JPH10292141A - Ink for ink jet recording, and device for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink for ink jet recording capable of giving prints little in blurs to plain paper, especially reclaimed paper, without deteriorating the color concentrations of the prints, excellent in abrasion resistance and substantially not causing the clogging of ink jet nozzles, by making the ink include a specified inorganic pigment, water and a specific organic additive. SOLUTION: This ink contains (A) 1-20 wt.% of an organic pigment whose surface is subjected to an oxidation treatment, e.g. carbon black which has a particle diameter of 50-200 nm and a dispersion degree of <=10, whose surface is subjected to an oxidation treatment using a hypochlorite, etc., and which has functional groups such as carbonyl groups or carboxylic groups and a surface active hydrogen content of >=1.5 mmol/g on the surface, etc., (B) water, (C) 1-30 wt.% of an organic additive solid at 25 deg.C, selected from urea compounds such as (thio)urea, trimethylolethane, saccharides, polyvinyl alcohol, etc., and, if necessary, (D) an aqueous resin emulsion, an aqueous resin dispersion, a surfactant, a water-soluble organic solvent, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink jet recording ink and an ink jet recording apparatus.

[0002]

2. Description of the Related Art In ink jet recording, ink is ejected as fine droplets from fine nozzles, and characters and figures are printed on plain paper.
This is a method of recording on a recording medium such as recycled paper or coated paper. A method of converting an electric signal into a mechanical signal using an electrostrictive element as an ink jet recording method, intermittently discharging ink stored in a nozzle head portion to record characters and symbols on the surface of a recording medium, a nozzle head A method of rapidly heating a part of the ink stored in a part very close to the discharge part to generate bubbles, and intermittently discharging the ink by volume expansion due to the bubbles, thereby recording characters and symbols on the surface of the recording medium. Have been put to practical use.

[0003] The ink used for such ink-jet recording must have good drying properties of the print, no bleeding of the print, uniform printing on the surface of the recording medium, and no mixing of colors in the case of multiple colors. Such characteristics are required. Particularly problematic here is that, when paper is used as the recording medium, bleeding due to fibers having different permeability, deterioration of image quality caused by bleeding of black ink and color ink at the boundary, and riding on the recording medium. Ink is peeled off when touched with a hand or the like.

As described in US Pat. No. 5,183,502, a conventional ink jet recording ink is obtained by adding Surfynol 465 (Air Products, U.S.A.), which is an acetylene glycol surfactant, to a dye ink. As in U.S. Pat. No. 5,196,056, addition of both diethylene glycol monobutyl ether and Surfynol 465 to a dye-based ink has been studied.

As examples using pigments, in many cases, studies have been made to ensure print quality by controlling ink wetting on the surface of paper while suppressing permeability, and these have been put to practical use. Alternatively, as a combination of glycol ether and a pigment, there is an example in which triethylene glycol monomethyl ether is used for a pigment dispersed using a dispersant as disclosed in Japanese Patent Application Laid-Open No. 56-14761.

There is also an example of a water-based pigment ink using a pigment whose surface active hydrogen content is at least a certain value by oxidizing the surface as disclosed in Japanese Patent Application Laid-Open No. 8-3498.

[0007]

However, in the prior art, plain paper, especially paper, is often used by increasing the permeability of pigment ink for the purpose of obtaining uniform printing on the surface of a recording medium and increasing the drying speed of printed matter. If the amount of ink ejected per unit area increases due to the reduced weight of ink droplets on recycled paper, etc., or even on special paper with a special coat layer, prints may spread or beard as a whole. There is a problem that a state blur occurs. Also, in particular, recycled paper is a collection of various paper components mixed with different penetration rates, but is liable to bleed due to the difference in the penetration rates. In order to reduce the bleeding, a method of heating paper is generally studied. However, if paper or other printing materials are heated during printing, it takes time to start up the heating unit in the apparatus to a predetermined temperature, the power consumption of the apparatus body increases, or paper or other printing materials are heated. There is a problem that the printed matter is damaged.

Further, in the case of printing on paper or the like having a normal sizing agent as a recording medium with an ink using a pigment, the pigment remains on the surface of the paper or the like unless the ink is imparted with a certain degree of permeability, resulting in poor abrasion resistance. There is also a problem of becoming. However, when the ink is given a certain degree of permeability, there is a problem in that the bleeding due to the ink penetrating into the space between paper fibers or the like is conspicuous, and the color density is lowered due to the ink penetrating deep into the paper.

Therefore, the present invention solves such a problem, and an object of the present invention is to enable printing with little bleeding on plain paper, especially recycled paper that has been frequently used in recent years, without lowering the color density. It has excellent abrasion resistance on plain paper, recycled paper, special paper with a special coat layer or a glossy medium while using pigments, hardly clogs around ink flow paths and nozzles, and uses carbon black. Because it is used, it has excellent water resistance, light resistance, and resistance to active gases such as ozone, and it is a surface oxidized type, so it is possible to lower the viscosity and increase the pigment concentration. An object of the present invention is to provide an ink jet recording ink and an ink jet recording apparatus that can be used.

[0010]

In order to solve the above-mentioned problems, the ink jet recording ink of the present invention is characterized by containing at least a surface-oxidized inorganic pigment, water and an organic additive solid at 25 ° C. . Further, an ink jet recording apparatus of the present invention is characterized by using the above ink for ink jet recording.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to an ink used for ink-jet recording, which is free from printing bleeding, capable of printing evenly on the surface of a recording medium, has a higher black color density, In view of the demand for properties such as recycled paper, specialty paper, and having sufficient fixability even on a glossy medium, and being less likely to cause clogging around ink channels and nozzles subjected to fine processing, This is the result of intensive studies.

In the ink jet recording ink of the present invention, the inorganic pigment is dispersed by a surface oxidation treatment. In the present invention, carbon black having a particle size of 50 to 200 nm and a degree of dispersion of 10 or less is subjected to a dispersion treatment by oxidizing the surface with hypochlorous acid, sulfonic acid or the like. And carbonyl group, carboxyl group, hydroxyl group,
Those having a functional group such as a sulfone group and a surface active hydrogen content of 1.5 mmol / g or more were used. In this case, the inorganic pigment can be dispersed in water without using a dispersant for dispersing the pigment.

Examples of the pigments subjected to the surface oxidation treatment as described above include Microjet CW1 manufactured by Orient Chemical Industry Co., Ltd. or a modified product thereof.

This dispersing method uses a dispersant which is generally used for dispersing carbon black in water and which is used in a random polymerization or a random copolymerization. Since the 剤 potential is low, the dispersing agent is contained in the ink for ink jet recording in the present invention. This is because the presence of components such as an organic solvent to be performed easily breaks the dispersion and does not have stability. Further, since the high molecular weight dispersant increases the viscosity of the pigment dispersion solution, the viscosity of the resulting ink becomes higher. In such a case, it becomes difficult to perform ejection by ink jet, and therefore, the amount of the pigment to be added must be kept low. Therefore, there is a problem that it is difficult to obtain a sufficient color density.

Therefore, it has been found that in order to increase the color density with a low viscosity in a system using a pigment, it is preferable to use a pigment whose surface can be dispersed in water by a surface oxidation treatment. .

The amount of the pigment which can be dispersed in water by the surface oxidation treatment is 1% by weight based on the total amount of the ink.
It is desirable that the content be at least 20% by weight. If the amount is less than 1% by weight, a sufficient color density cannot be ensured.
On the other hand, when the content exceeded 20% by weight, the pigment remained on the paper surface even if printing was possible, and the abrasion resistance was poor.

Further, the ink jet recording ink according to the present invention is characterized by containing an organic additive which is solid at 25 ° C. When pigment ink is printed on plain paper, recycled paper, special paper with a special coating layer, or glossy medium with an inkjet recording device, the pigment is attracted by ink penetration and diffuses, causing bleeding. Pigment penetrates into the voids between the fibers, causing whisker-like bleeding,
As a result, the print quality of the printed matter is significantly reduced. By adding a solid organic additive at 25 ° C. to the pigment ink, migration of the pigment was suppressed, bleeding was reduced, and print quality was improved.

In the case of printing on paper or the like having a usual sizing agent as a recording medium with an ink using a pigment, the pigment remains on the surface of the paper or the like unless the ink is imparted with a certain degree of permeability, resulting in poor abrasion resistance. There is a problem of becoming. However, when the ink is given a certain degree of permeability, there is a problem in that the bleeding due to the ink penetrating into the space between paper fibers or the like is conspicuous, and the color density is lowered due to the ink penetrating deep into the paper. The ink for inkjet recording according to the present invention, which contains an organic additive which is solid at 25 ° C., has a state in which the solid covers the pigment on the paper after printing, and the abrasion of the printed matter is improved.

