JP3820065B2 - Dynamic light scattering particle size distribution measuring apparatus and dynamic light scattering particle size distribution measuring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a particle size distribution measuring apparatus and a particle size distribution measuring method using dynamic light scattering.
[0002]
[Prior art]
In recent years, a particle size distribution measuring apparatus for measuring the particle size distribution of particles dispersed in a solvent (dispersion medium) of a sample to be measured has been proposed. That is, this particle size distribution measuring apparatus irradiates a measurement target sample with a laser beam having a specific wavelength, and makes scattered light incident upon the particle incident on a detector. At this time, the interference light of the scattered light generated by the Doppler shift of the laser beam irradiated to the Brownian moving particle is detected, and the frequency of the measured light intensity is analyzed by performing a Fourier transform on the detected signal of the diffused light and performing frequency analysis. Characteristics can be obtained. Next, it is proposed to measure the particle size distribution from the frequency characteristics of the light intensity.
[0003]
[Problems to be solved by the invention]
However, in order to obtain the particle size distribution from the frequency characteristics, it is necessary to perform complicated arithmetic processing, and accordingly, a high-performance computer is required. In addition, the calculation result may diverge and the particle size distribution may not be obtained. For this reason, in order to obtain the particle size distribution from the frequency characteristics, it is possible to convert the frequency characteristics into a convolution integral and deconvolute it, or to obtain the particle size distribution using a shift variant response function. However, this method inevitably reduces the analysis accuracy.
[0004]
Therefore, the present applicant has filed an application for “Particle Size Distribution Analysis Method” (Japanese Patent Application No. 10-310063) as of October 30, 1998. By using this particle size distribution analysis method, the particle size distribution can be obtained by inversely calculating the particle size distribution from the first type Fredholm integral equation by performing simple repeated calculation. Furthermore, a more accurate particle size distribution can be measured by matching the response function used in the reverse calculation process with various conditions at the time of measurement.
[0005]
Here, in order to make the particle size distribution obtained by the inverse calculation more accurate, the user can accurately set various parameters such as the temperature of the sample, the refractive index of the light, and the viscosity coefficient before the measurement. However, there is a problem that this input operation is troublesome. In particular, parameters such as the refractive index of light and the viscosity coefficient may be expressed in different units depending on the literature, and it is bothersome and error-prone to enter parameters such as the viscosity coefficient converted to the required unit diameter. Is also possible.
[0006]
Furthermore, among the parameters described above, the viscosity coefficient varies greatly depending on the type and temperature of the solvent, and this greatly affects the particle size distribution. Therefore, the viscosity coefficient is input taking into account the temperature of the sample at the time of measurement. There was also the problem of having to. In addition, literature values and the like are often known only about values at a rough temperature interval, such as 20 ° C., 25 ° C., etc., for changes in viscosity coefficient due to the temperature of various solvents.
[0007]
For this reason, in the past, the user had to estimate the viscosity coefficient at that time from a rough change in the viscosity coefficient examined by literature values before the measurement of the particle size distribution. However, there are individual differences in the estimated value of the viscosity coefficient, and it is difficult to know the accurate viscosity coefficient at the temperature at the time of measurement, especially when the literature value is small.
[0008]
The present invention has been made in consideration of the above-mentioned matters, and the object of the present invention is to automatically and accurately determine the viscosity coefficient of a solvent indispensable for the inverse calculation of the particle size distribution from the temperature at the time of measurement. An object of the present invention is to provide a dynamic light scattering particle size distribution measuring apparatus and a particle size distribution measuring method that can be used for calculation and calculation for particle size distribution calculation.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the dynamic light scattering particle size distribution measuring apparatus of the present invention irradiates a laser beam onto a sample to be measured , and is dispersed in the solvent of the sample to be measured and hits a particle that undergoes Brownian motion. Dynamic light that converts the scattered light generated by the shift into an electrical detection signal and inversely calculates the frequency characteristics of the light intensity obtained by Fourier transforming this detection signal to calculate the particle size distribution of particles contained in the sample In the scattering particle size distribution measuring apparatus, a storage unit that stores a plurality of types of solvents, and a solvent list display window that can display a solvent name selection window that displays a list of a plurality of types of solvents stored in the storage unit; A storage unit that stores approximate curves of temperatures and viscosity coefficients for the plurality of types of solvents, and a temperature sensor that measures the temperature of the sample to be measured, and a plurality of types displayed in the solvent name selection window When one of the solvent used for the measurement of the next size distribution from the solvent is selected, it sets the approximate curve equation of temperature and viscosity coefficient corresponding to the selected solvent automatically, with the measuring operation The temperature measured by the temperature sensor is input to the approximate curve equation to calculate the viscosity coefficient, and the calculated viscosity coefficient is substituted into the Stokes-Einstein equation to obtain a response function. The response function and the scattered light And an arithmetic processing unit that performs inverse calculation of the particle size distribution from a power spectrum obtained from an optical signal by a detector that detects interference light generated by the above.
[0010]
Further, the dynamic light scattering particle size distribution measuring method of the present invention irradiates the sample to be measured with laser light, and scatters the scattered light generated by the Doppler shift on the particles that are dispersed in the solvent of the sample to be measured and perform Brownian motion. Dynamic light scattering particle size distribution measurement that converts the detection signal into an electrical detection signal and inversely calculates the frequency characteristics of the light intensity obtained by Fourier transform of the detection signal to calculate the particle size distribution of the particles contained in the sample. In the method, a plurality of types of solvents and approximate curves of temperatures and viscosity coefficients for the plurality of types of solvents are stored, and a plurality of types of solvents displayed in a solvent name selection window showing a list of stored types of solvents. By selecting one solvent to be used for the next particle size distribution measurement from among the solvents, an approximate curve equation for the temperature and viscosity coefficient corresponding to the selected solvent is automatically set, and a temperature sensor is attached to the measurement operation. Therefore Enter the temperature measured on the approximate curve equation to calculate the viscosity coefficient, the calculated viscosity coefficient determined response function into equation Stokes Einstein, caused by the scattered light and the response function interference It is characterized in that inverse calculation of the particle size distribution is performed from a power spectrum obtained from an optical signal by a detector that detects light .
[0011]
Therefore, the user can select one solvent to be used for measurement of the next particle size distribution from multiple types of solvents, without causing troublesome input of numerical values or input errors. It determined the exact viscosity suitable for the temperature condition of, its precise since the viscosity can be input as an operation parameter of the response function, and easy to extremely more precise reverse the viscosity coefficient particle size distribution It can be reflected in the calculation, and the particle size distribution as accurate as possible can be obtained as the final purpose. Further, it is possible to prevent failure of the particle size distribution by a calculation error or input error.
[0012]
In addition, the present applicant has applied for a “particle size distribution analysis method” (Japanese Patent Application No. 10-309978: hereinafter referred to as the invention of the prior application) on October 30, 1998, and the various conditions at the time of measurement We have proposed a new analysis method that analyzes the particle size distribution using theoretical formulas by inputting combined calculation parameters. As the viscosity coefficient calculation parameter is input more accurately as in the present invention, the analysis of the particle size distribution proposed in the invention of the prior application can be performed with higher accuracy.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram schematically showing a configuration of a dynamic light scattering particle size distribution measuring apparatus of the present invention . In FIG. 1, reference numeral 1 denotes a measurement unit, which is configured as follows, for example. That is, 2 is a cell that accommodates the solvent 3 and particles (sample) 4 to be measured, 5 is a light source that irradiates the particles 4 with laser light 6, and 7 is a lens that condenses the laser light 6 in the cells 2.
[0014]
8 is a beam splitter that reflects the interference light 9 generated by the scattered light from the particles 4 (or a reflecting mirror provided with a transmission hole for the laser light 6), 10 is a lens that collects the interference light 9, and 11 is the interference light 9. It is a detector that converts it into an electrical detection signal. Reference numeral 12 denotes an amplifier that amplifies the detection signal, 13 denotes a filter, and 14 denotes an AD converter that converts the detection signal into a digital signal.
[0015]
In addition, reference numeral 15 denotes a temperature sensor for measuring the temperature of the samples 3 and 4 accommodated in the cell 2, and a signal from the temperature sensor 15 is also converted into a digital signal by the AD converter 14. The temperature sensor 15 may measure the temperature of the solvent 4 directly in a state immersed in the solvent 4 or may measure the temperature of the samples 3 and 4 from the outside of the cell 2.
[0016]
Reference numeral 16 denotes a measurement control unit that controls the entire apparatus including the measurement unit 1 and performs various calculations. The personal computer 16 has a storage unit such as a memory 18 and a hard disk 19, and an input / output unit such as a display unit 20 and a keyboard 21 in addition to a CPU 17 that performs arithmetic processing.
[0017]
Further, the memory 18 and the hard disk 19 store an analysis program for obtaining a particle size distribution from the detection signal and data relating to a viscosity coefficient and a refractive index corresponding to the type of solvent. In addition, since the analysis method of the particle size distribution by this analysis program can use the method shown in the application of a prior application, the detail is abbreviate | omitted.
[0018]
In the dynamic light scattering particle size distribution measuring apparatus having the above configuration, the laser light 6 emitted from the light source 5 passes through the beam splitter 8 and the lens 7 and is condensed in the cell 2. At this time, the laser beam 6 hits the Brownian-moving particles 3 dispersed in the solvent 3, and scatters the Doppler-shifted light by the Brownian motion of the particles 3. Then, interference light 9 is generated by the Doppler-shifted scattered light, and the interference light 9 is detected by the detector 11. The interference light 9 may be generated by interference between scattered lights, or may be generated by scattered light and non-scattered light.
[0019]
The detection signal of the interference light 9 detected by the detector 11 and the temperature of the samples 3 and 4 measured by the temperature sensor 15 are converted into digital signals by the AD converter 14 and input to the personal computer 16. The personal computer 16 processes information such as the temperature of the samples 3 and 4 and the type of the solvent 3 at the time of measurement using data stored in the memory 18 and the hard disk 19, so that various types of viscosity coefficient and refractive index of the solvent 3 are obtained. Calculate the parameters.
[0020]
FIG. 2 is a diagram for explaining a display condition setting method performed before the particle size distribution analysis processing by the analysis program, and is an example of a screen displayed on the display unit 20 of the personal computer 16. FIG. 2 particularly illustrates an input method for setting the refractive index and the viscosity coefficient, and 22 is a condition setting window for determining display conditions.
[0021]
In the state shown in FIG. 2, the tag 22a for setting the refractive index is selected, and the condition setting window 22 of this example is a sample refractive index setting unit 22b for setting the refractive index of the sample 4, and the refractive index of the solvent. It has a solvent refractive index setting unit 22c for setting, and a solvent viscosity setting unit 22d for setting the viscosity coefficient of the solvent. The solvent viscosity setting unit 22d is expressed by a quaternary equation (polynomial approximation equation) Fx in which the temperature is X and the viscosity coefficient is Y, and the relationship between the viscosity coefficient and the temperature depends on the size of each coefficient a to e. To be able to express.
[0022]
The personal computer 16 can accurately obtain the viscosity coefficient at the time of measurement by substituting the temperature measured by the temperature sensor 15 into the quartic equation Fx. The user can manually input various settings by numerical values using the input unit such as the keyboard 21 in these setting units 22b to 22d as in the past, but in this example, the condition setting window 22 is used. Has a dispersion solvent list display button 22e.
[0023]
That is, when the user presses the dispersion solvent list display button 22e, the dispersion medium list display window 23 is displayed. In this dispersion medium list display window 23, when a list display button is pressed, a solvent name selection window 23b showing a list of a plurality of types of solvents stored in the storage unit of the personal computer is displayed. One solvent used for measurement of the next particle size distribution can be selected from a plurality of types of solvents displayed in the selection window 23b.
[0024]
Further, when the user selects one solvent by the solvent name selection window 23b and then presses an OK button 23c, the personal computer 16 indicates the refractive index of the selected solvent already registered and the viscosity coefficient with respect to temperature. The following formula Fx is automatically set. Then, measurement of the particle size distribution is started.
[0025]
FIG. 3 is a block diagram showing the contents of the particle size distribution analysis process performed after selecting the solvent as described above. In FIG. 3, reference numeral 24 denotes a measurement operation by the measurement unit 1, and by this measurement operation 24, the measurement temperature X can be detected from the temperature sensor 15 and the optical signal 25 can be detected from the detector 11. On the other hand, 26 represents the solvent selection operation by the solvent name selection window 23b, and outputs the temperature-viscosity approximate expression Fx by the above-mentioned quaternary expression.
[0026]
Next, the personal computer 16 performs the viscosity calculation 27 by inputting the measurement temperature X to the temperature-viscosity approximate expression Fx, and the viscosity coefficient Y obtained by the viscosity calculation 27 and the measurement temperature X are expressed by the following equation (1). The Stokes-Einstein relational expression shown in FIG. 5 is used for the response function creation operation 28 for obtaining the response function from the Lorentz function. In the inverse calculation of the particle size distribution shown in 29, the particle size distribution F (D) is calculated from the response function obtained as described above and the power spectrum obtained from the optical signal 25.
KT
D = ―――――… Formula (1)
3πηDp
Where η is the viscosity coefficient Y, T is the measurement temperature X, Dp is the particle diameter, and the units are [mPaSec], [K], and [m], respectively.
[0027]
By configuring as described above, since accurate conditions such as the temperature and viscosity coefficient η of the samples 3 and 4 at the time of measurement are reflected in the creation of the response function, a more accurate particle size distribution F (D) Measurement is possible. In addition, it is not necessary for the user to input the numerical value of the viscosity coefficient as in the past, so that not only input mistakes such as incorrect units are generated, but also simple and easy to obtain a more accurate particle size distribution. Can do.
[0028]
In this example, the solvent refractive index can also be obtained by selecting the solvent through the solvent name selection window 23b. Therefore, it is necessary to obtain the Lorentz distribution shown in the following formula (2) using this refractive index. Can also be used to determine the scattering vector g.
4πn θ
g = ―――― sin ―――… Formula (2)
λ 2
[0029]
In the example described above, an example in which the solvent 3 of the sample to be measured is prepared in advance is disclosed, but the present invention is not limited to this. That is, before starting the measurement of the particle size distribution, the viscosity coefficient η with respect to the temperature of the solvent 3 may be measured so that a new solvent can be registered.
[0030]
For example, in the example shown in FIG. 2, an add button 23d is provided, and a new solvent 3 can be additionally registered by pressing the add button 23d. By doing in this way, it can respond to the case where a dispersing agent is added with respect to a solvent, the case where two liquids are mixed, etc. as addition of the new solvent 3, for example.
[0031]
The addition of a new solvent can be performed, for example, by the following procedure. That is, the viscosity coefficient η when the temperature of the new solvent is changed by a viscometer and a temperature sensor is measured at several points, and a polynomial approximation formula is created from these by an arithmetic method such as the least square method. Alternatively, several points of the viscosity coefficient η of the solvent with respect to temperature may be input with reference to literatures, and a polynomial approximation formula may be created from this. The created polynomial approximation can be changed by the user by arbitrarily changing the coefficients a to e.
[0032]
Then, by registering with an appropriate solvent name, it is possible to easily perform accurate measurement even if a new solvent is attached by simply selecting the solvent name. In addition, since the refractive index of the solvent can be registered at the same time, it can be called by the solvent name at the same time as the viscosity coefficient.
[0033]
The above example discloses an example in which the relational expression of the temperature-viscosity coefficient is a quartic expression, but the present invention does not limit the polynomial approximation expression representing the relational expression of the temperature-viscosity coefficient to the fourth order. It goes without saying that there is nothing.
[0034]
【The invention's effect】
As described above, according to the present invention, the user simply selects one solvent to be used for measurement of the next particle size distribution from a plurality of types of solvents displayed in the solvent selection window. Even if it is not input, it is possible to obtain an accurate viscosity coefficient suitable for the temperature condition at the time of measurement and automatically input it as a calculation parameter of the response function . Accordingly, a more accurate viscosity coefficient can be easily used for the inverse calculation of the particle size distribution, and the most accurate particle size distribution can be obtained as the final purpose. Further, it is possible to prevent failure of the particle size distribution by a calculation error or input error.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a dynamic light scattering particle size distribution measuring apparatus of the present invention.
FIG. 2 is a diagram showing a method of selecting a solvent by the dynamic light scattering particle size distribution measuring apparatus.
FIG. 3 is a diagram showing a processing flow of the dynamic light scattering particle size distribution measuring method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Solvent, 4 ... Sample to be measured, 6 ... Laser light, 9 ... Scattered light, 15 ... Temperature sensor, 17 ... Arithmetic processing part, 18, 19 ... Memory | storage part, F (D) ... Particle size distribution.

Claims (2)

By irradiating the sample to be measured with a laser beam, and converts to an electrical detection signal of scattered light caused by the Doppler shift hitting the particles Brownian motion was dispersed in a solvent of the sample to be measured, the detection signal by Fourier transform In a dynamic light scattering particle size distribution measuring apparatus that calculates the particle size distribution of particles contained in a sample by inversely calculating the obtained frequency characteristic of light intensity, a storage unit that stores a plurality of types of solvents, and the storage unit A solvent list display window capable of displaying a solvent name selection window showing a list of a plurality of types of solvents stored in the storage unit, a storage unit for storing approximate curves of temperature and viscosity coefficients for each of the plurality of types of solvents, which has a temperature sensor for measuring the temperature of the sample to be measured, one of the solvent used among a plurality of types of solvents to be displayed on the solvent name selection window for measurement of the following particle size distribution is selected Automatically sets an approximate curve equation of the temperature and viscosity coefficient corresponding to the selected solvent, and calculates the viscosity coefficient by inputting the temperature measured by the temperature sensor during the measurement operation into the approximate curve equation. Then, by substituting the calculated viscosity coefficient into the Stokes-Einstein equation, a response function is obtained, and the particle size distribution from this response function and the power spectrum obtained from the optical signal by the detector that detects the interference light caused by the scattered light A dynamic light scattering particle size distribution measuring apparatus, comprising an arithmetic processing unit that performs the inverse operation of the above. By irradiating the sample to be measured with a laser beam, and converts to an electrical detection signal of scattered light caused by the Doppler shift hitting the particles Brownian motion was dispersed in a solvent of the sample to be measured, the detection signal by Fourier transform In the dynamic light scattering type particle size distribution measuring method for calculating the particle size distribution of particles contained in a sample by inversely calculating the frequency characteristic of the obtained light intensity , a plurality of types of solvents and the temperature for each of the plurality of types of solvents Stores the approximate curve equation of the viscosity coefficient and selects one solvent used for measurement of the next particle size distribution from the plurality of types of solvents displayed in the solvent name selection window showing a list of the plurality of types of stored solvents. by selecting, automatically sets the approximate curve equation of temperature and viscosity coefficient corresponding to the selected solvent, type the temperature measured by the temperature sensor with the measuring operation in the approximate curve equation Calculating a viscosity coefficient, and assigns the calculated viscosity coefficient in the equation of Stokes Einstein seeking response function, power spectrum obtained from the optical signal by the detector for detecting the interference light generated by the scattered light and the response function dynamic light scattering particle size distribution measuring method characterized by performing the inverse of the particle size distribution and a.

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