Inkjet head, inkjet head manufacturing method and printing device

Abstract

To maintain stable liquid repellency over time.SOLUTION: An inkjet head 10 includes: a nozzle plate 11 formed with nozzles 12; pressure chambers 14 each of which communicates with the nozzle 12; a compression chamber 30 which compresses the pressure chambers 14; and a diaphragm 17 which transmits energy generated by the compression part 30 to the pressure chambers 14. A liquid repellent film 50 formed by a diamond-like carbon film, to which fluorine is added, is formed on an outer surface 11a of the nozzle plate 11.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to an inkjet head, a method for manufacturing an inkjet head, and a printing apparatus. [Background technology]

[0002] Inkjet printing devices that eject droplets from the nozzles of an inkjet head to form an image on a recording medium have been known for some time. When droplets are ejected from the nozzles of an inkjet head, ink may adhere to the periphery of the nozzle's ejection opening. This can cause the droplets to be ejected at a curved angle.

[0003] Therefore, for example, in Patent Document 1, a nozzle plate is formed by forming a silicone resin layer on an organic film using a silane coupling agent, an alkoxysilane compound, and a fluoroalkylsilane compound, and then forming a fluororesin layer on the silicone resin layer using a fluororesin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-230061 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the liquid-repellent properties of the nozzle surface are essential for stable droplet ejection, and therefore the liquid-repellent film must be stable over time. However, the conventional liquid-repellent film shown in Patent Document 1, for example, had the problem of poor stability over time when ink came into contact with it. In particular, the liquid-repellent properties of conventional liquid-repellent films quickly deteriorate when exposed to ink containing dispersed particles of inorganic compounds such as titanium oxide. This is because titanium oxide particles are hard and have an abrasive effect, which can wear away the liquid-repellent film.

[0006] The present invention has been made in view of the above points, and aims to provide an inkjet head that maintains stable liquid repellency over time even when ink containing an inorganic compound is used. [Means for solving the problem]

[0007] An inkjet head according to one aspect of the present disclosure includes a nozzle plate having nozzles formed therein, a pressure chamber communicating with the nozzles, a pressure applying unit for applying pressure to the pressure chamber, and a vibration plate for transmitting energy generated in the pressure applying unit to the pressure chamber, and a liquid-repellent film made of a diamond-like carbon film doped with fluorine is formed on the outer surface of the nozzle plate.

[0008] A printing device according to another aspect of the present disclosure includes the inkjet head described in the above aspect, a control unit that controls the ejection operation of the inkjet head, and a transport unit that moves the inkjet head and the printing medium relative to each other.

[0009] Another aspect of the present disclosure relates to a method for manufacturing an inkjet head that ejects droplets from nozzles formed in a nozzle plate and causes the droplets to land on a print medium, the method including a liquid-repellent film process for forming a liquid-repellent film made of a fluorine-added diamond-like carbon film on an outer surface of the nozzle plate, and a nozzle process for forming the nozzles in the nozzle plate on which the liquid-repellent film has been formed. [Effects of the Invention]

[0010] According to the present disclosure, a liquid-repellent film made of a fluorine-doped diamond-like carbon film is formed on the outer surface of the nozzle plate, which allows the ink to maintain stable liquid repellency over time even when a liquid containing an inorganic compound is ejected from the inkjet head. [Brief explanation of the drawings]

[0011] [Figure 1A] Schematic cross-sectional view showing the structure of an inkjet head [Figure 1B] A cross-sectional view showing the detailed positional relationship between the liquid-repellent film and the nozzle in Figure 1A. [Figure 1C] Cross section of Figure 1A along line AA [Figure 1D] View of the inkjet head from the print medium side [Figure 1E] FIG. 1B shows another example of the configuration of an inkjet head. [Figure 1F] FIG. 1B shows another example of the configuration of an inkjet head. [Figure 2] FIG. 10 is a diagram showing an example of the fluorine concentration of the liquid-repellent film of an inkjet head. [Figure 3] FIG. 10 is a diagram showing an example of the contact angle of the liquid-repellent film of an inkjet head. [Figure 4] Flowchart for explaining a manufacturing method of an inkjet head [Figure 5] FIG. 10 is a diagram showing the contact angle of the liquid-repellent film of the inkjet head according to the first embodiment. [Figure 6] FIG. 10 is a diagram showing the contact angle of the liquid-repellent film of the inkjet head according to Comparative Example 1. [Figure 7] FIG. 1 is a diagram showing a droplet ejection state of the inkjet head according to the first embodiment; [Figure 8] 1B according to another embodiment. [Figure 9] FIG. 10 is a diagram showing the state of droplet ejection from the inkjet head when a chip occurs. [Figure 10] FIG. 1 is a plan view showing the configuration of a printing device; [Figure 11] A side view showing the configuration of a printing device DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a preferred specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the superordinate concept of the present disclosure will be described as optional components.

[0013] <Inkjet head> FIG. 1 (FIGS. 1A to 1D) shows an example of the configuration of an inkjet head 10. As shown in FIG.

[0014] The inkjet head 10 of the present disclosure ejects ink droplets from nozzles formed in a nozzle plate 11, causing the droplets to land on a print medium. The ink to be ejected is not particularly limited. For example, (1) quantum dot luminescent ink containing quantum dot semiconductor particles or white decorative ink containing titanium oxide, (2) functional ink for constructing perovskite solar cells, (3) conductive ink containing metal nanoparticles, (4) biological ink containing cells, etc. may be ejected. Note that the inkjet head 10 may also eject liquids other than ink.

[0015] The inkjet head 10 includes a nozzle plate 11 in which one or more nozzles 12 are formed, a pressure chamber 14, a pressure unit 30, and a vibration plate 17. The inkjet head 10 is used to cause ink droplets 70 (see FIG. 7) ejected from the nozzles 12 to land on a print medium (not shown).

[0016] In the following description, the longitudinal direction of the inkjet head 10 is referred to as the Y direction, and the width direction perpendicular to the longitudinal direction is referred to as the X direction. The direction perpendicular to the X and Y directions is referred to as the Z direction. In the present disclosure, the nozzle plate 11 is arranged along the X and Y directions.

[0017] -Nozzle plate- As described above, the nozzle plate 11 is formed with nozzles 12 for ejecting ink contained in the pressure chambers 14 as droplets. The material of the nozzle plate 11 is not particularly limited, but is, for example, a metal such as stainless steel. The nozzles 12 are through-holes that are circular in plan view and that penetrate the nozzle plate 11 in the Z direction.

[0018] The diameter R of the nozzle 12 is, for example, about 5 to 50 μm. The nozzle 12 is formed by using, for example, laser processing, etching, or punching.

[0019] The shape of the nozzle 12 does not have to be a straight shape in cross section as shown in FIG. 1B. For example, as shown in the cross section of FIG. 1E, the nozzle 12 may have a so-called "cone shape" in which the opening of the nozzle 12 tapers gradually toward the outlet 12a. Alternatively, as shown in the cross section of FIG. 1F, the nozzle 12 may have a so-called "funnel shape" in which the opening of the nozzle 12 tapers gradually toward the outlet 12a and then becomes straight in cross section. The shapes of FIGS. 1E and 1F can be suitably realized by forming the nozzle 12 using laser processing.

[0020] Furthermore, as shown in FIG. 1A, the nozzle plate 11 may form part of the outer wall that defines the pressure chamber .

[0021] -Water-repellent film- The nozzle plate 11 has a liquid-repellent film 50 formed on its outer surface 11a (hereinafter simply referred to as the outer surface 11a) that faces the print medium, the liquid-repellent film 50 having ink-repellent properties (liquid-repellency).

[0022] The liquid-repellent film 50 is made of a diamond-like carbon film containing fluorine. The thickness of the liquid-repellent film 50 is not particularly limited, but is, for example, about 50 nm to 300 nm. If the liquid-repellent film 50 is too thin, the liquid repellency will be poor. On the other hand, if the liquid-repellent film 50 is too thick, the film stress will be large, causing the nozzle plate 11 to warp. In this warped state, it will be difficult to adhere the nozzle plate 11 to other components (e.g., the flow path plate 16) when assembling the inkjet head 10. By using a diamond-like carbon film containing fluorine as the liquid-repellent film 50, it will have excellent abrasion resistance.

[0023] Some inks contain particles of inorganic compounds such as titanium oxide. In conventional technology, titanium oxide can scrape away the liquid-repellent film, degrading the liquid-repellent properties. If the liquid-repellent properties around the nozzle are impaired, the ink spreads around the nozzle, preventing the formation of an appropriate meniscus. This prevents the inkjet head 10 from ejecting ink stably. In contrast, the inkjet head 10 of this embodiment uses a diamond-like carbon film, which makes the liquid-repellent film 50 wear-resistant, eliminating the problems associated with the conventional technology.

[0024] 1B and 1D, the liquid-repellent film 50 is formed with a gap secured to the nozzle 12. That is, the liquid-repellent film 50 is not formed within a certain distance L around the ejection port 12a of the nozzle 12. In other words, at the ejection port of the nozzle 12, a step portion 60 is provided between the outer surface 11a of the nozzle plate 11 and the surface 50a of the liquid-repellent film 50.

[0025] The gap is not particularly limited, but is, for example, about 10 nm to 500 nm, and more preferably 200 nm or less. The gap is set to about 500 nm because if the gap is too large, the wettability around the nozzle 12 increases, and there is a risk that the ink will wet and spread.

[0026] The liquid-repellent film 50 has a gradient in fluorine concentration in the depth direction D (Z direction). Specifically, the fluorine concentration is higher toward the surface 50a of the liquid-repellent film 50 and decreases toward the bottom surface (the surface in contact with the nozzle plate 11). For example, the fluorine concentration present in the liquid-repellent film 50 is approximately 1.0 atom % to 2.0 atom % near the surface and approximately 0.2 atom % to 0.5 atom % near the bottom surface.

[0027] Fig. 2 shows the results of measuring the fluorine concentration of the liquid-repellent film 50. The fluorine concentration was measured by energy dispersive X-ray spectroscopy (EDX). As shown in Fig. 2, it was found that fluorine was present at a concentration of 1.4 atomic % (atom %) near the surface of the liquid-repellent film 50 and at a concentration of 0.3 atomic % (atom %) near the bottom surface.

[0028] By providing the above-described fluorine concentration gradient, it is possible to improve the adhesion between the outer surface 11a of the nozzle plate 11 and the bottom surface of the liquid-repellent film 50, while ensuring the liquid repellency of the surface 50a of the liquid-repellent film 50. In addition, the ink meniscus can be formed more stably in the nozzle 12.

[0029] The relationship between contact angles α, β, and γ with respect to the ink droplet 70 is expressed by Equation 1. Contact angle α is the contact angle of the ink droplet 70 with the surface 50a of the liquid-repellent film 50. Contact angle β is the contact angle of the ink droplet 70 with the side surface 50b of the liquid-repellent film 50. Contact angle γ is the contact angle of the ink droplet 70 with the outer surface 11a of the nozzle plate 11. [Formula 1] Contact angle α > Contact angle β > Contact angle γ

[0030] There are two types of contact angles: static angle and receding angle. The static angle and receding angle will be explained below.

[0031] When a drop of liquid is dropped onto a solid surface, the liquid becomes round due to its own surface tension, and the relationship shown in [Equation 2] holds. [Equation 2] is called Young's equation. [Formula 2] γs = γL × cosθ + γSL γs: Surface tension of the solid γL: Surface tension of the liquid γSL: Interfacial tension between solid and liquid

[0032] The angle θ formed by the tangent of the ink droplet 70 and the solid surface at this time is called the contact angle. In particular, the contact angle when the liquid is stationary on the solid surface and has reached an equilibrium state is called the static angle.

[0033] On the other hand, when the interface between the liquid and solid is moving, i.e., when the interface of the droplet is moving, the contact angle is called the "advancing angle" and the "receding angle." Here, we focus on the receding angle, which is the dynamic contact angle after the solid surface is wetted with the liquid. The receding angle of the liquid-repellent film 50 relative to the ink is, for example, 30 degrees or more.

[0034] Figure 3 shows an example comparing the values ​​of the aforementioned contact angles α, β, and γ using specific inks as examples. In Figure 3, Ink X is an ink in which titanium oxide particles are dispersed in a solvent whose main component is water. Ink Y is an ink in which titanium oxide is dispersed in a liquid resin whose main component is acrylic monomer.

[0035] As shown in Figure 3, the relationship between the contact angles α, β, and γ is as shown in Equation 1 above for both inks X and Y. This prevents the liquid from adhering to the nozzle surface, enabling good droplet ejection. Note that ink X has a larger contact angle overall than ink Y, indicating that it has low wettability (is less likely to wet).

[0036] -Pressure chamber- Returning to FIG. 1, the pressure chamber 14 communicates with the nozzle 12. The pressure chamber 14 also communicates with the individual flow path 15 via the throttle section 20. The volume of the pressure chamber 14 changes due to the deformation of the vibration plate 17. This change in volume causes ink to be ejected from the nozzle 12. The resonance period of the ink changes depending on the volume of the pressure chamber 14 and the flow path resistance of the throttle section 20, and this changes the ejection volume and ejection speed of the ejected ink droplets 70. Therefore, it is necessary to optimally adjust the volume of the pressure chamber 14, etc., as necessary.

[0037] -Pressure section- The pressure unit 30 is provided corresponding to the pressure chamber 14 and is displaced by application of a voltage. For example, a stacked piezoelectric element of d33 mode or d31 mode, or a piezoelectric element utilizing a shear mode, can be used as the pressure unit 30. Furthermore, instead of the above-mentioned piezoelectric element, an energy generating element such as an electrostatic actuator or a heat generating element can also be used as the pressure unit 30.

[0038] -Vibration plate- The diaphragm 17 transmits energy generated by the pressure applying unit 30 to the pressure chamber 14. In FIG. 1, the diaphragm 17 is disposed between the pressure applying unit 30 and the pressure chamber 14 so as to be in contact with the pressure applying unit 30. The diaphragm 17 is deformed by the displacement of the pressure applying unit 30. The material from which the diaphragm 17 is made is not particularly limited, but may be, for example, a metal such as nickel or stainless steel, or a resin such as polyimide. The thickness of the diaphragm 17 is not particularly limited, but is preferably, for example, 5 to 50 μm.

[0039] Note that while Figure 1A shows only one nozzle 12 and its corresponding components (e.g., pressure chamber 14, throttle section 20, individual flow path 15, pressure section 30, etc.), multiple of these components are provided along the Y direction, as shown in Figure 1C.

[0040] -Ink flow path- The common flow path 51, the individual flow paths 15, and the throttle portion 20 are flow paths for ink.

[0041] FIG. 1C is a cross-sectional view showing the arrangement of the nozzles 12 and ink flow paths of the inkjet head 10. As shown in FIG.

[0042] 1C, the common flow path 51 communicates with the individual flow paths 15. The individual flow paths 15 communicate with the pressure chambers 14 via the throttle sections 20. That is, the common flow path 51 is connected to each of the pressure chambers 14 via each individual flow path 15 and each throttle section 20.

[0043] The common flow path 51 is connected to an ink reservoir (not shown). The ink reservoir is connected to an ink supply tank (not shown), which is an ink supply source. The ink reservoir can be considered a second ink supply tank located between the common flow path 51 and the ink supply tank. By pressurizing or depressurizing this ink reservoir, it is possible to control the circulating flow rate of ink flowing through the common flow path 51 and the individual flow paths 15 in the inkjet head 10. Furthermore, it is possible to control the pressure applied to the nozzles 12 and eject ink under appropriate conditions.

