JP2640298B2 - 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.
If necessary, the toner image is transferred onto a transfer material such as paper, and then fixed by means such as heating and pressing to obtain a copy. As a developer used in such an electrophotographic method, there are a two-component developer composed of a toner and a carrier and a one-component developer having the functions of a toner and a carrier at the same time.

The one-component developer includes a magnetic one-component developer and a non-magnetic one-component developer. Among them, a magnetic toner containing about 30 to 70% by weight of a magnetic powder is 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 developed into an electrostatic latent image.

It is known that a 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 disadvantage that the charge of the toner easily leaks through the transfer paper during the 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.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a toner for electrostatic charge development which has good transferability and provides a sufficient image density. .

[0008]

According to the present invention, there is provided a method for producing a magnetic powder comprising 30 powders.
The toner particles 100 parts by weight comprising 70% by weight, Ri carbon black the name adheres 0.5 to 10.0 parts by weight 0.2 to 2.0 part by weight of the resin particles,該樹
In the relationship between the applied temperature and the melt viscosity, the fat particles have (a) 8
3 × 10 ⁶ POISE at 5 ° C. , (b) 120 ° C.
5 × 10 ⁴ POISE, (c) 5 × 1 at 205 ° C.
0 ⁴ POISE, (d) 170 ℃ 3 × ¹⁰ 6 PO when
Points given by ISE (a), (b), (c), (d)
Are characterized by having a melt viscosity characteristic in a region connecting a straight line to the toner.

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, particles having an average particle diameter of 4 to 20 μm are obtained by mechanical pulverization and classification.

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, or thermoplastic polyester. Thermosetting resins such as a modified epoxy resin, a phenol resin, a melamine resin, and a urea resin can be used in addition to thermoplastic resins such as a plastic epoxy resin, a cellulose resin, and a copolymer resin of these monomers. Further, as the magnetic powder, spinel, perovskite, hexagonal, garnet, ferrite having an orthoferrite structure, magnetite, or the like is applied crystallographically. The structure of ferrite is a sintered body of an oxide such as nickel, zinc, manganese, magnesium, copper, lithium, barium, vanadium, chromium, calcium and a trivalent iron oxide.

Next, in the present invention, the toner particles 100
After 0.2 to 2.0 parts by weight of carbon black is mixed and adhered to the surface of the toner particles, 0.5 to 10.0 parts by weight of resin particles are additionally mixed and adhered to the surface of the toner particles. As the mixing means, a stirring mixer such as a turbine type mixer, a super mixer, a Henschel mixer or the like is preferably used. In addition, a mixer called a surface reforming machine such as a Nara Hybridization System manufactured by Nara Machinery Co., Ltd. or an Angmill manufactured by Hosokawa Micron Corporation may be used. The present invention imparts the conductivity required for development as a toner for electrostatic charge development by attaching carbon black to the toner particles, and partially adds the resin particles to the toner particles to partially modify the surface of the toner particles. It is an insulating material and imparts good transferability to the toner for electrostatic charge development.

In the present invention, the carbon black adhered to the surface of the toner particles can be used without any limitation on the number average particle diameter, oil absorption, pH and the like, and the following are commercially available products. For example, Cabot's Regal 400R, 660R, 330R, CSX
-99, Raven made by Columbia Carbon (RAVE
N) 410, 420, 430, 450, # 40, # 2400B, MA-100, manufactured by Mitsubishi Kasei Kogyo Co., Ltd., and Denka Black, manufactured by Denki Kagaku. These carbon blacks can be used alone or in combination of two or more kinds in various compositions.

The resin particles include thermoplastic resins such as styrene-acryl copolymer resin, styrene-butyl acrylate copolymer resin, polyester resin and low molecular weight polypropylene, epoxy resin, phenol resin, melamine resin, benzoguanamine resin and the like. Thermosetting resin particles, silicone resin particles, tetrafluoroethylene powder, condensed compound particles of urea and formaldehyde, nylon resin particles, and the like can be given. The melt viscosity characteristics of the resin particles according to the present invention as measured by an elevated flow tester are shown in FIG. 1 in terms of the relationship between the applied temperature and the melt viscosity, as shown in (a) 3 × 10 ⁶ POISE at 85 ° C.
(B) 5 × 10 ⁴ POISE at 120 ° C., (c) 2
A point given by 5 × 10 ⁴ POISE at 05 ° C. and 3 × 10 ⁶ POISE at (d) 170 ° C.
It is necessary to have the melt viscosity characteristic in the region connecting (b), (c) and (d) with a straight line, that is, in the region A. The reason is that the resin particles in the region B having a higher melt viscosity characteristic than the region A have a high melt viscosity and thus are difficult to adhere to the toner particles.
This is because the resin particles in the region have strong cohesiveness, so that the aggregates of the resin particles increase, the dispersion state of the resin particles in the toner particles is poor, and the resin particles hardly adhere uniformly to the surface of the toner particles.

In the toner for developing electrostatic charge of the present invention, ears are formed on the developing sleeve by a magnet roller.
Therefore, the magnetic powder contained in the toner particles needs to be 30 to 70% by weight. When the amount is less than 30% by weight, the magnetic force of the toner for electrostatic charge development becomes small, so that the transportability becomes poor. If the amount exceeds 70% by weight, not only is it difficult to disperse the magnetic powder in the binder resin, but also the amount of the conductive material such as carbon black is reduced, so that the conductivity is secured. Becomes difficult.

The resin particles used in the present invention preferably have an average particle diameter of 0.1 to 1.0 μm. When the particle size is smaller than 0.1 μm, not only the primary particles have strong cohesiveness but it is difficult to uniformly disperse and adhere to the toner particle surface, but also as a result of poor dispersion, the resin particles have a size equal to or larger than the toner particles. The toner particles remain as secondary aggregates, and toner aggregates are generated, which causes image defects. On the other hand, when the primary particles of the resin particles are larger than 1.0 μm, the dispersibility in the toner particles is good, but the adhesion to the toner particles is reduced, and it is not possible to secure good transferability.

Further, the amount of carbon black deposited is 0.2
If the amount is less than parts by weight, sufficient conductivity cannot be obtained, and the image density at the time of development becomes low. On the other hand, if the amount of carbon black is more than 2.0 parts by weight, the carbon black adheres to the toner particles in a supersaturated state. Absent. If the resin particles are less than 0.5 parts by weight, transferability to plain paper is poor. On the other hand, when the amount exceeds 10.0 parts by weight, the transferability is improved, but the conductivity of the toner is reduced and the developability is deteriorated.

[0017]

Embodiments of the present invention will be described below. Example 1 After mixing the above materials, the mixture was melt-kneaded and pulverized by a jet mill to obtain toner particles having a volume average particle diameter of 9.5 μm. 0.2 parts by weight of carbon black (CSX-99, manufactured by Cabot Corporation) was added to 100 parts by weight of the toner particles, and mixed with a Henschel mixer to deposit carbon black on the surface of the toner particles. Next, resin particles made of a styrene-butyl acrylate copolymer (TSF-2, manufactured by Fujikura Kasei Co., Ltd., having an average particle diameter of 0.2 μm) were added to the toner particles having carbon black attached thereto in a Henschel mixer.
Melt viscosity characteristics: 7.4 × 10 ⁵ POISE at 150 ° C.,
3.4 × 10 ⁵ POISE at 160 ° C .;
0 × 10 ⁵ POISE, 1.1 × 10 ⁵ PO at 180 ° C.
ISE) was added and mixed to obtain a toner for electrostatic charge development of the present invention in which carbon black and styrene-butyl acrylate copolymer resin particles adhered to the surface of the toner particles.

Example 2 An electrostatic charge developing toner of the present invention was obtained in the same manner as in Example 1 except that the amount of carbon black CSX-99 was changed to 2.0 parts by weight.

