JP2001125318A - Electrostatic latent image developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic latent image developer capable of stably forming an image and having a long service life and a quantity of electric charges adjustable in a wide range. SOLUTION: The electrostatic latent image developer contains (a) a magnetic resin coated carrier obtained by coating the catalyzed surfaces of magnetic particles as a carrier core material with a high polymer polyethylene resin formed by directly polymerizing an ethylene monomer, (b) a magnetic powdery carrier substantially comprising magnetic particles themselves and (c) an abrasive toner obtained by fixing fine abrasive grains on the surface of the base material of a toner in a weight ratio of 70:30:5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developer used in an electrophotographic method, an electrostatic recording method, an electrostatic printing method and the like employed in a copying machine, a laser printer, and the like.
Sometimes referred to as a developer. ).

[0002]

2. Description of the Related Art Conventionally, in a developer used in a two-component developing system, magnetic powder particles such as iron, magnetite or ferrite are usually used as a carrier for stably transporting toner. . A carrier comprising such magnetic powder particles (sometimes referred to as a magnetic powder carrier) has the advantages of a simple structure, excellent magnetic force, and low cost.

[0003] In addition, Japanese Patent Publication No.
A developer containing a mixed carrier consisting of a magnetic powder carrier and a magnetic resin carrier in which magnetic fine particles are dispersed in a binder resin is disclosed. Since such a developer has a large volume resistance value and contains a magnetic resin carrier having a high charge amount, the charge imparting force to the toner is increased, so that the generation of fog can be suppressed efficiently. There are advantages.

Further, in order to improve the durability of the carrier itself, Japanese Unexamined Patent Publication No. 9-204075 proposes a carrier coated with a magnetic resin. This magnetic resin-coated carrier is provided with a coating layer made of a high molecular weight polyethylene resin obtained by directly polymerizing ethylene monomer on the surface of the carrier core material using a catalyst supported on the surface of the carrier core material. I have. Therefore, the obtained polyethylene coating layer has excellent strength, and also has appropriate elasticity, and can absorb an impact force such as agitation, so that excellent durability can be obtained.

[0005]

However, the magnetic powder carrier conventionally used has a problem that the volume resistance value is small, the moisture resistance is poor, and poor charging is likely to occur. Also, since the magnetic powder carrier is heavy, toner components adhere to the carrier due to the impact of agitation in the developing device and tend to cause spent, thereby lowering the charging ability of the carrier and causing further poor charging. There was a problem that it was easy. Further, once charging failure occurs, it is difficult to stably transport the toner, the toner is scattered in the apparatus, and the white background of the visible image is easily fogged, and the image density is reduced. There was a problem of adverse effects.

Further, the developer disclosed in Japanese Patent Publication No. 292050 uses a magnetic powder carrier and a magnetic resin carrier in combination, but the magnetic resin carrier is
Since the binding between the magnetic particles and the binder resin is poor, there has been a problem that the binder resin is easily peeled off when used for a long time. Further, the magnetic resin carrier has a small specific gravity and has a charge per weight (specific charge Q).
/ M) was large, so that a problem that carrier pulling easily occurred was also observed. Therefore, in order to stably form an image and extend the life of the developer, the mixing ratio of the magnetic resin carrier has to be reduced. Therefore, since the compounding ratio of the magnetic powder carrier increases, there has been a problem that when used in combination with a color toner, the color developability of the obtained color image is easily reduced. That is, since the magnetic powder carrier has high blackness, if carrier pulling occurs when the compounding ratio of the magnetic powder carrier is high, the carrier may be conspicuous, particularly in a portion of the color image other than black, and Became turbid.

Further, since the magnetic resin-coated carrier disclosed in Japanese Patent Application Laid-Open No. 9-204075 itself has low blackness, even if it is used in combination with a color toner, it does not lower the color developability of the obtained image. Although small, the cost alone was relatively high and the resulting developer was likely to be expensive. In addition, the magnetic resin-coated carrier has a problem that the charge applying force to the toner is slightly lower than that of the magnetic powder carrier.

Therefore, it has been desired to develop a developer in which the charge amount of the mixed carrier can be more easily adjusted by adjusting the mixing ratio of the mixed carrier in a wide range, and furthermore, the carrier is less drawn. That is, the present invention has been made to solve the above-described problem, and a developer capable of stably forming an image, having a long life, and having a wide charge amount adjustment range, and having a small carrier pulling. The purpose is to provide.

[0009]

According to the electrostatic latent image developer of the present invention, (a) a magnetic resin-coated carrier having a coating layer composed of a high molecular weight polyethylene resin obtained by directly polymerizing an ethylene monomer; , (B) a magnetic powder carrier substantially consisting of magnetic particles themselves, and (c) a toner.

As described above, by combining (a) the magnetic resin-coated carrier and (b) the magnetic powder carrier to form a mixed carrier, (a) the magnetic resin-coated carrier can be replaced with a conventional magnetic resin carrier. It can be blended in a wider range than in the case where it is used. As a result, the required charge amount can be set arbitrarily and can be stably applied to the toner. Further, since the magnetic resin carrier having a higher magnetic force and a lower specific gravity than the magnetic resin carrier is used, the mixing ratio of the magnetic powder carrier can be reduced. Can be prevented. Therefore, even when used in combination with the color toner, the color development of the obtained image is less likely to be reduced.

In constituting the electrostatic latent image developer of the present invention, the compounding ratio (a) / (b) of (a) the magnetic resin-coated carrier and (b) the magnetic powder carrier is expressed by weight ratio. 85
It is preferable to set the value in the range of / 15 to 45/55. By limiting the compounding ratio to such a range, excellent fluidity of the carrier can be obtained while securing an initial charge amount equal to or more than a certain value.

In constituting the electrostatic latent image developer of the present invention, the volume resistivity of (a) a magnetic resin-coated carrier and (b) a magnetic powder carrier or one of the carriers is set to 1 × 10 It is preferable to set the value in the range of ² to 1 × 10 ¹⁴ Ω · cm. The volume resistance of the carrier is
If it is smaller than 1 × 10 ² Ω · cm, the image density may be lowered or the image quality may be deteriorated. On the other hand, if the volume resistance is larger than 1 × 10 ¹⁴ Ω · cm,
This is because carrier pulling and fogging may easily occur.

[0013] Further, in constituting the electrostatic latent image developer of the present invention, (a) the volume resistivity of the magnetic resin-coated carrier and V _a, and V _b the volume resistivity of the (b) magnetic powder carrier , The value of (V _a −V _b ) is changed to 10 to 1 × 10 ³ Ω ·
It is preferable that the value be in the range of cm. The reason is,
When two types of carriers are used, if there is an extreme difference in resistance between the carriers, cavitation carrier pulling is likely to occur, a development margin cannot be secured, and a carrier having extremely low resistance is mixed. This is because image leakage may occur due to leakage current flowing to the photoconductor. Therefore, (a) the volume resistance value of the magnetic resin-coated carrier is set to V _a
When the volume resistivity of the (b) magnetic powder carrier when the resistance difference between V _b and within a certain range, it is possible to perform a more stable conveyance of the toner.

