JP6213735B2 - Maintenance liquid for water-based inkjet recording - Google Patents

Description

  The present invention relates to a maintenance liquid for ink jet recording and an ink set which are preferably used for an ink jet printer using water-based ink.

  Ink-jet printing not only has the advantages of low noise and good operability in the equipment used, but also has the advantage of being easy to colorize and being able to use plain paper as a recording member. And widely used as an output machine at home.

  On the other hand, in industrial applications, it is expected to be used as an output device for digital printing due to the improvement of inkjet technology, and even for substrates with low absorbability by solvent ink or UV ink (plastic substrates such as PVC and PET). Printing machines capable of printing have actually been marketed. However, in recent years, the demand for water-based inks has increased from the standpoint of environmental friendliness.

  As water-based inks for ink jets, as described in Patent Documents 1, 2, and 3, the development of inks in which special printing papers such as plain paper and photographic glossy paper have been developed for a long time. On the other hand, in recent years, the application of the ink jet recording method is expected to be expanded, and the need for direct printing on a low-absorbent substrate such as PET and PVC used for outdoor advertisements and billboards is increasing. Conventional water-based inks perform drawing by absorbing liquid droplets on paper, so when printing on a substrate having low water absorption, the image is blurred and cannot be used. This is because the water-based ink hardly penetrates into the base material with respect to the base material having low absorbability, and the droplets are fused and spread. Therefore, in order to print water-based ink on a substrate with low absorbency as described above, the solvent is volatilized by heating the printing substrate using a heater during printing or by blowing dry air onto the printing part. And the ink had to be dried.

  In addition, when used as an outdoor advertising / signboard application, the pigment-based ink does not soak into the printing substrate and is present on the surface, so that sufficient scratch resistance cannot be obtained on the formed image. I have a problem. For this reason, there is a problem that the use is restricted or the surface is laminated and used.

  In order to improve the scratch resistance of an image formed with the aqueous pigment ink, a fixing binder resin such as a water-soluble resin or water-dispersible resin fine particles is added to the aqueous pigment ink. By adding each binder resin, the scratch resistance of the image is improved. However, the ink adhering to the vicinity of the discharge port (nozzle) of the ink jet head dries and forms and solidifies a resin film, thereby causing discharge bending and nozzle clogging during ink discharge. In particular, when printing water-based ink on a substrate with low absorbency, the temperature around the inkjet head rises when the ink is dried by a drying mechanism such as a heater or dry air during printing, Since the ink easily dries, problems such as ejection failure are likely to occur during long-term printing. In order to prevent such problems, inkjet printers are usually equipped with a cleaning mechanism for cleaning the nozzle surface (wiping the nozzle surface with a rubber blade or cloth) and a cap for preventing nozzle drying. ing. However, when an ink jet printer is used for a long period of time, there also arises a problem that the ink adhering to the surface of the ink jet printer member such as a blade or a head cap for wiping the nozzle surface is dried and solidified. For this reason, the generated ink solidified material adheres to the nozzle surface when wiping the nozzle surface or when the inkjet head is covered with a head cap, thereby causing problems such as non-ejection. Various measures are taken to deal with such a situation.

  As in Patent Documents 4, 5, 6, and 7, there have been inventions of cleaners and maintenance for cleaning the ink flow path of an ink jet printer, and after filling the ink flow path with maintenance liquid and storing it for a long time It is disclosed that the discharge stability can be maintained. However, since the cleaner and the maintenance liquid used in the above invention are not sufficiently moisturizing, they are used for head caps and wiping (wiping with a rubber blade or cloth) when the inkjet printer is used for a long time. Ink adhering to the blade of the ink was dried and solidified, resulting in problems such as adhesion of the ink solidified product to the nozzle surface and non-ejection. Further, when the nozzle surface is wiped using the maintenance liquid of the present invention, the ink adhering to the nozzle surface is insufficiently wiped and it is difficult to maintain excellent ejection stability.

  Patent Document 8 uses an organic solvent that is insoluble or sparingly soluble in water, thereby improving the solubility and redispersibility of the ink, and is excellent in ink cleaning properties and ejection stability after wiping the nozzle surface. A maintenance liquid is disclosed. However, because the maintenance liquid is not sufficiently moisturized, the ink adhering to the head cap and wiping blade dries and solidifies when the inkjet printer is used for a long time, and the solidified ink adheres to the nozzle surface. In addition, there is a problem of impairing the discharge stability.

JP 2001-072905 A JP 2003-012583 A Japanese Patent No. 3994734 Japanese Patent Publication No. 06-008437 Japanese Patent Publication No. 08-030200 Japanese Patent No. 5258535 Japanese Patent No. 5400260 JP 2010-137458 A

  The present invention has been made in view of the above, and is a water-based inkjet recording maintenance liquid that is excellent in moisture retention and maintenance in an inkjet printer that uses water-based ink, and that can maintain excellent discharge stability even when used for a long period of time. The purpose is to provide.

