US2143787A - Sound track for multilayer film - Google Patents

Description

Jan. 10, 1939. l.. D. MANNES ET AL M3778? SOUND TRACK FOR MULTILAYER FILM Filed Dec, ll, 1935 FHM +22 15 Z;

BLEACH, \\\QQ REEXPSE fvD DEVELOP SULF/IRE ATTORNEYS Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE SOUND TRACK FOR MULTILAYER FILM New Jersey Application December 11, 1936, Serial No. 115,404

2 Claims. (Cl. 535-2) This invention relates to sound tracks in photographic film and particularly to a method for producing a sound track in multi-layer film in which colored images are produced.

Our prior application, Serial No. 8,516, filed February 27, 1935, describes a method for producing natural colored images in photographic film having three differentially sensitized layers on one side of a support. According to the method described in our prior application the film is exposed to the object to be recorded and is then developed in an ordinary developer. The silver image is then removed by a suitable solvent. If a reversed image is to be formed or if a negative is desired the film is fixed to remove undeveloped silver halide and the remaining silver bleached tion which destroys the color images in the upper layers and again forms a developable salt in these layers. The upper layers are then again del veloped to form colored images and the upper or outermost layer again bleached and recolored to form a third colored image.

In the preferred form of the process described in our prior application the lowermost layer of the final film carries a minus red image, the middle layer carries a minus green image and the upper or outer layer carries a minus blue image. Of these three images the minus red image is the only one of the three which is at all suitable for the formation of a sound track, on account of its high degree of absorption of red light. This minus red image is on the bottom or inner emulsion layer and if the sound track is recorded or printed from the outer surface the passage of the light through the upper two emulsion layers decreases the resolving power of the lower layer image considerably below the required limit. The sound image might be recorded through the film support but this would require local or total removal of the backing with consequent danger of halation and the added problem of noise due to the recording of scratches on the film base. In our prior application we also proposed recordlng the sound image in all three emulsion layers.

Here too, however, there is a lowering of the resolving power of the image.

It is, therefore, an object of the present invention to provide an improved sound track in photographic film having three superposed differentially sensitized layers used for color photography. A further object is to provide a sound track which will not be affected by subsequent bleaching and color development steps of the multi-layer film. A still further object is to provide a. sound track in multi-layer film having a high resolving power.

As the upper emulsion layer of the multi-layer film described in our prior application, Serial No. 8,516 has a high resolving power, which is further increased, for blue light, by the presence of a yellow filter dye, this layer is well vsuited to the requirements of a sound track. However, the minus blue dye image remaining in this layer after development is virtually useless as it is nearly transparent to the photo-electric cell used in sound reproducing. It is, therefore, proposed to utilize the silver image in the top layer before it is finally removed by converting it to silver sulfide in the sound track area.

In the accompanying drawing Fig.`1 is a diagrammatic view of the apparatus used in the formation of a silver sulfide sound track;

Fig. 2 is a flow sheet showing the steps in the formation of the sound track; and

Fig. 3 is a. plan view showing the method ofl applying treating solutions to the sound track area of the film.

For a negative-positive process the sound track record can be confined to the top layer by recording or printing through a blue filter. For a reversal process the sound track may be confined to the surface layer by one of two methods. The first method is to record through a blue filter and fully flash the sound track through a yellow filter, thus clearing out the lower two layers, which are sensitive to red and green light, by reversal. This leaves the image in the upper layer only. The second method which is particularly applicable to direct camera recording is to use a lamp operated at suiciently low color temperature to give a predominantly yellow-orange light. An exposure which is sufficient to produce a correct sound image by blue light in the upper layer will then automatically over-expose the records in the lower two layers to give a relatively low density in these layers after reversal.

A conversion of the sound trackimage to silver sulfide may be effected at any stage in the process at which there is still silver in the image. In the case of the multi-layer film described in our prior point in the processing is after the blue-green development and'treatment in hypo at which point the nlm is dried. At this point the film contains images of metallic silver and blue-green dye in each of the layers as well as in the upper layer of the sound track area. The vsound track may be bleached to halide or other salts of silver, such as silver ferrocyanide, by means of an applicator rollers or other device affecting the sound track portion only. The sound track image is then converted to silver sulfide which is not affected by succeeding steps in the color development process. It is immaterial whether or not the blue-green dye image remains with the sound track silver sulde, as subsequent bleach baths will remove it.