Example 3 Example 1 was repeated except that the addition amount of carbon black CSX-99 was 1.0 part by weight and the addition amount of resin particles TSF-2 composed of styrene-butyl acrylate copolymer was 0.5 part by weight. In the same manner as in Example 1, an electrostatic charge developing toner of the present invention was obtained.

Example 4 The procedure of Example 4 was repeated except that the amount of carbon black CSX-99 was changed to 1.0 part by weight, and the amount of resin particles TSF-2 made of styrene-butyl acrylate copolymer was changed to 10.0 parts by weight. In the same manner as in Example 1, an electrostatic charge developing toner of the present invention was obtained.

Example 5 Example 1 was repeated except that the addition amount of carbon black CSX-99 was changed to 1.0 part by weight, and the addition amount of resin particles TSF-2 composed of a styrene-butyl acrylate copolymer was changed to 5.0 parts by weight. In the same manner as in Example 1, an electrostatic charge developing toner of the present invention was obtained.

Example 6 Carbon black (Denka Black, manufactured by Denki Kagaku) was added to 100 parts by weight of the toner particles obtained in Example 1.
0 parts by weight were added and mixed with a Henschel mixer to deposit carbon black on the surface of the toner particles. Next, resin particles made of styrene-butyl acrylate copolymer (TSF-2, manufactured by Fujikura Kasei Co., Ltd .;
2 μm, melt viscosity property; 7.4 × 10 ⁵ PO at 150 ° C.
ISE, 3.4 × 10 ⁵ POISE at 160 ° C., 170
2.0 × 10 ⁵ POISE at 180 ° C., 1.1 × 1 at 180 ° C.
(0 ⁵ POISE) was added and mixed, and resin particles of carbon black and styrene-butyl acrylate copolymer were adhered to the surface of the toner particles to obtain a toner for electrostatic charge development of the present invention.

Comparative Example 1 The toner particles obtained in Example 1 were used as a comparative electrostatic charge developing toner.

Comparative Example 2 To 100 parts by weight of the toner particles obtained in Example 1, only 1.0 part by weight of carbon black (CSX-99, manufactured by Cabot Corporation) was added and mixed with a Henschel mixer to obtain toner particles. Carbon black was adhered to the surface to obtain a comparative electrostatic charge developing toner.

Comparative Example 3 Example 1 was repeated except that the addition amount of carbon black CSX-99 was changed to 1.0 part by weight, and the addition amount of resin particles TSF-2 composed of styrene-butyl acrylate copolymer was changed to 15.0 parts by weight. In the same manner as in Example 1, a comparative electrostatic charge developing toner was obtained.

Comparative Example 4 To 100 parts by weight of the toner particles obtained in Example 1, 4.0 parts by weight of only carbon black (CSX-99, manufactured by Cabot Corporation) was added and mixed with a Henschel mixer to obtain toner particles. Carbon black was adhered to the surface to obtain a comparative electrostatic charge developing toner.

Comparative Example 5 Example 1 was repeated except that the addition amount of carbon black CSX-99 was 4.0 parts by weight, and the addition amount of resin particles TSF-2 composed of a styrene-butyl acrylate copolymer was 3.0 parts by weight. In the same manner as in Example 1, a comparative electrostatic charge developing toner was obtained.

Comparative Example 6 Example 1 was repeated except that the addition amount of carbon black CSX-99 was 4.0 parts by weight, and the addition amount of resin particles TSF-2 composed of a styrene-butyl acrylate copolymer was 15.0 parts by weight. In the same manner as in Example 1, a comparative electrostatic charge developing toner was obtained. Comparative Example 7 A mechanical strain is applied to the toner particles obtained in Example 1.
As a result, the resin particles and the carbon particles are fixed to the toner particles.
Was. Hybridizer (Model MHS-1 Nara Machinery Works)
And the fixing conditions were 6400 rpm for 5 minutes.
Was. Comparative Example 8 In Example 1, the carbon bra
The toner particles having the adhesion are removed by the same means as in Comparative Example 7.
Carbon black was fixed to the toner particles. Then the actual
The resin particles of Example 1 were prepared in the same manner as in Example 1 to obtain toner particles.
Toner that has only carbon attached to toner particles
Was prepared. Comparative Example 9 In Example 1, the resin particles were first added using a Henschel mixer.
The toner particles to which only the toner was adhered were subjected to the same method as in Comparative Example 7.
Sticked to toner particles. Note that the amount of resin particles
Same as Example 1. Then, the carbon black of Example 1 was used.
The toner is externally added to the toner particles in the same manner as in Example 1, and
A toner in which only fat particles were fixed to toner particles was prepared.

Using the electrostatic charge developing toners obtained in Examples 1 to 6 and Comparative Examples 1 to 6, the surface potential was set to 200 V
The continuous copying of up to 5,000 sheets was performed with a one-component developing type copying machine set as described above. Table 1 shows the results of evaluation of the initial characteristics in continuous copying, and Table 2 shows the results of evaluation after 5,000 sheets.
In Tables 1 and 2, the transfer efficiency is expressed by the weight (Md) of the developed toner on the photoconductor in a solid black pattern (50 mm × 200 mm) and the weight (Mt) of the toner transferred to plain paper in the same pattern. (Mt / Md) × 100 [%]. In addition, toner scattering was determined by charging the toner for electrostatic charge development into the developing device, and visually checking the inside of the device around the developing device after idling for 30 minutes based on the following evaluation criteria. The image density during development was measured by transferring the toner for electrostatic charge development onto the photoreceptor using the solid black pattern, peeling off the toner for electrostatic charge development on the photoreceptor with a transparent adhesive tape, and sampling. A transparent adhesive tape is attached to plain paper, and the image density of the toner for electrostatic charge development is measured with a reflection type image densitometer RD-9.
14 (manufactured by Macbeth). The image density at the time of fixing was measured by RD-914 after transferring and fixing the black solid pattern to plain paper after development. For fog, the difference in whiteness of plain paper before and after copying was measured with a Hunter color difference meter (manufactured by Nippon Denshoku Co., Ltd.).

As is clear from the results shown in Tables 1 and 2, the electrostatic charge developing toner of the present invention has an initial
The transfer efficiency was 80% or more in all of the characteristics after 0 sheets, and the image density was sufficient, and good results were obtained with no problem with fog and toner scattering. On the other hand, it was confirmed that the comparative toner for electrostatic charge development had low image density and transfer efficiency from the beginning, and had poor fog and toner scattering, which hindered practical use. Further, the toner particles of Comparative Examples 7 to 9 were
The performance was evaluated and the following results were obtained. As described above, the case where only carbon is attached (comparative example)
In 9), although the image density is good, the transferability is inferior. Resin grain
In the case where only the child was in the adhered state (Comparative Example 8), the transferability was relatively
Good but poor image density. When both are fixed (compared to
Comparative Example 7) is inferior in image density and transferability.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

According to the present invention, it is possible to provide a toner for electrostatic charge development having a sufficient image density, good transferability and free from fogging and toner scattering.

[Brief description of the drawings]

FIG. 1 is a view showing the melt viscosity characteristics of resin particles.

Claims (2)

(57) [Claims] 2. A toner according to claim 1, wherein the carbon black is contained in an amount of from 0.2 to 2.0 parts by weight and the resin particles are contained in an amount of from 0.5 to 1.0.
0 Ri Na with parts attached, the resin particles are tacky melting the applied temperature
In terms of degree, (a) 3 × 10 ⁶ PO at 85 ° C.
ISE, (b) 5 × 10 ⁴ POISE at 120 ° C.
(C) 5 × 10 ⁴ POISE at 205 ° C. , (d) 1
Point given by 3 × 10 ⁶ POISE at 70 ° C.
(A), (b), (c), and (d) in the area connecting the straight lines
An electrostatic charge developing toner having melt viscosity characteristics . 2. The resin particles having an average particle size of 0.1 to 1.0.
2. The electrostatic charge developing toner according to claim 1, wherein the toner has a particle size of μm.