  The above object of the present invention is achieved by the following configurations.

That is, the present invention provides an aqueous inkjet recording maintenance liquid containing one or more organic solvents having a boiling point of 180 ° C. or higher.
The viscosity of the maintenance liquid at 25 ° C. is 70 mPa · s or less,
The surface tension of the maintenance liquid at 25 ° C. is 50 mN / m or less,
The present invention relates to a maintenance liquid for water-based inkjet recording, wherein the content of water is 30% by weight or less with respect to the entire maintenance liquid.

  The present invention also relates to the maintenance liquid for aqueous ink jet recording, wherein the organic solvent having a boiling point of 180 ° C. or higher contains at least one organic solvent having a solubility parameter value (δ) of 21 or more.

  The present invention also relates to the maintenance liquid for water-based inkjet recording, wherein the content of the organic solvent having a boiling point of 180 ° C. or higher is 50% by weight or more based on the whole maintenance liquid.

  Furthermore, the present invention provides an inkjet recording comprising at least one pigment, a pigment dispersion resin, an organic solvent, a binder resin, and at least one aqueous inkjet ink composition containing water, and the aqueous inkjet recording maintenance liquid. It relates to an ink set.

  In the present invention, “maintenance” means immersing and cleaning the head cap and wiping blade provided in the ink jet printer with the maintenance liquid while the ink jet printer is in use and / or not in use, and storing it for a long time. This includes wiping the ink adhering to the nozzle surface and the like by wiping (wiping with a rubber blade dipped in maintenance liquid, cloth or paper) and discharging it stably.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the maintenance liquid for aqueous | water-based inkjet recording which is excellent in moisture retention and maintenance property in the inkjet printer which uses water-based ink, and can maintain the outstanding discharge stability even when used for a long time. .

  Next, the present invention will be described in detail.

Maintenance liquid:
The maintenance liquid for inkjet recording of the present invention is characterized in that it contains at least one organic solvent having a boiling point of 180 ° C. or higher and the water content is 30% by weight or less with respect to the entire maintenance liquid. This maintenance liquid has excellent maintainability in an ink jet printer using an aqueous pigment ink containing a binder resin, and can maintain excellent discharge stability even when used for a long period of time.

  In order to maintain excellent ejection stability when an inkjet printer is used for a long time, the ink adhering to the nozzle surface is wiped off by wiping, and further adhered to the inkjet printer members such as wiping blades and head caps. It is necessary to prevent the dried ink from drying and solidifying. In order to improve the wiping property of ink adhering to the nozzle surface and prevent the ink adhering to the ink jet printer member from being dried and solidified, the present inventors have intensively studied. As a result, at least one organic solvent having a boiling point of 180 ° C. or higher is used. By using the maintenance liquid that is contained above and the water content is 30% by weight or less, it has become clear that ink adhering to the nozzle surface can be sufficiently wiped off to prevent drying and solidification, and the present invention has been achieved.

  The reason why the maintenance liquid of the present invention can sufficiently wipe off ink adhering to the nozzle surface and prevent drying and solidification is not clear, but the following may be considered. When the nozzle surface is wiped using a maintenance liquid containing a large amount of water, it is considered that the ink adhering to the nozzle surface cannot be sufficiently wiped off due to poor wettability with respect to the nozzle surface of water. In addition, when water-based pigment ink is used, if the ink adhering to the nozzle surface is wiped off using a maintenance liquid containing a large amount of water, the pigment diffuses into the maintenance liquid, and wiping residue tends to occur. . On the other hand, since the maintenance liquid of the present invention has a water content in a suitable range, it has an optimum wettability with respect to the nozzle surface, so that it is possible to sufficiently wipe off the adhered ink. Further, the diffusion of the pigment into the maintenance liquid can be suppressed, and the ink adhesion due to the remaining wiping of the maintenance liquid can be reduced. Moreover, since the organic solvent which has a boiling point of a suitable range is contained, an organic solvent swells ink at the time of wiping off, and it becomes possible to improve wiping off property. Furthermore, since the maintenance liquid has high moisture retention, the maintenance performance for the head cap and the wiping blade provided in the ink jet printer is excellent, and drying and solidification can be prevented even if ink adheres. Therefore, it is possible to suppress the generation of dried ink solidified product, and it is possible to prevent adhesion of dried ink solidified product to the nozzle surface when wiping the nozzle surface or when the inkjet head is covered with a head cap. Thus, excellent discharge stability can be maintained even after long-term use.

  The maintenance liquid for inkjet recording of the present invention will be described below with reference to preferred embodiments.

  The organic solvent used in the present invention preferably has a boiling point of at least 180 ° C. from the viewpoint of ensuring moisture retention and excellent maintainability.

