JP7264348B2 - Electret elements and electronic devices - Google Patents

Description

The present invention relates to electret elements and electronic devices.

An electret film is a film that retains electric charges inside and forms an electric field to the outside even in the absence of an external electric field, and is being studied for use as one member that constitutes various electronic devices.
Techniques related to such electret films include, for example, those described in Patent Document 1 (Japanese Patent Laid-Open No. 8-41260) and Patent Document 2 (Japanese Patent Laid-Open No. 2010-89496).

Patent Document 1 discloses a cyclic olefin-based resin (A) and a modified polymer compound (B ) is described as an electret made of a resin composition containing

Further, ⁱⁿ Patent ^Document 2, a dielectric film ( B) is laminated via an adhesive layer (C) to form an electret (F) with a conductive layer.

JP-A-8-41260 JP 2010-89496 A

When the electretized film is used as an electret element, it is necessary to take out the electric charge generated by using the electric charge retained in the electretized film. In order to extract this electric charge to the outside, it is necessary to form an electrode layer for transmitting electric signals on at least one surface, preferably both surfaces, of the electret film.
However, according to the study of the present inventors, when the electrode layers are formed directly on both sides of the electretized film or formed via an adhesive layer, the charge held on the surface of the electretized film disappears. As a result, the charge held in the electret film cannot be effectively used, and the generated charge may not be sufficiently taken out to the outside. amount was found to decrease.
That is, the electret element using the conventional electret film has room for improvement in terms of effectively utilizing the retained charge and extracting the generated charge to the outside.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an electret element capable of extracting a large amount of charge.

The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, by providing an electrically insulated non-adhesive insulating layer at least partially between the electret film and the electrode layer, an electret element capable of extracting a large amount of electric charge can be obtained. Having found that, the present invention was completed.

According to the present invention, the following electret element and electronic device are provided.

[1]
an electret film (A) made of a non-fluorinated resin;
A non-adhesive insulating layer (B) provided on at least one surface of the electret film (A);
an electrode layer (C) provided on the non-adhesive insulating layer (B);
electret element.
[2]
In the electret element described in [1] above,
The electret element, wherein the non-adhesive insulating layer (B) has a thickness of 10 μm or more and 500 μm or less.
[3]
In the electret element described in [1] or [2] above,
An electret element in which the non-fluorine resin contains a cyclic olefin polymer.
[4]
In the electret element according to any one of [1] to [3] above,
An electret element in which the non-adhesive insulating layer (B) comprises an insulating resin layer.
[5]
In the electret element described in [4] above,
The electret element, wherein the insulating resin layer contains at least one selected from the group consisting of polyester-based resins, polyolefin-based resins, (meth)acrylic-based resins, styrene-based resins and fluorine-based resins.
[6]
In the electret element according to any one of [1] to [5] above,
According to ASTM D257, the non-adhesive insulating layer (B) has a volume resistivity of 1.0×10 ⁶ Ω·cm or more at 23° C., which is measured at an applied voltage of 500 V one minute after voltage application. electret element.
[7]
In the electret element according to any one of [1] to [6] above,
An electret element in which the non-adhesive insulating layer (B) has a water absorption of 0.5% by mass or less when immersed in water at a temperature of 23° C. for 24 hours, as measured according to ASTM D570.
[8]
In the electret element according to any one of [1] to [7] above,
An electret element further comprising an adhesive layer (D) between the non-adhesive insulating layer (B) and the electrode layer (C).
[9]
In the electret element according to any one of [1] to [8] above,
The electret element, wherein the electretized film (A) is a non-porous film.
[10]
In the electret element according to any one of [1] to [9] above,
An electret element, wherein the electret film (A) has a glass transition temperature of 80° C. or higher.
[11]
In the electret element according to any one of [1] to [10] above,
An electret element, wherein the electret film (A) has a dielectric constant of 3.0 or less at a frequency of 1 MHz.
[12]
In the electret element according to any one of [1] to [11] above,
An electret element that is film-like or sheet-like.
[13]
In the electret element according to any one of [1] to [12] above,
An electret element, wherein the electret film (A) has a thickness of 5 μm or more and 500 μm or less.
[14]
In the electret element according to any one of [1] to [13] above,
An electret element that is a sensor element or a power generation element.
[15]
An electronic device comprising the electret element according to any one of [1] to [14] above.
[16]
In the electronic device described in [15] above,
An electronic device selected from a power generation device, a biosignal acquisition device, a vibration detection device, a shock detection device and a displacement detection device.

ADVANTAGE OF THE INVENTION According to this invention, the electret element and electronic device which can take out many electric charges can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically an example of the structure of the electret element of embodiment which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically an example of the structure of the electret element of embodiment which concerns on this invention. FIG. 2 is a cross-sectional view schematically showing an example of the structure of an electret element corresponding to a comparative example of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the explanation thereof is omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to actual dimensional ratios. In addition, the numerical range "A to B" represents from A to B, unless otherwise specified.

1. Electret Element Hereinafter, the electret element 10 according to the present embodiment will be described.
1 and 2 are cross-sectional views schematically showing an example of the structure of an electret element 10 according to an embodiment of the invention.

As shown in FIG. 1, the electret element 10 according to the present embodiment includes an electret film (A) made of a non-fluorinated resin and a non-viscous film provided on at least one surface of the electret film (A). It comprises an adhesive insulating layer (B) and an electrode layer (C) provided on the non-adhesive insulating layer (B). In this embodiment, the entire surface of the electret film (A) on which the non-adhesive insulating layer (B) is provided is directly covered with the electrode layer (C) or the adhesive layer. is excluded from the electret element 10 according to

