JPS60115949A - Carrier for electrophotography developer - Google Patents

Abstract

PURPOSE:To improve moisture resistance of the surfaces of carrier particles under high humidity, and to execute sufficiently frictional electrification to a toner even under high-humidity environment by sticking a sublimable rust preventive to the surfaces of magnetic carrier particles. CONSTITUTION:A sublimable rust preventive 27 (example: commodity name: ''Anticall A'') is placed on a shelf 21b having a fine hole installed at the lower part of a hopper 21 of a circulation type fluidized bed drying machine 20, and also carrier particles 1 (example: ferrite carrier) are thrown onto it. Subsequently, an air blower 24 is operated, and a hot blast 23a heated by a heater 25 is jetted into the hopper 21 through a hole provided on the shelf 21b. As a result, the sublimable rust preventive 27 placed on the shelf 21b is evaporated, also the carrier particles 1 are whirled up, a thin protective film of the sublimable rust preventive 27 is formed on the surfaces of the carrier particles 1 and an object carrier for an electrophotography developer is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a carrier for an electrophotographic developer, and more particularly to a carrier for an electrophotographic developer used in a dry type electrophotographic X-copying machine and the like.

(Prior Art) Generally, as a process for obtaining a copy image in electrostatic recording method and electrophotographic method, the first step is to apply a corona discharge to the surface of a charge support made of a photoreceptor having photoconductivity. The charge support is uniformly charged with electrostatic charges, and then, as a second step, a light image corresponding to the document is exposed to form a group of static charges on the charge support. - Furthermore, as a sixth step, this electrostatic charge latent image is developed. For example, a dry magnetic two-component developer, which is a mixture of toner and carrier, is used.

Here, to explain the developer consisting of this toner and carrier, first of all, the toner is fine particles mixed with colored resin, carbon black, and other additives and crushed, and the carrier is magnetic particles such as iron powder. It is a particle having Then, when this toner and carrier are mixed by an appropriate means, they rub against each other and the toner is charged with a polarity opposite to that of the carrier (referred to as triboelectric charging). The polarity of the toner due to this triboelectric charging is opposite to the polarity of the electrostatic charge 11 ('I) formed on the surface of the charge support. Therefore, in the phenomenon process of the sixth step, the well-known When said toner is forced close to said charge support by means, said toner is electrostatically attracted to said latent electrostatic charge image formed on said charge support, and its dispersion causes the formation of said support. A BJ image @ (referred to as toner 1 image) is formed on the surface.As mentioned above, it is only the toner that is adsorbed, and the carrier is not adsorbed because its polarity is the same as the electrostatic charge #f image. Furthermore, as a fourth step, the toner particles are transferred to copy paper and fixed by suitable means to obtain a desired copy image.

Since a copy image is obtained by such a process, the above-mentioned toner is consumed each time a copy is made, and in extreme cases, the toner is consumed.
Since the copied image becomes unclear, it is necessary to replenish the developer with new toner as appropriate depending on the amount of toner consumed.

However, as the above five processes are repeated, the physical properties of the surface of the carrier made of magnetic particles change, and the frictional charging characteristics between this carrier and the toner also change. This makes it difficult to charge a large amount of charge.

Conventionally, the above-mentioned inverted carrier or magnetic particles such as iron powder or ferrite have been used, but if these magnetic particles are left in high humidity for a long period of time, the above-mentioned triboelectric properties change. As a result, the properties of the developer, which is a mixture, are significantly deteriorated as described above.

Therefore, many attempts have been made to stabilize performance even under high humidity conditions. For example, forming a coating layer of tree' on the surface is expected to stabilize performance under high humidity, but when actually used as a developer, this coating layer becomes mechanically unstable. If the resin used for the coating is destroyed and peeled off, or if the resin used for the coating deteriorates due to humidity, the triboelectric characteristics change, and as a result, the bright areas (white background) of the intended copy image change. is getting a little closer to the dark side 5
(It was called Capri).

(Objective) It is an object of the present invention to provide a carrier for an electrophotographic developer in which the surface physical properties of carrier particles that control magnetism exhibit stable performance even under high humidity, and which can sufficiently triboelectrically charge toner fine particles. purpose.

(Summary) In order to achieve the above object, the present invention improves the moisture resistance of the surface of the carrier particles under high humidity by attaching a row-edge rust preventive agent to the surface of the magnetic carrier particles. This feature is characterized in that the toner can be sufficiently triboelectrified with the toner in a high humidity environment.

(Example) Hereinafter, the present invention will be explained with reference to an illustrated embodiment.

In the present invention, a sublimable rust inhibitor is deposited on the surface of a carrier 1 (hereinafter referred to as undeposited carrier) made of spherical iron powder having an average particle diameter of 75 μm, as shown in FIG. 1, for example. For this purpose, a circulating bottle fluidized bed dryer unit as shown in FIG. 2 is used.

In this dryer tray, a funnel-shaped hopper 21 has its open lower end 21a fixed vertically to approximately the center of a relatively thick pedestal 22 by appropriate means, and the lower end 21a
1a is connected to an air pipe 26, and this air pipe 26 is connected to the base 2.
2 and is connected to a blower 24 provided outside the pedestal 22. The air sent from the blower 24 to the air pipe 23 is then transferred to the heater 2.
5 to become hot air at a temperature of 4° to 50° C., and the hot air is sent into the above-mentioned hot spring 21. A mounting shelf 21b having fine holes is provided horizontally slightly above the lower end 21a of the hot spring 21, and a sublimation rust preventive agent 27 is placed on this shelf, and the carrier is placed on top of the shelf 21b. 1 is inserted. As the hot air 23a blows upwards as shown by the arrow A, the single year 1 placed in the hopper 21 is blown up into the hot air <21, and at the same time, the hot air 23a blows the air into the 4111+
The sublimable rust preventive agent 27 placed on 21b is vaporized,
Fine particles of the rust preventive agent 27 that are blown up together with the carrier film in the hopper 21 and vaporized during this time adhere to the surface of the carrier film and form a protective film 27a.
(See Fig. 4), and a fine mesh ' is formed in the center of the lid 26 disposed at the upper opening of the hopper 21. ! An exhaust port 26a is provided with a 1" mesh 26b for discharging the hot air 23a.

In the hopper 21 on the side of the circulating fluidized bed dryer configured in this way, first, a sublimable rust preventive agent 27 (trade name: Anticol A) is placed on the shelf 21b.

(manufactured by Kirest Kagaku Co., Ltd.), and on top of that, 4 kg of the above-mentioned non-adherent carrier, and then the above-mentioned lid 26
put In the closed state, the power switch (not shown) is connected to the upper shelf 21b.
Since the hot air 23a is blown upward through the fine holes provided in the rust preventive agent 27, the rust preventive agent 27 is vaporized as described above.
And the above-mentioned carrier is soared. In this state, when the hot air 23a is continued to be fed for one hour, as shown in FIG.
(hereinafter referred to as an attached carrier) is formed.

Next, the above-mentioned adhered carrier 2fg obtained in this way
: A developer having a toner concentration of Swt was obtained by mixing styrene-acrylic resin and toner powder composed of carbon black or the like.

This developer was placed in a developing device of a commercially available copying machine (not shown) and forcedly stirred for 10 hours. Then, the amount of charge on the developer taken out from the developing device was measured using a blow-off charging test device, and the current value of the developer was also measured using a measuring device as shown in FIG. Here, the reason why the current value of the developer was measured is that in order to obtain a good quality copy image, the developer needs to be within a certain range of resistance. A current value was set as L, which was used as a substitute value for the above resistance value.

As shown in FIG. 3, the measuring device described above includes a well-known magnet roll 36 rotatably disposed inside a developing device 62, and an opening 32a is provided in the upper right corner of the developing device 62. A conductive aluminum drum 54 is disposed slightly above and to the right of the opening 32a in close proximity to the magnet roll 66. This drum 34 is connected to the positive pole of a DC current meter 35 via a DC ammeter 35, and the negative pole of this power source 36 is connected to the ground together with the magnet 36. And this magnetic roll 6
3 is rotated, a minute direct current flows through the developer 31 magnetically attached to the surface in the form of a brush.
This minute current is measured by the current Rf55.

Using the measuring device configured in 5 above, we measured a developer in which the adhered carrier Z and the donor were mixed (hereinafter referred to as the adhered developer), and a developer in which the unadhered carrier Z and toner were mixed (hereinafter referred to as the unadhered developer). The charge amount and current value with the agent 5) were measured in the following three cases.

(1) Initial value (2) After 10 hours of forced stirring (3) After 10 hours of forced stirring, then room temperature 30°C
1. After being left for a day and night in an environment with a humidity of 80%, the toner and toner concentration used in the above-mentioned powdered N developer were the same as in the case of the above-mentioned adhering developer.

The results are shown in the table below.

From this result, it can be seen that the adhered developer shows less change in both the band density and current value than the unadhered developer, and exhibits stable characteristics even under high humidity.

In addition, when we compared images of copies obtained with the copying machine using each of the above-mentioned developers after leaving them for a day and night, it was found that when the adhesive developer was used, there was no cuff on the copying acid and the initial state of adhesion remained. The image quality was comparable to that of a copy obtained using a developer.

On the other hand, when the unattached developing agent was used, the copy image had noticeable distortion.

(Effects) According to the present invention, it is possible to sufficiently triboelectrically charge the toner even under high humidity, so that a high-quality copy image can be obtained.

[Brief explanation of drawings]

Figure 1 is an enlarged front view of a conventionally used spherical carrier; Figure 2 is a cross-sectional view of a circulating fluidized bed dryer used for depositing rust preventive; and Figure 3 is a diagram showing developer An electric circuit diagram of a measuring device for measuring current value. FIG. 4 is an enlarged cross-sectional view of the carrier of the present invention. Carrier 20------Circulating fluidized bed dryer 21... Hopper 21b...φ/Shelf 26...Blow pipe 25/Fist/Skewer/Heater 27---Sublimation prevention Rust agent 61...Developer 66...McNet roll 34...Aluminum drum measure 1 Ward 2 Ward measure 3 Ward

Claims (1)

[Claims] A carrier for an electrophotographic developer, characterized in that a sublimable rust preventive agent is attached to the surface of carrier particles.