JP3253847B2 - Method and apparatus for manufacturing electret body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for manufacturing an electret body. According to the present invention, a dielectric body can be efficiently polarized, and for example, a surface-charged electret body whose surface is highly heterocharged (that is, charged by both positive and negative ions),
A piezoelectric electret body, a pyroelectric electret body, or the like can be manufactured.

[0002]

Conventionally, as a method for producing a surface-charged electret material such as electret fiber sheet, for example, Kokoku 3-54620 Patent, is described in KOKOKU 4-8539 Patent and Kokoku 5 -83283 No. JP- As described above, a method using a DC corona discharge has been generally known. According to this method, for example, as shown in FIG.
While the electretized fiber sheet 1 such as a nonwoven fabric is in contact with a ground electrode 8 made of a steel drum or a water electrode, a high DC voltage is applied between a discharge electrode 9 such as a wire electrode or a needle electrode and the ground electrode 8. And the fiber sheet 1 is electretized by DC corona discharge.

[0003] In the electret fiber sheet obtained by these methods, the electric charge is held in the constituent fibers as a polarization electric charge. That is, generally, the surface on the side to which a high DC voltage is applied is charged to the same polarity as the applied voltage, and the surface on the side in contact with the ground electrode is charged to the opposite polarity to the applied voltage. However, the degree and persistence of the charging were not always satisfactory. In the first place, as shown in FIG.
DC corona discharge based on a remarkable unequal electric field formed from the substrate and the flat electrode 8 has been used. In order to generate this corona discharge, it is necessary to generate a certain or more electric field strength between the needle-shaped electrode 9 and the flat plate electrode 8, that is, to make the electric field strength equal to or higher than the corona starting voltage. The corona start voltage increases as the distance between the needle electrode 9 and the flat electrode 8 increases.

For example, when the electretized object 1 shown in FIG. 1 is charged by corona discharge and the potential difference between the surface thereof and the corona discharge electrode (needle electrode) 9 falls below the corona start voltage, corona discharge does not occur. This is because the discharge electrode and the counter electrode (earth) are always linked in the DC corona. In order to further increase the surface potential (that is, the amount of charge on the surface) of the electretized body 1, it is necessary to apply a higher voltage. However, if the voltage is set too high, spark discharge may occur between the electrodes through a weak portion of the electretized body, causing damage such as making a large hole in the electretized body. In addition, when a thick nonwoven fabric such as felt is treated as an electretized body, the charge amount on the felt surface does not increase, so that reverse charge injection from the ground surface does not occur and the charge amount as a whole does not increase. . Therefore, even when the obtained felt was used as a filter, the effect was small and insufficient. [Journal of the Electrostatics Society of Japan Vol. 18, No. 2]
(1994), P. 119-127, and Journal of the Electrostatics Society of Japan Vol. 18, N
o. 5 (1994), P. 444-448].

Further, in the above-mentioned direct current corona discharge method, it is necessary to bring an electretized body such as a fiber sheet into close contact with a flat electrode surface such as a steel drum.
Therefore, for example, in the case of an object to be processed that is not flat, such as a mask or a pleated product, the charging process cannot be performed after processing into a finished product. That is, conventionally, after forming a fiber sheet or the like, the forming process into a product is performed after the charging process. However, there is a problem in that the charge is lost due to heat treatment during the forming process. In addition, if the electretized product is used for a long period of time, the effect of the electret is reduced, so that the electret may be required to be re-electretized. However, when the shape of the electretized body is a three-dimensional molded product,
With the conventional electretization method, it was difficult to perform the re-electretization process.

On the other hand, among electret bodies, an electret body exhibiting piezoelectricity is used for, for example, an acoustic element or a displacement element by utilizing its piezoelectricity. Conventionally, as a method for manufacturing a piezoelectric electret body, for example, a method in which an electrode is provided in direct contact with the surface of a dielectric to be processed and a high voltage is applied thereto has been known. In general, when a piezoelectric electret body is manufactured, the higher the applied voltage, the easier the polarization of the dielectric to be processed is, and the Curie temperature (the piezoelectric effect observed in the piezoelectric electret body in the low-temperature phase, As long as the temperature of the dielectric to be processed is higher, the polarization of the dielectric to be processed is more easily performed within a range where the phase transition occurs at that temperature and the temperature does not exceed the temperature at which the piezoelectric effect is not exhibited. However, if a certain high DC voltage is applied between the electrodes in the air, a discharge is generated between the electrodes at the end of the dielectric to be processed, and a dielectric breakdown of the air layer may occur. . When dielectric breakdown occurs in the air layer, a high voltage cannot be maintained, and the polarization efficiency is significantly reduced. Further, for example, if a high DC voltage is applied in the air while the temperature of the dielectric to be processed is increased by a heater or infrared rays or the like, the polarization of the dielectric to be processed becomes easy, but the temperature of the air also increases at the same time. Therefore, there is a disadvantage that the dielectric breakdown of the air layer is more likely to occur.

Therefore, as shown in FIG. 2, for example, a pair of electrodes 3a, 3b having a surface area slightly smaller than the surface area is provided on the polarization surface of the dielectric 2 to be processed into a predetermined shape. A method has been adopted in which a high DC voltage is applied between the electrodes 3a and 3b while the electrodes 2 and 3a and 3b are immersed in insulating oil 4 to polarize the dielectric 2 to be processed. For example, when a ceramic material is used as the dielectric 2 to be processed, after sintering the green sheet, a silver paste is applied to the surface and baked, so that the electrodes 3a and 3b are formed on the surface of the dielectric 2 to be processed. Then, by applying a DC high voltage in a state where the dielectric 2 to be processed and the electrodes 3a and 3b are immersed in the insulating oil 4, the air layer is polarized while preventing dielectric breakdown. Usually, in order to increase the polarization efficiency, the temperature of the insulating oil 4 is heated to about 100 ° C. to perform the polarization treatment. However, in the insulating oil, the temperature of the dielectric 2 to be processed may be increased more. Since it is difficult, dielectric breakdown of the air layer can be prevented, but there is a drawback that polarization efficiency is poor.

In the method shown in FIG. 2, the electrodes 3a and 3b need to be provided on the surface of the dielectric 2 to be processed, so that there is a disadvantage that the dielectric to be processed easily breaks down. Because, if there are minute irregularities on the surface of the dielectric to be processed,
Since the electrode itself provided on the surface also has minute irregularities, the electric field may be concentrated on the concave portion of the dielectric, causing dielectric breakdown. Also, if insulation breakdown occurs for other reasons,
Since the electrodes are in contact with each other, the charges accumulated on the electrodes may flow into the dielectric breakdown portion at a stretch and damage the dielectric to be processed. When dielectric breakdown occurs, the subsequent voltage does not increase, and the dielectric to be processed is greatly damaged. In this case, if the polarization plane of the dielectric to be processed is widened, the probability of dielectric breakdown increases, and at the same time, the amount of charge flowing into the dielectric breakdown portion increases, so that polarization of the dielectric to be processed having a large-area polarization plane is difficult. Met. In addition, since it is necessary to provide electrodes, the shape of the dielectric to be processed has been limited. Furthermore, in this method, it is necessary to provide an electrode on the surface of the dielectric material to be processed, and it is necessary to immerse the material in insulating oil, so that the operation is complicated and unsuitable for continuous processing.

[0009]

Accordingly, an object of the present invention is to limit the size and shape of a dielectric to be processed because it is not necessary to make contact with an electrode. However, it can process effectively, can apply a high voltage, can easily control the temperature of the dielectric material to be processed if necessary, and can process the dielectric material due to spark discharge or dielectric breakdown. It is an object of the present invention to provide an electretization means which is less likely to be damaged and which can satisfy the degree of charge and the durability.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is to provide a liquid crystal display device comprising: (1) a first ion-repellent electrode and a first ion-attractive electrode which are arranged to face each other and have a potential difference by a DC voltage; The positive ion or the negative electrode supplied from the first ion generating means is disposed between the electrode to be processed, which is disposed in a non-contact state with each of the electrodes, and the first ion repulsive electrode. Only one of the zwitterions is transferred from the first ion-repellent electrode to the first
(2) substantially simultaneously with the step (1), and (2a) non-contact with the dielectric to be processed, In a state, and between the second ion-repellent electrode disposed opposite to the first ion-repulsive electrode on the opposite side with respect to the dielectric to be processed, and the dielectric to be processed, Of the positive ion or negative ion supplied from the second ion generating means, the first ion
Only ions of the opposite polarity to the ions transferred from the ion generating means to the dielectric to be processed are in a non-contact state with the dielectric to be processed, and the first ions with respect to the dielectric to be processed The second ion repulsion is caused by a potential difference caused by a DC voltage provided between a second ion attraction electrode disposed opposite to the attraction electrode and the second ion repulsion electrode. Moving from the electrode in the direction of the second ion-attractive electrode and transferring it onto the dielectric to be processed, or (2b) in a non-contact state with the dielectric to be processed, and Of the positive ions or negative ions supplied from the second ion generating means disposed opposite to the first ion repulsive electrode with respect to the processing dielectric, the first ion generation is performed. From the means to the dielectric to be processed Transferring only ions of the opposite polarity to the charged ions of the dielectric to be processed from the second ion generating means to the dielectric to be processed by the attractive force of the charged dielectric to be processed. The method can be achieved by the method for manufacturing an electret body from the dielectric to be processed, characterized by including the following.