Further, in constituting the electrostatic latent image developer of the present invention, the bulk density of the magnetic resin-coated carrier (a) is defined as ρ
It is preferable that the relationship of ρ _b > ρ _a be satisfied, where _a is a, and (b) the bulk density of the magnetic powder carrier is ρ _b . With such a configuration, (b) the magnetic powder carrier is (a)
By attracting the magnetic resin-coated carrier, it is possible to more efficiently suppress the occurrence of carrier pulling in which the carrier adheres to the photoreceptor surface.

Further, in constituting the electrostatic latent image developer of the present invention, the ratio of the amount of toner added to the mixed carrier of (a) and (b) is set to a value within the range of 2 to 40% by weight. Is preferred. By limiting the amount of toner added to a value of 2% by weight or more in this manner, it is possible to effectively suppress a decrease in image density due to an excessive increase in the charge amount of the toner. Further, the amount of toner added was 40% by weight.
With the following values, it is possible to efficiently suppress scattering of the toner in the apparatus and occurrence of fog on a visible image due to an insufficient charge amount of the toner.

In forming the electrostatic latent image developer of the present invention, the toner is preferably a color toner. With this configuration, even when the carrier is attached to the photosensitive member together with the toner and printed by the carrier pulling, the color developability of the color visible image is reduced.

Further, in constituting the electrostatic latent image developer of the present invention, it is preferable to use, as the toner, an abrasive toner having fine abrasive particles fixed on the surface. As described above, by using the abrasive toner, the surface of the carrier can be polished with the abrasive of the toner itself. Therefore, it is possible to further suppress the occurrence of spent in which the toner accumulates and grows on the surface of the carrier with long-term use. Furthermore, by using an abrasive toner,
The surface of the photoreceptor can also be cleaned by polishing with an appropriate force. Therefore, it is possible to suppress the occurrence of the image flow due to the generation of the leak current.

In constituting the electrostatic latent image developer of the present invention, the abrasive fine particles are preferably conductive titania. With this configuration, the charge amount of the carrier increases, so that it is possible to efficiently prevent the carrier from being transferred to the photoconductor together with the toner. Further, since the conductive titania has high whiteness, even when the toner base material to which the abrasive is fixed is colored, it is possible to avoid the toner color from becoming cloudy due to the color of the abrasive. Since conductive titania is chemically stable, it can be combined with color toners of various color components. Further, since conductive titania is stable to heat, it is suitable for heating and fixing a developed visible image.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] The electrostatic latent image developer of the first embodiment is obtained by (a) directly polymerizing an ethylene monomer on the surface of magnetic particles as a carrier core material. Magnetic resin carrier having a coating layer made of a high molecular weight polyethylene resin obtained, (b) a magnetic powder carrier substantially consisting of magnetic particles themselves, and (c) abrasive fine particles adhered to the surface of a toner base material. Abrasive toner.

[I] Carrier coated with magnetic resin Carrier core material (1) Material As the material of the carrier core material used in the present invention, a known two-component carrier for electrophotography can be used, and specific examples include the following types. Ferrite, magnetite, and iron, nickel,
Metals such as cobalt and the like, copper, zinc, antimony, aluminum, lead, tin, bismuth, beryllium, manganese,
Magnesium, selenium, tungsten, zirconium,
Metals such as alloys or mixtures with metals such as vanadium and the like, and metal oxides such as iron oxide, titanium oxide and magnesium oxide, nitrides such as chromium nitride and vanadium nitride, and carbides such as silicon carbide and tungsten carbide. Mixture Ferromagnetic Ferrite Mixture of

(2) Shape and Particle Size The shape of the carrier core material is not particularly limited, and may be any one of a spherical shape, an irregular shape and the like. However, a spherical shape is preferable because it is easy to uniformly charge. In addition, the average particle size of the carrier core material is preferably, for example, a value in the range of 20 to 120 μm, and more preferably a value in the range of 25 to 80 μm. The reason for this is that if the average particle size of the carrier core material is less than 20 μm, the carrier may adhere (scatter) to the electrostatic latent image carrier (generally, the photoconductor). The average particle size is 120 μ
If m exceeds m, carrier streaks and the like may occur, resulting in deterioration of image quality characteristics (reduction of image density).

(3) Ratio of carrier core material The ratio of the carrier core material is preferably 90% by weight or more, and more preferably 95% by weight or more when the entire carrier is 100% by weight. Is more preferred. The reason for this is that when the ratio of the carrier core material is less than 90% by weight, the magnetic force is reduced, and the toner transportability may be reduced. Further, the ratio of the carrier core material indirectly defines the thickness of the coating layer of the carrier. However, if the composition ratio of the carrier core material is less than 90% by weight, the coating layer may have an excessive or uneven thickness. This is because it may be. For this reason, when the carrier is applied to the developer, problems such as peeling of the coating layer, an increase in the amount of charge, and the like, or the durability and charge stability required for the developer may not be satisfied. Because there is. Further, when the proportion of the carrier core material is less than 90% by weight, fine line reproducibility is deteriorated in terms of image quality, and image density may be reduced.

On the other hand, the upper limit of the composition ratio of the carrier core material is preferably such that the coating resin layer completely covers the carrier core material and the magnetic powder, and specifically, 99.5.
% Or less, preferably 99.0% by weight.
The following values are more preferable. The preferred range of the ratio of the carrier core material may be slightly different depending on the physical properties of the carrier core material and the coating method.

(4) Conductive layer Prior to coating the carrier core material particles with a high molecular weight polyethylene resin, the volume resistivity value is 1 × 10 ² to 1 × 10 ^2.
It is also preferable to provide a conductive layer having a value within the range of ¹⁰ Ω · cm. By providing such a conductive layer, more excellent developability can be obtained, and an image having a high image density and a clear contrast can be obtained. This is presumably because the presence of the conductive layer causes the electrical resistance of the carrier to be reduced appropriately, and the leakage and accumulation of electric charges are performed in a well-balanced manner.

As the type of the conductive layer, it is preferable to use one in which conductive fine particles are dispersed in an appropriate binder resin. Examples of such conductive fine particles include carbon black, carbon black such as acetylene black, carbide such as SiC, magnetic powder such as magnetite,
Examples include SnO ₂ and titanium black. On the other hand, as the binder resin, for example, polystyrene resin,
Poly (meth) acrylic resin, polyolefin resin,
Polyamide resin, polycarbonate resin, polyether resin, polysulfonic acid resin, polyester resin, epoxy resin, polybutyral resin, urea resin, urethane resin, silicone resin, fluorine resin, etc. Alternatively, a combination of two or more types may be used. Further, a mixture (polymer blend), a copolymer, a block polymer, a graft polymer and the like of these resins can also be mentioned.

The size and amount of the conductive fine particles are not particularly limited as long as various properties such as electric resistance of the finally obtained carrier are satisfied. The average particle size is such that it can be uniformly dispersed in the resin solution, specifically, 0.01 to
The value is preferably in the range of 2.0 μm, and more preferably in the range of 0.01 to 10 μm.

The addition amount of the conductive fine particles varies somewhat depending on the type of the conductive fine particles, but a value within the range of 0.1 to 60% by weight based on the binder resin of the conductive layer, preferably, It is appropriate to set the value in the range of 0.1 to 40% by weight. In particular, when the filling rate of the carrier is as small as about 90% by weight and the thickness of the coating layer is relatively thick, the reproducibility of continuous copying of fine wires using such a carrier is reduced. May occur,
By adding the above-described conductive fine particles, it is possible to efficiently prevent the occurrence.

The method of forming the conductive layer is not particularly limited, either. A solution in which conductive fine particles are dispersed in a binder resin is applied to the surface of the carrier core material by spray coating, dipping, or the like. It can be formed by applying by applying. The conductive layer can also be formed by kneading and pulverizing the carrier core material, the conductive fine particles, and the binder resin in a solution. Further, it can also be formed by directly polymerizing a polymerizable monomer on the surface of the carrier core material particles in the presence of the conductive fine particles. In addition, what formed the functional layer, such as a conductive layer, on the carrier core material particle may only be called carrier core material particle.

2. Coating layer composed of high molecular weight polyethylene resin (1) High molecular weight polyethylene resin The high molecular weight polyethylene resin constituting the coating layer is usually
Although simply referred to as polyethylene, in the present invention, as the molecular weight range, those having a number average molecular weight of 10,000 or more, or those having a weight average molecular weight of 50,000 or more are preferable, and more preferably a number average molecular weight of 40,000 or more, or Weight average molecular weight 2
More than 100,000 polyethylene resin. The reason is that, when the number average molecular weight is less than 10,000, the polyethylene resin becomes waxy, and after being dissolved in hot toluene or the like, the polyethylene resin can be coated by a normal permeation method or a spray method, but the mechanical strength is weak. Therefore, if used for a long time, the carrier may peel off from the carrier core material due to shearing force (shear) in the developing device. In addition, it is also preferable to add a functional resin composed of one kind alone or a combination of two or more kinds of conductive fine particles and antistatic fine particles having charge controllability to the coating layer made of a high molecular weight polyethylene resin.

(2) Coating Layer Forming Method of Coating Layer As a forming method of the coating layer made of high molecular weight polyethylene, it is preferable to employ a direct polymerization method.
It is also preferable to combine with a forming method such as an immersion method, a fluidized bed, a dry method and a spray drying. Here, the direct polymerization method refers to a method in which the surface of a carrier core material is previously treated with an ethylene polymerization catalyst, and then a polyethylene resin-coated carrier is produced while directly polymerizing (generating) ethylene on the surface. . That is, as a catalyst for ethylene polymerization,
An organoaluminum compound is added to a solid product obtained by previously contacting a highly active catalyst component and a carrier core material which contain titanium and / or zirconium or one of which is soluble in a hydrocarbon solvent (eg, hexane, heptane, etc.). Is added, suspended in a hydrocarbon solvent,
Further, it refers to a method of forming a polyethylene resin coating layer by supplying an ethylene monomer and polymerizing on the surface of the carrier core material. According to this forming method, since the polyethylene coating layer is directly formed on the surface of the carrier core material, the obtained coating layer is thin, has excellent strength and elasticity, and has excellent carrier durability. Become. The details of such a direct polymerization method are described in, for example,
0-106808 and JP-A-2-187770
And a similar method can be mentioned.

When fine particles having a charge imparting function or conductive fine particles are added to the coating layer, they may be added to the ethylene monomer and coexist when forming the coating layer. For example, if conductive fine particles or functional fine particles having a charge control ability are dispersed in a polymerization system, the functional fine particles are taken in when the coating layer is formed by polymerization, and the functional fine particles are incorporated. Can easily be formed.

Coating amount When the coating amount of the high molecular weight polyethylene is represented by the weight ratio of [high molecular weight polyethylene resin coating] / [carrier core material particles], it is in the range of 0.5 / 99.5 to 10/90. Is preferable, and more preferably, the value is in the range of 1/99 to 5/95. The reason for this is that if the weight ratio is more than 10/90, the coating layer becomes relatively thick, and the coating layer may be peeled off or the charge stability may not be satisfied. Also, in terms of image quality, thin line reproducibility is poor,
This is because a problem such as a decrease in image density may occur. On the other hand, if the weight ratio is less than 0.5 / 99.5, the coating layer becomes relatively thin, and it may be difficult to completely cover the carrier core material and the magnetic powder.

Silica Particles In addition, it is preferable to add silica particles having a positive charge characteristic or a negative charge characteristic to the coating layer by, for example, performing a surface hydrophobic treatment. By adding the silica particles as described above, the chargeability of the carrier can be easily controlled, and the mechanical strength of the coating layer can be improved. The average particle size of the silica particles is preferably set to a value of 40 nm or less as a primary particle size, and more preferably a value within a range of 10 to 30 nm. The reason for this is that if the temporary particle size of the silica particles exceeds 40 nm, the gap between the silica particles becomes large, and irregularities are generated on the carrier surface, which may lower the fluidity. Commercially available products of such silica particles include R812 and RY20 (trade name) manufactured by Nippon Aerosil Co., Ltd., and 2000 and 2000/4 (trade name) manufactured by Wacker Chemicals Co., Ltd. as positively chargeable silica. .

When the charge amount of the positively charged toner is to be increased, silica particles having negative charge characteristics are used. When the charge amount of the negatively charged toner is to be increased, silica particles having positive charge characteristics are added. Is preferred. When the charge amount of the toner is reduced, it is preferable to use silica particles having the same polarity as the toner.

Next, functional fine particles other than silica particles will be described. It is also preferable that the coating layer is modified by adding one kind or a combination of two or more kinds of conductive fine particles and charge characteristic particles having charge control ability. As such conductive fine particles, conventionally known conductive fine particles can be used. For example,
Carbon black, carbide such as SiC, conductive powder such as magnetite, SnO ₂ , titanium black and the like can be used. The average particle size of the conductive fine particles is 0.01
It is preferably within the range of 2.0 μm to 2.0 μm. Further, examples of the charging characteristic particles include the following negative charging characteristic resin (A) and positive charging characteristic resin (B).

(A) Negatively Charging Characteristic Resin As the negatively charging characteristic resin, for example, a fluorine-based resin (for example, vinylidene fluoride resin, ethylene tetrafluoride resin, ethylene trifluoride ethylene resin, ethylene tetrafluoride to hexafluoride) Ethylene chloride copolymer resin), vinyl chloride resin, celluloid) and the like.

(B) Positive Charging Characteristics Resin As the positive charging characteristics resin, for example, acrylic resin, polyamide resin (eg, nylon-6, nylon-6)
6, nylon-11, etc.), styrene resins (for example, polystyrene, ABS, AS, AAS, etc.), vinylidene chloride resins, polyester resins (for example, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyacrylate, polyoxy) Benzoyl, polycarbonate, etc.), polyether-based resins (eg, polyacetal, polyphenylene ether, etc.), polyethylene-based resins (eg, EVE, EEA,
EAA, EMAA, EAAM, EMMA, etc.).

3. Conductive Properties Although the optimum value of the conductive properties of the magnetic resin-coated carrier varies slightly depending on the developing system using the carrier, for example, the volume resistivity is 1 × 10 ² to 1
It preferably has a value within the range of × 10 ¹⁴ Ω · cm,
Those having a value in the range of 1 × 10 ³ to 1 × 10 ¹⁰ Ω · cm are more preferable, and those having a value in the range of 1 × 10 ⁴ to 1 × 10 ⁹ Ω · cm are more preferable. The reason for this is that if the volume resistance value is less than 1 × 10 ² Ω · cm, it may be difficult to suppress carrier pulling development and generation of fog. On the other hand, if the volume resistance value is 1
If it exceeds × 10 ¹⁴ Ω · cm, it may be difficult to suppress the deterioration of image quality due to a decrease in image density. The volume resistance value of the carrier was adjusted to a thickness of 0.5 cm by sandwiching the carrier to be measured between the upper and lower electrodes (electrode area: 5 cm ² ) and pressing it under a load of 1 kg, and then adjusting the thickness of the upper and lower electrodes. It can be calculated by applying a voltage of 1 to 500 V in between and measuring the flowing current value.

4. Average Particle Size The average particle size of the magnetic resin-coated carrier is not particularly limited, either. For example, the average particle size is preferably set to a value in the range of 20 to 120 μm, preferably 20 to 100 μm. The value is more preferably in the range, and even more preferably in the range of 20 to 80 μm. The reason is that the average particle size of the carrier is 20 μm.
If it is less than m, carrier development or fogging may occur. On the other hand, when the average particle size is 1
If the thickness exceeds 20 μm, the transportability of the carrier may decrease.

5. The magnetic resin-coated carrier described above has both a lower specific gravity and an apparent specific gravity than the magnetic powder carrier. For this reason, the magnetic resin-coated carrier has a large surface area per unit weight, and has a capability of imparting charge to toner particles even in a small amount. Further, this magnetic resin-coated carrier can reduce the occurrence of spent in a developing device of a small printer in which a large shearing force is applied at the time of mixing and stirring, and can also reduce the impact of the magnetic powder carrier during stirring. Even if the magnetic resin-coated carrier has been subjected to surface treatment such as surface coating, the stress at the time of stirring is relatively small.
Is characterized by being difficult to be polished and peeled.

[II] Magnetic Powder Carrier (1) Configuration Type As the magnetic powder carrier, for example, magnetic particles substantially composed of magnetic powder such as iron, magnetite or ferrite can be used. However, it is also preferable to form a resin film on the surface of the magnetic powder in order to improve the moisture resistance. As a resin forming such a resin film, a silicone resin, an epoxy resin, a polyester resin,
Acrylic resin, polyamide resin, styrene resin,
Examples include vinylidene chloride resin, polyether-based resin, and polyethylene-based resin. Among these resins, silicone resins are particularly preferred because of their excellent moisture-proof properties and lubricity. When a resin film is formed on the magnetic powder carrier, the amount of the resin film is preferably set to a value within the range of 0.01 to 1% by weight based on the total amount of the magnetic powder carrier.

Bulk Density It is desirable that the bulk density of the magnetic powder carrier is higher than the bulk density of the magnetic resin-coated carrier. For example,
The bulk density of the magnetic resin-coated carrier is preferably less than 2.3 g / cm ³ , while the bulk density of the magnetic powder carrier is preferably 2.3 g / cm ³ or more. With this configuration, the magnetic powder carrier attracts the magnetic resin-coated carrier, and it is possible to more efficiently suppress the occurrence of carrier pulling in which the carrier adheres to the photoconductor surface.

Average Particle Size The average particle size of the magnetic powder carrier is set to 20 to 130 μm.
m, preferably in the range of 20 to 110 μm
m is more preferably in the range of 20 to 90.
More preferably, the value is in the range of μm. The reason is that when the average particle size of the magnetic powder carrier is 20 μm, carrier pulling development or fogging may occur. On the other hand, the average particle size is 130 μm
If the ratio exceeds the above range, the transportability of the toner by the magnetic powder carrier may decrease.

The compounding ratio of the (b) magnetic powder carrier and the (a) magnetic resin-coated carrier described above can be set widely. For example, the mixing ratio (a) / (b) is 85 / by ratio
It is preferable to set the value in a range of 15 to 45/55,
The value is more preferably in the range of 75/25 to 50/50, and even more preferably in the range of 70/30 to 40/60. The reason for this is that if the mixing ratio (a) / (b) is smaller than 85/15, (a)
The defect of the magnetic resin-coated carrier can be sufficiently compensated for by the magnetic powder carrier of (b). For example, by lowering the image density and the dot reproducibility by improving the transportability of the toner. Can be. Further, by suppressing an increase in the charge amount due to use, the life of the electrostatic latent image developer can be extended. On the other hand, when the mixing ratio (a) / (b) is larger than 45/55,
The defect of the magnetic powder carrier of (b) can be sufficiently compensated for by the carrier coated with the magnetic resin of (a), and the occurrence of fog due to poor charging can be suppressed. Further, deterioration of charging failure due to spent can be suppressed, and the life of the electrostatic latent image developer can be extended. Furthermore, if it is larger than 50/50, it can be suppressed more effectively.

Further, when a magnetic resin-coated carrier, a magnetic powder carrier, and a toner are mixed to form an electrostatic latent image developer, the weight ratio is 60 to 80:40, respectively.
20: More preferably in the range of 4 to 6.

(2) Operation As described above, by using the magnetic powder carrier together with the magnetic resin-coated carrier, the spike from the sleeve becomes the spike centered on the magnetic powder carrier having a high magnetic force. When the carrier leaves the development zone, the magnetic resin-coated carrier is attracted to the high magnetic force carrier. As a result, it is possible to prevent occurrence of carrier pulling in which the magnetic resin-coated carrier moves to the photoconductor together with the toner. That is, when the magnetic resin-coated carrier is used alone without using the magnetic powder carrier, the magnetic resin-coated carrier has a low specific gravity, a large charge per weight (specific charge Q / M), and a relatively high magnetic force. Weak
This is because carrier pulling is likely to occur. It is conceivable to set the average particle size (for example, a value exceeding 100 μm) of the magnetic resin-coated carrier in order to prevent carrier pulling. However, in the case where the image quality becomes coarse and it becomes difficult to improve the toner concentration. There is.

Also, by using the magnetic resin-coated carrier and the magnetic powder carrier together, the magnetic powder carrier can eliminate the increase in the electric charge charged on the magnetic resin-coated carrier. Therefore, the charge amounts of the carrier and the toner during the development can be stabilized, and as a result, the charge retention force of the toner by the carrier exceeds the toner suction force due to the potential difference on the electrostatic latent image of the photoconductor. Such a situation can be avoided. As a result, the toner conveyed by the carrier can be sufficiently adhered onto the electrostatic latent image, so that a decrease in image density and deterioration in dot reproducibility are prevented, and the life of the electrostatic latent image developer is extended. be able to.

