JPH1143632A - Pigment ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pigment ink which spreads well, is free from missing among dots, and is excellent in setting quality and dryability by compounding a pigment. a dispersant, an anionic surfactant having an ether structure or structures, and water into the same. SOLUTION: A known pigment (A) is used. The dispersant (B) comprises an amphiphatic compd. (having a hydrophilic part comprising polyethylene oxide and a hydrophobic part comprising alkyl groups or arom. rings) and/or an anionic dispersant (a copolymer having anionic functional groups and alkyl groups or arom. rings). Pref., the anionic surfactant (C) is one having 1-10 ether structures per molecule and a mol.wt. of 200-1,000, an esp. effective one being a metal alkylsulfate. The amt. of ingredient A compounded is 0.1-20 wt. % of the ink ; and that of ingredient C compounded, 0.5-5 wt.%. A water-soluble org. solvent (e.g. ethylene glycol) and a water-soluble compd. (e. g. 1,2-butanediol) are also incorporated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment ink, and more particularly to a pigment ink suitable for an ink jet recording system in which ink droplets are ejected from a print head to perform recording, and more particularly, to forming an image on a recording medium. The present invention relates to a pigment ink having a good spread of ink and excellent print quality and drying property.

[0002]

2. Description of the Related Art In conventional ink jet recording, a dye ink in which various dyes are dissolved in water or a mixed solvent of water and an organic solvent has been used.

[0003] However, dye ink often has bleeding,
There were drawbacks in printing quality such as poor light resistance and water resistance.

Therefore, instead of dye inks, pigment inks having little bleeding, and having excellent light resistance and water resistance have been studied.

[0005] In order to obtain a uniform and clear image in the ink jet recording system, it is required that the bleeding of the ink used on the recording medium be suppressed and the ink spread on the recording medium be good. However,
While the pigment ink has less bleeding, the spread on the recording medium is inferior to the dye. In particular, since the recording medium dedicated to inkjet is designed to suppress the bleeding of the ink, the pigment ink cannot obtain a sufficient spread on the recording medium, and the gap between dots (white loss) occurs and the optical density is reduced. Will lead to a decline in Further, ink that does not spread sufficiently on the recording medium has poor drying properties.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pigment ink used for ink jet recording, which has a good ink spread, no gaps between dots (white gaps), and excellent print quality and drying properties. Is to provide.

[0007]

Means for Solving the Problems The pigment ink of the present invention comprises:
It is characterized by containing a pigment, a dispersant, at least one anionic surfactant having an ether structure, and water. The dispersant is composed of an amphiphilic compound and / or an anionic dispersant. Further, the amphiphilic compound has a hydrophilic portion composed of polyethylene oxide and a hydrophobic portion composed of an alkyl group and / or an aromatic ring.

The mechanism by which the pigment ink of the present invention exhibits the above-mentioned effects is not clear. However, it is considered that the combination of the anionic surfactant and the dispersant of the present invention functions to promote the spread of the ink on the recording medium. The ether structure contained in the anionic surfactant of the present invention, the polyethylene oxide in the anionic group and the dispersant, the dots spread on the recording medium due to the interaction of the anionic group,
The printing quality and drying property are improved.

The anionic surfactant of the present invention may be any as long as it has an ether structure and can be dissolved in an aqueous ink. A surfactant containing 1 to 10 ether structures in one molecule is preferable. This is to obtain a sufficient spread of the dots on the recording medium, prevent the ink from bleeding, and achieve excellent print quality. Those containing ethylene oxide as the ether structure are particularly effective.

[0010] Examples of the anionic functional group of the anionic surfactant of the present invention include a carboxyl group, a sulfone group, an alkyl sulfate group, and a phosphate group. These functional groups may be present as a metal salt such as sodium or an ammonium salt. Particularly, an alkyl sulfate metal salt is effective.

The molecular weight of the anionic surfactant of the present invention is preferably in the range of 200 to 1,000. This is to obtain a sufficient spread of the ink on the recording medium without increasing the viscosity of the ink.

