US1861872A - Photomechanical reproduction from half tones or line negatives - Google Patents

Description

June 7, 1932. MURRAY 1,861,872

n`fmuxmcmm1CAL REPRODUCTION vFROM HALF ToNEs 0R LINE NEGATIVES Filed March 12.*'1930 ine A?, exnderMurrqy.

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, Patented June 7, 1932 UNITED STATES PATENT OFFICE ALEXANDER MURRAY, Ol' ROCHESTER, NEW' YORK, ASSIGNOB '10 EASTIAN KODAK COMPANY, OI ROCHESTER, NEW YORK, A CORPORATION OF NEW 'YORK PHOTOHEOHANICAL mRODUCTION FROM HALF TONES OZB.v LINE. N EGATIVES Application :led Kirch lil,4 1930. Serial N0. 435,077.

'cation seran Number 374,238, med June 2'7,

This invention relates to photo-engraving and litho aphy and more particularly to photo-mei'anical reproductions from halftone or line negatives.

One object of the invention is to provlde copies or duplicates of photo-mechanical halftones or line negatives by a cheap and convenient method.

Another object is to provide a convenient and time-saving method of obtaining color proofs before the nal printing plate has been made. According to present ractlce by the usual indirect method used in lithography for obtaining the screen color positive, it is not possible to obtain a proof of any one of the color plates until the final plate has been made. If the retouchin'g is incorrect or for any reason the plate is imperfect, it is necessary either to discard one or two plates and the final lithographie plate, or to make an additional correctlon p ate, thereby adding greatly to the expense of the process. By my invention it is possible to obtain a color proof from the screen positive made from the original color separation negative before making the screen color negative and printing the latter on the final plate. It is then easily possible to correct or retouch so as to` give the proper color renderin at an early stage so 3o that the iinal stages o preparing the screen negative and the lithographie surfaces need not be repeated.

A method is needed for making a negative or positive containing stencil-like dots from a negativel or positive containing soft or graded dots. Also it frequently happens that a hote-mechanical negative becomes damage or broken in use and it will be de sirable to have a copy or duplicate of the same.. In other cases it would be desirable to have a number of such negatives without the trouble of producing them in the original manner. In still other cases the duplicate could be kept as a matter of record. The present invention represents a very cheap, convenient and rapid method of making such duplicates.

The method I propose is similar in some respects to that proposed for making negatives from printing forms described in my appli- 1929. The process, however, differs from that disclosed in the former application in several important details.

ReferenceA is made to the drawing.

Figure l is a cross section showing the negative which is to be duplicated and a sensltive layer on to which it is being printed.

Figure 2 shows the sensitive layer after it is inked, developed, and dyed.

Fi ure 3 shows the sensitive layer after it is accompanying inke developed, Idyed andthe ink removed.V

Figure 4 shows in cross section the rocess carried out on a plate coated with asp alt.

Figure 5 shows the dye image made from the form shown in Fig. 4.

Figure 6 shows a variation of the method where both an asphalt and shellac layer are used on the su port.

Figure 7 s ows the asphalt and shellac layer after the portion of the surface consisting of shellac has been removed.

Figure 8 shows the final surfaceconsisting of the dye image and clear shellac.

I will now describe my invention and two of its preferred forms as applied to the making of copies of photomechanical halftones or line negatives or positives .and to the method of making color proofs from them. I do not, of course limit myself to the two forms described.

The invention in its simplest form is applied to the making of duplicates ofphotomechanical negatives. For this purpose I first prepare ali ht sensitive surface by coating` a sheet of g ass orfllm 1 with a bichromated colloid layer 2 in a' manner well known in the art. Examples of the kinds of bichromated colloids which may be used are bichromated albumen, glue or gum arabic. This sensitive coating is, as shown in Fig. 1,

placed in contact with the negative to ber reproduced and comprising support 3 carrying the image layer 4 and exposed to light under it, rendering insoluble the portions reached by the light. After exposure, the printed surface is uniformly inked with a greasy ink. It is then developed by placing it in water which removes the soluble poradheres to the support and'this is then flowed with a dye disso ved in a solvent which does not attack the ink, and which forms a continuous film 7 of color on the surface except where the later is protected by the ink. This may or may not penetrate the very thin remaining layer 8 and is shown for purposes of illustration as a separate dye la er 7 in Fig. 2. The film 8 is so thin that itis not readily detectable and itsv existence is assumed from the fact that `dye adheres. At this stagethe reproduction consists of a relief colloid desi 5 covered with ink 6 and a background o dye 7, as shown in Figure 2. l

After dryin the ink is removed from the surface of t e support by the aid of a solvent, such as benzol, which does not attack the stain or the support. The result (Figure 3) is a negative resembling the original Parts Methyl alcohol-, 85 Aurine 10 Rubine 5 The above stain is typical of many othersl which may be used. The dye should be highly soluble and have a strong absorption from 500 my. into the near ultra-violet region of the spectrum. Y

For the purpose of obtaining color proofs from lithographie reproductions, I use a variation of the above method in the following way. Reference is made to the usual manner of carrying out the operation in a lithographie process. It is common practice first to make a set of color separation negatives. Screen positives are then prepared from these and the screen positives are then printed to form screen negatives. The latter are then printed on the prepared lithographic surface which usually consists of zinc or aluminum having a ained surface.

Lithographic stones may a so be used for` the purpose but their use has largelybeen discontinued. It is customary, also, to perform whatever retouching is required on the screen positive. Heretofore it has been nec essary to follow through this process to completion, that is, to the making of the final rinting surface before a color proof could 55 obtalned. By my invention I can obtain I tions not exposed to the light. A ver thin such color roofs from the screen positive residual. film 8 of the solu lecolloid rmly after it has en retouched and before making the screen negative and preparing the final printing surface. This, ofcourse, saves a great deal of time. result I proceed in a manner ana ogous to that given above as follows:

The method which I now propose may be used either with a screen positive or the Iscreen negative made from it. The former method of using a screen positive is to be preferred, however.

I prepare a sensitive printin surface 10 composed of a white metal suc as zinc or alumnum coated with as haltum which has been sensitized with io oform. This asphaltum is black and repellent to stain. This surface is exposed to light under the screen positive obtained in the usual lithogra hic process. The asphaltum coated meta is then developed with turpentine which washes olf the asphaltum which has not been affected by li ht, presumably leaving as before an excee ingly thin layer. After briefly drying I then immerse this plate in a stain as given above which is re elled by the in` soluble asphaltum. At thls stage we have a design consistin of black asphaltum 11 and the background ye 12. This is shown in Figure 4. The asphaltum of the design is.

now removed b treatment with carbon tetrachloride. here now remains on the plate a positive dye image 12 with clear spaces 13 as shown in Fig. 5. To obtain a proof from this plate, I press into intimate contact with it a sheet of suitable paper which has been moistened with a solvent for the d e. The solvent extracts the dye from the p ate and `transfers it to the paper, giving a positive colored proof on the paper. To obtain a proof of the proper color, it is of course necessary to use a suitable dye for the stain but this can readily be accomplished as there is a very large assortment of satisfactory dyes. In this manner color proofs can be obtained from each of the color separation screen positives. If any portion of the proof appears unsatlsfactor 1t is only necessary to go back and modify the screen positive by retouching.