Further, in general, inks using pigments have a problem that the solvent is volatilized around the flow paths and nozzles of the finely processed ink and the pigments are aggregated, so that clogging is likely to occur, and it is difficult to secure ejection stability. However, by adding a solid organic additive at 25 ° C., the volatilization rate of the solvent was reduced and clogging became difficult.

More preferable examples of the organic additive which is solid at 25 ° C. for obtaining the above effects include ureas such as urea, thiourea and tetramethylurea, trimethylolethane, trimethylolpropane, sugars, polyvinyl alcohol, and the like. Polyvinylpyrrolidone, having an average molecular weight of 1,000
There was polyethylene glycol which was 0 or more.

The above saccharides include monosaccharides and polysaccharides, such as glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucitolose, maltose, cellobiose, sucrose, trehalose, maltotriose and the like. Alginic acid and its salts, cyclodextrins, and celluloses.

The amount of the organic additive solid at 25 ° C. is desirably 1% by weight or more and 30% by weight or less based on the total amount of the ink. If the amount is less than 1% by weight, sufficient effects such as the improvement of the printing quality, improvement of the abrasion and improvement of the clogging property cannot be obtained, and if it exceeds 30% by weight, the viscosity increases and it is difficult to discharge stably. There is also an adverse effect, and the above-mentioned effect also reaches a plateau, so that further addition is meaningless.

Further, by adding an aqueous resin emulsion or an aqueous resin dispersion to the ink for ink jet recording of the present invention, the effect of the addition of the organic additive which is solid at 25 ° C. is further improved on the abrasion resistance of the printed matter. I could strengthen it.

As the aqueous resin emulsion, for example, an emulsion mainly containing acrylic acid and / or methacrylic acid could be used. Since acrylic acid and / or methacrylic acid are the main components, they can be stably present even in a water-soluble ink. However, the emulsion is an aqueous resin emulsion as a component, and is a styrene resin, a urethane resin, an acrylamide resin, an epoxy resin or It has been found that a mixture of these may be used.

Further, in the ink jet recording ink of the present invention, it was found that since the surface oxidation treatment type is used for the pigment, the emulsion is preferably of the anion type and the film formation temperature is preferably from 0 ° C. to 20 ° C. If the film forming temperature is lower than 0 ° C., the stability of the ink is deteriorated. If the film forming temperature is higher than 20 ° C., it takes a long time to improve the finger touch on the printing surface when printing in a low temperature environment.

Further, when an aqueous resin emulsion formed by a core-shell type is used,
In particular, there were effects such as improvement of printing quality, improvement of scratching property, improvement of clogging property, and the like. By being core-shell type,
Ingredients such as epoxy and urethane that can improve the touch property and fixability of the ink can be introduced into the core portion, and can be stably present in the aqueous solution as the ink in the shell portion.

Further, as the aqueous resin dispersion, fine particles containing a urethane compound as a main component could be used. The particle size of the fine particles is 20 nm or more and 100 nm or more.
When the particle size is reduced, a stable dispersion state in an aqueous system can be obtained.

A surfactant may be further added to the ink for ink jet recording of the present invention for the purpose of increasing the permeability of the ink. The surfactant to be added is preferably a surfactant having good compatibility with the ink system according to the present invention.
Examples thereof include amphoteric surfactants and nonionic surfactants. Examples of the amphoteric surfactant include lauryl dimethylamino acetate betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amide propyldimethylamino acetate betaine, polyoctyl polyaminoethyl glycine, and other imidazoline derivatives. is there. Nonionic surfactants include acetylene glycol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, and polyoxyethylene oleyl ether. Oxyethylene lauryl ether, polyoxyethylene alkyl ether, ethers such as polyoxyalkylene alkyl ether, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, Sorbitan monooleate, sorbitan sesquiolate, polyoxyethylene monooleate, polyoxyethylene steer Ester such as chromatography bets, and the like other fluorine alkyl esters, fluorine-containing surfactants such as perfluoroalkyl carboxylates.

Among them, acetylene glycol-based surfactants are particularly preferred from the viewpoint of printing quality and printing stability, and examples thereof include 2,4,7,9-tetramethyl-5.
-Decin-4,7-diol, 3,6-dimethyl-4-
Octin-3,6-diol, 3,5-dimethyl-1-
Acetylene glycols such as Hexin-3ol (for example, Surfynol 10 from Air Products (USA))
4, 82, 465, 485 or TG), among which surfynol 46 is particularly preferred.
Particularly good print quality was shown when 5, 104 or TG was used.

The amount of the surfactant to be added to the ink jet recording ink of the present invention is preferably 0.3% by weight or more and 2% by weight or less based on the total amount of the ink.
More preferably, the content is 0.5% by weight or more and 1.5% by weight or less. If it is less than 0.3% by weight, the effect of reducing bleeding is small,
It takes a long time to dry the print, and if it exceeds 2% by weight, there is a problem that the foam is easily formed. However, since the print quality reaches a peak, further addition is meaningless.

Further, a water-soluble organic solvent can be further added to the ink jet recording ink of the present invention for the purpose of improving the clogging property and increasing the solubility of the above-mentioned surfactant. Examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1, 3-
Butanediol, 1,5-pentanediol, 1,6-
Hexanediol, glycerin, thiodiglycol, mesoerythritol, pentaerythritol, 2-pyrrolidone, ethanol, methanol, butanol, propanol, alkyl alcohols having 1 to 4 carbon atoms such as isopropanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl Ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono -N-butyl ether, ethylene glycol Rumono -t- butyl ether, diethylene glycol mono -n- butyl ether, triethylene glycol monobutyl -n- butyl ether, diethylene glycol monobutyl -t- butyl ether, 1-methyl -
1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether,
Propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether,
Propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, etc. Glycol ethers, formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane, and the like, and these can be appropriately selected and used.

The amount of the water-soluble organic solvent to be added is preferably from 0.1% by weight to 60% by weight, more preferably from 1% by weight to 30% by weight, based on the total amount of the ink. If the amount is less than 0.1% by weight, the effect of the addition is small.

In the ink jet recording ink of the present invention, preservatives, antioxidants, conductivity adjusters, pH adjusters, viscosity adjusters, surface tension adjusters, oxygen absorbers, nozzle clogging are included as components. Additives such as inhibitors can be used as appropriate.

Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol,
Sodium pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one (Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN from ICI), etc. You can choose from

Examples of the pH adjusting agent, solubilizing agent or antioxidant include amines such as diethanolamine, triethanolamine, propanolamine and morpholine, and modified products thereof, potassium hydroxide, sodium hydroxide, and hydroxide. Inorganic salts such as lithium, ammonium hydroxide, quaternary ammonium hydroxide (such as tetramethylammonium), carbonates such as potassium carbonate, sodium carbonate and lithium carbonate, and other phosphates, or N-methyl-2-pyrrolidone, allohanate And L-ascorbic acid and its salts, such as allohanates such as methyl allohanate and biurets such as biuret, dimethyl biuret and tetramethyl biuret. In addition, commercially available antioxidants and ultraviolet absorbers can also be used. An example of this is Ciba Geigy's Tin
uvin 328, 900, 1130, 384, 292,
123, 144, 622, 770, 292, Irgac
or 252, 153, Irganox 1010, 107
6, 1035, MD1024, etc., or lanthanide oxides.

Further, as the viscosity modifier, rosins,
Alginic acids, polyvinyl alcohol, hydroxypropylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyacrylates, polyvinylpyrrolidone, gum arabic and the like.

With the ink jet recording apparatus using the ink for ink jet recording according to the present invention as described above, it was possible to achieve a dramatic improvement in print quality, abrasion and clogging.

[0038]

The present invention will be further described below with reference to examples and comparative examples.

First, the composition of the ink used in the evaluation described below is shown below. All figures are% by weight, and the remaining amount means that ion-exchanged water is added so that the whole becomes 100%. However, to the remaining amount of ion-exchanged water, Proxel XL-2 was added in an amount of 0.1 to 1% to prevent corrosion of the ink, and benzotriazole was added in an amount of 0.001 to 0.05% to prevent corrosion of the ink jet head members. .
The following components were mixed, stirred and dissolved at 25 ° C. for 2 hours, and then pressure-filtered at a pressure of ² kg / cm ² using a 0.8 μm diameter membrane filter (registered trademark of Advantech), and each ink was filtered. Obtained.

The pigments 1 to 7 in the ink jet recording ink containing an inorganic pigment, an organic solvent and water subjected to the surface oxidation treatment shown in the present invention were dispersed in water without adding a dispersant by the surface oxidation treatment with hypochlorous acid. Used carbon black.

In the following examples, the emulsion A is a core-shell type crosslinked structure made of a polymer using acrylic acid containing glycidoxide, and the shell portion is obtained by polymerizing acrylic acid to form a carboxyl group of acryloyl group on the surface. There is a structure.

In the following examples, dispersion A is
It is a fine particle mainly composed of a urethane compound having a particle diameter of 50 nm.

Example 1 Addition amount (% by weight) Pigment 1 6.0 Ethanol 5.0 Glycerin 15.0 Polyethylene glycol # 1,000 10.0 Deionized water Remaining Example 2 Pigment 2 6.0 Ethanol 5 0 Glycerin 10.0 Urea 10.0 Remaining ion-exchanged water Example 3 Pigment 3 6.0 Ethanol 5.0 Glycerin 10.0 Trimethylolpropane 10.0 Remaining ion-exchanged water Example 4 Pigment 4 6.0 Ethanol 5.0 Glycerin 10.0 Trimethylolpropane 10.0 Emulsion A 6.0 Deionized water Remaining Example 5 Pigment 5 6.0 Ethanol 5.0 Glycerin 10.0 Trimethylolpropane 10.0 Dispersion A 6. 0 Deionized water remaining amount Example 6 Pigment 6 6.0 Ethanol 5.0 Glycerin 15.0 Limethylolpropane 10.0 Olfin E1010 1.5 Ion-exchanged water Remaining Example 7 Pigment 7 6.0 Ethanol 5.0 Glycerin 15.0 Trimethylolpropane 10.0 Olfine E1010 1.5 2-Pyrrolidone 5.0 Diethylene glycol Monobutyl ether 5.0 Deionized water Remaining amount The composition of the ink used in the comparative example is as follows.

Comparative Example 1 Addition amount (% by weight) Pigment 1 6.0 Ethanol 5.0 Glycerin 15.0 Deionized water Remaining Comparative Example 2 Pigment 1 6.0 Ethanol 5.0 Glycerin 15.0 Polyethylene glycol # 600 10.0 Remaining amount of ion-exchanged water Comparative Example 3 Pigment 3 6.0 Ethanol 5.0 Glycerin 15.0 Trimethylolpropane 35.0 Remaining amount of ion-exchanged water Comparative Example 4 Pigment 2 30.0 Ethanol 5.0 Glycerin 15. 0 Urea 10.0 Remaining amount of ion-exchanged water Comparative Example 5 Pigment 6 30.0 Ethanol 5.0 Glycerin 15.0 Trimethylolpropane 10.0 Olfin E1010 6.0 Remaining amount of ion-exchanged water Comparative Example 6 Pigment 7 6.0 Ethanol 5.0 Glycerin 15.0 Trimethylolpropane 10.0 Olphin E1010 1.5 2-pyrrolidone 20.0 ethylene glycol monobutyl ether 20.0 Remaining ion-exchanged water Next, each of the above inks was mounted on an on-demand type ink jet recording apparatus using a head having 360 dpi and 64 nozzles. And a print test on a glossy medium. The papers used in these evaluations were ordinary papers commercially available in Europe, the United States and Japan, Conqueror papers, Faborit papers, and Mod papers.
o Copy paper, Rapid Copy paper, EPSON
EPP paper, Xerox 4024 paper, Xerox 1
0 paper, Neenha Bond paper, Riccopy 62
00 paper, Yamayuri paper and Xerox R paper. Glossy paper 1 is a pictorico type in which silica sol is coated on a polyester sheet, glossy paper 2 is a product in which a resin is applied on a polyester sheet, and is a swelling type in which ink is swollen. Glossy paper 3 has an average particle diameter of 500 nm on paper. Colloidal silica is applied using latex as a binder.

