JP4354121B2 - Dynamic light scattering particle size distribution analyzer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dynamic light scattering type particle size distribution measuring apparatus.
[0002]
[Prior art]
One of the particle size distribution measuring methods uses a dynamic light scattering type particle size distribution measuring apparatus. This dynamic light scattering type particle size distribution measuring apparatus accommodates a measurement sample in which particles are dispersed in a dispersion medium in a sample cell, irradiates the measurement sample with laser light, and is scattered by the particles. In addition to conventional organic pigments and ceramics, recently, research and development of advanced materials such as abrasives for semiconductor wafers and hard disks, and inkjet printers. There is a growing need in the field.
[0003]
[Problems to be solved by the invention]
By the way, in the conventional dynamic light scattering type particle size distribution measuring apparatus, conventionally, so-called batch processing for supplying a measurement sample to a sample cell at each measurement is mainstream, and the measurable concentration of the measurement apparatus is very high. Therefore, it is necessary to dilute and use a low-concentration or high-concentration sample as a measurement sample, and thus a method of automatically diluting the sample to a measurable range of concentration may be employed. This seems to be due to the fact that, in the past, users using this type of apparatus had a lot of know-how and databases for measurement by dilution.
[0004]
In diluting the sample, conventionally, a method of quantitatively collecting the sample and injecting the diluted solution quantitatively so as to be 100 times or 1000 times the sample has been employed.
[0005]
[Problems to be solved by the invention]
However, the purpose of the above method is to adjust the dilution of the measurement sample to the measurable concentration of the measurement device, and the sample (particles) that easily aggregates will be measured while being affected by the aggregation due to dilution. In some cases, the measurement was performed in a state different from the actual use state of the particles. When the particle size distribution measurement is performed in the state where the aggregation occurs, the scattered light intensity greatly changes, or even if diluted, the scattered light intensity becomes weak, and predetermined measurement cannot be performed.
[0006]
The present invention has been made in consideration of the above-mentioned matters. The purpose of the present invention is to measure the sample concentration used for measurement before the particle size distribution measurement, and automatically dilute the sample until the desired measurement concentration is reached. Thus, it is an object to provide a dynamic light scattering type particle size distribution measuring apparatus capable of efficiently performing a predetermined particle size distribution measurement.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a measurement sample in which particles are dispersed in a dispersion medium is accommodated in a sample cell, the laser beam is irradiated to the measurement sample, and the light scattered by the particles. In the dynamic light scattering type particle size distribution measuring apparatus for obtaining the particle size distribution based on the frequency intensity distribution of the dispersion medium, the dispersion medium and the particles are supplied, the dispersion bath for dispersing the particles in the dispersion medium, and the Prior to particle size distribution measurement, the sample cell is connected to the sample cell through a circulation channel, and the sample sample is supplied from the dispersion bath to the sample cell, and the measurement sample is irradiated with laser light. The concentration of the measurement sample is measured based on the scattered light intensity, the measured concentration is compared with a preset target concentration, and the concentration of the measurement sample can be adjusted based on the comparison result. Yes.
[0008]
In the dynamic light scattering particle size distribution measuring apparatus, a sample to be measured can be automatically diluted to a concentration (or concentration range) to be diluted. Since the concentration can be confirmed while preventing the change in the state of the sample due to dilution, there is no possibility of overdilution or insufficient dilution.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. 1 to 5 show one embodiment of the present invention. FIG. 1 schematically shows an example of a dynamic light scattering particle size distribution measuring apparatus according to the present invention. In this figure, 1 is a dispersion bath, 2 is a sample cell, and 1 and 2 are circulating. They are connected by a flow path 3.
[0010]
The dispersion bath 1 is composed of, for example, a cylindrical liquid tank, and mixes particles 4a as a measurement target sample with a dispersion medium 4b for dispersing the sample to form a measurement sample 4. An ultrasonic vibrator 5 that vibrates due to the above is provided to prevent the particles 4 a from aggregating in the dispersion bath 1.
[0011]
The sample cell 2 is a so-called flow cell, and has a sample inlet 2a formed at one end and a sample outlet 2b formed at the other end.
[0012]
The circulation channel 3 has one end connected to the bottom of the dispersion bath 1 and the other end connected to the sample inlet 2a of the sample cell 2, and one end connected to the sample outlet 2b of the sample cell 2. The other end is formed of a return pipe 3 b that opens into the distribution bus 1 at the upper part of the distribution bus 1.
[0013]
Explaining the configuration of the distribution bus 1 side, a three-way solenoid valve 6 and a circulation pump 7 are provided on the downstream side of the return pipe 3b, and the three-way solenoid valve 6 located on the more upstream side is the first one. The second ports 6a and 6b are connected to the return pipe 3b, respectively, and the dispersion medium storage tank 9 is connected to the third port 6c via the pipe 8. The three-way solenoid valve 6 is configured such that, for example, the ports 6b and 6c communicate with each other when the power is off, and the ports 6a and 6b communicate with each other when the power is on. Further, a particle supply hopper 10 for supplying separately weighed particles 4 a into the dispersion bath 1 and a dispersant supply pipe 11 for supplying a dispersant into the dispersion bath 1 are provided on the top of the dispersion bath 1. . Further, a drain pipe 13 having an on-off valve 12 is branched and connected to a portion of the forward pipe 3a close to the bottom of the distribution bus 1.
[0014]
As the dispersion medium 4b, for example, a liquid such as water (pure water), ethanol, or oil is used, and the dispersion medium 4b is properly used depending on the type of the particle 4a to be measured. Moreover, the said dispersing agent is what makes particles 4a disperse | distribute easily in the dispersion medium 4b, for example, repels particles, such as surfactant, and is supplied as needed.
[0015]
The configuration on the sample cell 2 side will be described. A laser light source 14 is provided on one side of the sample cell 2, and a laser beam from the laser light source 14 is provided in the optical path between the laser light source 14 and the sample cell 2. A lens 16 for collimating the light 15, a beam splitter 17, and a condenser lens 18 are provided in this order. The beam splitter 17 is provided with, for example, a hole through which the laser beam 15 passes in the center, and a reflection surface thereof is formed of a mirror formed in the direction of the sample cell 2, and the optical axis of the laser beam 15 emitted from the laser light source 14 and, for example, The laser beam 15 passing through the hole is bent at an appropriate angle of 90 ° or less with respect to the interference light 19 generated by the Doppler shift of the scattered light caused by the particles 4b in the sample cell 2. It is configured to reflect. The optical path of the interference light 19 reflected by the mirror 17 is provided with a lens 20 that collects the interference light 19 and a photodetector 21 that converts the interference light 19 into an electrical detection signal D (t). .
[0016]
A signal processing unit 22 amplifies the output D (t) of the photodetector 21 and converts it into a digital signal if necessary, and a detection signal D (t) output from the signal processing unit 23. ) To obtain a particle size distribution by data processing, a computer 25 for controlling various parts of the apparatus, and for performing various processes such as image processing for displaying the processing results in the CPU 24. A display device 26 for displaying processing results such as particle size distribution and various control screens is attached.
[0017]
Next, the operation of the dynamic light scattering particle size distribution measuring apparatus having the above configuration will be described with reference to FIGS. The dynamic light scattering particle size distribution measuring apparatus of this embodiment automatically performs the following operations according to a program built in the personal computer 25.
[0018]
(1) First, the on-off valve 12 is closed, and the weighed particles 4a and the dispersion medium 4b are put into the dispersion bath 1 (step S1 in FIG. 2). The dispersion medium 4b is supplied by supplying the appropriate amount of the dispersion medium 4b into the dispersion bus 1 by turning on the pump 7 for an appropriate time while the three-way solenoid valve 6 is off (the ports 6b and 6c are in communication). Is done. At this time, an appropriate amount of a dispersant may be added as necessary.
[0019]
(2) By turning on the three-way solenoid valve 6 and connecting the ports 6a and 6b, the circulation flow path 3 is opened, and by turning on the pump 7, the particles 4a and the dispersion medium 4b in the dispersion bath 1 are It circulates in the circulation channel 3 so as to return to the dispersion bath 1 through the forward tube 3a, the sample cell 2, the return tube 3b, the three-way solenoid valve 6 and the pump 7, whereby the particles 4a are dispersed in the dispersion medium 4b. Thus, the measurement sample 4 is sufficiently stirred and mixed (step S2 in FIG. 2). In this case, the ultrasonic vibrator 5 may be operated to prevent the particles 4 a from aggregating in the dispersion bath 1.
[0020]
(3) The measurement sample 4 is appropriately circulated, and after sufficiently stirring and mixing, with the pump 7 turned off, the laser light source 14 is turned on and the laser light 15 is sent to the measurement sample 4 in the sample cell 2. Irradiate. That is, the laser light 15 emitted from the laser light source 14 is condensed in the sample cell 2 through the collimating lens 16, the beam splitter 17 and the condensing lens 18. At this time, a part of the laser light passes through the cell wall surface, is dispersed in the dispersion medium 4b, hits the particles 4a that undergo Brownian motion, and laser light (scattered light) that is Doppler shifted by the Brownian motion is scattered. On the other hand, part of the laser light is scattered (non-scattered light) on the cell wall surface, and the laser light of the original frequency travels in the reverse direction. The scattered light and non-scattered light interfere with each other to become interference light, and are condensed on the photodetector 21 through the condenser lens 18, the beam splitter 17, and the lens 20.
[0021]
The interference light is converted into an electrical detection signal D (t) by the photodetector 21, appropriately processed by the signal processing unit 23, and digitized light scattering data is taken into the CPU 24. As shown in FIG. 3, the light scattering data has an amplitude Am corresponding to the concentration of the measurement sample 4, and the concentration (measurement concentration) of the measurement sample 4 can be obtained based on the amplitude Am ( Step S3 in FIG. The light scattering data may be fast Fourier transformed in the CPU 24 to obtain a power spectrum, and the particle size distribution state of the particles 4a may be obtained based on the power spectrum.
[0022]
Then, in the personal computer 25, the person in charge of measurement sets the target concentration (voltage value) using the screen shown in FIG. FIG. 4 shows an example of a screen on the display device 26 when performing automatic density adjustment. In this example, the voltage value representing the target density is 12.50V. Then, the measured density is compared with the target density (step S4 in FIG. 2). Here, as shown in FIG. 5, when the measured concentration (measured concentration voltage) matches the target concentration (target concentration voltage), the adjustment of the measured sample concentration is completed (step S5 in FIG. 2). ), Shift to particle size distribution measurement. In this particle size distribution measurement, as described in the above (3), the laser light source 14 is turned on and the measurement sample 4 in the sample cell 2 is irradiated with the laser light 15 and scattered by the particles 4a obtained at that time. The particle size distribution may be obtained based on the frequency intensity distribution of the emitted light.
[0023]
On the other hand, when the measured density does not match the target density, it is necessary to return to step S2 and further adjust the density of the measurement sample 4 as shown in FIG. That is, when the measured concentration (measured concentration voltage) is larger than the target concentration (target concentration voltage) 10.50 V, for example, 12.50 V as shown in the screen example of FIG. The measurement sample 4 is adjusted.
[0024]
Specifically, after opening the on-off valve 12 for about 1 to 2 seconds and discharging a part of the measurement sample 4 in the dispersion bath 1, the dispersion medium 4 b equal to the discharge amount is transferred from the dispersion medium storage tank 9 to the dispersion bath 1. It is supplied to and diluted. At this time, an appropriate amount of the dispersant may be supplied. Thereafter, the measurement sample 4 composed of the particles 4a and the dispersion medium 4b is circulated through the circulation channel 3 by the method described in (2) above, thereby obtaining the measurement sample 4 which is sufficiently stirred and mixed.
[0025]
Then, as shown in step S3, the concentration of the measurement sample 4 is measured again.
[0026]
Thereafter, the above operation is repeated until the concentration of the measurement sample 4 reaches the target concentration. When the concentration of the measurement sample 4 is smaller than the target concentration, the particles 4a may be added to the dispersion bath 1. Further, as the target density, a slight tolerance range of ± may be provided, and when the measured density falls within the tolerance range of the target density, the process may be shifted to the particle size distribution measurement.
[0027]
As described above, in the dynamic light scattering particle size distribution measuring apparatus of the present invention, prior to the particle size distribution measurement, the concentration of the measurement sample 4 is confirmed based on the scattered light intensity, and the sample concentration can be measured. Since it is diluted while checking whether or not it is within the range, there is no possibility of overdilution or insufficient dilution. Since the particle size distribution measurement can be performed in a state where the measurement sample 4 has a predetermined concentration, a highly accurate measurement result can be obtained, and the predetermined particle size distribution measurement can be performed efficiently.
[0028]
In particular, since the dispersion bath 1 and the sample cell 2 are connected by the circulation flow path 3, and the measurement sample 4 can be repeatedly circulated in the circulation flow path 3, the mixing and stirring of the particles 4a and the dispersion medium 4b can be performed reliably. In addition, it is possible to suppress a change in particle diameter due to aggregation and a sudden change in the intensity of scattered light associated therewith.
[0029]
As a method for diluting the measurement sample 4, the concentration may be quantitatively diluted by a multiple of 2. That is, the amount of the measurement sample 4 in the dispersion bath 1 is monitored by a sensor (not shown) provided in the dispersion bath 1, half the amount is drained, and the same amount of the dispersion medium 4b as this discharge amount is supplied, It is also possible to dilute two times and simply determine the dilution factor from the number of times this two-fold dilution.
[0030]
【The invention's effect】
As described above, in the dynamic light scattering particle size distribution measuring apparatus of the present invention, the dispersion bath and the sample cell are connected by the circulation flow path, and the sample from the dispersion bath is measured prior to the particle size distribution measurement. Supply a measurement sample to the cell, irradiate the measurement sample with laser light, measure the concentration of the measurement sample based on the intensity of scattered light obtained at that time, and set the measured concentration in advance. Since the concentration of the measurement sample can be adjusted based on the comparison result, it is possible to efficiently and automatically (unattended) diluting the measurement sample to the desired concentration. it can. Then, the concentration can be confirmed while preventing a change in state due to dilution. Therefore, a desired particle size distribution measurement can be performed in an optimum concentration state, and a highly accurate measurement can be performed efficiently.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an example of a dynamic light scattering particle size distribution measuring apparatus according to the present invention.
FIG. 2 is a flowchart illustrating an example of a procedure for adjusting a measurement sample performed prior to particle size distribution measurement by the measurement apparatus.
FIG. 3 is a diagram illustrating an example of a detection signal (light scattering data).
FIG. 4 is a diagram illustrating an example of a screen for performing automatic density adjustment.
FIG. 5 is a diagram illustrating an example of a screen for performing automatic density adjustment.
FIG. 6 is a diagram illustrating an example of a screen for performing automatic density adjustment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Dispersion bath, 2 ... Sample cell, 3 ... Circulation flow path, 4 ... Measurement sample, 4a ... Particle, 4b ... Dispersion medium, 15 ... Laser beam.

Claims (1)

A measurement sample in which particles are dispersed in a dispersion medium is accommodated in a sample cell, laser light is irradiated to the measurement sample, and the particle size distribution is determined based on the frequency intensity distribution of the light scattered by the particles. In the dynamic light scattering type particle size distribution measuring apparatus to be obtained, the dispersion medium and the particles are supplied, and a dispersion bath for dispersing the particles in the dispersion medium and the sample cell are connected by a circulation channel. Prior to the particle size distribution measurement, a measurement sample is supplied from the dispersion bath to the sample cell, the laser beam is irradiated to the measurement sample, and the measurement sample is measured based on the scattered light intensity obtained at that time. A dynamic light scattering type particle characterized in that the concentration is measured, the measured concentration is compared with a preset target concentration, and the concentration of the measurement sample can be adjusted based on the comparison result. Diameter distribution measuring device.

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