JPS5984258A - Electrophotographic dry type developer - Google Patents

Abstract

PURPOSE:To extend a life of a dry type developer and to protect its development performance from the effect of the environmental conditions by adding an alpha-Al2O3 and gamma-Al2O3 blended hard fine powder to a toner composed essentially of an amorphous conductive iron powder carrier and a toner contg. polyester as a principal resin component. CONSTITUTION:A mixture of alpha-Al2O3 and gamma-Al2O3 having 200-1,000mum and 20mum particle diameter, respectively, and 3:7-7:3 blend ratio is added to a dry type developer consisting of a carrier of amorphous conductive iron powder and a toner contg. a binder composed essentially of polyester resin and a pigment, such as carbon black, by 0.3-3.0wt% alumina mixture based on the toner. As a result, the obtained developer is not deteriorated in development performance by high humidity, and long in life, and it can obtain a good image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a dry type developer for electrophotography, and particularly to a developer with improved developer life and environmental characteristics.

If a developer is used repeatedly over a long period of time, its characteristics will deteriorate and image quality will be significantly impaired. For example, in a dry developer using an amorphous conductive iron powder carrier, the
The properties of the agent deteriorated after 1,000 copies, and the agent's lifespan was not sufficient.

In order to improve such characteristic deterioration due to long-term use and obtain a developer with a long service life, it has been known to add hard fine powder of silicon dioxide as a third additive to the developer. However, this additive has the disadvantage of impairing the environment R1'l as a side effect. Therefore, in place of the silicon dioxide, 01-IM with a silanol group called "hydrophobic silica" is used which has been hydrophobized, but this also causes PI deterioration in the environment and is not always effective. I'm not satisfied with it. 1! First, when a polyester resin is used as the -1:resin component of the toner with the aim of low-temperature fixing, the environmental characteristics are further deteriorated due to the influence of residual OH groups in the polyester resin.

The present invention is aimed at solving the above-mentioned conventional drawbacks, and more specifically, in 1iTi m, amorphous conductive iron powder is used as a carrier, and polyester resin is used as the main resin component. The objective is to increase the lifespan of the developer and improve its environmental characteristics in an electrophotographic dry developer using a toner containing the compound.

As a result of various studies in view of the object of the present invention, it has been found that the object of the present invention can be achieved by adding α-alumina and γ-aluminum powder as a third additive to the developer. As a result, the present invention has been completed.

The blend ratio of α alumina and γ alumina is α alumina: γ
Alumina-3 near to 3 is preferred.

Due to the difference in crystal structure, alumina hard fine powder has α and γ
Alumina is known. α alumina generally has a large particle size of 200 to 1000 mμ, and γ alumina has a particle size of 2
Many are around 0 mμ.

If only α-alumina is added to the developer, the fine alumina powder or aggregates thereof will float in the developer, probably due to the large particle size, making it unusable as a developer. . Furthermore, when gamma alumina is added alone to the developer, the negative charge amount of the toner is significantly reduced, possibly because gamma alumina has a strong positive charge series, and the performance of the developer is degraded. However, when a blend of α and γ alumina is used, the reason is not clear, but
There is no possibility that alumina will float in the ψ agent or that the toner charge amount will decrease, thereby damaging the +!111 power of the developer.

In the present invention, the total amount of τα and γ alumina added is 0.3 to 3. 5 to 1.5 wt%.

Examples of the present invention and comparative examples will be described below.

Example 1 90 parts by weight of a polyester resin (Atrac 382A, manufactured by Kao Atlas Rei) and 10 parts by weight of carbon black were mixed with a hot roll, cooled, and pulverized with a jet pulverizer.

Subsequently, the toner was classified using a classifier to obtain a toner having an average particle size of 9 tt.

For 100 parts by weight of this toner, α alumina and γ
Alumina blend fine powder (Product name Mechanox US-
10, particle size distribution 20 to 1000 mtt, manufactured by Uezai Kogyo Co., Ltd.) was added thereto and mixed and stirred using a Henschel mixer to obtain a toner containing α and γ aluminum rub 1 non-doped.

Adding 1 to 4 parts by weight of this α and γ alumina blend to an amorphous conductive carrier EFV iron powder (average particle size 100μ,
Nippon Iron Powder Co., Ltd.)) was added to 100 parts by weight, and milled using a ball mill.
After stirring for 0 minutes, a developer was obtained. Toner charge amount (hereinafter referred to as Q/M
It is abbreviated as ) was measured, (->18.0μC/(
It was I.