<Evaluation of Print Quality> The print quality of the printed matter using each ink was comprehensively evaluated by visual observation for thick and whisker-like bleeding due to thin line bleeding. The evaluation results were classified as follows. A: Very good printing quality B: Good printing quality C: Poor printing quality NG: Very poor printing quality Table 1 shows the evaluation results. However, in Table 1, "-" indicates that the viscosity of the ink was high and a stable ejection state could not be obtained.

[0046]

[Table 1]

As is clear from the results shown in Table 1, it is understood that excellent printing quality can be obtained by using the ink jet recording ink used in the present invention in combination with the ink jet recording apparatus.

<Evaluation of Fixing Property> The fixing property of the printed matter with each ink was evaluated by rubbing the printed matter with a finger and a water-soluble line marker. The evaluation results were classified as follows. A: Very good fixability B: Good fixability C: Poor fixability NG: Very poor fixability Table 2 shows the evaluation results. However, in Table 2,-indicates that the viscosity of the ink was high and a stable ejection state could not be obtained.

[0049]

[Table 2]

From the results shown in Table 2, it can be seen that a printed matter having excellent fixability can be obtained by using the ink jet recording ink according to the present invention in combination with the ink jet recording apparatus.

<Evaluation of Clogging Property> The clogging property of each ink was determined by leaving the head part of the ink jet recording apparatus open from the cap part after the printing test and leaving it under a constant temperature and humidity environment of 40 ° C. and 20% RH for 4 weeks. After that, a printing test was performed again to evaluate whether or not the ejection was stable. The evaluation results were classified as follows. A: Discharge after standing is extremely stable. B: Discharge after standing is slightly unstable but recovers immediately. C: Discharge after leaving is unstable and it takes time to recover. Table 3 shows the results of the evaluation, which is unstable and does not return. However, in Table 3,-indicates that the viscosity of the ink was high and a stable ejection state could not be obtained.

[0052]

[Table 3]

From the results in Table 3, it can be seen that by using the ink jet recording ink used in the present invention in combination with the ink jet recording apparatus, it is possible to obtain a system which is hardly clogged even when left at high temperature and low humidity with the head portion opened from the cap portion. You can see that it can be built.

The present invention should not be considered to be limited to these embodiments, and various modifications can be made without departing from the gist of the present invention.

[0055]

As described above, according to the present invention, printing with little bleeding can be performed on plain paper, especially recycled paper which has been frequently used in recent years, without lowering the color density. Excellent fixability on special paper with special coat layer and glossy media, hardly clogging around ink flow path and nozzle, and using carbon black, water resistance, light resistance or ozone The present invention provides an ink jet recording ink and an ink jet recording apparatus which have excellent resistance to active gases, are surface oxidized, can be reduced in viscosity, can increase pigment concentration, and can greatly improve color density of printing. It has the effect of.

Claims (10)

[Claims] 1. An ink jet recording ink comprising at least a surface-oxidized inorganic pigment, water and an organic additive solid at 25 ° C. 2. The ink for ink-jet recording according to claim 1, wherein the surface-oxidized inorganic pigment is carbon black. 3. The ink jet recording ink according to claim 1, wherein the surface oxidized inorganic pigment can be dispersed in water without using a dispersant for dispersing the pigment. 4. The ink for ink jet recording according to claim 1, wherein the amount of the inorganic pigment subjected to the surface oxidation treatment is 1% by weight or more and 20% by weight or less. 5. The organic additive which is solid at 25 ° C. includes ureas such as urea, thiourea and tetramethylurea;
Characterized in that it is one or more water-soluble organic additives selected from trimethylolethane, trimethylolpropane, saccharides, polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene glycol having an average molecular weight of 1,000 or more. Any one of claims 1 to 4
Item 7. The ink for inkjet recording according to item 1. 6. The ink jet recording apparatus according to claim 1, wherein the amount of the organic additive solid at 25 ° C. is 1% by weight or more and 30% by weight or less. ink. 7. The ink jet recording ink according to claim 1, further comprising an aqueous resin emulsion or an aqueous resin dispersion. 8. The ink for ink-jet recording according to claim 7, wherein the aqueous resin emulsion has a core-shell type structure. 9. The ink jet recording ink according to claim 7, wherein the aqueous resin dispersion is a fine particle mainly composed of a urethane resin, and the particle diameter of the fine particles is 20 nm or more and 100 nm or less. 10. An ink jet recording apparatus using the ink for ink jet recording according to claim 1. Description: