CA2042084A1

CA2042084A1 - Inks

Info

Publication number: CA2042084A1
Application number: CA002042084A
Authority: CA
Inventors: Eric Vieira; David G. Leppard; Hugh S. Laver; Vien Van Toan
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1990-05-10
Filing date: 1991-05-08
Publication date: 1991-11-11
Also published as: JPH04227773A; EP0459942A1; US5089050A; EP0459942B1; DE59104652D1; JP3306515B2

Abstract

Inks Abstract Inks, in particular for ink-jet printing, containing, as stabiliser, a water-soluble compound of the formula

Description

. 2~2~

A- 1 ~068/A

Inks The present invention relates to novel inks, in particular those ~or inkjet printing.

Inks, including those which are suitable for inkjet printing, usually contain water-soluble dyes. However, the latter, without exception, have lower light ~fastness than, for example, the coloured pigments used in conventional printing processes. As a consequence, the recordings produced by in~cjet printing are of limited perrnanence in light; after some time, they begin to fade or discolour.

In order to solve this problern, it has been proposed, for example, in US-A-4 256 493, to add a water-soluble UV absorber of the sulfonated hydroxybenzophenone type to inks.
The me~als salts of such compounds have also been proposed, in JP-A-6277/88, as light stabilisers for inkjet printing inks. However, benzophenones of this type and their salts have the disadvantage of causing discoloration with certain dyes, in particular black dyes.
Furthermore, JP-A-57/2()7 659 discloses the use of dihydroxybenzenes as stabilisers.
Gallic acid and 3,5-dimethoxy-4-hydroxybenzoic acid are also mentioned therein.
JP-A-62/lOS 971` discloses the use of diaL~cylhydroquinones, for example 2,5-di-t-amyl-hydroquinone, and of the sodium salt of 2-hydroxy-4-methoxy-S-sulfobenzophenone and 2,2'-dihydroxy-4,4'-dimethoxy-S-sulfobenzophenone. JP-A-58/183 769 describes N-alkanolamine salts of m-digallic acid as additives for inkjet printing inks. Furthermore, GB-A-2 088 777 describes water-insoluble phenol derivatives and their use in recording materials for inkjet printing.

Further phenol derivatives have now been found which are highly suitable for use in inks and are able to stabilise prints produced therewith.

The present application thus relates to an ink which contains nt least one water-soluble compollnd of the f~rrnula R~ R,~
C) R~

2~L2~

in which Rl is hyclrogen, alkyl having 1 to 4 carbon atoms,allyl or -CO-CH3, R3 and R4, independently of one another, are hyclrogen or -C02~M~, and Rs, R6 and R7, independently of one another, are hydrogen, alkyl in each case having 1 to 8 carbon atoms which is unsubstituted or substituted by -CO2R8, -Co2~M~3 or phenyl, or are -CO2R8 where R8 is a group of the formula tC~2C~20~RII in ~vhich Rll is hydrogen, alkyl having 1 to 4 carbon atoms or a group of the formula (la) R70 ~Y-CO-in which Rl is as defined above, Y is a direct bond or alkylene having 1 to 8 carbon atoms, and R60 and R70, independently of one another, are hydrogen or alkyl in each case having 1 to 8 carbon atoms, M~9 is a monovalent, divalent or ~ivalent metal cation, H~33 or a group of the formula ~9N(RI7)(Rl2)(Rl3)(Rl~) in which R17, Rl2, R13 and R14, independently of one another, are hyclrogen, alkyl in each case having 1 to 8 carbon atoms, alkyl having 2 to 8 carbon atoms which is substituted by 1 tO 3 hydroxyl groups or is inter;upted by oxygen, alkenyl in each case having 3 to S carbon atoms or benzyl, at least one of the substituents R3 to R7 being -Co2~'Mq3 0r-C02R8 The present invention also relates to a recording material which contains at least one compound of the forrnula (1), to a process for stabilising inkjet prints and to the novel compounds of the formula (ld).

Rl is hydrogen or alkyl having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, sec-propyl, butyl or tert-butyl, or furthermore allyl or -CO-CH3. l'he substituents R5, R6 and R7, independently of one another7 are hydrogen or alkyl having 1 to 8 carbon atoms, for example methyl, ethyl, butyl, hexyl, heptyl, octyl or a corresponcling branched isomer.
Suitable substituents for these alkyl radicals nre those of the forrnulae -CO2R8 ancl CO2~M~ ancl phenyl. Furtherrnore, Rs, R6 and R7 may alternatively be CO2R8.

R8 is a group of the formula tCH2CH20)l 20- - Rll in which Rll is hy~lrogen or nlkyl 2~0~

ha~ing 1 ~o 4 carbon ~toms, such as methyl, ethyl or butyl. Rll may fu~hennore be a group of the fonnula (la) R70 ~Y-CO-in which Rl is as defined above, Y is a direct bond or alkylene having 1 to 8 carbon atoms,for example methylene, ethylene, butylene, hexylene, octylene or a branched radical such as -C(CH3)2-CH2- and -C(CH3)2-CH2-CH2-CH2-, and R60 and R70, independently of one anosher, are hydrogen or alkyl in each case having 1 to 8 carbon atoms.

In the de~lnitions above, M0 is a monovalent, divalent or trivalent metal cation, such as Li0, Na~, K~E3, Mg2~, ca2~), Ba2~, Zn2~9, Al3~), Cr3~E' and Fe3~33, furtherrnore H~3 or an amms~nium group of the folmula ~N(RI7)(Rl2)(Rl3)(Rl4) in which R17~ R~2~ R13 and R
independently of one another, are hydrogen, alkyl having 1 to 8 carbon atoms, alkyl having 2 to 8 carbon atoms which is substituted by 1 to 3 hydroxyl groups or is interrupted by oxygen, or are alkenyl having 3 to 5 carbon atoms or benzyl. Examples of alkyl and alkenyl groups which are suitable for the substituents Rl7, R12~ Rl3 and Rl4 are those given above in the definitions of R1 and R2, The inks according to the invention have good light stability. They can be used, for example, for felt-tip pens, ink pads for rubber stamps, fountain pens and pen plotters and in offset, letterpress, flexographic and intaglio printing, and in ink ribbons for dot-matrix and letter-quality printing, but are preferably used in inkje~ printing.

In the printers used today in inkjet printing, a distinction is made between those with a continuous ink jet and "drop-on-demandl' printers, in particular 'Ibubblejetll printers. The inks according to the invention can be used for these printers. Printing is in particular on inkjet printing papers and films.

'I'he inks according to the invention m~y contain water-soluble solvents, for example mono-, di-, tri- or higher etllylelle glycols, propylene glycol, 1,4-butanediol, oi ethers of such glycols, thiodiglycol, glycerol and ethers and esters tilereof, polyglycerol, mono-, di-and triethanolamine, propanolamine, dimethylformamide, dimethyl sulfoxide, 2~2~8'~

dimethylacetamide, N-methylpyrrolidone, 1,3-dimethylimidazolidone, methanol, ethanol, isopropanol, n-propanol, diacetone alcohol, acetone, methyl ethyl ketone or propylene carbonate .

The inks according to the invention contain dyes as are known for the dyeing of natural fibres. Particular examples are monoazo, disazo or polyazo dyes, reactive dyes, triphenylmethane dyes, xanthene dyes and phthalocyanine dyes. Specific examples are Food Black 2, C.I. Direct Black 19, C.I. Sulphur Black 1, Acid Red 35, Acid Red 14, ~cid Red 52, Acid Yellow 17, Acid Yellow 23 and copper phthalocyanines, furthermore Direc~
Black 38, Direct Black 168, Acid Red 249, Direct ~ed 227, Direct Yellow 86, Direct Yellow 132, Acid Blue 9, Direct ~lue 86 and Direct Blue 199 and Reactive Red 40,and the azo dyes mentioned in EP-A-366 121.

The inks may also contain other conventional additives, for example binders, surfactants, biocides, corrosion inhibitors, sequestrants, pH buffers and conductivity additives. They may also contain further UV absorbers or light stabilisers. In general, however, the addition according ~o Ihe invention of a stabiliser of ~he forrnula (1) is sufficient to stabilise the ink.

Particularly suitable inks for continuous inkjet printing are those based on solvents.
Examples of solvents used are short-chain alcohols, ketones and Cellosolvs. Particularly suitable dyes for inks of this type are C.I. "solvent" and "disperse" dyes. Furthermore, inks of this type generally contain further additives which improve, for example, the viscosity, surface tensiorl or conductivity of the inks. Film-forming binders, such as cellulose nitrate, cellulose acetate phthalate and styrene-maleic acid copolymers may likewise be present in the inks.

Inks which are preferably suitable for use in "drop-on-demand" printers are those based on wax mixtures. They are solid at temperatures below about 50C. The desired melting point and the hardness and viscosity properties arise from appropriate mixtures of various waxes. Examples are carnuba, montan, para~fin and silicone waxes, furthermore fatty acid esters and fatty aeid arnides. These inks rnay a~ain contain adciitives such as antioxidnnts, polymc rs and the additives mentionecl for solvent-based inks.

Suitable stabilisers both for solvent-basecl inks and for wax-basecl inks are, in particular, compounds of the formllla ~1) which are readily soluble in organie solvents.

~208~

Furtherlrlore, inkjet printing inks are known which comprise more than one phase.
JP-A-75/0 117 067,79/0 118 237, 80/0 118 238, 81/~) 118 238 und 76/0 119 337 describe inks which comprise an aqueous phase in which the dye is soluble and an emulsion of oil drops, the UV absorbers and, if used, also antioxidants. In JP-A-73/0 117 067 and 82/0 118 238, the oil phase containing UV absorbers is microencapsulated and the dye is dissolved in the aqueous phase. By contrast, oil-soluble dyes can be dissolved in an oil together with UV absorbers and, if used, antioxidants. The oil is either emulsified or dispersed in an aqueous phase, as described, for example, in JP-A-74/0 117 067 and 72/0 117 067. The compounds of the forrnula (I) are highly suitable ~or stabilising inks of this type; they are water-soluble and can be dissolved in the aclueous phase.

The inks according to the invention preferably contain from 0.01 to 30 % by weight, in particular from 0.1 to 20 % by weight~ of at least one compound of the formula (1).

In a group of preferred inks, Rl in the compound of the forrnula (1) is hydrogen or alkyl having 1 to 4 carbon atoms, R3 and R4, independently of one another, are hydrogen or -C02~M~E', Rs~ R6 and R7, independently of one another, are hydrogen, alkyl in each case having 1 to 8 carbon atoms which is unsubstituted or substituted by -Co~M~9 or phenyl, and M~33 is a monovalent metal cation or H~33.

Further preferred inks are those in which, in the compound of the formula (1), Rl, R3, R5 and R6 are hydrogen, R7 is alkyl having 1 to 8 carbon atoms, and R4 is -Co29M(~3.

Other highly suitable inks are those in which the compound of the forrnula (1) conforms to the forrnula (lb) or (lc) in which M~3, Rs and R6 are as defined above, and Rll is hydrogen or methyl.

Examples of water-soluble cornpounds of the forrnula (1) which are suitable for use in recording rnaterials and inks are those of the forrnulae OH OCHs oc2~5 ~COOH ~COOH ,~!~COOH
(2) ~ (3) ~ (O ~

_,.~ ",~e~D

~2~

(5) b (6) ¢~ (7) ~3 COOH COOH COOH
OG3~17 OH OCH3 (8) ~b (9) [~ (10) [~
COOH COOH
COOH

OC2H5 OC3H7 OC4Hg (12) ~ (13) ~
COOH COOH COOH

~C4Hg ~C4Hg C4H~C4Hg (14) ~ (IS) ~ (16) COOH COOH COOH

c4~tC4H9 tC4H~COOH
(17) ~ (18) COOH ~ C~Hg ~2~

~3 ~) H C I COOH
,~C--CH2--COO Li 3 ( 19) ~ CH3 (~) ~ ~9 COO Li COOH
,~Y
(21) These compounds are preferably incorporated illtO inks and recording materials in the presence of bases, such as lithium hydroxide or potassium hydroxide.

Further examples of compounds of the formula (1) conform to the formulae OH
(22) ~,~C,,H9 COO~CH2CH20 ~H

OH
~ C4H9 (23) COO~CH2CH20-)~CH~

210~L20~

OH OH
(24) ~ ~C4tl~ ~ ~C~Hg Coo~cH2c~l2o 3 4 6 CO

OH OH
Ho2C~C4H9 (26) H2C~CH3 OH
(27) H9C4t~CO2(CH2CH20)n H
~ n=6 The recording materials according to the invention which are preferably used -for inkjet printing and contain a compound of the formula (1) comprise a base with a surface which can be printed by an ink jet. The base is usually paper or a plastic film and is normally coated on one side with a material which is capable of absorbing inks. This layer preferably contains SiO2 and polyvinyl alcohol.

Uncoated paper may also be employed, in which case the paper serves simultaneously as base material and ink-absorption layer. Furthernore, materials made from cellulose fibres and textile fibre materials, for example cotton fabric or cotton mixed fabric made from cotton and polyacrylamide or polyester, and which contain compounds of the formula (1 can also be used for inkjet printing.

The recording materials may also be transparellt, as in the case of overhead projection transparencies.

The compounds of the Eormula (I) can be incorporated into the base material even chlring production thereof, for example by addition to the pulp in paperrnaking. A second application method is the spraying of the base material with a solution oE the compolmds of the formula (1) in water or a readily volatile organic solvent. Particularly in the case of 2~2~

oil-soluble compolmds of the formllla (1), a suitable method is the spraying or impregnation of the material with an organic solution of a compound of the formula ( 1). It is also possible to use emulsions or dispersions.

Usually, however, a coating composition with a high dye affinity is coated onto the base material; in this case, the compounds of the formula (1) are added to this coating composition. The coating compositis~ns generally comprise a solicl filler, a binder and conventional additives.

The filler is the principal constituent of the coating composition in amount. Examples of suitable fillers are SiO2, kaolin, talc, clay, calcium silicate, magnesium silicate, aluminium silicate, gypsum, ~eolite, bentonite, dia~omaceous earth, vermiculite, st~lrch or the surface-modi~led SiO2 described in JP-A-60/260 377. Small amounts of white pigments, for example titanium dioxide, baryte, magnesium oxide, lime, chalk or magnesi~lmcarbonate, can be used with the filler in the coating composition so long as they do not significantly reduce the density of the inkjet print.

Coating compositions which are intended for transparent, projectable recording materials must not contain any light-scattering particles, such as pigments and fillers.

The binder binds the fillers to one another and to the base material. Examples of customary binders are water-soluble polymers, for example polyvinyl alcohol, partially hydrolysed polyvinyl acetate, cellulose ethers, polyvinylpyrrolidone and copolymers thereof, polyethylene oxide, salts of polyacrylic acid, sodium alginate, oxidised starch, gelatin, casein, vegetable gum, dextrin, albumin, dispersions and polyacrylates or acrylate-methacrylate copolymers, latices of natural or synthetic r~lbber, poly(meth)acrylamide, polyvinyl ethers, polyvinyl esters, copolymers of maleic acid, melamin resins, urea resins or chemically modi~led polyvinyl alcohols, as described in JP-A-61/134 290 and JP-A-61/134 291.

The binder can also contain an additional dye receptor or mordant which improves the fixing, of the clye to the coating. Dye receptors for acid dyes are cntionic or amphoteric.
~xamples of cationic receptors ~Ire polymeric ammoni~lm compollncls, for exnmplepolyvinylbenzyltrimethylammoni~lm chloride, polydiallyldimethylammonillm chloride, polymethaeryloxyethyldimethylhyclroxyethylammonillm chloride, polyvinylbenzylrnethylimiclazolillm chloride, polyvinylbenzylpicolinillm chlolicle and 2~0~

- lo -polyvinylbenzyltributylammoniulIl chloride. Other examples are basic polymers, for example poly(dimethylaminoelhyl) methacrylate, polyalkylenepolyamines and products of the condensation thereof with dicyanodiamide, amine-epichlorohydrin polycondensates and the compounds described in JP-A-57/36 69~, 57/64 591, 57/187 289, 57/191 ()84t 58/177 390, 58/208 357,59/20 696,59/33 176, 59/96 9~7, 59/198 1~8, 60/49 990, 60nl 796, 60/72 7~5, ~0/161 188, 60/1~7 5~2, 60/189 4~1, 60/189 a,82, 61/14 979,61/43 593, 61/57 37~, 61/57 3~0, 61/58 788, 61/61 887, 61/63 477, 61/72 581, 61/95 977, 61/134 291, 62/37 181, in US-A-4 547 405 and 4 554 181 and in DE-A-3 417 582 An exarnple of an amphoteric dye receptor is gelatin.

The coating with a high affinity for the dye may contain a number of further additives, for example antioxidants, further light stabilisers (also including UV absorbers which do not correspond to the light stabilisers according to the invention), viscosity improvers, optical whiteners, biocides and/or antistatics.

Examples of suitable antioxidants are, in particular, sterically hindered phenols and hydroquinones, for example the antioxidants mentioned in GB-A-2 û88 777 and JP-A-60/72 785, 60n2 786 and 60r71 796.

Examples of suitable light stabilisers are9 in particular, organic nickel compounds and sterically hindered amines, for example the ligh~ stabilisers rnentioned in JP-A-58/152 072~ 61/146 591, 61/163 886, 60n2 785 and 61/146 591, GB-A-2 088 777, JP 59/169 883 and 61/177 279.

Suitable U" absorbers, which can be added to a coating composition in combination with compounds oP the formula (1), are described, for example, in Research Disclosure No.
24239 (1984), page 284, GB-A-2 088,777 and EP-A-0 280 650. The W absorbers of the 2-hydroxyphenylbenzotriazole class, especially 2-(2'-hydroxy-3',5'-di-t-amylphenyl)-benzotria~ole and 2-(2'-hydroxy-3'-t-butyl-$'-~polyglycol propionate)-phenyl)benzotriazole, are particularly suitable for use together with compounds of the formula (1) in recording materials for inkjet printing. lJV absorbers can be added to the coating~ composition as an emulsion or as a dispersion. If the compound of the formula ( I) is an acid, it can be dissolved in the coating composition by adding a hyclroxi(le solution.
Compollnds oP the formula (1) which are not acids can either be dissolved clirectly in the coating composition or added to the coating composition in the form of an emulsion or suspension.

0 8 ~

The coating composition is generally applied to the base, for example paper, and dried by heating. The compouncls of the formula (I) can~ as stated above, also be applied to the recording material in a separate operation, alone or together with other components described above, as an aqueous solution. Application can be by spraying/ sizing in a sizing press, a separate casting operation or by dipping into a bath. Post-treatment of the recording material in this way must be followed by an ~dclitional drying operation.

The recording material preferab}y contains from l to 10,000 mg/m~, in particular trom 5û
to 2000 mg/m2, of at least one compound of the fonnula ~l).

Of the compounds of the formula (l) used according to the invention, those of the forrnula R60 ~
R70 ~ COOR8 where Rl, R8, R60 and R70 are as defined above, are no~el.

The compounds according to the invention are highly suitable as stabiliser s for dyes in inks, in particular inkjet printing inks, and in the prints produced therewith.

The compounds according to the invention can be prepared in a conventional manner, for example by esteli~ying ben~oic acid derivatives which are known per se using appropriate alcohols, transestelifying methyl benzoates or, if the molecule contains no hydroxyl groups, reacting the benzoic acid derivatives with acid chlorides.

The examples below illustrate the invention without representing a limitation. Parts and percentages are by weight, unless stated otherwise.

~le 1: Coating compositions based on SiO2/polyvinyl alcohol are prepared with and without a stabiliser of the forMula (l). In each case, 0.2 g of a l0 a/a solution of Invaclin JFC wetting agent (Ciba-Geigy AG), 0.4 g of Polyfix 601 as mordant (Showa High Polymer Co.), 0.2~ g of a stabiliser of the formula (l) and 20.7 g of water are aclded to 14.2 g of a l0 % solution of polyvinyl alcohol. 10 % lithium hydro~ide solutioll is added 2~208~

ill clropwise until the stabiliser has dissolved at a pH of about 7. 2.0 g of silica (Syloid type u j244, W.R. Grace Co.) are subsequently added and dispersed by rneans of ultrasound. The ~O resultant coating composi~ion is filtered through a polyester fibre screen with a mesh width of 24 llm. The pH is adjusted to 7.0 by adding 2N lithium hyclroxide solution. In the li blank sarnple, the stabiliser is replaced by the same amount of water.

,~! The coating compositions are coated onto photographic paper in a thickness of 50 ~lm using a wire coil. The coating obtained after drying with warm air has a dry weight of about 5.3 g/m2 (or 5.0 g/m2 without stabiliser) and contains 0.3 g/m2 of stabiliser.

I~ The recording material prepared in this way is printed with each of a yellow, a black and a il purple-red ink in a "Think-Jet" inkjet printer (Hewlett-Packard). The yellow ink contains ,, il 4 parts of C.I. Acid Yellow 23, 48 parts of diethylene glycol and 48 parts o~ water.

~l The purple-red and black inks are prepaied analogously, but using C.I. Acid Red 249 and i~ C-I- Food Blaclc 2 respectively.
.. The inks are filtered through an ultra~1lter having a pore size of 0.3 ~Lm and introduced into ~ the ink cartridge of the "Think-Jet" printer. Print~d samples having a dot density of 75 x j~S 75 dots per cm2 are produced.

,, After storage for one week in order to fully dry the inks, the colour density (intensity) of "''r the printed samples is rneasured using a densitometer ~Macbeth TR 924) with a Status A
s filter. The sample prints are then exposed to an illurnination intensity of 81 klux behind a ~ filter comprising 6 mm thick window glass in an Atlas Weather-o-meter with a xenon it~ lamp. The colour density was subsequently remeasured in order to determine the . percentage drop in colour density. ,, i The results are surnmarised in Tables 1-3 below. Low values indicate high light fastness.
The exposure energies; given in kJ/cm2, relate to the wavelength range from 300 to 800 nrn.

2~2~8~

Table 1:
__ , _ _ . _ D op in eolour den ;ity (%) Sample Stabiliser Acid Yellow 23 Aeid Red 249 Food Black 2 after 10 kJ/cm2 after 10 kJ/em2 after 60 kJ/cm2 . _ _ _ 1 None 51 50 27 2 3,5-Di-t-butyl-4- 39 41 24 methoxybenzoic aeid 3 3-t-Butyl-4-hydroxy- 28 29 20 benzoic acid _ Table 2:
_ _ _ _ Drop in eolour density (Yo) Sample Stabiliser Food Blaek 2 after 60 kJ/em2 .
1 None 36 2 2-Methoxybenzoie aeid 24 3 2-Ethoxybenzoie aeid 22 4 4-Methoxybenzoie aeid 21 4-Ethoxybenzoie aeid 21 6 4-Hydroxybenzoie aeid 18 2~20~

Table 3.
_ _ Drop in colour density (%) . ~
Sample Stabiliser Acid Yellow 23 Acid Red 249 Food Black 2 _ after 15 kJ/cm2 after 15 kJ/cm2 after 30 kJ/cm2 1 None 69 72 18 2 Salicylic acid 31 40 10 3 3-Hydroxybenzoic acid _ 51 13 Example 2: Example 2 is carried out like Example 1, but the ink contains Acid Blue 9 as dye.

Table 4:
I Drop in colour density (%) Sample StabiliserAcid ~lue 9 after S kJ/cm2 . _ _~ . . I
1 None 61 2 3-t-Butyl-4-hydroxybenzoic acid 43 _ _ _ _ _ The examples show that ~he compounds used according to the invention can providelong-term stabilisation for ink dyes.

Example 3: Example 3 is carried out like Example 1, but a commercially avclilable magenta ink is used for the inkjet print (most concentrated of the three magenta inks from an ink cartridge for the Canon IK-8C inkjet printer, called " lK-8C" in the examples below).

2~2~

r~bl~ 5:
_ .
Sample Stabiliser Drop in colour density (%) after S kJ/cm2 ___ 1 None 50 2 2-Methoxybenzoic acid 25 3 3-tert-Butyl-4-hydroxybenzoic acid 24 _ _ _ _ Example 4: A coating composition is prepared as in Example 1 containing 45 parts of polyvinyl alcohol and 55 parts of silica (Sylold, type 244, W.R. Grace Co.). After the composition has been neutralised using lithium hydroxide, a polyethylene-coated paper base is coated with a cast weight of 8 g/1m2.

Inkjet printing inks containing the following are prepared:
Dye (C.I. Acid Yellow 23) 4.0 g 4.0 g Stabiliser ~ o o g 1o.o g Deionised water 48.0 g 43.0 g Diethylene glycol 48.0 g 43.0 g An ink is prepared analogously, but with the C.I. Acid Yellow 23 replaced by the same amount of the dye C.I. Acid Red 249.

Furtherrnore, a commercially available magenta ink containing 0.4 g of stabiliser per 10 g is used for inkjet printing (IK-8C, Canon).

Prints are produced (180 dots/inch) on a Quiet-Jet printer (Hewlett-Packard) using said inks. The light fastness of the prints is determined as described in Example l. The results are summarised in Table 6.

2~2~4 Table 6:
_ _ Sample Stabiliser Drs)p in colour density (C/o), 10 kJ!cm2 Acid Yellow ~3 Acid Red 249 1 K-8C
_ 1 37 ~7 64 2 3-tert-Butyl-4-hydroxybenzoic acid* 9 12 18 3 4-Hydroxy-3-tert-pentylbenzoic acid* 11 10 16 4 3-tert-Butyl-3-hydroxybenzoic acid* 4 ~ lS
3-(5'-Carboxy-2'-methylpent-2'-yl)- 17 18 3û
4-hydroxybenzoic acid*
6 4-Hydroxy-3-tert-octylbenzoic acid* 11 11 16 7 4-Mydroxy-3-(1'-methyl-l'-phenyl- 17 12 20 _ ethyl)benzoic acid*

~ in the form of the lithium salt Example 5: It is usual to use cationic mordants to improve the water resistance of inkjet prints, but they also significan~ly reduce the light stability. The compounds used according to the invention prove to be effective stabilisers even in the presence of cationic mordants.

The coating composition used in Example 4 is additionally provided with a mordant (0.3 g/m2 of Polyfix 601, Showa High Polymer S:~o.). This coating composition is applied to a paper base and printed and exposed as described in Example 4 The light stability of the samples is shown in Table 7.

~20~

Table 7 . _ _ .
Sample Stabiliser Drop in colour denslty (5b), lû kJ/cm2 Acid Yellow 23 Acid Red 249 lK-8C
_ _ _ _ 2 3-tert-Butyl-4-hydroxybenzoic acid* 20 15 28 3 4-Hydroxy-3-tert-pentylbenzoic acid* 21 15 27 4 3-tert-Butyl-3-hydroxybenzoic acid* 13 15 26 3-(5'-Carboxy-2'-methylpent-2'-yl)- 19 27 36 4-hydroxybenzoic acid*
6 4-Hydroxy-3-tert-octylbenzoic acid* 18 16 26 7 4~Hydroxy-3-~1'-methyl-1'-phenyl- 20 14 29 ethyl,~benzoic acid*
_ _ _ _ .

* in the form of the lithium salt Exam~6- The stabilisers used in inks in Examples 4 and 5 are incorporated as described in Example 1 into a recording material for inkjet printing. The material is printed, dried and exposed as described in order to determine the drop in colour density. The results are shown in Table 8.

2~2~8~

1~ -Table 8 Sample St lbiliser Drop in colour density (%), 10 kJ/cm~
Aeid Yellow 23 Acid Red 249 . __ 2 3-tert-Butyl-4-hyc'Lroxybenzoie acid* 36 21 3 4-Hydroxy-3-tert-pentylbenzoic acid* 34 19 4 3-tert-Bwtyl-3-hyclroxybenzoic acid* 31 20 3-(5'-Carboxy-2'-methylpent-2'-yl)- 30 2 4-hydroxybenzoie acid~
6 4-Hydroxy-3-tert-octylbenzoic acid* 30 15 7 4-Hydroxy-3-(1'-methyl-1'-phenyl- 25 16 ethyl)benzoie acid*
_ * in the form of the lithium salt Exam~le 7: 16.36 g of polyvinyl alcohol (10 %) are mixed with 2.0 g of silica and 0.22 g of stabiliser and water and neu~alised using lithium hydroxide. The solution is appl;ed ~o a polyethylene-coated paper base in a cast weight of 5.3 g/m2 (S 0 g/m2 if no stabiliser is used). After drying, the coatings are pnnted as describecl in Example 1 with an ink eontaining Acid Red 249 as dye and exposed. The results are shown in Table 9.

