JP5359111B2 - Water-based inkjet ink - Google Patents

Description

  The present invention relates to a novel water-based inkjet ink used in a printing system by heating a recording medium. More specifically, high-quality images can be obtained at a higher speed by achieving both the suppression of Decap and a high drying speed. The present invention relates to an aqueous inkjet ink that can be used.

  In recent years, since an inkjet recording method can produce images easily and inexpensively, it has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters.

  Ink jet inks used in such ink jet recording methods include water-based ink-jet inks composed of water and a small amount of organic solvents, non-aqueous ink-jet inks that contain substantially no water, and heat-melt inks that are solid at room temperature. There are a plurality of ink-jet inks such as hot-melt ink for printing and actinic ray-curable ink-jet ink that is cured by actinic rays such as light after printing, and these are used properly depending on the application.

  On the other hand, non-water-absorbing recording media such as polyvinyl chloride are used in a wide range of applications such as outdoor postings that require long-term weather resistance and printed matter that requires adhesion to curved objects.

  As an example of an inkjet ink system that can be recorded on a polyvinyl chloride recording medium, a non-aqueous inkjet ink that contains an organic solvent such as cyclohexanone and does not substantially contain water is disclosed (for example, see Patent Document 1). .)

  Since the non-water-absorbing recording medium does not absorb ink, the scratch resistance of the printed matter has been a problem, but the problem has been solved by the inkjet ink. However, this ink-jet ink still has a problem of environmental burden that involves a large amount of organic solvent discharge during the drying process.

  On the other hand, water-based inkjet inks containing a fixing resin and improved in scratch resistance by heat drying have been proposed (see, for example, Patent Documents 2 and 3).

However, heating at the time of printing is effective to increase the drying speed and scratch resistance, but promotes ink drying on the head surface, so that there is a problem that intermittent ejection failure of ink called Decap is likely to occur.
Japanese translation of PCT publication No. 2002-526631 JP 2005-113147 A JP 2007-297586 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to achieve both suppression of intermittent ejection failure of ink due to Decap and fast drying speed, as well as non-water absorption in addition to water-absorbing recording media represented by paper. It is an object of the present invention to provide a water-based inkjet ink that can provide high-quality image quality and scratch resistance with respect to a recording medium.

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

1. An aqueous inkjet ink that is used to print to a non-water absorbing recording medium heated to 35 to 60 ° C.,
The water-based inkjet ink has a weight average molecular weight of 7000 to 20000 neutralized with at least a pigment , a polymer dispersant, and an amine having a boiling point of less than 200 ° C., and 3 based on the total mass of the water-based inkjet ink. % mass or more, organic and water-soluble acrylic resin contained in the following 6 mass%, and that at least one water-soluble organic solvent glycol ethers or carbon atoms are selected from 1,2-alkanediols with 4 or more The ink viscosity at 25 ° C. is 15 to 20 mPa · s, and the viscosity increases after printing on the recording medium.
The polymer dispersant has a weight average molecular weight of 5000 or more and 200000 or less ,
The water-soluble acrylic resin, wherein the water-soluble acrylic resin has (meth) acrylic acid and (meth) acrylic acid ester as copolymerization components, and has an acid value of 60 mgKOH / g or more and less than 80 mgKOH / g ink.

  2. At least one water-soluble organic solvent selected from the glycol ethers or 1,2-alkanediols having 4 or more carbon atoms is propylene glycol monoalkyl ether, dipropylene glycol monoalkyl ether, tripropylene glycol monoalkyl. 2. The water-based inkjet ink as described in 1 above, which is at least one selected from ether and 1,2-hexanediol.

  3. At least one of the pigments is C.I. I. 3. The water-based inkjet ink as described in 1 or 2 above, which is CI Pigment Yellow 155.

4). 4. The water-based inkjet ink according to any one of items 1 to 3, wherein the recording medium is a vinyl chloride sheet .

