Backing layers for imaging elements containing crosslinked elastomeric matte beads

CROSS REFERENCE TO RELATED APPLICATIONS
This application relates to commonly assigned copending application Ser. No. 08/847,634, filed simultaneously herewith and hereby incorporated by reference for all that it discloses.
FIELD OF THE INVENTION
This invention relates in general to imaging elements such as, for example, photographic elements and in particular to imaging elements comprising a support, an image-forming layer and a backing layer. More specifically, this invention relates to such imaging elements which have an improved backing layer that contains crosslinked, elastomeric matte beads that are strongly anchored in the backing layer and do not scratch the imaging side of the element.
BACKGROUND OF THE INVENTION
The imaging elements to which this invention relates can be of many different types depending on the particular use for which they are intended. Such elements include, for example, photographic, electrophotographic, electrostatographic, photothermographic, migration, electrothermographic, dielectric recording and thermal-dye-transfer imaging elements.
Layers of imaging elements other than the image-forming layer are commonly referred to as auxiliary layers. There are many different types of auxiliary layers such as, for example, subbing layers, backing layers, overcoat layers, receiving layers, stripping layers, antistatic layers, transparent magnetic layers, and the like.
One typical application for such an auxiliary layer is as a backing layer to provide resistance to scratches and abrasion. Backing layers may be applied directly onto the support material, applied onto a priming or "subbing" layer, or applied as an overcoat for an underlying layer such as an antistatic layer, transparent magnetic layer, antihalation layer and the like. When the backing layer is an overcoat for an antistatic layer the backing layer may need to protect the antistatic layer from attack by film processing solutions in order to preserve the antistatic properties of the film after image processing. Backing layers often contain matte beads in order to prevent blocking, ferrotyping, and the formation of Newton rings when the backside of the imaging element is in contact with other surfaces such as the imaging side of the element, steel or rubber rollers, and glass or metal surfaces during the manufacture, storage, and use of the element. For imaging elements used in the Graphic Arts industry, matte beads contained in the backing layer facilitate the use of a vacuum contacting process that is used in the printing and duplicating of images as described in U.S. Pat. No. 4,997,735.
Backing layers are typically very thin, abrasion resistant layers applied from aqueous or organic solvent solutions or dispersions containing glassy, hydrophobic polymers such as acrylics, cellulosics, or polyurethanes, for example. Such layers are typically one micron or less in thickness and often contain high concentrations of matte beads that protrude one or more microns out of the backing layer. When such backing layers contact surfaces during the manufacture and use of the imaging element the matte beads may be dislodged from the backing layer and create a fine dust of particles that can be attracted to or imbedded in the imaging layer. This may result in serious image defects in the imaging element.
Recently, significant advancements have been made with regard to the methods of manufacturing and processing imaging elements. For example, the speed for coating, finishing, cutting, and processing continues to increase in order to maximize productivity. However, this has also caused an increase in matte- induced scratches and abrasion marks on the imaging elements as the films are wound and unwound at high speeds. These scratches and abrasion marks may become visible during projection or be transferred during duplicating or printing, all of which are highly undesirable.
It is toward the objective of providing an improved backing layer for imaging elements that the present invention is directed. The backing layer contains matte beads that are not easily dislodged from the layer or cause scratches and abrasions on the imaging side of the element during the winding and unwinding operations that occur during the manufacture and use of the imaging element.
SUMMARY OF THE INVENTION
The present invention is an imaging element which includes a support, an image forming layer and a backing layer. The backing layer includes a film forming polymeric binder and crosslinked elastomeric matte beads having a glass transition temperature of 10.degree. C. or less.

DETAILED DESCRIPTION OF THE INVENTION
The imaging elements of this invention can be of many different types depending on the particular use for which they are intended. Details with respect to the composition and function of a wide variety of different imaging elements are provided in U.S. Pat. No. 5,300,676 and references described therein.
Photographic elements can comprise various polymeric films, papers, glass, and the like, but both acetate and polyester supports well known in the art are preferred. The thickness of the support is not critical. Support thickness of 2 to 10 mil (0.002 to 0.010 inches) can be used. The supports typically employ an undercoat or subbing layer well known in the art that comprises, for example, for polyester support a vinylidene chloride/methyl acrylate/itaconic acid terpolymer or vinylidene chloride/acrylonitrile/acrylic acid terpolymer.
The backing layers of the present invention comprise a film-forming polymeric binder and elastomeric matte beads. The backing layers of the invention may be applied from either aqueous or solvent coating compositions. The film-forming binder used in the present invention is not critical, binders that may be effectively employed include interpolymers of ethylenically unsaturated monomers such as acrylic acid and its esters, methacrylic acid and its esters, styrene and it derivatives, vinyl chloride, vinylidene chloride, butadienes, maleic acid, itaconates, vinyl pyrrolidone, acrylamides and methacrylamides, and the like. Other useful binder polymers include gelatin, polyvinyl alcohol, polyvinyl butyral, cellulosics, polyurethanes, polyesters, epoxies, and the base neutralized, carboxylic acid-containing latex polymers described in the commonly assigned copending application Ser. No. 712,006, filed Sep. 11, 1996, for example.
In contrast to prior art backing layers which utilize matte beads which are harder and have a higher Tg, it has been found that the elastomeric matte beads of the invention which have a lower Tg are resilient, therefore when the backing layer comes into contact with, for example, a roller or other hard surface, the force exerted on the matte beads temporarily deforms the bead. When matte beads having a high Tg are used, the matte beads are too rigid to deform and contact with a hard surface dislodges the matte bead. The crosslinked, elastomeric matte beads employed in the invention have a Tg of 10.degree. C. or less, preferably 0.degree. C. or less.
Another advantage when crosslinked, elastomeric matte beads are used according to the present invention is that they are less likely to cause scratches in the imaging layer when the front and back sides of the imaging element are brought into contact during the manufacture or use of the element. When inelastic, low Tg matte beads are used which are not partially crosslinked, they will permanently deform when the backing layer is exposed to high temperatures and pressures, for example, during the manufacturing process or when the imaging element is stored in roll form. Thus such matte beads are not desirable in the present invention.
Matte bead elasticity is determined by the amount of crosslinking agent employed in making the matte bead. If the amount of crosslinking agent used is too high, the matte beads produced will be too rigid. If the amount of crosslinking agent in the matte beads is too low, the matte beads will not only be deformed under pressure, but will also undergo nonelastic flow leading to permanent deformation, making recovery of their original shape impossible.
Thus, the crosslinked, elastomeric matte beads used in the invention have a combination of both the proper Tg and level of crosslinking agent in order to achieve the desired degree of elasticity.
U.S. Pat. No. 5,536,627 describes a photographic element comprising a protective overcoat on the front side of the element that comprises a hydrophilic binder and matte beads having a Rockwell hardness of less than M90. Such matte beads reduce matte bead cinch scratches and abrasions in the backing layer during the manufacture and use of the element. The matte beads have a Tg of at least 50.degree. C. to resist any large degree of mechanical deformation. This prior art does not teach or suggest the use of crosslinked, elastomeric matte beads having a Tg less than 10.degree. C., and in fact, teaches away from the use of such low Tg matte beads.
The crosslinked, elastomeric matte beads may be employed in any amount effective for the intended purpose. In general, good results are obtained at a coverage of from about 0.5 to about 250 mg/m.sup.2. The crosslinked, elastomeric matte beads generally have a particle size of from about 0.2 .mu.m to about 20 .mu.m, preferably from about 0.5 to 10 .mu.m.
In a particularly preferred embodiment, the crosslinked, elastomeric beads used in the invention are made from an interpolymer of ethylenically unsaturated monomers such as acrylic or methacrylic acid and their esters such as butyl-, ethyl-, propyl-, hexyl-, 2-ethyl hexyl-, 2-chloroethyl-, 4-chlorobutyl- or 2-ethoxyethyl-acrylate or methacrylate, hydroxyethyl acrylate or hydroxyethyl methacrylate, styrene and its derivatives, butadienes, ethylene, propylene, vinyl chloride, vinylidene chloride, itaconic acid and its esters, and the like.
The crosslinked, elastomeric beads may also comprise polycondensation products such as polyurethanes, polysiloxanes, polyesters, and polyethers. The beads may also be prepared from natural and synthetic rubbers such as those described in "Rubber Technology", Werner Hofmann, Hansen Publishers, New York, 1989. Such rubber materials include polyisoprene, fluoroelastomers, epichlorohydrin rubbers, polypropylene oxide rubbers, chlorinated polyethylene rubbber, natural rubber, and the like.
The elastomeric beads may be crosslinked with various crosslinking agents, which may also be part of the elastomeric interpolymer, such as divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-cyclohexylene-bis(oxyethyl) dimethacrylate, 1,4-cyclohexylene-bis(oxypropyl) diacrylate, 1,4-cyclohexylene-bis(oxypropyl) dimethacrylate, etc. The crosslinked, elastomeric matte beads may contain reactive functional groups capable of forming covalent bonds with the binder polymer by intermolecular crosslinking or by reaction with a crosslinking agent in order to promote further improve adhesion of the matte beads to the coated layers. Suitable reactive functional groups include: hydroxyl, carboxyl, carbodiimide, epoxide, aziridine, vinyl sulfone, sulfinic acid, active methylene, amino, amide, allyl, and the like. It is preferred that the elastomeric beads contain greater than 3 percent by weight of a crosslinking agent, most preferably from 3 to 40 percent by weight of a crosslinking agent.
U.S. Pat. No. 5,538,935 describes the use of crosslinked, elastomeric beads in the dye-receiving layer or the dye-receiving layer overcoat for thermal dye transfer materials. The elastomeric beads have a Tg of less than 45.degree. C. and are compressed under the weight of the thermal print head during printing, thereby allowing better contact between the dye-donor and dye-receiver elements. The '935 patent does not teach or suggest the benefit with respect to matte bead adherence of using crosslinked, elastomeric matte beads having a Tg less than 10.degree. C. in backing layers. In the present invention the matte bead Tg needs to be lower than the '935 patent since the function of the matte bead is different. In the '935 patent the matte bead must deform to allow closer contact between the donor and receiver material under the high temperatures that exist in the thermal dye transfer process.
In addition to the film-forming polymer and crosslinked, elastomeric matte beads, the backing layers in accordance with the invention may also contain suitable crosslinking 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 polymeric binder or the crosslinked, elastomeric matte beads present in the coating composition.
Other additional compounds that can be employed in the backing layer compositions of the invention include surfactants, coating aids, coalescing aids, lubricants, dyes, biocides, UV and thermal stabilizers, magnetic recording particles, and other addenda well known in the imaging art.
The backing layer compositions of the present invention may be applied at 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 dried at temperatures up to 150.degree. C. to give total dry coating weights of 20 mg/m.sup.2 to 10 gm.sup.2.
The backing layer of the invention may be applied onto unsubbed support, the subbing or undercoat layers previously described, antihalation layers containing soluble dyes or solid particle dyes, or antistatic subbing layers. In the case when the backing layer overlies an antistatic layer, preferred conductive agents for use in the antistatic subbing layer include;
(1) electrically conductive metal-containing particles including donor-doped metal oxides, metal oxides containing oxygen deficiencies, and conductive nitrides, carbides, and bromides. 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. No. 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.
(2) fibrous conductive powders comprising, for example, antimony-doped tin oxide coated onto non-conductive potassium titanate whiskers as described in U.S. Pat. No. 4,845,369 and 5,116,666 and antimony-doped tin oxide fibers or "whiskers" as described in pending U.S. Ser. No. 08/747,480 and U.S. Ser. No. 08/746,618 filed Nov. 12, 1996.
(3) the electronically-conductive polyacetylenes, polythiophenes, and polypyrroles of U.S. Pat. No.4,237,194, 5,310,981, and Japanese Patent Applications 2282245 and 2282248.
(4) the ionically-conductive cross-linked vinylbenzyl quaternary ammonium polymers of U.S. Pat. No. 4,070,189.
(5) the electronically-conductive 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.
In a particularly preferred embodiment, the imaging elements of this invention are photographic elements, such as photographic films, photographic papers or photographic glass plates, in which the image-forming layer is a radiation-sensitive silver halide emulsion layer. Such emulsion layers typically comprise a film-forming hydrophilic colloid. The most commonly used of these is gelatin and gelatin is a particularly preferred material for use in this invention. 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 comprising a support bearing a layer of light-sensitive silver halide emulsion 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 a support bearing 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 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, antihalation layers, 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 support can be any suitable support used with photographic elements. Typical supports include polymeric films, paper (including polymer-coated paper), glass and the like. Details regarding supports and other layers of the photographic elements of this invention are contained in Research Disclosure, Item 36544, September, 1994.
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.
The present invention is also directed to a single use camera having incorporated therein a photographic element as described above. Single use cameras are known in the art under various names: film with lens, photosensitive material package unit, box camera and photographic film package. Other names are also used, but regardless of the name, each shares a number of common characteristics. Each is essentially a photographic product (camera) provided with an exposure function and preloaded with a photographic material. The photographic product comprises an inner camera shell loaded with the photographic material, a lens opening and lens, and an outer wrapping(s) of some sort. The photographic materials are exposed in camera, and then the product is sent to the developer who removes the photographic material and develop it. Return of the product to the consumer does not normally occur.
Magnetic layers suitable for use in the elements in accordance with the present invention include those as described in Research Disclosure, November 1992, Item 34390, and U.S Pat. Nos. 5,395,743, 5,397,826, 5,113,903, 5,432,050, 5,434,037 and 5,436,120.
Single use camera and their methods of manufacture and use are described in U.S. Pat. Nos. 4,801,957; 4,901,097; 4,866,459; 4,849,325; 4,751,536; 4,827,298; European Patent Applications 460,400; 533,785; 537,225; all of which are incorporated herein by reference.
The photographic processing steps to which the raw film may be subject may include, but are not limited to the following:
1.) color developing .fwdarw. bleach-fixing .fwdarw. washing/stabilizing;
2.) color developing .fwdarw. bleaching .fwdarw. fixing .fwdarw. washing/stabilizing;
3.) color developing .fwdarw. bleaching .fwdarw. bleach-fixing .fwdarw. washing/stabilizing;
4.) color developing .fwdarw. stopping .fwdarw. washing .fwdarw. fixing .fwdarw. bleaching .fwdarw. washing .fwdarw. washing/stabilizing;
5.) color developing .fwdarw. bleach-fixing .fwdarw. fixing .fwdarw. washing/stabilizing;
6.) color developing .fwdarw. bleaching .fwdarw. bleach-fixing .fwdarw. fixing .fwdarw. washing/stabilizing;
Among the processing steps indicated above, the steps 1), 2), 3), and 4) are preferably applied. Additionally, each of the steps indicated can be used with multistage applications as described in Hahm, U.S. Pat. No. 4,719,173, with co-current, counter-current, and contraco arrangements for replenishment and operation of the multistage processor.
Any photographic processor known to the art can be used to process the photosensitive materials described herein. For instance, large volume processors, and so-called minilab and microlab processors may be used. Particularly advantageous would be the use of Low Volume Thin Tank processors as described in the following references: WO 92/10790; WO 92/17819; WO 93/04404; WO 92/17370; WO 91/19226; WO 91/12567; WO 92/07302; WO 93/00612; WO 92/07301; WO 02/09932; U.S. Pat. No. 5,294,956; EP 559,027; U.S. Pat. No. 5,179,404; EP 559,025; U.S. Pat. No. 5,270,762; EP 559,026; U.S. Pat. No.5,313,243; U.S. Pat. No. 5,339,131.
The present invention is also directed to photographic systems where the processed element may be re-introduced into the cassette. These system allows for compact and clean storage of the processed element until such time when it may be removed for additional prints or to interface with display equipment. Storage in the roll is preferred to facilitate location of the desired exposed frame and to minimize contact with the negative. U.S. Pat. No. 5,173,739 discloses a cassette designed to thrust the photographic element from the cassette, eliminating the need 20 to contact the film with mechanical or manual means. Published European Patent Application 0 476 535 A1 describes how the developed film may be stored in such a cassette.
The following examples are used to illustrate the present invention. However, it should be understood that the invention is not limited to these illustrative examples.
EXAMPLES
Preparation of crosslinked. elastomeric matte bead
A limited coalescence process (described in U.S. Pat. Nos. 4,965,131 and 5,133,912) was used to prepare matte beads containing the appropriate monomers. The specific procedure for making crosslinked, elastomeric matte beads comprising poly(n-butyl acrylate-co-ethylene glycol diacrylate) (95/5) was as follows:
A monomer mixture of 475 g n-butyl acrylate, 25 g ethylene glycol S diacrylate, and 5 g Vazo 52 (an azo-initiator from DuPont) was combined with a mixture of 3.7 g poly(methylaminoethanol adipate), and 30 g Ludox Tm dispersing agent (available from Dupont) in 1.5 L water. The mixture was stirred rapidly with a laboratory stirrer to obtain a crude emulsion. The crude emulsion was then passed through a Gaulin Homogenizer to obtain 7.5 .mu.m monomer droplets in water. The resulting suspension was heated at 49.degree. C. overnight in a 5 L flask to polymerize the monomer droplets. These crosslinked, elastomeric matte beads are designated B-1 and have a Tg of about -35.degree. C. This aqueous matte bead dispersion was used in aqueous-based backing layer coatings. For solvent-based coatings, the matte beads were isolated as dry material and then dispersed in the solvent coating composition. To obtain dry matte bead material, the beads were collected from the aqueous dispersion onto a funnel. The damp cake was slurried in methanol and the beads were then collected on a funnel again. This material was air dried at room temperature.
Crossliaked, elastomeric matte beads, designated B-2, comprising poly(ethyl acrylate-co-ethylene glycol dimethacrylate) 95/5 were prepared in an analogous manner. These matte beads have a mean particle diameter of about 3.0 .mu.m and a Tg of -7.5.degree. C.
Crosslinked, elastomeric matte beads, designated B-3, comprising poly(methyl acrylate-co-ethyl acrylate-co-ethylene glycol dimethacrylate) 45/50/5 without the Ludox Tm dispersing agent were also used in example coatings. These matte beads have a mean particle diameter of about 3.0 .mu.m and a Tg of 7.5.degree. C.
Comparative crosslinked matte beads, designated C-1, comprising poly(n-butyl methacrylate-co-ethylene glycol dimethacrylate) 95/5 and having a particle size of 3 .mu.m and a Tg of 38.degree. C. were also prepared. Comparative crosslinked matte beads, designated C-2, comprising poly(methyl acrylate-co-ethylene glycol dimethacrylate) 95/5 and having a particle size of 3 .mu.m and a Tg of 21.degree. C. were also prepared. Both matte beads C-1 and C-2 are comparable to those taught in U.S. Pat. No.5,538,935 which describes crosslinked, elastomeric matte beads with a Tg less than 45.degree. C. Other comparative matte beads were also used in the following coatings, these matte beads, designated C-3, comprise poly(methyl methacrylate). Matte beads C-3 are neither crosslinked nor elastomeric and have a particle size of about 3 .mu.m and a Tg greater than 100.degree. C.
Examples 1 and 2 and Comparative Samples A and B
Backing layers comprising a film-forming polyesterionomer binder (AQ55D, Eastman Chemical Co.) and polymeric matte beads were applied onto a subbed polyester support at a total dry coverage of 1000 mg/m.sup.2. The coatings contained 50 mg/m.sup.2 of matte beads. The coatings were evaluated for adherence of the matte bead in the coating by the following test. Sample strips were conveyed over a 1 inch diameter smooth, non-rotating stainless steel rod under constant tension produced by hanging a 500 gram weight to the end of the sample. The samples were conveyed such that the backing layer was in contact with the stainless steel rod. The matte beads dislodged during the test were collected on a piece of dark paper and the amount of particles dislodged was used to assess the matte adherence on a scale of excellent (little or no matte beads dislodged) to poor (many matte beads dislodged). The results are reported in Table 1.
TABLE 1______________________________________ MatteSample Bead Rating______________________________________Sample A C-1 PoorSample B C-3 PoorExample 1 B-2 ExcellentExample 2 B-3 Good______________________________________
It can been seen from the results presented in Table 1 that matte beads of the invention have superior adhesion compared to uncrosslinked, high Tg matte beads (i.e., C-3) or the crosslinked, elastomeric matte beads taught in the '935 patent (i.e., C-1).
Example 3 and Comparative Samples C and D
Backing layers prepared from a film-forming aqueous polyurethane dispersion (Neorez R960, Zeneca Resins) and polymeric matte beads were applied onto a subbed polyester support at a total dry coverage of 1000 mg/m.sup.2. The coatings contained 10 mg/m.sup.2 of matte beads. The coatings were evaluated for adherence of the matte bead using the method previously described. The results are reported in Table 2.
TABLE 2______________________________________ MatteSample Bead Rating______________________________________Sample C C-1 PoorSample D C-2 FairExample 3 B-3 Excellent______________________________________
It can been seen from the results presented in Table 2 that matte beads of the invention have superior adhesion compared to the crosslinked, elastomeric matte beads taught in the '935 patent (i.e., C-1 and C-2).
Examples 4 and 5
A backing layer (Example 4) was prepared from a film-forming aqueous polyurethane dispersion (Witcobond 232, Witco Corp.) and matte bead B- 1 aqueous dispersion. Another backing layer (Example 5) was coated from an acetone/methanol formulation prepared by dissolving Elvacite 2041 polymethyl methacrylate, (ICI Acrylics Inc.) binder and dispersing dry B-1 matte beads into the solvent mixture. The backing layers were applied onto a subbed polyester support at a total dry coverage of 4500 mg/m.sup.2. The coatings contained 25 mg/m.sup.2 of matte beads. The coatings were evaluated for adherence of the matte, bead using the method previously described. Examples 4 and 5 were found to have excellent and good matte adherence, respectively.
Examples 6 and 7 and Comparative Samples E and F
Backing layers prepared from Neorez R960 aqueous polyurethane dispersion and polymer matte beads were applied onto a subbed polyester support at a total dry coverage of1000 mg/m.sup.2 he coatings contained 50 mg/m.sup.2 of matte beads.
Samples of these backing layers were evaluated for their propensity to cause cinch scratches in an emulsion layer during front-to-back contact using the following. test. A photographic film, 35 mm.times.300 mm, was wrapped around a 100 mm diameter dram with the emulsion side out. The backing layer side of a 40 mm square sample was pressed against the emulsion layer of the above photographic film under a lever arm with a rubber pad between the backing layer and the lever arm. The rubber pad is used to insure uniform contact between the backing layer for the sample and the emulsion layer of the photographic film. A load of 500 grams is applied on the lever arm. During the cinch scratch test the sample with the backing layer remains stationary while the dram containing the photographic film rotates at a given speed ranging from 10 to 1000 ft/min. The propensity for the backing layer-containing matte, beads to cause cinch scratches was determined by visual inspection of the scratches in the emulsion layer after the test.
The cinch scratch test was conducted at a relative humidity of 80%. At this humidity the emulsion layer is quite soft and, therefore, this represents a severe test condition. The results found are reported in Table 3.
TABLE 3______________________________________ Cinch ScratchSample Matte Bead Rating______________________________________Sample E C-3 severe scratchesSample F C-1 slight scratchesExample 6 B-2 no scratchesExample 7 B-3 no scratches______________________________________
The results clearly show that backing layers containing the crosslinked, elastomeric matte beads of the invention provide superior resistance to cinch scratches compared to backing layers containing uncrosslinked, high Tg matte beads (i.e., C-3) and the crosslinked, elastomeric matte beads of the prior art (i.e., C-1).
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
4997735	Nitschke et al.	Mar 1991
5300676	Andree et al.	Apr 1994
5536627	Wang et al.	Jul 1996
5538935	Hasreiter, Jr. et al.	Jul 1996

Backing layers for imaging elements containing crosslinked elastomeric matte beads

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