Liquid ejection head

Abstract

To provide a liquid discharge head that can control a flow of an adhesive leaking out toward structures formed on a surface of a joined substrate.SOLUTION: The liquid discharge head comprises a first substrate 1, a second substrate 2 and a third substrate 3 having structures formed therein. The first substrate 1 is joined to the second substrate 2 through an adhesive 4, and the first substrate 1 is joined to the third substrate 3 through the adhesive 4. An opening whose corner part has a curvature radius of R2 is formed in the first substrate 1 and an opening whose corner part has a curvature radius of R1 is formed in the second substrate 1, where R1 and R2 satisfy a relational expression of R1<R2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] In recent years, in the manufacture of MEMS (Micro Electro Mechanical Systems) such as pressure sensors and acceleration sensors, devices have been produced that are composed of substrate assemblies in which substrates are bonded together with an adhesive, such as liquid ejection heads that eject liquid.

[0003] An example of a liquid ejection head is an inkjet recording head. An inkjet recording head has an energy generating element that provides energy for ejecting ink. An ejection port member is formed on the surface of a substrate, and the ejection port member has multiple ejection ports for ejecting ink. The substrate also has through-holes that serve as ink flow paths, and ink is supplied from the back side of the substrate to the front side through the through-holes. The through-holes and the ejection ports are connected, and ink that passes through the through-holes is ejected from the ejection ports by the force applied by the energy generating element. Examples of energy generating elements include elements such as heater elements that can boil ink by applying electrical current and heating, and elements such as piezoelectric elements that can apply pressure to liquid by using volume changes.

[0004] As an example of a device composed of a substrate assembly, Patent Document 1 discloses a liquid ejection device. Specifically, the device comprises a pressure generating chamber communicating with a nozzle opening, and a piezoelectric element having a piezoelectric layer and an electrode provided on the piezoelectric layer. Liquid stored in the pressure generating chamber is ejected through the nozzle opening. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-91272 Summary of the Invention

Problems to be Solved by the Invention

[0006] In a liquid ejection device such as Patent Document 1, generally, a plurality of substrates are joined using an adhesive. However, when joining these substrates, the protruding adhesive may affect the ejection characteristics with respect to the structure formed on the substrate surface to be joined. For example, the vibration characteristics may change due to the adhesive applied to the diaphragm of the piezoelectric element, or the supply port for supplying liquid to the common liquid chamber where the energy generating element is disposed may be clogged, resulting in a delay in liquid supply and affecting the ejection characteristics.

[0007] In view of the above problems, an object of the present invention is to provide a liquid ejection head capable of controlling the flow of the protruding adhesive with respect to the structure formed on the substrate surface to be joined.

Means for Solving the Problems

[0008] In order to solve the above problems, the present invention provides a liquid ejection head having a first surface and a second surface that is the back surface of the first surface, a first substrate having a structure formed on the first surface, a second substrate having a second surface facing the first surface of the first substrate, and a third substrate having a first surface facing the second surface of the first substrate. In the liquid ejection head, the first substrate and the second substrate are joined via an adhesive between the first surface of the first substrate and the second surface of the second substrate, and the first substrate and the third substrate are joined via an adhesive between the second surface of the first substrate and the first surface of the third substrate. An opening having a corner radius of curvature of R2 is formed in a region on the second surface side of the first substrate and on the back side of the structure, and an opening having a corner radius of curvature of R1 is formed in a region on the second surface side of the second substrate and facing the structure, and R1 and R2 satisfy the relationship R1 < R2.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a liquid ejection head that can control the flow of adhesive that has spilled out onto structures formed on the surfaces of substrates to be joined. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a bonded substrate according to a first embodiment of the present invention; [Figure 2] Cross-sectional views of each substrate of embodiment 1 [Figure 3] 1 is a cross-sectional view of a bonded substrate according to Embodiment 1 when a problem of the present invention occurs; [Figure 4] 1 is a cross-sectional view of the substrates of the first embodiment according to the present invention; [Figure 5] Graph showing the relationship between the radius of curvature, corner creep and protrusion width [Figure 6] 1 is a cross-sectional view of a bonded substrate according to a first embodiment of the present invention; [Figure 7] 1 is a cross-sectional view of a bonded substrate according to a second embodiment of the present invention; [Figure 8] Cross-sectional views of each substrate of embodiment 2 [Figure 9] 1 is a cross-sectional view of a bonded substrate according to a second embodiment of the present invention when a problem occurs. [Figure 10] 10 is a cross-sectional view of the case where the present invention is applied to each substrate of the second embodiment. [Figure 11] 1 is a cross-sectional view of a bonded substrate according to a second embodiment of the present invention; [Figure 12] 3 is a cross-sectional view of a bonded substrate according to a third embodiment. [Figure 13] Cross-sectional views of each substrate of embodiment 3 [Figure 14] 10 is a cross-sectional view of a bonded substrate according to a third embodiment of the present invention when a problem occurs. [Figure 15] 10A and 10B are cross-sectional views of the substrates of the third embodiment to which the present invention is applied; [Figure 16] 10 is a cross-sectional view of a bonded substrate according to a third embodiment of the present invention; [Figure 17] 10 is a cross-sectional view of a bonded substrate according to a fourth embodiment of the present invention; [Figure 18] Cross-sectional views of each substrate of embodiment 4 [Figure 19]10 is a cross-sectional view of a bonded substrate according to a fourth embodiment of the present invention when a problem occurs. [Figure 20] 10A and 10B are cross-sectional views of the substrates of the fourth embodiment according to the present invention; [Figure 21] 10 is a cross-sectional view of a bonded substrate according to a fourth embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] The radius of curvature in the present invention refers to the shape of the corner of the opening as seen in a plan view of each substrate viewed from the bonding surface. The depth direction depends on the depth of the opening, but it is preferable that the same radius of curvature be formed over at least half of the depth of the recess or through-hole from the adhesive inlet surface (bonding surface), more preferably at least three-quarters, and most preferably, the same radius of curvature be formed throughout.

[0013] Furthermore, although the present embodiment has been described taking the bonding of three substrates as an example, the present invention is not limited to this and can also be applied to the bonding of three or more substrates.

[0014] (Embodiment 1) Hereinafter, a liquid ejection head substrate according to a first embodiment of the present invention will be described with reference to the drawings. Note that, in the following embodiments, specific descriptions may be used to fully explain the present invention, but these are merely examples that are technically preferable and do not particularly limit the scope of the present invention.

[0015] A liquid ejection head is a component included in a recording device such as an inkjet printer. The recording device also includes a liquid storage unit that stores the 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] Fig. 1 is a cross-sectional view of a bonding substrate for a liquid ejection head according to Embodiment 1 of the present invention. Note that Fig. 1 does not show the effect of adhesive on openings, which is an issue of the present invention.

[0017] The liquid ejection head includes a first substrate 1, a second substrate 2, and a third substrate 3. These substrates have a first surface and a second surface designated by 1a, 1b, 2a, 2b, 3a, and 3b, respectively. Figures 2(a) to 2(c) are cross-sectional views of the bonded substrates of this embodiment 1 separated from each other.

[0018] The substrates are bonded together with adhesive 4 to form a substrate for a liquid ejection head. In other words, the bonded substrate has at least a plurality of bonding surfaces formed using adhesive.

[0019] The first substrate 1 is made of, for example, a silicon substrate, and has a vibrating membrane 6 provided on the first surface 1a, and a piezoelectric element 5 (structure) formed on the vibrating membrane 6. The second surface 1b has openings (spaces) that form pressure chambers 7. The vibrating membrane 6 forms the ceiling walls of the pressure chambers, and partitions the pressure chambers 7 into multiple chambers.

[0020] The second substrate 2 is made of, for example, a silicon substrate. The second substrate 2 is arranged so as to cover the piezoelectric elements 5. A recess 8 is formed on the second surface 2b of the second substrate facing the piezoelectric elements 5, and the second substrate is joined to the first surface 1a of the first substrate via an adhesive 4. A plurality of piezoelectric elements 5 corresponding to the plurality of pressure chambers 7 are housed in the recess 8.

[0021] A third substrate 3 is bonded to the second surface 1b of the first substrate. The third substrate 3 is made of, for example, a silicon substrate, and defines a pressure chamber 7 together with the second substrate 2 and the vibration membrane 6. The third substrate 3 has a liquid ejection flow path 9, and an ejection port 10 for ejecting liquid is formed at the bottom surface of the liquid ejection flow path. The ejection port 10 penetrates the third substrate 3 together with the liquid ejection flow path 9, and has an ejection port on the opposite side to the pressure chamber 7. Therefore, when a change in the volume of the pressure chamber 7 occurs, the liquid stored in the pressure chamber 7 passes through the liquid ejection flow path 9 and is ejected from the ejection port 10.

[0022] An ink tank (not shown) is disposed on the second substrate 2. A through-hole 11 is formed so as to penetrate the second substrate 2. The through-hole 11 of the second substrate 2 also penetrates the first substrate 1 and communicates with the pressure chamber 7 inside the substrate. Therefore, the liquid in the ink tank is supplied to the pressure chamber 7 through the through-hole 11.

[0023] A piezoelectric actuator is formed by disposing a piezoelectric element 5 on a vibration membrane 6. The piezoelectric element 5 includes a lower electrode (not shown) formed on a vibration membrane forming layer, the piezoelectric element 5 formed on the lower electrode, and an upper electrode (not shown) formed on the piezoelectric element.

[0024] 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, a sputtering method, and the piezoelectric film is formed by a sol-gel method, but may also be formed by a sputtering method.

[0025] The piezoelectric element 5 can be a PZT (lead zirconate titanate) film formed by, for example, a sol-gel method or a sputtering method. Such a piezoelectric element 5 is made of a sintered body of metal oxide crystal. By forming an interlayer film and a wiring layer so that the actuator section can be driven, the first substrate 1 that serves as the actuator substrate can be formed.

[0026] The piezoelectric element 5 is formed at a position facing the pressure chamber 7 across the vibration membrane 6. In other words, the piezoelectric element 5 is formed so as to be in contact with the surface of the vibration membrane 6 on the side opposite to the pressure chamber 7. The vibration membrane 6 has a property that allows it to deform in the direction facing the pressure chamber 7.

[0027] When a drive voltage is applied to the piezoelectric element 5 from a drive IC (not shown), the piezoelectric element 5 is deformed due to the inverse piezoelectric effect. This causes the vibration membrane 6 to deform together with the piezoelectric element 5, which in turn causes a change in the volume of the pressure chamber 7 and pressurizes the liquid.

[0028] The pressurized liquid passes through the liquid discharge flow path 9 and is discharged from the discharge port 10 in the form of minute droplets.

[0029] The processing of the substrates shown in Figures 2(a) to (c) is not particularly limited and is carried out using a general substrate processing process. For example, in the case of a silicon substrate, a semiconductor manufacturing process can be used. After forming a desired etching mask on the surface of the substrate, processing can be carried out by performing Si dry etching. The etching mask can be formed, for example, using a novolac-based photoresist, and by exposing, developing, and patterning it.

[0030] For Si dry etching, an etching technique known as the Bosch process, which uses SF gas for the etching step and C F gas for the coating step, can also be used. The radius of curvature of the corners of the opening according to the present invention can be changed as desired by changing the photoresist exposure mask.

[0031] Furthermore, openings on at least the surfaces of these substrates to be joined (for example, the second surface 1b of the first substrate and the first surface 3a of the third substrate) need to be processed before bonding, but substrate processing such as forming openings on surfaces other than those to be joined and thinning the substrates may be performed either before or after bonding.

[0032] A material that has high adhesion to the substrate is preferably used as the adhesive 4. A material that has high applicability with little air bubbles and other contaminants 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.

[0033] The adhesive 4 can be cured by a thermal curing method or a delayed UV curing method. If one of the substrates is UV transparent, the UV curing method can also be used. The adhesive is applied by spin-coating the adhesive onto a dry film and then transferring it to one of the substrates on the joining surface. However, the adhesive application method is not limited to this, and screen printing or, if the adhesive is a photosensitive adhesive, photolithography patterning can also be used.

[0034] The adhesive is preferably formed thick to eliminate voids during bonding, and the thickness of the film before bonding is 1.0 μm or more, preferably 2.0 μm or more, and more preferably 5.0 μm or more.

[0035] Although voids can be suppressed by increasing the thickness of the adhesive, the adhesive is more likely to overflow into the openings of the respective bonding surfaces, which makes the problem of the present invention more likely to occur.

[0036] FIG. 3 shows a cross-sectional view of the first substrate 1, second substrate 2, and third substrate 3 after they have been bonded together using adhesive 4. The affected area 12 of the adhesive shown in FIG. 3 will now be described. If the adhesive 4 is not controlled, it may overflow into the recess 8 on the second surface 2b of the second substrate and get on the vibration membrane 6. It may also creep up the corners of the pressure chamber 7 on the second surface 2b of the first substrate and get on the vibration membrane 6 in the same way. If the overflowing adhesive gets on the vibration membrane 6 in this way, it may affect the vibration characteristics and may have an impact on the ejection performance. Furthermore, overflowing adhesive may also narrow or clog the flow path of the through-hole 11, thereby affecting the ejection performance.

[0037] The present invention provides a bonded substrate using an adhesive having multiple bonding surfaces, and by specifying the relationship between the radius of curvature of the corners of the openings formed on each bonding surface, it is possible to control the protruding portion and thereby obtain good discharge performance.

[0038] Figure 5 shows the measurement results of creeping at the corners of the openings and the protrusion width of the bonding surface when substrates with openings with various curvature radii R were bonded using adhesive, with the curvature radius set to 8 μm as the base. Creeping here refers to the phenomenon in which adhesive that has protruded into the opening spreads along the corners of the opening in the height direction Z relative to the bonding interface XY due to surface tension. Protrusion width refers to the width of adhesive protruding from the opening in the X or Y axis on the same plane as the bonding interface XY. Figure 5 shows that as the curvature radius R increases, creeping tends to decrease and the protrusion width tends to increase. In particular, creeping suppression is sufficient when the curvature radius R exceeds 20 μm. Furthermore, as the curvature radius R decreases, creeping tends to increase and the protrusion width tends to decrease. In other words, by specifying the relationship between the curvature radii of the corners of openings on multiple bonding surfaces, adhesive protrusion can be controlled.

[0039] 4(a) to 4(c) show plan views of openings according to the present invention formed in the first substrate 1, the second substrate 2, and the third substrate 3. By reducing the radius of curvature R1 of the corners of the opening of the recess 8 in Fig. 4(a), the adhesive 4 that has overflowed onto the first surface 1a of the first substrate is actively forced to creep up through the corners of the recess 8, reducing the amount of overflow and suppressing the effect of the adhesive on the vibration membrane 6.

[0040] Furthermore, by increasing the radius of curvature R2 of the corner of the pressure chamber 7 in FIG. 4(b), it becomes possible to suppress the adhesive 4 protruding onto the first surface 3a of the third substrate from climbing up the corner of the pressure chamber 7, and it is possible to suppress the influence of the adhesive on the diaphragm 6. That is, by setting R1 < R2, it becomes possible to suppress the influence of the adhesive on the diaphragm 6. The opening having the radius of curvature of R2 is formed in a region on the second surface side of the first substrate and on the back side of the structure.

[0041] From the results of FIG. 5, R1 shown in FIGS. 4(a) to (c) promotes the climbing of the adhesive at the corner and is preferably less than 12 μm, more preferably 8 μm or less, in order to reduce the overhang width. From the viewpoint of suppressing the climbing of the adhesive at the corner, R2 is preferably greater than 20 μm, more preferably 30 μm or more.

[0042] Also, if the corner R3 of the opening of the through-hole 11 shown in FIG. 4(a) is such that the adhesive climbs up too much, the adhesive that has climbed up to the first surface 1a of the first substrate may reach and contaminate the first surface 1a of the first substrate. On the other hand, if the climbing of the adhesive is suppressed too much, the cross-sectional area of the through-hole 11 may become narrow or blocked, which may affect the flow of the ink. Therefore, it is preferable that R3 satisfies R1 < R3 < R2, and it is preferable that 12 μm ≤ R3 ≤ 20 μm.

[0043] When the through-hole 11 has a stepped portion 15 as shown in FIGS. 4(a') and (a''), the climbing adhesive accumulates at the stepped portion 15, and the arrival at the first surface 1a of the first substrate can be suppressed. Therefore, in a configuration having the stepped portion 15, the adhesive can actively climb up the corner. That is, it is preferable that R3 satisfies R3 ≤ R1 < R2. At this time, the radius of curvature of the through-hole 11 on the first surface 1a side of the first substrate across the stepped portion 15 may be made larger than R3 to suppress the arrival at the first surface 1a of the first substrate.

[0044] The opening shape of the liquid discharge flow path 9 is not particularly limited. However, if the adhesive that protrudes from the opening of the pressure chamber 7 reaches the liquid discharge flow path 9, it may affect the discharge port 10. Therefore, as shown in FIG. 4(c), when the radius of curvature of the corner of the liquid discharge flow path is R4, it is preferable that R2 = R4, and a configuration where R2 < R4 is more suitable.

[0045] FIG. 6 shows a cross-sectional view of a substrate in which a first substrate 1, a second substrate 2, and a third substrate 3 having the configuration according to the present invention as shown in FIGS. 4(a) to 4(c) are joined via an adhesive 4. By using the present invention, in a joined substrate having a plurality of joining surfaces, the protruding adhesive can be controlled and good discharge performance can be obtained without affecting the discharge performance.

[0046] (Embodiment 2) Hereinafter, a substrate for a liquid discharge head according to Embodiment 2 of the present invention will be described with reference to the drawings. In the embodiments described below, specific descriptions may be made in order to fully explain the present invention, but these are merely preferred examples technically and do not particularly limit the scope of the present invention. Further, the description of Embodiment 2 will focus on the differences from Embodiment 1.

[0047] In the drawings of the present embodiment, the discharge port is shown in an upward position and the liquid supply port is shown in a downward position. This shows the posture during the manufacture of the flow path forming portion of the liquid discharge head. In use, it is often used with the discharge port facing downward.

[0048] FIG. 7 is a cross-sectional view of a joined substrate for a liquid discharge head according to Embodiment 2 of the present invention. Note that FIG. 7 does not show the influence of the adhesive on the opening, which is a problem of the present invention. FIGS. 8(a) to 8(c) are cross-sectional views of each substrate of the present embodiment separated. Each substrate is joined with an adhesive 4 to form a substrate for a liquid discharge head.

[0049] The first substrate 1 is made of, for example, a silicon substrate, and has energy generating elements 16 and supply ports 18 corresponding to the energy generating elements 16 formed on its first surface 1a. An opening that forms a flow path 19 is formed on its second surface 1b. The supply ports 18 formed on the first substrate 1 and the flow path 19 are connected, and liquid is introduced from the flow path 19 through the supply ports 18 to a common liquid chamber 17 in which the energy generating elements 16 are arranged.

[0050] The second substrate 2 is made of, for example, a silicon substrate or a stainless steel substrate. The second substrate 2 is arranged so as to cover the energy generating elements 16, and a recess 8 that becomes a common liquid chamber 17 is formed on the second surface 2b of the second substrate, facing the energy generating elements 16. The recess 8 is bonded so as to accommodate a plurality of energy generating elements 16 corresponding to the plurality of common liquid chambers 17. In addition, an ejection port 10 that ejects liquid is formed on the bottom surface of the recess 8. The ejection port 10 penetrates the second substrate 2 together with the recess 8, and has an ejection port 10 corresponding to each energy generating element 16. Therefore, when a change in the volume of the common liquid chamber 17 occurs, the liquid stored in the common liquid chamber 17 is ejected from the ejection port 10. The second substrate 2 is bonded to the first surface 1a of the first substrate via an adhesive 4.

[0051] A third substrate 3 is bonded to the second surface 1b of the first substrate. The third substrate 3 is made of, for example, a silicon substrate, and has an opening 20 penetrating the third substrate 3 to convert the flow path.

[0052] A negative pressure control unit (not shown) generates a pressure difference between the liquid supply channel and the liquid recovery channel. This pressure difference causes the liquid in the liquid supply channel to flow from the supply port 18 to the common liquid chamber 17, and then via the supply port 18 to the liquid recovery channel.

[0053] This flow allows the thickened liquid, bubbles, foreign matter, etc., that are generated by evaporation from the ejection ports 10 and the common liquid chamber 17 when printing is paused to be recovered into the liquid recovery flow path. Also, it is possible to prevent the liquid in the ejection ports 10 and the common liquid chamber 17 from becoming thicker.

[0054] Furthermore, an ink tank (not shown) is disposed upstream of the third substrate 3. An opening 20 that converts the flow path formed in the third substrate 3 penetrates the flow path 19 and the supply port 18 of the first substrate 1, and communicates with the common liquid chamber 17. That is, in this embodiment, the supply port 18 serves as a supply path for the liquid ejected by the liquid ejection head.

[0055] A surface membrane layer (not shown) composed of a wiring layer connected to the energy generating elements 16, an interlayer insulating film, and the like is formed on the first surface 1a of the first substrate. The supply ports 18 and the flow paths 19 are formed by etching using an etching mask made of photoresist or the like. For example, if the energy generating elements 16 are electrothermal conversion elements, when a drive voltage is applied to the electrothermal conversion elements from a drive IC (not shown), bubbles are instantaneously generated in the liquid. Then, droplets are ejected from the ejection ports 10 by utilizing the pressure change that occurs in the common liquid chamber 17 due to the growth of the bubbles.

[0056] 8(a) to 8(c) is not particularly limited and is performed by a general substrate processing process as in embodiment 1. The radius of curvature of the corners of the openings according to the present invention can be changed as desired by changing the photoresist exposure mask. Furthermore, the openings on at least the surfaces to be bonded of these substrates must be processed before bonding, but substrate processing such as forming openings on surfaces other than the surfaces to be bonded and thinning the substrates may be performed before or after bonding.

[0057] The material, curing method, and application method of the adhesive 4 are the same as those in embodiment 1, and the adhesive is preferably formed thick to eliminate voids during bonding, with the thickness of the adhesive before bonding being 1.0 μm or more, preferably 2.0 μm, and more preferably 5.0 μm or more. By making the adhesive thicker, voids can be suppressed, but it becomes more likely for the adhesive to overflow into the openings of each bonding surface, making the problem of the present invention more likely to occur.

[0058] 9 shows a cross-sectional view of the first substrate 1, second substrate 2, and third substrate 3 after they have been bonded together using adhesive 4. The affected area 12 of the adhesive shown in FIG. 9 will now be described. If the overflow of adhesive 4 is not controlled, it may overflow into the recessed portion of the second surface 2b of the second substrate and get into the supply port 18. It may also creep up the corners of the flow path 19 on the second surface 2b of the second substrate and similarly get into the supply port 18.

[0059] If the overflowing portion of the adhesive 4 overlaps the supply port 18 in this way, the supply port 18 will be blocked, making it impossible to supply liquid to the common liquid chamber 17. Furthermore, in a configuration such as this embodiment in which the liquid in the liquid supply flow path flows from the supply port 18 to the common liquid chamber 17 and further via the supply port 18 to the liquid recovery flow path, the supply port 18 will become narrow. This makes it difficult to recover the thickened liquid, bubbles, foreign matter, etc. that has evaporated from the ejection ports 10 into the liquid recovery flow path, which may increase the viscosity of the liquid in the ejection ports 10 and the common liquid chamber 17 and affect ejection performance.

[0060] In the present invention, in a bonded substrate using an adhesive having multiple bonding surfaces as in this embodiment, the relationship between the radii of curvature of the corners of the openings formed on each bonding surface is specified, thereby controlling the protruding portions and achieving good discharge performance.

[0061] FIG. 10(a) to (c) show plan views of the openings according to the present invention formed in the first substrate 1, the second substrate 2, and the third substrate 3. By reducing the radius of curvature R1 of the corner of the opening of the recess 8 in FIG. 10(a), the adhesive 4 protruding onto the first surface 1a of the first substrate can be actively made to climb up through the corner of the recess 8, the protruding amount can be reduced, and the influence of the adhesive on the supply port 18 can be suppressed.

[0062] Furthermore, by increasing the radius of curvature R2 of the corner of the flow path 19 in FIG. 10(b), it becomes possible to suppress the adhesive protruding onto the first surface 3a of the third substrate from climbing up at the corner of the flow path 19, and the influence of the adhesive on the supply port 18 can be suppressed.

[0063] That is, by setting R1 < R2, it becomes possible to suppress the influence of the adhesive on the supply port 18. Also, the radius of curvature R5 of the opening 20 for converting the flow path of the third substrate 3 is such that when the adhesive protruding onto the first surface 3a of the third substrate reaches the opening 20 for converting the flow path, the adhesive may climb up the opening and reach the second surface 3b of the third substrate. For this reason, it is more preferable that R2 < R5. That is, it is more preferable that R1 < R2 < R5.

[0064] From the results of FIG. 5, R1 shown in FIGS. 10(a) to (c) is preferably less than 12 μm, more preferably 8 μm or less, in order to promote the climbing up of the adhesive at the corner and reduce the protruding width. From the viewpoint of suppressing the climbing up of the adhesive at the corner, R2 is preferably greater than 20 μm, more preferably 30 μm or more.

[0065] FIG. 11 shows a cross-sectional view of a substrate in which the first substrate 1, the second substrate 2, and the third substrate 3 having the configuration according to the present invention as shown in FIGS. 10(a) to (c) are joined via the adhesive 4. By using the present invention, in a joined substrate having a plurality of joined surfaces, the protruding adhesive can be controlled and good discharge performance can be obtained without affecting the discharge performance.

[0066] (Embodiment 3) Hereinafter, a liquid ejection head substrate according to a third embodiment of the present invention will be described with reference to the drawings. Note that, in the following embodiments, specific descriptions may be used to fully explain the present invention, but these are merely technically preferred examples and do not particularly limit the scope of the present invention. Furthermore, the description of the third embodiment will focus on the differences from the first embodiment.

[0067] Fig. 12 is a cross-sectional view of a liquid ejection head bonded substrate according to a third embodiment of the present invention. Note that Fig. 12 does not show the effect of the adhesive on the openings, which is an issue of the present invention. Figs. 13(a) to 13(c) are cross-sectional views of the respective substrates of this embodiment disassembled. The respective substrates are bonded with adhesive 4 to form the liquid ejection head substrate.

[0068] The first substrate 1 is made of, for example, a silicon substrate, and has a vibrating membrane 6 provided on the first surface 1a, a recess 8 formed on the vibrating membrane 6, and a piezoelectric element 5 formed on the bottom of the recess 8. Here, the recess 8 may be formed by processing the substrate, or as shown in Fig. 13(b'), it can be formed in a desired location by exposing and developing a permanent resist such as SU-8.

[0069] The second substrate 2 is made of, for example, a silicon substrate. The second substrate 2 is disposed so as to cover the piezoelectric element 5, and the second surface 2b of the second substrate and the first surface 1a of the first substrate are bonded via an adhesive 4.

[0070] Openings that form pressure chambers 7 are formed on the first surface 3a of the third substrate. The substrates are bonded together so that a plurality of piezoelectric elements 5 corresponding to the plurality of pressure chambers 7 are housed in recesses 8.

[0071] The third substrate 3 is made of, for example, a silicon substrate, and is formed with at least openings that become pressure chambers 7 and ejection ports 10 that eject liquid. Although the liquid ejection flow path described in embodiment 1 is not shown in embodiment 2, a liquid ejection flow path may be provided between the pressure chambers 7 and the ejection ports 10, as in embodiment 1.

[0072] The first surface 3a of the third substrate is joined to the second surface 1b of the first substrate, and the vibrating membrane 6 forms the ceiling wall of the pressure chamber 7, dividing the pressure chamber 7 into a plurality of chambers.

[0073] FIG. 14 shows a cross-sectional view of the first substrate 1, second substrate 2, and third substrate 3 after they have been bonded together using adhesive 4. We will now explain the affected area 12 of the adhesive shown in FIG. 14. If the overflow of adhesive 4 is not controlled, the overflowing adhesive may creep up around the corners of the recessed portion 8 on the first surface 1a of the first substrate and get on the vibration membrane 6. The overflowing adhesive may also occur in the pressure chamber 7 on the second surface 2b of the second substrate and get on the vibration membrane 6. If the overflowing adhesive gets on the vibration membrane 6 in this way, it may affect the vibration characteristics and may have an effect on the ejection performance.

[0074] In the present invention, by changing the radius of curvature of the corners of the openings formed on the bonding surfaces of the respective substrates, the protruding portions can be controlled, thereby achieving good discharge performance.

[0075] 15(a) to 15(c) show plan views of openings according to the present invention formed in the first substrate 1, the second substrate 2, and the third substrate 3. Increasing the radius of curvature R1 of the corners of the opening of the recess 8 in Fig. 15(b) prevents the adhesive 4 that has spilled onto the first surface 2a of the second substrate from creeping up from the corners of the recess 8, thereby suppressing the effect of the adhesive on the vibration membrane 6.

[0076] 15(c), the adhesive 4 that has spilled onto the first surface of the third substrate can creep up the corner of the pressure chamber 7, thereby suppressing the influence of the adhesive on the vibration membrane 6. In other words, by making R1>R2, it is possible to suppress the influence of the adhesive on the vibration membrane 6.

[0077] 5, R1 is preferably greater than 20 μm, more preferably 30 μm or greater, in order to prevent the adhesive from creeping up at the corners, and R2 is preferably less than 12 μm, more preferably 8 μm or less, in order to promote creeping up at the corners.

[0078] 15(a) , if the adhesive creeps up too much at the corner R3 of the opening of the through-hole 11, the creeping adhesive may reach the first surface 1a of the first substrate and contaminate the first surface 1a of the first substrate. On the other hand, if the creeping up of the adhesive is suppressed too much, the cross-sectional area of ​​the through-hole 11 may become narrow or be blocked, which may affect the flow of the liquid. Therefore, it is preferable that R3 satisfy the relationship R1>R3>R2, and it is preferable that 12 μm≦R3≦20 μm.

[0079] 16 shows a cross-sectional view of a first substrate 1, a second substrate 2, and a third substrate 3 having the configuration according to the present invention as shown in Figures 15(a) to 15(c), bonded together via an adhesive 4. By using the present invention, the adhesive that protrudes from the bonded substrates having multiple bonding surfaces can be controlled, and good ejection performance can be obtained without affecting the ejection performance.

[0080] (Embodiment 4) A liquid ejection head substrate according to a fourth embodiment of the present invention will be described below with reference to the drawings. Note that, although specific descriptions may be used in the following embodiments to fully explain the present invention, these are merely technically preferred examples and do not limit the scope of the present invention. The description of the fourth embodiment will focus on the differences from the second embodiment.

[0081] In the diagram of this embodiment, the ejection port is shown at the top and the liquid supply port is shown at the bottom, but this shows the position at the time of manufacturing the flow path forming part of the liquid ejection head, and when in use, it is often used with the ejection port at the bottom.

[0082] Fig. 17 is a cross-sectional view of a liquid ejection head bonding substrate according to a fourth embodiment of the present invention. Note that Fig. 17 does not show the effect of the adhesive on the openings, which is an issue of the present invention. Figs. 18(a) to 18(c) are cross-sectional views of the respective substrates of this embodiment disassembled. The respective substrates are bonded with adhesive 4 to form the liquid ejection head substrate.

[0083] The first substrate 1 is made of, for example, a silicon substrate, and has energy generating elements 16 and supply ports 18 corresponding to the energy generating elements 16 formed on its first surface 1a. Recesses 8 are formed on the first surface 1a of the first substrate, and the energy generating elements 16 are formed at the bottom of the recesses 8. Here, the recesses 8 may be formed by processing the substrate, or as shown in FIG. 18(b'), they can be formed in desired locations by exposing and developing a permanent resist such as SU-8.

[0084] The second substrate 2 is made of, for example, a silicon substrate or a SUS substrate, and has a plurality of ejection ports 10 formed thereon for ejecting liquid. The first surface 3a of the third substrate is bonded to the second surface 1b of the first substrate so that the ejection ports are located at positions corresponding to the energy generating elements 16. A recess formed on the first surface of the first substrate serves as a common liquid chamber 17. For example, if the energy generating elements 16 are electrothermal conversion elements, applying a drive voltage to the electrothermal conversion elements from a drive IC (not shown) instantaneously generates bubbles in the liquid. Then, droplets are ejected from the ejection ports 10 by utilizing the pressure change that occurs in the common liquid chamber 17 as the bubbles grow.

[0085] The third substrate 3 is made of, for example, a silicon substrate. A flow path 19 and a flow path conversion member are integrally formed on the third substrate 3. As in the second embodiment, the flow path 19 has a liquid supply flow path and a liquid recovery flow path formed therein, and a pressure difference caused by a negative pressure control unit (not shown) causes the liquid in the liquid supply flow path to flow from the supply port 18 to the common liquid chamber 17 and further via the supply port 18 to the liquid recovery flow path. An opening for flow path conversion is formed on the second surface 3b of the third substrate, and the opening penetrates the third substrate 3 together with the flow path 19.

[0086] A supply port 18 formed on the first substrate 1 and a flow path 19 formed on the second substrate 2 are connected, and liquid is introduced from the flow path 19 through the supply port 18 into a common liquid chamber 17 in which an energy generating element 16 is arranged.

[0087] Figure 19 shows a cross-sectional view of the first substrate 1, second substrate 2, and third substrate 3 after they have been bonded together using adhesive 4. We will now explain the affected area 12 of the adhesive shown in Figure 19. If the overflow of adhesive 4 is not controlled, the adhesive that has overflowed from the corners of recess 8 on first surface 1a of the first substrate may get onto supply port 18.

[0088] Furthermore, the liquid may spill out of the flow channel 19 on the second surface 2b of the first substrate, creep up around the corners of the flow channel 19, and get onto the supply port 18 in the same manner.

[0089] If the adhesive spills over into the supply port 18 in this way, the supply port 18 will be clogged, making it impossible to supply liquid. Furthermore, in a configuration like this embodiment in which the liquid in the liquid supply flow path flows from the supply port 18 to the common liquid chamber 17 and further via the supply port 18 to the liquid recovery flow path, the supply port 18 will become narrow. This makes it difficult to recover thickened liquid, bubbles, foreign matter, etc. that has evaporated from the ejection ports into the liquid recovery flow path, which may increase the viscosity of the liquid in the ejection ports 10 and the common liquid chamber 17 and affect ejection performance.

[0090] In the present invention, in a bonded substrate using an adhesive having multiple bonding surfaces as in this embodiment, the relationship between the radii of curvature of the corners of the openings formed on each bonding surface is specified, thereby controlling the protruding portions and achieving good discharge performance.

[0091] 20(a) to 20(c) show plan views of openings according to the present invention formed in the first substrate 1, the second substrate 2, and the third substrate 3. Increasing the radius of curvature R1 of the corners of the opening of the recess 8 in Fig. 20(b) prevents the adhesive 4 that has spilled onto the second surface 2b of the second substrate from creeping up the corners of the recess 8, thereby suppressing the effect of the adhesive on the supply port 18.

[0092] 20(c) is made smaller, the adhesive 4 that has spilled onto the first surface 3a of the third substrate can creep up the corner of the flow path 19, thereby suppressing the influence of the adhesive on the supply port 18. In other words, by making R1>R2, it is possible to suppress the influence of the adhesive on the supply port 18.

[0093] 11, from the viewpoint of suppressing creeping of the adhesive at the corners, R1 is preferably greater than 20 μm, more preferably 30 μm or greater, and from the viewpoint of promoting creeping at the corners, R2 is preferably less than 12 μm, more preferably 8 μm or less.

[0094] 20(a) to 20(c) show cross-sectional views of a first substrate 1, a second substrate 2, and a third substrate 3 of the configuration according to the present invention bonded together via an adhesive 4. By using the present invention, in a bonded substrate having a plurality of bonding surfaces, the adhesive that protrudes can be controlled, and good ejection performance can be obtained without affecting the ejection performance. [Explanation of symbols]

[0095] 1 First board 1a First surface of first substrate 1b second surface of first substrate 2 Second board 2a: first surface of second substrate 2b: second surface of second substrate 3 Third board 3a: First surface of third substrate 3b second surface of third substrate 4. Adhesive 5 Piezoelectric element 6. Vibration membrane 7. Pressure Chamber 8 recess 9 Liquid discharge channel 10 outlet 11 Through hole 12 Adhesive affected areas 13 Controlled Adhesion 14 Permanent Resist 15 Step 16 Energy generating element 17 Common liquid chamber 18 Supply port 19 Flow path 20 Flow path conversion opening

Claims

1. a first substrate having a first surface and a second surface opposite to the first surface, and having a structure formed on the first surface; a second substrate having a second surface opposite to the first surface of the first substrate; a third substrate having a first surface opposite to the second surface of the first substrate; In a liquid ejection head having the first substrate and the second substrate are bonded to each other via an adhesive between a first surface of the first substrate and a second surface of the second substrate; the first substrate and the third substrate are bonded to each other via an adhesive between the second surface of the first substrate and the first surface of the third substrate; an opening having a corner with a radius of curvature R2 is formed in a region on the second surface side of the first substrate and on the back side of the structure, an opening having a corner with a radius of curvature R1 is formed in a region facing the structure on the second surface side of the second substrate, A liquid ejection head characterized in that R1 and R2 satisfy the relationship R1<R2.

2. 2. A liquid ejection head according to claim 1, wherein a space formed by the opening on the second surface side of the first substrate and the third substrate is a pressure chamber.

3. an opening penetrating the second substrate and having a corner with a radius of curvature of R3 is further formed in the second substrate; 3. The liquid ejection head according to claim 1, wherein R1, R2 and R3 satisfy the relationship R1<R3<R2.

4. a through-hole penetrating the second substrate and having a step is further formed in the second substrate; When the radius of curvature of the corner of the opening of the through hole having a step on the second surface of the second substrate is R3, 3. The liquid ejection head according to claim 1, wherein R1, R2, and R3 satisfy the relationship R3≦R1<R2.

5. the third substrate is further formed with a discharge port for discharging a liquid and a liquid discharge flow path for supplying a liquid to the discharge port; When the radius of curvature of the corner of the liquid discharge flow path is R4, 5. The liquid ejection head according to claim 1, wherein R2 and R4 satisfy the relationship R4≧R2.

6. a discharge port is formed in the second substrate, a space formed by the opening of the second substrate and the first substrate is a common liquid chamber; a space formed by the opening of the first substrate and the third substrate is a flow path; 2. The liquid ejection head according to claim 1, wherein the structure is an energy generating element that generates energy for ejecting liquid from the ejection port.

7. an opening connected to the channel is further formed in the third substrate; When the radius of curvature of the corner of the opening of the third substrate is R5, 7. The liquid ejection head according to claim 6, wherein R1, R2 and R5 satisfy the relationship R1<R2<R5.

8. 8. The liquid ejection head according to claim 1, wherein R1<12 [mu]m and R2>20 [mu]m.

9. 7. A liquid ejection head according to claim 6, wherein the energy generating element is an electrothermal converting element.

10. 9. A liquid ejection head according to claim 1, wherein the structure is a piezoelectric element that generates pressure for ejecting liquid.

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