US2370461A - Half-tone intaglio textile printing roller and method of producing same - Google Patents

Description

Feb. 27, 19.45- R; HEBERLEIN ETAL HALFTONE INTAGLIO TEXTILE PRINTING ROLLER AND METHOD OF PRODUCING SAME Filed June 12, 1942 'PE/OE AET INVENTORS. P M

Y ATTORNEYS Patented Feb. 27, 1945 Y HALF-TONE INTAGLIO TEXTILE PRINTING ROLLER AND METHOD OF PRODUCING SAME Rudolf Heberlein,

Wattwil,

and Max Fretz,

Zurich, Switzerland, assignors to Heberleln Patent Corporation, New York, N. Y., a corporation of New York Application June 12, 1942, Serial No. 446,804

In Switzerland November 20, 1940 I Claims.

intaglio printing such as are used in the graphic arts. For example, in intaglio printing the ink is taken up from the design recesses or ink wells in the printing surface (such as a roller), and

perienced in utilizing conventional methods of the unetched portions of the roller are scraped free of ink by a doctor blade which is supported by the unetched portions of the roller (called flands). In the darker shadows or depths of color, the recesses are relatively great, and the unengraved portions of the roller, or lands," are relatively small in area; so that in textile printing a great problem has existed as to how to provide for the relatively large amount of ink withinthe etched portions or recesses while at the same time providing suitable lands to support the doctor without undue impairment of the image. In the absence of sumcient supporting area and distribution of the same in these shadow or darker fields of design, the doctor is not only subject to wear by the lands, but very quickly wears away the lands in the darker areas and this causes the doctor to remove from the recesses the printing medium especially required in these darker areas for proper printing. of the fabric.

In such previous attempts numerous methods have been employed, but those which have produced sufilcient lands have at the same time seriously detracted from the character of print resulting; and prior to this invention no satisfactory solution of this problem has been provided. In attempts heretofore made" to use the photographic process of halftone reproduction in intaglio textile printing, the known intaglio surfaces employed in the usual graphic arts have proven unsatisfactory because of the very'deep or extensive areas of the etching required (for supplying the large amount of ink necessary in fabric printing) since such extensive etching too.

greatly reduces the land areas.

In an effort to solve this problem it has been variously proposed to use a coarse mesh halfreproduces the design. As an attemptedcompromise it has been proposed to provide the design per se of a mesh of such fineness as to more or less satisfactorily reproduce the design and then overlay a much coarser mesh to provide a heavy grid formation of lands. This heavy super-imposed grid obviously obscures the desired design by obliterating a substantial portion. Other proposals have proven equally 'unsuccessful because where sufflcient lands have been provided, and suiilciently extensive recesses made for the requisite quantity of .ink, either the distribution of the ink has resulted in poor image reproduction or in the creation of a moire efi'ect on the printed fabric, or some other equally undesirable feature has been encountered. Accordingly heretofore reliance has'been made on hand engraving or mechanically made designs,

or localized covering during etching, repeat printing, etc. have been resorted to; as opposed to true photographic halftone reproductions utilized in the present invention.

One of the objects of the invention is to provide intaglio rollers capable of accurately reproducing on textile fabrics patterns or designs hav- .ing photographic tonal shade gradations.

Another object is to provide such rollers capable of reproducing such patterns on textile fabrics in multi-color.

Another object is to provide a method for directly transferring to said rollers the photographic halftone patterns and providing on said rollers suitable lands in the darker image areas.

Further objects of the invention will more fully appear from the following description taken in connection with the accompanying drawing,

certain figures of which illustrate by way of example certain steps in carrying out the process and product resulting therefrom.

Referring to the drawing:

Fig. 1 is a much enlarged perspectiveview somewhat diagrammatically illustrating an intaglio printing-surface of the prior art wherein the lands are in the form of continuous lines arranged in grid formation with the intervening spaces serving as ink recesses of equal area and tone, but this only-crudely and unsatisfactorily varying in depth to provide the tone gradations;

Fig. 2 is a much enlarged plan view somewhat diagrammatically illustrating an intaglio printing surface of the prior art intended for specific usein textile printing, in which the design is provided for as in Fig. 1, and with a supplemental grid design of relatively greatly increased mesh superimposed in order to furnish increase support for the doctor;

Fig. 3 somewhat diagrammatically illustrates ing the etched recesses of the same depth, and

varying the area of the recesses to provide for tone gradation:

Fig. 4 illustrates an enlarged halftone screen positiveof a portion of the design to be reproduced in accordance with this invention, and

Fig. 5 represents the corresponding screen positive portion 01- Fig. 4 after it has been treated in accordance with applicants invention;

Fig. 6 illustrates highly magnified portions of an intaglio printing surface made in accordance with this invention.

We have found that by selecting a relatively fine halftone 'mesh (rather than a relatively coarser one as heretofore proposed for textile printing) and by so employing it in the photolithographic process that the transparent dots of the screen diapositive in the darker field corre- -an intaglio printing surface of the prior art spend to the lands, and by controlling the size .of these dot lands in the darker. field areas of the design, a master positive may be prepared from. which the photographic halftone pattern may be transferred directly to the roller, which after treatment and etching results in a satisfactory intaglio printing surface on which lands in the darker areas are provided by separate dots closely disposed and furnishing an entirely satisfactory doctor support. Also, the deeply etched area surrounding said dots provides an ample supply of printing medium for textile fabric printing. Wehave also found that by etch ing the printing surface, surrounding said separate dot lands, to a depth of about 0.04 mm. (1. e.,

' .0015'7") this relatively large amount of printing printing) nevertheless it faithfully reproducesthe equivalent tonal depth gradations of the original design in amost pleasing manner. In other words, the intaglio surface which we provide for textile printing is in eifect the reverse of that employed in halftone intaglio printing onpaper. In our intaglio surface, in'the darker. areas or full tone darks of the image, the etched recesses or wells are the cross lines and the dots are the lands; whereas the' usual practice is to have the dots correspond'to the wells and the cross lines to the lands (see Figs.l and 3). Likewise, the original photographic halftone pattern is maintained and is not partially obliterated as has bee proposed heretofore (Fig; 2).

, 'I'o e xplain the process and for the sake of simplicity, let us start with thereproduction of a single color pattern which, however, otherwise shows all the diflerent shades. In order to obtain a screen transparent positive showing the true value of the shades, it is immaterial whether the screen picture is taken directly from the pattern or-whether one effects only subsequently-a-separation into points of different size, in accordance with the tonal gradation, by means of an ofl'set screen in a manner itselt well known in the art of photo -lithography.

of -dots per inch or finer.

It is often advisable to first produce a nega tive and toretouch the same. The screening can be effected (1) directly from the original or (2) via a halftone negative or positive. It is also immaterial whether this'is done through (a) a camera exposure with an offsetscreen havin transparent dots inserted between the camera and original or (b) through a contact print by means. of the oil'setscreen and with the use of a punctiform source of light. In both cases the picture is dissolved (separated) into dots of different sizes as known from photolithography due to the diffraction of the light through the screen.

The photographically produced dots vary in size in accordance with the lights or darks of the image, and in this way produce the halftones. It is important that the size of these dots is in the correct ratio to the shade value of the parts of the picture in question. Whatever photographic procedure is used to dissolve or separate the image into dots, in accordance with ourinvention, the resultant halftone photographic print must be of a relatively fine mesh, i. e., a fineness of the order of 100 per inch or finer. We have also obtained good results with a fineness of the order of 136 per inch. Since the invention contemplates using the dots as lands in V the darker tone areas, such a fineness in the relatively deep etching required for textile printing will furnish insuiiicient doctor support; and we therefore increase the; dot areas by suitably treating the photographic negative or positive in such portions only corresponding to the darker tones, while maintaining the same mesh fineness.

In the following typical example of a preferred form of'our process, it is assumed that a unit design is to be reproduced as a continuous or composite design on a strip of fabric. A photograph is first taken of ,the unit subject'(for example a blossom) and a negative is made and retouched if and as desired. A film positive is made from said negative, by suitable means such as an offset-screen, and this positive (Fig. 4) is so made as to have a halftone mesh fineness of the order On the positive thus made the image tones are defined by variations in the relative size of the black or dark dots, which are larger in' the darker tones and smaller in the lighter tones. In the deeper tone or dark image areas such as [0 (Fig. 4) the black dots are of such a size that they meet or join together in the general'form of a grid, which defines the intervening spaces so that they appear as white or transparent dots which may be of any desired geometric shape, depending upon the screen used. Conversely, in the lighter tone image areas such as l I (Fig. 4), the-black dots being relatively small appear on a field which assumes the general form of a white or transparent grid, Intermediate image tones vary in between these two extremes while the highlights such as I: may have no apparent screen effect. Throughout the entire tone range where screen efiects are apparent, the screen mesh is of the same fineness. If this positive were photographed as it is on a roller to be etched for intaglio textile printing, then in the deeper tone portions such as I the transparent dot areas would be so small that the subsequent etching of the roller; to the degree necessary to provide for textile printing, would result in insufiicient doctor support (or lands) while in the lighter portions such as H, or in intermediate. tones, ample doctorsupport would be. available. Hence the lighter tones and certain of the intermediate 2,370,461 Y i I 3 tones are covered over or protected, such as with a suitable coating, and selected darker areas are left uncovered for further treatment. The

positive film is next treated with a film photographic reducer such as potassium ferrocyanide reducer, or other means known in the photographic arts, to thereby increasethe size of the white or transparent dots in the darker tone areas tothat necessary for the resultant doctor support desired. Fig. 5 shows the positive film after such treatment wherein the enlargement of the transparent dots is apparent in the darker tone areas, such as m.

. A register negative may now be made from the positive shown in'Fig. 5, as by contact printing, and by suitable means such as a step and repeat? photocomposing machine, a composite master printed) is covered with an etch resist protectivematerial such as asphaltum and a positive of the design (i. e., the portions to be printed) is delineated by said asphaltum and presents the unprotected metallic surface of the roller to, be etched. The roller is then chemically etched in a manner familiar to those skilled in the art; the duration and intensity of etching depending to a great extent upon the fineness of the screening, etc. The resultant intaglio surface (Fig. 6) then presents in the shadows or darker tones such as 13 isolated dots Hi relatively closely spaced and surrounded by a recess 55, in the form of a grid, serving to hold the necessary quantity of ink or the like for textile fabric printing: while in the lighter tones, such as IS the unetched surface provides lands in the form of a grid ll in which ink wells l8 appear as dots. As above set forth, we have found that the number of these relief dots per inch should be at least of a fineness of the order of 100 per inch and we have obtained successful results with a fineness of the order of about 137 per inch, and also 175 per inch.

MuZti-color printing the respective colors red, blue and yellow and a film corresponding to the black print by the use of a red-violet color filter. Each reproduction corresponding to the respective four colors was reproduced in a halftone positive film in a inanembodying the features of our invention have been successfully utilized in a conventional textile printing machine to produce multi-color prints on textile fabrics presenting such accurate halftone values as to compare most favorably with the original colored subject thus copied.

It will of course be appreciated by those skilled in the art that instead of enlarging the transparent dots on the positive film by reducing the darker surrounding portions, as set forth in the preceding example; a screen negative may be' produced to break up the subject image into tonal values, and the small opaque dots in the darker tone areas may be enlarged by suitable photographic treatment, and a positive film printed from the altered negative so as to produce the desired enlargement of the'transparent dots on the positive film. Other variations from the examples herein described will readily occur to those skilled in the art as well known equivalents contemplated as falling within the scope of the invention.

It is of course obvious that the intermediate step of composing a continuous design from a unit design may be dispensed with in instances where it is desired only to produce the unit design; and in this case the unit design diapositive with the altered dot transparencies may be used to print directly upon the sensitized metallic printing surface.

Having thus described our invention with particularity with reference to a preferred method of carrying out the same and in connection with a product embodying a preferred form of the in vention, and having referred to some possible modifications, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without departing from the spirit and scope of the invention,-and we aim in the appended claims to cover such changes and modifications as are withinthe scope of the invention.

What we claim is:

1. In a process for ma an intaglio roller for textile fabric printingthe steps which comprise making a halftone positive photographic reproduction of the desired subject having a screen mesh of at least a fineness of the order of 1,00 per inch wherein the darker tones of the image pattern consist of light dots on a relatively dark field, photographically reducing said dark field to increase the area of said light dots in selected darker areas, to thereby produce an altered halftone photographic pattern of said subject in which enlarged separate light dots are defined on a dark field in said selected darker tones, photographically reproducing the altered halftone pattern onto a printing roller surface, and etching said roller in areas corresponding to the opacities of said altered halftone positive to thereby provide .an intaglio printing surface in which said darker tone areas of said image comprise continuous channels in the general form of a grid.

2. In a process for making an intaglio roller for textile fabric printing the steps which comner' set forth aboveand similarly corrected to a increase in the darker tones the size of the transparent dots for the purpose heretofore set forth;

the respective films suitably coordinated as to register and a separate roller produced for each corresponding color value in accordance with the process previously described. 'Multi-color rollers prise aking a halftone positive photographic reproduction of the desired subject havin a screen mesh of at least a fineness of the order of per inch wherein the darker tones of the image pattern consist of transparent dots on a relatively opaque field, photographically reducing said opaque field to increase the area of said transparent dots in selected darker areas only, to thereby produce an altered halitone photographic pattern of said subject, photographically reproducing the altered halftone pattern onto a printing roller surface, and etching said roller in areas corresponding to the opacities of said altered halftone positive to thereby provide an intaglio printing surface in which said darker tone areas of said image comprise continuous channels in the general form of a grid.

3. ma process for making an intaglio roller for textile fabric printing the steps which comprise making a halftone positive photographic reproduction of the desired subject having a relatively fine mesh wherein the darker tones of the image consist of transparent dots on a relatively opaque field, photographically reducing said opaque field to increase the area of said transparent dots in selected darker areas only, to thereby produce an altered halftone photographic image of said subject in which enlarged transparent dots are defined on a relatively opaque field in the darker tones, photographically reproducing the altered halftone image onto a printing roller surface, and etching said roller in areas corresponding to the opacities of said altered halftone posi-= tive to thereby provide an intaglio printing surface in which said darker tone areas of said an opaque field in the darkertones, enlarging the smaller dots in said dark tones while leaving said enlarged dots separated, photographically reproducing said altered positive pattern onto a metallic surface to be etched, and deeply etching said metallic surface in said darker tones surrounding said enlarged dots, whereby said closely spaced enlarged dots provide lands for supportimage comprise continuous channels inthe genmaking a positive halftone photographic pattern of a subject, said positive comprising fine screening providing closely spaced transparent dots on ing the doctor in intaglio printing and said etched surface in. said darker tone areas provides recessed areas inthe general form of a grid.

5. In a process for making an intaglio roller for textile fabric printing the steps which comprise making a negative photographic pattern of a subject, said negative comprising fine screening of the order of at least 100 per inch providing closely spaced opaque dots on a transparent field in darker tones, producing a. positive in which corresponding dots are transparent on an opaque field and wherein'the smaller dots in said darker tones are larger than those of said photograph but are smaller than required to touch each other, photographically reproducing said positive pattern onto a metallic surface to be etched, and etching said metallic surface in said darker tones surrounding said enlarged dots, whereby said closely spaced enlarged dots provide lands for supporting the doctor in intaglio printing and said etched surface in said darker tone areas provides recessed areas in, the general form of a grid.

RUDOLF HEBERLEIN.

FRETZ.

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