JP2686480B2 - Toner for electrostatic charge development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrostatic charge developing toner,
In particular, the present invention relates to a conductive electrostatic charge developing toner 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, if necessary,
It is fixed by a means such as heating and pressing to obtain a copy. Developers used in such an electrophotographic method include a two-component developer including a toner and a carrier, and a one-component developer having the functions of the toner and the 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 30 to 70% by weight of magnetic powder is used as the magnetic one-component developer. The magnetic toner is classified into conductive magnetic toner and insulating magnetic toner. The former is given a charge by electrostatic induction or charge injection, and the latter is given a charge by frictional charging and 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 having no edge effect can be obtained because the conductive magnetic toner itself serves as a developing electrode. However, the conductive magnetic toner has a drawback in that charges easily leak during electrostatic transfer, and transfer to plain paper is difficult.
Further, since only one layer of toner particles is developed on the photoconductor, it is difficult to secure image density. Hitherto, in order to solve these problems, there has been used means for using special paper subjected to high resistance treatment or adopting a pressure transfer method using a rubber roller. However, even if these means are used, the situation is still unsatisfactory.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art and has good transferability,
It is an object of the present invention to provide a toner for electrostatic charge development capable of obtaining a sufficient image density.

[0004]

According to the present invention, toner particles 10 containing 30 to 70% by weight of magnetic powder in a binder resin are provided.
A toner for electrostatic charge development, wherein carbon black having a volume resistivity of 30 Ω-cm or less is fixed in an amount of 0.2 to 5.0 parts by weight with respect to 0 parts by weight. Hereinafter, the present invention will be described in detail. The toner particles constituting the electrostatic charge developing toner of the present invention include a magnetic powder, a binder resin, a charge control agent such as a metal dye or nigrosine dye of a monoazo dye, which is optionally added, and a colorant such as carbon black. After well kneading with a heat kneader such as a hot roll, a kneader or an extruder, it is obtained as particles having an average particle diameter of 4 to 20 μm 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 resin. , Thermoplastic resins such as thermoplastic epoxy resins, cellulosic resins and copolymer resins of monomers constituting those resins, modified acrylic resins, phenol resins,
Thermosetting resins such as melamine resin and urea resin can be used. Particularly, the binder resin used in the present invention is 10
The melt viscosity at the measurement temperature of 0 ° C. is 5.0 × 10 ⁴ to 1.
It is preferably in the range of 0 × 10 ⁶ POISE. When the melt viscosity is less than 5.0 × 10 ⁴ POISE, problems such as filming on the photoconductor tend to occur, while 1.
If it exceeds 0 × 10 ⁶ POISE, the mechanical load at the time of melt-kneading becomes large, which may cause a problem in productivity. Further, as the magnetic powder, spinel, hexagonal crystal, garnet, ferrite or magnetite having an orthoferrite structure is applied crystallographically. The structure of ferrite is nickel, zinc, manganese, magnesium, copper,
It is a sintered body of an oxide of lithium, barium, vanadium, chromium, calcium or the like and a trivalent iron oxide.

Next, in the present invention, the toner particles 100
0.2 to 5.0 parts by weight of carbon black is fixed on the surface of the toner particles with respect to parts by weight. The means is
First, the toner particles and a predetermined amount of carbon black are mixed using a stirring mixer such as a turbine type stirrer, a super mixer, or a Henschel mixer to prepare a mixed powder of both. Next, this mixed powder is applied to a powder surface modifier (such as Nara Hybridizer manufactured by Nara Machinery Co., Ltd. or Ong Mill manufactured by Hosokawa Micron Co., Ltd.) to compress the carbon black particles mixed and adhered to the toner particles. Also, a frictional force is applied (hereinafter referred to as surface modification treatment) to fix the carbon black on the surface of the toner particles. In the present invention, "fixing" of carbon black to the surface of toner particles means that a compressive force and a frictional force act at the contact points of both particles, and at the contact points, heat above the melting point of the toner particles is instantaneously generated. , A phenomenon in which carbon black is firmly fixed to the surface of toner particles by fusion, and includes a state in which part or the whole of carbon black is buried.

In the present invention, by fixing carbon black on the surface of toner particles, the conductivity required for developing the toner is imparted, and by exposing the binder resin on the surface of the toner particles, a toner for electrostatic charge development is obtained. It provides good transferability. The volume resistivity of carbon black is 30
When it is larger than Ω-cm, good developability cannot be obtained regardless of the adhering amount of carbon black. or,
If the volume resistivity of carbon black is 30 Ω-cm or less, and if the mixed adhesion amount exceeds 5.0 parts by weight, good transferability cannot be obtained. On the other hand, if it is less than 0.2 parts by weight, good developability cannot be obtained. The volume resistivity in the present invention is 200 g / c of carbon black sample between the upper electrode and the lower electrode arranged in the cylinder.
It is obtained by loading so that a stress of m ² is applied, applying a voltage, and measuring the resistance value between the electrodes with a tester.

In the present invention, the carbon black fixed to the surface of the toner particles has a number average particle size, an oil absorption amount, and a P value as long as its volume resistivity is 30 Ω-cm or less.
The H and the like can be used without limitation, and the following are commercially available products. For example, Cabot CSX-9
9, Vulcan XC-72, Ketchin Black EC made by Lion Akzo, # 4500, # 5 made by Tokai Carbon
500, # 2555, # 3855, Denka Black manufactured by Denki Kagaku, and # 2400B manufactured by Mitsubishi Kasei. These carbon blacks may be used alone or
Various combinations of at least one species can be used. In the electrostatic charge developing toner of the present invention, ears are formed on the developing sleeve by the 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. On the other hand, if the amount is more than 70% by weight, not only it becomes difficult to disperse the magnetic powder in the binder resin, but also the conductive material such as carbon black is mixed in a small amount to ensure the conductivity. It will be difficult.