The content of the anionic surfactant of the present invention is preferably 0.5 to 5% by weight based on the whole ink composition. This is because the ink spread on the recording medium can be sufficiently obtained without increasing the viscosity of the ink to achieve excellent print quality.

The method for producing a pigment ink is as follows. A dispersion containing at least a pigment, a dispersant and water is dispersed and then the above-mentioned anionic surfactant is added and dispersed.
Dispersion may be performed in addition to the initial production. If necessary, various additives may be added to form an ink, or a dispersion having a high pigment concentration may be prepared first, and then a solvent, various additives, etc. may be added to dilute the ink to use it as an ink.

As the pigment of the present invention, conventionally known pigments such as black, cyan, magenta, yellow, red, green and blue can be used without any distinction. The pigments can be used in either dry or wet form.

The amount of the pigment used in the present invention is 0.1 to 20% by weight, preferably 1.0 to 10% by weight, based on the whole ink composition. When the content is within this range, the color tone and optical density of the ink can be satisfied, and the viscosity and storage stability of the pigment ink can be satisfied.

The two kinds of the amphiphilic compound and the anionic dispersant contained in the dispersant of the present invention may be used alone or in combination of two kinds.

The amphiphilic compound of the present invention has a molecular weight of 1500
~ 5000 is preferred. Within this range, the dispersion and dispersion stability of the pigment particles in the pigment ink can be increased. The proportion of polyethylene oxide in the amphiphilic compound is 80 to 97% by weight, preferably 85 to 95% by weight of the total amount. Within this range, the cohesive force between the pigments can be reduced, and the storage stability of the ink can be satisfied.

In the amphiphilic compound of the present invention, the amphiphilic compound whose hydrophobic portion is an alkylphenyl group is effective for improving the dispersibility of pigment particles. Generally, since most organic pigments contain an aromatic ring, if an alkylphenyl group having an aromatic ring is present in the hydrophobic portion of the amphiphilic compound of the present invention,
Due to the interaction with the aromatic or heterocyclic ring present in the pigment, the organic pigment is firmly adsorbed on the organic pigment particles, and the cohesive force between the organic pigments is more effectively reduced.

The anionic dispersant of the present invention is preferably a copolymer containing at least a unit containing an anionic functional group and a unit containing an aromatic ring and / or an alkyl group.

The anionic functional group of the anionic dispersant of the present invention includes, for example, a carboxyl group, a sulfone group, an alkyl sulfate group, a phosphate group and the like. These functional groups may be present as a metal salt such as sodium or an ammonium salt. The molecular weight of the anionic dispersant of the present invention is not particularly limited.
More preferably, it is 00. This is because the cohesive force between the pigments is reduced by the electrostatic repulsion force, while the coarse particles that are adsorbed on a plurality of pigment particles and aggregated are not formed.

The water-soluble compound of the present invention has 4 to 6 carbon atoms.
As long as two or three hydroxyl groups are bonded to the above hydrocarbon, one type or a mixture of two or more types may be used. For example, 1,2-butanediol, 1,4-butanediol, 1,3-butanediol, 2,4-pentanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,2- Cyclohexanediol,
1,4-cyclohexanediol, trimethylolethane, trimethylolpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,5
-Pentanetriol, 3-methyl-1,5-pentanediol, 3-hexene-2,5-diol and the like.

If the water-soluble organic solvent of the present invention is at least one selected from the group consisting of ethylene glycol, diethylene glycol and glycerin, it can maintain an appropriate viscosity together with the water-soluble compound. Also, it is effective in preventing nozzle clogging.

The polyethylene glycol of the present invention preferably has a molecular weight in the range of 200 to 2,000. This is to prevent nozzle clogging and not to increase the viscosity of the ink.

The total content of the water-soluble organic solvent of the present invention and the water-soluble compound or polyethylene glycol is from 8 to
Preferably it is 25% by weight. This is to prevent nozzle clogging and achieve excellent printing quality without delaying the drying time.

