JP2000172067A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a developing device where an image without any unevenness in density can be stably formed by providing suitable amount of carried developer and electrification. SOLUTION: In this developing device, the developer carrier 9 is provided with an elastic layer 11 and a conductive layer covering the surface of the elastic layer. The surface roughness Rz of the conductive layer is made to be 0.1 to 10 [μm], the coefficient of dynamic friction is made to be 0.2 to 0.7 and the wear resistance is made to be smaller than 700 [mg] in the JIS-K7311 wear resistance test. Furthermore, the product of the of vertical elastic coefficient E and film thickness t of the conductive layer is made to be smaller than 12,000. The vertical elastic coefficient E is made to be within an appropriate range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a developing device for visualizing an electrostatic latent image formed on a latent image carrier by using a developer thinly formed on a developer carrier.

[0002]

2. Description of the Related Art One of the developing methods using a one-component developer is a pressure contact developing method as disclosed in US Pat. According to this method, after a thin layer of developer is formed on a developer carrying member, the electrostatic latent image formed on the latent image carrying member is pressed and developed by the thin layer of developer to form a visible image. The characteristics required for the developer carrier include the ability to stably form a thin developer layer on the developer carrier and the capability of soft contact with the latent image carrier. It becomes important.

[0003] In a conventional developing apparatus, a method for stably forming a thin layer of developer on a developer carrier is disclosed in JP-A-60-135966. The coefficient is set to 0.5 to 0.7,
As disclosed in Japanese Patent Application Laid-Open No. 8-214177, the surface roughness of a developer carrying member has been made to be one to four times the particle diameter of the developer.

Further, as disclosed in Japanese Patent Application Laid-Open No. 2-259785, a developer carrying member used in a conventional pressure-contact developing type developing device is configured such that the developer carrying member is made of an elastic material and further has a surface roughness. By setting the Rz to 20 [μm] or less, a developer carrier capable of making soft contact with the latent image carrier and having a stable developer carrying capacity was obtained.

Further, as a method of enabling a soft pressure contact with a latent image carrier and effectively obtaining a developing electrode effect, as disclosed in JP-A-1-191880, flexibility is provided outside the elastic layer. A method has been proposed in which a conductive material layer is formed to form a developer carrier for pressure-contact development.

[0006]

However, if the surface roughness and the coefficient of friction of the developer carrying member are not appropriate, the transporting performance of the developer is deteriorated. For example, even if the surface roughness of the developer carrying member is small, However, if the developer carrier is made of a material having a large coefficient of friction, the amount of the developer to be conveyed becomes extremely large, and conversely, even if the friction coefficient of the surface of the developer carrier is small, the developer carrier It has been found that increasing the surface roughness increases the amount of developer transported, resulting in an image with a lot of background fog.

If the wear resistance of the surface of the developer carrier is low, the surface of the developer carrier is worn by rubbing with the developer, so that the surface roughness of the developer carrier changes with time. However, there has been a problem that a constant amount of developer transport cannot be obtained over a long period of time.

Further, if the developer carrier is made of a material having a low hardness, such as rubber, it is difficult to polish or roughen the surface, and it is very difficult to control the fluctuation of the outer diameter and the surface roughness. there were.

Further, if a flexible conductive layer is formed outside the elastic layer to form a developer carrying member, and the hardness of the elastic layer is reduced to realize soft contact with the latent image carrying member, the elasticity can be improved. The developer carrier or the elastic blade is deformed at the contact portion of the blade or the pressure contact portion with the photoconductor, and the developer is developed due to periodic vibration (so-called stick-slip phenomenon) generated when the distortion is released. There has been a problem that the amount of agent transport and the amount of development vary.

Further, the elastic layer having a low hardness tends to cause local compressive strain due to the contact force of an elastic blade or the like. Requires several rotations or more, so that the amount of developer transported partially increases and the amount of charge decreases, causing background fog and density unevenness.

Further, when a functional layer such as a conductive layer or a resistive layer is formed on the outside of the low hardness elastic layer by coating or bonding, the functional layer is pressed against the elastic blade or the latent image carrier. In order to repeatedly receive compressive deformation in the part, it is necessary to impart sufficient film strength and adhesion to the functional layer so as not to cause cracking of the functional layer and peeling from the elastic layer, but in general, a resin in which carbon black is dispersed Also, since the extensibility and flexibility of the functional layer such as a metal thin film are low, the elastic layer may deform without being able to follow the deformation of the elastic layer, or the elastic layer may be formed of a material having a low surface energy such as silicon rubber. In such a case, there has been a problem that the adhesion between the functional layer and the elastic layer is not sufficiently obtained, and the functional layer is easily peeled off.

Accordingly, the present invention solves such a problem. It is an object of the present invention to regulate a developer layer formed on a developer carrier to a suitable transport amount and charge amount suitable for development. It is an object of the present invention to provide a developing device capable of performing the above.

Another object of the present invention is to provide a developing device in which the surface of the developer carrying member is not significantly worn by rubbing with the developer, and therefore, the amount of developer transport and the amount of charge are stable for a long period of time. Equipment.

Further, another object of the present invention is to provide a developing device capable of easily performing polishing and controlling the surface roughness, so that the developer layer formed on the developer carrying member can be regulated to a suitable transport amount for the development. Equipment.

Further, another object of the present invention is to prevent stick-slip and partial compression set of the elastic layer from being easily generated even when the hardness of the elastic layer constituting the developer carrier is low. It is an object of the present invention to provide a developing device in which the amount of conveyance and the amount of development are not easily changed.

Further, another object of the present invention is that the functional layer formed on the surface of the developer carrying member is less liable to undergo plastic deformation or fatigue fracture with respect to compressive deformation and has sufficient adhesion to the elastic layer. Another object of the present invention is to provide a developing device having a long life and suitable for pressure welding development.

[0017]

The developing device of the present invention is a developing device which holds a thin layer of a developer layer on a developer carrier and transports the developer layer to a position facing the latent image carrier. hand,
The developer carrier has an elastic layer and a conductive layer coated on the surface of the elastic layer, and has a longitudinal elastic modulus E of the conductive layer.
[Kg / cm ² ] and the thickness t [cm] of the conductive layer are:
The formula: E × t ≦ 12000 is satisfied.

The developing device according to the present invention comprises:
A developing device for holding a thin-layered developer layer and transporting the developer layer to a position facing a latent image carrier, wherein the developer carrier includes an elastic layer and a conductive material coated on a surface of the elastic layer. and a layer, longitudinal elastic modulus E of the conductive layer, ^{wherein: 5 × r 3 / I ≦} E ≦ 40000 × r 3 / I [kg / cm ^{2] _{I = π × (d 1 4}} -d 2 ⁴ ) / 64 r = (d ₁ + d ₂ ) / 4 π: circumference d ₁ : outer diameter [cm] of conductive layer d ₂ : inner diameter [cm] of conductive layer.

Further, the surface roughness Rz of the conductive layer is
0.1 to 10 [μm], wherein the coefficient of kinetic friction between the outer surface of the conductive layer and the developer layer is 0.2
０．７0.7. Furthermore, the abrasion resistance of the conductive layer was 700 in the JIS-K7311 abrasion test.
[Mg] or less.

[0020]

According to the above construction of the present invention, the developer carrier has a structure in which the elastic layer and the conductive layer are arranged concentrically on the outer periphery of the shaft, and the surface roughness Rz of the conductive layer is 0.1 to 10%.
[Μm], the conductive layer surface is not clogged with the developer, and the developer does not cause poor charging, and the transport amount and the charge amount of the developer layer formed on the developer carrier are reduced. It is suitable for development, and can form an image with high density and little background fog.

Further, according to the above configuration of the present invention, by setting the dynamic friction coefficient of the outer surface of the conductive layer to 0.2 to 0.7, the transport amount of the developer formed on the developer carrier and the charging The amount is suitable for development, and a high-density and high-resolution image can be formed stably without causing image defects such as density fluctuation and background fog even during long-term use.

Further, according to the above configuration of the present invention, by setting the abrasion resistance of the conductive layer to 700 mg or less in the JIS-K7311 abrasion test, the surface of the developer carrier slides with the developer. Since there is no remarkable abrasion due to rubbing, and thus the surface roughness and the coefficient of friction do not change, the developer transport amount and the charge amount are stabilized over a long period of time.

Even if the elastic layer is made of a low-hardness material that is difficult to be polished, such as foamed rubber, the surface is covered with a conductive layer having an appropriate hardness, so that the surface is polished or roughened. Processing can be performed, and deflection of outer diameter and surface roughness can be easily controlled.

