JP2787688B2 - Electrostatic latent image developing method - Google Patents

Description

The present invention relates to a method for developing an electrostatic latent image using an electrostatic latent image developer containing magnetic toner particles and carrier particles.

<Prior Art> One-component developers using magnetic toners are widely known.

Charged magnetic toners in which a charge control agent is added to magnetic toners are also known (JP-A-55-48754 and JP-A-57-455).
No. 55, No. 57-45556, No. 57-45557).

However, in the case of these one-component toners, charge aggregation of the toner occurs, which causes image defects such as white stripes.

Therefore, JP-A-59-121054, JP-A-59-182464,
-210450, 59-210466, 59-216149, 62-
JP-A Nos. 42163, 62-275280 and 62-294259 describe chromium complexes of monoazo dyes such as Bontron S-34 (manufactured by Orient Chemical Industries) and Bontron N-01 which is a nigrosine dye (ibid.). A technique is disclosed in which a carrier is added to a charged magnetic toner internally added to a toner as a charge control agent to prevent toner aggregation.

In Japanese Patent Application Laid-Open No. 59-162563, although there is no specific description in the specification, the examples thereof show that Aizenspiron Black TRH (manufactured by Hodogaya Chemical Industry Co., Ltd.) which is a chromium complex of a monoazo dye. Discloses a developer in which a carrier is added to a charged magnetic toner in which is added as a charge control agent.

<Problems to be Solved by the Invention> The generation of white stripes is eliminated by the addition of these carriers.

However, in a magnetic brush type developing method using a developing device having a magnet and a developing sleeve, the magnet and the sleeve are rotated relative to each other. With this rotation, toner adheres to the sleeve surface, so-called sleeve adhesion occurs. Would.

This attachment of the sleeve is wavy on the sleeve, and if it is severe, a wavy pattern is formed on the image.

A main object of the present invention is to provide a method for developing an electrostatic latent image developer in which toner aggregation does not occur, white stripes do not occur, and adhesion of a sleeve is eliminated.

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

That is, the present invention comprises magnetic powder and resin, magnetic toner particles having an average particle diameter of 5 to 25 μm, and carrier particles having an average particle diameter of 10 to 45 μm, wherein the magnetic toner particles have an average particle diameter of 0.01 to 3 μm. 0.1 to 10% by weight of the magnetic particles are externally added, the average particle size of the magnetic particles is 0.5 to 20% of the average particle size of the magnetic toner, and the magnetic toner particles are a metal complex of an azo dye. And an electrostatic latent image developer containing no nigrosine dye and having a content of the carrier particles of 10 to 40% by weight is stored in a developing device provided with a magnet and a developing sleeve,
An electrostatic latent image developer for developing an electrostatic latent image on a photoconductor by rotating the magnet and the developing sleeve in opposite directions, and a magnetic brush type developing method using the developer.

<Operation> In the present invention, since magnetic particles are externally added to the magnetic toner particles, the adhesion of the sleeve is reduced.

<Specific Configuration of the Invention> Hereinafter, a specific configuration of the present invention will be described in detail.

The carrier particles contained in the developer of the present invention have an average particle diameter of 10 to 45 μm, more preferably 10 to 35 μm, and particularly preferably 15 to 30 μm.

When the average particle diameter exceeds 45 μm, the resolution is deteriorated, and the inside of the apparatus due to toner scattering is generated.

If the thickness is less than 10 μm, carrier pulling occurs.

In this case, the average particle diameter is represented by a 50% particle diameter in calculating a volume particle diameter of a measured value by the Microtrack method. That is, a sample dispersed in water using a dispersant is used, for example, in Microtrac STD (799).
What is necessary is just to calculate from the data obtained by performing volume-based measurement using the 1-0) type (manufactured by LEEDS & NORTHHRUP).

The carrier material to be used is not particularly limited, and various soft magnetic materials such as iron, magnetite, and various ferrites such as ferrite can be used. In this case, as ferrite, Mg-Cu-Zu ferrite, Ni-Zu ferrite, Cu-Zu
Any of various known compositions such as ferrite can be used.

These carrier particles may have a coating such as an acrylic resin, a silicone resin, or a fluororesin, if necessary, or include a binder such as a polyester resin or a styrene-acrylic resin as in the case of the toner described below. You may go out.

