JP2006314990A - Coater of electric insulating sheet and method for producing electric insulating sheet with coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coater and a coating method, in each of which the accumulated state of a coating liquid on an electric insulating sheet is stabilized in order to restrain a coating film from becoming uneven owing to the instability of the accumulated state of the coating liquid. <P>SOLUTION: The coater for coating the electric insulating sheet with the coating liquid while sustaining an identical charging polarity of the electric insulating sheet and the coating liquid in a process for coating one surface of the traveling electric insulating sheet with the coating liquid and the method for producing a coated electric insulating sheet are provided. In order to sustain the identical charging polarity of the electric insulating sheet and the coating liquid, the coater comprises any one or both of a sheet charger for imparting electrostatic charges to one surface of the electric insulating sheet and a coating liquid charger for imparting electrostatic charges to the coating liquid. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coating apparatus for an electrically insulating sheet and a method for producing an electrically insulating sheet with a coating film.

  In recent years, electrical insulating sheets, such as polyester films, have excellent properties in heat resistance, chemical resistance, and mechanical properties, so they are often used as magnetic recording materials, various photographic materials, electrical insulating materials, and various process paper materials. It is used for For this reason, surface characteristics suitable for each application may be required, and in order to satisfy this requirement, various coating layers (coating films) are formed on the surface of the sheet. For example, a coating layer made of these materials is formed by thinly applying a coating liquid such as magnetic material paint, ink paint, slippery paint, releasable paint, hard coat paint, etc. to the surface of the sheet. .

  As an apparatus for applying a coating liquid to the surface of an electrically insulating sheet that runs continuously, an application apparatus based on a coating bar method, a gravure roll method, a die method, a curtain method, or the like is known. In such a coating apparatus, the coating liquid is applied to the surface of the sheet while being measured so that the coating thickness of the coating liquid is a predetermined thickness with respect to the traveling sheet. For example, in the coating bar method, a coating liquid is applied to a traveling sheet, and the applied coating liquid is measured with a coating bar, while removing excess and smoothing the coating liquid to a predetermined thickness. Apply. In application of such a coating liquid, a “liquid reservoir” of the coating liquid is formed more or less near the coating smoothing means. For example, a “liquid pool” is formed in the gap between the coating bar and the surface of the sheet on the upstream side of the coating bar.

  The liquid reservoir is also called meniscus. The shape of the liquid pool is related to the viscosity and surface tension of the coating liquid. When a coating liquid is coated on a sheet, the shape of the liquid pool has an optimum range (size, uniformity in the sheet width direction, etc.). When a force in the sheet conveyance direction acts on the liquid pool, the coating liquid is uniformly applied to the sheet by the adhesion force of the coating liquid to the sheet.

  However, when the state of the liquid pool becomes unstable, a portion where the coating liquid is not applied or streaky coating unevenness may occur on the surface of the sheet. For example, in the coating bar type coating method, it is difficult to uniformly coat a relatively high viscosity coating liquid on the electrical insulating sheet.

  One of the causes that the liquid pool becomes unstable is the charging of the electrically insulating coating liquid. In the charged coating liquid, since each particle forming the coating liquid is charged and charged with the same polarity, a Coulomb force is generated between the particles and a repulsive force is generated between the particles. When the repulsive Coulomb force is increased, the coating liquid in the liquid pool is bumped and the shape of the liquid pool becomes unstable. Furthermore, when the particles repel each other, air becomes easy to bite into the coating liquid, and the shape of the liquid pool becomes increasingly unstable. When the coating liquid is applied to the surface of the sheet in such a state that the shape of the liquid pool is unstable, the coating thickness of the coating liquid becomes non-uniform and uneven coating of the coating liquid occurs.

  Conventionally, in order to prevent the occurrence of uneven coating of the coating liquid by stabilizing the liquid reservoir, the space containing the liquid reservoir is sealed from the outside, and the space is decompressed to stabilize the shape of the liquid reservoir. It was done to hold on. However, the mechanical structure of the coating apparatus provided with the decompressed space becomes complicated and increases in size. In particular, such a coating apparatus is not suitable as a coating apparatus that is used in a process of melt-forming a thermoplastic resin and then stretching and manufacturing an electrically insulating sheet, that is, in-line.

  In the above, the liquid pool of the coating liquid in the coating liquid coating process has been described, but according to the knowledge of the present inventors, the prior art actively uses the Coulomb force while controlling the charging of the coating liquid, There was no technology to stabilize the liquid pool.

  On the other hand, conventionally, the following are known as coating methods for applying a coating liquid using charging or discharging of an electrically insulating sheet.

  First application method: An application method comprising supplying a coating liquid onto a continuously running sheet to form a coating liquid layer, and charging the sheet immediately before coating to assist adhesion of the coating liquid to the sheet.

  Second application method: When a coating liquid is supplied onto a continuously running sheet to form a coating liquid layer, the sheet is neutralized immediately before coating to prevent disturbance of the coating liquid on the sheet, thereby preventing uneven coating. A coating method comprising suppressing.

  The first application method is intended to improve the wettability of the surface of the electrically insulating sheet, and is disclosed in Patent Document 1 or Patent Document 2. That is, the first coating method is a good method by introducing a functional group having polarity into the coated surface of the electrically insulating sheet by a conventionally known corona discharge treatment to increase the surface tension of the electrically insulating sheet. Imparts good wettability. Accordingly, at the same time, an electrostatic charge is imparted to the electrically insulating sheet, so that the sheet is charged.

  The device for corona discharge treatment is a grounding electrode that contacts the discharge electrode such as a wire for generating corona discharge provided on the coated surface side of the sheet and the opposite surface of the coated surface of the sheet, and supports the traveling of the sheet. Consists of rolls. The earth roll functions as a shield electrode (or a ground electrode or a ground counter electrode) for assisting corona discharge, and is used for setting the potential on the back surface of the electrically insulating sheet to 0V. The configuration of the charging device is shown in Patent Document 2.

  FIG. 15 is a schematic side view of a coating apparatus 150 having a corona discharge treatment apparatus 151 disclosed in Patent Document 2. In FIG. 15, the coating apparatus 150 includes a corona discharge processing apparatus 151 and a coating liquid supply apparatus 155 that are directed from the upstream side to the downstream side in the moving direction PSD of the electrical insulating sheet PS. The coating liquid supply device 155 includes a discharge unit 156 for the coating liquid PC and a pump 157 for supplying the coating liquid PC to the discharge unit 156. A backup roll 158 is provided facing the discharge means 156 and in contact with the opposite surface PS2 of the coating surface PS1 of the sheet PS. The coating liquid PC is discharged from the discharge means 156 toward the coating surface PS1 of the sheet PS and applied to the coating surface PS1. A liquid pool PCP of the coating liquid PC is formed between the coating surface PS1 and the discharge means 156. The coating liquid PC applied to the coating surface PS1 forms a coating liquid layer PCL on the coating surface PS1.

  The corona discharge treatment apparatus 151 includes a grounding counter electrode roll 152 provided in contact with the surface PS2 opposite to the coating surface PS1 of the sheet PS, and a coating surface on the coating surface PS1 side of the sheet PS facing the grounding counter electrode roll 152. A corona discharge electrode 153 is provided at a distance from PS1. The corona discharge electrode 153 is connected to a corona discharge treatment power source 154.

  The electrically insulating sheet PS is in contact with the grounded counter electrode roll 152 and is conveyed in the movement direction PSD. By the grounded counter electrode roll 152, the surface PS2 opposite to the coating surface PS1 of the sheet PS is set to 0V potential. When the sheet PS passes between the corona discharge electrode 153 and the grounded counter electrode roll 152, the sheet PS is exposed to a corona discharge space containing a large amount of ions and radicals, and a polar functional group is formed on the surface of the sheet PS. Is introduced. At the same time, an electrostatic charge is simultaneously applied to the sheet PS. By such treatment, the wettability of the surface of the sheet PS is improved, and adhesion of the coating liquid PC to the sheet PS is promoted by an attractive force due to an electrostatic charge.

  Patent Document 2 does not mention the specific charging polarity of the coating liquid. However, since it is a system that uses the suction force due to charging, the electrically insulating sheet PS and the coating liquid PC are of different polarity or 0V. It can be said that it is only a thing using the Coulomb force attracted as positive / negative polarity. According to the knowledge of the present inventors, such a method cannot stabilize the shape of the liquid pool PCP.

  On the other hand, the second coating method is disclosed in Patent Document 3 and Patent Document 4. However, these conventional methods do not sufficiently remove the static charge present on each surface of the electrically insulating sheet, and the application unevenness due to charging of the electrically insulating sheet cannot be eliminated.

  A conventional static eliminator uses a generally known static eliminator using corona discharge. Such a static eliminator includes a self-discharge type static eliminator that removes static electricity by generating a corona discharge at the tip of a brush by bringing a grounded brush-shaped conductor close to a charged electrical insulating sheet, or a needle-like electrode. 2. Description of the Related Art An AC type or DC type voltage application type static eliminator that applies a high frequency voltage or a high DC voltage to generate a corona discharge for static elimination is used. In the conventional static elimination method using corona discharge, the generated positive and negative ions are attracted by the Coulomb force due to the positive and negative electrostatic charges of the electrically insulating sheet, and neutralized with the negative and positive electrostatic charges to neutralize the sheet charge. Is.

  However, when positive and negative charges are mixed in a region on the electrically insulating sheet close to each other, the lines of electric force due to electrostatic charges are closed between the charged regions having different polarities. For this reason, the electric field becomes very weak at a position slightly apart, and necessary ions cannot be attracted from the static eliminator, and it is difficult to eliminate positive and negative electrostatic charges on the sheet.

  Similarly, the electric lines of force due to the electrostatic charges of the electrically insulating sheet, which are electrically charged with opposite polarities and are not electrically charged, are closed between the charged areas having different polarities on the front and back of the sheet. Therefore, necessary ions cannot be drawn from the static eliminator. In other words, with the conventional static eliminator, even if you try to remove the charge before coating, there is no effect on the sheet with both positive and negative charges, and the sheet with the reverse polarity on the front and back sides. The coating unevenness could not be completely prevented.

  On the other hand, with regard to charge control of the coating liquid, a charge supply device is provided in a part of the piping for supplying the coating liquid, and the charge of the charged coating liquid is removed or reversely charged, so that the coating liquid is applied to the sheet. Application is disclosed in Patent Document 5. FIG. 16 is a schematic longitudinal sectional view for explaining the technique disclosed in Patent Document 5.

  In FIG. 16, the charge supply device 161 includes a coating liquid supply pipe 162a, an electrode pipe 164 provided around the coating liquid supply pipe 162a via an insulator 163, and a position outside the electrode pipe 164. And an insulator 165 that covers and protects the electrode tube 164, and a high-voltage power source 166. The coating liquid supply pipe 162a forms a part of the coating liquid supply pipe 162. A high voltage is applied to the electrode tube 164 from the high voltage power source 166. According to the embodiment of Patent Document 5, the high voltage applied to the electrode tube 164 is 4 kV. When a high voltage is applied to the electrode tube 164, an induced charge is generated in the coating liquid supply tube 162a.

  However, in this charging device, since the electrode tube 45 is not in contact with the coating liquid, it is not possible to inject charges into the coating liquid, and the charging efficiency of the coating liquid is poor despite the high voltage applied. . Therefore, even when the charge of the charged coating liquid can be removed at a small flow rate of the coating liquid, the coating liquid cannot be charged to a sufficient level. In other words, the charge supply device 161 disclosed in Patent Document 5 is a charging device capable of efficiently charging a coating liquid made of an electrically insulating liquid in a continuously traveling electrically insulating sheet coating apparatus. Absent.

As described above, conventionally, there is no technique for stabilizing the liquid pool with a simple method without complicating the coating apparatus, and the conventional technique has a problem of uneven coating due to the instability of the liquid pool. It was. In particular, when the coating liquid is an electrically insulating liquid and has a high viscosity, the liquid pool is not stable and uneven coating tends to occur. Furthermore, charging of the electrically insulating sheet causes a coating unevenness, which is a problem. Furthermore, the electrically insulating coating liquid cannot be efficiently charged and supplied to the coating apparatus.
JP-A-11-128804 Japanese Patent No. 2597237 JP-A-10-259328 Japanese Patent No. 2817056 JP-A-9-253565 JP 2004-39421 A US Patent Application Publication No. 2005/0030694 Electrostatic Handbook (Edited by the Electrostatic Society) published by Ohmsha p. 319 Electrostatic Handbook (Edited by the Electrostatic Society) published by Ohmsha p. 179

  An object of the present invention is to solve the above-mentioned problems of the prior art, and when applying a coating liquid to the first surface of a traveling electrical insulating sheet, the electrical insulating sheet, the coating liquid supply device, and the coating liquid layer are smoothed. An object of the present invention is to provide a coating apparatus that stabilizes a liquid pool formed in a gap with a forming apparatus and is less likely to cause coating unevenness, and a method for manufacturing an electrically insulating sheet with a coating film. An electrical insulating sheet charging device provides a charging device and a charging method for uniformly charging a coating coated surface of an electrical insulating sheet and its opposite surface, which are less likely to cause uneven coating due to charging, to opposite polarities.

  Another object of the present invention is to provide a charging device and a charging method for an electrically insulating liquid capable of efficiently charging an electrically insulating liquid such as a coating liquid and controlling the charge amount with an arbitrary charging polarity.

  A coating apparatus according to the present invention for solving the above-described problems is as follows.

  An application device that applies a coating liquid to a first surface of an electrically insulating sheet that travels in a predetermined movement direction, the sheet charging device that applies an electrostatic charge to the first surface, and the sheet charging device And a first surface coating liquid supply device that is disposed downstream in the moving direction and supplies the coating liquid to the first surface, and the sheet charging device is provided by the first surface coating liquid supply device. A coating apparatus for an electrically insulating sheet, which is provided so as to impart to the first surface an electrostatic charge having the same polarity as the charging polarity of the coating liquid when supplied to the first surface. This coating apparatus is called the coating apparatus of the first aspect.

  A coating apparatus that applies a coating liquid to a first surface of an electrically insulating sheet that travels in a predetermined movement direction, the first surface coating liquid supply apparatus supplying the coating liquid to the first surface; A coating liquid charging device that imparts an electrostatic charge to the coating liquid before being supplied to the first surface, and the coating liquid charging device is configured to perform the first liquid coating by the first surface coating liquid supply device. A coating apparatus for an electrically insulating sheet provided so as to impart to the coating liquid an electrostatic charge having the same polarity as the charge polarity of the first surface when the coating liquid is supplied to the surface. This coating apparatus is referred to as the coating apparatus according to the second aspect.

  An application device that applies a coating liquid to a first surface of an electrically insulating sheet that travels in a predetermined movement direction, the sheet charging device that applies an electrostatic charge of a predetermined polarity to the electrically insulating sheet, and the application device A coating liquid supply device for supplying a liquid to the first surface, and a coating for applying an electrostatic charge having the same polarity as the predetermined polarity to the coating liquid before being supplied to the first surface. An electrically insulating sheet coating device comprising a liquid charging device. This coating apparatus is referred to as the coating apparatus according to the third aspect.

In the coating apparatus according to any one of the first to third aspects, the volume resistivity 10 ⁹ is disposed on the second surface of the electrically insulating sheet, which is disposed upstream in the moving direction of the coating liquid supply device on the first surface. The coating device for an electrically insulating sheet provided with a second surface coating solution supply device that supplies a coating solution of [Ω · cm] or less.

  In the coating apparatus according to any one of the first to third aspects, the coating liquid containing water is disposed on the second surface of the electrically insulating sheet, which is disposed upstream in the moving direction of the coating liquid supply apparatus on the first surface. An electrically insulating sheet coating device provided with a coating liquid supply device for a second surface to be supplied.

  In the coating apparatus according to any one of the first to third aspects, the first surface coating liquid supply device is disposed downstream in the moving direction, and is supplied from the first surface coating liquid supply device to the first surface. It is preferable that a coating liquid leveling device for the first surface for smoothing the coating liquid is provided so that the applied coating liquid forms a coating liquid layer having a predetermined coating thickness.

  The coating layer smoothing device for the first surface is preferably a coating layer smoothing device based on any one of a coating bar method, a gravure roll coating method, and a die method. Further, the first surface is a surface that exists on the upper side with respect to the direction of gravity, and the first surface has the first surface in a direction orthogonal to the moving direction and the normal direction of the electrical insulating sheet. It is preferable that the coating liquid is supplied from the coating liquid supply apparatus on the first surface, and the coating liquid smoothing apparatus on the first surface is a coating liquid smoothing apparatus based on a coating bar system.

  In the coating apparatus according to the first or third aspect, the sheet charging device includes one or more charging units, and the charging units are arranged to face each other with the electrical insulating sheet interposed therebetween, and the electrical insulation A first electrode unit disposed on a first surface side of the electrically conductive sheet; and a second electrode unit disposed on a second surface side of the electrically insulating sheet, wherein the first electrode unit Has a first ion generation electrode, and the second electrode unit has a second ion generation electrode, and the voltage applied to the first ion generation electrode and the second ion generation electrode The voltage applied to is preferably a DC voltage having substantially opposite polarities.

  The first electrode unit includes a first shield electrode that is disposed in the vicinity of the first ion generation electrode and has an opening, and the second electrode unit includes the second ion generation electrode. It is preferable to have the 2nd shield electrode which is arrange | positioned in the vicinity of and has an opening part.

  In the coating apparatus according to any one of the first to third aspects, there is provided an electrical insulating sheet static eliminator comprising at least two static eliminator units provided at intervals in the movement direction downstream of the coating apparatus in the movement direction. And each of the static elimination units is disposed on the second surface side and the third electrode unit disposed on the first surface side of the electrical insulating sheet so as to face each other with the electrical insulating sheet interposed therebetween. A fourth electrode unit, and the third electrode unit has a third ion generation electrode and a third shield electrode having an opening in the vicinity of the tip of the third ion generation electrode. The fourth electrode unit has a fourth ion generation electrode and a fourth shield electrode having an opening in the vicinity of the tip of the fourth ion generation electrode, and is applied to the third ion generation electrode. Voltage and the fourth The voltage applied to the ion generating electrode, preferably substantially opposite polarities alternating voltage of one another.

  In the coating apparatus according to the second or third aspect, the first surface coating liquid supply device includes a storage tank that stores the coating liquid, and a discharge unit that discharges the coating liquid onto the first surface. A pump that supplies the coating liquid from the storage tank to the discharge means; and a coating liquid supply pipe that conveys the coating liquid between the storage tank, the discharge means, and the pump. When the coating liquid is supplied to the first surface, it is preferable that the first surface is charged to a polarity opposite to the charging polarity of the first surface.

  In the coating apparatus according to the second or third aspect, the first coating liquid supply apparatus includes a storage tank that stores the coating liquid, a discharge unit that discharges the coating liquid onto the first surface, A pump for supplying the coating liquid from a storage tank to the discharge means; a coating liquid supply pipe for conveying the coating liquid between the storage tank, the discharge means and the pump; It is preferable to have a conductive portion that is electrically conductive and electrically insulated from the outside, and a voltage applying means for applying a voltage to the conductive portion at a portion that contacts the coating liquid.

  In the coating apparatus according to the second or third aspect, it is preferable that a charge detection means for detecting a charged state of the coating liquid is disposed upstream of the discharge means of the first coating liquid supply apparatus.

  In order to solve the above problems, a charging device for an electrically insulating liquid according to the present invention is as follows.

  A storage tank for storing the electrically insulating liquid; and a liquid supply pipe for conveying the electrically insulating liquid from the storage tank, wherein the liquid supply pipe is in a portion in contact with the electrically insulating liquid and is electrically conductive. And a conductor part that is electrically insulated from the outside, and a voltage applying means for applying a voltage to the conductor part, wherein the conductor part is in the region in contact with the electrically insulating liquid. Electrical insulation satisfying 0.02 ≦ k / h ≦ 20, where h [mm] is a length in a cross section perpendicular to the flow direction of the electrical insulating liquid, and k [mm] is a length in the flow direction of the liquid. Liquid charging device.

  It is preferable that a charge detection means for detecting a charged state of the electrically insulating liquid is disposed downstream of the conductor portion.

  It is preferable that a resistor interposed between the conductor portion and the voltage applying means is installed.

  In order to solve the above problems, a method for producing an electrically insulating sheet with a coating film according to the present invention is as follows.

  Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for producing a sheet, wherein the coating liquid is applied to the first surface. When the coating liquid is applied to the first surface, the charge polarity of the first surface and the charging polarity of the coating liquid are the same polarity. Sheet manufacturing method. This method for producing a coated electrical insulating sheet is referred to as the method for producing a coated electrical insulating sheet of the first aspect.

  Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for manufacturing a sheet, wherein the first surface is forcibly charged to the same polarity as the charging polarity of the coating liquid before applying the coating liquid to the first surface. Manufacturing method of adhesive sheet. This method for producing an electrically insulating sheet with a coating film is referred to as a method for producing an electrically insulating sheet with a coating film according to the second aspect.

  Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for producing a sheet, wherein the coating liquid is forcibly charged to the same polarity as the charging polarity of the first surface before the coating liquid is applied to the first surface. Manufacturing method of adhesive sheet. This method for producing an electrically insulating sheet with a coating film is referred to as a method for producing an electrically insulating sheet with a coating film according to the third aspect.

  Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for producing a sheet, wherein the coating liquid and the first surface are forcibly charged to the same polarity before applying the coating liquid to the first surface. Manufacturing method. This method for producing an electrically insulating sheet with a coating film is referred to as a method for producing an electrically insulating sheet with a coating film according to the fourth aspect.

In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the volume resistivity is applied to the second surface of the electrically insulating sheet before the coating liquid is applied to the first surface. The manufacturing method of the electrically insulating sheet | seat with a coating film which apply | coats the coating liquid of 10 < ⁹ > [ohm * cm] or less.

  In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the second surface of the electrically insulating sheet contains water before the coating liquid is applied to the first surface. The manufacturing method of the electrically insulated sheet with a coating film which apply | coats a coating liquid.

  In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the electrical insulating property with a coating film that makes the polarity of the electrical potential of the electrical insulating sheet the same as the charging polarity of the coating liquid. Sheet manufacturing method.

  In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the electrically insulating property with a coating film for charging the second surface of the electrically insulating sheet to a polarity opposite to that of the first surface. Sheet manufacturing method.

  In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, one or more charging units are provided for the electrically insulating sheet, and the charging unit is a normal line of the electrically insulating sheet. In the direction, the first ion generation electrode located on the first surface side and the second ion generation electrode located on the second surface side of the electric insulation sheet disposed opposite to each other with the electric insulation sheet interposed therebetween And by applying a DC voltage whose polarity does not change with time to the first and second ion generation electrodes, the polarity is temporally applied to the electrically insulating sheet from the first surface side. A first ion cloud having a single polarity that does not change is irradiated, and a second ion cloud having a single polarity that is substantially opposite to the first ion cloud from the second surface side is applied to the first ion cloud. Irradiate simultaneously with ion cloud irradiation to It is preferable to charge the gate.

In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the unit length of the charged charge density on the first surface and the charged charge density on the second surface immediately before the application of the electrically insulating sheet. The rate of change of the absolute value per unit is 0.18 [C / m ² / m] or less, the difference between the maximum value and the minimum value of the back balance potential is 340 [V], and Irradiating the first ion cloud with a single polarity whose polarity does not change with time from the first surface side so as to be apparently uncharged, and the first ion cloud from the second surface side. Preferably, the electrically insulating sheet is charged by irradiating a second ion cloud having a substantially opposite polarity and a single polarity simultaneously with the irradiation of the first ion cloud.

In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the absolute charge per unit length of the charged charge density on the first surface and the charged charge density on the second surface of the electrically insulating sheet. The rate of change of each value is 0.12 [C / m ² / m] or less, the difference between the absolute maximum value and the minimum value of the back surface equilibrium potential is 200 [V], and apparently none A first ion cloud having a single polarity whose polarity does not change with time is irradiated from the first surface side so as to be charged, and is substantially opposite to the first ion cloud from the second surface side. It is preferable that the electric insulating sheet is charged by irradiating a second ion cloud having a single polarity at the same time as the irradiation of the first ion cloud.

  In the manufacturing method of the electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the first surface is neutralized on the downstream side in the moving direction after the coating liquid is applied to the electrically insulating sheet. It is preferable.

  The electrical insulation sheet after application is neutralized by providing at least two static elimination units spaced from each other in the moving direction with respect to the electrical insulation sheet. In a line direction, a third ion generation electrode located on the first surface side of the electrical insulation sheet and the fourth ion production located on the second surface side, which are disposed to face each other with the electrical insulation sheet interposed therebetween. An alternating voltage having a polarity that changes smoothly with time to the third and fourth ion generation electrodes, to the electrical insulating sheet from the first surface side. The first ion cloud having a single polarity of which polarity is changed is irradiated to the electric insulating sheet, and the single polarity having a polarity substantially opposite to that of the first ion cloud is applied to the electrically insulating sheet from the second surface side. The second ion cloud is the first ion It is preferable that the irradiation is performed simultaneously with the cloud irradiation.

  In the manufacturing method of the electrically insulating sheet with a coating film according to any one of the first to fourth aspects, it is preferable to use an electrically insulating coating liquid as a coating liquid to be applied to the first surface of the electrically insulating sheet.

In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the volume resistivity at 25 ° C. of the coating liquid supplied to the first surface of the electrically insulating sheet is 10 ⁹ [Ω. -It is preferable that it is more than cm].

In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, an absolute value of a charge amount of a coating liquid supplied to the first surface of the electrically insulating sheet is 10 ⁻³ [C / m ³ ] or less.

In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, a flow rate of the coating liquid supplied to the first surface of the electrically insulating sheet is 5 × 10 ⁻⁵ [m ³ / min]. It is preferably 5 × 10 ⁻⁴ [m ³ / min] or less.

  In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the coating thickness before drying downstream of the coating liquid supply device of the coating liquid is 1 [μm] or more and 50 [μm] or less. It is preferable.

  In order to solve the above problems, a method for charging an electrically insulating liquid according to the present invention is as follows.

  When discharging the liquid through a pipe from a tank that stores the electric insulating liquid, a part of the pipe that is electrically insulated from the outside and brought into contact with the electric insulating liquid is contacted with the electric insulating liquid. A method for charging an electrically insulating liquid characterized by the above.

  It is preferable to detect a charged state of the electrically insulating liquid and control a voltage applied to the conductor portion. It is preferable that the voltage applied to the conductor portion is a DC voltage whose polarity does not change with time.

  In the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, the coating film made of the applied coating liquid may be composed of a hard coat material, a release material, and an antireflection material. preferable.

  In the method for manufacturing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects, it is preferable that the coating film made of the applied coating liquid is a hard coat material made of an acrylic resin.

  It is preferable that the electrically insulating sheet with a coating film produced by the method for producing an electrically insulating sheet with a coating film according to any one of the first to fourth aspects is used as a roll or roll. Typical examples of the electrically insulating sheet to which the present invention is applied include sheets and sheets of plastic film, fabric, paper, etc., but polyethylene terephthalate film, polyethylene naphthalate film, polypropylene film, polystyrene film. Plastic films such as polycarbonate film, polyimide film, polyphenylene sulfide film, nylon film, aramid film, and polyethylene film are particularly suitable for application of the present invention because of their high electrical insulation.

  In the present invention, “the first surface of the traveling electrically insulating sheet” is a surface on which the coating liquid is applied and the coating liquid layer is formed, out of the two main surfaces of the electrically insulating sheet. When the coating liquid is applied to the two surfaces of the electrically insulating sheet to form the coating liquid layer, the first surface is applied after the coating liquid is applied to the second surface downstream in the sheet moving direction. Refers to the surface to which is applied.

  In the present invention, “the charging polarity of the electrical insulating sheet and the charging polarity of the coating liquid are the same polarity” means the apparent charge density of the electrical insulating sheet or the back surface equilibrium potential of the coated surface on which the coating liquid is applied. It means that the charging polarity and the charging polarity of the coating liquid are the same.

The charging polarity of the coating liquid is a charging polarity at a value obtained by adding the positive and negative charge amounts of the coating liquid. The amount of the coating liquid for determining the charging polarity of the coating liquid is 10 ⁻⁴ [m ³ ] or more and 5 × 10 ⁻⁴ [m ³ ] or less. Even in the case where positive and negative charges are mixed in the electrically insulating coating liquid, the determination is made based on the charge polarity of the total value of the positive and negative charges regardless of the ratio and distribution state of the positive and negative charges.

In the present invention, “the coating solution is substantially uncharged” means that the charge amount of the coating solution is −2 × 10 ^{−5 to} + 2 × 10 ⁻⁵ [C / m ³ ] (− 2 nC / 100 ml to +2 nC / 100 ml).

  In the present invention, “static charge” refers to a charge of a substance that does not change with time, and the substance is charged by the generation of an electrostatic charge.

In the present invention, the “electrically insulating sheet” refers to a sheet having a surface resistivity of 10 ⁹ [Ω / □] or more, or a volume resistivity of 10 ⁹ [Ω · cm] or more, which is difficult to pass electricity.

In the present specification, “electrically insulating liquid (coating liquid)” refers to a liquid (coating liquid) having a volume resistivity of 10 ⁹ [Ω · cm] or more. The volume resistivity of the electrically insulating liquid (coating liquid) is determined between the two surfaces when the electrically insulating liquid (coating liquid) is filled in a cube having a side of 1 cm and a voltage is applied between the opposing surfaces. Expressed in electrical resistance. Actually, it is measured by applying a DC voltage using a cylindrical electrode. A liquid to be measured (coating solution) is placed in a cylindrical electrode having an inner cylinder electrode inside the outer cylinder electrode, a DC voltage of 15 V is applied between the outer cylinder electrode and the inner cylinder electrode, and the resistance value Rv [ Ω]. At an inner cylinder radius r1 [cm], an outer cylinder radius r2 [cm], and an electrode effective length l [cm], the volume resistivity ρv [Ω · cm] is Rv · (2πl) / (ln (r2 / r r1)).

  The volume resistivity of the electrically insulating liquid (coating liquid) can be measured simply by placing 100 ml of the liquid to be measured (coating liquid) thinly in an electrically insulating container and measuring two liquids (coating liquids). Terminals (diameter 2 mm, length 50 mm) are arranged in parallel with a distance of 50 mm, a DC voltage of 15 V is applied between the measuring terminals, and the resistance value [Ω] is read with a Simco Worksurface Tester. I can do it.

  Examples of the “coating bar” in the present invention include rods, wire bars in which a wire is wound around a rod, metering bars, and a bar with a groove in which a rod is cut.

  In this specification, “liquid reservoir” means that the coating liquid or the like is applied to an electrically insulating sheet or the like by any coating device from the closest part of the sheet to the coating liquid on the upstream side of the coating bar. This refers to a pool of coating liquid formed around the area of the gap between the sheet and the coating bar. Needless to say, the coating liquid remaining thinly on the surface of the coating bar or on the web surface during continuous coating is not a liquid pool here. This is because these thin coating liquids move following the movement of the coating bar and the web surface as they are, and are not the coating liquids in the accumulated state.

  In the application of the coating liquid, a “liquid reservoir” of the coating liquid is formed more or less near the application means. For example, a “liquid reservoir” is formed in the clearance with the upstream sheet of the coating bar type metering bar. The liquid pool is also called a meniscus. The liquid pool is also called a bead or a heel.

  In this specification, “a state in which the liquid pool is stable” refers to a state in which the surface shape of the liquid pool does not change significantly with time, and no periodic vibration or sudden deformation occurs in the surface shape of the liquid pool. State. In terms of time, it is ideal that the surface shape of the liquid pool does not change during all the time when the coating is performed on the sheet. If the surface shape of the liquid pool does not change for about 3 minutes from the beginning.

  In the present specification, “uniformity of the coating thickness” means that the coating liquid is continuously coated in the sheet moving direction with a predetermined width in the sheet width direction, and there is a variation in the amount of coating liquid applied. It is small and the thickness of the formed coating film is substantially uniform in the range where there is no problem. The range that can be said to be substantially uniform depends on the required accuracy of the coating thickness, but the variation in coating thickness is within 30%.

  In this specification, the “corona discharge treatment method” refers to a surface treatment method in which a functional group having polarity is introduced into the surface of an electrically insulating sheet to increase the surface tension of the sheet surface and improve wettability. This surface treatment is performed by creating a high electric field between the corona discharge electrode and the grounded counter electrode roll to generate corona discharge, for example, by forming a discharge space containing a large amount of ionized radicals. By exposing the sheet to this discharge space, the sheet surface is subjected to a discharge treatment, and polar groups (for example, —C═O group, —COOH, —OH group) are imparted to the sheet surface. The grounding counter electrode roll functions as a shield electrode (or a grounding electrode or a grounding counter electrode) for assisting corona discharge, and the back surface of the sheet is set to 0V potential.

  Here, the wettability is an index indicating the ease of spreading of the liquid on the surface of the solid that does not allow the liquid to penetrate. If the wettability of the sheet is high, the solid surface gets wet with the liquid. In this case, the contact angle between the solid surface and the droplet is generally less than 90 °.

  In this specification, “corona charging” means that positive or negative ions are generated by local breakdown of air due to corona discharge, and the ions are attached to the surface of the electrically insulating sheet to charge the sheet. say. Usually, the sheet surface is not directly exposed to the discharge space, and no polar group is formed on the sheet surface. Therefore, in that case, the surface tension of the electrically insulating sheet does not change and the wettability is not improved. In many cases, a corona charger has a structure in which a discharge electrode is surrounded by a shielded electrode, and a corona discharge is generated by applying a high voltage to the discharge electrode.

  In the present invention, “forcibly charging the first surface of the electrically insulating sheet to the same polarity as the charging polarity of the coating liquid” means that the first surface is irradiated with ions by “corona charging”. The first surface is forcibly charged to the same polarity as the charging polarity of the coating liquid.

  In the present specification, the “movement path of the electrically insulating sheet” refers to a predetermined space through which the electrically insulating sheet should pass for charging or charge removal.

  In the present invention, the “normal direction of the electrically insulating sheet” refers to the normal direction of this plane when the moving sheet is regarded as a plane having no slack in the width direction.

  In this specification, the “width direction” refers to a direction orthogonal to the moving direction and the normal direction of the electrical insulating sheet.

  In the present invention, “ion” refers to various forms of charge carriers such as electrons, atoms that have exchanged electrons, molecules with charge, molecular clusters, and suspended particles.

  In the present invention, an “ion cloud” is a group of ions generated by an ion generation electrode, and is a group of ions that are not fixed to a specific place but are floating while spreading in a certain space like a cloud.

  In the present invention, the “unipolar ion cloud” refers to an ion cloud in which the number of positive or negative ions is overwhelmingly larger than that of the other polarity. Normally, when the potential of the ion generating electrode is positive, a positive unipolar ion cloud is formed in the vicinity of the ion generating electrode, and when the potential of the ion generating electrode is negative, in the vicinity of the ion generating electrode. Then, a negative unipolar ion cloud is formed. However, if the polarity of the voltage of the ion generation electrode is reversed twice or more after the ions are generated in the vicinity of the ion generation electrode and before reaching the electric insulation sheet, the ion generation electrode and the electric insulation sheet are interposed. There are positive and negative ions, the positive and negative ions recombine, the concentration of ions decreases in the first place, and every time the polarity is reversed, the direction of the Coulomb force against the ions is also reversed. The ion cloud that is produced can no longer be a unipolar ion cloud.

  In the present invention, the “ion generating electrode” refers to an electrode that generates ions in the air near the tip of the electrode by corona discharge or the like by applying a high voltage. The “shield electrode” refers to an electrode that is disposed in the vicinity of the ion generation electrode and assists corona discharge at the tip of the ion generation electrode by applying an appropriate potential difference to the ion generation electrode.

  In the present invention, the “tip of the ion generation electrode” refers to a portion that forms an electric field for generating ions among the respective portions of the ion generation electrode and is closest to the virtual plane. Here, the “virtual plane” refers to a predetermined plane virtually assumed between the first and second ion generation electrodes.

  In many cases, the ion generation electrode extends in the width direction. In this case, when there is a part forming an electric field for generating ions in a cross section perpendicular to the width direction at each position in the width direction of the ion generation electrode, the part closest to the virtual plane is the width direction. The “tip” at that position. For example, if the ion generation electrode is a row of needle electrodes extending in the normal direction of the electrically insulating sheet provided at a predetermined interval in the width direction, the tip of the needle corresponds, and the ion generation electrode is the sheet In the case of a wire electrode formed of a wire extending in the width direction, the portion closest to the virtual plane in each part in the width direction of the wire corresponds.

  In the present invention, “the first and second ion generation electrodes are arranged to face each other” means that the first and second ion generation electrodes face each other across the sheet moving path and the first ions Shield electrode between the position of the leg of the perpendicular line dropped from the front end of the generation electrode to the plane including the position of the front end of the second ion generation electrode and parallel to the sheet moving path, and the position of the front end of the second ion generation electrode This means that no conductor exists.

There may be a case where two or more wire electrodes or two or more needle electrode rows arranged in the moving direction of the electrically insulating sheet constitute one ion generation electrode. However, when adjacent wire electrodes or needle electrode arrays operate as different ion generation electrodes, for example, between the vicinity of the tips of adjacent wire electrodes or needle electrode arrays, the AC voltage to be applied to these electrodes When there are conductors (for example, shield electrodes) having potentials different from each other by more than 1/2 of the effective value, when the voltages applied between the adjacent wire electrodes or needle electrode rows are different, the adjacent wire electrodes or needle electrode rows Is larger than the distance d ₁ between the tip of the electrode and the ion generating electrode facing the electrode, it is considered that they belong to another ion generating electrode, that is, another charging unit.

  In the present invention, “the third and fourth ion generation electrodes are arranged to face each other” is defined in the same manner.

  In the present specification, the “charged pattern” refers to a state in which at least a part of the electrically insulating sheet is locally positively and / or negatively charged. For example, the state (distribution) of charging can be confirmed as a pattern with fine powder (toner) or the like.

  In the present invention, the “rear surface equilibrium potential” of the first surface of the electrically insulating sheet means that the ground conductor is placed closer to the opposite surface (rear surface) closer than 20% of the sheet thickness or 10 μm, whichever is smaller. In the state in which the electric charge of the reverse polarity equivalent to the electric charge on the back surface is induced to the ground conductor, and thereby the electric potential on the back surface is substantially zero, the measurement probe of the surface electrometer is The potential of the first surface measured in the state of being sufficiently close to the sheet from the surface side of 1 to about 0.5 to 2 [mm]. As a measurement probe of the surface electrometer, a measurement probe having a small diameter of several millimeters or less is preferable. For example, a probe 1017 manufactured by Monroe, an opening diameter of 1.75 [mm] or 1017EH, an opening diameter of 0 .5 [mm].

  The charge distribution on the first surface is determined by using either a surface electrometer probe or a sheet with the ground conductor in close contact with the back surface using a movable means such as an XY stage. The back surface equilibrium potential is sequentially measured while moving at a low speed (about 5 [mm / sec]), and the obtained data is obtained by two-dimensional mapping. The back surface equilibrium potential of the second surface is measured in the same manner.

In the present invention, “charge density” (unit: [C / m ² ]) refers to the amount [C] of charge existing per unit area [m ² ] on a sheet.

Here, a method for determining the charge density by measuring the back surface equilibrium potential is shown below. The charge density is obtained from the relational expression σ = C · v between the electrostatic capacity C [μF / m ² ] per unit area of the sheet and the back surface equilibrium potential v. The capacitance C per unit area of the sheet is obtained by the relational expression C = ε ₀ ε _r / t of the capacitance per unit area of the parallel plate. Here, ε ₀ is a dielectric constant in a vacuum, and its value is 8.854 × 10 ⁻¹² [F / m]. ε _r is the relative dielectric constant of the film. t is the film thickness [m]. By using a surface potential meter having a field of view sufficiently small with respect to the magnitude of charging, it is possible to accurately know the local back surface equilibrium potential of a small area, and thus the local charged charge density.

  In this specification, the “apparent charge density” refers to the sum of local charge densities on both surfaces of the same position in the in-plane direction of the electrical insulating sheet. The local charge density refers to a charge density in the range of about 6 mm or less, preferably 2 mm or less, on the surface of the electrically insulating sheet.

In this specification, “apparently uncharged” means that the apparent charge density is substantially zero (−2 μC / m ² or more and ² μC / m ² or less) in each part in the in-plane direction of the electrical insulating sheet. The state that has become.

In this specification, “apparent charge removal” means that a portion where the apparent charge density is substantially non-zero (less than −2 μC / m ² or more than +2 μC / m ² ) is removed by charge removal. In other words, it means that an apparent uncharged state is achieved.

In this specification, “each surface of the sheet is uncharged” means that each charge density of the first surface and the second surface of the sheet is substantially zero (−2 μC / m ² or more and ² μC / m ^2). The following is the state.

  In the present invention, the “aerial potential” refers to a sheet potential measured in a state where an electrically insulating sheet is installed in the air. The sum of the charges on the front and back surfaces of the sheet is measured from the ground. The thickness of the sheet is sufficiently small relative to the distance to the ground, and the imaginary potential of the uncharged sheet, which is the sum of the charges on the front and back of the sheet, is virtually 0 V, without distinguishing between the charge on the front and back surfaces of the sheet. It is.

  In this specification, “each surface of the sheet is substantially uniformly charged” means the potential amplitude (pp) in the distribution of the back surface equilibrium potential of the first surface and the back surface equilibrium potential of the second surface. ) Is 100V or less. At this time, the back surface equilibrium potential of the first surface and the average value of the back surface equilibrium potential of the second surface may be any number. However, the average value is an absolute value and is preferably from 0 V to 2 kV.

  In this specification, each potential is a potential from the grounding point unless otherwise specified. In many cases, shield electrodes and backup rolls during coating are used while being grounded.

  In this specification, the coating thickness of the coating liquid is measured before drying the coating liquid downstream in the sheet moving direction of the coating apparatus for applying the coating liquid and the coating liquid layer smoothing apparatus for smoothing the coating liquid. Is done. Specifically, it is preferably within 2 to 10 seconds after coating and before starting drying. As a method for measuring the coating thickness, for example, a method of calculating by using the refraction of the coating liquid obtained from the optical interference waveform, or a coating liquid supply apparatus having a pump for discharging a fixed amount while measuring the coating liquid is used. In some cases, there is a method of calculating from the coating width in the sheet width direction and the moving speed of the sheet.

  In the present invention, “does not change with time” means that the state does not change over a period of 2 seconds or more, more preferably 20 seconds or more, and even more preferably 2 minutes or more. For example, “irradiating a first ion cloud of a single polarity whose polarity does not change in time from the first surface side of the electrical insulating sheet” means that without reversing the polarity with respect to the ground point, This refers to irradiation with an ion cloud that maintains the same polarity for 2 seconds or longer, preferably 20 seconds or longer, and more preferably 2 minutes or longer. However, polarity reversal due to non-periodic noise components such as white noise is not referred to as polarity reversal here.

  According to the present invention, as will be described later, as is apparent from the comparison between the examples and the comparative examples, the coating liquid applied to the surface of the electrical insulating sheet is less likely to cause uneven coating and repelling. A sheet coating apparatus is provided, which makes it possible to produce an electrically insulating sheet with a coating film with less coating application unevenness and coating repelling.

  If the charging polarity of the electrical insulating sheet and the charging polarity of the coating liquid are the same, the liquid pool of the coating liquid formed between the coating device and the sheet can be stabilized, and good coating with less uneven coating can be realized. I can do it.

  Further, the electric insulating liquid can be charged efficiently by a simple method of applying a voltage to a part of the liquid supply pipe. When the liquid is used as a coating liquid, an electrically insulating sheet with a coating film with little occurrence of coating unevenness can be produced.

  The invention will be further described by way of example with reference to the drawings. In the examples, a plastic film is used as the electrically insulating sheet. However, the present invention is not limited to this.

As described above, a coating apparatus or a coating method for coating a coating liquid on the surface of an electrically insulating film that is continuously running has been proposed. However, in the conventional coating apparatus or coating method, the shape of the “liquid reservoir” becomes unstable and uneven coating may occur. Below, the coating apparatus and the coating method which stabilize the liquid reservoir of this invention and suppress coating unevenness are demonstrated.
1 and 2 show an embodiment of the electrical insulating sheet coating apparatus of the present invention. 1 and 2, the electrically insulating sheet coating apparatus 10 of the present invention has sheet conveying means for continuously traveling the electrically insulating sheet S in a predetermined movement direction. A part of this sheet conveying means is shown with a rotatable conveying roll 11. In the drawing of the electrically insulating sheet S, the upper surface is the first surface S1 of the electrically insulating sheet S, and the lower surface is the second surface S2 of the electrically insulating sheet S. A predetermined moving direction of the electrically insulating sheet S is indicated by an arrow SD. The electrically insulating sheet S moves while traveling in the direction of the arrow SD while being supported by the transport roll 11 or the like.

  A sheet charging device 5 for providing an electrostatic charge to the first surface S1 is provided. A coating liquid supply device 20 for the first surface is provided downstream of the sheet charging device 5 in the moving direction SD of the electrically insulating sheet S. The coating liquid supply device 20 for the first surface supplies the coating liquid C1 to the first surface S1. The sheet charging device 5 imparts, to the first surface S1, an electrostatic charge having the same polarity as the charging polarity of the coating liquid C1 when it is supplied to the first surface S1 by the coating liquid supply device 20 on the first surface. .

  The coating apparatus 10 includes a first surface coating liquid smoothing apparatus 30 that applies a pre-measured coating liquid to the sheet S to uniformly smooth the coating thickness. The coating layer smoothing device 30 on the first surface is a coating layer smoothing device of a coating bar system using a rotating coating bar 31. The coating bar 31 measures the coating liquid C1 attached to the sheet S so as to have a predetermined coating amount, and smoothes the coating liquid layer. Since the coating bar 31 has meterability, it is also called a metering bar. The coating bar 31 is a wire bar in which a wire is wound around a rod having a diameter of several millimeters to several tens of millimeters. The wire diameter is 0. It is several mm to several mm. A coating bar 31 corresponding to the viscosity of the coating liquid C1 and a desired coating thickness is selected. As the coating bar 31, a rod bar, a grooved bar obtained by cutting a groove in the rod, or the like can also be used.

  The discharge portion of the coating liquid C1 to the first surface S1 of the coating liquid supply device 20 on the first surface is formed by the discharge means 21 in which a plurality of nozzles 21a are arranged at intervals in the width direction of the sheet S. ing. From the tip of each nozzle 21a of the discharge means 21, the coating liquid C1 is discharged uniformly without interruption toward the first surface S1.

  On the upstream side of the coating bar 31, a liquid pool CP1 of the coating liquid C1 supplied from the discharge means 21 is formed in contact with the first surface S1 and the surface of the coating bar 31. The coating liquid discharge means 21 is preferably provided so as to supply the coating liquid C1 directly to the liquid pool CP1. The supply of the coating liquid C1 to the liquid pool CP1 may be performed on the surface of the liquid pool CP1, or the coating liquid discharge port of the discharge means 21 may be inserted into the liquid pool CP1 and supplied directly into the liquid pool CP1. good. Further, the coating liquid may be supplied to the liquid pool CP1 at several places of the liquid pool CP1. Furthermore, the coating liquid is allowed to flow down on the smooth surface of the plate-like body having a smooth surface that is open to the atmosphere, and the coating liquid that flows down uniformly in the width direction of the first surface S1 is stored in the liquid pool CP1. It may be supplied (disclosed in Japanese Patent Application No. 2006-052448).

  The coating liquid supply device 20 on the first surface includes a storage tank 22 that stores the coating liquid C1, a pump 23, and a coating liquid supply pipe 24. The coating liquid supply pipes 24 are coupled to each other so as to transport the coating liquid C <b> 1 from the storage tank 22 through the pump 23 to the discharge means 21. The coating liquid C1 is quantitatively discharged from each nozzle 21a by the operation of the pump 23.

  The coating liquid C1 is easily triboelectrically charged by the coating liquid supply pipe 24 extending from the storage tank 22 to the discharge means 21. When two different substances come into contact with each other, a tribocharging phenomenon occurs, and electrostatic charges having opposite polarities are generated and charged respectively. At this time, the polarity to which each substance is charged is determined by the charge train. Therefore, by selecting an appropriate material for the coating liquid supply pipe 24 for the coating liquid C1 to be supplied, the coating liquid C1 is charged. Can be controlled.

  On the other hand, regarding this charging, the coating liquid supply apparatus 20 on the first surface has a coating liquid charging apparatus 40 attached to a part of the coating liquid supply pipe 24. The coating liquid charging device 40 is connected to a high voltage power supply 41. In this embodiment, the coating liquid charging device 40 is provided downstream of the pump 23, but the coating liquid charging device 40 may be provided upstream of the pump 23.

  The sheet charging device 5 for applying an electrostatic charge to the electrically insulating sheet S includes a unit 7c including an electrode 6c disposed on the first surface S1 side and a DC power source 5c coupled to the electrode 6c, The unit 7e includes an electrode 6e disposed on the surface S2 side and a DC power source 5e coupled to the electrode 6e. These units 7c and 7e are arranged to face each other with the electrically insulating sheet S interposed therebetween. The detailed configuration and operation of the sheet charging device 5 will be described later.

  In the coating apparatus 10, the sheet S is supplied to the coating apparatus 10 by one of the following two methods.

  In the first method, the melted resin is extruded from a die, discharged onto a cooling roll, removed from the mold, formed into a sheet shape, and then a film is applied from a film forming step of forming a thin film by stretching. 10 to supply directly. Here, this method is called an inline method. When the stretching process includes a longitudinal stretching process and a subsequent lateral stretching process, the coating liquid is applied in a state where the width of the film (sheet S) is narrow when the coating apparatus 10 is arranged before the lateral stretching process. Is applied, it is easy to apply. Further, when the transverse stretching step involves heating, the solvent of the coating liquid can be dried during this heating.

  In the second method, after the film is wound up into a roll shape through the above-described film forming process to form a film roll, the film is unwound from the film roll, and the unwound film is transferred to the coating apparatus 10. And supply method. Here, this method is called an off-line method.

  For example, the coating apparatus for forming a coating layer made of a hard coat material or a coating layer made of an optical material having an antireflection function or an optical filter function on the surface of the electrical insulating sheet is the above-mentioned in-line method. Applicable. In this case, after the sheet is stretched in the moving direction of the sheet, that is, after passing through the longitudinal stretching process, the sheet is moved to an application process for applying a coating liquid that forms the coating layer on the surface of the sheet, The sheet to which the coating liquid has been applied in the coating process can be advanced to a process of stretching in the width direction, that is, a lateral stretching process. Thereafter, the sheet may be further stretched as necessary.

  When the coating liquid C1 is supplied from the coating liquid discharge means 21 toward the first surface S1 immediately upstream in the moving direction SD of the sheet S of the coating bar 31, the moving direction SD of the sheet S of the coating bar 31 A liquid pool CP1 is formed on the upstream side.

  However, the shape of the liquid pool CP1 is difficult to be constant. This is due to the following reasons. Since the coating liquid C1 is usually electrically insulating, it is triboelectrically charged when the coating liquid C1 comes into contact with the storage tank 22 or the coating liquid supply pipe 24 and flows. Accordingly, the coating liquid C1 is more or less charged. In the charged coating liquid C1, the liquid particles have the same polarity and repel each other by Coulomb force, so that the outer shape of the liquid pool CP1 becomes unstable. Furthermore, this repulsion state makes it easier for air to get caught in the liquid pool CP1, and the outer shape of the liquid pool CP1 becomes increasingly unstable. Since the shape of the liquid pool CP1 becomes unstable, coating unevenness may occur in the coating liquid layer CL1 formed on the first surface S1 by applying the coating liquid C1. The coating unevenness forms a flow mark.

  The present inventors have found that the shape of the liquid pool CP1 can be stabilized by making the electrically insulating sheet S and the coating liquid C1 have the same polarity. Specifically, for example, in a situation where the coating liquid C1 is charged to a specific positive or negative polarity, the first surface (coating surface) S1 of the electrical insulating sheet S is the same as the coating liquid C1. The liquid is charged with a polar electrostatic charge, and the shape of the liquid pool CP1 is controlled and stabilized by charging the sheet S in the vicinity of the coating bar 31. On the contrary, when the polarity of the charge on the first surface (coating surface) S1 of the electrical insulating sheet S is a specific polarity, the charge polarity of the coating liquid C1 may be adjusted to this specific polarity.

  Further, when the inventors forcibly charge both the first surface (coating surface) S1 of the electrical insulating sheet S and the coating liquid C1 to the same polarity, the shape of the liquid pool CP1 is the most. I found it easy to stabilize. That is, when the sheet S is forcibly charged to the same polarity as the charging polarity of the coating liquid C1 or the liquid pool CP1, the shape of the liquid pool CP1 is stabilized. On the other hand, when the sheet S is charged to the opposite polarity of the coating liquid C1, the liquid pool CP1 is easily extended to the upstream side in the moving direction SD of the sheet S so as to be attracted to the sheet S, and the liquid pool CP1. It has been found that the outer shape of.

  An example of this state is shown in FIG. 3A. In FIG. 3A, if the charging polarity of the coating liquid C1 is positive, for example, the charging polarity of the first surface (coating surface) S1 of the electrical insulating sheet S is made positive so that the shape of the liquid pool CP1 is obtained. Is stabilized. That is, in FIG. 3A, the sheet charging device 5 (FIG. 1) arranged upstream of the coating liquid supply device 20 (FIG. 1) causes a positive static on the first surface (coating surface) S1 of the electrically insulating sheet S. When the charge is applied, at the same time, a negative electrostatic charge is applied to the second surface (the surface opposite to the coating surface) S2. The charging method will be described later.

  The positive and negative charges of the first surface S1 and the second surface S2 are equal in polarity with opposite polarities, and the sheet S is apparently uncharged. At this time, even if the second surface S2 of the electrically insulating sheet S is negatively charged, the negative charge is separated from the coating liquid C1 by the thickness of the sheet S. In the gap between the coating bar 31 and the electrical insulating sheet S, the negative charge on the second surface S2 is more effective than the electric field due to the positive charge on the first surface S1 effectively acting on the liquid pool CP1. Is small. Therefore, if the positive charge of the first surface S1 and the charge of the coating liquid C1 are the same, the liquid pool CP1 is stabilized in a shape having a curve outside the coating bar 31 and the electrically insulating sheet S. is there. In FIG. 3A, this state is shown by the external shape of the vertical cross section of the liquid pool CP1.

  FIG. 3B shows a state different from the case of FIG. 3A. In FIG. 3B, the coating liquid C2 is applied to the surface opposite to the first surface (coating surface) S1 of the electrical insulating sheet S, that is, the second surface S2, and the coating liquid layer CL2 is formed. If the charging polarity of the liquid C1 is, for example, positive, the liquid pool CP1 is stabilized by making the charging polarity of the first surface S1 of the electrical insulating sheet S positive. Thus, even when the coating liquid layers CL1 and CL2 are formed on both surfaces of the electrical insulating sheet S, the functions and effects of the present invention can be obtained effectively.

For example, when the water-soluble coating liquid C2 is applied to the second surface S2 and the coating liquid layer CL2 is formed, and then the electrically insulating coating liquid C1 is applied to the first surface S1, The two surfaces S2 may in effect act as electrical conductors. This is because, in a water-soluble coating liquid C2 containing water prepared by dissolving a water-soluble coating material in pure water, the volume resistivity is 10 ⁹ [Ω · cm] or less, more preferably 10 ⁶ Ω · cm. This is because it is as follows.

  In such a state, the coating liquid CL2 formed on the second surface S2 is grounded by the coating bar 31a (FIG. 7) that applies the coating liquid C2 to the second surface S2, and has a 0 [V] potential. It becomes. Even in such a state, the first surface S1 is charged with the same polarity as the charging polarity of the coating liquid C1, and the second surface S2 has no opposite polarity charge. The shape of the liquid pool CP1 is further stabilized, and coating unevenness hardly occurs.

  That is, as compared with the case shown in FIG. 3A, the electric field due to the electrostatic charge on the first surface S1 of the electrical insulating sheet S is more likely to act on the liquid pool CP1 in the case shown in FIG. 3B. For this reason, the shape of the liquid pool CP1 can be stabilized with a lower charge density of the sheet S. In FIG. 3A and FIG. 3B, the coating liquid C1 is positively charged, a positive charge is applied to the first surface S1, and the first surface S1 of the sheet S is positively charged with the same polarity as the coating liquid C1. However, the same effect can be obtained even when the coating liquid C1 is negatively charged and the first surface S1 is negatively charged with the same polarity as the coating liquid C1.

  The electrically insulating coating liquid C2 is applied to the second surface S2 opposite to the first surface S1 to form the coating liquid layer CL2, and then the electrically insulating coating is applied to the first surface S1. Even when the liquid C1 is applied, since the first surface S1 is charged with the same polarity as the charging polarity of the coating liquid C1, the shape of the liquid pool CP1 is stabilized and coating unevenness hardly occurs. . In this case, in addition to providing the first surface S1 with the same polarity as the charging polarity of the coating liquid C1, the “imaginary potential” measured when the sheet S is conveyed in the air. However, if the polarity is the same as that of the coating liquid C1, the shape of the liquid pool CP1 is stabilized and coating unevenness is less likely to occur.

  Next, the effect of setting the charging polarity of the first surface S1 of the electrical insulating sheet S and the charging polarity of the coating liquid C1 to the same polarity will be described.

  The principle of stabilizing the shape of the liquid pool CP1 is not clear. However, the present inventors presume that the shape of the liquid pool CP1 is stabilized by the phenomenon described below. Like the liquid pool CP1 of the coating liquid C1, the energy at the interface is dominant in determining the shape of the fine droplets or the very thin liquid surface. In order to obtain a low free energy state, the liquid will agglomerate in an attempt to minimize surface area. This energy is related to the surface tension [mN / m]. Usually, the liquid present in the gap between two objects is rounded down and tries to create a liquid pool (meniscus). However, inside the charged liquid pool CP1, it is considered that when the Coulomb force is generated between all the particles in the coating liquid C1, and the repulsive force exceeds the surface tension, the shape of the liquid pool CP1 becomes unstable. . Here, the total charge amount of the coating liquid particles is defined as q12. The amount of charge of the sheet S charged to the same polarity as the coating liquid C1 is newly added to this system. The charge amount of the sheet S is q3.

  A new Coulomb force (also a repulsive force) is generated between the charged sheet S and the charged coating liquid C1, and the coating liquid C1 tends to move away from the electrically insulating sheet S by this Coulomb force. That is, it is estimated that the shape of the liquid pool CP1 is stabilized because the Coulomb force repelling inside the coating liquid C1 is overcome and the coating liquid C1 tries to move away from the electrically insulating sheet S.

  Further, a coating bar 31 in the coating layer smoothing device 30 on the first surface is arranged downstream of the moving direction SD of the sheet S. In many cases, the coating bar 31 is a metal whose potential is stabilized, such as ground. The coating liquid C1 trying to move away from the electrical insulating sheet S stays in the liquid pool CP1, and the shape of the liquid pool CP1 is stabilized. As if the coating liquid C1 was pushed into the coating bar 31, the shape of the liquid pool CP1 is stabilized. That is, the main Coulomb forces acting on the coating liquid C1 are: A: surface energy and surface tension of the coating liquid, B: repulsive Coulomb force (with respect to q12) between the coating liquid particles, and C: charge on the sheet. And the Coulomb force (with respect to q3 and q12) between the coating liquids. When the relationship that the sum of the Coulomb force A and the Coulomb force C is greater than the Coulomb force B is satisfied, it is estimated that the shape of the liquid pool CP1 is stabilized.

When the shape of the liquid pool CP1 is stabilized, the charge amount of the electrical insulating sheet S needs a Coulomb force to stabilize the shape of the liquid pool CP1 if the absolute value of the charge amount of the coating liquid C1 is large. Therefore, it increases in proportion to the charge amount of the coating liquid C1. According to the knowledge of the present inventors, if the charge amount of the coating liquid C1 which is electrically insulating is about 10 ⁻⁴ [C / m ³ ] (= 10 [nC / 100 ml]), the electrically insulating sheet The charge amount of the first surface (coating surface) S1 of S needs to be 100 to 150 [V] as the back surface equilibrium potential of the first surface S1.

On the other hand, if the coating liquid C1 is in a substantially non-charged state, the Coulomb force that stabilizes the shape of the liquid pool CP1 is almost unnecessary, and even if the charge amount of the electrical insulating sheet S is very small, the liquid pool remains. The shape of CP1 can be stabilized. Specifically, the charge amount of the coating liquid C1 is substantially uncharged, that is, −2 × 10 ^{−5 to} + 2 × 10 ⁻⁵ [C / m ³ ] (− 2 to +2 [nC / 100 ml]. ), The shape of the liquid pool CP1 can be stabilized even when the charge amount of the first surface (coating surface) S1 is an uncharged state of −2 to +2 [μC / m ² ]. Note that the shape of the liquid pool CP1 can be stabilized even if excessive charging is applied to the first surface (coating surface) S1 with respect to the substantially uncharged coating liquid C1.

