Liquid dispensing head and method for manufacturing the same

Abstract

This invention provides a liquid dispensing head that enhances reliability against liquids by improving the liquid resistance of a common flow path with a high total liquid flow rate, without compromising the dispensing function of the discharge port. [Solution] A liquid discharge head comprising a laminated substrate formed by stacking a plurality of substrates, each including a nozzle substrate having a plurality of nozzles including discharge ports for discharging liquid, a flow path substrate having individual flow paths for supplying liquid to the nozzles and a common flow path that fluidly communicates with the plurality of individual flow paths, and a protective film made of at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide, which is continuously provided on the inner wall surface of the fluid path from the common flow path to the discharge port, wherein the thickness of the protective film in the common flow path is greater than the thickness of the protective film in the nozzle.

Description

Technical Field

[0001] The present invention relates to a liquid ejection head.

Background Art

[0002] In an inkjet recording head which is an example of a liquid ejection head, there is a structure in which a flow path including a nozzle opening (discharge port) for discharging a liquid is provided and a laminated substrate laminated via an adhesive. For example, a piezoelectric actuator which is a piezoelectric element is provided on one surface side of a substrate provided with a pressure chamber communicating with the discharge port, and by driving this piezoelectric actuator to deform a diaphragm and generate a pressure change in the pressure generation chamber, ink droplets are discharged from the discharge port.

[0003] Patent Document 1 discloses a configuration in which reliability is enhanced by providing a protective film having liquid resistance on a substrate formed of silicon. In Patent Document 1, a material composed of tantalum oxide, hafnium oxide, and zirconium oxide formed by an atomic layer deposition method is continuously provided on the inner wall of the flow path.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Among the flow paths provided in the laminated substrate, in a common flow path that fluidly communicates with a plurality of nozzles and supplies a liquid, the total flow rate of the liquid is larger than that of the nozzles. Therefore, it is preferable that the protective film is thick enough to sufficiently obtain the liquid resistance of the substrate having the common flow path.

[0006] In the configuration disclosed in Patent Document 1, where a protective film of uniform thickness is continuously provided on the inner wall of the flow path from the common flow path to the nozzle, increasing the thickness of the protective film to improve the liquid resistance of the common flow path results in an increased thickness of the protective film at the nozzle and discharge port. This can lead to instability in the opening width of the discharge port or even blockage of the discharge port.

[0007] Furthermore, if the protective film in the pressure chamber where the piezoelectric actuator is installed in the laminated substrate is made too large, the energy efficiency of the piezoelectric actuator will decrease.

[0008] In view of the above problems, the present invention aims to provide a liquid discharge head that enhances reliability against liquids by improving the liquid resistance of a common flow path with a large total liquid flow rate without impairing the discharge function of the discharge port. [Means for solving the problem]

[0009] An aspect of the present invention that solves the above problems is a liquid discharge head comprising a laminated substrate in which a plurality of substrates are stacked, each including a nozzle substrate provided with a plurality of nozzles including discharge ports for discharging liquid, a flow channel substrate having individual flow channels for supplying liquid to the nozzles and a common flow channel that is in fluid communication with the plurality of individual flow channels, and a protective film made of at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide, which is continuously provided on the inner wall surface of the fluid path from the common flow channel to the discharge port, wherein the film thickness of the protective film in the common flow channel is greater than the film thickness of the protective film in the nozzle. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a liquid discharge head with enhanced reliability against liquids by improving the liquid resistance of a common flow path with a large total liquid flow rate without impairing the discharge function of the discharge port. [Brief explanation of the drawing]

[0011] [Figure 1]A diagram showing an example of a liquid dispensing device and a diagram showing an example of a liquid dispensing head. [Figure 2] A perspective view showing a liquid discharge substrate according to a first embodiment of the present invention. [Figure 3] An enlarged cross-sectional view of the main part of a liquid discharge substrate according to the first embodiment of the present invention. [Figure 4] A cross-sectional view showing a method for manufacturing a liquid discharge substrate according to a first embodiment of the present invention. [Figure 5] An enlarged cross-sectional view of the main part of a liquid discharge substrate according to a second embodiment of the present invention. [Figure 6] A cross-sectional view showing a method for manufacturing a liquid discharge substrate according to a second embodiment of the present invention. [Figure 7] An enlarged cross-sectional view of the main part of a liquid discharge substrate according to a third embodiment of the present invention. [Figure 8] A plan view and a cross-sectional perspective view showing a liquid discharge substrate according to a fourth embodiment of the present invention. [Figure 9] A plan view and a cross-sectional view showing a liquid discharge substrate according to a fourth embodiment of the present invention. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are illustrative examples of the present invention and are not intended to limit the scope of the invention to these embodiments. Furthermore, while the following description uses a liquid ejection head using a piezoelectric element as an example, the present invention can also be applied to liquid ejection heads using a heat-generating resistance element or an electrothermal conversion element. In addition, the ejected liquid is not limited to ink, as long as it can be ejected from the liquid ejection head.

[0013] In the following description and drawings, the Z direction means the direction in which the silicon substrate described later is stacked, or the depth direction of the individual flow paths or holes described later. It is also the direction in which liquid is discharged from the discharge port described later. An arbitrary direction orthogonal to the Z direction is defined as the X direction. A direction orthogonal to both the Z direction and the X direction is defined as the Y direction. The diameter refers to the dimension in the XY plane, and the radial direction refers to the direction from the central axis of the hole to the outer periphery of the hole in the XY plane. In the case of a hole or through-hole with a circular cross-section, the diameter is equal to the diameter in the XY plane.

[0014] (Liquid ejection device) FIG. 1(a) is a schematic perspective view for explaining the schematic configuration of a liquid ejection device 1000 according to an embodiment of a liquid ejection device to which the present disclosure is applicable.

[0015] The liquid ejection device 1000 of the present embodiment is of a one-pass type that records an image on the recording medium 4 with a single movement of the recording medium, and the discharge ports are arranged so as to correspond to the entire width of the recording medium 4. The liquid ejection device 1000 is provided with a liquid ejection head 2, for example, detachably.

