US2358590A

US2358590A - Strip film

Info

Publication number: US2358590A
Application number: US414433A
Authority: US
Inventors: Frank T Powers
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-10-10
Filing date: 1941-10-10
Publication date: 1944-09-19
Anticipated expiration: 1961-09-19

Description

Sept. 19, 1944. F. T. POWERS; 2,358,590

STRIP FILM Filed Oct. 10, 1941 ANTI-ABRAS/ON M Mum/01v V I4 cauaolamoyfo 5; ADHESIVE I DYED LAYER l0 PAPER 7 W v: LEDNGTH Patented Sept. 19, 1944 UNITED STATES- PATENT OFFICE Frank '1. Powers, Glen-Cove, N. Y. Application October 10, 1041, Serial-No. 414,433

. I 4 Claims. The present invention relates to novel improvements in photoengraving and photome .chanical reproduction and more particularly to an improved strip film and halftone process for photomechanical use.

Objects and advantages of the invention will be set forthin part hereinafter and in part will be obvious herefrom, or may belearned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims. i

The invention consists in the novel parts, conabsorbing most of the light shorter than 5,500

A. Thus, the only light reaching the paper base and which might otherwise reflect from the-base is substantially completely absorbed, and substantially no light is reflected to the emulsion which might fog the photosensitive material.

The dyed support between the base member and the emulsion layer also preferably absorbs muchof the light scattered by the silver halide in the emulsion, so that both the scattered light, and the reflected light from the base are greatly reduced, causing a great reduction in structions, arrangements, combinations and'im-.

provements herein shown and described.

The accompanying drawing, referred to herein and constituting a part hereof, illustrates one embodiment'of the invention, and together with the description, serves to explain the principles of the invention.

Fig. 1 is a diagrammatic sectional view of a typical and illustrative sheet of photosensitive material in accordance with the present invention: and

Fig. 2 is a graphical representation of certain general characteristics of the various materials used with the present invention.

The present invention has for its object the provision of a novel and improved photosensitive sheet material particularly adapted for photomechanical use where relatively high contrast and resolvingpower are desired. A further obiectis the provision of a novel and improved in the making of halftone negatives which comprises a photosensitive film, such as a silver halide emulsion, releasably secured to a base, such as a sheet or web of paper. Incorporated in a thin layer permanently aflixed'to and carrying and supporting the emulsion,is a dye which allows the transmission of most of the light having a wavelength shorter than 5,500 A., and ab-, sorbs most of the light of a wave length longer than 5,500 A., while the base member is complementarily colored, as by coating, with a dye the light of a wave length shorter than 5,500 A.,

halation, an increase in contrast and a high effective resolving material.

The photosensitive film is releasably secured to the base member or other surface, and after development, fixation and washing, the photosensitive film may be removed from its base member and stripped onto a sheet of glass or other negative support. During the fixation and washingoperations some of the dyestufl may be washed out of the film and what remains does not substantially interfere with the transmission of light during the operation of printing the neeative on the metal. This printing operation is usually carried out by a carbon or mercury vapor are using a bichromated or chromated colloid as the photosensitive resist on the surface of the material to be etched. Furthermore, the dye with which the support is dyed is substantially transparent to the light with which the copy is illuminated, as' well as to the rays which principally afiect the emulsion layer, although I have found that some advantage is obtained in using a dye which filters out certain portions of the spectrum 0; the light used for illuminating the copy. The invention will be described in detail in connection with strip film particularly adapted for making halftone negatives using mercury vapor arcs as the source of light for the photographic and printing operations.

As shown in Fig. l, the strip film comprises a paper base 10, the upper surface of which is covalthough I prefer to use a dye. which absorbs all of the light from the violet to at least 5,000 A. Such a dye usually has an orange or reddish color, and in fact, orange and red-dyes in general are suitable, although their visual appearance is not always a sufllcient test of their suitability as some may have strong transmission bands in the 'blue' and violet.

power of the photosensitive The photosensitive fllm comprises a silver halide-gelatine emulsion H which is orthochromatic or panchromatic and is coated on thin support layer of dyed collodion l6, dyed and permanently attached to and in optical contact with the emulsion layer Id. The dye in support I! the colored'base member M by means of a thin adhesive layer i1 so that the first three layers are retained together during exposure and developing, and separate from the base member i during the fixing or subsequent washing. Thus, the silver halide emulsion laye containing the negative becomes detached from thepaper base member l0 and may be stripped on to a clear glass plate, with coating it against the glass plate.

In Fig. 2 of the drawing there is showndiagrammatically the-general relation of the different factors entering into the specific embodiment of the invention described above. In this diagram absorption of the various dyestuffs, the sensitivity of the silver halide, thechromated or bichromated photosensitive resist, and the principal lines of the mercury vapor arc spectrum are all plotted against wave length in a single diagram. v

As shown, the mercury vapor arc emits light having the approximate wave lengths 3,650 A., 4,080 A., 4,360 A., 5,460 A., 5,760 A. and 5,790 A., the vertical length of the lines indicating roughly the relative intensities of these various wave lengths in the mercury vapor arc spectrum.

Curve 20 shows, roughly, the sensitivity of the silver halide-gelatine emulsion, such as constitutes the layer I4, and this emulsion has a maximum sensitivity at approximately 4,000 A., and a secondary maximum sensitivity at approximately 5,500 A. No data is shown below 3,200 A. as light of the shorter wave length is not appreassaseo Y lengths scattered by the silver halide particles.

Curve 23 illustrates generally the sensitivity curve of a coating of chromated colloid such as is generally used in photosensitive resists for the printing of halftone negatives on copper, and may be considered typical of various cold top enamels, this sensitizing material having its max-' imum sensitivity at approximately 3,700 A. Curve 24 is a similar curve illustrating the sensitivity of bichromated colloids which have their maximum sensitivity at approximately 3,600 A.,

ciably transmitted by the various glass plates corresponding to the secondary maximum sensitivity at 5,500 A.

Curve 22 illustrates generally the absorption spectra of the orange dyeused for the coating of the paper base III, and this dye preferably absorbs most of the light of a wave length shorter than 5,500A. or at least 5,000 A.. thereby preventing reflection of any actinic rays transmitted through the emulsion layer it and dyed layers II and H a As anxample of a dye suitable for dyeing this layer H, toluene fast orange (Schultz No. 709) may be given assuitable. a l

The generally blue or bluish-green dye with which'the support I! .is dyed and the generally orange dyewitlrwhich the coating II is dyed are substantially complementary in color so that any light transmitted through the support I! is not and it will be noticed that both the chromated.

and 'bichromated colloids may be insolubilized by the mercury vapor are lines 3650 and 4080.

In actual practice it has been found that strip film, in accordance with the present invention,

yields negatives which have greatly increased contrast between the halftone dots and'the intervening portions, preserve the range of tones, reproduces much flner detail and can be etched and flnished in much shorter time than with similar negatives made on conventional strip'film material, and in many instances no re-etching, staging or hand finishing is required on the halftone photogravings. The strip film of the present I invention also allows much wider latitude in exposure, both in the camera and on the metal. In fact, by the use of the strip film material of the present invention, the usual staging or finishing operations, requiring a great deal of skill and consuming a great deal of time, are almost completely eliminated.

The exposure required for the negative in the camera is not greatly lengthened, as the bluish dyed support I! affects only the light transmitted by the emulsion and might be reflected by the base it to cause halation, as will be noted from

curves

20 and 2| in Fig. 2.

It will also be noticed from

curves

20 and 22 ofF'ig. 2 that the orange dye of coating I I almost completely absorbs any light which might affect the principal sensitivity of the silver halide emulsion, and such small amount of reflected light as might affect the emulsion in the neighbor- .hood of 5,500 A. is absorbed by the bluish dye insupport I 5.

During the fixing and washing operations fol-- lowing the development of the halftone negative,

some of the bluish dye may be removed from the support I! thereby increasing the transparency, but such dye as does remain, does not materially reduce the transmission of the light from the mercury vapor arc to which the photosensitive coating on the metal is sensitive, this light lying principally between the wave lengths 3,300 and 4,200 which is also the range of maximum transmission by the bluish dye.-

While I prefer to use an orange or reddish dye in the coating ll, it is also possible to use the.

, aasasao the thereby enabling the operator to readily see character of the negative and determine when development has been completed and whether or not the negative is of satisfactory quality.

It is not necessary, although vit is preferable, that any of the bluish dye remain in the support I! after development. Its effect is exerted primarily during the photographic steps in the camera, but to some extent, the same eflect is also obtained during the printing of the negative onto metal sensitized with the bichromate or other chromic acid salt sensitizer, the sensitiaer and blue dye being complementary to each other.

Emept as described, the operations in the production of a h on metal, may-be carried out with the present invention as with conventional strip film mate- 'rial, and the same developing and fixing solutions may, in general, be used.- 1

The invention in itsbroader aspects is not limited to the specific elements shown and described but departures may be made therefrom alftone negative and its printing r within the scope of the accompanying claims without departing'i'rom the principles of the invention and without sacrificing its chief advantages. 4 5

What I claim is:

1. A photosensitivc material for photomechan ical reproduction including a color sensitive silver halide emulsion layer sensitive to wave lengths substantially longer than 5500 A., a supporting v base, an interm tively fast to the treating solutions, the filtering layer transmitting light towhich a chromic acidsalt is sensitive and absorbing most of the reate filtering layer dyed relamainder oi the light andthe basebeing colored ical reproduction including a color sensitive silver halide emulsion layer sensitive to wave lengths; substantially longer than 5,500 A., a supporting base, and an intermediate filtering layer of permanently bluish dyed collodion, the filtering layer transmitting light to which a chromic acid salt is sensitive and absorbing most of the remainder oi the light and the base being colored substantially complementary to the color of the filtering layer and a releasable layer between the filtering layer and base.

3; A photographic negative strip film material for photomechanical use including a silver halide emulsion sensitized to light ofwavelengths substantially longerthan 5,500 A. supported on a layer colored with a substantially fast coloring material to transmitmost of the light oia wavelength shorter'than 5,500 A. and to absorb most oi the light of a wave length longer than 5,500 A.

' and emulsion are adherent for easy detachment substantially complementary .to the coloroi the filtering layer and a releasable layer between thefilter. layer and base.

with the colored layerintermediate the emulsion andbase, said colored 'base' absbrbing most or the light of a wave length shorter than 5,500 A.

and said colored layer transmitting most of the light or a wave, length shorter than 5,500 Land absorbing most 0! the light longer than 5.5001."

A photosensitive. material for photomechan-