Liquid discharge device, printing apparatus, and printing method

Abstract

A liquid discharge device includes a nozzle plate having a nozzle hole to discharge a liquid; a liquid chamber to supply the liquid to the nozzle hole; a needle valve having a tip end to move forward and backward in the liquid chamber to close or open the nozzle hole with the tip end; and a liquid repellent layer on a surface of the nozzle plate, the liquid repellent layer having surface free energy of less than 29 mJ / m2.

Description

[DESCRIPTION][Title of Invention]LIQUID DISCHARGE DEVICE, PRINTING APPARATUS, AND PRINTING METHOD [Technical Field]

[0001] The present embodiment relates to a liquid discharge device, a printing apparatus, and a printing method.[Background Art]

[0002] Solvent-based or water-based paints have been applied to a road surface, a floor, and a wall surface of a building by a spray method, brush painting, and roller painting method.

[0003] There is a method of discharging ink from a nozzle by an inkjet method for painting on a road surface, a wall surface of a building such as an exterior or interior, a wall surface of a civil structure such as a bridge or a tunnel, and a porous base material.In the inkjet method, ink droplets are applied to a base material in a dot shape, and thus it is possible to provide painting that enables drawing of high-definition characters and patterns, which is not possible in the conventional spray method, brush painting, and roller painting method.

[0004] Further, there have been presented a coating material spray nozzle as the nozzle and a control method of the same. The coating material spray nozzle can prevent liquid from leaking when a nozzle hole is closed and obtain accuracy in stable coating when the nozzle is opened (see, for example, Patent Literature (PTL) 1).[Summary of Invention][Technical Problem]

[0005] An object of an embodiment of the present embodiment is to provide a liquid discharge device that can perform stable discharging from a nozzle hole that has been continuously in an uncapped state (a state in which a nozzle is exposed without a lid for preventing drying of the nozzle) at a time of printing with discharging of high-viscosity liquid that is used for a road surface, a wall surface of a building such as an exterior or an interior, a wall surface of a civil structure such as a bridge or a tunnel, and a porous base material.[Solution to Problem]

[0006] According to an aspect of the present disclosure, a liquid discharge device is provided that includes a nozzle plate having a nozzle hole to discharge a liquid; a liquid chamber to supply the liquid to the nozzle hole; a needle valve having a tip end to move forward and backward in the liquid chamber to close or open the nozzle hole with the tip end; and a liquid repellentlayer on a surface of the nozzle plate, the liquid repellent layer having surface free energy of less than 29 mJ / m2.[Advantageous Effects of Invention]

[0007] According to an embodiment of the present embodiment, it is possible to provide a liquid discharge device that can perform stable discharging from a nozzle hole that has been continuously in an uncapped state (a state in which a nozzle is exposed without a lid for preventing drying of the nozzle) at a time of printing with discharging of high- viscosity liquid that is used for a road surface, a wall surface of a building such as an exterior or an interior, a wall surface of a civil structure such as a bridge or a tunnel, and a porous base material. [Brief Description of Drawings]

[0008] A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings. [FIG. 1]FIG. 1 is a schematic cross-sectional view of an example enlarging and illustrating a nozzle hole and a tip portion of a needle valve in a liquid discharge device according to a first embodiment of the present embodiment.[FIG. 2]FIG. 2 is a schematic cross-sectional view of an example enlarging and illustrating a nozzle hole and a tip portion of a needle valve in a liquid discharge device according to Modification1 of the first embodiment of the present embodiment.[FIG. 3]FIG. 3 is a schematic cross-sectional view of an example enlarging and illustrating a nozzle hole and a tip portion of a needle valve in a liquid discharge device according to Modification2 of the first embodiment of the present embodiment.[FIG. 4]FIG. 4 is a schematic configuration diagram illustrating an example of a liquid discharge device according to an embodiment of the present embodiment, and is a diagram illustrating an example of a state when a nozzle is closed.[FIG. 5]FIG. 5 is a schematic configuration diagram illustrating an example of the liquid discharge device according to the embodiment of the present embodiment, and is a diagram illustrating an example of a state when the nozzle is opened.[FIG. 6]FIG. 6 is a schematic side view illustrating an example of a liquid discharge device as a printing apparatus according to an embodiment of the present embodiment.[FIG. 7]FIG. 7 is a schematic plan view illustrating an example of a liquid discharge device as the printing apparatus according to the embodiment of the present embodiment.[FIG. 8]FIG. 8 is a schematic cross-sectional view of an example enlarging and illustrating a nozzle hole and a tip portion of a needle valve in a liquid discharge device (nozzle 14) used in Comparative Example 5.The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views. [Description of Embodiments]In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0009] Liquid Discharge deviceA liquid discharge device according to an embodiment of the present embodiment is a liquid discharge device including a nozzle unit that discharges liquid. The nozzle unit includes: a nozzle hole; a nozzle plate that forms the nozzle hole; a liquid chamber that supplies liquid to the nozzle hole; and a needle valve that closes or opens the nozzle hole with a tip end while moving forward and backward in the liquid chamber. A surface of the nozzle plate and a nozzle hole surface, on which a nozzle hole is formed, have a liquid repellent layer.

[0010] In the nozzle disclosed in PTL 1 (Japanese Unexamined Patent Application Publication No. 2022-64482), there has been a problem of being unable to stably discharge ink from the nozzle at a time of discharging the ink from the nozzle that has been in an uncapped state at a time of printing, when performing printing using conventional high- viscosity ink that is used for painting a road surface, a wall surface of a building such as an exterior or an interior, a wall surface of a civil structure such as a bridge or a tunnel, and a porous base material. As a result, for some print images, there is a nozzle that has been continuously in a state of not discharging the ink for a long time during printing. Therefore, there has been a disadvantage of occurrence of a positional shift of landing of the ink, coming off of the nozzle due to nondischarging, and the like.

[0011] Therefore, as a result of intensive studies by the persons who have conceived the present embodiment, the following has been found. Specifically, in the nozzle unit of the liquid discharge device, the surface of the nozzle plate and the nozzle hole surface, on which the nozzle hole 2 is formed, have the liquid repellent layer having surface free energy of less than 29 mJ / m2. Thus, surface free energy of the nozzle plate decreases, and ink repellency against ink is easily maintained. Therefore, discharging deflection can be suppressed by maintaining the ink repellency against the ink thickened by drying. As a result, when printing is performed using high-viscosity ink, the ink can be stably discharged from the liquid discharge device that has been continuously in an uncapped state.Note that the high-viscosity ink means ink having a viscosity of 1,000 mPa-s or more at a shear rate of 1 (1 / s).

[0012] Hereinafter, a liquid discharge device according to an embodiment of the present embodiment will be described with reference to the drawings.

[0013] First EmbodimentFIG. 1 is a schematic cross-sectional view of an example enlarging and illustrating a nozzle hole and a tip portion of a needle valve in a liquid discharge device according to a first embodiment of the present embodiment.The liquid discharge device according to the first embodiment includes a nozzle unit 10. The nozzle unit 10 includes a base 1, the nozzle hole 2 from which liquid is discharged, a nozzle plate 3 that forms the nozzle hole 2, a liquid chamber 4 that supplies liquid to the nozzle hole, and a needle valve 5 in the liquid chamber 4.An outer surface of the nozzle plate 3 and a nozzle hole surface, on which the nozzle hole 2 is formed, have a liquid repellent layer 6. The liquid repellent layer 6 is preferably provided on the entire outer surface of the nozzle plate 3 and the entire nozzle hole surface on which the nozzle hole 2 is formed.The liquid discharge device according to the first embodiment is omitted in FIG. 1, but may include a drive mechanism that moves the needle valve 5 forward and backward with respect to the nozzle hole 2.

[0014] The base 1 is a member that forms an outer wall of the nozzle unit 10. A material of the nozzle unit 10 is not limited in particular, and can be appropriately selected according to a purpose.

[0015] The nozzle hole 2 is a hole through which liquid is discharged.A diameter of the nozzle hole 2 is not limited in particular, and can be appropriately selected according to a purpose, but is 50 pm or more, and more preferably 100 pm or more. When the diameter is 50 pm or more, liquid or the like to be used for a road surface, a wall surfaceof a building such as an exterior or an interior, a wall surface of a civil structure such as a bridge or a tunnel, and a porous base material can be discharged.

[0016] The nozzle plate 3 forms the nozzle hole 2, and has the liquid repellent layer 6 on the outer surface and the surface on which the nozzle hole 2 is formed. The outer surface of the nozzle plate is a surface of the nozzle plate on a side opposite to a side on which the liquid chamber 4 is disposed.

[0017] The liquid repellent layer 6 is a layer having surface free energy of less than 29 mJ / m2.Since the nozzle unit 10 includes the liquid repellent layer 6 having surface free energy of less than 29 mJ / m2, it is easy to maintain ink repellency against ink, and it is possible to suppress discharging deflection by maintaining the ink repellency against the ink thickened by drying. As a result, when printing is performed using ink with high viscosity and high solid content, the ink can be stably discharged from the liquid discharge device that has been continuously in an uncapped state.

[0018] A method for calculating the surface free energy of the water repellent layer is not limited in particular, and can be appropriately selected according to a purpose. For example, the surface free energy can be measured by the following procedure using a contact angle meter DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.).Specifically, the surface free energy of the water repellent layer can be calculated by measuring contact angles of three kinds of liquid samples whose surface free energy is known for the water repellent layer, and solving simultaneous equations.When the surface free energy of the water repellent layer is ys, a dispersion component of surface energy of the water repellent layer is ysd, a dipole component of the surface energy of the water repellent layer is ysp, a hydrogen bond component of the surface energy of the water repellent layer is ysh, surface free energy of a liquid sample is YL, a dispersion component of surface energy of the liquid sample is y d, a dipole component of the surface energy of the liquid sample is YLP, a hydrogen bond component of the surface energy of the liquid sample is yLh, and a contact angle of the liquid sample on the water repellent layer is 9, the following Formulas (1), (2), and (3) are established.[Chemical Formula 1]By measuring a contact angle 9 for three kinds of liquid samples each of which YL, yu, YLP, and yLh are known for the water repellent layer, and substituting the measured contact angle 9into the above Formula (3), three formulas with ysd, Ysp, and ysh as variables are formed, and Ysd, Ysp, and Ysh can be obtained by solving these equations. By substituting the obtained Ysd, YsP, and Ysh into Formula (1), the surface free energy ys of the water repellent layer can be obtained.The above Formulas (1) and (2) are formulas in the Kitazaki-Hata theory.The above Formula (3) is a formula obtained by substituting formulas of the Kitazaki-Hata and Extended Fowkes into the Dupre formula and further modifying the Young-Dupre formula by using the substituted formula.In addition to the Kitazaki-Hata, there are theoretical formulas of Owens-Wendt and Kaelble-Uy. The surface free energy of the water repellent layer can be calculated by measuring a contact angle of two kinds of liquid samples whose surface free energy is known for the water repellent layer, substituting the contact angle into the Young and Dupre formula, and solving simultaneous equations.

[0019] The liquid repellent layer 6 preferably contains at least one of silicon (Si) or fluorine (F), and may contain other components as necessary.

[0020] The fluorine (F) may be contained in the liquid repellent layer 6 as a fluorine compound.The fluorine compound is not limited in particular, and can be appropriately selected according to a purpose. The examples of the fluorine compound include, but are not limited to, krytoxFSL (manufactured by DuPont), krytoxFSH (manufactured by DuPont), FOMBLINZ (manufactured by Solvay Solexis, Inc.), FLUOROLINK S 10 (manufactured by SolvaySolexis, Inc.), OPTOOL DSX (manufactured by Daikin Industries, Ltd.), FLUOROLINK CIO(manufactured by Solvay Solexis, Inc.), MORESCO PHOSFAROL A20H (manufactured byMatsumura Oil. Research Corp.), MORESCO PHOSFAROL ADOH (manufactured byMatsumura Oil. Research Corp.), MORESCO PHOSFAROL DDOH (manufactured byMatsumura Oil. Research Corp.), FLUOROSURF FG5010 (manufactured byFluoroTechnology Co., LTD.), FLUOROSURF FG5020 (manufactured by FluoroTechnologyCo., LTD.), FLUOROSURF FG5060 (manufactured by FluoroTechnology Co., LTD.), FLUOROSURF FG5070 (manufactured by FluoroTechnology Co., LTD.), DURASURF DP-500 (manufactured by HARVES Co., Ltd.), DURASURF DP-200 (manufactured by HARVES Co., Ltd.), DURASURF DS-5400 (manufactured by HARVES Co., Ltd.), DURASURF DH-100 (manufactured by HARVES Co., Ltd.), H-405TH (manufactured by HARVES Co., Ltd.), DH-610 (manufactured by HARVES Co., Ltd.), DS-6500 (manufactured by HARVES Co., Ltd.), DS-5800 (manufactured by HARVES Co., Ltd.), DS- 5935 (manufactured by HARVES Co., Ltd.), and the like. One type of the fluorine compound may be used alone, or two or more types of the fluorine compounds may be used in combination. Among these fluorine compounds, modified perfluoropolyoxetane (OPTOOL DSX manufactured by Daikin Industries, Ltd.) is preferable.

[0021] The liquid repellent layer 6 may contain silicon (Si) as a silicon compound.The silicon compound is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, a silicone resin and the like. The silicone resin is a resin having a siloxane bond formed by silicon (Si) and oxygen (O) as a basic skeleton. The silicone resin is commercially available in various forms such as oil, resin, and elastomer, and has various properties such as heat resistance, releasability, defoaming property, and adhesiveness in addition to water repellency which is of great interest in the present embodiment. Examples of the silicone resin include, but are not limited to, a room temperature curing type, a heat curing type, an ultraviolet curing type, and the like, and the silicone resin can be selected according to a preparation method and intended use.

[0022] In the liquid discharge device according to an embodiment of the present embodiment, a treatment film may be provided between the base and the liquid repellent layer containing at least one of silicon (Si) or fluorine (F).The treatment film is not limited in particular, and can be appropriately selected according to a purpose. Examples of the treatment film include, but are not limited to, a layer of an oxide film of SiOi, a film in which Si and a transition metal (for example, tantalum, niobium, titanium, hafnium, zirconium, tungsten) are bonded with O in between, and the like. In the case of an oxide film of SiCE, moisture is less likely to permeate, so that the base material is less likely to corrode. In the case of a film in which Si and a transition metal are bonded with O in between, a passive film having characteristics of a slightly soluble transition metal oxide at a wide pH is formed, and a more stable film can be formed even under acidic or alkaline conditions.

[0023] In forming the liquid repellent layer containing at least one of silicon (Si) or fluorine (F), a silanol compound having a silanol group (Si-OH) may be contained in the liquid repellent layer, and Si-OH may be condensed and bonded to the base or the treatment film in the silanol group. When the silanol group Si-OH is contained in the liquid repellent layer, a silanol group Si-OH of the liquid repellent layer is hydrogen-bonded to a hydroxyl group of the base and a silanol group Si-OH of the treatment film. Further, by adjusting temperature to room temperature or higher, dehydration condensation reaction of the hydrogen-bonded portion proceeds, and Si forms a covalent bond in the base and the treatment film with O in between, thereby improving adhesion.When silanol groups in the liquid repellent layer react with each other to form siloxane- bonded Si-O-Si, strength of the liquid repellent layer is improved. The silanol compound of the liquid repellent layer complements oxygen for oxygen deficiency in a surface oxidationstate of the base, thereby equalizing the surface state of the base and eliminating a portion that becomes a starting point of corrosion, to improve corrosion resistance.

[0024] Whether the liquid repellent layer 6 contains at least one of silicon (Si) or fluorine (F) can be measured by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIM), energy dispersive x-ray spectroscopy (EDS) or electron probe micro analyzer (EPMA) of an electron microscope, fluorescent X-ray, or the like. Further, by analyzing elements in a depth profile in a direction perpendicular to the outermost surface of the liquid repellent layer, from the outermost surface of the liquid repellent layer toward a surface in contact with the base or the liquid repellent layer of the needle valve by using the XPS and the TOF-SIM, silicon (Si) and fluorine (F) in a cross-sectional depth direction of the liquid repellent layer 6 can be analyzed.

[0025] An average thickness of the liquid repellent layer 6 is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 0.0001 pm or more and 5 pm or less. In order to lower the surface free energy of the water repellent layer and improve durability of the water repellent layer against wear, the thickness is more preferably 0.5 pm or more and 5 pm or less when the water repellent layer contains silicon (Si), and is more preferably 0.0005 pm or more and 0.02 pm or less when the water repellent layer contains fluorine (Si).

[0026] The liquid chamber 4 has a structure holding liquid and formed by the base 1 as an outer wall of the nozzle unit 10 and the nozzle plate 3 forming the nozzle hole 2.

[0027] The needle valve 5 is provided inside the liquid chamber 4. When the needle valve 5 moves forward and backward in the liquid chamber 4, the nozzle hole 2 can be closed or opened with a tip end of the needle valve 5. The forward and backward movement of the needle valve 5 can be controlled by, for example, a drive mechanism.A pressure applied to the liquid chamber 4 and the liquid by the needle valve 5 is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 0.2 MPa or more. When the pressure is 0.2 MPa or more, high- viscosity ink can be discharged.

[0028] The drive mechanism is not limited in particular, and can be appropriately selected according to a purpose. Examples of the drive mechanism include, but are not limited to, an electromagnetic drive type drive mechanism, a drive mechanism using a piezoelectric element, and the like.

[0029] Modification 1 of First EmbodimentFIG. 2 is a schematic cross-sectional view of an example enlarging and illustrating a nozzle hole and a tip portion of a needle valve in a liquid discharge device according to Modification1 of the first embodiment of the present embodiment.As compared with the first embodiment, Modification 1 of the first embodiment has the liquid repellent layer 6 on, in addition to the outer surface of the nozzle plate 3 and the nozzle hole surface on which the nozzle hole 2 is formed, a surface of the nozzle plate 3 on which the liquid chamber 4 is formed (hereinafter, may be referred to as an "inner surface of the nozzle plate 3". As a result, when liquid having a viscosity higher than the viscosity of the first embodiment is discharged to print, the liquid can be stably discharged from the nozzle that has been continuously in an uncapped state.

[0030] Modification 2 of First EmbodimentFIG. 3 is a schematic cross-sectional view of an example enlarging and illustrating a nozzle hole and a tip portion of a needle valve in a liquid discharge device according to Modification2 of the first embodiment of the present embodiment.The Modification 2 of the first embodiment includes the liquid repellent layer 6 also at a tip end of the needle valve 5 as compared with Modification 1 of the first embodiment. As a result, when liquid having a viscosity higher than the viscosity of the first embodiment and Modification 1 of the first embodiment is discharged to print, the liquid can be stably discharged from the nozzle that has been continuously in an uncapped state.

[0031] FIG. 4 is a schematic configuration diagram illustrating an example of a liquid discharge device according to an embodiment of the present embodiment, and is a diagram illustrating an example of a state when a nozzle is closed. FIG. 5 is a schematic configuration diagram illustrating an example of the liquid discharge device according to the embodiment of the present embodiment, and is a diagram illustrating an example of a state when the nozzle is opened.In FIGS. 4 and 5, the liquid discharge device of the present embodiment includes a nozzle hole 2 provided in a front surface of a base 1, an liquid chamber 4 that supplies ink to the nozzle hole 2, a needle valve 5 that is in the liquid chamber 4 and closes or opens the nozzle hole 2 with a tip end, a movable iron core 8 secured behind the needle valve, a fixed iron core 11 and an electromagnetic solenoid 12 provided to face the movable iron core 8, and a spring material 19 provided between the movable iron core 8 and the fixed iron core 11. The movable iron core 8, the spring material 19, the fixed iron core 11, and the electromagnetic solenoid 12 constitute an electromagnetic drive type drive mechanism for repeating closing and opening operations of the needle valve 5 on the nozzle hole 2.

[0032] In order to prevent the ink in the liquid chamber 4 from flowing out to a drive mechanism accommodation space 9 accommodating the drive mechanism, an elastic body diaphragm 7 isprovided so as to surround the needle valve 5, and a pressure P is applied to the ink in the liquid chamber 4 via an ink input passage 22.

[0033] In order to prevent the pressurized ink from leaking out from between the elastic body diaphragm 7 and the needle valve 5, the pressure P equivalent to a pressure applied to the ink through a pressurizing passage 13 is applied to gas or liquid in the drive mechanism accommodation space 9.

[0034] FIG. 4 illustrates a state in which the needle valve 5 closes the nozzle hole 2. At this time, no current flows through the solenoid 12, and the movable iron core 8 and the needle valve 5 following the movable iron core 8 are pushed forward by an action of the spring material 19. Therefore, the nozzle hole 2 can be closed as a result.

[0035] On the other hand, FIG. 5 illustrates a state in which the needle valve 5 opens the nozzle hole 2. At this time, a current flows in the solenoid 12, and the movable iron core 8 is attracted to the fixed iron core 11. Therefore, the needle valve 5 moves backward to open the nozzle hole 2.

[0036] As described above, for example, by supplying a pulse current to the solenoid 12 and appropriately controlling the pulse current, the nozzle hole 2 is opened and closed by the needle valve 5 to discharge ink, and printing can be performed on a three-dimensional material.

[0037] Reference numeral 17 indicates a pressurized ink tank coupled to the liquid chamber 4 via a circulation path 20. Ink is supplied from the ink tank 17 to the ink input passage 22, and the ink discharged from an ink output passage 21 returns to the ink tank 17 via a pump 18. The circulation of the pressurized ink in this manner prevents separation and sedimentation of an ink component, which helps to expand a range of types of ink that can be used.

[0038] The fixed iron core 11 is coupled with a gap adjustment bolt 15 and a nut 16. By rotating the nut 16, a position of the fixed iron core 11 can be changed. This change width is a distance between the needle valve 5 and the nozzle hole 2, that is, a change width of a nozzle gap, and can be adjusted by the gap adjustment bolt 15. Reference numeral 14 indicates a screw rattling preventing spring.

[0039] A discharging amount of ink can be controlled by adjusting a length of an energization time to the solenoid 12, that is, a length of an opening time of the nozzle hole 2.

[0040] By increasing the nozzle gap by using the functions of the gap adjustment bolt 15 and the nut 16, the discharging amount of ink can be increased.

[0041] Liquid that can be used in the embodiment of the present embodiment is not limited in particular, as long as the liquid is fluid and can be discharged from a nozzle. Examples of the liquid include, but are not limited to, ink, paint, and treatment liquid.The liquid is liquid to be used for painting a road surface, an exterior, and a porous base material.

[0042] InkThe ink contains a solvent, a resin, and thickening particles, and further contains other components as necessary.The ink is ink that exhibits a pseudoplastic flow. As a result, after the ink is discharged onto asphalt or the like on a road surface, the viscosity of the ink increases. Therefore, the ink is less likely to penetrate into the inside of the road surface, and a coating film is thickened to improve the concealability. At a time of discharging the ink from the nozzle by the inkjet method, the viscosity of the ink decreases, and thus discharging stability is improved.Even on a wall surface of a building such as an exterior or an interior, or a wall surface of a civil structure such as a bridge or a tunnel, the viscosity of the ink increases after the ink is discharged. Therefore, painting can be performed on the wall surface with the coating film thickened and concealability improved while dripping ink is prevented.As the viscosity of the ink, the viscosity at 25°C at a shear rate of 1 S-1is preferably 1,000 mPa- s or more.

[0043] Since the ink exhibits a pseudoplastic flow, after the ink is discharged onto asphalt or the like on a road surface, a viscosity of the ink increases, so that the ink is less likely to penetrate into the inside of the road surface, and a coating film is thickened to improve the concealability. At a time of discharging the ink from the nozzle by the inkjet method, the viscosity of the ink decreases, and thus discharging stability is improved.

[0044] The viscosity of the ink at a shear rate of 1 S-1at 25°C is preferably 1,000 mPa- s or more.

[0045] The viscosity of the ink at a shear rate of 5,000 S-1at 25°C is preferably 130 mPa- s or less, and more preferably 30 mPa- s or more and 80 mPa- s or less from the viewpoint of obtaining more excellent discharging stability.

[0046] A method for measuring the viscosity is not limited in particular, and can be appropriately selected according to a purpose. For example, the viscosity can be measured by MCR 301(manufactured by Anton Paar GmbH) using a cone plate (cone radius: 25 mm, cone angle: 1°).

[0047] Thickening ParticlesThe "thickening" of the thickening particles refers to a property that, in a solution such as ink containing particles, a viscosity increases when a shear rate is decreased and the viscosity decreases when the shear rate is increased, since the solution contains the particles. The thickening indicates that, in a state where 60 g of the thickening particles are dispersed in 100 mL of water at 25°C, a viscosity at a shear rate of 0.1 S-1is 100 mPa-s or more and 900,000 mPa- s or less, a viscosity at a shear rate of 5,000 S-1is 1 mPa- s or more and 200 mPa- s or less, and the viscosity increases when the shear rate is decreased, whereas the viscosity decreases when the shear rate is increased.

[0048] Since the ink contains the thickening particles, the viscosity of the ink according to the shear rate can be controlled. Specifically, by controlling the viscosity of the ink at 25°C at a shear rate of 1 S-1to 3.00 x 103mPa- s or more and 2.50 x 104mPa- s or less, a thick coating film of the ink can be formed to obtain excellent concealability of the base material. Furthermore, by controlling the viscosity of the ink at 25°C at a shear rate of 5,000 S-1to 130 mPa-s or less, the discharging stability of the ink can be improved.

[0049] On a road surface, a wall surface of a building such as an exterior and an interior, and a wall surface of a civil structure such as a bridge and a tunnel, a coating film having resistance to impact and abrasion is desired. Therefore, it is preferable that a coating film having high robustness and resistance to impact and abrasion is obtained, by containing thickening particles.

[0050] The thickening particles are not limited in particular, and can be appropriately selected according to a purpose. Examples of the thickening particles include, but are not limited to, fumed silica, precipitated silica, diatomaceous earth, bentonite, sepiolite, talc, calcium carbonate, barium sulfate, polyethylene oxide, and the like. Each type of thickening particles above may be used alone, or two or more types of the thickening particles may be used in combination. Among these types of thickening particles, calcium carbonate and talc are preferable from the viewpoint of robustness of the ink coating film.As the thickening particles, a mixed crystal may be used.The thickening particles and a non-particulate thickener may be used in combination. Examples of the non-particulate thickener include, but are not limited to, a non-particulate thickener that is in a form of resin and melt into paint to exhibit the effect of "thickening".

[0051] The calcium carbonate is not limited in particular, and can be appropriately selected according to a purpose, and for example, a commercially available product can be used.The commercially available product is not limited in particular, and can be appropriately selected according to a purpose. Examples of the commercially available product include, but are not limited to, UP-G (manufactured by Imerys Japan Co., Ltd., solid content: 100%), LUMINUS (manufactured by Maruo Calcium Co., Ltd., solid content: 100%), CALTEX 5 (Maruo Calcium Co., Ltd., solid content: 100%), SUPER #2000 (manufactured by Maruo Calcium Co., Ltd., solid content: 100%), SUPER SSS (Maruo Calcium Co., Ltd., solid content: 100%), SOFTON 1500 (BIHOKU FUNKA KOGYO CO., LTD., solid content: 100%), SOFTON 3200 (BIHOKU FUNKA KOGYO CO., LTD., solid content: 100%), BF100 (BIHOKU FUNKA KOGYO CO., LTD., solid content: 10%), LITON A-5 (BIHOKU FUNKA KOGYO CO., LTD., solid content: 100%), and the like.

[0052] The talc is not limited in particular, and can be appropriately selected according to a purpose, and for example, a commercially available product can be used.The commercially available product is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, NANO ACE D-600 (Nippon Talc Co., Ltd., solid content: 100%) and the like.

[0053] A content of the thickening particles is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 20.0 mass% or more and 55.0 mass% or less with respect to a total amount of the ink. As a result, it becomes easier to control the viscosity of the ink.

[0054] ResinThe resin is not limited in particular, and can be appropriately selected according to a purpose. Examples of the resin an include, but are not limited to, urethane resin, a polyester resin, an acrylic resin, a vinyl acetate resin, a styrene resin, a butadiene resin, a styrenebutadiene resin, a vinyl chloride resin, an acryl- styrene resin, an acryl- silicone resin, and the like. One type of the resin may be used alone, or two or more types of the resins may be used in combination.As the resin, resin particles including these resins may be used. By bringing the resin particles into a resin emulsion state in which the resin particles are dispersed in a solvent as a dispersion medium, it is possible to mix the resin particles with a material such as a coloring material or an organic solvent, to obtain ink. The resin particles may be suitably synthesized resin particles or a commercial product. Each type of the resin particles may be used alone, or two or more types of the resin particles may be used in combination.

[0055] A glass transition temperature of the resin is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 15°C or lower, and more preferably 0°C or lower from the viewpoint of cracking of the coating film when the film is thick.

[0056] A method for measuring the glass transition temperature is not limited in particular, and can be appropriately selected according to a purpose. For example, in a case of a resin emulsion, the glass transition temperature can be determined as follows.Specifically, in a petri dish made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and having a diameter of 50 mm, 4 g of a resin emulsion is put so as to be uniformly spread, and dried at 50°C for one week to obtain a resin film. From the obtained resin film, 5.0 mg of the obtained resin film is put in an aluminum sample container, and the sample container is placed on a holder unit and set in an electric furnace.Next, under a nitrogen atmosphere, the temperature is raised from 0°C to 150°C at a temperature raising rate of 10°C / min, then the temperature is lowered from 150°C to -80°C at a temperature lowering rate of 5°C / min, and then the temperature is further raised to 150°C at a temperature raising rate of 10°C / min, and a differential scanning calorimetry (DSC) curve is measured.From the obtained DSC curve, by analyzing an inflection part at the time of the second temperature rise by a midpoint method by using an analysis program in the DSC-60 system, the glass transition temperature (Tg) is determined.

[0057] The content of the resin is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 5% by mass or more and 30% by mass or less from the viewpoint of the robustness of the dry film.The content indicates a content of a solid content of the resin.

[0058] A ratio (A / B) of a content (A) of the thickening particles to a content (B) of the solid content of the resin is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 0.8 or more, more preferably 1.0 or more, and still more preferably 1.5 or more. When the ratio (A / B) is 0.8 or more, excellent discharging stability is obtained, and a thick coating film is formed to obtain excellent concealability of the base material.

[0059] SolventThe solvent is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, an organic solvent, water, and the like.

[0060] The organic solvent is not limited in particular, and can be appropriately selected according to a purpose. Examples of the organic solvent include, but are not limited to, ethers such aspolyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, polyhydric alcohols, a nitrogen-containing heterocyclic compound, amides, amines, sulfur-containing compounds, propylene carbonate, ethylene carbonate, and the like.

[0061] The polyhydric alcohols are not limited in particular, and can be appropriately selected according to a purpose. Examples of the polyhydric alcohols include, but are not limited to, dihydric alcohols, trihydric alcohols, and the like from the viewpoint of functioning as a wetting agent and obtaining excellent discharging stability.

[0062] Examples of the dihydric alcohols include, but are not limited to, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3 -butanediol, 1,4-butanediol, 2,3- butanediol, 3-methyl-l,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3 -pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3 -hexanediol, 2,5-hexanediol, 1,5-hexanediol, and the like. Examples of the trihydric alcohols include, but are not limited to, glycerin, 1,2,6-hexanetriol, 2-ethyl-l,3-hexanediol, ethyl-l,2,4-butanetriol, 1,2, 3 -butanetriol, 2,2,4-trimethyl-l, 3- pentanediol, petriol, and the like.

[0063] The polyhydric alcohol alkyl ethers are not limited in particular, and can be appropriately selected according to a purpose. Examples of the polyhydric alcohol alkyl ethers include, but are not limited to, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, and the like.The polyhydric alcohol aryl ethers are not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and the like.

[0064] The nitrogen-containing heterocyclic compound is not limited in particular, and can be appropriately selected according to a purpose. Examples of the nitrogen-containing heterocyclic include, but are not limited to, a nitrogen-containing heterocyclic compound such as 2-pyrrolidone, N-methyl-2 pyrrolidone, N-hydroxyethyl-2 pyrrolidone, l,3-dimethyl-2 imidazolidinone, s-caprolactam, and y-butyrolactone.

[0065] The amides are not limited in particular, and can be appropriately selected according to a purpose. Examples of the amides include, but are not limited to, formamide, N- methylformamide, N, N-dimethylformamide, 3-methoxy-N, N-dimethylpropionamide, 3- butoxy-N, N-dimethylpropionamide, and the like.

[0066] The amines are not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, monoethanolamine, diethanolamine, triethylamine, and the like.

[0067] The sulfur-containing compound is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, dimethyl sulfoxide, sulfolane, thiodiethanol, and the like.

[0068] The content of the organic solvent is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 7.0 mass% or less, and more preferably 5.0 mass% or less from the viewpoint of excellent drying property.

[0069] The content of the water is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 10 mass% or more and 90 mass% or less, and more preferably 20 mass% or more and 60 mass% or less with respect to a total amount of the ink, from the viewpoint of drying property and discharging reliability of the ink.

[0070] Other ComponentsOther components are not limited in particular, and can be appropriately selected according to a purpose. Examples of other components include, but are not limited to, a surfactant, a coloring material, a defoaming agent, an antiseptic and antifungal agent, a rust inhibitor, a pH adjusting agent, a film formation aid, and the like.

[0071] SurfactantThe surfactant is not limited in particular, and can be appropriately selected according to a purpose. Examples of the surfactant include, but are not limited to, a silicone-based surfactant, a fluorine-based surfactant, an amphoteric surfactant, a nonionic surfactant, an anionic surfactant, and the like. One type of the surfactant may be used alone, or two or more types of the surfactants may be used in combination.

[0072] The silicone-based surfactant is preferably a silicone -based surfactant that does not decompose even at a high pH.The silicone-based surfactant is not limited in particular, and can be appropriately selected according to a purpose. Examples of the silicone -based surfactant include, but are not limited to, a silicone-based surfactant having a modified group such as a polyether-modified silicone-based surfactant, side chain-modified polydimethylsiloxane, both-end-modified polydimethylsiloxane, one-end-modified polydimethylsiloxane, side-chain-both-end-modified polydimethylsiloxane, and the like. One type of the silicone-based surfactant may be used alone, or two or more types of the silicone-based surfactants may be used in combination.

[0073] The modified group is not limited in particular, and can be appropriately selected according to a purpose. However, modified groups having a polyoxyethylene group and a polyoxyethylene polyoxypropylene group are preferable from the viewpoint of exhibiting good properties as an aqueous surfactant.

[0074] As the silicone-based surfactant, an appropriately synthesized silicone-based surfactant may be used, or a commercially available product may be used.The commercially available product is not limited in particular, and can be appropriately selected according to a purpose. Examples of the commercially available product include, but are not limited to, products available from BYK Japan KK, Shin-Etsu Chemical Co., Ltd., Toray Dow Coming Silicone Co., Ltd., Nihon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., and the like.

[0075] The polyether-modified silicone-based surfactant is not limited in particular, and can be appropriately selected according to a purpose. Examples of the polyether-modified silicone- based surfactant include, but are not limited to, a compound obtained by introducing a polyalkylene oxide structure into an Si moiety side chain of dimethylsiloxane.The polyether-modified silicone-based surfactant is not limited in particular, and can be appropriately selected according to a purpose. Examples of the polyether-modified silicone- based surfactant include, but are not limited to, a polyether-modified silicone-based surfactant obtained by introducing a polyalkylene oxide structure represented by the following General Formula (S-l) into an Si moiety side chain of dimethylpolysiloxane.[Chemical Formula 2](where, in General Formula (S-l), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R' represents an alkyl group)

[0076] As the polyether-modified silicone -based surfactant, a commercially available product can be used.The commercially available product is not limited in particular, and can be appropriately selected according to a purpose. Examples of the commercially available product include, but are not limited to, KF-618, KF-642, and KF-643 (manufactured by Shin-Etsu ChemicalCo., Ltd.), EMALEX-SS-5602 and SS-1906EX (manufactured by Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, and FZ-2164 (manufactured by Toray Dow Coming Silicone Co., Ltd.), BYK-33 and BYK-387 (manufactured by BYK Japan KK), TSF4440, TSF4452, and TSF4453 (manufactured by Toshiba Silicone Co., Ltd.), and the like.

[0077] The fluorine-based surfactant is not limited in particular, and can be appropriately selected according to a purpose, but is preferably a perfluoroalkylsulfonic acid compound, a perfluoroalkylcarboxylic acid compound, a perfluoroalkylphosphoric acid ester compound, a perfluoroalkylethylene oxide adduct, or a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain, from the viewpoint of small foaming property. One type of the surfactant may be used alone, or two or more types of the surfactants may be used in combination.

[0078] The perfluoroalkylsulfonic acid compound is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, perfluoroalkylsulfonic acid, perfluoroalkylsulfonic acid salt, and the like.

[0079] The perfluoroalkyl carboxylic acid compound is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, a perfluoroalkyl carboxylic acid, a perfluoroalkyl carboxylic acid salt, and the like.

[0080] The polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain is not limited in particular, and can be appropriately selected according to a purpose. Examples of the poly oxy alkylene ether polymer compound include, but are not limited to, a sulfuric acid ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in a side chain, a salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in a side chain, and the like.

[0081] A counter ion of salt in the fluorine -based surfactant is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, NH(CH2CH2OH)3, and the like.

