JP2005073421A - Electrostatic attraction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electrostatic attraction device wherein degradation in attractive force due to attractive electric charges is prevented, and even if a conductive substance is attracted for a long time, deterioration in an attractive layer is virtually negligible. <P>SOLUTION: An attractive layer that meets the following conditions is used the volume resistivity of the attractive layer that is brought into contact with attracted substances should be varied in the direction of its film thickness, the volume resistivity should be higher on the side closer to the attraction surface than in the central part, and the volume resistivity of the portion close to the attraction surface is 1.0×10<SP>14</SP>Ωcm or higher. Thus, frictional charges and the like produced on the attractive layer are discharged to a pair of electrodes in a relatively short time, and a current passed between a conductive attracted substance and a pair of the electrodes is suppressed. Thus, the attractive layer as the path of the current is prevented from being deteriorated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrostatic adsorption device that adsorbs an object by electrostatic Coulomb force.

  A so-called electrostatic adsorption device that adsorbs an object by electrostatic Coulomb force has a wide range of industrial applications because it is magnetic adsorption and does not select an adsorption object. For example, an electrostatic adsorption device (see Patent Document 1) for holding a silicon wafer in a vacuum evaporation apparatus, an apparatus using an electrostatic adsorption device as a paper turning mechanism in a copy machine (see Patent Document 2), and a sheet attached An electronic blackboard (see Patent Document 3) having an electrostatic adsorption device is disclosed as a means for achieving this.

An electrostatic adsorption device is a reverse polarity charge due to electrostatic induction induced by an object in an electric field (in the case of a conductor) or an attractive force due to a Coulomb force between a reverse polarity polarization charge due to polarization (in the case of an insulator) and the electric field. In this apparatus, the object is adsorbed in the direction of the electrode forming the electric field.
As a method for generating an electric field, there are a method in which a voltage is applied to an electrode pair to give a potential difference and a method in which spontaneous polarization of a ferroelectric material is used, but the former is generally used.

The electrostatic adsorption device can apply an adsorption force to the object regardless of whether the object is a conductor or an insulator. However, in an electrostatic adsorption device that attracts an object with an electric field generated by applying a voltage to the electrode pair, if the object to be attracted is a conductor and the electrode pair is exposed, the electrode pair and the object to be attracted An object is short-circuited to make it difficult to form an adsorption electric field, and a problem current flows through the object to be adsorbed, which may damage the object. For this reason, in the electrostatic attraction apparatus described in Patent Document 1, the volume resistance of the electrode pair is devised to be 1.0 × 10 ^{9 to} 1.0 × 10 ¹² Ωcm, and an excessive current is applied to the object to be adsorbed. Is done to prevent the flow.

  Even if the electrode pair is exposed, if the object to be adsorbed is an insulator, there is no inconvenience that the electrode pair is short-circuited by the object to be adsorbed, but generally the potential difference between the electrode pair needs several hundred to several thousand volts. Therefore, there is a risk of electric shock when the electrode pair is exposed, and discharge between the electrode pair due to adhesion of moisture or dust may cause the adsorption operation to be incomplete. Therefore, some kind of electrode pair surface coating is required.

In order to avoid inconvenience due to the exposure of the electrode pair, an adsorption layer made of a thin dielectric film covering the surface of the electrode pair is installed (see Patent Documents 3 and 4).
By changing the electrode pair to such a structure, the distance between the electrode pair and the object to be adsorbed is increased by the thickness of the dielectric film, so that the attractive force is slightly reduced. However, since the electrostatic induction charge and the polarization charge can be generated on the object to be attracted, the attracting operation is sufficiently possible.

In this way, by covering the electrode pair with an adsorption layer made of a thin dielectric film, the problem caused by the exposed electrode pair is solved, there is no risk of electric shock, and the conductor and the insulator are adsorbed without distinction. An electrostatic chuck that can be used is realized.
However, on the other hand, when the electrode pair is covered with the adsorption layer, the ions adsorbed on the surface of the coating film, the generated triboelectric charges, etc. remain as they are, and a phenomenon of reducing the adsorption force occurs.
For this reason, the adsorption layer covering the electrode pair must be designed to simultaneously solve the problem of short circuit and electric shock during adsorption of the conductor and the problem of discharge of ions and charges trapped on the adsorption layer surface to the electrode pair. .
As an improvement of such an adsorption layer, it has been proposed to form a coating layer that further covers the adsorption layer and has a low water permeability and an oxygen barrier property (see Patent Document 4). Furthermore, it has also been proposed that the adsorption layer has a laminated structure with different surface resistance values, and a material having a high surface resistance is disposed on the adsorption surface side to obtain the optimum adsorption layer characteristics as a whole (see Patent Document 5). .

