US1873674A - Production of cinematograph film positives - Google Patents

Description

ug. 23, 1932. J, E. THORNTON L873674 PRODUCTION OF'CINEMATOGRAPH FILM PosITvEs Filed April 12, 1929 Alf. E .l

BNVENYOR Patented Aug. 23, 1932 AUNITED STATES PATENT OFFICE JHN EDWARD THORNTON, 0F ST. IBRELADE, JERSEY, CHANNEL ISLANDS, ASSIGNOR TO JOHN OWDEN-OBRIEN, 0F MANCHESTER, ENGLAND PRODUCTION OF CINEMAT'OGRAPH FILM POSITIVES Application i1ed April 12, 1929, Serial No. 354,715, and in Great Britain April 25, 1928.

This invention relates to the production,`

of cinematograph or other continuous filmpositives of two (or more) colors by means of a central support of transparent film-material suitablyv prepared with two adhesive substratums and two (or more) photographically produced -component images applied to such substratums upon opposite sides of the transparent support, by first preparing the images each upon a temporary support of porous paper, and then transferring and cementing the two images to the adhesive substratums by ressure-contact assisted by moisture, and su sequently developing both images simultaneously and removing and discarding the two temporary supports of paper.

The objects of the invention are twofold, v1z

(1) To enable a film to be produced with only one piece of transparent support or film material, and with two relief images which are exposed from the back (and developed from the front) Iwhilst on a temporary support of porous paper from which they are subsequently transferred on the one central permanent transparent support back-toback; and

(2) To provide a means or method by which absolutely accurate register of the two component images forming one picture can be ensured by a process of simultaneous registration and simultaneous transfer and cementing of the two images to the one central transparent support.

l State of the art Many investigators' have endeavoured to produce a continuous strip of cinematograph film with asingle support of transparent film and two diderently colored colloid relief images upon opposite sides of the support in accurate register with each other. One method for producing such an article hitherto has been by using two thin supports, each sensitized upon one side, exposing each in printing through the back of its trans arent support, developing the images from t e unrinted front slde of the film, and cementmg the two supports together back-to-back either before or after developing to form a single film. Both strips were perforated before printing, and the perforations served as means of registration when printing and when cementing. The result was technically satisfactory, but objections were made against this method upon the ground that two thin supports cost more to produce than one support of equal thickness to the two combined.

It has also been proposed to form two ref lief images upon two temporary supports and transfer them to a final support of transparent film, all threefbands being previously perforated alike to ensure registration. But as a means of accurate registration this proved useless owing to unavoidable variation in length relatively of the different strips, owing to expansion and contraction during the wet processes of transfer, and therefore the original perforations made in all three bands were at this stage not the same pitch in the transparent final support and the temporary supports. Therefore the original perforations made in the transparent support were useless as traction perforations because they did not place and locate the pictures correctly during projection.

The present invention is designed to overcomeboth'objections, which it accomplishes by the following combination of methods and of constructions:-

A. The images are printed by exposure to light through negatives on to sensitized colloid carried upon the front face of paper strips or temporary supports, both of which have identical perforations and therefore accurately register with each other when laid face-to-face.

B. The printed images upon the two telnporary supports are then accurately registered opposite each other, exposed-face towards exposed-face, by and upon a pair of registration sprockets, the teeth of which exactly fit the perforations of the printed strips.

C. The printed images are then transferred to the two prepared adhesive surfaces of the transparent film which forms the permanent support and at this stage has no perforations sic transfer being effected by pressure when all three bands are clamped together.

D. The printed images are then developed into relief images upon the permanent support of transparent film, the tem orary paper supports being discarded in t e process.

E. Finally a serles of traction perforations are made in the transparent support and the two-color positive is then complete or the transparent support may be perforated before the temporary supports arediscarded i. e. the punches for the perforations pass through both the film and the supports.

' The methods and means of carrying out the invention will now be described in fuller detail.

In carrying out the invention a doublewidth strip of porous paper is provided on its surface with a layer of suitable colloid such as soft gelatine, which is sensitized either with silver salts in the usual way as an emulsion or with bichromate salts applied by absorption.

Suitable coloring matter, preferably dye, is incorporated with the colloid during manufacture of the sensitized paper, in such manner that one half the width contains one color and the other half width contains the other color.

T his double-width paper positive strip is printed with two images from a double-width negative strip in known manner, either by Contact or by projection.

The margins are given a separate or supplementary exposure in order to produce insoluble solid relief margins, as in my specifi'- cations 1,674,810 and 1,67 2,352, instead of the usual transparent and bare margins of other processes.

After printing, the strip is longitudinally divided into two single-width strips, and these are next laid upon the non-perforated single-width transparent lm strip with one of the printed faces in contact with one of the substratums and the other printedV face in contact with the other substratum. To ensure satisfactory contact the surfaces are dampened, the simplest way of producing just the right condition being to pass the strip of transparent support through a water bath (which may contain a very small proportion of acetic acid) and press the dry faces of the printed strips into contact with the adhesive subtratums. After a suitable period of contact the adhesion of the two surfaces will be 'v sufficiently firm, but if preferred the tpiple according to the type of sensitized surface used.

For example, if the colloid has been sensitized with bichromate, development is effected by hot water alone which is applied to the back of the printed image through the porous paper, the hot water dissolving all soft colloid and allowing the paper to come away from the film and be discharged entirely, and leaving behind firmly attached to the transparent support a series of relief images of insoluble colloid.

lf, however, the sensitive colloid consists of a gelatino-silver emulsion it will, after printing, require the additional treatment of developing the silver image, then tanning the gelatine of the silver image in order to render it insoluble, and then total removal of the silver by means of the usual solvents; and

when all these operations have been completed the film is treated with hot water to dissolve and remove the soft gelatine and leave behind relief images of insoluble colloid, as in the previous example.

The coloring matter is preferably incor- A porated with the colloid in the form of transparent dyes at the time of manufacturing the sensitive paper, and therefore when the im ages are converted into reliefs they will be ready-colored relie-fs.

But the process can also be used with noncolored sensitive paper, in which case the relief images, when the developing and treatin processes have been completed, will be co orless and transparent. They are next dyed to the right colors by application of suitable dyes in a dyeing machine fed by ductor rollers, and are afterwards mordanted to permanently fix the colors.

The feature of the invention which renders the successful carrying out of the process possible is the means of registration. The invention will be described with reference to the accompanying drawing:

Fig. 1 is a diagrammatic viewl of the apparatus for carrying out the invention.

Fig. 2 isa transverse section through the temporary supports and the film strip.

Fig. 3 1s a transverse section through the finished film.

In the present invention this is eli'ected by the following combination of operations and methods (1) Making the transparent support withy out any registration perforations;

(2) Assembling the three strips with the printed paper stripsface-to-face with the sub- -tratumed transparent strip between the two;

lnent adhesion of the images to the transparent support;

(5) Simultaneously developing and treating the triple stripin a chamber C and removing the two temporary paper strips during the process;

(6) Finishing (and if'necessary dyeing) the two sets of images, then drying them,

and if desired adding an outer layer of protective varnish to each face in a chamber D;

(7) Adding the usual set of traction 1perforations by perforating the film after al the aforesaid operation are completed by punches E.

A suitable perforationsystem is described in my speciiication No. 1,169,097 and a suitable machine for registering, adhering and developing the strips and also for perforating is described in application Serial No. 366,743 led May 28, 1929.

In previously known and used methods of transferring two series of transfer images from two Apaper strips on to transparent film, it has been usual to transfer them separately one after the other, and generally one over the other. Inthe period between transferring the first and the second series of images one series would alter in length compared with the other, owing to expansion or contraction of either the paper strip or the transparent strip, or both, with the result that the two component images never registered accurately one over the other, and therefore when the picture was magnified upon the screen this difference, though slight in the prints, was greatly magnified, thus spoiling the result. v

In the present invention this serious defect is entirely eliminated, and accurate register ensured, by the hereinbefore described system of printing both sets of images simultaneously on the one double-width strip, and registering and transferring them simultaneously by two sets of registration devices which interlock as one common device only,

Tand developing them simultaneously.

These registering devices may comprise a pair of oppositely placed wheels or drums A having accurately cut sprocket teeth projecting from the surface of each drum, the two paper strips having such 'a series of accurately punched perforations which are accurately spaced to the same pitch as the sprocket teeth. f

To ensure the best results the teeth of one sprocket fit into holes in the other sprocket properly registered upon its own set of teeth and the other strip is likewise always properly registered upon its own set of teeth.

This pair of sprockets always brings the pair of paper strips to the impression point where all three strips are squeezed together. In effect they form a pair of smooth-faced drums or rollers, between which the images to be transferred and the transparent support are gripped, the paper strips passing over or around one half of each of the said drums. The drums may, if desired, be rubber covered to provide slightly yielding pads.

The above described method of obtaining accurate register requires that the pair of paper strips should be of greater width than the lm and that they should have the registration perforations in the margins outside the width of the film.

The same accurate registration can also be obtained with paper strips of the same width as the film strip and with the perforations in the usual margins commonly allowed in the film printing by employing two sprocket wheels the teeth of which do not themselves interlock but which are instead intergeared and driven from a common shaft through worm or bevel gearing. These sprocket wheels are arranged above the impression point the latter being obtained by the first pair of a series of pairs of smooth rollers. Thus the contact of the two paper strips with the film strip does not commence until after the paper strips have passed the registering sprocket wheels instead of at the interlocking sprocket wheels in the earlier described method of obtaining accurate registration.

In both methods two paper strips are independently registered by independent sprockets, but in both methods these sprockets are under one common control either by being interlocked or intergeared, and the blank film is drawn or fed forward by the usual means, and is accurately guided upon each side to the impression point so that it is accurately placed in the right track at the period of impression.

The transferring machine comprises a suitable frame provided with supply spools and receiving reels, and with suitable feed sprockets or drums for supporting and feeding the two paper strips and the transparent strip, and bringing them to the pressure rolls, after which the combined triple strip passes to developing and treating apparatus of any suitable known kind, but preferably to a machine such as described in my prior Patent No. 1,7 36.557 dated November 19, 1929. l

If four-color films are required the operations are repeated by transferring a second set of image-components on to and superinposed upon the first set.

The colors used in producing a film of this description are varied as required. For a two-color natural photograph one color will be orange-red and the other blue-green. For a stereoscopic picture of the non-registering type one image Will be red and the other green.

Monochrome pictures comprising images on one side only of the film support may be transferred and treated in'the same Way.

In my specifications Nos. 1,250,713 and 1,173,898 and 1,173,899, I have described a process for manufacturing a color film comprising a central transparent support With a differently-colored image upon each side, and which is produced by sensitizing the transparent support itself upon both sides and interposing a light-obstructing layer between the support and sensitized layers, and each sensitized layer is printed by exposure from its face side Whilst forming an integral part of the film.

In the present invention the central transparent support is plain and not sensitized, there are no light-obstructing layers, the sensitive layers are carried before printing upon separate temporary paper supports, they are, each printed from the face side of the sensitized layer, and .after printing the sensitized layers are cemented by their printed faces to the central transparent support so that the printed sides are inwards, and are finally developed into reliefs from the back of each print through the porous paper; therefore the former backs of each print become the outside fronts of the completed film (the images having been inverted in the process).

The negatives used in printing have one image of the pair reversed in relation to the other image.

What I claim as my invention and desire to protect by Letters Patent is 1. A process for the production of continuous strip cinematograph film positives comprising printing a series of partial images through negatives by exposure to light on t0 sensitized colloid carried on the front faces of porous paper strips, transferring the partial images so formed one on to each side of a strip of plain non-perforated lm base material, developing the images into reliefs simultaneously through the thin porous paper supports and stripping off the paper supports.

2. A process for the production of continuous strip cinematograph film positives comprising printing a series bf partial images through negatives by exposure to light on to sensitized colored colloid carried on the front faces of porous paper strips'transferring the partial images in accurate register one on to each side of a strip of plain non-perforated film base material, developing the images into reliefs simultaneously through the thin porous paper supports, stripping off the paper supports and finally perforating the film base material.

3. A process for the production of continuous strip cinematograph film positives comprising printing a series of partial images through a negative by exposure to light on to a sensitized orange-red colored colloid carried on'the front face of a porous marginally perforated paper strip, printing a further series of partial images through a negative by exposure to light on to a sensitized bluegreen colored c olloid carried on the front face of a second porous marginally perforated paper strip, transferring by pressure contact the partial images in accurate register from the porous strips, one on to each side of a strip of plain adhesive coated non-perforated film base material, developing the partial images into reliefs simultaneously through their porous paper supports, stripping 0E the a.- per supports and finally perforating the lm base material.

4. A process for the production of continuous strip cinematograph film positives comprising printing a series of partial images through negatives by exposure to light on to sensitized colored colloid carried on the front faces of porous paper strips, transferring the partial images in accurate register one on to each side of a strip of plain non-perforated film base material, developing the images into reliefs simultaneously through thin porous paper supports, stripping o' the paper supports, printing a further series of partial images through the negatives by exposure to light on to the front faces of further porous paper strips, transferringthe partial images 00 vno

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