JPS62229256A - Two-component type developer for electrophotography - Google Patents

Abstract

PURPOSE:To improve the temp. dependency of a two-component type developer by treating the surface of ferrite carrier particles to be used in combination with an electrodevelopable toner by the quaternary ammonium salt expressed by the specific formula. CONSTITUTION:The two-component type developer for electrophotography which consists of the magnetic carrier and electrodevelopable toner and is formed by treating the surface of the ferrite carrier particles with the quaternary ammonium salt expressed by the formula is used. The surface of the ferrite particles of the developer in which the ferrite particles treated with the quaternary ammonium salt in the above-mentioned manner are used as the magnetic carrier is protected by the quaternary ammonium salt, by which the temp. dependency is improved and the over-increase of an image density and fogging are effectively prevented even under high humidity.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a two-component developer for electrophotography, and more particularly to a two-component developer in which a magnetic carrier is surface-treated with a specific quaternary ammonium salt. O Regarding Developers (Prior Art) In two-component developers for electrophotography, it is known that the surface of the magnetic carrier used in combination with the toner is coated with various resins from the viewpoint of preventing spin-1 toner and preventing oxidation. It is being

Among these coated carriers, carriers for negatively charged toner are known whose surfaces are coated with acrylic resin or epoxy resin.

[Problems to be solved]

However, the conventionally known negative charging carrier is
Although it is effective in preventing spent toner and preventing oxidation, it is humidity-dependent, so the electrical resistance value decreases under high humidity, and the image density increases too much, leading to increased fogging. This will result in new problems.

Therefore, the technical object of the present invention is to provide a two-component developer in which spent toner and oxidation are effectively suppressed and humidity dependence is significantly improved.

(Means for Solving the Problems) In order to achieve the above-mentioned technical problem, the present invention provides that the surface of ferrite carrier particles used in combination with electrostatic toner is expressed by the following general formula, where R1 to R5 are It is an alkyl group or an aryl group, and each of these may be the same group.

X represents halogen.

n is a number from 0 to 2.

A product treated with a quaternary ammonium salt represented by is used.

(Function) According to the present invention, by using ferrite carrier particles that have been surface-treated with the above-mentioned quaternary ammonium salt, humidity dependence is significantly improved.

That is, as is clear from the examples described later, in a developer using ferrite particles treated with the above-mentioned quaternary ammonium salt as a magnetic carrier, excessive increase in image density and capri are effectively prevented even under high humidity. It is.

This fact is truly unexpected considering that quaternary ammonium salts are commonly used as surfactants and have hydrophilic groups.

Although the reason why the humidity dependence is significantly improved by protecting the surface of ferrite particles with the above-mentioned quaternary ammonium salt is still not clear, the present inventors speculate as follows. ing.

In other words, when the surface of ferrite particles is treated with a quaternary ammonium salt, hydrophilic halogen ions are preferentially captured on the ferrite surface, and water-repellent alkyl groups, phenyl groups, etc. are distributed on the outside. However, it is thought that this shields the ferrite particles from moisture in the atmosphere, and as a result, the ferrite particles are effectively protected from moisture even under high humidity conditions.

Further, in the present invention, it is extremely important that a phenyl group is present in the quaternary ammonium salt. For example, as is clear from the comparative examples described later, when ferrite particles are surface-treated using trimethylalkylammonium chloride as a quaternary ammonium salt, no improvement in humidity dependence is achieved. This seems to be because the ferrite particles are effectively protected from moisture only when a water-repellent and bulky group such as a phenyl group is present on the outside of the ferrite particles.

(Preferred Embodiment of the Invention) In the present invention, as the 84th class ammonium salt represented by the general formula (1) used for surface treatment of ferrite particles, specifically, the following are preferably used.

(1) General Formula In the formula, R represents an alkyl group having 10 to 22 carbon atoms, particularly 12 to 18 carbon atoms.

n is a number from 0 to 2, especially 1.

Dimethylalkylammonium chlorides represented by

(11) General formula, where R and R2 have 10 to 22 carbon atoms. In particular, it represents 12 to 18 alkyl groups.

n is a number from 0 to 2, especially 1.

Methyl dialkyl ammonium chlorides represented by

GiD general formula, In the formula, n represents a number from O to 2, particularly 1.

Trimethylammonium chloride represented by

(V) Other arylammonium chlorides in which the alkyl group bonded to the nitrogen atom in the general formulas (2) to (4) is substituted with an aryl group.

In addition, in the above-mentioned quaternary ammonium salt, ammonium bromides can also be used.

In the present invention, first, a ferrite carrier is used among various magnetic carriers. Ferrite carriers have a lower specific gravity and lower saturation magnetic flux density than ordinary iron powder carriers, so the formed ears are softer, and as a result, during development, it takes less time to rotate the developing sleeve or the magnet inside the sleeve. It is known that there is an advantage of low torque.

Furthermore, when a ferrite carrier is used, the electrical characteristics of the developer magnetic brush are relatively stable, and the speed
The ferrite carrier has the advantage of less toner generation.The ferrite carrier has a substantially spherical shape and a median particle size of generally 35 to 150 μm.
Particularly suitable is one in the range of 40 to 120 μm. The composition of ferrite is known, and includes what is generally called soft ferrite, such as, but not limited to, Zn-based ferrite, Ni-based ferrite, and C.
u-based ferrite, Mn-based ferrite, Mn-Zn-based ferrite, Mn-Mg-based ferrite, Cu-Zn-based ferrite, Ni-Zn-based ferrite, Mn-Cu-
Examples include Zn-based ferrite. Preferred ferrites are of the atomic type Mk, Fe35-65, Cu 5-15, Zn 5-15, and MnO-0.51.
It is a Cu-Zn type or Cu-Zn-Mn type ferrite consisting of.

These ferrites generally have a fine primary particle size of 0.5 to 7 μm, and are made by spray granulation or other means.
The particles are granulated into spherical particles, and then sintered by a method such as firing.

The electrical resistance of ferrite carriers, even those with high resistance,
It may be of low resistance, generally having a volume resistivity of 6 x 10 to 2 x 100, particularly 2.5 x 10 to 1.5 x 10.
'Omega saw' is used. In the present invention, the volume resistivity value is a value measured using a cell as described below.

Although the present invention can be applied to all ferrite carriers, it is desirable to use spherical sintered ferrite particles whose surface has irregularities based on primary particles as a ferrite carrier particularly suitable for the treatment according to the present invention.

FIG. 1 shows a scanning electron microscope of spherical sintered ferrite particles preferably used in the present invention.

These sintered ferrite particles generally have a diameter of 30 to 50 μm,
In particular, the median diameter of 40 to 45 μm (with a weight of 50 weight-1
1), but its apparent density is 1i (JIS Z-25
04-1966) is less than 2.6.9/CC, especially IC2
．． It is within the range of 30 to 2.501/cr.

According to a preferred embodiment of the present invention, by using sintered ferrite particles that are spherical and have fine irregularities on the surface, the charged polarity of the toner can be maintained constant, and the coating treatment can also reduce the tendency of moisture adsorption. Can be prevented.

Surface Treatment According to the present invention, the above-mentioned ferrite carrier is surface-treated with the above-mentioned quaternary ammonium salt.

This surface treatment can be easily carried out by immersing the ferrite carrier in a quaternary ammonium salt aqueous solution and then drying it. Of course, the coating is not limited to the dipping method, and it is also possible to use a sougere coating method or a fluidized bed coating device.

The amount of quaternary ammonium salt treated with respect to the magnetic carrier is 0.1-2. Oj
It is preferably 0.1 to 0.5 parts by weight, particularly 0.1 to 0.5 parts by weight. If it is less than 0.1 parts by weight, the desired improvement in humidity dependence cannot be achieved, and if it is more than 2.0 parts by weight, it will adversely affect the fluidity and charging characteristics of the carrier itself.

Toner The toner used must have an electrical resistance of 1.times.10@13 .OMEGA., particularly at least 5.times.100 .OMEGA., from the viewpoint of transferability. Furthermore, it goes without saying that the toner particles must be a colored toner having head weight and fixing properties. A granular composition having a particle size of 5 to 30 microns in which a coloring pigment, a charge control agent, etc. are dispersed in a binder resin is used. As the resin, a thermoplastic resin or an uncured or initial condensate thermosetting resin is used. Examples of these, in order of importance, are vinyl aromatic resins such as polystyrene, acrylic resins, polyvinyl acetal resins, etc. These include polyester resin, epoxy resin, phenol resin, petroleum resin, and olefin resin. As the pigment, for example, one or more of caden black, cadmium yellow, molybdenum orange, pyrazolone red, fast violet B, phthalocyanipple, etc. is used, and as the charge control agent, for example, Nigron paste (CI 50415) is used. , oil black (CI261
50), oil-soluble dyes such as Spiron black.

Naphthenic acid metal salts, fatty acid metal soaps, resin acid soaps, etc. are used as necessary.

The coated ferrite carrier and electrostatic toner are generally preferably used in a weight ratio of Zoo:3.5 to 100:11. This ratio also does not affect the electrical resistance of the magnetic brush of the developer. That is, as the amount ratio of the ferrite carrier increases, the electric resistance of the magnetic brush of the developer tends to decrease. The optimum ratio between the two is also closely related to the specific surface area of the ferrite carrier and the electrostatic toner. In a preferred embodiment of the present invention, the toner concentration (Ct ratio) of the mixture forming the magnetic brush is determined by the following formula, where Sc is the specific surface area of the ferrite carrier (cm2/
,! i': Actual value measured by transmission method), St is the specific surface area of the toner (cfR''/F: effective value calculated based on the average particle diameter measured using a Coulter counter, assuming that the toner is a true sphere). It is the specific surface area, the radius obtained from the average particle size is r (cIn), and the true specific gravity of the toner is ρ (J
i'/lyt<”), 5t=3/(r・ρ
), where k is a number from 0.80 to 1.07.