  However, in these attempts to improve the adsorption layer, methods for improving the adsorption power and improving the durability of the adsorption layer have been presented mainly when the adsorbent is an insulating substance. No improvement has yet been proposed for stable adsorption when the adsorbate is a conductive material. Therefore, the problem of the high current value flowing in the film thickness direction of the adsorption film when adsorbing the conductive material and the risk of short circuit between the conductive material and the electrode are not considered, and a method for solving them Also not presented. Furthermore, there is no mention of the range of the volume resistivity of the adsorption layer required for the stable adsorption of the conductive substance.

  FIG. 1 shows a cross-sectional view of a conventional electrostatic attraction apparatus viewed from the side. There may be a plurality of electrode pairs, and the planar configuration may be a comb-shaped electrode. Reference numerals 1 and 2 denote electrode pairs, 3 denotes an adsorption layer covering the electrode pairs, 4 denotes an adhesive layer, and 5 denotes a substrate as a holding material for the electrodes. An electric field is generated between the electrodes 1 and 2 due to the potential difference applied between the electrodes 1 and 2. The electric field is expressed by the electric force lines 7, but a part of the electric force lines passes through the adsorption layer 3 to generate a reverse charge due to electrostatic induction or polarization in the nearby object 8, and the coulomb force causes the adsorption layer 3 to Adsorb an object on the surface.

  In FIG. 1, when the adsorption layer 3 is an insulator, ions and frictional charges adsorbed on the surface of the adsorption layer 3 remain for a long time and cancel the electrode potential, so that the adsorption force decreases for a long time. In order to avoid this, a method is conceivable in which a slight conductivity is imparted to the adsorption layer 3 and the adsorption force is discharged to the electrode to prevent the adsorption force from being lowered. However, when the adsorption layer 3 has conductivity, when the object 8 is a conductor such as a metal, the adsorption layer 3 has a current in the path of electrode 1 -adsorption layer 3 -object 8 -adsorption layer 3 -electrode 2. Flows. In particular, when the conductivity is ionic conduction, the short-circuit current destroys the ionic substance exhibiting the conductivity. It also induces transfer of ionic substances in the polymer. These phenomena are accelerated as the current in the adsorbing layer is increased. In some cases, the adsorbing layer is discolored, and when the value exceeds a certain value, the molecular structure of the adsorbing layer 3 may be destroyed. On the other hand, depending on the metal adsorbed, there is a possibility that the corrosion proceeds from the surface in contact with the adsorption layer.

  In a typical electrostatic adsorption device, the thickness of the adsorption layer is a few tenths of the distance between the electrode pairs, so if the metal is adsorbed on the surface of the adsorption layer to which conductivity is imparted, the electrode-adsorption layer The current path length of the adsorbed metal, the adsorbed layer, and the other electrode is on the order of several tenths between the electrode pairs, and a current several tens of times greater than the current between the electrode pairs can be obtained. The destruction of the adsorption layer due to this cannot be ignored from the viewpoint of long-term reliability of the apparatus.

According to the experiment, when vinyl chloride (thickness: 100 μm) having a volume resistance of 1.0 × 10 ¹³ Ωcm is used as the adsorption layer 3 and the aluminum plate is adsorbed with an interelectrode potential difference of 1500 V, the adsorption layer is destroyed by current. The time when the adsorptive power becomes unstable was about 1000 hours. At least 5 years (43,000 hours) is necessary as a commercialized electrostatic adsorption device. Therefore, considering that the destruction of the adsorption layer due to current is proportional to the current value, ideally, the volume resistance of the adsorption layer 3 needs to be 50 times (about 5.0 × 10 ¹⁴ Ωcm).

On the other hand, the volume resistivity of the adsorption layer is ideally 1.0 × 10 ^{11 to} 1.0 × 10 ¹⁴ Ωcm in order to ideally remove adsorption charges such as triboelectric charge and ions on the adsorption layer surface. A rate is needed. For this reason, in order to avoid the occurrence of adsorption layer destruction, the highest priority is to suppress the current, and at least to remove adsorption charges such as frictional charges in a practical time (within 1 hour) It is preferable that a volume resistivity of 1.0 × 10 ^{14 to} 1.0 × 10 ¹⁵ Ωcm is stably obtained as the volume resistivity of the layer.

However, there are many characteristics required for the adsorption layer of the electrostatic adsorption device, such as heat resistance, weather resistance, water absorption, flexibility, color, and cost. While satisfying these characteristics, the adsorption layer It is not easy to give a prescribed volume resistivity to.
For example, a vinyl chloride resin and a PET resin suitable for the adsorption layer having a volume resistance lower than 1.0 × 10 ¹³ Ωcm can be obtained relatively easily by kneading a conductive material. However, it is difficult to obtain a volume resistance higher than 1.0 × 10 ¹³ Ωcm, and in particular, it is possible to stably obtain a uniform layer having a volume resistivity of 1.0 × 10 ^{14 to} 1.0 × 10 ¹⁵ Ωcm. It is difficult.
JP-A-5-315435 JP-A-5-2011175 JP-A-5-56201 JP-A-6-225556 Japanese Patent Laid-Open No. 61-152497

  That is, the object of the present invention is to prevent a decrease in the adsorption force due to retention of free charges, ions, frictional charges, etc. in the adsorption layer, and to generate a stable adsorption force, and for a long time of the conductor. It is an object of the present invention to provide an electrostatic adsorption device that can be used stably for a long period of time without being discolored or destroyed by the current flowing in the adsorption layer even by adsorption.

  In view of the above, the inventors can easily discharge the charges trapped in the adsorption layer to the electrode pair by examining the volume resistivity of the adsorption layer covering the electrode pair and the distribution in the film thickness direction. In addition, the present inventors have found an electrostatic adsorption device that does not break the adsorption layer even if the conductor is continuously adsorbed for a long time.

That is, the present invention includes at least a pair of positive and negative layered electrodes arranged on substantially the same plane in the vicinity of the back surface of the adsorption layer made of a layered dielectric, and means for applying a potential difference to the electrodes, In an electrostatic adsorption device that adsorbs an object to the surface of the adsorption layer by Coulomb force caused by polarization charges induced by an electric field generated by an electrode, the adsorption surface of the adsorption layer is more than the volume resistivity of the central portion of the adsorption layer. An electrostatic attracting device is provided, in which the volume resistivity in a portion close to is higher and the volume resistivity in the vicinity of the attracting surface is 1.0 × 10 ¹⁴ Ωcm or more.

By changing the volume resistivity of the adsorption layer in the film thickness direction, forming a portion with a high volume resistivity on the adsorption surface side, and setting the value of the volume resistivity to 1.0 × 10 ¹⁴ Ωcm or more Even if the conductor is adsorbed, the resistance value of the current path flowing from one electrode pair to the other electrode pair via the adsorption surface and the conductor increases, so that an excessive current does not flow through the path. The adsorption layer is not destroyed.

  As described above in detail, according to the present invention, there is no decrease in the adsorption force due to the charge accumulated in the adsorption layer, and the degradation of the adsorption layer can be ignored practically even when the conductor is adsorbed. Therefore, it can be used stably for a long period of time regardless of whether the object to be adsorbed is an insulating material or a conductive material.

  As the adsorption layer of the electrostatic adsorption apparatus of the present invention, a plastic film having a change in volume resistivity in the film thickness direction can be used in advance, and the adsorption layer is composed of the adsorption layer b on the electrode side and the volume thereof. You may have a laminated structure with the adsorption layer a of the adsorption surface side with high resistivity. By adopting such a laminated structure, a stable adsorption layer with a constant film thickness distribution can be easily produced.

The volume resistivity in the vicinity of the adsorption surface is 1.0 × 10 ¹⁴ Ωcm or more. If there is a layer having a volume resistivity of 1.0 × 10 ¹⁴ Ωcm or more in the vicinity of the adsorption surface, an excessive current flows through the adsorption surface and the path through the conductive material when the conductive material is adsorbed, and the adsorption layer is formed. It will not be destroyed. The volume resistivity is preferably 1.0 × 10 ¹⁵ Ωcm or more.
Further, an adsorption layer c having a volume resistivity of 1.0 × 10 ¹⁴ Ωcm or more can be provided further on the electrode side of the adsorption layer b. By providing such an adsorption layer c, the current value from the conductive adsorbent to the electrode pair through the adsorption layer can be further effectively reduced.
When the volume resistivity of the adsorption layer b is in the range of 1.0 × 10 ^{11 to} 9.9 × 10 ¹³ Ωcm, ions and charges trapped on the surface of the adsorption layer are discharged to the electrode pair in a relatively short time. It is easy and preferable.

The adsorption layer is usually 100 to 200 μm in thickness, and the preferred breakdown of the film thickness is preferably 0.5 to 30 μm for the adsorption layer a. The adsorption layer b preferably has a thickness of 5 to 300 μm. The adsorbing layer a may be formed by forming a layered region having a high volume resistivity along the adsorbing surface, thereby blocking the current path passing through the adsorbing surface and the conductor, and depends on the film thickness ratio of the adsorbing layer b. Will function if the adsorbed layer a has a volume resistivity of 1.0 × 10 ¹⁴ Ωcm or more. If it is 1.0 × 10 ¹⁵ Ωcm or more, the adsorption layer a can be set to a thickness of several μm, assuming an adsorption layer b of a normally used material.

  On the other hand, the adsorption layer b needs to be thicker than the adsorption layer a in order to secure a path through which trapped ions and charges are effectively discharged to the electrode pair in a short time. Therefore, the film thickness of the adsorption layer b is preferably 5 times or more, more preferably 10 times or more that of the adsorption layer a. By adding the adsorption layer c, the current path through the adsorption surface and the conductor is more effectively blocked, but the discharge path of trapped ions and charges is also blocked. It is preferable that the thickness is set to be as thin as the layer a.

Actually speaking, in combination with the volume resistivity, the total thickness of the adsorption layer is 50 to 150 μm, the low volume resistivity portion of the adsorption layer b is 80 to 98%, and the rest is the high volume of the adsorption layer a or the adsorption layer c. The resistivity part occupies, the volume resistivity of the adsorption layer b is 1.0 × 10 ^{12 to} 5.0 × 10 ¹³ Ωcm, and the volume resistivity of the adsorption layer a and the adsorption layer c is 1.0 × 10 ^{15 to} 5 It is preferably 0.0 × 10 ¹⁶ Ωcm.

The film thickness of each of the adsorption layer a, the adsorption layer b, and the adsorption layer c can be determined by calculating how much the equivalent resistance value in the film thickness direction is. For example, an adsorption layer having a volume resistivity of 1.0 × 10 ¹⁴ Ωcm and a thickness of 100 μm and a volume resistivity of 1.0 × 10 ¹⁵ Ωcm and a thickness of 9 μm in the cross-sectional direction has a volume resistivity (1 +9) × 10 ¹⁴ Ωcm and a thickness of 100 μm, that is, a resistivity equivalent to an adsorption layer having a volume resistivity of 5.0 × 10 ¹⁴ Ωcm and a thickness of 200 μm.

  Thus, by providing a portion whose thickness is changed in accordance with the volume resistivity in the cross-sectional direction, it is possible to effectively prevent a short circuit of the conductive adsorbent, and the current flowing through the adsorption surface Can also be suppressed to a low value to prevent changes in properties of the adsorbed layer and the object to be adsorbed. On the other hand, portions other than the portion near the suction surface can have a relatively low volume resistivity, and the resistance in the direction parallel to the suction surface can also be kept low. For this reason, the function of discharging adsorbed ions and triboelectric charges to the electrode pair in a short time can also be maintained.

The material used for the adsorption layer b (3b in FIG. 2) is polyester, polyurethane, polyvinyl chloride, polyvinylidene chloride, nylon, acrylic, polycarbonate, polyacetal, phenol, epoxy and other plastics, or two or more thereof. A mixed plastic plate or sheet, or a material obtained by laminating the same or different kinds of plates or sheets is used. Usually, the volume resistivity in the film thickness direction of the entire adsorption layer is set to a volume resistance of 1.0 × 10 ^{14 to} 1.0 × 10 ¹⁵ Ωcm in order to eliminate leakage through the conductive adsorbent. Is preferred. However, the volume resistivity of the adsorption layer b is preferably set in the range of 1.0 × 10 ^{11 to} 9.9 × 10 ¹³ Ωcm in order to easily discharge the free charge to the electrode pair in a short time. 1.0 × 10 ^{12 to} 5.0 × 10 ¹³ Ωcm is more preferable. As a plastic that can be set in such a volume resistance range, for example, polyvinyl chloride, nylon, polyester elastomer, and a resin represented by the following general formula (1) are preferably used.

（１）

(1)

Here, l, m and n represent the degree of polymerization l / (l + m + n) = 0 to 0.5
m / (l + m + n) = 0.5 to 0.995
n / (l + m + n) = 0-0.25
It shall be related. In general formula (1), ethylene vinyl alcohol copolymer resin, polyvinyl alcohol, and the like are included.

  The thickness of the adsorption layer can be appropriately set between 1 μm and 1 mm, depending on the voltage applied to the electrode of the electrostatic adsorption device and the assumed adsorption force. However, in order not to reduce the adsorption force due to the Coulomb force, 100 to 200 μm is preferable.

Further, when conductive plastic powder is contained in the plastic used for the adsorption layer b, the contribution of the non-ohmic conductive mechanism can be increased, and free charge can be discharged to the electrode pair in a shorter time.
As the conductive fine powder, it is preferable to use fine particles having a volume resistivity of 1.0 × 10 ^{6 to} 9.9 × 10 ¹⁰ Ωcm, and a volume resistance of 1.0 × 10 ^{10 to} 9.9 × 10 ¹⁰ Ωcm. It is more preferable to use fine particles having a ratio because it is easy to set the volume resistivity of the plastic within the above-mentioned preferred range by adjusting the amount of addition.

The adsorbing layer a and adsorbing layer c (3a and 3c in FIG. 2) preferably have a volume resistivity of 1.0 × 10 ¹⁴ Ωcm or more, and more preferably 1.0 × 10 ¹⁵ Ωcm or more. preferable. Such plastics include a mixed plastic sheet or film in which two or more of the same materials as described in the layer 3b are mixed, or a material obtained by laminating the same or different types of sheets or films, and the volume resistivity described above. Those satisfying the above are used. Specifically, acrylic resin, polyester resin, vinyl chloride resin, cellulose resin, polyamide resin, epoxy resin and the like are preferably used.

  The method for forming each layer is not particularly limited. A plastic film may be used for the adsorption layer b, and the adsorption layer a or the adsorption layer c may be formed on the film by applying a coating solution using a solvent, or a film may be used for each of the adsorption layers a, b, and c. You may laminate. Alternatively, each layer can be formed simultaneously by coextrusion.

About parts other than the adsorption layer in the electrostatic adsorption apparatus of this invention, it can manufacture using the manufacturing method of a conventionally well-known electrostatic adsorption apparatus.
The basic structure of the layered electrode portion (4 in FIG. 2) of the electrostatic attraction apparatus of the present invention is presented in the above-mentioned prior literature. There may be a plurality of electrode pairs, and the configuration on the plane may be, for example, a comb shape in order to increase the adsorption efficiency. The electrode having such a constant planar pattern can be formed by applying metal vapor deposition or a conductive paint containing metal powder or carbon powder on the insulating film-like support.

  FIG. 2 is a cross-sectional view of an example of an electrostatic adsorption device according to the present invention. The adsorption layer is composed of an adsorption layer b having a low volume resistivity, an adsorption layer a and an adsorption layer c having a high volume resistivity. Become. The low volume resistivity portion and the high volume resistivity portion may be the same material having different electrical conductivity or different materials having different electrical conductivity. Further, each of the adsorption layer a, the adsorption layer b, and the adsorption layer c may have a laminated structure. Furthermore, the substrate 5 is preferably an insulating film-like support having a volume resistivity equal to or higher than that of the adsorption layer a or the adsorption layer c.

