Substrate bonded body, manufacturing method and liquid ejection head

Abstract

To facilitate a size reduction and to improve reliability, in a substrate bonded body having a first substrate with an opening and a second substrate bonded to the first substrate by means of an adhesive.SOLUTION: A substrate bonded body includes a first channel substrate 5 having openings (common channels 13a, 13b) and a second channel substrate 6 bonded to a first surface via an adhesive 12, the opening of the first substrate being covered with the second substrate; wherein a groove-like recessed part 14 extending from a position exposed to the opening toward a position opposite to an opening edge of the opening in the first substrate is formed so that the adhesive 12 extruding from the bonding part reaches a surface facing the opening of the first channel substrate 5 in the second channel substrate 6, and wherein the adhesive 12 extruding from the bonded part during boding is absorbed in the recessed part 14.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an assembled substrate body formed by joining a plurality of substrates, a manufacturing method thereof, and a liquid ejection head using the assembled substrate body. [Background technology]

[0002] As an example of a structure obtained by microfabrication of a silicon substrate, there is a liquid ejection head that has an ejection port and ejects liquid toward a recording medium. A liquid ejection head is a type of substrate assembly, since it is manufactured by bonding a plurality of substrates with grooves, through-holes, and other recessed portions opened therein with an adhesive. In a liquid ejection head, the grooves and through-holes are used as flow paths for liquid, such as ink, to be ejected from the ejection ports. Therefore, when bonding substrates, it is necessary to prevent the recesses and through-holes from being blocked by the adhesive pushed out by pressing the bonding portion for bonding. Patent Document 1 discloses that a groove-shaped adhesive entry area that opens at the position where the two substrates are in contact with each other (i.e., the bonding portion) is provided in one substrate, and the adhesive entry area receives the pushed-out adhesive, thereby preventing the adhesive from blocking the recesses and through-holes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-162802 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a substrate assembly in which a groove, through hole, or other dug portion is opened on the surface of one of the substrates, the adhesive pushed out during joining tends to creep up the ridged portion on the side of the dug portion. The technology shown in Patent Document 1 cannot effectively prevent the adhesive from creeping up. Furthermore, the technology in Patent Document 1 requires the provision of an adhesive inlet area, which hinders miniaturization of the substrate assembly, and also reduces reliability due to the adhesive inlet area being blocked by the adhesive.

[0005] An object of the present invention is to provide a substrate assembly that is easy to miniaturize and has high reliability, and a liquid ejection head that utilizes such a substrate assembly. [Means for solving the problem]

[0006] The substrate bonded body of the present invention comprises a first substrate having a first surface and a second surface opposite to the first surface and having an opening formed on the second surface, and a second substrate bonded to the second surface via an adhesive, the opening being covered by the second substrate, and is characterized in that a recess is formed on a third surface, which is the surface of the second substrate facing the opening, extending from a position exposed to the opening toward a position facing the edge of the opening on the second surface so that adhesive that overflows from the bonded portion between the first substrate and the second substrate can reach it. Effect of the Invention

[0007] According to the present invention, it is possible to obtain a substrate assembly that is easily miniaturized and has high reliability, a method for manufacturing the same, and a liquid ejection head that uses such a substrate assembly. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a perspective view showing a recording element substrate which is an example of a substrate assembly. [Diagram 2] FIG. 2 is a diagram illustrating a recording element substrate according to the first embodiment. [Diagram 3] FIG. 4 is a diagram showing a cross-sectional shape of a recess. [Figure 4] FIG. 11 is a transparent top view showing another example of the arrangement of recesses. [Diagram 5] FIG. 2 is a cutaway perspective view showing a recording element substrate according to the first embodiment. [Figure 6] FIG. 13 is a diagram showing another example of a recording element substrate. [Figure 7] FIG. 13 is a diagram showing another example of a recording element substrate. [Figure 8] FIG. 13 is a diagram illustrating a recording element substrate according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Next, an embodiment of the present invention will be described. The embodiment shown below is intended to facilitate understanding of the present invention, but the present invention is not limited to the following embodiment. Furthermore, not all of the combinations of features described in the following embodiments are necessarily essential to solving the problems that the present invention is intended to solve. In each embodiment, the relative arrangement and shapes of the components are merely examples, and the scope of the present invention is not limited to these relative arrangements and shapes. In the following description, the same components are given the same reference numerals.

[0010] The present invention relates to a substrate assembly having a first substrate having an opening and a second substrate bonded to the first substrate via an adhesive, the opening on the first substrate side being covered by the second substrate. The opening formed in the first substrate is an opening due to a recessed portion formed by performing an etching process or the like on the surface of the first substrate, and the recessed portion may or may not penetrate the first substrate. Such a substrate assembly is obtained by, for example, performing microfabrication on silicon (Si) substrates or the like to obtain substrates, and then bonding these substrates via an adhesive, and is used in microdevices in the fields of MEMS (microelectromechanical systems) and electromechanical machines. In the following description, the substrate assembly according to the present invention will be described assuming that the substrate assembly is used in a liquid discharge head that discharges liquid such as ink from a discharge port. Therefore, before describing the substrate assembly according to the present invention, the liquid discharge head will be described.

