JPH05150630A - Developing device and developer carrying member - Google Patents

Abstract

PURPOSE:To prevent the generation of ghost phenomenon and to obtain developed images homogeneous in a longitudinal direction by forming the developer carrying member having a coating layer consisting of graphite particulates dispersed in a resin and setting the triboelectrifying power of the coating layer to a developer higher in the central part than at the end in the longitudinal direction of the developer carrying member. CONSTITUTION:The resin coating layer 10 contg. at least the crystalline graphite is formed as conductive particulates on the surface of a developing sleeve 2 as the developer carrying member. A cylindrical pipe 9 consisting of aluminum or stainless steel, etc., is used for the base body of the developing sleeve 2 coated with the coating layer 10. The content ratio of the conductive particulates in the coating layer 10 is varied in the central part U and end parts V, W of the sleeve 2 in order to increase the triboelectrifying power to the toner in the central part U than at the ends V, W of the sleeve 2. Or the polishing treatment of the coating layer 10 is varied between the central part U and end parts V, W of the sleeve 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for developing an electrostatic latent image formed on an image bearing member, and a developing device used in such a developing device for carrying a developer and transporting it to a developing area. The present invention relates to an agent carrying member.

[0002]

2. Description of the Related Art Conventionally, for example, a developing device for developing an electrostatic latent image formed on the surface of an electrophotographic photosensitive drum as an image carrier with a magnetic toner of a one-component developer has a developing sleeve as a developer carrier. By the friction of the magnetic toner particles,
An electrostatic image charge on the photosensitive drum and a charge having a polarity opposite to that of the development reference potential are applied to the magnetic toner particles, and this magnetic toner is applied extremely thinly on the developing sleeve to form a developing area where the photosensitive drum and the developing sleeve face each other. It is known that the toner is transported, and the magnetic toner flies and adheres to the electrostatic latent image on the surface of the photosensitive drum in the developing area to develop the electrostatic latent image as a toner image.

By the way, in such a developing device,
When a different pattern is developed after continuously developing an image with many white backgrounds, the history of the previous image appears in the later image. Such a phenomenon is called a ghost phenomenon, which occurs for the following reason.

That is, if the white background is continuous, the toner on the sleeve is not consumed, and the layer of finely charged toner that is excessively charged is electrostatically strongly adsorbed on the surface of the sleeve. This fine powder toner layer is less likely to transfer to the photosensitive drum, and hinders the triboelectric charging of the fresh toner supplied on this layer with the sleeve. Therefore, if a black image is to be formed after the white background is continuous, only a low-density black image can be obtained. This is considered to be the reason why the ghost phenomenon occurs. And such a ghost phenomenon is likely to occur particularly in a low humidity environment in which the toner is liable to be triboelectrically charged. Developing devices for preventing such a ghost phenomenon are disclosed in JP-A-1-276174 and 1-27726.
5, No. 2-176682. In this prior art, a sleeve is provided with an outer coat layer in which graphite fine particles are dispersed in a resin. The graphite fine particles allow the electric charge of the overcharged fine powder toner to flow out, and have high solid lubricity, so that the adsorption force of the fine powder toner to the sleeve is weakened. As a result, the formation of the fine powder toner layer as described above was prevented, and the occurrence of the ghost phenomenon could be suppressed.

However, in the above prior art device, a problem different from the ghost phenomenon has occurred.

That is, there is a slight difference in the image density between the central portion and the end portion in the longitudinal direction of the sleeve. Therefore, when the charge amount of the toner layer on the sleeve was measured, the charge amount of the toner was different between the end portion and the central portion in the sleeve longitudinal direction.

The reason for this is that, on the end side of the sleeve, the toner is subjected to the resistance by the side wall of the container, and the flow velocity becomes smaller than that of the central part of the sleeve, and as a result, the toner on the end side of the sleeve becomes more vigorous in the central part of the sleeve. It is presumed that this is because the contact time between the toner and the sleeve becomes long, and the triboelectric charge of the toner becomes larger at the end portion than at the central portion.

In any case, since the excessively charged toner adheres to the sleeve by a strong electrostatic mirror image force, it becomes difficult to transfer to the photosensitive member. Further, the toner newly supplied onto the toner layer becomes difficult to obtain the triboelectric charge necessary for development.

In some cases, due to the formation of the above-mentioned overcharged toner layer, the layer thickness of the toner at the end portion of the sleeve becomes excessively thick, resulting in black spots at the end portion of the developed image.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a developing device capable of preventing the occurrence of the above-mentioned ghost phenomenon and forming a developed image of good image quality at both the central portion and the end portion, and a developer carrying agent used therein. It is to provide a member.

[0011]

In the present invention, the developer carrying member used in the developing device has a coating layer in which fine graphite particles are dispersed in resin. The coating layer triboelectrically charges the developer, and its triboelectric charge imparting ability is higher in the central portion in the longitudinal direction of the developer carrying member than in the end portions in the longitudinal direction.

As described above, since the fine particles of graphite are contained in the coating layer of the developer carrying member, this causes the charges of the overcharged fine powder toner to flow out. Further, the solid lubricity of the graphite fine particles mechanically relaxes the adhesion of the fine powder toner to the developer carrying member. In this way, the occurrence of the ghost phenomenon is suppressed.

Further, with respect to the longitudinal direction of the developer carrying member, the triboelectric charge imparting ability of the coating layer is lower at the end portions than at the central portion, so that the developer at the end portions can be prevented from being triboelectrically charged more than necessary. .. Therefore, it is possible to form a developed image that is uniform in both the end portion and the central portion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 is an electrophotographic photosensitive drum as an image bearing member that carries an electrostatic latent image and rotates in the direction of arrow A. The photosensitive drum 1 may have an insulating layer on its surface. Alternatively, both can be used even if they do not have them. Of course, instead of the photosensitive drum 1, a sheet-shaped or belt-shaped image carrier can be used.

The photosensitive drum 1 is uniformly charged with, for example, a negative polarity by a charger (not shown), and then scanned with a laser beam modulated according to an image information signal, whereby a negative electrostatic latent image is formed. .. Image information light may be exposed to the photosensitive drum 1 by an LED array or the like instead of the laser beam.

In the developing area 7, the electrostatic latent image is reversely developed by the developing device D using the magnetic toner negatively charged by friction.

In the developing device D, a developing sleeve 2 as a developer carrying member is provided so as to face the photosensitive drum 1 in an opening portion of the developing container 4 containing the magnetic toner 5 as a one-component developer, the opening facing the photosensitive drum 1. Is equipped with.

The developing sleeve 2 carries the toner 5 in the container 4 on its surface, rotates in the direction of arrow B, and conveys the sleeve 2 to the developing area facing the photosensitive drum 1. The toner 5 carried on the developing sleeve 2 is located at a position facing the magnetic pole N ₁ of the plurality of magnetic poles of the permanent magnet 3 immovably arranged in the sleeve 2 through the sleeve 2.
A doctor blade 6 made of a magnetic material as a developer layer thickness regulating member that regulates the layer thickness to a predetermined thickness is provided with a predetermined gap from the developing sleeve 2. The magnetic field from the magnetic pole N ₁ is concentrated on the blade 6. In this embodiment, the gap between the doctor blade 6 and the developing sleeve 2 is about 50 μm.
It is set to ˜500 μm.

The present developing device has the above-described structure, and when the developing sleeve 2 is rotated in the direction of the arrow B by starting, the developing container 4
The toner 5 in the inside is rubbed against the surface of the developing sleeve 2,
An electric charge of a polarity for developing the electrostatic latent image is given to the toner 5,
It is applied to the surface of the developing sleeve 2. The layer of toner 5 applied to the surface of the developing sleeve is uniform and about 30 μm to 3 μm due to the magnetic field between the magnetic pole N _{1 of the} magnet 3 and the doctor blade 6.
The toner thin layer 5 ′ having a layer thickness of 00 μm is regulated. As described above, the toner 5 is conveyed as a thin toner layer 5'to the developing area 7 as the developing sleeve 2 rotates, and is used for developing the electrostatic latent image formed on the surface of the photosensitive drum 1. It Toner adheres to the light potential region of this latent image. The thickness of the toner layer 5 ′ is thinner than the minimum gap (for example, 50 to 500 μm) between the photosensitive drum 1 and the developing sleeve 2 in the developing area 7, and so-called non-contact development is performed.

An oscillating bias voltage, which is a direct current voltage superimposed on an alternating voltage, is applied to the developing sleeve 2 from an electric power source 8 to form an oscillating electric field in the developing area 7. The oscillating electric field accelerates the flight of toner from the sleeve 2 to the drum 1 to obtain a high-density image without fog.

According to the present invention, a resin coating layer 10 containing at least crystalline graphite as conductive fine particles is formed on the surface of the developing sleeve 2 in a thickness of 0.5 to 30 μm, as described later. Has been done. A cylindrical tube 9 made of aluminum, stainless steel, or the like is used as the base of the developing sleeve 2 to which the coating layer 10 is applied.

As the conductive fine particles, only crystalline graphite fine particles or amorphous carbon fine particles and crystalline graphite fine particles are used. The crystalline graphite that can be used in the present invention is roughly classified into natural graphite and artificial graphite. Artificial graphite was obtained by solidifying pitch coke with tar pitch or the like, firing it once at about 1200 ° C, and then placing it in a graphitization furnace and treating it at a high temperature of about 2300 ° C, whereby carbon crystals grew and changed to graphite. It is a thing. Natural graphite is completely graphitized by geothermal heat and underground high pressure for a long time, and is produced from the ground. These graphites are dark gray to black luster, very soft carbon crystals with smoothness, and their crystal structure belongs to hexagonal system and rhombohedral system, and has a complete layered structure. ing. As for electrical characteristics, free electrons exist between carbon-carbon bonds, making it a good conductor of electricity. In the present invention, both natural and artificial graphite can be used, but the average particle size of the graphite used is 0.5 μm to 20 μm.
About m is preferable.

Conductive amorphous carbon can be used as the carbon fine particles. Conductive amorphous carbon is generally defined as "an aggregate of crystallites formed by burning or thermally decomposing a hydrocarbon or a compound containing carbon in a state where an air supply is insufficient." The conductive amorphous carbon used in the present invention preferably has an average particle diameter of 10 m-80 m, more preferably 15-40 m.

Examples of the binder resin material in which the conductive fine particles are dispersedly contained include, for example, styrene resin, vinyl resin, polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin,
Thermoplastic resin such as fluororesin, fibrin resin, acrylic resin, epoxy resin, polyester resin, alkyd resin, phenol resin, melamine resin, polyurethane resin, urea resin, silicone resin, polyimide resin, or the like. A photocurable resin or the like can be used. Among them, those having releasability such as silicone resin and fluorine resin, or mechanical such as polyether sulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, phenol resin, polyester resin, polyurethane resin, styrene resin. Those having excellent properties are more preferable.

Next, the toner as a one-component developer usable in the present invention will be described.

As the binder resin for the toner, generally known resins can be used. For example, styrenes such as styrene, a-methylstyrene and p-chlorostyrene and their substitution products; acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid. Monocarboxylic acids having double bonds such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, acrylamide, etc. ;
For example, a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like, and its substitution products; for example, vinyls such as vinyl chloride, vinyl acetate, vinyl benzoate or vinyl esters. Or a polymer using vinyl monomers such as vinyl ethers such as vinyl ethyl ether, vinyl methyl ether, vinyl isobutyl ether, etc., or a copolymer using two or more kinds thereof; and further styrene- Butadiene copolymer, silicone resin, polyester resin,
Polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, etc .; these may be used alone or in combination of two or more. It can be used in combination.

Further, the toner may contain a pigment. For example, carbon black, nigrosine dye, lamp black, Sudan Black SM, First Yellow G, Benzidine Yellow, Pigment Yellow, India First Orange, Irgadine Red, Baranitroaniline Red, Toluidine Red, Carmine FB, Permanent Bordeaux FRR, Pigment
Orange R, Resor Red 2G, Lake Red C, Rhodamine FB, Rhodamine B Lake, Methyl Violet B Lake, Phthalocyanine Blue, Pigment Blue, Brilliant Green B, Phthalocyanine Green, Oil Yellow GG, Zapon First Yellow CGG, Kayaset Y963, Kayaset YG, Sumiplast Yellow GG, Zapon Fast Orange RR, Oil Scarlet, Sumiplast Orange G, Orazol Brown B, Zapon Fast Scarlet CG, Eisenspiron Red BE
H, oil pink OP, etc. can be applied.

In order to use the toner as a magnetic toner, magnetic powder is contained in the toner. Examples of such magnetic powder include powders of ferromagnetic metals such as iron, cobalt and nickel, and alloys and compounds such as magnetite, hematite and ferrite. The content of the magnetic powder is preferably about 15 to 70% by weight based on the weight of the toner.

Various releasing agents may be used in the toner. Examples of such releasing agents include polyfluorinated ethylene,
Examples thereof include fluororesins, fluorocarbon oils, silicone oils, low molecular weight polyethylenes and low molecular weight polypropylenes. A charge control agent may be added, if necessary, in order to facilitate positive charging or negative charging of the toner.

Materials such as these toner binder resins are mixed and kneaded by various methods, and then finely divided to obtain a toner having a desired particle size. If necessary, colloidal silica or the like is mixed with the obtained toner by external addition, and thus used as a developer.

As described above, since the sleeve 2 is coated with the resin layer 10 containing the graphite fine particles dispersed therein, a part of the charges of the overcharged fine particle toner is removed through the graphite fine particles. Further, due to the lubricating action of the graphite fine particles exposed on the surface of the layer 10, the adhesion of the fine powder toner to the sleeve surface is reduced. In this way, the occurrence of the above-mentioned ghost phenomenon is prevented.

The amorphous carbon fine particles are also included in the layer 10.
In the case where the fine particles are dispersed inside, the amorphous carbon fine particles also contribute to the removal of a part of the electric charge of the overcharged fine particle toner.

By the way, as described above, at the longitudinal end of the sleeve, the toner is more triboelectrically charged than at the center. Therefore, in order to increase the triboelectrification imparting ability for toner at the central portion of the sleeve rather than at the end portions thereof, in the following examples, the conductive particles are contained in the coating layer 10 at the central portion and the end portion of the sleeve 2. The ratio is made different, or the polishing treatment of the coating layer 10 is made different between the central portion and the end portion of the sleeve 2. In this way, the triboelectric charge imparting ability at the sleeve end is made smaller than at the sleeve central portion. This allows the toner on the sleeve to be imparted with a substantially uniform triboelectric charge over the length of the sleeve.

By the way, even in the longitudinal center portion of the sleeve, there arises a problem that a low density portion is formed in the form of vertical stripes on the image obtained by development. That is, it is a phenomenon in which characters become thin in a character image and density becomes low in a halftone image or a solid black image.

This phenomenon is named fading phenomenon. When the sleeve was observed when this fading phenomenon occurred, a toner layer having a uniform thickness was formed on the sleeve. However, when the triboelectric charge amount of the toner on the sleeve was measured, it was found that the charge amount of the toner in the area corresponding to the low-density vertical stripes in the image was lower than the normal value.

Although the reason why the toner charge amount is partially reduced as described above is not clear, it is not because the fluidity of the toner in the toner accumulation area adjacent to the sleeve in the developing device is partially deteriorated. It is guessed that.

In any case, the low-charged toner also passes through the developer layer thickness regulating portion as a layer having the same thickness as the normally-charged toner layer due to the frictional force with the sleeve. Therefore, the thickness of the toner layer is uniform on the sleeve.

The fading phenomenon is likely to occur in a high temperature and high humidity environment where the triboelectric charge of the toner tends to decrease.

Therefore, in a preferred aspect of the present invention, the slope (γ) of the work function measurement curve on the surface of the coating layer at the central portion of the sleeve is larger than 10 (cps / eV). This gradient γ corresponds to the quantum efficiency and the ability to impart triboelectric charge to the developer. When the inclination γ is 10 (cps / eV) or more, it is possible to impart good triboelectrification to the developer.

On the other hand, the slope γ corresponds to the exposure rate of the graphite fine particles on the surface of the coating layer, and thus to the degree of solid lubricity of the surface of the coating layer. Therefore, the inclination γ is 1
When it is 0 (cps / eV) or more, the developer particles become considerably slippery on the surface of the developer carrying member. Therefore, the low-charged developer cannot pass through the regulation member, and the normally frictionally charged developer adheres to the developer carrying member by electrostatic mirror image force and can pass through the regulation member.

Therefore, a uniform developer layer that is favorably triboelectrically charged is formed on the developer carrying member, and the fading phenomenon can be prevented even in an environment of high temperature and high humidity.

It also contributes to the stability of the density of the developed image during continuous printing on a large number of sheets.

In any case, at the central portion in the longitudinal direction, the friction on the surface of the developing sleeve is made small to increase the sliding property, so that the low-charge toner having a weak electrostatic adhesion to the sleeve is rubbed on the surface of the sleeve. Depending on the force, the concentrated magnetic field between the blade 6 and the magnet 3 (magnetic field curtain)
Of the normally charged toner having a suitable electrostatic adhesion force to the sleeve is allowed to pass through the concentrated magnetic field.

In the present specification, the work function which defines the slope γ is defined as the minimum energy required to extract one electron from the surface of a substance to the outside of the surface. For measuring work function, optoelectronic measuring device AC manufactured by Riken Keiki Co., Ltd.
-1 can be used. The characteristic of this measuring instrument AC-1 is that the work function of the surface of the developing sleeve 2 can be easily measured in the atmosphere. The present inventors have found that the work function measured by the measuring instrument AC-1 is the Kelvin method (contact potential method) (IBM, J. RES. DEVELOP22, 1).
It has been confirmed that the values are almost the same as the literature values of (978).

The work function measurement curve obtained by the measurement with the measuring instrument AC-1 is shown in FIG. In FIG. 2, the horizontal axis represents excitation energy [eV], and the vertical axis represents the number (yield) [cps] (counts per second) of emitted photoelectrons. In general, the emission of photoelectrons rapidly increases from a certain value and the measurement curve rises rapidly, and the point of the rise is defined as the work function value Wf. Further, the degree of photoelectron emission thereafter (on the right side of the point Wf) is defined by the slope γ of the measurement curve which is approximated by the straight line l.

In the above measurement, a sodium lamp was used as the measurement light source, and the emission intensity was 500 nW.
Is.

The embodiments of the present invention will be described in more detail below.

The raw materials of the magnetic toner as the one-component developer used in this embodiment are as follows.

Styrene-butyl acrylate-maleic acid n-butyl half ester copolymer 100 parts by weight Magnetite 55 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 kneaded, then pulverized and classified to have a weight average particle diameter of 12.2 μm and a particle diameter of 6.35 μm.
The number of m or less was adjusted to 23% by number% and the particle size of 20.2 μm or more was adjusted to 1.7% by weight to use as a magnetic toner.

A commercially available laser beam printer LBP-SX (manufactured by Canon Inc.) for evaluation by image formation.
Was remodeled and used. An output device capable of obtaining a plurality of types of image patterns was attached to this. Printer L
A commercially available cartridge for LBP-SX was used as a process cartridge (a photosensitive drum, a charger, a developing device, and a cleaner are integrally supported by a frame) used for BP-SX. A flange was attached to the end of the developing sleeve so that the following developing sleeve could be attached to the above cartridge. Image formation test is 15 ℃
It was carried out in two levels of environment of 10% RH, 32 ° C. and 85% RH.

The developing sleeve of Example 1 was rubbed against the toner at the center and both ends in the longitudinal direction of the sleeve due to the difference in the composition of the film-forming resin liquid used for forming the resin film layer 10 on the surface and the prescription regarding the diluting solvent. The charge imparting ability was controlled. As the film forming resin liquid, two kinds of A and B having the following formulations were used.

(Film forming resin liquid A) Phenolic resin (binder resin) 60 parts by weight Graphite 27 parts by weight Carbon black (amorphous carbon) 3 parts by weight Isopropanol + butanol (1: 1) mixed solvent 4
00 parts by weight (coating solution B) Phenol resin 60 parts by weight Graphite 54 parts by weight Carbon black 6 parts by weight Methyl ethyl ketone + toluene (1: 1) mixed solvent 4
00 parts by weight

The raw materials of the film forming resin solutions A and B were dispersed to a certain condition using a sand mill.
These film forming resin solutions A and B are aluminum cylindrical tubes (L
It can be attached to a BP-SX cartridge) with a spray gun. Application with the developing sleeve of Example 1 is shown in FIG.
Was performed as shown in FIG.

That is, the central area U in the longitudinal direction of the sleeve 2 is masked, and the resin liquid A is applied to both end areas V and W in the longitudinal direction of the sleeve 2 (the length in the longitudinal direction of the sleeve is about 20 mm, respectively). Spray applied.
Next, the both end regions V and W were masked, and the resin liquid B was spray-coated on the central region U. Then, after spray-coating both solutions, the phenol resin in the film-forming resin solutions A and B was heated and cured by standing in a constant temperature bath at 160 ° C. for 20 minutes. As a result, the central portion U of the resin coating layer 10 in the longitudinal direction of the sleeve is formed with the coating-forming resin liquid A to a film thickness of 10 μm,
Both ends V and W were formed with a film-forming resin solution B to a film thickness of 10 μm, and thus the developing sleeve of Example 1 was obtained.

The graphite content in the central portion U is
It is higher than both ends V and W.

On the other hand, in the developing sleeve of Comparative Example 1, the film forming resin liquid A was applied to the regions U, V and W, and 160
It was obtained by heating and curing at 20 ° C. for 20 minutes to form the entire resin film layer 10 with the resin liquid A to a film thickness of 10 μm. Similarly, in the developing sleeve of Comparative Example 2, the film forming resin solution B was applied to the regions U, V and W, and the resin film B was heated and cured at 160 ° C. for 20 minutes in the same manner to completely remove the resin film layer 10 from the resin solution. B film thickness of 10 μm
It was obtained by forming into.

These developing sleeves were subjected to development as described above, and images were formed by the development sleeves, and evaluation tests by image formation were conducted. Also, the slope γ [cps / eV] of the work function measurement curve of the developing sleeve central portion U and both end portions V and W
Was measured. The results obtained are shown in Table 1.

[0059]

[Table 1]

In Table 1, the image density shows the variation in the image density during continuous copying of a large number of sheets, and the measurement was made by observing the value of the solid black portion (5 mm square) with a Macbeth reflection densitometer. Regarding evaluation of charge-up and fading, ⊚ mark is very good, ∘ mark is good, and Δ mark is slightly inferior, but shows a practical level. These symbols are also common to the following Tables 2-4. Further, in Table 2, the first mark □ indicates that the image is visible but the density is low and below the practical level, and in Table 3, the first mark x indicates that it is very bad and not acceptable.

As shown in Table 1, in Example 1, the slope γ of the work function measurement curve on the surface of the developing sleeve was 10 or less at 6.5 and 7.0 at both ends of the sleeve (left V, right W). Lower than this, 1 in the central part (U), like 25
Since it is higher than 0, the triboelectric charge imparting ability to the toner is low at both end portions of the sleeve and high at the center portion. As a result, excessive charge up of the toner occurs in a low humidity environment of 15 ° C. and 10% RH. The image density was as high as 1.2 to 1.4. Even in a high humidity environment of 32 ° C. and 85% RH, the image had no fading and was very good, and the image density was as high as 1.1 to 1.3. All items have excellent results.

On the other hand, in Comparative Example 1, since the inclination γ of the work function measurement curve on the surface of the developing sleeve was lowered to 10 or less at both end portions and the central portion of the sleeve such as 7.0 to 7.5, 32 In a high humidity environment of 85 ° C. and 85% RH, the fading term was slightly inferior, and the image density was as low as 0.8 to 1.1. In Comparative Example 2, the slope γ of the work function measurement curve on the surface of the developing sleeve is 10 at both end portions and the central portion of the sleeve, as in 23 to 26.
Since the temperature is increased above, in a low humidity environment of 15 ° C. and 10% RH, the term of charge-up is slightly inferior, and the image density is as low as 0.8 to 1.3 and the eye value appears. became.

From the above, it is possible to prevent fading, particularly fading in a high temperature and high humidity environment, and to prevent sleeve ghost (particularly due to excessive charge-up of toner in a low humidity environment). In order to obtain a uniform image by development, the ability of the developing sleeve to impart triboelectric charge to the toner is reduced at both ends of the sleeve (the slope γ of the work function measuring curve on the surface of the developing sleeve is 10 or less, particularly preferably 11). It is understood that the height is made higher (in the above-mentioned inclination γ, it is larger than 10, and particularly preferably larger than 20) in the central portion of the sleeve.

In FIG. 3, reference numerals 41 and 42 denote left and right side walls of the container 4 containing the toner 5, and the sleeve 2 is rotatably supported by the side walls 41 and 42. Sleeve 2
Rotates by transmitting the driving force to the gear 21 fixed to it.

In addition to the film forming resin solution A, film forming resin solutions C, D, E and F having the following formulations were prepared and used. The developing sleeve 2 shown in FIG.
To the central portion U and both end portions V and W of the same, as shown in Table 2, are appropriately used and coated to prepare a developing sleeve having a resin coating layer 10 containing graphite.
It was set to ~ 6. However, the areas of both ends V and W are each 15 mm
And Then, image formation was performed in the same manner as in Example 1, and an evaluation test by image formation was performed.

(Film forming resin liquid C) Phenolic resin 60 parts by weight Graphite 56 parts by weight Carbon black 4 parts by weight Methyl alcohol + methyl cellosolve 200 parts by weight (Film forming resin liquid D) Phenolic resin 60 parts by weight Graphite 84 parts by weight Carbon Black 6 parts by weight Methyl alcohol + methyl cellosolve 250 parts by weight (coating solution E) Phenol resin 60 parts by weight Graphite resin 28 parts by weight Carbon black 2 parts by weight Methyl alcohol + methyl cellosolve 200 parts by weight (coating resin solution) F) Phenolic resin 60 parts by weight Graphite 54 parts by weight Carbon black 6 parts by weight Isopropanol + methyl ethyl ketone 200 parts by weight

Table 2 shows the results of the evaluation test by image formation and the measurement results of the slope γ of the work function measurement curve. The meanings of the symbols in Table 2 are as described above.

[0068]

[Table 2]

As shown in Table 2, in Examples 2 to 6, the slope γ of the work function measurement curve on the surface of the developing sleeve was 6.5 to 10.5 at both ends of the sleeve (left V, right W). It is low (the content ratio of graphite is small) and is high like 23 to 31 in the central portion (U) (the content ratio of graphite is large), and the triboelectric charge imparting ability to the toner is low at both ends of the sleeve. Since it is high in the central portion, as in the case of Example 1, excessive charge-up and image density of the toner in a low humidity environment of 15 ° C. and 10% RH, and image formation in a high humidity environment of 32 ° C. and 85% RH. Excellent results were obtained for both fading and image density.

On the other hand, in Comparative Examples 3 to 5, the slope γ of the work function measurement curve on the surface of the developing sleeve is as high as 10 or more at both end portions and the central portion of the sleeve, or conversely as low as 10 or less. Therefore, toner charge-up and image density in a low humidity environment of 15 ° C. and 10% RH, or fading in a high humidity environment of 32 ° C. and 85% RH, image density is slightly inferior. The result was.

In any of the developing sleeves of Examples 1 to 6 described above, there is a concern that the influence of the boundaries between the sleeve ends V and W of the surface resin coating layer and the central portion U may appear in the developed image. However, a detailed examination of the image did not show any such effect on the image.

In the above embodiments, the developing sleeve 2
By changing the composition of the resin coating layer 10 on the surface between the both ends and the central portion of the sleeve, the triboelectric charge imparting ability to the toner is set to be low at both ends of the sleeve and high at the central portion. By polishing the surface of the developing sleeve 2 after the formation, the above-mentioned triboelectric charge imparting ability can be set. In this case, the same resin liquid may be applied to the regions U, V and W. In any case, since the amount of graphite exposed on the surface of the coating layer can be adjusted by adjusting the amount of polishing for the coating layer, it is possible to adjust the triboelectric charge imparting ability and the lubricity of the toner.

The above polishing process can be carried out by rubbing a resin layer containing graphite fine particles, which has been coated on a sleeve substrate and dried, with a polishing member such as felt, woven cloth or paper which does not contain abrasive grains. preferable.

An example of the polishing method will be shown below.

The polishing material used for polishing was 100% wool manufactured by Hayashi Felt Co., Ltd., standard density 0.34 g / cm ^2.
The HW felt had a width of 40 mm, a length of 200 mm, and a thickness of 3 mm.

FIG. 4 shows the resin coating layer 1 on the surface of the developing sleeve 2.
1 is a schematic view showing a surface polishing apparatus capable of easily exposing crystalline graphite contained in 0. As shown in the figure, the developing sleeve 2 is in a vertical posture, the upper and lower ends thereof are fixed by the main shaft 12, and is rotated via the main shaft 12 by a driving device (not shown). A belt-shaped abrasive felt 13 fixed to a holder 14 is wound around the developing sleeve 2 and pulled in the direction of arrow a. The load measuring device 1 in which the tensile load at that time is directly connected to the holder 14.
5 is measured. The load measuring device 15 is provided on a feed base 16 which supports the load measuring device 15 and is movable together with the felt 13 in the longitudinal direction b of the developing sleeve 2.

Both ends of the developing sleeve 2 are fixed by the main shaft 12, and the developing sleeve 2 is rotated at a constant speed. However, the felt 13 is initially the resin coating layer 1 of the developing sleeve 2.
The felt 13 should not come into contact with the surface on which 0 is formed, and the felt 13 is located at the upper or lower end of the developing sleeve 2. Next, while the felt 13 is pulled by the load measuring device 15 through the holder 14 to which the felt 13 is fixed with a predetermined constant load, the feed base 16 is sent to the upper or lower side of the developing sleeve 2 at a certain constant speed, thereby developing Sleeve 2
The felt was brought into contact with the surface and the surface was polished while applying pressure to expose the crystalline graphite contained in the coating layer 10 on the surface of the developing sleeve 2.

FIG. 5A is an arbitrary sectional view of the surface of the developing sleeve 2 before polishing, and FIG. 5B is a similar sectional view after polishing. Binder resin 1 as shown in FIG.
8 and a resin coating layer 10 made of crystalline graphite 19
When the felt 3 comes into pressure contact with the surface of the coating layer 10, the surface layer of the coating layer 10 is crushed by the pressure and a force is applied in the shearing direction, so that shear fracture occurs, and as shown in FIG. The crystal of the graphite 19 covered with the thin film of the binder resin 18 is exposed, and the crystal plane 20 appears on the surface. At this time, the degree of exposure of the graphite 19 can be arbitrarily controlled by controlling the pressure of the felt 13. Further, by setting the width of the felt 13 to an arbitrary length, the degree of exposure of the graphite 19 can be similarly controlled. This coating layer 10
The binder resin 18 and the crystalline graphite 19 (or conductive amorphous carbon and the like if the coating layer 10 contains conductive amorphous carbon or the like) inside is peeled from the coating layer 10 by polishing, and thus the surface of the felt 13 is soft. It is gradually absorbed into the developing sleeve 2 and does not adhere to the surface of the developing sleeve 2 as a residue. Therefore, the surface of the developing sleeve 2 can be cleaned and polished.

Here, by controlling the polishing treatment amount of the coating layer, it is possible to control the exposure amount of graphite, and thus the inclination γ. The polishing amount is any one of the contact pressure of the polishing member (felt) to the coating layer, the relative speed between the coating layer and the polishing member, the polishing treatment time, and the like.
Or by adjusting any two or three,
Can be adjusted. And the one with a larger polishing amount (for example,
The greater the contact pressure and / or the greater the relative velocity), the greater the amount of graphite exposed to the surface of the coating layer, and the greater the inclination γ.

The polishing apparatus shown in FIG. 6 includes a payout shaft 26 for the felt web 13 and a take-up shaft 27. The felt 13 has a sleeve 22, pulleys 22, 23, 24, and
It is hung on 25 as shown. By displacing the pulleys 24 and 25 in the direction of arrow C, the pressure contact force of the felt 13 on the sleeve 2 can be adjusted, and by displacing the pulleys 22 and 23 in the direction of arrow d, the winding angle of the felt 13 around the sleeve 2 can be adjusted. θ can be adjusted. Member 2
Nos. 2 to 27 are mounted on one table, and by moving this table in the direction perpendicular to the paper surface, that is, in the longitudinal direction of the sleeve 2, the sleeve can be rubbed along the longitudinal direction. .. At that time, the sleeve 2 is rotationally driven. The sleeve 2 itself may be moved in the sleeve longitudinal direction without moving the table.

In any case, the polishing amount is changed during the movement of the table or the sleeve. As a result, the coating layer is polished at the central portion in the longitudinal direction of the sleeve so that the triboelectric charging ability is higher than at both end portions.

An example of the polished sleeve will be described in detail below.

The magnetic toners used in the following examples are as follows.

Styrene-butyl acrylate-acrylic acid copolymer 100 parts by weight Magnetite 50 parts by weight Negative charge control agent 2 parts by weight Low molecular weight polypropylene 4 parts by weight

The above raw material mixture was kneaded, then pulverized and classified to have a weight average particle size of 11.3 μm, a particle size of 6.35 μm or less is 28% by number%, and a particle size of 20.2 μm or more is 0.1% by weight. After adjusting to 7% (all measured by Coulter Counter TA-II), 0.6% colloidal silica
It was added externally and used as a magnetic toner.

The developing sleeve 2 according to the present invention was manufactured by the following method. The raw materials mixed in the film-forming resin liquid are as follows.

Phenol resin 30 parts by weight Crystalline graphite (average particle size 8 mm) 41 parts by weight Carbon black 4 parts by weight

The above raw materials were dispersed in 250 parts by weight of a mixed solvent of isopropyl alcohol / butyl alcohol (1: 1) using a sand mill to prepare a film-forming resin solution, which was prepared by using an aluminum cylindrical tube (previously Applying a spray gun to the ones with flanges attached to both ends,
Then, the coating layer was cured in an atmosphere of 150 ° C. to form a resin coating layer having a film thickness of about 9 mm.

Next, using the polishing apparatus of FIG. 6, the tension pressure of the felt 13 of the abrasive, the polishing time (the moving speed of the felt in the longitudinal direction of the developing sleeve 2), the contact angle of the felt with the developing sleeve, etc. are adjusted. Then, the surface of the developing sleeve was polished. Developing sleeve 2 of felt 13 shown in FIG.
The contact angle .theta. To the developing sleeve 2 is small at both ends of the developing sleeve 2 and large at the central portion. Further, the moving speed of the felt 13 in the direction perpendicular to the paper surface of FIG. 6 (direction along the longitudinal direction of the developing sleeve 2) was high at both ends and slow at the central part.

FIG. 7 is a view for explaining the manufactured developing sleeve, and the right end portion W of the developing sleeve as seen in the drawing.
When polishing in the direction from the center U to the left end V,
The right end W is a region where the contact angle of the felt 13 with the sleeve changes from small to large, and the moving speed of the felt 13 changes from large to small, and the left end V is the felt sleeve. The contact angle and the moving speed are opposite to each other, and the central portion U is a region where the contact angle is constant at the maximum and the moving speed is constant.

Points f, g, h, i, and j indicated by arrows in FIG. 7 are observation points on the surface of the developing sleeve. In this example, the observation point f is a position 5 mm inside from the left end of the resin coating layer forming region in FIG. 7, g is a position 20 mm inside as well, h is substantially the center of the region, and i and j are respectively g,
The position symmetrical with f is shown. In addition, the width of the charged electric charge of the toner measured is 30 m at both ends V and W of the developing sleeve.
The width of m and the central portion U were 30 mm centered on h.

When the state of the surface of the developing sleeve at each of these points was observed with an FE-SEM (field emission scanning electron microscope) or the like, it was apparent that the h portion was more strongly polished than the j and f portions. Which was shown in the exposed state of the graphite contained in the resin coating layer.
The g and i parts showed an intermediate appearance. Inclination γ [cps / e of the work function measurement curve on the surface of the developing sleeve
V] was obtained by measuring at these observation points.

Further, the above-described developing sleeve was incorporated into an LBP-SX cartridge and subjected to development, and an image forming test was carried out. At that time, the amount of triboelectric charge of the toner on the developing sleeve was measured. The results are shown in Table 3 together with the comparative examples.

[0094]

[Table 3]

In Table 3, the image density shows the variation in the image density over the entire screen during continuous copying of 500 sheets and was measured by a Macbeth reflection densitometer. The charge amount of the toner is obtained by sucking the toner applied on the developing sleeve after 100 sheets of copying and measuring the friction charge amount. As described above, the evaluation symbols are as follows: ◎ is very good, ○ is good, Δ is slightly inferior but practically no problem, □ is slightly inferior to the practical level, and X is impermissible. ..

As shown in Table 3, in Examples 7 to 12, the surface of the developing sleeve was polished so that the triboelectric charge imparting performance to the toner was low at both ends of the sleeve and high at the central portion. Image density in 10% RH environment, toner charge-up, toner charge on developing sleeve after 100 sheets of continuous copying, 32 ° C, 85% R
Good results were obtained for all items of image density and image fading in the H environment.

Examples 13 to 18 The developing sleeve 2 was manufactured by the following method. The raw materials mixed in the film-forming resin liquid are as follows.

Phenolic resin 30 parts by weight Crystalline graphite (average particle size 10 mm) 22.5 parts by weight Carbon black 2.5 parts by weight

A resin having a film thickness of about 8 mm was formed on the surface of the developing sleeve in the same manner as in Examples 7 to 12 except that 200 parts by weight of a mixed solvent of methyl alcohol / methyl cellosolve (1: 1) was used as the above raw material. The coating layer 10 was formed.

Next, as shown in FIG. 8, the R and S regions on both ends of the developing sleeve are not polished, but the region V (on the left side) inside the regions,
U (center part) and W (right side) were subjected to the same polishing process as in Examples 7 to 12. In FIG. 8, the width of each of the left outer edge R and the right outer edge S was 20 mm. An observation point m on the surface of the developing sleeve is a position 5 mm inside from the left end of the resin coating layer forming region in FIG.
Indicates positions symmetrical to n and m, respectively. The measurement of the toner charge and the image evaluation are the same as described above. The obtained results are shown in Table 4 together with Comparative Examples.

[0101]

[Table 4]

As shown in Table 4, in Examples 13 to 18, the surface of the developing sleeve was polished so that the triboelectric charge imparting performance to the toner was low at both ends of the sleeve and high at the central portion. As in Examples 7-12,
Image density under 15 ° C., 10% RH environment, toner charge-up, toner charge amount on developing sleeve after continuous copying of 100 sheets, image density under 32 ° C., 85% RH environment, image fading Good results were obtained for all Ding items.

Although not shown in Table 4, Example 13
In the images obtained in Nos. 18 to 18, no abnormalities appeared in the areas corresponding to the unpolished areas on both ends of the developing sleeve, for example, the abnormalities such as shading at the boundary with the polished area.

Also in these results, it is preferable that the central portion of the sleeve has an inclination γ of more than 10, more preferably more than 20, and the both ends have an inclination γ of 10 or less, more preferably 11 or less. It turns out to be preferable.

Further, the above-mentioned polishing treatment may be applied to the coating layer formed by using the resin solutions A to F or the coating layer formed by using the resin solutions G and H below.

(Resin film forming liquid G) Phenolic resin 30 parts by weight Natural graphite 27 parts by weight Carbon black 3 parts by weight Methyl alcohol + methyl cellosolve 200 parts by weight (Resin film forming liquid H) Phenol resin 15 parts by weight Artificial graphite 15 parts by weight 225 parts by weight of methyl alcohol + methyl cellosolve

In the above embodiments, the case where the magnetic toner is used as the one-component developer has been described, but the present invention is not limited to this, and can be applied to the case where the one-component developer made of a non-magnetic toner is used. Is.

[0108]

According to the present invention, a ghost phenomenon can be prevented, and a developed image of good quality can be obtained in which the central portion and the end portions are uniform.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a developing device of the present invention.

FIG. 2 is a graph showing a work function measurement curve measured on the surface of a developing sleeve of the developing device of FIG.

FIG. 3 is an explanatory diagram showing a coating surface of a film-forming resin liquid of a developing sleeve in Examples 1 to 6 of the present invention.

FIG. 4 is a perspective view showing a polishing device used for polishing the surface of the developing sleeve in the present invention.

5 is a cross-sectional view showing the state of the surface of the developing sleeve before and after the polishing process of FIG.

FIG. 6 is a plan view schematically showing a polishing device used in Examples 7 to 18 of the present invention.

FIG. 7 is an explanatory diagram showing a polished surface of the surface of the developing sleeve in Examples 7 to 12 of the present invention.

FIG. 8 is an explanatory diagram showing a polished surface of the surface of the developing sleeve in Examples 13 to 18 of the present invention.

[Explanation of symbols]

 1 Photosensitive Drum 2 Developing Sleeve 3 Magnet 5 Toner 6 Doctor Blade 10 Resin Coating Layer 13 Felt 17 Element Tube 18 Coating Resin 19 Crystalline Graphite

Claims (11)

[Claims] 1. A developing device comprising: a developer carrying member carrying a one-component developer and carrying it to a developing region; and a restricting member for restricting the layer thickness of the developer carried to the developing region. The developer carrying member has a coating layer in which fine graphite particles are dispersed in a resin, and the triboelectric charge imparting ability of the coating layer with respect to the developer is at the central portion in the longitudinal direction of the developer carrying member. Is higher than that at the end portion in the longitudinal direction. 2. The developing device according to claim 1, wherein the content ratio of the graphite fine particles in the coating layer is higher in the central portion than in the end portions. 3. The developing device according to claim 1, wherein the coating layer is subjected to a polishing treatment, and the polishing treatment amount is larger in the central portion than in the end portion. 4. The slope of the work function measurement curve of the surface of the coating layer is greater than 10 (cps / eV) at the central portion and 10 (cps / eV) or less at the end portion. The developing device according to any one of 1 to 3. 5. The developing device according to claim 1, wherein amorphous carbon fine particles are further dispersed in the coating layer. 6. The developing device according to claim 1, further comprising a power source that applies a vibration bias voltage to the developer carrying member. 7. A developer carrying member carrying a one-component developer and transporting it to a developing area, having a coating layer in which graphite fine particles are dispersed in a resin, and imparting triboelectric charge to the developer of the coating layer. The developer carrying member is characterized in that the ability is higher in the central portion in the longitudinal direction than in the end portion in the longitudinal direction. 8. The developer carrying member according to claim 7, wherein the content ratio of the fine graphite particles in the coating layer is higher in the central portion than in the end portions. 9. The developer carrying member according to claim 7, wherein the coating layer is subjected to a polishing treatment, and the polishing treatment amount is larger in the central portion than in the end portion. 10. The slope of the work function measurement curve on the surface of the coating layer is greater than 10 (cps / eV) at the central portion and 10 (cps / eV) or less at the end portion. 9 to any one of the developer carrying members. 11. The developer carrying member according to claim 7, wherein amorphous carbon fine particles are further dispersed in the coating layer.