[0016] The recording medium 4 is conveyed in the direction of arrow A by the conveyance unit 3, and recording is performed by the liquid ejection head 2. Also, in order to perform color recording, eight liquid ejection heads 2Ca, 2Cb, 2Ma, 2Mb, 2Ya, 2Yb, 2Ka, and 2Kb that eject inks of cyan (C), magenta (M), yellow (Y), and black (K) as liquids are used. When it is not necessary to distinguish the liquid ejection heads of each color, they are collectively referred to as "liquid ejection head 2". The liquid ejection head related to the present disclosure can be implemented in any form including the example of FIG. 2, and other forms are not limited.

[0017] (Configuration of liquid ejection head) FIG. 1(b) is a perspective view of a liquid ejection head 2 as an example to which the present disclosure is applicable. The liquid ejection head 2 has a plurality of liquid ejection substrates 1 having nozzles 140 and ejection ports 141 on a liquid ejection head body 2a. The ink to be ejected is supplied from a liquid tank (not shown) to the liquid ejection substrate 1 through a common supply port (not shown) of the liquid ejection head body 2a.

[0018] <First Embodiment> (Description of the Configuration of the Liquid Ejection Substrate) FIG. 2(a) is a perspective view of the liquid ejection substrate 1, and FIG. 2(b) is an exploded perspective view of the liquid ejection substrate 1 corresponding to FIG. 2(a).

[0019] The liquid ejection substrate 1 of the present embodiment is a laminated substrate in which a nozzle substrate 100, an actuator substrate (element substrate) 10, and a flow path substrate 20 are laminated in this order. The nozzle substrate 100, the actuator substrate 10, and the flow path substrate 20 of the present embodiment are all formed from silicon substrates. Each substrate is joined via an adhesive. In FIG. 2, the internal structure such as the flow path of the liquid ejection substrate 1 is omitted, and only the laminated structure of the substrates and the ejection port 141 are shown. The ejection port 141 is formed on the nozzle substrate 100, and a plurality of ejection ports 141 are provided along the X direction of the substrate to form a nozzle row, and further two rows of nozzle rows are formed in the Y direction.

[0020] FIG. 3 is a cross-sectional view showing a main part of the liquid ejection substrate 1 of the first embodiment at III-III in FIG. 2(a).

[0021] The nozzle substrate 100 is composed of a silicon substrate 110 and an insulating film 120, and includes a nozzle 140 having an ejection port 141. In the configuration of the present embodiment, the nozzle 140 communicates with the cavity 80 of the actuator substrate 10.

[0022] The actuator substrate 10 has a cavity 80 that serves as a liquid chamber communicating with the nozzle 140 and supports the vibrating membrane 60 via an insulating film 70. A piezoelectric element 45 is provided on the side of the vibrating membrane 60 opposite to the cavity 80 via an insulating film 50. The piezoelectric element 45 is covered with a protective film 40 on the side opposite to the insulating film 50. The insulating film 70 forms one surface of the cavity 80 and, together with the silicon sidewall portion of the actuator substrate 10 and the silicon 110 portion of the nozzle substrate 100, demarcates the cavity 80. Ink is supplied to the cavity 80 through a through-channel 35 that penetrates the protective film 40, the insulating film 50, the vibrating membrane 60, and the insulating film 70 in the Z direction, and through individual channels 30 that penetrate the channel substrate 20 in the Z direction.

[0023] The flow channel substrate 20 has a common supply channel 90 that supplies ink to multiple cavities 80. The common supply channel 90 is provided to extend in the Y direction (depth direction in the figure) in order to distribute the ink supplied from outside the liquid ejection substrate 1 throughout the entire substrate 1. The common supply channel 90 is in fluid communication with each individual cavity 80 via multiple individual channels 30 arranged in the Y direction (depth direction in the figure). In addition, the flow channel substrate 20 has cavities 85 that form a space around the piezoelectric element 45 and the vibrating membrane 60 that can be easily deformed.

[0024] By applying a drive voltage to the piezoelectric element 45, which acts as an ejection element, from a power supply (not shown), the vibrating membrane 60 vibrates, causing the cavity 80 to repeatedly expand and contract. The ink in the cavity 80, supplied from the common supply channel 90 through the individual channel 30, is pressurized, and the ink is ejected from the ejection port 141 in the Z direction. In summary, the ink supplied from outside the liquid ejection substrate 1 flows through the channels from the common supply channel 90 to the ejection port 141 and is ejected from the ejection port 141. In the configuration of this embodiment shown in Figure 3, the common supply channel 90, individual channel 30, through channel 35, cavity 80, and nozzle 140 constitute the channels from the common supply channel 90 to the ejection port 141.

[0025] In order to improve the liquid resistance of the common channel with a large total liquid flow rate without impairing the discharge function of the discharge port, in this embodiment, the entire substrate and the channel are covered with a protective film 500 that is resistant to the discharged liquid. The protective film 500 only needs to be resistant to the discharged liquid. It is more preferable that the protective film 500 is formed of at least one material selected from the group consisting of tantalum oxide, hafnium oxide, zirconium oxide, and titanium oxide, with tantalum oxide being the most preferred. In this embodiment, tantalum oxide was selected.

[0026] The protective film 500 continuously covers the inner wall surface of the flow path from the common supply flow path 90 to the discharge port 141. In other words, the protective film 500 is continuously provided over the liquid flow paths of the flow path substrate 20, actuator substrate 10, and nozzle substrate 100. This makes it possible to increase liquid resistance even in the flow paths at the joints between the components (substrates) that make up the liquid discharge substrate 1.

[0027] Furthermore, the protective film 500 has a thickness in the common supply channel 90 (film thickness in section B, Figure 3) that is thicker than the film thickness in the nozzle 140 and discharge port 141 (film thickness in section A, Figure 3).

[0028] The protective film 500 formed in section A, which has the discharge port 141, is designed so as not to be too thick from the perspective of affecting the discharge, while the protective film 500 formed in section B, which is the common supply channel 90, is made thicker to improve the liquid resistance of the common supply channel 90. As a result, the liquid resistance of the entire substrate can be improved to the common channel with a large total liquid flow rate without impairing the discharge function from the discharge port 141, thereby improving the reliability of the entire substrate.