  As a method for producing the electrostatic adsorption device of the present invention as shown in FIG. 2, for example, an epoxy resin, an acrylic resin or the like on the electrode side of the adsorption layer comprising the adsorption layer a, the adsorption layer b, and the adsorption layer c. The insulating adhesive or pressure-sensitive adhesive can be applied, and the substrate on which the electrode pattern is formed and the electrode can be bonded inside. At this time, the adhesive layer 4 itself made of an adhesive or a pressure-sensitive adhesive preferably has a high volume resistivity equal to or higher than that of the adsorption layer a and the adsorption layer c because of the necessity of insulating the electrode pair.

It is further advantageous for the electrostatic adsorption device that the surface of the adsorption layer can be made of a material having a high volume resistivity and different materials. Electrostatic adsorption devices often require curing, water, oil, and solvent resistance on their surfaces, depending on their application. For example, since the volume resistivity of nylon varies greatly depending on the environment, a surface coating treatment is essential for use as an adsorption layer. Further, since the vinyl chloride resin has a bleed phenomenon of a plasticizer, this is also preferably subjected to a surface coating treatment. These treated films are often insulators having a volume resistance of 1.0 × 10 ¹⁶ Ωcm or more. However, according to the present invention, by determining the thickness of these treatment films according to their volume resistance, it is possible to perform the multifunctional surface treatment so that these treatment films can also function as the adsorption layer a. It becomes possible.

  In FIG. 2, the conceptual diagram of the electrostatic attraction apparatus produced in the Example was shown as sectional drawing. 1 and 2 are electrode pairs, 3a, 3b and 3c are adsorption layers a and adsorption layers b covering the electrode pairs. It is the adsorption layer c. Reference numeral 4 denotes an adhesive layer, and 5 denotes an electrode holding material. A voltage is applied to the electrodes 1 and 2 by a power source 6. An electric field is generated between the electrodes 1 and 2 due to the potential difference applied between the electrodes 1 and 2. The electric field is expressed by the electric force lines 7, but a part of the electric force lines passes through the film 3 and generates a reverse charge due to electrostatic induction or polarization in the nearby object 8. For this reason, an object can be adsorbed on the surface of the adsorption films a and (3a) by Coulomb force.

  In the following, an adsorption sheet for an electrostatic adsorption apparatus was prepared using various materials for the adsorption layer a, the adsorption layer b, and the adsorption layer c.

A polyvinyl chloride resin film having a thickness of 100 μm and a volume resistivity of 2.4 × 10 ¹² Ωcm (using 30A conductive plasticizer manufactured by Riken Technos Co., Ltd.) is used as a film that can serve as the adsorption layer b, and the adsorption layer is formed on the film. An absorptive sheet was prepared by forming, by a coating method, an adsorbing layer a having a film thickness of 5 μm and a polymethylmethacrylate having a Tg of 100 ° C. (volume ratio: 1.2 × 10 ¹⁵ Ωcm, manufactured by Rohm & Haas Co., Ltd.).
On the other hand, a conductive paint containing carbon was screen-printed on a PET substrate sheet to form an electrode pattern having a thickness of 4 μm. As an electrode pattern, each electrode of the electrode pair basically has a comb-like shape, and the tooth part of one electrode of the electrode pair has entered the part between the teeth of the other electrode. The channel width between adjacent electrodes is 2 mm.
An adhesive layer with a thickness of 30 μm is formed on the electrode side of the adsorption sheet with an acrylic two-component curable pressure-sensitive adhesive, and the substrate sheet on which the electrode pattern is formed and the electrode are bonded together, and then a voltage is applied between the electrode pair. Thus, an electrostatic adsorption sheet for evaluation was obtained. Hereinafter, + 750V and -750V were applied to each electrode of the electrode pair, and the following experiment was performed with an interelectrode potential difference of 1500V.

  An adsorbing layer c having the same composition as that of the adsorbing layer a is formed on the opposite side of the adsorbing layer b of the adsorbing layer a of the adsorbing sheet prepared in Example 1, and an adsorbing sheet is produced. An electroadsorption device was formed.

On the same adsorption layer b as in Example 1, (polymethyl methacrylate used in Example 1) / isocyanate = 100/5 cross-linked product (volume resistance 7.2 × 10 ¹⁵ Ωcm) with a film thickness of 5 μm a was formed by a coating method to produce an adsorption sheet. As the isocyanate, Coronate HL (manufactured by Nippon Polyurethane Co., Ltd.) was used. An electrostatic chuck was formed in the same manner as in Example 1 using this suction sheet.

An adsorption sheet was formed in the same manner as in Example 3 except that the thickness of the adsorption layer a was 10 μm. An electrostatic chuck was formed in the same manner as in Example 1 using this suction sheet.

Application method of adsorbing layer a having a film thickness of 5 μm made of a crosslinked product (volume resistance 1.6 × 10 ¹⁵ Ωcm) of saturated polyester (Tg 65 ° C.) / Isocyanate = 100/5 on the adsorbing layer b similar to Example 1. An adsorption sheet was prepared. ) Eritel UE3201 (manufactured by Unitika) was used as the polyester. An electrostatic chuck was formed in the same manner as in Example 1 using this suction sheet.

(Examples 6 to 8, Comparative Example 1, Comparative Example 2, Examples 9 to 12, Comparative Example 3, and Comparative Example 4)
Hereinafter, adsorption sheets for Examples and Comparative Examples were prepared. Table 1 shows the types, shapes, and coating thicknesses of the raw materials used. An electrostatic adsorption device was formed in the same manner as in Example 1 using the produced adsorption sheets.
(Table 1)

ＵＶ塗料は、アクリディック１７８１３（大日本インキ社製）を用いた。
ＰＥＴ−１は、ポリエステルポリオールのシートであり、ヌーベラン（テイジン化成社製）を用いた。ヌーベランはポリマーに金属塩を坦持させ、導電性付与処理をしたものである。
ナイロンは東レ合成の１４０１ Ｎｏ．２０を用いた。
以上作製した吸着シートを静電吸着装置に組み込み、以下の試験方法によって評価した。

As the UV paint, ACRICID 17813 (Dainippon Ink Co., Ltd.) was used.
PET-1 is a sheet of polyester polyol, and Nouvelan (manufactured by Teijin Kasei Co., Ltd.) was used. Nouvelan is a product in which a metal salt is supported on a polymer and conductivity is imparted.
Nylon is Toray Gosei's 1401 No. 20 was used.
The suction sheet produced as described above was incorporated into an electrostatic suction device and evaluated by the following test method.

(1) Measurement of potential after friction When subjected to friction during energization, a charge in the direction opposite to the potential is generated on the surface of the adsorption layer.
By measuring the rate of disappearance of this charge over time, the adsorptive charge recoverability of the electrostatic adsorption device can be evaluated. In the measurement, the surface of the adsorption layer 3 is subjected to 20 reciprocating frictions with a tissue paper while the power supply 6 of the apparatus is turned on. After friction, the power is turned off, and the potential of the adsorption layer 3 surface is measured with the electrodes 1 and 2 grounded. Measure the values for 1 minute and 10 minutes after friction.

(2) Measurement of the rate of change in adsorption potential with time The sample was stored for 2 weeks with aluminum adsorbed on the surface of the adsorption layer under accelerated conditions of 40 ° C-80% with the device turned on to adsorb the aluminum. Measure the change in the surface potential of the part. The change in surface potential was divided by the surface potential before storage to obtain the rate of change in adsorption potential with time.

(3) Observation of appearance after accelerated test When a PVC sheet is used as the adsorption layer b, it is stored for 2 weeks at 40 ° C. and 80% with the power of the apparatus turned on, and the appearance of the adsorption layer surface (discoloration) Observe the changes. The observation results were evaluated on a five-point scale.
◎ No change ○ Colored slightly yellow or pink.
Δ Change to yellow × Change to yellow to brown.
XX Turns brown to dark brown.

(4) Surface wiping property The surface of the adsorbing layer on the electrostatic adsorbing sheet that was energized and left at room temperature for 2 weeks was wiped with a cloth moistened with water, and the easiness of wiping off the dirt was compared. The results were evaluated on a 5-point scale.
◎ Easy to remove and no dirt remains.
○ Easy to remove.
△ Hard to remove but can be removed.
× Some dirt remains difficult to remove.
XX Cannot be removed by wiping.

(5) Volume resistance The volume resistivity in the film thickness direction of the film and coating film used for the adsorption layer is measured.

  The measurement results are shown in Table 2, Table 3 and Table 4 below.

(Table 2)

(Table 3)

(Table 4)

As is clear from the results of Table 2, Table 3, and Table 4, those using a vinyl chloride resin for the adsorption layer b can suppress discoloration of the adsorption layer b after the accelerated test by laminating the adsorption layer a. it can. There was no change in the appearance of the adsorption layer b using PET or nylon using the accelerated test. However, in Comparative Example 3 in which the adsorption layer b is made of PET and the adsorption layer a is not used, it is known that the surface of the adsorption layer b that is in contact with aluminum is easily damaged. By laminating the adsorption layer a, such a change in the surface of the adsorption layer could be prevented. Moreover, it has confirmed that the comparative example 4 which used nylon for the adsorption layer b and did not use the adsorption layer a received aluminum corrosion. However, in Example 12 in which the adsorption layer a was laminated, aluminum was not corroded.
The adsorption layer a also functions as a coating layer. When the adsorption layer b is a vinyl chloride resin or PET, it can be seen that the surface wiping property of dust adsorbed by an electric field is improved. Moreover, when the adsorption layer b is nylon, it has been confirmed that moisture absorption of nylon is suppressed and volume resistivity is prevented from fluctuating due to environmental changes.

It is sectional drawing which shows the concept of the conventional electrostatic attraction apparatus. It is sectional drawing which shows notionally the structure of the electrostatic attraction apparatus of this invention.

Explanation of symbols

1, 2 Electrode pair 3 Adsorption layer 3a Adsorption layer a (High volume resistivity part)
3b Adsorption layer b (low volume resistivity part)
3c adsorption layer c (high volume resistivity part)
4 Adhesive layer 5 Substrate 6 Power supply 7 Electric field lines 8 Object to be adsorbed (conductive substance)

Claims (10)

An electric field generated by the electrodes, comprising at least a pair of positive and negative layered electrodes arranged on substantially the same plane in proximity to the back surface of the adsorption layer made of a layered dielectric, and means for giving a potential difference to the electrodes In the electrostatic adsorption device that adsorbs an object to the surface of the adsorption layer by the Coulomb force caused by the polarization charge induced in step 1, the volume resistivity in the vicinity of the adsorption surface of the adsorption layer is more than the volume resistivity in the central part of the adsorption layer. Is higher, and the volume resistivity in the vicinity of the suction surface is 1.0 × 10 ¹⁴ Ωcm or more.   The electrostatic adsorption device according to claim 1, wherein the adsorption layer has a laminated structure of an adsorption layer b on the electrode side and an adsorption layer a on the adsorption surface side having a higher volume resistivity than the adsorption layer b. The electrostatic adsorption apparatus according to claim 2, wherein the adsorption layer b has a volume resistivity of 1.0 × 10 ^{11 to} 9.9 × 10 ¹³ Ωcm. The electrostatic adsorption device according to claim 3, further comprising an adsorption layer c on the electrode side of the adsorption layer b, wherein the volume resistivity of the adsorption layer c is 1.0 × 10 ¹⁴ Ωcm or more.   The electrostatic attraction apparatus according to claim 4, wherein the adsorption layer a has a thickness of 0.5 to 30 µm, the adsorption layer b has a thickness of 5 to 300 µm, and the adsorption layer c has a thickness of 0.5 to 20 µm.   The electrostatic adsorption device according to claim 3, wherein the adsorption layer b contains a polyvinyl chloride resin. The electrostatic adsorption device according to claim 3, wherein the adsorption layer b contains nylon. The electrostatic adsorption device according to claim 3, wherein the adsorption layer b contains a polyester elastomer. The adsorption layer b is represented by the following general formula (1)

(1)
And an integer l, m, n representing the degree of polymerization is 1 / (l + m + n) = 0 to 0.5.
m / (l + m + n) = 0.5 to 0.995
n / (l + m + n) = 0-0.25
The electrostatic attraction apparatus of any one of Claims 3-5 containing resin which has the relationship represented by these. Each of the adsorption layer a and the adsorption layer c is one of the group consisting of an acrylic resin, a polyester resin, a vinyl acetate resin, a cellulose resin, a polyamide resin, and an epoxy resin. The electrostatic attraction apparatus according to any one of 9.

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