[0011] A liquid ejection head is mounted on a liquid ejection device and ejects liquid such as ink onto a recording medium for recording, for example. The liquid ejection head is mainly composed of a recording element substrate and an electric wiring substrate, and may be provided with a tank for storing liquid to be ejected. The recording element substrate is provided with recording elements that generate energy for ejecting liquid, and electric signal input terminals that send electric signals to the recording elements. The recording element substrate and the electric wiring substrate can be electrically connected via the electric signal input terminals, and recording by the liquid ejection device is possible by electrically contacting the terminals on the electric wiring substrate with contact pins on the carriage of the liquid ejection device. In addition to the recording elements, the recording element substrate is provided with an ejection port forming member in which ejection ports and individual flow paths that pass over the recording elements and communicate with the ejection ports are formed, and a flow path substrate in which common flow paths and supply paths that supply liquid to be ejected to the individual flow paths are formed. The flow path substrate is formed by bonding a substrate in which a common flow path is formed and a substrate in which a through flow path that supplies liquid to the common flow path is formed with an adhesive. Liquid ejection heads are required to be smaller, and to be capable of high-resolution and high-speed recording, and therefore to have ejection ports arranged at higher density. As liquid ejection heads become smaller and ejection port densities increase, it becomes necessary to form flow paths with higher resolution, and therefore it becomes necessary to reliably prevent blockages caused by adhesive in supply paths connecting common and individual flow paths. Therefore, it is required to minimize the amount of adhesive that creeps up when constructing a flow path substrate.

[0012] [First embodiment] 1 shows a recording element substrate used in a liquid ejection head in a first embodiment of the present invention. The recording element substrate 1 includes an ejection port forming member 2 in which a plurality of ejection ports 3 are formed in a row, a first flow path substrate 5 having a first surface 21 and a second surface 22 opposite to the first surface 21, and a second flow path substrate 6. The ejection port forming member 2 is formed on the first surface 21 of the first flow path substrate 5. A group of electrical signal input terminals 4 for electrically connecting to an electrical wiring substrate (not shown) is also formed on the first surface 21 of the first flow path substrate 5. The second flow path substrate 6 is bonded to the second surface 22 of the first flow path substrate 5 via an adhesive 12 (see FIG. 2).

[0013] FIG. 2(a) is a cross-sectional view of the recording element substrate 1 taken along line AA in FIG. 1, and FIG. 2(b) is a transparent top view of the main part of the second flow path substrate 6 viewed from the side of the first flow path substrate 5 without the ejection port forming member 2. The first surface 21 of the first flow path substrate 5 is provided with recording elements 9 that generate energy required for ejecting liquid, and further provided with wiring (not shown) for electrical signals for driving the recording elements 9. The recording elements 9 include electrothermal converters that foam the liquid with heat, and piezoelectric elements that deform by the piezoelectric effect to give kinetic energy to the liquid. The ejection port forming member 2 has a two-layer structure including an ejection port forming region 7 in which the ejection ports 3 are provided as through-holes, and a flow path forming region 8 between the ejection port forming region 7 and the first flow path substrate 5 in which individual flow paths are formed. At the position where the recording elements 9 are formed, pressure chambers 20 communicating with the ejection ports 3 are formed as part of the individual flow paths in the flow path forming region 8, and the recording elements 9 are configured to be able to impart energy for ejection to the liquid in the pressure chambers 20. A liquid repellent layer (not shown) may be formed on the surface of the ejection port forming area 7 in order to improve the ejection performance.

[0014] A pair of common flow paths 13a, 13b that supply liquid to the multiple ejection ports 3 are provided as groove-shaped recesses on the second surface 22 of the first flow path substrate 5 and open to the second surface 22. In this embodiment, the multiple ejection ports 3 form an ejection port row in the ejection port forming member 2, and the common flow paths 13a, 13b are provided on both sides of the ejection port row, respectively, and extend in the same direction as the ejection port row. At the innermost part in the depth direction of each of the common flow paths 13a, 13b, i.e., at the bottom as the recessed part, liquid flow paths 10a, 10b that penetrate the first surface of the first flow path substrate 5 and communicate with the pressure chamber 20 described above are formed. The liquid flow paths 10a, 10b function as a supply path for supplying liquid to the pressure chamber 20, and enable the liquid to flow between the common flow paths 13a, 13b and the pressure chamber 20.

[0015] The shape of the opening edge 15 of the common flow channels 13a, 13b on the second surface of the first flow channel substrate 5 is typically a long and narrow rectangle having four corners 24, each of which is at a right angle. Furthermore, on the side surface 25 of the common flow channels 13a, 13b formed as a groove-shaped dug-in portion, a ridge 26 (see FIG. 5) is formed that connects to the corners 24 at the opening edge 15. The ridge 26 here refers to a place where two planes intersect when viewed locally on the side surface 25 of the dug-in portion, or a linear region on the side surface 25 of the dug-in portion that has a smaller radius of curvature than the surrounding area.

