JP2010221670A - Printing method and printer of inkjet recording system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing method of an inkjet recording system, capable of executing high-speed printing on ink nonabsorptive recording media or others, superior in abrasion resistance, and hardly causing clogging in an inkjet head. <P>SOLUTION: The printing method for forming images by an inkjet recording system on the ink nonabsorptive recording media or others using an aqueous ink set is characterized in that (1) the aqueous ink set contains color inks including coloring agents and resin inks not containing coloring agents, (2) the color inks include the water insoluble coloring agents and resin components, (3) the resin inks includes a water soluble resin solvent, resin particles which is insoluble in water, but has compatibleness to the water soluble resin solvent, and has a specific particle size and a glass transition temperature, and a wax of a specific melting temperature, (4) the surface tension of the resin inks is higher than that of the color inks, (5) the method includes a step for recording by the resin inks after a step for recording by the color inks, (6) the method further includes a drying step. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink jet recording method and a recorded matter thereof. More specifically, the present invention relates to a printing method for forming an image on an ink-absorbing and water-absorbing recording medium by an ink jet recording method.

  The ink jet recording method is a recording method in which recording is performed by ejecting (discharging) ink droplets and attaching them to a recording medium such as paper. Due to recent advances in ink jet recording technology, ink jet recording methods have come to be used in the field of high-definition image recording (printing) that has so far been used for silver salt photography and offset printing. In addition, as a characteristic required for the ink used in the ink jet recording method, the ink jet head is capable of ejecting ink droplets stably for a long period of time without being clogged by drying. For images, quick drying and high durability are mentioned.

  As an overcoat composition for imparting high resistance to an image after printing, JP-A-2000-44858 (Patent Document 1) applies an overcoat composition obtained by removing a colorant from an ink composition. JP-A-2004-195451 (Patent Document 2) discloses a composition comprising an aqueous carrier, a humectant, a surfactant, and an addition polymer having an acid value exceeding 110. Things have been proposed.

However, when printing on an ink jet recording medium having high ink absorbability, there is a problem that the ink after drying is easily peeled off due to abrasion because the ink is not absorbed or is hardly absorbed.
In order to increase the abrasion resistance of the ink after drying, the amount of the colorant or resin component in the ink may be increased. However, in this case, the ink viscosity becomes high, and the ejection stability in high-speed printing is improved. It becomes difficult to secure. Also, the inkjet head is likely to be clogged. For this reason, in consideration of high-speed printing and prevention of clogging of the inkjet head, there is a limit to the amount of the colorant and resin component added to the ink.

JP 2000-44858 A JP 2004-195451 A

  Therefore, the present invention provides a printing method of an ink jet recording method that is capable of high-speed printing on an ink non-absorbing and low-absorbing recording medium, has excellent abrasion resistance, and is less likely to cause clogging of the ink jet head. The purpose is to provide.

  The present invention can be realized as the following application examples or forms so as to solve at least one of the above problems.

  Application Example 1 The printing method of the ink jet recording method described in this application example is a printing method in which an image is formed on a non-ink-absorbing and low-absorbing recording medium by an ink jet recording method using a water-based ink set. (1) The water-based ink set includes a color ink containing a colorant and a resin ink not containing a colorant, and (2) the color ink comprises the water-insoluble colorant, a resin component, (3) The resin ink includes a water-soluble resin solvent and a resin component, and the resin component is insoluble in water but is not dissolved in the water-soluble resin solvent. Includes thermoplastic resin particles having a particle diameter of 30 nm to 100 nm and a glass transition temperature of 40 ° C. or higher, and wax having a melting point of 100 ° C. or higher. (4) Surface tension of the resin ink But the color (5) The printing step includes a step of recording with the color ink, and a step of recording with the resin ink after at least the step of recording with the color ink ( 6) A drying process is included during and / or after printing.

  Application Example 2 The color ink includes thermoplastic resin particles and wax that are the same as the thermoplastic resin particles and wax contained in the resin ink as a resin component.

  Application Example 3 The color ink further includes a special color in addition to the process color, and the special color includes orange and green.

  Application Example 4 The printing apparatus described in this application example includes the above-described printing method.

  [Application Example 5] According to the printing method of the ink jet recording method described in this application example, high-speed printing is possible with respect to a non-ink-absorbing and low-absorbing recording medium, and the rubbing resistance is excellent. It is possible to provide an ink jet recording printing method that hardly causes clogging of an ink jet head.

  An inkjet recording printing method according to an embodiment of the present invention is a printing method for forming an image on an ink non-absorbing and low-absorbing recording medium by an inkjet recording method using a water-based ink set. ) The water-based ink set includes a color ink containing a colorant and a resin ink not containing a colorant. (2) The color ink includes the water-insoluble colorant, a resin component, and a water-soluble solvent. (3) The resin ink includes a water-soluble resin solvent and a resin component, and the resin component is insoluble in water but compatible with the water-soluble resin solvent. A thermoplastic resin particle having a particle diameter of 30 nm to 100 nm and a glass transition temperature of 40 ° C. or higher, and a wax having a melting point of 100 ° C. or higher. (4) The surface tension of the resin ink is the color ink (5) The printing step includes a step of recording with the color ink, and a step of recording with the resin ink after at least the step of recording with the color ink (6 ) Including a drying step during and / or after printing.

[recoding media]
In the present embodiment, the recording medium to be printed is a non-ink-absorbing and low-absorbing recording medium. A non-ink-absorbing and low-absorbing recording medium is a recording medium that does not have an ink absorbing layer or has a poor ink absorbing layer. More quantitatively, a non-ink-absorbing and low-absorbing recording medium has a water absorption of 10 mL / m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method. A recording medium is shown. This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPAN TAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method". As a non-ink-absorbing recording medium, for example, a plastic film coated on a substrate such as a plastic film or paper that has not been surface-treated for inkjet printing (that is, an ink-absorbing layer is not formed). And those having a plastic film adhered thereto. Examples of the plastic here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene. Examples of the recording medium with low ink absorption include printing paper such as art paper, coated paper, and matte paper.

[Water-based ink set]
The aqueous ink set used in the printing method according to the present embodiment includes a color ink containing a colorant and a resin ink not containing the colorant. Color ink is ink for forming color and monochrome images on a recording medium. Furthermore, the resin ink is used mainly for the purpose of imparting abrasion resistance to the printed matter by printing before, during, or after printing the above-described color ink. Hereinafter, each ink will be described.

[Color ink]
As described above, the color ink contains at least a water-insoluble colorant, a water-soluble and / or water-insoluble resin component, a water-soluble solvent, and a surfactant. Next, each component constituting the color ink will be described.

(Coloring agent)
Examples of the water-insoluble colorant include water-insoluble dyes or pigments, and a pigment is preferable. This is because a printed matter printed with an ink using a pigment is excellent in storage stability such as water resistance, gas resistance and light resistance. As the pigment, any of known inorganic pigments, organic pigments, and carbon black can be used. Among these, carbon black and organic pigments are preferred from the viewpoints of good color development and low sedimentation, which makes it difficult to settle during dispersion.
Specific examples of carbon black include furnace black, lamp black, acetylene black, channel black and the like (CI Pigment Black 7). 2300, 900, MCF88, no. 20B, no. 33, no. 40, no. 45, no. 52, MA7, MA8, MA77, MA100, No2200B, etc. (all trade names, manufactured by Mitsubishi Chemical Corporation), color black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Pretex 35, U, V 140U, Special Black 6, 5, 4A, 4, 250, etc. (all trade names, manufactured by Degussa), Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, 700, etc. (all trade names) Colombian Carbon), Regar 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400, Elftex 12, etc. (all trade names, manufactured by Cabot) It is done. In addition, these are description of an example of the carbon black suitable for this invention, and this invention is not limited by these. These carbon blacks may be used alone or as a mixture of two or more.

These pigments are added in an amount of 0.5 to 12% by mass, preferably 2 to 8% by mass, based on the total amount of the black ink.
Organic pigments include quinacridone pigments, quinacridone quinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, ansanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolo Examples include pyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments, and azo pigments.
Specific examples of the organic pigment include the following.
Examples of pigments used for cyan ink include C.I. I. Pigment blue 1, 2, 3, 15: 3, 15: 4, 16, 22, 60, etc .; I. Bat blue 4, 60 and the like, preferably C.I. I. Pigment Blue 15: 3, 15: 4, and 60 selected from the group consisting of 60 or more.
Examples of pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, C.I. I. Pigment violet 19 and the like, preferably C.I. I. Pigment red 122, 202, and 209, C.I. I. These are single or a mixture of two or more selected from the group consisting of CI Pigment Violet 19.
Examples of pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14C, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 119, 110, 114, 128, 129, 138, 150, 151, 154, 155, 180, 185, etc., preferably C.I. I. These are single or a mixture of two or more selected from the group consisting of CI Pigment Yellow 74, 109, 110, 128, 138, and 180.

The color ink preferably includes a special color in addition to the process colors of yellow, magenta, cyan, and black, and more preferably the special color is composed of orange and green. A non-ink-absorbing and low-absorbing recording medium does not have or lacks an ink absorbing layer / color-developing layer, and therefore has a lower color development than when printing on an ink-jet recording medium having high absorbency. For this reason, by adding a special color in addition to the process color, it is possible to obtain a high color even if the absorbency is low. Special colors include red, green, blue, orange, violet, and the like, with orange and green being particularly preferred.
Examples of pigments used in such orange ink include C.I. I. Pigment Orange 36 or 43, or a mixture thereof.
Examples of pigments used in green ink include C.I. I. Pigment Green 7 or 36 or a mixture thereof.

These pigments may be used by dispersing the resin using a dispersing resin, or may be used as a self-dispersing pigment by oxidizing or sulfonating the pigment surface with ozone, hypochlorous acid, fuming sulfuric acid or the like.
These pigments are contained in an amount of about 0.5% to 15% by mass, preferably about 2% to 10% by mass, based on the total amount of ink of each color.

(Resin component)
As the resin component, it is preferable to include a dispersant for dispersing the above-described pigment in an aqueous medium. Further, as a preferable dispersant, a dispersant commonly used for preparing a pigment dispersion, for example, a polymer dispersant can be used.

[Dispersant]
Preferred examples of the dispersant include polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, and styrene-acrylic acid copolymer. Polymer, styrene-methacrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer, Styrene-α-methylstyrene-acrylic acid-alkyl acrylate ester copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer Polymer, vinyl acetate-maleic acid ester Polymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers can be mentioned, and preferred dispersants are those that are not easily dissolved in a solvent or the like added to the ink. Esterification is preferable to those having a hydrophilic group terminal at the end of acrylic acid.
These copolymers preferably have a weight average molecular weight of about 3,000 to 50,000, more preferably about 5,000 to 30,000.
The addition amount of the dispersant may be appropriately added as long as the pigment is stably dispersed and the other effects of the present invention are not lost.

Furthermore, it is preferable that the resin component contains thermoplastic resin particles that are unnecessary for water but compatible with the water-soluble resin solvent, and wax. By including the thermoplastic resin particles, it is possible to improve the abrasion resistance of the color ink after drying. Further, the inclusion of the wax can improve the sliding property of the color ink after drying, and as a result, the rub resistance can be improved. Specific examples of the thermoplastic resin particles and wax will be described in the section of resin ink.
In addition, when the color ink includes thermoplastic resin particles and wax as the resin component, it is preferable that the same color includes the same thermoplastic resin particles and wax as those included in the resin ink. In this way, by including the same thermoplastic resin particles and wax as those contained in the resin ink, the compatibility of the resin components is improved, so that peeling at the interface between the color ink and the resin ink is prevented. it can.

(Water-soluble solvent)
The water-soluble solvent has a function of increasing the wettability of the color ink to the recording medium and wetting it uniformly in synergy with the surfactant described later. For this reason, it is preferable to add a water-soluble solvent to the color ink because printing unevenness and bleeding of the ink can be reduced. Examples of such water-soluble solvents include monohydric alcohols or polyhydric alcohols and derivatives thereof.
As the monohydric alcohol, a monohydric alcohol having 1 to 4 carbon atoms such as methanol, ethanol, n-propanol, i-propanol, or n-butanol can be used.
As polyhydric alcohols and derivatives thereof, divalent to pentavalent alcohols having 2 to 6 carbon atoms and complete or partial ethers of them with lower alcohols having 1 to 4 carbon atoms can be used. Here, the polyhydric alcohol derivative is an alcohol derivative in which at least one hydroxyl group is etherified, and does not mean a polyhydric alcohol itself that does not contain an etherified hydroxyl group.
Specific examples of these polyhydric alcohols and their lower alkyl ethers include 1,2-hexanediol, 1,3-hexanediol, 1,2-heptanediol, 1,3-heptanediol, 1,2-octane. Diols, diols such as 1,3-octanediol, 1,2-pentanediol, mono-, di- or triethylene glycol-mono or di-alkyl ether, mono-, di- or tripropylene glycol-mono or di-alkyl ether Preferably, 1,2-hexanediol, triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monopropyl ether, diethylene glycol monopentyl ether, or propylene glycol monobutyl , And the like ether.
The content of the water-soluble solvent is, for example, 0.5% by mass to 15.0% by mass, and preferably 1.0% by mass to 8.0% by mass with respect to the total amount of ink of each color.

(Surfactant)
The surfactant has a function of increasing the wettability of the color ink to the recording medium and wetting it uniformly in synergy with the water-soluble solvent described above. As the surfactant, a silicon-based surfactant and an acetylene glycol-based surfactant are preferable.
The silicon-based surfactant has an action of spreading uniformly so as not to cause ink printing unevenness and bleeding on the recording medium.
As the silicon-based surfactant, a polysiloxane compound or the like is preferably used, and examples thereof include polyether-modified organosiloxane. For example, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348 (above trade name, manufactured by Big Chemie Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (above trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) and the like can be mentioned, and BYK-348 is preferable.

  The content of the silicon surfactant is preferably 0.1% by mass to 1.5% by mass with respect to the total amount of ink of each color. When the content of the silicon-based surfactant is less than 0.1% by mass, the ink is difficult to uniformly spread on the recording medium, so that ink printing unevenness and bleeding are likely to occur. On the other hand, when the content of the silicon surfactant exceeds 1.5% by mass, the storage stability and ejection stability of the water-based ink composition may not be ensured.

The acetylene glycol-based surfactant is superior to other surfactants in that it has an excellent ability to maintain surface tension and interfacial tension, and has almost no foaming property. As a result, the color ink containing the acetylene glycol surfactant can appropriately maintain the surface tension and the interface tension with the printer member in contact with the ink such as the head nozzle surface, and this is applied to the ink jet recording method. In this case, the discharge stability can be improved. In addition, since the color ink containing an acetylene glycol surfactant exhibits good wettability and penetrability with respect to the recording medium, it is possible to obtain a high-definition image with less ink printing unevenness and bleeding.
Examples of acetylene glycol surfactants include Surfynol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61. , 82, DF37, DF110D, CT111, CT121, CT131, CT136, TG, GA (all trade names, manufactured by Air Products and Chemicals Inc.), Olphin B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP. 4001, EXP. 4036, EXP. 4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.), acetylenol E00, E00P, E40, E100 (all trade names, Kawaken Fine Chemical Co., Ltd.) and the like, and Surfynol 104PG-50 and DF110D are preferable.

The content of the acetylene glycol surfactant is preferably 0.05% by mass to 1.0% by mass with respect to the total amount of each color ink. When the content of the acetylene glycol-based surfactant is less than 0.05% by mass, the ink is difficult to uniformly spread on the recording medium, so that ink printing unevenness and bleeding are likely to occur. On the other hand, when the content of the acetylene glycol surfactant exceeds 1.0% by mass, the storage stability and ejection stability of the color ink may not be ensured.
Particularly preferred is a combination comprising a silicon surfactant and an acetylene glycol surfactant having an HLB value of 6 or less at the same time.
The surface tension of the color ink is preferably used in the range of 20.0 mN / m to 35.0 mN / m, more preferably 25.0 mN / m to 30.0 mN, in combination with the above water-soluble solvent and surfactant. / M range. The surface tension can be measured using, for example, a CBVP-Z type (manufactured by Kyowa Interface Science Co., Ltd.).

(water)
Water is the main medium of water-based ink, and preferable water is pure water such as ion exchange water, ultrafiltered water, reverse osmosis water, distilled water, or the like for the purpose of reducing ionic impurities as much as possible. Ultrapure water can be used. In addition, when water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is used, it is preferable because generation of mold and bacteria can be prevented when the pigment dispersion and aqueous ink using the pigment dispersion are stored for a long period of time. .

(Other components of color ink)
Further, water-soluble resin solvents, humectants, preservatives / fungicides, pH adjusters, dissolution aids, antioxidants, metal trapping agents, and the like are added as necessary. The water-soluble resin solvent will be described in the section of resin ink.
As the humectant, those which do not remain in the coating film upon drying are preferable. Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, hexylene glycol, 2,3 -Butanediol etc. are mentioned.
Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazoline-3-one (Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN from ICI) and the like.
Examples of the pH adjuster include inorganic alkalis such as sodium hydroxide and potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, morpholine, potassium dihydrogen phosphate or disodium hydrogen phosphate.
Examples of the solubilizer include allohanates such as urea, thiourea, dimethylurea, tetraethylurea, allophanate, and methyl allophanate, and biurets such as biuret, dimethylbiuret, and tetramethylbiuret.
Examples of the metal trapping agent include ethylenediaminetetraacetic acid disodium.

[Resin ink]
The resin ink contains a water-soluble resin solvent and thermoplastic resin particles and wax that are insoluble in water but compatible with the water-soluble resin solvent as a resin component. The term “compatible” refers to a combination that dissolves or swells when resin particles are mixed in a resin solvent. Hereinafter, each component will be described.

(Water-soluble resin solvent)
The water-soluble resin solvent is selected from water-soluble solvents that are compatible with the resin particles added simultaneously to the resin ink. Although there are optimum combinations depending on the resins used, for example, water-soluble heterocyclic compounds, water-soluble alkylene glycol alkyl ethers and the like are preferable. Specific examples include N-methyl-2-pyrrolidone, N-ethyl-2- Pyrrolidones such as pyrrolidone, N-vinyl-2-pyrrolidone, 2-pyrrolidone, dimethyl sulfoxide, ε-caprolactam, methyl lactate, ethyl lactate, isopropyl lactate, butyl lactate, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monomethyl ether Acetate, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol isopropyl Ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monopropyl ether, 1,4-dioxane and the like are preferable. In particular, in terms of the storage stability of resin ink, sufficient drying speed, and promotion of film formation of resin particles, alkylene glycol monoesters such as pyrrolidones, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, etc. Alkyl ethers are particularly preferred.

Although the water-soluble resin solvent is added to the resin ink, there is no problem even if it is added to the color ink, and it is effective for further strengthening the film formed by the resin particles.
The addition amount of the water-soluble resin solvent is preferably 1.0% by mass to 20.0% by mass, and more preferably 2.0% by mass to 15.0% by mass with respect to the total amount of the resin ink. When the addition amount of the water-soluble resin solvent is less than 1% by mass, the formation of a film of resin particles in the resin ink may be hindered, resulting in insufficient solidification and fixing of the resin ink. On the other hand, when the addition amount of the water-soluble resin solvent exceeds 20% by mass, the storage stability of the resin ink may be deteriorated.

(Thermoplastic resin particles)
The thermoplastic resin particles are compatible with the water-soluble resin solvent, so that a strong resin film can be formed after drying the resin ink, and the thermoplastic resin particles are formed at a temperature lower than the original glass transition temperature of the resin particles. Can do. By using unnecessary resin particles in water, it is possible to keep the viscosity of each ink low while adding a sufficient amount of resin components in the resin ink, and to ensure ejection stability in high-speed printing. preferable.
It is considered that the thermoplastic resin particles are present in the ink without being dissolved in the water-soluble resin solvent in a normal storage state (room temperature). That is, more than half of the main component in the ink is water, and the addition amount of the water-soluble resin solvent is as thin as 20% by mass or less, so even if the thermoplastic resin particles and the water-soluble resin solvent coexist in the ink, The plastic resin particles are not immediately dissolved. However, when the ink is ejected from the inkjet head onto the recording medium and dried, the water that is the main component in the ink begins to evaporate, and as a result, the water-soluble resin solvent in the ink is concentrated. The thermoplastic resin particles are in a dissolved state. Next, when all the water is evaporated, the solvent component starts to evaporate next, and the thermoplastic resin particles that have been dissolved (they are no longer particles because they are dissolved), but the water-soluble resin solvent evaporates. At the same time, a solid film is formed and solidified. Finally, only a solid component such as a colored component which is a solid component and a thermoplastic resin particle formed into a film so as to cover the color component is present on the recording medium.

  Specific examples of such water-insoluble thermoplastic resins include polyacrylic acid, polymethacrylic acid, polymethacrylic acid ester, polyethylacrylic acid, styrene-butadiene copolymer, polybutadiene, and acrylonitrile-butadiene copolymer. , Chloroprene copolymer, fluororesin, vinylidene fluoride, polyolefin resin, cellulose, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, polystyrene, styrene-acrylamide copolymer, polyisobutyl acrylate, polyacrylonitrile , Polyvinyl acetate, polyvinyl acetal, polyamide, rosin resin, polyethylene, polycarbonate, vinylidene chloride resin, cellulose resin, vinyl acetate resin, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic Polymers, vinyl chloride resin, polyurethane, and rosin esters, and the like is not limited thereto.

  The thermoplastic resin particles may be mixed with other components in the aqueous ink as a fine particle powder, but are preferably contained in the ink in the form of a resin emulsion. The reason is that the resin particles may be insufficiently dispersed even if they are added to the ink as they are, so that the emulsion form is preferable from the viewpoint of dispersibility. The emulsion is preferably an acrylic emulsion and more preferably a styrene-acrylic acid copolymer emulsion from the viewpoint of the storage stability of the resin ink.

In the present specification, “resin particles” are those in which a resin insoluble in water is dispersed in a particle form in a dispersion medium mainly composed of water, or a resin insoluble in water is mainly dispersed in a dispersion medium mainly composed of water. It means what is dispersed in the form of particles, and further includes the dried product. In addition, the term “emulsion” is intended to include a solid / liquid dispersion called dispersion, latex, or suspension.
If the resin is obtained in the form of an emulsion, it can be prepared by mixing the resin particles in water, optionally with a surfactant. For example, an emulsion of an acrylic resin or a styrene-acrylic acid copolymer resin is composed of a (meth) acrylic ester resin or a styrene- (meth) acrylic ester resin, and optionally a (meth) acrylic resin, It can be obtained by mixing the active agent with water. The mixing ratio of the resin component and the surfactant is usually preferably about 50: 1 to 5: 1. When the amount of the surfactant used is less than the above range, it is difficult to form an emulsion, and when the amount exceeds the above range, the water resistance of the ink tends to decrease or the adhesion tends to deteriorate. Absent.

  Commercially available resin emulsions can also be used as the resin emulsion. For example, Microgel E-1002, E-5002 (styrene-acrylic resin emulsion; manufactured by Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic resin emulsion; Dai Nippon Ink Chemical Co., Ltd.), Boncoat 5454 (styrene-acrylic resin emulsion; Dainippon Ink and Chemicals Co., Ltd.), SAE1014 (styrene-acrylic resin emulsion; manufactured by Nippon Zeon Co., Ltd.), or Cybinol SK- 200 (acrylic resin emulsion; manufactured by Seiden Chemical Co., Ltd.).

The thermoplastic resin particles are preferably included in a range of 5% by mass to 12% by mass in terms of solid content, and more preferably in a range of 6% by mass to 10% by mass with respect to the total amount of the resin ink. The preferred range of the content of these thermoplastic resin particles defines the upper limit value from the viewpoint of the appropriate ink jet physical properties and reliability (clogging, ejection stability, etc.) of the resin ink, and the effects of the present invention (such as abrasion resistance) ) From the viewpoint of more effectively obtaining a lower limit value.
Moreover, it is preferable that the glass transition temperature of a thermoplastic resin particle is 40 degreeC or more, More preferably, it is 60 degreeC or more, More preferably, it is 80 degreeC or more. With such thermoplastic resin particles, the dried ink can maintain a strong film in the normal use range, and can improve the abrasion resistance of the ink film. On the other hand, when the transition temperature is room temperature or lower, the printed image after drying has insufficient abrasion resistance, and nozzle clogging of the inkjet head tends to occur. In particular, in the printing method of the present invention, since ink is printed on a non-absorptive recording medium, the quick drying property of the ink is improved, and in the case of a resin having a glass transition temperature of room temperature or less, clogging in actual use is a problem. It becomes.

  In the present invention, the glass transition point (Tg) can be measured using a usual method, for example, a thermal analyzer such as a differential scanning calorimeter (DSC). An example of the thermal analyzer is SSC5000 manufactured by Seiko Denshi. The glass transition point (Tg) can be evaluated as a calculated value of the glass transition point when the resin is a copolymer. The glass transition point (Tg) of the copolymer and the methodology for its evaluation are as follows. The glass transition point (Tg) of a copolymer having a specific monomer composition can be determined by calculation using the Fox equation. Here, the Fox formula is for calculating the Tg of the copolymer based on the Tg of the homopolymer of the monomer for each monomer forming the copolymer, The details thereof are described in Bulletin of the American Physical Society, Series 2 (Volume of the American Physical Society, Series 2) Vol. 1, No. 3, p. 123 (1956). The concept of the term “calculated glass transition point” used in the specification of the present invention includes a glass transition point calculated by the Fox formula. The Tg of the homopolymer for various monomers that are the basis for calculating the Tg of the copolymer according to the Fox formula is, for example, Polymer Data Handbook Basics (Polymer Society), pages 525-546. Or actual values measured by a normal method can be employed.

  On the other hand, the average particle diameter of the thermoplastic resin particles contained in the resin ink is preferably 30 nm to 100 nm from the viewpoints of wear resistance of the printed image, clogging characteristics of the resin ink, and ejection stability. That is, when the particle diameter is smaller than 30 nm, the effect as an overcoat layer particularly in a paper-based medium is reduced. This is presumed to be due to the insufficient thickness of the coat layer with respect to the unevenness of the media surface. On the other hand, when the particle diameter is larger than 100 nm, it becomes difficult to obtain the abrasion resistance of the film-based media, and the clogging property of the resin ink is further deteriorated. The average particle diameter can be measured using, for example, MicrotracUPA150 (manufactured by Microtrac).

(wax)
Wax has the property of reducing the frictional resistance of the ink film surface after drying. Examples of components constituting such a wax include plant and animal waxes such as carnauba wax, candeli wax, beeswax, rice wax, and lanolin; paraffin wax, microcrystalline wax, polyethylene wax, oxidized polyethylene wax, petrolatum, and the like. Petroleum waxes; mineral waxes such as montan wax and ozokerite; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, stearamide, and natural and synthetic wax emulsions such as α-olefin / maleic anhydride copolymer The compounding wax or the like can be used singly or as a mixture of plural kinds. Among these, preferred types of wax are polyolefin wax, particularly polyethylene wax and polypropylene wax, and polyethylene wax is more preferable from the viewpoint of abrasion resistance against a non-ink-absorbing or low-absorbing recording medium. As the wax, commercially available products can be used as they are. For example, Nopcoat PEM17 (trade name, manufactured by San Nopco), Chemipearl W4005 (trade name, manufactured by Mitsui Chemicals), AQUACER 515 (trade name, Big Chemie Japan Co., Ltd.) Manufactured) and the like.

The wax content in the resin ink is preferably 0.5% by mass to 6% by mass, more preferably 1% by mass to 3% by mass in terms of solid content. The preferred range of the content of these waxes defines the upper limit value from the viewpoint of the appropriate ink jet physical properties and reliability (clogging, ejection stability, etc.) of the resin ink, and the effects of the present invention (rubbing resistance, etc.) are more enhanced. The lower limit is defined from the viewpoint of obtaining effectively.
Further, the melting point temperature of the wax is preferably higher than 90 ° C, more preferably 100 ° C or higher, and further preferably 130 ° C or higher. When the melting point of the wax is 90 ° C. or lower, the effect of improving the abrasion resistance of the printed matter is lowered. The reason is not clear, but it is considered that when the melting point is low, the wax dissolves due to heat generated by rubbing or contact, and the effect as an overcoat layer is reduced.

  The reason why the printed material has good abrasion resistance when the above-described thermoplastic resin particles and wax are used in combination is not clear yet, but is presumed as follows. The thermoplastic resin particles have a property of firmly fixing the color ink on the recording medium and making the resin film after drying firm. On the other hand, the wax has a characteristic of reducing the frictional resistance on the surface of the resin film. Thereby, it is presumed that the abrasion resistance of the printed matter is improved because it is possible to form a resin film that is hard to be scraped off from the outside and hardly peeled off from the recording medium.

(Other components of resin ink)
As other components, the resin ink contains a water-soluble solvent and a surfactant as necessary. About the kind of water-soluble solvent and surfactant, the thing similar to what is used with a color ink can be used. Here, the resin ink also preferably includes a silicon-based surfactant and an acetylene glycol-based surfactant having an HLB value of 6 or less as the surfactant. By using a combination of a silicon surfactant and an acetylene glycol surfactant, the ink can be similarly wetted to a wide range of recording media from non-absorbing to low-absorbing, and a printed matter with less printing unevenness can be obtained. Can do. For these components, the same materials as those described for the color ink are employed. These addition amounts can be appropriately adjusted according to the type of recording medium and ink.
The resin ink contains water as a main medium, similarly to the color ink. Further, as necessary, moisturizers, preservatives and fungicides, pH adjusters, dissolution aids, antioxidants, metal trapping agents and the like can be mentioned. For these materials, the same materials as those described for the color ink can be applied.
The surface tension of the resin ink is higher than that of the color ink and is preferably used in the range of 20.0 mN / m to 35.0 mN / m, more preferably in the range of 25.0 mN / m to 30.0 mN / m. .

[Printing method]
The printing method according to the present embodiment includes a step of printing color ink and resin ink on a recording medium using an ink jet recording method.
In the printing step, after the color ink is printed on the recording medium, the resin ink is printed on the color ink. After the color ink is printed, the resin ink is printed on the color ink, so that a large amount of the resin ink component is contained on the surface side of the print surface, and the abrasion resistance of the print surface can be improved.
By using the ink jet recording method, the resin ink can be selectively attached only to the place where the color ink is attached, and the consumption amount of the resin ink can be minimized. In addition, when a large amount of resin ink adheres to the entire paper surface, curling observed after drying can be suppressed.

Further, the method of recording the color ink and the resin ink on the recording medium may be multipass or single pass, but it is preferable to record in one pass or two passes from the viewpoint of high-speed printing. Here, one pass is a recording method in which all dots to be formed in the scanning area are recorded by one scanning of the recording head. That is, the color ink and the resin ink are printed in one pass means that the color ink and the resin ink dots to be recorded in the recording head scanning area complete the recording by one recording head scanning. It is. The two-pass is a method of recording dots to be recorded in the recording head scanning area by two recording head scans. Further, in the one-pass recording method, after the recording head is scanned once in the main scanning direction to record dots, the entire image is formed by repeatedly moving the recording medium by the recording area in the sub-scanning direction. And a method of forming an image by fixing the recording head and scanning the recording medium, and any of them can be suitably used. High-speed printing is possible by recording in one pass or two passes, and the productivity of recorded matter is increased.
For example, the print resolution for each color is 360 dpi (dot per inch) or more, the resolution ratio of the inkjet nozzle to the print resolution is in the range of 1 to 2 times, and the ink viscosity is 1.5 mPa · s to 15 mPa · s (20 ° C). In order to obtain high image quality, a high print resolution of 360 dpi or higher is desirable, and if the resolution ratio of the inkjet nozzle to the print resolution is in the range of 1 to 2 times, printing can be performed at high speed, and from the ink tank to the head. In order to supply ink stably, the ink viscosity is preferably 1.5 mPa · s to 15 mPa · s (20 ° C.). For example, in the case of a nozzle resolution of 360 dpi, the above-described requirements are preferable when printing at 360 dpi to 720 dpi.

In the high-speed printing as described above, the ink viscosity is preferably low. In the present embodiment, by separating the color ink and the resin ink, the viscosity of each ink is kept low while adding a sufficient amount of colorant in the color ink and a sufficient amount of resin component in the resin ink. And discharge stability can be ensured in high-speed printing.
For example, the viscosity of the resin ink and ink composition at 20 ° C. is preferably in the range of 1.5 mPa · s to 15 mPa · s, and more preferably in the range of 1.5 mPa · s to 10 mPa · s. Preferably, the resin ink and the ink composition have substantially the same viscosity. For example, one viscosity is set to 50% to 200% of the other viscosity. Accordingly, when both the resin ink and the ink composition are ejected from the ink jet recording head, it is advantageous in that the recording head, the flow path structure, and the drive circuit can be made the same.

The printing method according to the present embodiment preferably includes a drying step during printing and / or after printing. By adding a drying process, evaporation of liquid media (specifically, water and water-soluble solvents) in color inks and resin inks is promoted, resulting in high-quality images with little printing unevenness and bleeding and abrasion resistance. A recorded matter can be obtained in a short time, wrinkling of the recording medium can be prevented, and curling of the recording medium can be effectively prevented.
Furthermore, the heating during drying promotes the fusion of the resin particles contained in the color ink and the resin ink, and it is possible to form an excellent film, thereby further improving the abrasion resistance of the recorded matter. The heating temperature is not particularly limited as long as the liquid medium present in the color ink and the resin ink can evaporate and a film of the resin agent can be formed. About 150 degreeC is preferable, More preferably, it is about 40 degreeC-80 degreeC. When the temperature exceeds 100 ° C., the recording medium may be deformed and the like may be transported, and the ink near the nozzles of the inkjet head is affected by heat and the water evaporates. When the water-soluble resin solvent therein is concentrated, the thermoplastic resin particles present in the ink in the vicinity of the nozzles are dissolved and dried and solidified, so that problems such as nozzle clogging of the head frequently occur.
The drying / heating time is not particularly limited as long as the liquid medium present in the color ink and the resin ink evaporates and a film of the resin agent can be formed. The liquid medium type, resin type, and printing speed to be used are not limited. It can be set appropriately taking into account.

  The drying method is not particularly limited as long as it is a method for promoting the volatilization of the liquid medium contained in the color ink and the resin ink. Examples thereof include a method of applying heat to the recording medium before and after printing, a method of blowing air on the recording medium after printing, and a method of combining them. Specific examples include forced air heating, radiation heating, conduction heating, high frequency drying, microwave drying, and dry air blowing.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
(Color ink)
Each constituent component was blended in the blending amount shown in Table 1 (mass% of each component with respect to the total mass of the color ink) to obtain a color ink set A1.

(Resin ink)
Moreover, each component was mix | blended with the compounding quantity shown in Table 2 (mass% of each component with respect to the total mass of the resin ink), and resin ink B1-B14 was obtained.

(Ink set)
Then, an ink set including any one of the color ink set A1 shown in Table 1 and the resin inks B1 to B14 shown in Table 2 is prepared, and the conditions shown in Table 3 (Examples 1 to 8 and Comparative Examples 1 to 1). In Comparative Example 6), printing was performed by an inkjet method. In this example, a film made of polyethylene terephthalate (PET) and a film made of polyvinyl chloride were used as the ink non-absorbing recording medium, and a paper-based recording medium was used as the ink low-absorbing recording medium. For these three types of recording media, an ink jet printer PX-G930 (trade name, manufactured by Seiko Epson Corporation, nozzle resolution 180 dpi), which was adjusted to 40 ° C. by attaching a heater to the paper guide unit, was described in Table 3. Patches and images were printed at a printing resolution of 360 dpi using the ink set. First, print data of only color ink is sent to the printer, patches and images are printed on the recording medium, and then the print data of resin ink is sent to the printer, so that the print area of color ink is printed. The resin ink was solid printed.

The following evaluation was performed about the obtained recorded matter. Table 3 shows the results of the evaluation.
(Abrasion resistance evaluation)
The dried print media is set on a Gakushin type wear fastness tester AB-301 (trade name, manufactured by Tester Sangyo Co., Ltd.), and a friction piece (load; The abrasion resistance was evaluated by rubbing 50 times at 300 g). Evaluation was made according to the following criteria.
A: The image printing medium is free from image disturbance due to friction, and the white cotton cloth is free from dirt transferred from the recorded image.
B: Although image disturbance due to friction cannot be confirmed on the image print medium, the white cotton cloth shows some stains transferred from the recorded image.
C: Some background stains are visually recognized in the non-printed portion of the image print medium, and stains transferred from the recorded image can also be visually recognized on the white cotton cloth.
D: Stain is clearly visible in the non-printed portion of the image print medium, and the white cotton cloth is also soiled by contact with the recorded image.
* When smudged: It occurs when ink is applied to the non-printed part of the paper, and the printed part is rubbed and the surface is scraped and rubbed against the non-printed part according to the friction resistance evaluation.

(Clogging evaluation)
Using an inkjet printer PX-G930 (trade name, manufactured by Seiko Epson Corporation, nozzle resolution 180 dpi), it was confirmed that each ink was filled and ink could be ejected from all nozzles. Next, assuming that the printer has stopped due to a sudden accident such as a power failure, disconnect the power cord while the printer is operating, stop the printer with the inkjet head disconnected from the head cap, and After being left in a% Rh environment for 24 hours, the printer was turned on again to confirm and evaluate the ink discharge status. The evaluation criteria are as follows.
A: After the initial operation when the printer is turned on, ink can be ejected from all nozzles without any problem.
B: There are nozzles that do not discharge immediately after the initial operation when the printer is turned on. Ink can be ejected from all nozzles by several head cleaning operations.
C: There are nozzles that do not discharge immediately after the initial operation when the printer is turned on. Ink can be ejected from all the nozzles by several to ten cleaning operations.
D: There are nozzles that do not discharge immediately after the initial operation when the printer is turned on. Even if the cleaning operation is performed 10 times or more, ink cannot be ejected from all nozzles.

  The present invention has industrial applicability to a printing method for forming an image on a non-ink-absorbing and low-absorbing recording medium by an ink jet recording method.

Claims (4)

A printing method for forming an image on a non-ink-absorbing and / or low-absorbing recording medium by an ink jet recording method using a water-based ink set,
(1) The water-based ink set includes a color ink containing a colorant and a resin ink not containing the colorant.
(2) The color ink includes the water-insoluble colorant, a resin component, a water-soluble solvent, and a surfactant.
(3) The resin ink includes a water-soluble resin solvent and a resin component, and the resin component is insoluble in water but compatible with the water-soluble resin solvent, and has a particle size of 30 nm to 100 nm. And a thermoplastic resin particle having a glass transition temperature of 40 ° C. or higher and a wax having a melting point of 100 ° C. or higher,
(4) The surface tension of the resin ink is higher than that of the color ink and 35 mN / m or less,
(5) The printing step includes a step of recording with the color ink and a step of recording with the resin ink after at least the step of recording with the color ink. (6) A drying step during and / or after printing. An ink jet recording method.   2. The printing method according to claim 1, wherein the color ink includes the same thermoplastic resin particles and wax as the thermoplastic resin particles and wax contained in the resin ink as the resin component.   The printing method according to claim 1, wherein the color ink further includes a special color in addition to the process color, and the special color includes orange and green.   A printing apparatus comprising the printing method according to claim 1.