GB2134129A - Aqueous ink for ink-jet recording and ink-jet recording method using such ink - Google Patents

Abstract

An aqueous ink suitable for ink-jet recording comprises: (a) water; (b) a humectant; and (c) a water-soluble dye of the formula: <IMAGE> in which: R<1> is a hydrogen atom or an alkyl group; R<2> and R<3> are each a group of the formula <IMAGE> (in which R<7> is an alkyl or amino group M<+> is an alkali metal cation or an ammonium or substituted ammonium cation, m is 0, 1, 2 or 3, and n is 0, 1 or 2); R<4> is a halogen atom or an alkyl group; R<5> is a group -SO<->3 or -COO<->; R<6> is a hydrogen or halogen atom or a group -SO<->3M<+> (in which M<+> has the meaning defined above); p is 0, 1 or 2; and q is 0, 1 or 2. An ink-jet recording process comprises applying the ink to a recording medium containing a water-soluble salt of a polyvalent metal, an alkylamine salt, a quaternary ammonium salt, a compound containing at least two amino groups, a compound containing at least two amido groups of a basic polymeric material.

Description

SPECIFICATION Aqueous ink for ink-jet recording and ink-jet recording method using such ink The present invention relates to an aqueous ink for ink-jet recording and to an ink-jet recording method using the aqueous ink.

There have recently been researches, in the field of the ink-jet recording technique, aimed at improving the reproduction of coloured images, In particular, various studies have been made to develop inks capable of reproducing the three primary colours; cyan, magenta and yellow. At present, an ink capable of yielding images in a satisfactory magenta colour, having high water and light resistance and suitable for use in ink-jet recording has not been obtained. For instance, inks containing C.l. Acid Red 52 or C.l. Acid Red 227, both conventional magenta dyes, have the shortcomings that images made from the inks have poor colour tone and do not have sufficient light resistance for practical use.Further, inks containing C.l. Acid Red 92 or C.l. Acid Red 94, both other conventional magenta dyes, have the shortcomings that images made from the inks have poor light resistance and poor water resistance.

Furthermore, since there has not been obtained a magneta ink which is capable of yielding a perfect magenta colour, it is necessary, when attempting to produce a magenta colour, to select from a number of magenta inks an ink capable of yielding a colour which looks most similar to an ideal magenta. Occasionally, it is necessary to resort to particular colour correction means in order to reproduce magenta images which are well balanced in colour tone.

Generally, of the yellow, magenta and cyan dyes, the magenta dyes have peculiar reflection spectra and images made from magenta dyes tend most to fade or disappear when exposed to light, thus causing a significant decrease in image density and an improper colour balance in the images.

For the production of an ideal magenta colour by a magenta dye, it is required that the dye sufficiently reflect light in two separate reflection spectral bands, that is in the band ranging from 400 nm to 500 nm and in the band ranging from 600 nm to 700 nm, with a good balance of the light reflection in the two bands. However, it is extremely difficult for magenta dyes in general use to meet this requirement due to their chemical structures. The imbalance of the light reflection in the two bands makes the images produced reddish or bluish.Further, since dyes capable of yielding a colour very similar in colour tone to magenta contain strained chemical bonds in the molecule, they are vunerable to external effects, such as exposure to light, and their structure tends to be changed or decomposed by such effects, with the result that, in comparison with images formed from other dyes, images formed from the magenta dyes fade more easily.

In order to improve the shortcomings of the conventional magenta inks, in particular, for use in ink-jet recording, various proposals have been made, such as colour correction, particular choices of components in ink compositions and the use of a particular recording medium in combination therewith. However, a magenta ink which is sufficiently suitable for practical use in ink-jet recording has not yet been proposed.

An ink for use in ink-jet printing should satisfy the following conditions in order to yield a good print.

Firstly, in order that the ink be compatible with ink droplet formation and control of the direction of the ejected ink droplet streams, its viscosity, surface tension, specific electric conductivity, and density should each fall within certain appropriate ranges.

Secondly, no precipitates should be formed, due to coagulation, precipitation, chemical change of slightly soluble components or other causes, in the ink during an extended period of continuous use or storage, or during the periods when the apparatus is not in use. Not should the physical properties of the ink otherwise change during the above-mentioned periods. If the separated solid components of viscous materials in the ink become affixed around the nozzles, or if the physical properties of the ink change, deviating from the predetermined physical properties at the time of the preparation, the desired printing quality, the desired ink ejection stability, and the desired ink ejection response cannot be obtained since the ink ejection is generally performed from nozzles with a diameter of about 10-60 microns.

Thirdly, it is desirable that the ink should provide adequately high contrast and clearness in the printed image. In a conventional ink, the contrast and clearness in the printed images are increased by increasing the dye content of the ink. However, as the dye content increases, plugging of the nozzles occurs more easily. Therefore, there is desired a dye which is highly soluble in the solvent of the ink and has a high extinction coefficient. Such a dye, however, has not yet been obtained.

