JPH0743300A - Particle measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] As a dust monitor for liquids used in semiconductor manufacturing processes, it is possible to measure the particle size of individual particles by distinguishing them from bubbles, and also to identify the substance of particles. Realize a fine particle measuring device that can be used. [Constitution] In an apparatus for irradiating the upstream side 3 and the downstream side 3'of a flow cell 1 through which a liquid is irradiated with light and measuring fine particles by scattered light from the fine particles, an electrode 2 is installed in the flow cell 1 to generate an electric field. By applying, the fine particles are electrophoresed, the displacement amount thereof is detected by the array type photodetector 5, 5 ', the fine particles contained in the liquid are distinguished from the bubbles to measure the particle size, and the substance of the fine particles is measured. Also discriminate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle measuring device for measuring the concentration of dust in a liquid used in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Conventionally, in order to detect foreign matter particles (dust) existing in a liquid, a liquid containing the foreign matter particles is irradiated with laser light and scattered light from the foreign matter particles is detected.
The particle size was obtained from the intensity value of scattered light together with the concentration of the particles present in the liquid. This is described, for example, in JP-A-54-114260. Further, in Japanese Patent Laid-Open No. 1-3541, an electric field is applied to a fine particle liquid that has been wrapped in a sheath flow to flow, and the flow is shifted depending on the charged state of the fine particles, and positively charged fine particles are shifted in the sheath flow downstream thereof. Irradiating different colors of light to the incoming side and the side where the negatively charged fine particles are shifted,
A method for distinguishing and measuring fine particles having different charging states according to the color of scattered light is described. In this method, only charged fine particles are measured, and it is determined whether the fine particles are positively charged or negatively charged.

[0003]

Since a high degree of cleanliness is required for cleaning semiconductor wafers, it is necessary to control the quality of the cleaning liquid by timely measuring the concentration of fine particles of dust. However, the above-described conventional particle measuring device has a drawback that bubbles generated during the cleaning process are measured as dust. Moreover, only the concentration (number) of dust is measured, and no information about the substance of dust to know what is the pollution source necessary for dust management has been obtained.

The present invention has been made to solve such a problem, and distinguishes it from bubbles in a liquid, and further identifies the substance of fine particles so as to enable higher quality control in the semiconductor manufacturing process. It is an object of the present invention to provide a fine particle measuring device that can also perform

[0005]

To achieve this object, in the present invention, in a particle measuring apparatus for measuring particles in a liquid by light scattering, an electric field in a flowing liquid in a direction perpendicular to the flow is obtained. And a means for measuring the amount of displacement of the fine particles existing in the liquid in the direction of the electric field due to the electric field, so that the substances of the fine particles can be discriminated. In addition to this, the scattered light intensity from the fine particles is measured to measure the particle size of the fine particles, and the particle size distribution by substance of the fine particles is measured. An array-type photodetector is used to measure the amount of displacement of the fine particles.

Further, the number of detected fine particles in the ON state and the OFF state of the electric field application is measured, and the concentration of the fine particles and the bubble concentration present in the liquid are measured separately, and the difference or ratio between the detected numbers is calculated. indicate.

Further, a liquid sample in which polystyrene particles are suspended is used as a standard sample for the calibration of the correspondence between the amount of displacement of fine particles due to an electric field and the substance. Furthermore, in order to calibrate the strength of the applied electric field for distinguishing between fine particles and bubbles, polystyrene particles surface-treated so that the zeta potential is sufficiently small, and polystyrene particles not surface-treated, respectively. Using two kinds of suspended liquid samples, the difference in the number of detected fine particles when the electric field is ON and when the electric field is OFF is almost zero in the former case, and in the latter case, the strength of the applied electric field is set within a sufficiently measurable range.

[0008]

[Operation] Regarding the operation of the above-mentioned particle measuring device,
Hereinafter, description will be given with reference to FIGS.

