US2371773A - Method and means for making engraved plates - Google Patents

Description

METHODl AND MEANS FOR MAKING ENGRAVED PLTES Filed Dec. 5, 1940 UNTA NNE@ @No MEX/0550 AEEA M57 pm TE/PES/ST- cogT/NG 7 "il, Mfgf 22 4 f JlZ/// :1F29

5455 SHEET l Eso/pms 4x52 26j META/ Pm TE' l l Y /lod l 1 9 TPA/vs f-EQ SHEET TAN/VED 4N@ EXPOSED @EEA 25\ C D l l f l @IP 0 l L? i 5455 SHEET 5mm/N6 AYER I ETcH-L f6 J .y r//// ///7///////41 METAL PMTE/ INVENToR Z5 k.A HENRY T NEI/MANN 241 BY `n| 35m, n',

TRANS/:Ek SHE), lTam/NED AND EXPOSE@ En ATTORNEY TAN/VE@ 4N@ EXPOSE-D AEE/s f Jl` y E] f" ETCHED 1412EA @swr-con TED ,42E-A Patented Mar. 20, 19h45 r METHOD AND MEANS Foa Mame l ENGaAvED PLATES p Henry T. Neumann, New York, N. Y. lApplication December 5,1940, serial No. 3763.620

9 Claims.

Thisl invention relates to a method and means for making engraved plates, such as used in printing.

Heretofore it has been the practice to prepare plates of this character by coating a metal plate with a light-sensitive colloidal solution including a bichromate, exposing the dried colloidal film, and subsequently developing the same, washing away the undeveloped portions and etching the plate. This process has been extremely expensive due to the great skill and length of time required to properly prepare the colloidal solution.

and deposit it on the plate. Moreover, the proc- 4 ess could not be used practically if it was desired to enlarge the picture to be printed.

Among the objects. therefore of my invention is generally to improve .upon the prior practice, and to provide a highly practical and efficient method and means of the character described,

which shall be free from the disadvantages and drawbacks above set forth, and whereby may be obtained faithful reproduction of the original picture in great detail.

Other objects of this invention will in part be obvious and in part hereinafter pointed out.

In the accompanying drawing, in which is shown one of the various possible embodiments of this invention,

the relieved carrier layer has been removed and the portion of the `plate thus exposed etched; and

Fig. 1 is a diagram-matic sectional 'view of a l transfer film having a sensitized carrying lay loosely bonded to Ia pellucid base sheet;

Fig. 2 is an edge view thereof at the time of exposure;

l Fig. 3 is an edge view thereof subsequent to4 tanning;

Fig. 4 is an edge view thereof subsequent to fer sheet;

Fig. 8 is an vedge view of the relieved carrier layer on the metal plate after the transfer sheet has been removed; p

Fig. 9 is a sectional view through the carrier resist-coating has been applied;

Fig. 10 shows in section a metal plate after llayer disposed on the metal plate and after a l Fig. 11 is a sectional view of a finished etched f metal plate.

In accordance with my'invention, I prepare a novel photo-sensitive transfer film by applying to a pellucid flexible base 4sheet a carrier layer of flexible' pellucid material having particles of a suitable photo-sensitive material uniformly dispersed throughout. The base Vsheet and the car- .rler layer should'be vso constituted that they coact to form a loose or temporary bond which will permit the carrier layer to be stripped from the sheet while the film is dry but which will cause the sheet and layer to adhere sufliciently well to prevent separation during the developing, hardening and washing-out steps to which the film is subjected later in my process.

To this end, I employ a base sheet 20, such as a film of cellulose acetate, regenerated cellulose, a illm made from rubber such as pliolm, or the like, and mechanically coat one surface of the film, in any manner well known to the art, with a thin lm ofa substance which will loosely bond the ba'se sheet to a carrier layer. Such substance may comprise para-rubber which is dissolved in naphtha for coating purposes. permit the naphtha to dry out and leave a pellucid flexible film' 2| of para-rubber. The

prepared base layer is then coated on its bonded surface with a colloidal solution of sensitized silver bromide and gelatin, which is allowed to dry into a gelatinous carrier layer 22. v

The photo-sensitive transfer lm is then ready to be employed in accordance with the process hereinafter described. If desired, the film at this stage may be put up andfsold in lightproof packages to printing establishments for use in the manner now t'o be described.

In order to prepare an engraved printing plate from my novel photo-sensitive transfer film, I rst form a latent negative image of any desired picture in the lm, in accordance with any method well known to the art. Thus, for example, the latent image may be formed by contacting the film with a pellucid medium carrying the desired picture and passing a beam of actinic light through said medium. If the picture is not of the` ultimate size desired to be printed, an enlarging or reducing camera can be employed to form a'latent image of the required size directly on the transfer film. The transfer film, during exposure, should be so positioned with respect to the picture that the actiniclight beam modulated by the picture passes through the base After coating, I i thin sheet 20 sheet before reaching the sensitized colloidal layer (see Fig. 2).