The bleached silver halide sound track image may be converted to silver sulde in anumber of ways. The lm may be washed and immersed in developable sulde solution which will cause l.

conversion of the sound track portion only to silver sulde. The film may also be treated with ammonia and hydrogen sulfide vapor to convert the silver chloride-to silverA sulde. A further method oflocal sulding of the sound track area is to apply a sulfide solution by means of an applicator roller or other suitable device to the sound track portion of the lm after it emerges, thoroughly squeegeed, from either of the two differential bleaches used for halogenizing the upper or upper two layers in the dierential process described in our prior application, Serial No. 8,516.

In Fig. 1 of the accompanying drawing we have shown in diagrammatic form apparatus used in the preferred method of forming the silver sulfide' sound track, according to our invention. As shown therein the lm i0 which contains images of metallic silver and blue-green dye in the layers of the picture area and the upper layer of the sound track area is coated with water from the applicator portion il of the hopper i2.V The water may contain a small amount of a suitable wetting agent, such as saponin, to overcome the surface repellency oi the blue-green film and a small amount of a moisture-retaining'agent, such as glycol or glycerin, in order to prevent drying out of the moistened stripsat the edges during the subsequent gas-treating process.

'After being moistened on the sound track porltion the film is passed through a slit into chamber H4 and over a roller into chamber l5 in which it is treated with chlorine or brnmine gas which enters the chamber by a pipe I6.

The lm then passes out of chamber i 5 and over another. roller into a drying chamber I3 in which it is washed free of bleaching gas by a current of air which enters the chamber i 3 by means oi. conduit I1 and leaves by meansof conduit I8. The humidity of the current of air passed through the chamber I3 must be carefully controlled to prevent drying of the moistened film. The current of air is for the purpose only of removing the chlorine or bromine bleaching gas.

'I'he lm is then passed over a third roller into the chamber I9 and thence into the chamber 20 where it is treated with ammonium sulfide vapor' or hydrogen sulde gas entering through pipe 2 I. After this treatment the film passes over a fourth roller in chamber I9 and thence out of the cham. ber. The sulding agent used in chamber 20 may also be supplied by bubbling air of amwhich a slight suction is maintained. Since both of the gases used in the toning are heavier than air, they are retained in the toning vessels by gravity. Any air leaking into the suction boxes i8 and I9 is immediately, swept up by ducts 22, the toning gases being lostr only to a small degree by being carried away as surface layers on the illm. Y

It is important to control the humidity during the entire gas toning operation. If the humidity is'too low the moistened strip may become edgedried and if vthe humidity is too high, the picture area may be visibly affected and objectionable surface deposits may be formed. The gastoning operation should preferably be carried out at a temperature of 60 F. or lower. The humidity should be between about 40% and about `60%. This humiditymust also be maintained suciently high in the drying chamber i3 to prevent drying during the removal of the halogen gas. This chamber is kept at a temperature of 50 to 60 F., and a relative humidity of between 40% and 60%.

Y It is also important to remove any traces of free sulfide from the toned lm before the subsequent bleaching and color-forming development steps of our process. The purpose of the bleaching step following the recording of the sound according to our preferred method is to transform the silver images in certain layers of the picture area to silver halide which is developable. The presence` of any free sulfide in the bleach bath causes the silver image being bleached to be transformed to opaque silver instead of to silver halide. Such contamination of the picture with silver sulde would mean sacrificing picture quality in order` to obtain good sound quality.

The free sulfide is removed from the film by washing the film in chamber 23 by a spray of water from pipe 2&1. 'Ihe water jets are preferably directed obliquely across the lm from the picture area toward the sound track. This washing is followed by squeegeeing the film as shown at 25 after which it passes through a drying chamber 25, in which it is thoroughly dried, preferably by the use of warm air. The lm may also be treated with chlorine or bromine gas or with a solution of chlorine or bromine, to oxidize any unused suliide on the film.