  According to the present invention, the intermittent ejection failure of ink due to Decap is suppressed, and a high drying speed is achieved at the same time, and in addition to the water-absorbing recording medium represented by paper, no spots are generated on the non-water-absorbing recording medium. It was possible to provide a water-based inkjet ink that can provide high-quality image quality and scratch resistance.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor has at least a pigment, a polymer dispersant, 2% by mass or more and 10% by mass or less in a water-based inkjet ink used in a system for heating and printing a recording medium. A water-soluble acrylic resin and at least one water-soluble organic solvent selected from glycol ethers or 1,2-alkanediols having 4 or more carbon atoms, wherein the water-soluble acrylic resin is a (meth) acrylic An aqueous inkjet ink characterized by having an acid and (meth) acrylic acid ester as at least a copolymer component and having an acid value of 60 mgKOH / g or more and less than 80 mgKOH / g. In addition to the water-absorbing recording medium typified by paper Found that it is possible to realize an ink jet aqueous ink that high image quality and scratch resistance etc. does not occur unevenness can be obtained with respect to the water-absorbing recording medium, it is completed the invention.

  Hereinafter, the details of each component of the water-based inkjet ink of the present invention (hereinafter also simply referred to as ink) will be described.

[Water-soluble acrylic resin]
In the ink of the present invention, the water-soluble acrylic resin is contained in an amount of 2% by mass to 10% by mass based on the total mass of the ink. The water-soluble in the present invention means having a solubility of at least about 10% with respect to water.

  The water-soluble acrylic resin according to the present invention is required to have a function as a binder resin in order to improve the durability of the image, so that it is stably dissolved in the ink, but after being dried on the recording medium It is preferable that the resin is imparted with water resistance.

  As such a water-soluble acrylic resin, a resin having a hydrophobic component and a hydrophilic component in a certain balance is designed and used. One feature of the present invention is to use a water-soluble acrylic resin having at least (meth) acrylic acid as a hydrophilic component and (meth) acrylic acid ester as a hydrophobic component as a copolymer component. In particular, (meth) acrylic acid is preferably provided with water solubility by neutralization with a volatile base component. Furthermore, the acid value of the water-soluble acrylic resin used in the present invention is 60 mgKOH / g or more and less than 80 mgKOH / g. The acid value referred to in the present invention is represented by the number of milligrams of potassium hydroxide (mg KOH / g) required to neutralize the acidic component contained in 1 g of the resin.

  In the system for printing by heating the recording medium of the present invention, there is a problem that nozzle missing or ink droplet bending (Decap) is likely to occur due to drying of the ink jet recording head surface during intermittent emission. In the configuration of the present invention, it has been clarified by the present inventors that Decap can be effectively suppressed by using a water-soluble acrylic resin having an acid value in the range of 60 mgKOH / g or more and less than 80 mgKOH / g. .

  By adopting the configuration defined in the present invention, no clear interpretation has been reached regarding the mechanism by which the above-described effects are manifested. However, if the resin has an acid value of less than 80 mgKOH / g, it is relatively water-soluble among water-soluble resins. It is presumed that this is due to the fact that it has a pseudo micelle structure in the ink due to its balance with (meth) acrylic acid ester which is a hydrophobic component. That is, since the molecular chains of the water-soluble acrylic resin are shrinking, it is presumed that the Decap is suppressed as a result that the viscosity hardly increases even when the ink is dried on the head surface. Furthermore, by setting the lower limit of the acid value to 60 mgKOH / g or more, it is estimated that a certain degree of water solubility is maintained, and even when the surface of the ink jet recording head is dried, the redissolving ability is high and effective for Decap.

  Examples of the (meth) acrylic acid ester that is a copolymerization component used in the water-soluble acrylic resin according to the present invention include n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, ethyl methacrylate, and methacrylic acid. Acid butyl, glycidyl methacrylate and the like.

  In addition, as a copolymerization component of the water-soluble acrylic resin which concerns on this invention, well-known polymerizable reactive monomers, such as acrylonitrile, vinyl acetate, urethane, styrene, can be used. However, when a highly hydrophobic copolymer component such as styrene is used in the present invention, it is difficult to ensure water solubility.

  As a molecular weight of the water-soluble acrylic resin according to the present invention, those having an average molecular weight of 3000 to 30000 can be used. Preferably the thing of 7000-20000 can be used.

  The Tg of the water-soluble acrylic resin according to the present invention can be about -30 ° C to 100 ° C. Preferably, a temperature of about −10 ° C. to 80 ° C. can be used.

  As the polymerization method for the water-soluble acrylic resin according to the present invention, it is preferable to use solution polymerization.

  The (meth) acrylic acid of the water-soluble acrylic resin according to the present invention is preferably partially or completely neutralized with a base component. Examples of the neutralizing base in this case include alkali metal-containing bases such as sodium hydroxide and potassium hydroxide, and amines (for example, ammonia, triethylamine, 2-dimethylaminoethanol, 2-di-n-butylaminoethanol). Methyldiethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, triethanolamine, 2-methylaminoethanol, etc.) can be used. In particular, neutralization with amines having a boiling point of less than 200 ° C. is particularly preferable from the viewpoint of improving image durability.

  The addition amount of the water-soluble acrylic resin of the water-soluble acrylic resin according to the present invention is an amount of 2% by mass or more and 10% by mass or less in order to obtain unevenness of printed images, abrasion resistance and emission stability. It is necessary to use it, and it is preferable to use it in the range of 3 mass% or more and 6 mass% or less.

[Water-soluble organic solvent: glycol ethers, 1,2-alkanediols having 4 or more carbon atoms]
The ink of the present invention contains at least one water-soluble organic solvent selected from glycol ethers and 1,2-alkanediols having 4 or more carbon atoms from the viewpoint of obtaining high-quality images with suppressed spots. One of the characteristics is to contain.

  Specific examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, and dipropylene glycol monomethyl ether. , Dipropylene glycol monopropyl ether, tripropylene glycol monomethyl ether, and the like.

  Examples of 1,2-alkanediols having 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and the like. It is done.

  The addition amount of the water-soluble organic solvent according to the present invention is preferably 5% by mass or more and 30% by mass or less, more preferably 7% by mass or more and 20% by mass or less. This is effective from the viewpoint of achieving both the objective effect and the ink storage stability.

  Particularly preferred water-soluble organic solvents are propylene glycol monoalkyl ether, dipropylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, and 1,2-hexanediol. Further, in the propylene glycol monoalkyl ether, dipropylene glycol monoalkyl ether, and tripropylene glycol monoalkyl ether, it is possible to select the range in which the carbon number of the monoalkyl ether portion is 1 to 3, so that the object effect and ink storage of the present invention This is particularly preferable from the viewpoint of further ensuring stability.

  In addition to the glycol ethers or 1,2-alkanediols according to the present invention, conventionally known organic solvents can be added to the ink of the present invention as long as the object and effects of the present invention are not impaired.

  Specifically, as the organic solvent applicable to the present invention, an aqueous liquid medium is preferably used, and examples thereof include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tarcha Libutanol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodi Glycol), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethyl) Tanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethyl) Formamide, N, N-dimethylacetamide and the like).

  In the present invention, when a recording medium made of polyvinyl chloride is used, it is preferable to use an organic solvent that is highly swelled or soluble in polyvinyl chloride because the pigment fixing property can be improved.

  Specifically, heterocycles (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl) Sulfoxide, etc.) and sulfolane.

  The water, which is a constituent requirement of the ink of the present invention, is preferably contained in an amount of 40% by mass or more, more preferably 50% or more from the viewpoint of improving the drying property and the storage stability of the ink.

[Pigment]
As the pigment applicable to the ink of the present invention, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments and the like can be used. For example, organic pigments such as insoluble pigments and lake pigments can be used. Pigments and inorganic pigments such as carbon black can be preferably used. This pigment is used in the state of being dispersed in the ink by the polymer dispersant according to the present invention.

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

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

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 202, C.I. I. Pigment red 222, C.I. I. Pigment violet 19 and the like.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. And CI Pigment Yellow 155.

  In particular, for yellow pigments, C.I. I. CI Pigment Yellow 155 is preferable, but when glycol ethers or 1,2-alkanediols having 4 or more carbon atoms are used as the water-soluble organic solvent, the storage stability of the ink is remarkably lowered by the selection of the water-soluble acrylic resin. It turns out that there is a problem.

  With respect to this problem, the water-soluble acrylic resin having the characteristics defined in the present invention can be greatly improved.

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

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

  The average particle size of the dispersed state of the pigment contained in the ink of the present invention is preferably 50 nm or more and less than 200 nm.

  If the average particle size of the pigment dispersion is less than 50 nm or 200 nm or more, the stability of the pigment dispersion tends to be poor, and the storage stability of the ink tends to deteriorate.

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

  The pigment according to the present invention is preferably used after being dispersed by a disperser together with a dispersant and other necessary additives according to various desired purposes.

  As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. In particular, the particle size distribution of the ink produced by dispersion with a sand mill is sharp and preferable.

  The material of the beads used for sand mill dispersion is preferably zirconia or zircon from the viewpoint of contamination of bead fragments and ionic components. Furthermore, the bead diameter is preferably 0.3 mm to 3 mm.

(Polymer dispersant)
The polymer dispersant referred to in the present invention has a polymer component having a molecular weight of 5000 or more and 200000 or less. The polymer dispersant is selected from styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid and fumaric acid derivatives. Examples thereof include a block copolymer comprising at least one kind of monomer, a random copolymer and salts thereof, polyoxyalkylene, and polyoxyalkylene alkyl ether.

  In the case of an acidic polymer dispersant, it is preferably added after neutralization with a neutralizing base. Here, the neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, or morpholine.

  Moreover, in this invention, it is preferable that it is 10-100 mass% with respect to a pigment as addition amount of a polymer dispersing agent, and the range of 10-40 mass% is more preferable.

  The pigment dispersion used in the ink of the present invention is particularly preferably a so-called capsule pigment in which the pigment is coated with a resin. Various known methods can be used as a method of coating the pigment with the resin. Preferably, in addition to the phase inversion emulsification method and the acid precipitation method, the pigment is dispersed with a polymerizable surfactant, and the monomer is added thereto. It is preferable to select from a method of coating while polymerizing.

  As a more preferred method, the water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and after partially or completely neutralizing the acidic groups in the resin with a base, the pigment and ion-exchanged water are added and dispersed. After that, a production method in which an organic solvent is removed and water is added as necessary is preferable.

[Surfactant and other additives]
In the ink of the present invention, when a non-water-absorbing recording medium is used as the recording medium, it is preferable to use a surfactant from the viewpoint of imparting higher wettability. The surface tension of the ink for imparting wettability is preferably 30 mN / m or less, and more preferably 28 mN / m or less.

  The surfactant that can be used in the ink of the present invention can be used without particular limitation as long as the surface tension of the ink can be adjusted to 30 mN / m or less. Since the compound is contained, the ionicity of the surfactant is preferably an anion, nonion or betaine type.

  In the present invention, a fluorine-based or silicon-based surfactant that preferably has a high ability to reduce static surface tension, an anionic surfactant such as dioctyl sulfosuccinate that has a high ability to reduce dynamic surface tension, and a relatively low Nonionic surfactants such as molecular weight polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, acetylene glycols, pluronic surfactants, and sorbitan derivatives are preferably used. It is also preferable to use a fluorine-based or silicon-based active agent in combination with a surfactant having a high ability to reduce the dynamic surface tension.

