WO2011048405A1

WO2011048405A1 - Mixtures of magenta dyes and inks for use in ink-jet printing

Info

Publication number: WO2011048405A1
Application number: PCT/GB2010/051717
Authority: WO
Inventors: Gavin Wright; Christine Stewart-Liddon
Original assignee: Fujifilm Imaging Colorants Limited
Priority date: 2009-10-21
Filing date: 2010-10-12
Publication date: 2011-04-28
Also published as: GB0918435D0

Abstract

A mixture of dyes and salts thereof comprising: (a) a dye of Formula (1) and salts thereof: wherein R¹ and R² are independently H or optionally substituted alkyl; R³ is optionally substituted alkyl, optionally substituted aryl or optionally substituted heteroaryl; and n is greater than 0; and (b) an acid red xanthene dye and salts thereof wherein the ratio of the components (a) and (b) is in the range of from 95:5 to 5:95 parts by weight. Also compositions, inks, printing processes, printed materials and ink-jet cartridges.

Description

MIXTURES OF MAGENTA DYES AND INKS FOR USE IN INK-JET PRINTING

This invention relates to dyes mixtures, to compositions and inks for ink-jet printers, to printing processes, to printed substrates and to ink-jet printer cartridges.

Ink-jet printing is a non-impact printing technique in which droplets of ink are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate. The set of inks used in this technique typically comprise yellow, magenta, cyan and black inks.

With the advent of high-resolution digital cameras it is becoming increasingly common to print photographs using an ink-jet printer.

While ink-jet printers have many advantages over other forms of printing and image development there are many technical challenges to be addressed. For example, there are the contradictory requirements of providing ink colorants that are soluble in the ink medium and yet display excellent water-fastness (i.e. prints do not run or smudge when printed). The inks also need to dry quickly to avoid sheets sticking together after they have been printed, but they should not form a crust over the nozzles in the printer head. Storage stability is also important to avoid particle formation, in the ink cartridge, which could block the tiny print head nozzles. This is important since consumers can keep an ink-jet ink cartridge for several months. Furthermore, and especially important with photographic quality reproductions, the resultant images should not bronze or fade rapidly on exposure to light or common oxidising gases such as ozone.

For high quality photorealistic ink-jet printing it is particularly important that the shade and chroma of each colorant is exactly right so that any image may be optimally reproduced. To achieve this more than one colorant may be used in the ink.

Selecting which colorants to use in an ink is an art in itself since the chemist has to identify which mixture of colorants will yield a print with the required optical properties on a variety of diverse substrates. The chemist must also ensure that the selected mixture of colorants yield an ink which meets the demanding performance criteria as set out above. They also have to minimise the cost of the colorant(s), the most expensive component of the ink, without adversely effecting the inks performance.

The present invention provides a mixture of dyes and salts thereof comprising:

(a) a dye of Formula (1 ) and salts thereof:

Formula (1 )

wherein:

R¹ and R² are independently H or optionally substituted alkyl;

R³ is optionally substituted alkyl, optionally substituted aryl or optionally substituted heteroaryl; and

n is greater than 0: and

(b) an acid red xanthene dye and salts thereof:

wherein the ratio of the components (a) and (b) is in the range of from 95:5 to 5:95 parts by weight.

Preferably R¹ is methyl or ethyl.

Preferably R² is methyl.

Preferably R³ is Ci_-8alkyl, phenyl, naphthyl or a heteroaryl ring containing at least one nitrogen. More preferably R³ is t-butyl, phenyl, naphthyl or pyridyl.

Preferably n is in the range of 3 to 6. More preferably n is in the range of

3-5.

The sulfonic acid groups, represented by n, may be present as a substituent on any suitable site on compounds of Formula (1 ).

Preferably when R³ is t-butyl then n is 4 with one sulfonic acid on each of the component aniline and benzothiazole rings.

Preferably if R³ is phenyl then n is 5 with one sulfonic acid on each of the component aniline and benzothiazole rings and one on the R³ phenyl.

Preferably the acid red xanthene dye is selected from the group consisting of C.I. Acid Red 50 and salts thereof, C.I. Acid Red 52 and salts thereof and C.I. Acid Red 289 and salts thereof. More preferably the acid red xanthene dye is C.I. Acid Red 52 and salts thereof or C.I. Acid Red 289 and salts thereof.

Preferably the acid red xanthene dye and salts thereof is a single dye. However in some embodiments it is preferable to use a mixture of two or more acid red xanthene dyes and salts thereof. When a mixture of acid red xanthene dyes and salts thereof is used the acid red dyes are preferably C.I. Acid Red 52 and salts thereof and C.I. Acid Red 289 and salts thereof:

C.I. Acid Red 52 has the following structure:

C.I. Acid Red 52 and C.I. Acid Red 289 are commercially available from a number of suppliers. Preferably prior to use C.I. Acid Red 52 and C.I. Acid Red 289 are purified so as to convert them to a form suitable for ink-jet printing. Preferred purification steps include reverse osmosis to remove inorganic impurities and screening to remove particulate matter.

Preferably the ratio of the components (a) and (b) is in the range of from 95:5 to 25:75 parts by weight, more preferably in the range of from 75:25 to 25:75 and especially in the range of from 85:15 to 65:35 parts by weight.

The mixture of dyes according to the present invention may be used in the preparation of magenta inks for use in ink-jet printing. They may also be used to shade other coloured inks.

The dyes of Formula (1 ) are among the most effective of all magenta ink-jet dyes. However, they are extremely expensive to make. The applicants have found that by mixing the dyes of Formula (1 ) with the much cheaper acid red xanthene dye it is possible to obtain a dye mixture which surprisingly shows a technical performance close to that seen with the dyes of Formula (1 ) alone but which has a much lower unit cost.

Acid and basic groups on the dyes shown herein, particularly acid groups, are preferably in the form of a salt. Thus, the Formulae shown herein include the compounds in free acid and in salt form.

Preferred salts are alkali metal salts, especially lithium, sodium and potassium, ammonium and substituted ammonium salts (including quaternary amines such as ((CH₃)₄N⁺) and mixtures thereof. Especially preferred are salts with sodium and lithium.

The dyes disclosed herein may be converted into a salt using known techniques. The dyes disclosed herein may exist in tautomeric forms other than those shown in this specification. These tautomers are included within the scope of the present invention.

The dyes of Formula (1 ) may be prepared using those processes described in US 7,201 ,477 which is incorporated herein by reference.

According to a second aspect of the present invention there is provided a composition comprising a mixture of dyes and salts thereof, as described in the first aspect of the invention, and a liquid medium.

Preferred compositions according to the second aspect of the invention comprise:

(a) from 0.01 to 30 parts of a mixture of dyes and salts thereof according to the first aspect of the invention; and

(b) from 70 to 99.99 parts of a liquid medium;

wherein all parts are by weight.

Preferably the number of parts of (a)+(b)=100.

The number of parts of component (a) is preferably from 0.1 to 20, more preferably from 0.5 to 15, and especially from 1 to 5 parts. The number of parts of component (b) is preferably from 80 to 99.9, more preferably from 85 to 99.5 and especially from 95 to 99 parts.

Preferably component (a) is completely dissolved in component (b).

Preferably component (a) has a solubility in component (b) at 20°C of at least 10%. This allows the preparation of liquid dye concentrates that may be used to prepare more dilute inks and reduces the chance of the dye precipitating if evaporation of the liquid medium occurs during storage.

The inks may be incorporated in an ink-jet printer as a high concentration magenta ink, a low concentration magenta ink or both a high concentration and a low concentration ink. In the latter case this can lead to improvements in the resolution and quality of printed images. Thus the present invention also provides a composition (preferably an ink) where component (a) is present in an amount of 2.5 to 7 parts, more preferably 2.5 to 5 parts (a high concentration ink) or component (a) is present in an amount of 0.5 to 2.4 parts, more preferably 0.5 to 1 .5 parts (a low concentration ink).

Preferred liquid media include water, a mixture of water and organic solvent and organic solvent free from water. Preferably the liquid medium comprises a mixture of water and organic solvent or organic solvent free from water.

When the liquid medium (b) comprises a mixture of water and organic solvent, the weight ratio of water to organic solvent is preferably from 99:1 to 1 :99, more preferably from 99:1 to 50:50 and especially from 95:5 to 80:20. It is preferred that the organic solvent present in the mixture of water and organic solvent is a water-miscible organic solvent or a mixture of such solvents. Preferred water-miscible organic solvents include d-₆-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol and cyclohexanol; linear amides, preferably dimethylformamide or dimethylacetamide; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscible ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1 ,2,6-hexanetriol; mono-Ci_-4-alkyl ethers of diols, preferably mono-Ci_-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2-(2- methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2- methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides, preferably 2-pyrrolidone, N-methyl- 2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1 ,3-dimethylimidazolidone; cyclic esters, preferably caprolactone; sulfoxides, preferably dimethyl sulfoxide; and sulfones, preferably sulfolane. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-miscible organic solvents.

Especially preferred water-miscible organic solvents are cyclic amides, especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone; diols, especially 1 ,5-pentane diol, ethyleneglycol, thiodiglycol, diethyleneglycol and triethyleneglycol; and mono-Ci_-4-alkyl and Ci_-4-alkyl ethers of diols, more preferably mono- Ci_-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxy-2-ethoxy-2-ethoxyethanol.

When the liquid medium comprises organic solvent free from water, (i.e. less than 1 % water by weight) the solvent preferably has a boiling point of from 30 to 200°C, more preferably of from 40 to 150°C, especially from 50 to 125°C. The organic solvent may be water-immiscible, water-miscible or a mixture of such solvents. Preferred water-miscible organic solvents are any of the hereinbefore- described water-miscible organic solvents and mixtures thereof. Preferred water- immiscible solvents include, for example, aliphatic hydrocarbons; esters, preferably ethyl acetate; chlorinated hydrocarbons, preferably CH₂CI₂; and ethers, preferably diethyl ether; and mixtures thereof.

When the liquid medium comprises a water-immiscible organic solvent, preferably a polar solvent is also included since this may enhances the solubility of the dyes in the organic liquid medium. Examples of suitable polar solvents include Ci_-4-alcohols.

In view of the foregoing preferences it is especially preferred that where the liquid medium is organic solvent free from water it comprises a ketone (especially methyl ethyl ketone) and/or an alcohol (especially a Ci_-4-alkanol, more especially ethanol or propanol).

The organic solvent free from water may be a single organic solvent or a mixture of two or more organic solvents. It is preferred that when the liquid medium is organic solvent free from water it is a mixture of 2 to 5 different organic solvents. This allows a liquid medium to be selected that gives good control over the drying characteristics and storage stability of the ink.

Liquid media comprising organic solvent free from water are particularly useful where fast drying times are required and particularly when printing onto hydrophobic and non-absorbent substrates, for example plastics, metal and glass.

The liquid media may of course contain additional components conventionally used in ink-jet printing inks, for example viscosity and surface tension modifiers, corrosion inhibitors, biocides, kogation reducing additives and surfactants which may be ionic or non-ionic.

Although not usually necessary, further colorants may be added to the ink to modify the shade and performance properties.

It is preferred that the composition according to the invention is ink suitable for use in an ink-jet printer. Ink suitable for use in an ink-jet printer is ink which is able to repeatedly fire through an ink-jet printing head without causing blockage of the fine nozzles. To do this the ink must be particle free, stable (i.e. not precipitate on storage), free from corrosive elements (e.g. chloride) and have a viscosity which allows for good droplet formation at the print head.

Ink suitable for use in an ink-jet printer preferably has a viscosity of less than 20 cP, more preferably less than 10 cP, especially less than 5 cP, at 25°C.

Ink suitable for use in an ink-jet printer preferably contains less than 500ppm, more preferably less than 250ppm, especially less than 100ppm, more especially less than 10ppm in total of divalent and trivalent metal ions (other than any divalent and trivalent metal ions bound to a colorant of Formula (1 ) or any other colourant or additive incorporated in the ink).

Preferably ink suitable for use in an ink-jet printer has been filtered through a filter having a mean pore size below Ι Ομηη, more preferably below 3μηη, especially below 2μηη, more especially below 1 μηη. This filtration removes particulate matter that could otherwise block the fine nozzles found in many ink-jet printers. Preferably ink suitable for use in an ink-jet printer contains less than 500ppm, more preferably less than 250ppm, especially less than 100ppm, more especially less than 10ppm in total of halide ions, particularly chloride ions.

A third aspect of the invention provides a process for forming an image on a substrate comprising applying a composition, preferably ink suitable for use in an ink-jet printer, according to the second aspect of the invention, thereto by means of an ink-jet printer.

