Liquid ejecting head

Abstract

A liquid ejecting head is used that includes a bonding substrate of a first substrate and a second substrate that are laminated and bonded with an adhesive. In the liquid ejecting head, a bonding substrate has a liquid channel through which a first substrate and a second substrate communicate, an adhesive is disposed at a corner portion at a bonding position of the first substrate and the second substrate so as to form an arc shape protruding toward the corner portion on a cross section thereof, and the adhesive is disposed at the corner portion so as to form an arc shape protruding toward the corner portion. And a corner portion formed at a position corresponding to the liquid channel, the corner portion being formed by an end face of the first substrate and a plane of the second substrate, and the protective film being continuously provided from the first substrate through an adhesive disposed on the corner portion at the bonding position.

Description

Technical Field

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

[0002] One example of a functional device such as a MEMS (micro-electromechanical system) including a pressure sensor and an acceleration sensor and a microfluidic device is a liquid ejection head that ejects a liquid. A liquid ejection head is also called an inkjet recording head or a liquid jet head, and is a printing device for printing by ejecting a liquid. When manufacturing these devices, a device formed of a bonded substrate body is manufactured, which is a substrate bonded by an organic film (adhesive). In order to stabilize the ejection of the liquid ejection head and to improve the appearance of the print, a mechanism for circulating ink in the liquid ejection head is often provided in recent years.

[0003] As a method of reducing damage to joined substrates caused by ink, Japanese Patent Application Publication No. 2014-124887 proposes a method of forming a protective film for substrates joined via an organic film (adhesive). Summary of the invention

[0004] As described above, there is a need to further improve the stability of ejection and the printing appearance of a liquid ejection head using a bonded substrate. Therefore, it is particularly necessary to preferably protect the ink channel.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technique for protecting ink channels formed inside a liquid ejection head using bonded substrates.

[0006] The present invention provides a liquid ejection head, comprising:

[0007] A bonding substrate of a first substrate and a second substrate, wherein the first substrate and the second substrate are stacked and bonded with an adhesive, wherein

[0008] The bonding substrate is provided with a liquid channel, and the first substrate and the second substrate are connected through the liquid channel.

[0009] At a bonding position of the first substrate and the second substrate, the adhesive is arranged at a corner portion so as to form an arc shape convex toward the corner portion in its cross section, the corner portion being formed at a position corresponding to the liquid channel, the corner portion being formed by an end surface of the first substrate and a plane of the second substrate, and

[0010] At the bonding position, a continuous protective film is provided in such a manner as to reach the second substrate through the adhesive disposed on the corner portion from the first substrate.

[0011] According to the present invention, it is possible to provide a technology for protecting an ink channel formed inside a liquid ejecting head using a bonding substrate.

[0012] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic cross-sectional view of a bonding substrate for a liquid ejecting head;

[0014] Figures 2A to 2C is a schematic cross-sectional view showing a step of manufacturing the bonding substrate;

[0015] Figures 3A to 3C is an enlarged schematic diagram showing the performance of the adhesive in the joint;

[0016] Figures 4A to 4C is another enlarged schematic diagram showing the performance of the adhesive in the joint;

[0017] Figure 5A and 5B It is a cross-sectional view used to consider the expansion amount of the adhesive;

[0018] Fig. 6A and 6B is a cross-sectional view for comparison for considering the expansion amount of the adhesive;

[0019] Fig. 7A and 7B is a cross-sectional view for comparison for considering the expansion amount of the adhesive;

[0020] Figures 8A to 8C is a top view showing a change in the shape of the opening of the bonding substrate;

[0021] Figures 9A to 9C is a cross-sectional view showing a change in the shape of the substrate;

[0022] Figures 10A to 10C is a cross-sectional view showing a change in the shape of the substrate;

[0023] Figures 11A to 11C is a cross-sectional view showing a change in the shape of the substrate;

[0024] Fig. 12A and 12B is a schematic cross-sectional view of a method of controlling an adhesive;

[0025] Fig.13A and 13B is a schematic cross-sectional view of a method of controlling an adhesive;

[0026] Fig.14A and 14B is a schematic cross-sectional view of a method of controlling an adhesive;

[0027] Figures 15A to 15C is a schematic cross-sectional view of a bonding substrate according to Example 2;

[0028] Fig.16A and 16B is a schematic diagram showing an example of a printing element;

[0029] Fig.17 is a schematic diagram showing an example of a printing element unit; and

[0030] Fig.18 1 is a schematic diagram showing an example of a mode of a liquid ejecting head. DETAILED DESCRIPTION

[0031] Hereinafter, preferred embodiments of the technology disclosed herein will be described with reference to the accompanying drawings. The size, material, shape, relative arrangement, etc. of the components described below should be appropriately changed according to the structure of the device to which the present invention is applied and according to various conditions. Therefore, the embodiments are not to be construed as limiting the scope of the present invention to the following description. Any known or known technology in the art can be applied to structures and steps not particularly shown or described. Redundant descriptions can be omitted.

[0032] These embodiments describe the bonding of three substrates as an example, but the present invention is not limited thereto and is also applicable to the bonding of a plurality of substrates.

[0033] Here, the problems found by the present inventors regarding the conventional liquid ejection head will be described. The present inventors found that when ink is circulated in the ink channel of the liquid ejection head using the bonded substrate, when materials having different wettability levels (such as a protective film and an adhesive) exist in a mixed manner inside the ink channel, bubbles adhere to the area with poor wettability. In addition, in the liquid ejection head, the inner wall surface of the ink channel is easily eroded by the ink, and if exposed to the ink for a long time, the structure of the channel may be damaged. In particular, when the substrate is silicon, such damage due to the ink is likely to occur.

[0034] Japanese Patent Application Publication No. 2014-124887 as described above proposes a method of forming a protective film for substrates joined by an organic film (adhesive) as a method of reducing damage to the substrate caused by ink. However, according to the research of the present inventors, it was found that when a protective film is formed on the entire inner wall surface of the ink channel and the organic film (adhesive) as described in Japanese Patent Application Publication No. 2014-124887, bubbles adhere to any corner portion of the joining portion of the substrate and the ink flow is obstructed. Such bubble residues lead to poor ink jetting, which may deteriorate the appearance of the printed matter.

[0035] Then, due to the research of the present inventors, it was found that by setting R at the corner portion of the ink channel and by making the wettability inside the ink channel equal, the gathering of bubbles and the obstruction of the ink flow can be suppressed. This can improve the efficiency of ink circulation so as to improve the appearance of printing. The following embodiment specifically describes this structure of the invention of the present application. Example 1

[0036] Hereinafter, a substrate for a liquid ejection head according to Embodiment 1 of the present invention will be described with reference to the accompanying drawings. This embodiment shows an example of using a piezoelectric element as an energy generating element. However, the present invention is not limited to this, but can also be used to join a substrate having an element (e.g., a heating element) capable of boiling ink by electrical heating. An example of a liquid ejection head to which the present invention can be applied is a member of a printing device such as an inkjet printer. The printing device is also provided with a liquid storage portion for storing liquid to be supplied to the liquid ejection head, a conveying mechanism for a recording medium for printing, and the like.

[0037] Structure of bonding substrate

[0038] Figure 1 1 is a schematic cross-sectional view of a bonding substrate 80 for a liquid ejecting head according to Embodiment 1 of the present invention. The bonding substrate 80 of this embodiment is formed by connecting a first substrate 1, a second substrate 2, and a third substrate 3 by an adhesive 4, an ink channel 7 (liquid channel) is formed at the first substrate 1, a plurality of piezoelectric elements 5 and electrodes 6 are formed at the second substrate 2, and a plurality of ejection ports 8 are formed at the third substrate 3. That is, the bonding substrate 80 has at least a plurality of bonding surfaces bonded using an adhesive. A portion of the adhesive 4 overflowing from the bonding surface is absorbed in the groove 15.

[0039] The first substrate 1 is formed of, for example, a silicon substrate, and a first opening 7a forming an ink channel 7 is formed in the first substrate 1. The second substrate 2 is formed of, for example, a silicon substrate, and has a vibration membrane 11, and a piezoelectric element 5 is formed on the vibration membrane 11. The vibration membrane 11 forms the top plate of the pressure chamber 10 so as to separate a plurality of pressure chambers 10. Moreover, a second opening 7b communicating with the first opening 7a (so as to form the ink channel 7 for introducing liquid into the pressure chamber 10) is formed in the second substrate 2. The third substrate 3 is formed of, for example, a silicon substrate, and an ejection port 8 is formed in the third substrate 3, and a liquid is ejected through the ejection port 8. The ejection port 8 penetrates the third substrate 3. When the pressure chamber 10 is viewed from the third substrate side, a side of the face facing the pressure chamber 10 and a side of the face on the opposite side of the pressure chamber 10 are communicated through the ejection port 8. Therefore, a volume change in any pressure chamber 10 causes the liquid stored in the pressure chamber 10 to be ejected through the ejection port 8.

[0040] An ink tank (not shown) is arranged on the first substrate 1. Therefore, the liquid in the ink tank is supplied to the pressure chamber 10 through the first opening 7a.

[0041] On the vibration membrane 11, the piezoelectric element 5 is arranged to constitute a piezoelectric actuator. The piezoelectric element 5 is provided with a lower electrode (not shown) formed on the vibration membrane forming layer, the piezoelectric element 5 formed on the lower electrode, and an upper electrode (not shown) formed on the piezoelectric element. On the vibration membrane 11, an electrode 6 for external connection is also arranged.

