CA1268942A

CA1268942A - Merocyanine dye-donor element used in thermal dye transfer

Info

Publication number: CA1268942A
Application number: CA000543131A
Authority: CA
Inventors: Gary W. Byers; Derek D. Chapman
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1986-08-22
Filing date: 1987-07-28
Publication date: 1990-05-15
Anticipated expiration: 2007-05-15
Also published as: EP0257580A2; EP0257580A3; EP0257580B1; DE3778793D1

Abstract

MEROCYANINE DYE-DONOR ELEMENT USED
IN THERMAL DYE TRANSFER
Abstract A dye-donor element for thermal dye transfer comprises a support having thereon a merocyanine dye dispersed in a polymeric binder, the merocyanine dye being capable of transfer by diffusion to a dye-receiving element upon the application of heat and being incapable of ~ubstantial photolysis, the merocyanine dye being substituted or unsubstituted on the bridging methine carbon atoms.
In a preferred embodiment, the merocyanine dye has the formula:
wherein:
A represents -COR, -COOR, -CONHR, -CN, -SO2R or -SO2NR2; or A may be combined together with R1 to form a heterocyclic or carbocyclic ring system;
R1 represents -NHR, -NR2, -OR, -SR, or -R;
n represents 0 or 1;
Z represents the atoms necessary to complete a 5- or 6-membered substituted or unsubstituted heterocyclic ring; and each R independently represents a substituted or unsubstituted alkyl group of from 1 to about 6 carbon atoms or a substituted or unsubstituted aryl group of from about 6 to about 10 carbon atoms.

Description

~ 94~

MEROCYANINE DYE-DONOR ELEMENT USED
IN TB RMAL DYE TRANSFER
This invention relate~ to merocyanine dye-donor elements ~sed in thermal dye transfer which 5 have high ma~imum dye den~itie~.
In reeent years, thermal transfer systems have been developed to obtain prints from pictures which have been generated electron;cally rom a color video camera. According to one way of obtaining ~uch 10 prints, an electronic picture i8 first ~ubjected to color separation by color filter~. The respective color-separated images are then converted into electrical signals. These signal~ are then operated on to produce cyan, magenta and yellow electrical signals. These signals are then transmitted to a thermal printer. To obtain the print, a cyan, magenta or yellow dye-donor element iR placed face-to-face with a dye-receiving element. The two are then inserted between a thermal printing head and 20 a platen roller. A line-type thermal printing head is used to apply heat from ~he back of the dye-donor sheet. The thermal printing head has many heating elements and i8 heated up sequen~ally in re~ponse to ~; the cyan, magenta and yellow~slgnals~ The~proces~ is 25 then repeated for the other two color~. A color hard copy is thus obtained which corre~pondg to the original picture viewed on a ~creen. Further details of this process and an apparatus for carrying it out ~are contained in U.S. Patent No. 4,621,271 by 30 Brownstein entitled "Apparatus and~Method For ;~ Controlling A Thermal Printer Apparatus," issued ~November 4, 1986.
One of the major problem ~in ~electing a dye for thermal dye-transfer printing i8 to obtain~good ~tranæfer ePficiency to produce~;high maximum density.

