Substrate for liquid dispensing head and method for manufacturing the substrate for liquid dispensing head

Abstract

To provide a substrate for a liquid discharge head, which enables liquid to be stably discharged through a discharge hole.SOLUTION: A substrate for a liquid discharge head, which is used for a liquid discharge head, has a discharge hole for discharging liquid from the inside of the substrate to the outside thereof, in which a plurality of scallops which periodically varies a diameter of an inner peripheral surface of the discharge hole in a penetrating direction is formed on the inner peripheral surface. A width in the penetrating direction of the first scallop at the outermost side, of the plurality of scallops is smaller than a width of the second scallop arranged adjacently to the inside with respect to the first scallop, and a depth in a radial direction of the discharge hole of the first scallop is smaller than a depth of the second scallop.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a substrate for a liquid ejection head and a method for manufacturing the substrate for a liquid ejection head.

Background Art

[0002] As a liquid ejection device included in a liquid ejection type recording apparatus typified by an inkjet printer, the one disclosed in Patent Document 1 is known. The liquid ejection device has a structure in which an actuator substrate, a nozzle substrate, etc. are laminated, and includes a liquid flow path, a pressure chamber formed between the substrates, a discharge hole formed in the nozzle substrate, and a piezoelectric element provided on the actuator substrate. The piezoelectric element is provided on a movable film that forms a part of the wall portion of the pressure chamber, and the liquid (typically ink) stored in the pressure chamber is discharged through the discharge hole by the energy generated in the pressure chamber by the operation of the piezoelectric element.

[0003] The above-described discharge hole provided in the nozzle substrate may be formed by a Bosch process that penetrates a silicon substrate, as disclosed in Patent Document 2. According to the Bosch process, by alternately repeating etching and coating, a substantially vertical through-hole can be formed while recesses (called scallops) are formed on the side walls. Here, in the Bosch process, when the opening dimension becomes small (approximately 100 μm or less), as the hole depth increases, it becomes more difficult for ions and radicals to enter, and thus the scallops gradually become smaller. That is, a phenomenon is generally known in which the recess of the scallop at the initial stage of etching becomes large, and the recess of the scallop becomes small as the etching progresses. In particular, when etching is performed at a high rate from the viewpoint of productivity, it is known that the initial scallop becomes large. When implemented by a general manufacturing method, when a resist mask is formed on a silicon substrate and etching is performed, it is known that the above tendency occurs.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-091272 [Patent Document 2] Japanese Patent Publication No. 2021-116309 [Overview of the project] [Problems that the invention aims to solve]

[0005] The drive signal applied to the piezoelectric element consists of a pull signal to expand the pressure chamber and a push signal to contract the pressure chamber. When discharging liquid droplets, a pull-push-pull waveform is generally used. When discharging liquid droplets using this waveform, depending on the type of liquid, meniscus retraction occurs during the pull phase. However, the meniscus behavior at the discharge hole surface can become too large, preventing the meniscus from forming properly at the discharge hole surface, resulting in unstable discharge during the push phase. In particular, as mentioned above, if the initial scallop is large, a large angle in the scallop's recesses makes it difficult to form a meniscus. The meniscus may fall into the second or third recess of the scallop, causing the meniscus to form diagonally and preventing stable discharge.

[0006] Furthermore, this meniscus condition sometimes resulted in unstable dispensing, not only when using piezoelectric elements for dispensing, but also when driving the heater to boil the liquid and dispense it from the dispensing port. This is because the surface state of the liquid at the moment of dispensing becomes unstable, and especially when the scallop's recess is large, the meniscus vibration during refilling after dispensing becomes unstable.

