CA2060466A1 - Bichromophoric methine dyes - Google Patents

Abstract

O.Z. 0050/42225 Abstract of the Disclosure: Bichromophoric methine dyes useful for thermal transfer have the formula where A=N-Z-L-Y-W=8 , A and B are each the radical of an acidic CH compound, W is nitrogen or the radical

Description

O.Z. 005~/422~5 Bichromophoric methine dye~
The present invention relates to novel bichromo-phoriG methine dyes of the formula I
A=N~Z--L--Y~=B
where A and B are identical or different and each is indepen-dently of the other the radical of an acidic CH
compound, W is nitrogen or the radical CN
-C H=
L is a bridge member which does not permit any con- -jugation of ~-electrons between the radicals Z and Y, and Z and Y are identical or different and in conjunction with the bridge member L are each independently of the other a radical of the formula ~N--L-- , ~ R 2 CH 3 (~Ia) (IIb) (IIc) _, ~N--Rl, ~

~IId) (IIe) (IIf) Il ~N - L - or R4 ~ ~ Rl (IIg) (IIh) where -- 2 0 ~

2 O.Z. 0050/42225 n is 0 or 1, R1 and R5 are identical or different and each is indepen-dently of the other alkyl, alkoxyalkyl, alkoxy-carbonylalkyl or alkanoyloxyalkyl, which may ~ach have up to 10 carbon atoms and be hydroxyl- or cyano-sub~titutad, hydrogen, benzyl, cyclohexyl, phenyl or tolyl, R2 i5 hydrogen, C1-C8-alkyl, C1-C6-alkoxy or a radical of the formula R7-Co-NH-, R7-o-Co-NX- or R7-So2NH-, where R7 is phenyl, tolyl, benzyl or C1-C8-alkyl which may be interrupted by one or two o~ygen atom~ in ether function, R3 is hydrogen, methyl, ethyl or Cl-C4-alkoxy, R4 is hydrogen, halogen, C1-Ca-alkyl, un~ub~tituted or Cl-Cq-alkyl- or Cl-C4-alkoxy-~ub~tituted phenyl, un~ubstituted or Cl-C4-alkyl- or Cl-C4-alkoxy-sub-stituted benzyl, cyclohexyl, thienyl or the radical -NHR1, where Rl is a~ defined above, and R~ is hydrogen or Cl-C8-alkyl, and to a proce~ for the thermal tran~fer of these dyes.
Bichromophoric methine dyes with dicyanovinyl radicals are known for example from GB-~-1,201,925, US-A~3,553,245, DE-A-1,569,67B, D~ A-2,519,59~ or DE-A-3,020,473.
It iB an object of the present invention to provide novel bichromophoric methine dyes which should posse~s advantageou~ application properties.
We have found that ~hi~ ob-Ject i~ achieved by the bichromophoric methine dyes of the formula I defined at the beginning.
Any alkyl or alkylene appearins in the above-mentioned formula I may be either straight-chain o.r branched.
The bridge member L which does not permit any con~ugation of ~-electrons between the radicals Z and Y
conforms in general to the formula ~ ~ 2 a ~

3 O.Z 0~50~42225 where D is a chemical bond, oxygen, -SO2-, -O-CO-O-, 1,4-cyclohexylene, phenylene, -O-CO-(CH2)l-CO-O, -O- ( CH2 ) m~~ t -o-C0 ~ o-(cH2)m-o ~ C0-0- where 1 is 1-10 and cO-O-m i5 2-10, -0-C0 ~ cO-0- -0-cO
-0-C0 ~ or 0-C0 ~ o_ and CO--O--and E2 are identical or different and each i8 indepen-dently of the other a ~hemical bond or Cl-Cl5-alky-lene.
Suitable acidic CH compoundfi AH2 or BH2 from which the radicals A and B in formula I are derived are for example nitromethane, nitroethane and a compound of the formula C / /CoX
Xl X3 1 4 (IVa) (IVb) (I~c) o o X S~N~N--X 5 X 5`NJ~N--X S
0~0 ' ~CH 2 orN CH 2--CON~ 2 (IVd) (IVe) (IVf) where X1 is cyano, nitro, C1-C4-alkanoyl, unsubstituted or Cl-C4-alkyl-, C1-C~-alkoxy- or halogen-3ubstituted benzoyl, Cl-C4-alkylsulfon~l, unsubstituted or Cl-C4-alkyl-, Cl-C4~alkoxy or halogen-substituted phenyl--sulfonyl, carboxyl, Cl-C~-alko~ycarbonyl which may be 4 O.Z. 0050/422~
- interrupted by 1 or 2 oxygen atom~ in e~her func-tion, C5-C7-cycloalkoxycarbonyl, phenoxycarbonyl, caxbamoyl, Cl-C6-mono- or -dialkylcarbamoyl which may be interrupted by 1 or 2 oxygen atoms in ether function, C5-C7-mono- or -dicycloalkylcarbamoyl, unsubstituted or C1-C4-alkyl-, Cl-C4-alkoxy- or halogen-substituted phenylcarbamoyl, unsubstituted or Cl-C4-alkyl-, cyano-, C1-C4-alkoxy-, halogen- or nitro-substituted phenyl, 2-benzothiazolyl, 2-benz-imidazolyl, 5-phenyl-1,3,4-thiadiazol-2-yl or 2-hydroxyquinoxalin-3-yl, X2 is Cl~C~-alkyl or Cl-C4-alkoxy, X3 iS Cl-C4-alkoxycarbonyl~ phenylcarbamoyl or 2-benz-Lmidazolyl, X4 iS Cl-C4-alkyl, and X5 iS hydrogen, Cl-C4-alkyl or phenyl.
Radicals which may he mentioned in particular here are those derived from acidic CH compounds of the formula IVa or IVb.
Suitable radical~ Rl, R2, R4, R5, R~ and R7 are for example methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, isopentyl, neo-pentyl, tert-pentyl, hexyl, 2-methylpentyl, heptyl, octyl, 2-ethylhexyl and i~ooctyl.
R2 may also be for example, like R3, methoxy, ethoxy, propoxy, butox~ or 3ec-butoxy.
Rl and R5 may each also be for example nonyl, i ononyl, decyl, isodecyl, 2-metho~yethyl, 2-ethoxyethyl, 2-propoxyethyl, 2-butoxyethyl, 2- or 3-methoxypropyl, 2-or 3-ethoxypropyl, 2- or 3-propoxypropyl, 2- or 3-butoxy-propyl, 4-methoxybutyl, 4-ethoxybutyl, 4-butoxybutyl, 2-cy~noethyl, 3-cyanopropyl, 4-cyanobutyl, 2-hydroxy-e~hyl, O.z. 00~0/4222 -CH2) 2--O C--CH3, --(CH2) 2--C--0--C4Hg, --(CH2)4--C--O--CH(CH3) 2 or R

--(CH2) 3--C--O--C4Hg -R4 may also be for example phenyl, 2-, 3- or 4-methylphenyl, 2- or 4-isopropylphenyl, 2-butylphenyl, 2-, 3- or 4-methoxyphenyl, 2-propoxyphenyl, 4-butoxy-S phenyl, 2-(but-2-oxy)phenyl, benzyl, 2-, 3 or 4-methyl-benzyl, 2-, 3- or 4-methoxybenzyl, fluorin~, chlorine, bromine, 2-thi~nyl or 3-thienyl.
R2 may also be for example pentyloxy, isopentyl-oxy, neopentyloxy, hexyloxy, acetylamino, propionylamino, butyrylamino, 3-oxabutylcarbonylamino, 3-oxapentyl-carbonylamino,3-oxaheptylcarbonylamino,3,6-dioxaheptyl-carbonylamino, 3,6-dioxaoctylcarbonylamino, benzyl-carbonylamino, 2-, 3- or 4-tolylcarbonylamino, methoxy-carbonylamino,ethoxycarbonylamino,propoxycarbonylamino, isopropoxycarbonylamino, butoxycarbonylamino, pentyloxy-carbonylamino, hexyloxycarbonylamino, 3-oxapentyloxy-carbonylamino, b~nzylo~ycarbonylamino, methylsulfonyl-amino, ethylsulfonylamino, propylsulfonylamino, iso-propyl~ulfonylamino or butylsulfonylamino.
X1 is for example methoxycarbonyl, ethoxy~car-bonyl, propoxycarbonyl, isopropoxycarbonyl, butoxy-carbonyl, 2-methoxysthoxycarbonyl, methylcarbamoyl, ethylcarbamoyl, 2-methoxyethylcarbamoyl, cyclopentyl-oxycarbonyl, cyclohexyloxycarbonyl, cyclohep~yloxy-carbonyl, cyclopentylcarbamoyl, cyclohexylcarhamoyl or cycloheptylcarbamoyl.
E1 and E2 are each for example methylene, 1,2-et~ylQne, ethylidene, 1,2- or 1,3-propylene or l,4-, 1,3- or 2,3-bukylene.