[0042] The piezoelectric element 5 is formed at a position facing the pressure chamber 10 across the vibration membrane 11. That is, the piezoelectric element 5 is formed to be in contact with the surface of the vibration membrane 11 on the opposite side of the pressure chamber 10. The vibration membrane 11 is characterized in that it can be deformed in a direction opposite to the pressure chamber 10. As shown in the figure, a protective film 18 can be provided on the second substrate 2. The protective film 18 is made of, for example, SiN, and has a function of protecting the wiring layer, the piezoelectric element, etc. In the following description, the protective film 18 provided on the second substrate 2 is considered to be a part of the second substrate 2. That is, when the adhesive 4 is applied, the second substrate 2 and the protective film 18 are formed into one body, and therefore, based on this state, the boundary between the first substrate 1 and the second substrate 2 is determined.

[0043] Applying a driving voltage from a driving IC (not shown) to the piezoelectric element 5 through wiring causes the piezoelectric element 5 to deform by the inverse piezoelectric effect. This causes the vibration membrane 11 to deform together with the piezoelectric element 5, which causes a change in volume in the pressure chamber 10, thereby pressurizing the liquid (e.g., ink). The pressurized liquid is ejected in the form of droplets through the ejection port 8.

[0044] Bonding and adhesive performance

[0045] The following will describe in detail the bonding of the first substrate 1 and the second substrate 2 according to the present invention. In the present invention, an example of the first substrate 1 and the second substrate 2 is shown, but the present invention is not limited thereto. The present invention can be applied to the second substrate 2 and the third substrate 3, and can also be applied to these substrates when the number of substrates is larger.

[0046] Figures 3A to 3C The diagram shows a state where the second substrate 2 is bonded to the first substrate 1 via the adhesive 4 and a Si protective film is formed. Figures 4A to 4C Is Figure 3A The dashed line indicates an enlarged view of area B. Figures 4A to 4C Corresponding to Figures 3A to 3C . Figure 3A and 4A There is shown a state in which the adhesive 4 is applied to the bottom surface (the surface opposing the second substrate 2 ) of the first substrate 1 and then the first substrate and the second substrate are brought close to each other so as to be bonded.

[0047] Figure 3B and 4B The state after bonding is shown. At this time, the bonding of the substrates causes the adhesive 4 to flow out from the interface of the bonded substrates by capillary phenomenon, thereby forming an extended portion 4f. The outflow portion of the adhesive 4 is able to flow along the corner portion formed by the substrates, and therefore, the cross-sectional shape of the adhesive 4 surface at the corner portion on the bonding interface is an arc having a concave portion 4k. That is, in the cross section, on the corner portion C formed by the extension line of the end face 1t of the first substrate 1 and the plane 2p of the second substrate 2 (more precisely, the protective film 18 formed integrally with the second substrate 2 when the adhesive 4 is applied), the cross-sectional shape of the adhesive 4 forms an arc convex toward the corner portion C. Therefore, as the adhesive 4, it is preferable to select an adhesive that flows according to temperature, heat and / or load. The cross-sectional shape of the adhesive surface is an arc in this article. Figure 4B As shown in the sectional view of , at the bonding position, in the cross section, the surface of the adhesive is on the inner side (on the side closer to the corner portion) of a straight line (indicated by a dotted line in the figure) formed by a distance D1 of the adhesive 4 extending on the second substrate 2 (a distance of the adhesive 4 extending from the corner portion to the position farthest from the corner portion on the second substrate 2) and a distance D2 of the adhesive 4 extending on the first substrate 1 (a distance of the adhesive 4 extending from the corner portion to the position farthest from the corner portion on the first substrate 1).

[0048] The reason for using arc lines for expression is that, in many cases, due to the characteristics of the adhesive 4 (i.e., the adhesive 4 has fluidity to a certain extent), the surface becomes a curve in its cross section, but the surface does not have to be formed only by curves in the cross section, as long as the surface is inside the line D1-D2 (as described above), for example, it can be a combination of straight lines and curves. The curved part can be a circular arc, an elliptical arc, or any other curve. Any shape of the surface of the adhesive 4 will produce an effect to a certain extent, as long as the shape does not convex beyond the line D1-D2 (but is concave in the cross section).

[0049] Figure 3C and 4C 1 shows a state in which the protective film 9 is further formed. It has been found that the presence of the concave portion 4k on the base layer of the protective film 9 leads to the formation of a concave portion (circular concave portion R) also on the protective film 9 to be in direct contact with the ink.