To obtain a color proof from the final screen negative itis necessary to add another step to the process thus mentioned. A sheet of white metal 20 is coated with bichromated shellac. is exposed to light under t e screen negative. It is then developed with denatured alcohol which removes the parts unaffected b light leaving a relief 21. Here as before t ere is presumably left an exceedingly thin layer of the shellac. After drying, this surface is brushed over with a solution of black asphalt in benzine. This is done by gently rubbing the surface with a tuft of cotton or a soft pad, The asphalt adheres to the plate To accom lish thisv After drying, this surface I,

removed. This condition is represented in Figure 6. After the asphalt coating is dried,l

the shellac -remaining 1s now removed with alcoholic ammonia. The surface is now flowed with the staining solution whichis repelled by the asphalt, producing a dark asphalt image 22 in a dye background 2? as shown in Fig. 7. Finall after again drying, the asphalt 1s removed, eaving a stain or dye positive 23 on the plate with colorless portions 24 therebetween. Since these portions have been obtained by different means, these layer portions may not be o f equal thickness as shown (Figure 8). proof can then be obtained from this late in the same manner as before, that is, y pressing into contact with it a sheet of paper moistened with `a solvent for the dye.

V It is obvious that numerous methods of the practice and application of my invention are possible and I contemplate as included with- 1n my invention all such modifications and equivalents as fall withinthe scope of the ap nded claims. l

at I claim is:

1. A` process for making a copy of a printing image that comprises forming by photographic steps a layer having a relief image 1n which the relief is composed of portions which are repellent to stain and the other portions of which are receptive of stain, applying to the layer a stain which is contrastive 1n appearance with the repellent portions,

and then/transforming the stain repellant portions linto non-repellant portions which are also contrastive with the stain.

2. A process for making a copy of a printing image that comprises forming by photographic steps a layer having a relief image in whfch the relief is composed of portions which are dark andkrepellent to stain and the -other portions of 4which are receptive of stain, applyin to the layer a stain which is adherent to said other portions, thereby producing an image of dark insolubilized portions in a stain background, and then transforming these last named portions into light colored portions.

3. A process for making a copy of a printing image Vthat comprises exposing to light through the printing image a layer of material which is insolu ilized by light, transforming this layer by a process which includes removal of the soluble portions into a relief ima e in which the relief is composed of insolubilized portions which are Aclark and repellant to stain and the other portions are receptive of stain, applying to the layer a stain which is adherent to said other ortions, thereby producing an image of ark insolubilized portions in a stain background, and then transformin these last named portons into light colore porti ons.

4. A process for making a copy of a printdium which is not a then removing the ink.

5.. A process for making a copy of a printy' ing 1m which comprises ex sin to li ht througlighe printing image I:lola ger of gbichromatednlbimep, coverin a greasy eve oping wit water a l ing to th e layer a stain which is adhlareliilt o the portlons not` covered by ink, and then removing the ink.I

6. A process for making a copy of a printmg image that comprises formlng by photographic steps, a layer having a relief image in which the relief is composed of portions contalnmg a substance which is repellant to stam and other portions receptive of stain, applying to the layer a permanent stain which 1s contrastive in appearance with the 2repellant portions, and then removing the repellant portions of said relief image, leav the sta-1n in the unprinted portions of sai relief image.

7 A process for making a copy of a printmg image thatcomprises exposin to light through a prlntmg image a layer o material Whlch 1s msolubilized by liglht, transforming this ayer with this layer by a process whic includes remov-l al of the solubleportions into a relief im e in which the relief is composed of insolubllized portions which are repellant to stain and other portions which are receptive of stain, applying to the layer a permanent stain which is adherent to said other rtions, thereby producing an image of inso ubilized portlons in a stain background, and then transforming the insolubilized portions so that they are colorless and transparent.

8. process for making a color print that comprises formlng by photographlc ste a rellef image in an organic material in wEch the relief is the light affected portion, applylng a stain dissolved in a medium which 1s not a solvent for said relief and therefore does not penetrate said relief, the stain affecting the low portion, fected portion of the relief image with a me'- solvent for said stain, leaving the stain design and then transferring said stain design to a final support.

removing the light af- I zoo` 9. A process for making a color rint that i las .low porton, removing the light aected or- `tion of the relief image with a medium w ich is not a' solvent for stain leaving the stain design and thentransferring said stain j s design to a final support by moistening the sugport with a solvent for said stain design. lgned at Rochester, New York, this 6th day of March, 1930. I

ALEXANDER MURRAY.l

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