US1574357A - Photographic media and process - Google Patents

Description

Patented Feb. 23, 192 6. UNITED STATES 1,514,357 PATENT OFFICE.

MURRAY 0. BEEIBE AND ALEXANDER MURRAY, OF CINCINNATI, OHIO, ASSIGNOBS 1'0 THE. WADSWORTH WATCH CASE COMPANY, OF DAYTON, KENTUCKY, A'COBPORA- TION OF KENTUCKY.

No Drawing.

To all whom it may concern:

-Be it known thatwe, 'MURnAY C. BEEBE (a) and ALEXANDER MURRAY (6), (a) is a citizen of the United States, (b) is a subject of Great Britain, both residing at Cincinnati, in the county of Hamilton and State of Ohio, have invented certain new and useful Improvements in Photographic Media and Processes, of which the following is a specification.

This invention relates to improved photographic media and processes.

The primary object is to provide an improved photographic medium which is caable of being used advantageously in the industrial arts for varied purposes. The invention provides an improved light-sensitive, varnish-like medium adapted for various uses, a process of preparing such medium, and a photo-process employing the improved photo-sensitive medium.

In accordance with the preferred practice of the invention, a suitable oil isthickened to a state of incipient gelation and is incorporated in a varnish suitable for photographic uses, where further thickening,

- polymerizing, or hardening is selectively accomplished by the action of light projected upon or transmitted to a coating of the material in accordance with an image, design, or character upon a transparency through which the light is transmitted.

Also, in accordance with the preferred practice of the invention, use is made of accelerating agents in an improved manner.

Preferably, these accelerating agents are used in a varnish whlch comprises a lightsensitive oil, and preferably such oil is prevparatorily thickened to a state of incipient gelation. However, in this aspect, the invention is broad, and the accelerating agents may be used in accordance with the invention in a medium comprising any suitable constituents which are adapted to be hardened, set or rendered insoluble with respect to developing agents, selectively, under the action of light. It is preferred to employ as accelerating agents both a halogen-substituted hydrocarbon, such as iodoform, or an equivalent compound, and a metallic halide, such as an iodide of lead, and, in addition, one may employ, if desired, small proportions of ingredients useful as driers, such as metal. resinates, oxides, etc., com- PHOTOGBAPHIC MEDIA AND PROCESS..

Kpplication filed August 31, 1922. Serial No. 585,517.

monly employed as paint or varnish driers. If desire moreover, such driers may be converted largely or wholly into metallic halides by introducing a halogen, for example, lodlne, into the medium. The halogen co pounds which are formed are dispersed throughout the medium in colloidal form, and, under the action of light, will liberate halogen which canthus serve as a catalytic agent in the transformation which occurs under the action of light.

The thickening of the oil, or oils, may be accomplished by heating, oxidation, destructive distillation, halogenation, hydrogenation, vulcanization, etc.

In place of incipiently gelled oils, one may employ, with such special catalyzers, other suitable bases such as resins, fats, waxes, bitumens, rubber, etc. Any suitable combinatron of materials may be effected.

Some of the bases are particularly adapted to projection printing, and others are adapted to contact printing. The accelerating agents may be introduced into the medium in various ways, as will be understoo more fully from the description hereinafter given;

When a coating comprising a base of the character herein described and a suitable accelerating agent is applied as a coating to a suitable surface and is subjected to the selective action of light in accordance with a curs a selective hardening or setting of the coating, or a selective change in solubility. those portions transformed under the action of light becoming, ordinarily, insoluble in developing agents. Thus, there is formed in the coating an image which will remain on the coated surface after thesoluble' portions have been removed in the developing operation. Over printing may produce a reversal as to solubility or insolubility, as explained later. 7

Without intending to limit the invention, except as may be necessary in view of; the prior art, examples and steps are hereafter described which will enable the invention to be understood.

In the. practice of the invention, one may use as bases various substancegsuch as tung oil, perilla oil, soy bean oil, lard oil, cotton seed oil, fish oil, castor-oil, linseed oil, menhaden bil, gutta percha, caoutchouc, fossil and semi-fossil resins, fatty acids, waxes, bitumens, including so-callcd drying and non-drying oils, kerosene, synthetic resins, esters, etc., such as cellulose acetate.