  In the ink of the present invention, in addition to the above description, if necessary, the output stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performance improvement objectives are known. Various additives such as polysaccharides, viscosity modifiers, specific resistance regulators, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, antifungal agents, rust preventives, etc. may be appropriately selected and used. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, 57-87988, and 62-261476, Kaisho 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771 and JP-A-4-219266 Etc.

  The ink of the present invention having the above-described configuration preferably has an ink viscosity of 1 to 40 mPa · s at 25 ° C., more preferably 5 to 40 mPa · s, and still more preferably 5 to 20 mPa · s. is there.

[Non-water-absorbing recording medium]
Next, the non-water absorbent recording medium according to the present invention will be described.

  The ink of the present invention is particularly suitable for printing on a non-water-absorbing recording medium such as a polyvinyl chloride sheet, which is the object of the present invention.

  Examples of the non-water-absorbing recording medium include polymer sheets, boards (soft vinyl chloride, hard vinyl chloride, acrylic plates, polyolefins, etc.), glass, tiles, rubbers, and the like.

  In particular, a preferable non-water-absorbing recording medium capable of obtaining a good image and high image fastness is a recording medium having at least polyvinyl chloride on the recording surface side.

  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, manufactured by Kimoto Co., Ltd.), J-CAL-HGX, J-CAL-YHG, J-CAL-WWWG (above, manufactured by Kyo Show 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, 34P, S27P (manufactured by Grafityp), P-223RW, P-224RW, P-249ZW, P-284ZC (manufactured by Lintec Corporation), LKG-19, LPA-70, LPE-248, LPM-45 LTG-11, LTG-21 (manufactured by Shinsei Co., Ltd.), MPI 3023 (manufactured by Toyo Corporation), Napoleon Gloss PVC (manufactured by Futaki Electronics Co., Ltd.), JV-610, Y-114 ( As described above, manufactured by ICC Corporation), NIJ-CAPVC, NIJ-SPVCGT (hereinafter, manufactured by Nichie Corporation), 3101 / H12 / P4, 3104 / H12 / P4, 3104 / H12 / P4S, 9800 / H12 / P4, 3100 / H12 / R2, 3101 / H12 / R2, 3104 / H12 / R 2, 1445 / H14 / P3, 1438 / One Way Vision (manufactured by Intercoat), JT5129PM, JT5728P, JT5822P, JT5829P, JT5829R, JT5829PM, JT5829RM, JT5929PM (above, manufactured by Mactac, MP1100, MP1100, MP1100) MPI2001, MPI2002, MPI3000, 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, SJ T-V400F-1 (above, manufactured by Hiraoka Oryome Co., Ltd.), SPS-98, SPSM-98, SPSH-98, SVGL-137, SVGS-137, MD3-200, MD3-301M, MD5-100, MD5- 101M, MD5-105 (manufactured by Metamark), 640M, 641G, 641M, 3105M, 3105SG, 3162G, 3164G, 3164M, 3164XG, 3164XM, 3165G, 3165SG, 3165M, 3169M, 3451SG, 3551G, 3551M, 3631, 3641M , 3651G, 3651M, 3651SG, 3951G, 3641M (above, manufactured by Orafol), SVTL-HQ130 (manufactured by Lamy Corporation), SP300 GWF, SPCLEARAD vinyl l (above, manufactured by Catalina), RM-SJR (produced by Ryoyo Shoji Co., Ltd.), Hi Lucky, New Lucky PVC (above, produced by LG), SIY-110, SIY-310, SIY-320 (above, Sekisui Chemical) Industrial Co., Ltd.), PRINT MI Frontlit, PRINT XL Lightweight banner (above, manufactured by Endutex), RIJET 100, RIJET 145, RIJET165 (above, manufactured by Ritrama), NM-SG, NM-SM Co., Ltd. Manufactured), LTO3GS (manufactured by Lucio Co., Ltd.), easy print 80, performance print 80 (manufactured by Jetgraph Co., Ltd.), DSE 550, DSB 550, DSE 800G, DSE 802/137, V250WG, 300WG, V350WG (manufactured by Hexis Ltd.), Digital White 6005PE, 6010PE (or, Multifix Co., Ltd.).

