Nozzle Board

Abstract

In a nozzle substrate that is coated with a protective film to enhance its resistance to liquid, it is possible to measure the nozzle dimensions with high precision by white light interferometry. [Solution] A nozzle substrate is constructed by laminating a silicon substrate and a silicon oxide film covering the surface of the silicon substrate, and is provided with a nozzle that ejects liquid. The nozzle substrate has a through-hole that penetrates the nozzle substrate and communicates with the nozzle, and a protective film that is resistant to the liquid and covers at least the surface of the silicon oxide film and the inner wall surface of the through-hole. The reflectance of white light on the surface of the nozzle substrate, which is used when measuring the nozzle as a step using white light interferometry, is 0.2 or more.

Description

[Technical Field]

[0001] The present invention relates to a nozzle substrate having nozzles that eject liquid. [Background technology]

[0002] In an inkjet recording device, a head that ejects ink onto a recording medium includes a nozzle substrate having nozzles that eject ink. The nozzle substrate has a silicon substrate on the surface of which nozzles that eject ink are provided. Patent Document 1 describes a nozzle substrate configured by bonding glass to an SOI substrate, which is a silicon substrate covered with a silicon oxide film (SiO film).

[0003] To improve image quality in inkjet recording devices, various inks with different physical properties, such as color materials such as dyes and pigments, ink solvents for stably dissolving the color materials, and acidity or alkalinity, have been developed. Among these, pigment-based inks with a pH of approximately 8 to 9 are known to corrode the silicon and silicon dioxide (SiO) that make up the nozzle substrate. Patent Document 2 describes a technology for imparting ink resistance by continuously forming a protective film made of an oxide such as TaO from the droplet ejection side of the nozzle holes in a silicon nozzle substrate to the inner wall of the nozzle holes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5218164 [Patent Document 2] Patent No. 4692534 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to ensure the recording quality of an inkjet recording device, it is desirable to measure and manage dimensions such as the nozzle opening area of ​​the nozzle substrate with high precision. One method for measuring nozzle dimensions with high precision is to measure the step at the end of the nozzle opening using white light interferometry, which is a measurement method using white light (visible light). However, when the nozzle substrate is covered with a protective film, the reflected light of the white light used in white light interferometry is weak, and accurate measurement is sometimes not possible.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to enable accurate measurement of nozzle dimensions by white light interferometry in a nozzle substrate that has been coated with a protective film to enhance its resistance to liquids. [Means for solving the problem]

[0007] The present invention provides a nozzle substrate that is configured by laminating a silicon substrate and a silicon oxide film that covers the surface of the silicon substrate, and that is provided with a discharge port that discharges a liquid, a nozzle that penetrates the nozzle substrate and communicates with the discharge port; a protective film that is resistant to the liquid and that covers at least a surface of the silicon oxide film and an inner wall surface of the nozzle; and The nozzle substrate is characterized in that the reflectance of white light used when measuring the nozzle as a step by white light interferometry on the surface of the nozzle substrate is 0.2 or more. [Effects of the Invention]

[0008] According to the present invention, a nozzle substrate having improved resistance to liquids by being covered with a protective film is provided. In this case, it becomes possible to measure the nozzle dimensions with high accuracy by white light interferometry. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional view of the nozzle substrate of the first embodiment. [Figure 2]FIG. 1 is a diagram showing the relationship between the SiO film thickness, the TaO film thickness, and the reflectance in Example 1. [Figure 3] FIG. 1 is a diagram showing an appropriate film thickness in Example 1. [Figure 4] FIG. 10 is a cross-sectional view of a nozzle substrate according to a second embodiment. [Figure 5] FIG. 10 is a diagram showing the relationship between the SiO film thickness, the SiC film thickness, and the reflectance in Example 2. [Figure 6] FIG. 10 is a diagram showing an appropriate film thickness in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] A liquid ejection substrate 1 according to one embodiment of the present invention will be described with reference to Figures 1 and 4. The embodiment is an illustration of the present invention, and is not intended to limit the scope of the present invention to this embodiment. The liquid ejection substrate of the embodiment shown below is applied to a liquid ejection head using a piezoelectric element, but can also be applied to a liquid ejection head using a heat generating resistor element or an electrothermal conversion element. The liquid to be ejected is not limited to ink, as long as it can be ejected from the liquid ejection head.