When the electretized film is used as an electret element, it is necessary to take out the electric charge generated by using the electric charge retained in the electretized film. In order to extract this electric charge to the outside, it is necessary to form an electrode layer for transmitting electric signals on at least one surface, preferably both surfaces, of the electret film.
However, according to the study of the present inventors, when the electrode layers are formed directly on both sides of the electretized film or formed via an adhesive layer, the charge held on the surface of the electretized film disappears. As a result, it has become clear that in some cases the charges retained in the electret film cannot be effectively utilized, and the generated charges cannot be sufficiently taken out to the outside.
That is, the electret element using the conventional electret film has room for improvement in terms of effectively utilizing the retained charge and extracting the generated charge to the outside.
The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, by providing an electrically insulated non-adhesive insulating layer (B) at least partly between the electretized film (A) and the electrode layer (C), a large amount of charge is taken out. It was found for the first time that an electret element 10 capable of
Although the reason for this is not clear, by providing an electrically insulated non-adhesive insulating layer (B) at least partly between the electret film (A) and the electrode layer (C), Since the entire surface of both sides of the electretized film (A) can be prevented from being in direct contact with the electrode layer (C) or covered with the adhesive layer, the electric charges accumulated on the surface of the electretized film (A) are transferred to the electrode layer ( C) or it is thought that it becomes difficult to disappear through the adhesive layer. In addition, since the charge held in the non-adhesive insulating layer (B) between the electret film (A) and the electrode layer (C) can be effectively used, the electret film (A) It becomes possible to extract the electric charge to the outside.
That is, the electret element 10 according to the present embodiment is provided with an electrically insulated non-adhesive insulating layer (B) partly between the electret film (A) and the electrode layer (C). This makes it possible to extract a large amount of charge from the electret film (A) while suppressing the disappearance of the charge accumulated on the surface of the electret film (A).
Here, the electrically insulated non-adhesive insulating layer (B) may be provided on at least one surface of the electret film (A). When the electret film (A) has an electrically insulated non-adhesive insulating layer (B) on only one surface, the electrically insulated non-adhesive insulating layer (B) is provided. The electrode layer (C) on the side not covered may be formed directly on the surface of the electret film (A), or may be formed via an adhesive layer. When directly formed on the surface of the electretized film (A), the electrode layer (C) may be formed by applying a conductive paint, vapor-depositing a metal, or the like. When the adhesive layer and the electrode layer (C) are directly formed on only one surface of the electret film (A), they are preferably formed before the electret treatment.
Here, at least part of the electret film (A) and at least part of the non-adhesive insulating layer (B) are preferably in direct contact.

The shape of the electret element 10 according to this embodiment is not particularly limited, and examples thereof include a film shape, a sheet shape, and a plate shape. Among these, a film shape or a sheet shape is preferable.

In the electret element 10 according to the present embodiment, the area of one surface of the electret element 10 is preferably 25 cm ² or more from the viewpoint of extracting a large amount of charge more stably and from the viewpoint of further improving the output of the electret element 10. be.

Next, each layer constituting the electret element 10 according to this embodiment will be described.

<Electret film (A)>
The electret film (A) according to the present embodiment contains a non-fluorinated resin, has low hygroscopicity and excellent insulation from the viewpoint of the balance of charge retention, flexibility, moldability, handleability, cost, etc. It is more preferable to contain a non-fluorine-based thermoplastic resin because it has a high charge retention capacity. Here, the term "non-fluorine-based resin" refers to a resin containing no fluorine atoms.
The non-fluorine-based thermoplastic resin constituting the electret film (A) is not particularly limited, but examples thereof include cyclic olefin polymers, polyethylene resins, polypropylene resins, poly-4-methylpentene, and ethylene-propylene rubber. , Polyolefin resins such as ethylene-propylene-diene copolymers; ethylene-vinyl acetate copolymers; polystyrene resins; chlorine resins such as polyvinyl chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, and polyvinylidene chloride; Cyano-based resins such as polyvinyl cyanide and polyvinylidene cyanide; Polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polylactic acid; Polyamide resin; (meth) acrylic resin; polyimide resin; polyetherimide resin; polyamideimide resin; polycarbonate resin; modified polyphenylene ether resin; polyphenylene sulfide-based resin; polyetheretherketone-based resin; polybenzimidazole-based resin; polybenzoxazole-based resin; polymethylpentene-based resin.
These thermoplastic resins may be used singly or in combination of two or more.

Among these, as a thermoplastic resin, one or two or more resins selected from the group consisting of polyolefin resins, polyphenylene sulfide resins and polystyrene resins because of their excellent insulating properties and high charge retention. is preferred, polyolefin resins are more preferred, and cyclic olefin polymers are even more preferred.

The content of the resin in the electret film (A) according to the present embodiment is not particularly limited. % or more, more preferably 80 mass % or more, particularly preferably 90 mass % or more, and preferably 100 mass % or less.
This makes it possible to obtain an electret film (A) that is well balanced among charge retention, mechanical properties, handleability, moldability, flexibility, heat resistance, moisture resistance, transparency, and the like.

The electret film (A) according to this embodiment may be a single layer or two or more layers. That is, the number of electret films (A) can be one or more.
The form of the resin film used for forming the electret film (A) may be a non-stretched film or a uniaxially or biaxially stretched film. From the viewpoint of improving the heat resistance and mechanical strength of the modified film (A), it is preferably a uniaxially or biaxially stretched film.

The electret film (A) according to the present embodiment may be either a porous film or a non-porous film. is preferably Further, when the electretized film (A) is a non-porous film, the charge held on the surface of the electretized film is more likely to disappear. Therefore, when the electretized film (A) is a non-porous film, it is possible to extract a large amount of charge from the electretized film (A) while suppressing the disappearance of the charge accumulated on the surface of the electretized film (A). It is possible to more effectively obtain the effect of the present embodiment that it is possible to

In the electret film (A) according to the present embodiment, from the viewpoint of improving flexibility and transparency, the content of the inorganic filler in the electret film (A) is When is 100% by mass, it is preferably 0% by mass or more and 30% by mass or less, preferably 0% by mass or more and 20% by mass or less, more preferably 0% by mass or more and 10% by mass or less , 0% by mass or more and 5% by mass or less.
Examples of such inorganic fillers include calcium carbonate, calcined clay, silica, diatomaceous earth, clay, talc, titanium oxide, barium sulfate, alumina, zeolite, mica, sericite, bentonite, sepiolite, vermiculite, dolomite, Examples include wollastonite and glass fiber.

The electret film (A) according to the present embodiment preferably has a glass transition temperature of 80° C. or higher, more preferably 100° C. or higher, from the viewpoint of further improving charge retention at high temperatures. It is more preferably 110° C. or higher, and particularly preferably 120° C. or higher.
In addition, the electret film (A) according to the present embodiment preferably has a glass transition temperature of 220° C. or lower, more preferably 200° C. or lower, from the viewpoint of improving flexibility and transparency. °C or less is more preferable.

The dielectric constant at a frequency of 1 MHz of the electret film (A) according to the present embodiment is preferably 3.0 or less from the viewpoint of further improving charge retention and obtaining an electret element 10 having superior sensitivity. , 2.5 or less.

From the viewpoint of improving the sensitivity of the electret element 10, the electret film (A) according to the present embodiment has a load of 0.5 N in the thickness direction of the electret film (A), a dynamic load of ±0.25 N, and a frequency of 110 Hz. , the absolute value of the piezoelectric constant _d33 in the thickness direction, which is measured by applying a pressing force at a temperature of 23 ° C. and a humidity of 50%, is preferably 30 pC / N or more, more preferably 50 pC / N or more, It is more preferably 100 pC/N or more, still more preferably 150 pC/N or more, and particularly preferably 180 pC/N or more.
The upper limit of the absolute value of the piezoelectric constant _d33 in the thickness direction is not particularly limited, but is preferably 500 pC/N or less, more preferably 400 pC/N or less, from the viewpoint of better charge retention at high temperatures. It is preferably 300 pC/N or less, more preferably 300 pC/N or less.
In order to achieve such a piezoelectric constant _d33 , it is important, for example, to devise a corona charging method.

The electret film (A) according to the present embodiment is measured in accordance with ASTM D570 from the viewpoint of further improving charge retention under high temperature and high humidity conditions and obtaining an electret element 10 having excellent long-term reliability. The water absorption when immersed in water at a temperature of 23° C. for 24 hours is preferably 0.3% by mass or less, more preferably 0.1% by mass or less, and 0.05% by mass or less. More preferred. Although the lower limit of the water absorption of the electret film (A) according to the present embodiment is not particularly limited, it is, for example, 0.0001% by mass or more.

The thickness of the electret film (A) according to this embodiment is not particularly limited, but is, for example, 5 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less, more preferably 15 μm or more and 200 μm or less. When the thickness of the electret film (A) according to the present embodiment is within this range, the balance of mechanical properties, handleability, moldability, etc. is more excellent.

(Cyclic olefin polymer)
The electret film (A) according to this embodiment preferably contains a cyclic olefin polymer as the non-fluorine resin. This makes it possible to further improve the piezoelectric constant _d33 in the thickness direction. In addition, since the amount of charge generated (pyroelectricity) with respect to temperature change can be reduced, the electret element 10 that is less affected by temperature change can be obtained.

Examples of the cyclic olefin polymer include at least one selected from copolymers of ethylene or α-olefins and cyclic olefins and ring-opening polymers of cyclic olefins.

As a copolymer of ethylene or an α-olefin and a cyclic olefin, for example, polymers described in paragraphs 0030 to 0123 of International Publication No. 2008/047468 can be used.

For example, a polymer having an alicyclic structure in at least part of the repeating structural units (hereinafter also simply referred to as "a polymer having an alicyclic structure"), and an alicyclic structure in at least a part of the repeating units of the polymer Specifically, it preferably contains a polymer having one or more structures represented by the following formula (1).

ここで、上記式（１）中、ｘ、ｙは共重合比を示し、０／１００≦ｙ／ｘ≦９５／５を満たす実数である。ｘ、ｙはモル基準である。
ｎは置換基Ｑの置換数を示し、０≦ｎ≦２の実数である。
Ｒ^ａは、炭素原子数２～２０の炭化水素基よりなる群から選ばれる２＋ｎ価の基である。
Ｒ^ｂは、水素原子、または炭素原子数１～１０の炭化水素基よりなる群から選ばれる１価の基である。
Ｒ^ｃは、炭素原子数２～１０の炭化水素基よりなる群から選ばれる４価の基である。
Ｑは、ＣＯＯＲ^ｄ（Ｒ^ｄは、水素原子、または炭素原子数１～１０の炭化水素基よりなる群から選ばれる１価の基である。）である。
Ｒ^ａ、Ｒ^ｂ、Ｒ^ｃおよびＱは、それぞれ１種であってもよく、２種以上を任意の割合で有していてもよい。

Here, in the above formula (1), x and y represent copolymerization ratios and are real numbers satisfying 0/100≤y/x≤95/5. x and y are on a molar basis.
n indicates the substitution number of the substituent Q and is a real number of 0≦n≦2.
R ^a is a 2+n-valent group selected from the group consisting of hydrocarbon groups having 2 to 20 carbon atoms.
R ^b is a hydrogen atom or a monovalent group selected from the group consisting of hydrocarbon groups having 1 to 10 carbon atoms.
R ^c is a tetravalent group selected from the group consisting of hydrocarbon groups having 2 to 10 carbon atoms.
Q is COOR ^d (R ^d is a hydrogen atom or a monovalent group selected from the group consisting of hydrocarbon groups having 1 to 10 carbon atoms).
Each of R ^a , R ^b , R ^c and Q may be one kind, or may be two or more kinds in an arbitrary ratio.

In the above formula (1), R ^a is preferably one or more divalent groups selected from hydrocarbon groups having 2 to 12 carbon atoms, more preferably n=0. is a divalent group represented by the following formula (2), most preferably a divalent group in which p is 0 or 1 in the following formula (2). The structure of R ^a may be used alone or in combination of two or more.

ここで、上記式（２）中、ｐは、０～２の整数である。

Here, p is an integer of 0 to 2 in the above formula (2).

The copolymer of ethylene or α-olefin and cyclic olefin is a cyclic olefin copolymer represented by the following formula (3). For example, it consists of a structural unit (A) derived from ethylene or a linear or branched α-olefin having 3 to 30 carbon atoms and a structural unit (B) derived from a cyclic olefin.

ここで、上記式（３）中、Ｒ^ａは、炭素原子数２～２０の炭化水素基よりなる群から選ばれる２価の基である。
Ｒ^ｂは、水素原子、または炭素原子数１～１０の炭化水素基よりなる群から選ばれる１価の基である。
Ｒ^ａおよびＲ^ｂは、それぞれ１種であってもよく、２種以上を任意の割合で有していてもよい。
ｘ、ｙは共重合比を示し、５／９５≦ｙ／ｘ≦９５／５を満たす実数である。好ましくは５０／５０≦ｙ／ｘ≦９５／５、さらに好ましくは、５５／４５≦ｙ／ｘ≦８０／２０である。ｘ、ｙはモル基準である。

Here, in the above formula (3), R ^a is a divalent group selected from the group consisting of hydrocarbon groups having 2 to 20 carbon atoms.
R ^b is a hydrogen atom or a monovalent group selected from the group consisting of hydrocarbon groups having 1 to 10 carbon atoms.
Each of R ^a and R ^b may be one type, or two or more types may be used in an arbitrary ratio.
x and y represent copolymerization ratios and are real numbers satisfying 5/95≤y/x≤95/5. Preferably 50/50≤y/x≤95/5, more preferably 55/45≤y/x≤80/20. x and y are on a molar basis.

The copolymer of ethylene or α-olefin and cyclic olefin is preferably a copolymer of ethylene and cyclic olefin, and the cyclic olefin is bicyclo[2.2.1]-2-heptene, tetracyclo[4.4.0 .1 ^{2, 5} . 1 ^7,10 ]-3-dodecene, 1,4-methano-1,4,4a,9a-tetrahydrofluorene, one or two selected from the group consisting of cyclopentadiene-benzine adducts and cyclopentadiene-acenaphthylene adducts above, bicyclo[2.2.1]-2-heptene and tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]-3-dodecene is more preferred.
As the copolymer of ethylene or α-olefin and cyclic olefin, a polymer having one or more structures represented by the above formula (1) or a cyclic olefin system represented by the above formula (3) The copolymer may be a hydrogenated polymer.

A ring-opening polymer of a cyclic olefin can be used as the cyclic olefin polymer.
Examples of ring-opening polymers of cyclic olefins include ring-opening polymers of norbornene-based monomers, ring-opening polymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization thereof, and These hydrides etc. are mentioned.

Examples of norbornene-based monomers include, for example, bicyclo[2.2.1]hept-2-ene (common name: norbornene) and derivatives thereof (having a substituent on the ring), tricyclo[ ^{4.3.01 , 6} . 1 ^2,5 ]deca-3,7-diene (common name dicyclopentadiene) and its derivatives, 7,8-benzotricyclo[4.3.0.1 ^2,5 ]dec-3-ene (common name methanotetrahydrofluorene: 1,4-methano-1,4,4a,9a-tetrahydrofluorene) and its derivatives, tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]-3-dodecene (common name: tetracyclododecene) and derivatives thereof, and the like.
Examples of substituents on the ring of these derivatives include an alkyl group, an alkylene group, a vinyl group, an alkoxycarbonyl group, and an alkylidene group. In addition, the substituent can have 1 or 2 or more. Derivatives having a substituent on such a ring include, for example, 8-methoxycarbonyl-tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]dodeca-3-ene, 8-methyl-8-methoxycarbonyl-tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]dodeca-3-ene, 8-ethylidene-tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]dodeca-3-ene and the like.
These norbornene-based monomers may be used alone or in combination of two or more.

A ring-opening polymer of a norbornene-based monomer, or a ring-opening polymer of a norbornene-based monomer and other monomers capable of ring-opening copolymerization with the monomer component is prepared by a known ring-opening polymerization. It can be obtained by polymerization in the presence of a catalyst.
The ring-opening polymerization catalyst includes, for example, a metal halide such as ruthenium and osmium, a nitrate or an acetylacetone compound, and a reducing agent; , an organoaluminum compound; and the like.
Other monomers capable of ring-opening copolymerization with norbornene monomers include, for example, monocyclic cyclic olefin monomers such as cyclohexene, cycloheptene, and cyclooctene.

A hydride of a ring-opening polymer of a norbornene-based monomer, or a hydride of a ring-opening polymer of a norbornene-based monomer and another monomer capable of ring-opening copolymerization thereof is usually the above ring-opening It can be obtained by adding a known hydrogenation catalyst containing a transition metal such as nickel or palladium to a polymerization solution of the polymer to hydrogenate the carbon-carbon unsaturated bond.

In this embodiment, one type of cyclic olefin polymer may be used alone, or two or more types may be used in combination.

The content of the cyclic olefin polymer in the electretized film (A) according to the present embodiment is not particularly limited, but when the electretized film (A) as a whole is 100% by mass, it is preferably 60% by mass or more, and more It is preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, and preferably 100% by mass or less.
As a result, an electret film (A) with excellent balance of charge retention, mechanical properties, handleability, moldability, flexibility, heat resistance, moisture resistance, transparency, etc. under high temperature and high temperature and high humidity conditions is obtained. be able to.

(Additive)
Various additives may be added to the electret film (A) according to the present embodiment, depending on the purpose. The amount of the additive to be added is appropriately selected depending on the application within a range that does not impair the purpose of the present invention.
Examples of the above additives include heat stabilizers, weather stabilizers, slip agents, radiation resistant agents, plasticizers, lubricants, mold release agents, nucleating agents, friction and abrasion improvers, flame retardants, antistatic agents, coloring agents, antistatic agents. One or two or more additives selected from the group consisting of fogging agents, antiblocking agents, impact resistance agents, surface wetting agents, hydrochloric acid absorbers and metal deactivators are included.
In particular, when a thermoplastic resin is used as a raw material and a film is formed using an extruder or the like, the solid raw material is When the is pellets, it is preferable to add a lubricant to the exterior of the pellets in advance before feeding the pellets to the extruder.
Lubricants that suppress gelation due to such friction and shear include fatty acid amide-based lubricants, metallic soap-based lubricants, liquid lubricants, and the like. More specifically, in the case of fatty acid amide-based lubricants, ethylene bis-stearate amide, in the case of metal soap-based lubricants, calcium stearate, magnesium stearate, zinc stearate, and sodium stearate, and in the case of liquid lubricants, paraffin oil and naphthenic oil. The amount of these lubricants added is preferably 0.005 to 0.3 parts by mass, more preferably 0.01 to 0.1 parts by mass, with respect to 100 parts by mass of the raw material pellets. It is more preferably 0.03 to 0.08 parts by mass.
Here, when the amount of the lubricant added is equal to or more than the above lower limit, the effect of the lubricant can be more easily obtained, and the generation of gel can be further suppressed. On the other hand, when the amount of the lubricant added is equal to or less than the above upper limit, the haze of the film can be further reduced, and the transparency, appearance and mechanical properties can be further improved. As a method for adding a lubricant to pellets, which are solid raw materials made of a thermoplastic resin, a mixing device such as a tumbler mixer is used to uniformly mix the pellets and the lubricant.