Fourthly, the images printed from the ink should dry rapidly. In a conventional ink, a relatively large amount of a humectant is present in the ink in order to prevent the nozzles from being plugged with the dried ink during the periods when the recording apparatus is not in use. Because of the use of such a large amount of humectant, special paper capable of absorbing the ink quickly and well is employed for rapid drying of the printed images. However, the use of such special paper brings about spreading of the printed images and, of course, other paper such as plain paper cannot be used with the ink.

Fifthly, an ink for ink-jet recording should be such that the printed images are resistant to water, light and physical wear and are clear.

Many proposals have been made for a magenta ink for ink-jet printing, but from the viewpoint of practical use, a satisfactory ink which is capable of meeting the above-described requirements has not been found.

According to the invention there is provided an aqueous ink suitable for ink-jet recording comprising: (a) water; (b) a humectant; and (c) a dyestuff of the formula:

in which: R1 is a hydrogen atom or an alkyl group; R2 and R3 are each a group of the formula:

(in which: R7 is an alkyl or an amino group; M+ is an alkali metal, ammonium or substituted ammonium cation; mist, 1 ,2 or 3; and nits0,1 or 2): R4 is a halogen atom or an aluyl group; R5 is a group -SO3 or --COO-; R6 is a hydrogen or halogen atom or a group -SO3M+ (in which M has the meaning defined above); pisO, 1 or2;and qisO, 1 or2.

The invention also provides an ink-jet recording method in which images are recorded by use of the above aqueous ink on a recording medium containing at least one component selected from watersoluble salts of multivalent metals (i.e. metals having a valence of two or more), alkylamine salts, quaternary ammonium salts, compounds containing two or more amino groups, compounds containing two or more amido groups, and basic polymeric materials.

A principal component of the ink of the invention is the dyestuff of formula (I). A list of representative examples of such dyestuffs is given in Table 1 below.

In the dyestuff of formula (I) the cation M+ may for example, be Na+, Li+, K+, -N+H(CH2CH2OH)3, -N+H(CH3), -N+H(C2H5)3 or -NH+4. Thus M+ may for example be one of these in compounds 1-17 listed in Table 1 and where a dyestuff contain two or more cations M+ there may be the same or different. When the compounds R', R4 and R7 are alkyl groups they may suitably be lower alkyl groups such as methyl, ethyl, propyl or butyl groups.

Table 1

The magenta dyes for use in the present invention have the following properties.

(1) In terms of GATF colour evaluation values, the hue error of the dyes is 450 or less and their greyness is 35 or less. These values indicate that the dyes have a colour tone which is very close to the colour tone of an ideal magenta.

(2) They are highly soluble in (i) polyhydric alcohols and alkyl ethers thereof (which may be employed as components of humectants in the aqueous inks of the invention) and in (ii) water which is one of the main components of the aqueous inks of the invention. Due to this high solubility in polyhydric alcohols, alkyl ethers and water, high reliability of ink droplet ejection is obtained. The maximum solubility of the dyes in pure water is 18 wt.% or more, and their maximum solubility in diethylene glycol is 15 wt.% or more.

(3) Although the dyes are xanthene dyes, images formed from the dyes are highly resistant to light. For instance, the fading ratio thereof is 5% or less when exposed to the light of a carbon arc lamp for 6 hours.

When printing is effected with the dyes onto a recording medium containing a water-soluble salt of a multivalent metal, an alkylamine salt, a quaternary ammonium salt, a compound containing two or more amino groups, a compound containing two or more amido groups, or a basic polymeric material, the water resistance of the printed images is particularly high. For instance, when the images are immersed in water at 300C for 1 minute, the fading ratio thereof is 3% or less.

An aqueous ink of the invention comprises a dye of formula (I),water and a humectant. When necessary, a water-soluble preservative or anti-mould agent, a solubility-increasing agent for increasing the solubility of the dye, a pH adjustment agent, a viscosity adjustment agent and other additives can also be added to the ink.

The humectant may comprise a polyhydric alcohol and/or an alkyl ether of a polyhydric alcohol.

The humectant is preferably present in the ink in an amount of from 5 to 30% by weight.

Examples of polyhydric alcohols which may be employed as humectants include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin, polyethylene glycols and polypropylene glycols. Examples of alkyl ethers of polyhydric alcohols include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether and triethylene glycol monoethyl ether.

A mixture of glycerin and diethylene glycol is an especially effective humectant. A mixture of glycerin and diethylene glycol in a ratio of glycerin to diethylene glycol of from 1:1 to 1:5 is particularly useful, by which the initial properties of the ink can be maintained even for an extended period of continuous use of storage, or during the periods when the apparatus is not in use, whereby reliable ink droplet stability and ink droplet ejection response of the ink, particularly after a prolonged period of non-use of the apparatus, are obtained.

The mixture of glycerin and diethylene glycol may additionally contain one or more of the abovementioned other humectants; preferably in an amount of not more than 40 wt.% of the mixture of glycerin and diethylene glycol.

