LIQUID EJECTION HEAD AND METHOD OF INSPECTING THE LIQUID EJECTION HEAD

A liquid ejection head includes a first substrate having a recessed portion, and a second substrate. An energy generating element that generates energy to eject liquid is in the recessed portion and is placed on a surface of the second substrate that faces the recessed portion. An electrode electrically connected to the energy generating element is formed in an end portion of the energy generating element. Among recessed portion side surfaces, a side surface of the recessed portion close to the electrode is inclined with respect to a joint surface between the first substrate and the second substrate. The end portion of the energy generating element close to the electrode, an end portion of the joint surface close to the electrode, and an end portion of a bottom surface of the recessed portion close to the electrode are located in sequence from a middle of the energy generating element.

BACKGROUND

Field

The present disclosure relates to a liquid ejection head and a method of inspecting the liquid ejection head.

Description of the Related Art

Recording devices that perform recording by ejecting a liquid such as ink are known. Such a recording device has a liquid ejection head, and the liquid is ejected through the ejection port after receiving energy from an energy generating element provided in the liquid ejection head. An example of the energy generating element is a piezoelectric element. A system that pressurizes liquid by using a piezoelectric element is often referred to as a piezo system.

Japanese Patent Laid-Open No. 2021-171971 discloses a piezo-system liquid ejection head.FIG.4schematically illustrates a sectional view of the liquid ejection head disclosed in Japanese Patent Laid-Open No. 2021-171971. As illustrated inFIG.4, the liquid ejection head described in Japanese Patent Laid-Open No. 2021-171971 is formed by a plurality of substrates being joined together. In the liquid ejection head as described above, visible light inspection of the state of electrical connections and the like in an enclosed cavity (also simply referred to as an enclosed space or a recessed portion)12in which the piezoelectric element is housed may not be performed after the substrates are joined together. Accordingly, a near-infrared light microscope, which performs inspection by irradiation with near-infrared light, is used.

As illustrated inFIG.4, when the enclosed cavity12has a shape that widens toward the ejection port, that is, a folding-fan shape, near-infrared light for the inspection scatters in the folding-fan portion. As a result, the reflected near-infrared light does not sufficiently reach the near-infrared light microscope, and accordingly, there is an issue in that proper near-infrared light inspection cannot be performed.

SUMMARY

The present disclosure provides a liquid ejection head that can appropriately be used to inspect inside of an enclosed cavity (recessed portion) in a near-infrared light inspection.

According to an aspect of the present disclosure, a liquid ejection head includes a first substrate having a recessed portion, and a second substrate joined with the first substrate, wherein an energy generating element configured to generate energy for ejecting liquid is housed in the recessed portion of the first substrate and is placed on a surface of the second substrate that faces the recessed portion, wherein an electrode that is electrically connected to the energy generating element is formed in an end portion of the energy generating element, wherein, among side surfaces of the recessed portion, a side surface of the recessed portion close to the electrode is inclined with respect to a joint surface between the first substrate and the second substrate, and wherein the end portion of the energy generating element close to the electrode, an end portion of the joint surface close to the electrode, and an end portion of a bottom surface of the recessed portion close to the electrode are located in sequence from a middle of the energy generating element.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will be described in detail below. It should be noted that the embodiments described below are examples for sufficiently describing the present disclosure and do not particularly limit the scope of the present disclosure.

CONVENTIONAL EXAMPLES

FIG.1is an exploded perspective view of a liquid ejection head100.FIG.2is a sectional view taken along line II-II inFIG.3.FIG.3is a top view of the structure of the vicinity of an energy generating element18. As illustrated inFIGS.1and2, the liquid ejection head100includes a first substrate1, a second substrate2, and a third flow path substrate3. The first substrate1, the second substrate2, and the third flow path substrate3are plate-like members. A plurality of inlet ports11are formed in a first surface of the first substrate1, and recessed portions12are formed in a second surface facing away from the first surface. A plurality of energy generating elements18and a plurality of diaphragms13are formed on a first surface of the second substrate2, and pressure chambers14are formed in a second surface facing away from the first surface. A plurality of flow paths15are formed in a first surface of the third flow path substrate3, and ejection ports16are formed in a second surface so as to face the flow path15in the first surface.

The liquid ejection head100is formed by the first substrate1and the second substrate2being joined to each other with an adhesive agent and the second substrate2and the third flow path substrate3being joined to each other with an adhesive agent. The joint region is referred to as a joint surface17. The individual components including the first substrate1, the second substrate2, and the third flow path substrate3are formed by single crystal substrates of, for example, silicon (Si) by being machined by a semiconductor manufacturing technique, such as etching.

As illustrated inFIG.1, the plurality of ejection ports16arranged in the longitudinal direction are formed in the third flow path substrate3, and the ejection ports16are through-holes through which ink passes. The first substrate1is a plate-like member that forms an ink flow path, and the inlet ports11are formed in the first substrate1as illustrated inFIG.2. The inlet ports11are through-holes formed continuously with the plurality of the ejection ports16of the flow path substrate3via the pressure chambers14formed in the second substrate2.

As illustrated inFIG.2, the recessed portions12of the first substrate1are formed at positions facing the energy generating elements18of the second substrate2, and the recessed portions12fully house the energy generating elements18by the outside portions in contact with the second substrate2being joined via the joint surface17.

As illustrated inFIG.3, the energy generating elements18have electrodes for applying a voltage, and the electrodes up to the electrode ends are housed in the recessed portions. The wiring portions connected to the electrode ends are disposed under the joint surface between the first substrate1and the second substrate2. At this time, it is necessary to confirm that the energy generating elements18have been successfully housed in the recessed portions12. However, the conventional recessed portion illustrated inFIG.2has side surfaces inclined such that the opening decreases toward the bottom surface5of the recessed portion having been formed, from a surface of the first substrate1joined to the second substrate2.

Inspection using a near-infrared light microscope is generally performed to inspect, for example, the inside of silicon (Si) having being joined, but if there is an inclined portion with respect to the direction of irradiation of near-infrared light, an image cannot be obtained because the light scatters, and accordingly, the entire energy generating element18cannot be inspected.

FIG.4illustrates the scattering of light with respect to the direction of irradiation of near-infrared light in the structure in which the side surface of the recessed portion of the conventional liquid ejection head is inclined. InFIG.4, electrodes6are not illustrated. In the case of observation from the upper surface of the first substrate by using a near-infrared light microscope, since the portion from, for example, the end portion of the bottom surface to line b illustrated inFIG.3is shaded due to the shape of the side edge portion of the bottom surface of the recessed portion, the wiring portion connected to the energy generating element and the like cannot be optically inspected.

In addition, inFIG.5, even when the side surface of the recessed portion of the conventional liquid ejection head is orthogonal to the second substrate2, the near-infrared illuminating light is scattered on a curved surface that is present near the bottom surface. InFIG.5, the electrodes6are not illustrated. In the case of observation from the upper surface of the first substrate by using a near-infrared light microscope, since the portion from, for example, the end portion of the bottom surface to line a illustrated inFIG.3is shaded due to the shape of the side edge portion of the bottom surface of the recessed portion, the end portion of the energy generating element, the wiring portion, and the connecting portion thereof cannot be optically inspected.

First Embodiment

FIG.6is a sectional view of a liquid ejection head according to a first embodiment. InFIG.6, the electrodes6are not illustrated. As illustrated inFIG.6, a liquid ejection head101according to the embodiment includes the first substrate1, the second substrate2, and the third flow path substrate3, which are plate-like members. A plurality of inlet ports11are formed in the first surface of the first substrate1, and the recessed portions12are formed in the second surface facing away from the first surface.

A plurality of energy generating elements18are disposed on the first surface of the second substrate2, and pressure chambers14are formed in the second surface facing away from the first surface. The energy generating element may be a heating element or a piezoelectric element. A plurality of flow paths15and a plurality of ejection ports16are formed in the third flow path substrate3. In the liquid ejection head101, the joint surfaces17are formed by the first substrate1and the second substrate2being joined to each other and the second substrate2and the third flow path substrate being joined to each other with, for example, an adhesive agent.

As illustrated inFIG.6, the recessed portion12has side surfaces inclined such that the opening increases toward the bottom surface5of the recessed portion having been formed, from a surface of the first substrate1joined to the second substrate2. The bottom surface5of the recessed portion of the first substrate1can be considered to be optically flat because less light scatters thereon. The bottom surface5of the recessed portion is connected to a curved surface8of the recessed portion12at the end portion21of the bottom surface. The outline of the opening of the first substrate1close to the joint surface with respect to the second substrate2is represented by an end portion22of the joint surface, and the end portion22of the joint surface is closer to the energy generating element18than is the end portion21of the bottom surface.

FIGS.7and8illustrate the positional relationship between the energy generating elements18, the end portions22of the joint surfaces, and the end portion21of the bottom surface.FIG.7is a plan view illustrating the positional relationship.FIG.8is a schematic sectional view illustrating the positional relationship. InFIG.8, the electrodes6are not illustrated. Here, L1, L2, and L3 are defined as follows:L1: Distance (in the long side direction) from the middle E of the energy generating element18to the end portion9including the electrode of the energy generating element18,L2: Distance (in the long side direction) from the middle E of the energy generating element18to the end portion22of the joint surface, andL3: Distance (in the long side direction) from the middle E of the energy generating element18to the end portion21(optically flat portion of the bottom surface) of the bottom surface.

In this case, the following relationship holds in the present disclosure:

In addition, L1′, L2′, and L3′ are defined as follows:L1′: Distance (in the short side direction) from the middle E′ of the energy generating element18to the end including the electrode of the energy generating element18,L2′: Distance (in the short side direction) from the middle E′ of the energy generating element18to the end portion of the joint surface, andL3′: Distance (in the short side direction) from the middle E′ of the energy generating element18to the end of the optically flat portion of the bottom surface of the recessed portion.

In this case, the following relationship holds in the present disclosure:

FIG.9illustrates the scattering of light in the direction of irradiation of near-infrared light by the inclination of the side surfaces of the recessed portion and the curved surface8of the bottom surface portion of the liquid ejection head. InFIG.9, the electrodes6are not illustrated. In the case of observation from the upper surface of the first substrate by using a near-infrared light microscope, for example, the portion up to the end portion c of the bottom surface illustrated inFIG.3can be optically inspected due to the shape of the side edge portion of the bottom surface5of the recessed portion.

In the observation using a near-infrared light microscope under the conditions described above, the scattering of the light by the inclination of the side surfaces of the recessed portion and the curved surface8of the bottom surface portion does not interfere with the observation of the energy generating element. As a result, the connection portion between the energy generating element and the wiring, which is important for the liquid ejection head device, and the portion up to the end portion of the joint surface of an enclosed cavity, which has effects on the amplitude of vibration, can be inspected by using a near-infrared light microscope immediately after the flow path substrate is joined. Accordingly, appropriate feedback can be given to the manufacturing process even when an issue is found.

Second Embodiment

FIG.10is a sectional view of a liquid ejection head102according to a second embodiment. InFIG.10, the electrodes6are not illustrated. As illustrated inFIG.10, recessed portion23has side surfaces formed such that the opening increases toward the bottom surface of the recessed portion having been formed, from the surface of the first substrate1joined to the second substrate2. In the embodiment, only one of the side surfaces of the recessed portion is inclined toward the outer circumference of the head relative to the bottom surface of the recessed portion. The other side surface is recessed vertically from the joint surface toward the bottom surface of the recessed portion, and the bottom surface of the recessed portion of the first substrate that has been formed extends from the side surface portion continuous with the surface joined to the second substrate2to the end portion21of the bottom surface via a curved surface having a certain curvature.

On the side on which the side surface is inclined, the outline of the opening on the joint surface of the first substrate1that joins the second substrate2matches the end portion22of the joint surface, and the end portion22of the joint surface is closer to the energy generating element18than is the end portion21of the bottom surface.

In the structure described above, when one of the end portions of the energy generating element18is observed by using a near-infrared light microscope, the scattering of light by the inclination of the side surfaces of the recessed portion and the curved surface of the bottom surface portion does not interfere with the observation (the inspection of the state in the recessed portion) of the energy generating element.

The embodiment is effective when, for example, an important device is mounted on one side of the energy generating element18and has the advantage of enabling easy formation of the recessed portion and easy design of a region in which light scattering is to be avoided.

Third Embodiment

FIG.11is a sectional view of a liquid ejection head103according to a third embodiment. InFIG.11, the electrodes6are not illustrated. In the embodiment, as illustrated inFIG.11, the first substrate1has a second recessed portion24in which a terminal portion27electrically connected to the energy generating element18is housed. The second recessed portion24also has side surfaces inclined such that the opening increases toward the bottom surface of the recessed portion.

The bottom surface of the recessed portion that has been formed in the first substrate1extends from the side surface portion continuous with the surface joined to the second substrate2to an end portion25of the bottom surface via a curved surface having a certain curvature. The outline of the opening close to the joint surface of the first substrate1that joins the second substrate2matches an end portion26of the joint surface, and the end portion26of the joint surface is closer to the terminal portion27than is the end portion25of the bottom surface.

In observation using a near-infrared light microscope in accordance with the structure described above, it is possible to inhibit the scattering of light by the inclination of the side surface of the recessed portion and the curved surface of the bottom surface portion from interfering with the observation of the terminal.

According to the present disclosure, it is possible to provide a liquid ejection head in which the inside of the enclosed cavity (recessed portion) can be appropriately inspected by near-infrared light inspection.

This application claims the benefit of Japanese Patent Application No. 2022-162136, filed Oct. 7, 2022, which is hereby incorporated by reference herein in its entirety.