JPH0643690A - Production of electrophotographic toner - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the dispersibility of carbon black in the toner so that the distribution of carbon black becomes uniform and the amount of toner adhering per unit area is at least to obtain a satisfactory image density. To provide a method of manufacturing a toner for electrophotography that enables the toner. [Structure] When manufacturing an electrophotographic toner, a master batch containing a high content of carbon black is prepared in advance,
A method for producing an electrophotographic toner, which comprises blending this with a binder resin to adjust a desired component composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrophotographic toner, and more particularly to a method for producing an electrophotographic toner having improved dispersibility of carbon black.

[0002]

2. Description of the Related Art Conventionally, as a toner for electrophotography, a binder resin generally occupies 80 to 90% of the toner, and other components include about 5 to 15% of a coloring agent such as carbon black and about 1 to 5%. A charge control agent, a release agent such as several percent of polyethylene wax and polypropylene wax, and several percent of fine silica powder are added as an external additive for improving fluidity. Such a material is prepared by premixing a compound other than the external additive, and then subjected to steps such as melt-kneading, cooling, coarse / fine pulverization, and classification, and an external additive treatment is appropriately performed. Becomes

[0003]

By the way, in the case of producing a toner by the conventional production means as described above, particularly when carbon black is used as a colorant, it is caused by insufficient mixing, kneading and the like. The dispersibility of carbon black may deteriorate, and in such a state, the abundance in the toner particles varies, such as the toner particles remaining as aggregates, and as a result, the obtained image density varies. Will occur. However, in general, a certain amount of toner or more is required per unit area in order to obtain a desired image density. However, if there are variations as described above, more than the minimum required amount of toner is attached to the paper. The need arises,
Therefore, the toner consumption amount is increased.

As a countermeasure against this, it is conceivable to simply increase the content of carbon black to increase its content, but this alone rather lowers the electric resistance of the toner and causes toner scattering and white background fog (Back Ground, B
Problems such as an increase in G) may occur. Therefore,
It is important to improve its dispersibility without increasing the amount of carbon black, but no solution has yet been found. It is possible to increase the kneading time for the purpose of improving the dispersibility of carbon black,
In this case, molecular breakage of the resin may occur, which may cause image stains such as offset due to improper fixing during electrophotographic fixing accompanied by the deterioration of the resin due to such overheating. Absent. Therefore, it is an object of the present invention to improve the dispersibility of carbon black in a toner to make the distribution of carbon black uniform and to obtain a satisfactory image density with at least the amount of toner adhering per unit area. Another object of the present invention is to provide a method for producing an electrophotographic toner.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the gist thereof is to include carbon black in a high content in advance in the production of an electrophotographic toner. There is a method for producing an electrophotographic toner in which a masterbatch is prepared and blended with a binder resin to adjust a desired component composition, and it is particularly preferable that the carbon black content of the masterbatch is 10 to 40% by weight. It is a thing.

[0006]

In the present invention, when a toner is manufactured, a high content of carbon is basically obtained by mixing a binder resin with a high blending amount of carbon black and, if necessary, other blending components and kneading and pulverizing. A masterbatch containing black is prepared, and this is further mixed with a binder resin so as to be diluted with a binder resin to a carbon black content rate of a predetermined toner to form a toner by a conventional method. Is improved and the distribution thereof is made uniform, so that an image density that satisfies at least the toner adhesion amount per unit area can be obtained.

[0007]

The present invention will be described in detail below with reference to examples. First, the main point of the present invention is that a masterbatch containing a high content of carbon black is prepared in advance in the production of the electrophotographic toner. In this case, the masterbatch manufacturing means itself performs premixing, melt-kneading, cooling, and pulverization of the compound in accordance with the usual toner manufacturing process. The amount of carbon black is the main component, and the blending amount is preferably about 10 to 40% by weight as the content rate in the masterbatch. In addition, during the masterbatch production, it is possible to add in advance charge control agents, mold release agents, etc., which are blended in the usual toner manufacturing process. It can also be added during the process.

When the content of carbon black in the masterbatch exceeds 40% by weight, it becomes difficult to knead with the binder resin during kneading during the production of the masterbatch. On the other hand, if the content is less than 10% by weight,
Since it does not change much from the range of the conventional manufacturing method, the difference in the image quality and the like can be hardly seen compared with the toner obtained by the conventional method. Therefore, the high content range is preferably 10 to 40% by weight.

Next, in the present invention, the masterbatch obtained as described above is premixed with the binder resin in the same manner as in the conventional toner production method, and melt kneading, cooling, coarse / fine pulverization, classification, The toner is obtained through a process such as an external addition process. In this case, the components to which the other components such as the charge control agent are not added during the production of the masterbatch can be blended together during the preliminary mixing of the above masterbatch and the binder resin. It should be noted that for each compounding component such as carbon black, the masterbatch is diluted with a binder resin so that the target value of each component to be contained in the final product toner is obtained. Is adjusted to be about 5%. The toner thus obtained has excellent dispersibility of carbon black, and the aggregates of carbon black in the toner are smaller than those obtained by the usual means.

The present invention will be described in more detail below based on the experimental results. First, for the following Examples 1 to 3, first, the materials were melt-kneaded for each masterbatch composition, cooled, and pulverized to obtain a masterbatch,
With respect to the toner composition in which a binder resin or the like was added to each masterbatch, the materials were melt-kneaded, cooled, pulverized, and then classified to obtain toners having an average particle diameter of about 10 μm.
For comparison, as a comparative example, without preparing a master batch, a toner composition was directly melt-kneaded, cooled, pulverized, and then classified to obtain a toner having an average particle diameter of about 10 μm. I did.

Example-1 (Masterbatch composition) Binder resin Styrene acrylic resin 60% by weight Carbon black 25% by weight Charge control agent Quaternary ammonium salt 10% by weight Release agent Polypropylene wax 5% by weight (Toner composition) Binder resin Styrene Acrylic resin 80% by weight 20% by weight of the above masterbatch composition

Example-2 (Masterbatch composition) Binder resin Styrene acrylic resin 55% by weight Carbon black 35% by weight Release agent Polypropylene wax 10% by weight (Toner composition) Binder resin Styrene acrylic resin 86% by weight The above masterbatch composition 12 wt% Charge control agent Quaternary ammonium salt 2 wt%

Example-3 (Masterbatch composition) Binder resin Styrene acrylic resin 85.5% by weight Carbon black 10% by weight Charge control agent Quaternary ammonium salt 3% by weight Release agent Polypropylene wax 1.5% by weight (toner composition ) Binder resin Styrene acrylic resin 35% by weight The above masterbatch composition 65% by weight

Comparative Example (Toner Composition) Binder Resin Styrene Acrylic Resin 87 wt% Carbon Black 7 wt% Charge Control Agent Quaternary Ammonium Salt 2 wt% Release Agent Polypropylene Wax 2 wt%

The above four types of toner were actually used in an electrophotographic copying machine and evaluated. The evaluation items include the image density (Image Density, ID) at the beginning of copying and after 5,000 copies (5K) and the background fog (Back Ground,
BG), toner consumption, and toner scattering, respectively,
The overall evaluation is indicated by ⊚ very good, ○ good, Δ somewhat bad, and × bad. The larger the numerical value of ID, the higher the density, and the smaller the numerical value of BG, the better. Further, the toner consumption amount indicates the amount of toner consumed for 5000 sheets, and regarding the toner scattering, the state of toner stain in the developing tank is visually judged to judge whether it is good or bad. The above results are summarized in Table 1.

[0016]

[Table 1]

As can be seen from Table 1, the toners obtained by the method of the present invention all exhibit satisfactory characteristics. The cross-sections of the toner particles of the toners obtained in Examples and Comparative Examples were taken with a transmission electron microscope (TE).
According to M), it is recognized that the toners using the master batches in Examples 1 to 3 have smaller carbon black aggregates, and the carbon black is more uniformly dispersed. It was confirmed.

[0018]

According to the present invention, since the dispersibility of carbon black in the toner is improved, the distribution of carbon black becomes uniform, and at least the amount of toner adhering per unit area ensures a satisfactory image density. It is possible to reduce the cost of toner per copy,
Further, since the content of carbon black itself can be reduced as compared with the conventional toner, it is expected that the manufacturing cost can be reduced.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Norio Tateishi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Yoshitaka Urata 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Incorporated (72) Inventor Shintaro Hatano 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (2)

[Claims] 1. A method for producing an electrophotographic toner, wherein a masterbatch containing a high content of carbon black is prepared in advance, and the masterbatch is blended with a binder resin to adjust a desired component composition. Of manufacturing toner for toner. 2. The method for producing an electrophotographic toner according to claim 1, wherein the carbon black content of the masterbatch is 10 to 40% by weight.