US1518426A - Process of producing color negatives for photomechanical printing plates - Google Patents

Description

J. A. H. HATT PROCESS OF PRODUCING COLOR NEGATIVES FOR PHOTOMECHANICAL PRINTING PLATES Filed June 2, 3,919

IN VENTOR ORNE Y PatentedDec.9,1924.

UNITED STATES JOSEPH ARTHUR HENRY HAT'I, 0F BROOKLYN, NEW YORK.

Application filed June 2,

To all whom it ma concern:

Be it known t iat I, JOSEPH ARTHUR HENRY HA'IT, a citizen of the United States, and a resident of Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in rocesses of Producing Color Negatives for hotomechanical Printing Plates, of which the following is a specification.

The invention relates to a process for producing negatives for use in photo-mechanical color printing, especially three and four color work, which negatives shall be intrinsically correct in their color values for use with the ordinary or standard color printing inks, and thus be free from the necessity of later corrective hand work or the like. The invention will be more inclusively and also more specifically defined hereinafter in connection with a description and explanation of an exemplary embodiment thereof in the present preferred form of practicing the invention, including a detailed explanation thereof in so far as this may be necessary tothose skilled in the art.

The invention consists in the novel steps and processes herein disclosed; and its fur ther objectsand advantages will be set forth in part hereinafter, and in part will be obvious herefrom, or may be learned and ascertained through practice with the invention.

- The accompanying drawings represent diagrammatically certain steps of, and certain apparatus which; may be used in, the process.

The various figures are, respectively, diagrammatic representations as follows Fig. 1 the colors of an original or copy; Fig. 2 of the blue negative, made through a red filter on a panchromatic plate; Fig. 3 of the green blue negative; Fig. 4 of a positive of Fig. 2;

Fig. 5 of a composite negative of Figs.

2 and 3; i

Fig. 6 of a negative through the magenta filter on a panchromatic plate;

Fig. 7 of ,a negative made through the yellow filter on a panchromatic plate;

Fig. 8 of a negative madethrough a green filter on a green sensitive plate;

Fig. 9 of a negative made through a violet filter on an ordinary plate;

Fig. 10 of a negative made through a red filter on a panchromatic plate; I

1919. Serial No. 301,358.

Fig. 11 of a negative made through a green filter on a green sensitized plate;

Fig. 12 of a negative made through a violet filter on an ordinary plate;

Fig. 18 of a composite of the negatives of Figs. 10 and 11;

Fig. 14: of a composite of the negatives of Figs. 10 and 12;

Fig. 15 of a composite of the negative of Fig. 13 with that of Fig. 5;

Fig. 16 of a composite of the negative of Fig. 14 with that of Fig. 5.

In the drawings which are presented herewith as exemplary and explanatory of the and blended to a greater or lesser degree throughout the design. Also for clearness and ease of comparison, the negatives and positives are not shown in reverse, for as shown, the comparisons of color areas and relative degrees of opacity are much more easily and readily made. The drawings in the nature of the case are merely diagrammatic approximations of the density or relative density of the negatives. If the drawings be looked at with the eyes nearly closed, and especially from the back of the sheet, a better effect will be obtained.

Referring more particularly to the difiiculties and deficiencies of present methods and present common corrective practices. and pointing out the purposes and advantages of the present invention in relation thereto, it may be stated:

It is well known that color process negatives, that is, negatives for use in making color photo-mechanical process printing plates, from the standpoint of results obtained in printing with the best or standard inks used or obtainable, are deficient in proper or correct color values. The blue negative made through the red filter is comparatively correct as to color value. The yellow negative is less so, being deficient in the violets, purples, and blues, and the magenta negative made through the green filter is very deficient in the greens and blues. To correct the color values of these negatives for use in making three and four color printing plates. the common practice is to use skilled handwork on the negatives themselves, or on the positives or on the printing plates made therefrom. All of which is well known to those skilled in the art.

The object and purpose of the present invention is to provide a process of making color negatives. and color printing plates from the negatives. whereby the negatives and consequently the resulting printing plates are given the true color values in the process of making the negatives for the color plates. having especially in view the deficiencies outlined above and avoiding the additional troublesome and expensive supplementary corrective work referred to. The process of my present invention covers the elimination or correction of all errors and deficiencies of color in all the negatives and in all the resultant )rinting plates, in the process of making tie color negatives, in either three or four colo work.

One of the requirements in three and four color process work is a black negative which is as nearly correct in color value as is possible. The negative for the black printing plate is usually made on a panchromatic plate through a light yellow filter at one exposure. or it is made through a plurality of color filters, used in succession, making a part of the exposure through each. These methods are defective because the panchromatic plate is not sufficiently sensitive to green. and in any case the colors in such negatives never approach any where near the actual density of the white in the original.

As already'stated. a color chart or blocked colors are used in the drawings for the sake of clearness as the principle is the same as in copying a painting, a colored picture, or any art or commercial subject. In Fig. 1 the blocks of the respective primary and secondary colors are marked by name and are also provided with reference numerals, which numerals are applied throughout the diagrams of the negatives and corrective plates in the successive figures to the corresponding color values or color areas.

Accordingly the white is indicated by 1, magenta by 2. red by 3, yellow by at. green by 5, blue by 6, violet by 7 and black by 8.

My present invention provides as one of its features, a process of producing the negative for the black color plate which shall in itself have much more nearly a true color value. In making this black negative, I make a composite negative of the black from two separate negatives made in the camera, as follows:One negative, Fig. 2, that of the blue (on a panchromatic plate through a red filter) has to be made in any event and thus serves a double purpose. The other negative, Fig. 3, the magenta is made on a green sensitive plate through a blue-green or greenish-blue filter. The last-named negative is coated with a freslrsensitive emulsion and the duplicate of the blue negative is photographed thereon, using a positive of the blue negative, Fig. 4, for this purpose. This makes a composite of the two, Fig. 5, and is superior to the results obtained by the old method.

A composite black negative may be made through any two color filters that are complementary, and on suitable plates, but the above-mentioned way ispreferable on account of the s ecial efiiciency of the red filter on a pane iromatic plate, and the spe-' cial efficiency of a greenish blue filter on a green sensitive plate.

This composite black negative may be furtherimproved for color correction work, in certain cases, by making it a composite of three negatives. That is, if it is desired to have the black negative favor the magenta negative, or the yellow negative, as the case may be, either of these negatives may be used in addition to the afore-mentioned two, thus making a composite of three inor four color offset process work, these corrections should be done without interfering with the black parts in any of the negatives in each case. In four color relief it is desirable to modify the blacks in each of the color plates so as to compensate or allow for the .blaek printing plate. This, however, is not usually needed in the four color offset process, mainly on account of the fact that in this process the inks are necessarily used more sparingly in printing.

Referring now to making the correct-ions in the color negatives proper, that is, the negatives other than the black, in accordance with the present preferred form of carrying out the invention, the process is as follows: The sensitive photographic plates to be used are preferably all to be made on glass of one thickness, plane, with ice both sides parallel, and preferably using greenish blue filter, cutting out the red ra s.

it negative, Fig. 6, is made through the magenta filter on -..a panchromatic plate, which plate is placed in the camera so that the back or glass side is towards the lens, and accurately positioned. This negative is developed only to the extent necessary to make the color correction for the magenta ne ative through the green filter.

n speaking of a panchromatic dry plate I have reference to a plate in which the sensitive emulsion has been dyed with an anilin dye. so as to make it sensitive to practically all of the colors. The ordinary dry platewhich has not been so dyed is sensitive mainly to the violet end of the spectrum. The ordinary dry plate will be found to be very sensitive to green, blue (cyan blue) violet and pink or magenta. Magenta or pink does not appear in the spectrum, but it is a combination of the two end colors of the spectrum, the red at one end and the violet at the other. By dyeing the plate it becomes more sensitive to other colors, depending on the dye used. For example, a plate sensitized with a pan-- chromatic dye becomes very sensitive to the yellows and reds, in addition to the normal sensitiveness to ,blue, violet and pink. The panchromatic plate as made at.

'- has the property of absorbing, that is, not

allowing to pass through it, all green rays of light, magenta being the complementary color to green. That is, if all the pure colors were to be arranged in a circle in their proper relationship to each other, placing analogous colors next to each other, it would be found that magenta and een would lie 180 degrees apart. (See The Colorist by J. A. H. Hatt in Patent Ofiice library). Such a filter may bemade out of a film of gelatin suitably dyed and supported on a single glass plate, or between two glass plates. make a negative of a copy containing. all of the fundamental colors, and filter the light through a magenta color filter and intercept the light ona panchromatic dyed dry plate, we will have a negative resulting therefrom which may be represented by Fig. 6 on the drawing.

