JPS63108356A - Manufacture of toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To uniformly attach a hydrophobic silica to the outside of a toner in high efficiency without attaching toner particles to each other by executing mixing of the polymer toner with the hydrophobic silica in a liquid dispersion medium. CONSTITUTION:The polymer toner containing a thermoplastic resin and a colorant are mixed in the liquid dispersion medium, such as water, and then, the silica is externally attached by removing the medium, thus permitting shearing stress on the toner and addition of heat to the toner to be small, mixing dispersion to be enabled for a long time, and accordingly, external attachment of the hydrophobic silica to be executed without causing melt attaching of the toner particles with each other.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrostatic image developing method for developing an electrostatic image in image forming methods such as electrophotography, electrostatic photography, and electrostatic printing. This invention relates to a method for producing polymerized toner.

[Prior Art] Toners conventionally used in dry image forming methods such as electrophotography, electrostatic printing, and electrostatic recording are generally made by melt-mixing colorants and other additives in thermoplastic resin. After being uniformly dispersed, the particles are pulverized using a pulverizer and then classified using a classifier to obtain the desired particle size. Although the resulting toner is quite good, it does have potential problems due to the grinding process. That is, the toner obtained using the grinding method must have some brittleness in order to make the material easier to grind to some extent, but if it is too brittle it will be too finely pulverized and will not be suitable for later treatment. In order to obtain toner with a particle size distribution, it is necessary to cut the fine powder, which results in increased cysts.
Furthermore, in some cases, the toner is further pulverized in the developing device of a copying machine. In addition, when a material with a low melting point or a material that is pressure-fixed is used to improve thermal stability, a fusion phenomenon may occur in the crusher or classifier.
There may be cases where continuous production is not possible.

Other requirements for the toner are that it has JgIM charging characteristics suitable for development, that it forms a developed image with 1G1, that there is no change in performance even when released, and that there is no coagulation (blocking, etc.).
In particular, during fusing, the toner must be resistant to wear and tear, have appropriate heat fixing properties or pressure fixing properties, and not contaminate the surface of the photoreceptor. Offset phenomenon, where the toner image adheres to the toner image and is retransferred onto the copy paper, has always been a problem, and to prevent this, a release agent such as silicone oil is applied to the fixing roller on the side that contacts the toner image. has been carried out. However, in recent years, it has become common to prevent offset by containing polyolefins such as polypropylene and polyethylene in the toner and not applying or applying a release agent such as silicone oil to the fixing roller. . In recent years, attempts have been made to add a larger amount of polyolefin or to use a polyolefin with a lower melting point in order to further improve offset resistance, but these attempts tend to cause fusion in the crusher or classifier, making it difficult to crush. It was difficult to put it into practical use under the law.

Therefore, as a means to overcome the problems of the pulverization method, a polymerized toner produced from a polymerizable monomer by a suspension polymerization method has been proposed.

This toner is produced by a so-called suspension polymerization method, and contains 1 intermediate polymerization initiator for synthetic resins and 2 polymerization initiators.

Dispersion Stabilizer 9 A mixture of colorants, etc. is suspended in water and polymerized to directly produce toner. In this case, the toners all have a spherical shape, and pigments, etc. are contained inside the toner. Some of the things I do are: Therefore,
It is more advantageous than the pulverization method in terms of fluidity, problems with colorants, and manufacturing costs.Furthermore, unlike the pulverization method, there is no problem with the weave phenomenon during pulverization, so it is suitable for low melting point materials and pressure fixing materials. can be used.

However, stabilization of charging characteristics due to improvement in toner fluidity1
When hydrophobic silica is externally added for the purpose of improving image density, there is a problem in that strong shear stress and heat are applied to the toner and the hydrophobic silica, causing the toner to fuse together.

[Problem to be Solved by the Invention 1] The present invention is capable of uniformly adding hydrophobic silica externally to toner containing a low melting point material or pressure fixing material without causing toner fusion. Efficiency is the purpose of doing something.

[Means and effects for solving the problems 1 The present invention has the following features:
This is a method for producing a toner for developing an electrostatic image, which comprises mixing a polymerized toner containing at least a thermoplastic resin and a colorant with hydrophobic silica in a liquid dispersion medium, and then removing one dispersion medium.

The liquid dispersion medium may be one as long as it does not dissolve the polymerized toner.1 Usually, water is used.In the present invention, hydrophobic silica is externally added to the polymerized toner in the liquid dispersion medium. A resin that applies less shear stress and heat and has a low melting point or pressure fixability can be used as the toner binder. Conventional external addition of hydrophobic silica to dry polymerized toner requires high shearing force, so if it is repeated for a long time, the toner may fuse or the hydrophobic silica may become embedded in the toner. In contrast, the method of the present invention allows mixing and dispersion for a long time, making it possible to uniformly disperse hydrophobic silica with high efficiency.