The present invention also provides an ion-repellent electrode; an ion-attractive electrode disposed opposite to the ion-repellent electrode; and an ion-repellent electrode between the ion-repellent electrode and the ion-repellent electrode. Means for arranging the dielectric to be treated in a non-contact state; a positive electrode between the dielectric to be treated and the ion-repellent electrode arranged by the means for arranging the dielectric to be treated; Ion generating means capable of supplying negative ions and / or negative ions;
And moving only one of the positive ion or the negative ion supplied by the ion generating means from the ion-repellent electrode toward the ion-attracting electrode. Means for generating a potential difference that can be transferred to the electrode by applying a DC voltage between the ion-repellent electrode and the ion-withdrawing electrode. The present invention also relates to a manufacturing apparatus.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present specification, the term "electret body" means a dielectric that is at least partially polarized. The electret body usually has a state in which at least a part of the surface is polarized, a state in which the surface and its vicinity are polarized, and a state in which not only the surface and its vicinity but also the inside is deeply polarized. There are various polarization states,
All of these electret bodies having various polarization states are included in the electret body of the present invention. Therefore,
The electret body of the present invention includes a surface-charged electret body whose surface and, in some cases, the vicinity of the surface are further polarized, an electret body polarized not only to the surface but also to the inside, for example, a piezoelectric or pyroelectric electret body. Is included.

The above-mentioned difference in the polarization state of the electret body according to the present invention is caused by, for example, a difference in the type and shape of the material of the dielectric to be processed and the electret forming conditions. For example, when a fiber sheet or film made of a dielectric material such as a polyolefin resin such as polyethylene or polypropylene, a polyester resin, or a polycarbonate resin is formed into an electret, mainly the front and back surfaces and the vicinity thereof, or a range extending somewhat into or out, are positive and negative. The charge is trapped to generate a polarization state, and an external electric field is generated. On the other hand, for example, when an inorganic ferroelectric such as barium titanate is electretized, titanium ions (Ti ⁴⁺ ) in the crystal structure are displaced by an external electric field, and polarization at the molecular level based on the displacement occurs. Micro-polarization (dipole) from the material surface layer to the inside
Are continuously obtained. The electret body such as barium titanate shows piezoelectricity, but shows almost no external electric field because the polarization at the molecular level is continuous.

In the present invention, as long as it is a dielectric,
An electret body can be obtained by treating an arbitrary molded body made of an arbitrary organic material or an inorganic material. As the organic dielectric material, various organic polymer compounds, for example,
Polyolefins such as polyethylene and polypropylene,
Polyester, polycarbonate, polyvinyl chloride, fluorinated ethylene propylene copolymer (FEP), polyvinylidene fluoride (PVDF), or vinylidene fluoride
Trifluoroethylene copolymer and the like can be mentioned. Among these, in particular, fluorinated ethylene propylene copolymer (FEP), polyvinylidene fluoride (PVD)
F) or a vinylidene fluoride-trifluoroethylene copolymer is a ferroelectric. When a ferroelectric is processed according to the present invention, a piezoelectric or pyroelectric electret body is generally obtained. Further, as the inorganic dielectric material, for example, ceramic materials and the like can be mentioned, and in particular,
It is preferable to use an inorganic ferroelectric substance such as lead zirconate titanate (PZT), lead titanate, or barium titanate.

Further, in the present invention, a composite material of an inorganic material and an organic material can be used. Examples of the composite material include a combination of a piezoelectric ceramic and rubber, or a combination of a piezoelectric ceramic and a thermoplastic resin (for example, polyacetal or polyvinylidene fluoride). In the conventional method, it is necessary to arrange the material to be processed between the electrodes in a state of being in contact with at least one of the electrodes, so that the shape of the material to be processed is a sheet or film having a thickness that can be arranged between the electrodes. While limited, the present invention has no such limitation in principle. That is, in the present invention, the positive or negative ions supplied from the ion generating means are moved from the ion repulsive electrode toward the ion attraction electrode and transferred to the target dielectric at a distance where they can be transferred to the dielectric to be processed. As long as the dielectric, the ion generating means, the ion repulsive electrode, and the ion attracting electrode can be arranged, the dielectric to be processed can have any shape. For example, a polyhedral, columnar, rod-like, spherical, hemispherical, elliptical, pyramidal, plate-like, corrugated, sheet-like, film-like, or pipe-like molded product is included. In addition, in the conventional method, it was necessary to perform processing to a final product after performing electretization due to process restrictions, but in the present invention, forming processing to the final product (for example, forming a face shape for a forming mask) (Together with a bowl shape) and then electretization. Furthermore,
The above-mentioned molded body can be a porous body or a non-porous body, and the porous body can be a fibrous porous body or a foam.

As the fibrous porous material, for example, a woven fabric,
Examples include a knit, a fibrous porous film, and a molded body made of a nonwoven fabric. As a nonwoven fabric, for example,
Examples of the nonwoven fabric include a dry nonwoven fabric, a spunbonded nonwoven fabric, a melt-blown nonwoven fabric, a hydroentangled nonwoven fabric, and a wet nonwoven fabric. Since these fibrous porous bodies have a large number of pores having a relatively large diameter, even if the fibrous porous bodies are made of a ferroelectric material, when treated in the present invention, generally, Specifically, a surface-charged electret body is obtained. In particular, a fiber sheet such as a melt-blown non-woven fabric or a hydro-entangled non-woven fabric to which no fiber oil agent or adhesive is attached is suitable for producing a surface-charged electret. Examples of the foam include an open-cell foam made of a resin such as polyolefin, polyester, or polyurethane.

In the present invention, the first ion generating means and the second ion generating means are means capable of generating positive ions and / or negative ions used for charging the dielectric to be processed. Although there is no particular limitation, for example, an AC creeping discharge element, an ionizer element, a DC corona-type ion generating element, or an AC corona-type ion generating element can be used. It is preferable to use an AC creeping discharge element in that discharge can be caused. FIG. 3 shows a representative embodiment of the present invention in which an AC creeping discharge element is used as each of the first ion generating means and the second ion generating means. In this embodiment, two AC surface discharge elements 2
1 and 22 are arranged so as to face each other with a predetermined space. Each of the AC creeping discharge elements 21 and 22 has a structure in which discharge electrodes 41 and 42 are supported on one surface of dielectrics 31 and 32 and induction electrodes 51 and 52 are supported on the other surface. Two AC creeping discharge elements 21 and 22 are arranged such that surfaces carrying 41 and 42 face each other. The discharge electrodes 41 and 42 and the induction electrodes 51 and 52 are
As shown in FIG. 3, they are connected to AC power supplies 61 and 62, respectively. Generally, when a surface discharge is generated using an AC surface discharge element, the discharge electrode is grounded, whereas in the present invention, each discharge electrode 41, 42 is connected to a DC power source 7 respectively.
1, 72. In addition, each DC power supply 71, 72
The induction electrodes 5 are connected via the AC power supplies 61 and 62, respectively.
1 and 52 will also be connected. Generally AC power supply 6
Reference numerals 1 and 62 each include an AC generator and a transformer, and the DC power supplies 71 and 72 can be connected to a secondary ground terminal of the transformer.

The two AC surface discharge elements 21 shown in FIG.
22, the dielectric 11 to be processed is arranged in a non-contact state with those elements, and when an AC high voltage is applied from the AC power supplies 61 and 62, the discharge electrodes 41 and 42 cause the discharge electrode supporting surface of the dielectric to be applied. Ionization occurs along the side, and both positive and negative ions are generated, and creeping discharge occurs. At this time, when DC voltages V1 and V2 of different potentials are simultaneously applied to the discharge electrodes 41 and 42 from the DC power supplies 71 and 72, respectively, between the AC surface discharge elements 21 and 22 (that is, between the discharge electrodes 41 and 42). ), A DC electric field (hereinafter sometimes referred to as a charged electric field) is formed. Note that each DC voltage is simultaneously applied to the induction electrodes 51 and 52. For example, a positive voltage V1 is applied to the discharge electrode 41 of the AC surface discharge element 21.
Is applied to the discharge electrode 42 of the AC creeping discharge element 22 when each of the AC creeping discharge elements 2 generated when a negative voltage V2 is applied.
FIG. 4 shows the AC waveforms at 1 and 22. That is, the ground potential (0 V: x in FIG. 4) is applied to the AC surface discharge element 21.
Is applied with the DC positive potential V1 (FIG. 4A), the AC wave of the induction electrode 51 (FIG. 4B)
The voltage is increased by one, and the potential of the discharge electrode 41 also becomes V1. on the other hand,
Since a negative DC potential V2 (c in FIG. 4) is applied to the AC creeping discharge element 22 with respect to the ground potential (0 V: x in FIG. 4), the AC wave (d in FIG. 4) of the induction electrode 52 is The voltage drops by the DC component V2, and the potential of the discharge electrode 42 also becomes V2.

When a charged electric field is formed between the AC surface discharge elements 21 and 22 in this way, the discharge electrodes 41 and 42 function as an ion attracting electrode and an ion repelling electrode, respectively. For example, of the positive ions and the negative ions generated on the dielectric surface of the AC surface discharge element 21, only the positive ions are discharged from the discharge electrode 41 acting as the first ion repulsive electrode to the first ion attraction. It selectively moves in the direction of the discharge electrode 42 acting as an electrode, adheres to the dielectric material 11 disposed in the middle thereof, and charges the dielectric material to be processed. On the other hand, of the positive ions and the negative ions generated on the dielectric surface of the AC surface discharge element 22, only the negative ions are the discharge electrodes 42 acting as the second ion repulsive electrodes.
Electrode 41 acting as a second ion-attractive electrode from
, And adheres to the dielectric to be processed 11 arranged in the middle thereof, and charges the dielectric to be processed. Thus, the dielectric 11 to be treated is simultaneously treated with positive ions from one side and negative ions from the other, and the dielectric 11 to be treated is highly hetero-charged (ie charged by both positive and negative ions). Is done. The dielectric material 1 to be processed is charged by electric charges charged on both surfaces of the dielectric material 11 to be processed.
An electric field is formed inside 1 to polarize the dielectric 11 to be processed.

The DC voltages V1 and V2 only need to be different, and one may be ground and the other may be at a positive potential or a negative potential. Also in this case, the discharge electrodes 41 and 42 act as ion-repellent electrodes and ion-attractive electrodes with respect to the discharge electrodes 42 and 41 opposed to each other, so that the discharge electrodes 41 and 42 are formed on the dielectric surfaces of the AC surface discharge elements 21 and 22. Of the positive ions and negative ions, only one of the positive ions and the negative ions is selectively moved and adheres to the dielectric 11 to be disposed in the middle, and To charge. Note that, for example, a capacitor or the like is provided in the mechanism of the DC power supply devices 71 and 72 to prevent an AC wave from directly entering the DC power supply, thereby preventing a danger such as a short circuit.

The high-frequency AC voltage applied to generate the creeping discharge by the AC power supply is not particularly limited, but is preferably 0.2 KVp-p or more, more preferably 1 KVp-p or more (KVp-p is , Which indicates the voltage difference between the maximum value peak and the minimum value peak of the AC voltage). The upper limit of the AC voltage is not particularly limited as long as the dielectric of the surface discharge element is not damaged. The frequency is not particularly limited, but is preferably 0.1 to 100 KH.
z, more preferably 1 to 50 KHz. Voltage is 0.
When the frequency is less than 2 KVp-p, substantially no discharge occurs, and when the frequency is less than 0.1 KHz, an extremely high voltage is required for the discharge. When the frequency exceeds 100 KHz, the dielectric may be overheated and destroyed by dielectric heating. There is a problem such as occurrence of. The DC potential difference applied to the discharge electrodes 41 and 42 is not particularly limited as long as the desired charging is obtained and the dielectric breakdown does not occur, but is preferably 0.5 KV or more, and more preferably 0.5 KV or more. 1K
V or more. When the potential difference is less than 0.5 KV, a substantial charging amount becomes small, so that a sufficient charging effect cannot be obtained.

When a piezoelectric electret body is manufactured by the above-described method using the apparatus shown in FIG. 3, the applied DC voltage depends on the thickness of the object to be processed, the ease of polarization, and / or
Although it cannot be generally specified because it is affected by the polarization temperature, the value (V / V) obtained by dividing the applied DC voltage (V: unit = KV) by the thickness (t: unit = mm) of the object to be processed. t)
Is preferably 5 KV / mm or more. Discharge electrode 41,
When a very high charging voltage is applied to 42, the electric field strength can be reduced by increasing the distance between the electrodes, and damage to the dielectric to be processed due to spark discharge between the electrodes can be prevented. However, if the distance between the electrodes is too large,
Since the electric field intensity becomes too small and the moving speed of ions becomes slow, the amount of ions adhering to the dielectric to be processed becomes small, and the charging efficiency of the electret body is undesirably reduced.

As the AC creeping discharge element used in the present invention, a known element can be used. For example, plate or sheet glass, ceramic, plastic, or the like can be used for the dielectric. The thickness of the dielectric is not particularly limited, but if it is too thick, a very high voltage is required to discharge, and if it is too thin, the mechanical strength is reduced, and dielectric breakdown is likely to occur. Is preferred. As shown in FIG. 5, as the discharge electrode 41 of the AC creeping discharge element 21, a surface of a plastic film or the like is coated with a conductive paint, or a metal layer or a conductive resin layer is used as a grid electrode or a mesh electrode. Or a grid electrode or a mesh electrode made of a conductive metal such as aluminum or copper.

It is desirable that the discharge electrode 41 has a structure having an opening so that the dielectric 31 is exposed from below the discharge electrode 41 to the surface. The induction electrode 51 is also not particularly limited, but may be one in which a conductive paint is applied to the surface of a plastic film or the like, a plate electrode or a net-like electrode is formed by a metal layer or a conductive resin layer, or aluminum or copper. For example, a flat electrode or a reticulated electrode formed of a conductive metal or the like is suitable. In an AC creeping discharge element,
It is desirable that the length of the dielectric is longer than the length of the discharge electrode and the length of the induction electrode so that a direct discharge does not occur between the discharge electrode and the induction electrode at the end of the AC creeping discharge element. If the length of the dielectric cannot be made sufficiently long, it is preferable to insulate the end face of the induction electrode or the whole of the induction electrode with a dielectric such as a ceramic film or a polymer compound film. In addition, it is preferable to cover the discharge electrode with a dielectric film such as a ceramic film or a polymer compound film because consumption of the discharge electrode due to creeping discharge can be prevented.

The means for arranging the dielectric to be processed in a non-contact state with the ion generating means in the middle of ion generating means such as an AC creeping discharge element includes the action of ions on the dielectric to be processed. It is not particularly limited as long as it is a means capable of arranging the dielectric to be processed in the charged space without substantially hindering it.For example, if the dielectric to be processed is a continuous body such as a sheet, A support means such as a roll may be provided on both sides of the charged space, and may be arranged between the rolls so as to pass through the dielectric to be processed and pass through the charged space. When the dielectrics to be processed are independent one by one like a molding mask, a carrier made of an insulating mesh or the like is passed between the rolls described above, and the dielectric to be processed is placed thereon. It may be arranged so as to pass through the charged space.

In FIGS. 3 and 5, the AC creeping discharge element in the form of a flat plate has been described. However, the AC creeping discharge element may have various shapes. For example, by performing the present invention using a pair of AC creeping discharge elements 21 and 22 having an arc-shaped cross section, a dielectric to be processed having an arc-shaped cross section can be efficiently processed. Further, as shown in FIG. 6, a cylindrical dielectric to be processed can be efficiently processed by using a pair of cylindrical AC surface discharge elements 21 and 22. That is, the cylindrical AC creeping discharge element 21 having a large diameter and the cylindrical AC creeping discharge element 22 having a small diameter are arranged concentrically with a predetermined space. Each of the AC surface discharge elements 21 and 22 has discharge electrodes 41 and 4 on one surface of dielectrics 31 and 32, respectively.
2 and carrying the induction electrodes 51 and 52 on the other surface, and the two AC creeping discharge elements 21 and 22 are arranged such that the surfaces carrying the discharge electrodes 41 and 42 face each other.
22 is arranged. Discharge electrodes 41 and 42 and induction electrodes 51 and 5
2 is connected to an AC power supply (not shown), and the discharge electrodes 41 and 42 are connected to a DC power supply (not shown), respectively, as in the embodiment shown in FIG. The induction electrodes 51 and 52 are also connected to a DC power supply via an AC power supply). In the present invention, since the polarization can be performed without being restricted by the shape of the dielectric to be processed, the cylindrical dielectric to be processed can be processed even if an AC surface discharge element having a shape other than the cylindrical shape is used. be able to.

The present invention can be implemented by a combination of an AC creeping discharge element and a DC corona discharge element. That is, FIG. 7 shows a typical embodiment of the present invention in which an AC creeping discharge element is used as the first ion generating means and a DC corona discharge element is used as the second ion generating means. In the present invention, the DC corona discharge element is not particularly limited as long as it has an electrode capable of causing a DC corona discharge with the dielectric to be processed. For example, a discharge electrode such as a needle electrode Can be cited. In this embodiment, AC surface discharge element 21 and DC corona discharge element 23 are arranged so as to face each other with a predetermined space. The AC creeping discharge element 21 is made of the dielectric material 3 as described above.
1 has a structure in which the discharge electrode 41 is supported on one surface and the induction electrode 51 is supported on the other surface, and the two elements are arranged such that the surface supporting the discharge electrode 41 faces the DC corona discharge element 23. 21 and 23 are arranged. Discharge electrode 41
And the induction electrode 51 are connected to an AC power supply 61 in the same manner as described above. In addition, the discharge electrode 41 is grounded in the same manner as when a general creeping discharge is generated.

On the other hand, at least one (preferably a plurality of DC corona discharge elements)
In the embodiment shown in FIG. 7, eight ( 8 ) discharge electrodes (for example, needle electrodes) 43 are included. Although the type of the discharge electrode in the DC corona discharge element is not particularly limited, FIG. 7 shows a wire-like electrode. In another embodiment, the DC corona discharge element 23
There is also a means for grounding and applying a DC voltage to the discharge electrode 41 of the AC surface discharge element 21.

A dielectric material 11 to be processed is arranged between an AC creeping discharge element 21 and a DC corona discharge element 23 shown in FIG. 7 in a non-contact state with these elements, and an AC high voltage is applied from an AC power supply 61. Then, both positive and negative ions are generated on the discharge electrode supporting surface side of the dielectric surface, and creeping discharge occurs. At this time, when a high DC voltage is applied from the DC power supply 73 to the discharge electrode 43 at the same time, between the AC surface discharge element 21 and the DC corona discharge element 23 (that is, the discharge electrode 41 of the AC surface discharge element 21 and the DC corona discharge Element 2
A DC electric field (charged electric field) is formed between the discharge electrode 43 and the third discharge electrode 43). In this charged electric field, the AC surface discharge element 21
The discharge electrode 41 functions as an ion repellent electrode, and the discharge electrode 43 of the DC corona discharge element 23 functions as an ion attracting electrode. That is, of the positive polarity ions and the negative polarity ions generated on the dielectric surface of the AC creeping discharge element 21, only ions having a polarity opposite to the voltage polarity applied to the discharge electrode 43 are discharged from the discharge electrode 43 of the DC corona discharge element 23. And moves in the direction of the DC corona discharge element 23, adheres to the dielectric 11 to be disposed in the middle thereof, and charges the dielectric to be treated. Further, as the charged state of the dielectric 11 to be processed progresses, corona discharge is generated from the discharge electrode 43 of the DC corona discharge element 23 to the dielectric to be processed 11 and attracted from the AC creeping discharge element 21. Ions having a polarity opposite to that of the processed ions
And charges the dielectric to be processed. In this way, the processed dielectric material 11 is simultaneously treated with positive ions from one side and negative ions from the other, and is highly heterocharged. An electric field is formed inside the dielectric to be processed 11 by the electric charges charged on both surfaces of the dielectric to be processed 11, and the dielectric to be processed 11 is polarized. In this method, the dielectric 11 to be processed is located as close as possible to the DC corona discharge element 23 than the AC surface discharge element 21 so that the corona discharge can be generated from the DC corona discharge element 23 at the lowest possible applied voltage. It is desirable to arrange.

The AC creeping discharge can be generated by the same high-frequency AC voltage and frequency as described above. The DC voltage applied to the DC corona discharge element is not particularly limited, but the amount of charge greatly depends on the distance between the dielectric to be processed and the DC corona discharge element. cm, more preferably 3-10
It is desirable to apply the voltage so as to be KV / cm. When the electric field intensity is less than 1 KV / cm, it becomes substantially difficult to discharge, and when the electric field intensity exceeds 15 KV / cm, a spark discharge may occur due to dielectric breakdown of air. Since these values largely depend on the shape of the electrode and the material of the dielectric to be processed, they may be used outside the above range.

The present invention can be carried out by using an ionizer element as each of the first ion generating means and the second ion generating means, and a typical embodiment is shown in FIG. In this embodiment, two ionizer elements 2
4 and 25 are arranged with a predetermined space therebetween. Each of the ionizer elements 24 and 25 is a wire electrode,
DC corona discharge electrodes 84a, 85 composed of needle-like electrodes, etc.
a, earth electrodes 84b and 85b, and guide plates 84c and 85c for sending generated ions into the charged space.
a, 75a (74a and 75a have opposite polarities), and the ground poles 84b, 85b are connected to the ground, respectively. Each of the two ionizer elements 24 and 25 generates a positive ion and a negative ion by ionizing a reaction gas (for example, air) supplied from a direction indicated by an arrow B by applying a high DC voltage. Then, the light is emitted from the guide plates 84c and 85c in the direction indicated by the arrow C. On the other hand, the ion transfer electrodes 44 and 45
Are connected to DC power supplies 74a and 75a, respectively.
Since the potential polarity is the same as a and 85a, the ion transfer electrode 44 acts as an ion-repellent electrode for ions emitted from the guide plate 84c, and acts as an ion-repellent electrode for ions emitted from the guide plate 85c. Acts as an ion attracting electrode. On the other hand, the ion transfer electrode 45 is
It acts as an ion attracting electrode for ions emitted from c, and acts as an ion repellent electrode for ions emitted from the guide plate 85c. Therefore, FIG.
As shown in (2), the positive ions emitted from the ionizer element 24 move from the ion transfer electrode 44 toward the ion transfer electrode 45 and adhere to the dielectric 11 to be processed arranged in the middle thereof. Charge the processing dielectric. On the other hand, the negative ions discharged from the ionizer element 25 move from the ion transfer electrode 45 to the ion transfer electrode 44, and the processing target dielectric 1 disposed in the middle thereof moves.
1 and charges the dielectric to be processed. In this way, the processed dielectric material 11 is simultaneously treated with positive ions from one side and negative ions from the other, and is highly heterocharged. An electric field is formed inside the dielectric to be processed 11 by the electric charges charged on both surfaces of the dielectric to be processed 11, and the dielectric to be processed 11 is polarized.

The present invention can also be carried out by using a DC corona-type ion generating element as each of the first ion generating means and the second ion generating means, and a typical embodiment is shown in FIG. In this embodiment, two DC corona-type ion generating elements 26 and 27 are arranged so as to face each other with a predetermined space. Each DC corona type ion generating element 2
6 and 27 are composed of counter electrodes 86a and 87a and discharge electrodes 86b and 87b, respectively. The counter electrodes 86a and 87a are respectively DC power supplies 76a and 77a (however, 76a and 77a
The discharge electrodes 86b and 87b are connected to DC power supplies 76b and 77b, respectively (however, 76b and 77b have opposite polarities). The DC corona type ion generating elements 26 and 27 shown in FIG. 9 have five counter electrodes 86a and 8 respectively.
7a and four discharge electrodes 86b and 87b, but the number of electrodes can be changed according to the environment or purpose of use. The counter electrodes 86a, 87a and the discharge electrode 86
The b and 87b are not particularly limited as long as they can generate corona discharge. For example, a rod-shaped electrode can be used as a counter electrode, and a linear electrode or a needle-shaped electrode can be used as a discharge electrode.

In the DC corona-type ion generating element 26, the counter electrodes 86 from the DC power supplies 76a and 76b, respectively.
DC voltages V11 and V12 having the same polarity and different potentials are applied to the a and the discharge electrode 86b. Voltage V1
When the potential difference between 1 and V12 is greater than the electric field strength at which corona discharge occurs, and the absolute value of voltage V12 is greater than the absolute value of voltage V11, the voltage polarity of the voltage applied by DC power supplies 76a and 76b is the same. The ions are applied to the counter electrode 86
a and the discharge electrode 86b. In this case, if the voltages V11 and V12 are, for example, negative voltages, the counter electrode 86a and the discharge electrode 86b of the DC corona-type ion generator 26 are used.
And negative ion is generated. Also, in the DC corona-type ion generating element 27, the DC power supplies 77a and 7
7b to the counter electrode 87a and the discharge electrode 87b, respectively, apply DC voltages V13 and V14 having opposite polarities and different potentials from the voltage polarities applied by the DC power supplies 76a and 76b, respectively, and a potential difference between the voltages V13 and V14. Is larger than the electric field intensity at which corona discharge occurs and the absolute value of the voltage V14 is larger than the absolute value of the voltage V13, a voltage is generated between the counter electrode 86a and the discharge electrode 86b of the DC corona-type ion generating element 26. Ions of opposite polarity to the ions,
It is generated between the counter electrode 87a and the discharge electrode 87b. In this case, if the voltages V13 and V14 are, for example, positive voltages, positive ions are generated between the counter electrode 87a and the discharge electrode 87b of the DC corona-type ion generating element 27.

At this time, a DC electric field (charged electric field) is simultaneously formed between the DC corona-type ion generating element 26 and the DC corona-type ion generating element 27, so that the counter electrode 86a, the discharge electrode 86b, and the counter electrode 87a. And discharge electrode 87b
Act as an ion-repellent electrode and an ion-attractive electrode, respectively. For example, the voltages V11 to V1 exemplified above
4, the negative ions generated in the DC corona-type ion generating element 26 are displaced from the counter electrode 86a and the discharge electrode 86b acting as ion-repulsive electrodes to the counter electrode 87a and discharge electrode 86 acting as ion-attractive electrodes. 87b, and the dielectric material 11 to be treated
And charges the dielectric to be processed. On the other hand, positive ions generated in the DC corona-type ion generating element 27 are converted into a counter electrode 87a and a discharge electrode 87 that act as ion-repellent electrodes.
b from the counter electrode 86a acting as an ion-withdrawing electrode
And moves in the direction of the discharge electrode 86b, adheres to the dielectric 11 to be processed arranged in the middle thereof, and charges the dielectric to be processed. Thus, the dielectric 11 to be processed is highly hetero-charged and polarized as before.

The distance between the counter electrode and the discharge electrode capable of causing a DC corona discharge is preferably about 1 mm to 20 mm, and the potential difference between them depends on the electrode shape or distance, but is preferably about 0.1 KV to 20 KV. . The potential difference between the DC corona-type ion generating element 26 and the DC corona-type ion generating element 27 is not particularly limited,
Preferably, it is 1 KV or more. When the potential difference is less than 1 KV, a substantial charging amount becomes small, so that a sufficient charging effect cannot be obtained. The upper limit of this potential difference is not particularly limited as long as it does not cause dielectric breakdown. Alternatively, a DC corona-type ion generating element in which corona discharge occurs at both the counter electrode and the discharge electrode (ambipolar corona) can be used. The generating element has higher charging efficiency.

The present invention can be carried out by using an AC corona-type ion generating element as each of the first ion generating means and the second ion generating means. A typical embodiment is shown in FIG. In this embodiment, two AC corona type ion generating elements 28 and 29 are arranged so as to face each other with a predetermined space. Each of the AC corona-type ion generating elements 28 and 29 includes induction electrodes 88a and 89a and discharge electrodes 88b and 89b, respectively.
And discharge electrodes 88b and 89b are connected to AC power supplies 68 and 6 respectively.
I'm in contact with 9. In this embodiment, each induction electrode 8
8a and 89a are connected to DC power supplies 78 and 79, respectively, and the DC power supplies 78 and 79 are also connected to AC power supplies 68 and 69, respectively. Generally, the AC power supplies 68 and 69 include an AC generator and a transformer, and can be connected to the DC power supplies 78 and 79 from a secondary ground terminal of the transformer.
Each of the AC corona type ion generating elements 28 and 29 shown in FIG. 10 has five induction electrodes 88a and 89a and four discharge electrodes 88b and 89b, but the number of electrodes is changed according to the environment or purpose to be used. can do. The induction electrodes 88a and 89a are, for example, as shown in FIG.
It is preferable to cover with dielectrics 38 and 39 made of glass, ceramic, plastic or the like. This is because spark discharge can be prevented and stable corona discharge can be performed.

Two AC corona type ion generating elements 28,
29, the dielectric 11 to be processed is arranged in a non-contact state with these elements, and when an AC high voltage is applied from AC power supplies 68, 69, the discharge electrodes 88b, 89b and the induction electrodes 88a,
89a, both positive and negative ions are generated. At this time, when DC voltages V21 and V22 having different potentials are applied from the DC power supplies 78 and 79 at the same time, the DC power is applied between the AC corona-type ion generating elements 28 and 29 in the same manner as in the case of the AC creeping discharge element described above. World (hereinafter,
(Sometimes referred to as a charged electric field). When a charged electric field is formed between the AC corona-type ion generating elements 28 and 29, the induced electrodes 88a and 89a and the discharge electrodes 88b and 8
9b acts as an ion-repellent electrode and an ion-attractive electrode, respectively. For example, the positive voltage V2
When 2 is applied, only the negative ions of the positive ions and the negative ions generated in the AC corona-type ion generating element 28 are induced electrodes 88 acting as ion repulsive electrodes.
a from the discharge electrode 88b to the induction electrode 89a and the discharge electrode 89b acting as an ion-attracting electrode,
It adheres to the dielectric to be processed 11 arranged in the middle thereof,
Charge the dielectric to be processed. On the other hand, of the positive ions and the negative ions generated in the AC corona-type ion generating element 29, only the positive ions act as the ion attracting electrode from the inducing electrode 89a and the discharging electrode 89b acting as the ion repelling electrode. Inducing electrode 88a and discharging electrode 88b
, And adheres to the dielectric to be processed 11 arranged in the middle thereof, and charges the dielectric to be processed. Thus, the dielectric 11 to be processed is highly heterocharged and polarized as described above.

The high-frequency AC voltage applied for generating the AC corona discharge by the AC power source is not particularly limited, but is preferably about 0.1 KVp-p to 50 K.
Vpp, and the frequency is not particularly limited, but is preferably 0.1 to 100 KHz. Voltage is 0.
When the frequency is less than 1 KVp-p, the discharge does not substantially occur, and when the frequency is less than 0.1 KHz, an extremely large voltage is required for the discharge. When the frequency exceeds 100 KHz, the dielectric may be overheated due to dielectric heating and may be destroyed. Problems. The distance between the inducing electrode and the discharge electrode capable of causing an AC corona discharge is about 0.1 mm to 1 mm.
0 mm is preferred. The potential difference between the AC corona-type ion generating element 28 and the AC corona-type ion generating element 29, that is, the voltage difference (V22-V
21) is not particularly limited as long as it does not cause dielectric breakdown, but is preferably 0.5 KV or more, more preferably 1 KV or more. When the potential difference is less than 0.5 KV, a substantial electrification amount becomes small, so that a sufficient electret effect cannot be obtained.

It is to be noted that the present invention is not limited to FIGS.
In addition to the combination shown in FIG. 10 and FIG. 10, a combination of an AC creeping discharge element and an ionizer element, a combination of an AC creeping discharge element and a DC corona-type ion generating element, and an AC creeping discharge element and an AC corona-type ion generating element Combination with element, combination of ionizer element and DC corona discharge element, combination of ionizer element and DC corona type ion generator, combination of ionizer element and AC corona type ion generator, DC corona type ion generator and AC The present invention can also be implemented by a combination of a corona-type ion generating element, a combination of a direct-current corona-type ion generating element and a direct-current corona discharge element, or a combination of an alternating-current corona-type ion generating element and a direct-current corona discharge element. The present invention does not include an embodiment in which a DC corona discharge element is used as each of the first ion generator and the second ion generator. As described above, in the charging process using a DC corona discharge element, it is necessary to apply a high voltage between the electrodes. If the voltage is too high, spark discharge or dielectric breakdown occurs, and damage to the dielectric to be processed is prevented. This is because it may occur. When a piezoelectric electret body is manufactured, the dielectric to be processed is polarized by the action of an electric field formed by the charge on the surface of the dielectric to be processed. With charging, it is difficult to provide a charge required to form a sufficient electric field required for polarization.

In the present invention, the step of transferring positive and / or negative ions from the ion generating means to the dielectric to be processed can be performed while the dielectric to be processed is heated. As the heating conditions, it is desirable to maintain the temperature of the dielectric in a temperature range from room temperature to a temperature lower than the melting point of the dielectric to be processed. In particular, when manufacturing a piezoelectric or pyroelectric electret body, the ion transfer is performed while maintaining the temperature of the ferroelectric substance from room temperature to a temperature lower than the Curie temperature of the dielectric substance to be processed. Preferably, a step is performed. The heating means is not particularly limited, and various conventionally known heating means, for example, a heater such as an oven or a heating wire, or an infrared ray can be used.

The temperature of the dielectric to be processed during the ion transfer step is appropriately set according to, for example, the type of the dielectric to be charged, the conditions of the charging, or the polarization state required for the electret body. You can choose. For example, when manufacturing a piezoelectric or pyroelectric electret body exhibiting high polarization efficiency, it is preferable to select a temperature as high as possible within a range not exceeding the Curie temperature of the dielectric material to be processed. However, in some cases, if the temperature of the dielectric to be processed at the exit of the ion transfer process region does not exceed the Curie temperature, the temperature may be higher than the Curie temperature during the process.

The heating means may be arranged so that the charging space and the heating space overlap, or may be arranged so that the charging space and the heating space are separated. Further, the heat treatment can be performed before the ion transfer step and / or during the ion transfer step. For example, FIG. 11 illustrates one embodiment of the present invention in which an ion transfer step and a heat treatment are separated, and heat treatment is performed before the ion transfer step. A pair of heating means (for example, heater 9
2 and 93) and a pair of ion generating means (for example, AC creeping discharge elements 21 and 22) are arranged in series, and an insulating mesh or the like is interposed therebetween. Is provided in the direction indicated by the arrow A. The dielectric material 11 to be transported on the transport body 94 is sufficiently heated first while passing between the heaters 92 and 93, and then the AC surface discharge element 2 is heated.
The charging process is performed while passing between 1 and 22. The degree of heating by the heaters 92 and 93 may be such that the target dielectric 11 is heated to a desired temperature when passing between the AC surface discharge elements 21 and 22. Generally, as the temperature of the dielectric to be processed is higher, the polarization of the dielectric to be processed is more easily performed. Therefore, the polarization efficiency of the electret body can be improved by heating the dielectric to be processed.

When the dielectric 11 to be processed is passed between the AC creeping discharge elements 21 and 22 for a sufficient time, the temperature of the dielectric to be processed during the charging process is lowered by heat radiation, so that the dielectric 11 is polarized. The dielectric to be processed 11 is cooled as it is. Generally, the polarization state can be better fixed by performing the ion transfer step in a high temperature state and subsequently cooling in a state where an electric field is applied, so that the polarization efficiency of the electret body can be further improved. .

In the present invention, since it is not necessary to bring the dielectric to be treated into contact with the ion generating means, the ion-repellent electrode and the ion-withdrawing electrode, it is possible to treat the dielectric with substantially any shape. it can. In addition, charge treatment can be performed simply by disposing or passing between a pair of ion generating means, an ion-repellent electrode, and an ion-attractive electrode, and temperature control such as heating or cooling of a dielectric to be processed is also easy. Since there is no complicated operation, it is suitable for continuous processing. In addition, the charge amount can be increased simply by increasing the charge voltage.

Further, in the aspect of the present invention utilizing a surface discharge, an ionizer, a DC corona type ion generating element and / or an AC corona type ion generating element, the discharge voltage applied to the ion generating means, the dielectric material to be treated, Since the charging voltage applied to the ion-repellent electrode and the ion-attractive electrode for causing ions to act on is substantially independent, the final charge amount is independent of the distance between both ion generating means, It depends only on the potential difference applied between the ion-repellent electrode and the ion-withdrawing electrode. For this reason, it is possible to form an electret without being limited by the shape of the dielectric to be processed. Furthermore, even in the case of a thick fiber sheet such as a felt, the conventional method of applying only the direct current corona does not effectively inject the opposite charge due to reverse ionization,
Although the amount of charge was low, in the present invention, positive and negative ions act from the front and back of the dielectric to be processed, respectively, so that it is not necessary to cause reverse ionization and the dielectric can be charged effectively. Further, in the present invention, the electric field intensity between the ion-repellent electrode and the ion-withdrawing electrode can be reduced (when a very high charging voltage is applied, the distance between the electrodes should be increased). The danger of damage to the dielectric to be processed due to spark discharge, dielectric breakdown, etc. has been greatly reduced. Even if a dielectric breakdown occurs in a part of the dielectric to be processed during the charging process, the amount of charge flowing from the periphery thereof is limited, so that the dielectric to be processed is less damaged. In addition, even if the dielectric breakdown occurs, since the polarization is caused by the charged electric charge, the charging process can be continued as it is, and even the dielectric to be processed having a large area can be polarized. For example, in the case of manufacturing a film electret used in a microphone, in a conventional method, the electret is formed in a state in which the film is in close contact with a ground electrode by a method such as a DC corona discharge after the film is formed.

On the other hand, in the present invention, since it is not necessary to bring the dielectric to be treated into close contact with the ion generating means such as an electrode plate, it is possible to carry out the charging treatment simultaneously with the formation of the film. For example, as shown in FIG.
(Or resin 12 discharged from inflation die)
However, while in the molten state, the charging process can be performed using, for example, the AC surface discharge elements 21 and 22.
Of course, it is also possible to charge while performing the stretching treatment. In addition, it is preferable to perform charging while performing heat treatment because the charge is stabilized. In addition, the shape of the film may be corrugated.

The electret body obtained according to the present invention can be used, for example, for filters, masks, dust-proof clothing, etc., or sensors such as microphones and radiation dosimeters, and can be used in medical fields such as adhesives for rheumatic treatment. Can also be used. Further, in particular, the piezoelectric or pyroelectric electret obtained according to the present invention can be used for, for example, a sound wave generator, a sound wave detector, an electronic filter, or a high voltage generator. , A piezoelectric buzzer, an ignition element, an acceleration sensor, a speaker, a deep wound probe, a medical deep probe, a blood pressure monitor, a blood flow monitor, a hydrophone, or a surface acoustic wave (SAW) filter.

[0048]

EXAMPLES The present invention will be described below in more detail with reference to examples, but these examples do not limit the scope of the present invention. Example 1 A polypropylene melt-blown nonwoven fabric having a basis weight of 45 g / m ² and a thickness of 0.7 mm was used as a sample. As the electret forming apparatus, the apparatus shown in FIG. 3 was used, and the distance between the electrodes of the opposing surface discharge elements was 40 mm. The sample is passed between the surface discharge element 21 and the surface discharge element 22 to generate a surface discharge at each surface discharge element by applying an AC voltage of 6 KVp-p and a frequency of 23 KHz, and a potential difference between the discharge electrodes. At 10 KV, the sample was charged for 1 minute. Atmospheric dust was passed through the obtained electret melt-blown nonwoven fabric at a surface wind speed of 5 cm / sec to obtain an initial pressure loss of 0.3 to 0.5 μm.
m of air dust was determined. The collection efficiency was determined by measuring the number of particles of 0.3 to 0.5 μm before and after passing through the meltblown nonwoven fabric with a particle counter.
The initial pressure loss was 1.1 to 1.5 mmaq, and the collection efficiency was 90 to 95%.

COMPARATIVE EXAMPLE 1 A discharge electrode composed of 20 wires each having a diameter of 30 μm and a length of 250 mm and a copper flat earth electrode were arranged at an interval of 20 mm. A voltage of 16 KV was applied between the discharge electrode and the ground electrode, and the same sample (polypropylene melt-blown nonwoven fabric) used in Example 1 was passed between the discharge electrode and the ground electrode, and charged for 1 minute. did. The resulting electret meltblown nonwoven fabric has an initial pressure loss of 1.1 to 1.5 mmaq and a collection efficiency of 50 to 60%.
Met. Despite the fact that the distance between the electrodes was shorter than in Example 1 and the electret was formed under the condition that the applied voltage was large,
It can be seen that the collection efficiency is very low, and the material is not sufficiently electretized.

Example 2 An electret melt-blown nonwoven fabric was obtained by repeating the operation of Example 1 except that the distance between the electrodes of the opposing surface discharge elements was 120 mm. The initial pressure loss of the obtained electret melt-blown nonwoven fabric is 1.1 to 1.
At 5 mmaq, the collection efficiency was 90-95%. It was found that the electret can be formed in the same manner as in Example 1 even when the distance between the electrodes is increased.

Embodiment 3 As the electret forming apparatus, an apparatus shown in FIG. 7 was used.
The creeping discharge element 21 was arranged at a distance of 40 mm from the corona discharge electrode 43 composed of 20 wires having a diameter of 30 μm and a length of 250 mm. Voltage 6KVp-p, frequency 23K
A creepage discharge is generated in the surface discharge element 21 by applying an alternating current of Hz, and a potential difference between the discharge electrode 43 and the surface discharge element 21 is set to 10 KV. The same sample (made of polypropylene) as used in Example 1 is used. The melt-blown nonwoven fabric) was passed through a position about 5 mm from the discharge electrode 43 and charged for 1 minute. The initial pressure loss of the obtained electret melt-blown nonwoven fabric was 1.2 to 1.6 mmaq, and the collection efficiency was 90 to 95%.

Example 4 As a sample, a hydroentangled nonwoven fabric having a basis weight of 120 g / m ² , comprising 85% by weight of polypropylene fibers and 15% by weight of a polyethylene / polypropylene composite fiber, and a basis weight of 80 g
/ M ² melt blown nonwoven fabric and polypropylene fiber 4
0% by weight and polyethylene / polypropylene composite fiber 60
A needle-punched nonwoven fabric having a basis weight of 120 g / m ² and a mask formed into a bowl shape along the shape of the face was used. As the electret forming apparatus, the apparatus shown in FIG.
The distance between the 22 discharge electrodes was 120 mm. The sample is passed between the surface discharge element 21 and the surface discharge element 22 to generate a surface discharge in each of the surface discharge elements by applying an alternating current having a voltage of 6 KVp-p and a frequency of 23 KHz. When the potential difference is 15 KV,
The sample was charged for 1 minute. A test dust containing silica fine particles having an average particle diameter of 0.45 μm at a concentration of 30 mg / m ³ was applied to the obtained electret mask at a surface wind speed of 8 cm / m ^3.
It was passed under the condition of seconds, and the initial pressure loss and the collection efficiency were determined. Note that the collection efficiency was determined by measuring the concentration of particles before and after passing through a mask with a light scattering densitometer. The initial pressure loss is 3.3 to 3.8 mmaq, and the collection efficiency is 99.88 to 9
It showed a very excellent collecting ability of 9.97%.

Comparative Example 2 The same apparatus as in Comparative Example 1 was used, except that the discharge electrode and the ground electrode were arranged at an interval of 60 mm. A voltage of 30 KV was applied between the discharge electrode and the earth electrode, and the same sample (mask) used in Example 4 was passed between the discharge electrode and the earth electrode to be charged for 1 minute. The initial pressure loss of the obtained electretized mask is 3.3 to 3.8 mm.
At aq, the collection efficiency was 80-90%. Although the distance between the electrodes was shorter than that in Example 4, and the electret was formed under the condition that the applied voltage was large, it was found that the collection efficiency was considerably low and the electret was not sufficiently formed. The collection efficiency in a state where the mask is not electretized is 75 to 85%.

Example 5 A needle-punched nonwoven fabric having a basis weight of 240 g / m ² and a thickness of 1.5 mm, comprising 80% by weight of polypropylene fibers and 20% by weight of rayon fibers, was used as a sample. As the electretization device, the device shown in FIG. 3 was used, and the distance between the discharge electrodes of the facing surface discharge elements 21 and 22 was set to 120 m.
m. The sample was passed between the surface discharge element 21 and the surface discharge element 22, and a voltage of 6 KVp-p and a frequency of 2
A creeping discharge is generated in each creeping discharge element by applying an alternating current of 3 KHz, and the potential difference between the discharge electrodes is reduced by 15.
The sample was charged to KV for 1 minute. Atmospheric dust was passed through the obtained electretized needle-punched nonwoven fabric at a surface wind speed of 5 cm / sec, and the initial pressure loss and the efficiency of collecting atmospheric dust of 0.3 to 0.5 μm were determined.
The collection efficiency was determined by measuring the number of particles of 0.3 to 0.5 μm before and after passing through the needle punched nonwoven fabric with a particle counter. Initial pressure loss is 1.0 to 1.3m
At maq, the collection efficiency was 90-96%.

Comparative Example 3 An apparatus similar to that of Comparative Example 1 was used, except that the discharge electrode and the ground electrode were arranged at an interval of 20 mm. A voltage of 16 KV was applied between the discharge electrode and the earth electrode, and the same sample (needle-punched nonwoven fabric) used in Example 5 was passed in contact with the earth electrode and charged for 1 minute. The initial pressure loss of the obtained electretized needle-punched nonwoven fabric is 1.0 to 1.3 mmaq, and the collection efficiency is 60 to
70%. Although the electret was formed under the condition that the distance between the electrodes was shorter than that of Example 5, the collection efficiency was considerably low, and it was found that the electret was not sufficiently formed.

Example 6 A 50 μm thick polytetrafluoroethylene (PTFE) film was used as a sample. The apparatus shown in FIG. 3 was used as the electret forming apparatus, and the distance between the discharge electrodes of the facing surface discharge elements 21 and 22 was set to 40 mm.
The sample is passed between the surface discharge element 21 and the surface discharge element 22 to apply a voltage of 6 KVp-p and an alternating current of 23 kHz to generate a surface discharge at each surface discharge element. , -2KV
Alternatively, the sample was charged for 1 minute by applying -5 KV, changing the DC power supply 72 to ground, and setting the potential difference between the discharge electrodes to 1 KV, 2 KV or 5 KV, respectively. The sample immediately after charging was placed on a copper ground plate, and the surface potential of the sample immediately after charging was measured using a Trek surface electrometer model 344.
The results are shown in Table 1 below.

[0057]

[Table 1] Applied voltage -1KV -2KV -5KV Surface potential (table) -800 to -900 -1500 to -1800 -4400 to -4700 Surface potential (back) +800 to +900 +1500 to +1800 +4400 to +4700 Surface potential is almost At the same location, its homogeneity was also high.

Comparative Example 4 An apparatus similar to that of Comparative Example 1 was used, except that the discharge electrode and the ground electrode were arranged at intervals of 20 mm. A voltage of -10 KV was applied between the discharge electrode and the earth electrode, and the same sample (PTFE film) used in Example 6 was passed between the discharge electrode and the earth electrode and charged for 1 minute. . Example 6
The surface potential immediately after charging was measured in the same manner as described above. Discharge surface -100 V or less Opposite surface -50 V or less The charge amount was very small, and the charged voltage also varied.

[0059]

According to the present invention, the size and shape of the object to be electretized are not limited. Therefore, even a non-flat or thick electretized object can be effectively treated, and a high voltage can be applied. The temperature of the dielectric to be processed can be easily controlled if necessary, and the electretized body is less likely to be damaged by spark discharge or dielectric breakdown, and from both directions of the electretized body. By applying charges of different polarities at the same time, electretization treatment that can satisfy the degree and persistence of charging can be performed. In charging the film, it can be charged immediately after the T-die or the inflation die, and can also be charged during various processing steps such as a stretching step.

Further, according to the present invention, the charge amount depends only on the potential difference between the ion-repellent electrode and the ion-withdrawing electrode, without depending on the electric field strength between the ion-repellent electrode and the ion-withdrawing electrode. In addition, the space between the ion electrodes can be sufficiently widened, and the processing space for the object to be electret can be widened. In addition, since charge treatment can be performed simply by disposing or passing between a pair of ion generating means, an ion-repellent electrode, and an ion-attractive electrode, a complicated operation is not required and is suitable for continuous processing. I have. Further, since it is not necessary to use a high electric field strength, there is no spark discharge between the electrodes and there is no damage to the member to be charged. While the invention has been described in accordance with specific embodiments, it should be understood that modifications obvious to those skilled in the art are within the scope of the invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a conventional apparatus used for corona discharge.

FIG. 2 is a cross-sectional view schematically showing a conventional apparatus for manufacturing a piezoelectric electret body.

FIG. 3 is a cross-sectional view schematically showing one embodiment of the device of the present invention using a pair of AC surface discharge elements.

FIG. 4 is a graph showing an AC waveform obtained when AC and DC voltages are applied using the apparatus of FIG. 3;

FIG. 5 is a perspective view of an AC surface discharge element used in the apparatus of the present invention.

FIG. 6 is a cross-sectional view schematically showing another embodiment of the device of the present invention using a pair of cylindrical AC surface discharge elements.

FIG. 7 is a cross-sectional view schematically showing one embodiment of the device of the present invention using an AC surface discharge element and a DC corona discharge element.

FIG. 8 is a cross-sectional view schematically showing one embodiment of the device of the present invention using a pair of ionizers.

FIG. 9 is a cross-sectional view schematically showing one embodiment of the device of the present invention using a pair of DC corona-type ion generating elements.

FIG. 10 is a cross-sectional view schematically showing one embodiment of the device of the present invention using a pair of AC corona-type ion generating elements.

FIG. 11 is an explanatory view schematically showing one embodiment of the device of the present invention provided with a heating device.

FIG. 12 is an explanatory view schematically showing one embodiment in which the apparatus of the present invention is used for T-die extrusion molding.

[Explanation of symbols]

11. Dielectric to be treated; 21, 22 AC creeping discharge element; 23 DC corona discharge element; 24, 25 ionizer; 26, 27 DC corona-type ion generating element; 28, 29 AC corona-type ion generator; 3
1, 32, 38, 39 ··· dielectric; 41, 42, 43,
86b, 87b, 88b, 89b ··· discharge electrode;
5 ·· Ion suction electrode; 51, 52, 88a, 89a
.Induction electrodes; 61, 62, 68, 69 .. AC power supplies; 7
1,72,73,74a, 75a, 76a, 76b, 7
7a, 77b, 78, 79 DC power supply; 84a, 85
a corona discharge electrode; 84b, 85b earth electrode; 8
4c, 85c guide plate; 86a, 87a counter electrode; 91 die; 92, 93 heater;
-Carrier.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-33370 (JP, A) JP-A-3-279450 (JP, A) JP-A-3-65206 (JP, A) JP-A-2- 118169 (JP, A) JP-A-2-263420 (JP, A) JP-B-3-54620 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) D06M 10/00 H01G 7 / 02

Claims (14)

(57) [Claims] (1) A first ion-repellent electrode and a first ion-attractive electrode, which are arranged to face each other and have a potential difference caused by a DC voltage, are not in contact with each other. Between the dielectric to be treated and the first ion-repellent electrode, the positive ion or the negative ion supplied from the first ion generating means, Moving the first ion-repellent electrode from the first ion-repellent electrode toward the first ion-attractive electrode by an electric potential difference, and transferring it onto the dielectric to be processed; and (2) substantially the same as the step (1). At the same time, (2a) a second ion disposed in a non-contact state with the dielectric to be processed, and opposite to the first ion-repellent electrode with respect to the dielectric to be processed. A second electrode is provided between the repulsive electrode and the dielectric to be processed. Of the positive ions or negative ions supplied from the ion generating unit, the first of said
Only ions of the opposite polarity to the ions transferred from the ion generating means to the dielectric to be processed are in a non-contact state with the dielectric to be processed, and the first ions with respect to the dielectric to be processed The second ion repulsion is caused by a potential difference caused by a DC voltage provided between a second ion attraction electrode disposed opposite to the attraction electrode and the second ion repulsion electrode. Moving from the electrode in the direction of the second ion-attractive electrode and transferring it onto the dielectric to be processed, or (2b) in a non-contact state with the dielectric to be processed, and Of the positive ions or negative ions supplied from the second ion generating means disposed opposite to the first ion repulsive electrode with respect to the processing dielectric, the first ion generation is performed. From the means to the dielectric to be processed Transferring only ions of the opposite polarity to the charged ions of the dielectric to be processed from the second ion generating means to the dielectric to be processed by the attractive force of the charged dielectric to be processed. A method for producing an electret body from the dielectric to be processed, comprising: 2. The method according to claim 1, wherein a piezoelectric electret body is manufactured. 3. The process according to claim 1, wherein in the step (1) and the step (2), the temperature of the dielectric to be processed is maintained in a temperature range from room temperature or higher to lower than the Curie temperature of the dielectric to be processed.
Or the method of claim 2. 4. The method according to claim 1, wherein a surface-charged electret body is manufactured. 5. The process according to claim 1, wherein in the step (1) and the step (2), the temperature of the dielectric to be processed is maintained in a temperature range from room temperature to lower than the melting point of the dielectric to be processed. The method described in. 6. The creeping discharge element according to claim 1, wherein the first ion generating means is an AC creeping discharge element, an ionizer, an AC corona type ion generating element, or a DC corona type ion generating element. The method according to any one of claims 1 to 5, which is a DC corona discharge element, an ionizer, an AC corona type ion generation element, or a DC corona type ion generation element. 7. An AC creeping discharge element, wherein both the first ion generating means and the second ion generating means are AC creeping discharge elements, and the discharge electrode of the AC creeping discharge element as the first ion generating means is a first ion generating means. The electrode is a repulsive electrode for ions emitted from the electrode, and is an attracting electrode for ions emitted from the second ion generating means. The discharging electrode of the AC surface discharge element as the second ion generating means is the second electrode. The method according to any one of claims 1 to 5, wherein the electrode is a repulsive electrode for ions emitted from the ion generating means, and is an attracting electrode for ions emitted from the first ion generating means. 8. An AC creeping discharge element, wherein the first ion generating means is an AC creeping discharge element, the second ion generating means is a DC corona discharge element, and the discharge electrode of the AC creeping discharge element which is the first ion generating means is a 1 is a repulsive electrode of ions emitted from the ion generating means, the discharge electrode of the DC corona discharge element is a first ion-attractive electrode, and the DC corona discharge element and the AC creeping discharge element Perform corona discharge between the object charged by the attracted ions,
The method according to claim 1. 9. An ion-repellent electrode; an ion-attractive electrode disposed opposite to the ion-repellent electrode; a non-contact state between the ion-repellent electrode and the ion-repellent electrode. Means for arranging a dielectric to be treated; positive ions and / or ions between the dielectric to be treated arranged by the means for arranging the dielectric to be treated and the ion-repellent electrode; Or an ion generating means capable of supplying a negative ion; and only one of the positive ion and the negative ion supplied by the ion generating means is attracted to the ion by the ion repulsive electrode. A potential difference that can be moved in the direction of the neutral electrode and transferred to the dielectric to be processed is applied by applying a DC voltage between the ion-repellent electrode and the ion-attracting electrode. Means for producing an electret body. 10. A dielectric to be disposed which is disposed by means capable of disposing said dielectric to be disposed, and disposed opposite to said ion-repellent electrode with respect to said dielectric to be disposed;
A second ion-repellent electrode that is not in contact with the dielectric to be disposed, which is disposed by the means capable of disposing the dielectric to be processed; A second ion attraction that is disposed opposite to the ion-attractive electrode with respect to the processing dielectric and that is not in contact with the dielectric to be disposed that is disposed by means capable of disposing the dielectric to be processed; A positive electrode and / or a negative ion are supplied between the dielectric to be treated and the second ion-repellent electrode disposed by means capable of disposing the dielectric to be treated; A second ion generating means capable of performing the following steps; and a positive ion or a negative ion supplied by the second ion generating means, from the ion generating means to the dielectric to be processed. Only ions of the opposite polarity to the transferred ions are moved from the second ion-repellent electrode toward the second ion-attractive electrode and transferred to the dielectric to be processed. 10. The means according to claim 9, further comprising means for generating a potential difference by applying a DC voltage between the second ion-repellent electrode and the second ion-withdrawing electrode. Equipment. 11. The apparatus according to claim 9, wherein the ion generating means is selected from the group consisting of an AC creeping discharge element, an ionizer, an AC corona type ion generating element, and a DC corona type ion generating element. 12. The apparatus according to claim 9, wherein a pair of AC surface discharge elements is used. 13. A processing target dielectric disposed by means capable of disposing the processing target dielectric, disposed opposite to the ion-repellent electrode with respect to the processing target dielectric,
The apparatus further includes a DC corona discharge element that is a second ion generating means that is not in contact with the dielectric to be processed, which is disposed by a means capable of disposing the dielectric to be processed, and includes a discharge electrode of the DC corona discharge element. An ion-attractive electrode;
An apparatus according to claim 9. 14. The apparatus according to claim 9, further comprising means capable of heating the dielectric to be processed.