  Any organic solvent having a boiling point of 180 ° C. or higher can be used alone or in combination. For example, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, (# 200), polyethylene glycol (# 400), polyethylene glycol (# 600), dipropylene glycol, polypropylene glycol, 1,2- Propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1 , 2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether Ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol diethyl ether, diethylene glycol methyl butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, Triethylene glycol diethyl ether, triethylene glycol methyl butyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monomethyl ether, tripropylene glycol dimethyl ether Ether, 2-pyrrolidone, N-methylpyrrolidone, γ-butyrolactone, N-methyloxazolidinone, N, N-dimethyl-β-methoxydipropionamide, N, N-dimethyl-β-ethoxypropionamide, N, N-dimethyl -Β-butoxypropionamide and the like can be mentioned.

  When the ink is mixed and diluted in the maintenance liquid, depending on the type of the organic solvent, the pigment dispersion stability is often lowered and pigment aggregates are generated. When pigment agglomerates are generated during ink mixing and dilution, the agglomerates may adhere to the vicinity of the nozzle, which may impede stable ink discharge from the nozzle. It is desirable that the dispersion stability can be maintained.

  In order to maintain the dispersion stability when the ink is mixed and diluted in the maintenance liquid, the present inventors have intensively studied the solubility of the organic solvent. As a result, the solubility parameter value calculated by Hansen's method ( It has been found that the stability upon mixing and dilution can be improved by using an organic solvent having a suitable range of δ).

  From the viewpoint of preventing pigment aggregation when the ink is mixed and diluted in the maintenance liquid and ensuring stable ejection properties, the organic solvent having a boiling point of 180 ° C. or higher has solubility calculated by the Hansen method. It is preferable to contain at least one organic solvent having a parameter value (δ) of 21 to 30. When the solubility parameter value (δ) of the organic solvent having a boiling point of 180 ° C. or higher is less than 21, when the ink is mixed and diluted in the maintenance liquid, the dispersion stability of the pigment is lowered, and the pigment aggregate is formed. There is a possibility of adhering to the nozzle surface and impairing the ejection stability.

  The solubility parameter referred to in the present invention is a value generally used as an indicator of solubility and derived from the cohesive energy of molecules. Hansen's method is based on the solubility parameters based on the structure of each organic solvent with reference to page 68 of “Solubility Parameter Application Examples-Based on Mechanisms and Evaluation / Calculation Examples of Solubility” published by Information Technology Corporation. The parameter value (δ) was calculated.

  Examples of the organic solvent having a boiling point of 180 ° C. or higher and a solubility parameter value (δ) of 21 to 30 include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (# 200), polyethylene glycol (# 400, Polyethylene glycol (# 600), dipropylene glycol, polypropylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3- Butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-pyrrolidone, γ-butyrolactone, N-methyloxazolidinone, Include N- dimethyl -β- methoxy dipropionate amide.

  The content of the organic solvent having the boiling point of 180 ° C. or higher used in the present invention in the maintenance liquid is preferably 30% by weight or more, and has sufficient moisture retention when an inkjet printer is used for a long time. However, it is more preferably 50% by weight or more, and most preferably 70% by weight or more from the viewpoint of ensuring excellent maintainability.

  In addition, organic solvents other than those described above can be used singly or in combination as long as the content is within a suitable range that does not reduce the effect of the present invention.

  Other organic solvents include ethylene glycol monomethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol dimethyl ether. , 3-methoxy-1-butanol, 3-methyl-3-methoxy 1-butanol and the like.

  As the water contained in the maintenance liquid of the present invention, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions.

  The content of water in the maintenance liquid that can be used in the present invention is 30 with respect to the entire maintenance liquid from the viewpoint of having sufficient moisture retention and improving the wiping property of ink adhered to the nozzle surface. It is preferably no greater than wt%, more preferably no greater than 15 wt%, and particularly preferably no greater than 5 wt%. Most preferred is a maintenance liquid containing only an organic solvent. When the water content exceeds 30% by weight, the moisture retention of the maintenance liquid decreases, and when the inkjet printer is used for a long period of time, the maintenance liquid volatilizes and the ink attached to the wiping blade or head cap is removed from the maintenance liquid. It becomes difficult to immerse and clean with. Further, when the ink adhering to the nozzle surface is wiped off using the maintenance liquid, the pigment diffuses in the maintenance liquid, and the wiping residue is likely to occur.

  The maintenance liquid used in the present invention is based on the E-type viscometer of the maintenance liquid at 25 ° C. from the viewpoint of sufficiently wiping off ink adhering to the nozzle surface and maintaining the discharge stability even when an inkjet printer is used for a long time. The viscosity is preferably 1 mPa · s or more and 70 mPa · s or less. More preferably, it is 1 mPa · s or more and 60 mPa · s or less. When the viscosity of the maintenance liquid at 25 ° C. exceeds 70 mPa · s, the maintenance liquid is easily wiped off on the nozzle surface, and the maintenance liquid remaining in the vicinity of the nozzle may impair ink ejection stability.

  In addition, the maintenance liquid used in the present invention preferably has a surface tension at 25 ° C. of 20 mN / m or more and 50 mN / m or less from the viewpoint of improving the wiping property of ink adhered to the nozzle surface, and 20 mN / m. More preferably, it is 40 mN / m or less. When surface tension exceeds 50 mN / m, the wiping property of the ink adhering to the nozzle surface may be lowered.

  In addition to the above-mentioned components, the maintenance liquid of the present invention may contain other water-soluble organic solvents, preservatives, antifungal agents, antifoams to the extent that it does not impair the cleaning properties and mixing stability with the ink. An agent, a surface adjuster, a pH adjuster, and the like can be appropriately added. Examples of these addition amounts are in the range of 0.05 to 10% by weight with respect to the total amount of the maintenance liquid.

Aqueous inkjet ink composition:
The maintenance liquid of the present invention can be used as an ink set for ink jet recording together with at least one water-based ink jet ink composition.
The aqueous inkjet ink composition of the present invention contains at least a pigment, a pigment dispersion resin, water, an organic solvent, and a binder resin. Hereinafter, the ink composition will be described. A water-based inkjet ink composed of an ink composition may be referred to as ink.

  Conventionally known pigments can be used for the present invention.

Examples of the black pigment that can be used in the present invention include carbon black produced by a furnace method or a channel method. For example, these carbon blacks have a primary particle diameter of 11 to 40 mμm (nm), a specific surface area by the BET method of 50 to 400 m ² / g, a volatile content of 0.5 to 10% by weight, and a pH value of 2 to 2. Those having characteristics such as 10 are preferred. The following are mentioned as a commercial item which has such a characteristic. For example,
No. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (Mitsubishi Chemical), RAVEN1255 (Colombia), REGAL330R, 400R, 660R, MOGUL L (Cabot), Nexex 160IQ , Nexex 170IQ, Nipex 75, Printex 85, Printex 95, Printex 90, Printex 35, Printex U (manufactured by Degussa) and the like, and any of them can be preferably used.

  Examples of yellow pigments that can be used in the present invention include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 55, 74, 81, 83, 109, 113, 120, 128, 150, 151, 155, 183, and the like.

  Examples of magenta pigments that can be used in the present invention include C.I. I. Pigment Red 5, 7, 12, 22, 23, 31, 48 (Ca), 48 (Mn), 49, 52, 53, 57 (Ca), 57: 1, 112, 122; quinacridone solid solution, 146, 147, 150 238, 269, C.I. I. Pigment Violet 19 etc. are mentioned.

  Examples of cyan pigments that can be used in the present invention include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 16, 22, C.I. I. Vat Blue 4, 6 etc. are mentioned.

  As the pigment that can be used in the present invention, pigments of colors other than those described above, self-dispersing pigments, and the like can also be used. These pigments can be used alone or in combination of two or more in each color ink.

  In the present invention, the pigment is not limited to the above-described pigments, and can be used as an ink set in which other pigments are combined with special colors such as orange, green, and white and clear that does not contain pigments.

  The content of the pigment that can be used in the present invention is in the range of 0.1 to 20% by weight in the ink composition.

  In order to maintain the stability of the ink for a long time when using the pigment, it is preferable to use the pigment dispersed in an ink medium. In order to obtain a more stable ink, a pigment dispersion resin is used. It is preferable to disperse the pigment.

  As the pigment dispersion resin contained in the ink composition of the present invention, conventionally known ones can be used, but (meth) acrylic acid copolymers are generally used. This is because charge repulsion occurs between pigments in an aqueous solvent due to charge repulsion when the (meth) acrylic acid copolymer adsorbed on the pigment surface is ionized, and a stable pigment dispersion state can be maintained. Conceivable.

  The weight average molecular weight of the pigment-dispersed resin is preferably 5,000 to 100,000. When the weight average molecular weight is 5000 or less, the dispersion stability may decrease, and when the weight average molecular weight is 100000 or more, ejection may be affected. More preferably, the weight average molecular weight is 10,000 to 50,000, and still more preferably the weight average molecular weight is 15,000 to 30,000.

  The weight ratio of the pigment to the pigment dispersion resin is preferably 1/1 to 100/1. When the weight ratio of the pigment dispersion resin is greater than 1/1, the ink viscosity tends to increase. Moreover, when smaller than 100/1, a dispersibility may fall and stability may fall. The weight ratio of the pigment and the pigment dispersion resin is more preferably 2/1 to 50/1, and further preferably 2/1 to 20/1.

  In order to increase the coating film resistance of the ink composition and printed matter of the present invention, a binder resin can be used. It is preferable to use water-dispersible resin fine particles as the binder resin. Water-soluble resins and resin fine particles are generally known as binder resins for water-based inks. Generally, resin fine particles have a higher molecular weight than water-soluble resins, and can achieve high resistance. In addition, the resin fine particles can lower the viscosity of the ink, and a larger amount of resin can be blended in the ink. Therefore, it can be said that the resin fine particles are suitable for increasing the coating film resistance. Examples of the resin fine particles include acrylic, urethane, styrene butadiene, vinyl chloride, and polyolefin.

