JPH0659507A - Electrostatic image developer - Google Patents

Abstract

PURPOSE:To Lessen the disturbance in electrostatic charge by the fine powder of toners and toner spent and to increase the electrostatic charge speed of replenishing toners by using the specific toners and carriers and providing an adequate toner/carrier ratio. CONSTITUTION:The toners are pulverized by the laminar flow and eddy current motion of air generated by relative rotation in line grooves 5, 6 provided on the inside surface of a sleeve body 1 constituting a surface 3 of revolution of a pulverizing machine consisting of the rotating sleeve body and an inside core cylinder 2 and the outside surface of the inside core cylinder 2 constituting a surface 4 of revolution conjugate via spacing with the surface 3 of revolution along the generator parallel with the axis of rotation, by which the toner is formed. The grain size conditions thereof are such that the particles sized <=5mum are 5 to 25 number %, the particles sized <=12mum are <=5vol.% and the average volume grain size is 6 to 10mum. The weight average of one piece of the carriers is 0.10 to 1.50mug and the carriers are coated with a resin. The mixing ratio of the toners and the carriers is 10 to 45% concealing rate of the carrier particle surfaces with the toner particles. The electrostatic image developer is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image developer used in electrophotography, electrostatic recording and electrostatic printing.

[0002]

2. Description of the Related Art Although various properties are required for a developer,
Among them, the problems of dirt and fogging due to toner scattering are important. This is particularly remarkable in the case of a small-diameter toner aiming at high image quality in a two-component developer formed of toner and carrier. In two-component development, a difference in developability due to the toner particle size is unavoidable, and generally a larger particle size is easier to develop. Therefore, when a small-diameter toner is used for the purpose of improving the image quality, the fine toner tends to accumulate on the carrier surface, and they tend to hinder the charging of the newly replenished toner. As a result, the generated weakly charged toner is easily scattered by the centrifugal force formed by the rotation of the developing sleeve and the like.

In addition, the toner is susceptible to various types of stress in the developing device and is destroyed, so that fine powder is easily generated. Therefore, the above-mentioned problem of toner scattering has become a major problem with small-diameter toner.

As a method for reducing the fine powder in the toner in advance, a method in which the fine powder side is largely removed by air classification after crushing, or after crushing with a jet type crusher as in JP-A-62-209542, a machine is used. A method has been proposed in which fine particles having a size of 5 μm or less are fixed to a toner base by an expression strain force so that the amount of particles having a size of 5 μm or less becomes zero.

However, even if the fine powder is reduced or reduced to 0 in advance, it is not an essential solution because the generation and accumulation are repeated again in the developing device. Further, if there is no toner having a particle size of 5 μm or less, there is a problem that the effect of reducing the diameter of the toner is originally reduced for high image quality. The necessity of toner having a particle size of 5 μm or less is described in detail in JP-A-3-30783.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the object of the present invention is to prevent charge inhibition due to generation of fine powder, less toner spent, fast charging speed of toner, sharp charge amount distribution, high image density, low fog and high resolution. The purpose is to provide a developer with less toner scattering.

[0007]

According to the present invention, what is a toner crushing method for preventing generation of fine powder in a developing device, what is a carrier which does not give stress to the toner, and to give proper charging without giving stress to the toner? The following conclusions were obtained as a result of earnest research on what degree the carrier particle surface hiding ratio of the applied toner particles is.

That is, the above-mentioned object of the present invention is: in a two-component developer containing a toner and a carrier;
(1) In a crusher composed of an outer shell and an inner core that rotate relative to each other, on the inner surface of the outer shell that forms a rotating curved surface and the outer surface of the inner core that forms a common rotating curved surface with a gap in the rotating curved surface. ,
(2) The groove is formed by cutting along the generatrix parallel to the axis of rotation, and is crushed by the gap, the laminar flow of air generated in the groove by the relative rotation and the vortex motion.
The particle size condition is 5 to 25% by number of particles of 5 μm or less, 12
The particles having a size of μm or more are 5% by volume or less, and the average volume particle size is 6 to 10 μm, and the carrier has a mean weight of 0.10 to 1.50 μg and is coated with resin. The mixing ratio is achieved by the electrostatic image developer in which the hiding ratio of the surface of the carrier particles by the toner particles is 10 to 45%.

The reason why the developer of the present invention can achieve the above-mentioned object is not always clear, but it is presumed as follows.

That is, in the toner of the present invention, FIG.
One of the features is that it is crushed by a crusher as shown in.

FIG. 1 (1) is a sectional view taken along a plane including the rotary shaft of the crusher, and FIG. 1 (2) is a sectional view taken along a plane I-I perpendicular to the rotary shaft shown in (1). FIG.

In the figure, 1 is an outer jacket and 2 is an inner core cylinder. Reference numeral 3 is a rotation curved surface forming the inner surface of the outer sheath, and 4 is a rotation curved surface forming the outer surface of the inner core tube which is common to the above 3 with a gap h.

Reference numeral 5 designates a triangular groove cut away along the generatrix of the inner surface of the mantle, 5'denotes a convex ridge, 6 indicates a square groove cut off along the generatrix of the outer surface of the inner core, and 6 '. Is a rib having a convex portion.

When the inner core tube 2 rotates at the relative peripheral velocity νo, a laminar flow along the gap and a vortex flow in the triangular groove are generated,
By selecting the groove pattern, gap and relative rotation speed,
It is possible to exert a sufficient crushing force on large and small particles, at the same time it is possible to give a gentle impact to small particles and a strong striking force to large particles, and inevitably the particle size distribution is uniform.

The toner crushed by such a crusher is
Compared with the conventional jet crushing method (method of hitting the toner with a jet stream to the barrier), the generated toner particles are characterized by less ridge angles and cracks that are easily ground as fine powder. Therefore, it is considered that the toner does not easily generate fine powder due to the stress in the developing machine.

Further, the carrier M of the present invention has a low weight M of 0.10 to 1.50 μg and is coated with a resin capable of relaxing impact energy. It is presumed that crushing is reduced, and as a result, generation of fine toner powder is suppressed. Here, the weight of one carrier is defined by the following formula.

[0017] M = (4/3) π · R 3 · d c R: mean radius of the carrier (cm) d _c: true density [g / cm ^3] (weight) mean particle size of the carrier of the carrier Microtrac It is a value measured using (manufactured by Nikkiso Co., Ltd.). The true density of the carrier is a value measured by a dry automatic densimeter Acupic 1330-01 (manufactured by Shimadzu Corporation) using a constant volume expansion method.

Further, in the developer of the present invention, since the carrier surface hiding ratio of the toner is set to 10 to 45%,
It is considered that the impact and crushing effect of the carrier particles on the toner particles is small, and there is no charging failure of the replenishment toner due to the presence of excessive toner particles.

The carrier particle surface hiding ratio X of the toner particles is defined by the following equation.

X = (mR · d _c ) / (4M · r · d _t ) m: Toner weight [g] M: Carrier weight [g] r: Toner radius [cm] R: Carrier radius [cm] d _t toner true density [g / cm ^3] d _c: Although the destruction of the toner particles in a developing device carrier true density [g / cm ^3] the developer for the reason as described above can be greatly suppressed, further toner Since the particle size distribution of is optimized, high image quality is also achieved. Specifically, the particles having a particle size of 5 μm or less are not set to 0 at all, but from the viewpoint of resolution, 5% by number or more, and from the viewpoint of charging failure of the replenishment toner due to the presence of excess particles
It is set to 25% or less. Similarly in terms of resolution
It is characterized in that large particles of 12 μm or more are suppressed to 5% by volume or less and the volume average particle diameter is 6 to 10 μm.

The particle size distribution of the toner was measured by using a Coulter counter (Coulter Co.).

Next, the binder resin used in the toner according to the present invention is not particularly limited, and various resins can be used.

Specific examples include styrene resins, acrylic resins, styrene-acrylic copolymer resins, epoxy resins and polyester resins.

The polyester resin as the binder resin is obtained by polycondensation of a polyhydric alcohol monomer and a polycarboxylic acid monomer.

As the toner used in the present invention, all colorants used in ordinary toners can be used.
Specifically, carbon black, magnetite, nigrosine dye, aniline dye, ferrite and the like can be used. The addition amount of the colorant is controlled as necessary, but generally 0.1 to 20 wt% is added. While any colorant will accomplish the invention, more uniform fine dispersion of the colorant can provide even more desirable results. This is because if there is no colorant agglomerate, the stress is not concentrated and the toner destruction in the developing device can be further prevented.
Although various methods for improving the dispersion of the colorant have been proposed, "recycling of classified fine powder to the mixing step" is preferable from the viewpoint of cost and the like. The amount of fine powder to be recycled is preferably 5 wt% or more of the total raw material weight from the viewpoint of preventing toner destruction, and less than 50 wt% from the viewpoint of kneading stability.

Other toner components used as necessary include, for example, a charge control agent and a fixing property improving agent (release agent).
Etc. can be mentioned.

As the charge control agent, for example, a nigrosine type dye, a metal complex type dye, an ammonium salt type compound, an aminotriphenylmethane type dye or the like can be used.

