JP2013112801A - Inkjet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inkjet ink capable of substantially improving print image quality by virtue of excellent ink ejecting stability.SOLUTION: The inkjet ink includes a color material, a resin, water, a solvent in the range of 10 wt.% or more and 35 wt.% or less and a fluorine- or silicon-containing surfactant and has viscosity in the range of 20 cP or less. In the inkjet ink, the dynamic surface tension γafter 30 seconds by a plate method is in the range of 25 mN/m or more and 35 mN/m or less and the difference between the dynamic surface tension γand the dynamic surface tension γafter 600 seconds satisfies γ600-γ30 ≤-1 mN/m.

Description

  The present invention relates to an ink-jet ink, and more particularly to an ink-jet ink that can improve printing image quality.

  Conventionally, as inkjet ink, a technique for improving the image quality of printing by using a low surface tension and low viscosity ink and improving wettability with respect to a non-water-absorbing recording medium is known.

  Patent Document 1 describes that ink can be spread uniformly on a plastic film by reducing the surface tension of the ink.

  However, even if such a conventional technique is used, there is a limit to the substantial improvement in the print image quality.

JP 2009-114454 A

  As a result of studying this cause from various angles, the present inventors have unexpectedly discovered that when ink with low surface tension and low viscosity is used, there is an unexpected bending or nozzle missing when ejecting ink from an inkjet head. It has been found that (non-ejection) occurs frequently, and such instability of ink ejection is an obstacle to image quality improvement.

  On the other hand, conventionally, it has been known that a resin is contained in an ink for the purpose of improving fixability to a recording medium, dispersibility of a pigment, and the like. When the resin is contained as the above-described low surface tension and low viscosity ink, the injection stability is particularly easily impaired.

  If the ejection stability is impaired in the ink jet method, even if the ink behavior on the recording medium is excellent, there is a problem that it cannot be sufficiently exhibited and the image quality cannot be substantially improved.

  As a result of further intensive studies on improving the injection stability, the present inventor has surprisingly achieved low surface tension, by using a fluorine-based surfactant or a silicon-based surfactant, and specifying the physical properties of the ink. The inventors have found that the injection stability can be dramatically improved even when an ink having a low viscosity and containing a resin is used, and the present invention has been achieved.

  Since the fluorosurfactant or silicon surfactant has a relatively strong effect of reducing the surface tension, those skilled in the art thought that if these surfactants were selected, the injection stability was further impaired. However, on the contrary, the present invention that realizes the action of improving the injection stability is extremely unexpected.

  Note that Patent Document 1 discloses the use of an ink containing a silicon-based surfactant. However, there is no description regarding specific physical properties according to the present invention or improvement of injection stability. There is no suggestion, and only mentions the ink behavior after landing on the recording medium as described above, and it is difficult to consider the present invention.

  Accordingly, an object of the present invention is to provide an ink jet ink that can substantially improve printing image quality by being excellent in ink ejection stability.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

1.
An ink-jet ink comprising a colorant, a resin, water, a solvent in a range of 10 wt% to 35 wt%, and a fluorine-based or silicon-based surfactant and having a viscosity of 20 cP or less,
The dynamic surface tension γ ₃₀ after 30 seconds according to the plate method is in the range of 25 mN / m to 35 mN / m, and the difference from the dynamic surface tension γ ₆₀₀ after 600 seconds is γ ₆₀₀ −γ ₃₀ ≦ − An inkjet ink characterized by satisfying 1 mN / m.
2.
The fluorine-based or silicon-based surfactant is a composition obtained by adding the entire composition of the ink-jet ink excluding only the surfactant as the composition A and adding 1% by weight of the surfactant to the composition A. Is a fluorine-based surfactant that can lower the dynamic surface tension γ ₃₀ of the composition B by 7.5 mN / m or more with respect to the dynamic surface tension γ ₃₀ of the composition A. 2. The ink-jet ink as described in 1 above, which is a silicon-based surfactant that can be reduced by 5.0 mN / m or more.
3.
3. The inkjet ink as described in 2 above, wherein the fluorine-based or silicon-based surfactant is contained in a range of 0.005 wt% to 0.5 wt% with respect to the total amount of the inkjet ink.
4).
3. The inkjet ink according to 2 above, comprising the fluorine-based or silicon-based surfactant in a range of 0.02 wt% to 0.07 wt% with respect to the total amount of the inkjet ink.
5.
5. The ink-jet ink according to any one of 1 to 4, wherein the fluorine-based or silicon-based surfactant is a polymer-type surfactant.
6).
6. The ink-jet ink according to any one of 1 to 5, wherein the resin contains at least one kind having a glass transition temperature Tg of 80 ° C. or lower.
7).
7. The ink-jet ink according to any one of 1 to 6, wherein the total amount of the resin is in a range of 6% by weight or more with respect to the total amount of the ink-jet ink.
8).
8. The inkjet ink according to any one of 1 to 7, wherein the solvent contains at least one selected from 1,2-hexanediol or alkylene glycol alkyl ether.

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet ink which can improve the image quality of a printed image substantially by being excellent in ink ejection stability can be provided.

The figure explaining the effect | action of the inkjet ink which concerns on this invention

  Below, the form for implementing this invention is demonstrated.

  The dynamic surface tension refers to the surface tension when a certain time has elapsed after the liquid level is generated. In the present invention, it is the surface tension in the process of surface adsorption of the fluorine-based or silicon-based surfactant toward equilibrium, and refers to the surface tension after a predetermined time has elapsed since the liquid surface was formed.

  The dynamic surface tension can be measured by a bubble pressure method or a plate method. The time during which the dynamic surface tension according to the present invention is measured is 30 seconds / 600 seconds, and is usually measured after a very long time compared with the dynamic surface tension considered in the inkjet ink. It is preferable to measure by.

The ink-jet ink of the present invention (hereinafter, simply referred to as ink), the difference in dynamic surface tension gamma ₃₀ and gamma ₆₀₀ is measured in time on two different points of 30 seconds and 600 seconds after, gamma ₆₀₀ The relationship of −γ ₃₀ ≦ −1 mN / m is satisfied. That is, the condition is that the dynamic surface tension further decreases in a relatively large range of 1 mN / m or more after 30 seconds have passed and until 600 seconds.

  This is because the surface adsorption of the fluorine-based or silicon-based surfactant has not yet reached equilibrium at 30 seconds, and the amount of change in dynamic surface tension that changes until equilibrium is reached is large. Means.

  That is, the ink of the present invention has a specific surface tension behavior in which it takes a long time to reach equilibrium and the amount of change in dynamic surface tension in the process is large.

  The significance of the fact that the ink of the present invention has the specific surface tension behavior will be described.

First, since the ink of the present invention has a dynamic surface tension γ _{30 in} the range of 25 mN / m to 35 mN / m, the surface tension is relatively low, and the viscosity is in the range of 20 cP or less. Relatively low viscosity. The viscosity is a value measured with a standard solution for viscometer calibration specified in JIS Z 8809 and measured at 25 ° C. under normal pressure.

  In general, when an ink having a low surface tension and a low viscosity is used, the ink oozes out from the ink discharge port to the peripheral nozzle surface, and an ink pool is easily formed.

  Ink discharged from the ink jet head is suppressed by the ink reservoir, so that the discharge direction of the droplet is disturbed (discharge bend) or the droplet is not discharged (nozzle missing). Cause a defect.

  The present inventor prevents ink ejection failure even if ink having a low surface tension and a low viscosity is used as long as the ink of the present invention has the specific surface tension behavior described above. It was found that the injection stability is excellent.

  The present inventor considers the reason why the ink of the present invention is excellent in ink ejection stability as follows.

  FIG. 1 is a diagram for explaining the operation of the ink-jet ink according to the present invention, and shows a cross section in the vicinity of an ink discharge port in an ink-jet head.

  In FIG. 1, reference numeral 1 denotes an ink jet head, 2 denotes an ink discharge port provided in the ink jet head 1, 3 denotes a nozzle surface on which the ink discharge port 2 is formed, and 4 denotes an ink discharge port 2. It is an ink reservoir that has oozed out over the nozzle surface 3 in the vicinity thereof.

  As the ink is ejected from the ink ejection port 2, the ink in the ink reservoir 4 is replaced with new ink and stirred by the impact of ejection.

  At this time, if the ink reservoir 4 is divided into a central portion 4a covering the ink discharge port 2 and an end portion 4b covering the nozzle surface 3 around the ink discharge port 2, the ratio of replacement with new ink, and The stirring intensity is greater in the central portion 4a located on the ink ejection path than in the end portion 4b.

  Therefore, in the central portion 4a, compared with the end portion 4b, the surface adsorption equilibrium of the fluorine-based or silicon-based surfactant is inhibited, and a non-equilibrium state is maintained. On the other hand, equilibration proceeds at the end 4b that is not easily affected by the discharge operation.

  At this time, if the surface tension behavior of the ink takes a long time to reach equilibrium and the amount of change in the dynamic surface tension in the process is large, it is between the central portion 4a and the end portion 4b. The difference in dynamic surface tension becomes remarkable. That is, the surface tension is kept high at the central portion 4a where the balancing is hindered and the non-equilibrium state is maintained, while the surface tension is reduced at the end 4b where the balancing is progressing.

  As a result, a liquid flow F based on so-called Marangoni convection is generated so as to draw the end 4b having a small surface tension into the central portion 4a having a large surface tension.

  When the end 4b is drawn into the central portion 4a, the ink reservoir 4 contracts in the direction of the ink ejection port 2, and as a result, the formation of the ink reservoir 4 is prevented. More specifically, even if the ink reservoir 4 is formed, it can be reduced or eliminated, or the formation of the ink reservoir 4 can be prevented in advance.

  The action described above is considered to be one factor that the ink of the present invention has an effect of excellent ink ejection stability.

  Hereinafter, the inkjet ink of the present invention will be described more specifically.

In the inkjet ink of the present invention, the dynamic surface tension γ ₃₀ is 25 mN / m or more and 35 mN / m or less, and the difference from the dynamic surface tension γ ₆₀₀ is γ ₆₀₀ −γ ₃₀ ≦ −1 mN / m, preferably γ ₆₀₀ −γ ₃₀ ≦ −1.5 mN / m is satisfied. In a broad sense, as described above, it takes a long time to reach equilibrium, and the amount of change in dynamic surface tension in the process is large. One characteristic is that it has a specific surface tension behavior.

  In the present invention, in order to impart such a specific surface tension behavior to the ink and remarkably exhibit the effect of excellent ink ejection stability, as described below, in particular, a fluorine-based or silicon-based surfactant is used. The prescription is important.

