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JP2010089496

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DESCRIPTION JP2010089496
The present invention provides an electret provided with a conductive layer in which the
performance deterioration of the electret is reduced as much as possible when forming the
electret provided with a conductive layer as a material for electric / electronic input / output
devices. A dielectric film (B) 3 provided with conductive layers (E) 7 and 8 having a surface
resistance value of 1 × 10 to 9 × 10 Ω on at least one surface of an electretized film (A) 2
Electret (F) 1 provided with a conductive layer characterized in that 4 is laminated via adhesive
layers (C) 5 and 6. [Selected figure] Figure 1
Electret with conductive layer
[0001]
The present invention relates to an electretized film provided with a conductive layer having
good performance as a material for electric / electronic input / output devices by providing the
conductive layer on the electret.
[0002]
Electrets are used in various forms, such as films, sheets, fibers, non-woven fabrics, etc.,
depending on the mode of use.
In particular, electret filters formed by molding electrets have been widely used for applications
such as air filters. In addition, the application is spreading to various applications such as
04-05-2019
1
materials for electric / electronic input / output devices such as speakers, headphones, vibration
control devices, microphones, ultrasonic sensors, pressure sensors and the like. Electrets using a
porous resin film are known to exhibit a piezoelectric effect, and can be used for vibration
measurement, generation of sound, vibration control, detection of sound, and the like.
Applications of electrets using such polymer foams have been studied for applications such as
microphones, headphones, vibrators of acoustic devices such as speakers, pressure sensors in the
form of flexible sheets, etc., taking advantage of their light weight (Patent Document 1) ). In order
to use an electret using a porous resin film for an electric / electronic input / output device, it is
necessary to provide a conductive layer for transmitting an electric signal on at least one surface
thereof. As a method of providing a conductive layer, coating of a conductive paint, vapor
deposition of metal or the like is generally used, but in the coating method, there is a possibility
that the performance of the electret may deteriorate due to penetration of a solvent, and If the
temperature is raised too much, there is a disadvantage that the electret itself degrades. Further,
the vapor deposition method has a drawback that the temperature of the electret rises because
the vaporized metal directly contacts the electret, and the performance is lowered as in the
coating method.
[0003]
Japanese Patent Publication No. 05-041104
[0004]
An object of the present invention is to provide an electret provided with a conductive layer with
less deterioration in performance of the electret at the time of installation of the conductive layer.
[0005]
The inventors of the present invention conducted intensive studies to solve these problems, and
as a result of making the electret provided with a conductive layer having a specific structure, the
electret provided with a conductive layer having desired characteristics is provided. It has been
found that it can be provided, and the present invention has been accomplished.
That is, the present invention provides (1) a conductive layer (E) having a surface resistance
value of 1 × 10 <-2> to 9 × 10 <7> Ω on at least one surface of the electretized film (A) The
present invention relates to an electret (F) provided with a conductive layer characterized in that
a dielectric film (B) is laminated via an adhesive layer (C).
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(2) The electretized film (A) is preferably formed by electretizing a porous resin film (iii)
comprising a biaxially stretched resin film having pores, and (3) a further electretized film (A) It
is preferable to electretize a porous resin film (iii) provided with a surface layer (ii) consisting of a
stretched resin film on at least one surface of a core layer (i) consisting of a biaxially stretched
resin film having pores. (4) The core layer (i) contains 50 to 97% by weight of the thermoplastic
resin and 3 to 50% by weight of at least one of the inorganic fine powder and the organic filler,
and the surface layer (ii) has 30 to 97% by weight of the thermoplastic resin %, And 3 to 70% by
weight of at least one of an inorganic fine powder and an organic filler. (5) The thermoplastic
resin preferably contains a polyolefin resin.
[0006]
(6) The surface layer (ii) is preferably a uniaxially stretched film, (7) the core layer (i) and the
surface layer (ii) are formed by being stretched in at least one axial direction after lamination.
preferable. (8) The thickness of the core layer (i) is preferably 10 to 500 μm, and the thickness
of the surface layer (ii) is preferably 5 to 500 μm. (9) The porosity of the porous resin film (iii) is
preferably 5 to 95%. (10) The porous resin film (iii) preferably has an anchor coat layer (D) on at
least one surface thereof, (11) The basis weight of the anchor coat layer (D) is 0.001 to 5 g / m <
2> is preferable.
[0007]
(12) The dielectric film (B) is preferably a stretched film or a non-stretched film made of a
thermoplastic resin, (13) The film thickness of the dielectric film (B) is preferably 0.1 to 100 μm
. (14) The conductive layer (E) preferably comprises coating of a conductive paint or metal
deposition, and (15) the film thickness of the conductive layer (E) is preferably 0.01 to 10 μm.
(16) When laminating the dielectric film (B) provided with the conductive layer (E) on the
electretized film (A), it is preferable to laminate so that the conductive layer (E) is the outermost
layer.
[0008]
With the electret (F) provided with the conductive layer of the present invention, when the
conductive layer (E) is provided in the electret material, the electric / electronic input / output
material has high energy conversion efficiency and high mass productivity without lowering the
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3
performance of the electret. It became possible to provide
[0009]
It is a partially expanded sectional view of one aspect of the electret film (F) of the present
invention.
It is a schematic diagram of an example of the form at the time of carrying out the pressure
processing of stretched film (i). It is a schematic diagram of an example of a pressure processing
apparatus. It is a schematic diagram of an example of a heat processing apparatus. It is a
schematic diagram of an example of the batch type electretization apparatus used for this
invention. It is a schematic diagram of an example of the batch type electretization apparatus
used for this invention. It is a schematic diagram of an example of the continuous type
electretization apparatus used for this invention. It is a schematic diagram of an example of the
continuous type electretization apparatus used for this invention. It is a schematic diagram of the
falling ball apparatus used in the Example.
[0010]
The electret (F) provided with the conductive layer of the present invention comprises a dielectric
film (B) provided with a conductive layer (E) on at least one surface of the electretized film (A)
and an adhesive layer (C). It is obtained by laminating through. [Electretized Film (A)] The
electretized film (A) of the present invention is preferably obtained by electretizing a porous resin
film (iii) having pores. The porous resin film (iii) is a biaxially stretched resin film having pores,
or is used as a core layer (i) and provided with a surface layer (ii) consisting of a stretched resin
film on at least one side thereof It is more preferable that The porous resin film (iii) may be one
in which a non-reactive gas is infiltrated under pressure and then foamed under non-pressure
and subjected to heat treatment in order to make the porosity suitable. The porous resin film (iii)
can also be provided with an anchor layer (C) on at least one surface thereof in order to improve
the adhesion with the adhesive layer (C).
[0011]
[Core Layer (i)] The core layer (i) used in the present invention is mainly used to hold charge
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inside. Therefore, the core layer (i) is made of a biaxially stretched resin film having pores.
Preferably, the pores are made of a thermoplastic resin which is a polymer material having a
certain thickness or more and which is hard to conduct electricity in order to secure the
capacitance, and the pores formed inside by stretching as indicated by the porosity. Has a
structure that easily holds a charge. The thickness of the core layer (i) is preferably in the range
of 10 to 500 μm, more preferably in the range of 20 to 300 μm, and particularly preferably in
the range of 30 to 200 μm. If the thickness is less than 10 μm, the capacitance of the core layer
(i) is small and it is unsuitable for use in electrets, and it becomes difficult to control molding
with a uniform thickness, and dielectric breakdown occurs during electretization described later.
It is not preferable because it is easily caused and a local discharge is easily generated. On the
other hand, when it exceeds 500 μm, it becomes difficult to cause the charge to reach the inside
of the layer at the time of charge injection, which is not preferable because the desired
performance of the present invention can not be exhibited.
[0012]
The core layer (i) is preferably made of a thermoplastic resin that is a polymer material that is
difficult to conduct electricity. The type of thermoplastic resin used is not particularly limited. For
example, polyolefin resins such as high density polyethylene, medium density polyethylene, low
density polyethylene, propylene resin, polymethyl-1-pentene, ethylene / vinyl acetate copolymer,
ethylene / acrylic acid copolymer, maleic acid modified polyethylene, Functional groupcontaining polyolefin resins such as maleic acid-modified polypropylene, polyamide resins such
as nylon-6 and nylon-6, 6, polyethylene terephthalate and copolymers thereof, polybutylene
terephthalate, polybutylene succinate, polylactic acid, aliphatic Polyester resins such as polyester,
polycarbonate, atactic polystyrene, syndiotactic polystyrene and the like can be used. Among
these thermoplastic resins, it is preferable to use a polyolefin resin having a low hygroscopic
property and a high insulation property, and a functional group-containing polyolefin resin.
[0013]
Examples of polyolefin resins include homopolymers of olefins such as ethylene, propylene,
butene, butylene, butadiene, isoprene, chloroprene, methyl pentene and cyclic olefins, and
copolymers of two or more of these olefins. . Specific examples of polyolefin resins include high
density polyethylene, medium density polyethylene, propylene resins, copolymers of ethylene
and other olefins, and copolymers of propylene and other olefins. Among these polyolefin resins,
propylene resins are preferable in terms of processability, insulation, cost and the like. Examples
of propylene-based resins include propylene homopolymers and isotactic or syndiotactic
04-05-2019
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polypropylenes and polypropylenes having various degrees of stereoregularity, and also contain
propylene as a main component, ethylene, 1-butene, and the like. The copolymer which
copolymerized alpha olefins, such as 1-hexene, 1-heptene, 4-methyl- 1-pentene, etc. is mentioned.
The copolymer may be binary, ternary or higher, and may be a random copolymer or a block
copolymer.
[0014]
In the case of using a propylene-based resin as a thermoplastic resin, 2 to 25% by weight of a
resin having a melting point lower than that of polypropylene (propylene homopolymer) is used
in order to improve the stretchability to be described later. Is preferred. As such a resin having a
low melting point, high density to low density polyethylene can be exemplified. As a specific
example of a functional group containing polyolefin resin, the copolymer of the said olefins and
the functional group containing monomer which can be copolymerized is mentioned. Such
functional group-containing monomers include styrene, styrenes such as alpha methyl styrene,
vinyl acetate, vinyl alcohol, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl
laurate, vinyl stearate, vinyl benzoate Carboxylic acid vinyl esters such as vinyl butylbenzoate,
cyclohexanecarboxylic acid vinyl, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth)
acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl ( Meta) acrylate, 2-ethylhexyl (meth)
acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, isobonyl
(meth) acrylate, dicyclopentanone (Meth) acrylates, (meth) acrylamides, acrylic esters such as Nmethanol (meth) acrylamides, methyl vinyl ethers, ethyl vinyl ethers, propyl vinyl ethers, propyl
vinyl ethers, butyl vinyl ethers, cyclopentyl vinyl ethers, cyclohexyl vinyl ethers, benzyl vinyl
ethers, vinyl vinyl ethers, etc. The class is particularly representative. Among these functional
group-containing monomers, one or two or more kinds may be appropriately selected and
polymerized as needed.
[0015]
Furthermore, these polyolefin resins and functional group-containing polyolefin resins may be
graft-modified if necessary. Known methods can be used for graft modification. As a specific
example of a grafting monomer, graft modification with unsaturated carboxylic acid or its
derivative can be mentioned. Examples of the unsaturated carboxylic acid include acrylic acid,
methacrylic acid, maleic acid, fumaric acid, itaconic acid and the like. In addition, acid anhydrides,
esters, amides, imides, metal salts and the like can also be used as the above-mentioned
derivatives of unsaturated carboxylic acids. Specifically, maleic anhydride, itaconic anhydride,
citraconic anhydride, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, glycidyl
04-05-2019
6
(meth) acrylate, monoethyl maleate maleic acid Maleic acid diethyl ester, fumaric acid
monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid
diethyl ester, (meth) acrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-Nmonoethylamide, maleic acid -N, N-diethylamide, maleic acid-N-monobutylamide, maleic acid-N,
N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide,
fumaric acid -N, N- Diethylamide, fumaric acid-N-mo Butylamide, fumaric acid -N, Ndibutylamide, maleimide, N- butyl maleimide, N- phenylmaleimide, (meth) sodium acrylate, and
(meth) potassium acrylate.
[0016]
Usable graft modified products are generally graft modified by adding a graft monomer to a
polyolefin resin or a functional group-containing polyolefin resin in an amount of generally
0.005 to 10% by weight, preferably 0.01 to 5% by weight. It is. As a thermoplastic resin used for
core layer (i), 1 type may be selected from said thermoplastic resins, and may be used
independently, and 2 or more types may be selected and it may be used combining. . It is
desirable that at least one of an inorganic fine powder and an organic filler be added to the
thermoplastic resin used for the core layer (i). By the addition of the inorganic fine powder and
the organic filler, it becomes easy to form pores inside the core layer (i) by the stretching step
described later. More specifically, the core layer (i) preferably contains 50 to 97% by weight of
the above-mentioned thermoplastic resin, and 3 to 50% by weight of at least one of the inorganic
fine powder and the organic filler. More preferably, the core layer (i) contains 60 to 95% by
weight of a thermoplastic resin and 5 to 40% by weight of at least one of an inorganic fine
powder and an organic filler. When the content of the inorganic fine powder and the organic
filler, which become nucleating agents for the pores, is less than 3% by weight, the number of the
pores formed in the stretching step described later is small and the charge storage capacity is
poor, and the desired purpose is achieved. It is difficult to do. On the other hand, if it exceeds
50% by weight, the pores formed will communicate with each other, and even if the charge is
introduced, the charge is easily released from the surface or end face of the porous resin film (i)
via the communicating hole. This is not preferable because the charge tends to be unstable.
[0017]
When inorganic fine powder is added, one having an average particle diameter of usually 0.01 to
15 μm, preferably 0.05 to 5 μm, more preferably 0.1 to 3 μm, particularly preferably 0.5 to
2.5 μm. use. Specific examples of the inorganic fine powder include calcium carbonate, calcined
clay, silica, diatomaceous earth, white earth, talc, titanium oxide, barium sulfate, alumina, zeolite,
04-05-2019
7
mica, sericite, bentonite, sepiolite, vermiculite, dolomite, wollast Knight, glass fiber, etc. can be
used. In the present invention, the average particle size is referred to the manufacturer catalog
value. When an organic filler is added, it is preferable to select a type of resin different from the
thermoplastic resin as the main component. For example, when the thermoplastic resin is a
polyolefin resin, the organic filler may be polyethylene terephthalate, polybutylene terephthalate,
polycarbonate, nylon-6, nylon-6,6, cyclic olefin polymer, polystyrene, polymethacrylate, etc. It is
united, and it can use a non-compatible one having a melting point (for example, 170 to 300 °
C.) to a glass transition temperature (for example, 170 to 280 ° C.) higher than the melting
point of the polyolefin resin .
[0018]
A heat stabilizer (antioxidant), a light stabilizer, a dispersing agent, a lubricant, etc. can be
arbitrarily added to the thermoplastic resin used for core layer (i) as needed. When a heat
stabilizer is added, it is usually added in the range of 0.001 to 1% by weight based on the resin.
As specific examples of the heat stabilizer, stabilizers of sterically hindered phenol type,
phosphorus type, amine type and the like can be used. When a light stabilizer is added, it is
usually added in the range of 0.001 to 1% by weight based on the resin. As specific examples of
light stabilizers, light stabilizers such as sterically hindered amines, benzotriazoles, and
benzophenones can be used. Dispersants and lubricants are used, for example, for the purpose of
dispersing inorganic fine powder in a resin. The amount used is usually in the range of 0.01 to
4% by weight with respect to the resin. As specific examples of these, silane coupling agents,
higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acids,
polymethacrylic acids or salts thereof can be used.
[0019]
In the present invention, the core layer (i) is stretched in the film width direction and in the two
axial directions of the flow direction. A large number of pores are formed in the layer by
stretching, and charges are accumulated in the pores, so that the charge retention performance
of the electretized film (iii) is excellent. It is desirable that the pores formed in the core layer (i)
have large individual volumes, large numbers, and shapes independent of one another from the
viewpoint of retaining charge. The size of the holes can be larger in the biaxial direction than in
the stretching in only one direction. In particular, a film stretched in the width direction of the
film and in the two axial directions of the flow direction can form disk-like holes drawn in the
surface direction, so when charge is injected in the film thickness direction It is easy to
accumulate polarized charge. Therefore, a biaxially stretched resin film is used for the core layer
04-05-2019
8
(i) of the present invention.
[0020]
[Surface Layer (ii)] The surface layer (ii) used in the present invention improves the withstand
voltage in the electretization treatment of the porous resin film (iii), and charges accumulated in
the core layer (i) The layer is mainly composed of a stretched film provided on at least one side of
the core layer (i), preferably on both sides, mainly for the purpose of improving the retention of
the core layer (i). Preferably, in order to improve insulation resistance, it is made of a
thermoplastic resin which is a polymer material having a certain thickness or more and which is
difficult to conduct electricity, and has a uniaxially stretched resin film structure. The thickness
of the surface layer (B) is preferably in the range of 5 to 500 μm, more preferably in the range
of 7 to 300 μm, still more preferably in the range of 9 to 100 μm, and in the range of 10 to 50
μm Are particularly preferred, and most preferably in the range of 10 to 30 μm. If the
thickness is less than 5 μm, the effect of improving the insulation withstand voltage of the
porous resin film (iii) is insufficient, charge injection at high voltage can not be performed, and
an electretized film (A) having high charge is obtained It is hard to be On the other hand, when it
exceeds 500 μm, it becomes difficult to cause the charge to reach the inside during
electretization processing, which is not preferable because the desired performance of the
present invention can not be exhibited.
[0021]
As a thermoplastic resin which comprises surface layer (ii), the thing similar to the thermoplastic
resin mentioned by the term of core layer (i) can be used. It is preferable that the thermoplastic
resin used for surface layer (ii) and core layer (i) uses the resin of the same kind from a viewpoint
of the extending | stretching characteristic of a laminated body. The surface layer (ii) may or may
not contain the inorganic fine powder or the organic filler, but it is contained from the viewpoint
of modification of the electrical properties such as the dielectric constant of the surface layer (ii).
Is preferred. When it is contained, the same inorganic fine powder and organic filler as
mentioned in the section of the core layer (i) can be used. More specifically, the surface layer (ii)
preferably contains 30 to 97% by weight of the thermoplastic resin described above, and 3 to
70% by weight of at least one of the inorganic fine powder and the organic filler described above.
More preferably, the surface layer (ii) contains 40 to 95% by weight of a thermoplastic resin and
5 to 60% by weight of at least one of an inorganic fine powder and an organic filler, and 50 to
90% by weight of a thermoplastic resin It is particularly preferable to contain 10 to 50% by
weight of at least one of the inorganic fine powder and the organic filler. If the content of the
04-05-2019
9
inorganic fine powder and the organic filler is less than 3% by weight, the effect of modifying the
electrical properties can not be sufficiently obtained. On the other hand, if it exceeds 70% by
weight, it is not preferable because the charge tends to be unstable due to the dielectric effect by
the inorganic fine powder itself and the structure in which the charge easily escapes due to the
formation of mutually connected pores.
[0022]
When the inorganic fine powder and the organic filler are contained in the surface layer (ii), the
inorganic fine powder and the organic filler used in the core layer (i) may be of the same kind or
different kinds. . In particular, the addition of the inorganic fine powder is suitable for the
modification of the electrical properties of the surface layer (ii) because the dielectric constant is
generally higher than that of the thermoplastic resin. In particular, when using a resin having a
low dielectric constant such as a polyolefin resin as the thermoplastic resin, the core layer (i) is
obtained by applying a high voltage at the time of electretization treatment by containing an
inorganic fine powder or an organic filler. The charge can be made to reach to the surface, and
after electretization, the low dielectric characteristics of the polyolefin resin as the main
component provide the effect of retaining the charge of the core layer (i) without releasing it.
[0023]
The surface layer (ii) is a layer made of a stretched resin film as described above. This is because
the uniformity of the thickness (film thickness) can be improved by stretching, and the electrical
characteristics such as withstand voltage can be made uniform. If the thickness of the surface
layer (ii) is nonuniform, local electric discharge concentration is likely to occur particularly at a
thin portion during charge injection using a high voltage, and effective charge injection can not
be expected. Therefore, it is desirable that the surface layer (ii) be a uniaxially stretched resin film
with low void formation efficiency. When the surface layer (ii) is a biaxially stretched resin film,
as in the core layer (i), pores are formed with an inorganic fine powder or an organic filler as a
core, so that charge is generated by the surface layer (ii) The effect of holding is diminished.
[0024]
The surface layer (ii) is preferably stretched in at least one axial direction after lamination with
the core layer (i). By stretching after lamination with the core layer (i), the uniformity of the film
04-05-2019
10
thickness as the porous resin film (iii) is improved rather than laminating the stretched films
together, and as a result, the electricity such as withstand voltage The characteristics are
improved. The surface layer (ii) may have a multilayer structure of two or more layers, in
addition to the single layer structure. In the case of a multilayer structure, the design of a porous
resin film (iii) having higher charge retention performance by changing the type and content of
the thermoplastic resin, inorganic fine powder, and organic filler used in each layer Is possible.
