JP2008265059A - Inkjet recording reaction liquid, inkjet recording method and inkjet recording inkset - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording reaction liquid, which improves bleeding, a big problem at the printing on plain paper by inkjet recording method, develops no strike through, and enables favorable image formation reconciling fixability and color developing properties as well as continuous delivery by heat energy munch longer than ever, and to provide recording method employing thereof and further an inkset consisting of the reaction liquid and pigment ink. <P>SOLUTION: This inkjet recording reaction liquid is employed together with the pigment ink and develops reaction by the contact with the pigment ink and includes (a) multivalent metal salt, (b) boric acids and (c) liquid medium. Further, inkjet recording method employed thereof and an inkset consisting of the reaction liquid and the pigment ink are dealt. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reaction liquid for ink jet recording, an ink jet recording method, and an ink set for ink jet recording, which can obtain a high-quality color image on an ink jet recording medium, particularly plain paper.

  In the ink jet recording method, recording is performed by ejecting fine droplets of a recording liquid (ink) from an ink jet recording head, causing the liquid droplets to fly and adhering to a recording medium such as paper. As means for supplying discharge energy for flying droplets, there are various methods such as a method of using an electrothermal converter and discharging droplets by generating bubbles by applying thermal energy to ink. is there. Among these, the method of applying thermal energy to ink has a feature that a high-density multi-orifice of a recording head can be easily realized, and a high-resolution and high-quality image can be recorded at high speed (Patent Document 1).

  On the other hand, inks conventionally used for ink jet recording generally contain water as a main component and contain a water-soluble high-boiling solvent such as glycol for the purpose of drying and preventing clogging. As described below, there has been a problem that it is difficult to obtain a good image when such ink is used and the above-described ink jet recording is performed on plain paper as a recording medium. In particular, when a color image is to be obtained, this tendency is large because inks of different colors are superimposed one after another before the previously applied ink is completely fixed. Specifically, different colors ooze each other particularly at the boundary between the colors, resulting in a non-uniformly mixed state (hereinafter referred to as “bleeding”), so that a satisfactory image may not be obtained. .

  Patent Document 2 discloses adding a compound such as a surfactant to the ink as a means for improving bleeding in order to improve the permeability to a recording medium. However, in this method, although the bleeding is suppressed to some extent by increasing the penetration speed of the ink into the recording medium, the colorant in the ink may penetrate deep into the recording medium due to the effect of the surfactant. For this reason, the density and sharpness of the formed image are lowered, and the ink reaches the back surface of the recording medium so that the image can be seen through the back surface (hereinafter referred to as “back-through”). There was a case. In addition, since the wettability with respect to the surface of the recording medium is increased at the same time, the ink easily spreads on the recording medium. As a result, there is a problem that the resolution is lowered and the image looks blurred.

  As another means, a method of applying another liquid (reaction liquid) for improving an image on a recording medium prior to ink ejection has been proposed. For example, Patent Document 3 discloses a method in which a solution of a polymer such as carboxymethyl cellulose, polyvinyl alcohol, polyvinyl acetate or the like is previously applied to a recording medium and then recording is performed with ink. However, when this method is carried out, bleeding is improved, but it takes time to dry the image, resulting in another problem that the fixing property is poor.

  For this reason, there are the following proposals aimed at improving the above problems. For example, Patent Document 4 discloses a method of recording with an ink containing an anionic dye after applying a liquid containing an organic compound having two or more cationic groups per molecule. Patent Document 5 discloses a method of recording with ink after applying an acidic liquid.

  However, although bleeding is improved in any of the above cases, there are the following problems. That is, in any case, since the reactivity of the reaction solution is not so high, most of the reaction occurs inside the recording medium, resulting in the problem that the color developability is not improved and the problem of the show-through as described above. It was left.

  On the other hand, the following proposals have been made as methods using more effective materials for ink jet recording. For example, Patent Document 6 discloses a method for suppressing bleeding using a reaction between a polyvalent metal ion and a carboxyl group. Further, Patent Document 7 discloses a method for improving bleeding by reaction with a pigment, a resin emulsion, and a polyvalent metal salt. However, the reaction liquid for ink jet recording containing these polyvalent metal ions has the following problems although the effect as the reaction liquid is excellent. That is, when the ink jet recording method applied to the recording medium is based on the action of thermal energy, there is a problem that the discharge speed of the reaction liquid varies greatly depending on the driving frequency. Further, when the reaction liquid is continuously discharged for a long time, there is a problem that the discharge itself stops.

  Regarding the problem that the discharge speed of the reaction liquid fluctuates depending on the driving frequency, it is disclosed in Patent Document 8 that it can be improved by adding a certain salt typified by ammonium nitrate to the reaction liquid. However, in this case, although the dependency of the ejection speed on the driving frequency is certainly improved, there is a problem that the tendency of the ejection to stop by continuous ejection becomes more conspicuous. Patent Document 9 discloses that continuous discharge characteristics are improved by adding an acid having an amino group to a reaction solution containing polyvalent metal ions. However, there is no mention of longer-term continuous discharge characteristics.

Japanese Patent Publication No. 61-59911 JP 55-65269 A JP-A-56-89595 JP 63-29971 A Japanese Unexamined Patent Publication No. 64-9279 JP-A-5-202328 JP-A-9-207424 JP 2000-136337 A JP 2002-172847 A

  As described above, various effective proposals using ink and a reaction liquid have been made as one of means for improving bleeding and show-through. However, although some improvement can be seen in any case, it has not yet been able to satisfy all the problems.

  The present invention has been made in view of this point, and its main object is as follows. That is, for inkjet recording, which improves bleeding, which is a major problem when printing on plain paper by the inkjet recording method, and can form a good image with both fixability and color development without causing back-through. It is to provide a reaction solution. Furthermore, an object of the present invention is to provide a reaction liquid for ink jet recording that can be continuously ejected for a much longer period of time even when used in an ink jet recording system in which the ejection energy of droplets is thermal energy. . Another object of the present invention is to provide an ink jet recording method using the above excellent reaction liquid for ink jet recording, and an ink set comprising the reaction liquid and pigment ink.

  The above object is achieved by the present invention described below. That is, the present invention is an ink jet recording reaction liquid that is used together with a pigment ink and that reacts when contacted with the pigment ink, and includes (a) a polyvalent metal salt, (b) boric acids, and (c) a liquid. A reaction liquid for ink jet recording, comprising a medium.

  Another embodiment of the present invention provides a recording medium by applying energy to the above-described ink jet recording reaction liquid, applying the energy to the pigment ink after being discharged onto the recording medium and applied onto the recording medium, or before applying. The inkjet recording method is characterized in that each of the recording reaction liquid and the pigment ink is applied so as to come into contact with the recording medium.

  Another embodiment of the present invention is an ink jet recording comprising a combination of any one of the above-described reaction liquids for ink jet recording and a pigment ink that causes a reaction by contact with the reaction liquid for ink jet recording. Ink set.

  According to the present invention, by using the ink jet recording reaction liquid of the present invention together with the pigment ink, it is possible to obtain a color image having no high bleeding and good color development with respect to plain paper. The In addition to the above, the ejection characteristics of the inkjet recording reaction liquid of the present invention are not impaired even when used in an inkjet recording system in which the reaction liquid is applied to a recording medium by the action of thermal energy. Therefore, as a result, a clear and stable image can be obtained continuously over a long period of time.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. The reaction liquid for ink jet recording of the present invention reacts when it comes into contact with the pigment ink used together with the pigment ink, and comprises the following components (a) to (c). That is, it comprises (a) a polyvalent metal salt, (b) boric acids, and (c) a liquid medium. Hereinafter, these components will be described.

<Reaction liquid for inkjet recording>
(A) Multivalent metal salt The polyvalent metal salt is composed of a divalent or higher polyvalent metal ion and an anion that binds to these polyvalent metal ions.

  Although it does not specifically limit as a polyvalent metal ion, As a specific example, divalent metal ions, such as magnesium, calcium, barium, iron (II), copper (II), zinc, iron (III), and aluminum And trivalent metal ions. On the other hand, the anion is not particularly limited, but specific examples include bromide ion, chloride ion, nitrate ion, acetate ion, lactate ion, sulfate ion and the like.

Moreover, although it does not specifically limit as a specific example of a polyvalent metal salt, The following can be used. For example, chlorides such as magnesium chloride, calcium chloride, barium chloride, iron (II) chloride, copper (II) chloride, zinc chloride, aluminum chloride, iron (III) chloride;
Bromides such as magnesium bromide, calcium bromide, barium bromide, iron (II) bromide, copper (II) bromide, zinc bromide;
Nitrates such as magnesium nitrate, calcium nitrate, barium nitrate, iron (II) nitrate, copper (II) nitrate, zinc nitrate, aluminum nitrate, magnesium acetate;
Acetates such as calcium acetate, barium acetate, iron (II) acetate, copper (II) acetate, zinc acetate;
Lactates such as magnesium lactate and calcium lactate;
Examples include magnesium glycerophosphate, calcium glycerophosphate, and alum. These may contain crystal water in a normal form.

  The amount of the polyvalent metal salt as described above is not particularly limited, but when used in image formation, it reacts with the pigment ink used together to form an aggregate instantly. A sufficient concentration is sufficient. For example, the concentration in terms of polyvalent metal ions is 0.13 mol / kg or more and 1.2 mol / kg or less (reaction solution), and 0.2 mol / kg or more and 0.8 mol / kg or less (reaction solution). It is a suitable range. If the concentration in terms of polyvalent metal ions is lower than this, the effect as a reaction solution will be extremely reduced.On the other hand, if the concentration is too high, no improvement in the effect can be expected. A new problem may occur.

(C) Liquid medium As a liquid medium which comprises the reaction liquid of this invention, water, a water-soluble organic solvent, and other various additives are mentioned. Although it does not specifically limit as a water-soluble organic solvent, Specifically, what is listed below can be used. For example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol and tert-butyl alcohol;
Amides such as N, N-dimethylformamide and N, N-dimethylacetamide;
Ketones or ketoalcohols such as acetone and diacetone alcohol;
Cyclic ethers such as tetrahydrofuran and dioxane;
Ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-hexanediol, 1,6-hexane Glycols such as diol, diethylene glycol, triethylene glycol, thiodiglycol;
Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether;
Polyalkylene glycols such as polyethylene glycol and polypropylene glycol;
Triols such as glycerin, 1,2,6-hexanetriol, trimethylolpropane;
N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like may be mentioned, and these may be used alone or in combination of two or more.

