JP2009119773A - Nozzle plate for liquid discharging head and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nozzle plate for a miniaturized liquid discharging head capable of facilitating cleaning and a method for manufacturing the same. <P>SOLUTION: This nozzle plate for a liquid discharging head is made of an Si substrate having a plurality of through-holes and is so constituted that one opening of each through-hole functions as a discharge nozzle for discharging a liquid droplet. The opening of the discharge nozzle is formed in a rectangular shape. The plurality of discharge nozzles are arranged in a parallel movement relation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nozzle plate for a liquid discharge head and a method for manufacturing a nozzle plate for a liquid discharge head.

  In recent years, inkjet printers are required to print at high speed and high resolution. A semiconductor process for a silicon substrate or the like, which is a fine processing technique in the micromachine field, is used as a method for forming the components of the ink jet recording head used in this printer. For this reason, many methods for forming a fine structure by etching a silicon substrate have been proposed.

  A nozzle plate having nozzles used in an ink jet recording head is a plate-like member having a thickness of about several hundreds μm in which a plurality of nozzles having a minute opening having a diameter of 5 μm to 10 μm, for example. A liquid discharge head is constructed by attaching a body plate having an ink chamber, a pressure chamber, an ink supply path, etc., which communicates with a nozzle prepared separately, to this nozzle plate, and further providing an actuator such as a piezoelectric element for deforming the pressure chamber. To do. The liquid discharge head deforms the pressure chamber by an actuator, applies pressure to the liquid in the pressure chamber by this deformation, and discharges the liquid in the pressure chamber as droplets from the opening (discharge port) of the nozzle. At this time, recording is performed on the recording paper by using the liquid as recording ink, moving the recording head relative to the recording paper based on the recording signal, and appropriately discharging ink droplets.

  In this way, if ink droplets continue to be ejected from the ejection port, for example, when the liquid ejection head is not operating, the ink adhering to the periphery of the ejection port dries and the nozzle gradually becomes clogged. This causes a problem that an appropriate amount of ink does not reach the recording paper sufficiently. A blade (cleaning blade) that wipes the surface (discharge surface) of the nozzle plate with the discharge ports for discharging droplets so as not to cause problems such as deterioration in print quality or inability to print. There is a cleaning method in which a cleaning blade is moved to wipe off an ink reservoir that causes clogging in a state in which the nozzle is pressed. Examples of wiping include the following.

The cleaning blade has a liquid-absorbing part that wipes away the remaining cleaning liquid by pressing against the nozzle plate during cleaning of the liquid discharge head, and a pressure-contacting part that wipes away ink and foreign matters remaining by pressing the nozzle plate during ink filling and cleaning. Are individually provided. Switching between the liquid absorbing portion and the pressure contact portion of the blade is performed by moving the blade in a direction perpendicular to the carriage moving direction, and wiping is performed by moving in the carriage moving direction (see Patent Document 1).
JP 2003-376221 A

  The inventors conducted a cleaning experiment of a discharge port that discharges droplets by a method of wiping in one direction like the nozzle plate and cleaning blade of Patent Document 1. Specifically, as shown in FIG. 10, the cleaning blade 92 is moved in one direction (→ direction in the figure) to wipe the discharge surface 90 of the nozzle plate having a circular nozzle. The opening 94 was observed. As a result, there is a problem that unwiping remains occur in the portion indicated by A in the opening 94.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid discharge head nozzle plate that is easy to clean and a liquid discharge head nozzle plate manufacturing method. is there.

  Said subject is solved by the following structures.

1. In the nozzle plate for a liquid discharge head, which is composed of a Si substrate having a plurality of through holes, and one opening of the through hole is a discharge port for discharging a droplet.
The opening shape of the discharge port is a rectangle,
The nozzle plate for a liquid discharge head, wherein the plurality of discharge ports are arranged in a parallel movement relationship with each other.

  2. 2. The nozzle plate for a liquid discharge head according to 1, wherein the discharge ports are arranged at equal intervals.

3. The through-hole has a large-diameter portion having a rectangular opening on one surface of the Si substrate, and a rectangular opening on the other surface of the Si substrate, and has a cross-sectional area smaller than the cross-sectional area of the large-diameter portion. It consists of a small diameter part with the discharge port as an opening,
The two sides orthogonal to each other forming the opening shape of the large-diameter portion and the two sides orthogonal to each other forming the opening shape of the discharge port form two sets of parallel relations 1 Or the nozzle plate for liquid discharge heads of 2.

  4). The nozzle plate for a liquid discharge head according to any one of claims 1 to 3, wherein the rectangular shape of the opening of the discharge port is a square.

  5). The nozzle plate for a liquid discharge head according to any one of claims 1 to 4, further comprising a liquid repellent layer on a surface of the Si substrate having the discharge port.

6). A liquid discharge head nozzle plate manufacturing method for manufacturing the liquid discharge head nozzle plate according to claim 4,
Preparing a substrate having a film serving as an etching mask on the surface of the Si substrate having a crystal orientation in the thickness direction of (100) and an in-plane crystal orientation in the plane perpendicular to the thickness direction of (110);
Forming the etching mask on the film, wherein the mask pattern for forming a square including two sides parallel to the crystal orientation of (110) and a direction perpendicular to the crystal orientation as the shape of the discharge port is circular. ,
Performing a photolithography process and an etching process using the etching mask, and forming a through hole having a circular opening shape on the Si substrate based on the etching mask;
Immersing the Si substrate in which the circular through hole is formed in an alkaline solution to selectively etch the Si substrate, and forming the discharge port in which the opening shape of the through hole is square; and
And a step of removing the etching mask from the Si substrate after forming the square discharge port.

  7. 7. The method of manufacturing a nozzle plate for a liquid discharge head according to claim 6, wherein the etching process is a Si anisotropic dry etching process in which etching and sidewall protective film formation are alternately repeated.

  8). 8. The method for producing a nozzle plate for a liquid ejection head according to 6 or 7, further comprising a step of providing a liquid repellent layer on the surface of the Si substrate having the ejection port.

  According to the nozzle plate for a liquid discharge head of the present invention, the opening shape of the discharge ports for discharging a plurality of droplets is a rectangle, and the plurality of discharge ports are arranged in a translational relationship. For this reason, when wiping is performed along two mutually orthogonal side directions that form a rectangular shape of the discharge port, the discharge port can be in a state where there is almost no remaining wiping of the discharge liquid. Further, for example, if the rectangle is a square, the square opening has an opening that obtains the same discharge amount because the length of one side of the square is shorter than the diameter of the circle compared to a circle having the same cross-sectional area. The period of arranging a plurality can be further reduced.

  Also, according to the nozzle plate manufacturing method for a liquid discharge head, it is possible to efficiently manufacture a through-hole having a square opening shape for discharging droplets onto a Si substrate having a specific crystal orientation.

  Accordingly, it is possible to provide a nozzle plate for a liquid discharge head that is easy to clean and small, and a method for manufacturing a nozzle plate for a liquid discharge head that efficiently manufactures the nozzle plate for a liquid discharge head.

  Although the present invention will be described based on the illustrated embodiment, the present invention is not limited to the embodiment. In the nozzle plate for a liquid discharge head, when the discharge surface of a nozzle having a circular discharge port shape is wiped in one direction with a cleaning blade, wiping remains at the position indicated by A in the opening 94 in FIG. Furthermore, as shown in FIG. 11, the inventors performed wiping in a direction perpendicular to the direction in which the wiping direction was performed as described above. As a result, a wiping residue occurred at the position indicated by B in the opening 94 in FIG. Further, wiping was performed on the same opening 94 by changing the direction, for example, at an angle of 45 °, but it was found that although the remaining amount of wiping decreased, there was still wiping remaining.

  As a result of examining the wiping direction and the unwiped state as shown in FIGS. 10 and 11, the inventors have focused on making the nozzle opening shape a rectangle (including a square) instead of a circle. As shown in FIG. 9, the shape of the nozzle opening 84 is a square, and the cleaning blade 82 is first moved along a direction parallel to one of the two orthogonal sides of the opening 84 of the ejection surface 80 for wiping. If it does, there will be wiping residue in the position shown by C of Drawing 9 (a). Subsequently, as shown in FIG. 9B, it was found that when the cleaning blade 82 was moved along the direction parallel to the other of the two orthogonal sides, wiping was hardly caused. . In FIG. 9, the opening 84 is described as a square, but the same is true for a rectangle.

  Thus, in the nozzle plate in which a plurality of discharge ports having a rectangular opening shape are arranged in a parallel movement relationship on the discharge surface, by moving the cleaning blade in the direction of two sides of the rectangular opening shape, The discharge port can be cleaned well with almost no wiping residue remaining. Hereinafter, a nozzle plate having a square nozzle opening shape will be described.

  FIG. 1 schematically shows a nozzle plate 1, a body plate 2, and a piezoelectric element 3 constituting an ink jet recording head (hereinafter referred to as a recording head) H which is an example of a liquid discharge head.

  In the nozzle plate 1, a plurality of nozzles 11 having a square opening shape (opening in the discharge surface 12) for ink discharge are arranged. Further, the nozzle plate 1 is bonded to the body plate 2 so that the pressure chamber groove 24 serving as a pressure chamber, the ink supply path groove 23 serving as an ink supply path, the common ink chamber groove 22 serving as a common ink chamber, and the ink. A supply port 21 is formed.

  And the flow path unit M is formed by bonding the nozzle plate 1 and the body plate 2 so that the nozzle 11 of the nozzle plate 1 and the pressure chamber groove 24 of the body plate 2 correspond one-to-one. Hereafter, the reference numerals of the pressure chamber groove, the supply path groove and the common ink chamber groove used in the above description are also used for the pressure chamber, the supply path and the common ink chamber, respectively.

  Here, FIG. 2 schematically shows a cross section of the recording head H at the positions of Y-Y ′ of the nozzle plate 1 and X-X ′ of the body plate 2. As shown in FIG. 2, the piezoelectric element 3 is bonded to the flow path unit M to the surface of the bottom 25 of each pressure chamber 24 opposite to the surface to which the nozzle plate 1 of the body plate 2 is bonded. Thus, the recording head H is completed. A drive pulse voltage is applied to each piezoelectric element 3 of the recording head H, and vibration generated from the piezoelectric element 3 is transmitted to the bottom 25 of the pressure chamber 24, and the pressure in the pressure chamber 24 is changed by the vibration of the bottom 25. Thus, ink droplets are ejected from the nozzle 11.

  FIG. 3 shows a peripheral portion of the nozzle 11 as an example of the nozzle plate 1. 3A is a cross-sectional view, and FIG. 3B is a top view showing a state in which a plurality of nozzles 11 are arranged. In the nozzle plate 1 of FIG. 3, the nozzle 11 is formed on the Si substrate 30, and the liquid repellent layer 45 is provided on the ejection surface 12 of the nozzle 11. The nozzle 11 includes a large-diameter portion 15 and a small-diameter portion 14, and the large-diameter portion 15 and the small-diameter portion 14 both have a square cross-sectional shape, and the large-diameter portion 15 has a smaller cross-sectional area. Greater than part 14. The center of the opening shape of the large diameter portion 15 and the center of the opening shape of the small diameter portion 14 are concentric. The opening of the discharge surface 12 of the small diameter portion 14 is a discharge port.

  As shown in FIG. 3B, the opening shape of the discharge port of the nozzle 11 is a square, and the plurality of nozzles 11 are arranged in a line at equal intervals while maintaining a parallel movement relationship. In addition, two orthogonal sides forming the opening shape of the large diameter portion 15 and two orthogonal sides forming the opening shape of the small diameter portion 14 form two sets of parallel relations. Therefore, in this example, similarly to the small diameter portion 14, the large diameter portions 15 are arranged in a line at equal intervals while maintaining the relationship of translation.

  As shown in FIG. 3C, the nozzles 11 may be arranged in two rows in a staggered manner. Also in this case, similarly to FIG. 3B, the opening shape of the discharge port of the nozzle 11 is a square, and the plurality of nozzles 11 maintain a parallel movement relationship and are arranged in two rows at equal intervals. Yes. In addition, two orthogonal sides forming the opening shape of the large diameter portion 15 and two orthogonal sides forming the opening shape of the small diameter portion 14 form two sets of parallel relations.

Here, taking the small-diameter portion 14 as an example, when the opening shape of the discharge port of the small-diameter portion 14 is circular or square, a state where N cross-sectional areas of the discharge port are the same and arranged in a row at equal intervals L is shown in FIG. Shown in The diameter d of the circle is 2 / π ^1/2 times (about 1.13 times) the length a of one side of the square. Therefore, as shown in FIG. 4, when N small-diameter portions 14 are arranged in a line at equal intervals L, the circular small-diameter portions 14 are compared with the square small-diameter portions 14 by Δh (= ( Since it is long by 2 / π ^1/2 -1) × d), it is long in the arrangement direction by N × Δh. Comparing the case where the small-diameter portion 14 has a circular opening shape and a square shape, the small-diameter portions 14 can be arranged more densely when the opening shape is square. Therefore, the nozzle plate 1 can be reduced in size. The above description has been made by taking the small-diameter portion 14 as an example, but the large-diameter portion 15 is of course the same.

  The manufacture of the nozzle plate 1 made of Si will be described with reference to FIGS. The large-diameter portion 15 and the small-diameter portion 14 are formed from opposing surfaces of the Si substrate 30, respectively.

  The crystal orientation in the thickness direction of the Si substrate 30 is (100), and the crystal orientation (110) is in a plane perpendicular to the thickness direction. In order to facilitate the determination of the crystal orientation at the time of manufacturing the nozzle plate, it is preferable to provide an orientation flat (Orientation Flat) which is a notch for alignment in the direction of the crystal orientation (110) of the Si substrate 30 (FIG. 7). reference).

First, the formation of the large diameter portion 15 will be described with reference to FIG. A method for forming the large diameter portion 15 on the Si substrate 30 is not particularly limited, but an Si anisotropic dry etching method in which etching and coating are alternately repeated as in the small diameter portion 14 described later can be used. An Si substrate 30 is prepared in which thermal oxide films 32 and 31 made of SiO _{2 serving} as etching masks for etching by this Si anisotropic dry etching method are provided on both surfaces (FIG. 5A). The film serving as an etching mask is not limited to the above-described thermal oxide film, and any film may be used as long as it serves as an etching mask for dry etching of Si and etching of an alkaline solution described later. A membrane is mentioned. The thickness of the thermal oxide films 32 and 31 is set to a thickness that functions as a mask for subsequent Si anisotropic dry etching and etching with an alkaline solution.

  Next, after applying a photoresist 34 to the surface of the thermal oxide film 32 on the side where the large diameter portion 15 is to be formed (FIG. 5B), a photoresist pattern 34a for forming the large diameter portion 15 is formed (FIG. 5). 5 (c)). A top view showing the state of the photoresist pattern 34a on the Si substrate 30 is schematically shown in FIG. An enlarged portion K in FIG. 7 shows an enlarged circular resist pattern portion M15 for forming a circular etching mask for forming a large-diameter portion 15 described later. The circular resist pattern portion M15 for forming the large diameter portion 15 of the nozzle plate 1 is circular with respect to the orientation flat OF of the Si substrate 30, and the arrangement direction (arrow F) is the orientation flat direction (arrow G). Parallel. In this way, the large-diameter portions 15 are arranged in the direction of the crystal orientation (110), and two orthogonal sides of a square that is an opening shape of the large-diameter portion 15 formed by wet etching using an alkali solution described later. May be the same as the crystal orientation (110) direction and the direction perpendicular thereto.

A thermal oxide film pattern 32a is formed by dry etching using, for example, CHF ₃ using the photoresist pattern 34a as an etching mask (FIG. 5D), and this is used as an etching mask in the Si anisotropic dry etching method.

After removing the photoresist pattern 34a by ashing with oxygen plasma or the like (FIG. 5E), the large diameter portion 15 is formed by an Si anisotropic dry etching method in which etching and coating are alternately repeated (FIG. 5F). ). Etching apparatus for performing the anisotropic etching method, ICP (Inductive Coupling Plasma) RIE (Reactive Ion Etching) apparatus is preferably used, for example, as an etching gas during etching, sulfur hexafluoride (SF _6), at the time of coating Fluorocarbon (C ₄ F ₈ ) is used alternately as a deposition gas. The thermal oxide film pattern 32a is used as a subsequent etching mask with an alkaline solution. In the above description, the method for forming the large diameter portion 15 is an anisotropic etching method in which etching and coating are alternately repeated. However, the method is not limited to this. Moreover, what is necessary is just to determine formation conditions by conducting an experiment etc. using the method and apparatus which form the large diameter part 15 previously, and the depth (length) of the large diameter part 15 may become predetermined | prescribed depth.

  Next, the formation of the small diameter portion 14 will be described with reference to FIG. The small-diameter portion 14 is formed using a Si anisotropic dry etching method in which etching and coating are alternately repeated. The forming method is the same as that in the case of the large-diameter portion 15 and will be described below.

  In the Si substrate 30 in which the large-diameter portion 15 shown in FIG. 6A is formed, a photoresist 44 is applied to the surface of the thermal oxide film 31 on the side where the small-diameter portion 14 is formed (FIG. 6B). A photoresist pattern 44a for forming the small diameter portion 14 is formed (FIG. 6C). Since the center of the opening shape of the discharge port of the small diameter portion 14 is concentric with the center of the opening shape of the large diameter portion 15 and is formed so as to communicate with the large diameter portion 15, the direction in which the small diameter portions 14 are arranged has a large diameter. As in the case of the portion, the mask shape for forming the small-diameter portion 14 is circular, which is parallel to the orientation flat direction.

  A thermal oxide film pattern 31a is formed using the photoresist pattern 44a as an etching mask (FIG. 6D), and this is used as an etching mask in the Si anisotropic dry etching method. After the photoresist pattern 44a is removed (FIG. 6E), the small diameter portion 14 is formed through the large diameter portion 15 by the Si anisotropic dry etching method in which etching and coating are alternately repeated (FIG. 6F). )). The thermal oxide film pattern 31a after the formation of the small-diameter portion 14 is used as an etching mask with a subsequent alkaline solution.

  Next, wet etching is performed by immersing the Si substrate 30 in an alkaline solution. The Si substrate 30 can be selectively etched with a significantly different etching rate of the alkaline solution depending on the crystal orientation. That is, the etching rate in the crystal orientation (111) direction is more than 100 times slower than the etching rate in the (100) direction and the (110) direction, and the etching seems to stop when the etching progresses and the (111) plane is exposed. Behave. Using this etching property, when the Si substrate 30 is selectively etched with an alkaline solution, the opening shape can be processed from a circle to a square. Since the etching mask is circular and the etching action by the alkaline solution is limited, the shape of the opening becomes large as a whole, but the shape becomes a square because there is a direction in which the selective etching action is strong. Since this etching proceeds slowly, the shape can be easily controlled, so that the processing accuracy is very good, and a desired shape can be obtained.

  Examples of the alkaline solution for selectively etching the Si substrate include selectivity (also referred to as anisotropy), such as KOH and NaOH. However, the alkaline solution is not limited thereto, and a known selective etchant for Si is used. The concentration and temperature of these etching solutions may be appropriately set depending on a desired etching rate.

  To make the nozzle opening shape square, it is possible to provide a square mask and perform Si anisotropic dry etching, but the processing time is combined with the above dry etching and wet etching with an alkaline solution. It becomes longer compared. In addition, when wet etching with an alkaline solution is performed, the square corners of the nozzle opening shape can be appropriately rounded. Ink retention around corners and corners can be suppressed. Therefore, by combining dry etching and wet etching with an alkaline solution as in this example, it is possible to efficiently manufacture and obtain good discharge performance.

  In addition, when making the opening shape of a nozzle into a rectangle except a square, a rectangular mask can be provided and Si anisotropic dry etching can be performed, but it is not limited to this. Further, when the opening shape of the large-diameter portion is a rectangle other than a square, it can be formed by providing a rectangular mask and performing Si anisotropic dry etching as described above, but is not limited thereto.

FIG. 8 shows an example of a change in the size of the nozzle opening due to the wet etching of the alkaline solution. The horizontal axis indicates the immersion time (etching time) in the alkaline solution, and the vertical axis indicates the size of the nozzle opening. The size of the opening of the nozzle is indicated by a circumscribed circle diameter because the opening shape changes from a circle to a square as the etching progresses. In FIG. 8, at the start of etching, a nozzle having a diameter of about 3.7 μm and a circular shape indicates that the opening gradually increases as etching progresses. The conditions of the alkaline solution (aqueous solution) in this example are shown below.
(1) Alkaline liquid: Crink A-27-a (trade name, Yoshimura Oil Chemical Co., Ltd., main component: sodium metasilicate 19% by mass, pH = 12-13)
(2) Concentration (aqueous solution): 4% by volume
(3) Temperature: 80 ° C
In this example, the opening shape is recognized as a square around 60 minutes after the start of etching. For example, if a square opening with a diagonal length of about 7 μm (side length of about 5 μm) is to be formed, first a nozzle having a circular opening with a diameter of about 3.7 μm is formed, and then the above-mentioned It can be seen that it can be obtained by immersing in an alkaline solution under the above conditions for 120 minutes and etching.

  After obtaining the small-diameter portion 14 having a square opening of a desired size as a discharge port by immersing in an alkali solution as described above, the thermal oxide film patterns 31a and 32a are removed, and as shown in FIG. If a plurality of nozzle plates are formed on one Si substrate 30, the nozzle plate 1 is completed by separating the nozzle plates into individual nozzle plates using a dicing saw or the like (FIG. 6G).

  In the example described so far, the large-diameter portion 15 is first formed on the Si substrate 30 and then the small-diameter portion 14 is formed. However, in reverse order, the small-diameter portion 14 is first formed, and then the large-diameter portion 15 is formed. Can also be formed.

  As a preferred nozzle plate 1, a liquid repellent layer 45 is provided on the ejection surface 12 as shown in FIG. This will be described. By providing the liquid-repellent layer 45 on the discharge surface 12, it is possible to prevent the liquid discharged from the nozzle 11 from seeping out and spreading due to the liquid surface becoming familiar with the discharge surface 12. Specifically, for example, a material having water repellency is used if the liquid is aqueous, and a material having oil repellency is used if the liquid is oily. Generally, FEP (ethylene tetrafluoride, propylene hexafluoride) is used. ), PTFE (polytetrafluoroethylene), fluorosiloxane such as fluorosiloxane, fluoroalkylsilane, amorphous perfluororesin, and the like are often used, and the film is formed on the discharge surface 12 by a method such as coating or vapor deposition. The thickness of the film is not particularly limited, but is preferably about 0.1 μm to 3 μm.

  The liquid repellent layer 45 may be formed directly on the ejection surface 12 of the nozzle plate 1 or may be formed via an intermediate layer in order to improve the adhesion of the liquid repellent layer 45. .

(Example)
The example which manufactures the nozzle plate 1 using FIG. 5, FIG. 6 is demonstrated. A Si substrate 30 having a thickness of 200 μm was prepared. The crystal orientation of Si in the Si substrate 30 is (100) in the thickness direction, and (110) is in the plane perpendicular to the thickness direction. The in-plane crystal orientation is the same as the front and back surfaces. An orientation flat OF (notch) parallel to the direction of the crystal orientation (110) as shown in FIG. 7 is provided so that the direction of the crystal orientation (110) in the plane of the Si substrate 30 can be understood.

  First, 128 circular nozzles in which the diameter of the small-diameter portion 14 is 3.5 μm and the diameter of the large-diameter portion 15 is 60 μm, in which the opening shape of the nozzle plate 1 is a square nozzle, are prepared on the Si substrate 30 described above. . On both surfaces of the Si substrate 30, thermal oxide films 31 and 32 having a thickness of 1.2 μm are provided in advance as etching masks.

  A photoresist 34 is applied on the thermal oxide film 32 (FIG. 5B), and a photoresist pattern 34a is formed by photolithography (FIG. 5C). An etching process is performed using the photoresist pattern 34a to obtain a thermal oxide film pattern 32a as an etching mask (FIG. 5D). The photoresist pattern 34a is removed by an ashing method using oxygen plasma.

  Using the thermal oxide film pattern 32a, the Si substrate 30 was etched to a depth of 195 μm by Si anisotropic dry etching to form the large diameter portion 15 (FIG. 5D).

As a specific method of Si anisotropic dry etching, a Bosch process was used. Sulfur hexafluoride (SF ₆ ) was used as an etching gas, and fluorocarbon (C ₄ F ₈ ) was used alternately as a deposition (side wall protective film formation) gas.

Next, the small-diameter portion 14 is formed on the thermal oxide film 31 that is a SiO ₂ film by photolithography using a double-sided mask aligner so as to be concentric with the hole of the large-diameter portion 15 of the Si substrate 30 produced previously. A photoresist pattern 44a was formed (FIG. 6C).

  Thereafter, a thermal oxide film pattern 31a, which is an etching mask for forming a small diameter portion 14 having a diameter of 3.5 μm on the Si substrate 30 to be an opening of the nozzle on the ejection surface, was formed by etching (FIG. 6D). Thereafter, the photoresist pattern 36a was removed.

  Using the thermal oxide film pattern 31a, the Si substrate 30 was etched until it penetrated the large diameter portion 15 by Si anisotropic dry etching to form the small diameter portion 14 (FIG. 6F).

  In this state, when the opening shapes of the small diameter portion 14 and the large diameter portion 15 were observed with a microscope, the opening shape of the small diameter portion 14 was approximately φ3.7 μm in diameter, and the opening shape of the large diameter portion 15 was substantially circular having a diameter of approximately φ60 μm. Met.

  Next, selective etching was performed by immersing the Si substrate 30 formed with the small-diameter portion 14 and the large-diameter portion 15 as nozzles in the following alkaline solution. The alkaline solution was prepared by heating a 4% by volume aqueous solution of an alkaline solution (trade name: Crink A-27-a (Yoshimura Oil Chemical Co., Ltd., main component: sodium metasilicate 19% by mass)) to 80 ° C. The substrate 30 was immersed for 120 minutes.

  Thereafter, the etching masks 34a and 40a on both sides were removed by reactive ion etching (RIE).

  The Si substrate 30 having nozzle holes formed by the above procedure was individually separated with a dicing saw to produce a nozzle plate 1 having nozzle holes.

  Thereafter, after cleaning, the opening shape of the small-diameter portion 14 was observed with a microscope, and it was confirmed that one side was a square of about 5 μm. Moreover, when the opening shape of the large diameter portion 15 was also observed with a microscope, it was confirmed that one side with the four corners in the same direction as the opening shape of the small diameter portion 14 was square with a square of about 61 μm.

  Next, a body plate 2 as shown in FIG. 1 was manufactured. A pressure chamber groove 24 serving as a plurality of pressure chambers respectively communicating with the nozzle 11 using a known photolithography process (resist application, exposure, development) and a Si anisotropic dry etching technique using the Si substrate, and the pressure An ink supply groove 23 serving as a plurality of ink supply paths communicating with the chambers, a common ink chamber groove 22 serving as a common ink chamber communicating with the ink supply, and an ink supply port 21 were formed.

  Next, as shown in FIG. 1, the nozzle plate 1 and the body plate 2 that have been prepared so far are bonded together using an adhesive, and the piezoelectric plate serving as a pressure generating means is attached to the back surface of each pressure chamber 24 of the body plate 2. The element 3 was attached to form a liquid discharge head.

  In the same manner as described above, the size of the opening in the thermal oxide film pattern 31a which is an etching mask for forming the small diameter portion 14 on the Si substrate 30 and the immersion time in the alkaline solution are appropriately adjusted. Nozzle plates having small diameter portions 14 each having an opening shape of a square of 3.5 μm, 7 μm, and 9 μm were prepared. The large-diameter portion 15 was a square having approximately 61 μm on one side substantially the same as described above. Thereafter, in the same manner as described above, a liquid discharge head provided with these nozzle plates was produced.

Using a liquid discharge head provided with a nozzle plate in which the openings have the four types of small-diameter portions 14 described above, the ink was discharged, the discharge surface was cleaned, and the discharge surface was observed. . The cleaning method and observation were as follows.
(1) After performing continuous discharge for 10 minutes, the cleaning blade was moved once in the direction in which the nozzles are aligned in a row (X direction) to clean all the nozzles, and then the discharge surface was observed with a microscope.
(2) After 10 minutes of continuous discharge, the cleaning blade is moved once in the direction perpendicular to the direction in which the nozzles are lined up (Y direction) to clean all the nozzles, and then the discharge surface Was observed with a microscope.
(3) After 10 minutes of continuous discharge, the cleaning blade is moved once in the X direction to clean all nozzles, and then the cleaning blade is moved once in a direction perpendicular to the Y direction. After cleaning all the nozzles, the discharge surface was observed with a microscope.
(4) After 10 minutes of continuous discharge, the cleaning blade is moved 5 times in the X direction to clean all nozzles, and then the cleaning blade is moved 5 times in the direction perpendicular to the Y direction. After cleaning all the nozzles, the discharge surface was observed with a microscope.

The results are shown in Table 1 below. The symbols shown in the table indicate the following.
A: Almost completely wiped off.
○: Wiping off to a practical level.
X: The wiping state has not reached a practical level.

(Comparative example)
The nozzle plate and this nozzle plate were the same as in Example 1 except that the opening shape of the small diameter portion 14 was changed to a circular shape having a diameter of φ3.5 μm, φ5 μm, φ7 μm, and φ9 μm by dry etching without performing etching with an alkaline solution. A liquid discharge head provided was prepared.

  Thereafter, as in the example, each of the ink ejections was performed using a liquid ejection head having a nozzle plate in which the openings formed the small diameter portions 14 having the four types of sizes described above, and then the ejection surface was cleaned. The discharge surface was observed. The cleaning method and observation were the above (1), (2), (3), and (4). The results are shown in Table 1 together with the results of the examples.

  As Table 1 shows, cleaning is performed in the direction in which the nozzles are aligned in a row and in a direction perpendicular thereto, so that the nozzles with a square nozzle shape have better ink wiping. Was confirmed.

It is a figure which shows the example of a structure of an inkjet recording head. It is a figure which shows typically the cross section in an ink jet type recording head. It is a figure which shows an example of the peripheral part of a nozzle plate. (A) is a sectional view, (b) is a top view showing an example in which discharge ports are arranged, and (c) is a top view showing another example in which discharge ports are arranged. It is a figure explaining the arrangement density in case the opening shape of a small diameter part is a circle, and a square. It is a figure explaining the process of forming the nozzle hole of a nozzle plate. It is a figure explaining the process of forming the nozzle hole of a nozzle plate. It is a figure which shows the relationship of arrangement | positioning with the orientation flat of Si substrate, and the photoresist pattern for forming a mask pattern, and the enlarged circular resist pattern part. It is a figure which shows the relationship between the immersion time (etching time) in an alkaline solution, and the magnitude | size of a nozzle hole. It is a figure explaining the example of the remaining wiping at the time of cleaning the discharge surface of the nozzle whose discharge port is square shape with the cleaning blade. (A) is a state of wiping remaining when wiping is performed in the direction in which the discharge ports are arranged, and (b) is wiping remaining when wiping is further performed in a direction perpendicular to the direction in which the discharge ports are arranged. It is a figure explaining a mode. It is a figure explaining the example of the remaining wiping at the time of cleaning the discharge surface of the nozzle whose discharge outlet is circular as a prior art example with a cleaning blade. It is a figure explaining the example of the remaining wiping at the time of cleaning the discharge surface of the nozzle whose discharge outlet is circular as a prior art example with a cleaning blade.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Body plate 3 Piezoelectric element 11 Nozzle 12, 80, 90 Discharge surface 14 Small diameter part 15 Large diameter part 21 Ink supply port 22 Common ink chamber (groove)
23 Ink supply path (groove)
24 Pressure chamber (groove)
30 Si substrate 31, 32 Thermal oxide film 31a, 32a Thermal oxide film pattern 34a, 44a Photoresist pattern 45 Liquid repellent layer OF orientation flat H Recording head M15 Circular resist pattern portion

Claims (8)

In the nozzle plate for a liquid discharge head, which is composed of a Si substrate having a plurality of through holes, and one opening of the through hole is a discharge port for discharging a droplet.
The opening shape of the discharge port is a rectangle,
The nozzle plate for a liquid discharge head, wherein the plurality of discharge ports are arranged in a parallel movement relationship with each other. 2. The nozzle plate for a liquid discharge head according to claim 1, wherein the discharge ports are arranged at equal intervals. The through-hole has a large-diameter portion having a rectangular opening shape on one surface of the Si substrate, and a rectangular opening shape on the other surface of the Si substrate, and has a cross-sectional area smaller than the cross-sectional area of the large-diameter portion. It consists of a small diameter part with the discharge port as an opening,
The two sides orthogonal to each other forming the opening shape of the large-diameter portion and the two sides orthogonal to each other forming the opening shape of the discharge port form two sets of parallel relations. Item 3. A nozzle plate for a liquid discharge head according to Item 1 or 2. 4. The nozzle plate for a liquid discharge head according to claim 1, wherein the rectangular shape of the opening of the discharge port is a square. 5. 5. The nozzle plate for a liquid discharge head according to claim 1, further comprising a liquid repellent layer on a surface of the Si substrate having the discharge port. 6. A liquid ejection head nozzle plate manufacturing method for manufacturing the liquid ejection head nozzle plate according to claim 4,
Preparing a substrate having a film serving as an etching mask on the surface of the Si substrate having a crystal orientation in the thickness direction of (100) and an in-plane crystal orientation in the plane perpendicular to the thickness direction of (110);
Forming the etching mask on the film, wherein the mask pattern for forming a square including two sides parallel to the crystal orientation of (110) and a direction perpendicular to the crystal orientation as the shape of the discharge port is circular. ,
Performing a photolithography process and an etching process using the etching mask, and forming a through hole having a circular opening shape on the Si substrate based on the etching mask;
Immersing the Si substrate in which the circular through hole is formed in an alkaline solution to selectively etch the Si substrate, and forming the discharge port in which the opening shape of the through hole is square; and
And a step of removing the etching mask from the Si substrate after forming the square discharge port. The method for manufacturing a nozzle plate for a liquid discharge head according to claim 6, wherein the etching process is a Si anisotropic dry etching process in which etching and formation of a sidewall protective film are alternately repeated. 8. The method of manufacturing a nozzle plate for a liquid discharge head according to claim 6, further comprising a step of providing a liquid repellent layer on a surface of the Si substrate having the discharge port.

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