Therefore, .if we A panchromatic plate is again placed in the camera. in the same way as the first plate. just described, and the yellow filter used. This negative, Fig. 7, is developed sutliciently to make the corrections on the yellow negative through the violet filter.

While these two negatives are being developed and dried, the blue negative, Fig. 2, but reversed or left handed should be made on a panchromatic plate and placed glass side towards the lens, using a red-filterf Also the negative, Fig. 3, but reversed or left handed of the red color, is made through the green blue filter on a green sensitive plate, placed in the camera the same way.

Acomposite of these two negatives, is used for the black, and the blue negative alone is used for the blue printing plate,

as previously described.

The negative, Fig. 6, made with the magenta filter is then placed back in the camera in its original position, with a green sensitive plate behind and in contact with it, and an exposure made on it through the green filter, and through said correctlng magenta negative, which gives Fig. 8. The exposure in such case is modified, of course, by the magenta negative in front of it.

behind and in contact with it, on which an exposure is made through the violet filter, which gives Fig. 9.

Having made the composite negative of the black. Fig. 5, we then have negatives which for printing through the screen or the indirect process should produce a correct representation of the copy, when impressions from printing plates made therefrom are superposed in printing.

In order to work my process to the best advantage, it is advisable to use a tank filter, so that the light passes through the same glass for each negative. thus preserving the same location for each image.

In the foregoing, it will beobserved that the negative of the black is the reverse of the yellow (violet filter), negative, and the magenta (green filter) negative. This is not necessary, unless extra corrections for the black are desired. For the indirect process this makes no differen e, because in making the positive with the glass of the same thickness by the use of a compensating cover glass, the positives may bemade all facing the same way, and it has been found best in v emulsion.

case of these two negatives and place a plain glass plate in front of them.

When the process is to be used for printing through the screen work, an extra blue negative is made through the red filter straight or direct, if the other two are made reverse.

When the process is used for printing through the screen method, or it is desired to make corrections in the color negatives for the black, the magenta, yellow and blue negatives are rcsensitized with a sensitive The reverse black negative is placed in contact and register with each of them in succession, and a positive of the black is photographed on each of them and developed sufficiently for the elimination of the necessary amount of black from each. As previously mentioned, the black may be improved for this use by making a separate black negative for each color, and having it favor the color it is ,to be used with.

In the above process it is not necessary to use the magenta filter or the yellow filter.

.I can substitute for the magenta filter a.

double exposure made in part or succession through the violet filter and through the red filter. This will give about the same result, though not with the same convenience. In the same way, a divided exposure through the red and green filters will'give about the same result that the yellow filter will give. Exposures made with two filters may be substituted for the single exposures indicated above.

My invention includes also a process of making color corrections or color true plates without the use of the camera. In accordance with this feature of my invention the usual three color negatives are made straight, that is. not reversed. Fig. 10, representing the blue, Fig. 11 the magenta, and Fig. 12 the yellow negative. The black negative may be made in the usual way (straight), or preferably reversed and then a composite negative made as described in the previous process. If the black is made straight, it may be reversed afterwards by any of the usual reversing methods well known in the art.

With respect to the color negatives proper, that is other than the black, just referred to above, positives are made. by contact preferably, of the magenta, yellow and blue negatives. From the magenta and blue positives, a composite negative, Fig. 13, is made, producing anegative of the violet. which is used to correct the yellow negative. From the blue and yellow positives, a composite negative, Fig. 14, is made producing a negative of the green, which is used to correct the magenta negative. These composite negatives are then resensitized, and the reverse negative of the black, Fig. 5, is used to photograph a positive of the black on each of them, Fig. 15 representing this in the case of Fig. 13 and Fig. 16 representing it in the case of Fig. 14.

This results in isolating the violet .in one case, and in isolating the green in the other case. Cover positives may be made from these for the indirect method, or the original negatives may be resensitized with an emulsion, and a positive made directly on them from the composites. Anothermethod is to make two positives of the black reverse negative, which are-then resensitized and a double exposure made on each from one of the two pairs of positives. Or a single exposure from a positive obtained from a yellow filter negative may be made on one, and a single exposure from a positive obtained from a magenta filter negative may be made on the other, thus isolating the. violet and the green asin the previous case.

If we have a negative made through a magenta filter and a negative made through a yellow filter, this will obviate the necessity of making the double exposure explained above, and will simplify the work.

