JP2001125302A - Developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developer having stable electrostatic chargeability independently of an environmental change and capable of forming a clear image. SOLUTION: The developer contains rutile/anatase mixed crystal type titanium dioxide having 1×107-1×109 Ω.cm volume resistivity made hydrophobic by treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used in an image forming apparatus such as an electrophotographic apparatus, and more particularly to a developer suitable for forming a full-color image.

[0002]

2. Description of the Related Art Generally, silica is added to improve the fluidity of toner. However, since silica itself has a charging performance, when added in a large amount, the fluidity is improved, but the charging amount may be too high. Therefore, an image having a sufficient density cannot be obtained with this toner.

There is also a method in which silica is used in combination with silica having the opposite polarity. However, the amount of charge of each toner becomes non-uniform, which causes problems such as fog. Therefore, if the charge amount and the fluidity can be controlled by different materials, the fluidity can be improved and a toner having an appropriate charge amount can be obtained.

[0004] To achieve this, titanium oxide has been used as a material that does not significantly affect the charge amount and dramatically improves the fluidity. The crystal structures of titanium oxide include anatase type and rutile type. Since rutile-type titanium oxide has low surface activity and does not sufficiently hydrophobize the surface, titanium oxide having an anatase-type crystal structure has been used.

[0005] Titanium oxide having an anatase-type crystal structure shows good fluidity, but its volume resistivity is low, although it varies slightly depending on the surface treatment method. For this reason, the charge amount tends to change due to environmental changes such as temperature and humidity. For this reason, it is necessary to change the conditions in the copying machine main body depending on the environment, and a temperature / humidity sensor or the like is required in the copying machine main body, and control becomes complicated. However, attaching such a temperature and humidity sensor leads to an increase in cost. on the other hand,
Rutile-type titanium oxide, which is another crystal structure of titanium oxide, has a high volume resistivity and a small change in the amount of charge due to the environment, but has a lower ability to improve fluidity as compared with anatase-type titanium oxide.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a developer capable of forming a clear image having a stable chargeability with respect to environmental changes. Is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention firstly provides a colorant, a binder resin, and 1 × 10 ⁷ to 1 × 10
Provided is a developer containing a hydrophobically treated rutile / anatase mixed crystal type titanium oxide having a volume resistivity of ⁹ (Ω · cm).

[0008] Second, the present invention provides a colorant having an acid value of 15 or less.
Lower binder resin, and 1 × 10 ⁷Or 1 × 10
⁹(Ω · cm) hydrophobized treatment with volume resistivity
Containing mixed rutile / anatase titanium oxide
And a developer characterized by the following.

Thirdly, the present invention provides a colorant, a binder resin, a wax having an acid value of 20 or less, and a hydrophobizing treatment having a volume resistivity of 1 × 10 ⁷ to 1 × 10 ⁹ (Ω · cm). Provided is a developer containing the mixed rutile / anatase titanium oxide.

[0010] Fourth, the present invention relates to a hydrophobized rutile / anatase mixed crystal type oxidation having a volume resistivity of 1 × 10 ⁷ to 1 × 10 ⁹ (Ω · cm). Provided is a developer containing titanium and a zirconia metal complex.

Fifth, the present invention provides a coloring agent, a binder resin having an acid value of 15 or less, a wax having an acid value of 20 or less, 1 ×
Provided is a developer characterized by containing a hydrophobized rutile / anatase mixed crystal titanium oxide having a volume resistivity of 10 ⁷ to 1 × 10 ⁹ (Ω · cm) and a zirconia metal complex. .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developer of the present invention contains a colorant and
1 × 10 ⁷Or 1
× 10⁹(Ω · cm) with a specific volume resistivity
Added treated rutile / anatase mixed crystal type titanium oxide
Have been.

According to the present invention, titanium oxide having an anatase-type crystal structure exhibiting good fluidity, and having a high volume resistivity and a small change in the amount of charge due to the environment, By using a mixed crystal type titanium oxide with rutile type titanium oxide with low ability to improve fluidity within a range that maintains a predetermined volume resistance value, it has good fluidity against environmental changes. As a result, a developer having little change in chargeability can be obtained. By using such a developer, a good image can be formed without causing toner scattering or fogging.

In the developer of the present invention, a binder resin having an acid value of 15 or less is preferably used as the binder resin. By using such a binder resin, charging characteristics and image characteristics are improved.

The developer of the present invention preferably comprises
A wax having an acid value of 20 or less is further added. By using such a wax, the fixing property is further improved.

Further, a zirconia metal complex represented by the following general formula (1) is preferably further added to the developer of the present invention. By using such a charge controlling agent, a developer having more stable charging characteristics can be obtained.

[0017]

Embedded image

[0018]

The present invention will be described below in detail with reference to examples.

Example 1 and Comparative Examples 1 to 5 A toner was produced as follows.

4% by weight of a coloring agent is mixed with 100% by weight of a binder resin and melt-kneaded.
To obtain toner particles. 1% by weight of silica and 1% by weight of titanium oxide were externally added to the obtained toner particles to obtain a toner.

Here, as the titanium oxide to be used, various titanium oxides having different ratios of the anatase type crystal structure and the rutile type crystal structure were prepared as shown in Table 1 below.

The obtained developer was tested and evaluated as follows. The volume resistivity of titanium oxide was measured with a powder resistance measurement system manufactured by Mitsubishi Chemical Corporation and Hirester UP.

Environmental characteristics are low temperature and low humidity (10 ° C., 20% R
The charge amount under H) was divided by the charge amount under high temperature and high humidity (30 ° C., 85% RH).

The charge amount change rate was a value obtained by dividing the charge amount after passing 30K sheets by the charge amount before passing.

The fluidity was measured with a powder tester.

The image characteristics and fog were measured by Toshiba copier IMAG.
Images were formed with E MASTER 3850 and evaluated.

The toner scattering was evaluated by observing stains in the copying machine after passing 30K sheets. From the results of these measurements, the level at which there was no problem with use was O, the level that could be used somehow was Δ, and the level that could not be used was X. Table 1 below
The results obtained when the type of titanium oxide was changed are shown below.

[0028]

[Table 1]

As apparent from Table 1, the toner of Example 1 in which the resistance value of titanium oxide is in the range of 1 × 10 ⁷ to 1 × 10 ⁹ (Ω · cm) has an environmental characteristic of 1.2 or less. became. At this time, all the characteristics such as the image characteristics were dramatically improved. If the toner has environmental characteristics of 1.2 or less, there is no need to control the copier body using a temperature / humidity sensor or the like.

On the other hand, the toner of Comparative Example 1 to which only titanium oxide of the anatase type was externally added, because the resistance value of the titanium oxide alone was low, toner scattering was poor and fog was not so good. Was also bad. The environmental characteristics were also 1.53, and it was found that the amount of charge greatly changed depending on the environment, resulting in a deterioration in image characteristics.

Further, in the toner of Comparative Example 4 in which only rutile type titanium oxide was externally added, the resistance value of titanium oxide alone was high and the environmental characteristics were good, but the image characteristics and toner scattering were poor due to lack of fluidity. Bad, fog was not so good.

Comparative Examples 2 and 3 are toners in which the ratio of rutile-type and anatase-type titanium oxides is changed from that of Example 1, but the ratio of rutile-type titanium oxide is increased and the oxidation rate is increased. As a result, the resistance value of titanium was increased, and the environmental characteristics were also improved. The resistance value of the acid value titanium was less than 1 × 10 ⁷ (Ω · cm), and the toner of Comparative Example 2 still had insufficient environmental characteristics, and also had insufficient image characteristics and toner scattering. .

On the other hand, the resistance value of the titanium oxide in the toner of Comparative Example 3 exceed ^{1 × 10 9 (Ω · cm} ), although environmental properties is good, flowability deteriorates, deteriorating the image characteristics and toner scattering The result was.

In Comparative Example 5, a toner to which no titanium oxide was added was evaluated, but none of the evaluation items was satisfied.

From the above results, 1 × 10 ⁷ to 1 × 1
It was found that a toner satisfying all the characteristics can be obtained by adding a rutile / anatase mixed crystal type titanium oxide having a volume resistivity of ⁰⁹ (Ω · cm).

Examples 2 and 3 and Comparative Examples 6 to 8 Next, similar evaluations were made on toners using the titanium oxide used in Example 1 and changing the acid value of the binder resin as shown in Table 2 below. went. Table 2 shows the results.
Table 2 also shows Example 1.

[0037]

[Table 2]

As is clear from Table 2, in Examples 1 to 3, the acid value of the binder resin was 15 or less.
All properties were satisfied. However, Comparative Examples 6 to 8
In, the acid value of the binder resin is 20 or more,
It was found that as the acid value of the binder resin increased, all properties tended to deteriorate.

From this, 1 × 10 ⁷ to 1 × 10 ⁹ (Ω
When a rutile / anatase mixed crystal type titanium oxide having a volume resistivity of (cm) is used as an external additive and a binder resin having an acid value of 15 or less, preferably 10 or less, a toner satisfying all the characteristics is obtained. I found that I could get it.

Examples 4 to 6 In general, a wax can be added to the base of the toner in order to improve the fixability of the toner. The acid value of the wax is a factor that greatly affects the charge amount and the like. Therefore, the acid value was variously changed as shown in Table 3 below, and the same evaluation was performed. At this time, the same coloring material, titanium oxide and binder resin as in Example 1 were used. Table 3 shows the results.

[0041]

[Table 3]

As is apparent from Table 3, in Examples 4 to 6, the acid value of the wax was 20 or less, and all the properties were satisfied. However, in Comparative Examples 9 to 11, it was found that the acid value of the wax was 25 or more, and that all the properties tended to deteriorate as the acid value of the wax increased.

From this, 1 × 10 ⁷ to 1 × 10 ⁹ (Ω
The fixability is good by using a rutile / anatase mixed crystal type titanium oxide having a volume resistivity of (cm) as an external additive and using a wax having an acid value of 20 or less, preferably 15 or less, It was found that a toner satisfying all characteristics could be obtained.

Further, a charge control material (CCA) can be added to the toner particles to further stabilize the charging characteristics. In order to show different charging characteristics depending on the type of CCA, the same evaluation was performed by variously changing the type of CCA. At this time, the same titanium oxide and binder resin as in Example 1 were used. Table 4 shows the results.

[0045]

[Table 4]

As apparent from Table 4, in Comparative Examples 12 and 13, the zinc complex and the boron complex were used for CCA, respectively, but it was found that the environmental characteristics, image characteristics, and toner scattering tended to deteriorate. On the other hand, it was found that Example 7 using the zirconia complex for CCA satisfied all the characteristics, and the charge amount change rate was slightly improved.

From this, 1 × 10 ⁷ to 1 × 10 ⁹ (Ω
(Cm) Improve charging characteristics while maintaining image characteristics and the like by using rutile / anatase mixed crystal type titanium oxide having a specific volume resistivity of 4 cm as an external additive and using a zirconia complex as CCA. It was found that a toner could be obtained.

[0048]

The developer of the present invention has a concentration of 1 × 10 ⁷ to 1
The use of a hydrophobized rutile / anatase mixed crystal type titanium oxide having a volume resistivity of × 10 ⁹ (Ω · cm) provides a stable chargeability against environmental changes and a sharp An image can be formed.

Also, by using a binder resin having an acid value of 15 or less in combination with the developer of the present invention, charging characteristics and image characteristics are improved.

Further, by using a wax having an acid value of 20 or less in combination with the developer of the present invention, the fixing property is further improved.

Further, by using a zirconia metal complex in combination with the developer of the present invention, more stable charging characteristics can be obtained.

Claims (5)

[Claims] 1. A colorant, a binder resin, and 1 × 10
A developer containing a hydrophobized rutile / anatase mixed crystal type titanium oxide having a volume resistivity of ⁷ to 1 × 10 ⁹ (Ω · cm). 2. A colorant, a binder resin having an acid value of 15 or less, and a hydrophobized rutile / anatase mixed crystal having a volume resistivity of 1 × 10 ⁷ to 1 × 10 ⁹ (Ω · cm). A developer containing titanium oxide. 3. A coloring material, a binder resin, a wax having an acid value of 20 or less, and 1 × 10 ⁷ to 1 × 10 ⁹ (Ω · c).
m) a developer containing a hydrophobized rutile / anatase mixed crystal type titanium oxide having a specific volume resistivity of m). 4. A coloring material, a binder resin, a rutile / anatase mixed crystal titanium oxide having a volume resistivity of 1 × 10 ⁷ to 1 × 10 ⁹ (Ω · cm), and a zirconia metal complex. A developer comprising: 5. A coloring material, a binder resin having an acid value of 15 or less, a wax having an acid value of 20 or less, 1 × 10 ⁷ to 1 ×.
A developer containing a hydrophobically treated rutile / anatase mixed crystal titanium oxide having a volume resistivity of 10 ⁹ (Ω · cm) and a zirconia metal complex.