Liquid ejection head

Abstract

To provide a technique for protecting an ink flow passage formed inside a liquid discharge head using a joint substrate.SOLUTION: A liquid discharge head includes a joint substrate in which a first substrate and a second substrate are jointed with each other with an adhesive to be laminated with each other. The joint substrate has a liquid flow passage through which the first substrate is communicated with the second substrate. At a corner part formed at a position corresponding to the liquid flow passage, at a position where the first substrate is jointed to the second substrate, which is formed by an end face that the first substrate has and a plane that the second substrate has, the adhesive is arranged so that a cross section thereof forms a convex arc-shape toward the corner part. A protective film continuously extending from the first substrate through the adhesive arranged at the corner part to the second substrate is formed at the joint position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection head. [Background technology]

[0002] An example of a functional device, such as a microelectromechanical system (MEMS) (such as a pressure sensor or acceleration sensor) or a microfluidic device, is a liquid ejection head that ejects liquid. Liquid ejection heads are also called inkjet recording heads or liquid jet heads and are used in recording devices that eject liquid to perform recording. In the manufacture of these devices, devices are fabricated that are composed of substrate assemblies in which substrates are bonded together via an organic film (adhesive). In recent years, in order to improve the ejection stability and print quality of liquid ejection heads, a mechanism for circulating ink within the head is sometimes installed.

[0003] Here, Patent Document 1 (JP 2014-124887 A) proposes a method for forming a protective film on substrates bonded via an organic film (adhesive) as a method for reducing damage to bonded substrates caused by ink. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-124887 Summary of the Invention [Problem to be solved by the invention]

[0005] Thus, there is a demand for further improvements in ejection stability and print quality in liquid ejection heads using bonded substrates, and therefore there is a particular demand for suitable protection of the ink flow paths.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a technique for protecting ink flow paths formed inside a liquid ejection head using a bonding substrate. [Means for solving the problem]

[0007] The present invention employs the following configuration: A liquid ejection head including a bonded substrate in which a first substrate and a second substrate are laminated and bonded with an adhesive, the bonded substrate has a liquid flow path that connects the first substrate and the second substrate; At the joining position of the first substrate and the second substrate, before an end face of the first substrate and a flat surface of the second substrate; The angle is set at a position corresponding to the liquid flow path. Department is formed, At the corners, a portion protruding from the bonding surface between the first substrate and the second substrate is The adhesive is arranged so that a cross section thereof forms an arc-shaped convex shape toward the corner portion, When a direction in which the first substrate and the second substrate are stacked is defined as a stacking direction, and a direction intersecting the stacking direction and in which planes of the first substrate and the second substrate extend is defined as an extension direction, in the cross section of the corner, the adhesive is present on a side closer to the corner than a line connecting a position of the adhesive spread in the stacking direction that is farthest from the corner and a position of the adhesive spread in the extension direction that is farthest from the corner, At the bonding position, the first substrate Distribution A continuous protective film is provided so as to extend from the adhesive placed on the second substrate to the second substrate. And, At least one of the joining surfaces of the first substrate and the second substrate is provided with a groove for accommodating the adhesive. The liquid ejection head is characterized by the above features. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique for protecting ink flow paths formed inside a liquid ejection head using a bonded substrate. [Brief explanation of the drawings]

[0009] [Figure 1] Schematic cross-sectional view of a bonding substrate used in a liquid ejection head [Figure 2] Schematic cross-sectional view showing the manufacturing process of the bonded substrate [Figure 3] Enlarged schematic diagram to explain the behavior of adhesive during bonding [Figure 4]Further enlarged schematic diagram to explain the behavior of the adhesive during bonding [Figure 5] Cross-sectional view for examining the amount of adhesive protrusion [Figure 6] Cross-sectional view for comparison to examine the amount of adhesive overflow [Figure 7] Cross-sectional view for comparison to examine the amount of adhesive overflow [Figure 8] Top view showing variations in opening shape of bonded substrate [Figure 9] Cross-sectional view showing variations in board shape [Figure 10] Cross-sectional view showing variations in board shape [Figure 11] Cross-sectional view showing variations in board shape [Figure 12] Schematic cross-sectional view of adhesive control method [Figure 13] Schematic cross-sectional view of adhesive control method [Figure 14] Schematic cross-sectional view of adhesive control method [Figure 15] Schematic cross-sectional view of a bonded substrate according to embodiment 2. [Figure 16] Schematic diagram showing an example of a recording element [Figure 17] Schematic diagram showing an example of a recording element unit [Figure 18] Schematic diagram showing an example of a liquid ejection head configuration DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the technology disclosed herein will be described below with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described below should be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied. Therefore, the scope of the invention is not intended to be limited to the following description. Well-known or publicly known technologies in the relevant technical field can be applied to configurations and processes not specifically illustrated or described. Furthermore, redundant explanations may be omitted.