(Method for producing electret film (A))
The method for producing the electret film (A) according to this embodiment includes, for example, the following two steps.
(1) Step of preparing a resin film (2) Step of subjecting the obtained resin film to a corona charge treatment to form an electret Each step will be described below.

First, a resin film is produced.
The method for producing the resin film is not particularly limited, but for example, various known molding methods (cast molding, extrusion molding, inflation molding, injection molding, compression molding, calendar molding, etc.) are used to mold the resin into a film. a method obtained by
Among these methods for producing a resin film, casting a film using a single-screw extruder and a T-die is preferable from the standpoint of excellent mass productivity and reduced production costs. In particular, when the resin is a copolymer of ethylene or an α-olefin and a cyclic olefin, a film having high light transmittance, low haze and excellent transparency using a single-screw extruder and a T-die. In the case of obtaining, as film forming conditions, for example, the method described in JP-A-2005-343148 can be referred to, including the combined use of a polymer filter. In addition, for the purpose of imparting smoothness to the film during casting, as a method of pressing the molten web extruded from the T-die against the cast roll, a known electrostatic pinning method and a mirror-finished sleeve touch method (Chiba Machinery Co., Ltd.) (manufactured by Kogyo Co., Ltd.) or a known method of crimping a metal elastic roll can be used. Furthermore, the brittleness of the film may be improved by biaxially heating and stretching the film. Here, examples of techniques for biaxially heating and stretching the film include sequential stretching and simultaneous biaxial stretching.

Next, the obtained resin film is subjected to, for example, a corona charge treatment to convert the resin film into an electret. Thereby, the electret film (A) according to the present embodiment can be obtained.
Here, (1) the corona charging treatment is performed using needle-like electrodes in which the needles are arranged at regular intervals, (2) the distance between the electrodes during the corona charging treatment, (3) the voltage during the corona charging treatment, It is preferred to have a high degree of control over the three conditions of That is, an electret film (A) having a further excellent piezoelectric constant _d33 in the thickness direction can be obtained by a production method that highly controls various factors related to the above three conditions.
More specifically, it is preferable to fix a resin film between a needle-like electrode connected to a DC high-voltage power supply and a ground electrode and apply a voltage. At this time, it is preferable to set the distance between the needle-like electrode and the ground electrode to 20 to 50 mm and set the applied voltage to 15 to 30 kV or -30 to -15 kV.
As a result, an electric charge can be sufficiently injected into the resin film, and an electret film (A) having a further excellent piezoelectric constant _d33 in the thickness direction can be obtained.

<Non-Adhesive Insulating Layer (B)>
The non-tacky-adhesive insulating layer (B) is a layer that does not exhibit tacky-adhesiveness to the electret film (A) and the electrode layer (C) and has insulating properties.
The non-tacky-adhesive insulating layer (B) is not particularly limited as long as it does not exhibit adhesiveness to the electret film (A) and the electrode layer (C) and has insulating properties. Examples thereof include an insulating resin layer and an insulating inorganic layer. Among these, an insulating resin layer is preferable as the non-adhesive insulating layer (B).

As the resin forming the insulating resin layer, for example, a known thermoplastic resin or thermosetting resin can be used.
Although the thermoplastic resin is not particularly limited, for example, polyolefins such as cyclic olefin polymers, polyethylene resins, polypropylene resins, poly-4-methylpentene, ethylene-propylene rubber, and ethylene-propylene-diene copolymers Resin; ethylene-vinyl acetate copolymer; styrene resin; chlorine resin such as polyvinyl chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, and polyvinylidene chloride; fluorine-containing cyclic olefin polymer, polytetrafluoroethylene, Polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesin, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, etc. Fluorinated resin; Polyvinyl cyanide, cyano resin such as polyvinylidene cyanide; Polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid resin; Nylon 6, Nylon 66, Nylon 11, Polymetaxylene Polyamide resins such as adipamide; (meth) acrylic resins; polyimide resins; polyetherimide resins; polyamideimide resins; polycarbonate resins; modified polyphenylene ether resins; polysulfone-based resin; polyethersulfone-based resin; polyphenylene sulfide-based resin; polyetheretherketone-based resin; polybenzimidazole-based resin;
Thermosetting resins are not particularly limited, but for example, epoxy resins, oxetane resins, phenol resins, silicone resins, urethane resins, polyimide resins, urea resins, melamine resins, unsaturated polyester resins, and (meth)acryloyloxy groups. Resin etc. are mentioned.
These resins may be used singly or in combination of two or more.

Among these, thermoplastic resins are selected from the group consisting of polyester-based resins, polyolefin-based resins, (meth)acrylic-based resins, styrene-based resins, and fluorine-based resins because of their excellent insulating properties and high charge retention. One or two or more selected resins are preferred, and polyester-based resins are more preferred.

Examples of inorganic substances constituting the insulating inorganic layer include metal oxides, metal nitrides, and metal oxynitrides. Examples include silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, titanium oxide, tantalum oxide, germanium oxide, and magnesium oxide. These inorganic substances may be used singly or in combination of two or more.

The non-adhesive insulating layer (B) may be a single layer or two or more layers.
Further, when the non-adhesive insulating layer (B) is an insulating resin layer, the form of the resin film used for forming the insulating resin layer may be a stretched film, a uniaxially or biaxially stretched film. Although the film may be uniaxially or biaxially stretched, it is preferable from the viewpoint of improving the mechanical strength of the non-adhesive insulating layer (B).

From the viewpoint of improving the output stability of the electret element 10, the thickness of the non-adhesive insulating layer (B) is preferably 10 μm or more and 500 μm or less, more preferably 20 μm or more and 300 μm or less, still more preferably 25 μm or more and 150 μm or less. is.

The insulation property of the non-adhesive insulating layer (B) is not particularly limited as long as it has the insulation property of a general insulator. The volume resistivity of the non-adhesive insulating layer (B) at 23° C. is 1.0×10 ⁶ Ω·cm or more, preferably 1.0×10 ⁸ Ω·cm or more, and more It is preferably 1.0×10 ¹⁰ Ω·cm or more, more preferably 1.0×10 ¹² Ω·cm or more.

In the electret element 10 according to the present embodiment, the temperature is 23° C., measured in accordance with ASTM D570, from the viewpoint of further improving the charge retention under high temperature and high humidity conditions and obtaining an electret element 10 with excellent long-term reliability. The water absorption of the non-adhesive insulating layer (B) when immersed in water for 24 hours is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and 0.1% by mass or less. 05% by mass or less is more preferable. Although the lower limit of the water absorption rate of the non-adhesive insulating layer (B) according to this embodiment is not particularly limited, it is, for example, 0.0001% by mass or more.

The non-adhesive insulating layer (B) may be subjected to a surface treatment in order to improve adhesion with other layers. Specifically, corona treatment, plasma treatment, undercoat treatment, primer coat treatment, UV treatment, or the like may be performed.

<Electrode layer (C)>
Examples of the electrode layer (C) include aluminum foil, copper foil, zinc foil, gold foil, silver foil, platinum foil, nickel foil, titanium foil, chromium foil, tungsten foil, molybdenum foil, platinum foil, tantalum foil, niobium foil, Metal foil such as zirconium foil, stainless steel foil, alloy foil; metal oxide film such as ITO (indium tin oxide) film and tin oxide film; film such as organic conductive resin film; metal nanowire; A paint etc. are mentioned.
Although the thickness of the electrode layer (C) is not particularly limited, it is, for example, 0.01 μm or more and 50 μm or less, preferably 0.03 μm or more and 20 μm or less, more preferably 0.05 μm or more and 15 μm or less.

<Adhesive layer (D)>
The electret element 10 according to this embodiment may further include an adhesive layer (D) between the non-adhesive insulating layer (B) and the electrode layer (C), as shown in FIG. . Here, the adhesive layer (D) has a role of fixing the position of each layer so that the position of each layer does not shift.
In this embodiment, the adhesive layer and the adhesive layer are collectively referred to as an adhesive layer.

The adhesive constituting the adhesive layer (D) is not particularly limited, but for example, poly(meth)acrylic adhesive, silicone adhesive, polyurethane adhesive, olefin adhesive Adhesives, styrene adhesives, rubber adhesives, vinyl ether adhesives, polyester adhesives, epoxy adhesives, polyamide adhesives, polyvinyl acetate adhesives, ABS-based adhesives, UV-curable adhesives, and the like. In the present embodiment, pressure-sensitive adhesives and adhesives are collectively referred to as pressure-sensitive adhesives.
Among these, poly(meth)acrylic pressure-sensitive adhesives are preferable because they are excellent in weather resistance, transparency, etc., and can be used in a wide range of applications. Poly(meth)acrylic pressure-sensitive adhesives include emulsion type, solvent type, hot-melt type, solution type, and the like, and any type can be used in the present embodiment. Among these, emulsion-type poly(meth)acrylic pressure-sensitive adhesives are preferable from the aspects of safety, quality, and cost.

The adhesive layer (D) may contain other optional components as needed. Other optional components include tackifiers, adhesive microspheres, thickeners, pH adjusters, antifoaming agents, antiseptic and antifungal agents, pigments, inorganic fillers, stabilizers, wetting agents, wetting agents, and the like. . Examples of tackifiers include rosin resins, terpene resins, aliphatic petroleum resins, aromatic petroleum resins, hydrogenated petroleum resins, styrene resins, and alkylphenol resins.

Although the thickness of the adhesive layer (D) is not particularly limited, it is preferably 0.01 μm or more and 50 μm or less, and more preferably 0.03 μm or more and 30 μm or less.

The adhesive layer (D) can be formed, for example, by applying an adhesive agent onto the formation site. The adhesive may be dissolved in a solvent and applied as a coating liquid, may be applied as a water-based emulsion, or may be applied directly as a liquid adhesive.
As a method for applying the adhesive agent coating liquid, conventionally known coating methods such as gravure coater method, comma coater method, bar coater method, knife coater method, die coater method, roll coater method, etc.; Method: A screen printing method or the like can be used.

In addition, the electret element 10 according to the present embodiment further includes a packaging material for packaging the entire structural unit including the electret film (A), the non-adhesive insulating layer (B) and the electrode layer (C). You may prepare. In this case, a structural unit including an electret film (A), a non-adhesive insulating layer (B) and an electrode layer (C) is laminated and packaged with a packaging material. As a result, even if the adhesive layer (D) is not provided between the non-adhesive insulating layer (B) and the electrode layer (C), it is possible to prevent the layers from being displaced or peeled off. can be suppressed. That is, by laminating and packaging the structural unit including the electret film (A), the non-adhesive insulating layer (B) and the electrode layer (C) with the packaging material, it is possible to suppress the misalignment of each layer. , the position of each layer can be fixed.
The packaging material is not particularly limited, and known laminated films can be used. From the viewpoint of improving the long-term reliability of the electret element 10, a laminate film with excellent gas barrier properties is preferable, and a laminate film with high heat resistance that can maintain its shape and adhesiveness even when held at a high temperature of 100° C. or higher is more preferable. .

In addition, in the electret element 10 according to the present embodiment, at least a part of the peripheral portion of the structural unit including the electret film (A), the non-adhesive insulating layer (B) and the electrode layer (C) is fixed. may As a result, even if the adhesive layer (D) is not provided between the non-adhesive insulating layer (B) and the electrode layer (C), it is possible to prevent the layers from being displaced or peeled off. can be suppressed. The fixing material is not particularly limited, and examples thereof include adhesives, adhesives, adhesive tapes, adhesive tapes, clips, and the like.

The electret element 10 is not particularly limited, but may be, for example, a sensor element such as a piezoelectric sensor element or a pyroelectric sensor element, or a power generating element. element. Sensors using the electret element 10 include, for example, impact detection sensors, vibration detection sensors, displacement detection sensors, and the like.
The sensor according to this embodiment can be manufactured based on, for example, known information.

2. Electronic Device An electronic device according to this embodiment includes the electret element 10 according to this embodiment as one of its components.
Electronic devices using the electret element 10 according to the present embodiment include, for example, a power generation device, a biosignal acquisition device, a vibration detection device, a shock detection device, a displacement detection device, and the like.
The power generation device is a device that generates power by transferring electric charges injected into the electret element 10 to the outside. A biomedical signal acquisition device is, for example, a device for acquiring biomedical signals such as pulse, respiration, snoring, voice, and body movement. Examples of such biosignal acquisition devices include chairs, chair covers, seat belts, cushions, beds, futons, mattresses, bed pads, mattresses, pillows, clothing, shoes, neck wraps, wristbands, rings, bandages, and wristwatches. , eyeglasses, a toilet seat, a bathtub, a sofa, a floor, a weight scale, and the like, biosignals can be obtained from a living body such as a human body.
Vibration detectors, impact detectors, and displacement detectors are used, for example, to detect the presence of people or vehicles, or to detect shaking or abnormalities in buildings or structures, based on vibration, shock, or displacement. It is a device.

In the electronic device, the electret element 10 according to this embodiment can convert electrical energy received via the electrode layer (C) into mechanical energy. As a result, the electretized film (A) according to the present embodiment is deformed and vibrates, and a tactile feedback can be provided to the user.
Further, in the electronic device, the electret element 10 according to the present embodiment can convert mechanical energy of vibration received by the electronic device into electrical energy. The electrical energy is sent to another device or the like via the electrode layer (C).
Further, in the electronic device, the electret element 10 according to the present embodiment can convert electrical energy received via the electrode layer (C) into mechanical energy. As a result, the electret film (A) according to the present embodiment is deformed, vibrates, and can generate sound.
The electronic device according to this embodiment can be manufactured based on known information, for example.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can also be adopted.
Moreover, the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.

Hereinafter, the present embodiment will be described in detail with reference to examples and comparative examples. It should be noted that the present embodiment is not limited to the description of these examples.

1. Measuring method

(1) Generated voltage with respect to load An electret element cut into a square shape with a side of 10 cm and chamfered with a radius of about 1 cm was sandwiched between aluminum plates with a thickness of 1 mm, and both sides of the sample were measured with an electrometer (Model 617 manufactured by KEITHLEY). Programmable Electrometer). A compressive load of 0.2 N to 1 N was repeatedly applied in the thickness direction of the sample with a tensile tester (TENSILON RTG-1250, manufactured by A&D), and the voltage generated at that time was measured with an electrometer. The measurement was repeated 5 times, and the average value of the peak-to-peak values was adopted.

(2) Glass transition temperature A DSC (Differential Scanning Calorimetry) apparatus (DSC-60A manufactured by Shimadzu Corporation) was used to measure the glass transition temperature of the electret film.

(3) Water absorption Weight increase rate of the electret film and non-adhesive insulating layer when the electret film and non-adhesive insulating layer are immersed in water at a temperature of 23° C. for 24 hours according to ASTM D570. (=100×weight increase/weight of electret film before immersion) was measured as water absorption.

(4) Dielectric constant A precision LCR meter (manufactured by Agilent Technologies, 4284A) was used to measure the dielectric constant of the electret film at a frequency of 1 MHz.

(5) Volume Resistivity The volume resistivity (Ω·cm) of the non-adhesive insulating layer (B) was measured according to ASTM D257 at 23° C. at an applied voltage of 500 V one minute after voltage application.

[Example 1]
(Preparation of electret film (A1))
Ethylene and tetracyclo[4.4.0.1 ^2,5 . 1 ^7,10 ]-3-dodecene (ethylene content: 69 mol%, tetracyclo[4.4.0.1 ^2,5 .1 ^7,10 ]-3-dodecene content: 31 mol%), 0.05 parts by mass of ethylene bisstearic acid amide (Kao Wax EB-FF, manufactured by Kao Corporation) as a lubricant is added to the outside of the pellets. By extrusion molding, an unstretched nonporous film composed of a cyclic olefin polymer was obtained. Thereafter, the film was heated and stretched at a draw ratio of 2 in both the machine direction and the transverse direction using a biaxial stretching machine to obtain a non-porous film having a thickness of 50 μm.
Next, a non-porous film was fixed between a needle-shaped electrode connected to a DC high-voltage power supply and a ground electrode (inter-electrode distance: 35 mm). Here, a DC high voltage power source, a needle electrode and a ground electrode manufactured by Kasuga Denki Co., Ltd. were used for the device having a needle electrode and a ground electrode connected to a DC high voltage power source. Next, in an environment with a temperature of 23° C. and a humidity of 50% RH, a high direct current voltage (−20 kV) is applied to the non-porous film for 5 seconds to charge the non-porous film to electret film A1 (glass transition temperature : 125° C., water absorption: <0.01% by mass, dielectric constant at a frequency of 1 MHz: 2.3).

(Production of electret element)
As shown in FIG. 1, a PET film (manufactured by Toray Industries, Inc., product name: Lumirror S10, thickness: 50 μm, volume resistivity: 4 × 10 ¹⁷ Ω·cm, water absorption: 0.4% by mass), an aluminum foil (manufactured by Mitsubishi Aluminum Co., Ltd., FOIL, thickness 11 μm) as the electrode layer (C) was laminated to obtain an electret element. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Example 2]
(Preparation of electrode layer (C) with adhesive layer (D))
A water-based acrylic emulsion type adhesive (manufactured by 3M, SP-7533) was applied to one side of an aluminum foil (manufactured by Mitsubishi Aluminum Co., Ltd., FOIL, thickness 11 μm) to form a coating film. Then, the coating film was allowed to stand at 25° C. for 15 minutes and then dried by heating to obtain an electrode layer (C) with an adhesive layer (D).

(Production of electret element)
As shown in FIG. 2(a), a PET film (manufactured by Toray Industries, Inc., product name: Lumirror S10, Thickness: 50 μm, volume resistivity: 4×10 ¹⁷ Ω·cm, water absorption: 0.4% by mass), the electrode layer (C) with the adhesive layer (D) is attached to the non-adhesive The insulating layer (B) and the adhesive layer (D) were bonded together so as to be in contact with each other to obtain an electret element. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Example 3]
(Preparation of non-adhesive insulating layer (B) with adhesive layer (D))
PET film (manufactured by Toray Industries, Inc., product name: Lumirror S10, thickness: 50 μm, volume resistivity: 4×10 ¹⁷ Ω·cm, water absorption: 0.4% by mass) as the non-adhesive insulating layer (B) A water-based acrylic emulsion adhesive (manufactured by 3M, SP-7533) was applied to one side of the substrate to form a coating film. Then, the coating film was allowed to stand at 25° C. for 15 minutes and then dried by heating to obtain a non-adhesive insulating layer (B) with an adhesive layer (D).

(Production of electret element)
As shown in FIG. 2(b), on both sides of the electret film A1, a PET film (manufactured by Toray Industries, product name: Lumirror S10, thickness: 50 μm, volume resistivity An aluminum foil (manufactured by Mitsubishi Aluminum Co., Ltd., FOIL, thickness 11 μm), which is the electrode layer (C) ^, was laminated via an electrode layer (C). Next, on both sides of the obtained laminate, a non-adhesive insulating layer (B) with an adhesive layer (D) is applied so that the electrode layer (C) and the adhesive layer (D) are in contact with each other. They were laminated to obtain an electret element. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Example 4]
As the non-adhesive insulating layer (B), a PET film (manufactured by Toray Industries, product name: Lumirror S10, thickness: 12 μm, volume resistivity: 4×10 ¹⁷ Ω·cm, water absorption: 0.4% by mass) An electret element was obtained in the same manner as in Example 1 except that Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Comparative Example 1]
As shown in FIG. 3(a), aluminum foil (manufactured by Mitsubishi Aluminum Co., Ltd., FOIL, thickness 11 μm) was laminated on both sides of the electret film A1 obtained in Example 1 to obtain an electret element. That is, an electret element was obtained in the same manner as in Example 1 except that the non-adhesive insulating layer (B) was not provided. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Comparative Example 2]
Aluminum deposition films were formed by vacuum deposition on both surfaces of the electret film A1 obtained in Example 1, and an electret element was produced in which electrode layers (C) were formed on both surfaces.
Here, since the aluminum vapor deposition films are formed on the entire surfaces of the electret film A1, there is no electrically insulated region between the electret film A1 and the aluminum vapor deposition films. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Comparative Example 3]
An electret element as shown in FIG. 3(b) was obtained in the same manner as in Example 2, except that the non-adhesive insulating layer (B) was not provided. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Comparative Example 4]
As shown in FIG. 3(c), on both sides of the electret element obtained in Comparative Example 3, a PET film (manufactured by Toray Industries, product name: Lumirror S10, thickness: 50 μm, volume resistivity: 4×10 ¹⁷ Ω·cm, water absorption: 0.4 mass %) to obtain an electret element. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

[Comparative Example 5]
(Preparation of non-adhesive insulating layer (B) with adhesive layer (D))
PET film (manufactured by Toray Industries, Inc., product name: Lumirror S10, thickness: 50 μm, volume resistivity: 4×10 ¹⁷ Ω·cm, water absorption: 0.4% by mass) as the non-adhesive insulating layer (B) A water-based acrylic emulsion adhesive (manufactured by 3M, SP-7533) was applied to one side of the substrate to form a coating film. Then, the coating film was allowed to stand at 25° C. for 15 minutes and then dried by heating to obtain a non-adhesive insulating layer (B) with an adhesive layer (D).

(Production of electret element)
As shown in FIG. 3(d), on both surfaces of the electret film A1 obtained in Example 1, a non-adhesive insulating layer (B) with a tacky adhesive layer (D) is attached to the electret film A1. and the adhesive layer (D) were in contact with each other to obtain a laminate. Next, aluminum foil (manufactured by Mitsubishi Aluminum Co., Ltd., FOIL, thickness 11 μm) was laminated as an electrode layer (C) on both surfaces of the obtained laminate to obtain an electret element. Various evaluations were performed on the obtained electret element. Table 1 shows the results obtained.

As is clear from Table 1, it was found that the electret elements of the examples had a high generated voltage with respect to the load. Therefore, it can be understood that the application to various electronic devices is useful.

A electret film B non-adhesive insulating layer C electrode layer D adhesive layer 10 electret element

Claims (15)

an electret film (A) made of a non-fluorinated resin;
A non-adhesive insulating layer (B) provided on at least one surface of the electret film (A);
an electrode layer (C) provided on the non-adhesive insulating layer (B);
An electret element comprising
According to ASTM D257, the volume resistivity of the non-adhesive insulating layer (B) at 23° C. is 1.0×10 ⁶ Ω·cm or more, which is measured at an applied voltage of 500 V one minute after voltage application. electret element . an electret film (A) made of a non-fluorinated resin;
A non-adhesive insulating layer (B) provided on at least one surface of the electret film (A);
an electrode layer (C) provided on the non-adhesive insulating layer (B);
An electret element comprising
An electret element in which the non-adhesive insulating layer (B) has a water absorption of 0.5% by mass or less when immersed in water at a temperature of 23° C. for 24 hours, as measured according to ASTM D570. In the electret element according to claim 1 or 2 ,
The electret element, wherein the non-adhesive insulating layer (B) has a thickness of 10 μm or more and 500 μm or less. In the electret element according to any one of claims 1 to 3 ,
An electret element in which the non-fluorine resin contains a cyclic olefin polymer. In the electret element according to any one of claims 1 to 4 ,
An electret element in which the non-adhesive insulating layer (B) comprises an insulating resin layer. In the electret element according to claim 5 ,
The electret element, wherein the insulating resin layer contains at least one selected from the group consisting of polyester-based resins, polyolefin-based resins, (meth)acrylic-based resins, styrene-based resins and fluorine-based resins. In the electret element according to any one of claims 1 to 6 ,
An electret element further comprising an adhesive layer (D) between the non-adhesive insulating layer (B) and the electrode layer (C). In the electret element according to any one of claims 1 to 7 ,
The electret element, wherein the electretized film (A) is a non-porous film. In the electret element according to any one of claims 1 to 8 ,
An electret element, wherein the electret film (A) has a glass transition temperature of 80° C. or higher. In the electret element according to any one of claims 1 to 9 ,
An electret element, wherein the electret film (A) has a dielectric constant of 3.0 or less at a frequency of 1 MHz. In the electret element according to any one of claims 1 to 10 ,
An electret element that is film-like or sheet-like. In the electret element according to any one of claims 1 to 11 ,
The electret element, wherein the electret film (A) has a thickness of 5 μm or more and 500 μm or less. In the electret element according to any one of claims 1 to 12 ,
An electret element that is a sensor element or a power generating element. An electronic device comprising the electret element according to any one of claims 1 to 13 . 15. The electronic device of claim 14 , wherein
An electronic device selected from a power generation device, a biosignal acquisition device, a vibration detection device, a shock detection device and a displacement detection device.

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