JPH06274035A - Developing roller and developing device - Google Patents

Abstract

PURPOSE:To provide a developing roller having a resin magnet which is not thermally deformed by heating processing at the time of forming a resin coating layer by a developing sleeve having the resin coating layer and the developing roller having the resin magnet arranged inside the developing sleeve. CONSTITUTION:The developing roller 3 is provided with the developing sleeve 14 where the resin coating layer 17 is formed on a tube stock 18 through a heating processing stage, and a magnetic roller 13 supported by caps 22 and 23 inside the sleeve 14; and the magnet main body 15 of the roller 13 is the resin magnet whose binder is resin having thermal deformation temperature higher than heating temperature at the time of heating processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a developing device and a developing device for developing an electrostatic latent image formed on a latent image holding member such as an electrophotographic photosensitive member or an electrostatic recording dielectric. It relates to a developing roller.

[0002]

2. Description of the Related Art Conventionally, as a developing roller that has been put into practical use, a metal cylindrical tube (developing sleeve) made of aluminum, stainless steel, or the like and a magnet in which the magnet is arranged are used.

A one-component magnetic developer (hereinafter also referred to as a magnetic toner) is carried on a developing sleeve and conveyed to a developing area for developing an electrostatic latent image.

The magnetic toner obtains a triboelectric charge for developing the electrostatic latent image by friction with the developing sleeve.

However, in such a sleeve, various problems such as uneven toner layer (toner coat), defective coating, ghost, and reduction in density of developed image may occur. For example, as the sleeve rotates repeatedly, the charge amount of the toner coated on the sleeve becomes too high due to the contact with the sleeve, and the toner becomes immobile on the sleeve surface due to electrostatic mirroring force. It does not move from the sleeve to the latent image on the latent image holder. The so-called charge-up phenomenon is likely to occur especially under low humidity.

It is presumed that this is because an extremely thin metal oxide film is formed on the metal surface of the sleeve, and this interferes with the leakage of charges of the overcharged toner.

In any case, when such toner charge-up occurs, the toner in the upper layer is less likely to have tribo, resulting in an image in which the line image is thinned or the image density of a solid black image is reduced.

Further, since the toner consumption amount differs between the image portion (toner consuming portion) and the non-image portion of the latent image, the toner layer state on the sleeve changes and the charging state changes, so that the image density is once high. When the position on the sleeve where the solid image is developed comes next to the developing position and the halftone image is developed,
A phenomenon in which a trace of a solid image appears on an image, that is, a so-called ghost phenomenon is likely to occur.

Recently, in order to improve the quality of developed images,
The particle size of the toner is being reduced. In order to increase the resolution, sharpness, etc. and faithfully reproduce the latent image, it is general to use a toner having a weight average particle diameter of about 6 to 9 μm. Such a small particle size toner contains a considerable proportion of fine powder toner having a particle size smaller than the average particle size, but since the fine powder toner has a large surface area per weight, it is particularly prone to excessive charging, and thus If a small toner having a small particle size is used, the above-mentioned inconvenience becomes more remarkable.

As a method for solving such a phenomenon, instead of the conventional metal cylindrical tube sleeve, Japanese Unexamined Patent Publication No. 2-105.
No. 181, JP-A-3-36570, etc., a resin coating layer made of a binder resin, conductive fine powder, solid lubricant fine powder, etc. is formed on the surface of a metal cylindrical tube,
A method for use in a developing device has been proposed. By using this method, the above phenomenon is reduced.

It is considered that this is because the leak side of the excessively charged toner can be secured and the toner adhesion force to the sleeve due to the electrostatic mirroring force can be weakened.

In any case, for the resin coating layer, a coating prepared by kneading a binder resin, a conductive powder, and a solid lubricant powder with a solvent is applied to a metal cylindrical tube, which is then heat treated to dry the resin coating, It is formed by solidifying.

By the way, a so-called resin magnet (plastic magnet) in which magnetic powder is bound with a plastic binder is often used as the magnet arranged in the sleeve.

[0014]

When a developing roller coated with the above-mentioned paint and subjected to heat treatment is used on a metal cylinder having such a resin magnet mounted therein, the length of the developing roller is shown on the developed image. Density unevenness occurred in the direction.

As a result of examination, the resin magnet disposed inside the sleeve is deformed by the above heat treatment, so that the magnetic flux density distribution on the sleeve surface becomes non-uniform in the longitudinal direction of the developing roller. It was found that the density unevenness described above occurred due to the cause.

Therefore, an object of the present invention is a developing roller in which a resin coating layer is formed on the surface of a cylindrical body by heat treatment in a state where a resin magnet is mounted inside the cylindrical body, and the aforementioned image density unevenness occurs. It is an object of the present invention to provide a developing roller capable of preventing the above-mentioned phenomenon and a developing device equipped with such a developing roller.

[0017]

The developing roller of the present invention is a developing roller which carries a developer and conveys it to a developing area for developing an electrostatic latent image. The developing roller is formed on a cylindrical body and the surface of the cylindrical body. The resin coating layer, a magnet in which magnetic powder is bound with a binder resin, and a supporting means for supporting the magnet inside the cylindrical body. The developing roller is heat-treated while being supported by, and the heat deformation temperature of the binder resin of the magnet is higher than the heat-treatment temperature.

The developing device of the present invention includes a container for containing a developer, a developing roller for carrying the developer out of the developing container and carrying it to a developing area for developing an electrostatic latent image, and a developing roller for the developing area. A developing device comprising a regulating member for regulating the thickness of a developer layer to be conveyed, wherein the developing roller is used as a developing roller.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is an explanatory view of an embodiment of the present invention.

The developing device 10 includes a container 12 containing a one-component magnetic developer, so-called magnetic toner 11.

A developing sleeve 14 is arranged at the opening of the container 12. Inside the sleeve 14, the magnet roll 1
3 is stationary.

The roll 13 comprises a shaft 16 and a resin magnet 15 fixed to the shaft 16. The magnet 15 has four magnetic poles N ₁ , N ₂ , S ₁ and S _{2 in} the illustrated example.
The magnetic pole S ₁ applies toner from the sleeve 14 to the developing area 2 where the electrophotographic photosensitive drum 1 rotating in the arrow direction faces the sleeve 14 with a minute gap, that is, the electrostatic latent image formed on the drum 1. And forms a magnetic field in the development area 2 where this latent image is visualized. This magnetic field prevents so-called fog in which the magnetic toner adheres to the background portion of the image.

The magnetic pole N ₁ contributes to the regulation of the thickness of the toner layer 11 ′ which the sleeve 14 rotating in the direction of the arrow conveys to the developing area 13.

That is, with the sleeve 14 in between, the magnetic pole N ₁
A blade 19 made of a magnetic material such as iron is arranged to face. The magnetic lines of force from the magnetic pole N ₁ concentrate on the blade 19 to form a magnetic field curtain that regulates the layer thickness of the toner layer 11 ′.

Toner layer 11 'formed as described above
Is thinner than the minimum gap between the sleeve 14 and the drum 1 in the developing area 2. Therefore, in this example, the toner flies from the sleeve 14 and adheres to the drum 1. So-called non-contact development is performed. However, the present invention is also applicable to so-called contact development in which a magnetic brush of toner is brought into contact with the drum 1 to develop a latent image.

The magnetic pole S ₂ contributes to magnetically attract the magnetic toner in the container 12 to the surface of the sleeve 14, and the magnetic pole N ₂
Contributes to returning the toner on the sleeve 14 that has passed the developing area 13 to the inside of the container 12.

Spacer rollers 20 are provided coaxially with the sleeve 14 at both ends of the sleeve 14. The spacer rollers 20 are pressed against both ends of the drum 1 to keep the gap between the sleeve 14 and the drum 1 constant. The minimum gap between the sleeve 14 and the drum 1 in the developing area 2 is 50
It is set to ˜500 μm.

In order to improve the developing efficiency, a vibration bias voltage in which the maximum voltage and the minimum voltage are alternately repeated is applied to the sleeve 14 from the power source 21. Such an oscillating bias voltage is obtained by superimposing a DC voltage on an AC voltage.
In any case, such an oscillating bias voltage forms an oscillating electric field in the developing area 2, whereby the toner flies and adheres to the image portion of the electrostatic latent image. Of course, sleeve 14
Alternatively, a non-oscillating, constant-level DC bias voltage may be applied.

The magnetic toner obtains a triboelectric charge for developing the electrostatic latent image by friction with the sleeve 14. The toner is charged to the same polarity as the electrostatic latent image in the device that performs reversal development, and the toner is charged to the opposite polarity to the electrostatic latent image in the device that performs normal development.

In order to prevent the excessive charge-up of toner as described above, the developing sleeve 14 is made of aluminum,
A metal cylinder (uncoated pipe) 18 made of stainless steel or the like on which a resin coating layer 17 is provided is used.

In the resin coating layer 17, carbon black fine particles, for example, conductive fine particles are dispersed in a synthetic resin binder. Further, for example, graphite fine particles are dispersed as solid lubricant fine particles.

Carbon black leaks charges from excessively charged toner and contributes to controlling the toner charge amount to an appropriate level. The graphite fine particles also contribute to leaking the electric charge from the overcharged toner and controlling the toner charge amount to an appropriate level. In this way, it is possible to prevent excessively charged up fine powder toner from electrostatically and firmly adhering to the surface of the sleeve in a very thin layer.

Further, the graphite fine particles weaken the adhesion of the toner to the sleeve due to this solid lubricating property, and hinder the formation of the above-mentioned extremely thin layer of the fine powder toner.

As the synthetic resin binder, for example, a thermosetting phenol resin can be used.

In any case, since the above resin coating layer 17 is an oxidation resistant coating, it is possible to prevent excessive charge-up of the toner for a long period of time, and therefore, faithful development of fine lines, formation of a high-density image, and ghost phenomenon. Can be prevented for a long period of time.

A specific example of the above resin coating layer 17 will be described in detail later, but the thickness of the layer 17 is 0.5 to 30 μm.
m, volume resistance is preferably 10 ^{−3 to} 10 ² Ω · cm.

The magnet body 15 is a resin magnet as described above. Usually, the magnet roll is configured in such a manner that the central shaft body 16 made of metal or plastic is surrounded by the molded body 15 of the magnet. As a manufacturing method, a method of directly molding the shaft body 16 as a center, a method of laminating a molded magnet piece in a roll shape with the shaft body 16 as a center, and inserting and adhering the shaft body 16 into a hollow molded magnet body are performed. There is a method to create it.

As a method for forming the molded body 15, after mixing the binder resin and the magnetic powder, the mixture is kneaded and dispersed by using a roll mill, an extruder or the like, cooled, pulverized and pelletized to be a raw material. This is melted again and subjected to compression molding, injection molding or the like to obtain a magnet piece or a cylindrical molded body. At this time, apply a magnetic field in the mold,
The material may be magnetically oriented. Of course, it may be integrally molded around the shaft body 16. The magnet roll having the shaft body 16 is once demagnetized, and then the magnet roll 13 having the magnetic poles shown in FIG.

The shaft 16 and the magnet body 15 which is the magnetizing portion may be integrally formed of the same material by injection molding or the like.

Examples of the binder resin will be described later. It is bound with a binder resin.

As the magnetic powder, hexagonal ferrite, samarium-cobalt alloy, neodymium-iron-boron alloy, etc. are used. The mixing ratio of the magnetic powder is
100 to 200 relative to 100 parts by weight of the binder resin
About 0 parts by weight of magnetic powder is used.

The structure of the developing roller 3 will be described in more detail with reference to FIG.

The developing roller 3 is provided with the developing sleeve 14 and the magnet roller 13 as described above.

The developing roller 14 further has cap members 22 and 23 at both ends of the sleeve 14. The large diameter portions 221 and 231 of the cap members 22 and 23 are fitted to the inner surfaces of both ends of the metal cylinder 18 of the sleeve 14.
The cap members 22 and 23 are fixed to the sleeve 14 by a method such as press fitting, adhesion, or caulking.

The developing roller 3 further has bearings 24 and 25 held by the cap members 22 and 23.
The bearings 24 and 25 support the shaft 16 of the magnet roll 13 at both longitudinal ends of the magnet body 15. As a result, the sleeve 14 becomes the magnet roll 13
Can be rotated relative to.

The shaft portion 22 of the cap members 22 and 23
2, 232 are the side walls 121, 12 of the container 12, respectively.
It is rotatably supported by bearings 26 and 27 which are held by 2. As a result, the sleeve 14 can rotate in the direction of the arrow in FIG.

The shaft portion 232 of the cap member 23 is hollow, and one end of the shaft 16 of the magnet roller 13 penetrates through this hollow portion and is exposed to the outside. One end 161 of the shaft 16 is fixed to the arm 28 fixed to the side wall 122. As a result, even if the sleeve 14 rotates,
The magnet roller 13 is held stationary.

The shaft portion 22 of the cap members 22 and 23
2, 232 support bearings 29, 30 respectively, and the bearings 29, 30 respectively bear the spacer roller 20.
Is supported. As described above, the spacer roller 20 contacts both ends of the drum 1 to keep the gap between the sleeve 14 and the drum 1 constant.

The shaft 222 of the cap member 22 has a gear 3
1 is fixed. The gear 31 meshes with a driving force transmission gear (not shown), receives the rotational driving force of the sleeve 14, and rotates the sleeve 14 in the arrow direction of FIG.

Before forming the resin coating layer 17 of the sleeve 14, the metal cylinder 18, the magnet roll 13, and the cap members 22 and 23 are assembled into the shape shown in FIG.

This assembly process can be carried out arbitrarily. To give an example thereof, first, the cap member 22 having the bearing 24 fixedly held as shown in the drawing is provided at one end of the metal cylinder (element pipe) 18. Then, the magnet roll 13 is inserted into the raw tube 18, one end of the shaft 16 is fitted into the bearing 24, and then the cap member 23 holding and holding the bearing 25 is fixed. While being fitted to the shaft 16, it is fitted into the other end of the raw pipe 18, and the cap member 23 is fixed to the raw pipe 18 as described above.

In this way, the magnet roll 13 and the tube 1
After the 8 is integrated by the cap members 22 and 23, the coating material to be the resin coating layer 17 is applied to the raw pipe.
If necessary, before that, the element tube is ground with reference to the shaft portions 22 and 232 so that the element tube 18 has a uniform roundness along the longitudinal direction with respect to the rotation axis. Good.

Further, before the coating of the coating material on the base pipe 18, the base pipe 18
The surface may be blasted with irregular-shaped abrasive grains or spherical particles. The adhesive force of the resin coating layer 17 increases on the surface of the raw tube 18 thus roughened, and the surface of the resin coating layer 17 has an appropriate roughness, so that the toner The conveyance force is improved, and the effect of controlling the triboelectric charge amount of toner to an appropriate level is improved. However, it is not essential to roughen the surface of the raw tube 18.

The step of roughening the raw pipe 18 as described above may be carried out before or after assembling the members 13, 22, 23 to the raw pipe, if necessary.

In any case, as described above, the resin coating layer 1
The coating material of No. 7 is applied to the surface of the raw tube 18 in which the magnet roller 13 is supported inside by the cap members 22 and 23. This coating is carried out by a known appropriate method such as a spray method or a dipping method.

By the way, as described above, when the resin coating layer 17 is formed on the surface of the raw tube 18 of the developing sleeve, since the coating material for coating comprises a solvent, a resin, and a pigment as required, It is necessary to apply a high temperature to the coating film of the base pipe 18 in order to remove the solvent after coating the base pipe 18 and further to cure or cure the binder resin. At that time, when the thermal deformation temperature of the binder resin used for the magnet 15 is low, the resin of the magnet 15 is deformed by crystallization,
Deformation due to distortion inside the magnet 15 is caused. This causes non-uniformity or reduction in magnetic force, which causes image fogging and uneven coating on the sleeve, resulting in non-uniform images.

The present invention solves such an inconvenience.

As a result of the examination, when the heat distortion temperature of the binder resin used for the magnet 15 and the heat treatment temperature at the time of forming the resin coating layer 17 are compared, it is found that the heat distortion temperature of the binder resin for the magnet is preferably high. did. That is, in order to suppress the change in the magnetic force of the magnet 15 within a range in which there is no practical problem, the binder resin material for the magnet is selected so that the heat deformation temperature of the binder resin of the magnet 15 is higher than the heat treatment temperature of the coating layer 17. It turns out that it is preferable to choose. The heat distortion temperature is ASTM D64
The temperature is determined as the temperature at which the test piece shows a predetermined deformation amount (0.254 mm) when the temperature is continuously raised at a constant rate under a constant load.

The above heat treatment is carried out in a known heating furnace.

It can be used as a binder resin for the magnet 15. As a resin having a high heat deformation temperature that is unlikely to be deformed by heating and a general heat deformation temperature (in parentheses) of the resin, for example, polycarbonate (135
C), polyphenylene sulfide (138 C), polyoxymethylene (123 C), modified polyphenylene oxide (130 C), polysulfone (175 C), polyether sulfone (210 C), polyarylate (16
4 ° C.), wholly aromatic polyester (180 to 360 ° C.),
Polyether ether ketone (152 ° C), polyamideimide (260 ° C), polyetherimide (200 ° C)
Etc. Of course, the material is not limited to this as long as the material complies with the gist of the present invention.

If necessary, an inorganic filler such as alumina, silica, calcium carbonate, glass, or talc may be added to these resin molding materials, or they may be used for molding.

If necessary, a small amount of a lubricant such as hydrocarbons, metallic soaps, fatty acids, fatty acid amides and fatty acid esters may be added and used.

Next, the resin film 17 formed on the sleeve surface of the developing roller will be described.

As the binder resin material for the film, generally known resins can be used. For example, styrene resin, vinyl resin, polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, fluororesin, fibrin resin, thermoplastic resin such as acrylic resin, epoxy resin, polyester resin, alkyd resin , Phenol resin, melamine resin,
Polyurethane resin, urea resin, silicone resin, polyimide resin or the like can be used.

As the conductive fine powder added to the resin, conductive carbon black, metal powder such as aluminum, copper, nickel and silver, conductive powder such as antimony oxide, indium oxide, titanium oxide and tin oxide can be used. Examples thereof include metal oxides, metal short fibers, carbon fibers and the like.

The addition amount of these is 0.1 to 300%, preferably 1 to 150% with respect to the binder resin.

The solid lubricant fine particles added to the binder resin are, for example, graphite, molybdenum disulfide, boron nitride, zinc stearate, etc., and the addition amount of these is 0.1 to 400 relative to the binder resin. %,
It is preferably about 1 to 200%.

It is preferable that appropriate fine irregularities are formed on the surface of the coating layer 17 of the sleeve. By forming the fine irregularities, the toner transportability is improved, and the control of the toner triboelectric charging is also improved. As the size of the appropriate fine irregularities, generally, the center line average roughness Ra (JIS B06
In the notation method of 01), it is about 0.3 to 5.0 (μm), preferably about 0.5 to 3.0 (μm).

In a paint in which a large amount of pigment is dispersed, suitable fine irregularities are formed as they are after coating. However, when it is desired to adjust the size of the fine irregularities, the fine irregularities are previously formed on the metal cylindrical tube 18 as described above. It is also possible to form irregularities by sandblasting or sanding, and then apply the coating.

In order to form the fine irregularities, additive particles having a particle size of about 0.1 to 30 μm may be added to the coating material. Examples of such an unevenness forming material include polyethylene, phenol, polymethylmethacrylate,
Spherical resin particles such as nylon, silicon, polyvinylidene fluoride, etc., metal oxide powders such as silica, alumina, titanium oxide, iron oxide, etc., fine metal powders such as copper, zinc, cinnamon etc. should be adjusted to the required surface roughness. It can be selected and used.

The material of the resin coating layer 17, that is, the type of binder resin and the type of additive such as conductive fine powder to be added depends on the combination with the toner to be used and the developing process conditions to be used. Selected. The heating temperature when forming the resin layer 17 is mainly determined by the properties of the binder resin.

Further, the binder resin material used for the magnet 15 is selected to have a heat deformation temperature lower than the above heating temperature. As a result, the magnet 15 can be prevented from being deformed even if it is subjected to the heat treatment when forming the resin coating layer 17.

Next, a concrete example will be described.

Example 1 The following magnetic toner was prepared.

Styrene-butyl acrylate-maleic acid-n-butyl half ester copolymer 100 parts by weight Magnetite 90 parts by weight Negative charge control agent 2 parts by weight Low molecular weight polypropylene 5 parts by weight

The above raw material mixture was mixed with a Henschel mixer, kneaded with a twin-screw extruder, cooled, and coarsely crushed with a hammer mill. Next, fine pulverization was performed with a jet mill, and then classification was performed with an elbow jet classifier to adjust the toner particle size. 100 for Coulter Multisizer II
When a particle size distribution was measured by attaching a μm aperture, the particle size distribution was 10.5% in the number average of particles having a weight average particle size of 8.5 μm and 4 μm or less, and 1.8% in the weight percentage of 12.7 μm or more. It was toner.
Next, 0.9 parts by weight of colloidal silica was externally added and mixed with 100 parts by weight of the toner by a Henschel mixer, and then sieved with a 100 mesh sieve to obtain a one-component developer (toner).

The magnet 15 used is as follows.

Hexagonal ferrite powder 300 parts by weight Polycarbonate resin (heat distortion temperature 135 ° C.) 40 parts by weight Zinc stearate 1 part by weight

The above materials were mixed by a Henschel mixer, kneaded by a roll mill, cooled, pulverized and pelletized. Using these pellets, several fan-shaped moldings were made by an injection molding machine. Using this, pressure molding was performed again in such a form that it was bonded around the stainless steel shaft 16 to obtain a cylindrical molded body. Next, this molded body was magnetized to form a 4-pole magnet 15 as shown in FIG.
The strength of the magnetic force of this magnet was measured. The measurement was performed at the center position of the magnetic pole and on the outer surface of the developing sleeve tube 18, and the measurement head was scanned in the longitudinal direction of the sleeve. At this time, the N ₁ pole is 820 ± 20 G (Gauss) (however, mean value ± displacement width is shown), the S ₁ pole is 960 ± 15 G, and the N ₂ pole is 73
It was 5 ± 20 G and the S ₂ pole was 570 ± 15 G.

Next, this magnet is connected to the developing sleeve tube 1.
8, and the flanges 22 and 23 were attached and bonded to both ends.

Next, the surface of the developing sleeve was subjected to a blast treatment using irregular-shaped abrasive grains (Alundum # 250).

Next, a resin layer was applied to this developing sleeve. As the coating material for coating, the following coating materials were used. Polymethylmethacrylate resin 50 parts by weight Crystalline graphite 20 parts by weight Carbon black 5 parts by weight Toluene 300 parts by weight

The polymethylmethacrylate resin was put into toluene and refluxed while heating at 120 ° C. to dissolve the resin in toluene. Then after cooling it,
Crystalline graphite and carbon black were charged and transferred to a sand mill for dispersion. The viscosity of the paint after dispersion was about 25 mPas. This coating material was used to coat the developing sleeve tube 18 with a coating device equipped with a temperature control device, a rotating device for rotating the work, and a spray gun that moves up and down in the coating booth. The coating was carried out with the magnet roller 13 still inside the tube. 12 after coating
It was placed in an oven at 0 ° C. and dried for 30 minutes. The film thickness of the resin layer 17 after drying was 10 μm, and the volume specific resistance value of the coating film 17 was 1.5 Ωcm. In addition, using a surface roughness measuring device SE-3300 manufactured by Kosaka Laboratory, a feed speed of 0.
5 mm / sec. The measured length was 2.5 mm, the roughness cutoff λc was 0.8, and the auto-leveling was ON. As a result, the surface roughness was Ra = 0.82 μm.

Next, the magnetic force of the magnet of the developing roller was measured again. As a result, on the surface of the sleeve, the N ₁ pole is 815 ± 25G and the S ₁ pole is 955 ± 20.
The G and N ₂ poles showed a value of 735 ± 25 G and the S ₂ pole showed a value of 570 ± 20 G, and there was almost no change in magnetic force.

Next, an electrostatic latent image was developed using this developing roller and the image quality was evaluated. Development is 23 ° C / 10% R
It was performed in a low humidity environment of H and a high temperature and high humidity environment of 32 ° C./85% RH. A Canon GP-55 copier was used for development. The developing device is as schematically shown in FIG. A durability test was performed on 50,000 copies of A4 size paper, and image quality was examined. The image density of the solid black image is D = 1.40 ± 0.
In the range of 07, 32 ° C./85% RH, D =
It was within the range of 1.34 ± 0.08, and there was no problem in the solid black and the uniformity of halftone, and there were no stripes or obi on the solid image. Moreover, the phenomenon such as resolution and line scattering did not occur. Further, even in the environment of 23 ° C./10% RH, the occurrence of ghost was not so good. The image density is a value measured by a Macbeth reflection densitometer.

After the durability test, the developing roller was disassembled and the deformation of the magnet roll was confirmed. No expansion or contraction of the magnet roll, warpage or bending was observed. As a result of measuring the dimensions of the magnet roll, there was almost no change after the magnet roll was made, and the surface of the magnet roll was almost horizontal.

Comparative Example 1 In Example 1, the image quality was evaluated by developing the latent image only by blasting without providing the resin layer 17 on the surface of the developing roller. The surface roughness of the developing sleeve was 0.78 μm. 23 ° C / 10% RH
Then, there was an image showing the ghost quite clearly.
Further, the fog at 32 ° C./85% RH was at a level lower than that in Example 1.

Comparative Example 2 A magnet roll was prepared by using a polyvinyl chloride resin (heat distortion temperature 70 ° C.) instead of the polycarbonate resin in Example 1, and the magnet roll was formed on the developing sleeve in the same manner as in Example 1. The resin layer was formed. The resin layer had the same film thickness and resistance. The surface roughness was also equal to Ra = 0.84 μm. The magnetic force of the developing roller before coating is 810 ± 20 G for the N ₁ pole and 94 for the S ₁ pole.
0 ± 20G, N ₂ pole is 720 ± 20G, S ₂ pole is 555 ±
It was 15G. When the magnetic force was measured again after coating and heating, the N ₁ pole was 700 ± 85 G and the S ₁ pole was 820 ± 105.
670 ± 75G for G and N ₂ poles, 520 ± 65G for S ₂ poles
That was a big change. This developing roller is used in the first embodiment.
When the latent image was developed in the same manner as above, the fog was poor,
A lot of streaks and obi-like light and shade also occurred in the solid image. Also, the image density was low.

When the developing roller was disassembled and the horizontalness of the surface of the magnet roll with respect to the shaft center was checked using a laser length measuring machine, it was confirmed that the bulge shape of the magnet roll and the wavy state of the surface were considerably present. . It can be considered that heating causes a deformation, a dimensional change and a magnetic orientation change, which leads to such a magnetic force change.

Example 2 As the toner, the following magnetic toner was used.

Styrene-butyl acrylate resin 100 parts by weight Magnetite 85 parts by weight Negative charge control agent 3 parts by weight Low molecular weight polypropylene 4 parts by weight

The particle size distribution after classification has a weight average particle size of 8.
The number percentage of particles of 6 μm or 4 μm or less is 9.6.
%, And the weight percentage of particles of 12.7 μm or more is 2.4.
%Met. 0.8% by weight of colloidal silica and 1.5% by weight of strontium titanate were externally added and mixed, and sieved to obtain a developer (toner).