The charge control agent is contained in an amount of 0 to 5 wt% with respect to the binder resin weight of the toner.

In the case of a color toner, a colorless or white one is preferable in order not to impair the colorability of the color toner.

As the fixability improving agent (release agent), for example, low molecular weight polyolefin such as low molecular weight polypropylene, low molecular weight polyethylene, low molecular weight polybutene, etc.,
Fatty acid esters such as maleic acid ethyl ester, maleic acid butyl ester, stearic acid methyl ester, stearic acid butyl ester, palmitic acid cetyl ester and montanic acid ethylene glycol ester, partial saponification products thereof, natural paraffin, micro wax, synthetic paraffin, etc. Paraffin wax, stearic acid amide, olefinic acid amide, palmitic acid amide, lauric acid amide, behenic acid amide, methylenebisstearamide, amide waxes such as ethylenebisstearamide, carnauba wax and the like can be used. .

A preferable content ratio is 1 with respect to the toner.
~ 6 wt%.

Further, in order to improve the fluidity of the toner, inorganic fine particles may be further added to and mixed with the toner particles in the outer periphery of the toner particles.

Examples of such inorganic fine particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, chromium oxide, cerium oxide, antimony trioxide, zirconium oxide and carbonized. Fine particles such as silicon can be used. In particular, silica fine particles and titanium oxide fine particles are preferable.

The addition ratio of the inorganic fine particles is 0.05 to 1 w of the toner.
t% is preferred.

It is preferable to use hydrophobized inorganic particles.

Such hydrophobic treatment is carried out by using, for example, the fluidizing agent fine particles as described above, a silane coupling agent such as dialkyldihalogenated silane, trialkylhalogenated silane, alkyltrihalogenated silane, hexaalkyldisilazane, or dimethyl. It can be carried out by reacting with a hydrophobic treatment agent such as silicone oil such as silicone oil at a high temperature.

Further, in order to improve the cleaning property of the cleaning system using a blade, a fatty acid metal salt such as zinc stearate may be added and mixed in a proportion of 0.01 to 50% by weight based on the weight of the developer.

In the present invention, when a two-component type developer is prepared, a carrier is further used in addition to the toner and the inorganic fine particles.

As the carrier of the present invention, a resin-coated carrier obtained by coating the surface of magnetic particles with a resin is used.

The magnetic particles constituting the carrier include
A substance that is strongly magnetized in that direction by a magnetic field, such as iron,
Ferrite, magnetite and other iron, nickel, cobalt and other ferromagnetism metals or alloys, compounds containing these elements, alloys that do not contain ferromagnetism elements but become ferromagnetism by appropriate heat treatment For example, particles made of an alloy of a type called a Heusler alloy such as manganese-copper-aluminum or manganese-copper-tin or chromium dioxide can be used. Among them, since ferrite has a lower true density than metals such as iron and nickel, the weight of one carrier can be reduced even with a large particle size. This is preferable because it is possible to achieve both reduction of stress on the toner and prevention of carrier adhesion.

Here, ferrite is a general term for magnetic oxides containing iron, and MO.Fe ₂ O ₃ (M is a divalent metal)
It is not limited to the spinel type ferrite represented by the chemical formula. Such ferrite can be suitably used in the present invention because various magnetic properties can be obtained by changing the composition of the contained metal component. Among them, copper-zinc type ferrite and copper-magnesium type ferrite are particularly preferable because they have higher electric resistance than manganese-zinc type ferrite and nickel-zinc type ferrite and exhibit excellent triboelectric charging ability.

As the binder resin for the resin for coating the resin-coated carrier, for example, a styrene-acrylic copolymer,
Silicone-based resin, fluorine-based resin and the like can be preferably used.

[0043]

EXAMPLES Next, the present invention will be specifically described with reference to examples.

First, a toner and a carrier were prepared as described below, and these were mixed to prepare a developer, and the characteristics were checked and evaluated.

Preparation of Toner: Toner 1 100 parts by weight of polyester A 7.5 parts by weight of acidic furnace black 2 parts by weight of carnauba wax 2 parts by weight of ethylenebisstearic acid amide 2 parts by weight A high speed stirring type mixer is used to prepare a twin-screw kneader. Impact crusher KTM
Finely pulverized with -X (Kawasaki Heavy Industries).

The operating conditions of the crusher are as follows.

Operating conditions of crusher Raw material particle size: 11 μm (medium crushed by impact crusher) Grinding rotor rotation speed: 17800 rpm Classifier rotation speed: 3000 rpm Total air flow: 2.4 Nm ³ / min Secondary air flow: 0.1 Nm ³ / min Supply rate: 2.4 kg / H Volume average particle size (D50V) of pulverized product is 7.6 μm. The pulverized product was classified into a toner having a volume average diameter of 8.0 μm by a wind classifier. This toner has a particle size distribution of 5 μm or less, 20% by number, 12
The volume average particle size distribution (D50
P) was 6.4 μm. When this toner was observed with a scanning electron microscope, it had a sharp corner. True specific gravity is
1.32. The powder having D50V = 4.5 μm collected on the fine powder side in this classification is hereinafter referred to as “fine powder for recycling”.

To 100 parts by weight of the above toner, 0.6 parts by weight of hydrophobic silica was externally added.

Polyester A was synthesized as follows.

<Production Example of Polyester> Polyester A Neopentyl glycol 132 g Ethylene glycol 60 g Terephthalic acid 279 g Dibutyltin laurate 1.5 g The above materials were thermometer, stainless steel stirring rod,
The mixture was placed in a glass 4-necked flask having a capacity of 2 [l] equipped with a glass nitrogen introduction tube and a fluidized condenser, and reacted for 5 hours while stirring at 170 ° C. under normal pressure in a nitrogen atmosphere in a mantle heater, Continue the reaction at 210 ℃, ASTM E28
-When no change in softening point equivalent to -51T is observed, 108 g of 1,2,4-benzenetricarboxylic anhydride is added and the reaction is continued at 210 ° C to obtain a softening point equivalent to ASTM E28-51T. The progress of the reaction was further traced, and when the softening point reached 141.3 ° C, the reaction was stopped and cooled to room temperature to obtain polyester A.

Toner 2 Polyester A 100 parts by weight Acidic Furnace Black 7.5 parts by weight Carnauba wax 2 parts by weight Ethylenebisstearic acid amide 2 parts by weight Recycled fine powder (10 wt%) 12 parts by weight Impact type crusher KTM after kneading with a shaft kneader, then coarse crushing, and then medium crushing
Finely pulverized with -X (Kawasaki Heavy Industries). The volume average particle size (D50V) of the pulverized product is 7.6 μm. The pulverized product was classified into a toner having a volume average diameter of 8.2 μm by a wind classifier. The particle size distribution of this toner is 15% by number below 5 μm and 1.5% by volume above 12 μm.
And the number average particle size distribution (D50P) was 6.8 μm. When this toner was observed with a scanning electron microscope, it had a shape with a ridge angle and no cracks. The true specific gravity was 1.32.

To 100 parts by weight of the above toner, 0.6 part by weight of hydrophobic silica was externally added.

Toner 3 Polyester A 100 parts by weight Acidic furnace black 7.5 parts by weight Carnauba wax 2 parts by weight Ethylenebisstearic acid amide 2 parts by weight Recycled fine powder (10 wt%) 47 parts by weight Impact type crusher KTM-
Finely pulverized with X (manufactured by Kawasaki Heavy Industries). The volume average particle size (D50V) of the pulverized product is 7.6 μm. The pulverized product was classified into a toner having a volume average diameter of 8.8 μm by a wind classifier. The particle size distribution of this toner was 10 number% below 5 μm and 1 volume% above 12 μm, and the number average particle size distribution (D50P) was 7.4 μm. When this toner was observed with a scanning electron microscope, it had a shape with a ridge angle and no cracks. The true specific gravity was 1.32.

To 100 parts by weight of the above toner, 0.6 part by weight of hydrophobic silica was externally added.

Comparative Toner (1) The same raw materials as in Toner 1 were mixed with a high-speed stirring type mixer, kneaded with a twin-screw kneader, and then roughly crushed, and an air flow type crusher I type jet mill (Japan Pneumatic Machine) was used. The volume average particle size (D50V) of the crushed product is 7.6 μm. The pulverized product was classified into a toner having a volume average particle size of 8.0 μm with a wind power classifier. The particle size distribution of this toner was 20 number% below 5 μm, 1.2 volume% above 12 μm, and the number average particle size distribution (D50P) was 6.4 μm. When this toner was observed with a scanning electron microscope, it had a square shape. Also, there were cracks on the toner surface. The true specific gravity was 1.32.

0.6 part by weight of hydrophobic silica was externally added to 100 parts by weight of the above.

Comparative Toner (2) Comparative Toner 1 and the method of Example 1 of JP-A-63-244051 were used to treat 5 μm or less to 2% by number. 12 μm or more 4% by volume, D50V is 9.3 μm, D50P is 8.9 μm. When this toner was observed with a scanning electron microscope, it was found that the fine particles had a shape with sharp corners fixed to the toner base. True specific gravity is 1.
32.

To 100 parts by weight of the above toner, 0.6 parts by weight of hydrophobic silica was externally added.

Preparation of Carrier: Carrier 1 Resin-coated ferrite carrier having an average particle size of 80 μm (true specific gravity
4.8). The average weight of one carrier is 1.29 μg.

Carrier 2 Resin-coated ferrite carrier having an average particle size of 60 μm (true specific gravity
4.8). The average weight of one carrier is 0.54 μg.

Comparative carrier (1) Resin-coated ferrite carrier with an average particle size of 120 μm (true specific gravity 4.
8). The average weight of one carrier is 4.34 μg.

Preparation of Developer: Developer 1 Toner 1 75 g Carrier 1 1800 g Toner concealed area ratio on carrier surface 37.9% Developer 2 Toner 1 75 g Carrier 2 1800 g Toner concealed area ratio on carrier surface 28.4% Developer 3 Toner 2 75g Carrier 2 1800g Toner concealment area ratio on carrier surface 27.7% Developer 4 Toner 3 75g Carrier 2 1800g Toner concealment area ratio on carrier surface 25.8% Developer 5 Toner 3 90g Carrier 2 1800g Toner concealment on carrier surface Area ratio 37.2% Developer 6 Toner 3 36g Carrier 2 1800g Toner concealment area ratio on carrier surface 12.4% Comparative developer (1) Comparative toner (1) 75g Comparative carrier (1) 1800g Toner concealment area ratio on carrier surface 52.5 % Comparative developer (2) Comparative toner (2) 180g Carrier 2 1800g Concealed area ratio of toner on carrier surface 61.4% Comparative developer (3) Toner 3 18 g Carrier 2 1800 g Toner concealed area ratio on carrier surface 6.8% Evaluation method) 1. Fine powder generation test Put the developer in the developer of electrophotographic copying machine u-5070 (made by Konica), rotate it for 2 hours under the condition that the linear velocity of the sleeve is 792 mm / sec, and toner in the developer after the initial and after 2 hours. The particle size distribution of was measured with a Coulter counter.

2. Image quality and toner spent An electrophotographic copying machine u-5070 (manufactured by Konica) was used to measure the resolution and fog density after 50 kC. Visual resolution was used, and fogging density was measured using a Macbeth densitometer.

3. Toner scattering 2. The toner scattering around the developing device after 50 kC was divided into 5 stages.

Rank 1 ...- Stain on the front and back of the image Rank 2 ...- Stain on the back of the image Rank 3 ...- No stain on the image but fairly scattered around the developing unit Rank 4 ... Somewhat toner scattering Yes Rank 5 ... No toner scattering The results are shown in Table 1.

[0066]

[Table 1]

[0067]

EFFECTS OF THE INVENTION The toner of the present invention has no ridge angles or cracks that cause generation of fine powder, and has a carrier with a low self-weight as a developer and an appropriate toner / carrier ratio. Occurrence is suppressed. As a result, there is little charge inhibition and toner spent due to toner fine powder, and the charging speed of the replenishment toner is high. Therefore, high image density, low fog, less toner scattering, and high resolution due to the presence of appropriate toner fine powder can be obtained.

[Brief description of drawings]

FIG. 1 shows an example of a crusher according to the present invention, (1) is a sectional view taken along a plane including a rotation axis, and (2) is a partial cutaway of the sectional view taken along a plane perpendicular to the rotation axis. FIG.

FIG. 2 is a diagram illustrating the principle of the crushing operation of a conventional crusher.

[Explanation of symbols]

 1 Outer body 2 Inner core 3 Rotational curved surface of inner surface of outer sheath 4 Rotational curved surface of outer surface of inner core 5 Triangular groove on inner surface of outer jacket 5'Ridge along the triangular groove 6 Square groove on outer surface of inner core 6 ′ Line ridges along the square groove

Claims (1)

[Claims] 1. A two-component developer containing a toner and a carrier; the toner comprises: (1) In a crusher composed of an outer shell and an inner core that rotate relative to each other, Grooves are cut along the generatrix parallel to the axis of rotation on the outer surface of the inner core tube that forms a common curved curved surface with a gap on the curved surface. It is pulverized by laminar and vortex motion of air. (2) The particle size condition is 5-25% by number of particles of 5 μm or less, 5% by volume or less of particles of 12 μm or more, and a volume average particle. The carrier has a diameter of 6 to 10 μm, and the carrier has an average weight of 0.10 to 1.50 μg.
And a mixture ratio of the toner and the carrier is such that the hiding ratio of the surface of the carrier particles by the toner particles is 10 to 45%.