KR100561866B1 - Piezo-electric type inkjet printhead and manufacturing method thereof - Google Patents

Abstract

A piezoelectric inkjet printhead and a method of manufacturing the same are disclosed. The disclosed piezoelectric inkjet printhead has two substrates bonded to each other, a lower substrate and an upper substrate. An ink flow path is formed symmetrically with respect to each of the bonding surfaces of the lower substrate and the upper substrate. The ink flow path includes a common flow path having an ink inlet and a manifold, a plurality of restrictors, and a separate flow path having a plurality of pressure chambers and a plurality of nozzles. On the outer surface of each of the lower substrate and the upper substrate, a piezoelectric actuator is provided to provide a driving force for ejecting ink to each of the plurality of pressure chambers. According to such a configuration, since a larger driving force can be provided to a pressure chamber of the same size as in the prior art, ink ejection performance is improved, and since the number of substrates used is reduced compared with the prior art, the manufacturing process is simplified and the manufacturing cost is reduced.

Description

Piezoelectric inkjet printhead and its manufacturing method {Piezo-electric type inkjet printhead and manufacturing method}

1 is a cross-sectional view for explaining a general configuration of a conventional piezoelectric inkjet printhead.

2 is an exploded perspective view showing a specific example of a conventional piezoelectric inkjet printhead.

3 is a partial cross-sectional view of a conventional printhead cut in the longitudinal direction of the pressure chamber shown in FIG.

4 is a graph showing a change in volume and volume of ejected droplets according to the viscosity of the ink.

5 is an exploded perspective view showing a piezoelectric inkjet printhead partially cut according to a preferred embodiment of the present invention.

6 is a partial cross-sectional view of an assembled state of a printhead according to a preferred embodiment of the present invention cut in the longitudinal direction of the pressure chamber shown in FIG.

7A to 7I are cross-sectional views for explaining a step of forming an ink flow path on a substrate in a method of manufacturing a piezoelectric inkjet printhead according to the present invention.

8 is a cross-sectional view illustrating a step of stacking and bonding a lower substrate and an upper substrate.

9A to 9C are cross-sectional views illustrating a step of forming a piezoelectric actuator on an upper substrate and a lower substrate to complete a piezoelectric inkjet printhead according to the present invention.

<Explanation of symbols for the main parts of the drawings>

110 ... lower substrate 120 ... upper substrate

111,121 ... first silicon layer 112,122 ... intermediate oxide film

113,123 Second silicon layer 115,125 Insulation film

131 Ink inlet 132 Manifold

133 ... Restrictor 134 ... Pressure Chamber

135 ... Nozzle 140,150 ... Piezo Actuator

141,151 ... base electrode 142,152 ... piezoelectric film

143,253 ... drive electrode

The present invention relates to an inkjet printhead, and more particularly, to a piezoelectric inkjet printhead having a structure capable of increasing a driving force applied to a pressure chamber and a manufacturing method thereof.

In general, an inkjet printhead is an apparatus for ejecting a small droplet of printing ink to a desired position on a recording sheet to print an image of a predetermined color. The ink ejection method of the inkjet printer includes an electro-thermal transducer (bubble jet method) in which a bubble is generated in the ink by using a heat source to eject the ink with this force, and a piezoelectric material. There is an electro-mechanical transducer (piezoelectric method) in which ink is ejected by a volume change of ink caused by deformation of the piezoelectric body.

A general configuration of the piezoelectric inkjet printhead described above is shown in FIG. Referring to FIG. 1, the manifold 2, the restrictor 3, the pressure chamber 4, and the nozzle 5 constituting the ink flow path are formed inside the flow path forming plate 1. The piezoelectric actuator 6 is provided in the upper part of 1). Manifold (2) is a passage for supplying the ink flowing from the ink reservoir (not shown) to each of the pressure chamber (4), the restrictor (3) is the ink flow into the pressure chamber (4) from the manifold (2) It is a passage. The pressure chamber 4 is a place where the ink to be discharged is filled, and the volume thereof is changed by driving the piezoelectric actuator 6 to generate a pressure change for ejecting or inflowing ink.

The flow path forming plate 1 is mainly formed by cutting a plurality of thin plates of a ceramic material, a metal material or a synthetic resin material to form a portion of the ink flow path as described above, and then stacking the plurality of thin plates. The piezoelectric actuator 6 is provided above the pressure chamber 4, and has a form in which a piezoelectric thin plate and electrodes for applying a voltage to the piezoelectric thin plate are stacked. Accordingly, the portion of the flow path forming plate 1 that forms the upper wall of the pressure chamber 4 serves as the diaphragm 1a that is deformed by the piezoelectric actuator 6.

Referring to the operation of a conventional piezoelectric inkjet printhead having such a configuration, when the diaphragm 1a is deformed by the driving of the piezoelectric actuator 6, the volume of the pressure chamber 4 is reduced, and thus the pressure chamber ( The ink in the pressure chamber 4 is discharged to the outside through the nozzle 5 by the pressure change in 4). Subsequently, when the diaphragm 1a is restored to its original shape by the drive of the piezoelectric actuator 6, the volume of the pressure chamber 4 is increased, and ink is discharged from the manifold 2 by the pressure change. It enters into the pressure chamber 4 via 3.

As a specific example of such a piezoelectric inkjet printhead, FIG. 2 shows a conventional piezoelectric inkjet printhead disclosed in US Pat. No. 5,856,837. 3 is a partial cross-sectional view of a conventional printhead cut in the longitudinal direction of the pressure chamber shown in FIG.

2 and 3 together, the conventional piezoelectric inkjet printhead is formed by stacking and bonding a plurality of thin plates 11 to 16. That is, at the bottom of the printhead, a first plate 11 having a nozzle 11a for discharging ink is disposed, and a second plate having a manifold 12a and an ink discharge port 12b formed thereon ( 12 are stacked, and the third plate 13 having the ink inlet 13a and the ink outlet 13b is stacked thereon. The third plate 13 is provided with an ink inlet 17 for introducing ink from an ink reservoir (not shown) into the manifold 12a. A fourth plate 6 having an ink inlet 14a and an ink outlet 14b is stacked on the third plate 13, and both ends thereof communicate with the ink inlet 14a and the ink outlet 14b, respectively. The fifth plate 15 on which the pressure chamber 15a is formed is stacked. The ink inlets 13a and 14a serve as a passage through which ink flows from the manifold 12a into the pressure chamber 15a, and the ink outlets 12b, 13b and 14b are discharged from the pressure chamber 15a. It serves as a passage through which ink is discharged toward the nozzle 11a. The sixth plate 16 that closes the upper portion of the pressure chamber 15a is stacked on the fifth plate 15, and the drive electrode 20 and the piezoelectric film 21 are formed thereon as a piezoelectric actuator. Therefore, the sixth plate 16 functions as a diaphragm vibrated by the piezoelectric actuator, and the volume of the pressure chamber 15a beneath it is changed by the bending deformation thereof.

The first, second and third plates 11, 12, 13 are generally formed by etching or pressing metal thin plates, and the fourth, fifth and sixth plates 14, 15, 16 are formed. Is generally formed by cutting a ceramic material in the form of a sheet. Meanwhile, the fifth plate 12 on which the manifold 12a is formed may be formed by injection molding or pressing a thin plastic material or an adhesive in the form of a film, or may be formed by pasting the adhesive in the form of a paste. It can be molded by screen printing. And the piezoelectric film 21 formed on the 6th plate 16 is shape | molded by apply | coating and sintering the ceramic material of the paste state which has piezoelectric property.

As described above, in order to manufacture the conventional piezoelectric inkjet printhead shown in FIG. 2, each of a plurality of metal plates and ceramic plates are separately processed by various processing methods, and then stacked and stacked together with each other by a predetermined adhesive. It goes through a complicated process of joining. In addition, in the conventional printhead, the number of plates constituting it is relatively large, and thus, there is a disadvantage in that the number of processes for aligning the plates increases, so that the alignment error is also large. When an alignment error occurs, the flow of ink through the ink flow path is not smooth, which degrades the ink ejection performance of the printhead.

The conventional piezoelectric inkjet printhead has a structure in which one actuator is provided for one pressure chamber. However, in general, in the case of ejecting ink using a piezoelectric inkjet printhead, as shown in FIG. 4, as the viscosity of the ink increases, the flow resistance increases so that the volume and ejection speed of the ejected droplets decrease. As a result, the overall ink ejection performance is lowered.

Therefore, in the high viscosity ink ejection, a larger driving force is required to ensure satisfactory ink ejection performance, so that the driving voltage applied to the piezoelectric actuator is increased. However, as the driving voltage increases, the lifespan of the piezoelectric element is shortened, which causes a problem that the durability of the piezoelectric inkjet printhead decreases. In order to prevent this problem, the driving voltage should be lowered. In this case, the width of the diaphragm should be widened to obtain sufficient driving force even at a low driving voltage. This increases the volume of the pressure chamber, which in turn increases the size of the inkjet printhead. For this reason, as the viscosity of the ink increases, the size of the inkjet printhead increases, so that the manufacturing cost thereof increases.

Therefore, in order to solve this problem, a piezoelectric inkjet printhead having a new structure capable of efficiently discharging high viscosity ink has been required.

The present invention has been made to solve the above problems of the prior art, in particular, a piezoelectric inkjet printhead provided with two piezoelectric actuators for one pressure chamber to increase the driving force applied to the pressure chamber, and a manufacturing method thereof. The purpose is to provide.

The present invention to achieve the above technical problem,

A lower substrate and an upper substrate bonded to each other;

It is formed symmetrically to each of the lower substrate and the bonding surface of the upper substrate, and includes a common flow path having an ink inlet and a manifold, and a plurality of restrictors, and a separate flow path having a plurality of pressure chambers and a plurality of nozzles Ink flow path; And

And a piezoelectric actuator formed on an outer surface of each of the lower substrate and the upper substrate to provide a driving force for ejecting ink to each of the plurality of pressure chambers.

Here, the lower substrate and the upper substrate are preferably made of an SOI wafer having a structure in which a first silicon layer, an intermediate oxide film, and a second silicon layer are sequentially stacked. In this case, the ink flow path is formed in the first silicon layer, and the second silicon layer serves as a diaphragm in which the second silicon layer is bent and deformed by driving the piezoelectric actuator.

The plurality of nozzles may be formed to communicate with the outside through side surfaces of the lower substrate and the upper substrate. The manifold is formed long in one direction, the ink inlet is formed on one side of the manifold, the plurality of pressure chambers may be arranged in one row on the other side of the manifold. In this case, the ink inlet is preferably formed long along the longitudinal direction of the manifold so that ink can be supplied through the entire one side of the manifold.

The piezoelectric actuator; A base electrode formed on the outer surface of each of the lower substrate and the upper substrate, a piezoelectric film formed on the surface of the base electrode, and a driving electrode formed on the surface of the piezoelectric film to apply a driving voltage to the piezoelectric film. have. In this case, the base electrode preferably has a two-layer structure in which a Ti layer and a Pt layer are sequentially stacked.

As described above, the piezoelectric actuators provided on the lower substrate and the upper substrate may be simultaneously controlled by one control unit or may be controlled by two control units.

In addition, the present invention provides a method of manufacturing a printhead of the above-described structure.

The preparation method of the present invention is:

Preparing a lower substrate and an upper substrate;

Finely processing one surface of each of the lower substrate and the upper substrate in the same manner to form an ink flow path having a shape symmetrical with each other on the lower substrate and the upper substrate;

Bonding the lower substrate and the upper substrate such that respective flow path formation surfaces face each other; And

And forming a piezoelectric actuator on the outer surface of each of the lower substrate and the upper substrate to provide a driving force for ejecting ink.

Here, it is preferable to use an SOI wafer having a structure in which a first silicon layer, an intermediate oxide film, and a second silicon layer are sequentially stacked as the lower substrate and the upper substrate.

In this case, the flow path forming step; Etching the first silicon layer from the surface to a predetermined depth to form an ink inlet, a plurality of restrictors, and a plurality of nozzles; and dry etching the first silicon layer using the intermediate oxide layer as an etch stop layer. Preferably, the method includes forming a fold and a plurality of pressure chambers. In this case, the ink inlet, the restrictor, and the nozzle may be formed at different depths.

In the bonding step, the bonding between the lower substrate and the upper substrate is preferably performed by a silicon direct bonding (SDB) method.

In addition, before the piezoelectric actuator forming step, the step of forming a silicon oxide film as an insulating film on the outer surface of each of the lower substrate and the upper substrate may be further provided.

In addition, the piezoelectric actuator forming step may include; Sequentially stacking a Ti layer and a Pt layer on outer surfaces of each of the lower substrate and the upper substrate, forming a base electrode, forming a piezoelectric film on the surface of the base electrode, and driving electrodes on the surface of the piezoelectric film. It is preferable to include the step of forming a.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements, and the size of each element may be exaggerated for clarity and convenience of description. In addition, when one layer is described as being on top of a substrate or another layer, the layer may be present over and in direct contact with the substrate or another layer, with a third layer in between.

Figure 5 is an exploded perspective view showing a part of the piezoelectric inkjet printhead according to a preferred embodiment of the present invention, Figure 6 is a print according to a preferred embodiment of the present invention cut in the longitudinal direction of the pressure chamber shown in FIG. Partial cross-sectional view of the assembled state of the head.

5 and 6 together, the piezoelectric inkjet printhead according to the present invention is formed by laminating and bonding two substrates 110 and 120. Each of the two substrates 110 and 120 is provided with piezoelectric actuators 140 and 150 for generating an ink flow path and a driving force for ejecting ink.

The ink flow path includes an ink inlet 131 through which ink is introduced from an ink reservoir (not shown), a pressure chamber 134 that fills ink to be ejected and generates a pressure change for ejecting ink, and an ink inlet Manifold 132, which is a common flow path for supplying ink introduced through 131 to the plurality of pressure chambers 134, and a separate flow path for supplying ink from the manifold 132 to each pressure chamber 134. It consists of an instructor 133 and a nozzle 135 through which ink is discharged from the pressure chamber 134.

The two substrates 110 and 120 are both made of a single crystal silicon wafer. Accordingly, ink flow paths may be precisely and easily formed on each of the two substrates 110 and 120 by using micromachining techniques such as photolithography and etching. In particular, the two substrates 110 and 120 are preferably made of a silicon-on-insulator (SOI) wafer. In general, an SOI wafer includes a first silicon layer 111 and 121, an intermediate oxide film 112 and 122 formed on the first silicon layer 111 and 121, and an intermediate oxide film 113 and 123. It has a laminated structure of two silicon layers 113 and 123. The first silicon layers 111 and 121 are made of silicon single crystal and have a thickness of about several tens of micrometers to several hundreds of micrometers, and the intermediate oxide films 112 and 122 oxidize the surfaces of the first silicon layers 111 and 121 by oxidizing the surfaces. It may be formed, the thickness is about 1 ~ 2㎛. The second silicon layers 113 and 123 are also made of silicon single crystal, and the thickness thereof is about several micrometers to several tens of micrometers.

The reason why the SOI wafer is used as the two substrates 110 and 120 is that the height of the pressure chamber 134 can be adjusted accurately. That is, since the intermediate oxide films 112 and 122 forming the intermediate layer of the SOI wafer serve as an etch stop layer, the pressure chamber 134 is determined when the thickness of the first silicon layers 111 and 121 is determined. The height of is also determined accordingly. In addition, the second silicon layers 113 and 123 forming the bottom wall and the ceiling wall of the pressure chamber 134 may be bent and deformed by the piezoelectric actuators 140 and 150 to change the volume of the pressure chamber 134. The thickness of the diaphragm is also determined by the thicknesses of the second silicon layers 113 and 123. This will be described in detail later.

In detail, a manifold having a predetermined depth is formed long in one direction on the upper surface of the lower substrate 110. On one side of the manifold 132, an ink inlet 131, which is a passage through which ink enters the manifold 132 from an ink reservoir (not shown), is formed to a predetermined depth from an upper surface of the lower substrate 110. In particular, the ink inlet 131 is preferably formed long along the longitudinal direction of the manifold 132. This is to allow ink to be supplied from the ink reservoir through the entire side of the manifold 132, so that a more uniform ink supply can be made to each of the plurality of pressure chambers 134.

On the other side of the manifold 132, a plurality of pressure chambers 134 having a longer rectangular parallelepiped shape in the flow direction of the ink are arranged in one row. The pressure chamber 134 may be formed to the same depth as the depth of the manifold 132 from the upper surface of the lower substrate 110.

Between the manifold 132 and the pressure chamber 134, a restrictor 132, which is a separate flow path connecting one end of each of the manifold 132 and the pressure chamber 134, is pressurized from the upper surface of the lower substrate 110. It is formed to a depth shallower than the chamber 134. The width of the restrictor 133 may be smaller than the width of the pressure chamber 134 as shown, but may be the same as the width of the pressure chamber 134. The restrictor 133 not only serves as a passage for supplying ink from the manifold 132 to the pressure chamber 134, but also ink is discharged from the pressure chamber 134 toward the manifold 132 when the ink is discharged. It also serves to suppress backflow. In order to suppress such a back flow of the ink, the restrictor 132 is preferably formed such that its cross-sectional area is smaller than the cross-sectional area of the pressure chamber 134 within a range capable of supplying an appropriate amount of ink to the pressure chamber 134. .

A nozzle 135 for discharging ink from the pressure chamber 134 is formed at the other end of each of the pressure chambers 134 so as to communicate with the outside of the lower substrate 110. The nozzle 135 is formed to have a relatively shallow depth from the upper surface of the lower substrate 110, the width thereof is also narrower than the width of the pressure chamber 134.

On the other hand, the same ink flow path as that formed on the upper surface of the lower substrate 110 is formed symmetrically on the bottom surface of the upper substrate 120. Therefore, detailed description of the ink flow path formed on the bottom surface of the upper substrate 120 will be omitted.

As described above, in the inkjet printhead according to the present invention, the components forming the ink flow path are disposed on each of the lower substrate 110 and the upper substrate 120, and the bonding of the two substrates 110 and 120. It has a shape symmetrical with respect to the plane. That is, the ink inlet 131, the manifold 132, the restrictor 133, the pressure chamber 134, and the nozzle 135 constituting the ink flow path all have one plane, that is, two substrates ( On the joint surfaces 110, 120.

Piezoelectric actuators 140 and 150 are formed on outer surfaces of each of the lower substrate 110 and the upper substrate 120.

Specifically, a silicon oxide film is formed on the upper surface of the upper substrate 120 as the insulating film 125. The insulating film 125 has not only an insulation function between the upper substrate 120 and the piezoelectric actuator 150, but also a function of suppressing diffusion between the upper substrate 120 and the piezoelectric actuator 150 and controlling thermal stress. The piezoelectric actuator 150 includes a base electrode 151 serving as a common electrode, a piezoelectric film 152 deformed by application of a voltage, and a driving electrode 153 for applying a voltage to the piezoelectric film 152. It is provided. The base electrode 151 is formed on the entire surface of the insulating film 125, it is preferably made of two metal thin film layer of Ti layer and Pt layer. The Ti / Pt layer not only functions as a common electrode, but also a diffusion barrier layer that prevents inter-diffusion between the piezoelectric layer 152 formed thereon and the upper substrate 120 thereunder. barrier layer). The piezoelectric film 152 is formed on the base electrode 151 and is disposed at a position corresponding to the pressure chamber 134. The piezoelectric film 152 is deformed by the application of a voltage, and the deformation of the piezoelectric film 152 flexures the second silicon layer 123 of the upper substrate 120, that is, the diaphragm, forming the upper wall of the pressure chamber 134. Will be The driving electrode 153 is formed on the piezoelectric film 152 and serves to apply a voltage to the piezoelectric film 152 as described above.

The insulating film 115 and the piezoelectric actuator 140 are formed on the bottom surface of the lower substrate 110 as described above. The role of the insulating film 115 is the same as the insulating film 125 formed on the upper substrate 120 described above. The piezoelectric actuator 140 also includes a base electrode 141, a piezoelectric film 142, and a driving electrode 143, and their respective structures and roles are the same as described above.

As described above, in the inkjet printhead according to the present invention, piezoelectric actuators 140 and 150 are disposed above and below the pressure chamber 134, respectively. That is, two piezoelectric actuators 140 and 150 are provided for one pressure chamber 134.

Referring to the operation of the piezoelectric inkjet printhead according to the present invention having such a configuration is as follows. Ink introduced into the manifold 132 from the ink reservoir (not shown) through the ink inlet 131 is supplied into each of the plurality of pressure chambers 134 through the restrictor 133. When the ink is filled in the pressure chamber 134, when the voltage is applied to the piezoelectric films 142 and 152 through the driving electrodes 143 and 153 of the piezoelectric actuators 140 and 150, the piezoelectric films 142 and 152 As a result, the second silicon layers 113 and 123 of each of the lower substrate 110 and the upper substrate 120 serving as the diaphragm are bent into the pressure chamber 134. The volume of the pressure chamber 134 is reduced by the bending deformation of the second silicon layers 113 and 123, and the ink in the pressure chamber 134 is increased by the pressure in the pressure chamber 134. 135) is discharged to the outside.

Subsequently, when the voltage applied to the piezoelectric films 142 and 152 of the piezoelectric actuators 140 and 150 is cut off, the piezoelectric films 142 and 152 are restored to their original shape, and thus the second silicon layers 113 and 123 serving as diaphragms. ) Is restored to its original shape, thereby increasing the volume of the pressure chamber 134. Accordingly, ink flows from the manifold 132 into the pressure chamber 134 through the restrictor 133 due to the decrease in pressure in the pressure chamber 134 and the surface tension of the ink formed in the nozzle 135 by the meniscus. do.

As described above, in the piezoelectric inkjet printhead, as the viscosity of the ink increases, the flow resistance for the ink flowing in the ink flow path increases, so the magnitude of the driving force required for ink ejection must increase. The ink ejection performance of the piezoelectric inkjet printhead depends on the magnitude of the driving force. The larger the volume of the pressure chamber, ie the exclusion volume, which is reduced by the bending of the drive, ie the diaphragm, by the application of the drive voltage, the greater the driving force is required.

The exclusion volume is proportional to the area and displacement of the diaphragm (generally the displacement at the center), and in a given structure the displacement of the diaphragm increases in proportion to the drive voltage.

The area of the diaphragm is generally determined by the size of the pressure chamber, and the maximum displacement of the diaphragm is determined by the maximum driving voltage that the piezoelectric film can tolerate. For reference, the maximum driving voltage is determined in relation to the durability of the piezoelectric film.

In the piezoelectric inkjet printhead according to the present invention, unlike the conventional printhead in which one piezoelectric actuator is provided for one pressure chamber, as described above, by configuring two piezoelectric actuators for one pressure chamber, There is an advantage that the driving force is approximately doubled. That is, since the diaphragm driven by each of the two piezoelectric actuators is disposed above and below the pressure chamber, the exclusion volume is doubled for the same driving voltage, and thus the driving force is also doubled. As such, when the driving force is increased twice, the ink ejection performance is improved compared to the conventional printhead even when the viscosity of the ink is increased compared to the pressure chamber of the same size.

In addition, when a printhead having the same driving force as a conventional piezoelectric inkjet printhead is manufactured by using the new structure proposed by the present invention as described above, the size of the printhead is reduced by about half compared with the prior art. Can be. That is, when configured to have the same exclusion volume, since the length of the diaphragm and the piezoelectric actuator can be reduced by half, the volume of the pressure chamber is reduced by half, thereby reducing the size of the piezoelectric inkjet printhead by about half. It can be. For reference, the pressure chamber occupies most of the volume occupied by the ink flow path in the piezoelectric inkjet printhead.

On the other hand, when a printhead having a volume of the same pressure chamber as that of a conventional piezoelectric inkjet printhead is to be manufactured, the driving voltage can be reduced by half. When the driving voltage is lowered as described above, the life of the piezoelectric film is extended, so that a piezoelectric inkjet printhead excellent in overall durability can be obtained. In addition, when the life of the piezoelectric film is set in the same manner as in the related art, the piezoelectric inkjet printhead capable of discharging ink of higher viscosity based on the volume of the same pressure chamber is increased because the driving force increases twice with the same driving voltage. I can make it.

Meanwhile, in the piezoelectric inkjet printhead according to the present invention, two piezoelectric actuators may be connected to one control unit and configured to be controlled at the same time. Two piezoelectric actuators may be connected to the two control units so as to be controlled. It can also be configured. In particular, in the latter case, since the waveforms of the driving voltages applied to the two piezoelectric actuators can be controlled respectively, the speed of the discharged droplets and the volume of the droplets can be more efficiently controlled.

Hereinafter, a method of manufacturing a piezoelectric inkjet printhead according to the present invention will be described with reference to the accompanying drawings.

First, a general description of a preferred manufacturing method of the present invention, first manufacturing a lower substrate and an upper substrate on which the components constituting the ink flow path, and then laminated and bonded two prepared substrates, and finally the upper substrate The piezoelectric inkjet printhead according to the present invention is completed by forming a piezoelectric actuator on the lower substrate. In this case, since each of the lower substrate and the upper substrate is manufactured in a symmetrical shape through the same process, only a method of forming an ink flow path in the lower substrate will be described below for convenience of description.

7A to 7I are cross-sectional views for explaining a step of forming an ink flow path on a substrate in a method of manufacturing a piezoelectric inkjet printhead according to the present invention.

First, referring to FIG. 7A, in the present embodiment, the lower substrate 110 is formed of a single crystal silicon substrate. This is because silicon wafers widely used in the manufacture of semiconductor devices can be used as they are and are effective for mass production. The thickness of the lower substrate 110 is approximately 50 to 200 μm, which may be appropriately determined according to the height of the pressure chamber. In addition, it is preferable to use an SOI wafer as the lower substrate 110 because the height of the pressure chamber can be accurately formed. As described above, the SOI wafer has a laminated structure of the first silicon layer 111, the intermediate oxide film 112, and the second silicon layer 113. In particular, the second silicon layer 113 has a thickness of several micrometers to several tens of micrometers as a condition for optimizing the thickness of the diaphragm.

When the lower substrate 110 is placed in an oxidation furnace and wet or dry oxidation, the upper and lower surfaces of the lower substrate 110 are oxidized to form silicon oxide films 161 and 162.

Next, as shown in FIG. 7B, photoresist PR is applied to the surface of the silicon oxide film 161 formed on the upper surface of the lower substrate 110. Subsequently, the coated photoresist PR is developed to form a first opening 171 for forming a nozzle on the upper surface of the lower substrate 110, a second opening 172 for forming a restrictor, and an ink inlet. A third opening 173 for forming is formed.

Next, as shown in FIG. 7C, the photoresist PR is used as an etch mask using the silicon oxide film 161 of the exposed portions through the first, second and third openings 171, 172, and 173. The top surface of the lower substrate 110 is partially exposed by removing by dry etching such as reactive ion etching (RIE). In this case, the silicon oxide layer 161 may be removed by wet etching instead of dry etching.

Next, as shown in FIG. 7D, the lower substrate 110 of the exposed portion is etched by a predetermined depth using the photoresist PR as an etch mask, whereby the nozzle 135, the restrictor 133, and the ink inlet are formed. 131 is formed. In this case, etching of the lower substrate 110 may be performed by a dry etching method using reactive ion etching (RIE) or inductively coupled plasma (ICP). Subsequently, when the photoresist PR is stripped, the lower substrate 110 as shown in FIG. 7E is prepared.

On the other hand, the above is shown and described as a strip of the photoresist PR after dry etching the lower substrate 110 by using the photoresist (PR) as an etching mask, otherwise, first the photoresist (PR) The lower substrate 110 may be dry etched using the silicon oxide layer 161 as an etch mask. That is, when the silicon oxide film 161 formed on the upper surface of the lower substrate 110 is relatively thin, etching is performed while leaving the photoresist PR intact, and when the silicon oxide film 161 is relatively thick, the photoresist ( After the PR is stripped, it is preferable to perform etching using the silicon oxide film 161 as an etching mask.

In addition, the nozzle 135, the restrictor 133, and the ink inlet 131 are simultaneously formed and described on the upper surface of the lower substrate 110. However, when the depths of the nozzle 135, the restrictor 133, and the ink inlet 131 are different from each other, the process of forming them is performed separately. That is, the steps of FIGS. 7B to 7D are repeatedly performed for the nozzle 135, the restrictor 133, and the ink inlet 131, respectively.

Next, referring to FIG. 7F, photoresist PR is applied to the entire surface of the resultant product of FIG. 7E. Subsequently, the coated photoresist PR is developed to form a fourth opening 174 for forming a pressure chamber and a fifth opening 175 for forming a manifold on the upper surface of the lower substrate 110.

Subsequently, dry etching such as reactive ion etching (RIE) is performed using the silicon oxide layer 161 of the portions exposed through the fourth and fifth openings 174 and 175 as the photoresist PR as an etching mask. By removing it, the top surface of the lower substrate 110 is partially exposed, as shown in FIG. 7G. In this case, the silicon oxide layer 161 may be removed by wet etching instead of dry etching.

Next, as shown in FIG. 7H, the lower substrate 110 of the exposed portion is etched by a predetermined depth using the photoresist PR as an etching mask to form the pressure chamber 134 and the manifold 132. . In this case, etching of the lower substrate 110 may be performed by a dry etching method using an inductively coupled plasma (ICP).

In addition, when the SOI wafer is used as the lower substrate 110 as illustrated, the intermediate oxide film 112 of the SOI wafer serves as an etch stop layer. In this step, the first silicon layer 111 may be used. ) Is only etched. Therefore, when the thickness of the first silicon layer 111 is adjusted in the wafer polishing process, the pressure chamber 134 can be accurately adjusted to a desired height.

After the pressure chamber 134 and the manifold 132 are formed as described above, the photoresist PR is stripped, and the remaining silicon oxide films 161 and 162 are removed by etching, as shown in FIG. 7I. The lower substrate 110 in the same state is completed.

8 is a cross-sectional view illustrating a step of stacking and bonding a lower substrate and an upper substrate.

Referring to FIG. 8, the upper substrate 120 is stacked on the lower substrate 110 prepared through the above-described steps and bonded to each other. As described above, the upper substrate 120 may be prepared through the steps illustrated in FIGS. 7A to 7I. In detail, the two substrates 110 and 120 are aligned using a mask aligner with their respective flow path forming surfaces facing each other. In this case, since only two substrates 110 and 120 are used in the present invention, an alignment error between the substrates 110 and 120 may be minimized. In addition, bonding between the two substrates 110 and 120 may be performed by a well-known silicon direct bonding (SDB) method. Here, the silicon direct bonding (SDB) method, the two silicon substrates (110, 120) in close contact with the two silicon substrates (110, 120) through the heat treatment, such as annealing (annealing) without using an adhesive It is a method of direct bonding.

When the two substrates 110 and 120 are laminated and bonded as described above, an ink flow path for ink flow in the inkjet printhead is formed between the two substrates 110 and 120 in a perfect form. That is, a common flow path leading from the ink reservoir (not shown) to the manifold 132 through the ink inlet 131, from the manifold 132, the restrictor 133, the pressure chamber 134, and the nozzle 135. The individual flow path leading to) is completed.

9A to 9C are cross-sectional views illustrating a step of forming a piezoelectric actuator on an upper substrate and a lower substrate to complete a piezoelectric inkjet printhead according to the present invention.

First, referring to FIG. 9A, in a state in which the upper substrate 120 is stacked and bonded on the lower substrate 110, a silicon oxide film is formed as an insulating layer 125 on an outer surface, that is, an upper surface of the upper substrate 120. . However, the step of forming the insulating film 125 can be omitted. That is, when an oxide film having a sufficient thickness is already formed on the upper surface of the upper substrate 120 in the annealing process in the above-described silicon direct bonding (SDB) step, it is not necessary to form the insulating film 125 thereon again.

Subsequently, the base electrode 151 of the piezoelectric actuator is formed on the insulating film 125. The base electrode 151 may be formed of two metal thin layers of a Ti layer and a Pt layer. The base electrode 151 may be formed by sequentially depositing Ti and Pt on the entire surface of the insulating film 125 by sputtering. The base electrode 151 serves as a common electrode of the piezoelectric actuator.

Next, as shown in FIG. 9B, the piezoelectric film 152 and the driving electrode 153 are formed on the base electrode 151. Specifically, the piezoelectric material in a paste state is applied to the upper portion of the pressure chamber 134 by screen printing at a predetermined thickness, and then dried for a predetermined time. Various piezoelectric materials may be used, but a conventional lead zirconate titanate (PZT) ceramic material is preferably used. Subsequently, an electrode material such as Ag-Pd paste is printed on the dried piezoelectric film 152. Next, the piezoelectric film 152 is sintered at a predetermined temperature, for example, 900 to 1,000 占 폚.

As a result, the piezoelectric actuator 150 including the base electrode 151, the piezoelectric film 152, and the driving electrode 153 is formed on the upper substrate 120.

As illustrated in FIG. 9C, the base electrode 141, the piezoelectric film 142, and the driving electrode 143 are sequentially stacked on the outer surface of the lower substrate 110, that is, the bottom surface thereof, thereby forming the piezoelectric actuator 140. Form. The method of forming the piezoelectric actuator 140 on the lower substrate 110 is the same as the method of forming the piezoelectric actuator 150 on the upper substrate 120 described above.

Meanwhile, although the piezoelectric actuator 150 is first formed and described above on the upper substrate 120, the piezoelectric actuator 140 may be formed on the lower substrate 120 first. In addition, the process of forming the piezoelectric actuators 150 and 140 on each of the upper substrate 120 and the lower substrate 110 may be performed together.

Finally, a dicing process of cutting the two substrates 110 and 120 in the bonded state by a chip unit, and a polling process of generating piezoelectric properties by applying an electric field to the piezoelectric films 142 and 152. After passing through, the piezoelectric inkjet printhead according to the present invention is completed.

While the preferred embodiments of the present invention have been described in detail, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. For example, the method of forming each component of the printhead in the present invention is merely exemplary, and various etching methods may be applied, and the order of each step of the manufacturing method may be different from that illustrated. Therefore, the true technical protection scope of the present invention will be defined by the appended claims.

As described above, the piezoelectric inkjet printhead and its manufacturing method according to the present invention have the following effects.

First, by providing two piezoelectric actuators for one pressure chamber, it is possible to provide a larger driving force to the pressure chamber of the same size as the conventional. Therefore, since the ejection speed and ejection volume of the ink droplets are increased, improved ejection performance can be ensured even for high viscosity ink.                     

Second, when manufacturing a printhead having the same driving force as a conventional inkjet printhead, since the size of the pressure chamber can be reduced by about half, the manufacturing cost of the printhead can be reduced.

Third, when the pressure chamber of the same size as the conventional inkjet printhead is maintained and the pressure chamber of the same size is maintained, the driving voltage applied to the piezoelectric actuator can be lowered by about half. Therefore, the life of the piezoelectric body can be extended and an inkjet printhead excellent in durability can be obtained.

Fourth, the two piezoelectric actuators may be controlled together by one control unit or may be controlled by the two control units, respectively. In particular, when controlling the two piezoelectric actuators, respectively, it is possible to more efficiently control the speed and volume of the discharged droplets.

Fifth, by forming the ink inlet so that ink can be supplied to the entire side of the manifold, uniform ink supply can be made to each of the plurality of pressure chambers.

Sixth, since the number of substrates to be bonded is reduced as compared with the prior art, the conventional problem due to the alignment error between the substrates is solved, and the number of manufacturing steps of the printhead is significantly reduced. Therefore, there are many advantages such as shortening of the overall manufacturing period of the printhead, reduction in manufacturing cost, and increase in yield due to reduction of defective rate.

Claims (18)

A lower substrate and an upper substrate bonded to each other; It is formed symmetrically on each of the lower substrate and the bonding surface of the upper substrate, the ink inlet through which the ink is introduced, the manifold through which the ink flowing through the ink inlet connected to the ink inlet flows; A plurality of pressure chambers filled with ink to be discharged, a restrictor for supplying ink from the manifold to each of the plurality of pressure chambers by connecting the manifold and each of the plurality of pressure chambers, An ink passage connected to each of the pressure chambers and including a plurality of nozzles for ejecting ink from the plurality of pressure chambers; And A piezoelectric actuator formed on an outer surface of each of the lower substrate and the upper substrate so as to correspond to each of the plurality of pressure chambers to provide a driving force for ejecting ink to each of the plurality of pressure chambers. Anticorrosive inkjet printheads. The method of claim 1, The lower substrate and the upper substrate are each formed of an SOI wafer having a structure in which a first silicon layer, an intermediate oxide film, and a second silicon layer are sequentially stacked, and the ink flow path is formed on the first silicon layer. 2. A piezoelectric inkjet printhead, characterized in that the silicon layer serves as a diaphragm that is deflected and deformed by driving the piezoelectric actuator. The method of claim 1, The plurality of nozzles are piezoelectric inkjet printhead, characterized in that formed in communication with the outside through the side of the lower substrate and the upper substrate. The method of claim 1, The manifold is formed long in one direction, the ink inlet is formed on one side of the manifold, the plurality of pressure chambers are piezoelectric inkjet printhead, characterized in that arranged in one row on the other side of the manifold. The method of claim 4, wherein The ink introduction port is a piezoelectric inkjet printhead, characterized in that formed long along the longitudinal direction of the manifold so that ink can be supplied through the entire one side of the manifold. The method of claim 1, An piezoelectric inkjet printhead, characterized in that an insulating film is formed on the outer surface of each of the lower substrate and the upper substrate, the piezoelectric actuator is formed on the surface of the insulating film. The piezoelectric actuator of claim 1, further comprising: a piezoelectric actuator; A base electrode formed on the outer surface of each of the lower substrate and the upper substrate, a piezoelectric film formed on the surface of the base electrode, and a driving electrode formed on the surface of the piezoelectric film to apply a driving voltage to the piezoelectric film. Piezoelectric inkjet printhead characterized in that. The method of claim 7, wherein The base electrode is a piezoelectric inkjet printhead, characterized in that it has a two-layer structure in which a Ti layer and a Pt layer are sequentially stacked. The method of claim 1, The piezoelectric actuators provided on each of the lower substrate and the upper substrate are simultaneously controlled by one control unit. The method of claim 1, A piezoelectric actuator provided on each of the lower substrate and the upper substrate is controlled by two control units, respectively. Preparing a lower substrate and an upper substrate; One surface of each of the lower substrate and the upper substrate is finely processed in the same manner, an ink inlet through which ink is introduced, a manifold through which ink flowing through the ink inlet flows, and ink to be discharged A plurality of pressure chambers each filled with a plurality of pressure chambers, a restrictor for supplying ink from the manifold to each of the plurality of pressure chambers by connecting the manifold and each of the plurality of pressure chambers; Forming an ink flow path connected to each other, the ink flow path including a plurality of nozzles for ejecting ink from the plurality of pressure chambers, in a shape symmetrical with each other on the lower substrate and the upper substrate; Bonding the lower substrate and the upper substrate such that respective flow path formation surfaces face each other; And Forming a piezoelectric actuator that provides a driving force for ejecting ink to correspond to each of the plurality of pressure chambers on outer surfaces of each of the lower and upper substrates; Manufacturing method. The method of claim 11, And a SOI wafer having a structure in which a first silicon layer, an intermediate oxide film, and a second silicon layer are sequentially stacked as the lower substrate and the upper substrate. The method of claim 12, wherein the forming of the flow path; Etching the first silicon layer from the surface by a predetermined depth to form an ink inlet, a plurality of restrictors, and a plurality of nozzles; And dry etching the first silicon layer using the intermediate oxide layer as an etch stop layer to form a manifold and a plurality of pressure chambers. The method of claim 13, And the ink inlet, the restrictor, and the nozzle are formed at different depths. The method of claim 11, In the bonding step, the bonding between the lower substrate and the upper substrate is carried out by a silicon direct bonding (SDB) method of manufacturing a piezoelectric inkjet printhead. The method of claim 11, And forming a silicon oxide film as an insulating film on an outer surface of each of the lower substrate and the upper substrate before the piezoelectric actuator forming step. The method of claim 11, wherein the piezoelectric actuator forming step; Sequentially forming a Ti layer and a Pt layer on outer surfaces of each of the lower substrate and the upper substrate to form a base electrode; Forming a piezoelectric film on the surface of the base electrode; Forming a drive electrode on the surface of the piezoelectric film comprising the method of manufacturing a piezoelectric inkjet printhead. The method of claim 17, The piezoelectric film forming step may include forming a piezoelectric film by applying a piezoelectric material in a paste state to the base electrode at a position corresponding to the pressure chamber by screen printing and then sintering the piezoelectric film. Manufacturing method.

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