US1912482A - Photographic printing element - Google Patents

Description

June 6,1'933. wg C, HUEBN'ER 1,912,482

PHOTOGRAPHIC PRINTING ELEMENT.

Filed June 6. 1928 Wi i 72 563 Patented June 6, 1933 UNITED STATES PATENT ori-lcs WILLIAM C. HUEBNER, OF CHICAGQILOLINOIS PHOTOGRAPHIC PRINTING ELEMENT Application filed June 6, 1928.l Serial No. 283,201.

This invention relates to improvements'r in photographic printing element, and more particularly to photographic printing plates having corrected values, for use in making press plates on photo-composing machines.

In the commercial printing art, a great many of the printing or press plates used are made by photographic process, as for instance, press plates for offset printing presses in which most of the commercial color printing is now done. One of the most dificult steps, requiring the highest degree of training and skill in the preparation of such plates, is that \of retouchingfl As well known, when a glass or film negative has been made of the subject or image ultimately to be reproduced by printing, almost invariably certain areas of the negative will require a reduction of the values and other areas an increase of values in order that the proper values corresponding with'the original subject, may he obtained from the printing inks in the printed product, and it is the province of the retoucher to estimate or determine the amounts of such increase or reduction and to treat the negative accordingly by any of the known methods.

Heretofore, the retoucher has always been very seriously handicapped in determining the extent of changes necessary in the values, primarily because there has been no available background or contrasting surface beneath the lm proper ofthe negative, since the negative has always, heretofore, been transparent, it having been the universal belief that completely transparent negatives were necessary in the art. Consequently, as the retoucher has endeavored to, say, 'reduce the size of the 'actinically hardened very a minute dots or particles of the photographic film coating (which dots or particles correspond to the ultimate ink-conveying or printing units on the press plate) he has been unable to obtain a direct basis of comparison of such dots or-particles, or corre.- sponding printing units, with a white surface on which the printing is later to be done. Hence retouching has always involved much uncerifainty, even by the most skilled worker, and has required the taking of numerous proofs or trial impressions and the retouchin'g over and over of the negative, or corresponding positive, or both, before the final photographic printing plate has been considered satisfactory for use in photo- 5a graphing directly on the press plate. Obviously, the diliiculties and disadvantages referred to involve excessive labor and time, resulting in high cost.

The foregoing difliculties and disadvantages have been stated as applying to the making of a single photographic printing plate as, for instance, when only a single color impression is to be made. When multi-color print-ing is considered and which involves the making of a color separation negative for each ofthe color inks to be printed with, it will beseen that the diiiiculties in the retouching step are greatly/multiplied. All of the colorseparation nega-tives or corresponding 7U positives may be retouched until each alone appears to be satisfactory but upon obtaining proofs of the several color impressions, it

is frequently discoveredrthat corresponding areas of two (or more) of the negatives will 7: require retouching,r.where t-he separate colors are combined in the printing to produce a color intermediate the two separate colors.

An object of my invention, therefore, is to provide a new article of manufacture by 8U which photographic printing elements, negatives or positives, such as used in the making of press plates, having corrected values, may be produced in less time, at less expense, with greater ease and greater certainty thanhere- 8 5 tofore. f

Another object of my invention is `to provide a special photographic printing element,'negative or positive, characterized by the fact that it will both transmity and diffuse light rays andalso afford a' comparison background immediately beneath the developed photographic film proper.

Other objects of the invention will more clearly appear from the description and claims hereinafter following.

In the drawing forming a part of this specification, Figure l is a plan view of a photographic'glass plate negative, having my improvements incorporated therein, this of illustration is greatly magnified in order to clearly illustrate the invention.

In the preferred manner of carrying out my invention, I first take a glass plate of the character and quality commonly heretofore .substantially pure white and semi-opaque andused for photographic negatives and having the usual transparent and light-transmitting characteristics, this main glass plate being indicated by the reference 10. As will be understood, the same will be of any desired size corresponding to the size of the subject to be reproduced or photographed, of suitable thickness, and smooth and polished, as customary in the art.

'lhe plate 10 is ,then preferably sprayed with a low point fusible glass, to provide a very thin film or layer thereof over one entire surface or side of the plate. This film or layer of low point fusible glass, commercially obtainable in a very fine comminuted condit-ion, suspended in oil, is then fired, thusv evaporating the oil or other medium of suspension and leaving a permanently affixed, Very thin, layer or film of the fused glass on the surface of the plate l0, which film or layer is indicated by the reference 11, on that exposed portion of the plate in- Figure 1. The fused glass layer or film thus obtained is preferably the layer or film will be of approximately .001 or .002 of an inch in thickness, this thickness being, of course, greatly exaggerated in Figures 2 and 3. Another characteristic of the fused glass film or layer is that it presents a grained or very minutely toothed surface effect which, in turn, is of extreme importance in connection with my invention for two principal reasons. One reason is that the grained or minutely toothed surface effect provides an excellent surface for the retention or anchoring thereto of the chemical solutions later applied and which form the light-sensitive or photographic film proper. The second is that the grains or minute tooth-like projections, while permitting the ready transmission of light through the fused glass layer and main plate 10, nevertheless effectively serve to cause a certain amount of diffusion of the light when impinging upon the said grained surface, the function of this being brought out hereinafter.

After the plate 10 has been prepared with its fused glass layer 11, a coating of lightsensitive film 12, preferably having an albumen base, is applied, the negative then being ready for exposure.

In making the exposure, a previously taken negative of the subject or image to be reproduced and which may be a color separation negative, taken through a half-tonescreen, if for color printing, is then placed in close or intimate contact with the film side of my improved photographie plate. A layer ol': velvet, felt, or equivalent material, capable of absorbing light rays and preventing reflection or refraction thereof, is placed on the opposite or non-film side of the photographie plate. The exposure is then made.

To the exposed photographic printing plate, is then applied, as by rolling, a layer of prin ting ink, preferably an ink having very little varnish and characterized by a short drying period and opaque.

After the layer of opaque ink has dried, the now exposed and inked photographie plate is then placed in a water bath and developed. Those portions of the sensitive film acted upon by the actinic rays will, as Well understood in the photographic art, be hardened, thus producing throughout the photographic film proper, myriads of hardened dots or particles such as indicated at 13, 14 and l5. in Figure 2, and which dots or particles correspond to the ink-conveying dots or units ultimately appearing on the printing or press plate, as will be understood by those skilled in the art.

The photographic plate, after being developed and in the bath, as above indicated, has all of the surplus ink removed and also those portions of the photographie film properwhich were not acted upon by the light, said surplus ink and soft portions of' the photographic film proper being washed away, thus leaving on the surface of the. photogra hic plate, a myriad of dots or units 15, from between which have been removed the soft or non-actinically treated portions 16-16 of the film proper.

During the exposure of the photographic plate, a certain amount of the light rays is 'diffused by the fused glass film ll. thus producing with respect to each of the dots or particles 13, 14, 15, an adjacent area, as indicated at 17, which is semi-hardened by the actinic action and in the removal and washing away of thesurplus ink and film coating` these portions of semi-hardened film 17 will remain, as will be understood.

The next step in the treatment of the plate. is that of the retouehing after the portions 16 of the film 12 have.bee n removed. The plate, lstill in the Water bath, -is then treated frictionally on those areas where a reduction in the values (that is, size) of the ink-conveyors or units is desired. This frictional treatment may be done in 'any suitable manner, as by the use of camel hair brushes, erasers or rolled paper stumps. Referring to Figure 3, the ink-conveying unit or particle 13 is shown as the same as when the plate was developed and washed. -The next adjacent unit 114 is shown with its value or size reduced, as by removal of the portions 17 which were immediately adjacent the same at the end of the developing and Washing step. In this connection, due to the surrounding portions 17 produced by the diffused light being only semi-hardened, they maybe readily removed bythe frictional action, thus facilitating and speeding up the operation.

After the reduction of the values in those areas where desired, the photographic plate is then taken out of the bath and dried, after which the ink dots or portions are coated with lamp black or other suitable opaque mixture. In those portions or areas Where the values require an increase, said areas or portions are filled in by a lithographiev crayon, opaque ink, or other suitable substance, capable of blocking the passage of light, as well understood in the art', thus increasing the sizes, as indicated at 115 in Figure 3.-

rIhe photographic plate is now completed and corrected, as to values, and ready for exposure, either against another negative or, if desired, directly against a sensitized press plate and on either of which will be -reproduced photographically the ink-conveying units, dots or particles having the desired and corrected values to produce the final print.

In the event the corrected value photographic plate is to have the image thereon transferred to another negative, the two film surfaces are brought into intimate conta-ct and a lay- .er of velvet, felt or equivalent light-absorbing material placed on the back side of the negative to be exposed, the lightbeing passed through the prepared photographic plate when making the exposure. As will be understood, the negative to which-the image is transferred in the illustration referred to, may be of glass, film, paper or other suitable material.

By preparing the photographic plates'with the white light-transmitting and diffusing film of fused glass 11, the semi-hardening of the sensitive film proper, as above described,

is obtained and in addition the retoucher has available in correcting the values, a white surface immediately adjacent the ink-conveying units or particles so as to obtain a direct contrast or background for the units or-pa-rticles and by which he is enabled to correctly judge the amount or degree to which the ink-conveying units shall be increased or decreased With reference to the white paper on which the printing is ultimately to be done. In this manner, greater accuracy as to the desirable values is obtained more quickly than in any of the heretofore known methods of retouching or value correcting methods and hence, the cost of producing the printing plate is correspondingly reduced.

In actual practice, when the fused layer or film of glass has been-applied to the main glass plate,thesamewillbethoroughlywashed film of such a thickness as to just cover the grains or toothlike projections of the fused layer, this initial sensitive film then being.

hardened throughout by exposing the same and developing, after which a second film or layer or sensitized material will be applied on the first layer or film and the exposures then made, as hereinbefore described.

Another expedient sometimes employed where the printing units or dots on the ori ginal negative are too large in certain areas and it is desired to reduce the values there/of in making my improved plate, is to stain the desired areas of the original negative with a red aniline dye, the strength of the latter being graduated in proportion to the degree of reduction required. As will be understood by those skilled in the art, where the original negative is a color separation negativ-e with half-tone dots, the application of the dye to the desired areas will reduce the amount of light that may be transmitted therethrough when the exposure is made against my im-l standpoint of expansion or contraction, and

also because it retains its White semi-opacity even when wet. I am aware, however, that a film or layer having semi-opaque, light-transmitting the light-diffusing characteristics may otherwise be obtained, as for instance, by the use of a white lacquer suitably reduced by proper solvents that will dry out, thus leaving the -desired film.

I claim':

1. As an article of manufacture, a photographic printing plate for retouching, said plate having the main portion thereof composed of glass of customary transparent and smooth surface characteristics and provided on one face thereof with an applied, extremely thin, semi-opaque film which remains substantially pure white under dry and wet conditions and through which light is adapted to be uniformly transmitted and slightly diffused; and exposed, light-hardened and developed particles of a previously applied light-sensitive film on said semi-opaque film, the non-hardened areas of said previously applied light sensitive film being removed to thereby leave the corresponding areas of the semi-opaque film directly visible, said directly llO visible areas of the semi-opaque film prescntv for said light-hardened particles to thereby provide a comparative surface when the plate is being retouched While either Wet or dry.

2. As an article of manufacture, a photographic printing plate for retouching, said plate having the main portion thereof composed of glass of customary transparent characteristics and provided on one face thereof with an applied, extremely thin, substantially pure white, semi-opaque film of fused glass and which film is adapted for uniform transmission of light therethrough and slight diffusion; and a layer of light-sensitive film applied on said semi-opaque fused glass film, said semi-opaque fused ilm presenting a substantially pure White background, While either dry or Wet, for the lightsensitive film to thereby provide a comparative surface while the plate is being retouched.

3. A photographic printing element for photographically printing after the values thereon have' been -corrected by retouching, said element comprising: a transparent foundation layer; a thin, substantially pure white, uniform, light-transmitting, light-diffusing, semi-opaque, layer extending over and adhered to one surface of the foundation layer, said semi-opaque layer being of material unatl'ectcd by light and retaining its whiteness when both wet and dry; and exposed, lighthardened and developed particles of a previously applied light-sensitive ilm on said semi-opaque film, the non-hardened areas of said previously applied light sensitive film being ren'ioved to thereby leave the corresponding arcas of the semi-opaque film directly visible, said directly visible arcas of the white semi-opaque layer, While dry or wet` presenting a substantially white comparative background for retouching said light-hardened particles.

. In witness that I claim the foregoing I have hereunto subscribed my name this 23rd day of May, 1928.

WILLIAM C. HUE BNER.

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