JP2002212470A - Ink jet ink and image forming method - Google Patents

Abstract

(57) [Problem] To provide a conductive inkjet ink excellent in ejection stability and high-temperature storage stability. SOLUTION: The ink of the present invention comprises at least a coloring material,
An inkjet ink comprising water, a water-soluble organic solvent (wetting agent) and a conductive agent, wherein the conductive agent is an ionic substance having a formula weight of 200 or less, and the relative dielectric constant of the ink is 64.0 or more. It is characterized by the following. This ink is
When the conductivity is 0.7 to 50 mS / cm, the conductive agent content is 0.0
Each is preferably 5 to 5% by weight. In Examples, Pigment Yellow 138, polyoxyethylene (n = 40)
A pigment dispersion is prepared from β-naphthyl ether, pionin A-51-B and distilled water, and choline nitrate as a conductive agent, glycerin and diethylene glycol as water-soluble organic solvents, and an anionic surfactant are added.
By mixing, an intended ink was prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive ink-jet ink excellent in discharge stability and high-temperature storage stability, and to an image forming method using the ink.

[0002]

2. Description of the Related Art The ink jet recording system has the advantage that the process is simpler than other recording systems, so that full-color printing is easy, and a high-resolution image can be obtained even with a device having a simple structure. Inkjet recording systems are roughly classified into continuous systems and on-demand systems.Of the continuous systems, charge-controlled inkjet printers require good ink generation to control the generation of droplets and the direction of flight. The conductivity must be set in an appropriate range. In some cases, even in an on-demand system such as a piezo system or a thermal inkjet system, the remaining amount of ink is detected by measuring the conductivity. Usually, surfactants and dyes added to the ink are ionized in the ink and exhibit a certain degree of conductivity. However, this alone is insufficient, and it is necessary to add a conductive agent to impart higher conductivity.

As the conductive agent, JP-A-54-85804, JP-A-55-50073, and JP-A-55-8
2175, JP-A-55-115478, JP-A-56-36559, JP-A-56-16148
No. 0, JP-A-57-83569 and the like. However, the mere use of the conductive agent described in these publications tends to cause clogging due to aggregation of the ink, and the ejection stability and high-temperature storage stability were not sufficient.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a conductive ink jet ink having excellent ejection stability and high-temperature storage stability, and an image forming method using the same. Is to provide.

[0005]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that the use of an ionic substance having a formula weight of 200 or less as a conductive agent and the relative permittivity of ink of 64.0 or more enables The inventors have found that the problem is solved, and reached the present invention.

That is, according to the first aspect of the present invention, in an ink jet ink comprising at least a coloring material, water, a water-soluble organic solvent (wetting agent) and a conductive agent, an ionic substance having a formula weight of 200 or less is used as the conductive agent. And a relative dielectric constant of the ink is 64.0 or more.

According to a second aspect of the present invention, there is provided an ink-jet ink according to the first aspect, wherein the conductivity is not less than 0.7 mS / cm and not more than 50 mS / cm.

The invention according to claim 3 is the invention according to claim 1 or 2
Wherein the content of the conductive agent is 0.05% by weight or more and 5% by weight or less.

According to a fourth aspect of the present invention, there is provided an ink-jet ink according to any one of the first to third aspects, wherein the coloring material is a pigment.
According to a fourth aspect of the present invention, there is provided an ink jet ink characterized in that the pigment is carbon black. Further, in the sixth aspect of the present invention, in the fifth aspect, the pigment is a self-dispersible carbon black. It is ink for use.

[0010] The invention according to claim 7 is the ink jet ink according to claim 4, wherein the pigment is Pigment Yellow 138. The invention according to claim 8 is the ink according to claim 4, wherein the pigment is Pigment Red 122.
The invention according to claim 9 is the inkjet ink according to claim 4, wherein the pigment is Pigment Blue 15.

According to a tenth aspect of the present invention, in any one of the fourth to ninth aspects, the pigment has an average particle diameter of 30 nm or more.
An ink-jet ink characterized by having a thickness of not more than 00 nm.

The invention according to claim 11 is the invention according to claims 1 to 10
The content of the coloring material is 1% by weight or more,
An inkjet ink characterized by being at most 0% by weight.

[0013] The invention according to claim 12 is the invention according to claims 1 to 11.
Wherein the content of the water-soluble organic solvent is 5% by weight or more and 50% by weight or less.

The invention according to claim 13 is the invention according to claims 1 to 12
An image forming method using the ink described in any one of the above, and printing with an ink jet printer.

[0015]

Embodiments of the present invention will be described below. The ink-jet ink of the present invention is an ink-jet ink comprising at least a coloring material, water, a water-soluble organic solvent (wetting agent), and a conductive agent. An inkjet ink having a dielectric constant of 64.0 or more.

By using an ionic substance having a formula weight of 200 or less as the conductive agent, the amount of addition required for securing necessary conductivity can be reduced. On the other hand, the conductivity tends to increase as the relative dielectric constant of the ink increases.
By setting it to 0 or more, adverse effects such as salting out and aggregation when the conductive agent is added can be minimized. In order to secure the stability required for the ink, it is essential that the above two conditions are simultaneously satisfied.

The formula weight of the conductive agent is 200 or less, more preferably 180 or less. When the formula amount of the conductive agent exceeds 200, the amount of the conductive agent added when securing the conductivity increases, and as a result, salting out of the dye and aggregation of the pigment are likely to occur.

Examples of the conductive agent having a formula weight of 200 or less include C1 to C10 carboxylic acids as anions, chloride ions, bromine ions, iodine ions, nitrate ions, sulfate ions, nitrite ions, thiocyanate ions, and lithium ions as cations. , Sodium ion, potassium ion, cesium ion, ammonium ion, monomethyl ammonium ion, dimethyl ammonium ion, trimethyl ammonium ion, tetramethyl ammonium ion, monoethyl ammonium ion, diethyl ammonium ion, triethyl ammonium ion, tetraethyl ammonium ion, monopropyl ammonium Ion, dipropylammonium ion, tripropylammonium ion, tetrapropylammonium ion, monobutylammonium Ion, dibutyl ammonium ions, tributylammonium ions, monoethanolammonium ion, diethanolammonium ion, triethanolammonium ion, among salt comprising choline include formula weight of 200 or less of salt.

The relative dielectric constant of the ink is 64.0 or more,
More preferably, it is 68.0 or more. When the relative dielectric constant of the ink is less than 64.0, aggregation tends to occur during high-temperature storage. To increase the dielectric constant of the ink,
There are methods such as increasing the proportion of water in the ink or decreasing the proportion of a material having a small relative dielectric constant in the ink.
Conversely, there are methods for reducing the relative dielectric constant of the ink, such as reducing the proportion of water or increasing the proportion of a material having a small relative dielectric constant in the ink.

The relative dielectric constant of the ink used in the present invention is calculated by calculating the sum of “specific dielectric constant × weight” of components other than pigments and ionic substances contained in the ink in an amount of 1% by weight or more. It is divided by the total weight. In addition, the “relative permittivity” in this specification is “Chemical Handbook Revised 2nd Edition”
, "Beilstein" if not listed
Are the values described respectively.

The conductivity of the ink is 0.7 mS / c.
m or more and 50 mS / cm or less. The conductivity is 0.
If it is less than 7 mS / cm, it may be difficult to detect the remaining amount due to insufficient conductivity, while if it is more than 50 mS / cm, adverse effects such as salting out and aggregation due to the conductive agent tend to be remarkable.

The content of the conductive agent is preferably 0.05% by weight or more and 5% by weight or less. 0.05% by weight of conductive agent
If less, required conductivity cannot be secured, while 5% by weight
If it is larger, salting out, aggregation and the like are likely to occur.

In the present invention, any of a dye and a pigment can be used as a coloring material. As dyes, acid dyes, basic dyes, direct dyes, food dyes, disperse dyes, reactive dyes, and the like can be used.

As the pigment used in the present invention, any of a self-dispersible pigment having an ionic substituent chemically bonded and a pigment dispersed with a dispersant other than the self-dispersible pigment can be used. Examples of the black pigment include self-dispersible carbon black, carbon black produced by a furnace method or a channel method, and the like.

As the yellow pigment, Pigment Yellow 1, Pigment Yellow 2, Pigment Yellow 3,
Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 16, Pigment Yellow 17, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 93, Pigment Yellow 95, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 114, Pigment Yellow 120, Pigment Yellow 128, Pigment Yellow 129, Pigment Yellow 138, Pigment Yellow 150, Pigment Yellow 151, Pigment Yellow 154, Pigment Yellow 155, Pigment Yellow 180 and the like.

As magenta pigments, Pigment Red 5, Pigment Red 7, Pigment Red 12, Pigment Red 48 (Ca), Pigment Red 48 (M
n), Pigment Red 57 (Ca), Pigment Red 57: 1, Pigment Red 112, Pigment Red 122, Pigment Red 123, Pigment Red 168, Pigment Red 184, Pigment Red 2
02, Pigment Violet 19 and the like.

Examples of cyan pigments include Pigment Blue 1, Pigment Blue 2, Pigment Blue 3, Pigment Blue 15, Pigment Blue 15: 3, Pigment Blue 15: 4, Pigment Blue 16, Pigment Blue 22, Pigment Blue 60, and Bat Blue. 4,
Bat Blue 60 and the like.

By using carbon black as the black pigment, Pigment Yellow 138 as the yellow pigment, Pigment Red 122 as the magenta pigment, and Pigment Blue 15 as the cyan pigment, a well-balanced ink having excellent color tone and light fastness can be obtained. be able to.

Examples of the water-soluble organic solvent include methanol, ethanol, 1-propanol, 2-propanol and 1-propanol.
Alcohols such as butanol, 2-butanol and isobutyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol and 1,4-butane Diols, polyhydric alcohols such as glycerin, monoether derivatives and diether derivatives obtained by dehydration condensation of the polyhydric alcohols and the alcohols, N-methylpyrrolidone, pyrrolidone derivatives such as 2-pyrrolidone, acetone,
Examples include ketones such as methyl ethyl ketone, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and nonionic surfactants and preservatives. Incidentally, the content of the water-soluble organic solvent,
The content is preferably 5% by weight or more and 50% by weight or less based on the total amount of the recording liquid (ink).

Examples of the surfactant for adjusting the surface tension of the ink include various anionic, cationic and amphoteric surfactants. Examples of the surfactant include a linear alkyl group, a branched alkyl group, an unsaturated alkyl group, an alkylphenyl group, and an alkylnaphthyl group as a hydrophobic group, and a carboxylate, a sulfonate, a sulfate, and a phosphoric acid as a hydrophilic group. A surfactant having an ester salt, an ammonium salt, a pyridinium salt or the like can be used.

When a pigment is used, the average particle size of the pigment in the ink is preferably 30 nm or more and 200 nm or less. When the average particle size of the pigment is larger than 200 nm, not only clogging of the nozzle is likely to occur, but also sharpness of the color tone is poor,
If it is less than 30 nm, it is difficult to disperse the pigment, which increases the cost and tends to deteriorate the storage stability and light resistance. The average particle size in the present invention is measured by an electrophoretic light scattering photometer “ELS-800” manufactured by Otsuka Electronics Co., Ltd.

The content of the coloring material is 1% by weight or more and 10% by weight.
Is preferably 1% by weight or more and 7% by weight or less. If the amount is less than 1% by weight, the image density is low and the sharpness of the print is lacking. If the amount is more than 10% by weight, not only the viscosity of the ink tends to increase, but also nozzle clogging tends to occur.

The ink is prepared by stirring and mixing a dye or pigment dispersion, water, a water-soluble organic solvent, a surfactant and the like,
It is obtained by filtering coarse particles with a centrifuge or the like and degassing.

As a printing method using the above-mentioned ink, there are a continuous jet type and an on-demand type. Also,
Examples of the on-demand type include a piezo method, a thermal inkjet method, and an electrostatic method.

[0035]

EXAMPLES Hereinafter, Examples 1 to 12 and Comparative Examples 1 to 3 of the present invention will be described, but the present invention is not limited to these Examples. In the examples and comparative examples, “parts” represents “parts by weight”.

(1) Preparation of Pigment Dispersion After premixing each of the following pigment dispersion formulations 1 to 3,
In a 1 liter vessel, 900 g of zirconia beads having a diameter of 0.3 mm was added, and the mixture was dispersed for 24 hours by a Campe tabletop sand mill to obtain pigment dispersions (A) to (C). Also, after premixing the following pigment dispersion formulation 2,
The mixture was placed in a 1-liter vessel, 900 g of zirconia beads having a diameter of 0.3 mm was added, and the mixture was dispersed for 30 minutes by a batch tabletop sand mill manufactured by Campe to obtain a pigment dispersion (D). On the other hand, Cabot's CAB-O as a black pigment dispersion was used.
-JET300 (solid content concentration 15%) (E) was used.

[Pigment Dispersion Formulation 1] Pigment Yellow 138 30 parts (LIONOGEN YELLOW 1010, manufactured by Toyo Ink Mfg. Co., Ltd.) polyoxyethylene (n = 40) β-Naphthyl ether 15 parts Pionein A-51-B (manufactured by Takemoto Yushi Co., Ltd.) 0.1 parts Distilled water ……………………………… …………………… 155 copies

[Pigment Dispersion Formulation 2] Pigment Red 122 ... 30 parts (FASTGEN SUPER MAGENTA RG, manufactured by Dainippon Ink and Chemicals, Inc.) Polyoxyethylene ( n = 40) β-naphthyl ether 15 parts Pionein A-51-B (manufactured by Takemoto Yushi Co., Ltd.) 0.1 part Distilled water ………………………… …………………………… 155 copies

[Pigment Dispersion Formulation 3] Pigment Blue 15: 3: 30 parts (manufactured by Toyo Ink Mfg. Co., Ltd., LIONOL BLUE FG-7351) polyoxyethylene ( n = 40) β-naphthyl ether 15 parts Pionein A-51-B (manufactured by Takemoto Yushi Co., Ltd.) 0.1 part Distilled water ………………………… …………………………… 155 copies

(2) Preparation of Ink for Ink Jet Inks were prepared according to the formulations of Examples 1 to 12 and Comparative Examples 1 to 3 shown in [Table 1] and [Table 2] below, and after stirring for 30 minutes, a pore diameter of 1 The mixture was filtered through a 0.2 μm membrane filter and degassed under vacuum to obtain inks (a) to (o).

[0041]

[Table 1]

[0042]

[Table 2]

The following Tables 1 and 2 are supplemented: (i) In Example 3, 15 parts of 1,3-butanediol was added, and in the other Examples and Comparative Examples 1 to 3, It was not added. (Ii) In Example 1, 15 parts of diethylene glycol was used,
In Comparative Example 3, 30 parts thereof were added, and in the other Examples and Comparative Examples 1 and 2, this was not added. (Iii) 0.3 parts of "polyoxyethylene (3) alkyl (C13) ether sodium acetate" was added as an anionic surfactant commonly to Examples 1 to 12 and Comparative Examples 1 to 3.

With respect to the obtained inks (a) to (o),
The following items (I) to (III) were measured and calculated. Further, experiments of items (IV) and (V) were performed. Example 1
12, Tables 3 and 4 summarize the results of Comparative Examples 1 to 3. (I) Relative dielectric constant (II) Conductivity (III) Average particle size (IV) Using ink left at 70 ° C. for 28 days,
Printing was performed using MJ-930C manufactured by PSON and DeskJet 880C manufactured by Hewlett-Packard, and the ejection stability was evaluated. (V) The above-mentioned DeskJet880C black head (516
45A), the ink was removed, washed with pure water, filled with the evaluation ink, dried at 50 ° C. for 60 minutes, then set in a printer, and a solid image was printed to evaluate clogging (print mode: Econo, Plain paper).

[0045]

[Table 3]

[0046]

[Table 4]

In Tables 3 and 4, * 1 indicates the ink ejection stability when MJ-930C was used.
2 shows the ink ejection stability when using DeskJet 880C. In "clogging", "no head clogging" is indicated by "○",
“There is clogging of the head” is indicated by “×”.

[0048]

As is apparent from the above description, according to the present invention, it is possible to provide an ink jet ink excellent in ejection stability and high-temperature storage characteristics despite addition of a conductive agent. Therefore, by printing with an ink jet printer using this ink, a high quality image can be stably obtained.

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Claims (13)

[Claims] At least a coloring material, water, a water-soluble organic solvent,
An ink-jet ink comprising a conductive agent, wherein an ionic substance having a formula weight of 200 or less is used as the conductive agent, and the relative dielectric constant of the ink is 64.0 or more. 2. An electric conductivity of 0.7 mS / cm or more, 50 m or more.
The inkjet ink according to claim 1, wherein the S / cm is not more than S / cm. 3. The content of the conductive agent is 0.05% by weight or more,
3. The composition according to claim 1, wherein the content is 5% by weight or less.
3. The ink for inkjet according to item 1. 4. The ink-jet ink according to claim 1, wherein the coloring material is a pigment. 5. The ink-jet ink according to claim 4, wherein the pigment is carbon black. 6. The ink-jet ink according to claim 5, wherein the pigment is a self-dispersible carbon black. 7. The ink jet ink according to claim 4, wherein the pigment is Pigment Yellow 138. 8. The inkjet ink according to claim 4, wherein the pigment is Pigment Red 122. 9. The ink-jet ink according to claim 4, wherein the pigment is Pigment Blue 15. 10. The pigment has an average particle size of 30 nm or more,
The inkjet ink according to any one of claims 4 to 9, wherein the thickness is 0 nm or less. 11. The inkjet ink according to claim 1, wherein the content of the coloring material is 1% by weight or more and 10% by weight or less. 12. The method according to claim 1, wherein the content of the water-soluble organic solvent is 5% by weight or more and 50% by weight or less.
12. The ink-jet ink according to any one of 11. 13. An image forming method using the ink according to claim 1 for printing with an ink jet printer.