CA1126077A - Antistatic photographic element containing an alkyl sulfide terminated surfactant with pendant carboxylic groups - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The susceptibility of polymeric film supports or polymeric coated paper to the accumulation of static electric charges can be greatly lessened by coating or swabbing such support or the uncoated side of a finished photographic film and paper with a polyfunctional anionic oligomeric surfactant or the alkali metal salt thereof, of the formula:

Description

Background of the Invention This invention relates to photographic film and resin coated papers having improved antistatic properties, and to a method of producing such antistatic photographic film and resin coated paper. A continuing problem during the manufacture and use of photographic film and resin coated papers is that electrical charges tend to accumulate on them.
These static charges are produced as a result of friction on the film or paper from rollers and other parts of the machines through which it passes during slitting or unwinding the film, by contact with dissimilar surfaces, by handling the film, and by various other causes which are familiar to those skilled in photographic art. Electrostatic discharges can also occur as motion picture film is transported rapidly through a camera or projector. When static discharge occurs in film prior to development, it is evident after processing as irregular streaks or patterns in the film. Processed film may accumulate electrical charges in like ma~ner which causes it to accumulate dust, lint and various particles. This type of accumulation is particularly bothersome in the case of projection of slides or motion picture ~ilm as it results in distortion of the projected image, and occasionally, in permanent scratching of the film surface.
Many methods o~ dimin;shing the tendency to accumulate electrical charges on photographic film have been suggested. U.S. Patents 2,074,647; 2,584,337; 2,649,374;

2,725,297; 3,399,995; 3,625,695; 3,630,742 discuss antistatic treatment using resins or polymeric compounds. Compounds of this type, although effective in improving the antistatic properties of the film are usually deficient in that the antistatic layer rubs off in use, and can cause undesirable accumulations oE dust or Elakes in the apparatus. It is also common Eor such zntistatLc composLtions to Eorm slurrles or Elocculent masses durlng processlng thereby creating cl:LfEiculties.
Polymers and copolymers such as those described in U.S. Patent 2,074,647 are usually quite tacky and are subject to pick-off and flocking.
This is particularly unsuitable in that during unwinding of the fi]m base, prior to emulsion coating, since areas of pick-off can produce uneven coating, and when present in significant quantities actually increases static discharge. Emulsion-coated rolls which are treated with this type of antistatic polymer may present an undesirable physical appearance due to pick-off.
The present invention seeks to provide photographic polymeric film supports, photographic films and polymeric coated photographic papers which have a minimum tendency to accumulate static charges~ Eurther, the present invention seeks to provide photographic polymer film supports, photographic films and polymeric resin coated paper having improved antistatic properties and slippage characteristics.
Summary of the Invention It has been found that the static susceptibility of photographic motion picture film coated on photographically inert polymeric film bases such as cellulose acetate, cellulose fonnate, cellulose propionate, cellulose buterate, cellulose acetate-propionate, cellulose acetate butyrate, cellulose nitrate, as well as film-forming polymers such as polyvinyl-chloride, copolymers of vinylchloride-vinylacetate, copolymers of vinyl-chloride, vinylidene chloride, polyamides, polystyrene, polycarbonate, polyethylene terepthalate and the like can be reduced by the present invention. Photographically inert paper stocks which can be treated by the ~^~ - 2 -present invention are those normally used in photographic applications which have one or both sides coated with a resinous film. The susceptibility of films and paper to accumulation of e]ectric charges can be greatly dlminished and nearly totally el:Ln~inatecl by applylng to the surface thereof an alkylsulficle terminated oligomer of the formula:

H IRl R-S ( CH2-C ~ ~ 2 1 ~ H
C C - OH
O
wherein R is an alkyl radical of 6-12 carbon atoms, Rl is H or methyl, a + b is from 4-50 and a/(a + b) is from O to 0.6. Oligomers of this type are made by Uniroyal Chemical and sold under the name of Polywe ~. These antistats are applied from liquids depending upon their being an alkali salt or a free acid in amounts ranging from 0.1 to 1.0~ based on the solvent volume. The alkali metal salts " -- ~

- 3 -are applied from water while the free acids are generally applied from a polar solvent such as methanol, acetone or ethylene glycol monoethylether. It has been found to be advantageous to include a compound or composition which also improves slippage properties when cine film is treated with an antistat. A preferred type of slippage improver would be selected from silicone surfactants or an organo modified silicone copolymer composition. The thickness of the dried antistatic backing layer can range from about 0.05 to ~.5 micron in thickness, dep~nding upon the solids concentration of the solution. The amount of total solids deposited upon the inert plastic base can be varied from 0O5 to 10 milligrams per square foot, as desired, by changing the concentration of the surfactant in the solution employed for the coating operation.

The photographic ~ilms and resin coated papers treated in accordance with the pre~ent invention have significantly lower surface reactivity and excellent adherence characteristics with respect to the antista~ coating. Th~
antistat compositions of this invention are photographically acceptable and are free of the more annoying problems which have been observed with other antistatic backwashes even when applied yrior to emulsion coating. The treated films are free of tackiness and are not subjéct to pick-off and blocking.
- The preferred alkyl sulfide terminated oligomers for use in the present invention are designated as Polywe ~ KX-3 and Polywet~ KX-4 and Polywet~ KX-5. A detailed description Y,tJ~7 of these oligomers which are generally useEul as emulsifiers is found in U.S. Patent 3,498,942 of Dannals. The oligomers are generally used in their alkali metal salt form, preferably the potassium salt, in which form they are usually dispersed in water. These solutions may in turn be diluted with other suitable solvents and applied to the photographically inert polymeric filmbase or resin coated paper by coating, dipping, brushing or other usual ways of applying the solution or dispersion to such a polymeric support. After ~pplication of the antistatic composition, the polymeric film base is dried, leaving a final product, the surface of which is provided with a layer of the particular oligomer used.

The oligomeric surfactants which are preferred for use in the present invention are potassium salts. The Polywet ~ RX-3, KX-4 and KX-5 are both polymeric and polyvalent. They have molecular weights ranging from about 1200 to lS00, have long chains to which are attached substituents which provide multiple ionic charges and in addition have at one end a hydrocarbon chain. This configuration provides a hydrophilic chain of considerable length to one end of which is attached an oliophilic hydrocarbon moiety. This may account for the improved a~tistat properties imparted by coatings of these surfactants.

The differences between individual surfactants of the type used in the present invention is the result of the differing ratios of the monomers from which they are built and the sequence in which they occur along the chain. KX-3 has ~ ~ ' ? ~

molecular weight of about 1500 and a Brookfield viscosity using a ~o. 3 spindle at 20 rpm of about 380. KX-4 has a molecular weight of about 1500 and a Brookfield viscosity using a No. 4 spindle at 20 rpm of about 4200. KX-5 has a molecular weight of about 1200 and a Brookfield viscosity using a No. 3 spindle at 20 rpm about 1200. These measurements were taken using a potassium salts in water at a solids content of about 4~% 1 at a pH between 6.5 and 8~0.

The relative susceptibility of treated filmbase and paper to build-up of elPctric charges was evaluated in accordance with certain tests which measure the conductivity and the resistivity of the treated filmbase and paper. The relative susceptibility of film or paper to the build-up of 15 static charge is related to the conductivity and resistivity of said film or pap~er. These characteristics may be measured by the use of a static electricity generating and measuring device such as that described in U.S. Patent 2,584,337.
Surface resistivity as defined in USP 2649374 is an indication of the electrical resistance of a film sample. It is determined by measuring the resistance in megohms between two electrodes. These values are influenced by the width and spacing between the electrodes but these considerations may be disregarded since these fact~rs are kept constant during comparison tests.
Another indication of susceptibility of a treated filmbase or coated paper may be had by a somewhat subjective test. The film is simply rubbed a pre-determined number of times with a fabric such as nylon in a controlled enviornment.
This charge test simulates handling of the film during loading of the camera, or rubbing or guiding the film while splicing or loading the film into a processing unit for the development or even the handling of film during projection. A simple manifestation of this test is to hold the rubbed filmbase near suspended cotton threads and observe the degree of attraction the base has for the thread. Effective antistat treatments will result in a film which despite rubbing, will not attract threads to any significant extent. When ~he antistat treatment is ineffective or no antistat coating has been applied, rubbing will produce sufficient charge to attract the threads toward the base. This test also gives indication of the film or papers likelihood ~o become charged and attract lint, dust and other debris~

It has also been noted that the antistat treatment of the present invention applied to the underside of a film base as a back-wash does not flake or erode off onto the camera rollers or pressure plates. This problem has been known to occur in earlier antistat applications. It also avoids the undesirable accumulation of dust or flakes in the camera itself. In certain instances, particularly in which polymers have been used to form the antistat coating, there is a possibility of a scumming residue forming in the processing solutions which may adhere to the film. Slides or movie film to which such residue attaches itself will be esthetically J ~

unattractive and give poor images when projected. The antistats of the present invention have been found to be compatible with the processing solutions and do not form a sludge or scum.
S The strong adherence of the antistat of the present invention to the underside of film yet to be coated with emulsion is particularly advantageous in that it avoids pick-off of the antistat or other coating during the unwinding preceding the emulsion coating. The pick-off can result in areas o~ the upper side o~ the base which are not coatable and which show up as spots or other visual defects upon imaging and processing the finished film. The antistat of the present invention are also compatible with lubricant compounds such as silicone surfactants or organo modified silicone lubricants.
This permits the production o~ a film which not only has improved antistat characteristics, but desirable slippage properties which improve the ease of advance in cameras and other hardware.
The following examples are given by way of exemplification and not by limitation. It will be obvious to workers skilled in the art that many modifications may be made therein without departing from the scope or spirit o~ the present invention and claims.

EX~MPLE 1 ~

Antistat coating solvent solutions were prepared comprising 40 parts methyl Cellosolve , 40 parts ethanol, 15 parts acetone, and 5 parts water containing respectively O.OS, 0.1, 0.2, 0.3 and 0.5 parts of Polywet ~ KX-~ which had been first dissolved in the water and then diluted to volume with other solvents. The five solutions were filtered and coated on cine acetate filmbase via conventional bead application technique~ Another coating was prepared which had been treated in a similar manner by a similar solvent composition - but without the antistat compound addition. After drying, the resistivity of the coated side of the films was obtained as is noted:
Surface Resistivity 1. Control-no antistat Greater than 104 megohms 2. 0.05% antistat 1.3 x 103 megohms 3. 0.10% antistat ~.6 x 102 megohms

4. 0.20% antistat 5.0 xlO megohms

5. 0.30% antistat 5.0 x 10 megohms

6. 0.50% antistat 3.8 x 10 megohms (Samples cgnditioned 24 hrs~ at 21 C., 50% R~) Resistivity readings of 10~ are recognized as providing effective antistat protection, 103 readings generally are marginal while 104 and greater readings result in unacceptable cine film performance. The addition of 0.1~ silicone surfactant or an organo-modified silicone copolymer composition to the antistat composition results in at least 50~ increase in slipperiness with no impairment to the antistat propertie In certain types of cine film, it is an advantage to provide enhanced slippage characteristics to the film to promote ease of advance through the cameraO
In another test, sections of the films prepared above were slit to 35mm width and in a 55~ R~ enviornment were rubbed similarly with a cotton cloth. Each film was passed h~ Ji~J

near a suspended cotton string. The attraction of the string to the film was readily noted with the Control strip. However only slight to no attraction of the string was noted with the samples coated with the an~istat composition. This test indicates from practical experience, that effective antistat properties have been provided to the film using ~he composition of the invention.

EX~MPLE 2 Antistat solutions were prepared comprising deionized water and 0~25r 0.6, 0.75, and 1.0% parts Polywe KX-5 by volume. The solutions were filtered and applied to polyethylene coated photographic paper base by means of a conventional metering technique. An uncoated section of resin coated photographic paper base was retained as a control. The resistivity of the treated side of the resin coated paper was obtained and is noted as is the coating appearance of the antistat coating:

Sur~ace Resistivity 1. Control-no treatment Greater than 104 megohms 2. 0.25% antistat 40 x 104 megohms repellent appear.
3. 0.60% antistat 6.0 x 102 megohms 4. 0.75% antistat 4.0 x 102 megohms acceptable coating 5. 1.00% an~istat 4.0 x 102 meyohms acceptable appear.

(Samples conditioned 24 hours at_21C, 50% RH) - Practical experience with the static behavior of resin coated paper base, particularly in slitting operation, indicates that resistivity readings of 102 provide effective antistat protection.

-Antistat solutions were prepared comprising 40 parts methyl Cellosolve , 40 parts ethanol, 15 parts acetone, and 5 parts water containing 0.22 parts of Polywet~ KX-3 which had been first dissolved in the water and then diluted to volume with the other solvents. The solutions were filtered and coated on cine acetate filmbase via conventional bead application technique. Another coating was prepared which had been treated in a similar manner by a similar solvent composition - but without the antistat compound addition.
After drying, the resistivity o~ the coated side of the films was obtained as is noted below:

Surface Resistivity Control-no antistat Greater than 104 megohms 0.22% KX-3 antistat 1.4 x 102 (Samples conditioned 24 hours at 21C, 50~ RH) Resistivity readings of 102 are recognized as providing effective an istat protection, 103 readings generally are marginal while 104 readings result in unacceptable cine film performance. The addition of 0.1%
silicone surfactant or an organo-modified sili~one copolymer composition to the solvent composition results in at least 50%
increase in slipperiness and with no impairment of the antistat properties~ In certain types of cine film, it is an advantage to provide slippage characteris~ics to the ~ilm to promote ease of advance through the camera~

~ ~ ~t~

In another test, sections of the films prepared above were slit to 35 mm width and in a 55~ RH envlornment were rubbed similarly with a cotton cloth. Each film was passed near a suspended cotton string. The attraction of the string to the film was readily noted with the control strip.
Rowever, only slight to no attraction of the string was noted with samples coated with the antistat composition. This test indicates from practical experience that e~fective antistat proper~ies have been provided to the film using the composition of the invention.

Antistat solutions were prepared comprising deionized water and 0.46 and 0.56 parts Polywet ~ RX-3 by volume. The solutions were filtered and applied to polyethylene coated photographic paper base via a conventional metering technique. An uncoated sec~ion of resin coated pho~ographic paper ~ase was retained as a controlO The resistivity of the treated side of the resin coated paper was obtained and i5 noted as is the coating appearance of the antistat coating:
Sur~face Resistivi~y 1. Control-no treatment Greater than 104 megohms 2. 0.46~ RX-3 antistat 3 x 102 megohms-but a non-uniform coating 3. 0.56% RX-3 antistat 1.3 x 10 megohms~uniform coatinq The static behaviour of resin coated paper base, particularly in slitting operation, is such that resistivity r ~
.~S3 readings of 102 are recognized as showing effective antistat protection. Coating aids, particularly those of the anionic or nonionic type common to those used in the art can be added to the antistat rinse solution to aid in uniformity of the coating treatment. This may permit the use of a lower concentration of the antistat.
( EX~MPLE 5 Antistat solutions were prepared comprising 23.5 parts methanol, 76.5 parts acetone and 0.15 parts Polywet~RX-4 which was first dissolved in the methanol and then diluted to volume with the ace~one. The solutions were filtered and coated on cellulose acetate film such as tinted base normally used for color print film via conventional bead application technique. After drying the resistivity of ~he coated side of the film was 102 megohms which provides effective antistat protection. These antistat properties are particularly necessary during the handling of the film during the coating and packaging of the sensitized product as well as during the performance of the film in the camera cartridge. Lower concentrations in range of 0.10 parts of XX-4 provided high resistivity values whil~ concentrations above 0.2 parts cause a solution haze which can result in a slight haæe on the coated film.

Antistat solutions were prepared comprising 83.5 parts methanol, 16.5 parts acetone and 0.92 parts Polywet KX-4 which was first dissolved in the methanol and then diluted to volume with the acetone. The solutions were filtered and coated on photographic grade polyester base via conventional bead application technique. After drying, the resistivity of the coated side of the polyester film was obtained and is noted below:
Surface Resistivity 1. Control-no antistat 100 x 104 (off scale) 2. 0.1% XX-4 Antistat 3.0 x 102 (Sam~les conditioned 24 hours at 21C.,50~ RH) Th~ lower resistivity of the KX-4 treated base from practical experience provides antis~at protection during the manufacturing and finishing tslitting and packaging~ of Aerial film prcduct. Also static problems during Aerial film camera operation are minimized.

Aqueous coating solutions were prepared with 0.138, 0.23, 0.34, 0~46, 0.58 and 0.69 parts Polywet~ RX-4 solids by volume. The solutions were filtered and applied to resin (polyethylene) coated photographic paper base via a conventional metering coating technqiue. An uncoated section of resin coated photographic paper base was retained as a Control. Inspection of the coating appearance showed non-uniformity with the 0.138 - 0.23 part concentration. The 0.34 parts was marginal for coating appearance. Concentrations of 0.46 parts and higher produced satisfactory coatings.
Resistivity readings of the treated side of these ~Z~

satisfactory coatings were all in 102 megohms range. The untreated paper base had high resistivity in the greater than 104 megohms range.
Surface Resistivity 1. 0.138% K%-4 Antistat 8 x 102 megohms 2. 0.23% KX-4 Antistat 5 x 102 megohms 3. 0.34% KX-4 Antistat 3 x 102 megohms 4. 0.46% KX-4 Antistat 3 x 102 megohms 5. 0.57% KX-4 Antistat 1.5 x 102 megohms 6. 0~69% RX-4 Antistat 1.5 x 102 megohms (Samples conditioned 24 hours at 21C., 50% R~) Additional trials with the KX-4 concentration reduced to 0.23 parts could be coated satisfactorily by adding coating aids such as Union Carbide's Tergitol 4 - Atlas Brij 30 combinations or Saponin, or other compatible coating aids normally used by those in the art. Resistivity of these coatings showed resistivity in the 102 megohm range - very similar ~o the resistivity values obtained with the 0.23 parts KX-4 concentratisn which coated with non-uniformity when used by itself. In other words, the KX-4 still fu~ctioned as an antistat but at lower concentrations could only provide a more uniform coating when used in combination with a compatible coating aid.
It is to be understood that the invention described above may be modified in various ways without departing from the spirit thereof or the scope of the invention as claimed.

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A light sensitive photographic element comprising a silver halide emulsion on a support susceptible to the accumula-tion electric charges thereon which is provided on at least one surface thereof with an antistatically effective amount of an alkyl sulfide terminated oligomer, or a photographically accep-table salt thereof, of the formula:

wherein R is an alkyl of 6 to 12 carbon atoms, R1 is H or methyl, a + b is from 4 to 50 and a/(a + b) is from 0 to 0.6.

2. A photographic element as set forth in claim l wherein the alkyl sulfide terminated oligomer is present in the form of its alkali metal salt.

3. A photographic element as set forth in claim l wherein the alkyl sulfide terminated oligomer is present in the form of its potassium salt.

4. A photographic element as set forth in claim l wherein the support element is selected from the group consisting of polymeric photographic film base and resin coated paper.

5. A photographic element as set forth in claim 1 wherein alkyl sulfide terminated oligomer is present in an amount of 0.5 to 10 milligrams per square foot and when dried forms a layer from 0.05 to 0.5 microns thick.