In addition to the method of processing the surface of the conductive layer, a method in which the elastic layer is coated with the conductive layer, or a method in which the conductive layer previously processed to a desired surface roughness is coated on the elastic layer, is very useful. Even a soft elastic layer can easily bring its surface into a state suitable for development, and processing of the conductive layer itself is not affected by the elastic layer, so that it becomes easy.

In general, when surface treatment such as polishing or surface roughening is performed on the surface of the conductive layer, if the hardness is too low, the workability is reduced, and if the hardness of the conductive layer is too high, the workability is reduced. The flexibility decreases, and a sufficient nip width cannot be obtained at the contact portion with the photoreceptor, or fatigue fracture occurs at a portion where bending stress is repeatedly applied. However, the longitudinal elastic modulus E [k
g / cm ² ] and the thickness t [cm] of the conductive layer satisfy the formula: E × t ≦ 12000, the rigidity of the conductive layer can be improved in a range having sufficient flexibility, and Since it does not cause fatigue failure due to repeated stress, it is suitable as a developer carrier for press-contact development where the surface of the developer carrier is constantly exposed to deformation. Also, since sufficient flexibility can be imparted to the conductive layer, soft contact with the latent image carrier can be achieved by making the elastic layer low hardness, and the contact width with the elastic blade and the latent image carrier can be provided. , The charge amount of the developer can be improved, and high-speed printing can be performed. Furthermore, since the rigidity of the conductive layer can be set to a state of good workability, the surface roughness and the friction coefficient of the conductive layer can be easily changed to a state suitable for development. An image with less fog and density fluctuation can be formed.

Further, according to the above configuration of the present invention, the developer carrying member has a structure in which the elastic layer and the conductive layer are arranged concentrically on the outer periphery of the shaft, and the longitudinal elastic coefficient E of the conductive layer is
^{Formula: 5 · r 3 / I ≦} E ≦ 40000 · r 3 / I [kg / cm ^{2] _{I = π × (d 1 4}} -d 2 4) / 64 r = (d 1 + d 2) / 4 π: Circumference d ₁ : Outer diameter of conductive layer [cm] d ₂ : Inner diameter of conductive layer [cm] If the elastic layer has a very low hardness, it can be used with an elastic blade or a photosensitive member. Since the contact pressure can be effectively dispersed by the rigidity of the conductive layer, periodic micro-vibration (stick-slip) that occurs when releasing the locally generated compressive deformation and partial compression of the elastic layer are permanent. Distortion can be prevented, so that the transport amount and charge amount of the developer are stable, and an image with less density fluctuation can be formed.

Even when a functional layer such as a magnetic field generating layer is provided on the surface of the conductive layer, the conductive layer does not locally undergo large deformation. In addition to being less likely to occur, there is a wide selection of materials that can be used as the conductive layer, so it is easy to arrange the functional layer, for example, by using the same type of material as the magnetic paint to improve the adhesion with the magnetic paint. can do.

Hereinafter, the present invention will be described in detail with reference to examples.

[0029]

(Embodiment 1) FIG. 1 is a schematic cross-sectional view of a developer carrier used in a developing device according to an embodiment of the present invention. The conductive elastic layer 11 and the conductive tube 12 are provided concentrically, and the tube 12 is made by dispersing conductive particles of carbon black 22 in a binder 21 to impart conductivity. The layer thickness should be such that these dispersions have sufficient flexibility even when the tube hardness increases.
(Mm) or less, preferably 0.5 (mm) or less,
Since the tube has sufficient flexibility, the developer carrier 9
Even if the developer is pressed against a latent image carrier (not shown) to perform development, the pressing pressure is effectively relieved by the elastic layer 11 so that soft contact is possible. Can form an image without solidification.

FIG. 2 is a schematic cross-sectional view of the developing device of the present invention. The latent image carrier 1 is formed by coating an organic or inorganic photoconductive photosensitive layer 3 on a conductive support portion 2. The photosensitive layer 3 is charged by a charging device such as a corona charger or a charging roller. After being charged by the device 4, light emitted from a light source 5 such as a laser or an LED is selectively irradiated on the photosensitive layer 3 through an imaging optical system 6 in accordance with an image to obtain a potential contrast and obtain an electrostatic latent image. Form an image. On the other hand, the developing device 7 transports and develops the developer 8, and removes the developer 8 from the separation supply roller 1.
By rubbing between the developer carrying member 7 and the developer carrying member 9, triboelectric charging is applied, and the developer is held on the developer carrying member 9 by electrostatic force.
The charge amount is adjusted by a thin leaf spring-like elastic blade 13 made of a non-magnetic or magnetic metal or resin to make the layer thinner to an appropriate amount, and then the developer carrier 9 is rotated to convey the thin layer of developer. Things. When the developer 8 on the developer carrier 9 is transported to the pressure contact portion between the developer carrier 9 and the latent image carrier 1, the developer 8 is formed by the potential contrast of the latent image carrier 1 and the developing bias applying unit 14. Latent image carrier 1 according to development electric field
And the electrostatic latent image is visualized. Further, an image of the developer is transferred onto the recording paper 16 using a transfer device 15 such as a corona transfer device or a transfer roller, and the developer is fixed on the recording paper using heat or pressure, and a desired image is formed on the recording paper. What you get.

FIG. 3 is an explanatory diagram showing the developing characteristics of the developing device of the present invention.

FIG. 3A shows the surface roughness Rz of the tube.
[Μm] and is an explanatory diagram showing a relationship between dynamic friction coefficient mu _k,
It is divided into the following five areas according to the developer carrying capacity and the developer charge amount.

Area 1: good developer transport amount and charge amount area Region 2: insufficient developer transport amount area Region 3: insufficient developer charge amount area 4: unstable area 1 area 5: unstable area 2 In a), the area 1 is an area in which both the surface roughness and the coefficient of dynamic friction of the tube are appropriate, the developer is not fused or clogged on the surface, and the developer is stably transported for a long period of time. Therefore, a good image free from background fog and insufficient density can be stably formed. In the region 2, both the surface roughness and the coefficient of kinetic friction are small, and the ability to hold and transport the developer on the tube surface is low. In the region 3, both the surface roughness and the coefficient of kinetic friction are large, and the developer carrying capacity is too large, so that an excessive amount of the developer is carried. . Region 4 has a very smooth surface state and a moderately large coefficient of kinetic friction, so that a good image can be initially formed. However, the developer easily adheres to or clogs the surface of the tube, and is stable for a long time. It is difficult to form an image. Region 5 is
A good image can be formed initially with a low coefficient of kinetic friction and a moderately large surface roughness.However, the transport amount tends to fluctuate due to changes in the remaining amount of the developer and fluidity, so the image is stable for a long time. Is difficult to form.

FIG. 3 (b) is a diagram showing A, A in FIG. 3 (a).
For three types of tubes having a relationship between the surface roughness indicated by B and C and the dynamic friction coefficient, the tube surface roughness Rz [μ
FIG. 5 is a diagram showing the relationship between the amount of developer transport [mg / cm ² ] and the amount of developer charge [μc / g] with respect to [m].

In FIG. 3 (b), the developer carrying member on which the tube A has been applied cannot provide a sufficient developer conveying force in a region where the surface roughness Rz is 0.1 [μm] or less, and the When the surface roughness Rz is 10 [μm] or more, a sufficient amount of developer charge cannot be obtained, and an image with a lot of background fog is obtained. However, a sufficient image was obtained.

The developer carrying member having the tube B attached thereto has a surface roughness Rz of 0.05 [μm] or less, an insufficient amount of the developer to be conveyed, resulting in an image of insufficient density, and a dynamic friction coefficient of 0.75 or more. In the region, ground fog occurs due to insufficient developer charge, and in the region where the surface roughness Rz is 0.05 to 0.1 [μm] and the dynamic friction coefficient is 0.7 to 0.75, an initially good image is obtained. Was formed, but filming occurred, which was not preferable. In a region where the surface roughness Rz was 0.1 [μm] or more and the dynamic friction coefficient was 0.7 or less, it was possible to form an image with good density and resolution. Was.

The developer carrying member having the tube C attached thereto has a kinetic friction coefficient of 0.1 or less, the amount of the developer conveyed is insufficient, resulting in an image of insufficient density, and the developer having a surface roughness Rz of 30 [μm] or more. Ground fog occurs due to insufficient charge amount, a region where the dynamic friction coefficient is 0.1 to 0.2, and a surface roughness Rz is 10 to 30.
In the [μm] region, the amount of developer transported and the amount of charge are liable to fluctuate depending on the remaining amount and fluidity of the developer.
In the [μm] region, an image with good density and resolution was stably obtained.

In addition to the above-described experiments of transporting the developer carrying member to which the three types of tubes A, B, and C are attached, many experiments were repeated. As a result, the surface roughness Rz of the developer carrying member was set to 0. 1
[Μm] or more, the developer can be stably conveyed without clogging the surface of the developer carrier, and by setting the surface roughness Rz to 10 [μm] or less, the developer charge amount can be sufficiently increased. And an image with less ground fog can be obtained. Further, the surface roughness R of the developer carrier surface
z is set to 0.1 to 10 [μm] and the kinetic friction coefficient to the developer is set to 0.2 to 0.7, so that development can be performed regardless of the remaining amount of the developer in the developer hopper and the fluidity of the developer. The developer can be transported stably, and even when used for a long period of time, there is no filming of the developer on the tube surface, and an image having a high density and no background fog can be formed stably.

In this embodiment, a one-component non-magnetic developer having a volume average particle diameter of 10 [μm] is used as a developer, and a thickness of 0.1 [m
m], a stainless steel elastic blade having a surface roughness Rz of 0.05 [μm] and an urging (regulating) force of 1 [kg] was used. When the biasing force of the elastic blade is strong, the developer hardly passes under the elastic blade, so that the surface roughness of the developer carrier or the friction coefficient is increased to increase the developer carrying ability. For example, when the urging load of the elastic blade is about 1.5 [kg], the surface roughness Rz of the developer carrier is desirably about 3 [μm]. In addition, the smaller the particle size of the developer, the more difficult the regulation becomes, and the larger the amount of the developer transported. Therefore, it is necessary to reduce the surface roughness of the developer carrier.

In this embodiment, the dynamic friction coefficient μ _k between the developer carrier and the developer layer was measured using a parallel plate type shear tester (PTHN-13BA type: Sankyo) as shown in FIG. More specifically, a developer layer of 4 [mm] is formed in a gap between two shear fixing plates 31 each having the tube 12 adhered to the surface thereof, and a vertical stress σ is formed. Is obtained from the shearing force τ when 100 [gf / cm ² ] is applied.

The developer carrier 9 used in this embodiment is obtained by integrally forming an elastic layer 11 made of foamed silicone rubber on the outer periphery of a stainless steel shaft 10 by the LTV method. Is 4 [wt
%], The conductive material is made conductive to a volume resistivity of about 10 ⁵ [Ω · cm], and the rubber hardness is 40 degrees by an Asker C type hardness meter.

The tube 12 is a conductive and flexible tube in which conductive particles are dispersed in a binder.
More specifically, it is a tube formed by dispersing 6 [wt%] of carbon black in a polyurethane resin to a volume resistivity of 10 ⁴ [Ω · cm], and extruding the film with a thickness of 50 [μm],
The outer surface is subjected to sandblasting so that the surface roughness Rz becomes 2 [μm], and the dynamic friction coefficient is 0.4.

The conductive and heat-shrinkable tube 12 coated on the outer periphery of the elastic layer 11 is firmly held on the elastic layer 11 by its gripping force. The conduction is ensured, and the development can be performed by applying the development bias voltage to the shaft.

The inner diameter of the tube 12 before heat shrinkage is φ22
[Mm], and after inserting the elastic layer 11 into the tube 12 before the heat shrinkage, the environment was decompressed and further 120 [° C.]
Then, the tube 12 was shrunk by heating to form a developer carrier by covering the outer periphery of the elastic layer 11.

The binder 21 forming the tube 12
In addition to polyurethane resin, vinyl chloride, fluororesin, polyethylene, polypropylene, polyester, polyamide resin, polyolefin, epoxy resin, vinyl copolymer resin such as vinyl acetate, vinyl alcohol, vinyl butyral, vinyl formal, vinyl ethyl ester or Polyamide or nitrocellulose or cellulose acetobutyrate or a blend thereof with another resin can be used, for example, by blending vinyl acetate, vinyl chloride and polyurethane, or by blending cellulose acetobutyrate and vinyl formal It is possible to design a binder that complements each other's properties and achieves both dispersibility and mechanical strength.
DM, fluoro rubber, silicone rubber, chloroprene rubber,
Any material having elasticity or flexibility, such as a rubber material such as natural rubber, isoprene rubber, butadiene rubber, neoprene rubber, and NBR, can be used as a binder. Further, as the conductive particles dispersed in the tube 12, it is preferable that a sufficient amount of conductivity is obtained with a small amount of addition, and that the flexibility of the tube is hardly reduced. For example, conductive carbon black or the like is preferable. Yes, it is desirable that carbon black has the ability to form a strong structure, and that works to significantly reduce the electrical resistance as the amount of carbon black added increases, for example, Ketjen black, acetylene black, lamp black, High-structure furnace black or the like can be used, and particularly, acetylene black or the like having good conductivity is suitable. A smaller particle size is desirable for lowering the conductivity because a larger surface area per unit amount can be obtained.

The method of manufacturing the tube 12 is as follows.
Extrusion molding, compression molding, transfer molding, injection molding, vacuum molding, blow molding, etc. can be used,
In particular, according to the extrusion molding method, since a tube having a constant thickness can be continuously produced, the production cost can be reduced. In addition, the surface roughness Rz of the extrusion die is 0.1 to 10 μm.
m], a desired surface roughness can be imparted to the surface of the tube, so that surface treatment such as sandblasting can be omitted, and it is particularly desirable to manufacture an inexpensive developer carrier.

The material constituting the shaft 10 may be a conductive material such as a resin in which conductive powder such as stainless steel, steel, copper, aluminum, and carbon black is dispersed when developing by applying a developing bias from the shaft. It is possible to use a material having a sufficient bending strength against the pressing force.

The material constituting the elastic layer 11 must have elasticity in order to relieve the pressure contact with the latent image carrier, and its hardness is 80 degrees by Asker C type hardness meter (manufactured by Kobunshi Keiki Co., Ltd.). The following is desirable, and in order to prevent the deterioration of the developer, it is more desirably 50 degrees or less, and urethane rubber, silicone rubber, fluorine rubber, EPDM, chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber,
Polysulfide rubber, butyl rubber, chloroprene rubber, natural rubber, isoprene rubber, butadiene rubber, neoprene rubber, NBR, etc. can be used in the form of a rubber, a foam or a roller having a skin layer on the outer periphery of the foam, All resins that can be formed into elastic foams, such as polyurethane resin, styrene resin, vinyl chloride resin, polyethylene resin, and methacrylic resin, and resins such as elastomers, which have a large amount of elastic deformation and a short recovery time to the original state, etc. Can be used.

In order to dispose the elastic layer 11 on the outer periphery of the shaft 10, besides the method of integrally molding the shaft and the elastic layer, the elastic layer may be previously formed into a hollow cylindrical shape and then fitted or adhered. Can be. (Embodiments 2 to 6) FIG. 4 is a schematic cross-sectional view of a developer carrying member used in a developing device according to another embodiment of the present invention and an explanatory diagram of mechanical characteristics. Members having the same names and the same functions are given the same numbers and their explanation is omitted. FIG.
1A, a developer carrier 9 is obtained by integrally forming a foamable elastic layer 11 made of silicone rubber on the outer periphery of a stainless steel shaft 10.
1 has a skin layer 42 which is naturally formed in a portion in contact with the mold,
[Wt%] By dispersing, the volume resistivity is 10 ⁵ [Ω · cm]
The rubber hardness is 25 degrees with an Asker C-type hardness meter.

The outer periphery of the elastic layer 11 is covered with a conductive and heat-shrinkable tube 12.
Is adhered on the elastic layer 11 by a conductive adhesive, the conduction between the surface of the heat-shrinkable tube and the shaft is secured, and the developing bias voltage can be applied to the shaft to perform development.

The inner diameter of the tube 12 before heat shrinkage is φ24
[Mm], and the outside diameter φ
After inserting the elastic layer 11 of 20.5 [mm], the environment is decompressed and further heated to shrink the tube 12, and the outer periphery of the elastic layer 11 is coated so as to cover a developer carrier having an outer diameter of φ20 [mm]. And

The tube 12 is a conductive and flexible tube in which conductive particles are dispersed in a binder.
More specifically, 6 [wt.
%] Dispersed volume resistivity of about 10 ⁴ [Ω · cm], film thickness of 50
A tube formed by extrusion molding of [μm], the outer periphery of which is subjected to sandblasting so that the surface roughness Rz becomes 2 [μm], and the dynamic friction coefficient is 0.4
5

In this embodiment, an image is formed by using a developer carrier having a changed abrasion resistance of the tube in the developing device shown in FIG. 2, and more specifically, a binder constituting the tube. , And a developer printing test was performed for each developer carrying member to evaluate the surface roughness and printing image quality.

The developer has a volume average particle diameter of 10 μm.
m], and a one-component magnetic developer having a magnetic powder content of 20 [wt%] was used, and an image was formed with an urging load of the developer carrier against the latent image carrier of 1 [kg].

Table 1 shows that 50 sheets of A4 size paper were printed.
The 10-point average roughness Rz of the surface of the tube 12 at the time of 00 sheets, 10,000 sheets, 20,000 sheets, and 50,000 sheets, and image quality evaluation results of a line image and a solid image formed on the latent image carrier are shown. In Table 1, the amount of wear is determined by JI
It shows the amount of wear of the tube 12 by the S-K7311 abrasion test (wear wheel H22, 1000 rotation wear).

[0056]

[Table 1]

As a result, in Examples 2 to 6, a 600 [DPI] line image was formed on the latent image carrier 1 without being crushed, and a high density solid image having an OD value of 1.4 or more was formed. An image could be formed. Furthermore, A4 size paper 5
Even after the image formation of 0000 sheets, 6
A line image of 00 [DPI] was formed without being crushed, and a high-density image having an OD value of 1.4 or more could be formed, and a decrease in the density of a solid image was 0.1 or less. (Comparative Examples 1 and 2) In this comparative example, as the tubes 12 constituting the developer carrier 9, those having a wear amount of 700 [mg] or more according to the JIS-K7311 wear test were used. A durability print test was performed in the same manner as in the above. The surface of the tube 12 has a surface roughness Rz of 2
Sand blasting was performed so as to obtain [μm].

Table 2 shows the types of binders constituting the tube 12 used in this comparative example, JIS-K731.
1 Abrasion amount of tube by abrasion test, and 5,000 sheets, 10,000 sheets, 20,000 sheets, 50 sheets of A4 size paper
The surface roughness after printing 000 sheets and the image quality evaluation result of the printed image are shown.

[0059]

[Table 2]

As a result, initially, a 600 [DPI] line image was formed on the latent image carrier 1 without being crushed, and a high density image having an OD value of 1.4 or more could be formed. However, in Comparative Example 1, when images of 20,000 sheets of A4 size paper were continuously formed, the surface of the tube 12 was worn, and as a result, a sufficient amount of developer transport was not obtained. A solid image having a high image density cannot be formed.

In Comparative Example 2, the surface of the tube 12 was worn when images corresponding to 5,000 sheets of A4 size paper were continuously formed, and the density of the solid image became insufficient. When printing was continued,
Innumerable streak-like scratches occur in the circumferential direction of the tube 12, the developer is locally fused to the tube surface, and the formed image has a lot of background fog and a line of 600 [DPI]. The image has been crushed.

FIG. 4B shows the change over time of the wear amount of a tube using an acrylic resin as a binder. FIG. 4C shows the relationship between the wear amount of the tube surface and the surface roughness Rz. Is shown. Since the surface of the tube is constantly rubbed through the developer particles at the position facing the elastic blade and the electrostatic latent image carrier, the surface wears over time as shown in FIG. As a result, as shown in FIG. 4 (c), the surface roughness Rz sharply decreases as the wear amount increases, and particularly, the wear amount of the tube immediately after the start of use of the developer carrier is large. The initial change in the amount of developer conveyed also increased.

Therefore, if a tube having low abrasion resistance is used on the surface of the developer carrying member, the surface of the tube can be developed even if the amount of developer transport and the amount of charge suitable for development are initially obtained. When the surface roughness and the coefficient of friction of the tube become unsuitable for transporting the developer and applying the charge, an image having insufficient density is formed. Further, when the tube is damaged or the like, the transport amount of the developer becomes non-uniform, which causes an image with a lot of background fog and a decrease in reproducibility of fine lines.

As described above, the material of the tube covering the elastic layer was determined according to the JIS-K7311 wear test (wear wheels H22, H22,
In this case, when the wear amount is set to 700 mg or less, the tube surface is not easily worn away even when the developer is rubbed intensely, and the surface roughness is maintained over a long period of time. As a result, a fixed developer carrier was obtained, so that an image having sufficient image density and good resolution could be stably obtained. Also, by setting the material of the tube to a wear amount of 200 mg or less in the above-described wear test, it is possible to reduce a large amount of abrasion of the tube which occurs initially. It has become possible to obtain an image with little fluctuation in density over the whole area.

The tube is made of polyurethane, fluorine resin, polyethylene, nylon, polycarbonate, vinyl chloride, etc., and has a wear amount of 700 mg in the JIS-K7311 abrasion test (wear wheel H22,100).
Polyurethane having an abrasion amount of 200 [mg] or less and having sufficient flexibility is particularly desirable. (Embodiment 7) FIG. 5 is a schematic cross-sectional view of a developer carrying member used in a developing device in another embodiment of the present invention. The same numbers are assigned and the description is omitted. In FIG. 5A, a developer carrier 9 is obtained by integrally forming a foamed elastic layer 11 made of urethane on the outer periphery of a stainless steel shaft 10, and the elastic layer 11 is made of carbon black of 7 wt. %], The conductive material is made conductive to a volume resistivity of about 10 ⁶ [Ω · cm], and has a rubber hardness of 37 degrees by an Asker C-type hardness meter.

A conductive tube 1 is provided on the outer periphery of the elastic layer 11.
2 is coated, and the tube 12 is made of a material that is easy to charge the developer to a desired polarity, has good abrasion resistance, and is easy to control the surface roughness. Since the tube is provided with continuity, conduction between the tube surface and the shaft can be established, it is possible to apply a developing bias voltage to the shaft to perform development. The outer periphery of the tube 12 is subjected to sandblasting so that the surface roughness Rz becomes 5 [μm], and the dynamic friction coefficient is 0.6.

The tube 12 is formed in a sleeve shape having an outer diameter of 20 mm and a thickness of 50 μm by extrusion in advance, and the elastic layer 1 having an outer diameter of 21 mm is formed.
1 is fitted inside the tube 12 while being elastically deformed to form a developer carrying member.

Since the elastic layer 11 is a foamed material, its hardness can be greatly reduced, so that the pressure contact force with the photoreceptor can be effectively relaxed and soft contact can be achieved, and the developer carrying for pressure contact development can be carried out. Although it is desirable as a form of the body, if the developer is directly conveyed on the surface, a large amount of the developer is conveyed by the cells exposed on the surface of the elastic layer. Would. In the present invention,
By coating the outer peripheral surface of the elastic layer 11 with a tube, the surface state can be easily processed to a proper surface roughness for the developer conveyance regardless of the cell density of the foam, so that the stable developer conveyance can be maintained for a long time. It is now possible to perform over.

As the form of the elastic layer 11, besides the foam as shown in FIG. 5 (a), very low-hardness rubber or thermoplastic elastomer can be used. Is difficult to polish, and as shown in FIG. 5 (b), grinding marks having a 10-point average roughness Rz of 30 [μm] or more are likely to occur. This causes the transfer of the developer and the occurrence of filming of the developer. Also in this case, if the outer circumference of the elastic layer is covered with a tube as in the present invention, the surface state can be easily processed to a surface roughness suitable for developer transport regardless of the grinding marks of the elastic layer. Even if the elastic layer is a foam or a material having a low hardness that is hardly polished, the developer can always be stably transported for a long period of time. In addition, since the surface of the developer carrying member can be processed with a single tube, the surface roughness can be easily controlled without being affected by the elastic layer. (Embodiments 8 to 19) FIG. 5 (a) is a schematic cross-sectional view of a developer carrier used in a developing device according to another embodiment of the present invention. The members having the same functions are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 5A, the developer carrier 9 is
An elastic layer 11 made of foamable silicone rubber is integrally formed on the outer periphery of a shaft 10 made of stainless steel.
The outer periphery of 1 is further covered with a tube 12.

Since the outer periphery of the elastic layer 11 is covered with the tube 12, even if the elastic layer 11 is formed of a member such as a foam having a cell opening on the surface, the developer is clogged in the cell. Surface of the developer carrying member regardless of grinding marks on the elastic layer, even if the elastic layer is made of a material having poor abrasive properties, such as low-hardness rubber, etc. Can easily be processed to a surface roughness suitable for transporting the developer, so that the developer can always be transported stably. Furthermore, when a large amount of a plasticizer is added to the elastic layer in order to make the developer carrier low in hardness, the plasticizer gradually oozes out to the surface of the developer carrier and loses the elasticity of the elastic layer. The plasticizer oozes into the developer, causing deterioration of the charging performance and fluidity of the developer and filming on the surface of the developer carrier. This can prevent the plasticizer from seeping out to the surface of the developer carrier, and prevent filming of the developer and an increase in the hardness of the elastic layer.

Since the developer carrier in this embodiment is used in a state in which it is pressed against the latent image carrier, the tube covering the surface of the elastic layer is sufficiently formed so as not to lose the elasticity of the developer carrier. It is necessary to have high flexibility and not to cause fatigue failure due to repeated compressive stress.

However, in general, when the surface of the tube is subjected to surface processing such as polishing or surface roughening, the workability is deteriorated if the hardness is too low, and the workability is deteriorated if the hardness of the tube is too high. Flexibility is reduced and fatigue fracture occurs when bending stress is repeatedly applied.

In the present embodiment, a chip for covering the elastic layer
Longitudinal modulus of elasticity E [kg / cm ^Two] And its thickness t
[Cm] variously, 50,000 sheets of A4 size paper
Printing test. For the printing test, a volume average particle size of 10
[Μm], magnetic powder content 20 [wt%]
Using an image agent to urge the developer carrier against the latent image carrier
The test was performed with a load of 1 [kg]. Also tube
Has an outer diameter of 20 [mm]. Displays the results of the durability printing test
3 is shown.

In Table 3, ◎ in “Evaluation” means that the tube did not break even after printing 100,000 sheets of A4 size paper, and no filming of the developer occurred on the surface of the tube. This shows a case where an image can be formed with good density and fine line reproducibility. The circle indicates that the tube did not break after printing 100,000 sheets of A4 size paper, but the filming of the developer occurred on the tube surface at the end of printing about 20,000 sheets. Is shown.

[0076]

[Table 3]

In the present embodiment, 60
0 [DPI] image is formed without collapse.
Even after printing 100,000 sheets of A4 size paper,
The tube does not break due to fatigue, and therefore the surface of the elastic layer
Roller coated with tube as developer carrier
Also, the press-contact development was successfully performed. (Examples 20 to 27) In this example, the elastic layer was coated.
Longitudinal modulus of tube E to be covered [kg / cm ^Two], Ju
The tube thickness t [cm] and the tube outer diameter d [cm]
100,000 prints on A4 size paper
Was done.

[0078]

[Table 4]

In the printing test, the volume average particle diameter was 10 μm
m], and a test was performed using a one-component magnetic developer having a magnetic powder content of 20 [wt%] and an urging load of the developer carrier on the latent image carrier of 1 [kg]. The outer diameter of the tube was 20 [mm].

Table 4 shows the results of the durable printing test. Table 4
In the middle, “Evaluation” indicates that the tube was not broken even after printing 100,000 sheets on A4 size paper.
Further, a case where filming of the developer does not occur on the tube surface and an image with good image density and fine line reproducibility can be formed is shown. The circle indicates that the tube does not break after printing 100,000 sheets of A4 size paper.
This shows the case where filming of the developer has occurred on the surface of the tube at the end of printing of 10,000 sheets.

In this embodiment, the outer diameter is 0.5 to 5 [c
m], an image of 600 [DPI] was formed on the latent image carrier without being crushed, and 100,000 sheets of A4 size paper were durable printed on the latent image carrier. Even after this, the tube did not break due to fatigue. Therefore, even when the roller having the surface of the elastic layer coated with the tube was used as the developer carrying member, the press-contact development was successfully performed. (Embodiments 28 to 31) In this embodiment, a developer carrying member having a structure in which an elastic layer and a tube are formed concentrically on the outer periphery of a shaft as shown in FIG. On the other hand, when the image was formed while being pressed with an urging load of 1 [kg], a durable printing test was performed by changing the film thickness of the tube, and image defects and the state of the tube were observed.

In this example, silicon rubber was used as the elastic layer, and a nickel electroformed tube having an outer diameter of 10 mm was used as the tube, and the silicon rubber was foamed inside the nickel electroformed tube to perform integral molding. A developer carrier was used.

Table 5 shows the results of the durability print test. Table 5
Medium, "Stress S", when pressing the tube against the photoreceptor,
Indicates the maximum bending stress S [kg / cm ² ] generated in the tube. In Table 5, ◎ in “Evaluation” means that the tube did not break even after the developer carrier rotated 10 ^6, no filming of the developer occurred on the tube surface, and the image density and fine line reproduction were observed. This shows a case where an image having good characteristics can be formed. In addition, ○ indicates a case where the tube does not break after the developer carrier rotates 10 ⁶ times, but filming of the developer occurs on the tube surface.

[0084]

[Table 5]

In Examples 28 to 31, the durability printing test was performed by changing the film thickness t of the tube.
D value 1.4 or more high-density image can be formed stably, also without tube to fatigue failure even after the developer carrying member ¹⁰⁶ rotates, thus coating the tube surface of the elastic layer Even when the roller was used as the developer carrying member, the pressure contact development was successfully performed. Further, the modulus of longitudinal elasticity E [kg / c
The product E × t of m ² ] and the film thickness t [cm] of the tube is 900.
When the value is 0 or less, an image of 600 [DPI] can be formed on the latent image carrier without collapse even after the developer carrier rotates 10 ⁶ , and an image with good fine line reproducibility is formed over a long period of time. Was especially desirable.

In this embodiment, a nickel electroformed tube is used as a tube. However, even when a resin such as polyurethane or vinyl chloride is used, Ext is 12,000.
If it is below, even when the developer carrier is used while rotating more than 10 ^{6, the} tube was not broken, and the pressure welding development was successfully performed. (Comparative Examples 3 to 6) Comparative Examples 3 to 6 are Examples 28 to 31.
And the modulus of longitudinal elasticity of the tube E [kg / c
m ² ] and the film thickness t [cm], a durability printing test was performed, and image defects and the state of the tube were observed.

FIG. 6 is an explanatory view of the mechanical characteristics of the tube constituting the developer carrier used in the developing device in this comparative example. As shown in FIG. When an image is formed while a developer carrying member having a structure in which layers and tubes are formed concentrically is pressed against a latent image carrying member with an urging load of 1 kg, the maximum value generated in the tube is obtained. This graph shows the relationship between the bending stress S (kg / cm ² ) and the number of bendings (the number of rotations of the developer carrying member) N at which the tube causes fatigue failure. In this comparative example, a silicone rubber was used as the elastic layer, a nickel electroformed tube was used as the tube, and the outer diameter of the developer carrying member (outer diameter of the tube) was 10 mm.

Table 6 shows the results of the durability print test. Table 6
Medium, "Stress S", when pressing the tube against the photoreceptor,
Indicates the maximum bending stress S [kg / cm ² ] generated in the tube. In Table 5, "X" in "Evaluation" indicates that the tube constituting the developer carrier was fatigued and broken by repeated stress during the durability printing test, and the image formation could not be continued. In the case of △, although the tube did not break after the developer carrier rotated 10 ⁶ , the tube was deformed to give an image with uneven density, and the filming of the developer on the tube occurred. This indicates that a high-resolution image could not be formed, and that fatigue failure occurred when the durable printing test was further continued.

[0089]

[Table 6]

In Comparative Example 3 and FIG. 6, the film thickness was 0.00
When a tube was formed from an 8 cm nickel electroformed tube and subjected to pressure welding development, the maximum bending stress generated in the tube was 1680 [kg / cm ² ]. Furthermore, was subjected to endurance printing test using the developer carrying member, the tube had fatigue fracture by repeated stress when the developer carrying member was about ¹⁰⁵ rotates.

In Comparative Example 4 and FIG.
When a tube was formed from a 6 cm nickel electroformed tube and subjected to pressure welding development, the maximum bending stress generated in the tube was 1,260 [kg / cm ² ]. In addition, when a durable printing test was performed using this developer carrier, the tube did not break after about 10 ⁶ rotations of the developer carrier, but the tube was deformed and an image having uneven density was obtained. Also, filming of the developer occurred on the tube, and a high-resolution image could not be formed. Further, when the durable printing test was continued, the tube was shortly broken due to repeated stress.

Accordingly, the elastic layer and the tube are formed concentrically on the outer periphery of the shaft to form a developer carrier for pressure-contact development, and the product (E × t) of the longitudinal elastic coefficient E of the tube and the film thickness t of the tube is obtained. If it is 12000 or less, the diameter of the general developer carrier is 0.5 to 5 cm and the urging load (linear pressure) on the latent image carrier is 0 to 200 g / cm.
The tube formed on the surface of the developer carrier does not break due to repeated bending stress applied to the tube when performing pressure welding development. Also, even if a material whose surface shape is difficult to control, such as a foam or rubber with low hardness, is used for the elastic layer,
By coating the outer periphery of the elastic layer with a tube, the surface of the developer carrier can be easily processed into a state suitable for transporting the developer, and the tube does not repeatedly break due to fatigue stress. A developer carrier suitable for development can be obtained.

Further, an elastic layer and a tube are formed concentrically around the outer periphery of the shaft to form a developer carrier for press-contact development, and the product of the longitudinal elastic coefficient E of the tube constituting the developer carrier and the film thickness t ( If Ext) is 9000 or less, the developer is less likely to cause filming on the surface of the developer carrier even during long-time image formation, and it is possible to stably form an image with sufficient density. Became.

As described above, the (E ×
By coating a tube having t) of 12,000 or less,
A developer carrier that can make a soft contact with the latent image carrier and secure a wide development nip can be obtained. Therefore, the developer solidifies and filming of the developer occurs on the developer carrier. This makes it possible to obtain an image with less density unevenness at a high speed without causing damage to the latent image carrier. (Embodiments 32 to 38) FIG. 7 is a schematic cross-sectional view of a developer carrier used in a developing device according to another embodiment of the present invention, in which members having substantially the same names and functions as those in FIG. Are denoted by the same reference numerals and description thereof is omitted. In FIG. 7A, a developer carrier 9 has an elastic layer 11 (longitudinal elastic coefficient = 8) made of polyurethane foam on the outer periphery of a shaft 10 made of stainless steel.
[Kg / cm ² ]).

The outer periphery of the elastic layer 11 is covered with a conductive and heat-shrinkable tube 12.
Is directly adhered to the shaft 10, so that even if the elastic layer 11 is made of a non-conductive material, conduction between the heat-shrinkable tube and the shaft is ensured, and development is performed by applying a developing bias voltage to the shaft. That makes it possible.

The inner diameter of the tube 12 before heat shrinkage is φ22
[Mm], and after inserting the elastic layer 11 into the tube 12 before the heat shrinkage, the environment was decompressed and further 100 [° C.]
Then, the tube 12 was shrunk by heating to form a developer carrier by covering the outer periphery of the elastic layer 11.

The tube 12 is a conductive and flexible tube in which conductive particles are dispersed in a binder.
More specifically, it is an extruded tube in which 6 [wt%] of carbon black is dispersed in a polyurethane resin to have a volume resistivity of 10 ⁴ [Ω · cm], and the outer surface thereof has a surface roughness Rz of 1 [μm]. As described above, the sand blast treatment is performed, the dynamic friction coefficient is 0.5, and the amount of abrasion according to the JIS-K7311 abrasion test is 100 [mg].

In this embodiment, printing is performed by changing the hardness of the elastic layer (Asker C hardness) [degree], the film thickness t [cm], and the longitudinal elastic coefficient E [kg / cm ² ] of the tube. An experiment was conducted to observe image defects and the surface state of the latent image carrier.

Table 7 shows the results of the printing experiment.

In Table 7, ○ in “Evaluation” indicates 600
The line image of [DPI] was formed without thickening or tailing at the end of the image, and no filming or the like of the developer was observed on the tube even after forming 10,000 images. High density solid images having an OD value of 1.4 or more with no background fog can be formed stably, and there is no fixation of the developer or scratches on the latent image carrier. Also, △
Although a line image of 600 [DPI] could be formed without causing line thickening or tailing at the end of the image,
This indicates that filming of the developer has occurred on the tube after the image formation on the sheet.

[0101]

[Table 7]

In FIG. 7A, since the elastic modulus of the elastic layer 11 is very small at 8 [kg / cm ² ], if the developer is directly conveyed on the surface of the elastic layer, At the upstream of the contact position between the latent image carrier 1 and the elastic layer 11 and the elastic blade 13, raised portions of the elastic layer as shown by A and B in FIG. 7B are formed, and the distortion is released. As a result, the elastic layer 11 or the elastic blade 13 generates a periodic vibration (stick-slip), causing a density fluctuation. In the case where the elastic layer 11 is made of a material that easily causes compression set, the developer carrier is compressed by a contact member such as an elastic blade when not in operation to cause permanent deformation, and the developer conveyance amount is changed. I will.

Therefore, in this embodiment, the elastic layer 11
Is coated with a tube having an appropriate longitudinal modulus of elasticity E and film thickness t to improve the developer transportability and chargeability, and the elasticity generated upstream of the portion where the developer carrier is pressed. The swelling of the layer is prevented beforehand by the rigidity of the tube 12, and the tube 12 has sufficient flexibility so that it can be softly pressed against the photoreceptor, and a sufficiently wide developing nip can be secured, so that high density Thus, high-resolution images can be printed at high speed.

Further, even when the developer carrier is not in operation, the pressing force of the abutting member such as an elastic blade can be effectively dispersed by the rigidity of the tube. This makes it possible to use the layer as a layer, to reduce the hardness of the elastic layer, to manufacture the developer carrying member at low cost, and the like. (Comparative Examples 7 to 11) This comparative example corresponds to Examples 32 to 38, and in the developer carrying member shown in FIG.
Hardness of elastic layer (Asker C hardness) [degree], tube thickness t [cm], longitudinal elastic modulus E [kg / c]
m ² ] was changed, and a printing experiment was performed to observe image defects and the surface state of the latent image carrier.

The developer carrier 9 was manufactured with the same material, shape and manufacturing method as those in Examples 32 to 38, and was mounted on the developing device shown in FIG. 2 to perform a printing experiment.

Table 8 shows the results of the printing experiment.

[0107] In Table 8, × ⁺ is in the "evaluation", flexible because the stiffness of the tube 12 coated is too high on the outer circumference is decreased in the elastic layer 11, can be sufficiently relieve pressure pressure of the developer carrying member That is, the developer is fixed (filming) on the tube 12 and the latent image carrier, and countless scratches are generated on the surface of the latent image carrier. Also, ×
^-, despite coating the tube 12 to the outer periphery of the elastic layer 11, upstream of the portion where the developer carrying member is brought into pressure contact,
A part where the surface of the developer carrier is raised is generated,
This indicates that the developer carrier and the elastic blade vibrated periodically, and only an image having density fluctuation and ground fog could be formed.

[0108]

[Table 8]

(Embodiment 39) FIG. 8 is an explanatory view of the mechanical characteristics of a developer carrier used in a developing device in another embodiment of the present invention, and is shown in FIG. 7 (a). 3 shows conditions under which the developer carrying member having the above configuration is mounted on the developing device shown in FIG. 2 to perform printing and prevent the occurrence of stick-slip.

In FIG. 7A, when the hardness of the elastic layer 11 is 30 degrees or less in Asker C type hardness (manufactured by Kobunshi Keiki Co., Ltd.), the elastic layer is easily deformed. 1
1 and latent image carrier 1 or elastic layer 11 and elastic blade 1
The stick-slip phenomenon occurs in the contact portion of No. 3.

The present applicant has proposed that by coating the outer periphery of the elastic layer 11 with a tube 12 having a longitudinal elastic modulus E and a film thickness t satisfying the following expression, the portion where the developer carrying member is pressed against the tube is pressed. The swelling of the elastic layer that occurs upstream is prevented by the rigidity of the tube.

[0112] 5 · r ³ / I ≦ E [kg / cm ^{2] _{I = π × (d 1 4}} -d 2 4) / 64 r = (d 1 + d 2) / 4 [cm] t = (d ₁ −d ₂ ) / 2 [cm] π: circumference ratio d ₁ : outer diameter of tube [cm] d ₂ : inner diameter of tube [cm] However, if the rigidity of the tube 12 is too large, the flexibility of the tube is lost. Therefore, the longitudinal elastic modulus E of the tube must satisfy the following equation.

E ≦ 40000 · r ³ / I [kg / cm ² ] When the hardness of the elastic layer 11 is large, the tube 1
If the film thickness t and the longitudinal elastic modulus E are too large, the flexibility is lost. If the hardness of the tube is 35 degrees or more with an Asker C type hardness tester (manufactured by Kobunshi Keiki Co., Ltd.), It is desirable that the modulus of longitudinal elasticity E satisfies the following expression.

E ≦ 150 · r ³ / I [kg / cm ² ] The film thickness t of the tube 12 may be any value as long as it satisfies the above relational expression, but if it is too thin, handling becomes difficult. , 0.0015 ≦ t [cm] or more is desirable.

When the developer carrier of this embodiment was used in the developing apparatus shown in FIG. 2 to continuously form a line image, character image and solid image of 600 [DPI] over 10,000 sheets, it was very soft. Since the outer periphery of the elastic layer is covered with a flexible tube, the pressure between the developer carrier and the latent image carrier is reduced, and there is no occurrence of stick-slip or permanent deformation of the elastic layer. Pressing development becomes possible without solidifying the developer or damaging the latent image carrier, and a 600 [DPI] line image can be formed without causing line thickening or tailing at the end of the image. No fusing such as filming of the developer was observed on the tube even after the image formation was performed, and a high-density solid image having an OD value of 1.4 or more without fog was stabilized for a long period of time. It could be formed.

The material constituting the tube 12 may be resin, rubber, Ni, Cu,
Any material that can be formed into a thin cylinder, such as a metal such as Zn or Al or an alloy containing them, can be used. Preferably, it is processed into a heat-shrinkable tube, and the hardness of the elastic layer is adjusted by the gripping force. A possible heat-shrinkable resin or the like is desirable. (Embodiment 40) FIG. 9 is a schematic cross-sectional view of a developer carrier used in a developing apparatus according to another embodiment of the present invention.
Members having substantially the same names and functions as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In FIG. 9, the developer carrier 9
Is obtained by integrally forming an elastic layer 11 made of silicone rubber on the outer periphery of a stainless steel shaft 10.
Has a structure in which a skin layer 42 is provided on the outer periphery of the foam layer 41, and is made conductive to a volume resistivity of about 10 ⁷ [Ω · cm] by dispersing 3% by weight of carbon black. The hardness is 25 degrees with an Asker C hardness tester.

The outer periphery of the elastic layer 11 is covered with a conductive and heat-shrinkable tube 12.
Is adhered on the elastic layer 11 by a conductive adhesive, the conduction between the surface of the heat-shrinkable tube and the shaft is secured, and the developing bias voltage can be applied to the shaft to perform development.

The inner diameter of the tube 12 before heat shrinkage is φ24.
[Mm], and after inserting the elastic layer 11 into the tube 12 before the heat shrinkage, the environment was decompressed and further 120 [° C.]
Then, the tube 12 was shrunk by heating to form a developer carrier by covering the outer periphery of the elastic layer 11.

The tube 12 is a conductive and flexible tube in which conductive particles are dispersed in a binder.
More specifically, a volume resistivity of 10 ⁴ [Ω · cm] in which 6% by weight of carbon black is dispersed in a polyurethane resin, and a film thickness of 5%
This is a tube formed by extrusion molding of 0 [μm].

The magnetic field generating layer 81 is formed by applying a magnetic coating material in which carbon black and magnetic powder are dispersed in a binder onto the tube 12 by a roller coating method. 0.5 [mm] or less, desirably 0.1
(Mm) obtained by the following, Examples of carbon black are suitable good acetylene black conductivity, 10 ⁴
[Ω · cm].

Further, a polyester resin was used as the binder, but polyurethane, epoxy resin,
Vinyl acetate, vinyl alcohol, vinyl butyral, vinyl formal, vinyl ethyl ester and other vinyl copolymer resins or polyamides or nitrocellulose or cellulose acetobutyrate or blends thereof with other resins can be used. By blending vinyl, vinyl chloride, and polyurethane, or blending cellulose acetobutyrate and vinyl formal, etc., it is possible to design a binder that complements each other's properties and achieves both dispersibility and mechanical strength.

As the magnetic powder, a magnetic powder known as a magnetic recording material or a magnet material can be used. More specifically, a magnetic material containing at least one element of Fe, Ni, Co, Mn, and Cr can be used. , For example, γ-Fe _{2
O 3, Ba-Fe, Ni} -Co, Co-Cr, Mn-A
1 and the like can be used.

The outer periphery of the magnetic field generating layer 81 has a surface roughness Rz of 1
[Μm], the coefficient of kinetic friction is 0.5, the abrasion amount according to the JIS-K7311 abrasion test is 150 [mg], and the magnetic head has a pitch of 100 [μm] in the circumferential direction by a magnetic head. Magnetized.

When the developer carrying member of this embodiment was used in the developing device shown in FIG. 2 to continuously form a line image, a character image and a solid image of 600 [DPI] over 10,000 sheets, it was very soft. Since the outer periphery of the elastic layer is covered with a flexible tube, the pressure between the developer carrier and the latent image carrier is reduced, and there is no occurrence of stick-slip or permanent deformation of the elastic layer. Pressing development becomes possible without solidifying the developer or damaging the latent image carrier, and a 600 [DPI] line image can be formed without causing line thickening or tailing at the end of the image. No fusing such as filming of developer was observed on the tube even after the image was formed, and a high-density solid image with an OD value of 1.4 or more without fog was stabilized for a long period of time. It could be formed.

In addition, despite the fact that silicone rubber having poor adhesion to the magnetic field generating layer was used as the elastic layer, the surface was covered with a tube (polyurethane resin) of a material that can easily adhere to the magnetic field generating layer. A magnetic field generating layer can be disposed on the developer carrying member with sufficient adhesion strength. Therefore, the magnetic field generating layer is less likely to be peeled or cracked by an external force such as a compressive deformation, and a developer carrying member suitable for pressure-contact development is provided. I got it.

Further, since the magnetic field generating layer 81 is magnetized so that the minimum magnetization reversal pitch is 100 [μm] or less, the leakage magnetic flux attracting the magnetic developer is approximately several tens from the surface of the magnetic field generating layer. [Μm], the developer was uniformly thinned, and at the same time, the variation in the amount of the developer transported on the developing roller due to the formation of the magnetic brush was suppressed, and an image with less density unevenness could be stably formed. (Embodiment 41) FIG. 5 (a) is a schematic cross-sectional view of a developer carrier used in a developing device according to another embodiment of the present invention. The members are assigned the same reference numerals and the description is omitted. In FIG. 5A, the developer carrier 9 is obtained by integrally molding an elastic layer 11 made of foamed silicone rubber on the outer periphery of a stainless steel shaft 10. The layer 42 has a volume resistivity of about 10 ⁷ [Ω · cm] by dispersing 3 [wt%] of carbon black, and has a rubber hardness of 27 degrees with an Asker C type hardness meter. is there.

The outer periphery of the elastic layer 11 is covered with a conductive and heat-shrinkable tube 12 in which magnetic powder is dispersed, and the tube 12 is covered with a conductive adhesive.
Since it is adhered on the upper side, conduction between the tube surface and the shaft is ensured, and development can be performed by applying a developing bias voltage to the shaft.

The inner diameter of the tube 12 before heat shrinkage is φ22
[Mm], after inserting the elastic layer 11 into the tube 12 before the heat shrinkage, the environment is decompressed, and further heated to 90 ° C. to shrink the tube 12 to cover the outer periphery of the elastic layer 11. To form a developer carrier.

The tube 12 is a conductive and flexible tube in which conductive particles are dispersed in a binder.
More specifically, a volume resistivity of 10 ⁴ [Ω · cm] in which 6% by weight of carbon black is dispersed in a polyurethane resin, and a film thickness of 5%
This is a tube formed by extrusion molding of 0 [μm].

The tube 12 is a heat-shrinkable tube in which carbon black and magnetic powder are dispersed in a binder, and its film thickness can be increased even if the content of the magnetic powder increases and the hardness of the tube increases. 0.5 [mm] to have flexibility
Hereinafter, it is desirably 0.1 mm or less. As carbon black, acetylene black having good conductivity is suitable.

Further, a polyurethane resin was used as the binder. In addition, EPDM, polyvinyl chloride, fluorine resin, fluorine rubber, silicon rubber, polyethylene,
Heat-shrinkable materials such as polypropylene, linear polyester, polyamide resin, crystalline polyolefin, cross-linked polyolefin, non-cross-linked polyolefin, crystalline polyolefin copolymer, and PET can be used.

As the magnetic powder, a known magnetic powder as a magnetic recording material or a magnet material can be used. More specifically, a magnetic material containing at least one element of Fe, Ni, Co, Mn, and Cr can be used. , For example, γ-Fe _{2
O 3, Ba-Fe, Ni} -Co, Co-Cr, Mn-A
1 and the like can be used.

The outer circumference of the tube 12 has a surface roughness Rz of 1
[Μm], the coefficient of kinetic friction is 0.45, the abrasion amount according to the JIS-K7311 abrasion test is 160 [mg], and the magnetic head has a pitch of 100 [μm] in the circumferential direction. Magnetized.

The developer carrier of this embodiment was used in the developing apparatus shown in FIG. 2 to continuously form 600 [DPI] line images, character images and solid images over 10,000 sheets. Since the outer periphery of the elastic layer is covered with a flexible tube, the pressure between the developer carrier and the latent image carrier is reduced, and there is no stick-slip or permanent compression set of the elastic layer. Pressing development becomes possible without solidifying the developer or damaging the latent image carrier, and a 600 [DPI] line image is formed without generating a thick line or tailing at the end of the image. No fusing such as filming of developer was observed on the tube even after the image was formed, and a high-density solid image with an OD value of 1.4 or more without fog was stabilized for a long period of time. It could be formed.

Further, despite the fact that a foam which is difficult to apply a magnetic paint was used as the elastic layer, the heat-shrinkable tube in which the magnetic powder was dispersed was covered, so that the magnetic layer having a uniform thickness was formed on the surface of the elastic layer. The developer layer can be easily disposed, and the magnetic field generating layer (tube in which the magnetic powder is dispersed) does not undergo peeling or cracking due to external force such as compression deformation, and a developer carrier suitable for pressure contact development can be obtained. I was able to.

Further, since the tube 12 is magnetized so that the minimum magnetization reversal pitch is 100 [μm] or less, the leakage magnetic flux attracting the magnetic developer is approximately several tens [μm] from the surface of the magnetic field generating layer. ), The variation of the amount of the developer conveyed on the developing roller due to the formation of the magnetic brush was suppressed to a fine pitch, and an image with less density unevenness was stably formed.

In FIGS. 1 to 9, the present invention is not limited only by the configuration shown in the drawings. In particular, the structure of the tube 12 is not limited to those shown in FIGS. 1, 4, 5, 7, and 9; an additive such as a dispersant may be added to the binder of the tube; It is also possible to improve the developing electrode effect by dispersing particles to make it a floating electrode. , Abrasion resistance, prevention of bias leak, improvement of developer transport characteristics, and development electrode effect. Further, a configuration in which fine holes are formed in the tube surface or a mesh shape is possible.

The arrows indicate the directions of rotation of the respective members, but do not limit the present invention.

Further, the developing method can be used regardless of whether it is regular development or reversal development.

Further, the developer used in the present invention can be used regardless of whether it is a magnetic developer or a non-magnetic developer. Further, a one-component developer, a two-component developer, or a 1.5-component developer can be used. As the component-based developer, all known developers can be used, and any of a resin-based developer and a wax-based developer may be used. As is known, the composition of the developer is obtained by adding a magnetic powder, a colorant, an external additive, and other additives to a resin, and is prepared by a pulverization method, a polymerization method, or the like.

Although the embodiments have been described above, the present invention can be applied not only to the above embodiments but also to a wide range of developing apparatuses such as electrophotography. Particularly, the present invention is effective when applied to printers, copiers, facsimiles and displays. It is.

[0142]

As described above, the developer carrier has a structure in which the elastic layer and the conductive layer are arranged concentrically on the outer periphery of the shaft, and the surface roughness Rz of the conductive layer is 0.1 to 10 μm.
m], by setting the dynamic friction coefficient to 0.2 to 0.7,
The developer conveyance amount and the charge amount can be stably maintained over a long period of time, which is suitable for development.

The abrasion resistance of the conductive layer was measured in accordance with JIS-K7.
By setting the content to 700 mg or less in the 311 abrasion test, the surface of the developer carrier is not significantly worn by rubbing with the developer, and the fluctuation of the surface roughness and the friction coefficient can be suppressed. As a result, the developer conveyance amount and the charge amount are stabilized.

Further, even if the elastic layer is made of a material having low hardness, for example, foamed rubber, the surface is covered with a conductive layer having a suitable rigidity, so that the surface can be polished or roughened. In addition to easy control of diameter fluctuation and surface roughness, even when a functional layer such as a magnetic field generating layer is provided on the outer periphery of the elastic layer, there is a wide selection range of materials that can be used as the conductive layer. The arrangement of the functional layer can be facilitated, for example, by using the same type of material as the paint to improve the adhesion to the magnetic paint.

Further, since the surface roughness of the conductive layer can be processed by the conductive layer alone, accurate processing can be easily performed without being affected by the elastic layer.

Further, the modulus of longitudinal elasticity of the conductive layer E [kg / c
When m ² ] and the thickness t [cm] of the conductive layer satisfy the formula: E × t ≦ 12000, the rigidity of the conductive layer can be improved within a range having sufficient flexibility, and the repetitive stress can be increased. The surface condition of the conductive layer can be easily processed and
It can be controlled and can be used as a developer carrier for press-contact development where the surface of the developer carrier is constantly exposed to deformation. Furthermore, since sufficient flexibility can be imparted to the conductive layer, soft contact with the latent image carrier is enabled by making the elastic layer low hardness, and the contact width with the elastic blade and the latent image carrier is further reduced. , The charge amount of the developer can be improved and high-speed printing can be performed.

Further, by imparting appropriate rigidity to the conductive layer, even when the hardness of the elastic layer is extremely low, the contact pressure with the elastic blade or the photosensitive member can be effectively dispersed by the rigidity of the conductive layer. Furthermore, it is possible to prevent the occurrence of periodic micro-vibration (stick-slip) which occurs when releasing the locally generated compressive deformation and the occurrence of partial compression set of the elastic layer.

Furthermore, even when a functional layer such as a magnetic field generating layer is provided on the surface of the conductive layer, the conductive layer does not locally undergo large deformation, so that the functional layer does not peel or crack against compressive deformation or the like. It is unlikely to occur, so that mechanical properties such as adhesion and flexibility of the functional layer can be improved.

Further, even if a foam is used as the elastic layer, the outer periphery of the elastic layer is covered with the conductive layer, so that the opening of the cell exposed on the surface of the elastic layer can be closed. An image with less background fog can be formed without clogging the surface of the developer with the developer. Also, when a magnetic paint or the like is applied to the surface of the developer carrier, the surface can be made smooth, so that a functional layer such as a magnetic field generating layer can be easily formed on a foam that is difficult to apply. Can be arranged.

Further, by dispersing a functional powder such as a magnetic powder in a conductive layer covering the outer periphery of the elastic layer to form a functional layer,
Even if the elastic layer is made of a material such as silicone rubber, which is difficult to adhere to, the functional layer can be easily disposed, and the functional layer is not easily peeled off when the pressure welding development is performed, and the production can be easily performed. .

Further, if the outer periphery of the elastic layer is covered with a conductive layer, the bleeding of the plasticizer and the like contained in the elastic layer can be prevented, and the clogging of the elastic layer with the developer can be prevented. A layer and a developer are less deteriorated, and a long-life developer carrier can be obtained.

Therefore, according to the present invention, there is an excellent effect that it is possible to provide an inexpensive developing device which has few image defects such as background fogging and tailing and can stably obtain a high-resolution image for a long period of time. Things.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a developer carrier used in a developing device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the developing device of the present invention.

FIG. 3 is an explanatory diagram showing development characteristics of the development device of the present invention.

FIG. 4 is a schematic cross-sectional view of a developer carrier used in a developing device according to another embodiment of the present invention and an explanatory diagram of mechanical characteristics.

FIG. 5 is a schematic cross-sectional view of a developer carrying member used in a developing device according to another embodiment of the present invention.

FIG. 6 is an explanatory diagram of mechanical characteristics of a tube constituting a developer carrier used in a developing device in the comparative example.

FIG. 7 is a schematic cross-sectional view of a developer carrier used in a developing apparatus according to another embodiment of the present invention.

FIG. 8 is an explanatory diagram of mechanical characteristics of a developer carrier used in a developing device according to another embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view of a developer carrier used in a developing device according to another embodiment of the present invention.

[Explanation of symbols]

 1 Latent image carrier 7 Developing device 8 ······ Developer 9 ·········· Developer support 10 ····· Shaft 11 ······ Elastic layer 12 ······ Tube 13 ··· ································································· Binder 22 Carbon black 41 Foamed layer 42 ..... Skin layer 81 ..... Magnetic Generating layer

Claims (5)

[Claims] 1. A developing device for holding a thin layer of a developer layer on a developer carrier and transporting the developer layer to a position facing a latent image carrier, wherein the developer carrier comprises an elastic layer And a conductive layer coated on the surface of the elastic layer. The longitudinal elastic modulus E [kg / cm ² ] of the conductive layer and the thickness t [cm] of the conductive layer are represented by the following formula: E × t ≦ 12000. 2. A developing device for holding a thin layered developer layer on a developer carrier and transporting the developer layer to a position facing a latent image carrier, wherein the developer carrier comprises an elastic layer. And a conductive layer coated on the surface of the elastic layer, and the modulus of longitudinal elasticity E of the conductive layer is represented by the formula: 5 × r ³ / I ≦ E ≦ 40000 × r ³ / I [kg / cm ² ] ^{_{I = π × (d 1 4}} -d 2 4) / 64 r = (d 1 + d 2) / 4 π: circle ratio d _1: the outside diameter of the conductive layer (cm) d _2: inside diameter of the conductive layer [ cm]. 3. The surface roughness Rz of the conductive layer is 0.1 to
The developing device according to claim 1, wherein the thickness is 10 μm. 4. The developing device according to claim 1, wherein a dynamic friction coefficient between the outer surface of the conductive layer and the developer layer is 0.2 to 0.7. 5. The conductive layer according to JIS-K7
A developing device characterized in that the amount is 700 [mg] or less in a 311 abrasion test.