[0009]

Embodiments of the present invention will be described below. Example 1 Polyester resin (HP-320 manufactured by Nippon Synthetic Chemical Industry Co., Ltd., 45 parts by weight, melt viscosity at 100 ° C .: 2.6 × 10 ⁵ POISE) Magnetic powder (EPT-500 manufactured by Toda Kogyo Co., Ltd.) 45 parts by weight Carbon black ( Tokai Carbon Co., Ltd. # 5500) 10 parts by weight The above materials were mixed, melt-kneaded, and pulverized by a jet mill to obtain toner particles having a volume average particle diameter of 9.5 μm. To 100 parts by weight of the toner particles, 0.5 parts by weight of carbon black (CSX-99 manufactured by Cabot Corporation) having a volume resistivity of 7.4 Ω-cm was added and mixed with a Henschel mixer to obtain the surface of the toner particles. A carbon black was attached to. Next, the same mixed powder was used for 7000 using a hybridizer (NHS-1 type manufactured by Nara Machinery Co., Ltd.).
The surface modification treatment is performed under the condition of rpm for 5 minutes to fix the carbon black on the surface of the toner particles, and
The binder resin was exposed on the surface of the toner particles to obtain the electrostatic charge developing toner of the present invention. Example 2 As carbon black fixed to the surface of toner particles, C having a volume resistivity of 17.5 Ω-cm manufactured by Cabot Corporation was used.
An electrostatic charge developing toner of the present invention was obtained in the same manner as in Example 1 except that the addition amount of SX-99 was 4.0 parts by weight. Example 3 The same procedure as in Example 1 was carried out except that 3.0 parts by weight of Ketjen Black EC having a volume resistivity of 7.4 Ω-cm manufactured by Lion Akzo Co., Ltd. was used as the carbon black fixed to the surface of the toner particles. An electrostatic charge developing toner of the invention was obtained.

Comparative Example 1 A toner for electrostatic charge development of Comparative Example was obtained in the same manner as in Example 1 except that carbon black was not fixed to the surface of the toner particles. However, the surface modification treatment with the hybridizer was performed in Example 1.
I went under the same conditions. Comparative Example 2 CS having a volume resistivity of 7.4 Ω-cm manufactured by Cabot Corporation as carbon black fixed to the surface of toner particles.
A toner for electrostatic charge development of a comparative example was obtained in the same manner as in Example 1 except that 7.0 parts by weight of X-99 was used.

Using the electrostatic charge developing toners obtained in Examples 1 to 3 and Comparative Examples 1 and 2 above, a continuous copying of up to 5000 sheets was performed with a one-component developing type copying machine in which the surface potential was set to 200V. I went. Table 1 shows the initial evaluation results in continuous copying, and Table 2 shows the evaluation results after 5000 copies.
In Tables 1 and 2, the transfer efficiency is defined as the ratio (Mt) of the developing toner weight Md on the photoconductor in the solid black pattern (50 mm × 200 mm) and the transfer toner Mt on the plain paper in the same pattern. / Md) × 100 (%). Also, as for toner scattering, toner is thrown into the developing device,
The in-machine stain around the developing device after the idling for a minute was visually judged based on the following evaluation criteria. ○ --- No toner scattering. △ --Toner was scattered under the developing unit. × --Toner was scattered all over the upper and lower parts of the developing device. The image density (ID) at the time of development is determined by developing the electrostatic charge developing toner on the photoconductor using the black solid pattern and peeling off the electrostatic charge developing toner on the photoconductor with a transparent adhesive tape. The sample was sampled, the transparent adhesive tape was attached to plain paper, and the image density of the electrostatic charge developing toner was measured with a reflective image densitometer RD-914 manufactured by Macbeth. Regarding the image density at the time of fixing, after the above black solid pattern was developed, it was transferred and fixed on plain paper and the image density was measured by a reflection type densitometer RD-914 manufactured by Macbeth. For the fog, the difference in whiteness of the transfer paper before and after copying was measured with a Hunter color difference meter manufactured by Nippon Denshoku Co., Ltd. The results are shown in Tables 1 and 2.

[0012]

[Table 1]

[0013]

[Table 2]

According to this, the toner for electrostatic charge development of the present invention has a transfer efficiency of 80% or more in both initial characteristics and characteristics after copying 5,000 sheets, has sufficient image density, and is free from problems such as fog and toner scattering. The results were obtained. On the other hand, it was confirmed that the toner for electrostatic charge development of Comparative Example had lower image density and transfer efficiency than the initial stage, poor fog and toner scattering, and impeded practical use.

[0015]

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.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP 54-139545 (JP, A) JP 2-69767 (JP, A) JP 62-246075 (JP, A) JP 57- 139752 (JP, A) JP-A 1-224776 (JP, A) JP-A 2-100059 (JP, A) JP-A 4-101158 (JP, A)

Claims (1)

(57) [Claims] 1. A melt viscosity at a measuring temperature of 100 ° C. 5.
The volume resistivity is 30 Ω-c with respect to 100 parts by weight of toner particles containing 30 to 70% by weight of magnetic powder in the binder resin in the range of 0 × 10 ^{4 to} 1.0 × 10 ⁶ POISE.
A conductive toner for electrostatic charge development, characterized in that carbon black of m or less is fixed within a range of 0.2 to 5.0 parts by weight.