[0029] (Film thickness of protective film) Experiments have shown that the thickness of the protective film 500 is preferably 20 nm or more from the viewpoint of liquid resistance. However, in the case of a laminated structure in which multiple substrates are joined with adhesive, as in the embodiment, the mechanical strength of the protective film is also required, so it is desirable that the thickness of the protective film 500 be 50 nm or more. In this embodiment, as an example, tantalum oxide was adopted because it is a high-purity material and has high density, resulting in high mechanical strength of the film. The film density of tantalum oxide is 7.5 to 8.5 g / cm³. 3 That's what I decided.

[0030] Furthermore, in the common supply channel 90, if the channel substrate 20 is thick and the height of the common supply channel 90 is high, roughness such as unevenness may occur on the inner wall surface of the common supply channel 90 due to the effects of etching during channel formation. For this reason, in order to suppress the occurrence of pinholes in the protective film 500 in the common supply channel 90, it is desirable that the thickness of the protective film 500 in the common supply channel 90 be 80 nm or more.

[0031] Furthermore, the thickness of the protective film 500 formed in section A of Figure 3, i.e., the common supply channel 90, is preferably less than 160 nm. This stabilizes the opening width of the discharge port 141 and makes it easier to achieve uniform discharge performance.

[0032] Two factors affected by the thickness of the protective film 500 will be explained. The first is a factor related to the continuous coverage of the protective film 500, and the second is a factor related to the energy efficiency of the piezoelectric element 45.

[0033] First, let's explain the continuous coverage of the protective film 500. In this embodiment, the protective film 500 is formed in the flow channels that extend across multiple substrates of the liquid discharge substrate 1, which is formed by stacking and joining a nozzle substrate 100, an actuator substrate 10, and a flow channel substrate 20 in that order. Furthermore, as mentioned above, the thickness of the protective film 500 differs near the discharge port 141 and near the common supply flow channel 90. Therefore, from the viewpoint of needing to stably and continuously cover members (substrates) with different coating thicknesses, it is desirable that the difference in the thickness of the protective film 500 in the flow channels be small.

[0034] If the difference in film thickness of the protective film 500 in the flow channel between adjacent substrates exceeds three times, the resulting film stress will also exceed three times, making the generation of shear stress significant. This can lead to uneven deformation at the joint between substrates, potentially causing the protective film to peel off between components. To suppress this peeling of the protective film 500 between joined substrates, it is preferable to minimize the difference in film thickness between the substrates, specifically, a difference of less than three times is preferable.

[0035] In this embodiment, the thickness of the protective film 500 formed on the actuator substrate 10 and the nozzle substrate 100 is set to 40 nm, and the thickness of the protective film 500 formed on the channel substrate 20 is set to 100 nm, thereby keeping the difference in thickness of the protective film 500 between the substrates to about twice the original thickness. This enhances the continuous coverage of the channel by the protective film 500.

[0036] Next, we will explain the energy efficiency of the piezoelectric element. When a driving voltage is applied to the piezoelectric element 45, the vibrating film 60 vibrates, and the cavity 80 repeatedly expands and contracts, causing ink to be ejected from the ejection port 141. Therefore, high energy efficiency is required when transferring the ejection energy from the piezoelectric element 45 to the ink in the cavity 80. For example, if a thick protective film 500 is formed in the cavity 80 near the piezoelectric element 45, the ejection performance, such as the ejection amount and initial velocity, will decrease accordingly. For this reason, in order to avoid reducing the energy efficiency of the piezoelectric element 45, it is desirable that the thickness of the protective film 500 formed on the vibrating plate (Figure 3, part C) near the piezoelectric element 45 and driven by the piezoelectric element 45 be less than 160 nm.

[0037] The preferred film thickness of the protective film 500 has been described above. When comparing the thickness of the protective film 500 formed on the inner wall surface of the flow path from the common supply flow path 90 to the discharge port 141 in "Part A," "Part B," and "Part C," it is preferable to compare the average film thickness in a diameter range of approximately 100 μm. To directly obtain the film thickness of each element, the film thickness of the target element can be directly measured using a cross-sectional SEM or TEM. Alternatively, an indirect measurement method can be used, in which a flat area on the same plane, approximately 5 mm away from the target element, is measured using an ellipsograph or XRR.

[0038] (Manufacturing method for liquid dispensing heads) Figure 4 shows the method for manufacturing the liquid discharge substrate 1 according to the first embodiment shown in Figure 3.

[0039] As described above, in this embodiment, a liquid-resistant protective film continuously covers the inner wall of the flow path from the common supply flow path 90 to the discharge port 141 within the liquid discharge substrate 1. Any method can be used to form this protective film. It is desirable to form the protective film by atomic layer deposition (ALD) in order to ensure coverage of the joints between components and to cover both sides of the substrate and the inside of the flow path.

[0040] First, a channel substrate 20 is prepared by processing a silicon substrate with a common supply channel 90 and individual channels 30 using silicon etching or the like, and further providing a cavity 85 (Figure 4(a)). Then, a protective film 510 is deposited on the entire surface of the channel substrate 20, including the walls of the channels, using atomic layer deposition (ALD) (Figure 4(b)). In this embodiment, the protective film 510 is, as an example, tantalum oxide with a thickness of 40 nm.

[0041] Next, an actuator substrate 10 is prepared on a silicon substrate having an insulating film 70, a vibrating film 60, and an insulating film 50 on a silicon layer, and a piezoelectric element 45 and a protective film 40 covering the piezoelectric element 45 (Figure 4(c)), and is bonded to the flow channel substrate 20 (Figure 4(d)).

[0042] Furthermore, a protective film can be provided on the actuator substrate 10 in advance.

[0043] Next, a cavity 80 is formed on the actuator substrate 10 by silicon etching or the like, and then a through-channel 35 is formed from the cavity 80 to the individual channels 30 of the flow channel substrate 20 (Figure 4(e)).

[0044] Next, an SOI substrate 100 consisting of a silicon layer 110, a silicon oxide film 120, and a silicon layer 130 is prepared as the nozzle substrate 100 (Figure 4(f)), and it is bonded to the actuator substrate 10 (Figure 4(g)).

[0045] Subsequently, the silicon layer 130 is polished and removed until the silicon oxide film 120 is exposed, and the nozzle 140 and discharge port 141 are formed on the nozzle substrate 100 by silicon etching or the like (Figure 4(h)).

