Inkjet head, method for manufacturing the same, and image forming apparatus

Abstract

To provide an inkjet head in which the adhesive strength of the nozzle plate does not easily decrease even when using alkaline inks, etc. [Solution] The inkjet head comprises a substrate 111 having a passivation film on its surface, a base layer 710 covering the surface, a nozzle plate having a plurality of ejection holes, and a resin layer 720 disposed on one surface of the substrate in contact with the base layer. The base layer contains silicon (Si) and carbon (C), and the resin layer is a cured product of a resin composition containing an epoxy compound and a polythiol compound having two or more thiol groups in its molecule, thereby achieving a reduction in adhesive strength.

Description

Technical Field

[0001] The present invention relates to an inkjet head, a method for manufacturing the same, and an image forming apparatus.

Background Art

[0002] An image forming apparatus having an inkjet head discharges a liquid such as ink little by little from a plurality of discharge holes (nozzles) of the inkjet head. Then, the image forming apparatus lands the discharged liquid at a predetermined position on a recording medium to form an image.

[0003] The inkjet head includes a plate-like nozzle plate having a plurality of discharge holes and other members that constitute ink flow paths, pressure chambers, and the like. The nozzle plate and the other members are joined by a resin adhesive.

[0004] Patent Document 1 discloses an inkjet head that uses, as the above resin adhesive, a cured product of a resin composition containing a specific epoxy compound and a polythiol compound having two or more thiol groups in the molecule. According to Patent Document 1, the resin layer obtained by curing the above specific epoxy compound is difficult to absorb ink, and thus is difficult to swell when the inkjet head is used. Therefore, it is said that the above resin layer can suppress a decrease in the ejection reliability of the inkjet head due to a decrease in the rigidity of the flow path portion caused by a decrease in the Young's modulus due to swelling and a decrease in the pressure of the flow path through which ink flows.

[0005] Patent Document 1 further discloses a nozzle plate, which is bonded to the resin layer, having a treatment layer containing silicon (Si) and oxygen (O) formed on the surface of a substrate such as stainless steel (SUS). According to Patent Document 1, the Si contained in this treatment layer enhances adhesion to the resin layer. Furthermore, according to Patent Document 1, the strong Si-O bond contained in the treatment layer is resistant to corrosion even when in contact with liquids such as ink, thus increasing the durability of the inkjet head. The inkjet head described in Patent Document 1 improves adhesion and durability through this treatment layer containing Si and O. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2015-221541 [Overview of the project] [Problems that the invention aims to solve]

[0007] According to Patent Document 1, the above-mentioned resin layer can suppress the decrease in ejection reliability of the inkjet head. However, according to the inventors' studies, the inkjet head described in Patent Document 1 suffers from a significant decrease in adhesive strength between the nozzle plate and other components, especially when using alkaline inks or inks containing high concentrations of methylpyrrolidone.

[0008] The present invention has been made in view of the above problems. An object of the present invention is to provide an inkjet head having a resin layer obtained by curing a specific epoxy compound, and which is less likely to experience a decrease in adhesive strength between the nozzle plate and other components even when using alkaline inks or inks containing high concentrations of methylpyrrolidone. Another object of the present invention is to provide a method for manufacturing the above inkjet head. Yet another object of the present invention is to provide an image forming apparatus having the above inkjet head. [Means for solving the problem]

[0009] One aspect of the present invention for solving the above problems relates to the following inkjet heads [1] to [8]. [1] A nozzle plate having a substrate having a passivation film on its surface, and a base layer covering the surface, and having a plurality of discharge holes, The substrate has a resin layer on one surface that is in contact with the underlying layer, The aforementioned subsoil contains silicon (Si) and carbon (C), The aforementioned resin layer is a cured product of a resin composition containing an epoxy compound represented by general formula (I) and a polythiol compound having two or more thiol groups in its molecule, in an inkjet head.

[0010] [ka]

[0011] (In general formula (I), R1 is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is independently a linking group represented by general formula (II), m is a number between 0.1 and 50, and L is independently an integer between 0 and 3.)

[0012] [ka]

[0013] (In general formula (II), R3 and R4 independently represent a hydrogen atom, or a methyl group in which some or all of the hydrogen atoms are substituted with fluorine atoms.) [2] The resin layer is a cured product of a resin composition further comprising an imidazole compound represented by general formula (III). [1] The inkjet head described above.

[0014] [ka]

[0015] (In general formula (III), R5, R6 and R7 each independently represent an atom or substituent selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group; R8 independently represents an alkylene group having 1 to 20 carbon atoms, or an arylene group; when k is 1, R9 is an atom or substituent selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, and a cyanomethyl group, and when K is an integer of 2 or more and 6 or less, it is a hydrocarbon group having 1 to 20 carbon atoms, j is 0 or 1, and k is an integer of 1 or more and 6 or less.) [3] The substrate contains at least one element selected from the group consisting of chromium (Cr), iron (Fe), nickel (Ni), molybdenum (Mo), and palladium (Pd). The inkjet head according to [1] or [2]. [4] The underlayer has a maximum peak P of the binding energy of the Si2p orbital on the surface part measured by X-ray photoelectron spectroscopy, which is 99.6 (eV) or more and 101.9 (eV) or less. The inkjet head according to any one of [1] to [3]. [5] In the underlayer, the atomic number distribution of oxygen (O) in the depth direction within the layer of the underlayer measured by X-ray photoelectron spectroscopy is larger on the surface side opposite to the substrate and smaller on the substrate side. The inkjet head according to any one of [1] to [4]. [6] In the underlayer, the atomic number distribution of oxygen (O) measured by X-ray photoelectron spectroscopy is larger on the surface side where the resin layer is disposed and smaller toward the other surface opposite to the resin layer. The inkjet head according to any one of [1] to [5]. [7] The nozzle plate has a liquid-repellent layer on the other surface opposite to the resin layer. The inkjet head according to any one of [1] to [6]. [8] The underlayer continuously covers the surface of the substrate constituting the discharge hole from the liquid-repellent layer to the resin layer. The inkjet head according to [7].

[0016] Another aspect of the present invention for solving the above problems relates to a method for manufacturing an inkjet head as described below in [9] to

[12] . [9] A step of preparing a substrate having multiple ejection holes and having a passivation film formed on its surface, The process of forming a base layer containing silicon (Si) and carbon (C) on the surface of the substrate, A step of placing a resin composition containing an epoxy compound represented by general formula (I) and a polythiol compound having two or more thiol groups in its molecule on one surface of the substrate, in contact with the underlying layer, A step of curing the resin composition, A method for manufacturing an inkjet head, comprising the characteristics of an inkjet head. [ka] (In general formula (I), R1 is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is independently a linking group represented by general formula (II), m is a number between 0.1 and 50, and L is independently an integer between 0 and 3.) [ka] (In general formula (II), R3 and R4 independently represent a hydrogen atom, or a methyl group in which some or all of the hydrogen atoms are substituted with fluorine atoms.)

[10] A step of forming a liquid-repellent layer on the surface of the substrate on which the underlayer has been formed, The process includes removing the liquid-repellent layer from one of the surfaces before placing the resin composition. [9] The method for manufacturing an inkjet head as described above.

[11] The removal of the liquid-repellent layer is performed by a plasma removal method.

[10] The method for manufacturing an inkjet head as described above.

[12] The underlayer is formed by a chemical vapor deposition method. A method for manufacturing an inkjet head as described in any of [9] to

[11] .

[0017] Another aspect of the present invention for solving the above problems relates to the image forming apparatus described below

[13] . An image forming apparatus having an inkjet head as described in any of

[13] [1] to [8]. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an inkjet head having a resin layer obtained by curing a specific epoxy compound, and which is less likely to experience a decrease in adhesive strength between the nozzle plate and other components even when using alkaline inks or inks containing high concentrations of methylpyrrolidone. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a diagram showing the schematic configuration of an inkjet printer equipped with an inkjet head according to an embodiment. [Figure 2] Figure 2 is a block diagram showing the main components of the control system for an inkjet printer. [Figure 3] Figure 3 is a schematic diagram showing the arrangement of inkjet heads in the head unit of an inkjet printer. [Figure 4] Figure 4 is a perspective view showing the external appearance of the inkjet head. [Figure 5A] Figure 5A is a schematic diagram showing the main components of a cross-section of the head chip in an inkjet head, along the short direction. [Figure 5B] Figure 5B is a schematic diagram showing the main components of a cross-section of the head chip along the longitudinal direction in an inkjet head. [Figure 6] Figure 6 is a schematic diagram showing the planar configuration around the nozzle in an inkjet head. [Figure 7] Figure 7 is a schematic diagram showing the main cross-sectional configuration of the first substrate (nozzle plate) and the second substrate (piezoelectric element) in the inkjet head according to the embodiment, near the nozzle (region 59a shown in Figure 5B). [Figure 8]Figure 8 is a schematic diagram showing the main cross-sectional configuration of the first substrate (nozzle plate) and the second substrate (piezoelectric element) in an inkjet head of a modified example of this embodiment, near the nozzle (region 59a shown in Figure 5B). [Figure 9] Figures 9A to 9D schematically show the method for manufacturing an inkjet head according to an embodiment. [Figure 10] Figures 10A to 10C schematically show the method for manufacturing an inkjet head according to an embodiment. [Modes for carrying out the invention]

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0021] [Inkjet Printer 1] Figure 1 is a schematic diagram showing the configuration of an inkjet printer equipped with an inkjet head according to this embodiment, and Figure 2 is a block diagram showing the main parts of the control system of the inkjet printer. The inkjet printer described below is an example of an image forming apparatus.

[0022] As shown in Figures 1 and 2, the inkjet printer 1 includes a transport unit 10, a supply unit 20, an ejection unit 30, an ink supply unit 40, a drawing unit 50, a reading unit 60, an operation display unit 70, an input / output interface 80, and a control unit 90, etc.

[0023] The transport unit 10 has multiple transport components, including a transport belt 11, a drive roller 12, and a driven roller 13. The transport unit 10 transports the recording medium M by the transport operation of the transport belt 11 and other components. Specifically, in the transport unit 10, the transport belt 11 is stretched over the drive roller 12 and the driven roller 13, and is driven by rotating the drive roller 12. As a result, the recording medium M supplied from the supply unit 20 is transported to the drawing unit 50 while placed on the transport surface 11a of the transport belt 11, and after being drawn (also called image formation or printing) in the drawing unit 50, it is transported to the discharge unit 30.

[0024] The recording medium M can be any medium capable of fixing the ink ejected from the inkjet head 55. For example, the recording medium M is a sheet-like medium made of paper, cloth, or resin. However, the recording medium M is not limited to a sheet-like medium; it may also be a roll-shaped medium such as paper, cloth, or resin. An example of a resin-based recording medium M is a PCB (Printed Circuit Board) substrate. In the case of a PCB substrate, the inkjet printer 1 can be used to print solder resist or marking ink onto the PCB substrate. Other examples of recording medium M that can be used for drawing include the metal body of an automobile, building materials (exterior walls, roofing materials, tiles, etc.), and metal cans (metal cans for storing food and beverages, etc.).

[0025] Figure 1 illustrates a transport unit 10 that transports a recording medium M using a transport belt 11 as an example of an image forming apparatus. However, the transport unit 10 is not limited to a transport belt 11; it may also be configured to transport the recording medium M using drums or rollers.

[0026] The supply unit 20 includes a supply loading unit 21 for stacking and storing multiple recording media M, a supply transport unit 22 for transporting and supplying the recording media M from the supply loading unit 21 to the transport unit 10, and the like. The supply loading unit 21 is configured to be able to move up and down, and when the topmost recording media M is transported to the transport unit 10 by the supply transport unit 22, the supply loading unit 21 rises so that the recording media M that becomes the topmost after the transport can be transported to the supply transport unit 22.

[0027] The discharge unit 30 includes a discharge loading unit 31 for loading and storing multiple recording media M, and a discharge transport unit 32 for transporting the recording media M discharged from the transport unit 10 to the discharge loading unit 31. The discharge loading unit 31 is configured to be able to move up and down, and when the recording media M are transported from the discharge transport unit 32 to the discharge loading unit 31, the discharge loading unit 31 lowers.

[0028] The supply and transport section 22 and the discharge and transport section 32, for example, have multiple rollers and transport the recording medium M by rotating the rollers. The supply and transport section 22 and the discharge and transport section 32 are not limited to rollers; they may also be composed of belts, or a combination of rollers and belts.

[0029] When a roll-shaped medium is used as the recording medium M, an unwinding roller that stores the roll-shaped medium in a wound state and a winding roller that winds up the roll-shaped medium are used instead of the supply loading section 21 and the discharge loading section 31. The roll-shaped medium is transported to the transport section 10 by rotating the unwinding roller and wound onto the winding roller by rotating the winding roller.

[0030] Furthermore, a post-processing device for performing post-processing on the recording medium M, on which an image has been formed by the drawing unit 50, may be provided between the transport unit 10 and the discharge unit 30. An example of a post-processing device is a fixing device for fixing ink to the recording medium M. For example, when using ultraviolet-curable ink, a fixing device is used that irradiates the recording medium M with ultraviolet light to fix the ink to the recording medium M. When using water-based ink or solvent-based ink, a fixing device is used that fixes the ink to the recording medium M by drying or other methods. In addition, devices other than a fixing device may be used as post-processing devices, such as a cutting device for cutting the recording medium M to a desired length.

[0031] The configurations of the transport unit 10, the supply unit 20, and the discharge unit 30 can be changed in various ways depending on the type of recording medium M to be drawn on.

[0032] The ink supply unit 40 is a device that supplies ink to the first sub-tank 52a of the drawing unit 50, which will be described later. The ink supply unit 40 has a main tank 41 and components related to ink supply (e.g., a pump and valves, etc.) which are not shown. The main tank 41 stores the ink to be supplied to the first sub-tank 52a at room temperature. The ink supply unit 40 uses a pump or the like (not shown) to supply ink from the main tank 41 to the first sub-tank 52a via a flow path 42.

[0033] The heating unit 95 is positioned upstream of the drawing unit 50 in the transport direction T of the recording medium M, and heats the recording medium M, which is transported by the transport belt 11, to a predetermined temperature. The heating unit 95 is connected to the control unit 90 (see Figure 2) and controlled by the control unit 90.

[0034] For example, the heating unit 95 has an infrared heater or the like, and power is supplied to the infrared heater based on a control signal supplied from the control unit 90, causing the infrared heater to generate heat and heat the recording medium M to a predetermined temperature. Depending on the type of ink used, the heating unit 95 may not be necessary. In Figure 1, the inkjet printer 1 has the heating unit 95 located on the upper side of the transport belt 11. However, the inkjet printer 1 may also have a heating unit on the lower side of the transport belt 11 instead of (or in addition to) the heating unit 95, and heat the transport belt 11 to heat the recording medium M.

[0035] The drawing unit 50 includes a carriage 51, a first sub-tank 52a, a second sub-tank 52b, flow channels 53a, 53b, 53c, a head drive unit 54, an inkjet head 55, etc. (see Figures 1 and 2).

[0036] Note that in Figure 1, for the sake of simplicity, only one ink supply unit 40 and drawing unit 50 are shown. However, the ink supply unit 40 and drawing unit 50 are arranged according to the number of colors used. For example, when using four colors, yellow (Y), magenta (M), cyan (C), and black (K), four ink supply units 40 and drawing units 50 are arranged, and the drawing units 50 are arranged at predetermined intervals along the transport direction T.

[0037] Furthermore, although multiple second sub-tanks 52b and heads 55 are connected downstream of the first sub-tank 52a, only one of each is shown in Figure 1 for the sake of simplicity.

[0038] The carriage 51 is a housing that internally holds the first sub-tank 52a, the second sub-tank 52b, the flow channels 53a, 53b, 53c, the head drive unit 54, the head 55, and other equipment and components necessary for image formation. The carriage 51 may also have an ink heating unit, although it is not shown in the figures, which heats and maintains the ink inside the carriage 51.

[0039] The first sub-tank 52a is connected downstream of the main tank 41. The first sub-tank 52a stores the ink supplied from the main tank 41 within the carriage 51. The ink in sub-tank 52 is supplied to the second sub-tank 52b via the flow path 53a using a pump or the like (not shown) within the carriage 51.

[0040] Multiple second sub-tanks 52b are connected downstream of the first sub-tank 52a. The second sub-tanks 52b store the ink supplied from the first sub-tank 52a within the carriage 51. The ink in the second sub-tanks 52b is supplied to the manifold 56 of the head 55, described later, via the flow path 53b using a pump or the like (not shown) within the carriage 51. In addition, a portion of the ink supplied to the manifold 56 is recirculated (recovered) to the second sub-tank 52b via the flow path 53c, making it possible to resupply it to the manifold 56. In other words, the ink circulates between the second sub-tank 52b and the manifold 56 via the flow paths 53b and 53c. These circulation flow paths also include multiple individual circulation flow paths 111a, a common circulation flow path 112a, and a vertical circulation flow path 112b (see Figures 5A, 5B, and 6), all of which will be described later.

[0041] The head drive unit 54 outputs a drive voltage corresponding to the image data of the image to be formed to the piezoelectric element 58 of the head 55, which will be described later, based on the control of the control unit 90, which will be described later. The drive voltage from the head drive unit 54 drives the piezoelectric element 58, causing it to eject an amount of ink corresponding to the image data from the nozzle 59 of the head 55, which will be described later.

[0042] Multiple heads 55 are connected to the downstream side of each of the multiple second sub-tanks 52b. In other words, multiple second sub-tanks 52b and heads 55 are connected to the downstream side of the first sub-tank 52a.

[0043] The head 55 includes a manifold 56 (an example of a common supply channel), individual supply channels 57, piezoelectric elements 58, nozzles 59, individual circulation channels 111a, a common circulation channel 112a, and a vertical circulation channel 112b (see Figures 5A, 5B, and 6). The head 55 has multiple nozzles 59, and the number of individual supply channels 57 and piezoelectric elements 58 is provided according to the number of nozzles 59.

[0044] The manifold 56 is connected to a plurality of individual supply channels 57, and the ink supplied to the manifold 56 is supplied to the individual supply channels 57. Each individual supply channel 57 is a chamber that has an internal space in which ink ejected from the nozzle 59 can be temporarily stored, either partially or entirely. A piezoelectric element 58 is provided on the wall surface of each individual supply channel 57. The nozzle 59 has one end connected to the individual supply channel 57 and the other end is an open end.

[0045] A drive voltage from the head drive unit 54 is applied to the piezoelectric element 58. When a drive voltage from the head drive unit 54 is applied to the piezoelectric element 58, the piezoelectric element 58 deforms in accordance with the applied drive voltage, causing the individual supply channel 57 to deform. This deformation of the individual supply channel 57 causes a pressure change in the ink in the individual supply channel 57 that is supplied to the nozzle 59.

[0046] Therefore, when the drive voltage from the head drive unit 54 is applied to the piezoelectric element 58, the piezoelectric element 58 and the individual supply channel 57 deform, causing a pressure change in the ink in the individual supply channel 57. As a result, the ink in the individual supply channel 57 is ejected from the nozzle 59. In this way, an image can be formed on the recording medium M by ejecting the ink from the nozzle 59.

[0047] In the carriage 51, the head 55 may be configured to perform image formation in a single pass (one-pass) method, or to perform image formation in multiple passes (multi-pass) method. In the single-pass method, the carriage 51 has a number of heads 55 equal to the image formation width in the width direction of the recording medium M (in the direction perpendicular to the transport direction T of the recording medium M) (see Figure 3). As shown in Figure 3, the multiple heads 55 are arranged in one or more rows with their longitudinal direction aligned along the width direction of the recording medium M, and in each head 55, the multiple nozzles 59 are arranged linearly or in a grid along the longitudinal direction of the head 55.

[0048] The reading unit 60 is positioned downstream of the drawing unit 50 in the transport direction T of the recording medium M and reads the image (for example, a predetermined pattern image) formed on the recording medium M that is transported by the transport belt 11. The reading unit 60 outputs the reading result of the predetermined pattern image to the control unit 90. Based on the reading result, the control unit 90 changes the image formation conditions, such as the image formation position and the driving conditions of the head 55.

[0049] Although not shown in the diagram, the inkjet printer 1 is also equipped with a maintenance unit for performing maintenance such as cleaning the print head 55.

[0050] The operation display unit 70 is, for example, a flat panel display such as a liquid crystal or organic EL (Electro-Luminescence) with a touch panel. The operation display unit 70 displays operation menus for the user, information related to image data, and various statuses of the inkjet printer 1. The operation display unit 70 also has multiple keys to accept various input operations from the user.

[0051] The input / output interface 80 mediates the transmission and reception of data between the external device 99 and the control unit 90. The input / output interface 80 is composed of, for example, various serial interfaces, various parallel interfaces, or a combination thereof.

[0052] The external device 99 is, for example, a personal computer or a facsimile machine, and supplies print jobs, image data, etc., to the control unit 90 via the input / output interface 80.

[0053] The control unit 90 includes a CPU (Central Processing Unit) 91, RAM (Random Access Memory) 92, ROM (Read Only Memory) 93, a storage unit 94, and the like.

[0054] The CPU 91 reads various control programs and setting data stored in the ROM 93, stores them in the RAM 92, and executes the programs to perform various calculations. For example, the control unit 90 generates a drive signal for the image to be formed based on the image data received from the input / output interface 80 and outputs it to the head 55.

[0055] RAM92 provides the CPU91 with a working memory space and stores temporary data. RAM92 may also include non-volatile memory.

[0056] ROM93 stores various control programs and setting data executed by the CPU91. Alternatively, rewritable non-volatile memory such as EEPROM (Electrically Erasable Programmable Read Only Memory) or flash memory may be used instead of ROM93.

[0057] The storage unit 94 stores print jobs and image data related to print jobs that are input from an external device 99 via the input / output interface 80. For the storage unit 94, for example, a non-volatile semiconductor memory (so-called flash memory) or an HDD (Hard Disk Drive) may be used, and DRAM (Dynamic Random Access Memory) may also be used in combination.

[0058] The control unit 90 is connected to the transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, drawing unit 50, reading unit 60, operation display unit 70, input / output interface 80, heating unit 95, etc. The control unit 90 provides overall control of the operation of the inkjet printer 1. The transport unit 10, supply unit 20, discharge unit 30, ink supply unit 40, drawing unit 50, reading unit 60, operation display unit 70, input / output interface 80, heating unit 95, etc. are controlled by the control unit 90 to perform predetermined processes.

[0059] The inkjet printer 1 having the above configuration supplies the recording medium M from the supply unit 20 to the transport unit 10 under the control of the control unit 90, draws on the recording medium M transported to the transport unit 10 with the drawing unit 50, and transports the image-formed recording medium M to the discharge unit 30.

[0060] [Head (inkjet head) 55] Next, the configuration of the inkjet head (head 55) according to this embodiment will be described. The configuration described here is for the head 55 alone. Note that the configuration of all heads 55 in the inkjet printer 1 may be the same, or the inkjet printer 1 may include heads 55 with configurations different from the one described below.

[0061] Figure 4 is a perspective view showing the external appearance of the head 55.

[0062] The print head 55 comprises a housing 101 and an exterior member 102 that engages with the housing 101 at its lower end, with the main components housed inside the housing 101 and the exterior member 102. The exterior member 102 is provided with an inlet 103a for supplying ink from the outside, and outlets 103b and 103c for discharging ink to the outside. A manifold 56 connected to the inlet 103a is also provided inside the exterior member 102. The exterior member 102 is also provided with a plurality of mounting holes 104 for attaching the inkjet print head 55 to the base of the carriage 51.

[0063] Figures 5A and 5B show the main components of the head tip in head 55. Figure 5A schematically shows the main components of the cross-section along the short direction of the head tip, and Figure 5B schematically shows the main components of the cross-section along the long direction of the head tip. Figure 6 schematically shows the planar configuration around the nozzle in head 55.

[0064] The components housed inside the housing 101 and exterior member 102 of the head 55 include the head chip 110. As shown in Figures 5A and 5B, the head chip 110 is constructed by laminating and bonding together a plurality of substrates (first substrate 111, second substrate 112, and third substrate 113). The first substrate 111, second substrate 112, and third substrate 113 become the lower layer, middle layer, and upper layer, respectively, during use.

[0065] The first substrate 111 is a nozzle plate. The first substrate 111 is provided with a plurality of nozzles 59 (discharge holes), each of which is a hole that penetrates in the thickness direction (corresponding to the ink discharge direction, which is typically along the vertical direction), arranged in a row along its longitudinal direction. In the illustrated example, there are 6 nozzles 59 per example, but the number may be less than 6.

[0066] The first substrate 111 is also provided with multiple individual circulation channels 111a that communicate with each of the multiple nozzles 59. Each of the multiple individual circulation channels 111a is a groove that extends parallel to each other in the short-side direction of the head 55 from the downstream end of the individual supply channel 57 that communicates with the corresponding nozzle 59, and all of them communicate with the common circulation channel 112a.

[0067] The second substrate 112 is provided with a plurality of individual supply channels 57 arranged in a row along its longitudinal direction, each of which is a through-hole in the thickness direction and communicates with a corresponding nozzle 59. In the illustrated example, there are 6 nozzles 59 per row, so there are also 6 individual supply channels 57 per row. In the following description, when the 6 individual supply channels 57 are described separately, they will be referred to as individual supply channels 57-1, 57-2, 57-3, 57-4, 57-5, and 57-6, and when they are not distinguished, they will simply be referred to as "individual supply channels 57". The relative positions of individual supply channels 57-1, 57-2, 57-3, 57-4, 57-5, and 57-6 are such that the larger the branch number of the reference numeral, the further away they are from the inlet 103a of the manifold 56, that is, they are located downstream of the manifold 56.

[0068] Each of the multiple individual supply channels 57 communicates with a manifold 56, which functions as a common supply channel, at its uppermost point. The multiple individual supply channels 57 are separated by partitions equipped with piezoelectric elements 58. The piezoelectric elements 58 are electrically connected to the head drive unit 54 by electrodes and wiring (not shown). The piezoelectric elements 58 are driven in response to a drive voltage signal applied from the head drive unit 54 via electrodes and wiring, causing repeated shear-mode type displacements in the partitions of the individual supply channels 57, thereby fluctuating the ink pressure, and in response to this pressure fluctuation, the ink is ejected from the nozzles 59. In other words, the head 55 according to this embodiment is an inkjet head that performs shear-mode type ink ejection.

[0069] The second substrate 112 is, for example, a ceramic piezoelectric material (a component that deforms in response to applied voltage). Examples of piezoelectric materials include PZT (lead zirconate titanate), lithium niobate, barium titanate, lead titanate, and lead metaniobate.

[0070] The second substrate 112 is provided with a common circulation channel 112a through which all of the individual circulation channels 111a communicate at their downstream ends. The common circulation channel 112a is a groove on the back surface of the second substrate 112 that extends along the longitudinal direction of the head 55. The downstream end of the common circulation channel 112a communicates with a vertical circulation channel 112c, which is also provided on the second substrate 112. The vertical circulation channel 112c communicates with the outlet 103c, enabling ink circulation.

[0071] The third substrate 113 is provided with a manifold 56 that extends along the longitudinal direction of the head 55, and through which all of the multiple individual supply channels 57 communicate at their uppermost reaches. The manifold 56 is a groove provided on the back side of the third substrate 113. The third substrate 113 may be a resin substrate such as polyimide, or a metal substrate such as SUS.

[0072] Figure 7 is a schematic diagram showing the main cross-sectional configuration of the first substrate 111 (nozzle plate) and the second substrate 112 (piezoelectric element 58) in the inkjet head 55 of this embodiment, near the nozzle 59 (region 59a shown in Figure 5B).

[0073] In this embodiment, the first substrate 111 has a passivation film 111b, and its surface is covered with a base layer 710. The second substrate 112 is bonded to the first substrate 111 by a resin layer 720 placed on one surface of the first substrate in contact with the base layer 710. In this embodiment, specific materials are used for the base layer 710 and the resin layer 720. By selecting these materials, alkali resistance and solvent resistance are enhanced, making it less likely for the adhesive strength between the first substrate 111 and the second substrate 112 to decrease even when using alkaline inks or inks containing high concentrations of methylpyrrolidone.

[0074] Furthermore, a liquid-repellent layer 730 is formed on the surface of the first substrate 111 opposite to the resin layer 720, on the side from which the ink is ejected and flies (hereinafter simply referred to as the "ejection-side surface" or "the other surface"). By providing the liquid-repellent layer 730, the adhesion of ink and foreign matter to the nozzle opening surface can be suppressed, and the occurrence of ink ejection defects caused by the adhesion of such ink and foreign matter can be suppressed. The liquid-repellent layer 730 can be a known liquid-repellent layer made of a silane coupling agent or a fluororesin. From the viewpoint of increasing the bonding strength with the base layer 710 (described later) by forming siloxane bonds, a silane coupling agent is preferred.

[0075] The first substrate 111 is a substrate having a metal, and a passivation film 111b is formed on its surface. The passivation film 111b has the effect of increasing the alkali resistance of the substrate. The metal contained in the first substrate 111 is not limited as long as it can form a passivation film 111b, but can be iron (Fe), aluminum (Al), bismuth (Bi), chromium (Cr), indium (In), tin (Sn), niobium (Nb), nickel (Ni), tantalum (Ta), tungsten (W), zinc (Zn), and palladium (Pd), etc. The passivation film 111b can contain these metals. Specifically, the first substrate 111 can be a substrate formed from a metallic material such as iron (for example, stainless steel (SUS)), aluminum, nickel, preferably SUS.

[0076] The thickness of the first substrate 111 is not particularly limited, but can be 10 μm or more and 500 μm or less, and preferably 30 μm or more and 150 μm or less.

[0077] The alkali resistance of the passive film 111b varies depending on the type of metal. The effect of suppressing the decrease in adhesive strength by the configuration of this embodiment is particularly noticeable when a passive film 111b with low alkali resistance is formed. From this viewpoint, it is preferable that the first substrate 111 contains at least one element from among chromium (Cr), iron (Fe), nickel (Ni), molybdenum (Mo), and palladium (Pd). For example, the first substrate can be a layer formed from stainless steel (SUS) or nickel containing these elements.

[0078] The base layer 710 contains silicon (Si) and carbon (C). Preferably, the base layer contains Si-C bonds. For example, the base layer 710 can be a layer formed of silicon carbide (SiC). By providing a base layer 710 containing Si and C at the bonding surface between the first substrate 111 and the second substrate 112, the alkali resistance and solvent resistance of these bonding surfaces can be improved. In addition, the base layer 710 containing Si and C has good adhesion to the resin layer 720 formed from a material described later. Due to these effects, in this embodiment, the adhesive strength between the first substrate 111 and the second substrate 112 is less likely to decrease even when using alkaline inks or inks containing high concentrations of methylpyrrolidone.

[0079] The base layer 710 only needs to cover the portion of the surface of the first substrate 111 (the surface of the passivation film 111b) to which the second substrate 112 is joined via the resin layer 720. The base layer 710 may also cover the entire surface of the first substrate 111 on the side facing the second substrate 112. The base layer 710 may also cover the surface inside the hole of the nozzle 59. Furthermore, the base layer 710 may also cover the entire surface of the first substrate 111 on the discharge side.

[0080] In particular, it is preferable that the underlayer 710 continuously covers the surface of the first substrate 111 between the liquid-repellent layer 730 and the resin layer 720. In this region, the passivation film 111b of the first substrate 111 is exposed and is susceptible to degradation by alkaline inks or inks containing high concentrations of methylpyrrolidone. By covering this region with the underlayer 710, degradation of the first substrate 111 by the ink can be suppressed. Preferably, the underlayer 710 continuously covers the surface of the first substrate 111 on the side of the second substrate 112, the surface inside the nozzle 59 hole, and the discharge side surface.

[0081] Figure 8 is a schematic diagram showing the main cross-sectional configuration of the first substrate 111 (nozzle plate) and the second substrate 112 (piezoelectric element 58) in an inkjet head 55 of a modified example of this embodiment, near the nozzle 59 (region 59a shown in Figure 5B). As shown in Figure 8, the base layer 710 partially covers the surface of the first substrate 111 on the side facing the second substrate 112, however, it may be arranged to cover the portion to which the second substrate 112 is joined via the resin layer 720.

[0082] The underlying layer 710 preferably has a maximum peak P of the Si2p orbital binding energy on its surface, measured by X-ray photoelectron spectroscopy (XPS), between 99.6 (eV) and 101.9 (eV). In this embodiment, specifically, a Quantera SXM manufactured by ULVAC-PHI can be used as the XPS measuring device. Monochromatic Al Kα rays (1486.6 eV) are used as the X-ray source. The detection area is set to 100 μmφ, the extraction angle to 45°, and the detection depth to approximately 4 nm to 5 nm for measurement. PHI Multipak can be used as the analysis software.

[0083] Preferably, the distribution of oxygen (O) atoms in the depth direction of the underlying layer 710, as measured by X-ray photoelectron spectroscopy (XPS), is higher on the surface side opposite to the first substrate 111 and lower on the surface side facing the first substrate 111. By distributing more oxygen atoms on the surface side of the underlying layer 710, it is easier to form covalent bonds and hydrogen bonds with the liquid-repellent layer 730, thereby increasing the adhesive strength of the liquid-repellent layer 730. Note that the distribution of oxygen (O) atoms on the surface side opposite to the first substrate 111 refers to the amount of oxygen (O) atoms in the region of the underlying layer 710 extending 5 nm in depth from the surface opposite to the first substrate 111. Similarly, the distribution of oxygen (O) atoms on the surface side facing the first substrate 111 refers to the amount of oxygen (O) atoms in the region of the underlying layer 710 extending 5 nm in depth from the surface on the first substrate 111 side.

[0084] Furthermore, it is preferable that the atomic distribution of oxygen (O) measured by X-ray photoelectron spectroscopy (XPS) in the base layer 710 is higher on one surface side where the resin layer 720 is located, and decreases towards the discharge side surface (the other surface) opposite to the resin layer 720 (for example, the atomic distribution inside the nozzle 59 decreases towards the discharge side surface (the other surface)). By distributing more oxygen atoms on the discharge side surface where the liquid-repellent layer 730 is located, it is easier to form covalent bonds and hydrogen bonds with the liquid-repellent layer 730, thereby increasing the adhesive strength of the liquid-repellent layer 730.

[0085] Furthermore, it is preferable that the carbon (C) atom distribution of the underlayer 710, as measured by X-ray photoelectron spectroscopy (XPS), is higher on the surface side facing the first substrate 111 and lower on the surface side opposite the first substrate 111. By reducing the number of carbon atoms on the surface side of the underlayer 710, it is easier to form covalent bonds and hydrogen bonds between it and the liquid-repellent layer 730, thereby increasing the adhesive strength of the liquid-repellent layer 730.

[0086] The thickness of the underlayer 710 is preferably 1 nm to 1000 nm, more preferably 5 nm to 300 nm, and even more preferably 10 nm to 200 nm.

[0087] The thickness of the underlayer 710 may vary depending on the location. For example, it may be thicker around the nozzle 59 (discharge hole) than in other areas. By increasing the thickness of the underlayer 710 around the nozzle 59 (discharge hole), which forms the ink flow path, the ink resistance of the first substrate 111 can be further improved.

[0088] The resin layer 720 is a cured product of a resin composition containing an epoxy compound represented by general formula (I) and a polythiol compound having two or more thiol groups in its molecule.

[0089] [ka]

[0090] In general formula (I), R1 is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R2 is independently a linking group represented by general formula (II). m is a number between 0.1 and 50. L is independently an integer between 0 and 3.

[0091] [ka]

[0092] In general formula (II), R3 and R4 independently represent a hydrogen atom or a methyl group in which some or all of the hydrogen atoms are substituted with fluorine atoms.

[0093] The epoxy compound represented by general formula (I) forms a three-dimensionally crosslinked polymer when cured. Because this polymer is impermeable to ink, it can form a resin layer 720 that does not easily absorb ink and does not swell during use.

[0094] From the viewpoint of improving the ink resistance and heat resistance of the resin layer 720, it is preferable that the epoxy compound represented by general formula (I) is the epoxy compound represented by general formula (I-1).

[0095] [ka]

[0096] In general formula (I-1), R1 is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. m is a number between 0.1 and 50. L is independently an integer between 0 and 3.

[0097] The content of the epoxy compound represented by general formula (I) is preferably 10 parts by mass or more and 100 parts by mass or less, and more preferably 30 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the total amount of epoxy compound contained in the resin composition. When the content of the epoxy compound represented by general formula (I) is within this range, it is easy to achieve both heat resistance and chemical resistance of the resin layer 720.

[0098] Furthermore, the resin composition preferably further contains an epoxy compound represented by general formula (IV).

[0099] [ka]

[0100] In general formula (IV), R is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0101] The content of the epoxy compound represented by general formula (IV) is preferably 10 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the total amount of epoxy compounds contained in the resin composition. When the content of the epoxy compound represented by general formula (IV) is within this range, the ink resistance of the resin layer 720 tends to be increased.

[0102] Furthermore, the resin composition preferably further contains an epoxy compound represented by general formula (V).

[0103] [ka]

[0104] In general formula (V), R 10 and R 11 These are independently hydrogen atoms or alkyl groups having 1 to 4 carbon atoms.

[0105] The content of the epoxy compound represented by general formula (V) is preferably 5 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of the total amount of epoxy compounds contained in the resin composition. When the content of the epoxy compound represented by general formula (V) is within this range, it is easy to form the resin layer 720 and easy to improve the adhesion of the resin layer 720.

[0106] In addition to these, the resin composition may also contain various epoxy compounds depending on the purpose. Other examples of epoxy compounds include polyglycidyl ether compounds of mononuclear polyhydric phenol compounds such as hydroquinone, resorcinol, pyrocatechol, and phloroglucinol; polyglycidyl ether compounds of polynuclear polyhydric phenol compounds such as dihydroxynaphthalene, biphenol, methylenebisphenol (bisphenol F), methylenebis(orthocresol), ethylidenebisphenol, isopropylidenebisphenol (bisphenol A), isopropylidenebis(orthocresol), tetrabromobisphenol A, 1,3-bis(4-hydroxycumylbenzene), 1,4-bis(4-hydroxycumylbenzene), 1,1,3-tris(4-hydroxyphenyl)butane, 1,1,2,2-tetra(4-hydroxyphenyl)ethane, thiobisphenol, sulfonylbisphenol, oxybisphenol, and terpenephenol; ethylene glycol, propylene glycol, butylene glycol, hexanediol, polyglycol, thiodiglycol, glycerin, trim This includes polyglycidyl ethers of polyhydric alcohols such as tyrolpropane, pentaerythritol, sorbitol, and bisphenol A-ethylene oxide adducts, as well as maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, suberic acid, adipic acid, azelaic acid, sebacic acid, dimeric acid, trimeric acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and endomethylenetetrahydrophthalic acid. Homopolymers or copolymers of glycidyl esters or glycidyl methacrylates of aliphatic, aromatic or alicyclic polybasic acids, epoxy compounds having a glycidylamino group including N,N-diglycidylaniline, bis(4-(N-methyl-N-glycidylamino)phenyl)methane, and diglycidyl orthotoluidine, vinylcyclohexene diepoxide, dicyclopentanediene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,This includes epoxidized cyclic olefin compounds containing 4-epoxy-6-methylcyclohexylmethyl-6-methylcyclohexanecarboxylate and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, epoxidized polybutadiene and epoxidized styrene-butadiene copolymers, as well as heterocyclic compounds containing triglycidyl isocyanurate or their end isocyanates that have been reacted to form prepolymers with internal crosslinking, or these have been increased in molecular weight with polyvalent active hydrogen compounds (polyvalent phenols, polyamines, carbonyl group-containing compounds, polyphosphate esters, etc.).

[0107] From the viewpoint of sufficiently enhancing curability, the resin composition preferably has an epoxy equivalent of 70 to 3,000 of the total epoxy compounds, and more preferably 90 to 2,000.

[0108] The polythiol compound acts as a curing agent for the epoxy compound mentioned above.

[0109] Polythiol compounds are not limited to compounds having two or more thiol groups in their molecule. Examples of polythiol compounds include trimethylolpropanetris (thioglycolate), pentaerythritol tetrakis (thioglycolate), ethylene glycol dithioglycolate, trimethylolpropanetris (β-thiopropionate), pentaerythritol tetrakis (β-thiopropionate), dipentaerythritol poly(β-thiopropionate), and thiol compounds obtained by the esterification reaction of polyols and mercapto organic acids.

[0110] The polythiol compounds may include alkyl polythiol compounds containing 1,4-butanedithiol, 1,6-hexanedithiol, 1,10-decanedithiol, etc., terminal thiol group-containing polyethers, terminal thiol group-containing polythioethers, thiol compounds obtained by the reaction of epoxy compounds with hydrogen sulfide, and thiol compounds having terminal thiol groups obtained by the reaction of polythiol compounds with epoxy compounds. These polythiol compounds may be produced using a basic substance as a reaction catalyst. Therefore, it is preferable to reduce the alkali metal ion concentration to 50 ppm or less by dealkalization treatment. Dealkalization treatment can be carried out by dissolving the polythiol compound in an organic solvent such as acetone or methanol, neutralizing it with an acid such as dilute hydrochloric acid or dilute sulfuric acid, and removing the resulting salt by extraction, washing, etc. Alternatively, dealkalization treatment can also be carried out by adsorption removal using an ion exchange resin or separation and purification by distillation.

[0111] The polythiol compound is preferably dipentaerythritol hexa(3-mercaptobutyrate) or 1,3,5-tris(3-mercaptopropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. These polythiol compounds easily provide both storage stability and curability.

[0112] The mixing ratio of the epoxy compound to the polythiol compound in the resin composition is preferably such that the thiol equivalents / epoxy equivalents ratio is 0.2 or more and 2.0 or less, and more preferably 0.5 or more and 1.5 or less. When the mixing ratio is 0.2 or more, the resin composition can be cured in a short time. When the mixing ratio is 2.0 or less, the heat resistance of the resin layer 720 tends to be improved.

[0113] The resin composition may further contain an imidazole compound represented by general formula (III).

[0114] The above imidazole compounds act as curing accelerators or base catalysts.

[0115] [ka]

[0116] In general formula (III), k is an integer between 1 and 6, preferably 1 and 2. j is 0 or 1, preferably 1.

[0117] In general formula (III), R5, R6, and R7 independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group.

[0118] Examples of alkyl groups having 1 to 20 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, tert-pentyl, hexyl, isohexyl, octyl, 2-ethylhexyl, tert-octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Examples of aryl groups include phenyl and naphthyl groups. These functional groups may be substituted with halogens and hydroxyl groups, etc.

[0119] R5, R6, and R7 are preferably independently one of a hydrogen atom, a methyl group, an ethyl group, and a phenyl group.

[0120] In general formula (III), R8 represents one of the following: an alkylene group having 1 to 20 carbon atoms, an arylene group, or a -CH2CH2COO- group.

[0121] Examples of alkylene groups having 1 to 20 carbon atoms include methylene, ethylene, propane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, octane-1,8-diyl, 2-methylhexane-1,6-diyl, and decane-1,10-diyl. Examples of arylene groups include phenylene and naphthylene. These linking groups may be substituted with halogens, hydroxyl groups, etc.

[0122] R8 is preferably a methylene group or a -CH2CH2COO- group.

[0123] In general formula (III), when k is 1, R9 is one of the following: a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, or a cyanomethyl group. When k is 2 to 6, R9 is a hydrocarbon group having 1 to 20 carbon atoms.

[0124] Examples of hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups and aryl groups having 1 to 20 carbon atoms.

[0125] The examples of alkyl groups and aryl groups having 1 to 20 carbon atoms as described above include the linking groups exemplified as R5, R6, and R7.

[0126] Specific examples of imidazole compounds represented by general formula (III) include the following compounds.

[0127] [ka]

[0128] [ka]

[0129] [ka]

[0130]

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[0131]

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[0132]

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[0133]

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[0134]

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[0135]

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[0136]

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[0137]

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[0138]

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[0139]

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[0140]

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[0141]

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[0142]

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[0143]

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[0144]

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[0145]

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[0146]

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[0147]

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[0148]

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[0149]

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[0150]

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[0151] The content of the imidazole compound is not particularly limited. For example, the content of the imidazole compound can be 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the epoxy compound.

[0152] From the viewpoint of increasing the adhesive strength of the resin layer 720, the resin composition preferably contains a silane coupling agent represented by general formula (VI).

[0153] [ka]

[0154] In general formula (VI), R 12 and R 13 These are independently alkyl groups having 1 to 4 carbon atoms.

[0155] Examples of alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, propyl, isopropyl, and butyl groups.

[0156] In general formula (VI), R 14 This is an alkylene group or an arylene group having 1 to 20 carbon atoms.

[0157] Examples of alkylene groups having 1 to 20 carbon atoms include methylene, ethylene, propane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, octane-1,8-diyl, 2-methylhexane-1,6-diyl, and decane-1,10-diyl. Examples of arylene groups include phenylene and naphthylene. These linking groups may be substituted with halogens or hydroxyl groups.

[0158] In general formula (VI), R 15 This is one of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or an aryl group.

[0159] In general formula (VI), h and i are integers whose sum is 3.

[0160] Examples of alkyl groups having 1 to 20 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, tert-pentyl, hexyl, isohexyl, octyl, 2-ethylhexyl, tert-octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Examples of aryl groups include phenyl and naphthyl groups. These functional groups may be substituted with aryl groups, heterocyclic groups, amines, amides, imines, halogens, or hydroxyl groups.

[0161] Specific examples of silane coupling agents represented by general formula (VI) include 3-aminopropyl-trimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)aminopropyltrimethoxysilane, N-(2-aminoethyl)aminopropylmethyldimethoxysilane, and 3-phenylaminopropyltrimethoxysilane.

[0162] The resin composition may also contain other silane coupling agents besides the silane coupling agent represented by general formula (VI), titanate-based coupling agents, and aluminate-based coupling agents.

[0163] Other examples of silane coupling agents include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, N-2(-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2(-aminoethyl)-3-aminopropylmethyldiethoxysilane, N-2(-aminoethyl)-3-aminopropyltrimethoxysilane, N-2(-aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, (1,3-dimethylbutylidene)-propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N,N-bis(3-(trimethoxysilane) This includes ethylenediamine (propyl)propyl, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, 3-phenylaminopropyltrimethoxysilane, hydrochloride of aminoethyl-3-aminopropyltrimethoxysilane, hydrochloride of N-(2-(vinylbenzineamino)ethyl)-3-aminopropyltrimethoxysilane, 1,2-ethanediamine, N-{3-(trimethoxysilyl)propyl}-N-{(ethenylphenyl)methyl} derivative hydrochloride, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, and 3-isocyanatetopropyltriethoxysilane.

[0164] Examples of the titanate-based and aluminate-based coupling agents mentioned above include tetra-i-propoxytitanium, tetra-n-butoxytitanium, tetrakis(2-ethylhexyloxy)titanium, titanium-i-propoxyoctylene glycolate, di-i-propoxybis(acetylacetonate)titanium, poly(di-i-propoxyoxytitanium), poly(di-n-butoxyoxytitanium), di-n-butoxybis(triethanolamine)titanium, diisopropoxybis(triethanolamine)titanium, isopropyltri(N-amideethylaminoethyl)titanium, and acetalkoxyaluminum diisopropylate.

[0165] Furthermore, these coupling agents are preferably those having epoxy groups or amine groups. Of these, epoxy group coupling agents are preferred from the viewpoint of suppressing reaction progression during storage.

[0166] The resin composition may also contain other curing catalysts, reactive or non-reactive diluents (plasticizers) including monoglycidyl ethers, dioctyl phthalate, dibutyl phthalate, benzyl alcohol, and coal tar, fillers or pigments such as glass fibers, carbon fibers, cellulose, silica sand, cement, kaolin, clay, aluminum hydroxide, bentonite, talc, silica, finely powdered silica, titanium dioxide, carbon black, graphite, iron oxide, and bituminous substances, lubricants such as candelilla wax, carnauba wax, wood wax, privet wax, beeswax, lanolin, whale wax, montan wax, petroleum wax, fatty acid wax, fatty acid esters, fatty acid ethers, aromatic esters, and aromatic ethers, adhesive resins including xylene resin and petroleum resin, thickeners, thixotropic agents, antioxidants, light stabilizers, ultraviolet absorbers, flame retardants, defoamers, rust inhibitors, colloidal silica, and other additives such as colloidal alumina.

[0167] The resin layer 720 preferably has an average thickness of 0.3 μm to 10.0 μm, and more preferably 0.5 μm to 6.0 μm. The thinner the average thickness of the resin layer 720, the higher the adhesive reliability. The thicker the average thickness of the resin layer 720, the higher the initial strength. The average thickness of the resin layer 720 can be measured by embedding it in epoxy resin, exposing the cross-section with a polishing machine, and observing it with a scanning electron microscope (SEM).

[0168] [Manufacturing method for the head (inkjet head) 55] Figures 9A to 9D and 10A to 10C show a part of the manufacturing method of the head 55.

[0169] First, as shown in Figure 9A, a substrate is prepared that will serve as the material for the first substrate 111 (nozzle plate) having a plurality of nozzles 59 (discharge holes). The substrate contains the material described above, and a passivation film 111b is formed on its surface.

[0170] Next, as shown in Figure 9B, ejection holes (nozzles 59) are formed in the substrate. The nozzles 59 can be formed by known methods depending on the material of the substrate, such as etching, laser processing, punching, and electroforming. In this way, the first substrate 111, which is a nozzle plate, can be obtained.

[0171] Next, as shown in Figure 9C, a base layer 710 is formed on the surface of the first substrate 111. The base layer 710 can be formed by vapor deposition, sputtering, atomic layer deposition, or chemical vapor deposition (CVD). Of these, CVD is preferred because it is easy to form a layer containing silicon (Si) and carbon (C). For example, a base layer 710 having Si-C bonds can be formed by CVD using silicon carbide or trimethoxysilane. It is preferable to form the base layer 710 by applying the material from the discharge side surface of the first substrate 111. At this time, the applied base layer 710 material wraps around through the nozzle 59. This allows the base layer 710 to be formed on the surface of the second substrate 112 as well.

[0172] At this time, the area in which the underlayer 710 is formed can be adjusted by applying a mask to the surface of the first substrate 111 as needed. In this embodiment, the underlayer 710 is formed so as to cover at least the portion of the surface of the first substrate 111 (the surface of the passivation film 111b) to which the second substrate 112 is joined via the resin layer 720. In other words, the joined portion is not masked. In this way, as shown in Figure 8, the underlayer 710 can also be formed so as to partially cover the surface of the first substrate 111 on the second substrate 112 side, but to cover the portion to which the second substrate 112 is joined via the resin layer 720. It is preferable not to apply a mask to the surface of the first substrate 111 between the liquid-repellent layer 730 and the resin layer 720, and to form the underlayer 710 on this surface. It is even more preferable not to apply a mask to the surface of the first substrate 111 at all and to form the underlayer 710 on the entire surface of the first substrate 111.

[0173] Furthermore, after forming the underlayer 710, it is preferable to clean the surface of the first substrate 111 by a known method to remove foreign matter.

[0174] Next, as shown in Figure 9D, a liquid-repellent layer 730 is formed on the surface of the first substrate 111 (the surface of the underlayer 710).

[0175] Specifically, plasma treatment in oxygen gas is used to form OH groups on the surface of the substrate layer 710, thereby increasing its wettability. Then, the first substrate 111 is immersed in a liquid repellent that will form the liquid repellent layer 730. The liquid repellent can be, for example, a solution obtained by diluting a silane coupling agent with a solvent such as water, and further adding a surfactant. However, the method of applying the liquid repellent is not limited to this. The liquid repellent may also be applied by CVD, spray coating, spin coating, and wire bar coating. After that, the liquid repellent layer 730 is formed by a known method such as heat treatment. After the liquid repellent layer 730 is formed, it is preferable to remove any remaining liquid repellent by ultrasonic cleaning or the like.

[0176] By methods such as immersion, a liquid-repellent layer 730 is formed on the entire surface of the first substrate (one surface and the other surface), as shown in Figure 9D. After this, the liquid-repellent layer 730 is removed from the parts of the first substrate 111 excluding the discharge-side surface by a plasma removal method or the like. For example, a mask can be applied to the part of the discharge-side surface where the liquid-repellent layer 730 remains, and plasma etching can be performed using a mixed gas of CF4 and oxygen, or oxygen gas. The flow rate at this time can be 30 sccm or more and 300 sccm or less. The pressure at this time can be 10 Pa or more and 70 Pa or less. The microwave output at this time can be 100 W or more and 300 W or less. The processing time at this time can be 10 seconds or more and 20 minutes or less.

[0177] In this way, a substrate with a liquid-repellent layer 730 formed on the discharge-side surface can be obtained, as shown in Figure 10A.

[0178] Furthermore, this plasma etching allows for the distribution of more oxygen atoms on the surface side of the substrate layer 710. Specifically, the distribution of oxygen (O) atoms in the depth direction within the substrate layer 710 can be made more abundant on the surface side opposite to the first substrate 111 and less abundant on the side facing the first substrate 111. In addition, this plasma etching allows for the distribution of more oxygen atoms on the discharge-side surface of the substrate layer 710. Moreover, the distribution of oxygen (O) atoms in the substrate layer 710 at the nozzle 59 can be made more abundant on the surface side where the resin layer 720 is located and less abundant toward the discharge-side surface (the other surface) opposite to the resin layer 720.

[0179] Furthermore, this plasma etching allows for the distribution of more carbon atoms in the interior of the underlying layer 710. Specifically, the distribution of carbon (C) atoms in the depth direction within the underlying layer 710 can be made more abundant on the surface side facing the first substrate 111 and less abundant on the surface side opposite to the first substrate 111.

[0180] Next, as shown in Figure 10B, a resin composition 720a (described above), which will be the material for the resin layer 720, is applied to the portion of one surface of the first substrate 111 where the second substrate 112 (piezoelectric element 58) will be joined. The resin composition 720a can be applied by a known method. After that, as shown in Figure 10C, the second substrate 112 is placed, and the resin composition 720a is cured by a known method, thereby joining the second substrate 112 to the first substrate 111 with the resin layer 720. Alternatively, the resin composition 720a (described above), which will be the material for the resin layer 720, may be applied to the portion of the surface of the second substrate 112 where the first substrate 111 will be joined, by a known method, and the resin composition 720a is cured by a known method after the first substrate 111 has been placed, thereby joining the first substrate 111 to the second substrate 112 with the resin layer 720. Furthermore, the head 55 can be obtained by joining other substrates by a known method.

[0181] Although embodiments of the present invention have been specifically described above, the present invention is not limited to the specific embodiments described above. Various modifications and changes are possible to the specific examples described above within the scope of the gist of the present invention as described in the claims. [Examples]

[0182] The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0183] 1. Fabrication of the inkjet head Two types of materials were prepared for the nozzle plate: a stainless steel (SUS) substrate with a chromium (Cr) oxide film (passivation film) formed on its surface, and a nickel substrate with a nickel (Ni) oxide film (passivation film) formed on its surface.

[0184] 1-1. Inkjet head 1 A 108 nm thick underlayer was formed on a SUS substrate using a plasma CVD apparatus (SAMCO PD-200ST). Tetramethylsilane (Si(CH3)4) was used as the material gas, and argon was used as the carrier gas. The material gas flow rate was 30 sccm, and the carrier gas flow rate was 10 sccm. The deposition temperature was 25°C. The RF power during deposition was 500 W.

[0185] XPS analysis of the formed sublayer under the following conditions revealed that the maximum peak P(eV) of the Si2p orbital binding energy was 100.4(eV). XPS measurement device: Quantera SXM manufactured by ULVAC-PHI. X-ray source: Monochromatic Al Kα rays (1486.6 eV) Detection area: 100 μmφ Take-out angle: 45° Detection depth: Approximately 4nm to 5nm

[0186] Subsequently, the substrate, whose surface had been cleaned, was immersed in a silane coupling compound (Optool DSX, manufactured by Daikin Industries, Ltd., a silane-terminated perfluoropolyether compound) HFE7200 (manufactured by 3M Corporation). After removal, it was left in the air (20°C, 30% humidity) for 12 hours, and then heated at 100°C for 60 minutes to form a liquid-repellent layer. Furthermore, a mask was applied to the discharge surface, and plasma etching was performed for 10 minutes at an oxygen gas flow rate of 50 sccm, a pressure of 20 Pa, and a microwave output of 200 W to remove the liquid-repellent layer from unwanted areas.

[0187] Subsequently, discharge holes were formed in these substrates by laser processing to create nozzle plates.

[0188] As an epoxy compound represented by general formula (I), 60 parts by mass of phenol novolac type epoxy resin (trifunctional or higher, jER grade 152 (manufactured by Mitsubishi Chemical Corporation)) and 40 parts by mass of triglycidyl-p-aminophenol were prepared. As a polythiol compound having two or more thiol groups in its molecule, 102 parts by mass of trimethylolpropanetris (3-mercaptobutyrate) was prepared. As an imidazole compound represented by general formula (III), 2-ethyl-4-methylimidazole was prepared. As a coupling agent, 2 parts by mass of aminopropyltrimethoxysilane was prepared. These were mixed while cooling to obtain a resin composition.

[0189] A resin composition was applied to the area of ​​the nozzle plate where the piezoelectric element would be bonded, after the base layer had been formed and the surface had been cleaned, to a coating thickness of 2.5 μm. Then, a SUS304 substrate (second substrate) was brought into contact with the resin composition and heated to 80°C while being pressurized at 10 cN·m. After 3 hours, it was confirmed that the resin composition had hardened into a resin layer and that the second substrate had adhered to the nozzle plate.

[0190] The bonded assembly formed by bonding the nozzle plate and the second substrate in this manner was designated as a simulated inkjet head 1.

[0191] After the inkjet head 1 was manufactured, the nozzle plate was peeled off and the adhesive was removed. Then, argon (Ar) was used as the etching ion species. + The following XPS measurements were performed while etching the surface of the nozzle plate using a rare gas ion sputtering method. The etching rate was set to 0.05 nm / sec. XPS measurement device: Quantera SXM manufactured by ULVAC-PHI. X-ray source: Monochromatic Al Kα rays (1486.6 eV) Targets for measurement: Si2p, C1s, O1s, N1s Take-out angle: 45° Detection interval: Measured every 1 nm

[0192] XPS measurements revealed that the distribution of oxygen (O) atoms in the depth direction within the underlying layer was higher in the region 5 nm from the surface opposite the substrate (SUS) and lower in the region 5 nm from the surface on the substrate (SUS) side. Furthermore, the distribution of oxygen (O) atoms in the underlying layer was higher on the surface where the piezoelectric element and resin layer are located and lower on the discharge surface where the liquid-repellent layer is located.

[0193] 1-2. Inkjet head 2 A simulated inkjet head 2 was obtained in the same manner as the inkjet head 1, except that the underlying layer was an SiO2 film formed by sputtering using silicon (Si) as the target and O2 as the reaction gas.

[0194] Similar to inkjet head 1, XPS analysis of the underlying layer revealed that the maximum peak P(eV) of the Si2p orbital binding energy was not observed in the range of 99.6(eV) to 101.9(eV). Furthermore, the distribution of oxygen (O) atoms in the depth direction within the underlying layer did not change in the thickness direction, nor did it change on both sides of the nozzle plate.

[0195] 1-3. Inkjet head 3 A simulated inkjet head 3 was obtained in the same manner as the inkjet head 1, except that a base layer was not formed.

[0196] 1-4. Inkjet head 4 A simulated inkjet head 4 was obtained in the same manner as the inkjet head 1, except that a resin layer was formed using a resin composition that did not form a base layer, did not contain a polythiol compound, and instead contained 14 parts by mass of a modified aliphatic amine (jER-cured grade TO184 (manufactured by Mitsubishi Chemical Corporation)), which is a polyamine, instead of an imidazole compound.

[0197] 1-5. Inkjet head 5 A simulated inkjet head 5 was obtained in the same manner as the inkjet head 1, except that a nickel substrate was used instead of a stainless steel substrate, and ejection holes were formed by electroforming.

[0198] Similar to inkjet head 1, XPS analysis of the underlying layer revealed that the maximum peak P(eV) of the Si2p orbital bonding energy was 100.4(eV). Furthermore, the distribution of oxygen (O) atoms in the depth direction within the underlying layer was higher in the region 5 nm from the surface opposite the substrate (SUS) and lower in the region 5 nm from the surface on the substrate (SUS) side. Additionally, the distribution of oxygen (O) atoms in the underlying layer was higher on the surface where the piezoelectric element and resin layer are located and lower on the ejection side surface where the liquid-repellent layer is located.

[0199] 2. Evaluation The resulting simulated inkjet heads 1 to 5 were immersed in simulated ink.

[0200] As a simulated ink, Ink 1 was defined as an ink containing 75% by mass of N-2-methylpyrrolidone and 25% by mass of 2-n-butoxyethyl acetate. Ink 1 is an ink that simulates a strong solvent ink containing methylpyrrolidone. Ink 2 was defined as an aqueous solution in which sodium bicarbonate and sodium carbonate were added to adjust the pH to 11. Ink 2 is an ink that simulates an alkaline ink.

[0201] After immersion for a predetermined time, the presence or absence of detachment of the second substrate from the nozzle plate was checked, and ink resistance was evaluated. The evaluation criteria are as follows. A. No peeling occurred even after immersion at 60°C for 4 weeks. In case B, no delamination occurred after immersion at 60°C for one week, but delamination did occur after immersion at 60°C for four weeks. Delamination occurred after immersion at 60°C for one week.

[0202] The results are shown in Table 1.

[0203] [Table 1]

[0204] As shown in Table 1, the inkjet head, which is a cured product of a resin composition in which the base layer contains silicon (Si) and carbon (C) and the resin layer contains an epoxy compound represented by the general formula (I) and a polythiol compound having two or more thiol groups in the molecule, is less likely to have a decrease in the adhesion strength between the nozzle plate and other members even when using alkaline ink or ink containing methylpyrrolidone.

[0205] This application claims the priority of Japanese Patent Application No. 2024-017974 filed on February 8, 2024. The matters described in the specification, claims, and drawings of the application at the time of filing are incorporated herein by reference.

Industrial Applicability

[0206] The present invention is useful as an inkjet head and an inkjet recording apparatus having high durability even when using alkaline ink or ink containing methylpyrrolidone.

Explanation of Signs

[0207] 1 Inkjet printer 10 Conveyor section 11 Conveyor belt 11a Conveyor surface 12 Driving roller 13 Driven roller 20 Supply section 21 Supply loading section 22 Supply conveyor section 30 Discharge section 31 Discharge loading section 32 Discharge conveyor section 40 Ink supply section 41 Main tank 42 Flow path 50 Drawing section 51 Carriage 52a First sub-tank 52b Second sub-tank 53a, 53b, 53c flow paths 54 Head drive unit 55 Inkjet head 56 Manifold (common supply flow path) 57 Individual supply flow path 58 Piezoelectric element 59 Nozzle 60 Reading unit 70 Operation display unit 80 Input / output interface 90 Control unit 91 CPU 92 RAM 93 ROM 94 Storage unit 95 Heating unit 99 External device 101 Housing 102 Exterior member 103a Inlet 103b, 103c Outlet 104 Mounting hole 110 Head chip 111 First substrate 111a Individual circulation flow path 111b Immobile membrane 112 Second substrate 112a Common circulation flow path 112b Vertical circulation flow path 113 Third substrate 710 Underlayer 720 Resin layer 720a Resin composition 730 Liquid-repellent layer

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