JPH05142195A - Method for measuring charge control agent dispersed state in developer - Google Patents

Abstract

PURPOSE:To accurately measure not only the concn. of the charge control agent present on the surface of toner but also the surface area of the charge control agent, that is, the dispersed particle size thereof in the dispersed state of said agent as numerical data. CONSTITUTION:In measuring the surface dispersion state of a charge control agent in a developer, toners or carriers 6 whose surfaces are constituted of a resin composition containing the charge control agent are dispersed in a water-containing water miscible org. solvent 2 dissolving the charge control agent but not a resin to measure the potential difference accompanied by the dissolution of the charge control agent and, from the obtained dissolution curve, the surface concn. and surface area of the charge control agent are evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a dispersed state of a charge control agent in a developer. More specifically, the concentration and surface area of the charge control agent present on the surface of the developer can be accurately measured. Regarding how to measure.

[0002]

2. Description of the Related Art Development of an electrostatic latent image in electrophotography is
The toner is charged with a polarity opposite to that of the electrostatic latent image. In order to control the charge polarity and charge amount of this toner,
It is widely practiced to blend a charge control agent such as a metal complex salt dye into a toner. It is also known that the state of dispersion of the charge control agent in the toner, particularly the state of dispersion on the surface, has a great influence on the characteristics of the toner.

Conventionally, as a method for measuring the distribution state of the charge control agent in the toner, there is a surface dye concentration method in which the charge control agent (dye) on the toner surface is dissolved in methanol and the absorbance is measured.

[0004]

According to the above measuring method, it is possible to know the concentration of the charge control agent contained in the toner, which is present on the toner surface, that is, the surface dye concentration. However, even if the values of the surface dye concentration method are the same, the charging performance of the toner is different, which causes carrier contamination or insufficient charging.

It is considered that this is because the surface area of the charge control agent may be different even if the concentration of the charge control agent on the toner surface is the same, and the charging characteristics of the toner are changed due to this difference. Thus, not only in the concentration of the charge control agent on the surface but also in the dispersed particle size or surface area thereof, in order to accurately grasp the state of dispersion of the charge control agent in the toner, in the research and development of the toner and in the actual manufacturing thereof. It is necessary to measure in an accurately digitized state.

The present inventors have studied a method of directly observing the dispersed particle size of the charge control agent on the surface of the toner. However, the present analyzers, for example, a scanning electron microscope (SEM) and a transmission electron microscope (TEM) are used. , X-ray analysis (EPMA) and the like have revealed that the accuracy of analysis has not reached the level of identifying the dispersed particle size of the charge control agent on the surface of the toner, which is difficult.

Therefore, the object of the present invention is to obtain not only the concentration of the charge control agent present on the surface of the toner or the like, but also the surface area in the dispersed state, that is, the dispersed particle size, with high precision and numerical data. Is to provide a method that can be measured as.

[0008]

According to the present invention, a toner or carrier at least the surface of which is composed of a resin composition containing a charge control agent is contained in water containing a charge control agent which does not dissolve the resin. A developer characterized by being dispersed in a water-miscible organic solvent, measuring the potential difference associated with the dissolution of the charge control agent, and evaluating the surface concentration of the charge control agent and the surface area of the charge control agent from the resulting dissolution curve. A method for measuring the surface dispersion state of a charge control agent therein is provided.

In the present invention, the formula relating to the total concentration of the charge control agent on the dissolved toner surface is "Equation 1" E _max. = E ₀ -B * log (C ₀ ) where C ₀ : charge control on the toner surface Concentration when the total amount of the agent is dissolved (mol / l) E _{max .} : Dissolution saturation potential (mV) E ₀ : Reference potential of pH 1 of glass electrode (mV) B: Potential gradient (mV / pH) Also, E ₀ , B is represented by the constant of the glass electrode device, and the surface concentration C ₀ of the charge control agent can be evaluated based on E _max .

Further, in the present invention, the equation relating to the surface area of the charge control agent on the surface of the dissolved toner is "Equation 2" t∞ = 3C ₀ / KS ₀ where S ₀ is the total surface area of the charge control agent on the toner surface ( m ² ) K: dissolution rate constant t ∞: dissolution saturation time (min.), and the surface area S ₀ of the charge control agent present on the toner surface is evaluated based on t ∞, K and C _0. can do.

[0011]

The present invention utilizes the phenomenon that the charge control agent is essentially an electrolyte, and dissociates to generate ions during the dissolution process. For example, a metal complex salt dye, which is a typical negative charge control agent, has the following formula when dissolved in a water-containing water-miscible organic solvent such as methanol.

[Chemical 1] In the formula, A and B represent the residues of the diazo component and the coupling component each having a phenolic hydroxyl group at the ortho position,
M represents a polyvalent metal such as chromium, iron or cobalt, and dissociates into ions. When dissociated into ions, an electrical measurement can be made from this solution. That is, when focusing on [H +] among the dissociated ions, it is understood that the measurement of [H +] is a method that has been already performed using a pH meter or the like, and potential difference measurement is possible. In the metal-containing dye of the above “Chemical formula 1”, an inorganic or organic cation may be contained in place of the hydrogen ion, but in this case also, dissociation of water molecules is induced to generate hydrogen ion. To do.

On the other hand, in the above-mentioned surface dye concentration method, the reason why there is little information about the distribution of the charge control agent obtained is that the saturated dissolution amount of the charge control agent is measured, but the process until the saturated dissolution amount is reached is measured. That is, no information is obtained from the aspect of dissolution, that is, speed. However, the surface area of the charge control agent naturally affects the dissolution rate of the charge control agent. If the dissolution process of the charge control agent from the toner can be electrically measured, it becomes possible to accurately measure the change with time of dissolution, that is, the speed measurement.

According to the present invention, a toner or a carrier, at least the surface of which is composed of a resin composition containing a charge control agent, is dispersed in an organic solvent which does not dissolve the resin but does dissolve the charge control agent, thereby controlling the charge. The potential difference is measured as the agent dissolves. That is, only the charge control agent in the resin composition constituting the surface of the toner or carrier is selectively dissolved in the solvent, and the ions of the charge control agent in the solution are accurately detected with time by potentiometric titration. It will be.

In FIG. 1 for explaining the potentiometric titration according to the present invention, an organic solvent 2 which does not dissolve a resin but dissolves a charge control agent is filled in a measuring container 1, and a glass electrode 3 and The reference electrode 4 is immersed. These electrodes are connected to the potentiometer 5. At the time of measurement, the toner or carrier 6 to be measured is dispersed. The charge control agent on the surface of the toner or the carrier 6 is eluted into the solvent and at the same time dissociated into ions in the solvent, which ions are detected by the glass electrode 3 and displayed as a potential difference by the potentiometer 5.

Here, the formula for the time change of the concentration when the charge control agent is dissolved in a solvent is as follows:

## EQU3 ## C = C ₀ {1- (1-KS ₀ t / 3C ₀ ) ³ } In the formula, C: concentration of the charge control agent dissolved in the solvent (mol
/ L) t: time (min.) C ₀ : concentration when the total amount of the charge control agent on the toner surface is dissolved (mol / l) S ₀ : total surface area (m ² ) of the charge control agent on the toner surface K: dissolution It is represented by a rate constant, and the concentration C is C ₀ , K, S ₀ and t
Is a functional system of.

Here, 1-KS ₀ t / 3 in the equation (3)
When C ₀ = ₀ , C reaches the saturation concentration C ₀ , so when the dissolution saturation time is represented by t ∞, the formula is “Equation 2” t ∞ = 3C ₀ / KS _{0 In the} formula, S ₀ : charge control of toner surface The total surface area (m ² ) of the agent is expressed by K: dissolution rate constant t ∞: dissolution saturation time (min.), And the dissolution saturation time t ∞ is K, C ₀ ,
It becomes a functional system of S ₀ .

From the equation (2), the following equation

[Mathematical formula-see original document] t ∞ = 3 / (K · M · V · S _S ) M: Molecular weight of charge control agent V: Solvent volume (l) S _S : Specific surface area (m ² / g) of charge control agent And t ∞ can be represented by S _S.

Expression of "Equation 3" using "Equation 2" is an equation.

## EQU5 ## It is expressed by C = C ₀ {1- (1-t / t∞) ³ }, and the concentration C is a functional system of C ₀ and t ∞.

Next, the expression expressing the concentration of the charge control agent present on the toner surface as a potential difference using a glass electrode is

[Equation 6] E = E ₀ −B * log {[H ⁺ ] _{C = 0} + C} In the formula, E: potential difference (m in association with dissolution of charge control agent)
V) [H ⁺ ] _{C = 0} : It is represented by the hydrogen ion concentration when C = 0.

FIG. 2 showing the result of actual potentiometric titration.
In, the horizontal axis represents time and the vertical axis represents potential difference. Plot A in the figure is the potential difference measurement result for the toner containing no charge control agent, while plot B is the potential difference measurement result for the toner containing the charge control agent. From this result, it is estimated that the potentiometric titration curve in the elution process of the charge control agent is a functional system of "Equation 1".

When the concentration C of "Equation 6" reaches the saturation concentration C ₀ , it is represented by the following equation "Equation 1" E _max. = E ₀ -B * log (C ₀ ) and E _max. Can be expressed as a function of C ₀ .

In practice, the same charge control agent is added in an amount of 0.001 to
A total of 0.04 g of the charge control agent was dissolved in 150 ml of methanol, and the relationship between the solution saturation potential E _max. (Vertical axis) of the glass electrode and the logarithm of the concentration C ₀ (horizontal axis) of the charge control agent having a known concentration _. Is plotted in FIG. This Figure 3
From this, it is confirmed that the relationship between E _max. And the logarithm of C ₀ is a functional system of “Equation 1”.

Next, the relationship between the surface area and K of the charge control agent will be considered. When the charge control agent is dissolved in a solvent, if the weight of the charge control agent is the same, the dissolution rate is proportional to the surface area

## EQU7 ## dC / dt = K * S S: It is represented by the surface area (m ² ) of the charge control agent at time t. This equation is a differential equation that leads to "Equation 3". Therefore, it is understood that K is a value representing the amount of the charge control agent that elutes in a unit time per 1 m ^{2 of} the charge control agent in contact with the solvent, and is a characteristic value of the dissolution rate of the charge control agent in the solvent.

Actually, the same charge control agent (molecular weight M = 670) having the same weight (0.005 g) but different particle size, that is, the charge control agent (CC having an average particle size of 4 μm)
AA) and the average particle size of 7 μm (CCA-B) were measured with a solvent volume V = 0.15 (l), and the result is as shown in FIG. 4, and the gradient of the potential difference measurement curve depends on the surface area. It is understood that it will change.

The specific surface area of CCA-A and CCA-B is determined by BET specific surface area measurement, and the dissolution saturation time t ∞ is determined by potential difference measurement, and the dissolution curve formula K = 3 / (t ∞ ·
K was calculated from M · V · S _S ).

[0026]

[Table 1] ──────────────────────────────────── Sample average particle size (μm) Specific surface area S _S (m ² / g) t ∞ K ──────────────────────────────────── CCA-A 4 11.582 9.3 2.78 × 10 ^-4 CCA-B 7 7.432 14.9 2.71 × 10 ^-4 ───────────────────────────────── ────

From the results, each sample (CCA-A and C
It is clear that K of CA-B) shows the same value, and K is a specific value of the dissolution rate of the charge control agent. Thereby, the relationship of t∞ = 3C ₀ / KS ₀ = 3 / (K · M · V · S _S ) was proved by the BET method. Therefore, by obtaining the dissolution saturation potential E _max. And the dissolution saturation time t ∞, the concentration C ₀ of the charge control agent and the surface area S ₀ of the charge control agent can be obtained.

[0028]

【Example】

(Measurement conditions) In the present invention, as the solvent, any water-containing water-miscible organic solvent that does not dissolve the resin but does dissolve the charge control agent is used. As the solvent to be used, a water-miscible solvent such as an alcohol type, an ether type, a ketone type, an ester type, an amide type, or a combination thereof is used depending on the combination of the resin constituting the toner or the coated carrier and the charge control agent. However, alcohol solvents having 7 or less carbon atoms, particularly methanol, are preferable in that they can dissolve the charge control agent well and hardly dissolve the resin. These organic solvents have a high affinity for water and usually contain a non-removable amount of water. This water may be used for dissociation into ions, or water may be positively added.

The concentration of the toner or coated carrier dispersed in the solvent varies depending on the concentration of the charge control agent contained and the measuring time, but generally speaking, 1.33 to 33.3 g / l, Especially 3.33 to 13.33 g / l
It should be in the range of. Further, the measurement time is such that the potential difference over time eventually saturates at a certain value, but generally, a measurement of about 5 to 30 minutes is sufficient.

The potentiometric titration is performed using any of the electrodes conventionally used for this application, but is preferably performed using a glass electrode. The titration device may be any device, but in this example, a potentiometric titration device manufactured by Kyoto Electronics Manufacturing Co., Ltd. was used.

(Measurement Sample) The sample to be measured in the present invention is
Any toner or carrier may be used as long as at least the surface thereof is formed of a resin composition containing a charge control agent. The present invention is particularly useful when the charge control agent is a negative charge control agent composed of a metal complex salt dye, but the present invention is not limited to this case, and other negative charge control agents and positive charge control agents can be used. It can also be advantageously applied to agents. This is p
It can be easily understood that the H measurement can measure not only acid but also alkali.

(Calculation of Surface Concentration and Surface Area) In order to calculate the surface concentration and surface area from the dissolution curve obtained by the potentiometric method, the surface concentration can be calculated from the equation of the dissolution curve by determining the saturation potential. .. The surface area can be calculated from the surface concentration, the substance specific constant K, and the dissolution saturation time.

(Examples) The present invention will be described in more detail by the following examples. Using the apparatus shown in FIG. 1, the sample is a toner having the same surface dye concentration by the absorbance method shown below (charge control agent molecular weight M = 670, charge control agent dissolution rate constant K = 2.75 × 10 ⁻ FIG. 5 shows the result of the potentiometric measurement (solvent amount V = 0.15 (l)) using ⁴ ).

[0034]

[Table 2] ──────────────────── Sample surface dye concentration (absorbance) ──────────────────── Toner A 0.1262 Toner B 0.1257 ─────────────────────

From the dissolution curve of FIG. 5, E₀= -491 (m
V), B = 52 (mV / pH), E _max.= -277 (m
V), and the surface concentration C₀I asked.
Further, the dissolution saturation time was calculated from the dissolution curve in FIG.
2 ”formula, surface area S₀I asked. The results are shown in the table below.
You

[0036]

[Table 3] ──────────────────────────────────── Sample t ∞ (min.) C ₀ ( mol / l) K S ₀ ──────────────────────────────────── toner A 10.0 7.7 × 10 ^{- 5} 2.75 × 10 ^-4 8.4 × 10 ^-2 Toner B 15.9 7.7 × 10 ^-5 2.75 × 10 ^-4 5.3 × 10 ^-2 ────────────────────── ───────────────

From the above, it is understood that the surface concentration and surface area of the charge control agent can be determined by the present invention. It is also understood that the surface area of the charge control agent is different even in the samples (toner A and toner B) having the same surface dye concentration by the absorbance method.

[0038]

According to the present invention, a toner or carrier at least the surface of which is composed of a resin composition containing a charge control agent is dispersed in an organic solvent which does not dissolve the resin but dissolves the charge control agent, By measuring the potential difference associated with the dissolution of the charge control agent, not only the concentration of the charge control agent present on the surface of the toner, etc., but also the surface area in the dispersed state can be accurately and numerically analyzed from the obtained dissolution curve. As a result, it becomes possible to measure in more detail the relationship between the toner charging characteristics and the manufacturing conditions when manufacturing and researching and developing the toner and the like.

[Brief description of drawings]

FIG. 1 is a layout diagram for explaining potentiometric titration according to the present invention.

FIG. 2 is a graph showing the results of potentiometric titration of a toner containing a charge control agent and a toner containing no charge control agent.
The horizontal axis represents time and the vertical axis represents the potential difference.

FIG. 3 is a graph plotting the relationship between the final potential (vertical axis) and the logarithm of the concentration of the charge control agent (horizontal axis) when the weight of the charge control agent is changed.

FIG. 4 shows the results of potentiometric titration of the same charge control agent having different particle sizes, that is, a charge control agent (CCA-A) having an average particle size of 4 μm and an average particle size of 7 μm (CCA-B). It is a graph which shows.

FIG. 5 is a dissolution curve as a result of an experimental example.

[Explanation of Symbols] 1 is a measuring container, 2 is an organic solvent, 3 is a glass electrode, 4 is a reference electrode, 5 is a potentiometer, and 6 is a toner or carrier to be measured.

Claims (6)

[Claims] 1. A toner or carrier, at least the surface of which is composed of a resin composition containing a charge control agent, is dispersed in a water-containing water-miscible organic solvent which does not dissolve the resin but does dissolve the charge control agent. A method for measuring the surface dispersion state of a charge control agent in a developer, which comprises measuring the potential difference associated with dissolution of the control agent, and evaluating the surface concentration of the charge control agent and the surface area of the charge control agent from the resulting dissolution curve. .. 2. An equation relating to the total concentration of the charge control agent on the dissolved toner surface is represented by the following formula: E _max. = E ₀ −B * log (C ₀ ) where C ₀ : the total amount of the charge control agent on the toner surface is Concentration when dissolved (mol / l) E _{max .} : Dissolution saturation potential (mV) E ₀ : Reference potential (mV) of pH 1 of glass electrode B: Potential gradient (mV / pH) Further, E ₀ and B are glass The measurement method according to claim 1, wherein the surface concentration C ₀ of the charge control agent is evaluated based on E _max . 3. An equation relating to the surface area of the charge control agent on the surface of the dissolved toner is as follows: t ∞ = 3C ₀ / KS ₀ where S ₀ : total surface area (m ² ) K of the charge control agent on the toner surface: The dissolution rate constant t ∞ is represented by a dissolution saturation time (min.), And the surface area S ₀ of the charge control agent present on the toner surface is evaluated based on t ∞, K, and C _0. Measuring method. 4. The measuring method according to claim 1, wherein the charge control agent is a metal complex salt dye. 5. The measuring method according to claim 1, wherein the organic solvent is an alcohol having 7 or less carbon atoms. 6. A glass electrode for measuring the potential difference.
The measurement method described.