[0046] Subsequently, a protective film 520 is further deposited on the assembled body of the flow channel substrate 20, actuator substrate 10, and nozzle substrate 100 shown in Figure 4(h) by ALD (Figure 4(i)). In this embodiment, the protective film 520 is, as an example, tantalum oxide with a thickness of 60 nm. A liquid discharge head was manufactured using the liquid discharge substrate 1 manufactured through the above process.

[0047] The manufacturing process described above makes it possible to sufficiently increase the thickness of the protective film in the common supply channel 90 while reducing the thickness of the protective film at the nozzle 140 and discharge port 141 in the liquid discharge substrate 1. In the example described above, the thickness of the protective film 500 in the common supply channel 90 (Figure 3, thickness of the protective film in section B) is 100 nm, which is the sum of the 40 nm thick protective film 510 deposited on the channel substrate 20 and the 60 nm thick protective film 520 deposited on the entire liquid discharge substrate 1. On the other hand, the thickness of the protective film at the nozzle 140 and discharge port 141 (Figure 3, thickness of the protective film in section A) is limited to the thickness of only the 60 nm thick protective film 520 deposited on the entire liquid discharge substrate 1.

[0048] Furthermore, since the protective film 520 is not formed in the cavity 85, which is a closed space during the deposition of the protective film 520, the only protective film formed on the surface of the flow channel substrate 20 is a protective film 510 with a thickness of 40 nm.

[0049] <Second Embodiment> The same parts as in the first embodiment described above will not be explained. Figure 5 is a cross-sectional view showing the configuration of the second embodiment of the present invention. In this embodiment as well, the entire substrate and the flow path are covered with a liquid-resistant protective film 600.

[0050] Similar to the first embodiment, the protective film 600 has a thickness in the common supply channel 90 (film thickness in section B, Figure 5) that is greater than the film thickness in the nozzle 140 and discharge port 141 (film thickness in section A, Figure 5). In this embodiment, the film thickness of the protective film 600 in section C (see Figure 5) inside the cavity 80 near the piezoelectric element 45 is also adjusted.

[0051] In order to avoid reducing the energy efficiency of the piezoelectric element 45, it is preferable that the thickness of the protective film in "section C" inside the cavity 80 near the piezoelectric element 45, which is the operating region of the actuator when the piezoelectric element 45 is driven, is not too thick. Furthermore, from the viewpoint of vibration characteristics, it is desirable that the thickness of the protective film 600 in "section C" be less than 160 nm.

[0052] In addition, in order to prevent the protective film 600 from peeling off between the substrates that make up the liquid discharge substrate 1 (nozzle substrate 100, actuator substrate 10, and flow path substrate 20), it is desirable that the difference in the thickness of the protective film 600 between each substrate does not become too large. Specifically, it is preferable that the difference in thickness be less than 3 times.

[0053] Based on the above, in this embodiment, the thickness of the protective film 600 in sections A, B, and C increases in the order of A, C, and B. The protective film 600 formed in section A, which has the discharge port 141, is made so as not to be too thick from the viewpoint of discharge effect, and the protective film 600 formed in section C is made so as not to be too thick from the viewpoint of vibration characteristics, while the thickness of the protective film 600 formed in section B, which is the common supply channel 90, is made thicker to improve the liquid resistance of the common supply channel 90. As a result, the liquid resistance of the entire substrate can be improved to the common channel with a large total liquid flow rate without impairing the discharge performance, and the reliability of the entire substrate can be improved. Furthermore, the thickness of the protective film 600 is configured to increase in stages toward the common supply channel 90 in the channel from the common supply channel 90 to the discharge port 141. As a result, it is possible to prevent a decrease in the energy efficiency of the piezoelectric element and improve the continuous coverage of the protective film, and further improve the reliability of the liquid discharge substrate.

[0054] In this embodiment, the thickness of the protective film 600 is varied by different numbers of layers constituting the protective film 600 covering the inner wall of the flow path in each of sections A, B, and C. Specifically, the protective film 600 in section A consists only of protective film 630, the protective film 600 in section C includes protective films 610, 620, and 630, and the protective film 600 in section B includes protective films 620 and 630. Furthermore, the protective film 630 that can come into contact with the liquid flowing in the flow path continuously covers the inner wall of the flow path in the liquid discharge substrate 1 from the common supply flow path 90 to the discharge port 141. This makes it possible to increase liquid resistance even in the flow path at the joint between the members (substrates) constituting the liquid discharge substrate 1.

[0055] In this embodiment, as an example, the thickness of the protective film 600 was set to 60 nm in section A, 80 nm in section C, and 100 nm in section B.

[0056] (Manufacturing method for liquid dispensing heads) Figure 6 shows a part of the manufacturing process of the liquid discharge substrate 1 according to the second embodiment.

[0057] First, a channel substrate 20 is prepared by processing a silicon substrate with a common supply channel 90 and individual channels 30 using silicon etching or the like, and further providing a cavity 85 (Figure 6(a)). Then, a protective film 610 is deposited over the entire surface of the channel substrate 20 using atomic layer deposition (ALD) (Figure 6(b)). In this embodiment, as an example, the protective film 610 is made of tantalum oxide with a thickness of 20 nm.

[0058] Next, an actuator substrate 10 is prepared on a silicon substrate having an insulating film 70, a vibrating film 60, and an insulating film 50 on a silicon layer, and a piezoelectric element 45 and a protective film 40 covering the piezoelectric element 45 (Figure 6(c)), and is bonded to the flow channel substrate 20 (Figure 6(d)).

[0059] Next, a cavity 80 is formed on the actuator substrate 10 by silicon etching or the like, and then through-channels 35 are formed from the cavity 80 to the individual channels 30 of the flow channel substrate 20 (Figure 6(e)).

[0060] Next, a protective film 620 is deposited on the laminate of the flow channel substrate 20 and the actuator substrate 10 by atomic layer deposition (ALD) (Figure 6(f)). In this embodiment, the protective film 620 is, as an example, tantalum oxide with a thickness of 20 nm.

[0061] Next, an SOI substrate 100 consisting of a silicon layer 110, a silicon oxide film 120, and a silicon layer 130 is prepared as the nozzle substrate 100 (Figure 6(g)), and it is bonded to the actuator substrate 10 (Figure 6(h)).

