JPH0670554A - Electrostatic actuator - Google Patents

Abstract

PURPOSE:To provide an electrostatic actuator which is reformed so that the positioning of the through hole part can be performed easily and accurately. CONSTITUTION:In an electrostatic actuator, wherein a stator where 3 electrodes 2 are arranged at specified intervals on an insulating supporter 1 and a mover 6 which has given positive and negative charges to an insulating thin leaf 4 are arranged to contact with each other, a low shrinking polyester film, where the longitudinal and lateral thermoshrinkage percentages after processing for two hours at 150 deg.C are both 0.4% or less, is used as the insulating supporter 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator, and more particularly, to an electrostatic actuator improved so that the position of a through hole can be easily and accurately aligned.

[0002]

2. Description of the Related Art An electrostatic actuator comprises a stator in which electrodes are arranged on an insulating support at predetermined intervals and a mover in which a resistive layer is provided on an insulating thin film such as an insulating film.
The stator and the mover are arranged so as to be in contact with each other. Then, due to the action of static electricity, the mover is instantly levitated and moved while preventing friction (Proceedings of the Annual Conference of the Institute of Electrical Engineers of Japan 1989).
1, JP-A-2-285978).

The electrostatic actuator is characterized in that the size of the electrodes and the gap can be reduced to increase the force density and can be easily miniaturized. Therefore, the electrostatic actuator is expected to be applied as a small driving device such as a sheet conveying mechanism in a word processor or a facsimile, and as a driving device for other minute mechanical systems.

FIGS. 1A to 1D are explanatory views of the driving principle of an electrostatic actuator (electrostatic film actuator) in which a moving element is composed of an insulating film.
(1) is an insulating support, (2) is a strip electrode, (3) is a stator, (4) is an insulating film, (5) is a resistor layer,
(6) indicates a mover, and (7) to (9) indicate electric wires.

First, as shown in FIG. 1A, a positive voltage is applied to the electric wire (7) and a negative voltage is applied to the electric wire (8). Thereby, due to the potential difference between the electric charge existing in the electrode connected to the electric wire (7) and the electric charge existing in the electrode connected to the electric wire (8),
An electric current flows through the resistor layer (5), and electric charges are induced at the boundary between the insulating film (4) of the mover (6) and the resistor layer (5) to reach an equilibrium state. This charge is shown in FIG.
It can be replaced with the image charge shown by the dotted line in (b). Since the polarities of the electric charges are different from the polarities of the electric charges, the mover (6) is attracted to the stator (3) in the state of FIG. 1B.

Next, as shown in FIG. 1C, a negative voltage is applied to the electric wire (7), a positive voltage is applied to the electric wire (8), and a negative voltage is applied to the electric wire (9). As a result, the charge in the electrode can be instantaneously moved, but the induced charge of the mover (6) cannot be immediately moved because the resistance value of the resistor layer (5) is high. as a result,
A repulsive force is generated between the mover (6) and the stator (3). The repulsive force reduces the friction between the stator (3) and the mover (6), and the negative and positive induced charges (in terms of mirror image charge) resulting from applying a voltage to the electric wire (9). ), A rightward driving force is generated in the mover (6).

FIG. 1D shows the result of the mover (6) moving to the right by one pitch of the electrode due to the driving force. When moving the mover (6) to the left,
A positive voltage may be applied to the electric wire (9). In the applied voltage pattern (the pattern shown in FIG. 1C) in the above-described movement operation for each pitch of the electrodes, the electric wires (7) and (8) have the voltages opposite to those in the state shown in FIG. 1C, the induced charge (and in terms of the image charge) in FIG. 1C is attenuated.

Therefore, in order to continuously move the mover (6) to the right by one electrode pitch, it is necessary to repeat the charge charging operation and the moving operation. For example, the pattern shown in Table 1 below. It is necessary to repeatedly apply the above voltage. The voltage pattern illustrated in Table 1 is a one-cycle voltage pattern, (G) indicates a state in which no voltage is applied (ground state), and (C ₁ ) to (C ₂ ) and (A ₁ ) to (A ₃ ) shows a charge charging operation and a transfer operation, respectively, (C ₁ ) shows the state shown in FIG.
(A ₁ ) is the state shown in FIG.

[0009]

[Table 1] C ₁ A ₁ C ₂ A ₂ C ₃ A ₃ (1 cycle) Electric wire (7) + − G − − + (8) − + + − G − (9) G − − + + −

The drive voltage pattern is, for example,
In the case of an electrode having a three-phase structure, as shown in Table 1, various patterns can be adopted as long as the pattern is such that a grounding state is provided at an appropriate timing and the charge charging operation and the transfer operation can be repeated. For example, it is also possible to adopt a pattern in which (C ₂ ) and (C ₃ ) are omitted in the patterns exemplified in Table 1. Such a deformation pattern can be easily achieved by using, for example, a stepping motor drive IC.

In order to stably and continuously move the electrostatic actuator for each pitch of the electrodes, the surface specific resistivity of the mover (6) (resistor layer (5)) is in the range of 10 ¹² to 10 ¹⁵ Ω / □. It has to be. The reason is as follows. That is, when the surface specific resistance of the mover (6) is large, it takes a relatively long time to charge the charge, and when it is small, the induced charge is instantly attenuated. However, in the case of the electrostatic actuator shown in FIG. 1, since the resistance value of the insulating film that constitutes the moving element is too large, the above-mentioned resistor layer is provided on the insulating film and a slight electric conductivity is provided. Need to be imparted. As a matter of course, in the known electrostatic actuator shown in FIG. 1, instead of the insulating film (4), another insulating thin leaf having a resistance value similar to that may be used. .

[0012]

However, the electrostatic actuator is still in the research stage, and the details of each element have to be examined for practical use.
In particular, the stator has the following problems. That is, for example, in the case of forming a strip electrode having a three-phase structure, it is necessary to connect the strip electrode provided on the insulating support to the collective electric wire through a through hole. The processing of the through holes is usually performed using an NC machine tool, and an insulating film is used as the insulating support from the viewpoint of drilling workability. However, as finer patterns and larger areas of the strip-shaped electrodes are advanced, it becomes difficult to align the through holes.

According to the knowledge of the present inventors, the alignment of the through holes is affected by the pitch deviation of the electrodes provided on the insulating film, and the thermal contraction rate is large, so that the insulating property with poor dimensional stability is obtained. In the film, the deviation of the electrode pitch is large, and it is difficult to align the through hole portion and the accuracy is poor. The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrostatic actuator improved so that the position of a through hole portion can be easily and accurately aligned.

[0014]

That is, the gist of the present invention is that a stator in which electrodes are arranged at a predetermined interval on an insulating support and a mover in which positive and negative charges are applied to an insulating thin leaf are in contact with each other. In the electrostatic actuator configured as described above, as the above-mentioned insulating support, a low-shrinkage polyester film having a thermal shrinkage rate of 0.4% or less in both a longitudinal direction and a lateral direction after being treated at 150 ° C. for 2 hours is used. The present invention resides in an electrostatic actuator.

The present invention will be described in detail below. In the basic configuration of the electrostatic actuator of the present invention, the constituent material of the moving element (6) is not limited to the insulating film in FIG.
Further, it is the same as the known electrostatic actuator shown in the figure, except that the structure of the moving element is not limited to the one provided with a resistor layer. Therefore, in the following description,
For the sake of convenience, reference is made to FIG. 1 where (4) in FIG. 1 is an insulating thin leaf body. The electrostatic actuator of the present invention comprises a stator (3) in which electrodes (2) are arranged on an insulating support (1) at a predetermined interval, and a mover (6) in which positive and negative charges are applied to an insulating thin leaf body (4). ) Consists of.