The ink-jet printer preferably applies the ink to the substrate in the form of droplets that are ejected through a small orifice onto the substrate. Preferred ink- jet printers are piezoelectric ink-jet printers and thermal ink-jet printers. In thermal ink-jet printers, programmed pulses of heat are applied to the ink in a reservoir by means of a resistor adjacent to the orifice, thereby causing the ink to be ejected from the orifice in the form of small droplets directed towards the substrate during relative movement between the substrate and the orifice. In piezoelectric ink-jet printers the oscillation of a small crystal causes ejection of the ink from the orifice.

The substrate is preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper.

Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character. Photographic quality papers are especially preferred. Photographic quality paper give a print with a finish which is similar in quality to that typically seen with silver halide photo printing.

A fourth aspect of the present invention provides a material preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper more especially plain, coated or treated papers printed with a mixture of dyes and salts there of as described in the first aspect of the invention, a composition according to the second aspect of the invention or by means of a process according to the third aspect of the invention.

It is especially preferred that the printed material of the fourth aspect of the invention is a print on a photographic quality paper printed using a process according to the third aspect of the invention.

A fifth aspect of the present invention provides an ink-jet printer cartridge comprising a chamber and a composition, preferably ink suitable for use in an ink- jet printer, wherein the composition, preferably the ink, is in the chamber and the composition is as defined and preferred in the second aspect of the present invention. The cartridge may contain a high concentration ink and a low concentration ink, as described in the second aspect of the invention, in different chambers.

The invention is further illustrated by the following Examples in which all parts and percentages are by weight unless otherwise stated.

Examples 1 -8

The following dyes, which are Examples of component A, were prepared using those processes as described in US 7,201 ,477:

Example 9

Preparation of Inks

Inks were prepared by dissolving 3 parts (in total) by weight of dyes according to Table 1 in 97 parts by weight of a liquid medium comprising % by weight:

Diethylene glycol 7%

Ethylene glycol 7%

2-Pyrollidone 7%

Surfynol^R™ 465 1 %

Tris buffer 0.2%

Water 77.8%

and adjusting the pH of the ink to 8-8.5 using sodium hydroxide. Surfynol 465 is a surfactant from Air Products. Table 1

Ink-jet Printing

Inks prepared as described above were filtered through a 0.45 micron nylon filter and then incorporated into empty print cartridges using a syringe.

These inks were printed on to Canon Professional Photo Paper (PR101 ). The optical density and colouristic values of the prints were determined from reflectance spectra obtained using a Gretag^R™ spectrolino spectrophotometer set to the following parameters:

Measuring Geometry 0 45°

Spectral Range 380 - 730nm

Spectral Interval 10nm

llluminant D65

Observer 2° (CIE 1931 )

Density Ansi A

External Filler None

Calculation of the Predicted ROD

The one constant Kubelka-Munk model was used to convert the reflectance spectrum (R) into the ratio of the absorption coefficient (K) to scattering coefficient (S) (Kang, H.R. J. Imag. Tech., 17, 2, 1991 , 76-83). This ratio is then treated as a single entity.

This model assumes that there are no boundaries in the system (i.e. no correction is used for the refractive index change between air and print) and the scattering is assumed to be constant. Also the K/S ratios for individual components are assumed to be additive at each wavelength: Thus The K/S values for the wavelength range of 380 to 730nm for the inks were calculated from the reflectance spectra measured at 100% print depth as described above.

The K/S values for the prints of the inks described above were scaled to reflect the dye concentration in a particular ink.

The scaled K/S spectra for each dye on each paper were then summed at each wavelength to give the K/S values for the blended ink spectrum.

The blended ink K/S spectrum was then converted into the corresponding reflectance spectrum using the following equation, where R = reflectance. The K/S ratio is again treated as a single entity.

Table 2

Table 2 below shows the results of the optical density measurements and the colouristic values obtained compared with those calculated according to the Kubelka-Munk model.

From Table 2 it can be seen that when the two dyes are blended, as in the ink examples 2, 3 and 4, then they have better values (higher optical density and chroma) than would be expected from the calculated spectra.

Further Inks

The inks described in Tables A and B may be prepared using a dye mixture comprising 4 parts of the dye of any one of Examples 1 to 8 and 2 parts of C.I. Acid Red 52 or C.I. Acid Red 289. The dye indicated in the first column is dissolved in 100 parts of the ink as specified in the second column on. Numbers quoted in the second column onwards refer to the number of parts of the relevant ink ingredient and all parts are by weight. The pH of the ink may be adjusted using a suitable acid or base. The inks may be applied to a substrate by ink-jet printing.