A second method for sulfiding the sound track employs the application of a liquid bath containing a soluble sulfide. The bath employs a quinone bleaching agent and hydrochloric acid and converts the sound track to silver sulfide in a single operation. The liquid -sulflding bath may be applied by applicator II in the same manner as the water of the gas toning method. A suitable liquid sulfide bath may have the foll lowing composition:

The sodium sulfide used in ythis formula may vary from a few tenths of 1% to about 3% or more of the amount of solution by weight.

Glycerin grams Hydrochloric acid grams-- 20 Y Quinone s. grams-- 5 Sodium sulde grams-- 35 `Water liter l In this method of sulnding an after-treatment is also necessary to oxidize or remove unused sulfide. This may be done by treating with chlorine or bromine gas as described above, or by strip application of a chlorine or bromine solution.

In Fig. 2 of the drawing we have shown the series of steps of forming the silveri sulfide sound track as represented by successive sectional views of the iilxn. As shown therein 21 represents a multi-layer iilm having a transparent base. The sound track portion of the iilm is exposed through a mask 2l which prevents exposure of the picture area, the sound being recorded by a suitable recording device, the objective of which is represented at 29. The sound track may be recorded before or after exposure of the picture area of the iilm.

After development the sound track area of the film appears as an image 30 inthe upper layer of the film and a iogged image 3| in the two lower layers of the iilm. It is assumed that the sound track is formed in a fllm being processed according to the reversal method and that the lower two layers have been fogged by one of the methods described above.

After bleaching, re-exposure and development of the film in the usual way as performed in the reversal method, the sound track appears as complementary image 32, the fogged image in the lower layers being removed by this treatment. After suliiding by one of the methods described above, the sound track appears as silver sulfideas shown at 33. The film is then ready for the remaining processing steps to i'orm colored images in the picture area.

Fig. 3 shows in enlarged form the applicator roller il used to apply the water or suliiding solution to the film I0. 'The liquid applied to the sound track in this way is represented at 34.

'I'he sound track formed of silver sulfide according to our method has a number of advantages. It is easy to form by a suliiding method such as those described above, it is opaque to the photo-electric cell used in sound reproducing, and it is not aiiected by successive processing steps of bleaching and color development according to our preferred method of forming colored images. We are aware that photographic sound records of silver sulfide have been described hitherto, for example, by J. G. Capstai in U. S. Patent No. 1,973,463, granted September 11, 1934. Disclosures of this type do not, however, suggest a solution of the present problem, in which it is desired to form a sound track in a iilm which may contain latent picture images in adjacent layers and which will not require some special treatment, such as varnishing, to prevent its destruction by subsequent steps of our process employing bleach baths and colorforming developing operations.

Our method is susceptible of numerous modications and is to be limited only by the scope of the appended claims.

What we claim is:

1. The method of forming sound and naturalcolor picture images in a film having a plurality of layers sensitive to different spectral regions on one side of a transparent support, which consists in forming positive images of metallic silver in bcthsound and picture areas, converting only the silver sound image to silver sulfide, and then successively subjecting the film to a series of bleaching and coloring steps to successively convert different of the picture images to images of silver and a different dye, the bleaching step being one which affects metallic silver but not silver sulfide and converts the picture image to developable salts, and the coloring step being a color-forming development in which a colorforming compound couples with the oxidization product of the developer and in which the silver sulfide sound image is not affected.

2. The method of forming sound and naturalcolor picture images in a filmY having a plurality of layers sensitive to different spectral regions onv one side of a transparent support, which consists in forming images of metallic silver in rboth sound and picture areas, the sound image being formed only in an upper layer of the film and the lower layers being fogged, subjecting the lm to a reversal development to produce complementary silver and dye images in the picture area and the sound area of the upper layer, and clearing the sound area of the lower layers, converting only the sound image to silver suliide, and then successively subjecting the iilm LEOPOLD D. MANNES. LEOPOLD GODOWSKY, JR.

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