JPH115933A - Black pigment ink and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a black pigment ink excellent in setting quality and storage stability by incorporating a neutral or basic carbon black having a specified volatile content and a specific surface area, an amphiphatic compd. of which the hydrophilic part is polyethylene oxide and the hydrophobic part is an alkyl group, an anionic dispersant, an acetylenic glycol, and water into the same. SOLUTION: A neutral or basic carbon black having a volatile content of 4% or lower and a specific surface area of 100-400 m<2> /g and pref. being ultrafine particles with an average particle size of 100 nm or lower, an amphiphatic compd. of which the hydrophilic part is polyethylene oxide and the hydrophobic part is an alkyl group and/or an arom. ring and which pref. contains 80-97 wt.% polyethylene oxide part and pef. has a mol.wt. of 1.500-5.000, an anionic dispersant pref. being a copolymer comprising units having anionic functional groups and units having arom. rings and/or alkyl groups, an acetylenic glycol, and water are incorporated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a black pigment ink,
In particular, the present invention relates to an ink suitable for an ink jet recording system in which recording is performed by discharging ink droplets from a print head, and more particularly to a black pigment ink excellent in print quality and storage stability.

[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. In particular, there is a high demand for pigmentation of black ink used in texts. As a black pigment, carbon black is generally studied.

For example, JP-A-4-110363 discloses an aqueous pigment ink in which carbon black is dispersed with a styrene-acrylic acid-acrylate copolymer.

[0006]

However, pigment inks have problems such as dispersibility and storage stability of pigment particles in the ink, and are not completely solved.

An object of the present invention is to provide a black pigment ink used for ink jet recording, which has excellent printing quality and storage stability.

[0008]

The black pigment ink of the present invention has a volatile content of 4% or less and a specific surface area of 100 to 400.
m ² / g neutral or basic carbon black, an amphiphilic compound in which the hydrophilic portion is polyethylene oxide and the hydrophobic portion is an alkyl group and / or an aromatic ring, an anionic dispersant, acetylenic glycol, and water. A black pigment ink characterized by being a solution containing the same.

As a result of our intensive studies, carbon black was obtained by combining an amphiphilic compound in which the hydrophilic part was polyethylene oxide and the hydrophobic part was an alkyl group and / or an aromatic ring, an anionic dispersant and acetylenic glycol. Has been found to improve the dispersibility of the ink, to provide an ink having high dispersion stability of carbon black particles, and to easily redisperse the pigment once settled. Therefore, the carbon black can be uniformly dispersed with a low viscosity, the printing quality is excellent, and the pigment that has settled once can be easily redispersed.

[0010] Regardless of the type of carbon black, hydrophobic groups such as aromatic rings are present on the surface of carbon black.
The mechanism of how the amphiphilic compound, anionic dispersant, and acetylenic glycol affect the hydrophobic groups on the carbon black surface is not clearly understood, but is presumed as shown below. As for the amphiphilic compound, the alkyl group and / or the aromatic ring are in a state of being adsorbed to the hydrophobic group on the surface of the carbon black, and the polyethylene oxide reduces the cohesive force between the carbon blacks due to steric repulsion. With respect to the anionic dispersant, the unit containing an aromatic ring and / or an alkyl group is in a state of being adsorbed to a hydrophobic group on the surface of the carbon black, and the carbon black is subjected to electrostatic repulsion caused by the unit containing an anionic functional group. The cohesion between them is reduced. Acetylene glycol does not directly improve the dispersion of carbon black, but plays a role in assisting the dispersibility of the amphiphilic compound and the anionic dispersant.

[0011] Further, according to our intensive studies, it was found that the results of the high-temperature storage test significantly differed depending on the type of carbon black. In particular, carbon black, which contains a large amount of volatile components, causes problems such as clogging of the print head due to aggregation of carbon black particles when stored at high temperatures. Although the volatile matter contains a large amount of a polar group such as carboxylic acid, the amphiphilic compound of the present invention does not adsorb to the polar group such as the carboxylic acid, but to a hydrophobic group on the surface of carbon black. When the volatile content increases, during the long-term storage of the black pigment ink of the present invention, aggregation of carbon black particles occurs due to this polar group directly or through a solvent or the like, and clogging in a print head or the like easily occurs, The printing quality is also insufficient. Therefore, for the above reasons, the volatile matter of the carbon black used in the present invention must be suppressed to 4% or less. If the volatile matter of the carbon black is 4% or less, the storage stability of the ink can be satisfied.

The specific surface area of carbon black is 10
In the range of 0 to 400 m ² / g and neutral or basic carbon black, the viscosity of the ink is not high,
The storage stability of the ink can be improved.

The amount of the carbon black 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. If you keep 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 particle size of carbon black in the black pigment ink of the present invention may be 100 nm or less. If it exceeds this, sedimentation of carbon black particles may occur during long-term storage of the ink.

The amphiphilic compound of the present invention has a molecular weight of 150
0 to 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 dispersant of the present invention is 80 to 97% by weight, preferably 85 to 95% by weight based on the total amount. Within this range, the cohesive force between carbon blacks can be reduced, and the storage stability of the ink can be satisfied.

Further, among the amphiphilic compounds of the present invention, the amphiphilic compound whose hydrophobic part is an alkylphenyl group is effective for improving the dispersibility of carbon black particles. Carbon black has an aromatic ring such as a phenyl group or a naphthyl group on the surface regardless of the production method. Therefore, the alkylphenyl group is more strongly adsorbed to the aromatic ring on the surface of the carbon black, and the carbon black particles can be more effectively dispersed.

The amount of addition of the amphiphilic compound of the present invention is 0.1 to 20% by weight, preferably 0.1 to 10% by weight, based on the whole ink composition. For example, the dispersibility of the carbon black particles and the storage stability of the ink can be improved.

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,
And a phosphate group. 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, but is more preferably from 1,000 to 30,000. This is because the cohesive force between the carbon blacks is reduced by the electrostatic repulsion force, while the coarse particles that are adsorbed on the plurality of carbon black particles and aggregated are not formed.

The addition amount of the anionic dispersant of the present invention is 0.1 to 20% by weight, preferably 0.1 to 10% by weight, based on the whole ink composition.
It can increase the storage stability of the ink and lower the viscosity of the ink.

The weight ratio of the carbon black of the present invention to the total amount of the amphiphilic compound and the anionic dispersant is 1: 2 to 2.
Preferably it is 3: 1. This is to obtain excellent print quality.

The amount of acetylenic glycol used is 0.01 to 3% by weight, preferably 0.05 to 1% by weight, based on the whole ink composition. In this case, the dispersibility and storage stability of the carbon black particles can be improved.

The black pigment ink of the present invention has a volatile content of 4%.
Neutral or basic carbon black having a specific surface area of 100 to 400 m ² / g, an amphiphilic compound having a hydrophilic portion of polyethylene oxide and a hydrophobic portion of an alkyl group and / or an aromatic ring, an anionic dispersant , Other than acetylenic glycol and water, at least one water-soluble organic solvent selected from the group consisting of ethylene glycol, diethylene glycol and glycerin,
By including a water-soluble compound in which two or three hydroxyl groups are bonded to a hydrocarbon having 4 to 6 carbon atoms or polyethylene glycol, the clogging characteristics of the print head can be further improved.

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.

[0027] The molecular weight of the polyethylene glycol of the present invention is preferably 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 weight ratio of the sum of the amphiphilic compound and the anionic dispersant of the present invention to the water-soluble compound or polyethylene glycol is preferably in the range of 1: 5 to 1: 1. This is to prevent nozzle clogging.

The black pigment ink has a volatile content of at least 4
% Or less and a specific surface area of 100 to 400 m ² / g neutral or basic carbon black, an amphiphilic compound in which the hydrophilic part is polyethylene oxide and the hydrophobic part is an alkyl group and / or an aromatic ring, anionic dispersion Or a mixture comprising an acetylenic glycol and water, or at least one selected from the group consisting of ethylene glycol, diethylene glycol and glycerin.
2 kinds of water-soluble organic solvents and hydrocarbons having 4 to 6 carbon atoms
Alternatively, a water-soluble compound having three hydroxyl groups bonded thereto or polyethylene glycol may be added and dispersed. Various additives are added as needed to form an ink. It is also possible to first prepare a dispersion having a high pigment concentration, dilute it by adding a solvent, various additives, and the like, and use the resulting dispersion as an ink.

