JPH0816800B2 - Method for producing electrostatic image toner - Google Patents

Description

The present invention relates to a method for producing a toner for developing an electrostatic latent image formed in electrophotography, electrostatic printing, electrostatic recording or the like.

[Conventional technology]

Usually, toners for electrostatic images are produced by dry blending a binder resin, a colorant, a charge control agent, and other additives that are added as necessary to a predetermined composition, and then melt-kneading, pulverizing and classifying steps. It In this electrostatic charge image toner, the performance of the toner such as uniform triboelectricity and copy image density is affected by the dispersion state of the colorant, charge control agent, etc. in the binder resin.

Conventionally, powdery carbon black or beaded carbon black has been mainly used as the colorant. The toner using such powdery carbon black has a problem of poor dispersion in the binder resin due to a large amount of air being mixed in during melt kneading, which significantly reduces the kneading action.
On the other hand, in the toner using the bead-like carbon black, it was not possible to obtain a uniform dispersed state in the binder resin as in the case of the powdery carbon black because of its peculiar property although air was not mixed during the melt-kneading. .

As described above, when the dispersion state of carbon black in the toner becomes non-uniform, a sharp charge amount distribution cannot be obtained in the triboelectrification property, and therefore nonpolar toner or reverse polarity toner is apt to occur, which causes friction when multiple sheets are copied. This has been a cause of problems such as a decrease in electrification property, background fog, and deterioration of image quality.

[Problems to be Solved by the Invention]

It is an object of the present invention to provide a toner with a sharp charge distribution which is necessary for high-quality copying by using a specific bead-shaped carbon black.

[Means for solving the problem]

That is, the gist of the present invention is that the particle size distribution is 149 μm to 840 μm.
Melt kneading bead-shaped carbon black having a bead hardness of 5 to 40 g with a binder resin in a range of m,
A method for producing a toner for electrostatic charge images, which comprises pulverizing and classifying and dispersing the carbon black in a binder resin.

 Hereinafter, the present invention will be described in detail.

The bead-like carbon black constituting the toner of the present invention is 149 μm by a dry granulation method or a wet granulation method of carbon black powder produced by a furnace method or the like.
It is produced by granulating so as to have a particle size distribution of m to 840 μm and a bead hardness of 5 to 40 g.

The dry granulation method uses a tumbling granulator, etc., where carbon black powder moves in a chamber divided into several parts while being compressed by rollers in a rotating drum. It is what is granulated.

On the other hand, in the wet granulation method, water having a water content slightly lower than the plastic limit is added to carbon black powder to stir and roll to granulate, and the water added to the carbon black after granulation is removed. Is dried using a rotary dryer, an airflow dryer or the like.

In the dry granulation method, the particle size distribution and bead hardness which are numerically limited in the present invention can be obtained by changing the number of chambers of the rolling granulator, the weight of the roller, the rotation speed of the drum and the like. Further, in the wet granulation method, it is possible to control within the numerical limit range of the present invention by changing the addition amount of water, the stirring rotation speed and the like.

The measuring method of bead hardness referred to in the present invention is ASTM No. D-
According to 3313-74.

The bead-like carbon black having a bead hardness of less than 5 g measured by the above-mentioned method causes excessive crushing during the melt-kneading to cause air inclusion, while it exceeds 40 g because it is too hard.
Grindability is poor and good dispersion in the binder resin cannot be obtained. Also, the particle size distribution of the bead-like carbon black (however, the measuring method depends on the sieving method) needs to be 149 μm to 840 μm, and if it is less than 149 μm, the air inclusion seen in the powdery carbon black occurs. However, good dispersion cannot be obtained, and when it exceeds 840 μm, the bead-like carbon black is too large, so that it is not sufficiently pulverized and uniform dispersion cannot be obtained.

Examples of commercially available bead-shaped carbon black in the present invention include, for example, Cabot's trade name ACB300,
These bead-like carbon blacks are satisfactorily dispersed in the binder resin because individual beads are uniformly crushed during melt-kneading.

Hereinafter, materials other than the colorant used in the toner of the present invention will be described in detail.

As the binder resin, a thermoplastic resin generally used as a binder resin for toner can be used, and examples thereof include styrene resin, polyacrylic acid ester resin, styrene-acrylic acid ester copolymer resin, polyvinylidene chloride resin, Examples thereof include polyvinyl acetate resin, phenol resin, epoxy resin and polyester resin. Further, these resins are not limited to one type, but can be used as a mixture of two or more types depending on the purpose.

As the charge control agent, nigrosine dyes, quaternary ammonium salts, metal complex dyes, titanates or carbonates such as Ca and Ba, alkoxylated amines, various polyamide resins such as nylon, condensation polymers containing amino groups, etc. A polyamine resin or the like is appropriately selected and used according to the desired charging polarity of the toner.

In addition, other additives such as lubricants, abrasives, and fixing agents that are blended into the toner as required include, for example, polytetrafluoroethylene powder, metal salts of higher fatty acids, cerium oxide, low molecular weight polyethylene, low molecular weight polypropylene, etc. Can be used.

〔Example〕

Next, the present invention will be specifically described with reference to examples. In addition,
The present invention is not limited to the following examples unless it exceeds the gist.

Examples 1 to 5 and Comparative Examples 1 to 7 Carbon black MA-100 manufactured by Mitsubishi Kasei Co., Ltd. was granulated, and
A bead-like carbon black having the particle size distribution and the lower and upper limits of bead hardness as shown in the table was prepared. However, for Comparative Example 1, powdery carbon black was used as it was.

Next, each carbon black shown in Table 1 was dry blended with the following materials at a predetermined mixing ratio, and then melt-kneaded, pulverized and classified, and then negatively charged and had an average particle diameter of 12 μm.
The toner for electrostatic charge image of the present invention and the toner for comparison were obtained.

Next, for each 6 parts by weight of each toner obtained above, a silicon-coated ferrite carrier (F65-10 manufactured by Nippon Iron Powder Co., Ltd.) was used.
100 parts by weight of 0) were mixed to prepare a developer.

The developers based on the above Examples 1 to 5 and Comparative Examples 1 to 7 were set in an electronic copying machine (A4 size, copy speed: 50 sheets / min), and a continuous copying durability test up to 100,000 sheets was performed.

Table 2 shows the evaluation results for triboelectric charge and ground fog up to 100,000 sheets. Here, the triboelectric charge amount was measured by the blow-off method, and the ground fog was measured in the non-image area with a Macbeth reflection densitometer. As shown in Table 2, it was confirmed that the toner using the beaded carbon black of the present invention had a stable triboelectric charge amount up to 100,000 sheets and had very little background fog. Further, in order to further clarify the action and effect of the beaded carbon black of the present invention, the measurement results of the charge amount distribution after 100,000 sheets of continuous copying in Examples 1 to 5 and Comparative Examples 1 to 7 are shown in FIGS. Shown in Figure 12. Charge amount distribution measuring device A q / d meter manufactured by PES was used. As is clear from FIGS. 1 to 12, it was confirmed that the toner using the beaded carbon black of the present invention has a sharp charge amount distribution.

〔The invention's effect〕

As described above, according to the present invention, the bead-like carbon black having a specific particle size distribution and bead hardness is contained in the binder resin in the toner in a uniform dispersed state, whereby the toner for the electrostatic image is sharp. It is possible to provide a charge amount distribution, and as a result, it is possible to provide a manufacturing method capable of obtaining an electrostatic charge image toner having stable image characteristics in a large number of copies.

[Brief description of drawings]

FIG. 1 to FIG. 5 are graphs showing charge amount distributions after 100,000 sheets of continuous copying of the electrostatic charge image toner of the present invention corresponding to Examples 1 to 5, and FIGS. 6 to 12. The figures show Comparative Examples 1 to 7
FIG. 6 is a diagram showing a charge amount distribution after continuous copying of 100,000 copies of a comparative electrostatic image toner corresponding to the above.

Claims (1)

[Claims] 1. A bead-like carbon black having a particle size distribution in the range of 149 μm to 840 μm and a bead hardness in the range of 5 to 40 g is melt-kneaded, pulverized and classified with a binder resin to form the binder resin. A method for producing an electrostatic charge image toner, comprising: