JP2996792B2 - Measuring method of electrostatic charge amount and apparatus used therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the amount of electrostatic charge on a charged object and a measuring apparatus used therefor, and more particularly, to a method suitable for measuring static electricity on the surface of a charged object.

[0002]

2. Description of the Related Art As a device for measuring the amount of charge of a charged object, it comprises a double container of a metal inner container and an outer container. The inner container is insulated from the ground, but the outer container is grounded. There is known a measuring device called a Faraday cage in which a voltmeter and a capacitor are connected between the outer container and a voltmeter. The measurement of the charge amount of the charged object is performed by putting the charged object in an inner container.

The amount of charge of a charged object that moves continuously, such as a film and a thread, is measured by a simulated Faraday cage installed on a movement path so as to surround a part thereof.

[0004]

However, the above-mentioned conventional measuring apparatus has the following problems. First, since a charged object to be measured must be completely placed in a metal inner container for measurement, it is not possible to measure a charged object having a relatively large size that cannot be accommodated in a container. Further, the obtained measurement value is an integrated value of all charges on the surface and inside of the charged object, and it is impossible to measure only the surface charge of the charged object or to locally measure the charge. Therefore, it is difficult to evaluate the measured value of a charged object having a non-uniform charge distribution or a charged object having a mixture of positive and negative charges.

On the other hand, in the measurement using the simulated Faraday cage, since the zero point is an important reference value, it is necessary to frequently perform the zero adjustment, and there is a problem that the measurement management is complicated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method capable of simply and accurately measuring the electric charge only on the surface of a charged object. .

The inventor of the present invention has conducted a number of experiments to achieve the above object. As a result, when a polar organic solvent is brought into contact with a charged object, only the surface of the charged object is charged from the surface of the charged object regardless of whether the charge is positive or negative. They have found that they migrate to polar organic solvents and have completed the present invention.

That is, according to the present invention, a polar organic solvent is brought into contact with a charged object with a liquid or a vapor, and when the polar organic solvent is a vapor, the vapor of the polar organic solvent is condensed on the surface of the charged object to discharge static electricity of the charged object. This is a method for measuring the amount of electrostatic charge, characterized by measuring the amount of electrostatic charge of a recovered polar organic solvent after transferring to a polar organic solvent in a liquid state.

Table 1 shows that a Teflon plate (30 cm square) charged by rubbing with a cotton cloth is charged with isopropyl alcohol (hereinafter referred to as I).
PA. ) Is contacted for the treatment time shown in Table 1, and then the IPA adhering to the Teflon plate is air-dried, and changes in the charged voltage before and after are summarized.

The Teflon plate charged to -26 to -25 kV can be easily discharged to 0 kV simply by immersing the Teflon plate in IPA, spraying IPA on the Teflon plate, or bringing the vapor of IPA into contact with the Teflon plate. However,
When a polar organic solvent is brought into contact with a charged object with steam,
It is necessary that a phase change from a solvent vapor to a liquid occurs on the surface of the charged object, that is, a condensation phenomenon occurs on the surface of the charged object.

[0011]

[Table 1]

A Teflon disk (125 mm in diameter and 2 mm in thickness) triboelectrically charged in the same manner as described above is used as a commercially available Faraday cage (hereinafter referred to as FC.
0 pF. ) Was measured and the charge amount was -0.14 [mu] C. Take out this disk and I
Sprinkle 10 ml of PA evenly over the entire Teflon disk,
When the whole amount was collected in the FC and the amount of charge of the IPA was measured, it was also -0.14 μC. Further, after the Teflon disk sprinkled with IPA was air-dried, the Teflon disk was again placed in the FC and measured, and the charge amount was 0 μC. From the above, it can be seen that all the charges on the Teflon plate have been transferred to IPA.

Table 2 shows the results of measuring the charge of the IPA by putting the IPA in contact with a frictionally charged Teflon plate (30 cm square) and a glass plate (20 cm square) similar to the above into a FC. 10 ml of IPA was evenly sprinkled on a Teflon plate and a glass plate, and the whole amount was collected in the FC. In the case of a charged Teflon plate, a negative charge is transferred during IPA, and in the case of a glass plate, a positive charge is transferred. That is, both positive and negative charges move from the charged object to the IPA side. However, in the case where the charging process is not performed, the charge in the IPA is not detected even if the same operation is performed.

[0014]

[Table 2]

Further, the surface of the Teflon plate was rubbed thoroughly with a cotton cloth to charge the surface, and then IPA was sprinkled evenly, and the dropped IPA was put into the FC to check the time change of the charge amount. As a result, the IPA in the FC was completely evaporated after 8 hours, but the measured value did not change and remained constant even when the IPA was evaporated or with the passage of time.

As described above, when a charged object is brought into contact with a polar organic solvent, both positive and negative charges are transferred to the polar organic solvent, and the charge does not disappear over time. Even if the solvent is evaporated, the transferred electric charge does not move to the vapor side at all.

The present invention has been completed based on such findings.

As the charged object in the present invention, an object charged with static electricity on the surface is used without any limitation as long as it is not dissolved in a polar organic solvent.

As the polar organic solvent in the present invention, known organic solvents can be used without any limitation. In particular, in order to transfer the surface charge of the charged object efficiently and completely, those having a dipole moment of 0.5 Debye or more are preferable. Specific examples of polar organic solvents that can be suitably used in the present invention include ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol and isopropyl alcohol; phenols such as phenol and cresol; Chlorinated hydrocarbons such as 1,1-trichloromethane are preferred, and alcohols having 3 or less carbon atoms are most preferred from the viewpoint of charge transfer effect.

When the polar organic solvent is flammable, water may be added to the above-mentioned polar organic solvent from the viewpoint of safety. Since the static elimination performance is constant at a water concentration of 60% by weight or less in the polar organic solvent, the effects of the present invention can be sufficiently achieved even when the polar organic solvent contains 60% by weight or less of water.

The method for bringing a charged organic substance into contact with a polar organic solvent includes a method in which the polar organic solvent is sprayed directly from a nozzle or the like in a liquid state to make contact with the charged substance, And the like.

When the polar organic solvent is used as a liquid, when the polar organic solvent has a high resistivity, the polar organic solvent flows through the nozzle, causing flow charging of the polar organic solvent itself. The charge amount is added. Therefore,
It is preferable that the material of the nozzle employs a conductor such as a metal, and the charge of the solvent is eliminated by short-circuiting the nozzle portion to ground.

Further, when a polar organic solvent having a low resistivity is used, the polar organic solvent ejected from the nozzle may form a continuous conductor by bridging the nozzle to the charged object. In addition, the static electricity of the charged object may escape from the nozzle through the polar organic solvent. To prevent this, the polar organic solvent ejected from the nozzle becomes discontinuous droplets from the nozzle to the charged object, and the charged object and the polar organic solvent supply system are completely insulated by air. Is preferred.

When a polar organic solvent is brought into contact with a charged object with a liquid, the polar organic solvent is recovered in a liquid state.
On the other hand, when the polar organic solvent is brought into contact with the charged object with vapor, it is necessary to condense the solvent vapor on the surface of the charged object and recover the polar organic solvent in a liquid state.

The amount of electrostatic charge of the polar organic solvent dropped from the charged object is measured by a known measuring device. As the measuring device, the above-mentioned FC can be suitably used.

In the method of the present invention, the following electrostatic charge amount measuring device can be suitably used. That is, the container comprises a double container of an inner container and an outer container having at least surfaces made of a conductor, and spraying means positioned above the double container and spraying a polar organic solvent on the charged object. The electrostatic container is insulated from the inner container, but the outer container is grounded, and is an electrostatic charge amount measuring device provided with an electric quantity measuring means in which a voltmeter and a capacitor are connected between the inner container and the outer container.

FIG. 1 is a schematic diagram showing a typical embodiment of the electrostatic charge amount measuring device of the present invention.

The present apparatus comprises a storage tank 1 for storing a polar organic solvent.
0, a nozzle 11 for spraying a polar organic solvent on the charged object,
Inner container 1 that accepts polar organic solvent falling from charged objects
2. An outer container 13 installed so as to surround the inner container 12 and grounded and short-circuited to the ground, an electrostatic voltmeter 14 connected between the inner container and the outer container, and connected in parallel with the electrostatic voltmeter. It is composed of a capacitor 15.

The polar organic solvent in the storage tank 10 can be supplied to the nozzle 11 through the pipe 17 by the pressure of the nitrogen gas from the nitrogen gas supply pipe 16 through the pipe 17. The nozzle 11 is made of a conductor, for example, metal, and the nozzle itself is grounded.

An inner container 12 and an outer container 13 surrounding the inner container 12
It is sufficient that at least the surface is formed of a conductor.
For example, a conductor such as a metal foil may be formed on the surface of an insulator such as plastic, or the whole may be formed of a metal such as stainless steel, copper, or iron.
The shape and dimensions may be appropriately determined so that the polar organic solvent falling from the charged object can be completely recovered.

The inner container 12 and the outer container 13 are open at the top to the atmosphere, and the charged object 20 is placed above the inner container 12. The polar organic solvent that is sprayed on the charged object and falls after coming into contact with the charged object is collected in the inner container 12.

An electrostatic voltmeter 14 is connected between the inner container and the outer container, and a capacitor 15 is connected in parallel with the electrostatic voltmeter 14. It is preferable to use a styrene capacitor, a ceramic capacitor, or the like having good insulation as the capacitor.

Generally, the capacitance (C ₀ ) of the capacitor may be determined so as to satisfy the following conditions.

C ₀ is selected so that the measured potential is within the measurement range of the measuring instrument.

The capacitance between the inner container of the FC and the outer container is C ₁ , the capacitance of the conductor is C ₂ , and the capacitance of the voltmeter is C ₃
Then, C ₀ is selected so as to satisfy the following equation.

[0036] _{C 0 >> C 1 + C 2} + C 3 wires leading to the potential of the inner container to the electrometer, it is preferable to use a shielded cable.

The measurement of the charge amount using the electrostatic charge amount measuring device described above is performed as follows. First, after charging the inner container to zero by grounding the inner container 12,
Make the inner container insulated. Charged object 20 to be measured
Is installed above the inner container, and sprays a polar organic solvent from the nozzle 11 onto the surface of the charged object. The charge amount (Q) of the polar organic solvent, which comes into contact with the charged object and drops by gravity and accumulates in the inner container 12, is calculated by the following equation from the reading (V) of the voltmeter 14 and the capacity (C) of the capacitor 15. You.

Q = C · V After completion of the measurement, the collected polar organic solvent is drain valve 1
8 is discharged to the outside from the drain 19 by opening.

[0039]

The method for measuring the amount of electrostatic charge according to the present invention is characterized in that when a charged object is brought into contact with a polar organic solvent, both positive and negative static electricity on the surface of the charged object can be completely transferred to the polar organic solvent side. I use. by this,
The charge amount of the charged object can be accurately measured and evaluated from the charge amount in the polar organic solvent.

In the present invention, since the charged object is not directly put in the inner container of the FC, the charged amount of the charged object having a relatively large size that cannot be accommodated in the inner container can be measured.

Further, according to the present invention, only the surface charge of a charged object can be measured.

Further, in the case of a charged object having a large volume resistivity, only the charge of the portion in contact with the polar organic solvent is irreversibly transferred to the polar organic solvent. And the charge density distribution can be determined.

Further, in the measurement of the moving charged object, the zero adjustment of the inner container can be easily performed, so that the measurement management becomes easy.

[0044]

【Example】

Example 1 Various materials were frictionally charged by the electrostatic charge amount measuring device shown in FIG. 1, and IPA was sprayed in a liquid state to measure the surface charge amount. The capacity of the capacitor used at this time is 40
0 pF. The results are shown in Table 3.

[0045]

[Table 3]

Example 2 Example 2 was carried out in the same manner as in Example 1, except that the IPA sprayed on the charged object was changed from liquid to vapor. A heater was attached to the outside of the storage tank 10, a valve was installed in a pipe connecting the tank and the nozzle 11, and steam was supplied to the surface of the charged object by opening and closing the valve. Various materials are triboelectrically charged and steam is sprayed in the same manner as in Example 1,
The phase of the liquid was changed to liquid on the surface of the charged object, and the amount of charge of the liquid dropped from the surface of the charged object was measured. Table 4 shows the results.
Almost the same results were obtained with vapor as with liquid.

[0047]

[Table 4]

Example 3 The charge amount of the Teflon silicon wafer carrier was measured in exactly the same manner as in Example 1 except that the polar organic solvents shown in Table 5 were used instead of IPA. Table 5 shows the results.

[0049]

[Table 5]

[Brief description of the drawings]

FIG. 1 is a schematic view of an electrostatic charge amount measuring device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Storage tank 11 Nozzle 12 Inner container 13 Outer container 14 Electrostatic voltmeter 15 Capacitor 16 Nitrogen gas supply pipe 17 Pipe 18 Drain valve 19 Drain 20 Charged object

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 29/24

Claims (2)

(57) [Claims] 1. A charged organic substance is brought into contact with a polar organic solvent by liquid or vapor, and when the polar organic solvent is vapor, the vapor of the polar organic solvent is condensed on the surface of the charged substance, and the static electricity of the charged substance is converted into a liquid state polarity. A method for measuring the amount of electrostatic charge of a polar organic solvent collected after transferring to an organic solvent. 2. A double container comprising an inner container and an outer container having at least a surface made of a conductor, and spraying means positioned above the double container and spraying a polar organic solvent on the charged object. The container is insulated from the ground, but the outer container is grounded, and is equipped with an electric quantity measuring means having a voltmeter and a capacitor connected between the inner container and the outer container, characterized in that the electrostatic charge amount measuring device is provided. .