US-20260129372-A1 - DRIVER UNIT AND HEADPHONE

US20260129372A1US 20260129372 A1US20260129372 A1US 20260129372A1US-20260129372-A1

Abstract

Provided are a driver unit of a headphone, in which, in a case where a driver unit including a piezoelectric film having a formed curved portion is applied to the headphone, deformation of the curved portion of the piezoelectric film in a case of wearing the headphone can be suppressed, and deterioration in sound quality can be suppressed; and a headphone. The driver unit includes a piezoelectric film which has a piezoelectric layer consisting of a polymer-based piezoelectric composite material containing piezoelectric particles in a matrix containing a polymer material and electrode layers provided on both surfaces of the piezoelectric layer, and a perforated plate having at least one through-hole, in which the piezoelectric film has a curved portion which is formed to protrude to one main surface side and to be recessed to the other main surface side, the perforated plate is laminated on a concave surface side of the curved portion of the piezoelectric film, and in the through-hole, a first air chamber defined by the concave surface of the piezoelectric film and the perforated plate communicates with an outside.

Inventors

Tetsu Miyoshi

Assignees

FUJIFILM CORPORATION

Dates

Publication Date: 20260507
Application Date: 20251229
Priority Date: 20230630

Claims (20)

1 . A driver unit comprising: a piezoelectric film which has a piezoelectric layer consisting of a polymer-based piezoelectric composite material containing piezoelectric particles in a matrix containing a polymer material and electrode layers provided on both surfaces of the piezoelectric layer; and a plate-shaped perforated plate having at least one through-hole, wherein the piezoelectric film has a curved portion which is formed to protrude to one main surface side and to be recessed to the other main surface side, the perforated plate is laminated on a concave surface side of the curved portion of the piezoelectric film, and in the through-hole, a first air chamber defined by the concave surface of the piezoelectric film and the perforated plate communicates with an outside.
2 . The driver unit according to claim 1 , wherein a proportion of a total area of the through-holes to an area of the curved portion of the piezoelectric film in a plan view is 3% to 70%.
3 . The driver unit according to claim 1 , further comprising: an acoustic absorption layer consisting of a porous material which is disposed to cover the through-hole on a surface of the perforated plate opposite to the piezoelectric film.
4 . The driver unit according to claim 1 , wherein a shape formed by a boundary line of the curved portion of the piezoelectric film is circular.
5 . The driver unit according to claim 1 , further comprising: a series resistor connected between the electrode layers of the piezoelectric film and a signal source which drives the piezoelectric film.
6 . A headphone comprising: the driver unit according to claim 1 ; a housing which has an opening portion and accommodates the driver unit; and an ear pad which is disposed on an opening portion side of the housing.
7 . The headphone according to claim 6 , wherein a second air chamber defined by the driver unit and the housing communicates with an outside.
8 . The headphone according to claim 6 , wherein the housing is disposed on the concave surface side of the piezoelectric film of the driver unit.
9 . The headphone according to claim 6 , further comprising: a protector ring which is disposed to be in contact with the ear pad between the driver unit and the ear pad, wherein the protector ring has an opening portion which penetrates in a direction perpendicular to a surface in contact with the ear pad, the protector ring is in contact with a region of 30% or more of a total area of the ear pad in a case of being viewed in the direction perpendicular to the surface in contact with the ear pad, and a shortest distance between the protector ring and the piezoelectric film of the driver unit is 0.3 mm or more.
10 . The driver unit according to claim 2 , further comprising: an acoustic absorption layer consisting of a porous material which is disposed to cover the through-hole on a surface of the perforated plate opposite to the piezoelectric film.
11 . The driver unit according to claim 2 , wherein a shape formed by a boundary line of the curved portion of the piezoelectric film is circular.
12 . The driver unit according to claim 2 , further comprising: a series resistor connected between the electrode layers of the piezoelectric film and a signal source which drives the piezoelectric film.
13 . A headphone comprising: the driver unit according to claim 2 ; a housing which has an opening portion and accommodates the driver unit; and an ear pad which is disposed on an opening portion side of the housing.
14 . The headphone according to claim 13 , wherein a second air chamber defined by the driver unit and the housing communicates with an outside.
15 . The headphone according to claim 7 , wherein the housing is disposed on the concave surface side of the piezoelectric film of the driver unit.
16 . The headphone according to claim 13 , further comprising: a protector ring which is disposed to be in contact with the ear pad between the driver unit and the ear pad, wherein the protector ring has an opening portion which penetrates in a direction perpendicular to a surface in contact with the ear pad, the protector ring is in contact with a region of 30% or more of a total area of the ear pad in a case of being viewed in the direction perpendicular to the surface in contact with the ear pad, and a shortest distance between the protector ring and the piezoelectric film of the driver unit is 0.3 mm or more.
17 . The driver unit according to claim 3 , wherein a shape formed by a boundary line of the curved portion of the piezoelectric film is circular.
18 . The driver unit according to claim 3 , further comprising: a series resistor connected between the electrode layers of the piezoelectric film and a signal source which drives the piezoelectric film.
19 . A headphone comprising: the driver unit according to claim 3 ; a housing which has an opening portion and accommodates the driver unit; and an ear pad which is disposed on an opening portion side of the housing.
20 . The headphone according to claim 19 , wherein a second air chamber defined by the driver unit and the housing communicates with an outside.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a Continuation of PCT International Application No. PCT/JP2024/023163 filed on Jun. 26, 2024, which claims priority under 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2023-108023 filed on Jun. 30, 2023 and Japanese Patent Application No. 2024-102098 filed on Jun. 25, 2024. The above applications are hereby expressly incorporated by reference, in their entirety, into the present application. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driver unit and a headphone using the driver unit. 2. Description of the Related Art As a thin speaker, it has been proposed to use a piezoelectric film in which a piezoelectric layer is sandwiched between an electrode layer and a protective layer. For example, WO2016/017632A discloses an electroacoustic conversion film (piezoelectric film) including a polymer-based piezoelectric composite material in which piezoelectric particles are dispersed in a viscoelastic matrix consisting of a polymer material having viscoelasticity at normal temperature, and a pair of electrode pairs laminated on both surfaces of the polymer-based piezoelectric composite material, in which the electroacoustic conversion film has one or more protrusions which are formed in a convex shape to protrude to one main surface side. SUMMARY OF THE INVENTION The present inventor has studied adopting the piezoelectric film in a driver unit of a headphone. In a case of being used as the driver unit of a headphone, it is necessary to be small and light and to generate high-quality sound in a wide band. Therefore, the present inventor has considered that, in a case of adopting the piezoelectric film in the driver unit of the headphone, it is appropriate to use the piezoelectric film itself as a vibration plate, and to use a piezoelectric film having one or more protrusions (curved portions) which are formed in a convex shape to protrude to one main surface side, as a configuration in which the piezoelectric film can be made broadband with a vibration plate (piezoelectric film) which can be mounted on the headphone. In the headphone, it is known that a sound pressure in a low-frequency range is improved by bringing an ear and an ear pad into close contact with each other to put an internal air chamber (inside a housing) into a substantially sealed state, that is, by using a so-called sealed type or quasi-sealed type. However, according to the studies of the present inventor, in a configuration in which a driver unit including a piezoelectric film having a curved portion which is formed in a convex shape to protrude to one main surface side is incorporated into the headphone, in a case where the ear and the ear pad are brought into close contact with each other to put the inside of the housing into a substantially sealed state, resonance or the like in a high-frequency range occurs in the housing, and thus a variation (also referred to as a ripple, a peak, or a dip on a frequency characteristic) occurs in the frequency characteristic in the high-frequency range, and a flat frequency characteristic is not obtained, which is a problem. An object of the present invention is to solve such a problem of the related art, and to provide a driver unit and a headphone in which, in a case where a driver unit including a piezoelectric film having a formed curved portion is applied to the headphone, a frequency characteristic can be improved. In order to solve the above-described problems, the present invention has the following configuration. [1] A driver unit comprising: a piezoelectric film which has a piezoelectric layer consisting of a polymer-based piezoelectric composite material containing piezoelectric particles in a matrix containing a polymer material and electrode layers provided on both surfaces of the piezoelectric layer; anda plate-shaped perforated plate having at least one through-hole,in which the piezoelectric film has a curved portion which is formed to protrude to one main surface side and to be recessed to the other main surface side,the perforated plate is laminated on a concave surface side of the curved portion of the piezoelectric film, andin the through-hole, a first air chamber defined by the concave surface of the piezoelectric film and the perforated plate communicates with an outside. [2] The driver unit according to [1], in which a proportion of a total area of the through-holes to an area of the curved portion of the piezoelectric film in a plan view is 3% to 70%. [3] The driver unit according to [1] or [2], further comprising: an acoustic absorption layer consisting of a porous material which is disposed to cover the through-hole on a surface of the perforated plate opposite to the piezoelectric film. [4] The driver unit according to any one of [1] to [3], in which a shape formed by a boundary line of the curved portion of the piezoelectric film is circular. [5] The driver unit accord