JPH0147786B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method and apparatus for measuring the particle characteristics of electrophotographic toner, particularly the particle diameter and charge amount of toner particles. [Description of the Prior Art] Generally, the particle size, polarity, and charge amount of toner particles used in electrophotographic copying machines affect the quality of development of the toner particles onto the latent image on the photoreceptor drum and the development efficiency. It affects the transfer quality and transfer efficiency of developed toner particles onto paper. Therefore, these toner particle characteristics ultimately affect the clarity of the copied image and the presence or absence of fog caused by adhesion of fine toner particles (a phenomenon in which toner particles adhere to an area that should be white, resulting in a black image). , is an extremely important characteristic for the copying performance of a copying machine. Conventionally, particle size measurement methods for measuring this type of property include particle size measurement methods using various mesh sieves, air classification measurement methods, particle size measurement methods using a microscope, and particle size measurement methods using particles dispersed in a liquid. A method of measuring particle size from an electric pulse based on the resistance change that occurs in the electrodes on both sides of the pore when the particle passes through the pore (edited by the Chemical Society of Japan, "New Experimental Chemistry Course 18 Interfaces and Colloids", Maruzen) Publishing, 1975, P368-P407). In addition, to measure the amount of charge, a developer mixture of toner particles and iron powder carrier is placed on a mesh provided at the bottom end of the cage, and compressed gas (compressed air or nitrogen gas) is supplied from a nozzle provided at the top end of the cage.
A blow-off method in which the toner and carrier are charged by friction while stirring, the toner particles are blown away from the cage, and the amount of reverse charge on the remaining carrier is determined from the electric capacitance (Oguchi, Kubo, Yoshida: Electrophotography;
Volume 16, No. 2, 10, 1978) is widely known.
This blow-off method involves frictional charging caused by the collision of toner or carrier with the mesh.
The disadvantage is that the measured value changes depending on the measurement conditions, and it is difficult to measure the absolute value of the toner charge amount, making it complicated for normal use. Therefore, in recent years, this blow-off method has been improved,
A method of separating the carrier and toner by the difference in their attraction to a magnet without using a mesh (Nakajima, Tanaka, Horie: Electrophotography, Vol. 18, No. 3, 22,
1980), has been developed. However, in all of these measurement methods, each characteristic is measured individually, and the state of distribution cannot be determined, but only an average value can be obtained. [Object of the Invention] The present invention provides a method for toner particles that can simultaneously and easily measure the distribution states and average values of toner particles such as the particle size and charge amount, which cannot be obtained by conventional measurement methods, with good reproducibility. The object of the present invention is to provide a method and apparatus for measuring particle diameter and charge amount. [Summary of the Invention] The first feature of the present invention is to provide a laminar air flow that is rectified in a direction perpendicular to the direction of gravity, and to apply a constant DC electric field in a direction that is perpendicular to the direction of gravity and perpendicular to the laminar air flow. The present invention provides a method for measuring the particle diameter and charge amount of toner particles, in which toner particles to be measured fall naturally into a space to which is applied, and the state in which the toner particles are distributed in the space is observed. The second feature of the present invention is that two parallel electrode plates are arranged parallel to the direction of gravity and a constant DC voltage is applied, and a means for generating a laminar air flow in a direction perpendicular to the direction of gravity; means for causing the toner particles to be measured to naturally fall between the two electrode plates; and a means for receiving the toner particles disposed below the means for causing the toner particles to fall naturally. The present invention provides a measuring device for measuring the particle diameter and charge amount of toner particles, including a measuring plate. [Principle of the Invention] The principle of the present invention is to utilize the difference in falling speed based on Stokes' law due to the radius of toner particles and the difference in electric force based on the amount of charge of toner particles in an electric field to Three-dimensional chromatography is performed using this method. That is, as shown in FIG. 1, a constant DC voltage is applied between two parallel electrode plates 1 and 2 arranged parallel to the direction of gravity (Z direction), and these two electrode plates 1 and A laminar air flow is created between the two electrode plates 1 and 2 in a direction (X direction) parallel to the direction of gravity and perpendicular to the direction of gravity. (b) A toner drop tube 3 is provided, and after being mixed with the carrier in advance, the charged toner particles 5 separated from the carrier are allowed to naturally fall from the toner drop tube 3 onto a measurement plate 6 placed perpendicular to the direction of gravity. The particle diameter, charge amount, etc. of the toner particles 5 that have fallen onto the measurement plate 6 can be determined from the X and Y coordinates on the measurement plate 6 using the theory described below. Now when there is a laminar flow velocity v of air in the X direction, t
The position x of the toner particle after the time is expressed by the following equation. x=vt...(1) Also, the equation of motion of the toner particles in the Y direction is expressed by the following equation from the viscous resistance of air according to Stokes' law, the electric charge q of the toner particles, and the electric force qE based on the electric field E. . md ² y/dt ² +6πηady/dt=qE...(2) Here, m is the toner particle mass, η is the air viscosity,
a is the toner particle radius. Using equation (2), we obtain the following equation. y=-mqE/(6πηa) ² (1-e ^-6 〓〓 ^a/mt )+qE/6π
ηa...(3) Also, the equation of motion of toner particles falling in the Z direction is given by the following equation. z=mg/6πηat...(4) Stokes' law used in equations (2) to (4) holds true when the Reynolds number in the following equation is 1 or less, so
In the measuring device of the present invention, experimental conditions are selected so as to satisfy the following equation. R _e =ρadz/dt/η≦1 (5) where ρ is the toner particle density. Further, assuming that the shape of the toner particles is spherical, the toner particle mass m is expressed by the following equation. m=4/3πa ³ ρ ...(6) If you solve it using the above equations (1), (3), (4), and (6), you can find that the toner particle falling time t, the toner particle charge amount q, and the toner particle Unknown variables such as radius a and toner particle mass m can be determined. [Description by Example] Next, an example of an apparatus for carrying out the measuring method of the present invention will be described in detail based on the drawings. FIG. 2 is a central vertical sectional view of an apparatus according to an embodiment of the present invention. In FIG. 2, each symbol corresponds to each symbol in FIG. 1, respectively. Electrode plates 1, 2 and measurement plate 6
is arranged approximately at the center of the wind barrel 7 whose cross section forms three sides of a square. FIG. 3 is an external perspective view showing details of the electrode plates 1, 2 and the measurement plate 6. The electrode plates 1, 2 and the measuring plate 6 are mounted on a plastic base 9. In addition, inside the wind barrel 7, two electrodes as shown in FIGS.
A large number of different types of air baffle plates 10 and 11 are arranged.
These air rectifier plates 10 and 11 are made of plate-like material with a certain depth and are configured so that the cross section is grid-like.As shown in FIG. They are alternately combined so that the intersection of the other air baffle plate 11 is located approximately in the center of the grid space. Further, as shown in FIGS. 2 and 6, a toner drop tube 3 for dropping toner particles 5 is installed vertically on the lid 13 of the wind cylinder 7 between the electrode plates 1 and 2 and above the measuring plate 6. It will be penetrated into. This toner drop tube 3
It is made of glass and has a thick top end and a thin bottom end. Furthermore, a suction fan 14 that rotates at a constant speed is attached to one end of the wind barrel 7 to suck the air inside the wind barrel 7. In the device configured in this way, the toner drop tube 3
When charged toner particles 5 are allowed to naturally fall into a space where an electric force and a laminar air flow are generated, a distribution of toner particles as shown in FIG. 7 is generated on the measurement chart on the measurement plate 6. The measurement chart shown in FIG. 7 is white and has a sticky surface, allowing easy observation of the distribution of fallen toner particles, and is detachably attached to the measurement plate 6. From FIG. 7, it is shown that toner particles dropped from the intersection of the X and Y axes, that is, from above the origin (on the Z axis), have a particle size distribution in the Since the electric force received differs depending on the electric field applied to the toner particles and the amount of charge on each toner particle, if the X-axis is taken as the center line, a charge amount distribution is shown in which many particles fall at positions above the X-axis. FIG. 8 is a contour map of the particle radius (indicated by a broken line) and the amount of charge (indicated by a solid line) of toner particles determined from the above-mentioned theoretical formula, superimposed on the measurement chart shown in FIG. 7. Thereby, the particle radius and charge amount of each toner particle can be easily and easily measured. Note that a contour map of the particle radius and charge amount of the toner particles may be printed on the measurement chart in advance. Furthermore, in order to grasp the particle radius and charge amount of each toner particle as more condensed quantitative characteristics, the state of distribution of toner particles in the X direction and the Y direction is measured as quantitative data. Figure 9 shows the measurement chart shown in Figure 7.
−timent 720, Image Analyzing Computer
Ltd., UK), which shows the measurement status of toner particle distribution in the X and Y directions, and it is possible to quantify the toner concentration in a minute width slit perpendicular to the X and Y directions. Note that the toner particle distribution may be quantified by other analysis means instead of this image analysis device. The distributions in the X and Y directions obtained by the above quantification can be calculated as a particle radius distribution and a charge amount distribution, respectively, using the above theoretical formula, and can also be expressed as a histogram shown in FIG. By analyzing FIG. 10, the average values and standard deviations of particle radius and charge amount can be determined from each distribution. Note that it is also possible to easily obtain the characteristics of toner particles to be measured by preparing a variety of distribution state models with known toner particle characteristics and comparing and observing the distribution state of the toner particles to be measured in the measurement chart with these distribution state models. can. In addition, although we have shown an example in which the surface of the measurement chart is sticky, since the toner component is a thermoplastic resin with a low melting point, if a heating device that can heat the measurement chart is installed, the toner can be used without making it sticky. The state of particle distribution can be recorded. [Explanation of Example Data] Next, a specific example measured using the apparatus of this example will be described. The example shown here is just an example, and does not limit the scope of the present invention. Example Two types of commercially available toner particles were measured.
One type is two-component toner particles (hereinafter referred to as "commercial toner A"), and the other type is one-component toner particles (hereinafter referred to as "commercial toner B"). These toner particles were stored at a temperature of 25°C and a humidity of 50%.
RH, laminar air velocity 5cm/sec, electric field 380V/cm,
Each toner was allowed to fall naturally under measurement conditions at a height of 10 cm from the measurement plate in the drop hole of the toner drop tube. FIG. 11 shows the distribution of toner particles of commercially available toner A, and FIG. 12 shows the distribution of toner particles of commercially available toner B falling onto the measurement chart. Using the image analysis device and microcomputer, the data of particle radius distribution and charge amount distribution of this measurement chart were quantified, and the results shown in Table 1 were obtained.

〔Effect of the invention〕

As described above, according to the present invention, charged toner particles to be measured are caused to naturally fall into a space where an electric force and a laminar air flow act perpendicularly to the direction of gravity and in directions perpendicular to each other. By observing the distribution state of falling toner particles on a flat surface placed on a It is possible to grasp not only the average value of the data but also the distribution state. By preparing a large number of types, toner particle characteristics can be determined simply and quickly without using the above-mentioned theoretical formula, which has an excellent effect of making it suitable for industrial use.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating the principle of the present invention. Second
The figure is a central vertical sectional view of an apparatus according to an embodiment of the present invention. FIG. 3 is an external perspective view of the electrode plate and measurement plate. FIGS. 4 and 5 are perspective views of the air baffle plate. Figure 6 is a cross-sectional view of AA' in Figure 2. FIG. 7 is a measurement chart showing the distribution state of toner particles placed on a measurement plate and falling. FIG. 8 is a diagram in which a contour map of toner particle radius and charge amount determined from a theoretical formula is superimposed on the measurement chart shown in FIG. 7. Figure 9 shows the measurement chart shown in Figure 7.
FIG. 3 is a diagram showing the measurement status of toner particle distribution in the Y direction. Figure 10 is a histogram of particle radius distribution and charge amount distribution calculated from the same measurement chart. FIGS. 11 and 12 are measurement charts showing the distribution state of commercially available toner particles using the apparatus of this embodiment. 1, 2... Electrode plate, 3... Toner drop tube, 5...
...Toner particles, 6...Measurement plate, 7...Wind cylinder, 9...
... Base, 10, 11 ... Air rectifier plate, 13 ...
Lid, 14...Suction fan.

Claims (1)

[Claims] 1. A space in which a laminar air flow rectified in a direction perpendicular to the direction of gravity is applied, and a constant DC electric field is applied in a direction perpendicular to the direction of gravity and perpendicular to the laminar air flow, A method for measuring the particle diameter and charge amount of toner particles by allowing the toner particles to be measured to fall naturally and observing the state in which the toner particles are distributed in the above-mentioned space. 2 Claim 1 that captures the state in which toner particles to be measured are distributed in space on a plane perpendicular to the direction of gravity
Method for measuring the particle diameter and charge amount of toner particles as described in Section 3. 3 The direction of the air laminar flow is the X direction, the direction in which the electric force acts is the Y direction, and the direction of gravity is the Z direction, and the toner particles to be measured fall naturally from the Z axis, and the state in which the toner particles are distributed in space is defined as the X direction. - When captured on the Y plane, x=vt md ² y/dt ² +6πηady/dt=qE z=mg/6πηat m=4/3πa ³ ρ (where v: air laminar velocity, t: falling time, m:
Toner particle radius a and toner particle charge amount q are determined from the formula: toner particle mass, η: air viscosity, a: toner particle radius, q: toner particle charge amount, E: electric field, ρ: toner particle density). Range 2nd
Method for measuring the particle diameter and charge amount of toner particles as described in Section 3. 4. Obtaining the particle size and charge amount of the toner particles to be measured by comparing and observing the state in which the toner particles to be measured are distributed in space with a distribution state model in which the particle size and charge amount of the toner particles are known in advance. The method for measuring the particle diameter and charge amount of toner particles according to item 1 or 2. 5 Two parallel electrode plates arranged parallel to the direction of gravity and to which a constant DC voltage is applied, and an air layer between these two electrode plates in a direction parallel to the electrode plates and perpendicular to the direction of gravity. of toner particles, comprising means for generating a flow, means for causing the toner particles to be measured to fall naturally between the two electrode plates, and a measuring plate disposed below the means for causing the toner particles to fall naturally and receiving the toner particles. Device for measuring particle size and charge amount. 6. The device for measuring the particle diameter and charge amount of toner particles according to claim 5, wherein the measuring plate is perpendicular to the direction of gravity. 7. The device for measuring the particle diameter and charge amount of toner particles according to claim 5 or 6, which is configured such that a light-colored and adhesive measuring chart is detachably attached to the surface of the measuring plate. 8. The device for measuring the particle diameter and charge amount of toner particles according to claim 7, wherein a contour map in which the particle diameter and charge amount of the toner particles are known is printed in advance on the measurement chart.