JP2887713B2 - Electrostatic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for electrostatic charge development, and more particularly to a conductive toner for electrostatic charge development containing magnetic powder.

[0002]

2. Description of the Related Art Generally, in electrophotography, an electric latent image is formed on a photoreceptor, and the latent image is developed with toner.
After transferring the toner image to a transfer material such as paper as necessary,
The image is fixed by means such as heat and pressure to obtain a copy. As a developer used in such an electrophotographic method, there are a two-component developer including a toner and a carrier, and a one-component developer having both functions of a toner and a carrier. The one-component developer includes a magnetic one-component developer and a non-magnetic one-component developer. Among them, a magnetic toner containing 30 to 70% by weight of a magnetic powder is usually used as the magnetic one-component developer. . Magnetic toners are classified into conductive magnetic toners and insulating magnetic toners. The former is provided with charge by electrostatic induction or charge injection, and the latter is provided with charge by frictional charging and is developed into an electrostatic latent image.

It is known that the one-component developing method using a conductive magnetic toner has an advantage that a uniform image without an edge effect can be obtained because the conductive magnetic toner itself serves as a developing electrode. However, the conductive magnetic toner has a drawback that the charge of the toner easily leaks through the transfer paper at the time of electrostatic transfer, and it is difficult to transfer the toner to plain paper. Further, since only one layer of toner particles is developed on the photoreceptor, there is a disadvantage that it is difficult to secure image density. Conventionally, in order to solve these problems, means using special paper subjected to a high resistance treatment or adopting a pressure transfer method using a rubber roller has been used. However, using these measures is not yet satisfactory.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art and provides a toner for electrostatic charge development having good transferability while maintaining good developability of a conductive magnetic toner. The purpose is to provide.

[0005]

SUMMARY OF THE INVENTION The present invention provides a method for producing Fe ₃ O ₄ .
0.1 to 5 parts by weight of a charge controlling agent is fixed to the surface of the toner particles based on 100 parts by weight of the toner particles containing the magnetic powder having a content of 98% or more , and the volume resistivity is Is 1 × 10 ³ to 1 × 10 ⁵ Ω · cm.

Hereinafter, the present invention will be described in detail. The toner particles constituting the toner for electrostatic charge development of the present invention include a magnetic powder, a binder resin, a charge controlling agent such as a metal dye of a monoazo dye or a nigrosine dye as needed, and a coloring agent such as carbon black. After kneading well with a heat kneader such as a kneader, an extruder or the like, the particles are mechanically pulverized and classified into particles having a volume average particle diameter of 4 to 12 μm, preferably 4 to 9 μm. In this case, the smaller the volume average particle diameter of the toner particles, the better the developability. However, if the volume average particle diameter is 4 μm or less, the transferability is poor, the flowability is poor, and the transportability on the magnet sleeve is poor. Inferior. On the other hand, when the thickness is 12 μm or more, the developability is insufficient,
This is not preferable because the image quality of lines and characters deteriorates.

In the present invention, the binder resin used for the toner particles is polystyrene, polyethylene, polypropylene, vinyl resin, polyacrylate, polymethacrylate, polyvinylidene chloride, polyacrylonitrile, polyether, polycarbonate, thermoplastic polyester, In addition to thermoplastic resins such as thermoplastic epoxy resins, cellulosic resins and copolymer resins of these monomers, thermosetting resins such as modified acrylic resins, phenol resins, melamine resins, and urea resins can be used. In particular, the binder resin used in the present invention has a melt viscosity at a measurement temperature of 100 ° C. of 5.0 × 10 ^{4 to} 1.0 × 10 ⁶ POI.
It is desirable to be in the range of SE. Melt viscosity is 5.0 ×
If it is less than 10 ⁴ POISE, problems such as filming on the photoreceptor are likely to occur, while 1.0 × 10 ⁶ POISE
If it is larger than ISE, mechanical addition during melt-kneading becomes too large, which may cause a problem in productivity.
As the magnetic powder, spinel, perovskite, hexagonal, garnet, ferrite having an orthoferrite structure, magnetite, etc. are applied crystallographically. The structure of the ferrite used in the present invention is nickel, zinc,
It is a sintered body of an oxide such as manganese, magnesium, copper, lithium, barium, vanadium, chromium, and calcium, and a trivalent iron oxide. The saturation magnetization of the magnetic powder is 10
Preferably, it is 40 emu / g. 10 emu / g
If it is less than 3, the magnetic attraction force to the magnet roller is insufficient, and the toner transportability is deteriorated. On the other hand, 40 emu
/ G, the dispersibility of the magnetic powder in the toner particles is deteriorated, and poor charging of the toner particles is liable to occur, which impairs the transferability, and further, the adsorbing force to the magnet roller is too strong, resulting in poor developability. Is not preferred.

The present invention is characterized in that 0.1 to 5 parts by weight of a charge controlling agent is fixed to 100 parts by weight of the toner particles obtained by the above operation in order to improve the developing property and the transferring property. And Here, the fixation means that the toner particles and the charge controlling agent are mixed in advance using a stirring mixer such as a turbine-type stirrer, a super mixer, a Henschel mixer, and the obtained mixed powder is added to the surface of the powder. Apply to a reformer (Nara Machine Co., Ltd. Nara Hybridizer, Hosokawa Micron Co., Ltd. Ongmill, etc.) and apply compression and frictional force to the fine particles mixed and attached to the toner particles, and the melting point of the toner particles or more Means that the charge control agent is firmly fixed to the surface of the toner particles by utilizing the heat generated instantaneously. In this case, the fixation includes a state where a part and the whole of the charge control agent is buried in the surface of the toner particles.
As the charge control agent used in the present invention, those used for ordinary insulating toners can be used, but from the viewpoint of easiness of fixing operation, those having a volume average particle diameter of 5 μm or less are desirable. Commercially available products include the following. For example, in the case of an azo chromium complex salt, T-9 manufactured by Hodogaya Chemical Co., Ltd.
5, T-4-48, S-44, S manufactured by Orient Chemical Co.
-81 and the like. In addition, T-77 manufactured by Hodogaya Chemical Co., Ltd., Nigrosine EX manufactured by Orient Chemical Co., Ltd. for a nigrosine dye, and Bontron P-51 manufactured by Orient Chemical Co., Ltd. for a quaternary ammonium salt.
Is mentioned. The amount of the charge control agent fixed to the toner particles of the present invention is 0.1 to 5 parts by weight based on 100 parts by weight of the toner particles. If the amount is less than 0.1 part by weight, the triboelectrification by the charge control agent is insufficient. Therefore, a sufficient charge amount cannot be obtained, and good developability and transferability cannot be obtained. On the other hand, when the amount exceeds 5 parts by weight, the amount of the charge control agent is excessive, and the conductivity of the toner particle surface is impaired, and the developability is deteriorated.

Next, in the present invention, the volume resistivity of the toner for electrostatic charge development must be in the range of 1 × 10 ³ to 1 × 10 ⁶ Ω · cm. Volume specific resistivity is 1 × 10 ³ Ω
If it is less than cm, the charge once injected into the toner for electrostatic charge development during development tends to leak, so that not only sufficient developability is not obtained but also good transferability is not ensured. On the other hand, when the volume resistivity exceeds 1 × 10 ⁶ Ω · cm, sufficient charge injection is not performed, and the developability is not satisfied. As a means for reducing the resistance of such toner particles, basically, a magnetic powder having a low specific volume resistivity is contained. As the magnetic powder having a low volume specific resistivity, a magnetic powder having a Fe ₃ O ₄ content of 98% or more can be suitably used. Further, it is desirable that carbon black having a low volume resistivity is contained simultaneously with the magnetic powder. As the carbon black having a low volume specific resistivity, a carbon black having a specific surface area of 900 m ² / g or more can be suitably used. It is also effective to fix carbon black or other conductive fine particles (hereinafter referred to as conductive fine particles) on the surface of the toner particles in order to adjust the volume resistivity. The means of fixing is the same as the case of the charge control agent, and the timing of the fixing operation of the conductive fine particles is simultaneous with the charge control agent,
Alternatively, a method in which the charge control agent is fixed after fixing the conductive fine particles first may be used.

As the conductive fine particles used in the present invention, for example, carbon black having a volume resistivity of 30 Ω · cm or less is desirable, and can be used without any limitation on the number average particle diameter, oil absorption, PH and the like. However, commercially available products include the following. For example, CSX-99 (7.4 Ω · cm) manufactured by Cabot Corporation, Vulcan XC-
72 (12.4 Ωcm) , Ketchin Black EC (17.5 Ωcm) manufactured by Lion Akzo, # 4500 (16.9 Ωcm) manufactured by Tokai Carbon Co., # 5500
(14.8Ω · cm) , # 2555 (26.1Ω · c)
m) , # 3855 (14.5 Ω · cm) , Denka Black (28.6 Ω · cm) manufactured by Denki Kagaku, and # 2400B (27.1 Ω · cm) manufactured by Mitsubishi Kasei Corporation.
These carbon blacks can be used alone or in various combinations of two or more. The specific volume resistivity in the present invention is determined by measuring a toner sample between an upper electrode and a lower electrode provided in a cylinder by 200 g / c.
It is obtained by loading so as to apply a stress of m ² , applying a voltage of 2 V, and measuring the resistance value between the electrodes with a tester.

[0011]

In the present invention, the fixation of the charge control agent causes
In addition to charging by charge injection due to the inherent conductivity of the toner for electrostatic charge development, frictional charging by a charge control agent is added to ensure good developability on the photoreceptor, and in the process of transferring to paper etc. Good transferability is ensured by the charge of the charge control agent.

[0012]

Embodiments of the present invention will be described below. Example 1 Polyester resin (HP-32 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
0 Melt viscosity at 100 ° C. is 2.6 × 10 ⁵ POI
SE) 65 parts by weight magnetite (Kanto Denka Kogyo K
BI-20V, the content of _{Fe 3 O 4; 99.5%)} 25
10 parts by weight of carbon black (Ketchin EC manufactured by Lion Akzo) 10 parts by weight After mixing the above materials, melt-kneading,
The mixture was pulverized with a jet mill to obtain toner particles A having a volume average particle diameter of 8.5 μm. The saturation magnetization of the toner particles A was measured and found to be 19 emu / g. The volume resistivity was measured to be 2.0 × 10 ⁸ = Ω · cm. Next, carbon black (CSX-99, manufactured by Cabot Corporation) was added to 100 parts by weight of the toner particles A.
5 parts by weight and an azo chromium complex salt (T
Using a Henschel mixer with a capacity of 10 liters, 0.25 parts by weight of -95 (volume average particle diameter 2.0 μm) was stirred under the conditions of a rotation speed of 2500 rpm and a processing time of 1.5 minutes to obtain a mixed powder. . Next, using a hybridizer (NHS-1 type, manufactured by Nara Machinery Co., Ltd.), the carbon black and the charge control agent were fixed to the surface of the toner particles A at a rotation speed of 6400 rpm and a processing time of 3 minutes. Thus, an electrostatic charge developing toner of the present invention was obtained. When the volume resistivity of the toner for electrostatic charge development was measured, it was 7 × 10 ³ Ω ·
cm.

Example 2 1.5 parts by weight of carbon black (CSX-99 manufactured by Cabot Corporation) and azo chromium complex salt (T-95 manufactured by Orient Chemical Co., Ltd.) were used based on 100 parts by weight of the toner particles A of Example 1.
(Volume average particle diameter: 2.0 μm) and 1.0 part by weight were mixed and fixed in the same manner as in Example 1 to obtain a toner for electrostatic charge development of the present invention. The volume specific resistivity of the toner for electrostatic charge development was measured to be 9 × 10 ³ Ω · cm.

Example 3 To 100 parts by weight of the toner particles A of Example 1, 1.5 parts by weight of carbon black (CSX-99 manufactured by Cabot) and an azo chromium complex salt (T-95 manufactured by Orient Chemical Co., Ltd.)
4.5 parts by weight (volume average particle size: 2.0 μm) were mixed and fixed in the same manner as in Example 1 to obtain a toner for electrostatic charge development of the present invention. The volume specific resistivity of the toner for electrostatic charge development was 5 × 10 ⁴ Ω · cm.

Example 4 The same ingredients as in Example 1 were mixed, melt-kneaded, and pulverized to obtain toner particles B having a volume average particle diameter of 11.5 μm. Next, carbon black (CSX-99 manufactured by Cabot Corporation) was added to 100 parts by weight of the toner particles B in an amount of 1.0%.
Parts by weight and an azo-based chromium complex (T-manufactured by Orient Chemical Co., Ltd.)
95 volume average particle diameter 2.0 μm) and 1.0 part by weight were mixed and fixed in the same manner as in Example 1 to obtain a toner for electrostatic charge development of the present invention. The volume specific resistivity of the electrostatic charge developing toner was measured to be 8 × 10 ³ Ω · cm.

Example 5 The same compounding materials as in Example 1 were mixed, melt-kneaded, and pulverized to obtain toner particles C having a volume average particle diameter of 5.0 μm. Next, 3.5 parts of carbon black (CSX-99 manufactured by Cabot Corporation) was added to 100 parts by weight of the toner particles C.
Parts by weight and an azo-based chromium complex (T-manufactured by Orient Chemical Co., Ltd.)
95 volume average particle diameter of 2.0 μm) and 2.0 parts by weight were mixed and fixed in the same manner as in Example 1 to obtain a toner for electrostatic charge development of the present invention. The volume specific resistivity of the electrostatic charge developing toner was measured to be 7.5 × 10 ³ Ω · cm.

Comparative Example 1 The toner particles A used in Example 1 were used as a comparative electrostatic charge developing toner. The volume specific resistivity of the toner for electrostatic charge development was measured to be 2.0 × 10 ⁸ Ω · cm.

Comparative Example 2 The toner particles B used in Example 4 were used as a comparative electrostatic charge developing toner. The volume specific resistivity of the electrostatic charge developing toner was measured to be 8.0 × 10 ⁷ Ω · cm.

Comparative Example 3 The toner particles C used in Example 5 were used as a comparative electrostatic charge developing toner. The volume specific resistivity of the toner for electrostatic charge development was measured to be 3.5 × 10 ⁹ Ω · cm.

Comparative Example 4 To the toner particles B used in Example 4, 1.0 part by weight of carbon black (CSX-99 manufactured by Cabot Corporation) was mixed, and the same fixing treatment as in Example 1 was performed. A comparative electrostatic charge developing toner having a specific resistivity of 5 × 10 ³ Ω · cm was obtained.

Comparative Example 5 To the toner particles B used in Example 4, 1.0 part by weight of carbon black (CSX-99 manufactured by Cabot) and an azo chromium complex salt (T-95 manufactured by Orient Chemical Co., Ltd.)
(Volume average particle size: 2.0 μm) and 7.0 parts by weight, and then subjected to the same fixing treatment as in Example 1 to give a volume specific resistivity of 3.0 × 10 ⁷ Ω · cm for comparison. An electrostatic charge developing toner was obtained.

Comparative Example 6 In Example 1, the magnetic powder was EPT-1 manufactured by Toda Kogyo KK
000 (Fe ₃ O ₄ content: 96.5%)
A toner having a volume average particle diameter of 8.3 μm
Particle D was obtained. When the saturation magnetization of the toner particles D was measured.
At that time, it was 20 emu / g. Also, the volume resistivity
Was 5.0 × 10 ⁹ Ω · cm. Next
On the surface of the toner particles D, the same carbon
Fix black and azo chromium complex under the same conditions and compare
To obtain an electrostatic charge developing toner. The toner for electrostatic charge development
When the specific volume resistivity was measured, 5 × 10 ⁵ Ω · c
m. Table 1 summarizes the measurement results of the physical properties of the toners for electrostatic charge development obtained in Examples 1 to 5 and Comparative Examples 1 to 6 .

[Table 1]

Next, the above Examples 1 to 5 and Comparative Examples 1 to 5
Using the electrostatic charge developing toner obtained in Step 6 , the surface potential was set to 20
Continuous copying was performed up to 5,000 sheets with a copier of the one-component developing system set at 0 V. The evaluation results are shown in Table 2.

[Table 2]

In Table 2, the transfer efficiency is defined as the ratio of the weight Md of the developed toner on the photoreceptor in a solid black pattern (50 mm × 200 mm) to the weight Mt of the toner transferred to plain paper in the same pattern. (Mt / Md) × 100%. Further, the toner scattering was determined by visually inspecting the inside of the developing device around the developing device after the toner was thrown into the developing device for 30 minutes, based on the following evaluation criteria. ：: No toner scattering. Δ: The toner was scattered at the lower part of the developing device. X: The toner was scattered over the entire upper and lower portions of the developing device. The image density during development (ID) is determined by developing the electrostatic charge developing toner on the photoreceptor using the solid black pattern and peeling off the electrostatic charge developing toner on the photoreceptor with a transparent adhesive tape. Then, the transparent adhesive tape was attached to plain paper, and the image density of the toner for electrostatic charge development was measured with a reflection type image densitometer RD-914 manufactured by Macbeth. The image density (ID) at the time of fixing is determined by developing the above solid black pattern,
Transfer and fix to plain paper, Macbeth reflection image densitometer R
The image density was measured on D-914. Fog was measured by measuring the difference in whiteness of the transfer paper before and after copying with a Hunter color difference meter manufactured by Nippon Denshoku Co., Ltd. According to this, the toner for electrostatic charge development of the present invention has a transfer efficiency of 80% or more in both the initial characteristics and the characteristics after 5,000 copies, has a satisfactory image density, and has good results without any problem of fog and toner scattering. I got it. On the other hand, the electrostatic charge developing toner of the comparative example has a lower image density and transfer efficiency than the initial stage, and fog and toner scattering are poor.
It was confirmed that it would cause problems in practical use.

[0025]

According to the present invention, developability, that is, sufficient image density can be maintained and good transferability which has not been possible in the past, can be obtained while being a conductive magnetic toner.
Therefore, it is possible to provide an electrostatic charge developing toner free from fogging and toner scattering.

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein 100 parts by weight of toner particles containing a magnetic powder having a Fe ₃ O ₄ content of 98% or more .
0.1 to 5 parts by weight of a charge controlling agent is fixed to the surface of the toner particles, and has a volume specific resistivity of 1 × 10 ³ to 1 ×.
An electrostatic charge developing toner having a resistivity of 10 ⁵ Ω · cm. 2. The toner according to claim 1, wherein the volume specific resistivity is 3 on the surface of the toner particles.
2. The electrostatic charge developing toner according to claim 1, wherein carbon black of 0 Ω · cm or less is fixed.