Technical Field
[0001]
The present invention relates to a fiber-like
piezoelectric element to be used in a touch input device
or pointing device, or for surface form measurement or
10 the like. More specifically, it relates to a sensor that
can generate sufficient electrical output as a touch
sensor merely by rubbing the surface of a fiber-like
piezoelectric element, and that can obtain positional
information and shape information about an object to be
15 measured, by rubbing the surface of an object to be
measured with the fiber-like piezoelectric element.
[0002]
The present invention relates to a braided
piezoelectric element using piezoelectric fibers, to a
20 fabric-like piezoelectric element using the braided
piezoelectric element, and to a device using the
foregoing.
[0003]
The present invention further relates to a braided
25 piezoelectric element using piezoelectric fibers, having
the braid covered with a conductive layer, to a fabriclike
piezoelectric element using the braided
piezoelectric element, and to a device using the
foregoing.
30 [0004]
The present invention still further relates to a
transducer that outputs an electrical signal in response
to shape deformation due to external force, and/or whose
shape deforms by input of an electrical signal. More
35 specifically, it relates to a fabric-like transducer that
is flexible and is able to undergo three-dimensional
shape deformation.
Background Art
[0005]
- 2 -
Recent years have seen a drastic increase in input
devices employing touch panel systems, i.e. "touch input
5 devices". With the development of thin display
technology for bank ATMs and station ticket-vending
machines, as well as cellular phones, portable gaming
devices, portable music players and the like, there has
been a massive increase in devices employing touch panel
10 systems as the input interface.
[0006]
Recently, for cellular phones and smartphones, many
systems are being used with touch input devices installed
on display devices that employ liquid crystals or organic
15 electroluminescence, allowing direct input on the screen.
To further increase the convenience of portable devices
such as smartphones, which are undergoing constant
advancements, it is preferred to have multiple touch
input means instead of only a device for input onto the
20 screen.
[0007]
For example, when it is attempted to execute input
with the finger on the display screen of a smartphone,
the smartphone is held with one hand while input is
25 executed with fingers of the other hand, thus requiring
manipulation using both hands. However, if a touch
sensor or the like is incorporated into the smartphone
housing, the advantage of being operable with one hand is
provided.
30 [0008]
One example of this is disclosed in PTL 1, as a
system whereby a touch sensor or the like is incorporated
into a section of the housing at a non-display-screen
portion, such as the back of the display screen that is
35 not normally used as a sensor, and screen data items or
anchor points are selected by the sensor. Input devices
that implement touch sensors such as in PTL 1 include
5
- 3 -
electrostatic capacitive systems, resistance film-type
systems, optical systems, electromagnetic induction
systems and systems using piezoelectric sheets.
[0009]
An example of a system using a piezoelectric sheet
is disclosed in PTL 2. A piezoelectric sheet system
differs from the touch sensors of electrostatic
capacitive systems or resistance film systems, in that
the single element can simultaneously detect both
10 pressure applied to the sensor and positional
information, thus allowing diverse types of input
information to be provided. Moreover, PTL 2 discloses an
example of using the piezoelectric polymer polylactic
acid, as a specific example of a piezoelectric sheet
15 member.
[0010]
A piezoelectric sheet comprising polylactic acid, as
disclosed in PTL 2, is an excellent element that can be
flexibilized and that can simultaneously detect
20 positional information and stress with the single
element, but in order to obtain sufficient electrical
output it is necessary to warp the piezoelectric sheet to
some extent by the stress during input. A piezoelectric
sheet comprising polylactic acid generates electrical
25 output by shearing stress applied to the sheet, but
sufficient electrical output cannot be obtained by
tension or compression. In order to obtain large
electrical output, therefore, it is necessary to warp the
sheet by pressing force from the direction perpendicular
30 to the plane of the piezoelectric sheet. For example,
considering that the piezoelectric sheet is laminated on
or integrated with the housing on the back side of the
smartphone, it is spatially difficult to warp the sheet
by pressing force applied to the sheet in the direction
35 perpendicular to the sheet, and it has been a goal to
generate sufficient electrical output simply by rubbing
the surface of the piezoelectric element. In addition,
- 4 -
the housing surface of a smartphone or the like is not
always a flat plane and may include numerous threedimensional
irregularities in its shape for reasons of
design maintenance, and it has been desirable for the
5 piezoelectric elements used in it to be flexible.
[0011]
Also, PTL 3 discloses a piezoelectric fiber
technology in which a piezoelectric polymer is oriented
by adding twists. The piezoelectric fibers described in
10 PTL 3 yield electrical output through tension or
compression of the fibers, by having the fibers pretwisted
via special production methods. However, PTL 3
discloses absolutely no technology for generating and
extracting sufficient electrical output in response to
15 shearing stress by rubbing of fiber surfaces. Thus, it
is extremely difficult to incorporate such a
piezoelectric fiber element into a smartphone housing or
the like, and extract sufficient electrical output by
relatively small amounts of applied stress such as
20 rubbing the surface with a finger or the like.