[Example] Hereinafter, the present invention will be described in detail based on Examples.

Example I A rrimer composition was prepared by mixing the components listed in L in a 7 triter at a temperature of 80° C. for 4 hours. 254 parts by weight of the obtained monomer composition were mixed with 12 parts by weight of amino-modified silica (too much Erosil 200 treated with 5 parts by weight of 7-minopropyltoxytoxysilane) and 0.5 parts by weight of the monomer composition obtained. IN!
'to! 1200 parts of distilled water heated to 70°C containing 25 parts by weight of acid were added to an aqueous medium with stirring using a TK homomixer, and after addition, the mixture was heated at 10.00 Or, p, for 15 minutes.
The mixture was stirred with m, and 1-dispersion granulation was carried out.

After granulation, the liquid temperature was lowered to 60°C, and 2.2' was added as a polymerization initiator.
3 parts by weight of -7zobis(2,4-dimethylvaleronitrile) and 1.2'-7zobisisobutyronitrile.
5 parts by weight were added to the aqueous medium and stirred for 30 minutes. Furthermore, the stirring was changed to paddle blade stirring, and the mixture was stirred at 60° C. for 10 hours to complete the polymerization.

The obtained aqueous medium containing the polymerized toner is cooled and dehydrated,
The amino-modified silica was dissolved and removed by washing with a sodium hydroxide solution and washed with water to obtain a polymerized toner having a volume average particle size of 7.1 μm.

Separately hydrophobic silica, (Aerosil R972, Japan 7 x
Rosil ntJ) 12.7g Tozta/-ru 22
A hydrophobic silica dispersion was prepared by dispersing a mixture of 0 g and 1.200 g of water in one homomixer at 10.00 Or, p, m for 40 minutes.

254 g of the polymerized toner and the hydrophobic silica dispersion were mixed and dispersed in a homomixer for 40 minutes at 10.00 Or, p, m, and then filtered and dried to give a volume average particle size of 7.1.
A polymerized toner of μ■ was obtained.

Comparative Example 1 A polymerized toner was produced in the same manner as in Example 1 except that hydrophobic silica was not externally added.

Comparative Example 2 5 parts of hydrophobic silica (Aerosil R972) was added to 1 part of the toner 100 rri of Comparative Example 1, and the mixture was stirred with a coffee mill for 1 minute to produce a toner with external addition of hydrophobic silica.

Toner evaluation and image output results Example 1. Table 1 shows the results of the 100-liter mesh sieve test and the results of the toner of Comparative Example 1.2.

l) Mesh sieve test method 2 g of toner was placed on a 1001L mesh having a diameter of 5 cm, and the mesh was moved by hand for 3 minutes, and the weight of the toner remaining on the mesh L was measured.

2) Image production conditions A developer is prepared by mixing 10 parts by weight of toner with 90 parts by weight of insulating carrier particles (75 parts by weight of triiron tetroxide and 25 parts by weight of epoxy resin) of type J& having an average particle diameter of 404 m. Then, development was carried out under the following conditions.

The developing device shown in FIG. 1 was used. Image carrier l
is a selenium photoreceptor! 2, and the peripheral speed of the image carrier l is 100
mm/sec, the highest potential of the electrostatic image formed on the image carrier 1 is +750V, the outer diameter of the sleeve (developer carrier) 2 is 20
It is a table ■, and its circumferential speed is 100 layers/second.

The magnetic flux density in the vertical direction of the sleeve surface of the N and S poles of the magnet roller 3 is 1000 Gauss, and the thickness of the developer layer is 200 Gauss.
Gap between sleeve 2 and image carrier l 300 ILm
, the bias voltage applied to the sleeve is DC voltage component +
200v, AC voltage component 3.0K) 1400V at lz
I developed it using lipstick.

(Table 1 [Effects of the Invention]) As shown in Table 1 below, according to the present invention, hydrophobic silica can be externally added efficiently and without causing toner fusion.
Images with stable high image density can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a developing device used in an example of the present invention and a comparative example. l...Photosensitive drum, 2...Sleeve. 3...Magne roller, 4...Developer, 5.6...
Developing bias power supply, 7... Elastic member, 8... Supply roller, 9... Developer layer regulating member. 10...Doctor blade, 11...Aluminum cylinder, 12...Selenium photoreceptor.

Claims (1)

[Claims] (1) A method for producing a toner for developing electrostatic images, which comprises mixing a polymerized toner containing at least a thermoplastic resin and a colorant with hydrophobic silica in a liquid dispersion medium, and then removing the dispersion medium.