Another method where it is desired to have the corrections on the principal negatives and to in lude corrections for the black, so as to allow for the black printing plate, is as follows Reverse negatives are made, respectively. of the green, Fig. 6, and violet, Fig. 7. as previously explained, by placing the glass side of the sensitive plates towards the lens. A reverse negative is also made of the two component parts used to form the black negative, Fig. 5, as explained previously. The regular three color negatives are then made straight. The magenta negative is then resensitized, and the positive of the green reverse negative is photographed on it. This makes a correction for the green, and eliminates part of the black.

The yellow negative is also resensitized. and the reverse violet negative is photographed thereon. This corrects the yellow in the violet region and also eliminates part of the black. The blue negative which needs no color correction is then resensitized, and the black reverse negative is photographed on it, taking out about the same amount as was eliminated from the other two. The bla k negative may be underexposed on the final printing plate. so as to yield about the same amount of black as was removed from the three three color negatives.

It will be understood that the invention is not limited to the details of the various described steps, but that changes may be made therein without departing from the principles of the invention, and without sacrificing its chief advantages.

\Vhat I claim as my invention is 1. The process of making color printing plates which comprises isolating the green and black colors on a reversed negative and using this negative in the camera as a mask for the magneta ne ative.

2. The process 0 making color printing plates which comprises isolating the violet and black colors on a reversed negative and using this negative in the camera as a mask for the yellow negative.

3. The process of making color printing plates employing a magenta negative which comprises isolating the green color from the other colors and from the black in the form of a positive and photographing this positive on the magenta negative.

4. The process of making color printing plates employing a yellow negative which comprises isolating the violet color from the other colors and from the black in the form of a positive and photographing this positive on the yellow negative.

5. The process of making color printing plates employing a magenta negative which comprises isolating the green and black from the other colors and photographing them on the magenta negative as a correcting positive.

6. The process of making color printing plates employing a yellow negative which comprises isolating the violet and black from the other colors and photographing them as a positive on the yellow negative as a corrective of that negative.

7. The process of making color printing plates employing a magenta negative which comprises isolating the green and black from the other colors and making a positive thereby and applying the positive to the magenta negative as a correcting cover glass.

8. The process of making color printing plates employing a yellow negative which comprises isolating the violet and black from the other colors and making a positive thereby and applying the positive to the yellow negative as a correcting cover glass.

9. As an article to be used in making color printing plates, a reversed negative a part of a relative degree of opacity and location corresponding to the combined isolated green and black colors.

10. As an article to be used in making color printing plates, a reversed negative :1 part of a relative degree of opacity and location corresponding to the combined isolated violet and black colors.

11. As an article to be used in making color printing plates, a positive plate a part of a relative degree of opacity and location corresponding to the green color isolated from the other colors and the black.

12. As an article to be used in making color printing plates, a positive plate a part of a relative degree of opacity and location corresponding to the violet color isolated from the other colors and the black.

13. As an article to be used in making color printing plates, a correcting positive plate a part of a relative degree of opacity and location corresponding to the green and black isolated from the other colors.

14. As an article to be used in making color printing plates, a correcting positive plate a part of a relative degree of opacity and location corresponding to the violet and black isolated from the other colors.

15. As an article to be used in making color printing plates, a correcting positive a part of a relative degree of opacity and location corresponding to only a correcting color or colors selectively isolated from the other colors.

16. As an article to be used in making color printing plates, a correcting negative a part of a relative degree of opacity and location corresponding to only a correcting color or colors selectively isolated from the other colors.

17 The process of making color printing plates which comprises making a negative by selectively isolating one or more corrective colors and employing this negative as a corrective means optionally either in the camera or on the copy in connection with one of the usual three or four color negatives.

18. The process of making color printing plates which comprises making a positive by selectively isolating one or more corrective colors and employing this positive as a corrective means in connection with one of the usual three or four color positives.

19. As an article to be used in making color printing plates, a positive auxiliary plate apart of a relative degree of opacity and location corresponding to only a cor rective color.

20. As an article to be used in making color printing plates, a negative auxiliary plate, apart of a relative degree of opacity and location corresponding to only a corrective color.

21. The process of making color printing plates which comprises making a negative a part of a relative degree of opacity and location corresponding to a rimary color for three color printing, making a plate of a degree of opacity corresponding only to a corrective coloring, and using them together in making a printing plate giving correct color values for the printing inks.

In testimony whereof, I have signed my name to this specification.

JOSEPH ARTHUR HENRY HATT.

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