First, in FIG. 1, a liquid to be measured containing fine particles is caused to flow in a flow cell 1 at a constant flow rate U (m / s). Electrodes 2 of length X (m) are installed on both sides of this flow path,
A voltage is applied between these to generate an electric field perpendicular to the direction of fluid flow, causing the charged particles to move by electrophoresis. When the strength of the applied electric field is constant, the movement of the particles in the liquid due to the electric field causes the particles to migrate at a constant speed at all times because the viscous force and the electric force of the external liquid are balanced. This migration velocity is obtained as follows in the detection regions 6 and 6'set corresponding to the array type photodetectors 5 and 5 ', respectively, upstream and downstream of the region to which an electric field is applied. First, a standard particle is caused to flow in the absence of an electric field to clarify the correspondence between the detection positions of the two array type photodetectors. Next, when an electric field is applied, the correspondence between the detection positions of the two array type photodetectors is displaced. From this deviation amount d (m), the electrophoretic velocity S (m
/ S) is obtained as follows.

[0010]

[Equation 1]

Therefore, the zeta potential ζ (V) is obtained as follows.

[0012]

[Equation 2]

Here, η is the kinematic viscosity of the sample solution, ε is the dielectric constant of the sample solution, and E is the strength of the electric field (V / m).

Under the above conditions, it is assumed that the velocity distribution of fine particles in the cross section of the flow channel in the flow cell 1 is not the velocity distribution in the Poiseuille flow, but is uniform. Similarly in the velocity distribution of Poiseuille flow, the electrophoretic velocity S
The deviation d of the detection position has a functional relationship, which is different from the mathematical expression 1, but the electrophoretic velocity S can be similarly derived from the deviation amount d by correcting with the functional relationship, and the zeta potential can be obtained by the mathematical expression 2. If the E is constant, this zeta potential ζ changes with η and ε of the particulate matter and the external liquid, and the degree of dependence on the particle size and shape of the particulate is very small (Katsuichi Ikeda, Colloid Chemistry (1986) Sohua. Bunch). Therefore, in a constant external liquid, it becomes possible to discriminate the substance of fine particles at this zeta potential, that is, the electrophoretic velocity.

Generally, the electrophoretic velocity of colloidal particles is 1
It is a few (μm / s) for an electric field of (v / cm). Therefore, when the distance between the electrodes is 1 (mm), the voltage is 10
At (V), the electric field is 100 (V / cm), and thus the migration velocity of charged particles is several hundreds (μm / s). If the length of the electrode is 1 (cm) and the flow rate is 10 (cm / s), the detection position shift due to electrophoresis is several tens (μ).
m), and when measured at a magnification of several hundred times, the length of the detector is several mm, and the array length is 1 (cm) and the number of element divisions is about 20. A general array type photodetector. Can sufficiently detect the deviation. The experimental values of the migration velocity of a few substances (intensity of electric field 5.5 V / mm, in ultrapure water) are polystyrene particles (100 ± 20 μm / s,
Negative charge), Al ₂ O ₃ particles (50 ± 10 μm / s, positive charge), polystyrene particles whose surface is modified with a carboxyl group (20 ± 5 μm / s, negative charge), and the like. Moreover, these migration velocities do not depend on the particle size in the range of the particle size of 10 μm or less. Therefore, the material of the detected fine particles can be specified by creating a correspondence table of these migration rates for each substance. Further, it has been clarified by experiments by the present inventors that the migration velocity of bubbles is zero. The above migration speed is when the external liquid is pure water, but since the value changes depending on the viscosity and dielectric constant of the external liquid, it is necessary to correct the correspondence relationship between the migration speed and the substance according to the external liquid. . At that time, by adding fine particles made of a known material to the liquid to be measured, measuring the migration speed by the above method, and correcting the migration speed of unknown fine particles It is also possible to identify the substance of fine particles.

In order to measure the deviation amount d for each fine particle, the distance between the two array type photodetectors 5 and 5 '(distance: L
(M)) needs to be temporally correlated. Since the fine particles detected by the upstream array-type photodetector 5 pass L / U (s) after passing through the downstream-side array-type photodetector 5 ', at this moment, the downstream-side array-type photodetector 5' The detected fine particles can be regarded as the same as the fine particles detected by the upstream array-type photodetector 5, whereby d is determined by the difference between the detection positions on the two arrays. As a specific method for obtaining the temporal correlation, the detection signal of the upstream array type photodetector 5 is supplied to the gate signal generating circuit 8 and L / U.
The delay circuit 12 for delaying by (s) may be input to the gate circuit 9 for the signal of the downstream array type photodetector 5 '.

Furthermore, the particle size of each substance can be measured by measuring the intensity of scattered light from the particles simultaneously with the measurement of the migration velocity of the particles.