When the surface layer (ii) is provided on both sides of the core layer (i), the composition and
configuration of each of the front and back may be the same, or different compositions and
configurations may be used.
[0025]
[Lamination] Various known methods can be used to laminate the core layer (i) and the surface
layer (ii). Specific examples include a co-extrusion method using a multi-layer die using a feed
block or a multi-manifold, and an extrusion lamination method using a plurality of dies.
Furthermore, a method of combining a co-extrusion method using a multilayer die and an
extrusion lamination method may be mentioned. As described above, the core layer (i) is
preferably a biaxially stretched film, and the surface layer (ii) is preferably a uniaxially stretched
film. Then, from the viewpoint of film thickness uniformity, it is preferable to stretch in at least
one axial direction after laminating the core layer (i) and the surface layer (ii). Therefore, for
lamination of the core layer (i) and the surface layer (ii), it is preferable to extrude and laminate
the surface layer (ii) on the core layer (i) stretched in the uniaxial direction. After extrusion
lamination of the surface layer (ii) onto the core layer (i), the core layer (i) is biaxially stretched
by stretching the laminate in a direction substantially perpendicular to the stretching axis of the
core layer (i) A porous resin film (iii) having a uniform film thickness can be obtained, which is a
film and the surface layer (ii) is a uniaxially stretched film.
[0026]
[Stretching] Stretching of the core layer (i), the surface layer (ii), and the porous resin film (iii)
which is a laminate thereof can be performed by various known methods. The stretching method
includes longitudinal stretching method using circumferential speed difference of rolls,
transverse stretching method using tenter oven, rolling method, simultaneous biaxial stretching
method by combination of tenter oven and linear motor, tenter oven and pantograph The
simultaneous biaxial stretching method by combination etc. can be mentioned. Moreover, the
simultaneous biaxial stretching method by the tubular method which is a stretching method of an
inflation film can be mentioned. The temperature at the time of drawing can be carried out within
04-05-2019
11
the range of not less than the glass transition temperature of the main thermoplastic resin used
in each layer and not more than the melting point of the crystal part. When stretching a porous
resin film (iii) which is a laminate of the core layer (i) and the surface layer (ii), the stretching
temperature is adjusted according to the layer having a larger basis weight (usually the core
layer (i)) You just set it.
[0027]
The temperature is 1 to 70 ° C. lower than the melting point of the thermoplastic resin used as
an index. Specifically, when the thermoplastic resin of each layer is a propylene homopolymer
(melting point 155 to 167 ° C.), it is 100 to 166 ° C., and when it is high density polyethylene
(melting point 121 to 136 ° C.) It is 70-135 ° C. The stretching speed is preferably in the range
of 20 to 350 m / min. The magnification of stretching is not particularly limited, and is
appropriately determined in consideration of the characteristics of the thermoplastic resin used
for the porous resin film (iii), the porosity to be obtained as described later, and the like. The
stretching ratio is, for example, about 1.2 to 12 times, preferably 2 to 10 times in the case of
uniaxial stretching when using a propylene homopolymer or copolymer thereof as the
thermoplastic resin. When stretching in the biaxial direction, the area magnification (the product
of the longitudinal magnification and the lateral magnification) is 1.5 to 60 times, preferably 4 to
50 times. When other thermoplastic resins are used, they are 1.2 to 10 times, preferably 2 to 5
times, when stretched in a uniaxial direction, and 1.5 to 20 in area magnification when stretched
in a biaxial direction. Times, preferably 4 to 12 times.
[0028]
[Porous Resin Film (iii)] The porous resin film (iii) obtained through the above-mentioned
lamination step and drawing step is designed as one suitable for forming an electretized film (A)
by charge injection. There is. The porous resin film (iii) preferably has a porosity in a certain
range in order to secure the capacitance. The porous resin film (iii) preferably has a surface
resistance value equal to or greater than a predetermined value in order to make it difficult for
the accumulated charge to escape to the outside. In the present invention, as the pores in the
porous resin film (iii) hold a charge, the higher the proportion, the more the capacitance can be
secured, but if it is too high, the proportion of the insulating thermoplastic resin decreases, and It
is difficult to stably maintain a high charge state for a long period of time because the
communicating holes also increase. The surface specific resistance value of the porous resin film
(iii) is to determine the ease of charge release of the film (iii). If the surface resistivity is too small,
discharge through the film surface is likely to occur.
04-05-2019
12
[0029]
[Porosity] The porosity of the porous resin film (iii) is preferably 5 to 95%, which is calculated by
the following formula (1), including one subjected to pressure treatment described later, and 6 It
is more preferably -85%, still more preferably 7-75%, and particularly preferably 8-65%. It is
preferable that a large number of these pores are present in the film as fine pores. By the
presence of the pores, the number of interfaces in the resin film is increased, and the
performance capable of accumulating electric charge inside is improved as compared to the resin
film without the pores, and an electretized film (A) having high performance is obtained. Can.
However, excess vacancies may cause charge to escape.
[0030]
[Anchor Coat Layer (D)] The surface of the porous resin film (iii) is adhered to an adhesive, a
vapor-deposited metal film, etc. for the purpose of further laminating other materials and
expanding the use after electretization. In order to improve the properties, it is preferable to
provide an anchor coat layer (D) on one side or both sides. It is preferable to use a polymer
binder for the anchor coat layer (D), and specific examples of the polymer binder include
polyethyleneimine, alkyl modified polyethyleneimine having 1 to 12 carbon atoms, and poly
(ethyleneimine-urea) Polyethylenimine polymers such as: polyaminepolyamide polymers such as
ethyleneimine adduct of polyamine polyamide and epichlorohydrin adduct of polyamine
polyamide; acrylic acid amide-acrylic acid ester copolymer, acrylic acid amide-acrylic acid esterAcrylic acid ester based polymers such as methacrylic acid ester copolymer, derivative of
polyacrylamide, oxazoline group-containing acrylic acid ester based polymer; polyvinyl alcohol
based polymer including polyvinyl alcohol and its modified product; polyvinyl pylori Watersoluble resins such as polyethylene glycol and the like; polypropylene-based polymers such as
chlorinated polypropylene, maleic acid-modified polypropylene and acrylic acid-modified
polypropylene, and additionally polyvinyl acetate, polyurethane, ethylene-vinyl acetate
copolymer, polyvinylidene chloride, The organic solvent dilution resin or water dilution resin of
thermoplastic resins, such as an acrylonitrile nitrile butadiene copolymer and polyester, etc. are
mentioned. Among these, a polyethyleneimine polymer, a polyamine polyamide polymer, a
polyvinyl alcohol polymer, and a polypropylene polymer are preferable because of their excellent
anchoring effect on the porous resin film (iii).
