JP3598050B2 - How to measure sieve opening diameter - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for measuring the opening diameter of a sieve.
[0002]
[Prior art]
The required average particle size and the distribution of the particle size differ depending on the kind, purpose, and use of the powder handled in various fields. In particular, in the case of powders used for spacers for liquid crystal display elements, conductive particles for anisotropic conductive films, fillers for liquid chromatography, lubricants for films, or toners for developing electrostatic images, the particle size distribution is narrowed. There is a need to.
Above all, the powder used as the spacer for the liquid crystal display element needs to have a particularly narrow particle size distribution, and the raw material powders produced by various methods are precisely adjusted to have the target particle size and particle size distribution. It must be used separately.
[0003]
Generally, in order to narrow the particle size distribution of the powder, a so-called classifier is used. As a classifier, a cyclone, a sedimentation tower, a sieve, or the like is used in a dry type or a wet type. However, in cyclones that perform classification using the balance between centrifugal force and gravity in swirling flow, there are particles that short-pass through the classification zone due to their structure, so there is a limit to narrowing the particle size distribution. In addition, there is a problem that, although a small amount, particles largely deviate from the particle size distribution remain.
Further, in a sedimentation tower that classifies using a difference in sedimentation velocity in a medium, the sedimentation velocity changes due to factors such as temperature and vibration, so it is difficult to increase the classification accuracy, and the particle diameter is small. Since the sedimentation speed is extremely low, a large amount of time is required for classification. An apparatus in which a settling tower is improved to supply a medium from below and overflow from above is also proposed, but has the same problem as the above-mentioned settling tower.
[0004]
On the other hand, a sieve performs classification based on whether or not it passes through a certain mesh. Since it does not have the above-described problems, it is suitable for classification of particles having a small particle diameter. Of these, screens with rectangular holes made by plating, called electroformed sieves, have very good openings, high classification accuracy, and can be processed into holes smaller than the thickness. It has a clean cross section without any defects and is an excellent sieve.
In order to perform classification with high accuracy using a sieve, it is premised that the size of the opening diameter of the sieve is accurately grasped, but all of the conventionally known measuring methods have problems. For example, for electric sieves, there is a method of determining the size of the opening diameter according to the plating conditions (speed / time) when producing the sieve. However, since the size of the opening diameter tends to fluctuate depending on the environment at the time of plating production. Poor accuracy. In addition, the method of measuring the length of the aperture using various microscopes requires measurement of many apertures, which is complicated. In addition, a method of determining the size of the aperture diameter from the amount of light transmitted by irradiating light to the sieve or a method of determining the size of the aperture diameter by passing a fluid through the sieve and measuring the passage property (time, etc.) In this case, a reference sample is required. However, when the number of lines or the like changes, the relationship between the amount of light transmitted or the transmissivity and the size of the aperture diameter greatly changes, so that a complicated process is required. Further, in any of the above methods, there is a problem that accuracy is reduced when the size of the opening diameter of the sieve has a distribution. In the case of a sieve having a small opening diameter, the particle diameter that can pass through due to the influence of the line portion or the pressure loss tends to be smaller than that of the opening portion. It does not accurately represent the particle size that can pass through a sieve.
[0005]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a method for accurately measuring the opening diameter of a sieve that accurately represents the particle diameter that can actually pass through the sieve by a simple operation.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the method for measuring the opening diameter of the sieve of the present invention is a method for measuring the opening diameter of a sieve having an opening diameter of 0.2 to 50 μm,
After classifying powder having a particle size distribution satisfying the following conditions (a) to (c) by the sieve,
(A) 10% diameter is larger than expected sieve opening diameter (b) 90% diameter is smaller than expected sieve opening diameter (c) Difference between 10% diameter and 90% diameter is 2 μm or more The maximum particle size of the powder that has passed through the sieve is measured, and the value is defined as the opening diameter of the sieve.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the classification is performed by the same method as the actual classification and the opening diameter of the sieve is measured, so that the measurement can be performed with high accuracy. The measurement powder used for classification at this time has a particle size distribution satisfying the following conditions (a) to (c).
(A) 10% diameter is larger than expected sieve opening diameter (expected opening diameter) (b) 90% diameter is smaller than expected sieve opening diameter (expected opening diameter) (c) 10% diameter The expected pore diameter where the difference between the diameter and the 90% diameter is 2 μm or more is between the 10% diameter and the 90% diameter of the measured powder, and the ratio of the particles having the particle diameter near the cut point is high, so that the measurement is performed accurately It can be performed. Further, since the difference between the 10% diameter and the 90% diameter of the measured powder is as large as 2 μm or more, even if a difference occurs between the expected opening diameter and the actual opening diameter, the accuracy is not affected. In addition, since the distribution of the particle size of the measurement powder is wide, measurement can be performed even when the variation in the opening diameter of the sieve is large. The measurement powder used here preferably has a spherical shape and an aspect ratio of 1.5 or less.
[0008]
The expected opening diameter of the sieve can be roughly estimated from the number of wires and the plating conditions (speed / time) at the time of producing the sieve. In addition to this, it is possible to roughly estimate from observation using various microscopes and the light transmittance.
After measuring the opening diameter of the sieve according to the present invention, since the classification is actually performed using the sieve, it is preferable to use a measurement powder that does not become an impurity during the actual classification, It is most preferable to use the same type as that to be classified. Powders such as organic cross-linked polymer particles, inorganic particles, and organic-inorganic composite particles are used for classification.
[0009]
As a classification method, a wet method using a dispersion in which a measurement powder is dispersed in a liquid medium is preferable. Compared to the dry method using an inert gas or air as a medium, the wet method has higher ultrasonic irradiation efficiency and dispersion stability, and less particles adhere to the sieve. In particular, particles having a small particle size of about 10 μm or less used for a spacer for a liquid crystal display element or the like have a strong cohesive force, so that dispersion may be insufficient by a dry method.
The liquid medium in which the powder to be measured is dispersed can be appropriately selected depending on the material of the sieve to be used, the pore size, the number of lines, the properties of the powder, the particle size distribution, and the like.
[0010]
It is preferable that the concentration of the measurement powder in the dispersion is lower than that in the ordinary classification, in order to prevent the particles from being deposited on the sieve. Specifically, it is preferably 0.01 to 30% by weight, more preferably 0.1 to 20% by weight. If the concentration is lower than the above range, a large amount of time is required for classification.
After classification using the powder, the maximum particle size of the powder that has passed through the sieve is measured, and the value is defined as the opening diameter of the sieve. Therefore, the pore size measured according to the present invention accurately represents the particle size that can actually pass through the sieve.
As a method for measuring the maximum particle diameter of the powder that has passed through the sieve, a general method such as a particle size distribution measurement such as a Coulter counter method, a light scattering method, a sedimentation method, or a particle diameter measurement using various microscopes is employed. can do.
[0011]
The sieve to be measured in the present invention is used for classification based on whether or not the sieve passes through a certain aperture, and there is no particular limitation as long as the pore size is 0.2 to 50 μm. Examples thereof include a sieve obtained by knitting a fine wire, a metal foil or the like in which fine holes are formed by etching, and a screen having a rectangular hole formed by plating, which is called an electric sieve. In general, when the mesh size is 10 μm or more, a knitted sieve having a fine wire is used. When the mesh size is smaller than 10 μm, a metal foil or the like having fine holes formed by etching or an electric sieve is used. These have very good openings compared to those obtained by knitting fine wires, and can improve classification accuracy. In particular, the electric sieve is capable of drilling holes smaller than its thickness and has a clean cross-sectional shape without side edges, making it easy to adjust the hole diameter and the number of holes per unit, as well as the hole diameter distribution. Is very good, and classification can be performed very accurately.
[0012]
As a method of manufacturing an electric sieve, a conductive film is formed on a glass plate corroded in a cross-line shape with high precision by physical plating such as vacuum evaporation and sputtering, or chemical plating such as electrolytic plating and electroless plating. After that, there is a method of removing the plating layer other than the groove of the corroded portion, forming a mesh on the plating layer by a method such as electrolytic plating, and peeling the mesh from the glass plate. After the mesh thus produced is peeled off from the glass base plate, it may be further subjected to electrolytic plating if necessary. Also, as another manufacturing method, a vacuum plating, physical plating such as sputtering on a glass flat plate, or electrolytic plating, forming a conductive film by chemical plating such as electroless plating, after applying a resist on the film, There is also a method in which a pattern having a predetermined shape is formed, a portion other than the pattern is removed by etching, and the resultant is peeled off from the glass base plate, followed by electrolytic plating.
[0013]
FIG. 1 shows an example of a classification device provided with an electric sieve, but the present invention is not limited thereto. In FIG. 1, the electric sieve 1 is fixed by being sandwiched between a housing upper part 4 and a housing lower part 4 '. A support 2 for increasing the strength of the electric sieve 1 is provided, and is connected to the housings 4 and 4 'via a packing 3 made of an elastomer. An ultrasonic irradiation chip 5 is inserted into the housing upper part 4, whereby the medium in the housing is irradiated with ultrasonic vibration. In the housing upper part 4, a medium circulation line 6, 6 ′ and a medium supply line 7 are provided. The dispersion obtained by dispersing the measurement powder in the liquid medium is charged in the housing upper part 4, and particles smaller than the opening diameter of the electric sieve move together with the medium to the housing lower part 4 '. As the operation proceeds, particles smaller than the opening diameter of the electric sieve existing in the housing upper part 4 decrease, and finally, the particles having a larger particle diameter starting from the opening diameter of the electric sieve ( The particles can be classified into particles remaining in the housing upper part 4) and particles having a small particle diameter (particles moved to the housing lower part 4 ').
[0014]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.
(Example 1)
Using a device shown in FIG. 1, a nickel-based electric sieve having an expected pore size of 5.5 μm (Sieve A) was spherical and had an average particle size of 5.21 μm, a 10% size of 6.22 μm, and a 90% size. Of powder 1 having a particle size of 4.15 μm was classified.
In the classification, methanol was used as a dispersion medium for the powder, and classification was performed for 5 minutes under the condition that the concentration of the dispersion was 2 wt%.
[0015]
The dispersion flowing out to the lower portion of the housing during the classification was collected, and the particle size was measured using a Coulter Multisizer IIE after the classification. As a result, the maximum particle size was 5.76 μm. The powder 1 was classified again, and the particle size of the dispersion flowing out to the lower portion of the housing was measured. The result was 5.76 μm, which was the same value as the first time, and reproducibility was confirmed.
(Example 2)
Using a device shown in FIG. 1, a nickel-based electric sieve having an expected opening diameter of 2.0 μm (sieve B) was spherical and had an average particle diameter of 2.83 μm, a 10% diameter of 4.52 μm, and a 90% diameter. Was classified to 1.27 μm.
[0016]
In the classification, methanol was used as a dispersion medium of the powder, and classification was performed for 10 minutes at a dispersion concentration of 0.5 wt%.
The dispersion flowing out to the lower part of the housing during the classification was collected, and the particle size was measured by Coulter Multisizer IIE after the classification. As a result, the maximum particle size was 2.43 μm.
(Example 3)
Using a device shown in FIG. 1, a nickel-based nylon sieve having a predicted opening diameter of 10 μm (sieve C) is spherical and has an average particle diameter of 9.10 μm, a 10% diameter of 8.21 μm, and a 90% diameter of 11%. The powder 3 having a size of .48 μm was classified.
[0017]
In the classification, methanol was used as a dispersion medium for the powder, and classification was performed for 2 minutes under the condition that the concentration of the dispersion was 10 wt%.
The dispersion flowing out to the lower portion of the housing during the classification was collected, and the particle size was measured using a Coulter Multisizer 11E after the classification. As a result, the maximum particle size was 10.2 μm.
(Comparative Example 1)
In Example 1, instead of powder 1, comparative powder 1 having a spherical shape with an average particle diameter of 4.95 μm, a 10% diameter of 5.45 μm, and a 90% diameter of 3.22 μm (5% diameter of 5.22 μm). 72 μm).
[0018]
In the classification, methanol was used as a dispersion medium for the powder, and classification was performed for 10 minutes at a dispersion concentration of 2 wt%. As a result, almost the entire amount of the dispersion flowed out to the lower portion of the housing. The dispersion flowing out to the lower portion of the housing was collected and subjected to particle size measurement using a Coulter Multisizer IIE. As a result, a discontinuous portion was observed in a region of 5.4 μm or more, and the maximum particle size was 5.57 μm Met. The classification of the comparative powder 1 was performed again, and the particle size of the dispersion flowing out to the lower portion of the housing was measured. The result was 5.70 μm, and it was found that the dispersion was large between the first time and the second time. It is considered that the reason for such a large variation is that in Comparative Example 1, the number of particles caught on the sieve was extremely small, and the pore size was inaccurate.
[0019]
(Comparative Example 2)
In Example 2, instead of powder 2, comparative powder 2 having a spherical average particle diameter of 3.58 μm, a 10% diameter of 5.16 μm, and a 90% diameter of 2.27 μm (95% diameter of 1.27 μm). (66 μm).
In the classification, methanol was used as a dispersion medium for the powder, and the classification was performed for 10 minutes under the condition that the concentration of the dispersion was 0.5 wt%. It could not be measured.
(Comparative Example 3)
In Example 3, instead of the powder 3, the comparative powder 3 having a spherical shape with an average particle diameter of 9.07 μm, a 10% diameter of 8.21 μm, and a 90% diameter of 9.98 μm was classified.
[0020]
In the classification, methanol was used as a dispersion medium for the powder, and the classification was performed for 2 minutes under the condition that the concentration of the dispersion was 10 wt%. The dispersion flowing out to the lower portion of the housing was collected and subjected to particle size measurement using a Coulter Multisizer IIE.
[0021]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the opening diameter of the sieve which accurately represented the particle diameter which can actually pass through a sieve can be measured with simple operation.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating an example of a classification device provided with an electric sieve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric sieve 2 Support 3 Packing 4 Housing upper part 4 'Housing lower part 5 Ultrasonic irradiation chip 6, 6' Medium circulation line 7 Medium supply line

Claims (2)

A method for measuring an opening diameter of a sieve having an opening diameter of 0.2 to 50 μm,
After classifying powder having a particle size distribution satisfying the following conditions (a) to (c) by the sieve,
(A) 10% diameter is larger than expected sieve opening diameter (b) 90% diameter is smaller than expected sieve opening diameter (c) Difference between 10% diameter and 90% diameter is 2 μm or more Measuring the maximum particle diameter of the powder that has passed through the sieve, and defining the value as the opening diameter of the sieve. The method according to claim 1, wherein the sieve is an electric sieve.

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