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Many of the dyes proposed for use are not suitable because they yield inadequate transfer densities at reasonable coating coverages.
It would be desirable to provide dyes which haue high transfer densities used in thermal dye-transfer printing.
Japanese Patent Publication 60/214994 relates to cyanine or merocyanine dyes which are u5ed in an image recording material. Those dyes, however,.
are not used in a thermal dye transfer system.
Instead, those dyes are light bleachable, such as by flash exposure, to bleach or destroy the dye. Thus, those dyes undergo substantial photolysis or decomposition when exposed to radiant energy. In addition, those dyes absorb at wauelengths substantially beyond the uisible spectrum, unlike the dyes of the present inuention.
Belgian Patent 647,036 relates to cyan dyes hauing a benz~c,d]-indole ring which are used ~o dye acrylic fibers. There is no disclosure in this patent, howeuer, that such dyes woulcd be useful in a thermal transfer element.
dye donor element in accordance~with the :~ : inuention comprises a support ha~ing thereon~a dye layer comprising a:merocyanine dye dispersed in a ~ ~:
:: ~polymeric binder, the merocyanine dye being capabl:e of transfer by diFfusion~to a dye-receiuing:element upon the application of heat and:being incapable of substantial photolysis, the~merocyanine~dye being substituted or unsubstituted on the bridging methine carbon atoms. By saying~ that the dyes of the :~
inuention are~"incapable:~:o~ substantial pho~olysis' is rneant that ~the~dyes~:of the inuention:do not : : ~ : wndergo:any s~ubstantial decomposition when exposed to ~; 35 radiant ener4~
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~3-By appropriate selection of substituents, the merocyanine dyes employed in the invention may be of cyan, magenta or yellow hue.
In a pre~erred embodiment of the in~ention, the merocyanine ciye has the formula:
o ~ _~ C--Z ~I/C=CH- ~CH=CH) --CH=C~

R
.
wherein:
~ represents - COR, - COOR, - CONHR, - CN, -SO2R or -SO2NR2; or ~ may be combined together with Rl to form a heterocyclic or carbocyclic ring system such as O O
--R ~ R
t=l or ='\ N/ ~

l represents -NHR, -NR2, -OR, -SR,~ or~-R; ;~
n represents O:or l;
Z represents the atoms~necessary~to complete a~::
5- or 6-membered: subst:ituteci-:or unswbstituted heterocyclic ring:~s~uch~as 3H-indole~, benzoxazol~e, thiazoline, benzimidazole, oxazole, thiazole; and each X~independently:repres~ents a substituted or ~ unsubstituted~alkyl group of from 1 to about 6:
carbon~:~at~oms: such:as~methyl,~ ethyl,~ propyl, ~ :
isopropyl,~ butyl,:pent:yl,~::hexyl or~such~a1kyl groups substituted with hy:droxy, ~cyloxy~, alkoxy, ~: aryl, cyano, acyl~ami~do, hal~ogen, etc.; or a substitut~Rd~ or unsubs~itùted aryl group of from : about 6 to:about:lO carbon atoms:such as phenyl, p-tolyl, m-chlorophenyl:,~ p-methoxyphenyl, n~bromophe:nyl, o-tol:yl, etc.:

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In a preferred embodiment of the in~ention, and R in the abo~e formula are combined together to form the following ring system:

ll ~ R 2 wherein K is CH3 or C6H5; R3 is CH3, H
or COOC2H5; and n is 0.
In another preferred embodiment of the inuention, ~ and R in the abo~e formula are combined together~ to form the fol10wing ring system:

~ 20 U N~ ~ S LX~C6H5 : and n is 0. ~ :
: In yet:another preFerred embodiment of t:he invention, ~ is -CN,~n is O:and R is phenyl or an alkyl g~roup:of from l~:to~about~6 carbon ato~s.;:
: Compounds:i~n:cluded within the scope of the n~ention 1nclude the~followlng~dyes~
~HUe C H 3~; ,C H 3 ~ : 0 t~ CH ~ H I~~C6H~S~

35 ~ CH3 ~ :

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CH3~ ,~CH3

2) ~ =CH--CH=^~

3 ) I~ , ,Y N--C H ~ ~
~ =N
H
3 ~ :

4) I~ U /---CH--CH=-/ ¦ 6 5 ~ ~
N/ n 6 5 O

S ) ~ ii \'--CH--CH=-/ r 0 o C2H5 25~: : CH3 --CU--CH=.i 6 5 CH CH ~ ~
f~ C--C4Hg(t) 3 5 ~ \N~ ~CN

CH :

~, ~

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o 3\ i 3 11 8 )Cl ~ ¢ \~=CH--CH=^~
~/ \N/ CN

O :
0 : 7 C~i 3 C2 s o I \~=CH--CH--/ ~ 15 5 , C H
12 5 o N/~=CH--CH=./ ~ 2 5 2Hs~ o N~ ~c H 5 12) I ~: y: .=CH--GH=~ 2 30 ~ C~ S
C 2 H 5 ~ ~ :

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O

5 13) ~ =CH-CH=-~

~2H5 o _CH_c~ 6 5 O
: C2H5 ~ :
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O
: 15 C6H5 ~ O\-_CH-CH=~ ~ 2 5 _ ~ N- ~

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6)~ C6H~- ~~ CH-CH ~ S~

`17)~ C6H5- D-~ CH CH ~ -C6H5 ;C2H5 ~ CH3 18) C6H;-~-0 ~ -: : : : :
::
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19~ =CH-CH=v 20) I~ `~' \. CH-CH=./ ~ 2 5 O

21) ~ CH-cH .~ ~ 6 5 :
:~ 15~ C6 5 ::: : I O
C2~15 C~13~ ~CH3 ) ~ =CH-CH=C/ 2 2 5 : 25~ CH3\~/CH3 23) t~ CH-CH / 2C2 5 CH3~ CH3 CONHC:H
24) ~ =CH-CH=~ 6 5 NHc6H

CH3 ~

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_g_ CH3~ / 3 ~

25) ~ =CH-CH=4\
S

C~3\ /CH3 26) I t `~ - CH-CH=~
~/ ~ ~ t=~-CH3 CH3\ /CH8 - 27) t ~ \ =CH-CH=~s/

; CH3 C6H

28)I~ `i " H CH /~~\ 0 2CC~I3 ~ CH3~ ~

:25~ CH CH3 ~ 0 29) t ~ \ -CH-CH=~/ ~ 2 5 CH3j /CH3 ~; 0 ~ :
-C H
30) ~ =C-CH=~ ~ 5 35 ~ CH3;~ C~H~5 ~Lz~
--1~
5H~ ~C~3 31 ) ~ =C--CH=-~S_T 2 5 ~./ N CHO ~S

3 2 ~t' `' c CH .~ `. 5 C6H5 o C2H5 O

t u =C H--C H=.~
~ ~ 1S , i~I, \N/ /-=\
CH ~-_ G

2Q~ ~34) ~ U ~.=CH--C=~ t ;:

25 35~ \ C C~H~C02C2H~5 C6L15~ N~ ~ C2C2H5 `:C6H 5 ~

:C ; ~ C6H5~ 2H5 ~x6~9a~2 3 7 ) U t 1~CH3 ~ C6H5 ~ \ ~ =CH C ~t=~

CH3~ ~CH3 0 ; 3B) ~-~ / \ CH / ~ 6 5 :
/ \N/ ~= : :
C6H CH3 ~ : :
: ~ ;

CH 0 3\ ~ 3 : I CH3 : 20 :
H ~0 CH~ , 3 40) ~ CH CH ~ C6H5 ::25:~ : : CH3 : ~ 3 4~ ;C6H5 ~ .=CH-CH=~ 6 5 J-CH~
35~;~4~ =CH-CH- ~ ~S

;C2HS ~ C2HS~
: ~

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43 ) ~ =CH--CH=~
! ~ ~S

~enta Hue ~ o 44) ~ =CH--CH_-~ X
:, ~
2 5 ~ CH3 3` ./ 3 u ,-=CH--CH=CH--CH=~/ ~ 6 5 N/ t=N

C~3 ~ CH~3 5~ 6) ~ =CH--CH=-~ 6 5 CH 2CH ( CH 3 ); 2 47i ~~ ~t ~ U--CH=~

: ~ , :

O
48 ) f ~ ~=CH--CH=CH--CH~ 6 5 2 5 ~ ~:

lo I~ =CH ~ H=.~ \-_o CH2cH(cH3)2 C2H5 ~ `

50) ~I~ ,u~ ll-lf-& H `

t 0 CH2C~I(C 3~2 C Y a n H u e C02c2H5:::
CH~rH(W~

'=CH--CH--~

H~CH¦~H~3~ 6~5 :

lX6~39 53 ~ =Cl~-OE~=- U_N~C=O

~~ ~ ~6}I5CN
C~2C~(C~3)2 A dye-barrier layer may be employed in the dye-donor elements of the invention to improve the density of the transferred dye. Such dye-barrier layer materials include hydrophilic material3 such as those described and claimed in U.S. Patent 4,700,208 entitled "Dye-Barrier/Subbing Layer for ~ye-Donor Element Used in Thermal Dye Transfer" by Vanier, Lum and Bowman, issued October 13, 1987.
The dye in the dye-donor element of the invention is dispersed i~ a polymeric binder such as a cellulose derivative, e.g., cellulose acetate hydrogen phthalate, cellulose acetate,~cellulose 20~ acetate propionate, cellulose acetate butyrate, cellulose triacetate~; a polycarbOnate;
poly(styrene-co-acrylonitrile),~a poly(~ulfone) or a po~ly(phenylene oxide).~ The binder;;may~be u~sed at a coverage of from about~0;.1~to about~5 g/m ; 25 ~ The dye layer~o~ the~dye-donor eleme~t may be~coated on~the support or~pr~inted~thereon~by~a~
` printing technique ~uch a~ a gravur~ process.
Any materia~l can be used as the support ~or the~dye-donor element of the invention provided it is 30:~dimensionally stable~ and~can~withstand~the~heat of~
the~thermal~pri~ting`~heads.~Such~materials~;include polyesters àuch~as~poly~ethylcn~e terephthalate);~
polyamides; poly~arbonate~ glassine paper; condenser u;~ paper; cellulose~esters~suGh~as~cellulo~e acetate;~
35 ~fluoriDe polym-r~ ~uch a~polyvinyl~den- Sluo-ide or ~: , ~ : :

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poly(tetrafluoroethylene-co-hexafluoropropylen~);
polyethers such as polyoxymethylene; polyacetals;
polyolefins such as polystyrene, polyethylen~, polypropylene or methylpentane polymers; and polyimides such as polyimide-amides and polyether-imides. The support genera:Lly has a thickness of from about 2 to about 30 ~m. It may also be coated with a subbing layer, if desired.
The re~erse side of the dye-donor elbment may be coated with a slipping layer to prevent the printing head from sticking to the dye-donor element. Such a slipping layer would comprise a lubricating material such as a surface actiue agent, a liquid lubricant, a solid lubricant or mixtures thereof, with or without a polymeric binder.
Preferred lubricating rnaterials include oils or semi-crystalline organic solids that melt below 100~C
such as poly(vinyl stearate), beeswax, perfluorinated alkyl ester polyethers, poly(caprolactone), carbowax or poly(ethylene glycols). Suitable polyrneric binders for the slipping layer include poly(~inyl alcohol-co-butyral), poly(~inyl alcohol-co-ace~al) ~ poly(styrene), poly(~inyl acetate),~ ce11ulo~se acetate -~ ~ butyrate, cellulose acetgte, or ethyl cellulose.
The amount of the lubricating material to be used in the slipping layer depends largely on the type of l~bricating material, but is generally in the range of about .001 to~about 2 g/m2. If ~
polymeric binder is employed, the lubricating material is present in the r~ange of 0.1 to 50 weight~
~ %, preferably 0.5 to 40, of the~polymerîc binder : ~ employed.
he dye-recei~ing element that is used with the dye-donor ~lement of the in~ention usually comprises a support ha~in~ thereon a dye image-recei~ing layer. The support may be a~

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transparent film such as a poly(ether sulfone), a polyimide, a cellulose ester such as cellulose acetate, a poly(vinyl alcohol-co~acetal) or a poly(ethylene terephthalate). The 6upport for the dye-receiving element may also be reflective such as baryta-coated paper, white polyester (polyester with white pigment incorporated therein), an ivory paper, a condenser paper or a synthetic paper such as duPont TyvekTM. In a preferred embodiment, polyester with a white pigment incorporated therein i3 employed.
The dye image-receiving layer may comprise, for example, a polycarbonate, a polyurethane, a polyester, polyvinyl chloride, poly(styrene-~Q-acrylo-nitrile), poly(caprolactone) or mixture~ t~ereof.
The dye image-receiving layer may be present in any amount which is effective for the intended purpose.
In general, good results have been obtained at a concentration of from about 1 to about 5 g/m .
As noted above, the dye-donor elements o~
the invention are used to form a dye transfer image.
Such a process comprises imagewise-heating a~
dye-donor element as described above and transferring a dye image to a dye-receiving element to form the dye transfer image.
The dye-donor element of the invention may be used in sheet form or in a continuous roll or ribbon. If a continuou~ roll or ribbon i8 employed, it may have only the yellow;dye thereon as described above or may have alternating areas of other 30 different dyes, æuch as sublimable cyan and!or ::
magenta and/or black or other~dyes. ~Such dyes are disclosed in U.S. Patent~ 4,541,830. Thus, one-, two-, three- or four-color elements (or higher numbers alæo) are included~within the scope of the ~ 3S~invention.

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--, 6~ ~2 In a preferred embodiment of the invention, the dye-donor element comprises a poly(ethylene terephthalate) support coated with ~equential repeating areas of cyan, magenta and th~ yellow dye as described above, and the above proce~s ~eps are sequentially performed for each color to obtain a three-color dye transfer image. Of course, when the process is only performed for a single color, then a monochrome dye transfer image i8 obtained.
Thermal printing head~ which can be used to transfer dye from the dye-donor elements of the invention are available commercially. There can be employed, for example, a Fujitsu Thérmal Head (FTP-040 MCSOOl)TM, a TDK Thermal ~ead F415 15 H~7-1089TM or a Rohm Thermal ~ead KE 2008-F3TM.
A thermal dye transfer assemblage of the invention compri 8 es a) a dye-donor element as described above, and b~ a dye-receiving element as described above, ~ ~
the dye-receiving element being~;in a superposed relationship with the dye-donor element 80 that the dye layer of the donor element i8 in contact wi~th the dye image-receiving layer of the receiving element.
The above as~emblage~compri#ing these two elements may be prea~sembled as an integral unit when a monochrome image iB to be obtained. This may be done by temporarily adhering~the two elements 30~ together at their margins. ~After transfer, the `dye-receiving element i8 then peeled apart to reveal the dye transfer image. ~ ~
When a three-color mage i8 to be obtalned, the above assemblage i formed on three occa~ions ~during the tlme when heat is~applied by~the thermal~
pri~ting head. A~ter the~firsk~dye i~transferred, "~

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the elements are peeled apart. ~ second dye-donor element (or another area of the donor element with a different dye area) is then bro~ght in register with the dye-receiuing element and the process repeated.
The third color is obtained in the same m~nner.
The following examples are pro~ided to illustrate the in~ention.

: CH3\ ~CH3 3-methyl-1-phenyl~4-~ C H [2-(1,3,3-trimethyl t ~ ~=CH-CH=~/ 6 5 indol-2-ylidene)-N/ t ethylidene]-2-pyrazolin-To a suspension of 25.0 9 (0.056 mole) 1,3,3-tri~lethyl-2-(2-N-phenylacetamido~inyl)-3--pseudo-: indolium iodide in:150 mL:~acetonitrile were aclded 9.~ g (0.056 mole): 3-met:hyl-1-phenyl-5-pyrazolin-5-;~ ~ one ~nd 10.0 mL;(0.072 mole) triethylamine. The ~ :
reaction was heated at refl~ux for 30 min.,~cooled to : 0-5C and the product collected by filtration and washed with cold acetonltrlle. ~:fter drying in air the yield of material melting at 199-200C was 18.7 g (93.5%). The ~-max in acetone was 476 nm.

: : : : Example 2 - Yellow:DYes yellow~dy:e-donor element was prepared by 30:~coating the following~1ayers~in the order~recited on a 6 ~m poly(ethyl~ene t~erephthalate) swpport: :
: 1) Dye-barrier layer of poly(acrylic) acid (0.16 g~m ) coated~from water, and 35:

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2) Dye layer containing a yellow dye as identified in the following Table (0.63 mmoles/m2), a celluloEe acetate binder (40% acetyl) at a weight equal to 1.2X that o~ the dye, and FC-431 (3M Corp.) surfactant (2.2 mg/m2), coated from a 2-butanone/cyclohexanone solvent mi~ture.
On the back side of the element was coated a slipping layer of the type disclosed in U.S. Pa~ent 4,717,711 of Vanier et al, issued January 5, 1988.
A dye-receiving element was prepared by coating a solution of Makrolon 5705TM~(~ayer AG
Corporation~ polycarbonate resin (2.9 g/m2 in a methylene chloride and trichloroethylene solvent mixture on an ICI Melinex 990TM white polyester suppor~ .
The dye 8 ide of the dye-donor element strip 0.75 inche~ (19 mm) wide was placed in contact with the dye image-receiving layer of the dye receiver 20 ~element of the same width. The ~semblage was fastened in the jaws o~ a stepper~motor~driven pulling~device.; The assemblage~was laid on top of a -0.55 (14 mm) diameter rubber~rQller and a~TDK~Thermal esd (No. L-133)TM and waB~ pressed~with;a~spring~at~
25~ a force of 8. 0 pounds (3~. 6 kg) :ag~aiDs~t~ the:~dye - donor element side of the aæsemblage~pushing it~against the~
rubber roller.
The imaging electronics were activated caus~ing the pulling~device to draw the~assemblage 30 ~between the prin~ing head~and~ro~ler at 0.123 inches/s~ec (3.1 mm/sec).~Coincidentally, the r~eæ~istive elements~iD~;the~hermal~pr~in~head were pulse-heated at increments from O to 8.~3 msec to generate;a gradua~ed~density~test patter~n. The~
3s~volt~a~e 8upplied to~the print~head was approximately :
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22u representing approximately 1,5 watts/dot (12 mjoules/dot) for maximum power.
The dye-receiuing element was sep~rated from the dye-donor element and the stàtws ~ blue reflection density at the rnaximurn density was read.
The following results were obtained:

Table 1 10_ m~ Status ~ Blue D-~ax 1 1.9 2 1.9 4 1.8 1.9 6 2.5

7 2,5 9 1.4 1.5 20 37 1.3 38 1.8 39 ~ 1.6 2iO
41 ~ ~ 2.0 2~542 2.3 ; 43 ~ 1.9 Control Cmpd.l 0.9 Control C~pd.2 1.1 Control Cmpd.3 1.1 : 30~ Co ntrol Cmpd.4 0.3 : : :
: ~ : : : :

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el ow control cornpound structures:

Control Compound 1 o 0 C~
~ Similar to Dye 1 C4HgtC~~C~C-NH~- ~ ~s-Cl of EP~ 147,747 N- ~ N(C2H5)2 _ntrol Com~ d 2 ~ 1 Disperse ~ellow 3O
o~ ~-N-N~ -NHCCH ~ldrich Chemical ~ ~ \._./ 3 J60/030,393 c~3 Control C~ d 3 C~_~ H U
~ -N- ~ ~-CH3 Similar to .=;~.\U/ U/-~l IP 60/ ,, 25 Contro ~ 4 ~ :

~ ~ t ~ Lurafix Yellow 138 : O~ / ~ ! B~SF Corp.
` 30~ ~ \ ~ , JP 60/053,565 The abo~e results indic~te that the ~: merocyanine yellow dyes of the in~ention produce ; 35 higher maximum density than a uariety of control dyes.

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ExamelQ~ nta Dyes Example 2 was repeated except that ma~enta dyes 44-46 and 48-50 were employed and the Green Status ~ maximum density was measurecl. The following 5 rRs~lts were obtained:
Table 2 und ~0 44 2 5 2.8 46 2.7 : 48 1.9 49 : 1.8 1.6 Control Cmpd.5 0.6 Control Cmpd.6 1.6 Maqenta control compound structures:
~n~ L~ar~æ~nd 5 .~
: : ~:
NH

Describeci in JP 60/253,$95.
:
: 30 : : : :

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Control _o~ d 6 ~s\ ,11, ,1~ /SC6H5 !~ u u ~I
t ~ :
O OH

Described in JP 60/159,091.
10The abo~e results indicate ~hat with one exception, the merocyanine magenta dyes of the in~ention produce higher maximum density than prior art magenta anthraquinone. control dyes.

_x~le 4 - Cvan Dyes Example 2 was repeated except that cyan:dyes:
51-53 were employed and the Red Status ~ maximum : : density was measured. The following results were obtained:
Table 3 9mE5~ 9~t~ g~e=~y~

25 52 ~ 1.3 ~ 53 Control Cmpd~7 ~ 1.2 :; Control :Cmpd.8 ~ ~ : 0.6 :
: : 30 ~, :

~ 35:

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:: :

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: '` . ' `: , . . ~ ' '.'! . : ' ' .' ' " ~: ` : ` ' ' ` ' :, ":' ' :, `':,,:: ''` . ''` . ` :: ' :. ,.: :'.:` `'' ~ :'' ' ,: : ' '` ~, ' .:' ~24-~yLn control com~und structures: ~

Con 1 Comp~und 7 ~ :

OH O NH(CH2)20H :~
,U, ,1 U
~
OH O NH(CH2)20 ~ 10 ~ ~, ~escribed in JP 60/172,591.

' .
0 NHCH~
I~ ,U~ ,Uit~t Descr1bed in JP 60/151 097~and J~P~61lO35~ q3 The abo~e results:indicate that the;
merocyanine cyan dyes~ of~the in~en:tion:produ~ce~hi~her~
maximum density than pr1or art~nthraqu1none~cyan 2:5 :controI:dy~s :
The invention has~bee`n described`in~etail~
with particular reference~to:~preferred embodiments :thereof, but it will be u~derstood that variatio~s and: modifi~ation:s:can be:~e~fected within the spirit 30:~ànd s~ope~of~the invent1o:n~

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Claims

WHAT IS CLAIMED IS:

1. A dye-donor element for thermal dye transfer comprising a support having thereon a dye layer comprising a merocyanine dye dispersed in a polymeric binder, said merocyanine dye being capable of transfer by diffusion to a dye-receiving element upon the application of heat and being incapable of substantial photolysis, said merocyanine dye being substituted or wnsubstituted on the bridging methine carbon atoms.

2. The element of Glaim 1 wherein said merocyanine dye has the formula:
wherein:
A represents -COR, -COOR, -CONHR, -CN, -SO2R or -SO2NR2; or A may be combined together with R1 to form a heterocyclic or carbocyclic ring system;
R1 represents -NHR, -NR2, -OR, -SR, or -R;
n represents 0 or 1;
Z represents the atoms necessary to complete a 5- or 6-membered substituted or unsubstituted heterocyclic ring; and each R independently represents a substltuted or unsubstituted alkyl group of from 1 to ahout 6 carbon atoms or a substituted or unsubstituted aryl group of from about 6 to about 10 carbon atoms.

3. The element of Claim 2 wherein A and R1 are combined together to form the following ring system:
wherein R2 is CH3 or C6H5; R3 is CH3, H
or COOC2H5: and n is 0.

4. The element of Claim 2 wherein A and R1 are combined together to form the following ring system:
or and n is 0.

5. The element of Claim 2 wherein A is -CN, n is 0 and R1 is phenyl or an alkyl group of from 1 to about 6 carbon atoms.

6. The element of Claim 2 wherein said merocyanine dye is of yellow hue.

7. The element of Claim:2: wherein said merocyanine dye is of magenta hue.

8. The element of Claim 2 wherein said merocyanine dye is of cyan hue.

9. The element of Claim 1 wherein said support comprises poly(ethylene terephthalate), said dye layer comprises sequential repeating areas of cyan, magenta and yellow dye, and at least one of said dyes being said merocyanine dye.

10. In a process of forming a dye transfer image comprising imagewise-heating a dye-donor element comprising a support having thereon a dye layer comprising a dye dispersed in a polymeric binder and transferring a dye image to a dye-receiving element to form said dye transfer image, the improvement wherein said dye comprises a merocyanine dye which is capable of transfer by diffusion to a dye-receiving element upon the application of heat and is incapable of substantial photolysis, said merocyanine dye being substituted or unsubstituted on the bridging methine carbon atoms.

11. The process of Claim 10 wherein said merocyanine dye has the formula:
wherein:
A represents -COR, -COOR, -CONHR, -CN, -SO2R or -SO2NR2; or A may be combined together with R1 to form heterocyclic or carbocyclic ring system;
R1 represents -NHR, -NR2, -OR, -SR, or -R;
n represents 0 or 1;
Z represents the atoms necessary to complete a 5- or 6-membered substituted or unsubstituted heterocyclic ring; and each R independently represents a substituted or unsubstituted alkyl group of from 1 to about 6 carbon atoms or a substituted or unsubstituted aryl group of from about 6 to about 10 carbon atoms.

12. The process of Claim 10 wherein said support is poly(ethylene terephthalate) which is coated with sequential repeating areas of cyan, magenta and yellow dye, at least one of said dyes being said merocyanine dye, and said process steps are sequentially performed for each color to obtain a three-color dye transfer image.

13. In a thermal dye transfer assemblage comprising:
a) a dye-donor element comprising a support having thereon a dye layer comprising a dye dispersed in a polymeric binder, and b) a dye-receiving element comprising a support having thereon a dye image-receiving layer, said dye-receiving element being in a superposed relationship with said dye-donor element so that said dye layer is in contact with said dye image-receiving layer, the improvement wherein said dye comprises a merocyanine dye which is capable of transfer by diffusion to a dye-receiving element upon the application of heat and is incapdb1e of substantial photolysis, said merocyanine dye being substituted:or unsubstituted on the bridging methine carbon atoms.

14. The assemblage of Claim 13 wherein said merocyanine dye has the formula:

wherein:
A represents -COR, -COOR, -CONHR, -CN, -SO2R or -SO2NR2; or A may be combined together with R1 to form a heterocyclic or carbocyclic ring system;
R1 represents -NHR, -NR2, -OR, -SR, or -R;
n represents 0 or 1;
Z represents the atoms necessary to complete a 5- or 6-membered substituted or unsubstituted heterocyclic ring; and each R independently represents a substituted or unsubstituted alkyl group of from 1 to about 6 carbon atoms or a substituted or unsubstituted aryl group of from about 6 to about 10 carbon atoms.

15. The assemblage of Claim 14 wherein A
and R1 are combined together to form the following ring system:

wherein R2 is CH3 or C6H5; R3 is CH3, H
or COOC2H5; and n is 0.

16. The assemblage of Claim 14 wherein A
and R1 are combined together to form the following ring system:
IMG> or and n is 0.

17. The assemblage of Claim 14 wherein A is -CN, n is 0 and R1 is phenyl or an alkyl group of from 1 to about 6 carbon atoms.

18. The assemblage of Claim 14 wherein said merocyanine dye is of yellow hue.

19. The assemblage of Claim 14 wherein said merocyanine dye is of magenta hue.

20. The assemblage of Claim 14 wherein said merocyonine dye is of cyan hue.