US1993576A - Monopack process - Google Patents

Description

' MoNoPAcK PnocEss Filed Ag. 1o, 195:5

y WMMW Patented Mar. 5, i935 MoNorAcK raocEss y Leonard T. Troland, deceased, late oi Cambridge,

Mass., by Cambridge Trust Company, Cambridge, Mass., executor, assigner to Technicolor Motion Picture Corporation, Hollywood, Calif., a corporation of Maine Application August 10,

11 Clas.

In certain branches of the photographic art, especially in color photography, emulsions are sometimes used which bear different photographic records in distinct layers or strata thereof. Films or plates of this type are usually termed monopacks, and various methods have been proposed -to separate the records that are superposed in these monopacks. For example, a master' positive can be made from the superposed records, for example two color separation negatives made according to the methods disclosed in the inventors Reissue Patent No. 18,680, entitled Color photography, dated December d, 1932. Subsequently, the outer image can be chemicallyA eliminated as Adescribed and claimed in the inventors copending application Serial No. 477,873, flled August 26, 1930. The master positive and the remaining lower negative record can then be superposed in register, and a so-called duplicate negative printed therefrom. This duplicate negative represents the lphotographic equivalent of the removed outer negative and can be used together with the remaining original negative Vlike any other pair oi color separation negatives. It will be apparent to any one skilled in the art that this method can also be employed wii emulsions containing more than two recor y No matter whether the separation of the superposed monopack records is accomplished according to the afore-.mentionemor other heretofore proposed methods, the resulting set of separated records is imperfect due to the fact that it is practically impossible to give to the inner and outer record layers (that is, the strata adjacent to, and removed from the common support,y

respectively) equivalent treatments subsequent to exposure, so that the nal records do not correspond to an equal degree to the exposures which they received. The diiiiculty of imparting equal treatment to the layers is due to the inuence which the outer record exerts upon the diiiusion properties of the agents used for developing the latent silver halide records, which properties-include all penetration and distribution characteristics Within the emulsion. 'Quite frequently, portions of an inner record which lie directly beneath heavily exposed parts of the upper record receive less development than portions underneath lightly exposed portions of the outer stratum, so that in eiect a positiveimage 'corresponding to the outer record is impressed upon4 the inner record. It is possible somewhat to mitigate this effect by making the development as complete as possible, butit is very Vdiiiicult by a heavily exposed part of the upper record,

1933, Serial No'. 684,545

and often impossible to eliminate it completely. It the main object of the present invention to rectify the above-described inuence of an outer record of a monopack upon an inner record thereof. Another object is the elimination of an 5V outer record by a chemical process in a quick, inexpensive and reliable manner by rectifying, at the same time, the detrimental influence of the outer upon the inner record, exerted during the preceding development process. 10

These, and other objects of the invention will be'apparent from the following description illustrating the genus of the invention by describing a concrete embodiment thereof. The

description refers to a drawing which represents 15` a ow` diagram with schematical lm cross sections illustrating the steps of the process.

It has been found that the above-described undesirable iniluence of the outer record upon the lower emulsion stratum, during devel- 20 opment', can be neutralized by a controlled reduction of both records with an agent which diffuses into4 the emulsion in a similar manner as the developing agent, but acts chemically in the opposite sense, and therefore undoes the un- 25 desirablegeect of the developer. In other words, the emulsion is treated with an agent which reduces the photographic density of the portions of the lower record which,v during development, have not been influenced by the other record, 30 and which are `in most cases purposely overdeveloped, to an intensity which approximates that of the other portions of that record, that is, those portions' whose development was retarded by the outer record. The term reducing 3 is in this connection not employed in its chemical sense, but in its photographical meaning, which implies the diminution of the metallic silver contents of a photographic record. Preferably this treatment is connected with a chemical 4.0 elimination of the upper record, using an agent which irst bleaches the outer record and then begins to reduce or bleach the inner record in the same manner, whereby .the eiect of the outer recordA upon the inner record has the same ex- 45 tension but the opposite algebraic sign as compared with the effect of the developer. The reduction ofthe inner record is more eiective in parts where the developer has not been retarded that is, at the lighter densities of the upper record, Where both developer and reducer can diffuse more' readily. In order to obtain this effect in the best possible manner, the diiusion relationships during reduction should operate physically v'in the same manner as during development, whereas chemically, the record reducing effect should be arithmetically opposite the preceding recordproducing effect of the developer. The better these conditions are fulfilled, the more perfect is the corrected inner record.

In this manner the unfavorable eiect of development is eliminated, together with the removal of the outer image. Sometimes, it is advantageous to employ the reducer also for correcting the excessive density of the inner record, (which is often a consequence of the forced development generally used in suchv processes), by carrying the reducing action somewhat iurther as necessary for correcting the development effect.

In carrying out this invention, any photographic reducer having the above described physical and chemical properties can be used, but ferricyanide or persulate reducers have been found to be particularly suitable, and an embodiment utilizing such a reducer will now be described.

The exposed monopack, as shown at A of the flow sheet, comprises a support S, an upper latent record U, and a. lower latent record L in different strata of the emulsion E, these latent images being substantially undistorted records of respective color aspects which is indicated by uniform shading of the exposed portions (high lights) of the two strata. After development, the silver records are distorted, as indicated at B, where the portions K of lower record L' are shown as of lower density than the remainder H of record L', due to the shielding action of those portions of the upper record which overlap with K, thereby somewhat delaying diffusion of the developer through U into L. It is evident that K is in eiect a positive impression of record U upon record L.

After development and the customary subsequent treatment which may include nxation, the nlm is placed in a bath of an approximately 15% solution of potassium ferri-cyanide (or a weak solution of Farmers reducer, about 3% to 4%), where it remains until the upper record has dappeared entirely, and the lower record is corrected by elimination of the impression thereon of a positive of the upper record, which takes, in normal cases, approximately 5 to 10 seconds, whereupon the lm is given a. very short rinse in water of about room temperature which has the purpose of removing the ferri-cyanide from the lm surface, and nnally bathe the hlm in a 40% solution of sodium thiosulfate. The illm has then a structure as indicated at C, the outer record being eliminated from upper emulsion stratum M and the inner record N being of correct density, without any impression of the outer record.

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

It is claimed:

1. The method of separating superposed photographic records on the same side of a nlm which comprises developing the latent records, and subsequently bleaching the outer record and correcting the detrimental eiect of the outer record upon the inner record during4 development, by treatment with a photographic reducer whose diiiusion characteristics are similar to those of the developer,

of the object iield,`

2. The method of treating monopack lms which comprises developing the superposed latent records of said hlm, bathing the film in an agent having a ditusion substantially equal to that of the developer and affecting photographic records in a sense algebraically opposite to the action of the developer, and interrupting the action of said agent upon elimination of the eiect of an outer record of said nlm upon an inner record thereof, during development.

. 3. The method of separating the superposed photographic records of a monopack nlm which comprises development of the latent recordsthereof, whereby the outer record is impressed upon the inner recor subsequent treatment of said nlm in a solution of potassium ferri-cyanide until the complete outer record and the impression of the outer record upon the inner record are substantially eliminated, an immediately following short rinse in water, and subsequent xation.

4. The method of separating the superposed photographic records of a monopack nlm which comprises development of the latent records thereof, whereby the outer record is impressed upon the inner record, subsequent treatment of said nlm in Farmers reducer until the complete outer record and the impression o! the outer record upon the inner record are substantially eliminated, an immediately following short rinse in water, and subsequent nxation.

5. The method of compensation for the influence during developmentoi' a certain record of a nlm upon a separate and substantially coextensive second record of the same nlm which comprises the step of photographically reducing said second record with an agent having diffusion characteristics substantially similar to those of the developer.

6. The method of compensating for the innuence of an outer record of a monopack nlm upon an inner record of the iilm during development, which comprises the step of controlled photographic reduction of said inner record with an agent having a diiiusion substantially equal to that of the developer.

'1. The methodof compensating for the influence during development of a certain record of aiilmuponaseparateandsubstantally coextensive second record imderneath thereof on the same nlm, which comprises development of both latent records, and subsequent treatment with anagentwhichphysicallypenen'ates thelmin a manner similar to that ot the developer, but whose eiIect upon the density of a photographic record is substantially oppositeto that o! the developer.

A8. The method of separating the photographic records of `a miopack nlm which comprises developing the superposed latent records, making a master positive of the superposed negatives, treating the nlm with a photographic reducer having diffusion properties similar to those of the developer lmtil the outer record is bleached and the eiIect of the outer record upon the inner record during development is eliminated, and making a duplicate negative of said bleached record by copying said master positive and said inner record in simerposed registered position.

9. The method of separating superposed photographicrecords onthesamesideof a iilmwhich comprises developing both records, and subsequently photographically reducing the lower record under control of the upper record, to a degree substantially eliminating the eect of the upper record upon development of the lower record.

I0. 'Ihe method of separating superposed photographic records on the same side of a nlm which comprises substantially overdeveloping both records, and subsequently photographically reducingthe lower record under control of the upper record, to a degree substantially eliminating the effect of the upper record upon development of the lower record.

ll. 'Ihe method of separating superposed photographicrecords on the same side o! a nlm which comprises developing the latent records until they are substantially overdeveloped, the lower record receiving a reduced amount of development underneath the upper record commensurate to the retardation of the developer by said upper record, and photographically reducing said records with an agent being retarded substantially like said developer `until said upper record is substantially bleached and said lower record is brought to a. density approximately conforming to its latent state by said reducing action as controlled by the retardation eected by said upper record similar to the retardation of the developer.

' CAMBRIDGE TRUST COMPANY, Executor of the Last Will and Testament of Leonard T. Troland, Deceased.

By A. MEAD WHEELER,

Its Asst. Secy.

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