[0031]
04-05-2019
13
The basis weight of the anchor coat layer (D) is preferably 0.001 to 5 g / m <2> as solids
conversion basis weight, more preferably 0.005 to 3 g / m <2>, 0 More preferably, .01 to 1 g / m
<2>. If the basis weight of the anchor coat layer (D) is less than 0.001 g / m <2>, the effect of
providing the anchor coat layer (D) can not be sufficiently obtained. On the other hand, when it
exceeds 5 g / m <2>, it becomes difficult to keep the basis weight of the anchor coat layer (D)
which is a coating layer uniform, and the runout of the basis weight makes the porous resin film
(iii) The uniformity of the electrical properties is impaired, the cohesion of the anchor coat layer
(D) is insufficient, the anchor effect is reduced, or the surface resistance of the anchor coat layer
(D) is reduced to 1 × 10 <13>. It is less than Ω, which is not preferable because the charge is
not easily injected during electretization of the porous resin film (iii) and does not reach the core
layer (i) to exhibit the desired performance of the present invention. The coating of the anchor
coat layer (D) can be formed by forming a coating on the film (i) with a known coating apparatus
and drying. Specific examples of the coating apparatus include die coater, bar coater, squeeze
coater, comma coater, lip coater, roll coater, curtain coater, gravure coater, spray coater, blade
coater, reverse coater, air knife coater and the like. Be It is preferable to apply | stack lamination
| stacking of the anchor coat layer (D) to porous resin film (iii), before implementing the belowmentioned electret-ized process.
[0032]
[Pressure Treatment] As pressure treatment, the porous resin film (iii) is placed in a pressure
vessel, and non-reactive gas is introduced by pressure into the pressure vessel, so that the pores
of the core layer (i) are not formed. It is possible to infiltrate the reactive gas and then expand the
pores in a non-pressurized environment. Specific examples of the non-reactive gas to be used
include nitrogen, carbon dioxide, inert gases such as argon and helium, or a mixed gas of these or
air. Although the expansion effect can be obtained even when using a gas other than the nonreactive gas, use of the non-reactive gas from the viewpoint of the safety during pressure
treatment and the safety of the obtained porous resin film (iii) Is desirable. The pressure of the
pressure treatment is preferably in the range of 0.2 to 10 MPa, more preferably 0.3 to 8 MPa,
still more preferably 0.4 to 6 MPa. If the pressure is less than 0.2 MPa, a sufficient expansion
effect can not be obtained because the pressure is low. On the other hand, when the pressure
exceeds 10 MPa, the pores of the core layer (i) can not withstand the internal pressure in a nonpressure environment and can be broken, so that the state of the film can not be maintained. The
pressure treatment time is preferably in the range of 1 hour or more, more preferably 1 to 50
hours. If the pressure treatment time is less than 1 hour, the nonreactive gas does not sufficiently
fill the pores of the core layer (i), or if the porosity of the core layer (i) is less than 1 hour In the
stretched film (i) to be filled, diffusion of non-reactive gas occurs during heat treatment of the
04-05-2019
14
subsequent operation, and a stable expansion ratio can not be obtained. In addition, when the
porous resin film (iii) in a winding shape was subjected to pressure treatment, it was wound
together with a buffer sheet as shown in FIG. 2 so that non-reactive gas could easily penetrate
into the winding interior. It is desirable to prepare the winding in advance. As a specific example
of the buffer sheet, it is possible to use an expanded polystyrene sheet, an expanded polyethylene
sheet, an expanded polypropyne sheet, a non-woven fabric, a paper, a cloth, or the like having
communication holes. The pressure treatment is carried out by pressurizing this winding with a
non-reactive gas using a pressure vessel as shown in FIG.
[0033]
[Heat Treatment] The porous resin film (iii) subjected to pressure treatment requires heat
treatment. The porous resin film (iii) expands by pressure treatment and returning to the nonpressurized environment. However, as it is, the infiltrated non-reactive gas gradually escapes and
returns to its original thickness. By performing the heat treatment, the expansion effect can be
maintained even after the non-reactive gas is removed and the inside of the pores is reduced to
the atmospheric pressure. The temperature of the heat treatment can be performed within a
known temperature range suitable for thermoplastic resins mainly used for the core layer (i) and
not lower than the glass transition temperature of the thermoplastic resin and not higher than
the melting point of the crystal part. When the thermoplastic resin of core layer (i) is a propylene
homopolymer (melting point 155-167 degreeC), specifically, it exists in the range of 80-160
degreeC. Moreover, the heating method can also use a well-known method. Specific examples
thereof include hot air heating by hot air from a nozzle, radiation heating by an infrared heater,
and contact heating by a roll with a temperature control function. During the heat treatment, the
elastic modulus of the porous resin film (iii) is low and it is easy to be crushed if a load is applied,
so the non-contact type hot air heating or radiation heating tends to obtain a high expansion
ratio. As a non-contact type heat treatment apparatus, an apparatus as shown in FIG. 4 may be
mentioned. The porosity of the porous resin film (iii) is increased by performing the pressure
treatment and the heat treatment. The porosity of the porous resin film (iii) is in the range of 5 to
95%, preferably 10 to 90%. If the porosity is less than 5%, the charge storage capacity is low, and
the performance as an electrical / electronic input / output device material is inferior. On the
other hand, if it exceeds 95%, the recoverability in the thickness direction is lowered and the
durability is deteriorated.
[0034]
[Electretization] In order to make the porous resin film (iii) into an electretized film (A), it is
04-05-2019
15
necessary to carry out an electretization treatment. Several processing methods can be
considered as such electretization processing. For example, a method of holding both surfaces of
the film (i) by a conductor and applying a direct current high voltage or a pulse high voltage
(electro electretization method) or a method of electretization by irradiating γ rays or an
electron beam (radio electretization Method etc. are known. Among them, the electretization
method (electro electretization method) using a direct current high voltage is a small-sized
apparatus, and the load on the operator and the environment is small, and such high as the
porous resin film (iii) of the present invention Suitable for electretization of molecular materials.
As a preferable example of the electretization apparatus which can be used in the present
invention, as shown in FIG. 5, a porous resin film (iii) is fixed between the needle electrode 30
connected to the DC high voltage power supply 29 and the ground electrode 31 A method of
applying a voltage, as shown in FIG. 6, while fixing the porous resin film (iii) between the wire
electrode 32 connected to the DC high voltage power supply 29 and the ground electrode 31 and
applying a predetermined voltage Method of moving, method of passing the porous resin film (iii)
while applying a predetermined voltage between the needle electrode 33 connected to the DC
high voltage power supply 29 and the roll 34 connected to the ground as shown in FIG. As
shown in FIG. 8, the porous resin film (iii) is passed while applying a predetermined voltage
between the wire electrode 35 connected to the DC high voltage power supply 29 and the roll 34
connected to the ground. And a method to.
[0035]
The porous resin film (iii) can store more electric charge therein by electretization treatment by
direct current high voltage discharge. The voltage of the electretization process relates to the
thickness of the porous resin film (iii), the porosity, the material of the resin or the filler, the
processing speed, the shape, material and size of the electrode used, and the electretized film to
be finally obtained ( Although it may be changed depending on the charge amount of A) and the
like, the preferable range is 10 to 100 KV, more preferably 12 to 70 KV, and still more
preferably 15 to 50 KV. If the voltage for electretization processing is less than 10 KV, the charge
injection amount is insufficient and the initial performance of the present invention is not
exhibited. On the other hand, if it exceeds 100 KV, local spark discharge is likely to occur, and
partial destruction of the porous resin film (iii) tends to occur. Also, if it exceeds 100 KV, the
injected electric charge is likely to flow from the surface of the porous resin film (iii) to the end
face and flow to the earth electrode, and the electretization efficiency tends to deteriorate.
[0036]
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16
The electretization process may inject excess charge into the porous resin film (iii), in which case
a discharge phenomenon occurs from the electretized film (A) after the treatment, causing
inconvenience in the later process. There is. Therefore, the electretized film (A) can be subjected
to a diselectrification treatment after the electretization treatment. By performing the static
elimination process, the charge excessively given by the electretization process can be removed
to prevent the discharge phenomenon. For such static elimination processing, known methods
such as a voltage application type static elimination (ionizer) and a self-discharge type static
elimination can be used. Although these general static eliminators can remove the charge on the
surface, they can not remove the charge accumulated in the inside of the core layer (i),
particularly in the pores. Therefore, there is no effect that the performance of the electretized
film (A) is greatly reduced by the static elimination treatment. The electretization treatment is
preferably performed at a temperature not lower than the glass transition temperature of the
main thermoplastic resin used for the porous resin film (iii) and not higher than the melting point
of the crystal part. If it is higher than the glass transition point, the molecular motion of the
amorphous part of the thermoplastic resin is active, and molecular arrangement suitable for the
given charge is made, so that efficient electretization processing is possible. On the other hand, if
it exceeds the melting point, the porous resin film (iii) can not maintain its structure, so the
desired performance of the present invention can not be obtained.
[0037]
[Dielectric Film (B)] The electret (F) provided with the conductive layer of the present invention
has the dielectric film (B) on at least one surface of the electretized film (A) and the adhesive
layer (C). It is obtained by laminating. The dielectric film (B) which concerns can use the
stretched film and non-stretched film which consist of thermoplastic resins. The type of
thermoplastic resin used for the dielectric film (B) is not particularly limited. For example,
polyolefin resins such as high density polyethylene, medium density polyethylene, low density
polyethylene, propylene resin, polymethyl-1-pentene, ethylene / vinyl acetate copolymer,
ethylene / acrylic acid copolymer, maleic acid modified polyethylene, Functional groupcontaining polyolefin resins such as maleic acid-modified polypropylene, polyamide resins such
as nylon-6 and nylon-6, 6, polyethylene terephthalate and copolymers thereof, thermoplastic
polyester resins such as polybutylene terephthalate and aliphatic polyester , Polycarbonate,
atactic polystyrene, syndiotactic polystyrene and the like can be used. 0.1-100 micrometers is
preferable, as for the film thickness of a dielectric film (B), 0.5-70 micrometers is more
preferable, and 1-50 micrometers is still more preferable. If the film thickness is less than 0.1
μm, the thickness is too thin and wrinkles are likely to occur during lamination, which tends to
cause defects in the conductive layer (E). On the other hand, if it exceeds 100 μm, the signal
does not reach the electretized film (A) through the dielectric film, or the sound and vibration are
hard to be transmitted to the electretized film (A), resulting in the electric / electronic input /
04-05-2019
17
output device The performance when used is inferior.
[0038]
[Conductive Layer (E)] The dielectric film (B) is required to have a conductive layer (E) on one
side. As a method of providing a conductive layer (E) in a dielectric film (B), coating of a
conductive paint, vapor deposition of a metal, etc. are mentioned. Specific examples of the
conductive paint include metal particles such as gold, silver, platinum, copper and silicon, tindoped indium oxide (ITO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), and
aluminum-doped Mixtures of conductive metal oxide particles such as zinc oxide or carbon
particles with solutions and / or dispersions of binder components such as acrylic resins,
urethane resins, ether resins, ester resins, epoxy resins, etc., polyaniline And solutions and / or
dispersions of conductive resins such as polypyrrole and polythiophene. The coating of the
conductive paint can be formed by forming a coating on the support with a known coating
apparatus and drying. Specific examples of the coating apparatus include a die coater, a bar
coater, a comma coater, a lip coater, a roll coater, a curtain coater, a gravure coater, a spray
coater, a blade coater, a reverse coater, an air knife coater and the like. As a specific example of
the metal deposition film, a metal such as aluminum, zinc, gold, silver, platinum, nickel or the like
is vaporized under reduced pressure and directly attached to the surface of the dielectric film (B)
to form a thin film. Alternatively, the metal may be vaporized under reduced pressure to be once
attached to the surface of the transfer film to form a thin film, and then transferred to the surface
of the dielectric film (B). 0.01-10 micrometers is preferable, as for the film thickness of a
conductive layer (E), 0.03-7 micrometers is more preferable, and 0.05-5 micrometers is still more
preferable. If the film thickness is less than 0.01 μm, the conductive layer tends to have
unevenness in signal transmission performance. On the other hand, if it exceeds 10 μm, the
weight of the conductive layer becomes heavy, so that sound and vibration are difficult to be
transmitted, and the performance when used in an electric / electronic input / output device
becomes inferior.
[0039]
[Adhesive Layer (C)] The electret (F) provided with the conductive layer of the present invention
has a dielectric film (B) on at least one surface of the electretized film (A) and an adhesive layer
(C). It is obtained by laminating. When laminating the dielectric film (B) having the conductive
layer (E) on the electretized film (A), the conductive layer (E) may be the outermost layer, and the
conductive layer (E) may be laminated. ) And the adhesive layer (C) may be in contact with each
other. Generally, it is preferable to laminate such that the conductive layer (E) provided on the
04-05-2019
18
laminated dielectric film (B) is the outermost layer (the opposite side to the electretized film (A)).
If the conductive layer (E) is set to face the electretized film (A), the electric signal is more easily
picked up, but it is difficult to install a signal transmission cable or connector on the conductive
layer (E). turn into. For lamination, an adhesive such as a solvent-based adhesive, a waterdispersed adhesive, or a hot melt adhesive is applied, sprayed, or melt-extrusion laminated onto
the electretized film (A) or dielectric film (B). It can be provided as an adhesive layer by a method,
and it can carry out by usual methods, such as lamination by which, or fusion lamination using a
heat fusible film or a melt extrusion film, etc. via this. In general, it is preferable to first provide
these adhesive layers on the dielectric film (B) because the heat history on the electretized film
(A) is reduced.
[0040]
Examples of solvent-based adhesives and water-dispersed adhesives include resins made of
acrylic resins, urethane resins, ether resins, ester resins, epoxy resins, rubber resins, silicone
resins, ABS resins, etc. The components are dissolved, dispersed, emulsion-dispersed or diluted in
the phase using a conventionally known solvent, and the liquid adhesive in the form of a solution
or emulsion, which is fluid and coatable. It is representative. Coating of these adhesives is
performed by a die coater, a bar coater, a comma coater, a lip coater, a roll coater, a gravure
coater, a spray coater, a blade coater, a reverse coater, an air knife coater or the like. After that,
smoothing is performed if necessary, and a drying process is performed to form an adhesive
layer. Generally, these adhesives are applied so that a weighing may be 0.5 to 25 g / m <2>, and
an adhesive layer is provided. When an adhesive is used, the adhesive is applied to the side of the
dielectric film (B) without the conductive layer (E), and then the electretized film (A) is
superposed and pressure-bonded with a pressure roll. Just do it.
[0041]
Examples of the hot melt adhesive include polyolefin resins such as polyethylene and ethylene /
vinyl acetate copolymer, polyamide resins, polybutyral resins and urethane resins. When a hot
melt adhesive is used, the surface of the dielectric film (B) without the conductive layer (E) may
be coated by a method such as beat coating, curtain coating, slot coating, or melting from a die
The film may be extruded and laminated, and then the electretized film (A) may be laminated and
pressure bonded with a pressure roll. The lamination of the electretized film (A) and the dielectric
film (B) may be before or after the electretization treatment of the porous resin film (iii), but the
dielectric film (B) is provided on both sides At least one side must be after the electretization
process has been performed. Even if the dielectric film (B) is laminated on both sides and then
04-05-2019
19
electretization is performed, the charge may escape through the conductive layer (E) and the
charge may reach the inside of the porous resin film (iii) It is not possible to achieve the desired
performance of the present invention.
[0042]
[Thickness] The thickness of the porous resin film (iii) and the electretized film (A) of the present
invention is measured using a thickness meter in accordance with JIS-K-7130: 1999. The
thickness of the surface layer (ii) is obtained by cooling the sample to be measured with liquid
nitrogen to a temperature of -60 ° C. or less and placing the sample on a glass plate with a razor
blade (manufactured by Sick Japan Co., Ltd., trade name) : A proline blade is hit at a right angle
and cut to prepare a sample for cross-sectional measurement, and the obtained sample is voided
using a scanning electron microscope (manufactured by JEOL Ltd., trade name: JSM-6490) The
boundary between the core layer (i) and the surface layer (ii) is determined from the shape and
composition, and the thickness of the surface layer (ii) which is not easily crushed is calculated
from the product of the observed value and the magnification. The thickness of the core layer (i)
is then determined from the difference between the total thickness of the film and the thickness
of the surface layer (ii).
[0043]
[Surface resistance value] The surface resistance value of the present invention is 23 ° C.,
relative humidity 50%, and in the case where the surface resistance value is 1 × 10 <7> Ω or
more, it is 2 in accordance with JIS-K-6911. It measures using the electrode of the heavy ring
method. When the surface resistance value is less than 1 × 10 <7> Ω, it is a value obtained by
measurement according to the four-terminal method in accordance with JIS-K-7194. It is
desirable that the surface resistance value of the porous resin film (iii) used in the present
invention is adjusted to 1 × 10 <13> Ω or more. When the surface resistance value is less than
1 × 10 <13> Ω, when the porous resin film (iii) is subjected to the electretizing treatment, the
charge easily escapes along the surface and sufficient charge injection is not performed. It is
desirable that the surface resistance value of the conductive layer (E) be adjusted in the range of
1 × 10 <−2> to 9 × 10 <7> Ω. When the surface resistance value exceeds 9 × 10 <7> Ω, the
transmission efficiency of the electric signal is poor, and the performance as an electric /
electronic input / output device material tends to be deteriorated. On the other hand, in order to
provide a conductive layer less than 1 × 10 <-2> Ω, it is necessary to provide a thick conductive
layer, and there is no problem in the transmission of electrical signals, but it is not preferable
from the viewpoint of sound and vibration transmission. .
04-05-2019
20
[0044]
Hereinafter, the present invention will be more specifically described using examples,
comparative examples and test examples. Materials, amounts used, proportions, operations and
the like described below can be appropriately changed without departing from the spirit of the
present invention. Accordingly, the scope of the present invention is not limited to the specific
examples shown below. In addition,% described below is weight% unless otherwise stated.
Examples of production of electrets provided with the conductive layer of the present invention
and materials used in the examples are summarized in Table 1.
[0045]
[0046]
Production Example 1 After kneading the thermoplastic resin composition a with an extruder set
at 230 ° C., it is fed to an extrusion die set at 250 ° C. and extruded into a sheet, which is
cooled by a cooling device An unstretched sheet was obtained.
The unstretched sheet was heated to 135 ° C. and stretched five times in the longitudinal
direction. After kneading the plastic resin composition c with an extruder set at 250 ° C., it was
extruded into a sheet and laminated on each of the front and back surfaces of the 5 × stretched
film prepared above to obtain a laminated film of a three-layer structure . Next, the laminated
film of this three-layer structure is cooled to 60 ° C., heated again to about 145 ° C. using a
tenter oven, stretched by 8 times in the transverse direction, and then by a heat setting zone
adjusted to 160 ° C. Heat treatment was performed. Thereafter, after cooling to 60 ° C., the ear
portion is slit, and both surfaces are subjected to corona surface treatment, and the anchor agent
A is coated on both sides such that the coating amount after drying is 0.01 g / m <2>. Dried in an
oven at 80 ° C. to form an anchor layer (D), and the thickness 60 μm of a three-layer
[10/40/10 μm: stretched layer configuration (1 axis / 2 axis / 1 axis)] structure A porous resin
film (iii) having a porosity of 26% was obtained.
[0047]
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21
Production Example 2 After kneading the thermoplastic resin composition b in an extruder set at
230 ° C., the thermoplastic resin composition b is fed to an extrusion die set at 250 ° C. and
extruded into a sheet, which is cooled by a cooling device An unstretched sheet was obtained.
The unstretched sheet was heated to 150 ° C. and stretched four times in the longitudinal
direction. After kneading the plastic resin composition d with an extruder set at 250 ° C., it was
extruded into a sheet and laminated on each of the front and back surfaces of the 4 × stretched
film prepared above to obtain a laminated film of a three-layer structure . Next, the laminated
film of this three-layer structure is cooled to 60 ° C., heated again to about 150 ° C. using a
tenter oven, stretched 7.5 times in the transverse direction, and then heat set at 160 ° C. Heat
treatment was performed by zones. After cooling to 60 ° C., the ear portion is then slit, and both
surfaces are subjected to corona surface treatment, and the anchor agent B is coated on both
sides so that the coating amount after drying is 0.02 g / m <2>. Dried in an oven at 80 ° C. to
form an anchor layer (D), and the thickness 100 μm of a three-layer [20/60/20 μm: stretched
layer configuration (1 axis / 2 axis / 1 axis)] structure A porous resin film (iii) having a porosity
of 38% was obtained.
[0048]
Production Example 3 After kneading the thermoplastic resin composition a with an extruder set
at 230 ° C., the thermoplastic resin composition a is fed to an extrusion die set at 250 ° C. and
extruded into a sheet, which is cooled by a cooling device A non-stretched sheet was obtained.
The unstretched sheet was heated to 145 ° C., and stretched by four times in the longitudinal
direction using a large number of roll groups different in peripheral speed difference to obtain a
four-fold stretched film. Then, after knead | mixing the plastic resin composition a with the
extruder set to 250 degreeC, it supplies to the extrusion die | dye set to 250 degreeC, extrudes in
a sheet form, and the surface of the 4-times stretched film adjusted above. It laminated | stacked
on each and the back surface, and obtained the laminated film of 3 layer structure. Next, the
laminated film is cooled to 60 ° C., heated again to about 150 ° C. using a tenter oven,
stretched 8-fold in the lateral direction, and then subjected to annealing in an oven adjusted to
160 ° C. After cooling to 60 ° C., the ear portion is slit, corona surface treatment is applied to
both sides, and anchor agent C is coated on both sides so that the coated amount after drying is
1.0 g / m <2>. A stretched film having a thickness of 72 μm and a porosity of 9% was obtained
with a three-layer structure (a / a / a = 16/40/16 μm, stretched layer configuration (1 axis / 2
axes / 1 axis)).
[0049]
[Production Examples 4 to 6] The porous resin films (iii) obtained in Production Examples 1 to 3
04-05-2019
22
are cut out into A4 size, placed in a pressure vessel, pressurized at a pressure of 1.0 MPa for 8
hours, and taken out immediately at 95 °. Heat treatment was performed for 30 seconds in an
oven set to C.
[0050]
[0051]
[Examples 1 to 4 and 6] In the manufacturing examples 1 to 4 and 6 on the ground electrode
plate of the electretization apparatus shown in FIG. 2 set at a needle distance of 10 mm for the
main electrode and a distance of 10 mm for the main electrode Place the obtained porous resin
film (iii), increase the applied voltage little by little from 1 KV, and measure the voltage at which
the porous resin film (iii) is destroyed by local spark discharge, and the voltage is 1 KV lower
than this spark discharge voltage The electret treatment was carried out to obtain an electretized
film (A).
The adhesive paint described in Table 1 was coated on the opposite side of the conductive layer
of the dielectric film (I or II) described in Table 1 with a bar coater so that the coating amount
after drying was 4 g / m <2>. After being processed and dried in an oven set at 40 ° C. for 1
minute, the both surfaces of the electretized film (A) were bonded to produce an electret (F)
provided with a conductive layer.
The types of dielectric films used are shown in Table 3.
[0052]
[Example 5] The adhesive paint described in Table 1 is applied to the opposite surface of the
conductive layer of the dielectric film I by a bar coater so that the applied amount after drying is
4 g / m <2>, After drying for 1 minute in an oven set at 40 ° C., the porous resin film (iii)
obtained in Production Example 5 was bonded to one side. The dielectric film I of the porous
resin film (iii) is bonded on the ground electrode board of the electretization device shown in FIG.
2 set to a needle distance of 10 mm for the main electrode and a distance of 10 mm for the main
electrode to the ground electrode. The voltage applied is raised little by little from 1 KV, and the
voltage at which the porous resin film (iii) is destroyed by local spark discharge is measured, and
04-05-2019
23
the voltage is 1 KV lower than this spark discharge voltage. The electret treatment was carried
out to obtain an electretized film (A). Furthermore, another surface of the conductive layer of the
dielectric film I is coated with the adhesive paint described in Table 1 so that the coated amount
after drying is 4 g / m <2>, and set to 40 ° C. After drying in an oven for 1 minute, this was
bonded to the electret-treated surface of the electretized film (A) to produce an electret (F)
provided with a conductive layer.
[0053]
Comparative Example 1 The porous resin film obtained in Production Example 5 (iii. On the
ground electrode plate of the electretization device described in FIG. 2) set to the needle distance
10 mm of the main electrode and the distance 10 mm between the main electrode and the
ground electrode. ), Increase the applied voltage little by little from 1 KV, measure the voltage at
which the porous resin film (iii) is destroyed by local spark discharge, and perform electret
treatment at a voltage 1 KV lower than this spark discharge voltage. Film (A) was obtained. The
electretized film (A) is made 5 cm square and a conductive layer (E) is formed of a 0.03 μm thick
gold deposited film on both sides using a gold deposition apparatus (product name: Ion Sputter
E101 manufactured by Hitachi, Ltd.) did.
[0054]
[Test Example] (Generated Voltage) Electrets provided with the conductive layers of Examples 1
to 6 and Comparative Example 1 are cut out to a size of 5 cm × 5 cm, and conductive tape
(manufactured by Sumitomo 3M Limited, trade name: AL-25BT) Attach lead wires to the front
and back sides using the ball), and use the falling ball device described in FIG. 9 to measure an
iron ball having a diameter of 11 mm and a weight of 5.5 g from a height of 3.6 cm. Drop it onto
an electretized film (F) equipped with a conductive layer placed on a non-oriented polypropylene
film 100 μm) The maximum voltage generated by the impact of the falling ball was measured
five times, the average value was calculated, and the evaluation was made according to the
following criteria. The evaluation results and the measured maximum voltages are shown in
Table 3. ○: Good Maximum voltage (average value) 200mV or more Δ: Slightly good Maximum
voltage (average value) 10mV or more and less than 200mV ×: Defective Maximum voltage
(average value) less than 10mV
[0055]
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[0056]
As shown in Table 3, it can be seen that the electret (F) provided with the conductive layers of
Examples 1 to 6 can convert the impact energy of the falling ball into an electrical signal.
In addition, it is understood that in Comparative Example 1 in which the conductive layer is
provided directly on the electretized film (A), the charge accumulated by the damage caused by
the heat of the metal deposition treatment escapes and the performance can not be exhibited. .
[0057]
The electret (F) provided with the conductive layer of the present invention is characterized in
that the conductive layer is indirectly provided on the electretized film (A), and there is no quality
deterioration in the processing step, and mass productivity is also high. . Therefore, materials for
electric / electronic input / output devices such as speakers, headphones, ultrasonic transducers,
ultrasonic motors, vibration control devices, microphones, ultrasonic sensors, pressure sensors,
acceleration sensors, strain sensors, fatigue / crack sensors, and power generators. As the
industrial applicability is great.
[0058]
1 electret (F) 2 electretized film (A) 3, 4 dielectric film (B) 5, 6 adhesive layer (C) 7, 8 conductive
layer (E) 9 core layer (i) 10 provided with a conductive layer , 11 surface layer (ii) 12 winding for
pressure treatment 13 porous resin film (iii) 14 buffer sheet 15 pressure container 16 pressure
container lid 17 pressure valve 18 pressure reducing valve 19 stand 20 shaft 21 compressor 22
porosity Resin film (iii) Take-up device 23 Buffer sheet take-up device 24 Hot air device 25 Guide
roll 26, 27 Cool roll 28 Porous resin film (iii) 29 DC high voltage power supply 30, 33 needle
electrode 31 Ground electrode 32, 35 wire Electrode 34 Roll connected to ground 36
Electretized film with conductive layer (iii) 37 insulating film 38, 39 lead wire 40 transparent
acrylic pipe 41 iron ball 42 electromagnet 43 high speed recorder
04-05-2019
25
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