US3222174A

US3222174A - Process and material for the manufacture of etched printing plates

Info

Publication number: US3222174A
Application number: US66316A
Authority: US
Inventors: Rott Andre; Verelst Johan Lodewijk
Original assignee: Gevaert Photo Producten NV
Current assignee: Gevaert Photo Producten NV
Priority date: 1959-11-03
Filing date: 1960-10-31
Publication date: 1965-12-07
Anticipated expiration: 1982-12-07
Also published as: NL244985A; CH399182A; NL100818C; BE584847A; GB938960A; DE1422490A1

Description

Dec. 7, 1965 A. RoTT ETAL 3,222,174 PROCESS AND MATERIAL FOR THE MANUFACTURE OF ETCHED PRINTING PLATES Filed 001;. 31, 1960 ATTORNEYS United States Patent i PRCESS AND MATERIAL `FRTH'E MANUFAC- The present invention relates to etched printing plates, and more particularly to photographic stripping material used for the manufacture of such printing plates.

The processes for the manufacture of etched metal printing plates by means of photographically obtained gelatin images manufactured and `hardened on stripping lm are generally known. This stripping lm mainly consists of a light-sensitive and unhardened gelatino silver halide emulsion layer coated on a thin -cellulose ester lilm, called a permanent support, which in its turn is applied in such a way to a thicker transparent film support, called a temporary support, that it can be stripped olf. For this temporary support the raw materials used for the manufacture of photographic supports, eg., cellulose esters, polyesters, polycarbonates, polysulfonates and polyamides can be used. l

In these processes, the following treatments for instance are applied:

(l) The light-sensitive layerof the stripping film is exposed through a screen and a diapositive. l

(2) The light-sensitive layer is treated with a tanning developer and, as the case may be, fixed, washed and dried.

(3) The treated stripping lm is transferred onto the wetted metal surfa-ce byvpressing with a roller.

(4) The temporary support is removed.

(5 The permanent support is removed.

v(6) The non-hardened gelatin is washed away wit warm water and the gelatin relief obtained is dried.

(7) The metal surface is etched.

The removal of the temporary support is effected easily by stripping olf; the removal of the permanent support, however, is a delicate treatment which easily leads to failures.

For the removal of the permanent support, the following conventional techniques are employed:

(a) The layer serving as permanent support and usually consisting of nitrocellulose is dissolved with acetone or with another solvent, such` as described in U.S. Patent 2,650,878. The control of the complete removal of such nitrocellulose permanent support, however, is diicult and if said removal is not properly accomplished this may lead to irregularities in the subsequent treatment of the emulsion layer with warm water.

(b) The permanent support Vconsisting of nitrolcellulose is allowed to swell in methanol or ethanol and is then treated with warm water whereby it can be stripped off since the subjacent unhardenedemulsion melts off.

The penetration of `sufficient water for enabling this melting olf requires, however, much time and a rather high temperature of the water. p

A particular d-iliculty for removing the permanent support arises if in the previous treatment the hardening of the image layer has reached the permanent support. In order to avoid this evil, it is known to apply a special low-melting gelatin layer between the light-sensitive layer and the permanent support (Belgian patent specification 564,233).

Now we have found that the permanent support can be removedfaster and without supply of heat by stripping u 3,222,174 Patented Dec. 7, 1965 it as a coherent membrane which is `done by wetting this support for a few seconds with armixture containing a solvent for this support and a less, volatile nonsolvent and then evaporating the mixture in the air for a few seconds.

The accompanying drawing shows a sectional View of a stripping film which is suitable for the application of the process according to the present invention and wherein the layers represent:`

(1) an anti-halation layer (2) a subbing layer (3) a temporary support (4) astripping layer (5) a permanent or thin support -of cellulose ester containing 5-40 plast-icizr (6) asubbing layer (7) alightfsensitiveemulsion,

