Inkjet head, method for manufacturing inkjet head, and printing device

Abstract

The present application relates to an inkjet head, a manufacturing method of an inkjet head, and a printing device. The inkjet head (10) includes a nozzle plate (11) that forms a nozzle (12), a pressure chamber (14) that communicates with the nozzle (12), a pressurizing section (30) that pressurizes the pressure chamber (14), and a vibrating plate (17) that transmits energy generated by the pressurizing section (30) to the pressure chamber (14). A liquid-repellent film (50) is formed on an outer surface (11a) of the nozzle plate (11), and the liquid-repellent film (50) is composed of a diamond-like carbon film to which fluorine is added.

Description

Technical Field

[0001] This invention relates to inkjet heads, methods for manufacturing inkjet heads, and printing apparatus. Background Technology

[0002] Previously, inkjet printing apparatuses were known to form images on recording media by ejecting droplets from the nozzles of an inkjet head. In an inkjet head, when droplets are ejected from the nozzles, ink sometimes adheres to the area around the ejection side opening of the nozzle. Thus, the ejection angle may be distorted when droplets are ejected from the nozzles.

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

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-230061 Summary of the Invention

[0007] One embodiment of the inkjet head of the present invention comprises: a nozzle plate having nozzles formed thereon; a pressure chamber communicating with the nozzles; a pressurizing section for pressurizing the pressure chamber; and a vibrating plate for transmitting energy generated by the pressurizing section to the pressure chamber, wherein an hydrophilic film is formed on the outer surface of the nozzle plate, the hydrophilic film being composed of a diamond-like carbon film with added fluorine.

[0008] Another aspect of the present invention relates to a method for manufacturing an inkjet head, the inkjet head ejecting droplets from a nozzle formed on a nozzle plate and causing the droplets to fall onto a printing medium, wherein the method for manufacturing the inkjet head includes: an hydrophilic film step in which an hydrophilic film composed of a fluorine-added diamond-like carbon film is formed on the outer surface of the nozzle plate; and a nozzle step in which the nozzle is formed on the nozzle plate on which the hydrophilic film is formed. Attached Figure Description

[0009] Figure 1A This is a cross-sectional schematic diagram showing the structure of the inkjet head.

[0010] Figure 1B It is shown Figure 1A A cross-sectional schematic diagram showing the detailed relationship between the position of the hydrophobic film and the nozzle.

[0011] Figure 1C yes Figure 1A A sectional view along line AA.

[0012] Figure 1DThis is a diagram showing the inkjet head as viewed from the side of the printed medium.

[0013] Figure 1E This illustrates other structural examples of inkjet heads, and... Figure 1B A fairly accurate diagram.

[0014] Figure 1F This illustrates other structural examples of inkjet heads, and... Figure 1B A fairly accurate diagram.

[0015] Figure 2 This is a diagram showing an example of the fluoride concentration in the hydrophobic film of an inkjet head.

[0016] Figure 3 This is a diagram showing an example of the contact angle of the hydrophobic film of an inkjet head.

[0017] Figure 4 This is a flowchart illustrating the manufacturing method of an inkjet head.

[0018] Figure 5 This is a diagram showing the contact angle of the hydrophobic film of the inkjet head in Example 1.

[0019] Figure 6 This is a diagram showing the contact angle of the hydrophobic film of the inkjet head in Comparative Example 1.

[0020] Figure 7 This is a diagram showing the ejection state of droplets from the inkjet head of Example 1.

[0021] Figure 8 Other implementation methods, and Figure 1B A fairly accurate diagram.

[0022] Figure 9 This is a diagram showing the ejection state of droplets from the inkjet head when a notch is formed.

[0023] Figure 10A This is a top view showing the structure of the printing apparatus.

[0024] Figure 10B This is a top view showing the structure of the printing apparatus.

[0025] Figure 11 This is a side view showing the structure of the printing apparatus.

[0026] Explanation of reference numerals in the attached figures:

[0027] 9. Printing apparatus

[0028] 10 inkjet heads

[0029] 11 Nozzle Plate

[0030] 12 nozzles

[0031] 14 Pressure Chamber

[0032] 17. Vibrating plate

[0033] 30 Pressurization section

[0034] 50. Liquid-repellent membrane. Detailed Implementation

[0035] Since the hydrophobicity of the nozzle surface is essential for the stable ejection of droplets, the long-term stability of hydrophobic films is sought. However, for example, existing hydrophobic films, such as those shown in Patent Document 1, suffer from insufficient long-term stability in ink contact. In particular, the hydrophobicity of existing hydrophobic films is significantly reduced compared to inks containing particles of inorganic compounds such as titanium dioxide. This is because titanium dioxide particles are hard and have an abrasive effect, thus grinding the hydrophobic film.

[0036] The present invention was made in view of the above-mentioned problems, and its object is to provide an inkjet head that can maintain stable hydrophobicity over time even when using ink containing inorganic compounds.

[0037] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the embodiments described below are all preferred examples of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, and connection methods shown in the following embodiments are examples and are not intended to limit the present invention. Therefore, in the constituent elements of the following embodiments, constituent elements not described in the technical solution representing the highest concept of the present invention will be described as arbitrary constituent elements.

[0038] <Inkjet head>

[0039] Figures 1A to 1D The diagram shows a structural example of the inkjet head 10.

[0040] The inkjet head 10 of the present invention causes ink droplets to fall onto the printing medium by ejecting ink droplets from a nozzle formed on a nozzle plate 11. There is no particular limitation on the type of ink ejected. For example, it may eject (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, or (4) biological ink containing cells, etc. It should be noted that the inkjet head 10 may also eject liquids other than ink.

[0041] The inkjet head 10 includes a nozzle plate 11 forming one or more nozzles 12, a pressure chamber 14, a pressurizing section 30, and a vibrating plate 17. The inkjet head 10 is used to actuate ink droplets 70 (see reference) ejected from the nozzles 12. Figure 7 It lands on the printed medium (illustration omitted).

[0042] In the following description, the length direction of the inkjet head 10 is referred to as the Y direction, and the width direction orthogonal to the length direction is referred to as the X direction. Furthermore, the direction orthogonal to both the X and Y directions is referred to as the Z direction. In this invention, the nozzle plate 11 is arranged along both the X and Y directions.

[0043] -Nozzle Plate-

[0044] As described above, a nozzle 12 is formed on the nozzle plate 11 for ejecting ink contained in the pressure chamber 14 as droplets. The material of the nozzle plate 11 is not particularly limited, and can be, for example, stainless steel or other metals. The nozzle 12 is a through hole formed along the Z direction in the nozzle plate 11, which is circular when viewed from above.

[0045] The diameter R of the nozzle 12 is, for example, about 5 to 50 μm. The nozzle 12 is formed, for example, by laser processing, etching or punching.

[0046] It should be noted that the shape of nozzle 12 may not be shown in the sectional view. Figure 1B Such a straight line shape. For example, like... Figure 1E As shown in the cross-sectional view, the nozzle 12 opening can also be inclined in a manner that gradually narrows towards the nozzle outlet 12a, a so-called "mortar shape". Additionally, as... Figure 1F As shown in the cross-sectional view, it can also be a so-called "funnel shape" where the opening of the nozzle 12 gradually narrows towards the outlet 12a, becoming a straight line in the cross-sectional view. It should be noted that... Figure 1E and Figure 1F The shape can be appropriately achieved by using laser processing to form the nozzle 12.

[0047] In addition, such as Figure 1A As shown, the nozzle plate 11 can also form part of the outer wall of the pressure chamber 14.

[0048] -Hydrophobic membrane-

[0049] For the nozzle plate 11, a hydrophobic film 50 with ink-repellent properties (hydrophobicity) is formed on the outer surface 11a (hereinafter referred to as outer surface 11a) opposite to the printing medium.

[0050] The efflorescent film 50 is composed of a fluorine-containing diamond-like carbon film. The thickness of the efflorescent film 50 is not particularly limited, for example, it is approximately 50 nm to 300 nm. If the efflorescent film 50 is too thin, it lacks efflorescence. On the other hand, if the efflorescent film 50 is too thick, the film stress increases, causing the nozzle plate 11 to warp. If it warps, it becomes difficult to bond it to other components (e.g., the flow path plate 16) when assembling the inkjet head 10. By using a fluorine-containing diamond-like carbon film as the efflorescent film 50, it exhibits excellent wear resistance.

[0051] There are also cases where the ink contains particles of inorganic compounds such as titanium dioxide. In the prior art, the liquid repellency can sometimes be degraded because titanium dioxide erodes the liquid repellent film. If the liquid repellency around the nozzle is impaired, the ink wets and spreads near the nozzle, failing to form a proper meniscus. As a result, the inkjet head 10 cannot eject ink stably. To address this, the inkjet head 10 of this embodiment uses a diamond-like carbon film, thereby providing wear resistance to the liquid repellent film 50 and preventing the problems described in the prior art.

[0052] like Figure 1B and Figure 1D As shown, the hydrophobic film 50 is formed in a manner that ensures a gap relative to the nozzle 12. That is, the hydrophobic film 50 is not formed within a certain distance L around the nozzle 12 outlet 12a. In other words, at the nozzle 12 outlet, a stepped portion 60 is provided between the outer surface 11a of the nozzle plate 11 and the surface 50a of the hydrophobic film 50. In this embodiment, the nozzle plate 11 includes a first opening having a first diameter. The hydrophobic film 50 includes a second opening aligned with the first opening, and the second opening has a second diameter larger than the first diameter. The nozzle 12 is formed by the first opening and the second opening.

[0053] The gap is not particularly limited, for example, it is about 10nm to 500nm, and more preferably below 200nm. If the gap is too large, the wettability around the nozzle 12 will be high, and the ink may wet and spread.

[0054] The fluorine concentration in the hydrophobic film 50 exhibits a gradient relative to the depth direction D (Z direction). Specifically, the fluorine concentration is higher closer to the surface 50a of the hydrophobic film 50 and decreases as it approaches the bottom surface (the surface in contact with the nozzle plate 11). For example, the fluorine concentration present in the hydrophobic 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.

[0055] Figure 2 The results of determining the fluorine concentration in the liquefactive film 50 are shown. The fluorine concentration was determined using energy dispersive X-ray spectroscopy (EDX). Figure 2 As shown, fluorine exists at a concentration of 1.4 atomic% near the surface of the hydrophobic film 50 and at a concentration of 0.3 atomic% near the bottom surface.

[0056] By setting a fluorine concentration gradient as described above, the adhesion between the outer surface 11a of the nozzle plate 11 and the bottom surface of the hydrophobic film 50 can be improved, and the hydrophobicity at the surface 50a of the hydrophobic film 50 can be ensured. In addition, the meniscus of ink at the nozzle 12 can be formed more stably.

[0057] The relationship between the contact angles α, β, and γ relative to the ink droplet 70 is shown in [Equation 1]. Contact angle α is the contact angle of the surface 50a of the hydrophobic film 50 relative to the ink droplet 70. Contact angle β is the contact angle of the side surface 50b of the hydrophobic film 50 relative to the ink droplet 70. Contact angle γ is the contact angle of the outer surface 11a of the nozzle plate 11 relative to the ink droplet 70.

[0058] [Formula 1]

[0059] Contact angle α > Contact angle β > Contact angle γ

[0060] There are two types of contact angles: the rest angle and the recoil angle. The rest angle and recoil angle will be explained below.

[0061] When a liquid is dropped onto a solid surface, it becomes round due to its own surface tension, and the relationship shown in [Equation 2] holds true. [Equation 2] is called Young's equation.

[0062] [Equation 2]

[0063] γs=γL×cosθ+γSL

[0064] γs: Surface tension of a solid

[0065] γL: Surface tension of the liquid

[0066] γSL: Interfacial tension between solid and liquid

[0067] The angle θ between the tangent of the ink droplet at this point and the solid surface is called the contact angle. The contact angle when the liquid is stationary and in equilibrium on the solid surface is called the rest angle.

[0068] On the other hand, the contact angle under the dynamic state of liquid-solid interface movement, i.e., the movement of the liquid droplet interface, is called the "advance angle" and the "receding angle." Here, we focus on the dynamic contact angle, i.e., the receding angle, after the solid surface is wetted by the liquid. The receding angle of the lipolytic film 50 relative to the ink is, for example, 30 degrees or more.

[0069] Figure 3 This example demonstrates a comparison of the aforementioned contact angles α, β, and γ using a specific ink as an example. Figure 3 Ink X is an ink in which titanium dioxide particles are dispersed in a solvent with water as the main component. Ink Y is an ink in which titanium dioxide is dispersed in a liquid resin with acrylic monomers as the main component.

[0070] like Figure 3 As shown, the relationship between contact angles α, β, and γ is the same as that described in [Equation 1] for any of inks X and Y. This prevents liquid from adhering to the nozzle surface, thus ensuring good droplet ejection. It should be noted that the contact angle of ink X is generally larger than that of ink Y, indicating low wettability (difficult to wet).

[0071] -Pressure Chamber-

[0072] Referring back to Figure 1, pressure chamber 14 is connected to nozzle 12. Furthermore, pressure chamber 14 is connected to independent flow path 15 via throttling section 20. The volume of pressure chamber 14 changes according to the deformation of vibrating plate 17. Ink is ejected from nozzle 12 due to this volume change. The ink's resonant period changes due to the volume of pressure chamber 14 and the flow path resistance of throttling section 20, thereby changing the ejection volume and velocity of the ejected ink droplets 70. Therefore, it is necessary to adjust the volume of pressure chamber 14 and other parameters to an optimal level as needed.

[0073] -Pressure section-

[0074] The pressurizing part 30 is provided corresponding to the pressure chamber 14 and is displaced by the application of voltage. For example, a stacked piezoelectric element in d33 or d31 mode, or a piezoelectric element utilizing a shear mode, can be used as the pressurizing part 30. Alternatively, an energy-generating element such as an electrostatic actuator or a heating element can be used instead of the aforementioned piezoelectric element.

[0075] -Vibrating Plate-

[0076] The vibrating plate 17 transfers the energy generated by the pressurizing part 30 to the pressure chamber 14. In Figure 1, the vibrating plate 17 is positioned between the pressurizing part 30 and the pressure chamber 14 in contact with the pressurizing part 30. The vibrating plate 17 deforms due to the displacement of the pressurizing part 30. The blank material constituting the vibrating plate 17 is not particularly limited, and can be made of metals such as nickel and stainless steel, or resins such as polyimide. The thickness of the vibrating plate 17 is not particularly limited, but is preferably 5 to 50 μm.

[0077] It should be noted that, in Figure 1A The diagram shows only one nozzle 12 and its corresponding components (e.g., pressure chamber 14, throttling section 20, independent flow path 15, pressurizing section 30, etc.), but... Figure 1C As shown, there are multiple of these components arranged along the Y direction.

[0078] -Flow path of ink-

[0079] The common flow path 51, the independent flow path 15, and the throttling section 20 are the flow paths of the ink.

[0080] Figure 1CThis is a cross-sectional schematic diagram showing the configuration of the nozzle 12 of the inkjet head 10 and the ink flow path.

[0081] like Figure 1C As shown, the common flow path 51 is connected to the independent flow path 15. The independent flow path 15 is connected to the pressure chamber 14 via the throttling section 20. That is, the common flow path 51 is connected to each of the plurality of pressure chambers 14 via each of the independent flow paths 15 and each of the throttling sections 20.

[0082] The common flow path 51 is connected to an ink accumulator (not shown). The ink accumulator is connected to an ink supply tank (not shown), which serves as the ink supply source. The ink accumulator can be considered a second ink supply tank existing between the common flow path 51 and the ink supply tank. By pressurizing or depressurizing the ink accumulator, the circulation flow rate of the ink flowing in the common flow path 51 and the independent flow path 15 within the inkjet head 10 can be controlled. Furthermore, the pressure applied to the nozzle 12 can be controlled, thereby ejecting ink in an appropriate manner.

[0083] exist Figure 1C In the diagram, one side of the common flow path 51, located on the left and right sides, is connected to the supply port (not shown), and the other side is connected to the discharge port (not shown). Ink flows from the aforementioned ink accumulator into the common flow path 51 on one side via the supply port, and from the common flow path 51, it flows through each independent flow path 15 and each throttling section 20 into each pressure chamber 14. Ink flowing from each pressure chamber 14 into the common flow path 51 on the other side is discharged from the discharge port. The discharged ink is recovered by an ink recovery tank connected to the ink supply tank and flows back into the ink supply tank.

[0084] The width of the throttling section 20 is narrower than the width of the independent flow path 15. As a result, the pressure wave in the pressure chamber 14 generated by the deformation of the vibrating plate 17 has difficulty escaping into the independent flow path 15. As a result, the ink in the pressure chamber 14 is ejected from the nozzle 12 as ink droplets 70.

[0085] <Inkjet head manufacturing method>

[0086] The following is for reference Figure 4 The flowchart below provides a detailed explanation of the manufacturing method of the inkjet head 10.

[0087] The nozzle plate 11 is supported by a flat nozzle plate blank. The nozzle plate blank is made of stainless steel, nickel or other metals, polyimide resin or other organic materials, or silicon.

[0088] In step S1, a hydrophobic film 50 composed of a fluorine-containing diamond-like carbon film is formed on the outer surface 11a of the nozzle blank. The formation (film formation) of the diamond-like carbon film is performed using a CVD (Chemical Vapor Deposition) method (e.g., thermal CVD, photochemical CVD, plasma CVD). In CVD, a gas or liquid is vaporized. The gas is then energized using heat or light, or plasmaized using high frequency, thereby free-radicalizing the raw material and causing it to adsorb and deposit on the substrate.

[0089] As a method to introduce fluorine, hydrocarbon gases such as acetylene (C2H2) and fluorine-containing gases can be used as feed gases. Alternatively, the surface of the diamond-like carbon film can be treated with a fluorine-containing gas after film formation, thereby modifying the surface of the diamond-like carbon film with fluorine. It should be noted that the liquid-repellent film 50 is preferably formed by gradually increasing the fluorine concentration in the feed gas starting from the middle of film formation.

[0090] In the subsequent step S2, a nozzle 12 is formed on the nozzle blank on which the hydrophobic film 50 is formed, and the nozzle plate is configured as a nozzle plate 11.

[0091] The method for forming the nozzle 12 is not particularly limited, and for example, the following methods can be used. For example, the nozzle 12 can also be formed by laser processing of the nozzle blank. Alternatively, the nozzle 12 can be formed by grinding the periphery of the hole after punching a hole in the nozzle blank. Alternatively, the nozzle 12 can also be formed by etching.

[0092] In the subsequent step S3, the inkjet head 10 is assembled.

[0093] Specifically, the aforementioned pressure chamber 14, independent flow path 15, vibrating plate 17, common flow path 51, and throttling section 20 (hereinafter collectively referred to as "constituent elements") are manufactured, for example, by thermal diffusion bonding of multiple metal plates processed by etching or the like. Alternatively, these constituent elements can also be manufactured by etching silicon material or the like.

[0094] The nozzle plate 11 is bonded to the flow path plate 16, which has an independent flow path 15 and a throttling section 20. The flow path plate 16 is also bonded to the vibrating plate 17. The outer shell 18, which forms the frame of the inkjet head 10, is bonded to the structure formed by the aforementioned bonding. A common flow path 51 is provided in the outer shell 18. Furthermore, the inkjet head 10 is completed by attaching the pressure section 30 to the vibrating plate 17.

[0095] In summary, the method for manufacturing the inkjet head 10 of the present invention includes: an hydrophilic film step of forming an hydrophilic film 50 composed of a diamond-like carbon film with added fluorine on the outer surface 11a of the nozzle plate 11; and a nozzle step of forming a nozzle 12 on the nozzle plate 11 on which the hydrophilic film 50 is formed.

[0096] In this way, by forming the nozzle 12 after the hydrophobic film 50 is formed on the nozzle plate 11, a portion around the nozzle 12 where the hydrophobic film 50 is not formed is formed. This improves the straight-line flight of the ink droplets 70.

[0097] Printing apparatus

[0098] The inkjet head 10 mentioned above can also be set in Figure 10A , Figure 10B and Figure 11 The printing apparatus 9 shown is equipped with a transport unit. The structure of the transport unit is not particularly limited, but may, for example, consist of a base 1, a guide 2 mounted on the base 1, a movable part 7 that moves along the guide 2, a transport stage 3 connected to the movable part 7 and transporting the substrate in the scanning direction, a gantry frame 4 mounted on the base 1, and a linear head 5 mounted on the gantry frame 4. The linear head 5 is a structure in which multiple inkjet heads 10 are arranged as a unit. Although not shown, the printing apparatus 9 also includes a control unit in addition to the above. The control unit controls the ejection action of the inkjet heads 10. The control unit may consist of, for example, a CPU (processor) and a memory that stores information such as the program used to operate the CPU and the processing results in the CPU.

[0099] Specifically, the control unit generates a drive voltage signal that is applied to the pressure unit 30. The control unit uses this drive voltage signal to control the pressure application operation of the pressure unit 30. Since the pressure unit 30 is bonded to the vibrating plate 17, the control of the pressure unit 30 has the same effect as the control of the vibrating plate 17, and the ejection operation of the inkjet head 10 can be controlled by controlling the pressure unit 30.

[0100] The transfer table 3 causes relative movement between the inkjet head 10 and the printed medium 6 on which the ink droplets 70 fall.

[0101] Evaluation of Examples and Comparative Examples Based on Type of Hydrophobic Film>

[0102] The following describes the evaluation of the respective embodiments and comparative examples.

[0103] Here, the durability of the hydrophobicity is evaluated by comparing the contact angles of the hydrophobic film 50. In Example 1, a fluorine-containing diamond-like carbon film was used as the hydrophobic film 50. In contrast, in the comparative example, instead of the hydrophobic film 50 described above, a film formed by a dehydration condensation reaction based on silane coupling, as described in Patent Document 1, was used as the hydrophobic film. Apart from the hydrophobic film, the structures of the examples and the comparative examples are the same.

[0104] In this comparative evaluation, the contact angle was measured using a DSA100 contact angle meter (manufactured by KRUSS). Durability was evaluated by measuring the initial contact angle of the hydrophilic film 50 and the contact angle after 300 rubs with a cloth while an aqueous ink containing titanium oxide was adhered to the surface of the hydrophilic film 50 (hereinafter referred to as the contact angle after the friction test). The titanium oxide particle size was approximately 1 μm.

[0105] (Example 1)

[0106] In Example 1, an inkjet head is used in which the aforementioned hydrophobic film 50, which is composed of a fluorine-containing diamond-like carbon film, is formed on the outer surface 11a of the nozzle plate 11 by CVD.

[0107] In addition, in Example 1, after a hydrophobic film 50 is formed on the outer surface of the nozzle plate 11 using CVD, the nozzle 12 is formed using laser processing. During this manufacturing process, a stepped portion 60 is provided as shown in FIG1. ​​The hydrophobic film 50 has a thickness of 120 nm, and the gap L between it and the nozzle 12 is 170 nm.

[0108] Figure 5 The contact angle of the hydrophobic film 50 of Example 1 is shown. Figure 5 As shown in the bar chart on the left, in the initial state, the stationary angle is 97° and the receding angle is 82°. Additionally, as... Figure 5 As shown in the bar chart on the right, the contact angle after the friction test is 95° at rest and 61° at recoil.

[0109] From the inventor's perspective, it is known that in order to stably eject ink droplets 70, the contact angle of the hydrophobic film 50 needs to be 40° or more when used as a recoil angle.

[0110] In Example 1, it can be seen that by adopting the structure of this embodiment, although the contact angle of the hydrophobic film 50 is reduced by the grinding of titanium oxide, it can still stably eject droplets over time.

[0111] Figure 7 The flight state of the ink droplet 70 when using the inkjet head 10 of Example 1 is shown. The meniscus of the ink droplet 70 is stably formed from the outer surface 11a of the nozzle plate 11 from which the hydrophobic film 50 is not formed to the side surface 50b of the hydrophobic film 50. Thus, it can be seen that the ink droplet 70 flies in a state with good straight-line stability.

[0112] (Comparative Example 1)

[0113] In Comparative Example 1, instead of the hydrophobic film 50 of Example 1, an inkjet head was used to form a hydrophobic film based on a dehydration condensation reaction formed on the outer surface 11a of the nozzle plate 11 by spin coating.

[0114] Figure 6 The contact angle of the hydrophobic film of Comparative Example 1 is shown. Figure 6 As shown in the bar chart on the left, in the initial state, the stationary angle is 83° and the receding angle is 82°. Additionally, as... Figure 6 As shown in the bar chart on the right, the contact angle after the friction test is 62° at rest and 5° at recoil.

[0115] Furthermore, titanium dioxide has a very high hardness and thus an abrasive effect. Therefore, depending on the type of hydrophilic film, the hydrophilic film is abraded by titanium dioxide, reducing its hydrophilicity. Although not illustrated, it can be confirmed that in Comparative Example 1, most of the hydrophilic film was abraded by titanium dioxide, resulting in a significant reduction in the contact angle.

[0116] Here, with a recoil angle of 5°, the ink is not repelled, and it becomes a state where the ink wets and spreads on the hydrophobic film 50. In this state, the meniscus formed by the nozzle 12 is difficult to maintain stably, and the droplets are difficult to fly correctly.

[0117] As described above, the inkjet head 10 of this embodiment includes: a nozzle plate 11 on which nozzles 12 are formed; a pressure chamber 14 communicating with the nozzles 12; a pressurizing section 30 that pressurizes the pressure chamber 14; and a vibrating plate 17 that transmits the energy generated by the pressurizing section 30 to the pressure chamber 14. Furthermore, a hydrophobic film 50 composed of a fluorine-added diamond-like carbon film is formed on the outer surface 11a of the nozzle plate 11.

[0118] According to this embodiment, since a hydrophobic film 50 composed of a diamond-like carbon film is formed on the outer surface 11a of the inkjet head 10, sufficient reliability and durability can be maintained. This prevents ink from adhering to the outer surface 11a, resulting in good droplet ejection. The same effect can be obtained using a printing apparatus employing the inkjet head 10 described above.

[0119] Furthermore, in the above-described embodiment, a region where the hydrophobic film 50 is not formed, i.e., a non-formation region of the hydrophobic film 50, is provided within a certain distance (e.g., 10 nm to 500 nm) around the nozzle outlet. In other words, a stepped portion 60 is provided between the outer surface 11a of the nozzle plate 11 and the surface 50a of the hydrophobic film 50 in the nozzle outlet 12a of the nozzle 12.

[0120] This further improves the reliability and durability of the inkjet head 10. Specific examples will be shown in the "Other Embodiments" section below.

[0121] In the above embodiment, the contact angle α of the surface 50a of the hydrophobic film 50 relative to the ink droplet 70 ejected from the nozzle 12, the contact angle β of the side surface 50b of the hydrophobic film 50 relative to the ink droplet 70 ejected from the nozzle 12, and the contact angle γ of the outer surface 11a of the nozzle plate 11 relative to the ink droplet 70 ejected from the nozzle 12 are the relationships described in [Equation 1].

[0122] This allows for the suppression of the adhesion of particles, binders, and other components contained in the ink. Consequently, clogging caused by particles and binders can be prevented, resulting in stable ejection over time. As a result, high-quality printing can be achieved.

[0123] <Other Implementation Methods>

[0124] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from its spirit.

[0125] For example, in the above embodiment, an example of providing a non-forming region where no hydrophobic film 50 is formed within a certain distance L around the nozzle 12 outlet 12a of the nozzle 12 has been described, but it is not limited to this.

[0126] For example, a non-forming region for the hydrophobic film 50 may not be provided around the outlet 12a of the nozzle 12. That is, as... Figure 8 As shown, the inner wall surface 12b of the nozzle 12 can also be configured such that the side surface of the hydrophobic film 50 is substantially the same plane.

[0127] In this case, if the contact angle of the surface 50a of the hydrophobic film 50 relative to the ink is set as α, the contact angle of the side surface 50b of the hydrophobic film 50 is set as β, and the contact angle of the inner wall surface 12b of the nozzle 12 is set as θ, then the relationship between the respective contact angles α, β, and θ is as shown in [Equation 3].

[0128] [Formula 3]

[0129] Contact angle α > Contact angle β > Contact angle θ

[0130] This prevents liquid from adhering to the nozzle surface, ensuring efficient droplet ejection. Furthermore, 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 hydrophobic film 50. Consequently, the ink droplet 70 can fly in a straight line with good stability.

[0131] exist Figure 8In the structure, after forming the nozzle 12 on the nozzle plate 11, a liquid-phobic film 50 composed of a fluorine-containing diamond-like carbon film can be formed by CVD.

[0132] It should be noted that, in the formation of the hydrophobic film 50, by forming the hydrophobic film 50 in a state where the part of the nozzle 12 is covered, it is possible to set the state where the hydrophobic film 50 is not formed in the nozzle 12.

[0133] In this case, such as Figure 8 As shown, unlike the case of Embodiment 1 described above, the hydrophobic film 50 is formed around the nozzle exit immediately adjacent to the nozzle 12. When cleaning the inkjet head 10 (e.g., nozzle 12), the cleaning cloth may sometimes come into contact with the hydrophobic film 50. Alternatively, the printed medium may unintentionally come into contact with the hydrophobic film 50. Thus, as... Figure 9 As shown, due to friction with the cloth or the printing medium, gaps may be generated at the corners of the hydrophobic film 50 (diamond-like carbon film) around the nozzle 12 outlet 12a.

[0134] exist Figure 9 The image shows the flight state of the ink droplet 70 when it is propelled by an inkjet head 10 with a notch created in the hydrophobic film 50. (See image for details.) Figure 9 In this case, if a gap is formed, the meniscus becomes an asymmetrical shape on the hydrophobic film 50, impairing the straightness of the ink droplet 70. In contrast, as shown in Embodiment 1 above, by providing a non-forming region of the hydrophobic film 50 around the nozzle 12's outlet 12a, it is possible to make it difficult for the hydrophobic film 50 to form gaps. As a result, the reliability and durability of the inkjet head 10 can be further improved.

[0135] According to the present invention, a hydrophobic film composed of a fluorine-added diamond-like carbon film is formed on the outer surface of the nozzle plate. Therefore, the hydrophobicity remains stable over time even when liquids containing inorganic compounds are ejected from the inkjet head.

[0136] Industrial availability

[0137] As explained above, the inkjet head, inkjet head manufacturing method, and printing apparatus of the present invention are useful for ejecting, for example, quantum dot luminescent ink containing quantum dot semiconductor particles, white decorative ink containing titanium oxide, functional ink for constituting perovskite solar cells, conductive ink containing metal nanoparticles, and biological ink containing cells, etc., and have high industrial applicability.

Claims

1. An inkjet head, comprising: A nozzle plate having nozzles formed thereon; A pressure chamber, which is connected to the nozzle; The pressurizing unit pressurizes the pressure chamber; and The vibrating plate transmits the energy generated by the pressurizing section to the pressure chamber. A hydrophobic film is formed on the outer surface of the nozzle plate. This hydrophobic film is composed of a diamond-like carbon film with added fluorine. The hydrophobic film did not form within a certain distance around the nozzle outlet. The specified distance is between 10nm and 500nm.

2. The inkjet head according to claim 1, wherein, The fluorine concentration in the liquefactive film decreases as the depth from the surface increases.

3. The inkjet head according to claim 1 or 2, wherein, At the nozzle outlet, a stepped portion is provided between the outer surface of the nozzle plate and the surface of the hydrophobic film.

4. The inkjet head according to claim 1 or 2, wherein, The contact angle α of the surface of the hydrophobic film relative to the droplet ejected from the nozzle, the contact angle β of the side surface of the hydrophobic film relative to the droplet ejected from the nozzle, and the contact angle γ of the outer surface of the nozzle plate relative to the droplet ejected from the nozzle satisfy the condition of Equation 1. Equation 1: Contact angle α > Contact angle β > Contact angle γ.

5. A method for manufacturing an inkjet head, wherein the inkjet head ejects droplets from a nozzle formed on a nozzle plate and causes the droplets to fall onto a printing medium, wherein, The method for manufacturing the inkjet head includes: A hydrophobic film process, wherein a hydrophobic film composed of a fluorine-added diamond-like carbon film is formed on the outer surface of the nozzle plate; and In the nozzle process, the nozzle is formed on the nozzle plate on which the hydrophobic film is formed. The hydrophobic film did not form within a certain distance around the nozzle outlet. The specified distance is between 10nm and 500nm.

6. The method for manufacturing an inkjet head according to claim 5, wherein, In the nozzle process, the nozzle plate is irradiated with a laser to form the nozzle.

7. A printing apparatus comprising: The inkjet head according to any one of claims 1 to 4; A control unit that controls the action of ejecting droplets from the inkjet head; and The transport unit moves the inkjet head relative to the printing medium.

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