JPH08283635A - Ink composition for ink jet recording - Google Patents

Abstract

PURPOSE: To obtain an ink composition satisfying rubbing resistance and water resistance of printed and having excellent storage stability by containing an in-water dispersive pigment, a thermoplastic resin emulsion and ethylenediamine tetraacetate. CONSTITUTION: The objective composition contains at least (A) a composition wherein (i) an inorganic or an organic pigment such as carbon black in an amount of preferably 0.5-30wt.% (especially 1.0-12wt.%) is dispersed in water by a beads mill, and, if necessary, using (ii) a dispersant such as an acrylic resin, (B) a thermoplastic resin such as a styrene/acrylate copolymer in an amount of preferably about 5-40wt.% and (C) ethylenediamine tetraacetate in an amount of preferably 0.01-0.5wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition for an ink jet printer which ejects ink droplets from a recording head to obtain an ink image on a recording medium.

[0002]

2. Description of the Related Art As a conventional ink for ink jet recording of a type in which a recording image is written by ejecting ink droplets onto a recording medium, water is used for the purpose of improving ejection stability from nozzles and ink storage stability. An ink composed of a water-soluble dye and an organic solvent was used.

However, inks using a water-soluble dye as a colorant have problems in light resistance and water resistance such as dye decoloration and hue change.

Therefore, in JP-B-62-1426, JP-A-2-255875, and JP-A-4-18462, the water resistance, the pigment, and the resin emulsion are contained as the constituent components of the ink, thereby improving the water resistance. An ink has been reported which solves the problem of light fastness and also solves the character bleeding, which has been a problem of conventional dye-based inks.

[0005]

However, the above-mentioned conventional ink has the following problems.

The ink contains water-insoluble substances such as pigments and resin emulsions. Due to changes in the pH of the ink during storage, the ink may aggregate, settle, deteriorate, etc., and the storage stability of the ink may be improved. The problem is that
This also causes clogging of the ink discharge nozzles due to aggregates and the like.

In view of the above-mentioned problems of conventional ink jet inks, the present invention solves the problems of these conventional examples. The first purpose is to improve the abrasion resistance of printed matter,
It is to provide an ink for ink jet recording satisfying water resistance, and a second object thereof is to prevent a problem such as clogging of an ink discharge nozzle due to aggregates or sedimentation even if the ink is left for a long time. The purpose of the present invention is to provide an ink having excellent storage stability.

[0008]

The ink composition for ink jet recording of the present invention is characterized by containing at least a pigment and a thermoplastic resin emulsion dispersed in water, and ethylenediaminetetraacetic acid, and further comprising ethylenediaminetetraacetic acid. It is characterized by containing 0.01% to 0.5%.

In the ink composition of the present invention containing at least a pigment dispersed in water, a thermoplastic resin emulsion and ethylenediaminetetraacetic acid, since the pigment and the thermoplastic resin emulsion are essential components, the abrasion resistance of the printed matter, Water resistance can be ensured. Further, in order to secure the storage stability of the ink, it is necessary to keep these dispersions in the initial state for a long time, and the ethylenediaminetetraacetic acid is contained in the ink to maintain the initial pH. It is possible to prevent the ink ejection nozzle from being clogged by suppressing the occurrence of ink sedimentation, aggregation, viscosity change, and the like.

The ink jet recording ink of the present invention comprises
It is characterized in that it contains a pigment dispersed in water, a thermoplastic resin emulsion and ethylenediaminetetraacetic acid.

Conventionally, water has been mainly used as the ink solvent because of its low viscosity, excellent safety, easy handling, low cost, and no odor. As the ink material, pure water or ultrapure water that has undergone a purification process such as ion exchange or distillation is desirable.