[0007] The objective of the present invention is to provide a technology that enables stable liquid discharge from a discharge port. [Means for solving the problem]

[0008] To achieve the above objective, the substrate for the liquid discharge head of the present invention is A substrate used in a liquid discharge head, having discharge holes for discharging liquid from the inside to the outside of the substrate, wherein a plurality of scallops are formed on the inner circumferential surface of the discharge holes, causing the diameter of the inner circumferential surface to change periodically in the direction of penetration, The width in the through-direction of the first scallop, which is the outermost of the plurality of scallops, is narrower than the width of the second scallop adjacent to the first scallop on the inner side. The width of the first scallop is narrower than the width of the third scallop, which is located on the inner side of the second scallop. The radial depth of the discharge hole of the first scallop is shallower than the depth of the second scallop. Ku, The depth of the first scallop is shallower than the depth of the third scallop. The third scallop becomes narrower in width and shallower in depth as it approaches the inner side. Characterized by 。 [Effects of the Invention]

[0009] According to the present invention, stable liquid discharge from the discharge port becomes possible. [Brief explanation of the drawing]

[0010] [Figure 1] This is a scalloped cross-section of a typical Bosch process. [Figure 2] This is an explanatory diagram of the drive signal applied to the piezoelectric element. [Figure 3] This is a schematic diagram illustrating the difference in the method of setting the meniscus between a conventional example and an embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view showing the general configuration of the substrate for the liquid discharge head of Example 1. [Figure 5] This is an explanatory diagram of the substrate configuration and process flow of Embodiment 1 of the present invention. [Figure 6] This is the discharge hole formation flow for Example 1 of the present invention. [Figure 7] This is a cross-sectional view of the liquid discharge port of Example 1 and Example 2 of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, exemplary detailed descriptions of embodiments for implementing the present invention will be given based on examples with reference to the drawings. Note that dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment should be appropriately changed according to the configuration of the device to which the invention is applied and various conditions. Also, not all combinations of the features described in this embodiment are essential for the solution means of the present invention. The components described in the embodiment are merely examples and are not intended to limit the scope of the present invention thereto.

[0012] <Example 1> The substrate according to an embodiment of the present invention is used for a liquid ejection head, and the liquid ejection head is a member included in a recording device such as an inkjet printer. In an inkjet printer, the liquid ejection head is used as an inkjet recording head for recording a desired image on a recording material by ejecting ink as an image recording liquid onto the recording material. The recording device is also provided with an ink tank as a liquid storage unit for storing the liquid supplied to the liquid ejection head, a conveyance mechanism for a recording material such as a sheet which is an object to be recorded, and the like.

[0013] (Configuration of Substrate for Liquid Ejection Head) FIG. 4 is a schematic cross-sectional view schematically showing a cross-sectional configuration of a substrate 4 for a liquid ejection head (hereinafter, substrate 4) according to Example 1 of the present invention. The substrate 4 is generally a structure in which an actuator substrate 41 and a nozzle substrate 42 are laminated. The actuator substrate 41 generally has a configuration in which a first flow path substrate 411 and a second flow path substrate 412 are laminated. Each substrate is joined via an adhesive layer.

[0014] The substrate 4 has a supply port 40 through which ink is supplied on one surface (the first surface), and discharge holes 49 for discharging ink are formed on the other surface (the second surface) on the opposite side. An ink flow path (liquid flow path) connects between the supply port 40 and the discharge holes 49. The supply port 40 and the discharge holes 49 are located at different positions in the surface direction of the substrate 4, and when viewed in the thickness direction of the substrate 4 (the direction perpendicular to the surface of the substrate 4), the ink flow path has a flow path configuration in which the supply port 40 and the discharge holes 49 do not overlap each other. The ink flow path communicates from the supply port 40 to the discharge holes 49 through the first flow path 47, the second flow path 43, and the third flow path 48, and is configured to extend in a bent manner in the direction perpendicular to and parallel to the surface of the substrate 4 inside the substrate 4. Specifically, the first flow path 47 extending perpendicularly to the surface of the substrate 4 from the supply port 40 is formed by the through holes 471 and 472. Also, the second flow path 43 extending (spreading) parallel to the surface of the substrate 4 is formed by the cavity 431 and the nozzle substrate 42. Then, a flow path extending perpendicularly to the surface of the substrate 4 again is formed from the third flow path 48, which is a liquid discharge flow path having a larger diameter than the discharge holes 49, to the discharge holes 49.

