CN115556485A

CN115556485A - Ink jet head, method of manufacturing ink jet head, and printing apparatus

Info

Publication number: CN115556485A
Application number: CN202210720546.9A
Authority: CN
Inventors: 中谷修平; 入江一伸
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2021-07-01
Filing date: 2022-06-23
Publication date: 2023-01-03
Also published as: KR20230005762A; JP2023007189A

Abstract

The invention relates to an ink jet head, a method of manufacturing the ink jet head, and a printing apparatus. An ink jet head (10) is provided with: a nozzle plate (11) in which nozzles (12) are formed; a pressure chamber (14) which communicates with the nozzle (12); a pressurizing unit (30) that pressurizes the pressure chamber (14); and a vibration plate (17) that transmits energy generated by the pressurization unit (30) to the pressure chamber (14). A lyophobic film (50) is formed on the outer surface (11 a) of the nozzle plate (11), and the lyophobic film (50) is a diamond-like carbon film to which fluorine is added.

Description

Ink jet head, method of manufacturing ink jet head, and printing apparatus

Technical Field

The invention relates to an ink jet head, a method of manufacturing the ink jet head, and a printing apparatus.

Background

Conventionally, there is known an inkjet printing apparatus which forms an image on a recording medium by ejecting liquid droplets from nozzles of an inkjet head. In the inkjet head, when liquid droplets are ejected from the nozzles, ink may adhere to the periphery of the ejection-side opening of the nozzles. Thus, when a droplet is discharged from the nozzle, the discharge angle may be curved.

For this reason, for example, in patent document 1, a silicone resin layer is formed on an organic film using a silane coupling agent, an alkoxysilane compound, and a fluoroalkyl silane compound as a nozzle plate, and a fluorine resin layer is formed on the silicone resin layer using a fluorine resin.

Prior art documents

Patent literature

Patent document 1: japanese patent laid-open No. 2007-230061

Disclosure of Invention

An inkjet head according to an aspect of the present invention includes: a nozzle plate in which nozzles are formed; a pressure chamber in communication with the nozzle; a pressurizing section that pressurizes the pressure chamber; and a diaphragm that transmits energy generated by the pressure portion to the pressure chamber, wherein a lyophobic film is formed on an outer surface of the nozzle plate, and the lyophobic film is formed of a diamond-like carbon film to which fluorine is added.

Another aspect of the present invention relates to a method of manufacturing an inkjet head that ejects liquid droplets from nozzles formed in a nozzle plate and lands the liquid droplets on a print medium, the method including: a lyophobic film step of forming a lyophobic film made of a diamond-like carbon film to which fluorine is added on an outer surface of the nozzle plate; and a nozzle step of forming the nozzle in the nozzle plate on which the liquid repellent film is formed.

Drawings

Fig. 1A is a schematic sectional view showing the structure of an inkjet head.

Fig. 1B is a schematic sectional view showing the positional relationship between the liquid repellent film and the nozzle in fig. 1A in detail.

Fig. 1C isbase:Sub>A sectional view taken along linebase:Sub>A-base:Sub>A of fig. 1A.

Fig. 1D is a view of the inkjet head viewed from the printing medium side.

Fig. 1E is a view corresponding to fig. 1B, showing another configuration example of the inkjet head.

Fig. 1F is a view corresponding to fig. 1B, showing another configuration example of the inkjet head.

Fig. 2 is a graph showing an example of the fluorine concentration of the liquid repellent film of the ink jet head.

Fig. 3 is a diagram illustrating an example of a contact angle of a liquid repellent film of an inkjet head.

Fig. 4 is a flowchart for explaining a method of manufacturing the ink jet head.

Fig. 5 is a graph showing the contact angle of the lyophobic film of the ink jet head of example 1.

Fig. 6 is a graph showing the contact angle of the lyophobic film of the ink jet head of comparative example 1.

Fig. 7 is a diagram illustrating a droplet ejection state of the inkjet head of example 1.

Fig. 8 is a view corresponding to fig. 1B in another embodiment.

Fig. 9 is a diagram illustrating a state of ejection of droplets from the inkjet head when a notch is generated.

Fig. 10A is a plan view showing the structure of the printing apparatus.

Fig. 10B is a plan view showing the structure of the printing apparatus.

Fig. 11 is a side view showing the structure of the printing apparatus.

Description of reference numerals:

9. printing device

10. Ink jet head

11. Nozzle plate

12. Nozzle for spraying liquid

14. Pressure chamber

17. Vibrating plate

30. Pressurization part

50. And (4) lyophobic films.

Detailed Description

Since the liquid repellency of the nozzle surface is essential for stable liquid droplet ejection, the liquid repellent film is required to be stable over time. However, for example, the conventional lyophobic film shown in patent document 1 has a problem that the stability with time against ink contact is insufficient. In particular, the liquid repellency of the conventional liquid repellent film is significantly reduced compared to an ink in which particles of an inorganic compound such as titanium oxide are dispersed. This is because the titanium oxide particles are hard and have a polishing action, and the lyophobic film is ground.

The present invention has been made in view of the above problems, and an object thereof is to provide an ink jet head capable of maintaining liquid repellency stably over time even when an ink containing an inorganic compound is used.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are all preferred specific examples of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, connection modes, and the like shown in the following embodiments are examples, and are not intended to limit the present invention. Therefore, among the components of the following embodiments, components that are not described in the technical means that represents the uppermost concept of the present invention will be described as arbitrary components.

< ink jet head >

Fig. 1A to 1D show a configuration example of the inkjet head 10.

The inkjet head 10 of the present invention ejects ink droplets from nozzles formed in a nozzle plate 11 to cause the droplets to land on a print medium. The ink to be ejected is not particularly limited. For example, (1) a quantum dot light-emitting ink containing quantum dot semiconductor particles or a white decorative ink containing titanium oxide, (2) a functional ink for constituting a perovskite solar cell, (3) a conductive ink containing metal nanoparticles, and (4) a biological ink containing cells and the like are ejected. The inkjet head 10 may eject a liquid other than ink.

The inkjet head 10 includes a nozzle plate 11 having one or more nozzles 12, a pressure chamber 14, a pressurizing unit 30, and a vibration plate 17. The inkjet head 10 is used to land ink droplets 70 (see fig. 7) ejected from the nozzles 12 on a print medium (not shown).

In the following description, the longitudinal direction of the inkjet head 10 is referred to as the Y direction, and the width direction orthogonal to the longitudinal direction is referred to as the X direction. The direction orthogonal to the X direction and the Y direction is referred to as a Z direction. In the present invention, the nozzle plate 11 is arranged along the X direction and the Y direction.

Nozzle plate-

As described above, the nozzle plate 11 is provided with the nozzles 12 for ejecting the ink contained in the pressure chambers 14 as liquid droplets. The material of nozzle plate 11 is not particularly limited, and is, for example, a metal such as stainless steel. The nozzle 12 is a through hole formed in the nozzle plate 11 so as to penetrate in the Z direction and has a circular shape in plan view.

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

The shape of the nozzle 12 may not be a straight shape as shown in fig. 1B in a cross-sectional view. For example, as shown in the cross-sectional view of fig. 1E, the opening of the nozzle 12 may be inclined so as to gradually narrow toward the discharge port 12a, so-called "mortar-like". As shown in the cross-sectional view of fig. 1F, the opening of the nozzle 12 may be a so-called "funnel" shape that is linear in the cross-sectional view after gradually narrowing toward the discharge port 12 a. The shapes of fig. 1E and 1F can be appropriately realized by forming the nozzle 12 by laser processing.

As shown in fig. 1A, the nozzle plate 11 may form a part of an outer wall that partitions the pressure chamber 14.

Hydrophobic membranes

The nozzle plate 11 has a liquid repellent film 50 having a property of repelling ink (liquid repellent property) formed on an outer surface 11a (hereinafter, simply referred to as the outer surface 11 a) facing the printing medium.

The liquid repellent film 50 is made of a diamond-like carbon film containing fluorine. The thickness of the lyophobic film 50 is not particularly limited, and is, for example, about 50nm to 300 nm. If the film thickness of the lyophobic film 50 is too thin, lyophobicity is poor. On the other hand, when the thickness of the lyophobic film 50 is too large, the film stress increases, and the nozzle plate 11 warps. When the ink jet head 10 is assembled in such a warped state, it is difficult to bond the ink jet head to another member (for example, the channel plate 16). The use of the fluorine-containing diamond-like carbon film as the liquid repellent film 50 provides excellent wear resistance.

Here, the ink may contain particles of an inorganic compound such as titanium oxide. In the prior art, titanium oxide shaves off the lyophobic film, which may deteriorate lyophobicity. If the liquid repellency around the nozzles is impaired, the ink wets and spreads near the nozzles, and an appropriate meniscus cannot be formed. Thus, the inkjet head 10 cannot stably eject ink. On the other hand, since the ink jet head 10 of the present embodiment uses a diamond-like carbon film, the liquid repellent film 50 has abrasion resistance, and thus the problems of the conventional technique described above do not occur.

As shown in fig. 1B and 1D, the liquid repellent film 50 is formed so as to ensure a gap with respect to the nozzle 12. That is, the liquid repellent film 50 is not formed within a certain distance L around the discharge port 12a of the nozzle 12. In other words, the step 60 is provided between the outer surface 11a of the nozzle plate 11 and the surface 50a of the liquid-repellent film 50 at the ejection port of the nozzle 12. In the present embodiment, the nozzle plate 11 includes a first opening having a first diameter. The lyophobic 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 of a first opening and a second opening.

The gap is not particularly limited, and is, for example, about 10nm to 500nm, and more preferably 200nm or less. If the gap is too large, the wettability around the nozzle 12 is high, and the ink may spread.

The lyophobic film 50 has a gradient in fluorine concentration with respect to the depth direction D (Z direction). Specifically, the fluorine concentration is higher as the distance from the surface 50a of the liquid repellent film 50 is closer, and the fluorine concentration becomes lower as the distance from the bottom surface (the surface in contact with the nozzle plate 11) is closer. For example, the fluorine concentration in the lyophobic film 50 is about 1.0atom% to 2.0atom% in the vicinity of the surface, and about 0.2atom% to 0.5atom% in the vicinity of the bottom.

Fig. 2 shows the results of measuring the fluorine concentration of the lyophobic film 50. The fluorine concentration was determined by Energy Dispersive X-ray analysis (EDX: energy Dispersive X-ray Spectroscopy). As shown in fig. 2, it is understood that fluorine is present at a concentration of 1.4 atomic% (atom%) in the vicinity of the surface of the lyophobic film 50, and fluorine is present at a concentration of 0.3 atomic% (atom%) in the vicinity of the bottom surface.

By providing the gradient of the fluorine concentration as described above, adhesion between the outer surface 11a of the nozzle plate 11 and the bottom surface of the liquid-repellent film 50 can be improved, and liquid repellency at the surface 50a of the liquid-repellent film 50 can be ensured. In addition, the meniscus of the ink at the nozzle 12 can be formed more stably.

The relationship of the contact angles α, β, γ with respect to the ink droplet 70 is shown in [ formula 1 ]. The contact angle α is a contact angle of the surface 50a of the liquid repellent film 50 with respect to the ink droplet 70. The contact angle β is a contact angle of the side surface 50b of the liquid repellent film 50 with respect to the ink droplet 70. Contact angle γ is the contact angle of outer surface 11a of nozzle plate 11 with respect to ink droplet 70.

[ formula 1]

Contact angle alpha > contact angle beta > contact angle gamma

Here, there are two kinds of contact angles, that is, an angle of repose and an angle of receding. Hereinafter, the angle of repose and the receding angle will be described.

When a liquid is dropped on a solid surface, the liquid is rounded by its own surface tension, and the relationship shown in [ equation 2] is established. [ formula 2] is referred to as Young's formula.

[ formula 2]

γs＝γL×cosθ+γSL

γ s: surface tension of solid

γ L: surface tension of liquid

γ SL: interfacial tension of solid and liquid

The angle θ formed by the tangent to the ink droplet 70 and the solid surface at this time is referred to as a contact angle. Herein, a contact angle at which a liquid is at rest on a solid surface and reaches an equilibrium state is referred to as an angle of repose.

On the other hand, the contact angle in a dynamic state in which the interface between the liquid and the solid moves, that is, the interface of the liquid droplet moves is referred to as an "advancing angle" and a "receding angle". Here, attention is paid to the dynamic contact angle, i.e., receding angle, after the solid surface is wetted with the liquid. The receding angle of the liquid-repellent film 50 with respect to the ink is, for example, 30 degrees or more.

Fig. 3 shows an example in which the values of the contact angles α, β, γ described above are compared with a specific ink as an example. In fig. 3, the ink X is an ink in which particles of titanium oxide are dispersed in a solvent mainly containing water. The ink Y is an ink in which titanium oxide is dispersed in a liquid resin containing an acrylic monomer as a main component.

As shown in fig. 3, it is understood that the relationship between the contact angles α, β, γ is the relationship of the above-described [ formula 1] in both of the inks X, Y. This prevents the liquid from adhering to the nozzle surface, and thus enables favorable droplet discharge. The contact angle value of ink X is larger than the contact angle value of ink Y as a whole, and the wettability is low (wetting is difficult).

Pressure chamber

Returning to fig. 1, the pressure chamber 14 communicates with the nozzle 12. The pressure chamber 14 communicates with the independent flow path 15 via the throttle 20. The volume of the pressure chamber 14 changes according to the deformation of the vibration plate 17. The ink is ejected from the nozzle 12 due to the change in the volume. The resonance period of ink changes due to the volume of the pressure chamber 14 and the flow path resistance of the orifice 20, and the ejection volume and the ejection speed of the ejected ink droplets 70 change. Therefore, the volume of the pressure chamber 14 and the like need to be optimally adjusted as necessary.

-a pressurization part

The pressurizing unit 30 is provided corresponding to the pressure chamber 14 and is displaced by application of a voltage. As the pressurizing unit 30, for example, a d33 mode or d31 mode laminated piezoelectric element or a piezoelectric element using a shear mode can be used. In addition, instead of the piezoelectric element, an energy generating element such as an electrostatic actuator or a heat generating element may be used as the pressurizing portion 30.

-a vibrating plate-

The vibration plate 17 transmits energy generated by the pressurization part 30 to the pressure chamber 14. In fig. 1, the diaphragm 17 is disposed between the pressurizing portion 30 and the pressure chamber 14 so as to be in contact with the pressurizing portion 30. The vibrating plate 17 is deformed by the displacement of the pressing portion 30. The material constituting the vibrating plate 17 is not particularly limited, and is made of, for example, metal such as nickel or stainless steel, or resin such as polyimide. The thickness of the vibrating plate 17 is not particularly limited, and is preferably 5 to 50 μm, for example.

In fig. 1A, only one nozzle 12 and its corresponding components (for example, the pressure chamber 14, the throttle section 20, the independent flow path 15, the pressurizing section 30, and the like) are shown, but as shown in fig. 1C, a plurality of these components are provided along the Y direction.

Flow path of ink-

The common channel 51, the independent channels 15, and the throttle section 20 are channels of ink.

Fig. 1C is a schematic cross-sectional view showing the arrangement of the nozzles 12 and the ink channels of the inkjet head 10.

As shown in fig. 1C, the common flow path 51 communicates with the independent flow path 15. The independent flow path 15 communicates with the pressure chamber 14 via the throttle portion 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 throttle units 20.

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) as a supply source of ink. The ink reservoir can be said to be a second ink supply tank that exists between the common flow path 51 and the ink supply tank. By pressurizing or depressurizing this ink reservoir, the circulation flow rate of the ink flowing through the common channel 51 and the independent channel 15 in the inkjet head 10 can be controlled. Further, the pressure applied to the nozzles 12 can be controlled to eject the ink in an appropriate state.

In fig. 1C, one of the common channels 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). The ink flows from the ink reservoir to one of the common channels 51 through the supply port, and flows from the common channel 51 to the pressure chambers 14 through the individual channels 15 and the throttle units 20. The ink flowing from each pressure chamber 14 into the other common channel 51 is discharged from the discharge port. The discharged ink is recovered by an ink recovery tank connected to the ink supply tank, and flows into the ink supply tank again.

The width of the throttle portion 20 is narrower than the width of the independent flow path 15. This makes it difficult for the pressure wave in the pressure chamber 14 generated by the deformation of the diaphragm 17 to escape to the independent flow path 15. Thereby, the ink in the pressure chamber 14 is ejected as ink droplets 70 from the nozzle 12.

< method for manufacturing ink jet head >

Hereinafter, a method of manufacturing the ink jet head 10 will be specifically described with reference to the flowchart of fig. 4.

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

In step S1, a lyophobic film 50 made of a diamond-like carbon film containing fluorine is formed on the outer surface 11a of the nozzle plate raw material. For forming (film formation) the diamond-like carbon film, a CVD (Chemical Vapor Deposition) method (for example, thermal CVD, optical CVD plasma CVD) is used. In the CVD method, a gas or liquid is gasified. Then, the gas is energized by heat or light, or is plasmatized by high frequency, so that the raw material substance is made into radicals, adsorbed and deposited on the substrate.

As a method for making fluorine contained, for example, a hydrocarbon gas such as acetylene (C2H 2) or a gas containing fluorine can be used as a raw material gas. Alternatively, the surface of the diamond-like carbon film may be modified with fluorine by treating the surface of the film with a gas containing fluorine after the formation of the diamond-like carbon film. The liquid repellent film 50 is preferably formed by gradually increasing the fluorine concentration in the source gas from the middle of the film formation.

In the subsequent step S2, the nozzle 12 is formed as the nozzle plate 11 on the nozzle plate blank on which the liquid repellent film 50 is formed.

The method of forming the nozzle 12 is not particularly limited, and the following method can be used, for example. For example, the nozzles 12 may be formed by laser processing a nozzle plate material. The nozzle 12 may be formed by punching a nozzle plate material to form a hole and then polishing the periphery of the hole. In addition, the nozzle 12 may be formed by etching.

In the following step S3, the assembly of the inkjet head 10 is performed.

Specifically, the pressure chamber 14, the independent flow path 15, the diaphragm 17, the common flow path 51, and the orifice 20 (hereinafter, collectively referred to as "components") are manufactured by, for example, thermal diffusion bonding of a plurality of metal plates processed by etching or the like. These components may be formed by etching of a silicon material or the like.

The nozzle plate 11 is bonded to a flow path plate 16 in which the independent flow path 15 and the orifice 20 are formed, and the flow path plate 16 is bonded to the diaphragm 17. The housing 18, which is a housing of the inkjet head 10, is bonded to the structure formed by the bonding. The common flow path 51 is provided in the casing 18. Further, the pressurizing unit 30 is bonded to the vibration plate 17, thereby completing the ink jet head 10.

As described above, the method of manufacturing the ink jet head 10 of the present invention includes: a liquid repellent film step of forming a liquid repellent film 50 made of a diamond-like carbon film to which fluorine is added on an outer surface 11a of the nozzle plate 11; and a nozzle step of forming nozzles 12 in the nozzle plate 11 on which the lyophobic film 50 is formed.

In this way, by forming the nozzle 12 after the lyophobic film 50 is formed on the nozzle plate 11, a portion where the lyophobic film 50 is not formed is formed around the nozzle 12. This can improve the straightness of the flight of the ink droplets 70.

< printing apparatus >

The inkjet head 10 may be provided in the printing apparatus 9 shown in fig. 10A, 10B, and 11. The printing device 9 includes a conveyance unit. The structure of the conveying unit is not particularly limited, and includes, for example, a base 1, a guide 2 disposed on the base 1, a movable unit 7 movable along the guide 2, a conveying table 3 connected to the movable unit 7 and conveying the substrate in the scanning direction, a gantry 4 disposed on the base 1, and a line head 5 attached to the gantry 4. The line head 5 is configured by arranging a plurality of ink jet heads 10 in a row to form a unit. Although not shown, the printing apparatus 9 includes a control unit in addition to the above. The control unit controls the ejection operation of the inkjet head 10. The control unit is constituted by, for example, a CPU (processor), and a memory storing information such as a program for operating the CPU and a processing result in the CPU.

Specifically, the control unit generates a drive voltage signal to be applied to the voltage applying unit 30. The control unit controls the pressurizing operation of the pressurizing unit 30 using the drive voltage signal. Since the pressurization unit 30 is bonded to the diaphragm 17, the control of the pressurization unit 30 has the same effect as the control of the diaphragm 17, and the ejection operation of the ink jet head 10 can be controlled by the control of the pressurization unit 30.

The conveyance stage 3 moves the inkjet head 10 and the print medium 6 on which the ink droplets 70 are landed relative to each other.

< evaluation of examples and comparative examples based on the kind of lyophobic film >

The following describes the evaluation of each of examples and comparative examples.

Here, as the evaluation of the durability of the lyophobicity, a comparative evaluation of the contact angle of the lyophobic film 50 was performed. In example 1, a diamond-like carbon film containing fluorine was used as the liquid repellent film 50. In contrast, in the comparative example, a film formed by a dehydration condensation reaction by silane coupling as in patent document 1 was used as the lyophobic film instead of the lyophobic film 50 described above. The examples and comparative examples all have the same structure except for the lyophobic film.

In this comparative evaluation, the contact angle was measured using a contact angle meter DSA100 (manufactured by KRUSS). Evaluation of durability the initial contact angle of the lyophobic film 50 and the contact angle after 300 wipes with a cloth in a state where an aqueous ink containing titanium oxide is attached to the surface of the lyophobic film 50 (hereinafter referred to as the contact angle after the rubbing test) were measured. The particle size of the titanium oxide is about 1 μm.

(example 1)

In example 1, an inkjet head was used in which the aforementioned 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.

In example 1, the liquid repellent film 50 was formed on the outer surface of the nozzle plate 11 by CVD, and then the nozzle 12 was formed by laser processing. In this manufacturing process, a step 60 is provided as shown in fig. 1. The thickness of the water-repellent film 50 was 120nm, and the gap L between the nozzle 12 and the film was 170nm.

Fig. 5 shows the contact angle of the lyophobic film 50 of example 1. As shown in the left column diagram of fig. 5, in the initial state, the angle of repose is 97 °, and the receding angle is 82 °. As shown in the right bar graph of fig. 5, the contact angle after the friction test was 95 ° at the angle of repose and 61 ° at the angle of retreat.

Here, as the inventors' knowledge, it is necessary that the contact angle of the liquid repellent film 50 be 40 ° or more as a receding angle in order to stably discharge the ink droplet 70.

In example 1, it is understood that, by adopting the structure of the present embodiment, the liquid repellent film 50 is ground by titanium oxide and the contact angle is lowered, but liquid droplets can be stably ejected over time.

Fig. 7 shows a flying state when the ink droplets 70 are flown using the inkjet head 10 of embodiment 1. The meniscus of the ink droplet 70 is stably formed from the outer surface 11a of the nozzle plate 11 where the lyophobic film 50 is not formed to the side surface 50b of the lyophobic film 50. This makes it clear that the ink droplets 70 fly with good straightness.

Comparative example 1

In comparative example 1, an ink jet head in which a lyophobic film formed by a dehydration condensation reaction based on silane coupling was formed on the outer surface 11a of the nozzle plate 11 by a spin coating method was used instead of the lyophobic film 50 of example 1.

Fig. 6 shows the contact angle of the lyophobic film of comparative example 1. As shown in the left-hand bar chart of fig. 6, in the initial state, the angle of repose is 83 ° and the receding angle is 82 °. As shown in the right bar graph of fig. 6, the contact angle after the friction test was 62 ° in the angle of repose and 5 ° in the angle of retreat.

In addition, titanium oxide has a very high hardness and has a polishing effect. Therefore, the lyophobic film is ground by titanium oxide depending on the kind of lyophobic film, and lyophobicity is lowered. Although not shown, it was confirmed that in comparative example 1, most of the liquid repellent film was ground with titanium oxide, and the contact angle was greatly reduced.

Here, in the state of the receding angle of 5 °, the ink is not repelled, and the ink wets and spreads on the liquid repellent film 50. In this state, the meniscus formed by the nozzle 12 is difficult to stably exist, and the droplet is difficult to fly correctly.

As described above, the inkjet head 10 of the present embodiment includes: a nozzle plate 11 formed with nozzles 12; a pressure chamber 14 communicating with the nozzle 12; a pressurizing unit 30 that pressurizes the pressure chamber 14; and a vibration plate 17 that transmits energy generated by the pressurization part 30 to the pressure chamber 14. A lyophobic film 50 made of a diamond-like carbon film to which fluorine is added is formed on the outer surface 11a of the nozzle plate 11.

According to the present embodiment, since the liquid repellent film 50 made 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 the ink from adhering to the outer surface 11a, and thus enables satisfactory ejection of droplets. The printing apparatus using the ink jet head 10 described above can obtain the same effect.

In the above-described embodiment, the region where the liquid repellent film 50 is not formed, that is, the non-formation region of the liquid repellent film 50 is provided within a certain distance (for example, 10nm to 500 nm) around the ejection port of the nozzle. In other words, in the ejection orifice 12a of the nozzle 12, the 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.

This can further improve the reliability and durability of the ink jet head 10. In this regard, a specific example will be described below in "another embodiment".

In the above-described embodiment, the relationship between the contact angle α of the surface 50a of the liquid-repellent film 50 with respect to the ink droplet 70 ejected from the nozzle 12, the contact angle β of the side surface 50b of the liquid-repellent film 50 with respect 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 with respect to the ink droplet 70 ejected from the nozzle 12 is the relationship of the above-described [ expression 1 ].

This can suppress adhesion of particles, a binder, and the like contained in the ink. Therefore, clogging due to particles, a binder, and the like can be suppressed, and stable discharge over time can be achieved. As a result, high quality printing can be achieved.

< other embodiment >

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, in the above-described embodiment, the example in which the non-formation region where the liquid repellent film 50 is not formed is provided at the certain distance L around the discharge port 12a of the nozzle 12 has been described, but the present invention is not limited thereto.

For example, the non-formation region of the liquid repellent film 50 may not be provided around the discharge port 12a of the nozzle 12. That is, as shown in fig. 8, the inner wall surface 12b of the nozzle 12 may be substantially flush with the side surface of the liquid repellent film 50.

In this case, when the contact angle of the surface 50a of the liquid repellent film 50 with respect to the ink is α, the contact angle of the side surface 50b of the liquid repellent film 50 is β, and the contact angle of the inner wall surface 12b of the nozzle 12 is θ, the relationship among the contact angles α, β, and θ is as [ equation 3].

[ formula 3]

Contact angle alpha > contact angle beta > contact angle theta

This prevents the liquid from adhering to the nozzle surface, and enables satisfactory ejection of liquid droplets. In addition, 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 droplets 70 to fly with good straightness.

In the structure of fig. 8, after the nozzles 12 are formed on the nozzle plate 11, the lyophobic film 50 made of a fluorine-containing diamond-like carbon film may be formed by CVD.

In the formation of the lyophobic film 50, the lyophobic film 50 is formed in a state of masking the portion of the nozzle 12, whereby the lyophobic film 50 can be set to a state of not being formed in the nozzle 12.

In this case, as shown in fig. 8, unlike the case of the foregoing example 1, the liquid-repellent film 50 is formed to be in a state of being in close proximity to the periphery of the ejection port of the nozzle 12. When cleaning the inkjet head 10 (for example, the nozzle 12), the cleaning cloth may come into contact with the liquid repellent film 50. Alternatively, the printed media may inadvertently come into contact with the lyophobic film 50. As shown in fig. 9, the liquid repellent film 50 (diamond-like carbon film) may be chipped at the corner portion around the discharge port 12a of the nozzle 12 due to friction with the cloth, the print medium, or the like.

Fig. 9 shows a flying state when the ink droplets 70 are caused to fly by using the ink jet head 10 in which the liquid repellent film 50 is chipped. As shown in fig. 9, if a notch is formed, the meniscus has an asymmetric shape on the liquid-repellent film 50, and the straightness of the ink droplet 70 is impaired. On the other hand, as in example 1 described above, by providing the non-formation region of the lyophobic film 50 around the discharge port 12a of the nozzle 12, the lyophobic film 50 can be made less likely to be chipped. This can further improve the reliability and durability of the ink jet head 10.

According to the present invention, the lyophobic film made of the diamond-like carbon film to which fluorine is added is formed on the outer surface of the nozzle plate. This makes it possible to maintain a liquid repellency that is stable over time even when a liquid containing an inorganic compound is ejected from the inkjet head.

Industrial applicability

As described above, the ink jet head, the method for manufacturing the ink jet head, and the printing apparatus according to the present invention are useful for discharging quantum dot light-emitting ink containing quantum dot semiconductor particles, white decorative ink containing titanium oxide, functional ink for constituting a perovskite solar cell, conductive ink containing metal nanoparticles, biological ink containing cells and the like, for example, and have high industrial applicability.

Claims

1. An ink jet head includes:

a nozzle plate in which nozzles are formed;

a pressure chamber in communication with the nozzle;

a pressurizing unit that pressurizes the pressure chamber; and

a vibrating plate that transmits energy generated by the pressure section to the pressure chamber,

a lyophobic film is formed on the outer surface of the nozzle plate, and the lyophobic film is a diamond-like carbon film added with fluorine.

2. An ink jet head according to claim 1,

the lyophobic film becomes deeper as the depth from the surface becomes, and the fluorine concentration becomes smaller.

3. An ink jet head according to claim 1 or 2,

the liquid repellent film is not formed within a certain distance around the ejection port of the nozzle.

4. An ink jet head according to claim 3,

the certain distance is 10nm to 500nm.

5. An ink jet head according to claim 1 or 2,

a stepped portion is provided between an outer surface of the nozzle plate and a surface of the liquid-repellent film at an ejection port of the nozzle.

6. An ink jet head according to any of claims 1 to 4,

a relationship between a contact angle α of the surface of the liquid repellent film with respect to the liquid droplet ejected from the nozzle, a contact angle β of the side surface of the liquid repellent film with respect to the liquid droplet ejected from the nozzle, and a contact angle γ of the outer surface of the nozzle plate with respect to the liquid droplet ejected from the nozzle satisfies a condition of expression 1,

formula 1: contact angle α > contact angle β > contact angle γ.

7. A method of manufacturing an ink jet head which ejects liquid droplets from nozzles formed in a nozzle plate and lands the liquid droplets on a print medium,

the method of manufacturing the ink jet head includes:

a lyophobic film step of forming a lyophobic film made of a diamond-like carbon film to which fluorine is added on an outer surface of the nozzle plate; and

and a nozzle step of forming the nozzle in the nozzle plate on which the liquid repellent film is formed.

8. A method of manufacturing an ink jet head according to claim 7,

in the nozzle step, the nozzle plate is irradiated with laser light to form the nozzle.

9. A printing apparatus includes:

an ink jet head according to any one of claims 1 to 6;

a control unit that controls an operation of ejecting the liquid droplets from the inkjet head; and

and a conveying unit that moves the inkjet head and the print medium relative to each other.