Ink-jet recording apparatus and ink-jet recording method

Abstract

To provide an inkjet recording apparatus capable of forming an image having high glossiness and high hiding ratio and excellent in adhesion to a substrate.SOLUTION: An inkjet recording apparatus includes a pretreatment head that ejects pretreatment liquid onto a recording medium, and a recording head that ejects ink onto at least a part of a region of the recording medium onto which the pretreatment liquid has been ejected. Surface roughness of the recording medium is 0.30 μm or more and 0.40 μm or less. The pretreatment liquid contains an aqueous medium and resin. Content rate of the resin in the pretreatment liquid is 10 mass% or more and 30 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus and an inkjet recording method. [Background technology]

[0002] There is a demand for technology for printing on non-absorbent recording media such as packaging materials, labels, and films. For example, Patent Document 1 describes a laminate containing a printing layer and a first substrate. The surface of the first substrate is, for example, a surface resin layer. The surface roughness (Ra) of the surface resin layer based on JIS (Japanese Industrial Standards) B-0601 is, for example, 0.5 μm to 2.0 μm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-98284 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the surface resin layer of the laminate described in Patent Document 1 has a rough surface, the glossiness of the printed image tends to be low.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an inkjet recording apparatus and an inkjet recording method that can form an image having high gloss and hiding power and excellent adhesion to a recording medium. [Means for solving the problem]

[0006] The inkjet recording device according to the present invention includes a pretreatment head that ejects a pretreatment liquid onto a recording medium, and a recording head that ejects ink onto at least a portion of the area of ​​the recording medium onto which the pretreatment liquid has been ejected. The surface roughness of the recording medium is 0.30 μm or more and 0.40 μm or less. The pretreatment liquid contains an aqueous medium and a resin. The content of the resin in the pretreatment liquid is 10% by mass or more and 30% by mass or less.

[0007] The inkjet recording method according to the present invention includes a pretreatment step of ejecting a pretreatment liquid onto a recording medium, and an ink ejection step of ejecting ink onto at least a portion of the area of ​​the recording medium onto which the pretreatment liquid has been ejected. The surface roughness of the recording medium is 0.3 μm or more and 0.4 μm or less. The pretreatment liquid contains an aqueous medium and a resin. The content of the resin in the pretreatment liquid is 10% by mass or more and 30% by mass or less. [Effects of the Invention]

[0008] The inkjet recording apparatus and inkjet recording method according to the present invention can form an image with high gloss and hiding power, and also with excellent adhesion to the recording medium. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing an example of a circuit configuration of an inkjet recording apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described. In the following, the volume median diameter (D 50 ) is a value measured using a dynamic light scattering particle size distribution analyzer ("Zetasizer (registered trademark) Nano ZS" manufactured by Spectris Inc.) unless otherwise specified. Each component described in this specification may be used alone or in combination of two or more.

[0011] [First embodiment: inkjet recording apparatus] An inkjet recording apparatus according to a first embodiment of the present invention will be described below. The inkjet recording apparatus of the present invention includes a pretreatment head and a recording head. The pretreatment head ejects a pretreatment liquid onto the recording medium. The recording head ejects ink onto at least a portion of the area of ​​the recording medium onto which the pretreatment liquid has been ejected. The surface roughness of the recording medium is 0.30 μm or more and 0.40 μm or less. The pretreatment liquid contains an aqueous medium and a resin. The resin content in the pretreatment liquid is 10% by mass or more and 30% by mass or less. Hereinafter, the "resin contained in the pretreatment liquid" may be referred to as a "pretreatment resin."

[0012] The inkjet recording apparatus of the present invention, having the above-described configuration, can form an image with high gloss and hiding power and excellent adhesion to the recording medium (adhesion to the substrate). The reason for this is presumed to be as follows.

[0013] The surface roughness of the recording medium used in the inkjet recording device of the present invention is 0.30 μm or more and 0.40 μm or less, and the surface of the recording medium has appropriate irregularities. These irregularities ensure good adhesion between the recording medium and the pretreatment liquid ejected onto the recording medium, improving adhesion to the substrate.

[0014] On the other hand, the greater the unevenness of the surface of the recording medium (the greater the surface roughness), the lower the glossiness of the image formed on the recording medium. Therefore, in the present invention, the content of the pretreatment resin in the pretreatment liquid is set to 10% by mass or more. If the content of the pretreatment resin is 10% by mass or more, an appropriate amount of the pretreatment resin ejected onto the recording medium flows into the recesses on the surface of the recording medium, thereby appropriately reducing the unevenness of the surface of the recording medium. As a result, the glossiness of the image formed on the recording medium is increased.

[0015] On the other hand, the smaller the surface irregularities of the recording medium (the smaller the surface roughness), the lower the concealment rate of the image formed on the recording medium. Therefore, in the present invention, the content of the pretreatment resin in the pretreatment liquid is set to 30% by mass or less. If the content of the pretreatment resin is 30% by mass or less, the pretreatment resin ejected onto the recording medium does not flow excessively into the recesses on the surface of the recording medium, and the concaves and convexes on the surface of the recording medium do not become excessively small. As a result, the concealment rate of the image formed on the recording medium is increased.

[0016] From the above, the ink jet recording apparatus of the present invention can form an image having high gloss and hiding power, and also having excellent adhesion to the substrate.

[0017] <Recording Media> As already mentioned, the surface roughness of the recording medium is 0.30 μm or more and 0.40 μm or less. In order to form an image with excellent adhesion to the substrate, the surface roughness of the recording medium is preferably 0.32 μm or more. In order to form an image with high gloss, the surface roughness of the recording medium is preferably 0.38 μm or less.

[0018] The inkjet recording apparatus of the present invention is suitable for forming an image on a non-absorbent recording medium. The recording medium is preferably a non-absorbent recording medium. Non-absorbent recording media are inferior in ink (particularly aqueous ink) absorption compared to absorbent recording media. In the case of a non-absorbent recording medium, the absorption amount of an aqueous medium is, for example, 1.0 g / m 2 The non-absorbent recording medium includes, for example, a resin recording medium, a metal recording medium, and a glass recording medium.

[0019] The resin contained in the resin recording medium is preferably a thermoplastic resin. Specific examples of the resin include polyethylene terephthalate (PET), polypropylene, polyethylene, and polyvinyl chloride. In order to form an image with excellent adhesion to the substrate, the resin contained in the resin recording medium is preferably PET or polypropylene, and more preferably PET.

[0020] Examples of resin recording media include resin sheets and resin films. Examples of resin sheets include polypropylene sheets and PET sheets, more specifically, biaxially oriented polypropylene (OPP) sheets and biaxially oriented PET sheets. Examples of resin films include polypropylene films and PET films, more specifically, OPP films and biaxially oriented PET films. When an image is formed on a resin recording medium using the inkjet recording apparatus of the present invention, the surface (printing surface) of the recording medium may be subjected to a corona discharge treatment.

[0021] <Pretreatment liquid> By ejecting the pretreatment liquid onto the recording medium, an image with excellent adhesion to the substrate can be formed. The pretreatment liquid ejected from the pretreatment head provided in the inkjet recording apparatus of the present invention contains an aqueous medium and a pretreatment resin. The pretreatment liquid may further contain at least one of a surfactant and other components, as necessary. Note that although the ink described below contains a pigment, the pretreatment liquid does not necessarily contain a pigment.

[0022] As already mentioned, the content of the pretreatment resin in the pretreatment liquid is 10% by mass or more and 30% by mass or less. To form an image with high gloss, the content of the pretreatment resin in the pretreatment liquid is preferably 15% by mass or more, and more preferably 20% by mass or more. To form an image with high hiding power, the content of the pretreatment resin in the pretreatment liquid is preferably 25% by mass or less.

[0023] The pretreatment resin that lands on the recording medium from the pretreatment head forms a pretreatment resin film on the recording medium. The pretreatment resin that lands on the recording medium from the pretreatment head flows down into the recesses of the uneven surface of the recording medium, filling at least a portion of the recesses. Therefore, the thickness of the pretreatment resin film present in the recesses of the uneven surface of the recording medium is thicker than the thickness of the pretreatment resin film present in the protruding portions. By adjusting the amount of pretreatment resin that fills at least a portion of the recesses, the gloss and hiding ratio of the image formed on the recording medium can be adjusted within a desired range.

[0024] The amount of pretreatment liquid ejected from the pretreatment head (ejection amount) is preferably 0.1 pL or more and 10 pL or less per pixel, more preferably 0.5 pL or more and 5 pL or less, and even more preferably 1 pL or more and 3 pL or less. The amount of pretreatment resin ejected from the pretreatment head (ejection amount) is preferably 0.2 pL or more and 0.6 pL or less per pixel. To form an image with high gloss, the amount of pretreatment resin ejected from the pretreatment head is preferably 0.3 pL or more and more preferably 0.5 pL or more per pixel. To form an image with high hiding power, the amount of pretreatment resin ejected from the pretreatment head is preferably 0.2 pL or less per pixel. The amount of pretreatment resin ejected from the pretreatment head per pixel can be calculated using the formula: "Amount of pretreatment resin ejected per pixel (pL) = Amount of pretreatment liquid ejected from the pretreatment head per pixel (pL) × Content of pretreatment resin in pretreatment liquid (mass%) / 100."

[0025] (Pretreatment resin) Examples of pretreatment resins include urethane resins, polystyrene resins, acrylic resins, olefin resins (more specifically, polyethylene resins and polypropylene resins), vinyl resins (more specifically, vinyl chloride resins, polyvinyl alcohol, vinyl ether resins, and N-vinyl resins), polyester resins, polyamide resins, and copolymers of these resins (more specifically, styrene-acrylic resins and styrene-butadiene copolymers). The polarity of the pretreatment resin is, for example, anionic. However, the polarity of the pretreatment resin may also be nonionic or cationic.

[0026] The pretreatment resin is preferably uniformly dispersed in the pretreatment liquid. In order to optimize the ejection properties of the pretreatment liquid from the pretreatment head and the storage stability of the pretreatment liquid, the pretreatment resin is preferably in a particulate form in the pretreatment liquid, and more preferably in an emulsified particulate form. When the pretreatment resin is in an emulsified particulate form, the pretreatment resin may be a self-emulsifying resin or a forced-emulsifying resin. The self-emulsifying resin is a hydrophilic resin having a hydrophilic group or a hydrophilic segment, and self-disperses in the pretreatment liquid. The forced-emulsifying resin is a hydrophobic resin that is forcibly emulsified in the pretreatment liquid by a surfactant.

[0027] The pretreatment resin is preferably a urethane resin, and more preferably a self-emulsifying urethane resin. The pretreatment resin is preferably an emulsified particulate urethane resin. Examples of urethane resins include urethane resins having an ester bond and an ether bond in their molecular chain (isocyanate ester-ether urethane resins), urethane resins having an ether bond in their molecular chain (isocyanate ether urethane resins), urethane resins having an ester bond in their molecular chain (isocyanate ester urethane resins), and urethane resins having a carbonate bond in their molecular chain (isocyanate carbonate urethane resins). Since the formed image is less likely to discolor, the urethane resin is preferably a non-yellowing type.

[0028] When the pretreatment resin is particulate, the volume median diameter of the pretreatment resin particles is preferably 1 nm or more and 200 nm or less, more preferably 10 nm or more and 100 nm or less, and even more preferably 20 nm or more and 40 nm or less. If the volume median diameter of the pretreatment resin particles is 1 nm or more, the storage stability of the pretreatment liquid can be optimized. If the volume median diameter of the pretreatment resin particles is 200 nm or less, the ejection performance of the pretreatment liquid from the pretreatment head can be optimized. The volume median diameter of the pretreatment resin particles is measured by light scattering using, for example, a particle size distribution analyzer (Microtrac UPA-EX150 manufactured by Microtrac Bell Co., Ltd.).