In the present invention, the fluorine-based or silicon-based surfactant is composed of the entire composition of the ink-jet ink excluding only the surfactant as the composition A, and 1% by weight of the surfactant is added to the composition A. when the composed composition was composition B, and a fluorine-based surfactant a dynamic surface tension gamma ₃₀ of composition B can be lowered more than 7.5 mN / m with respect to the dynamic surface tension gamma ₃₀ of composition a It is preferable that it is a silicon-based surfactant that can be reduced by 5.0 mN / m or more (hereinafter may be referred to as Condition A).

  When the fluorine-based or silicon-based surfactant satisfies the condition A, the amount of change in surface tension in the process until the dynamic surface tension reaches equilibrium becomes significantly large. That is, based on FIG. 1 described above, the difference in surface tension between the central portion 4a in which the balancing is difficult to proceed and the end portion 4b in which the balancing is advanced becomes significant, and the formation of the ink reservoir 4 is prevented. There is an effect that the ink ejection stability is remarkably excellent.

  In the present invention, the fluorine-based or silicon-based surfactant is preferably a polymer-type surfactant.

  The polymer type surfactant referred to in the present invention means a surfactant having an average molecular weight of 1000 or more, and particularly preferably the total molecular weight of the hydrophobic portion is 1000 or more. Even when the surfactant is in an emulsion state in the ink, it may be sufficient if it satisfies the average molecular weight.

  In the present invention, the term “fluorine-based surfactant” refers to a surfactant in which a part or all of the surfactant is substituted with a fluorine atom in place of a hydrogen atom bonded to carbon of a hydrophobic group of a normal surfactant. Of these, those having a perfluoroalkyl group in the molecule are preferred.

  Among the fluorosurfactants, some are from DIC under the trade name Megafac, from Asahi Glass under the trade name Surflon, from 3M under the trade name Novec, They are commercially available from I Dupont Nemeras & Company under the trade name Zonyls.

  The silicone surfactant is preferably a polyether-modified polysiloxane compound, such as KF-905 manufactured by Shin-Etsu Chemical, BYK375, BYK333, BYK331, BYK348 manufactured by Big Chemie, Momentive Performance Materials, Inc. Examples thereof include TSF4440, TSF4445, TSF4446, and Shin-Etsu Silicone KF351.

  Conventionally, in an inkjet ink, in order to prevent the composition of the ink near the nozzle from being changed due to the influence of drying or the like, or from the viewpoint of robustness at the time of production, the physical properties do not change due to fluctuations in the content of the surfactant. Usually, a sufficient amount of a surfactant is added (specifically, an addition amount corresponding to a critical micelle concentration or higher), but in the present invention, the inkjet ink is the above-described one. It is preferable to contain a fluorine-based or silicon-based surfactant that satisfies the condition A in a state sufficiently lower than the critical micelle concentration.

  Specifically, the fluorine-based or silicon-based surfactant satisfying the condition A is preferably in the range of 0.005% by weight to 0.5% by weight, more preferably 0.02%, based on the total amount of the ink-jet ink. It is contained in the range of not less than 0.07% by weight.

  If the content of the surfactant satisfying the condition A is low, the average migration time until the surfactant in a sparsely dispersed state in the liquid is adsorbed on the surface becomes long, so that the equilibrium is reached. It will take a long time to reach. That is, when the surfactant satisfies the condition A, the amount of change in the surface tension in the process until the surface tension reaches equilibrium is increased, and at the same time, the amount of the surfactant is low. It will take a long time to reach. As a result of these synergistic effects, as described in the example of FIG. 1, the difference in surface tension between the central portion 4a in which the equilibration is difficult to proceed and the end portion 4b in which the equilibration has proceeded becomes further remarkable, and the ink pool 4 is prevented, and the ink ejection stability is further improved.

In the present invention, the maximum value of the decrease range in which the dynamic surface tension decreases from 30 seconds to 600 seconds is not particularly limited. The present inventor has reduced width be in the range of up to about _{10mN / m (γ 600 -γ 30} ≦ -10mN / m), was confirmed by a test that could easily form the formulations described above .

  Next, other components constituting the inkjet ink of the present invention will be described.

  The inkjet ink of the present invention contains a solvent in the range of 10% by weight to 35% by weight.

  The solvent that can be contained in the ink-jet ink of the present invention is not particularly limited, but 1,2-hexanediol can be suitably used from the viewpoint of suitably bringing out the surface tension reducing action of a fluorine-based or silicon-based surfactant. Or it is preferable that at least 1 sort (s) chosen from alkylene glycol alkyl ether is included.

  Examples of the alkylene glycol alkyl ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol mono Butyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, etc. Can Mashiku illustrated, in particular, diethylene glycol monobutyl ether and dipropylene glycol monomethyl ether are preferred.

  As described above, the inkjet ink of the present invention has a viscosity of 20 cP or less. Viscosity in such a range can be achieved by adjusting the components of the ink-jet ink, and can be easily achieved especially by the solvent and the resin formulation described below.

  The resin contained in the inkjet ink of the present invention is not particularly limited, but preferably contains at least one resin having a glass transition temperature Tg of 80 ° C. or lower.

  Conventionally, when a resin having a glass transition temperature Tg of 80 ° C. or less is included, it is easy to obtain advantages such as excellent fixability to a recording medium, but an ink reservoir is easily formed, and the adverse effect of impairing ink ejection stability is caused. There was a problem that occurred. On the other hand, in the ink-jet ink of the present invention, even when a glass transition temperature Tg includes a resin having a temperature of 80 ° C. or lower, an effect excellent in ink ejection stability can be obtained. There is an effect of further improving the image quality of the recorded image.