7~ ~J
~ o,z, 0050/422Z5 D is for example o o o o o o o .
Il 11 11 11 11 11 11 11 ~C-CH 2--C~, ~C--( CH 2 ) 2--C~ ~C--( CH 2 ) 3--C--O--~ --O--C--( CH 2 ) 4-C~--, O O O O O O
~C--( CH 2 ) 5--C~, --(}C--( CH 2 ) 6--C (}, --(}C--( CH 2 ) 7--C{~, O O O O O O
~}C--( C H 2 ) 8 e{}, {)--C--( CH 2 ) g--C{)--, --(}C--( CH 2 ) I o--C-O--, {)--(CH2)2~, {~(CH2)3--/}~ ~(CH2)4~, ~(CH2)5~, -O--(CH2)6-0--, -{}(cH2)7 (}~ ~(CH2)8~, ~(CH2)9-0--, {}(cH2)lo--0--~
O O O O
~C~(CH2) 2~3C~, ~C~(CH2) 3~3C--O--, O O O O
-o-C ~ o-(cH2)4 ~ C-O-, O e~ (CH2)5 ~ C-o-, -o o o o -o-c ~ (cH2, 6~e 0 O-e~ (CH2)7 ~ c-o-, 1l (CH2)s ~ c-o-, -o-C ~ (CH2)3 ~ c-o-or -o-C ~ (CH2)lo ~ C-O-.

Preference is given to bichromophoric methine dyes of the formula III
NC CN
C=N-Z- L-Y-N=C (III) Q Q
where the radicals Q are identical or di~ferent and each 18 cyano, C~-C6-- alkoxycarbonyl or C1-C3-monoal~ylcarbamoyl, where the alkyl group~ may in each ca3e be interrupted by l or 2 oxygen atom~ in ether function~ C5-C7-cycloalkoxy-carbonyl, C5-C7-monocyclo lkylcarbamoyl, phenoxy-carbonyl or monophsnylcarbamoyl, and Z, L-and Y are aach a~ dsfined above.

J~
7 O.Z. 0050/422~5 Preference is further given to bichromophoric methine dyes of the formula I where the radicals Z-L and Y-L conform to the formulae IIa to IIg~
Preference is further given to bichromophoric methine dyes of the formula I where Rl and R5 are each independently of the other hydrogen, unsubstituted or cyano- or acetoxy-~ubstituted Cl-C6-alkyl, benzyl or cyclohexyl, R2 is hydrogen, methyl, methoxy or acetylamino, R3 is hydrogen, methyl, ethyl or methoxy, R4 is hydrogen, Cl-C6-alkyl, unsubstituted or methyl-or methoxy-substituted phenyl, 2-thienyl or 3-thienyl, and R6 i8 hydrogen or Cl-C6-alkyl.
Particular preference is given to bichromophoric methine dyes of the formula III where Q is cyano.
Particular preference is further given to bichromophoric methine dyes of the formula I where the bridge member L has the formula -El-D-E2-where El and EZ are each indspendently of the other Cl-C4~alky-lene and D i a chemical bond, oxygen, -SO2-, -O-CO-(C~2~l-C--~
-O-C ~ (C~2)m ~ C~ where 1 is from 2 to cO~
4 and m i~ from6 to 10, -O-C ~ C~ o-C

or -C-C
CO~
~he novel methine dyes of formula I can be obtained by method~ known per se, a~ described for example in GB 1,201,925, US-A-3,553,245, D~-A-1,569,678, DE-A-2,519,592, DR-A-3,020,473l US-A-2,889,335 or EP-A-284,560.
- A pre~erred procedure compri~es for example first 2 ~

8 O.Z. 0050/42225 using an appropriate bridge member to link together the two groups Z and Y which will act in the dye as donors and then converting the resulting intermediates (herein-after referred to as dye precursors) into bichromophoric methine dyes I by the incorporation of for example cyanovinyl groups.
The procedure will be exemplified in explanation with synthesis schemes for preparing certain bichromo-phoric methine dyes I. ~ere z, y~ Q, p~l, R2, R3, 1 and m are each as defined above.

9 0OZ. 0050/~222 a) Synthesis of dye precur~or5 divinyl ~fone ZH2 . ~ HZ--( CH 2 ) 2--50 2--CH=CH 2 ¦ YH2 HZ--(CH2) 2--S2--(cH2) 2--YH
p,toluene~fonyl chloride HZ-(CH2)2-OH HZ--(CH2) 2~52~CH 3 ~ ¦ HY--(CH2) 2--OH
HZ--(CH2) 2--YH HZ--(CH2) 2--(cH2) 2--'~H
b) Incorporation of ~ymmetrical acceptor groups into the chromophores:
bl) Condensation Sodium nitrite H-Z-(C~)2-Y-H ----__________ ON_Z_ ( CH 2 ) 2 - Y - NO
hydrochloric acid Condensation ¦ ~

CN~ ~CN
~C=N--Z--( CH 2 ) 2--Y-N=C~
~: Q Q
b2) Oxidative coupl'ng ~ CN
Silver nitrate C\2 : x Ni~ration ~ ~ z (CH2)2 Y H - ~ H2N-Z-(CH2)2-Y-NH2 : R~ion ,.. . ... .

a O.Z. 0050/42225 c) Incorporation of asymmetrical acceptor groups R3 R~
NC~ ~ RI R~ (CH2)m--C~CI

R3 (CH2) 1--OH
C N R 2 Ni~rosation NC~ R I
C N ~N R 1 R 3 R3 (CH2)l{~c~(cH2)m-N~l NC~ Rl CH 2--X
C N "~--`N R 1 R 3 Condensation R3 (CH2) I--O--C(}(CH2)m--N~
~NO

NC~ R 1 CN ~N~ 11 R 3 R3 (CH2) 1--0--CO~(CH2)m~~~N=C\CN

The other dye precursor can be converted in a similar manner9 The novel dye~ I ~how advantageou~ ~olubility in organic 3slvent3.
The pre~ent invention further provides a novel process for the thermal tran3fer of dye~.
In thermal transfex printing, a tran~fer sheet which contains a thermally trans~erable dye within one or moxe binders with or without suitable ~ssistants on a support, is heated from the back with an energy source, for example a thexmal head, in short thermal pulse (duration: fractions of a ~econd), which cau~e~ the dye to migrate out of the transfe.r sheet and to diffuse into the surface coating of a receiving medium. The es~ential ~ f) ~
11 O.Z. 0050/42225 advantage of this process is that the amount of dye to be transferred (and hence the color gradation3 can easily be controlled via the energy to be emitted by the ener~y source.
5In general, color recording i5 carried out using the three subtractive primariec yellow, magenta and cyan (and if necessary black). To permit optimum color recording, the dyes must have the following properties:
- ready thermal transferability, - minimal tendency to migrate within or out of the surface coating of the receiving medium at room temperature, - high thermal and photochemical stability and resis-tance to moisture and chemic~ls, - suitable hue~ for subtractive color mixing, - a high molar absorption coefficient, - and no tendency to-cry~tallize out on storage of the transfer sheet.
It i~ known from experience that these require-20ments are very difficult to meet at one and the same time.
For this reason, most of the dyec used for thermal transfer printing do not have the required property profile.
25It has now been found that the transfer of bichromophoric methine dye~ from a support to plastic-coated paper with the aid of a thermal head is advan-tag20u81y pOBsible using a support on which there is or are situated one or more dyes of the abovementioned 30formula I.
Compared with the dye~ hitherto used in existing proce~3e~, the dyes tran~ferred in the process of the in~ention generally are notable for improved fixation in :~ the receiving medium at room temperature, readier thermal 35tran~ferability, higher light fastne~, higher ~tability to moisture and chemical substances, better ~olubility in organic solvents, higher color ribbon stability and 2 ~
12 O.Z. 0~50/42225 high~r cleanness of hue.
It i5 al30 surprising that the dyes of the formula I are readily transferable and possess a high color ribbon stability, despite having a very high molecular weight.
Prior art thermal transfer printing systems generally utilize mixtures of monochromophoric dyes in order to absorb about a third of the incident white light each in the cyan and in particular in the magenta region.
This requires that the dyes used must have exactly the same transfer characteristicq in order that a given output of the energy source used may produce equal coloring~ in the receiving medium (receptor~. This requirement is met in the process of the invention. One result i~ that for example an improved black is obtained on utilizing trichromatic systems.
Owing to their high molar extinction coefficients and ~teep absorption flanks (high brilliance), the dyes of the formula I used in the novel proces are advan-tageously suitable for preparing a trichromatic systemrequired for subtractive color mixing.
In addition, the ready transferability permits a wide range of receptor plastics and hence optimal adapta-tion of the dyes within the overall syste~ (donor/recep-tor).
To prepare the dye supports required for theprocess of the invention, the dye~ are incorporated into a 3uitable organic solvent or into mixtures of solvents with o~ or more binders and with or without assistants to form a printing ink in which ths dye is preferably present in a molecularly dispersed, ie. dissolved, form.
The printing ink can be applied to the inert support by means of a dockor and air dried.
Suitable organic ~olvents for the dyes I are for example those in which the solubility of the dye~ I at 20C i~ greater than 1% by weight, preferably qreater than~5% by w~ight.

2~ ,3~

13 O.Z. 0~50/42225 Examples are ethanol, propanol, isobutanol, tetrahydrofuran, methylene chloride, methyl ethyl ketone, cyclopentanone, cyclohexanone, toluene, chlorobenzene and mixtures thereof.
Suitable binders are all resins or polymer materials which are soluble in organic solvents and which are capable of binding the dye to the inert support in such a way that it won't rub off. Preference is here given to those binders whlch, after the printing ink has been air dried, hold the dye in the form of a clear, transparent film in which no visible crystallization of the dye occurs.
Such binders are mentioned for example in earlier Patent Application ~P-A-441,282 or in the relevant patent applications cited therein. Furthermore, ~aturated linDar polye ters may be mentioned.
Preferred binders are ethylcellulose, ethyl-hydroxyethylcellulose, polyvinyl butyrate, polyvinyl acetate and saturated linear polyesters.
The weight ratio of binder:dye ranges in general from 1:1 to 10:1.
Suitable ~istant~ are for example release agent~ a3 mentioned in earlier German Patent Application P 40 04 612.5 or in the relevant patent application~
cited therein.
Suitable inert supports are described Por example in the earlier Patent Application ~P-A^441,282 or in the relevant patent application~ cit~d th~rein. The thickness o~ tha support for the dye is in general from 3 to 30 ~m, pr0ferably from 5 to 10 ~m.
The dye receptor layer can in principle be made of any high temperature re~istant plastic having affinity for the dyes to be tran ferred, for example modified polycarbonate~ or polye ter3. Further details are di cer-nible for example ~rom earlier Patent Application EP-A-4~1,282 or the relevant Patent Application~ cited therein.

~ ~3 ~ f 14 o.z. 0050/42225 Transfer is effected by means of an energy source, for example by means of a laser or by means of a thermal head which latter must be heatable to ~ 300C in order that dye transfer may take place within the time span t: 0 < t ~ 15 msec. In the course of transfer the dye migrates out of the transfer sheet and diffuses into the surface coating of the receiving medium.
The dyes of the present invention are also advantageously suitable for dyeing synthetic materials, for example polyesters, polyamides or polycarbonates.
Textile fabrics of polyester or polyamide or polyester/cotton blends may be mentioned in par icular.
The novel dyes are al~o advantageous for th~
production of color filters, as described, for example, in EP-A-399,473. Finally, they can also advantageously be used as colorants for the production of toners for electrophotography.
The Examples which follow will further illustrate the invention. Percentages are by weight, unless other-wise stated.I. Preparation of methine dye~
EXAMPLE A

CH~ CH2-CH2-O-II ~ (CH2)s ~ C-O-CH2-CH2 ~ H
50 g of 1,9-dibromononane, 58.1 g of ethyl 4-hydroxybenzoate and 94.2 g of potassium carbonate were suspended at room temperature in 500 ml of N,N-dimethyl-formamld2 (anhydrous) and then heated at 100C until starting material was no longer detectable by thin layer chromatography. The cold reaction mixkure was iltered with suction, and the solvent was removed under reduced pre~sure. The residue was recrystallized from methanol (37.4 g of pure substance), admixed with 300 ml of ethanol, and added to a mixture of 19.9 g of potassium hydroxide in 260 ml of ethanol, and the mixture was raised to the refluxing temperature. After complete ~ ',3 0.Z. 0050/42225 hydrolysis (check by TLC), the mixture was cooled down to room temp~rature and filtered with suction, and the residue was suspended in water, acidified by hydrochloric acid, again filtered off with suction and washed neutral.
28.3 g of pure substance were o~tained.
lH NMR (CDCl3, TMS): ~ = 1.10 - 1.90 (m, 14 H, CH2), 4.05 (t, 4 H), OCH2), 7.00 (d, 4 H, aromatic H), 7.90 (d, 4 H, aromatic H, 12.15 (s, 2 H, COOH) ppm 28 g of the product obtained were suspended in 120 ml of thionyl chloride and dissolved by heating to the refluxing temperature. After the reaction had ended, the solution was cooled down to room temperature, the reaction prcduct wa~ precipitated with petroleum ether, and the precipitate was filtered off with suction, washed with petroleum ether (IR: COCl, 1760 - 1740 cm~l) and then dissolved in 50 ml of methylene chloride. This solution wa~ added dropwise to 22.9 g of N-(2-hydroxyethyl)-N-ethyl-~-methylaniline, a spatula tip of 4-dimethylamino-pyridine and 6.5 g o~ triethylamine in 50 ml of anhydrous methylene chloride at from 0 to 5C. Then stirring wa~
continued at room temperature until ths reaction had ended. ~he reaction mixture wa~ stirred into ice-water, and the mixture was acidified with dilute hydrochloric acid and extracted with methylene chloride. The organic phase wa3 washed neutral with water and dried, and the solvent was r~moved under reduced pre~ure lyield: 42 g, R~ value: 0.32 ~:1 v/v toluene/ethyl acetate - TLC alumi-num sheet~, silica gel 60 F254 from E. Merck).
EXAMPLE B
NC~c N ~ ,C2H5 H5C2~ ~ N-C~

10.16 g of the compound of the formula CH3 N`C ,N ~ H3 were dis~olvedin 100 ml of water and 50 ml of concentrated -16 0.Z. 0050/42225 hydrochloric acid. 19 ml of 23% strength by weight aqueous sodium nitrite solution were then added dropwise at 0-5C, and the mixture was subsequently stirred at 0-5C for 2 hours. After the nitrosation had ended, the mixture was adjusted to pH 8 with 25% strength by weight aqueous ammonium hydroxide solution, and the nitroso compound was taken up in neutral form in methylene chloride. After 4 g of malodinitrile and 30 ml of acetic anhydride had been added, the mixture was briefly heated to 70C and then cooled down to room tempçrature. On addition of 100 ml of isopropanol and 10 ml of water the target product precipitated and was filtered off with suction. Washing with methanol left 5.3 g of dye (^ 35.8%
of theory); melting point: 86C; R~ value 0.33 9:1 v/v toluene/ethyl acetate ~LC aluminum sheets, silica gel 60 F254 from E. Merck; ~ (tetrahydrofuran)o 497 nm.
EXAMPLE C

NC ~3 C 2H4~CO--CH 2--CH 2--CO--O--C 2H 4' ~N C~CN

11.12 g of the compound of formula ~N~ C 2H5~N_~
CH 3 C 2H4~CO--CH 2--CH 2--CO~C 2H4 CH 3 were nitrosated as described in Example B and then sondensed with 3.4 g of malodinitrile in 30 ml of acetic anhydride. The reaction mixture W?S subsequently admixed with 220 ml o~ i~opropanol, whereupon an oil precipitated which on ~tanding over the weekend formed crystals. The precipitate was filtered off with ~uction and washed with a little isopropanol. 6.04 g (- 40.4% of theory) of dye were obtained. R~ value: 0.20 8:2 v/v toluene/ethyl acetate TLC aluminum sheets, silica gel 60 F254 from E.
Merck; ~maX (tetrahydrofuran): 492 nm.
The same method wa~ u~ed to obtain the dyes of formula .

-17 O.Z. 0050/4~225 ,C=N~N~ ,N~rJ=C

li~ted below in Table 1.

Example No. E L R~ value ~m~ [
D H ~CO~CO--O 0, 46 a) 484 E H O--CO~CO O0, 46 a) ~85 f CH3 ~C~3co O 0, 30 b) 492 a) Eluent: 3:2 v/v toluene/ethyl acetate 5 b) Eluent: 8:2 ~/v toluene/ethyl acetate In each case development was carried out on TLC aluminum sheets, ~ilica gel 60 F254 from E. Merck.
II. Transfer of methine dye~
For a ~imple qùantitative examination of the tran~fer characteristics of the dyes, large hotplates were used instead of a thermal printing head and the tran~fer temperature was varied within the range 70C < T ~ 120C, the transfer time having besn fixed at 2 minutes.
~) General recipe for coating the ~upport with dye:
1 g of binder wa3 dis~olved in 8 ml of 8:2 v/v toluene/ethanol at 40-50C. A solution of x g of dye in 5 ml of tetrahydrofuran wa~ added with stirring and any in~oluble residue wa filtered off. The print paste thu~
obtained wa~ applied with an 80 ~m doctvr to a polyester aheet tthickne~s: 6-10 ~m) and dried with a hairdryer.
~) Te~t for thermal tran~ferability The dye~ used were te~ted in the following way:
the polyester ~heet donor containing the in-test dye in the coating composition on the fxont wa~ placed with the coated front on a commercially available ~heet of 2, ~ t 3-j 18 O.Z. OOS0/42225 receptor paper (hereinafter described) and pressed down.
Donor and receptor were then ~Jrapped in aluminum foil and heated between two hotplates at variou temperatures T
(within the temperature range 70~C < T < 120C). The amount of dye which diffuses into the bright plaitics layer of the receptor is proportional to the optical density (= absorbance A). The latter was determined photometrically. A plot of the logarithm of the absor-bance A of the colored receptor papers measured within the temperature range between 40 and 110C against the reciprocal of the corresponding absolute temperature is a straight line from whose slope it is possible to calculate the activation energy ~ET for the transfer experiment:
~log~
~ET = 2 . 3 X R X ---To complete the characterization, the temperature T* [C], at which the absor~ance A of the colored recep-tor papers attains the value 1, is additionally takenfrom the plots.
The dyes li~ted below in Table 2 were processed according to ~) and the resulting dye-coated supports were examined for transferability according to ~). The Table lists for each example the thermal transfer para-meters T* and ~ET~ the absorption maxima of the dyes ~m~
(measured in methylene chloride), the binder~ used and the weight ratio of the dye: binder.
The key to the abbreviation~ is as follows:
D Y dye B = binder V = Vylon~ 290 from Toyobo CP = cellulose propionate HCVPP - Hitachi Color Video Print Paper ~receptor) PBTP = polybutylene terephthalate film (receptor) 19 0, Z . 0050/42225 ,n u~

<

* V V

~ cr ~

Z Z ~- .
~, a I I ~ ~

m , ~

~ = O ~. i CL T 1 T

o o ~

Z O O
a) ~ ~ g ~

O.Z~ 0050/42225 The same method can be used to transfer the following methine dyes:
Example No.

7 NC~( ~`CH 3 CH SO CH 2--CH 2' ~3CN)~CN

~N~H 3 CH 2--50 2--CH 2--CH 2 ~CN

NC~(C~CH 2--CH 2--50 2--CH 2--CH 2 ~CN

NC-4 ~ CH 2--CH 2--S0 2--CH rCH 2 ~CN

I l NC~ ~3N`c ,N~
NC

t2 ~CN N~ CH SO CH2 - cH2~cNcN

NC~C~ CH2--CH2--SOrcH2 - cH2H~N

21 O.Z. 0050/42225 Example No, NC~ CH 2--CH 2--SO 2--CH 2--CH 2 ~CIY

NC~N I N1CN
~CH 2~CH 2 - CH 2 - ISI - CW 2--CH 2~CH 2~$3 CN CN
NClN 1l o NlCN
16 ~3~O--C--( CH 2 ) 4--C--O~3 CN CN
NCJ~N R 1l NlCN
17 (~CH 2~C--( CH 2 ) 4-C~CH 2~3 ,N~,N~

18 NC~ N`C2H5 R H5 IC~_CN
- NC CH 2--CH 2~C~CH 2--CH 2 CH 3CN

NC~< ~--N~C2HS ,1~CN
H3C CH2--CH2~1CH2) 2~CH2 - CH2 CH3CN

CN H~C 2 CN
NC~( ~--N~C2H5 8 N~N~CN
H 3C CH Z--CH 2~C~CH 2--~H 2 CH 3 .'''''' : .

