JP2791560B2 - Manufacturing method of electrophotographic toner - Google Patents

Description

The present invention relates to a method for producing an electrophotographic toner for developing a latent image in electrophotography.

<Conventional Technology> As a developing toner in an electrostatic image development in an electrophotographic apparatus, a one-component toner using no carrier or a two-component toner using a carrier is used.

These one-component and two-component toners are usually manufactured as follows.

First, a resin, a wax, a pigment, a charge control agent and the like are mixed, melt-kneaded and cooled, and then pulverized and classified to obtain charged toner particles. A fluidizing agent, a resistance controlling agent, and the like are externally added to the charged toner particles, and mixed with a Henschel mixer or the like to adhere the fluidizing agent to the toner surface.

As the fluidizing agent, silica fine particles as disclosed in JP-A-46-5792 are generally used, and the average particle size of such silica fine particles is about 0.01 to 5 μm.

Further, as the resistance control agent, metal oxide fine particles such as titanium oxide are generally used, and these are also used with an average particle diameter substantially equivalent to the above.

<Problems to be Solved by the Invention> However, in such a conventional toner for electrophotography, if tens of thousands of copies are continuously made, the image density changes with time, fog increases, and stains in the machine occur. Would.

This is considered to be due to a problem in the stability of charging of the toner, and the fact that the charging does not rise quickly at the time of toner supply.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an electrophotographic toner which is excellent in toner charge stability, has a rapid charge rising characteristic, has no change in image density during continuous copying, has little fog, and has little in-machine contamination. To provide.

<Means for Solving the Problems> Such an object is achieved by the present invention described below.

(1) Silica fine particles are externally added to the charged toner particles and mixed to form a toner. Separately, the charged toner particles and the metal oxide fine particles having an average particle diameter of 0.01 to 5 μm are subjected to mechanical strain. A method for producing a toner for electrophotography, comprising mixing, fixing and integrating the metal oxide fine particles on the surface of the charged toner particles to form a toner, and mixing both toners.

<Action> In the present invention, the metal oxide fine particles can be fixed to the toner particles in a well-dispersed state by mixing the metal oxide fine particles with the charged toner particles under a mechanical strain force. It will be much faster. Further, the dispersibility of the external additive is improved by mixing the toner in which metal oxide fine particles are fixed and integrated on the surface of the charged toner particles and the toner in which silica fine particles are externally added to the charged toner particles. , The function of the external additive is exhibited even more effectively,
Moreover, charging stability and rising characteristics are improved.

<Specific Configuration of the Invention> The metal oxide fine particles of the present invention are a metal,
There is no particular limitation as long as it is at least one oxide of Li, Be, Na to Al, K to Ge, Rb to Sb, and Cs to Po.

However, since this metal oxide functions as a so-called resistance control agent or additionally as an abrasive, etc., titanium oxide, titanium oxide, Calcium oxide, strontium titanate, barium titanate, magnesium titanate, zinc oxide, selenium oxide, aluminum oxide, cerium oxide, zirconium oxide, chromium oxide, and the like are preferable.

In the present invention, the metal oxide fine particles have a volume average particle diameter of 0.01 to 5 μm, preferably 0.01 to 4 μm.

When the particle diameter is less than the above range, the rising characteristics of charging become insufficient. Exceeding the above range causes image quality deterioration such as fogging and resolution.

The volume average particle diameter may be measured by a Coulter counting method, and the 50% average particle diameter of the measured volume particle diameter may be determined. In this case, the electrolytic solution was Isoton II
(Coulter Electronics Co., Ltd.), for example, by using a Coulter Counter TA-II (manufactured by Coulter Electronics) having an aperture diameter of 100 μm.

Alternatively, in the case of about 1 μm or less, the volume average particle diameter is determined by observation with an electron microscope.

Such metal oxide fine particles are contained in the electrophotographic toner in a total amount of 0.1 to 10% by weight, particularly 0.1 to 5% by weight.

As the chargeable toner particles to be used, any of known chargeable toner particles for a one-component developer or a two-component developer may be used, but the present invention is applied to a two-component developer. It has a particularly high effect.

The toner particles for a two-component developer to be used are not particularly limited, but the following toner particles are preferably used in order to obtain a high-quality toner image having excellent image density, resolution, gradation and the like. .

The volume average particle size is preferably 5 to 25 μm, particularly preferably 8 to 15 μm. If this value is less than the above range, deterioration of fog, poor cleaning occurs, it is disadvantageous in terms of cost.
Toner scattering tends to be a problem.

As the charging polarity of the toner particles, an appropriate polarity may be selected depending on the material of the photoreceptor to be used, the developing process, and the like.

The toner particles are made of a resin containing a resin and a colorant, and further contain a charge control agent, wax, and the like as needed.

The resin used for the toner particles may be selected from known resins according to a fixing method such as heating or pressure bonding, and is not particularly limited, and examples thereof include the following.

Olefin resin, acrylic resin, styrene copolymer,
One or more of various resins such as vinyl resin, polyamide resin, alkyd resin, epoxy resin, and polyester resin.

Of these resins, styrene-acrylic resins and polyester resins are preferred, and styrene-acrylic resins are particularly preferred.

The colorant may be selected according to the purpose, and is not particularly limited. Suitable coloring agents include, for example, the following.

Black pigments such as carbon black, acetylene black, channel black, and aniline black; yellow pigments such as Dialite Yellow GR and Variotor Yellow 1090; red pigments such as permanent red E5B and rhodamine 2B; blue pigments such as copper phthalocyanine and cobalt blue Green pigments such as Pigment Green B; orange pigments such as pyrazolone orange;

The content of such a coloring agent depends on the amount of the resin 100 of the toner particles.
It is preferably about 1 to 10 parts by weight based on parts by weight.

It is to be noted that a one-component toner may be used without using such a coloring agent, or in addition to this, by using magnetic powder as a coloring agent.

The charge control agent is added as needed to control the charge polarity, charge amount, and the like. In the present invention, an appropriate known charge control agent may be selected according to the intended polarity, charge amount, and the like, and there is no particular limitation. For example, metal complex salt azo dyes, nigrosine dyes and the like can be mentioned, and these are selected according to required characteristics.

The content of such a charge control agent depends on the resin of the toner particles.
It is preferably about 0.1 to 5 parts by weight based on 100 parts by weight.

Wax is added as a release agent as needed to prevent offset. In the present invention, the wax used is not particularly limited, and various known waxes, for example, polyethylene wax, polypropylene wax, silicon wax, etc. may be used, and these are selected according to required characteristics. The content of such a wax is preferably about 1 to 7 parts by weight based on 100 parts by weight of the resin of the non-magnetic toner particles.

Also, if necessary, in the case of magnetic toner particles, the magnetic powder to be contained is not particularly limited, and known magnetic powders such as magnetite and various ferrites may be used. Is the choice.
Such magnetic powder is preferably contained in an amount of about 5 to 70 parts by weight based on 100 parts by weight of the resin of the magnetic toner particles.

The chargeable toner particles may contain a resistance adjuster and the like in addition to the above.

The chargeable toner particles may be manufactured by an ordinary toner manufacturing method, for example, as described below.

The necessary additives are selected from the above-mentioned colorants, charge control agents, waxes and other additives as internal additives, and these predetermined amounts and resins are melted and kneaded, and after cooling,
Coarsely pulverized with a hammer mill, cutter mill, or the like. Next, after finely pulverized by a jet mill, ang mill, etc.,
Preferably, the particles are classified so as to be within the above-mentioned volume average particle size range to obtain charged toner particles.

In the present invention, metal oxide fine particles are fixed and integrated on the surface of the charged toner particles as described above to obtain a toner.

In the present invention, to fix and integrate the metal oxide fine particles with the charged toner particles means that the metal oxide fine particles are embedded in the surface of the toner particles. That is, when observed with an electron microscope, it can be confirmed that the metal oxide fine particles are embedded in the surface of the toner particles, and it is extremely difficult to separate the adhered and integrated particles, and it is substantially difficult to separate them. Is to keep the state.

The toner having such a structure exhibits extremely excellent charge rising characteristics and charge stability.

In this case, without adhering and integrating the metal oxide fine particles, a charge rising characteristic is obtained only by mixing with a Henschel mixer, a grind mixer, or a V blender or a Nauta mixer, and attaching the metal oxide fine particles to the toner particles. And the charging stability is extremely deteriorated.

In order to integrate the chargeable toner particles and the metal oxide fine particles, it is preferable to apply pressure when mixing the two particles. There is no particular limitation on the pressure applying means, and any pressure applying means may be used as long as the pressure applying means can be integrated as described above. However, in the present invention, the particles can be used in a dry state, and the cost can be reduced. Therefore, it is preferable to use a means for applying a mechanical strain force.

The mechanical strain force is to apply mechanical energy, mainly impact force, between particles to cause a mechanochemical reaction in some cases. As an apparatus for applying such a mechanical strain force, for example, Japanese Patent Application Laid-Open No. 63-42728
It is a powdery and granular material processing apparatus as described in Japanese Patent Application Publication No. H06-27139, and specifically, a mechanofusion system manufactured by Hosokawa Micron Corporation, a hybridization system manufactured by Nara Machinery Co., Ltd., and the like are suitable.

In the toner particles having the metal oxide fine particles fixed on the surface thus obtained, the content of the fixed metal oxide fine particles is preferably 0.05 to 10% by weight, more preferably 0.1 to 5% by weight. When the amount of adhered fine particles falls within the above range, the effect of the present invention is extremely excellent.

The electrophotographic toner of the present invention uses a mixture of charged toner particles having metal oxide fine particles fixed on the surface thereof and charged toner particles having no metal oxide fine particles fixed on the surface.

The method for producing a toner for electrophotography according to the present invention includes the steps of: adding silica fine particles as an external additive to a chargeable toner particle that does not adhere metal oxide fine particles to its surface using a Henschel mixer, a grind mixer, or the like; V-blender the charged toner particles having the fine particles fixed on the surface,
Mix with a Nauta mixer or the like. As a result, the dispersibility of the external additive is improved, the function of the external additive is more effectively exhibited, and the charging stability and the rising characteristics are improved.

Silica fine particles have a function as a fluidizing agent.

The volume average particle size of the silica fine particles is preferably 0.00
It is 1 to 0.5 μm, more preferably 0.005 to 0.1 μm. With such a volume average particle size, agglomeration is prevented and fluidity is improved. In addition, charging stability and rising characteristics are also improved.

Further, from the viewpoint of stability under environmental conditions, it is preferable that the silica fine particles are made hydrophobic by surface treatment.

The silica fine particles suitably used in the present invention include R-972, R-974 and R-97 manufactured by Nippon Aerosil Co., Ltd.
6, RX-200 and the like.

The content of the chargeable toner particles and the silica fine particles in the electrophotographic toner of the present invention is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of all the chargeable toner particles. Department. When the content of the silica fine particles is in the above range, the aggregation preventing effect, the charging stability, and the rising characteristics are improved.

When the silica fine particles are fixed to the surface of the charged toner, the effect of preventing aggregation is insufficient, and the charging stability and the rising characteristics are deteriorated.

Further, in the above, in order to realize the above-mentioned effects, the amount of the externally attached silica fine particles is determined by changing the amount of the toner particles not fixing the metal oxide fine particles on the surface to the toner particles fixing the metal oxide fine particles on the surface. In general, the former is about 0.1 to 20% by weight, and the latter is 0% by weight.
About 5% by weight, and the former may be about twice or more larger than the latter.

Further, the toner particles to which the metal oxide fine particles are fixed are compared with the toner particles to which the metal oxide fine particles are not fixed, as a whole.
It may be mixed so as to be about 70 to 95% by weight, preferably about 80 to 95% by weight.

Further, the following can be used as other external additives.

Inorganic compounds such as silicon carbide, calcium carbonate and barium carbonate; organic polymer compounds such as polymethyl methacrylate (PMMA), polyethylene, nylon, silicone resin, phenolic resin, benzoguanamine and polyester; polytetrafluoroethylene and polyvinylidene fluoride Fluorinated organic polymer compounds; fatty acid metal salts such as zinc stearate and magnesium stearate; charge control agents such as metal complex dyes and nigrosine dyes;

 These may be subjected to a surface treatment.

However, these may be attached or fixed to the charged toner, and the external addition may be performed to the toner particles to which the metal oxide fine particles are fixed or to the non-fixed toner particles.

The addition amount of these external additives is 0.1 to
It is about 5% by weight. The average particle size is 0.01 to 5 μm.
m.

In addition, the electrophotographic toner of the present invention is preferably mixed with carrier particles and used as a two-component developer. At this time, the effect of the present invention is further enhanced.

The carrier particles to be used are not particularly limited, and known carrier particles composed of Fe, various ferrites, and the like may be used. However, ferrite is preferably used because charging control is easy.

In the present invention, the volume average particle size of the carrier particles is preferably 20 to 120 μm, and more preferably 50 to 100 μm.

In the electrophotographic developer of the present invention composed of such carrier particles and the electrophotographic toner,
The content of the electrophotographic toner is preferably 2 to 12% by weight, and more preferably 3 to 10% by weight.

Further, the electrophotographic toner of the present invention may be used as a one-component developer.

Such an electrophotographic developer of the present invention exhibits a predetermined effect when used in a magnetic brush developing method or, if necessary, in a dry developing method such as a cascade method, a bristle brush method, or a powder cloud method.

<Example> Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

Styrene-acrylic resin (KB-1010 manufactured by Mitsubishi Rayon Co., Ltd.) 86 parts by weight Polypropylene wax (Viscol 550P manufactured by Sanyo Chemical Industry Co., Ltd.) 4.5 parts by weight Carbon black (average particle size 0.02 μm) (MA-100 manufactured by Mitsubishi Chemical Industry Co., Ltd.) 7.5 2 parts by weight of a charge control agent (monoazo dye chromium complex) (Eizenspilon Black TRH manufactured by Hodogaya Chemical Co., Ltd.) was dissolved and kneaded, cooled, and coarsely pulverized with a hammer mill. Subsequently, the resultant was finely pulverized by a jet mill and classified to prepare charged toner particles having a volume average particle diameter of 11 μm.

Metal oxide fine particles and silica fine particles were added to the above-mentioned charged toner particles by the following method to obtain an electrophotographic toner, and then the carrier (TF-3044 manufactured by TDK Co., Ltd., having an average particle diameter of 100) was obtained.
μm, Hc18Oe at 5000 Oe, σm40emu / g)
Commercially available copier (manufactured by Toshiba Corporation) as a developer with a toner concentration of 4%
BD-7610) to perform a life test.

Example 1 Titanium oxide fine particles (T-805 average particle size 0.03 μm, manufactured by Nippon Aerosil Co., Ltd.) were added to the above-mentioned charged toner particles at 0.5% by weight and mixed for 20 minutes while applying a mechanical strain to obtain a base toner. Produced.

Separately, silica (Nippon Aerosil R-97)
(2 average particle diameter: 0.01 μm) was added in an amount of 4% by weight and mixed with a Henschel mixer to prepare a conc. Toner.

The base material toner and the conc toner were mixed at a ratio of 9: 1 with a V blender to obtain a toner. This is referred to as toner 1.

Example 2 0.5 wt% of selenium oxide fine particles (ROX.M average particle diameter 1.7 μm, manufactured by Tohoku Metal Chemical Co., Ltd.) was added to the above-mentioned charged toner particles, and mixed for 20 minutes by mechanical strain to prepare a base toner. did. Hereinafter, a chargeable toner was obtained under the same conditions as in Example 1 above. This is referred to as toner 2.

Example 3 0.5% by weight of strontium titanate fine particles (ST average particle diameter: 1.0 μm, manufactured by Fuji Titanium Co., Ltd.) was added to the above-mentioned charged toner particles by 0.5% by weight, and mixed by mechanical strain for 20 minutes to prepare a base toner. .

Hereinafter, a chargeable toner was obtained under the same conditions as in Example 1 above. This is referred to as toner 3.

Comparative Example 4 Titanium oxide fine particles (T-805, manufactured by Nippon Aerosil Co., Ltd.) were added to the above-mentioned charged toner particles in an amount of 0.5% by weight, and mixed by mechanical strain for 20 minutes to prepare a base toner.

To the base toner, 0.3% by weight of the silica fine particles of Example 1 was added and mixed with a V blender to obtain a chargeable toner. This is referred to as toner 4.

In each of the above Examples and Comparative Example 4, when each base material toner was observed with a scanning electron microscope, it was confirmed that the metal oxide fine particles were embedded in the surface of the toner particles.

Further, it was confirmed that the silica fine particles adhered to the surface of the toner particles in each of the toner concentrates and the base material toner of Comparative Example 4.

Next, for comparison, a charged toner obtained by preparing the base toner by mixing the same metal oxide particles as the toners 1 to 3 above without applying a mechanical strain was prepared as follows. .

Comparative Example 1 0.5% by weight of titanium oxide fine particles (T-805, manufactured by Nippon Aerosil Co., Ltd.) was added to the above-mentioned charged toner particles, and mixed with a V blender to prepare a base toner.

Hereinafter, a chargeable toner was obtained under the same conditions as in Example 1 above. This is referred to as toner 5.

Comparative Example 2 0.5% by weight of selenium oxide fine particles (ROX.M manufactured by Tohoku Metal Chemical Co., Ltd.) was added to the above-mentioned charged toner particles, and mixed with a V blender to prepare a base toner. Hereinafter, a chargeable toner was obtained under the same conditions as described above. This is referred to as toner 6.

It was confirmed that the metal oxide fine particles of each base toner adhered to the toner particle surfaces.

With respect to each of the toners 1 to 6, the image density, the charge amount, and the fog inside the fogging machine were measured at the initial stage and after copying 20,000 sheets and 40,000 sheets continuously.

 Table 1 shows the above results.

As is evident from Table 1, Examples 1 to 3 obtained extremely good results in image density, charge amount, fog, and in-machine contamination as compared with the Comparative Example.

Further, FIG. 1 shows the results of measurement of the rise of the charge amount by performing ball mill stirring on the toners 1, 2, 4, and 5 described above.

The toner density and carrier in FIG. 1 are the same as those described above.

From FIG. 1 and Table 1, it can be seen that the toner of the present invention shows a favorable rise in charging. It can be seen that these contribute to the stability of the image density and the contamination inside the apparatus.

On the other hand, the toner of the comparative example has a poor start-up characteristic and a large movement, resulting in a very poor characteristic shown in Table 1.

<Effects of the Invention> As described above, the toner for electrophotography of the present invention is excellent in the stability of chargeability and the rising characteristics, and as a result, the effects such as less image density change and fog during continuous copying and less in-machine contamination are obtained. Having.

[Brief description of the drawings]

FIG. 1 is a graph showing the charge rising characteristics of the electrophotographic toner of the present invention.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Takahashi 1-1-13 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-59-17560 (JP, A) JP-A-62 -246074 (JP, A) JP-A-63-85756 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/00-9/10 362

Claims (1)

(57) [Claims] A toner is obtained by externally adding and mixing silica fine particles with charged toner particles to form a toner. Separately, the charged toner particles and metal oxide fine particles having an average particle size of 0.01 to 5 μm have a mechanical strain force. And mixing to form a toner by fixing and integrating the metal oxide fine particles on the surface of the charged toner particles to form a toner, and mixing both toners.