  The total amount of the resin contained in the inkjet ink of the present invention is preferably in the range of 6% by weight or more with respect to the total amount of the inkjet ink. Thus, even if the resin content is high, the present invention provides an effect of excellent injection stability. The total amount of resin means not only the fixing resin contained in order to obtain the fixability to the recording medium, but also other resins such as a pigment dispersion resin that disperses the pigment. This is the total amount of resin.

  Hereinafter, the fixing resin will be described, and the pigment dispersion resin will be described later in the description of the coloring material.

  The fixing resin has a function of fixing (adhering) the landed ink droplets to the recording medium. In addition, the fixing resin is required not only to improve the abrasion resistance and water resistance of the ink film but also to have a function of increasing gloss and optical density. Therefore, it is more preferable that the fixing resin is easily dispersed in an aqueous solvent composed of water and a solvent, has a certain degree of transparency, and has compatibility with other ink components.

  The fixing resin used in the ink of the present invention is not particularly limited as long as it can be dissolved or dispersed in an aqueous solvent, and is preferably a water-soluble resin or an aqueous dispersion polymer fine particle. It is more preferable to use a water-soluble resin because of its high solubility and stability in aqueous solvents.

  Water-soluble resins that can be used in the present invention include acrylic resins, styrene-acrylic resins, acrylonitrile-acrylic resins, vinyl acetate-acrylic resins, polyvinyl alcohol resins, polyurethane resins, polyamide resins, and polyester resins. And polyolefin resins. Among these, acrylic resins, polyamide resins, polyvinyl alcohol resins, and polyurethane resins are preferable, and acrylic resins are more preferable.

  The acrylic resin may be a homopolymer of (meth) acrylic acid ester or a copolymer of (meth) acrylic acid ester and another copolymerizable monomer. A copolymer of (meth) acrylic acid ester and another copolymerization monomer is particularly preferred because it has a high degree of freedom in designing the resin structure, is easily synthesized by a polymerization reaction, and is low in cost. The content ratio of the structural unit derived from the (meth) acrylic acid ester in the copolymer is preferably 60 to 100% by mass, and 80 to 100% by mass with respect to all monomers constituting the copolymer. It is more preferable.

  Examples of (meth) acrylic acid esters include (meth) acrylic acid alkyl esters. Especially, the alkyl ester of (meth) acrylic acid (The carbon number of alkyl is 1-12) is preferable. The (meth) acrylic acid ester may be one type or two or more types. Examples of preferable combinations of two or more kinds of (meth) acrylic acid esters include methyl methacrylate, alkyl acrylate (alkyl has 1 to 12 carbon atoms), and methacrylic acid alkyl ester (alkyl has carbon number 2-12) are included.

  Examples of other copolymerization monomers in the copolymer of (meth) acrylic acid ester and other copolymerization monomers include monomers having acidic groups. Examples of the monomer having an acidic group include acrylic acid, methacrylic acid, itaconic acid and the like. Among them, copolymers of (meth) acrylic acid esters and other copolymerization monomers include methyl methacrylate as the main monomer, alkyl acrylate (alkyl having 1 to 12 carbon atoms), and alkyl methacrylate. The copolymer is preferably a copolymer obtained by polymerizing an ester (the alkyl has 2 to 12 carbon atoms) and a monomer having an acidic group as another copolymer monomer. Constituent units derived from main monomers (methyl methacrylate, alkyl acrylate (alkyl has 1 to 12 carbon atoms) and methacrylic acid alkyl ester (alkyl has 2 to 12 carbon atoms)) contained in the copolymer The total content of is preferably 80 to 95% by mass with respect to all monomers constituting the copolymer.

  At least a part of the acidic groups contained in the acrylic resin is preferably neutralized with a base from the viewpoint of increasing the solubility in an aqueous solvent. Examples of the base to be neutralized include alkali metal or alkaline earth metal hydroxides (for example, NaOH, KOH, etc.); amines (for example, alkanolamine, alkylamine, etc.); ammonia and the like. Among them, the resin neutralized with ammonia and / or amines is a resin from which ammonia and / or amines have been removed because ammonia and / or amines evaporate together with the aqueous solvent from the ink after fixing on the recording medium. The solubility of the is reduced. A cured ink film containing such a resin is preferable because it has water resistance. Among them, amines are preferable. Specific examples of amines include triethylamine, 2-dimethylaminoethanol, 2-di-n-butylaminoethanol, methyldiethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, triethanolamine, Examples include ethanolamine and 2-methylaminoethanol.

  The acid value of the water-soluble resin used in the present invention is preferably 50 to 300 mgKOH / g, and more preferably 50 to 130 mgKOH / g. If the acid value of the water-soluble resin is less than 50 mgKOH / g, the resin may not be sufficiently soluble in water and may not be sufficiently soluble in an aqueous solvent. On the other hand, if the acid value of the water-soluble resin is more than 300 mgKOH / g, the ink film becomes soft and the abrasion resistance decreases.

  The acid value of the water-soluble resin in the present invention refers to the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of the water-soluble resin. The acid value measurement and hydrolysis acid value measurement of JIS K 0070 It can be measured by (total acid value measurement).

  The content of the neutralizing base depends on the acid value and content of the water-soluble resin, but the number of chemical equivalents is 0.5 to 5 times the number of chemical equivalents of acidic groups contained in the water-soluble resin. It is preferable to make it. When the content of the neutralizing base is less than 0.5 times the number of chemical equivalents of the acidic groups contained in the water-soluble resin, the effect of increasing the dispersibility of the acrylic resin is sufficiently obtained. It may not be possible. On the other hand, if the content of the neutralizing base is more than 5 times the number of chemical equivalents of the acidic groups contained in the water-soluble resin, the water resistance of the ink film is reduced, discoloration, odor, etc. May occur.

The weight average molecular weight (Mw) of the water-soluble resin is preferably 2.0 × 10 ^{4 to} 8.0 × 10 ⁴ , and more preferably 2.5 × 10 ^{4 to} 7.0 × 10 ^4. . If the weight average molecular weight is less than 2.0 × 10 ⁴ , the fixing ability of the ink is small, and the resulting image may not have sufficient abrasion resistance. On the other hand, when the weight average molecular weight (Mw) is more than 8.0 × 10 ⁴ , the viscosity of the ink is too high, and the ejection stability from the nozzle may be lowered.

  The glass transition temperature (Tg) of the fixing resin is preferably 30 to 100 ° C. If the Tg is less than 30 ° C., the resulting image may not have sufficient abrasion resistance, or blocking may occur. On the other hand, when Tg is higher than 100 ° C., it is considered that the ink film after drying becomes too hard and brittle, and the abrasion resistance may be lowered.

  The content of the fixing resin is preferably 1 to 15% by mass, and more preferably 3 to 10% by mass with respect to the entire ink. If the content of the fixing resin is less than 1% by mass, the function of fixing a color material such as a pigment on the recording medium may not be sufficiently obtained. On the other hand, when the content of the fixing resin is more than 15% by mass, the viscosity of the ink is increased, and the injection stability may be lowered.

  The water-based ink of the present invention may contain water-based dispersed polymer fine particles in order to increase the abrasion resistance of the ink film.

  The water-based dispersed polymer fine particles can be composed of the same water-soluble resin as described above. The average particle size of the water-based dispersed polymer fine particles is preferably 300 nm or less, and more preferably 130 nm or less, from the viewpoint that the nozzle of the head is not clogged and an image having good gloss is obtained. Further, the average particle size of the polymer fine particles is preferably 30 nm or more from the viewpoint of production stability.

  The content of the water-dispersible polymer fine particles is preferably 0.7 to 8% by mass with respect to the entire ink, from the viewpoint of easy fixing to a recording medium and long-term storage stability of the ink. More preferably, it is mass%.

  Examples of water-dispersed polymer fine particles include polyacrylic resin, polystyrene-acrylic, polyacrylonitrile-acrylic, vinyl acetate-acrylic, polyurethane resin, polyamide resin, polyester resin, polyolefin resin, vinyl chloride resin and their co-polymers. A polymer etc. are mentioned.

  The coloring material contained in the inkjet ink according to the present invention may be a dye, a pigment, or a mixture thereof. Of these, pigments are preferred from the viewpoints of durability and abrasion resistance of the obtained image. Examples of the dye include water-soluble dyes such as acid dyes, direct dyes and basic dyes; disperse dyes containing colored polymers or colored waxes; oil-soluble dyes and the like.

  The pigment may be a known organic pigment or inorganic pigment. Examples of organic pigments include azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments; phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, And polycyclic pigments such as quinophthalone pigments; dye lakes such as basic dye type lakes and acid dye type lakes; nitro pigments; nitroso pigments; aniline black; and daylight fluorescent pigments.

  Specific examples of the pigment are shown below, but the present invention is not limited to these exemplified compounds.

  Preferred examples of organic pigments for magenta, red or violet 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 8, C.I. I. Pigment red 12, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 17, C.I. I. Pigment red 22, C.I. I. Pigment red 23, C.I. I. Pigment red 41, 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 112, C.I. I. Pigment red 114, 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 146, C.I. I. Pigment red 148, C.I. I. Pigment red 149, C.I. I. Pigment red 150, C.I. I. Pigment red 166, C.I. I. Pigment red 170, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 220, C.I. I. Pigment red 202, C.I. I. Pigment red 222, C.I. I. Pigment red 238, C.I. I. Pigment red 245, C.I. I. Pigment red 258, C.I. I. Pigment red 282, C.I. I. Pigment violet 19, C.I. I. Pigment Violet 23 and the like are included.

  Preferred examples of organic pigments for orange, yellow or brown include C.I. I. Pigment orange 13, C.I. I. Pigment orange 16, C.I. I. Pigment orange 31, C.I. I. Pigment orange 34, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 3, 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 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 43, C.I. I. Pigment yellow 55, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 81, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 139, C.I. I. Pigment yellow 147, C.I. I. Pigment yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 153, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 175, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 181, C.I. I. Pigment yellow 185, C.I. I. Pigment yellow 194, C.I. I. Pigment yellow 199, C.I. I. Pigment yellow 213, C.I. I. Pigment Brown 22 and the like are included.

  Preferred examples of organic pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15: 5, C.I. I. Pigment blue 16, C.I. I. Pigment blue 29, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 etc. are included.

  Examples of organic pigments for black include C.I. I. Pigment black 5, C.I. I. Pigment black 7 and the like are included. Examples of organic pigments for white include C.I. I. Pigment White 6 etc. are included.

  Examples of inorganic pigments include carbon black and titanium oxide.

  The ink of the present invention may further contain a pigment dispersion resin (pigment dispersant) in order to enhance the dispersibility of the pigment. Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, and the like.

