Liquid ejection head and method for regenerating liquid ejection head

Abstract

To impart liquid repellency to a nozzle substrate by a simple manufacturing process.SOLUTION: The liquid discharge head includes a nozzle substrate having a nozzle for discharging a liquid, a liquid repellent film having liquid repellency to the liquid is provided on the surface of the nozzle substrate, the liquid repellent film contains a filler composed of a plurality of needle-shaped particles, and irregularities are formed on the surface of the liquid repellent film by the plurality of needle-shaped particles.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection head and a method for remanufacturing a liquid ejection head. [Background technology]

[0002] A liquid ejection head, such as an inkjet head, generally includes a nozzle substrate having nozzles for ejecting liquid. For example, Patent Document 1 describes a liquid ejection head including a nozzle plate having a water-repellent uneven structure due to the lotus effect on the droplet ejection surface. The uneven structure is formed by laser processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-147350 Summary of the Invention [Problem to be solved by the invention]

[0004] In the liquid ejection head described in Patent Document 1, the concave-convex structure of the nozzle plate needs to be formed by laser processing, and therefore there has been a demand for simplification of the manufacturing process. [Means for solving the problem]

[0005] In order to solve the above problems, a liquid ejection head according to a preferred aspect of the present disclosure includes a nozzle substrate having a nozzle for ejecting a liquid, and a liquid-repellent film having liquid-repellent properties against the liquid is provided on the surface of the nozzle substrate, the liquid-repellent film containing a filler composed of a plurality of acicular particles, and unevenness caused by the plurality of acicular particles is formed on the surface of the liquid-repellent film.

[0006] A preferred embodiment of the present disclosure provides a method for regenerating a liquid ejection head, which includes a nozzle substrate having nozzles for ejecting liquid, and a first liquid-repellent film that is liquid-repellent to the liquid, is provided on the surface of the nozzle substrate, and the liquid-repellent film contains a filler composed of a plurality of acicular particles, and the surface of the liquid-repellent film has irregularities formed by the plurality of acicular particles. When the thickness of the first liquid-repellent film reaches a predetermined value or less, a new second liquid-repellent film is formed on the surface of the nozzle substrate. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the configuration of a liquid ejection device. [Figure 2] FIG. 2 is an exploded perspective view of the liquid ejection head according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 3 is an explanatory diagram of a nozzle substrate of the liquid ejection head shown in FIG. [Figure 5] FIG. 1 is a diagram showing an example of a needle-shaped particle. [Figure 6] FIG. 10 is an explanatory diagram of a state in which the liquid-repellent film has been scraped off. [Figure 7] FIG. 10 is an explanatory diagram of the lifespan of a liquid-repellent film. [Figure 8] 5A to 5C are explanatory diagrams of a method for regenerating a liquid ejection head according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0009] For convenience, the following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. In the following, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. Furthermore, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction. The Z1 direction corresponds to "upward" or "top," and the Z2 direction corresponds to "downward" or "bottom." Hereinafter, viewing in the Z1 or Z2 direction may be referred to as "planar view."

[0010] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°.

[0011] A: Embodiment A1: Overall configuration of the liquid ejection device 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100. The liquid ejection device 100 is an inkjet printing device that ejects ink, which is an example of a "liquid," in the form of droplets toward a recording medium M. The recording medium M is, for example, printing paper. Note that the recording medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0012] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 10, a control module 20, a transport mechanism 30, a movement mechanism 40, a plurality of liquid ejection heads 50, and a maintenance mechanism 60.

[0013] The liquid container 10 stores ink. Specific examples of the liquid container 10 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the liquid container 10 is arbitrary.

[0014] The control module 20 controls the operation of each element of the liquid ejection device 100. The control module 20 includes, for example, a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and a storage circuit such as a semiconductor memory. Here, the control module 20 outputs a drive signal Com for driving the liquid ejection head 50, and a control signal SI for controlling the driving of the liquid ejection head 50.

[0015] The transport mechanism 30 transports the recording medium M along the Y axis under the control of the control module 20.

[0016] The movement mechanism 40 reciprocates the liquid ejection head 50 along the X axis under the control of the control module 20. The movement mechanism 40 has a substantially box-shaped transport body 41 called a carriage that houses the liquid ejection head 50, and an endless transport belt 42 to which the transport body 41 is fixed. In this embodiment, the movement mechanism 40 not only reciprocates the liquid ejection head 50 along the X axis over the entire width of the recording medium M, but is also movable to a position that overlaps with the maintenance mechanism 60 in the direction along the Z axis. The number of liquid ejection heads 50 mounted on the transport body 41 is not limited to one, and may be multiple. In addition to the liquid ejection head 50, the aforementioned liquid container 10 may also be mounted on the transport body 41.

[0017] Each of the plurality of liquid ejection heads 50 ejects ink supplied from the liquid container 10 from each of the plurality of nozzles N onto the recording medium M under the control of the control module 20. This ejection is performed in parallel with the transport of the recording medium M by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, thereby forming an ink image on the surface of the recording medium M.

[0018] In the example shown in Fig. 1, the number of liquid ejection heads 50 is four. The number of liquid ejection heads 50 is not limited to the example shown in Fig. 1 and may be any number, and may be one, or a plurality of three or less, or five or more. The arrangement of the plurality of liquid ejection heads 50 is also not limited to the example shown in Fig. 1 and may be any arrangement.

[0019] The maintenance mechanism 60 is a mechanism for performing maintenance on the liquid ejection head 50. The maintenance mechanism 60 of this embodiment has a wiping member 61.

[0020] The wiping member 61 is a porous member for wiping the surface of a nozzle substrate 530 (described later) of the liquid ejection head 50, and is made of, for example, a fibrous material such as a woven or nonwoven fabric, or a sponge. The wiping member 61 is disposed at a position offset in the direction along the X-axis from the transport area of ​​the recording medium M. When the wiping member 61 wipes the nozzle substrate 530, the movement mechanism 40 positions the liquid ejection head 50 at a position overlapping with the wiping member 61 as viewed in the direction along the Z-axis. At this time, the liquid ejection head 50 may be moved in the direction along the X-axis relative to the wiping member 61 by driving the movement mechanism 40, or the wiping member 61 may be moved in the direction along the X-axis or Y-axis relative to the liquid ejection head 50 by driving a mechanism separate from the movement mechanism 40.

[0021] The wiping member 61 may wipe the nozzle substrates 530 of the multiple liquid ejection heads 50 all at once, or may selectively and individually wipe the nozzle substrate 530 of one of the multiple liquid ejection heads 50. The size, shape, arrangement, and other aspects of the wiping member 61 are not limited to the example shown in FIG. 1 and may be arbitrary. For example, the wiping member 61 may be disposed at a position offset in the X2 direction from the transport area of ​​the recording medium M, or may be composed of multiple wiping members divided for each liquid ejection head 50. The maintenance mechanism 60 may have, in addition to the function of performing the wiping operation using the wiping member 61, a function of performing suction cleaning to suck out ink from the nozzles N of the liquid ejection head 50, a function of capping all of the nozzles N of the liquid ejection head 50, and the like.

[0022] A2: Liquid ejection head Fig. 2 is an exploded perspective view of a liquid ejection head 50 according to an embodiment. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2. An example of the configuration of the liquid ejection head 50 will now be described.

[0023] As shown in FIGS. 2 and 3, the liquid ejection head 50 has a plurality of nozzles N arranged in a direction along the Y axis.

[0024] The multiple nozzles N of the liquid ejection head 50 are divided into a first nozzle row Ln1 and a second nozzle row Ln2 that are arranged at intervals along the X-axis. Each of the first nozzle row Ln1 and the second nozzle row Ln2 is a collection of multiple nozzles N that are linearly arranged along the Y-axis.

[0025] The liquid ejection heads 50 are configured to be substantially symmetrical with respect to each other in the direction along the X-axis. However, the positions of the multiple nozzles N of the first nozzle row Ln1 and the multiple nozzles N of the second nozzle row Ln2 in the direction along the Y-axis may or may not match. 2 and 3 illustrate a configuration in which the positions of the multiple nozzles N of the first nozzle row Ln1 and the multiple nozzles N of the second nozzle row Ln2 in the direction along the Y-axis match each other.

[0026] As shown in FIGS. 2 and 3, the liquid ejection head 50 has a communication substrate 510, a pressure chamber substrate 520, a nozzle substrate 530, a vibration absorber 540, a vibration plate 550, a plurality of piezoelectric elements 560, a protection substrate 570, a case 580, and a wiring substrate 590.

[0027] The communication substrate 510 and the pressure chamber substrate 520 are stacked in this order in the Z1 direction to form a flow path for supplying ink to the multiple nozzles N. A vibration plate 550, multiple piezoelectric elements 560, a protective substrate 570, a case 580, a wiring substrate 590, and a drive circuit 600 are disposed in an area positioned in the Z1 direction from the stack of the communication substrate 510 and the pressure chamber substrate 520. On the other hand, a nozzle substrate 530 and a vibration absorber 540 are disposed in an area positioned in the Z2 direction from the stack. Each element of the liquid ejection head 50 is generally a plate-like member elongated in the Y direction, and is joined to each other, for example, by an adhesive. Each element of the liquid ejection head 50 will be described in order below.

[0028] The nozzle substrate 530 is a plate-like member provided with a plurality of nozzles N of each of the first nozzle row Ln1 and the second nozzle row Ln2. Each of the plurality of nozzles N is a through-hole that allows ink to pass through. Thus, the nozzle substrate 530 has nozzles N that eject ink. Here, the surface of the nozzle substrate 530 facing the Z2 direction is the nozzle surface FN. The nozzle substrate 530 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as dry etching or wet etching. However, other known methods and materials may also be used as appropriate to manufacture the nozzle substrate 530. Furthermore, the cross-sectional shape of the nozzle N is typically circular, but is not limited thereto and may be non-circular, such as polygonal or elliptical.