In the present invention, 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 even if other organic solvents are mixed. 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 surface tension of the black pigment ink obtained in the present invention is preferably from 20 to 70 dyne / cm. Further, the viscosity at 25 ° C. is preferably 10 cP or less, more preferably 5 cP or less. Since water is usually used as a solvent, the viscosity of the ink is 1 cP or more. By having the above-mentioned surface tension and viscosity, the black pigment ink obtained in the present invention can be stably printed by an inkjet printer.

The dispersing machine for producing the black pigment ink of the present invention may be any commonly used dispersing machine. For example, a container driving medium mill such as a roll mill, a ball mill, a centrifugal mill, a planetary ball mill, a sand mill, etc. And a medium stirring mill such as a high-speed rotation mill or a stirring tank type mill. As a specific method for producing a black pigment ink, there is a method of dispersing the ink using a planetary ball mill or a sand mill using ceramic beads having a particle diameter of 0.01 to 1.0 mm. In this case, it is preferable that the acceleration is 5 to 50 G in the case of a planetary ball mill and 50 to 90% of a ceramic bead at a peripheral speed of 5 to 20 m / s in a sand mill.

In the present invention, ink jet inks such as a surfactant, an anti-clogging agent for a print head, an antifoaming agent for an ink, an anti-drying agent, a bactericide, a humectant, a pH adjuster, and a water-resistance imparting agent for printing. Various additives conventionally used in printer inks 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. Further, the black 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.

[0037]

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

Example 1 The following composition was dispersed in a sand mill for 4 hours using zirconia beads having a particle size of 0.3 mm to obtain a dispersion.

14 parts by weight of carbon black (Printex 75 manufactured by Degussa, volatile matter: 1.2%, specific surface area: 150 m ² / g) 6 parts by weight of amphiphilic compound (Nonipol 400 manufactured by Sanyo Chemical) 2 parts by weight of anionic dispersant (Joncryl 62, molecular weight 8500, manufactured by Johnson Polymer) 1 part by weight of acetylenic glycol 77 parts by weight of ion-exchanged water While stirring 35 parts by weight of this dispersion, 8 parts by weight of diethylene glycol, 7 parts by weight of 1,5-pentanediol and ion-exchanged water 52 parts by weight were dropped over 30 minutes to obtain an ink. The volatile content of carbon black was determined from the difference in weight before and after heating the carbon black at 950 ° C. for 7 minutes. The specific surface area was measured by a BET method using nitrogen adsorption.

(Example 2) While stirring 35 parts by weight of the dispersion of Example 1, 8 parts by weight of diethylene glycol, 6 parts by weight of polyethylene glycol (molecular weight: 300) and 53 parts by weight of ion-exchanged water were taken for 30 minutes. The ink was obtained by dropping.

Example 3 The carbon black of Example 1 was manufactured by Degussa Printex 85 (volatile content: 1.0%, specific surface area: 200 m ² / g), and the amphiphilic compound was manufactured by Sanyo Chemical Co., Ltd., Nonipol 700, anionic dispersion. An ink was obtained in the same manner as in Example 1 except that the agent was changed to Joncryl61J (molecular weight: 12,000) manufactured by Johnson Polymer.

Comparative Example 1 An ink was obtained in the same manner as in Example 1 except that the carbon black of Example 1 was changed to Degussa Special Black 4A (volatile content: 14%, specific surface area: 180 m ² / g). Was.

Comparative Example 2 A styrene-acrylic acid-butyl acrylate copolymer (acid value: 60, weight average molecular weight: 1) was used in place of the amphiphilic compound and the anionic dispersant of Example 1.
(3000) An ink was obtained in the same manner as in Example 1 except for using 8 parts by weight.

FIG. 1 shows the particle size of the pigment in the inks obtained in the examples and comparative examples, the storage stability of the ink, the presence or absence of head clogging, the quality and the viscosity of printing.

In this chart, the pigment particle size was evaluated by a scanning electron microscope (S-4000, manufactured by Hitachi). The storage stability was as follows. .Times.5 times or more, x
１．５1.5 times was designated as Δ, and the others were designated as ○. The redispersibility was evaluated by using a pigment centrifuged at 10,000 G for 3 hours in a centrifuge and forcedly settled. ○ indicates that the pigment was easily redispersed, and Δ indicates that the redispersion was difficult. I have.
The viscosity was measured using a viscometer (R100 type, manufactured by Toki Sangyo).
Measured in ° C. For head clogging, after printing a certain amount of characters, the head was left at 50 ° C for 7 days without capping, etc., and then a cleaning operation was performed to recover nozzle clogging. It was determined whether it was possible. The case where normal printing was able to be performed by 1 to 5 cleaning operations is indicated by “○”, the case where normal printing is performed by 6 to 10 cleaning operations is indicated by “△”, and the normal printing is performed by 11 or more cleaning operations. The case is represented by x. The print quality was measured by measuring the optical density of a recording pattern printed on plain paper by an ink jet printer using a Macbeth portable densitometer (RD-12000 manufactured by Sakata Inx).

[0046]

As is apparent from FIG. 1, the black pigment ink according to the present invention has a volatile content of 4% or less and a specific surface area of 100 to 400 m ² / g in neutral or basic carbon black in a hydrophilic part. Is dispersed by an amphiphilic compound in which the hydrophobic portion is an alkyl group and / or an aromatic ring, an anionic dispersant, and acetylenic glycol, so that the printing quality is excellent and the storage stability is excellent. .

[Brief description of the drawings]

5 is a table showing the particle diameter of pigment in ink obtained in Examples and Comparative Examples, storage stability of ink, presence or absence of head clogging, print quality and viscosity.

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

Claims (10)

[Claims] 1. The method according to claim 1, wherein the volatile component is 4% or less and the specific surface area is 10%.
0 to 400 m ² / g neutral or basic carbon black, an amphiphilic compound in which the hydrophilic part is polyethylene oxide and the hydrophobic part is an alkyl group and / or an aromatic ring, an anionic dispersant, acetylenic glycol, A black pigment ink containing water. 2. The carbon black has an average particle diameter of 100.
2. The black pigment ink according to claim 1, wherein the black pigment ink is ultrafine particles having a diameter of not more than nm. 3. The method according to claim 1, wherein said amphiphilic compound contains 80 to 97% by weight of polyethylene oxide.
The black pigment ink of the above. 4. The molecular weight of the amphiphilic compound is from 1500 to 1500.
2. The black pigment ink according to claim 1, wherein the weight is 5,000. 5. The black pigment ink according to claim 1, wherein the hydrophobic part of the amphiphilic compound is an alkylphenyl group. 6. The method according to claim 1, wherein the anionic dispersant is a copolymer containing at least a unit containing an anionic functional group and a unit containing an aromatic ring and / or an alkyl group. Black 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 black pigment ink according to claim 1, wherein the black pigment ink contains a hydrophilic compound or polyethylene glycol. 8. The black pigment ink according to claim 1, which is used in an ink jet recording system in which recording is performed by discharging ink droplets from a print head. 9. The method according to claim 9, wherein the black pigment ink is 10 ° C. at 25 ° C.
The black pigment ink according to claim 1, which has a viscosity of cP or less. 10. A composition having a volatile content of 4% or less and a specific surface area of 1%.
100 to 400 m ² / g neutral or basic carbon black, an amphiphilic compound in which the hydrophilic portion is polyethylene oxide and the hydrophobic portion is an alkyl group and / or an aromatic ring, an anionic dispersant, acetylenic glycol, A method for producing a black pigment ink, comprising dispersing with ceramic beads having a particle diameter of 0.01 to 1.0 mm in the presence of water.