[0082] The fluorine-based surfactant is not limited in particular, and can be appropriately selected according to a purpose, but is preferably a compound having 2 to 16 fluorine-substituted carbon atoms, and is more preferably a compound having 4 to 16 fluorine-substituted carbon atoms.Examples of the fluorine -based surfactant include, but are not limited to, a perfluoroalkylphosphoric acid ester compound, a perfluoroalkyl ethylene oxide adduct, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain, and the like. Among these fluorine -based surfactants, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain is preferable since a foaming property is low. In particular, fluorine-based surfactants represented by General Formula (F- 1) and General Formula (F-2) are preferable.[Chemical Formula 3]General Formula (F-l)(in the compound represented by General Formula (F-l) above, m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40 in order to impart water solubility) [Chemical Formula 4]C<iF.j l>... C H!C H (O H) C fiy- o - (C HJC HJO) - ¥General Formula (F-2)(in the compound represented by General Formula (F-2) above, Y is H, or m is an integer of 1 to 6 in CmFim+i, or m is an integer of 4 to 6 in CH2CH(OH)CH2 - CmF2m+i, or p is an integer of 1 to 19 in CpFhp + 1. n is an integer of 1 to 6. a is an integer of 4 to 14.

[0083] As the fluorine-based surfactant, a commercially available product may be used.The commercially available product is not limited in particular, and can be appropriately selected according to a purpose. Examples of the commercially available product include, but are not limited to: SURFLON S-l l l, S-112, S-113, S-121, S-131, S-132, S-141, and S- 145 (all of which are manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all of which are manufactured by Sumitomo 3M Limited); MEGAFACE F-470, F-1405, and F-474 (all of which are manufactured by Dainippon Ink and Chemicals, Inc); ZONYL TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, and UR, and CAPSTONE FS-30, FS-31, FS-3100, FS-34, and FS-35 (all of which are manufactured by The Chemours Company); FT-110, FT-250, FT-251, FT-400S, FT- 150, and FT-400SW (all of which are manufactured by NEOS Co. Ltd.);POLYFOX PF-136A, PF-156A, PF-151N, PF-154, and PF-159 (manufactured by OMNOVA Solutions Inc.); and UNIDYNE DSN-403N (manufactured by Daikin Industries, Ltd.).Among these products, FS-3100, FS-34, and FS-300 manufactured by The Chemours Company, FT-110, FT-250, FT-251, FT-400S, FT-150, and FT-400SW manufactured by NEOS Co. Ltd., POLYFOX PF- 15 IN manufactured by OMNOVA Solutions Inc., and UNIDYNE DSN-403N manufactured by Daikin Industries, Ltd. are preferable in particular, from the viewpoint of remarkably improving good printing quality, color developability in particular, and permeability to paper, wettability, and level dyeing property.

[0084] The amphoteric surfactant is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, laurylaminopropionate, lauryldimethylbetaine, stearyldimethylbetaine, lauryldihydroxy ethylbetaine, and the like. One type of the amphoteric surfactant may be used alone, or two or more types of the amphoteric surfactants may be used in combination.

[0085] The nonionic surfactant is not limited in particular, and can be appropriately selected according to a purpose. Examples of the nonionic surfactant include, but are not limited to, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, ethylene oxide adduct of acetylene alcohol, and the like. One type of the nonionic surfactant may be used alone, or two or more types of the nonionic surfactants may be used in combination.

[0086] The anionic surfactant is not limited in particular, and can be appropriately selected according to a purpose. Examples of the anionic surfactant include, but are not limited to, salts such as polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, and polyoxyethylene alkyl ether sulfate. One type of the anionic surfactant may be used alone, or two or more types of the anionic surfactants may be used in combination.

[0087] A content of the surfactant is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 0.001 mass% or more and 5 mass% or less, and more preferably 0.05 mass% or more and 5 mass% or less from the viewpoint of excellent wettability and discharging stability and improvement of image quality.

[0088] Color materialThe coloring material is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, a pigment and a dye. Examples of the pigment include, but are not limited to, inorganic pigments and organic pigments. Each type of the pigments may be used alone, or two or more types of the pigments may be used in combination. A mixed crystal may also be used.

[0089] The pigment is not limited in particular, and can be appropriately selected according to a purpose. Examples of the pigment include, but are not limited to, a black pigment, a yellow pigment, a magenta pigment, a cyan pigment, a white pigment, a green pigment, an orange pigment, and a glossy pigment and a metallic pigment such as gold and silver.

[0090] The inorganic pigment is not limited in particular, and can be appropriately selected according to a purpose. Examples of the inorganic pigment include, but are not limited to, titaniumoxide, iron oxide, aluminum hydroxide, barium yellow, cadmium red, chromium yellow, and carbon black produced by a known method such as a contact method, a furnace method, or a thermal method.

[0091] The organic pigment is not limited in particular, and can be appropriately selected according to a purpose. Examples of the organic pigment include, but are not limited to, an azo pigment, a polycyclic pigment (for example, a phthalocyanine pigment, a perylene pigment, a perinone pigment, an anthraquinone pigment, a quinacridone pigment, a dioxazine pigment, an indigo pigment, a thioindigo pigment, an isoindolinone pigment, quinophthalone pigment, and the like), a dye chelate (for example, a basic dye-type chelate, an acidic dye-type chelate, and the like), a nitro pigment, a nitroso pigment, aniline black, resin hollow particles, inorganic hollow particles, and the like. Among these organic pigments, an organic pigment having good affinity with a solvent are preferable.

[0092] Specifically, examples of pigment used for black-and-white printing include, but are not limited to: carbon blacks (i.e., C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper, iron (i.e., C.I. Pigment Black 11), and titanium oxide; and organic pigments such as aniline black (i.e., C.I. Pigment Black 1). Specific examples of the pigments for color include, but are not limited to, C.I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, and 213; C.I. Pigment Orange 5, 13, 16, 17, 36, 43, and 51; C.I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49: 1, 52:2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63:2, 64: 1, 81, 83, 88, 101 (rouge), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, and 264; C.I. Pigment Violet 1 (Rhodamine Lake), 3, 5: 1, 16, 19, 23, and 38; C.I. Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15: 1, 15:2, 15:3, 15:4, (Phthalocyanine Blue), 16, 17: 1, 56, 60, and 63; C.I. Pigment Green 1, 4, 7, 8, 10, 17, 18, and 36; and the like.

[0093] The pigment is preferably used by being dispersed in the ink.Examples of a method of dispersing the pigment to obtain the ink include, but are not limited to, a method of introducing a hydrophilic functional group to the pigment to make the pigment self-dispersible, a method of coating a surface of the pigment with a resin to disperse the pigment, a method of dispersing the pigment by a dispersant, and the like.Examples of the method of introducing a hydrophilic functional group to the pigment to make the pigment self-dispersible include, but are not limited to, a method of adding a functional group such as a sulfone group or a carboxyl group to a pigment (for example, carbon) such that the pigment can be dispersed in water.Examples of the method for coating a surface of the pigment with a resin to disperse the pigment include, but are not limited to, a method for making a pigment encapsulated in a microcapsule such that the pigment can be dispersed in water. In this case, the pigment may be referred to as a resin-coated pigment. In this case, it is not necessary to coat all the pigments to be used with the resin, and uncoated pigments or partially coated pigments may be contained.In the method of dispersing the pigment by the dispersant, low-molecular dispersants and high-molecular dispersants, represented by known surfactants, may be used. More specifically, any of anionic surfactants, cationic surfactants, ampholytic surfactants, nonionic surfactants, and the like may be used as the dispersant depending on the property of the pigment. RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and naphthalenesulfonic acid Na formalin condensate can also be suitably used as the dispersant. Each of the above dispersants may be used alone or in combination with others.

[0094] The dye is not limited in particular, and can be appropriately selected according to a purpose, and examples thereof include, but are not limited to, an acidic dye, a direct dye, a reactive dye, and a basic dye. Each type of the pigments may be used alone, or two or more types of the pigments may be used in combination.Specific examples of the dyes include, but are not limited to, C.I. Acid Yellow 17, 23, 42, 44, 79, and 142, C.I. Acid Red 52, 80, 82, 249, 254, and 289, C.I. Acid Blue 9, 45, and 249, C.I. Acid Black 1, 2, 24, and 94, C.I. Food Black 1 and 2, C.I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, and 173, C.I. Direct Red 1, 4, 9, 80, 81, 225, and 227, C.I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, and 202, C.I. Direct Black 19, 38, 51, 71, 154, 168, 171, and 195, C.I. Reactive Red 14, 32, 55, 79, and 249, C.I. Reactive Black 3, 4, and 35, and the like.

[0095] A content of the coloring material is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 1.0 mass% or more and 15.0 mass% or less, and more preferably 1.0 mass% or more and 10.0 mass% or less with respect to a total amount of the ink.

[0096] A 99th percentile (P99) in a range of 0.1 pm or more and 100 pm or less in a particle diameter distribution of International Organization for Standardization (ISO) max distance on a number basis in the ink is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 9 pm or less. As a result, a viscosity of the ink at a shear rate of 5,000 S-1at 25°C can be further controlled.When the P99 is 9 pm or less, a flow of ink in a flow path becomes smooth and the discharging stability can be improved when there is a flow path having a width of several tens pm to several hundreds pm, in the flow path from when the ink is supplied to when the ink is discharged by the nozzle in the printing apparatus.

[0097] A method for measuring the P99 in the particle size distribution of ISO max distance described above is not limited in particular, and can be appropriately selected according to a purpose. For example, measurement can be performed using an injection-type imageanalysis particle size distribution meter IF-3200.Specifically, by diluting the ink with water so that particles in the ink can be observed, and using the injection-type image analysis particle size distribution meter IF-3200, The P99 can be measured in a range in the range of 0.1 pm to 100 pm in particle size distribution of ISO max distance on the number basis in the particles in the ink. Since a dilution amount varies depending on an amount and a size of the particle component in the ink, it is necessary to adjust a dilution ratio so that the individual particle size in the ink can be observed. When the ink is aggregated with water, the ink may be diluted with a solvent (for example, cyclohexane or the like) with which the ink does not aggregate.

[0098] A glass transition temperature of a dried fdm (hereinafter, may be referred to as a "coating film") of the ink is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 15°C or less.A method for measuring the glass transition temperature is not limited in particular, and can be appropriately selected according to a purpose, but the glass transition temperature can be measured using a differential scanning calorimeter (TA-60WS and DSC-60, manufactured by Shimadzu Corporation).Specifically, in a petri dish made of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and having a diameter of 50 mm, first, 4 g of the ink is put so as to be uniformly spread, and dried at 50°C for one week to obtain a dried film of the ink. From the obtained dried film, 5.0 mg of the obtained dried film of ink is put in an aluminum sample container, and the sample container is placed on a holder unit and set in an electric furnace.Next, under a nitrogen atmosphere, the temperature is raised from 0°C to 150°C at a temperature raising rate of 10°C / min, then the temperature is lowered from 150°C to -80°C at a temperature lowering rate of 5°C / min, and then the temperature is further raised to 150°C at a temperature raising rate of 10°C / min, and a DSC curve is measured.From the obtained DSC curve, by analyzing an inflection part at the time of the second temperature rise by a midpoint method by using an analysis program in the DSC-60 system, the glass transition temperature (Tg) is determined.

[0099] A content of the resin in the dried film of the ink is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 10 mass% or more and 60 mass% or less.The content indicates a content of a solid content of the resin.

[0100] A content of the solid content in the ink is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 45 mass% or more, and more preferably 55 mass% or more from the viewpoint of favorable drying property and excellent concealability. The solid content is a solid component contained in the ink, and examples thereof include, but are not limited to, the thickening particles, a resin, and a pigment.

[0101] A static surface tension of the ink is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 35 mJ / m2or less, and more preferably 30 mJ / m2or less at 25 °C from the viewpoint of suitably leveling the ink on the base material and shortening a drying time of the ink.

[0102] A pH of the ink is not limited in particular, and can be appropriately selected according to a purpose, but is preferably 7 or more and 12 or less, and more preferably 8 or more and 11 or less, from the viewpoint of preventing corrosion of a metal member in contact with liquid.

[0103] Method for Manufacturing InkA method for producing the ink is not limited in particular, and can be appropriately selected according to a purpose. The ink can be obtained, for example, by dispersing or dissolving constituent components in an aqueous medium, and further stirring and mixing as necessary. The stirring and mixing can be performed using, for example, a stirrer using an ordinary stirring blade, a magnetic stirrer, a high-speed disperser, or the like.

[0104] Printing Method and Printing Apparatus

[0105] The term "inkjet printing apparatus" as used herein refers to a liquid discharge device that can discharge ink of the present embodiment, the treatment liquid, or the like onto a printing object.

[0106] Hereinafter, an example of a liquid discharge device as an inkjet printing apparatus will be described with reference to the drawings. Note that the present embodiment is not limited to the following embodiment.FIG. 6 is a schematic side view illustrating an example of a liquid discharge device as a printing apparatus according to an embodiment of the present embodiment. FIG. 7 is a schematic plan view illustrating an example of the liquid discharge device as the printing apparatus according to the embodiment of the present embodiment.A liquid discharge device 1000 is disposed so as to face a printing object 100. A carriage C is equipped with a head 300 to discharge ink as an example of liquid, toward the printing object 100. A Z-axis rail 103 holds the carriage C so that the carriage C is movable in a Z- direction.An X-axis rail 101 holds the Z-axis rail 103 such that the Z-axis rail 103 holding the carriage C is movable in an X-direction. A Y-axis rail 102 holds the X-axis rail 101 so that the X- axis rail 101 is movable in a Y-direction. Here, the X axis is an example of a "first axis", the Y axis is an example of a "second axis intersecting the first axis", and the Z axis is an example of a "third axis intersecting the first axis and the second axis". The carriage C is an example of a "liquid discharge device", and the head 300 is an example of a "liquid discharging head".

[0107] The liquid discharge device 1000 includes a Z-direction driver 92 and an X-direction driver 72. The Z-direction driver 92 moves the carriage C in the Z-direction along the Z-axis rail 103. The X-direction driver 72 moves the Z-axis rail 103 in the X-direction along the X-axis rail 101. The liquid discharge device 1000 further includes a Y-direction driver 82 that moves the X-axis rail 101 in the Y-direction along the Y-axis rail 102. The Z-direction driver 92 is an example of a "first driver", and moves the carriage C in the direction of the Z axis intersecting the X axis and the Y axis. The movement of the carriage C and the head 300 in the direction of the Z-axis may not be parallel to the Z-direction, and may be an oblique movement as long as the movement includes at least a component in the Z-direction. The carriage C further includes another Z-direction driver 93. The Z-direction driver 93 is an example of a "second driver", and moves the head 300 in the direction of the Z-axis with respect to the carriage C.The liquid discharge device 1000 configured as described above discharges ink from the head 300 toward the printing object 100 while moving the carriage C in the directions of the X- axis, Y-axis, and Z-axis, and performs drawing on the printing object 100. Note that the printing object 100 is illustrated in the form of a flat plate, but may be a surface close to vertical or a surface having a large radius of curvature, such as an automobile, a truck, or an aircraft.

[0108] Base MaterialThe base material (hereinafter, may be referred to as a "printing object") means a target object to be printed using the ink of the present embodiment, and means an object to which the ink or the treatment liquid can be at least temporarily attached.The base material is not limited in particular, and can be appropriately selected according to a purpose, but a road surface, an exterior, and a porous base material are preferable.A shape, a structure, and a material of the base material are not limited in particular, and can be appropriately selected according to a purpose. Examples include, but are not limited to, siding (ceramic -based, resin-based, wood-based, and metal-based), asphalt, asphalt felt, concrete, glass, cloth, paper, plastic, wood, metal (brass, iron, aluminum, stainless steel (SUS), copper, and the like), a material obtained by subjecting a non-metal base material to metal coating treatment by a technique such as vapor deposition, and the like.

[0109] Examples of the porous base material include, but are not limited to, a base material having high ink permeability, such as asphalt or sponge.Examples

[0110] Hereinafter, examples of the present embodiment will be described, but the present embodiment is not limited to these examples at all.

[0111] Production of Nozzle 1By performing coating with use of OPTOOL DSX (manufactured by Daikin Industries, Ltd.) by a dipping method on a LETTER ROBO head (head mounted on LETTER ROBO, manufactured by Ricoh Digital Painting Company, Ltd.) after improvement in which a nozzle diameter is made 300 pm, a liquid repellent layer containing fluorine and having a fdm thickness of 0.01 pm was formed as illustrated in FIG. 3. At this time, a portion where the liquid repellent layer containing fluorine was not to be formed was masked with a water- soluble resin or a tape. After the liquid repellent layer containing fluorine was applied and formed, the masking was peeled off. Heating was performed at 120°C for one hour to apply and form the liquid repellent layer containing fluorine, to produce a nozzle 1 (nozzle diameter: 300 pm). A layer containing fluorine and having a film thickness of 0.01 pm was formed on a SUS plate by a similar method, and surface free energy was measured and found to be 13 mJ / m2.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0112] Production of Nozzle 2A nozzle 2 (nozzle diameter: 300 pm) was produced by a method similar to the method for producing the nozzle 1 except that a liquid repellent layer containing fluorine and having a fdm thickness of 0.01 pm was formed as illustrated in FIG. 2 by coating by a dipping method. A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0113] Production of Nozzle 3A nozzle 3 (nozzle diameter: 300 pm) was produced by a method similar to the method for producing the nozzle 1 except that a liquid repellent layer containing fluorine and having a fdm thickness of 0.01 pm was formed as illustrated in FIG. 1 by coating by a dipping method. A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0114] Production of Nozzle 4Using DOWSIL SR2400 Resin (manufactured by Dow Toray Co., Ltd.), a liquid repellent layer containing silicon is formed as illustrated in FIG. 3 by depositing about 1 mg / cm2by the dipping method. At this time, a portion where the layer containing silicon was not to be formed was masked with a water-soluble resin or a tape. After the liquid repellent layer containing silicon was applied and formed, the masking was peeled off. Heating and curing were performed at 150°C for two hours to apply and form the liquid repellent layer containing silicon, to produce a nozzle 4 (nozzle diameter: 300 pm). A liquid repellent layer containing silicon deposited about 1 mg / cm2was formed by a similar method, and the surface free energy was measured and found to be 22 mJ / m2.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0115] Production of Nozzle 5A nozzle 5 (nozzle diameter: 300 pm) was produced by a method similar to the method for producing the nozzle 4 except that a liquid repellent layer containing silicon is formed as illustrated in FIG. 2 by depositing about 1 mg / cm2by the dipping method.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0116] Production of Nozzle 6A nozzle 6 (nozzle diameter: 300 pm) was produced by a method similar to the method for producing the nozzle 4 except that a liquid repellent layer containing silicon is formed as illustrated in FIG. 1 by depositing about 1 mg / cm2by the dipping method.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0117] Production of Nozzle 7A nozzle 7 (nozzle diameter: 50 pm) was produced by a method similar to the method for producing the nozzle 1 except that the nozzle diameter is 50 pm.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0118] Production of Nozzle 8A nozzle 8 (nozzle diameter: 600 pm) was produced by a method similar to the method for producing the nozzle 1 except that the nozzle diameter is 600 pm.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0119] Production of Nozzle 9A nozzle 9 (nozzle diameter: 900 m) was produced by a method similar to the method for producing the nozzle 1 except that the nozzle diameter is 900 pm.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0120] Production of Nozzle 10A liquid repellent layer containing polyimide and having a film thickness of 0.3 pm was formed by coating by a dipping method using KEMITITE CT4112 (manufactured by Kyocera Chemical Co., Ltd.) mainly containing polyamic acid, which is a precursor of polyimide, as illustrated in FIG. 3. At this time, a portion where the polyimide layer was not to be formed was masked with a water-soluble resin, a tape, or the like. After the polyimide liquid repellent layer was applied and formed, the masking was peeled off. After the temperature was gradually raised to 110°C and heating was performed for 60 minutes, heating was performed at 200°C for 20 minutes, and the temperature was further gradually raised to 360°C and heating was performed for 60 minutes to form a polyimide layer, to produce a nozzle 10 (nozzle diameter: 300 pm). A polyimide liquid repellent layer having a film thickness of 0.3 pm was formed on a SUS plate by a similar method, and surface free energy was measured and found to be 50 mJ / m2.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0121] Production of Nozzle 11A nozzle 11 (nozzle diameter: 300 pm) was produced by a method similar to the method for producing the nozzle 10 except that the liquid repellent layer was formed as illustrated in FIG. 2.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0122] Production of Nozzle 12A nozzle 12 (nozzle diameter: 300 pm) was produced by a method similar to the method for producing the nozzle 10 except that the liquid repellent layer was formed as illustrated in FIG. 1.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0123] Production of Nozzle 13A nozzle 13 (nozzle diameter: 300 pm) was produced, which includes a base containing SUS on which a liquid repellent layer is not formed, a nozzle hole, a liquid chamber, and a needle valve. Surface free energy of SUS was measured and found to be 33 mJ / m2.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0124] Production of Nozzle 14As illustrated in FIG. 8, a nozzle 14 (nozzle diameter: 300 pm) was produced, which includes a base containing SUS, a nozzle hole, a liquid chamber, and a needle valve having a tip end covered with perfluoroelastomer having a thickness of 200 pm.A shape of the produced nozzle, a compound contained in the water repellent layer, surface free energy of the water repellent layer, and a nozzle diameter are illustrated in Table 1.

[0125] [Table 1]

[0126] Preparation of White Pigment DispersionA mixture was premixed, including: 200 parts by mass of C.I. Pigment White 6 (manufactured by TAYCA CORPORATION, product name "JR-403", number average primary particle diameter 250 nm, aspect ratio 2, surface treatment: Al, Si) as a pigment; 56 parts by mass of a pigment dispersant (trade name: TEGO Dispers 651, manufactured by Evonik Industries AG); and 744 parts by mass of distilled water.Thereafter, using a bead mill disperser (UAM-015 manufactured by Kotobuki Industries Co., Ltd.), dispersion was performed at a peripheral speed of 10 m / s and a liquid temperature of 30°C for 15 minutes by using zirconia beads having a diameter of 0.03 mm (density 6.03 x 10-6 g / m2), and then coarse particles were centrifuged using a centrifuge (Model-3600manufactured by KUBOTA Corporation), to obtain a white pigment dispersion (solid content: 20.0 mass%) having an average particle diameter of 250 nm.

[0127] Preparation of Cyan Pigment DispersionIn an automatic polymerization reactor (manufactured by TOROU SANGYO CO., LTD.: polymerization tester DSL-2AS model) including a reaction vessel equipped with: a stirring device; a dropping device; a temperature sensor; and a reflux device having a nitrogen introduction device in an upper portion, 550 g of methyl ethyl ketone was added to the reaction vessel, and the inside of the reaction vessel was purged with nitrogen while being stirred.Thereafter, the inside of the reaction vessel was heated to 80°C while being maintained in a nitrogen atmosphere, and then a mixed solution was added dropwise over four hours by a dropping device. The mixed solution was a mixed solution of 75.0 g of methacrylic acid 2- hydroxyethyl, 77.0 g of methacrylic acid, 80.0 g of styrene, 150.0 g of butyl methacrylate, 98.0 g of butyl acrylate, 20.0 g of methyl methacrylate, and 40.0 g of "PERBUTYL (registered trademark) O" (manufactured by NOF CORPORATION).After completion of the dropwise addition, the reaction was further continued at the same temperature for 15 hours to obtain a methyl ethyl ketone solution of an anionic group - containing styrene- acrylic copolymer having an acid value of 100, a weight average molecular weight of 21,000, and a Tg (calculated value) of 31°C. After completion of the reaction, a part of methyl ethyl ketone was distilled off under reduced pressure, to obtain a copolymer solution in which a nonvolatile content was adjusted to 50%.A mixing tank equipped with a cooling jacket was charged with 1,000 g of copper phthalocyanine (SEIKALIGHT BLUE A612 manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), 800 g of the copolymer solution, 143 g of a 10% aqueous sodium hydroxide solution, 100 g of methyl ethyl ketone, and 1,957 g of water, and the mixture was stirred and mixed to obtain a mixed liquid.The obtained mixed liquid was passed through a dispersing device (SC Mill SC 100 manufactured by Mitsui Mining Co., Ltd.) filled with zirconia beads having a diameter of 0.3 mm, and dispersed under the condition of a rotation speed of 2,700 rpm, 40°C or lower (a constant temperature was set by passing cold water through the cooling jacket) for six hours by a circulation system (a system in which the dispersion liquid discharged from the dispersing device was returned to the mixing tank).After completion of the dispersion, the dispersion stock solution was removed from the mixing tank, and then the mixing tank and a channel of the dispersing device were washed with 10,000 g of water. The water was mixed with the dispersion stock solution, to obtain a diluted dispersion liquid.The obtained diluted dispersion liquid was put in a glass distillation device, and a total amount of methyl ethyl ketone and a part of water were distilled off. After cooling to roomtemperature, 10% hydrochloric acid was added dropwise with stirring to adjust the pH to 4.5, and then a solid content was filtered with a Nutsche filter (a filter dryer manufactured by Nippon Chemical Industrial Co., Ltd.) and washed with water. The cake was placed in a container, 200 g of a 20% aqueous potassium hydroxide solution was added thereto, then the mixture was dispersed with a disper (TK homodisper manufactured by Tokushu Kika Kogyo Co., Ltd.), and water was further added thereto to adjust a nonvolatile content. As a result, a cyan pigment dispersion (concentration of pigment-containing material: 20.0 mass%) containing composite particles (pigment-containing material) was obtained, in which copper phthalocyanine was coated with a carboxyl group -containing styrene-acrylic copolymer neutralized in potassium hydroxide.

[0128] Preparation of Resin EmulsionA mixture was emulsified with a batch-type homomixer to prepare a monomer pre-emulsion. The mixture was a mixture of 55.4 parts by mass of methyl methacrylate as a monomer, 44.6 parts by mass of 2-ethylhexyl acrylate, 1.5 parts by mass of AQUALON KH-20 (manufactured by DKS Co., Ltd.) as an emulsifier, and 53.1 parts by mass of ion-exchanged water.Into a four-necked flask having a volume of 2 L and equipped with a stirrer, a nitrogen inlet tube, a reflux condenser, a thermometer, and a raw material inlet, 89.4 parts by mass of ion- exchanged water was put and stirred, while nitrogen is introduced and the liquid temperature was warmed to 60°C.Into the reaction vessel, 0.5 parts by mass of AQUALON KH20 as an emulsifier and 6 parts by mass of a 5% ammonium persulfate aqueous solution (0.3 parts by mass of ammonium persulfate) were added.Thereafter, 10 minutes after the 5% aqueous ammonium persulfate solution was added to the reaction vessel, the monomer pre-emulsion was continuously added dropwise from the dropping tank over five hours, and 6 parts (0.3 parts as ammonium persulfate) of the 5% aqueous ammonium persulfate solution was intermittently added dropwise from another dropping tank at 70°C over five hours. After completion of the dropwise addition, aging was performed with the temperature maintained at 70°C for three hours.Thereafter, the mixture was cooled to 50°C, ammonia water was added, and the mixture was filtered with a 180 mesh polyester filter cloth to obtain a resin emulsion A.A part of the obtained resin emulsion A was dried at 150°C for 30 minutes, and the solid content concentration was measured in accordance with Japanese Industrial Standards (JIS) K5601-1-2, and found to be 50.0%. A glass transition temperature of the resin emulsion A was measured by the following method and found to be 0°C.

[0129] Measurement of Glass Transition Temperature (Tg) of Resin EmulsionSpecifically, in a petri dish made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and having a diameter of 50 mm, 4 g of a resin emulsion was put so as to be uniformly spread, and dried at 50°C for one week to obtain a resin film. From the obtained resin film, 5.0 mg of the obtained resin film was put in an aluminum sample container, and the sample container was placed on a holder unit and set in an electric furnace.Next, under a nitrogen atmosphere, the temperature was raised from 0°C to 150°C at a temperature raising rate of 10°C / min, then the temperature was lowered from 150°C to -80°C at a temperature lowering rate of 5°C / min, and then the temperature was further raised to 150°C at a temperature raising rate of 10°C / min, and a DSC curve was measured.From the obtained DSC curve, by analyzing an inflection part at the time of the second temperature rise by a midpoint method by using an analysis program in the DSC-60 system, the glass transition temperature (Tg) was determined.

[0130] Production of Ink 1A mixture was obtained by mixing 5.0 mass% of propylene glycol and 9.0 mass% of ion- exchanged water as solvents, 30.0 mass% of the resin emulsion A as a resin, and 20.0 mass% of the white pigment dispersion as a coloring material, and the mixture was stirred for 30 minutes so as to be uniform. Then, 36.0 mass% of calcium carbonate (UP-G, manufactured by Imerys Japan Co., Ltd.) as thickening particles was added, and the mixture was further stirred at high speed for one hour so as to be uniform, thereby obtaining ink 1.

[0131] Production of Ink 2A mixture was obtained by mixing 5.0 mass% of propylene glycol and 2.0 mass% of ion- exchanged water as solvents, 33.0 mass% of the resin emulsion A as a resin, and 20.0 mass% of the white pigment dispersion as a coloring material, and the mixture was stirred for 30 minutes so as to be uniform. Then, 40.0 mass% of calcium carbonate (UP-G, manufactured by Imerys Japan Co., Ltd.) as thickening particles was added, and the mixture was further stirred at high speed for one hour so as to be uniform, thereby obtaining ink 2.

[0132] Production of Ink 3A mixture was obtained by mixing 5.0 mass% of propylene glycol and 20.0 mass% of ion- exchanged water as solvents, 35.0 mass% of the resin emulsion A as a resin, and 20.0 mass% of the white pigment dispersion as a coloring material, and the mixture was stirred for 30 minutes so as to be uniform. Then, 20.0 mass% of calcium carbonate (UP-G, manufactured by Imerys Japan Co., Ltd.) as thickening particles was added, and the mixture was further stirred at high speed for one hour so as to be uniform, thereby obtaining ink 3.

[0133] Production of Ink 4A mixture was obtained by mixing 14.0 mass% of ion-exchanged water as a solvent, 30.0 mass% of the resin emulsion A as a resin, and 20.0 mass% of the white pigment dispersion as a coloring material, and the mixture was stirred for 30 minutes so as to be uniform. Then, 36.0 mass% of calcium carbonate (UP-G, manufactured by Imerys Japan Co., Ltd.) as thickening particles was added, and the mixture was further stirred at high speed for one hour so as to be uniform, thereby obtaining ink 4.

[0134] Production of Ink 5A mixture was obtained by mixing 4.0 mass% of propylene glycol and 10.0 mass% of ion- exchanged water as solvents, 30.0 mass% of the resin emulsion A as a resin, and 20.0 mass% of the cyan pigment dispersion as a coloring material, and the mixture was stirred for 30 minutes so as to be uniform. Then, 36.0 mass% of calcium carbonate (UP-G, manufactured by Imerys Japan Co., Ltd.) as thickening particles was added, and the mixture was further stirred at high speed for one hour so as to be uniform, thereby obtaining ink 5.

[0135] Viscosity of inkFor the viscosity of the ink, by using MCR 301 (manufactured by Anton Paar GmbH) with a cone plate (cone radius: 25 mm, cone angle: 1°), a viscosity (mPa-s) at a shear rate of 1 S-1at 25°C, a viscosity (mPa- s) at a shear rate of 5,000 S-1at 25°C, and a viscosity (mPa- s) at a shear rate of 0.1 S-1at 25°C were measured. The viscosities of the ink 1 to 5 were as illustrated in Table 1. A unit of each numeral of the compositions in Table 1 indicates "% by mass".

[0136] [Table 2]

[0137] Example 1The following "discharging stability after uncapping" was evaluated for a combination of the nozzle 1 and the ink 1. The results are illustrated in Table 2.

[0138] Discharging Stability After UncappingAfter setting the ink in various heads and initially discharging the ink for three minutes, the ink was exposed to the atmosphere without capping the nozzle for 10 minutes and 20 minutes. Then, discharging evaluation was performed again for three minutes, and the discharging stability was evaluated based on the following evaluation criteria. An evaluation result having the discharging stability of "C" or more is in a practical range.Evaluation CriteriaA: No bending or shaking of the discharging occurs, and the discharging can be stably performed.B: Bending or shaking of the discharging may slightly occur, but the discharging can be stably performed.C: Bending or shaking of discharging may occur, but a degree of bending or shaking is within an allowable range.D: Bending or shaking of discharging may occur, and stable discharging cannot be performed or discharging cannot be performed.

[0139] Examples 2 to 13 and Comparative Examples 1 to 5The "discharging stability after uncapping" in Example 1 was evaluated with a combination of the nozzle and the ink described in Table 2. The results are illustrated in Table 3.

[0140] [Table 3]

[0141] Aspects of the present embodiment are, for example, as follows.Aspect 1According to Aspect 1, a liquid discharge device includes a nozzle unit that discharges high- viscosity liquid, in which the nozzle unit includes a nozzle hole, a nozzle plate having the nozzle hole, a liquid chamber that supplies liquid to the nozzle hole, and a needle valve that closes or opens the nozzle hole with a tip end while moving forward and backward in the liquid chamber, and on a surface of the nozzle plate, a liquid repellent layer having surface free energy of less than 29 mJ / m2is provided.Aspect 2According to Aspect 2, the liquid discharge device of Aspect 1 further includes a liquid repellent layer on an outer surface of the nozzle plate and on a surface on which the nozzle hole is formed.Aspect 3According to Aspect 3, the liquid discharge device of Aspect 1 or Aspect 2 further includes a liquid repellent layer on an inner surface of the nozzle plate.Aspect 4According to Aspect 4, the liquid discharge device of any one of Aspect 1 to Aspect 3 further includes a liquid repellent layer at a tip end of the needle valve.Aspect 5According to Aspect 5, in the liquid discharge device of any one of Aspect 1 to Aspect 4, the liquid repellent layer contains at least one of silicon (Si) or fluorine (F).Aspect 6According to Aspect 6, in the liquid discharge device of Aspect 5, the liquid repellent layer contains at least one of a fluorine-modified hydrocarbon or an organosilicon compound. Aspect 7According to Aspect 7, in the liquid discharge device of Aspect 5, the liquid repellent layer contains a fluorine-modified hydrocarbon in which a silanol group is condensed and bonded. Aspect 8According to Aspect 8, in the liquid discharge device of Aspect 5, the liquid repellent layer contains a siloxane polymer having a siloxane bond as a main chain and an organic group in a side chain.Aspect 9According to Aspect 9, in the liquid discharge device of any one of Aspect 1 to Aspect 8, the nozzle hole has a diameter of 50 pm or more.Aspect 10According to Aspect 10, a printing apparatus includes a discharging means that discharges liquid from the liquid discharge device of any one of Aspect 1 to Aspect 9.Aspect 11According to Aspect 11, in the printing apparatus of Aspect 10, a solid content of the liquid is 45 mass% or more.Aspect 12According to Aspect 12, in the printing apparatus of Aspect 10 or Aspect 11, the liquid is ink or paint.Aspect 13According to Aspect 13, a printing method includes a discharging step of discharging high- viscosity liquid from the liquid discharge device of any one of Aspect 1 to Aspect 9. The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and / or features of different illustrative embodiments may be combined with each other and / or substituted for each other within the scope of the present invention. Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above.This patent application is based on and claims priority to Japanese Patent Application No. 2023-203108, filed on November 30, 2023, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.[Reference Signs List]

[0142] 1 base2 nozzle hole3 nozzle plate4 liquid chamber5 needle valve6 liquid repellent layer7 elastic body diaphragm8 movable iron core9 drive mechanism accommodation space10 spring material11 fixed iron core12 solenoid13 pressurizing passage14 screw rattling preventing spring15 gap adjustment bolt16 nut17 ink tank18 pump20 circulation path21 ink output passageC carriage72 X-direction driver82 Y-direction driver92 Z-direction driver93 Z-direction driver100 printing object101 X-axis rail102 Y-axis rail103 Z-axis rail300 head1000 liquid discharge device[Citation List][Patent Literature]

[0143] [PTL 1]Japanese Unexamined Patent Application Publication No. 2022-64482

Claims

CLAIMS[CLAIMS]

1. A liquid discharge device comprising: a nozzle plate having a nozzle hole to discharge a liquid; a liquid chamber to supply the liquid to the nozzle hole; a needle valve having a tip end to move forward and backward in the liquid chamber to close or open the nozzle hole with the tip end; and a liquid repellent layer on a surface of the nozzle plate, the liquid repellent layer having surface free energy of less than 29 mJ / m2.

2. The liquid discharge device according to claim 1, wherein the liquid repellent layer is on: an outer surface of the nozzle plate; and a nozzle hole surface of the nozzle hole.

3. The liquid discharge device according to claim 1 or 2, wherein the liquid repellent layer is further on an inner surface of the nozzle plate.

4. The liquid discharge device according to claim 1 or 2, wherein the needle valve includes another liquid repellent layer on the tip end of the needle valve.

5. The liquid discharge device according to claim 1 or 2, wherein the liquid repellent layer includes at least one of silicon (Si) or fluorine (F).

6. The liquid discharge device according to claim 5, wherein the liquid repellent layer includes at least one of a fluorine-modified hydrocarbon or an organosilicon compound.

7. The liquid discharge device according to claim 5, wherein the liquid repellent layer includes a fluorine-modified hydrocarbon including a silanol group condensed and bonded.

8. The liquid discharge device according to claim 5, wherein the liquid repellent layer includes a siloxane polymer having: a siloxane bond as a main chain; and an organic group as a side chain.

9. The liquid discharge device according to claim 1 or 2, wherein the nozzle hole has a diameter of 50 pm or more.

10. A printing apparatus comprising the liquid discharge device according to claim 1 or 2 to discharge the liquid onto a medium.

11. The printing apparatus according to claim 10, wherein a solid content of the liquid is 45 mass% or more.

12. The printing apparatus of claim 10, wherein the liquid includes ink or paint.

13. A printing method comprising: discharging a liquid from the liquid discharge device according to claim 1 or 2.

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