US1535700A - Selective photographic hardening - Google Patents

Description

' LEONARD T. 'IRQLAND, OF MALDEN, MASSACHUSETTS, ASSIGINOB T KALMUS,

' tion, whereby the other Patented Apr. 28, 1925.

I 1,535,700 UNITED STATES'PATENT OFFICE- COH- strocx & wnsoo'r'r me, or :eos'ron, MASSACHUSETTS, A CORPORATION OF mAssA- onosn'r'rs.

snnn'c'rrvr. iHOTOGBAPHIC HABDENING.

NO Drawing.

To all whom it may concern:

Be it known that LEONARD T. TROLAND, a citizen of the United States, and resident of Malden, in the county of Middlesex and State of Massachusetts, has invented new' and useful Improvements in Selective Photographic Hardening, of which the following is a specification.

This invention relates to the selective treatment of the exposed and unexposed portions of light-sensitive films by which one of the portions, for example the exposed portion, is made harder than the other porthe two portions react differently to subsequent treatment, as for example a hot water etch in which the relatively soft portion is dissolved oii leaving portion in relief or a dye bath in which the dye is"; absorbed predominately by one portion.

It has been proposed to efiect this selective hardening in the developing process by employing a pyro developer comprising pyrogallic acid and an accelerator such as sodium hydroxide or ammonium hydroxide. However, such developers have proved unsatisfactory, particularly in the production of motion picture film where a high degree of perfection and uniformity *is required, owing to their inherent tendencies to harden the unexposed as well as the exposed ortions, to vary fromtime to time in tieir action, to leave the exposed portions more or less For example, the princi al objection to a developer containing so ium hydroxide is its strong tendency to harden the unexposed as well as the ex osed portions of the film; and the chief ob ection to the use of ammofriable, to produce chemical fog, etc.

nium hydroxide, particularly in developing motion ieture film, is the difficulty of securin uni orm results in successive mixtures, this being largely due tothe strong tendency of ammonium hydroxide to lose strength by evaporation when in the concentrated condition in which it is kept prior to mixing with the developer.

Objects of the invention are to provide a film treatin .com osition and method by which the a oresai selective hardening may be effected throughout long series of images with uniformit to restrict the hardening to one of the, a oresaid portions of the film,

to make the hardened portion of the film firmer and less friable, to reduce the chemi- 1 Application filed September 13, 1922. Serial No. 588,086.

cal fogging action of the com osition, to

increase the speed of action of t e composition without substantially affecting the quality-of the action, and to produce relief images which are more sharply etched and WhlCll are less likely to become scratched or otherwise mutilated'in production or in subsequent use.

According to the resent invention the developer and/or har enin composition is prepared by mixing with a eveloper and/or hardener such as pyrogallic acid or other suitable polyhydroxybenzene, a fixed alkali accelerator such as sodium hydroxide and a salt of a relatively weak alkali, such as ammonium chloride orbromide or other halide.

The admixture of the salt of a weak base eliminates the objectionable eii'ectsof the fixed alkali accelerator which have heretofore rendered its use unsatisfactory. Instead of hardening the'light-sensitive film more or less throughout, as pyro developers containing fixed alkali accelerators have heretofore done unless employed with a restrainer such as sodium sulphite, the fixed alkali and alkali halide product is notably free from this tendency. Moreover, in making relief images by etching 011' the unexposed portion of the film, the soft and delicate nature of the reliefs made with a hardener cont ining 'sulphite is avoided with this developer which 'ields exceptionally firm reliefs' and the re 'efs are much more sharply defined, esfpecially in machine 0 eration, than relie s produced by an or inary pyro-ammonia developer.

A small amount of citric acid may be incorporated in the pyro stock solution for its preservative action on the solution before the developer is mixed. As is customary, potassium bromide may be added to the mixture to restrain fog, but as above stated one of theadvantages of the fixed alkali and halide of a weak base combination is that it has this function. .'A satisfactory formula for use in developing and hardening motion picture film in a continuous machine is as follows: pyrogallic acid .82 gms, citric acid, .02 gms, tassium bromide .40 gms, sodium hydroxi e .34 gms, ammonium chloride .17 gms, and enough water to make a total of 100 c. c.

The sodium hydroxide and ammonium chloride react to some extent to form sodium chloride and ammonium hydroxide;

and better results seem to be attained by separately adding the sodium hydroxide and ammonium chloride just before use.-

The preferred method of mixing is to mix the pyro in water, then mix in the chloride, and then add the sodium hydroxide.

To make relief positives with positive stock having therein a yellow dye as disclosed in the applications of Eastman A, Weaver Serial No. 512,300 and Serial No. 512,391, filed November 2, 1921, the development should be carried on for about two minutes at a temperature of F. and the temperature of the etch Water should be about 130 F.

