JPH0980901A - Developing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device and an image forming device where excess stress on toner on a developing roller is controlled and the toner is uniformly and stably stuck so as to substantially become a monolayer on the developing roller. SOLUTION: The developing device 5 possesses the developing roller 8 performing developing by selectively moving a part of the toner stuck on the outer periphery to the outer peripheral surface of a photoreceptor drum by a specified pattern corresponding to a latent image, and a developing roller blade 9 adjusting the thickness of a toner layer formed on the outer periphery of the developing roller 8 by abutting on the outer periphery of the developing roller 8; and the developing roller blade 9 is composed of a band plate-like rubber elastic body, and the tip of the blade 9 is brought into contact with the outer periphery of the developing roller 8 so as to make the deflection quantity δ of the tip of the blade 9 is 2-4mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus and a developing apparatus used therein.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic system such as an electrophotographic printer has a charging device for uniformly and uniformly charging the surface of a photosensitive drum as a latent image holding member, and a charging device for uniformly charging the surface. A latent image forming device such as a laser device that writes an electrostatic latent image on the surface of the photoconductor, a developing device that develops the electrostatic latent image with toner, and a portion that transfers the developed toner image to transfer paper or the like. Have.

The developing device of such an image forming apparatus has a developing roller and a blade for the developing roller. When the developing roller rotates in the developing device, the toner in the developing device adheres to the outer peripheral surface due to electrostatic force due to friction. The developing roller blade contacts the outer peripheral surface of the rotating developing roller and adjusts the layer thickness of the toner layer formed on the outer peripheral surface of the developing roller. That is, the blade for the developing roller is for scraping off a part of the toner particles adhering to the developing roller, adjusting the layer thickness of the toner particles, and making the charge amount of the passing toner uniform.

A part of the toner adhered to the outer peripheral surface of the developing roller is selectively moved to the surface of the photosensitive drum in a latent image pattern when the surface of the developing roller approaches the surface of the photosensitive drum, and the photosensitive drum is exposed. The electrostatic latent image of is developed and a toner image is formed on the surface of the photosensitive drum. This toner image is
The image is formed on the transfer paper by being transferred to the transfer paper.

[0005]

In the blade for the developing roller used in such a developing device, it is important that the toner is uniformly and thinly attached to the outer peripheral surface of the developing roller. If the toner does not uniformly adhere to the outer peripheral surface of the roller, photoconductor fog occurs when the electrostatic latent image is developed on the surface of the photosensitive drum. The photoconductor fog is a phenomenon in which toner having a polarity opposite to that of the toner to be attached to the photoconductor drum is attached to the photoconductor drum, which makes uniform charging difficult and causes a problem such as deterioration of image quality.

A blade made of stainless steel is known as a conventional blade for a developing roller. However, with this stainless steel blade, the amount of electrostatic charge of the toner on the developing roller tends to vary, and the toner is easily filmed (the toner is fused by frictional heat to form a film). Further, with a stainless steel blade, it is difficult to form the toner substantially uniformly in a single layer on the developing roller.

A blade made of a rubber elastic body has also been proposed, but when the blade is in contact with any amount of deflection, a substantially single toner layer is formed on the outer peripheral surface of the developing roller. It wasn't clear what could be done. For example, traditionally, the blade
It was thought that it would be good to press it strongly against the surface of the developing roller.

However, if the development is carried out while the blade is strongly pressed against the developing roller, the stress on the toner is increased and the durability is deteriorated. Further, if the development is performed with the blade strongly pressed against the development roller, the torque of the development roller is mechanically increased, which may cause a so-called jitter phenomenon. The jitter phenomenon is a phenomenon in which horizontal stripes are generated according to the number of teeth of the gear for driving the developing roller.

Further, in such a developing device, the charge amount of the toner is likely to vary, and it is not sufficient to uniformly adhere the toner onto the developing roller so that the toner becomes a substantially single layer. there were. In the developing device, it is important to form a substantially single-layer toner layer on the outer peripheral surface of the developing roller, which enables good development.