[0011] Furthermore, although the present embodiment has been described with reference to an example in which three substrates are bonded together, the present invention is not limited to this and can also be applied to bonding a plurality of substrates together.

[0012] Here, we will explain the problems that the inventors have found with conventional liquid ejection heads. The inventors discovered that when ink is circulated within an ink flow path in a liquid ejection head using a bonded substrate, if materials with different wettabilities, such as a protective film and an adhesive, are mixed within the ink flow path, air bubbles will adhere to areas with poor wettability. Furthermore, the inner wall surface of the ink flow path in a liquid ejection head is easily eroded by ink, and if exposed to ink for a long period of time, the flow path structure may collapse. This type of damage by ink is particularly likely to occur when the substrate is a silicon substrate.

[0013] The aforementioned Patent Document 1 (JP 2014-124887 A) proposes a method for reducing ink-induced damage to substrates by forming a protective film on substrates bonded via an organic film (adhesive). However, the inventors' investigations revealed that when a protective film is formed from the inner wall surface of the ink flow path to the organic film (adhesive) as in Patent Document 1 (JP 2014-124887 A), air bubbles adhere to the corners of the bonded substrates and ink flow stagnation occurs. Such air bubble accumulation can lead to poor ink ejection and degrade print quality.

[0014] As a result of the inventor's investigations, it was found that by providing rounded corners in the ink flow path and making the wettability in the ink flow path uniform, it is possible to suppress the accumulation of air bubbles and the stagnation of ink flow. This improves the ink circulation efficiency and enhances print quality. In the following embodiment, such a configuration of the present invention will be specifically described.

[0015] (Embodiment 1) A liquid ejection head substrate according to a first embodiment of the present invention will be described below with reference to the drawings. While this embodiment shows an example in which a piezoelectric element is used as the energy generating element, the present invention is not limited thereto and can also be applied to bonding of substrates having an element that can boil ink by heating through electrical current, such as a heater element. A liquid ejection head to which the present invention is applied is a component included in a recording device such as an inkjet printer. The recording device also includes a liquid storage unit that stores liquid to be supplied to the liquid ejection head, a transport mechanism for the recording medium on which recording is performed, and the like.

[0016] (Configuration of the bonded substrate) 1 is a cross-sectional schematic diagram of a bonding substrate 80 for a liquid ejection head according to a first embodiment of the present invention. The bonding substrate 80 of this embodiment is formed by bonding, via an adhesive 4, a first substrate 1 having an ink flow path 7 (liquid flow path), a second substrate 2 having a plurality of piezoelectric elements 5 and electrodes 6 formed thereon, and a third substrate 3 having a plurality of ejection ports 8 formed thereon. In other words, the bonding substrate 80 has at least a plurality of bonding surfaces that are bonded together using an adhesive. If the adhesive 4 overflows from the bonding surfaces, it is absorbed by grooves 15.

[0017] The first substrate 1 is made of, for example, a silicon substrate and has a first opening 7a that forms an ink flow path 7. The second substrate 2 is made of, for example, a silicon substrate and has a vibrating membrane 11, on which a piezoelectric element 5 is formed. The vibrating membrane 11 forms the ceiling wall of the pressure chamber 10 and separates the pressure chambers 10. The second substrate 2 also has a second opening 7b that communicates with the first opening 7a and forms the ink flow path 7 for introducing liquid into the pressure chambers 10. The third substrate 3 is made of, for example, a silicon substrate and has an ejection port 8 that ejects liquid. The ejection port 8 penetrates the third substrate 3. The ejection port 8 connects the surface of the third substrate facing the pressure chamber 10 with the surface opposite the pressure chamber 10. Therefore, when a volume change occurs in the pressure chamber 10, the liquid stored in the pressure chamber 10 is ejected from the ejection port 8.

[0018] An ink tank (not shown) is disposed on the first substrate 1. Therefore, the liquid in the ink tank is supplied to the pressure chamber 10 through the first opening 7a.

[0019] A piezoelectric element 5 is disposed on the vibration membrane 11, constituting a piezoelectric actuator. The piezoelectric element 5 includes a lower electrode (not shown) formed on the vibration membrane forming layer, the piezoelectric element 5 formed on the lower electrode, and an upper electrode (not shown) formed on the piezoelectric element. An electrode 6 for external connection is also disposed on the vibration membrane 11.

[0020] The piezoelectric element 5 is formed at a position facing the pressure chamber 10 across the vibration membrane 11. That is, the piezoelectric element 5 is formed so as to contact the surface of the vibration membrane 11 opposite the pressure chamber 10. The vibration membrane 11 has the property of being deformable in the direction facing the pressure chamber 10. As shown in the figure, a protective film 18 may be provided on the second substrate 2. The protective film 18 is made of, for example, SiN, and has the function of protecting the wiring layer, the piezoelectric element, and the like. In the following explanation, the protective film 18 provided on the second substrate 2 is considered to be part of the second substrate 2. That is, since the second substrate 2 and the protective film 18 are integrated when the adhesive 4 is applied, the ranges of the first substrate 1 and the second substrate 2 are considered based on this state.

