JPH1095944A - Pigment ink for inkjet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject ink excellent in printing quality and enabling the protection of the nozzle of a printing head from clogging by compounding a pigment, a dispersant, a water-miscible organic solvent, a water-soluble compound and water. SOLUTION: This ink is composed of (A) a pigment, (B) a polyethylene oxidecontaining dispersant, (C) a water-miscible organic solvent of at least one kind selected from ethylene glycol, diethylene glycol and glycerin, (D) a water-soluble compound in which 2-3 hydroxyl groups are attached to a 4-6C hydrocarbon (e.g. 1,2-butanediol or 1,4butanediol) and (E) water. The total content of the component C and the component D is preferably 8-16wt.% based on the total ink composition. Further, the compounding ratio of the component C to the component D is preferably (2:1) to (1:5) by weight. This composition enables the holding of softness even after solidification of the ink caused by evaporation of water in the ink, and accordingly the formed solid can be removed by cleaning, etc.

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 for performing recording by discharging ink droplets from a print head, and more particularly to a discharge performance and print quality in an ink jet recording apparatus. The present invention relates to a pigment ink which is excellent.

[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, the dye ink has drawbacks such as a large amount of bleeding, poor print quality, poor light fastness and poor water fastness.

[0004] Therefore, a study has been conducted on a pigment ink which is less bleeding, has excellent print quality, and is excellent in light resistance and water resistance. However, since a pigment insoluble in water is used in the pigment ink, there are problems such as dispersion stability of the pigment particles in the ink and clogging of the nozzle of the print head.

Conventionally, when nozzle clogging occurs in the print head, a cleaning mechanism is provided inside the printer to remove the clogging, and a cap is attached to the nozzle when not in use to prevent nozzle clogging. To prevent drying of the ink. In the case of the dye ink, even if solids are generated in the nozzle portion due to drying of the ink, it can be easily redissolved by a cleaning operation.However, since the pigment ink uses a water-insoluble pigment, the ink is When dried, the pigments agglomerate and produce solids that are difficult to redissolve. As described above, the problem of nozzle clogging is one of the causes of delay in practical use of pigment ink.

As a solution to this, for example, Japanese Patent Application Laid-Open No.
64 have been proposed. Here, in an ink composition comprising a pigment, a polymer dispersant, an aqueous medium and a penetrant, the aqueous medium is composed of water, a non-volatile organic solvent and a lower alcohol, and the non-volatile solvent is 30 parts by weight with respect to 100 parts by weight of water.
It is preferred to use up to 80 parts by weight.

[0007]

It is said that by adding such a large amount of a non-volatile solvent, clogging is improved and the drying speed is also excellent. With the progress of speeding up and speeding up, the drying speed is insufficient with the amount of the non-volatile solvent described in JP-A-3-157664, and the viscosity of the ink increases, and the quality of high-speed and high-definition printing is satisfied. Is no longer possible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pigment ink used for ink jet recording which has excellent print quality and does not cause clogging of nozzles of a print head.

[0009]

The pigment ink for ink jet recording of the present invention comprises a pigment, a dispersant containing a polyethylene oxide chain, and at least one water-soluble organic solvent selected from the group consisting of ethylene glycol, diethylene glycol and glycerin. It is characterized by containing a water-soluble compound in which two or three hydroxyl groups are bonded to a solvent and a hydrocarbon having 4 to 6 carbon atoms, and water.

According to what we have found, the reason why nozzle clogging has been improved is presumed to be that solids produced by drying of the pigment ink have soft properties. Therefore, even when a cleaning operation is performed, the solid matter can be easily re-dissolved, peeled off from the nozzles to perform normal printing, and a pigment ink which is excellent in printing quality and does not cause nozzle clogging can be provided. it can.

Although the mechanism by which the pigment ink of the present invention exhibits the above-mentioned effects is not clear, two or three hydroxyl groups are bonded to the polyethylene oxide-containing dispersant adsorbed on the pigment surface and the hydrocarbon having 4 to 6 carbon atoms. The water-soluble compound and at least one water-soluble organic solvent selected from the group consisting of ethylene glycol, diethylene glycol and glycerin interact with water through a hydrophobic bond and / or a hydrogen bond in the ink. Even if the water in the ink evaporates and the ink solidifies, the solid matter has a soft property, so that nozzle clogging can be easily prevented by a cleaning operation or the like.

The polyethylene oxide-containing dispersant of the present invention only needs to contain a polyethylene oxide chain and have a group that can be adsorbed on the pigment. The polyethylene oxide-containing dispersant preferably has a molecular weight in the range of 1,000 to 5,000. This is for preventing aggregation of the pigments and preventing the viscosity of the ink from increasing. There is no problem in using other dispersants in combination. The water-soluble organic solvent of the present invention may be at least one selected from the group consisting of ethylene glycol, diethylene glycol and glycerin.

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.

The total content of the water-soluble organic solvent and the water-soluble compound of the present invention is 8 to 16% by weight based on the whole ink composition.
It is preferred that This prevents nozzle clogging,
This is to achieve excellent printing quality without delaying the drying time.

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

The weight ratio of the dispersant of the present invention to the water-soluble compound is preferably in the range of 1: 5 to 1: 1. This is to prevent nozzle clogging.

It is preferable that the weight ratio of the pigment of the present invention to the dispersant containing polyethylene oxide is 1: 2 to 3: 1. This is to obtain excellent print quality.

The method for producing a pigment ink for ink-jet recording is as follows.
At least one water-soluble organic solvent selected from the group consisting of diethylene glycol and glycerin, and / or
Alternatively, a water-soluble compound having 2 or 3 hydroxyl groups bonded to a hydrocarbon having 4 to 6 carbon atoms is added and dispersed, or the water-soluble organic solvent and the water-soluble compound are added from the beginning of production and dispersed. You may. 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 pigment ink for ink jet recording obtained in the present invention has a surface tension of 20 to 70 dyne / cm and a viscosity of 1 to 20 cP, so that stable printing by an ink jet printer can be achieved. Becomes possible.

In the present invention, as the solvent, a mixed solvent of water and at least one water-soluble organic solvent selected from the group consisting of ethylene glycol, diethylene glycol and glycerin is used. There is no problem. 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-dihydroxyethyl urea, urea, acetonylacetone, pentaerythritol, hexylene 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 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.

The pigment ink for ink jet recording of the present invention may be produced by using a container driving medium mill such as a ball mill, a centrifugal mill, or a planetary ball mill, a high-speed rotation mill such as a sand mill, or a medium stirring mill such as a stirred tank mill. .

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 water-based 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.

[0026]

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

[0027]

【Example】

Example 1 Magenta pigment (Chromine Fine Magenta 6887, manufactured by Dainichi Seika) 10 parts by weight Polyethylene oxide-containing dispersant (Sonyyo Chemical Nonipol 200) 10 parts by weight Acetylene glycol 1.5 parts by weight Deionized water 80 parts by weight Dispersion liquid A 50 parts by weight The above composition was pulverized with a planetary ball mill for 15 hours and then dispersed to obtain a dispersion A.

Diethylene glycol 7 parts by weight 1,5-pentanediol 6 parts by weight Ion-exchanged water 37 parts by weight After mixing with the above composition, pigment ink A for inkjet recording
Was prepared.

Example 2 A dispersion B was obtained in the same manner as in Example 1 except that the same amount of a yellow pigment (LIONOL YELLOW GGTN manufactured by Toyo Ink) was used instead of the magenta pigment of Example 1, and a dispersion B was obtained. In the same manner as in the above, a pigment ink B for inkjet recording was produced.

Example 3 Example 1 was repeated except that the same amount of a cyan pigment (KET Blue 111 manufactured by Dainippon Ink) was used in place of the magenta pigment of Example 1.
After a dispersion C was obtained in the same manner as in Example 1, a pigment ink C for inkjet recording was produced in the same manner as in Example 1.

Example 4 Carbon black pigment (Printex 150T manufactured by Degussa) 10 parts by weight Polyethylene oxide-containing dispersant (Jeffamine M-2000 manufactured by San Techno Chemical) 10 parts by weight Ion-exchanged water 80 parts by weight Disperse in time and disperse D
I got

Dispersion D 50 parts by weight Diethylene glycol 6 parts by weight 1,5-pentanediol 7 parts by weight Ion-exchanged water 37 parts by weight After mixing with the above composition, pigment ink D for inkjet recording
Was prepared.

Comparative Example 1 50 parts by weight of dispersion liquid A of Example 1 50 parts by weight of ion-exchanged water After mixing with the above composition, pigment ink E for ink jet recording
Was prepared.

Comparative Example 2 Dispersion A of Example 1 50 parts by weight 1,5-pentanediol 13 parts by weight Ion-exchanged water 37 parts by weight After mixing with the above composition, pigment ink F for ink-jet recording was used.
Was prepared.

Comparative Example 3 50 parts by weight of the dispersion A of Example 1 13 parts by weight of diethylene glycol 37 parts by weight of ion-exchanged water After mixing with the above composition, the pigment ink G for inkjet recording was used.
Was prepared.

Comparative Example 4 Magenta pigment (Chromium Fine Magenta 6887 manufactured by Dainichi Seika) 10 parts by weight Sodium naphthalenesulfonate / formalin condensate 5 parts by weight Acetylene glycol 1.5 parts by weight Ion-exchanged water 80 parts by weight The above composition Was ground in a planetary ball mill for 15 hours and then dispersed to obtain a dispersion H.

Dispersion H 50 parts by weight Diethylene glycol 7 parts by weight 1,5-pentanediol 6 parts by weight Ion-exchanged water 37 parts by weight After mixing with the above composition, pigment ink H for inkjet recording
Was prepared.

Table 1 shows the particle size, viscosity, presence / absence of head clogging, and printing quality of the pigment in the ink obtained in each of the examples.

[0039]

[Table 1] Particle size (nm) Viscosity (cps) Clogging Print quality Example 135 35 ２ 1.2 Example 236 3.6 1.2 Example 335 2.9 １ 1.3 Example 4 38 3.4 ○ 1.2 Comparative Example 1 35 2.5 × <1.0 Comparative Example 2 35 3.5 Δ1.0 Comparative Example 3 35 3.6 × 1.0 Comparative Example 4 60 5 0.3 × <1.0 In this table, the particle size of the pigment was determined by scanning electron microscope (S-
4000). Viscosity is measured by a viscometer (Toki Sangyo R
100 type) at 25 ° C. For head clogging, after printing a certain amount of characters, leave the printer at 50 ° C for 7 days without capping, etc., then perform a cleaning operation to recover nozzle clogging. It was determined whether or not was possible. A case where normal printing was able to be performed by 1 to 5 times of cleaning operation was evaluated as “○”, and 6 to 6 times.
A symbol indicates a case where normal printing was performed by ten cleaning operations, and a symbol X indicates a case where normal printing was performed by 11 or more cleaning operations. The print quality was determined by using a Macbeth portable densitometer (RD-1200 manufactured by Sakata Inx) using a recording pattern printed on plain paper with an inkjet printer.
Optical density was measured using 0).

As is clear from this table, the pigment ink for ink jet recording according to the present invention has a low viscosity, has no clogging of the head, and is excellent in print quality.

[0041]

The pigment ink for ink jet recording produced by the method of the present invention has a property that the solid is soft even if the water in the ink evaporates and the ink solidifies. Therefore, it is easily peeled off by a cleaning operation or the like, nozzle clogging is prevented, and printing quality is excellent.

Continuing from the front page (72) Inventor Sachie Kawazu 1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell Co., Ltd.

Claims (6)

[Claims] 1. A pigment, (B) a polyethylene oxide-containing dispersant, (C) at least one water-soluble organic solvent selected from the group consisting of ethylene glycol, diethylene glycol and glycerin, D) 4 carbon atoms
6. A pigment ink for inkjet recording, comprising: a water-soluble compound in which two or three hydroxyl groups are bonded to hydrocarbons of Nos. 6 to 6, and (E) water. 2. The ink jet recording apparatus according to claim 1, wherein the content of (C) + (D) is 8 to 16% by weight based on the total amount of the pigment ink for ink jet recording according to claim 1. Pigment ink. 3. The weight ratio of (C) to (D) is 2: 1.
2. The pigment ink for ink-jet recording according to claim 1, wherein the ratio is in the range of from 1: 5 to 1: 5. 4. The weight ratio of (B) to (D) is 1: 5.
The pigment ink for inkjet recording according to claim 1, wherein the ratio is in the range of from 1 to 1. 5. The molecular weight of (B) is from 1,000 to 5,000.
The pigment ink for inkjet recording according to claim 1, wherein 6. The weight ratio of (A) to (B) is 1: 2.
2. The pigment ink for inkjet recording according to claim 1, wherein the ratio is from 1 to 3: 1.