  The content of the water-soluble organic solvent as described above in the reaction liquid for inkjet recording of the present invention is not particularly limited. For example, the content in the total mass of the reaction solution is in the range of 3% by mass to 60% by mass, and more preferably in the range of 5% by mass to 30% by mass.

  The reaction solution of the present invention may contain various additives. As various additives used, a so-called “curling inhibitor” that suppresses warping of the recording medium after recording can be used as appropriate in addition to a surfactant, an antifoaming agent, an antiseptic, and the like.

(B) Boric acids The above is the basic composition of the reaction solution preferably used in the present invention. The feature of the present invention is that, in addition to these, boric acids are further components of the reaction solution. The boric acids used in the present invention are oxo acids generated by hydrating acid-boron such as orthoboric acid, metaboric acid and tetraboric acid (in the present invention, these are generally called boric acids) and salts of these boric acids. That is. Specific examples include boric acid, sodium borate (borax), and ammonium borate.

  The addition amount of boric acids constituting the reaction solution of the present invention is not particularly limited, but is preferably as follows. If the addition amount is too small, a predetermined effect cannot be expected, so it is preferable that the amount be in the range of 0.0005 mol / kg to 0.15 mol / kg (reaction solution). In addition, it is desirable to contain 1/300 or more by molar ratio with respect to the polyvalent metal ions in the reaction solution. Since the boric acids as described above are added to the reaction solution of the present invention, the following effects can be obtained if the reaction solution is used together with pigment ink for image formation. That is, the frequency dependence of the ejection speed when the reaction liquid is ejected by the action of thermal energy, specifically, the phenomenon that the ejection speed of the droplets decreases or stops as the drive frequency increases, and Both the deterioration phenomenon of continuous discharge durability performance over a long time is improved.

  The details of the mechanism by which the effects as described above are obtained by adding boric acids to the reaction solution are unknown. However, as a matter of fact, due to the addition of boric acids as described above, the phenomenon "If nothing is added, precipitates are generated on the surface of the heater that imparts heat energy to the reaction solution, and then the surface of the heater is roughened and breaks." It is observed that it is greatly suppressed. The present inventors consider the reason why such an effect can be obtained by the configuration of the present invention as follows.

  That is, the polyvalent metal salt constituting the reaction solution locally forms a very strong alkaline environment due to the thermochemical reaction on the heater surface, and part thereof becomes an oxide and precipitates. Although the heater surface is protected by a corrosion-resistant material, the heater surface is damaged if the strong alkaline environment continues for a long time, and it is necessary to neutralize it by some method. However, generally known acids are not effective in neutralizing local portions because they immediately release protons in a neutral to weakly alkaline environment. However, boric acids are characterized by having a basic acid group that becomes a weak acid having a relatively large pKa value at 25 ° C. For this reason, protons are released for neutralization only when the alkali is extremely strong. Therefore, it can be presumed that only the strong alkaline environment in the vicinity of the heater surface can be selectively neutralized, and the above-described effects are obtained. In addition, pKa said here represents the logarithm value of the reciprocal number of acid dissociation constant Ka, and means a strong acid, so that a numerical value is small, and a weak acid, so that a numerical value is large.

  Conventionally, boric acid compounds are sometimes used because they are effective in preventing ink burns in an ink jet recording system in which droplets are ejected by generating bubbles by applying thermal energy to the ink. However, this technique is fundamentally different from the present invention, and citric acid, which is known as an effective anti-kogation agent, has the opposite effect to the above, and so only for the prevention of kogation. It has also been found that the present invention cannot be achieved with the compounds.

  The reaction liquid of the present invention is preferably colorless, but it may be light in the range that does not change the color tone of each color ink when mixed with pigment ink on a recording medium. Furthermore, the following are mentioned as a suitable range of the various physical properties of the reaction liquid in this invention from which the above effects are acquired. The pH is adjusted in the range of 1.0 to 6.0, the viscosity at 25 ° C. is in the range of 1 mPa · s to 30 mPa · s, and the surface tension is in the range of 28 mN / m to 52 mN / m. Is preferred.

<Pigment ink>
Next, the pigment ink in the case where an ink set is used in combination with the ink jet recording reaction liquid of the present invention having the above-described configuration will be described. In the present invention, it is preferable to use a pigment ink that reacts by contact with the reaction liquid for inkjet recording of the present invention.

(Pigment)
First, the pigment will be described. As the pigment, any pigment conventionally used for pigment inks for ink jet recording can be used. Specific examples of the black pigment include carbon black. For example, carbon black produced by a furnace method or a channel method and having the following physical properties can be used.
(1) The primary particle size is 15 nm or more and 40 nm or less,
(2) The specific surface area by BET method is 50 m ² / g or more and 300 m ² / g or less,
(3) DBP oil absorption is 40 ml / 100 g or more and 150 ml / 100 g or less,
(4) Volatile content is 0.5% or more and 10% or less,
(5) Those having a pH value of 2 to 9 or the like are preferably used.

Examples of commercially available products having such characteristics include the following, and any of them can be preferably used.
No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, no. 2200B (Mitsubishi Chemical Corporation),
RAVEN 1255 (above Colombia),
REGAL400R, REGAL330R, REGAL660R, MOGUL L (above Cabot)
Color Black FWl, Color Black FW18, Color Black S170, Color Black S150,
There are Printex 35, Printex U (manufactured by Degussa) and the like.

  As the color pigment, those having a primary particle size of about 15 nm to about 300 nm are preferably used. Specifically, examples of yellow pigments include C.I. I. Pigment yellow 1, 2, 3, 13, 16, 17, 74, 83, 109, 110, 128, 138, 180 and the like. Examples of magenta pigments include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 112, 122, 254, C.I. I. Pigment violet 19 and the like. Examples of cyan pigments include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 16, 22, C.I. I. Bat Blue 4 (CI Pigment Blue 60), 6 and the like.

  Of course, the present invention is not limited to these. In addition to the above, a newly produced pigment such as a self-dispersing pigment can of course be used. Further, the pigment in the pigment ink used in the present invention is used in a mass ratio of 1% by mass to 20% by mass, preferably 2% by mass to 12% by mass with respect to the total mass of the pigment ink. Is preferred.

(Dispersant)
Further, the pigment dispersant of the pigment ink used in the present invention may be any hydrophilic material, specifically, a hydrophilic resin (polymer dispersant), a surfactant, or the like. Is mentioned. The hydrophilic resin that functions as a pigment dispersant can be obtained by polymerizing monomers as raw materials as listed below. Although the specific example of a monomer is not specifically limited, For example, the following can be mentioned. Styrenes such as styrene, α-methylstyrene, 4-t-butylstyrene, 4-chloromethylstyrene, 4-styrenesulfonic acid and salts thereof;
Vinylnaphthalenes such as 1-vinylnaphthalene and 2-vinylnaphthalene;
(Meth) acrylic acid and salts thereof, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid-n-butyl, (meth) acrylic acid benzyl, (meth) acrylic acid-2-hydroxyethyl (Meth) acrylic acids such as polyethylene glycol mono (meth) acrylate;
Maleic acid and its salts, maleic acids such as dimethyl maleate, maleic anhydride;
Itaconic acids and salts thereof, itaconic acid monomethyl and salts thereof, itaconic acids such as dimethyl itaconate;
Fumaric acids and salts thereof, fumaric acids such as dimethyl fumarate;
(Meth) acrylamides such as (meth) acrylamide, N-methylol (meth) acrylamide, 2-acrylamido-2-methylpropanesulfonic acid and salts thereof;
N-vinylformamide, N-vinylacetamide, vinyl acetate, N-vinylpyrrolidone and the like can be mentioned. A hydrophilic resin can be obtained by copolymerization using at least two of these monomers (of which at least one is a hydrophilic monomer or a monomer that becomes hydrophilic when subjected to appropriate treatment). . The steric structure may be any of a block copolymer, a graft copolymer, or a random copolymer. Moreover, what is necessary is just to select a polymerization method suitably according to the monomer to be used, such as radical polymerization and ionic polymerization.

  Alternatively, natural resins such as rosin, shellac and starch can be preferably used. These resins are soluble in an aqueous solution in which a base is dissolved, and are alkali-soluble resins. The preferred weight average molecular weight is in the range of 1,000 to 30,000, more preferably in the range of 3,000 to 15,000. In addition, when using these hydrophilic resins as a pigment dispersant, it is preferable to contain them in the range of 0.1% by mass or more and 5% by mass or less with respect to the total mass of the pigment ink.

In addition, the surfactant acting as a pigment dispersant is not particularly limited, but the following can be used. For example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants and the like can be mentioned, and any commonly used surfactant can be preferably used. Specifically, examples of the anionic surfactant include fatty acid soaps having 12 to 18 carbon atoms such as laurate and myristate;
Alkylbenzene sulfonates such as dodecylbenzene sulfonate;
Alkyl naphthalene sulfonates such as isopropyl naphthalene sulfonate;
Dialkyl sulfosuccinic acid ester salts such as di (2-ethylhexyl) sulfosuccinic acid ester salt;
Higher alcohol sulfates having 12 to 18 carbon atoms such as sulfated oils and dodecyl sulfates;
Alkyl ether sulfates such as polyoxyethylene dodecyl ether sulfate;
Polyoxyethylene alkylphenyl ether sulfates such as polyoxyethylene nonylphenyl ether sulfate;
Alkyl ether phosphate salts such as polyoxyethylene dodecyl ether phosphate salts;
Examples thereof include alkyl phosphate ester salts such as dodecyl phosphate ester salt and octadecyl phosphate ester salt.

Examples of the cationic surfactant include aliphatic amine salts having 8 to 24 carbon atoms such as octylamine salt, dodecylamine salt and stearylamine salt;
Aliphatic quaternary ammonium salts such as octadecyltrimethylammonium chloride;
Benzalkonium salts;
Benzethonium salts;
C12-18 pyridinium salts such as cetylpyridinium chloride;
And imidazolinium salts.

Examples of amphoteric surfactants include carboxybetaines such as lauryl dimethyl betaine;
Aminocarboxylates such as N-dodecylglycine;
Examples include imidazolinium betaines such as 2-dodecyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers having 12 to 22 carbon atoms such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether;
Polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether;
Polyoxyethylene adducts of acetylene diol;
Polyoxyethylene polyoxypropylene block polymers and alkyl ethers thereof;
Polyoxyethylene glycerin fatty acid esters;
Polyoxyethylene sorbitan fatty acid esters;
Polyoxyethylene sorbitol fatty acid esters;
Polyethylene glycol fatty acid esters such as polyethylene glycol lauryl ester;
And sorbitan fatty acid esters.

  These surfactants may be used singly or in appropriate combination of two or more, and the dispersed pigment particles are negative in order to appropriately use these surfactants and to have a favorable reactivity with the polyvalent metal salt. What is necessary is just to design so that it may be electrically charged.

  The pigment ink containing the pigment and the dispersant as described above is preferably adjusted to be neutral or alkaline. In this way, it is possible to improve the solubility of the hydrophilic material used as the dispersant and to obtain a pigment ink that is further excellent in long-term storage stability. However, in this case, it may cause corrosion of various members used in the ink jet recording apparatus, so it is desirable that the pH be in the range of 7 to 10.

The pH adjuster used at this time is not particularly limited. Specifically, for example, various organic amines such as diethanolamine, triethanolamine, tetramethylammonium hydroxide;
Inorganic alkali agents such as hydroxides of alkali metals such as sodium hydroxide, lithium hydroxide and potassium hydroxide;
Organic acids such as acetic acid and lactic acid and mineral acids such as hydrochloric acid, sulfuric acid and nitric acid can be used.

(Aqueous liquid medium)
A suitable aqueous liquid medium constituting the pigment ink used in the present invention is a mixed solvent of water and a water-soluble organic solvent. Although it does not specifically limit as a water-soluble organic solvent used by mixing with water, Specifically, the following are mentioned. For example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol;
Amides such as N, N-dimethylformamide and N, N-dimethylacetamide;
Ketones or ketoalcohols such as acetone and diacetone alcohol;
Cyclic ethers such as tetrahydrofuran and dioxane;
Ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-hexanediol, 1,6-hexane Glycols such as diol, diethylene glycol, triethylene glycol, thiodiglycol;
Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether;
Polyalkylene glycols such as polyethylene glycol and polypropylene glycol;
Triols such as glycerin, 1,2,6-hexanetriol, trimethylolpropane;
N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like can be mentioned. These may be used alone or in combination of two or more. The content of these water-soluble organic solvents is not particularly limited, but is generally in the range of 3% by mass to 50% by mass, more preferably 3% by mass to 40% by mass of the total mass of the pigment ink. It is the range of the mass% or less.

(Additive)
In addition to the above-described components, the pigment ink used in the present invention can be appropriately added with a surfactant, an antifoaming agent, an antiseptic, and the like as necessary in order to obtain desired physical properties. . In particular, it is preferable to add an appropriate amount of the surfactant that functions as a penetration enhancer because it plays a role of promptly penetrating the liquid components of the reaction liquid and the pigment ink into the recording medium. In this case, the addition amount is preferably 0.05% by mass or more and 10% by mass or less, and preferably 0.5% by mass or more and 5% by mass or less.

Examples of the surfactant used in the above include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants and the like, and any commonly used surfactant is preferably used. be able to. Examples of the anionic surfactant used in this case include the following. For example, fatty acid soaps having 12 to 18 carbon atoms such as laurate and myristate;
Alkylbenzene sulfonates such as dodecylbenzene sulfonate;
Alkyl naphthalene sulfonates such as isopropyl naphthalene sulfonate;
Dialkyl sulfosuccinic acid ester salts such as di (2-ethylhexyl) sulfosuccinic acid ester salt;
Higher alcohol sulfates having 12 to 18 carbon atoms such as sulfated oils and dodecyl sulfates;
Alkyl ether sulfates such as polyoxyethylene dodecyl ether sulfate;
Polyoxyethylene alkylphenyl ether sulfates such as polyoxyethylene nonylphenyl ether sulfate;
Alkyl ether phosphate salts such as polyoxyethylene dodecyl ether phosphate salts;
And alkyl phosphoric acid ester salts such as dodecyl phosphoric acid ester salt and octadecyl phosphoric acid ester salt.

Examples of the cationic surfactant include aliphatic amine salts having 8 to 24 carbon atoms such as octylamine salt, dodecylamine salt and stearylamine salt;
Aliphatic quaternary ammonium salts such as octadecyltrimethylammonium chloride;
Benzalkonium salts;
Benzethonium salts;
C12-18 pyridinium salts such as cetylpyridinium chloride;
And imidazolinium salts.

Examples of amphoteric surfactants include carboxybetaines such as lauryl dimethyl betaine;
Aminocarboxylates such as N-dodecylglycine;
Examples include imidazolinium betaines such as 2-dodecyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers having 12 to 22 carbon atoms such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether;
Polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether;
Polyoxyethylene adducts of acetylene diol;
Polyoxyethylene polyoxypropylene block polymers and alkyl ethers thereof;
Polyoxyethylene glycerin fatty acid esters;
Polyoxyethylene sorbitan fatty acid esters;
Polyoxyethylene sorbitol fatty acid esters;
Polyethylene glycol fatty acid esters such as polyethylene glycol lauryl ester;
And sorbitan fatty acid esters.
These surfactants may be used alone or in appropriate combination of two or more.

(Preparation method of pigment ink)
The pigment ink used in the present invention comprising the above components can be produced as follows. First, a pigment is added to an aqueous medium containing at least a hydrophilic material as a dispersant and water, and after mixing and stirring, a dispersion treatment is performed, and a centrifugal treatment is performed as required to obtain a desired dispersion. Get. At this time, it is effective to perform premixing for 30 minutes or more before the dispersion treatment. That is, such a premixing operation is preferable because it improves wettability of the pigment surface and promotes adsorption of the dispersant on the pigment surface.

  Any dispersing machine that is generally used can be used as the dispersing machine used in the above-described pigment dispersion treatment. Specifically, a ball mill, a roll mill, a sand mill, etc. are mentioned, for example. Among these, a high speed type sand mill is preferably used. Examples of such include a super mill, a sand grinder, a bead mill, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).

  In the pigment ink used in the ink jet recording method, a pigment having an optimum particle size distribution is used in order to satisfy clogging resistance. Here, specific methods for obtaining a pigment having a desired particle size distribution include the following methods, but any method may be used. That is, changing the size of the grinding media of the disperser, increasing or decreasing the filling rate of the grinding media, adjusting the processing time, classifying with a filter or centrifuge after grinding, and a combination of these methods Etc. can be applied.

  Next, the additive components as mentioned above are appropriately added to this dispersion and stirred to obtain the pigment ink used in the present invention. The preferred range of various physical properties of the pigment ink in the present invention is that the pH is in the range of 5 to 10, the viscosity at 25 ° C. is in the range of 1.5 mPa · s to 30 mPa · s, and the surface tension is 28 mN / m to 52 mN. What was adjusted so that it might become the range below / m was preferable. In addition, by making a difference in the surface tension between the reaction liquid and the pigment ink, the reaction liquid and the pigment ink can be sufficiently mixed on the recording medium, and then rapidly penetrated. In this way, it is possible to further improve not only the color developability but also the fixability for high-speed printing.

<Inkjet recording method>
The above-described reaction liquid for ink jet recording is particularly suitable for the following ink jet recording system. Energy is applied to the recording medium by giving energy to the reaction liquid and then ejecting it onto the recording medium and applying it onto the recording medium or before applying it, and applying the ink to the recording medium, and the reaction liquid and the pigment ink Are in contact with each other on the recording medium. Moreover, it is preferable to apply to the system in which the energy is thermal energy.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the following description, “part” or “%” is based on mass unless otherwise specified.

[Synthesis Example 1 (Preparation of pigment dispersion)]
-Random copolymer consisting of styrene-acrylic acid-ethyl acrylate (acid value 200, weight average molecular weight 9,000) 1.4 parts-1.0 part monoethanolamine-5.0 parts diethylene glycol-81 parts ion-exchanged water .6 parts

The above components are mixed and heated to 70 ° C. in a water bath to completely dissolve the resin component. To this solution, 10 parts of carbon black (FW18, manufactured by Degussa) and 1 part of isopropyl alcohol were added, premixed for 30 minutes, and then dispersed under the following conditions.
・ Disperser: Sand grinder (Igarashi Machine)
・ Crushing media: Zirconium beads, 1 mm diameter ・ Filling rate of grinding media: 50% (volume ratio)
-Grinding time: 3 hours Further, centrifugal separation (12,000 rpm, 20 minutes) was performed to remove coarse particles to obtain a black (K) pigment dispersion.

[Synthesis Examples 2 to 4 (Preparation of pigment dispersion)]
As a pigment, the carbon black (FW18, manufactured by Degussa) used in Synthesis Example 1 was replaced with the following pigment in the same manner as in Synthesis Example 1, except that the cyan (C) of Synthesis Examples 2 to 4 was used. , Magenta (M) and yellow (Y) color pigment dispersions were obtained. The cyan (C) pigment dispersion of Synthesis Example 2 contains C.I. I. Pigment Blue 15: 3 was used. The magenta (M) pigment dispersion of Synthesis Example 3 includes C.I. I. Pigment Red 7 was used. The yellow (Y) pigment dispersion of Synthesis Example 4 includes C.I. I. Pigment Yellow 74 was used.

[Production Example 1 (Preparation of Pigment Ink K1)]
Using the black pigment dispersion obtained in Synthesis Example 1, an ink containing a pigment was produced according to the following composition ratio to obtain a pigment ink. The surface tension of the obtained pigment ink was 38 mN / m.
-Pigment dispersion liquid of Synthesis Example 1-10.0 parts of glycerin-5.0 parts of ethylene glycol-1.0 part of acetylenol EH (manufactured by Kawaken Fine Chemicals)-54.0 parts of ion-exchanged water

[Production Example 2 (Preparation of Pigment Ink C1)]
A pigment ink C1 containing a pigment was prepared in the same manner as in Production Example 1 except that the cyan pigment dispersion obtained in Synthesis Example 2 was used instead of the pigment dispersion obtained in Synthesis Example 1. The obtained pigment ink had a surface tension of 37 mN / m.

[Production Example 3 (Production of Pigment Ink M1)]
A pigment ink M1 containing a pigment was prepared in the same manner as in Production Example 1 except that the magenta pigment dispersion obtained in Synthesis Example 3 was used instead of the pigment dispersion obtained in Synthesis Example 1. The surface tension of the obtained pigment ink was 36 mN / m.

[Production Example 4 (Preparation of Pigment Ink Y1)]
A pigment ink Y1 containing a pigment was prepared in the same manner as in Production Example 1 except that the yellow pigment dispersion obtained in Synthesis Example 4 was used instead of the pigment dispersion obtained in Synthesis Example 1. The obtained pigment ink had a surface tension of 37 mN / m.

[Production Example 5 (Preparation of pigment ink K2)]
Using the black pigment dispersion obtained in Synthesis Example 1, an ink containing a pigment was produced according to the following composition ratio to obtain a pigment ink. The surface tension of the obtained pigment ink was 51 mN / m.
-Pigment dispersion liquid of Synthesis Example 1-10.0 parts of glycerin-5.0 parts of ethylene glycol-0.1 part of acetylenol EH (manufactured by Kawaken Fine Chemicals)-54.9 parts of ion-exchanged water

[Production Example 6 (Preparation of Pigment Ink C2)]
A pigment ink C2 containing a pigment was prepared in the same manner as in Production Example 5 except that the cyan pigment dispersion obtained in Synthesis Example 2 was used instead of the pigment dispersion obtained in Synthesis Example 1. The surface tension of the obtained pigment ink was 49 mN / m.

[Production Example 7 (Preparation of Pigment Ink M2)]
A pigment ink M2 containing a pigment was prepared in the same manner as in Production Example 5 except that the magenta pigment dispersion obtained in Synthesis Example 3 was used instead of the pigment dispersion obtained in Synthesis Example 1. The surface tension of the obtained pigment ink was 49 mN / m.

[Production Example 8 (Production of Pigment Ink Y2)]
A pigment ink Y2 containing a pigment was prepared in the same manner as in Production Example 5 except that the yellow pigment dispersion obtained in Synthesis Example 4 was used instead of the pigment dispersion used in Synthesis Example 1. The surface tension of the obtained pigment ink was 48 mN / m.

[Production Example 9 (Preparation of reaction solution S1)]
・ Diethylene glycol 10.0 parts ・ Calcium nitrate tetrahydrate 10.0 parts ・ Sodium borate (borax) 0.2 part ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 0.1 part ・ Ion-exchanged water 79.7 parts After mixing and dissolving the above components, pressure filtration was further performed with a membrane filter (manufactured by MILLIPORE) having a pore size of 0.22 μm, and the pH was adjusted to 4.0 to obtain a reaction solution S1. The surface tension of the obtained reaction liquid was 35 mN / m.

[Production Example 10 (Preparation of reaction solution S2)]
・ Diethylene glycol 10.0 parts ・ Calcium nitrate tetrahydrate 10.0 parts ・ Sodium borate (borax) 0.2 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 1.6 parts ・ Ion-exchanged water 78.2 parts Except having set it as said component, pH was adjusted to 4.0 after the process similar to manufacture example 9, and reaction liquid S2 was obtained. The surface tension of the obtained reaction liquid was 31 mN / m.

[Production Example 11 (Preparation of reaction solution S3)]
-Diethylene glycol 10.0 parts-Magnesium nitrate hexahydrate 12.0 parts-Sodium borate (borax) 0.2 part-Acetylenol EH (manufactured by Kawaken Fine Chemicals) 0.1 part-Ion-exchanged water 77.7 parts Except having set it as said component, pH was adjusted to 6.0 after the process similar to manufacture example 9, and reaction liquid S3 was obtained. The surface tension of the obtained reaction liquid was 35 mN / m.

[Production Example 12 (Preparation of reaction solution S4)]
・ Diethylene glycol 8.0 parts ・ Methyl alcohol 5.0 parts ・ Calcium nitrate tetrahydrate 8.0 parts ・ Sodium borate (borax) 0.2 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 0.1 part ・78.7 parts of deionized water After the same treatment as in Production Example 9 except that the above components were used, the pH was adjusted to 4.0 to obtain a reaction solution S4. The surface tension of the obtained reaction liquid was 34 mN / m.

[Production Examples 13 to 15 (Preparation of reaction solutions S5 to S7)]
Prepared with the same composition except that sodium borate (borax) was removed from each composition of the reaction liquids S1 to S3 obtained in Production Examples 9 to 11 and the reduced amount was water, and reaction liquids S5 to S7 were prepared. It was. In addition, the surface tension of the obtained reaction liquid was the same as the case where sodium borate (borax) was included.

[Production Example 16 (Preparation of reaction solution S8)]
・ Diethylene glycol 10.0 parts ・ Calcium nitrate tetrahydrate 10.0 parts ・ Citric acid 0.2 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 0.1 part ・ Ion-exchanged water 79.7 parts Except for the above, after the same treatment as in Production Example 9, the pH was adjusted to 4.0 to obtain a reaction solution S8. The surface tension of the obtained reaction liquid was 35 mN / m.

[Production Example 17 (Production of reaction solution S9)]
・ Diethylene glycol 10.0 parts ・ Calcium nitrate tetrahydrate 10.0 parts ・ Ammonium nitrate 0.2 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 0.1 part ・ Ion-exchanged water 79.7 parts After the same treatment as in Production Example 9, the pH was adjusted to 4.0 to obtain a reaction solution S9. The surface tension of the obtained reaction liquid was 35 mN / m.

[Production Example 18 (Preparation of reaction solution S10)]
・ Diethylene glycol 10.0 parts ・ Calcium nitrate tetrahydrate 10.0 parts ・ Glutamic acid 0.2 parts ・ Acetylenol EH (manufactured by Kawaken Fine Chemicals) 0.1 part ・ Ion-exchanged water 79.7 parts Other than the above ingredients After the same treatment as in Production Example 9, the pH was adjusted to 4.0 to obtain reaction solution S10. The surface tension of the obtained reaction liquid was 36 mN / m.

[Example 1]
Using the pigment inks K1, C1, M1, and Y1 obtained in Production Examples 1 to 4 and the reaction liquid S1 obtained in Production Example 9, the following image formation test was performed. Specifically, an evaluation drawing pattern (ISO JIS-SCID No. 5 bicycle) 5 using an inkjet drawing apparatus for evaluation examination loaded with these and plain paper (PPC paper manufactured by Canon Inc .: office planner) is used. 000 sheets were continuously printed. At that time, the reaction liquid S1 was applied to the paper prior to the ink dots of all the pigment inks. As a printing condition, a recording head having a recording density of 1,200 dpi and a discharge volume of 4 pl per dot was used, and the driving condition was a driving frequency of 15 kHz. The environmental conditions for the print test were unified at a temperature of 25 ° C. and a relative humidity of 55%. As an evaluation method, bleeding of the obtained printed matter, that is, the color mixing degree of the portion where each ink was printed adjacently was visually observed, and at the same time, the color development property and the through-through property were also visually observed. As a result, even in the 5,000th printed image, no occurrence of bleeding was observed, and a clear printed matter was obtained. In addition, the color developability and back-through property of the black and color print portions were also very good as compared with the case where the reaction solution S1 was not applied.

[Examples 2 to 8]
The same evaluation as in Example 1 was performed with the combination of the pigment ink and the reaction liquid shown in Table 1, and the bleeding, color developability, and back-through property were visually evaluated. The results are shown in Table 1.

[Comparative Example 1]
A continuous printing test similar to that in Example 1 was conducted except that the reaction solution S5 obtained in Production Example 13 was used instead of the reaction solution S1 obtained in Production Example 9, and evaluation including bleeding was evaluated by visual observation of the printed matter. went. As a result, color unevenness derived from the difference in color developability began to occur at several locations in the image after 500 sheets had been printed, and the color developability of the entire image became poor after 700 sheets. Further, at the time of 2,000 sheets, the image was not much different from the condition where the reaction solution was not used, so the continuous printing test was stopped. This seems to be because the discharge of the reaction liquid from the recording head was stopped, and after that, recovery operation was attempted by means such as sucking the reaction liquid directly from the nozzle of the recording head. The reaction solution could not be discharged. Here, when the nozzle which stopped discharging was observed with a microscope, it was confirmed that the heater surface was greatly damaged.

[Comparative Examples 2 to 11]
The same evaluation as in Example 1 was performed with the combination of the pigment ink and the reaction liquid shown in Table 1, and the bleeding, color developability, and back-through property were visually evaluated. The results are shown in Table 1.

  As described above, by using the ink jet recording reaction liquid of the present invention together with the pigment ink, it is possible to obtain a high-quality color image that is free from bleeding with respect to plain paper and has good color development. At the same time, even when the reaction liquid is applied to the recording medium by the action of thermal energy, the reaction liquid for ink jet recording of the present invention does not impair the discharge characteristics. As a result, a clear and stable image can be obtained over a long period of time. Can be obtained continuously.

Claims (5)

  A reaction liquid for ink-jet recording that is used together with a pigment ink and reacts when contacted with the pigment ink, and includes (a) a polyvalent metal salt, (b) boric acids, and (c) a liquid medium. A reaction liquid for ink jet recording.   The reaction liquid for ink jet recording according to claim 1, wherein the boric acid is a compound selected from the group consisting of boric acid, sodium borate (borax), and ammonium borate.   After energy is applied to the reaction liquid for ink jet recording according to claim 1 or 2 and discharged onto the recording medium and applied onto the recording medium, or before application, the pigment ink is supplied with energy toward the recording medium. An ink jet recording method comprising: applying the ink so that the recording reaction liquid and the pigment ink are in contact with each other on the recording medium.   The inkjet recording method according to claim 3, wherein the energy is thermal energy.   An ink set for ink-jet recording, comprising a combination of the ink-jet recording reaction liquid according to claim 1 or 2 and a pigment ink that reacts by contact with the ink-jet recording reaction liquid.