2 ~
22 0 . z, 0050/4222 Exampl~3 No.
C~ IC2H5 H3C CH3 21NC-4/ ~ N-CH2-CH2-SO2-CH2-CH2-N ~ CH3 CN ~ CN

NC CN

C~3_ IC2H5 H3C CH3 22NC-~/ ~ N-CH2-CH2-SO2-CH2-CH2-N ~ CN

NC CN

H9C402C ~ CN CH3 CH3 NC ~ CN
23 ~ CN
H3COCHN Nl'~`HCH3 H3C-~N,~ NHCOCH3 CH2--~H2--S02 CH2--CH2 H13C602C ~ CN CH3 CH3 NC~r~CN
24 N ~ ~ CN
H3COCHN~ ~ ~ CH3 H3H,~7,1~_~1~CH3 CH2 -l~H2 - so2 - cH2 - cH2 25NC--4 ~ N-CH2-CH2-SO2-CH2-CH2-N ~ CN
CN NC

I~_CH2-CH2-502-CH2-CH2 N ~ ~-CN
CN NC

27NC ~ N--CH2--CH2--O-CH2--CH2--~ ~CN
CN NC

,~ . , .

' 2 ~

, 23 0 . Z ~ 005~/42225 Example No.

CN C2H5 HgC4 CN
28 ,~=N~N / ~CN
~ CH2--CH2--0--(CH2) 2----CH2--CH2 CH3 CN

29 ~=N~3N N~N=~
O~N H3C CH2--CH2--0--(CH2) 2----CH2--CH2 CH3 N02 CN C4H9 HgC4 C02C4Hg ~CN~3N 8 ~N~Na~
H9C402C CH2--CH2--o--C~30--CH2--CH2 co2C4Hs CN C4Hg HgC4 CN
31 ~=N~3N~ 1l / ~N=~
~ CH3 (CH2--CH2) 2--O--C--O (CH2--CH2) 2 CH3 ~

.

Claims (4)

1. A bichromophoric methine dye of formula I
(I) A=N-Z-L-Y-W=8 where A and B are identical or different and each is indepen-dently of the other the radical of an acidic CH
compound, W is nitrogen or the radical , L is a bridge member which does not permit any con-jugation of .pi.-electrons between the radicals Z and Y, and Z and Y are identical or different and in conjunction with the bridge member L are each independently of the other a radical of the formula , , , (IIa) (IIb) (IIc) , , , (IId) (IIe) (IIf) or (IIg) (IIh) where n is 0 or 1, R1 and R5 are identical or different and each is O.Z. 0050/42225 independently of the other alkyl, alkoxyalkyl, alkoxy-carbonylalkyl or alkanoyloxyalkyl, which may each have up to 10 carbon atoms and be hydroxyl- or cyano-substituted, hydrogen, benzyl, cyclohexyl, phenyl or tolyl, R2 is hydrogen, C1-C8-alkyl, C1-C6-alkoxy or a radical of the formula R7-CO-NH-, R7-O-CO-NH- or R7-SO2NH-, where R7 is phenyl, tolyl, benzyl or C1-C8-alkyl which may be interrupted by one or two oxygen atoms in ether function, R3 is hydrogen, methyl, ethyl or C1-C4-alkoxy, R4 is hydrogen, halogen, C1-C8-alkyl, unsubstituted or C1-C4-alkyl- or C1-C4-alkoxy-substituted phenyl, unsubstituted or C1-C4-alkyl- or C1-C4-alkoxy-sub-stituted benzyl, cyclohexyl, thienyl or the radical -NHR1, where R1 is as defined above, and R6 is hydrogen or C1-C8-alkyl.

2. A methine dye as claimed in claim 1 of the fsrmula III

(III) where the radicals Q are identical or different and each is cyano, C1-C6-alkoxycarbonyl or C1-C6-monoalkylcarbamoyl where the alkyl groups may in each case be interrupted by 1 or 2 oxygen atoms in ether function, C5-C7-cycloalkoxy-carbonyl, C5-C7-monocycloalkylcarbamoyl, phenoxy-carbonyl or monophenylcarbamoyl, and Z, L and Y are each as defined in claim 1.

3. A methine dye as claimed in claim 2, wherein Q is cyano.

4 A process for transferring bichromophoric methine dyes from a support to plastic-coated paper with the aid of an energy source, which comprises using a support on which there is or are one or more dyes of the formula I
as claimed in claim 1.