[0015] Note that the flow path configuration shown here is merely an example. For example, a flow path configuration may be employed that includes a plurality of flow path portions extending in a direction intersecting the thickness direction of the substrate 4 (the direction parallel to the surface of the substrate 4). Also, a flow path configuration may be used that includes branch flow paths extending so as to branch for each of the plurality of discharge holes 49.

[0016] The through-hole 471 is provided through the first flow channel substrate 411 of the actuator substrate 41, and the opening on the side opposite to the side connected to the through-hole 472 forms the supply port 40. The through-hole 472 is provided so as to penetrate the second flow channel substrate 412 of the actuator substrate 41 at a position overlapping with the through-hole 471. The second flow channel 43 is formed by a cavity 431, which is a recess provided on the joint surface between the second flow channel substrate 412 of the actuator substrate 41 and the nozzle substrate 42, and the nozzle substrate 42 that covers the cavity 431. The through-hole 472 opens at the bottom of the cavity 431. The third flow channel 48 is a flow channel formed by a through-hole that is connected to the discharge hole 49 and penetrates the nozzle substrate 42. The third flow channel 48 opens in the nozzle substrate 42 in the portion that covers the cavity 431 of the second flow channel substrate 412 (the portion that forms the second flow channel 43). The discharge hole 49 extends perpendicularly to the surface of the nozzle substrate 42, connected to the third flow path 48, and opens on the surface of the substrate 4 (nozzle substrate 42) facing the object to be discharged (the second surface).

[0017] The actuator substrate 41 includes a pressure chamber 432, a vibrating membrane (movable membrane) 45 that forms a partition wall between the pressure chamber 432 and the cavity 431, and a piezoelectric element 44 provided on the pressure chamber 432 side of the vibrating membrane 45. The pressure chamber 432 is formed by a recess provided on the joint surface of the first flow channel substrate 411 with the second flow channel substrate 412, and the second flow channel substrate 412 covering this recess. The portion of the second flow channel substrate 412 that covers the recess forms the vibrating membrane 45, and the piezoelectric element 44 is mounted thereon. The third flow channel 48 of the nozzle substrate 42 opens relative to the cavity 431 at a position facing the vibrating membrane 45.

[0018] The ink supplied from the ink tank (not shown) passes through the ink channel from the supply port 40. The ink is ejected from the ejection hole 49 upon receiving energy generated by the piezoelectric element 44. The ink ejected from the ejection hole 49 adheres to the image recording surface of the recording material positioned opposite the ejection hole 49, forming (recording) an image on the recording material.

[0019] In this embodiment, a substrate configuration using a piezoelectric element as the energy generating element in the actuator section of the substrate for the liquid discharge head is illustrated; however, a substrate configuration using other pressure generating means such as an electroheat exchange element may also be used.

[0020] The substrate 4 according to this embodiment 1 is characterized by the inner circumferential shape of the ejection hole 49, as shown in the enlarged view of the ejection hole 49 in Figure 4. Specifically, the inner circumferential surface of the ejection hole 49 formed by the Bosch process has a shape in which multiple recesses are arranged in the direction of penetration by periodically changing its diameter in the direction of penetration, i.e., multiple scallops are formed. In this embodiment, the ejection hole 49 is configured such that the multiple scallops forming its inner circumferential surface satisfy a predetermined relationship between the depth of the ejection hole 49 in the radial direction and the width of the ejection hole 49 in the direction of penetration. The details will be described later.

[0021] Figures 5(a) to 5(c) are schematic cross-sectional views illustrating the manufacturing process of a liquid discharge head substrate according to an embodiment of the present invention. Figure 5(a) shows the actuator substrate 41, and Figure 5(b) shows the nozzle substrate 42. Figure 5(c) shows the assembled liquid discharge head substrate 4 according to this embodiment, formed by laminating and bonding the actuator substrate 41 and the nozzle substrate 42.

[0022] As shown in Figures 5(a) and 5(b), the actuator substrate 41 and the nozzle substrate 42 are prepared separately, and the substrate 4 is formed by joining them together. Note that the configuration shown in Figure 5(c) is the inverted version of the configuration shown in Figure 4.