First, the stator (3) will be described. In the present invention, the insulating support (1) that constitutes the stator (3) has a low shrinkage in which the thermal shrinkage in both the longitudinal and transverse directions after treatment for 2 hours at 150 ° C. is 0.4% or less. It is important to use a transparent polyester film.

The above polyesters include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid or their esters with ethylene glycol,
It is produced by polycondensation with glycols such as diethylene glycol, 1,4-butanediol, neopentyl glycol and 1,4-cyclohexanedimethanol.
As the polycondensation method, known methods exemplified in the following (1) and (2) can be arbitrarily adopted.

(1) A method of carrying out transesterification between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol to carry out polycondensation. (2) A method in which an aromatic dicarboxylic acid and a glycol are directly esterified to form a bisglycol ester of an aromatic dicarboxylic acid or a low polymer thereof, and then polycondensed at a temperature of 240 ° C. or higher under reduced pressure. For the polycondensation, ordinary catalysts, stabilizers and other various additives can be optionally used.

Typical examples of the above polyesters include polyethylene terephthalate, polyethylene naphthalate and polycyclohexane dimethylene terephthalate. And polyester is a homopolymer,
It may be a copolymer obtained by copolymerizing the third component or a blend thereof. Further, various stabilizers, ultraviolet absorbers, lubricants, pigments, plasticizers and the like may be added to the polyester.

The polyester film can be obtained by forming a raw material polyester into a film by a known method.
As a film forming method, a method in which a polyester sheet obtained by melt extrusion on a casting drum is stretched in the longitudinal direction by a roll stretching method and then stretched in the lateral direction by a stenter is preferably adopted. Then, as a method for reducing the shrinkage of the polyester film, a method of subjecting the obtained film to a relaxation heat treatment is suitable. The relaxation heat treatment is usually performed at a temperature of about 180 to 200 ° C., and the treated film is wound after being cooled.

The above relaxation heat treatment is usually performed as off-line processing, but it can also be performed as in-line processing after film formation and before winding the film. Also,
For example, in accordance with the method described in Japanese Patent Laid-Open No. 61-160224, the in-line processing and the off-line processing relaxation heat treatment can be performed to highly improve the flatness of the film. Then, after the heat-relaxed film is cut into a predetermined size, about 100 to 20
If the heat treatment is performed again in the oven maintained at 0 ° C. for a predetermined time, a higher degree of shrinkage reduction can be achieved.

In the present invention, it is necessary that the heat shrinkage of the polyester film after being treated at 150 ° C. for 2 hours is 0.4% or less, preferably 0.3% or less in both the longitudinal and transverse directions. When the heat shrinkage ratio exceeds 0.4% in either the longitudinal direction or the lateral direction, sufficient dimensional stability of the polyester film cannot be obtained, and the through hole portion can be accurately aligned. The electrostatic actuator of the invention is unattainable.

In the present invention, the low-shrinkage polyester film used as the insulating support (1) has a thickness of
It is usually in the range of 50 to 200 μm. Further, the low-shrinkage polyester film can be appropriately imparted with a function that does not impair the function of the electrostatic actuator, such as flame retardancy and oligomer generation preventing property, according to a known method. As the low-shrinkage film, there is, for example, a polyimide film in addition to the polyester film. However, the polyester film is inexpensive because it is widely used, whereas the polyimide film is expensive, and therefore, it is not suitable as a material film for an electrostatic actuator that requires cost reduction for practical use. Absent.

The method of forming the electrode (2) is not particularly limited, but a method of laminating a conductive material on the insulative support (1) to form an electrode by an etching method, or an insulating property by a screen printing method. Examples thereof include a method of directly forming an electrode on the support (1). FIG. 2 is an explanatory view showing an example of the strip electrode (2), but the circular lands shown at the top and bottom represent through holes. Drilling is usually done
This is performed using an NC machine tool, and each strip electrode is connected to an electric wire (collective electric wire) through such a through hole.

The strip electrodes (2) provided on the insulative support (1) may be provided side by side on the surface of the insulative support (1) or embedded in the insulative support (1). It may be provided. And, in order to improve the insulating property of the electrode,
It is preferable that an insulating layer is formed on the surface of the strip electrode (2) by a method such as printing or coating, and the strip electrode (2) is embedded between the insulating support (1) and the insulating layer. FIG. 3 is a cross-sectional explanatory view showing an example of the strip electrode (2). After the strip electrode (2) is formed on the insulating support (1), an insulating paste or the like is printed on the surface of the strip electrode (2) for insulation. A layer (10) is provided.

The distance between the strip electrodes (2) is preferably made finer in order to improve the driving force of the electrostatic actuator, such as the generated force and the driving voltage.
m or less, preferably 300 μm or less. And
As the electrode (2), a strip electrode is usually adopted as described above, but a dot type electrode may be used. Further, the structure of the electrode (2) is usually a three-phase structure, but
The structure is not limited to this, and may be a 3n (n is an integer) structure.

Next, the mover (6) will be described. The insulating thin leaf body (4) constituting the moving element (6) is composed of a film (sheet) made of an insulating material. The insulating material is not particularly limited, and various synthetic resins having good insulating properties, ceramics, glass and the like can be used. Then, as specific examples of the synthetic resin, epoxy resin, polyimide resin, polyester resin, polypropylene resin, polyvinylidene chloride resin, polystyrene resin,
Examples thereof include polyamide resin, polyvinyl chloride resin, polyethylene resin, polyvinyl alcohol resin and the like. When the insulating thin leaf body (4) is composed of a synthetic resin film, a particularly preferable film is a polyester film such as polyethylene terephthalate film or polyethylene-2 in view of density, flexural modulus and wrinkle resistance.
It is a 6-naphthalate film.

The method for applying positive and negative charges to the insulating thin leaf body (4) is the same as in the known electrostatic film actuator shown in FIG. 1, in which the insulating thin leaf body (4) is provided with a resistor layer (5). There is a method of providing it. Specifically, for example, a method of applying an antistatic agent having a weak antistatic effect to the surface of the insulating thin leaf body (4) can be used. In this case, the surface resistivity of the resistor layer (5) needs to be in the range of 10 ¹² to 10 ¹⁵ Ω / □, preferably around 10 ¹⁴ Ω / □. The resistor layer (5) may be provided on either the surface of the moving element (6) that contacts the stator (3) or the other surface, but the latter surface is preferable.

The method of applying positive and negative charges to the insulating thin leaf body (4) is not limited to the above method, and various other methods obvious to those skilled in the art can be adopted. For example, when the insulating thin leaf body (4) is made of a synthetic resin film,
There is a method of kneading a conductive substance such as carbon black to make the insulating thin leaf body (4) itself a resistor having the same resistivity as above. Furthermore, a method of providing a strip electrode on the insulating thin leaf body (4), a method of using an ion generator, a method of using an electret material for the insulating thin leaf body (4), and the like can be mentioned.

The method of providing the strip-shaped electrode on the insulating thin leaf body (4) is not particularly shown, but in FIG. 1, the strip-shaped electrode of the two-phase structure corresponding to the electric wires (7) and (8) is used as the strip-shaped electrode of the stator. This is a method provided correspondingly to (2), in which positive and negative voltages are constantly applied to these electric wires, and positive and negative charges existing in each strip electrode are used instead of the image charge and. In addition, the method of using an ion generator is to arrange an insulating thin leaf body (4) in contact with a stator (3) and apply positive and negative voltages to the electric wires (7) and (8) to induce electric charges. After that, from an ion generator known as a static eliminator (a device designed to apply an AC voltage to a needle electrode to cause a corona discharge, and to generate positive and negative ion winds against a charged object with a blower) Is applied to the surface of the insulating thin leaf body (4), and the ionized air layer formed on the surface of the insulating thin leaf body (4) is used instead of the image charge and. As the ion generator, various static eliminators described in “Static Handbook” (Static Society of Japan, published by Ohmsha Ltd., first edition, page 819) can be used.

