JPH02126267A - Developer for electrophotography - Google Patents

Abstract

PURPOSE:To expedite rising of the electrostatic charge of the toner and to enhance the flowability thereof using the toner added with specific blended particles. CONSTITUTION:The developer is formed of the toner formed by adding the blended particles (A) fixed and integrated with fine silica particles and fine metal oxide particles to the toner particles and the carrier contg. a resin and magnetic powder. The carrier is preferably the particle having >=10<9>OMEGA.cm electric resistance and is preferably the resin-coated carrier or resin carrier. The toner has preferably positive chargeability. The formation of the toner by forming the particles A acting as a flocculation preventive agent by emedding silica, etc., to the surface of titanium oxide or the like and sticking the particles A to the surface of the toner particles.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic toner for developing a latent image in electrophotography and an electrophotographic developer containing magnetic particles.

<Prior Art> One type of developer used for electrostatic image development in an electrophotographic apparatus is a two-component electrophotographic developer containing an electrophotographic toner and carrier particles. .

A two-component electrophotographic developer is usually produced as follows.

First, resin, wax, pigment, charge control agent, etc. are mixed,
After melting, mixing, and cooling, it is crushed and classified to obtain charged toner particles. A fluidizing agent, a resistance controlling agent, etc. are externally added to the charged toner particles, and mixed with a Henschel mixer or the like to adhere the fluidizing agent, resistance controlling agent, etc. to the toner surface.

Furthermore, a two-component electrophotographic developer is obtained by mixing toner with carrier particles composed of Fe, various ferrites, and the like.

Two-component electrophotographic developers charge toner particles through friction between carrier particles and toner particles, and perform development using electrostatic force.

Incidentally, as carrier particles, resin-coated carrier particles are known in which magnetic powder is coated with a resin and contains resin and magnetic powder.

By using this material, stable triboelectric charging properties of the toner can be obtained over a long period of time.

In order to obtain a good image with an electrophotographic developer using such resin-coated carrier particles, it is necessary that the toner charge rise quickly and that the toner is resistant to agglomeration (having good fluidity). Also, if the above characteristics are good, it is possible to reduce the change in image quality over time during continuous copying.

However, when resin-coated carrier particles are used, the conventional method of incorporating a charge control agent into the toner does not provide sufficient rapidity in charging the toner.

Furthermore, in the electrophotographic developer described above, silica particles such as those disclosed in Japanese Patent Application Laid-Open No. 46-5782 and the like are generally used as a fluidizing agent to prevent agglomeration.

An electrophotographic developer using resin-coated carrier particles as carrier particles and silica particles as a fluidizing agent for preventing agglomeration is disclosed, for example, in Japanese Patent Application Laid-Open No. 129866/1983.

The invention described in this publication relates to an electrophotographic developer comprising a toner containing fine alumina particles and/or fine titanium oxide particles and fine silica particles on the surface of the toner particles, and carrier particles. The effect is to obtain good fluidity and stable triboelectric charging properties of the toner. It is said that the above effects are further improved by using resin-coated carrier particles as the carrier particles.

<Problems to be Solved by the Invention> However, in the toner particles of the electrophotographic developer obtained by the above manufacturing method, individual particles are generally amorphous and have a wide particle size distribution.

For this reason, conventionally used fluidizing agents such as silica particles and mixed particles described in JP-A-62-129866 cannot be said to have a sufficient effect of preventing toner aggregation.

Further, there is a drawback that the fluidity of the toner is still insufficient and the charge build-up of the toner is slow.

As a result, the image quality is insufficient, and the image quality such as image density, fog, and resolution changes significantly over time during continuous copying.

The same situation applies when so-called resin carrier particles or magnetic toner particles are used as a developer instead of resin-coated carrier particles.

The present invention provides that when resin-coated carrier particles, resin carrier particles, magnetic toner particles, etc. are used as a developer, the toner charges quickly and rises quickly, and has excellent fluidity.
As a result, an object of the present invention is to provide an electrophotographic developer using a non-magnetic toner that has good image quality and exhibits small changes over time in image quality such as image density, fog, and resolution during continuous copying.

Means for Solving the Problems> Such objects are achieved by the following inventions (1) to (5).

(1) An electrophotographic toner containing toner particles containing one or more types of composite particles in which fine silica particles and fine metal oxide particles are fixed and integrated, and magnetic particles containing resin and magnetic powder particles. An electrophotographic developer characterized by:

(2) The electrophotographic developer according to (1) above, wherein the magnetic particles have an electrical resistance of 109Ω·Cl11 or more.

(3) The electrophotographic developer according to (1) or (2) above, wherein the magnetic particles are resin-coated carrier particles.

(4) The above (1) wherein the magnetic particles are resin carrier particles.
) or the electrophotographic developer described in (2).

(5) The electrophotographic developer according to any one of (1) to 4) above, wherein the electrophotographic toner has positive chargeability.

<Function> When the electrophotographic developer of the present invention uses resin-coated carrier particles or resin carrier particles as a carrier, or uses magnetic toner particles in combination, the electrophotographic developer of the present invention contains silica fine particles and metal oxide fine particles in a non-magnetic toner. By adding composite particles in which toner particles are fixed and integrally bound together as an aggregation prevention agent, toner aggregation can be prevented and good fluidity can be obtained.

Furthermore, the toner can be charged quickly and stable triboelectric charging properties can be obtained.

Therefore, by using the developer of the present invention, good and stable image quality with little change over time can be obtained during continuous copying.

Such an effect is much greater than when metal oxide fine particles are mixed and used.

<Specific Structure of the Invention> As the metal oxide used in the present invention, an appropriate metal oxide may be selected depending on the charging characteristics such as the polarity and amount of charge of the toner particles used, the type of photoreceptor used, etc.

However, since metal oxides function as so-called resistance control agents or as abrasives in addition to this, titanium oxide and titanate Calcium, strontium titanate, barium titanate, magnesium titanate, zinc oxide, selenium oxide, aluminum oxide, cerium oxide, zirconium oxide, chromium oxide, etc. are preferred, and titanium oxide, aluminum oxide, zinc oxide, etc. are more preferred. .

Good fluidity of toner particles cannot be obtained with materials other than metal oxides.

The volume average particle diameter of the metal oxide fine particles is preferably:
It is 0.01-5-, more preferably 0.03-4-. When the particle size is within the above range, a greater agglomeration prevention effect is obtained, the fluidity of the toner is improved, and charging rises more quickly.

In addition, in the case of a particle size of one house or less, it is measured using an electron microscope.

In the present invention, the metal oxide fine particles and the silica fine particles are used in a fixed and integrated manner, but it is preferable to use silica fine particles having a smaller volume average particle diameter than the metal oxide fine particles as a flow prevention agent.

The volume average particle diameter of the silica fine particles is preferably 0.5
μs or less, more preferably 0.001 to 0.5−1, particularly preferably 0.01 to 01−1.

When the volume average particle diameter is within the above range, a greater agglomeration prevention effect is obtained, the fluidity of the toner is improved, and charging rises more quickly.

Further, from the viewpoint of stability under various environmental conditions, the silica fine particles are preferably made hydrophobic by surface treatment.

The silica fine particles preferably used in the present invention include R-972, R-974, and R-972 manufactured by Nippon Aerosil Co., Ltd.
976, RX-200, etc.

In the present invention, the metal oxide fine particles and the silica fine particles described above are fixed and integrally formed into composite particles, which are used as an anti-agglomeration agent.

In the present invention, the term "metal oxide fine particles and silica fine particles fixedly fixed together" means that the silica fine particles are embedded in the surface of the metal oxide fine particles.

In other words, when observed with an electron microscope, it can be confirmed that the silica particles are embedded in the surface of the metal oxide particles, and it is extremely difficult to separate them because they are firmly fixed together. It maintains the state in which it is.

It is thought that the anti-aggregation agent for composite particles having such a structure exhibits an extremely excellent anti-aggregation effect for the following reasons.

Silica fine particles have a high effect of physically preventing agglomeration of toner particles, and in particular, hydrophobic silica fine particles are less likely to lose their effectiveness even under high temperature and high humidity. However, when fine silica particles having a small volume average particle diameter are used to enhance the effect of preventing physical aggregation of toner particles, the effect of preventing electrical aggregation of toner particles decreases.

On the other hand, metal oxide fine particles have almost no effect of physically preventing aggregation of toner particles, but silica fine particles embedded in the surface of metal oxide fine particles physically prevent aggregation of toner particles.

Furthermore, composite particles in which fine metal oxide particles and fine silica particles are fixed and integrated have a large volume average particle diameter, so the amount of charge is low, and electrical aggregation of toner particles can be prevented.

In addition, by adopting such a configuration, the amount of silica fine particles used can be reduced compared to when trying to obtain the same level of fluidity as the present invention with only silica fine particles, so cleaning performance is less likely to deteriorate. Furthermore, the photoreceptor is less likely to be damaged.

As a result, in the present invention, much superior properties can be obtained compared to when silica fine particles and metal oxide fine particles are mixed and added to toner particles.

In order to fix the metal oxide fine particles and the silica fine particles, it is preferable to apply pressure when mixing the metal oxide fine particles and the silica fine particles. There is no particular restriction on the pressure application means, and any pressure application means may be used as long as it can achieve the above-mentioned integrated state. However, in the present invention, fine particles can be used in a dry state, and the cost is low. Since it is advantageous, mechanical strain force is marked +>
It is preferable to use a means for zeroing.

Mechanical strain force is a force that applies mechanical energy, mainly impact force, between particles, and in some cases causes a mechanochemical reaction.

An example of a device that applies such a mechanical strain force is a powder processing device such as that described in Japanese Patent Application Laid-open No. 63-42728, etc., and specifically, a mechanical device manufactured by Hosokawa Micron Co., Ltd. Fusion system, hybridization system manufactured by Nara Kikai Seisakusho Co., Ltd., etc. are suitable.

These devices, for example, rotate a casing containing powder at high speed to form a powder layer on its inner circumferential surface, and also apply compression or friction to the powder layer on the inner circumferential surface of the casing. , scraping, dispersing, and stirring at the same time.

In this case, using the above device, the mixing time is about 5 to 15 minutes, the casing rotation speed is about 700 to 120 Orpm,
The temperature may be approximately 15°C to 35°C, and other conditions may be normal.

The content of fine silica particles in the composite particles thus obtained is preferably 40 to 95% by weight, more preferably 50 to 80% by weight.

When the content of silica fine particles is within the above range, the agglomeration prevention effect is further improved, and in addition to reducing the change in image quality over time, it is also possible to improve the cleaning performance.

Although only one kind of the above-mentioned composite particles may be used, two or more kinds may be used as necessary.

Note that the composite particles may contain one or more kinds of metal oxide fine particles and one or more kinds of silica fine particles.

As the charged toner particles contained in the electrophotographic developer of the present invention, any known non-magnetic charged toner particles for two-component developers may be used.

The volume average particle size of the chargeable toner particles used is 5 to 25 μm, more preferably 6 to 20 μm, particularly preferably 8 to 12 μm.
- is preferable.

If the average particle size is less than 5, fogging will worsen, cleaning problems will occur, and this will be disadvantageous in terms of cost.

Moreover, if it exceeds 25μ, problems arise such as deterioration of resolution and toner scattering.

Coulter counting method is used to measure the volume average particle diameter.
What is necessary is to find a 50% average particle size of the volume particle size of the measured value.
At this time, the electrolyte is Isoton II (Coulter
For example, a Coulter Counter TA-II (manufactured by the same company) with an aperture diameter of 100 mm may be used.

Furthermore, as the particle size distribution, when the average particle size is a,
It is preferable that H/2 or less is 10% by volume or less, particularly about 0 to 6% by volume.

Further, it is preferable that the content of 21 or more is 10% by volume or less, particularly about 0 to 6% by volume.

By using a toner having such a particle size distribution, the yield and yield of toner can be improved, and manufacturing can be facilitated.

As for the charging polarity of the toner particles, an appropriate polarity may be selected depending on the material of the photoreceptor used, the developing process, etc., but it is usually preferable to set the toner particles to be positively charged.

The toner particles are composed of a resin and a resin containing a colorant, and may further contain a charge control agent, wax, etc., if necessary.

The resin used for the toner particles may be selected from known resins depending on the fixing method such as heating or pressure bonding, and is not particularly limited (for example, the following resins may be used).

One or more types of resins such as olefin resins, acrylic resins, styrene copolymers, vinyl resins, polyamide resins, alkyd resins, epoxy resins, and polyester resins.

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

The coloring agent may be selected depending on the purpose (there is no particular restriction). Examples of suitable coloring agents include the following.

Y color pigments such as carbon black, acetylene black, channel black, aniline black; Dialite Yellow GR, Variotol Goro-1090
Red pigments such as Permanent Red E5B and Rhodamine 2B; Blue pigments such as copper fucrocyanine and cobalt blue; Green pigments such as Pigment Green B; Orange pigments such as Pyrazolone Orange.

The content of such a colorant is based on 100% resin of toner particles.
The amount is preferably about 1 to 10 parts by weight.

A charge control agent is added as necessary to control charge polarity, charge amount, etc. In the present invention, a known appropriate charge control agent may be selected depending on the intended polarity, charge amount, etc. (There are no particular limitations. Examples include metal complex azo dyes, nigrosine dyes, etc.) In the case of positive charging, nigrosine dyes and the like are preferred.

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

Wax is added as a mold release agent as necessary to prevent offset. The wax used in the present invention is not particularly limited (although various known waxes such as polyethylene wax, polypropylene wax, silicone wax, etc. may be used, these are selected depending on the required characteristics. The wax content is 1 to 7 parts by weight based on 100 parts by weight of the resin of the non-magnetic toner particles.
It is preferable that it is about 100% heavy.

In the present invention, it is preferable to use non-magnetic toner particles, but if necessary, magnetic toner particles may also be used. In that case, there is no particular restriction on the magnetic phase contained,
A known magnetic phase such as magnetite, various ferrites, etc. is added in an amount of 5 to 7 parts per 100 parts by weight of the resin of the magnetic toner particles.
Preferably, the amount is 0 parts by weight radical.

In addition to these, the toner particles may also contain a resistance adjuster and the like.

The toner particles may be manufactured by a conventional toner manufacturing method (for example, as described below).

Select the necessary internal additives from among the colorants, charge control agents, waxes, and other additives mentioned above,
A predetermined amount of these and the resin are melted and kneaded, cooled, and then coarsely ground using a hammer mill, cutter mill, or the like. Next, the toner particles are finely pulverized using a jet mill, an ong mill, etc., and then classified to have the above-mentioned volume average particle diameter range to obtain chargeable toner particles.

The thus obtained charged toner particles are dry mixed with one or more types of composite particles in which the above-mentioned silica particles and metal oxide particles are fixed and integrated using a Henschel mixer, a grind mixer, a blender, a Nauta mixer, etc. Ru.

As a result, the composite particles are attached to the surfaces of the chargeable toner particles, and an electrophotographic toner is obtained. On this occasion,
Composite particles can be processed by mechanical strain, heat, etc. as necessary.
It may be fixedly fixed and embedded on the surface of the chargeable toner particles.

The content of the charged toner particles and composite particles in the electrophotographic toner is preferably 0.1 to 2 parts by weight, more preferably 0.1 to 2 parts by weight, per 100 parts of the toner particles.
It is 3 to 1.2 parts by weight.

When it is within the above range, the effect of preventing agglomeration of the electrophotographic toner will be even higher, the fluidity will be improved, and the charging will start up more quickly.

It is also possible to externally add inorganic or organic fine particles such as a resistance adjuster, a colorant, and other fluidity improvers as additive particles to the electrophotographic toner.

Examples of these include, if necessary, silica particles and metal oxides, as well as inorganic particles such as silicon carbide, calcium carbonate, barium carbonate, and calcium silicate, magnetic particles, PMMA, polyethylene, and nylon. ,Silicone resin,
Polymer beads such as phenolic resin, benzoguanamine resin, polyester, polytetrafluoroethylene, polytetrafluoroethylene,
Fluorine-containing organic fine particles such as polyvinylidene fluoride, fatty acid metal salts such as zinc stearate and magnesium stearate, black pigments such as carbon black, acetylene black, channel black, and aniline black, Dialite Yellow GR, Variol Yellow 1090
Examples include yellow 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, and charge control agents.

In addition, although only one type of these additive particles may be used, two or more types can also be used in combination as required.

Furthermore, a mold release agent can also be externally added as additive particles.

These additive particles are dry mixed with the toner particles.

At this time, each additive particle may be subjected to a titanate-based, aluminum-based, silane-based coupling agent, silicone oil, or other organic or inorganic treatment for surface hydrophobization treatment and surface dispersion improvement treatment. can.

These additive particles have an average particle size of about 0.005 to 5-.

Further, the amount of external addition is about 0.5% by weight or less of the composite particles.

Similar to the above-mentioned composite particles, such additive particles are dry-mixed using a non-shell mixer, etc., and are adsorbed or fixed to the toner particle surface, or are further bonded to the toner particle surface by mechanical strain force, heat, etc. It is fixed and embedded.

The polarity of the electrophotographic toner particles in the electrophotographic developer of the present invention is preferably positively charged as described above.

By having positive chargeability, the effects of the present invention are further improved, and charging rise characteristics and fluidity are improved.

The electrophotographic developer of the present invention is prepared by mixing the above electrophotographic toner and magnetic particles.

The magnetic particles contain resin and magnetic powder particles.

Among such magnetic particles, resin-coated carrier particles are most preferable.

Magnetic powders include iron, manganese, cobalt, nickel,
Metals such as chromium or their alloys, chromium oxide,
Metal oxides such as iron sesquioxide and triiron tetroxide, and general formula M
O” Fe, 03 (M is Fe, Mn, Co, Ni, Mg
, one or more metals selected from the group of monovalent or divalent metals such as Zn, Cd, Ba, and Li), which are conventionally known as magnetic materials, such as ferrite, etc. It is possible.

The resin used may be selected from known resins, such as those listed below.

One or more types of resins such as silicone resins, olefin resins, acrylic resins, styrene copolymers, vinyl resins, polyamide resins, alkyd resins, epoxy resins, and polyester resins.

Among these resins, silicone resins and acrylic resins are particularly preferred.

The volume average particle diameter of the resin-coated carrier particles is 40 to 10
It is preferably about 0 μs, more preferably about 45 to 75 μs.

Moreover, it is preferable that the thickness of the resin coat is about 0.01 to 2 μm.

In addition, the electrical resistance of the resin-coated carrier particles is 109Ω・
It is preferably at least am, more preferably at least 10 Ω·cm.

When the electrical resistance is within the above range, the effects of the present invention are further improved.

Electrical resistance is measured according to the usual method.

The coating method for the resin coating may also be according to a conventional method.

Further, resin carrier particles may be used instead of resin-coated carrier particles.

As the resin used for the resin carrier particles, any of the resins for resin-coated carrier particles mentioned above can be used, but styrene-acrylic copolymer resins and polyester resins are particularly preferred.

Further, as the magnetic powder particles, any of the above magnetic powder particles can be used.

The volume average particle diameter of the magnetic powder particles is preferably 0.05 to 1.0-1, more preferably 0.1 to 0.5-1.

The average particle size of the resin carrier particles is 15 to 50 units,
More preferably, it is 20 to 30P.

Further, the electrical resistance thereof is preferably 10 9 Ω·am or more, more preferably 1O 13 Ω·cm or more.

Further, the ratio of resin in the resin carrier particles is 10 to 50
It is preferably about % by weight.

Within the above range, the effects of the present invention are further improved.

These resin carrier particles can be manufactured by a normal toner manufacturing method (for example, they can be manufactured as follows.

Select the necessary internal additives from among the waxes and other additives mentioned above, melt and knead predetermined amounts of these with resin and magnetic powder, and after cooling, use a hammer mill, cutter mill, etc. Coarsely grind. Next, the particles are finely pulverized using a jet mill, an ong mill, etc., and then classified to fall within a predetermined volume average particle size range to obtain resin carrier particles.

In addition, magnetic L-ner particles having an average particle size of 15 to 35 particles may be used as the magnetic particles.

In the electrophotographic developer of the present invention comprising magnetic particles and a top-distributed electrophotographic toner, the content of the electrophotographic toner is preferably 2 to 20% by weight.

In particular, when using resin-coated carrier particles or resin carrier particles as the magnetic particles, the toner content is
It is preferably 2 to 20% by weight, more preferably 3 to 15% by weight.

Such an electrophotographic developer of the present invention exhibits a predetermined effect when used in a dry development method such as a magnetic brush development method or a cascade development method.

<Example> Hereinafter, specific examples of the present invention will be given, will be explained in more detail.

Examples 1 to 4 Styrene-acrylic resin Invention (KB-1010, manufactured by Mitsubishi Rayon Co., Ltd.) 85 parts by weight Polypropylene wax (Viscol 550P, manufactured by Mitsubishi Chemical Industries, Ltd.) 5 parts by weight Carbon black (MA-1oo, manufactured by Mitsubishi Chemical Industries, Ltd.) 8 Part by weight Charge control agent (N-01 manufactured by Orient Chemical Co., Ltd.) 2 parts by weight The above composition was melted and kneaded, cooled, and coarsely ground using a hammer mill. Next, it was finely pulverized with a jet mill and classified to have a volume average particle size a of 10.5 m and a particle size distribution of 21
Positively charged toner particles containing 0.0% by volume of H/2 or less and 0.3% by volume of H/2 or less were prepared.

Next, the following composite particles 1 to 3 were produced.

(Composite particles 1) 40 parts by weight of titanium oxide fine particles (P-25 manufactured by Nippon Aerosil Co., Ltd.) with a volume average particle size of 0.04 and 40 parts by weight of titanium oxide fine particles with a volume average particle size of 0.04.
02- silica fine particles (RX-20 manufactured by Nippon Aerosil Co., Ltd.
0) 60 parts by weight while applying mechanical strain force.
The mixture was fixed and fixed to obtain composite particles 1. The mixing time was 5 minutes, the casing rotation speed was 800 rpm, and the temperature was 20°C.

(Composite particles 2) 25 parts by weight of aluminum oxide fine particles (RX-C, manufactured by Nippon Aerosil Co., Ltd.) with a volume average particle size of 0.03% and silica fine particles (manufactured by Nippon Aerosil Co., Ltd.) with a volume average particle size of 0.01%.
Composite particles 2 were obtained by mixing and fixing 75 parts by weight of R-972) while applying mechanical strain. The mixing time was 5 minutes, the casing rotation speed was 1000 rpm, and the temperature was 23°C.

(Composite particles 3) 40 parts by weight of zinc oxide fine particles (manufactured by Honjo Chemical Co., Ltd., conductive zinc oxide) with a volume average particle size of 3- and a volume average particle size of 0.0
1- Silica fine particles (manufactured by Nippon Aerosil Co., Ltd. R-972
) and 60 parts by weight were mixed to form a solid S-body while applying mechanical strain to obtain composite particles 3. Mixing time is 7 minutes.
The casing rotation speed was 11000 rpm and the temperature was 28°C.

As a result of observing the cross sections of Composite Particles 1 to 3 using a transmission electron microscope and a scanning electron microscope, it was confirmed that silica fine particles were embedded in the surface of each metal oxide fine particle.

Premix composite particles 1 and composite particles 2 at a weight ratio of 2:1, add 0.5 parts by weight to 100 parts by weight of the positively charged toner particles, and mix with a Henschel mixer,
Toner 1 was produced.

Premix composite particles 1 and 3 at a weight ratio of 3:1, add 0.5 parts by weight to 100 parts by weight of the above positively charged toner particles, and mix with a Henschel mixer,
Toner 2 was produced.

Toner 3 was prepared by mixing 0.5 parts by weight of composite particles 2 and 100 parts by weight of the positively charged toner particles described above using a Henschel mixer.

Toner 4 was prepared by mixing 0.5 parts by weight of composite particles 1 and 100 parts by weight of the positively charged toner particles described above using a Henschel mixer.

As a result of observing Toners 1 to 4 using a transmission electron microscope and a scanning electron microscope, it was confirmed that each composite particle was attached to the surface of positively charged toner particles.

For comparison, the silica fine particles and aluminum oxide fine particles used in Composite Particle 2 were premixed at a weight ratio of 1:1, and 0.5 parts by weight of this was added to 100 parts by weight of the positively charged toner particles. , and mixed with a Henschel mixer to produce Toner 5.

Furthermore, for comparison, silica fine particles and titanium oxide fine particles were premixed with the same composition as composite particle 1, and this was
．． Toner 6 was prepared by mixing 5 parts by weight and 100 parts by weight of the positively charged toner particles described above in a Henschel mixer.

Note that in toner 5.6, the premixed silica fine particles and aluminum oxide fine particles or titanium oxide fine particles were not subjected to fixation-imaging treatment.

Each of these toners 1 to 6 was subjected to the following fluidity test and measurement of change in charge amount over time.

The fluidity test was determined by vibrating 20 g of toner on a 100 mesh sieve and measuring the amount of toner remaining on the sieve 30 seconds later. A powder tester manufactured by Hosokawa Micron Co., Ltd. was used for the measurement, and the judgment criteria were as follows.

Remaining toner amount: 088g or less20 0.8-1.5g: △ ], 5g or more: × The results are shown in Table 1.

To measure the change in charge amount over time, use the following resin-coated carrier particles to prepare various developers with a toner concentration of 4.0% by weight, and measure the charge amount of each toner by stirring in a ball mill and using a blow-off charge amount measuring device. Company Toshiba Chemical TB-2
00) was used. The measured value is a 10 second value,
The results are shown in Figure 1.

Next, each toner 1 to 6 was coated with Mg-Cu having an electrical resistance value of 1011 Ω·am or more under an applied voltage of 1 kV.
- Electrophotographic developers 1 to 6 with a toner concentration of 4.0% by weight, which are mixed with resin-coated carrier particles having a Zn ferrite carrier shell (TFC-C230 manufactured by TDK Corporation).
I got it.

The resin-coated carrier particles contain Mg-C as magnetic powder particles.
It contains u-Zn ferrite particles and has a resin coating of acrylic resin. Moreover, the volume average particle diameter is 75-1 resin coating thickness 0.25μ.

A continuous copying test of 30,000 copies was conducted using each of these electrophotographic developers 1 to 6, and image density, fog, and resolution were measured.

For the continuous copying test, a commercially available electrophotographic copying machine was used, and the manuscript for copying was a Data Quest chart, an electrophotographic society chart running test pattern, or the like.

The image density is a value obtained by measuring the density of the copied image at the initial stage and after copying 30,000 copies using a Macbeth densitometer (manufactured by Macbeth Co., Ltd.).

Fog is determined by measuring the white background area of the toner image (electronic photography society chart) and the white background area of plain paper using a Photovolt densitometer (manufactured by Tokyo Denshoku Co., Ltd.) at the initial stage and after 30,000 copies have been made, and by calculating the difference between these measured values. It is divided by the measured value of the white background of plain paper and presented as a ratio.

The resolving power was measured using a line densitometer (manufactured by Tokyo Denshoku Co., Ltd.) for the initial resolving power and the resolving power of the copied image after 30,000 copies were made.

The results are shown in Table 1.

It is clear from Table 1 that the toner of the present invention has excellent fluidity, and changes over time in image density, fog, and resolution are small.

Furthermore, from FIG. 1, it can be seen that in the present invention, toner charging rises quickly.

Example 5 As magnetic powder particles, magnetite with a volume average particle diameter of 0.5 tones and a styrene-acrylic copolymer resin were used, and resin carrier particles with a volume average particle diameter of 30 - containing 75% by weight of magnetic powder particles were used. I got it. Further, the electrical resistance was IQ+3Ω·cm or more under an applied voltage of 1 kV.

This product was mixed with the above-described toners 1 to 4 to form a developer, and when a continuous copying test was conducted using a commercially available electrophotographic copying machine, results equivalent to or better than those of Examples 1 to 4 were obtained.

<Effects of the Invention> When an electrophotographic developer using the resin-coated carrier particles or resin carrier particles of the present invention or using magnetic toner particles in combination, the toner has good fluidity as described above, and the toner has good fluidity. Because the charge rises quickly, good image quality can be obtained. When trying to obtain a high-quality toner image with improved resolution, gradation, etc., it is necessary to use small-sized toner particles with a volume average particle size of, for example, 8- or less. Although the fluidity of the toner is significantly reduced, the present invention can also prevent such aggregation of the toner.

Further, by using the present invention, stable images with little change over time in image quality such as image density, fog, and resolution can be obtained during continuous copying.

Moreover, such effects are much higher than when using a mixture of silica particles and metal oxide particles.

4,

[Brief explanation of drawings]

No. Figure 1 is In the electrophotographic developer of the present invention to FIG.

Claims (5)

[Claims] (1) An electrophotographic toner containing toner particles containing one or more types of composite particles in which fine silica particles and fine metal oxide particles are fixed and integrated, and magnetic particles containing resin and magnetic powder particles. An electrophotographic developer characterized by: (2) The electrophotographic developer according to claim 1, wherein the magnetic particles have an electrical resistance of 10^9 Ω·cm or more. (3) The electrophotographic developer according to claim 1 or 2, wherein the magnetic particles are resin-coated carrier particles. (4) Claim 1, wherein the magnetic particles are resin carrier particles.
or the electrophotographic developer described in 2. (5) The electrophotographic developer according to any one of claims 1 to 4, wherein the electrophotographic toner has positive chargeability.