Water-soluble preservative and anti-mould agents which may be employed include, for example, 2,2-dimethyl-6-acetoxy-dioxane-1,3, sodium dehydroacetate, butyl p-hydroxy benzoate, potassium sorbate, 2-pyridinethiol-1-oxide sodium salt, anionic surface active agents, Deltop 33 (commercially available from Takeda Chemical Industries Ltd.), and Hokucide LX-2 (commercially available from Hokko Chemical Industry Co., Ltd.).

Water is the main solvent component of the inks of the invention and the following solubilityincreasing agents for increasing the solubility of the dyes can be mixed with water: amine derivatives, such as triethanolamine; nitrogen-containing heterocyclic compounds, such as N-methyl-2pyrrolidone, 2-pyrrolidone and 1 ,3-dimethyl imidazolidinone; intermolecular esters of hydroxycarboxylic acids, such as valerolactone and caprolactone; and acetates of hydroxyalkyl ethers, such as ethylene glycol monomethyl ether acetate.

Any viscosity adjustment agent can be used from among many generally well known chemicals, provided it does not have adverse effects on the solvents and dyes used. Examples of suitable viscosity adjustment agents include polyvinyl alcohol, hydroxyethylcellulose, carboxymethylcel lu lose, methylcellulose, water-soluble acrylic resin, gum arabic, dextrin, casein, pectin, gum tragacanth and polyvinyl pyrrolidone.

Any suitable material may be used as pH adjustment agent provided it does not have an adverse effect on the ink and can adjust the pH of the ink to pH of, preferably, 9.0 to 1 1.0. Examples of such pH adjustment agents include amines, such as diethanolamine and triethanolamine; alkali metal hydroxides, such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide; and alkali metal carbonates, such as lithium carbonate, sodium carbonate and potassium carbonate.

Other additives which may be used are as follows.

In order to maintain the specific electric conductivity of the ink to above 1 m-'. cm-' (at 250C), specific electric conductivity adjustment agents may be used and examples of such agents include inorganic salts such as potassium chloride, ammonium chloride, sodium sulphate and sodium carbonate; and water-soluble amines such as triethanolamine.

Chelating agents such as, for example, sodium ethylenediaminetetraacetate, trisodium nitrilotriacetate, hydroxyethyl ethylenediamine trisodiu m acetate, diethylene triamino pentasodiu m acetate and uramil disodium acetate.

Rust preventing agents for the nozzles such as, for example, acid sulphites, sodium thiosulphate, ammonium thioglycolate, diisopropyl ammonium nitrite, pentaerythritol tetranitrate and dicyclohexyl ammonium nitrite.

Other additives, for example, water-soluble ultraviolet-ray-absorbing agents, water-soluble infrared-ray-absorbing agents and magnetic fluids in which ultrafine magnetite particles are dispersed, and latex emulsions can be employed as thought necessary in specific embodiments of an aqueous ink for ink-jet recording or for use in a specific apparatus.

In an ink-jet recording method according to the present invention, images are recorded by use of the above-described aqueous inks on a recording medium which contains a treatment agent which is a water-soluble salt of a multivalent metal, an alkylamine salt, a quaternary ammonium salt, a compound containing two or more amino groups, a compound containing two or more amido groups or a basic polymeric material.

The recording medium for use in this ink-jet recording method can be prepared, for example, by the following two methods: In one method, a layer containing a treatment agent is formed on a support material. In the other method, a support material is immersed in a solution containing a treatment agent, so that the support material is impregnated with the treatment agent, without forming the first mentioned layer thereon.

Somehow in the former method, a better result is obtained when a slightly larger amount of the treatment agent is used than in the latter method.

When preparing the recording medium using a water-soluble salt of a multivalent metal, it is preferable to use the salt in an amount of 0.2 g/m2 or more, more preferably in an amount of 1.0 g/m2 or more.

Specific examples of suitable water-soluble metal salts include, as salts of divalent metals, MgCI2, CaBr2, CaCI2, Ca(NO3)2, Cal2, ZnCI2, ZnBr2, Znl2, Zn(ClO3)2, ZnSO4, Zn(NO3)2, Sari2, SrCI2, Sr(NO3)2, BaCI2, Ba(NO3)2, Ba(OH)2, Bawl2, BaBr2,. Fe(NO3)2, Ni(NO3)2, NiSO4, Nix12, CuCI2 and CuSO4; as salts of trivalent metals, AICI3, Al2(SO4)3, Al(NO3)3, ScCI3, Sc(NO3)3, Sc2(SO4)3, Ga(NO3)3, GaCI3, Ga2(SO4)3, InCI3, Fe(NO3)3 and alums; and as salts of tetravalent metals, TiCI4, GeCI4, Zr(SO4)2, SnCI4, Sn(SO4)2 and Pb(CH3COO)2.

Of these water-soluble metal salts, AICI3, Al2(SO4)3, Al(NO3)2, ZnCl2, ZnSO4, SnCI4, Cacti2, MgCI2 and InCI3 are particularly preferred.

When preparing the recording medium using an alkylamine salt as treatment agent, it is preferable to use the alkylamine alkylene in an amount of 0.05 g/m2 or more, more preferably in an amount of 0.2 g/m2 or more. Specific examples of alkylamine salts are the acetates and chlorides of mono-n-alkylamines containing from 10 to 20 carbon atoms.

When preparing the recording medium using a quaternary ammonium salt as treatment agent, it is preferable to use the quaternary ammonium salt in an amount of 0.1 g/m2 or more. Specific examples of quaternary ammonium salts include lauryltrimethylammonium bromide, lauryltrimethylammonium chloride, cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, octaisoquinolinium bromide, octaisoquinolinium chloride, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride.

When preparing the recording medium using a compound containing two or more amino groups of a compound containing two or more amido groups as treatment agent, it is preferable to use the compound in an amount of 0.05 g/m2 or more, more preferably in an amount of 0.1 g/m2 or more.

Specific examples of compounds containing two or more amino groups and compounds containing two or more amido groups are as follows: (1) Condensation products of o- or p-toluidine and formaldehyde, for example,

(2) Menthol derivatives, for example,

(3) Products prepared by addition of epichlorohydrin to ethylenediamine; (4) Aminobenzoate derivatives, for example,

(5) Other compounds having two amino groups, for example,

(amanozine)

(p-aminonorephedrine) and (kynurenine) When preparing the recording medium using a basic polymeric material as treatment agent, it is preferable to use the basic polymeric material in an amount of 0.05 g/m2 or more, more preferably in an amount of 0.1 g/m2 or more.

Specific examples of such basic polymeric materials are (1) polyvinyl compounds containing the following quaternary ammonium salt groups;

(in which each of the groups R is a hydrogen or halogen atom) or an alkyl, phenyl, hydroxyl or alkoxy group; Y represents an ether linkage, an ester linkage, an alkylene group, a group -CH2CH2O- or a phenylene group, and n is an integer of from 10 to 1,000); and (2) natural proteins, such as gelatin and albumin.

When the recording medium is prepared by impregnating a support with a treatment agent, there can be employed as support material, plain paper, non-sized paper or a water-absorbing plastic film, and the support material is impregnated with the treatment agent by immersing the support material in a solution or dispersion of the treatment agent or by applying the solution or dispersion to the support material. For example, as the support material, plain paper with a size degree of 20 sec or less, with a whiteness of 75% or more, with a smoothness ranging from 10 to 1 50 and with an air permeability of 3 sec to 120 sec is employed.

When the recording medium is prepared by forming a layer containing a treatment agent, there may be employed as support material, paper consisting essentially of cellulose, synthetic paper, a plastic film, a glass plate, a metal plate or a metal foil, without taking into consideration the inkabsorbing properties of the support material. The layer formed on the support, in addition to the treatment agent, may additionally comprise a binder agent and other additives such as pigments.

Binder agents for this purpose can be roughly classified into two groups, that is, resin-type binder agents and latex-type binder agents. Examples of resin-type binder agents include oxidized starch, etherified starch, esterified starch, dextrin, casein, gelatin, arabic gum, vegetable protein cellulose, ca rboxymethylcellulose, hydroxyethylcell ulose, cellulose derivatives, polyvinyl alcohol, polyvinylpyrrolidone, maleic anhydride resin, polyvinyl acetate, polyvinyl butyral, polyacrylamide, combinations of the above polymers, copolymers of the above polymers, and modified polymers of the above polymers.Examples of latex-type binder agents include polyvinyl acetate latex, styreneisoprene copolymer latex, styrene-butadiene copolymer latex, acrylic polymer latex, acrylic derivative-vinyl acetate copolymer latex, methyl methacrylate-butadiene copolymer latex, and combinations and modifications of the above latexes.

Examples of pigments which may be present in the layer include clay, talc, diatomaceous earth, calcium carbonate, calcium sulphate, magnesium carbonate, magnesium sulphate, barium sulphate, titanium oxide, zinc oxide, zinc sulfide, zinc carbonate, titanium white, aluminium silicate, silicon oxide, calcium silicate, aluminium oxide, aluminium hydroxide and zeolite. Of these, calcium carbonate, magnesium carbonate, barium sulphate and titanium white are most preferred.

The treatment-agent-containing layer can be prepared by various methods. For example, in one method, a layer consisting of a binder agent and additives is formed on a support material and the treatment agent is then applied to the layer. In another method, a solution or dispersion of a binder agent, additives and treatment agent is applied to the support material and the layer is then dried.

More specifically, in the first mentioned method, a dispersion consisting essentially of a binder agent and additives is applied to a support material (for example, by blade coating, air-knife coating, roll coating, wire bar coating, spray coating, gravure coating or reverse roller coating) and the applied dispersion is dried by application of hot air or heat thereto, with the amount of coating being from 0.1 g/m2 to 60 g/m2, more preferably from 3 g/m2 to 20 g/m2, whereby a first layer is formed on the support material. To the first layer, a liquid containing the treatment agent in an amount of from 0.1 wt.% to 30 wt.% is applied (for example by one of the above-mentioned coating methods) and is then dried, whereby a recording medium for use in the present invention is prepared.

The recording medium which is prepared by the just mentioned method or by impregnating the support material with a treatment agent is then suitably subjected to calendering at a temperature of from 500C to 2000 C, more preferably from 600C to 1200 C, with application of a pressure of from 10 kg/cm to 1 50 kg/cm, more preferably from 50 kg/cm to 80 kg/cm, whereby the recording performance of the recording medium can be improved.

In order that the invention may be well understood the following examples are given by way of illustration only.

Example 1 A mixture of the components listed below was heated to 700C and stirred until completely dissolved. The pH of the mixture was adjusted to 10.0 by the addition of NaOH. The mixture was then filtered twice through a membrane filter with a 0.2 micron mesh, to give an aqueous ink No. 1 according to the present invention.

wt% Dye ( 1 ) in Table 1 (M=Na) 3.0 Diethylene glycol 22.5 Glycerin 7.5 Deltop 33 (commercially available from Takeda Chemical Industries. Ltd.) 0.2 Deionised water 66.8 The ink was then subjected to the following tests: (1) Image clarity and image dryness test The ink was caused to issue from a nozzle with an inner diameter of 30 microns, with vibrations at a frequency of 100 KHz, by which vibrations the ink was ejected in a stream broken into individual drops, and was then caused to impinge on a sheet of commercially available high quality paper, an inkjet recording sheet commercially available from Jujo Paper Mfg. Co., Ltd. and an ink-jet recording sheet commercially available from Mitsubishi Paper Mills, Ltd. As a result, clear images were obtained on each of the sheets.The time required to dry the printed image was not more than 10 seconds at normal room temperature and humidity.

(2) Storage test Samples of the ink were tightly sealed in glass containers and subjected to the following storage tests: a. Stored at -200C for one month; b. Stored at 40C for one month; c. Stored at 200C for one year; and d. Stored at 900C for one week.

No separation of precipitates from the ink was observed on storage. In addition, no changes were detected in the properties or colour of the ink.

(3) Ink droplet ejection stability test Ink-jet printed as was done in the above-described image clarity and image dryness test was continuously performed for 1,000 hours. There was no evidence of either clogging of the nozzle or change in ejection direction of the ink droplets; rather, stable recording was maintained.

(4) Ink droplet ejection response test After ink-jet printing was performed as outlined in (1), the apparatus and ink were allowed to stand at room temperature and humidity for one month, after which they were used again to perform ink-jet recording under the same conditions as previously stated in (1). As in (3) above, there was no change in the ink droplet ejection stability.

The above test was repeated in the same manner, except that the apparatus and ink were allowed to stand at 400 C, 30% RH for one week, instead of being allowed to stand at room temperature and humidity for one month. The result was that again no change was observed in the ink droplet ejection stability.

(5) Light resistance of recorded images The recorded images were exposed to the light of a carbon arc lamp for 6 hours. The fading ratio of the images was not more than 5%.

Examples 2-5 and comparative examples 1-3 The procedure of Example 1 was repeated using the dyestuffs and preservatives listed in Table 2 and using the dyestuff and water in the amounts listed in the Table, the amounts of diethylene glycol, glycerin and preservative being as in Example 1.

Table 2 Dye Water Example amount amount No. Dye (wit.%) Preservative (wit.%) 2 No. 2 in Table 1 (M=Li) 2.5 Hokucide LX-2 67.3 3 No. 3 in Table 1 (M=Li) 3.0 Deltop 33 66.8 4 No. 6 in Table 1 (M=Na) 3.0 Hokucide LX-2 66.8 5 No.9 in Table 1 (M=Li) 2.5 Deltop 33 67.3 Comp. 1 C. Acid Red 92 3.0 Deltop 33 66.8 Comp. 2 C.l. Acid Red 52 2.5 Deltop 33 67.3 Comp. 3 C.I. Direct Red 9 2.5 Deltop 33 67.3 The resultant inks were subjected to the same tests as described in Example 1.

The results were as shown in Table 3.

Table 3 Compara- Compara- Compara Examples tive tive tive 2-5 Examples Example2 Example3 Image Clarity a Image Dryness Good Good Good Good Preservability Good Poor Poor Good Ink Droplet Ejection Stability Good Good Good Poor Ink Droplet Ejection Response Good Poor Good Poor Light Resistance Good No Good No Good Poor The inks of Examples 2-5 were as good as the ink of Example 1 with respect to image clarity and image dryness, storage, ink droplet ejection stability, ink droplet ejection response and light resistance of the recording images.

In contrast to this, the ink of comparative Example 1 had poor storage and ink droplet ejection response. With respect to the light resistance of the recorded images, this ink was far from practical use. The ink of comparative Example 2 had poor storage and poor light resistance.

The ink of comparative Example 3 had poor ink droplet ejection stability, ink droplet ejection response and light resistance of the recorded images.

Example 8 (a) A mixture of the components listed below was heated to 700 C, stirred until completely dissolved, and then filtered twice through a membrane filter with a 0.45 ,um mesh to give an aqueous ink according to the invention.

wt.% Dye (1) in Tabie 1 (M=Na) 3.0 Glycerin 5.5 Diethylene glycol 16.5 Sodium dehydroacetate 0.2 Sodium thiosulphate 0.01 Sodium ethylenediaminetetraacetate 0.01 Deionised water 74.78 (b) A mixture of the following components was dispersed in a ball mill for 10 hours to give a dispersion.

wt.% Calcium carbonate powder 30 Aluminium hydroxide powder 8 Styrene-butadiene copolymer latex (solid components) 18 Water 44 The dispersion was applied to a sheet of high quality paper having a thickness of 80 ,um by a doctor blade at a rate (based on solids) of 13 g/m2, and was then dried at 1 200C for 5 minutes, whereby a base layer for a recording layer was formed on the paper.

To this base layer, there was applied, by air-knife coating, a 6% aqueous solution of aluminium chloride in a wet coating amount of 30 g/m2 and the applied solution was then dried at 1 00C for 10 minutes to give a recording medium. This recording medium was then calendered at 650C under a pressure of 65 kg/cm, to give an ink-jet recording medium.

(c) Ink-jet printing was performed on recording of medium (b) using the aqueous ink of (a), and the aqueous ink and the printed images were subjected to the following tests: (1) Image clarity and image dryness test (as described in Example 1) Clear images were obtained on the paper. The time required to dry the printed image was not more than 10 seconds at normal room temperature and humidity.

(2) Storage test (as described in Example 1) No separation of precipitates from the ink was observed in storage. In addition, no changes were detected in the properties or colour of the ink.

(3) Ink droplet ejection stability test (as described in Example 1) There was no evidence of either clogging of the nozzle or change in ejection direction of the ink droplets, rather, stable recording was maintained.

(4) Ink droplet ejection response test (as described in Example 1) After standing at room temperature and humidity for one month, there was no change in the ink droplet ejection stability. After standing at 400 C, 30% RH for one week, no change was observed in the ink droplet ejection stability.

(5) Colour evaluation of printed images The colour of the printed images was evaluated with respect to the hue error and greyness thereof in accordance with the GATF Colour Evaluation Method.

(6) Water resistance of printed images The resistance of the printed images to water was measured by immersing the recording medium having the printed images in water at 300C for 1 minute and measuring the change in image density of the printed images, from which the fading ratio thereof was assessed.

(7) Light resistance of printed images The printed images were exposed to the light of a carbon arc lamp for 6 hours. The fading ratio of the reflected image density of the images was calculated in accordance with the following formula: Change in Image Density x100 Initial Image Density The results of the above tests are shown in Table 4.

Example 7 (a) An ink was prepared as described in Example 6 from the following components.

wt.% Dye (1) in Table 1 (M=Li) 4.0 Glycerin 10.0 Diethylene glycol 20.0 Deltop 33 (commercially available from Takeda Chemical Industries, Ltd.) 0.5 Deionized 65.5 (b) A 5 wt.% aqueous solution of polyvinylpyridine bromide was applied to an inkjet printing sheet (commercially available from Mitsubishi Paper Mills, Ltd.) by an air-knife coating method in an amount of 0.5 g/m2 when dried and the sheet was then dried at 1 200C for 5 minutes, to give an ink-jet recording medium.

(c) Ink-jet printing was performed on the recording medium of (b) using the ink of (a) above and the printed images were subjected to the same tests as described in Example 6. The results are shown in Table 4.

Example 8 (a) An ink was prepared as described in Example 6 from the following components.

wt.% Dye (1) (M=Na) 6.0 Diethylene glycol 12.0 Glycerin 4.0 Triethanolamine 5.0 Hokucide LX-2 (commercially available from Hokko Chemical Industri Co.

Ltd.) 0.5 Deionised water 72.5 (b) A 3 wt.% aqueous solution of octadecylammonium acetate was applied at a rate of 0.6 g/m2 when dried to a sheet of plain paper with a size degree of 1 sec and with a thickness of 95 ym, to give an ink-jet recording medium.

(c) Ink-jet printing was performed on the recording medium of (b) using the ink of (a).

The ink and the printed images were subjected to the same tests as described in Example 6. The results are shown in Table 4.

Example 9 (a) An ink was prepared as described in Example 6 from the following components.

wt.% Dye (1 ) in Table 1 (M=Ka) 3.0 Glycerin 5.5 Diethylene glycol 16.5 Potassium dehydroacetate 0.2 Potassium thiosulphate 0.01 Potassium ethylenediaminetetraacetate 0.01 Deionised water 74.78 (b) Ink-jet printing was performed on the recording medium prepared in Example 6 (b) using the aqueous ink of (a), and the aqueous ink and the printed images were subjected to the same tests as described in Example 6. The results are shown in Table 4.

Comparative Example 4 An ink was prepared as described in Example 6 from the following components.

wt.% C.I. Acid Red 92 4.0 Glycerin 10.0 Diethylene glycol 20.0 Deltop 33 (commercially available from Takeda Chemical Industries, Ltd.) 0.5 Deionised water 65.5 Ink-jet printing was performed with this ink on the same commercially available ink-jet printing sheet employed in Example 7.

The ink and the printed images were subjected to the same tests as described in Example 6. The results are shown in Table 4.

Table 4 Compara Example Example Example Example tive 6 7 8 9 Example4 Image Clarity Et Image Dryness Good Good Good Good Good Preservability Good Good Good Good Good Ink Droplet Ejection Stability Good Good Good Good Good Ink Droplet Ejection Response Good Good Good Good Good Hue Error 37 38 41 37 43 Greyness 14 10 12 14 18 Water Resistance 1.3% 2.0% 1.8% 1.3% 48% Light Resistance 3.2% 5.0% 2.4% 3.2% 38% As can be seen from the results shown in Table 3, the images printed on the recording media for use in the present invention are exceedingly resistant to water and light in comparison with the comparative example.

Example 10 (a) An ink was prepared as described in Example 6 from the following components.

wt.% Dye (18) in Table 1 3.0 Glycerin 5.5 Diethylene glycol 16.5 Sodium dehydroacetate 0.2 Sodium thiosulphate 0.01 Sodium ethylenediaminetetraacetate 0.01 Pure water 74.78 (b) A mixture of the following components was dispersed in a ball mill for 10 hours to give a dispersion.

wt.% Calcium carbonate powder 36 Aluminium hydroxide powder 4 Styrene-butadiene copolymer latex (solid components) 18 Casein 5 Water 37 The thus prepared dispersion was applied to a sheet of high quality paper having a thickness of 80 jum by using a doctor blade at a rate (based on solids) of 13 g/m2 and was then dried at 1 200C for 5 minutes, whereby a base layer for a recording layer was formed on the paper.

To this base layer, there was applied, by air-knife coating, a 6% aqueous solution of aluminium chloride at a rate of 1.5 g/m2 when dried and the applied solution was then dried at 1 00C for 10 minutes, so that a recording medium was prepared. This recording medium was then calendered at 650C under a pressure of 65 kg/cm. to give an ink-jet recording medium.

(c) Ink-jet printing was performed on the recording medium of (b) using the ink of (a), by causing the ink to issue from a nozzle with an inner diameter of 30 Mm, with vibrations at a frequency of 1 00 KHz.

The aqueous ink and the printed images were subjected to the same colour evaluation test, water resistance test and light resistance test as described in Example 6.

The results are shown in Table 5.

Example 11 An ink was prepared as described in Example 6, except that the solution was filtered through a 0.25 ssum membrane filter, from the following ingredients.

wt.% Dye (20) in Table 1 4.0 Glycerin 4.0 Diethylene glycol 13.0 Deltop 33 (commercially available from Takeda Chemical Industries, Ltd.) 0.5 Deionized water 78.5 Ink-jet printing was performed on the recording medium of Example 7(b) by use of the above prepared aqueous ink under the same conditions as in Example 6.

The aqueous ink and the printed images were subjected to the same tests as described in Example 6. The results are shown in Table 5.

Example 12 An ink was prepared as described in Example 11 from the following components whereby an aqueous ink No. 1 2 for ink-jet recording according to the present invention was prepared.

wt.% Dye (22) in Table 1 6.0 Diethylene glycol 22.0 Glycerin 6.0 Triethenolamine 5.0 Hokucide LX-2 (commercially available from Hokko Chemical Industry, Co.

Ltd.) 0.5 Deionised water 60.5 Ink-jet printing was performed on the recording medium of Example 8(b) using the above prepared aqueous ink under the same conditions as in Example 6.

The aqueous ink and the printed images were subjected to the same tests as described in Example 6. The results are shown in Table 5.

Comparative Example 5 An ink was prepared as described in Example 11 from the following components.

wt.% C.I. Acid Red 92 4.0 Glycerin 4.0 Diethylene glycol 13.0 Deltop 33 (commercially available from Takeda Chemical Industries, Ltd.) 0.5 Deionised water 78.5 Ink-jet printing was performed on an ink-jet printing sheet (commercially available from Mitsubishi Paper Mills, Ltd.) under the same conditions as in Example 6.

The ink and the printed images were subjected to the same tests as described in Example 1 The results are shown in Table 5.

Table 5 Example Example Example Comparative 10 11 12 Example5 Hue Error 36 39 43 43 Water Resistance 1.3% 2.5% 1.8% 48% Light Resistance 2.8% 1.9% 1.8% 38% As can be seen from the results shown in Table 5, the images printed on the recording mediums for use in the present invention are very resistant to water and light in comparison with the comparative example.

Claims (28)

Claims

1. An aqueous ink suitable for ink-jet recording, comprising: (a) water; (b) a humectant; and (c) a water-soluble dye of the formula:

in which: R1 is a hydrogen atom or an alkyl group; R2 and R3 are each a group of the formula

(in which R7 is an alkyl or amino group M+ is an alkali metal cation or an ammonium or substituted ammonium cation, mis 0, 1 , 2 or 3, and nisO,1 or2); R4 is a halogen atom or an alkyl group; R5 is a group -503 or --COO-; R6 is a hydrogen or halogen atom or a group -SO3M+ (in which M+ has the meaning defined above); pius0,1 or2;and qisO, 1 or2.