Although the principle of discriminating the substance of the fine particles in the liquid has been described above, the method for distinguishing the fine particles from the bubbles can be easily performed as compared with the above, which will be described below. This effect will be explained with reference to FIG. 9 and the obtained data, FIG. Figure 9
As shown in FIG. 1, a set of electrodes 2 is installed upstream of the flow in the flow cell 1, and light is irradiated downstream thereof. The scattered light generated in pulses from the fine particles that have passed through the part 6 of the irradiation region 3 is condensed by the lens 4 and detected by the photodetector 5, and the amplifier 7
Also, the number of detections of scattered light pulses per unit time is measured for each peak value by the device configuration including the peak hold circuit and the A / D converter 10, the memory 11, the control computer 13, and the output device 14. At the time of measurement, the electric field between the electrodes 2 is repeatedly turned on and off at regular time intervals to measure fine particles. The strength of the applied electric field is set to a value such that the charged particles passing through the detection region 6 are sufficiently reduced by electrophoresis when the electric field is ON. The bubbles are not charged, so the electric field is ON
Although not affected by -OFF, the charged particles are sufficiently reduced when the electric field is ON, so that it is possible to distinguish charged dust particles from bubbles. An example of data obtained by repeating the electric field ON-OFF is shown in FIG. 10. The number of counts per unit time when the electric field is ON is derived from bubbles, and the number of counts per unit time when the electric field is ON and OFF is shown. It is determined that the difference originates from fine particles other than bubbles. Naturally, the count number per unit time when the electric field is ON includes dust particles having a small zeta potential in addition to the bubbles, so the actual bubble concentration is
It is correct to judge that it is below the count level when the electric field is ON. In any case, in the present invention, it is possible to measure fine particles by removing the influence of bubbles.

[0019]

【Example】

(Embodiment 1) FIGS. 1A and 1B are configuration diagrams of a first embodiment of a particle measuring apparatus according to the present invention. Figure 1 (a)
FIG. 1 is a diagram showing a flow cell and a particle detection system, and FIG. 1B is a diagram showing a relationship between an irradiation optical system and a water flow system.

First, a liquid containing fine particles to be measured is caused to flow through a quartz flow cell 1 from a liquid tank 15 to be measured at a constant flow rate U (m / s) using a pump 18. A platinum electrode 2 is formed on the side surface of the flow channel in the flow cell 1. The distance between the electrodes 2 is l (m), and the length of the electrodes 2 is X (m). Using the half mirror 20 and the mirror 21 from the laser light source 17, two laser beams 3,
3'is irradiated to the upstream and downstream parts of the electrode 2 in the flow cell 1, respectively. The irradiation transmitted light is blocked by the beam stopper 22. The scattered light from the fine particles passing through the irradiation areas 3 and 3'is focused by the lenses 4 and 4'on the detection surfaces of the array type photodetectors 5 and 5 ', respectively, and collected. The array type array of the photodetectors 5, 5'is installed in a direction perpendicular to the flow of particles. The number of arrays is n, and each is ch
Each element is numbered as (1), ch (2), ... Ch (n). The relationship between the imaging of the irradiation area and the detection surface of the array detector is indicated by the two detection areas 6 and 6 '(the distance between them is L (m)) shown in the irradiation areas 3 and 3'. You can The signals detected by the array type photodetectors 5 and 5'are passed through amplifier circuits 7 and 7 ', respectively. A signal detected by the detector 5 on the upstream side is used as a trigger for a predetermined time (time required for particles to pass between the two detection regions 6 and 6 ', L /
After U (s), detection is performed by the downstream detector 5 '.
For this purpose, the signal of the amplifier 7 is input to the gate circuit 9 through the gate signal generating circuit 8 and the delay circuit 12. When at least one element ch (i) of the upstream detector 5 detects a particle, the gate circuit 9 performs L / U (s) for all the detection elements of the downstream detector 5 '. The gate opens. The detection signals from both detectors 5 and 5'are digitized by the peak value detection circuit and the AD conversion circuit 10 and 10 ', respectively, and the peak value of the signal is digitized. The difference from the element number of the detector 5 ′ on the side is stored in the memory 11.

In the above apparatus, when the sample liquid is flown without applying a voltage to the electrode 2, at least the particles detected by the upstream detector 5 are similarly detected by the downstream detector 5 '. Need to be adjusted so that Furthermore, the particles detected by the element ch (i) of the upstream detector 5 are adjusted so that they are also detected by the element ch (i) of the downstream detector 5 '. However, if the detection element numbers are deviated, they may be corrected later. Hereinafter, it is described that the detection element numbers are not displaced. Voltage is constantly applied to the electrode 2 during normal measurement. The value of this voltage is determined so that the distance that the charged fine particles to be measured migrate during X / U (s) is about the length of the regions 6 and 6 '. However, when a voltage is applied, electrolysis of water occurs and bubbles are generated on the electrodes, but it is necessary to set the flow velocity so that the bubbles do not enter the detection regions 6 and 6 '. A method of covering the electrode 2 with an insulator is also conceivable in order to prevent generation of bubbles. In this case, no current flows and electrolysis of water does not occur, which is convenient for measurement. Since the migration velocity (S) is proportional to the zeta potential of the charged particles in a constant electric field, the difference between the element number in the upstream detector 5 and the element number in the downstream detector 5'is the zeta potential. Proportional. Further, since the substance can be known from the zeta potential, the particle size can be estimated from the scattered light intensity for each substance. Display examples of the measurement results are shown in a), b), and c) of FIG. On the other hand, since the bubbles have zero zeta potential, it is possible to distinguish the bubbles by the zeta potential.

In the above embodiments, the trigger signal may be the detection signal of any detection element of the upstream detector 5, but the fine particles detected by the detection elements at both ends of the array are the detectors on the downstream side. In 5 ', due to the movement due to electrophoresis, it deviates from the detection area depending on the charge code,
Only positive or negative charge can be measured.
Therefore, the trigger signal for measuring the zeta potential may be limited to the detection signal in the detection element at the center of the upstream detector 5. When the flow cell 1 made of a chemically resistant material such as sapphire is used, it becomes possible to measure fine particles in a reactive liquid such as hydrofluoric acid.

Further, in the above embodiment, the array direction of the array type photodetector and the direction of the flow of the sample liquid are vertical, but it may be better to incline a little from the vertical. This is because there is a slight gap between the individual detection elements of the array detector, and this gap reduces the detection efficiency of particles. Therefore, when the array detector is not completely perpendicular to the flow direction of the sample liquid but is licked, it is possible to effectively eliminate the gap with respect to the flow of fine particles.

(Embodiment 2) In the embodiment 1, the detection area 6,
6'is set in two places to measure the charged state of the fine particles, but in the second embodiment, a case where the charged state of the fine particles is measured in only one detection region will be described with reference to FIG. .

First, a liquid containing fine particles to be measured is caused to flow in a flow cell 1 made of quartz at a constant flow rate U (m / s). A platinum electrode 2 is formed on the side surface of the flow channel in the flow cell 1. The distance between the electrodes 2 is l (m), and the length of the electrodes 2 is X (m). The laser light 3 is applied to the downstream portion of the electrode 2 in the flow cell 1. The scattered light from the fine particles passing through the irradiation area is focused by the lens 4 on the detection surface of the array type photodetector 5. Array type photodetector 5
The array of is oriented perpendicular to the flow of particles. The number of arrays is n, ch (1), ch
(2), ... Number each element with ch (n). The relationship between the image formation of the irradiation area and the detection surface of the array type photodetector 5 can be shown by the detection area 6 shown in the drawing during the irradiation 3. The signal detected by the array type photodetector 5 passes through the amplifier circuit 7.

FIG. 4 schematically shows the concentration distribution in the detection region 6 of fine particles when the electric field is OFF, and the shift of the concentration distribution of plus and minus charged particles and neutral particles when the electric field is ON. . Compared with the concentration distribution of fine particles when the electric field is OFF, the distribution of positively charged particles and the distribution of negatively charged particles are shifted in different directions when the electric field is ON, so the total distribution shape of charged particles and non-charged particles changes. To do. The voltage and flow rate applied between the electrodes are
It is necessary to set the range within which this change in distribution shape can be detected. In this case, the number of counts per unit time at the detection element at the center of the array type photodetector 5 does not change from that when the electric field is OFF, and the count number at both ends of the array type photodetector 5 changes when the electric field is OFF. . The electric field O actually measured is shown in FIG.
The distribution of the number of counts per unit time for each detection position (element number) of the array type photodetector 5 at the time of FF and the distribution of the number of counts per unit time when the electric field is ON are shown. The number of counts per unit time at the central portion when the electric field is ON is the same as that when the electric field is OFF, but the number of counts on both ends of the array type photodetector 5 decreases unlike when the electric field is OFF. In the array type photodetector 5, the number of counts per minute at the detection element on the + electrode side is cn, the number of counts per minute at the detection element on the-electrode side is c1, and the count per minute at the center. If the number is c0, the concentration of negatively charged particles is c0-
c1, the positively charged particle concentration is proportional to c0-cn, and the neutral particle concentration is proportional to c1 + cn-c0.

As described above, the concentration of fine particles can be measured for each charged state even when there is only one detection region.

(Embodiment 3) In the embodiment 1, the zeta potential can be measured for each fine particle, but in the embodiment 2, since the position before the fine particles pass through the electric field region is unknown,
It was not possible to measure the charge state of each fine particle. Therefore, in this embodiment, the improvement method of the second embodiment will be described with reference to FIG.

First, as shown in FIG. 6, one set of electrodes 2'was added to the flow cell 1 of Example 2, the charged particles were concentrated on the side surface of the flow cell 1 by the electrode 2 on the upstream side, and the electrode 2 on the downstream side was formed. An electric field in the opposite direction is applied to ′, and the particles are electrophoresed according to the zeta potential, and the migration amount is the same as in Example 2, including the lens 4, the array-type photodetector 5, the amplifier 7, the peak hold circuit, and The measurement is performed by the detection system including the AD converter 10. However, with this method, it is impossible to distinguish between the fine particles that go straight and the fine particles that bend and flow in the electric field. That is, it is impossible to distinguish between uncharged bubbles and charged fine particles for each fine particle. However, by comparing the count number distribution of the array detection position under the condition of applying the electric field with the count number distribution of the array detection position under the condition of not applying the electric field, the bubble concentration and the particle concentration for each zeta potential are compared. It can be measured. However, if the electrode 2'and the detection region 6 are symmetrically installed on the flow cell 1, positively charged particles and negatively charged particles cannot be distinguished. Therefore, as shown in FIG. 6, when negatively charged particles are mainly measured, The positive electrode of the downstream electrode 2'is installed apart from the side surface so that positively charged particles do not flow into the particle detection region 6. There is also a method in which the detection region 6 is provided only near the negative side of the downstream electrode 2'and the measurement is performed under a low electric field where positively charged particles are not detected.

With the above measures, for example, when the positively charged particles are not detected, the bubble concentration and the concentration distribution of the negatively charged particles for each zeta potential can be measured as follows. First, the electric field of the upstream electrode 2 is ON
At, the count number distribution per constant time when the electric field of the downstream electrode 2'is turned off is measured with respect to the detection position.
This is designated as A distribution. This A distribution contains only bubbles. Next, the count number distribution is measured with the electric fields of both the upstream and downstream electrodes 2, 2'ON. This distribution is called B distribution. This distribution includes the distribution of bubbles and charged particles containing zeta potential information. Therefore, B
With −A, a concentration distribution of negatively charged particles for each zeta potential can be obtained. That is, the fine particle concentration for each substance can be obtained.

(Fourth Embodiment) A fourth embodiment will be described with reference to FIG. This embodiment is an embodiment in which a function of concentrating the charged particles by an electric field is added to the first embodiment so that the charged particles flow concentratedly in a part of the detection region 6.

FIG. 7 shows a case where the negatively charged particles are concentrated by the three electrodes 2 on the upstream side.
It should be noted in this example that the electrodes are shielded against the liquid by an insulating material to prevent generation of bubbles due to electrolysis of the liquid. This example is the same as Example 1.
It overcomes the disadvantage that the negatively charged particles that have passed through the end of the detection region 6 in (1) pass outside the detection region 6'due to migration due to an electric field, and the zeta potential may not be measured. On the contrary, when mainly measuring the positively charged particles, the directions of the electric fields of the electrodes 2 on the upstream side may be reversed.

As described above, increasing the detection efficiency of fine particles by providing the detection region or means for applying an electric field upstream of the detection region is also effective for measuring fine particles in a gas.

(Fifth Embodiment) Next, a fifth embodiment will be described with reference to FIG.

This embodiment corresponds to an improved version of Embodiments 1 and 4, and is characterized in that concentration by an electric field is simultaneously performed on both positive and negative charged particles. That is, this is an example in which the plus and minus charged particles are once concentrated on both side walls, further upstream of the detection region 6 on the upstream side. In the case of this embodiment, compared with the case of the embodiment 4, both positive and negative charged particles due to migration due to an electric field both upstream and downstream detection regions 6 and 6 '.
So as to pass through with a high probability, both upstream and downstream electrodes 2,
Adjustment is possible by the voltage applied to 2 '. The difference from Example 4 is that both charged particles of both signs can be detected and measured with high efficiency.

(Sixth Embodiment) A sixth embodiment will be described with reference to FIGS.

As shown in FIG. 9, one set of electrodes 2 is installed in the flow cell 1 upstream of the flow, and light is irradiated downstream thereof. The scattered light generated in a pulse form from the fine particles that have passed through the part 6 of the irradiation region 3 is condensed by the lens 4 and detected by the photodetector 5, and the amplifier 7, the peak hold circuit and the A /
D converter 10, memory 11, control computer 13,
The number of detections of scattered light pulses per unit time is measured for each peak value with the device configuration including the output device 14. At the time of measurement, the electric field between the electrodes 2 is repeatedly turned on and off at regular time intervals to measure fine particles. The strength of the applied electric field is set to such a value that the charged particles passing through the detection region 6 are sufficiently reduced by the displacement caused by electrophoresis when the electric field is ON. For this setting, polystyrene particles whose surface was modified with a carboxyl group to lower the zeta potential (electrophoretic velocity in ultrapure water was 20 μm / s under an electric field strength of 5.5 V / mm) were measured. The count was set to 1/10 or less when the electric field was turned on. Since the bubbles are not charged, there is no influence of the electric field ON-OFF, but the fact that the charged particles are sufficiently reduced when the electric field is ON is used to distinguish the charged dust particles from the bubbles.

An example of data obtained by repeating the electric field ON-OFF for 10 minutes each is shown in FIG. 10. The number of counts per 10 minutes when the electric field is ON is derived from bubbles, and the electric field is ON and OFF for 10 minutes. It is determined that the difference in the number of counts per hit originates in fine particles other than bubbles. To be exact, the electric field is ON
Since the number of counts per 10 minutes at that time includes dust particles having a small zeta potential in addition to the bubbles, it can be determined that the actual concentration of the bubbles is equal to or lower than the count number level when the electric field is ON. As a display example of the measurement result of this embodiment, in addition to FIG. 10, it is also possible to display a temporal change in the difference between the data of the black and white circles before and after in FIG. In the case of this display, the change in concentration of only fine particles not containing bubbles is shown.

(Seventh Embodiment) A seventh embodiment will be described with reference to FIGS. In this embodiment, charged particles and bubbles are separated and measured.

FIG. 11 shows the internal structure of the flow cell of this embodiment.
Shown in. The light irradiation area is set in parallel with the flow of fine particles, and platinum electrodes are installed on both sides thereof. The strength of the applied electric field is 3000 V / mm. Since the air bubbles are not charged, they flow straight ahead without depending on the electric field, but since the dust particles are charged, they enter the irradiation area obliquely when an electric field is applied, and the counting rate (the number of detections per unit time) ) Increases. To increase the detection efficiency by this electric field,
Bubbles are irrelevant.

FIG. 12 shows an example in which polystyrene particles are measured by repeatedly turning on and off the electric field. By multiplying the difference between the count rate when the electric field is turned on (the number of detections per unit time) and the count rate when the electric field is turned off by a constant, the particle concentration without bubbles can be measured. FIG. 13 shows the result of actually separating and measuring the sample containing bubbles. To generate bubbles, install an ultrasonic bubble generator upstream of the flow cell
It was done by N-OFF. The fine particles are polystyrene particles having a particle size of 0.8 μm. It can be seen that the concentration of polystyrene particles is measured almost constant even when bubbles are generated, and is measured separately from the bubbles.

[0042]

As described above, in the fine particle measuring apparatus according to the present invention, the electrodes are provided in the flow cell for flowing the liquid sample to form the electric field, and the fine particles in the liquid are electrophoresed by the electric field. The particle size can be measured at the same time as the particle size measurement, and the particle concentration can be distinguished from air bubbles.

[Brief description of drawings]

FIG. 1A is a diagram showing a configuration of a flow cell and a particle detection system of Example 1, and FIG. 1B is a diagram showing a relationship between an irradiation optical system and a water flow system.

2 is a display example of measurement results obtained in Example 1. FIG.

FIG. 3 is a diagram showing a device configuration of a second embodiment.

FIG. 4 is a diagram showing the measurement principle of Example 2;

5 is a diagram showing an example of a data display obtained in Example 2. FIG.

FIG. 6 is a diagram showing a device configuration according to a third embodiment.

FIG. 7 is a diagram showing a device configuration according to a fourth embodiment.

FIG. 8 is a diagram showing a device configuration according to a fifth embodiment.

FIG. 9 is a diagram showing a device configuration of a sixth embodiment.

FIG. 10 is a diagram showing an example of a data display obtained in Example 6;

11 is a diagram showing the inside of the flow cell of Example 7. FIG.

FIG. 12 is an example of data on which the principle of Example 7 is based.

FIG. 13 is a diagram showing an example of measurement results obtained in Example 7.

[Explanation of symbols]

1 ... Flow cell 2, 2 '... Electrode 3, 3' ... Laser light 4, 4 '... Lens 5, 5' ... Array type photodetector 6, 6 '... Detection area 7, 7' ... Amplifier 8 ... Gate signal generation Circuit 9 ... Gate circuit 10, 10 '... Peak hold circuit and AD converter 11 ... Memory 12 ... Delay circuit 13 ... Control computer 14 ... Output device 15 ... Measured liquid tank 16 ... Electrode power supply 17 ... Laser light source 18 ... Pump 19 ... Waste liquid tank 20 ... Half mirror 21 ... Mirror 22 ... Beam stopper

Front page continued (72) Inventor Yoshitoshi Ito 1-280 Higashi Koikekubo, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Tadashi Suda 2-6-2 Otemachi, Chiyoda-ku, Tokyo Engineering Co., Ltd.

Claims (8)

[Claims] 1. A fine particle measuring apparatus for measuring fine particles in a liquid by light scattering, a means for applying an electric field to a flowing liquid in a direction perpendicular to the flow of the liquid, and an electric field of the fine particles by the electric field. And a means for measuring the amount of displacement in the direction. 2. The fine particle measuring device according to claim 1, further comprising means for measuring the amount of displacement of the fine particles in the electric field direction and measuring the intensity of scattered light from the fine particles. 3. The fine particle measuring device according to claim 1, wherein an array type photodetector is used as a means for measuring the displacement amount of the fine particles due to the electric field. 4. A liquid sample in which polystyrene particles are suspended in a liquid to be measured is used as a means for calibrating the correspondence between the displacement amount of the fine particles due to the electric field and the substance, and the displacement amount of the polystyrene particles is The fine particle measuring device according to claim 1, 2 or 3, which is measured and calibrated. 5. The detection number of the fine particles in the ON state and the OFF state of the electric field application can be measured by means for detecting the fine particles provided in the electric field forming region or in the downstream of the electric field forming region. The fine particle measuring device according to claim 1, 2, 3, or 4, characterized in that. 6. The ON state and the OFF state of the electric field application are temporally repeated, and the difference or the ratio of the number of detection of the fine particles in the ON state and the OFF state of the electric field application is displayed respectively. The fine particle measuring device according to claim 5. 7. As a means for calibrating the strength of an applied electric field for distinguishing and measuring the fine particles and the bubbles, a positively or negatively charged residue is added to the surface treatment so that the zeta potential becomes sufficiently small. Two types of liquid samples in which the polystyrene particles subjected to the treatment and the polystyrene particles not subjected to the surface treatment are suspended in the liquid to be measured are used, and the electric field application is turned on for the two types of liquid samples.
The number of detected fine particles in the OFF state and that in the OFF state were measured, and there was no difference in the detected number between the ON state and the OFF state for the liquid sample of polystyrene particles subjected to the surface treatment. The strength of the applied electric field is set so that the difference in the number of detections in the ON state and the OFF state can be sufficiently measured for a liquid sample of polystyrene particles that has not been treated. Alternatively, the fine particle measuring device according to item 6. 8. An apparatus for measuring fine particles in a fluid by light scattering, wherein the detection efficiency of fine particles is enhanced by a detection region of the fine particles or an electric field formed upstream of the detection region.