JPS6281646A - Ferrite carrier - Google Patents

Abstract

PURPOSE:To raise the heat resisting property and to prevent the aggregation and to extend the shelf life of the titled carrier by coating the surface of the ferrite particles with a mixed resin obtd. by adding a prescribed amount of a melamine-formaldehyde resin to a thermoplastic resin. CONSTITUTION:The titled carrier is prepared by coating the surface of the ferrite carrier used to a two components developer with the mixed resin obtd. by adding 3-20wt% of the melamine-formaldehyde resin to the thermoplastic resin such as an acryl-, a styrene-, and a styrene acryl- resin, etc. Preferably, a reaction accelerator may be added to said mixed resin. The ferrite particles are coated with the thermoplastic resin by mixing the ferrite particles with the prescribed mixed resin while heating, whereby the thermoplastic resin changes to the thermosetting resin and then, goes into concave parts of the ferrite particles. Thus, the heat resisting property of the toner is ferrite particles. Thus, the heat resisting property of the toner is improved,and the aggregation of the toner makes difficult. The titled toner has the electrostatic chargeability, and may be maintained a desired image quality, even if said toner is used for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a ferrite carrier used in a two-component developer, and in particular has heat resistance to prevent agglomeration.

Some of the developers used in conventional technology developing devices are two-component types consisting of toner and carrier, and the carrier includes ferrite particles (for example, Japanese Patent Publication No. 56-52305 and Japanese Patent Application Laid-open No. 58-202458). It is used. In order to improve the density of the developed image and the copy density, the ferrite carrier needs to be suitable for proper band modification, and the ferrite carrier needs to be temperature resistant to prevent toner from adhering. For this reason, some ferrite particles have their surfaces coated with resin. The resin used for coating is heated to + If ・ to increase the coating work.
Those having Tpp properties (for example, JP-A No. 47-13954 and JP-A No. 57-120946) are generally used.

Problem Qi to be Solved by the Invention A ferrite carrier is a conventional ferrite carrier in which the surface of ferrite particles is coated with a plastic resin.

In a room where the temperature was high, the ferrite carriers coagulated together and lost their function as carriers, making it impossible to obtain good image quality when copying with a developing device.

To solve the problem, T'-1 is applied to the surface of the ferrite particles by heat Bf ・TJ
It is a ferrite carrier coated with a mixed resin in which 3 to 20 wt% of melamine-formalin resin is added to the resin.

Q n (As the plastic resin, resins such as acrylic, styrene acrylic, and styrene are used.This type of heat ii)
Adding melamine formalin resin to plastic resin, 100~
Upon heating at 170° C., a crosslinking reaction occurs, converting the thermoplastic resin into a curable resin. It is possible to adjust the heat resistance by increasing or decreasing the addition td of melamine formalin resin in the range of 3 to 20 wt% relative to the thermoplastic resin.
This does not eliminate the properties of the styrene acrylic resin that is the base resin; however, with melamine-formalin resin, sufficient crosslinking reaction does not occur when the concentration is less than 3 wt%, so conversion from thermoplastic resin to thermosetting resin is not possible. If the amount of melamine-formalin resin is more than 20vt%, the effect of improving heat resistance and abrasion resistance will be insufficient.

Because formalin acts strongly, thermoplastic resin (i)
The electroconductivity will change significantly and the image quality will deteriorate.

The ferrite particles used have an average particle size of 30 to 200 pm, and these ferrite particles have irregularities on the surface and
- Foot heat [When Ir plastic resin and melamine-formalin resin are mixed while heating, the thermoplastic resin becomes thermosetting and enters the four parts of the ferrite particles, forming a coating.

Example Styrene acrylic resin was made into an emulsion by a known method, and the styrene acrylic emulsion (trade name: Showa Kobunshi Co., Ltd., AP-2881) was mixed with ferrite particles (trade name: Meke Metal Co., Ltd., KBN-100, Feather). Average particle size 9
0#Lm). In this case, l0w for the weight of the resin in the styrene acrylic emulsion.
t% melamine formalin resin (trade name: Showa Kobunshi [
Milben 850) and 1 wt % of a reaction accelerator (trade name: Showa Kobunshi Co., Ltd. LL-10) are added to styrene-acrylic emulsion and sprinkled on ferrite particles brought into a heated fluidized state. The heating temperature in this case is approximately 150℃
Then, the surface of the ferrite particles was coated with a resin with a solid content of 3% by weight.

Note that the styrene acrylic resin in the styrene acrylic emulsion undergoes a crosslinking reaction by adding the melamine formalin resin to become a thermosetting resin and is coated.

In the above examples, melamine formalin resin 10vt%,
Two types of ferrite carriers manufactured at 25 wt%, a ferrite carrier coated only with conventional styrene acrylic resin, and a non-coated carrier were used, and the environmental conditions were 20°C and 60% R.1. DeU
- Copying is carried out using a Big 3000 copying machine.
The image density was evaluated according to the number of copies, and the comparison was shown in the drawing.As can be seen from the drawing, the example containing 10 wt% melamine formalin maintains the image density even when the number of copies is larger than that of the conventional one. It can be seen that the value does not decrease. In the case of 25% melamine-formalin resin, formalin acts strongly, and the charging characteristics of the base resin change greatly, resulting in a decrease in image quality such as a decrease in image density.

An environmental test was also conducted to examine the cohesiveness of the ferrite carrier particles when they were kept at 50°C for 48 hours. In addition, cohesiveness 1
It was [1 view]. In Example L, melamine-formalin resin was used at 5 wt%, 10 wt%, and 20 vt%.

Four types of ferrite carriers manufactured as 25%,
A test was conducted on a conventional ferrite carrier coated with only styrene acrylic I[t, and the results are shown in the table below.As is clear from the table below, the product of this example did not agglomerate, and as a ferrite carrier it was 9! Delicious.

[Table] Note that if the amount of added melamine-formalin resin is less than 3 wt%, sufficient crosslinking reaction will not occur.

The effect of improving heat resistance and wear resistance is small, and ferrite carriers tend to aggregate.

Effects of the Invention The ferrite carrier of the present invention is a coating material in which 3 to 2 Qwt% of melanin-formalin resin is added to a heat-of-Q1 resin. can be converted into thermosetting resin. Therefore, the ferrite carrier has excellent heat resistance and is resistant to agglomeration, and also has 77'f electrical property, so that desirable developed image quality can be obtained even after long-term use.

[Brief explanation of drawings]

The drawing is a graph showing the r'A relationship between the image density and the number of copies when developing using the ferrite carrier of the present invention and the conventional ferrite carrier. Applicant [1 Ritsu Metal Co., Ltd. agent Patent attorney Katsutsugu Maki x) / Coating carrier styrene acrylic only 0 styrene acrylic + Polmarine (IOwtZ) Δ
of'"
(25wtyo) (Number of copies xlooo)

Claims (2)

[Claims] (1) A ferrite carrier in which the surfaces of ferrite particles are coated with a mixed resin in which 3 to 20 wt% of melamine-formalin resin is added to a thermoplastic resin such as acrylic, styrene, or styrene-acrylic. (2) The ferrite carrier according to claim 1, wherein a reaction accelerator is added to the mixed resin to be coated.