The coercive force Hc of such a carrier is preferably 50 Oe or less, more preferably 20 Oe or less at 5000 Oe. This is because if it exceeds 50 Oe, there is a tendency for transport failure to occur.

Further, for example, the maximum magnetization σ _m at 5000 Oe is 25 to 220 emu /
g, more preferably 30 to 210 emu / g, and particularly preferably 30 to 100 emu / g for a ferrite carrier.

If σ _m is less than 25 emu / g, carrier pulling tends to occur. If σ _m exceeds 220 emu / g, the ears of the magnetic brush become hard and scratches on the photoreceptor tend to occur.

These magnetic properties may be measured using a vibrating magnetometer. Further, the electric resistance is 1 × 10 ⁵ Ω when 100 V is applied.
As described above, it is particularly preferable to be about 1 × 10 ⁶ to 2 × 10 ¹² Ω.

If it is less than 1 × 10 ⁵ Ω, the brush streak tends to increase, and if it is too large, the density tends to be hard to appear.

 The measurement of the electric resistance is performed as follows.

That is, 0.2 g of the carrier is inserted between parallel metal plates spaced apart by 7 mm, and the carrier is sandwiched by magnets from the outside of the metal plate. Thereafter, for example, the application of voltage is started from 10 V by using a super insulation meter SM-10E or SM-5 (both manufactured by Toa Denpa Co., Ltd.), and the voltage is sequentially applied up to 1000 V. The direct reading at this time may be used as the electric resistance.

The carrier specific gravity according to JIS Z2504 is 2.1.
3.33.3 g / cm ³ , particularly preferably 2.1-2.8 g / cm ³ .

In order to manufacture such a carrier, for example, the following may be performed. First, put the soft magnetic material into the mixer,
The mixture is made into a slurry and mixed, and further crushed by an attritor.

These are granulated by a spray drier, dried, and further classified by a shifter to adjust the particle size.

These are fired in an electric furnace, and these are roughly crushed by a crusher and then crushed by a vibration method.

After that, shifter,
Adjust the particle size using an air classifier. If necessary, coating can be carried out with a coating machine, and re-grain size can be adjusted after heat treatment, and a coating carrier can be used.

Further, it is of course possible to produce the image by using other various known methods.

Next, the average particle diameter of the magnetic toner particles used is 5 to 25.
μm, more preferably 6 to 25 μm, particularly preferably 8 to
20 μm.

When the average particle size is less than 5 μm, the fluidity of the developer deteriorates, and caking or sleeve adhesion of the developer occurs. When the average particle size exceeds 25 μm, the resolution deteriorates and the fixability becomes poor.

In measuring the average particle size of the toner particles, the volume particle size of the measured value is calculated by the Coal counter method, and the 50% average particle size is defined as the average particle size.

In the call counter method, Isoton II (manufactured by Coulter Electronics Co., Ltd.) is used as an electrolytic solution, for example, a Coulter Counter TA-II having an aperture diameter of 100 μm.
(Coulter Electronics Co., Ltd.) is used for volume-based measurement.

In general, the particle size distribution is preferably such that the average particle size is 2 or more and about 5% or less, and / 2 or less is about 5% or less.

The magnetic toner particles having such a particle size contain a magnetic powder and a resin.

Examples of the magnetic powder include metals such as iron, manganese, cobalt, nickel and chromium, and alloys thereof, metal oxides such as chromium oxide, iron sesquioxide, and triiron tetroxide, and the general formula MO.Fe ₂ O ₃ (M is Fe, Mn, Co, Ni, Mg, Zn, Cd, B
Any of the materials conventionally known as magnetic materials, such as ferrites represented by one or more metals selected from the group of monovalent or divalent metals such as a and Li), can be used.

The average particle diameter described above is preferably from 0.01 to 10 μm, particularly preferably from 0.05 to 3 μm.

On the other hand, a styrene copolymer resin is particularly preferable as the resin.

The styrene copolymer resin is obtained by a copolymerization reaction between a styrene monomer and a copolymerizable vinyl monomer.

In this case, as the copolymerizable monomer, styrene and its derivatives, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate,
Α-ethylhexyl acrylate, α-hydroxyethyl acrylate, hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, Α-hydroxyethyl methacrylate, hydroxypropyl methacrylate, etc., acrylates or methacrylates, acrylamide, diacetone acrylamide, amides, such as N-methylol acrylamide, etc., vinyl esters, ethylene olefins, And ethylenically unsaturated carboxylic acids.

 In addition, a polyester resin can also be used.

The polyester resin is obtained by a polycondensation reaction between a polybasic acid component and a polyhydric alcohol component.

As the polybasic acid in this case, oxalic acid, malonic acid,
Succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sevesic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-
Examples thereof include resin group polycarboxylic acids, aromatic polycarboxylic acids, alicyclic polycarboxylic acids, and anhydrides thereof represented by cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid.

As polyhydric alcohols, ethylene glycol, propylene glycol, trimethylene glycol,
1,4-butanediol, 1,5-pentanediol, 1,6-
Hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, pinacol, hydrobenzoin, benzpinacol, cyclopentane-1,2-diol, cyclohexane 1 Aliphatic alcohols, aromatic polyalcohols and alicyclic polyalcohols typified by 1,2-diol and cyclohexane-1,4-diol.

Other resins include ethoxy resin, silicone resin, fluorine resin, polyamide resin, acrylic resin, polyurethane resin, polyether resin, polyvinyl alcohol resin, polyethylene, ethylene-vinyl acetate copolymer,
Polypropylene and the like.

These resins may be used alone, but may be used as a mixture of two or more as needed. Further, as a method for producing these resins, solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, contact polymerization, high-pressure polymerization, low-pressure polymerization, and our polymerization method It can be produced by a conventionally known polymerization method such as an appropriate combination.

The amount of magnetic powder in magnetic toner particles formed from these resins and magnetic powder is 10 to 70% by weight, more preferably 20 to 60% by weight.
% By weight.

If the amount is less than 10% by weight, the magnetic force from the magnet inside the developing machine is not sufficiently transmitted, and fog and toner scattering tend to be deteriorated. If it exceeds 70% by weight, the fixability of the toner tends to deteriorate.

Various internal additives may be further added to such magnetic toner particles.

 One example of the internal additive is a wax.

Waxes are for so-called offset development measures that occur during fixing by a fixing roll,
For example, low molecular weight polyethylene, polypropylene, metal salts of fatty acids, and silicone oil are used.

Such materials include polyethylene such as High Wax 100P and High Wax 110P [Mitsui Petrochemical Industry Co., Ltd.], polypropylene such as Viscol 550P and Viscol 330P [Mitsui Kasei Kogyo Co., Ltd.], and zinc stearate 60.
1. Fatty acid metal salts such as zinc stearate CP [Nitto Kasei Kogyo] and silicone oils such as silicone oil KF96 and silicone oil KF69H [Shin-Etsu Silicone Co., Ltd.].

A fluorine resin is also effective as a release agent having such a function.

These substances having a releasing action are preferably contained in an amount of 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, per 100 parts by weight of the toner particles.

Carbon black MA-100 [Mitsubishi Kasei Kogyo Co., Ltd.], Ketjen Black EC-DJ600 [Lion Akzo Co., Ltd.], 671 Miloli Blue [Dainichi Seika Kogyo Co., Ltd.] And inorganic or organic pigments such as conductive titanium oxide (Titanium Industry Co., Ltd.).

These are preferably contained in an amount of 0.1 to 10 parts by weight, particularly 0.1 to 5 parts by weight, per 100 parts by weight of the toner particles.

In addition, examples of the internal additive include a fluidity improver and a resistance adjuster described below.

Thus, in the toner particles, the magnetic powder and the resin are contained, and in addition, if necessary, waxes, pigments, and the like are contained, but an azo dye as a charge control agent, particularly a metal of a monoazo dye, In particular, it is preferable that no chromium complex or nigrosine dye is contained.

Among the charge control agents, especially in a system in which a metal complex of an azo dye or a nigrosine dye is internally added, especially when the initial toner content in the developer is increased to make the toner rich, toner scattering and an increase in background fog are caused. This is because the density tends to decrease, and toner spent is liable to occur.

Examples of such a metal complex of a monoazo dye include those having the following structural formula.

(However, R ₁ , R ₂ , R ₃ and R ₄ each represent an aromatic polar group, M represents a metal, and Cat represents a cation.) In addition, metal complexes of various known azo dyes Is not contained.

Further, as the nigrosine dye, various known dyes are included.

Further, it is preferable that a metal complex dye is not contained.

Examples of the metal complexes of these azo dyes and nigrosine dyes include Aizen spiron black TRH and T-3.
7, T-77 [hereinafter Hodogaya Chemical Co., Ltd.], Bontron S-34, S-31, S-32, E-81, E-82, N-01, N
-02, N-03, N-04, N-05, N-07 [hereinafter, Orient Chemical Industry Co., Ltd.], Kayaset Black T-2,
Kaya Set Black T-3, Kaya Set Black 004
[The above is Nippon Kayaku Co., Ltd.].

The internal addition of other charge control agents, especially dye-based ones, is not limited as described above, but also has the same tendency as described above, so it is preferable not to add them.

Examples of such dye-based charge control agents include quaternary ammonium salt-based dyes such as Bontron P-51 (Orient Chemical Co., Ltd.) and Kayaset Charge N-1 (Nippon Kayaku Co., Ltd.).

To such toner particles, a resistance adjusting agent, a color adjusting agent or a coloring agent, a fluidity improving agent and the like can be externally added.

In these examples, colloidal silica, titanium oxide,
Metal oxides such as zinc oxide and alumina; inorganic fine powders such as silicon carbide, calcium carbonate, barium carbonate, and calcium silicate; polymer beads such as PMMA, polyethylene, nylon, silicone resin, phenolic resin, benzoguanamine resin, and polyester; Fluorinated organic fine powders such as ethylene fluoride, polytetrafluoroethylene, and vinylidene fluoride; metal salts of fatty acids such as zinc stearate and magnesium stearate; black pigments such as carbon black, acetylene black, channel black, and aniline black; Yellow pigments such as Yellow GR, Variore 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, Such as orange pigments such as Zoron'oren'nji and the like.

Although these substances may be used alone,
If necessary, two or more types can be used in combination.

 Further, the above-mentioned release agent can be externally added.

These may be, as described above, kneaded by being internally added to the toner particle composition, or may be externally added and dry-mixed or thermally or mechanically fixed to the surface of the toner particles. For example, when necessary, the forms can be combined as needed.

Further, each substance may be subjected to a coupling agent such as titanate, aluminum, or silane, a silicone oil, other organic treatment, or an inorganic treatment for surface hydrophobizing treatment and surface dispersion improving treatment.

These external additives have a particle size of about 0.01 to 5 μm. The external addition amount is about 0.1 to 5% by weight.

It is preferable that the above-mentioned charge control agent, particularly, a metal complex of an azo dye or a nigrosine dye is not externally added.

Under such a premise, magnetic particles are further externally added to the magnetic toner particles.

The magnetic particles to be externally added may be those described above as the material of the magnetic powder contained in the magnetic toner particles.

Further, the average particle size is 0.01 to 3 μm, more preferably 0.05 to 3 μm.

When the average particle diameter is less than 0.01 μm, the effect of preventing the adhesion of the sleeve decreases. On the other hand, if the thickness exceeds 3 μm, the fixing property is deteriorated, and the magnetic particles remain in the developer, giving an adverse effect.

In this case, more preferable results are obtained when the average particle diameter of the magnetic particles is 0.5 to 20% of the average particle diameter of the magnetic toner particles.

The coercive force Hc of the magnetic particles used is, for example, preferably from 60 to 250 Oe, particularly preferably from 70 to 220 Oe.

Below 60 Oe and above 250 Oe, the effectiveness of the present invention tends to decrease.

On the other hand, the coercive force of the magnetic powder internally added to the magnetic toner particles
Hc is preferably from 60 to 250 Oe, particularly preferably from 70 to 220 Oe. The value obtained by dividing the coercive force Hc of the magnetic particles by the coercive force Hc of the magnetic powder is preferably 0.25 to 4.

As a result, the effect of preventing the adhesion of the sleeve is further enhanced.

Further, for example, the maximum magnetization σ _m of the magnetic particles and the granular powder at 5000 Oe is preferably about 60 to 100 emu / g, respectively. Thereby, the effect of preventing the adhesion of the sleeve is further improved.