  By increasing the glass transition temperature (Tg) of the water-dispersible resin fine particles, it is possible to improve resistance such as scratch resistance and chemical resistance, preferably in the range of 50 to 100 ° C., more preferably Is in the range of 75-90 ° C.

  As described above, the water-dispersible fat fine particles are excellent in film formability, but the ink is easily dried and is easily solidified on the nozzle surface. Once the film is formed, it does not re-dissolve, so the ink adhering to the nozzle surface must be wiped off before forming the film. Since the maintenance liquid of the present invention is excellent in the wiping property of ink adhering to the nozzle surface, even when the water-dispersed resin fine particles are used as the binder resin, the ink adhering to the nozzle surface is sufficiently wiped off, and the ink is dried on the nozzle surface. It is possible to suppress solidification.

  A conventionally known organic solvent can be used as the organic solvent contained in the ink of the present invention.

  As the organic solvent that can be used in the present invention, glycol ethers and diols are preferable, and (poly) alkylene glycol monoalkyl ether and alkanediol having 3 to 6 carbon atoms are particularly preferable.

  Specific examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, triethylene Glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene Glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, 3-methoxybutanol, 3-methyl-3-methoxybutanol, and the like.

  Specific examples of diols include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, Examples include 1,2-hexanediol, 1,6-hexanediol, and 2-methyl-2,4-pentanediol.

  From the viewpoint of reducing bleeding on the substrate having low absorbency among the above organic solvents and obtaining excellent printing quality, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, 1,2-propanediol, It is preferable to use 1,2-butanediol, 1,3-butanediol, 1,2-hexanediol, and 2-methyl-2,4-pentanediol.

  These solvents may be used alone or in combination.

  Furthermore, depending on the type of substrate to be printed, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methyl-2-oxazolidinone, 3-ethyl for the purpose of improving its solubility Adding nitrogen-containing compounds such as 2-oxazolidinone, N, N-dimethyl-β-methoxydipropionamide, N, N-dimethyl-β-ethoxypropionamide, N, N-dimethyl-β-butoxypropionamide You can also.

  The content of the organic solvent that can be used in the present invention is generally in the range of 3 to 60% by weight, preferably in the range of 3 to 50% by weight, based on the total amount of the ink composition.

  As the water contained in the ink composition of the present invention, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions.

  The content of water that can be used in the present invention is in the range of 10 to 90% by weight, more preferably 10 to 80% by weight, based on the total amount of the ink composition.

  In the ink composition of the present invention, a surfactant can be used for the purpose of adjusting the surface tension and ensuring wettability on a substrate having low absorbency. Examples of the surfactant include acetylene series, silicon series, acrylic series, and fluorine series.

  In addition to the above-described components, the ink of the present invention can be appropriately added with additives such as an antifoaming agent and an antiseptic agent in order to obtain an ink having desired physical properties as required. As an example of the addition amount of these additives, 0.01 to 10% by weight, preferably 0.01 to 5% by weight is suitable based on the total weight of the ink composition.

  Examples of the method for preparing the ink of the present invention comprising the components described above include the following methods, but the present invention is not limited to these. First, a pigment is added to an aqueous medium in which at least a pigment-dispersed resin and water are mixed, and after mixing and stirring, dispersion processing is performed using a dispersion means described later, and centrifugation is performed as necessary. To obtain a desired pigment dispersion. Next, if necessary, a water-soluble organic solvent or an appropriately selected additive component as listed above is added to this pigment dispersion, and the mixture is stirred and filtered as necessary to obtain the ink of the present invention. And

  In the ink preparation method of the present invention, as described above, a pigment dispersion obtained by carrying out a dispersion treatment is used for ink preparation, but before the dispersion treatment carried out during the preparation of the pigment dispersion. It is effective to perform premixing. That is, premixing may be performed by adding a pigment to an aqueous medium in which at least a pigment dispersion resin and water are mixed. Such a premixing operation is preferable because it can improve the wettability of the pigment surface and promote the adsorption of the dispersed resin onto the pigment surface.

  The disperser used in the pigment dispersion treatment may be any disperser that is generally used, and examples thereof include a ball mill, a roll mill, a sand mill, a bead mill, and a nanomizer. Among these, a bead mill is preferably used. Examples of such include a super mill, a sand grinder, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).

  Furthermore, in the pigment premixing and dispersion treatment, the pigment dispersion resin may be dissolved or dispersed only in water, or may be dissolved or dispersed in a mixed solvent of an organic solvent and water.

  Since the ink composition of the present invention is for inkjet recording, it is preferable to use a pigment having an optimum particle size distribution. That is, in order to allow ink containing pigment particles to be suitably used in the ink jet recording method, it is preferable to use a pigment having an optimum particle size distribution in view of demands such as nozzle clogging resistance. Examples of a method for obtaining a pigment having a desired particle size distribution include the following methods. Reduce the size of the grinding media of the disperser as mentioned above, increase the filling rate of the grinding media, increase the processing time, classify with a filter or centrifuge after grinding, etc. There are methods such as a combination of these methods.

