JPH1090995A - Developer carrier and developing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing carrier capable of preventing sticking of developer to the developer carrier while maintaining proper image density and high image quality and a developing device using the same. SOLUTION: A developer carrier 4 includes a resin layer 4b made of a connecting resin containing conductive fine particles, the outer peripheral surface of a cylindrical base body 4a being coated with the resin layer 4b. Uneven portions larger than toner particles in diameter and smaller than the same are formed on the surface of the resin layer 4b. For the uneven portion larger than toner particles in diameter, calculated average roughness Ra is within a range of 1.3 to 1.8μm and, for the uneven portion smaller than toner particles in diameter, an effective length SRIr is 104% or lower. A developing device 3 carries one-component developer 6 filling a developer container 5 onto the developer carrier 4, regulates the developer 6 to have a uniform thickness by a developer layer thickness regulating member 7, applies an electric field between an image holder 1 and the carrier 4 and develops an electrostatic latent image 2 on the image holder 1 by the developer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a developing device in an image forming apparatus employing an electrophotographic method such as a laser printer and a facsimile. More specifically, a developer carrier that conveys a developer whose amount of adhesion to the resin layer surface is regulated by the developer layer thickness regulating member to a development area, and an electric field between the electrostatic latent image carrier and the developer carrier The present invention relates to a developing device for developing an electrostatic latent image formed on the surface of an electrostatic latent image holding member.

[0002]

2. Description of the Related Art In an image forming apparatus employing an electrophotographic system, a method of developing an electrostatic latent image formed on an electrostatic latent image holding member (photoreceptor) depends on the type of developer used and the like. Various methods are conventionally known. Among them, a developing device in which the developer carrying property is improved by subjecting the surface of the developer carrying member to a roughening process is disclosed in, for example, JP-A-55-140858, JP-A-56-11131728, and JP-A-57-66455. It is described in gazettes and the like. In a developing device using a one-component developer, a charge of a polarity necessary for developing an electrostatic latent image is given to the developer by frictional charging with a developer carrier. The developer carrier having been subjected to the surface roughening also contributes to appropriate frictional charging of the developer. Further, in the one-component developing apparatus, a developer carrier having a resin layer in which conductive fine particles are dispersed is used on the surface to improve the control of frictional charging property and the control of transportability and to prevent image defects. In these developer carrying members, the surface roughness is defined by an index such as an arithmetic average roughness Ra. For example, Japanese Patent Application Laid-Open No. 4-6089 discloses that the surface roughness after coating a substrate subjected to a surface roughening treatment with a conductive resin is defined as an arithmetic average roughness Ra in a range of 0.8 to 2.5 μm. doing.

However, in a conventional one-component developing apparatus using a developer carrying member having a resin layer formed on the surface, the developer tends to adhere to the surface of the developer carrying member, and thus, the development which causes a decrease in image density is difficult. Agent sticking (toner filming) may occur. Further, in the developer carrier having the resin layer formed thereon, conductive fine particles having a particle diameter of several nm to several μm or less of the toner particle diameter are added to the resin layer, and these conductive fine particles are deposited on the surface of the developer carrier. Protrusions are formed, which causes mechanical fixation of the developer. As described above, the adhesion of the developer to the developer carrier is caused by the adhesion between the developer and the developer carrier, the transfer of thermal energy from the developer carrier to the developer, or the transfer of the developer by the developer carrier. This is caused by mechanical shaving. That is, irregularities smaller than the toner particle diameter on the surface of the developer carrying member are involved. Arithmetic average roughness Ra and the like are excellent as indices representing irregularities equal to or larger than the toner particle diameter. Due to the low sensitivity in the direction, it cannot be used as an index indicating the unevenness. Therefore, it is difficult to avoid the fixation of the developer to the developer carrier only by the conventional regulation of the surface roughness.

[0004]

As described above, there is a problem that it is difficult to avoid sticking of the developer in the conventional developer bearing member having the surface coated with the resin layer. Accordingly, the present invention is directed to solving the above-described problems, and a developing method capable of avoiding sticking of a developer to a developer carrying member while maintaining proper image density and high image quality. An object of the present invention is to provide a developer carrier and a developing device using the developer carrier.

[0005]

SUMMARY OF THE INVENTION The present inventor has sought to solve the problem of sticking of a developer to a developer carrier in a developing device having a developer carrier having a conductive resin layer as a surface layer. After extensive studies and studies, the effective line length SRlr is newly introduced as an index of the surface roughness in addition to the conventional arithmetic average roughness Ra, and the effective line length is made smaller than the conventional value. As a result, it has been found that the above-mentioned object is achieved, and the present invention has been accomplished. That is, in the developer carrier of the present invention, a resin layer composed of a binder resin containing conductive fine particles is coated on the outer peripheral surface of the cylindrical substrate, and the resin layer surface has irregularities larger than the toner particle diameter and the toner particle diameter. Smaller irregularities are formed, irregularities larger than the toner particle diameter are in the range of 1.3 to 1.8 μm in arithmetic average roughness Ra, and irregularities smaller than the toner particle diameter are 104% or less in effective line length SRlr. There is a feature. Further, a developing device of the present invention is characterized by using the above-mentioned developer carrier.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the developer carrier of the present invention, a resin layer for carrying the developer is coated on the outer peripheral surface of the cylindrical substrate. The resin layer is formed of a conductive layer containing at least conductive fine particles in a binder resin, and the conductive fine particles are dispersed in the binder resin. As the cylindrical substrate, a non-magnetic conductive member such as aluminum or stainless steel is used. Examples of the binder resin constituting the resin layer include phenol resin, melamine resin, urea resin, alkyd resin, epoxy resin, polyamide, polyimide, polyester, polyurethane, polycarbonate, polyphenylene oxide, polyether sulfone, acrylic resin, and styrene resin. Resins, fluorine-based resins, silicone resins, and the like, which are excellent in releasability, are preferably used.

The conductive fine particles dispersed in the resin layer include:
Carbon black, carbon beads obtained by granulating the carbon black, carbon fibers, carbon-based substances such as graphite, copper,
Conductive metals or alloys such as silver, aluminum and stainless steel, conductive metal oxides such as tin oxide, indium oxide, antimony oxide, titanium oxide, Sn ₂ O—In ₂ O ₃ composite oxide, potassium titanate, etc. Fine powder such as a conductive whisker is used. In the present invention, conductive fine particles larger than the toner particle diameter are dispersed in the resin layer to form irregularities larger than the toner particle diameter on the surface of the resin layer, thereby controlling the developer transportability. At this time, irregularities smaller than the toner particle diameter are simultaneously formed on the surface of the resin layer according to the surface shape and the surface distribution of the conductive fine particles. Further, it is preferable to disperse conductive fine particles having a size larger than and smaller than the toner particle size in the resin layer.
In that case, it becomes easy to control the resistance of the developer carrier to an appropriate value, and an appropriate charge amount can be given to the developer. In addition, the toner particle diameter means its volume average particle diameter, and a toner in the range of 4 to 13 μm is usually used.

The primary average particle diameter of the former conductive fine particles is
It is preferable that the diameter is larger than the used toner particle diameter and 15 μm or less. As an example, when a developer having a volume average particle diameter of 7 μm is used, conductive fine particles having an average particle diameter of 10 μm are used. As the specific fine particles, graphite, carbon beads, and the like having an effect of imparting lubricity to the resin layer are preferably used. It is preferable that the latter conductive fine particles have a primary average particle diameter smaller than the toner particle diameter and 10 nm or more (approximately several hundred nm in secondary average particle diameter) or more. Specific examples of the fine particles include, but are not particularly limited to, carbon black having an action of preventing excessive charging of the developer. The preferred use amount (content) of the conductive fine particles varies depending on the type of the fine particles.
The former can be used together with the larger conductive fine particles in the range of 30 to 60 parts by weight, and the latter smaller conductive fine particles can be used in the range of up to 30 parts by weight or less.

Regarding the unevenness of the surface of the developer carrying member in which the conductive fine particles are dispersed, the arithmetic average roughness Ra is 1.3 to 1.8 μm.
m. The average roughness Ra is obtained by measuring the unevenness of the resin layer surface using a stylus type surface roughness measuring device (surfcom: manufactured by Tokyo Seimitsu Co., Ltd.) and averaging the measured values at ten points. . Here, the average roughness Ra is 1.3.
If it is less than μm, the surface of the resin layer becomes too smooth and the amount of developer transported decreases, making it difficult to maintain an appropriate image density. On the other hand, when the average roughness Ra exceeds 1.8 μm, the transport amount of the developer increases, so that the developer layer on the image becomes thick, which causes deterioration of image quality such as thickening of fine lines. Further, since the amount of development becomes excessive, the amount of developer used increases, which affects running costs.

In the present invention, the effective line length SRlr is employed as an index representing the unevenness smaller than the toner particle diameter. This means that the frequency component of the toner particle diameter or more is cut off from each frequency component of the cross-sectional shape of the resin layer surface, and the total length (a) of the obtained roughness curve is divided by the measurement section length (b) and displayed as a percentage. It was done. FIG. 1 shows a roughness curve of the surface of the resin layer after the cutoff, in which the length in the radial direction with respect to the circumferential direction of the developer carrier is emphasized. Then, the effective line length SRlr is defined as follows. SRlr (%) = (a / b) × 100 In order to avoid sticking of the developer to the surface of the developer carrying member, it is necessary to reduce irregularities smaller than the toner particle diameter. Effective line length SRlr of unevenness is 1
Must be less than 04%. When the resin layer of the developer carrier is formed by a coating method, the effective line length SRlr is determined depending on the type and the molecular weight of the binder resin, the particle diameter of the conductive fine particles, the compounding amount, dispersibility, application conditions, and the like. Can be adjusted. In order to determine the effective line length SRlr, it is necessary to measure very minute irregularities on the surface of the developer carrying member. Therefore, in the present invention, instead of the stylus type surface roughness measuring device,
A three-dimensional surface shape analyzer (RD500: manufactured by Electronic Engineering Laboratory) is used. This analyzer analyzes the shape of the sample surface from reflected electron signals of a scanning electron microscope (S4200: manufactured by Hitachi, Ltd.).

As the binder resin, a phenol resin is particularly preferably used in terms of the surface properties of the resin layer, mechanical strength, cost and the like. The phenol resin preferably has a weight average molecular weight Mw of 4500 or more before crosslinking. That is, when the molecular weight Mw is less than 4500, the dispersibility of the conductive fine particles smaller than the toner particle diameter becomes poor. When the dispersibility is deteriorated, the particle diameter of the secondary aggregate of these conductive fine particles increases, and these secondary aggregates are exposed on the surface of the developer carrier after coating, and irregularities smaller than the toner particle diameter increase. As a result, the effective line length SRlr exceeds 104%. As a result, the transfer of thermal energy from the developer carrier to the developer is promoted, and the developer is mechanically shaved by the developer carrier, so that the developer is fixed to the developer carrier.

The resin layer can be formed as follows. First, a coating liquid is prepared by mixing a binder resin, conductive fine particles, a diluent (solvent), and various additives as necessary, and further uniformly dispersing a solid content with a sand mill or the like. At this time, the viscosity and the film forming property of the coating solution are adjusted by adjusting the mixing ratio of the diluent. Next, the surface of the cylindrical substrate is coated by an air spray method or the like while spraying a coating solution while rotating, and the binder resin is cured at 130 to 250 ° C. Diluents include hydrocarbons such as hexane, benzene, toluene and xylene, methyl ethyl ketone,
Examples include ketones such as cyclohexanone, alcohols such as ethanol, isopropanol and butanol, ethers such as dibutyl ether, tetrahydrofuran and propylene glycol monomethyl ether, and esters such as ethyl acetate, butyl acetate and ethyl butyrate. These diluents, the binder resin and the conductive fine particles may be used alone or as a mixture of two or more different substances. In the resin layer thus formed, the conductive fine particles are in a dispersed state, and at least a part of the conductive fine particles protrudes from the surface of the resin layer, and as described above, irregularities larger than the toner particle diameter are small. Fine irregularities coexist.

By the way, as the content of the conductive fine particles with respect to the binder resin increases, the volume ratio also increases, and in general, the ratio of the conductive fine particles exposed on the surface of the resin layer increases. At the same time, as the volume of each of the conductive fine particles smaller than the toner particle diameter increases, the rate of exposing these fine particles to the resin layer surface also increases. Even if the conductive fine particles smaller than the toner particle diameter are dispersed in the resin, they reaggregate to form secondary particles, and thus the degree of unevenness formed on the surface of the resin layer depends on the secondary particle diameter. This secondary particle diameter also changes depending on the dispersion method and the weight average molecular weight of the binder resin before crosslinking. The effective line length SRlr is determined solely by the degree of exposure of the conductive fine particles smaller than the toner particle diameter to the resin layer surface, and the particle diameter of the conductive fine particles and the content in the binder resin are represented by the following formula. When the relationship is satisfied, the effective line length SRlr can be suppressed to 104% or less. That is, it is possible to prevent the developer from sticking to the surface of the developer carrier by adjusting the content and the particle size of the conductive fine particles larger and smaller than the toner particle size with respect to the binder resin. . 4.5 × 10 ³ × (R ₁ ) ³ V ₁ + (R ₂ ) ³ V ₂ <300 where R ₁ is the secondary particle diameter (μm) of the conductive fine particles smaller than the toner particle diameter in the resin layer. , V ₁ is the content (g) of the conductive fine particles smaller than the toner particle diameter per 1 g of the binder resin.
R ₂ is the particle diameter (μm) of the conductive fine particles larger than the toner particle diameter after being dispersed in the coating solution, and V ₂ is the content of the conductive fine particles larger than the toner particle diameter per 1 g of the binder resin ( g).

The developer used in the developing device of the present invention can be a magnetic one-component developer or a non-magnetic one-component developer because an appropriate charge amount can be obtained by frictional contact with a developer carrier. preferable. However, it is also possible to use a two-component developer using a carrier. In order to improve the fluidity and chargeability of the developer, silica,
An external additive such as titania can be added. The primary particle diameter of the external additive is preferably in the range of 5 to 50 nm.

The operation of the present invention is as follows. In addition,
For easy understanding, the components of the present invention are denoted by the same reference numerals in parentheses as those corresponding to the components of the developing device shown in FIG.
In the developer carrier (4) according to the first aspect of the present invention, irregularities larger than the toner particle diameter on the surface of the resin layer (4b) have an arithmetic average roughness R.
Since a is in the range of 1.3 to 1.8 μm, it is possible to maintain a proper amount of developer transport and image density, and it is possible to prevent image quality deterioration such as reduction in image density and thickening of thin lines. Absent. Also, effective line length is used as an index of fine surface roughness.
By introducing SRlr, irregularities smaller than the toner particle diameter on the surface of the resin layer (4b) are reduced by an effective line length SRlr of 104.
% Or less. As a result, the developer (6) can be prevented from sticking, and a decrease in image density can be prevented. The developer carrier (4) according to the second aspect of the present invention
The conductive fine particles larger than the toner particle diameter are dispersed in the resin layer (4b). Therefore, the arithmetic average roughness Ra can be easily adjusted to the above range by using the conductive fine particles having an appropriate particle diameter range.

The developer carrier (4) of the present invention is obtained by dispersing conductive fine particles smaller than the toner particle size together with conductive fine particles larger than the toner particle size in the resin layer (4b). Therefore, by using two types of large and small conductive fine particles having an appropriate particle diameter range, the developer (6) can be given an appropriate charge amount. According to a fourth aspect of the present invention, the particle diameter of the conductive fine particles and the content in the binder resin satisfy the following relational expression. In the formula, R ₁ , V ₁ , R ₂ , and V ₂ mean the above-mentioned particle diameters or contents. 4.5 × 10 ³ × (R ₁ ) ³ V ₁ + (R ₂ ) ³ V ₂ <300 When the relationship between the particle size and the content satisfies the above formula, the effective line length SRlr is 104%. Since
The developer does not adhere to the surface of the carrier. According to a fifth aspect of the present invention, the developer carrier (4) uses a phenol resin as a binder resin constituting the resin layer (4b) and has a weight average molecular weight Mw before crosslinking of 4500 or more. According to the present invention, the resin layer (4b) in which the effective line length SRlr is adjusted to 104% or less can be easily obtained, so that the developer (6) adheres to the surface of the developer carrier (4). The image density can be prevented from lowering. The developing device according to claim 6 (3).
Uses the developer carrier (4) according to any one of the first to fifth aspects of the present invention. Therefore, the same effects as those of the above-described inventions can be obtained.

[0017]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples. In FIG. 2, an electrostatic latent image holder 1 is a photoconductive drum having a negatively charged organic photosensitive layer, and is uniformly charged by a charging unit (not shown), and then irradiated with image light. The electrostatic latent image 2 is formed by the potential difference generated by the operation. The surface potential when the electrostatic latent image 2 is formed is, for example, −600 V in the image portion and −120 V in the background portion that becomes a white display portion during image formation. The developing device 3 includes the image carrier 1
And a developer carrier 4 disposed opposite to the developer carrier. The developer carrier 4 has a cylindrical aluminum base 4a having an outer diameter of 18 mm and a wall thickness of 0.7 mm, and a resin layer 4b in which conductive fine particles are dispersed on a peripheral surface thereof. The resin layer 4b
It is formed of a coating film having a thickness of about 20 μm formed by applying a coating liquid described later in which conductive fine particles are dispersed in a binder resin and a diluent, onto the substrate 4a.

The developing container 5 is filled with a magnetic one-component developer 6 having a volume average particle diameter of 7 μm. The developing container 5 accommodates the developer carrier 4 and is arranged so that the surface of the carrier 4 partially exposed at a portion opened to face the image carrier 1 is close to the image carrier 1. Have been. In the container 5, an agitator (not shown) for bringing the developer 6 toward the carrier 4 is rotatably arranged. Developer carrier 4
Transports the developer 6 carried on the surface to a development area close to the image holding member 1 by its rotation. The minimum gap between the carrier 4 and the image carrier 1 in the developing area is set to be about 200 μm. Inside the carrier 4, a plurality of magnets are arranged along a peripheral surface, and a magnet roll 4c fixed so as not to rotate is provided. The plurality of magnets form a magnetic pattern in which S poles and N poles are arranged along the peripheral surface. According to this magnetic pattern, the developer 6 can be attracted to the surface of the carrier 4. I have.

The developer layer thickness regulating member 7 includes a developer carrier 4
It comprises an elastic member 7a in contact with the surface and a leaf spring 7b to which the elastic member 7a is bonded. The other end of the leaf spring 7b is fixedly supported on the upper wall of the container 5 via a support member. The elastic member 7a has a width of 15 mm, a thickness of 1.00 mm, and a rubber hardness of 65.
ウ made of urethane rubber, leaf spring 7b is 0.1m thick
m of stainless steel. Substrate 4a of developer carrier 4
The DC superimposed AC voltage which is a bias voltage is applied by a high voltage AC power supply and a DC power supply connected in series,
An alternating electric field is generated between a conductive substrate (not shown) of the image carrier 1 and the substrate 4a.

The operation of the developing device according to the present embodiment is as follows. The developer 6 in the container 5 is carried on the resin layer 4 b having irregularities larger and smaller than the toner particle diameter by rotation of the developer carrier 4. The developer 6 on the resin layer 4b is rubbed by the elastic member 7a by the pressing force of the leaf spring 7b for urging the developer layer thickness regulating member 7 against the surface of the carrier 4. As a result, an appropriate amount of the developer 6 for developing the electrostatic latent image 2 is thinned on the carrier 4 and at the same time, the developer 6
A uniform and sufficient triboelectric charge can be imparted to the toner. The thinned developer 6 is conveyed to the developing area with the rotation of the carrier 4, and charged in the alternating electric field generated in the gap between the carrier 4 and the image carrier 1. Flies and reciprocates. In addition, the particles of the developer 6 collide with each other due to the reciprocating motion, and the entire developer 6 becomes cloud-like. The cloud of the developer 6 is attracted to the electrostatic latent image 2 of the image carrier 1 by the DC component of the bias voltage, and the development is completed.

Example 1 A method for forming the resin layer (4b) is described below. Binder resin Phenol resin (Mw: 4500) 100 parts by weight Conductive fine particles Carbon black (primary average particle diameter: 10 nm) 20 parts by weight Graphite (volume average particle diameter: 7.5 to 9.0 μm) 50 parts by weight Diluent Propylene glycol monomethyl ether 100 parts by weight Isopropanol 150 parts by weight The conductive fine particles in the resin liquid having the above composition are dispersed by a sand mill, and the obtained coating liquid is used as an aluminum substrate (4a).
After spraying and applying on top, 160
The resin was cured by heating at 30 ° C. for 30 minutes to form a resin layer (4b). The arithmetic average roughness Ra of the surface of the resin layer (4b) was measured by the stylus type surface roughness measuring instrument and found to be 1.7 μm.
In addition, the effective line length SR
The lr was found to be 103.4%. The above resin layer
The magnet roll (4c) is fixed inside the substrate (4a) coated with (4b), and thus the developer carrier (4) is fixed.
Was prepared.

A second embodiment is substantially the same as the first embodiment.
To 6 and Comparative Examples 1 to 9 were prepared. In each of the examples and comparative examples, the difference from the method for forming the resin layer shown in the example 1, the average roughness Ra and the effective line length SRlr were described.
Is shown. Example 2 Weight average molecular weight Mw of phenol resin before crosslinking was 480
A resin layer was formed in the same manner as in Example 1 except that 0 was set. The average roughness Ra of the resin layer surface was 1.5 μm, and the effective line length SRlr was 102.9%. Example 3 Weight average molecular weight Mw of phenol resin before crosslinking was 500
A resin layer was formed in the same manner as in Example 1 except that 0 was set. The average roughness Ra of the resin layer surface was 1.3 μm, and the effective line length SRlr was 102.5%.

Example 4 A resin layer was formed in the same manner as in Example 1. However, in comparison with Example 1, the number of revolutions of the spray device, the discharge amount, and the distance between the spray gun and the base (4a) were changed. The average roughness Ra of the surface of the formed resin layer is 1.8 μm, and the effective line length is
SRlr was 103.5%. Example 5 A resin layer was formed in the same manner as in Example 1. However, in Examples 1 and 4, the number of revolutions of the spray device, the discharge amount, and the distance between the spray gun and the base were changed. The average roughness Ra of the formed resin layer surface is 1.3 μm, and the effective line length SR
lr was 103.0%. Example 6 A resin layer was formed in the same manner as in Example 1, except that only 40 parts by weight of carbon beads having a volume average particle diameter of 10 μm were used as the conductive fine particles. Average roughness R of this resin layer surface
a is 1.4 μm and the effective line length SRlr is 102.4%
Met.

Comparative Example 1 The weight average molecular weight Mw of the phenol resin before crosslinking was 400.
A resin layer was formed in the same manner as in Example 1 except that 0 was set. The average roughness Ra of the resin layer surface was 1.6 μm, and the effective line length SRlr was 105.2%. Comparative Example 2 The weight average molecular weight Mw of the phenol resin before crosslinking was 410
A resin layer was formed in the same manner as in Example 1 except that 0 was set. The average roughness Ra of the resin layer surface was 1.5 μm, and the effective line length SRlr was 104.8%. Comparative Example 3 Weight average molecular weight Mw of phenol resin before crosslinking was 430
A resin layer was formed in the same manner as in Example 1 except that 0 was set. The average roughness Ra of the resin layer surface was 1.4 μm, and the effective line length SRlr was 104.2%.

Comparative Example 4 The weight average molecular weight Mw of the phenolic resin before crosslinking was 380
A resin layer was formed in the same manner as in Example 1 except that 0 was set. The average roughness Ra of the resin layer surface was 1.4 μm, and the effective line length SRlr was 106.2%. Comparative Example 5 Weight average molecular weight Mw of phenol resin before crosslinking was 300
A resin layer was formed in the same manner as in Example 1 except that 0 was set. The average roughness Ra of the resin layer surface was 1.7 μm, and the effective line length SRlr was 108.2%. Comparative Example 6 A resin layer was formed in the same manner as in Example 1. However, the number of revolutions of the spray device, the discharge amount, and the distance between the spray gun and the base were changed from those of the examples. The average roughness Ra of the surface of the formed resin layer was 2.0 μm, and the effective line length SRlr was 103.5%.

Comparative Example 7 A resin layer was formed in the same manner as in Example 1. However, in each of Examples and Comparative Example 6, the number of revolutions of the spray device, the discharge amount, and the distance between the spray gun and the base were changed. The average roughness Ra of the surface of the formed resin layer was 1.1 μm, and the effective line length SRlr was 103.3%. Comparative Example 8 A resin layer was formed in the same manner as in Example 6, except that the amount of carbon beads used was changed to 50 parts by weight. The average roughness Ra of the resin layer surface was 2.1 μm, and the effective line length SRlr was 102.9%. Comparative Example 9 A resin layer was formed in the same manner as in Example 6, except that the amount of carbon beads used was changed to 20 parts by weight. The average roughness Ra of the resin layer surface was 1.0 μm, and the effective line length SRlr was 102.7%.

The above arithmetic mean roughness Ra and effective line length
SRlr is summarized in Table 1 below. Further, Examples 1 to 5
In Comparative Examples 1 to 7, the secondary particle diameter R ₁ (μm) of carbon black in the resin layer (4b) and the particle diameter R ₂ of graphite in the coating solution immediately after being dispersed by a sand mill were used.
(μm) was measured. The obtained particle diameter, the content V ₁ (0.2 g) of carbon black smaller than the toner particle diameter and the content V ₂ (0.5 g) of graphite larger than the toner particle diameter per 1 g of the phenol resin are substituted into the above equations. Then, a numerical value representing the relationship between the particle size of the conductive fine particles and the content in the binder resin was determined. Table 1 shows the results. Table 1
As shown in the figure, when the effective line length SRlr is 104% or less,
Numerical values calculated according to the equation representing the relationship between the particle diameter and the content were all less than 300.

[0028]

[Table 1]

(Copy Test) The developer carrier (4) prepared in Examples 1 to 6 and Comparative Examples 1 to 9 was incorporated in a digital copying machine (Able 1320: manufactured by Fuji Xerox Co., Ltd.), RH 85%). In the obtained copy sample, the initial image density and the image density after 1000 prints were measured with a densitometer (Model 404A: manufactured by X-Rite). The reduction rate of the image density is 100% of the initial image density.
The ratio of the decrease in density after 0 sheets was calculated as a percentage. The thickening of the thin line was evaluated from the result of observation with an optical microscope after copying a straight line having a width of 100 μm. "Developer fixation" means that the number of prints is 100
At the time of 0 sheets, the presence or absence of the developer fixed to the developer carrying member was visually evaluated. Table 2 shows the results. Evaluation of developer sticking ○: No sticking ×: Sticking

[0030]

[Table 2]

With the developer carrying member of each of the examples, practically satisfactory results were obtained with respect to the initial image density, the reduction rate of the image density after 1000 sheets, the thickening of the fine line, and the fixing of the developer. On the other hand, in the developer carrying member of each comparative example in which the arithmetic average roughness Ra is out of the range of 1.3 to 1.8 μm or the effective line length SRlr is more than 104%, some image defects occurred. That is, when the average roughness Ra was less than 1.3 μm, the amount of the developer required for development was insufficient due to the shortage of the amount of the developer transported, and as a result, the initial image density was reduced. Average roughness Ra
Is larger than 1.8 μm, the thickness of the thin line was increased due to an excessive amount of the developer. Further, when the effective line length SRlr is larger than 104%, the developer adheres to the developer carrier, so that the image density after printing 1,000 sheets has been greatly reduced.

FIGS. 3 and 4 are graphs showing the results of the above Examples and Comparative Examples. FIG. 3 is a graph showing a window of the arithmetic mean roughness Ra and the effective line length SRlr of the surface of the developer carrier, and a portion surrounded by a frame indicates an embodiment of the present invention. FIG. 4 shows the relationship between the effective line length SRlr on the surface of the developer carrying member and the reduction rate of the image density, and the numbers in the figure show the numbers of comparative examples. As is apparent from FIG. 4, when the effective line length SRlr of the surface of the developer carrying member is 104% or less, the image density does not decrease at all or hardly. This means that sticking of the developer to the developer carrier is avoided.

[0033]

According to the developer carrier and the developing device of the present invention, the irregularities larger than the toner particle diameter on the surface of the resin layer are in the range of 1.3 to 1.8 μm in arithmetic average roughness Ra, and the toner The irregularity smaller than the particle diameter is the effective line length SRlr
And 104% or less, the image density was appropriate, the fine line was not thickened, and the sticking of the developer to the developer carrier could be avoided.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a minute uneven shape on the surface of a resin layer for explaining an effective line length SRlr as an index of a surface roughness of a developer carrying member.

FIG. 2 is an explanatory diagram of a one-component developing device shown as one embodiment of the present invention.

FIG. 3 is a graph showing a window of an arithmetic mean roughness Ra and an effective line length SRlr of the surface of a developer carrying member.

FIG. 4 is a graph showing the relationship between the effective line length SRlr on the surface of a developer carrying member and the rate of decrease in image density.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrostatic latent image holding body, 2 ... Electrostatic latent image, 3 ... Developing device, 4
... developer carrier, 4a ... cylindrical substrate, 4b ... resin layer, 5
... developer container, 6 ... developer, 7 ... developer layer thickness regulating member.

Claims (6)

[Claims] 1. A resin layer comprising a binder resin containing conductive fine particles is coated on the outer peripheral surface of a cylindrical substrate, and irregularities larger than the toner particle diameter and irregularities smaller than the toner particle diameter are formed on the surface of the resin layer. The unevenness larger than the toner particle diameter is in the range of 1.3 to 1.8 μm in arithmetic average roughness Ra, and the unevenness smaller than the toner particle diameter is 1 in the effective line length SRlr.
A developer carrying member having a content of not more than 04%. 2. The developer carrier according to claim 1, wherein the conductive fine particles are larger than a toner particle diameter. 3. The developer carrier according to claim 1, wherein the resin layer simultaneously contains conductive fine particles larger than the toner particle diameter and conductive fine particles smaller than the toner particle diameter. 4. The developer carrier according to claim 3, wherein the particle diameter of each of the conductive fine particles and the content in the binder resin satisfy a relationship represented by the following formula. 4.5 × 10 ³ × (R ₁ ) ³ V ₁ + (R ₂ ) ³ V ₂ <300 In the formula, R ₁ , V ₁ , R ₂ and V ₂ mean the following particle diameters or contents. R ₁ : secondary particle diameter (μm) of conductive fine particles smaller than toner particle diameter V ₁ : content of conductive fine particles smaller than toner particle diameter
(g) / g (binder resin) R ₂ : particle size after dispersion of conductive fine particles larger than toner particle size (μm) V ₂ : content of conductive fine particles larger than toner particle size
(g) / g (binder resin) 5. The binder resin is a phenol resin,
The phenol resin has a weight average molecular weight of 4500 before crosslinking.
The developer carrier according to any one of claims 1 to 4, which is as described above. 6. A developer carrying a one-component developer filled in a developing container on a developer carrier, and regulating the developer on the developer carrier to a uniform thickness by a developer layer thickness regulating member. 2. A developing device for developing an electrostatic latent image on a surface of an electrostatic latent image holding member with a developer by applying an electric field between the electrostatic latent image holding member and the developer holding member, wherein the developer holding member is used as the developer holding member. A developing device using any one of the above-described items.