The composition ratio of the water-soluble organic solvent of the present invention to the water-soluble compound or polyethylene glycol is preferably in the range of 2: 1 to 1: 5 by weight. This is to prevent nozzle clogging and achieve excellent printing quality without delaying the drying time.

The pigment ink obtained in the present invention has a surface tension of 20 to 70 dyne / cm.
By having a viscosity of 1 to 20 cP, stable printing by an inkjet printer becomes possible.

In the present invention, there is no problem even if an organic solvent other than water is mixed as the solvent. For example, triethylene glycol, tripropylene glycol, dimethyl sulfoxide, diacetone alcohol, glycerin monoallyl ether, propylene glycol, polyethylene glycol, thiodiglycol, N-methyl-2-pyrrolidone, 2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2 -Imidazolidinone, sulfolane, trimethylolpropane, neopentyl glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoallyl ether,
Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, β-dihydroxyethylurea, urea, acetonylacetone, pentaerythritol, Xylene glycol,
Ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monophenyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, triethylene glycol Diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene Glycol monomethyl ether,
Glycerin monoacetate, glycerin diacetate,
Glycerin triacetate, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, cyclohexanol, 1-butanol, 2,5-hexanediol, ethanol,
n-propanol, 2-propanol, 1-methoxy-2-propanol, furfuryl alcohol, tetrahydrofurfuryl alcohol and the like.

For the production of the pigment ink of the present invention, a container driving medium mill such as a ball mill, a centrifugal mill, and a planetary ball mill, a high-speed rotation mill such as a sand mill, or a medium stirring mill such as a stirring tank mill may be used.

In the present invention, various additives conventionally used in inks for ink jet printers, such as an antifoaming agent, a bactericide and a pH adjuster, can be used in combination.

The ink of the present invention can be used not only as an ink for an ink-jet printer, but also as a general aqueous printing ink or paint, or for a special use such as a color filter for a liquid crystal display. . Furthermore, the ultrafine organic pigment obtained by the production method of the present invention can be used as a non-aqueous ink or paint by replacing an aqueous solvent.

Recording media used for ink-jet printing using the ink of the present invention include plain paper, known ink-jet special paper, special film, and special OHP.
Film and the like.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to specific examples.

[0033]

(Example 1) 10 parts by weight of a magenta pigment (Chromofine Magenta 6879 manufactured by Dainichi Seika) 4.2 parts by weight of an amphiphilic compound (Nonipol 200 manufactured by Sanyo Chemical Co., Ltd.) Anionic dispersant (manufactured by Johnson Polymer, John Krill 62) 0.9 parts by weight Acetylene glycol 0.9 parts by weight 84 parts by weight ion-exchanged water The above composition was pulverized by a planetary ball mill for 15 hours, and then dispersed to obtain Dispersion A.

Dispersion A 50 parts by weight Alkyl sulfate ester salt (manufactured by NOF Corporation, Persoft EFK, active ingredient 25%) 7 parts by weight Diethylene glycol 5 parts by weight Polyethylene glycol (molecular weight 200) 10 parts by weight Ion-exchanged water 28 parts by weight After mixing with the composition, a pigment ink A was prepared.

(Example 2) 10 parts by weight of a yellow pigment (LION YELLOW WGGTN manufactured by Toyo Ink) 10 parts by weight of an amphiphilic compound (Nonipol 200 manufactured by Sanyo Chemical) 1.5 parts by weight of acetylenic glycol 80 parts by weight of ion-exchanged water The composition was pulverized with a planetary ball mill for 15 hours, and then dispersed to obtain a dispersion B.

Dispersion B 50 parts by weight Alkyl sulfate ester salt (manufactured by NOF CORPORATION, Persoft EFK, active ingredient 25%) 7 parts by weight Diethylene glycol 5 parts by weight 1.5 pentanediol 10 parts by weight Ion-exchanged water 28 parts by weight Mixed with the above composition Thereafter, a pigment ink B was prepared.

Example 3 Cyan Pigment (KET Blue 111 manufactured by Dainippon Ink) 10 parts by weight Amphiphilic compound (Nonipol 200 manufactured by Sanyo Chemical) 10 parts by weight Acetylene glycol 1.5 parts by weight Ion-exchanged water 80 parts by weight Part The above composition was ground in a planetary ball mill for 15 hours, and then dispersed to obtain a dispersion C.

Dispersion C 50 parts by weight Alkyl sulfate ester salt (manufactured by NOF Corporation, Persoft EFK, active ingredient 25%) 7 parts by weight Diethylene glycol 5 parts by weight Polyethylene glycol (molecular weight 200) 10 parts by weight Ion-exchanged water 28 parts by weight After mixing with the composition, a pigment ink C was prepared.

Example 4 10 parts by weight of carbon black pigment (Printex 150T manufactured by Degussa) 10 parts by weight of amphiphilic compound (Nonipol 200 manufactured by Sanyo Chemical Industries) 80 parts by weight of ion-exchanged water The above composition was dispersed in a planetary ball mill for 15 hours. Dispersion D
I got

Dispersion D 50 parts by weight Alkyl sulfate salt (manufactured by NOF Corporation, Persoft EFK, active ingredient 25%) 7 parts by weight Diethylene glycol 5 parts by weight Polyethylene glycol (molecular weight 200) 10 parts by weight Ion-exchanged water 28 parts by weight After mixing with the composition, a pigment ink D was prepared.

(Example 5) 50 parts by weight of the dispersion liquid A of Example 1 Alkyl sulfate (manufactured by NOF Corporation, Persoft EFT, active ingredient 36%) 5 parts by weight Diethylene glycol 10 parts by weight Polyethylene glycol (molecular weight 200) 5 Part by weight Deionized water 30 parts by weight After mixing with the above composition, a pigment ink E was prepared.

Comparative Example 1 50 parts by weight of the dispersion A of Example 1 5 parts by weight of diethylene glycol 10 parts by weight of polyethylene glycol (molecular weight 200) 35 parts by weight of ion-exchanged water After mixing with the above composition, a pigment ink F was prepared.

(Comparative Example 2) 50 parts by weight of Dispersion A of Example 1 sodium dodecylbenzenesulfonate (Nyutrex Powder F, manufactured by NOF Corporation, active ingredient 40%) 5 parts by weight Diethylene glycol 5 parts by weight Polyethylene glycol (molecular weight 200) 10 parts by weight Deionized water 30 parts by weight After mixing with the above composition, a pigment ink G was prepared.

(Comparative Example 3) 50 parts by weight of Dispersion A of Example 1 Alkyl ether sulfate (manufactured by NOF Corporation, Persoft EFK, active ingredient 25%) 1 part by weight Diethylene glycol 5 parts by weight 1.5 pentanediol 10 parts by weight Ion Exchange water 34 parts by weight After mixing with the above composition, a pigment ink H was prepared.

(Comparative Example 4) 50 parts by weight of the dispersion A of Example 1 5 parts by weight of diethylene glycol 10 parts by weight of polyethylene glycol (molecular weight 200) 10 parts by weight of alkyl ether sulfate (manufactured by NOF Corporation, Persoft EFT, active ingredient 36%) 30 5 parts by weight ion-exchanged water 5 parts by weight After mixing with the above composition, a pigment ink I was prepared.

(Comparative Example 5) Cyan pigment (KET Blue 111 manufactured by Dainippon Ink) 10 parts by weight Cationic dispersant (T-Coat BCX-3940 manufactured by Toyo Ink) 10 parts by weight Acetylene glycol 1.5 parts by weight Ion 80 parts by weight of exchanged water The above composition was pulverized by a planetary ball mill for 15 hours, and then dispersed to obtain a dispersion E.

Dispersion E 50 parts by weight Alkyl ether sulfate (manufactured by NOF CORPORATION, Persoft EFK, active ingredient 25%) 7 parts by weight Diethylene glycol 5 parts by weight Polyethylene glycol (molecular weight 200) 10 parts by weight Ion-exchanged water 28 parts by weight After mixing with the composition, a pigment ink J was prepared.

Using the inks obtained in each of the examples, plain paper (Xerox, K) and paper for inkjet printers (Kao, paper for Super Fine) with an inkjet printer (Epson system, MJ-510C).
Was printed. Table 1 shows the particle size, viscosity, optical density, whitening, and drying property of the pigment in the ink.

[0049]

[Table 1] Particle size Viscosity Optical density Whitening Drying Plain paper Dedicated paper Plain paper Dedicated paper Plain paper Dedicated paper Example 1 35 3.2 1.3 1.6 ○ ○ ○ ○ Example 2 36 3.7 1.2 1.5 ○ ○ ○ ○ Example 3 35 3.1 1.2 1.5 ○ ○ ○ ○ Example 4 38 3.5 1.2 1.7 ○ ○ ○ ○ Example 5 34 3.5 1.3 1.6 ○ ○ ○ ○ Comparative example 1 35 3.2 <1.0 1.1 △ × × △ Comparative example 2 36 3.3 1.0 1.2 △ × × △ Comparative Example 3 35 3.4 <1.0 1.1 △ × × △ Comparative Example 4 36 3.5 1.0 1.2 △ △ △ Comparative Example 5 61 5.2 <1.0 1.1 △ × × △ In this table, the pigment particle size is the scanning electron microscope. (Hitachi S-
4000). Viscosity is measured by a viscometer (Toki Sangyo R
100 type) at 25 ° C. The optical density is measured using a Macbeth portable densitometer (manufactured by Sakata Inx)
RD-12000). The whiteness was evaluated as follows: ○ when there is no whitening or slight whitening but no practical problem, 、 when whitening becomes practically problematic depending on the pattern, and whitening is practically impossible. The case was evaluated as x. The drying property was evaluated by performing solid printing, and 5 seconds after printing, determining whether or not the image was transferred to the back side of the paper by overlaying another blank paper on the recorded image. The case where transfer was scarcely observed was evaluated as ○, the case where some transfer was observed was evaluated as Δ, and the case where transfer was remarkable was evaluated as x.

As is clear from this table, Comparative Example 1 does not contain an anionic surfactant, Comparative Example 2 has no ether structure, and Comparative Example 3 does not have an ether structure.
Is low in the content of an anionic surfactant, Comparative Example 4 is high in the content of an anionic surfactant, and Comparative Example 5 is poor in spread of a dot because it contains a cationic surfactant. It is getting more and more. On the other hand, it can be seen that the pigment inks of the present invention represented by Examples 1 to 5 have good spread of dots, no white spots, and are excellent in print quality and drying property.

[0051]

The pigment ink produced by the method of the present invention has good spread of the ink on the recording medium. Therefore, there is no missing between dots (white missing), the printing quality is excellent, and the drying property is good.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yuichi Sakurai 1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell Co., Ltd.

Claims (7)

[Claims] 1. A pigment ink comprising a pigment, a dispersant, an anionic surfactant having an ether structure, and water. 2. The pigment ink according to claim 1, wherein the dispersant comprises an amphiphilic compound and / or an anionic dispersant. 3. The amphipathic compound wherein the hydrophilic portion is polyethylene oxide and the hydrophobic portion is an alkyl group and / or
3. The pigment ink according to claim 2, comprising an aromatic ring. 4. The pigment ink according to claim 1, wherein the anionic surfactant is an anionic surfactant having 1 to 10 ether structures in one molecule. 5. The molecular weight of the anionic surfactant is 2
The pigment ink according to claim 1, wherein the number is from 00 to 1,000. 6. The pigment ink according to claim 1, wherein the anionic surfactant is contained in an amount of 0.5 to 5% by weight based on the total amount of the pigment ink. 7. At least one water-soluble organic solvent selected from the group consisting of ethylene glycol, diethylene glycol and glycerin, and a water-soluble organic solvent in which two or three hydroxyl groups are bonded to a hydrocarbon having 4 to 6 carbon atoms. The pigment ink according to claim 1, wherein the pigment ink contains a hydrophilic compound or polyethylene glycol.