2. An ink as claimed in claim 1 in which M+ is a sodium, lithium or potassium cation.

3. An ink as claimed in claim 1, in which M+ is a tris(ss-hydroxyethyl)ammonium trimethylammonium or triethylammonium cation.

4. An ink as claimed in any one of the preceding claims in which the humectant comprises a polyhydric alcohol and/or an alkyl ether of a polyhydric alcohol.

5. An ink as claimed in claim 4 containing from 5 to 30% by weight of humectant.

6. An ink as claimed in claim 4 or claim 5 in which the polyhydric alcohol is ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin, polyethylene glycol or polypropylene glycol.

7. An ink as claimed in any one of claims 4-6 in which the alkyl ether of a polyhydric alcohol is ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether or triethylene glycol monoethyl ether.

8. An ink as claimed in claim 6 in which the humectant comprises a mixture of glycerin and diethylene glycol.

9. An ink as claimed in claim 8, in which the ratio of glycerin to diethylene glycol is from 1:1 to 1:5.

10. An ink as claimed in any one of the preceding claims, further comprising a water-soluble preservative and anti-mould agent.

11. An ink as claimed in any one of the preceding claims, further comprising an agent for increasing the solubility of the dye in the ink, which agent is triethanolamine, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1 ,3-dimethyl imidazolidinone, valerolactone, caprolactone or ethylene glycol monomethyl ether acetate.

12. An ink as claimed in any one of the preceding claims further comprising a viscosity adjustment agent.

13. An ink as claimed in any one of the preceding claims further comprising a pH adjustment agent capable of controlling the pH of the ink to a pH of from 9.0 to pH 1 1.0.

14. An ink as claimed in claim 1 substantially as hereinbefore described with reference to the Examples.

1 5. An ink-jet recording method for recording images on a recording medium in which an ink as claimed in any one of the preceding claims is applied to a recording machine containing a watersoluble salt of a multivalent metal, an alkylamine salt, a quaternary ammonium salt, a compound containing two or more amino groups, a compound containing two or more amido groups, or a basic polymeric material.

1 6. A method as claimed in claim 1 5 in which the recording medium contains at 0.2 g/m2 of multivalent metal salt.

17. A method as claimed in claim 1 5 or claim 1 6 in which the multivalent metal salt is MgCI2, Cabs,, CaCI2, ZnCI2, ZnBr2, Znl2, Zn(ClO3)2, ZnSO4, Zn(NO3)2, Sari2, SrBr2, SrCI2, Sr(NO3)2, BaCI2, Ba(NO3)2, Ba(OH)2, Bal2, BaBr2, Fe(NO3)2, Ni(NO3)2, NiSO4, Nix12, Cut12, CuSO4, AICI3, Al2(SO4)3; Al(NO3)3, ScCI3, Sc(NO3)3, Sc2(SO4)3, Ga(NO3)3, GaCI3, Ga2(SO4)3, InCI3, Fe(NO3)3, ialums, TiCI4, GeCI4, Zr(SO4)2, SnCI4, Sn(SO4)2 or Pb(CH3COO)2.

18. A method as claimed in claim 15 in which the recording medium contains at least 0.05 g/m2 of the alkylamine salt.

19. A method as claimed in claim 15 or claim 18 in which the alkylamine salt is an acetate or chloride of a mono-n-alkylamine containing from 10 to 20 carbon atoms.

20. A method as claimed in claim 15 in which the recording medium contains at least 0.1 g/m2 of quaternary ammonium salt.

21. A method as claimed in claim 15 or claim 20 in which the quaternary ammonium salt is lauryltrimethylammonium bromide, lauryltrimethylammonium chloride, cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, octaisoquinolinium bromide, octaisoquinolinium chloride, hexadecyltrimethylammonium bromide or hexadecyltrimethylammonium chloride.

22. A method as claimed in claim 15 in which the recording medium contains at least 0.5 g/m2 of a compound containing at least two amino groups or a compound containing at least two amido groups.

23. A method as claimed in claim 1 5 or claim 22 in the compound having two or more amino groups is a condensation production of o- orp-toluidine and formaldehyde, an addition compound of epichlorohydrin and ethylene diamine, or an amino benzoate derivative.

24. A method as claimed in claim 15 or claim 22 in which the compound having two or more amido groups is a menthol derivative.

25. A method as claimed in claim 1 5 in which the recording medium contains at least 0.05 g/m2 of basic polymeric material.

26. A method as claimed in any one of claims 1 5-25, in which the recording medium comprises a support material impregnated with a water-soluble salt of a multivalent metal, an alkylamine salt, a quaternary ammonium salt, a compound containing two or more amino groups or a basic polymeric material.

27. A method as claimed as claimed in any one of claims 1 5-25 in which the recording medium comprises a support having formed therein a layer containing a water-soluble salt of a multivalent metal, an alkylamine salt, a quaternary ammonium salt, a compound containing two or more amino groups, a compound containing two or more amido groups or a basic polymeric material.

28. A method as claimed in claim 25 substantially as hereinbefore described with reference to the Examples.