JP2007296817A - Liquid discharge head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid discharge head with a piezoelectric driving portion having improved durability by preventing current concentration in the end portion of a piezoelectric body. <P>SOLUTION: The piezoelectric driving portion 20 constituted by laminating a cylindrical lower electrode 21, a piezoelectric layer 22, and an upper electrode 24 is provided on an outer peripheral face of a cylindrical base material 10 having a flowing path 12 for compressing an ink and discharging outlet 11. A mixed layer 23 comprising a mixed material formed by mixing a piezoelectric material and an insulating material is provided on both ends of the cylindrical piezoelectric layer 22 comprising a piezoelectric material to prevent the electric concentration by making the resistance of the mixed layer larger than that of the piezoelectric layer 22. The films of the piezoelectric layer 22 and the mixed layer 23 are formed using a gas deposition method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid discharge head used in a liquid discharge type recording apparatus or the like.

  A liquid discharge type recording apparatus such as an ink jet printer is a technique that is very advantageous compared to other device forming means in terms of material utilization efficiency and environmental load because a material can be drawn directly on a substrate.

  In the liquid discharge method, a voltage is applied to a pressure generator composed of a laminate of a piezoelectric element using PZT (lead zirconate titanate), a metal plate, and ceramics to generate pressure and discharge the liquid. There is a method. Moreover, what uses an electrothermal conversion element is also known.

  In the former method, there is known a method in which an elongated cylindrical piezoelectric body having a diameter of about 0.1 to 1 mm is provided in the middle from the tank to the discharge port, and this portion functions as a pressurizing pump to discharge droplets. ing. This is called a Gould-type ink jet head, and as disclosed in Patent Document 1 and Patent Document 2, electrodes are formed on the inner surface and outer surface of a cylindrical piezoelectric body, and a lead wire for applying a driving voltage is provided. It is connected. The inner electrode of the cylindrical piezoelectric body is fixed to a hollow pipe that penetrates the piezoelectric element by adhesion. The hollow pipe is made of an insulating material such as glass in order to avoid electrical contact with the cylindrical piezoelectric body. An ink tube for supplying ink from an ink tank or the like is connected to one end of the hollow pipe and the other end Are formed with ejection openings for ejecting ink droplets. Further, a Kaiser type disclosed in Patent Document 3 and a shear mode type using a piezoelectric ceramic disclosed in Patent Document 4 are widely known.

  An important reliability item in the liquid discharge head using these piezoelectric bodies is the resistance of the piezoelectric bodies. When the resistance of the piezoelectric body is low, current flows between the electrodes, and heat generation and smoke generation occur. This phenomenon is because migration occurs between the electrodes of the piezoelectric body, the conductive state is established, and Joule heat is generated by passing a current.

That is, it is considered that the above-mentioned various phenomena occur when the resistance decreases in part of the piezoelectric body due to the film thickness distribution and film density of the piezoelectric body.
JP 7-317660 A JP-A-8-336967 Japanese Patent Publication No.53-12138 Japanese Patent Laid-Open No. 63-247051

  As a conventional method for forming a piezoelectric body of a liquid discharge head, there is a method of forming a piezoelectric layer on a substrate by a sputtering method, a screen printing method, a gas deposition method or the like. In these methods, the thickness of the piezoelectric layer is made uniform. It was difficult to make. In particular, when the thickness of the piezoelectric layer is increased, it is difficult to make the thickness uniform, and the thickness may be reduced at the end of the piezoelectric layer. As a result, current concentration occurs at the end of the piezoelectric layer, and the piezoelectric layer may generate heat or smoke, and may be damaged. In addition, the liquid ejection head applies a voltage and ejects a liquid such as ink by repeated displacement of the piezoelectric layer, but the electrode layer may be damaged by repeated displacement.

  SUMMARY An advantage of some aspects of the invention is that it provides a liquid discharge head that does not cause damage to the piezoelectric body due to current concentration during voltage application. .

  The liquid discharge head of the present invention includes a piezoelectric drive unit having a pair of electrodes and a piezoelectric body sandwiched between the pair of electrodes, corresponding to a flow path communicating with a discharge port for discharging a liquid. In the liquid discharge head, the piezoelectric body includes a side edge portion made of a mixed material in which a piezoelectric material and an insulating material are mixed, and a main body portion made of a piezoelectric material other than the side edge portion. .

  As a manufacturing method of the mixed layer of the piezoelectric material and the insulating material constituting the edge portion of the piezoelectric body sandwiched between the lower electrode and the upper electrode, it is preferable to use a gas deposition method. When using the gas deposition method as the method for forming the mixed layer, the gas deposition method is used to aerosolize the insulating material in an aerosol chamber separate from the aerosol chamber that generates the piezoelectric material, and at the end of the piezoelectric layer. Spray toward the substrate. Thereby, a mixed layer of a piezoelectric material and an insulating material can be easily formed. Furthermore, as a manufacturing method of the piezoelectric layer sandwiched between the lower electrode and the upper electrode or the mixed layer of the piezoelectric material and the insulating material, an offset printing method or a screen printing method can be applied.

  As the insulating material, a material that can withstand high temperatures due to polarization treatment or the like performed for improving the characteristics of the piezoelectric material is used. In particular, it is preferable to use a metal oxide as the insulating material.

  By forming the side edge portion of the piezoelectric body from a mixed material of a piezoelectric material and an insulating material, the resistance of the side edge portion where the film thickness tends to be thin is increased. Even if the thickness of the piezoelectric body is non-uniform and the end portion is particularly thin, current concentration does not occur because the resistance of the side edge portion including the insulating material is large. Further, since the resistance is increased at the end of the piezoelectric drive unit, the displacement at the time of voltage application is reduced, and the breakage of the electrode can be reduced.

  The best mode for carrying out the invention will be described with reference to the drawings.

  As shown in FIG. 1, a piezoelectric drive unit 20 is provided around a glass cylindrical base material 10, and the piezoelectric drive unit 20 includes a cylindrical lower electrode 21 and a piezoelectric layer 22 constituting a piezoelectric body. , A mixed layer 23 and an upper electrode 24 constituting the side edge of the piezoelectric body. The cylindrical base material 10 has a discharge port 11 at one end, and the internal space of the cylindrical base material 10 constitutes a flow path 12 that is a pressure generation chamber for pressurizing a liquid such as ink. In addition, the base material which forms the flow path 12 is not limited to a cylindrical base material, and may have any shape.

  Moreover, as shown in FIG. 2, the structure which has the taper-shaped part 13 opened to the discharge outlet 11 at the front-end | tip of the cylindrical base material 10 may be sufficient.

  For forming the lower electrode 21, any film forming method such as an arc heating type gas deposition method, a sputtering method, or a vapor deposition method may be used.

  The structure of the lower electrode 21 is often formed with Ti as the lowermost layer and Pt thereon, but is not limited to these materials, and the film thickness is not limited. The piezoelectric layer 22 and the mixed layer 23 are formed by a gas deposition method using aerosol (see FIG. 3). For the raw material powder of the piezoelectric layer 22, a piezoelectric material such as PZT particles having an average primary particle size of 0.1 to 0.5 μm is used, the powder in the container is aerosolized, and the particles suspended above the lower electrode through the nozzle 21 is sprayed on. As the raw material powder of the mixed layer 23, an insulating material having an average primary particle size of 0.1 to 0.2 μm is used. It injects toward the part. The particle size of the raw material powder of the piezoelectric layer 22 and the raw material powder of the mixed layer 23 may be any particle size that allows film formation, and is not limited thereto.

As a method of forming the piezoelectric layer 22 and the mixed layer 23, a gas deposition method is preferable, but a screen printing method or an offset printing method may be used. A typical piezoelectric material is PZT, and insulating materials include BaTiO ₃ , BaTiZrO ₃ , SrTiO ₃ , SrCO ₃ , ZnO, BaO, Al ₂ O ₃ , TiO ₂ , and SiO ₂ . Thus, materials that can withstand high temperatures and materials with high dielectric constants are preferable, but are not limited to the above materials.

  Next, Ti and Pt are formed as the upper electrode 24 by the arc heating gas deposition method in the same manner as the lower electrode 21. Similarly to the lower electrode 21, the upper electrode 24 may use any film forming method such as an arc heating gas deposition method, a sputtering method, and a vapor deposition method. As in the case of the lower electrode 21, Ti is often formed on the lowermost layer and Pt is formed thereon, but the structure is not limited to these materials, and the film thickness is not limited.

  Next, the gas deposition method will be described.

  As shown in FIG. 4, the gas deposition method is a technique for forming a film by spraying ultrafine particles having a particle diameter of several nm to several tens of nm or fine particles of several tens of nm to several μm onto the workpiece W from the nozzle 100. . The gas deposition method includes an ultrafine particle generation chamber 101 for generating ultrafine particles, or an aerosolization chamber 111 for supplying existing fine particles, as shown in FIG. 5, and includes a film formation chamber 102, a transfer tube 103, and the like. Is done.

  In the ultrafine particle generation chamber 101, in the inert gas atmosphere supplied from the pipe 104, the evaporation material 106 is heated by an arc by the arc electrode 105, resistance heating, high-frequency induction heating, laser, or the like, and evaporated to generate an inert gas. Collide with and cool to produce ultrafine metal particles. Alternatively, various gases such as an inert gas or air are introduced into the aerosolization chamber 111, and the fine particles are fluidized by vibration, stirring, or the like to be aerosolized.

  Next, the ultrafine particle generation chamber 101 or the aerosolization chamber 111 and the film formation chamber 102 are guided to the film formation chamber 102 through the transfer pipe 103 by the pressure difference between them, and sprayed from the nozzle 100 connected to the transfer pipe 103. A pattern is formed directly on the workpiece W. At this time, an arbitrary pattern can be drawn by scanning the workpiece W as indicated by an arrow.

  In particular, the gas deposition method using aerosol is sometimes called aerosol deposition.

  A lower electrode, a piezoelectric body, and an upper electrode were formed on a cylindrical substrate made of tempered glass having an inner diameter of 600 μm and an outer diameter of 700 μm as shown in FIG. The lower electrode was formed by an arc heating gas deposition method. As for the film structure, Ti: 50 nm was formed on the lowermost layer, and Pt: 700 nm was formed thereon. At this time, a cylindrical substrate was placed under the nozzle, and film formation was performed while rotating with a rotating jig. As the nozzle, a slit type nozzle having an opening of 300 μm × 15 mm was used. The substrate was formed without heating.

The conditions at the time of film formation are as follows.
・ Ultrafine particle generation chamber pressure: 70KPa
-Film formation chamber pressure: 1 KPa
-Gas used: He
・ Gas flow rate: 7L / min
・ Substrate rotation speed: 6 rpm
・ Arc power: 35A, 18-28V
・ Nozzle opening diameter: 300μm × 15mm

Next, a PZT film (piezoelectric layer) and a mixed layer were formed by an aerosol gas deposition method using the apparatus shown in FIG. PZT-LQ (trade name: manufactured by Sakai Chemical Co., Ltd.) having an average primary particle size of 0.1 to 0.5 μm was used as the raw material powder for the PZT film. The raw material was put into a heated aerosolization chamber to be stirred and fluidized, and the particles which were aerosolized and floated on the upper part were guided to the film formation chamber by a differential pressure and jetted from the nozzle onto the lower electrode. SrTiO ₃ having an average primary particle size of 0.1 to 0.2 μm was used as the raw material powder for the mixed layer. The raw materials were charged into the aerosolization chamber, the powder was stirred and fluidized, and the particles that were aerosolized and floated on the upper part were guided to the film formation chamber by a differential pressure and jetted from the nozzle toward the end of the piezoelectric layer.

  Similar to the production of the lower electrode, the cylindrical substrate was rotated to form a PZT film having a length of 10 mm and a thickness of 10 μm on the electrode, and a mixed layer having a length of 2 mm and a thickness of 10 μm on the side surface of the PZT film.

The conditions for forming the PZT film are as follows.
・ Aerosolization chamber pressure: 40 KPa
-Film formation chamber pressure: 1 KPa
-Gas used: Dry air-Substrate rotation speed: 6 rpm
・ Nozzle opening diameter: 300μm × 10mm

The conditions for forming the mixed layer are as follows.
・ Aerosolization chamber pressure: 40 KPa
-Film formation chamber pressure: 1 KPa
-Gas used: Dry air-Substrate rotation speed: 6 rpm
・ Nozzle opening diameter: 300μm × 2mm

  Next, the upper electrode was formed by an arc heating type gas deposition method in the same manner as the lower electrode. The nozzle used for forming the upper electrode is 300 μm × 10 mm, the length of the deposited part is 10 mm, and the film thickness is 500 nm. The other film formation conditions are the same as when the lower electrode is formed, but the pressure in the film formation chamber is slightly different because the nozzle diameter is different.

  In this manner, the upper and lower electrodes, the PZT film, and the mixed layer were formed on the cylindrical base material, and baked at 600 ° C. for 1 hour in an air atmosphere. Thereafter, lead wires were attached to the lower electrode and the upper electrode, respectively, and a voltage of 100 V for 2 hours was applied in an air atmosphere at 120 ° C. to polarize the PZT film.

A voltage was applied to the liquid discharge head provided with the upper and lower electrodes, the piezoelectric layer, and the mixed layer thus obtained, and the durability of the liquid discharge head was examined. Even when a voltage of 1 × 10 ¹⁰ times was applied to the liquid discharge head, the head was not destroyed.

  In the configuration shown in FIG. 2, a lower electrode, a piezoelectric body, and an upper electrode are formed on a cylindrical substrate made of tempered glass having an inner diameter of 600 μm, an outer diameter of 700 μm, a tip inner diameter of 30 μm, and a tip outer diameter of 100 μm and a tapered portion at the tip. did.

  A sputtering method was used for the lower electrode. As for the film structure, Ti: 50 nm was formed on the lowermost layer, and Pt: 200 nm was formed thereon. The film formation range was 15 mm from the tip position of the tapered portion to the ink supply side, and a film was formed while rotating the cylindrical substrate using a metal mask having a 15 mm opening attached to a rotating jig.

Next, as in Example 1, a PZT film (piezoelectric layer) and a mixed layer were formed by a gas deposition method using aerosol. PZT-LQ (trade name: manufactured by Sakai Chemical Co., Ltd.) having an average primary particle size of 0.1 to 0.5 μm is used as a raw material powder for the PZT film, and the powder in the container is agitated and fluidized to form an aerosol. The suspended particles were guided to the film formation chamber by a differential pressure and sprayed from the nozzle onto the lower electrode. The raw material powder of the mixed layer is BaTiO ₃ having an average primary particle size of 0.1 to 0.2 μm. The powder in the container is agitated and fluidized, and the aerosolized particles are formed into a film formation chamber by a differential pressure. The nozzle was jetted toward the end of the piezoelectric layer.

  Similarly to the production of the lower electrode, the substrate on which the electrode was formed was rotated to form a PZT film having a length of 10 mm and a thickness of 10 μm on the electrode, and a mixed layer on the side surface of the PZT film having a length of 2 mm and a thickness of 10 μm.

The conditions for forming the PZT film are as follows.
・ Aerosolization chamber pressure: 40 KPa
-Film formation chamber pressure: 1 KPa
-Gas used: Dry air-Substrate rotation speed: 6 rpm
・ Nozzle opening diameter: 300μm × 10mm

The conditions for forming the mixed layer are as follows.
・ Aerosolization chamber pressure: 40 KPa
-Film formation chamber pressure: 1 KPa
-Gas used: Dry air-Substrate rotation speed: 6 rpm
・ Nozzle opening diameter: 300μm × 2mm

  Next, the upper electrode was formed by sputtering in the same manner as the lower electrode. The film forming method is substantially the same as that of the lower electrode, but the opening is 12 mm in the length direction of the cylindrical base material.

  In this manner, the upper and lower electrodes, the PZT film, and the mixed layer were formed on the cylindrical base material, and baked at 600 ° C. for 1 hour in an air atmosphere. Thereafter, lead wires were attached to the lower electrode and the upper electrode, respectively, and a voltage of 100 V for 2 hours was applied in an air atmosphere at 120 ° C. to polarize the PZT film.

A voltage was applied to the liquid discharge head provided with the electrode, piezoelectric layer, and mixed layer thus obtained, and the durability of the liquid discharge head was examined. Even when a voltage of 1 × 10 ¹⁰ times was applied to the liquid discharge head, the head was not destroyed.

3 is a schematic cross-sectional view illustrating a main part of the liquid ejection head according to Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a main part of a liquid discharge head according to Embodiment 2. FIG. It is a figure explaining the film-forming process of the piezoelectric layer and mixed layer by a gas deposition method. It is a figure which shows an arc type gas deposition apparatus. It is a figure which shows an aerosol-type gas deposition apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cylindrical base material 11 Discharge port 12 Flow path 20 Piezoelectric drive part 21 Lower electrode 22 Piezoelectric layer 23 Mixed layer 24 Upper electrode

Claims (4)

  In the liquid discharge head provided with a piezoelectric drive unit having a pair of electrodes and a piezoelectric body sandwiched between the pair of electrodes corresponding to the flow path communicating with the discharge port for discharging the liquid, the piezoelectric body A liquid discharge head, comprising: a side edge portion made of a mixed material in which a piezoelectric material and an insulating material are mixed; and a main body portion made of a piezoelectric material other than the side edge portion.   The liquid discharge head according to claim 1, wherein the mixed material includes a piezoelectric material and a metal oxide. The mixed material is made of PZT (lead zirconate titanate) and at least one of BaTiO ₃ , BaTiZrO ₃ , SrTiO ₃ , SrCO ₃ , ZnO, BaO, Al ₂ O ₃ , TiO ₂ and SiO ₂ as raw materials. The liquid discharge head according to claim 1, wherein:   The liquid discharge head according to claim 1, wherein the side edge portion is formed by a gas deposition method.

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