  In order to effectively exhibit the functions and effects of the present invention, it is important that the charged state of the coating liquid C1 and the charged polarity of the electrical insulating sheet S have the same polarity. Therefore, not only the electrical insulating sheet S but also the charging polarity of the coating liquid C1 is preferably controlled.

  In the coating apparatus 10 shown in FIG. 1, a coating liquid charging apparatus 40 in a state of being electrically insulated from the others is provided in a part of the coating liquid supply pipe 24. The voltage applying means is a high voltage power source 41, and the coating liquid charging device 40 is connected to the high voltage power source 41. The application polarity and application voltage of the high-voltage power supply 41 can be set to charge the coating liquid C1. The applied polarity is positive or negative, and the absolute value of the applied voltage is preferably 3 kV or less, particularly 2 kV or less. A preferable lower limit value of the applied voltage is 0.1 kV. This is because when a high voltage of 3 to 4 kV or more is applied in absolute value, corona discharge may occur in the applied conductor (particularly, end or local tip).

  The voltage to be applied may be a direct current or may be intermittently applied at a constant interval. If the charged state of the coating liquid C1 is observed and the liquid pool CP1 is charged while the shape of the liquid pool CP1 is stable, that is sufficient. If there is no need for the coating liquid charging device 40, it is possible to refrain from using it without applying a voltage. In this way, the charging polarity of the coating liquid C1 is controlled so that the charging polarity of the coating liquid C1 and the charging polarity of the electrical insulating sheet S are the same.

Next, the case where the coating liquid C1 is neutralized to an uncharged state is described. The charge amount of the coating liquid C1 is related to the applied polarity of the high-voltage power supply 41, the applied voltage [V], and the coating liquid flow rate [m ³ / min]. When the coating liquid C1 can be charged with the same polarity as the polarity applied to the high-voltage power supply 41, the charge amount of the coating liquid C1 is determined in proportion to the applied voltage of the high-voltage power supply 41. Therefore, by selecting the applied polarity and applied voltage of the high-voltage power supply 41, it is possible to obtain a substantially uncharged coating liquid C1.

For example, if the charging polarity of the coating liquid C1 is positive, a negative polarity applied voltage is applied to the coating liquid C1. At this time, the charge amount of the coating liquid C1 after this charge adjustment is measured, and if the result is still positive, the applied voltage is increased, and if the result is negative, the applied voltage is decreased and readjustment is performed. To do. As a result, the charged charge amount of the coating liquid C1 becomes −2 × 10 ^{−5 to} + 2 × 10 ⁻⁵ [C / m ³ ] (−2 to + 2n [C / 100 ml]), and the substantially non-charged coating is applied. Liquid C1 can be obtained.

  The coating liquid charging device 40 will be described. The length in the cross section perpendicular to the direction in which the coating liquid C1 flows is defined as the length h [mm] at the portion of the coating liquid charging device 40 that is in contact with the electrically insulating coating liquid C1, and the length in the direction in which the liquid flows. The length is k [mm]. If the length k is too long, it is difficult to connect the coating liquid supply pipe 24 while electrically insulating the part, or the coating liquid charging device 40 becomes large. In addition, when the length h increases, the amount of the coating liquid C1 that contacts the inner wall of the portion decreases, and the charging efficiency of the coating liquid C1 deteriorates. Therefore, the necessary flow rate and pressure loss of the coating liquid C1 are taken into consideration. Thus, the length h is preferably selected to be small. That is, in the coating liquid charging device 40, the length k is short, and may be a ring shape in an extreme case, and preferably satisfies the relationship of 0.02 ≦ k / h ≦ 20.

  Here, a method for measuring the charge amount of the coating liquid will be described. A Faraday cage method is widely known as a method for measuring the charge polarity and charge amount of a coating liquid. Also, a detection electrode is placed inside the pipe through which the coating liquid flows, and a method for measuring the potential, or an electrically insulated conductor electrode is placed inside the pipe through which the coating liquid flows, and the potential is measured. There is also a method.

  Measurement of the charge amount of the coating liquid by the Faraday cage is performed by providing a branch in the coating liquid pipe, guiding a part of the coating liquid to the Faraday cage, and measuring the charge polarity and the charge amount. Non-patent document 1 discloses the detection of the charge of the coating liquid by the Faraday cage. The Faraday cage is a method for measuring the total amount of charge of a charged object that can be collected. The Faraday cage includes a metal inner container that houses the charged object, a metal outer container that is electrically insulated and grounded, a capacitor, and a voltmeter. Consists of.

  When the inner container is sufficiently larger than the charged object, all electric lines of force generated from the charge + Q of the charged object converge on the inner surface of the inner container. -Q is induced on the outer surface of the inner container with a charge + Q having the same size and sign. If the capacitance between the inner container and the outer container is Cf, the potential Vf is Vf = Q / Cf. Therefore, the charge Q can be known by measuring the potential Vf. Actually, a measuring capacitor Cs is connected in parallel with Cf, and the voltage V across the both ends is measured. As the voltmeter, an electrometer having an extremely large input impedance is used.

The charging polarity of the coating liquid is determined by measuring the sum of the coating liquids that can be collected and determining whether the average value is positive or negative. The charging state of the coating liquid is determined by the polarity of the sum of all the positive and negative charge amounts regardless of the positive / negative ratio and distribution state even if positive and negative charges are mixed. In other words, the charge amount of the coating liquid was fractionated from the pipe of the coating liquid, the 10 ^-4 to 5 × 10 ^-4 m ³ amount of the coating liquid, placed in a Faraday cage, and read the charge polarity and charge quantity, It is obtained by converting the value of the charge amount of the obtained coating liquid into the charge amount of the coating liquid per unit volume [m ³ ].

  FIG. 7 shows another embodiment of the coating apparatus of the present invention. In FIG. 7, the coating apparatus 10 a has a configuration in which an aqueous coating liquid (water-soluble coating liquid) C <b> 2 is applied in advance to the second surface S <b> 2 of the electrical insulating sheet S illustrated in FIG. 3B. is there. For this purpose, the coating liquid C2 is applied to the second surface S2 of the electrically insulating sheet S downstream of the sheet charging device 5 and upstream of the coating liquid supply device 20 on the first surface in the moving direction SD of the sheet S. A coating liquid supply device 20a for the second surface to be applied is provided.

  In the coating liquid supply device 20a on the second surface, a coating liquid discharge means 21a similar to the coating liquid discharge means 21 is provided. Since the coating liquid supply device 20a on the second surface has substantially the same configuration as the coating liquid supply device 20 on the first surface, the illustration of the coating liquid supply piping and the like to the coating liquid discharge means 21a is omitted. Yes. A second surface coating layer smoothing device 30a that adjusts the thickness of the coating liquid discharged from the coating liquid discharging means 21a and applied to the second surface S2 is provided on the downstream side of the coating liquid discharging means 21a. The second surface coating layer smoothing device 30 a has a coating bar 31 a similar to the coating bar 31.

  The coating apparatus 10a of FIG. 7 is arrange | positioned before the horizontal extending process after the vertical extending process in the film forming process mentioned above. That is, the coating device 10a is used in an in-line method. The sheet S stretched in the longitudinal stretching step includes a sheet charging device 5, a second surface coating solution supply device 20 a, a second surface coating solution smoothing device 30 a, and a first surface coating solution supply device 20. The coating layer smoothing device 30 on the first surface is sequentially passed to reach the charge removal device 50. The static eliminator 50 will be described later.

  The sheet charging device 5 applies a charge having the same polarity as that of the coating liquid C1 to the first surface S1 of the sheet S, and a charge having the opposite polarity to the second surface S2. The charged state at this time will be described later. In this state, the water-soluble coating liquid C2 is applied to the second surface S2, and the measured and smoothed coating liquid layer CL2 is formed on the second surface S2 by the coating bar 31a. Thereafter, an electrically insulating coating liquid C1 is applied to the first surface S1.

  As described above, the coating liquid layer CL2 on the second surface S2 is entirely at 0 V potential by the grounded coating bar 31a. In this state, since the first surface S1 is charged with the same polarity as the charging polarity of the coating liquid C1, the coating liquid C1 supplied from the coating liquid supply device 20 on the first surface is In the coating bar 31, the liquid pool CP1 is stably formed, and coating unevenness on the first surface S1 of the coating liquid C1 hardly occurs.

  Next, the coating liquid will be described. The viscosity of the coating solution is determined by the balance with the moving speed of the sheet. The viscosity of the coating liquid is preferably 10 to 2000 [mP · s]. When the viscosity of the coating liquid is too low, it is difficult to form a liquid pool, and a small liquid pool is formed on the coating bar side due to the charging applied to the sheet. In order to prevent this, the viscosity of the coating liquid is preferably 10 [mP · s] or more. On the other hand, when the viscosity of the coating liquid is high, an unapplied part is generated in the width direction of the sheet, and the application omission is likely to occur, and the application thickness is likely to increase. In order to prevent this, the viscosity of the coating liquid is preferably 2000 [mP · s] or less.

When the coating thickness is thick, the supply of the coating liquid from the coating liquid supply apparatus is large, and the coating liquid to be applied is also large, so that the liquid pool tends to become unstable. Furthermore, when the amount of the supplied coating liquid is large, the Coulomb force for moving the coating liquid away from the electrically insulating sheet decreases in inverse proportion to the square of the distance, and the liquid pool tends to become unstable. Conversely, if the coating thickness is too thin, the liquid pool also becomes small, so that the effect of stabilizing the liquid pool due to charging is weak. Therefore, the coating thickness is preferably 1 to 50 [μm]. The flow rate of the coating liquid supplied to the coating apparatus is preferably approximately 5 × 10 ^{−5 to} 5 × 10 ⁻⁴ [m ³ / min] depending on the moving speed of the sheet and the desired coating thickness.

In the case of forcibly charging the coating liquid, if the charge amount becomes excessive, the coating liquid is not stably discharged when the coating liquid is supplied. Therefore, the absolute value of the charging amount of the coating liquid is 10 ⁻³ [C / M ³ ] or less.

  4, 5A and 5B show another embodiment of the coating apparatus of the present invention. In the coating apparatus 10b of FIG. 4, the electrically insulating sheet S travels and moves in the direction of the arrow SD while being supported by the transport roll 11 or the like. The coating liquid supply device 20 on the first surface has a bar support 21s having a manifold, a coating liquid guide groove 21g formed in the bar support 21s, and a coating liquid supply for supplying the coating liquid C1 to the coating liquid guide groove 21g. The pipe 24 and the coating liquid storage tank 22 for supplying the coating liquid C1 to the coating liquid supply pipe 24 are provided. A coating liquid charging device 40 is attached to a part of the coating liquid supply pipe 24.

  In the coating apparatus 10b, the first surface (coating surface) S1 of the electrically insulating sheet S to which the coating liquid C1 is applied is the lower surface of the sheet S in the drawing. That is, the first surface S1 is a lower surface in the direction of gravity. The coating liquid C1 is supplied from the storage tank 22 through the coating liquid supply pipe 24 to the coating liquid guide groove 21g.

  A sheet charging device 5 that applies an electrostatic charge to the electrically insulating sheet S is provided on the upstream side of the coating liquid supply device 20 on the first surface. The sheet charging device 5 includes an electrode 6c and an electrode 6e arranged to face each other with the electrically insulating sheet S interposed therebetween. The electrode 6c is connected to the first DC power supply 5c, and the electrode 6e is connected to the electrode 6e. The second DC power source 5e is connected. Voltages having different polarities are applied to the first DC power supply 5c and the second DC power supply 5e.

  FIG. 5A shows a state where the vicinity of the coating bar 31 of the coating apparatus 10b of FIG. 4 is enlarged. However, the coating liquid supply device 20 on the first surface in FIG. 4 is replaced with a coating liquid pan 21p. In FIG. 5A, the coating bar 31 of the coating layer smoothing device 30 rotates in the same direction as the moving direction SD of the electrical insulating sheet S. On the upstream side of the coating bar 31, a liquid pool CP1 is formed. At this time, negative electrostatic charges are uniformly applied to the lower surface of the electrically insulating sheet S, which is the first surface (coating surface) S1, by the sheet charging device 5 (FIG. 4). The liquid pool CP1 is stabilized by controlling the charging polarity of the coating liquid C1 to the negative polarity by the coating liquid charging device 40 (FIG. 4).

  FIG. 5A shows a shape in which the liquid pool CP1 has a curved line outside the shortest distance between the coating bar 31 and the electrical insulating sheet S. However, depending on the coating liquid, the liquid pool CP1 is recessed inward from the straight line of the shortest distance. The shape may be stable. By maintaining the liquid pool CP1 in a stable shape, uneven coating of the coating liquid C1 hardly occurs in the coating liquid layer CL1.

  5B, the coating liquid C2 is applied to the second surface S2 of the electrical insulating sheet S of FIG. 5A, and the coating liquid is applied to the first surface S1 of the electrical insulating sheet S on which the coating liquid layer CL2 is formed. An example in which C1 is applied is shown. In FIG. 5B, even when the coating liquid C2 is applied to the second surface S2, if the charging polarity of the coating liquid C1 is negative, for example, the first surface (coating) Construction surface) By making the charging polarity of S1 negative, the liquid pool CP1 is stabilized. In the case where the coating liquid layer CL2 of the second surface S2 is formed of the aqueous coating liquid C2, a more stable liquid pool CP1 is formed by the action described in the description of FIG. 3B, and the coating liquid C1. Coating unevenness is suppressed.

  FIG. 6 shows another embodiment of the coating apparatus of the present invention. In the coating apparatus 10c of FIG. 6, the electrically insulating sheet S travels in the direction of the arrow SD while being supported by the transport roll 11 or the like. The sheet charging device 5, the first surface coating solution supply device 20, and the coating solution charging device 40 are disposed at the positions shown in FIG. 6.

  The coating liquid supply device 20 on the first surface of the coating device 10c is a coating device including a die head 21d. The electrically insulating sheet S unwound from the roll-shaped electrically insulating sheet roll body is changed in the direction of arrow SD in the direction of arrow SD while the moving direction SD is changed by the plurality of conveying rolls 11. A coating liquid C1 discharged from the die head 21d is applied to S1, and a coating liquid layer CL1 is formed. The formed coating liquid layer CL1 is then dried by a drying device, and is finally wound into a roll by a winding device. The illustration of the electrically insulating sheet roll body, the drying device, and the winding device is omitted.

  In the state where the electrical insulating sheet S travels in close contact with the surface of the backup roll 11a, the coating liquid C1 discharged from the die head 21d is applied to the first surface (coating surface) S1, and the coating liquid layer CL1. Is formed. The backup roll 11a is provided in order to make the electrical insulating sheet S run stably and to keep the gap with the die head 21d constant. As the backup roll 11a, for example, a metal roll plated with hard chrome or a metal roll coated with an elastic body is used.

  A positive electrostatic charge is applied to the first surface (coating surface) S1 from the sheet charging device 5, and a negative electrostatic charge is applied to the second surface S2 on the opposite side. On the backup roll 11a, the charge on the second surface S2 in contact with the metal surface is apparently offset by the charge of the opposite polarity induced on the metal surface that is the conductor. On the other hand, the charge on the first surface S1, which is the opposite surface of the metal surface, is also partially compensated by the charge induced on the metal surface, but the compensation effect is increased by the distance of the sheet S from the metal surface. Since it is small, the electric charge becomes apparent on the first surface S1. Even in such a case, the negative charge polarity of the first surface S1 works effectively, and the liquid pool CP1 can be stabilized by making the charge polarity of the coating liquid C1 the same.

  Next, a preferred charging method for the electrically insulating sheet will be described. As one of the charging methods, a technique for imparting, to the sheet, non-contact charging that stabilizes the liquid pool with Coulomb force will be described. Furthermore, as a more preferable charged state, a charging method for making it difficult for uneven coating caused by charging of the electrically insulating sheet to occur in the applied coating liquid layer will be described. These methods for charging the electrically insulating sheet are effectively used in the practice of the present invention.

  First, the charged state of the electrically insulating sheet will be described. The electrically insulating sheet has a high surface resistivity and volume resistivity. Therefore, the charged electric charge can hardly move in the in-plane direction or the thickness direction of the sheet as it is. In the electrical insulating sheet in such a state, when a discharge occurs, for example, when a negative electrostatic charge is locally deprived excessively, a portion having a positive electrostatic charge may be generated. At this time, discharge traces, which are traces of discharge, may occur in the electrically insulating sheet. This discharge mark is called a static mark. When the static mark is generated, a state in which a positive electrostatic charge and a negative electrostatic charge are mixed occurs in the in-plane distribution of charges on the surface of the sheet or on the front and back surfaces of the sheet.

The charge amount based on the positive and negative electrostatic charges mixed on the surface of the sheet is very large, from several to about 500 [μC / m ² ] when expressed in charge density. When the positive and negative charged regions are mixed on the first and second surfaces of the sheet, the charge on each surface is opposite in polarity and the charge density is several tens to 500 [μC / m ² ]. The sum of the charge densities of both surfaces is several to several tens [μC / m ² ] or less. A state where the sum of the charge densities is −2 [μC / m ² ] or less or +2 [μC / m ² ] or more is referred to as “apparently non-charged” state.

  When the positive and negative charges are close to each other and mixed, the electric lines of force due to the electrostatic charge of the sheet are closed between the charged regions having different polarities. Therefore, the electric field becomes very weak at a position slightly apart. The surface potential measured in a state where the sheet is conveyed in the air is referred to as “aerial potential”. This “aerial potential” is a value obtained by measuring the total charge on the front and back surfaces of the sheet from the ground. The “aerial potential” is measured as a total sum without distinguishing the charging of the front surface and the back surface of the sheet, with the thickness of the sheet being sufficiently small with respect to the distance from the ground. For this reason, even if strong charges of opposite polarity exist on the front and back surfaces, if the positive and negative charges are the same amount, the charge appears to be zero, and the value of the fictitious potential is almost zero. Become. In this way, even if the sheet has almost zero “imaginary potential”, that is, a sheet that is not charged and looks good at first glance, the sheet actually has positive and negative charged charges. There are often many.

  FIG. 18 is a schematic side view illustrating an example of a charged state of the electrical insulating sheet. In FIG. 18, the existence state of electric charges is schematically drawn with the number of existing electric charges. In FIG. 18, positive charge PC1 (four) and negative charge NC1 (six) on the first surface S1 of the electrical insulating sheet S, and positive charge PC2 (five) and negative charge on the second surface S2. NC2 (4 pieces) exists. Therefore, the electrically insulating sheet S is in a state where the sum of the charged charges on the two surfaces is not zero and is not “apparently uncharged”.

  On the other hand, FIG. 17 is a schematic side view for explaining another example of the charged state of the electrically insulating sheet. In FIG. 17, the existence state of electric charges is schematically drawn with the number of existing electric charges. In FIG. 17, positive charge PC1 (four) and negative charge NC1 (four) are provided on the first surface S1 of the electrically insulating sheet S, and positive charge PC2 (four) and negative charge NC2 are provided on the second surface S2. (4) exists. These charges form a pair of opposite polarities on the first surface S1 and the second surface S2. Therefore, the electrically insulating sheet S is in an “apparently uncharged” state in which the sum of the charged charges on the two surfaces is substantially zero. In this case, normally, the overhead potential is also substantially zero.

The charge density of each surface of the sheet S can be known by the following method. The charge density can be known by bringing one side of the sheet S into close contact with the conductor and measuring the “back surface equilibrium potential”. The measurement of the back surface equilibrium potential is performed by bringing the probe of the surface potentiometer sufficiently close to the sheet S to about 1 to 2 [mm]. The local charge density σ on the measurement surface is obtained by the relation σ = C · v between the obtained back surface equilibrium potential v [V], the capacitance C [μF / m ² ] per unit area, and the charge density σ. [ΜC / m ² ] can be obtained.

In a thin sheet such as a film, the capacitance C per unit area is equal to the capacitance C per unit area of the parallel plate = ε ₀ ε _r / t (where ε ₀ is the dielectric constant in vacuum: 8 854 × 10 ⁻¹² [F / m], ε _r is the relative dielectric constant of the sheet, and t is the sheet thickness [m]). By reversing the surface to be in close contact with the conductor, the back surface equilibrium potential v [V] and the charge density [μC / m ² ] of each surface of the sheet can be known.

  Next, coating unevenness caused by charging in which both sides of the sheet are mixed will be described. According to the knowledge of the present inventors, as disclosed by the present inventors in Japanese Patent Application No. 2005-20934, as a preferable condition for the mechanism of occurrence of uneven coating and the charged state of the sheet in which uneven coating does not occur, There are three conditions. By satisfying all three conditions, coating unevenness can be suppressed to a level where there is virtually no problem.

First condition: A state where the charge on the front and back of the sheet is balanced, “apparently uncharged”, and the total charge density in each part is −2 to +2 [μC / m ² ].

  Second condition: a state in which the charge density existing on each of the front and back surfaces of the sheet is sufficiently small, and the difference between the maximum value and the minimum value of the back surface equilibrium potential is 340 [V] or less, more preferably 200 [V] or less. .

Third condition: The charge density existing on each of the front and rear surfaces of the sheet is sufficiently small, and the rate of change of the charged charge density is 0.18 [C / m ² / m] or less, more preferably 0.12 [C / m ² / m] State of being below.

  The limiting conditions for uneven coating include physical properties parameters of the coating liquid (surface tension, surface energy, viscosity, charge amount of the coating composition), and physical properties parameters of the sheet (surface tension, surface energy, surface roughness) The degree of coating unevenness is also related to the contact time with the metal roll and the ease of movement of the coating, but if any of the above conditions is satisfied, coating unevenness will not occur. There are many cases. Next, each condition will be described with the mechanism of coating unevenness.

  The first condition is a condition for preventing the occurrence of uneven coating when the sheet is coated while being held in the air. This condition is to keep the sheet apparently uncharged. In a sheet having an imaginary potential of several [kV] to several tens [kV], uneven coating due to charging occurs. The charged state in this case is as shown in FIG. 18, for example. In this state, it is not apparently uncharged in each part of the sheet.

On the other hand, the apparently uncharged sheet shown in FIG. 17 is less likely to cause coating unevenness when held in the air. This is because the electric field is closed between the first surface and the second surface of the sheet, so that a strong electric field is not applied to the coating liquid even if coating is performed in this state. In this state, the sheet is in a charged state in which the total charge density in each part of the sheet is −2 to +2 [μC / m ² ]. As a method of knowing that the total charge density is −2 to +2 [μC / m ² ], there is a method of sprinkling toner on a sheet floating from the ground and confirming that the toner does not adhere locally. This is because in many cases, if there is a local charge having an absolute value of 2 [μC / m ² ] or more, the toner usually adheres to the sheet.

  The second condition and the third condition will be described. The second and third conditions are conditions related to coating unevenness that occurs when the sheet is held on a metal roll or the like. Sheets are not only transported in the air, but often travel on rolls. For example, the sheet travels on a backup roll of a coater or a transport roll that changes the moving direction of the sheet. The sheet is in a state in which the coating liquid is applied to the other surface of the backup roll in a state where the one surface is in close contact with the metal surface of the backup roll.

  This state is shown in FIG. In FIG. 19, in the case of a sheet S in which the front surface (first surface) S1 and the back surface (second surface) S2 of the sheet S are charged with the same amount of opposite polarity, that is, a sheet with zero potential at the time of imaginary. In the case of S, the charges PC2 and NC2 of the second surface S2 of the sheet S that are in contact with the surface of the electric conductor 190 having a metal surface are induced by the induced charges CIE of opposite polarity induced on the surface of the electric conductor 190, Apparently offset.

  On the other hand, the charge on the first surface S1 to which the coating liquid located on the opposite side of the second surface S2 in contact with the surface of the electric conductor 190 is applied is somewhat the charge induced on the surface of the electric conductor 190. It is compensated with. However, since the first surface S1 is located farther from the surface of the electric conductor 190 than the second surface S2, the compensation effect is small accordingly. For this reason, the charge is manifested on the first surface S1. Similarly, when the coating liquid containing water is applied to the second surface S2 of the sheet S and then the coating liquid is applied to the first surface S1, the electric charge becomes apparent on the first surface. . The charging in which the positive and negative charges on each surface of the sheet S based on the manifestation of the charges is mixed causes uneven coating. In this case, with the “apparently non-charged” sheet S in which both surfaces are charged with equal amounts of opposite polarities, the coating unevenness cannot be solved.

  The second condition is that when the electrically insulating sheet S travels in contact with a backup roll or the like and the coating liquid is applied to the surface opposite to the surface in contact with the roll, coating unevenness does not occur. It is a condition to make it. Under these conditions, the difference between the maximum value and the minimum value of the absolute values of the back surface equilibrium potentials of the first surface S1 and the second surface S2 of the sheet S is kept small. If the second condition is not satisfied, an electric field mainly acting in the thickness direction of the sheet S based on the electrostatic charge existing on the first surface (coating surface) S1 acts on the coating liquid layer CL1, and coating unevenness is caused. appear. The thickness of the coating liquid layer CL1, that is, the coating thickness of the coating liquid, is proportional to the magnitude of the absolute value of the back surface equilibrium potential, and becomes thicker at a location where the absolute value of the back surface equilibrium potential is large, and the absolute value of the back surface equilibrium potential is small. It becomes thinner at the point.

  When positive and negative charges are present, the minimum value of the absolute value of the back surface equilibrium potential is 0V, and the coating thickness at the boundary between positive and negative charges, that is, at 0V is the thinnest, and the back surface balance In proportion to the absolute value of the potential, the coating thickness of the charged portion increases. When the minimum value and the maximum value of the absolute value of the back surface equilibrium potential are hardly different, there is almost no difference in the coating thickness over the entire coating surface. For example, if the absolute maximum value and minimum value of the back surface equilibrium potential exceed 340 [V], the coating thickness increases overall, but if the difference between the maximum value and the minimum value is small, uneven coating may occur. Must not. In many cases, even if the coating thickness is increased as a whole, there is no problem if there is no coating unevenness.

  The third condition is a condition for preventing coating unevenness that is likely to occur when the positively charged portion and the negatively charged portion are alternately present at a fine cycle. This is a condition for preventing coating unevenness due to an electric field acting in a direction along the sheet surface based on positive and negative electrostatic charges on each surface of the sheet S. The charging pattern in which the positive charging portion and the negative charging portion are alternately present at a fine cycle has a discharge mark. Based on the electrostatic charge existing on the first surface (coating surface) S1, mainly the positively charged portion and negatively charged portion, or the positively charged portion and uncharged portion, or negatively charged adjacent to each other surface of the sheet S. The electric field in the direction along the surface of the portion and the non-charged portion acts on the coating liquid layer CL1, and coating unevenness occurs. The coating unevenness due to the electric field in the direction along the surface of the sheet S has a feature that the thickness of the coating liquid layer CL1 is increased at the boundary between the positively charged portion and the negatively charged portion.

  The conventional technique disclosed in Patent Document 2, that is, the charged state of the sheet PS subjected to the corona discharge treatment shown in FIG. 15 will be described. When a monopolar electrostatic charge is applied to the first surface (coating surface) PS1 of the sheet PS by the corona discharge treatment device 151, usually only the first surface (coating surface) PS1 is strongly charged. When the sheet PS is peeled from the grounded counter electrode roll 152, a discharge is generated, and a discharge mark is generated on the second surface PS2. That is, local positive and negative charges are imparted to each surface of the sheet PS. Further, since the corona discharge treatment uses unstable discharge, the electrostatic charge on the second surface PS2 is often in a non-uniform state.

  In such a case, the first surface PS1 and the second surface PS2 have an electrostatic charge of opposite polarity, and the balance of the electrostatic charges on both surfaces is not “apparently uncharged”. This state does not satisfy the first condition for suppressing the uneven application, and as described above, the uneven application occurs when the sheet PS is being conveyed in the air. Even if the charge removal of the sheet PS is performed after the corona discharge treatment and an apparently uncharged state can be achieved, there are local positive and negative charged patterns on each surface of the sheet PS. For this reason, the sheet PS cannot satisfy the second condition and the third condition, and is in a charged state in which coating unevenness is likely to occur. That is, when a corona discharge treatment is performed by applying a unipolar electrostatic charge to the first surface (coating surface) PS1 of the sheet PS and charging it, the surface of the sheet PS does not appear to be uncharged. A locally charged pattern is formed on the surface, which causes uneven coating.

  When coating unevenness due to charging of the electrical insulating sheet becomes a problem, a method for charging the electrical insulating sheet described below is preferably used as a solution to this problem.

  FIG. 8 is a schematic side view of an example of a sheet charging device for an electrically insulating sheet that is preferably used in the coating apparatus of the present invention. As shown in FIG. 1, FIG. 4, FIG. 6 or FIG. 7, a coating solution supply device and a coating solution layer smoothing device are downstream of the sheet charging device 5 shown in FIG. Is located. FIG. 9 is an enlarged side view of an example of a charging unit in the sheet charging device 5 of FIG.

  In FIG. 8, the sheet charging device 5 includes a left guide roll 5 a and a right guide roll 5 b that convey the sheet S. There may be no guide roll 5b. A traveling electrical insulating sheet S is stretched between the guide roll 5a and the guide roll 5b, and the guide rolls 5a and 5b are rotated clockwise by a driving force of a motor (not shown), so that the direction of the arrow SD is reached. In addition, the sheet S continuously moves at a speed u [m / min]. N charging units CU1,..., CUn are provided between the guide roll 5a and the guide roll 5b at a position facing each other with the sheet S interposed therebetween.

  The first charging unit CU1 includes a first electrode unit ENd-1 and a second electrode unit ENf-1. The first electrode unit faces the first surface S1 of the sheet S and is spaced from the first surface S1. The second electrode unit ENf-1 faces the second surface S2 of the sheet S and is provided at an interval from the second surface S2. The first electrode unit ENd-1 and the second electrode unit ENf-1 face each other across the sheet S.

  When k is an integer from 1 to n, the kth charging unit CUk is composed of a first electrode unit EUd-k and a second electrode unit EUf-k. The first electrode unit faces the first surface S1 of the sheet S and is spaced from the first surface S1. The second electrode unit ENf-k faces the second surface S2 of the sheet S and is spaced from the second surface s2. The first electrode unit ENd-k and the second electrode unit ENf-k face each other with the sheet S interposed therebetween.

  Next, the configuration of the kth charging unit CUk in the sheet charging device 5 will be described. This description is made with the first charging unit CU1 as a representative. The number N of charging units and the interval between the units are selected according to use conditions.

  The first electrode unit EUd-1 includes a first ion generation electrode 5d-1, a first shield electrode 5g-1 having an opening with respect to the first ion generation electrode, and an insulating member. The second electrode unit includes a second ion generation electrode 5f-1, a second shield electrode 5h-1 having an opening with respect to the second ion generation electrode, and an insulating member.

  The opening of the first shield electrode 5g-1 opens toward the sheet S in the vicinity of the tip of the first ion generation electrode 5d-1. When the first and second shield electrodes 5g-1 and 5h-1 are given an appropriate potential difference between the first and second ion generation electrodes 5d-1 and 5f-1, the respective ions It has a function of assisting discharge in the generation electrodes 5d-1 and 5f-1. Further, the sheet S has a function of irradiating the sheet S substantially uniformly with ions irradiated from the first and second ion generation electrodes facing each other. This is because the local electric field concentration due to the reverse polarity voltages of the opposed first and second ion generation electrodes is reduced by the shield electrodes 5d-1 and 5f-1. This prevents ions from being intensively irradiated directly under the ion generation electrode due to local electric field concentration.

The leading end of the first ion generating electrode 5d-1 and the leading end of the second ion generating electrode 5f-1 are spaced apart by d ₁ -1 in the normal direction of the sheet S, and in the moving direction SD of the sheet S. Arranged at intervals of d ₀ −1. Further, the first shield electrode 5g-1 and the second shield electrode 5h-1 are provided such that the portions closest to the sheet S are spaced apart by d ₃ -1 in the normal direction of the sheet S. ing.

  The first ion generation electrode 5d-1 and the second ion generation electrode 5f-1 of each charging unit CUk (1 to n) are connected to the first DC power supply 5c and the second DC power supply 5e having opposite polarities. Has been. The first and second shield electrodes 5g-1 and 5h-1 are grounded.

  The first ion generation electrodes 5dk (1 to n) of each charging unit CUk (1 to n) are all connected to a DC power source having the same polarity, and the second ion generation electrodes 5fk (1 to n) are first ions. The generator electrodes are all connected to a DC power source having the same polarity but opposite polarity. Note that the number of DC power sources may be one, or a plurality of units may be used to change the applied voltage.

  The DC power supply has a pulsation rate of 5% or less, more preferably 1% or less, in which the output voltage maintains the same polarity for at least one second without reversing the polarity with respect to the ground point. Was used. The lower limit of the pulsation rate is not particularly considered, but is practically 0.01% or more. This is because a higher precision DC power supply than this becomes expensive.

The number of charging units in FIG. 1, FIG. 4, FIG. 6 or FIG. 7 is 2 to 4, and the distance d ₂ in the moving direction SD of the sheet S at the tip of each adjacent ion generating electrode is 50 [mm]. . Although two to four charging units are used, the number of charging units may be appropriately selected depending on the conveyance speed of the sheet S and the charge amount desired to be applied. In addition, the polarity of the voltage to be applied to the first and second ion generation electrodes may be appropriately selected.

  In the above-described embodiment, the first and second ion generation electrodes of each charging unit and the corresponding shield electrodes have substantially the same form, and have substantially the same potential. It was configured as follows. Further, the voltage value applied to the first ion generation electrode was made substantially the same as the voltage value applied to the second ion generation electrode. In general, the ion generation electrodes do not necessarily have substantially the same form, and the applied potentials may not be the same potential. The size, positional relationship, and applied voltage only have to satisfy the usage conditions for each individual ion generation electrode. The voltage applied to the first ion generating electrode and the voltage applied to the second ion generating electrode of each charging unit may be slightly different from each other as long as the voltage and the like are within the range of the above-described effects. There is no problem.

  Next, the operation of the sheet charging device 5 in FIG. 8 will be briefly described. The operation of the charging unit CUk will be briefly described. This description will be made with the first charging unit CU1 as a representative. The case where a positive voltage is applied to the first ion generation electrode 5d-1 and a negative voltage is applied to the second ion generation electrode 5f-1 in the first charging unit CU1 will be described. At this time, positive ions are generated from the first ion generation electrode 5d-1, and negative ions are generated from the second ion generation electrode 5f-1. When the electric field strength between the first ion generation electrode 5d-1 and the second ion generation electrode 5f-1 is strong, positive and negative ions are forcibly irradiated to the electrical insulating sheet S by the electric field. The positive ions generated from the first ion generating electrode 5d-1 and the negative ions generated from the second ion generating electrode 5f-1 are respectively opposed to the first and second ion generating electrodes 5d-1, 5f. It is drawn to the vicinity of the electrical insulating sheet S along the electric lines of force −1 and adheres to the electrical insulating sheet S.

At this time, since positive and negative charges are simultaneously applied to the first surface S1 and the second surface S2, the electrically insulating sheet S can maintain an apparently non-charged state, so that the first and second ion generations Positive and negative ions generated by the electrodes are charged in a sufficient amount in the electrically insulating sheet S. When the moving speed u of the sheet S is about 100 [m / min], ions of about 10 to 30 [μC / m ² ] are irradiated per charging unit. When the moving speed u of the sheet S becomes low, the ion irradiation amount per unit area increases, and the ion irradiation amount increases in inverse proportion to the speed u. In addition, since the front and back of the sheet S are opposite in polarity and the amount of charge is substantially equal, the sheet S is in an apparent non-charged state.

This ion irradiation is characterized in that a constant charge density [μC / m ² ] is superimposed regardless of the thickness of the sheet S. Regarding the intensity of ion irradiation, when the applied voltage V [V] increases, the amount of ions generated from the ion generating electrode increases substantially in proportion to the applied voltage. In addition, since the voltage of the opposing ion generating electrode is increased, the ions generated at the opposing ion generating electrode are accelerated in proportion to the electric field and attracted to the surface of the sheet S. Therefore, the intensity of ion irradiation increases in proportion to the square of the applied voltage V. On the other hand, when the distance between the first and second ion generation electrodes of each charging unit is reduced, the distance between the opposite ion generation electrodes is reduced, so that the electric field is increased. The generated ion cloud is condensed and strengthened. Therefore, if the distance is reduced, ion irradiation is considered to increase in inverse proportion to the square.

  Here, in Patent Document 6, as the form of the ion generation electrode arranged on each surface of the sheet, the three wire electrodes to which a DC voltage of the same polarity is applied are arranged in parallel with the sheet moving direction. There is disclosed a static eliminator that performs irradiation only once.

  By applying voltages of substantially opposite polarities to the first and second ion generating electrodes of the charging unit, the unipolar of substantially opposite polarity from the first and second ion generating electrodes of each charging unit. When a pair of ion clouds is generated at the same time and this is irradiated onto the electrical insulating sheet at the same time, a plurality of charging units are installed in parallel to generate ion clouds of the same polarity, so that the space of the ion cloud expands, as if it were a static elimination gate. It holds as. This is because the positive and negative ions are less likely to be bonded, and sufficient ions can be held in the static elimination gate. The ions are easily diffused in the longitudinal direction due to repulsion of the same polarity ions, and the number of charging units is simply reduced. You can get more effect than increased.

  With the sheet charging device 5 of FIG. 8, the first surface S1 and the second surface S2 of the electrically insulating sheet S can be charged in the same direction in the width direction with the same polarity and the opposite polarity. This charged state is a state in which all of the first condition, the second condition, and the third condition for suppressing coating unevenness are satisfied. Further, when there is a local charge distribution on each surface of the electrical insulating sheet S, for example, when there is a charging pattern by the above-described corona discharge treatment, each sheet of the electrical insulating sheet S is processed by the sheet charging device 5. The local charge distribution on the surface is made uniform, and the first surface S1 of the electrically insulating sheet S can be charged with the same polarity as the coating liquid C1.

  The positive ions and the negative ions irradiated from the sheet charging device 5 are charged to the first surface S1 and the second surface S2, for example, the first surface S1 is positive and the second surface S2 is negative and strong. Charge. At this time, more positive ions are selectively attracted to the negative charge NC1 of the first surface S1, and positive ions are selectively moved away from the positive charge PC1 of the first surface S1. That is, the first surface S1 is filled with a positive polarity while reducing the difference between the positive charge PC1 and the negative charge NC1 existing on the first surface S1. For the second surface S2, the polarity is reversed and the same effect is obtained. Thus, the distribution of the charge density due to the positive charge and the negative charge is smoothly adjusted to a level where there is no problem, and coating unevenness is less likely to occur. In addition, the first surface S1 is uniformly charged with the same polarity as the coating liquid C1, the liquid pool CP can be stabilized, and a flow mark is hardly generated.

Next, the maximum allowable amount of uniform charging on each surface of the sheet S will be described. The maximum charge density that the electrical insulating sheet S can hold in the atmosphere is approximately 27 [μC / m ² ] until dielectric breakdown occurs in the air. This value is obtained when the material of the sheet S is polyester and the thickness is 1 to 100 μm. However, when the thickness of the electrically insulating sheet S is as thin as 0.5 mm or less and the conductor is in close contact with the back surface (the surface opposite to the surface to which the coating liquid is applied), the surface charge of the insulator is different from the charge. Is induced on the back surface, the electric field strength of the insulator surface is weakened, and charging exceeding the maximum charge density is allowed.

The charge density allowed on the surface of the sheet S is inversely proportional to the distance from the back conductor. According to Non-Patent Document 2, when the thickness of the insulator is 8 [mm], when the surface charge density is 250 [μC / m ² ] or more, a discharge accompanied by strong light emission occurs along the surface of the insulator. Therefore, when the first surface S1 and the second surface S2 are the same amount of oppositely charged sheets S, and the thickness of the sheet S is 500 [μm] or less, it is apparent in a normal air conveyance state. Since it is non-charged, no discharge occurs, there is no upper limit of the allowable charge density, and the upper limit of the uniform charge amount that a maximum charge density of 5 [mC / m ² ] is allowable when placed on a metal plate Can be considered.

Actually, depending on the thickness [m] of the electrically insulating sheet S, the back surface equilibrium potential for stabilizing the liquid pool CP is often 300 to 800 [V]. When the thickness of the electrical insulating sheet S is 0.0003 [m], the back equilibrium potential of 500 [V] is about 44 [μC / m ² ] in terms of charge density when _εr is 3. . If the charge of the coating liquid C1 becomes strong, the charge of the sheet S needs to be increased. The charge amount per charging unit is 10 to 30 [μC / m ² ] when the sheet S is moving at 100 [m / min], so the number of charging units may be about two. become. However, since it differs depending on conditions such as the distance d ₁ between the ion generation electrodes of the charging unit, the applied voltage V, and the line speed, it cannot be generally stated, but the conditions of the sheet charging device 5 are confirmed while confirming the stability of the liquid pool CP. Should be set.

  Next, a post-process (addition process) in which the charge polarity of the electrical insulating sheet S and the charge polarity of the coating liquid C1 are set to the same polarity to stabilize the liquid pool CP and suppress coating unevenness will be described. Even if the electrically insulating sheet on which the coating film is formed is charged without any problem, it is preferable that the finished product is not charged. Next, a static elimination method for that purpose will be described.

  Electrical insulation sheet with electrification in which positive and negative electrostatic charges are mixed, electrical insulation sheet with opposite polarity charged in equal amounts, and electrical insulation with electrification by the above corona discharge treatment, which could not be achieved with conventional static eliminators Next, a method for neutralizing the neutral sheet will be described.

  An example of a static eliminator for carrying out this static elimination method is shown in FIGS. This static elimination method or the static elimination device itself is disclosed in Patent Document 7. FIG. 10 is a schematic vertical cross-sectional side view of the static eliminator 50, and FIG. 11 is an enlarged schematic vertical cross-sectional side view showing the positional relationship of members in an example of the static eliminator unit in the static eliminator 50.

  As shown in FIG. 1, FIG. 4, FIG. 6, or FIG. 7, the sheet charging device, the coating liquid supply device, and the coating liquid layer smoothing are upstream of the static elimination device 50 in FIG. The device is located. As illustrated in FIG. 10, the static eliminator 50 includes the DC power source 5 c and the DC power source 5 e that are the DC power source 5 c and the AC power source 5 q shown in the sheet charging device of FIG. 8, respectively. The static eliminator is configured to apply alternating voltages having opposite polarities to the ion generating electrode.

  Next, the operation of the static eliminator 50 shown in FIGS. 10 and 11 will be briefly described. The operation of the static elimination unit SUk will be described with the first static elimination unit SU1 in the uppermost stream in the sheet moving direction as a representative. In the first static elimination unit SU1, an AC voltage whose polarity is reversed in time is applied to the third ion generation electrode 50d-1 and the fourth ion generation electrode 50f-1, and the time polarity is inverted. Thus, positive and negative ions are generated from the third and fourth ion generation electrodes.

  A case where a positive voltage is applied to the third ion generation electrode 50d-1 and a negative voltage is applied to the fourth ion generation electrode 50f-1 will be described. At this time, positive ions are generated from the third ion generation electrode 50d-1, and negative ions are generated from the fourth ion generation electrode 50f-1. When the electric field strength between the third ion generation electrode 50d-1 and the fourth ion generation electrode 50f-1 is strong, positive and negative ions are forcibly irradiated to the electrical insulating sheet S by the electric field. The positive ions generated from the third ion generation electrode 50d-1 and the negative ions generated from the fourth ion generation electrode 50f-1 are respectively opposite to the third and fourth ion generation electrodes 50d-1, Along the electric lines of force 50f-1 are drawn to the vicinity of the electrical insulating sheet S and adhere to the electrical insulating sheet S. At this time, in the vicinity of the electrically insulating sheet S having positive and negative charges on the first surface S1 and the second surface S2, positive ions and negative ions are negatively charged on the electrically insulating sheet S or positive. The electrostatic charge is more selectively attracted to the negative electrostatic charge and the positive electrostatic charge by the Coulomb force. Accordingly, the negative electrostatic charge on the first surface S1 and the positive electrostatic charge on the second surface S2 of the electrically insulating sheet S are neutralized.

  Next, the phase of the AC voltage applied to the third and fourth ion generation electrodes of each static elimination unit is reversed, a negative voltage is applied to the third ion generation electrode 50d-1, and the fourth ion generation electrode When a positive voltage is applied to 50f-1, ions having a polarity opposite to that of the previous ions are generated from the third and fourth ion generation electrodes. The negative electrostatic charge on the first surface S1 and the positive electrostatic charge on the second surface S2 are neutralized. By repeating this, the positive electrostatic charge and the negative electrostatic charge on each surface of the electrically insulating sheet S can be removed. As a result, the electrically insulating sheet S is sufficiently discharged. The neutralization device 50 shown in FIG. 10 is particularly effective for neutralization when the electrical insulating sheet S moves at a low speed, and positive and negative charges are applied to the entire area of the electrical insulating sheet S by the neutralization device 50. Can remove static electricity well.

  Moreover, the static elimination method demonstrated below is also preferably used (Japanese Patent Application No. 2005-339817). While moving the electrically insulating sheet S, the sheet S is moved from the first surface S1 side and the second surface S2 side of the sheet S at the same time, with substantially opposite polarities to each other in time. Irradiate a pair of ion clouds whose polarity does not change, and then the polarity of the first surface S1 and the second surface S2 of the sheet S is reversed simultaneously with the previous irradiation. A method of removing static electricity by irradiating each surface with a pair of ion clouds whose polarity does not change. In this static elimination method, irradiation is performed so that the amount of ions of each polarity becomes substantially equal.

  In the static eliminator for carrying out this static eliminating method, the DC power source 5c of the sheet charging device of FIG. A power source 5e is connected to each of the remaining third / fourth ion generation electrodes, and DC voltages having opposite polarities are applied to the third and fourth ion generation electrodes.

Next, a coating liquid charging apparatus in an example of the coating apparatus of the present invention will be described in detail with reference to FIGS. FIG. 12 is a schematic side view of an example of a coating liquid charging apparatus, and FIG. 13 is an enlarged schematic side view of a part of the coating liquid charging apparatus of FIG. In FIG. 12, the coating liquid C <b> 1 is stored in the storage tank 22. A coating liquid supply pipe 24 is led out from the storage tank 22, discharge means 21 is provided at the end of the coating liquid supply pipe 24, and a pump 23 is connected to the coating liquid supply pipe 24 between the storage tank 22 and the discharge means 21. A coating liquid charging device 40 is provided. The coating liquid charging device 40 is connected to a high voltage power supply 41. The coating liquid C1 flows through the coating liquid supply pipe 24 at a flow rate L [m ³ / min] by the action of the pump 23, and is discharged from the discharge means 21 toward the sheet S (FIG. 1).

  As shown in FIG. 13, the charge imparting element 42 of the coating liquid charging device 40 is an electrically conductive member electrically insulated from the outside, and is connected to the coating liquid supply pipe 24 by a joint 43. When the coating liquid supply pipe 24 is an electrical conductor, the joint 43 is formed of an electrical insulator. When the coating liquid supply pipe 24 is formed of an electrical insulator, the joint 43 may be an electrical conductor or an electrical insulator.

  The charge imparting element 42 of the coating solution charging device 40 may be located at any of the straight portion, the curved portion, and the T-shaped piping portion of the coating solution supply pipe 24. In any place, the coating liquid charging device 40 can be easily incorporated because it can be spatially separated from the discharge means 21 of the coating liquid C1, and in particular, the coating apparatus 10 (FIG. 1) is installed in the explosion-proof area. In the case of discharging the coating liquid C1, it is often preferable that the high voltage portion need not be provided in the explosion-proof area and can function safely.

  The charge imparting element 42 of the coating liquid charging device 40 has a length in the cross section perpendicular to the flowing direction of the coating liquid at a site in contact with the electrically insulating coating liquid, h [mm], and a length in the flowing direction of the coating liquid. When k [mm] is set, it is preferable that the relationship of 0.02 ≦ k / h ≦ 20 is satisfied.

  The charge detecting means 44 for detecting the charge of the coating liquid C1 includes, for example, a method of measuring the potential of the coating liquid C1 by providing a detection electrode in the coating liquid supply pipe 24, and the potential of the electrically insulated conductor electrode. Consists of using a measuring method. Specifically, although depending on the length of the coating liquid supply pipe 24 in the direction perpendicular to the flow direction of the coating liquid C1, a detection electrode made of an electric conductor having a diameter of 2 mm and a length of 50 mm is connected to the coating liquid supply pipe 24. And place it in the center. By measuring the potential of the detection electrode from the 0V ground point and converting it to the charge amount, the charge polarity and the charge amount of the coating liquid C1 are measured.

  In this method of detecting the charge of the coating liquid C1, the potential of the coating liquid C1 can be continuously monitored online. When this monitoring is used, for example, the charging polarity of the coating liquid C1 is detected upstream of the charging application element 42 of the coating liquid charging device 40, and the applied polarity and application of the voltage applied to the charging application element 42 by the high voltage power source 41 are applied. The voltage can be controlled online. Further, the charging state of the coating liquid C1 can be detected downstream of the charge imparting element 42 of the coating liquid charging device 40, and it can be confirmed whether the charging polarity and the charging amount are obtained as desired. Specifically, when the detected charge amount of the coating liquid C1 is small, the charge amount of the coating liquid C1 can be controlled to be increased by increasing the applied voltage of the high-voltage power supply 41.

  The principle that the coating liquid C1 can be charged efficiently is not clear, but it is assumed that the coating liquid C1 is charged by the mechanism as follows. By applying a high voltage to the coating liquid supply pipe 24 through which the coating liquid C1 passes, the electrically insulating coating liquid that passes through the charge imparting element 42 of the coating liquid charging device 40 is near the wall surface of the coating liquid supply pipe 24. Forming an electric double layer. Since the charge imparting element 42 is connected to the high-voltage power supply 41 and the potential thereof is constant, the carrier drift current and the diffusion current in the electric double layer are balanced. However, in the coating liquid supply pipe 24, the electric double layer is not stabilized due to the pulsating flow of the coating liquid C1 by the pump 23 or the laminar flow of the coating liquid C1, and the drift current and the diffusion current become unbalanced, and the charging imparting element It is estimated that charges are injected from 42 into the coating liquid C1, and the coating liquid C1 is charged.

  Next, the high voltage applied to the charge imparting element 42 of the coating liquid charging device 40 will be described. The combustible vapor generated by the coating liquid may be ignited by electrostatic discharge. Depending on the type of combustible vapor, the corona discharge energy may exceed the minimum ignition energy, and the applied voltage is preferably in a range where no corona discharge occurs. Corona discharge is likely to occur at a pointed end or end, and in general, corona discharge may occur when a voltage exceeding 3 kV is applied. Therefore, a voltage of 3 kV or less, more preferably 2 kV or less is preferably applied to the charging element 42.

The result of charging the coating liquid C1 when using the coating liquid charging device 40 is shown in the graph of FIG. The graph of FIG. 14 shows the relationship between the flow rate R of the coating liquid C1 and the charge amount Q. The horizontal axis represents the flow rate R [10 ⁻⁶ m ³ / min] of the coating liquid C1, and the vertical axis represents the coating liquid charge amount Q [10 ⁻⁵ C / m ³ ]. In the graph of FIG. 14, the solid line indicates the result when the applied voltage is 2 kV, and the dotted line indicates the result when the applied voltage is 1 kV. This data was obtained under the following conditions. The charge imparting element 42 is composed of a ring-shaped conductor having the same diameter as the coating liquid supply pipe 24, and a voltage is applied thereto from the high voltage power source 41. The used coating liquid C1 is an acrylic emulsion having a hard coat performance when dried, and is an electrically insulating liquid. The coating liquid C1 is fed from the storage tank 22 to the coating liquid supply pipe 24 by the pump 23, and is applied to the charge imparting element 42 at a flow rate of 2 × 10 ^{−5 to} 2 × 10 ⁻⁴ [m ³ / min]. Was fed to the discharge means 21 while being in contact with each other. Using the above-mentioned Faraday cage, the difference in the charge amount of the coating liquid C1 before and after passing through the charge imparting element 42 was measured.

  As is apparent from the graph of FIG. 14, the electrically insulating coating liquid C <b> 1 is forcibly charged by passing through the charge imparting element 42 of the coating liquid charging device 40. The charge amount to the coating liquid C1 is much larger than the charge amount due to frictional charging with the coating liquid discharge pipe 24, the storage tank 22, and the like. That is, the coating liquid C1 can be charged efficiently by a simple method in which a part of the coating liquid supply pipe 24 is used and a voltage is positively applied to the coating liquid C1.

  The charging polarity of the coating liquid C1 can be the same as the applied polarity of the coating liquid charging device 40. The larger the applied voltage, the larger the charge amount of the coating liquid C1, and the smaller the flow rate of the coating liquid C1. As the amount of charge increases. When the flow rate of the coating liquid C1 is necessary for the coating liquid supply device 20, the flow path of the coating liquid C1 is temporarily divided, and the flow rate of the coating liquid C1 per one divided flow path is reduced. The desired charge amount of the coating liquid C1 can be easily obtained. That is, the coating liquid charging device 40 can be used to divide the flow of the coating liquid and charge at least one of the divided flow of the coating liquid. Thereafter, the charged coating liquids are separately or merged and discharged from the coating liquid discharging means, and applied to the sheet.

  A protective resistor 44 may be inserted between the charge imparting element 42 of the coating liquid charging device 40 and the high-voltage power supply 41. In particular, when a DC high voltage is used as the high-voltage power supply 41, if a protective resistor 44 is inserted, excessive current does not flow through the system in the event of a short circuit, and charging of the coating liquid C1 is performed safely. I can do it. In general, since it is better that a current of 1 mA or more does not flow out of the system due to a sudden short circuit, it is preferable to provide a protective resistor 44 with a current value of 1 mA or less with respect to the absolute value of the maximum applied voltage. When the protective resistor 44 having a very high resistance value is used, the applied voltage is likely to drop when a minute current flows, and the resistance value is preferably approximately 2 MΩ to 10 MΩ. The presence of the protective resistor 44 has no effect on the charged state of the coating liquid C1, so that the protective resistor 44 is effectively used depending on the situation.

  Next, examples of applying the coating liquid to the electrically insulating sheet using the coating apparatus of the present invention and comparative examples will be shown. Various evaluation methods appearing in the examples and comparative examples are as follows.

Method for evaluating the shape of the liquid pool CP:
Using a film as the electrically insulating sheet S, the shape of the liquid pool CP in which the shape of the coating liquid C1 is a curved surface in the gap between the film and the coating bar 31 is visually confirmed for 30 seconds. evaluated.

  Stable: The state where the shape of the liquid pool CP does not change significantly with time and the shape is stable. A state in which no periodic vibration or sudden deformation occurs.

  Unstable: A state in which the shape of the liquid pool CP has changed greatly over time and the shape is not constant.

Evaluation method of coating unevenness:
A film was used as the electrical insulating sheet S, and the coating liquid C1 was applied to the film, and the presence or absence of a region where the coating unevenness, that is, the coating thickness of the coating liquid was locally different was examined. The occurrence of coating unevenness was visually confirmed after the sheet S passed through the coating device, and evaluated in the following two stages.

Good: No coating unevenness Defective: Coating unevenness Investigation method for apparently non-charging:
It investigated by the presence or absence of toner adhesion. In a state where the sheet S is separated from the ground conductor by a sufficient distance with respect to the thickness of the sheet S, for example, 100 times or more of the thickness of the sheet S, the toner for electrophotography is sprinkled on the sheet S, and the local toner The adhesion was investigated.

As described above, the toner adheres to the portion of the sheet S where the apparent charge density is high. Usually, if there is a local charge with an apparent charge density of ² μC / m ² or more in absolute value, the toner adheres to the sheet S. Therefore, in the sheet S where the toner is not locally attached, it can be determined that there is no local place where the apparent charge density is ² μC / m ² or more in absolute value. The state of toner adhesion was confirmed and evaluated in the following two stages.

Good: No toner is attached and the sheet S is apparently uncharged. Defective: The toner is attached and the sheet S is not apparently uncharged. Measurement of the back surface equilibrium potential of each surface of the electrically insulating sheet S. Method:
As the electrical insulating sheet S, a sheet S in a state of being charged in advance before starting application was used. The surface opposite to the surface to be evaluated of the electrical insulating sheet S was brought into close contact with a metal roll (hard chrome plating roll having a diameter of 10 [cm]), and the potential was measured. Measurement is performed by bringing the sheet S and the metal roll into close contact so that there is substantially no gap. In this state, the sensor (monro probe 1017EH, opening diameter 0.5 [mm]) of the electrometer (monro model 244) is placed at a position 0.5 [mm] from the surface of the sheet S, The potential was measured while rotating the metal roll at a low speed to obtain a back surface equilibrium potential v [V]. The field of view when placed at the 0.5 [mm] position is in the range of 0.25 [mm] or less in diameter from the Monroe catalog. The low-speed rotation uses a linear motor, and the rotation speed is about 0.3 [m / min].

  The back surface equilibrium potential in the plane of the sheet S is determined by first scanning the electrometer in the width direction of the sheet S about 20 mm, determining the position in the width direction where the maximum value is obtained, and fixing the position in the width direction. The potential was measured by scanning the electrometer in the moving direction SD of the sheet S, that is, in the longitudinal direction of the sheet S. Ideally, the back surface equilibrium potential in the plane of the sheet S is ideally measured in a two-dimensional manner, but by approximating the potential distribution in the plane of the sheet S by the above-described method, There is no problem in practical use. In the case where the width of the sheet S exceeds 1 m, the measurement is performed using a sample sheet obtained by cutting out about 200 mm at substantially the center and the end in the width direction of the sheet S. In addition, when the charging location is known in advance in the surface of the sheet S, the measurement is performed using a sample sheet from which the charging location is cut out.

The distribution of the charge density σ [μC / m ² ] was obtained from the distribution of the obtained back surface equilibrium potential v [V]. The charge density was determined from the relational expression σ = C · v between the electrostatic capacity C [μF / m ² ] per unit area of the sheet S and the back surface equilibrium potential v. The capacitance C per unit area of the sheet S was obtained by the relational expression C = ε ₀ ε _r / t of the capacitance per unit area of the parallel plate. Where ε ₀ is the dielectric constant in vacuum: 8.854 × 10 ⁻¹² [F / m], ε _r is the relative dielectric constant of the sheet (value is 3), and t is the thickness of the sheet [m ]. Furthermore, in order to obtain the change rate of the charge density, the distribution curve of the charge density was differentiated by the in-plane length of the sheet S to obtain the maximum change rate. The charged state was evaluated in the following two stages.

Good: A charged state in which the difference between the maximum and minimum absolute values of the back surface equilibrium potential is 340 V or less and the change rate of the charge density is 0.18 [C / m ² / m] or less.

Defect: Charged state in which the difference between the maximum and minimum absolute values of the back surface equilibrium potential is 340 V or more, or the change rate of the charge density is 0.18 [C / m ² / m] or more.

Method for measuring electrical resistance of coating liquid C1 (simple method):
About 50 ml of the coating liquid C1 was accommodated in an electrically insulating container in an expanded state. Two measuring terminals (diameter 2 mm, length 50 mm) were arranged in parallel in the coating liquid C1 with a distance of 50 mm. A direct current of 15 V was applied between the terminals, and the resistance value [Ω] was read. For the measurement, a Worksurface Tester manufactured by Simco was used. The measurement was performed at 25 ° C. ± 1 ° C.

Measuring method of charge amount of coating liquid C1:
The charge amount of the coating liquid C1 was measured using a Faraday cage. Monroe Electronics Nano Coulomb meter model 284 was used for the Faraday cage. A branch is provided in the coating liquid supply pipe 24 for the coating liquid C1, and a coating liquid C1 having an amount of 0.3 × 10 ⁻³ [m ³ ] is supplied at a flow rate of 0.02 to 0.2 × 10 ⁻³ [m ³ / min. ], And put in a Faraday cage to measure the charge amount. The measurement was performed at room temperature.

Method for measuring viscosity of coating liquid C1:
About 200 ml of coating liquid C1 is put in a container, and a B-type viscometer (single cylinder type rotational viscometer according to JISZ8803 (1991), rotor No. 4 manufactured by Tokyo Keiki) is applied to the coating liquid C1 in the container. The rotor was rotated at a rotational speed of 20 [rotations / minute], and the viscosity [mPa · s] was read.
[Example 1]
The melted polyethylene terephthalate is extruded from a film extrusion die onto a casting drum, cooled by the casting drum, formed into a film, and then stretched three times in the longitudinal direction to form a uniaxially stretched film. Was supplied as a film (electrically insulating sheet) S to a coating apparatus 10a shown in FIG. That is, the coating liquid was applied to the film S using an in-line method. The width of this uniaxially stretched film (“Lumirror” manufactured by Toray Industries, Inc.) is about 1000 [mm], and the thickness is 350 [μm].

  After the film S passed through the sheet charging device 5 described later, the coating liquid C2 was applied to the second surface S2. The application of the coating liquid C2 to the second surface S2 was performed by discharging the coating liquid C2 from the discharge means 21a of the coating liquid supply device 20a to the second surface S2. By applying the coating liquid C2 to the second surface S2, the coating liquid layer CL2 was formed on the second surface S2. As the coating liquid C2, a coating liquid made of a water-soluble easily adhesive substance was used.

Immediately after the coating liquid layer CL2 was formed on the second surface S2, the coating liquid C1 was applied to the first surface S1. The application of the coating liquid C1 to the first surface S1 was performed by discharging the coating liquid C1 from the discharge means 21 of the coating liquid supply apparatus 20 onto the first surface S1. As the discharge means 21, a nozzle-type discharge means in which nozzles having an inner diameter of the coating liquid discharge port of 2 mm are arranged in the coating width direction of the coating liquid at intervals of 40 mm (nozzle arrangement pitch) was used. As a pump 23 provided in the middle of a coating liquid supply pipe 24 that connects the discharge means 21 and the storage tank 22 for the coating liquid C1, a diaphragm pump (manufactured by Takumina Co., Ltd., with a pulsation rate of 3. 5% or less) was used. The discharge amount of the coating liquid C1 from the discharge means 21 was set to 0.24 m ³ / min. The coating liquid supply pipe 24 is provided with a temperature controller for adjusting the temperature of the coating liquid C1 and setting the viscosity to a desired value.

  As the coating bar 31 of the coating liquid layer smoothing device 30, a coating bar in which a wire having a diameter of 0.356 mm was wound around a bar having a diameter of 19 mm and a length of 1200 mm without any gap was used. As shown in FIG. 7, the coating bar 31 is provided in a state where the film S is pushed down in a direction perpendicular to the moving direction SD of the film S.

  The coating liquid C1 was directly supplied from the discharge means 21 onto the surface of the liquid pool CP1 formed in the gap portion between the coating bar 31 and the film S. The drop distance of the coating liquid from the discharge means 21 to the surface of the liquid pool CP1 at this time was 40 mm. The coating width of the coating liquid on the first surface S1 was 380 mm, and the coating liquid C1 was applied to almost the center of the film S.

  The kind and physical property value of the used coating liquid C1 are as follows.

Acrylic emulsion with a solid content concentration of 3% by weight in the coating solution. Electrical resistance of the coating solution: 10 ⁹ Ω · cm
Surface tension of coating liquid: 50 [mN / m]
Viscosity of coating liquid: 700 [mP · s] However, value at coating liquid temperature 30 ° ± 2 Coating thickness of coating liquid: Value before drying and solidification of coating liquid: 25 μm, Value after drying and solidification of coating liquid: 7 μm
In order to charge the film S, as the sheet charging device 5, a charging device having electrodes opposed to each other as shown in FIGS. 8 and 9 was used. The electrodes were placed with the film S sandwiched so that the electrodes were orthogonal to the moving direction SD of the film S and parallel to the surface of the film S. The number N of charging units was two. The distance d ₁ between the upper and lower ion generation electrode tips was set to 35 [mm]. The film S was made to pass through the approximate center between the electrodes. The distance d ₂ between adjacent ion generation electrode tips in the moving direction SD of the film S was 55 [mm].

  The power sources 5c and 5e connected to the ion generation electrodes 5d and 5f were connected to each other so as to have opposite polarities by using a DC power source, and the applied polarity was determined so that the first surface S1 was positive. A DC power source having a pulsation rate of 5% or less was used. Two levels of voltages of 4.5 [kV] and 6.0 [kV] were applied to the first and second ion generation electrodes, and the shield electrodes 5g and 5h were both grounded. A positive voltage is applied to the first ion generation electrodes of all the charging units, and a negative voltage is applied to the second ion generation electrodes of all the charging units. The second surface S2 was uniformly charged with a reverse polarity.

The charging polarity of the coating liquid C1 was positive polarity, and the charging amount of the coating liquid C1 was + 20 × 10 ⁻⁵ [C / m ³ ]. Since the charging of the coating liquid C1 was obtained by frictional charging with the coating liquid supply pipe 24 and the like, a high voltage was not applied to the coating liquid charging device 40, that is, the applied voltage was set to 0V.

Downstream of the coating bar 31, a sheet neutralizing device 50 with the electrodes shown in FIGS. The electrodes were placed with the film S sandwiched so that the electrodes were orthogonal to the moving direction SD of the film S and parallel to the surface of the film S. The number N of static eliminating units was two. The distance d ₁ between the upper and lower ion generation electrode tips was set to 35 [mm]. The film S was made to pass through the approximate center between the electrodes. The distance d ₂ between adjacent ion generation electrode tips in the moving direction SD of the film S was 55 [mm].

  The power sources 5p and 5q connected to the ion generating electrodes 50d and 50f were connected to each other so as to have opposite phases by using an AC power source having a frequency of 60 Hz. A voltage of 7.0 [kV] in effective value was applied to each of the third and fourth ion generation electrodes, and the shield electrodes 50g and 50h were both grounded. An AC voltage was applied to the third ion generation electrode and the fourth ion generation electrode of each static elimination unit so that the effective value was 7.0 [kV], and the phase was 180 [degrees] in reverse phase.

When the coating liquid C1 is applied with both the charging polarity of the first surface S1 of the film S and the coating liquid C1 being positive, the liquid pool CP1 is stabilized, and the coating liquid layer CL1 on the first surface S1 The coating unevenness of the coating liquid C1 was not seen. The characteristics of the film S obtained in Example 1 are shown in Table 1.
[Example 2]
The coating liquid C1 was applied to the film S under the same conditions as in Example 1 except that the conditions in Example 1 shown in Table 1 were changed to the conditions in Example 2 shown in Table 1. Table 1 shows the characteristics of the film S obtained in Example 2.
[Comparative Example 1]
The coating liquid C1 was applied to the film S under the same conditions as in Example 1 except that no high voltage was applied to the sheet charging device 5 and the first surface S1 of the film S was in an uncharged state. . Table 1 shows the characteristics of the film S obtained in Comparative Example 1.
[Comparative Example 2]
The coating on the film S was performed under the same conditions as in Example 1 except that the sheet charging device 5 changed the first surface S1 of the film S to a charged state opposite to the charging polarity of the coating liquid C1. The liquid C1 was applied. Table 1 shows the properties of the film S obtained in Comparative Example 2.

In Table 1, in Examples 1 and 2, the charging polarity of the first surface S1 of the film S and the charging polarity of the coating liquid C1 supplied to the first surface S1 are the same polarity, and the liquid pool CP1 is Stable, no coating unevenness occurred, and a good coating solution was applied. On the other hand, as shown in Comparative Example 1, unless the film S is charged with the same polarity, the liquid pool CP1 is unstable, and the liquid pool CP1 is partially reduced or increased. Therefore, a flow mark, which is one type of coating liquid coating unevenness, occurred in the coating liquid layer CL1. Further, as shown in Comparative Example 2, when the film S and the coating liquid C1 are charged with opposite polarities, the liquid pool CP1 is unstable, and the liquid pool CP1 is attracted to the film S by the Coulomb attractive force. The liquid pool CP1 tends to be partially reduced. For this reason, a flow mark, which is one type of coating liquid application unevenness, occurred.
[Comparative Example 3]
The melted polyethylene terephthalate is extruded from a film extrusion die onto a casting drum, cooled by the casting drum, formed into a film, and then stretched three times in the longitudinal direction to form a uniaxially stretched film. Was supplied as a film (electrically insulating sheet) S to a coating apparatus 10a shown in FIG. That is, the coating liquid was applied to the film S using an in-line method. Similar to Example 1, the coating liquid C2 was applied to the second surface S2. As the coating liquid C2, a coating liquid was used from a water-soluble easy-adhesive substance.

Instead of using the sheet charging device 5 for corona charging the film S used in Example 1 and the sheet neutralizing device 50, a conventional corona discharge treatment device 151 for charging the film shown in FIG. 15 is used. It was. The corona discharge treatment device 151 was disposed at the position of the sheet charging device 5 in FIG. A voltage of 15 kV was applied to the corona discharge treatment electrode 153, and the voltage of the grounded counter electrode roll 152 was set to 0V. The film S was exposed to the corona discharge space, the wettability of the surface of the film S was improved, and a monopolar charge was given to the surface of the film S. Moreover, the static eliminator was arrange | positioned between the corona discharge treatment apparatus 151 and the coating device 10a, and static elimination of the film S was performed. The static eliminator is composed of ten electrode application type static eliminators arranged on one side of the film S. A voltage having an effective value of 7 [kV] was applied to the static eliminator using an AC power supply having a frequency of 60 [Hz]. The other conditions were the same as in Example 1, and the coating liquid C1 was applied to the film S. Table 2 shows the properties of the film S obtained in Comparative Example 3.
[Comparative Example 4]
The coating liquid C1 was applied to the film S under the same conditions as in Comparative Example 3, except that the conditions of Comparative Example 3 shown in Table 2 were changed to the conditions of Comparative Example 4 shown in Table 2. Table 2 shows the properties of the film S obtained in Comparative Example 4.
[Comparative Example 5]
The coating liquid C1 was applied to the film S under the same conditions as in Comparative Example 3 except that the conditions of Comparative Example 3 shown in Table 2 were changed to the conditions of Comparative Example 5 shown in Table 2. Table 2 shows the properties of the film S obtained in Comparative Example 5.

  In Table 2, in Comparative Example 3, the charge polarity of the film S and the coating liquid C1 was opposite, the liquid pool CP1 was not stable, and a flow mark was generated. In general, the aerial potential of the film S that has been subjected to corona discharge treatment tends to be negative and hardly has the same polarity as the charging polarity of the coating liquid C1. In addition, since the state of apparently uncharged and the state of the back surface equilibrium potential of each surface of the film S are poor, coating unevenness due to local charging of each surface of the film S occurred.

As shown in Comparative Examples 4 and 5, when the charging polarity of the film S is the same as the charging polarity of the coating liquid C1, the liquid pool CP1 tends to be more stable than the case of Comparative Example 1, but the liquid pool CP1. Could not be completely stabilized. This is because the charge applied by the corona discharge treatment is not uniform in the moving direction SD of the film S, and the shape of the liquid pool CP1 changes due to the difference in charge amount. For this reason, the liquid pool CP1 was not stabilized, and the generation of flow marks was observed. The frequency of occurrence of flow marks was less than that of Comparative Example 1. In addition, since the charging state of the back surface equilibrium potential of each surface of the film S was poor, coating unevenness due to local charging of each surface of the film S occurred.
[Example 3]
The melted polyethylene terephthalate is extruded from a film extrusion die onto a casting drum, and then the film is stretched three times in the longitudinal direction to form a uniaxially stretched film. The uniaxially stretched film is formed into a film (electrically insulating sheet) S. As a moving speed of 25 m / min. To the coating apparatus 10a shown in FIG. That is, the coating liquid was applied to the film S using an in-line method. The width of this uniaxially stretched film (“Lumirror” manufactured by Toray Industries, Inc.) is about 1000 [mm], and the thickness is 300 [μm].

  After the film S passed through the sheet charging device 5 described later, the coating liquid C2 was applied to the second surface S2. Application of the coating liquid C2 to the second surface S2 was performed by discharging the coating liquid from the discharge means 21a of the coating liquid supply apparatus 20a to the second surface S2. By applying the coating liquid C2 to the second surface S2, the coating liquid layer CL2 was formed on the second surface S2. As the coating liquid C2, a coating liquid made of a water-soluble easily adhesive substance was used. Examples of the water-soluble easily adhesive substance include terephthalic acid, isophthalic acid, and ethylene glycol. This water-soluble easy-adhesive substance was diluted with water so that the solid content concentration was 3% by weight, to obtain a coating liquid C2.

  Immediately after the coating liquid layer CL2 was formed on the second surface S2, the coating liquid C1 was applied to the first surface S2. The application of the coating liquid C1 to the first surface S1 was performed by discharging the coating liquid C1 from the discharge means 21 of the coating liquid supply apparatus 20 onto the first surface S1. As the discharge means 21, a nozzle-type discharge means in which nozzles having an inner diameter of a coating liquid discharge port of 2 mm are arranged in the coating width direction of the coating liquid at intervals of 40 mm (nozzle arrangement pitch) was used. As the pump 23 provided in the middle of the coating liquid supply pipe 24 that couples the discharge means 21 and the storage tank 22 for the coating liquid C1, a pump for quantitatively discharging the coating liquid was used. The first surface S1 of the coating liquid C1 was applied in the same manner as in Example 1 while changing the temperature of the coating liquid C1 and changing the viscosity of the coating liquid C1 to 450 to 2000 [mP · s].

  The kind and physical property value of the used coating liquid C1 are as follows.

Acrylic emulsion with a solid content concentration of 3% by weight in the coating solution. Electrical resistance of the coating solution: 10 ⁹ Ω · cm
In order to charge the film S, as the sheet charging device 5, a charging device having electrodes opposed to each other as shown in FIGS. 8 and 9 was used. The electrodes were placed with the film S sandwiched so that the electrodes were orthogonal to the moving direction SD of the film S and parallel to the surface of the film S. The number N of charging units was two. The distance d ₁ between the upper and lower ion generation electrode tips was set to 35 [mm]. The film S was made to pass through the approximate center between the electrodes. The distance d ₂ between adjacent ion generation electrode tips in the moving direction SD of the film S was 55 [mm].

  The power sources 5c and 5e connected to the ion generation electrodes 5d and 5f were connected to each other so as to have opposite polarities by using a DC power source, and the applied polarity was determined so that the first surface S1 was positive. The shield electrodes 5g and 5h were both grounded. A voltage of −5 to +5 [kV] is applied to each first ion generation electrode of all charging units, and a voltage of +5 to −5 [kV] is applied to each second ion generation electrode of all charging units. Was applied to uniformly charge the first surface S1 and the second surface S2 to opposite polarities.

The charge amount of the coating liquid C1 was −4 × 10 ⁻⁵ [C / m ³ ]. The charging of the coating liquid C1 was due to frictional charging with the coating liquid supply pipe 24 and the like. Application was performed while applying a high voltage of −2 [kV] to +2 [kV] to the coating liquid charging device 40 of the coating liquid C1 to charge the electrically insulating coating liquid C1.

  Downstream of the coating bar 31, a sheet neutralizing device 50 with the electrodes shown in FIGS. The electrodes were placed with the film S sandwiched so that the electrodes were orthogonal to the moving direction SD of the film S and parallel to the surface of the film S. The number N of static eliminating units was two. The conditions for static elimination by the static eliminator 50 were the same as in Example 1.

When the coating liquid was applied with both the first surface S1 of the film S and the coating liquid C1 having both positive and negative polarities, the liquid pool CP1 was stabilized and no coating unevenness was observed. Table 3 shows the characteristics of the film S obtained in Example 3.
[Example 4]
The coating liquid C1 was applied to the film S under the same conditions as in Example 3 except that the conditions in Example 3 shown in Table 3 were changed to the conditions in Example 4 shown in Table 3. Table 3 shows the characteristics of the film S obtained in Example 3.
[Example 5]
The coating liquid C1 was applied to the film S under the same conditions as in Example 3 except that the conditions in Example 3 shown in Table 3 were changed to the conditions in Example 5 shown in Table 3. Table 3 shows the characteristics of the film S obtained in Example 5.
[Comparative Example 6]
The coating liquid C1 was applied to the film S under the same conditions as in Example 3 except that the conditions in Example 3 shown in Table 3 were changed to the conditions in Comparative Example 6 shown in Table 3. Table 3 shows the properties of the film S obtained in Comparative Example 6. As shown in Table 3, when the charging polarity of the first surface S1 and the coating liquid C1 is opposite, the liquid pool CP1 is not stable and a flow mark is generated.
[Comparative Example 7]
The coating liquid C1 was applied to the film S under the same conditions as in Example 3 except that the conditions of Example 3 shown in Table 3 were changed to the conditions of Comparative Example 7 shown in Table 3. Table 3 shows the characteristics of the film S obtained in Comparative Example 7. As shown in Table 3, when the charging polarity of the first surface S1 and the coating liquid C1 is opposite, the liquid pool CP1 is not stable and a flow mark is generated.

[Example 6]
As the coating liquid C1, an acrylic emulsion having electrical insulation properties and hard coat performance was used. The coating liquid C1 was charged using a coating liquid charging device 40. The electrical resistance value of the used coating liquid C1 was 10 ⁹ [Ω · cm]. The coating liquid C <b> 1 is supplied from the storage tank 22 by the pump 23 to the discharge means 21 through the coating liquid supply pipe 24. The flow rate of the coating liquid C1 was set to 0.02 to 0.2 × 10 ⁻³ [m ³ / min]. As the coating liquid supply pipe 24, a fluorine-based PFA tube (inner diameter: 10 mm, outer diameter: 12 mm, manufactured by Nitta Moore) was used.

  The liquid charging device 40 is composed of a charge imparting element 42 (FIG. 13) made of a conductor, and the front and rear thereof are connected to the coating liquid supply pipe 24 using stainless steel (SUS) tube joints 43 and 43.

  As the charge imparting element 24, two types of conductors were prepared: a tubular type (type A) and a T-shaped type (type B). Type A was a stainless steel pipe (inner diameter 10 mm, outer diameter 12 mm, length 25 mm). Type B is a pipe joint (name: 1/2, inner diameter: 12.5 mm, length: 40 mm, material: stainless steel), and these two joints are used to branch and join the flow path to form a T-shaped branch. The voltage described below was applied to the mold piping. When the length in the cross section perpendicular to the flowing direction of the coating liquid C1 is h [mm] and the length in the flowing direction of the coating liquid C1 is k [mm], the value of k / h of type A is 2.5. And the value of k / h for Type B was 3.2. In this example, type A was used.

A high voltage power source was connected to the electrically insulated conductor part and a voltage was applied. The coating liquid C1 flowing inside the coating liquid supply pipe 24 passes through the coating liquid supply pipe 24 while being in contact with a high-voltage conductor. The charge amount of the coating liquid C1 after passing through the coating liquid charging device 40 was measured. When no voltage was applied to the coating liquid charging device 40, that is, when the voltage was 0 V, the charge amount of the coating liquid C1 was + 11 × 10 ⁻⁵ [C / m ³ ]. Table 4 shows the charging state of the coating liquid C1 in Example 6.
[Example 7]
The coating liquid C1 was charged under the same conditions as in Example 6 except that the conditions in Example 6 shown in Table 4 were changed to the conditions in Example 7 shown in Table 4. Table 4 shows the charging state of the coating liquid C1 in Example 7.
[Example 8]
The coating liquid C1 was charged under the same conditions as in Example 6 except that the conditions in Example 6 shown in Table 4 were changed to the conditions in Example 8 shown in Table 4. Table 4 shows the charging state of the coating liquid C1 in Example 8.
[Example 9]
The coating liquid C1 was charged under the same conditions as in Example 6 except that the conditions in Example 6 shown in Table 4 were changed to the conditions in Example 9 shown in Table 4. Table 4 shows the charging state of the coating liquid C1 in Example 9.
[Example 10]
The coating liquid C1 was charged under the same conditions as in Example 6 except that the conditions in Example 6 shown in Table 4 were changed to the conditions in Example 10 shown in Table 4. Table 4 shows the charging state of the coating liquid C1 in Example 10.
[Example 11]
The coating liquid C1 was charged under the same conditions as in Example 6 except that the conditions in Example 6 shown in Table 4 were changed to the conditions in Example 11 shown in Table 4. Table 4 shows the charging state of the coating liquid C1 in Example 11.
[Example 12]
The coating liquid C1 was charged under the same conditions as in Example 6 except that the conditions in Example 6 shown in Table 4 were changed to the conditions in Example 12 shown in Table 4. Table 4 shows the charging state of the coating liquid C1 in Example 12.
[Example 13]
The coating liquid C1 was charged under the same conditions as in Example 6 except that the conditions in Example 6 shown in Table 4 were changed to the conditions in Example 13 shown in Table 4. Table 4 shows the charging state of the coating liquid C1 in Example 13.
[Comparative Example 8]
As Comparative Example 8, a conventional charge supply device 161 shown in FIG. 16 was used. The electrically insulated coating liquid supply pipe 162a was surrounded by an electrode tube 164 with a gap therebetween, and the coating liquid supply pipe 162a and the electrode tube 164 were electrically insulated by an insulator 163. A high voltage was applied to the electrode tube 164 from the high voltage power source 166. Table 4 shows the charging state of the coating liquid C1 in Comparative Example 8.

  In the present invention, by adjusting the electrical balance between the coating liquid and the electrically insulating sheet to which the coating liquid is applied, there is no occurrence of uneven coating of the coating liquid on the surface of the electrically insulating sheet, or Since the coating can be performed in a state in which the occurrence of coating unevenness is suppressed as much as possible, it is suitable for manufacturing an electrically insulating sheet having a uniform coating film. In addition, as a sheet | seat which apply | coats the coating liquid with which this invention is applied, there exist single wafers, such as webs, such as a plastic film and paper, a silicon wafer, and a glass substrate.

FIG. 1 is a schematic side view of an embodiment of a coating apparatus of the present invention. FIG. 2 is a schematic plan view of a part of the coating apparatus shown in FIG. FIG. 3A is a schematic side view illustrating an example in which the coating liquid is applied to the electrically insulating sheet using the coating apparatus illustrated in FIG. 1. FIG. 3B is a schematic side view for explaining another example when the coating apparatus shown in FIG. 1 is used to apply the coating liquid to the electrically insulating sheet. FIG. 4 is a schematic side view of another embodiment of the coating apparatus of the present invention. FIG. 5A is a schematic side view for explaining an example when the coating apparatus shown in FIG. 4 is used to apply a coating liquid to an electrically insulating sheet. FIG. 5B is a schematic side view illustrating another example in which the coating liquid is applied to the electrically insulating sheet using the coating apparatus illustrated in FIG. 4. FIG. 6 is a schematic side view of still another embodiment of the coating apparatus of the present invention. FIG. 7 is a schematic side view of still another embodiment of the coating apparatus of the present invention. FIG. 8 is a schematic side view of an example of an electrical insulating sheet charging device preferably used in the coating apparatus of the present invention. FIG. 9 is an enlarged schematic side view of a part of the charging device for the electrically insulating sheet shown in FIG. FIG. 10 is a schematic side view of still another example of an electrical insulating sheet static eliminator preferably used in the coating apparatus of the present invention. FIG. 11 is an enlarged schematic side view of a part of the static eliminator for the electrically insulating sheet shown in FIG. FIG. 12 is a schematic side view of an example of an electrically insulating liquid charging device preferably used in the coating apparatus of the present invention. 13 is an enlarged schematic side view of a part of the electrically insulating liquid charging device shown in FIG. FIG. 14 is a graph showing the relationship between the applied voltage and the charged state of the electrically insulating liquid in an example of the coating apparatus of the present invention. FIG. 15 is a schematic side view of a conventional coating apparatus. FIG. 16 is a schematic longitudinal sectional view of a conventional coating liquid charging device. FIG. 17 is a schematic side view illustrating an apparently uncharged state of the electrical insulating sheet. FIG. 18 is a schematic side view for explaining another charged state of the electrically insulating sheet. FIG. 19 is a schematic side view for explaining the charged state when the conductor layer is in close contact with one surface of the electrically insulating sheet.

Explanation of symbols

C1: Coating liquid (coating liquid applied to the first surface)
C2: Coating liquid (coating liquid applied to the second surface)
CIE: Inductive charge CP1: Coating liquid pool (Coating liquid pool of coating liquid C1)
CP2: Coating liquid pool (Coating liquid pool of coating liquid C2)
CL1: Coating liquid layer (coating liquid layer formed by the coating liquid C1)
CL2: Coating liquid layer (coating liquid layer formed by the coating liquid C2)
LEF: Electric field line NC1: Negative charge on the first surface NC2: Negative charge on the second surface PC1: Positive charge on the first surface PC2: Positive charge on the second surface PS: Electrical insulating sheet PS1: Electricity First surface of insulating sheet PS2: Second surface of electrically insulating sheet PSD: Direction of movement of electrically insulating sheet S: Electrical insulating sheet S1: First surface of electrically insulating sheet S2: Electrical insulating property Second surface of sheet SD: Direction of movement of electrically insulating sheet 5: Sheet charging device
5a: Guide roll
5b: Guide roll
5c: First DC power supply
5d: first ion generation electrode
5d-1 to 5dn: first ion generation electrode
5e: Second DC power supply
5f: second ion generation electrode
5f-1 to 5f-n: second ion generation electrodes
5g: First shield electrode
5g-1 to 5g-n: first shield electrode
5h: Second shield electrode
5h-1 to 5h-n: second shield electrode
CU1: First charging unit
CU2: Second charging unit
CUk: kth charging unit
EUd-k: the first electrode unit in the k-th unit
EUf-k: second electrode unit in the k-th unit 10: coating device 10a: coating device 10b: coating device 10c: coating device 11: transport roll 20: coating liquid supply device (first coating liquid C1) Supply device)
20a: Second surface coating liquid supply apparatus (coating liquid C2 supply apparatus)
21: Discharge means (discharge means for coating liquid C1)
21a: Discharge means (discharge means for coating liquid C2)
22: Storage tank 23: Pump 24: Coating liquid supply piping 30: Coating liquid layer smoothing device on the first surface 30a: Coating liquid smoothing device on the second surface 31: Coating bar 31a: Coating bar 40 : Coating liquid charging device 41: High-voltage power supply 42: Charging element 43: Joint 50: Sheet neutralizing device
50d: third ion generating electrode
50f: fourth ion generation electrode
50d-1 to 50dn: third ion generation electrode
50f-1 to 50f-n: fourth ion generation electrode
5p: First AC power source
5q: Second AC power source
SU1: First static elimination unit
SU2: Second static elimination unit
SUk: k-th static elimination unit d ₀ : distance [mm] in the moving direction of the sheet between the leading edge of the first ion generating electrode and the leading edge of the second ion generating electrode
d ₁ : distance [mm] in the sheet normal direction between the tips of the first and second ion generation electrodes
d ₂ : Distance [mm] in the sheet moving direction between the tips of the first ion generation electrodes of the adjacent static elimination units
d ₃ : shortest distance [mm] in the sheet normal direction between the first and second shield electrodes
d ₄ : width [mm] in the moving direction of the sheet of the opening of the first and second shield electrodes
150: Coating apparatus 151: Corona discharge treatment apparatus 155: Coating liquid supply apparatus 161: Charge supply apparatus 162: Coating liquid supply pipe 162a: Coating liquid supply pipe 164: Electrode tube

Claims (41)

An application device that applies a coating liquid to a first surface of an electrically insulating sheet that travels in a predetermined movement direction, the sheet charging device that applies an electrostatic charge to the first surface, and the sheet charging device And a first surface coating liquid supply device that is disposed downstream in the moving direction and supplies the coating liquid to the first surface, and the sheet charging device is provided by the first surface coating liquid supply device. A coating apparatus for an electrically insulating sheet, which is provided so as to impart to the first surface an electrostatic charge having the same polarity as the charging polarity of the coating liquid when supplied to the first surface. A coating apparatus that applies a coating liquid to a first surface of an electrically insulating sheet that travels in a predetermined movement direction, the first surface coating liquid supply apparatus supplying the coating liquid to the first surface; A coating liquid charging device that imparts an electrostatic charge to the coating liquid before being supplied to the first surface, and the coating liquid charging device is configured to perform the first liquid coating by the first surface coating liquid supply device. A coating apparatus for an electrically insulating sheet provided so as to impart to the coating liquid an electrostatic charge having the same polarity as the charge polarity of the first surface when the coating liquid is supplied to the surface. An application device that applies a coating liquid to a first surface of an electrically insulating sheet that travels in a predetermined movement direction, the sheet charging device that applies an electrostatic charge of a predetermined polarity to the electrically insulating sheet, and the application device A coating liquid supply device for supplying a liquid to the first surface, and a coating for applying an electrostatic charge having the same polarity as the predetermined polarity to the coating liquid before being supplied to the first surface. An electrically insulating sheet coating device comprising a liquid charging device. A first liquid which is disposed upstream of the first surface coating liquid supply device in the moving direction and supplies a coating liquid having a volume resistivity of 10 ⁹ [Ω · cm] or less to the second surface of the electrical insulating sheet. The coating device for an electrically insulating sheet according to claim 1, wherein a coating liquid supply device for the second surface is provided. A second surface coating liquid supply device that is disposed upstream of the first surface coating liquid supply device in the moving direction and supplies a coating liquid containing water to the second surface of the electrical insulating sheet. The electrical insulating sheet coating apparatus according to claim 1, wherein the electrical insulating sheet coating apparatus is provided. The coating liquid disposed on the downstream side in the moving direction of the coating liquid supply device on the first surface and supplied to the first surface from the coating liquid supply device on the first surface is a coating liquid having a predetermined coating thickness. The coating device for an electrically insulating sheet according to any one of claims 1 to 3, further comprising a coating layer smoothing device for a first surface that smoothes the coating solution so as to form a layer. The electric liquid layer smoothing device according to claim 6, wherein the first surface coating layer smoothing device is a coating layer smoothing device based on any one of a coating bar method, a gravure roll coating method, and a die method. Insulating sheet coating device. The first surface is a surface that exists on the upper side in the direction of gravity, and in the direction perpendicular to the moving direction and the normal direction of the electrical insulating sheet, the first surface is the first surface. The electrically insulating sheet according to claim 7, wherein the coating liquid is supplied from the coating liquid supply apparatus, and the coating layer smoothing apparatus on the first surface is a coating layer smoothing apparatus based on a coating bar system. Coating device. The sheet charging device includes one or more charging units, and the charging units are arranged to face each other with the electric insulating sheet interposed therebetween, and are arranged on the first surface side of the electric insulating sheet. A first electrode unit; and a second electrode unit disposed on a second surface side of the electrical insulating sheet, wherein the first electrode unit includes a first ion generation electrode; The second electrode unit includes a second ion generation electrode, and a voltage applied to the first ion generation electrode and a voltage applied to the second ion generation electrode are substantially equal to each other. The electrical insulating sheet coating apparatus according to claim 1, wherein the electrical insulating sheet is a reverse polarity DC voltage. The first electrode unit includes a first shield electrode disposed in the vicinity of the first ion generation electrode and having an opening, and the second electrode unit includes the second ion generation electrode. The coating apparatus for an electrically insulating sheet according to claim 9, further comprising a second shield electrode disposed in the vicinity of the first shield electrode and having an opening. The discharging device has a discharging device for an electrically insulating sheet composed of at least two discharging units provided at intervals in the moving direction downstream of the coating device in the moving direction. A third electrode unit disposed on the first surface side of the electrically insulating sheet and a fourth electrode unit disposed on the second surface side opposite to each other across the insulating sheet; The third electrode unit includes a third ion generation electrode and a third shield electrode having an opening in the vicinity of the tip of the third ion generation electrode. An ion generation electrode and a fourth shield electrode having an opening in the vicinity of the tip of the fourth ion generation electrode, and a voltage applied to the third ion generation electrode and the fourth ion generation electrode The applied voltage is Coating apparatus of the electrical insulating sheet according to any one of claims 1 to 10 which is substantially opposite polarities alternating voltage of the. The first surface coating liquid supply device includes a storage tank that stores the coating liquid, a discharge unit that discharges the coating liquid onto the first surface, and a discharge unit that discharges the coating liquid from the storage tank to the discharge unit. A pump for supplying, and a coating liquid supply pipe for conveying the coating liquid between the storage tank, the discharge means, and the pump; and the coating liquid supply pipe supplies the coating liquid to the first surface. 4. The electrical insulating sheet coating apparatus according to claim 2, wherein the electrical insulating sheet is charged to a polarity opposite to the charging polarity of the first surface. The first surface coating liquid supply device includes a storage tank that stores the coating liquid, a discharge unit that discharges the coating liquid onto the first surface, and a discharge unit that discharges the coating liquid from the storage tank to the discharge unit. A supply pump; and a coating liquid supply pipe that conveys the coating liquid between the storage tank, the discharge unit, and the pump; and the coating liquid supply pipe is in a portion that contacts the coating liquid, The electrical insulating property according to claim 2 or 3, further comprising: a conductive part that is electrically conductive and electrically insulated from the outside; and a voltage applying unit that applies a voltage to the conductive part. Sheet coating device. The electrical insulating sheet coating apparatus according to claim 13, wherein charge detection means for detecting a charged state of the coating liquid is installed upstream of the discharge means of the first coating liquid supply device. A storage tank for storing the electrically insulating liquid; and a liquid supply pipe for transporting the electrically insulating liquid from the storage tank, wherein the liquid supply pipe is in a portion in contact with the electrically insulating liquid and is electrically conductive. And a conductor part that is electrically insulated from the outside, and a voltage applying means for applying a voltage to the conductor part, wherein the conductor part is in the region in contact with the electrically insulating liquid. A structure that satisfies 0.02 ≦ k / h ≦ 20, where h [mm] is a length in a cross section perpendicular to the flow direction of the electrically insulating liquid and k [mm] is a length in the flow direction of the liquid. An electrically insulating liquid charging device characterized by the above. The charging device for an electrically insulating liquid according to claim 15, further comprising a charge detecting unit that detects a charged state of the electrically insulating liquid. 16. The electrical insulating liquid charging device according to claim 15, further comprising a resistor interposed between the conductor portion and the voltage applying means. Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for producing a sheet, wherein the coating liquid is applied to the first surface. When the coating liquid is applied to the first surface, the charge polarity of the first surface and the charging polarity of the coating liquid are the same polarity. Sheet manufacturing method. Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for manufacturing a sheet, wherein the first surface is forcibly charged to the same polarity as the charging polarity of the coating liquid before applying the coating liquid to the first surface. Manufacturing method of adhesive sheet. Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for producing a sheet, wherein the coating liquid is forcibly charged to the same polarity as the charging polarity of the first surface before the coating liquid is applied to the first surface. Manufacturing method of adhesive sheet. Electric insulation with a coating film, wherein a coating liquid is applied to the first surface of an electrically insulating sheet traveling in a predetermined moving direction, and a coating film made of the applied coating liquid is formed on the first surface. A method for producing a sheet, wherein the coating liquid and the first surface are forcibly charged to the same polarity before applying the coating liquid to the first surface. Manufacturing method. The coating liquid having a volume resistivity of 10 ⁹ [Ω · cm] or less is applied to the second surface of the electrical insulating sheet before the coating liquid is applied to the first surface. The manufacturing method of the electrically insulating sheet | seat with a coating film in any one. The coating film according to any one of claims 18 to 22, wherein a coating liquid containing water is applied to the second surface of the electrically insulating sheet before the coating liquid is applied to the first surface. A method for producing an electrically insulating sheet. The manufacturing method of the electrically insulating sheet | seat with a coating film in any one of Claim 18 thru | or 23 which makes the polarity of the electrical potential of the said electrically insulating sheet | seat the same polarity as the charge polarity of the said coating liquid. The manufacturing method of the electrically insulating sheet | seat with a coating film of Claim 18, 19 or 21 which charges the 2nd surface of the said electrically insulating sheet with the polarity opposite to the said 1st surface. One or more charging units are provided for the electric insulating sheet, and the electric charging unit is disposed opposite to the electric insulating sheet with the electric insulating sheet interposed therebetween in the normal direction of the electric insulating sheet. A first ion generation electrode located on the first surface side and a second ion generation electrode located on the second surface side. The first and second ion generation electrodes are polar in time. By applying a DC voltage that does not change, the first insulating sheet is irradiated with a first ion cloud having a single polarity whose polarity does not change with time from the first surface side, and the second surface A second ion cloud having a single polarity substantially opposite to the first ion cloud from the side is irradiated simultaneously with the irradiation of the first ion cloud to charge the electrically insulating sheet. With coating as described in 18, 19, 21 or 25 A method for producing an electrically insulating sheet. The rate of change in absolute value per unit length of the charged charge density on the first surface and the charged charge density on the second surface immediately before application of the electrical insulating sheet was 0.18 [C / m ² / m, respectively. And the difference between the maximum value and the minimum value of the absolute value of the back surface equilibrium potential is 340 [V], and the first ion cloud and the second 27. The method for producing an electrically insulating sheet with a coating film according to claim 18, wherein the electrically insulating sheet is irradiated with an ion cloud. The rate of change in absolute value per unit length of the charge charge density on the first surface and the charge charge density on the second surface of the electrical insulating sheet is 0.12 [C / m ² / m] or less, respectively. And the difference between the maximum value and the minimum value of the absolute value of the back surface equilibrium potential is 200 [V], and the first ion cloud and the second ion cloud are defined so as to be apparently uncharged. 28. The method for producing an electrically insulating sheet with a coating film according to claim 18, 19, 21, 21, 25, 26 or 27, wherein the electrically insulating sheet is irradiated. The coating-coated electrically insulating sheet according to any one of claims 18 to 28, wherein the first surface is neutralized on the downstream side in the moving direction after the coating liquid is applied to the electrically insulating sheet. Method. The electrical insulation sheet after application is neutralized by providing at least two static elimination units spaced from each other in the moving direction with respect to the electrical insulation sheet. In a line direction, a third ion generation electrode located on the first surface side of the electrical insulation sheet and the fourth ion production located on the second surface side, which are disposed to face each other with the electrical insulation sheet interposed therebetween. An alternating voltage having a polarity that changes smoothly with time to the third and fourth ion generation electrodes, to the electrical insulating sheet from the first surface side. The first ion cloud having a single polarity of which polarity is changed is irradiated to the electric insulating sheet, and the single polarity having a polarity substantially opposite to that of the first ion cloud is applied to the electrically insulating sheet from the second surface side. The second ion cloud is the first ion The manufacturing method of the electrically insulating sheet | seat with a coating film of Claim 29 irradiated simultaneously with the irradiation of a cloud. 31. The electrically insulating sheet with a coating film according to claim 18, wherein an electrically insulating coating liquid is used as a coating liquid to be applied to the first surface of the electrically insulating sheet. Production method. 32. The coated film according to claim 31, wherein the volume resistivity at 25 ° C. of the coating liquid supplied to the first surface of the electrical insulating sheet is 10 ⁹ [Ω · cm] or more. A method for producing an electrically insulating sheet. The absolute value of the charge amount of the coating liquid supplied to the first surface of the electrical insulating sheet is set to 10 ^-3 [C / m ³ ] or less. The manufacturing method of the electrically insulating sheet | seat with a coating film of description. The flow rate of the coating liquid supplied to the first surface of the electrical insulating sheet is 5 × 10 ⁻⁵ [m ³ / min] or more and 5 × 10 ⁻⁴ [m ³ / min] or less. The manufacturing method of the electrically insulating sheet | seat with a coating film in any one of Claims 18 thru | or 33. The electrical insulation with a coating film according to any one of claims 18 to 34, wherein a coating thickness before drying downstream of the coating liquid supply apparatus of the coating liquid is 1 [μm] or more and 50 [μm] or less. Manufacturing method of adhesive sheet. When discharging the liquid through a pipe from a tank that stores the electric insulating liquid, a part of the pipe that is electrically insulated from the outside and brought into contact with the electric insulating liquid is contacted with the electric insulating liquid. A method for charging an electrically insulating liquid characterized by the above. 37. The method for charging an electrically insulating liquid according to claim 36, wherein a charging state of the electrically insulating liquid is detected and a voltage applied to the conductor portion is controlled. 37. The method for charging an electrically insulating liquid according to claim 36, wherein the voltage applied to the conductor portion is a DC voltage whose polarity does not change with time. 36. The electrical insulating property with a coating film according to any one of claims 18 to 35, wherein the coating film comprising the applied coating liquid is composed of a hard coating material, a release material, and an antireflection material. Sheet manufacturing method. 40. The method for producing an electrically insulating sheet with a coating film according to claim 39, wherein the coating film made of the applied coating liquid is a hard coat material made of an acrylic resin. 41. A process for producing an electrically insulating sheet roll body with a coating film, wherein the electrically insulating sheet with a coating film produced by the method for producing an electrically insulating sheet with a coating film according to claim 39 or 40 is wound up and made into a roll body. .

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