Liquid ejection head

Abstract

A liquid ejection head comprising: a first substrate having a first surface and a second surface opposite to the first surface, the first surface having a structure; 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. The first substrate, the second substrate, and the third substrate are bonded together by an adhesive. The second surface of the first substrate has an opening in an area located on the rear side of the structure, and the opening has corners each having a curvature radius of R2. The second surface of the second substrate has an opening in an area facing the structure, and the opening has corners each having a curvature radius of R1. The curvature radii R1 and R2 satisfy R1. <R2。

Description

Technical Field

[0001] The present disclosure generally relates to liquid ejection heads. Background Art

[0002] Microelectromechanical system (MEMS) devices manufactured in recent years, such as pressure sensors and acceleration sensors, include devices each having a substrate set formed by bonding substrates together with an adhesive. Examples of such devices include a liquid ejecting head that ejects liquid.

[0003] Examples of such a liquid ejection head include an inkjet print head. The inkjet print head includes an energy generating element that applies energy for ejecting ink.

[0004] The front surface of the substrate has an ejection port defining member. The ejection port defining member has a plurality of ejection ports for ejecting ink. The substrate has a through-hole serving as an ink channel, through which ink is supplied from the rear surface of the substrate to the front surface. The through-hole is connected to the ejection port. After passing through the through-hole, the ink is ejected through the ejection port by the force applied by the energy generating element. Examples of the energy generating element include an element capable of boiling ink by applying electrical heat (e.g., a heater element) and an element capable of pressurizing a liquid by utilizing a change in volume (e.g., a piezoelectric element).

[0005] Japanese Patent Laid-Open No. 2013-91272 discloses a liquid ejecting device, which is an exemplary apparatus including a substrate assembly. Specifically, the liquid ejecting device includes a pressure generating chamber communicating with a nozzle orifice and a piezoelectric element. Each piezoelectric element includes a piezoelectric layer and an electrode positioned on the piezoelectric layer. Liquid accumulated in the pressure generating chamber is ejected through the nozzle orifice.

[0006] In liquid ejection devices similar to those disclosed in Japanese Patent Laid-Open No. 2013-91272, multiple substrates are typically bonded together with an adhesive. However, the adhesive may overflow from the structure located at the substrate bonding surface and affect ejection characteristics. For example, the adhesive may overlap with the vibrating plate of the piezoelectric element, causing changes in vibration characteristics. The adhesive may also clog the supply port for liquid to the common liquid chamber containing the energy generating element, hindering the liquid supply and thus affecting the ejection characteristics. Summary of the Invention

[0007] The present disclosure provides a liquid ejection head having controlled adhesive flow relative to a structure at a bonding surface of a substrate.

[0008] One aspect of the present disclosure provides a liquid ejection head comprising: a first substrate having a first surface and a second surface opposite to the first surface, the first surface having a structure; 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. The first substrate and the second substrate are bonded together by an adhesive located between the first surface of the first substrate and the second surface of the second substrate. The first substrate and the third substrate are bonded together by an adhesive located between the second surface of the first substrate and the first surface of the third substrate. The second surface of the first substrate has an opening, which is located in an area on the rear side of the structure and has corners with a curvature radius of R2. The second surface of the second substrate has an opening, which is located in an area facing the structure and has corners with a curvature radius of R1. The curvature radii R1 and R2 satisfy R1 <R2。

[0009] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a cross-sectional view of the bonding substrate in the first embodiment.

[0011] Figures 2A to 2C is a cross-sectional view of each substrate in the first embodiment.

[0012] Figure 3 is a cross-sectional view of a bonded substrate, illustrating the problem solved in the present disclosure.

[0013] Figures 4A to 4C as well as Figure 4A 'and Figure 4A " is a cross-sectional view of each substrate formed according to the first embodiment of the present disclosure.

[0014] Figure 5 is a graph showing the relationship between the radius of curvature, the extension of the adhesive along the corner, and the overflow width of the adhesive.

[0015] Figure 6 is a cross-sectional view of a bonded substrate formed according to the first embodiment of the present disclosure.

[0016] Figure 7 is a cross-sectional view of a bonding substrate in the second embodiment.

[0017] Figures 8A to 8C is a cross-sectional view of each substrate in the second embodiment.

[0018] Figure 9 is a cross-sectional view of a bonded substrate, illustrating the problem solved in the present disclosure.

[0019] Figures 10A to 10C is a cross-sectional view of each substrate formed according to the second embodiment of the present disclosure.

[0020] Figure 11 is a cross-sectional view of a bonded substrate formed according to a second embodiment of the present disclosure.

[0021] Figure 12 is a cross-sectional view of a bonding substrate in the third embodiment.

[0022] Figures 13A to 13C and Figure 13B ' is a cross-sectional view of each substrate in the third embodiment.

[0023] Figure 14 is a cross-sectional view of a bonded substrate, illustrating the problem solved in the present disclosure.

[0024] Figures 15A to 15C is a cross-sectional view of each substrate formed according to the third embodiment of the present disclosure.

[0025] Figure 16 is a cross-sectional view of a bonded substrate formed according to a third embodiment of the present disclosure.

[0026] Figure 17 is a cross-sectional view of a bonding substrate in a fourth embodiment.

[0027] 18A to 18C and Figure 18B ' is a cross-sectional view of each substrate in the fourth embodiment.

[0028] Figure 19 is a cross-sectional view of a bonded substrate, illustrating the problem solved in the present disclosure.

[0029] Figures 20A to 20C is a cross-sectional view of each substrate formed according to the fourth embodiment of the present disclosure.

[0030] Figure 21 is a cross-sectional view of a bonded substrate formed according to a fourth embodiment of the present disclosure. DETAILED DESCRIPTION

[0031] The following describes embodiments of the present disclosure with reference to the accompanying drawings. The sizes, materials, shapes, and relative positions of the components described herein may be appropriately changed depending on the configuration and various conditions of the device to which the present disclosure is applied, and are therefore not intended to limit the scope of the present disclosure to the following embodiments. It should be noted that known or publicly known techniques in the art are applicable to configurations or steps not specifically shown or described herein. Repeated descriptions may be omitted.

[0032] As used herein, the term "radius of curvature" refers to the shape of each corner of an opening in a plan view of each substrate when viewed from the bonding interface. Depending on the depth of the opening (e.g., a recess or through-hole) from the surface (bonding interface) through which the adhesive flows, preferably, at least half the depth of the opening has the same radius of curvature; more preferably, at least three-quarters the depth of the opening has the same radius of curvature; and most preferably, the entire depth of the opening has the same radius of curvature.

[0033] The following embodiment will describe an example of bonding three substrates. The embodiment is not limited to this example and is applicable to bonding three or more substrates.

[0034] First embodiment

[0035] A substrate for a liquid ejecting head according to a first embodiment of the present disclosure will be described below with reference to the accompanying drawings. In order to fully illustrate the present disclosure, specific statements may be given in the following embodiments. These statements are given as examples and are not specifically intended to limit the scope of the present disclosure.

[0036] The liquid ejection head is a member included in a printing apparatus such as an inkjet printer. The printing apparatus also includes a liquid containing portion that contains liquid to be supplied to the liquid ejection head and a conveying mechanism for a print medium to be printed.

[0037] Figure 1 1 is a cross-sectional view of a bonding substrate for a liquid ejection head according to a first embodiment of the present disclosure. Figure 1 The effect of the adhesive on the opening or the problem to be solved by the present disclosure is not shown.

[0038] The liquid ejecting head includes a first substrate 1, a second substrate 2, and a third substrate 3. The first substrate 1 has a first surface 1a and a second surface 1b. The second substrate 2 has a first surface 2a and a second surface 2b. The third substrate 3 has a first surface 3a and a second surface 3b. Figures 2A to 2C is a cross-sectional view of substrates separated from each other in the first embodiment.

[0039] The respective substrates are bonded together to form a liquid ejection head substrate with an adhesive 4. In other words, the bonded substrate has a plurality of bonding surfaces with at least an adhesive.

[0040] The first substrate 1 is, for example, a silicon substrate. The first surface 1a has a vibrating membrane 6 . The vibrating membrane 6 has a piezoelectric element 5 (structure) thereon. The second surface 1b has openings (spaces) serving as pressure chambers 7 . The vibrating membrane 6 serves as the ceiling of the pressure chambers and defines a plurality of pressure chambers 7 .

[0041] The second substrate 2 is, for example, a silicon substrate. The second substrate 2 is provided to cover the piezoelectric elements 5. The second surface 2b of the second substrate 2 has recesses 8 facing the piezoelectric elements 5 and is bonded to the first surface 1a of the first substrate 1 via an adhesive 4. The recesses 8 receive the plurality of piezoelectric elements 5, which are arranged in a one-to-one correspondence with the plurality of pressure chambers 7.

[0042] The third substrate 3 is bonded to the second surface 1 b of the first substrate 1 . The third substrate 3 is, for example, a silicon substrate, and defines a pressure chamber 7 together with the first substrate 1 and the vibration membrane 6 .

[0043] The third substrate 3 has a liquid ejection channel 9. The bottom of the liquid ejection channel 9 has an ejection port 10 for ejecting liquid. The ejection port 10 and the liquid ejection channel 9 extend through the third substrate 3. The ejection port 10 is located on the side of the third substrate 3 opposite the pressure chamber 7. Therefore, a change in the volume of the pressure chamber 7 causes the liquid accumulated in the pressure chamber 7 to pass through the liquid ejection channel 9 and be ejected from the ejection port 10.

[0044] An ink cartridge (not shown) is mounted on the second substrate 2. The second substrate 2 has a through hole 11 extending through the second substrate 2. The through hole 11 of the second substrate 2 further extends through the first substrate 1 and communicates with the pressure chamber 7 in the first substrate 1. Therefore, the liquid in the ink cartridge is supplied to the pressure chamber 7 through the through hole 11.

[0045] The piezoelectric element 5 is provided on the vibration film 6, thereby forming a piezoelectric actuator. The piezoelectric actuator includes a lower electrode (not shown) on the vibration film forming layer, the piezoelectric element 5 on the lower electrode, and an upper electrode (not shown) on the piezoelectric element 5.

[0046] The vibration film forming layer is formed by, for example, plasma chemical vapor deposition (CVD). Then, a hydrogen barrier film (not shown), a lower electrode (not shown), a piezoelectric film, and an upper electrode (not shown) are sequentially formed. The lower electrode and the upper electrode are formed by, for example, a sputtering process. The piezoelectric film is formed by a sol-gel process. The piezoelectric film can be formed by a sputtering process.

