CA2135483A1 - Imageable articles having dye selective interlayers - Google Patents

Abstract

Copolymers of acrylonitrile and vinylidene chloride are used as selective diffusion interlayers in dye-diffusive photothermographic imaging constructions. The interlayers have sufficient permeability to be useful for constructions in which cationic dyes must be diffused from an emulsion layer into an image-receiving layers, but have insufficient permeability to the unoxidized leuco dye precursor. Use of these interlayers in multicolor dye-diffusive imaging constructions increases image stability and color separation in the final image.

Description

WO 93t25~36 .)J 1 ~ ~ 4 ~ 3 Pc~ S93/03183 ,, , ~GEABLlE ARTICLE~ 7ING D~E
SELlECrlVE INT~R.S

`I 5 ~LD OFmE INVENllON
.j This in~ention relates to photothcrmographic matcrials and in particular, it relates to dry silYer systems capa.ble of producing colored images.
''i BACKGROVND OlF T~E AlRT
¦ 10 Imaging systems capable of producing multiple colors ol~en rely upon - barrier interlayers to separate adjacent im~ging chemistries. In some cases, such as those in which a dye image is rormed and dirfuscd to a recei~ing layer, the 3 interlayer must not only separate imaging chemistries, but be permeable to dye~
as well. Dry silver based imagea~le ar~ic3es sre one Iype o~ ;maging system tha~.¦ lS employ interlayers in this mann~r.
Dry sil~er compositions or emulsions a~e photolhcsmographic compositions . .-and contain a light-insensiti~e, reducible silver source; a light-se~itive silver !
source; and a reducing agent ~or the light-insensitive, reducible silYer source.The light-serls;tive material is generally photographic silver halide which must be in catalytic proximity to the light-insensitive, reducible silver source. Catalytic proximity requires an intimate physical association oî these two materials so t~al when silYer specks or nuclei are generated by the irradiation or iight exposure of the photograpllic sil~er halide, those nuclei are able to ~atalyze the reduction of lhe light-insgnsitiYe, reducible silver source by the reducing agenl. It has bee~
25 ,;, ~ long understood that sil~er halide is a calalyst for the reduction of sil~er ions and ; ~; that the silYer-generating~; light-sensitiYe sil~er h~lide catalyst pro~enitor may be placed into catalylic proximity~ wiLh the silver sour~e :in a number of difrerent rashions, such as by partisl metathgsis of the light-insensilive, reducible silver :: s~urce~ wi~h a halogen-corltainillg source; coprecipitation of sil~er halide andl 30 ~ light-insensitive, reducible sil~er source materi~l; and other methods that t~
9~ intirnale3y ~ssociate the silYer halide and the silver s~urce, wo93/2sg36 ~ ~3~ 3 PCl/US93/03183 ~ ~
In both photo~raphic and photothermograpllic cmulsions, exposure of the .!~ photographic sil~er halide to light produees small clusters of silYer atorns. The l3 image-wise d~tribution of these clusters o~ sil~er atoms is known in the art as ~
; .~ latent image as this latent image generally is not Yisible by ordinary mealls and S the light-sensiti~e artiele must be furlher processcd isl order to produce a Yisual image. The visual image is produced by the catalytic reduction of silver ions ~h;ch are in catalytic proximity to the sil~er hzllidc grains bearing the latentimage.
In color dry sil~er imaging systems, a lcuco dye or other color forming ~10 system is typically incorpornted as a reducing a~cnt for the light-insensitive, reducible silver source, generally in eoml)ination with a spectral scnsitizer Sol the sil~er halide. The leuco dye is oxidized upon de~elopment, thercby giving a i:~
colored image. Irl full color constructions, spcctrally sensitized emulsisn layers are typically coated onto a substrate ~nd scparaled by one or more barrier interlayers.
.. Re~idual silYer stain is a m~jor problcm wilh certairl dry silver colQr constructions known in the art. This has be~n oYercome by ~using the developed dye image to dirruse rrom the dry silvcr l~ycr to an ;mslg~rcceiving layer that is then stripped from the emulsion l~yer(s). In th~s c~se, a barrier interlayer must serve the dual roles o~ separating the chcmistries o~ neighboring emulsîon layers and allowing diSfus;on of the dye im~ge undcr the~n~l processingsonditions. In addition to the dye image~ other components oî the emulsion layer~ also diffuse to the image-receiving layer undcr therm~l processing conditions. In this regard, unoxidized lcuco dyes from the emulsion layers tend to dif~use to the imslge-receiving l~yer where they oxidizc oYer time, l~ading to low print stability and poor color separation. I~crefsre, thcre is a need fur interlayers which allow dye images, but not neutr~l Icuco dyes, to di~ruse to the i.¦ imag~receiving lay~r. Depend;ng on tlle p~rticul~r ingredients of a givcn dry silYer layer, the deYelopment may be best carricd out, for ex~mple, under acidic or basic conditions.
~: VVhen multiple dry silver layers with incomp~tible dcYelopillg chemistries are employed, it is very di~ cult to keep deYelopment conditions w;thin one ~ry il .

~, WO 93/25936 ~13 .~ ~ 8 3 pcr/us93/o3183 ' ~!,`i 3 sil~er layer from af~ecting the development oï ne~rby or adjacent dry silver layers. As a result~ it is often adYantageous to coat dry sil~er layers w;~h dirfe~ent deYeloping cnnditions on opposite sides of a transparent substrate. .
, U.S. Pat. No. 4,594,307 discloses a heat de~elopable photographic material ~ S that produces a pure and stable dye image by the oxidation-reduction reaetion !~. betY~een a reducib;e, light-insensitiYe organic silver salt and a leuco dye reducing agent wherein the dye formed is transferre~ to an image-rcc~iYing lay~r by continuing the heating for dcYelopment in ordcr to scparate ~he dye ~ormed from the silver images and other rcsidu:ll chemicalsc ; .
The generation of color dry silYer imagcs h.~ becn accomplisiled using .~ microencapsulated constructions and tri-pack (ycllow/magcnta/cysn) mullilayer ,., construc~ions, such as those discloscd ill U.S. Pal. Nos. 4,883,747 and 4,923,792 The cited patents above employcd Gantrez S-97 polystyrene, Vinol 523 partially hydrolyze~ poly:vinyl alcohol, and Butvar I~76 polyYinyl butyral ~s barrier interlayers. These c~nstruclions gencrally ha~Ye substantial sil~er and :: sensitizer stain present that af~ects the imDge color separatioll. The stain :problem can be o~ercomq by causing llle d~veloped:~dye imzlge to dirruse from the : imng~r~rming laycrs into a reccptor laycr tllslt is subseqllclllly stripped ~rom the ~ : rest ot Ihe construction. The success of this type of appro~ch dep~n~ in large part on the ability of b~rrier interl~ycrs posilioncd between the im~ge-îorming laye~s of ~he tri-pack cor~truction to se~ecti~ely permit m;gration o~ the imageti ` : ~ ~ :
~ forming dyes while col~trolling the migration of othcr im~ge-forn~ing l~yer : componealts, particuiarly u:noxidized neutral leuco dyes.
U.S. Pat. Nos. 4,021,240; 4,460,681; and 53077?188 disc~ose the use Or multipl.el image-forming ~l~yers scparated by b:lrricr interlny~

U~Y O}~ ~ ~INVEI~ON
; ~ By the present invention,:it bas been~discoYered lhat copolymers Or acrylonitrile and~ ~inylidene chloride are userul as interlayers in dye-di~fusive 30 : : ~ imageabie articles~employlng cationic:~nd neutral ~ycs and that these ~opolymers baYe the ability to selectively all~w~ cationic dye dirfusion~while hindering neutral leuco dye ~diîfilsion. ~

~ 1 ~ 5 ~
~1 .
:~. Wo 93/25936 Pcr/us93/03183 ;., 4 ln one embodiment, the present inYention pro~ides imageable articles ,~ comprising: (a) an imag~forming l?llyer comprising a leuco dye ~hich ~orms a cationic dye upon oxidation; (b) an image-rccei~ing layer; and (c) a polymgric .~ interlayer interposed bctween the image-forming and imag~receiving layers, the ~5 polymeric interlayér comprising an acrylonitril~vinylidene chloride copolymer.
In another embodiment, the præsent invention providcs imageable articles comprising a substrate coated on one side thereof wilh an im~g~receiving laycr, the imag~receiving layer ha~;ng coated thereon at least one imag~forrning layer separated from the image recciving layer by a polymeric intcrlaycr, tlle io polymeric interlayer comprising a copolymcr of acrylonitrile and Yinylidene ehioride and the image-forming layer comprising a neutrally charged leuco dye which forms a c~tionic dye upon oxidation.
In still another embodiment, the present in~ention proYides a method ~f purifying a mixture comprising a neutral lcuco dye and a cationic dye, the ~15 method comprising he~t;ng the mixture comprising nelltral Icuco dye and cationic dye while in intims}te contslct wilh a layer comprising a copolymer of acrylonitrile and ~inylidene chloride, ;thereby causing the cationic dye to diffuse throu~h the ; layer away from the neutral Icuco dyé.
By the phase "intimat~ cont~ct", it is meant ~hat the mixture containing tbe neutral leuco and cationic dyes~ must be in direct contact with the layer, typically an interlayer,: comprisin~ the ~ acrylonitril~inylîdene chloride copol~er. For example, the dye-containing mixture m~y be o~ercoated wi~h the polymeric layer. In another passible ~rrangement, the dy~containing mixturie :~ ~ is applied to one substrate and the polymeric l~yer is applicd to another substrate : 25 and then the two st~uctures ~re lamin~ted ~ogether such that the dy~containing mixture and the polymcric layer ~re in direct con~a~t wi~h one anothc'r.

DErAlLEl)~DESCRlPllON OF TI~ INYEN~ON
e present: invention pro~lides image~ble articlcs having improved imagie 3 0; ~ stability which comprise: ~(n)~ao Lmage-torming layer comprising a neutral leuco dye which generates ~ cationic dye upon oxidation; (b) ~n image-receiYing l~y~r;and ~c~ a polymeric interl;~yer interpos~ etween ~he imag~forming and im~ge~

:;

~WO 93/2~936 ~ 1 3 ~ ~ ~ 3 Pcr/US93/û31i83 s 5 receiving layers~ the polymeric interlayer comprising a copolymer of acrylonitrile .. 1 .
and ~inylidene chloride.
While single color applicatinns are envisioned, the greatest benef~t of the present invention may be obtained in multicolor or fuU color applications. TheseS latter applications typically comprise a substrate co~tcd with a dye receiving layer, the dye recei~ ing layer ha~ing coated thereon a plurality of imaging layers separated by polymcric interlayers. At lei~st one of said interlayers comprises a copolymer of acrylonitrile and vinylidene chloride.
~Iternatively, the image-recei~ing }ayer m~y be supplied as an external i Ocomponent carried on a second substrate that is brough~ into conhct ( i.e., laminated) with a rlrst substralc bcaring an im~g~torrning layer during processing such that the dye image is transferrcd from the rlrst substrate to thc image-receiving layer. In that c~se, tlle lamin~tcd construclion constitutes an imaged construction according to the prescnt invention.
Ima~e-Fonn~ cr~
The image f:orming layer m~y be of any type known in the imaging art in which a colored dye imi~ge is formed by oxid~tion of a neutral leuco dye to forma cationic dye.
WIn a preîerred embodiment, the image-forming layer(s) comprise(s) a dry silver composition which comprises ~n intun~te mixture of a light-sensitive silver halide; a light-insensitive, reducible~ silYer source such~as a silYer sa!t of an organic acid~(e.g., silver behen~te, silver benzimidazolate, or silYer saccharine);
and an auxiliary reducing agent. ~ As used herein ~the phrase "auxili~ry reducing ~ ~5 ~agent" refers to an additional reducing agent (e.g., phenol, hind~red phenol, 'h~ ~~ methjl gall~te, catechbl, pyrogallol, hydroquinone, etc~ for the ligllt-insènsitive, reduciblé source of silver~ in addition to; the~ lcuco dye which also functions as a ` ~reducing agent ~for silver ion. ~Norm~lly, dry si!ver~compositions furlher comprise ; a~spectral;sensitizer.~Sueh~a muxture is~usu~lly~prcparcd in a solYent as ~
3!~dispersion that~ is spread~as a layer on a suitable substrate. When dry, the layer ;~exposed~to~a ;light~ iinage and thereafter,~ a reproduction Or the image is ~developed ~y heating the~ coated substrate.

Pcr/US93/03183 Imaging layer(s) of the present invention may comprise a single coated layer or a pluraility of sequentially coaited sublayers in which the Yarious ' com,pQnents are dispersed. In cases where the imaging layers comprise a plurality of sub!ayers, the sublayer containing the silYer halide is referred to as ~¦ S an emlllsion layer.
,.~
Stl)~er Hlalide .ly SilYer halides known in tbe art for use in photothermography are useîul in the present in~ention and includè, but are not limitcd to, xil~er chloride, silYer i~ la chlorobromide, silver chloroiodide, silver b~romide, sil~er iodobromide, silYer ~hloroiodobromide, and silYer iodide.
The silYer halide used in the present inYention msy be used as is.
HoweYer, it may be chemically sensitized with a chemical sensitizing agent such as compounds Or sulrur, s~lenium, or tcllurium, eac.; compounds Or gold~
.:, , 15 platinum, p~ dium, rbodiurrl or iridium, ~tc~ reducing agent such as tin halide, etc.; or a combioa~ion of the f~regoing Det~iils thereoî are describcd in , James, T.H. ~e l~eo~ of ~ie Photog~aphic ~rocess, Fourth Ed.; MacMiUan:
New York, 1977; pp. 149-169.
, Th~ light sensiti~e silver halidle used in the pr~scnt ir~entîon is preferably employed in the range of about .01-15 w~ight percent, and more preferably in the range of about 0.1 to 10 weigllt p~rc~nt, bslsed upo~ the tot~l weight of ~ch imaging layer in which :the silrer h~lide is present.
~g~ :
! :
Sensi~i~er ~ ~5 The sensitizer employed in the dry silYer composition m~y be any dye ,~ kno~n in the photographie art to spe~trally sensitize` silY~r halide. N~n-limiting examples oî sensitizing~ dyes th~t can be employed include cyanine dyes, merocyanine dyes, complex cyanine ~dyes, complex merocyaning dyesg holopolar cyanille dyes, hemicyanille dyes, styryl dyes9 ~nd hemioxonol dyes. Of these 30 ~ dyes~ cyanine dyes, merocyanine: dyes, and complex merocyanine dyes are prefèrred.
' }l~
`.;li ~

~13 :~ 4 8 3 WO 93/25936 pcr/us93/o3l 83 ~ ~ I
An appropriate amount of sensitizing dye added is generally in the range of from about 10-~ to 10 1 mole, and pre~rably from 10-~ to 10-3 mole per . mole of sO~er halide.
Light-Insensitive, Reducible Organic Silver Sal~
S T}ae light-insensitire, reducible organic silYer salt that can be used in the ~1 present in~ention is a silver salt that is comparati~ely stable to ligh~ and which forms a silYer ~nage by reac~ing with the aboYe disclosed leuco compound or an auxiliary reducing agent that is co~xisling with tlle leuco compound, if dcsir~d, i~3 when it is heated to a temperature Or ab~e about B0~ C, and preferably, above .:10 about 100 C in the presence of exposed sil~er halideO Suitable organic silver L
salts include silvel salts of organic compounds ha~ing a carboxyl group.
Preferred examples thereor include sil~er salls of aliphatic and aromatic ~;~ carbQxylic acids. Preferred examples of silvcr salls Or aliphatic carboxyl;c acids .~ include sil~er behenate, silver steara~e, silver oleate, silYer laurate, sil~er ~15 caproate, silYer myrist~le, sil~er p;~lmitatc, silvcr malcslle, sil~er îumarate, silver tartarate, silver linoleate, silver butyrate, silver camphoratc, and mLxtures tbereof, etc. Sil~ er salts that arc sllbstituted with a halogcll atom or a hydroxyl group can also be ef~ecti~cly used. Prcl~rred cxamplcs of sil~ler s~l~s of aromatic ~! ; c~lrboxylic acids and other carboxyl grou~containillg compourlds incllld~ sil~er ,~ 20 benzoate, a silver-substitoted benzoate such as silYer 3,5-dihydroxybenzoate, sil~er o-methylbenzoate, silver m-methylbenzoate, silv~rp-m~hylbenzoate, silver . 2,4-dichloroben~oate, sil~!er ace~amidobenxoate, silYer p-ph~nyl benzoate, etc.9 I!`
~; sil~er gallate, silver tannatc, silver phthalate~ silYer terephthalate, silYer salicylate, silver phcnyl~cet~tc, silver pyrom~llitatc, silv~r salts of 3-carbox~ethyl-~methyl~-thiazoline^2-thiones or the like as d~sclosed in U.S.
Pat. No. 3,7859830 nnd silver s~lts Or alipha~ic carboxylic acids containing !$1 ~:~ thioether group as describ~d in U.S. Pnt. ~No. 39330,663. Sil~er salts of compoullds cosltaining mercapto or thions groups and deriYaliYe~ thereo~ ca3l als,o .~ be used. Pre~erred examples of th~e compounds include silvcr 3-mercapt~4-~'30; pherlyl-1,2,4-triazolate, silYer 2-mercaptolbenzimidazolate$ sil~er ~-mercapt~S-aminolhiadiazol~tel silver 2-(S-ethylglycolnmido)ben~otlli~zol~te; silYer salts of thioglycolic acids such as silr~r salts oî S~alkyl thioglycolic acids (wherein the ;~
..;
t 1 ~ ~

1 wo 93/25~36 ~ 13 ~i 4 ~ ~ P~r/US93/031~3 ~

: ,~ alkyl group has from 12 to 2~ c~rbon atoms); sil~er salts of dithiocarboxylic acids .1 such as sil~er dithioacetate, sil~er thioamidoate, silver lL-methyl-2-phenyl-~thiopyridin~5-c~rboxylate, sil~er tri~zinethiolate, silver 2-sulrldobenzoxazole;
and silver salts as disclosed in U.S. ~at. No. 49123,274. Furthermore, silver salts S o~ a compound containing an arnino group can be used. PrcfeIrcd examples of these compounds include sil~er salts of benzotriazoles, such as silYer benzotriaxolate, silver s~lts of nllcyl-substitute~ benzotriazoles such as silver methylbenzotriazolate, ctc.; sil~er salts Or h~logen-substitutcd bcnzotriazole~ such as silYer 5-chlorobenzotriazolate, ctc.; sil~!cr s~lts of carboinllidoberlzotriazoles, ~10 etc.; sil~er salts of 1 ,2~4-triazolcs and 1-H-tctrazoles as dcscri~ed in IJ.S. rat. No.
;~ 4,220,709; sil~er salts of irnidazoles; and the like.
The silvcr halide and the organic silYer salt tllat l~orm a starting point o~
development should be in reactive association (i.e., in the same layer, in adjacent !, ',~
layers, or In layers separated from ~ach other by an intermediate layel ha~ing ~15 a thickn~ ol less ~h~ nicron). 3t is pref~rrcd ~h:lt ~lle silYICr h~lidc and the ~: orgallic silver salt ~re present in the s~me laycr.
The silver halide ànd t11e organic silver salt that are separately fo3med in a lbindcr can be mLxed before use to prepare a coatillg solution, but it is aJsoefrecti~e to blend both of ~h~m in a b~ll mill for a long tune. Furlher, it is ef~eetiYe to use a process which comprises adding a halogen-colltain;alg compound i~ the organic silver salt prepared to par~ially ~onvert the silver Qt' the organ;c silver salt to sil~er halide.
~:`
u~l Methods of preparing these silver halide and organic silYer salts and manners of blending thcm are dcscribed in Research Disclosure No. 17029 and U.S. Pat. No. 3,700,458.
.j l'he light~insensitive, reducil)le source ol~ silver is preîerably pres~nt in an amount of îrom û.1 to 50 weight peri ent, and more pr~6erably from about 1-5 .; j ~j weight percent, based upnn the total wcight oî cach imaging layer(s) in whicll the silYer source is present.
A suitable coating amount o~ the light-sensitiYe silYer halide and the organic silY~r salt employed in the prescnt inYention is in a total from 50 mg lo 3 ! WO 93/25936 ¦ 3 5 4 8 3 Pcr/us93/o3 1 83 10 glm2 calculated as an amount of silvcr, as discloscd~ for example, in U.S. Pat.
. No. 4,478,927.
' ' .
Leuco l)ye ~ S Suitable leuco dyes for use in the present in~ention are compounds that '.5~ oxidize to form a dye image. In practiee of the prescnt inYention, at lenst one s im~ging layer must comprise a lcllco form oî a c~tionic dye and al l~ast one other .",~ .
im~ging layer must comprisc a lcuco form of a neutr~al dye.
Prererred neutral leuco dyes are phcnolic lcuco dyes sucll as 2-(3,S-di-t-butyl ~hydroxyphenyl~4,5-3-diphenylimidazoleor bis(3,~-di-t 3 -butyl~4hydroxypbellyl)phenylmethanc. Such phenolic le~co dyes useful in ;! pract;ce o~ the present in~ention are discloscd in ltJ.S. Pat. Nos. 4,374,921;
;~ 4~460,681; 4,594,307; and 4,780~010.
The leuco dyes uscdl in tll~ prescnt invcn~ion may be any eolorless or liglllly colQrcd compound lllnl rorms a visiblc ~yc upon oxid~tion. The compound must be oxidiz~ble to a colored state. Compoun~ that are both pH
sensitiYe and oxidizable to ~ colorcd state arc uscrul, but not prefcrred, while~I c~nnpounds only se~ iYe to ehanges in pl~ are not includcd wilhin thc tcrm ;~ I'leuco dyes" since they are not oxidi~able to a colorcd form. The dyes formed rrom the leuco dye in the ~arious color-i~orming l~yers should, of course9 be different. A di~rerence of at least 60 nm in rellective maximum absorbiance is preferred. More prercrably, the absorbsnce maximum of dyes form~d will differ by at least $~100 nm. When three dyes are to be formed, t~vo sllould preferably ~, di~er by at least tllese minimums and the thîrd should preferably dif~er from a~
least one of the olh~r dyes by at lcast 125 and more pref~ral)ly, by at lcast 150 nm. Any leuco dye capable oî bcing oxidized by silYcr ion to form a Yisible dye is usc~ul in the present inven~ion as preYiuusly notcd. Leuco dyes sucll as thosc 11~ disclosed In IJ.S. Pat~ Nos. 3,442,224; 49021,25Q; 4,022,~17 and 4,368,247 are ;' also ~Iseful in the present in~ention.
i~
J 3Q Other leuco dyes may~be used i~ ~maging layers as well, for example, benzylldene leuco compounds disclosed in U.S. Pat; No. 4,923,792. Ihe rcdueed ~; form of the dyes must absorb less strongly in t}le Yisible region o~ thc i:q .
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~13~8~ .
j.~i3 WO 93/25936 PCr/lJS93/03183 Il ,! lo ,d electromagnetic spectrum and be oxidized by silver ions back to the original colored ~orm of the dye. Ben~lidene dyes have extremely sharp spectral char- ¦
acteristics giYing high color purity ot low gray leYel. The dyes ha~re large extinction coe~ ciellts, typic~lly on the order of 104 to 1Q5 and possess good S compatibility and heat stability~ The dyes are readily synthesized and the ,. reàuced leuco ~orms of the compounds are Yery stable.
jr~, The dyes generated by ~he leuco compounds employed in the ~i photothermographic elements of the present in~ention ~re known and are .j;; disclosed, for example, ;n 171e Colour Index; The Society o~ Dyes and Colourists:
Yorkshire, Engl~nd, 1971; Vol. 4, p. 4437; and Vcnk;ltaramarl, K. 77~e ~emistry of Syn~hehc Dyes; Ac~demic rress: New York, 19i2; Vol. 2, p. 1206; U.S~ Pat.
, j~ .
No. 4,478,927, and Hamer~ F.M. 11le Cyanine Dyes a~ld P~elated Compol~nds;
lnterscience Publishers: New York, 1964; p. 492.
The leuco compounds may rc;ldily be synlh~iud by tcchniques knQwn in . 15 tbe art. There nr~ mzlny known mclhods of synthcsis from pr~cursors sincc thc :
reaction is a simple tw~step hydrogell reduction. Suitable methods are disclosed, for example, in: F.X. Smîth et al. T~ tedron Lett. 19839 24(45), 49~1-4954; X.
Huang. L. Xe, Synth. Commun. 1986, 16~13) 1701-1707; II. Zimmcr et a!. J- Org.
; Chem. 1~60, 25, 1234-5; M. Sekiya et al. C1tem~ P~arm~ Butl. 1972, 20(2), 343;
I
Ibid 1974, 2?(2), 448; and T. Sohd~ et al. Cllem. Pharm. JB~I~. 1~3, 31(2) ~60-5.
Further, as ~ther image forming matcrials, mater;als wh~re the mobility of the compound haYing a dye p~rt changes as a result of an oxid~tion-reduction reaction with silver halide, or an organic silYer salt at high ~emperature, can be used, as disclos~d in Jap~ncs~ Patcnt Applic~tion No. 165û54 (19$4). ~any o~
25 ! the abov~discloscd matcri~ls are matcria!s wberçin an image~wise distribution of mobile dyes correspondillg to ~xposure ~s for ncd in ~he light-sensitive m~te~ ial ; ~ b~ heat developmeot. Processes of obtaining nsible images by transferring the : dyes of the image to a dye f;xing: materi~l ~dif~usion transfer) haYe been ` described i~l the abov~described cited patents and JapaDese Patent Application !

Nos. 168,439 ~1984) and 182?447 (1984).
The total amount Or leuco dye utilized in ~he present inYention should 1` .
preferably be in thc range o~ 1-5Q weight pcrcent, and more preferably in the : ~ :

~; . WO 93t2~936 2 1 ~ 5 4 ~ ~ PCrtUSs3/03183 ... ,:...................................... 11 range o~ 5-2û weight percent, bascd UpOIl the total weight of each individual layer in ~Yhich the leuco dye is(are) employed.
When the heat developable light-sens;tiYe matcrial used ;n this in~ention is h~t deYeloped in a substantially watcr-free condition afler, or simultaneously S with, image-wise exposure, a ~nobile dye image is obtained simultaneously with ~, the formation of a silver image either in exposed areas or in unexposed areas with exposed light-sensiti~e silver halide.
The light-sensiti~e sil~er halide and the organic silver salt oxidizing agent us~d in the present invention ~rc generally added to at least one bindcr as ,Uh 10 disclosed herein below. Fu~lhcr, the dye releasing redox compound is disperscd in the binder.
- The binder(s) that can be used in the present in~ention cara be employed indi~idually or in combination with one another. The binder may be hydrophilic or hydrophobic. A typical hydrophillc binder is a transparent or transh~cent ~i~ 15 hydrophilic colloid, examplcs o~ which include a n;ltural sul~stance, for example, ,,l a protein ssJch as gelatin, ~ gclatin dcriYati~c, a cellulose ~criYati~e, etc., a i 3 '.~ polysaccharide such as starch, gum arabic, pullulan, dextrin, etc., and a ,!' synthetic polymer, ror example, a water-soluble poly~inyl compound such as :~ polyvinyl alcohol, poly~inyl pyrrolidone, acrylamide pO~ fCl~ etc. An~ther . 20 example of a hydrophilic bindcr is a dtispe~scd vinyl cofmpound in If~lex fo~n which is used for the 1?urpose Of~ increfasing di~ncfnsional stability of a '~ photographic material.
Preferably, the polymeric bindcr is present in an amount in the range ;fl from l-g9 weight percent, and more preferf~bly, frnm 2~80 weight percent in ~li 2S ~ch layer in ~hich the polymferic binder iS efS11fpl0yed.
e coatinfg antiount of the bindcr used in the present inYention is 20 fg or less per m2; preferably, 10 g or less per m2; and more preferably, 7 g or less per '~1 m2.
f~ he preferred photothea~lographic silYcr contaming polymer is polyYi~yl butyral, but ethyl cellulose, methacrylate copolymersj maleic anhydride ester f.~i ij`~;f; ' copolymers, polystyrene, and butadiene-styrene copolymers can be used (w~ere applicable~ according to the particular solvcllts used.

.~j .

, WO 93/~5936 pcr/usg3/o3183 '`. ';
. 12 In the photographic light-sensitiYe material and the dye f;xing material ,~l utilized in the present in-en~ion, the photographic emulsion layer and other billder layers may co~taila inorganic or organic hardeners. It is possible to use ~j chromium salts such as chromium alum, chromium ase~ate, c~c.; aldehydes such as formaldehyde, glyoxal, glutaraldehyde, etc.; N-methylol compollnds such as dimethylolurea, methylol dimethylhydantoin, etc.; dioxane deriYatives such as ,3-dihydroxydioxane, etc.; actiYe ~inyl compounds such as 1,3,$-triacryloylhexahydro-s-triazine, I,3-Yinylsulronyl-2-propanol,ctc.; active halogen compounds such as 2,4-dichloro-6-hydroxy-s-triazine~ etc~; ~nd mucohalogenic :!
acids such as mlscochloric acid, mucophenoxychloric acid, etc ..`
~ma~Receiqin~ ~ycr Dyes generated during thermal developmcnt Or light-exposed regions o~ the emulsion layers migrate under devclopmcnt conditiosls into a dye receiYing layerwhcrein they are retain~d. The dyc rccciYing l~ycr may bc composcd oî a polymeric material ha~ing afrlni~y for the dyes employed. Nece~sarily, it will ary depending on the ionic or neutra1 characteristics o~ the dyes.
Examp~es of organic polymeric materials uscd in tlhe dye rcceiving material o~ this inYention include poiystyrene having a molecular ~eight of ~,000 ` 20 to 85,000, polystyrene dcrivati~es h~Ying substituents with not mvre than 4 carbon ato~s, poly~inyl cyclohexene, polydivinylbenzene, polyYinylpyrrolidirle, pnly~inylcarbazole, polyallyll)cnzene, polyvinyl ~lcohol, polyac~tals such as i polyYinyl formal and poly~inyl butyral, polyvinyl chloride9 chlorinated polyethylene, polytrirluoroethylelle, polyacrylonitrile, poly(N,N~
dimethylallyla~ de), polyacrylates ha~ing a p-cyanophenyl group, a pentachlorophenyl group or a 2,~dichloropherlyl ~roup, poly(acI yl ~: chloroacrylate),poly(me~hylmeth~cryl~te),poly(~thylmethacryl~t~gpoly(propyl methac~late~, polytisopropyl methacrylate)~ poly~isobutyl methacryl~te), poly(telt-butyl methacrylatc3, ~poly(cyclohexyl me~h~crylate), polycthylcne glycol ~, dimethacrylate,, poiy(cyanoefhyl meth~crylate), polyesters such ~s polyethylenc terephthalate, polysulfone ~ ~isphenol A polycarbonate, polycarbonates, polyanhydrides, polyarnides, and cellulose acetatc. The synthetic polymers ~, ` Wo 93t2593S .4J 13 ~ ~ ~3 ,3 pcr/us93/o3183 :~ 13 ,,. described in "Polymer Handbook", 2nd edition (edited by J~ Brand~p and E.
H. Irnmergut, published by John Wiley and Sons, Inc.~ are also u seful. These polymerie substances may be used singly or a plurality oî them may be used in the fo~m of a copolymer~
"`'''i S
Int~rla~ers Interlayers employed in the present inYentioll are selected from polymeric materials that are selectively pe~neable to the dyes used to form the de~eloped image. They are prererably coated from solrents in wlhich the preYiously coated emulsion layer is not solllble. At least one oF the interlayers employed in thc i~ present invention must be a copolymer oî acrylonitrile and vinylidene chloride, ' The eopolymer may be either a block or random copolymer. The mole ratio Or : acrylonitrile to ~inylidene chloride should be from about Q.2 to 0.95:1;
.` preferably, ~rom about 0.4 to 0.9:1; and most prererabiy, ~rom about 03 to .. ~ 15 ~1.8:1.
InterJayers o~ the present il2Yelltion pr~Yide a measls for improving image ~;~ stability and optionally color separation of cationic dyes~ This is accomplished by interposing interlayer~ cornprising copolymcrs of acrylonitr;le and vinylidene chloride betwecn image-îorming layer(s) contailiing leuco dyes (l:hat oxidLze to~orm cationic dyes) and tlle image-receiYing layer. In tl-is arrangement, the cationic dyes preferentially dirïuse to the im~ge-recei~!ing layer relative to the .~ ne~ltral, unuxidized leuco dyes. The lessened amount of neut~al leuco dye in the imag~receiving layer improYes long terrn print stability. In a preferred embodimellt of t!he presen~ invention, the r,rst coated interlayer comprises a copo~ymer oî acrylonitrile and vinylidene chloride copolymcr and the ~lrst coated '' 1 ~nagling layer colltains a leuco dye ~h~t forms a c~tionic dye UpOIl oxid;ltion.
~i These polymer C~ll be uscd ~s interl~ycrs in a construction o~ an ~t least two color, and preferably o~ &n at le~st three color photothermographic color recordillg system~ This type of ~onsgrucfiorl wilh the prope~ sol~ellt selestion is collducive to the use of samultaneous multiple coating techniques with good color ~I separation. It also enabl~ the simultaneous thermal deYelopment of at least two ,:

r q ~1 æ~35 .~3 WO 93/25936 pcr/us93/o3l83 or more individual color-forming photothermographic systemsi haYing different chemistr~es, but similar thermal properties.
Preferably, the interlayers employed in the imageable artieles of the ,;.~ present inventioll should be impermeable to the sol~vent emplsyed in any layers subsequently coated onto it. The test for detcrmîning if an interlayer polymer ~s impelmeable to lhe solYent of the nex~ layer can be simply performeà. First, a layer containing a sensitized, halidized silver salt of a âatty carboxylic ~for example 10-32 carbon atoms, pre~eral~ly 12-~8 e~rbon atoms) acid and poly(~inyl ?' .~1 butyral) polymcr is coatcd onto a su;table substrate. A second coating comprising a candidate interlayer polymer is applied arter the ~Irst coating has ~j dried. The liast layer contains the appropriate solvent, a eolor forming Ij~ - de~eloper, and toning agent reactant~ l'he dried coatiligs are gi~en an excessive ,1j ~ light exposure and then heated for 60 seconds at 120-130C. The test is positive ~ if no color or ~age is foraned.
`~i 15 The imageable elements of the present invention optionally may be ,~ o~ercoated with a protecti~e coating. Suiaable materials ror the protective ~i coating include, but are not limited to, polymcrs that are insoluble in aqueous ; syste~Tas, soluble in some organic solvents, and ;mperYious to certain other .~ organlc solvents. The "barrier" polymer, which is ~he ~ourth layer and pl~eferabb contains the color re~cfants, is normally a m~thyl methacrylate polymer (preferably a h~rd polymer or copolymer with a Tukon hardness o~ 20 or more), copo~ymer, ~r blend wilh other polymcrs or copolymers (ror example, copolymers with n-butyl acrylate, butyl methacrylate, and other aerylates such ~; as acrylic acid, methacrylic acid, acrylic anhyàride? and the like)7 polystyrene, or a combination of a poly~inyl chloride terpolymer with a butadien~styrene ' I ~ cop'olymèr. The barrier layer may be rrosslinked also~ This would be pre~er~bly ; .
: done by the inchlsion of a latent or acti~atable crosslinkirlg agent. Crosslinking : ` could then be e~fected af~er coating.
e theoay of th~s proc~ss is essentially lhe same for a light-sensitive material comprising a negative emulsion and a light-sensitiYe material compr~sing ~ a direct positiYe emulsion and only di~t~rs in that the portion to be deYeloped is 1~ an: exposed area in one and an unexposed area in the oth~r~ Aecordingly, even ` :~
,~
, '; ~ :

:~ w~ g3J25936 ~ 3 S 4 ~ 3 pcr/uss3/o3183 . .. .
i., 15 `: ~hen a direct pssitiYe emulsion is us~d, a dye ilnage providing good color reproducibility is obtained in the same way as in the case o~ a negative emulsion.
Heating in a substantially water-free condition, as used herein, means heating at a temperature oî 80 to 250Q C. The term "substantially water-free :~. S condition" means that the reaction system is in equilibrium with water in he air, .. ;and that water for inducing ~r promoting the reaction ~s not particularly orpositively supplied from exterior to the element. Such a condit;on is described at page 374 of "The Theory of the I'hotographic Processl', 4lh Edition ~T. H.
~, James, published by Macmillan Co.~.
10The coating solution used in the present invention may be prepared by separately forming a silver halide and an organis silYer salt oxidizing agent and mixing them before use. It is also e~ectivc to mLY the two in a bali mill îor a lollg period o~ time. Another eff~ctive method comprises adding a halo~en-containing compound to the prepared orgalnic silver salt oxidizing agent and 15forming silYer halide by the rcaction of the halogcn-containing compound with sil~er in the organic silver s~lt oxidizing agent.
The Yarious layers comprising the imageable arlicles of the present ,, invelltion may conlain sur~ce active agents for Yarious purposes; for example, as coating aids or for preYentiola Or electrical chargillg, improYement of 20lubricating properties, emulsirlcation, prevention o~ adhes;on, ~mpro~ement ofphotographic properties (~or example, accelcration of de~elopment pro~iding hard tones or sensitization), etc. ~or examplc, it is possible to use llonionic surface a~tiYe age~ uch as saponin (stcroid), alkylene oxide deri~ati~es (for example, polyethylene glycol/polypropylene glycol condensates, polyelhylene 25glycol alkyl ethers or polyethylene glycol alkylaryl elh~rs, polyethylene glycol estèrs, polyethylen/e giycol sorbitan eslcrs, polyalkylene glycol alkyliamilles or ,i amides9 polyethylene~:oxide adducts of silicone, ctc.~g glycidol deriYatiYcs tfor example, alkenylsuccinic acid polyglycerides, alkylphellol polyglycerides~ etc.), polyhydrie alcohol aliphatic acid esters or saccharide alkyl esters, etc.; anionic 30surface ~ctive agents containillg acid groups such as a cs~boxyl group~ a sulro group~ a phospho group, a sul~ate~group, a phosphate group, etc., such as alkylcarboxylic acid salts, alkylsulSollic acid salts~ alkylb~n~enesulfonic acid salts, ' `

~y 21~5~'3 . . . WO 93/~5936 Pcr/u~93/ 03 1 83 . .

alkylnaphthalellesulfonic acid salts, alkyl sulfuric a~id es~ers, alkylphosphoric ;1 acid esters, N-acyl-N-alkyltaurines, sul~osuccinic acid esters, sulfoalkyl polyoxyethylene allcyl phenyl ethers, polyoxyethylene alkylphosphoric-acid esters, etc.; ampholytic surface acti~e ~gents such as amino acids, aminoalkylsulfonic `~ S acids, aminoalkylsulfuric ac;d esters or phosphoric acid esters, alkyl betaines, amine oxides, etc.; and cationic surface a~tiYe agents such as alkylamine salts,. aliphatic or ~romatic quaternary asrunonium salts, heterocyclic quaternary allunonium salts such as pyridinium salts, imida~olium salts, etc., aliphatic orheterocyclic phosphonium salts, aliphatic or hetcrocyclic sulronium salts, ets.
,~j 10 Of the above-disclosed surface actiYc agents, polyethylene glycol type 3 nonionic surface actiYe agents haYing a repeatirlg unit o~ ethylene oxide in their . molecules are o~ten preSerably incorporatcd into the light-sensitiYe material. Ia ` 3 iS particularly pre~erred that the molecule contaills 5 or more of the recurring units of ethylene oxide.
lhe light-sensitive m~teri:ll used in the prescnt invention may contain, i~
desired or necessary, ~arious additi~es known for he~t deYelopable light-sensitive 4, materials and m~y haYe a layer or layers other than the light-sensiti~e laycr such as, for example, an antist~tic layer, an elcctrically conducti~e layer, a protective layer, an intermediate layer, an antihalation layer9 a stripp~ble layer, etc.
Tbe imageable articlcs Or the present in~en~ion are coated on a substrate.
Suitable substrates il~clude rigid and flexible substrates; metals ~for example,` steei and aluminum plates, sheets, and foils~; films or pl~tes composed of ~arious film-fo~ing synthetic or high polymers inclllding addit;on polymers (for example, polyt~inylidene chloride, polyYinyl chloride, polyYinyl acetate, polystyrene, polyisobutylene polymers, and copolymcrs thereof~, and linear condensation polymers : (~or example, polyethylene terephth'~ tc, ., , : polyhexamet~ylene ad;p~te, and polyilexam~thylcne adipamide/adipate);
`;~
nonwoYcn wood byproduct based substrates such as paper and cardboard; and gl~ss. Substrates may be transparent or opaque.
3 0 Especially use~ul substrates are films of cellulose acetatc ~llms such as cellulose triacetate or diaeetate, fllms of polyamides dcriYed from a combin~tion of heptamethylenediam~ne and terephlhalic acid9 ~ combination of :

~ WO 93/25936 ? i 3 5 ~ ~ 3 Pcr/~S93/03183 .: ~

~, lluorenedipropylamine and adipic acid, a combination of hexame~hylenediamine .~ and diphenic acid, and a combination of hexamethylenediamine and isoph~halic ~!1 acid, f'llms o~ polyesters deri~ed from a combination of diethylene glycol and diphenylcarboxylic acid and a combination of bis-p-carboxyphenoxybutane a~d S ethylene glycol, a polyethylene terephthalate f~llm, and a polycarbonate film.
The ~llms may be modified; îor example, polyethylene terephthalate f~
~,~
modif~led by such modifiers as cyclohexane dime~hanol, isophthalic acid, methoxypolyethylerle glycol, or 1 ,2-dicarbomelhoxybenzenesulfonic acid are effective.
The ~Ibs~rate used for the light-sensitiYe material in ~he present invention is one that has good d~m~nsional stability at the processing temperature. The polyesters described in U.S. Pat. No. 3,634,089 are prcferably used. More preferably, a polyethylene tcrephthalate ~llm is used.
i If necessary, two or more lay~rs may be applicd at the same ~ime as , 15 disclosed in U.S" Pat. No. 2,7S1,791 ~nd ~ritish P~t. No. 837~095.
In th~ present inverltion, the latent image obtained after exposure of the ~1 heat-sensiti~e material c~n be de~elopcd by h~atlng the matcrial at a mod~rately elevated temperature of, for example, ~bout 80 to about 250C.9 for about O.S
second to about 300 seco~ds. By increa~ing or decreasing th~ heating time, the temperatu~e m~y be higher or lo~er within the abo~e range. T~mperatures in ~, the range of ahout 110 to about 160C are especially useîul. Heating may be carried out by typical heating me~ns such as a hot plate, an iron9 a hot roller,a heat generator using carbon or titanium white, or the likeO
The imageable articles of the present in~ention are prepared by COsltiDg . 25 methods generally kno~n in the art and disclosed in U.S. Pat. Nos. 4,452~883 and 2,761,791 and Bri~ish Patent No. 837,095. ~ i ~Ieating for transfer of the dyes call ~e erfected by using the same heating me~ns as exemplifled for the heat deYelopment. To increase the qllality of the ~l dye image transferred to the dye receivillg lay~r, it is preferred to pre~ent an ~¦ 30 increase in fogging by the occurrence "r unl~ccssary de~elopment during dye transfer~ Fol this purpos~, it is especially ~ective to include 5 compound that .~
;~ reacts with the sil~er halide and/or can have the silvel halide adsorbed thereon ,, ;j ~!:

~ ~i35~S~
Ii WO 93/25936 . Pcr/uS93/03183 '~ !
as a development stopping agent and/or an anti~oggant in any one of the layers j~ constituting the dye receir;ng material. Such a eompound is preferably included in the dye receiving layer or a layer pro~ided abo~e the dye reeei~ing layer, such as a protecti~e layer, because it rapidly inhibits excessi~e de~elopmcnt of the ,I S light-sensiti~e layer during transîer o~ the dye by heating and a sharp and clear ~I dye image can be obtained. Such compounds include, for example, a nitrogen-containing heterocyclic compound, preferably a 5- or ~membered heterocyclic compound contai~ g a nitrogen atom.
,.~
;~ 10 The following non limiling examples further illustrate the present in~ention.
,~ .
~. ' The materials used in the rollowing ~xamplcs were obtained from standard commercial Yendors, such as Aldrich Chemical Co. ~ ilwaukee, Wl), unless ctherwise noted.
The dyes referred to in the following exasnples haYe the follo~ing st~dural formulae:
i :

~ .
~; ~

~ I ' I " I ' " ~ 1 j !

,'~

`: ' :
~ .
.
::
: ' ~ : `
: :~
~ ~ .
`~
.;'~

~!: wo 93~25936 ~21 3 5 ~ ~ 3 Pcr/us93/o3l83 i~i C'H3CH20~

,~ ~H3CH2 O N

;:"~
Red Sensitizi~lg Dye A (prepared according to i~ U.S. Pa~. No. 3,719,495) ~j ~
S

o l(~H(CH3)2 ~

. . H~ 3 ~ 2 Oil Blue A

,~o NI~CH2~ 3)2 ` (C~3 ~H2)2 Cl-~3~ :~
Basic Blue 3 : : :
:
: :

~s~; : :

~i~

` ~13~3 Wo 93/25936 Pcr/us93/o3183 ; -.. , . (~N\
N~--~(~2~H 3~2 : Sol~ent Yello~ 56 l,j ,~, 10 3 '~his example describes prep~ration of acrylonitril~iny~idene ehloride copol,ymers utilued in the present ialvention. l'he monomers ~ere distilled fromcalcium hydride under ~itrogen prior to polyL~erization. A solution of 6a m}
~ ylidene chloride, 33 ml ~crylonitrile, and 160 mg azobls(isobutyronitrile) wash~,ted to retlwY for two days. Ihe result~nt solution was precipitated by dropwise addition to methaDol. ~e precipitated polymer w,~ ltered9 . red~olYed in tetr~hydrofilran, and reprecipit~ted by addition to methalml.
, Follo~ing filtration, the purilied copolymer w~s dried in v~cr~o. I'he resultsnt polymer ~ad the ~ollowing composition: S0 mol% styrene ~nd: 50 mol~
vinyliidene chloride. The con~ersion of monomers was abollt 4~.
: :
~3x~mp~ 2 Diffussoll~ o~ dyes through copolymer ra~ o~ the in~e~tion were condllcted : ~s lollows: The copolyme~s were coatcd ~om a 10 wt% soiution in tetrahydrofu~all as a 1 ~mil thick layer on a Iransparent substraée ItYpe OR477410û
primed polyester, 3M: Compsny, St. Paul, ;ML~ and oven dried at 80C. A
second layer consisfing of 10 wt% poly(Y;nyl butyral) aJld 1 wt % dye in m~thanol ; ~ c!oated onto~the flrst layer. The ~oatirl~s ~Irere;~ir dried. ~The coatillgs ~ere ;; th~n heated to 140 C ~r ~arying times~ Absorbanee measuremeDts were made ; 30 ~nd; the top lay~r was ~remoYed by repeated application and remo~al Or Scotcll `~ ~;; ` ::r~rand: Magic transparent t~pe (3M Company, ~St. Paul, MOt and the absorban~e orthe~coated substrate:was measurcd. ~e percerlt dye dif~usion was c alculated~
, .
~ 1~

:i~
W093/2s936 t 13~ 4~3 pcr/us93/o3lB3 ; % Dye Transfer = A~o~tom layer) / A~bo~h l~yers) .:,, i Dyes used for e~aluation of polymer dL~usi~ity were Oil Blue A (DuPont Company, Wîlmington, Dli~), Basic Blue 3 (a cationic oxazine dye), and Sol~ent ' ~ S Yello~ 56 (an ~zo dye). The results for seYeral copolymers are prescnted in Tnble 1.
.
,,.~
.. ~
"' Table 1 ~.~ Copolymer Dye Transfer r~ 10 (Mol% Acrylonitrile / Mol%
~i Vinylidene Chloride),HeatingT~me Solrent OilBlucBasic Blue 3 ;~ Yellow 56 .~'l ~50 / ~0, 05 min 4.1 9.3 45.0 ;~
50 / 50, 5 min 4.8 10.7 77.1 .
50 1 50, 10 min 5.9 14.8 88.0 , 15 80 / 20, 0.5min 10.7 29.4 30.6 ~!
80 / 20~ ~ min 15.3 31.2 49.5 , xam~es 3 i~
~ 1~% solution of a copolymer of ~inyl chloride and ~inyl acetate (9:1) in methyl ethyl ketone was coate~ at a wet thicklless of 0.0B mm onto an opaque polyester f~llm substrate and dried in an oYen at a temperature of 80 C ~or fi~e m~utes to ~orm all imag~recei~ing lalyer.
A dispersioll of silYel behenate half soap (1 mole sil~er beh~nate to 1 mole ~5 bebenis acidl, 10~o ~soiids) in toluene was made by ~ homogenizatlon process~ A
. 110 g portion oî the 10% hal~ soa~p dispersion was diluted with 380 g ethallol.
Then 0.4 g poly(Yinyl butyral~ was added to the dilute dispersion and dissolved.Mercuric bromide (10 ml of a solution containing 1.~ g mercuric lbromide in 100 ; ml methanoi) was added to the dispersion ~Yith stirring. Additional poly(Yinyl 30 : butyral) (26 g) haYing a poly(vinyl alcohol) cdntent in the range of 9~-t3~o was added to the dispersion, hereina~ter r~rred to as Dispersion A.

4 8 ~
. . WO 93/25~36 PCI /~IS93/031 83 `, 22 ;;, 3M Fluorad FC-431 surfactant ~3 drops, a lluorochemical coat~ng additiYe employed as a stripping agent) was added to a 25g aliquot of Dispersionand mLxed. The r esultant dispersion w~s coated onto ~he imag~receiYing layer at a wet thickness o~ 0.0$ mm and dried in an o~en at a temperature of 80 C
:! S for ~ min to îorm a strippable blank emuLsion layer.
. j The following polymer solutions were coated oYer the blank emulsion layer at a ~et thickness oî 0.08 mm and dried in an air oYen at a temperature of $0 C for 5 min to folm an interlayer:
, Com~: An interl~ycr coating solution was prepared by dissolving 3.S% o~ a copolymer of Yinylidene chloride and ~inyl chloride (1:20, obtained from Scientil~lc Polymer Products, Inc.) in tetrahydrofuran.
14~ - Example 3~ An intcrl~yer co~ting solution was prepared by dissolYing 3.5% of a copolymer of poly;lcry30nitrile and Yinylidene chloride (1:4) in tetrahydrofuran.
I~xample 4: An interlayer coating solution was prepared by dissol~ g ~ 3.55b oî a copolymer of polyacrylonitrile ~nd vinylidene chloride (1:1) in !~.' tetrahydrofuran.
Cyan leuco dye (0,3g, 3,6-bis(diethylamino)-9-(4-methylbenzoyl)phenoxazhle obtained from Hodogaya Chemical as I~7û4) was dissolved in 3 ml toluene. The sulution was muY~d with 1 ml of a solution containing 0.005 g of a red sensituing Dye A in 150 ml toluene and 50 ml methanol, 0.1 g 4methylphthalic acid, and a 25 g a3iquot oî Dispersioll A. The resulting mLxed dispersion: was coated onto the interlayer at a w~t thickncss of0.13 mm and dri~d hl an o~!ell at a temperature of 80 C for 5 min to for~a ~
i;~
cya~ ~mulsion layer.
Strips ~ere then cut ~rom the resultant co~ted sheets and exposed to light ~: in an EG&G sensitometer through a W~atten 25 r~d f~lltcr ror 10-3 see to produce heat~deYelopable latent imnges ;n the~emulsion layer. Th exposed sheets were heal-de~veloped ~at a temperature o~ ~38 C on a he~t blanket for 30 sec. The 30 ~ portion of the element containing the photothermographic emulsiorl layers and the interlayer was then stripped away from the image-receiYing layer~ Cyan dye ` ~

~:
., `, ! . WO 93/2s936 ~ ~ 3 5 ~ ~ 3 PC~/USg3/03l83 ... .
i ~mages correspollding to the red light exposed area of the shee~ ~ere obser~ed to haYe been transîerred to the imag~reeeiYing layer.
~ Additionally, N-bromosuccinimide solution (0.08 g in 50 ml acetone and ~0 ml toluene) was dropped ~appro~cimately 0.015 ml) on the non-exposed area `.,~, S Or the imagc receiYing layer. Ilhe leuco dye ~hich had been transferred to the :.~ j image receiving layer th~ough the emulsion layers and the interlayer was oxidized by the l~-bromosuccinimide solution and îormed cyan dye.
The treatcd area was dried at room temperature ~or 30 min. The optical density of the oxidized dye by the oxidizing agcnt was measured by the ~10 densitometer using a red f;lter to determine the dif~usion of the leuco dye. The results are gi~en in Table 2.
`''~`1 -~` .
Table 2 , . .~
Sample Optical Density oî Expo~ed Optical Dellsity of Non-Area (corresponds to exposed area ~corresponds diîfusion of oxidized dye) to diffusion of lelJco dye) I ~
Comparative Example A 2.27 1.52 ~xample 3 1.32 0.44 . Example 4 ~ 1.25 0.91 , ~ . _ The results in the preceding table show that the copolymers of E:xamples 3 and 4 decrease the di~fusion o~ neutral l~uco dye while permitting the dirfusion of the oxidized (cationic~ forrsl of the dye relati~e to Comparati~e Example A.
1 ! 'i ~ : ' Reasonable modifications and variations are possible from the foregoing discliosllre withou~ departing ~rrom either the :spirit or scope Or the present ~ 25 invention as defined by the claims.

: ' :

,

Claims (20)

WHAT IS CLAIMED IS:

1. An imageable article comprising: (a) an image-forming layer comprising a neutral leuco dye which generates a cationic dye upon oxidation; (b) an image-receiving layer, and (c) a polymeric interlayer interposed between saidimage-forming and image-receiving layers, said polymeric interlayer comprising an acrylonitrile-vinylidene chloride copolymer.

2. The imageable article according to Claim 1 wherein said imaging layer further comprises a light-insensitive, reducible silver source; a light-sensitive silver halide; a polymeric binder; and a sensitizer.

3. The imaging article according to Claim 2 wherein said light-insensitive, reducible silver source comprises a silver salt of an aliphatic carboxylic acid.

4. The imaging article according to Claim 3 wherein said light-insensitive, reducible silver source comprises silver behenate.

5. The imaging article according to Claim 2 wherein said light-sensitive silver halide comprises silver bromide.

6. The imaging article according to Claim 2 wherein said imaging layer further comprises toning agent.

7. The imaging article according to Claim 1 wherein the mole ratio of acrylonitrile to vinylidene chloride in said interlayer is from about 0.2 to 0.95:1.

8. The imaging article according to Claim 7 wherein the mole ratio of acrylonitrile to vinylidene chloride in said interlayer is from 0.4 to 0.9:1.

9. A dry silver photothermographic element comprising a substrate coated on one side thereof with an image-receiving layer, said image-receiving layer having coated thereon at least one image-forming layer separated from saidimage receiving layer by a polymeric interlayer, said polymeric interlayer comprising an acrylonitrile-vinylidene chloride copolymer and said image-forminglayer comprising a neutral leuco dye that forms a cationic dye upon oxidation.

10. The dry silver photothermographic element according to Claim 9 wherein said image-forming layer further comprises a light-insensitive, reducible silver source; a light-sensitive silver halide; a polymeric binder; and a sensitizer.

11. The dry silver photothermographic element according to Claim 10 wherein said light-insensitive, reducible silver source comprises a silver salt of an aliphatic carboxylic acid.

12. The dry silver photothermographic element according to Claim 11 wherein said light-insensitive, reducible silver source comprises silver behenate.

13. The dry silver photothermographic element according to Claim 10 wherein said light-sensitive silver halide comprises silver bromide.

14. The dry silver photothermographic element according to claim 10 wherein said imaging layer further comprises toning agent.

15. The dry silver photothermographic element according to Claim 9 wherein the mole ratio of acrylonitrile to vinylidene chloride in said interlayer is from about 0.2 to 0.95:1.

16. The dry silver photothermographic element according to Claim 15 wherein the mole ratio of acrylonitrile to vinylidene chloride in said interlayer is from about 0.4 to 0.9:1.

17. A method of purifying a mixture comprising a neutral leuco dye and a cationic dye, said method comprising heating said mixture which is in intimate contact with a layer comprising an acrylonitrile-vinylidene chloride copolymer, thereby causing said cationic dye to diffuse through said layer away from said neutral leuco dye.

18. The method of Claim 17 wherein the mole ratio of acrylonitrile to vinylidene chloride in said interlayer is from 0.2 to 0.95:1.

19. The method of Claim 18 wherein the mole ratio of acrylonitrile to vinyl chloride in said interlayer is from about 0.4 to 0.9:1.

20. The method of Claim 17 wherein said heating is conducted at a temperature in the range of 80°-250°C.