[III] Abrasive Toner (1) Structure The structure of the (c) abrasive toner will be described with reference to FIG. FIG. 1 is a model diagram of the abrasive toner shown in FIG. 1C, and shows that the abrasive particles 15 are fixed on the surface of the toner base particles 13 of the toner 11. The fixing of the abrasive fine particles to the surface of the toner base particles is performed, for example, by uniformly mixing the toner base particles and the abrasive fine particles, and attaching the abrasive fine particles to the surface of the toner base particles, and then mechanically or thermally. The abrasive particles are driven into the toner base particles by applying a strong impact. That is, the abrasive particles are
It is preferable that the part is not completely buried in the toner base particles, but is fixed in a state where a part thereof protrudes from the surface of the toner base particles.

(2) Manufacturing Method A device for fixing abrasive fine particles is commercially available as a surface reforming device or system, and examples thereof are as follows. For example, as the dry mechanochemical method, a mechanochemical (trade name) manufactured by Okada Seiko Co., Ltd. and a mechanofusion system (trade name) manufactured by Hosokawa Micron Co., Ltd. may be mentioned. Examples of the method using the high-speed airflow impact method include a hybridization system (trade name) manufactured by Nara Machinery Co., Ltd. and a cryptotron system (trade name) manufactured by Kawasaki Heavy Industries, Ltd.

Examples of the wet method include Dispercoat (trade name) manufactured by Nisshin Flour Milling Co., Ltd. and Coatmizer (trade name) manufactured by Freund Corporation. In addition, as a method by a heat treatment method, Surfing (trade name) manufactured by Nippon Pneumatic Industries Co., Ltd. can be exemplified. Spray drying (trade name) manufactured by Okawara Kakoki Co., Ltd. can be used as a fixing device by another method.

(3) Fine Abrasive Particles Type 1 Fine abrasive particles are fine particles such as alumina, zirconia, and titanium oxide (titania).
And fine particles such as metal oxides. In particular, titanium oxide has high whiteness, and thus is preferable because, even when the toner base material to which the abrasive is fixed is colored, it is possible to avoid a decrease in the color development of the toner due to the color of the abrasive. Since titanium oxide is chemically stable, it can be combined with color toners of various color components. Furthermore, since titanium oxide is stable to heat, it is suitable for fixing a developed visible image by heating.

Type 2 The abrasive fine particles have a volume resistivity of 0.1 to 100 Ω.
It is preferable to show conductivity in the range of cm. The reason for this is that the use of the conductive abrasive particles increases the charge amount of the carrier, so that the carrier can be efficiently prevented from migrating to the photoconductor together with the toner. The conductive abrasive particles can be easily obtained by subjecting the electrically insulating abrasive particles to a conductive treatment such as a tin oxide treatment or an indium oxide treatment.

Hardness In consideration of application to an amorphous silicon photoreceptor (α-Si photoreceptor) having an amorphous-silicon carbide (SiC) layer as a photoreceptor surface protective layer 31 (see FIG. 3), an abrasive is used. The Mohs hardness of the fine particles is preferably set to a value of 8 or more, and more preferably a value in the range of 8 to 9. That is, since the Mohs hardness of the SiC layer is about 8, an excellent polishing effect can be obtained by using abrasive fine particles having such a hardness.

Average Particle Diameter The average particle diameter of the abrasive fine particles is in the range of D / d = 10 to 50, where D is the average particle diameter of the toner base particles and d is the average particle diameter of the abrasive fine particles. It is preferable that the average particle diameter is in the range of D / d = 10 to 40. This is because the fine abrasive particles are firmly fixed to the surface of the toner base particles, and the polishing effect of the fine abrasive particles is increased. The abrasive fine particles may be subjected to a surface treatment for the purpose of charge adjustment or prevention. Further, for the purpose of adjusting the fluidity or the like, other fine particles may be used in combination.

(4) Toner Base Particles As the toner base particles, those having the same constitution as those of the conventional toner are used, and are constituted by blending, for example, a binder resin, a colorant, a charge control agent, an offset preventing agent and the like. be able to. Further, a magnetic material may be added to obtain a magnetic toner. As such a binder resin, a vinyl resin such as a styrene-acrylic copolymer,
A polyester resin or the like is used. As the colorant, various pigments and dyes such as carbon black are used. Note that color toner may be used by using a plurality of pigments. In addition, as a charge control agent,
A quaternary ammonium compound, nigrosine, a nigrosine base, crystal violet, a triphenylmethane compound and the like are used. Further, as the anti-offset agent and the fixing improving auxiliary, olefin wax such as low molecular weight polypropylene, low molecular weight polyethylene or a modified product thereof can be used. Further, magnetite, ferrite and the like can be used as the magnetic material.

The toner base particles can be obtained by a conventionally known method, for example, by melt-kneading the components with a twin-screw extruder, a kneader or the like, pulverizing them with a jet mill or the like, and classifying them. The average particle size of the toner is generally preferably 20 μm or less, more preferably 15 μm or less.

(5) Function When the abrasive toner as described above is used, the toner 11 is polished on the surface of the magnetic powder carrier during the stirring and mixing of the developer, and the spent toner is fused to the surface of the magnetic powder carrier. The material is removed by polishing. Therefore, the spent does not deposit or grow beyond a certain amount, and stable image quality can be obtained over a long period of time. In addition, the spent amount is quantified as the spent amount for both carriers from the resistance value and the total carbonaceous material.

Further, when an image is formed by transferring an electrostatic latent image using an abrasive toner, the toner comes into contact with the surface layer of the photoreceptor and friction as in the development and cleaning of the photoreceptor. In this case, the surface of the photoreceptor can be effectively polished. In particular, it is effective for an α-Si-based photoreceptor having a SiC layer as a surface phase.

[Second Embodiment] Next, an embodiment relating to an image forming method using an electrostatic latent image developer (developer) of the present invention will be described.

(1) Photoconductor First, the configuration of a photoconductor of an image forming apparatus to which a developer is applied will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of a main part for describing a layer configuration of a photosensitive layer of the photosensitive drum. As shown in FIG. 2, the photosensitive layer of the photoreceptor 21
A light absorbing layer 25 made of Si: Ge: H, etc., a carrier injection blocking layer 27 made of Si: H: B: O, etc., and a carrier excitation / transport layer 29 made of Si: H, etc., on a conductive substrate 23.
(Photoconductive layer) and surface protective layer 31 are sequentially formed.

The surface protective layer (also referred to as a SiC layer) 31 has a thickness of, for example, 0.3 to 1 × 10 μm.
Of SiC, more preferably α-SiC (amorphous silicon carbide). The surface of this SiC layer is not smooth, and many fine projections (cones) exist on the surface. In addition, the SiC layer has strong hydrophilicity, and ion products generated by corona discharge adhere to the SiC layer. For this reason, continuous printing,
When printing is started under high humidity conditions, toner adheres to the photosensitive drum and toner filming occurs, and hydrophilic compounds such as ammonium nitrate adhere as ion products. For this reason, the charge of the photoconductor leaks, and a phenomenon of so-called “image deletion” occurs. Moreover, these products have a strong tendency to accumulate between the minute projections of the SiC layer, which is the surface protection layer 31, and therefore, image cleaning cannot be prevented by ordinary cleaning.

On the other hand, the abrasive toner (c) is
Abrasive particles 15 are used to polish the vicinity of the tip of the minute protrusion of the SiC layer to smooth the surface of the SiC layer,
An ion product deposited between the minute projections is removed to prevent image deletion, thereby contributing to securing development stability.
Moreover, since the abrasive toner has abrasive fine particles on the surface of the toner, it does not exert an excessive abrasive power. Therefore, even when polished with a cleaning blade, a rubbing roller, or the like, the surface of the α-Si photoreceptor is not significantly damaged.

(2) Image Forming Method Next, with reference to FIG. 3, a method of forming an image using the electrostatic latent image developer of the present invention will be described together with a configuration example of an image forming apparatus. FIG. 3 is a schematic diagram for explaining the configuration of the image forming apparatus. This image forming apparatus is the same as a conventional general image forming apparatus except that a rubbing roller (pressing member) 49 is provided. In FIG. 3, illustration of the carrier is omitted.

Around the drum-shaped α-Si photoreceptor 21, a corona charger 41, an LED head 43 (exposure device),
A developing roller 45, a transfer machine 47, a rubbing roller 49, and a cleaning blade 51 are provided. Corona charger 4
1, uniform charging of the surface of the photoconductor 21, LED head 4
After the formation of the electrostatic latent image by the selected image exposure by 3, the developer 61 is supplied to the surface of the photoconductor 21 by the developing roller 45, and a visible image composed of the toner 11 is formed by development. At this time, the surface of the photoconductor 21 is rubbed by the toner 11 in the developer 61, and the SiC layer (not shown) on the surface is polished. Further, since the abrasive fine particles 15 are firmly fixed to the toner base particles 13, they do not fall off and do not cause poor development or image defects.

The toner 11 on the surface of the photoreceptor 21 is
The image is transferred onto the paper 63 (transfer material) by the transfer machine 47, and subsequently fixed on the paper 63 by a fixing device (not shown). In the transfer step, not all of the toner 11 on the surface of the photoconductor 21 is transferred to the paper 63, but part of the toner 11 (residual toner) remains on the photoconductor 21. The residual toner 11 is pressed against the surface of the photoreceptor 21 by the rubbing roller 49 to polish the surface SiC layer, and further, the polishing effect of the abrasive fine particles 15 of the toner 11 increases.

Next, the remaining toner 11 on the photoreceptor 21 is
The toner is removed from the surface of the photoconductor 21 by the cleaning blade 51.
In 1, the SiC layer on the surface of the photoconductor 21 is polished by the abrasive fine particles 15 of the toner 11 by the mechanical force applied between the cleaning blade 51 and the photoconductor 21. An elastic roller is used as the rubbing roller 49, and the rubbing roller 49 is pressed against the surface of the photoconductor 21, and is rotated by applying a shearing stress to the photoconductor 21. The surface (not shown) of the body 21 is polished and cleaned. Photoconductor 2
By attaching a heater to the inner surface of the heater 1 and heating it, the effect of preventing image flow can be further improved.

[0067]

Embodiments of the present invention will be described below. (1) Production of magnetic resin-coated carrier Preparation of titanium-containing catalyst component 200 g of dehydrated n-heptane at room temperature and magnesium stearate dehydrated in advance at 120 ° C. under reduced pressure (266 kPa (2 mmHg)) in a 500-ml flask purged with argon. 1.5 g (25 mmol) was added to form a slurry. 0.44 g of titanium tetrachloride (2.
(3 mmol), the temperature was raised, and the mixture was reacted under reflux for 1 hour to obtain a viscous transparent titanium-containing catalyst (active catalyst).

Evaluation of activity of titanium-containing catalyst component 400 ml of dehydrated hexane, 0.8 mmol of triethylaluminum, 0.8 mol of diethylaluminum chloride were placed in an autoclave having an inner volume of 1 liter and purged with argon.
Millimol and 0.004 mmol of the titanium-containing catalyst prepared above as titanium atoms were sampled and charged, and the temperature was raised to 90 ° C. At this time, the internal pressure is 14
It was 7 kPa (1.5 kg / cm ² G). continue,
Hydrogen was supplied into this autoclave and 539 kPa
(5.5 kg / cm ² G), the total pressure was 931
Ethylene was continuously supplied so as to maintain kPa (9.5 kg / cm ² G). In this state, polymerization of ethylene was performed for 1 hour to obtain 70 g of polyethylene. The polymerization activity was 365 kg / g · Ti / Hr, and the MFR (melt flowability at 190 ° C., 21.168 N (load: 2.16 kg) measured based on JIS K 7210) of the obtained polyethylene was 40 g. / Min.

Production of Polyethylene-Coated Carrier A sintered ferrite powder F-2535 (trade name) (manufactured by Powder Tech, average particle size 65 μm) was placed in an autoclave having an internal volume of 2 liters and purged with argon.
The temperature was raised to 80 ° C., and the pressure was reduced for 1 hour (1330 kPa (10
mmHg)) Drying was performed. Thereafter, the temperature was lowered to 40 ° C., and 800 ml of dehydrated hexane was stored, and stirring was started. Subsequently, after adding 5.0 mmol of diethylaluminum chloride and 0.05 mmol of the titanium-containing catalyst component prepared above as titanium atoms, the reaction was carried out for 30 minutes, the temperature was further raised to 90 ° C., and 4 g of ethylene was introduced. . At this time, the internal pressure of the autoclave was 294 kP
a (3.0 kg / cm ² G). Thereafter, hydrogen was supplied and the internal pressure was increased to 313.6 kPa (3.2 kg / cm ^2).
G) and the polymerization was started by adding 5.0 mmol of triethylaluminum.
Minutes, the internal pressure is 225.4 kPa (2.3 kg / cm
² G) and stabilized.

Next, 5.5 carbon black (manufactured by Mitsubishi Chemical Corporation, MA-100 (trade name)) was placed in the autoclave.
g and 100 ml of dehydrated hexane, and then the internal pressure was increased to 421.4 kPa (4.3 kg /
cm ² G), while continuously supplying ethylene, the supply was stopped when a total of 40 g of ethylene was supplied into the system, and the direct polymerization was carried out for 45 minutes.
Thus, 1005.5 g of carbon black-containing polyethylene resin-coated ferrite was obtained. The powder obtained by drying the obtained carbon black-containing polyethylene resin-coated ferrite exhibited a uniform black color. From the electron micrograph, it was observed that the ferrite surface was thinly covered with the polyethylene resin, and that the carbon black was uniformly dispersed in the polyethylene resin. When the composition ratio of the carbon black-containing polyethylene resin-coated ferrite was measured by TGA (thermal balance), the composition ratio of ferrite: carbon black: polyethylene was 90.5: 0.5: 4.0 by weight. there were. When the weight average molecular weight of the coated polyethylene in the obtained carbon black-containing polyethylene resin-coated ferrite was measured using GPC,
6,000.

Next, the carbon black-containing polyethylene resin-coated ferrite was classified with a 125 μm sieve.
Large-diameter particles of 125 μm or more were removed. The classified carbon black-containing polyethylene resin-coated ferrite is placed in a fluidized bed type airflow classifier having a tower diameter of 14 cm, and heated (115 ° C.) so that the airflow linear velocity of the classifier body becomes 20 (cm / s). Was introduced, and the carbon black-containing polyethylene resin-coated ferrite was flowed for 10 hours to obtain a primary carrier.

The thus obtained primary carrier 10k
g was placed in a 20-liter Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd., Model FM20C / I (trade name)).
The temperature (processing temperature) in the Henschel mixer was set to 70 ° C. by flowing hot water into a jacket provided around the Henschel mixer. While maintaining the temperature at 70 ° C., stirring was performed for 2.0 hours, and a mechanical impact was applied to smooth the surface of the primary carrier.

Thereafter, in order to completely remove fine powder and agglomerated powder generated by the Henschel mixer, a sieving treatment (# 1)
(25 mesh) and classification treatment (using a fluidized bed type air flow classifier, linear velocity 20 cm / s, 2 hours) to obtain a magnetic resin-coated carrier (sometimes referred to as a secondary carrier). When the surface of the obtained magnetic resin-coated carrier was observed with a scanning electron microscope (SEM), it was confirmed that a polyethylene coating layer was formed on the surface, the surface was extremely smooth, and the entire surface was close to a true sphere. did. The properties of the obtained magnetic resin-coated carrier were as shown in column A of Table 1, with an average particle size of 75 μm and a volume resistivity of 1 × 10
¹⁰ Ω · cm, bulk density 2.1 g / cm ³ , saturation magnetization 6
It was 2 emu / g (130.2 emu / cm ³ ).
In addition, since the magnetic resin-coated carrier used in the present invention is coated with polyethylene, the bulk density of the carrier is the same as the bulk density of a normal carrier (for example, 2.7 to 3.0 for a Cu-Zn-based carrier). 3g / cm ³ )
And the magnetic properties between the photoreceptor and the developing roller tend to decrease. However, as mentioned above,
Since a general saturation magnetization value of 2 emu / g was obtained, there is no practical problem.

[0074]

[Table 1]

In Table 1 above, the volume resistance value
In the column of "1 × 10 ^TenTo "1E + 1
0 ”and“ 1 × 10⁸Is written as "1E + 08"
And "1 × 10^FifteenIs written as “1E + 15”.
In Table 1 above, "cm^Three"For convenience
It is described as "cm @ 3".

(2) Production of Magnetic Powder Carrier In this embodiment, when producing a magnetic powder carrier,
A composite ferrite based on ₂ O ₃ and CuO.ZnO was used. The properties of the obtained uncoated magnetic powder carrier were as shown in column B of Table 1 above, with an average particle size of 90 μm.
m, volume resistance value is 1 × 10 ⁸ Ω · cm, and bulk density is 2.7.
g / cm ³ , and the saturation magnetization is 64 emu / g (172.8 e
mu / cm ³ ).

(3) Production of Abrasive Toner In this example, in producing an abrasive toner, the following materials were sufficiently kneaded with a high-speed mixer, pulverized and classified to obtain toner base particles having an average particle diameter of 10 μm. . 90 parts by weight of styrene-n-butyl acrylate copolymer (copolymerization ratio 80/20) 5 parts by weight of carbon black (MA-100 (trade name) manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 3 parts by weight of polypropylene wax (Sanyo) Biscol (trade name, manufactured by Kasei Kogyo Co., Ltd.) 2 parts by weight of charge control agent (Copy Blue PR (trade name, manufactured by Hoechst))

To the toner base particles, 1.5% by weight of conductive titania (TiO ₂ ) having an anatase crystal structure was added as abrasive fine particles. The primary particle diameter of the abrasive particles is 0.1 to 0.5 μm and the volume resistivity is within a range of 10 to 1 × 10 ³ Ω · cm ³ , and the particles are subjected to a hydrophobic treatment (in this embodiment, titanate). Treated). The amount of the fine abrasive particles added to the toner base particles was in the range of 0.5 to 3% by weight. The properties of the resulting abrasive toner are shown in Table 1 below.
As shown in the column, the average particle size is 90 μm, and the volume resistance value is 1
× 10 ⁸ Ω · cm, bulk density was 2.7 g / cm ³ , and saturation magnetization was 64 emu / g (172.8 emu / cm ³ ).

Next, the magnetic coated resin carrier (a), magnetic powder carrier (b) and abrasive toner (c) produced as described above were mixed at different weight ratios of A: B: C. Thus, the electrostatic latent image developers of the first to fourth examples and the first and second comparative examples were prepared. First, in the first embodiment, the mixing ratio of the developer was set to A: B: C = 80: 20: 5. Further, in the second embodiment, the mixing ratio of the developer is set to A:
B: C = 60: 40: 5. Further, in the third embodiment, the compounding ratio of the developer was A: B: C = 40: 60: 5. In the fourth embodiment, the mixing ratio of the developer is A:
B: C was set to 20: 10: 5. In the first comparative example, the compounding ratio of the developer was A: B: C = 100: 0: 5. Further, in the second comparative example, the compounding ratio of the developer was A:
B: C was set to 0: 100: 5.

Then, the charge amount and the fluidity of the developer in the compounding ratio of each of the above Examples and Comparative Examples were measured. The charge amount was measured by the QM meter method manufactured by Trek. In addition, the measurement of fluidity is based on JIS
Performed by the Z-2502 method. The measurement results are shown in Table 2 below.

[0081]

[Table 2]

Further, the measurement results are shown in the graph of FIG. The above six mixing ratios are given on the horizontal axis of the graph of FIG. 4, the left vertical axis represents the charge amount (μC / g), and the right vertical axis represents the fluidity (fall time: seconds). . The curve I in the graph is obtained by connecting white circle plots of the measurement results of the charge amount. Curve II is obtained by connecting white square plots of the measurement results of fluidity. As shown by the curve I in the graph of FIG. 4, the charge amount tends to increase as the ratio of the magnetic resin-coated carrier in FIG. On the other hand, as shown by the curve II, the fluidity tends to increase as the ratio of the magnetic powder carrier (b) increases. And, in order to perform stable image formation, the developer contains
It is necessary to ensure a certain amount of charge and flowability.

Judging from the curves I and II, the range satisfying such conditions is such that the value of (a) / (b) is 8
It is desirable to be within the range of 5/15 to 45/55.
In particular, when the value of (a) / (b) is in the range of 75/25 to 50/50, it is possible to secure a charge amount of 15 μC / g or more and to secure fluidity of 35 seconds or less. Understand. Further, it can be seen that when the value of (a) / (b) is around 70/30, a charge amount of 16 μC / g or more and a fluidity of 34 seconds or less can be secured.

Next, initial image characteristics and durability test results were performed on the compounding ratio when only the charge amount was high, when both the charge amount and fluidity were high, and when only the fluidity was high. As an example where only the charge amount is high and the fluidity is low,
In the fifth embodiment, the mixing ratio of the developer is set to A: B: C = 9.
0: 10: 5. As an example in which both the charge amount and the fluidity are high, in the sixth embodiment, the compounding ratio of the developer is
A: B: C = 70: 30: 5. Further, as an example in which the charge amount is low and only the fluidity is high, the compounding ratio of 40: 60: 5 in the third embodiment described above was adopted.

Table 3 shows the test results of the initial image characteristics and the durability of the developers having the compounding ratios of the fifth, sixth and third examples. In the test, a modified FS-3500 (trade name) manufactured by Kyocera Corporation was used as an evaluation machine. The modified machine was set so that the gap between the photosensitive member and the sleeve was 0.6 mm, and the gap between the developer regulating blade and the sleeve was 0.6 m.
m, and the potential of the white background portion (non-electrostatic latent image portion) of the photoconductor is 5
The voltage after application of the photosensitive member was set to 15 V, the potential applied to the sleeve was set to 350 V, and the peripheral speed ratio between the photosensitive member and the sleeve was set to 2.0 times.

[0086]

[Table 3]

As shown in Table 3, the tests for the initial image characteristics were carried out under the following environmental conditions for the image density, dot reproducibility, and white background fog. Room temperature, normal humidity (25 ° C-60%, sometimes referred to as NN environment) Low temperature, low humidity (10 ° C-20%, sometimes referred to as LL environment) High temperature, high humidity (33 ° C-85%, HH environment) May be called.)

When measuring the dot reproducibility,
400 g of the evaluated developer was stored in the printer, and actual printing was performed using A4 paper in a state where the surface potential was fixed at 400 V and the bias voltage was fixed at 300 V. And
The dot reproducibility was evaluated according to the following criteria. ：: No image defect is generated Δ: Slight image defect is recognized X: Image defect is generated

Further, the fogging property of the white background was evaluated according to the following criteria. ：: No fog is generated at all. Δ: Fog is slightly observed. X: Fog is clearly observed.

As shown in Table 3, the image density and the dot reproducibility tend to improve as the blending ratio of the magnetic powder carrier (b) increases. On the other hand, the fogging property of the white background tends to improve as the blending ratio of the magnetic resin-coated carrier (a) increases. In particular, in the case of the third embodiment in which the mixing ratio of the magnetic powder carrier was high, fogging was observed in a high-temperature and high-humidity environment (HH environment) because the magnetic powder carrier had low moisture resistance.

In the durability test, 300,000 sheets (300
(k sheets) were continuously printed, and the results of evaluating the change in image density and the change in charge amount based on the following criteria are shown in Table 3. In measuring the image density, the image density of the solid portion of the developed image was periodically measured with a Macbeth densitometer, and the change in image density was evaluated according to the following criteria. ：: Constant image density is maintained even after 300,000 sheets are continuously printed. Δ: Image density gradually decreases. ×: Image density rapidly decreases.

In measuring the charge amount, the charge amount was measured by a blow-off charge measuring device. The amount of charge was evaluated according to the following criteria. ：: The charge amount changes within an appropriate range. Δ: The charge amount changes within an approximately appropriate range. X: The charge amount becomes too high or too low.

As shown in Table 3 above, in the case of the sixth embodiment in which the mixing ratio A: B: C = 70: 30: 5,
Both the transition of the image density and the transition of the charge amount are good. However, in both the fifth embodiment in which A is excessive and the third embodiment in which B is excessive, changes in image density and charge amount tend to be deteriorated, and the life tends to be shortened. In particular, the fifth case where A is excessive
In the case of the embodiment, the charge amount of the carrier becomes excessive and the charge-up occurs.

Therefore, A: B: C = 70: 30: 5
And the value of A / B = (a) / (b) is 85/15 to 4
5/55, more preferably 75/25 to 50 /
It can be seen that when it is within the range of 50, a long-life electrostatic latent image developer capable of stably forming an image can be obtained.

[0095]

As described above in detail, according to the present invention, the use of the mixed carrier composed of the magnetic resin-coated carrier (a) and the magnetic powder carrier (b) allows stable use. A long-life electrostatic latent image developer capable of forming an image is obtained. Further, since the compounding ratio can be changed in a wide range, the necessary charge amount can be arbitrarily set to stably impart the toner, and when the developer contains an abrasive toner, the The surface can be cleaned by polishing with a suitable force. As a result, it is possible to suppress the occurrence of the image flow due to the generation of the leak current. If the developer of the present invention containing an abrasive toner is used in an image forming apparatus provided with an α-Si photoreceptor, which is a photoreceptor which is inherently hard to wear and can be used for a long time, the photoreceptor can be used for a long time. become able to. As a result, it is possible to provide not only a long life of the developer but also a long life printer.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an abrasive toner according to an embodiment.

FIG. 2 is a schematic cross-sectional view of a main part of a photoconductor.

FIG. 3 is a schematic diagram illustrating a configuration of an image forming apparatus.

FIG. 4 is a diagram illustrating measurement results of a charge amount and a fluidity according to a composition ratio of an electrostatic latent image developer of an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Toner 13 Toner base particle 15 Fine abrasive particles 21 Photoreceptor 23 Conductive substrate 25 Light absorption layer 27 Carrier injection blocking layer 29 Carrier excitation / transport layer 31 Surface protection layer 41 Corona charger 43 LED head 45 Developing roller 47 Transfer device 49 Rubbing roller 51 Cleaning blade 61 Developer 63 Paper

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoshio Ozawa 2-14-19 Tamagawadai, Setagaya-ku, Tokyo F-term (reference) 2Y005 AA08 AA21 AB10 BA02 BA06 BA11 BA18 CA13 CB07 CB18 DA09 EA01 EA06 EA07 EA10

Claims (9)

[Claims] 1. A magnetic resin-coated carrier having a coating layer composed of a high-molecular-weight polyethylene resin obtained by direct polymerization, (b) a magnetic powder carrier substantially composed of magnetic particles, and (c) a toner. And an electrostatic latent image developer comprising: 2. The (a) magnetic resin-coated carrier,
(B) Mixing ratio with magnetic powder carrier ((a) / (b))
The electrostatic latent image developer according to claim 1, wherein the weight ratio is within a range of 85/15 to 45/55. 3. The volume resistivity of the (a) magnetic resin-coated carrier and (b) the magnetic powder carrier or any one of the carriers is set to 1 × 10 ² to 1 × 10 ¹⁴ Ω · c.
3. A value within a range of m.
The electrostatic latent image developer as described in the above. 4. When (a) the volume resistance value of the magnetic resin-coated carrier is V _a and the (b) volume resistance value of the magnetic powder carrier is V _b , (V _a −V _b ) Value from 10
4. The electrostatic latent image developer according to claim 1, wherein the electrostatic latent image developer has a value within a range of 1 × 10 ³ Ω · cm. Wherein said the bulk density of (b) magnetic powder carrier and [rho _b, wherein the bulk density of the magnetic resin-coated carrier (a) is taken as [rho _a, satisfy the relationship ρ _b> ρ _a The electrostatic latent image developer according to claim 1, 2, 3, or 4, wherein 6. The method according to claim 1, wherein the ratio of the amount of the toner added to the mixed carrier of (a) and (b) is a value within a range of 2 to 40% by weight. 4
Or the electrostatic latent image developer according to 5. 7. The electrostatic latent image developer according to claim 1, wherein the toner is a color toner. 8. The toner according to claim 1, wherein the toner is an abrasive toner having abrasive fine particles fixed on the surface of a base material of the toner. Electrostatic latent image developer. 9. The electrostatic latent image developer according to claim 8, wherein the abrasive fine particles are conductive titania.