[0021] When a drive voltage is applied to the piezoelectric element 5 via wiring from a drive IC (not shown), the piezoelectric element 5 is deformed by the inverse piezoelectric effect. This causes the vibration membrane 11 to deform together with the piezoelectric element 5, which in turn causes a change in the volume of the pressure chamber 10, pressurizing the liquid such as ink. The pressurized liquid is ejected from the ejection port 8 as minute droplets.

[0022] (Joint and adhesive behavior) Next, the bonding of the first substrate 1 and the second substrate 2 according to the present invention will be described in detail. The present invention will be described using an example of the first substrate 1 and the second substrate 2, but is not limited to this. The present invention may also be applied to the second substrate 2 and the third substrate 3, or, if there are more substrates, to the space between those substrates.

[0023] Figures 3(a) to 3(c) show how a second substrate 2 is bonded to a first substrate 1 via an adhesive 4, forming a Si protective film. Figures 4(a) to 4(c) are enlarged views of region B indicated by the dashed line in Figure 3(a). Figures 4(a) to 4(c) correspond to Figures 3(a) to 3(c), respectively. Figures 3(a) and 4(a) show how an adhesive 4 is applied to the underside of the first substrate 1 (the surface facing the second substrate 2), and then the first substrate and second substrate are brought close to each other and bonded.

[0024] Figures 3(b) and 4(b) show the state after bonding. At this time, the adhesive 4 flows out from the interface between the bonded substrates due to capillary action, forming a protruding portion 4f. The flowed-out adhesive 4 then flows along the corner formed by the substrates, resulting in an arc-shaped cross section of the surface of the adhesive 4 at the corner of the bonded interface, with a recessed portion 4k. That is, at the corner C formed by the extension of the end face it of the first substrate 1 and the flat surface 2p of the second substrate 2 (more precisely, the protective film 18 that is integrated with the second substrate 2 when the adhesive 4 is applied), the cross section of the adhesive 4 forms an arc-shaped convex shape toward the corner C. Therefore, it is preferable to select an adhesive 4 that flows in response to temperature, heat, and load. Here, the cross-sectional shape of the adhesive surface being arc-shaped means that, as shown in the cross-sectional view of Figure 4(b), at the joining position, the cross-section of the adhesive surface is on the inner side (closer to the corner) than the straight line (shown by the dashed line in the figure) formed by the distance D1 over which the adhesive 4 has spread to the second substrate 2 (the distance from the corner of the adhesive 4 spread to the second substrate 2) and the distance D2 over which the adhesive 4 has spread to the first substrate 1 (the distance from the corner of the adhesive 4 spread to the first substrate 1).

[0025] Note that, due to the characteristics of adhesive 4 having a certain degree of fluidity, the cross section of the surface is often curved, and therefore the term "arc" is used; however, as long as the condition that the surface is located inside the D1-D2 line is met as described above, the cross section of the surface does not have to be composed of curves only; for example, it can be a combination of straight lines and curves. The curved portion may be a circular arc, an elliptical arc, or another type of curve. Regardless of the shape of the cross section of the surface of adhesive 4, as long as it is recessed rather than raised above the D1-D2 line, a certain degree of effect can be achieved.

[0026] 3(c) and 4(c) show the state after the protective film 9 has been further formed. It can be seen that the presence of the recessed portion 4k in the base layer of the protective film 9 also forms a recessed portion (recessed rounded portion R) in the protective film 9 that comes into direct contact with ink.

[0027] (Consideration of adhesive overflow) Figures 5 to 7 show examples with different amounts of adhesive overflowing. Figures 5(a), 6(a), and 7(a) show the state of adhesive overflowing, while Figures 5(b), 6(b), and 7(b) show the state after the protective film 9 has been formed.

[0028] 5(a) and 5(b) show an example in which the distance D1 and the distance D2 are different due to the difference in wettability of the adhesive 4 between the first substrate 1 and the second substrate 2. In this example, the cross-sectional shape of the recess is closer to an elliptical arc rather than a circular arc, but the effects of the present invention can be obtained even in such a case.

[0029] 6(a) and 6(b) show cases where the amount of adhesive 4 that protrudes from the joint is small due to the surface characteristics of the first substrate 1 and the second substrate 2, the fluidity of the adhesive 4, etc. In this case, the effect of suppressing bubble accumulation when circulating ink is smaller than in the cases of FIG. 4(c) and FIG. 5(a). However, some degree of effect can be obtained.

[0030] 7(a) and 7(b) show a state in which the adhesive does not overflow and remains inside the space between the substrates. In this case, as shown in FIG. 7(b), the shape of the protective film 9 is not rounded. As a result, the effect of suppressing bubble accumulation when ink is circulated in the ink flow path is significantly reduced.

[0031] (Variations of opening and cross-sectional shape) The openings in the substrates are formed using processing methods such as dry etching, wet etching, or laser. The top views of Figures 8(a) to 8(c) show examples of different shapes of the first openings 7a that form the ink flow paths 7. The symbol B indicates the position corresponding to region B in Figure 3(a). The behavior of the bonding substrate interface between the two substrates also differs depending on the shape.

[0032] Furthermore, the cross-sectional views of Figures 9 to 11 show how the behavior of the adhesive 4 changes depending on the cross-sectional shape of the first substrate 1. Figures 9(a) to 9(c) show a case where the width of the first substrate 1 increases as it approaches the second substrate 2. In this case, the cross section of the base of the first substrate 1 forms an acute angle. Figures 10(a) to 10(c) show a case where the width of the first substrate 1 decreases as it approaches the second substrate 2. In this case, the base of the first substrate 1 forms an obtuse angle. Figures 11(a) to 11(c) show scallops when the first opening 7a is formed using the Bosch dry etching process.

[0033] In either case, it is important to form the adhesive inside the line formed by D1 and D2, as shown in Figures 9(b), 10(b), and 11(b). To achieve this, it is preferable to appropriately select the materials of the first substrate 1 and the second substrate 2, the type of adhesive 4, etc. Even in these cases, it is possible to provide a suitable R to the protective film 9, just as in the case where the edge face of the first substrate 1 is perpendicular to the plane of the second substrate 2.

[0034] (Adhesive overflow control) As mentioned above, if the adhesive 4 remains inside the space between the substrates, the effects of the present invention cannot be obtained. However, if the adhesive 4 significantly protrudes from the space between the bonded substrates, it may block the ink flow path 7 formed on the bonded surface or may protrude into the second opening that houses the piezoelectric element, affecting ejection. Therefore, it is preferable that the type of adhesive 4 does not have excessive fluidity, and the amount applied must be appropriate.

[0035] Here, the direction in which each substrate is stacked is referred to as the stacking direction (Z-direction in the figure), the direction in which each substrate extends, intersecting the stacking direction, is referred to as the extension direction (X-direction in the figure), and the direction in which the edge faces of the substrates continue at the opening, intersecting the stacking direction and extension direction (e.g., the direction in which the first substrate 1 forms a boundary with the first opening 7a), is referred to as the edge direction (Y-direction in the figure). The inventors have found that in the present invention, the distance (D2) between the recessed portion 4k of the adhesive 4 in the stacking direction and the distance (D1) between the recessed portion 4k in the extension direction of each substrate is preferably 3 μm to 20 μm, more preferably 5 μm to 15 μm. In the case of Figure 4(b), since the recessed portion 4k is approximately arc-shaped, the distances D1 and D2 can be collectively referred to as the "arc width D." The arc width D can be controlled by providing a groove for containing adhesive on the surface of the substrate at the bonding interface or by optimizing the thickness of the adhesive film. The same concept can be applied to the case where the recessed portion 4k is not arc-shaped. For example, when the distance D2 in the stacking direction and the distance D1 in the substrate extending direction are different as shown in FIG. 5(a), either D1 or D2 Both are preferably 3 μm or more and 20 μm or less, and it is more preferable that both D1 and D2 are 5 μm or more and 15 μm or less.

[0036] In the bonded substrate 80, the region where the electrode pads and piezoelectric elements are formed and the region where the ink flow path 7 are formed may be adjacent to each other via a substrate. For example, in the region indicated by dashed line A in FIG. 2(a), the ink flow path 7 is formed on the right side of region A, and the electrode storage section 16 where the electrode 6 is disposed is formed on the left side. In this case, if the adhesive 4 spills out to the left of dashed line A, it may cover the electrode, which is undesirable from the standpoint of performance and quality. The same applies to the piezoelectric element 5. On the other hand, it is desirable to spill out the adhesive 4 to the extent that an appropriate recess is formed on the side of the region where the ink flow path 7 is formed.

[0037] Therefore, we consider a method for causing the adhesive 4 to appropriately overflow at the desired position. Figure 12(a) is an enlarged view of the area indicated by the dashed line A. As shown here, a groove 15 for accommodating the adhesive 4 is provided in the corresponding area of ​​the first substrate 1, closer to the side (left side) where overflow is not desired. This makes it possible to suppress overflow of the adhesive on the left side, as shown in Figure 12(b). On the other hand, an appropriate amount of adhesive 4 overflows on the right side, forming a recess 4k. For simplicity, one groove 15 is shown in the figure, but multiple grooves may be provided.

[0038] 13(a) and 13(b), a configuration may be adopted in which a groove 15 for accommodating adhesive 4 is provided on the second substrate 2 side. Also, grooves 15 may be provided on both the first substrate 1 and the second substrate 2.

[0039] As shown in Figures 14(a) and 14(b), overflow can also be controlled by controlling the area on the substrate where the adhesive 4 is applied. In the illustrated example, an adhesive-free area 4m is provided on the left side of the underside of the first substrate 1 where overflow of the adhesive 4 is to be prevented. Note that the amount of adhesive 4 applied in the left side area may not be zero, but may be less than that on the right side. The amount applied may also be gradually reduced from the right side to the left side.

[0040] <Joining process> Next, a series of steps for producing the bonded substrate 80 will be described. This process starts with the step of manufacturing the ink flow paths 7, pressure chambers 10, grooves 15, electrode housing portions 16, etc. in the first to third substrates by combining existing techniques such as etching and lithography, and also arranging the piezoelectric elements 5, electrodes 6, wiring (not shown), etc.

[0041] (Substrate manufacturing process) Silicon is a suitable material for the first substrate 1, the second substrate 2, and the third substrate 3. Other materials that can be used include silicon carbide, silicon nitride, various types of glass (quartz glass, borosilicate glass, alkali-free glass, soda glass), various types of ceramics (alumina, gallium arsenide, gallium nitride, aluminum nitride), and resin. The thickness of the first substrate 1 and the second substrate 2 is, for example, 625 μm. The first opening 7a of the first substrate 1 and the second opening 7b of the second substrate 2 are formed at positions that allow them to communicate with each other after bonding to form the flow path 7.

[0042] On the first substrate 1, a lower electrode (not shown), a piezoelectric element 5 on the lower electrode, and an upper electrode (not shown) on the piezoelectric element are formed on a vibration film forming layer. An electrode 6 is also formed in the electrode housing portion 16. The vibration film forming layer is formed by, for example, plasma CVD. Next, a hydrogen barrier film (not shown), a lower electrode (not shown), a piezoelectric film, and an upper electrode (not shown) are formed in this order. The lower electrode and the upper electrode are formed by, for example, sputtering, and the piezoelectric film is formed by a sol-gel method, but may also be formed by sputtering.

[0043] The piezoelectric element 5 is made of PZT (titanium dioxide) formed by, for example, a sol-gel method or a sputtering method. A lead zirconate oxide film can be applied. Such a piezoelectric element 5 is made of a sintered body of metal oxide crystal. An actuator substrate can be formed by forming an interlayer film and wiring (not shown) so that the actuator section can be driven.

[0044] Pressure chambers 10 and grooves 15 are formed on the second substrate 2 by sputtering or the like. A protective film 18 may also be provided between each substrate. As shown in FIG. 2(a), the second substrate 2 is configured such that piezoelectric elements and electrodes are formed on a substrate made of silicon.

[0045] (Adhesive application process) The adhesive 4 can be formed by a direct writing method using a dispenser or patterning such as photolithography. In addition, since the wettability of the bonding interface and the adhesive is also important, the substrate surfaces may be subjected to a surface treatment such as oxygen plasma before bonding. Other methods for applying the adhesive 4 include a transfer method using glass or PET as a substrate, screen printing, and dispense application. The thickness of the organic film is not particularly limited, but is preferably 0.1 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0046] A material with high adhesion to the substrate is preferably used as the adhesive 4. A material with high applicability and little air bubble contamination is also preferred, as is a low-viscosity material that allows for easy thinning of the adhesive. The adhesive preferably contains a resin selected from the group consisting of epoxy resin, acrylic resin, silicone resin, benzocyclobutene resin, polyamide resin, polyimide resin, and urethane resin. Examples of curing methods for the adhesive 4 include a thermal curing method and a delayed ultraviolet curing method. If one of the substrates is ultraviolet-transparent, an ultraviolet curing method can also be used.

[0047] Here, an example of the transfer method is shown. First, a substrate for adhesive transfer was prepared, and a benzocyclobutene solution was spin-coated to a thickness of 3 μm as the adhesive 4. A PET film was used as the transfer substrate. After coating, a baking process was performed at 100°C for 5 minutes to volatilize the solvent. The adhesive 4 formed on the transfer substrate was brought into contact with the bonding surface of the first substrate 1 while applying heat, and the adhesive 4 was transferred to the first substrate 1.

[0048] (Joining process) The first substrate 1 and the second substrate 2, on which the adhesive 4 has been applied, are bonded by heating the substrates to a predetermined temperature in a bonding device and then applying pressure for a predetermined time. These bonding parameters are set appropriately depending on the adhesive material. Furthermore, bonding in a vacuum is preferable to prevent air bubbles from being mixed into the bonded area. As shown in Figure 3(b), during bonding, the adhesive 4 softens due to heating and is further pressurized, causing the adhesive 4 to flow into the opening from the bonding surface.

[0049] If a large amount of gas is emitted from the adhesive 4 during the protective film formation process following the bonding process, the protective film 9 may crack or peel off. Therefore, if the adhesive 4 is a thermosetting type, it may be heated in a bonding device until it hardens. Alternatively, the substrate assembly may be removed after bonding and heated separately in an oven or the like to accelerate hardening. If the adhesive 4 is a UV-delay type, it is preferable to irradiate the adhesive 4 with a specified amount of UV light before bonding and then bond the substrates. After bonding, it is preferable to further heat the substrate assembly to sufficiently accelerate hardening. If the adhesive 4 is a UV-curable type, after bonding the substrates, it is hardened by irradiating the adhesive 4 with a specified amount of UV light through a UV-transparent substrate. After bonding, it is preferable to further heat the substrate assembly to sufficiently accelerate hardening.

[0050] Here, an example will be described in which the above-mentioned benzocyclobutene solution is used as the adhesive 4 and bonded by thermal curing. At this time, the first substrate 1 and the second substrate 2 are aligned using a bonding alignment device and heated in a vacuum to bond them. The degree of vacuum is 100 Pa or less. The temperature was 150°C. After cooling, the bonded substrate 80 was removed from the apparatus and subjected to heat treatment at 250°C for 1 hour in an oven in a nitrogen atmosphere to harden the adhesive 4. At this time, the protrusion width D of the adhesive 4 was 10 μm. The second substrate 2 was thinned to a thickness of 100 μm using a grinding device. Similarly, a third substrate 3 made of silicon and having a thickness of 625 μm was bonded, and then thinned to a thickness of 100 μm using a grinding device. An outlet 8 was formed on the second surface of the third substrate 3 (the surface opposite to the surface facing the second substrate 2) to form the bonded substrate 80. By bonding in this manner, the bonded substrate 80 shown in FIG. 2(a) is formed.

[0051] (Protective film formation process) 2(b), a protective film 9 is formed uniformly from the first surface of the bonding substrate 80 to the second surface along the inner wall of the ink flow path and on the adhesive. The protective film 9 is formed by repeating surface saturation adsorption of a source gas and at least one agent selected from the group consisting of an oxidizing agent and a nitriding agent by atomic layer deposition (ALD).

[0052] The protective film 9 preferably contains an inorganic element and contains at least one element selected from the group consisting of Ta, Ti, Zr, Nb, V, Hf, and Si in the form of a simple substance, oxide, nitride, or carbide. Among these, the protective film 9 preferably contains at least one oxide of an element selected from the group consisting of Ta, Ti, Zr, Nb, V, Hf, and Si, and more preferably contains at least one compound selected from the group consisting of TaO, TiO, SiOC, SiC, SiCN, TaN, TiN, and HfO.

[0053] If the protective film 9 is formed directly on the organic film (adhesive 4), peeling of the protective film 9 may occur due to the force acting at the interface between the protective film 9 and the organic film (adhesive 4) if the adhesion between the protective film 9 and the organic film (adhesive 4) is weak, if the adhesion is sufficient but the protective film 9 is not rigid enough, or if both the adhesion and rigidity are insufficient. If the protective film 9 peels off, ink may seep in from the peeled area, damaging the organic film (adhesive) and causing poor bonding between the substrates. Furthermore, peeling of the protective film 9 may cause debris to move around in the flow path, affecting ejection performance.

[0054] From these viewpoints, it is desirable for the protective film 9 to have a certain thickness, and if the film thickness is too thick, peeling or the like may occur due to film stress in the protective film, so the film thickness is 50 nm or more and 250 nm or less, more preferably 80 nm or more and 180 nm or less. The protective film 9 may be formed by other methods such as sputtering or CVD.

[0055] Here, we describe an example of ALD deposition of a bonded substrate 80 manufactured by the thermal curing method. A thermal ALD-TaO film was formed using an ALD deposition system. The deposition cycle consisted of transporting a vaporized gas containing Ta in its molecules into the furnace together with nitrogen and spraying it for 2.5 seconds, followed by thorough nitrogen purging and exhaust. Next, transporting a vaporized oxidizer gas into the furnace together with nitrogen and spraying it for 5 seconds, followed by thorough nitrogen purging and exhaust. This cycle constitutes one cycle, and the same cycle was repeated approximately 2,000 times to deposit a tantalum oxide film to a thickness of 130 nm at a deposition temperature controlled at 230°C ± 10°C, resulting in a bonded substrate 80 coated with a protective film 9. This process resulted in the formation of the bonded substrate 80 shown in FIG. 2(b).

[0056] (Liquid-repellent film formation process) Next, as shown in FIG. 2(c), a liquid-repellent film 12 was formed on the protective film 9 formed on the second surface (the surface on the ejection port 8 side) of the bonding substrate 80. There are no particular limitations on the liquid-repellent film 12 as long as it is water-repellent to ink, and for example, a material containing a fluorine-based polymer can be used. When a fluorine-based polymer is used as the liquid-repellent film 12, a base film is provided as appropriate. This can improve the adhesion between the protective film 9 and the liquid-repellent film 12. The base film is, for example, a silicon oxide film. Before forming the liquid-repellent film 12, a surface treatment such as ashing may be performed.

[0057] By applying the bonded substrate manufactured in this way to a liquid ejection head, it was found that by providing rounded corners in the ink flow path and making the wettability in the ink flow path uniform, it is possible to suppress air bubble accumulation and ink flow stagnation, thereby improving ink circulation efficiency and print quality.

[0058] (Embodiment 2) Figure 15 is an enlarged cross-sectional view of the area indicated by the dashed line C in Figure 2(a). Here, the bonding of the second substrate 2 and the third substrate 3 will be described, but the basic configuration is similar to that of the bonding of the first substrate 1 and the second substrate 2. Figure 15(a) is a cross-sectional view of the area C before the substrates are bonded. The second substrate 2 has an overhanging portion 2h above the area where the adhesive 4 protrudes.

[0059] Figure 15(b) shows a cross-sectional view of the substrates after bonding. By bonding the second substrate 2 with an overhang 2h, a continuous recessed portion 2r is formed in the depth direction of the figure. By appropriately setting the film thickness of the adhesive 4 when applied and the adhesive storage area, the amount of adhesive 4 that protrudes can be made to extend from the adhesive interface along the wall to the corners of the upper surface. As a result, in addition to the recessed portion 4k1 that continues to the bonding surface, second recessed portions 4k2 can also be formed at the corners of the overhang 2h. The distance D2' in the stacking direction of the second recessed portion 4k2 and the distance D1' in the extension direction are set as follows. This allows for a more preferable R-shape to be obtained when the protective film 9 is formed, as shown in Figure 15(c), to suppress bubble accumulation during ink circulation.

[0060] As described above, by using the present invention, when substrates are bonded together using an adhesive, the adhesive is provided in a concave arc shape to cover the corners between the bonded substrates, and a continuous protective film is provided along the substrate surface, flow path, and adhesive, thereby making it possible to obtain a liquid ejection head that suppresses the accumulation of air bubbles in the ink flow path and the stagnation of ink flow.

[0061] (Embodiment 3) (Application example) The manufacturing method of the bonding substrate 80 according to the embodiment can be applied to the manufacturing of a liquid ejection head. FIG. 16 is a schematic diagram showing an example of a printing element that can be applied to a liquid ejection printing apparatus or the like. FIG. 16(a) is a schematic diagram showing the ink supply port side as the upper surface, and FIG. 16(b) is a schematic diagram showing the ink ejection port side as the upper surface. FIG. 17 is a schematic diagram showing an example of a printing element unit in which the printing element of FIG. 16 and an electric wiring board are electrically connected. FIG. 18 is a schematic diagram showing an example of an inkjet type liquid ejection head using the printing element unit of FIG. 17.

[0062] 16 has a three-layer structure in which an ink flow path substrate 122, an ink discharge energy generating substrate 123, and an ink discharge substrate 124 are bonded together by an adhesive layer 21. The first substrate 1 in the embodiment corresponds to the ink flow path substrate 122. The portion corresponding to the second substrate 2 is the ink discharge energy generating substrate 123. The portion corresponding to the third substrate 3 is the ink discharge substrate 124.

[0063] The ink ejection substrate 124 is provided with a plurality of ink ejection ports 126 for ejecting ink. The ejection ports 8 shown in the first embodiment can be applied to this. The ink flow path substrate 122 is also formed with ink flow paths 125 for guiding ink to the plurality of ink ejection ports 126. The ink flow path 7 shown in the first embodiment can be applied to this. The ink ejection energy generation substrate 123 is provided with an ink ejection energy generating element for generating energy for ejecting ink from the ink ejection ports 126. An energy generating element (not shown) is provided. In addition, a terminal 24 is provided as an electrical connection portion for electrically connecting the energy generating element to the outside in order to supply power to the energy generating element. A recording element 121 having such a three-layer structure space portion 23 is obtained by the bonded substrate manufacturing method of the embodiment.

[0064] The recording element unit 131 in FIG. 17 is formed by connecting the recording element 121 in FIG. 16 with an electric wiring board 132. The terminals 24 of the recording element 121 are electrically connected one-to-one with the lead portions 133 of the electric wiring board 132 using wire bonding via an electric connection member 134. The electric connection member 134 may be made primarily of, for example, any one of gold, copper, aluminum, and silver, or an alloy containing two or more of these metals. The electrical connection method is not limited to wire bonding, and may also be bump bonding, a lead terminal, an NCP, or an ACF.

[0065] The liquid ejection head 141 in Figure 18 is made up of a support member 142 that joins the recording element unit 131 in Figure 17, a face cover 143 that protects the recording element unit 131, and a flow path member 144 that supplies ink. The recording element unit 131 has two units (131a, 131b) arranged, with the ink ejection orifices 126 on the upper side in the figure. Ink is supplied to the inkjet recording element unit 131 via the flow path member 144 and support member 142, and ink can be ejected by applying an electrical signal to the electrical wiring board 132.

[0066] [Configuration 1] A liquid ejection head including a bonded substrate in which a first substrate and a second substrate are laminated and bonded with an adhesive, the bonded substrate has a liquid flow path that connects the first substrate and the second substrate; a corner formed at a position corresponding to the liquid flow path at a joining position of the first substrate and the second substrate, the corner being formed by an end face of the first substrate and a flat surface of the second substrate, the adhesive being arranged so that a cross section thereof has an arc-like shape that is convex toward the corner; At the joining position, a continuous protective film is provided so as to extend from the first substrate through the adhesive disposed at the corner portion to the second substrate. A liquid ejection head characterized by: [Configuration 2] The adhesive placed at the corners is the adhesive that is applied to the joining surfaces when the first substrate and the second substrate are joined, and that has spilled out during the joining. 2. The liquid ejection head according to configuration 1, [Configuration 3] When a direction in which the first substrate and the second substrate are stacked is defined as a stacking direction, and a direction intersecting the stacking direction and in which the planes of the first substrate and the second substrate extend is defined as an extension direction, in the cross section of the corner, the adhesive is located closer to the corner than a line connecting a position of the adhesive spread in the stacking direction that is farthest from the corner and a position of the adhesive spread in the extension direction that is farthest from the corner. 3. The liquid ejection head according to configuration 2. [Configuration 4] At least one of the first substrate and the second substrate is provided with a groove for accommodating the adhesive. 4. The liquid ejection head according to configuration 2 or 3. [Configuration 5] The groove is provided to control the amount of adhesive that spills over the corner. 5. The liquid ejection head according to configuration 4. [Configuration 6] In the cross section of the corner, the width of the adhesive spreading in the stacking direction and the width of the adhesive spreading in the stretching direction are both 5 μm or more and 15 μm or less. 4. The liquid ejection head according to configuration 3. [Configuration 7] The thickness of the protective film is 80 nm or more and 180 nm or less. 4. The liquid ejection head according to claim 2, wherein the liquid ejection head is a liquid ejection head. [Explanation of symbols]

[0067] 1: first substrate, 2: second substrate, 3: third substrate, 4: adhesive, 7: ink flow path, 9: protective film

Claims

1. A liquid ejection head including a bonded substrate in which a first substrate and a second substrate are laminated and bonded together with an adhesive, the bonded substrate has a liquid flow path that connects the first substrate and the second substrate; a corner portion is formed at a position where the first substrate and the second substrate are joined, the corner portion being located at a position corresponding to an end surface of the first substrate, a flat surface of the second substrate, and the liquid flow path; the adhesive protruding from the bonding surface between the first substrate and the second substrate is disposed at the corner portion so as to have a cross section that is arc-shaped and convex toward the corner portion; When a direction in which the first substrate and the second substrate are stacked is defined as a stacking direction, and a direction intersecting the stacking direction and in which planes of the first substrate and the second substrate extend is defined as an extension direction, in the cross section of the corner, the adhesive is present on a side closer to the corner than a line connecting a position of the adhesive spread in the stacking direction that is farthest from the corner and a position of the adhesive spread in the extension direction that is farthest from the corner, a continuous protective film is provided at the joining position so as to extend from the first substrate through the disposed adhesive to the second substrate; A liquid ejection head, characterized in that a groove for accommodating the adhesive is provided on at least one of the bonding surfaces of the first substrate and the second substrate.

2. The groove is provided to control the amount of adhesive that spills over the corner.

2. The liquid ejection head according to claim 1.

3. In the cross section of the corner, the width of the adhesive spreading in the stacking direction and the width of the adhesive spreading in the stretching direction are both 5 μm or more and 15 μm or less.

3. The liquid ejection head according to claim 1, wherein the ink is a liquid having a thickness of 100 nm or less.

4. The thickness of the protective film is 80 nm or more and 180 nm or less.

3. The liquid ejection head according to claim 1, wherein the ink is a liquid having a thickness of 100 nm or less.

5. A liquid ejection head as described in claim 1 or 2, characterized in that the second substrate includes a second protective film different from the protective film on the surface facing the first substrate.

6. A liquid ejection head as described in claim 1 or 2, characterized in that scallops are formed on the end surface of the first substrate.

7. An electrode storage section in which an electrode is provided is formed between the first substrate and the second substrate, 3. The liquid ejection head according to claim 1, wherein the groove is also formed at a position closer to the electrode housing portion than the liquid flow path in the extension direction.

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