[0029] The thermal melting temperature of the pretreatment resin is preferably 90°C or higher and 200°C or lower, more preferably 100°C or higher and 190°C or lower. The thermal softening temperature of the pretreatment resin is preferably 50°C or higher and 200°C or lower, more preferably 150°C or higher and 180°C or lower. The glass transition point of the pretreatment resin is preferably -50°C or higher and 120°C or lower, more preferably -40°C or higher and 110°C or lower. The glass transition point of the pretreatment resin is determined, for example, by measuring a test film using a dynamic viscoelasticity measuring device ("Rheogel-E4000" manufactured by UBM Corporation). The thermal softening temperature and thermal melting temperature of the pretreatment resin are each determined, for example, by measuring a test film using a flow tester ("CFT-500D" manufactured by Shimadzu Corporation). The measured flow initiation temperature is considered to be the thermal softening temperature, and the 1 / 2 method temperature is considered to be the thermal melting temperature. The above-mentioned measurement film can be obtained, for example, by preparing a film with a thickness of 500 μm from the pretreatment resin and drying the film at room temperature for 15 hours, at 80°C for 6 hours, and at 120°C for 20 minutes.

[0030] The pretreatment resin may be of one type or of two or more types. The content of the urethane resin in the pretreatment resin is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and still more preferably 100% by mass.

[0031] (aqueous medium) The aqueous medium contained in the pretreatment liquid is a medium containing water. The aqueous medium may function as a solvent or a dispersion medium. Specific examples of the aqueous medium include an aqueous medium containing water and a water-soluble organic solvent.

[0032] (water) The water content in the pretreatment liquid is preferably 60% by mass or more and 75% by mass or less.

[0033] (Water-soluble organic solvent) Examples of the water-soluble organic solvent contained in the pretreatment liquid include glycol compounds, glycol ether compounds, lactam compounds, nitrogen-containing compounds, acetate compounds, thiodiglycol, glycerin, and dimethyl sulfoxide.

[0034] Examples of glycol compounds include ethylene glycol, 1,3-propanediol, propylene glycol, 1,2-pentanediol, 1,5-pentanediol, 1,2-octanediol, 1,8-octanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, and tetraethylene glycol.

[0035] Examples of glycol ether compounds include diethylene glycol diethyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, dipropylene glycol methyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether (also called butyl triglycol), and propylene glycol monomethyl ether.

[0036] Lactam compounds include, for example, 2-pyrrolidone and N-methyl-2-pyrrolidone.

[0037] Examples of nitrogen-containing compounds include 1,3-dimethylimidazolidinone, formamide, and dimethylformamide.

[0038] An example of the acetate compound is diethylene glycol monoethyl ether acetate.

[0039] Suitable examples of the water-soluble organic solvent contained in the pre-treatment liquid include glycol compounds and glycol ether compounds, and more suitable examples of the water-soluble organic solvent contained in the pre-treatment liquid include propylene glycol and triethylene glycol monobutyl ether.

[0040] The content of the water-soluble organic solvent in the pretreatment liquid is preferably from 1% by mass to 30% by mass, and more preferably from 5% by mass to 20% by mass.

[0041] (surfactant) The surfactant optimizes the compatibility and dispersion stability of the components contained in the pretreatment liquid. The surfactant also optimizes the wettability of the pretreatment liquid to the recording medium. The surfactant in the pretreatment liquid is preferably a nonionic surfactant. Examples of nonionic surfactants that can be contained in the pretreatment liquid include acetylene glycol surfactants (e.g., surfactants containing an acetylene glycol compound), silicone surfactants (e.g., surfactants containing a silicone compound), and fluorosurfactants (e.g., surfactants containing a fluororesin or a fluorine-containing compound). Examples of acetylene glycol surfactants include ethylene oxide adducts of acetylene glycol and propylene oxide adducts of acetylene glycol. The pretreatment liquid preferably contains a silicone surfactant. The surfactant content in the pretreatment liquid is preferably 0.01% by mass or more and 1.00% by mass or less, more preferably 0.03% by mass or more and 0.20% by mass or less. (Other ingredients) The pretreatment liquid may further contain known additives (for example, a dissolution stabilizer, a drying inhibitor, an antioxidant, a viscosity adjuster, a pH adjuster, and an anti-mold agent) as needed.

[0042] (Method for preparing pretreatment solution) The pretreatment liquid can be produced, for example, by uniformly mixing an aqueous medium, a pretreatment resin, and other components (e.g., a surfactant and at least one other component) that are added as needed using a stirrer. In producing the pretreatment liquid, after the components are uniformly mixed, foreign matter and coarse particles may be removed using a filter (e.g., a filter with a pore size of 5 μm or less).

[0043] <Ink> The ink ejected from the recording head of the inkjet recording apparatus of the present invention contains a pigment and an aqueous medium, and preferably further contains at least one of a pigment-coating resin, a binder resin, a surfactant, and other components.

[0044] (pigment) In the ink, the pigment, for example, constitutes a pigment particle together with a pigment-coating resin. The pigment particle is, for example, composed of a core containing the pigment and a pigment-coating resin that coats the core. The pigment-coating resin exists, for example, in a state of being dispersed in a solvent. From the viewpoint of optimizing the color density, hue, and stability of the ink, the volume median diameter of the pigment particles is preferably 30 nm or more and 200 nm or less, and more preferably 70 nm or more and 130 nm or less.

[0045] Examples of pigments include yellow pigments, orange pigments, red pigments, blue pigments, purple pigments, black pigments, and white pigments. Examples of yellow pigments include CI Pigment Yellow (74, 93, 95, 109, 110, 120, 128, 138, 139, 151, 154, 155, 173, 180, 185, and 193). Examples of orange pigments include CI Pigment Orange (34, 36, 43, 61, 63, and 71). Examples of red pigments include CI Pigment Red (122 and 202). Examples of blue pigments include CI Pigment Blue (15, more specifically 15:3). Examples of purple pigments include CI Pigment Violet (19, 23, and 33). Examples of black pigments include CI Pigment Black (7). Examples of white pigments include zinc oxide, titanium oxide, antimony white, zinc sulfide, baryte powder, barium carbonate, clay, silica, white carbon, talc, calcium carbonate, mica, kaolin, and alumina white. A white pigment is preferred as the pigment because it allows the formation of a base image with a high hiding power, and the ink is preferably a white ink containing a white pigment.

[0046] The pigment content in the ink is preferably 0.5% by mass or more and 10.0% by mass or less, and more preferably 1.0% by mass or more and 5.0% by mass or less. By setting the pigment content to 0.5% by mass or more, the ink can form an image with a desired image density. Furthermore, by setting the pigment content to 10.0% by mass or less, sufficient ink fluidity can be ensured.

[0047] (pigment coated resin) The pigment coating resin is a resin that is soluble in the aqueous medium of the ink. A portion of the pigment coating resin is present, for example, on the surface of the pigment particle to optimize the dispersibility of the pigment particle. A portion of the pigment coating resin is present, for example, in a dissolved state in the aqueous medium of the ink.

[0048] The pigment coating resin preferably has anionic properties. Examples of pigment coating resins include styrene-acrylic resins, styrene-maleic acid copolymers, styrene-maleic acid half ester copolymers, vinyl naphthalene-acrylic acid copolymers, and vinyl naphthalene-maleic acid copolymers. Styrene-maleic acid copolymers are preferred as pigment coating resins because they allow pigment particles to be suitably dispersed in the ink. Examples of styrene-maleic acid copolymers include styrene-maleic anhydride copolymers, and more specifically, polyether-modified styrene-maleic anhydride copolymers.

[0049] The content of the pigment coating resin in the ink is preferably 0.1% by mass to 10.0% by mass, and more preferably 0.5% by mass to 5.0% by mass. By setting the content of the pigment coating resin to 0.1% by mass to 10.0% by mass, the ejection stability of the ink can be sufficiently ensured.

[0050] In the ink, the content of the pigment coating resin relative to 100 parts by mass of the pigment is preferably from 10 to 200 parts by mass, and more preferably from 50 to 150 parts by mass. By setting the content of the pigment coating resin to from 10 to 200 parts by mass, the ejection stability of the ink can be optimized.

[0051] (binder resin) The binder resin improves the adhesion of the ink to the film formed by the pretreatment liquid. Examples of the binder resin include the same resins as those described for the pretreatment resin. The polarity of the binder resin is preferably anionic. If the binder resin is anionic, it is likely to coexist in the ink with pigment particles that also preferably have anionic properties (for example, pigment particles having an anionic pigment-coating resin). However, the polarity of the binder resin may be nonionic or cationic.

[0052] The binder resin is preferably uniformly dispersed in the ink. In order to optimize the ejection properties of the pretreatment liquid from the recording head and the storage stability of the ink, the binder resin is preferably in a particulate form in the ink, and more preferably in an emulsified particulate form. When the binder resin is in an emulsified particulate form, the binder resin may be a self-emulsifying resin or a forced emulsifying resin.

[0053] The binder resin is preferably a urethane resin, and more preferably a self-emulsifying urethane resin. The binder resin is preferably an emulsified particulate urethane resin. Examples of urethane resins include urethane resins having an ester bond and an ether bond in the molecular chain (isocyanate ester-ether urethane resin), urethane resins having an ether bond in the molecular chain (isocyanate ether urethane resin), urethane resins having an ester bond in the molecular chain (isocyanate ester urethane resin), and urethane resins having a carbonate bond in the molecular chain (isocyanate carbonate urethane resin). Since the formed image is less likely to discolor, the urethane resin is preferably a non-yellowing type.

[0054] When the binder resin is particulate, the volume median diameter of the binder resin particles is preferably 1 nm to 200 nm, more preferably 10 nm to 100 nm, and even more preferably 20 nm to 40 nm. The thermal melting temperature of the binder resin is preferably 90°C to 200°C, and more preferably 100°C to 190°C. The thermal softening temperature of the binder resin is preferably 50°C to 200°C, and more preferably 150°C to 180°C. The glass transition point of the binder resin is preferably -30°C to 120°C, and more preferably 30°C to 110°C. The volume median diameter of the binder resin particles, as well as the glass transition point, thermal softening temperature, and thermal melting temperature of the binder resin, are each measured, for example, by the same method as described for the pretreatment resin.

[0055] The binder resin may be of one kind or of two or more kinds. The content of the urethane resin in the binder resin is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and still more preferably 100% by mass.

[0056] The content of the binder resin in the ink is preferably 1.0% by mass or more and 12.0% by mass or less, and more preferably 2.0% by mass or more and 6.0% by mass or less. By setting the content of the binder resin to 1.0% by mass or more, it is possible to optimize the adhesion of the ink to the film formed by the pretreatment liquid. By setting the content of the binder resin to 12.0% by mass or less, it is possible to optimize the ejection stability of the ink.

[0057] (aqueous medium) The aqueous medium contained in the ink is a medium containing water. The aqueous medium may function as a solvent or a dispersion medium. Specific examples of the aqueous medium include an aqueous medium containing water and a water-soluble organic solvent.

[0058] (water) The water content in the ink is preferably 25.0% by mass or more and 80.0% by mass or less, and more preferably 40.0% by mass or more and 70.0% by mass or less.

[0059] (Water-soluble organic solvent) Examples of the water-soluble organic solvent contained in the ink include the same solvents as those described for the water-soluble organic solvent contained in the pretreatment liquid. Suitable examples of the water-soluble organic solvent contained in the ink include glycol compounds and glycol ether compounds. More suitable examples of the water-soluble organic solvent contained in the ink include propylene glycol and butyl triglycol. The content of the water-soluble organic solvent in the ink is preferably 10.0% by mass or more and 50.0% by mass or less, and more preferably 25.0% by mass or more and 45.0% by mass or less.

[0060] (surfactant) The surfactant optimizes the compatibility and dispersion stability of each component contained in the ink. The surfactant also optimizes the wettability of the ink to the recording medium. The surfactant contained in the ink is preferably a nonionic surfactant. Examples of the nonionic surfactant contained in the ink include the same compounds as those described for the nonionic surfactant contained in the pretreatment liquid. The ink preferably contains an acetylene glycol surfactant. The content of the surfactant in the ink is preferably 0.01% by mass or more and 3.00% by mass or less, and more preferably 0.03% by mass or more and 1.00% by mass or less.

[0061] (Other ingredients) The ink may further contain known additives (e.g., dissolution stabilizers, drying inhibitors, antioxidants, viscosity adjusters, pH adjusters, and anti-mold agents) as needed. Examples of pH adjusters include strongly basic compounds, more specifically, lithium hydroxide, sodium hydroxide, and potassium hydroxide. The content of the pH adjuster in the ink is preferably 0.001% by mass or more and 1.000% by mass or less, and more preferably 0.002% by mass or more and 0.005% by mass or less.

[0062] The ink provided in the inkjet recording apparatus of the present invention is, for example, a heat-drying ink (for example, a non-ultraviolet curable ink), but the ink provided in the inkjet recording apparatus of the present invention may also be an ultraviolet curable ink.

[0063] (Ink manufacturing method) The ink can be produced, for example, by uniformly mixing a pigment dispersion containing a pigment, an aqueous medium, and other components (for example, at least one of a pigment-coated resin, a binder resin, a surfactant, and other components) that are added as needed using a mixer. In producing the ink, after the components are uniformly mixed, foreign matter and coarse particles may be removed using a filter (for example, a filter with a pore size of 5 μm or less).

[0064] (Pigment dispersion) The pigment dispersion is a dispersion containing a pigment. Preferably, the pigment dispersion further contains a pigment-coated resin. Water is preferred as the dispersion medium for the pigment dispersion. The pigment content in the pigment dispersion is preferably 5.0% by mass or more and 70.0% by mass or less, and more preferably 10.0% by mass or more and 50.0% by mass or less. The pigment-coated resin content in the pigment dispersion is preferably 1.0% by mass or more and 10.0% by mass or less, and more preferably 2.0% by mass or more and 6.0% by mass or less. The pigment dispersion can be prepared by wet-dispersing a pigment, a pigment-coated resin, a dispersion medium (e.g., water), and optional components (e.g., surfactants) using a media-type wet disperser. In wet dispersion using a media-type wet disperser, for example, small particle size beads (e.g., D 50 The material of the beads is not particularly limited, but hard materials (for example, glass and zirconia) are preferred.

[0065] <Configuration of Inkjet Recording Apparatus> Next, the configuration of the inkjet recording apparatus of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0066] An inkjet recording apparatus 100 according to a first embodiment, which is one example of an inkjet recording apparatus of the present invention, will be described with reference to Fig. 1. Fig. 1 is a diagram showing one example of the inkjet recording apparatus 100. In Fig. 1, for convenience, the direction from right to left is defined as the positive direction of the X axis, the direction from back to front is defined as the positive direction of the Y axis, and the direction from bottom to top is defined as the positive direction of the Z axis.

[0067] 1, inkjet recording apparatus 100 is an apparatus that records an image on a sheet P using a single color of ink, and includes a housing 100a, a paper feed unit 1, a transport unit 2, an image forming unit 3, a discharge unit 4, an operation panel unit 6, the sheet P, a pretreatment liquid (not shown), and ink (not shown). The housing 100a houses the paper feed unit 1, the transport unit 2, the image forming unit 3, and the discharge unit 4. The sheet P corresponds to an example of a "recording medium."

[0068] The paper feed unit 1 stores a plurality of sheets P. The paper feed unit 1 includes a paper feed cassette 11 and a paper feed roller 12. The paper feed cassette 11 stores at least one sheet P. The paper feed roller 12 sends out the sheet P from the paper feed cassette 11 to the conveying unit 2.

[0069] The image forming unit 3 forms an image on the sheet P. The image forming unit 3 has a first heating unit 30, a pre-processing head 31, a recording head 32, an imaging unit 33, and a second heating unit 34. The first heating unit 30, the pre-processing head 31, the recording head 32, the imaging unit 33, and the second heating unit 34 are arranged in this order in the conveying direction D1 of the sheet P.

[0070] The first heating section 30 heats the first transport unit 24 of the transport section 2. The first transport unit 24 will be described later. The first heating section 30 also heats (preheats) the sheet P before the pretreatment liquid and ink are ejected. The heating temperature of the first heating section 30 is preferably 30°C or higher and 50°C or lower.

[0071] The pretreatment head 31 contains a pretreatment liquid and ejects the pretreatment liquid onto the sheet P. The ejection amounts of the pretreatment liquid ejected from the pretreatment head 31 and the pretreatment resin ejected from the pretreatment head 31 are preferably the amounts described above in the <Pretreatment Liquid> section.

[0072] The recording head 32 contains ink. The recording head 32 ejects the ink onto the sheet P. Specifically, the recording head 32 ejects the ink onto at least a part of the area of ​​the sheet P onto which the pretreatment liquid has been ejected. The amount of ink ejected from the recording head 32 is preferably 0.1 pL or more and 20 pL or less per pixel.

[0073] The imaging unit 33 captures an image formed on the sheet P in order to determine whether the glossiness of the image formed on the sheet P is high or low.

[0074] The second heating section 34 heats the sheet P after the pretreatment liquid and ink have been ejected, and dries the pretreatment liquid and ink. The heating temperature of the second heating section 34 is preferably 70°C or higher and 90°C or lower.

[0075] The transport unit 2 transports the sheet P from the paper feed unit 1 to the discharge unit 4. Specifically, the transport unit 2 includes a plurality of transport guides 21, a plurality of transport roller pairs 22, a registration roller pair 23, a first transport unit 24, and a second transport unit 25. The transport guide 21 forms a transport path for the sheet P. The transport roller pair 22 transports the sheet P along the transport path. The registration roller pair 23 adjusts the transport timing of the sheet P to the first transport unit 24 to coincide with the timing at which the image forming unit 3 ejects pretreatment liquid and ink. The first transport unit 24 faces the first heating unit 30, the pretreatment head 31, the recording head 32, the imaging unit 33, and the second heating unit 34. The first transport unit 24 transports the sheet P in the transport direction D1 in the area directly below the first heating unit 30, the pretreatment head 31, the recording head 32, the imaging unit 33, and the second heating unit 34. The second transport unit 25 transports the sheet P sent out from the first transport unit 24 toward the discharge section 4 in a transport direction D2.

[0076] The discharge unit 4 discharges the sheet P to the outside of the housing 100a. The discharge unit 4 has a discharge tray 41 and a pair of discharge rollers 42. The pair of discharge rollers 42 sends the sheet P to the discharge tray 41.

[0077] The operation panel unit 6 accepts instructions from the user. The operation panel unit 6 includes a display unit 61 and operation buttons 62. The display unit 61 displays various processing results. The operation buttons 62 include a start button, arrow keys, and a numeric keypad. The start button is a button for causing the inkjet recording apparatus 100 to execute various functions (processes). The arrow keys are buttons for changing the selection. The numeric keypad is a button for inputting numerical values.

[0078] Next, the circuit configuration of the inkjet recording apparatus 100 will be described with reference to Fig. 2 in addition to Fig. 1. Fig. 2 is a block diagram showing an example of the circuit configuration of the inkjet recording apparatus 100.

[0079] As shown in FIG. 2, the inkjet recording apparatus 100 includes a pretreatment head 31, a recording head 32, an imaging unit 33, a control unit 70, and a storage unit 80.

[0080] The storage unit 80 includes a main storage device such as a read-only memory (ROM) and a random access memory (RAM), and stores computer programs and various data.

[0081] The control unit 70 includes a processor such as a CPU (Central Processing Unit). The control unit 70 controls the operation of each element of the inkjet recording apparatus 100 by executing a computer program stored in the storage unit 80. Specifically, the control unit 70 controls the operation of each of the pre-treatment head 31, recording head 32, and imaging unit 33 that constitute the image forming unit 3.

[0082] The control unit 70 determines the level of glossiness of the image formed on the sheet P based on the image captured by the imaging unit 33. Then, the control unit 70 changes the amount of pretreatment liquid ejected from the pretreatment head 31 depending on the glossiness of the image formed on the sheet P. Specifically, if the glossiness of the image formed on the sheet P is lower than a predetermined value, the control unit 70 increases the amount of pretreatment liquid droplets ejected from the nozzles of the pretreatment head 31 compared to when the glossiness is a predetermined value. If the glossiness of the image formed on the sheet P is higher than the predetermined value, the control unit 70 decreases the amount of pretreatment liquid droplets ejected from the nozzles of the pretreatment head 31 compared to when the glossiness is a predetermined value.

[0083] The inkjet recording apparatus 100 according to the first embodiment, which is an example of an inkjet recording apparatus according to the present invention, has been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiment and can be embodied in various forms without departing from the spirit and scope of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiment. For example, some components may be omitted from all components shown in the embodiment. The drawings are primarily schematic illustrations of the individual components for ease of understanding, and the number of components shown may differ from the actual number due to the convenience of drawing. Furthermore, the components shown in the above-described embodiment are merely examples and are not particularly limited. Various modifications are possible within a scope that does not substantially deviate from the effects of the present invention.

[0084] For example, in the above-described embodiment, the inkjet recording apparatus 100 is an apparatus that records an image using ink of a single color, but this is not limiting. The inkjet recording apparatus 100 may also be an apparatus that records a color image using ink of multiple colors.

[0085] Furthermore, in the above-described embodiment, the recording medium is a sheet P of cut paper, but this is not limiting, and the recording medium may be a continuous film.

[0086] Furthermore, in the above-described embodiment, the imaging unit 33 captures the image formed on the sheet P, but this is not limited to this. The imaging unit 33 may capture the image of the sheet P before the pretreatment liquid and ink are ejected. In this case, the imaging unit 33 is provided upstream of the pretreatment head 31 in the conveyance direction D1 of the sheet P. In this case, the control unit 70 changes the amount of pretreatment liquid ejected from the pretreatment head 31 depending on the glossiness of the sheet P before image formation.

[0087] Furthermore, in the above-described embodiment, the control unit 70 changes the amount of pretreatment liquid ejected from the pretreatment head 31 in accordance with the glossiness of the image formed on the sheet P, but this is not limited to this. When the operation panel unit 6 receives an instruction from the user to select the gloss mode, the control unit 70 may increase the amount of pretreatment liquid ejected from the pretreatment head 31 by a predetermined amount (for example, the amount of pretreatment liquid stored in the storage unit 80 in advance) based on the instruction.

[0088] [Second embodiment: inkjet recording method] Next, an inkjet recording method according to a second embodiment of the present invention will be described. The inkjet recording method of the present invention includes a pretreatment step of ejecting a pretreatment liquid onto a recording medium, and an ink ejection step of ejecting ink onto at least a portion of the area of ​​the recording medium onto which the pretreatment liquid has been ejected. The surface roughness of the recording medium is 0.3 μm or more and 0.4 μm or less. The pretreatment liquid contains an aqueous medium and a pretreatment resin. The content of the pretreatment resin in the pretreatment liquid is 10% by mass or more and 30% by mass or less. For the same reasons as those described in the first embodiment, the inkjet recording method of the present invention can form images with high gloss and hiding power and excellent adhesion to the recording medium. The inkjet recording method of the present invention is carried out, for example, using the inkjet recording apparatus of the first embodiment. The recording medium, pretreatment liquid, and ink used in the second embodiment, as well as the configuration of the inkjet recording apparatus that can be used in the second embodiment, are the same as those in the first embodiment, and therefore will not be described here. [Example]

[0089] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0090] <Resin dispersion> The commercially available resin dispersions used to prepare the pretreatment liquid are shown below. Resin dispersion A: "Superflex (registered trademark) 470" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (resin content in resin dispersion: 38% by mass, resin: non-yellowing isocyanate carbonate-based self-emulsifying urethane resin, resin polarity: anionic, resin glass transition point: -31°C, resin thermal softening temperature: 97°C, resin thermal melting temperature: 138°C) Resin dispersion B: "Superflex (registered trademark) 130" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (resin content in resin dispersion: 35% by mass, resin: non-yellowing isocyanate ether-based self-emulsifying urethane resin, resin polarity: anionic, resin glass transition point: 101°C, resin thermal softening temperature: 174°C, resin thermal melting temperature: 216°C)

[0091] <Preparation of pretreatment solution> Pretreatment solutions (P1) to (P8) were prepared by mixing the components to obtain the compositions shown in Table 1 below.

[0092] [Table 1]

[0093] The abbreviations used in Table 1 are as follows: %:mass% PG: Propylene glycol BTG: butyl triglycol Surfactant: Silicone surfactant ("Silface (registered trademark) SAG503A" manufactured by Nissin Chemical Industry Co., Ltd.) Resin content: the content of the pretreatment resin in the pretreatment liquid. The content of the pretreatment resin in the pretreatment liquid was calculated using the formula "content of pretreatment resin in pretreatment liquid = content of resin dispersion in pretreatment liquid × resin content in resin dispersion." -:Does not contain any of the relevant ingredients

[0094] <Preparation of pigment dispersion DW> The pigment dispersion DW used in preparing Ink W was prepared as follows. Mixture I was obtained by mixing 75 parts by weight of a pigment dispersion resin ("DISPERBYK-190" manufactured by BYK Japan, an aqueous solution of polyether-modified styrene-maleic anhydride copolymer, nonvolatile content: 40% by weight) with 425 parts by weight of ion-exchanged water. Mixture I and 500 parts by weight of a white pigment ("JR-804" manufactured by Teika Corporation) were mixed using a homodisper at a stirring speed of 5,000 rpm for 1 hour to obtain mixture II. Media (zirconia beads with a diameter of 0.2 mm) were placed in the vessel of a bead mill (manufactured by Nippon Coke and Engineering Co., Ltd.) to achieve a filling rate of 80% by volume relative to the vessel's capacity. Mixture II was then added to the vessel, and the contents of the vessel were dispersed using the bead mill. Thus, pigment dispersion DW was obtained.

[0095] <Preparation of Ink W> A beaker was charged with 30 parts by weight of propylene glycol, 10 parts by weight of butyl triglycol, 1 part by weight of an acetylene glycol surfactant ("Surfynol® 104" manufactured by Nissin Chemical Industry Co., Ltd.), 0.5 parts by weight of a 1% sodium hydroxide aqueous solution, 10 parts by weight of the above-mentioned pigment dispersion DW, a binder resin dispersion ("Superflex® 130" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., binder resin content: 35% by weight), and water. The amount of binder resin dispersion added was such that the binder resin content was 5 parts by weight. The amount of water added was such that the total amount of the mixture in the beaker was 100 parts by weight. The contents of the beaker were mixed using a mixer ("Three-One Motor BL-600" manufactured by Shinto Scientific Co., Ltd.) at a stirring speed of 400 rpm to obtain a mixed solution. The mixed solution was filtered using a filter (pore size: 5 μm) to remove foreign matter and coarse particles contained in the mixed solution. In this way, Ink W was obtained.

[0096] <Film preparation> Films (M1) to (M6) shown in Table 2 below were prepared. Specifically, films (M1) to (M5) with the surface roughness shown in Table 2 were obtained by sandblasting the surface of a polyester film ("Lumirror (registered trademark) S010" manufactured by Toray Industries, Inc.). Film (M6) with the surface roughness shown in Table 2 was obtained by sandblasting the surface of a polypropylene film ("Torayfan (registered trademark) 2548" manufactured by Toray Industries, Inc.). Brown fused alumina was used as the abrasive for sandblasting. The surface roughness of each film was adjusted to the values ​​shown in Table 2 by changing the size of the abrasive used for sandblasting (specifically, the abrasive particle size number specified in JIS (Japanese Industrial Standards) R 6001). The larger the abrasive size (the smaller the particle size number), the greater the surface roughness of the film. For example, an abrasive with particle size number F220 was used for sandblasting M1.

[0097] [Table 2]

[0098] The abbreviations used in Table 2 are as follows: Lumirror S010: Biaxially stretched PET film ("Lumirror (registered trademark) S010" manufactured by Toray Industries, Inc.) Torayfan 2548: OPP film (Toray Industries, Inc. "Torayfan (registered trademark) 2548")

[0099] The surface roughness (Ra) shown in Table 2 was measured using a confocal microscope ("OPTELICS (registered trademark) HYBRID+" manufactured by Lasertec) at a lens magnification of 100. After filtering with a median filter, the surface roughness Ra was analyzed.

[0100] <Evaluation> [Evaluation machine] A one-pass inkjet recording device (a test machine manufactured by Kyocera Document Solutions Inc.) was used as the evaluation machine. The evaluation machine was equipped with a transport section, a pretreatment head, and a recording head. In the evaluation machine, the pretreatment head was located upstream in the film transport direction, and the recording head was located downstream, parallel to each other. Ink W was filled into the recording head of the evaluation machine. The recording head was set to an applied voltage of 21 V, a driving frequency of 20 kHz, a head temperature of 32°C, and a resolution of 1200 dpi. When forming an image with the evaluation machine, the transport section was preheated to 40°C. Furthermore, when forming an image with the evaluation machine, the film transport speed was set to 30 m / min.

[0101] [Preparing the inkjet recording device] The pretreatment head of the evaluation machine described above was filled with the pretreatment liquid shown in Table 3 below. The ejection amount per pixel of the pretreatment head was set to the amount shown in Table 3. The films shown in Table 3 were set in the evaluation machine. In this way, inkjet recording devices (A-1) to (A-10) and (B-1) to (B-9) were obtained. Note that the "%" and "resin content" used in Table 3 are synonymous with the "%" and "resin content" used in Table 1, respectively. The "-" used in Table 3 indicates that no pretreatment liquid was used.

[0102] [Table 3]

[0103] The glossiness, hiding power, and adhesion to the substrate of the evaluation image were evaluated by the following methods. The evaluation results are shown in Table 4 below.

[0104] [Formation of evaluation image] Using each of the inkjet recording devices (A-1) to (A-10) and (B-1) to (B-9), a solid image of the pretreatment liquid was formed on a film, and then a solid image of the ink was formed on the solid image of the pretreatment liquid. The film on which the image was formed was then dried at 80°C for 120 seconds using a hot air dryer. In this way, an image (evaluation image) formed on a film (evaluation film) using each inkjet recording device was obtained.

[0105] Glossiness The glossiness of the evaluation image was measured using a glossmeter (Elcometer "Elcometer J480T") under the condition of incident / reflected angle = 60° / 60°. The glossiness was judged according to the following criteria. If the evaluation was poor, it was recorded as "NG" in Table 4 below.

[0106] (Gloss standard) Particularly good: gloss level 80 or higher Good: Glossiness is 40 or more but less than 80 Poor: Glossiness less than 40

[0107] [Concealment rate] The K value of the evaluation image was measured with the evaluation film placed on the hiding rate test paper. The K value of the hiding rate test paper itself was also measured. A fluorescence spectrodensitometer (Konica Minolta's "FD-5") was used to measure the K value. The hiding rate of the evaluation image was calculated using the formula "Hiding rate = {1 - (K value of evaluation image / K value of hiding rate test paper)} x 100". The hiding rate was judged according to the following criteria. If the evaluation was poor, it was marked "NG" in Table 4 below.

[0108] (Criteria for concealment) Particularly good: Concealment rate of 84.0% or more Good: Concealment rate is 80.0% or more but less than 84.0% Poor: Concealment rate is less than 80.0%

[0109] [Adhesion to substrate] Six grid-like (checkerboard-like) cuts were made in each of the evaluation images on the evaluation film, spaced 1 mm apart, to form 25 squares with 1 mm sides. Adhesive tape was applied to each of the cut evaluation images, and the tape was peeled off at an angle of approximately 60 degrees (peeling treatment). The adhesive tape was peeled off at a speed such that the time from start to finish of peeling was 1 second. After the peeling treatment, the evaluation film was observed. Adhesion to the substrate was evaluated according to the following criteria.

[0110] (Base material adhesion standard) A (particularly good): After the peeling process, not a single square of peeling was observed in the evaluation image. B (good): After the peeling treatment, peeling of 1 to 3 squares was confirmed in the evaluation image. C (poor): After the peeling treatment, peeling of 4 to 6 squares was observed in the evaluation image. D (particularly poor): After peeling treatment, peeling of 7 or more squares was observed in the evaluation image.

[0111] [Table 4]

[0112] The resin content in the pretreatment liquid (more specifically, the pretreatment liquid (P7)) provided in the inkjet recording apparatuses (B-1) and (B-2) was more than 30% by mass. The concealment ratio of the images formed by the inkjet recording apparatuses (B-1) and (B-2) was evaluated as poor.

[0113] The inkjet recording apparatus (B-3) did not use a pretreatment liquid. The gloss level of the image formed by the inkjet recording apparatus (B-3) was evaluated as poor, and the adhesion to the substrate was evaluated as particularly poor.

[0114] The resin content in the pretreatment liquid (more specifically, the pretreatment liquid (P1)) provided in the inkjet recording apparatuses (B-4) to (B-5) was less than 10% by mass. The glossiness of the images formed by the inkjet recording apparatuses (B-4) to (B-5) was evaluated as poor.

[0115] The surface roughness of the recording media (more specifically, each of the films (M3) and (M5)) provided in the inkjet recording devices (B-6) to (B-7) and (B-9) was less than 0.30 μm. The substrate adhesion of the images formed by the inkjet recording devices (B-6) to (B-7) was evaluated as poor. The substrate adhesion of the images formed by the inkjet recording device (B-9) was evaluated as particularly poor, and the hiding ratio was also evaluated as poor.

[0116] The surface roughness of the recording medium (more specifically, the film (M4)) included in the inkjet recording device (B-8) was greater than 0.40 μm. The glossiness of the image formed by the inkjet recording device (B-8) was evaluated as poor.

[0117] On the other hand, as shown in Table 3, the inkjet recording apparatuses (A-1) to (A-10) were equipped with a pretreatment head and a recording head. The surface roughness of the recording medium (more specifically, each of the films (M1), (M2), and (M6)) was 0.30 μm or more and 0.40 μm or less. The pretreatment liquid (more specifically, each of the pretreatment liquids (P2) to (P6) and (P8)) contained an aqueous medium and a resin, and the resin content in the pretreatment liquid was 10% by mass or more and 30% by mass or less. The inkjet recording apparatuses (A-1) to (A-10) were able to form images with high gloss and hiding power and excellent adhesion to the substrate. [Industrial Applicability]

[0118] The inkjet recording apparatus and inkjet recording method according to the present invention can be used to form an image. [Explanation of symbols]

[0119] 2: Conveyor section 31: Pre-processing head 32: Recording head 70: Control unit 100: Inkjet recording device P: Sheet (recording medium)

Claims

1. a pretreatment head that ejects a pretreatment liquid onto a recording medium; a recording head that ejects ink onto at least a part of the area of ​​the recording medium onto which the pretreatment liquid has been ejected; the surface roughness of the recording medium is 0.30 μm or more and 0.40 μm or less; the pretreatment liquid contains an aqueous medium and a resin, The inkjet recording apparatus, wherein the content of the resin in the pretreatment liquid is 10% by mass or more and 30% by mass or less.

2. 2. The inkjet recording apparatus according to claim 1, wherein the resin contained in the pretreatment liquid is an emulsified particulate urethane resin.

3. 3. The inkjet recording apparatus according to claim 1, wherein the amount of the resin contained in the pretreatment liquid ejected from the pretreatment head is 0.2 pL or more and 0.6 pL or less per pixel.

4. 3. The inkjet recording apparatus according to claim 1, wherein the pretreatment liquid does not contain a pigment, and the ink contains a white pigment.

5. 3. The inkjet recording apparatus according to claim 1, wherein the recording medium is a non-absorbent recording medium.

6. a control unit for controlling the operation of the pretreatment head; The inkjet recording apparatus according to claim 1 , wherein the control unit changes the amount of the pretreatment liquid ejected from the pretreatment head in accordance with the glossiness of the image formed on the recording medium.

7. a pretreatment step of ejecting a pretreatment liquid onto a recording medium; an ink ejection step of ejecting ink onto at least a part of the area of ​​the recording medium onto which the pretreatment liquid has been ejected, the surface roughness of the recording medium is 0.3 μm or more and 0.4 μm or less; the pretreatment liquid contains an aqueous medium and a resin, The inkjet recording method, wherein the content of the resin in the pretreatment liquid is 10% by mass or more and 30% by mass or less.

Images