[0012]
It is generally known that polylactic acid fibers
oriented by uniaxial stretching produce virtually no
polarization in response to stretching or compression
25 stress in the direction of the stretching axis or the
direction perpendicular to it, and therefore yield
essentially no electrical output by the relatively small
applied stress generated by rubbing the fiber surfaces
with a finger. On the other hand, it is known that
30 application of force in a direction that is neither
parallel nor perpendicular to the stretching axis of the
polylactic acid piezoelectric fibers, i.e. shearing
stress, produces polarization, thereby exhibiting the
function as a piezoelectric body.
35 [0013]
PTL 4 discloses a fiber-like piezoelectric element
that allows electrical output to be extracted from the
- 5 -
relatively small applied stress of rubbing the surface
with a finger or the like. In PTL 4, carbon fiber is
used as the conductive fiber for the constituent element
of the fiber-like piezoelectric element. However, when
5 this fiber-like piezoelectric element is applied for
purposes requiring repeated durability, because carbon
fiber has weak flexural rigidity, the fiber will
gradually break making it impossible to obtain
quantitative piezoelectricity, and potentially causing
10 the piezoelectric property to gradually decrease. In
addition, when it is attempted to obtain height or shape
information of an object to be measured using a braided
piezoelectric element as the contact probe, the carbon
fiber breaks and the tip becomes sharper, and the
15 characteristic rigidity of the carbon fiber can
potentially damage the surface of the object to be
measured4
[0014]
Moreover, there has been increasing interest in
20 recent years for "wearable sensors 11
, which have made
their debut as products in the form of eyeglasses or
wristwatches. However, such devices produce the
sensation of being worn, and are more desirably in the
form of fabrics, i.e. clothing, which are the ultimate
25 wearable form. Piezoelectric elements using the
piezoelectric effect of piezoelectric fibers are known as
such types of sensors. For example, PTL 4 discloses a
piezoelectric element comprising two conductive fibers
and one piezoelectric fiber, with points of contact
30 between them, while including a piezoelectric unit
disposed on essentially the same plane. Also, PTL 3
discloses a piezoelectric material which is a fiber-like
or molded article made of a piezoelectric polymer
wherein, in order to generate piezoelectricity by tensile
35 force applied in the axial direction, the construction
includes added twists in a direction different from the
direction of the tensile force that is to be applied.
- 6 -
[0015]
On the other hand, recent years have seen a drastic
increase in input devices employing touch panel systems,
i.e. "touch input devices". With the development of thin
5 display technology for bank ATMs and station ticketvending
machines, as well as smartphones, cellular
phones, portable gaming devices, portable music players
and the like, there has been a massive increase in
devices employing touch panel systems as the input
10 interface. As means for realizing such touch panel
systems there are known systems using piezoelectric
sheets or piezoelectric fibers. For example, PTL 2
discloses a touch panel employing a piezoelectric sheet
made of L-polylactic acid having a stretching axis
15 oriented in a prescribed direction.
[0016]
In such wearable sensors or touch panel system
sensors, it is desirable to extract a high electrical
signal even for small amounts of stress produced in the
20 piezoelectric material by small deformation applied to
the piezoelectric material. For example, it is desirable
to stably extract a high electrical signal even for
relatively small amounts of stress produced in the
piezoelectric material by movement of stretching out the
25 finger, or the action of rubbing the surface with the
finger.
[0017]
The piezoelectric fiber of PTL 4 is an excellent
material that can be applied for various purposes, but it
30 cannot always output a high electrical signal in response
to stress produced by relatively small amounts of
deformation, nor does this publication disclose
technology for obtaining a high electrical signal.
35
[0018]
The piezoelectric fibers described in PTL 3 can
output an electrical signal in response to tension or
compression on the piezoelectric fibers, by having the
- 7 -
piezoelectric fibers pre-twisted via special production
methods. However, PTL 3 does not disclose any technology
for producing an adequate electrical signal in response
to bending or stretching of the piezoelectric fibers, or
5 shearing stress due to rubbing of the surfaces of the
piezoelectric fibers. Therefore, when such piezoelectric
fibers are used, it is difficult to extract a sufficient
electrical signal simply by stress produced by relatively
small amounts of deformation such as rubbing of the
10 surface.
[0019]
The piezoelectric sheet of PTL 2 can output an
electrical signal by deformation (stress) of the
piezoelectric sheet. However, because it is still in a
15 sheet form, it has poor flexibility and cannot be used to
allow free bending in the manner of a fabric.
[0020]
Moreover, the piezoelectric element described in PTL
4 has bare conductive fibers serving as the signal wire,
20 and .therefore in order to suppress noise signals it is
necessary to construct a separate noise shielding
structure. Therefore, the piezoelectric element
described in PTL 4 still has room for improvement toward
its implementation.
25 [0021]
Wearable sensors that have piezoelectric elements
mounted in fabrics from which they extract signals have
also been disclosed (PTLs 5 and 6). However, because
they require a separate structure on the surface of a
30 woven or knitted fabric, they are poorly suited for free
form surfaces and have poor touch sensation, while also
lacking practicality due to problems of manageability,
workability and processability. In addition, a fabric
structure formed of a piezoelectric material and a
35 conducting material in the form of a film also exists
(PTL 7), but it likewise has poor suitability to free
form surfaces and poor touch sensation, and lacks
- 8 -
practicality due to problems of manageability,
workability and processability.
[0022]
There has also been proposed a fabric sensor
5 composed entirely of fibers, which detects resistance
between conductive fibers (PTL 8), but this detects
pressure on the fabric without directly detecting shape
deformation-.
10
15
[0023]
PTL 4 discloses a piezoelectric element including a
piezoelectric unit comprising two conductive fibers and
one piezoelectric fiber, disposed on essentially the same
plane while having points of contact between them, and a
technique for arranging multiple piezoelectric units in
parallel on the plane. However, it nowhere suggests
higher functions based on selective responses to
electrical signals for stress at specific locations or in
specific directions, or compositing with piezoelectric
units in the thickness direction of the element, and
20 therefore further improvements in this technology have
been a topic of interest.
[0024]
Another issue has been the output of unintended
signals during direct contact with the human body or
25 contact with electrified objects.
30
Citation List
Patent Literature
[0025]
[ PTL 1]
189792
[PTL 2]
253517
[PTL 3]
[PTL 4]
Japanese Unexamined Patent Publication No. 2001-
Japanese Unexamined Patent Publication No. 2011-
Japanese Patent Publication No. 3540208
International Patent Publication No.
35 W02014/058077
[PTL 5] Japanese Patent Public Inspection No. 2007-518886
[PTL 6] Japanese Unexamined Patent Publication HEI No. 6-
- 9 -
323929
[PTL 7] Japanese Unexamined Patent Publication No. 2002-
203996
[PTL 8] Japanese Unexamined Patent Publication No. 2006-
5 284276
Summary of Invention
Technical Problem
[0026]_
The present invention has been accomplished in light
10 of this background, and its first object is to provide a
fiber-like piezoelectric element that can extract
electrical output by relatively small applied stress such
as rubbing of the surface with the finger or the like,
and to provide a fiber-like piezoelectric element that
15 can withstand repeated friction on the surface or tip
section of the piezoelectric element.
[0027]
The second object is to provide a fiber-like
piezoelectric element capable of extracting a large
20 electrical signal even by stress produced by relatively
small deformation.
[0028]
The third object is to provide a fiber-like
piezoelectric element capable of extracting a large
25 electrical signal even by stress produced by relatively
small deformation, and capable of controlling noise
signals.
[0029]
The fourth object is to provide a flat transducer
30 that can selectively respond with an electrical signal to
stress at a specific location or in a specific direction1
by using fiber materials and forming a conventional woven
or knitted fabric structure, as well as to provide a
device that uses a signal from the transducer and/or a
35 device that functions by inputting an electrical signal.
[0030 l
The fifth object is to provide a fabric-like
- 10 -
transducer with a low malfunction rate, highly
practicality and extreme flexibility, by using fiber
materials and forming a conventional woven or knitted
fabric structure, as well as to provide a device that
5 uses a signal from the transducer and/or a device that
functions by inputting an electrical signal.
Solution to Problem
[0031]
As a result of ardent research directed toward
10 achieving the first object, the present inventors have
completed this invention upon finding that electricity
can be efficiently extracted by a braided piezoelectric
element which is a combination of a conductive fiber and
a piezoelectric polymer, wherein the surface of the
15 conductive fiber serving as the core is covered with the
piezoelectric polymer.
[0032]
Specifically, the present invention provides the
following 1 to 13 as means for achieving the first object
20 of the invention (first invention).
1. A piezoelectric element including a braid
comprising a conductive fiber and piezoelectric fibers,
the braid having the conductive fiber as the core, and
the piezoelectric fibers being covering fibers that cover
25 the periphery of the conductive fiber.
2. The piezoelectric element according to 1 above,
wherein the flexural rigidity of the conductive fiber is
no greater than 0.05 x 10-4 N·m2/m.
3. The piezoelectric element according to 1 above,
30 wherein the conductive fiber is a metal coated organic
fiber.
35
4. The piezoelectric element according to any one of
1 to 3 above, wherein the piezoelectric fibers include
mainly polylactic acid.
5. The piezoelectric element according to 4 above,
wherein the piezoelectric fibers include mainly poly-Llactic
acid or poly-D-lactic acid with an optical purity
5
- 11 -
of 99% or greater.
6. The piezoelectric element according to any one of
1 to 5 above, wherein the piezoelectric fibers are
uniaxially oriented and include crystals.
7. The piezoelectric element according to any one of
l to 6 above, which detects the amount of stress applied
to the covering fibers and/or the location at which it is
applied .
. 8. The piezoelectric element according to 7 above,
10 wherein the stress to be detected is frictional force
between the surfaces of the covering fibers and the
surface of the contacting object.
9. The piezoelectric element according to 7 above,
wherein the stress to be detected is resistance in the
15 direction perpendicular to the surfaces or tip sections
of the covering fibers.
20
10. A sensor using the piezoelectric element
according to any one of 1 to 9 above.
11. A device comprising:
a piezoelectric sensor according to 10 above,
amplification means that amplifies an electrical
signal outputted from the piezoelectric sensor in
response to applied pressure, and
output means that outputs the electrical signal that
25 has been amplified by the amplification means.
30
35
12. The device according to 11 above, the device
further comprising transmission means that transmits the
electrical signal that has been outputted from the output
means, to an external device.
13. A device comprising:
the piezoelectric sensor according to 10 above,
output means that outputs an electrical signal from
the piezoelectric sensor in response to applied pressure,
and
transmission means that transmits the electrical
signal outputted from the output means, to an external
device.
- 12 -
[0033]
Moreover, as a result of ardent research directed
toward achieving the second object, the present inventors
have completed this invention upon finding that
5 electricity can be efficiently extracted by a braided
piezoelectric element as a combination of a conductive
fiber and piezoelectric fibers, wherein the surface of
the conductive fiber serving as the core is covered with
the braided piezoelectric fibers.
10 [0034]
Specifically, the invention provides the following
14 to 21 as means for achieving the second object of the
invention (second invention).
14. A braided piezoelectric element comprising a
15 core formed of a conductive fiber and a sheath formed of
braided piezoelectric fibers covering the core, wherein
the piezoelectric fibers include polylactic acid as a
main component, the winding angles of the piezoelectric
fibers with respect to the conductive fiber being between
20 15° and 75°, inclusive.
25
15. The braided piezoelectric element according to
14 above, wherein the total fineness of the piezoelectric
fibers is at least 1/2 times and no greater than 20 times
the total fineness of the conductive fiber.
16. The braided piezoelectric element according to
14 above, wherein the fineness per piezoelectric fiber is
at least 1/20 times and no greater than 2 times the total
fineness of the conductive fiber.
17. A fabric-like piezoelectric element comprising a
30 fabric that includes the braided piezoelectric element
according to any one of 14 to 16 above.
18. The fabric-like piezoelectric element according
to 17 above, wherein the fabric further includes
conductive fibers that cross and contact with at least
35 part of the braided piezoelectric element.
19. The fabric-like piezoelectric element according
to 18 above, wherein among the fibers forming the fabric
- 13 -
and crossing the braided piezoelectric element, at least
30% are conductive fibers.
20. A device comprising a braided piezoelectric
element according to any one of 14 to 16 above,
5 amplification means that amplifies an electrical signal
outputted from the braided piezoelectric element in
response to applied pressure, and output means that
outputs the electrical signal that has been amplified by
the amplification means.
10 21. A device comprising a fabric-like piezoelectric
element according to any one of 17 to 19 above,
amplification means that amplifies an electrical signal
outputted from the fabric-like piezoelectric element in
response to applied pressure, and output means that
15 outputs the electrical signal that has been amplified by
the amplification means.
[0035]
Moreover, as a result of ardent research directed
toward achieving the third object, the present inventors
20 have completed this invention upon finding that an
electrical signal can be efficiently extracted and noise
signals can be suppressed, by a braided piezoelectric
element as a combination of a conductive fiber and
piezoelectric fibers, wherein the surface of the
25 conductive fiber serving as the core is covered with the
braided piezoelectric fibers, and a conductive layer is
also provided around the periphery.
[0036]
Specifically, the invention provides the following
30 22 to 32 as means for achieving the third object of the
invention (third invention).
22. A braided piezoelectric element comprising a
core formed of a conductive fiber, a sheath formed of
braided piezoelectric fibers covering the core, and a
35 conductive layer provided around the periphery of the
sheath.
23. The braided piezoelectric element according to
- 14 -
22 above, wherein the coverage factor of the sheath by
the conductive layer is 25% or greater.
24. The braided piezoelectric element according to
22 or 23 above, wherein the conductive layer is formed of
5 fibers.
25. The braided piezoelectric element according to
any one of 22 to 24 above, wherein the piezoelectric
fibers include polylactic acid as the main component, and
the winding angle of the piezoelectric fibers with
10 respect to the conductive fibers is between 15° and 75°,
-inclusive.
26. The braided piezoelectric element according to
any one of 22 to 25 above, wherein the total fineness of
the piezoelectric fibers is at least 1 and no greater
15 than 20 times the total fineness of the conductive
fibers.
27. The braided piezoelectric element according to
any one of 22 to 25 above, wherein the fineness per
piezoelectric fiber is at least 1/20 times and no greater
20 than 2 times the total fineness of the conductive fibers.
28. A fabric-like piezoelectric element comprising a
fabric that includes the braided piezoelectric element
according to any one of 22 to 27 above.
29. The fabric-like piezoelectric element according
25 to 28 above, wherein the fabric further includes
conductive fibers that cross and contact with at least
part of the braided piezoelectric element.
30. The fabric-like piezoelectric element according
to 29 above, wherein among the fibers forming the fabric
30 and crossing the braided piezoelectric element, at least
30% are conductive fibers.
31. A device comprising a braided piezoelectric
element according to any one of 22 to 27 above,
amplification means that amplifies an electrical signal
35 outputted from the braided piezoelectric element in
response to applied pressure, and output means that
outputs the electrical signal that has been amplified by
- 15 -
the amplification means.
32. A device comprising a fabric-like piezoelectric
element according to any one of 28 to 30 above,
amplification means that amplifies an electrical signal
5 outputted from the fabric-like piezoelectric element in
response to applied pressure, and output means that
outputs the electrical signal that has been amplified by
the amplification means.
10
[0037]
Moreover, as a result of ardent research directed
toward achieving the fourth object, the present inventors
have completed this invention upon finding that a
combined arrangement of conductive fibers and
piezoelectric fibers functions as a piezoelectric
15 element, and further that by layering a flat transducer
comprising a piezoelectric element or the like and
forming a composite, it is possible to selectively
produce an electrical signal in response to stress at a
specific location or in a specific direction.
20 [0038]
Specifically, the invention provides the following
33 to 48 as means for achieving the fourth object of the
invention (fourth invention).
33. A transducer composed of at least two sheets or
25 fabrics, at least one of the sheets or fabrics comprising
the following layer A, and at least one of the layers
other than layer A comprising the following layer B.
Layer A: A flat transducer that outputs or inputs an
electrical signal, including a piezoelectric unit wherein
30 a conductive fiber and a piezoelectric fiber are arranged
on approximately the same plane so as to provide
electrical connection, the transducer having a function
of mutually converting between stress in a specific
location or direction and an electrical signal as
35 selective output or input.
Layer B: A flat transducer that outputs or inputs an
electrical signal, the transducer having a function of
5
- 16 -
mutually converting between a signal in a specific
location or direction differing from that of layer A or a
signal of a different type than that of layer A, and an
electrical signal as selective output or input.
34. The transducer according to 33 above, including
at least one layer that is the following layer C, between
layer A and layer B.
Layer C; A layer having the function of reducing
noise caused by electrical interference between layer A
10 and layer B.
35. The transducer according to 33 or 34 above,
wherein the piezoelectric unit includes two conductive
fibers and one piezoelectric fiber, arranged in the
order: conductive fiber, piezoelectric fiber, conductive
15 fiber.
36. The transducer according to 33 or 34 above,
having contact points where the conductive fibers and the
piezoelectric fiber are in mutual physical contact.
37. The transducer according to 33 or 34 above,
20 wherein insulating fibers are arranged so that the
conductive fibers in the piezoelectric unit are not ln
electrical connection with the conductive fiber and/or
piezoelectric fiber in the other piezoelectric unit.
38. The transducer according to 33 or 34 above,
25 wherein the piezoelectric fiber includes mainly
polylactic acid.
39. The transducer according to 33 or 34 above,
wherein the piezoelectric fiber includes mainly poly-Llactic
acid or poly-D-lactic acid with an optical purity
30 of 99% or greater.
40. The transducer according to 33 or 34 above,
wherein the piezoelectric fiber is uniaxially oriented
and includes crystals.
41. The transducer according to 33 or 34 above,
35 wherein the conductive fibers are metal-plated fibers.
42. The transducer according to 33 or 34 above,
which is a woven or knitted fabric containing a plurality
- 17 -
of the piezoelectric units.
43. The transducer according to 42 above, which is a
woven fabric containing a plurality of the piezoelectric
units, its woven texture being a plain weave, twill
5 weave, satin weave or a composite weave thereof.
44. The transducer according to 43 above, employing
a combination of a plurality of the woven or knitted
fabrics.
45. A device comprising a transducer according to
10 any one of 33 to 44 above, amplification means that
amplifies an electrical signal outputted from the
transducer in response to applied pressure, and output
means that outputs the electrical signal that has been
amplified by the amplification means.
15 46. The device according to 45 above, the device
further comprising transmission means that transmits the
electrical signal that has been outputted from the output
means, to an external device.
47. A device comprising the transducer according to
20 any one of 33 to 44 above, output means that outputs an
electrical signal from the transducer in response to
applied pressure, and transmission means that transmits
the electrical signal outputted from the output means to
an external device.
25
30
48. A device comprising receiving means that
receives an electrical signal, and a transducer according
to any one of 33 to 44 above, to which an electrical
signal received by the receiving means is applied.
[0039]
Moreover, as a result of ardent research directed
toward achieving the fifth object, the present inventors
have completed this invention upon finding that a
combined arrangement of conductive fibers and
piezoelectric fibers functions as a piezoelectric
35 element, and further that by layering a conductive sheet
or conductive fabric on the piezoelectric element, it is
possible to provide a highly practical transducer that is
resistant to malfunction.
[0040]
- 18 -
Specifically, the invention provides the following
49 to 64 as means for achieving the fifth object of the
5 invention (fifth invention).
49. A layered transducer comprising at least two
sheets or fabrics, at least one of the sheets or fabrics
comprising the following layer A, and at least one of the
layers other than layer A comprising the following layer
10 B.
Layer A: A transducer that outputs or inputs an
electrical signal, including a piezoelectric unit wherein
a conductive fiber and a piezoelectric fiber are arranged
on approximately the same plane so as to provide
15 electrical connection.
Layer B: A conductive sheet or conductive fabric
having a sheet resistance of no greater than 104 Q/sq.
50. The transducer according to 49 above, further
having the following layer C layered between layer A and
20 layer B.
Layer C: An insulating sheet or insulating fabric
having a sheet resistance of 106 D/sq. or greater.
51. The transducer according to 49 or 50 above,
wherein the piezoelectric unit includes two conductive
25 fibers and one piezoelectric fiber, arranged in the
order: conductive fiber, piezoelectric fiber, conductive
fiber.
52. The transducer according to 49 or 50 above,
having contact points where the conductive fibers and the
30 piezoelectric fiber are in mutual physical contact.
53. The transducer according to 49 or 50 above,
wherein insulating fibers are arranged so that the
conductive fibers in the piezoelectric unit are not in
electrical connection with the conductive fiber and/or
35 piezoelectric fiber in the other piezoelectric unit.
54. The transducer according to 49 or 50 above,
wherein the piezoelectric fiber includes mainly
- 19 -
polylactic acid.
55. The transducer according to 49 or 50 above,
wherein the piezoelectric fiber includes mainly poly-Llactic
acid or poly-D-lactic acid with an optical purity
5 of 99% or greater.
56. The transducer according to 49 or 50 above,
wherein the piezoelectric fiber is uniaxially oriented
and includes crystals.
57. The transducer according to 49 or 50 above,
10 wherein the conductive fibers are metal-plated fibers.

CLAIMS
1. A piezoelectric element including a braid
comprising a conductive fiber and piezoelectric fibers,
the braid having the conductive fiber as the core, and
5 the piezoelectric fibers being covering fibers that cover
the periphery of the conductive fiber.
10
2. The piezoelectric element according to claim 1,
wherein the flexural rigidity of the conductive fiber is
no greater than 0. 05 x 10-4 N ·m2 /m.
3. The piezoelectric element according to claim 1,
wherein the conductive fiber is a metal coated organic
fiber.
4. The piezoelectric element according to any one
of claims 1 to 3, wherein the piezoelectric fibers
15 include mainly polylactic acid.
20
5. The piezoelectric element according to claim 4,
wherein the piezoelectric fibers include mainly poly-Llactic
acid or poly-D-lactic acid with an optical purity
of 99% or greater.
6. The piezoelectric element according to any one
of claims 1 to 5, wherein the piezoelectric fibers are
uniaxially oriented and include crystals.
7. The piezoelectric element according to any one
of claims 1 to 6, which detects the amount of stress
25 applied to the covering fibers and/or the location at
which it is applied.
8. The piezoelectric element according to claim 7,
wherein the stress to be detected is frictional force
between the surfaces of the covering fibers and the
30 surface of the contacting object.
35
9. The piezoelectric element according to claim 7,
wherein the stress to be detected is resistance in the
direction perpendicular to the surfaces or tip sections
of the covering fibers.
10. A piezoelectric sensor using the piezoelectric
element according to any one of claims 1 to 9.
11. A device comprising:
- 222 -
a piezoelectric sensor according to claim
10,
amplification means that amplifies an
electrical signal outputted from the piezoelectric sensor
5 in response to applied pressure, and
output means that outputs the electrical
signal that has been amplified by the amplification
means.
12. The device according to claim 11, the device
10 further comprising transmission means that transmits the
electrical signal that has been outputted from the output
means, to an external device.
13. A device comprising:
the piezoelectric sensor according to
15 claim 10,
output means that outputs an electrical
signal from the piezoelectric sensor in response to
applied pressure, and
transmission means lhat transmits the
20 electrical signal outputted from the output means, to an
external device.
14. A braided piezoelectric element comprising a
core formed of a conductive fiber and a sheath formed of
braided piezoelectric fibers covering the core, wherein
25 the piezoelectric fibers include polylactic acid as a
main component, the winding angles of the piezoelectric
fibers with respect to the conductive fiber being between
15° and 75°, inclusive.
15. The braided piezoelectric element according to
30 claim 14, wherein the total fineness of the piezoelectric
fibers is at least 1/2 times and no greater than 20 times
the total fineness of the conductive fiber.
16. The braided piezoelectric element according to
claim 14, wherein the fineness per piezoelectric fiber is
35 at least 1/20 times and no greater than 2 times the total
fineness of the conductive fiber.
17. A fabric-like piezoelectric element comprising
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a fabric that includes the braided piezoelectric element
according to any one of claims 14 to 16.
18. The fabric-like piezoelectric element according
to claim 17, wherein the fabric further includes
5 conductive fibers that cross and contact with at least
part of the braided piezoelectric element.
19. The fabric-like piezoelectric element according
to claim 18, wherein among the fibers forming the fabric
and crossing the braided piezoelectric element, at least
10 30% are conductive fibers.
20. A device comprising a braided piezoelectric
element according to any one of claims 14 to 16,
amplification means that amplifies an electrical signal
outputted from the braided piezoelectric element in
15 response to applied pressure, and output means that
outputs the electrical signal that has been amplified by
the amplification means.
21. A device comprising a fabric-like piezoelectric
element according to any one of claims 17 to 19,
20 amplification means that amplifies an electrical signal
outputted from the fabric-like piezoelectric element in
response to applied pressure, and output means that
outputs the electrical signal that has been amplified by
the amplification means.
25 22. A braided piezoelectric element comprising a
30
core formed of a conductive fiber, a sheath formed of
braided piezoelectric fibers covering the core, and a
conductive layer provided around the periphery of the
sheath.
23. The braided piezoelectric element according to
claim 22, wherein the coverage factor of the sheath by
the conductive layer is 25% or greater.
24. The braided piezoelectric element according to
claim 22 or 23, wherein the conductive layer is formed of
35 fibers.
25. The braided piezoelectric element according to
any one of claims 22 to 24, wherein the piezoelectric
5
10
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fibers include polylactic acid as the main component, and
the winding angle of the piezoelectric fibers with
respect to the conductive fibers is between 15° and 75°,
inclusive.
26. The braided piezoelectric element according to
any one of claims 22 to 25, wherein the total fineness of
the piezoelectric fibers is at least 1 and no greater
than 20 times the total fineness of the conductive
fibers.
27. The braided piezoelectric element according to
any one of claims 22 to 25, wherein the fineness per
piezoelectric fiber is at least 1/20 times and no greater
than 2 times the total fineness of the conductive fibers.
28. A fabric-like piezoelectric element comprising
15 a fabric that includes the braided piezoelectric element
according to any one of claims 22 to 27.
29. The fabric-like piezoelectric element according
to claim 28, wherein the fabric further includes
conductive fibers that cross and contact with at least
20 part of the braided piezoelectric element.
25
30. The fabric-like piezoelectric element according
to claim 29, wherein among the fibers forming the fabric
and crossing the braided piezoelectric element, at least
30% are conductive fibers.
31. A device comprising a braided piezoelectric
element according to any one of claims 22 to 27,
amplification means that amplifies an electrical signal
outputted from the braided piezoelectric element in
response to applied pressure, and output means that
30 outputs the electrical signal that has been amplified by
the amplification means.
32. A device comprising a fabric-like piezoelectric
element according to any one of claims 28 to 30,
amplification means that amplifies an electrical signal
35 outputted from the fabric-like piezoelectric element in
response to applied pressure, and output means that
outputs the electrical signal that has been amplified by
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the amplification means.
33. A transducer composed of at least two sheets or
fabrics, at least one of the sheets or fabrics comprising
the following layer A, and at least one of the layers
5 other than layer A comprising the following layer B.
Layer A: A flat transducer that outputs or inputs an
electrical signal, including a piezoelectric unit wherein
a conductive fiber and a piezoelectric fiber are arranged
on approximately the same plane so as to provide
10 electrical connection, the transducer having a function
of mutually converting between stress in a specific
location or direction and an electrical signal as
selective output or input.
Layer B: A flat transducer that outputs or inputs an
15 electrical signal, the transducer having a function of
mutually converting between a signal in a specific
location or direction differing from that of layer A or a
signal of a different type than that of layer A, and an
electrical signal as selective output or input.
20 34. The transducer according to claim 33, including
at least one layer that is the following layer C, between
layer A and layer B.
Layer C: A layer having the function of reducing
noise caused by electrical interference between layer A
25 and layer B.
35. The transducer according to claim 33 or 34,
wherein the piezoelectric unit includes two conductive
fibers and one piezoelectric fiber, arranged in the
order: conductive fiber, piezoelectric fiber, conductive
30 fiber.
36. The transducer according to claim 33 or 34,
having contact points where the conductive fibers and the
piezoelectric fiber are in mutual physical contact.
37. The transducer according to claim 33 or 34,
35 wherein insulating fibers are arranged so that the
conductive fibers in the piezoelectric unit are not in
electrical connection with the conductive fiber and/or
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piezoelectric fiber in the other piezoelectric unit.
38. The transducer according to claim 33 or 34,
wherein the piezoelectric fiber includes mainly
polylactic acid.
5 39. The transducer according to claim 33 or 34,
wherein the piezoelectric fiber includes mainly poly-Llactic
acid or poly-D-lactic acid with an optical purity
of 99% or greater.
40. The transducer according to claim 33 or 34,
10 wherein the piezoelectric fiber is uniaxially oriented
and includes crystals.
41. The transducer according to claim 33 or 34,
wherein the conductive fibers are metal-plated fibers.
42. The transducer according to claim 33 or 34,
15 which is a woven or knitted fabric containing a plurality
of the piezoelectric units.
43. The transducer according to claim 42, which is
a woven fabric containing a plurality of the
piezoelectric units, its woven texture being a plain
20 weave, twill weave, satin weave or a composite weave
thereof.
25
44. The transducer according to claim 43, employing
a combination of a plurality of the woven or knitted
fabrics.
45. A device comprising a transducer according to
any one of claims 33 to 44, amplification means that
amplifies an electrical signal outputted from the
transducer in response to applied pressure, and output
means that outputs the electrical signal that has been
30 amplified by the amplification means.
46. The device according to claim 45, the device
further comprising transmission means that transmits the
electrical signal that has been outputted from the output
means, to an external device.
35 47. A device comprising the transducer according to
any one of claims 33 to 44, output means that outputs an
electrical signal from the transducer in response to
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applied pressure, and transmission means that transmits
the electrical signal outputted from the output means, to
an external device.
48. A device comprising receiving means that
5 receives an electrical signal, and a transducer according
to any one of claims 33 to 44, to which an electrical
signal received by the receiving means is applied.
49. A layered transducer comprising at least two
sheets or fabrics, at least one of the sheets or fabrics
10 comprising the following layer A, and at least one of the
layers other than layer A comprising the following layer
B.
Layer A: A transducer that outputs or inputs an
electrical signal, including a piezoelectric unit wherein
15 a conductive fiber and a piezoelectric fiber are arranged
on approximately the same plane so as to provide
electrical connection.
Layer B: A conductive sheet or conductive fabric
having a sheet resistance of no greater than 10 4 0/sq.
20 50. The transducer according to claim 49, further
having the following layer C layered between layer A and
layer B.
Layer C: An insulating sheet or insulating fabric
having a sheet resistance of 10 6 0/sq. or greater.
25 51. The transducer according to claim 49 or 50,
30
wherein the piezoelectric unit includes two conductive
fibers and one piezoelectric fiber, arranged in the
order: conductive fiber, piezoelectric fiber, conductive
fiber.
52. The transducer according to claim 49 or 50,
having contact points where the conductive fibers and the
piezoelectric fiber are in mutual physical contact.
53. The transducer according to claim 49 or 50,
wherein insulating fibers are arranged so that the
35 conductive fibers in the piezoelectric unit are not in
electrical connection with the conductive fiber and/or
piezoelectric fiber in the other piezoelectric unit.
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54. The transducer according to claim 49 or 50,
wherein the piezoelectric fiber includes mainly
polylactic acid.
55. The transducer according to claim 49 or 50,
5 wherein the piezoelectric fiber includes mainly poly-Llactic
acid or poly-D-lactic acid with an optical purity
of 99% or greater.
56 The transducer according to claim 49 or 50,
wherein the piezoelectric fiber is uniaxially oriented
10 and includes crystals.
57. The transducer according to claim 49 or 50,
wherein the conductive fibers are metal-plated fibers.
58. The transducer according to claim 49 or 50,
which is a woven or knitted fabric containing a plurality
15 of the piezoelectric units.
59. The transducer according to claim 58, which is
a woven fabric containing a plurality of the
piezoelectric units, its woven texture being a plain
weave, twill weave, satin weave or a composite weave
20 thereof.
60. The transducer according to claim 59, employing
a combination of a plurality of the woven fabrics.
61. A device comprising a transducer according to
any one of claims 49 to 60, amplification means that
25 amplifies an electrical signal outputted from the
transducer in response to applied pressure, and output
means that outputs the electrical signal that has been
amplified by the amplification means.
62. The device according to claim 61, the device
30 further comprising transmission means that transmits the
electrical signal that has been outputted from the output
means, to an external device.
63. A device comprising the transducer according to
any one of claims 49 to 60, output means that outputs an
35 electrical signal from the transducer in response to
applied pressure, and transmission means that transmits
the electrical signal outputted from the output means, to
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an external device.
64. A device comprising receiving means that
receives an electrical signal, and a transducer according
to any one of claims 49 to 60, to which an electrical
5 signal received by the receiving means is applied.