US2122404A - Processes of making lithographic reproductions - Google Patents

Description

- UNITED. STATES PATENT OFFICE PROCESSES OF MAKING LITHOGRAPHIC REPRODUCTIONS Fred Harvey Bloom, Fort Belvoir, Va.

No Drawing. Application June 18, 1936, Serial No. 85,929

14 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty there This invention is a continuation in part of my pending application, entitled Processes of making lithographic reproductions, filed December 20, 1934, Serial No. 758,456, and relates to the art of lithography; more especially it is directed to a process for the production of a lithographic plate having a light sensitive surface selectively responsive to the tone values of a negative, the light affected areas of the plate being sufiiciently hardenedv after exposure to permit the immediate transfer of the plate to the press for printing purposes without further manipulation other than the usual washing treatment with developing ink and drying.

One object of this invention is to provide a process for the production of lithographic plates by means of which a photographic negative in graduated tones, or a photographic line negative or their combination, may be transferred directly to a lithographic plate without the use of such intermediaries as cameras, the like.

half-tone screens and Another object of this invention is to provide a process for the production of a lithographic plate surfaced with a light sensitive substance intimately combined with a light absorbing desensitizing material, the mixture functioning to form a light sensitive film adapted to be hardened selectively in accordance with the tone graduations of the negative.

Another object of this invention is to provide a process for the production of lithographic plates wherein an ammonium bichromate solution is intimately combined with an albuminous dye substance, the mixture when of a metallic plate and drie applied to the surface d, providing a printing plate which may be used for printing directly from the negative, so that, the proceeding from the exposure to the finished plate, may be accomplished in a few minutes and with better 0 results than are now possible by the use of lithographic methods requiring a much longer time interval.

Other objects of this inv ention are; to produce a lithographic plate affording an image which occasion demands; to provide a lithographic procwhich clear, evenly colored reproductions ess by are obtained over an exten ded period and at high press speed; and to provide a process by which a lithographic plate may be produced with less labor and expense and in a shorter time than has heretofore been possible in this art.

Photo-mechanical reproductions are usually made as follows:

Line drawings A negative is placed in a printing frame in contact with the coated surface of a sensitized plate and exposed to the rays of an arc lamp for a suitable time interval depending upon the subject Tone graduation work A positive photographic print of the subject is secured and rephotographed using a half-tone screen to produce a half-tone negative in which the subject has been broken up into dots, the number and size of which depend on the mesh 25 of the screen. After this half-tone negative has been developed and dried, it is ready to be exposed to the light in contact with the sensitized plate. From this point on, the procedure is similar to that described in connection with line drawings, except it involves more etching, counter-etching and rolling up. Moreover, the production of a half-tone printing plate in accordance with the preceding mode of operation, quite frequently necessitates several half-tone negatives before a satisfactory plate is obtained, as the dots are sometimes so small, they readily wash ofi, even though hardened by exposure to light.

The preceding lithographic methods, embody limitations with respect to manipulation and expense, which workers in this field have attempted to overcome through the use of processes which enable the plate to be printed directly from the negative without the use of intermediaries in the nature of cameras and screens. Most of these effortshave included the use of a lithographic plate having a light sensitive surface composed of a chromatized colloid. These methods however, have to a large extent been cast aside, as the images produced lacked the strength and flexibility necessary to withstand long press runs at high speed. This want of flexibility and strength as the run progressed resulted in unevenly colored and blurred prints.

It is therefore the aim and purpose of the instant invention to produce alithographic plate, which after exposure for the prescribed time interval and when washed, inked and dried may be transferred to the press and utilized to produce clear, even-colored reproductions. This result has been obtained by the use of-an albuminousdye-mixture intimately combined with an ammonium bichromate solution, the mixture being automatic in its operation, so that when any portion of the negative has been exposed to light for the time interval required to properly print that portion of the negative, the light affected areas of the plate are so hardened as to retard subsequent action of the light rays and hence such portions will not be further materially affected by light rays within the exposure period. Each graduation of tone as it receives the required exposure is similarly hardened by the light action and the result is that no portion of the plate will be over-exposed, assuming a reasonable exposure limit.

Thus a lithographic plate is provided by means of which it is possible to print a photograph direct from the negative, securing the proper tone values for all parts of the negative, and the full amount of detail contained in the negative. short, the instant invention provides in a lithog aphic plate production, all that the same negatii/ would give in an ordinary photographic print on paper, with exception of loss-in detail caused by the plate. This loss of detail, never large, varies inversely with the fineness of the grain of the plate.

To carry the present invention into effect the procedure is as follows:

Preparation of the sensitizing solution tion. This mixture is stirred with a stirring rod until the albumen has absorbed suificient water to appear moist and when this has occurred it is gently agitated with an egg-beater'until all of the albumen has been dissolved, and then allowed to stand from three to five hours, the time required to reduce the heavy foam produced by the eggbeater, to a thin layer.

Ammonium bichromate solution To provide a suitable ammonium bichromate solution for this process, 322 grains of ammonium bichromate are dissolved in four ounces of hot water. The solution is then slowly filtered into a thirty-two ounce graduate through absorbent cotton. This filtering operation should be carried out with a clean glass funnel into the bowl of which there has been placed a piece of suitably moistened absorbent cotton about three inches square. The center of the piece of absorbent cotton should be forced'into the neck of the funnel with a stirring rod or'the like, but care should be exercised not to pack the cotton to an extent which would interfere with the filtering process.

Immediately after the ammonium bichromate solution has been filtered, the pheno-safranineegg-albumen-mixture is poured into the bowl of the funnel, the thin layer on the surface of the albumen mixture having been first removed.

' acid to one gallon of Before the contents of the funnel have started to filter through, a half of monia (25 Baum) is added. The solution is then slowly filtered into the graduate containing the ammonium bichromate filtrate. When the filtration oi the egg-albumen-pheno-sai'ranine-ammonium solution has been completed the contents of the graduate, which should be about twenty-four ounces, are refiltered and the resulting filtrate poured into acontainer preferably a colored bottle.

Although in the preceding description phenosafranine identified in the color index of the Soclety of Dyers and Colorists, published January 1926, as diamino-phenyl-diphenazonium-chloride, color index No. 840, has been designated as the desensltizing dye, it is to be understood that various other desensltizing dyes such as-Pinocryptol Green, Methylene Blue, Rhodamine, Malachite Green, and ictoria Blue may be employed.

In the color index of the Society of Dyers and Colorists, published January, 1934, the preceding dyes in the order of their enumeration have the following color index numbers: 824a, 922, 761, 657-3, and 729 respectively.

Coating the plate Before receiving its sensitizing coating, the plate is placed under a water tap, swilled and treated with a solution consisting of two ounces of nitric acid and four ounces of potassium alum to one gallon of water. Instead of the nitric acid and potassium alum solution, just mentioned, a solution consisting of two ounces of glacial acetic water may be used. After the plate has been treated with one of these solutions (a piece of cheese-cloth being preferably used for this purpose), and while it is still wet, the plate is fiowed hereinabove defined. The sensitizer is usually distributed over the face of the plate and'dried by means of a whirler, rotating at 'a speed of about sixty revolutions a minute. When it has been dried the plate should be placed in the vacuum printing frame without undue delay.

Exposure of the plate The plate having been suitably mounted in the vacuum printing frame, it is exposed under a negative to a thirty ampere open are light at a distance of approximately 30 inches. The time of exposure for the average negative is one minute and forty-five seconds. Denser negatives require a longer, thinner or flat negatives less exposure. Should the negative be very dense it is advisable to shorten the distance of the are light from 30 inches to 26 inches, and in the event the negative is very flat or thin, the distance of the are light from the printing frame should be increased to 34 inches. All of the above distances and exposures are based on a 30-ampere open are light.

The plate having been removed from the vacuum printing frame is treated with an even coating of developing ink applied with a piece of cotton. The plate is then dried for a short period.