It has been found that the various bases enumerated are naturally slightly sensitive to the action of light. In application, Serial No. 516,865, filed November 21, 1921, there is described a process employing preferably a varnish which utilizes that property of Chinawood oil, combined with a suitable sensitizer or accelerator, whereby selective drying, or hardening, under the action of light occurs. In application, Serial No. 542,124, filed March 8, 1922, light-sensitive varnishes employing oils and method of preparin such varnishes are setforth; and

ing, hardening,-

ciency of lead, cobalt, manganese,

the pro uctionof latent images in such varmshes on the principle of selective dryor insolubilizing oleaginous media in accordance with a projected or transmitted light image is described. The present invention utilizes such oils in lightsensitive varnishes, and also comprises the use of broadly equivalent bases, but the oils employed, are preparatorily subjected to a thickening or polymerizing process which carries them to a' state of incipient gelation near theoritical point, leaving the oils in such condition thatthey can be quick-.

ly transformed into such a state of insolubility as is desirable for the purposes of the invention. -i

It may be said, in general, that any nonaqueous colloid, which changes from sol to a gel condition in the light, or exhibitsselective solubility under the action of light, especially in the presence of a halogen, a metal'salt, or other accelerator, or combination of accelerators may be used. I

Continued. research has shown that the precise chemical reactions cannotbe fully specified, for the reason that the useful efiiupon their varying hysical properties, such assolubility, state 0 aggregation, dispersion, and internal structure. I

Among many accelerators that may he used, we have found that the following cooperate efficiently with the bases enumerated: metallic resinates, oleates, linoleates, tungates, etc, or any soluble-salt particularly copper, mercury,

silver, cadmium, bismuth, etc., alone or in combination with each other or with the halogens, iodine, chlorine, bromine, or com= unds thereof, singly or incombination. e have also further found that phosphorus, aluminum chloride and aluminum bromide act as accelerators; and in addition such catalyzers as-are recognized as suitable for halogenation."

- In the main, it may be said that the bases. -mentioned are .more or less light-sensitive.

given. As has been of such light-sensitive substances; 'formmg bases, depends,among other things, f

For instance,- cooked tung oil at the end of fifteen minutes exposure indicates'a reaction .to light. The addition of iodine, alone, to

mg very considerably-J Such additions of lead resinate. and iodine are desirable up to a certain point only. Beyond such point, which may be a saturation point, an increase in theseingredients, and especially in iodine,

is not desirable. In general, the accelerators are to be used in relatively small proportions,

as indicated by the. examples hereinafter tive oils, like tung oil, are made more sensitive by the addition of lead resinates, manganese peroxide, lead peroxide, etc. Also, we have found that cobalt linoleat orlead oleate in benzo1\(benzene), with iodine, is sensitive to light action. Also, lead resinate and iodine in a solution of gutta-percha and benzol produce a light-sensitive 'medium, which, under varying light action, becomes selectively insoluble in a manner similar to the other substances Which'have been mentioned In media which are slightly sensitive to light, a visible image may be produced. However, such'image is not always easily developed by a solvent which will act efiiciently in cases where accelerators areemployed in-the media. When, undersuch circumstances, the solvent does notremove the base, varying li ht action, have selective properties whereby it will variably absorb stains. The simplest form of developer which readily. dissolves the unreacted ,part of the sensitive base is soap and water.

A reversed image. from the'same subject is produced by overprinting. With some mixtures, even better positives are secured than negatives..- As an example, we have found by actual demonstration that a 'negati ve print is secured in fifteenseconds and underthe same conditions of light, etc.-, a positive is secured in an exposure of twenty seconds. In general terms, reversal is secured by approximately doublin .the-exposure. The sensitivity of cooke tung 5i] alone is such as to give an impression in fifteen minutes, while with the addition of accelerators having-catalyzing characteristics the exposure has been reduced to but two seconds under the same conditions.

While it has been known that some oils, such as tung 'oil, are somewhat sensitive to light, it may be stated that-the raw oils do not become highly sensitive, even when accelerators are added. By thickening the oils indicated, light-sensientirely such base will, due to the to a state of incipient gelation in accordance with the present invention, their light-sensi tivity can be increased very greatly, and, in

' some cases, hundreds of times. Among the special treatments which may be employed for preparing the oils, We may mention that when heat is applied to many oleaginous substances they gradually thicken. or polymerize. By continuing the heating sufliciently long, a solid insoluble substance is finally obtained. The heating is to be discontinued before that condition is reached. Of the numerous oils mentioned above, tung oil most rapidly reaches this condition. Moreover, tung oil, when thus heated, reaches a rather sharply defined critical point, beyond which, if the heating is continued, the oil will quickly change to a complete gel. -As the oil approaches the state of incipient gelation, the aggregates having molecular characteristics increase inrsize, thus decreasing their degree of dispersion. In ingredients of this kind, during the period of cooking, at the critical point of incipient gelling, before the change to a full gel, they arein a condition of maximum sensitivity to light and are also in condition to be readily incorporated with suitable solvents and thinning agents to form a light-sensitive varnish. In preparing a non-aqueous light-sensitive medium, itis preferableto start with tung oil, subject it to heat to the point of incipient gelling, and combine it with photographically cooperating diluents, accelerators, etc.

I It should be stated that many organic ma terials have similar characteristics, and so may be used as bases. Among these maybe mentioned gutta percha, fossil and semifossil resins, asphaltites, synthetic resins and esters such as cellulose acetate, vinyl acetate,

etc., and waxes because they manifest sensitivity to light in an analogous manner. We have formed images by the use of these alternative materials which are similar in appearance and also show properties found in images produced on coatings composed of suitably treated oils, etc. In the other applications hereinbefore identified, iodine and the metallic compounds mentioned therein, are now more definitely referred to and'we find that in addition bromine and chlorine or combinations of these are even more effective than one halogen alone. We also find that compounds of the halogens which liberate halogens under the action of light the base have certain applications. Among such .substances may be mentioned iodates, tetra iodo pyrrole, iodoform, bromoform, halogen sorption products of dye stufis, etc.

We have found that the sensitivity of an oil is further increased by oxidation, so that, for exam 'le, by aerating or blowing tune oil, that 1s, heating the oil to about 85 in the presence of and passing air through it, and adding only traces of an accelerator the time for print ing is only two minutes. Through the use of cooperating accelerators the time of printing is reduced to a few seconds.

We are not limited to the use of drying or semi-drying oils, as so-callednon-drying oils may be thickened or polymerized to the point of incipient gelling by destructive distillation, halogenation, hydrogenation, vulcanization, or otherwise. For instance, castor oil is thickened by distilling off the lighter constituents until the residue begins to PO13? merize, at which time the'addition of accelarators yields a light sensitive medium. Lard oil thickened by chlorination and heated to a highly viscous stage is light sensitive and may be accelerated in the same manner as the drying oils. Kerosene becomes available in our process by halogenation and dehalogenation which converts it-into an unsaturated oil.

In the earlier applications referred to, the accelerating action of various pigments, especially of the-oxides, was described. In some 'cases we have found that re-agents such as phosphorus, or others that are soluble in the medium but which precipitate as insoluble compounds under the influence of light, act as accelerators to completely gel the i'ncipiently gelled medium, and thus give greater printing selectivity for contrast. In this connection, for example, we have found that lead iodide formsmore rapidly in the light than in the dark.

In general, we have observed that the image grows from the supporting surface and that the nature of the surface has an important influence on the sensitivity and other properties of the print. For example, less exposure is required on a zinc than on a copper or brass support. Where it is desirable to modify the effect of the supporting surface a protective film of a dye, shellac, lacquer, glue albumen, etc., may be used.

We-have also found, as previously stated, that the speed of printing by our process is greatly accelerated by heat, which may be supplied in the form of a blast of hot air to the image during its exposure. also been found that minute quantities of halogen carriers, such as aluminum chloride, aluminum bromide, antimony chloride, also phosphorus, phosphorus oxychloride, etc., fluorescent dyes such as rhodamine, phenosafranine, eosine, etc., become cooperative accelerators to the main reactions.

The surface which is to receive an image is coated with the sensitive medium by flowing, brushing, spraying, whirling, etc. .The surface maythen be exposed for the requisite time and thereafter developed with a solvent that removes the unconverted portions of the coating. Theremaining parts of the coating may serve to receive the action of It has 1 any suitable mordant or to confine the action of an etching agent to the areas laid bare. Our light-sensitive media are specially adapted, to the successful production of photographic images, whether in continuous tone or otherwise. Attempts made heretofore to do'this have not proved practical because of the slow reaction to light of the coating mediums used. The improved varnish may be used very advantageously in the industrial arts. It may, for example, be used in the photographic processes set forth in the application of Murray C. Beebe, No. 542,124, mentioned above.

We do not limit ourselves to the employment of optical projection, as under certainconditions our sensitive coatings are 'sufliciently dry to admit of contact printing.

For contact printing, we have found advantages in using a solid colloid, such as lead oleate or bitumen or gutta percha in combi nationwith a halogen or a halogen-forming substance, e. g. tetra-iodopyrrole or .iodoform the halogen liberated by light rendering is e solid or dry film selectively soluble in suitable developers such as fatty acids, concentrated or dilute As an instance of procedure with a base other than tung oil, we may state that a varnish composed of 100 gms. incipiently gelled linseed oil, 20 gmscumar resin, 40 gms. kauri resin, 10 gms. lead tungate, 50. cc. solvent naphtha and 30 cc. benzol (benzene) may be used. gms. of this varnish sensitized with 20 cc. of a 5% solution of iodine in benzo1 and 5 cc. of a 5% solution of pyridine in bcnzol is suiiiciently sensitized to. produce a rint under a two minute exposure.

y preparing a perilla oil varnish in substantially the same way and sensitized inthe same way as above referred to, the time of printing under the same lighting conditions is reducedto about one sixth of the time mentioned for the linseed oil composition. Prints made-inthis manner are de'- velopable a number of different ways, one

- of which requires about one minute by means of a solution of 150 cc. butyl alcohol, 25 cc. benzine, 10 cc. ter 'ineol. The prints, after develo ment, may e washed in alcohol and staine in any desired manner, such for instance, as by a solution of 150 cc. butyl alcohol, 150 cc.- benzine, 25' cc. carbon tetrachloride, 30 gms. oil blue dye, and 20 gms. phenol, after which they are further washed out with alcohol and dried. If desired the printed and developed imagesmay be hardened by immersing them 1n :1 solution of aluminum chloride, iodine in potassium iodide solution, tannic acid, etc.

As a further exeznplification, a tung oil varnish repared andsensitized as follows, exposed y projection, and developed'with soap and water, gives prints in a few secthe linseed oil adaptation; such a varnish is composed of 32% tung oil, 3% lead resinate, 62.0% bcnzol and 3% iodine. The oil .is treated by heating with the lead resinate for 30-60 minutes at 250 C.

In addition, a gutta percha adaptation will give a print'under lighting conditions similar to theprevious exemplitications, by projection or contact, in about .five minutes. A working relation of ingredients is exemplified in the following: gutta percha, 8.6%, carbon tetrachloride 55.2%, benzol 34.5%, iodine 0.85% and lead resinate 0.85%. Development may proceed with an application of benzinc.

The oils, fats, etc. ordinarily contain unsaturated fatty acids, or glycerides of fatty acids, which doubtless play an important part in the transformation which occurs in the medium under the selective action of light.

From the description given, it will be understood that'incipiently gelled oil and other bases mentioned are equivalents in the broad sense that they afford constituents in the varnish which are ofthick consistency, but which may be dissolved and carried as hydrophobic colloids in a suitable. solvent and thinningmedium, and are capable of being rapidly. transformed selectively to an insoluble condition under the action of light; Also, that these substances aflord constituents which are quickly converted to the insoluble state through the influence of halogen liberated under the action of light. The expression gell-like body, as employed in appended claims, is intended to include-incipiently gelled oils, as well as other bases, hav-- ing the characteristics'of gels, resins, etc., mentioned above. As indicated, however, some of these bodies which are suitable bases may, in some state or condition, assume either a soft resinous form or a solid resinous form. They have, in general, a plastic or semi-plastic character before being dissolvedand thinned. 1

' The expressions oil red, oil blue, oil yellow, etc. are applied to dye stuifs which are insoluble in water, but soluble in oil.

As non-aqueous colloids are used in the pres-. ent process, it play be desirable to 'dye the film to enable the progress of development to be noted. Any. oil dye, provided the medium in which it is dissolved does not also dissolve the printed image, may be used.

Oil redhas been found to be a good dye Q onds, under similar lighting conditions to It may be added that a number of the halogen-liberating compounds heretofore mentioned as being suitable for use as sensitizers, such as iodoform, bromoform, and tetra-iodopyrrole, may be classified as organo halogen compounds, which, in this process are halogen-liberating compounds. Such compounds are especially .useful as sensitizers in connection with non-aqueous, or hydrophobic, colloids:which are capable of being transformed, 0r hardened, under the action of light.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as per-- missible, in view of the prior art.

What we regard as new, and desire to secure by Letters Patent, is:

1. A photographic medium comprising a suitable base, which base comprises a hydrophobic gell-like body sensitive to the action of light, and a catalytic accelerator incorporated with said base. 2. A photographic medium comprising a suitable base which comprises a hydrophobic gell-like body sensitive to the action of light, and an accelerator which serves as a catalyzer in the transformation of said body under the action of light.

3. A photographic medium comprising an incipiently gelled oleaginous base, and an accelerator adapted to expedite the transformation of said base under the action of light. Y

4. A photographic medium comprising an incipiently gelled oleagino'us base which comprises a fatty acid compound, and an accelerator having,'under the action of light, a catalytic action facilitating the transfor mation of said base.

5. A photographic medium comprising a light-sensitive varnish which comprises a light-sensitive incipiently gelled oil.

6. A photographic medium comprising an incipiently gelled oil adapted to be transformed under the action of light, and an ac celerator serving to expedite such transformation.

7. A photographic medium comprising an incipiently gelled oil adapted to be transformed under the action of' light, and an accelerator acting as a catalyzer under the influence of ligh 8. A photographic medium comprising a base which comprises a non-aqueous gelllike body capable of being transformed under the action of light. and an accelerator comprising a-halogen-liberating compound.

9. A photographic medium comprising a varnish which comprises a non-aqueous gelllike body capable of being transformed under the action of light, and a halogen-liberating agent.

10. A photographic medium comprising,

means comprising a halogen-substituted hydrocarbon and a metallic halide.

13. A photographic medium comprising an incipiently gelled oil, a natural resinous compound, and accelerating means comprising a h alogen-substitutedhydrocarbon and a metallic halide.

14. A photographic medium comprising an incipiently gelled oil, a natural resinous compound, an accelerating agent comprising a halogen-substituted hydrocarbon and a metallic halide, and a. diluent.

15. A photographic medium. comprising incipiently gelled tung oil, and an accelerating agent adapted to accelerate the selective action of light upon-said medium when the medium is subjected tophotographic action.

16. A photographic medium comprising iucipiently gelled tung oil, a natural resinous compound, and an accelerating agent adapted to accelerate the selective action of light upon said medium when the mediumsuitable base which comprises: a gell-like body sensitive to the action of light, and accelerating means comprising iodoform.

20. A photographic medium comprising a suitable base which comprises: a hydrophobic gell-like body sensitive to. the action of light, and accelerating means comprising iodoform and an iodide.

21. A photographic mediiim-comprising a suitable basewhich comprises: constituents adapted to be transformed under the action of light, and accelerating means comprisiug a halogen-substituted hydrocarbon and a metallic halide.

22. A photographic medium comprising a suitable base of gell-like character and sensitive to the action of light, and accelerating means comprising halogen-substituted hydrocarbon and a metallic halide.

23. A photographic medium comprising a suitable base of gell-like character and sensitive to the action of light, and accelerating means com rising a metallic halide and an ,additional alogen-liberating agent.

halide and another halogen-liberating com- 27. 'The process of preparing a light-sensi tive medium which comprises: incorporattive to the action' of .colloid under the action of light.

ing with a base which comprises a gell-like non-aqueous colloid which is sensitive to the action of light an accelerating agent adapted to expedite the transformation of said 28. The process of preparing a light sensitive medium, which comprises: incorporating with a base which comprises a gell-like non-aqueous colloid which is sensiht, accelerating means comprising a metallic halide and another halogen-liberating compound.

29. The process" of preparing a photographic medium which comprises: incorpofratmg with anon-aqueous gall-like colloid an, accelerator comprising a metallic halide :another halogen-liberating compound, and incorporating also therewith a diluent.

30. The process of preparing. a photoaphic medium which comprises: producmg an incipiently gelled o' and incorpocrating therewithan accelerating agent.

. wit

31. The process of preparing a photoaphic medium which com rises: producmg an incipiently gelled oi and incorporating therewith accelerating means com.- prising a metallic halide and another halogen-1i erating compound.

