WO2022190804A1

WO2022190804A1 - Projection screen

Info

Publication number: WO2022190804A1
Application number: PCT/JP2022/006316
Authority: WO
Inventors: 裕介香川; 輝男芦川
Original assignee: 富士フイルム株式会社
Priority date: 2021-03-11
Filing date: 2022-02-17
Publication date: 2022-09-15
Also published as: TW202301019A; JPWO2022190804A1

Abstract

The present invention addresses the problem of preventing, in a projection screen in which a piezoelectric acoustic film is adhered to the rear surface-side, audio output at the rear surface-side from wrapping around to the projection surface-side. The problem is solved by having a screen body, a piezoelectric acoustic film adhered to the surface on the reverse side of the video projection surface of the screen body, and a sound-insulating sheet that is provided so as to cover the surface on the reverse side of the projection surface of the screen body.

Description

projection screen

The present invention relates to a projection screen for projecting images.

2. Description of the Related Art Image projection systems that project and interfere images on a screen are used for conferences, home theaters, and the like.
In such image projection systems, audio as important as video is provided, for example, by speakers located behind and/or to the sides of the screen onto which the image is projected.
However, these systems required a space for installing speakers.

On the other hand, a method is also known in which sound is output from the screen by attaching a piezoelectric acoustic film to the back of the screen on which the image is projected and vibrating the screen with the piezoelectric acoustic film.

For example, Patent Document 1 discloses a screen surface that displays image information, a piezoelectric layer formed on the back surface of the screen surface, an electrode that supplies power to the piezoelectric layer, and a modulator that modulates the supplied power according to an acoustic signal. A screen having a circuit is described.
Patent Document 2 discloses a projection screen in which a speaker made of a piezoelectric acoustic film (piezoelectric film) having electrode films laminated on both sides is attached to either the back or front surface of a sheet-like screen body. Have been described.

JP 2006-339954 A JP 2007-187976 A

A screen provided with a piezoelectric acoustic film on the back surface of a projection surface vibrates the entire surface of the screen by driving the piezoelectric acoustic film, and the vibration of the screen outputs sound.
Therefore, a screen having such a piezoelectric acoustic film is in a state as if sound is being output from an image, and a high sense of realism can be obtained.

Here, when actually viewing an image, it is preferable that the sound is output only on the projection surface side of the image. However, according to the study of the present inventors, in the configuration in which the piezoelectric acoustic film is attached to the rear surface of the screen, the entire surface of the screen vibrates, so that sound is output from the rear surface as well.
The sound output on the rear surface side wraps around to the projection surface side and is also output from the projection surface side.

The sound output from the back side is the sound of the phase opposite to that of the projection surface side.
Therefore, when the sound output on the rear side reaches the projection surface side, the sound output on the projection surface side and the sound output on the projection surface side partially cancel each other, and when the image is observed on the projection surface side, the sound output decreases. be in a state like

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art. To provide a projection screen capable of preventing a turnaround and a decrease in sound output on the projection surface side.

In order to achieve such an object, the present invention has the following configurations.
[1] A screen body for projecting images;
a piezoelectric acoustic film attached to the surface of the screen body opposite to the image projection surface;
A projection screen, comprising: a sound insulation sheet provided to cover a surface of a screen body opposite to a projection surface.
[2] The projection screen according to [1], having a space between the screen body and the piezoelectric acoustic film and the sound insulating sheet.
[3] The projection screen according to [1] or [2], wherein the sound insulation sheet is detachable.
[4] The projection screen according to any one of [1] to [3], wherein the piezoelectric acoustic film is flexible.
[5] a first supporting member that supports one side of the screen body, and a second supporting member that supports a side of the screen body opposite to the side supported by the first supporting member;
The projection screen according to any one of [1] to [4], which has a tensioning mechanism that brings the first support member and the second support member closer to each other and separates them from each other.
[6] The projection according to [5], which has a fine adjustment mechanism for adjusting the distance between the first support member and the second support member while the first support member and the second support member are separated by the lifting mechanism. screen for.
[7] The projection screen according to any one of [1] to [6], wherein the piezoelectric acoustic film has a piezoelectric layer and electrode layers provided on both sides of the piezoelectric layer.
[8] The projection screen of [7], wherein the piezoelectric layer is a polymeric composite piezoelectric body having piezoelectric particles in a polymeric material.
[9] The projection screen of [8], wherein the polymer material of the polymer composite piezoelectric body is cyanoethylated polyvinyl alcohol.

According to the present invention, in a projection screen having a piezoelectric acoustic film attached to the surface side, it is possible to prevent sound output from the rear side from reaching the projection surface side, so that when an image is observed on the projection surface side, , it is possible to prevent the voice output from being lowered.

FIG. 1 is a diagram conceptually showing an example of the projection screen of the present invention. FIG. 2 is a conceptual diagram for explaining the configuration of the projection screen shown in FIG. FIG. 3 is a conceptual diagram for explaining the configuration of the projection screen shown in FIG. 1. FIG. FIG. 4 is a conceptual diagram for explaining the configuration of the projection screen shown in FIG. FIG. 5 is a conceptual diagram for explaining the operation of the projection screen shown in FIG. 1. FIG. FIG. 6 is a conceptual diagram for explaining the action of the projection screen shown in FIG. FIG. 7 is a conceptual diagram for explaining the action of the projection screen shown in FIG. FIG. 8 is a diagram conceptually showing an example of a piezoelectric acoustic film forming a piezoelectric element. FIG. 9 is a conceptual diagram for explaining an example of a method for producing a piezoelectric acoustic film. FIG. 10 is a conceptual diagram for explaining an example of a method for producing a piezoelectric acoustic film. FIG. 11 is a conceptual diagram for explaining an example of a method for producing a piezoelectric acoustic film. FIG. 12 is a conceptual diagram for explaining the projection screen shown in FIG.

The projection screen of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

The description of the constituent elements described below may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
Also, the drawings shown below are conceptual diagrams for explaining the projection screen of the present invention, and the size, thickness, shape, positional relationship, etc. of each member may differ from the actual one. different.
In this specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.

FIG. 1 conceptually shows an example of the projection screen of the present invention. In FIG. 1, the left drawing is a view of the projection screen of the present invention as seen from the rear side, and the right drawing is a cross section taken along the line AA of the left drawing.
In addition, the back side indicates the surface side of the screen main body on which the image is projected, which is opposite to the projection surface of the image.

A projection screen 10 shown in FIG. 2 support members 54 , a tensioning mechanism 56 , a sound insulating sheet 59 and leg members 78 .
In FIG. 1, the rear view on the left side omits the sound insulation sheet 59 in order to clearly show the configuration of the projection screen 10. However, in the projection screen 10, as shown in the cross-sectional view on the right side, A sound insulation sheet 59 is provided so as to cover the entire rear surface side of the screen body 50 (see FIG. 12).
Also, in the cross-sectional view on the right side, hatching is omitted in order to clearly show the configuration of the projection screen 10 .

In the present invention, the terms "first" and "second" in the first support member 52, the second support member 54, etc. are used for the sake of convenience in order to distinguish each member and to explain the projection screen 10 of the present invention. It is what we are doing.
Therefore, the first and second parts of the supporting member or the like have no technical meaning, and are irrelevant to the position, usage condition, and the like.

In the illustrated example, the screen main body 50 is a known projection screen onto which images are projected. In the illustrated example, the screen body 50 has a rectangular shape, one long side of which is supported by the first supporting member 52 and the other long side of which is supported by the second supporting member 54 .
The first support member 52 and the second support member 54 are detachably supported by a lifting mechanism 56 that brings the first support member 52 and the second support member 54 closer to each other and separates them from each other.
The tensioning mechanism 56 has a cylindrical first frame member 58 and a second frame member 60 . Both ends of the first frame member 58 and the second frame member 60 are engaged with bendable hinge members 62 . As will be described later, the first support member 52 is engaged with the first frame member 58 and the second support member 54 is engaged with the second frame member 60, so that the first support member 52 and the second support member 54 It is detachably supported by the lifting mechanism 56 .
By bending the hinge member 62, the first frame member 58 or first support member 52 and the second frame member 60 or second support member 54 are brought closer together (see FIG. 5), and as shown in FIG. Extending member 62 separates first frame member 58 or first support member 52 and second frame member 60 or second support member 54 . A state in which the hinge member 62 is linearly extended and the first support member 52 and the second support member 54 are separated is a state in which the screen main body 50 is stretched.
Hinge member 62 is detachably supported by leg member 78 by engaging both ends of first frame member 58 and second frame member 60 with leg member 78 . The leg members 78 are for supporting the screen main body 50 in an upright state during image projection.
The above configuration will be described in detail later.

As described above, the screen body 50 is a known projection screen used for projecting images.
Therefore, the screen main body 50 is formed of various materials such as resin such as vinyl chloride, paper such as Japanese paper, and cloth such as canvas, as long as it can project an image. Various sheet materials are available.

Also, like a normal projection screen, the screen body 50 is flexible and is wound around the first support member 52 and/or the second support member 54 when not in use.

The screen body 50 may be light transmissive or light blocking.
However, the screen main body 50 is light-shielding in that the projected image can be suitably displayed and the piezoelectric acoustic film 24 attached to the back surface can be prevented from being visually recognized by the viewer of the image. is preferred.

As described above, in the projection screen 10 , the screen body 50 has one long side supported by the first support member 52 and the other long side supported by the second support member 54 .
As conceptually shown in FIG. 2, the first support member 52 is composed of a cylindrical main body 52a and a C-shaped cover 52b covering the main body 52a with the exception of a portion. One long side of the screen main body 50 is supported by the first support member 52 by being sandwiched between the main body 52a and the C-shaped cover 52b.
The second support member 54 is similarly composed of a cylindrical main body 54a and a C-shaped cover 54b covering the main body except for a part (see FIG. 4). The long side of the screen body 50 opposite to the side of the first support member 52 is similarly supported by the second support member 54 by being sandwiched between the main body 54a and the C-shaped cover 54b.

The first support member 52 and the second support member 54 are detachably supported by a lifting mechanism 56 that brings the first support member 52 and the second support member 54 closer to each other and separates them from each other.
The tensioning mechanism 56 has cylindrical first and

second frame members

58 and 60 and two hinge members 62 .

The hinge member 62 has a plate-like first arm 62a and a plate-like second arm 62b. The first arm 62a and the second arm 62b are rotatably connected by connecting one end thereof with a rotating shaft 62c.
The tensioning mechanism 56 engages one hinge member 62 near one end of the first frame member 58 and the second frame member 60, and one hinge member 62 near the other end of the first frame member 58 and the second frame member 60. By engaging another hinge member 62 to the , it becomes a square frame shape.

The first frame member 58 engages the first arms 62a of the hinge member 62 near both ends. Specifically, as conceptually shown in FIG. 3, the first frame member 58 has engaging members 58a near both ends. The engaging member 58a and the end of the first arm 62a of the hinge member 62 are engaged by the rotating shaft 62d, so that the first frame member 58 and the first arm 62a, that is, the hinge member 62 are rotated. movably engaged.
On the other hand, the second frame member 60 engages the second arms 62b of the hinge member 62 near both ends. Specifically, as conceptually shown in FIG. 4, the second frame member 60 has engaging members 60a near both ends. The engaging member 60a and the end of the second arm 62b of the hinge member 62 are engaged by the rotation shaft 60f, so that the second frame member 60 and the second arm 62b, that is, the hinge member 62 are rotated. movably engaged.
3 and 4, the first support member 52, the second support member 54, the first frame member 58, and the second frame member 60 are shown in cross section, but hatching is omitted for the sake of simplicity. ing.

Therefore, by bending the hinge member 62, the first frame member 58 and the second frame member 60 are brought closer to each other, and by linearly extending the hinge member 62 from the bent state, the first frame member 58 and the second frame member are moved. The member 60 can be separated.
As described above, the first support member 52 is supported by the first frame member 58, and the second support member 54 is supported by the second frame member 60, respectively. Therefore, by bending and stretching the hinge member 62, the first support member 52 and the second support member 54 can be brought closer to each other and separated from each other.
The hinge member 62 can be fixed and released in a linearly extended state or a slightly bent state by a known method such as fitting of a concave portion and a convex portion, or a fixing member that moves in the longitudinal direction. It's becoming

As shown in FIG. 3, the first frame member 58 is provided with fixing pins 58b at predetermined intervals in the longitudinal direction. Further, the main body 52a of the first support member 52 is provided with through holes 52c corresponding to the fixing pins 58b. By inserting the fixing pin 58 b of the first frame member 58 into the through hole 52 c of the first support member 52 , the first support member 52 is detachably supported by the first frame member 58 , that is, the lifting mechanism 56 .
As shown in FIG. 4, the second frame member 60 is also provided with fixing pins 60b at predetermined intervals in the longitudinal direction. Further, the main body 54a of the second support member 54 is provided with through holes 54c corresponding to the fixing pins 60b. By inserting the fixing pin 60 b of the second frame member 60 into the through hole 54 c of the second support member 54 , the second support member 54 is detachably supported by the second frame member 60 , that is, the lifting mechanism 56 .

As shown in FIG. 1, the first frame member 58 of the lifting mechanism 56 has a first support member 52 and a second support by adjusting the distance between the first support member 52 and the first frame member 58 . A fine adjustment mechanism 80 is provided to adjust the tension of the screen body 50 by adjusting the distance to the member 54 .
The fine adjustment mechanism 80 will be detailed later.

The tensioning mechanism 56 that supports the first support member 52 and the second support member 54 is detachably supported by two leg members 78 at both ends of the first frame member 58 and the second frame member 60 .
The leg member 78 is a rod-shaped member erected at the installation position of the projection screen 10, and serves to support the screen main body 50 in an upright state during image projection. A leg portion 78c is provided at the lower end of the leg member 78 in order to maintain the upright state when the lifting mechanism 56, that is, the screen body 50 is supported.

An upper support member 78a and a lower support member 78b are secured to the leg member 78 .
Both the upper support member 78a and the lower support member 78b are bar-shaped. The upper support member 78 a is inserted into the first frame member 58 of the hoisting mechanism 56 . On the other hand, the lower support member 78b is inserted into the second frame member 60 of the hoisting mechanism 56. As shown in FIG. The foot members 78 thereby support the tensioning mechanism 56 .
In addition, in the leg member 78, the upper support member 78a is fixed. On the other hand, the lower support member 78b is detachably fixed by changing the height, that is, the position of the leg member 78 in the longitudinal direction.

A method for raising the screen body 50 in the projection screen 10 will be described below with reference to the conceptual diagrams of FIGS. 5 to 7, the sound insulating sheet 59 is omitted in order to clearly show the configuration of the projection screen 10. FIG.

First, as shown in FIG. 5, the upper support members 78a of the leg members 78 are inserted into both ends of the first frame member 58 of the lifting mechanism 56, and the lifting mechanism 56 is supported by the standing leg members 78.

As described above, the screen body 50 is supported on one longitudinal side by the first supporting member 52 and on the other longitudinal side by the second supporting member 54, and is wound around the first supporting member 52 and/or the second supporting member 54. It is written.
Spread the screen body 50 wound around the first support member 52 and/or the second support member 54, and insert the fixing pin 58b of the first frame member 58 into the through hole 52c of the first support member 52 (main body 52a). (see Figure 3).
Further, the fixing pin 60b of the second frame member 60 is inserted into the through hole 54c of the second support member 54 (main body 54a) (see FIG. 4).
Thereby, the first support member 52 and the second support member 54 , that is, the screen body 50 are supported by the lifting mechanism 56 .

At this point, the hinge member 62 of the lifting mechanism 56 is bent as shown in FIG.
Next, as shown in FIG. 6, the hinge member 62 is extended linearly. As a result, the first frame member 58 and the second frame member 60, that is, the first support member 52 and the second support member 54 are separated, and the screen main body 50 is stretched.

Further, as shown in FIG. 7, the lower support member 78b is inserted into the second frame member 60, and the lower support member 78b is fixed to the leg member 78, thereby fixing the screen main body 50 in a stretched state.

Here, in the first frame member 58 of the lifting mechanism 56, the distance between the first support member 52 and the second support member 54 is adjusted by adjusting the distance between the first support member 52 and the first frame member 58. A fine adjustment mechanism 80 is provided that adjusts to adjust the tension of the screen body 50 . In the illustrated example, as an example, four fine adjustment mechanisms 80 are provided at equal intervals in the longitudinal direction.
When the lower support member 78b is inserted into the second frame member 60 and fixed, if the tension of the screen body 50 is insufficient, the fine adjustment mechanism 80 adjusts the gap between the first frame member 58 and the first support member 52. is widened to stretch the screen body 50 more strongly.
Conversely, when the lower support member 78b is inserted into the second frame member 60 and fixed, if the tension of the screen body 50 is too strong, the first frame member 58 and the first support member 52 are separated by the fine adjustment mechanism 80. The tension of the screen body 50 is weakened by narrowing the interval between and.

The fine adjustment mechanism 80 is not limited, and any known method for adjusting the interval between two rod-shaped members arranged side by side in a direction orthogonal to the longitudinal direction can be used.
As an example, as conceptually shown in FIG. 2, a method of using an adjustment screw 80a that is idle in the first frame member 58 and screwed into the first support member 52 (main body 52a) and a cam mechanism are used. A method to be used is exemplified.

In the illustrated example, four fine adjustment mechanisms 80 are provided as an example.
However, the present invention is not limited to this, and as long as the distance between the first support member 52 and the first frame member 58 can be uniformly adjusted in the longitudinal direction, the number of fine adjustment mechanisms 80 may be three or less, or five. It can be more than that.

5 to 7, the foot member 78, the lifting mechanism 56, the screen main body 50, the first support member 52 and the second support member 54 can be dismantled. Then, the screen body 50 can be wound around the first support member 52 and/or the second support member 54 .
Further, in the first supporting member 52, the C-shaped cover 52b is removed from the main body 52a, and in the second supporting member 54, the C-shaped cover 54b is removed from the main body 54a. It can be removed from the support member 54 .

In the projection screen of the present invention, the lifting mechanism for the screen main body 50 is not limited to the illustrated example, and various known lifting mechanisms for the screen on which images are projected can be used.
That is, the projection screen of the present invention is known as long as it has the screen main body 50, the piezoelectric acoustic film 24 attached to the back surface of the screen main body 50, and the sound insulation sheet 59 covering the back side of the screen main body. Various tensioning mechanisms are available for projection screens.

In the projection screen 10 having such a screen body 50 tensioning mechanism, the piezoelectric acoustic film 24 is attached to the back surface of the screen body 50, that is, the surface opposite to the image projection surface.

In the illustrated example, two piezoelectric acoustic films 24 are attached to the screen main body 50 while being separated from each other in the longitudinal direction in order to reproduce sound in stereo. However, in the present invention, the number of piezoelectric acoustic films 24 is not limited, and the number of piezoelectric acoustic films 24 may be one or three or more such as four.
In addition, the position where the piezoelectric acoustic film is attached to the screen main body 50 is also appropriately determined according to the size of the screen main body 50, the size of the piezoelectric acoustic film 24 in the surface direction of the screen main body 50, the number of the piezoelectric acoustic films 24, and the like. , should be set.

In the projection screen 10, the piezoelectric acoustic film 24 vibrates the screen body 50 to output sound.
In the present invention, the piezoelectric acoustic film 24 is not limited, and is a known piezoelectric acoustic film that can be attached to the back side of the screen on which an image is projected and can vibrate the screen body 50 to output sound. 24 are available in a variety.

FIG. 8 conceptually shows an example of the piezoelectric acoustic film 24 in a sectional view. In FIG. 8 and the like, hatching is omitted in order to simplify the drawing and clearly show the configuration.
In the following description, unless otherwise specified, "cross section" indicates a cross section in the thickness direction of the piezoelectric acoustic film. The thickness direction of the piezoelectric acoustic film is the stacking direction of each layer.

The piezoelectric acoustic film 24 shown in FIG. 8 includes a piezoelectric layer 26, a first electrode layer 28 laminated on one side of the piezoelectric layer 26, and a first protective layer 32 laminated on the first electrode layer 28. , a second electrode layer 30 laminated on the other surface of the piezoelectric layer 26 , and a second protective layer 34 laminated on the second electrode layer 30 .

In the piezoelectric acoustic film 24, the piezoelectric layer 26 is not limited, and various known piezoelectric layers used for various piezoelectric acoustic films (piezoelectric films) can be used.
In the piezoelectric acoustic film 24, the piezoelectric layer 26 is preferably a polymer composite piezoelectric material as conceptually shown in FIG. 8, containing piezoelectric particles 40 in a polymer matrix 38 containing a polymer material. .

Here, the polymer composite piezoelectric body (piezoelectric layer 26) preferably satisfies the following requirements. In the present invention, normal temperature is 0 to 50°C.
(i) Flexibility For example, when gripping a loosely bent state like a document like a newspaper or magazine for portable use, it is constantly subjected to a relatively slow and large bending deformation of several Hz or less from the outside. become. At this time, if the polymer composite piezoelectric material is hard, a correspondingly large bending stress is generated, and cracks occur at the interface between the polymer matrix and the piezoelectric particles, which may eventually lead to destruction. Therefore, the polymer composite piezoelectric body is required to have appropriate softness. Moreover, stress can be relieved if strain energy can be diffused to the outside as heat. Therefore, it is required that the loss tangent of the polymer composite piezoelectric material is appropriately large.
(ii) Sound quality The speaker vibrates piezoelectric particles at frequencies in the audio band of 20 Hz to 20 kHz, and the vibration energy causes the entire diaphragm (polymer composite piezoelectric body) to vibrate as one, thereby reproducing sound. be. Therefore, the polymer composite piezoelectric body is required to have appropriate hardness in order to increase the transmission efficiency of vibration energy. Also, if the frequency characteristics of the speaker are smooth, the amount of change in sound quality when the lowest resonance frequency f ₀ changes as the curvature changes becomes small. Therefore, the loss tangent of the polymer composite piezoelectric body is required to be moderately large.

It is well known that the lowest resonance frequency f ₀ of the speaker diaphragm is given by the following equation. where s is the stiffness of the vibration system and m is the mass.

At this time, as the degree of curvature of the piezoelectric acoustic film, that is, the radius of curvature of the curved portion increases, the mechanical stiffness s decreases, so the lowest resonance frequency f ₀ decreases. That is, the sound quality (volume and frequency characteristics) of the speaker changes depending on the radius of curvature of the piezoelectric acoustic film.

In summary, the polymer composite piezoelectric body is required to behave hard against vibrations of 20 Hz to 20 kHz and softly against vibrations of several Hz or less. Also, the loss tangent of the polymer composite piezoelectric body is required to be moderately large with respect to vibrations of all frequencies of 20 kHz or less.

In general, polymer solids have a viscoelastic relaxation mechanism, and as temperature rises or frequency falls, large-scale molecular motion causes a decrease (relaxation) in storage elastic modulus (Young's modulus) or a maximum loss elastic modulus (absorption). is observed as Among them, the relaxation caused by the micro-Brownian motion of the molecular chains in the amorphous region is called principal dispersion, and a very large relaxation phenomenon is observed. The temperature at which this primary dispersion occurs is the glass transition point (Tg), and the viscoelastic relaxation mechanism appears most prominently.
In the polymer composite piezoelectric body (piezoelectric layer 26), by using a polymer material having a glass transition point at room temperature, in other words, a polymer material having viscoelasticity at room temperature, as a matrix, vibration of 20 Hz to 20 kHz is suppressed. This realizes a polymer composite piezoelectric material that is hard at first and behaves softly with respect to slow vibrations of several Hz or less. In particular, it is preferable to use a polymer material whose glass transition point Tg at a frequency of 1 Hz is at normal temperature for the matrix of the polymer composite piezoelectric material, because this behavior is preferably exhibited.

The polymer material that forms the polymer matrix 38 preferably has a maximum loss tangent Tan δ of 0.5 or more at a frequency of 1 Hz in a dynamic viscoelasticity test at room temperature.
As a result, when the polymer composite piezoelectric body is slowly bent by an external force, stress concentration at the polymer matrix/piezoelectric particle interface at the maximum bending moment portion is alleviated, and high flexibility can be expected.

In addition, it is preferable that the storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of the polymer material forming the polymer matrix 38 is 100 MPa or more at 0°C and 10 MPa or less at 50°C.
As a result, the bending moment generated when the polymeric composite piezoelectric body is slowly bent by an external force can be reduced, and at the same time, it can behave rigidly against acoustic vibrations of 20 Hz to 20 kHz.

Further, it is more preferable that the polymer material that forms the polymer matrix 38 has a dielectric constant of 10 or more at 25°C. As a result, when a voltage is applied to the polymer composite piezoelectric material, a higher electric field is applied to the piezoelectric particles in the polymer matrix, so a large amount of deformation can be expected.
On the other hand, however, in consideration of ensuring good moisture resistance and the like, it is also suitable for the polymer material to have a dielectric constant of 10 or less at 25°C.

Polymer materials that satisfy these conditions include cyanoethylated polyvinyl alcohol (cyanoethylated PVA), polyvinyl acetate, polyvinylidene chloride core acrylonitrile, polystyrene-vinylpolyisoprene block copolymer, polyvinylmethylketone, and polybutyl. Methacrylate and the like are preferably exemplified.
Commercially available products such as Hybler 5127 (manufactured by Kuraray Co., Ltd.) can also be suitably used as these polymer materials.

As the polymer material constituting the polymer matrix 38, it is preferable to use a polymer material having a cyanoethyl group, and it is particularly preferable to use cyanoethylated PVA. That is, in the piezoelectric acoustic film 24, the piezoelectric layer 26 preferably uses a polymer material having a cyanoethyl group as the polymer matrix 38, and particularly preferably uses cyanoethylated PVA.
In the following description, the above-mentioned polymeric materials represented by cyanoethylated PVA are collectively referred to as "polymeric materials having viscoelasticity at room temperature".

These polymer materials having viscoelasticity at room temperature may be used alone or in combination (mixed).

In the piezoelectric acoustic film 24, the polymer matrix 38 of the piezoelectric layer 26 may be made of a plurality of polymer materials, if necessary.
That is, for the polymer matrix 38 constituting the polymer composite piezoelectric body, in addition to the above-described polymer material having viscoelasticity at room temperature, other materials may be used as necessary for the purpose of adjusting dielectric properties and mechanical properties. dielectric polymer material may be added.

Examples of dielectric polymer materials that can be added include polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, and polyvinylidene fluoride-trifluoroethylene copolymer. and fluorine-based polymers such as polyvinylidene fluoride-tetrafluoroethylene copolymer, vinylidene cyanide-vinyl acetate copolymer, cyanoethylcellulose, cyanoethylhydroxysaccharose, cyanoethylhydroxycellulose, cyanoethylhydroxypullulan, cyanoethylmethacrylate, cyanoethylacrylate, cyanoethyl Cyano groups such as hydroxyethylcellulose, cyanoethylamylose, cyanoethylhydroxypropylcellulose, cyanoethyldihydroxypropylcellulose, cyanoethylhydroxypropylamylose, cyanoethylpolyacrylamide, cyanoethylpolyacrylate, cyanoethylpullulan, cyanoethylpolyhydroxymethylene, cyanoethylglycidolpullulan, cyanoethylsaccharose and cyanoethylsorbitol. Alternatively, polymers having cyanoethyl groups, and synthetic rubbers such as nitrile rubbers and chloroprene rubbers are exemplified.
Among them, polymer materials having cyanoethyl groups are preferably used.
Moreover, in the polymer matrix 38 of the piezoelectric layer 26, these dielectric polymer materials are not limited to one type, and a plurality of types may be added.

In addition to dielectric polymer materials, thermoplastic resins such as vinyl chloride resins, polyethylene, polystyrene, methacrylic resins, polybutene and isobutylene, and phenolic resins are used for the purpose of adjusting the glass transition point Tg of the polymer matrix 38. , thermosetting resins such as urea resins, melamine resins, alkyd resins and mica may be added.
Furthermore, a tackifier such as rosin ester, rosin, terpene, terpene phenol, and petroleum resin may be added for the purpose of improving adhesiveness.

In the polymer matrix 38 of the piezoelectric layer 26, the addition amount of the polymer material other than the polymer material having viscoelasticity at room temperature is not limited, but the proportion of the polymer matrix 38 is 30% by mass. It is preferable to:
As a result, the characteristics of the polymer material to be added can be expressed without impairing the viscoelastic relaxation mechanism in the polymer matrix 38, so that the dielectric constant can be increased, the heat resistance can be improved, and the adhesion between the piezoelectric particles 40 and the electrode layer can be improved. Favorable results can be obtained in terms of improvement and the like.

The polymer composite piezoelectric material that forms the piezoelectric layer 26 contains piezoelectric particles 40 in such a polymer matrix. The piezoelectric particles 40 are dispersed in a polymer matrix, preferably uniformly (substantially uniformly).
The piezoelectric particles 40 are preferably ceramic particles having a perovskite or wurtzite crystal structure.
Examples of ceramic particles constituting the piezoelectric particles 40 include lead zirconate titanate (PZT), lead zirconate lanthanate titanate (PLZT), barium titanate (BaTiO ₃ ), zinc oxide (ZnO), and A solid solution (BFBT) of barium titanate and bismuth ferrite (BiFe ₃ ) is exemplified.

The particle size of the piezoelectric particles 40 may be appropriately selected according to the size and application of the piezoelectric acoustic film 24 . The particle size of the piezoelectric particles 40 is preferably 1 to 10 μm.
By setting the particle size of the piezoelectric particles 40 within the above range, favorable results can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.

In the piezoelectric acoustic film 24, the quantitative ratio of the polymer matrix 38 and the piezoelectric particles 40 in the piezoelectric layer 26 depends on the size and thickness of the piezoelectric acoustic film 24 in the plane direction, the application of the piezoelectric acoustic film 24, and the piezoelectric acoustic film. 24 may be appropriately set in accordance with the characteristics required for 24 .
The volume fraction of the piezoelectric particles 40 in the piezoelectric layer 26 is preferably 30-80%, more preferably 50-80%.
By setting the amount ratio between the polymer matrix 38 and the piezoelectric particles 40 within the above range, favorable results can be obtained in terms of achieving both high piezoelectric characteristics and flexibility.

In addition, in the piezoelectric acoustic film 24, the thickness of the piezoelectric layer 26 is not limited, and may be appropriately adjusted according to the size of the piezoelectric acoustic film 24, the application of the piezoelectric acoustic film 24, the properties required of the piezoelectric acoustic film 24, and the like. , should be set.
The thickness of the piezoelectric layer 26 is preferably 8-300 μm, more preferably 8-200 μm, still more preferably 10-150 μm, particularly preferably 15-100 μm.
By setting the thickness of the piezoelectric layer 26 within the above range, favorable results can be obtained in terms of ensuring both rigidity and appropriate flexibility.

The piezoelectric layer 26 is preferably polarized (poled) in the thickness direction. The polarization treatment will be detailed later.

In the piezoelectric acoustic film 24, the piezoelectric layer 26 is a polymer containing piezoelectric particles 40 in a polymer matrix 38 made of a polymer material having viscoelasticity at room temperature, such as cyanoethylated PVA, as described above. It is not limited to composite piezoelectrics.
That is, in the piezoelectric acoustic film 24, various known piezoelectric layers used for piezoelectric films can be used for the piezoelectric layer 26. FIG.

As an example, a high-performance dielectric material containing similar piezoelectric particles 40 in a matrix containing a dielectric polymer material such as the polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, and vinylidene fluoride-trifluoroethylene copolymer described above may be used. Molecular composite piezoelectric material, piezoelectric layer made of polyvinylidene fluoride, piezoelectric layer made of fluorine resin other than polyvinylidene fluoride, and piezoelectric layer made by laminating a film made of poly-L-lactic acid and a film made of poly-D-lactic acid, etc. is also available.
However, as described above, the screen main body 50 is hard against vibrations of 20 Hz to 20 kHz and behaves softly against slow vibrations of several Hz or less, and has excellent flexibility, which provides excellent acoustic characteristics. In order to obtain a piezoelectric acoustic film 24 that suitably follows winding, a polymer containing piezoelectric particles 40 in a polymer matrix 38 made of a polymer material having viscoelasticity at room temperature, such as cyanoethylated PVA, is used. A composite piezoelectric is preferably used as the piezoelectric layer 26 .

The piezoelectric acoustic film 24 shown in FIG. 8 has the second electrode layer 30 on one surface of the piezoelectric layer 26 and the second protective layer 34 on the surface of the second electrode layer 30 . Also, the piezoelectric layer 26 has a first electrode layer 28 on the other surface thereof, and a first protective layer 32 on the surface of the first electrode layer 28 . In the piezoelectric acoustic film 24, the first electrode layer 28 and the second electrode layer 30 form an electrode pair.
In other words, in the laminated film that constitutes the piezoelectric acoustic film 24, both surfaces of the piezoelectric layer 26 are sandwiched between electrode pairs, that is, the first electrode layer 28 and the second electrode layer 30, and the first protective layer 32 and the second electrode layer 30 are sandwiched between the electrode pairs. It has a structure sandwiched between two protective layers 34 .
Thus, the regions sandwiched by the first electrode layer 28 and the second electrode layer 30 are driven according to the applied voltage.

In the present invention, the terms "first" and "second" in the first electrode layer 28 and the second electrode layer 30 are used for the sake of convenience in describing the piezoelectric acoustic film 24. As shown in FIG.
Therefore, the first and second parts of the piezoelectric acoustic film 24 have no technical significance and are irrelevant to the actual usage conditions.

In addition to these layers, the piezoelectric acoustic film 24 has an adhesive layer for attaching the electrode layer and the piezoelectric layer 26 and an adhesive layer for attaching the electrode layer and the protective layer. You may
The adhesive may be an adhesive or an adhesive. Also, as the adhesive, a polymer material obtained by removing the piezoelectric particles 40 from the piezoelectric layer 26, ie, the same material as the polymer matrix 38, can be suitably used. The adhesive layer may be provided on both the first electrode layer 28 side and the second electrode layer 30 side, or may be provided on only one of the first electrode layer 28 side and the second electrode layer 30 side. good.

In the piezoelectric acoustic film 24, the first protective layer 32 and the second protective layer 34 cover the first electrode layer 28 and the second electrode layer 30, and impart appropriate rigidity and mechanical strength to the piezoelectric layer 26. playing a role. That is, in the piezoelectric acoustic film 24, the piezoelectric layer 26 containing the polymer matrix 38 and the piezoelectric particles 40 exhibits excellent flexibility against slow bending deformation, but may may lack rigidity and mechanical strength. The piezoelectric acoustic film 24 is provided with a first protective layer 32 and a second protective layer 34 to compensate for this.
The first protective layer 32 and the second protective layer 34 have the same configuration, except for the arrangement position. Therefore, in the following description, when there is no need to distinguish between the first protective layer 32 and the second protective layer 34, both members are collectively referred to as protective layers.

There are no restrictions on the protective layer, and various sheet materials can be used. As an example, various resin films are preferably exemplified. Among them, polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), polycarbonate (PC), polyphenylene sulfite (PPS), polymethyl methacrylate (PMMA), due to their excellent mechanical properties and heat resistance. ), polyetherimide (PEI), polyimide (PI), polyamide (PA), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), and resin films made of cyclic olefin resins are preferably used. .

The thickness of the protective layer is also not limited. Also, the thicknesses of the first protective layer 32 and the second protective layer 34 are basically the same, but may be different.
If the rigidity of the protective layer is too high, it not only restricts expansion and contraction of the piezoelectric layer 26, but also impairs its flexibility. Therefore, the thinner the protective layer, the better, except when mechanical strength and good handling properties as a sheet are required.

If the thickness of each of the first protective layer 32 and the second protective layer 34 is not more than twice the thickness of the piezoelectric layer 26, favorable results can be achieved in terms of ensuring both rigidity and appropriate flexibility. is obtained.
For example, when the thickness of the piezoelectric layer 26 is 50 μm and the first protective layer 32 and the second protective layer 34 are made of PET, the thicknesses of the first protective layer 32 and the second protective layer 34 are each preferably 100 μm or less. , 50 μm or less, and more preferably 25 μm or less.

In the piezoelectric acoustic film 24, the first protective layer 32 and the second protective layer 34 are provided as a preferred embodiment, and are not essential constituents. That is, in the electroacoustic transducer of the present invention, the piezoelectric acoustic film 24 may have only the first protective layer 32 or only the second protective layer 34. It may be an object that does not have
However, considering the strength, handleability, protection of the electrode layer, etc. of the piezoelectric acoustic film 24, the piezoelectric acoustic film preferably has both the first protective layer 32 and the second protective layer 34 as shown in the figure.

In the piezoelectric acoustic film 24, the first electrode layer 28 is provided between the piezoelectric layer 26 and the first protective layer 32, the second electrode layer 30 is provided between the piezoelectric layer 26 and the second protective layer 34, formed respectively. The first electrode layer 28 and the second electrode layer 30 are provided for applying an electric field to the piezoelectric acoustic film 24 (piezoelectric layer 26).

The first electrode layer 28 and the second electrode layer 30 are basically the same except for their positions. Therefore, in the following description, when there is no need to distinguish between the first electrode layer 28 and the second electrode layer 30, both members are collectively referred to as electrode layers.

In the piezoelectric acoustic film, the material for forming the electrode layer is not limited, and various conductors can be used. Specifically, carbon, palladium, iron, tin, aluminum, nickel, platinum, gold, silver, copper, chromium, molybdenum, alloys thereof, indium tin oxide, and PEDOT/PPS (polyethylenedioxythiophene-polystyrenesulfone Acid) and other conductive polymers are exemplified.
Among them, copper, aluminum, gold, silver, platinum, and indium tin oxide are preferred. Among them, copper is more preferable from the viewpoint of conductivity, cost, flexibility, and the like.

In addition, the method of forming the electrode layer is not limited, and a vapor phase deposition method (vacuum film formation method) such as vacuum deposition and sputtering, a method of forming a film by plating, a method of attaching a foil formed of the above materials, a coating method, or the like. Various known methods such as the method of
Among them, a thin film of copper or aluminum formed by vacuum deposition is preferably used as the electrode layer because the flexibility of the piezoelectric acoustic film 24 can be ensured. Among them, a copper thin film formed by vacuum deposition is particularly preferably used.

The thicknesses of the first electrode layer 28 and the second electrode layer 30 are not limited. Also, the thicknesses of the first electrode layer 28 and the second electrode layer 30 are basically the same, but may be different.
Here, as with the protective layer described above, if the rigidity of the electrode layer is too high, not only will the expansion and contraction of the piezoelectric layer 26 be restricted, but also the flexibility will be impaired. Therefore, the thinner the electrode layer, the better, as long as the electrical resistance does not become too high.

In the piezoelectric acoustic film 24, if the product of the thickness of the electrode layer and the Young's modulus is less than the product of the thickness of the protective layer and the Young's modulus, the flexibility is not greatly impaired, which is preferable.
For example, when the protective layer is PET (Young's modulus: about 6.2 GPa) and the electrode layer is made of copper (Young's modulus: about 130 GPa), and the thickness of the protective layer is 25 μm, the thickness of the electrode layer is 1.2 μm or less is preferable, 0.3 μm or less is more preferable, and 0.1 μm or less is particularly preferable.

In the piezoelectric acoustic film 24, the piezoelectric layer 26 is sandwiched between the first electrode layer 28 and the second electrode layer 30, and in a preferred embodiment, this laminate is sandwiched between the first protective layer 32 and the second protective layer 34. It has a configuration that
In such a piezoelectric acoustic film 24, it is preferable that the loss tangent (Tan[delta]) at a frequency of 1 Hz by dynamic viscoelasticity measurement has a maximum value of 0.1 or more at room temperature.
As a result, even if the piezoelectric acoustic film 24 is subjected to a relatively slow and large bending deformation of several Hz or less from the outside, the strain energy can be effectively diffused to the outside as heat. It is possible to prevent cracks from occurring at the interface with

The piezoelectric acoustic film 24 preferably has a storage elastic modulus (E') at a frequency of 1 Hz measured by dynamic viscoelasticity measurement of 10 to 30 GPa at 0°C and 1 to 10 GPa at 50°C.
Accordingly, the piezoelectric acoustic film 24 can have a large frequency dispersion in the storage elastic modulus (E') at room temperature. That is, it can act hard against vibrations of 20 Hz to 20 kHz and soft against vibrations of several Hz or less.

In addition, the piezoelectric acoustic film 24 has a product of thickness and storage elastic modulus (E′) at a frequency of 1 Hz measured by dynamic viscoelasticity measurement at 0° C. of 1.0×10 ⁶ to 2.0×10 ⁶ N/. It is preferably 1.0×10 ⁵ to 1.0×10 ⁶ N/m at 50° C. m.
As a result, the piezoelectric acoustic film 24 can have appropriate rigidity and mechanical strength within a range that does not impair flexibility and acoustic properties.

Furthermore, the piezoelectric acoustic film 24 preferably has a loss tangent (Tan δ) of 0.05 or more at 25°C and a frequency of 1 kHz in a master curve obtained from dynamic viscoelasticity measurement.

An example of a method for manufacturing the piezoelectric acoustic film 24 will be described below with reference to FIGS. 9 to 11. FIG.
First, a laminated body 42b conceptually shown in FIG. 9 is prepared in which the second electrode layer 30 is formed on the surface of the second protective layer 34 . Furthermore, a laminated body 42a conceptually shown in FIG. 11 is prepared in which the first electrode layer 28 is formed on the surface of the first protective layer 32. Next, as shown in FIG.

