JP3122766B2 - Two-component developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer used for developing an electrostatic latent image in electrophotography and the like.

[Industrial applications]

[0002]

2. Description of the Related Art Electrophotography has been widely known, and a typical Carlson method forms an image through the following steps.

(1) A charging step for uniformly charging the photosensitive member by corona discharge or the like. (2) An exposure step of selectively irradiating the photosensitive member with light by image exposure (analog exposure) or signal exposure (digital exposure) by scanning with laser light or the like to form an electrostatic latent image.

(3) A developing step of developing an electrostatic latent image with a developer to attach toner and form a toner image on a photoreceptor. (4) A transfer step of transferring the toner image on the photoreceptor to paper or the like. (5) A fixing step of fixing the transferred toner by heat, pressure, or the like.

Further, a non-Carlson type image forming method in which a developer reservoir is formed on a photoreceptor, charge is injected into the photoreceptor via the developer to charge the photoreceptor, and an image signal is exposed from the back side of the photoreceptor and developed simultaneously. A method is also known, and is usually called an optical back exposure recording system.

In any of such image forming methods, the performance of the developer greatly affects the success or failure of each step.

[0007] In view of the constitution, developers are broadly classified into two-component developers consisting of toner and carrier, and one-component developers consisting only of toner. In the former case, the friction with the carrier is mainly determined. , And in the latter case, the toner is charged by friction between toner particles or between the toner and the sleeve.

In such a two-component developer, if the particle size of the toner is reduced in order to increase the resolution of the image, the toner is likely to scatter inside the machine. Also, specific charge (Q / M)
And the image quality tends to be unstable. In particular, the environmental dependency due to changes in temperature and humidity becomes strong, and the image quality greatly changes.

Furthermore, amorphous silicon (a-S
In a photoreceptor or the like using the i) type photoconductive layer, an abrasive is added to the toner in order to prevent the occurrence of image deletion. However, in this case, the carrier is apt to deteriorate, and therefore, scatter in the apparatus is apt to occur. This causes a serious problem particularly when a toner having a small particle diameter is used.

[0010] Conventionally, in a two-component developing method, a small amount of a magnetic material has been added to a toner in order to prevent scattering in a machine. However, in this case, the magnetic force of the toner is generally about 1 to 3 emu / g in saturation magnetization.
It is merely added for the purpose of compensating the charge balance of the toner.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the environmental stability of a toner in a two-component developer and to prevent the toner from scattering in a machine.

[0012]

Means for Solving the Problems A two-component developer of the present invention, in the two-component developer containing a toner and a carrier, the average particle diameter of the magnetic material in the toner is not more 0.5μm or less, an average toner Particle size is 3-8μm, 5μm or less
The content is 5% by weight or more, and the content of 10 μm or more is 5 layers.
% Or less, and the saturation magnetization Tσs of the toner is 3 to 15 e.
mu / g, the ratio Cσs / Tσs of the saturation magnetization Cσs of the carrier and the saturation magnetization Tσs of the toner is in the range of 25 to 4, and the abrasive is mixed with the developer or the abrasive is added to the toner surface. It is characterized by the following.

[0013]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the toner preferably has an average particle size of 3 to 8 .mu.m, and more preferably has a content of toner particles of 5 .mu.m or less of 5 wt% or more and a content of toner particles of 10 .mu.m or more. It is preferably 5% or less.
By using such a small particle size toner, high resolution of an image can be realized. Further, even if the toner is reduced in particle size, the two-component developer of the present invention can stabilize the image quality for a long time, prevent scattering in the apparatus, and achieve high durability.

The toner has a saturation magnetization σs of 3 to 15 emu /
g, preferably 4 to 15 emu
/ G, more preferably 5 to 10 emu / g. If the saturation magnetization s of the toner is less than 3 emu / g, the carrier cannot sufficiently hold and control the toner, resulting in a large change in image quality due to a change in the environment and scattering inside the machine. On the other hand, the saturation magnetization s of the toner is 15e
If the value exceeds mu / g, the toner is difficult to separate from the carrier, and the image density is reduced. Further, since the toner is not refreshed from the carrier surface, the carrier is contaminated by the toner (so-called spent).

In the present invention, the balance of the magnetic force between the magnetic carrier and the toner is important, and the ratio between the carrier saturation magnetization (Cσs) and the toner saturation magnetization (Tσs) is Cσ.
s / Tσs = 25 to 4, preferably 15 to 6. If the ratio is too large, the toner will not be sufficiently retained on the carrier surface, and the image quality will change due to a change in the environment, and scattering in the machine will occur. On the other hand, when the ratio is small, it is difficult to obtain an image density, and depending on environmental conditions, a so-called “carrier pull” occurs in which the carrier is developed together with the toner.

As the carrier, any of a non-coated carrier using magnetic powder as it is and a coated carrier in which the surface of the magnetic powder is coated with an organic coating agent can be used, but a non-coated carrier is preferable. The coated carrier is inferior in durability because the charge imparting property is changed when the surface coating agent is deteriorated by use. In particular, an abrasive for polishing the surface of the carrier or the photoconductor is added to the developer. Sometimes this tendency becomes significant.

Generally, a non-coated carrier tends to have a lower toner Q / M and a lower image quality than a coated carrier. However, it has been found that when the particle size of the toner is reduced and an appropriate magnetic force is applied to the toner, the toner is sufficiently retained on the surface of the non-coated carrier, and image quality equal to or higher than that of the coated carrier is obtained.

As the material for the carrier, any material can be used as long as it is a magnetic material, but ferrite is particularly preferred.

The toner can be manufactured by an ordinary method using a commonly used material such as a binder resin.
A magnetic material that imparts a magnetic force to the toner may be added to the inside of the toner (dispersed in a binder resin) or may be held on the toner surface (fixed to the toner surface). However,
Since it is generally difficult to keep 5% by weight or more of a magnetic material on the toner surface, it is preferable to add most of the magnetic material to the inside of the toner.

The magnetic material to be added to the toner is not particularly limited as long as it can impart a constant magnetic force to the toner, but magnetite is particularly preferred. The average particle size of the magnetic material is preferably 0.5 μm or less in consideration of the reduction in the size of the toner particles.

In the toner of the present invention, a binder resin,
In addition to the magnetic material, other components such as a colorant, an anti-offset agent, a fixing improving auxiliary, and a charge control agent can be included as necessary.

Various colorants and pigments, including carbon black, are used as colorants; anti-offset agents; fixing aids include low molecular weight polypropylene, low molecular weight polyethylene or modified olefin waxes thereof; and charge control agents. Nigrosine, quaternary ammonium compounds, triaminotriphenylmethane compounds, crystal violet and the like can be used. The toner may be positively or negatively chargeable.

The toner of the present invention can be prepared by a conventional method, for example,
It is obtained by melt-kneading the components with a screw extruder, a kneader, or the like, followed by pulverization with a jet mill or the like, and classification.

The toner of the present invention is used as a two-component developer by being mixed with a carrier. However, an abrasive may be further mixed (externally added) or the abrasive may be fixed to the toner surface. By adding an abrasive, the surface of the carrier is polished and constantly refreshed to prevent the carrier from being spent. In addition, when the carrier is used for an a-Si photosensitive member, a countermeasure against image deletion can be realized.

As the abrasive, metal oxides such as alumina, zirconium oxide and titanium oxide are used.

[0026]

According to the present invention, an appropriate magnetic force is imparted to the toner and the balance with the magnetic force of the carrier is reduced, whereby the dependency on the environment is reduced.
Thus, the fluctuation of the image density due to the change of the temperature and the humidity is greatly improved, and the strong magnetic force prevents the toner from scattering in the apparatus. Furthermore, even when the diameter of the toner is reduced, Q
/ M can be prevented from being dependent on the environment and scattering inside the apparatus due to the change in / M, so that the diameter of the toner can be reduced.

[0027]

【Example】

(1) Measurement Method of Saturation Magnetization A toner or a carrier is filled in a cylindrical case for powder, measured by a vibrating sample magnetometer (VSM), and measured at 23 ° C. in an applied magnetic field of 10 kOe (10 KOe).
The measured value at is defined as the saturation magnetization.

(2) Initial Image Density The initial image density is measured by a Macbeth densitometer. (3) In-machine scattering Continuous printing is performed using a drum photoreceptor, and after printing 10,000 sheets, the in-machine scattering is determined based on the level of toner dropped to the lower part of the developing device according to the following criteria.

○: no scattering at all △: slight scattering observed ×: severe scattering

The operating environment of the printer was tested under the following three conditions of normal temperature and normal humidity, high temperature and high humidity, and low temperature and low humidity, and the scattering in the machine was evaluated. NN environment: 23 ° C-60% RH HH environment: 33 ° C-85% RH LL environment: 10 ° C-20% RH

[0031] (4) the developer after carrier spent ten thousand prints washed with methanol except toner from the carrier, and C ₁ to measure the total carbon amount of the carrier. Meanwhile, washed with further hot toluene were separated carrier with methanol and dried to measure the total carbon content, which is referred to as C _2. Spent amount = C
Determine the spent amount by ₁ -C _2, and evaluated according to the following criteria.

：: no spent at all △: slight spent observed ×: severe spent

Example 1 100 parts by weight of styrene / n-butyl acrylate copolymer (copolymerization ratio: 80/20) 5 parts by weight of carbon black (MA-100, manufactured by Mitsubishi Chemical Industry Co., Ltd.) 5 parts by weight of polypropylene wax (Viscol 550P) , Sanyo Chemical Industries, Ltd.) 4 parts by weight Triaminotriphenylmethane compound 2 parts by weight (Copy Blue PR, manufactured by Hoechst) Magnetite (BL-100, manufactured by Titanium Industry Co., Ltd.) 15 parts by weight

The toner materials having the above mixing ratios are mixed by a super mixer, kneaded using a twin screw extruder (PCM-30, manufactured by Ikegai Iron Works Co., Ltd.), cooled, pulverized and classified.
A classified product having an average particle size of 7 μm was obtained, and 1% of fine alumina particles were added thereto and mixed to obtain a positively chargeable toner.

The obtained toner was sufficiently mixed with a non-coated ferrite carrier having an average particle size of 80 μm at a concentration of 4% to prepare a two-component developer. At this time, the saturation magnetization Tσs of the toner is 10.1 emu / g, the saturation magnetization Cσs of the carrier is 65 emu / g, and Cσs / Tσs =
6.4. The saturation magnetization of magnetite added to the toner was 85 emu / g.

Using the above-described two-component developer, an LED manufactured by Kyocera Corporation is used as an exposure light source, and is continuously output by an a-Si drum printer using an a-Si photosensitive drum, and image density, scattering in the machine, The carrier spent was evaluated, and the results are shown in Table 1 together with the following Examples and Comparative Examples.

Example 2 A toner was prepared and evaluated in the same manner as in Example 1 except that the amount of magnetite was changed to 6 parts by weight.

Comparative Example 1 A toner was prepared and evaluated in the same manner as in Example 1 except that the amount of magnetite was changed to 3 parts by weight.

Comparative Example 2 A toner was prepared and evaluated in the same manner as in Example 1 except that the amount of magnetite was changed to 30 parts by weight.

[0040]

[Table 1] Toner magnetic force ratio Initial image After 10km run After 10km run Saturated magnetized carrier in the machine Tσs (emu / g ) Cσs / Tσs concentration NN HH LL Spent actual 1 10.1 6.4 1.4 ○ ○ ○ ○ Application 2 4.3 14.8 1.45 ○ ○ ○ ○ Example ratio 1 2.2 29.5 1.50 △ × △ ○ Comparison 2 18.0 3.6 1.1 ○ ○ ○ × Example

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-210450 (JP, A) JP-A-59-216149 (JP, A) JP-A-59-218457 (JP, A) JP-A-59-218457 218458 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/083 G03G 9/08 371 G03G 9/10

Claims (1)

(57) [Claims] 1. A two-component developer containing a toner and a carrier, wherein the average particle size of the magnetic material in the toner is 0.5 μm or less, and the average particle size of the toner is 3 to 8 μm and the content is 5 μm or less.
The content is 5% by weight or more and the content of 10 μm or more is 5% by weight.
%, The saturation magnetization Tσs of the toner is 3 to 15 emu / g, the ratio Cσs / Tσs of the saturation magnetization Cσs of the carrier and the saturation magnetization Tσs of the toner is in the range of 25 to 4, and the developer contains an abrasive. Or a polishing agent is added to the surface of the toner.