Such magnetic particles are externally added to the magnetic toner particles. That is, the magnetic particles are dry-mixed with the magnetic toner particles, and are adsorbed or fixed on the surface of the magnetic toner particles, or are fixedly integrated with the surface of the toner particles by mechanical strain or heat, or embedded. Is what is being done.

Magnetic particles are added to such magnetic toner particles in an amount of 0.1 to 10% by weight, particularly 1 to 8% by weight, based on the magnetic toner particles.

If the amount is less than 0.1% by weight, the effect of the present invention is not obtained. If the amount is more than 10% by weight, fog increases and the fixing rate deteriorates.

As magnetic properties of the magnetic toner to which such magnetic particles are externally added, the coercive force Hc is preferably 60 to 250 Oe, particularly preferably 70 to 220 Oe.

When Hc exceeds 250 Oe, the spikes of the toner tend to be hard and the toner concentration tends to decrease.

Further, the maximum magnetization σ _m at 5000 Oe is preferably 15 to 60 emu / g.

When sigma _m exceeds 60 emu / g, the developing property deteriorates, there is a tendency to lower the density, also when less than 15 emu / g, toner scatter tends to occur.

The bulk density is 0.2 to 0.8 g / cm ³ , especially 0.4 to 0.7 g / cm ³
It is preferred that

In order to produce such a magnetic toner, as one example, the raw material composition is sufficiently mixed with a Henschel mixer, and then kneaded with a hot-melt kneader. Thereafter, the mixture is cooled, coarsely crushed by a hammer mill, and finely crushed by a jet impact mill.

Then, after removing the excess fine powder region with an air classifier, the external additive and the magnetic particles are dry-mixed with a Henschel mixer, and then the excess coarse powder region is removed with an air classifier and the predetermined particles are removed. A toner having a diameter distribution is obtained.

Of course, various other known methods may be used.

5000 of such magnetic toner (T) and carrier (C)
The ratio of the sigma _m in oe, the σ _mT / σ _mc 0.04~2.4, it is more preferably at from 0.08 to 1.7.

This is because if it is less than 0.04, it becomes difficult to mix, and if it exceeds 2.4, it becomes difficult to obtain a concentration.

Such a magnetic toner and a carrier are mixed at an initial concentration of 10 to 40% by weight of the carrier content to form a developer.

When the initial carrier concentration in the developer exceeds 40% by weight,
Stability such as density, fogging, and resolution during multi-sheet copying, particularly continuous copying of many sheets, deteriorates.

On the other hand, if the content is less than 10% by weight, toner aggregation which should be originally improved occurs, and white stripes frequently occur.

In such a case, the initial carrier concentration is 12 to 38% by weight,
Particularly when the content is 15 to 35% by weight, more preferable results can be obtained.

At the time of mixing, a Nauta mixer, a V blender, or the like may be used.

To develop a latent electrostatic latent image using such a developer,
It can be performed as follows.

First, the developer is stored in the developing device at the above initial carrier concentration.

The developing device is of a magnetic brush developing type, and it is preferable that the developing device magnetically transports the developer to the developing area by rotation of a magnet.

Of these, for example, JP-A-54-119935 and JP-A-55-191993.
It has a magnet roll and a developing sleeve roll described in No. 32073 and the like, and the magnet and the developing sleeve rotate in opposite directions.

In such a developing device, the effect of the present invention is particularly remarkably realized.

In addition, the developer of the present invention can be applied to various known developing systems.

Copying is performed by storing the developer in such a developing device.
At this time, when the toner concentration becomes 20 to 60% by weight, only the toner is periodically replenished.

By replenishing only the toner, extremely stable image quality can be maintained even when a large number of sheets are copied.

It should be noted that any known structure can be applied to the structure of the photoconductor and the copying machine.

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

Example 1 preparation toner composition of the magnetic toner A: magnetic powder BL-500 55 parts by weight [Titanium Industry Co., Ltd.] average particle diameter _{0.3μm Hc (5000Oe) 750e σ m} (5000Oe) 85emu / g styrene - acrylic Resin 43.5 parts by weight [Nippon Carbide Industry Co., Ltd.] Polypropylene 550P 2.5 parts by weight [Sanyo Chemical Co., Ltd.] External additives A1 to A5: (based on 100 parts by weight of toner composition A) A1 Silica R-974 0.8 parts by weight [manufactured by Nippon Aerosil Co., Ltd.] Average particle size 12 mμm Zinc stearate 601 (W) 0.1 parts by weight [manufactured by Nitto Kasei Kogyo Co., Ltd.] Average particle size 4 μm (after classification) A2 silica R-974 0.8 parts by weight 0.1 parts by weight of zinc stearate 601 (W) magnetic particles BL-500 2 parts by weight A3 silica R-974 0.8 parts by weight Zinc stearate 601 (W) 0.1 parts by weight magnetic particles BL-500 4 parts by weight A4 silica R-974 0.8 Parts by weight Zinc stearate 601 (W) 0.1 parts by weight Magnetic particles BL 500 6 parts by weight A5 silica R-974 0.8 parts by weight Zinc stearate 601 (W) 0.1 parts by weight Magnetic particles BL-500 15 parts by weight Toner composition B: Magnetic powder BL-500 55 parts by weight [manufactured by Titanium Industry Co., Ltd.] Styrene-acrylic resin 41 parts by weight [Mitsubishi Rayon Industries, Ltd.] Polypropylene 550P 5 parts by weight [Sanyo Chemical Co., Ltd.] External additives B1 to B5: (based on 100 parts by weight of toner composition B) B1 Silica R-974 0.8 parts by weight Zinc stearate 601 (W) 0.1 parts by weight B2 Silica R-974 0.8 parts by weight Zinc stearate 601 (W) 0.1 parts by weight Magnetic particle Zn ferrite 2 parts by weight [manufactured by TDK Corporation] Average particle size _{0.4μm Hc (5000Oe) 1400e σ m} (5000Oe) 88emu / g B3 silica R-974 0.8 part by weight of zinc stearate 601 (W) 0.1 parts by weight magnetic particles Zn ferrite 4 parts by weight B4 silica R-974 0.8 part by weight Zinc stearate 601 (W) 0.1 parts by weight Magnetic particles ZnFe Light 6 parts by weight B5 silica R-974 0.8 parts by weight Zinc stearate 601 (W) 0.1 parts by weight Magnetic particle Zn ferrite 15 parts by weight Toner compositions A and B are sufficiently mixed with a Henschel mixer, and then mixed with a hot-melt kneader. After kneading, the mixture was cooled and coarsely pulverized with a hammer mill. Then, it was pulverized by a jet impact mill.

Then, after removing the excessive fine powder area with an air classifier, using a Henschel mixer, an external additive corresponding to compositions A and B was added.
A1-A5 and B1-B5 were dry-mixed. Thereafter, the excess coarse powder area was removed by an air classifier to obtain a toner having a predetermined particle size distribution.

In this manner, the toners A1 to A5 and the toners B1 to B5 having the physical properties shown in Table 1 below, both having a volume average particle diameter of 11 μm.
I got

Carrier preparation composition (mol%) _{carrier: 16NiO-33ZnO-51Fe 2 O} 3 _{carrier: 10.5Mg (OH) 2 -20ZnO-} 7.5CuO-62Fe 2 O 3 _{carrier: 10.5Mg (OH) 2 -20ZnO-} 7.5CuO- 62Fe ₂ O _{3 The} above components were put into a mixer, mixed in a slurry state, and further pulverized with an attritor.

This was granulated by a spray drier, dried, and fired in an electric furnace. Carriers and base materials having different carrier resistances were obtained depending on the firing conditions at this time.

The carrier, the carrier, and the base material of the carrier were adjusted to the target particle size by a shifter and an air classifier to obtain a carrier having the following average particle size. Average carrier particle size (μm) : 8,12,17,20,25,33,40: 8,13,17,22,25,35,40: 9,13,16,20,25,35,41 Carrier Physical properties Next, a carrier having a particle size of 25 μm is used, and the toners A1 to A5, B1 to B5
And an initial carrier concentration of 23% by weight.

Each developer was housed in a developing device in a reversal type toner image transfer type electrophotographic printer using an organic photoconductor as a photoconductor.
In the developing device, the developing sleeve has a small gap between the developing sleeve and the photosensitive drum, and has a built-in magnet roller that rotates at high speed.

Here, the developing sleeve is rotated at a low speed in the direction opposite to the photosensitive member, the magnet roller inside is rotated in the direction opposite to the developing sleeve, and a developing bias is applied to the developing sleeve. An agitator for preventing toner aggregation is provided in the developing device.

In this developing device, the developer is mixed and stirred by the rotation of the developing sleeve, and the toner and the carrier are supplied to the peripheral surface of the developing sleeve while being frictionally charged with each other.

At this time, the developing conditions of the electrostatic latent image in the printer are as follows.

Sleeve roll 1300 x 1 / 7rpm 18mm Magnetic roll 1300rpm, 6 poles, surface magnetic flux 700G Drum-sleeve gap 0.30mm Blade-sleeve gap 0.27mm Developing bias -525V DC Surface potential -640V (OPC drum) In such a developing device Copying was repeated using the toner, toner and carrier at the initial densities shown in Table 1 below, and the following experiment was conducted.

1) Carrier pulling Three black solid patterns are printed successively on an actual machine, white spots (white spots) appearing on the image at that time are counted, and the average of the three sheets is obtained.

2) Toner scattering With a real machine, a continuous 1000-sheet printer was used, and the scattering was visually checked.

3) Print a group of lines with a resolution of 240 DPI and 300 DPI and visually check them with a 10x loupe. At that time, determine whether each line can be confirmed as an independent line. And make a comprehensive judgment. Judgment 300DPI 240DIP ○ ○ ○ △ × ○ × × × 4) Fog Measure the reflectance (A) of the paper before passing it with REFLECTOMETER MODELTC-6D manufactured by Tokyo Denshoku Co., Ltd. Next, the reflectance (B) of the target non-developing portion of the printer object is measured.

 For fogging, the value of AB (the value of the difference in reflectance) is used.

5) White streaks White streaks do not cause the developer to be replenished on the sleeve because the developer agglomerated powder or coarse particles present on the sleeve-blade gap obstruct the flow of the developer. The missing part of the character was judged as follows.

In this case, when judging a white stripe, an initial sampling image was taken, and printing was continuously performed on 1000 sheets while sampling at a pitch of 200 sheets. In this case, in a continuous printer other than at the time of sampling, the black portion becomes 5% of the total area. Paper passing was performed with a 5% print pattern.

：: None at all △: Occurred during running, but no longer occurred during running.

×: There is always one or more. 6) Density change width Measure the density using REFLECTOMETER MODELTC-6D manufactured by Tokyo Denshoku Co., Ltd.

At this time, the density (A) of the density (A) at the time of the initial printing and the density (B) at the time of the continuous printing under the same conditions as the above 5) is expressed as:
The maximum value of -B was determined.

7) Adhesion of sleeve After adding toner, after printing 100 sheets continuously, the surface of the sleeve is blown off with air, and it is checked whether or not clumps remain in the shape of a sleeve, and whether or not a wave pattern due to the clumps is generated in the image. Identified visually.

The occurrence of only agglomerates was evaluated as Δ, the occurrence of agglomerates and wavy pattern was evaluated as x, and the absence of sleeve attachment was evaluated as o.

The toner was supplied when the toner concentration reached 50% by weight.

8) Fixing rate After printing a 1-inch square black solid pattern, the black solid image was rubbed 10 times with a metal cylindrical bar (diameter 50mm, weight 1000g) to which gauze was attached with double-sided tape.
Measure the density before and after rubbing the printed matter. Fixing rate is calculated by the following formula.

The above 4) fog, 5) white stripes,) sleeve adhesion and 8) fixing rate are shown in Table 3 below. From the results shown in Table 3, it was found that the magnetic toner particles had a value of 0.
It can be seen that the external addition of magnetic particles of 1 to 10% by weight eliminates the occurrence of adhesion of the sleeve and prevents the fixing performance and the fog from being deteriorated.

Example 2 A similar experiment was conducted using the toners A3 and B3 of Example 1 and a carrier having a particle size of 25 μm, while changing the initial carrier amount in the developer.

Table 4 shows the changes in 5) white stripes and 6) the density change width during continuous printing of 1,000 sheets.

If the carrier concentration is less than 10% by weight in the combination of the carrier and the toners A3 and B3, the white streak due to toner aggregation, which should be originally improved, cannot be improved.

On the other hand, if the amount exceeds 40% by weight, it becomes difficult to immediately supply the toner to the carrier after the toner is replenished critically during continuous printing, which causes a problem in the stability of density.

For this reason, the ratio of the carrier to the total initial developer must be in the range of 10% by weight to 40% by weight.

Example 3 An experiment was conducted by changing the carrier particle size. Table 4 shows the results.

 The initial carrier concentration is 23% by weight.

In the combination of the carrier and the toners A2 and B2, when the carrier particle size is 10 μm or less, the development of the carrier pull becomes remarkable. On the other hand, if the thickness exceeds 45 μm, the resolution is deteriorated, and the inside of the apparatus due to toner scattering becomes remarkable.

Example 4 Using the initial developer (toner 100 g, carrier 30 g, carrier average particle diameter 25 μm), every time the toner indicator was turned on, toner was added 100 g / time and 5% was added.
10,000 continuous prints were performed with a print pattern having a density of The toner indicator lights when the toner concentration reaches 50% by weight.

Combination of developer Developer 1 Carrier x Toner A3 Developer 2 Carrier x Toner B3 Developer 3 Carrier x Toner A3 Developer 4 Carrier x Toner B3 Developer 5 Carrier x Toner C3 Developer 6 Carrier x Toner D3 Table 6 Shown in

The toner C3 and the toner D3 are obtained by replacing the toner composition A in the toner A3 with the following toner compositions C and D, respectively, and externally adding an external additive A3 thereto.

Toner composition C: magnetic powder BL-500 55 parts by weight Styrene-acrylic resin 42.5 parts by weight [manufactured by Nippon Carbide Industry Co., Ltd.] Polypropylene 550P 2.5 parts by weight Aizen Spiron Black TRH [manufactured by Hodogaya Chemical Co., Ltd.] 1 part by weight Toner composition D: magnetic powder BL-500 55 parts by weight Styrene-acrylic resin 42.5 parts by weight [Mitsubishi Rayon Co., Ltd.] Polypropylene 550P 5 parts by weight Bontron S-34 1 part by weight [Orient Chemical Co., Ltd.] Made It was confirmed that a stable image could be obtained without causing carrier deterioration and deterioration of the photoconductor by each developer in the combination of the carrier and the toners A3 and B3.

In the above description, the toners A3 and B3 include a monoazo dye chromium complex Aizen Spiron Black TRH (manufactured by Orient Chemical Co., Ltd.), Bontron S-34, and (Hodogaya Chemical Co., Ltd.) as charge control agents. With carrier concentration 10
In the developing agents 5 and 6 in which the developer was prepared at 4040% by weight, in addition to the above-mentioned properties being lowered, especially the inside fouling increased and the background fog increased.

Although the example of the negative charge type toner has been described above, such a result is the same in the case of the positive charge type toner. At this time, the same results as described above were obtained when a nigrosine dye such as Bontron N-01 (manufactured by Hodogaya Chemical Co., Ltd.) was internally added as a charge control agent.

<Effect> According to the present invention, adhesion of the sleeve is significantly reduced.

 Also, there is no toner aggregation and no white streaks.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Motohiko Makino 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-62-251759 (JP, A) JP-A-61 JP-A-289360 (JP, A) JP-A-58-65442 (JP, A) JP-A-63-98556 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/083 G03G 9/10 G03G 15/08 507

Claims (2)

(57) [Claims] (1) The composition contains a magnetic powder and a resin, and has an average particle size of 5 to 5.
25 μm magnetic toner particles and carrier particles having an average particle diameter of 10 to 45 μm, wherein the magnetic toner particles are externally added with 0.1 to 10% by weight of magnetic particles having an average particle diameter of 0.01 to 3 μm. The average particle size of the magnetic toner is 0.5 to 20% of the average particle size of the magnetic toner, the magnetic toner particles do not contain a metal complex of an azo dye and a nigrosine dye, and the content of the carrier particles is 10 to 40% by weight of an electrostatic latent image developer is stored in a developing device having a magnet and a developing sleeve, and the magnet and the developing sleeve are rotated in opposite directions to develop the electrostatic latent image on the photoreceptor. Electrostatic latent image developing method. 2. An additional supply of only a magnetic toner.
Electrostatic latent image developing method.