This developer has the desirable characteristics of both the well-known pyro-soda and pyroamnionia developers Without the undesirable characteristics of either. It has the uniformity and reliability of pyro-soda, and the selectivity in hardening of pyroammonia; at the same time it produces less chemical fog than pyro-ammonia so that the developer may be made stron er and the development more complete, an it does not tend to harden the unexposed portions of the emulsion as does pyro-soda. Moreover, this developer seems to be unique in that it produces firmer, sharper, less delicate and less friable reliefs.

This developer eliminates the use of a restrainer such as sodium sulphite which is easily oxidized and unreliable in action and which has a softening effect upon the reliefs, making all the gelatine spongy. The probable explanation of this marked difference in results is that the sulphite developer restrains the hardeningaction throughout both the exposed and unexposed portions Whereas the developer herein claimed avoids any tendency to harden in the unexposed portion inasmuch as it avoids chemical fogmg. -VVhat I claim:

1. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a hardener for hardening one of said portions, a fixed alkali accelerator and a salt of a weak base.

2. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a developer adapted to harden one of said portions, a fixed alkali accelerator, and a halide of a weak base.

3. Acomposition for treating light-sensitive film having exposed and unexposed portions which is constizuted essentially of a polyhydroxybenzene, a fixed alkali accelerator, and a halide of a weak base.

4. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a developer adapted to harden the exposed portions, a fixed alkali accelerator, and an ammonium halide.

5. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a polyhydroxybenzene developer, a fixed alkali accelerator, and ammonium chloride.

6. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a hardener for hardening one of said portions, sodium hydroxide and a salt of a weak base.

7. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a developer adapted to harden one of said portions, sodium hydroxide and a halide of a weak base.

8. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a polyhydroxybenzene, sodium hydroxide and a halide of. a weak base.

9. A composition for treating light-sensitive film having exposed and unexposed portions which is constituted essentially of a developer adapted to harden the exposed portions, sodium hydroxide and an ammonium halide.

10. A composition for treating lightsensitive film having exposed and unexposed portions which is constituted essentially of a polyhydroxybenzene developer, sodium hydroxide and ammonium chloride.

11. The art of treating light-sensitive film having exposed and relatively unexposed portions which comprises mixing with a developer Whose oxidization product is a hardener, a fixed alkali and a salt of a Weak base in such proportions as to convert the fixed alkali at least in part into an accelerator having less tendency to harden one of said portions of the film, and hardening the othe of said portions of the film with the mixture.

12. The artof treating light-sensitive film having exposed and relatively unexposed portions which comprises mixing with a polyhydroxybenzene, a fixed alkali and a halide of a weak base in such proportions as to convert the fixed alkali at least in part into an accelerator having less tendency to harden the unexposed portions of the film, and hardening the exposed portions of the film with the mixture.

13. The art of treating light-sensitive film having exposed and relatively unexposed portions which comprises mixing with a developer adapted to harden the exposed portion, sodium hydroxide and a halide of a weak base in such proportions as to convert the sodium hydroxide at least in part into an accelerator having less tendency to harden one of said portions of the film, and

' droxide into hardening the other of said portions of the film with the mixture.

14. The art of treating light-sensitive film having exposed and relatively unexposed portions which comprises mixing with a polyhydroxybenzene, sodium hydroxide and a salt of a weak hose in such proportions as to convert the sodium hyan accelerator having less tendency to harden the unexposed portions of the film, and hardening the exposed portions ofthe film with the mixture.

15. The art of treating light-sensitive filislliedhaving exposed and relatively unexpo with a developer ada ted to harden the exposed portion, a fix alkali and an ammonium salt, thereh to term on ammonia accelerator, and hardening one of said portions withthe mixture.

16. The art of treating light-sensitive him having exposed and relatively unex posed portions which. comprises mixing with a polyhydro benzene, a fixed alkali and ammonium chi oride, thereb to form an ammonia accelerator, and her ening said exposed portions with the mixture.

Y 17. The art of treating light-sensitive film having exposed and relatively unexportions "which comprises mixing posed portions which comprises mixing with a hardener, sodium hydroxide and ammonium chloride, thereby to form sodium chloride and ammonium hydroxide, and

'film having exposed and relatively unexposed portions. which oomgrises mixin with pyrogailic acid, sodium ydroxide an ammonium chloride, thereby to form sodium chloride and ammonium hydroxide, and

hardening said exposed portions with the mixture. I I

,19. A composition for treating lightsensitive film having exposed and unexposed portions which comprises'a developer whose oxidation product is a hardener, sodium h droxide, ammonium chloride, sodium chloride and ammonium hydroxide.

'20. A composition for treating lightsensitive film having exposed and unexposed portions droxxgenzene, sodium hydroxid ammonium c oride, sodium chloride an ammonium hydroxide.

Signed by me at Boston, Massachusetts this nineteenth da of August 1922.

LEOiIARD TROLAND.

which comprises a polyhy-