The following abbreviations are used in Tables A and B:

PG = propylene glycol

DEG = diethylene glycol

NMP = N-methyl pyrrolidone

DMK = dimethylketone

IPA = isopropanol

2P = 2-pyrrolidone

MIBK = methylisobutyl ketone

P12 = propane-1 ,2-diol

BDL = butane-2,3-diol

TBT = tertiary butanol

TABLE A

Dye Water PG DEG NMP DMK I PA 2P MIBK

2.0 80 5 6 4 5

3.0 90 5 5

10.0 85 3 3 3 6

2.1 91 8 1

3.1 86 5 4 5

1 .1 81 9 10

2.5 60 4 15 3 3 6 5 4

5 65 20 10 5

2.4 75 5 10 5 5

4.1 80 3 5 2 10

3.2 65 5 4 6 5 10 5

5.1 96 4

10.8 90 5 5

10.0 80 2 6 2 5 1 4

1 .8 80 5 15

2.6 84 1 1 5

3.3 80 4 10 6

12.0 90 7 3

5.4 69 2 20 2 1 3 3

6.0 91 4 5

TABLE B

Dye Water PG DEG NMP TBT BDL PI2

3.0 80 20

9.0 90 5 5

1 .5 85 5 5 5

2.5 90 6 4

3.1 82 4 8 6

0.9 85 10 5

8.0 90 5 5

4.0 70 10 4 5 1 1

2.2 75 10 10 3 2

10.0 91 9

9.0 76 9 7 3 5

5.0 78 5 1 1 6

5.4 86 7 7

2.1 70 5 10 5 5 5

2.0 90 10

2 88 12

5 78 5 7 10

8 70 2 20 8

10 80 10 10

10 80 20

Claims

A mixture of dyes and salts thereof comprising

a dye of Form la (1 ) and salts thereof:

Formula (1 )

wherein:

R¹ and R² are independently H or optionally substituted alkyl;

n is greater than 0: and

(b) an acid red xanthene dye and salts thereof:

2. A mixture of dyes and salts thereof as claimed in claim 1 wherein R¹ is methyl or ethyl.

3. A mixture of dyes and salts thereof as claimed in either claim 1 or claim 2 wherein R² is methyl.

4. A mixture of dyes and salts thereof as claimed in any one of the preceding claims wherein R³ is t-butyl, phenyl, naphthyl or pyridyl.

5. A mixture of dyes and salts thereof as claimed in any one of the preceding claims wherein n is in the range of 3 to 5.

6. A mixture of dyes and salts thereof as claimed in any one of the preceding claims wherein R³ is t-butyl and n is 4 with one sulfonic acid on each of the component aniline and benzothiazole rings.

7. A mixture of dyes and salts thereof as claimed in any one of claims 1 to 5 wherein R³ is phenyl and n is 5 with one sulfonic acid on each of the component aniline and benzothiazole rings and one on the R³ phenyl.

8. A mixture of dyes and salts thereof as claimed in any one of the preceding claims wherein the acid red xanthene dye is selected from the group consisting of

C.I. Acid Red 50 and salts thereof, C.I. Acid Red 52 and salts thereof and C.I. Acid Red 289 and salts thereof.

9. A mixture of dyes and salts thereof as claimed in any one of the preceding claims wherein the acid red xanthene dye is C.I. Acid Red 52 and salts thereof or

C.I. Acid Red 289 and salts thereof.

10. A mixture of dyes and salts thereof as claimed in any one of the preceding claims wherein the ratio of the components (a) and (b) is in the range of from 85:15 to 65:35 parts by weight.

1 1 . A composition comprising a mixture of dyes and salts thereof, as described in any one of claims 1 to 10, and a liquid medium.

12. A composition as claimed in claim 10 which is ink suitable for use in an ink- jet printer.

13. A process for forming an image on a substrate comprising applying ink suitable for use in an ink-jet printer, according to claim 12, thereto by means of an ink-jet printer.

14. A material printed with a mixture of dyes and salts thereof as described in any one of claims 1 to 10.

15. An ink-jet printer cartridge comprising a chamber and ink suitable for use in an ink-jet printer, according to claim 12, wherein the ink is in the chamber.