After exposure, the film is developed in the usual manner, slightly washed, and then placed in a suitable hardening bath. Such hardening bath may be prepared in the following manner:

I form a. stock solution A comprising 500 cc. of water, 20 grams of ammonium bichromate, 4 cc. of sulphuric acid, and sumcient water to make one liter. Stock solution B is prepared by adding l5 grams of sodium chloride to sufficient water to make one liter. The hardening bath is then made by adding one part of solution A and one part of solution B to six parts of water.

After the transfer-nlm is removed from the hardening bath,it is submerged for about three or four minutes in lukewarm water having a temperature ranging from about 110 to 150 F., in order to wash away the unexposed and untanned gelatin23. This will leave a relief fllm comprising the base sheet to which is loosely bonded a tanned silver gelatin negative image 24. The transfer film at this stage may be either left wet or dried before proceeding tothe next step.

I next place the relief transfer illm in cold water and superpose the same upon a transfer sheet 25 which is also held `under water. The gelatin side of the transfer film is placed against the transfer side of the transfer sheet. The superposed sheet and film are then lifted out oi' the water and squeegeed on a at surface to remove water and to firmly press the 'sheets t0- gether. I next allow the assembled film and to dry and then strip on the base sheet of the transfer illm.

At this time, due to the loose bond between the tanned gelatin layer 22 and the base sheet 20, and due to the much greater adhesion be tween the hardened gelatin layer 24 and the transfer side of the transfer sheet 25, the hardened gelatin layer 23 will be detached from the base layer 20 and will adhere to the transfer sheet 25.

Any standard transfer sheet or decalcomania may be used in the above step of my process as the bondrbetween the colloidal layer and base sheet is only slight and is of a much lesser order .than the bond created in my process between the contacted dried film and sheet and between the transfer layer and backing layer of the dried transfer sheet'. Such transfer sheet, by -way of example, may consistof a thin backing layer of porous paper on which a thin coating of a starch and sugar solution has been applied and allowed to dry, and over which a layer of gelatin has been formed and-also allowed to dry.

I next prepare a metal plate 26, such as is commonly used in the printing art for engraving and which has an absolutely clean surface. The transfer sheet 25 with the hardened gelatin image 24 adhered thereto and the metal plate 28 are submerged in a bath of cold water and the image side of the transfer sheet 25 superposed against the clean surface of the metal plate 26. The sheet and plate are removed from the bath in contacting krelationship and squeegeed to remove water and to firmly press the sheet and plate together. The assembled sheet and plate are then allowed to dry.

Next the contacting sheet and plate are dipped in a hot water bath for about two to three minutes, said bath being kept at a temperature of about from 110'? to 150 F. While in the bath, the backing layer of the transfer sheet is reasvmvs moved and the transfer layer dissolved, leaving the tanned hardened silver gelatin negative image 24 firmly adhering to the clean surface of the metal plate 25. 'Ihe plate is then removed and allowed to dry.

After drying the entire plate 26 is dipped into a resist-coating solution, made up by way of example of 1 gram of powdered asphaltum to 100 cc. of carbon tetrachloride. The plate4 is then removed from this solution and allowed to drain so as to form an even asphaltum coat 21 which is permitted to dry. Y

Subsequently the clean coated side of the plate 28 is exposed to a source of high temperature, such as an open ilame. 'I'his dehydrates and shrinks the gelatin and causes the portion 28 of the asphaltum coating 2l overlying the same to become extremely brittle and shot with minute cracks, but does not raiect the portion 29 of the asphaltum in contact with the plate. After heating, the coated plate 26 is dipped in an alkali bath comprising, by way of example, a solution of sodium hydroxide to dissolve and wash away the gelatin. At the same time, the portions 28 of the asphaltum coating overlying the image break away, leaving a positive asphaltum image 29 which is afaithful reproduction in great detail of the original image. The plate 26 is nally dipped in an etching bath, such Aas is well knownI in theart, and consisting by way of example of a nitric acid solution having a small percentage of gum incorporated therein so as to produce an even etching` action. If desired, the plate may be used in its last mentioned condition. However, the asphaltum coating 29 on the raised or unetched portions of the plate may be removed by treating the same with carbon tetrachloride.

It will thus be seen that there is provided a method and means for making engraved plates in which the several objects of this invention are achieved, and 'which is well adapted to'meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiments above set forth, it is to be understood that all matter herein set `forth is to be interpreted as illustrative and not in a, limiting sense.-

Hav-ing thus describedlmy invention, I claim as new and desire to secure by Letters Patent: 1. A method of preparing an engraved plate from a picture in which method there is used a transfer film including a pellucid base sheet having a thin pellucid bonding layer on one surface thereof, the other surface of said bonding layer having loosely adhered thereto a pellucid carrier layer having particles of rphoto-sensitive silver halide uniformly dispersed therethrough: said method comprising exposing said transfer lm through the base and bonding layers thereof to a beam of actinic light modulated by said picture to form a, photographic image in said carrier layer. transferring said carrier layer image from said film to a plate, which is t0 be engraved, in such manner that the surface o'f said image which originally contacted the bonding layer is in contact'with the plate, and then etchplate defined by said transferred from the film to the plate and wherein such transference is effected by first transferring said image fromsaid nlm to a transfer sheet and then transferring the imlage from said sheet to the plate.

4. A method as set forth in claim 1 wherein, before the carrier layer image is transferred from the nlm tothe plate, saidimage is developed, the portions of the carrier layer including said image hardened, and the portions of said layer not including said image washed away to form a layer negatively relieved in accordance with the pictur 5. A method as set forth in claim 1 wherein,

before the carrier layer image is transferred from the nlm to the plate, said image is developed, the portions of the carrier layer including said image hardened, and the portions of said layer not including said image washed away to form "a layer negatively relieved in accordance with the picture, and wherein such transference of said image is eiected by nrst adhering the relieved and hardened carrier layer to a transfer sheet with the surface of the relieved layer not in contact with the bonding layer in contact with the transfer sheet, then stripping away the base sheet to leave said relieved layer adhered to the transfer sheet, next adhering said relieved and hardened carrier layer to the plate with the surface of said layer voriginally contacting the bonding layer in contact with said plate, and lastly stripping the transfer sheet away from said relieved layer. Y

6. In a lmethod of preparing an engraved plate from a picture, those steps comprising exposing a transfer nlm including a pellucid base sheet having a thin pellucid bonding layer on one surface thereof, the other surface of said loosely adhered thereto a pellucid carrier layer having particles of photosensitive silver halide uniformly dispersed therethrough to a beam of actinic light which passes through said base sheet and said bonding layer, said beam being modulated by said picture to form a photographic image in said nlm which presents a nat surface to said bonding layer, hardening said image, transferring said image bonding layer having from said nlm to a plate with the nat surface of' said image contacting said plate, applying a resist layer to the portions of the plate within the picture area `not covered by the image. and then,

removing the image.

1. In a method of preparing an engraved plate from a picture, those steps comprising exposing a. transfer nlm including a pellucid base having a thin pellucid bonding layer on one surface thereof, the othersurface of said bonding layer having loosely adhered thereto a pellucid carrier layer having particles of photo-sensitive uniformly dispersed therethrough to a beam of actinic light which passes through said base sheet and said bonding layer, said beam being modulated by said -picture to form a photographic image in said nlm which presents a nat surface to said bonding layer, hardening said image, transferringsaid image from said nlm to a plate with the nat surface of said image contacting 'said plate, applying a resist layer to cover the picture area ofl the plate, and then lucid carrier layer having particles of photo--` sensitive silver halide uniformly dispersed therethrough to a beam of actinic light which passes through said base sheet and said bonding layer, said beam being modul-ated by said picture to form a photographic image in said nlm which presents a, nat surface to said bonding layer, hardening said from said nlm to a plate with the nat surface of said image contacting said plate, applying a resist layer to cover the entire plate, and then removing the image and those portions of the resist layer. covering the image.

9. A method of preparing an engraved yplate 'i from a picture, comprising exposing a transfer nlm including a pellucid base sheet having a thin pellucid bonding layer on one surface thereof, the other surface of said bonding layer having loosely adhered thereto a pellucid carrier layer having particles of yuniformly dispersed therethrough to a beam sheet s i resist coat to dry,

` ing said image of actinic light which4 passes through said base sheet and said bonding layer, said beam being modulated by said picture to form a latent photographic image in said nlm which presents a nat surface to said bonding layer. developing said image, hardening the portions of said layer including said image, washing away the portions of said layer not includto form a layer negatively relieved in accordance with said picture, adhering said film to a transfer sheet with said relief layer inccntact with theltransfer side of said transfer sheet, stripping said base sheet to leave said relief layer adhering .to the transfer side of the said transfer sheet, adhering said transfer sheet to a plate with the nat surface of the relief image in contact with said plate, stripping said transfer sheet from said relief layer, covering the surface of the plate to which said relief layer is adhered with a resist coat, .allowing the applying heat to said plate, washing away. the relief laver and portions of the resist. coat covering the samefand etching the portions of the plate thus exposed.

v HENRY T.

image, transferring said image' photo-sensitive silver halide

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