  The pigment is preferably added to the ink as a pigment dispersion in order to disperse stably. The pigment dispersion may be any dispersion that can be stably dispersed in an aqueous solvent. A pigment dispersion in which a pigment is dispersed with a dispersion resin; a capsule pigment in which the pigment is coated with a water-insoluble resin: a surface-modified, dispersion resin And self-dispersing pigments that can be dispersed without containing.

  The dispersion resin used in the pigment dispersion in which the pigment is dispersed with the dispersion resin is preferably a water-soluble resin. Preferred examples of such water-soluble resins include styrene-acrylic acid-acrylic acid alkyl ester copolymers, styrene-acrylic acid copolymers, styrene-maleic acid copolymers, styrene-maleic acid-acrylic acid alkyl esters. Copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer Polymers and the like are included. Further, a water-soluble resin that can be used as the fixing resin may be used as the pigment dispersion resin.

  The water-insoluble resin in the capsule pigment in which the pigment is coated with a water-insoluble resin is a resin that is insoluble in water in a weakly acidic to weakly basic range. Specifically, a resin having a solubility in an aqueous solution having a pH of 4 to 10 is 2% or less. Examples of water-insoluble resins include acrylic resins, styrene-acrylic resins, acrylonitrile-acrylic resins, vinyl acetate resins, vinyl acetate-acrylic resins, vinyl acetate-vinyl chloride resins, polyurethane resins, silicon- Examples include acrylic resins, acrylic silicon resins, polyester resins, and epoxy resins. The average particle diameter of the capsule pigment is preferably about 80 to 200 nm from the viewpoints of ink storage stability, color developability, and the like.

  The capsule pigment (pigment fine particles coated with a water-insoluble resin) can be produced by a known method. For example, a water-insoluble resin is dissolved in an organic solvent (for example, methyl ethyl ketone), and a base component is further added to partially or completely neutralize acidic groups contained in the water-insoluble resin. A pigment and ion-exchanged water are added to the obtained solution and mixed and dispersed. Thereafter, the organic solvent is removed from the obtained solution, and ion-exchanged water is further added as necessary to prepare a capsule pigment. Alternatively, there is a method in which a monomer is added to a solution in which a pigment and a polymerizable surfactant are dispersed and a polymerization reaction is performed to coat the pigment with a resin.

The weight average molecular weight (Mw) of the aforementioned dispersion resin and water-insoluble resin is preferably 3.0 × 10 ^{3 to} 5.0 × 10 ⁵ , more preferably 7.0 × 10 ^{3 to} 2.0 × 10. ⁵ .

  The mass ratio of the pigment to the dispersion resin is preferably 100/150 to 100/30 for the pigment / dispersion resin. From the viewpoint of enhancing the durability of the image, the ejection stability of the ink, and the storage stability, it is more preferably 100/100 to 100/40.

  The pigment can be dispersed by, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like.

  From the viewpoint of removing the coarse particles of the pigment dispersion and making the particle size distribution of the pigment fine particles uniform, the pigment dispersion is subjected to a centrifugal separation process or a filtration process using a filter before being added to the ink. Also good.

  The self-dispersing pigment may be a commercial product. Examples of commercially available self-dispersing pigments include CABO-JET200, CABO-JET300 (manufactured by Cabot Corp.), Bonjet CW1 (manufactured by Orient Chemical Industries Ltd.), and the like.

  The inkjet ink of the present invention can contain other surfactants in addition to the above-described fluorine-based surfactant or silicon-based surfactant.

  Examples of other surfactants include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, Preferred examples include nonionic surfactants such as polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts, and particularly anionic surfactants and nonionic interfaces. It is preferred to use an activator.

  The ink of the present invention may further contain other components as necessary. Examples of other components include preservatives, antifungal agents, rust inhibitors, antifoaming agents, viscosity modifiers, penetrants, pH adjusters, drying inhibitors (eg urea, thiourea, ethylene urea, etc.), etc. included.

  The antiseptic and the antifungal agent have a function of maintaining the storage stability of the ink for a long period of time. The preservative and the antifungal agent are not particularly limited, and for example, aromatic halogen compounds (for example, Preventol CMK), methylene dithiocyanate, halogen-containing nitrogen sulfur compounds, 1,2-benzisothiazolin-3-one (for example, PROXEL) GXL).

  As a recording medium used when recording an image on a recording medium by the ink jet method using the ink jet ink of the present invention, a recording medium having a high ink absorbing ability such as plain paper, coated paper, ink jet exclusive paper, and fabric is also applied. Although it is possible, when using a low water-absorbing recording medium (recording medium with low ink absorbability) or a non-water-absorbing recording medium (recording medium not having ink absorbability), it exhibits a superior effect. This is also effective when the recording medium is made of polyvinyl chloride.

  In the present invention, by using a low water-absorbing or non-water-absorbing recording medium, the durability and glossiness of the image can be further enhanced, and a high-quality image can be obtained, and it can withstand long-term use outdoors. Is possible.

  Examples of the low water-absorbing recording medium include coated paper such as printing paper. Commercially available recording media with low water absorption include, for example, Ricoh Business Cogross 100 (manufactured by Ricoh Co., Ltd.), OK Top Coat +, OK Kanto +, SA Kanofuji + (manufactured by Oji Paper Co., Ltd.), Super MIdal, Aurora Coat, Ulite, Space DX (manufactured by Nippon Paper Industries Co., Ltd.), α mat, Mu Coat (manufactured by Hokuetsu Paper Co., Ltd.), Raijin Art, Raitori Super Art (manufactured by Chuetsu Pulp Co., Ltd.), Tokuhishi Art, Pearl Coat N (Mitsubishi Paper Co., Ltd.).

