CA1248387A - Elements having hydrophilic layers containing hydrophobes in polymer particles and a method of making same - Google Patents

Abstract

- i -ELEMENTS HAVING HYDROPHILIC LAYERS CONTAINING
HYDROPHOBES IN POLYMER PARTICLES AND A METHOD
OF MAKING SAME
Abstract of the Disclosure Disclosed herein are elements, including radiation-sensitive elements (e.g. color photographic paper products) which have, on a support, a substantially crystal- and agglomeration-free hydrophilic layer. This layer comprises a hydrophilic composition comprising a hydrophilic binder and water-insoluble polymer particles dispersed therein. These particles have recurring units derived from one or more ethylenically unsaturated polymerizable monomers, and comprise from about 0.5 to about 10 percent, based on total monomer weight, of a hydrophobe uniformly distributed throughout. Particularly useful polymer particles are those having recurring units derived from at least one monomer having a crosslinkable moiety.
Particularly useful hydrophobes are optical brighteners. A method of making these elements is also disclosed herein.

Description

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ELEMENTS HAVING HYDROPHILIC LAYERS CONTAINING
HY~ROP~lO~ES IN POLYMER PARTICLES AND A METHOD
OF MAKING SAME
FIELD OF THE INVENTION
This invention relates to elements, including radiation-sensi~ive elements (e.g. color photographic elements). In particular, it relates to such elements having a hydrophilic layer which contains a hydrophobic compound ~e.g. optical brightener) uniformly distributed in polymeric particles. This invention also relates to a method of making such elements.
BACKGROUND OF THE INVENTION
Several techniques have been used heretofore to distribute hydrophobic compounds (hereinafter, "hydrophobe"), particularly non-polymeric compounds such as color-forming couplers, ul~raviolet light absorbing materials, optical brighteners, etc.~
uniformly throughout layers of gelatin or other hydrophilic binder materials in the manufacture of radiation sensitive products. One of the simplest of these techniques involves mechanically dispersing the hydrophobe in solid or liquid form in the binder material by passing a blend of the hydrophobe and material several times through a high energy mill.
This technique, however, generally produces unsuitable dispersions which are often uns~able.
Another technique i8 described in U. S.
Patent 4,203,716 (issued May 20, 1980 to Chen). That technique involves "loading" polymeric latex particles with the hydrophobe using an organic solvent. Generally, "loading" involves (1) dissolving the hydrophobe in a suitable water-miscible organic solvent; (2)mixing the resulting solution with polymeric latex particles;
and (3) removing residual solvent as deslred, partlcularly if necessary to drive the "loading"

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~Z~ 7 , process to completion, or to provide material sufficiently "loaded" with the hydrophobe. The "loaded" latex is then usually dispersed in a hydrophilic binder in preparation for coating.
Depending upon the hydrophobe, sometimes only a limited amOunt of hydrophobe can be successfully "loaded" into latex particles, and any residual hydrophobe must be removed to prevent deleterious image effects. Often some of the hydrophobe "leaches" out of the la~ex particles and forms "crystals." Such crystals deleterlously affect image quality (e.g. reduce sharpness) and, when clumped together, reduce layer smoothness which is important for very thin coatings. This leached-out hydrophobe can also wander into adjacent layers, causing ~dditional problems.
U. S. Patent 3,418,127 (issued December ~4, 1968 ~o Millikan) discloses a method of finely dispersing a fluorescent compound in latex particles by mixing the fluors in polymerizable monomers and emulsion polymerizing the monomers having the fluors therein. The resulting latex purportedly can be coated and dried to form a thin film, preferably over the radiation-sensitive layers of a photographic element. Similarly, W. German Patent 2,509,342 (published September 11, 1975) teaches the incorporation oE optical brighteners into polymeric particles by dissolving the optical brighteners in polymerizable monomers and emulsion polymerizing the monomers. Emulsion polymerization proceeds in micelles formed by water-soluble surfactant.
Additional monomer and hydrophobe migrate from monomer droplets through the water phase and into the micelles prior to polymerization. The resulting latex is purportedly mixed with a compatible colloid (e.g. gelatin) and coated either with a photographic emulsion or in a separate layer in~a photographic element.
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, However, attempts to prepare substantially cryst~l- and agglomeration-free hydrophilic coating compositions according to the teaching of W. German Patent 2,509,342 have been unsuccessful. In particular, as illustrated ln Example 1 herelnbelow, the polymer particles of a latex having an optical brightener dissolved therein tended to agglomerate during polymerization. This tendency to agglomerate appeared to increase with time and the resul~ing polymeric mass could not be coated to form a thin film.
Hence, there is a need in the art for a way to provide relatively inexpensive and simply-made hydrophilic compositions containing hydrophobes which can be coated to provide substantially crystal- and agglomeration-free hydrophilic layers on a substrate.
SUMMARY OF THE INVENTION
The present invention overcomes the problems described above. It provides elements, including radiation-sensitive elements, which comprise polymer particles having a hydrophobe, e.g. an optical brightener, uniformly distributed ~hroughout. These particles are distributed in a hydrophilic layer which is substantially crystal-free, meaning that substantlally all (preferably at least 99 percent) of the hydrophobe is distributed within particles of polymer. The hydrophilic layer is substantially agglomeration-free, meaning very few, if any, of the polymer particles have agglomerated. Rather, the particles are distributed throughout the hydrophilic la!yer. It has also been found th~t hydropho~es are less likely to wander in the elements of this invention.
It is believed that the advantageæ of this invention are obtained because the monomers c~ntaining the hydrophobe are dispersed~in the aqueous medium and allowed to polymerize as a .

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'7 suspension of fine monomer droplets. This technique avoids the problems encountered with emulsion polymerization of hydrophobe-containing monomers wherein the monomer containing hydrophobe must migrate through water and cross the interface of latex micelles. During such migration, the monomer tends to migrate faster than the hydrophobe.
Therefore, ~he concentration of the hydrophobe in the monomer droplets outside the micelles increases to a point where the hydrophobe concentra~ion reaches a saturation point in those droplets, and hydrophobe crystallization then occurs.
Therefore, in accordance with this invention, an element comprises a support having thereon a subs~antially crystal- and agglomer-ation-free hydrophilic layer. This layer comprises a hydrophilic composition comprising a hydrophilic binder and water-insoluble polymer particles dispersed therein. These particles have recurring units derived from one or more ethylenically unsaturated polymerizable monomers and comprise from about 0.5 to about 10 percent, based on total monomer weight, of a hydrophobe uniformly distributed throughout.
In a preferred embodiment, the elements of this invention are radiation-sensitive elements (e.g.
color photographic paper products) which have the hydrophilic layer described above located between the support and the radiation-sensitive layer(s). The hydrophobe in this embodiment is an optical brightener.
This invention also compriæes a method of making the element described hereinabove. The steps of this method comprise:
(a) dissolving from about 0.5 to about 10 percent, based on total monomer weight, of a hydrophobe in solution with one or more ethylenically unsaturated polymerizable monomer~;

, '7 (b) dispersing the æolution formed in (a) as fine droplets in water under conditions sufficient to promote polymerization of the monomers in the suspended droplets and ~o form polymeric particles having the hydrophobe uniformly distributed throughout the particles;
(c) dispersing the polymeric particles in a hydrophilic binder to form a hydrophilic composition;
and 1~ (d) applying the hydrophilic composltion to a support to form a substantially crystal- and agglomeration-free hydrophilic layer.
In a preferred embodiment of this invention, a radiation-sensitive composition is applied over the hydrophilic layer formed in step (d).
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-4 are photomicrographs taken at 250x magnificat~on of "loaded" latex emulsions and hydrophilic coating compositions comprising same prepared according to the teaching of U. S. Patent 4,203,716, noted hereinabove.
FIGS. 5-8 are photomicrographs taken at 250x magnification of suspensions of polymeric particles and of elements containing hydrophillc coating compositions comprising those particles prepared according to this invention.
FIGS. 9 and 10 are cross-sectional W -fluorescence micrographs taken at lOOOx magnification o~ a prior art element and an element of this invention, respectively.
DETAILED DESCRIPTION OF THE INVENTION
The hydrophobe useful in the practice of this invention is a compound which is es6entially insoluble~in distilled water at 25C. Preferably, the dissolved concentration of hydrophobe in water under these conditions is le6s than about 0.5 weight percent~, ba~ed on the~weight o~ the w~ter. Any such :
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hydrophobe can be used in the practice of this inven-tion as long as it can be dissolved or uniformly dis-persed in the ethylenically unsaturated polymer~zable monomer(s) to be used in making ~he polymer particles .described hereinbelow. Preferably, the hydrophobe is soluble in the monomers at a concentration of at least 8 weight percen~, based on the total monomer weight.
Examples of useful functional classes of hydrophobes include, but are not limited to, photo-graphic dyes; photographic dye-forming couplers;
photographic developing agents or other photographic addenda; optical brighteners; ultraviolet light ab-sorbing compounds; and others known to one skilled in the photographic art. Specific photographic addenda which can act as hydrophobes include those compounds used to perform coupling, silver halide development oxidized developer scavenging, absorb light of cer-tain wavelengths, spectral sensitizing or desensi-tizing, or diffusion transfer dye image-forming.
Examples of such hydrophobes are listed in consider-able detail in U. S. Paten~ 4,203,716 (noted herein-above); and in Research Disclosure, publicat~ons 15162 (November, 1976) and 17643 (December, 1978), paragraphs III, IV, VI, VII and VIII (Research Disclosure is published by Kenneth Mason Publications .
Limited, Emsworth, Hampshire, P010 7DD, United Kingdom). Mixtures of:hydrophobes can be used if desired.
Hydrophobes of particular usefulness in the practice of this invention are optical brighteners.
In general, useful optical brighteners include such classes of compounds as: oxazoles; oxadiazoles, in-cluding benzoxazoles; imldazoles 9 including benz-imidazoles; pyrazolines; coumarins; stilbenes;

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,, ` ` ~' ~ ; ' triazines; imidazolones; naphthotriazoles; ace~yl-enes; vinylene compounds; and others known to a skilled worker in the ar~; Specific examples of such--optical brighteners are described in Reseerch Disclosure, publication 17643, par~graph V, noted hereinabove, U. S. Patent 3,666,680 (issued May 30, 1972 to Briggs) and W. German OLS 2,509,342, noted hereinabove ~o illustrate optical brighteners useful in this invention.
0f the many classes of optical brighteners which can be used in the practice of this invention, the stilbene and naphthotriazole compounds are pre-ferred, with such brighteners as Uvitex OB~, Tinopal PCRm and Tinopal SFG~ being particularly useful. These optical brighteners are commercially available from Ciba-Geigy, Ardsley, New York.
The amount of hydrophobe in the polymer particles can be varied widely dependin~ upon in-tended use, but generally it is from about 0.5 to about 10 weight percent, based on total weight of the monomers in which it is dissolved. Preferably, ~he amount is from about 1 to about ~, and more prefer-ably between about 2 and about 5, weight percent, based on the total monomer weight.
The polymer particles useful in the practice of this invention are composed of water-insoluble homopolymers or copolymers having recurring units derived from one or more ethylenically unsaturated polymerizable monomer6. These copolymers can have re~curring units derived from two or more of such monomers, preferably one of which is a monomer having rrosslinkable moieties in the molecule. Such mono-mers are described in more detail hereinbelow.
Preferably, the water-insoluble polymeric particles useful in this invention comprise polymers characterized by ~he structure:

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~ ~ '`. '' ' ' ( A -)w (- ~ )x (~ C )y wherein -A- represents randomly reCurring unit~ in the polymer chain derived from one or more vinyl aromatics; vinyl esters; olefins and diolefins, or esters of ~ unsaturated polymerizable carboxylic acids. Examples of useful vinyl aromatics include styrene, ~-methylstyrene, ~-bromostyrene, o-chlorostyrene, 2-vinylmesitylene, l-vinylnaphthalene, m- and ~-vinyltoluene, 3,4-dichlorostyrene and the like. Useful vinyl esters include, for example 9 vinyl acetate, vinyl propionate, vinyl butyrate and the like. Examples of useful esters of ~,~-unsaturated polymerizable carboxylic acids include methyl acrylate, methyl methacrylate, _-bu~yl acrylate, n-butyl methacrylate, t-butyl methacrylate, benzyl methacrylate, methyl ~-bromoacrylate, 4-chlorobutyl acrylate, cyclohexyl acrylate, 2-norbornylmethyl acrylate, 2-ethylhexyl acrylate, lauryl methacrylate, tetrahydrofurfuryl methacrylate, 2-ethoxyethyl methacrylate, 3-chloro-propyl acrylate, 2-2-dimethylbutyl acrylate, and the like. Useful olefins and diolefins include, for example, ethylene, propylene, l,3-butadiene, isoprene, chloroprene, cyclopentadiene, 5-methyl-1,396-heptatriene, and the like.
Preferably -A- represents randomly recurrlng units derived from one or more vinyl aromatics, e.g.
styrene, or esters of a-~-unsaturated polymerizable carboxylic acids, e.g. methyl methacrylate, butyl acrylate and tetrahydrofurfuryl methacrylate. More preferably, -A- ls derived from styrene or methyl methacrylate or bo~h.
In the above-identified structure, B-represents randomly recurring units in ~he polymer chain derived from one or mQre ethylenically unsaturated polymerizable~monomers havLng one or more :
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'7 g anionic moieties, e.g. sulfo, phosphono or c~rboxy moieties (including ~lk~li metal or ammonium salts thereof). These recurring units contribute to the dispersibility of the polymer particles in hydrophilic binders. ExRmples of useful monomers having such anionic moieties include 4-acryloyloxybu~ane-1-sulfonic acid, sodium salt;
3-acryloyloxy-1-methylpropane-1-sulfonic acid, sodium salt; acrylic and methacrylic acids and alkali metal l~ salts thereof; m- and ~-styrenesulfoni~ acid and alkali metal salts thereofi 3-methacryloyloxy-propane-l-sulfonic acid, sodium salt; lithium methacrylate, N-[3-(N-phenylsulfonyl-N-sodio-sulamoyl)phenyl~acrylamide, N-[2-(N-methyl-sulfonyl-N-potassiosulfamoyl)ethyl]methacrylamide, ammonium p-styr~nesulfonate, 2-acrylamido-

2-me~hylpropanesulfonic acid~ sodium salt, and the like.
Preferably, -B- represents randomly recurring units derived from one or more monomers having sulfo or carboxy moieties, such as styrenesulfonic acids or alkali metal salts thereof, acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid. More preferably, -B-is derived from styrenesulfonic acids or salts thereof.
Also, in the above-identified structure, -C~
represents randomly recurring units in the polymer chain derived from one or more ethylenically unsaturated polymeriz~ble monomers having crosslinkable moieties. Such units contribute to the water-insolubility of the resulting polymer. They also make the polymer less soluble in organic solvents generally used in coating operation~ and thereby reduce the tendency of the hydrophobe to wander.

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These monomers c~n have two or more ethylenically unsaturated moieties which crosslink during polymerization (e.g. diacrylates, divinylbenzene, etc~). Alternatively, they c~n have moieties which do not react to provide crosslinking during polymerization, but provide crosslinking because of reaction with a hardener or with another moiety on a different monomer. Such monomers include, for example, 2-acetoacetoxyethyl methacrylate, N-(2-acetoacetoxyethyl)acrylamide, N-~2-acetoacetamidoethyl)acrylamide and 2-aminoethyl methacrylate hydrochloride. Monomers having two or more ethylenically unsaturated sites available for reaction include, for example, diacrylates;
dimethacrylates; triacrylates; trimethacrylates;
divinyl compounds; and the like. Examples o~ such monomers include divinylbenzene, ethylene dimethacrylate, 2,2~dimethyl-1,3-propylene diacrylate, propylidene dimethacrylate, 1,6-hexamethylene diacrylate, phenylethylene dimethacrylate, tetramethylene dime~hacrylate, 2,2,2-trichloroethylidene dimethacrylate, ethylenebis(oxyethylene) diacrylate, oxydiethylene diacrylate, ethylidyne trimeth~crylate, allyl acrylate, vinyl allyloxyacetate, l-vinyloxy-2-allyloxyethane, 2-crotonoyloxyethyl methacrylate, diallyI phthalate, triallyl cyanurate, 2-(S-phenyl-2,4-pentadienoyloxy)ethyl methacrylate, N,NI-methyl-enebisacrylamide, N,N'-bis(methacryloyl~urea, and the like.
Preferably, -C- represents randomly recurring units derived from one or more diacrylates or dimethacrylates, e.g. ethylene diacrylate or ethylene dimethacrylate or both.
The polymers useful in the practice o~ this invention can also comprise minor amounts (less than about 5 weight percentj of randomly recurring unlts . .

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'7 in the polymer chain derived from one or more ethylenically unsaturated polymerizable monomers other ~han ~hose described for A-, -B- or -C-hereinabove. Generally, these units are present in very small amounts in the polymer chain so as not to delete.iously ~ffect polymer water insolubility Or other desirable polymer properties. For ex~mple, they can be derived from vinyl amides (e.g.
acrylamide, methacrylamide, N-isopropylmethacryl-amide, N-isopropylacrylamide, N-(3,6-di~hiahep~yl)-acrylamide, etc.); vinyl nitriles (e.g.
acrylonitrile, methacrylonitrile, 3-buteneni~rile 9 etc.); vinyl ketones ~e.g. methyl vinyl ketone, diacetone acrylamide, etc.); vinyl halides ~e.g.
vinyl chloride, vinyl bromide, vinylidene chloride, etc.); vinyl ethers (e.g. allyl methyl ether, allyl phenyl ether, 2-chlorovinyl methyl ether, etc.);
N-vinylsuccinamide; N-vinylphthalimide; N-vlnyl-pyrazolidinone; and others known to one gkilled in the polymer chemistry art.
Generally, the proportions of the various units vf the poIymer 6tructure defined herein are as follows: w represents a weight percent of from about 80 to 100, and preferably, from about 90 to about 99 weight percent; x represents a weight percent of from 0 to about 20, and preferably from about 0.5 to about 5 and more preferably from ~bout 1 to about 3 weight percent; and y represents ~ weight percent of from 0 to about 5, preferably from about 0.5 to about 5, and more preferably from about 2 to ~bout 4) weight percent. All wei~ht percentages are based on total monomer weight.
In a preferred embodiment of thls invention wherein the hydrophob~s are optical brightener6, w is generally from about gO ~o 100 weight percent, x is from O to about 5 weight percent and y is from 0 to about 5 weight percent.

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-lZ-Although the glass transition temperature (Tg) of the polymers useful in the practice of this invention can be varied widely, they generally have a glass transition temperature (Tg) greater than about 70C, and preferably in the range of from about 90 to about 120C, in order to prevent diffusion of hydrophobe into the coated layers during drying and storage and to improve compatibility with coating addenda. The glass transition temperature can be determined by any convenient method suitable for this purpose. For example, one such method is differential scanning calorimetry as described in Techniques and MethodS of Polymer Evaluation, Volume 2, Marcel Dekker, Inc., N.Y., N.Y., 1970.
lS Examples of polymers useful in the practice of this invention include:
poly(methyl methacrylate);
poly(methyl methacrylate-co-styrene) (80:20 weight ratio~;
poly(n-butyl acrylate~co-~etrahydrofurfuryl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid, sodium salt) (35:60:5 weight ratio);
poly(methyl methacrylate-co-methacrylic acid) (95:5 weight ratio);
poly(n-butyl methacrylate-co-methacrylic acid) (80:20 weight ratio);
poly(methyl methacrylate-co-ethylene dimethacrylate) (98:2 weight ratio);
poly(methyl methacrylate-co-styrene-co-ethylene dimethacrylate) (49:49:2 weight ratio);
poly(methyl methacrylate-co-styrene-co-styrene sodium sulfonate-co-ethylene dimethacrylate3 ~48.5:48.5:1:2 weight ratio);
poly(methyl methacrylate-co-styrene-co-divinylbenzene) (49:49:2 weight ratio); and poly~methyl methacrylate-co-styrene-co-sodium~s~yrenesulfonate-co-divinylbenzene) (48.5:48.5:1:2 weight ratLo).

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'7 The polymer partlcles useful in the practice of this invention are generally prepared by addition polymerization of the monomers in an aqueous suspension. This is commonly known as "suepension polymerization." It can be carried out in batch~
semi-continuous or continuous operations, as is well known in the art.
Generally, the method of this invention includes dissolving the hydrophobe(s) in solution with the ethylenically unsaturated polymerizable monomers. The monomer solution is then dlspersed as fine droplets in water and subjected to conditions sufficient to promote suspension polymer~zation of the monomers. Although, it i8 not always required, it is advantageous to use one or more polymerizatlon initiators to initiate polymerization and promote its completion. At least one of the initiators~ if used, is oleophilic and is dissolved in the monomers along with the hydrophobe. Useful oleophilic initiators include azo compounds, such as the VAZ0~ initiators commercially available from DuPont, Wilmington, Delaware, e.g. VAZo-64~ which ~s 2,2'-azobis(2-methylpropionitrile), VAZ0-52~ which is 2,2'-azobis(2,4-dimethylvaleronitrile), VAZo-33 which is 2,2'-azobis(2,4~dimethyl-4-methoxy-valeron~trile) and VAZ0-67~ which ls 2,2'-azobis(2-methylbutanenitrile); peroxides, such as lauroyl peroxide and benzoyl peroxide; and others known to one skilled in the art. Water-soluble polymerization inltiators can be u~ed in addition to oleophilic initiators as long as there is su~icient oleophilic initiator to initiate the polymerization of the suspended monomer droplets and an insubstantial amount of emulsion polymerization occurs.
~ One or more surface active agents ~i.e~
surfactant~s) are ~180 often employed in suspen~ion ~, :
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'7 polymerization to aid in keeping the digper6ed monomer droplets from clumping together in the aqueous medium. At least one of the surfactants, if used, is oleophilic and is incorporated into the reaction mixture by dissolving it in the monomer(s) along with the hydrophobe.
It is often desirable to agitate the monomers in a suitable manner while the hydrophobe, initiator or surfactant is added and dissolved therein. Also, it may be advantageous to heat the monomers prior to and during such addition to facilitate dissolution. Normally, if this is done, the temperature of the monomers is maintained at greater than room temperature (20-25C), but less than the temperature at which the monomers undergo spontaneous polymerization (this varies with the monomer(s) and initiators used). Generally, the temperature used for this purpose is in the range of rom about 30 to about 45C.
Once the hydrophobe iB dissolved within the monomers, the resulting solution is dispersed in water as fine droplets and subiected to pressure and temperature conditions suitable for polymeriza~ion of the monomers in the suspended droplets and formation ,5 of small, suspended polymer particles. The monomer solution is generally present in droplet form in thls dispersion in a range of from about 20 to about 50 percent, based on total dispersion weight. The pressure employed in the polymer~zation is generally only that needed to maintain the reaction mixture in lliquid form, and is usually atmospheric pres~ure.
The polymeriz~tion temperature is subiect to wide variation as it depends upon several variables including the monomers~ initiator and weight percent of monomers in the dlspersion. However, generally the temperature is in the range of from about 20C to about 120C, and preferably from about 50 to about -." .,-' :

70C. The temperature can vary during the polymerization reaction becau~e of the evolution of heat from the reaction i~self.
The monomer solution can be dispersed in ~he aqueous medium prior to polymerization in any suitable manner which may depend upon the polymerization technique (batch, continuous or semi-continuous) employed. Generally, the solution is dispersed in the aqueou6 phase by any means which produces high shear sufficient to form very fine droplets containing monomer, hydrophobe and preferably, oleophilic lnitiator ~nd ~urfactant. For example, such dispersing can be accomplished by mechanical means such as high-speed stirring Or 15 vigorous agitation of some manner, or by pumping a monomer-water mixture through a small orlfice or high shear mill into a reactor vessel.
Once polymerization has begun, it i6 continued until sub6tantially all monomer has reac~ed. This may take up to 24 hours, depending upon the polymerization condition6 employed.
Specific details of polymerization of the monomers having the hydrophobe dissolv2d therein are illustrated in the examples presented hereinbelow.
The resulting polymer is in the form of small particles, the size of which can be varied by changing the dispersing conditions or amount of surfactant. The average particle size is generally in the range of from about 0.1 to about 20 microns, with polymer particles in the ran&e of from about 0.4 to about 1 microns being particularly useful in the preferred embodiment of this invention utilizing optical brighteners ~s the hydrophobe.
The resulting aqueous suspension of polymsric particles can be used dixectly aft~r-polymerization. Water may be removed, if desired, to increase~the percent æolids of the suspenslon.
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. , -The polymeric su6pension is then uniformly dispersed in one or more hydrophilic binder materials, or "vehicles" as they are often called in the art, to form a hydrophilic compo~i~ion. Such binders act as peptizers for ~he polymer~c particles to reduce their tendency to settle. Suitable hydrophilic binders include both naturally-occurring substances, such as proteins (e.g. gelatin, gelatin derivatives, cellulose derivatives), polysaccharideS
(e.g. dextran), gum arabic, etc.; and synthetic polymeric substances such as water-soluble polymers (e.g. poly(vinyl alcohol), acrylamide polymers, poly(vinyl pyrrolidones), etc.), and others known to one skilled in the art, as described, for example, in Research Disclosure, publication 17643, noted hereinabove, paragraph IX. Gelatin is a preferred binder in the practice of this inventlon.
Generally, the polymeric particles are present within a binder in an amount of at least about 15, and preferably from about 20 to about 70, percent based on total dry weight of hydrophilic composition. This corresponds to a coating coverage of polymeric particles of at least about 20 mg/m2 of coated surface area. Particles of different polymers containing the same or different hydrophobes can be used in the same hydrophilic composition, if desired.
Once the particles are blended in the binder, the resulting hydrophilic composition c~n be purified, if desired, in any suitable manner to remove ~ny unwanted addenda.
The described hydrophilic composition can be npplied to a suitable substrate, such as a conventional 0upport, using conventional ~echniques to provide an element having a hydrophilic layer.
Additional compositions can be applied simultaneously or subsequen~ly to form addit~onal layers over or .

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' .Z ~ 7 under the hydrophilic layer. It i8 specifically contemplated to apply these compositions to a support using coating hoppers or other coating npparatus conventionally employed in preparing singl~ or multiple layer radiation-sensitive elements. Useful coating and drying ~echniqueOE and gupports (e.g.
paper, polymeric film6, glass, etc.) are described, for example, in Research Disclosure, publication 17643, noted hereinabove, paragraphs XV and XVII.
The hydrophilic layer so formed is substantially crystal- and agglomeration-free. As used herein, "substantially crystal-free" and "substantially agglomeration-free" refer to a layer having substantially no crystals of hydrophob~ or agglomerations of polymer particles within the layer. In other words, substantially all hydrophobe (preferably at least 99 percent) is in polymer particles rather than external to the particles, and very few polymer particles are stuck together.
Generally, in the elements of this invention, less than 5 crystals of hydrophobe can be observed in a

3.5 x 4.5 in. (8.9 x 11.4 cm) area of the layer containing the hydrophobe as observed at 250x magnification. (See FIGS. 7 and 8 which are photomicrographs of a coated composition containing an optical brightener in an element o~ this invention).
The hydrophilic compositions described herein can be used in radiation-sensitive elements of various types. Generally, the coating coverage of the hydrophilic composition depends upon its use and the type of element i~ is incorporated into.
Radiation-sensitive elements of this inven~ion include, for example, image transfer materials, lithographic materials, physicAl development materials, radiographic mater~als, dry development material~, negative- and positive-working . ~

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color-forming materials (including color films and color photographic papers), black-and-white films and papers, and the like. The details of such materials are well known in the art and are described, for example> in Rese-a-rc-h- Disclosure, publication 17643, noted hereinabove.
In a preferred embodiment of this lnventlon, the described hydrophilic compositions are useful in multilayer color photographic paper products hsving a lU resin-coated photographic paper support and a plurality of color-forming silver halide emulsion layers coated thereon.
The hydrophilic compositions can be used in any location in the radiation-sensitive elements of lS this invention, including within the radiation-sensitive layers themselves. Preferably, however~ they are coated as individual hydrophilic layers, above, below or in between radiation-sensitive layers. In a preferred embodiment, the hydrophilic composition conta~ns an optical brightener as the hydrophobe and is incorporated between the support and the radiation-senæi~ive layer(s) to provide an optical brightener layer.
The following examples are provided to illustrate the practice of this lnvention.
Example 1 Part A
A photographic element of ~his invention containing an optical bri8htener hydrophilic layer was prepared in the following m~nner: ~
Methyl methacrylate (ll.S kg) monomer was added to a 40 L reactor vessel and warmed to 40C
with gentle stirring. Uvltex OB~ (386 g~, an optical bri~htener~commercially-available from Ciba-Geigy (located in Ard~ley, New York), was added to the~stirring monOmer until it was comple~ely :

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i7 dissolved. Then, Aerosol OT-100'~ (230 g), an oleophilic surfactant commercially ava~lable from American Cyanamid ~located in Wayne, New Jer6ey), and 2,2'~azobis(2-methylpropionitrile) polymerization initiator (57.5 g) were similarly added to and dissolved in the monOmer. Once all of the reagent6 were dissolved, stirring in the vessel was increased to about 200 rpm and distilled water (26.8 kg) heated to 50C was added to the monomer solution.
The resulting dispersion was ~tirred for an additional 10 minutes and then pumped through a commercially-available high shear M~nton-Gaulin mill at 2850 rpm using an orifice clearance of 0.004 in (0.01 cm) and a flow rate of 1.5 L/min. into another 40 L reactor vessel where stirring was set at 40 rpm and the temperature controlled a~ 65C. The time for pumping through the mill was about 26 minutes. This high shear dispersing mean~ provided very fine droplets of monomer in the aqueous phase.
Polymerization began immediately and was allowed to proceed for about 2 hours at 65C to give a suspension of polymeric particles of about 25% solids.
With the temperature maintained ~t 65C, gelatin (1.56 kg) was added to ~he polymer suspension with agitation. The resulting hydrophilic composition was kept at 65C and stirred at 40 rpm for about l hour, filtered through a 30~ filter at 65~C and chill set at 40C. The yield of hydrophilic composition was about 39 kg.
3U The hydrophllic composition 80 prepared was coated on a polyethylene support to provide an element of this $nvention having ~ubstantially no crystals or agglomerations.
~Part B
Several ~ttempts were made to prepare-an element according to the teaching of W. GPrman OLS
2,509~342 noted~hereinabove. The procedure Rnd ~:

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, j ' ' 8 ~ ~7 materials of that teaching were used with the following minor exceptionsO
1. Tinopal PCR~ (available from Ciba-Geigy Co.) was used as the optical brightener in place of ~he equivalent, gimilarly 8tructured Optlcal brightener B; Tinopal PCR~ is a stilbenetriazole having the structure:

.~ CH=C~

2. Triton 770~ (available from Rohm &
Haas, Philadelphia, Pennsylvania) was used as the surfactant in place of the equivalent sodium octylphenoxypolyethoxysulfonate surface active agent illus~rated in Example 2 of the reference; and 3. Sodium lauryl sulfate was used in place of the equivalent sodium alkyloxyethylsulfonate in ~ solution B.
In the preparation of ~he latex, solution A
was warmed to 40C to dissolve the optical brightener in the monomers. After 4 hours of polymerization according to the reference teaching (i.e.
conventional emulsion polymerization with conventional stirring), the resulting latex was a sticky~ rubbery mass that could not be coated on a substrate. No high shear dispersion technique was used to form small monomer droplets within the aqueous medium. It was apparent that the latex polymer particles and optical brightener had agglomerated into an unusable mass- These results occurred with each attempt to practice the reference teaching.
Example 2 Crystal- and Agglomeration-Free Element This is a compar~tive ex&mple comparing an element of this invention to an element of the prior art.

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: :

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.

Part A
A "lo~ded" latex was prepared according to the teaching of U. S. Patent 4,203,716 (noted hereinabove).
Distilled water (10.3 kg) was added to a 40 L reaction vessel and agitated at 120 rpm while heating to 85C. A nitrogen atmosphere was maintained throughout the preparation. Pota6sium persulfate initiator (100 g) was dissolved in distilled water (2.5 kg) and the resulting solution was added to the reactor vessel along with Tri~on 770~ surfactant (125 g, 30% solids). In a head tank, sodium hydroxide (190 g) was added to distilled water (8.75 kg) while being maintained at 20-25C.
2-Acrylamido-2-methylpropanesulfonic acid monomer (500 g) was added to the head tank wlth good mixing and the pH of the dispersion was adjuated to 3.3 with sodium hydroxide. Also added to the head tank were potassium persulfate initiator (50 g3 dissolved in distilled water (1.25 kg), Triton 770 surfactant (125 g, 30% solids), butyl acrylate monomer (3 kg) and tetrahydrofurfuryl methacrylate monomer (6.5 kg). An air mixer was used o emulsify the monomer mixture in the head tank.
When the temperature of the eontents of the reactor vessel was stabilized at 85C, a solution of sod~um meta bisulflte inltiator (30 g) in distilled water (500 g) was added to the reaction vessel.
Simultaneously, addition of the monomer mixture to the reactlon vessel from the head tank was begun ~nd continued over 45 mlnutes. Following total ~ddition of the monomer mixture, the emulsion polymeri~ation was allowed to~proceed for 3 hours at 8SC. After this time, the;latex was~cooled to 25C and filtered through a 1~ Ful~lo~ filter ~available from Fulflo Corporatlon located in Lebanon, Indiana).
Further purification was acco=plished by dLafiltering :
:

:
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, '7 the latex (diluted to 10% solids with distilled water) for 5 turnovers through a 20 K polysulfone membrane, and then concentrating it to 22.5% solidS
by ultrafiltration.
To a 80 L vessel were added tetrahydrofuran solvent (23.3 kg), Uvitex OB~ optical brightener (408.2 ) and ~iostat PE-878~ biocide (32.6 ml).
Biostat PE-878m is commercially available from Eastman Kodak Company located in Rochester, New York. The resulting mixture was agitated with a stirrer at 90 rpm and the temperature was gradually adjusted to 55C. An antifoam agent SAG 10~
(28.6 g) (commercially available from Union carbide located in Hackensack, New Jersey~ was added to 36.3 1~ kg of the purified latex. When the vessel contents had reached 38-4~C, the latex was added rapidly and vacuum was applied. About 15.1 kg of the solvent was distilled off at 75 mm Hg at 45C and the vacuum was then released. A sample of ~he resulting "loaded"
latex was removed and evaluated as explained below.
Once the temperature had reached 55C, dry gelatin (1633 g) was sifted ~nto the vessel with good mixing to provide a coating composition of ~he remaining "loaded" latex. The mixing was continued for 30 minutes after gel addition. The resulting hydrophilic coating composition was then filtered through a 5~ Fulflo~ filter and chill-set until use.
The sample of 'iloaded" latex removed prior to gel addition and a sample of the hydrophilic cbating composition made with gel were~ evaluated for crystals and agglomerations by coating the samples on separate glass~substratPs and drying the coatings to form coated elements. These elements were examined with an optical microscope at 250x magnification using polarized illumination. Table I hereinbelow lists the elements evaIuated to obtain the pictures of Figures 1-4 taKen at that magnification.

.

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.

Table I

Keeping Figure Element Conditions _ 1 "Loaded" Latex None-tested immediately after ~oating and drying 2 I'Loaded" Latex Element of FIG. 1 kept

4 hours at 60C

3 Hydrophilic None-tested immediately Composition after coating and drying 4 Hydrophilic Element of FIG. 3 kept Composition 4 hours at 60 C

In Figures 1-4, crystals appear as bright needle-like spots on the dark background. As can be seen from FIG. 19 the "loaded" latex coated without binder and evaluated immediately after coating contained many very fine cryætals immediately after coating. These crystals became well-formed rectangles and needles after keeping for 4 hours at 60C as seen in~FIG. 2. These keeping condltions represent melt-hold condi~ions~ FIGS. 3 and 4 are pictures of hydrophilic compositions cont&ining a 3~ "loaded" latex and a binder. L~rge numbers of optical brightener crystals can be observed. FIG. 4 indicates that the number of crystals increaæes under conventional melt-hold conditions. ;
The samples of "loaded" latex and hydroph~lic compositLon were also evaluated for agglomerations~us~ng electr~on microscopic technLques.~ The presence~of~agglomerat~ons was .

. : : . '` ;~

observed in each sample with the number of agglomera~ions greater under conventional melt-hold conditions (4 hours at 60C).
Part B
An element of the present invention was prepared in the following manner.
A suspension of polymeric particles was prepared according to the procedure described in Example 1 (Par~ A) using tetrahydrofurfuryl methacrylate, _-butyl acrylate and 2-acrylamido-2-me~hylpropanesulfonic acid as monomers and Uvitex OB~ op~ical brightener as the hydrophobe.
The suspension containing polymer particles was taken from the reaction vessel after which the vessel was cleaned. The suspension was returned to the vessel and the pH was ad~usted to 7 with 10~
sodium hydroxide at 60C and 200 rpm stirring. A
sample of the suspension was taken for evaluation as described below. A 10% gelatin solution in water was ~dded to the reac~ion vessel and s~irring was continued for another 15 minutes.
The resulting hydrophilic composition was filtered through cheesecloth and chill-set. Little or no coagulum was found in the reaction vessel.
A sample of the suspension ~aken prior to gelatin addition and a sample of the hydrophilic composition containing gelatin were coated and evaluated for crystals and aggIomerations a~
described for the "loaded" latex in Part A
hereinabove. Table II ~elow lists the corresponding elements evaluated.

, :

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: , : , 3 ~ 7 Table II

Keeping Figure Element Condition~ _

5 Suspension None tested immediately containing after coating and polymer particles drying

6 Suspension Element of ~IG. 5 kept containing 4 hours at 60C
polymer particles

7 Hydrophilic None-tested lmmediately Composition after coating and . drying

8 Hydrophilic Element of FIG. 7 kept Composition 4 hours at 60 C

In Figure~ 5~8, as in Part A, crystals appear as bright needle-llke spots in the dark background. As can be seen from the Figures, a few large crystals &ppear in the suspension immediately 2S after coating (FIG. 5). Further, there i8 little change under conventional melt-hold conditions (FIG.
6). The~element containing the hydrophilic composition has only 3 crys~als in a 3.5 x 4.5 in.
~8.9 x 11.4 cm) coated area viewed at 250x magnification (FIGS. 7 and 8). ~It is quite clear that the elements shown in FIGS. 7 and 8, which are prepared according to the practice of this invention, exhibit significant improvement over the elements prepar d in Part A according to the prior art (FIGS.
3 and 4). ~ ~
~ ~ The~ Suspen6ion of polymer particles and hydrophilic composition containing same were al~o ::
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evaluated for agglomerations using electron microscopic techniques. Substantially no agglomerations were observed in either the suspension or composition, even after keeping under the melt-hold conditions.
Example 3 A photographic elemen~ of this invention containing an optiral brightener hydrophilic layer was prepared in the following manner. This example differs from Example 1 in that the polymer of this example is a crosslinked polymer.
Methyl methacrylate (1.15 kg), styrene (1.15 kg) and ethylene dimethacrylate (46 g) monomers and Aerosol OT-100'~ (23 g) surfactant were stirred in a reactor vessel at 30C until the surfactant was dissolved. Uvitex OB~ (80 g) brightener and 2,2'-azobis(2-methylpropionitrile~ (11.5 g) were similarly added to and di~solved ln ~he monomer solution. Once all of the reagen~s were di6solved in the monomers, stirring in the vessel was increased to about 200 rpm and an aqueous solution of Aerosol A268~ surfactant (46 g in 5.4 L distilled water) was added to the monomer solution.
The resulting dispersion was stirred for an additional 5 minutes and then pumped through a commerci&lly-available higl shear Manton-Gaulin mill at 3800 rpm using an orifice clearance of 0.004 in (Q.01 cm) and a flow rate of 1.5 L/min. into another reactor vessel where stirring was set at 40 rpm and the temperature controlled at 70C. Polymerlzation proceeded for 20 hours at 70C to give a suspension of polymeric par~icles of about 30% solids.
This suspension was mixed with gelatin to provide a hydrophilic composition as described in Example l hereinabove. The resulting composition was coated on a resin-coated support to provide an element o~ this invention.

:: :
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Example 4 A polymeric suspension of poly(methyl methacrylate-co-styrene-co-~-styrene sodium sulfon~te-co~ethylene dimethacrylate) (48.5:48.5:1:2 weight ratio) particles containing Uvitex OB~
optical brightener was prepared as described in Example 3. This suspension was mixed with gelatin and incorporated as a brightener layer in a color photographic paper product having the following lU format using conven~ional coating techniques ~nd materials.
Over-co-at gelatin ~ U.5-2 g/m~
Ultraviolet Light gelatin 0.5-2 g/m ~bsorbing Layer W light absorber 0.1-0.6 g/m2 AgClBr (15:85 mole %
Cl:Br) ~0.1-0.5 g/m2 Ag Cyan Dye Layer gelatin 1-2 g/m cyan dye-providing coupler la 0.4-0.8 g/m2 Ultraviolet Light gelatin 0.5-2 g7m2 Absorbing Layer W light absorber 0.1-0.6 g/m2 AgClBr (15:85 mole %
Cl:Br 0.1-0.5 g/mZ Ag Magenta Dye gelatin 1-2 g/m Layer magent~ dyebproviding coupler 2 0.4-0.8 g/m2 Interlayer gelatin 0.5-2 g/m 2 Ag~l~r (lZ:88 mole ~/O
Cl:Br 0.1-0.5 g/m2 Ag Yellow Dye Layer gel~tin 1 2 g/m 2 yellow dye-providing coupler 3C 0.8-1.5 g/m2 ~ lF~ymer par~icleS ~.S-Z
: Uvitex OB~ :
Brightener Layer bri~htener 0.03-0.06 g/m2 gelat~n0.8-1.~5 g/m2 / / / /
/ / / Polyethylene-coated Paper Support / /
~ / / / / /. /~. / / / / / / / /

. .

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-' ' , -28~
aCoupler 1 OH t-C
Cl\ /o~ ~ COCHO - ~ ~o-t-C
H C / \ ~ CzHs s 2 Cl Cl\ ~-\ /Cl i1 Coupler 2 ~ Cl\
Cl ~ - t~4Hg COCHO~ --OH
n-CI2H 2 s CCoupler 3 Cl\
., .
(cH3)3ccocHcoNH
O ~HCO(CH2) 30- ~ ~ -t-C5HI
~ \ t-C/sH
i~ ,i!

~!
i~ ,i!
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E~ch gelatin-cont~aining layer was hardened with bis(vinylsulfonylmethyl) ether At 1.8% based on the gelatin coverage.
A control paper product was similarly prepared except that the brightener layer was omitted.
Without imagewise exposure, a sample of each element W8S f~ixed for 4 minutes at 38C with a conventional fixing~composition, washed 3 minutes at 38~C and processed~with the Kodak Ektaprint~ 2 process ~seel"using:Kodak Ektaprint 2 Chemicals," ~nd Ed., Eastman Kodak Co~ Publication Z-122, 1980). The :
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reflection density (Dmin3 of each sample Was then measured using a Wratten 25 filter for the red, Wratten 106 filter for the green and Wratten W48 and 2A filters for the blue. The regults are presented in Table I below.
Table I
Density (Dmin) Red_ Green Blue Control 0.116 0.127 0.128 Example 4 0.115 0.124 0.114 It can be seen from these data that while the red and green Dmins are substantially identical for both elements, ~he blue Dmin is signlflcantly decreased in the element containing the brigh~ener layer. These results indicate the effectiveness of the brightener incorpora~ed in the polymer particles~
Examples 5 and 6 These examples are similar to Example 4 except that the polymer particles con~aining an optic~l brightener are incorporated in the ~nterlayer between the magenta and yellow dye layers instead of ~ separate brightener layer.
Uvitex OB~was incorporated in poly(n-butyl acrylate-co-tetrahydro~urfuryl methacrylate-co-2-acrylamido~2-methylpropanesulfonic acid, sodium salt) (30:65:5 weight ratio) particles tExample 5) and poly~methyl methacrylate-co-ethylene d'imethacrylate) (98.2 weight ratio) particles (Example 6) according to the procedure described in Example 3. ~
~ The resulting polymer ~uspensions were incorporated in the interlayer and elements were prepared as described in Example 4. A control element~was also prepared like the control element of Example 4.

:
. : :

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A sample of each element was processed and the yellow Dmin lev~l of each measured as described in Example 4. The difference in control Dmin and example Dmin are shown in Table II below.
Table II
Change in Yellow (Dmin) Example 5 -0.1 Example 6 -0.1 These data indicate the brightening effectiveness of the brightener-containing polymeric particles in the interlayers of the elements.
Example 7 This example illustrateæ the incorporation of a cyan dye-forming coupler in polymer particles and the use of such particles in a photographic element.
The coupler was incorporated into poly(_-butyl methacrylate-co-methacrylic acid) particles in the following manner:
_-Butyl methacrylate (114 g) a me~hacrylic acid (36 g), 2-[~-(2,4-di-t-pentylphenoxy)-butyramido]-4,6-dichloro-S-ethylphenol (90 g) and Aerosol OT~ surfactant (7.2 g) were placed in a 1 L
vessel and heated At 50C under a nitrogen atmosphere until all materials were dissolved. Distilled water (600 g) was placed in a conventional blender, heated to 60C and the monomer solution was added thereto and mixed at high speed for 5 minutes. The resulting dispersion was added to a 2 L reaction vessel and heated to 70C, after which K2S208 (1.8 g in lO mL of water) and Na2S20s (0.72 g in lO mL of water) were added to the vessel. After two hours of reaction, the resulting suspension was filtered to~remove A small amount of coagulum and the filtrate~ WAS ad~usted to pH 5.5.

: :
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.
.
- ~ ' '~ ', .
, : - -:. ~:, 3 ~'7 The polymer particle suspension was then warmed to 50-60C and a 5% golution of gelatin containing 52g of dry gelatin was gradually added.
The resulting hydrophilic composition was gtirred for 30 minutes at 50C.
This hydrophilic composition was coated in a photosensitive emulsion layer on a polyethyl-ene-coated paper support. The coating coverages were 0.3 g/m2 Ag, 2.8 g/m2 gelatin and 1.24 g/m2 polymer particles. The gelatin was hardened with bis(vinylsulfonylmethyl) ether at 1~75% based on gelatin weight.
The resulting element was exposed for 0.1 sec. to a 3000K light ~ource through a Wratten 29 filter and a graduated neutral density tablet, and processed with the Ektaprint~ 2 process described in Example 4. Sensitometric evaluation of the element indicated that it exhibited suitable cyan dye color.
0 Example 8 Comparison of optical Brightener Wandering in Elements This is a comparative example showing the reduced tendency of an opt~cal brightener to wander in a multilayer photographic paper product of this invention compared to the wandering tendency of the same optical brightener in a similar paper product prepared according to th prior art, as in Part A of Example 2 hereinabove.
The elements of this example had the 0 following general structure:
overcoat layer , . . .._ .
cyan dye l~yer W -li~ht absorbing layer magenta dye layer ~ _ .
_~nterlayer yellow dye layer , .
.....

~, .

~ Z ~ 7 optical brigh~ener layer polYethylene resln coating / / / / / pape~ S~uppo~r~//////~

The specific ingredients of each layer other than the optical brightener layer are not critical to the purpose of this example 3 but are conventional in the photographic chemistry ar~.
The optic~l brightener layer of the element of this invention contained gelatin as the hydrophilic binder (0.8-1.5 g/m2) and particles of poly(n-butyl acrylate-co-tetrahydrofurfuryl methacrylate-co 2-acrylamido~2-methylpropane6ulfonic acid, sodium salt) (49:49:2 weight ratio) (0.5-2 g/m 2) containing Uvi~ex OB~ optical brightener (0.03-0.06 g/m2) uniformly dispersed throughout the particles.
The optical brightener layer of the Control element contained a "loaded" latex (0.5-2 g/m2) like ~hat described in Part A of Example 2 of poly(methyl methacrylate-co-styrene-co-ethylene dimethacrylate~ t35:60:5 weight ratio) dispersed in 2~ gelatin (0.8 1.5 g/m2). The latex was "loaded"
with about 1 weight percent of Uvitex OB~ optical brightener although not all of the brightener was in latex particles.
UV-fluore6cence microscopy was used to study the optical brightener wandering in each element.
cross-section of esch element was sub~ected ~o fluorescent light at 1000x using an ultraviolet llght filter. FIG. 9 is a photograph of the cross-section of ~he Control element.~ The light areas again6t the dark background indicate considerable wanderin~ of the optical brightener from the visually bright optical bri8htener layer. FIG. 10, however, .~ ~ .. :., . :
: .
. ' ' :' ~' ' ' ' ` ~

L2~Lt~t;.~lyt~7 illustrates that little wandering occurred in the element of this invention.
The invention hats been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

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Claims (25)

I CLAIM:

1. An element comprising a support having thereon a substantially crystal- and agglomer-ation-free hydrophilic layer, said layer comprising a hydrophilic composition comprising a hydrophilic binder and water-insoluble polymer particles dispersed therein, said polymer particles having recurring units derived from one or more ethylenically unsaturated polymerizable monomers and comprising from about 0.5 to about 10 percent, based on total monomer weight, of a hydrophobe uniformly distributed throughout, said polymer particles being characterised by the structure:
wherein -A- represents randomly recurring units derived from one or more vinyl aromatics, olefin and diolefins, vinyl esters or esters of .alpha.,.beta.-unsaturated polymerizable carboxylic acids;
-B- represents randomly recurring units derived from one or more ethylenically unsaturated polymerizable monomers having one or more anionic moieties; -C-represents randomly recurring units derived from one or more ethylenically unsaturated polymerizable monomers having a crosslinkable moiety; w represents a weight percent from about 80 to 100; x represents a weight percent of from 0 to about 20; and y:
represents a weight percent of from about 0 to about 5, all based on total monomer weight.

2. The element of claim 1 wherein said hydrophobe is present in said polymer particles in an amount of from about 1 to about 8 percent, based on total monomer weight.

3. The element of claim 1 wherein said hydrophobe is a photographic dye; photographic dye-forming coupler; photographic developing agent;
an optical brightener; or an ultraviolet light absorbing compound.

4. The element of claim 3 wherein said hydrophobe is an optical brightener.

5. The element of claim 1 wherein said polymer particles have recurring units derived from two or more ethylenically unsaturated polymerizable monomers, at least one of said monomers having a crosslinkable moiety.

6. The element of claim 1 wherein said polymer particles are dispersed in said binder in an amount of at least about 15 percent based on total dry composition weight.

7. A radiation-sensitive element comprising a support having thereon one or more hydrophilic layers at least one of which is a radiation-sensitive layer, and at least one of which is a substantially crystal- and agglomeration-free hydrophilic layer comprising a hydrophilic composition comprising a hydrophilic binder and water-insoluble polymer particles dispersed therein said polymer particles having recurring units derived from one or more ethylenically unsaturated polymerizable monomers and comprising from about 0.5 to about 10 percent, based on total monomer weight, of a hydrophobe uniformly distributed throughout, said polymer particles being characterized by the structure:

wherein -A- represents randomly recurring units derived from one or more vinyl aromatics, olefins and diolefins, vinyl esters or esters of .alpha.,.beta.-unsaturated polymerizable carboxylic acids;
-B- represents randomly recurring units derived from one or more ethylenically unsaturated polymerizable monomers having one or more anionic moieties; -C-represents randomly recurring units derived from one or more ethylenically unsaturated polymerizable monomers having a crosslinkable moiety; w represents a weight percent from about 80 to 100; x represents a weight percent of from 0 to about 20; and y represents a weight percent of from about 0 to about 5, all based on total monomer weight.

8. The element of claim 7 wherein said radiation-sensitive layer is a photographic silver halide emulsion layer.

9. The element of claim 7 which is a multilayer color photographic element.

10. The element of claim 7 wherein said hydrophobe is an oxizole, oxadiazole, imidazole, pyrazoline, coumarin, stilbene, triazine, imidazolone, naphthotriazole, acetylene or vinylene optical brightener.

11. The element of claim 10 wherein said optical brightener is a stilbene or naphthotriazole.

12. The element of claim ? wherein said substantially crystal- and agglomeration-free hydrophilic layer is interposed between said support and said radiation-sensitive layer(s).

13. The element of claim 7 wherein -A-represents randomly recurring units derived from one or more vinyl aromatics or esters of .alpha.,.beta.-unsaturated polymerizable carboxylic acids;
-B- represents randomly recurring units derived from one or more monomers having one or more sulfo or carboxy moieties; and -C- represents randomly recurring units derived from one or more diacrylates or dimethacrylates.

14. The element of claim 7 wherein w is from about 90 to about 99 weight percent; x is from about 0.5 to about 5 weight percent; and y is from about 0.5 to about 5 weight percent.

15. A color photographic paper product comprising a paper support having thereon a plurality of photographic color-forming silver halide emulsion layers, and between said support and said emulsion layers, a substantially crystal- and agglomeration-free hydrophilic layer comprising a hydrophilic composition comprising a hydrophilic binder and water-insoluble, crosslinked polymer particles dispersed therein, said polymer particles having recurring units characterized by the structure:
wherein -A- represents randomly recurring units derived from one or more vinyl aromatics or esters of .alpha.,.beta.-unsaturated polymerizable carboxylic acids;
-B- represents randomly recurring units derived from one or more monomers having one or more sulfo or carboxy moieties; -C- represents randomly recurring units derived from one or more diacrylates or dimethacrylates; with from about 90 to about 100 weight percent; x is from 0 to about 5 weight percent; and y is from about 0 to 5 weight percent based on total monomer weight, said polymer particles comprising from about 2 to about 5 percent, based on total monomer weight, of an optical brightener uniformly distributed throughout.

16. The paper product of claim 15 wherein said optical brightener is a stilbene or naphthotriazole.

17. The paper product of claim 16 wherein said optical brightener is 2,5-bis(6-butyl-2-benzoxa-zolyl)thiophene.

18. The paper product of claim 15 wherein said polymer particles are composed of poly(methyl methacrylate-co-styrene-co-ethylene dimethacrylate).

19. The paper product of claim 15 wherein said hydrophilic binder is gelatin.

20. A method of making the element of claim 1, said method comprising the steps of:
(a) dissolving from about 0.5 to about 10 percent, based on total monomer weight, of a hydrophobe in solution with one or more ethylenically unsaturated polymerizable monomers;
(b) dispersing said solution in water as fine droplets under conditions sufficient to promote polymerization of said monomers in said droplets and to form polymeric particles having said hydrophobe uniformly distributed throughout said particles;
(c) dispersing said polymeric particles in a hydrophilic binder to form a hydrophilic composition, and (d) applying said hydrophilic composition to a support to form a substantially crystal- and agglomeration-free hydrophilic layer.

21. The method of claim 20 wherein a radiation-sensitive composition is applied over said hydrophilic layer.

22. The method of claim 20 wherein said hydrophobe is an optical brightener.

23. The method of claim 20 wherein step (a) is carried out at a temperature greater than room temperature but less than the temperature at which spontaneous polymerization of said monomers occurs.

24. The method of claim 20 wherein said hydrophilic binder is gelatin.

25. The method of claim 20 wherein an oleophillc surface active agent and an oleophilic polymerization initiator are dissolved in said monomers prior to polymerization.