[0047] The piezoelectric element 5 may include a lead zirconate titanate (PZT) film formed, for example, by a sol-gel process or a sputtering process. The piezoelectric element 5 comprises a sintered body of metal oxide crystals. Interlayers and wiring layers are formed to enable the actuator to be driven, thereby forming the first substrate 1 serving as the actuator substrate.

[0048] The piezoelectric element 5 is located on the side of the vibration membrane 6 opposite to the pressure chamber 7. In other words, the piezoelectric element 5 is located on the surface of the vibration membrane 6 opposite to the pressure chamber 7.

[0049] The diaphragm 6 is deformable toward the pressure chamber 7 .

[0050] The driving voltage applied to the piezoelectric element 5 by a driver integrated circuit (IC) (not shown) causes the piezoelectric element 5 to deform due to the inverse piezoelectric effect. Consequently, the vibrating membrane 6 also deforms along with the piezoelectric element 5, causing the volume of the pressure chamber 7 to change. This pressurizes the liquid.

[0051] The pressurized liquid passes through the liquid ejection channel 9 and is ejected from the ejection port 10 as minute liquid droplets.

[0052] Figures 2A to 2C The substrate processing shown is not particularly limited and is performed using a typical substrate manufacturing process. For example, a semiconductor manufacturing process can be used for a silicon substrate. A desired etching mask is formed on the surface of the substrate, and then Si dry etching is performed to process the substrate. For example, a novolac-based photoresist can be used as the etching mask. The substrate can be formed by exposure, development, and patterning.

[0053] For example, for Si dry etching, an etching method known as the Bosch process can be used. This process includes etching using SF6 gas and coating using C4F8 gas. By changing the photoresist exposure mask, the radius of curvature of the corner of each opening in the first embodiment of the present disclosure can be changed to any value.

[0054] Although at least the openings of the surfaces to be joined of these substrates (for example, the second surface 1b of the first substrate 1 and the first surface 3a of the third substrate 3) need to be processed before the substrates are joined together, substrate processing such as opening formation at surfaces other than the surfaces to be joined and substrate thinning can be performed before or after the substrates are joined together.

[0055] For the adhesive 4, a material having high viscosity to the substrate can be appropriately used. In addition, a material containing few bubbles and showing good coating properties can be used. In addition, a material with low viscosity to allow the adhesive to be thinned can be used. The adhesive can include resins such as epoxy resins, acrylic resins, silicone resins, benzocyclobutene resins, polyamide resins, polyimide resins, and polyurethane resins.

[0056] Examples of a curing method of the adhesive 4 include thermal curing and ultraviolet (UV) radiation delayed curing.

[0057] In the case where any substrate can transmit ultraviolet light, ultraviolet curing can also be used. The method of applying the adhesive comprises applying the adhesive to a dry film in a spin coating manner, and transferring the adhesive to any one of the surfaces to be joined of the substrate. The adhesive can be applied in any other manner (e.g., by screen printing). If the adhesive is a photosensitive adhesive, photolithographic patterning can be used.

[0058] The adhesive may be formed to a relatively thick thickness to eliminate gaps when bonding the substrates. Before bonding the substrates, the thickness of the adhesive is 1.0 μm or more, preferably 2.0 μm or more, and more preferably 5.0 μm or more.

[0059] Thickening the adhesive can reduce or eliminate voids, but increases the likelihood that the adhesive will overflow into openings at the joining surfaces. A problem that the present disclosure is intended to solve may arise.

[0060] Figure 3 4 is a schematic cross-sectional view of a first substrate 1, a second substrate 2 and a third substrate 3 bonded together with an adhesive 4. Figure 3 The portion 12 affected by the adhesive. If the adhesive 4 is not controlled and prevented from overflowing, the adhesive 4 may overflow into the recessed portion 8 of the second surface 2b of the second substrate 2 and overlap with the vibrating membrane 6. In addition, the adhesive 4 may overflow into the pressure chamber 7 of the second surface 1b of the first substrate 1, extend along the corner of the pressure chamber 7, and similarly overlap with the vibrating membrane 6. The overlap between the overflowing portion of the adhesive and the vibrating membrane 6 affects the vibration characteristics of the vibrating membrane 6, thereby affecting the ejection performance. The through hole 11 serving as a channel may be narrowed or clogged due to the overflowing portion of the adhesive, which may affect the ejection performance.

[0061] According to the first embodiment of the present disclosure, the relationship between the curvature radii of the corners of the openings at the bonding surfaces of substrates bonded together with an adhesive is defined to control overflow of the adhesive, thereby achieving good ejection performance.

[0062] Figure 5 The measured values ​​of the extension of the adhesive along the corners of the substrate opening and the measured values ​​of the width of the adhesive overflowing at the bonding surface of the substrates bonded together with the adhesive are shown, and the ratio of each measured value to the reference value when the curvature radius is 8 μm is shown. Substrates including openings with different curvature radii R were prepared for the experiment. The term "extension" used herein refers to the phenomenon that the surface tension causes the adhesive overflowing into the opening to extend along the corners of the opening in the height direction Z relative to the bonding interface XY. The term "overflow width" used herein refers to the dimension of the adhesive overflowing into the opening along the X-axis or Y-axis on the same plane as the bonding interface XY. See Figure 5 A larger radius of curvature R means less stretching and a relatively larger overflow width. In particular, a radius of curvature R of 20 μm or greater indicates sufficient suppression of stretching. In contrast, a smaller radius of curvature R means increased stretching and a relatively smaller overflow width. In other words, the relationship between the curvature radii of the corners of the opening defining the multiple surfaces to be joined can control adhesive overflow.

[0063] Figures 4A to 4CPlanar view of the openings of the first substrate 1, the second substrate 2, and the third substrate 3 in the first embodiment of the present disclosure. Figure 4A The small radius of curvature R1 at each corner of the opening serving as the recess 8 allows the adhesive 4 that overflows on the first surface 1a of the first substrate 1 to actively extend along the corners of the recess 8, thereby reducing the amount of overflow. This can reduce or eliminate the influence of the adhesive 4 on the vibrating film 6.

[0064] In addition, Figure 4B The large radius of curvature R2 at each corner of the pressure chamber 7 can inhibit the adhesive 4 that overflows on the first surface 3a of the third substrate 3 from extending along the corners of the pressure chamber 7. This can reduce or eliminate the influence of the adhesive 4 on the vibrating film 6. In other words, when the radius of curvature R1 and R2 satisfy R1 < R2, the influence of the adhesive 4 on the vibrating film 6 can be reduced or eliminated. The opening with the radius of curvature R2 is located in the area within the second surface 1b of the first substrate 1, and this area is located at the rear side of the structure.

[0065] As Figure 5 shown, Figure 4A the radius of curvature R1 for promoting the extension of the adhesive along the corners and reducing the adhesive overflow width is preferably less than 12 μm, and more preferably less than or equal to 8 μm. Figure 4B The radius of curvature R2 for inhibiting the extension of the adhesive along the corners is preferably greater than 20 μm, and more preferably greater than or equal to 30 μm.

[0066] For the radius of curvature R3 at each corner of the opening serving as the through hole 11 in Figure 4A if the adhesive extends excessively along the corners, it may cause the adhesive to reach and contaminate the first surface 2a of the second substrate 2. In contrast, if the extension of the adhesive along the corners is excessively inhibited, it may cause the adhesive to reduce the cross-sectional area of the through hole 11 or block the through hole 11, thereby affecting the flow of the ink. Therefore, the radius of curvature R3 can satisfy R1 < R3 < R2 and 12 μm ≤ R3 ≤ 20 μm.

[0067] Figure 4A Both 'and 4A" show the through hole 11 including the stepped portion 15. In such a case, the adhesive 4 extends along the corners and accumulates at the stepped portion 15, thereby inhibiting the adhesive 4 from reaching the first surface 2a of the second substrate 2. Therefore, the stepped portion 15 allows the adhesive 4 to actively extend along the corners. In other words, the radius of curvature R3 can satisfy R3 ≤ R1 < R2. In this case, the portion of the through hole 11 closer to the first surface 2a of the second substrate 2 than the stepped portion 15 can have a radius of curvature greater than the radius of curvature R3. Such a radius of curvature can inhibit the adhesive 4 from reaching the first surface 2a of the second substrate 2.

[0068] The liquid ejection channel 9 may have any opening shape. However, the adhesive 4 overflowing into the opening serving as the pressure chamber 7 may reach the liquid ejection channel 9 and affect the ejection port 10. For this reason, as shown in FIG. Figure 4C As shown, the curvature radius R4 of each corner of the liquid injection channel 9 preferably satisfies R2=R4, and more preferably satisfies R2 <R4。

[0069] Figure 6 It is based on Figures 4A to 4C The first embodiment of the present disclosure is shown in a cross-sectional view of substrates, or first substrate 1, second substrate 2, and third substrate 3, bonded together by adhesive 4. The first embodiment of the present disclosure controls adhesive overflow in bonded substrates having multiple bonding surfaces and allows the bonded substrates to have good ejection performance without being affected by the adhesive.

[0070] Second embodiment

[0071] A substrate for a liquid ejecting head according to a second embodiment of the present disclosure will be described below with reference to the accompanying drawings. In the embodiments described below, specific statements may be given to fully illustrate the present disclosure. These statements are provided as examples and are not intended to limit the scope of the present disclosure. The following description will focus on the differences between the second embodiment and the first embodiment.

[0072] Although the drawings of the second embodiment show that the liquid ejection head is oriented so that the ejection port is located at the top and the liquid supply port is located at the bottom, such an orientation is adopted when manufacturing the channel-defining member of the liquid ejection head. In most cases, the liquid ejection head is oriented so that the ejection port is located at the bottom when in use.

[0073] Figure 7 : is a cross-sectional view of a bonding substrate for a liquid ejection head according to a second embodiment of the present disclosure. Figure 7 The effect of the adhesive on the opening or the problem to be solved by the present disclosure is not shown. Figures 8A to 8C 4 is a cross-sectional view of substrates separated from each other in Embodiment 2. The respective substrates are bonded together with an adhesive 4 to form a liquid ejection head substrate.

[0074] The first substrate 1 is, for example, a silicon substrate. The first surface 1a has energy generating elements 16 and supply ports 18 corresponding to the energy generating elements 16. The second surface 1b of the first substrate 1 has openings, each of which serves as a channel 19. The supply ports 18 communicate with the channels 19 in the first substrate 1, so that liquid is guided from the channels 19 through the supply ports 18 to the common liquid chamber 17 having the energy generating elements 16 therein.