〔Recording method〕
In the ink jet recording method using the ink of the present invention, when an image is recorded on a recording medium using the ink of the present invention, the surface temperature on the recording surface side of the recording medium is heated and recorded. Heating the recording medium is preferable from the viewpoint of significantly improving the drying and thickening speed of the ink, obtaining high image quality, and improving the durability of the formed image.

  By heating to 35 ° C or higher as the heating temperature of the recording medium, it is possible to effectively suppress spots that are particularly likely to occur on non-absorbent recording media, and in addition to easily obtaining sufficient image durability, the drying time can also be shortened. Preferably, when the temperature is 80 ° C. or lower, an image can be stably formed without greatly affecting ink ejection.

  More preferably, the recording surface temperature of the recording medium is heated to 35 ° C. or more and 60 ° C. or less.

  As a heating method of the recording medium, a heating heater is incorporated in the recording medium conveyance system or platen member of the ink jet recording apparatus and heated from the back side of the non-water-absorbing recording medium, or non-contact from below or above with a lamp or the like. The heating method can be selected.

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

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

Example 1
<< Preparation of pigment dispersion >>
As a polymer dispersant, a premixed solution of styrene-acrylic acid copolymer (John Cryl 678, molecular weight 8500, acid value 215) 3.0%, pigment (Pigment Yellow 155) 15%, and ion-exchanged water as the balance was added. After mixing, the mixture was dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads to prepare a pigment dispersion having a pigment content of 15%. The average particle diameter of the pigment particles contained in this pigment dispersion was 122 nm. The particle size was measured using a Zetasizer 1000HS manufactured by Malvern.

<Synthesis of water-soluble acrylic resin>
50 g of methyl ethyl ketone was added to a flask equipped with a dropping funnel, a nitrogen introducer, a reflux condenser, a thermometer and a stirring device, and heated to 75 ° C. while bubbling nitrogen. Thereto, a mixture of 87.2 g of methyl methacrylate, 7.8 g of acrylic acid, 5 g of 2-acrylamido-2-methylpropanesulfonic acid, 50 g of methyl ethyl ketone, and 500 mg of initiator (AIBN) was dropped from a dropping funnel over 3 hours. did. It heated and refluxed for 6 hours after dripping. After allowing to cool, the mixture was heated under reduced pressure to distill off methyl ethyl ketone.

  The polymer residue was dissolved in a solution in which dimethylaminoethanol equivalent to 1.05 mol of acrylic acid added as a monomer was dissolved in 100 ml of ion-exchanged water. It adjusted with ion-exchange water and obtained water-soluble acrylic resin aqueous solution A-1 of 30% of solid content. Next, a water-soluble acrylic resin aqueous solution A-2 to A having a solid content of 30% was prepared in the same manner as in the preparation of the water-soluble acrylic resin aqueous solution A-1, except that the monomer composition and amount were changed as shown in Table 1. -4 was prepared.

<< Preparation of water-based inkjet ink >>
(Preparation of ink 1)
While stirring 26.7 parts of the pigment dispersion prepared above, 13.3 parts of the water-soluble acrylic resin aqueous solution A-1 having a solid content of 30% was added, and then each additive shown below was added. After sequentially adding to prepare an ink composition, ink 1 was obtained by filtration through a 0.8 μm filter. The prepared ink 1 had a viscosity at 25 ° C. of 9.2 mPa.s. s.

Pigment dispersion 26.7 parts Water-soluble resin aqueous solution A-1 (solid content 30%) 13.3 parts 1,2-hexanediol 8.0 parts Tripropylene glycol monomethyl ether 12.0 parts Propylene glycol 10.0 parts Silicon Surfactant (manufactured by Shin-Etsu Chemical Co., Ltd., KF-351A) 0.3 part Amount of ion-exchanged water to 100 parts (Preparation of inks 2 to 16)
In the preparation of the ink 1, the inks 2 to 16 were similarly prepared except that the type and addition amount of the water-soluble acrylic resin, the type and addition amount of the organic solvent, and the pigment type were changed to the configurations shown in Table 2. Prepared. The addition amount of the organic solvent in each ink was adjusted so that the viscosity value with respect to ink 1 was in the range of ± 10%.

  In addition, the detail of each additive described in Table 2 with the abbreviation is as follows.

<Water-soluble organic solvent>
1,2-HDO: 1,2-hexanediol TPGME: Tripropylene glycol monomethyl ether DPGME: Dipropylene glycol monomethyl ether PGPE: Propylene glycol monopropyl ether DEGBE: Diethylene glycol monobutyl ether PG: Propylene glycol Gly: Glycerin <Pigment>
PY155; C.I. I. Pigment Yellow 155
PB15: 4; C.I. I. Pigment Blue 15: 4
<Evaluation of ink>
Each of the inks prepared above was evaluated according to the following method. For inks 1 to 16, the surface tension measured by the plate method was in the range of 26 to 28 mN / m, and the average dispersed particle size of the pigment measured by the dynamic light scattering method was in the range of 95 to 150 nm.

(Evaluation of Decap)
Each ink was loaded into an ink jet printer equipped with a drop-on-demand piezo type ink jet head (nozzle number 512 (256 × 2 rows), nozzle diameter 39 μm, nozzle interval 70.5 μm (141 μm × 2 rows)). Next, a 35 × 35 mm square image was recorded in one scan on the recording medium under the conditions of a head scanning speed of 200 mm / second, an ink droplet volume of 42 pl, and a recording density of 360 × 360 dpi. After stopping the inkjet head for 20 seconds at a position 5 mm apart from the image, a square image was recorded adjacently in the same manner. Similarly, the head stop time was changed to 1 minute and 3 minutes, and adjacent square images were recorded at intervals of 5 mm (a total of five adjacent square images at intervals of 5 mm). In addition, dpi as used in the field of this invention represents the number of dots per 2.54 cm.

  In addition, for 3 minutes after the image formation from the start of printing, the recording medium was heated with a heater from the back, and the surface temperature of the recording medium was controlled to 50 ± 2 ° C. The surface temperature of the recording medium was measured using a non-contact thermometer (IT-530N type, manufactured by Horiba, Ltd.).

  As the recording medium, JT5929PM (manufactured by Mactac), which is a recording medium made of polyvinyl chloride, was used.

  Using the square image formed as described above, the head stop time at which the disturbance of the edge of the image due to abnormal ejection of ink started to occur was determined, and Decap was evaluated according to the following criteria.

○: Disturbance is not observed at the edge of the image even after 3 minutes of the head stop time, and a good print image is obtained. Δ: Disturbance is not observed at the edge of the image after 1 minute of the head stop time, but after 3 minutes. Is a practically acceptable range to the extent that some disturbance is observed. ×: Disturbance is observed at the edge of the image after 20 seconds of the head stop time, and is outside the allowable range for practical use. Is a practically preferable range.

(Evaluation of image drying)
Using an ink jet printer similar to the above, 35 × is applied to JT5929PM (manufactured by Mactac), which is a recording medium made of polyvinyl chloride, under conditions of a head scanning speed of 200 mm / second, an ink droplet volume of 42 pl, and a recording density of 360 × 360 dpi. A 100 mm image was recorded in one scan. Note that the recording medium was heated with a heater from the back side as in the case of Decap.

  Overlay the plain paper (full color PPC paper type 6000 made by Ricoh Co., Ltd.) on each image surface with heater heating time of 1 minute, 3 minutes, 10 minutes, rub with your finger with a load of about 3N, and evaluate the image drying property according to the following criteria did.

○: No color transfer to plain paper when heater heating time is 3 minutes △: No color transfer to plain paper when heater heating time is 10 minutes ×: Color transfer to plain paper is recognized even when heater heating time is 10 minutes In this case, Δ to ○ are practically preferable ranges.

(Evaluation of abrasion resistance)
Each recorded image prepared in the evaluation of image drying property was allowed to stand at 23 ° C. and 55% relative humidity for 12 hours, and then the image was rubbed with dry cotton (Kanakin No. 3), and the abrasion resistance was evaluated according to the following criteria.

○: Image is hardly changed even after rubbing 50 times or more. Δ: Image density is lowered while rubbing 20 to 50 times. ×: Image density is lowered while rubbing less than 20 times. Is a practically preferable range.

(Evaluation of plaque resistance)
About each recorded image created in evaluation of image drying property, the occurrence state of the spot in a formed image was visually evaluated, and the spot tolerance was evaluated according to the following criteria.

○: No occurrence of spots at all and good quality. △: Spots are partially seen, but in a practical range. ×: Spots are generated on the entire surface, and the quality is outside the acceptable range for practical use. In the evaluation rank, Δ to ○ are practically preferable ranges.

(Evaluation of ink storage stability)
Each ink prepared was stored in a glass bottle in a sealed state at 70 ° C. for 2 weeks, and then the strobe light emission type ink flight observation device described in FIG. 2 of JP-A-2002-363469 was used to determine the discharge cycle. The ink storage stability was evaluated according to the following criteria by monitoring the flying state of each ink from the inkjet printer using a CCD camera with the light emission period synchronized.

○: No abnormality in emission for all nozzles in ink stored for 2 weeks. Δ: Nozzle where bending in the flight direction is observed in ink stored for 2 weeks, but within a practically acceptable range. In such ink, clogging occurs at one or more nozzles, which is outside the allowable range for practical use.

  Table 2 shows the results obtained as described above.

  As is clear from the results shown in Table 2, the ink satisfying the requirements of the present invention is effective in suppressing the Decap and improving the drying speed, and also shows good results in other evaluation items. On the other hand, the ink of the comparative example that does not satisfy the requirements of the present invention has a practically unacceptable result in any evaluation item.

Claims (4)

An aqueous inkjet ink that is used to print to a non-water absorbing recording medium heated to 35 to 60 ° C.,
The water-based inkjet ink has a weight average molecular weight of 7000 to 20000 neutralized with at least a pigment , a polymer dispersant, and an amine having a boiling point of less than 200 ° C., and 3 based on the total mass of the water-based inkjet ink. % mass or more, organic and water-soluble acrylic resin contained in the following 6 mass%, and that at least one water-soluble organic solvent glycol ethers or carbon atoms are selected from 1,2-alkanediols with 4 or more The ink viscosity at 25 ° C. is 15 to 20 mPa · s, and the viscosity increases after printing on the recording medium.
The polymer dispersant has a weight average molecular weight of 5000 or more and 200000 or less ,
The water-soluble acrylic resin, wherein the water-soluble acrylic resin has (meth) acrylic acid and (meth) acrylic acid ester as copolymerization components, and has an acid value of 60 mgKOH / g or more and less than 80 mgKOH / g ink.   At least one water-soluble organic solvent selected from the glycol ethers or 1,2-alkanediols having 4 or more carbon atoms is propylene glycol monoalkyl ether, dipropylene glycol monoalkyl ether, tripropylene glycol monoalkyl. The aqueous inkjet ink according to claim 1, wherein the aqueous inkjet ink is at least one selected from ether and 1,2-hexanediol.   At least one of the pigments is C.I. I. The water-based inkjet ink according to claim 1, which is CI Pigment Yellow 155. The water-based inkjet ink according to any one of claims 1 to 3, wherein the recording medium is a vinyl chloride sheet .