[0016] A second flow path substrate 6 is bonded to the second surface 22 of the first flow path substrate 5 via an adhesive 12. The second flow path substrate 6 is provided with through-holes 11 communicating with the common flow paths 13a and 13b. Only the through-path 11 communicating with one common flow path 13a is shown in the figure, because the figure shows only a part of the recording element substrate. A through-path 11 communicating with the other common flow path 13b is provided at another position in the direction in which the ejection port row extends. As a result, one through-path 11 communicates with the other second through-path (not shown) via the common flow path 13a, the liquid flow path 10a, the pressure chamber 20, the liquid flow path 10b, and the common flow path 13b. In such a liquid ejection head, there are two types of ejection of liquid from the ejection port 3. In the first form, liquid is supplied from both through-flow paths 11 to the pressure chamber 20 via the common flow paths 13a, 13b and the liquid flow paths 10a, 10b, and by driving the recording element 9, ejection energy is imparted to the liquid in the pressure chamber 20 and the liquid is ejected from the ejection port 3. In the second form, liquid is supplied from one through-flow path 11a to the pressure chamber 20 via the common flow path 13a and liquid flow path 10a, and liquid not ejected from the ejection port 3 is collected from the other through-flow path (not shown) via the liquid flow path 10b and the common flow path 13b.

[0017] In the recording element substrate 1 shown in Fig. 2(a), the first flow path substrate 5 and the second flow path substrate 6 correspond to the first substrate and the second substrate of the substrate assembly according to the present invention, respectively. The common flow paths 13a, 13b, which are recessed portions, form openings in the second surface 22 of the first flow path substrate 5. By joining the first flow path substrate 5 and the second flow path substrate 6, the common flow paths 13a, 13b forming the openings are covered by the second flow path substrate 6. Of the surfaces of the second flow path substrate 6, the surface 23 facing the common flow paths 13a, 13 corresponds to the third surface.

[0018] Silicon is preferably used as the substrate material constituting the first flow path substrate 5 and the second flow path substrate. In addition to silicon, inorganic silicon compounds such as silicon carbide and silicon nitride, various glasses such as quartz glass and borosilicate glass, semiconductors such as gallium arsenide, ceramics such as alumina, and resins can also be used as substrate materials constituting each of the flow path substrates 5 and 6. Each of the flow path substrates 5 and 6 can be formed by microfabrication of these substrate materials. Methods for forming the common flow paths 13a and 13b and the through flow paths 11 in the substrate include dry etching, wet etching, and laser processing. In addition, in order to adjust the depth of the common flow paths 13a and 13b, that is, the height in the cross-sectional direction, the thickness of the first flow path substrate 5 may be reduced by polishing using back grinding or CMP (chemical mechanical polishing). The discharge port forming member 2 may be provided on the first surface 21 of the first flow path substrate 6 before bonding the first flow path substrate 5 and the second flow path substrate 6. Alternatively, the ejection port forming member 2 may be provided on the first surface 21 after the first flow path substrate 5 and the second flow path substrate 6 are joined together.

[0019] Next, the bonding of the first flow path substrate 5 and the second flow path substrate 6 with an adhesive will be described in detail. Since the second surface 22 of the first flow path substrate 5 has groove-shaped recesses that form the common flow paths 13a and 13b, the adhesive is applied to the entire surface of the second surface 22 of the first flow path substrate 5 except for the positions of the openings of the recesses. Instead of application, an adhesive layer may be transferred. Then, the first flow path substrate 5 and the second flow path substrate 6 to which the adhesive has been applied or transferred are brought into contact with each other and pressed, and the adhesive is cured in this state, thereby bonding the first flow path substrate 5 and the second flow path substrate 6. When the adhesive 12 is pressed before curing, there is a possibility that the adhesive 12 is pushed out from the bonding portion and protrudes into the common flow paths 13a and 13b. As shown in FIG. 5 described later, the adhesive 12 is likely to creep up the wall-shaped side surface 25 of the common flow paths 13a and 13b, especially the ridge 26 formed on the side surface 25 connected to the above-mentioned corner portion 24 (or corner portions 24a and 24b). As a result, if the amount of the adhesive 12 that overflows is large, the overflowed adhesive 12 may clog the liquid flow paths 10a and 10b. In this embodiment, in order to reduce the amount of the adhesive 12 that overflows, a groove-shaped recess 14 that receives the overflowed uncured adhesive 12 is provided on the surface 23 of the second flow path substrate 6 facing the common flow paths 13a and 13b on the first flow path substrate 5 side. The adhesive 12 overflows from the opening edge 15 of the opening by the common flow paths 13a and 13b on the second surface of the first flow path substrate 5. Therefore, the recess 14 is provided so as to extend from a position exposed to the common flow paths 13a and 13b on the surface 23 of the second flow path substrate 6 toward a position corresponding to the opening edge 15 of the common flow paths 13a and 13b. The adhesive 12 that has flowed into the recess 14 is cured in the recess 14 in a subsequent curing process.

[0020] As described above, the adhesive 12 is likely to creep up at the ridges 26 on the side surfaces of the common flow paths 13a and 13b. Therefore, the recesses 14 can be provided so as to extend from the positions exposed to the common flow paths 13a and 13b toward the positions corresponding to the corners 24 at the opening edges 15 of the common flow paths 13a and 13b. In the example shown in FIG. 2(b), the position of one end of the groove-shaped recess 14 corresponds to the corners 24 of the opening edges 15. The recesses 14 can be provided only at the corners 24 at the opening edges 15 of the common flow paths 13a and 13b where the creeping up of the adhesive 12 has a large effect on the liquid flow paths 10a and 10b. Since the opening edges 15 of the common flow paths 13a and 13c are rectangular, a pair of long sides of the rectangle are sides 15a and 15c, and one of the short sides is side 15b. The sides 15a to 15c constitute the opening edge 15. Here, side 15c is the side at the base of the wall separating common flow paths 13a, 13b. If sides 15a to 15c of opening edge 15 are defined in this manner, in the illustrated example, liquid flow path 10a is formed at a position close to side 15b and closer to side 15c than side 15a. In such a case, recess 14 is provided corresponding to corner 24 where side 15b and side 15c intersect, but recess 14 can be omitted at corner 24 where side 15a and side 15b intersect, which is far from liquid flow path 10a and is considered to be less affected by creeping up of adhesive 12.

[0021] In this embodiment, the recess 14 is provided to absorb the overflowing adhesive 12, and in order to absorb a larger amount of adhesive 12, it is preferable that the adhesive 12 flows over the entire length of the groove-shaped recess 14. Capillary force contributes greatly to the flow of the adhesive 12 into the recess 14. From this viewpoint, it is preferable that the width of the groove-shaped recess 14 is smaller than the depth of the recess 14. By reducing the width, a larger capillary force can be generated, and by increasing the depth, the amount of adhesive that can be accommodated in the recess 14 can be increased. By making the recess 14 in this manner, it is possible to promote the active flow of the adhesive 12 into the recess 14 and to suppress the concentration of the adhesive 12 at the corner portion 24 of the opening edge 15. The length of the recess 14 can be appropriately determined, but from the viewpoint of increasing the amount of adhesive 12 that can be accommodated and preventing the adhesive 12 from creeping up, it is preferable that the length is longer than the depth of the common flow paths 13a and 13b in the first flow path substrate 5. It is preferable that the groove-shaped recess 14 has only one end in the longitudinal direction extending to a position facing the opening edge 15 of the common flow paths 13a and 13b. The other end of the recess 14 is preferably outside the range that the adhesive 12 protruding from the opening edge 15 reaches on the surface 23 of the second flow path substrate 6. In other words, the groove-shaped recess 14 is preferably configured so that the adhesive 12 flows in from only one side. If the adhesive 12 flows into the recess 14 from both ends in the longitudinal direction, the amount of adhesive 12 received from the corners 24, where it is particularly desired to prevent the adhesive 12 from creeping up, decreases.

[0022] FIG. 3 is a diagram for explaining the cross-sectional shape of the groove-shaped recess 14, and shows a cross section taken along line LL in FIG. 2(a). The cross-sectional shape of the recess 14 can be appropriately selected according to the application of the substrate assembly, which is, for example, a liquid discharge head. FIG. 3(a) shows a recess 14 having a square or rectangular cross-sectional shape. This cross-sectional shape can increase the amount of adhesive 12 contained per length of the recess 14, so this recess 14 is preferably used when the amount of adhesive 12 that protrudes or creeps up is large. The recess 14 shown in FIG. 3(b) has an inverted triangular cross-sectional shape that narrows as it becomes deeper, and here, the dihedral angle between both side surfaces of the recess 14 is less than 90° (i.e., an acute angle), so that a strong capillary force can be generated. The recess 14 shown in FIG. 3(b) is preferably used when the strongest capillary force is required. The recess 14 shown in FIG. 3(c) has a semi-elliptical cross-sectional shape, so that the strength reduction of the second flow path substrate 6 due to the formation of the recess 14 is small, and has a relatively large cross-sectional area. The recess 14 shown in Fig. 3(c) is preferably used when it is required to suppress the amount of adhesive 12 protruding or creeping up, and also when the strength of the substrate is required. The recess 14 shown in Fig. 3(d) has an isosceles trapezoidal cross-sectional shape with the upper base facing the surface 23 of the second flow path substrate 6 and the lower base longer than the upper base, and has a relatively large cross-sectional area and a strong capillary force due to the acute angle provided in the cross-section. The recess 14 shown in Fig. 3(d) is preferably used when it is required to increase the amount of adhesive 12 that can be accommodated in the recess 14.

[0023] The groove-shaped recess 14 in the second flow path substrate 6 may be formed by dry etching, wet etching, laser processing, or the like. As shown in FIG. 4(a), the recess 14 may extend beyond the position facing the corner 24 at the opening edge 15 to the position where the second surface 22 of the first flow path substrate 5 and the surface of the second flow path substrate 6 are actually bonded by the adhesive 12. This configuration allows more excess adhesive 12 to be absorbed, and is therefore suitable when the length of the recess formed in the groove shape is restricted. However, the length extending beyond the corner 24 is preferably 1 / 2 or less of the thickness X of the wall separating the common flow paths 13a and 13b. Alternatively, as shown in FIG. 4(b), the recess 14 may extend to a position where the adhesive 12 protruding from the bonding portion can reach, even if it is close to the corner 24 at the opening edge 15 but does not reach the position of the corner 24. Such a situation may occur when there is a deviation in alignment when bonding the first flow path substrate 5 and the second flow path substrate 6. When the recess 14 does not reach a position facing the corner 24 at the opening edge 15, the distance between the end of the recess 14 and the corner 24 is within the amount of overflow of the adhesive 12. Specifically, it is preferable that the distance D from the corner 24 where the sides 15b and 15c intersect to the end of the recess 14 is within 1 / 2 of the amount of overflow of the adhesive Y, and that the recess 14 is arranged so as not to reach the side 15a. By arranging the recess 14 in this manner, the overflowing adhesive 12 is prevented from concentrating on the corner 24 of the opening edge 15, and thus the adhesive 12 can be prevented from creeping up along the ridges 26 of the side surfaces 25 of the common flow paths 13a and 13b.

[0024] The adhesive 12 used for bonding the first flow path substrate 5 and the second flow path substrate 6 is preferably made of a material that has high adhesion to these flow path substrates 5 and 6. In addition, the material of the adhesive 12 is preferably a material that is less likely to be mixed with air bubbles and has high applicability, and is preferably a low-viscosity material that makes it easy to make the thickness of the adhesive 12 thin. Specifically, the material used for the adhesive 12 preferably contains any resin selected from the group consisting of epoxy resin, acrylic resin, silicon resin, benzocyclobutene resin, polyamide resin, polyimide resin, and urethane resin. The adhesive 12 can be cured using a heat curing method or an ultraviolet delayed curing method. When at least one of the flow path substrates 5 and 6 has ultraviolet transparency, the adhesive 12 can also be cured using an ultraviolet curing method. The first flow path substrate 5 and the second flow path substrate 6 are bonded by applying the adhesive 12, heating the flow path substrates 5 and 6 to a predetermined temperature in a bonding device, and then applying pressure for a predetermined time and pressure. These bonding parameters are appropriately set according to the material used for the adhesive 12. In order to prevent air bubbles from entering the bonded portion, it is preferable to perform the bonding in a vacuum. After bonding, it is preferable to further heat the bonded portion to sufficiently promote curing.

[0025] FIG. 5 is a cutaway perspective view showing the recording element substrate 1 of this embodiment configured as a substrate bonded body as described above. When the first flow path substrate 5 and the second flow path substrate 6 are bonded by the adhesive 12, the adhesive 12 is pushed out from the bonded portion and overflows into the common flow paths 13a and 13b. In the case of this embodiment, most of the overflowing adhesive 12 before hardening flows into the groove-shaped recess 14 and is accommodated in the recess 14. As a result, the amount of the adhesive 12 creeping up along the edge 26 connected to the corner 24a where the recess 14 is provided among the corners 24a and 24b of the opening edge 15 of the common flow paths 13a and 13b is smaller than that of the corner 24b where the recess 14 is not provided. This reduces the risk that the liquid flow paths 10a and 10b are blocked by the adhesive 12 that has creeped up.

[0026] In the technique of providing an adhesive inlet region disclosed in Patent Document 1, when two substrates are bonded with an adhesive, a groove-shaped adhesive inlet region is provided so as to open to the bonded portion. In terms of the above-mentioned embodiment, the adhesive inlet region is formed inside the wall separating the pair of common flow paths 13a and 13b, which is a dug portion, and the thickness of the wall cannot be made thin, which hinders miniaturization of the liquid ejection head. In contrast, in this embodiment, a recess 14 for absorbing adhesive is provided at a position facing the common flow paths 13a and 13b on the surface 23 of the second flow path substrate 6, so that the wall separating the pair of common flow paths 13a and 13b can be made sufficiently thin. In addition, in the technique described in Patent Document 1, the adhesive that overflows from the bonded portion does not necessarily flow into the adhesive inlet region, and some of the adhesive overflows into the dug portion of the substrate, which may cause blockage of the flow path. In contrast, in this embodiment, the adhesive 12 that protrudes onto the dug-in portion (common flow paths 13a, 13b) side can be more reliably captured in the recess 14, preventing the adhesive 12 from creeping up. Furthermore, in the technology described in Patent Document 1, when the adhesive flows into the adhesive entry area, a gap may remain in the back of the adhesive entry area, and the expansion and contraction of the air in the gap may cause deformation of the substrate, but in this embodiment, such deformation of the substrate is less likely to occur.

[0027] When the thickness X of the wall separating the pair of common flow paths 13a, 13b is small, or when the opening edge 15 is not rectangular, the amount of adhesive 12 that protrudes toward the common flow paths 13a, 13b during bonding may vary greatly depending on the location. Below, a case where the amount of adhesive 12 protruding along the opening edge 15 of the common flow paths 13a, 13b is not uniform will be described.

[0028] FIG. 6 shows the recording element substrate 1 in the case where the thickness X of the wall separating the common flow paths 13a and 13b is small, and the adhesive 12 largely protrudes along the wall toward the common flow paths 13a and 13b. FIG. 6(a) is a schematic plan view showing the distribution of the protruding adhesive 12 on the surface 23 of the second flow path substrate 6, and FIG. 6(b) is a transparent top view of the main part of the second flow path substrate 6 viewed from the first flow path substrate 5 side, assuming that the discharge port forming member 2 is not provided. The distribution of the adhesive 12 shown in FIG. 6(a) is the distribution when the recess 14 is not provided on the surface 23 of the second flow path substrate 6. In this example, the wall separating the common flow paths 13a and 13b corresponds to the side 15c of the opening edge 15. If the thickness of this wall is thin, the adhesive 12 protrudes more along the side 15c than on other sides. In such a case, as shown in FIG. 6(b), a groove-shaped recess 14 can be provided on the surface 23 of the second flow path substrate 6 so as to connect to the side 15c instead of the corner 24 of the opening edge 15. The recess 14 is formed on the surface 23 of the second flow path substrate 6 so as to extend from the position exposed to the common flow paths 13a and 13b toward the side 15c in a direction perpendicular to the direction in which the side 15c extends. The number of groove-shaped recesses 14 provided so as to connect to the side 15c is not limited to one, and as shown on the side of the common flow path 13b in the figure, a plurality of recesses 14 may be provided so as to be parallel to one side 15c. By providing the recess 14 in this manner, the amount of the adhesive 12 protruding along the side 15c can be substantially reduced, and the protruding adhesive 12 can be prevented from concentrating on the corner 24 of the opening edge 15. This can prevent the adhesive 12 from creeping up the side surfaces 25 of the common flow paths 13a and 13b, particularly along the ridges 26.

[0029] The common flow paths 13a and 13b are usually provided in a long and narrow rectangular shape, and the inner angle of each corner 24 at the opening edge 15 is 90° (right angle). However, the inner angle of the corner 24 is not limited to 90°, and when the inner angle is smaller than 90° (i.e., acute angle), the overflowing adhesive 12 is likely to concentrate at the corner 24. FIG. 7 shows a recording element substrate 1 in which the inner angle of each corner 24 at the opening edge 15 of the common flow paths 13a and 13b is not 90°. FIG. 7(a) is a schematic plan view showing the distribution of the overflowing adhesive 12 on the surface 23 of the second flow path substrate 6, and FIG. 7(b) is a transparent top view of the main part of the second flow path substrate 6 viewed from the side of the first flow path substrate 5 assuming that the discharge port forming member 2 is not provided. The distribution of the adhesive 12 shown in FIG. 7(a) is the distribution when the recess 14 is not provided on the surface 23 of the second flow path substrate 6. In the example shown here, the inner angle of the corner 24 formed by the side 15b and the side 15c at the opening edge 15 is less than 90° (i.e., an acute angle), and the inner angle of the corner 24 formed by the side 15a and the side 15b is more than 90° (i.e., an obtuse angle). In this case, the concentration of the protruding adhesive 12 at the corner 24 formed by the side 15a and the side 15b is significant, so as shown in FIG. 7(b), a groove-shaped recess 14 connected to the side 15b and a groove-shaped recess 14 connected to the side 15c are provided on the surface 23 of the second flow path substrate 6. The two recesses 14 may intersect as shown in the figure. By arranging the recess 14 in this manner, the protrusion of the adhesive 12 along each of the sides 15b and 15c is suppressed, and the concentration of the adhesive 12 at the corner 24 formed by the sides 15b and 15c is suppressed. As a result, it is possible to suppress the adhesive 12 from creeping up along the ridge 26 continuing to the corner 24 on the side surface 25 of the common flow paths 13a, 13b.

[0030] [Second embodiment] The groove-shaped recess 14 formed on the surface 23 of the second flow path substrate 6 to accommodate the overflowing adhesive 12 may be divided into a plurality of sections along its length, and each divided section may have a different cross-sectional shape. The recording element substrate 1 of the second embodiment is used in the liquid ejection head shown in FIG. 1 like the one in the first embodiment, but the groove-shaped recess 14 formed on the surface 23 of the second flow path substrate 6 is divided into two sections along its length. FIG. 8 shows the recording element substrate 1 in the second embodiment. FIG. 8(a) is a transparent view of the second flow path substrate 6 seen from the first flow path substrate 5 side with the ejection port forming member 2 removed, and FIG. 8(b) and FIG. 8(c) are cross-sectional views along the lines BB and CC in FIG. 8(a), respectively. The recording element substrate 1 of the second embodiment differs from that of the first embodiment shown in FIG. 1 only in the configuration of the groove-shaped recess 14 formed on the surface 23 of the second flow path substrate 6. Therefore, for the recording element substrate 1 of the second embodiment, a cross-sectional view corresponding to the cross-sectional view taken along line AA in FIG. 1 will be omitted.

[0031] As in the first embodiment, the groove-shaped recess 14 extends from a position exposed to the common flow paths 13a and 13b on the surface 23 of the second flow path substrate 5 to a corner 24 formed by the sides 15b and 15c. The recess 14 is divided into two sections along its longitudinal direction: a recess 14b which is a section on the side closer to the corner 24 (i.e., one end side) and a recess 14c which is a section on the side farther from the corner 24 (i.e., the other end side). FIG. 8(b) shows a cross section of the recess 14b, and FIG. 8(c) shows a cross section of the recess 14c. A large amount of adhesive 12 flows into the recess 14b which is the section closer to the corner 24, so the width of the groove is wide. On the other hand, a strong capillary force is required to make the adhesive 12 flow into the recess 14c which is the section farther from the corner 24, so the width of the groove is narrower than that of the recess 14b.

[0032] In the second embodiment, the number of divisions when dividing the groove-shaped recess 14 into a plurality of sections along its longitudinal direction is not limited to 2, and may be 3 or more. In the second embodiment, it is sufficient that in two adjacent sections of the recess 14, the width of the recess 14 in the section farther from the corner 24 of the opening edge 15 is narrower than the width of the recess 14 in the section closer to the corner 24. EXAMPLES

[0033] Next, an example will be described in which the recording element substrate 1 described with reference to FIG. 2 is actually produced as a substrate assembly according to the present invention, and a liquid ejection head is manufactured.

[0034] First, a silicon substrate was prepared on which a recording element 9 made of TaSiN, an electric circuit (not shown) for driving the recording element 9, and an electric signal input terminal 4 were formed on a first surface 21, and a grinding device was used to thin the second surface 22 of the silicon substrate until the substrate thickness became 625 μm. Then, common flow paths 13a, 13b and liquid flow paths 10a, 10b were formed on the silicon substrate, thereby obtaining a first flow path substrate 5. In forming the common flow paths 13a, 13b, first, patterning was performed using a photolithography technique using a positive resist. Using the patterned positive resist as a mask, the second surface 22 of the silicon substrate was etched by applying the Bosch process to form the common flow paths 13a, 13b. At this time, the etching process was performed for a predetermined time so that the depth of the common flow paths 13a, 13b became 450 μm. Next, in the same manner as in the formation of the common channels 13a and 13b, etching was performed on the first surface 21 of the silicon substrate to form 50 μm square holes as the liquid channels 10a and 10b at positions communicating with the common channels 13a and 13b. This completed the first channel substrate 5.

[0035] For the second flow path substrate 6, a silicon substrate having a thickness of 725 μm was prepared separately from the first flow path substrate 5, and a through flow path 11 having a depth of 350 μm and a groove-like recessed portion 14 having a depth of 150 μm were formed by the same procedure as for forming the flow path in the first flow path substrate 5. At this point, the through flow path 11 does not penetrate the silicon substrate. Also, at this time, the end of the recessed portion 14 was separated by 10 μm from the corner portion 24 formed by the side 15b and the side 15c. Thereafter, the silicon substrate was thinned from the surface opposite to the surface on which the recessed portion 14 was formed, so that the through flow path 11 penetrated the silicon substrate, and the second flow path substrate 6 having a thickness of 300 μm was completed.

[0036] Next, a transfer substrate for transferring the adhesive was prepared, and a benzocyclobutene solution was spin-coated to a thickness of 3 μm on the transfer substrate as the adhesive 12. A PET (polyethylene terephthalate) film was used as the transfer substrate. In addition, in order to volatilize the solvent after coating, the transfer substrate was baked at 100° C. for 5 minutes. Thereafter, the adhesive 12 formed on the transfer substrate was brought into contact with the second surface 22 of the first flow path substrate 5 while applying heat, thereby transferring the adhesive 12 to the first flow path substrate 5.

[0037] Next, while performing alignment using a bonding alignment device, the first flow path substrate 5 and the second flow path substrate 6 were bonded by heating at a temperature of 150°C in a vacuum with a degree of vacuum of 100 Pa or less. After the bonding was completed and cooled, the first flow path substrate 5 and the second flow path substrate 6 were taken out of the device in the bonded state and heat-treated at 250°C for 1 hour in an oven in a nitrogen atmosphere to harden the adhesive 12. This completed a substrate bond in which the first flow path substrate 5 and the second flow path substrate 6 were bonded. The adhesive 12 extruded from the bonded portion flowed into the recess 14 and hardened in that state.

[0038] Next, a negative photosensitive resin was dissolved in a PGMEA (propylene glycol-1-monoethyl ether-2-acetate) solvent and spin-coated on the PET film, and dried at 100°C in an oven to form a dry film. The dry film on the FET film was then transferred to the surface 22 on which the recording elements 9 were formed in the first flow path substrate 5, and the PET film was peeled off. After the dry film was transferred in this manner, exposure and PEB (post-exposure bake) were performed to form a latent image of the flow path formation region 8. Next, a dry film was similarly laminated, exposure and PEB corresponding to the ejection port formation region 7 were performed, and development was performed to form the pressure chamber 20 and the ejection port 3 at the same time, completing the liquid ejection head. In the obtained liquid ejection head, no flow path blockage was observed in the liquid flow paths 10a and 10b.

[0039] The disclosure of this embodiment includes the following configurations and methods.

[0040] (Configuration 1) A substrate assembly including a first substrate having a first surface and a second surface opposite to the first surface, the first substrate having an opening formed in the second surface, and a second substrate bonded to the second surface via an adhesive, the opening being covered by the second substrate, A substrate bonded body, characterized in that a recess is formed on a third surface of the second substrate, which is the surface facing the opening, and extends from a position exposed to the opening toward a position facing the edge of the opening on the second surface, so that the adhesive that overflows from the joint between the first substrate and the second substrate can reach the third surface.

[0041] (Configuration 2) The substrate assembly according to configuration 1, wherein the opening edge on the second surface has a corner, and the recess extends from a position on the third surface exposed to the opening toward a position opposite the corner.

[0042] (Configuration 3) The substrate assembly according to configuration 2, wherein the recess reaches a position on the third surface facing the corner.

[0043] (Configuration 4) The substrate bonded body according to configuration 2, wherein the recess extends beyond a position on the third surface facing the corner portion to a position where the second surface and the third surface are bonded via the adhesive.

[0044] (Structure 5) The substrate assembly of claim 1, wherein the opening edge on the second surface has a corner with an interior angle of less than 90°, and two recesses are provided extending along two sides of the opening edge that sandwich the corner with the interior angle of less than 90°.

[0045] (Configuration 6) The substrate assembly according to configuration 5, wherein the two recesses are each formed as a groove and intersect on the third surface.

[0046] (Structure 7) A substrate assembly as described in Structure 1, wherein the opening edge on the second surface has a plurality of corners, and two or more of the recesses are provided, each extending along a side between two adjacent corners of the opening edge.

[0047] (Configuration 8) The substrate assembly according to any one of configurations 1 to 7, wherein the recess is formed in a groove shape having one end extending toward a position facing the edge of the opening.

[0048] (Configuration 9) The substrate assembly according to configuration 8, wherein the depth of the recess is greater than the width of the recess.

[0049] (Configuration 10) The substrate assembly according to configuration 8 or 9, wherein an end of the protruding adhesive on the third surface is between the other end of the recess and an edge of the opening.

[0050] (Configuration 11) The substrate bonded body according to any one of Configurations 8 to 10, wherein the protruding adhesive is present between the other end of the recess and an edge of the opening on the third surface.

[0051] (Configuration 12) The substrate assembly described in Configuration 11, wherein the recess is divided into a plurality of sections along the longitudinal direction of the recess, and between two adjacent sections, the width of the recess in the section closer to the one end is narrower than the width of the recess in the section closer to the other end.

[0052] (Structure 13) A substrate bonded body described in any one of Structures 1 to 12, wherein the opening is an opening of a recessed portion formed in the first substrate, and a through hole is formed at the bottom of the recessed portion, penetrating to the first surface of the first substrate.

[0053] (Configuration 14) A substrate assembly according to configuration 13, a recording element disposed on the first surface of the first substrate, and a discharge port; A liquid ejection head, characterized in that liquid supplied from the opening via the through hole is ejected from the ejection port by driving the recording element.

[0054] (Method 1) A method for producing a substrate bonded body, comprising bonding a first substrate having a first surface and a second surface opposite to the first surface and having an opening formed in the second surface to a second substrate with an adhesive, comprising: applying or transferring the adhesive to the second surface; a step of bonding and pressing the first substrate and the second substrate together after the applying or transferring step; After pressing, curing the adhesive; having A method for manufacturing a substrate bonded body, characterized in that the adhesive, before hardening, which has overflowed from a joint by pressing, is caused to flow into a recess formed in the surface of the second substrate so as to extend from a position exposed in the opening toward a position facing the edge of the opening on the second surface. [Explanation of symbols]

[0055] 5. First flow path substrate 6 Second flow path substrate 12. Adhesive 13a, 13b Common flow path 14, 14b, 14c Recess 15 Opening edge Areas 15a, 15b, and 15c 21 First Surface 22 Second Surface 23 The Third Surface

Claims

1. A substrate assembly comprising: a first substrate having a first surface and a second surface opposite to the first surface, the first substrate having an opening formed in the second surface; and a second substrate bonded to the second surface via an adhesive, the opening being covered by the second substrate; a recess is formed on a third surface of the second substrate, the third surface facing the opening, the recess extending from a position exposed to the opening toward a position facing an edge of the opening on the second surface so that the adhesive that has overflowed from the joint between the first substrate and the second substrate can reach the third surface; A substrate assembly, characterized in that the recess is in contact with an edge connecting to a corner of the edge of the opening, or in contact with an area where the first substrate and the second substrate are in contact in the side area of ​​the opening.

2. 2. The substrate assembly of claim 1, wherein the recess extends beyond a position on the third surface facing the corner portion to a position where the second surface and the third surface are joined via the adhesive.

3. 2. The substrate assembly according to claim 1, wherein the opening edge on the second surface has a corner portion whose interior angle is less than 90°, and two recesses are provided extending along two sides of the opening edge that sandwich the corner portion whose interior angle is less than 90°.

4. The substrate assembly according to claim 3 , wherein the two recesses are each formed as a groove and intersect on the third surface.

5. The substrate assembly according to claim 1 , wherein the opening edge has a plurality of corners on the second surface, and two or more of the recesses are provided, each extending along a side between two adjacent corners of the opening edge.

6. The substrate assembly according to claim 1 , wherein the recess is formed in a groove shape with one end extending toward a position facing the edge of the opening.

7. The substrate assembly according to claim 6 , wherein the depth of the recess is greater than the width of the recess.

8. 7. The substrate assembly according to claim 6, wherein the opening is an opening of a recessed portion formed in the first substrate, and the length of the recessed portion is longer than the depth of the recessed portion.

9. The substrate assembly according to claim 6 , wherein an end of the adhesive protruding from the third surface is located between the other end of the recess and the edge of the opening.

10. 10. The substrate assembly according to claim 9, wherein the recess is divided into a plurality of sections along the longitudinal direction of the recess, and the width of the recess in a section closer to the one end of each of the adjacent two sections is narrower than the width of the recess in a section closer to the other end.

11. 2. The substrate assembly according to claim 1, wherein the opening is an opening in a recessed portion formed in the first substrate, and a through hole is formed at the bottom of the recessed portion, penetrating to the first surface of the first substrate.

12. a substrate assembly according to claim 11, a recording element disposed on the first surface of the first substrate, and a discharge port; A liquid ejection head, characterized in that the liquid supplied from the opening via the through-hole is ejected from the ejection port by driving the recording element.

13. A method for manufacturing a substrate assembly, comprising: bonding a first substrate, the first substrate having a first surface and a second surface opposite to the first surface and an opening formed in the second surface, to a second substrate using an adhesive; applying or transferring the adhesive to the second surface; a step of joining and pressing the first substrate and the second substrate together after the applying or transferring step; After pressing, curing the adhesive; and the adhesive that has squeezed out from the bonding portion by pressing is caused to flow into a recess formed in the surface of the second substrate so as to extend from a position exposed to the opening toward a position facing an edge of the opening on the second surface; A method for manufacturing a substrate bonded body, characterized in that the recess is in contact with an edge connecting to a corner of the edge of the opening, or in contact with an area on the side of the opening where the first substrate and the second substrate are in contact.

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