Although the exact mechanism of this surprising effect is not quite known, it can be admitted that the act-ion of the mixture of the solvent and the non-solvent (e.g. acetone and water) occurs asfollows: during the first seconds of the action of the acetone lon the nitrocellulose, the molecules of the latter are solvated by the acetone molecules, so Athat the thin nitrocellulose layer obtains a jellylike consistency. `Duringv the subsequent short drying period, the acetone concentration falls together with thel degree of solvation.. From acertain moment the consistncy of the nitrocellulose suddenly changes from jellylike into a more coherent and half-solid state which perhaps means that the` acetone is no longer held by solvation but by absorption by the nitrocellulose. This transition is quite sharp, `occurs practically discontinuously and is accelerated by the cooling action of the acetone evaporation. The usually occurring white coloring of the nitrocellulose i-s explained by the precipitation of the latter caused by the Water present. By the strong swelling and ilocculati-on, the permanent support consisting of nitrocellulose has lost contact with the subjacent gelatin layer and can be stripped therefrom very easily. A

The new process is more reliable if an adapted amount of a swelling agent for the permanent support, such as e.g. ethanol, is added to the mixture of solventand nonsolvent used. Hereby the time schedule for stripping off the permanent support is considerably widened so that on drying there is no risk that the permanent support will become adhered again to the gelatin.

`In order to expedite this process care should be taken that on manufacturing the material herein applied, the

, cellulose ester lm serving as permanent support contains a relatively` considerable amount of plasticizer; for this purpose a pla-sticizer in an amount ranging from 5 to 40% but preferably of at least 10% can be added to the casting composition from which the permanent support is cast, or, if the temporary support consists of a cellulose ester, a support can be used which contains a large amount of plasticizer which afterwards can pass into the permanent support by diffusion.

Suitable plasticizers are eng. triphenylphosphate, tricresylphosphate, Palatino] A, Palatinol M, Palatino O (trade names for diethylphthalate, dimethylphthalate, resp, di(methoxyethyl)-phthalate, marketed by Badische Anilin- & Soda-Fabrik A.G., Ludwigshafen/Rh), Santicizer (trade name for tolyldiphenylphosphate, marketed by Monsanto Chemical Company, St. Louis, Mo., U.S.A.), Sipalin (trade name for dicyclohexyl ad-ipate marketed by Deutsche Hydrierwerke A.G., Dusseldorf-Holthausen) and Triacetin (trade name for glycerine triacetate marketed by Farbenfabriken Bayer A.G., Leverkusen). The thickness of the subbing layer between thevernulsion layer and the permanent support mustbe very thin if nomplasticizer is incorporated in the permanent support. Thus e.g. for a temporary cellulose 3 ester support and for a permanent support which coritains no plasticizer, this subbirig layer r'iust not be thicker than 0.2,u.. If, however, in the permanent support a relatively large amount of plasticizer is incorporated, the

thickness of the aforesaid subbing layer is not as critical. Preferably, however, a thickness smaller than 0.4/1. is used. In the new process no warm water is needed for the removal of the permanent support (treatment 5). Since it is also possible to exclude the use of warm water in treatment 6 by carrying out the Washing away of the non-hardened gelatin parts (treatment 6) with peptizing solutions such as aqueous solutions of ammonium bromide, sodium salicylate, potassium rhodanide or urea, or with proteolytic enzymes, the application of the process acording to the present invention enables to exclude before etching (treatment 7) the prolonged cooling of the cppr cylinder serving as printingplate. In this way the whole process of the'n-ariufctdre of printing plates is considerably shortened. i

The following examples illustrate the invention without limiting, however, the scope thereof.

EXAMPLE l Materal.-A stripping lm is manufactured by applying successively the following layers onto the front side of a cellulose triacetate support (I) of a thickness of 0.15 mm., the rear side of which is provided with the usual photographic subbing (II) and anti-halation layers (III).

(1) A stripping layer (IV) from the following composition:

Nitrocellulose g 8 Ethylcellulose g 4 Methanol cc 700 Acetone cc 250 n-Butanol cc 50 (2) A permanent support (V) from the following composition:

Nitrocellulose g 40 Tricresylphosphate g 10 Dicthylether cc-- 200 Ethanol cc 700 n-Butanol cc 100 (3) A subbing layer (VI) from the following composition:

Gelatin g 2 Water cc 17 Acetic acid cc-- 1 Methanol to cc-- 1000 (4) An ortho-chromatically sensitized silver chloro-- bromide emulsion (VII) with normal gradation and which does not contain hardeners at all.

Treatment 1 This light-sensitive material is rst exposed through a gravure screen and then through a continuous tone diapositive.

Treatment 2 The exposed material is treated for 3 minutes in a development solution of the following composition: Sodium sulfate (anhydrous) g-- 5 Sodium sulte (anhydrous) g-.. 20 Pyrocatechol g 6 Pyrogallol g 8 1% solution of 6nitrobenzimidazole in methanol cc 8 Water to oc 1000 Hereupon the developed material is immersed for 3 minutes into a solution consisting of Sodium carbonate (anhydrous) g 170 Water to cc- 1000 The developed material is then fixed for 5 min. in a solution consisting of Water cc 800 Sodium thiosulfate g 200 Potassium metabisulte g 25 Water to M cc-- 1000 Treatment 3 After washing and drying, the lm sheet is transferred, by pressing, onto a wetted copper plate.

Treatment 4 After 1 min. the temporary support is removed by stripping.

Treatment 5 A mixture consisting of Acetone cc 400 Ethanol cc-- 500 Water cc 100 is poured onto the plate and after 15 sec. of action and 15 sec. of drying at the air, the nitrocellulose membrane is stripped olf.

Treatment 6 The unhardened gelatin of the image layer is washed out with warm water whereupon the subsisting resist is dried. The image areas which are not to be etched are covered.

Treatment 7 The plate is then etched with aqueous fcrric chloride solutions as usual in gravure.

EXAMPLE 2 A stripping film is manufactured by successively applying the following layers to the front side of a polyethylene terephthalate support (I) of 0.10 mm. thickness, the rear side of which is provided with the usual photographic subbing (II) and antihalation layers (III):

(l) A stripping layer (IV) from the following composition:

Copolymer of vinylidenechloride and acrylonitrile g 20 Methylene chloride cc 250 Ethyl acetate cc 250 Acetone cc 530 (2) a permanent support (V) from the following composition:

Cellulosetriacetate g 40 Triphenylphosphate g 16 Methylene chloride cc 500 Ethanol cc 250 Dichloroethane cc-- 250 (3) a subbing layer (VI) from the following composition:

(4) a silver chloro-bromide emulsion such as in Example 1.

This stripping lm is further exposed, developed and fixed as in Example l.

After washing and drying, the film sheet is transferred by pressing onto a wetted copper printing cylinder. After 1 min., the temporary support is removed by stripping. The cylinder is then washed with a mixture consisting of:

Acetone cc 85 Methanol cc 'l0 Wat-er cc 5 AfterlS sec. of action the cylinder is dried for a short time in the air whereupon the cellulosetriacetate sheet is stripped -oif as a coherent membrane. Next, the gelatin image layer is washed out for 6 to 10 min. with an unheated aqueous solution of sodium salicylate. After this washing period, the remaining gelatin relief is treated by pouring thereon an unheated mixture consisting of ethanol (800 cc.) and water (200 ce), and quickly dried in a cold air current. Immediately thereafter the etching can be started.

We claim:

1. A process of making an etched printing member lby means of a photographic light-sensitive stripping ilm, said lm having an unhardened gelatino silver halide emulsion layer carried on a thin permanent support of cellulose ester containing about 5-40% by weight plasticizer, which support is adhesively joined to a temporary support by a stripping layer, by the steps comprising:

(l) Exposing the emulsion `layer separately through a screen and to an image to be printed;

(2) Photographically developing the thus-exposed lm lby tanning development, fixing, and washing;

(3) Applying the iilm to a metal printing member by pressing the washed, developed gelatino layer there- `of into contact with the moistened surface of said member;

(4) Stripping the temporary support from the lm so applied while said permanent support and gelatino layer remain on said member;

(5) Infusilng the remainder of the ilm while in place `on the printing member after step 4) with a liquid mixture containing by volume at least about 40% of a water-miscible organic ketone, which is a solvent for said permanent support, at least about 5% of water, and up to about of a lower alkanol;

(6) Allowing the residual mixture remaining on the lm after step 5) to evaporate for a brief period until tight adherence as a coherent sheet of the permanent support of the gelatino layer is loosened;

(7) Forcibly peeling said permanent support from said emulsion layer while mantaining the layer not substantially above room temperature, leaving said emulsion layer intact;

(8) Washing unhardened gelatin from said gelatino layer to produce a relief image in hardened developed gelatin emulsion of the image to be printed; and

(9) Applying an etching solution to the printing member carrying said lrelief image to etch the image into the memiber surface.

