the emulsion a light-restraining agent such as tartrazine or a chrome yellow pigment which hasthe property of absorbing or slowin down the action of the printing rays su ciently' to enable the dark portions of the negative which is being reproduced to be registered on the sensitized particles in the emulsion adjacent the carrier. before the printing rays coming through light portions of the negative have penetrated the emulsion so deeply as to form a printing surface which is too thick in the portions corresponding to said light portions of the negative. after the printing surface has been treated and the portions of emulsionunaffected by light removal. The use of these light-restraining agents, however, has disadvantages, among which may be mentioned their detrring efiect on the sex st '10 I have discovered that excellent resiilts may tized emulsion so that a longer time of exposure is required. Although this additional time of exposure is not a serious handicap in plate photography, it is important in motion picture photography where the speed of running the'large number of individual pictures upon a motion terial factor.

picture fihn through the printer is a ma- In order to overcome these disadvantages,

. be-obtained by the use of a developer solution containin potassium iodide which within certain limits seems to have the property of holding the lighter tones and at the the characteristics desirable for a contact transfer printing surface. A softness of result also is obtained without the too contrasting eifects which are undesirable.

A sample formulafor a developing solu tion containing potassium iodide is as follows: v

ayrogallic acid 1O grs.

ater to 1oz.

, Y ,B. I I. j Sodium carbonate 7O grs. Potassium iodide.. 50grs. Water to.. 5ozs. ,Use one part of A to 5 arts of B. Within certain limits sodium su phite may be used with I tassium iodide, the exact amounts of whlch will be determined by the articular work in hand. A sample formu a for a developing solution containing potassium iodide and sodium, sulphite is as follows:

Water; 8.5 oz. 1lciyro llic acid 11 grs. eto 9 grs. Potasium bromide -1, 4 grs. Sodium carbonate 200 grs. .Sodium sulphite 40to60grs. Potassium iodide f 20 to 90'grs. Metol is' monomethylparamidophenolsul- P a -0 His customary in photographic work and particularly in motion picture work to control the evenness of fimshed prints by varying the amount of light exposurein' different stages of the photographic process. This is y particularly desirable in motion picture .work in order to give an even lighting efl'ect to the .completed film where the parts have been taken under va ing lightm condi tions. In addition to is evenness gf lighting eflect, I have found it possible to control the evenness of the pictures with relation to the difierence between light and dark portions, so that some pictures will not be more contrasting than other pictures but greater degrees of produced havi that all will have substantially the same de-.

gree of softness or evenness of gradation.

A thousand foot reel of ordinary motion pictures, for example, ordinarily consists of many different scenes taken under var ing light conditions. In making prints om the negative of such a picture, the uneven' ness in lighting can be.reducedby varying between light and dark portions, so that the.

completed motion picture will have a uniformity of appearance most pleasin to the eye. Toaccomplish this result I rst develop those portions of a picture in whichv .the degree of gradation between'lights and shades is at a minimum in a developer solution containing a minimum-amount of potassium iodide. When this portion of the film has been developed, more otassium iodide is added and a ortion of t e film developed in which the egree of gradation between lights and shades is eater than in the first ortion developed. 1s added as portions of the film having adation are reached until the entire film 1s finished. This will result in a completed film in which not only is there evenness of lighting but evenness of gradation between the light and dark portions of the film. In making still pictures ore potassium iodide posed emulsion without destroying the light shades so that a less contrastin or more soft picture is obtained, particular y in the pro uction of a printlng surface suitable for a dye or ink contact transfer process. If, on the other hand, an amount of sodium sulphite sufiicient to reduce heavy shades I was used, it .would destroy the light shades.

It is this 'p-roperty'of potassium iodide of re ducing the heavy shades without destroying the light shades which makes it possib e to obtaina uniform product as well as a desirable surface for contact transfer printing.

Many modifications of my invention will be'apparent to those skilled in the art without departing therefrom or from the scope of the invention, my invention not being limited to the embodiments thereof chosen for purposes of illustration but consisting of a potassium iodidecomposition of matter,

whereby the im-ageis retained. close to the earner and any series of pictures may be the same egree of gradation between .lig t and dark portions thereof.

What I claim is: 1. A developing and hardening composi tioncontaining a hardening substance. and" an agent adapted partially to neutralize said mamas hardening substance comprising potassium iodid, in such an effective amount as to permit only a selective area of hardening.

2. A developing and hardening composition containing pyrogallic acid, and potassium iodid in such an effective amount as to permit only a selective area of hardening.

3. A developing and hardening composition containing pyrogallic acid as a hardening substance and a mixture adapted partially to neutralize said hardening substance comprising potassium iodid and sodium carbonate, the latter being present in sufiicient quantity with respect to the iodid, to prevent complete neutralization of the hardening effect of the pyrogallic acid so as to permit only a selective area of hardening.

4. A developing and hardening composition comprising an iodid salt present in insufficient quantity to completely neutralize the hardening effect of the composition, whereby only a selective area of hardening will result.

5. A- developing and hardening composition for photographic processes comprising the following:

Pyrogallic acid 10 grs. Sodium carbonate; 1,350 grs. Potassium iodid 250 grs.

ater 26 ozs.

6. A developing and hardening composition for photographic (processes comprising Water, pyrogallic aci metol, potassium bromide, SOdlllHl carbonate, and potassium iodid.

7. A developing and hardening composition for photographic processes comprising water, p-yroga-llic acid, metol, potassium bromide, sodium carbonate, potassium iodid, and sodium sulphite.

In testimony that I claim the foregoing, I have hereunto set my hand this 30th day of September, 1919.

ROBERT JOHN.