[0044] 1C, one of the common flow paths 51 provided on the left and right sides of the drawing communicates with a supply port (not shown), and the other communicates with a discharge port (not shown). Ink flows from the ink reservoir described above into one common flow path 51 via the supply port, and then flows from the common flow path 51 into each pressure chamber 14 via each individual flow path 15 and each throttle section 20. The ink that flows from each pressure chamber 14 into the other common flow path 51 is discharged from the discharge port. The discharged ink is recovered in an ink recovery tank connected to the ink supply tank and flows back into the ink supply tank.

[0045] The throttle portion 20 has a width narrower than the width of the individual flow path 15. This makes it difficult for the pressure wave generated in the pressure chamber 14 by the deformation of the vibration plate 17 to escape to the individual flow path 15. As a result, the ink in the pressure chamber 14 is ejected from the nozzle 12 as an ink droplet 70.

[0046] <Inkjet head manufacturing method> The method for manufacturing the inkjet head 10 will be specifically described below with reference to the flowchart of FIG.

[0047] A flat nozzle plate material is used as the base of the nozzle plate 11. The nozzle plate material is made of stainless steel, nickel or other metal material, polyimide resin material or other organic material, or silicon material.

[0048] In step S1, a liquid-repellent film 50 made of a fluorine-containing diamond-like carbon film is formed on the outer surface 11a of the nozzle plate material. The diamond-like carbon film is formed (deposited) using a CVD (Chemical Vapor Deposition) method (e.g., thermal CVD, photo CVD, or plasma CVD). In the CVD method, a gas or liquid is vaporized and gasified. Then, energy is applied to the gas using heat or light, or the gas is converted into plasma using high frequency waves, thereby converting the raw material into radicals, which are then adsorbed and deposited on the substrate.

[0049] As a method for incorporating fluorine, for example, a hydrocarbon gas such as acetylene (C2H2) and a gas containing fluorine may be used as a raw material gas. Alternatively, after the diamond-like carbon film is formed, the surface of the film may be treated with a gas containing fluorine to modify the surface of the diamond-like carbon film with fluorine. Note that the liquid-repellent film 50 is preferably formed by gradually increasing the fluorine concentration in the raw material gas during the film formation.

[0050] In the next step S2, nozzles 12 are formed in the nozzle plate material on which the liquid-repellent film 50 has been formed, thereby forming the nozzle plate 11.

[0051] The method for forming the nozzle 12 is not particularly limited, and the following methods can be used, for example. For example, the nozzle 12 may be formed by laser processing the nozzle plate material. Alternatively, the nozzle 12 may be formed by punching a hole in the nozzle plate material and then polishing the periphery of the hole. Alternatively, the nozzle 12 may be formed by etching.

[0052] In the next step S3, the inkjet head 10 is assembled.

[0053] Specifically, the pressure chambers 14, individual flow paths 15, diaphragm 17, common flow path 51, and throttle portion 20 (hereinafter collectively referred to as "components") are fabricated by, for example, thermal diffusion bonding of multiple metal plates processed by etching, etc. These components may also be fabricated by etching a silicon material, etc.

[0054] The nozzle plate 11 is bonded to a flow path plate 16 in which individual flow paths 15 and throttle portions 20 are formed, and the flow path plate 16 is also bonded to a vibration plate 17. A housing 18, which serves as the case for the inkjet head 10, is bonded to the structure formed by the above bonding. A common flow path 51 is provided in the housing 18. Furthermore, the pressurizing portion 30 is bonded to the vibration plate 17, thereby completing the inkjet head 10.

[0055] In summary, the method for manufacturing the inkjet head 10 according to the present disclosure includes a liquid-repellent film process for forming a liquid-repellent film 50 made of a diamond-like carbon film containing fluorine on the outer surface 11a of the nozzle plate 11, and a nozzle process for forming nozzles 12 in the nozzle plate 11 on which the liquid-repellent film 50 has been formed.

[0056] In this way, by forming the nozzle 12 after forming the liquid-repellent film 50 on the nozzle plate 11, a portion where the liquid-repellent film 50 is not formed is formed around the nozzle 12. This makes it possible to improve the straightness of the flight of the ink droplets 70.

[0057] <Printing device> The inkjet head 10 described above may be included in a printing device 9 shown in FIGS. 10 and 11. The printing device 9 includes a transport unit. The configuration of the transport unit is not particularly limited, but may include, for example, a base 1, a guide 2 arranged on the base 1, a movable unit 7 movable along the guide 2, a transport table 3 connected to the movable unit 7 and transporting the substrate in the scanning direction, a portal gantry 4 arranged on the base 1, and a line head 5 attached to the portal gantry 4. The line head 5 is a single unit formed by arranging multiple inkjet heads 10 side by side. Although not shown, the printing device 9 also includes a control unit. The control unit controls the ejection operation of the inkjet head 10. The control unit may include, for example, a CPU (processor) and a memory for storing information such as programs for operating the CPU and processing results from the CPU.

[0058] Specifically, the control unit generates a drive voltage signal to be applied to the pressure applying unit 30. The control unit uses the drive voltage signal to control the pressure applying operation of the pressure applying unit 30. Because the pressure applying unit 30 and the diaphragm 17 are bonded together, control of the pressure applying unit 30 is synonymous with control of the diaphragm 17, and the ejection operation of the inkjet head 10 can be controlled by controlling the pressure applying unit 30.

[0059] The conveying table 3 moves the inkjet head 10 relative to the print medium 6 onto which the ink droplets 70 land.

[0060] <Evaluation of Examples and Comparative Examples Depending on the Type of Liquid-Repellent Film> The evaluation of each of the Examples and Comparative Examples will be described below.

[0061] Here, the durability of the liquid repellency was evaluated by comparative evaluation of the contact angle of the liquid repellent film 50. In Example 1, a diamond-like carbon film containing fluorine was used as the liquid repellent film 50. In contrast, in the comparative example, instead of the liquid repellent film 50, a film formed by a dehydration condensation reaction using silane coupling as in Patent Document 1 was used as the liquid repellent film. Apart from the liquid repellent film, the example and comparative example had the same configuration.

[0062] In this comparative evaluation, the contact angle was measured using a contact angle meter DSA100 (manufactured by KRUSS). Durability was evaluated by measuring the initial contact angle of the liquid-repellent film 50 and the contact angle after wiping the surface of the liquid-repellent film 50 with a cloth 300 times with water-based ink containing titanium oxide attached (hereinafter referred to as the contact angle after the friction test). The particle size of the titanium oxide was approximately 1 μm.

[0063] Example 1 In Example 1, an inkjet head was used in which the liquid-repellent film 50 made of a fluorine-containing diamond-like carbon film was formed on the outer surface 11a of the nozzle plate 11 by CVD.

[0064] In Example 1, after forming a liquid-repellent film 50 on the outer surface of the nozzle plate 11 by CVD, the nozzles 12 were formed by laser processing. In this manufacturing process, a step portion 60 was provided as shown in Fig. 1. The film thickness of the water-repellent film 50 was 120 nm, and the gap L between the water-repellent film 50 and the nozzles 12 was 170 nm.

[0065] Fig. 5 shows the contact angle of the liquid-repellent film 50 of Example 1. As shown by the bar graph on the left side of Fig. 5, in the initial state, the static angle was 97° and the receding angle was 82°. Furthermore, as shown by the bar graph on the right side of Fig. 5, the contact angles after the friction test were 95° and 61°, respectively.

[0066] Here, the inventors have found that in order for ink droplets 70 to be ejected stably, the contact angle of the liquid-repellent film 50 needs to be a receding angle of 40° or more.

[0067] In Example 1, it was found that by adopting the configuration of this embodiment, the liquid-repellent film 50 was scraped off by titanium oxide, reducing the contact angle, but droplets could be ejected stably over time.

[0068] 6 shows the flight state of ink droplets 70 when they are caused to fly using the inkjet head 10 of Example 1. The meniscus of the ink droplets 70 is stably formed from the outer surface 11a of the nozzle plate 11 where the liquid-repellent film 50 is not formed to the side surface 50b of the liquid-repellent film 50. This demonstrates that the ink droplets 70 fly in a straight line.

[0069] (Comparative Example 1) In Comparative Example 1, an inkjet head was used in which, instead of the liquid-repellent film 50 of Example 1, a liquid-repellent film formed by a dehydration condensation reaction using silane coupling was formed on the outer surface 11a of the nozzle plate 11 by spin coating.

[0070] Figure 6 shows the contact angle of the liquid-repellent film of Comparative Example 1. As shown by the bar graph on the left side of Figure 6, in the initial state, the static angle was 83° and the receding angle was 82°. Furthermore, as shown by the bar graph on the right side of Figure 6, the contact angles after the friction test were 62° and 5°, respectively.

[0071] Titanium oxide is extremely hard and has an abrasive effect. Therefore, depending on the type of liquid-repellent film, titanium oxide can abrade the film, reducing its liquid repellency. Although not shown, in Comparative Example 1, it was confirmed that most of the liquid-repellent film was abraded by titanium oxide, resulting in a significant reduction in the contact angle.

[0072] Here, when the sweepback angle is 5°, the ink is not repelled, and the ink spreads wet on the liquid-repellent film 50. In this state, it is difficult for the meniscus formed at the nozzle 12 to remain stable, and it is difficult for the droplets to fly accurately.

[0073] As described above, the inkjet head 10 according to this embodiment includes the nozzle plate 11 in which the nozzles 12 are formed, the pressure chambers 14 communicating with the nozzles 12, the pressurizing unit 30 that pressurizes the pressure chambers 14, and the diaphragm 17 that transmits the energy generated in the pressurizing unit 30 to the pressure chambers 14. The nozzle plate 11 has an outer surface 11a on which a liquid-repellent film 50 made of a diamond-like carbon film to which fluorine has been added formed.

[0074] According to this embodiment, the liquid-repellent film 50 made of a diamond-like carbon film is formed on the outer surface 11a of the inkjet head 10, thereby maintaining sufficient reliability and durability. This prevents ink from adhering to the outer surface 11a, allowing for good droplet ejection. The same effect can be achieved with a printing device using the inkjet head 10 described above.

[0075] In the above embodiment, a region where the liquid-repellent film 50 is not formed is provided within a certain distance (for example, 10 nm to 500 nm) around the nozzle outlet, i.e., a region where the liquid-repellent film 50 is not formed. In other words, at the outlet 12a of the nozzle 12, a step portion 60 is provided between the outer surface 11a of the nozzle plate 11 and the surface 50a of the liquid-repellent film 50.

[0076] This can further improve the reliability and durability of the inkjet head 10. This point will be explained in detail in the "Other embodiments" section below, showing specific examples.

[0077] In the above embodiment, the relationship between the contact angle α of the surface 50a of the liquid-repellent film 50 with the ink droplets 70 ejected from the nozzles 12, the contact angle β of the side surface 50b of the liquid-repellent film 50 with the ink droplets 70 ejected from the nozzles 12, and the contact angle γ of the outer surface 11a of the nozzle plate 11 with the ink droplets 70 ejected from the nozzles 12 is expressed by the relationship in [Equation 1] above.

[0078] This makes it possible to prevent adhesion of particles and binders contained in the ink, thereby preventing clogging due to particles and binders and achieving stable ejection over time, resulting in higher print quality.

[0079] <Other embodiments> The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0080] For example, in the above embodiment, an example was described in which a non-formation area where the liquid-repellent film 50 is not formed is provided within a certain distance L around the ejection port 12a of the nozzle 12, but the present invention is not limited to this.

[0081] For example, it is possible to eliminate the need for an area where the liquid-repellent film 50 is not formed around the ejection port 12a of the nozzle 12. In other words, as shown in Fig. 8, the inner wall surface 12b of the nozzle 12 and the side surface of the liquid-repellent film 50 may be configured to be substantially flush with each other.

[0082] In this case, too, if the contact angle of the ink on the surface 50a of the liquid-repellent film 50 is α, the contact angle of the side surface 50b of the liquid-repellent film 50 is β, and the contact angle of the ink on the inner wall surface 12b of the nozzle 12 is θ, the relationship between the contact angles α, β, and θ is as shown in [Equation 3]. [Formula 3] Contact angle α > Contact angle β > Contact angle θ

[0083] This prevents the liquid from adhering to the nozzle surface, enabling good droplet ejection. Also, the meniscus of the ink droplet 70 is stably formed from the inner wall surface 12b of the nozzle 12 to the side surface 50b of the liquid-repellent film 50. This allows the ink droplet 70 to fly in a good straight line.

[0084] In the configuration of FIG. 8, after forming the nozzles 12 on the nozzle plate 11, it is preferable to form the liquid-repellent film 50 made of a diamond-like carbon film containing fluorine by using the CVD method.

[0085] In forming the liquid-repellent film 50, the liquid-repellent film 50 can be formed in a state where the nozzle 12 is masked, so that the liquid-repellent film 50 is not formed inside the nozzle 12.

[0086] In this case, as shown in Fig. 8, unlike in the case of the above-described Example 1, the liquid-repellent film 50 is formed right up to the periphery of the ejection port of the nozzle 12. In this case, as shown in Fig. 9, chipping may occur in the corners of the liquid-repellent film 50 (diamond-like carbon film) around the ejection port 12a of the nozzle 12 due to friction with the print medium.

[0087] Figure 9 shows the flight state of ink droplets 70 when they are ejected using an inkjet head 10 in which a chip has occurred in the liquid-repellent film 50. When a chip occurs as shown in Figure 9, the meniscus becomes asymmetrical on the liquid-repellent film 50, impairing the straightness of the ink droplets 70. In contrast, as shown in the first embodiment above, by providing an area in which the liquid-repellent film 50 is not formed around the ejection port 12a of the nozzle 12, it is possible to make the liquid-repellent film 50 less likely to be chipped. This can further improve the reliability and durability of the inkjet head 10. [Industrial Applicability]

[0088] As described above, the inkjet head, inkjet head manufacturing method, and printing apparatus disclosed herein are useful for ejecting, for example, quantum dot luminescent ink containing quantum dot semiconductor particles, white decorative ink containing titanium oxide, functional ink for constructing perovskite solar cells, conductive ink containing metal nanoparticles, and biological ink containing cells, etc., and have high industrial applicability. [Explanation of symbols]

[0089] 9 Printing device 10 Inkjet head 11 Nozzle plate 12 nozzles 14 Pressure Chamber 17 Diaphragm 30 Pressure section 50 Liquid repellent film

Claims

1. a nozzle plate in which nozzles are formed; a pressure chamber communicating with the nozzle; a pressurizing unit that pressurizes the pressure chamber; a vibration plate that transmits energy generated by the pressure unit to the pressure chamber, a liquid-repellent film made of a diamond-like carbon film containing fluorine is formed on the outer surface of the nozzle plate; the liquid-repellent film is not formed within a certain distance around the ejection port of the nozzle, The fixed distance is 10 nm to 500 nm. Inkjet head.

2. 2. The ink jet head according to claim 1, wherein the liquid repellent film has a fluorine concentration that decreases with increasing depth from the surface.

3. 3. The inkjet head according to claim 1, wherein a step is provided between the outer surface of the nozzle plate and the surface of the liquid-repellent film at the ejection opening of the nozzle.

4. A method for manufacturing an inkjet head that ejects droplets from nozzles formed in a nozzle plate and causes the droplets to land on a print medium, comprising: a liquid-repellent film process for forming a liquid-repellent film made of a fluorine-doped diamond-like carbon film on the outer surface of the nozzle plate; a nozzle step of forming the nozzle in the nozzle plate on which the liquid-repellent film is formed, the liquid-repellent film is not formed within a certain distance around the ejection port of the nozzle, The fixed distance is 10 nm to 500 nm. A method for manufacturing an inkjet head.

5. The method for manufacturing an inkjet head according to claim 4 , wherein the nozzle step comprises forming the nozzles by irradiating the nozzle plate with a laser.

6. The inkjet head according to any one of claims 1 to 3; a control unit that controls an operation of discharging droplets from the inkjet head; A printing device including a transport unit that moves the inkjet head and the print medium relative to each other.

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