Using this developer, 10,000 sheets were continuously copied using a robot machine, and the resulting images were clear and free from background smudges, and were comparable to the initial images. When Q/M was measured, it was (-)17.5 μC/a, which was almost unchanged.

In addition, in order to evaluate the environmental characteristics, high humidity (3
0°C, 90%) environmental tests were conducted.

The toner and carrier were spread on a stainless steel bat in a 90% atmosphere at 30°C, and after conditioning the humidity for 90 minutes, they were placed in a ball mill bot and stirred for 30 minutes, then the Q/M was measured, and it was (-) 17. It was Oμcya, and there was almost no difference from that produced at normal temperature and normal humidity. It has been confirmed that the environmental characteristics are very good.

5- Comparative Example 1 Hydrophobic silicon dioxide hard fine powder (average particle size IG ml, trade name) was added to the dried part of the toner 100 produced in Example 1.
R0=972, Nippon Aero Girnet TL! 4) 1i1i parts were added and mixed and stirred using a Henschel Migisser to obtain 2M silicon-added 1 hener.

A developer was prepared using this 1-ner in the same manner as in Example 1, and its life characteristics were evaluated using a robot machine. Even after 10,000 sheets were continuously copied, the images remained good, and the Q/M did not change from the initial value. It was confirmed that the agent life was good.

Furthermore, in order to evaluate the environmental characteristics, 30
Environmental tests 1 to 1 were conducted in a 90% atmosphere at ℃.

When Q/M was measured (-) 5.071c, 7g
However, it was reduced to 1/3 or less compared to when it was at room temperature and humidity. In addition, there was significant toner scattering.

Although the addition of silicon dioxide is effective in improving the life of the agent, it has been confirmed that it causes a significant deterioration of the environmental properties6.

Example 2 100 parts by weight of polyester resin, 10 parts by weight of carbon black
After mixing 1 part of the weight with a hot roll, the same procedure as in Example 1 was carried out to obtain 1 to 1-gner having an average particle size of 9 μm.

1 part of α, γ alumina blend hard fine powder (particle size 20 to 400 mμ, trade name Mechanox N0.7-A, manufactured by Uezai Kogyo Co., Ltd.) was added to this 1-no-1ooau part. Add, mix with Henshi Lumikizer, and add α,
A toner containing γ alumina was obtained.

This α, γ aluminum addition 1 to ner 5-fold hanging part is an irregular conductive +! The mixture was added to 100 parts by weight of 1vY powder carrier (average particle size: 60 μm, manufactured by Kanto Denka T Gyoen 1) and stirred in a ball mill for 30 minutes to prepare a developer. When Q/M was measured, (
-) It was 22.0μC10.

In the same manner as in Example 1, the robot machine performs continuous io, ooo
Although the camera was beaded, there was no deterioration in its life and the image remained the same as the initial image. Q/M is (-> 21.5flO/
g, there was almost no change.

In addition, an environmental test was conducted at 30°C in a 90% atmosphere, and the Q/M was (-) 20.0llc/! ] Thea V)
, the fluctuation was extremely small compared to that at room temperature and humidity.

The ME recognized that the environmental condition was 14 in good condition.

Comparative Example 2 1 of γ alumina (average particle size 20 mμ, manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts by weight of 1 to 1 used in Example 1.
．． 0 part by weight was added and mixed and stirred to obtain γ-alumina-added 1-ner.

This γ-alumina-added 1-4 parts by weight of henna was added to EFV iron powder (average particle size 100μ>100,000 parts) and stirred in a ball mill to obtain a developer. When Q/M was measured,
(-) There was no 6.0 μC/QL/, and there was a lot of 1heno-- scattering, making it impossible to use it as a developer.

Comparative Example 4 Alpha alumina (trade name Mechanox UB-7, particle size 200-4
00 mμ, manufactured by Juri Kogyo Co., Ltd.) was added to 1.0 mold portion, and mixed and stirred to obtain 1171 g of α-alumina-added 1 hener.

1 to 4 parts by weight of α-alumina additives were added to 100 parts by weight of EFV iron powder (average particle size: 100 μm), and the mixture was stirred in a ball mill to obtain a developer. Visual inspection of the developer revealed that aggregates believed to be alpha alumina were scattered throughout the developer, making it unsuitable for use as a developer.

Patent applicant: Ricoh Co., Ltd. Agent: Patent attorney Hidetake Komatsu −〇−

Claims (1)

[Claims] In an electrophotographic dry developer containing an amorphous conductive iron powder carrier and a toner whose main resin composition is a polyester resin, it is preferable to add α-alumina and γ-alumina blend hard fine powder to the developer. Characteristic dry developer for electrophotography.