[0023] First, as shown in Figure 5(a), an actuator substrate 41 is prepared. The actuator substrate 41 is made of, for example, a silicon substrate and has multiple cavities 431, 432 and through holes 471, 472. In this embodiment, a piezoelectric element 44 is formed in the actuator portion of the actuator substrate 41. The actuator substrate 41 supports the vibrating membrane 45. The vibrating membrane 45 forms the top wall of the cavity 431 and partitions the cavity 431. The piezoelectric element 44 is placed on the vibrating membrane 45. Interlayer films and wiring layers are formed on the actuator substrate 41 so that the actuator portion can be driven.

[0024] Next, as shown in Figure 5(b), the nozzle substrate 42 is prepared. In this embodiment, a third channel 48, which serves as a liquid discharge channel, is formed on the nozzle substrate 42 by dry etching. In addition, in this embodiment, an oxide film 46 is formed on the side of the nozzle substrate 42 opposite to the liquid discharge channel 48.

[0025] Then, as shown in Figure 5(c), the actuator substrate 41 and the nozzle substrate 42 are joined together. Subsequently, a resist mask 61 is formed on the surface of the oxide film 46, and the discharge holes 49 are formed by dry etching (see Figure 6; details will be described later), thereby forming the substrate 4 for the liquid discharge head of this embodiment 1.

[0026] The nozzle substrate 42 is bonded to the back surface of the actuator substrate 41 (the side of the first flow channel substrate 412 on which the cavity 431 is provided). The nozzle substrate 42 is made of, for example, an SOI substrate in which an oxide film 46 and silicon are bonded, and is bonded to the back surface of the actuator substrate 41, and together with the actuator substrate 41 and the vibrating membrane 45, it defines the cavity 431 (second flow channel 43). The nozzle substrate 42 has a third flow channel 48 that overlaps with the cavity 431, and an ejection hole 49 is formed connected to it. The ejection hole 49 penetrates the nozzle substrate 42, and the upstream opening of the ink flow channel faces the cavity 431 via the third flow channel 48. Therefore, when the volume of the cavity 431 (second channel 43) changes due to the driving of the piezoelectric element 44, the liquid accumulated in the cavity 431 passes through the third channel 48 and is discharged from the discharge hole 49.

[0027] A piezoelectric element 44 is arranged on the vibrating membrane 45, forming a piezoelectric actuator. The piezoelectric element 44 is formed in a position facing the cavity 431, with the vibrating membrane 45 in between. That is, the piezoelectric element 44 is formed to be in contact with the surface of the vibrating membrane 45 opposite to the cavity 431. The vibrating membrane 45 is composed of a first electrode film formed on the vibrating membrane 45, a second electrode film arranged on the first electrode film, and a piezoelectric layer sandwiched between them, and has the characteristic of being deformable in the direction facing the cavity 431.

[0028] Figure 2 is an explanatory diagram of the drive signal (Pull-Push-Pull waveform) applied to the piezoelectric element. Note that in Figure 2, the flow path configuration of the substrate 4 is shown in a simpler form than in Figure 4, etc. When a drive voltage is applied to the piezoelectric element 44 from a drive IC (not shown), it deforms due to the inverse piezoelectric effect, deforming the vibrating membrane 45. The drive signal applied to the piezoelectric element 44 consists of a pull signal (Pull) that expands the pressure chamber 432 by deforming the vibrating membrane 45, and a push signal (Push) that contracts the pressure chamber 432. When discharging liquid droplets, a Pull-Push-Pull waveform is generally used. When discharging liquid droplets using this waveform, depending on the type of liquid, meniscus retraction occurs during the Pull phase.

[0029] By applying a pull-push-pull waveform drive voltage, the cavity 431 expands and contracts, causing a volume change and pressurizing the liquid inside the cavity 431. Specifically, as the cavity 431 expands, liquid is drawn in, and a meniscus M forms on the surface of the discharge hole 49. Subsequently, as the cavity 431 contracts, the pressurized liquid passes through the third channel 48 and is discharged from the discharge hole 49 as a minute droplet D.

[0030] (Conventional discharge port configuration) Figure 1 is a schematic cross-sectional view showing the configuration of scallops (recesses) 12 that make up the inner surface of an ejection hole 13 when the ejection hole 13 is formed in a Si substrate 11 by a general Bosch process. In the Bosch process, the ejection hole 13 is gradually formed by repeatedly creating scallops 12 from the ejection side toward the cavity side. Here, in a general Bosch process, as mentioned above, the size of the formed scallops 12 gradually decreases as the hole depth increases, making it more difficult for ions and radicals to enter. In other words, the size of the scallops 12 is larger in the initial stages of etching, and decreases as etching progresses.

[0031] Here, it has been found that in droplet ejection, when the cavity expands and liquid is drawn in, the shape of the scallops on the inner surface of the ejection hole affects the meniscus state, and in particular, the larger the scallops on the outermost surface, the less likely a meniscus is to form.

[0032] Figure 3(a) is a schematic cross-sectional view showing the morphology of the meniscus M formed in the ejection hole 13 of a conventional example. As described above, when the meniscus is retracted during the pull phase of signal driving of a piezoelectric element, the meniscus behavior at the ejection hole surface can become too large, preventing the meniscus from forming properly at the ejection hole surface, which can lead to unstable ejection during the push phase. In particular, as shown in Figure 3(a), when the outermost scallop 12 formed in the initial stages of etching is larger than the inner scallop 12, a large angle of the scallop 12 makes it difficult to form the meniscus M. As a result, the position of the meniscus M becomes unstable, and the meniscus M may fall onto the second or third scallop 12, causing the meniscus M to be stretched at an angle, which can lead to unstable ejection.

[0033] (Configuration of the discharge port in the embodiment of the present invention) Figure 7(a) is a schematic cross-sectional view illustrating the cross-sectional configuration of the discharge hole 49 in Embodiment 1 of the present invention, and Figure 7(b) is a schematic cross-sectional view illustrating the cross-sectional configuration of the discharge hole 49 in Embodiment 2 of the present invention. As shown in Figures 7(a) and 7(b), the inner circumferential surface of the discharge hole 49 in this embodiment is composed of a plurality of scallops (recessed portions that are concave in the radial direction of the discharge hole 49) arranged in the direction through the discharge hole 49, with their diameters periodically changing in the direction through the discharge hole 49. The first scallop 50a, located furthest to the discharge side (furthest to the outside of the substrate 4), is formed to be smaller than the second scallop 50b, which is adjacent to the first scallop 50a on the cavity side (inside the substrate 4).

[0034] A single scallop can be defined as the region between two small-diameter peak positions, which are positioned on either side of a large-diameter peak position, in the inner circumferential shape of the discharge hole 49, where expansion and contraction of diameter are repeated in the through-direction. The distance between the two small-diameter peak positions in the through-direction of the discharge hole 49 can be defined as the width L1 of a single scallop. Furthermore, the expansion peak position can be defined as the deepest position in a single scallop, and the difference between this deepest position and the small-diameter peak positions flanking it can be defined as the depth L2 of the scallop. Note that the cross-sections of the discharge holes shown in Figures 1, 3, 4, 6, and 7 are cross-sections that include the central axis of the discharge hole.

[0035] In this embodiment, the discharge hole 49 is configured such that the width L1a of the first scallop 50a is narrower than the width L1b of the second scallop 50b, and the depth L2a of the first scallop 50a is shallower than the depth L2b of the second scallop 50b. This configuration results in a relative increase in the shape stability of the meniscus in the first scallop 50a compared to that in the second scallop 50b. As a result, the meniscus formation position is stabilized in the first scallop 50a.

[0036] Furthermore, in this embodiment, the discharge hole 49 is configured such that the first scallop 50a is smaller than the third scallops 50c to 50e, which are located on the interior side of the substrate 4, compared to the second scallop 50b. That is, the width L1a of the first scallop 50a is narrower than the widths L1c to L1e of the third scallops 50c to 50e, and the depth L2a of the first scallop 50a is shallower than the depths L2c to L2e of the third scallops 50c to 50e. With this configuration, the shape stability of the meniscus in the first scallop 50a is relatively increased throughout the entire discharge hole 49.

[0037] Furthermore, in this embodiment, the ejection hole 49 is configured such that the ratio of the depth L2a to the width L1a in the first scallop 50a (L1 / L2) is L1 / L2 ≥ 4. This configuration further enhances the stability of meniscus formation. As disclosed in Patent Document 2, satisfying the condition L1 / L2 ≥ 4 reduces ink residue, especially in the ejection of water-based inks, and also reduces the occurrence of ejection failures due to ink drying at steps.

[0038] Furthermore, in this embodiment, the discharge hole 49 is configured such that the ratio of the depth L2 to the width L1 of the multiple scallops forming its inner circumferential surface, excluding the first scallop 50a, is L1 / L2 < 4. This configuration makes it possible to relatively improve the shape stability of the meniscus in the first scallop 50a across the entire discharge hole 49.

[0039] Figure 3(b) shows the shape of the meniscus M formed in the discharge hole 49 of Embodiment 1 of the present invention. This is a schematic cross-sectional view. Figure 3(c) is a schematic cross-sectional view showing the shape of the meniscus M formed in the discharge hole 49 of Embodiment 2 of the present invention. As shown in Figures 3(b) and 3(c), according to this embodiment, the position of the meniscus M is stable and the discharge of droplets is stable.

[0040] (Formation flow of discharge holes in embodiments of the present invention) Figures 6(a) to 6(d) show the detailed formation flow of the discharge hole 49 in Embodiment 1 of the present invention.

[0041] First, as shown in Figure 6(a), a resist mask 61 for opening liquid ejection holes 49 is formed on the surface of the oxide film 46 by photolithography (etching mask formation step).

[0042] Next, as shown in Figure 6(b), the oxide film 46 is removed by dry etching (oxide film removal step). The thickness of the oxide film 46 is formed to a thickness of 0.2 μm to 2.0 μm, which is preferable. The thickness is between 0.5 μm and 1.0 μm. Reactive ion etching can and is preferred as a method for etching the oxide film 46 to form openings. For example, a mixed gas of C4F8 gas, CF4 gas, and Ar gas can be used as the gas for etching, and this can be carried out by reactive ion etching using an ICP (inductively coupled plasma) apparatus.

[0043] However, reactive ion etching equipment with other types of plasma sources may also be used. For example, ECR (electron cyclotron resonance) equipment and NLD (magnetic neutral line discharge) plasma equipment can also be used.

[0044] As an example of the conditions for oxide film etching, for instance, the gas pressure is controlled in the range of 0.1 Pa to 5.0 Pa, the gas flow rate in the range of 10 sccm to 1000 sccm, the coil power in the range of 1000 W to 2000 W, and the platen power in the range of 300 W to 500 W. Preferably, by setting the C4F8 gas flow rate in the range of 30 sccm to 100 sccm, etching byproducts and deposit film 62 are more easily formed at the bottom of the opening.

[0045] Furthermore, when the oxide film 46 is etched under the etching conditions described above, the angle θ of the opening end of the oxide film 46 (the peripheral edge surrounding the opening of the discharge hole 49) can be inclined to form an inclined surface 46a with respect to the surface of the substrate 4. The inclined surface 46a is an inclined peripheral surface surrounding the opening of the discharge hole 49 and is a tapered surface that widens in diameter as it moves away from the surface of the nozzle substrate 42 of the substrate 4 covered by the oxide film 46 toward the outside of the substrate. By forming such an inclined surface 46a, it is possible to easily form a liquid meniscus at the opening edge of the discharge hole 49. It is preferable that the angle θ between the inclined surface 46a, which is the end of the oxide film 46, and the surface of the substrate 4 (nozzle substrate 42) be 75° or more and less than 90°.

[0046] In Example 1 of the present invention, the oxide film 46 was removed by reactive ion etching. A mixed gas of C4F8 gas, CF4 gas, and Ar gas was used as the etching gas. The oxide film etching conditions were controlled as follows: gas pressure of 0.3 Pa, gas flow rate of 500 sccm, coil power of 1500 W, and platen power of 400 W. The angle θ between the inclined surface 46a at the open end of the oxide film and the surface of the substrate 4 was approximately 80°.

[0047] Next, as shown in Figure 6(c), the ejection holes 49 are penetrated by reactive ion etching, which involves alternating etching and coating (ejection hole formation process). With etching byproducts and deposit film 62 formed at the bottom of the opening after oxide film etching, Si dry etching was performed using the Bosch process. As a result, as shown in Figure 6(c), the Si is etched after the etching byproducts and deposit film 62 are removed during the first Si etching. Therefore, the width L1 and depth L2 of the first outermost scallop 63 are formed smaller than the width L1 and depth L2 of subsequent scallops. As a result, the inner circumferential shape of the discharge hole 49 was made such that the meniscus is less likely to break when liquid is drawn in during the pull process, thus achieving stable discharge. In other words, even when performing high-rate etching conditions for high productivity, it became possible to form a liquid discharge hole with a shape that facilitates the formation of a meniscus with a small initial scallop width and depth.

[0048] For silicon etching conditions, SF6 gas was used as the etching gas and C4F8 gas as the coating gas in the Bosch process. It is preferable to control the gas pressure in both the etching and coating steps within the range of 0.1 Pa to 50 Pa and the gas flow rate within the range of 50 sccm to 1000 sccm. In this embodiment, the gas pressure in both the etching and coating steps was controlled at 10 Pa and the gas flow rate at 500 sccm. By controlling the etching step time within the range of 5 to 20 seconds and the coating step time within the range of 1 to 10 seconds, a highly vertical flow path can be formed. For a more preferable high rate, the gas pressure can be increased to 10 Pa or higher, the gas flow rate to 500 sccm or higher, and the etching step time can be increased by 5 seconds or more. In this embodiment, the etching step time was controlled to 10 seconds and the coating step time to 5 seconds.

[0049] Through the above process, an ejection hole 49 is formed that penetrates the nozzle substrate 42, as shown in Figure 6(d). The scallop shape formed in the ejection hole 49 by silicon etching is such that the relationship between the width L1 and depth L2 of the surface scallop 50a is greater than the L1 / L2 of the surface scallop 50b below it.

[0050] Here, more preferably, the L1 / L2 value of the surface scallop 50a is L1 / L2 ≥ 4, and the L1 / L2 value of the surface scallops 50b to 50e below the surface is L1 / L2 < 4. The larger L1 / L2, the wider and shallower the scallop, so the surface becomes closer to flat, which is advantageous in terms of forming a meniscus.

[0051] In this embodiment, the surface irregularities of the outermost meniscus 50a were L1 / L2 = 4.3, while the scallops 50b to 50e below it had an L1 / L2 < 4. Note that the number and shape of the scallops 50 shown in each figure are merely illustrative examples and are not limited to the configurations shown in each figure.

[0052] According to the liquid discharge head substrate 4 obtained through the above process, the meniscus behavior in the discharge hole 49 is stabilized, and stable discharge can be achieved.

[0053] <Example 2> This section describes a substrate for a liquid discharge head according to Embodiment 2 of the present invention. Here, we will focus on the differences between Embodiment 2 and Embodiment 1.

[0054] As shown in Figures 3(c) and 7(b), the substrate for a liquid discharge head according to Embodiment 2 of the present invention has a configuration in which the substrate surface through which the discharge holes open to the outside is not covered with an oxide film, unlike the substrate for a liquid discharge head in Embodiment 1. The manufacturing process is the same as in Embodiment 1 up to the point where the discharge holes 49 are drilled through using the Bosch process. In Embodiment 2, after forming the discharge holes 49 using the same process as in Embodiment 1, a step is added to remove the oxide film from the substrate surface.

[0055] Thus, even without an oxide film on the substrate surface, the width L1a and depth L2a of the outermost scallop 50a are smaller than the width and depth of the other scallops 50b to 50e. A crack is formed. Therefore, similar to the substrate in Example 1, the meniscus can be made less likely to break when liquid is drawn in during the pull process, and stable discharge can be achieved.

[0056] The liquid ejection head substrate of Example 2 allows for a different contact angle of the liquid at the ejection hole compared to the liquid ejection head substrate of Example 1. Specifically, in the substrate of Example 1, where an oxide film 46 is coated over the ink used as the ejection liquid, the contact angle is lower on the oxide film 46 and higher on the surface of the silicon nozzle substrate 42. The required contact angle may differ depending on the type of ejection liquid, and this can be addressed by selectively forming the oxide film 46. [Explanation of Symbols]

[0057] L1…Scallop width of liquid discharge hole, L2…Scallop depth of liquid discharge hole, 41…Actuator substrate, 42…Nozzle substrate, 431…Cavity, 44…Piezoelectric element, 45…Vibrating film, 46…Oxide film, 471, 472…Through holes, 48…Liquid discharge channel, 49…Discharge hole, 61…Resist mask, 62…Etching by-products and deposit film, 50a…Scallop at the outermost surface of the discharge hole, θ…Angle of the oxide film edge

Claims

1. A substrate used in a liquid discharge head, having discharge holes for discharging liquid from the inside to the outside of the substrate, wherein a plurality of scallops are formed on the inner circumferential surface of the discharge holes, causing the diameter of the inner circumferential surface to change periodically in the direction of penetration, The width of the first scallop, which is the outermost of the plurality of scallops, in the through-direction is narrower than the width of the second scallop, which is adjacent to the first scallop on the inner side. The width of the first scallop is narrower than the width of the third scallop, which is located on the inner side of the second scallop. The radial depth of the discharge hole of the first scallop is shallower than the depth of the second scallop. The depth of the first scallop is shallower than the depth of the third scallop. The third scallop is characterized in that the width becomes narrower and the depth becomes shallower as it approaches the inner side, in a substrate for a liquid discharge head.

2. A substrate for use in a liquid discharge head, having discharge holes for discharging liquid from the inside of the substrate to the outside, wherein a plurality of scallops are formed on the inner circumferential surface of the discharge holes, the diameter of the inner circumferential surface being periodically changed in the direction of penetration, The width of the first scallop, which is the outermost of the plurality of scallops, in the through-direction is narrower than the width of the second scallop, which is adjacent to the first scallop on the inner side. The radial depth of the discharge hole of the first scallop is shallower than the depth of the second scallop. When the width is L1 and the depth is L2, The ratio of the depth to the width (L1 / L2) in the first scallop is L1 / L2 ≥ 4, A substrate for a liquid discharge head, characterized in that the ratio of the scallops among the plurality of scallops, excluding the first scallop, is L1 / L2 < 4.

3. A substrate for use in a liquid discharge head, having discharge holes for discharging liquid from the inside of the substrate to the outside, wherein a plurality of scallops are formed on the inner circumferential surface of the discharge holes, the diameter of the inner circumferential surface being periodically changed in the direction of penetration, The width of the first scallop, which is the outermost of the plurality of scallops, in the through-direction is narrower than the width of the second scallop, which is adjacent to the first scallop on the inner side. The radial depth of the discharge hole of the first scallop is shallower than the depth of the second scallop. In a liquid discharge head substrate which is a structure in which a plurality of substrates including a nozzle substrate through which the discharge hole passes are stacked, The nozzle substrate is formed from silicon, The surface of the nozzle substrate through which the outer opening of the discharge hole is located is coated with an oxide film. The substrate for a liquid discharge head, characterized in that the peripheral edge of the oxide film surrounding the opening of the discharge hole has an inclined circumferential surface that widens in diameter towards the outer side.

4. The substrate for a liquid discharge head according to claim 3, characterized in that the angle of the inclined circumferential surface with respect to the surface of the nozzle substrate is 75° or more and less than 90°.

5. A liquid flow path leading to the discharge hole, A vibrating membrane that constitutes a part of the partition wall forming the liquid flow path, A pressure chamber separated from the liquid flow path by the vibrating membrane, A piezoelectric element provided on the vibrating membrane, Furthermore, A substrate for a liquid discharge head according to any one of claims 1 to 4, characterized in that the piezoelectric element is deformed to change the volume of the liquid flow path, thereby generating pressure to discharge the liquid from the discharge hole.

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