US2278423A - Cinematographic film and method - Google Patents

Description

April 1942- w. A. CALL AHA N 2,278,423 CINEMATOGRAPHIC FILM AND METHOD Filed July 31, 1940 S/MULTANEOUS OR CONSECUTIVE} EXPOSURE 0F MATRIX 6 PICTURES AND MARGINS I 9 7 t I l LJ l 2 r 22-P-\ M- Z? HARDEN/NG DEVELOPMENT W 2/- ETCHING AND BLEACH/N6 8 5 L 3 MATRIX FILM M J Fatented Apr. 7, 1942 NlTED s'rarss gra n omnmroommc rimu arm Mn'rnop Walter A. Gallahan, Burbank, Calif assignor to Technicolor Motion Picture Corporation, Hollywood, Calif., a corporation of Maine Application July 31, 1940, Serial No. 348,611

tCiaims.

In printing motion pictures by imbibition it.is customary to use cinematographic matrices comprising picture records in the form of gelatin re liefs which absorb dye in proportion to the depth of the gelatin throughout the different portions of each record, the dye being imbibed by the picture from the dyed matrix when the two films are pressed together face to face. To prevent the relief records from floating oh the film in the etching process it is customary to expose the film through the back so that the exposed portions of the emulsion are next to the film and then to develop the emulsion so that it is less soluble throughout the exposed portions than in the unexposed portions. Thus in etching edges of the relief records until the edge of the picture film contacts the bare margin of the matrix film. Thus the sharpness of the bend depends onthe width of the bare margin; if the a bare margin is narrow the bendis sharp and if off the more soluble unexposed portions with warm water each relief record corresponding to the hardened exposed portions is left firmly matrix film is bare from its edges to the inner ends of the sprocket holes; and in a matrix having no sound-track the bare margin on the sound-track side is still wider.

In dye printing a picture film with a matrix film the two film's must be pressed tightly to gether while in wet condition to bring them into sufiiciently intimate contact for the imbibition of dye from the matrix to the other film and inasmuch as it takes several minutes for the migration of the dyethe films must be kept in in-v timate contact for some time. The only practical way to accomplish this is to feed the two films together between pressure rollers and then to rely upon adhesion to hold the films together as they tendency for the films to separate along the lateral edges of the picture areas, particularly along the narrower bare margin of the matrix opposite thesound-track margin, after they leave the pressure rollers and before the dye transfer is completed, resulting in faulty transfer along the lateral edges of the pictures.

The present invention isbased on the discovery that the aforesaid tendency to separate is due to a deformation of one or both films as they pass between the pressure rollers, namely a sharp bending of one mm toward the other film alon th aligned edges of the relief records. Usually the margin of the picture film is bent over the the bare margin is wide the bend is not so sharp. Consequently the deformation is less along the side of the matrix which is bare in the soundtrack zone as well as between and outside the sprocket holes.

If the aforesaid deformation is'sharp enough to give the picture film a more or less permanent set a slight arch remains in the picture film after it leaves the aforesaid pressure rollers and, as the 5 bent margin swings back more or less toward its normal plane after leaving the rollers, the films tend to pull apart along the edges of the relief records due to the aforesaid arch. In the case of a matrix having no sound-track the deformation along the sound-track side is usually not great enough to cause much trouble, but in the case of bare margins which are narrow the aforesaid arching seriously interferes with dye transfer along the edges of the picture.

According to the present invention the margin of the'matrix film is exposed so that the process-' ing which hardens the picture areas throughout the exposed or non-exposed portions also hardens sulting defamation. when using the type of processing in which the exposed portions are rendered less solublethan the unexposed portions, the exposure of'both picture areas and margin are effected by light transmitted through the back.

of the film; Either one or both margins of the margin or margins preferably approximates the average'exposure of the picture areas so that the average thickness of the relief records approximates that of the shim or shims. It will be understood of course that the margins may be steps of the method;

film may be exposed depending upon particular requirements. The degree of exposure of the Fig. 2 is a side elevation partly in section of apparatus for exposing the margins of a film; H8.8isasectiononlinel8of1"i8.2;

' Fig. 4 is a'section on line 4-lof Fig. 2;

Fig. is a top plan view of apparatus for applying hardening solution to the margins of a film; and

Fig. 6 is a side elevation of the apparatus showninFig.5. I

The particular embodiment of the invention chosen for the purpose of illustration comprises a picture film P which is printed by imbibition from a matrix film M (bottom of Fig. 1), the picture film comprising the usual transparent backing I and a coating of gelatin 2 into which the dye migrates from the relief records 3 on the transparent backing l of the matrix. In the matrix shown in the drawing the position of the sound-track zone is indicated at 5 without anyback it is developed with a developer which hardens the gelatin throughout the exposed portions while leaving the gelatin throughout the unexposed portions relatively soluble. After being uniform throughout the marginal areas because the preliminary'exposure is uniform throughout these areas. Following the etching step the marginal shims may be further hardened, as indicated in the third rectangle of Fig. 1, by applying hardening solution; to the marginal portions of the film as hereinafter described. This not only serves to increase the resistance of the shims to wear but it'also tends to prevent absorption of dye by the shims. After the matrix has been thus completed it is soaked in dye of the appropriate kind and color, then rinsed, and then pressed against the film to be printed by imbibition as indicated at the bottom of Fla. 1. As mentioned above the film P to be printed is first wet to soften the gelatin coating after which the two films are roiled together face to face to squeeze out all intervening air and superficial liquid, thereby to cause the wet films to adhere together long enough for the dye to migrate from the matrix to the other film. By virtue of the shims l the margins of the film P cannot be bent down .over the lateral edges of the relief records 8, thereby avoiding the aforesaid arching and faulty transfer along the lateral edges of the pictures.

- While the margins of the film may be exposed in any one of various ways, typical means is i1- lustrated in Figs. 2, 3 and 4 where M designates the aforesaid matrix, H a light housing containing alamp l2 for exposing the margins of the matrix through the slots It. The film may be fed continuously through the passageway [4 between the rear wall lb of the housing ll and the film gate 18.

One of the various ways of additionally hardening the shims 8 is shown in Figs. 5 and 6 where 2| are soft brushes which wipe the margins of the film M as it passes to the roller 22. The brushes 2| are mounted in the lower ends of inclined tubes 23 which may be supplied with hardening solutions through flexible'tubes 24 leading from a suitable reservoir. The tubes 23 are mounted in a clamp 25 which is supported by a suitable bracket 26. Of the various solutions suitable for use in hardening the marginal shims the following are recommended: an approximately 10% solution of aluminum chloride followed by a rinse in dilute ammonia, or ferric chloride (10% in alcohol) followed by a dilute ammonia rinse..

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. The method of processing motion picture film to produce picture records in relief, which comprises exposing the picture areas of the film to the images to be recorded, exposing the margin of the film between the sprocket holes and the edge of the film to light, developing the film to render the exposed and non-exposed portions of the gelatin differentially soluble, etching off the more soluble gelatin to leave not only the records in relief but also a layer of gelatin along said margin, and then hardening said marginal layer to reduce its dye absorptivity and to increase its resistance to wear without correspondingly hardening the picture area.

- 2. The method of printing a motion picture film by imbibition from a matrix film, which comprises exposing the picture areas of the matrix film to the images to be recorded, exposing the margin of the matrix film with light, developing the matrix fihn to render the exposed and nonexposed portions of the gelatin differentially soluble, etching oil! the more soluble portions of the gelatin to leave not only the records in relief but also a layer of gelatin alongsaid margin, then hardening said marginal layer to reduce its dye absorptivity and to increase its resistance to wear without correspondingly hardening the picture area, dyeing the matrix film, and pressing the two films together to print by imbibition, said marginallayer of gelatin serving to hold said margin from bending toward the other film when the two films are pressed together.

WALTER, A. CALLAHAN.

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