[0062] Subsequently, the silicon layer 130 is polished and removed, and the nozzle 140 and discharge port 141 are formed on the nozzle substrate 100 by silicon etching or the like (Figure 6(i)).

[0063] Next, a protective film 630 is deposited on the assembled body of the flow channel substrate 20, actuator substrate 10, and nozzle substrate 100 shown in Figure 6(i) by ALD (Figure 6(j)). In this embodiment, the protective film 620 is, for example, tantalum oxide with a thickness of 60 nm. A liquid discharge head was manufactured using the liquid discharge substrate 1 produced through the above process.

[0064] The above manufacturing process makes it possible to sufficiently increase the thickness of the protective film in the common supply channel 90 while reducing the thickness of the protective film 600 at the nozzle 140 and discharge port 141 in the liquid discharge substrate 1. In the above example, the thickness of the protective film 600 in the common supply channel 90 (Figure 5, thickness of protective film 600 in section B) is 100 nm, which is the sum of the 20 nm thick protective film 610 deposited on the channel substrate 20, the 20 nm thick protective film 620 deposited on the channel substrate 20 and the actuator substrate 10, and the 60 nm thick protective film 630 deposited on the entire liquid discharge substrate 1. In addition, the thickness of the protective film 600 inside the cavity 80 near the piezoelectric element 45 (Figure 5, thickness of protective film 600 in section C) is 80 nm, which is the sum of the 20 nm thick protective film 620 and the 20 nm thick protective film 630. Furthermore, the thickness of the protective film 600 at the nozzle 140 and discharge port 141 (Figure 5, thickness of protective film 600 in section A) is limited to the thickness of the 60 nm thick protective film 630 that is deposited over the entire liquid discharge substrate 1.

[0065] Furthermore, since protective film 620 is not formed in the cavity 85, which is a closed space during the deposition of protective films 620 and 630, the only protective film formed on the surface of the flow channel substrate 20 is protective film 610 with a thickness of 40 nm.

[0066] In this embodiment, the film thickness in the fluid path is varied by depositing the protective film multiple times. As a result, the number of layers of the laminated protective film 600 is greater than that of section B of the common channel 90 (3 layers), section C in the cavity 80 (2 layers), and section A near the nozzle 140 (1 layer). In other words, the protective film 600 includes a laminated portion, and the number of layers of the laminated protective film 600 is greater in the cavity (liquid chamber) than in the nozzle, and greater in the common channel than in the cavity.

[0067] <Third Embodiment> The same parts as those described in the first and second embodiments above will not be described. Figure 7 is a cross-sectional view showing a liquid discharge head of a third embodiment of the present invention. In this embodiment as well, the entire substrate and the flow path are covered with a liquid-resistant protective film 700. The protective film 700 has a protective film 710 that covers the flow path substrate 20 and a protective film 720 that continuously covers the fluid path.

[0068] In this embodiment, the protective film 700 has a thickness in the common supply channel 90 (film thickness in section B, Figure 7) that is thicker than the film thickness in section C inside the cavity 80 near the piezoelectric element 45. This improves the liquid resistance of the common supply channel 90 while suppressing a decrease in the energy efficiency of the piezoelectric element 45, thereby improving the reliability of the liquid discharge substrate.

[0069] <Fourth Embodiment> The same parts as those described in the first to third embodiments above will not be described. The present invention is also applicable to a liquid discharge substrate in which liquid circulates inside and outside a cavity 80, which is a pressure chamber that supplies liquid to a nozzle 140. Figure 8(a) is a view of the liquid discharge substrate of the liquid discharge head of this disclosure from the nozzle side and a view from the opposite side. Figure 8(b) is a schematic cross-sectional view of VIIIb-VIIIb in Figure 8(a). Figure 8(c) is a partially enlarged view of Figure 8(b). The liquid discharge substrate 1 is composed of four substrates: a nozzle substrate 100, an actuator substrate 10, a flow path substrate 20, and a damper substrate 11. The actuator substrate 10 has a liquid chamber 80, a vibrating membrane 60, and a piezoelectric element 45. The flow path substrate 20 has individual flow paths 30, a common flow path 90, and grooves that form voids surrounding the piezoelectric element 45. The damper substrate 11 has a damper membrane 111, a damper chamber 112, and a common opening 114. Ink is supplied to the nozzle substrate 100 from the common opening 114 formed in the damper substrate 11 via the flow channel substrate 20, and the ink is ejected from the ejection port 141 and applied to the recording medium 4 (see Figure 1(a)). The liquid ejection head 2 has an electrical circuit board (not shown) for supplying the power and signals necessary to eject the liquid, and is connected to the terminals 10a of each liquid ejection substrate 1 by wiring (not shown).

[0070] Figure 9(a) is an enlarged plan perspective view of a part of the liquid discharge substrate 1 relating to the liquid discharge head of this disclosure, and is a view from the side opposite to the discharge port 141 side. Figure 9(b) is a cross-sectional view taken from IXb-IXb in Figure 9(a). As shown in Figure 9(a), in the liquid discharge substrate 1 of this embodiment, a plurality of nozzle rows are formed in the X direction, with the discharge port 141, nozzle 140, liquid chamber (pressure chamber) 80, individual flow channels 30 communicating with the liquid chamber 80, and piezoelectric elements 45 that generate pressure in the liquid chamber 80 as constituent units. As shown in Figure 9(b), piezoelectric elements 45 for discharging liquid by pressure are arranged at positions corresponding to each discharge port 141. Along each nozzle row, an individual supply flow channel 30a that forms the individual flow channel 30 extends on one side, and an individual recovery flow channel 30b that forms the individual flow channel 30 extends on the other side. The individual supply channels 30a and individual recovery channels 30b are channels extending in the Z direction provided on the liquid discharge substrate, and each is in communication with the nozzle 140. Furthermore, the individual supply channels 30a and individual recovery channels 30b are each connected to a common channel 90, which consists of a common supply channel 90a and a common recovery channel 90b. The connection points of the individual supply channels 30a, individual recovery channels 30b, common supply channel 90a, and common recovery channel 90b are individual openings. A damper structure 113, consisting of a damper chamber 112 and a damper membrane 111, is formed on the surface facing the surface having the individual openings. A common opening 114, consisting of a common supply opening 114a and a common recovery opening 114b, is formed on the damper substrate 11 on which the damper structure 113 is formed, for the connection of the common supply channel 90a and the common recovery channel 90b, respectively. The common supply channel 90a and the common recovery channel 90b are formed extending in the X direction, which is along the nozzle row, and are formed on the side opposite to the discharge surface with respect to the piezoelectric element 45 in the Z direction, where the liquid is discharged.

