Liquid discharge head and method for producing the same

Abstract

To provide a liquid discharge head with a protective film formed with high patterning precision and to provide a method for producing the same.SOLUTION: A method for producing a liquid discharge head 100 with a substrate comprises: preparing the substrate having an uneven region 13 with a plurality of concave and convex portions; forming a protective film 8 in a second region 22 that, while covering with a mask member 14 a first region 21 which is a part of the uneven region, is not covered by the mask member in the uneven region; and making a part of the protective film move from the second region to the first region by capillary force.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Structures obtained by microfabricating silicon are widely used in the fields of MEMS and functional devices of electromechanical devices. As an example thereof, there is a liquid ejection head that ejects a liquid. As an example of its use, there is a liquid ejection head of a liquid ejection recording method that lands ejected liquid droplets on a recording medium to perform recording. The liquid ejection head of the liquid ejection recording method includes a substrate provided with an energy generating element that generates energy used to eject a liquid, and a discharge port that discharges ink supplied from a liquid supply port provided on the substrate.

[0003] In recent liquid ejection heads, improvements in printing performance such as high resolution and high-speed printing, and miniaturization and densification of the liquid ejection head in manufacturing have been demanded. Therefore, a silicon substrate is used for the flow path forming substrate and the nozzle substrate, and each substrate is bonded with an adhesive to be manufactured.

[0004] When the droplet ejection head ejects ink droplets, ink may adhere to the surface of the nozzle substrate due to the influence of ink mist or the like. If ink adheres to the surface of the nozzle substrate, when ink droplets are ejected from the discharge port, the ink droplets may be affected and the ejection direction of the ink droplets may vary. Therefore, a protective film (ink repellent film) is formed on the surface of the nozzle substrate to prevent the adhesion of ink to the periphery of the nozzle, thereby improving the ejection characteristics of the ink droplets.

[0005] When joining a mounting member to the surface of a nozzle substrate on which a protective film is formed, the protective film inhibits the adhesion between the adhesive and the substrate. Therefore, it is necessary to form an area without a protective film for adhesion while forming a protective film around the nozzle on the surface of the nozzle substrate. As a method of patterning the protective film to form the protective film only in a desired area, for example, Patent Document 1 below describes a method of patterning the film by using a hard mask in film formation by vapor deposition. When vaporizing a liquid repellent on a substrate in a vacuum chamber, the protective film can be patterned into the opening pattern of the hard mask by masking the substrate surface with the hard mask.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0007] In the method described in Patent Document 1, the vaporized protective film forming member passes through the opening of the mask member, so that the protective film is patterned on the substrate surface of the portion corresponding to the opening pattern of the mask member. Therefore, the patterning accuracy is affected by the mechanical alignment accuracy between the mask member and the substrate surface (workpiece). In addition, in order to avoid scratches and generation of foreign matter due to contact between the mask member and the nozzle substrate surface, a certain space is provided between the substrate surface and the mask member. Therefore, when the vaporized protective film forming member passes through the opening of the mask member, it may also wrap around to the portion protected by the mask member, resulting in a decrease in the patterning accuracy of the protective film.

[0008] In view of the above problems, an object of the present invention is to provide a liquid ejection head in which a protective film is formed with high patterning accuracy and a method for manufacturing the same.

Means for Solving the Problems

[0009] In order to solve the above problems, a method for manufacturing a liquid ejection head according to the present invention is a method for manufacturing a liquid ejection head having a substrate, the method comprising: preparing the substrate having a concavo-convex region in which a plurality of concavo-convex portions are formed; forming a protective film on a second region of the concavo-convex region that is not covered by the mask member while covering a first region, which is a part of the concavo-convex region, with a mask member; and moving a part of the protective film from the second region to the first region by capillary force.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a liquid ejection head in which a protective film is formed with high patterning accuracy and a method for manufacturing the same.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the matters of the present invention, and not all of the combinations of features described in the present embodiments are essential for the solution means of the present invention. The same reference numerals are assigned to the same components.

[0013] (First Embodiment) (Liquid Ejection Head) FIG. 1 is a cross-sectional view of a liquid ejection head 100 according to the present embodiment. A liquid ejection head is a member that is disposed in a liquid ejection apparatus in a state of being mounted on a carriage (not shown) for mounting the liquid ejection head 100, and records images, characters, etc. by ejecting liquid.

[0014] The liquid ejection head 100 includes a flow path substrate 1 that forms a flow path, an actuator substrate 2 that generates pressure for ejecting liquid from ejection ports, and a nozzle substrate 3 on which the ejection ports are formed. Each substrate is joined via an adhesive 4.

[0015] Piezoelectric elements 5 are disposed on the surface of the actuator substrate 2 as actuators. As the piezoelectric elements 5, for example, PZT (lead zirconate titanate) films formed by a sol-gel method or a sputtering method can be applied. Such piezoelectric elements are composed of a sintered body of a metal oxide crystal. Note that although the liquid ejection head of the present embodiment has piezoelectric elements 5 as actuators, it may be a thermal conversion element that converts supplied power into heat and generates pressure.

[0016] The flow path substrate 1 made of silicon is disposed so as to cover the piezoelectric elements 5 and is joined to the surface of the actuator substrate 2 via an adhesive 4. Further, the nozzle substrate 3 is joined to the back surface of the actuator substrate 2 via an adhesive 4.

[0017] An ink tank (not shown) is disposed on the flow path substrate 1, and a liquid flow path portion 6 is formed so as to penetrate the flow path substrate 1. The liquid flow path portion 6 communicates with the inside of the actuator substrate and leads to a plurality of ejection ports (nozzles) 7 formed in the nozzle substrate. That is, the liquid supplied from the ink tank is supplied to the plurality of ejection ports 7 through the liquid flow path portion 6. Note that each substrate can be formed by dry etching. The shapes of the flow path and the nozzle are not limited to those illustrated.

[0018] When a driving voltage is applied from a driving IC (not shown) to the piezoelectric element 5, the piezoelectric element 5 deforms due to the inverse piezoelectric effect. By applying a driving voltage of a Pull-Push-Pull waveform, the volume inside the cavity expands and contracts, resulting in a volume change, and a meniscus is formed on the surface of the discharge port 7 when the liquid in the liquid flow path is pressurized. Then, the pressurized liquid is discharged as droplets from the discharge port 7 by contracting.

[0019] Figure 2 is a top view of the nozzle substrate 3 of the liquid discharge head 100 according to the present embodiment. In the liquid discharge head 100 of the present embodiment, a protective film 8 is formed on the nozzle substrate 3 with high patterning accuracy. The protective film 8 is not limited as long as it can protect the nozzle substrate 3 from ink mist, but it is preferable that the dynamic receding contact angle of the liquid with respect to the protective film is 100° or more so that the ink mist does not easily adhere to the nozzle substrate 3. Further, the protective film 8 is preferably a water-repellent film containing perfluoropolyether. Also, the film thickness of the protective film 8 is not particularly limited, but it is preferably 20 nm or more. The nozzle substrate 3 of the present embodiment has an uneven region where a plurality of minute unevennesses are formed, so that the protective film 8 is formed with high patterning accuracy.

[0020] Next, a method of forming an uneven region on the nozzle substrate 3 of the liquid discharge head 100 of the present embodiment, that is, a step of preparing a substrate having an uneven region where a plurality of unevennesses are formed will be described. Figure 3 is a schematic view showing a method of forming an uneven region on the nozzle substrate 3. First, a laminated substrate in which a flow path substrate 1, an actuator substrate 2, and a nozzle substrate 3 are laminated is prepared. In Figure 3, the actuator substrate 2 and the nozzle substrate 3 are omitted.

[0021] Next, as shown in Figure 3(a), an etching mask is formed in a region of the nozzle substrate 3 that does not become an uneven region (non-uneven region). The etching mask 12 can be formed by exposing and developing the applied resist.

[0022] Next, as shown in FIG. 3(b), the nozzle substrate 3 is etched to form a plurality of unevennesses in the region where the protective film is to be formed. As a method for forming the uneven region 13, it is preferable to employ dry etching using an etching gas or sandblasting to form minute unevennesses, but it is not limited thereto. Further, since the uneven region 13 may damage the discharge port if formed in the vicinity of the discharge port 7, it is preferable that the uneven region 13 is not formed in the vicinity of the discharge port 7.

[0023] Finally, as shown in FIG. 3(c), by removing the etching mask 12, a substrate having an uneven region in which a plurality of unevennesses are formed can be prepared. Note that it is preferable that the uneven region is such that the tips of adjacent convex portions and the tips of concave portions are connected by a slope. Here, the tip of the convex portion represents the highest portion among the convex portions, and the tip of the concave portion represents the deepest portion among the concave portions.

[0024] Next, a method for forming the protective film 8 on the nozzle substrate 3 will be described. FIG. 4 shows a schematic diagram for explaining the process of forming the protective film 8 on the nozzle substrate 3. First, as shown in FIG. 4(a), while covering a first region 21, which is a part of the uneven region of the nozzle substrate 3, with a mask member 14, a protective film is vapor-deposited on a second region 22 of the uneven region that is not covered by the mask member 14. Thereby, the protective film 8 is formed on the second region 22, but the protective film 8 is not formed on the first region 21. Note that it is preferable that an underlayer film (not shown) is formed on the second region where the protective film 8 is formed. Further, before forming the protective film 8, it is preferable to clean the surface of the nozzle substrate. As the cleaning method, for example, plasma treatment, ion beam cleaning, UV ozone cleaning, or the like can be used.

[0025] In the second region 22 where the protective film 8 is formed, a plurality of minute irregularities are formed. Therefore, when left standing for a certain period of time after the protective film 8 is formed, as shown in FIG. 4(b), the protective film 8 moves from the second region 22 to the first region 21 due to the capillary force acting between the protective film 8 and the irregularities. Then, as shown in FIG. 4(c), when the protective film 8 that has reached the first region 21 reaches a region where no irregularities are formed, it stops moving further. Thereby, the pattern of the protective film can be controlled within the region having the irregular shape.

[0026] In the present embodiment, by having the irregularity region, after the protective film 8 is formed in the second region 22, the protective film 8 moves to the first region 21. That is, if the protective film 8 is vapor-deposited on a region narrower than the region where the protective film 8 is desired to be formed on the nozzle substrate 3, the protective film can be formed on a region wider than that. Therefore, even if the protective film forming agent enters between the nozzle substrate 3 and the mask member 14 when the protective film 8 is vapor-deposited, since that region (the first region) is the region where the protective film 8 is to be formed, a decrease in patterning accuracy is suppressed.

[0027] Also, the irregular shape is minute irregularities of a degree at which capillary force acts, and the cross-sectional shape is preferably, for example, a rectangular shape or a V-shaped (tapered shape where the width becomes narrower toward the depth direction). The pattern width (average width between adjacent convex portions) of the irregular shape is preferably smaller than the average depth of the concave portion.

[0028] As shown in FIG. 5, the irregularity region 13 may be present at least on the outermost periphery of the region where the protective film is to be formed. For example, as shown in FIG. 5(a), the irregularity region 13 may be formed on the outermost peripheral portion of the protective film forming region 9 where the protective film 8 is desired to be formed. At this time, as shown in FIG. 5(b), the protective film 8 is patterned so that the end of the pattern overlaps the irregularity region, and after leaving it standing for a certain period of time to move the protective film 8, the pattern of the protective film 8 can be controlled to the shape of the protective film forming region 9 (FIG. 5(c)).

[0029] In addition, compared with the protective film 8 formed on a surface without irregularities, the protective film 8 formed on the irregularity region has higher wiping resistance due to the anchor effect. Thereby, even when the nozzle substrate 3 is wiped for cleaning, the risk of damage to the protective film 8 can be suppressed.

Example

[0030] Examples of the present invention are shown below.

[0031] (Example 1) First, a joined substrate 11 in which a flow path substrate 1, an actuator substrate 2, and a nozzle substrate 3 made of SUS were joined was prepared. Next, a resist excellent in etching resistance was applied to the nozzle substrate 3, and an etching mask 12 was formed by exposure and development. Next, the nozzle substrate 3 was dry-etched to form an irregularity region having an arithmetic mean height Sa of 104 nm. Here, the arithmetic mean height represents the average of the absolute values of the height differences of each point with respect to the average plane of the nozzle substrate surface.

[0032] Next, a protective film 8 made of perfluoropolyether was formed on the surface of the nozzle substrate 3 on which an underlayer film (not shown) was formed by vapor deposition. The protective film 8 was formed by film formation at 200 Å for 1 minute by a resistance heating method. The film formation was performed without heating, and when the degree of vacuum reached ×10 -3 Pa without introducing gas. Next, as shown in Fig. 4(a), the protective film 8 was patterned in the second region by providing a clearance (space) of 0.5 mm on the surface of the nozzle substrate 3 at the time of film formation and installing a mask member 14. The formed film thickness was 76.8 nm.

[0033] Next, it was left standing at room temperature (25 °C) for 24 hours, and the excess protective film that was not fixed was moved from the second region 22 to the first region 21, so that not only the second region 22 but also the first region 21 was covered with the protective film 8. The liquid ejection head 100 was manufactured through the above steps.

[0034] (Example 2) A liquid ejection head 100 was manufactured in the same manner as in Example 1, except that a silicon substrate with an arithmetic mean height Sa of the uneven region of 225 nm was used as the nozzle substrate 3.

[0035] (Comparative Example 1) A liquid ejection head 100 was manufactured in the same manner as in Example 1, except that a silicon substrate was used as the nozzle substrate 3 and no uneven region was formed.

[0036] (Evaluation) It was observed whether the surplus protective film moved from the second region 22 to the first region 21. And the pattern accuracy of the protective film 8 at this time was evaluated. The evaluation criteria are as follows.

[0037] Pattern accuracy A: The protective film 8 is formed only inside the protective film formation region 9. Pattern accuracy B: The protective film 8 is formed both inside and outside the protective film formation region 9. In addition, the protective films formed for Example 1, Example 2, and Comparative Example 1 were immersed in a fluorine-based liquid to remove the surplus protective film not bonded to the surface, leaving only a single layer of the protective film bonded to the surface. Note that the film thickness T of the protective film at this time was 16.2 nm. Even in this state, standing was performed to evaluate the movement of the protective film.

[0038] Table 1 shows the evaluation results in the examples and comparative examples.

[0039]

Table 1

[0040] (Evaluation Results) In Example 1 and Example 2, the movement of the surplus protective film from the second region 22 to the first region 21 was observed, and the pattern accuracy was good. On the other hand, in Comparative Example 1, the movement of the surplus protective film from the second region 22 to the first region 21 was not observed.

[0041] Also, no movement of the protective film was observed in the protective film (T = 16.2 nm) after removing the surplus protective film. Based on these results, it is presumed that the layer of the protective film bonded to the substrate surface cannot move, and the surplus protective film not bonded to the substrate surface is moving. And it is presumed that the protective film does not move even if the arithmetic mean height Sa of the uneven region is too small with respect to the film thickness T of the protective film, and movement occurs when the ratio of T to Sa is within a certain range.

[0042] The presumed mechanism regarding this movement phenomenon of the protective film is as follows. In the case of a surface without unevenness as in Comparative Example 1, as shown in Fig. 6(a), movement does not occur by aggregation due to surface tension. Also, as shown in Fig. 6(b), when T is sufficiently large with respect to Sa, it is presumed that the contribution of aggregation due to surface tension is much larger than the capillary force in the uneven region, so it is equivalent to the case of a surface without unevenness. As shown in Fig. 6(c), when T is of the same degree as Sa, the ratio of the contact area with the substrate surface to the surface area of the protective film increases, the contribution of the capillary force in the uneven region becomes larger than the aggregation due to surface tension, and the protective film moves through the gaps of the unevenness. When the volume of the protective film filling the gaps of the unevenness becomes larger than the volume of the unfilled protective film, it is presumed that the contribution of the capillary force becomes larger than the contribution of the surface tension, and in such a case, the ratio of T to Sa satisfies T / Sa ≤ 2. That is, it is preferable that the film thickness of the protective film is 2 times or less the arithmetic mean height of the uneven region.

[0043] From the above experimental results and presumed mechanism, it is necessary for the movement of the liquid-repellent film that there is a surplus protective film rather than the layer bonded to the substrate surface (20 nm ≤ T), and the ratio of T to Sa is T / Sa ≤ 2. It is more preferable that T / Sa ≤ 1 where the contribution of the capillary force is even larger. The movement of the protective film is caused by standing in an environment at room temperature (25°C), and the movement speed was about 1.0 to 1.5 mm / day from Example 1 and Example 2.

[0044] From the above, by the movement of the protective film in the uneven region of the substrate surface, a liquid ejection head in which the protective film is formed with high patterning accuracy can be provided.

[0045] In the present embodiment, the nozzle substrate 3 has been described as an example of the substrate on which the protective film is formed, but other substrates used for the liquid ejection head 100 may also be used. For example, the actuator substrate 2 or the flow path substrate 1 may be used.

[0046] Summarizing the present invention above, the present invention includes the following configurations.

[0047] (Configuration 1) A method for manufacturing a liquid ejection head having a substrate, a step of preparing the substrate having an uneven region in which a plurality of unevennesses are formed; a step of forming a protective film on a second region of the uneven region that is not covered by the mask member while covering a first region that is a part of the uneven region with a mask member; a step of moving a part of the protective film from the second region to the first region by capillary force; A method for manufacturing a liquid ejection head, comprising the above steps.

[0048] (Configuration 2) The method for manufacturing a liquid ejection head according to Configuration 1, wherein the substrate is a substrate on which a discharge port for discharging liquid is formed.

[0049] (Configuration 3) The method for manufacturing a liquid ejection head according to Configuration 2, wherein a contact angle of the liquid with respect to the protective film is 100° or more.

[0050] (Configuration 4) The method for manufacturing a liquid ejection head according to any one of Configurations 1 to 3, wherein the protective film is a water-repellent film containing perfluoropolyether.

[0051] (Configuration 5) The method for manufacturing a liquid ejection head according to any one of Configurations 1 to 4, wherein a film thickness of the protective film formed in the step of forming the protective film is 20 nm or more.

[0052] (Configuration 6) In the method for manufacturing a liquid ejection head according to any one of Configurations 1 to 5, the film thickness of the protective film formed in the step of forming the protective film is not more than twice the arithmetic mean height of the plurality of unevennesses.

[0053] (Configuration 7) In the method for manufacturing a liquid ejection head according to any one of Configurations 1 to 6, the average width between adjacent convex portions in the unevenness region is smaller than the average depth of the concave portions in the unevenness region.

[0054] (Configuration 8) In the method for manufacturing a liquid ejection head according to any one of Configurations 1 to 7, in the unevenness region, adjacent convex portions and concave portions are connected by a slope.

[0055] (Configuration 9) In the method for manufacturing a liquid ejection head according to any one of Configurations 1 to 8, the step of moving is performed with the substrate being stationary.

[0056] (Configuration 10) A liquid ejection head having a substrate, wherein the substrate has an unevenness region in which a plurality of unevennesses are formed on a part of the surface of the substrate, and a protective film is formed on at least a part of the unevenness region, and no protective film is formed outside the unevenness region.

[0057] (Configuration 11) The liquid ejection head according to Configuration 10, wherein the substrate has ejection ports for ejecting liquid.

[0058] (Configuration 12) The liquid ejection head according to Configuration 11, wherein the contact angle of the liquid with respect to the protective film is 100° or more.

[0059] (Configuration 13) The liquid ejection head according to any one of Configurations 10 to 12, wherein the protective film is a water-repellent film containing perfluoropolyether.

[0060] (Configuration 14) 14. The liquid ejection head according to any one of configurations 10 to 13, wherein the protective film has a thickness of 20 nm or more.

[0061] (Configuration 15) 15. The liquid ejection head according to any one of configurations 10 to 14, wherein the protective film has a thickness that is equal to or less than twice the arithmetic mean height of the plurality of projections and recesses.

[0062] (Configuration 16) 16. The liquid ejection head according to any one of configurations 10 to 15, wherein an average width between adjacent convex portions of the concave-convex region is smaller than an average depth of concave portions of the concave-convex region.

[0063] (Configuration 17) 17. The liquid ejection head according to any one of configurations 10 to 16, wherein the uneven region has adjacent convex portions and concave portions connected by slopes. [Explanation of symbols]

[0064] 1. Flow channel substrate 2 Actuator Board 3 Nozzle Board 7 Outlet 8 Protective film 13 Uneven area 14 Mask material 100 Liquid ejection head

Claims

1. A method for manufacturing a liquid ejection head having a substrate, comprising: preparing the substrate having a concavo-convex region in which a plurality of concavo-convexities are formed; forming a protective film on a second region of the concavo-convex region that is not covered by the mask member while covering a first region, which is a part of the concavo-convex region, with a mask member; moving a part of the protective film from the second region to the first region by capillary force; A method for manufacturing a liquid ejection head, characterized by comprising the above steps.

2. The method for manufacturing a liquid ejection head according to claim 1, wherein the substrate is a substrate on which ejection ports for ejecting liquid are formed.

3. The method for manufacturing a liquid ejection head according to claim 2, wherein the contact angle of the liquid with respect to the protective film is 100° or more.

4. The method for manufacturing a liquid ejection head according to claim 1, wherein the protective film is a water-repellent film containing perfluoropolyether.

5. The method for manufacturing a liquid ejection head according to claim 1, wherein the film thickness of the protective film formed in the step of forming the protective film is 20 nm or more.

6. The method for manufacturing a liquid ejection head according to claim 1, wherein the film thickness of the protective film formed in the step of forming the protective film is not more than twice the arithmetic mean height of the plurality of concavo-convexities.

7. The method for manufacturing a liquid ejection head according to claim 1, wherein the average width between adjacent convex portions in the concavo-convex region is smaller than the average depth of the concave portions in the concavo-convex region.

8. The method for manufacturing a liquid ejection head according to claim 1, wherein in the concavo-convex region, adjacent convex portions and concave portions are connected by a slope.

9. The method for manufacturing a liquid ejection head according to claim 1, wherein the step of moving is performed with the substrate in a stationary state.

10. A liquid ejection head having a substrate, wherein: the substrate has a concavo-convex region in which a plurality of concavo-convexities are formed on a part of the surface of the substrate; a protective film is formed on at least a part of the concavo-convex region, and no protective film is formed outside the concavo-convex region.

11. The liquid ejection head according to claim 10, wherein the substrate has ejection ports for ejecting liquid.

12. The liquid ejection head according to claim 11, wherein the contact angle of the liquid with respect to the protective film is 100° or more.

13. The liquid ejection head according to claim 10, wherein the protective film is a water-repellent film containing perfluoropolyether.

14. The liquid ejection head according to claim 10, wherein the film thickness of the protective film is 20 nm or more.

15. The liquid ejection head according to claim 10, wherein the film thickness of the protective film is not more than twice the arithmetic mean height of the plurality of irregularities.

16. The liquid ejection head according to claim 10, wherein an average width between adjacent convex portions in the irregularity region is smaller than an average depth of a concave portion in the irregularity region.

17. The liquid ejection head according to claim 10, wherein adjacent convex and concave portions in the irregularity region are connected by a slope.

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