Clearing the plate After receiving its coating of developing ink the plate is placed in a tray of water, the latter being at a .temperature of 90-97 F., and in a few seconds the image appears, whereupon the background is removed, using for this purpose a moist piece of cotton. Care should be exercised in the ounce of strong amwith the sensitizing solution hasty treatment during this operation, 111812;?"

suit in a ruined plate. A rotary motion with the cotton is recommended, as rubbing from right to left and up and down may produce a streaky image. Should difficulties be encountered in the operation of clearing the image due to overexposure, it has been found expedient to aid removal with a solution consisting of four tablespoons of sodium bicarbonate to one gallon of water. This solution is applied by dipping a wet piece of cotton into the bicarbonate solution and applying it to the entire plate surface. After the plate has been treated with the bicarbonate solution, the removal operation is continued as prev'ously stated. When satisfactorily cleared, the late is dried and then positioned on the press for the run. In the event the plate is not to be used immediately, it is gummed and filed.

The procedure for reproducing line drawings from plates prepared in accordance with this invention, with exception of the exposure interval, is similar to that described in connection with the reproduction of photographs, portraits and the like. The exposure interval for line drawings may cover a period of from one to fifteen minutes, without ruining the plate. This flexibility of exposure constitutes quite an aid to a novice in the art, owing to the assurance which it gives. Alteration of the image on a plate produced as hereinabove described, becomes a comparatively simple matter. For instance, should it be necessary to make an addition to the image on the plate, the latter is swilled and treated with a weak hydrochloric acid solution consisting of one ounce of hydrochloric acid and one gallon of water. After this treatment with the hydrochloric acid solution, the requisite addition is made using for the purpose, a preparation commercially identified as Tusche. When the addition has been made the plate is allowed to stand approximately thirty minutes, until the work has been dried and hardened. To remove a portion of the image on a plate the latter is swilled and the undesirable part of the image erased by means of a snake-stone or gamberger stick. After the erasure, the plate is again swilled and treated with the hydrochloric acid solution as in making the addition.

In conclusion, it is evident the instant invention materially simplifies procedure in the lithographic art and makes it possible for an individual possessing but little experience in this field, to be trained so as to be able to produce excellent lithographic reproductions in a relatively short time.

Having described my invention, what I claim as 'new and wish to secure by Letters Patent is:

1. A process for producing a printing plate, consisting in treating egg-albumin in the presence of heat with a light desensitizing-dye, then after allowing the albumin and dye mixture to stand for a predetermined period, combining the mixture with an ammonium bichromate solution, then coating a plate with this chromatized mixture to form a light sensitive surface adapted to be selectively hardened in accordance with the tone values of a negative, exposing the surface to the action of light, the light affected areas of the surface, when hardened by exposure, being further unaffected to any material extent by light rays during the exposure period and then inking, washing, clearing and drying.

2. A process consisting in introducing egg albumin into a light desensitizing-dye solution in the. presence of heat, then after allowing this solution to stand for a period of three to five hours, combining the dye-treated albumin with an ammonium bichromate solution, then coating a plate with the mixture thus formed, to produce a light sensitive surface adapted to be selectively hardened in accordance with the tone values of the negative, then exposing said surface to the action of light, the light affected areas of the surface hardened by exposure, being further unaffected to any material extent by the light rays during the exposure period and then inking, washing, clearing and drying.

3. A process for producing a printing plate consisting in introducing egg albumin into a light desensitizing dye solution in the presence of heat and within the temperature range of 120 to 135 F., allowing this solution to stand from three to five hours, combining the mixture with an ammonium bichromate, solution, then coating a plate with the chromati d mixture to form a light sensitive surface adapted to be selectively hardened in accordance with the tone values of the negative, exposing said surface to the action of light, the light affected areas of the surface when hardened by exposure, being further unaffected to any material extent by the light rays during the exposure period and then inking, washing, clearing and drying.

4. A process for producing a printing plate which consists in preparing a light desensitizing dye solution adding eitherpowdered or flaked egg albumin to the dye solution in the presence of heat, then after allowing this mixture to stand from three to five hours, combining the solution with an ammonium bichromate solution, coating the plate with this chromatized mixture to form a light sensitive surface adapted to be selectively hardened in accordance with the tone values of the negative, then exposing said surface, the light affected areas of the surface when hardened by exposure being further unaffected to any material extent by light rays during the exposure period inking, washing, clearing and drying.

5. A process for producing a printing plate consisting in preparing a light desensitizing dye solution, adding either powdered or flaked egg albumin to the dye solution in the presence of heat, then after allowing the mixture to' stand from three to five hours, combining it with the addition of ammonia, to an ammonium bichromate solution to form a light sensitive surface adapted to be selectively hardened in accordance with the tone values of the negative, exposing said surface to the action of light, the light aifected areas of the surface when hardened by light being further unaifected to any material extent by light rays during the exposure period inking, washing, clearing and drying.

6. A process for producing a lithographic plate, consisting in preparing a light desensitizing dye solution, introducing egg albumin into the solution in the presence of heat and within a temperature range of 120 to 135 F., then after allowing the mixture to stand from three to five hours adding ammonia with the addition of an ammonium bichromate solution, coating a printing plate with the chromatized mixture to form a light sensitive substance, adapted to be selectively hardened in accordance with the tone values of the negative, exposing said surface to light, the light affected areas of the surface when hardened by exposure, being further unaflected to any material extent by light rays during the exposure period inking, washing, clearing and drying.

u HHH HHHHHHH H 7. A process for producing a printing plate, consisting in preparing a, diamino-phenyldlphenazonium-chioride solution, introducing egg albumin into the solution in the presence of heat and within a temperature range of 120 to l35 F., then align allowing the mixture to stand from three to five hours, adding the mixture, with the addition of ammonia, to an ammoniumbichromate solution and then coating a printing plate with the mixture to form a light sensitive substance, adapted to be selectively hardened in accordance with the tone values of the negative, exposing said surface to the action of light, the light afiejyedareas of the surface when so hardened to e .posure of light, being further unaifected to any material extent by light rays during the exposure period inking, washing, clearing and drying.

8. A light sensitive element comprising a'sub-' stantially gelatin-free egg-albumin, treated in the presence of heat with a light desensitizing dye and containing a chromatizing agent and which after exposure to'light and without fur- I ther treatment other than inking, washing and clearing, will produce clear and evenly colored prints at high speed and over an extended press run.

9. A light sensitive element comprising a 'substantially gelatin-free egg-albumin, treated in the presence of heat and within the temperature range of 120 to 135 F., with a light desensitizing dye and containing a chromatizing agent and which after exposure to light and without further treatment, other than inking, washing and clearing, will produce clear and evenly colored prints at high speed and over an extended press run.

10. A light sensitive element comprising substantially gelatin-free egg-albumin treated in the presence of heat with a light desensitizing dye and containing an ammonium bichromate, and which after exposure to light and without further treatment other than inking, washing and clearing, will produce clear and evenly colored prints.

11. A light sensitive element comprising substantially gelatin-free egg-albumin treated in the presence of heat and within a temperature range of 120 to 135 5., and with a light desensitizing dye containing an ammonium bichromate, which after exposure to light and without further treatment other than inking, washing and clearing, will produce non-blurred and evenly colored prints at high speed and over an extended press run.

12. A light sensitive element comprising a sub= stantially gelatin free egg-albumin treated in the presence of heat with pheno-safranine and containing a .chromatizing agent and which after exposure to light and without further treatment other than inking, washing and clearing, will produce clear and evenly colored prints at high speed.

13. A light sensitive element comprising a substantially gelatin free egg-albumin treated in the presence of heat with pinocryptol green, and containing a chromatizing agent and which after exposure to light and without further treatment other than inking, washing and clearing, will produce clear and evenly colored prints at high speed.

. 14. A light sensitive element comprising a substantially gelatin free egg-albumin treated in the presence of heat with methylene blue, and containing a chromatizing agent and which after ex- .posure to light and without further-treatment other than inking, washing and clearing, will produce clear and evenly colored prints at high speed.

FRED HARVEY BLOOM.