JPH11181341A - Ink jet recording ink and ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet recording ink having rapid driability on paper, excellent water resistance and frictional resistance, good long-term storage stability, a high ability to attain good printing quality and other properties essential to an ink jet recording ink and to provide an ink jet recording method. SOLUTION: In the ink jet recording ink essentially consisting of water, a water-soluble organic solvent, a self-water-dispersible pigment, and a surfactant, the surface tension of the ink is 40 m/m or below, the drying time is below 5 sec when a solid image with an image coverage ratio of 100% is printed on plain paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel ink-jet ink and a new ink-jet recording method used in an ink-jet recording apparatus (printer, copier, fax, word processor, plotter, etc.).

[0002]

2. Description of the Related Art Liquid or molten solid ink is discharged from nozzles, slits, porous films, etc.
The so-called ink jet type recording apparatus for recording on cloth, film, etc. has been studied vigorously due to its advantages of small size, low cost, quietness, etc., and recently, good printing on so-called plain paper such as report paper, copy paper, etc. In addition to a black single-color printer capable of obtaining quality, many products capable of performing full-color printing are commercially available, and have come to occupy a large position in the field of printing apparatuses. The ink used in the ink jet recording apparatus is mainly composed of a solvent, a coloring material, and an additive. Regarding inkjet inks, (1) high-resolution, high-density uniform images without bleeding and fogging on paper, (2) no clogging due to ink drying at nozzle tips Good ejection stability; (3) good ink drying on paper;
There are required characteristics such as (4) good image robustness and (5) good long-term storage stability.

Various measures have been taken as an improvement measure to satisfy these required characteristics. The drying property of the ink on the paper (3) is important for increasing the speed of the recording apparatus and for preventing color mixture bleeding when performing color printing. Conventionally, the improvement has been made by using a highly permeable or volatile solvent or by adding a surfactant. In regard to the image fastness of (4), a number of disclosures have been made on inks using pigments instead of dyes as coloring materials, as measures for improving water resistance. However, the pigment ink has a drawback that the water resistance is improved but the friction resistance is inferior to the dye ink. Regarding the long-term storage stability of (5), inks using pigments generally tend to be inferior to dye inks. As a method for improving the drawbacks when using these pigments, US Pat. No. 5,571,311 introduces a substituent containing a water-solubilizing group into carbon black, and JP-A-8-81646 discloses a method in which a water-soluble monomer is polymerized on the carbon black surface. A method for oxidizing carbon black is disclosed in JP-A-8-3498. As described above, various inks have been proposed, but the long-term storage stability is good, the drying property on plain paper is fast, and good print quality is obtained.
Further, no ink having excellent water resistance / rub resistance has been found. Although improvements have been suggested in the past,
In any of the methods, the required characteristics of the ink-jet are not attained to a sufficiently satisfactory level, and the desired characteristics have not been obtained.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object the purpose of fast drying on paper and excellent water / rub resistance. It is an object of the present invention to provide an ink and a recording method, which have good long-term storage stability, can obtain better print quality, and sufficiently satisfy other characteristics required for an inkjet ink.

[0005]

The object of the present invention is to provide an ink jet recording ink containing water, a water-soluble organic solvent, a pigment self-dispersible in water and a surfactant as essential components, and the surface tension of the ink is 40 mN / m. Drying time when printing a solid image with the image area ratio of 100% or less on plain paper
The problem is solved by providing an inkjet recording ink that is less than a second. Further, the present invention provides an ink jet recording ink having the above characteristics, further comprising:
(A) The number average dispersed particle size of the pigment dispersed particles in the ink is 15
(B) When the volume average particle diameter of the pigment dispersed particles in the ink is mv and the number average particle diameter is mn, mv / mn is 3.0 or less, and (c) 1 liter of the ink It is preferable that the number of pigment particles having a particle diameter of 0.5 μm or more is 5 × 10 ¹⁰ or less. In the present invention, it is preferable that the self-dispersible pigment is a pigment obtained by hydrophilizing carbon black in the above-mentioned ink for ink jet recording.
Further, the present invention provides the method for producing an ink for inkjet recording, comprising a step of dispersing a self-dispersible pigment in water in water, wherein the dispersing step is performed by using at least one type of an ultrasonic homogenizer or a high-pressure homogenizer. A manufacturing method including one or more of the steps is provided. The present invention also provides an ink jet recording method in which an ink droplet is ejected from an orifice according to a recording signal to perform recording on a recording material, wherein the ink for inkjet recording is used as an ink.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The water-dispersible pigment in the present invention is a pigment that contains a large number of water-solubilizing groups on the surface and is stably dispersed without the presence of a dispersant. Acid / base treatment, coupling agent treatment for ordinary so-called pigments,
By performing a surface modification such as a polymer grafting treatment, a plasma treatment, and an oxidation / reduction treatment, it contains more water-solubilizing groups than ordinary pigments and can be self-dispersed.

[0007] Raven 5250 is a pigment that is the basis of surface modification.
Raven 3500, Raven 5750, Raven 1080, Regal 330R, Mo
gul L, Monarch 1000, Color Black FW2, Black Pear
l Carbon black such as L, Printex V, Special Bk 4A, Mitsubishi NO.25 etc. is easy to use, but CIigment Blue 1, C.
I.Pigment Blue 3, CIPigment Blue 15, CIPigment
Blue 15-3, CIPigment Blue 16, CIPigment Blue
Cyan pigment such as 60, CI Pigment Red 5, CI Pigment R
ed 12, CIPigment Red 48, CIPigment Red112, C.
I. Pigment Red 122, CIPigment Red 146, CIPigmen
magenta pigments such as Red 168, CI Pigment Red 202, C.I.
I. Pigment Yellow 1, CIPigment Yellow 2, CIPigm
ent Yellow 3, CIPigment Yellow 13, CIPigment Y
ellow 16, CIPigment Yellow 73, CIPigment Yello
w 83, CIPigment Yellow 98, CIPigment Yellow 11
4, CIPigment Yellow 128, CIPigment Yellow 154
And other color pigments. Commercially available water-dispersible pigments are Cab-o-je manufactured by Cabot.
In addition to t-200, Cab-o-jet-300, IJX-55, Microjet Black CW-1 manufactured by Orient Chemical Co., and the like, it is also sold by Nippon Shokubai.

[0008] The water contained in the surface-modified pigment
Solubilizing groups can be nonionic, cationic or anionic
Is also possible, but mainly sulfonic acid groups, carboxyl groups,
A hydroxyl group and a phosphate group are desirable. Sulfonic acid group, carboxy
In the case of sil group, hydroxyl group, phosphate group, the free acid state
It can be used in the form of
I do not care. When forming a salt, the acid counterion is generally
Li⁺, Na⁺, K ⁺, NH_Four ⁺And organic amines
Preferably. The pigment content is based on the total ink amount
Preferably in the range of 0.1-20% by weight, more preferably 0.5%
-15% by weight, more preferably 1-10% by weight. face
When the content of the filler increases, the clogging resistance at the nozzle tip
Worsens. Conversely, if the content is low,
Unsuitable concentration cannot be obtained.

The number-average dispersed particle size of these pigments in the ink is preferably in the range of 15 to 100 nm, more preferably in the range of 15 to 50 nm. When the number average dispersed particle size is in this range, clogging hardly occurs and storage stability is excellent. Number average dispersed particle size is 15nm
Below the range, the surface area per unit volume of the particles increases, and the contact area between the particles in the ink tends to increase, or the viscosity of the ink increases and clogging tends to occur. Conversely, when the average particle size is 50 nm or more, dispersion tends to be unstable, and when the average particle size is 100 nm or more, aggregation and sedimentation of the pigment tend to be observed. The dispersion particle size distribution in the present invention is a ratio of the volume average dispersed particle size to the number average dispersed particle size, and is preferably 3.0 or less, more preferably 2.5 or less. When the dispersed particle size distribution is wide, even if the number average dispersed particle size is in the above range, aggregation and sedimentation tend to easily occur with some large dispersed particles as nuclei. The dispersion particle size distribution as described above can be achieved by adjusting the amount of the surfactant described below in an appropriate range. In addition to the above-mentioned reason, in particular, in the case of a method characterized by ejecting ink by applying thermal energy, in order to suppress scorching on the heater, particles having a particle diameter larger than 0.5 μm contained in the ink are used. Number 5
It is preferably at most × 10 ¹⁰ / dm ³ , more preferably at most 3 × 10 ¹⁰ / dm ³ . 0.5 μm particle size
In order to keep the number of particles larger than m in the above range, it is desirable to incorporate a step of removing coarse particles by centrifugation or filtration in the step of producing the ink. When a large amount of surfactant is added to shorten the drying time, the number of particles tends to increase in a normal pigment dispersion, and the number of particles larger than 0.5 μm can be suppressed by using a self-dispersible pigment. Will be possible.

In order to achieve the above object of the present invention, in addition to using a pigment which can be self-dispersed in water, the ink has a surface tension of 40 mN / m or less and an image area ratio of 100%.
When the solid image is printed on plain paper, the drying time needs to be less than 5 seconds. Surface tension is 40mN /
If it exceeds m, the wettability to the recording material is poor, and the drying property and the friction resistance are not improved. The surface tension is 20m
It is preferably at least N / m. If it is less than 20 mN / m, bleeding or strike-through tends to occur because the recording material is too wet. The surface tension is adjusted mainly by the addition of a surfactant. In addition, the influence of the type and amount of a water-soluble organic solvent and a self-dispersible pigment is also taken into consideration. In the present invention, a solid image having an image area ratio of 100% is a solid image in which the amount of ink per unit area is in a range of approximately 1.2 to 2.0 mg / cm ^2. In order for the time to be less than 5 seconds, a penetrant must be included in the ink. The penetrant is preferably a surfactant. In the case of a surfactant, any of nonionic, anionic, amphoteric and cationic surfactants can be used, but from the viewpoint of the dispersion stability of the pigment, a nonionic surfactant or an anionic surfactant is preferable, and particularly, a nonionic surfactant is preferable. Agents are preferred.

Examples of nonionic surfactants include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, and polyglycerin. Fatty acid esters,
Polyoxyethylene sorbite fatty acid ester, polyoxyethylene sterol, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene fatty acid amide, polyoxyethylene polyoxypropylene block copolymer, tetramethyldesinediol, tetramethyldesinediol ethylene oxide adduct, etc. Is raised. Examples of anionic surfactants include alkyl benzene sulfonate, alkyl phenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, higher fatty acid ester sulfate, higher fatty acid ester sulfonate, and higher alcohol ether. Sulfates and sulfonates, higher alkyl sulfosuccinates, formalin condensates of naphthalene sulfonates, polystyrene sulfonates, polyacrylates, polyoxyalkylene alkyl ether phosphates,
Polyoxyalkylene alkyl ether carboxylate,
Alkyl sulfates, acrylic acid-acrylate copolymers and the like can be mentioned. Other silicone surfactants such as polysiloxane polyoxyethylene adducts and perfluoroalkyl carboxylate, perfluoroalkyl sulfonate, fluorosurfactants such as oxyethylene perfluoroalkyl ether, spiculisporic acid and rhamnolipid, Biosurfactants such as lysolecithin can also be used.

These surfactants may be used alone or as a mixture. These surfactants not only have the effect of increasing the penetration rate, but also contribute to improving the wiper cleaning properties of the ink jet head. The addition amount of these surfactants is preferably 0.5 to 4.0 wt.%, More preferably 0.7 to 3.0 wt.%. When it is less than the lower limit value, it is difficult to achieve that the drying time is less than 5 seconds when the solid image with insufficient image penetration and the image area ratio of 100% is printed on plain paper, and at the upper limit value or more, the image is easily blurred. At the same time, the particle size distribution of the dispersion is widened and aggregation / sedimentation of the pigment and clogging of the nozzle are easily caused. The surfactant HL
B is considered in consideration of permeability and dissolution stability in ink.
Preferably it is in the range of 5-25.

If the steady-state flow viscosity of the ink is too low, it tends to spill out of the nozzle, and at the same time, the pigment particles tend to move, so that aggregation tends to occur. mP
It is preferably in the range of as.

The conductivity of the ink is 0.03 to 0.4 s / m.
And more preferably 0.05 to 0.3 s / m. If less than 0.03, dissociation of the self-dispersible pigment surface is insufficient and dispersibility is poor, and 0.4
If it exceeds s / m, the electric double layer around the pigment particles becomes thin, the distance between the particles becomes short, and the dispersibility of the pigment deteriorates.
It is desirable to minimize the required amount of electrolytes other than self-dispersible pigments so that the ink conductivity is not too high.

The ink may contain a compound selected from urea, thiourea, ethylene urea, ethylene thiourea, methyl urea, dimethyl urea, methyl thiourea, and dimethyl thiourea as a discharge stabilizing agent. These addition amounts are preferably in the range of 0.5 to 15% by weight, more preferably in the range of 1 to 10% by weight.

Water-soluble organic solvents are often used in ink-jet inks to prevent evaporation of water. For example, ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol,
Polyhydric alcohols such as triethylene glycol, glycerin, trimethylolpropane, 1,2,6-hexanetriol, 1,5-pentanediol, dipropylene glycol, sugars such as glucose, fructose, galactose, mannose, xylose, and diethylene glycol Glycol ethers such as monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monobutyl ether _;
Ethanol, isopropyl alcohol, lower alcohols such as 1-propanol, thiodiethanol, 2-mercaptoethanol, thioglycerol, sulfolane, sulfur-containing solvents such as dimethyl sulfoxide, 2-pyrrolidone, N-
Nitrogen-containing solvents such as methyl-2-pyrrolidone, cyclohexylpyrrolidone, monoethanolamine, triethanolamine, and diethanolamine. In the case of a solvent having high hydrophobicity, the dispersion of the self-dispersible pigment tends to deteriorate, so that the SP value is preferably 12 or more. These may be used alone or as a mixture of two or more kinds.However, when the content of these water-soluble organic solvents increases, the ink viscosity increases, the ejection stability, and the ejection responsiveness decrease. About 1 to 60% by weight, more preferably about 3 to 50%
% By weight.

Further, hydrochloric acid, sulfuric acid, nitric acid,
Acids such as acetic acid, citric acid, oxalic acid, malonic acid, boric acid, phosphoric acid, phosphorous acid, and lactic acid; bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia; and phosphates and oxalic acid Various buffers such as salts, amine salts, and good buffers are used. The pH of the present ink is preferably pH 4-12, more preferably pH 5-11, in consideration of the storage stability of the ink and erosion of the head and the cartridge member.

In addition, acetamide, betaine and the like as solubilizers, polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethylene glycol, cellulose derivatives and the like as physical property modifiers, cyclodextrin, polycyclodextrin, macrocyclic amines as clathrates, It may contain crown ethers and the like, and if necessary, a fungicide, a rust preventive, a bactericide, an antioxidant,
Chelating agents, dendrimers, polymer emulsions and the like may be contained.

When the content of Mg and Fe in the ink is increased, in addition to promoting the aggregation of the pigment, when using a recording method in which the ink is ejected by applying thermal energy, the burning on the heater tends to increase. 5 ppm
Desirably less than. The removal of Mg and Fe can be performed alone or in combination with washing with water, filtration with a reverse osmosis membrane / ultrafiltration membrane, use of an ion exchange resin, adsorption with activated carbon / zeolite, or the like. Since Mg and Fe are mainly mixed from the pigment, it may be removed by an effective and appropriate method in the state of the pigment itself / the pigment dispersion / ink. In the process of producing the ink of the present invention, it is preferable to use an apparatus selected from an ultrasonic homogenizer or a high-pressure homogenizer that does not use a dispersion medium in order to prevent the metal from being mixed. In the same process,
It is desirable to include a coarse particle removal step by centrifugation.
As mentioned above, the particle diameter contained in the ink is 0.5 μm
As the number of larger particles increases, dispersion instability and burning on the heater increase, but coarse particles can be efficiently removed by using a centrifugal separation method. When performing the centrifugal separation operation, a lower pigment concentration is more effective for removing coarse particles. These inks are superior in dispersion stability to CB ink using a general dispersant when a recording method in which ink is ejected by applying thermal energy is also effective in improving the scorching on the heater. In addition, by forming and discharging one droplet by applying a plurality of pulses, the effect of increasing the discharge stability in continuous discharge by obtaining a stable drop amount was obtained.

Further, by mixing the ink of the present invention and a fixing agent on a recording material, an image having higher resolution, higher density and higher fixing can be obtained. The fixing agent is a material for suppressing the penetration of the coloring material in the ink, and examples thereof include polyvalent metal salts, organic amines and salts thereof, quaternary ammonium salts, cationic polymers, nonionic polymers, and anionic polymers. These fixing agents may be applied to a recording material before or after or simultaneously with ink recording in the form of an aqueous solution or the like. As a method of application, a method of applying the ink to a recording material by discharging from an orifice according to a signal similarly to ink is effective and efficient.

As described above, in an ink jet recording ink containing water, a water-soluble organic solvent, a pigment self-dispersible in water, and a surfactant as essential components, the ink has a surface tension of 40%.
An ink jet recording ink characterized by having a drying time of less than 5 seconds when a solid image having a mN / m or less and an image area ratio of 100% is printed on plain paper is fast drying on paper, It has excellent friction resistance, good long-term storage stability, good print quality, and can be free from problems such as clogging. The mechanism of the above-mentioned improvement by adding a self-dispersible pigment and a surfactant in water in combination is not fully understood,
The following is presumed. Regarding the dispersion stability of the ink, in the case of a normal pigment-dispersed ink, the water-insoluble pigment is aggregated by the action of the dispersant adsorbed on the pigment.
Dispersed without settling. On the other hand, the pigment of the present invention which is self-dispersible in water is self-dispersed without a dispersant. When a large amount of penetrants are present in the ink, if the interaction between the penetrant and the dispersant is strong, the dispersant may gradually separate from the adsorbed pigment and cause aggregation / sedimentation of the pigment. However, there is no such concern in the case of a self-dispersible pigment. Regarding the drying property and printing quality, even if the same penetrant is used, the pigment has a larger particle diameter than the dye, so it is difficult to pass through the voids in the recording material,
It is considered that excessive permeation is suppressed, and even if the drying time is short, bleeding is small and strike-through is suppressed. Regarding the abrasion resistance, in the case of an ink having a high surface tension, the ink has poor wettability to the recording material, but the surface tension is 40 mN.
/ M or less, the wettability is improved, so that the contact area between the ink and the recording material is increased, and it is considered that the fixability is improved. Further, it is considered that the clogging is advantageous because there is no adverse effect due to the interaction between the dispersant and the penetrant when the proportion of the penetrant on the nozzle surface is increased as compared with the ordinary pigment-dispersed ink.

[0022]

The present invention will be described below in more detail with reference to examples and comparative examples. In the following examples, the criterion as to whether or not self-dispersion in water is possible is to disperse a mixture containing a pigment in water without using a dispersant using an ultrasonic homogenizer, a nanomizer, a microfluidizer, a ball mill, or the like. The dispersion was diluted with water to a pigment concentration of about 5%, the initial pigment concentration was measured, 100 g of the dispersion was left in a glass bottle for one day, and the pigment concentration in the upper layer was measured to be 98% or more of the initial concentration. It was decided. For example, when an ultrasonic homogenizer is used, the dispersion is performed at an output of 300 W for about 30 minutes. The method for measuring the pigment concentration is not particularly limited, and may be any of a method of measuring the solid content by drying the sample, and a method of diluting the sample to an appropriate concentration and calculating from the transmittance. If there is a method to find it, it may be used. In the following Examples and Comparative Examples, as for the self-dispersibility of the pigment used, the numerical value obtained based on the above criteria is shown as [Self-dispersibility:]. Example 1 Cab-o-jet-300 (manufactured by Cabot Corporation) was diluted to a carbon concentration of 10% by weight, and then centrifuged (8000 rpm, 40 min) to obtain a pigment dispersion (carbon concentration of 8.5% by weight). Was. [Self dispersibility: 100%] Pigment dispersion liquid 50 parts by weight Polyoxyethylene polyoxypropylene block polymer (HLB about 12) 2 parts by weight Glycerin (SP value about 20) 15 parts by weight Pure water 33 parts by weight Each of the above components Was sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 2 Microjet Black CW-1 (manufactured by Orient) was centrifuged.
(7000r.pm, 30min) to prepare a pigment dispersion (carbon concentration 16.
5% by weight). [Self-dispersibility: 100%] 30 parts by weight of the above pigment dispersion Surfynol 465 (HLB about 13) 1 part by weight Urea 5 parts by weight Ethylene glycol (SP value about 18) 20 parts by weight Pure water 44 parts by weight Each of the above components Was sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 3 Pigment dispersion used in Example 1 50 parts by weight Polyoxyethylene polyoxypropylene block polymer (HLB about 12) 6 parts by weight Glycerin (SP value about 20) 15 parts by weight Pure water 29 parts by weight Were sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 4 After treating Cab-o-jet-300 (manufactured by Cabot) with an ultrasonic homogenizer for 30 minutes, centrifugation (7000 rpm, 2 rpm) was performed.
0 min) to obtain a pigment dispersion (carbon concentration: 12.8%).
[Self-dispersibility: 100%] 40 parts by weight of the above pigment dispersion 20 parts by weight of propylene glycol (about 16 in SP value) 0.7 parts by weight of Surfynol 440 (about 6 in HLB) Surfinol 485 (about 16 in HLB) 1.3 Parts by weight Ethylene urea 3 parts by weight Pure water 35 parts by weight The above components were sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 5 Microjet Black CW-1 (manufactured by Orient) was diluted to a 10% concentration, centrifuged (8000 rpm, 20 min), and then filtered under pressure through a 5 μm filter followed by a 2 μm filter. Thus, a pigment dispersion (carbon concentration: 7.9% by weight) was obtained.
[Self-dispersibility: 100%] 50 parts by weight of the above carbon black dispersion 10 parts by weight of diethylene glycol (SP value of about 15) 5 parts by weight of 2-pyrrolidone (SP value of about 13) 3 parts by weight of polyethylene glycol fatty acid ester (HLB of about 11) Pure water 32 parts by weight The above components were sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 6 Surface oxidation treatment of carbon black (Raven 5750) with sodium hypochlorite (treatment condition: 1.7 times by weight of sodium hypochlorite with respect to carbon black was mixed in water. , About 95 ° C
For 10 hours. ), The pH was adjusted to 7.5 after desalting, and the mixture was dispersed using an ultrasonic homogenizer using pure water as a solvent. After dispersion, centrifugation (7000r.
pm, 20 min) to obtain a pigment dispersion (carbon concentration 15%). [Self-dispersibility: 99%] 30 parts by weight of the above pigment dispersion 10 parts by weight of triethylene glycol (SP value about 14) 1.5 parts by weight of polyoxyethylene alkyl ether carboxylate (HLB about 20) N, N-bis (2-Hydroxyethyl) -2-aminomethylethanesulfonic acid 0.5 part by weight NaOH 0.1 part by weight Pure water 58 parts by weight The above components were sufficiently mixed, filtered under pressure with a 1 μm filter, and the ink was dried. Prepared.

Example 7 Carbon black (Mitsubishi MA-100) was treated with sodium styrene sulfonate as a graft polymer (treatment conditions: carbon black was subjected to peroxidation with sodium persulfate, and then about 0.1 g / g of carbon black was used. 2 g of sodium styrenesulfonate
Was added and stirred to carry out the treatment. ), And then dispersed with an ultrasonic homogenizer using pure water as a solvent for 40 minutes.
Thereafter, the mixture was centrifuged (8000 rpm, 40 min) to obtain a pigment dispersion (carbon concentration: 7.8% by weight). [Self-dispersibility: 98.5%] 60 parts by weight of the above pigment dispersion 10 parts by weight of thiodiethanol (SP value about 14) 2.0 parts by weight of polyoxyethylene octyl phenyl ether (about 9 HLB) 5 parts by weight of urea Pure water 23 parts by weight Each of the above components was sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 8 Carbon black subjected to plasma treatment (treatment conditions: surface treatment of carbon black was performed by applying a high-frequency voltage in the presence of O ₂ gas to discharge the carbon black).
Bk 4A) was dispersed for 40 minutes using a high-pressure homogenizer with water as a solvent so as to have a carbon concentration of 20%, and then centrifuged (7000 rpm, 30 minutes).
(Carbon concentration 15.6% by weight). [Self-dispersibility: 9
9.5%] The above pigment dispersion 30 parts by weight Trimethylolpropane (SP value about 15) 10 parts by weight Glycerin (SP value about 20) 10 parts by weight Polyoxyethylene sorbitan fatty acid ester (HLB about 7) 2 parts by weight Pure water 48 parts by weight Each of the above components was sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 9 3 parts by weight of the pigment dispersion used in Example 1 20 parts by weight of N-methyl-2-pyrrolidone (SP value about 11) 0.01 parts by weight of polyoxyethylene perfluoroalkyl ether (HLB about 13) Part Polyoxyethylene nonyl phenyl ether (HLB about 8) 1.5 parts by weight Urea 6 parts by weight Pure water 69.5 parts by weight The above components were sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink. .

Example 10 30 parts by weight of the pigment dispersion of Example 2 15 parts by weight of propylene glycol (SP value of about 13) 3 parts by weight of isopropyl alcohol (SP value of about 12) Polyoxyethylene oleyl ether (HLB of about 12) 5 parts by weight EDTA 0.1 parts by weight Pure water 50.4 parts by weight The above components were sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Example 11 30 parts by weight of the pigment dispersion of Example 6 10 parts by weight of 1,5-pentanediol (SP value of about 13) 2 parts by weight of diethylene glycol monohexyl ether (SP value of about 10) Na-p-toluenesulfonic acid 0.3 part by weight Surfynol 440 (HLB about 6) 1.0 part by weight Pure water 56.7 parts by weight The above components were sufficiently mixed, and filtered under pressure with a 1 μm filter to prepare an ink.

Example 12 Pigment dispersion of Example 4 35 parts by weight Glucose (SP value about 19) 15 parts by weight Silicone polyoxyethylene adduct (HLB about 7) 3 parts by weight Styrene-acrylate-acrylic acid emulsion 1 Parts by weight Urea 3 parts by weight PROXEL GXL 0.03 part by weight Pure water 43 parts by weight The above components were sufficiently mixed, and filtered under pressure with a 1 μm filter to prepare an ink.

Example 13 A plasma-treated phthalocyanine pigment (treatment condition: a carbon black surface treatment was performed by applying a high-frequency voltage in the presence of O ₂ gas to discharge the pigment) and a pigment concentration of 20%
Using a high-pressure homogenizer with water as a solvent for 40 minutes, and then centrifuged (7000 rpm, 3
0 min), perform an activated carbon adsorption treatment, and then filter through a 5 μm filter to obtain a pigment dispersion (phthalocyanine pigment concentration 1
4.7%). [Self-dispersibility: 99%] 28 parts by weight of the above pigment dispersion glycerin (SP value about 20) 18 parts by weight Polyoxyethylene polyoxypropylene alkyl ether (HLB about 10) 1.5 parts by weight Ethanol (SP value about 14) 0.5 parts by weight N- (2-acetamido) iminodiacetic acid 0.5 parts by weight KOH 0.1 parts by weight Pure water 51.4 parts by weight Mix the above components sufficiently and filter with a 2 μm filter under pressure. And an ink was prepared.

Example 14 5 parts by weight of the pigment dispersion of Example 5 1,2,6-hexanetriol (SP value about 14) 10 parts by weight Ethylene glycol (SP value about 18) 10 parts by weight Oxyethylene oleyl ether (HLB) About 10) 1.3 parts by weight Pure water 73.7 parts by weight The above components were sufficiently mixed, and filtered under pressure with a 1 μm filter to prepare an ink. A resolution of 600 dpi was adopted, in which a single droplet was formed by applying a drive signal consisting of a main pulse, a pre-pulse, and a pause between the pre-pulse and the main pulse, which was prototyped for evaluation.
An image quality test, a rub resistance test, a clogging resistance test, and an ink storage stability test were performed using a thermal inkjet printer. These test results were all ○.

Example 15 An ink having the same composition was prepared in the same manner as in Example 13 except that the centrifugal separation process and the activated carbon adsorption process were not performed.

Comparative Example 1 50 parts by weight of the pigment dispersion used in Example 1 10 parts by weight of glycerin (SP value: about 20) 40 parts by weight of pure water The above components were sufficiently mixed and filtered under pressure with a 1 μm filter. And an ink was prepared.

Comparative Example 2 30 parts by weight of the pigment dispersion used in Example 2 0.1 part by weight of Surfynol 465 (about 13 HLB) 5 parts by weight of urea 20 parts by weight of ethylene glycol (SP value of about 18) 20 parts by weight Pure water 45 parts by weight Part The above components were sufficiently mixed, and filtered under pressure with a 1 μm filter to prepare an ink.

Comparative Example 3 Carbon Black (Regal 330R) [Self-dispersibility: Dispersion 5 parts by weight, gelation not performed] 1 part by weight of Na methacrylate-butyl methacrylate copolymer Surfynol 465 (HLB about 13) 1 part by weight Urea 5 parts by weight Ethylene glycol (SP value about 18) 20 parts by weight Pure water 68 parts by weight A carbon black dispersion liquid is prepared from carbon black, Na methacrylate-butyl methacrylate copolymer and pure water (preparation conditions: ultrasonic homogenizer) (Output 1200
(W) for 30 minutes), and then the above-mentioned other components were sufficiently mixed and filtered under pressure with a 1 μm filter to prepare an ink.

Comparative Example 4 Carbon black (Mitsubishi MA-100) [Self-dispersibility: less than 50 parts by weight of 5 parts by weight] 1 part by weight of styrene-Li maleate copolymer Surfinol 465 (HLB about 13) 0.05 part by weight urea 5 Parts by weight Ethylene glycol (SP value approx. 18) 20 parts by weight Pure water 69 parts by weight After preparing a carbon black dispersion with carbon black, styrene-Li maleic acid copolymer and pure water, the above-mentioned other components are thoroughly mixed. The mixture was filtered under pressure through a 1 μm filter to prepare an ink.

[Evaluation of Ink] Examples 1 to 15
The inks prepared in Comparative Examples 1 to 4 were evaluated for ink characteristics based on the following evaluation criteria. (1) Ink surface tension was measured using a Wilhelmy surface tensiometer in an environment of 23 ° C. and 55% RH. (2) In an environment with an ink viscosity of 23 ° C and 55% RH, a shear rate of 1,400 s ^-1
Was measured. (3) Conductivity meter AOL-4 manufactured by DKK in an environment with ink conductivity of 23 ° C and 55% RH
It was measured using 0. (4) Number Average Dispersion Particle Size and / or Dispersion Particle Size Distribution of Ink The ink was measured at 23 ° C. using a Microtrup UPA manufactured by Leeds & Northrup. (5) When the number of particles larger than 0.5 μm contained in the ink was 23 C, Accusiz manufactured by Particle Sizing Systems
using er TM770 Optical Particle Sizer, and the obtained value was converted into a value per ink 1 dm ^3.

(6) The amount of Mg and Fe contained in the ink The ink is diluted with pure water, and Mg and Fe in the ink diluent are diluted.
The Fe content was measured using an ICP elemental analyzer and converted to the concentration in the ink. (7) In an environment with an ink drop amount of 23 C and 55% RH, using a prototype head with a resolution of 600 dpi, a 1/4 tone (2035 × 128 dots) at a frequency of 6 kHz was used.
The ink was ejected three times, the ink was received on a small piece of the ink absorber, the weight was measured, and the ejection weight of one drop was calculated. (8) Drying time test In an environment of 23 C and 55% RH, using a thermal inkjet printer with a resolution of 600 dpi prototyped for evaluation,
Using FX-L paper (manufactured by Fuji Xerox Co., Ltd.) as a typical plain paper, print a solid image of 10 mm x 50 mm with an image area ratio of 100%, and after printing, the droplets are visually invisible from the paper The time until was measured. (9) Image quality test For the prepared ink, a resolution of 600 d prototyped for evaluation
Using pi's thermal inkjet printer, FX-L paper (manufactured by Fuji Xerox) as a typical plain paper,
A 1 dot line, solid image print test was performed. As the evaluation items, line bleeding and the uniformity of the edge of the solid image were examined, and the evaluation was performed according to the following criteria. a) Line bleeding ○ ・ ・ ・ ・ ・ No bleeding. Δ: Slight bleeding. ×: There is a whisker-like bleeding in many parts. b) Uniformity of solids: No disturbance. Δ: There is slight disturbance. ×: Lack of smoothness due to rattling.

(10) Abrasion resistance test The prepared ink was tested for evaluation at a resolution of 600 d.
An image was printed using a thermal ink jet printer of pi. One day after printing, the image portion was rubbed with a finger, and the degree of discoloration of the image portion and the stain on the non-image portion were evaluated according to the following criteria.・ ・ ・: No decrease in image density was observed, and the non-image portion was completely free of dirt. Δ: The image density hardly decreased, but the non-image portion was slightly stained. X: Image density is reduced, and stains on non-image areas are conspicuous.

(11) Clogging resistance test The prepared ink was tested at a resolution of 600 d for evaluation.
Using a thermal ink jet printer of pi, the apparatus was allowed to stand in an environment of 23 C, 55% RH without capping after the ejection was stopped, and the standing time until image disturbance occurred when the ejection was restarted was measured. The evaluation was performed according to the following criteria. ○ ・ ・ ・ ・ ・ 1min or more △ ・ ・ ・ ・ ・ 0.5min ~ 1min × ・ ・ ・ ・ ・ Less than 0.5min

(12) Ink Storage Stability Test The prepared ink was stored at 60 ° C. and -20 ° C. for one month, and then re-filtered with a 1 μm filter. Printing was performed using an inkjet printer. The evaluation was performed according to the following criteria. ○ ... No change in filterability before and after storage. No change in image density. △ ・ ・ ・ ・ ・ A slight decrease in filtration speed is observed after storage,
No change in image density. X: The filter clogged with the ink after storage was severe, and the image density was greatly reduced. Tables 1 to 4 show the above results.

Table 1

[Table 1]

Table 2

[Table 2]

Table 3

[Table 3]

Table 4

[Table 4]

Example 16 The following evaluation was carried out using the ink of Example 1 and the ink having the following composition. Cyan Ink ZENECA dye Projet Fast Cyan.2 4 parts by weight Butyl carbitol 5 parts by weight Thiodiethanol 15 parts by weight Pure water 76 parts by weight The above components are mixed and dissolved well, and filtered under pressure with a 0.45 μm filter. Was prepared. Magenta Ink Dye Proj instead of ZENECA Dye Projet Fast Cyan.2
et Ingredients were mixed and dissolved with the same composition except that Fast Magenta 2 was used, followed by pressure filtration with a 0.45 μm filter to prepare an ink. Yellow ink Dye Proj instead of ZENECA dye Projet Fast Cyan.2
et Ingredients were mixed and dissolved with the same composition except that Fast Yellow 2 was used, followed by pressure filtration with a 0.45 μm filter to prepare an ink.

(13) Overlay image quality test Using a thermal ink-jet printer with a resolution of 600 dpi that was prototyped for evaluation, FX-L paper (manufactured by Fuji Xerox Co., Ltd.)
A printing test was performed on a solid image pattern in which one dot line and each color were adjacent. As the evaluation items, line bleeding and uniformity of a portion adjacent to the solid image were examined, and the evaluation was performed according to the following criteria. a) Line bleeding ○ ・ ・ ・ ・ ・ No bleeding △ ・ ・ ・ ・ ・ Slight bleeding × ・ ・ ・ ・ ・ Whispered bleeding in many parts b) Solid uniformity ○ ・ ・ ・ ・ ・ No disturbance Δ: Slightly disturbed ×: Lack of smoothness due to rattling All of the evaluation results of a) and b) were ○.

Example 17 The following evaluation was carried out using the ink of Example 1 and a fixing agent having the following composition. Fixing agent A Styrene-Na maleic acid copolymer 4 parts by weight Diethylene glycol 15 parts by weight Polyoxyethylene lauryl ether (HLB about 8) 0.1 part by weight Isopropyl alcohol 2 parts by weight Pure water 79 parts by weight Resolution of 600 dpi made for evaluation Using the thermal inkjet printer described above, the ink of Example 1 was overprinted on FX-L paper (manufactured by Fuji Xerox Co., Ltd.) as a typical plain paper within 5 s after discharging adhesive A, and the image of (9) was printed. The same evaluation as the quality test and the friction resistance test of (10) were performed.
The image density was higher than that of Example 1, and the results of the image quality test and the rub resistance test were all ○.

Example 18 The following evaluation was carried out using the ink of Example 2 and a fixing agent having the following composition. Fixing agent B Stearyltrimethylammonium chloride 1 part by weight Polyallylamine hydrochloride 5 parts by weight Glycerin 20 parts by weight Pure water 74 parts by weight The same evaluation as in Example 17 was performed. The image density was higher than that of Example 2, and the results of the image quality test and the rub resistance test were ○.

[0054]

Since the ink of the present invention has the above-mentioned constitution, when used in ink-jet recording, it quickly dries on paper, has excellent water / rub resistance, has good long-term storage stability, and has good print quality. Is good and does not cause problems such as clogging.

Claims (17)

[Claims] 1. An ink jet recording ink comprising water, a water-soluble organic solvent, a pigment self-dispersible in water and a surfactant as essential components, and has a surface tension of 40 mN / m.
An ink for inkjet recording, wherein the drying time is less than 5 seconds when a solid image having an image area ratio of 100% or less is printed on plain paper. 2. The pigment-dispersed particles in the ink (a) have a number average dispersed particle diameter of 15 to 100 nm, and (b) the pigment dispersed particles in the ink have a volume average particle diameter of mv and a number average particle diameter of m.
When n is set, mv / mn is 3.0 or less, and (c)
The ink-jet recording ink according to claim 1 having a particle diameter contained in the ink in 1 liter number of 0.5μm or more pigment particles is 5 × 10 ¹⁰ or less, and wherein the. 3. An ink having a surface tension of 20 to 40 mN /
m, viscosity 1.8-4.0 mPas, conductivity 0.0
The ink for inkjet recording according to claim 1, wherein the ink is in a range of 3 to 0.4 s / m. 4. The ink jet recording ink according to claim 1, wherein the surfactant is at least one of an anionic surfactant and a nonionic surfactant. 5. The ink for ink jet recording according to claim 1, wherein the HLB of the surfactant is in the range of 5 to 25. 6. The method according to claim 1, wherein the surfactant is 0.5 to 0.5% by weight of the ink.
2. The ink jet recording ink according to claim 1, wherein the ink is contained in an amount of 4.0% by weight. 7. The ink jet recording ink according to claim 1, wherein Mg and Fe contained in the ink are each less than 5 ppm. 8. The ink jet recording apparatus according to claim 1, wherein the ink further contains at least one compound selected from urea, thiourea, ethylene urea, methyl urea, ethylene thiourea, and dimethyl urea. ink. 9. The ink according to claim 1, wherein the self-dispersible pigment is obtained by hydrophilizing carbon black. 10. A method for producing an ink jet recording ink comprising a step of dispersing a self-dispersible pigment in water in water, wherein the dispersing step is performed by using at least one of an ultrasonic homogenizer and a high-pressure homogenizer. The method for producing an ink for inkjet recording according to claim 1, comprising one or more steps. 11. The method according to claim 10, further comprising a step of removing coarse particles by centrifugation. 12. An ink jet recording method according to claim 1, wherein the ink is ejected from an orifice in accordance with a recording signal to perform recording on a recording material. An ink-jet recording method, characterized in that: 13. The ink jet recording method according to claim 12, wherein the ink is ejected by applying thermal energy to the ink. 14. The ink-jet recording method according to claim 12, wherein one droplet is formed and discharged by applying a plurality of pulses. 15. The ink jet recording method according to claim 12, wherein the ink and the fixing agent are mixed on the recording material. 16. The ink jet recording method according to claim 15, wherein a fixing agent is discharged from an orifice according to a recording signal and applied to a recording material. 17. The ink jet recording method according to claim 16, wherein the fixing agent is a cationic substance and / or a polymer substance.