Electroacoustic converter film, flexible display, vocal cord microphone, and musical instrument sensor

Patent metadata

Field	Value
Publication number	US-9761784-B2
Application number	US-201414229606-A
Country	US
Kind code	B2
Filing date	Mar 28, 2014
Priority date	Sep 30, 2011
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

Provided is an electroacoustic converter film including: a polymeric composite piezoelectric body having piezoelectric particles dispersed in a viscoelastic matrix which is formed of a polymer material exhibiting viscoelasticity at ordinary temperatures; thin film electrodes formed on both sides of the polymeric composite piezoelectric body; and protective layers formed on surfaces of the thin film electrodes. The electroacoustic converter film serves as a speaker capable of being integrated with a flexible display without impairing lightweightness or flexibility, and has considerable frequency dispersion in the storage modulus and also has a local maximum of the loss tangent around ordinary temperatures. A flexible display, a vocal cord microphone and a musical instrument sensor, in each of which the electroacoustic converter film is used, are also provided.

First claim

What is claimed is:

1. An electroacoustic converter film, comprising: a polymeric composite piezoelectric body having piezoelectric particles dispersed in a viscoelastic matrix which is formed of a polymer material exhibiting viscoelasticity at ordinary temperatures; thin film electrodes formed on both sides of the polymeric composite piezoelectric body; and protective layers formed on surfaces of the thin film electrodes,
wherein the polymeric composite piezoelectric body is subjected to polarization processing,
the polymer material has a glass transition temperature of 0° C. to 50° C. at a frequency of 1 Hz, and
the polymer material has a cyanoethyl group.

2. The electroacoustic converter film according to claim 1 , wherein a loss tangent (tan δ) at a frequency of 1 Hz obtained by dynamic viscoelasticity measurement of the electroacoustic converter film has a local maximum of 0.1 or more within a temperature range of 0° C. to 50° C.

3. The electroacoustic converter film according to claim 1 , wherein a storage modulus (E′) at a frequency of 1 Hz obtained by dynamic viscoelasticity measurement of the electroacoustic converter film is 10 to 30 GPa at 0° C. and 1 to 10 GPa at 50° C.

4. The electroacoustic converter film according to claim 1 , wherein a product of a thickness of the electroacoustic converter film and a storage modulus (E′) at a frequency of 1 Hz obtained by dynamic viscoelasticity measurement of the electroacoustic converter film is 1.0×10 6 N/m to 2.0×10 6 N/m at 0° C. and 1.0×10 5 N/m to 1.0×10 6 N/m at 50° C.

5. The electroacoustic converter film according to claim 1 , wherein, on a master curve obtained from dynamic viscoelasticity measurement of the electroacoustic converter film, a loss tangent (tan δ) at 25° C. and at a frequency of 1 kHz is 0.05 or more.

6. The electroacoustic converter film according to claim 1 , wherein a loss tangent (tan δ) at a frequency of 1 Hz obtained by dynamic viscoelasticity measurement of the polymer material has a local maximum of 0.5 or more within a temperature range of 0° C. to 50° C.

7. The electroacoustic converter film according to claim 1 , wherein a storage modulus (E′) at a frequency of 1 Hz obtained by dynamic viscoelasticity measurement of the polymer material is 100 MPa or higher at 0° C. and 10 MPa or lower at 50° C.

8. The electroacoustic converter film according to claim 1 , wherein the polymer material has a relative dielectric constant of 10 or more at 25° C.

9. The electroacoustic converter film according to claim 1 , wherein the polymer material is cyanoethylated polyvinyl alcohol.

10. The electroacoustic converter film according to claim 1 , wherein the piezoelectric particles are present in the polymeric composite piezoelectric body at a volume fraction of 50% or higher.

11. The electroacoustic converter film according to claim 1 , wherein the piezoelectric particles are ceramic particles having a perovskite crystal structure or a wurtzite crystal structure.

12. The electroacoustic converter film according to claim 11 , wherein the ceramic particles are particles of lead zirconate titanate, lead lanthanate zirconate titanate, barium titanate, zinc oxide, or a solid solution of barium titanate and bismuth ferrite.

13. The electroacoustic converter film according to claim 1 , wherein the protective layers have a thickness at most two times as large as a thickness of the polymeric composite piezoelectric body.

14. The electroacoustic converter film according to claim 1 , wherein a product of a thickness and a Young's modulus of the thin film electrodes is smaller than a product of a thickness and a Young's modulus of the protective layers.

15. The electroacoustic converter film according to claim 1 , wherein the protective layers are formed of polyethylene terephthalate, polypropylene, polystyrene, polycarbonate, polyphenylene sulfite, polymethyl methacrylate, polyetherimide, polyimide, polyethylene naphthalate, or a cyclic olefin resin.

16. The electroacoustic converter film according to claim 1 , wherein the thin film electrodes are formed of copper, aluminum, gold, silver, platinum, or indium tin oxide.

17. A flexible display, comprising the electroacoustic converter film according to claim 1 that is attached to the flexible display exhibiting flexibility on a side opposite with a side where an image display surface is located.

18. A vocal cord microphone, which uses the electroacoustic converter film according to claim 1 as a sensor.

19. A musical instrument sensor, which uses the electroacoustic converter film according to claim 1 as a sensor.

Assignees

• Fujifilm Corp

Inventors

• Miyoshi Tetsu

Classifications

• H04R7/04 Primary

  Plane diaphragms · CPC title

• H04R1/46

  Special adaptations for use as contact microphones, e.g. on musical instrument, on stethoscope (throat mountings H04R1/14) · CPC title

• G02F2001/133394

  Physics · mapped topic

• H04R31/003

  for diaphragms or their outer suspension · CPC title

• G10H2220/531

  made of piezoelectric film · CPC title