JP3291587B2 - Manufacturing method of electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an electrophotographic toner.

[0002]

2. Description of the Related Art A toner for electrophotography imparts fluidity to a classified product obtained by mixing, melt-kneading, pulverizing and classifying raw materials containing a binder resin, a dye / pigment, a charge control agent, a wax and the like. It is obtained by adding an agent or the like. In this case, a step of removing coarse particles in the toner is required at the final stage of the manufacturing process. The coarse particles are generated by compression in a damper of a manufacturing plant, fusion inside a pipe, granulation in a mixing device, and the like, and cause various disadvantages if used without being removed. For example, when copying, sand-like fogging on the image occurs, or coarse particles are formed between the sleeve and the blade of the developing device, that is, vertical streak-like unevenness occurs. In addition, since coarse particles create a gap between the photosensitive drum and the paper to which the toner is transferred, the transfer to the paper becomes uneven, causing problems such as unevenness, and the process of removing this is indispensable. It is.

Conventionally, a gyro shifter shown in FIG. 2 and a vibrating sieve shown in FIG. 3 have been generally used. However, it is very difficult to sieve fine powder such as toner, and clogging of the screen is likely to occur, and good products overflow on the coarse particle side to be removed. Therefore, it was necessary to introduce a considerably large device. Up to now, in the gyro shifter shown in FIG. 2, the brush 21 and the like are placed on the screen 22 and clogging is prevented by rubbing strongly. Was a heavy burden. In addition, there is also a problem that the brush fragments are mixed into the toner, and further, the aperture of the screen is widened by the action of the brush,
The problem of the inclusion of coarse particles to be removed often occurred.

Further, recently, in order to achieve high image quality of a copy, a toner having a smaller particle size has been used more often than ever, and a finer sieve has been required. The conventional sieve has a limit of about 100 μm, and if it is finer than that, the throughput will drop extremely,
Recruitment was difficult.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an electrophotographic toner which has solved the above-mentioned problems.

That is, an object of the present invention is to provide a method for producing an electrophotographic toner which enables sieving with a finer screen.

It is still another object of the present invention to provide a method for producing an electrophotographic toner which prevents coarse particles from entering due to a change in screen aperture.

Another object of the present invention is to provide a method for producing an electrophotographic toner capable of extending the life of a screen.

Another object of the present invention is to provide a method for producing an electrophotographic toner in which foreign matter such as brush fragments is not mixed.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for producing an electrophotographic toner comprising a classifying step of removing coarse particles in a toner containing a negative charge control agent. A screen made of resin, a blade provided inside the screen, which rotates about a center axis of the screen as a rotation axis, and a plurality of blades that collide with the screen by centrifugal force due to the rotation of the blade to give microvibration. use the classification device having a ball in the該分classification step
By be Rukoto relates to a method of manufacturing a toner for electrophotography, which comprises removing the coarse fraction in the toner.

FIG. 1 is a schematic sectional view of a classification device used in the present invention. The blades 12 rotate at high speed inside the cylindrical screen 11. The toner supplied from the toner supply port 13 collides with the blade 12 to be disaggregated and collides with the screen 11 by centrifugal force, and the toner having a particle size smaller than the aperture passes through the toner collection unit 14. The collected coarse particles move inside the screen and are discharged from the coarse particle discharge port 15. An elastic ball 16 exists inside the screen 11, and the screen 11 rotates in accordance with the rotation of the blades.
To prevent clogging.

A feature of the classifier used in the present invention is that, first of all, the coagulation of toner is sufficiently released by the rotating blades. In a conventional classifier, rubber balls and the like are placed on a screen or a screen unit and dislodged by their movement. However, the capacity is not sufficient, and the throughput is reduced. In the classifier used in the present invention, since the coagulation is broken by the blade rotating at a high speed, it is possible to cause sufficiently dispersed toner to collide with the screen.

The second feature is that a strong centrifugal force acts on the toner to pass the toner through the screen. In the conventional apparatus, the toner is caused to pass through the screen only by gravity. However, in the apparatus used in the present invention, the toner can be more strongly passed through the screen.

A third feature is that the ball of the elastic body inside the screen collides with the screen to give a slight vibration to prevent clogging. Unlike brushes used in conventional gyro shifters, etc., they only apply micro-vibration to the screen.Since they are very small and small enough, they do not damage the screen. No change in aperture occurs. Further, since the elastic ball is used, no fragments are mixed into the toner.

The blades used in the classification device of the present invention may be, for example, a plurality of plate-like blades attached to a rotating shaft, and the number of rotations is generally in the range of 500 to 2000 rpm. As the screen to be used, any of known materials can be used. However, a resin screen made of a resin such as polyester is preferable because an elastic ball gives a slight vibration. The elastic ball to be used is a general ball of urethane or the like having a diameter of several millimeters, and about 10 balls exhibit a sufficient effect.

In the classification device of the present invention, all known dry toners can be sieved. In particular, when the particle size is 1
It is very effective for sieving toner having a small particle size of 0 μm or less. These toners require more precise sieving using a screen having an opening of about 70 to 90 μm, but the classification device of the present invention can sufficiently cope with the sieving. Further, since a screen having an aperture of 50 μm can be used, it can be used for the production of finer toner of 6 μm or less.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Classifiers (a) to (c), toners (1) and (2)
Was prepared.

Classifier (a): The configuration shown in FIG. 1 was used, and seven urethane balls having a diameter of 6.5 mm were used. Classifier (b): The configuration shown in FIG. 2 is adopted, and a brush 21 is placed on a screen 22. The classified toner is discharged from 3 and the coarse particles are discharged from 24. The brush 21 moves so as to draw a circle in the horizontal direction. Classifier (c): The configuration shown in FIG. 3 is adopted, and classification is performed by vibration. The toner passing through the screen 31 is discharged from 32 and the coarse particles are discharged from 33.

Toner (1): The toner (1) having the above formulation has a particle size of 8.5 μm, and 0.7% of hydrophobic silica (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd.) is externally added using a Henschel mixer. Toner (2): The toner (2) having the above formulation has a particle size of 8.2 μm, and 0.7% of hydrophobic silica (trade name: R-812, manufactured by Nippon Aerosil Co., Ltd.) is externally added using a Henschel mixer.

An experiment was conducted in which the toners (1) and (2) passed through the classifiers (a) to (c). Table 1 shows the results. The rotation speed of the blade in the first embodiment is 100
0 rpm, and the rotation speed of the blade in the second embodiment is 12
00 rpm.

[0021]

[Table 1]

The classifier according to the present invention is excellent in the throughput and the durability of the screen, has no coarse particles,
Screens with an aperture of 0-70 μm could also be used.

[0023]

As described above, by using the present invention, in the process of removing coarse particles in the toner, the processing amount is much larger than in the prior art, so that the apparatus can be downsized and the height of the screen can be reduced. It is possible to achieve a long life, to prevent coarse particles from jumping in, and to prevent the debris such as brushes from being mixed, and it is possible to use a screen having an aperture of 50 to 70 μm, which has been impossible in the past. And it can be seen that the present invention is very useful industrially.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a classification device used in the present invention.

FIG. 2 is a schematic sectional view showing an example of a conventional classifier.

FIG. 3 is a schematic sectional view showing an example of a conventional classifier.

Claims (4)

(57) [Claims] 1. A method for producing an electrophotographic toner comprising a classification step of removing coarse particles in a toner containing a negative charge control agent, comprising: a screen formed of a cylindrical fixed polyester resin; The classifying step includes a blade provided inside the screen, the blade rotating around the center axis of the screen as a rotation axis, and a plurality of balls that collide with the screen by centrifugal force generated by the rotation of the blade to apply micro-vibration. the in to Rukoto use, electrophotographic method for producing a toner, and removing the coarse fraction in the toner. 2. The method for producing an electrophotographic toner according to claim 1, wherein in the classifying step, coarse particles in the toner to which hydrophobic silica is externally added are removed. 3. The method for producing an electrophotographic toner according to claim 1, wherein the toner contains at least an unsaturated polyester resin or a styrene / n-butyl acrylate / divinylbenzene copolymer. . 4. The screen has an aperture of 50 to 70 μm.
The method for producing an electrophotographic toner according to claim 1, wherein m is m.