  Examples of non-water-absorbing recording media include resin substrates, metal substrates, glass substrates, and the like. The resin base material may be a resin base material (including plates, sheets, and films) preferably made of a hydrophobic resin, a composite base material of the resin base material and other base materials (paper, etc.), and the like. Examples of the hydrophobic resin include polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride, polyethylene terephthalate (PET), and preferably vinyl chloride.

  Specific examples of the recording medium made of polyvinyl chloride include SOL-371G, SOL-373M, SOL-4701 (manufactured by Big Technos Co., Ltd.), glossy vinyl chloride (manufactured by Systemgraph Co., Ltd.), KSM-VS, KSM- VST, KSM-VT (above, Kimoto Co., Ltd.), J-CAL-HGX, J-CAL-YHG, J-CAL-WWWG (above, Kyosho Osaka Co., Ltd.), BUS MARK V400 F vinyl, LITEcal V -600F vinyl (above, manufactured by Flexcon), FR2 (manufactured by Hanwha), LLBAU13713, LLSP20133 (above, manufactured by Sakurai Co., Ltd.), P-370B, P-400M (above, manufactured by Kambo Plus Co., Ltd.), S02P, S12P, S13P , S14P, S22P, S24P, S34 , S27P (above, manufactured by Grafityp), P-223RW, P-224RW, P-249ZW, P-284ZC (above, manufactured by Lintec Corporation), LKG-19, LPA-70, LPE-248, LPM-45, LTG -11, LTG-21 (above, manufactured by Shinsei Co., Ltd.), MPI 3023 (produced by Toyo Corporation), Napoleon Gloss PVC (manufactured by Futaki Electronics Co., Ltd.), JV-610, Y-114 (above, IKEC Corporation) NIJ-CAPVC, NIJ-SPVCGT (Nichie Co., Ltd.), 3101 / H12 / P4, 3104 / H12 / P4, 3104 / H12 / P4S, 9800 / H12 / P4, 3100 / H12 / R2, 3101 / H12 / R2, 3104 / H12 / R2, 1445 / 14 / P3, 1438 / One Way Vision (manufactured by Inetrcoat), JT5129PM, JT5728P, JT5822P, JT5829P, JT5829R, JT5829PM, JT5829RM, JT5929PM (above, manufactured by Mactac), MPI1005, MPI1MP MPI3021, MPI3500, MPI3501 (above, manufactured by Avery), AM-101G, AM-501G (above, manufactured by Ginichi Co., Ltd.), FR2 (manufactured by Hanwha Japan Co., Ltd.), AY-15P, AY-60P, AY-80P , DBSP137GGH, DBSP137GGL (above, manufactured by Insight Inc.), SJT-V200F, SJT-V400F-1 (hereafter Manufactured by Hiraoka Orizome Co., Ltd.), SPS-98, SPSM-98, SPSH-98, SVGL-137, SVGS-137, MD3-200, MD3-301M, MD5-100, MD5-101M, MD5-105 (and above) (Made by Metamark), 640M, 641G, 641M, 3105M, 3105SG, 3162G, 3164G, 3164M, 3164XG, 3164XM, 3165G, 3165SG, 3165M, 3169M, 3451SG, 3551G, 3551M, 3631, 3641M, 3651G, 3651M, 3651G 3641M (above, manufactured by Orafol), SVTL-HQ130 (made by Lamy Corporation), SP300 GWF, SPCLEARAD vinyl (above, Catalina) ), RM-SJR (manufactured by Ryoyo Shoji Co., Ltd.), Hi Lucky, New Lucky PVC (manufactured by LG), SIY-110, SIY-310, SIY-320 (manufactured by Sekisui Chemical Co., Ltd.), PRINT MI Frontlit, PRINT XL Light weight banner (above, manufactured by Endutex), RIJET 100, RIJET 145, RIJET165 (above, made by Ritrama), NM-SG, NM-SM (manufactured by Niei Kakko Co., Ltd.), LTO3GS , Easy Print 80, Performance Print 80 (above, manufactured by Jetgraph Corporation), DSE 550, DSB 550, DSE 800G, DSE 802/137, V250WG, V300WG, V350WG (above, He XS), Digital White 6005PE, 6010PE (and above, manufactured by Multifix), and the like.

  Examples of the present invention will be described below, but the present invention is not limited to such examples.

1. Preparation of ink In the formulations shown in Tables 1 and 2, the following fixing resin, solvent, surfactant, and pigment dispersion were mixed with ion-exchanged water to be 100% by weight to obtain inks 1 to 27. The dynamic surface tension γ ₃₀ and ₆₀₀ were measured for each ink.

(resin)
Polyester urethane resin ("Yukot UWS-145" manufactured by Sanyo Chemical Co., Ltd. (solid content: 35% by weight))
Styrene acrylic resin (“J70” manufactured by BASF (solid content: 30% by weight))
Styrene acrylic resin ("Joncrill 501" manufactured by BASF; solid content 30% by weight) [* added as pigment dispersion]

(solvent)
Dipropylene glycol monomethyl ether (DPGME)
Diethylene glycol monobutyl ether (DEGBE)
1,2-hexanediol (12HD)
Triethylene glycol monobutyl ether (TEGBE) [* added as a pigment dispersion]

(Surfactant)
As the fluorosurfactant, DIC "Megafac 477", DIC "Megafac 444", DIC "Megafac 553", NEOS "Factent 400sw (active ingredient 50%; Table 1) % By weight is based on the active ingredient.) "Or" Factent 215 "manufactured by NEOS, and as a silicon surfactant," BYK333 "manufactured by BYK Chemie, which is a polyether-modified siloxane," BYK331 "manufactured by BYK. “BYK348” manufactured by Big Chemie, “TSF4446” manufactured by Momentive Performance Materials, or “KF351” manufactured by Shin-Etsu Silicone Co., Ltd. was used.

(Pigment dispersion (pigment dispersion))
As a dispersion resin, 30 parts by weight of Joncryl 501 (manufactured by BASF; solid content: 30% by weight), 3 parts by weight of triethylene glycol monobutyl ether, and 52 parts by weight of ion-exchanged water are heated and stirred and mixed. I. 15 parts by weight of Pigment Blue 15: 3 was added and premixed, and then dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads to obtain a cyan pigment dispersion having a pigment solid content of 15% by weight. Obtained.

(Measurement of dynamic surface tension)
The dynamic surface tensions γ ₃₀ and ₆₀₀ were measured based on the Wilhelmi plate method using the dynamic surface tension measurement mode of an automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Chemical Co., Ltd.). In the measurement, the measurement was started immediately after the ink was poured into the petri dish, and vibration was not applied during the measurement.

2. Printing conditions A piezo-type inkjet head (manufactured by Konica Minolta IJ Co., Ltd.) having 512 nozzles is filled with the ink obtained above, and the ink droplet ejection speed is adjusted to 6 m / s, 7 m / s by adjusting the head voltage. It changed to s and 8 m / s, A4 gradation printing at each discharge speed was performed, and the injection stability was evaluated according to the following evaluation criteria.

(Evaluation criteria for injection stability)
In each of the following evaluation items, the discharge rate indicates a ratio of normal discharge excluding discharge bend and nozzle missing.
(Double-circle): The discharge rate when A4 gradation printing is finished with ink droplets of 8 m / s is 99% or more.
○: The condition of ◎ is not satisfied, and the discharge rate when the A4 gradation printing is completed at an ink droplet discharge speed of 7.5 m / s is 99% or more.
Δ: The condition of ◯ is not satisfied, and the discharge rate when the A4 gradation printing is finished at an ink droplet discharge speed of 7 m / s is 99% or more.
X: The condition of Δ is not satisfied, and the discharge rate when the A4 gradation printing is completed at an ink droplet discharge speed of 6 m / s is 99% or more.
Xx: The condition of x is not satisfied, and the ejection rate when the A4 gradation printing is finished at an ink droplet ejection speed of 6 m / s is 99% or less.

  The evaluation results are shown in Tables 1 and 2.

3. Evaluation From Tables 1 and 2, the dynamic surface tension γ ₃₀ is in the range of 25 mN / m to 35 mN / m and the difference from the dynamic surface tension γ ₆₀₀ is γ ₆₀₀ −γ ₃₀ ≦ −1 mN / m. It can be seen that the inks 15, 16 and 18 to 23 satisfying the condition of the present invention satisfying the condition satisfy the injection stability.

In particular, it can be seen that the inks 16 and 19 to 22 satisfying γ ₆₀₀ −γ ₃₀ ≦ −1.5 mN / m are further excellent in ejection stability.

  On the other hand, it can be seen that the inks 1 to 14, 17 and 24 to 27 which do not satisfy the conditions of the present invention are inferior in ejection stability.

1: Inkjet head 2: Ink ejection port 3: Nozzle surface 4: Ink reservoir 4a: Central portion 4b: End portion

Claims (8)

An ink-jet ink comprising a colorant, a resin, water, a solvent in a range of 10 wt% to 35 wt%, and a fluorine-based or silicon-based surfactant and having a viscosity of 20 cP or less,
The dynamic surface tension γ ₃₀ after 30 seconds according to the plate method is in the range of 25 mN / m to 35 mN / m, and the difference from the dynamic surface tension γ ₆₀₀ after 600 seconds is γ ₆₀₀ −γ ₃₀ ≦ − An inkjet ink characterized by satisfying 1 mN / m. The fluorine-based or silicon-based surfactant is a composition obtained by adding the entire composition of the ink-jet ink excluding only the surfactant as the composition A and adding 1% by weight of the surfactant to the composition A. Is a fluorine-based surfactant that can lower the dynamic surface tension γ ₃₀ of the composition B by 7.5 mN / m or more with respect to the dynamic surface tension γ ₃₀ of the composition A. The inkjet ink according to claim 1, wherein the inkjet ink is a silicon-based surfactant that can be reduced by 5.0 mN / m or more.   The inkjet ink according to claim 2, comprising the fluorine-based or silicon-based surfactant in a range of 0.005 wt% to 0.5 wt% with respect to the total amount of the inkjet ink.   The inkjet ink according to claim 2, comprising the fluorine-based or silicon-based surfactant in a range of 0.02 wt% or more and 0.07 wt% or less with respect to a total amount of the inkjet ink.   The inkjet ink according to claim 1, wherein the fluorine-based or silicon-based surfactant is a polymer-type surfactant.   The inkjet resin according to claim 1, wherein the resin contains at least one kind having a glass transition temperature Tg of 80 ° C. or less.   The ink-jet ink according to claim 1, wherein the total amount of the resin is in a range of 6% by weight or more with respect to the total amount of the ink-jet ink.   The ink-jet ink according to claim 1, wherein the solvent contains at least one selected from 1,2-hexanediol or alkylene glycol alkyl ether.

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