JP3066833B2 - Air cleaning device, air cleaning method and clean room - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides an air purifying apparatus used in a clean room of a semiconductor factory or a genetic recombination facility, an air purifying method using the air purifying apparatus, and the air purifying apparatus. About clean room.

(Prior art) There are various types of air filters for air cleaning, from coarse dust to fine dust, depending on the dust collection performance. However, in a clean room where high air cleanliness is required, generally an ultra-high performance filter for fine dust is used. A filter is used. This ultra-high-performance filter is formed by forming ultra-fine glass fiber filter paper having an average fiber diameter of 1 μm or less at a right angle to the direction of air flow and forming a fiber layer having a thickness of 1 mm or less. %, The pressure loss of the air flow is small.

However, in a super LSI manufacturing environment that requires the strictest cleanliness even in a clean room, for example, in a manufacturing environment compatible with 4 Mbit of integration, submicron particles cause defective products, and it is necessary to remove them, but the diameter is 0.08 μm Although the above particles can be removed, there is a problem that aerosol particles of 0.01 μm or less cannot be completely collected even by the ultra high performance filter.

For this reason, a membrane filter having pores in the order of μm, which has a high aerosol particle collection efficiency, has been considered. However, since the porosity is as low as 90% or less and the pressure loss is large, it is currently used for sampling fine particles. Alternatively, it is used for removing fine particles under high pressure, but generally has not reached a stage where it can be put to practical use.

Also, various types of electrostatic filters for collecting particles by electrostatic attraction have been developed. Typical examples include a two-stage electrostatic precipitating filter, a particle charging type filter, an external electric field type filter, and the like.

However, these electrostatic filters have a drawback that the static electricity effect decreases as particles accumulate in the dust collecting portion, and the reliability in performance is not as high as that of the ultra-high performance filter. Although it has been put into practical use as a simple air purifier, it has not been adopted in a clean room.

Therefore, with the current technology, there is still no satisfactory air purifying device capable of collecting aerosol particles in the air with high efficiency, and air that can be conventionally applied to a clean room such as an VLSI manufacturing environment. There was a need for a cleaning device.

On the other hand, the present inventor has made various studies on removing aerosol particles in the air in view of such a situation.

When the air filtered by the ultra-high performance filter is measured with a condensed nuclei type particle concentration meter (commonly called a CNC counter) capable of detecting fine particles of 0.01 μm, a value of zero is obtained. Therefore, particles of 0.01 μm or more in the air have been completely removed.

However, it was found that when the air filtered by the ultra-high performance filter was further passed through a corona discharge type ion generator for preventing static electricity, dust adhered to the tip of the discharge electrode needle.

This is because fine aerosol particles in the air, which cannot be detected even by a condensed nuclei type particle densitometer, pass through an ultra-high performance filter and are generated in an uneven electric field formed near the discharge electrode needle. It is considered that the particles are sucked and aggregated into large particles by the chemical action of the corona discharge from the discharge electrode needle. Then, they found that air containing such fine aerosol particles aggregated into large particles can be removed again by filtering the air with an ultra-high performance filter.

According to the study of the present inventors, when performing a corona discharge from the discharge electrode needle, increasing the applied voltage improves the efficiency of agglomerating aerosol particles in the air, but on the other hand, increases the corona discharge. As a result, it has been found that the electrode needle is worn and a large amount of dust is generated. Since the ultra-high-performance filter has a low porosity, when a large amount of dust is generated due to the exhaustion of the electrode needles as described above, the ultra-high-performance filter adsorbs the dust and quickly loses its function as a filter.

Then, as a result of further study by the present inventor, by setting the voltage applied to the discharge electrode needle to 2.5 kV to 5 kV, the corona discharge can be performed, while the electrode needle is consumed by the corona discharge. Knowing that there is no
The present invention has been completed.

(Problems to be Solved by the Invention) The present invention is capable of collecting aerosol particles in the air with high efficiency, being adaptable to a clean room such as an VLSI manufacturing environment, and capable of withstanding long-term use. It is an object to provide a cleaning device, an air cleaning method using the air cleaning device, and a clean room provided with the air cleaning device.

(Means for Solving the Problems) In order to achieve the above object, the first air cleaning device of the present invention comprises a large number of protruding electrode needles on a high voltage electrode to which a voltage of 2.5 kV to 5 kV is applied. A non-uniform electric field generator provided with a ground electrode opposed to the electrode needle, and a clean room for collecting fine dust by a filtering action of a filter medium for filtering air passing through the non-uniform electric field generator. An air cleaning device comprising an ultra-high-performance filter, wherein the electrode needle of the high-voltage electrode is a needle-like electrode needle made of tungsten or stainless steel.

Further, the second air purifying device of the present invention has a capacity of 2.5 kV to 5 kV.
A high-voltage electrode to which a voltage is applied is provided with a large number of protruding electrode needles, and an uneven electric field generator in which a ground electrode is disposed opposite to the electrode needle, and passed through the uneven electric field generator. A stainless steel fiber or carbon steel having an ultra-high-performance filter for a clean room that collects fine dust by a filtering action of a filter medium to filter air, and wherein the high voltage electrode has a large number of fibers protruding on its surface as electrode needles. An air purifying device comprising a conductive fiber layer of fibers.

In the air cleaning method of the present invention, the high-voltage electrode is provided with a large number of protruding electrode needles, and the high-voltage electrode of the uneven electric field generating device in which a ground electrode is disposed opposite to the electrode needle.
By applying a voltage of 2.5 kV to 5 kV and passing air through the non-uniform electric field generator, aerosol particles in the air passing through the non-uniform electric field generator are aggregated, and the aerosol particles are filtered by a filter medium. The filter is grown to a size that can be filtered by a clean room ultra-high performance filter that collects fine dust, and the air that has passed through the unequal electric field generator is filtered through the clean room ultra-high performance filter. An air cleaning method for collecting aerosol particles with the ultra-high-performance filter for a clean room, wherein the electrode needle of the high-voltage electrode is a needle-like electrode needle made of tungsten or stainless steel, or
An air cleaning method, wherein the high-voltage electrode comprises a conductive fiber layer of stainless steel fiber or carbon steel fiber having a large number of fibers projecting on the surface thereof as electrode needles.

Further, the clean room of the present invention has a non-uniform electric field in which a high voltage electrode to which a voltage of 2.5 kV to 5 kV is applied is provided with a large number of protruding electrode needles, and a ground electrode is arranged opposite to the electrode needle. A clean room provided with an air purifying device including a device and an ultra-high-performance filter for a clean room that collects fine dust by a filtering action of a filter medium in order to filter air that has passed through the unequal electric field generating device; The electrode needle of the voltage electrode is a needle-shaped electrode needle made of tungsten or stainless steel, or the conductive electrode of stainless steel fiber or carbon steel fiber in which the high voltage electrode has a large number of fibers protruding on its surface as an electrode needle. A clean room characterized by a fiber layer.

(Function) According to the present invention, according to the means, when a voltage is applied to the high-voltage electrode, an uneven electric field is formed near the protruding electrode needle facing the ground electrode. As a result, not only the electrostatic attraction generated in the uneven electric field becomes strong, but also a corona discharge is generated from the electrode needle. Normally, by applying a voltage of 2.5 kV or more at which corona discharge occurs, aerosol particles in the air are aggregated on the high voltage electrode,
The aerosol particles are collected by the ultra-high-performance filter by growing this to a size that can be filtered by the ultra-high-performance filter.

Also, when the applied voltage is increased, the efficiency of agglomerating aerosol particles in the air is improved, but on the other hand, the corona discharge becomes intense, which causes the electrode needle to be consumed and a large amount of dust to be generated. However, it absorbs dust and impairs its function as a filter. Therefore, by setting the applied voltage to 5.0 kV or less, the consumption of the electrode needle is prevented, and the generation of dust is reduced.

The electrode needle is preferably made of a conductive material in the shape of a needle, and among them, tungsten is preferable because it generates less dust.

The conductive fiber layer can be constituted by a fiber layer made of stainless steel fiber or carbon steel fiber, but since the surface of these fiber layers has microscopic projections of many fibers, A uniform unequal electric field can be formed in the vicinity.

(Example) An example of the present invention will be described with reference to FIG. 1 and FIG.

FIG. 1 shows that the electrode needle of the high-voltage electrode is made of a conductive material (for example,
FIG. 2 schematically shows an air purifying apparatus according to the first embodiment using needle-shaped electrodes made of tungsten (tungsten), and FIG. 2 schematically shows an air purifying apparatus according to the second embodiment in which a high-voltage electrode is formed of a conductive fiber layer. Shown in

As shown in FIG. 1, the air cleaning device 1 of the first embodiment includes a high voltage generator 2 and a high voltage electrode 4 connected to the high voltage generator 2 and having a plurality of protruding electrode needles 3. A non-uniform electric field generator 6 comprising a ground electrode 5 disposed opposite to the electrode needle 3 of the high voltage electrode 4 and a position for filtering the flow of air passing through the non-uniform electric field generator 6. And an ultra-high performance filter 7 provided.

In the unequal electric field generator 6, a high-voltage electrode 4 made of a metal bar is arranged in a central space of a frame 8.

The high voltage electrode 4 has a large number of electrode needles 3 protruding at symmetrical positions in the vertical direction of the metal rod. One end of the metal rod is connected to a high voltage generator 2 for generating an AC high voltage via a high voltage cable 9. ing. The ground electrode 5 facing the high-voltage electrode 4 is made of a metal rod, and is connected in parallel to the upper and lower surfaces of the frame body 8 facing the respective electrode needles 3. Have been.

As the ultra-high performance filter 7, an ULPA filter generally used in the final stage of a clean room filter system is used, and filters the air that has passed through the unequal electric field generator 6 described above. The filter 7 is formed by forming ultrafine glass fiber filter paper having an average fiber system of 1 μm or less into a fiber layer having a thickness of 1 mm or less arranged at almost right angles to the flow direction of air. Yes, the filter strength is maintained by the addition of the binder. ULPA filters are
It has a performance of 99.9995% or more in the collection efficiency of DOP particles with a rated air volume of 0.1 μm.

The air cleaning device 1 of the first embodiment thus configured
In the method, an AC high voltage of 4 kV is applied from the high voltage generator 2 to the high voltage electrode 4, an uneven electric field is formed near the electrode needle 3, and a corona is applied to a local high electric field range of the uneven electric field. Discharge occurs. When air is caused to flow through the uneven electric field generator 6 by means (not shown), the aerosol particles in the air are sucked toward the electrode needle 3 having a strong electric field, and grow into large particles due to the aggregation action.

As a result, the aerosol particles that have passed through the unequal electric field generator 6 and are aggregated into large particles are less likely to pass through the ultra-high-performance filter 7, and are mostly collected in the ultra-high-performance filter 7. it can.

The voltage applied to the high voltage electrode 4 will be described. The graph shown in FIG. 3 is an experimental result when an AC high voltage is applied to the stainless needle (SUS304), and shows the amount of corona discharge generated at each applied voltage and the amount of dust generated by the consumption of the stainless needle due to the corona discharge. Starting voltage of corona discharge is 2.5kV
When the voltage exceeds 5 kV, corona discharge wears out the stainless steel needles and suddenly generates dust. When a large amount of dust is generated as described above, the dust adheres to the ultra-high performance filter 7 and the porosity of the filter fiber layer is rapidly reduced, so that the life of the filter is shortened.

Therefore, it is appropriate that the applied voltage is equal to or higher than the corona discharge starting voltage and equal to or lower than the dust generation voltage, and must be in the range of 2.5 kV to 5 kV. Further, even if the applied voltage is a DC high voltage, the same effect as the AC high voltage is obtained,
In this case, it is preferable to provide two sets of positive and negative high voltage electrodes 4 in the unequal electric field generator 6.

By providing the uneven electric field generators 6 in multiple stages, it is needless to say that the agglomeration action of the aerosol particles can be further enhanced, and the collection efficiency thereof can be improved.

Next, a second embodiment will be described. As shown in FIG. 2, this is an air cleaning device 14 in which the high-voltage electrode 12 and the ground electrode 13 are formed by a conductive fiber layer made of stainless steel fiber or carbon steel fiber, which is the same as in the first embodiment. The high-voltage electrode 12 is installed in the central space of the frame 8, connected to the high-voltage generator 2 via the high-voltage cable 9, and the ground electrode 13 is connected to the high-voltage electrode 12 on the upper and lower surfaces of the frame 8. They are arranged facing each other.

In such a configuration, a large number of fine fibers protrude on the surface of the conductive fiber layer, and these act as electrode needles 15, and a uniform uneven electric field is formed on the fiber layer surface, The aerosol particles in the air can be aggregated and collected by the ultra-high performance filter 7. Further, since the conductive fiber layer has a high porosity, no pressure loss occurs even when the conductive fiber layer is installed in an air flow.

(Effects of the Invention) As is clear from the above description, the present invention provides a configuration of an air cleaning device in which a high voltage electrode to which a voltage of 2.5 kV to 5 kV is applied is provided with a large number of protruding electrode needles. A non-uniform electric field generator in which a ground electrode is arranged opposite to the electrode needle, and an ultra-high-performance filter for a clean room for collecting fine dust by a filtering action of a filter medium for filtering air passing through the non-uniform electric field generator (A) the electrode needle of the high-voltage electrode is a needle-like electrode needle made of tungsten or stainless steel; or (b) a plurality of high-voltage electrodes protruding from the surface thereof. An air purifier characterized by comprising a conductive fiber layer of stainless steel fiber or carbon steel fiber using the above fibers as electrode needles. By adopting such a configuration of the air cleaning device, when a voltage of 2.5 kV to 5 kV is applied to the high voltage electrode, an uneven electric field is formed near the electrode needle, and the electrode needle removes dust. A corona discharge is generated within a range that does not occur, and aerosol particles in the air can be aggregated into large particles and collected by an ultra-high-performance filter. There is an effect of providing an air cleaning method and a clean room provided with the air cleaning device.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is an explanatory view of an air purifying apparatus of the first embodiment. FIG. 2 is a second embodiment in which a high-voltage electrode is made of a conductive fiber layer. FIG. 3 is a graph showing a corona discharge caused by applying a voltage to an electrode needle and the amount of dust generated on the electrode needle. 1,14 Air cleaning device 3,15 Electrode needle 4,12 High voltage electrode 5,13 Ground electrode 6 Unequal electric field generator 7 Ultra high performance filter

Continuing on the front page (72) Inventor Takao Okada 3150 Iiyama, Atsugi-shi, Kanagawa Prefecture Inside the Takasago Thermal Engineering Co., Ltd. (72) Inventor Soichiro Sakata 3150 Iiyama, Atsugi-shi, Kanagawa Prefecture Inside the Takasago Thermal Engineering Co., Ltd. (72 ) Inventor Kenkichi Izumi 1-10-8 Motomiya, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Shisied Static Electricity Co., Ltd. Yokohama Plant (72) Inventor Hidemi Nagata 1-10-8 Motomiya, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Shisied Static Electricity Co., Ltd. Yokohama Plant (56) References JP-A-52-126573 (JP, A) JP-A-61-21715 (JP, A) JP-A-59-16556 (JP, A) JP-A-61-197057 (JP, A) Japanese Utility Model Showa 54-1545871 (JP, U) Japanese Utility Model Showa 56-52038 (JP, U)

Claims (4)

(57) [Claims] A non-uniform electric field generating device comprising: a high voltage electrode to which a voltage of 2.5 kV to 5 kV is applied, a plurality of protruding electrode needles, and a ground electrode arranged opposite to the electrode needle; An ultra-high-performance filter for a clean room that collects fine dust by a filtering action of a filter medium in order to filter air that has passed through the unequal electric field generator, wherein the needle of the high-voltage electrode is made of tungsten or stainless steel. An air purifier characterized by being an electrode needle. 2. A non-uniform electric field generator, wherein a high voltage electrode to which a voltage of 2.5 kV to 5 kV is applied is provided with a large number of protruding electrode needles, and a ground electrode is arranged opposite to the electrode needle. An ultra-high-performance filter for a clean room that collects fine dust by a filtering action of a filter medium in order to filter air that has passed through the unequal electric field generating device, wherein the high-voltage electrode has a large number of fibers projecting on its surface. An air purifying device comprising a conductive fiber layer of stainless steel fiber or carbon steel fiber used as a needle. 3. A voltage of 2.5 kV to 5 kV is applied to the high voltage electrode of the uneven electric field generating device in which a plurality of protruding electrode needles are provided on the high voltage electrode, and a ground electrode is arranged opposite to the electrode needle. And aerosol particles in the air passing through the unequal electric field generator are aggregated by passing air through the unequal electric field generator, and the aerosol particles are collected by the filtering action of the filter medium to collect fine dust. The grown aerosol particles for the clean room are grown by filtering the air that has passed through the unequal electric field generator through the clean room ultra-high performance filter by growing the filter to a size that can be filtered by a clean room ultra-high performance filter. An air cleaning method for collecting with an ultra-high performance filter, wherein the electrode needle of the high-voltage electrode is a needle-shaped electrode needle made of tungsten or stainless steel. , Or air cleaning method characterized by comprising the conductive fiber layer of stainless steel fibers or carbon steel fibers a number of fibers that the high voltage electrode projecting on the surface with the electrode needle. 4. A non-uniform electric field generator, wherein a high voltage electrode to which a voltage of 2.5 kV to 5 kV is applied is provided with a large number of protruding electrode needles, and a ground electrode is arranged opposite to the electrode needle. A clean room provided with an air purifying device including a clean room ultra-high-performance filter that collects fine dust by a filtering action of a filter medium to filter air that has passed through the unequal electric field generating device, wherein the high-voltage electrode The electrode needle is a needle-shaped electrode needle made of tungsten or stainless steel, or the high-voltage electrode is formed of a conductive fiber layer of stainless steel fiber or carbon steel fiber having a large number of fibers projecting on its surface as electrode needles. Clean room characterized by becoming.