USRE22736E - Photomechanical process - Google Patents

Description

March 1946- A. MURRAY ETAL PHOTOMECBANIGAL PROCESS Original Fil ed April 5, 1940 4% F76. v -/0 /z FILTER /5 V Lg /7 FLUORESCENT 3L LIGHT ONLY ORIGINAL (FLUORESCENT P/GMENTJ) VISUAL HL/E 0F PAINT PROPORT/O/YS 0F FLUORESCENT ALEXA/YDERMz/RRAY JOHN/4.6. YuLE INVENTORS I BY al PR/MAR GREEN ATTORNEY Reissued Mar. 26, 1946 PHOTOMECHANICAL PROCESS Alexander Murray and John A. C. Yule, Rochester, N.'Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey OriginalNo. 2,278,114, dated March 31, 1942, Se-

rial No. 328,066, April 5, 1940. Application for reissue November 8, 1945, Serial No. 627,504

4 Claims.

This invention relates to photomechanical processes and particularly to processes for the reproduction of colors.

It is an object 01' the invention to provide a method and means for making color separation records which require little or no retouching in order to reproduce colors accurately.

It is also an object of the invention to provide such a method of making color separation records which will not require any step of color correction such as masking.

It is an object of the present invention to pr vide a method of making color separation positives directly from a colored original.

It is a particular object of the invention to provide a palette of artists paints with which a picture can be painted, which picture will have the natural appearance desired and still can be reproduced directly without retouching.

It is an object of a special embodiment of the invention to provide a palette 01 artists paints particularly-adapted to be reproduced by a photomechanical process employing a black printer and a method of employing this palette of paints.

' According to the present invention, an original. paintingto be reproduced photomechanically is created by the artist with inks, dyes, or paints, containing three fluorescent ingredients. For simplification the word paint will be used to cover all artists coloring materials. These ingredients are such that their fluorescent hues are mutually separable spectrally. That is, they are of such fluorescent color (e. g. violet, green, and red) that their spectral distribution of intensity curves do not overlap or if they do overlap, it is only partial and there is in each of the three hues one wave-length portion which is not in the other support for the original should contain no fluorescent ingredients. A black ink (or other black paint) must contain all three ingredients except in one special embodiment described later wherein it contains no fluorescent ingredients.

The other factors which determine the amounts of fluorescent ingredients in any one material are the fluorescent efliciency of the ingredient in each material and the amount of ingredient used in the other materials. Certain pigments absorb ultra violet and/or the fluorescent wavelengths themselves more than other pigments do. Thus a red pigment, say, may require ten times as much fluorescent ingredient as a yellow pigment in order to give the same effect. Thus the ingredients are effectively but not actually in proportion to the subtractive color contents of two. In either case, any one of the hues can be 1 selected by a suitable color filter which absorbs the other two hues completely.

In simple theory the relative amounts of the three ingredients in each paint are proportional to the subtractive color contents of the hue or that paint. Actually they are also proportional to other factors to be discussed below. Roughly, the subtractive color contents are the amounts of yellow, magenta, and blue-green making up the hue; more exactly they are the amounts 0! minus blue, minus green, and minus red. We

,speak of primary color components" (white is made up of all three primary colors) and of subtractive color contents (white has no subtractivecolor contents). For example, a yellow paint must" tain only one of these fluorescent in gredi a white paint it used and the white the materials. Furthermore the proportionality needs to be satisfied only for "each of the three ingredients separately, not relative to one another because in the process, exposures are made separately to each fluorescent hue and need not be equal. For example in one particular set-up we have used, we expose 10 seconds for one hue and 5 minutes for another. 1

Positive color separations are made for this original by photographing it successively on three. diiierentphotosensitive layers using fluorescent light only and in each case using only one of the fluorescent hues. This is accomplished by illuminating the original with fiuoroactivating light such as ultra-violet (all visible light having been filtered out) and then by using suitable filters allowing one only of the fluorescent hues to reach the sensitive film in each case.

Ifa black printer is to be used, it may be prepared byany of the usual methods, but we prefer to use the method described by one of us in U. S. 2,161,378, Murray, since it combines uniquely with a special modification or the present invention;

The result has the advantage that none of the color printers print where only the black printer need print, i. e. where the original picture is made up entirely of a black pigment. v

To meet the requirements of U. S. 2,161,378,

this special embodiment of the present invention employs coloring materials for creating the original which with exception of the black, reflect or transmit infra-red freely (i. e. do not absorb it). The black pigment used absorbs infrared and an infrared separation negative makes a black printer which is a practically perfect one of the type which reproduces only those blacks and grays in the original which are made of the black pigment used in creating the original. To conlight indicated by arrows I! which fluorescent light;

form with the present invention in its simplest form, this black pigment would contain all three fluorescent ingredients since it includes all three subtractive colors. However, to gain the advantage of this special embodiment wherein no color printers will print where there is only black in the original, this black pigment is made up with no fluorescent ingredient, the same as white is. v Thus this special embodiment of the invention employsa palette of coloring materials for creating the original, which palette includes a black paint which contains no fluorescent ingredient and a plurality oi. other paints or inks which contain three fluorescent ingredients in respective proportion to the subtractive color contents of the hues of these other coloring materials, (flu.- orescent emciency being taken into account as before). The color separation positives are then made in the same way as when intended for a three-color process and the black positive is made from an infrared separation negative.

other objects and advantages of the invention will be apparentfrom the following description when read in connection with the accompanying drawing in which:

Fig. 1 illustrates one embodiment tion. 1

Fig. 2 illustrates the optical properties of the artists color materials employed by the present invention.

Fig. 3 is included merely toasslst in explaining the principles underlying the invention.

In Fig. 1 an original painting in including'flucrescent pigments is illuminated by sources H 01' illumination which send out fluoro-activating causes the original III to fluoresce. The light sources H are such (tor example an ultra-violet arc with a 111- ter to absorb the visible light) that none of the light [2 (before or after direct reflection by the of the invenorange, etc. He may also employ a white and/or a black paint or ink. According to the invention each of these paints includes a fluorescent ingredient, the relative eflective amounts oi the ingredients in any one paint being in proportion to the subtractive color contents of that paint. As pointed out, the actual amounts depend on the absorption 01' the fluorescent light and of the fluoro-activating light by the paint and-on the amounts used in the other paints. For example. a magenta paint'which contains no yellow or blue-green content would include only one of the ingredients, namely, that whose fluorescent hue is labeled hue I" in circle Zll. Similarly yellow would include only the ingredient having hue II" and blue-green would include only the ingredient having hue III. A primary red paint on the other hand would include effectively equal amounts of the ingredients having hues I and II." In this example, if the primary red' paint absorbs ultra-violet and light of hue I much more than the magenta paint, one would require more of hue I ingredient in the primary red paint than hall of that in the magenta paint. The onehalf value is predicted from simple theory. Also the actual proportion of the hue I ingredient to the hue II ingredient in the primary red paint depends on the relative efliciency of these ingredients and the exposures to be given for each hue. The amount of fluorescent ingredient in the blue-green paint 2| is illustrated by the block 22. The corresponding blocks for the magenta and yellow are thesame size to indicate that with the differences in exposure taken into account,

original In) is of the same wavelength as the V The light coming irom the original Ill indicated by arrows II is made up of fluorescent light and reflected light. A fllter II is placed in the path of this light from the original to absorb all wave lengths included in the light I2 and to transmit only fluorescent light I5. Of course the fllter Il may absorb some of the fluorescent light of the hue to be transmitted and always absorbs any fluorescen light of other hues. By means oi. a lens li, a photosensitive layer I1 is in printing relation to the original in and is exposed by the fluorescent light I5.

According to the present invention, the original I II is made up of pigments containing three fluorescent ingredients having different hues which are mutually separable spectrally. Therefore, the light It may include fluorescent light from all three fluorescent pigments and by proper selection of fllter ll. the process illustrateffectively equal amounts of the ingredients must be used. The amount of fluorescent ingredients in primary green 23 is illustrated by equal blocks 24, but 01' course this means that the relative amounts of the two ingredients in primary green must be such that their fluorescent intensities are effectively equal, when measured with respect to the spectral sensitivity of the photographic films to be used and the exposures to be given. Any intermediate color such. as orange indicated by the broken line 25 would have relative amounts of the fluorescent ingredients indicated by the blocks 26 and 21 corresponding to the subtractive color contents of this hue-orange.

Since orange is made up mainly of yellow with a small amount of magenta the block 26 is larger than the block 21.

Another way of looking at this phase of the matter, which is a little complicated because of is, of course, directly in terms of the subtractive color contents, (applying the term to areas of the original in this case). This simplifies the mathematicsbecause only the three colors are present. From this latter point of view, any areas on the original Ill requiring for their reproduction equal amounts of blue-green ink should have eflectively equal amounts of the hue III ingredient. That is, any blue, blue-green, orgreen areas whose brightnesses are such that they are equivalent in blue-green, require equal amounts of blue-green in their reproduction and hence should contain effectively equal amounts of hue III ingredient. A green area made of superimposing blue-green and yellow coloring materials will contain equal (effectively) amounts of the corresponding ingredients and willoi course-contain just as much hue. III ingredient as when the yellow is omitted and only blue-green is used. However, when all of this is transferred from a discussion of areas to one of coloring materials on a palette, a green paint contains only half as much (eifectivcly) of ingredient hue III" as does a blue-green paint. The point is that over a unit area there is twice as much paint when the yellow is added as when the blue-green is alone so that the proportion of hue III ingredient to total paint is halved althoughthe proportion to area is unchanged.

The actual fluorescent hues of the fluorescent ingredients are immaterial. For example hue I may be violet, hue 11 may be green and hue III may be red. As long as the fluorescent hues are mutually separable spectrally, it does not matter in what order they appear in circle 20.

'By selecting the proper amounts of fluorescent ingredients in each of the paints, all or most retouching is eliminated from subsequent processes. The difliculty in compounding a paint which has exactly the correct fluorescence throughout all of its range of tints may in some cases result in slightly excessive brightness of the pastel shades, but any retouching required is considerably less than that formerly used and for most purposes for which we have used this process, no retouching has been necessary. The amount of fluorescent ingredient indicated by the block 22 in the blue-green paint 2| should be effectively proportional to the density required in a blue-green separation positive forming-the bluegreen printer. Similarly, the amounts of the ingredients represented by the blocks 24 should correspond to the required printer densities to be used with the yellow and blue-green inks in the final process to reproduce primary green as it appears in the original. That is, the blocks 22, 24, 26, and 21 are representative of the effective amounts of fluorescent ingredients required in terms of final printer densities required.

From Fig. 2, it is obvious that the present invention must result in positives directly. When using ordinary non-fluorescent pigments, the more of the pigment present at any point the greater is the optical density of that point. In

ing hue II. The fluorescent hue circle is rotated 60 degrees relative to the circle 20* of Fig. 2. Color separation records made using the fluorescent hues only from such an arrangement would be dense where the colors are densest and hence positive in density. However, (leaving out the theoretical possibility of shifting to new primaries and having subtractive inks with hues corresponding to ordinary primary colors which cent hues in the circle ZO-so that the visual hues of the fluorescent ingredients (not their fluorescent hues which are labeled I, II, and III) correspond most nearly to the visual hues of the paints in which they are to be used. It is also desirable that the fluorescent ingredients be chemically stable and stable to light and to exposure to the atmosphere. For aqueous paints the fluorescent ingredients are preferably nonvolatile, water insoluble, pulverable materials of relatively low optical density in their own visual color, but of high density to ultra-violet to increase fluorescence efiiciency. The following fluorescent materials are satisfactory when used with mercury vapor lamps as a source of fluoroactivating light: chrysene, anthracene with a trace of naphthacene (or chrysene with 1% naphthacene) and rhodamine G precipitated with a water insoluble gum or resin.

the present case however, a large amountof pigment corresponds to a large amount of fluorescent material and hence to increased brightness. Thus the film ll when processed has a high density (due to high brightness of fluorescence) wherever the original has a high density of pigment. Thus the result is a positive.

In this general connection, Fig. 3 illustrates why the present invention is restricted tothe making of positives directly, which is of course one of its added advantages. It is customary in ordinary three-color work to photograph the original through primary filters red, green, and blue to give negatives. If one were to attempt to modify the present invention to give negative in the same way and arranged so that the I pigments were made up with fluorescent ingredients added in proportion to the primary color components as illustrated in Fig. 3, the resultant records would be negative as far as colors, are

concerned, but they would be positive as far as density is concerned. That is, the records would be white where the original was white and would be black where the original is black. A subtractive color, for example blue-green, as shown by 3| would be made up of equal portions 32 of fluorescent hues II and III. Similarly a primary color such as primary green shown by 33 would as shown by block 34 contain only one of the fluorescent ingredients, namely that hav- Chrysene when illuminated with light of 365 millimicron wave length through a filter (such as C orning Glass Co. #584) absorbing the visible spectrum fluoresces with a violet light of about 400 to 450 millimicrons. A filter (such as a com-. bination of Wratten #34 and Wratten #2A) transmitting only this latter Wave length band or part of it, may be used over a camera by which a color separation positive is to be made.

' Since this latter filter combination transmits red,

be added to the combination.

only orthoor blue-sensitive emulsions should be used therewith or a red-absorbing filter should Pure anthracene plus 1 per cent naphthalene when excited by ultra-violet light of the same wave length (365) fluoresces in the green region from about 500 to 600 millimicrons. A Wratten #61 filter used over the camera will prevent fluorescent light from 'the other ingredients reaching the film orif ortho films are used, an ordinary yellow filter will do. In a copending application by one of us (Yule) serial number filed concurrently herewith an alternative green fluorescent material consisting of chrysene recrystallized with 1% naphthacene is described.

One per cent rhodamine G in sandarac resin when illuminated by a mercury vapor lamp directly (i. e. no filter over the lamp) is excited by the 546 and 577 millimicron lines of mercury and fluoresces in the 600 to 700 millimicron region of the spectrum. A'Wratten #25 Red Filter on the camera lens prevents both the light titles of the fluorescent ingredients will vary with the types or emulsion usedin the camera,

the transmissions or the filters and the nature Purple (primary blue).

of the printing inks to be used, we have found that the following points are satisfactory for creating an original to be reproduced by a process using commercial inks now in use and with regular panchromatic or orthochromatic emulsions.

Pigment Paint color Fluorescent ingredient taining naphthaccno I 3% Hausa yellow.

Orange red (pri- 17% Toluidinc Toner.

55% Gum sandarac inury rod). cost G (I?) Rhodarn e Anthra ene containing naphtbacene Light Orangelted 0.5% Hausa yellow. 2.7% Gum sandarac i 1.7% Toluidine Toner. containing Rhoda- 47% Silicon dioxide. mine G (1%). 47% Blane fixe. 1.1% Anthracene connaphtbacene 50% of above magenta aint. 51% of above process b 1e paint.

Orange 50% of above yellow paint. I 5)% of above orange red paint. Yellow Greeu 50% of above yellow paint.

7 50% oi above green paint.

Greenish Blue 50% oi above process blue paint.

a 50% of above green paint.

From' the above it will be seen that chrysene is the fluorescent ingredient corresponding to hue III in Fig. 2, anthracene plus 1% naphthacene or chrysene with 1% naphthacene is the ingredient corresponding to hue II, and sandarac containing rhodamine G is the one corresponding to hue I.

Blane fixe is a commercial barium sulfate (B21604). Chrysene can be prepared as described in Yules copending application mentioned above. In determining the proportions of the fluorescent ingredients in the above paints, the green was made up first with the maximum possible fluorescence. This, of course, determines the strength 01' the hue II and hue III fluorescence required in the other paints. V The (deep) orange-red was then made up relating the hue II to the hue I and fixing the amount of hue I fluorescence required; exposure times are selected to make the brightness oi the fluorescent hues efiectively equal.

In each case the solid materials given in the above table are groundto a suitable consistency in an aqueous solution of gum arabic (30% solution) or other suitable vehicle.

Thus we have a palette 0! artists colors having incorporated in each a quantity of fluorescent ingredient (effectively) directly proportional to one of the subtractive color contents of that one. That is, the amounts of any one of the fluorescent ingredients in the difierent coloring materials are proportional (not necessarily linearly) to the subtractive color contents of the materials and inversely proportional (again not necessarily lin early) to the fluorescent emciency of the ingredient in those materials. The fluorescent emciency depends on the absorption by each material of the fiuoro-activating light and ofthe fluorescent light. It is not necessary that the amounts or the diflerent ingredients bear any special reis made with a non-fluorescent black ink on non-.

fluorescent white base and is then tinted with washes of fluorescent paints such as those described above. The color separation positives are made using the light sources and filters above described, but none of the printers will have any printing density at the points corresponding to the black lines in the original. The original is then illuminated with a light so frared such as incandescent tungsten, the filter is changed to a. Wratten 88A, and an exposure is made on a high contrast infrared-sensitive plate. Upon development, this gives a negative or the black pen lines only with no trace of the colors. A contact positive made on a high contrast plate such as Kodalith completes the set of color positives to be used in so-called fourcolor reproduction. In the latter process, highlight screen negatives are made from the color separation positives and a line negative is made from the black positive. These are printed on metal and etched in the usual manner to produce a set of printing plates.

In common with the broad process, this special embodiment has the following advantages. Color correction is completely eliminated. The step of making separation negatives is also eliminated. A large density jump can be created between the white background and the lightest color tints because, being non-fluorescent the background density is not increased by exposure. This results in a positive from which "highlight negatives are easily made and thus manual opaquing of the highlights on negatives is unnecessary. Correct color positives for photogravure and collotype can be made in a single photographic step.

This special embodiment has the additional advantages that the black pen'lines are eliminated from the color separations automatically. Also this process provides that color comics can be properly reproduced by an economical photographic process, ireeing the art from the limitations of the Ben Day process now used.

Sometimes this special embodiment is a little difiicult to operate if the original contains fine black lines because when the threecolors are not on properly in register with the black, white lines appear. This is due to the fact that the presence of the black lines in the original, even if underlying the other colors, greatly reduce the fluorescence. This may be overcome by making the black outline drawing first and then overlaying this outline with translucent material such as tracing paper and coloring on the translucent material. The black outline drawing and the overlay are separately photographed. Of course, it is not necessary to restrict the photographing of the black outline drawing to infrared or any other specific type in this case. Alternatively the black outline can be made with a bleachable black ink which is bleached before making the color separations.

urce rich in inone material having a What we claim and desire to secure by Letters 'Patent 01 the United States is:

l. The method of producing color separation positives for use in a photomechanical color printing process which comprises creating an original with coloring materials containingthree fluorescent ingredients of different fluorescent hues, the ingredients corresponding respectively to the three subtractive, i. e. yellow, magenta, and blue-green, color contents of the materials, there being at least one material having a yellow content, one material having a magenta content and blue-green content and there being at least two materials having one subtractive color contentin common and in each pair of coloring materials which have a subtractive color content in common, the relative amounts of the ingredient corresponding to this subtractive color content being proportional to the amounts of this content in the pair of materials and inversely proportional to the fluorescent efliciency of that ingredient in those materials, placing three photo-sensitive layers successively in printing relation to'the original, illuminating the original with fluoro-activatin'g light, exposing the layersrespectively to fluorescent light only oi said different hues and developing the layers. 1

2. The method of producing color separation positives for use in a photomechanical color printing process which comprises creating the original with at least four different coloring materials containing three fluorescent ingredients,

each one, in all the materials in which it occurs, being in relative proportion to the amounts of one of the subtractive color contents respectively of the hues of the coloring materials, the fluorescent hues of the three ingredients being different and mutually separable spectrally, illuminating the original with fluoro-activating light, exposing three photosensitive layers successively in printing relation to fluorescent light only and respectively or each fluorescent hue only from the original and developing the layers.

3. The method of producing color separation positives to be used in a photomechanical color printing process employing three color printers the original with at least five coloring materials of which black contains no fluorescent, ingredient and absorbs infrared and of which the others do not absorb infrared and contain three fluorescent ingredients of mutually spectrally separable fluorescent hues, corresponding respectively to the three subtractive colors, yellow,- magenta and blue green, the relative amounts of each ingredient in the materials which contain that ingredient being proportional to the. amounts of the corresponding subtractive color content in those materials and inversely proportional to the fluorescent efllciencies or the ingredients in the materials, placing three photosensitive layers successively in printing relation to the original, illuminating the original with fluoro-activating light, exposing the layers respectively to fluorescent light only and of said difierent hues, developing the layers, placing the fourth photosensitive layer in printing relation to the original, illuminating the original with infrared light, exposing the fourth layer to infrared light only from the original, developing the layer to a negative and making a positive therefrom.

4.'The method of producing color separation positives to be used in a photomechanical color printing process employing three color printers and one black printer which comprises creating a black outline drawing corresponding to the portions of an original to be reproduced by the black printer, overlaying this drawing with translucent o! the original on color materials the translucent material with containing three fluorescent ingredients of mutually spectrally separable fluorescent hues, there being at least two materials having a subtractive color content in common, the relative amounts of each ingredient in the materials in which it occurs being proportional 40 to one of the subtractive color contents of the land one black printer which comprises creating I hues of the materials and inversely proportional to the fluorescent emciencies of the ingredients in the materials, separately photographing the black outline drawing and making a positive thereof and separately illuminating the overlay with fluoro-activating light, placing three hotosensitive layers successively in printing relation to the overlay, exposing the layers respectively to fluorescent light onl or said diflerent hues and developing the layers.

ER MURRAY. JOHN A. C. YULE.

material, creating the color portions

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