The thickness of the insulating thin leaf material (4) cannot be unconditionally determined because the force generated by the electrostatic actuator varies depending on the method of applying charges to the insulating thin leaf material, but it is usually set to 10 μm or more. It Then, when the method of providing the resistor layer (5) on the insulating thin leaf body (4) is adopted as the method of applying the electric charge, it is preferably in the range of 10 to 200 μm. Whatever method is used to apply the charge, the thickness of the insulating thin leaf body (4) is determined by setting the distance between the strip electrodes (2) arranged on the insulating support (1) as P and strip shape. The surface of the electrode (2), the insulating thin leaf body (4), and the resistor layer (5) (if the insulating thin leaf body (4) is provided with a strip electrode, the strip electrode is formed, and if an ionized air layer is formed, it is If the distance from the boundary surface to
It is preferable to set the range to satisfy the relationship of G / P <0.4.

[0032]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the following examples, the heat shrinkage rate of polyethylene terephthalate film (PET film) was measured by the following method. That is, the sample film is 50 cm (Lo) long and 15 m wide in each of the longitudinal (longitudinal) direction and the lateral (width) direction.
After being cut out at m and heat-treated, the length (L) of the film is measured, and the heat shrinkage rates in the machine direction and the transverse direction are obtained from the following equations. Thermal contraction rate = [(Lo-L) / Lo] × 100 (%)

Example 1 (1) Preparation of PET film with low shrinkage The heat shrinkage ratio after heat treatment at 150 ° C. for 2 hours was 1.0% in the longitudinal direction.
Approximately 190% of biaxially stretched PET film with a transverse direction of 0.2%
The film was passed through an oven maintained at 0 ° C. and subjected to a low shrinkage treatment under the conditions of a treatment time of 10 seconds and a tension of 40 g / mm ² at the time of treatment to obtain a low shrinkage PET film. The heat shrinkage percentage of the above low shrinkage PET film after treatment at 150 ° C. for 2 hours was 0.3% in the longitudinal direction and 0.1% in the transverse direction.

(2) Preparation of Stator Using the screen masks shown in Table 2 below and the conductive inks shown in Table 3 by the screen printing method, as shown in FIG. A band-shaped electrode was formed to be a stator. The screen printer used was 2400 manufactured by Mitani Electronics.

[0035]

[Table 2] <Screen mask> Plate-making material: Stainless steel gauze (wire diameter: about 20 μm, mesh: 400 mesh) Electrode pitch: 200 μm (printed electrode width 100 μ
m) Electrode size: 80 mm x 200 mm

[0036]

[Table 3] <Conductive ink> Conductive fine particles: Silver (average particle size: about 3 μm) Resin binder: Polyester resin Solvent: Butylcellosolve acetate Viscosity (25 ° C.): About 30,000 cps (Brookfi
(measured by eld method)

<Formation of Electrode> First, a conductive ink was printed on a PET film using a urethane squeegee and dried with hot air at 80 ° C. for 30 minutes. The thickness of the silver ink after drying is about 5 μm and the surface resistivity is about 1Ω.
It was / □. Then, using another screen mask, a transparent polyester resin was screen-printed on the entire electrode printing surface on the PET film excluding the circular land portion. The transparent polyester resin had a thickness of 10 μm, and the drying conditions after printing were the same as above.

(2) Connection The diameter of the circular land portion is 0.2 m using an NC machine tool.
m was punched, and then a through hole was made conductive by silver paste using a dispenser for connection. In the drilling process, the electrode pitch was hardly displaced, the process was performed well, and the position of the through hole was easily and accurately aligned.

(3) Preparation of moving element A PET film having a thickness of 25 μm was spray-coated on one side of the film with an antistatic agent having a weak antistatic effect to form a resistor layer to obtain a moving element. The surface resistivity of the resistor layer was 2 × 10 ¹⁴ Ω / □.

(4) Manufacture of Electrostatic Actuator The electrostatic actuator of the present invention was manufactured by stacking the stator manufactured in (1) above and the mover manufactured in (3) above. The above electrostatic actuator is shown in FIG.
When driven under the drive conditions shown in Table 4 below according to the procedure shown in (d), it was confirmed that the mover could be continuously driven. Moreover, it was confirmed that the moving element could be driven up to 2 kHz and 40 cm / s.

[0041]

[Table 4] <Driving conditions> Initial charging time: 1 s Charging time: 9 ms Moving time: 1 ms Driving frequency: 100 Hz Driving voltage: ± 200 V

Example 2 The low-shrinkage PET film obtained in Example 1 was treated with 500 mm ×
It was cut into 500 mm and heat-treated in an oven kept at about 180 ° C. for 1 hour to obtain an ultra-low shrinkage PET film. The ultra-low shrink PET film at 150 ° C for 2
The heat shrinkage rate after the time treatment is 0.2% in the vertical direction and 0.
It was 05%. Using the ultra-shrinkable PET film described above, an electrostatic actuator was prepared through the same operation as in Example 1. In the drilling process in the wire connection operation, the electrode pitch was hardly displaced, the process was carried out satisfactorily, and the position of the through hole portion was easily and highly accurately aligned. In addition, in a drive test under the same conditions as in Example 1, it was confirmed that the mover could be driven up to 2 kHz and 40 cm / s.

Comparative Example 1 The heat shrinkage ratio after heat treatment at 150 ° C. for 2 hours was 1.0% in the longitudinal direction.
Using a biaxially stretched PET film of 0.2% in the transverse direction,
An electrostatic actuator was produced through the same operation as in Example 1. In the punching process in the connection operation, the vertical electrode shrinkage was large because the shrinkage rate of the film in the vertical direction was large, and the process was not performed well.

[0044]

According to the present invention described above, there is provided an electrostatic actuator improved so that the through hole portion can be easily and accurately aligned. Therefore, the present invention largely contributes to the practical application of the electrostatic actuator.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a driving principle of an electrostatic actuator.

FIG. 2 is an explanatory plan view showing an example of a strip electrode.

FIG. 3 is a cross-sectional explanatory view showing an example of a strip electrode.

[Explanation of symbols]

 (1): Insulating support (2): Strip electrode (3): Stator (4): Insulating film or insulating thin sheet (5): Resistor layer (6): Moving element (7) to ( 9): Electric wire (10): Insulation layer

Front page continued (72) Inventor Tomio Tomita 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Sanryo Kasei Co., Ltd.Institute of Research Laboratories (72) Inventor Etsuo Hatabe 2-14-40 Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Living Systems Research Institute Co., Ltd. (72) Inventor Yoshihiro Nagata 2-14-40 Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Corporation Living Systems Research Laboratories (72) Inventor Keihide Ozaki 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa (72) Inventor Seiji Sakamoto 1000 Kamoshida-cho, Midori-ku, Yokohama, Kanagawa Daifoil Hoechst Co., Ltd. Central Research Center

Claims (1)

[Claims] 1. An electrostatic actuator comprising a stator having electrodes arranged on an insulating support at a predetermined interval and a moving member having positive and negative charges applied to an insulating thin sheet, the electrostatic actuator comprising: An electrostatic actuator comprising a low-shrinkage polyester film having a heat shrinkage ratio of 0.4% or less in both the machine direction and the transverse direction after being treated at 150 ° C. for 2 hours, as a flexible support.