[0050] Consider the expansion of adhesives

[0051] Figures 5A to 7B Examples of different expansion amounts of the adhesive are shown. Figure 5A , 6A and 7A show the expansion of the adhesive, Figure 5B , 6B7A and 7B show the state after the protective film 9 is formed.

[0052] Figure 5A and 5B An example is shown in which the distances D1 and D2 are different because the wettability of the first substrate 1 and the second substrate 2 to the adhesive 4 is different. In the case shown in these figures, the cross-sectional shape of the concave portion is not a circular arc, but more similar to an elliptical arc. Even in this case, the effect of the present invention can be obtained.

[0053] Fig. 6A and 6B The case where the amount of expansion of the adhesive 4 extending outward from the bonding portion is small due to the surface characteristics of the first substrate 1 and the second substrate 2, the fluidity of the adhesive 4, etc. is shown. In this case, the effect of suppressing the accumulation of bubbles when the ink circulates becomes greater. Figure 4C The situation and Figure 5A It should be noted that the effect is obtained to a certain extent.

[0054] In contrast, Fig. 7A and 7B Indicates a state where the adhesive does not spread but stays in the space held between the substrates. In this case, Figure 7B As shown, the protective film 9 does not form R. Therefore, the effect of suppressing the accumulation of bubbles when the ink circulates in the ink channel becomes very weak.

[0055] Variations in opening and cross-sectional shape

[0056] In order to form the opening formed through the substrate, a processing method such as dry etching and wet etching or a processing method using laser is used. Figures 8A to 8C The top view of FIG. 7 shows examples of different shapes of one of the first openings 7a forming the ink channel 7. Reference numeral B denotes a shape corresponding to Figure 3A The position corresponds to region B. This shape difference also changes the performance at the interface of the bonding substrate.

[0057] and, Figures 9A to 11C are cross-sectional views, each of which shows a state in which the behavior of the adhesive 4 changes according to different cross-sectional shapes of the first substrate 1 . Figures 9A to 9C The following case is shown: the closer the first substrate 1 is to the second substrate 2, the wider the first substrate 1 is in the cross section of the first substrate 1. In this case, the base of the first substrate 1 has an acute angle in the cross section. Figures 10A to 10C The following case is shown: the closer the first substrate 1 is to the second substrate 2, the narrower the first substrate 1 is in a cross section of the first substrate 1. In this case, the base of the first substrate 1 has an obtuse angle. Figures 11A to 11CThe scalloped edge when the first opening 7 a is formed by the Bosch process for dry etching is shown.

[0058] In any case, it is important to form the bond inside the straight line formed by D1 and D2, such as Fig. 9B , 10B 11B. For this purpose, it is preferable to appropriately select the materials of the first substrate 1 and the second substrate 2, the type of the adhesive 4, etc. Even in any of these cases, as in the case where the end surface of the first substrate 1 is perpendicular to the plane of the second substrate 2, a preferred R can be formed on the protective film 9.

[0059] Controlling the amount of adhesive expansion

[0060] As described above, when the adhesive 4 stays in the space held between the substrates, the effect of the present invention cannot be obtained. However, on the contrary, the extreme expansion of the adhesive 4 outward from the space held between the bonded substrates may block the ink channel 7 formed on the bonded surface, and / or may expand across the second opening where the piezoelectric element is stored, thereby affecting the ejection. Therefore, the adhesive 4 is preferably a type without excessive fluidity, and its coating amount must be appropriate.

[0061] Here, the direction in which the substrates are stacked is defined as the stacking direction (Z direction in the drawings), the direction intersecting the stacking direction and in which the substrates extend is defined as the extension direction (X direction in the drawings), and the direction intersecting the stacking direction and the extension direction and in which the end faces of the substrates are continuous in the opening portion (for example, the direction in which the first substrate 1 forms a boundary with the first opening 7a) is defined as the end face direction (Y direction in the drawings). The inventors have found that in the present invention, the distance (D2) of the concave portion 4k of the adhesive 4 along the stacking direction and the distance (D1) thereof along the extension direction in which the substrates extend are both preferably at least 3 μm and not more than 20 μm, and more preferably at least 5 μm and not more than 15 μm. Figure 4B In the case of the concave portion 4k having an approximately arc shape, the distances D1 and D2 may be collectively referred to as "arc width D". The arc width D may be controlled by providing a groove for storing the adhesive on the surface of any substrate at the bonding interface or by appropriately optimizing the film thickness of the adhesive. The same method may be applied even when the concave portion 4k does not have an arc shape. For example, Figure 5A As shown, when the distance D2 along the stacking direction and the distance D1 along the substrate extension direction are different, both D1 and D2 are preferably at least 3 μm and not more than 20 μm, more preferably at least 5 μm and not more than 15 μm.

[0062] In the bonding substrate 80, the region where the electrode pad or the piezoelectric element is formed and the region where the ink channel 7 is formed may be adjacent to each other via the substrate. Figure 2A, in the region indicated by the dotted line A, the ink channel 7 is formed on the right side of the region A, and the electrode storage portion 16 where the electrode 6 is arranged is formed on the left side thereof. At this time, the expansion of the adhesive 4 on the left side of the dotted line A covers the electrode, which is not desirable in terms of performance and quality. The foregoing also applies to the piezoelectric element 5. In contrast, it is desirable that the adhesive 4 expands in the region where the ink channel 7 is formed until a suitable concave portion is formed.

[0063] Therefore, a method of appropriately spreading the adhesive 4 at a desired position is conceivable. Fig. 12A is an enlarged view of the area indicated by the dotted line A. As shown here, the groove 15 for storing the adhesive 4 is arranged closer to one side (left side) of the corresponding area of ​​the first substrate 1 (where the adhesive is not expected to spread). This can suppress the adhesive from spreading on the left side, as shown in FIG. Fig. 12B In contrast, the adhesive 4 is expanded by an appropriate amount on the right side, thereby forming a concave portion 4k. For simplicity, the number of the groove 15 in the drawings is 1, but a plurality of grooves 15 may be provided.

[0064] like Fig.13A and 13B As shown, the groove 15 for storing the adhesive 4 can be provided on the second substrate 2. The groove 15 can also be provided in the first substrate 1 and the second substrate 2, respectively.

[0065] like Fig.14A and 14B As shown, the expansion can also be controlled by controlling the substrate area where the adhesive 4 is formed. In the example shown, the adhesive uncoated portion 4m is provided on the left area of ​​the bottom surface of the first substrate 1 (where it is desired to prevent the expansion of the adhesive 4). On the left area, the amount of adhesive 4 applied can be less than that on the right area, but not zero. The amount applied can gradually decrease from the right to the left.

[0066] Joining steps

[0067] Next, a series of steps for manufacturing the bonded substrate 80 will be described. These steps start from the stage of creating the ink channels 7, the pressure chambers 10, the grooves 15, the electrode storage portions 16, etc. on the first substrate 1 to the third substrate by a known method (e.g., a combination of etching and photolithography) and arranging the piezoelectric element 5, the electrode 6, wiring (not shown), etc.

[0068] Steps for manufacturing substrate

[0069] As the material of the first substrate 1, the second substrate 2, and the third substrate 3, silicon is preferred. In addition to silicon, silicon carbide, silicon nitride, any of various glasses (quartz glass, borosilicate glass, alkali-free glass, soda-lime glass), any of various ceramics (aluminum oxide, gallium arsenide, gallium nitride, aluminum nitride), or resin may be used. For example, the first substrate 1 and the second substrate 2 are each set to have a thickness of 625 μm. The first opening 7a of the first substrate 1 and the second opening 7b of the second substrate 2 are formed at such a position that they are connected to each other after being joined to form the channel 7.

[0070] A lower electrode (not shown), a piezoelectric element 5 on the lower electrode, and an upper electrode (not shown) on the piezoelectric element are formed on the vibration film forming layer of the first substrate 1. The electrode 6 is formed in the electrode storage portion 16. For example, the vibration film forming layer is formed by plasma CVD. Then, a hydrogen barrier film (not shown), a lower electrode (not shown), a piezoelectric body film, and an upper electrode (not shown) are sequentially formed. For example, the lower electrode and the upper electrode are formed by sputtering, and the piezoelectric body film is formed by sol-gel processing, but it may also be formed by sputtering.

[0071] A PZT (lead zirconate titanate) film formed by, for example, sol-gel processing or sputtering can be applied to each piezoelectric element 5. Such a piezoelectric element 5 is formed of a sintered compact of metal oxide crystals. An actuator substrate can be formed by forming an intermediate layer and wiring (not shown), thereby enabling the actuator unit to be driven.

[0072] In the second substrate 2, the pressure chamber 10 and the groove 15 are formed by sputtering. A protective film 18 may be provided between the substrates. Figure 2A As shown, the second substrate 2 has a structure in which piezoelectric elements and electrodes are formed on a substrate made of silicon.

[0073] Steps for applying adhesive

[0074] The adhesive 4 is formed in a direct writing manner by dispensing or patterning by photolithography or the like. Since the wettability of the bonding interface to the adhesive is also important, the substrate may be surface treated with oxygen plasma or the like before bonding. Examples of other methods of applying the adhesive 4 include a transfer method using glass or PET as a base material, screen printing, and dispensing application. The thickness of the organic film is not particularly limited, but is preferably 0.1 μm to 10 μm, more preferably 1 μm to 5 μm.

[0075] As adhesive 4, it is preferred to use any material with high adhesion to substrate. Any material including less bubbles etc. and having high coating property is preferred, and any material with such low viscosity that the thickness of adhesive is easily reduced is also preferred. Adhesive preferably comprises any resin selected from the following group, and the group comprises epoxy resin, acrylic resin, silicone resin, benzocyclobutene resin, polyamide resin, polyimide resin and polyurethane resin. The example of the curing system of adhesive 4 comprises thermal curing system and ultraviolet delayed curing system. When any substrate has ultraviolet transmittance, ultraviolet curing system can also be used.

[0076] Here, an example of the transfer method will be shown. First, a base material for transfer adhesive is prepared, and a benzocyclobutene solution as adhesive 4 is spin-coated so that adhesive 4 is 3 μm. A PET film is used as the base material for transfer. After coating, it is baked at 100° C. for 5 minutes to volatilize the solvent. While heating, the adhesive 4 formed on the base material for transfer contacts the bonding surface of the first substrate 1, so that the adhesive 4 is transferred to the first substrate 1.

[0077] Joining steps

[0078] The first substrate 1 and the second substrate 2 formed with the adhesive 4 are heated to a predetermined temperature in a bonding device, and then pressurized at a predetermined pressure for a predetermined period of time, so as to be bonded together. These bonding parameters are appropriately set according to the material of the adhesive. Bonding in a vacuum is preferred because it suppresses the inclusion of bubbles in the bonding portion. During the bonding process, the adhesive 4 is softened by heating and further pressurized, so that the adhesive 4 flows from the bonding surface into the opening, such as Figure 3B shown.

[0079] In the step of forming the protective film after the bonding step, a large amount of degassing from the adhesive 4 may cause the protective film 9 to rupture or peel off. Therefore, when the adhesive 4 is a thermosetting type, the adhesive 4 can be heated inside the bonding device until it is cured. After bonding, the curing can be accelerated by taking out and heating the bonded substrate bodies separately in a furnace or the like. When the adhesive 4 is a UV-delay type, it is preferred that the bonding is performed after the adhesive 4 is irradiated with a prescribed amount of ultraviolet rays in advance before bonding. After bonding, it is preferred that the bonded substrate bodies are further heated so as to sufficiently accelerate the curing. When the adhesive 4 is a UV-curing type, after the substrates are bonded, the adhesive 4 is irradiated with a prescribed amount of ultraviolet rays through a substrate having ultraviolet transmittance so as to be cured. After bonding, it is preferred that the bonded substrate bodies are further heated so as to sufficiently accelerate the curing.

[0080] Here, an example of bonding by thermal curing when the above-mentioned benzocyclobutene solution is used as the adhesive 4 will be introduced. At this time, the first substrate 1 and the second substrate 2 are bonded by heating in a vacuum while being positioned using a bonding alignment device. The vacuum degree is set to a maximum of 100 Pa and the temperature is set to 150°C. The bonded substrate 80 after the bonding is completed is taken out of the device after cooling and heat-treated at 250°C for 1 hour in a furnace in a nitrogen atmosphere to cure the adhesive 4. At this time, the expansion width D of the adhesive 4 is 10μm. The second substrate 2 is thinned by a grinding device until its thickness reaches 100μm. Similarly, a third substrate 3 made of silicon with a thickness of 625μm is bonded and then thinned by a grinding device until its thickness reaches 100μm. The injection port 8 is formed through the second surface of the third substrate 3 (the surface opposite to the surface facing the second substrate 2) to form a bonded substrate 80. By this bonding, a bonding substrate 80 is formed as shown in FIG. Figure 2A The bonding substrate 80 is shown.

[0081] Steps for forming a protective film

[0082] Then, if Figure 2B As shown, the protective film 9 is uniformly formed along the inner wall of the ink channel and the top of the adhesive from the first surface of the bonding substrate 80 to the second surface. The protective film 9 is formed by repeating surface saturation adsorption of at least one agent selected from the group consisting of an oxidizing agent and a nitriding agent and a raw material gas by atomic layer deposition (ALD method).

[0083] The protective film 9 contains an inorganic element, preferably a single substance, an oxide, a nitride or a carbide of at least one element selected from the group consisting of Ta, Ti, Zr, Nb, V, Hf and Si. Among them, it preferably contains an oxide of at least one element selected from the group consisting of Ta, Ti, Zr, Nb, V, Hf and Si, and more preferably contains at least one compound selected from the group consisting of TaO, TiO, SiOC, SiC, SiCN, TaN, TiN and HfO.

[0084] When the adhesive force between the protective film 9 and the organic film (adhesive 4) is weak, when the rigidity of the protective film 9 is insufficient even when the adhesive force is maintained, or when both the adhesive force and the rigidity are insufficient, forming the protective film 9 directly on the organic film (adhesive 4) may cause the protective film 9 to peel off due to any force acting on the interface between the protective film 9 and the organic film (adhesive 4). When the protective film 9 peels off, it is considered that the ink entering from the portion where the protective film 9 peels off damages the organic film (adhesive), which results in poor bonding of the substrate. It is also considered that the peeling of the protective film 9 will constitute foreign matter floating in the channel, which may affect the ejection performance.

[0085] In view of the above, it is preferred that the protective film 9 has a thickness of a certain degree or more. In contrast, an excessively large film thickness may cause peeling due to, for example, film stress of the protective film. Therefore, the thickness is at least 50 nm and not more than 250 nm, more preferably at least 80 nm and not more than 180 nm. The method of forming the protective film 9 may be any other method, such as sputtering and CVD.

[0086] Here, an example of subjecting the bonding substrate 80 produced by the aforementioned thermal curing method to ALD film formation will be introduced. At this time, a thermal ALD-TaO film is formed using an ALD film forming apparatus. At this time, the cycle of film formation is as follows. A gas formed by evaporating a substrate having Ta in its molecules is delivered to the furnace together with nitrogen gas to be sprayed for 2.5 seconds, after which nitrogen purge and exhaust are fully performed. Then, a gas formed by evaporating an oxidant is delivered to the furnace together with nitrogen gas to be sprayed for 5 seconds, after which nitrogen purge and exhaust are fully performed. The above cycle as one cycle is repeated approximately 2000 times, so that a 130 nm tantalum oxide film is stacked at a film formation temperature controlled to 230°C±10°C, thereby obtaining a bonding substrate 80 coated with a protective film 9. Thus, a film is formed as follows. Figure 2B The bonding substrate 80 is shown.

[0087] Steps for forming a liquid-proof film

[0088] Then, if Figure 2C As shown, a liquid-repellent film 12 is formed on the protective film 9 formed on the second surface (the surface on the ejection port 8 side) of the bonding substrate 80. The liquid-repellent film 12 is not particularly limited as long as it repels ink, and for example, a material containing a fluorine-based polymer can be used. When a fluorine-based polymer is used as the liquid-repellent film 12, appropriately providing an intermediate film can improve the adhesion between the protective film 9 and the liquid-repellent film 12. For example, the intermediate film is a silicon oxide film. Before forming the liquid-repellent film 12, a surface treatment such as ashing may be performed.

[0089] It has been found that the bonding substrate prepared as described above for a liquid ejection head can suppress the accumulation of bubbles and the obstruction of the ink flow by making the corner portion in the ink channel have R and by making the wettability inside the ink channel equal. This can improve the efficiency of ink circulation so as to improve the appearance of printing. Example 2

[0090] Figures 15A to 15C Is Figure 2A The enlarged cross-sectional view of the region indicated by the dotted line C is shown. Here, the bonding of the second substrate 2 and the third substrate 3 will be described. The basic structure is the same as that of the bonding of the first substrate 1 and the second substrate 2. Fig.15A 2 is a cross-sectional view of region C before the substrates are bonded. When viewed from the region where the adhesive 4 spreads, the second substrate 2 has an upward protrusion 2h.

[0091] Fig. 15B is a cross-sectional view when the substrates are joined. Joining the second substrate 2 having the protrusion 2h results in providing a portion 2r which is continuously recessed in the depth direction of the drawing. Under appropriate conditions of the film thickness of the adhesive 4 when applied and appropriate conditions of the adhesive storage portion, the amount of expansion of the adhesive 4 can reach such an extent that the expansion advances from the bonding interface along the wall to the corner portion on the top surface. As a result, in addition to the concave portion 4k1 continuous with the joining surface, a second concave portion 4k2 can also be formed on the corner portion of the protrusion 2h. The distance of the second concave portion 4k2 along the stacking direction is defined as D2′, and its distance along the extension direction is defined as D1′. As described above, as Fig. 15C As shown, when the protective film 9 is formed, a more preferable R-shape for suppressing the accumulation of bubbles in the ink circulation can be obtained.

[0092] As described above, the use of the present invention can lead to a liquid ejection head that suppresses bubble aggregation and ink flow obstruction in the ink channel by providing an adhesive and providing a protective film (the adhesive covers the corner portion between the bonding substrates in an arc-shaped concave form, and the protective film is continuous along the surface of the substrate, the channel, and the adhesive in the substrate formed by bonding with the adhesive). Example 3

[0093] Application Examples

[0094] The method of manufacturing the bonding substrate 80 according to any of the embodiments can be used as a method of manufacturing a liquid ejection head. Fig.16A and 16B is a schematic diagram showing an example of a printing element that can be used in a liquid jet printing apparatus or the like. Fig.16A is a schematic diagram when the ink supply port side is the top surface, Fig. 16B It is a schematic diagram when the ejection port side for liquid such as ink is the top surface. Fig.17 is a schematic diagram showing an example of a printing element unit, Fig.16A and 16B The printing element and the electrical wiring substrate are electrically connected to the printing element unit. Fig.18 It means when Fig.17 A schematic diagram of an example of when a printing element unit is used as a liquid ejection head of an inkjet system.

[0095] Fig.16A and 16BThe printing element 121 in the embodiment has a three-layer structure of an ink channel substrate 122, an inkjet energy generation substrate 123, and an inkjet substrate 124, which are bonded by an adhesive layer 21. The first substrate 1 according to the embodiment corresponds to the ink channel substrate 122. The portion corresponding to the second substrate 2 is the inkjet energy generation substrate 123. The portion corresponding to the third substrate 3 is the inkjet substrate 124.

[0096] The inkjet substrate 124 is provided with a plurality of inkjet ports 126 for ejecting ink. For them, the ejection ports 8 shown in Embodiment 1 can be used. Ink channels 125 for introducing ink into the plurality of inkjet ports 126 are formed in the ink channel substrate 122. For them, the ink channels 7 shown in Embodiment 1 can be used. The inkjet energy generation substrate 123 is provided with an energy generation element (not shown) that generates energy so as to eject ink from the inkjet ports 126. In order to supply power to the energy generation element, a terminal 24 is also provided, which serves as an electrical connection member for electrical connection with the outside. Such a printing element 121 having a three-layer structure with a space portion 23 is obtained by the method for manufacturing the bonding substrate according to any embodiment.

[0097] Fig.17 The printing element unit 131 is connected by Fig.16A and 16B The printed element 121 and the electrical wiring substrate 132 are formed. Using wire connection, the terminal 24 of the printed element 121 and the lead portion 133 of the electrical wiring substrate 132 are electrically connected to each other through the electrical connection member 134, respectively. The electrical connection member 134 may be any member as long as its main component is any one of metals such as gold, copper, aluminum and silver or an alloy containing at least two of these metals. The electrical connection method is not limited to wire connection, but may be convex connection, lead terminal, NCP or ACF.

[0098] Fig.18 The liquid ejecting head 141 is bonded by Fig.17 The printing element unit 131 is composed of a support member 142, a cover 143 for protecting the printing element unit 131, and a channel member 144 for supplying ink. In the printing element unit 131, two units (131a and 131b) are aligned, and the ink ejection port 126 is on the top side of the drawing. The ink can be ejected by supplying ink to the inkjet printing element unit 131 (through the channel member 144 and the support member 142) and giving an electrical signal to the electrical wiring substrate 132.

[0099] Although the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention 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 ejection head, comprising: A bonding substrate of a first substrate and a second substrate, wherein the first substrate and the second substrate are stacked and bonded with an adhesive, wherein The bonding substrate is configured to have a liquid channel, and the first substrate and the second substrate are connected through the liquid channel. At a bonding position of the first substrate and the second substrate, the adhesive is arranged at a corner portion so as to form an arc shape convex toward the corner portion in its cross section, the corner portion being formed at a position corresponding to the liquid channel, the corner portion being formed by an end surface of the first substrate and a plane of the second substrate, and At the bonding position, a continuous protective film is provided in such a manner as to reach the second substrate through the adhesive disposed on the corner portion from the first substrate.

2. The liquid ejecting head according to claim 1, wherein: When the first substrate and the second substrate are bonded, the adhesive disposed on the corner portion is an extension of the adhesive applied on the bonding surface.

3. The liquid ejecting head according to claim 2, wherein: When the direction in which the first substrate and the second substrate are stacked is defined as the stacking direction, and the direction intersecting the stacking direction and in which the planes of the first substrate and the second substrate extend is defined as the extension direction, on the cross section at the corner portion, the expansion of the adhesive is on the side closer to the corner portion than the line connecting the position farthest from the corner portion in the expansion along the stacking direction and the position farthest from the corner portion in the expansion along the extension direction.

4. The liquid ejecting head according to claim 2 or 3, wherein: At least one of the first substrate and the second substrate is provided with a groove configured to store an adhesive.

5. The liquid ejecting head according to claim 4, wherein: The groove is provided to control the spreading amount of the adhesive at the corner portion.

6. The liquid ejection head according to claim 3, wherein: In the cross section at the corner portion, the extension of the adhesive in the lamination direction and the extension of the adhesive in the extension direction each have a width of at least 5 μm and not more than 15 μm.

7. The liquid ejecting head according to claim 2 or 3, wherein: The protective film has a film thickness of at least 80 nm and not more than 180 nm.

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