Piezoelectric actuator, method of manufacturing same, and liquid ejection head

Abstract

The piezoelectric actuator comprises: a supporting substrate; a thermal stress controlling layer which is formed on the supporting substrate; and a piezoelectric body which is formed as a film onto the thermal stress controlling layer on the supporting substrate at a higher temperature than room temperature, wherein the thermal stress controlling layer reduces a film stress induced by formation of the piezoelectric body.

1 . A piezoelectric actuator, comprising: 
 a supporting substrate;    a thermal stress controlling layer which is formed on the supporting substrate; and    a piezoelectric body which is formed as a film onto the thermal stress controlling layer on the supporting substrate at a higher temperature than room temperature,    wherein the thermal stress controlling layer reduces a film stress induced by formation of the piezoelectric body.    
     
     
         2 . The piezoelectric-actuator as defined in  claim 1 , wherein: 
 the thermal stress controlling layer has a thermal expansion coefficient which is selected according to a first thermal expansion coefficient and a second thermal expansion coefficient, the first thermal expansion coefficient being a thermal expansion coefficient of piezoelectric body, the second thermal expansion coefficient being a thermal expansion coefficient of the supporting substrate.    
     
     
         3 . The piezoelectric actuator as defined in  claim 2 , wherein: 
 when the second thermal expansion coefficient is higher than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is lower than the second thermal expansion coefficient.    
     
     
         4 . The piezoelectric actuator as defined in  claim 2 , wherein: 
 when the second thermal expansion coefficient is higher than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is lower than the first thermal expansion coefficient.    
     
     
         5 . The piezoelectric actuator as defined in  claim 2 , wherein: 
 when the second thermal expansion coefficient is lower than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is higher than the second thermal expansion coefficient.    
     
     
         6 . The piezoelectric actuator as defined in  claim 2 , wherein: 
 when the second thermal expansion coefficient is lower than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is higher than the first thermal expansion coefficient.    
     
     
         7 . The piezoelectric actuator as defined in  claim 1 , wherein the thermal stress controlling layer has a prescribed thickness required for reducing a thermal stress remaining in the piezoelectric body.  
     
     
         8 . The piezoelectric actuator as defined in  claim 1 , wherein the thermal stress controlling layer also serves as an electrode for driving the piezoelectric body.  
     
     
         9 . The piezoelectric actuator as defined in  claim 1 , wherein an electrode which drives the piezoelectric body is formed between the thermal stress controlling layer and the piezoelectric body.  
     
     
         10 . The piezoelectric actuator as defined in  claim 1 , wherein a thickness of the supporting substrate is 30 μm or less.  
     
     
         11 . The piezoelectric actuator as defined in  claim 1 , wherein a thickness of the piezoelectric body is 1 μm or greater.  
     
     
         12 . The piezoelectric actuator as defined in  claim 1 , wherein the piezoelectric body is formed by an aerosol deposition method.  
     
     
         13 . The piezoelectric actuator as defined in  claim 12 , wherein: 
 the piezoelectric body formed by the aerosol deposition method is a PZT piezoelectric film; and    a crystal a-axis length of the PZT piezoelectric film is in the range of 2.025 to 2.040 Angstroms.    
     
     
         14 . The piezoelectric actuator as defined in  claim 1 , wherein the thermal stress controlling layer is formed by at least one of a sputtering method, a plating method, and an aerosol deposition method.  
     
     
         15 . The piezoelectric actuator as defined in  claim 1 , wherein: 
 the supporting substrate is made of stabilized zirconia; and    the thermal stress controlling layer is made of platinum having a thickness of 2 to 5 μm.    
     
     
         16 . The piezoelectric actuator as defined in  claim 1 , wherein: 
 the supporting substrate is made of stabilized zirconia; and    the thermal stress controlling layer is made of iridium having a thickness of 1 to 5 μm.    
     
     
         17 . The piezoelectric actuator as defined in  claim 1 , wherein: 
 the supporting substrate is made of silicon; and    the thermal stress controlling layer is made of platinum having a thickness of 10 μm or less.    
     
     
         18 . The piezoelectric actuator as defined in  claim 1 , wherein: 
 the supporting substrate is made of silicon; and    the thermal stress controlling layer is made of nickel having a thickness of 1 to 5 μm.    
     
     
         19 . The piezoelectric actuator as defined in  claim 1 , wherein: 
 the supporting substrate is made of silicon; and    the thermal stress controlling layer is made of titanium oxide having a thickness of 2 to 5 μm.    
     
     
         20 . A liquid ejection head, comprising: 
 a pressure chamber which fills with a liquid;    a nozzle which ejects the liquid from the pressure chamber; and    a piezoelectric actuator which comprises a supporting substrate; a thermal stress controlling layer which is formed on the supporting substrate; and a piezoelectric body which is formed as a film onto the thermal stress controlling layer on the supporting substrate at a higher temperature than room temperature,    wherein the thermal stress controlling layer reduces a film stress induced by formation of the piezoelectric body; and    the supporting substrate is a diaphragm in which the liquid is ejected from the nozzle by changing a volume of the pressure chamber.    
     
     
         21 . The liquid ejection head as defined in  claim 20 , wherein: 
 the thermal stress controlling layer has a thermal expansion coefficient which is selected according to a first thermal expansion coefficient and a second thermal expansion coefficient, the first thermal expansion coefficient being a thermal expansion coefficient of piezoelectric body, the second thermal expansion coefficient being a thermal expansion coefficient of the supporting substrate.    
     
     
         22 . The liquid ejection head as defined in  claim 21 , wherein: 
 when the second thermal expansion coefficient is higher than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is lower than the second thermal expansion coefficient.    
     
     
         23 . The liquid ejection head as defined in  claim 21 , wherein: 
 when the second thermal expansion coefficient is higher than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is lower than the first thermal expansion coefficient.    
     
     
         24 . The liquid ejection head as defined in  claim 21 , wherein: 
 when the second thermal expansion coefficient is lower than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is higher than the second thermal expansion coefficient.    
     
     
         25 . The liquid ejection head as defined in  claim 21 , wherein: 
 when the second thermal expansion coefficient is lower than the first thermal expansion coefficient, the thermal stress controlling layer has a thermal expansion coefficient which is higher than the first thermal expansion coefficient.    
     
     
         26 . The liquid ejection head as defined in  claim 20 , wherein the thermal stress controlling layer has a prescribed thickness required for reducing a thermal stress remaining in the piezoelectric body.  
     
     
         27 . The liquid ejection head as defined in  claim 20 , wherein the thermal stress controlling layer also serves as an electrode for driving the piezoelectric body.  
     
     
         28 . The liquid ejection head as defined in  claim 20 , wherein an electrode for driving the piezoelectric body is formed between the thermal stress controlling layer and the piezoelectric body.  
     
     
         29 . The liquid ejection head as defined in  claim 20 , wherein a thickness of the supporting substrate is 30 μm or less.  
     
     
         30 . The liquid ejection head as defined in  claim 20 , wherein a thickness of the piezoelectric body is 1 μm or greater.  
     
     
         31 . The liquid ejection head as defined in  claim 20 , wherein the piezoelectric body is formed by an aerosol deposition method.  
     
     
         32 . The liquid ejection head as defined in  claim 31 , wherein: 
 the piezoelectric body formed by the aerosol deposition method is a PZT piezoelectric film; and    a crystal a-axis length of the PZT piezoelectric film is in the range of 2.025 to 2.040 Angstroms.    
     
     
         33 . The liquid ejection head as defined in  claim 20 , wherein the thermal stress controlling layer is formed by at least one of a sputtering method, a plating method, and an aerosol deposition method.  
     
     
         34 . The liquid ejection head as defined in  claim 20 , wherein: 
 the supporting substrate is made of stabilized zirconia; and    the thermal stress controlling layer is made of platinum having a thickness of 2 to 5 μm.    
     
     
         35 . The liquid ejection head as defined in  claim 20 , wherein: 
 the supporting substrate is made of stabilized zirconia; and    the thermal stress controlling layer is made of iridium having a thickness of 1 to 5 μm.    
     
     
         36 . The liquid ejection head as defined in  claim 20 , wherein: 
 the supporting substrate is made of silicon; and    the thermal stress controlling layer is made of platinum having a thickness of 10 μm or less.    
     
     
         37 . The liquid ejection head as defined in  claim 20 , wherein: 
 the supporting substrate is made of silicon; and    the thermal stress controlling layer is made of nickel having a thickness of 1 to 5 μm.    
     
     
         38 . The liquid ejection head as defined in  claim 20 , wherein: 
 the supporting substrate is made of silicon; and    the thermal stress controlling layer is made of titanium oxide having a thickness of 2 to 5 μm.    
     
     
         39 . A method of manufacturing a piezoelectric actuator, comprising the steps of: 
 forming a thermal stress controlling layer on a supporting substrate; and    forming a piezoelectric film by an aerosol deposition method in which an aerosol containing a powder of a piezoelectric material is sprayed onto the thermal stress controlling layer to accumulate the powder onto the thermal stress controlling layer,    wherein the thermal stress controlling layer is formed in the step of forming the thermal stress controlling layer so as to have a thermal expansion coefficient and a thickness for reducing deformation of the supporting substrate due to thermal stress in the piezoelectric film.