2. The method of claim 2 wherein said cellulose ester is selected from the group consisting of cellulose acetate and cellulose nitrate, said organic ketone is acetone, and said alkanol contains up t-o two carbon atoms.

References Cited by the Examiner UNITED STATES PATENTS 2,614,932 10/19'52 Nadeau et al. 96-83 X 2,650,877 9/1963 Boyer 96-83 X 2,805,948 9/ 1957 Gerhardt et al. 96-83 2,892,711 6/1959 Sanford et al. 96-83 2,993,790 7/ 1961 Grumbine 96-35 3,057,722 10/1962 Alles 96--35 NORMAN G. TORCHIN, Primary Examiner.

MILTON STEARMAN, Examiner.

Claims

1. A PROCESS OF MAKING AN ETCHED PRINTING MEMBER BY MEANS OF A PHOTOGRAPHIC LIGHT-SENSITIVE STRIPPING FILM, SAID FILM HAVING AN UNHARDENED GELATINO SILVER HALIDE EMULSION LAYER CARRIED ON A THIN PERMANENT SUPPORT OF CELLULOSE ESTER CONTAINING ABOUT 5-40% BY WEIGHT PLASTICIZER, WHICH SUPPORT IS ADHESIVELY JOINED TO A TEMPORARY SUPPORT BY A STRIPPING LAYER, BY THE STEPS COMPRISING: (1) EXPOSING THE EMULSION LAYER SEPARATELY THROUGH A SCREEN AND TO AN IMAGE TO BE PRINTED; (2) PHOTOGRAPHICALLY DEVELOPING THE THUS-EXPOSED FILM BY TANNING DEVELOPMENT, FIXING, AND WASHING: (3) APPLYING THE FILM TO A METAL PRINTING MEMBER BY PRESSING THE WASHED, DEVELOPED GELATINO LAYER THEREOF INTO CONTACT WITH THE MOISTENED SURFACE OF SAID MEMBER; (4) STRIPPING THE TEMPORARY SUPPORT FROM THE FILM SO APPLIED WHILE SAID PERMANENT SUPPORT AND GELATINO LAYER REMAIN ON SAID MEMBER; (5) INFUSING THE REMAINDER OF THE FILM WHILE IN PLACE ON THE PRINTING MEMBER AFTER STEP 4) WITH A LIQUID MIXTURE CONTAINING BY VOLUME AT LEAST ABOUT 40% OF A WATER-MISCIBLE ORGANIC KETONE, WHICH IS A SOLVENT FOR SAID PERMANENT SUPPORT, AT LEAST ABOUT 5% OF WATER, AND UP TO ABOUT 50% OF A LOWER ALKANOL; (6) ALLOWING THE RESIDUAL MIXTURE REMAINING ON THE FILM AFTER STEP 5) TO EVAPORATE FOR A BRIEF PERIOD UNTIL TIGHT ADHERENCE AS A COHERENT SHEET OF THE PERMANENT SUPPORT OF THE GELATINO LAYER IS LOOSENED; (7) FORCIBLY PEELING SAID PERMANENT SUPPORT FROM SAID EMULSION LAYER WHILE MAINTAINING THE LAYER NOT SUBSTANTIALLY ABOVE ROOM TEMPERATURE, LEAVING SAID EMULSION LAYER INTACT; (8) WASHING UNHARDENED GELATIN FROM SAID GELATINO LAYER TO PRODUCE A RELIEF IMAGE IN HARDENED DEVELOPED GELATIN EMULSION OF THE IMAGE TO BE PRINTED; AND (9) APPLYING AN ETCHING SOLUTION TO THE PRINTING MEMBER CARRYING SAID RELIEF IMAGE TO ETCH THE IMAGE INTO THE MEMBER SURFACE.