Examples of pigments that can be used in the ink of the present invention include organic pigments and inorganic pigments.
For black, furnace black, lamp black,
Carbon black (CI pigment black 7) such as acetylene black and channel black, or copper oxide, iron oxide (CI pigment black 1)
1), metals such as titanium oxide, aniline black (C.
I. Pigment Black 1) and other organic pigments. For color, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 1
2 (this as yellow AAA), 13, 14, 17, 24, 3
4, 35, 37, 42 (yellow iron oxide), 53, 55, 8
1, 83 (This As Yellow HR), 95, 97, 98, 10
0, 101, 104, 108, 109, 110, 11
7, 120, 138, 153, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanentlet 2B (B
a)), 48: 2 (permanentlet 2B (Ca)), 48: 3 (permanentlet 2B (Sr)), 48: 4 (permanentlet 2B (Mn)), 4
9: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B),
60: 1, 63: 1, 63: 2, 64: 1, 81 (Rotamine 6G
Rake), 83, 88, 101 (bengara), 104, 1
05, 106, 108 (Cadmium Let), 112, 11
4,122 (quinacridone magenta), 123,146,14
9, 166, 168, 170, 172, 177, 17
8, 179, 185, 190, 193, 209, 21
9, C.I. I. Pigment Blue 1, 2, 15 (Phthalocyanine Blue R), 15: 1, 15: 2, 15: 3 (Phthalocyanine Blue)
G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17:
1, 56, 60, 63, and the like, and other processed pigments such as graft carbon whose surface is treated with a resin or the like can be used.

The amount of addition is preferably 0.5 to 30% by weight, more preferably 1.0 to 12% by weight. If the addition amount is less than this, the printing density cannot be secured, and if the addition amount is more than this, structural viscosity occurs in the viscosity characteristic of the ink, and the ejection stability cannot be secured.

A pigment having a particle size of 25 μm or less is used, and a pigment having a particle size of 1 μm or less is preferably used.

Further, in order to uniformly disperse these colorants, if necessary, a dispersant is added to the pigment in an amount of 0.5 to 200 wt.
%, Preferably 1 to 50 wt%, more preferably 10 to 30 wt%, and it is desirable to carry out dispersion treatment with a bead mill or the like.

Typical examples of the dispersant for dispersing the pigment used in the ink of the present invention include acrylic resins, and specific examples of such acrylic resins include, for example, styrene-acrylic acid copolymers and acrylic resins. Acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid-
Acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic Examples thereof include salts such as acid-acrylic acid alkyl ester copolymers.

As a substance (counter ion) which forms a salt with the above-mentioned dispersant, for example, aminomethyl propanol, 2-aminoisopropanol, triethanolamine, morpholine, aqueous ammonia, etc. can be used. Further, propylene glycol, isopropanol and the like may be used as a dissolution aid.

Further, in order to obtain the dissolution stability of the dispersant, it is necessary to add a pH buffer solution so that the salt in the dispersant is easily ion-dissociated to adjust the ink to an optimum pH value.

Specific examples of the pH buffer solution include potassium hydrogen phthalate, potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium tetraborate, potassium hydrogen tartrate, sodium hydrogen carbonate, sodium carbonate, tris (hydroxymethyl) amino. Methane, tris (hydroxymethyl) aminomethane hydrochloride, etc. are used.

The thermoplastic resin emulsion that can be used in the ink of the present invention includes styrene-acrylic acid ester copolymer, polyacrylic acid ester, polymethacrylic acid ester, polyethylacrylic acid ester,
Styrene-butadiene copolymer, butadiene copolymer,
Acrylonitrile-butadiene copolymer, chloroprene copolymer, crosslinked acrylic resin, crosslinked styrene resin, fluororesin, vinylidene fluoride, benzoguanamine resin, polyolefin resin, styrene-methacrylic acid ester copolymer, polystyrene, styrene-acrylamide copolymer Coalesce, n-isobutyl acrylate, acrylonitrile, vinyl acetate, acrylamide, polyvinyl acetal, rosin resin, polyethylene, vinylidene chloride resin, vinyl acetate resin, ethylene-vinyl acetate copolymer,
Animal and plant waxes such as vinyl acetate-acrylic copolymer, vinyl chloride resin, polyethylene wax, montan wax, alcohol wax, synthetic oxidation wax, α-olefin-maleic anhydride copolymer, carnauba wax, etc.
There are lanolin, paraffin wax, microcrystalline wax, and the like, but any one having excellent fastness when formed on a recording medium can be used.

In order to maintain the dispersion stability of these thermoplastic resin emulsions as well as the pigment, it is necessary to adjust the pH of the ink to the optimum pH. Therefore, in order to maintain the dispersion stability of both the pigment and the thermoplastic resin emulsion, it is necessary to maintain the pH value of the ink within the optimum range for both.

The softening temperature and MFT of the above thermoplastic resin emulsion are preferably 60 to 100 ° C., more preferably 65 ° C. to 100 ° C. in order to prevent deterioration of the ink when left at high temperature and to reduce energy required for heat fusion. 90 ° C is good.

These thermoplastic resin emulsions may be used alone or in combination of two or more, but the ink viscosity increases as the amount added is increased, so that the total amount of the ink is 5 to 5 with respect to the total amount of the ink. It is preferable to suppress the addition amount to about 40% by weight.

The ethylenediaminetetraacetic acid that can be used in the ink of the present invention may be any commercially available one. Further, disodium ethylenediaminetetraacetate and calcium disodium ethylenediaminetetraacetate are particularly preferable. When the added amount is 0.01% or less, the pH maintaining action is lowered. Further, when the amount is too large, viscosity increase with time is observed during storage, and in order to suppress them, the addition amount is preferably 0.01% to 0.5%.

Further, the ink of the present invention has
A saccharide can be used for the purpose of improving the fixability of the ink on the recording medium. Specific examples include glucose, xylose, sucrose (sucrose), maltose, arabinose, maltitol, monosaccharides such as starch, disaccharides,
Examples include polysaccharides and glycosides.

Further, urea, thiourea, ethylene urea and the like can be added for the purpose of preventing nozzle drying.

Further, a hydrophilic high-boiling point low-volatile solvent is added to the ink of the present invention in order to impart the effects of nozzle clogging resistance, moisture retention and dispersion stability. Specific examples include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol,
High boiling point and low volatility polyhydric alcohols such as dipropylene glycol, hexylene glycol, polyethylene glycol and polypropylene glycol are used, or their monoether compounds, diether compounds, ester compounds such as ethylene glycol monomethyl ether,
Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, etc. are used, and other N-methyl-2pyrrolidone, 1.3-dimethylimidazolidinone, monoethanolamine, N, N −
No bleeding occurs with hydrophilic high-boiling low-volatile solvents such as nitrogen-containing organic solvents such as dimethylethanolamine, N, N-diethylethanolamine, diethanolamine, Nn-butyldiethanolamine, triisopropanolamine, triethanolamine. It can be added in a range.

For the purpose of improving the drying property, highly volatile monohydric alcohols such as ethanol, propanol, isopropanol and butanol can be added to water as the main solvent in a small amount.

[0029]

EXAMPLES Examples of the ink composition for ink jet recording of the present invention will be described in detail below.

Table 1 shows examples and composition examples of the ink composition for ink jet recording of the present invention.

[0031]

[Table 1]

Examples 1 to 7 of the ink composition of the present invention were carried out by the following manufacturing method, but the invention is not limited thereto.

An aqueous dispersion comprising a pigment, a styrene-acrylic acid copolymer (addition amount: pigment ratio 0.2) as a dispersant, and triethanolamine (addition amount: neutralization equivalent of the styrene-acrylic copolymer). Was dispersed in a bead mill, and it was confirmed by microscopic observation that the pigment particles were in a monodispersed state. Then, a pH-adjusted thermoplastic resin emulsion and a hydrophilic high-boiling point low-volatile solvent were added, and the mixture was stirred for another 30 minutes. And mix thoroughly. In the case of this ink, the pH value is 8 to
Adjusted to a range of 10. Thereafter, ethylenediaminetetraacetic acid was added and completely dissolved, and then the dispersion was filtered through a membrane filter having a pore size of 10 μm to remove dust and coarse particles to obtain a recording ink.

The manufacturing method of Comparative Examples 1 and 2 was as follows.

Comparative Example 1 An ink composition obtained by removing the ethylenediaminetetraacetic acid from the ink composition of Example 2 was used.
An ink was prepared in the same manner as described above.

(Comparative Example 2) A water-soluble dye was used as a colorant, a solvent, ethylenediaminetetraacetic acid and water were mixed and stirred at room temperature for 30 minutes or more to completely and uniformly dissolve it to obtain an ink.

Next, evaluation was performed using each of the above ink compositions.

Among the evaluation items, the storage reliability of the ink composition was 1. pH change, 2. Sedimentation, 3. 3. Changes in viscosity and robustness of printed matter Water resistance, 5. Five items of abrasion resistance were evaluated.

Regarding evaluation items 1 to 5, Examples 1 to 7 were used.
And the ink compositions of Comparative Examples 1 and 2 in a closed state at 60 ° C.
It was left for 1 month and evaluated. The actual printing was evaluated by performing a printing test with an inkjet recording device described below.

FIG. 1 is a perspective view showing a characteristic constitution of an ink jet printer used for evaluation of the present invention.

The recording head 2 is an ink jet recording head of the type using a piezoelectric element, in which a plurality of nozzles are arranged in an arbitrary matrix, and a carriage device which moves in parallel to the platen 1 at a position facing the platen 1. It is installed in 7.

Further, a heater 6 is arranged inside the platen 1, and the platen 1 is heated by a temperature sensing means (not shown) and a heater control means (not shown) so that the surface temperature becomes equal to or higher than the softening temperature of the thermoplastic resin emulsion in the ink. Are controlled. In this implementation, the platen temperature is 120
It is controlled to reach ℃.

The softening temperatures of the thermoplastic resins used in the ink of this example were all 70 ° C to 90 ° C.

An ink container 21 is connected to the recording head 2 and ink is supplied as necessary. Platen 1
Is a laminate of silicone rubber or the like as a surface layer around an aluminum tube, the paper pressing rollers 3 and 4 are in contact with each other, the recording paper 5 is placed along the platen 1, and a drive (not shown) is provided. It is rotated by the device.

The recording head 2 to which the ink is supplied from the ink container 21 ejects ink droplets from its nozzle according to the printing pattern, and the recording paper 5 whose surface temperature is heated above the softening temperature of the thermoplastic resin emulsion in the ink. Write the ink image on top. When the ink is heated on the recording paper, the solid content concentration rises and the viscosity rapidly increases, and the thermoplastic resin emulsion fuses to prevent bleeding and the like, resulting in high print quality and fastness. To be

The results of evaluation of the ink compositions of Examples of the present invention and Comparative Examples are shown below.

The evaluation criteria are as follows. 1. pH change ⊚: No change from the initial value ◯: Change is within 5% of the initial value, which is an allowable level ×: Change is 5% or more from the initial value Sedimentation ◎: No sedimentation occurs ◯: There is some sedimentation, but it recovers with a slight stirring. ×: Sedimentation occurs, it does not recover with a slight stirring. 3. Viscosity change ⊚: No change from initial value ◯: Change is within 5% of initial value, which is an allowable level ×: Change is at least 5% from initial value 4. Water resistance ◎: Printing does not bleed even if water drips on the print ◯: Edge is blurred when water drips on the print, but it is at an acceptable level ×: Printing prints when water drips on the print It will flow 5. Abrasion resistance ◎: No scumming even when rubbed strongly with finger ◯: Scrubbing with finger is visually recognizable, but scumming is allowable level x: Visible even if touched lightly with finger Table 2 shows the results of evaluation of the ink examples and the ink comparative examples based on the above-mentioned evaluation conditions and judgment criteria in which scumming occurs.

[0048]

[Table 2]

As shown in Table 2 above, when the ink composition of the present invention was used, the initial pH and viscosity were maintained even after being left for a long time, there was no sedimentation, and the storage stability was excellent.

Further, the printed matter obtained by the ink after standing was a high quality image and was excellent in fastness such as water resistance and abrasion resistance.

On the other hand, with the composition of Ink Comparative Example 1,
The changes in pH and viscosity were large, the formation of aggregates was observed, and the ejection characteristics were unstable, and printing was impossible. Further, with the composition of Ink Comparative Example 2, although the storage stability was within the allowable range, sufficient performance could not be obtained in terms of the fastness of the printed matter.

[0052]

In the ink composition of the present invention containing at least the pigment dispersed in water, the thermoplastic resin emulsion, and the organic acid, the pigment and the thermoplastic resin emulsion are essential components, and therefore the abrasion resistance of the printed matter is improved. The effect of satisfying the robustness such as water resistance was obtained.

Further, since the initial pH can be maintained by containing ethylenediaminetetraacetic acid in the ink, the dispersion system is kept in the initial state for a long time, and the ink is allowed to settle, aggregate and increase in viscosity. Can be suppressed,
The effect is that the storage stability becomes high.

Further, for printing, there is no clogging of the ink discharge nozzle due to agglomerates or the like, and the effect of excellent discharge stability was obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an inkjet recording apparatus used for evaluation of ink composition examples of Examples and Comparative Examples of the present invention.

[Explanation of symbols]

 1: Platen 2: Recording Head 3: Paper Pressing Roller 4: Paper Pressing Roller 5: Recording Paper (Recording Medium) 6: Heater 7: Carriage 21: Ink Container

Claims (2)

[Claims] 1. An ink composition for ink jet recording, comprising at least a pigment dispersed in water, a thermoplastic resin emulsion, and ethylenediaminetetraacetic acid. 2. The ethylenediaminetetraacetic acid is added to 0.0
The ink composition for inkjet recording according to claim 1, wherein the ink composition comprises 1% to 0.5%.