JP2905338B2 - Electrophotographic carrier and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic carrier in a two-component developer and a method for producing the same, and more particularly, to an electrophotographic carrier having excellent abrasion resistance and durability and its use. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In the electrophotographic method, an electrostatic latent image is formed on the surface of a photoreceptor by utilizing a photoconductive phenomenon, developed with a developer, and fixed on a transfer sheet or the like. Conventionally, in order to visualize an electrostatic latent image, a two-component developer in which a carrier and a toner are mixed has been used, as is known by a cascade method, a magnetic brush method, or the like. The carrier of the two-component developer is brought into a desired polarity state and charged state together with the toner by frictional charging with the toner. For this reason, the carrier is coated on the surface of the core material with a resin, the charge amount and polarity of the carrier are controlled, and the desired charge characteristics are imparted.

The problem of the carrier for electrophotography is that, due to repeated use thereof, the charge characteristics and resistance value of the carrier due to wear of the resin coating layer, peeling of the coating resin from the core material surface, and spent toner, etc. Etc., and adversely affect development. In fact, the present inventors
Such wear, peeling of the resin layer, or the phenomenon of toner smearing is tracked and confirmed by a scanning electron microscope (SEM) photograph, and long-term use is also possible by X-ray analysis, carbon analysis, static resistance measurement, and the like. The adverse effects such as a change with time of the carrier accompanying the analysis were also analyzed.

Conventionally, various methods have been proposed in order to solve the above-mentioned problems of the carrier. For example, a method of using a coating resin having excellent durability, a method of increasing the adhesion between the core material of the carrier and the resin by using an additive or the like, a method of reducing a stress applied to the carrier on the device, and the like can be given.

However, in the above-mentioned method for improving the carrier, the technology relating to the surface properties of the core material of the carrier and the adhesion of the coating resin is not sufficiently described, and in general, a smooth surface and a convex surface are not provided. The improvement is achieved by using an as-molded core material such as an uneven surface having a portion or a surface having holes in a sponge shape. For this reason, if the entire surface of the core material of the carrier is smooth, there is a large adverse effect on the adhesiveness of the resin coating and the peeling of the resin, and the carrier characteristics are likely to change. Further, when the core material has a large number of convex portions (those having large area convex portions and few concave portions) on the surface thereof, the carrier characteristics are liable to change similarly to the above, and the disadvantage as a developer is disadvantageous. Occurs. The sponge-shaped core material has problems such as difficulty in adjusting the coating amount in the coating operation. Therefore, an object of the present invention is tough and excellent in durability against abrasion and peeling of a coating resin, little change over time in charging characteristics and resistance value characteristics, etc., and maintain initial image quality even after long-term use. An object of the present invention is to provide a carrier for electrophotography and a method for manufacturing the same.

[0005]

Means for Solving the Problems The inventors of the present invention have confirmed what conditions are necessary for producing a carrier with a small characteristic change while confirming the surface condition of a core material by an analysis method such as an SEM photograph. As a result of intensive investigation into the application to manufacturing, it was found that by treating the surface of the core material into a specific shape, the carrier has extremely durability and can achieve the above object. . That is, the present invention is based on the above findings, a core material having a large number of dimples formed on the surface thereof, and an electrophotographic carrier comprising a coating resin for coating the surface of the core material, the core material having a dimple,
The longest diameter S of the dimple (the length of the dimple in the major axis direction)
Length ratio of the core material particles to the diameter L (the longest dimple diameter S)
/ The diameter L of the core material particles is 0.03 to 0.15.
And a carrier for electrophotography characterized by the following. Such a carrier shows little wear and peeling of the coating resin even after long-term repeated use. This is demonstrated by analysis of SEM photographs and the like, and the initial image quality can be maintained even for repeated continuous use in a two-component developer. It was also clarified that high quality images were always provided on copy paper.
The present invention also provides a physical treatment on the surface of the carrier core material,
And forming a dimple by at least one or more recesses forming process chemical treatment, there is provided a method of manufacturing the electrophotographic carrier, which comprises coating a resin on the core material thereafter .

Hereinafter, an electrophotographic carrier according to the present invention and a method for producing the same will be described in detail. 1A is a plan view of a core material of the electrophotographic carrier according to the present invention, and FIG. 1B is a partial cross-sectional view taken along line II of FIG.
FIG. 2 is a side view showing a dimple formed on the surface of the core material. The electrophotographic carrier of the present invention basically comprises a core material having a large number of dimples formed on the surface thereof, and a coating resin for coating the surface of the core material. As shown in FIG. 1, the core material of the carrier preferably has a substantially spherical shape, and preferably has an average particle diameter of 30 to 100 μm. The core material 1 is made of at least one core material selected from iron powder, ferrite, and magnetite.
It is preferably 1 and is properly used depending on the target hardware conditions. However, it is particularly preferable to use ferrite particles in order to easily form a dimple and to reduce development torque.

As shown in FIG. 2, it is desirable that the dimple 2 formed on the surface of the core material 1 by a method described later has an elliptical or spherical depression, and the longest diameter S of the dimple 2 (the length of the dimple in the major axis direction). Length) and the length L of the core material particle diameter (the longest diameter S of the dimple 2 / the core material particle diameter L).
Is preferably in the range of 0.03 to 0.15, particularly 0.08 to 0.12. Below the above range, the peeling of the coating resin becomes large, and above the above range, it becomes difficult to control the resistance value characteristics and the like of the carrier by the amount of resin coating. The maximum depth T of the dimple 2 on the surface of the core material 1 and the above dimple
2 The length ratio with the longest diameter S (maximum depth T / longest diameter S)
It is desirable to be in the range of 0.1 to 0.6, especially 0.3 to 0.5. When the depth is less than the above depth, the surface of the core material 1 is not much different from that having a smooth surface, and peeling of the coating resin easily occurs.When the above range is exceeded, it is difficult to manage the resistance value characteristics and the like of the carrier by the resin coating amount. Become. The average distance W between the adjacent dimples 2 is preferably in the range of 0.05 to 0.20 times, particularly 0.10 to 0.15 times the particle diameter L of the core material 1. Below the above range, it becomes difficult to control the resistance value characteristics and the like of the carrier by the amount of resin coating, and above the above range, the peeling of the coating resin becomes large.

The coating resin for the carrier may be a resin known per se, and is not limited to the use as long as it has been conventionally used as a carrier coating resin. For example, silicone resins (silicone resins and their derivatives), fluorine resins, styrene resins, acrylic resins, methacrylic resins, polyester resins, polyamide resins, epoxy resins, polyether resins, phenol resins, etc. These can be used alone or in combination, and can also be used as a copolymer. The coating amount of the resin varies depending on the type of the resin and the charging characteristics required for the carrier.
Is preferably in the range of 0.2 to 1.2% by weight based on the weight of

In such an electrophotographic carrier, the coating resin hardly peels off from the surface of the core material 1 even when subjected to mechanical stress. Even when used repeatedly, there is little wear and peeling of the coating resin. This is proved by analysis of SEM photographs and the like, which will be described later. In the image quality evaluation, the initial image quality is maintained, and a high-quality image is formed on the copy paper even after continuous use.

Next, a method of manufacturing the electrophotographic carrier according to the present invention will be described. The manufacturing method basically includes a physical treatment or a chemical treatment, or a combination of these treatments. It is manufactured by forming a dimple 2 on the surface and coating the core material 1 with the resin. The physical treatment for forming the dimple 2 is any one of compression, shearing, impact, and friction or a combination thereof, and these treatments include a ball mill, a vibration mill, a sand mill, a pulverizer, an attritor, a Henschel mixer, and the like. Can be performed using at least one device selected from the above devices.

The chemical treatment includes sintering, coagulation, immersion, heating,
This is a treatment by any one of electrolysis or a combination of these. Specifically, it includes granulation and surface modification, including powder generation processes such as evaporative agglomeration, gas phase reaction, solvent evaporation, and precipitation. Quality, etc., and particularly preferable basic surface treatment methods include a core material 1 in a fluidized state.
A method of forming a dimple 2 by spraying an acidic liquid (including other erosion liquids) on the particles may be used. The dimple 2 treatment in the present invention is desirably a treatment method combining the above-mentioned physical treatment and chemical treatment. Strictly, an intermediate treatment combining these treatments is desirable, and scanning is performed by a scanning electron microscope or the like. Meanwhile, the respective processes are appropriately combined so that the dimple 2 is formed on the core material 1 while satisfying the above conditions.

When the core material 1 is coated with the above-mentioned coating resin by the most basic method, the resin is dispersed or dissolved in a general solvent such as toluene, and the coating resin solution is prepared. The treatment is performed by immersing the treated core material 1 in the preparation solution or spraying the preparation solution with the core material 1 fluidized in advance. After coating, it is desirable to stabilize and stabilize the coating layer by appropriate drying treatment such as heat treatment. In such a method for producing an electrophotographic carrier according to the present invention, the core material 1 described above is used.
Can be manufactured so as to satisfy the conditions, and the durable carrier for electrophotography can be provided.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the carrier for electrophotography according to the present invention and a method for producing the same will be described in detail below. The present invention is not limited to the following embodiments. [Example 1] As an initial raw material, metal oxides previously sized to 10 µm or less were Fe ₂ O ₃ : MgO: Zn, respectively.
O: MnO ₂ : CuO = 47: 28: 20: 1: 4 mol% was prepared, mixed with a Henschel mixer of Mitsui Miike Seisakusho, and calcined at 900 ° C. for 3 hours in a kiln. . The powder that had undergone the quasi-spinelization reaction by calcination was mixed with water, and ground with a ball mill for 8 hours. To this aqueous solution, a binder (polyvinyl alcohol) and a dispersant were added by several weight% to obtain a slurry-like solution. This slurry was granulated and dried with a spray dryer (if necessary, granulated into particles of an appropriate size using a kneader). The granulated pellets were fired in an electric furnace at 1320 ° C. for 4 hours to prepare ferrite powder composed of appropriate primary particles.
This was sieved with a gyro shifter to obtain carrier particles (non-coated core material) having desired particle size and resistance value.

A concave portion is formed at the joint surface between the primary particles due to the crystal growth of the primary particles during sintering. The formation ratio is controlled by various conditions such as the properties of the raw material, additives, calcination, calcination, and pulverization. . For this reason, the surface properties of the core material obtained by the above operation were confirmed by SEM images. Based on this, the conditions (strength, time) of the core material for the dimple treatment were set. For example, for 10 kg of the most basic finished carrier particles (core material), 40 kg of Miki Pulley Co., Ltd.
By performing physical treatment at 110 rpm for 1 hour using a 0 W ball mill, the following dimple-type core material according to the present invention was manufactured.・ Average particle diameter of core material 100 μm, ratio of longest diameter of dimple / diameter of core material particle 0.10, maximum ratio of dimple / diameter of core material particle 0.4, average distance between adjacent dimples / The diameter of the core material particles is 0.12.

To 100 parts by weight of the core material after the above physical treatment, 0.75 parts by weight of methyl-dimethyl silicone resin (SR2410 manufactured by Toray Dow Corning Co., Ltd.) was dispersed in toluene, and a resin solution (coating solution) was obtained. Was prepared. This resin solution is spray-coated on the core material using a fluid coating apparatus. Thereafter, a heat treatment was performed in the fluidized bed at about 290 ° C. for about 30 minutes to produce the resin-coated carrier of the present invention.

The coated carrier 10 thus obtained is
With respect to 00 parts by weight, 55 parts by weight of a commercially available black toner were mixed with a 5-liter V-blender to obtain a two-component developer, and a continuous actual test was performed using an electrophotographic copying machine having a commercially available OPC photoreceptor. went. As a result, even after 100,000 copies, a copied image with little image fog, little fog, and high image density was obtained. In addition, as a result of observing the abrasion and peeling of the coating agent on the carrier surface at the initial stage and after the 100,000-sheet continuous actual printing test by SEM,
It was confirmed that the surface state was almost the same as the initial state even after 0000 sheets. Furthermore, it was confirmed by analysis of surface silicon (Si) by X-ray analysis and measurement of the static resistance value of the carrier that the change was small.

Example 2 10 kg of a commercially available smooth surface spherical ferrite material (manufactured by DM Steward) was fluidized with a self-made fluid coating apparatus, sprayed with 500 ml of dilute hydrochloric acid, washed, and subjected to a series of chemical treatments. The following dimple-type core material according to the present invention was manufactured. -Average particle diameter of core material 80 m, ratio of longest diameter of dimple / diameter of core material particle 0.15, ratio of maximum depth of dimple / diameter of core material particle 0.6, average distance between adjacent dimples /
The diameter of the core material particles is 0.20. A resin coating similar to that of Example 1 and a developer thereof were produced on the above-mentioned core material, and a similar actual test was performed. As a result, a high quality image which was almost the same as the initial image quality even after 100,000 sheets was obtained.

[Comparative Example 1] A two-component developer was prepared in the same manner as in Example 1 except that a resin material was coated on a core material having a uniformly smooth surface property, that is, a core material having no dimple. , A similar live-action test was performed. As a result, the initial image density is sufficient, but as the actual shooting test progresses,
Fog increased, and the image quality became more noticeable. Further, as a result of confirming the surface image of the carrier by SEM, abrasion of the coating agent was observed, and the amount of silicon on the surface by X-rays was reduced more than in the other examples.

[0019]

The carrier for electrophotography according to the present invention is tough and excellent in durability against abrasion and peeling of the coating resin, has little change over time in charging characteristics and resistance value, and has a long initial image quality. It can be maintained even during the use of the period.

[Brief description of the drawings]

1 (a) is a plan view of a core material of an electrophotographic carrier according to the present invention, and FIG. 1 (b) is a cross-sectional view taken along line II of FIG. 1 (a).

FIG. 2 is a side view of a core material of the electrophotographic carrier according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 core material 2 dimple L diameter of core material S maximum diameter of dimple T maximum depth of dimple W average distance between adjacent dimples

──────────────────────────────────────────────────の Continued on front page (72) Inventor Masatomo Hayashi 425 Kanai, Shibukawa-shi, Gunma Kanto Denka Kogyo Co., Ltd. (72) Inventor Shinji Mita 425 Kanai, Shibukawa-shi, Gunma Kanto Denka Kogyo Co., Ltd. (56) References JP-A-61-140953 (JP, A) JP-A-61-158339 (JP, A) JP-A-64-88557 (JP, A) JP-A-4-93954 (JP) JP, A) JP-A-61-205953 (JP, A) JP-A-3-229271 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/10

Claims (8)

(57) [Claims] 1. An electrophotographic carrier comprising a core material having a large number of dimples formed on a surface thereof, and a coating resin coating the surface of the core material , wherein the core material has a dimple having a longest diameter S ( Demp
Of the core material particles) and the length of the diameter L of the core material particles.
The ratio (longest dimple diameter S / diameter L of core material particles) is 0.
03 to 0.15.
rear. 2. The core material according to claim 1 , wherein
Length ratio between the maximum depth T of the pull and the longest diameter S of the dimple
(Maximum depth of dimple T / Maximum diameter of dimple S) is 0.1 to
2. The electrophotographic carrier according to claim 1, wherein the ratio is 0.6. 3. The dimple of the core material according to claim 1 , wherein
The average distance W between the samples is 0.1 mm of the diameter L of the core material particles.
3. The electrophotograph according to claim 1, wherein the magnification is from 0.5 to 0.20.
For carrier. 4. A method of physically treating a surface of a core material to form a starch.
And then coating the core material with resin.
The electrophotographic carrier according to claim 1, wherein
Production method. 5. The method according to claim 1, wherein the physical treatment is compression, shearing, impact, or friction.
5. A method according to claim 4, wherein said processing is any one of rubbing or a combination thereof.
A method for producing the electrophotographic carrier according to the above. 6. A chemical treatment of the surface of a core material to form a starch.
And then coating the core material with resin.
The electrophotographic carrier according to claim 1, wherein
Production method. 7. The method according to claim 1, wherein the chemical treatment comprises sintering, agglomeration, immersion, heating,
Either heat or electrolysis or a combination of these
A method for producing an electrophotographic carrier according to claim 6. 8. The physical and chemical treatments on the surface of the core material.
To form a dimple, and then apply resin to the core material.
4. An electronic photograph according to claim 1, wherein the electronic photograph is coated.
Manufacturing method of true carrier.