[0075] The second substrate 2 is, for example, a silicon substrate or a stainless steel substrate. The second substrate 2 is configured to cover the energy generating element 16. The second surface 2b of the second substrate 2 has a recess 8, which serves as a common liquid chamber 17 facing the energy generating element 16. The second substrate 2 is bonded to the first substrate 1 so that the recess 8 receives a plurality of energy generating elements 16 arranged in a one-to-one correspondence with the plurality of common liquid chambers 17. The top of each recess 8 has an injection port 10 for liquid injection. The injection port 10 and the recess 8 extend through the second substrate 2 and correspond to the energy generating element 16. Therefore, the volume change of the common liquid chamber 17 causes the liquid accumulated in the common liquid chamber 17 to be ejected from the injection port 10. The second substrate 2 is bonded to the first surface 1a of the first substrate 1 by an adhesive 4.

[0076] The third substrate 3 is bonded to the second surface 1 b of the first substrate 1 . The third substrate 3 is, for example, a silicon substrate and has an opening 20 for channel switching. The opening 20 extends through the third substrate 3 .

[0077] The opening 20 for channel switching enables the channel 19 to include a liquid supply channel and a liquid collection channel. A negative pressure control unit (not shown) generates a pressure difference between the liquid supply channel and the liquid collection channel. This pressure difference causes the liquid in the liquid supply channel to flow through the supply port 18 to the common liquid chamber 17 and further through the supply port 18 to the liquid collection channel.

[0078] This flow allows, for example, liquid whose viscosity has increased by evaporation through the ejection ports 10, bubbles, and foreign matter to be collected from the ejection ports 10 and the common liquid chamber 17 in a printing stop state into the liquid collection channel. This can suppress the increase in viscosity of the liquid in the ejection ports 10 and the common liquid chamber 17.

[0079] Furthermore, an ink cartridge (not shown) is provided upstream of the third substrate 3. An opening 20 for channel switching in the third substrate 3 communicates with the channel 19 and the supply port 18 in the first substrate 1 and also communicates with the common liquid chamber 17. In the second embodiment, the supply port 18 serves as a supply path for liquid ejected by the liquid ejection head.

[0080] The first surface 1a of the first substrate 1 has a surface film layer (not shown), which includes a wiring layer and an insulating interlayer connected to the energy generating element 16. Supply port 18 and channel 19 are formed by etching using an etching mask (for example, the etching mask is made using a photoresist). For example, it is assumed that the energy generating element 16 is an electrothermal conversion element. Under the effect of the driving voltage applied by a driver IC (not shown), the electrothermal conversion element instantly generates bubbles in the liquid. The pressure change in the common liquid chamber 17 caused by the growth of the bubble is used to spray droplets through the ejection port 10.

[0081] As in the first embodiment, Figures 8A to 8C The substrate processing shown is not particularly limited and is performed using a typical substrate manufacturing process. By changing the photoresist exposure mask, the radius of curvature of the corner of each opening in the second embodiment of the present disclosure can be changed to any value. Although at least the openings of the surfaces to be joined of these substrates need to be processed before joining the substrates together, substrate processing such as forming openings on surfaces other than the surfaces to be joined and substrate thinning can be performed before or after joining the substrates together.

[0082] The material used for the adhesive 4, the method for curing the adhesive 4, and the method for applying the adhesive 4 are the same as those of the first embodiment. The adhesive can be formed to a thicker thickness to eliminate gaps when bonding the substrates. Before bonding the substrates together, the thickness of the adhesive is 1.0 μm or more, preferably 2.0 μm or more, and more preferably 5.0 μm or more. Thicker adhesive can reduce or eliminate gaps, but increases the possibility that the adhesive will overflow into the opening at the bonding surface. This may cause problems to be solved by the present disclosure.

[0083] Figure 9 4 is a schematic cross-sectional view of a first substrate 1, a second substrate 2 and a third substrate 3 bonded together with an adhesive 4. Figure 9 The adhesive 4 is not controlled and prevented from overflowing, so that the adhesive 4 may overflow into the recessed portion of the second surface 2 b of the second substrate 2 and block the supply port 18. In addition, the adhesive 4 may overflow into the channel 19 of the second surface 1 b of the first substrate 1, extend along the corner of the channel 19, and similarly block the supply port 18.

[0084] The overflow of adhesive 4 blocking supply port 18 may block supply port 18, preventing liquid from being supplied to common liquid chamber 17. In the configuration described in the second embodiment, in which liquid in the liquid supply channel flows through supply port 18 to common liquid chamber 17 and further through supply port 18 to the liquid collection channel, supply port 18 may be narrowed by the overflow of adhesive. This may make it difficult to collect, for example, liquid whose viscosity has increased due to evaporation through ejection port 10, bubbles, and foreign matter into the liquid collection channel. As a result, the liquid in ejection port 10 and common liquid chamber 17 may increase in viscosity, thereby affecting ejection performance.

[0085] According to the second embodiment of the present disclosure, the relationship between the curvature radii of the corners of the openings at the bonding surfaces of substrates bonded together with an adhesive is defined to control overflow of the adhesive, thereby achieving good ejection performance.

[0086] Figures 10A to 10CPlanar view of the openings of the first substrate 1, the second substrate 2, and the third substrate 3 in the second embodiment of the present disclosure. Figure 10A The small curvature radius R1 at each corner of the opening serving as the recess 8 allows the adhesive 4 that overflows on the first surface 1a of the first substrate 1 to actively extend along the corners of the recess 8, thereby reducing the overflow amount. This can reduce or eliminate the influence of the adhesive 4 on the supply port 18.

[0087] In addition, Figure 10B The large curvature radius R2 at each corner of the channel 19 in can suppress the extension of the adhesive 4 that overflows on the first surface 3a of the third substrate 3 along the corners of the channel 19. This can reduce or eliminate the influence of the adhesive 4 on the supply port 18.

[0088] In other words, when the curvature radii R1 and R2 satisfy R1 < R2, the influence of the adhesive 4 on the supply port 18 can be reduced or eliminated. In addition, the adhesive 4 that overflows on the first surface 3a of the third substrate 3 may block the opening 20 for channel conversion, extend through the opening, and reach the second surface 3b of the third substrate 3. For this reason, the curvature radius R5 at each corner of the opening 20 for channel conversion in the third substrate 3 can satisfy R2 < R5 or R1 < R2 < R5.

[0089] As Figure 5 shown, Figure 10A The curvature radius R1 for promoting the extension of the adhesive along the corners and reducing the adhesive overflow width is preferably less than 12 μm, more preferably less than or equal to 8 μm. Figure 10B The curvature radius R2 for suppressing the extension of the adhesive along the corners is preferably greater than 20 μm, more preferably greater than or equal to 30 μm.

[0090] Figure 11 is a cross-sectional view of the substrates joined together by the adhesive 4 or the first substrate 1, the second substrate 2, and the third substrate 3 formed according to the second embodiment of the present disclosure as shown in Figures 10A to 10C The second embodiment of the present disclosure controls the overflow of the adhesive in the joined substrates having multiple joining surfaces and allows the joined substrates to have good ejection performance without being affected by the adhesive.

[0091] Third Embodiment

[0092] The substrate for a liquid ejection head according to the third embodiment of the present disclosure will be described below with reference to the drawings. In the embodiments described below, specific statements may be given in order to fully illustrate the present disclosure. These statements are given as examples and are not specifically used to limit the scope of the present disclosure. The following description will focus on the differences between the third embodiment and the first embodiment.

[0093] Figure 12is a cross-sectional view of a bonding substrate for a liquid ejection head according to a third embodiment of the present disclosure. Figure 12 The effect of the adhesive on the opening or the problem to be solved by the present disclosure is not shown. Figures 13A to 13C 4 is a cross-sectional view of substrates separated from each other in the third embodiment. The respective substrates are bonded together with an adhesive 4 to form a liquid ejection head substrate.

[0094] The first substrate 1 is, for example, a silicon substrate. The first surface 1a has a vibration membrane 6 and a recess 8 located on the vibration membrane 6. The piezoelectric element 5 is located at the bottom of the recess 8. The recess 8 can be formed by processing the substrate. Figure 13B As shown in FIG. 1 , the recess 8 can be formed at a desired position by, for example, performing exposure and development using a permanent resist 14 (such as SU-8).

[0095] The second substrate 2 is, for example, a silicon substrate and is provided so as to cover the piezoelectric element 5. The second surface 2b of the second substrate 2 is bonded to the first surface 1a of the first substrate 1 via an adhesive 4.

[0096] The first surface 3a of the third substrate 3 has openings serving as pressure chambers 7. The respective substrates are bonded together so that the recesses 8 receive the plurality of piezoelectric elements 5 arranged in a one-to-one correspondence with the plurality of pressure chambers 7.

[0097] The third substrate 3 is, for example, a silicon substrate and has at least an opening serving as a pressure chamber 7 and an ejection port 10 for liquid ejection. Although the liquid ejection channel shown in the first embodiment is not shown in the third embodiment, the liquid ejection channel may be located between the pressure chamber 7 and the ejection port 10 as in the first embodiment.

[0098] The first surface 3a of the third substrate 3 is bonded to the second surface 1b of the first substrate 1. The vibration membrane 6 serves as a top wall of each pressure chamber 7 and defines a plurality of pressure chambers 7.

[0099] Figure 14 4 is a schematic cross-sectional view of a first substrate 1, a second substrate 2 and a third substrate 3 bonded together with an adhesive 4. Figure 14 The adhesive 4 is located in the portion 12 affected by the adhesive. If the adhesive 4 is not controlled and maintained to prevent overflow, the adhesive 4 may overflow into the recessed portion 8 of the first surface 1a of the first substrate 1, extend along the corner of the recessed portion 8, and overlap with the vibrating membrane 6. In addition, the adhesive 4 may overflow into the pressure chamber 7 of the first surface 3a of the third substrate 3 and overlap with the vibrating membrane 6. The overlap between the overflowing portion of the adhesive and the vibrating membrane 6 may affect the vibration characteristics of the vibrating membrane 6, thereby affecting the ejection performance.

[0100] According to the third embodiment of the present disclosure, the curvature radius of the corners of the openings at the bonding surfaces of the respective substrates is changed to control overflow of the adhesive, thereby achieving good ejection performance.

[0101] Figures 15A to 15C A plan view including openings of the first substrate 1 , the second substrate 2 , and the third substrate 3 in the third embodiment of the present disclosure. Figure 15B The large curvature radius R1 of each corner serving as the opening of the recess 8 can suppress the adhesive 4 overflowing on the first surface 1 a of the first substrate 1 from extending along the corner of the recess 8 , thereby reducing or eliminating the influence of the adhesive 4 on the vibration membrane 6 .

[0102] also, Figure 15C The small curvature radius R2 at each corner of the pressure chamber 7 allows the adhesive 4 overflowing from the first surface 3a of the third substrate 3 to extend along the corner of the pressure chamber 7, thereby reducing or eliminating the effect of the adhesive 4 on the diaphragm 6. In other words, the effect of the adhesive 4 on the diaphragm 6 can be reduced or eliminated when the curvature radii R1 and R2 satisfy R1>R2.

[0103] like Figure 5 As shown, the curvature radius R1 for inhibiting the adhesive from extending along the corner is preferably greater than 20 μm, more preferably greater than or equal to 30 μm. The curvature radius R2 for promoting the adhesive from extending along the corner is preferably less than 12 μm, more preferably less than or equal to 8 μm.

[0104] For Figure 15A Regarding the curvature radius R3 of each corner of the opening serving as through-hole 11, excessive extension of the adhesive along the corners may cause the adhesive to reach and contaminate first surface 2a of second substrate 2. In contrast, excessively suppressing the adhesive's extension along the corners may cause the adhesive to reduce the cross-sectional area of ​​through-hole 11 or even clog it, thereby affecting liquid flow. Therefore, the curvature radius R3 can satisfy the following conditions: R1 > R3 > R2, and 12 μm ≤ R3 ≤ 20 μm.

[0105] Figure 16 It is based on Figures 15A to 15C The third embodiment of the present disclosure is shown in a cross-sectional view of substrates, or first substrate 1, second substrate 2, and third substrate 3, bonded together by adhesive 4. The third embodiment of the present disclosure controls adhesive overflow in bonded substrates having multiple bonding surfaces and allows the bonded substrates to have good ejection performance without being affected by the adhesive.

[0106] Fourth embodiment

[0107] A substrate for a liquid ejecting head according to a fourth embodiment of the present disclosure will be described below with reference to the accompanying drawings. In the embodiments described below, specific descriptions may be given to fully illustrate the present disclosure. These descriptions are provided as examples and are not intended to limit the scope of the present disclosure. The following description will focus on the differences between the fourth embodiment and the second embodiment.

[0108] Although the drawings of the fourth embodiment show that the liquid ejection head is oriented so that the ejection port is located at the top and the liquid supply port is located at the bottom, such an orientation is adopted when manufacturing the channel-defining member of the liquid ejection head. In most cases, the liquid ejection head is oriented so that the ejection port is located at the bottom when in use.

[0109] Figure 17 : is a cross-sectional view of a bonding substrate for a liquid ejection head according to a fourth embodiment of the present disclosure. Figure 17 The effect of the adhesive on the opening or the problem to be solved by the present disclosure is not shown. Figures 18A to 18C 4 is a cross-sectional view of substrates separated from each other in the fourth embodiment. The respective substrates are bonded together with an adhesive 4 to form a liquid ejection head substrate.

[0110] The first substrate 1 is, for example, a silicon substrate. The first surface 1a has energy generating elements 16 and supply ports 18 corresponding to the energy generating elements 16. The first surface 1a of the first substrate 1 has a recess 8. Each energy generating element 16 is located at the bottom of the recess 8. The recess 8 can be formed by processing the substrate. Figure 18B As shown in FIG. 1 , the recess 8 can be formed at a desired position by, for example, performing exposure and development using a permanent resist 14 (such as SU-8).

[0111] The second substrate 2 is, for example, a silicon substrate or a stainless steel substrate, and has a plurality of ejection ports 10 for liquid ejection. The second surface 2b of the second substrate 2 is bonded to the first surface 1a of the first substrate 1 so that the ejection ports 10 are aligned with the corresponding energy generating elements 16. The recess 8 at the first surface 1a of the first substrate 1 is used as a common liquid chamber 17. For example, it is assumed that the energy generating element 16 is an electrothermal conversion element. Under the action of a driving voltage applied by a driver IC (not shown), the electrothermal conversion element instantaneously generates bubbles in the liquid. The pressure change in the common liquid chamber 17 caused by the growth of the bubbles is used to eject droplets through the ejection ports 10.

[0112] The third substrate 3 is, for example, a silicon substrate. The third substrate 3 has a channel 19 integral with the channel switching member. As in the second embodiment, the channel 19 includes a liquid supply channel and a liquid collection channel. A pressure differential generated by a negative pressure control unit (not shown) causes liquid in the liquid supply channel to flow through a supply port 18 to the common liquid chamber 17 and further through the supply port 18 to the liquid collection channel. The second surface 3b of the third substrate 3 has an opening 20 for channel switching. The opening 20 and the channel 19 extend through the third substrate 3.

[0113] The supply port 18 in the first substrate 1 communicates with the channel 19 in the third substrate 3 so that liquid is guided from the channel 19 through the supply port 18 to the common liquid chamber 17 having the energy generating element 16 therein.

[0114] Figure 19 4 is a schematic cross-sectional view of a first substrate 1, a second substrate 2 and a third substrate 3 bonded together with an adhesive 4. Figure 19 If the adhesive 4 is not controlled and prevented from overflowing, the adhesive 4 may overflow into the recess 8 of the first surface 1a of the first substrate 1, extend along the corner of the recess 8, and block the supply port 18.

[0115] Furthermore, the adhesive 4 may overflow into the channel 19 at the second surface 1 b of the first substrate 1 , extend along the corner of the channel 19 , and similarly block the supply port 18 .

[0116] The overflow of adhesive 4 blocking supply port 18 may block supply port 18, preventing liquid from being supplied to common liquid chamber 17. In the configuration described in the fourth embodiment, in which liquid in the liquid supply channel flows through supply port 18 to common liquid chamber 17 and further through supply port 18 to the liquid collection channel, supply port 18 may be narrowed by the overflow of adhesive. This may make it difficult to collect, for example, liquid whose viscosity has increased due to evaporation through ejection port 10, bubbles, and foreign matter into the liquid collection channel. As a result, the liquid in ejection port 10 and common liquid chamber 17 may increase in viscosity, thereby affecting ejection performance.

[0117] According to the fourth embodiment of the present disclosure, the relationship between the curvature radii of the corners of the openings at the bonding surfaces of substrates bonded together with an adhesive is defined to control overflow of the adhesive, thereby achieving good ejection performance.

[0118] Figures 20A to 20C A plan view including openings of the first substrate 1, the second substrate 2, and the third substrate 3 in the fourth embodiment of the present disclosure. Figure 20BThe large curvature radius R1 of each corner serving as the opening of the recess 8 can inhibit the adhesive 4 overflowing on the second surface 2 b of the second substrate 2 from extending along the corner of the recess 8 , thereby reducing or eliminating the influence of the adhesive 4 on the supply port 18 .

[0119] also, Figure 20C The small curvature radius R2 at each corner of the channel 19 allows the adhesive 4 overflowing from the first surface 3a of the third substrate 3 to extend along the corner of the channel 19, thereby reducing or eliminating the effect of the adhesive 4 on the supply port 18. In other words, the effect of the adhesive 4 on the supply port 18 can be reduced or eliminated when the curvature radii R1 and R2 satisfy R1>R2.

[0120] like Figure 5 As shown, the curvature radius R1 for inhibiting the adhesive from extending along the corner is preferably greater than 20 μm, more preferably greater than or equal to 30 μm. The curvature radius R2 for promoting the adhesive from extending along the corner is preferably less than 12 μm, more preferably less than or equal to 8 μm.

[0121] Figure 21 It is based on Figures 20A to 20C The fourth embodiment of the present disclosure is shown in a cross-sectional view of substrates, or a first substrate 1, a second substrate 2, and a third substrate 3, bonded together by an adhesive 4. The fourth embodiment of the present disclosure controls adhesive overflow in a bonded substrate having multiple bonding surfaces and allows the bonded substrate to have good ejection performance without being affected by the adhesive.

[0122] An embodiment of the present disclosure can provide a liquid ejection head capable of controlling the flow of an adhesive overflowing with respect to a structure located at a bonding surface of a substrate.

[0123] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A liquid ejecting head comprising: a first substrate having a first surface and a second surface opposite to the first surface, the first surface having a structure; a second substrate having a second surface facing the first surface of the first substrate; as well as a third substrate having a first surface facing the second surface of the first substrate, The first substrate and the second substrate are bonded together by an adhesive located 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 together by an adhesive located between the second surface of the first substrate and the first surface of the third substrate. The second surface of the first substrate has an opening, the opening being located in the region of the rear side of the structure and having corners each having a curvature radius of R2, wherein the curvature radius R2 is used to suppress the adhesive from extending along the corners having the curvature radius R2. The second surface of the second substrate has an opening, the opening being located in a region facing the structure and having corners each having a curvature radius R1, wherein the curvature radius R1 is used to promote the adhesive to extend along the corners having the curvature radius R1. The curvature radii R1 and R2 satisfy R1 <R2。 2. The liquid ejecting head according to claim 1, wherein The opening at the second surface of the first substrate and the third substrate define a space serving as a pressure chamber.

3. The liquid ejecting head according to claim 1, wherein The second substrate further has an opening extending through the second substrate, and the opening extending through the second substrate has corners with a curvature radius of R3, and The curvature radii R1, R2 and R3 satisfy R1 <R3<R2。 4. The liquid ejecting head according to claim 1, wherein The second substrate further has a through hole extending through the second substrate and including a stepped portion, The through hole including the step portion has an opening located at the second surface of the second substrate, the opening having corners each having a curvature radius of R3, and The curvature radii R1, R2 and R3 satisfy R3≤R1 <R2。 5. The liquid ejecting head according to claim 1, wherein The third substrate further has an ejection port for ejecting liquid and a liquid ejection channel for supplying liquid to the ejection port. The liquid ejection channel has corners with a curvature radius of R4, and The curvature radii R2 and R4 satisfy R4 ≥ R2. The liquid ejecting head according to claim 1 , wherein The second substrate has an injection port, The opening of the second substrate and the first substrate define a space serving as a common liquid chamber, The opening of the first substrate and the third substrate define a space serving as a channel, and The structure is an energy generating element configured to generate energy for ejecting liquid through the ejection port.

7. The liquid ejecting head according to claim 6, wherein The third substrate also has an opening connected to the channel, The opening of the third substrate has corners with a curvature radius of R5, and The curvature radii R1, R2 and R5 satisfy R1 <R2<R5。 8. The liquid ejecting head according to claim 1, wherein R1<12 μm and R2>20 μm.

9. The liquid ejecting head according to claim 6, wherein The energy generating element is an electrothermal conversion element.

10. The liquid ejecting head according to claim 1, wherein The structure is a piezoelectric element configured to generate pressure for liquid ejection.

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