Multilayer body that includes piezoelectric body
View Patent ↗A multilayer body includes a piezoelectric body and a first acoustic matching layer in direct or indirect contact with the piezoelectric body. The first acoustic matching layer includes a plastic foam containing a plurality of closed pores. An average pore size of the closed pores is not smaller than 1 μm and not larger than 100 μm. The first acoustic matching layer has a density of not less than 10 kg/m 3 and not more than 100 kg/m 3 .
1. A multilayer body comprising: a piezoelectric body; and a first acoustic matching layer in direct or indirect contact with the piezoelectric body, wherein the first acoustic matching layer includes a plastic foam containing a plurality of closed pores, an average pore size of the closed pores is not smaller than 1 μm and not larger than 100 μm, the first acoustic matching layer has a density of not less than 10 kg/m 3 and not more than 100 kg/m 3 , and an average distance between the adjacent closed pores is not shorter than 50 nm and not longer than 400 nm.
2. The multilayer body according to claim 1 , wherein an acoustic impedance of the first acoustic matching layer is in a range of not less than 5×10 3 kg/s·m 2 and not more than 350×10 3 kg/s·m 2 .
3. The multilayer body according to claim 1 , wherein an acoustic velocity in the first acoustic matching layer is not lower than 500 m/s.
4. The multilayer body according to claim 1 , wherein the plastic foam is a polymethacrylimide foam.
5. The multilayer body according to claim 1 , wherein a thickness of the first acoustic matching layer is substantially equal to ¼ of a wavelength λ of an acoustic wave propagating in the first acoustic matching layer.
6. The multilayer body according to claim 1 , further comprising a second acoustic matching layer disposed between the piezoelectric body and the first acoustic matching layer,
wherein the second acoustic matching layer has a density being not less than 50 kg/m 3 and not more than 1500 kg/m 3 and being larger than the density of the first acoustic matching layer.
7. The multilayer body according to claim 6 , wherein a relation between an acoustic impedance Za of the first acoustic matching layer and an acoustic impedance Zb of the second acoustic matching layer satisfies Za<Zb.
8. The multilayer body according to claim 6 , wherein a thickness of the second acoustic matching layer is substantially equal to ¼ of a wavelength λ of an acoustic wave propagating in the second acoustic matching layer.
9. The multilayer body according to claim 6 , wherein the second acoustic matching layer is arranged in direct contact with the first acoustic matching layer and the piezoelectric body.
10. The multilayer body according to claim 6 , further comprising a structural support layer having a density of not less than 1000 kg/m 3 between the first acoustic matching layer and the second acoustic matching layer.
11. The multilayer body according to claim 10 , wherein a thickness of the structural support layer is less than ⅛ of a wavelength λ of an acoustic wave propagating in the structural support layer.
12. The multilayer body according to claim 1 , wherein the first acoustic matching layer is directly bonded to the piezoelectric body.