First, the term Sc/(St+S
c) is a term related to the specific surface area of the carrier and toner, and specifically, it is the ratio of the surface y occupied by the carrier to the total surface area of a composition in which the carrier and toner are mixed in equal weights (hereinafter simply referred to as the surface area occupied by the carrier). This is a numerical value that represents the rate (referred to as the rate).

Therefore, in this aspect of the present invention, when an electrostatic image is developed with a two-component developer under conditions such that the carrier surface area occupancy rate or its neighborhood value is equal to the toner concentration, the image becomes This results in an improvement in density, a reduction in Capri density, an improvement in resolution, and an improvement in gradation.

Toner concentration (ct 4 ) and carrier surface area occupancy (S
c/(St+Sc) e%) can be evaluated by determining the ratio of both, that is, k=Ct/[Se/(St+Sc)] coefficient k.

Although this coefficient differs depending on the shape of the ferrite carrier used, in the present invention, this coefficient k is set to a value of 0, 80 to 1.07 as described above, and particularly in the range of 0.90 to 1.04 for spherical ferrite particles. By doing so, it is possible to obtain high image density, low Capri density, high resolution, and excellent gradation, and these characteristics hardly deteriorate not only at the beginning of development, but also after continuous copying of 40,000 sheets. effect is achieved.

Example 1 The quaternary ammonium salts used for surface treatment are shown in the table below.

Surface Treatment Method Sample 2.51 of Group 1 in Table 1 was dissolved in 500 g of distilled water to prepare a 0.5% adjustment solution. Ferrite carrier 5009 was immersed in this adjustment solution, stirred for 20 minutes, filtered, and left in a dryer at 105°C for 2 hours to evaporate water.
A surface-treated carrier according to 1 was obtained. 42 in a similar way
．． Surface-treated carriers were prepared using 3 and 4.5, respectively.

The ferrite carrier used here has an electrical resistance of 4.3X
It has a specific surface area of 396 cm''/Ji' and a specific surface area of 109 Ω.The electric resistance values in the text were determined from the current value when the cell shown below was filled with a ferrite carrier and a voltage of 500 V was applied. Cell size T20 x 30
The electrode is made of Xi Om acrylic and has an area of 110X.
It is made of 30mm steel.

The humidity dependence was confirmed by filling the prepared surface-treated carrier and untreated ferrite carrier into the cells used above, and controlling the humidity to 404,601°80%.
This was done by determining the electrical resistance value after each sample was left in a box for 24 hours.

FIG. 2 shows the changes in electrical resistance of the surface-treated carrier and the untreated carrier at various humidity levels. Here, the solid line indicates the surface-treated carrier, and the chain line indicates the untreated ferrite carrier.

Further, ◯ indicates A1, ■ indicates A2, Δ indicates black 3, Δ indicates black 4, and M indicates surface treated carrier prepared using black 5.

From this figure, it can be seen that the surface-treated carriers made with Black 1 and Black 2 have almost no change in resistance due to humidity compared to untreated ferrite carriers and surface-treated carriers according to Gen. 3.4.5. Wax Example 2 /F, Surface treated carrier prepared in 1 and toner (average particle size 12.57 ttm + specific surface area 4200 crn"/
l, made by Tomoesha) to create a developer, and! When the toner specific charge was determined using a low-off charge measurement device, it was -16.
It was 4μa/fi. Here, the toner concentration is the above (5
) is set to the value calculated by the formula.

Next, use this developer in a plain paper copying machine (Mitasha,!l)
When copying was carried out using DC-211), a good image was obtained under R-H40. Further, even when the width was R-H80, a good image was obtained with no increase in image density and no capri.

Example 3 A developer was prepared in the same manner as in Example 2 using the surface-treated carrier prepared in Coffin 2, and a copying test was conducted. The specific charge of the toner at the time of developer preparation was -14.9 μc/g, and R-
Clear images with no capri were obtained under H80%.

Example 4 /Example 2 using the surface treatment medium prepared in I64
When I made a developer in the same way as above and conducted a copying test, I found that
At 80% R-H, the image density increased significantly, the image was unclear, and copies with many capri were obtained. Example 5 A developer was prepared in the same manner as in Example 2 using an untreated ferrite carrier, and a copy test When I did this, R-a4
At below 0%, a clear image was obtained, but at R-I (80%), the image was blurred with many capri.

[Brief explanation of drawings]

Figure 1 is a scanning electron micrograph (X2000) showing the surface structure of spherical sintered ferrite particles suitably used in the present invention.
It is. FIG. 2 is a graph showing the humidity dependence of ferrite carriers (surface treated and untreated).

Claims (1)

[Claims] (1) In a two-component developer for electrophotography consisting of a magnetic carrier and electrostatic toner, the two-component developer has a magnetic carrier having the following general formula, ▲mathematical formula, chemical formula, table, etc.▼ In the formula , R_1 to R_3 are an alkyl group or an aryl group, and each of these may be the same group. X represents halogen. n is a number from 0 to 2. A two-component developer for electrophotography, characterized by comprising ferrite particles surface-treated with a quaternary ammonium salt represented by: