JP2011157417A - Inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide aqueous inkjet ink which prevents minus curl from occurring immediately after printing, improves conveyance property, and is excellent also in planarity of a final print. <P>SOLUTION: The inkjet ink contains ≥25 mass% of a water-compatible solvent with an Sp value of 19-26 and has a water content of 20-55 mass%, wherein the inkjet ink contains (1) a 5-10C 1,2-alkanediol or acetylene glycol surfactant and (2) a silicone surfactant or a fluorine surfactant. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aqueous inkjet ink used for inkjet printing.

  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, and special printing such as color filters. In particular, ink jet recording devices that emit and control fine dots, ink with improved color reproduction gamut, durability, and emission suitability, ink absorbency, coloring material 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 dedicated paper, there are problems in that the recording media that can be used are limited and the cost of the recording media is increased.

  On the other hand, in the office, there is an increasing need for a system capable of performing full color printing at high speed without being restricted by a recording medium (for example, plain paper, coated paper, art paper, plain paper double-sided printing, etc.).

  Water-based ink-jet inks are widely used as ink-jet inks. However, when image recording according to the above system is performed using such water-based ink-jet inks, the paper on which the images are recorded immediately after printing (cockling) ) And curled prints over time.

  In order to reduce curling and cockling, a method of including a large amount of a hydrophobic solvent in the ink has been disclosed (see Patent Documents 1 and 2). This method is effective and can suppress the occurrence of curling and cockling even on plain paper.

  However, when high-speed printing such as single pass is performed using these inks and printing methods, curling during storage does not occur and no wavy phenomenon occurs immediately after printing, but from the printer when solid printing on paper The discharged paper curls the printing surface outward (this is a phenomenon similar to cockling, but the final printed surface does not wavy, so in the present invention, it is referred to as a minus curl for distinction). It has been understood that there is a problem. In particular, this problem occurs remarkably when the ink is applied to paper having a coat layer of a part of white pigment.

  This phenomenon recovers in a few seconds as the ink evaporates, so it was not a problem for low-speed printing. However, in the case of high-speed printing, there is a transport problem because it is discharged immediately after printing or moves to the next process. Is likely to occur.

  The present invention relates to an ink containing a large amount of such a solvent. An ink containing glycol monoether and 1,2-alkanediol (Patent Document 3) and an ink containing 1,2-alkanediol, silicone surfactant and glycol ether monobutyl ether (Patent Document 4) are disclosed. However, an ink satisfying the constitution of the present invention which satisfies a constitution containing a large amount of a hydrophobic solvent with a particularly small amount of water has not been disclosed. In addition, these are all problems related to quality improvement, and the problem of minus curl related to conveyance, which is the effect of the present invention, is not shaken, and the curl and cockling of printed matter are not mentioned at all. .

Japanese Patent Application Laid-Open No. 2001-353962 JP 2005-220296 A JP 2001-354889 A JP 2003-306620 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a water-based inkjet ink that prevents the occurrence of negative curl immediately after printing, improves transportability, and is excellent in flatness of a final printed matter. It is to provide.

  In the ink-jet ink having a structure containing a large amount of the hydrophobic solvent and containing a small amount of water according to the present invention, the present invention relates to a negative curl immediately after the ink landing, 1) a C2-C10 1,2-alkanediol interface. It has been found that this problem can be solved by adding an activator or acetylene glycol surfactant and 2) a silicone surfactant or a fluorosurfactant to the ink. In this configuration, it is possible to obtain a smooth printed matter with water-based ink-jet ink without any problems in the above-mentioned conveyance.

  Although the reason is not clear, both the agent corresponding to 1) and the agent corresponding to 2) are agents used as penetrants, and these agents are effective in a constitution containing a large amount of the hydrophobic solvent of the present invention and containing a small amount of water. The inventor speculates that this may be achieved. In particular, the occurrence of minus curl is conspicuous in coated paper having a slightly absorbing white pigment layer, and is considered to be caused by the interaction between the ink and the surface of the paper. For example, the inclusion of these penetrants makes it easier for the white pigment layer and the ink to blend together, or the penetrability improvement allows the ink to pass through the pigment layer and the ink to pass through to the fibers under the coat layer. However, the actual principle is not clear.

  In addition, these agents are known to have a relatively strong penetrating effect, and it can be expected to exert a sufficient penetrating effect even in a solvent-rich system such as the present invention. Among them, only this agent is useful for improving minus curl, and the reason why the effect is produced only when used together is not clear and cannot be predicted.

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

  1. In an ink-jet ink containing 25 mass% or more of a solvent having an Sp value of 19 or more and 26 or less and having a water content of 20 mass% or more and 55 mass% or less, 1) 1 having 5 to 10 carbon atoms , 2-alkanediol or acetylene glycol surfactant, and 2) an ink-jet ink comprising a silicone surfactant or a fluorine surfactant.

  2. 2. The ink-jet ink as described in 1 above, wherein the solvent compatible with water having an Sp value of 19 or more and 26 or less is alkylene glycol monoalkyl ether.

  3. The alkylene glycol monoalkyl ether is dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether or 3-methyl-3-methoxybutanol. 3. The ink-jet ink as described in 2 above.

  4). 1 to 3 above, wherein the total content of glycerin and a solvent having a vapor pressure compatible with water having an Sp value greater than 26 is 1.33 Pa or more is less than 10% by mass of the ink mass. The inkjet ink of any one.

5. The glycol ether that is soluble in water but incompatible with water has a vapor pressure of 133.32 × 10 ² Pa or less, and the glycol ether is dissolved in the ink. The inkjet ink of any one of 1-4.

  According to the present invention, it is possible to provide a water-based inkjet ink that can prevent the occurrence of minus curl immediately after printing, improve the transportability, and obtain an image with good flatness of the final printed matter.

The figure which shows the image image | photographed for the minus curl measurement.

  Hereinafter, although the form for implementing this invention is demonstrated, this invention is not limited to these.

  The present invention relates to an ink-jet ink containing 25 mass% or more of a solvent having an Sp value of 19 or more and 26 or less and having a water content of 20 mass% or more and 55 mass% or less. 10 to 12 alkanediol or acetylene glycol surfactants, and 2) a silicone surfactant or a fluorine surfactant.

  In the present invention, in particular, by including 1) a 12-alkanediol or acetylene glycol surfactant having 5 to 10 carbon atoms and 2) a silicone surfactant or a fluorosurfactant, occurrence of negative curl immediately after printing is prevented. In addition, it is possible to provide a water-based inkjet ink that can improve the transportability and can provide an image with good final flatness.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail.
(Ink solvent composition)
The ink of the present invention is characterized by containing a small amount of water and a large amount of solvent. By including water in the ink, it is possible to produce high-quality images on absorbent media, such as plain paper and coated paper for printing, and prevent ink from penetrating on plain paper. be able to. On the other hand, when water is included in the ink, the water content in the ink swells in the substrate made of cellulose fibers, so-called paper, and curling occurs according to cockling and storage of the printing unit.
(Water volume)
The water content capable of obtaining such a high-quality printed product without causing curling or cockling is 20% by mass or more and 55% by mass or less. Preferably they are 25 mass% or more and 50 mass% or less, More preferably, they are 30 mass% or more and 45 mass% or less. When the water content is less than 20% by mass, the image quality is deteriorated and the show-through occurs. When the water content exceeds 55% by mass, curling and cockling are deteriorated, and conveyance in high-speed printing becomes difficult.
(SP value)
The ink of the present invention contains a large amount of solvent due to the low water content. The solvent of the present invention at that time is a solvent having an SP value of 19 or more and 26 or less and compatible with water. At this time, when the SP value is higher than 26, since the solvent has a property close to water, cockling and particularly curling deteriorate as in the case where the amount of water is increased. Although there is no problem as an effect when the SP value is low, when the SP is less than 19, the ink cannot be mixed without mixing with water.

As for the solubility parameter (SP value), in the present invention, a value calculated from the evaporation energy and molar volume value of atoms and atomic groups by Hansen (Hansen Solubility Parameters a user's handbook) Reference) is used as the SP value.
(Compatibility)
It is difficult to use a solvent that is incompatible with water even within the range of the SP value. The fact that water and solvent are compatible means that water and its solvent dissolve without separation or emulsification at any ratio in the range of 15 to 40 ° C. If water and solvent are not compatible, problems such as ink cannot be prepared in the first place or ink separation occurs when the water-solvent ratio in the ink changes due to evaporation of moisture in the head, etc. It is not preferable.
(Amount of solvent)
The amount of a solvent compatible with water having an SP value of 19 or more and 26 or less in the present invention is 25% by mass or more. When the amount of these solvents together with the water content is 25% by mass or less, other solvents are included, curling and cockling deteriorate, and conveyance in high-speed printing becomes difficult. The upper limit of the content of the compatible solvent having an SP value of 19 or more and 26 or less desired from the amount of water is preferably less than 75% by mass.
(Specific examples of solvent types)
Specific examples of the solvent compatible with water having an SP value of 19 or more and 26 or less according to the present invention include alkylene glycol monoalkyl ether, alkylene glycol, alkylene glycol dialkyl ether, alcohol, alkanediol, alkanetriol, Examples include lactone, lactane, amide compounds and the like.

Of these, alkylene glycol monoalkyl ether which is a monoalkyl ether of diol (glycol) is particularly preferable. Since these agents have only one hydroxyl group in the molecule, they are effective in preventing curling and are low in viscosity despite being hydrophobic and compatible with water. It is easy to produce an ink that satisfies the ink characteristics. As an agent having a high effect of the present invention and having no safety problem, alkylene glycol monoalkyl ether is dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol An agent selected from ethylene glycol monoethyl ether and 3-methyl-3-methoxybutanol is preferred.
(Other solvents and vapor pressure)
In addition to the above solvent, other solvents may be included as long as the configuration and effects of the present invention are not impaired. These may be included for the purpose of adjusting the viscosity and increasing the solubility of pigments and other additives.
(A solvent having a Sp value greater than 26 and a vapor pressure compatible with water of 1.33 Pa or less)
As a solvent compatible with water having an Sp value of 19 or more and 26 or less, and a solvent that can be added to the ink, a vapor pressure having an Sp value greater than 26 and compatibility with water is 1. And a solvent of 33 Pa or less. For example, 1,2,6-hexanetriol, glycerin, 1,3,5 pentanetriol, diethylene glycol, triethylene glycol, diglycerol and the like can be mentioned.

When a solvent having a high vapor pressure is contained, curling occurs when the solvent evaporates after printing. For this reason, the thing whose vapor pressure is 1.33 Pa or less is preferable from a viewpoint of suppressing evaporation. In addition, when the solvent contains a large number of solvents having a plurality of hydroxyl groups in the molecule, the curl tends to be deteriorated. Therefore, the solvent is preferably selected from solvents having a low vapor pressure and containing no diol or triol. Although the vapor pressure is 1.33 Pa or less, it is preferable not to contain much glycerin. Based on these conditions, it is preferable that a solvent having a vapor pressure of 1.33 Pa or higher which is compatible with glycerin and water having an Sp value of greater than 26 is preferably not included in the ink of the present invention. When included in the ink as a carry-in from the material, it is preferable that the total of these solvents be used while being suppressed to less than 10% by mass of the ink mass.
(Solvent that is soluble in water but incompatible with water)
(Glycol ether that is soluble in water but incompatible with water)
Further, the ink of the present invention contains a glycol ether that is soluble in water but incompatible with water, in addition to a solvent that is soluble in water and having a Sp value of 19 to 26. It is preferable.

Specific examples of glycol ethers that are soluble in water but incompatible with water have a vapor pressure of 133.32 × 10 ² Pa or less include, for example, polypropylene glycol having a molecular weight of 400 or more, and a degree of polymerization of polypropylene glycol of 400. And triol type polypropylene glycol having a molecular weight of 700 or more, tetrapropylene glycol monomethyl ether, propylene glycol monobutyl ether, and the like.

  In the present invention, the glycol ether that is soluble in water but not compatible with water is soluble without causing separation or white turbidity with water at 2% by mass or less, but at a certain ratio higher than that. Means glycol ether which causes separation or cloudiness. When the glycol ether is added to water (25 ° C.) while stirring until it becomes 10 times (mass), and it causes separation or white turbidity at any rate during the addition, it is soluble in water. It is determined that the glycol ether is incompatible with water.

A glycol ether that is soluble in water but incompatible with water and has a vapor pressure of 133.32 × 10 ² Pa or less can be contained as long as it is not separated. A preferable amount is 5% by mass or more and 20% by mass or less, and particularly preferably 10% by mass or more and 20% by mass or less with respect to the mass of the ink.

  In this case, the present invention contains 25% by mass or more of a solvent compatible with water having an Sp value of 19 or more and 26 or less (that is, a solvent having a small SP value). However, since the solvent having a small SP value is concentrated into a hydrophobic atmosphere, it is not separated even if glycol ether that is incompatible with water is concentrated.

  As a result, curling and cockling are less likely to occur, and the total amount of solvent in the ink can be reduced.

It should be noted that it is difficult to dissolve in the ink a sufficient amount to increase the curl prevention effect even if a slightly soluble alcohol in water other than glycol ether is used, which is not preferable from the viewpoint of curling improvement.
(Additive basic composition)
The most characteristic feature of the present invention is that the following two interface additives 1) and 2) are used in combination with the ink having the solvent composition described above.
1) C1-C10 1,2-alkanediol or acetylene glycol activator 2) Silicone surfactant or fluorine surfactant (1,2-alkanediol, acetylene glycol surfactant, silicone surfactant, fluorine Surfactant)
As the 1,2-alkanediol having 5 to 10 carbon atoms, 1,2-hexanediol and 1,2-pentanediol are preferable because of their good solubility in ink. With 1,2-butanediol, the effects of the present invention cannot be obtained, and with alkanediols having more than 10 carbon atoms, a content sufficient to obtain the effects of the present invention cannot be dissolved in the ink. The content is preferably 1% by mass to 10% by mass and more preferably 2% by mass to 5% by mass with respect to the ink mass.

  The acetylene glycol surfactant refers to acetylene glycol or acetylene glycol added with ethylene oxide or propylene oxide. Examples include the Surfinol series from Nissin Chemical Industry Co., Ltd. and the acetylenol series from Kawaken Fine Chemical Co., Ltd. As the acetylene glycol, those in which ethylene glycol is added to the hydroxyl group to increase the solubility in water are preferable to acetylene glycol itself, and the addition number of ethylene oxide is preferably between 2 and 8. The acetylene glycol surfactant is preferably contained in an amount of 0.5% by mass or more and 2% by mass or less from the viewpoint of exerting the effects of the present invention and not losing other performances. It is more preferable to make it contain below.

  As the silicone surfactant or the fluorine surfactant, those having a solubility of 0.1% by mass or more in water and a surface tension of 28 mN / m or less when dissolved by 0.3% by mass are preferable. As an agent satisfying such properties, for example, KF351 manufactured by Shin-Etsu Silicone Co., Ltd., BYK348 manufactured by Big Chemie Japan Co., Ltd., and Megafac F444, F553 manufactured by DIC Co., Ltd. are used as fluorine surfactants. Etc. The content varies depending on the type of activator used, but is preferably 0.1% by mass or more and 1% by mass or less.

As a combination, an acetylene glycol surfactant is used as a compound corresponding to 1), and a compound containing 0.7% by mass to 1.8% by mass is preferable. Although 12 diols are effective in terms of negative curl, they are solvents that are less effective in terms of preventing curling, and may cause bleeding depending on the paper, so acetylene glycol surface activity It is preferable to select an agent.
(Pigments, additives)
The ink of the present invention contains various functional additives in addition to the solvents described above.

  The ink of the present invention contains a colorant and further additives as described later in the above solvent as necessary. Examples of the hue of the colorant used in the present invention include yellow and magenta. , Cyan, black, blue, green, and red are preferably used, and yellow, magenta, cyan, and black colorants are particularly preferable.

  The ink of the present invention is a dye ink in which the colorant is a dye, or a pigment ink that forms a dispersion containing fine pigment particles, or a colorant that is insoluble in the solvent that constitutes the inkjet ink. The present invention can be applied to various ink-jet inks such as a dispersion ink composed of a molecular 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, for oil-soluble dyes that form colored fine particles together with the polymer or the like and serve as a colorant, they 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 dispersed A dye or the like is 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 colorant, and a pigment that does not have solubility in the solvent system is preferable from the viewpoint of exerting the intended effect 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 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, when red, green, blue and 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, etc. are 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 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.

  The average particle size of the pigment dispersion used in the ink of the present invention is preferably 10 nm to 200 nm, more preferably 10 nm to 100 nm, and still more preferably 10 nm to 50 nm. When the average particle diameter of the pigment dispersion is 100 nm or less, it is more preferable from the viewpoint of dispersion stability. When the average particle diameter of the pigment dispersion is 10 nm or less, the stability of the pigment dispersion and the storage stability of the ink are improved. It is preferable from the viewpoint.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

  In the inkjet ink of the present invention, a surfactant other than the surfactant of the present invention can be used as an additive during dispersion. As the surfactant, any of cationic, anionic, amphoteric and nonionic can be used.

  Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like.

  Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, acylated peptide, alkyl sulfonate, Alkylbenzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol sulfate, secondary higher alcohol Sulfate ester, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, monoglyculate, fatty acid alkylolamide sulfate, alkyl ether phosphate ester, alkyl phosphate ester Examples include tellurium salts.

  Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

  Nonionic activators include polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester, Oxyethylene 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, polyoxyethylene Fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetyl Glycol, acetylene alcohol, and the like.

  In the ink of the present invention, the total content of calcium ions, magnesium ions and iron ions, which are polyvalent metal ions of the ink, is preferably 10 ppm or less, more preferably 0.1 to 5 ppm, particularly Preferably it is 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.

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 modifiers, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, antifungal agents, rust preventives, and the like can be appropriately selected and used. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicon oil, ultraviolet absorbers described in JP-A-57-74193, 57-87988, and 62-261476, As described in JP-A-57-74192, 57-87989, 60-72785, 61-146591, JP-A-195091 and 3-13376. Anti-fading agents, fluorescent brightening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, etc. Can be mentioned.
(Inkjet, head, one-pass)
In the image forming method using the ink-jet ink of the present invention, for example, an ink-jet print can be obtained by ejecting ink as droplets from an ink-jet head based on a digital signal and attaching the ink to a medium using a printer loaded with the ink-jet ink. .

  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.

  Since the problem of the present invention mainly relates to the problem that occurs during high-speed printing, as a printing method of an inkjet printer, when printing is performed using a line head type recording head with respect to a shuttle head type recording head In addition, the present invention is effective.

The line head type ink jet head refers to an ink jet head having a length equal to or greater than the width of the printing range. As a line head type ink jet head, one head may be larger than the width of the printing range, or a configuration in which a plurality of heads are combined to exceed the width of the printing range as disclosed in Japanese Patent Application Laid-Open No. 2007-320278. May be.
(Ink properties for inkjet)
The ink of the present invention having the above-described structure preferably has an ink surface tension of 20 to 40 mN / m at 25 ° C., more preferably 20 to 35 mN / m, and still more preferably 22 to 35 mN / m. It is. The ink viscosity is preferably 1 to 40 mPa · s at 25 ° C., more preferably 5 to 40 mPa · s, and still more preferably 5 to 15 mPa · s. 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).
(Paper, printing coated paper)
The recording medium used in the present invention is not particularly limited, but non-coated paper, special printing paper, and non-coated paper belonging to a part of information paper, and white pigment and starch or rubber latex on the paper surface. It is desirable to use a printing coated paper having a coating layer.

  The composition of the non-coated paper according to the present invention is mainly made by chemical pulp, sizing agent and filler represented by LBKP and NBKP, and other paper making aids are used as necessary, and paper is made by a conventional method. 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.

  The configuration of the coated paper according to the present invention is such that a coating layer containing a white pigment made of kaolin, calcium carbonate, etc., and starch, SB latex, etc. as a binder is provided on the non-coated paper.

Preferably it has from 60 g / ^{m 2} of 360 g / ^{m 2} as the basis weight as the thickness of the paper.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “part” or “%” in the examples represents “part by mass” or “% by mass”.

Example 1
(Preparation of pigment dispersion)
After mixing 15 parts by mass of MA100 (manufactured by Mitsubishi Chemical) as a pigment, 15 parts by mass of Jonkrill 501 (manufactured by BASF), 15 parts by mass of DPGME (dipropylene glycol monomethyl ether) and 55 parts by mass of water Then, 200 g of zirconia beads having a diameter of 0.5 mm were placed in a polypropylene plastic bottle and sealed, and dispersed for 5 hours in a paint shaker to obtain a black dispersion (pigment dispersion) having a pigment concentration of 15% by mass.
(Preparation of ink)
The pigment dispersion is mixed with a solvent and each additive so as to have the composition shown in Tables 1 and 2, and then the liquid is filtered through a # 3500 mesh metal filter, followed by a membrane deaeration treatment using a hollow fiber membrane. And inks 1 to 40 were produced.
(Evaluation)
Each ink was evaluated as follows.
(Evaluation of minus curl)
The ink was applied to a SA Kinfuji (manufactured by Oji Paper Co., Ltd.) with a weight of 81.4 g / m ² cut into A5Y with a # 3 wire bar.

Regarding the curled state of each sample, the average of the rising edge of the paper edge at two seconds after application (two locations) was measured three times, and the average of the three times was used as measurement data. At this time, curl with the coated surface outward was generated for all the samples, and therefore, numerically, it is considered to fall and becomes a negative value (see FIG. 1). Since the curl state changes with time, photographing is performed, and measurement of an image photographed at 2 seconds after application (two ends of the paper edge 1 and the paper edge 2 so that measurement can be performed at a correct scale at the time of photographing) The minus curl value was obtained by making it come to the front (see FIG. 1). The obtained minus curl value was evaluated for minus curl according to the following evaluation criteria.
◎: Minus curl occurrence is −30 mm or more ○: Minus curl occurrence is −40 mm or more Δ: Minus curl occurrence is −50 mm or more ×: Minus curl occurrence is smaller than −50 mm or in a cylindrical shape (Evaluation of cock ring)
Using a shuttle head type piezo-type recording head having a nozzle diameter of 25 μm and a nozzle number of 512, the recording resolution is 1440 × 1440 dpi (dpi indicates the number of dots per 2.54), and the ink adhesion amount is 8 ml / each. A 10 cm square solid black was printed on a new NPI (A4 Oji Paper Co., Ltd.) having a weight of 81.4 g / m ² so that m ² , 10 ml / m ² and 15 ml / m ² were obtained. At this time, the cockling state immediately after printing was visually examined, and the cockling was evaluated according to the following evaluation criteria.
◎: Cockling is hardly noticed at any dose ○: Cockling is hardly noticed at an amount of 10 ml / m ² or less, but cockling occurs at a dose of 15 ml / m ² △: 8 ml Cockling is hardly noticed at / m ² , but cockling occurs in other samples. ×: Cockling is observed even at 8 ml / m ² .
(Evaluation of curl)
Using a shuttle head type piezo-type recording head with a nozzle diameter of 25 μm and a nozzle number of 512, the recording resolution is 1440 × 1440 dpi (dpi indicates the number of dots per 2.54), and the ink adhesion amount is 14 ml / each. Solid black was printed on a new NPI (A4 Oji Paper Co., Ltd.) with a weight of 81.4 g / m ² so as to be m ² . The prepared sample was dried in a flat state with a hot air dryer at 55 ° C. for 30 seconds and then stored at 25 ° C. and 50 RH% for 1 week.

The rise of the edge of the printed material after one week was measured, and the average of the rise of the curls at the four corners was treated as data, and the curl (curl after aging) was evaluated according to the following evaluation criteria.
◎: Edge rise is less than 10 mm ○: Edge rise is 10 mm or more and less than 15 mm Δ: Edge rise is 15 mm or more and less than 25 mm x: Edge rise is 25 mm or more .
(Evaluation of storage stability)
Each ink was stored at 70 ° C. for 1 day, and the change in particle size before and after storage was examined.
◎: Change in particle size is less than 3% ○: Change in particle size is 3% or more and less than 5% Δ: Change in particle size is 5% or more and less than 7% ×: Change in particle size is 7% or more or gelation or separation Was.

  Table 3 shows the evaluation results.

  Abbreviations in Table 1 are as follows.

* 1: Solvent DPGME: Dipropylene glycol monomethyl ether (Sp value: 21.5) compatible with water having an Sp value of 19 to 26 in the present invention
* 2: Solvent 126HT: 1,2,6-hexanetriol (Sp value: 36.8) having a vapor pressure of 1.33 Pa or less that is compatible with water having an Sp value of greater than 26 according to the present invention.
Gly: Glycerin (Sp value: 34.9)
2PDN: 2-pyrrolidinone (Sp value: 30.4)
12BuDO: 1,2-butanediol (Sp value: 27.3)
12HD: 1,2-hexanediol (Sp value: 27.3)
* 3: Glycol ether PPG400 having a vapor pressure not compatible with water of the present invention of 133.32 × 10 ² Pa or less: Polypropylene glycol polymerization degree 400 (not compatible with water, Sp value: 19)
PGmBE: Propylene glycol monobutyl ether (not compatible with water, Sp value: 18.1)

* 4: The present invention 1) 1,2-alkanediol or acetylene glycol surfactant having 5 to 10 carbon atoms, etc. 12HD: 1,2-hexanediol orphine E1010: acetylene glycol-based activator, Nisshin Chemical Co., Ltd. Company Emar A60: Polyoxyethylene distyrenated phenyl ether, POE lauryl ether manufactured by Kao Chemical Co., Ltd .: Polyoxyethylene lauryl ether (Emulgen 120, manufactured by Kao Corporation, HLB = 15.3)
12BuDO: 1,2-butanediol * 5: 2) of the present invention 2) Silicone surfactant or fluorine surfactant KF351: Silicone activator, Shin-Etsu Silicone Co., Ltd. MegaFax 444: Fluorine activator, manufactured by DIC Corporation

  As is apparent from Tables 1 to 3, according to the configuration of the present invention, it is possible to prevent the occurrence of minus curl immediately after printing, to improve the transportability, and to obtain an image with good flatness of the final printed matter. Moreover, also from the result of each additive, in the solvent composition of the present invention, it is effective only when a combination of a C5-C10 12 alkanediol or acetylene glycol activator and a silicone activator or a fluoroactivator is used. It was understood that

1 Edge 1 of paper
2 Edge 2 of paper
3 Minus curl (curl with the coated surface on the outside)
4 Negative curl value

Claims (5)

  In an ink-jet ink containing 25 mass% or more of a solvent having an Sp value of 19 or more and 26 or less and having a water content of 20 mass% or more and 55 mass% or less, 1) 1 having 5 to 10 carbon atoms , 2-alkanediol or acetylene glycol surfactant, and 2) an ink-jet ink comprising a silicone surfactant or a fluorine surfactant.   The inkjet ink according to claim 1, wherein the solvent having an Sp value of 19 or more and 26 or less and compatible with water is an alkylene glycol monoalkyl ether.   The alkylene glycol monoalkyl ether is dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether or 3-methyl-3-methoxybutanol. The ink-jet ink according to claim 2.   The total content of glycerin and a solvent having a vapor pressure compatible with water having an Sp value greater than 26 is 1.33 Pa or more is less than 10% by mass of the ink mass. The inkjet ink according to any one of the above. A glycol ether that is soluble in water but incompatible with water has a vapor pressure of 133.32 × 10 ² Pa or less, and the glycol ether is dissolved in the ink. Item 5. The inkjet ink according to any one of Items 1 to 4.

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