JP2951773B2 - Developing device and developing roller used therein - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing apparatus for developing an electrostatic latent image using a one-component developer, and more particularly, to a developer carrier for the same.
That is, it relates to improvement of the developing roller.

[0002]

2. Description of the Related Art A developing apparatus using a one-component developer is frequently used in an electrophotographic copying machine or an electrophotographic printer.

Japanese Patent Application Laid-Open Nos. 55-140858, 56-131172, and 57 discloses a developing device in which the surface of a developer carrying member is subjected to a surface roughening treatment to improve the developer conveying performance.
-66455 and the like.

In a developing device using a one-component developer, toner particles are charged to a polarity for developing a latent image by friction between the toner particles and a developer carrier. The developer carrier having been subjected to the above-described surface roughening also contributes to appropriately frictionally charge the toner particles.

On the other hand, the developer is not consumed in a region of the developer carrier that faces the non-image portion of the image carrier. However, if the non-consumed state continues, the developer carrier bears an electrostatic reflection force. Although it is thought to be caused by this, the fine powder developer layer adheres strongly and not only is not easily consumed even in the image area of the image carrier, but also reduces the charge amount of the developer on the fine powder developer layer. I will. For this reason, a ghost image is generated on the developed image, and the quality of the image is degraded.

That is, as shown in FIG. 6, a non-printed portion (white background) continues, and a portion (a) where only a thin developer is applied even when printing is performed, and a dark portion because printing is continued. Density unevenness occurs between the portion (b) where development is performed. The ghost mechanism is deeply related to the fine powder layer formed on the developer carrier. In other words, there is a clear difference in the particle size distribution of the toner lowermost layer of the developer carrier between the toner consuming portion and the toner non-consuming portion, and the fine powder layer is formed in the toner lowermost layer in the non-consuming portion. is there. Since the fine powder has a large surface area per volume, the amount of triboelectric charge per mass is larger than that having a large particle diameter, and the fine powder is strongly restrained electrostatically to the developer carrier by the mirroring power. . For this reason, the toner on the portion where the fine powder layer is formed cannot be sufficiently frictionally charged with the developer carrying member, so that the developing ability is reduced and appears as a ghost on an image.

[0007]

However, in recent years, in order to improve the image quality of electrophotographic apparatuses, the particle size of toner has been further reduced. For example, in the case of an electrophotographic laser beam printer, when the printing density is increased to 600 dpi (23.6 pel) which is doubled from the conventional 300 dpi, the electrostatic latent image is faithfully reproduced by increasing the resolution and sharpness. This can be relatively easily solved by using a toner having a particle size of about 9 μm to 4 μm.

An example of such a small particle size toner is as follows.
The volume average particle size is 6.0 μm, and the volume average particle size is 3.5
For example, a toner having a particle size of about 20% or less in a number distribution and a particle size of 16 μm or more in a volume distribution of about 1% or less in a volume distribution.

However, such a small particle size toner has a large specific surface area per volume as compared with the conventional toner, so that the charge amount per volume and weight increases and, as described above, the fine powder amount increases. Due to the increase, the resin component in these small particle diameter toners becomes abundant, and as a result, the surface of the developer carrier is likely to be contaminated by the high frictionally charged fine powder of these small particle diameter toners. This makes it easier for ghosts to occur, as described above.

As a countermeasure against the above-mentioned phenomenon, Japanese Patent Application Laid-Open No. 1-276174 discloses a technique in which a surface layer in which carbon black fine particles, graphite fine particles and the like are dispersed in a binder resin is provided on a developer carrying member to leak the charge of the charged fine powder. , 1
-277265 and 2-176682.

Although the above technique is excellent in ghost prevention effect, the surface layer is easily peeled off partly during use for a long period of time, and the surface layer is abraded and smoothed to charge the toner. There is a point that the properties and transportability are deteriorated and the toner layer becomes uneven, and the above-mentioned improvement is desired. It is also one of the improvements desired in the above prior art to easily form a surface layer having a desired average surface roughness.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing apparatus capable of preventing strong adhesion of developer fine powder to a developing roller and obtaining a developed image having a good density without a decrease in density for a long period of time.

Another object of the present invention is to provide a long-term
A developing roller capable of suppressing the deterioration of the frictional charging ability and transporting ability of the developer, forming a uniform developer layer over a long period of time, and easily obtaining a resin layer having a desired average surface roughness. , And a developing device provided with the same.

[0014]

According to one feature of the present invention, the developing roller has an average surface roughness Ra of 1.0 to 3.
In a developing roller having a resin layer on a 0 μm substrate, an average surface roughness Ra of the resin layer is 0.8 to 2.5 μm.
m, and the average interval Sm of the irregularities on the surface of the resin layer is 3
0 to 70 μm.

Since the resin layer is applied to the rough surface of the substrate, the resin layer strongly adheres to the substrate and is difficult to peel off, and a change in the roughness of the surface of the resin layer due to use is suppressed to a small extent. And it is easy to form a resin layer having a required average surface roughness.

Further, according to the present invention, an appropriate surface roughness can be obtained at the time when the resin layer is provided on the substrate due to the above characteristics, and no special post-process for roughening the surface is required.

[0017]

FIG. 1 is a block diagram showing an embodiment of the developing device of the present invention. In this developing device, an electrostatic latent image on an image carrier is developed using a one-component magnetic developer.

First, the one-component magnetic developer used in the present invention will be described.

The one-component magnetic developer is a binder resin for a magnetic toner as a main component, which is a homopolymer of styrene such as polystyrene and polyvinyltoluene and a substituted product thereof; a styrene-propylene copolymer and a styrene-vinyltoluene copolymer. Copolymer, styrene-vinylnaphthalene copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene- Methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether Copolymer,
Styrene-based copolymers such as styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate , Polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, polyacrylic resin, rosin, modified rosin,
Tempel resins, phenolic resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin wax, carnauba wax and the like can be used alone or in combination.

As the coloring material which can be further added to the magnetic toner, conventionally known carbon black, copper phthalocyanine, iron black and the like can be used.

As the magnetic fine particles contained in the magnetic toner, a substance which is magnetized when placed in a magnetic field is used.
Powders of ferromagnetic metals such as iron, cobalt and nickel, or alloys and compounds such as magnetite, γ-Fe ₂ O ₃ and ferrite can be used.

[0022] These magnetic fine particles is preferably a BET specific surface area by the nitrogen adsorption method 1-20 m ² / g, especially 2.5~12m ² / g, further Mohs hardness magnetic powder 5-7 is preferred. The content of the magnetic powder is preferably from 10 to 70% by weight based on the weight of the toner.

The toner may contain a charge control agent, if necessary, such as a metal complex salt of a monoazo dye, salicylic acid,
A negative charge control agent such as a metal complex salt of alkyl salicylic acid, dialkyl salicylic acid or naphthoic acid is used. Further, the toner has a volume resistivity of 10 ¹⁰ Ωcm or more, particularly 10 ¹² Ωcm.
cm or more is preferable in terms of triboelectric charge retention and electrostatic transferability. The volume resistivity referred to here is 100% for toner.
It is molded at a pressure of kg / cm ² , an electric field of 100 V / cm is applied thereto, and is defined as a value converted from a current value one minute after the application.

The triboelectric charge of the negatively chargeable toner is -8 μc
/ G to −20 μc / g. -8
If it is less than μc / g, the image density tends to be low, and the effect under high humidity is particularly remarkable. On the other hand, if it exceeds -20 [mu] c / g, the charge of the toner is too high, and the line image or the like becomes thin.

The negatively chargeable toner particles are as follows. That is, a carrier iron powder not coated with a resin having a main particle size of 10 g of toner particles and 200 to 300 mesh left overnight under an environment of 25 ° C. and 50 to 60% RH (for example, manufactured by Nippon Iron Powder Co., Ltd.) EFV200 / 300) 90
g in an aluminum pot having a volume of about 200 cc in the above environment (holding in hand and shaking up and down about 50 times), and using an aluminum cell having a 400 mesh screen. The amount of triboelectric charge of the toner particles is measured by an ordinary blow-off method.
A toner particle having a negative triboelectric charge measured by this method is defined as a negatively chargeable toner particle.

The silica fine particles used as an external additive for improving the fluidity of the magnetic toner include so-called dry silica produced by vapor phase oxidation of a silicon halide, dry silica called fumed silica, or water. So-called wet silica produced from glass or the like can be used, but dry silica having few silanol groups on the surface and inside and having no production residue is preferable. In the case of fumed silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide in the production process. Is also included.

The silica fine particles are preferably subjected to a hydrophobic treatment. For the hydrophobic treatment, a conventionally known hydrophobic treatment method is used, and hydrophobicity is imparted by chemically treating with an organosilicon compound which reacts with or physically adsorbs silica fine powder. As a preferred method, the silica fine powder produced by the vapor phase oxidation of the silicon halide is treated with the silane coupling agent or simultaneously with the silane coupling agent and treated with the organosilicon compound.

Finally, when the treated silica fine powder is hydrophobized so as to exhibit a hydrophobicity measured by a methanol titration test in a value in the range of 30 to 80, such a silica powder is treated. This is preferable because the triboelectric charge distribution of the developer containing the silica fine powder exhibits sharp and uniform negative chargeability.

Here, the methanol titration test is an experimental test for confirming the degree of hydrophobicity of silica fine powder having a hydrophobicized surface.

In order to evaluate the degree of hydrophobicity of the treated silica fine powder, the "methanol test" as defined herein is performed as follows. Test silica fine powder 0.2g
Is added to 50 ml of water in a 250 ml Erlenmeyer flask. Methanol is titrated from the burette until all of the silica is wetted. At this time, the solution in the flask is constantly stirred with a magnetic stirrer. The end point is observed as the entire amount of fine silica powder is suspended in the liquid, and the degree of hydrophobicity is expressed as the percentage of methanol in the liquid mixture of methanol and water at the end point.

The amount of the silica fine particles is effective when the amount is 0.05 to 3 parts by weight based on 100 parts by weight of the toner, and is particularly preferable when 0.1 to 2 parts by weight is added. It is possible to provide a developer having excellent stability and exhibiting chargeability. In a preferred embodiment of the addition form, it is preferable that 0.01 to 1 part by weight of silica fine powder with respect to the weight of the toner is attached to the surface of the toner particles.

Other additives such as a tetrafluoroethylene resin, a lubricant such as zinc stearate, or a fixing aid (for example, low-molecular-weight polyethylene) or a conductive agent, as long as they do not substantially adversely affect the magnetic toner. A metal oxide such as tin oxide may be added as a property imparting agent.

In the production of the toner, the constituent materials are kneaded well by a heat kneader such as a hot roll, kneader, extruder, etc., and then the toner is obtained by mechanical pulverization and classification. Is obtained by dispersing and spraying the toner, or by a polymerization method in which a predetermined material is mixed with a monomer to constitute a binder resin to form an emulsified suspension and then polymerized to obtain the toner. Each method such as the method can be applied.

Hereinafter, a developing device according to an embodiment of the present invention will be described.

In FIG. 1, an image carrier, for example, an electrophotographic photosensitive drum 1 for carrying an electrostatic latent image formed by a known process is rotated in the direction of arrow B. The developing sleeve 8 as a developer carrier carries the magnetic toner 4 as a one-component magnetic developer supplied by the hopper 3 and rotates in the direction of arrow A, thereby causing the developing sleeve 8 to rotate.
And the photosensitive drum 1 conveys the toner 4 to the developing area D where the toner 4 faces. A magnet 5 is arranged in the developing sleeve 8 to magnetically attract and hold the magnetic toner 4 on the developing sleeve 8. The toner 4 obtains a triboelectric charge that can develop the electrostatic latent image on the photosensitive drum 1 by friction with the developing sleeve 8.

In order to regulate the layer thickness of the magnetic toner 4 conveyed to the developing area D, a regulating blade 2 made of a ferromagnetic metal is set to be about 200 to 300 μm from the surface of the developing sleeve 8.
From the hopper 3 so as to face the developing sleeve 8 with a gap width of. When the lines of magnetic force from the magnetic pole N _{1 of the} magnet 5 concentrate on the blade 2, a thin layer of the magnetic toner 4 is formed on the developing sleeve 8. Blade 2
For example, a non-magnetic blade can be used.

The thickness of the thin layer of the magnetic toner 4 formed on the developing sleeve 8 is
It is preferable that the distance be smaller than the minimum gap between the photosensitive drum 1 and the photosensitive drum 1. The present invention is particularly effective for a developing device of a type that develops an electrostatic latent image with such a thin toner layer, that is, a non-contact developing type developing device. However, in the developing area, the thickness of the toner layer is
The present invention can also be applied to a developing device having a thickness not less than the minimum gap between them, that is, a contact developing type developing device.

For the sake of simplicity, the following description will be made by taking a non-contact developing type developing device as an example.

In order to cause the developing sleeve 8 to fly the toner 4 from the toner layer of the magnetic toner 4, which is a one-component magnetic developer, carried on the developing sleeve 8 toward the photosensitive drum 1, a developing bias voltage is applied by the power supply 9. Applied. When a DC voltage is used as the developing bias voltage, a voltage having a value between the potential of the image portion of the electrostatic latent image (the region where the toner 4 adheres and is visualized) and the potential of the background portion is used. 8
Is preferably applied. On the other hand, in order to increase the density of the developed image or improve the gradation, an alternating bias voltage may be applied to the developing sleeve 8 to form an oscillating electric field in which the direction is alternately reversed in the developing region D. In this case, it is preferable to apply to the developing sleeve 8 an alternating bias voltage on which a DC voltage component having a value between the potential of the image portion and the potential of the background portion is superimposed.

In so-called regular development in which toner is adhered to a high potential portion of an electrostatic latent image having a high potential portion and a low potential portion to visualize the toner, a toner charged to a polarity opposite to the polarity of the electrostatic latent image is used. On the other hand, in so-called reversal development in which toner is attached to a low-potential portion of an electrostatic latent image to visualize the toner, a toner charged to the same polarity as the polarity of the electrostatic latent image is used. Note that the high potential and the low potential are expressed by absolute values. In any case, the toner 4 is charged to a polarity for developing the electrostatic latent image by friction with the developing sleeve 8. The silica externally added to the toner 4 is also charged by friction with the developing sleeve 8.

FIG. 2 is a block diagram showing another embodiment of the developing device of the present invention, and FIG. 3 is a block diagram showing still another embodiment of the developing device of the present invention.

In the developing device shown in FIGS. 2 and 3, as a member for regulating the layer thickness of the magnetic toner 4 on the developing sleeve 8, a material having rubber elasticity such as urethane rubber or silicone rubber, phosphor bronze, stainless steel or the like is used. An elastic plate 20 made of a material having metal elasticity is used. The elastic plate 20 is pressed against the developing sleeve 8 in the developing device of FIG. 2 in a direction opposite to the rotation direction in the developing device of FIG. It is characterized in that it is brought into pressure contact with the body in the same direction as the rotation direction. In such a developing device, a thinner toner layer can be formed on the developing sleeve 8. 2 and 3
The other structure of the developing device is basically the same as that of the developing device shown in FIG. 1. In FIGS. 2 and 3, the same reference numerals as those shown in FIG. 1 indicate the same members.

The developing device for forming a toner layer on the developing sleeve 8 as described above as shown in FIGS. 2 and 3 can be used for a device using a one-component magnetic developer containing a magnetic toner as a main component. It is also suitable for those using a one-component non-magnetic developer whose main component is a non-magnetic toner. In any case, since the toner is rubbed onto the developing sleeve 8 by the elastic plate 20, the amount of triboelectric charge of the toner is increased, and the image density is improved. Therefore, it is suitable for coping with a shortage of toner charge in a high quality environment.

Now, the above-mentioned developing sleeve (developing roller)
Reference numeral 8 denotes a resin substrate layer 7 containing and dispersing at least graphite fine particles formed on the surface of the sleeve substrate 6 provided with the fine irregularities, that is, the rough surface. Magnetic toner 4
Is charged by the resin coating layer 7 to a polarity for developing a latent image. The contained graphite fine particles are exposed on the surface of the resin coating layer 7. Since graphite leaks excessive charge of the toner 4 and has excellent solid lubricating properties, it helps to reduce the adhesion of the fine powder toner to the developing sleeve 8.

As shown in FIG. 4, the surface of a metal cylinder made of aluminum, stainless steel, brass or the like is roughened by sandblasting, or as shown in FIG. A material different from graphite, preferably a fine powder of a hard inorganic material, is applied to a metal cylinder 6 ′ such as brass, and an adhesive force to a resin different from the binder resin of the resin coating layer 7, preferably to the metal constituting the cylinder. The resin coating layer 7 is formed by applying an intermediate layer 6 ″ dispersed in a resin stronger than the binder resin.

FIG. 4 is a partially enlarged sectional view of the developing sleeve 8 using the former sleeve base 6, and FIG. 5 is a partially enlarged sectional view of the developing sleeve 8 using the latter sleeve base 6. .

Hereinafter, description will be made in accordance with an embodiment of the present invention.

Example 1 As shown in FIG. 4, the surface of the developing sleeve substrate 6 was subjected to sandblasting with irregular-shaped abrasive grains (abrasive grains having an irregular shape and a plurality of sharp points). Forming a rough surface 10, forming a resin coating layer 7 on the rough surface 10,
Developing sleeve Nos. 2 to 4 according to the present invention were produced. The developing sleeve No. 1 for comparison did not perform sandblasting on the surface of the substrate 6 and did not form the rough surface 10.

A drawn pipe made of an aluminum alloy (3003) was used for the sleeve substrate 6, and sandblasting was performed with Alundum abrasive grains. A general blast air type sand blasting machine (Pneumatic blaster manufactured by Fuji Seisakusho) was used for blasting. The processing time was set to 60 seconds, and the sleeve substrate was rotated at a rotation speed of 20 rpm.

Table 1 shows the blasting conditions of the substrates of the developing sleeve Nos. 1 to 4 and the average surface roughness (Ra) after the blasting.

The average surface roughness (Ra) is measured according to JIS B
It indicates the center line average roughness defined in −0601, and is expressed in units of μm in this specification.

[0052]

[Table 1]

For the formation of the coating layer 7, a resin paint having the contents shown in Table 2 containing graphite fine particles and carbon black fine particles was used. Each part by weight shown in Table 2 was mixed, mixed with glass beads using a paint shaker and dispersed for 3 hours to obtain a paint. After adjusting the solid content of the paint to 25%, the surface of the sleeve substrate 6 was air-sprayed. To form a coating layer 7.

[0054]

[Table 2]

Table 3 shows the adhesion weight (coating amount) of the coating layer 7 of the developing sleeves Nos. 1 to 4 and the average surface roughness Ra of the coating layer in Table 3 as surface roughness (after). The average surface roughness Ra of the sleeve substrate shown in Table 1 is shown again in Table 3 as the surface roughness (before).

[0056]

[Table 3]

The above-described developing sleeve Nos. 1 to 4 were incorporated in the developing device of the image forming apparatus, and a copying experiment was performed.
The developing sleeve was evaluated.

The image forming apparatus used was a laser beam printer LBPSX manufactured by Canon Inc., and continuous 5000 copies were made in an environment where both temperature and humidity were normal. Table 4 shows the results.

[0059]

[Table 4]

The meaning of each mark in Table 4 is as follows. ◎ ：
Excellent: ○: Excellent, Δ: No practical problem, ×: Practical problem, XX: Unusable.

An analysis of the results obtained will be added below. The results shown in Table 4 are obtained for continuous copying of 5000 sheets in an environment where both temperature and humidity are low and an environment where both are high. Obtained similarly.

(A) Image Density When the developing sleeves Nos. 1 to 4 are compared, only the developing sleeve No. 1 of the comparative example has a low image density. This is because, in the developing sleeve Nos. 2 to 4 of the present invention, the rough surface 10 of fine irregularities having an appropriate roughness of 1.0 to 3.0 was formed on the surface of the sleeve substrate 6. This is because the surface of the coating layer 7 applied and formed on the rough surface 10 becomes a rough surface having an appropriate roughness. That is, in the developing sleeve Nos. 2 to 4,
This is because the toner conveying force on the sleeve surface was increased and the amount of toner coating on the sleeve surface was increased, while the surface roughness of the developing sleeve No. 1 was too small to be present.

Table 5 shows the Sm value of the developing sleeve surface (showing the average distance between irregularities on the resin layer surface) and the surface roughness (before).
(This is the surface roughness Ra of the sleeve base shown in Table 1.)

[0064]

[Table 5]

From the viewpoint of the average interval Sm value of the unevenness,
In order to increase the toner coating amount, as shown in Table 5, the appropriate Sm value on the developing sleeve surface is 30 to 70 μm.
m.

The mean spacing of the irregularities (mean spacing of pr
ofile irregularities) Sm is specified in section 6.4 of ISO 4287 / 1-1984.

(B) Ghost and density unevenness The ghost and density unevenness are at a level that is practically no problem in developing sleeves Nos. 1 to 4, and among these, developing sleeve No. 3 is particularly excellent. I understand. These prevent the above-mentioned coating layer from appropriately leaking the charge of the overcharged fine powder, and prevent the overcharged fine powder layer from being formed on the sleeve surface due to the good solid lubricity of graphite. Because.

(C) Peeling of Film While the developing sleeve No. 1 of the comparative example was remarkably peeled, the developing sleeves Nos. 2 to 4 of the present invention blasted the surface of the substrate 6 to a predetermined level. It is considered that the adhesion of the coating layer 7 to the substrate was improved due to the formation of the rough surface 10, and thus the coating did not peel off.

Although the case where the aluminum base is used as the developing sleeve base 6 has been described above, the invention is not limited to this.
As the substrate, a copper alloy, a stainless alloy or the like could be used. As described above, the roughness of the rough surface 10 on the surface of the substrate 6 is preferably 1.0 to 3.0 with the average surface roughness Ra, and was effective in this range.

The above shows that the surface roughness of the resin coating layer 7 formed on the rough surface 10 of the substrate 6 is excellent when the average surface roughness Ra is in the range of 1.2 to 2.4 μm. But,
According to the confirmation by the present inventors, Ra was 0.8 to 0.8.
It was effective in the range of 2.5 μm.

Example 2 As shown in FIG. 5, the surface of a cylindrical substrate 6 '(corresponding to the substrate of sleeve No. 1 shown in Table 1) made of an aluminum drawn material was roughened by blasting. Instead of directly forming the intermediate resin layer 6 ″ containing titanium oxide fine particles as a filler according to the formulation shown in Table 6, a sleeve substrate 6 is formed. The surface of the resin layer 6 ″ has a fine particle filler in the resin. The dispersion results in a rough surface 12 having fine irregularities. In each of Nos. 5 to 8, the coating amount of the intermediate resin layer was 4.08 g / m ² .

[0072]

[Table 6]

Then, a coating layer 7 was formed on the roughened surface 12 using a resin coating having the contents shown in Table 7 to obtain developing sleeve Nos. 5 to 8 of the present invention.

[0074]

[Table 7]

Table 8 shows developing sleeve Nos. 5 to 8.
In each of Nos. 5 to 8, the coating amount of the coating layer 7 was 8.0.
g / m ² .

[0076]

[Table 8]

The developing sleeve Nos. 5 to 8 described above were
As in the case of Example 1, a copy experiment was performed by incorporating the image forming apparatus into the developing device of the image forming apparatus, and the developing sleeve was evaluated. Table 9 shows the results.

[0078]

[Table 9]

[0079]

[0080]

In the case where the coating layer 7 is applied on the intermediate layer 6 ″ in this manner, as shown in the developing sleeve No. 8, good results can be obtained even when the average surface roughness Ra is 3.0 μm. This is probably because the rough surface shape of the coating layer 7 differs between the case of FIG. 4 and the case of FIG.

In any case, the average surface roughness Ra is 1.0
It can be seen that a sufficient toner conveying force and an appropriate toner triboelectric charge can be obtained in the range of from 3.0 to 3.0 μm. Further, from the viewpoint of the average interval Sm value of the unevenness, it can be seen that a good toner conveying force can be obtained when the Sm value is in the range of 40 to 70 μm.

In the example of FIG. 5, the binder resin (first resin) used for the resin layer 6 ″ containing the fine particle filler (titanium oxide in Table 6) as the base of the developing sleeve 8 is:
It is desirable that the adhesiveness to the aluminum substrate 6 'is stronger than the adhesiveness of the binder resin (second resin) of the coating layer 7 to the aluminum substrate 6'. Thereby, the coating layer 7 is less likely to be separated from the sleeve than when the coating layer 7 is directly applied to the base 6 '. The coating layer 7 and the intermediate layer 6 ″ are different from each other even if they are of different types, so that they are easily compatible with each other and have a strong adhesive force. Therefore, as compared with the case of FIG. Even if the roughness Ra is small, the coating layer 7 is hard to separate from the sleeve.

As described above, the improvement of the adhesive force to the metal base 6 'is shared by the first resin constituting the intermediate layer 6 ", and the second resin constituting the coating layer 7 has the second hardness. 1
Desirably, the hardness is higher than the hardness of the resin. This is to suppress wear of the coating layer 7.

In order to give the coating layer 7 an appropriate average surface roughness Ra, the volume average particle diameter of the fine particle filler (titanium oxide in Table 6) dispersed in the intermediate layer 6 ″ is determined by the graphite dispersed in the coating layer 7. It is preferably larger than the volume average particle size of the fine particles.

As shown in Table 6, the reason why carbon black fine particles are dispersed in the intermediate layer 6 ″ is that the addition of the carbon black fine particles disperses the carbon black fine particles more than the case where only the fine particle filler is dispersed. The electric resistance can be reduced, so that the excessively charged electric charge of the toner flowing from the coating layer 7 can be easily flown to the metal substrate 6 ', and the effect of the developing bias voltage can be easily exerted.

Since the fine particle filler such as the above-mentioned titanium oxide mainly contributes to the surface roughening of the intermediate layer 6 ″, the carbon black fine particles dispersed in the intermediate layer 6 ″ have a more average particle size than the above fine particle filler. Is preferably smaller.

Instead of titanium oxide, silica, potassium titanate, barium titanate, or the like can be used as the fine particle filler for the intermediate layer 6 ″. A good result is obtained when the coating amount of the intermediate layer 6 ″ on the metal cylinder 6 ′ is ² to 8 g / m ² .

4 and 5, the resin coating layer 7 contains graphite fine particles and carbon black fine particles (the carbon black contributes to the effective leakage of the overcharged portion of the toner 4). However, it was effective to include at least graphite fine particles. The volume average particle size of graphite is suitably from 0.5 to 15 μm. Volume average particle size of carbon black is 5 to 300 mμ
Was appropriate.

Since graphite also utilizes its solid lubricity, it is preferable that graphite has an average particle size larger than that of carbon black. The ratio (weight ratio) of the resin of the coating layer 7 to graphite and carbon black, that is, resin / {(graphite) + (carbon black)} is 1/1 to 3/1.
The range was excellent.

The amount of the resin coating layer 7 attached was 8.0 mg / m 2.
^Although the case of ² was shown, the range of 4 to 12 mg / m ² shows good results.

In each of the above examples, a phenol resin was used as the resin binder for the coating layer 7, but other than that, epoxy, melamine, polyamide, silicone, polytetrafluoroethylene, polyvinyl chloride, polycarbonate, polystyrene, polymethacrylate, etc. And other resins could be used.

In the example of FIG. 5, as the binder resin used for the intermediate layer 6 ″, in addition to the polyester resin shown in Table 6,
Phenol resin, Teflon resin, epoxy resin, melamine resin, urea resin can be used. This middle layer 6 ″
It is preferable to select a resin that satisfies the above-described characteristics in relation to the resin of the coating layer 7. The intermediate layer 6 ″
When carbon black fine particles are further dispersed in addition to the above-mentioned fine particle filler, the volume average particle diameter of the carbon black fine particles is suitably from 5 to 300 μm as described above.

The weight ratio of the resin to the fine particle filler and the carbon black in the intermediate layer, that is, (resin) / {(fine particle filler) + (carbon black)} is 1/5 to
It was excellent at 3/1.

The present invention can be applied to a developing device using a one-component non-magnetic developer. In that case, the magnet 5 is unnecessary in the examples of FIGS.

Since the present invention has a remarkable ghost preventing effect, it is suitable for a developing apparatus using a one-component developer containing a small particle size toner having a volume average particle size of 4 to 9 μm. To develop an electrostatic latent image using developer particles frictionally charged on the surface of a developing sleeve (developing roller), the minimum gap in the developing section between the developing sleeve and the image carrier is 50 to 5 mm.
00 μm is appropriate.

[0097]

As described above, the developing roller of the developing device according to the present invention has an average surface roughness Ra of 1.0 to 3.0.
A resin layer is provided on a substrate having a thickness of 0 μm, the average surface roughness Ra of the resin layer is 0.8 to 2.5 μm, and the average interval Sm of irregularities on the surface of the resin layer is 30 to 70 μm. (1) Even if a small particle size toner is used as a one-component developer, a good image free from density reduction, density unevenness and ghost can be obtained for a long period of time. (2) Since the resin layer is applied to the rough surface of the base, the resin layer strongly adheres to the base to prevent deterioration, peeling, scratches, etc. of the resin coating layer, thereby extending the life of the developing roller. Can be. Further, (3) by applying the resin layer to the rough surface of the base, an appropriate surface roughness can be obtained at the time when the resin layer is provided on the base, and a special post-process for roughening the surface is required. do not do. Such an effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a developing device of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the developing device of the present invention.

FIG. 3 is a configuration diagram showing still another embodiment of the developing device of the present invention.

FIG. 4 is a partially enlarged sectional view of a developing sleeve in the developing device of the present invention.

FIG. 5 is a partially enlarged sectional view of another example of the developing sleeve in the developing device of the present invention.

FIG. 6 is an explanatory diagram of a ghost phenomenon.

[Explanation of symbols]

 2 Regulator blade 4 Toner 6 Sleeve base 6 'Metal base 6 "Intermediate layer 7 Resin coating layer 8 Developing sleeve 10 Rough surface 12 Rough surface 20 Elastic plate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-73275 (JP, A) JP-A-47-13088 (JP, A) JP-A-58-57164 (JP, A) JP-A-62 70879 (JP, A) JP-A-57-181569 (JP, A) JP-A-61-138261 (JP, A) JP-A-1-276174 (JP, A) JP-A-2-105181 (JP, A) JP-A-2-105183 (JP, A) JP-A-2-10971 (JP, A) JP-A-1-103857 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08-15/095

Claims (6)

(57) [Claims] 1. An average surface roughness Ra of 1.0 to 3.0 μm.
In the developing roller having a resin layer on the substrate, the average surface roughness Ra of the resin layer is 0.8 to 2.5 μm, and the average interval Sm of the irregularities on the surface of the resin layer is 30 to 7
A developing roller having a thickness of 0 μm. 2. The resin layer has a volume average particle size of 0.5 to
2. The developing roller according to claim 1, comprising 15 [mu] m graphite particles. 3. The adhesion amount of the resin layer on the base is:
The developing roller according to claim 1, wherein the developing roller has a weight of 4 to 12 g / m ² . 4. The developing roller according to claim 2, wherein carbon black particles are further dispersed in said resin layer. 5. The developing roller according to claim 1, wherein the substrate is subjected to sandblasting using irregular-shaped abrasive grains. 6. A developing device comprising the developing roller according to claim 1. Description: