Topcoat for motion picture film

FIELD OF THE INVENTION
The present invention relates to an improved motion picture film, and more particularly to a motion picture film that resists tar adsorption and stain absorption.
BACKGROUND OF THE INVENTION
Motion picture photographic films have long used a carbon black-containing layer on the backside of the film. This backside layer provides both antihalation protection and antistatic properties. The carbon black is applied in an alkali-soluble binder that allows the layer to be removed by a process that involves soaking the film in alkali solution, scrubbing the backside layer, and rinsing with water. This carbon black removal process, which takes place prior to image development, is both tedious and environmentally undesirable since large quantities of water are utilized in this film processing step. In addition, in order to facilitate removal during film processing, the carbon black-containing layer is not highly adherent to the photographic film support and may dislodge during various film manufacturing operations such as film slitting and film perforating. Carbon black debris generated during these operations may become lodged on the photographic emulsion and cause image defects during subsequent exposure and film processing.
After removal of the carbon black-containing layer the film's antistatic properties are lost. Undesired static charge build-up can then occur on processed motion picture film when transported through printers, projectors or on rewind equipment. Although these high static charges can discharge they cannot cause static marks on the processed photographic film. However, the high static charges can attract dirt particles to the film surface. Once on the film surface, these dirt particles can create abrasion or scratches or, if sufficiently large, the dirt particles may be seen on the projected film image.
In U.S. Pat. No. 5,679,505, a motion picture print film is described which contains on the backside of the support, an antistatic layer and a protective overcoat. The protective overcoat is comprised of a polyurethane binder and a lubricant. The polyurethane binder has a tensile elongation to break of at least 50% and a Young's modulus measured at 2% elongation of at least 50000 lb/in.sup.2. The tough, flexible overcoat has excellent resistance to abrasion and scratching during manufacture, printing, and projection, while acting as an effective processing barrier for the underlying antistat layer.
However, post-processing tar deposits and stain have been a problem with protective overcoats in motion picture film. This tar is derived mostly from polymeric oxidized developer. The present invention relates to eliminating tar pickup during processing by providing a very thin topcoat over the polyurethane layer. The topcoat is obtained by the coating and drying of a coating composition comprising gelatin-coated, latex particles. The topcoat is effective at coverages so low that the excellent physical properties conferred upon the support by the polyurethane are retained.
In copending commonly-assigned United States Patent Application Ser. No. 08/856,711 now U.S. Pat. No. 5,786,134, is described a motion picture film having a topcoat that resists processor tar pickup. The topcoat contains at least 20 percent by weight of a hydrophilic colloid such as gelatin.
It would be desirable to provide a stain resistant topcoat of that resists processor tar stain, is readily manufactured and provides good physical properties.
SUMMARY OF THE INVENTION
This invention relates to a motion picture film having a support and having, in order, on one side thereof an antihalation undercoat and at least one silver halide emulsion layer and having, in order, on the opposite side thereof an antistatic layer, a protective overcoat; characterized in that said protective overcoat includes a polyurethane binder, the polyurethane binder has a tensile elongation to break of at least 50% and a Young's modulus measured at a 2% elongation of at least 50000 lb/in.sup.2, and a topcoat farthest from the support which comprises gelatin-coated, latex particles.
DETAILED DESCRIPTION OF THE INVENTION
The photographic film support materials used in the practice of this invention are synthetic high molecular weight polymeric materials. These support materials may be comprised of various polymeric films, but polyester and cellulose triacetate film supports, which are well known in the art, are preferred. The thickness of the support is not critical. Support thickness of 2 to 10 mils (0.002-0.010 inches) can be employed, for example, with very satisfactory results. The polyester support typically employs an undercoat or primer layer between the antistatic layer and the polyester support. Such undercoat layers are well known in the art and comprise, for example, a vinylidene chloride/methyl acrylate/itaconic acid terpolymer or vinylidene chloride/acrylonitrile/acrylic acid terpolymer as described in U.S. Pat. Nos. 2,627.088, 2,698,235, 2,698,240, 2,943,937, 3,143,421, 3,201,249, 3,271,178 and 3,501,301.
The antihalation undercoat used in this invention functions to prevent light from being reflected into the silver halide emulsion layer(s) and thereby causing an undesired spreading of the image which is known as halation. Any of the filter dyes known to the photographic art can be used in the present invention as a means of reducing halation. Thus, for example, water-soluble dyes can be used for this purpose. Such dyes should be incorporated in the antihalation undercoat with a mordant to prevent dye diffusion. Alternatively, and preferably, a solid particle filter dye is incorporated in the antihalation undercoat.
Useful water-soluble filter dyes for the purpose of this invention include the pyrazolone oxonol dyes of U.S. Pat. No. 2,274,782, the solubilized diaryl azo dyes of U.S. Pat. No. 2,956,879, the solubilized styryl and butadienyl dyes of U.S. Pat. Nos. 3,423,207 and 3,384,487, the merocyanine dyes of U.S. Pat. No. 2,527,583, the merocyanine and oxonol dyes of U.S. Pat. Nos. 3,486,897, 3,652,284 and 3,718,472, the enamino hemioxonol dyes of U.S. Pat. No. 3,976,661, the cyanomethyl sulfone-derived merocyanines of U.S. Pat. No. 3,723,154, the thiazolidones, benzotriazoles, and thiazolothiazoles of U.S. Pat. Nos. 2,739,888, 3,253,921, 3,250,617, and 2,739,971, the triazoles of U.S. Pat. No. 3,004,896, and the hemioxonols of U.S. Pat. Nos. 34,215,597 and 4,045, 229. Useful mordants are described, for example, in U.S. Pat. Nos. 3,282,699, 3,455,693, 3,438,779, and 3,795,519.
Preferred examples of solid particle filter dyes for use in the antihalation underlayer of this invention are those described in U.S. Pat. No. 4,940,654. These solid particle filter dyes are compounds represented by the following formula(I):
�D-A).sub.y !-X.sub.n (I)
where
D is a chromophoric light-absorbing moiety, which, when y is 0, comprises an aromatic ring free of carboxy substituents,
A is an aromatic ring, free of carboxy substituents, bonded directly or indirectly to D,
X is a substituent, other than carboxy, having an ionizable proton, either on A or on an aromatic ring portion of D, having a pKa of about 4 to 11 in a 50/50 mixture (volume basis) of ethanol and water,
y is 0 to 4,
n is 1 to 7, and
the compound has a log partition coefficient of from about 0 to 6 when it is in unionized form.
Examples of filter dyes according to formula (I) include the following: ##STR1##
To promote adhesion of the antihalation underlayer to the support, primer layers as hereinabove described are advantageously employed, especially when the support is a polyester support.
The use of film-forming hydrophilic colloids as binders in photographic elements, including photographic films and photographic papers, is very well known. The most commonly used of these is gelatin and gelatin is a particularly preferred material for use in this invention. It can be used as the binder in the antihalation underlayer and in the silver halide emulsion layer(s). Useful gelatins include alkali-treated gelatin (cattle bone or hide gelatin), acid-treated gelatin (pigskin gelatin) and gelatin derivatives such as acetylated gelatin, phthalated gelatin and the like. Other hydrophilic colloids that can be utilized alone or in combination with gelatin include dextran, gum arabic, zein, casein, pectin, collagen derivatives, collodion, agar-agar, arrowroot, albumin, and the like. Still other useful hydrophilic colloids are water-soluble polyvinyl compounds such as polyvinyl alcohol, polyacrylamide, poly(vinylpyrrolidone), and the like.
The photographic elements of the present invention can be simple black-and-white or monochrome elements or they can be multilayer and/or multicolor elements.
Color photographic elements of this invention typically contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single silver halide emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as is well known in the art.
A preferred photographic element according to this invention comprises at least one blue-sensitive silver halide emulsion layer having associated therewith a yellow image dye-providing material, at least one green-sensitive silver halide emulsion layer having associated therewith a magenta image dye-providing material and at least one red-sensitive silver halide emulsion layer having associated therewith a cyan image dye-providing material.
In addition to an antihalation underlayer and one or more emulsion layers, the elements of the present invention can contain auxiliary layers conventional in photographic elements, such as overcoat layers, spacer layers, filter layers, interlayers, pH lowering layers (sometimes referred to as acid layers and neutralizing layers), timing layers, opaque reflecting layers, opaque light-absorbing layers and the like.
The light-sensitive silver halide emulsions employed in the photographic elements of this invention can include coarse, regular or fine grain silver halide crystals or mixtures thereof and can be comprised of such silver halides as silver chloride, silver bromide, silver bromoiodide, silver chlorobromide, silver chloroiodide, silver chorobromoiodide, and mixtures thereof. The emulsions can be, for example, tabular grain light-sensitive silver halide emulsions. The emulsions can be negative-working or direct positive emulsions. They can form latent images predominantly on the surface of the silver halide grains or in the interior of the silver halide grains. They can be chemically and spectrally sensitized in accordance with usual practices. The emulsions typically will be gelatin emulsions although other hydrophilic colloids can be used in accordance with usual practice. Details regarding the silver halide emulsions are contained in Research Disclosure, Item 36544, September, 1994, and the references listed therein.
The photographic silver halide emulsions utilized in this invention can contain other addenda conventional in the photographic art. Useful addenda are described, for example, in Research Disclosure, Item 36544, September, 1994. Useful addenda include spectral sensitizing dyes, desensitizers, antifoggants, masking couplers, DIR couplers, DIR compounds, antistain agents, image dye stabilizers, absorbing materials such as filter dyes and UV absorbers, light-scattering materials, coating aids, plasticizers and lubricants, and the like.
Depending upon the dye-image-providing material employed in the photographic element, it can be incorporated in the silver halide emulsion layer or in a separate layer associated with the emulsion layer. The dye-image-providing material can be any of a number known in the art, such as dye-forming couplers, bleachable dyes, dye developers and redox dye-releasers, and the particular one employed will depend on the nature of the element, and the type of image desired.
Dye-image-providing materials employed with conventional color materials designed for processing with separate solutions are preferably dye-forming couplers; i.e., compounds which couple with oxidized developing agent to form a dye. Preferred couplers which form cyan dye images are phenols and naphthols. Preferred couplers which form magenta dye images are pyrazolones and pyrazolotriazoles. Preferred couplers which form yellow dye images are benzoylacetanilides and pivalylacetanilides.
Protective overcoats of the present invention may be successfully employed with a variety of antistatic layers well known in the art. The antistatic layer of this invention may include a variety of electrically conductive metal-containing particles, such as metal oxides, dispersed in a binder material. Many of these metal oxide particles do not require chemical barriers to protect them against harsh environments, such as photographic processing solutions. However, since many of these metal oxides require high particle loading in a binder to obtain good conductivity, i.e. antistatic properties, the physical properties are degraded and an abrasion resistant topcoat is required for good physical durability of the layers. Examples of useful electrically conductive metal-containing particles include donor-doped metal oxides, metal oxides containing oxygen deficiencies, and conductive nitrides, carbides, and borides. Specific examples of particularly useful particles include conductive TiO.sub.2, SnO.sub.2, V.sub.2 O.sub.5, Al.sub.2 O.sub.3, ZrO.sub.2, In.sub.2 O.sub.3, ZnO, ZnSb.sub.2 O.sub.6, InSbO.sub.4, TiB.sub. 2, ZrB.sub.2, NbB.sub.2, TaB.sub.2, CrB, MoB, WB, LaB.sub.6, ZrN, TiN, WC, HfC, HfN, and ZrC. Examples of the patents describing these electrically conductive particles include; U.S. Pat. Nos. 4,275,103, 4,394,441, 4,416.963, 4,418,141, 4,431,764, 4,495,276, 4,571,361, 4,999,276, 5,122,445 and 5,368,995. Also included are:
Semiconductive metal salts such as cuprous iodide as described in U.S. Pat. Nos. 3,245,833, 3,428,451, and 5,075,171.
Fibrous conductive powders comprising, for example, antimony-doped tin oxide coated onto non-conductive potassium titanate whiskers as described in U.S. Pat. Nos. 4,845,369 and 5,116,666.
Conductive polymers, such as, the cross-linked vinylbenzyl quaternary ammonium polymers of U.S. Pat. No. 4,070,189 or the conductive polyanilines of U.S. Pat. No. 4,237,194.
A colloidal gel of vanadium pentoxide or silver-doped vanadium pentoxide as described in U.S. Pat. Nos. 4,203,769, 5,006,451, 5,221,598 and 5,284,714.
However, the preferred antistatic layer contains vanadium pentoxide as described in one of the aforementioned patents. The antistatic layer described in U.S. Pat. No. 4,203,769 is prepared by coating an aqueous colloidal solution of vanadium pentoxide. Preferably, the vanadium pentoxide is doped with silver. A polymer binder, such as an anionic vinylidene chloride-containing terpolymer latex or a polyesterionomer dispersion, is preferably employed in the antistatic layer to improve the integrity of the layer and to improve adhesion to the undercoat layer. Typically the dried coating weight of the vanadium pentoxide antistatic material is about 0.5 to 30 mg/m.sup.2. The weight ratio of polymer binder to vanadium pentoxide can range from about 1:5 to 500:1, but, preferably 1:1 to 10:1. Typically, the antistatic layer is coated at a dry coverage of from 1 to 400 mg/m.sup.2 based on total dry weight. The electrical resistivity of the antistatic layer is preferably from about 7 to about 11 log .OMEGA./sq, and most preferably less than 9 log .OMEGA./sq.
The antistatic coating formulation may also contain a coating aid to improve coatability. The common level of coating aid in the antistatic coating formula is 0.01 to 0.30 weight percent active coating aid based on the total solution weight. However, the preferred level of coating aid is 0.02 to 0.20 weight percent active coating aid based on total solution weight. These coating aids can be either anionic or nonionic coating aids such as paraisononyphenoxy-glycidol ethers, octylphenoxy polyethoxy ethanol, sodium salt of alkylaryl polyether sulfonate, and dioctyl esters of sodium sulfosuccinic acid, which are commonly used in aqueous coatings. The coating may be applied onto the film support using coating methods well known in the art such as hopper coating, skim pan/air knife, gravure coating, and the like.
The antistatic layer of this invention is overcoated with a polyurethane. Preferably, the polyurethane is an aliphatic polyurethane. Aliphafic polyurethanes are preferred due to their excellent thermal and UV stability and freedom from yellowing. The polyurethanes of the present invention are characterized as those having a tensile elongation to break of at least 50% and a Young's modulus measured at an elongation of 2% of at least 50,000 lb/in.sup.2. These physical property requirements insure that the overcoat layer is hard yet tough to simultaneously provide excellent abrasion resistance and outstanding resiliency to allow the topcoat and antistat layer to survive hundreds of cycles through a motion picture projector. The polyurethane overcoat is preferably coated from a coating formula containing from about 0.5 to about 10.0 weight percent of polymer to give a dry coverage of from about 50 to about 3000 mg/m.sup.2. The dry coverage of the overcoat layer is preferably from about 300 to 2000 mg/m.sup.2.
The polyurethane may be either organic solvent soluble or aqueous dispersible. For environmental reasons, aqueous dispersible polyurethanes are preferred. Preparation of aqueous polyurethane dispersions is well-known in the art and involves chain extending an aqueous dispersion of a prepolymer containing terminal isocyanate groups by reaction with a diamine or diol. The prepolymer is prepared by reacting a polyester, polyether, polycarbonate, or polyacrylate having terminal hydroxyl groups with excess polyfunctional isocyanate. This product is then treated with a compound that has functional groups that are reactive with an isocyanate, for example, hydroxyl groups, and a group that is capable of forming an anion, typically this is a carboxylic acid group. The anionic groups are then neutralized with a tertiary amine to form the aqueous prepolymer dispersion. The chemical resistance of the polyurethane overcoat can be improved by adding a crosslinking agent that reacts with functional groups present in the polyurethane, for example, carboxyl groups. Crosslinking agents such as aziridines, carbodiimides, epoxies, and the like are suitable for this purpose. The crosslinking agent can be used at about 0.5 to about 30 weight percent based on the polyurethane. However, a crosslinking agent concentration of about 2 to 12 weight percent based on the polyurethane is preferred.
The present invention includes a topcoat over the polyurethane protective overcoat to reduce or eliminate tar pickup. The topcoat contains gelatin-coated, latex particles. The gelatin-coated, latex particles utilized in this invention preferably have an average diameter of about 10 nm to about 1000 nm. More preferably, the particles have an average diameter of 20 to 500 mn. The gelatin can be any of the types of gelatin known in the photographic art. These include, for example, alkali-treated gelatin (cattle bone or hide gelatin), acid-treated gelatin (pigskin or bone gelatin), and gelatin derivatives such as partially phthalated gelatin, acetylated gelatin, and the like.
The latex particle coated with gelatin is a water-dispersible, nonionic or anionic interpolymer prepared by emulsion polymerization of ethylenically unsaturated monomers or by post emulsification of preformed polymers. In the latter case, the preformed polymers may be first dissolved in an organic solvent and then the polymer solution emulsified in an aqueous media in the presence of an appropriate emulsifier. Representative polymer particles include those comprising polymers and interpolymers of styrene, styrene derivatives, alkyl acrylates or alkyl methacrylates and their derivatives, olefins, vinylidene chloride, acrylonitrile, acrylamide and methacrylamide and their derivatives, vinyl esters, vinyl ethers and urethanes. In addition, crosslinking monomers such as 1,4-butyleneglycol methacrylate, trimethylolpropane, triacrylate, allyl methacrylate, diallyl phthalate, divinyl benzene, and the like may be used in order to give a crosslinked polymer particle. The polymer particle may be a core-shell particle as described, for example, in U.S. Pat. No. 4,497,917. The gelatin-coated latex particle can be prepared either by having at least a part of its emulsion polymerization conducted in the presence of gelatin and/or by adding gelatin and a grafting agent after completion of the emulsion polymerization or post emulsification in order to link the polymer particle and gelatin through the grafting agent.
Gelatin-coated polymer particles have been described in the photographic art. U.S. Pat. No. 2,956,884 describes the preparation of polymer latices in the presence of gelatin and the application of such materials in photographic emulsion and subbing layers. U.S. Pat. No. 5,330,885 describes a silver halide photographic imaging element containing a photographic emulsion layer, emulsion overcoat, backing layer, and backing layer overcoat in which at least one layer contains a polymer latex stabilized by gelatin. In the '885 patent, the polymer latex stabilized by gelatin is preferably added to a hydrophilic colloid light sensitive emulsion layer or a hydrophilic colloid light insensitive layer to improve the dimensional stability of the imaging element. The '885 patent does not teach the use of such polymer latexes as topcoats for polyurethane protective overcoats to prevent processor tar deposits. U.S. Pat. No. 5,374,498 describes a hydrophilic colloid layer provided on the photographic emulsion layer side of the support that contains a latex comprising polymer particles stabilized with gelatin. U.S. Pat. Nos. 5,066,572 and 5,248,558 describe case-hardened gelatin-grafted soft polymer particles that are incorporated into photographic emulsion layers to reduce pressure sensitivity. U.S. Pat. No. 5,698,384 describes an electrically-conductive layer comprising electrically-conductive fine particles and gelatin-coated, water insoluble polymer particles.
The gelatin/polymer weight ratio of the gelatin-coated latex particle is preferably 20/80 to 80/20. At gelatin/polymer ratios less than 20/80 the polymer particle is not sufficiently coated with gelatin to provide resistance to tar deposits and for ratios greater than 80/20 there is insufficient polymer particle to provide desirable physical properties such as freedom from ferrotyping and blocking, especially at high humidity.
The stain resistant topcoat of the present invention may comprise the gelatin-coated, latex particles in combination with another polymer. In a preferred embodiment, the other polymer is a water soluble or water dispersible polymer. Water soluble polymers include, for example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, cellulosics, polystyrene sulfonic acid and its alkali metal salts or ammonium salts, water soluble (meth)acrylic interpolymers, and the like. Water dispersible polymers that may be used in conjunction with the gelatin-coated, latex particles include latex interpolymers containing ethylenically unsaturated monomers such as acrylic and methacrylic acid and their esters, styrene and its derivatives, vinyl chloride, vinylidene chloride, butadiene, acrylamides and methacrylamides, and the like. Other water dispersible polymers that may be used include polyurethane and polyester dispersions. Preferably, the stain resistant topcoat layer contains at least 50 weight % of the gelatin-coated, latex particle.
The stain resistant topcoat compositions in accordance with the invention may also contain suitable crosslinling agents including aldehydes, epoxy compounds, polyfunctional aziridines, vinyl sulfones, methoxyalkyl melamines, triazines, polyisocyanates, dioxane derivatives such as dihydroxydioxane, carbodiimides, and the like. The crosslinking agents may react with the functional groups present on the gelatin-coated latex polymer, and/or the other water soluble or water dispersible polymer present in the coating composition.
The topcoat may additionally contain fillers for improving the modulus of the layer, lubricants, and additives such as matte beads for controlling the ferrotyping characteristics of the surface.
Examples of reinforcing filler particles include inorganic powders with a Mohs scale hardness of at least 6. Specific examples are metal oxides such as g-aluminum oxide, chromium oxide, (e.g., Cr.sub.2 O.sub.3), iron oxide (e.g., alpha-Fe.sub.2 O.sub.3), tin oxide, doped tin oxide, such as antimony or indium doped tin oxide, silicon dioxide, alumino-silicate and titanium dioxide; carbides such as silicon carbide and titanium carbide; and diamond in fine powder.
A suitable lubricating agent can be included to give the topcoat a coefficient of friction that ensures good transport characteristics during manufacturing and customer handling of the photographic film. Many lubricating agents can be used, including higher alcohol esters of fatty acids, higher fatty acid calcium salts, metal stearates, silicone compounds, paraffins and the like as described in U.S. Pat. Nos. 2,588,756, 3,121,060, 3,295,979, 3,042,522 and 3,489,567. For satisfactory transport characteristics, the lubricated surface should have a coefficient of friction of from 0.10 to 0.40. However, the most preferred range is 0.15 to 0.30. If the topcoat coefficient of friction is below 0.15, there is a significant danger that long, slit rolls of the photographic film will become unstable in storage or shipping and become telescoped or dished, a condition common to unstable film rolls. If the coefficient of friction is above 0.30 at manufacture or becomes greater than 0.30 after photographic film processing, a common condition of non-process surviving topcoat lubricants, the photographic film transport characteristics become poorer, particularly in some types of photographic film projectors.
Aqueous dispersed lubricants are strongly preferred since lubricants, in this form, can be incorporated directly into the aqueous topcoat formula, thus avoiding a separately applied lubricant overcoat on the topcoat layer. The aqueous dispersed lubricants of carnauba wax, polyethylene oxide, microcrystalline wax, paraffin wax, silicones, stearates and amides work well as incorporated lubricants in the aqueous topcoat. However, the aqueous dispersed lubricants of carnauba wax and stearates are preferred for their effectiveness in controlling friction at low lubricant levels and their excellent compatibility with aqueous binders.
In addition to lubricants, matting agents are important for improving the transport of the film on manufacturing, printing, processing, and projecting equipment. Also, these matting agents can reduce the potential for the topcoat to ferrotype when in contact with the emulsion side surface under the pressures that are typical of roll films. The term "ferrotyping" is used to describe the condition in which the backside topcoat, when in contact with the emulsion side under pressure, as in a tightly wound roll, adheres to the emulsion side sufficiently strongly that some sticking is noticed between the protective topcoat and the emulsion side surface layer when they are separated. In severe cases of ferrotyping, damage to the emulsion side surface may occur when the protective topcoat and emulsion side surface layer are separated. This severe damage may have an adverse sensitometric effect on the emulsion.
The topcoat of the present invention may contain matte particles. The matting agent may be silica, calcium carbonate, or other mineral oxides, glass spheres, ground polymers and high melting point waxes, and polymeric matte beads. Polymeric matte beads are preferred because of uniformity of shape and uniformity of size distribution. The matte particles should have a mean diameter size of about 0.5 to about 3 micrometers. However, preferably the matte particles have a mean diameter of from about 0.75 to about 2.5 micrometers. The matte particles can be employed at a dry coating weight of about 1 to about 100 mg/m.sup.2. The preferred coating weight of the matte particles is about 15 to about 65 mg/m.sup.2. The surface roughness (Ra, ANSI Standard B46.1, 1985) in microns should be in the range 0.010 to 0.060 to prevent ferrotyping of the emulsion surface. The preferred Ra value range is from 0.025 to 0.045 for best performance. If the Ra value is below 0.025, there is insufficient surface roughness to prevent slight emulsion surface marking from ferrotyping between the backing and emulsion. If the Ra value is above 0.045, there is sufficient surface roughness with these size matte particles to show some low level of emulsion granularity and loss of picture sharpness, especially under the very high magnifications typical of movie theater projection.
The above described additives, including lubricants, matte beads, and fillers can also be present in the underlying polyurethane overcoat.
The stain resistant topcoat layers of the present invention may be applied from aqueous coating formulations containing up to 20% total solids by coating methods well known in the art. For example, hopper coating, gravure coating, skim pan/air knife coating, spray coating, and other methods may be used with very satisfactory results. The coatings are applied as part of the motion picture film support manufacturing process and are dried at temperatures up to 150.degree. C. to give a dry coating weight of about 1 mg/m.sup.2 to about 5000 mg/m.sup.2, preferably, the dry coating weight is about 2 mg/m.sup.2 to about 500 mg/m.sup.2.

The present invention is illustrated by the following examples. However, it should be understood that the invention is not limited to these illustrative examples.
EXAMPLES
Preparation of Gelatin-coated, Latex Particles.
Preparation of gelatin-coated latex P-1: A small particle methyl methacrylate-co-methacrylic acid (97/3 weight ratio) latex was prepared via semi-continuous emulsion polymerization using Triton 770 (Product of Rohm & Haas) as surfactant and potassium persulfate as initiator. The latex had a mean particle size of 75 nm by light scattering and a solids content of 23%. This latex was grafted to gelatin by the following procedure: 434 g of latex was diluted with 1200 g of distilled water in a 3 L round-bottom 3-necked flask equipped with a condenser and overhead stirrer. The flask was immersed in a constant temperature bath at 60.degree. C. and the pH adjusted to 8.0 with triethylamine. 9.0 g of 1-(4-morpholinocarbonyl)-4-(2-sulfoethyl)pyridinium hydroxide, inner salt was added as a solid to the diluted latex, an amount of grafting reagent equivalent to 85% of the latex acid groups. Reaction was allowed to proceed for 20 minutes, during which time 75 g of gelatin was dissolved in 750 g of water at 60.degree. C. and the pH raised to 8.0 with triethylamine. The gelatin solution was then added by dropping funnel and reaction continued an additional 20 minutes. The product was then cooled and stored in a refrigerator. It is noteworthy that despite the high level of grafting and lack of purification of the product, this gelatin-coated latex could be remelted after 9 months with no sign of instability.
Preparation of gelatin-coated latex polymers P-2 to P-4: Additional gelatin-coated latices were prepared in a manner analogous to Example 1 using a 60:30:10 ratio poly(methyl methacrylate-co-butyl acrylate-co-methacrylic acid) latex at the latex to gelatin ratios shown in Table 1. For these examples the amount of grafting reagent was reduced to 20% of latex acid groups.
TABLE 1______________________________________ Gelatin/PolymerPolymer Latex Polymer Composition Ratio______________________________________P-1 Poly(methyl methacrylate-co- 43/57 methacrylic acid) 97/3P-2 Poly(methyl methacrylate-co-butyl 50/50 acrylate-co-methacrylic acid) 60/30/10P-3 Same as P-2 25/75P-4 Same as P-2 10/90(Comparativeparticle)______________________________________
The polyurethane overcoats used in the examples were composed of Sancure 898 (B. F. Goodrich Company) and contained 6 percent by weight (based on polymer) of an aziridine crosslinker.
Preparation of Support Containing an Antistatic Formulation.
A subbed polyester support was prepared by first applying a subbing terpolymer of acrylonitrile, vinylidene chloride and acrylic acid to both sides of the support before drafting and tentering so that the final coating weight was about 90 mg/m.sup.2.
An antistatic formulation consisting of the following components was prepared at 0.078% total solids:
______________________________________Terpolymer of acrylonitrile, vinylidene chloride and acrylic 0.094%acid,Vanadium pentoxide colloidal dispersion, 0.57% 4.972%Rohm & Hass surfactant, Triton X-100, 10% 0.212%Demineralized water 94.722%______________________________________
The antistatic formulation was coated over the subbed polyester support on the side opposite to the antihalation layer to give a dry coating weight of about 12 mg/m.sup.2.
Comparative Sample A comprised the following: a protective overcoat formulation was applied over the antistat layer. The overcoat formulation consisted of the following components:
______________________________________ Dry Coverage, mg/m.sup.2______________________________________Polyurethane dispersion, 32% 972Carnauba wax dispersion, Michemlube 160, 25% 0.65Matte, polymethyl methacrylate beads, 147 .mu.m, 23.8% 26.9Polyfunctional aziridine crosslinker CX-100, 50% 60.8Rohm & Haas surfactant, Triton X-100, 10% 10.8______________________________________
A urethane overcoat identical to Comparative Sample A--excepting the camauba wax was omitted--was prepared and the topcoats described in Table 2 were applied. All coatings contained 0.06% active Triton X-100 as coating aid. Comparative Samples B, C, and D comprised a topcoat containing a non-gelatin-coated latex polymer (this was the latex used to prepare P-2). Comparative Samples E, F, and G comprised a topcoat containing a gelatin-coated latex polymer in which the gelatin/polymer ratio was less than 20/80 (in this case, for polymer P-4 the gelatin/polymer ratio was 10/90). Comparative Sample H comprised a topcoat that contained only 20 wt % of a gelatin-coated latex polymer.
Tar Test
During routine film development, by-products of oxidized color developer will form brown, oily residue that may be adsorbed by the film surface and may create permanent, brown stained spots, i.e. tar.
A simulated developer tar test was performed on the samples to determine their propensity for tar/stain build-up. The test was done at 42.degree. C. and involved smearing tar harvested from a developer tank onto the coating immersed in a developer bath followed by removal of the tar using dilute sulfuric acid. The resultant stain or tar is indicative of the propensity of the coating for tar adsorption. The resistance to tar stain was visually rated on a scale of 1 to 5, with 1 being the best performance, (i.e., no tar stain) and 5 being the worst performance (i.e., severe tar stain). The results are tabulated in Table 2.
TABLE 2______________________________________ Dry Cover- Tar age StainCoating Composition mg/m.sup.2 Rating______________________________________Comparative Polyurethane protective overcoat only 1000 5Sample AComparative Poly(methyl methacrylate-co-butyl 50 5Sample B acrylate-co-methacrylic acid) 60/30/10Comparative Poly(methyl methacrylate-co-butyl 200 4Sample C acrylate-co-methacrylic acid) 60/30/10Comparative Poly(methyl methacrylate-co-butyl 500 4Sample D acrylate-co-methacrylic acid) 60/30/10Comparative P-4 50 4Sample EComparative P-4 200 5Sample FComparative P-4 500 5Sample GExample 1 P-1 50 1Example 2 P-1 200 1Example 3 P-1 500 1Example 4 P-2 50 1Example 5 P-2 200 1Example 6 P-2 500 1Example 7 P-3 50 3Example 8 P-3 200 2Example 9 P-3 500 3Example 10 P-2/Sancure 898 polyurethane, 50/50 200 2Comparative P-2/Sancure 898 polyurethane, 20/80 200 4Sample H______________________________________
As shown in Comparative Sample A, the polyurethane coating has very poor resistance to picking up developer tar, as do the coatings of the other Comparative Samples. In contrast, the coatings of the invention exhibit excellent resistance to tar stain, even when employed as extremely thin layers relative to the underlying polyurethane. In addition, the coatings of the invention were transparent and had excellent adhesion to the polyurethane.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Number	Name	Date
4855219	Bagchi et al.	Aug 1989
5330885	Takamuki et al.	Jul 1994
5679505	Tingler et al.	Oct 1997
5698384	Anderson et al.	Dec 1997
5770353	Wang et al.	Jun 1998
5786134	Nair et al.	Jul 1998

Topcoat for motion picture film

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