32. The process of preparing a photographic medium which comprisesz'producing an incipiently gelled. oil and incorporating therewith accelerating means comprising .a' metallic-halide and a halogensubstituted hydrocarbon;

33. The process of forming} light-sensitive medium which comprises: forming an incilpien'tl gelled oil, incorporating thereacce crating means, comprising a-metal lic halide and another halogen-liberating aphic medium comprising a f compound, and incorporating also therewith a diluent.

34. The process of forming a light-sensitive medium which comprises: producing'an incipiently gelled oil and incorporating therewith a natural resinous compound and an accelerator.

35. The process of forming a light-sensitive medium which comprises: producing an incipiently gelled oil and incorporating therewith a natural resinous compound and an accelerator comprising a metallic halide and another halogen-liberating compound.

36. The process of forming a light-sensitive medium which comprises: reducing an ,oil to an incipiently gelled condition and incorporating therewith a halogen-liberating agent.

37. The process of producing a lightsensitive medium which comprises: reducing tung oil to an incipiently gelled condi tion. incorporating therewith an accelerator which comprises a halogen-liberating agent. and combining the said ingredients with a. thinning agent. g

38. The process of producing a resistant image,- design, oi character on a surface which comprises: applying to said surface a coating comprising-a gell-like base which is capable of being transformed into a hardened state, asolvent and thinning medium carrying said base, and an accelerator; acting upon said coating selectively with light in accordance with an image, design, or character to effect the desired transformation; and subjecting the coating to a developing operation.

39.. The process of producing a resistant image. design, or character on a surface which comprises: applying to said surface a coating comprising a gell-like base which is capable of being transformed into a hardened state, a solvent and thinning medium carrying said base. and an accelerator comprising a halogen-liberating com-pound; acting upon said coating selectively with light in accordance with an image, design, or character to eiiect the desired transformation; .and subjecting the coating to a developing operation.

40. The process of j producing a resistant image, design, or character on a surface which comprises; applying to said surface 7 a coating comprising a: gell-like base which is capable of being transformed into a hardened state, a solvent and thinning medium carrying said base, and an accelerator comprising a metallic halide and another halogen-liberating compound; acting upon said coating selectively with light in accordance with an image, design. or char acter to effect the desired transformation; and subjecting the coating to a developing operation.

41. The process of producing a resistant image, design, or character on a surface which comprises: applying to said surface a coating which comprises an incipiently gelled oil, a suitable solvent and thinning medium, and a halogen-liberating compound; acting upon said coating selectively with light transmitted in accordance with an image, design, or character; and developing the' print 42. A photographic medium comprising hydrophobic colloids adapted to be transformed under the action of light, and accelerating means comprising an organohalogen compound adapted to liberate halogen under the action of light.

43. A photographic medium comprising hydrophobic colloids adapted to be transunder the action of light an accelerating agent comprising an organo-halogen compound adapted to liberate halogen under the action of light.

47. A photographic process which comprises: applying to a surface a coating comprising hydrophobic colloids capable of be-.

ing transformed into a hardened state under the action of light and. having incorporated therein an or ano-halogen-liberatmg com und; and su jecting said coating to the se ective action of light in accordance with an image, design or character,

48. A photographic process which comprises: applyin to a surface a coating comprising hydrop obic colloids capable of being transformed into a hardened state under the action of light and haying incorporated therein an organo-halogen-liberat ing compound; subjecting said coating to the selective action of light in accordance with. an image, design or character; and subjecting the coating to a developing operation.

49. A photographic process which comprises: applying to a surface a coating composed of a solution comprising hydrophobic colloids capable of being transformed into a hardened state under the action of light and having incorporated therein a halogen-substituted hydrocarbon; and subjecting said coating to the selective actionof light in accordance with an image, design or character to effect the desired transformation.

50. A photographic process which comprises: applying to a surface a coating composed of a solution comprising hydrophobic colloids capable. of being transformed into a'hardened state under the action of light and having incorporated therein iodoform; and subjecting said coating to the'selective action of light in accordance with an image, design or-' character to effect the desired transformation. v

51. A photographic process which comprises: applying to a surface a coating composed of a solution comprising hydrophobic colloids capable of being transformed into a hardened state under the action of light and having incorporated therein iodoform;

subjecting said coating to the selective ac-- tion of light in accordance with an image, design or character to effect the desired transformation; and subjecting the coating to a developing operation.

- In testimony whereof w'e our signatures.

MURRAY C. BEEBE.

ALEXANDER MURRAY.