[0029] Although not shown in Figures 2 and 3, a liquid-repellent film 5, which will be described later, is provided on the nozzle surface FN, which is the surface of the nozzle substrate 530. The liquid-repellent film 5 is a film that has liquid-repellent properties against ink due to the lotus effect. The liquid-repellent film 5 will be described later with reference to Figures 4 to 8. Note that "liquid repellency" refers to the property of repelling ink, and is the property of having a contact angle with ink of 90° or more (preferably 120° or more, and more preferably 150° or more). Note that when the target liquid is water or a water-based liquid, "liquid repellency" can also be said to be water repellency, which is the property of repelling water.

[0030] The communication substrate 510 is provided with a flow path R1, a plurality of supply flow paths Ra, and a plurality of communication flow paths Na for each of the first nozzle row Ln1 and the second nozzle row Ln2. The flow path R1 is a flow path provided in common to a plurality of nozzles N, communicates with the plurality of nozzles N, and is a flow path upstream of the nozzles N, and is configured as an elongated hole extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. Each of the supply flow path Ra and the communication flow path Na is a flow path configured as a through-hole formed for each nozzle N. Each supply flow path Ra communicates with the flow path R1.

[0031] The communication substrate 510 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example, in the same manner as the above-described nozzle substrate 530. However, other known methods and materials may also be used appropriately to manufacture the communication substrate 510.

[0032] The pressure chamber substrate 520 is a plate-like member in which a plurality of pressure chambers C, called cavities, are provided for each of the first nozzle row Ln1 and the second nozzle row Ln2. The pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the X axis in a plan view.

[0033] The pressure chamber substrate 520 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example, in the same way as the nozzle substrate 530. However, other known methods and materials may also be used appropriately to manufacture the pressure chamber substrate 520.

[0034] The pressure chambers C are located between the communication substrate 510 and the vibration plate 550. A plurality of pressure chambers C are arranged in the direction along the Y axis for each of the first nozzle row Ln1 and the second nozzle row Ln2. The pressure chambers C are also in communication with the communication flow path Na and the supply flow path Ra. Therefore, the pressure chambers C are in communication with the nozzles N via the communication flow path Na, and are in communication with the flow path R1 via the supply flow path Ra.

[0035] A vibration plate 550 is disposed on the surface facing the Z1 direction of the pressure chamber substrate 520. The vibration plate 550 is a plate-like member that can vibrate elastically, and is vibrated by a piezoelectric element 560. Details of the vibration plate 550 will be described later with reference to FIG.

[0036] On the surface of the vibration plate 550 facing the Z1 direction, a plurality of piezoelectric elements 560 are arranged corresponding to the nozzles N of each of the first nozzle row Ln1 and the second nozzle row Ln2. Each piezoelectric element 560 is a passive element that deforms when supplied with a potential according to the drive signal Com, and generates pressure fluctuations in the ink in the pressure chambers C. Each piezoelectric element 560 has an elongated shape extending in the direction along the X axis in a plan view. The plurality of piezoelectric elements 560 are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers C. The piezoelectric elements 560 overlap the pressure chambers C in a plan view. The above-mentioned piezoelectric elements 560 apply pressure to the pressure chambers C that communicate with the nozzles N that eject ink. Details of the piezoelectric elements 560 will be described later with reference to FIG. 5.

[0037] Protective substrate 570 is a plate-like member placed on the surface of diaphragm 550 facing the Z1 direction, and protects multiple piezoelectric elements 560 and reinforces the mechanical strength of diaphragm 550. Here, multiple piezoelectric elements 560 are housed in space S between protective substrate 570 and diaphragm 550. Protective substrate 570 is made of, for example, a resin material.

[0038] The case 580 is a case for storing ink to be supplied to the multiple pressure chambers C. The case 580 is made of, for example, a resin material. The case 580 is provided with a flow path R2 for each of the first nozzle row Ln1 and the second nozzle row Ln2. The flow path R2 is a space connected to the aforementioned flow path R1 and is formed as an elongated hole extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. The flow path R2 communicates with the nozzles N and, together with the flow path R1, functions as a reservoir R for storing ink to be supplied to the multiple pressure chambers C. The case 580 is provided with an inlet HL for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chambers C via each supply flow path Ra. Note that the position and number of the inlet HL for each reservoir R are not limited to the examples shown in FIGS. 2 and 3 and may be any.

[0039] The vibration absorber 540, also called a compliance substrate, is a flexible resin film that forms the wall surface of the reservoir R and absorbs pressure fluctuations of the ink inside the reservoir R. The vibration absorber 540 may also be a flexible thin metal plate. The surface of the vibration absorber 540 facing the Z1 direction is bonded to the communication substrate 510 with an adhesive or the like.

[0040] The wiring board 590 is mounted on the surface of the diaphragm 550 facing the Z1 direction and is a mounting component for electrically connecting the control module 20 and the liquid ejection head 50. The wiring board 590 is a flexible wiring board such as a COF (Chip On Film), an FPC (Flexible Printed Circuit), or an FFC (Flexible Flat Cable). A drive circuit 600 is mounted on the wiring board 590 of this embodiment. Under the control of the control module 20, the drive circuit 600 switches whether or not to supply pulses included in the drive signal Com output from the control module 20 to each of the multiple piezoelectric elements 560 of the liquid ejection head 50. As described above, the wiring board 590 supplies the drive signal Com that drives the piezoelectric elements 560. Note that the wiring board 590 may be a rigid board. In this case, the drive circuit 600 is mounted on the rigid board or on a flexible board connected to the rigid board.

[0041] A3: Nozzle board Fig. 4 is an explanatory diagram of the nozzle substrate 530 of the liquid ejection head 50 shown in Fig. 2. As shown in Fig. 4, a liquid-repellent film 5 is provided on the nozzle surface FN of the nozzle substrate 530. Fig. 4 schematically shows the configuration of the liquid-repellent film 5. The area in which the liquid-repellent film 5 is formed needs only to be an area surrounding the nozzles N on the nozzle surface FN, and does not have to be the entire area of ​​the nozzle surface FN.

[0042] The liquid-repellent film 5 includes a filler 5a and a binder 5b. The filler 5a is made up of a plurality of acicular particles PA. The binder 5b is a resin composition that bonds the plurality of acicular particles PA together and also bonds the plurality of acicular particles PA to the nozzle substrate 530. Such a liquid-repellent film 5 is formed, for example, by applying a solution containing the filler 5a and the binder 5b to the nozzle substrate 530 and then curing or solidifying the solution. Note that the liquid-repellent film 5 may include, in addition to the filler 5a and the binder 5b, various additives, or may include fillers other than acicular particles, for example.

[0043] The acicular particles PA are either rod-shaped particles that extend one-dimensionally, or particles that protrude in different directions two- or three-dimensionally. As a result, an unevenness FA formed by the multiple acicular particles PA is formed on the surface of the liquid-repellent film 5, more specifically, on the surface of the liquid-repellent film 5 facing the Z2 direction. The unevenness FA is a fine structure that produces a lotus effect on the ink.

[0044] The size of the convex and concave portions that make up the unevenness FA is not particularly limited as long as it can produce a lotus effect on the ink, and for example, the depth of the concave portions is 1 μm or less and the average spacing between the convex portions is 10 μm or less.

[0045] Here, if the average length (ZSm) of the surface roughness of the irregularities FA is greater than the average length (ZSm) of the surface roughness of the wiping member 61, the gaps in the filler 5a can be narrowed, and as a result, dust is less likely to get into the gaps in the filler 5a when the nozzle substrate 530 is cleaned using the wiping member 61. The average length (ZSm) of the surface roughness is a collective term for the average length PSm of the cross-sectional curve elements, the average length RSm of the roughness curve elements, and the average length WSm of the waviness curve elements, which are horizontal parameters, and is obtained by measurement using an atomic force microscope (AFM) in accordance with JIS B 0601.

[0046] On the other hand, when the average length (ZSm) of the surface roughness of the irregularities FA is smaller than the average length (ZSm) of the surface roughness of the wiping member 61, there is an advantage that dust and the like that has entered the gaps in the filler 5a can be easily removed by the wiping member 61. In addition, there is an advantage that the surface tension of the wiping member 61 increases, making it easier for the wiping member 61 to hold the cleaning liquid.

[0047] From the viewpoint of easily forming irregularities FA having a fine structure that produces a lotus effect on the ink, the needle-shaped particles PA are preferably particles having a shape that protrudes in different directions two-dimensionally or three-dimensionally.

[0048] FIG. 5 is a diagram showing an example of acicular particles PA. In the example shown in FIG. 5, each of the multiple acicular particles PA is a four-legged block having multiple needle portions 5a1. Here, the number of needle portions 5a1 possessed by each acicular particle PA is four, and the four needle portions 5a1 protrude in three-dimensionally different directions from each other. In this way, the multiple needle portions 5a1 of each acicular particle PA protrude in three-dimensionally different directions from each other, so that the multiple acicular particles PA can stably form unevenness FA on the surface of the liquid-repellent film 5 regardless of the posture of each acicular particle PA. Furthermore, even if the liquid-repellent film 5 is scraped, new unevenness FA can stably appear on the surface of the liquid-repellent film 5 due to the multiple acicular particles PA. Therefore, the liquid repellency of the surface of the nozzle substrate 530 can be maintained stably for a long period of time.

[0049] In contrast, when the acicular particles PA are one-dimensional rod-shaped, the acicular particles PA tend to be arranged parallel to the surface of the nozzle substrate 530, making it difficult to stably form unevenness FA on the surface of the liquid-repellent film 5 using multiple acicular particles PA.

[0050] Even in an embodiment in which the needle portions 5a1 protrude two-dimensionally in different directions, the unevenness FA due to the needle portions PA can be more stably formed on the surface of the liquid-repellent film 5 than in an embodiment in which the needle particles PA have a one-dimensional shape such as a rod shape. The shape of the needle portions 5a1 is not limited to a tapered shape as shown in FIG. 5 and may be, for example, a shape of a constant width. The cross-sectional shape of the needle portions 5a1 is not particularly limited and may be any shape. The number of needle portions 5a1 possessed by the needle particles PA is not limited to four and may be three or less or five or more.

[0051] The average particle size Wp of the filler 5a should be such that the irregularities FA can produce the lotus effect, and is preferably, for example, 0.1 μm or more and 10 μm or less. It is also preferably equal to or less than half the diameter Wn of the nozzle N. This prevents the filler 5a from clogging the nozzle N. Even if the filler 5a does enter the nozzle N, the filler 5a can be discharged from the nozzle N by flushing the liquid ejection head 50. The "average particle size" is, for example, the average value of the values ​​obtained by measuring the major and minor diameters of a total of 10 random acicular particles PA within the field of view of the SEM and dividing the sum by 2.

[0052] The constituent material of the filler 5a may be any material that is resistant to ink and has a higher hardness than the binder 5b, and examples thereof include inorganic oxides such as alumina, potassium titanate, wollastonite, zinc oxide, and aluminum borate; simple metals such as chromium, copper, iron, and nickel; carbon-based materials such as carbon nanotubes, graphite, and silicon carbide; inorganic nitrides such as silicon nitride; and composite materials thereof. Among these, inorganic oxides or inorganic nitrides, or carbon nanotubes or graphite, are preferably used as the constituent material of the filler 5a. The filler 5a may be subjected to a surface treatment such as a siloxane treatment to enhance adhesion to the binder 5b.

[0053] When the filler 5a is made of an inorganic oxide or an inorganic nitride, wear of the filler 5a can be suppressed. As a result, the liquid repellency of the surface of the nozzle substrate 530 can be maintained stably for a long period of time. An example of the tetrapod block-shaped particles made of zinc oxide is "Panatetra (registered trademark)." The filler 5a may also be made of ceramics.

[0054] When the filler 5a is made of carbon nanotubes, the resistance of the liquid-repellent film 5 to ink can be increased.

[0055] The hardness of the filler 5a is preferably higher than the hardness of the wiping member 61 that wipes the surface of the nozzle substrate 530. As a result, even when the liquid-repellent film 5 is wiped with the wiping member 61, the filler 5a is not easily scraped off, and the liquid-repellent properties of the liquid-repellent film 5 can be maintained for a long period of time. Furthermore, even if the liquid-repellent film 5 is scraped off, the shape of the acicular particles PA of the filler 5a remaining on the liquid-repellent film 5 does not change, and the liquid-repellent properties of the liquid-repellent film 5 can be maintained.

[0056] The content of filler 5a in liquid-repellent film 5 is not particularly limited as long as it can form the irregularities FA that produce the lotus effect, but is preferably, for example, 20% by mass to 80% by mass, more preferably 30% by mass to 75% by mass, and even more preferably 30% by mass to 50% by mass. If the content of filler 5a in liquid-repellent film 5 is within this range, separation of filler 5a is suppressed and the irregularities FA that produce the lotus effect can be easily formed.

[0057] The binder 5b is not particularly limited, and various resins can be used, as long as it is a resin that is resistant to ink and has adhesive properties to the acicular particles PA and the nozzle substrate 530. The fluorine-based resin is not particularly limited, and examples thereof include perfluoroalkyl, perfluoroalkenyl, and perfluoropolyether.

[0058] In this way, the acicular particles PA and the nozzle substrate 530 are bonded to each other via the binder 5b, and since the filler 5a is not directly chemically bonded to the nozzle substrate 530, aggregation of the filler 5a on the nozzle substrate 530 can be suppressed.

[0059] Furthermore, since the acicular particles PA are bonded to one another via the binder 5b, the plurality of acicular particles PA are not directly chemically bonded to one another, and therefore aggregation of the filler 5a can be suppressed.

[0060] Furthermore, the surface of each acicular particle PA is covered with binder 5b. Therefore, if binder 5b is a fluorine-based resin, the surface of filler 5a is covered with a film made of fluorine-based resin. This can enhance the liquid repellency of liquid-repellent film 5.

[0061] Furthermore, the content of binder 5b in liquid-repellent film 5 is not particularly limited, but is preferably a level necessary and sufficient for bonding acicular particles PA and nozzle substrate 530. This allows voids Va to be formed between acicular particles PA in liquid-repellent film 5, as shown in Fig. 4. As a result, even if liquid-repellent film 5 is scraped, the unevenness FA that effectively produces the lotus effect on the surface of liquid-repellent film 5 can be maintained.

[0062] The thickness of the liquid-repellent film 5 is not particularly limited, but is preferably larger than the average particle size of the filler 5a, and is preferably between two and ten times the average particle size of the filler 5a. This allows the unevenness FA that produces the lotus effect on the surface of the liquid-repellent film 5 to be maintained even if part of the liquid-repellent film 5 is scraped off in the thickness direction.

[0063] FIG. 6 is an explanatory diagram of the state of the liquid-repellent film 5 after it has been scraped off. When the liquid-repellent film 5 with thickness T is scraped off by ΔTa, as shown in FIG. 6, the liquid-repellent film 5A with thickness Ta remains, but the irregularities FA that produce the lotus effect are maintained on the surface of the liquid-repellent film 5A. Here, the thickness Ta of the liquid-repellent film 5A is greater than the average particle size of the filler 5a. ΔTa is the difference between the thickness Ta of the liquid-repellent film 5A and the thickness T of the liquid-repellent film 5.

[0064] In the liquid ejection head 50 described above, liquid repellency can be imparted to the surface of the nozzle substrate 530 by forming the liquid-repellent film 5. Therefore, mechanical processing to form an uneven shape on the surface of the nozzle substrate 530 is not required. Furthermore, even if the liquid-repellent film 5 is scraped, the filler 5a in the liquid-repellent film 5 appears on the surface of the liquid-repellent film 5, so the unevenness FA formed by the plurality of acicular particles PA on the surface of the liquid-repellent film 5 is maintained. Therefore, the liquid repellency of the liquid-repellent film 5 is unlikely to decrease. Furthermore, even if the liquid repellency of the liquid-repellent film 5 decreases, the liquid ejection head 50 can be restored by forming a new liquid-repellent film 5 without replacing the nozzle substrate 530.

[0065] In contrast, the liquid-repellent film 5 made of fluororesin has low abrasion resistance, and is therefore easily scraped off by cleaning the nozzle N surface, etc., and the liquid-repellent properties are easily reduced.

[0066] A4: How to refurbish a liquid ejection head FIG. 7 is an explanatory diagram of the lifespan of the liquid-repellent film 5. FIG. 7 shows a state in which the liquid-repellent film 5 with thickness T is worn down by ΔTb, resulting in the liquid-repellent film 5B with thickness Tb. ΔTb is the difference between the thickness Tb of the liquid-repellent film 5B and the thickness T of the liquid-repellent film 5. Here, if the thickness Tb of the liquid-repellent film 5B is equal to or less than the average particle size of the filler 5a, it is difficult to maintain the irregularities FA that create the lotus effect on the surface of the liquid-repellent film 5B.

[0067] FIG. 8 is an explanatory diagram of a method for regenerating a liquid ejection head 50 according to an embodiment. In the method for regenerating a liquid ejection head 50, when the thickness of the liquid-repellent film 5 reaches a predetermined value or less, for example, when the liquid-repellent film 5 is scraped off to become a liquid-repellent film 5B with a thickness Tb, a new liquid-repellent film 5C is formed on the surface of the nozzle substrate 530, as shown in FIG. 8. The liquid-repellent film 5B before regeneration is an example of a "first liquid-repellent film," and the new liquid-repellent film 5C is an example of a "second liquid-repellent film." In the example shown in FIG. 8, the liquid-repellent film 5C is formed by forming a film on the liquid-repellent film 5C. Note that the liquid-repellent film 5C may also be formed by forming a film on the nozzle substrate 530 after removing the liquid-repellent film 5C.

[0068] In the above-described regeneration method, when the thickness of the liquid-repellent film 5 reaches a predetermined level or less, a new liquid-repellent film 5C is formed on the surface of the nozzle substrate 530, making it possible to reuse the nozzle substrate 530. This makes it possible to reduce the cost of regenerating the liquid ejection head 50.

[0069] B: Modified example The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Any of the following embodiments can be combined as desired within the scope of their compatibility.

[0070] B1: Variation 1 The configuration of the liquid ejection head 50, excluding the liquid-repellent film 5, is not limited to the above-mentioned example and may be any configuration. For example, in the above-mentioned embodiment, the upper electrode 563 is a common electrode, but the present invention is not limited to this example, and the upper electrode 563 may be an individual electrode for each piezoelectric element 650. In this case, the lower electrode 561 may be a common electrode shared by multiple piezoelectric elements 560.

[0071] B2: Variation 2 In each of the above-described embodiments, a serial-type liquid ejection device 100 in which a transport body 41 equipped with a liquid ejection head 50 moves back and forth has been exemplified, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the recording medium M.

[0072] B3: Variation 3 The liquid ejection device 100 exemplified in the above embodiment may be employed in various devices such as facsimile machines and copiers, in addition to devices dedicated to printing, and the applications of the present disclosure are not particularly limited. However, the applications of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device for manufacturing biochips, for example.

[0073] C: Notes A summary of this disclosure is provided below.

[0074] (Appendix 1) A first aspect, which is a preferred example of the liquid ejection head of the present disclosure, comprises a nozzle substrate having a nozzle for ejecting liquid, and a liquid-repellent film having liquid-repellent properties against the liquid is provided on the surface of the nozzle substrate, and the liquid-repellent film contains a filler composed of a plurality of acicular particles, and the plurality of acicular particles form irregularities on the surface of the liquid-repellent film.

[0075] In the above-described embodiment, liquid repellency can be imparted to the surface of the nozzle substrate by forming a liquid-repellent film. Therefore, mechanical processing to form an uneven shape on the surface of the nozzle substrate is not required. Furthermore, even if the liquid-repellent film is scraped, the filler in the liquid-repellent film appears on the surface of the liquid-repellent film, so the unevenness caused by the multiple acicular particles on the surface of the liquid-repellent film is maintained. Therefore, the liquid repellency of the liquid-repellent film is unlikely to decrease. Furthermore, even if the liquid repellency of the liquid-repellent film decreases, the liquid ejection head can be restored by forming a liquid-repellent film without replacing the nozzle substrate.

[0076] (Supplementary Note 2) In the second aspect, which is a preferred example of the first aspect, each of the plurality of acicular particles has a plurality of needle portions that protrude in two-dimensional or three-dimensional directions that are different from one another. In the above aspect, since the plurality of needle portions of the acicular particles protrude in two-dimensional or three-dimensional directions that are different from one another, it is possible to stably form unevenness due to the plurality of acicular particles on the surface of the liquid-repellent film regardless of the posture of each acicular particle. Furthermore, even if the liquid-repellent film is scraped, it is possible to stably form new unevenness due to the plurality of acicular particles on the surface of the liquid-repellent film. Therefore, it is possible to maintain stable liquid repellency on the surface of the nozzle substrate for a long period of time.

[0077] (Note 3) In a third aspect, which is a preferred example of the first or second aspect, the average particle size of the filler is equal to or less than half the diameter of the nozzle. This aspect prevents the filler from clogging the nozzle. Even if the filler does get into the nozzle, the filler can be expelled from the nozzle by flushing the liquid ejection head.

[0078] (Appendix 4) In a fourth aspect, which is a preferred example of any of the first to third aspects, the filler is made of an inorganic oxide or an inorganic nitride. In this aspect, wear of the filler can be suppressed. As a result, stable liquid repellency of the surface of the nozzle substrate can be maintained for a long period of time.

[0079] (Supplementary Note 5) In a fifth aspect which is a preferred example of any of the first to third aspects, the filler is made of carbon nanotubes or graphite. In this aspect, the resistance of the liquid-repellent film to ink can be improved.

[0080] (Supplementary Note 6) In a sixth aspect which is a preferred example of any of the first to fifth aspects, the filler is not directly chemically bonded to the nozzle substrate. In the above aspect, aggregation of the filler on the nozzle substrate can be suppressed.

[0081] (Supplementary Note 7) In a seventh aspect which is a preferred example of any one of the first to sixth aspects, the plurality of acicular particles are not directly chemically bonded to one another. In the above aspect, aggregation of the filler can be suppressed.

[0082] (Appendix 8) In an eighth aspect which is a suitable example of any one of the first to seventh aspects, the surface of the filler is covered with a film made of a fluorine-based resin. In this aspect, the liquid-repellent property of the liquid-repellent film can be enhanced.

[0083] (Appendix 9) In a ninth aspect, which is a preferred example of any of the first to eighth aspects, the hardness of the filler is higher than the hardness of a wiping member that wipes the surface of the nozzle substrate. In this aspect, even when the liquid-repellent film is wiped away with the wiping member, the filler is not easily scraped off, so the liquid-repellent properties of the liquid-repellent film can be maintained for a long period of time. Furthermore, even if the liquid-repellent film is scraped off, the shape of the acicular particles of the filler remaining on the liquid-repellent film does not change, so the liquid-repellent properties of the liquid-repellent film can be maintained.

[0084] (Appendix 10) In a tenth aspect which is a suitable example of any of the first to ninth aspects, the mean length (ZSm) of the surface roughness of the asperities is greater than the mean length (ZSm) of the surface roughness of a wiping member which wipes the surface of the nozzle substrate. In the above aspect, the gaps in the filler can be narrowed, and as a result, dust is less likely to enter the gaps in the filler when the nozzle substrate is cleaned using the wiping member.

[0085] (Appendix 11) In an eleventh aspect, which is a preferred example of any of the first to tenth aspects, the mean length (ZSm) of the surface roughness of the asperities is smaller than the mean length (ZSm) of the surface roughness of a wiping member that wipes the surface of the nozzle substrate. This aspect has the advantage that dust and the like that has entered gaps in the filler can be easily removed by the wiping member. Another advantage is that the surface tension of the wiping member is increased, making it easier for the wiping member to retain cleaning liquid.

[0086] (Appendix 12) A twelfth aspect, which is a preferred example of the method for regenerating a liquid ejection head of the present disclosure, is a method for regenerating a liquid ejection head comprising a nozzle substrate having a nozzle for ejecting a liquid, wherein a first liquid-repellent film that is a liquid-repellent film having liquid-repellent properties to the liquid is provided on the surface of the nozzle substrate, the liquid-repellent film containing a filler composed of a plurality of acicular particles, the surface of the liquid-repellent film being uneven due to the plurality of acicular particles, and when the thickness of the first liquid-repellent film reaches a predetermined value or less, a new second liquid-repellent film that is the liquid-repellent film is formed on the surface of the nozzle substrate.

[0087] In the above-described embodiment, when the thickness of the first liquid-repellent film reaches a predetermined level or less, a new second liquid-repellent film is formed on the surface of the nozzle substrate, allowing the nozzle substrate to be reused, thereby reducing the cost of remanufacturing a liquid ejection head. [Explanation of symbols]

[0088] 5...liquid-repellent film, 5A...liquid-repellent film, 5B...liquid-repellent film (first liquid-repellent film), 5C...liquid-repellent film (second liquid-repellent film), 5a...filler, 5a1...needle portion, 5b...binder, 10...liquid container, 20...control module, 30...transport mechanism, 40...movement mechanism, 41...transport body, 42...transport belt, 50...liquid ejection head, 60...maintenance mechanism, 61...wiping member, 100...liquid ejection device, 510...communicating substrate, 520...pressure chamber substrate, 530...nozzle substrate, 540...vibration absorber, 550...vibration plate, 560...piezoelectric element, 561...lower electrode , 563...upper electrode, 570...protective substrate, 580...case, 590...wiring substrate, 600...drive circuit, 650...piezoelectric element, C...pressure chamber, Com...drive signal, FA...unevenness, FN...nozzle surface, HL...inlet, Ln1...first nozzle row, Ln2...second nozzle row, M...recording medium, N...nozzle, Na...communicating flow path, PA...acicular particles, R...reservoir, R1...flow path, R2...flow path, Ra...supply flow path, S...space, SI...control signal, T...thickness, Ta...thickness, Tb...thickness, Va...gap, Wn...diameter, Wp...average particle size.

Claims

1. a nozzle substrate having nozzles for discharging a liquid; a liquid-repellent film having liquid-repellency to the liquid is provided on a surface of the nozzle substrate; the liquid-repellent film contains a filler made of a plurality of needle-shaped particles; the plurality of needle-shaped particles form irregularities on the surface of the liquid-repellent film; A liquid ejection head characterized by:

2. Each of the plurality of acicular particles has a plurality of needle portions that protrude in two-dimensional or three-dimensional directions different from each other.

2. The liquid ejection head according to claim 1.

3. The average particle size of the filler is ½ or less of the diameter of the nozzle.

2. The liquid ejection head according to claim 1.

4. The filler is composed of an inorganic oxide or an inorganic nitride.

2. The liquid ejection head according to claim 1.

5. The filler is composed of carbon nanotubes or graphite.

2. The liquid ejection head according to claim 1.

6. the filler is not directly chemically bonded to the nozzle substrate; 2. The liquid ejection head according to claim 1.

7. the plurality of acicular particles are not directly chemically bonded to each other; 2. The liquid ejection head according to claim 1.

8. The surface of the filler is covered with a film made of a fluorine-based resin.

2. The liquid ejection head according to claim 1.

9. the hardness of the filler is higher than the hardness of a wiping member that wipes the surface of the nozzle substrate; 2. The liquid ejection head according to claim 1.

10. an average length (ZSm) of the surface roughness of the irregularities is greater than an average length (ZSm) of the surface roughness of a wiping member that wipes the surface of the nozzle substrate; 2. The liquid ejection head according to claim 1.

11. an average length (ZSm) of the surface roughness of the irregularities is smaller than an average length (ZSm) of the surface roughness of a wiping member that wipes the surface of the nozzle substrate; 2. The liquid ejection head according to claim 1.

12. A method for regenerating a liquid ejection head including a nozzle substrate having nozzles that eject liquid, comprising: a first liquid-repellent film that is a liquid-repellent film having liquid-repellency to the liquid is provided on a surface of the nozzle substrate; the liquid-repellent film contains a filler made of a plurality of needle-shaped particles; the liquid-repellent film has a surface on which irregularities are formed by the plurality of needle-like particles; When the thickness of the first liquid-repellent film reaches a predetermined thickness or less, a second liquid-repellent film is formed as a new liquid-repellent film on the surface of the nozzle substrate. A method for regenerating a liquid ejection head.

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