Ultrasonic transducer employing piezoelectric polymeric material

• US 4,577,132 A
• Filed: 10/19/1984
• Issued: 03/18/1986
• Est. Priority Date: 07/05/1983
• Status: Expired due to Fees

• Current Assignee: Toray Industries Incorporated
• Original Assignee: Toray Industries Incorporated
• Inventors: Ohigashi, Hiroji, Koga, Keiko, Nakanishi, Toshiharu
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US06/662,946
• Time in Patent Office: 515 Days
• Field of Search: 310/800, 310/357, 310/334-335, 29/25, 29/35, 264/22, 526/250, 526/255, 428/421, 427/100, 361/233
• US Class Current: 310/311
• CPC Class Codes: B06B 1/0688 with foil-type piezoelectric elements, e.g. PVDF
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

An ultrasonic transducer is disclosed which includes a vibrating element comprising a sheet of a piezoelectric polymeric material which consists essentially of a copolymer of about 65 to 82 mol percent of vinylidene fluoride and about 35 to 18 mol percent of ethylene trifluoride. The polymeric material is formed into a film of the desired thickness and then heated to a temperature greater than about the crystal phase transition temperature and less than about the melting-point temperature for a period of time of about ten minutes to about two hours to produce a heat-treated film. The heat-treated film is poled in an electrical field of from about 50 to about 1,500 kilovolts per centimeter to give the film a thickness extensional electromechanical coupling factor of at least 0.05 and preferably greater than 0.2.

Claims

1. An ultrasonic transducer having a piezoelectric vibrating element that vibrates in a thickness extensional mode, comprising a sheet of piezoelectric material consisting essentially of a copolymer vinylidene fluoride and ethylene trifluoride, having the value of the thickness extensional electromechanical coupling factor (K_t) of at least 0.05.

2. An ultrasonic transducer as claimed in claim 1 in which the thickness extensional electromechanical coupling factor (K_t) is greater than 0.1.

3. An ultrasonic transducer as claimed in claim 1 in which the thickness extensional electromechanical coupling factor (K_t) is greater than 0.2.

4. An ultrasonic transducer as claimed in claim 1 in which the copolymer consists essentially of 65 to 95 mole percent of vinylidene fluoride and 35 to 5 mole percent of ethylene trifluoride.

5. An ultrasonic transducer having a piezoelectric vibrating element comprising a sheet of piezoelectric material consisting essentially of a copolymer vinylidene fluoride and ethylene trifluoride, having the value of the thickness extensional electromechanical coupling factor (K_t) of at least 0.05, the sheet expanding and contracting in a direction perpendicular to the sheet in response to a vibration-inducing input applied to the sheet so that the piezoelectric vibrating element vibrates in a thickness extensional mode.

6. An ultrasonic transducer as claimed in claim 5 in which the thickness extensional electromechanical coupling factor (K_t) is greater than 0.1.

7. An ultrasonic transducer as claimed in claim 5 in which the thickness extensional electromechanical coupling factor (K_t) is greater than 0.2.

8. An ultrasonic transducer as claimed in claim 5 in which the copolymer consists essentially of 65 to 95 mol percent of vinylidene fluoride and 35 to 5 mol percent of ethylene trifluoride.