Laminated piezoelectric body, laminated piezoelectric body manufacturing method, and ultrasound transducer and ultrasound diagnostic device using laminated piezoelectric body

1. An ultrasound transducer comprising:

only three mutually laminated piezoelectric layers of equal thickness;

a plurality of electrodes arranged at interlayers of the mutually laminated piezoelectric layers and on surfaces of piezoelectric layers at both ends; and

two connecting wirings which mutually connect the respective piezoelectric layers in parallel by coupling farther-side electrodes of mutually adjacent piezoelectric layers, wherein

a first-level piezoelectric layer of the laminated piezoelectric layers includes a fixed end-side and an opposite side on which the others of the piezoelectric layers are laminated,

the respective piezoelectric layers are arranged such that an orientation of the residual polarization or the crystal axis of the first-level piezoelectric layer is in a first direction, an orientation of the residual polarization or the crystal axis is in the first direction for a second-level piezoelectric layer that is in contact with the first-level piezoelectric layer and in a second direction, which is an opposite direction to the first direction, for a third-level piezoelectric layer that in contact with the second-level piezoelectric layer, and

the mutually laminated piezoelectric layers transmit an ultrasound wave into a subject and receive an ultrasound wave from the subject.

2. The ultrasound transducer according to claim 1 , wherein

each of the piezoelectric layers is further split into two piezoelectric layers in a thickness direction and the two piezoelectric layers are mutually connected in parallel to constitute one set to be laminated, and

for each of the split piezoelectric layers, front and back sides of the piezoelectric layer are reversed so that the orientation of the residual polarization or the crystal axis is consistent with an electrical displacement or a sign of an electric field in a distortion distribution within the laminated piezoelectric layers.

3. The ultrasound transducer according to claim 1 , wherein

the fixed-end side of file first-level piezoelectric layer is fixed to a rear layer by sandwiching the electrode therebetween, and defines a fixed end in a vibration of the first-level piezoelectric layer.

4. An ultrasound transducer comprising:

only six mutually laminated piezoelectric layers of equal thickness;

a plurality of electrodes arranged at interlayers of the mutually laminated piezoelectric layers and on surfaces of piezoelectric layers at both ends; and

two connecting wirings which mutually connect the respective piezoelectric layers in parallel by coupling farther-side electrodes of mutually adjacent piezoelectric layers, wherein

a first-level piezoelectric layer of the laminated piezoelectric layers includes a fixed end-side and an opposite side on which the others of the piezoelectric layers are laminated,

the respective piezoelectric layers are arranged to have a periodicity such that an orientation of the residual polarization or the crystal axis of the first-level piezoelectric layer is in a first direction, an orientation of a residual polarization or a crystal axis for a second-level piezoelectric layer that is in contact with the first-level piezoelectric layer is in the first direction; and an orientation of a residual polarization or a crystal axis for a third-level piezoelectric layer that is in contact with the second-level piezoelectric layer, and for a fourth-level piezoelectric layer that is in contact with the third-level piezoelectric layer is in a second direction, which is an opposite direction to the first direction, and an orientation of a residual polarization or a crystal axis for a fifth-level piezoelectric layer that is in contact with the fourth-level piezoelectric layer, and for a sixth-level piezoelectric layer that is in contact with the fifth-level piezoelectric layer is in the first direction, and

the mutually laminated piezoelectric layers transmit an ultrasound wave into a subject and receive an ultrasound wave from the subject.

5. The ultrasound transducer according to claim 4 , wherein

each of the plurality of piezoelectric layers is arranged such that each orientation of a residual polarization or a crystal axis in the each of the plurality of piezoelectric layers is in a direction which reduces sensitivity in a first resonance mode and increases sensitivity in a second resonance mode of a higher order than the first resonance mode with respect to the orientation of the residual polarization or the crystal axis of the first-level piezoelectric layer, and

wherein the second resonance mode is a resonance mode of a third or higher order created by an expansion and contraction of the laminated piezoelectric layers in a thickness direction.

6. An ultrasound diagnostic device comprising:

an ultrasound transducer which transmits an ultrasound wave into a subject that is a measurement object and which receives an ultrasound wave originating from the subject;

a transmitting unit which supplies a transmission ultrasound signal to the ultrasound transducer;

a receiving unit which performs predetermined signal processing on a reception signal received by the ultrasound transducer; and

an image processing unit which creates a tomographic image of an internal state of the subject based on the reception signal from the receiving unit, wherein the ultrasound transducer is a laminated piezoelectric body including:

only three mutually laminated piezoelectric layers of equal thickness; a plurality of electrodes arranged at interlayers of the mutually laminated piezoelectric layers and on surfaces of piezoelectric layers at both ends; and two connecting wirings which mutually connect the respective piezoelectric layers in parallel by coupling farther-side electrodes of mutually adjacent piezoelectric layers, wherein a first-level piezoelectric layer of the laminated piezoelectric layers includes a fixed end-side and an opposite side on which the others of the piezoelectric layers are laminated,

the respective piezoelectric layers in the ultrasound transducer are arranged such that an orientation of the residual polarization or a crystal axis of the first-level piezoelectric layer on a fixed end-side is in a first direction, an orientation of a residual polarization or a crystal axis is in the first direction for a second-level piezoelectric layer that is in contact with the first-level piezoelectric layer and in a second direction, which is an opposite direction to the first direction, for a third-level piezoelectric layer that is in contact with the second-level piezoelectric layer, and

the mutually laminated piezoelectric layers being configured to at least one of transmit an ultrasound wave into a subject and receive an ultrasound wave from the subject.

7. The ultrasound diagnostic device according to claim 6 , wherein the laminated piezoelectric body in the ultrasound transducer is used for both transmitting and receiving ultrasound waves, and the ultrasound transducer transmits an ultrasound wave in a 3λ/4 resonance mode.

8. The ultrasound diagnostic device according to claim 6 , wherein the laminated piezoelectric body in the ultrasound transducer is used for receiving an ultrasound wave as a first piezoelectric body, the ultrasound transducer further includes a second piezoelectric body that transmits an ultrasound wave of a fundamental wave component in a λ/4 resonance mode, and the second piezoelectric body and the first piezoelectric body are laminated in this order from a side of a rear layer.

9. The ultrasound diagnostic device according to claim 8 , wherein the first piezoelectric body is made of a material containing an organic polymer as a main component.

10. The ultrasound diagnostic device according to claim 8 , wherein

the second piezoelectric body is made of an inorganic material, the first piezoelectric body is made of a material containing an organic polymer as a main component, and a member for acoustic matching purposes is not interposed between the first piezoelectric body and the subject.

11. The ultrasound diagnostic device according to claim 6 , wherein the laminated piezoelectric body in the ultrasound transducer is used for receiving an ultrasound wave as a first piezoelectric body, the ultrasound transducer further includes two second piezoelectric bodies that transmit an ultrasound wave of a fundamental wave component in a λ/4 resonance mode, and the second piezoelectric bodies are provided in parallel on both sides of the first piezoelectric body.

12. The ultrasound diagnostic device according to claim 6 , wherein

the transmitting unit supplies a transmission signal to the laminated piezoelectric body in the ultrasound transducer as a coded pulse voltage, and

the receiving unit performs pulse compression on the reception signal received by the laminated piezoelectric body in the ultrasound transducer and causes the image processing unit to process the pulse-compressed signal.

13. The ultrasound diagnostic device according to claim 6 , wherein

the fixed-end side of the first-level piezoelectric layer is fixed to a rear layer by sandwiching the electrode therebetween, and defines a fixed end in a vibration of the first-level piezoelectric layer.

14. A ultrasound diagnostic device comprising:

an ultrasound transducer which transmits an ultrasound wave into a subject that is a measurement object and which receives an ultrasound wave originating from the subject;

a transmitting unit which supplies a transmission ultrasound signal to the ultrasound transducer;

a receiving unit which performs predetermined signal processing on a reception signal received by the ultrasound transducer; and

an image processing unit which creates a tomographic image of an internal state of the subject based on the reception signal from the receiving unit, wherein

the ultrasound transducer is a laminated piezoelectric body including:

only six mutually laminated piezoelectric layers of equal thickness; a plurality of electrodes arranged at interlayers of the mutually laminated piezoelectric layers and on surfaces of piezoelectric layers at both ends; and two connecting wirings which manually connect the respective piezoelectric layers in parallel by coupling farther-side electrodes of mutually adjacent piezoelectric layers, wherein a first-level piezoelectric layer of the laminated piezoelectric layers includes a fixed end-side and an opposite side on which the others of the piezoelectric layers are laminated,

the respective piezoelectric layers in the ultrasound transducer are arranged such that an orientation of the residual polarization or the crystal axis of the first-level piezoelectric layer on a fixed end-side is in a first direction, an orientation of a residual polarization or a crystal axis for a second-level piezoelectric layer that is in contact with the first-level piezoelectric layer is in the first direction; and an orientation of a residual polarization or a crystal axis for a third-level piezoelectric layer that is in contact with the second-level piezoelectric layer, and for a fourth-level piezoelectric layer that is in contact with the third-level piezoelectric layer is in a second direction, which is an opposite direction to the first direction, and an orientation of a residual polarization or a crystal axis for a fifth-level piezoelectric layer that is in contact with the fourth-level piezoelectric layer, and for sixth-level piezoelectric layer that is in contact with the fifth-level piezoelectric layer is in the first direction, and

the mutually laminated piezoelectric layers transmit an ultrasound wave into a subject and receive an ultrasound wave from the subject.