The laminate 42b may be produced by forming a copper thin film or the like as the second electrode layer 30 on the surface of the second protective layer 34 by vacuum deposition, sputtering, plating, or the like. Similarly, the laminate 42a may be produced by forming a copper thin film or the like as the first electrode layer 28 on the surface of the first protective layer 32 by vacuum deposition, sputtering, plating, or the like.
Alternatively, a commercially available sheet having a copper thin film or the like formed on a protective layer may be used as the laminated body 42b and/or the laminated body 42a.
The laminate 42b and the laminate 42a may be the same or different.

In addition, when the protective layer is very thin and the handling property is poor, a protective layer with a separator (temporary support) may be used as necessary. As the separator, PET or the like having a thickness of 25 to 100 μm can be used. The separator may be removed after the electrode layer and protective layer are thermocompression bonded.

Next, as conceptually shown in FIG. 10, the piezoelectric layer 26 is formed on the second electrode layer 30 of the laminate 42b, and the piezoelectric laminate 46 is formed by laminating the laminate 42b and the piezoelectric layer 26. make.

The piezoelectric layer 26 may be formed by a known method suitable for the piezoelectric layer 26 .
For example, a piezoelectric layer (polymer composite piezoelectric layer) in which piezoelectric particles 40 are dispersed in a polymer matrix 38 shown in FIG. 8 is manufactured as follows.
First, a polymer material such as cyanoethylated PVA is dissolved in an organic solvent, and piezoelectric particles 40 such as PZT particles are added and stirred to prepare a paint. Organic solvents are not limited, and various organic solvents such as dimethylformamide (DMF), methyl ethyl ketone, and cyclohexanone can be used.
After the laminate 42b is prepared and the paint is prepared, the paint is cast (applied) to the laminate 42b and dried by evaporating the organic solvent. As a result, as shown in FIG. 10, a piezoelectric laminate 46 having the second electrode layer 30 on the second protective layer 34 and the piezoelectric layer 26 laminated on the second electrode layer 30 is produced. do.

There are no restrictions on the method of casting the coating material, and known methods (coating equipment) such as bar coaters, slide coaters and doctor knives can all be used.
Alternatively, if the polymer material can be melted by heating, the polymer material is heated and melted, and the piezoelectric particles 40 are added to the melted material, which is then extruded or otherwise laminated as shown in FIG. A piezoelectric laminate 46 as shown in FIG. 9 may be produced by extruding a sheet onto the body 42b and cooling.

As described above, in the piezoelectric acoustic film 24, the polymer matrix 38 may be added with a polymer piezoelectric material such as PVDF in addition to the polymer material having viscoelasticity at room temperature.
When these polymeric piezoelectric materials are added to the polymeric matrix 38, the polymeric piezoelectric materials to be added to the paint may be dissolved. Alternatively, the polymer piezoelectric material to be added may be added to a polymer material that has been melted by heating and has viscoelasticity at room temperature, and then melted by heating.

After the piezoelectric layer 26 is formed, it may be calendered, if desired. Calendering may be performed once or multiple times.
As is well known, calendering is a process in which a surface to be treated is heated and pressed by a hot press, hot rollers, or the like to flatten the surface.

Further, the piezoelectric layer 26 of the piezoelectric laminate 46 having the second electrode layer 30 on the second protective layer 34 and the piezoelectric layer 26 formed on the second electrode layer 30 is subjected to a polarization treatment ( polling).
The method of polarization treatment of the piezoelectric layer 26 is not limited, and known methods can be used. For example, electric field poling, in which a DC electric field is directly applied to an object to be polarized, is exemplified. When electric field poling is performed, the first electrode layer 28 may be formed before the polarization treatment, and the electric field poling treatment may be performed using the first electrode layer 28 and the second electrode layer 30. .
Further, when the piezoelectric acoustic film 24 is manufactured, the polarization treatment is performed not in the surface direction of the piezoelectric layer 26 but in the thickness direction.

Next, as conceptually shown in FIG. 11, the previously prepared laminate 42 a is laminated on the piezoelectric layer 26 side of the piezoelectric laminate 46 with the first electrode layer 28 facing the piezoelectric layer 26 .
Further, this laminate is thermocompression bonded using a heat press device, a heating roller, etc., with the first protective layer 32 and the second protective layer 34 sandwiched between them, thereby forming the piezoelectric laminate 46 and the laminate 42a. to paste together.
As a result, the piezoelectric layer 26, the first electrode layer 28 and the second electrode layer 30 provided on both surfaces of the piezoelectric layer 26, and the first protective layer 32 and the second protective layer 34 formed on the surface of the electrode layer A piezoelectric acoustic film 24 is produced.

The piezoelectric acoustic film 24 produced by performing such a production process is polarized in the thickness direction rather than in the surface direction, and excellent piezoelectric properties can be obtained without stretching after the polarization treatment. Therefore, the piezoelectric acoustic film 24 has no in-plane anisotropy in piezoelectric properties, and expands and contracts isotropically in all directions in the plane direction when a driving voltage is applied.

The electrode layer of the piezoelectric acoustic film 24 is connected to a lead electrode for electrical connection with an external device such as a power supply, and the lead wire is connected to a connection wire 64 having a speaker amplifier connection portion 64a. be.

In the projection screen 10 of the present invention, there are no restrictions on the method of connecting the electrode layers and the extraction electrodes, and various methods can be used.
As an example, a method of inserting a sheet-like lead electrode between the electrode layer and the piezoelectric layer and connecting the connection wiring 64 to the lead electrode is exemplified. Note that the extraction electrode may be inserted between the electrode layer and the protective layer. Alternatively, the connection wiring 64 may be inserted directly between the electrode layer and the piezoelectric layer or between the electrode layer and the protective layer.
Another method is to form a through hole in the protective layer, provide an electrode connection member formed of a metal paste such as silver paste so as to fill the through hole, and provide a lead electrode in this electrode connection member.
As another method, a method is exemplified in which a part of the protective layer and the electrode layer protrudes from the piezoelectric layer in the plane direction, and the lead electrode is connected to the protruded electrode layer. The connection between the extraction electrode and the electrode layer may be performed by a known method such as a method using a metal paste such as silver paste, a method using solder, or a method using a conductive adhesive.
Examples of suitable methods for extracting electrodes include the method described in Japanese Patent Application Laid-Open No. 2014-209724 and the method described in Japanese Patent Application Laid-Open No. 2016-015354.

Such a piezoelectric acoustic film 24 is attached to the screen main body 50 with an adhesive (not shown).
In the present invention, various known adhesive materials can be used as long as they can adhere the screen main body 50 and the piezoelectric acoustic film 24 together. Therefore, even a layer made of an adhesive (adhesive), which has fluidity when pasted together and then becomes a solid, is a gel-like (rubber-like) soft solid when pasted together. A layer made of an adhesive (adhesive material) that does not change its gel state after that, or a layer made of a material having the characteristics of both an adhesive and an adhesive may be used. The adhesive material may be formed by applying an adhesive agent having fluidity such as a liquid, or may be formed using a sheet-like adhesive agent.

In the projection screen 10 , the piezoelectric acoustic film 24 is obtained by sandwiching the piezoelectric layer 26 between the first electrode layer 28 and the second electrode layer 30 .
Piezoelectric layer 26 preferably has piezoelectric particles 40 in a polymer matrix 38 . Preferably, piezoelectric layer 26 comprises piezoelectric particles 40 dispersed in polymer matrix 38 .

When a voltage corresponding to an audio signal (acoustic signal) is applied to the second electrode layer 30 and the first electrode layer 28 of the piezoelectric acoustic film 24 having such a piezoelectric layer 26, the piezoelectric particles 40 are generated according to the applied voltage. expands and contracts in the direction of polarization. As a result, the piezoelectric acoustic film 24 (piezoelectric layer 26) shrinks in the thickness direction. At the same time, due to the Poisson's ratio, the piezoelectric acoustic film 24 also expands and contracts in the plane direction.
This expansion and contraction is about 0.01 to 0.1%.
As described above, the thickness of the piezoelectric layer 26 is preferably about 10-300 μm. Therefore, the expansion and contraction in the thickness direction is as small as about 0.3 μm at maximum.
On the other hand, the piezoelectric acoustic film 24, that is, the piezoelectric layer 26, has a size much larger than its thickness in the planar direction. Therefore, for example, if the length of the piezoelectric acoustic film 24 is 20 cm, the piezoelectric acoustic film 24 expands and contracts by a maximum of about 0.2 mm due to voltage application.

The expansion and contraction of the piezoelectric acoustic film 24 bends the screen body 50, and as a result, the screen body 50 vibrates in the thickness direction. The thickness direction is, in other words, a direction perpendicular to the surface direction of the screen body 50 .
The vibration in the thickness direction causes the screen body 50 to output sound. That is, the screen body 50 vibrates according to the magnitude of the voltage (driving voltage) applied to the piezoelectric acoustic film 24 and outputs sound according to the driving voltage applied to the piezoelectric acoustic film 24 .

Moreover, as described above, in the piezoelectric acoustic film 24, the preferable thickness of the piezoelectric layer 26 is at most about 300 μm. Moreover, the piezoelectric acoustic film 24 using the piezoelectric layer 26, which is a polymeric composite piezoelectric material, has very good flexibility.
Therefore, the piezoelectric acoustic film 24 is very thin and has good flexibility. Therefore, by using such a piezoelectric acoustic film 24, the piezoelectric acoustic film 24 suitably follows the winding of the screen body 50 when the screen body 50 is wound. As a result, the screen body 50 to which the piezoelectric acoustic film 24 is adhered can be suitably wound.

In addition, in the projection screen 10 of the present invention, the piezoelectric acoustic film is not limited to a single layer as in the illustrated example, and may be a laminate of a plurality of piezoelectric acoustic films 24 . In this regard, the same applies to the various piezoelectric acoustic films described above, in addition to the piezoelectric acoustic film 24 .
When a plurality of piezoelectric acoustic films 24 are laminated, a plurality of cut sheet-shaped piezoelectric acoustic films 24 may be laminated, or as described in, for example, International Publication No. 2020/095812. Thus, a plurality of layers may be laminated by folding one piezoelectric acoustic film 24 one or more times.
As mentioned above, the piezoelectric acoustic film 24 is very thin and has good flexibility. Therefore, even a laminate obtained by laminating a plurality of layers has good flexibility and can be suitably wound.

In the present invention, when a plurality of piezoelectric acoustic films 24 are laminated, it is preferable that the piezoelectric acoustic films 24 adjacent to each other by lamination are adhered with an adhesive.
The adhesive (adhesive layer) has fluidity when it is pasted together, and then becomes solid. It may be an adhesive that does not change its state, or it may be made of a material that has the characteristics of both an adhesive and an adhesive. However, it is preferable to use an adhesive that finally becomes a solid as the sticking agent in that the expansion and contraction of the laminated piezoelectric acoustic film 24 can be transmitted appropriately without loss.

As described above, the projection screen 10 of the present invention is provided with the sound insulating sheet 59 covering the rear side of the screen body 50 as conceptually shown in the sectional view (right side) of FIG. 1 and FIG.
Since the projection screen 10 of the present invention has such a sound insulation sheet 59, the reverse phase sound from the back side of the screen main body 50 wraps around to the projection surface side, and part of the sound output from the projection surface side to prevent it from canceling out with

As described above, the screen provided with the piezoelectric acoustic film on the back surface of the projection surface vibrates the entire surface of the screen due to the piezoelectric acoustic film, and the vibration of the screen outputs sound. Therefore, the screen is in a state in which sound is output from the screen, and sound with a high degree of realism can be output.
However, in this screen, since the entire screen vibrates, the sound of the opposite phase is also output from the back side and wraps around to the projection surface side. Since this anti-phase sound partially cancels out the sound output on the projection surface side, the sound output decreases when the image is observed on the projection surface side.

On the other hand, the projection screen 10 of the present invention is provided with a sound insulating sheet 59 covering the rear side of the screen main body 50 .
In the illustrated example, the sound insulation sheet 59 is attached to the first support member 52 and the second support member 54 with Velcro, and covers the entire surface of the screen body 50 .

Since the projection screen 10 of the present invention has such a sound insulation sheet 59, the sound insulation sheet 59 insulates the sound of the opposite phase output from the back side of the screen main body 50, and the sound of the reverse phase output from the back side is blocked. To prevent phase sound from going around to the projection surface side.
As a result, according to the projection screen 10 of the present invention, when viewed from the projection side of the projection screen 10, sound pressure reduction due to cancellation of sound is suppressed, and images with appropriate output audio can be viewed. be able to.

In the projection screen 10 of the present invention, the sound insulating sheet 59 is not limited, and various known sheet-like materials can be used.
As an example, various sheet-like materials used as the screen main body 50 made of resin such as vinyl chloride, paper such as Japanese paper, and cloth such as canvas cloth are exemplified. When the sound insulation sheet 59 is used as the screen body 50, the screen body 50 and the sound insulation sheet 59 may be the same or different.
In addition, as the sound insulation sheet 59, a sheet-like material made of a porous material such as rubber or urethane foam, or a non-woven fabric such as felt can be used.

In the projection screen 10 of the present invention, it is preferable that a space exists between the screen body 50 and the piezoelectric acoustic film 24 and the sound insulating sheet 59, as shown in the cross-sectional view of FIG.
In other words, in the projection screen 10 of the present invention, it is preferable that the screen body 50 and the piezoelectric acoustic film 24 and the sound insulation sheet 59 do not come into contact with each other.

If the screen body 50 and/or the piezoelectric acoustic film 24 and the sound insulation sheet 59 are in contact with each other, the sound insulation sheet 59 will also vibrate. As a result, it is not possible to prevent the opposite phase sound generated on the back side of the screen main body 50 from going around to the projection surface side, and part of the sound output on the projection surface side is canceled.
On the other hand, since the screen main body 50 and the piezoelectric acoustic film 24 are separated from the sound insulation sheet 59, the sound insulation sheet 59 is prevented from vibrating, and the opposite phase sound is prevented from reaching the projection surface side. can be more suitably prevented.

The size of the gap between the screen body 50 and the piezoelectric acoustic film 24 and the sound insulating sheet 59 is not limited. and the sound insulation sheet 59 are kept apart.
Therefore, the distance between the screen main body 50 and the piezoelectric acoustic film 24 and the sound insulating sheet 59 is determined according to the device configuration and the like, while the screen main body 50 vibrates and outputs sound. 24 and the sound insulation sheet 59 may be set appropriately.

If the screen body 50 and the piezoelectric acoustic film 24 and the sound insulation sheet 59 do not come into contact with each other, the sound insulation sheet 59 may be stretched up with a certain amount of tension, or may be fixed in a loosened state where no tension is applied. .

The sound insulation sheet 59 is preferably detachable. That is, the projection screen 10 preferably has a mechanism for attaching and detaching the sound insulation sheet.
In the illustrated example, the sound insulation sheet 59 is detachably fixed to the first support member 52 and the second support member 54 with Velcro, as described above.

As described above, when the projection screen 10 is not in use, the screen body 50 is removed from the lifting mechanism 56 together with the first support member 52 and the second support member 54, and the first support member 52 and/or the second support member 54 are removed. It is wound on member 54 .

If the sound insulation sheet 59 cannot be removed during this winding, the screen body 50 and the sound insulation sheet 59 must be wound together. It is difficult to wind the screen body 50 and the sound insulation sheet 59 together. Moreover, depending on the winding method, the screen body 50 may be wrinkled, folded, or torn.
On the other hand, by making the sound insulation sheet 59 detachable, the screen body 50 and the sound insulation sheet 59 can be separately wound up, making it easier to wind them up and preventing wrinkles in the screen body 50. It is possible to suitably prevent inconvenience such as entering.

In the projection screen 10, the method of making the sound insulating sheet 59 detachable, that is, the detachable mechanism, is not limited to the method using Velcro, and various known methods of making the sheet-like material detachable can be used. is.
Examples include a method using a hook (hook-shaped member) and a ring (hole) for hooking the hook, a method using a magnet, and a method using meshing of unevenness provided on a sheet.

In the illustrated projection screen 10 , the sound insulation sheet 59 is provided so as to cover the entire rear surface of the screen body 50 .
However, the present invention is not limited to this, and the sound insulation sheet 59 may cover a portion of the back surface of the screen body 50 . However, the sound insulation sheet 59 preferably covers the entire back surface of the screen body 50 in order to suitably prevent the opposite phase sound generated on the back side of the screen body 50 from reaching the projection surface.

Although the projection screen of the present invention has been described in detail above, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

Hereinafter, the present invention will be described in more detail by giving specific examples of the present invention. The present invention is not limited to this example, and the materials, amounts used, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. can.

[Preparation of Piezoelectric Acoustic Film]
A piezoelectric acoustic film was produced by the method shown in FIGS.
First, cyanoethylated PVA (CR-V, manufactured by Shin-Etsu Chemical Co., Ltd.) was dissolved in dimethylformamide (DMF) at the following compositional ratio. After that, PZT particles as piezoelectric particles were added to this solution at the following composition ratio, and the mixture was stirred with a propeller mixer (rotation speed: 2000 rpm) to prepare a paint for forming a piezoelectric layer.
・PZT particles・・・・・・・・・・300 parts by mass ・Cyanoethylated PVA・・・・・・・・30 parts by mass ・DMF・・・・・・・・・・・・70 parts by mass The PZT particles are composed of powders of Pb oxide, Zr oxide and Ti oxide, which are the main components, so that Zr = 0.52 mol and Ti = 0.48 mol with respect to Pb = 1 mol. Mixed powder obtained by wet-mixing in a ball mill was fired at 800° C. for 5 hours and then pulverized.

On the other hand, a sheet-like material was prepared by vacuum-depositing a copper thin film with a thickness of 0.1 μm on a PET film with a thickness of 4 μm. That is, in this example, the first electrode layer and the second electrode layer are 0.1 m-thick copper-evaporated thin films, and the first protective layer and the second protective layer are 4 μm-thick PET films.
Using a slide coater, the previously prepared paint for forming the piezoelectric layer was applied onto the second electrode layer (copper-deposited thin film) of the sheet-like material. The paint was applied so that the thickness of the coating film after drying was 40 μm.
Next, the sheet-like material coated with the paint was dried by heating on a hot plate at 120° C. to evaporate the DMF. As a result, a laminate having a second electrode layer made of copper on a second protective layer made of PET and a piezoelectric layer (polymer composite piezoelectric layer) having a thickness of 30 μm thereon was produced. .

The produced piezoelectric layer was subjected to polarization treatment in the thickness direction.

A sheet-like product obtained by vapor-depositing the same thin film on a PET film was laminated with the first electrode layer (copper thin film side) facing the piezoelectric layer on the laminate in which the piezoelectric layer had been subjected to the polarization treatment.
Next, the laminate of the laminate and the sheet-like material is thermocompressed at a temperature of 120° C. using a laminator device to adhere and bond the composite piezoelectric body and the first electrode layer, as shown in FIG. A piezoelectric acoustic film as shown in was produced.

[Example 1]
A vinyl chloride screen body of 1200×1600 mm was prepared. Also, the produced piezoelectric acoustic film was cut into squares of 120×120 mm.
This screen body was divided into two parts in the longitudinal direction, and a piezoelectric acoustic film was adhered to the center of each area. The piezoelectric acoustic film was attached using a double-sided adhesive tape.
A projection screen as shown in FIGS. 1 and 12 was produced using the screen main body to which the piezoelectric acoustic film was adhered.
The same sound insulating sheet as used for the screen main body was used, and was fixed to the first supporting member and the second supporting member with Velcro to cover the entire rear surface of the screen main body. Therefore, this projection screen has an attachment/detachment mechanism for attaching/detaching the sound insulating sheet.
Further, a space was provided between the piezoelectric acoustic film and the screen main body and the sound insulating sheet so that the two do not come into contact with each other.

[Example 2]
A projection screen was produced in the same manner as in Example 1, except that the screen body was divided into four equal parts in the lateral direction and the longitudinal direction, and the same piezoelectric acoustic film was adhered to each region.

[Example 3]
A projection screen was produced in the same manner as in Example 1, except that Japanese paper was used as the screen body and the sound insulation sheet.
[Example 4]
A projection screen was produced in the same manner as in Example 1, except that canvas was used as the screen body and the sound insulation sheet.

[Example 5]
The same procedure as in Example 1 was performed, except that the positions where the sound insulation sheets were attached to the first support member and the second support member were changed so that no space was provided between the piezoelectric acoustic film and the sound insulation sheet, and the two were brought into contact with each other. A projection screen was made.

[Example 6]
A projection screen was produced in the same manner as in Example 1, except that an adhesive was used to prevent the sound insulation sheet from being removed from the first support member and the second support member.

[Comparative Example 1]
A projection screen was produced in the same manner as in Example 1, except that the sound insulating sheet was not provided.

The following evaluation was performed using the produced projection screen.
When a still image and a moving image were projected onto the main screen using a projector, the projected images could be viewed satisfactorily.

[Sound pressure]
The sound pressure was measured using a sound level meter at a distance of 1 m from the screen main body and at the central position in the longitudinal and lateral directions.
In measuring the sound pressure, pink noise of 500 to 20 kHz was input by a constant current amplifier. The voltage was adjusted to give a 20 Vrms input at 1 kHz. The sound pressure level of Example 2 was evaluated as 5 out of 5, and the evaluation was lowered by 1 each time the sound pressure decreased by 1 dB.

[Windability]
The produced projection screen was dismantled into the leg members, the tensioning mechanism, the screen main body, the first supporting member and the second supporting member as described above. Furthermore, in the case where the sound insulation sheet is detachable, the sound insulation sheet is removed from the first support member and the second support member.
After that, the screen body was wound around the first supporting member. In addition, the winding was performed manually, and was wound so as not to generate a gap to the extent that winding misalignment did not occur easily.
After the screen body was wound up, it was allowed to stand still for one day. After that, the wound screen body was unfolded and the presence or absence of wrinkles and folds was evaluated.
A when no wrinkles or folds were found on the screen body,
B when wrinkles and folds are found on the screen body,
and evaluated.
Results are shown in the table below.

As shown in the above table, according to the projection screen of the present invention having the sound insulation sheet on the back side of the screen body, the noise is higher than that of Comparative Example 1, which is the conventional projection screen without the sound insulation sheet. pressure can be obtained.
As shown in Examples 1 and 6, a higher sound pressure can be obtained by providing a space between the screen body and the piezoelectric acoustic film and the sound insulating sheet. In addition, as shown in Examples 1 and 6, since the sound insulation sheet has a mechanism for attaching and detaching the sound insulation sheet, the sound insulation sheet can be removed and the screen can be wound up when the screen is not in use. It is possible to prevent wrinkles or the like from entering the screen.
From the above results, the effect of the present invention is clear.

It can be suitably used for projecting video with audio output.

Reference Signs List 10 projection screen 24 piezoelectric acoustic film 26 piezoelectric layer 28 first electrode layer 30 second electrode layer 32 first protective layer 34 second protective layer 38 polymer matrix 40

piezoelectric particles

42a, 42b laminate 46 piezoelectric laminate 50 Screen main body 52 First supporting member 52a Main body 52b C-shaped cover 52c Through hole 54 Second supporting member 54a Main body 54b C-shaped cover 54c Through hole 56 Lifting mechanism 58 First frame member

58a Engaging member

58b Fixing pin 60 Second frame member

60a engaging member

60b fixing pin 62 hinge member 62a first arm 62b

second arm

62c, 62d, 62f rotating shaft 64 connection wiring 64a speaker amplifier connecting portion 78 foot member 78a upper supporting member 78b lower supporting member 78c foot 80 fine adjustment Mechanism 80a Adjusting screw

Claims

A screen body for projecting images,
a piezoelectric acoustic film attached to the surface of the screen body opposite to the image projection surface;
A projection screen, comprising: a sound insulation sheet provided to cover a surface of the screen body opposite to the projection surface.
The projection screen according to claim 1, wherein a space is provided between the screen body and the piezoelectric acoustic film, and the sound insulation sheet.
The projection screen according to claim 1 or 2, wherein the sound insulation sheet is detachable.
The projection screen according to any one of claims 1 to 3, wherein the piezoelectric acoustic film is flexible.
a first supporting member that supports one side of the screen body, and a second supporting member that supports a side of the screen body opposite to the side supported by the first supporting member;
5. The projection screen according to any one of claims 1 to 4, further comprising a tensioning mechanism that brings the first support member and the second support member closer to each other and separates them from each other.
6. The apparatus according to claim 5, further comprising a fine adjustment mechanism for adjusting the distance between the first support member and the second support member while the first support member and the second support member are separated by the lifting mechanism. projection screen.
The projection screen according to any one of claims 1 to 6, wherein the piezoelectric acoustic film has a piezoelectric layer and electrode layers provided on both sides of the piezoelectric layer.
The projection screen according to claim 7, wherein the piezoelectric layer is a polymeric composite piezoelectric body having piezoelectric particles in a polymeric material.
The projection screen according to claim 8, wherein the polymer material of the polymer composite piezoelectric body is cyanoethylated polyvinyl alcohol.