JP4362859B2 - Inkjet recording head and printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording head used for an ink jet printer or the like and a manufacturing method thereof. The present invention also relates to a printer including the above-described ink jet recording head.
[0002]
[Prior art]
The ink jet recording head includes a piezoelectric element formed by sequentially laminating at least a piezoelectric film and an upper electrode on a vibration plate, and a protective film covering the piezoelectric element. As the piezoelectric element is thinned and the ink jet recording head is miniaturized and highly integrated, the thickness of the protective film that protects the piezoelectric element is becoming non-negligible. In particular, when the vibration plate vibrates by driving the piezoelectric element, the protective film of the piezoelectric element also vibrates with the vibration plate. Therefore, the displacement amount of the entire vibration part including the vibration plate, the piezoelectric element, and the protective film is reduced. The film is greatly affected by the film thickness. Further, since the neutral surface of the vibration part is shifted to the upper electrode side from the piezoelectric film, there is a problem that a sufficient amount of displacement and characteristics cannot be secured.
[0003]
[Problems to be solved by the invention]
However, it is difficult to reduce the thickness of the protective film because the function of the protective film itself such as moisture resistance is reduced.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording head that can secure a displacement amount and characteristics of a vibrating portion without reducing the thickness of a protective film, can be highly integrated, and has high performance.
[0005]
It is another object of the present invention to provide a printer having the above-described ink jet recording head and having a high printing speed and a high resolution.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, an ink jet recording head of the present invention includes a piezoelectric element formed by sequentially laminating at least a piezoelectric film and an upper electrode on a vibration plate, and covering the piezoelectric element with the vibration plate. A protective film that is in close contact, and has a surface on the diaphragm that has higher adhesion to the protective film than the upper electrode.
[0007]
Since the adhesiveness between the upper electrode and the protective film is low, the protective film can ensure the displacement amount and characteristics of the vibrating part without inhibiting the vibration of the vibrating part. Thereby, high performance and high integration of the ink jet recording head can be realized.
[0008]
In the ink jet recording head, it is preferable that the protective film is peeled off from the upper electrode when the piezoelectric element is driven. Thereby, since the upper electrode and the protective film are peeled off, a sufficient amount of displacement can be obtained without the vibration of the vibration part being greatly affected by the protective film.
[0009]
In the ink jet recording head, it is preferable that an adhesive layer having higher adhesion to the protective film than the upper electrode is laminated on the vibration plate, and the protective film is laminated on the adhesive layer. Thereby, peeling with a diaphragm and a protective film can be prevented.
[0010]
In the ink jet recording head, a pressure chamber surrounded by a side wall is formed on a surface of the diaphragm opposite to the piezoelectric element forming surface, and the piezoelectric element forming surface of the diaphragm is opposed to the side wall. It is desirable that an adhesion layer having higher adhesion to the protective film than the upper electrode is laminated at a position where the protective film is formed, and the protective film is laminated on the adhesion layer. This is because the position facing the partition wall has a small amplitude, and thus it is difficult to inhibit the vibration of the vibration part even if the protective film is closely attached.
[0011]
In the ink jet recording head, the protective film is preferably made of parylene. Since parylene has low adhesion with platinum and iridium that are usually used for the upper electrode, it can be made lower in adhesion than the contact surface with the diaphragm.
[0012]
In the ink jet recording head, it is desirable that a chromium layer is laminated on the diaphragm and the protective film is laminated on the chromium layer. Since chromium has high adhesiveness with parylene, the adhesiveness between the protective film and the diaphragm can be enhanced.
[0013]
In the ink jet recording head, it is desirable to have a gas layer between the protective film and the upper electrode. Thereby, the displacement amount of the vibration part can be further increased.
[0014]
A printer according to the present invention includes the ink jet recording head. Since the above-described ink jet recording head capable of high performance and high integration is used, a printer with high printing speed and high resolution can be provided.
[0015]
The method for manufacturing an ink jet recording head according to the present invention includes a step of sequentially stacking at least a piezoelectric film and an upper electrode on a vibration plate to form a piezoelectric element, and a step of forming a protective film covering the piezoelectric element. A step of forming a protective film such that a contact surface having higher adhesion than a contact surface of the protective film with respect to the upper electrode is formed between the protective film and the diaphragm; and the piezoelectric element. Applying a voltage to the upper electrode to peel off the protective film. As a result, the protective film and the upper electrode are peeled off, and an ink jet recording head capable of high integration with a large amount of displacement of the vibration portion and high performance can be easily manufactured. In addition, by manufacturing a printer using the ink jet recording head manufactured by this method, a printer with high printing speed and high resolution can be easily manufactured.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
(Overall configuration of inkjet printer)
FIG. 1 is a perspective view illustrating the structure of a printer in which the ink jet recording head of this embodiment is used. In this printer, a main body 2 is provided with a tray 3, a discharge port 4, and operation buttons 9. Furthermore, an ink jet recording head 1, a supply mechanism 6, and a control circuit 8 are provided inside the main body 2.
[0018]
The ink jet recording head 1 includes a plurality of piezoelectric elements formed on a substrate, and is configured to be able to eject ink from nozzles corresponding to ejection signals supplied from the control circuit 8.
[0019]
The main body 2 is a housing of the printer, and a supply mechanism 6 is arranged at a position where the paper 5 can be supplied from the tray 3, and the ink jet recording head 1 is arranged so that printing can be performed on the paper 5. The tray 3 is configured to be able to supply the paper 5 before printing to the supply mechanism 6, and the discharge port 4 is an outlet for discharging the paper 5 that has been printed.
[0020]
The supply mechanism 6 includes a motor 600, rollers 601 and 602, and other mechanical structures (not shown). The motor 600 is rotatable in response to the drive signal supplied from the control circuit 8. The mechanical structure is configured so that the rotational force of the motor 600 can be transmitted to the rollers 601 and 602. The rollers 601 and 602 are rotated when the rotational force of the motor 600 is transmitted, and the paper 5 placed on the tray 3 is drawn by the rotation, and is supplied by the head 1 so as to be printable. Yes.
[0021]
The control circuit 8 includes a CPU, a ROM, a RAM, an interface circuit, and the like (not shown). The control circuit 8 supplies a drive signal to the supply mechanism 6 in correspondence with print information supplied from a computer via a connector (not shown), and discharge signals. Can be supplied to the ink jet recording head 1. In addition, the control circuit 8 can perform operation mode setting, reset processing, and the like in response to an operation signal from the operation panel 9.
[0022]
Since the printer of this embodiment includes an inkjet recording head that can be highly integrated with high performance, which will be described later, the printer has a high printing speed and a high resolution.
[0023]
(Configuration of inkjet recording head)
FIG. 2 is an explanatory diagram of the structure of the ink jet recording head according to the present embodiment. As shown in the drawing, the ink jet recording head 1 includes a nozzle plate 10, a pressure chamber substrate 20, and a vibration plate 30. This head constitutes an on-demand type piezo jet head.
[0024]
The pressure chamber substrate 20 includes a cavity (pressure chamber) 21, a side wall (partition wall) 22, a reservoir 23, and a supply port 24. The cavity 21 is a space for storing ink or the like formed by etching a substrate such as silicon. The side walls 22 are formed so as to partition the cavities 21. The reservoir 23 is a flow path for filling the cavities 21 with ink in common. The supply port 24 is formed so that ink can be introduced from the reservoir 23 into each cavity 21. The shape of the cavity 21 and the like can be variously modified by an ink jet method. For example, it may be a planar Kyser shape or a cylindrical Zoltan shape. Further, the cavity may be configured for one chamber type or may be configured for two chamber types.
[0025]
The nozzle plate 10 is bonded to one surface of the pressure chamber substrate 20 so that the nozzle holes 11 are disposed at positions corresponding to the cavities 21 provided in the pressure chamber substrate 20. The pressure chamber substrate 20 to which the nozzle plate 10 is bonded is further housed in a housing 25 to constitute the ink jet recording head 1.
[0026]
The diaphragm 30 is bonded to the other surface of the pressure chamber substrate 20. The diaphragm 30 is provided with a piezoelectric element (not shown). The vibration plate 30 is provided with an ink tank port (not shown) so that ink stored in an ink tank (not shown) can be supplied into the pressure chamber substrate 20.
[0027]
(Layer structure)
FIG. 3 is a cross-sectional view for explaining a more specific structure of the ink jet recording head of this embodiment. This sectional view is an enlarged view of a section corresponding to one piezoelectric element. As shown in the figure, the diaphragm 30 is configured by laminating an insulating film 31 and a lower electrode 32, and the piezoelectric element is configured by laminating a piezoelectric film 41 and an upper electrode 42 on the lower electrode 32. . A protective film 51 that covers the piezoelectric element is laminated on the upper surface of the diaphragm 30 and the piezoelectric element. In particular, the ink jet recording head 1 is configured by connecting piezoelectric elements, cavities 21 and nozzle holes 11 at a constant pitch. The pitch between the nozzles can be appropriately changed in design according to the printing accuracy. For example, they are arranged to be 400 dpi (dot per inch).
[0028]
The insulating film 31 is made of a non-conductive material, for example, silicon dioxide (SiO ₂ ) formed by thermally oxidizing a silicon substrate, and is deformed by deformation of the piezoelectric film layer, so that the pressure inside the cavity 21 is instantaneously changed. It is possible to increase it. Although the lower electrode 32 is formed on the insulating film 31, a zirconium oxide film may be formed between the insulating film 31 and the lower electrode 32.
[0029]
The lower electrode 32 is one electrode for applying a voltage to the piezoelectric film layer, and is made of a conductive material such as platinum (Pt). The lower electrode 32 is not limited to this, and may be made of iridium (Ir), which is a metal having the same FCC structure as platinum. The lower electrode 32 shown in the drawing is formed in the same region as the insulating film 31 so as to function as an electrode common to a plurality of piezoelectric elements formed on the pressure chamber substrate 20. However, it may be formed in the same size as the piezoelectric film 41, that is, in the same shape as the upper electrode 42. In this case, the insulating film 31 constitutes the diaphragm 30.
[0030]
The piezoelectric film 41 is a piezoelectric ceramic crystal having a perovskite structure, for example, and is formed on the diaphragm 30 in a predetermined shape. Its composition, for example, lead zirconate titanate _{(Pb (Zr 0 56, Ti} 0 44) O 3:.. PZT) other, lead lanthanum titanate _{((Pb, La) TiO 3} ), zirconium acid lead lanthanum ( (Pb, La) ZrO ₃₎ or magnesium niobate zirconium titanate _{(Pb (Mg, Nb) (} Zr, Ti) O 3: PMN-PZT), zirconium acid titanate, barium (Ba (Zr, Ti) O ₃ : BZT), barium titanate (BT), and the like.
[0031]
The upper electrode 42 becomes the other electrode for applying a voltage to the piezoelectric film layer, and is made of a conductive material such as platinum (Pt) or iridium (Ir).
[0032]
The protective film 51 is made of a material having low adhesion to the upper electrode, such as parylene, and covers the piezoelectric element together with the vibration plate 30. It is desirable that the adhesion is so low that the protective film 51 is peeled off from the upper electrode 42 when the piezoelectric element is driven.
[0033]
On the diaphragm 30, it is necessary that a portion having higher adhesion to the protective film 51 than the upper electrode 41 exists. In particular, it is desirable to form an adhesion layer 50 that improves the adhesion between the diaphragm and the protective film. The adhesion layer 50 is made of, for example, chromium (Cr) and has high adhesion with the parylene constituting the protection film 51, so that the entire protection film is prevented from peeling from the ink jet recording head. The adhesion layer 50 is desirably formed in a portion where the substrate 20 remains without being etched, that is, a portion facing the side wall 22. This is because the portion facing the side wall 22 is the portion with the smallest amplitude in the diaphragm 30, and even if a protective film is in close contact therewith, it is difficult to inhibit the vibration of the diaphragm. An air layer may be formed between the protective film 51 and the upper electrode 42.
[0034]
(Printing operation)
A printing operation in the configuration of the ink jet recording head 1 will be described. When a drive signal is output from the control circuit 8, the supply mechanism 6 operates and the paper 5 is conveyed to a printable position by the head 1. When no discharge signal is supplied from the control circuit 8 and no voltage is applied between the lower electrode 32 and the upper electrode 42 of the piezoelectric element, the piezoelectric film 41 is not deformed. No pressure change occurs in the cavity 21 provided with the piezoelectric element to which no discharge signal is supplied, and no ink droplet is discharged from the nozzle hole 11.
[0035]
On the other hand, when a discharge voltage is supplied from the control circuit 8 and a constant voltage is applied between the lower electrode 32 and the upper electrode 42 of the piezoelectric element, the piezoelectric film 41 is deformed. In the cavity 21 provided with the piezoelectric element to which the discharge signal is supplied, the vibration plate 30 is greatly bent. For this reason, the pressure in the cavity 21 increases instantaneously, and ink droplets are ejected from the nozzle holes 11. Arbitrary characters and figures can be printed by individually supplying ejection signals to the piezoelectric elements at the positions to be printed in the head.
[0036]
(Production method)
Next, a method for manufacturing the ink jet recording head according to this embodiment will be described. 4 and 5 are cross-sectional views of the manufacturing process of the ink jet recording head according to the present embodiment.
[0037]
Insulating film forming step (S1)
An insulating film 31 is formed on the silicon substrate 20. The silicon substrate 20 has a thickness of about 200 μm, for example. The insulating film 31 is formed to a thickness of about 1 μm, for example. For the production of the insulating film, a known thermal oxidation method or the like is used to form a silicon dioxide film. Note that a zirconium oxide film (not shown) having a thickness of about 400 nm may be further formed on the insulating film 31.
[0038]
Lower electrode forming step (S2)
Next, the lower electrode 32 is formed on the insulating film 31. The lower electrode 32 is formed by laminating platinum or iridium with a thickness of 200 nm, for example. These layers are manufactured using a known electron beam evaporation method, sputtering method, or the like.
[0039]
In this embodiment, the lower electrode 32 is formed on the entire surface of the substrate. However, the present invention is not limited to this, and the following piezoelectric film formation may be performed after the lower electrode is patterned into a predetermined shape.
[0040]
Formation of piezoelectric precursor film (S3)
Next, a piezoelectric precursor film 41 ′ is formed on the lower electrode 32. The piezoelectric precursor film is configured as an amorphous film before being crystallized by the processing described later to become the piezoelectric film 41. In this embodiment, a precursor film such as lead zirconate titanate (PZT) is formed by a sol-gel method. The PZT film forming method is not limited to the sol-gel method, but may be a MOD (Metal-Organic Decomposition) method or the like.
[0041]
In the sol-gel method, a metal organic compound such as a metal alkoxide is hydrolyzed and polycondensed in a solution system. Specifically, first, a solution (sol) containing a metal organic compound is applied onto a substrate and dried. Examples of the metal organic compound used include alkoxides such as methoxides, ethoxides, propoxides, and butoxides that constitute inorganic oxides, and acetate compounds. Inorganic salts such as nitrates, oxalates and perchlorates may be used.
[0042]
This mixed solution is applied on the lower electrode to a thickness of 20 nm, for example. At the applied stage, each metal atom constituting PZT is dispersed as an organometallic complex.
[0043]
After application, the sol solvent is evaporated by drying at a constant temperature for a certain time. For example, the drying temperature is set to, for example, 150 ° C. or more and 200 ° C. or less. Preferably, it is dried at 180 ° C. The drying time is, for example, 5 minutes or more and 15 minutes or less. Preferably, it is dried for about 10 minutes.
[0044]
After drying, it is further degreased for a certain period of time at a certain degreasing temperature in an air atmosphere. The degreasing temperature is preferably in the range of 400 ° C to 600 ° C. This is because crystallization starts at a temperature higher than this range, and sufficient degreasing cannot be performed at a temperature lower than this range. Preferably, it is set to about 450 ° C. to 550 ° C. The degreasing time is, for example, 5 minutes or more and 90 minutes or less. This is because crystallization starts in a time longer than this range, and degreasing is not sufficient in a time shorter than this range. Preferably, degreasing is performed for about 10 minutes. The organic matter coordinated to the metal by degreasing dissociates from the metal, causes an oxidative combustion reaction, and is scattered in the atmosphere. Through the above steps, the piezoelectric precursor film 41 ′ is formed.
[0045]
Crystallization step (S4)
The piezoelectric precursor film 41 ′ obtained by the above process is crystallized by heat treatment to form the piezoelectric film 41. Although the sintering temperature varies depending on the material, for example, heating is performed at 650 ° C. for 5 to 30 minutes. As the heating device, an RTA (Rapid Thermal Annealing) device, a diffusion furnace, or the like can be used.
[0046]
By this crystallization, the piezoelectric film 41 is formed. In this embodiment, the piezoelectric film 41 is formed by performing the sol coating, drying, degreasing, patterning, and crystallization processes once. However, the piezoelectric film 41 is not limited to this, and is repeated twice or more times. The film 41 may be thickened, for example, about 1.4 μm.
[0047]
Upper electrode forming step (S5)
The upper electrode 42 is formed on the piezoelectric film 41 formed as described above. As the upper electrode 42, platinum (Pt), iridium (Ir), or other metal is used, and a film is formed by DC sputtering to a film thickness of 50 nm.
[0048]
Piezoelectric element forming step (FIG. 5: S6)
Next, after spin-coating a resist on the upper electrode 42, patterning is performed by exposure and development in accordance with the position where the ink chamber is to be formed. The upper electrode 42 and the piezoelectric film 41 are etched by ion milling or the like using the remaining resist as a mask. A piezoelectric element is formed by the above process. In this step, the lower electrode may be similarly etched.
[0049]
Formation of adhesion layer (S7)
Next, an adhesion layer 50 made of a material (such as chromium) having high adhesion to the protective film 51 is formed on the vibration plate 30 with a thickness of about 50 nm. The adhesion layer 50 is preferably formed in a portion facing the side wall 22 around the ink chamber.
[0050]
Formation of protective film (S8)
Next, a protective film 51 made of a material having low adhesion to the upper electrode (parylene or the like) is formed on the vibration plate 30, the adhesion layer 50 and the upper electrode 42 to a thickness of about 1 μm. In the illustrated example, the protective film 51 is formed on the entire surface of the vibration plate 30. However, the present invention is not limited to this, and the protective film 51 may not be formed on the entire surface of the vibration plate as long as the piezoelectric element can be covered and adhered to the vibration plate 30.
[0051]
Formation of ink jet recording head (S9, S10)
Further, the ink chamber 21 is formed on the ink chamber substrate 20, and the nozzle plate 10 is formed. Specifically, an etching mask is applied to the ink chamber substrate 20 in accordance with the position where the ink chamber is to be formed, for example, dry etching using an active gas such as parallel plate type reactive ion etching, or a potassium hydroxide aqueous solution. The ink chamber substrate 20 is etched to a predetermined depth by wet etching using, thereby forming the ink chamber 21. The portion remaining without being etched becomes the side wall 22.
[0052]
Further, the nozzle plate 10 is bonded to the ink chamber substrate 20 using a resin or the like. When the nozzle plate 10 is joined to the ink chamber substrate 20, the nozzles 11 are aligned so as to be arranged corresponding to the respective spaces in the ink chamber 21.
[0053]
The adhesion layer 50 and the protective film 51 may be formed (S7, S8) after the ink chamber 20 and the nozzle plate 10 are formed (S9, S10).
[0054]
Finally, the protective film 51 is peeled off from the upper electrode 42 with low adhesion by driving the piezoelectric element. This peeling step is preferably performed before ink is introduced into the ink chamber 21. Further, an inert gas may be injected between the upper electrode 42 and the protective film 51 as necessary to form a gas layer. Through the above steps, an ink jet recording head is formed.
[0055]
【The invention's effect】
According to the present invention, it is possible to provide an ink jet recording head capable of securing a displacement amount of the vibrating portion without reducing the thickness of the protective film, and capable of high performance and high integration. Further, it is possible to provide a printer having the above-described ink jet recording head and having a high printing speed and a high resolution.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating a structure of a printer in which an ink jet recording head according to an embodiment is used.
FIG. 2 is an explanatory diagram of a structure of an ink jet recording head according to the present embodiment.
FIG. 3 is a cross-sectional view illustrating a specific structure of an ink jet recording head of the present invention.
FIG. 4 is a cross-sectional view of a manufacturing process of the ink jet recording head according to the present embodiment.
FIG. 5 is a cross-sectional view of a manufacturing process of the ink jet recording head according to the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Nozzle plate, 20 ... Pressure chamber board | substrate, 30 ... Vibration plate, 31 ... Insulating film, 32 ... Lower electrode, 41 ... Piezoelectric thin film layer, 42 ... Upper electrode, 21 ... Cavity, 51 ... Protective film, 50 ... Adhesion layer

Claims (4)

A pressure chamber disposed on the first surface of the diaphragm and surrounded by side walls;
A piezoelectric film formed on the second surface opposite to the first surface of the diaphragm, and disposed above the pressure chamber;
An upper electrode disposed on the piezoelectric film;
An adhesion layer disposed above the side wall of the second surface of the diaphragm and not disposed below the piezoelectric film;
A protective film that adheres closely to the adhesive layer and covers the upper electrode;
The ink jet recording head , wherein the adhesion between the adhesion layer and the protective film is higher than the adhesion between the upper electrode and the protection film .   2. The ink jet recording head according to claim 1, wherein the protective film is made of parylene. 3. The ink jet recording head according to claim 1 , wherein the adhesion layer is made of a chromium layer . A printer comprising the ink jet recording head according to any one of claims 1 to 3 .

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