JP5930858B2 - Method for determining particle mass concentration in a dispersion containing particles and liquid - Google Patents

Description

  The present invention relates to a method for determining the mass concentration of particles in a dispersion containing particles and a liquid.

  Examples of the dispersion liquid containing particles and liquid include a developer used in printing using electrophoresis. The developer contains toner particles as particles dispersed in a liquid support. Hereinafter, the description will be made mainly with reference to the developer, but the present invention is not limited thereto.

  A charge image consisting of colored and non-colored areas on a charge image carrier (for example photoconductor), corresponding to the image to be printed, for monochromatic or multicolor printing on printing materials such as sheets or rolls Is known to form. The colored area of the charge image is visualized as a toner image by toner particles on the charge image carrier by the development station. The toner image thus formed is transferred to the printing material by the first transfer station and transferred to the printing material at the second transfer station. Subsequently, the toner image is fixed at a fixed station.

  In order to color the charged image, a developer containing at least charged toner particles and a support liquid can be used. A printing method using electrophoresis in a digital printer is known from, for example, US Publication No. 2006/0150836 or US Publication No. 2008/279597. After the charge image of the image to be printed is formed on the charge image carrier, the development station colors the charge image with toner particles to form a toner image. Here, as the developer, a support liquid containing silicone oil and having ink particles (toner particles) dispersed therein is used. The developer is supplied to the charge image carrier by the developing roller, and the developer is supplied from the tank to the developing roller. Subsequently, during development, the image film formed on the charge image carrier from the toner image embedded in the support liquid is drawn off from the charge image carrier by the first transfer unit and onto the printing material in the second transfer zone. Transcribed.

  In such printing methods using a developer, an electrophoretic process is used to move toner particles in the support liquid to the printing material. The fixedly charged toner particles drift to the printing material in the support liquid as a transport agent. The transport here is controlled by the electric field between the first transfer roller and the printing material. The premise is that, in addition to the charge and electric field formation of the toner particles, a support liquid layer having a sufficient thickness that allows the toner particles to stray inside is formed, and a sufficient concentration of the toner particles in the support liquid is formed. It is to prepare.

  The developer used in the printing press is formed by mixing a toner stock solution containing toner and a support solution in a developing station, for example, a mixing unit. In order to form a print image without any problem, it is necessary that the developer contains sufficient toner particles, that is, the toner mass concentration in the developer has a set value. In this case, in the printing operation, the developer is removed from the mixing unit and partially applied to the printing material.

  In other words, in order to effectively develop a charge image without hindrance, a defined toner mass concentration and a defined electrophoretic mobility of toner particles in the support liquid must be achieved.

  When setting the toner mass concentration and mobility of toner particles in the support liquid, it is required to determine the toner mass concentration and toner particle mobility at the developing station. For example, when the toner mass concentration with respect to the developer is in the range of 2% to 40%, an electroacoustic process for obtaining the electrophoretic mobility is known, but this requires the knowledge of accurate toner mass concentration. .

  US Publication No. 2011/58838 discloses a method for determining a toner mass concentration in a developer. Here, at least one ultrasonic wave is applied to the developer. The basis for this is that the sound velocity of sound waves propagating in the developing solution within a predetermined temperature limit range and within a certain supporting solution is determined mainly depending on the components of the toner particles in the supporting solution. It is. Therefore, the ultrasonic traveling time in the developer is measured along the set measurement section, and the sound speed that is a measure of the toner mass concentration in the developer is obtained therefrom. Thus, the toner mass concentration of the developer can be determined by measuring the traveling time of the sound wave in the developer. In the initial measurement process, the functional relationship between the ultrasonic travel time and the toner mass concentration is determined in consideration of the developer temperature under a plurality of developers having a known toner concentration, and the calculated value is calculated. The time and toner mass concentration are stored as a table, for example. This table is used to determine the toner mass concentration by measuring the travel time of ultrasonic waves through the developer. In some cases, it may be necessary to interpolate between each value in the table. Similar methods for determining the mass concentration in the dispersion are known, for example, from US Pat. No. 6,817,229, US Pat. No. 5,121,629, and US Pat. No. 7,768,891.

  US Pat. No. 5,245,290 discloses a measuring device for determining the electrophoretic mobility of charged particles in a liquid. A dispersion liquid to be inspected containing charged particles is sealed in the measurement cell, and the electrophoretic mobility of the charged particles is detected. First, an alternating electric field that vibrates particles in a liquid is applied to the measurement cell, and then the speed of sound waves formed by the vibrating particles is evaluated. From the electric field and the average velocity of the particles in the liquid, particle electrophoresis is performed. The degree is concluded. Formulas for calculating the dynamic mobility of particles in a dispersion are described on pages 89-101 of RWO'Brien et.al., "Colloids and Surfaces A", Physiochem. Eng. Aspects, 218 (2003). Has been.

  In the known measurement method, since the measurement is performed in various measurement cells having probe probe volumes with different mass concentrations or electrophoretic degrees of particles, there arises a problem that the measurement accuracy is lowered due to the concentration difference and the temperature difference.

US Publication No. 2006/015836 US Publication No. 2008/279597 US Open 2011/58838 US Pat. No. 6,817,229 US Pat. No. 5,121,629 U.S. Pat. No. 7,764,891 US Open No. 5245290

R.W.O'Brien et.al., "Colloids and Surfaces A", Physiochem. Eng. Aspects, 218 (2003), pp. 89-101

  Therefore, the problem to be solved by the present invention is to provide a method capable of measuring both the mass concentration and the electrophoretic mobility of particles in a dispersion in one measurement process. A dispersion is a liquid in which particles are dispersed in a liquid.

  The problem is that an AC field having a variable frequency, for example, an AC electric field, is applied to the dispersion in the measurement cell, and the particles in the dispersion are vibrated by the AC field to form sound pressure waves on the particles in the dispersion. Then, the sound pressure wave amplitude (ESA signal) is measured based on the frequency, the maximum amplitude of the sound pressure wave is detected, the frequency corresponding to the maximum amplitude is obtained as the resonance frequency of the sound pressure wave, and the particles in the dispersion liquid are obtained from the resonance frequency. This is solved by obtaining the mass concentration of

  The functional relationship between the resonance frequency and the mass concentration of the particles in the dispersion is obtained in advance in an initial measurement process in which the mass concentration of the particles in the dispersion is known, and is stored as a table, for example.

It is a figure which shows the measuring apparatus which measures the mass concentration and dynamic mobility of the particle | grains in a dispersion liquid. It is a figure which shows the Example of the measurement cell used with a measuring apparatus. It is a graph which shows the functional relationship of the sound pressure wave amplitude ESA and the frequency in a measurement cell. It is a graph which shows the functional relationship between the mass concentration of particle | grains, and the resonant frequency of the sound pressure wave in a measurement cell.

  Various embodiments of the invention result from the dependent claims.

  The electrophoretic mobility of the particles in the dispersion is determined by a measuring device. This is because the electrophoretic mobility can be concluded from the ESA signal and the electric field strength (see R.W.O'Brien et.al., "Colloids and Surfaces A" above).

  The advantage of the method of the present invention is that both the mass concentration of particles in the dispersion and the mobility in the dispersion can be determined in a single measurement process. As a result, an improvement in measurement accuracy is achieved with respect to a measured quantity of mass concentration of particles in the dispersion and mobility in the dispersion. For the developer, this means that the toner mass concentration and electrophoretic mobility can be accurately measured. This is important for parameter control in the liquid management part of a printing press that uses a developer for developing charge carriers.

  Hereinafter, the present invention will be described in detail according to the illustrated embodiment.

  The present invention is based on a known measuring apparatus that measures electroacoustic pressure amplitude ESA (Electroacoustic Sonic Amplitude) of a sound pressure wave in a dispersion.

  In describing the present invention, hereinafter, a dispersion containing particles in a liquid is handled, and the mass concentration and mobility of the particles in the dispersion are determined. In an advantageous embodiment, the dispersion is an electrophotographic printing developer, which contains toner particles as particles and, for example, mineral oil or silicone oil as liquid. The liquid is also called a support liquid or carrier.

1, the embodiment of the measuring apparatus MA which can be obtained mass concentration TK and dynamic mobility of charged particles in the dispersion mu _d and at the same time is shown in block diagram. The dispersion liquid is filled in the measurement cell MZ, and the detailed structure of the measurement cell MZ is shown in FIG. An AC electric field U (f) is applied to the dispersion in the measurement cell MZ, where U is the voltage of the AC electric field and f is the frequency of the AC electric field. The particles are vibrated by the alternating electric field, thereby generating a sound pressure wave in the dispersion. A sound pressure wave amplitude ESA (f) as an output signal and a temperature T of the measurement cell MZ are output to the output side of the measurement cell MZ. The flow here is controlled by the control unit ST, the alternating voltage U (f) is supplied to the measurement cell MZ, and the ESA signal ESA (f) is received. The control unit ST transmits the ESA signal to the processor unit PR, and the processor unit PR obtains the mass concentration TK of the particles in the dispersion from the ESA signal. The mass concentration TK is stored in the memory unit SP. The memory unit SP may include, as other known dispersion parameters, the speed of sound c in the liquid of the dispersion, the viscosity η of the liquid, the density difference Δρ between the particles and the liquid, and the like. These parameters are supplied to the control unit ST, and the dynamic mobility μ _d of the particles in the dispersion is determined from the parameters of ESA, TK, c, η, Δρ according to the following formula (2). This flow takes place in the measuring cell MZ under a defined temperature T. When measuring the cell temperature T changes, changes occur in the mobility mu _d and sound pressure amplitude ESA particles.

  FIG. 2 shows an example of the structure of the measuring cell MZ. The measuring cell MZ has a probe chamber 2 filled with the dispersion liquid 1. The probe chamber 2 is composed of, for example, a cylindrical acoustic resonator, and a plurality of electrodes 3 are provided on a plane parallel to the upper surface and the lower surface, and an AC electric field 4 is applied between the electrodes. An alternating electric field 4 applied between the electrodes 3 excites periodic motion in the charged particles in the dispersion, but the amplitude is maximized to the resonance frequency in the probe chamber 2 by adjusting the frequency of the electric field 4. . At this time, sound pressure waves are generated in the probe chamber 2 by the vibrating particles. This sound pressure wave is amplified by an acoustic resonator and has different sound pressure wave amplitudes depending on the frequency of the AC electric field 4. The sound pressure wave in the dispersion 1 formed by the alternating electric field 4 is supplied to the sound pressure converter 6 through the acoustic conducting rod 5 and converted into an electric signal there. The amplitude of this signal is obtained as an ESA signal depending on the frequency f of the AC electric field 4. In addition, the temperature of the probe chamber 2 is measured by the temperature sensor 7. For example, the probe chamber 2 has an electrode distance of up to 3 mm, and an AC voltage 80 V having a variable frequency in a region up to 1 MHz is applied to the electrode 3.

  The sound pressure wave amplitude (ESA signal) is measured depending on the set frequency, and as an example, the curve of FIG. 3 showing the functional relationship between the sound pressure wave amplitude and the frequency f is obtained. From the curve in FIG. 3, the resonance frequency is obtained by evaluation with frequency decomposition. This resonant frequency is determined by the geometry of the probe chamber 2 and the acoustic properties of the dispersion. FIG. 3 shows that the maximum value of the sound pressure wave amplitude ESA is located at the resonance frequency 891 kHz, for example. FIG. 3 shows the functional relationship between the sound pressure wave amplitude and the frequency for the developer containing toner particles.

  When the mass concentration TK of the particles in the dispersion is different, various resonance frequencies are obtained. Here, the mass concentration TK of the particles in the dispersion is estimated from the resonance frequency of the dispersion obtained by the measurement. If the functional relationship between the resonance frequency and the particle mass concentration is obtained in the preceding initial measurement process using the dispersion having the known mass concentration TK, the particle mass concentration TK can be obtained from the measured resonance frequency. . FIG. 4 shows a graph of the developer. Here, the temperature and the supporting liquid are constant, and the resonance frequency is measured at five known toner mass concentrations TK depending on the toner mass concentration TK. When the resonance frequency of the developer is measured by the measuring device of FIG. 1 and the toner mass concentration is unknown, the toner mass concentration TK can be read from the graph of FIG. The curves in FIG. 4 are stored in the processor unit PR as a table. Therefore, unlike the prior art where the sound velocity is first detected and then the toner mass concentration is estimated from the sound velocity using the table obtained in the initial measurement process, the toner mass concentration TK is directly estimated from the resonance frequency. be able to. The measurement of the speed of sound using the traveling time of the sound wave in the conventional probe chamber is inaccurate compared with the calculation of the resonance frequency in the present invention.

  Furthermore, according to the above-mentioned RWO'Brien et.al., “Colloids and Surfaces A”, it can be obtained by using the measuring device of FIG. 1 by the ESA signal and the resonance frequency under a predetermined temperature T. The mobility in the probe volume can be obtained by evaluating the mass concentration TK. It is assumed that the following parameters are known for the following equation (2): sound pressure wave amplitude ESA, mass concentration TK, sound velocity c in liquid, liquid viscosity η, and density difference Δρ between particles and liquid. It is that. The sound pressure wave amplitude ESA is measured by the measurement cell MZ. The mass concentration TK is obtained from the resonance frequency in the processor unit PR. Further, the parameters of the sound velocity c in the liquid and the density difference Δρ between the particles and the liquid are known for each dispersion (for example, developer) to be examined. The developer liquid is also called a support liquid or carrier.

Parameters affecting sound pressure wave amplitude (ESA) are according to RWO'Brien et.al., "Colloids and Surfaces A"
ESA = c * Δρ * TK * μ _d * G (1)
And where
c: sound velocity in liquid of dispersion Δ: density difference between particles and liquid TK: particle mass concentration μ _d : dynamic mobility of particles G: calibration coefficient (for example, including characteristics of measurement cell MZ)
It is.

From the ESA value, the value of the dynamic mobility μ _d of the particle is expressed as μ _d = ESA / c * Δρ * TK * G (2)
Can be calculated as G is determined during mobility measurement calibration.

  When obtaining the particle mass concentration TK, excitation of sound waves in the measurement cell MZ can be performed by a photoacoustic process. For example, excitation is performed using a light beam (laser light) having an appropriate wavelength that allows the dispersion to sufficiently absorb the light beam.

MA measuring device, MZ measuring cell, ST control unit, PR processor unit, SP memory unit, 1 dispersion, 2 probe chamber, 3 electrode, 4 AC voltage source, 5 acoustic conducting rod, 6 sound pressure transducer, 7 temperature sensor , ESA sound pressure wave amplitude, speed of sound in the liquid in c dispersion, the density difference between the Δρ particles and liquid, TK particle mass concentration, mu _d dynamic mobility, excited with G calibration coefficient, U (f) frequency f Voltage, f frequency

Claims (9)

A method for determining a particle mass concentration in a dispersion containing particles and a liquid,
An alternating current field having a variable frequency is applied to the dispersion liquid in the measurement cell (MZ), the particles in the dispersion liquid are vibrated by the alternating current field, and sound pressure waves are formed in the particles in the dispersion liquid. ,
Sound pressure wave amplitude (ESA) is measured based on the frequency, the maximum amplitude of the sound pressure wave is detected, the frequency corresponding to the maximum amplitude is determined as the resonance frequency of the sound pressure wave,
The mass concentration (TK) of the particles in the dispersion is obtained from the obtained resonance frequency by the functional relationship between the resonance frequency and the mass concentration (TK) determined in the initial measurement process. A method for determining the mass concentration of particles in a dispersion. Forming the alternating field with an alternating voltage having a configurable frequency;
A method for determining the mass concentration of particles in the dispersion according to claim 1. Forming the AC field using a photoacoustic effect;
A method for determining the mass concentration of particles in the dispersion according to claim 1. In the initial measurement process, the functional relationship between the resonance frequency and the mass concentration (TK) is a dispersion having a known mass concentration (TK) in the measurement cell (MZ) under a predetermined temperature (T). liquid filling the, and detects the resonance frequency of the filled dispersion, by describing the functional relationship between the resonant frequency and the mass concentration (TK) in the table, determined,
Read the mass concentration (TK) of the particles in the other dispersion from the table according to the resonance frequency measured in the other dispersion.
A method for determining the mass concentration of particles in the dispersion according to claim 1. The dispersion is a developer containing toner particles and a support liquid, and used for developing a charge image in an electrophotographic printer.
A method for determining a particle mass concentration in a dispersion according to any one of claims 1 to 4. In the measurement cell (MZ), the sound pressure wave amplitude (ESA) is measured depending on the frequency, and the measured value is supplied to the control unit (ST).
The measurement value is supplied from the control unit (ST) to the processor unit (PR), the resonance frequency is obtained from the measurement value by the processor unit, and the mass concentration (TK) is obtained based on the resonance frequency. Output to
A method for determining a particle mass concentration in a dispersion according to any one of claims 1 to 5. By the control unit (ST), the mass concentration (TK), the sound pressure wave amplitude (ESA), the known dispersion parameter (c) of the sound velocity in the liquid of the dispersion liquid, the particles and the liquid in the dispersion liquid, The dynamic electrophoretic mobility (μ _d ) of the particles in the dispersion is obtained from the density difference (Δρ) between
A method for determining the mass concentration of particles in the dispersion according to claim 6. The dynamic electrophoretic mobility μ _d is expressed by the formula μ _d = ESA / c * Δρ * TK * G
Where c is the speed of sound, Δρ is the density difference between the particle and the liquid, TK is the mass concentration, and G is a frequency dependent calibration factor,
A method for determining a particle mass concentration in the dispersion according to claim 7. The mass concentration (TK) and the dynamic electrophoretic mobility (μ _d ) are simultaneously determined in one measurement process.
A method for determining the mass concentration of particles in the dispersion according to claim 8.

Images