[0011] In the following description and drawings, the Z direction indicates the direction in which the silicon substrate and the silicon compound film (silicon oxide film) are stacked. In this embodiment, an example is shown in which the direction in which the through-hole communicating with the nozzle (opening) penetrates the nozzle substrate (depth direction of the through-hole) is parallel to the Z direction. Any direction perpendicular to the Z direction is defined as the X direction. The direction perpendicular to both the Z direction and the X direction is defined as the Y direction. The diameter of a nozzle or through-hole refers to the dimension in the XY plane, and the radial direction refers to the direction from the center 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.

[0012] (Configuration of liquid ejection head) 1 is a cross-sectional view showing a main part (part) of a liquid ejection substrate 1 included in an ink ejection head of an inkjet recording device of Example 1. The inkjet recording device including the liquid ejection substrate 1 is also provided with an ink ejection head provided with the liquid ejection substrate 1, a liquid storage unit that stores liquid to be supplied to the ink ejection head, a transport mechanism for a recording medium on which recording is performed, and the like.

[0013] The actuator substrate 10b is made of silicon and is disposed below the nozzle substrate 111. The actuator substrate 10b supports a vibration membrane 60 via a protective film 40 and an insulating film 50. The vibration membrane 60 is bonded to an insulating film 70. The insulating film 70 forms one surface of a cavity 80 and defines the cavity 80 together with the actuator substrate 10b and the silicon substrate 20. A flow path substrate 10a is disposed below the actuator substrate 10b. Ink is supplied to the cavity 80 through a through-hole 30 that penetrates the flow path substrate 10a in the Z direction (stacking direction), and a liquid flow path 35 that penetrates the protective film 40, insulating film 50, vibration membrane 60, and insulating film 70 in the Z direction. The cavity 80 communicates with a nozzle 90.

[0014] A piezoelectric element 45 is disposed between the protective film 40 and the insulating film 50. The piezoelectric element 45 is an example of an actuator element that generates energy to eject ink in the cavity (in the cavity 80) from the ejection port 100. A cavity 85 is formed on the opposite side of the protective film 40 from the side on which the piezoelectric element 45 is provided. A silicon substrate 20 and a silicon oxide film 110 (silicon compound film) form a nozzle substrate 111. The silicon substrate 20 has a nozzle 90 that communicates with the cavity 80. An ejection port 100 through which ink is ejected is formed on the most downstream side of the nozzle 90 in the ejection direction. The diameter of the ejection port 100 is determined by the amount of ink ejected, and is, for example, approximately 5 μm to 50 μm.

[0015] When a driving voltage is applied to the piezoelectric element 45 from a power supply (not shown), the vibrating membrane 60 vibrates, and the The cavity 80 repeatedly expands and contracts. When the ink in the cavity 80 is pressurized, the ink passes through the nozzle 90 and is ejected from the ejection port 100.

[0016] The nozzle substrate 111 to which the actuator substrate 10b is bonded will now be described in detail. The nozzle substrate 111 is made of an SOI substrate in which a silicon oxide film 110 and a silicon substrate 20 are bonded. The SOI substrate is bonded to the actuator substrate 10b, and then the silicon portion is ground and polished to thin it until the silicon oxide film 110 is exposed, thereby producing the nozzle substrate 111. Thereafter, the ejection ports 100 are formed by etching, and the liquid ejection substrate 1 of FIG. 1 can be produced.

[0017] 1, in the liquid ejection substrate 1 of Example 1, a protective film 1001 with a high refractive index is used to coat the surface of the nozzle substrate 111, the inner wall surfaces of the nozzles 90, the cavities 80 which are flow paths communicating with the nozzles 90, the liquid flow paths 35, and the inner wall surfaces of the through-holes 30, thereby providing ink resistance. The protective film 1001 is formed by ALD film formation (atomic layer deposition).

[0018] In the liquid ejection substrate 1 of Example 2, as shown in Figure 4, only the surface of the nozzle substrate 111 and the inner wall surfaces of the nozzles 90 are partially covered with a protective film 1002. In this case, the protective film 1002 is formed by PECVD (plasma enhanced chemical vapor deposition). In any of the configurations of the examples, ink resistance can be improved by covering the nozzle 90 portion with a protective film that has high ink resistance.

[0019] To ensure the recording quality of the inkjet recording device, it is desirable that the opening dimensions of the nozzles 90 of the liquid discharge substrate 1 (diameter of the discharge ports 100) are constant. If the opening dimensions of the nozzles 90 are not constant, the accuracy of the amount of ink droplets discharged will decrease, resulting in a decrease in recording quality. In order to maintain the opening dimensions of the nozzles 90 at a constant level, it is necessary to measure the minute openings of the nozzles 90 with high precision. One method for measuring the opening dimensions of the nozzles 90 is to measure the step at the opening end of the nozzle 90 non-contactly using white light interferometry.

[0020] When the discharge port 100 of the nozzle 90 is covered with the protective film 1001 or 1002 as in Examples 1 and 2, it may not be possible to properly measure the opening dimensions of the nozzle 90 by white light interferometry. In particular, the intensity of light with a central wavelength of approximately 530 nm of the white light (light having a continuous wavelength of approximately 380 to 780 nm) used in measurements by white light interferometry, reflected from the nozzle substrate 111, may be lower than the intensity required to properly perform the measurement.

[0021] Therefore, in Examples 1 and 2, configurations that enable appropriate measurement by white light interferometry will be described.

[0022] Example 1 In the first embodiment, as shown in FIG. 1, a TaO film is formed as a protective film 1001 by the ALD method over the entire liquid discharge substrate 1.

[0023] Table 1 shows the film thickness of the silicon oxide film 110 (SiO film) and the protective film 1001 (TaO film), the white light reflectance of the nozzle substrate 111, whether the opening dimensions of the nozzle 90 can be measured by white light interferometry, and whether or not there is ink resistance. [Table 1]

[0024] The thickness of the silicon oxide film 110 can be adjusted by the etching time, and the thickness of the protective film 1001 can be adjusted by the film formation time.

[0025] Figure 2 is a diagram showing the relationship between the silicon oxide film 110 (SiO film) and the protective film 1001 (TaO film) and reflectance. Figure 2 shows the reflectance of a substrate obtained by simulation when a substrate consisting of a silicon substrate with a SiO film and a TaO film simply laminated thereon is irradiated with light having a wavelength of 530 nm. Figure 2 shows the reflectance in the form of a contour map with the horizontal axis representing the thickness of the SiO film and the vertical axis representing the thickness of the TaO film. In the simulation, the analysis was performed with the refractive index of the SiO film set to 1.46 and the refractive index of the TaO film set to 2.18.

[0026] From the results of the simulation analysis in Table 1 and Figure 2, it was found that in order to properly measure the opening dimensions of the nozzle 90 by white light interferometry for a liquid ejection substrate 1 entirely covered with a TaO film as a protective film, the reflectivity of the nozzle substrate 111 must be 0.2 or higher.

[0027] Fig. 3 is a diagram showing the appropriate thicknesses of the SiO film and the TaO film, which was obtained based on the simulation analysis diagram of Fig. 2, with the horizontal axis (X axis) representing the SiO film thickness and the vertical axis (Y axis) representing the TaO film thickness.

[0028] In FIG. 3, the shaded areas indicate the ranges of values ​​that the SiO film thickness and the TaO film thickness must satisfy in order to obtain a reflectance that can be appropriately measured by white light interferometry.

[0029] In Figure 3, based on the simulation analysis diagram of Figure 2, the portion of the nozzle substrate 111 where the reflectance is 0.2 or more was determined using a linear function. Specifically, when points of high reflectance in the simulation analysis diagram of Figure 2 are connected with a linear function, a straight line with a slope of -1.5 is obtained (Y = -1.5X). Due to the periodicity characteristics, +180n (n: 0, 1, 2, 3, 4, 5) is added to the intercept term. In addition, the tolerance b = -40 to 40.

[0030] In summary, the range of values ​​that the SiO and TaO film thicknesses must satisfy to obtain a reflectance that can be measured appropriately by white light interferometry can be expressed as follows: If the thickness of the oxide film is X [nm], the thickness of the TaO film is Y [nm], and the tolerance is b [nm], Y=-1.5X+180n+b n=0, 1, 2, 3, 4, 5 |b|≦40 Y>0

[0031] When the entire surface and inner wall surfaces of the nozzle substrate 111 are covered with a protective film 1001 (TaO film) by the ALD method, the thickness X of the silicon oxide film 110 (SiO film) constituting the nozzle substrate 111 and the thickness Y of the protective film 1001 (TaO film) are set to satisfy the above formula. This ensures that the reflectance of the white light used in white light interferometry at the nozzle substrate 111 is 0.2 or higher, allowing the opening dimensions of the nozzle 90 to be properly measured by white light interferometry. Therefore, it becomes possible to properly manage the opening dimensions of the nozzle 90 based on the measurement results, and it becomes possible to maintain consistent recording quality in an inkjet recording device equipped with a liquid ejection substrate 1 having the nozzle substrate 111. With this liquid ejection substrate 1, it becomes possible to impart ink resistance not only to the vicinity of the ejection orifice 100 of the nozzle 90 and the surface of the nozzle substrate 111, but also to the entire flow path of the liquid ejection substrate 1.

[0032] Example 2 In the second embodiment, as shown in FIG. 4, a SiC film is formed as a protective film 1002 by PECVD only on the surface of the liquid discharge substrate 1 and the inner wall surface of the nozzle 90 .

[0033] Table 2 shows the film thickness of the silicon oxide film 110 (SiO film) and the protective film 1002 (SiC film), the white light reflectance of the nozzle substrate 111, whether the opening dimensions of the nozzle 90 can be measured by white light interferometry, and whether or not there is ink resistance. [Table 2]

[0034] The thickness of the silicon oxide film 110 can be adjusted by the etching time, and the thickness of the protective film 1002 can be adjusted by the film formation time.

[0035] Figure 5 is a diagram showing the relationship between the silicon oxide film 110 (SiO film) and the protective film 1002 (SiC film) and reflectance. Figure 5 shows the reflectance of a substrate obtained by simulation when a substrate consisting of a silicon substrate with a SiO film and a SiC film simply laminated thereon is irradiated with light having a wavelength of 530 nm. Figure 5 shows the reflectance in the form of a contour map with the horizontal axis representing the thickness of the SiO film and the vertical axis representing the thickness of the SiC film. In the simulation, the analysis was performed with the refractive index of the SiO film set to 1.46 and the refractive index of the SiC film set to 2.45.

[0036] From the results of the simulation analysis in Table 2 and Figure 5, it was found that in order to properly measure the opening dimensions of the nozzle 90 by white light interferometry for a liquid ejection substrate 1 in which the nozzle 90 portion is covered with a SiC film as a protective film, the reflectivity of the nozzle substrate 111 must be 0.2 or more.

[0037] Fig. 6 is a diagram showing appropriate film thicknesses of SiO and SiC films, which were obtained based on the simulation analysis diagram of Fig. 5, with the horizontal axis (X axis) representing the SiO film thickness and the vertical axis (Y axis) representing the SiC film thickness.

[0038] In FIG. 6, the shaded areas indicate the ranges of values ​​that the SiO film thickness and the SiC film thickness must satisfy in order to obtain a reflectance that can be appropriately measured by white light interferometry.

[0039] In Figure 6, based on the simulation analysis diagram of Figure 5, the portion of the nozzle substrate 111 where the reflectance is 0.2 or more was determined using a linear function. Specifically, when points of high reflectance in the simulation analysis diagram of Figure 5 are connected with a linear function, a straight line with a slope of -1.636 is obtained (Y = -1.636X). Due to the periodicity characteristics, +180n (n: 0, 1, 2, 3, 4, 5) is added to the intercept term. In addition, the tolerance b = -40 to 40.

[0040] In summary, the range of values ​​that the SiO film thickness and SiC film thickness must satisfy in order to obtain a reflectance that can be properly measured by white light interferometry can be expressed as follows: That is, if the thickness of the silicon oxide film is X [nm], the thickness of the SiC film is Y [nm], and the tolerance is b [nm], then: Y=-1.636X+180n+b n=0, 1, 2, 3, 4, 5 |b|≦40 Y>0

[0041] When the surface of the nozzle substrate 111 and the nozzle 90 portion are covered with a protective film 1002 (SiC film) by PECVD, the thickness X of the silicon oxide film 110 (SiO film) constituting the nozzle substrate 111 and the thickness Y of the protective film 1002 (SiC film) are set as described above. This ensures that the reflectance of the white light used in white light interferometry at the nozzle substrate 111 is 0.2 or higher, allowing the opening dimensions of the nozzle 90 to be properly measured by white light interferometry. Therefore, it becomes possible to properly manage the opening dimensions of the nozzle 90 based on the measurement results, and it becomes possible to maintain constant recording quality in an inkjet recording device equipped with a liquid ejection substrate 1 having the nozzle substrate 111. With this liquid ejection substrate 1, it becomes possible to impart ink resistance to the vicinity of the ejection orifices 100 of the nozzles 90 and the surface of the nozzle substrate 111.

[0042] The disclosure of this embodiment includes the following configuration. (Configuration 1) A nozzle substrate having a silicon substrate and a silicon oxide film covering a surface of the silicon substrate stacked together, the nozzle substrate having a discharge port for discharging a liquid, a nozzle that penetrates the nozzle substrate and communicates with the discharge port; a protective film that is resistant to the liquid and that covers at least a surface of the silicon oxide film and an inner wall surface of the nozzle; and A nozzle substrate characterized in that the reflectance of white light used when measuring the nozzle as a step by white light interferometry on the surface of the nozzle substrate is 0.2 or more. (Configuration 2) 2. The nozzle substrate according to configuration 1, wherein the reflectance of light with a wavelength of 530 nm, among the light used in the white light interferometry, on the surface of the nozzle substrate is 0.2 or more. (Configuration 3) 3. The nozzle substrate according to claim 1, wherein the protective film is a TaO film. (Configuration 4) When the thickness of the silicon oxide film is X [nm], the thickness of the TaO film is Y [nm], and the tolerance is b [nm], Y=-1.5X+180n+b n=0, 1, 2, 3, 4, 5 |b|≦40 Y>0 4. The nozzle substrate according to claim 3, (Configuration 5) 3. The nozzle substrate according to claim 1, wherein the protective film is a SiC film. (Configuration 6) When the thickness of the silicon oxide film is X [nm], the thickness of the SiC film is Y [nm], and the tolerance is b [nm], Y=-1.636X+180n+b n=0, 1, 2, 3, 4, 5 |b|≦40 Y>0 6. The nozzle substrate according to claim 5, (Configuration 7) an actuator substrate disposed below the silicon substrate, the actuator substrate having a cavity communicating with the nozzle and an actuator element that generates energy for ejecting the liquid in the cavity from the ejection port; a flow path substrate disposed below the actuator substrate and having a flow path communicating with the cavity; and 7. The nozzle substrate according to any one of configurations 1 to 6, wherein the protective film covers the inner wall surfaces of the cavity and the flow channel. [Explanation of symbols]

[0043] 20: silicon substrate, 90: nozzle, 100: discharge port, 110: silicon oxide film, 111: nozzle substrate, 1001: protective film

Claims

1. A nozzle substrate having a silicon substrate and a silicon oxide film covering a surface of the silicon substrate stacked together, the nozzle substrate having a discharge port for discharging a liquid, a nozzle that penetrates the nozzle substrate and communicates with the discharge port; a protective film that is resistant to the liquid and that covers at least a surface of the silicon oxide film and an inner wall surface of the nozzle; and A nozzle substrate, characterized in that the reflectance of white light used when measuring the nozzle as a step by white light interferometry on the surface of the nozzle substrate is 0.2 or more.

2. 2. The nozzle substrate according to claim 1, wherein the reflectance of light with a wavelength of 530 nm, among the light used in the white light interferometry, on the surface of the nozzle substrate is 0.2 or more.

3. 3. The nozzle substrate according to claim 1, wherein the protective film is a TaO film.

4. When the thickness of the silicon oxide film is X [nm], the thickness of the TaO film is Y [nm], and the tolerance is b [nm], Y=-1.5X+180n+b n=0, 1, 2, 3, 4, 5 |b|≦40 Y>0 The nozzle substrate according to claim 3 , which satisfies the above.

5. 3. The nozzle substrate according to claim 1, wherein the protective film is a SiC film.

6. When the thickness of the silicon oxide film is X [nm], the thickness of the SiC film is Y [nm], and the tolerance is b [nm], Y=-1.636X+180n+b n=0, 1, 2, 3, 4, 5 |b|≦40 Y>0 The nozzle substrate according to claim 5 , which satisfies the above.

7. an actuator substrate disposed below the silicon substrate, the actuator substrate having a cavity communicating with the nozzle and an actuator element that generates energy for ejecting the liquid in the cavity from the ejection port; a flow path substrate disposed below the actuator substrate and having a flow path communicating with the cavity; and The nozzle substrate according to claim 1 , wherein the protective film covers inner wall surfaces of the cavity and the flow channel.

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