Table 9:
.
. _ _ _ ~
Sample Stabiliser Drop in colour density (%), 10 kJ/cm~
_--'- `- -- SO -' 2 Polyethylene glycol (350) monomethyl 33 ether 4-tert-butyl-3-hyclroxybenzoate 3 Polyethylene glycol (600) 4-tert-butyl- 32 3-hyclroxyben~oate 4 Polyethylene glycol (350) 4-tert-butyl- 33 3-hydroxybenxoate ._.
,~

2~2~

Exannple 8: Preparation s)f polyethylene glycol monomethyl ether (3~0) 3-tert-butyl-4-hydroxybenzoate 10 g of methyl 3-tert-butyl-4-hyclroxybenzoate are dissolved in 20 ml of xylene and 18.5 g of polyethylene glycol monomethyl ether (350). The solution is treated with 0.25 g of sodium methoxide and stirred at 135C for 48 hours. The solvent is removecL, and the residue is suspended in saturated sodium chloride solution. The solution is extracted with ethyl acetate, the organic phase is dried and evaporated, and the compound is purified by chromatography, giving 11.0 g of the product in the form of a pale yellowish oil.

Example 9: Preparation of 4-acetoxy-3-tert-butylbenzoic acid A mixture of 82.0 g of 2-tert-butyl-4-methylphenol, 140.0 g of acetic anhydride and 3.0 g of hydrobromic acid (48 %) is heated at 90C for 1 hour. 280.0 g of acetic acid, 2.5 g of cobalt(II) acetate (tetrahyclrate) and 2.5 g of manganese(II) bromide (tetrahydrate) are added, and oxygen (30 ml/min) is passed through the solution at 110C. The acetic acid is partially removed by applying a vacuum. The reaction nlixture which remains is poured into S00 ml of water and ~11tered, giving 99.5 g (84 %~ o~ the product in the form of colourless crystals having a melting point of rom 180 to 182C.

Example 10: Preparation of 3-acetoxy-4-tert-butylbenzoic acid 32.8 g of 2-tert-butyl-5-methylphenol are oxidised by the procedure given in Example 9 to give 34.5 g (73 %) of the product in the form of colourless crystals having a melting point of from 141 to 143C.

Example 11: Preparation of 4-acetoxy-3-tert-pentylbenzoic acid 3S.7 g of S-methyl-2-tert-pentylphenol are oxidised as described in Example 9 to give 13.7 g (27.5 %) of the product in the form of colourless crystals having a melting point of from 164 to 166C.

Example 12: Preparativn of 4-acetoxy-3-tert-octylbenzoic acid 44.0 g of 4 methyl-2-tert-octylphenol are oxiclised as described in Example 9 to give 'IS. 1 g (77 %) of the product in the form of colourless crystals having a rmeltillg point of from 151 to lSSC.

~x mple 13: Preparation of 4-acetoxy-3-(1-methyl-1-phenylethyl)bellzoic acicl 45.2 g of 4-methyl-3-(1-methyl-1-phenylethyl)phc nol .~e oxidised as described in 20~2a8~

Example 9 to give 44.1 g (74 %) of the procluct in the forrn of colourless crystals having a melting point of from 195 to 199C.

E~<ample 14: Preparation of 4-acetoxy-3-(5'-methoxycarbonyl-2'-1nethylpent-2'-yl)-benzoic acid 42.6 g of 2-(5'-methoxycarbonyl-21-methylpent-2'-yl)-4-methylphenol are oxidised as described in Example 9 to give 27.1 g (49 %) of the product in the form of colourless crystals having a melting point of from 106 to 10~C.

Example lS: Preparation of 3-tert-butyl-4-hydroxybenzoic acid 50.0 g of 4-acetoxy-3-tert-blltylben~oic ac;d are dissolved in 200 g of methanol. A
solution of 10.2 g of sodium hydroxide in 180 ml of water is added. The mixture is refluxed for 3 hours. The methanol is removed, and the mixture is acidified withhydrochloric acid (10 %) at 10C. The precipitate is filtered off and washed, giving 40.6 g of product in the form of colourless crystals having a melting point of from 158 to 159C.

Exam~ 16: Preparation of 4-tert-butyl-3-hydroxybenzoic acid 30.0 g of 3-acetoxy-4-tert-butylbenzoic acid are reacted by the method of Example lS to give 22.8 g (90 %) of product in the form of colourless crystals having a melting point of from 188 to 190C.

Example 17: Preparation of 4-hydroxy-3-tert-pentylbenzoic acid 20.0 g of 4-acetoxy-3-tert-pentylbenzoic acid are reacted by the method of Example lS to give 16.8 g (95 %) of 4-hydroxy-3-tert-pentylbenzoic acid in the form of colourless crystals having a melting point of from 139 to 142C.

Example 18: Preparation of 4-hydroxy-3-tert-octylbenzoic acid 20.0 g of 4-acetoxy-3-tert-octylbenzoic acid are reacted by the rnethod of Example lS to give 16.0 g ~93 %) of 4-hydroxy-3-tcert-octylbenzoic acid in the form of colourless crystals having a melting yoint of from 209 to 210C.

Exam~ 19: Preparation of 4-hydroxy-3-(1-methyl-1-phenylethyl)benzoic acid 2(),0 g of 4-acetoxy-3-(1-methyl-1-phenylethyl)benzoic acid are reactecl by the method of l~xample 15 to give 1S.8 g (93 %) of 4 hydroxy-3-( I-methyl-l-phenylethyl)benzoic acicl in the form of colourless crystals having a melting point of from 134 to 135C.

1~20: Preparation of 4-hydroxy-3-(S'-carboxy-2'-methylpellt-2'-yl)benzoic acicl 2al~2~8~

A solution of 10.0 g of 4-acetoxy-3-(5'-methoxyc~rbonyl-2'-methylpent-2'-yl)benzoic acid in 35 g of rnethanol is treated with a solution of 8.0 g of potassium hydroxide in 100 ml of water. The mixture is refluxed for 7 hours, cooled, diluted with 200 ml of water which has been acidified using concentrated hydrochloric acid, and extracted with ethyl acetate. The extract is dried over magnesium sulfate, the solvent is removed, and the residue is recrystallised from aqueous ethanol, giving 6.9 g (83 %) of 4-hydroxy-3-~5'-carboxy-2'-methylpent-2'-yl~benzoic acid of rnelting point 213 to 219C.

Claims

1. An ink which contains at least one water-soluble compound of the formula (1) in which R1 is hydrogen, alkyl having 1 to 4 carbon atoms,allyl or -CO-CH3, R3 and R4, independently of one another, are hydrogen or -CO2?M?, and R5, R6 and R7, independently of one another, ale hydrogen, alkyl in each case having 1 to 8 carbon atoms which is unsubstituted or substituted by -CO2R8, -CO2?M? or phenyl, or are -CO2R8 where R8 is a group of the formula in which R11 is hydrogen, alkyl having 1 to 4 carbon atoms or a group of the formula (1a) in which R1 is as defined above, Y is a direct bond or alkylene having 1 to 8 carbon atoms, and R60 and R70, independently of one another, are hydrogen or alkyl in each case having 1 to 8 carbon atoms, M? is a monovalent, divalent or trivalent metal cation, H? or a group of the formula ?N(R17)(R12)(R13)(R14) in which R17, R12, R13 and R14, independently of one another, are hydrogen, alkyl in each case having 1 to 8 carbon atoms, alkyl having 2 to 8 carbon atoms which is substituted by 1 to 3 hydroxyl groups or is interrupted by oxygen, alkenyl in each case having 3 to 5 carbon atoms or benzyl, at least one of the substituents R3 to R7 being -CO2?M?or-CO2R8.

2. An ink according to claim 1, in which, in the compound of the formula (1), R1 is hydrogen or alkyl having 1 to 4 carbon atoms, R3 and R4, independently of one another, are hydrogen or -CO2?M?, R5, R6 and R7, independently of one another, are hydrogen, alkyl in each case having 1 to 8 carbon atoms which is unsubstituted or substituted by -CO2?M? or phenyl, and M? is a monovalent metal cation or H?.

3. An ink according to claim 1, in which, in the compound of the formula (1), R1, R3, R5 and R6 are hydrogen, R7 is alkyl having 1 to 8 carbon atoms, and R4 is -CO2?M?.

4. An ink according to claim 1, of the formula (1b) in which R5, R6 and M? are as defined in claim 1.

5. An ink according to claim 1, of the formula (1c) in which R5 and R6 are as defined in claim 1, and R11 is hydrogen or methyl.

6. The use of an ink according to any one of claims 1 to 5 in ink-jet printing.

7. A recording material which contains at least one compound of the formula (1) used according to any of claims 1 to 5.

8. A recording material according to claim 7, which is suitable for ink-jet printing.

9. A process for stabilising ink-jet prints, which comprises applying, as ink, an aqueous solution containing a water-soluble dye and at least one compound of the formula (I) to a recording material for ink-jet printing, and drying the ink.

10. A process for stabilising ink-jet prints, which comprises applying, as ink, an aqueous solution containing a water-soluble dye to a recording material for ink-jet printing which contains at least one compound of the formula (1), and drying the ink.

11. A compound of the formula (1d) in which R1, R8, R60 and R70 are as defined in claim 1.

FD 4.3/KH/ga*/hdr*