JPH07925Y2 - Device for measuring physical properties of liquid developer for electrostatic photography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an apparatus for measuring physical properties of a liquid developer used in a copying machine or the like.

(Prior Art) Various devices have been conventionally proposed as a device for measuring the physical properties of a liquid developer.

For example, FIGS. 3 to 7 show examples of mobility (also referred to as mobility) and ζ (jitter) potential measurement, and FIG. 3 shows an example of mobility measurement by a microscopic method, and polycarbonate. The cell 1 has a platinum electrode (also used for voltage application and voltage measurement) 2 and is a sample (thin solution) from the three-way cock 3.
Was supplied and non-aqueous electrophoresis was measured by the microscope 4, but it could not be observed by the microscope unless it was a thin solution, and it was not possible with toner particles having a small particle size.

Fig. 4 shows an example of mobility measurement by the general boundary movement method.
The platinum electrode 5 is provided in the U-shaped tube 6, and the cock 3 is used to immerse the sample through the U-shaped tube 7 to the platinum electrode 5 by the cock 3, while the constant voltage power source 8 transfers the DC high voltage (200 to 1200) to the electrode 9.
V) is added, and the electrode 9 is moved up and down with the electrode adjusting screw 10 and the potential is measured with the platinum electrode 5.

FIG. 5 shows an example of mobility measurement using laser light interference.
There is a pigment dispersion region (sample) 14 in a portion surrounded by the spacer 11, the electrode (+) 12 and the transparent electrode (-) 13, and a particle-free region 15 is formed when a high DC voltage is applied between both electrodes. Then, by irradiating the boundary 18 between the pigment dispersion region 14 and the particle-free region 15 with the laser beam 17 through the glass prism 16,
The mobility of the sample is measured from the interference beam 19 of the laser beam irradiated at the boundary 18.

The measurement method shown in FIGS. 4 and 5 cannot be measured unless the boundary between the layer in which the toner particles as the sample are present and the layer in which the toner particles are not present cannot be clarified, that is, in the example of FIG. 6 is the sample level, which is the position of the boundary 18 in the example of FIG.

FIG. 6 shows an example of mobility measurement by the electrophoretic transport method, which further comprises a small chamber 21 in the sample tank 20 and a DC power source 22 to electrodes 23, 2.
Apply high DC voltage to 4 and measure the mobility.

This is because, due to this structure, the space between the electrodes 23 and 24 is widened and sufficient electric field strength cannot be obtained.

For such various measuring methods, there is a measuring apparatus shown in FIG. 7 which has been used conventionally as a mobility measurement by the electrodeposition method. This has a developing electrode 26 arranged in a brass cylinder 25, and has a toner dispersion layer 27 in this cylinder. The (−) side of a high-voltage DC power supply 28 is used as the cylinder 25, and the (+) side is used as ground. Apply an electric field. On the other hand, in the balance 29, one end of the electrode wire 30 connected to the developing electrode 26 is immersed in the KCL solution 31, and the other electrode wire 32 also immersed in the KCL solution 31 has an ammeter 3
Connect 3 and measure.

This is above and below the toner dispersion layer 27 in the cylinder 25 (27A
-27B) voltage is applied between the electrodes, so it is limited for electrodes (27
A-27B) is wide and it is difficult to apply high voltage.
Sufficient electric field strength cannot be obtained.

In addition, there is a laser Doppler method, which measures the movement of each toner particle using the laser Doppler effect. However, this was not a simple method due to some restrictions such as being performed in a dilute solution and being impossible to measure at a high voltage in a non-aqueous solution.

Next is the Q / m measurement method. This is a method in which a DC voltage is applied to a sample (toner) and the integrated value of the current flowing at that time is divided by the weight of the electrodeposited toner to obtain the value. However, this has a drawback that the electric current cannot be separated by charges other than the toner particles (counter ions, dissolved same-polarity ions).

(Problems to be Solved by the Invention) As described above, each of the physical properties of the liquid developer (toner) for electrostatic photography has its merits and demerits, and it has the same developer concentration and the same electric field strength as those of the copying machine. Therefore, an apparatus for accurately measuring the physical properties of the liquid developer, that is, the mobility, ζ potential, Q / m and the like has been desired.

An object of the present invention is to provide a physical property measuring device that satisfies the above demands.

(Structure and Operation) In order to achieve the above object, the present invention has a stage on which a counter electrode for development having a known weight is removably mounted and which can be moved at a constant speed, and is positioned with a constant gap with respect to the counter electrode. Consists of a developing counter electrode for applying a high voltage, a tank for supplying liquid developer to the gap between the two counter electrodes, and a measuring instrument having a probe for measuring the potential of the toner layer after development by both counter electrodes. After the potential of the toner layer is measured, the removable developing counter electrode is removed,
It is characterized in that the weight of the toner layer is measured.

When the measurement principle according to the present invention is applied, the electrodeposition rate is expressed by dm / dt = aμE (1). Here, a is toner concentration, μ is mobility (also referred to as mobility), and E is electric field strength.

If the Q / m of the toner layer is constant, the charge amount of the electrodeposition layer is proportional to the electrodeposition toner layer and inversely proportional to the electrostatic capacity. here
Q / m represents the amount of charge per unit mass of toner.

As a result, it can be assumed that the effective electric field strength E decreases in proportion to the square of the electrodeposition layer, as in the case of Q / m induction described later.

E = Eo−Km ² (2) Here, Eo is the electrolytic strength given by voltage application, and K is the blocking coefficient.

Assuming that the effective toner concentration a does not change during development, dm / dt = aμ (Eo−Km ² ) (3) From equations (1) and ( ² ) ... Here, t, a, and Eo are set values, and m is a value (g / cm ² ) obtained from an experiment, so that the mobility μ and the blocking coefficient K can be determined if there are several examples of data. Now, if the mobility is known, the ζ potential can be obtained from the migration equation (5) in a non-aqueous solution.

ζ = 1.5 ημ / ε _l (5) where η is the viscosity of the developer and ε ₁ is the dielectric constant of the developer.

Next, the principle of Q / m measurement is explained.

The surface potential Vt of the electrodeposition layer is expressed by the integral formula (6).

Vt = ∫ ₀ ^d σx / ε _d dx = σ d ² / 2ε _d (6) where σ is the volume charge density of the electrodeposition layer, ρ is the dielectric constant of the electrodeposition layer, and d is the thickness of the electrodeposition layer. Then, it is shown by the equation (7).

d = m / _ad ρ _d (7) Further, the volume charge density σ is expressed by the equation (8).

σ = (Q / m) _ad ρ _d (8) Now, substituting equations (7) and (8) into equation (6),
Equation (9) is obtained, and from this, Q / m can be obtained from the slope of the graph of the square of the electrodeposition layer and the potential of the electrodeposition layer.

(Embodiment) FIG. 1 shows the structure of an embodiment of the present invention, in which a moving stage 34 is movable at a constant speed in the direction of the arrow, and a movable counter electrode 35 of known weight is detachable on this moving stage . In the developer tank 36, the developer to be measured is put, the moving stage is started, the electromagnetic valve 37 is opened, and the developer is supplied. A high voltage power source 38 applies a high voltage between the developing counter electrode 39 and the moving counter electrode 35 which faces the developing counter electrode 39 with a constant gap therebetween for developing. A surface electrometer 40 has a probe 41 for measuring the electric potential of the toner layer 42.

When the operation of such a device is described, the moving stage 34 is moved below the developer tank 36 at a constant speed. Solenoid valve 37
Spreads the developer evenly on the upper surface of the moving counter electrode 35 when the moving counter electrode 35 comes directly under the moving speed of the moving stage.

Next, the high-voltage power supply 38 is switched on, and the developing counter electrode 39
A high voltage (DC voltage) is applied to the developer (toner layer 42) in the gap between the moving counter electrode 35 and the developing electrode 35 for development. The potential of the developed toner layer 42 (toner particles) is measured by the probe 41 of the surface electrometer 40.

Next, the weight of the toner layer is measured by measuring the moving counter electrode 35 having a known weight.
With. In this case, it may be carried out after drying or may be carried out by immersing it in a solvent.

FIG. 2 shows a graph of the square of the electrodeposition weight of the toner layer obtained by the above-mentioned measuring apparatus using CT5085 toner manufactured by Ricoh Co., Ltd., and the measurement result of the toner layer potential. The slope of this graph and 264 Vcm
Q / m was calculated from ⁴ / mg ² and the dielectric constant ρ2.65 of the toner layer based on the equation (9) above.
4.5 μc / g was obtained.

(Advantages of the Invention) With the configuration described above, the present invention can measure the mobility of the toner layer, the ζ potential, the development amount, Q / m, etc. under the condition of the electric field strength in which the actual copying machine is operating. By measuring the potential decay rate of the toner layer, C and R can be measured.

[Brief description of drawings]

FIG. 1 is a block diagram of a physical property measuring apparatus according to an embodiment of the present invention, FIG. 2 is a graph showing a measurement result of a toner layer according to FIG. 1, and FIGS. ζ
It is a figure which shows electric potential measurement. 34 ... moving stage, 35 ... moving counter electrode, 36 ... developer tank, 37 ... electromagnetic valve, 38 ... high-voltage power supply, 39 ...
… Counter electrode for development, 40 …… Surface potential meter, 41 …… Probe, 42 …… Toner layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Kazuhiko Umemura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References Japanese Patent Publication 5-52901 (JP, B2)

Claims (1)

[Scope of utility model registration request] 1. A stage, on which a counter electrode for development having a known weight is removably mounted, and which is movable at a constant speed, and one for high voltage application, which is positioned with a constant gap with respect to the counter electrode. A counter electrode, a tank for supplying a liquid developer to the gap between the two counter electrodes, and a measuring instrument having a probe for measuring the potential of the toner layer after development by the two counter electrodes. A device for measuring physical properties of a liquid developer for electrostatic photography, characterized in that the removable counter electrode for development is removed and the weight of the toner layer is measured.