US2304942A - Method of preparing color print plates - Google Patents

Description

Dec. 15, 1942.

W. S. MARX, JR

METHOD OF PREPARING COLOR PRINT PLATES Filed Nov. 16, 1939 Poems Dec. 15, 1942 UNITED STATES PATENT OFFICE mnon OI PREPARING COLOR M11 PLATES Walter S. Marx, Jr., Park Ridge, 11]., assignor to PrintingArta Research Laboratories, Inc.,

Santa Barbara, CaliL, a corporation or Delawere Application November 1, 1,39, Serial No. 304,785

a new and improved method oi. preparing plates ior printing in multicolor, so as to eliminate the necessity of using skilled operators for securing correct color rendering and blending.

A iurther object of the invention is to provide an improvement in eiilciency and results over the current methods of preparing color-printing plates, and more specifically over the method commonly known as the Benday process.

Other objects of this invention are set iorth in the iollowing description and drawing, which illustrate certain preferred embodiments.

In the drawing:

Fig. 1 illustrates diagrammatically certain apparatus whichmay be used in the carrying out oi. the methodaccordingtothe presentinvention, and

Fig.2isalscadiagrammatieviewoicertain alternative apparatus which can be employed to a like end.

'I'hepreterredoithepresentinvention will be described in connection with the preparation or colored comic supplements and cartoons irom a black-and-white pen drawing such as is usually furnished to the engraver in existing methods, although it is to be understood that the invention has other applications as will hereinafter be referred to.

According to the present invention such a black-and-white pen drawing is first photographed without a screen so as to produce a negative from which is prepared a line positive on any suitable light-permeable or transparent material and such as glass or Celluloid, the size of such line positive or transparency being of the beilll used as a guide receptive of coloring material, and this may comprise applying thereto a solution consisting of:

Parts Water 88 Egg albumen 8 Ammonium hydroxide 4 With the surface oi the positive transparency in proper condition, the transparency is colored by local applications oi various transparent coloring materials so as to produce the desired color scheme, the black lines which have been produced for applying the said col- Three dliierent color separation negatives are next made from the colored transparency and for this purpose the apparatus illustrated in eitherFig.l0r2isutililed.

Reierringflrst 01 all to Fig. i, C indicates an orthodox process camera and L the lens thereof, whilst B indicates a copy board disposed in iront oi the lens and on which is mounted in any suitable way a sheet of white paper P. A suitable sensitised negative element N is mounted within the camera, and in trout thereoi and la eiiectual contact therewith is placed the colored transparency T, preferably with its colored surface facing the sensitised suriaceoi the negative N. In treat 01 the transparency T is positioned the hall-tone screen 8, whilst on or adjacent the lens L is positioned the appropriate color separation filter P.

On exposure the light transmitted from the white paperPthroughthelensL isusedtoiorm an image or the transparency T on the negative element N, said light beingflrst filtered by the iilter l" and then broken up into a halt-tone pattorn by the screen 8. Thus the resulting nega-" tive is a color separation halt-tone and may be printed directly on metal and etched and proceesedintheusualwaytcprovideoneplateoi the multicolor series.

Asimilarnegativeismadeinthesameway for each or the remaining colors, Irom which the remaining plates, to complete the multicolor series, can be produced, the appropriate color separation filter F of course being placed in position prior to the exposure 0! each negative. In addition, the necessary black printing plate must be provided and this can be conveniently obtained from the negative previously 'used in making the positive t T.

Alternatively, the color separation halt-tone negatives can be obtained in accordance with the invention with the apparatus of Pig. 2. In this case, instead of the camera C and light source comprising the white paper P there is provided the proiection prin apparatus A having the lampA' andlensnand whichlsttermaycarry the appropriate color separation iliter I" as before,

In front of and below the lens is placed the half-tone screen S; below this. and preferably spaced therefrom, such as by bars X, is located ods described with reference to both Fig. l and Fig. 2 the color separation negatives are obtained by means of transmitted light as opposed to reflected light and with the colored transparency in effectual contact with the said negatives.

In this connection it should be pointed out that the value of transmitted light in color separation procedure is much more efficient than the value of reflected light as used in common practice for the following reasons: (a) Reflected light is degraded by secondary surface reflection and interreflection; (b) Current lens construction is such that various wave lengths of light are not socurately focused in one plane; (c) The types of glass commonly used'in color corrective lenses is such that the color corrective efficiency is far from perfect; and (d) Incident light is such that it may be degraded by surrounding foreign refiections and by lights which may by accident strike the color'drawing in use. 7

As opposed to the above disadvantages: in.)

,Transmitted light cannot be degraded where the color transparency is in effectual contact with the negative element; (b) All wave lengths of light are at once accurately in (me plane without the use of a lens and without the necessity for focusing; and According to the Grotthous- Draper law, only light which is absorbed can have an effect; thus by absorbing actinic light first through the color separation filter and second through the color transparency, greater color separation distinction is achieved than if said light were first reflected from colored art and then pass through the separation filter. as is the From the above it will be appreciated that by ored areas.

separation negatives to an auxiliary exposure in the presence of ultra-violet light.

For instance, if the colored areas of the positive transparency T contain an efllcient absorbent of ultra-violet light, for example:

Distilled water ..c. c 1000 Quinine bisulfate -grams 90 Sulfuric acid, C. P c. c Egg albumen, C. P gramsthese areas will prevent the penetration of ultraviolet light. And conversely, the uncolored areas,

namely backgrounds, highlights, etc., will trans-.

mit ultra-violet light. Thus if, after the normal color separation exposure, as hereinbefore described, is completed, the screen is removed and the color separation negatives are Sublected to an additional exposure in the presence of ultraviolet light, the screen pattern or dots will be obliterated in those sections of the negatives corresponding to the uncolored sections of the positive transparency T. Those sections of the negatives directly behind the colored sections of the positive transparency will not be afl'ected by the ultra-violet light, since that light is effectually absorbed before it reaches the negative, by the ultra-violet absorbent included in the colored sections.

The advantage of thus obliterating screen pattern in the, high-light areas or sections consists in eliminating the hand labor usually required to opaque these areas or sections on the screened negatives so that subsequently they will print upon the metal as areas which are entirely free of dot pattern, 1. e., as perfectly white or uncol- It is understood that while the method according to the present invention has been more perpreparing the color transparency T on a lightpermeable material, mounting said transparency in eifectual contact with the negative element N and exposing the latter so arranged to a source of transmitted light, all of the advantages above mentioned are realized by the present method.

A further advantage of the present method consists in that in the event of breakage of a color separation negative careful refocusing: is no longer necessary, because by the present method the original color transparency by being mounted in effectual contact with a new negative element will, of course, provide a color separation negative of the exact size of the one broken.

Further, the least expensive method for color printing which has heretofore been accepted is the Ben Day process." The prior process, however, does not provide fine, delicate and' numerous shadinss'and gradations of color, which must he produced by hand. On the contrary. by the present method such fine, delicate and numerous shadings are made photo-automatically.

The efliciency of this invention may be funther greatly improved by the addition, to the transparent coloring materials used ,to color the positive transparency T, of an ultra-violet absorbcnt material and by subjecting the color ticularly described in connection with the production of preparing plates for printing cartoons or comic supplements in multicolor, it has other applications and such, for example, as the re- 7 production of photographs which may be similarly reproduced by preparing a colored transparent positive thereof. transparency may be made either by hand-coloring or by direct photographic means, and such as, for instance,

by what is currently commonly known as a "Kodachrome" transparency? In this case, there being no previously made blackprinting negativc, all three, four or more color separation negatives are made while the transparency is in contact with the negative inside the camera.

Further and finally, whilst the present invention relates particularly" to the printing of colcred cartons, colored supplements and the like, by means of high speed rotary newspaper presses, it is also applicable to the well mown color printing processes, using two, three, foul-or more coiors, and to fine screen reproductions.

I claim: I

1. In the art of preparing printing plates for multicolor printing of matter, said matter con taining black lines, those steps which t in photographically prinnng a black-and-white positive of said matter upon a light-permeable material, preparing a coiorfmhcme with transparent colors upon said positive, and I' -F ring therefrom half-tone screen separation negatives by contact photographic printing.

2. In the art of preparing printing plates for multicolor printing or matter, said matter containing black lines, those steps which consist in 'photographically preparing a negative of said white positive upon a light-permeable material from said negative, coloring said positive transparency with transparent colors, and preparing therefrom half-tone screen separation negatives by contact photographic printing. I

3. In the artoi' preparing printing plates for multicolor printing of matter, said matter containing black lines, those steps which consist in photographically preparing a negative or. said matter, photographically printing a black-andwhite positive upon a. light-permeable material from said negative, coloring said positive transparency with transparent colors, preparing therefrom half-tone screen separation negatives by contact photographic printing, and preparing the black printing plate from the negative used originally in preparing the black-and-white positive.

4. In the art of preparing printing plates for multicolor printing of matter; said matter containing black lines, those steps which consist in photographically printing a black-and-white positive 01 said matter upon a light-permeable material, coloring said positive with transparent colors, placing said positive in eiiectual contact with a sensitized negative element and then exposing said negative to a source of transmitted light with a half-tone screen and a color separation filter interposed between said positive and said source of transmitted light.

5. In the art oi preparing printing plates for multicolor printing oi matter, said matter containing black lines, those steps which consist in photographically printing a black-and-white positive of said matter upon a light-permeable material, coloring said positive with transparent colors, placing said positive in effectual contact with a sensitized negative element inside a camera and then exposing said negative to a source of transmitted light with a halt-tone screen and a color separation filter interposed between said positive and said source or transmitted light.

6. In the art oi preparing printing plates for multicolor printing of matter, said matter containing black hues. those steps which consist in photographically printing a black-and-white positive oil/said matter upon a light-permeable material, preparing a transparent color scheme thereon, and preparing color separation halitone negatives from said color transparency by mounting said transparency in eflectual contact with a photo-sensitive negative element insidea camera.

7. In the art oi preparing printing plates for multicolor printing of matter, said matter containing black lines, those steps which consist in photographically printing a black-and-white positive of said matter upon a light-permeable mtaerial, preparing a transparent color scheme thereon, preparing color separation halt-tone negatives from said color transparency by mounting said transparency in efiectual contact with a photo-sensitive negative element inside a camera, and repeating the last mentioned step once for each color separation negative.

8. In the art oi preparing printing plates tor multicolor printing or matter, said matter containing black lines, those steps which consist in photographically preparing a negative of said matter, photographically printing a black-andwhite positive upon a light-permeable material from said negative, coloring said positive with transparent coloring material, preparing color separation halt-tone negatives from said color transparency by mounting said transparency in eflectual contact with a photo-sensitive negative element inside a camera, repeating the last mentioned step once for each color separation negative, and preparing the black printing plate from the negative used originally in preparing the black-and-white positive! I 9. In the art of preparing printing plates for multicolor printing of matter, said matter containing black lines, those steps which consist in photographically printing a black-and-white positive of said matter upon a light-permeable material, coloring said positive with transparent coloring material, successively placing said positive in effectual contact with a plurality oi sensitized negative elements and then exposing it whilst in contact with each of said negative elements to a source of transmitted light and with a half-tone screen and an appropriate color separation filter interposed between said positive and the said source of light whereby to produce a plurality of halt-tone color separation negatives, one for each color.

' i0. Inthe art of preparing printing plates for multicolor printing ot matter, those steps which consist in mounting a colored transparency of said matter, the colors of which transparency include an absorbent oi ultra-violet light, in eiiectual contact with a photo-sensitive element, preparing a color separation halt-tone negative from said color transparency in said position by means of transmitted light and then resaid negative in the presence 01 ultra-violet light only.

11. In the art oi preparing printing plates for multicolor printing at matter, those steps which consist in photographically printing a black-andwhite positive of said matter upon a lightpermeable material, preparing upon said positive a color scheme with transparent colors having included therein an absorbent oi ultra-violet light, preparing from said positive a halt-tone screen separation negative by contact photographic printlng and re-cxposing said negative in the presence of ultra-violet light only.

12. In the art of preparing printing plates for multicolor printing or matter, those steps which consist in producing the desired color scheme upon a positive transparency oi said matter in I transparent colors containing an absorbent of ultra-violet light, producing halt-tone separation negatives from said colored transparency with the aid of transmitted light, re-exposing said negatives in the presence or ultra-violet light only and utilizing said negatives ior preparing the printing plates corresponding to the respective colors.

' 13. In the art oi preparing printing plates for multicolor printing of matter, said matter containing black lines, those steps which consist in photographically printing a black-and-white positive of said matter upon a light-permeable material, coloring said positive with coloring matter including an absorbent oi ultra-violet light, placing said positive in effectual contact with a sensitized negative element, exposing said negative to a source of transmitted light with a halt-tone screen and a color separation filter interposed between said positive and said source or transmitted light, removing the screen and filter and --exposing the negative element in the presence of ultra-violet light only whereby to eiiace screen pattern in the areas of said negative corresponding to the high-light sections of said matter.

WALTER S. MARX, JR.

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