JP2008247941A - Inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink that prevents curling and ink strike-through in plain paper recording and, even when the printed matter thereof and an electrophotographic print are preserved in piles, causes no sticking of the electrophotographic print. <P>SOLUTION: The inkjet ink contains at least water and at least 50 mass% and at most 80 mass% of an organic solvent having a boiling point of 150-300°C therein, where at least 50 mass% and at most 80 mass% of at least one selected from among alkane diols represented by general formula (1) or (2) are contained in the inkjet ink as the organic solvent. R<SB>1</SB>-CH(OH)-CH(OH)-CH<SB>2</SB>-R<SB>2</SB>(1). R<SB>1</SB>-CH(OH)-CH<SB>2</SB>-CH(OH)-R<SB>2</SB>(2). In the formulae, R<SB>1</SB>is a hydrogen atom or a methyl group and R<SB>2</SB>is a hydrogen atom, a methyl group or an ethyl group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet ink, and more particularly to a novel inkjet ink.

  In recent years, the inkjet recording method can be easily and inexpensively produced images, and thus has been applied to various printing fields such as photographs, various printing, marking, special printing such as color filters, and the like. In particular, ink jet recording devices that emit and control fine dots, ink with improved color reproduction range, durability, and emission suitability, ink absorbency, colorant color development, surface gloss, etc. are dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper.

  However, in an inkjet image recording system that requires special paper, there is a problem that a recording medium that can be used is limited and the cost of the recording medium is increased.

  On the other hand, in the office, there is a growing need for a system that can perform full-color printing on plain paper at high speed. As for the composition of the ink-jet ink, it can be printed at high speed, has good character reproducibility on plain paper, and shows through when printing (the phenomenon that the printed ink passes through the recording medium and the image appears on the back), Various studies have been made from the viewpoints of no occurrence, quick permeation into paper, and quick drying (see, for example, Patent Documents 1 and 2).

In response to these problems, the present inventor considered that the solvent of a normal water-based inkjet ink is composed of a small amount of a high-boiling organic solvent and a large amount of water, whereas the solvent is a small amount of water and a large amount of a specific high-boiling organic solvent. The present inventors have found an ink (for example, see Patent Documents 3 to 6) that can simultaneously prevent both curling and back-through by using an inkjet ink composed of a solvent. In particular, a monool having one hydroxyl group is preferable as the organic solvent having a high boiling point. However, it has been found that when a printed matter printed with the ink according to these inventions is stored in an overlapping manner with an electrophotographic printed matter, sticking between the electrophotographic prints may occur. The reason is that the inks of these inventions contain more organic solvent having a higher boiling point than ordinary water-based inks, so that they tend to remain in paper and dissolve the electrophotographic toner.
JP 2004-217930 A JP 2005-193660 A JP 2004-29014 A JP 2004-31738 A JP 2004-31739 A JP 2004-31740 A

  An object of the present invention is to provide an ink-jet ink that prevents curling and back-through in plain paper recording and that does not cause sticking of electrophotographic prints even when the printed matter and the electrophotographic printed matter are stored in an overlapping manner. There is.

  The above object of the present invention can be achieved by the following configuration.

  1. In an ink jet ink containing at least water and an organic solvent having a boiling point of 150 ° C. to 300 ° C. in the ink jet ink, the organic solvent contains at least the following general formulas (1) and (2). An ink jet ink comprising at least one selected from alkanediols represented by the formula: 50% by mass or more and 80% by mass or less in the ink jet ink.

Formula _{(1) R 1 -CH (OH} ) -CH (OH) -CH 2 -R 2
Formula _{(2) R 1 -CH (OH} ) -CH 2 -CH (OH) -R 2
(In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group or an ethyl group.)
2. The alkanediol represented by the general formula (1) or the general formula (2) is at least one selected from 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol. 2. The inkjet ink as described in 1 above.

  According to the present invention, there is provided an ink-jet ink that prevents curling and back-through in plain paper recording, and does not cause sticking of electrophotographic prints even when the printed matter and the electrophotographic printed matter are stored in an overlapping manner. did it.

  The present invention will be described in more detail. Electrophotographic toner includes pulverized toner and polymerized toner, and styrene / acrylic resin and polyester resin are generally used as the material. As a result of a new study on the toner solubility of an organic solvent having a high boiling point, the present inventor has found that the diol as a high boiling point organic solvent can significantly reduce the toner solubility as compared with monool. This seems to be because the polarity of the toner and the polarity of the solvent are closer to the monool than to the diol. In general, however, diols give poorer curl of plain paper prints than monools. This is because the hydrogen bond due to hydroxyl groups of cellulose on paper dissociates and the phenomenon of curl that occurs because hydrogen bonds occur at different positions after swelling, and in the case of monool, curl is reduced because it is easy to block dissociated hydroxyl groups of cellulose. This is probably because such a mechanism does not work in diol. However, it has been found that the use of an alkanediol represented by the above general formula (1) or (2) among the diols results in low curl of plain paper printed matter as well as low toner solubility.

  The reason for this is that in these alkanediols, the two hydroxyl groups are close to each other in the molecule. I think it's easy to block.

"solvent"
The present invention includes an inkjet ink containing at least water and an organic solvent having a boiling point of 150 ° C. or higher in an inkjet ink (hereinafter, also simply referred to as ink), and containing the organic solvent in an amount of 50% by mass to 80% by mass. The organic solvent contains at least 50% by mass to 80% by mass of the alkanediol represented by the above general formula (1) or (2) in the ink.

  The present inventor has already found that the content of the organic solvent having a boiling point of 150 ° C. or higher in the ink can be compatible with a small amount of print curl of plain paper and a small amount of ink back-through. The higher the ratio of the organic solvent having a boiling point of 150 ° C. or higher, the better the print curl. On the contrary, the back-through is better, the lower the ratio of the organic solvent having a boiling point of 150 ° C. or higher. It has been found that by containing an organic solvent having a boiling point of 150 ° C. or more in an amount of 50% by mass or more and 80% by mass or less in the ink, plain paper print curl can be reduced and ink back-through can be reduced. Furthermore, as a result of the study, the present inventors have been able to keep the toner solubility low by selecting the alkanediol represented by the general formula (1) or (2) as the organic solvent having a boiling point of 150 ° C. or higher. I understood.

  Specific examples of the alkanediol represented by these general formulas include 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 2,3-butanediol, and 2,3-pentanediol. 2,3-hexanediol, 1,3-butanediol, 1,4-pentanediol, 2,4-pentanediol, and 1,2-hexanediol.

  By containing these alkanediols in an amount of 50% by mass or more and 80% by mass or less in the ink, it is possible to obtain an ink with less print curl and back-through of plain paper and low toner solubility. Further, among the alkanediols of the above general formulas (1) and (2), those selected from 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol are obtained when water is evaporated. This is desirable because the increase in viscosity is low and the decap characteristics during ink ejection become better.

  In addition to the alkanediol represented by the general formula (1) or (2) of the present invention, the following solvents may be used in combination. For example, alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, Dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, Morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine , Triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclic rings ( Examples thereof include 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide), and the like.

《Coloring material》
The inkjet ink of the present invention preferably contains a color material. As the hue of the color material used in the ink of the present invention, for example, color materials that form yellow, magenta, cyan, black, blue, green, and red inks are preferably used, and particularly preferably yellow, magenta, cyan, Each color material is black.

  The ink of the present invention is a dye ink whose color material is a dye, or a pigment ink or a color material that forms a dispersion containing fine pigment particles that is insoluble in the solvent that constitutes the inkjet ink. Examples include various ink-jet inks such as a dispersion ink made of a polymer dispersion.

  Examples of the dye that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and specific compounds thereof include For example, the dye illustrated in Unexamined-Japanese-Patent No. 2002-264490 can be mentioned.

  In addition, oil-soluble dyes that form colored fine particles together with polymers, etc., and become colorants, are usually soluble in organic solvents that do not have a water-soluble group such as carboxylic acid and sulfonic acid, and are insoluble in water, such as disperse dyes. Etc. are selected. Also included are dyes that exhibit oil solubility by salting a water-soluble dye with a long-chain base. For example, acid dyes, direct dyes, salt-forming dyes of reactive dyes and long-chain amines are known. .

  However, in the ink of the present invention, it is preferable to use a pigment as the coloring material, and a pigment that does not have solubility in the solvent composition according to the present invention is preferable from the viewpoint of exerting the intended effects of the present invention.

  As the pigment that can be used in the present invention, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments, and the like can be used, for example, organic pigments such as insoluble pigments and lake pigments, An inorganic pigment such as carbon black can be preferably used. The pigment is present in a dispersed state in the water-based ink. The dispersion method may be any of self-dispersion, activator dispersion, polymer dispersion, and microcapsule dispersion, but the polymer dispersion and microcapsule dispersion are fixed. From the viewpoint of sex.

  The insoluble pigment is not particularly limited, for example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  In addition to the above pigments, when red, green, blue, or intermediate colors are required, the following pigments are preferably used alone or in combination. I. Pigment Red; 209, 224, 177, 194, C.I. I. Pigment Orange; 43, C.I. I. Vat Violet; 3, C.I. I. Pigment Violet; 19, 23, 37, C.I. I. Pigment Green; 36, 7, C.I. I. Pigment Blue; 15: 6 or the like is used.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  The average particle size of the pigment dispersion used in the ink of the present invention is preferably 50 nm or more and less than 200 nm. When the average particle size of the pigment dispersion is less than 50 nm or 200 nm or more, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring instrument using a dynamic light scattering method, an electrophoresis method, or the like. Accurate and often used.

  The pigment used in the present invention is preferably used after being dispersed by a disperser together with a dispersant and other necessary additives according to various desired purposes. As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. Among them, the dispersion by sand mill is preferable because the particle size distribution is sharp when the dispersion is aimed at an average particle diameter of around 100 nm. The material of the beads used for sand mill dispersion is preferably zirconia or zircon from the viewpoint of contamination of bead fragments and ionic components. Further, the bead diameter is preferably 0.1 mm or more and 0.5 mm.

<Pigment dispersant>
Examples of the polymer dispersant for dispersing the pigment according to the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, polyphosphates, and the like. Activators such as oxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide, or styrene, styrene derivatives, vinyl A block copolymer comprising at least two monomers selected from naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, and randoma Copolymer and can be exemplified salts thereof.

  In the present invention, the addition amount of the pigment dispersant is preferably 10 to 100% by mass with respect to the pigment.

<Surfactant>
In the dispersion of the pigment according to the present invention, a surfactant can be used as an additive. As the surfactant used in the present invention, any of cationic, anionic, amphoteric and nonionic surfactants can be used, but it is particularly preferable to use a nonionic surfactant from the viewpoint of dispersion stability.

  Nonionic activators include, for example, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester , Polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, poly Oxyethylene fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide , Acetylene glycol, acetylene alcohol, and the like.

  Further, it is preferable to use a surfactant in order to accelerate the penetration of ink droplets after ink ejection into plain paper, and such a surfactant has an adverse effect on the ink, such as storage stability. The surfactant is not limited as long as it does not affect the surface, and the same surfactants as those used as an additive at the time of dispersion can be used.

《Polyvalent metal ion》
In the ink of the present invention, the total content of calcium ions, magnesium ions and iron ions, which are polyvalent metal ions, is preferably 10 ppm or less, more preferably 0.1 to 5 ppm, particularly preferably. 0.1-1 ppm.

  By setting the content of polyvalent metal ions in the inkjet ink to the amount specified above, an ink having high dispersion stability can be obtained. The polyvalent metal ion according to the present invention is contained in sulfates, chlorides, nitrates, acetates, organic ammonium salts, EDTA salts and the like.

《Other additives》
In the ink of the present invention, in addition to the above description, if necessary, the output stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performance improvement objectives are known. Various additives such as polysaccharides, viscosity modifiers, specific resistance regulators, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, antifungal agents, rust preventives, etc. may be appropriately selected and used. For example, fine oil droplets such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, 57-87988 and 62-261476, As described in Kaisho 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A Nos. 59-42993, 59-52689, 62-280069, 61-242871, and JP-A-4-219266 Can be mentioned.

  In addition, the dissolved oxygen concentration in the ink of the present invention is preferably 2 ppm or less at 25 ° C. By setting this dissolved oxygen concentration condition, the formation of bubbles can be suppressed, and the emission stability even in high-speed printing. An ink jet recording method having excellent properties can be realized. As a method for measuring the dissolved oxygen dissolved in the ink, for example, it can be measured using a dissolved oxygen measuring device DO-14P (manufactured by Toa Radio).

"Recording method"
In the image recording method using the ink of the present invention, for example, an ink jet print is obtained by ejecting ink as droplets from an ink jet head based on a digital signal and adhering it to plain paper by a printer loaded with ink jet ink. It is done.

  When forming an image by ejecting the ink of the present invention, the ink jet head to be used may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, thermal ink jet) Any ejection method such as a mold, a bubble jet (registered trademark) mold, or the like may be used.

  Among them, in the ink jet recording method according to the present invention, the ink of the present invention is ejected from a piezo ink jet recording head having a nozzle diameter of 30 μm or less to perform recording on plain paper, and further, the nozzle diameter is 30 μm or less. It is preferable to perform recording on plain paper by discharging from a piezo-type ink jet recording head having a line head.

"recoding media"
The plain paper used in the ink jet recording method using the ink of the present invention is not particularly limited, but non-coated paper, special printing paper, and 80 to 200 μm uncoated paper belonging to a part of information paper are desirable. The construction of the plain paper according to the present invention is made by a conventional method using mainly chemical pulps represented by LBKP and NBKP, sizing agents and fillers, and using other paper making aids as necessary. As the pulp material used for the plain paper according to the present invention, mechanical pulp and recycled paper recycled pulp may be used in combination, and there is no problem even if these are used as the main material.

  Examples of the sizing agent internally added to the plain paper according to the present invention include rosin size, AKD, Alnicel succinic anhydride, petroleum resin-based size, epichlorohydrin, cationic starch, and acrylamide.

  Examples of the filler internally added to the plain paper according to the present invention include finely divided silicic acid, aluminum silicate, diatomaceous earth, kaolin, kaolinite, halloysite, nacrite, dickite, pyrophyllite, sericite, titanium dioxide, bentonite and the like. Is mentioned.

  Further, the plain paper according to the present invention may contain a water-soluble polyvalent metal salt from the viewpoint of enhancing the strike through of the ink of the present invention and the fixability of the pigment. The water-soluble polyvalent metal salt is not particularly limited. For example, aluminum, calcium, magnesium, zinc, iron, strontium, barium, nickel, copper, scandium, gallium, indium, titanium, zirconium, tin, lead, etc. It is added as a salt such as a metal salt, sulfate, nitrate, formate, succinate, malonate, chloroacetate or p-toluenesulfonate. Further, a water-soluble inorganic polymer such as polyaluminum chloride may be used as a salt of a water-soluble polyvalent metal ion. The water solubility is preferably at least 0.1% by mass, more preferably 1% by mass. Among these, a water-soluble salt composed of aluminum, calcium, aluminum, magnesium, and zinc is preferable because its metal ion is colorless. Particularly preferred are aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum acetate, calcium chloride, calcium sulfate, calcium nitrate, calcium acetate, magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium acetate, zinc chloride, zinc sulfate, zinc nitrate, Zinc acetate. In the present invention, in addition to plain paper, high-quality paper, art paper, coated paper, cast-coated paper, glossy paper, ink jet paper, and the like can be widely used.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<Preparation of inkjet ink>
(Preparation of pigment dispersion)
(Preparation of magenta pigment dispersion)
The following additives are mixed, put together with 200 g of zirconia beads having a diameter of 0.5 mm in a polypropylene plastic bottle, sealed, and dispersed for 5 hours using a paint shaker. A magenta pigment with a magenta pigment content of 15% A dispersion was prepared.

C. I. Pigment Red 122 15 parts Jonkrill 501 (manufactured by Johnson Polymer Co., Ltd.) (solid content 30% aqueous solution) 20 parts 1,2-butanediol 50 parts 3-methoxy-3-methyl-butanol 6 parts water 19 parts [Preparation of Ink 5 ]
1,2-butanediol, 3-methoxy-3-methyl-butanol and water were added to the magenta pigment dispersion prepared above, the pigment concentration in the ink was 4% by mass, 1,2-butanediol was 80% by mass, The remainder was adjusted with water so that -methoxy-3-methyl-butanol was 10% by mass, and the mixture was added and sufficiently stirred. Next, this mixed solution was filtered through a # 3500 mesh metal filter, and deaerated with a hollow fiber membrane, whereby magenta ink 5 was prepared.

[Preparation of inks 1 to 4 and 6 to 23]
In preparing ink 5, magenta inks 1-4 and 6-22 were prepared in the same manner as ink 5 except that 1,2-butanediol had the composition of organic solvents 1 and 2 shown in Table 1. did.

The boiling point of the organic solvent used is shown below.
1,2-butanediol: 191 ° C
1,3-butanediol: 208 ° C
1,4-butanediol: 235 ° C
2,3-butanediol: 182 ° C
1,2-pentanediol: 206 ° C
1,5-pentanediol: 239 ° C
1,2-hexanediol: 223 ° C
Tripropylene glycol monobutyl ether: 273 ° C
Ethylene glycol monoisopropyl ether: 140 ° C
An organic solvent having a boiling point of 300 ° C. or higher cannot be used for ink jet ink because it is solid or has a very high viscosity.

《Image evaluation》
An on-demand type ink jet having a maximum recording density of 720 × 720 dpi using a piezo head having a nozzle diameter of 25 μm, a drive frequency of 12 kHz, a nozzle number of 128, and a nozzle density of 180 dpi (hereinafter, dpi represents the number of dots per 2.54 cm). An image was produced using a printer (manufactured by Konica Minolta).

[Toner solubility]
10 solid prints are printed and placed on top of each other, and 500 black solid prints are printed on top of each other using a color laser printer, magiccolor 7300 (manufactured by Konica Minolta), which is an electrophotographic method. For one week. As a result of observing the number of sheets from the bottom of the electrophotographic print after one week, no sticking was observed at 25 ° C, but there was a difference at 60 ° C. Evaluation was performed.

A: No sticking B: 1 sticking C: 2-3 sticking D: 4-10 sticking E: 11 or more sticking

〔curl〕
A solid print was printed, left in a 25 ° C. and 50% environment for 3 days, visually observed and evaluated.

A: No curling at all B: Slight curling has occurred C: Weak curling has occurred D: Some expansion and contraction is observed, and strong curling has occurred E: Remarkable contraction is observed, quite strong Curling has occurred.

[Back-through]
The back side of the solid print was visually observed for evaluation.

A: No ink bleed or see-through is observed on the back side B: Ink bleed or slight see-through is observed on the back side C: Ink bleed or show-through appears slightly on the back side D: Ink on the back side Bleeding and show-through are strongly recognized. E: Ink bleeding and show-through are recognized quite strongly on the back surface.

[Decap resistance]
Using a share mode piezo-type recording head (manufactured by Konica Minolta) with 256 nozzles, the inside of the head is set to 35 ° C., and the ink droplet velocity at an ejection interval of 50 milliseconds is 8 m / sec. The voltage applied to the recording head was adjusted so that Next, the emission interval time was changed, and the relative ratio of the droplet velocity was measured by applying the following equation, and the decap resistance was evaluated according to the following criteria.

  For example, 100 ink droplets are ejected at an ejection interval of 50 milliseconds, 100 droplets are ejected again at an ejection interval of 50 milliseconds after the interval time t seconds from the first ejection, and the first ink droplet after the interval time t seconds is reached. Is measured as a droplet velocity after an interval time t.

Relative ratio of droplet velocity (%) = (droplet velocity after ejection interval t seconds) / (droplet velocity at ejection interval 50 milliseconds) × 100
A: The interval time t at which the relative ratio of droplet velocity is 70% or less is 10 seconds or more B: The interval time t at which the relative ratio of droplet velocity is 70% or less is 1 second or more and less than 10 seconds C : The interval time t at which the relative ratio of the droplet velocity is 70% or less is 0.3 seconds or more and less than 1 second. D: The interval time t at which the relative proportion of the droplet velocity is 70% or less is less than 0.3 seconds. It is.

  From the table, it can be seen that the ink-jet ink of the present invention prevents curling and back-through, and does not cause sticking of electrophotographic prints even when the printed matter and the electrophotographic printed matter are stored in an overlapping manner.

Claims (2)

In an ink jet ink containing at least water and an organic solvent having a boiling point of 150 ° C. to 300 ° C. in the ink jet ink, the organic solvent contains at least the following general formulas (1) and (2). An ink jet ink comprising at least one selected from alkanediols represented by the formula: 50% by mass or more and 80% by mass or less in the ink jet ink.
Formula _{(1) R 1 -CH (OH} ) -CH (OH) -CH 2 -R 2
Formula _{(2) R 1 -CH (OH} ) -CH 2 -CH (OH) -R 2
(In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group or an ethyl group.) The alkanediol represented by the general formula (1) or the general formula (2) is at least one selected from 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol. The inkjet ink according to claim 1.