[0071] In the liquid ejection substrate 1 shown in Figure 9, the liquid chamber 80 corresponding to the piezoelectric element 45 in each nozzle row has a length of 110 μm in the X direction. The liquid chambers 80 and ejection ports 141 are spaced at 150 dpi intervals. By offsetting these nozzle rows in the X direction to form four rows, a high-density nozzle arrangement of 600 dpi on the recording medium becomes possible. In this embodiment, four nozzle rows are used to achieve a 600 dpi configuration, but the system is not limited to this, and eight nozzle rows may be used to achieve a 1200 dpi configuration.

[0072] Next, the flow of liquid within the liquid discharge substrate 1 will be explained. When liquid is supplied to the common supply opening 114a, the liquid flows through the common supply channel 90a, then through the individual supply channels 30a of each element, through the liquid chamber 80 and nozzle 140, through the individual recovery channel 30b, and then through the common recovery channel 90b to the common recovery opening 114b. As a result, the liquid supplied from the common supply opening 114a flows to the common recovery opening 114b and can be recovered. By applying a differential pressure to the liquid flowing through the common supply opening 114a and the common recovery opening 114b from an external source such as a pump or hydrostatic pressure, the liquid can be circulated.

[0073] In a configuration where liquid circulates as described above, the total flow rate of liquid flowing through the flow channel substrate 20 increases. Therefore, the present invention, which enhances liquid resistance in the common flow channel 90 (common supply flow channel 90a and common recovery flow channel 90b) of the flow channel substrate 20 and improves reliability, can be more favorably adopted. In this embodiment as well, the entire substrate and the flow channel are covered with a liquid-resistant protective film 800. Specifically, the protective film is continuously provided on the inner wall surface of the fluid path from the common flow channel 90 through the liquid chamber 80 to the discharge port 141. Note that Figures 8 and 9 omit the protective film. The thickness of the protective film in the fluid path is the same as in the second embodiment, with section B > section C > section A.

[0074] <Other Embodiments> The configuration of the present invention is not limited to the embodiments described above, and can be applied to liquid dispensing substrates of various configurations.

[0075] For example, in the embodiment described above, the liquid discharge substrate 1 had a configuration in which a flow channel substrate 20, an actuator substrate 10, and a nozzle substrate 100 were stacked, but the configuration is not limited to this as long as it has a common flow channel and a nozzle. For example, another substrate may be interposed between the nozzle substrate 100 and the actuator substrate 10. Alternatively, a flow channel substrate having a common flow channel communicating with multiple nozzles or multiple cavities as pressure chambers may be interposed between a nozzle substrate having a nozzle and an actuator substrate having a piezoelectric element. Furthermore, the common flow channel and the piezoelectric element may be formed on the same substrate.

[0076] Furthermore, in the embodiments described above, the flow path substrate 20, actuator substrate 10, and nozzle substrate 100 were formed from silicon substrates, but they may be formed from materials other than silicon, such as resin or metal. In this case, the material of the protective film covering the inner wall surface of the fluid path should be selected according to the substrate material and the liquid flowing through the flow path.

[0077] In the embodiments described above, the film thickness in the fluid path was varied by depositing the protective film multiple times. However, a protective film may be formed in a single deposition process that is continuously provided on the inner wall surface of the fluid path from the common channel to the discharge port, and in which the film thickness in the common channel is greater than the film thickness in the nozzle. Furthermore, the protective film may be a laminated film of different materials.

[0078] In the embodiment described above, the thickness of the actuator substrate 10 in the direction perpendicular to the surface of the liquid discharge substrate 1 was greater than the thickness of the nozzle substrate 100, and the thickness of the flow path substrate 20 was greater than the thickness of the actuator substrate 10 in the laminated configuration. However, the relationship between the substrate thicknesses is not limited to this.

[0079] Furthermore, although the above-described embodiment used a thin-film piezoelectric element as the pressure generating means for discharging droplets from the discharge port 141, it is not limited to this. For example, a thick-film piezoelectric actuator formed by methods such as attaching a green sheet, or a longitudinal vibration type piezoelectric actuator that alternately stacks piezoelectric material and electrode-forming material to expand and contract in the axial direction can be used. In addition, as a pressure generating means, a device can be used in which a heating element is placed in the pressure generating chamber and droplets are discharged from the nozzle opening by bubbles generated by the heat generated by the heating element, or a so-called electrostatic actuator that generates static electricity between a diaphragm and an electrode, deforming the diaphragm with electrostatic force and discharging droplets from the nozzle opening.

[0080] <Technical Features of This Disclosure> This disclosure includes the following configuration and method:

[0081] (Composition 1) A nozzle substrate having multiple nozzles, including discharge ports for dispensing liquid, A flow channel substrate having individual flow channels for supplying liquid to the nozzle, and a common flow channel that communicates fluid to a plurality of the individual flow channels, A laminated substrate in which multiple substrates including and are stacked, A protective film is provided continuously on the inner wall surface of the fluid path from the common channel to the discharge port, comprising at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide. A liquid discharge head wherein the thickness of the protective film in the common channel is greater than the thickness of the protective film in the nozzle.

[0082] (Configuration 2) A nozzle substrate having multiple nozzles, including discharge ports for dispensing liquid, An element substrate comprising a pressure chamber for supplying liquid to the nozzle, and a discharge element for discharging liquid from the discharge port, A flow path substrate having individual flow paths for supplying liquid to the pressure chamber, and a common flow path that communicates fluid to a plurality of the individual flow paths, A laminated substrate in which multiple substrates including this are stacked in this order, A protective film is provided continuously on the inner wall surface of the fluid path from the common channel through the pressure chamber to the discharge port, comprising at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide. A liquid discharge head wherein the thickness of the protective film in the common channel is greater than the thickness of the protective film in the pressure chamber.

[0083] (Composition 3) The laminated substrate includes an element substrate comprising a pressure chamber that supplies liquid to the individual channels and to the nozzle, and a discharge element for discharging liquid from the discharge port. The protective film is provided continuously on the inner wall surface of the fluid path, including the pressure chamber. The liquid discharge head according to configuration 1, wherein the thickness of the protective film in the common channel is greater than the thickness of the protective film in the pressure chamber.

[0084] (Composition 4) The liquid discharge head according to configuration 3, wherein the thickness of the protective film in the pressure chamber is greater than the thickness of the protective film in the nozzle.

[0085] (Composition 5) The substrate is a liquid dispensing head according to any one of configurations 1 to 4, wherein the substrate is formed of a silicon substrate.

[0086] (Composition 6) A liquid dispensing head according to any one of configurations 1 to 5, wherein the difference in thickness of the protective film between two adjacent substrates is less than three times.

[0087] (Composition 7) A liquid discharge head according to configuration 2 or 3, wherein the thickness of the element substrate in a direction perpendicular to the surface of the laminated substrate is greater than the thickness of the nozzle substrate, and the thickness of the flow channel substrate is greater than the thickness of the element substrate.

[0088] (Composition 8) A liquid dispensing head according to any one of configurations 1 to 7, wherein adjacent substrates are joined via an adhesive.

[0089] (Composition 9) The liquid dispensing head according to any one of configurations 1 to 8, wherein the protective film includes a portion that is a laminated film.

[0090] (Composition 10) The liquid discharge head according to configuration 9, wherein the number of layers of the protective film, which is a laminated film, is greater in the common channel than in the nozzle.

[0091] (Composition 11) The protective film includes a portion that is a laminated film, The liquid discharge head according to configuration 3, wherein the number of layers of the protective film, which is a laminated film, is greater in the pressure chamber than in the nozzle, and greater in the common flow path than in the pressure chamber.

[0092] (Composition 12) The liquid dispensing head according to any one of configurations 1 to 11, wherein the thickness of the protective film in the common channel is 80 nm or more.

[0093] (Composition 13) A liquid dispensing head according to any one of configurations 1 to 12, wherein the thickness of the protective film at the nozzle is less than 160 nm.

[0094] (Composition 14) The liquid dispensing head according to configuration 2 or 3, wherein the thickness of the protective film in the pressure chamber is less than 160 nm.

[0095] (Method 15) A nozzle substrate having multiple nozzles, including discharge ports for dispensing liquid, A flow channel substrate having individual flow channels for supplying liquid to the nozzle, and a common flow channel that communicates fluid to a plurality of the individual flow channels, A method for manufacturing a liquid dispensing head having a laminated substrate in which substrates including are stacked, A step of forming a first protective film on the surface of the channel substrate, including the inner wall surface of the individual channels and the common channel, using at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide, A step of directly or indirectly stacking the flow channel substrate and the nozzle substrate, A step of forming a second protective film that continuously covers the inner wall surface of the fluid path from the common channel to the discharge port, using at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide, A method for manufacturing a liquid dispensing head that includes [a specific component].

[0096] (Method 16) A method for manufacturing a liquid dispensing head according to method 15, wherein the first protective film and the second protective film are formed by atomic layer deposition (ALD).

[0097] (Composition 17) The laminated substrate includes an element substrate comprising a pressure chamber that supplies liquid to the individual channels and to the nozzle, and a discharge element for discharging liquid from the discharge port. The step of forming the first protective film that covers the surface of the flow channel substrate, including the inner wall surface of the fluid path, A step of directly or indirectly stacking the flow channel substrate and the element substrate, A step of forming a third protective film that continuously covers the surface, including the inner wall surface of the fluid path from the common channel to the pressure chamber, using at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide; A step of directly or indirectly stacking the element substrate and the nozzle substrate, The step of forming the second protective film that continuously covers the inner wall surface of the fluid path from the common flow path through the pressure chamber to the discharge port, A method for manufacturing a liquid dispensing head according to method 15 or 16, comprising the elements in this order. [Examples]

[0098] Examples and comparative examples of the present invention are shown below, and the present invention will be described in more detail. However, the present invention is not limited to the following examples.

[0099] <Example 1> In Example 1, the liquid discharge substrate 1 shown in Figure 3 was used. The thickness of the flow channel substrate 20 was 600 μm, the thickness of the actuator substrate 10 was 100 μm, and the thickness of the nozzle substrate 100 was 20 μm. The diameter of the discharge port 141 was φ10 μm. Tantalum oxide was used for the protective film 500 (protective films 510 and 520).

[0100] Liquid ejection substrates 1 with the configuration shown in Table 1 were fabricated and designated as Experimental Examples 1-1 to 1-9. For these substrates, a water-soluble pigment ink with a pH of approximately 8-9 was used as the ejection liquid, and their liquid resistance, printing stability, and energy efficiency were evaluated. Furthermore, the continuous coating performance of the protective film 500 in the flow channels inside the liquid ejection substrate 1 was also evaluated. The evaluation criteria were marked with ○, △, ▲, and ×, from best to worst. Based on these evaluations, an overall evaluation was performed using the following criteria. A: All four evaluation criteria are marked with a circle (○). B: Includes △ in four evaluation items. C: Includes ▲ in four evaluation items.

[0101] The evaluation results are shown in Table 1.

[0102] [Table 1]

[0103] <Example 2> In Example 2, the liquid discharge substrate 1 shown in Figure 5 was used. The thickness of the flow channel substrate 20 was 600 μm, the thickness of the actuator substrate 10 was 100 μm, and the thickness of the nozzle substrate 100 was 20 μm. The diameter of the discharge port 141 was φ10 μm. Tantalum oxide was used for the protective film 600 (protective films 610, 620, and 630).

[0104] Liquid ejection substrates 1 with the configuration shown in Table 2 were fabricated and designated as Experimental Examples 2-1 to 2-9. For these substrates, water-soluble pigment inks with a pH of approximately 8-9 were used as the ejection liquid, and their ink resistance, print stability, and energy efficiency were evaluated. Furthermore, the continuous coating performance of the protective film 600 in the flow channels inside the liquid ejection substrate 1 was also evaluated. Based on these evaluations, an overall evaluation was performed using the same criteria as in Example 1. The evaluation results are shown in Table 2.

[0105] [Table 2]

[0106] In the experimental examples of Examples 1 and 2 shown in Tables 1 and 2, no samples exhibited significantly poor liquid resistance. Regarding print stability, slight irregularities were observed in experimental examples 1-7 to 1-9 and 2-7 to 2-9, where the film thickness in section A of the protective film 500 was thicker. Regarding energy efficiency, experimental examples 1-7 to 1-9 and 2-5 to 2-9, where the film thickness in section C of the protective film 500 was thicker, showed lower efficiency compared to other experimental examples, and in experimental examples 2-6, 2-8, and 2-9, where the film thickness was particularly thick, the efficiency was unacceptably low. Regarding the continuous coverage of the protective film, peeling of the protective film between substrates was observed in experimental examples 1-3, 1-6, and 1-9, where there was a large difference in film thickness between substrates. [Explanation of symbols]

[0107] 1 Liquid discharge board 2 liquid dispensing heads 10 Actuator board 20 Flow channel substrate 30 individual channels 80 Liquid chamber (pressure chamber) 90 Common channel 100 Nozzle Substrates 140 nozzles 141 Discharge port 500, 600, 700 protective film

Claims

1. A nozzle substrate having multiple nozzles, including discharge ports for dispensing liquid, A flow channel substrate having individual flow channels for supplying liquid to the nozzle, and a common flow channel that communicates fluid to a plurality of the individual flow channels, A laminated substrate in which multiple substrates including and are stacked, A protective film is provided continuously on the inner wall surface of the fluid path from the common channel to the discharge port, comprising at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide. A liquid discharge head wherein the thickness of the protective film in the common channel is greater than the thickness of the protective film in the nozzle.

2. A nozzle substrate having multiple nozzles, including discharge ports for dispensing liquid, An element substrate comprising a pressure chamber for supplying liquid to the nozzle, and a discharge element for discharging liquid from the discharge port, A flow path substrate having individual flow paths for supplying liquid to the pressure chamber, and a common flow path that communicates fluid to a plurality of the individual flow paths, A laminated substrate in which multiple substrates including this are stacked in this order, A protective film is provided continuously on the inner wall surface of the fluid path from the common channel through the pressure chamber to the discharge port, comprising at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide. A liquid discharge head wherein the thickness of the protective film in the common channel is greater than the thickness of the protective film in the pressure chamber.

3. The laminated substrate includes an element substrate comprising a pressure chamber that supplies liquid to the individual channels and to the nozzle, and a discharge element for discharging liquid from the discharge port. The protective film is provided continuously on the inner wall surface of the fluid path, including the pressure chamber. The liquid discharge head according to claim 1, wherein the thickness of the protective film in the common channel is greater than the thickness of the protective film in the pressure chamber.

4. The liquid discharge head according to claim 3, wherein the thickness of the protective film in the pressure chamber is greater than the thickness of the protective film in the nozzle.

5. The liquid dispensing head according to claim 1 or 2, wherein the substrate is formed of a silicon substrate.

6. The liquid dispensing head according to claim 1 or 2, wherein the difference in thickness of the protective film between two adjacent substrates is less than three times.

7. The liquid discharge head according to claim 2 or 3, wherein the thickness of the element substrate in a direction perpendicular to the surface of the laminated substrate is greater than the thickness of the nozzle substrate, and the thickness of the flow channel substrate is greater than the thickness of the element substrate.

8. The liquid dispensing head according to claim 1 or 2, wherein the adjacent substrates are joined via an adhesive.

9. The liquid dispensing head according to claim 1 or 2, wherein the protective film includes a portion that is a laminated film.

10. The liquid discharge head according to claim 9, wherein the number of layers of the protective film, which is a laminated film, is greater in the common channel than in the nozzle.

11. The protective film includes a portion that is a laminated film, The liquid discharge head according to claim 3, wherein the number of layers of the protective film, which is a laminated film, is greater in the pressure chamber than in the nozzle, and greater in the common flow path than in the pressure chamber.

12. The liquid discharge head according to claim 1 or 2, wherein the thickness of the protective film in the common channel is 80 nm or more.

13. The liquid dispensing head according to claim 1 or 2, wherein the thickness of the protective film at the nozzle is less than 160 nm.

14. The liquid dispensing head according to claim 2 or 3, wherein the thickness of the protective film in the pressure chamber is less than 160 nm.

15. A nozzle substrate having multiple nozzles, including discharge ports for dispensing liquid, A flow channel substrate having individual flow channels for supplying liquid to the nozzle, and a common flow channel that communicates fluid to a plurality of the individual flow channels, A method for manufacturing a liquid dispensing head having a laminated substrate in which substrates including are stacked, A step of forming a first protective film covering the surface of the channel substrate, including the inner wall surface of the individual channels and the common channel, using at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide, A step of directly or indirectly stacking the flow channel substrate and the nozzle substrate, A step of forming a second protective film that continuously covers the inner wall surface of the fluid path from the common channel to the discharge port, using at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide. A method for manufacturing a liquid dispensing head that includes [a specific component].

16. A method for manufacturing a liquid dispensing head according to claim 15, wherein the first protective film and the second protective film are formed by atomic layer deposition (ALD).

17. The laminated substrate includes an element substrate comprising a pressure chamber that supplies liquid to the individual channels and to the nozzle, and a discharge element for discharging liquid from the discharge port. The step of forming the first protective film that covers the surface of the flow channel substrate, including the inner wall surface of the fluid path, A step of directly or indirectly stacking the flow channel substrate and the element substrate, A step of forming a third protective film that continuously covers the surface, including the inner wall surface of the fluid path from the common channel to the pressure chamber, using at least one material selected from the group consisting of tantalum oxide, hafnium oxide, and zirconium oxide; A step of directly or indirectly stacking the element substrate and the nozzle substrate, The step of forming the second protective film that continuously covers the inner wall surface of the fluid path from the common flow path through the pressure chamber to the discharge port, A method for manufacturing a liquid dispensing head according to claim 15 or 16, comprising the elements in this order.

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