JPH07121369B2 - Particle charging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for charging particles in a space, and more particularly to a device for charging particles in a space by photoelectrons generated by a photoelectric effect in an electric field. In the field of charging and utilizing the fine particles, (a) a field of collecting and removing the charged fine particles to obtain a cleaning gas or a cleaning space, a field of obtaining a cleaning liquid, and (b) charging particles , The field of measuring the concentration and particle size of fine particles in gas or space such as air or exhaust gas, or liquid, (c) the surface modification of fine particles, control of charge amount, separation of fine particles, classification, etc. There is.

[0002]

2. Description of the Related Art A number of proposals have been made by the present inventor regarding charging and utilization of fine particles by photoelectrons generated by irradiating a photoelectron emitting material with ultraviolet rays. Among the things that the present inventor has proposed in the gas cleaning relationship, the ones that are particularly relevant to the present invention are as follows. (1) JP-A-61-178050 (US Patent 4,
750,917) (2) JP-A-63-100955 (3) JP-A-1-262954 (4) Japanese Patent Application No. 2-295422 No. 62-242838 (2) Japanese Patent Application Laid-Open No. 2-47536 (3) Japanese Patent Application No. 1-134781.

Further proposed in connection with separation / classification is Japanese Patent Application No. 1-177198. Other proposals regarding charging conditions include (1) Japanese Patent Application No. 1-
120563, (2) Japanese Patent Application No. 1-1205564,
(3) Japanese Patent Application No. 3-105093, (4) Japanese Patent Application No. 3-1
There is 31640 issue. In addition, the proposals related to photoelectron emitting materials include (1) Japanese Patent Application No. 1-155857.
(2) Japanese Patent Application No. 2-153335, (3) Japanese Patent Application 2-2
78123 and (4) Japanese Patent Application No. 2-295423. These methods are effective depending on the application field,
There is room for improvement in specific applications in specific areas.
For example, in the case of using an ultraviolet lamp containing a part of low-wavelength ultraviolet as an ultraviolet source, when the ultraviolet rays are applied to the air in the processing space, fine particles (ultrafine particles) may be generated from the air. In such a case, for example, in charging and collecting fine particles, the load of charging and collecting fine particles by photoelectrons becomes large, which is a problem. That is, the burden on the charging section / collecting section becomes large, and there is a need for improvement.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, it is an object of the present invention to provide a fine particle charging device which does not generate fine particles due to the irradiation of ultraviolet rays in the space to be treated. .

[0005]

In order to achieve the above object, in the present invention, an ultraviolet source, a photoelectron emitting material for generating photoelectrons by irradiation of ultraviolet rays, and a device for charging fine particles in a space having an electrode for setting an electric field are provided. A space portion in which a photoelectron emitting portion including the photoelectron emitting material and an electrode is present and a space portion other than the space (hereinafter, referred to as a treated space portion) are divided by a light shielding material that blocks transmission of ultraviolet rays. . The light shielding material can also serve as a photoelectron emitting material, and
In the charging device, it is preferable that the wall surface forming the space portion is made of a material having a low ultraviolet ray reflectance. Further, in the particle charging device of the present invention, the position of the light shielding member is between the photoelectron emitting portion and the space to be processed, and the shape is such that the particles present in the space to be processed are the photoelectron emitting portion (electrode and photoelectron emitting area). Any material may be used as long as it can be quickly moved between materials.

Next, each structure of the present invention will be described in detail. The photoelectron emitting material may be any material as long as it emits photoelectrons upon irradiation with ultraviolet light, and a material having a smaller photoelectric work function is more preferable.
r, Ca, Y, Gd, La, Ce, Nd, Th, Pr,
Be, Zr, Fe, Ni, Zn, Cu, Ag, Pt, C
d, Pb, Al, C, Mg, Au, In, Bi, Nb,
Any one of Si, Ti, Ta, U, B, Eu, Sn, P and W or a compound or alloy or mixture thereof is preferable, and these are used alone or in combination of two or more kinds. As the composite material, a physical composite material such as amalgam can also be used. For example, compounds include oxides, borides, and carbides, and oxides include BaO, SrO, and Ca.
O, Y ₂ O ₅ , Gd ₂ O ₃ , Nd ₂ O ₃ , ThO ₂ , Z
rO ₂ , Fe ₂ O ₃ , ZnO, CuO, Ag ₂ O, La
₂ O ₃ , PtO, PbO, Al ₂ O ₃ , MgO, In ₂
There are O ₃ , BiO, NbO, BeO, etc., and boride includes YB ₆ , GdB ₆ , LaB ₅ , NdB ₆ , CeB.
₆ , BuB ₆ , PrB ₆ , ZrB _{2 and the} like, and as carbides, UC, ZrC, TaC, TiC, Nb.
C, WC, etc.

As the alloy, brass, bronze, phosphor bronze, an alloy of Ag and Mg (Mg is 2 to 20 wt%), Cu
Alloy of Be and Be (1-10 wt% Be) and Ba and Al
The alloy of Ag and Mg can be used, and the alloy of Ag and Mg, the alloy of Cu and Be, and the alloy of Ba and Al are preferable. The oxide can also be obtained by heating only the metal surface in air, or by oxidizing with a chemical.
As another method, it is also possible to heat before use to form an oxide layer on the surface to obtain a stable oxide layer for a long period of time. As an example of this, an alloy of Mg and Ag can form an oxide film on its surface in water vapor at a temperature of 300 to 400 ° C., and this oxide thin film is stable for a long period of time.

Further, as the present inventor has proposed, a photoelectron emitting material having a multiple structure can be preferably used (Japanese Patent Application No. 1-155857). Also, a substance capable of emitting photoelectrons in a thin film form may be added to an appropriate base material and used (Japanese Patent Application No. 2-278123). As an example of this, there is a thin film of Au added as a substance capable of emitting photoelectrons on quartz glass as a UV transparent substance (base material) (Japanese Patent Application No. 2-295423). The shape of these materials to be used may be any shape such as a rod shape, a cotton shape, a lattice shape, a plate shape, a pleated shape, a curved surface shape, and a wire mesh shape, but a shape having a large irradiation area of ultraviolet rays and a large contact area with a processing space is used. It is preferable that the fine particles existing in the space to be processed (described later) can be rapidly moved to the photoelectron emitting portion depending on the device. The irradiation source for emitting photoelectrons from the photoelectron emitting material may be any one as long as it emits photoelectrons by irradiation. In addition to the ultraviolet rays described in this example, electromagnetic waves, lasers, and radiations can be appropriately selected and used according to application fields, device scales, shapes, effects, and the like. Of these, ultraviolet rays are usually preferred in terms of effects and operability.

Any kind of ultraviolet light may be used as long as the photoelectron emitting material can emit photoelectrons by its irradiation.
Depending on the field of application, those having a sterilizing action are also preferable. The type of UV light depends on the application field, work content,
It can be appropriately determined depending on the use, economy and the like. For example, in the biological field, it is preferable to use deep ultraviolet rays together from the viewpoint of bactericidal action and efficiency. As the ultraviolet ray source, any one can be used as long as it emits ultraviolet rays,
It can be appropriately selected and used depending on the application field, the shape of the device, the structure, the effect, the economical efficiency and the like. For example, a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube, or the like can be used as appropriate. In the biological field, sterilization wavelength 2
It is preferable to use an ultraviolet ray having a wavelength of 54 nm because the sterilizing effect can be used together.

Next, the positions and shapes of the photoelectron emitting material and the electric field electrode will be described. Photoelectron emitting material and / or the electrodes, in a portion of space suitable position in space in the presence of fine particles, the electric field between the electrodes and the photoelectron emitting material is disposed so as to form a photoelectron emitting member - and () An electric field (electric field) is formed between the electrodes (+). Due to the electric field, photoelectrons are efficiently emitted from the photoelectron emitting material (photoelectron emitting portion). The position or shape of the electrode or the photoelectron emitting material can be appropriately selected depending on the space in which the particles are present, and if the applied voltage for the electric field can be lowered and the photoelectrons from the photoelectron emitting material can charge the particles in the space. Any of them may be used, and can be appropriately determined by a preliminary test or the like in consideration of the field of use, device scale, shape, effect, economy, and the like. Any material can be used for the electrode material as long as it is a conductor, and various electrode materials in known charging devices can be preferably used. The inventor has already proposed the installation position and shape of the electrode and the photoelectron emitting material (Japanese Patent Application No.
It is preferable to configure as follows.

Next, the light shielding material which is a feature of the present invention will be described. Any light-shielding material may be used as long as it can be installed so that the ultraviolet light from the ultraviolet light source is not directly irradiated to the space to be processed. The installation position is between the photoelectron emission unit (described later) and the space to be processed. The shape may be any shape as long as the particles existing in the space to be processed can move to the photoelectron emitting portion. Usually, any one of plate-like, lattice-like, pleat-like, net-like, and curved-surface-like ones or two or more kinds thereof can be appropriately combined and used. FIG. 2 shows an example (cross-sectional view) of the shape of the light shielding material. In addition, the light shielding material can have the function of a photoelectron emitting material. Further, the light shielding material can be used as a photoelectron emitting material. The use of these can be appropriately determined depending on the field of use, the shape of the device, the scale, the effect, etc. of the charging device.

Further, it is preferable that the wall surface in the charging device is made of a material having a small reflectance of ultraviolet rays, because the generation of fine particles in the charging device is suppressed. For example, when the wall surface of the space to be processed is made of a black material, when (partly) ultraviolet rays enter the space to be processed, the reflection from the wall surface is reduced and the generation of fine particles is suppressed. As a method for reducing the reflectance of ultraviolet rays on the wall surface, a known method for reducing the reflectance of ultraviolet rays can be appropriately used.

The electric field voltage used in the present invention is 0.1 V / cm.
~ 2 kV / cm. The suitable strength of the electric field can be determined by carrying out preliminary tests and studies as appropriate depending on the field of use, conditions, device shape, scale, effect, economical efficiency and the like. In the field of charging and using fine particles, the collecting material (dust collecting material) for charged fine particles is
Any material can be used as long as it can collect charged fine particles. Various electrode materials such as a dust collecting plate and a dust collecting electrode in an ordinary charging device, and an electrostatic filter method are generally used, but the electrode is made of steel wool, and the collection part itself such as a tungsten wool electrode constitutes the electrode. Structured ones are also effective. Electrec material can also be preferably used. For use in cleaning a closed space where gas flow is small or negligible, it is preferable that the electric field electrode material also serves as or is integrated with the charged fine particle collecting material because the apparatus can be made compact.
For example, among the above-mentioned charged particulate matter collecting materials, various electrode materials such as a dust collecting plate, a dust collecting electrode, or a wool-like electrode material such as a steel wool electrode and a tungsten wool electrode are used as an electric field electrode and a collection of charged particulate matter. It is preferable because it can be combined with the above.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Example 1 Air cleaning in a wafer storage of a semiconductor factory will be described with reference to the basic configuration diagram of the present invention shown in FIG. Enclosed space air cleaning of a wafer stocker 1 is (gas does not flow, the space that can be regarded as stationary state), the ultraviolet lamp 2 is installed on one side of the wafer stocker 1, the reflecting surface 5 of the ultraviolet photoelectron emitting member 3, an electrode 4 for setting an electric field and a collector 4 for charged fine particles (in this configuration, the electrode also serves as a collector).

That is, the fine particles (fine particle substances) 6 in the wafer storage 1 are charged by the photoelectrons 7 emitted from the photoelectron emitting material 3 irradiated by the ultraviolet lamp 2, and become charged fine particles 8 which are charged fine particles 8. Are collected by the collection member 4 of charged fine particles, and the to-be-processed space (cleaning space, A) where the wafer exists is highly cleaned. Here, the light shielding material 9 is installed between the processed space portion A and the photoelectron emission portion B.
The light shielding material 9 is a combination of a plurality of plate-shaped metal plates, and the particles 6 existing in the space A to be processed are processed on the upper, central, and lower portions so that they can move to the photoelectron emission area B. The same portion is provided between the space portion A and the photoelectron emitting portion B.

The photoelectron emitting material 3 here is a glass material on which Au is added in the form of a thin film, and there is another invention of the present inventors regarding the photoelectron emitting material having such a structure. Japanese Patent Application No. 2-295423). In this way, the fine particles (particulate matter) 6 in the wafer storage 1 are collected and removed, and the wafer storage becomes clean air. In the above,
For the irradiation of the photoelectron emitting material with ultraviolet rays, the curved reflecting surface 5 is used to efficiently irradiate the plate-shaped photoelectron emitting material 3 with ultraviolet rays from the ultraviolet lamp 2. The electrode 4 is the photoelectron emission material 3
It is installed to perform photoelectron emission from an electric field. That is, an electric field is formed between the photoelectron emitting material 3 and the electrode 4 (photoelectron emitting portion, B). The charging of the fine particles is efficiently performed by the photoelectrons 7 generated by irradiating the photoelectron emitting material 3 with ultraviolet rays in an electric field. The electric field voltage here is 50 V / cm.

The electrode 4 is used to collect the charged particles. As the electrode material, a wire mesh Cu-Zn material is used after being plated with gold, and the electrode material is installed at a position 1 cm from the photoelectron emitting material (position 0.03 with respect to the distance 1 of the total length A + B). 10,
Reference numeral 11 denotes a wafer carrier and a wafer, respectively. In this example, it is preferable to provide an agitating part for the air flow in a part of the wafer storage because the particle removal rate is increased. As this method, there is a heating section for making a temperature difference and a mechanical stirring section, which can be appropriately used. In this example, the wall surface is the photoelectron emitting material 3, and the electric field electrode material 4 is provided in the space where the fine particles are present.
Although the light shielding material 9 is provided, the light shielding material 9 may be used with a function of emitting photoelectrons (for example, a Cu—Zn material is coated with Au to serve as a (−) pole). In this case, the photoelectron emission becomes both the photoelectron emitting material 3 and the light shielding material 9, and the fine particles are effectively charged.

Example 2 The following sample gas was put into the purifier having the construction shown in FIG. 1, and ultraviolet rays were radiated with and without a light-shielding material, and the particle concentration in the purifier was measured using a particle counter (particle counter). I checked. Purifier size: 30 liters Photoelectron emission material; Quartz glass with Au added in thin film form Electrode material: Wire mesh Cu-Zn at a position 1 cm from the photoelectron emission material (total distance to the wall surface facing the photoelectron emission material) Installed at the position of 0.03 for one) Light-shielding material: Plate stainless steel from the electrode material 1 as shown in FIG.
Alternately installed at positions of 1.5 cm and 1.5 cm Charged particle collector; UV lamp used as electrode material; Sterilization lamp Electric field voltage; 50 V / cm Sample gas (inlet gas); Medium gas ... Air concentration (class) ..200 (class; number of fine particles of 0.1 μm or more in 1 ft ³ ) Irradiation time: 3 hours

As a result, a fine particle concentration of 0.1 μm or more was measured with a measuring instrument. The results are shown in Table 1 as the number of fine particles in ft ³ .

[Table 1] As a blank, when the particle concentration in the purifier after being left for 3 hours in the case of irradiation with ultraviolet rays was examined, 76% of the initial concentration (inlet concentration) was recognized (measured). In this example, the example of air cleaning has been described, but the particulate matter can be charged and used without any limitation in the field of use.

[0020]

According to the present invention, the following effects can be obtained. (1). When irradiating the photoelectron emission material with ultraviolet rays under an electric field, by installing a light shielding material in the space between the photoelectron emission part and the space to be processed, the ultraviolet rays are not irradiated to the space to be processed and The generation of fine particles has disappeared. (2). The shape of the light-shielding material is plate-like, lattice-like, pleated, mesh-like, or curved-like, or a combination of two or more thereof, so that both parts pass through between the photoelectron emitting part and the processed space part. By providing the opening portion with the light shielding material, the fine particles in the processing target space portion (A) where the fine particles are present were effectively charged by the photoelectrons from the photoelectron emitting portion (B). (The fine particles in A were easily charged because they quickly met the photoelectrons through the opening.)

(3). By using a photoelectron-emitting substance as the material of the light-shielding material, photoelectrons were also emitted from the light-shielding material, and the charging of the fine particles became effective. Since the light shielding material can be a photoelectron emitting material, the charging device has a simple configuration and structure depending on the field of use. (4). By making the wall surface of the charging device a material with a low UV reflectance, particle generation due to UV wall reflection was suppressed.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an air purifier in a wafer storage using a charging device of the present invention.

FIG. 2 is a cross-sectional view showing the shape of a light shielding material.

[Explanation of symbols]

1: Wafer storage, 2: Ultraviolet lamp, 3: Photoelectron emitting material, 4: Electrode, 5: Reflecting surface, 6: Fine particles, 7: Photoelectron,
8: charged fine particles, 9: light shielding material

Claims (2)

[Claims] 1. A charging device for particles in a space having an ultraviolet ray source, a photoelectron emitting material for generating photoelectrons by irradiation of ultraviolet rays, and an electric field setting electrode, and a photoelectron emitting portion including the photoelectron emitting material and the electrode. A device for charging fine particles in a space, characterized in that the space portion and the other space portion are divided by a light shielding material that blocks transmission of ultraviolet rays. 2. The device for charging particles in a space according to claim 1, wherein the light shielding material also serves as a photoelectron emitting material.