The following magnet rolls were used.

Hexagonal ferrite powder 320 parts by weight Polysulfone resin (heat distortion temperature 175 ° C.) 40 parts by weight Lead stearate 1 part by weight

Using the above materials, a 4-pole magnet roll 13 was prepared in the same manner as in Example 1. Further, it was similarly incorporated in the developing sleeve tube 18.

After blasting the developing sleeve tube 18 in the same manner as in Example 1, a resin layer was formed on the developing sleeve using the following paint. Phenol resin 50 parts by weight Crystalline graphite 21 parts by weight Carbon black 2 parts by weight 2-Propanol / methanol mixed solution 230 parts by weight

The above raw materials were dispersed in a sand mill while being adjusted to room temperature to obtain a dispersion liquid (paint) having a viscosity after dispersion of about 50 mPa. This was coated on a blank tube in the same manner as in Example 1, and after coating, it was heated in an atmosphere of 155 ° C. for 50 minutes to cure the resin. The thickness of the resin layer 17 after drying is 10 μm,
The volume specific resistance value of the coating film 17 was 0.73 Ωcm.
The surface roughness Ra was 0.75 μm.

The magnetic force of the magnet 15 before the resin layer 17 is formed is as follows: N ₁ pole is 830 ± 15 G, S ₁ pole is 990 ± 20 G, N ₂ pole is 750 ± 15 G, and S ₂ pole is on the surface of the raw tube 18. 5
The magnetic force of the magnet after heating for forming the resin layer on the surface of the sleeve 14 is 65 ± 15 G.
N ₁ pole is 825 ± 20G, S ₁ pole is 995 ± 15G, N ₂
The pole is 755 ± 20G, the S ₂ pole is 565 ± 15G,
Little changed.

Next, using this developing roller, a durability test was performed on 50,000 copies of A4 size paper under the same conditions as in Example 1 to evaluate the image quality. The image density of a solid black image is D = 1.43 in the environment of 23 ° C / 10% RH through durability.
In the range of ± 0.05, in the environment of 32 ° C / 85% RH,
It was within the range of D = 1.35 ± 0.09, and there was no problem with solid black or uniformity of halftone, and there were no lines or obi on a solid image. Further, the phenomenon such as resolution and scattering of lines did not occur. Also, 23 ° C / 10%
Even in the RH environment, the occurrence of ghosts was not so good.

<Comparative Example 3> The toner used in Example 2 was used.

A magnet roll was prepared using a polycarbonate resin (heat deformation temperature of 135 ° C.) instead of the polysulfone resin of the magnet roll used in Example 2, and the magnet sleeve was formed on the developing sleeve in the same manner as in Example 2. Then, a resin layer was formed. The resin layer 17 has a film thickness of 10 μm, a volume resistivity value of 0.73 Ωcm, and a surface roughness Ra = 0.77 μ.
m, and an equivalent resin layer was obtained. The magnetic force of the developing roller before coating has a N ₁ pole of 830 ± 20 G on the surface of the raw tube.
S ₁ pole is 930 ± 20G, N ₂ pole is 740 ± 15G, S ₂
The pole was 570 ± 15G. When the magnetic force was measured again after coating and heat curing, the N ₁ pole on the surface of the sleeve 14 was 820 ± 65 G, the S ₁ pole was 930 ± 65 G, the N ₂ pole was 740 ± 55 G, and the S ₂ pole was 550 ± 55 G. The change of the central value and the displacement range are not so large as those of the comparative example 2, but the example 2
Compared with, the uniformity of magnetic force was lower. Using this developing roller, an image was formed in the same manner as in Example 2. As a result, a sufficient image density was obtained with no problem, but there was no problem with solid black or halftone, and white streaks and white obi were conspicuous. It was an image. Especially in halftone, it was a white obi. Fog is 23 ° C / 10% RH, 32 ° C / 8
Both environments at 5% RH were inferior to the sample of Example 2.

Example 3 As the toner, the following magnetic toner was used.

Polyester resin 100 parts by weight Magnetite 80 parts by weight Negative charge control agent 4 parts by weight Low molecular weight polypropylene 6 parts by weight

The particle size distribution after classification has a weight average particle size of 8.
Number percentage of particles of 4 μm or 4 μm or less is 10.5
%, The weight percentage of particles of 12.7 μm or more is 1.2
%Met. To this, 1.0% by weight of colloidal silica and 2.0% by weight of strontium titanate were externally added and mixed, and sieved to obtain a developer (toner).

The following magnet rolls were used. Hexagonal ferrite powder 330 parts by weight Polysulfone resin (heat distortion temperature 175 ° C) 40 parts by weight Lead stearate 1 part by weight

Using the above materials, a 4-pole magnet roll 13 was prepared in the same manner as in Example 1. Further, it was similarly incorporated in the developing sleeve.

After blasting the developing sleeve tube 18 in the same manner as in Example 1, a resin layer 17 was formed on the developing sleeve using the following paint.

Silicone resin 50 parts by weight Crystalline graphite 10 parts by weight Carbon black 10 parts by weight Nigrosine dye 2 parts by weight n-hexane 370 parts by weight

The above raw materials were dispersed in a sand mill while being adjusted to room temperature to obtain a dispersion liquid (paint) having a viscosity after dispersion of about 30 mPa. This was coated on the base tube 18 in the same manner as in Example 1, and after coating, it was heated in an atmosphere at 130 ° C. for 70 minutes to cure the resin. The film thickness of the resin layer 17 after drying is 10 μm.
m, and the volume resistivity of the coating film 17 was 0.54 Ωcm. The surface roughness Ra was 0.86 μm.

The magnetic force of the magnet before forming the resin layer 17 is 825 ± 15 G for the N ₁ pole and 9 for the S ₁ pole on the surface of the raw tube.
50 ± 20G, N ₂ pole is 740 ± 15G, S ₂ pole is 580
While it was ± 15 G, the magnetic force of the magnet after heating for forming the resin layer was 8 for the N ₁ pole on the sleeve surface.
25 ± 20G, S ₁ pole is 955 ± 15G, N ₂ pole is 740
± 20G and S ₂ poles were 575 ± 15G, and hardly changed.

Next, using this developing roller, a durability test of 50,000 copies of A4 size paper was conducted under the same conditions as in Example 1 to evaluate the image quality. The image density of a solid black image is D = 1.40 in an environment of 23 ° C./10% RH through durability.
In the range of ± 0.07, in the environment of 32 ° C / 85% RH,
It was within the range of D = 1.35 ± 0.08, and there was no problem in the uniformity of solid black and halftone, and there were no stripes or obi on a solid image. Moreover, the phenomenon such as resolution and line scattering did not occur. Also, 23 ° C / 10%
Even in the RH environment, the occurrence of ghosts was not so good.

<Example 4> The same toner as that in Example 3 was used.

A magnet roller was prepared in the same manner as in Example 3, except that 45 parts by weight of polyphenylene sulfide (heat deformation temperature of 138 ° C.) was used instead of the polysulfone resin of the magnet roll used in Example 3. Further, it was similarly incorporated in the developing sleeve tube.

Further, after blasting the blank tube, the coating material used in Example 3 was applied in the same manner as in Example 3 and heat-dried and cured to prepare a developing roller.

The magnetic force of the magnet before forming the resin layer is 845 ± 20 G for the N ₁ pole and 950 ± 2 for the S ₁ pole on the surface of the raw tube.
0G, N ₂ pole is 730 ± 15G, S ₂ pole is 550 ± 20G
On the other hand, the magnetic force of the magnet after heating for forming the resin layer is 840 ± 2 for the N ₁ pole on the sleeve surface.
0G, S ₁ pole is 950 ± 20G, N ₂ pole is 730 ± 20
The G and S ₂ poles were 545 ± 15 G, and hardly changed.

Then, using this developing roller, a durability test of 50,000 copies of A4 size paper was conducted in the same manner as in Example 3,
The image quality was evaluated. The result was almost the same as that of Example 3, and the image density of the solid black image was 23 ° C /
In the environment of 10% RH, D = 1.40 ± 0.07, and in the environment of 32 ° C./85% RH, D = 1.35 ±
It was within the range of 0.08, and there was no problem in solid black and uniformity of halftone, and there were no stripes or obi on a solid image. Moreover, the phenomenon such as resolution and line scattering did not occur. Further, even in the environment of 23 ° C./10% RH, the ghost did not occur at all.

By the way, if a so-called glass fiber reinforced resin in which glass fibers are dispersed is used as the binder resin of the resin magnet, the selection range of materials is widened, and from the viewpoints of ease of molding and dispersion of additives as well. Good results are obtained.

The glass fiber reinforced resin having a high heat deformation temperature which hardly causes deformation by heating and a typical heat deformation temperature (in parentheses) of the glass fiber reinforced resin are, for example, nylon 6 + glass fiber <GF> 30. % Mix (190 ° C), nylon 66 + GF30% (240
℃), polyoxymethylene + GF25% (163 ℃),
Polycarbonate + GF30% (145 ° C), modified polyphenylene oxide + GF30% (140 ° C), polybutylene terephthalate + GF30% (210 ° C), polyethylene terephthalate + GF30% (242 ° C),
Polyphenylene sulfide + GF 40% (260
℃), polyethersulfone + GF30% (216
C), polysulfone + GF30% (185%), polyarylate + GF15% (167 ° C), wholly aromatic polyester + GF30-40% (230 ° C-300 ° C), polyetheretherketone + GF30% (300 ° C),
Polyamide imide + GF 30% (275 ° C.), polyether imide + GF 30% (210 ° C.), high density polyethylene + GF 30% (132 ° C.) and the like. Of course, it is not limited to this as long as it is in accordance with the gist of the present invention.

If necessary, an inorganic filler such as alumina, silica, calcium carbonate, glass or talc may be added to these resin molding materials, or they may be used for molding.

If necessary, a small amount of a lubricant such as hydrocarbons, metallic soaps, fatty acids, fatty acid amides and fatty acid esters may be added and used.

An example of using a resin magnet in which glass fibers are dispersed will be illustrated below.

Example 5 The following magnetic toner was prepared. Styrene-butyl acrylate 100 parts by weight Magnetite 90 parts by weight Negative charge control agent 3 parts by weight Low molecular weight polypropylene 3 parts by weight

The above raw material mixture was mixed with a Henschel mixer, kneaded with a twin-screw extruder, cooled, and coarsely crushed with a hammer mill. Next, fine pulverization was performed with a jet mill, and then classification was performed with an elbow jet classifier to adjust the toner particle size. 100 for Coulter Multisizer II
When a particle size distribution was measured by attaching an aperture of μm, the number average particle size of 8.0 μm, the number percent of particles of 4 μm or less was 12.2%, and the weight percent of 12.7 μm or more was 0.3%. It was a toner having. Next, 1.0 part by weight of colloidal silica was externally added and mixed with 100 parts by weight of the toner by a Henschel mixer, and then sieved with a 100 mesh sieve to obtain a developer (toner).

The following magnet rolls were used. Hexagonal ferrite powder 300 parts by weight Glass fiber mixed polyoxymethylene resin (heat distortion temperature 1
63 ° C) 45 parts by weight (polyoxymethylene resin 35 parts by weight, glass fiber 10
Parts by weight) zinc stearate 1 part by weight

The above materials were mixed by a Henschel mixer, then kneaded by a roll mill, cooled, pulverized and pelletized. Using these pellets, several fan-shaped moldings were made by an injection molding machine. Using this, pressure molding was performed again in such a form that it was bonded around the stainless steel shaft 16 to obtain a cylindrical molded body. Next, this molded body was magnetized to obtain a 4-pole magnet 15 as shown in FIG. The strength of the magnetic force is 820 ± 20G for the N ₁ pole on the tube surface.
(Gauss), S ₁ pole is 950 ± 15G, N ₂ pole is 755 ±
The 20 G and S ₂ poles were 550 ± 15 G.

Next, irregularly shaped abrasive grains (Alundum # 250) were formed on the surface of the developing sleeve tube in which this magnet was incorporated.
Was used for blasting.

Next, a resin layer was applied to this developing sleeve tube. As the coating material for coating, the following coating materials were used. Phenolic resin 100 parts by weight Crystalline graphite 45 parts by weight Carbon black 5 parts by weight 2-Propanol / methanol mixed solution 300 parts by weight

The above raw materials were dispersed in a sand mill while being adjusted to room temperature to obtain a dispersion liquid (paint) having a viscosity after dispersion of about 45 mPa. The coating sleeve was coated with this coating material by a coating device equipped with a temperature control device, a rotating device for rotating the work, and a spray gun that moved up and down in the coating booth. The coating was performed with the magnet inside the tube. After coating, it was placed in an oven at 155 ° C. and dried for 50 minutes. The film thickness of the resin layer 17 after drying was 10 μm, and the volume resistivity of the coating film was 0.85 Ωcm. Also, a surface roughness measuring device SE-33 manufactured by Kosaka Laboratory
00, a feed speed of 0.5 mm / sec. , Measurement length 2.5 mm, roughness cutoff λc = 0.8, result of measurement with auto-leveling ON, surface roughness Ra =
It was 0.75 μm.

Next, the magnetic force of the magnet of this developing roller.
Was measured again. As a result, the sleeve surface
Above, N₁The pole is 815 ± 20G, S₁The pole is 950 ± 20
G, N ₂The pole is 760 ± 25G, S₂The pole is 545 ± 20G
The value was shown, and the change in magnetic force hardly occurred.

Next, using this developing roller, a durability test was performed on 50,000 copies of A4 size paper under the same conditions as in Example 1, and a comparison was made. The image density of a solid black image is D = 1.41 ± in an environment of 23 ° C / 10% RH through durability.
In the range of 0.06, 32 ° C / 85% RH environment, D
= 1.35 ± 0.07, and there was no problem with the uniformity of solid black and halftone, and there were no lines or obi on a solid image. Moreover, the phenomenon such as resolution and line scattering did not occur. Also, 23 ° C / 10% RH
Even in this environment, the occurrence of ghosts was not so good.

After the durability test, the developing roller was disassembled, and the deformation of the magnet roll was confirmed. No expansion or contraction of the magnet roll, warpage or bending was observed. As a result of measuring the dimensions of the magnet roll, there was almost no change after the magnet roll was made, and the surface of the magnet roll was almost horizontal.

Comparative Example 4 A magnet roll was prepared in the same manner as in Example 5, except that the polycarbonate resin and the glass fiber were not used and only 45 parts by weight of polyvinyl chloride resin (having a heat distortion temperature of 70 ° C.) was used. A resin layer was formed on the developing sleeve in the same manner as in 5. The resin layer had the same film thickness and resistance. Surface roughness Ra = 0.82μ
It was made equal to m. The magnetic force of the developing roller before coating is 810 ± 15 G for the N ₁ pole and 940 ± 2 for the S ₁ pole on the surface of the raw tube.
0G, N ₂ pole is 730 ± 15G, S ₂ pole is 560 ± 15G
Met. When the magnetic force was measured again after coating on a bare tube and drying, the N ₁ pole was 720 ± 70 G, the S ₁ pole was 800 ± 100 G, the N ₂ pole was 660 ± 80 G, and the S ₂ pole was 515 ± 75 G on the sleeve surface. That was a big change. When development was performed in the same manner as in Example 5 using this developing roller, fog was inferior and many streaks and obi-like light and shade were generated in a solid image. Also, the image density was low.

When the developing roller was disassembled and the horizontalness of the surface of the magnet roll with respect to the shaft center was checked using a laser length measuring machine, it was confirmed that the bulge shape of the magnet roll and the wavy state of the surface were considerably present. . It can be considered that heating causes a deformation, a dimensional change and a magnetic orientation change, which leads to such a magnetic force change.

Example 6 The following magnetic toner was used as the toner. Styrene-butyl-acrylate maleic acid-n-butyl half ester copolymer 100 parts by weight Magnetite 90 parts by weight Negative charge control part 2 parts by weight Low molecular weight polypropylene 4 parts by weight

As for the particle size distribution after classification, the weight average particle size was 8.
The number percentage of particles of 1 μm or 4 μm or less is 12.0.
%, The weight percentage of particles of 12.7 μm or more is 0.3
%Met. To this, 1.0% by weight of colloidal silica and 1.5% by weight of strontium titanate were externally added and mixed, and sieved to obtain a developer (toner).

The following magnet rolls were used. Hexagonal ferrite powder 350 parts by weight Glass fiber mixed polyphenylene sulfide resin (heat deformation temperature 260 ° C.) 55 parts by weight (resin 40 parts by weight, glass fiber 15 parts by weight) Lead stearate 1 part by weight

Using the above materials, a 4-pole magnet roll was prepared in the same manner as in Example 1. Further, it was similarly incorporated in the developing sleeve.

The developing sleeve tube was blasted in the same manner as in Example 1, and then the resin layer 17 was formed on the developing sleeve using the following paint. Polymethylmethacrylate resin 100 parts by weight Crystalline graphite 40 parts by weight Carbon black 5 parts by weight Nigrosine dye 5 parts by weight Toluene 600 parts by weight

The polymethylmethacrylate resin was put into toluene and refluxed while heating at 120 ° C. to dissolve the resin in toluene. Next, after cooling this, crystalline graphite, carbon black, and nigrosine dye were added and transferred to a sand mill for dispersion. The viscosity of the paint after dispersion was about 30 mPa. This is applied to the tube in the same manner as in Example 1, and 120 ° C. after application.
It was heated and dried in the atmosphere of 30 minutes. Further on,
The temperature of the dryer was raised to 170 ° C., and heat treatment was further performed for 40 minutes. The film thickness of the resin layer 17 after drying was 10 μm, and the volume resistivity value of the coating film 17 was 0.94 Ωcm. The surface roughness Ra was 0.87 μm.

The magnetic force of the magnet before the resin layer 17 is formed is
On the surface of the raw tube, the N ₁ pole is 830 ± 15G, and the S ₁ pole is 950
± 20G, N ₂ pole is 750 ± 15G, S ₂ pole is 555 ± 1
While the magnetic force of the magnet after heating for forming the resin layer was 5 G, the N ₁ pole was 835 ± on the sleeve surface.
15G, S ₁ pole is 950 ± 20G, N ₂ pole is 750 ± 20
The G and S ₂ poles were 555 ± 15 G, and hardly changed.

Next, using this developing roller, a durability test of 50,000 copies of A4 size paper was conducted under the same conditions as in Example 1 to evaluate the image quality. The image density of a solid black image is D = 1.42 in the environment of 23 ° C / 10% RH through durability.
In the range of ± 0.07, in the environment of 32 ° C / 85% RH,
It was within the range of D = 1.35 ± 0.09, and there was no problem with solid black or uniformity of halftone, and there were no lines or obi on a solid image. Moreover, the phenomenon such as resolution and line scattering did not occur. Also, 23 ° C / 10% R
Even in the H environment, the occurrence of ghost was not so good.

<Comparative Example 5> As the toner, the toner used in Example 6 was used.

A magnet roll was prepared by using only 55 parts by weight of a polycarbonate resin (having a heat distortion temperature of 135 ° C.) of the magnet roll used in Example 6 without using polysulfone resin and glass fiber. The resin layer 17 was formed on the developing sleeve in the same manner as in 6. The resin layer 17 has a film thickness of 10 μm and a volume resistivity value of 0.
It was 94 Ωcm and surface roughness Ra = 0.87 μm, and the resin layer was equivalent. The magnetic force of the developing roller before coating is 840 ± 20 G for the N ₁ pole and 960 ± 20 for the S ₁ pole on the surface of the raw tube.
20G, N ₂ pole is 750 ± 15G, S ₂ pole is 550 ± 15
It was G. When the magnetic force was measured again after coating and heat curing, the N ₁ pole was 835 ± 70 G, S ₁ on the sleeve surface.
The pole is 950 ± 60 G, the N ₂ pole is 750 ± 60 G, and the S ₂ pole is 545 ± 55 G.
Although not so large, compared with Example 6, the uniformity of magnetic force was reduced. Example 6 using this developing roller
When it was developed in the same manner as above, it was an image in which white stripes and white obi were conspicuous in solid black and halftone. Especially in halftone, it was a white obi. Fog is 23 ° C / 1
Example 6 in both 0% RH and 32 ° C./85% RH environments
Inferior to the sample.

Example 7 The following magnetic toner was used as the toner. Polyester resin 100 parts by weight Magnetite 90 parts by weight Negative charge control agent 5 parts by weight Low molecular weight polypropylene 5 parts by weight

The particle size distribution after classification has a weight average particle size of 8.
The number percentage of particles of 5 μm or 4 μm or less is 10.5.
%, The weight percentage of particles of 12.7 μm or more is 1.5
%Met. To this, 1.1% by weight of colloidal silica and 2.0% by weight of strontium titanate were externally added and mixed, and sieved to obtain a developer (toner).

The following was used as the magnet roll. Hexagonal ferrite powder 350 parts by weight Nylon 66 resin mixed with glass fiber (heat distortion temperature 240
C.) 52 parts by weight (40 parts by weight of resin, 12 parts by weight of glass fiber) 1 part by weight of zinc stearate

Using the above materials, a 4-pole magnet roll was prepared in the same manner as in Example 1. Further, it was similarly incorporated in the developing sleeve.

The developing sleeve tube was blasted in the same manner as in Example 1, and then the resin layer 17 was formed on the developing sleeve using the following paint. Silicone resin 100 parts by weight Crystalline graphite 40 parts by weight Carbon black 10 parts by weight n-hexane 600 parts by weight

The above raw materials were dispersed in a sand mill while being adjusted to room temperature to obtain a dispersion liquid (paint) having a viscosity after dispersion of about 30 mPa. This is coated in the same manner as in Example 1,
After coating, the resin was cured by heating in an atmosphere of 150 ° C. for 50 minutes. The film thickness of the resin layer 17 after drying is 10 μm, and the coating film 1
The volume specific resistance value of No. 7 was 0.85 Ωcm. Also,
The surface roughness Ra was 0.69 μm.

The magnetic force of the magnet before the resin layer 17 is formed is
N ₁ pole is 805 ± 10G and S ₁ pole is 980 on the surface of the raw tube.
± 20G, N ₂ pole 730 ± 15G, S ₂ pole 540 ± 1
While the magnetic force of the magnet after heating for forming the resin layer was 5G, the N ₁ pole was 810 on the surface of the sleeve.
± 20G, S ₁ pole is 975 ± 15G, N ₂ pole is 730 ± 2
It was 0 G, S ₂ pole 540 ± 20 G, and hardly changed.

Next, using this developing roller, a durability test of 50,000 copies of A4 size paper was conducted under the same conditions as in Example 1 to evaluate the image quality. The image density of a solid black image is D = 1.42 in the environment of 23 ° C / 10% RH through durability.
In the range of ± 0.07, in the environment of 32 ° C / 85% RH,
It was within the range of D = 1.34 ± 0.08, there was no problem in the uniformity of the halftone of solid black, and there were no stripes or obi on the solid image. Moreover, the phenomenon such as resolution and line scattering did not occur. Also, 23 ° C / 10% R
Even in the environment of H, the ghost did not occur at all.

<Example 8> The same toner as that in Example 7 was used.

Instead of the nylon 66 resin of the magnet roll used in Example 7, polybutylene terephthalate (polybutylene terephthalate containing 30% glass fiber having a thermal expansion coefficient of about 210 ° C.) was used, and the other amount was the same. A magnet roller was produced in the same manner as in Example 7. Further, it was similarly incorporated in the developing sleeve.

Further, after subjecting the tube to blast treatment, the tube used was coated with the coating material used in Example 7 in the same manner as in Example 7 and heat-dried and cured to prepare a developing roller.

The magnetic force of the magnet before the resin layer 17 is formed is
N ₁ pole is 825 ± 10G and S ₁ pole is 960 ± 20 on the tube.
The G and N ₂ poles were 760 ± 20G, and the S ₂ poles were 580 ± 15G, whereas the magnetic force of the magnet after heating for forming the resin layer was 825 ± 20 for the N ₁ pole on the sleeve surface.
G, S ₁ pole is 955 ± 20G, N ₂ pole is 760 ± 20G,
The S ₂ pole was 575 ± 15 G, and hardly changed.

Next, using this developing roller, a durability test of 50,000 copies was conducted in the same manner as in Example 1 to evaluate the image quality. The result was almost the same as that of Example 7, and the image density of the solid black image was 32 ° C./85% within the range of D = 1.42 ± 0.07 in the environment of 23 ° C./10% RH throughout the durability test.
In the RH environment, it was within the range of D = 1.35 ± 0.08, and there was no problem in the solid black or the uniformity of halftone, and there were no stripes or obi on the solid image. Moreover, the phenomenon such as resolution and line scattering did not occur.
Further, even in the environment of 23 ° C./10% RH, the occurrence of ghost was not so good.

In the above embodiment, the magnet is fixedly supported in the rotary sleeve, but the present invention can also be applied to the one in which the magnet is rotated to develop the latent image. Also, the number of poles of the magnet is not limited to four.

As a member for controlling the layer thickness of the developer, a non-magnetic blade can be used instead of the magnetic blade 19, and a silicone rubber blade, a urethane rubber blade, or a metal leaf spring such as phosphor bronze is used as a sleeve. It is also possible to regulate the layer thickness of the developer that is brought into pressure contact with and conveyed to the developing area.

[0159]

As described above, according to the present invention,
It is possible to prevent excessive charge-up of toner, obtain line images and solid black images with sufficient density, generate ghosts, obtain uniform halftone images, and obtain high-quality images without uneven density of solid images. Image can be formed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

[Explanation of symbols]

 3 Developing Roll 15 Magnet 14 Developing Sleeve 17 Resin Coating Layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ikki Saiki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Michiko Orihara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canonon Within the corporation

Claims (8)

[Claims] 1. A developing roller which carries a developer and conveys it to a developing area for developing an electrostatic latent image, a cylinder, a resin coating layer formed on the surface of the cylinder, and a binder for magnetic powder. The resin-bonded magnet and supporting means for supporting the magnet inside the cylinder are provided, and the resin coating layer is heat-treated while the magnet is supported inside the cylinder. And the heat deformation temperature of the binder resin of the magnet is higher than the heat treatment temperature. 2. The developing roller according to claim 1, wherein the binder resin of the magnet is a resin in which glass fibers are dispersed. 3. The developing roller according to claim 1, wherein conductive particles are dispersed in the resin coating layer. 4. The developing roller according to claim 3, wherein a solid lubricant is further dispersed in the resin coating layer. 5. A container for containing a developer, a developing roller for carrying the developer out of the developing container and carrying it to a developing area for developing an electrostatic latent image, and a developer layer carried by the developing roller for the developing area. In a developing device having a regulating member for regulating the thickness of the cylindrical body, the developing roller includes a cylindrical body, a resin coating layer formed on the surface of the cylindrical body, and a magnet in which magnetic powder is bound with a binder resin. A supporting means for supporting the magnet inside the cylindrical body, and the resin coating layer is heat-treated while the magnet is supported inside the cylindrical body, and the binder resin of the magnet. The thermal deformation temperature of the developing device is higher than the heat treatment temperature. 6. The developing device according to claim 5, wherein the binder resin of the magnet is a resin in which glass fibers are dispersed. 7. The developing device according to claim 5, wherein conductive particles are dispersed in the resin coating layer. 8. The developing device according to claim 7, wherein a solid lubricant is further dispersed in the resin coating layer.