  When printing with an ink jet printer using the ink jet ink composition of the present invention, it is preferable to perform printing while heating the printing medium to 40 to 80 ° C. By printing while heating, the ink droplets are dried immediately after landing on the print medium, so that bleeding is unlikely to occur and a high quality printed matter can be obtained. Furthermore, printing is performed while spraying dry air on the printing unit at the time of printing, whereby the volatilization of the solvent is promoted, and it is possible to obtain a clearer and superior print quality with less droplet bleeding.

A known print medium for ink jet printing the ink composition of the present invention can be used. For example, paper media such as high-quality paper, coated paper, art paper, cast paper, synthetic paper, and inkjet paper, and plastic media such as polyvinyl chloride sheets, PET films, and PP films. These may have a smooth print medium surface or an uneven surface, or may be transparent, translucent, or opaque. Further, two or more of these print media may be bonded to each other. Furthermore, a peeling adhesive layer or the like may be provided on the opposite side of the printing surface, or an adhesive layer or the like may be provided on the printing surface after printing.

  Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “part” represents “part by weight”, and “%” represents “% by weight”.

(Manufacture of maintenance liquid)
The raw materials shown in Table 2 and Table 3 were mixed and stirred until sufficiently uniform, followed by filtration using a 1 μm membrane filter to obtain maintenance liquids of Examples 1 to 36 and Comparative Examples 1 to 6.

(Manufacture of pigment dispersion resin)
A reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer was charged with 93.4 parts of triethylene glycol monomethyl ether and replaced with nitrogen gas. The inside of the reaction vessel was heated to 110 ° C., and a mixture of 35.0 parts of lauryl methacrylate, 35.0 parts of styrene, 30.0 parts of acrylic acid, and 6.0 parts of V-601 (manufactured by Wako Pure Chemical Industries) was added for 2 hours. Over the course of the polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, and then 0.6 part of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the reaction was further continued at 110 ° C. for 1 hour to prepare a pigment dispersion resin 1 solution. Obtained. The weight average molecular weight of the pigment dispersion resin 1 was about 16000.
Further, after cooling to room temperature, 37.1 parts of dimethylaminoethanol was added for neutralization. This is the amount that neutralizes 100% of acrylic acid. Further, 200 parts of water was added to make it aqueous. 1 g of this was sampled, heated and dried at 180 ° C. for 20 minutes to measure the non-volatile content, and water was added so that the non-volatile content of the previously aqueous resin solution was 20%. As a result, an aqueous solution having a non-volatile content of 20% of the pigment dispersion resin 1 was obtained.

(Manufacture of water-dispersible resin particles)
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a refluxing vessel was charged with 40 parts of ion exchange water and 0.2 part of Aqualon KH-10 (Daiichi Kogyo Seiyaku) as a surfactant. -10 parts of ethylhexyl acrylate, 57 parts of methyl methacrylate, 30 parts of styrene, 2 parts of dimethylacrylamide, 1 part of methacrylic acid, 53 parts of ion-exchanged water and 1.8 parts of Aqualon KH-10 (Daiichi Kogyo Seiyaku) as a surfactant An additional 1% of the pre-emulsion previously mixed with was added. After raising the internal temperature to 60 ° C. and sufficiently purging with nitrogen, 10 parts of a 5% aqueous solution of potassium persulfate and 20 parts of a 1% aqueous solution of anhydrous sodium bisulfite were added to initiate polymerization. After maintaining the reaction system at 60 ° C. for 5 minutes, the remaining pre-emulsion, 5% aqueous solution of potassium persulfate, and 1% aqueous solution of anhydrous sodium bisulfite were maintained for 1.5 hours while maintaining the internal temperature at 60 ° C. The mixture was added dropwise and stirring was continued for 2 hours. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C. Diethylaminoethanol was added to adjust the pH to 8.5, and the non-volatile content was adjusted to 40% with ion exchange water to obtain a resin fine particle water dispersion. The obtained resin fine particle water dispersion was designated as water dispersible resin fine particles 1. The calculated glass transition temperature of the water-dispersible resin fine particles 1 is 80 ° C.

(Manufacture of pigment dispersion)
[Production of cyan pigment dispersion]
Pigment Blue 15: 3 as pigment, 202.9 parts of pigment dispersion resin 1 aqueous solution and 37.1 parts of water were charged into a mayonnaise bottle, predispersed with a disper, and then dispersed as zirconia with a diameter of 0.5 mm. This dispersion was carried out for 2 hours using a 0.6 L dyno mill filled with 1800 g of beads to obtain a cyan pigment dispersion. This cyan pigment dispersion was designated as Pigment Dispersion A.

[Production of magenta pigment dispersion]
A magenta pigment dispersion was obtained in the same manner as the cyan pigment dispersion, except that Pigment Red 122 was changed to 20 parts as the pigment. This magenta pigment dispersion was designated as pigment dispersion B.

[Production of yellow pigment dispersion]
A yellow pigment dispersion was obtained in the same manner as the cyan pigment dispersion, except that Pigment Yellow 120 was changed to 20 parts as the pigment. This yellow pigment dispersion was designated as Pigment Dispersion C.

[Production of black pigment dispersion]
A black pigment dispersion was obtained in the same manner as the cyan pigment dispersion, except that the carbon black was changed to 20 parts as the pigment. This black pigment dispersion was designated as Pigment Dispersion D.

(Ink production)
[Manufacture of cyan ink]
20 parts of pigment dispersion A, 15 parts of water dispersion of water-dispersible resin fine particles 1, 20 parts of 1,2-butanediol, 5 parts of 2-pyrrolidone, and 1 part of Surfynol 440 (available from Air Products and Chemicals Inc.) Ink 1 was obtained by mixing 39 parts of water and 39 parts of water and filtering with a 1 μm membrane filter.

[Manufacture of magenta ink]
20 parts of pigment dispersion B, 15 parts of water dispersion of water-dispersible resin fine particles 1, 20 parts of 1,2-butanediol, 5 parts of 2-pyrrolidone, and 1 part of Surfynol 440 (available from Air Products and Chemicals Inc.) Ink 2 was obtained by mixing 39 parts of water and 39 parts of water and filtering with a 1 μm membrane filter.

[Manufacture of yellow ink]
20 parts of pigment dispersion C, 15 parts of water dispersion of water-dispersible resin fine particles 1, 20 parts of 1,2-butanediol, 5 parts of 2-pyrrolidone, and 1 part of Surfynol 440 (manufactured by Air Products and Chemicals Inc.) Ink 3 was obtained by mixing 39 parts of water and 39 parts of water and filtering with a 1 μm membrane filter.

[Manufacture of black ink]
20 parts of pigment dispersion D, 15 parts of water dispersion of water-dispersible resin fine particles 1, 20 parts of 1,2-butanediol, 5 parts of 2-pyrrolidone, and 1 part of Surfynol 440 (available from Air Products and Chemicals Inc.) Ink 4 was obtained by mixing 39 parts of water and 39 parts of water and filtering with a 1 μm membrane filter.

(Organic solvent)
Table 1 shows the physical properties of the organic solvents used in Examples and Comparative Examples.

The evaluation method of the produced maintenance liquid is shown below.

(Evaluation 1: Evaluation of viscosity of maintenance liquid)
The viscosity (η) at 25 ° C. of the maintenance liquids obtained in Examples 1 to 36 and Comparative Examples 1 to 6 was measured using an E-type viscometer (TVE-20L manufactured by Toki Sangyo Co., Ltd.). The evaluation criteria were as follows.
<Evaluation criteria>
0: 1 mPa · s <η ≦ 10 mPa · s
1: 10 mPa · s <η ≦ 20 mPa · s
2: 20 mPa · s <η ≦ 30 mPa · s
3: 30 mPa · s <η ≦ 40 mPa · s
4: 40 mPa · s <η ≦ 50 mPa · s
5: 50 mPa · s <η ≦ 60 mPa · s
6: 60 mPa · s <η ≦ 70 mPa · s
7: 70 mPa · s <η

(Evaluation 2: Evaluation of surface tension of maintenance liquid)
The surface tension value ((sigma)) in 25 degreeC of the maintenance liquid obtained in Examples 1-36 and Comparative Examples 1-6 was measured using CBVP-Z (made by Kyowa Interface Science). The evaluation criteria were as follows.
<Evaluation criteria>
2: 20 mN / m <σ ≦ 30 mN / m
3: 30 mN / m <σ ≦ 40 mN / m
4: 40 mN / m <σ ≦ 50 mN / m
5: 50 mN / m <σ

(Evaluation 3: Evaluation of moisture retention of maintenance liquid)
The maintenance liquid obtained in Examples 1 to 36 and Comparative Examples 1 to 6 was put in 5 g in a mentum can having a diameter of 45 mm and a height of 13.5 mm, and the mentum can containing the maintenance liquid was allowed to stand on a hot plate at 50 ° C. for 4 hours. The weight change of the maintenance liquid after being placed was measured. The weight change (Δ) was calculated based on the following general formula (1).

General formula (1)
Δ (%) = (weight of maintenance liquid before drying−weight of maintenance liquid after drying at 50 ° C. for 4 hours) / weight evaluation standard of maintenance liquid before drying was as follows.

<Evaluation criteria>
A: Δ ≦ 5%
○: 5% <Δ ≦ 15%
Δ: 15% <Δ ≦ 35%
×: 35% <Δ

(Evaluation 4: Evaluation of maintainability for printer members)
An ink jet printer was filled with inks 1 to 4, and solid printing with a printing rate of 100% was performed for 1 hour while heating PVC to 50 ° C. with a platen heater in an environment of 25 ° C. After printing, the printer member after immersing a head cap and a wiping rubber blade as a printer member in the maintenance liquid obtained in Examples 1 to 36 and Comparative Examples 1 to 6 in an environment of 25 ° C. for one week. A visual evaluation was made on the adhesion state of the ink on the surface. The evaluation criteria were as follows.
<Evaluation criteria>
◎: No adhesion of dried ink solidified product ○: Adhesion of dried ink solidified product hardly observed △: Dryed solidified product of ink adhered to a part of the surface of the printer member X: The dried and solidified product of the ink adheres to the entire surface of the printer member

(Evaluation 5: Evaluation of ink wiping property on the nozzle surface of the inkjet head)
An ink jet printer equipped with a mechanism capable of wiping the nozzle surface of the ink jet head (wiping with a rubber blade) is filled with ink 1 to 4, and PVC is heated to 50 ° C. by a platen heater in an environment of 25 ° C. Solid printing with a printing rate of 100% was carried out for 1 hour. The nozzle surface of the inkjet head after printing was wiped with a rubber blade immersed in the maintenance liquids obtained in Examples 1 to 36 and Comparative Examples 1 to 6, and the ink wiping property was visually evaluated. The evaluation criteria were as follows.
<Evaluation criteria>
◎: Ink is sufficiently wiped off, and no ink adheres to the nozzle surface. ○: Ink is wiped off, and ink is hardly observed on the nozzle surface. Δ: Ink is not wiped off slightly, and ink is slightly on the nozzle surface. Adhesion is observed x: Ink is not sufficiently wiped off, and ink is clearly observed on the nozzle surface

(Evaluation 6: Evaluation of ejection stability)
Fill the above inkjet printer with ink 1 to 4 and perform solid printing with a printing rate of 100% and printing width of 1m while heating PVC to 50 ° C with a platen heater in an environment of 25 ° C. The nozzle surface of the inkjet head was wiped with a rubber blade immersed in the maintenance liquids obtained in Examples 1-36 and Comparative Examples 1-6. Thereafter, a nozzle check pattern was printed to count the number of missing nozzles, and the number was evaluated. The evaluation criteria were as follows.
<Evaluation criteria>
◎: No missing nozzle when printing length is 10m ○: No nozzle missing when printing length is 4-9m △: No nozzle missing when printing length is 1-3m ×: Nozzle missing number is 5% or more with respect to all nozzles when printing length is 1m 10 Less than% xx: The printing length is 1 m and the number of missing nozzles is 10% or more with respect to all nozzles.

(Evaluation 7: Ink dilution stability against maintenance liquid)
After adding and mixing 50 μl of ink 1 to 4 separately to 50 ml of the maintenance liquid obtained in Examples 1 to 36 and Comparative Examples 1 to 6, the mixture was stored in a constant temperature bath at 70 ° C. The presence or absence was visually evaluated. The evaluation criteria were as follows.
<Evaluation criteria>
A: No aggregation was observed after 2 weeks storage at 70 ° C. ○: No aggregation was observed after 1 week storage at 70 ° C .: Slight agglomeration after 1 week storage at 70 ° C. Occurrence of

Said evaluation result is shown in Table 2 about Examples 1-36. Comparative Examples 1 to 6 are shown in Table 3.

  As shown in Table 2, both the maintenance liquid of the present invention and the ink set using the maintenance liquid exhibit excellent moisture retention and maintenance properties.

  On the other hand, in the comparative example which is out of the scope of the present invention, it is shown that all the evaluation items are satisfied and a maintenance liquid having a practical quality cannot be obtained. In Comparative Examples 1 and 2 in which the water content is outside the range of the present invention, the moisture retention is not sufficient, and excellent maintainability and discharge stability are not obtained. Similarly, in Comparative Examples 3, 4, and 5 using an organic solvent whose boiling point is outside the scope of the present invention, since the moisture retention is insufficient, maintainability on the head cap is impaired and ejection stability is also ensured. Not done. In Comparative Example 6 containing no organic solvent, excellent maintainability is not obtained.

Claims (4)

In an aqueous inkjet recording maintenance liquid containing one or more organic solvents having a boiling point of 180 ° C. or higher,
The viscosity of the maintenance liquid at 25 ° C. is 70 mPa · s or less,
The surface tension of the maintenance liquid at 25 ° C. is 50 mN / m or less,
A maintenance liquid for water-based inkjet recording, wherein the content of water is 30% by weight or less with respect to the entire maintenance liquid. Boiling point is the organic solvent above 180 ° C., solubility parameter values ([delta]) aqueous inkjet recording maintenance liquid according to claim 1, characterized in that contains at least one or more organic solvents is 21 or more. For the entire content maintenance liquid of the organic solvent having a boiling point of above 180 ° C., according to claim 1 or 2 aqueous inkjet recording maintenance liquid, wherein the 50 wt% or more. It has at least 1 or more types of water-based inkjet ink composition containing a pigment, pigment dispersion resin, an organic solvent, binder resin, and water, and the maintenance liquid for water-based inkjet recording in any one of Claims 1-3. Ink set for inkjet recording.