An object of the present invention is to prevent excessive stress on the toner on the developing roller and to uniformly and stably adhere the toner onto the developing roller so that the toner is substantially a single layer. And to provide an image forming apparatus.

[0011]

Means for Solving the Problems The inventors of the present invention have made earnest studies on a blade for a developing roller, and as a result, the blade is made of a rubber elastic body and the bending amount of the blade with respect to the developing roller is set within a predetermined range. The inventors have found that it is possible to suppress excessive stress on the toner on the developing roller and uniformly adhere the toner on the developing roller so that the toner is substantially a single layer, and have completed the present invention.

That is, in the developing device according to the present invention, a part of the toner adhered to the outer periphery is transferred to the outer peripheral surface of the latent image carrier.
A developing roller that selectively moves in a predetermined pattern corresponding to a latent image to perform development, and adjusts the thickness of a toner layer formed on the outer periphery of the developing roller by contacting the outer periphery of the developing roller. A developing device having a blade for a developing roller, wherein the roller blade is made of a strip-shaped rubber elastic body, the base end of the blade is supported by a holder, and the free end of the blade is the developing roller. The free end of the developing roller comes into contact with the outer periphery of the developing roller in a direction opposite to the rotation direction of the developing roller so that the free end bends, and the bending amount of the free end is 2 to 4 mm. Characterize.

Blade for Developing Roller The blade for developing roller used in the present invention is in the form of a strip that is in contact with the developing roller in the axial direction. The base end of the blade is supported by a holder made of a conductive rigid body, and the angle at which the blade contacts the developing roller is preferably adjustable.

In the present invention, the tip of the free end of the blade is in contact with the outer periphery of the developing roller so that the free end is bent in the direction opposite to the rotating direction of the developing roller with respect to the base end. The amount of bending of the tip of the blade at that time will be described later. The length of this blade (the length from the fixed end to the free end: the free end length 1) is not particularly limited, but preferably 10 to 12
mm. The blade thickness t is preferably 1.
It is about 2 to 1.5 mm. The width of the blade has a length corresponding to the axial length of the developing roller. The free end of the blade may have a shape of a gentle arc, or may have a shape having an acute angle, a right angle, or an obtuse angle.

The developing roller blade preferably used in the present invention is made of a rubber elastic body, and its compression set is preferably 10% or less, more preferably 4 to 8%.
It is. The smaller the compression set, the better, but it cannot be set to 0 in reality, so the range is in the above range. The compression set is measured by JISK6262.

When the compression set exceeds 10%, the blade pressed against the developing roller is subject to permanent set and the linear pressure of the blade against the roller may decrease over time.
Further, the repulsion elastic modulus of the developing roller blade preferably used in the present invention is preferably 30 to 50%. The impact resilience is measured by the Lupke method JISK6255
By. When the impact resilience is less than 30%, the plasticity of the material tends to be strong and the toner layer on the developing roller tends to be thick, and when it exceeds 50%, the elasticity of the material is so strong that the toner repels and the toner layer becomes thin. Tends to be too much.

The Young's modulus of this blade is 80 to 120.
It is preferably kg / cm ² . When the Young's modulus of the blade is less than 80 kg / cm ² , the pressure contact force with the developing roller is insufficient and the toner layer tends to be too thick. When the Young's modulus of the blade is larger than 120 kg / cm ² , the pressure contact force with the developing roller is too large, and the toner layer tends to be too thin. Further, in this case, the rotation torque to the developing roller increases, and a phenomenon such as jitter (horizontal stripes corresponding to the number of teeth of the gear for driving the developing roller) tends to occur.

The electrical resistance of this developing roller blade is
It is preferably 10 ⁶ Ω or less. It is preferable that this electric resistance is low, but in the manufacturing method of the conductive blade made of a rubber elastic body,
Since the resistance is reduced by adding carbon, the elasticity of the rubber elastic body tends to be lowered too much when the content of carbon is increased.

This developing roller blade has an electric resistance of 1
If it exceeds 0 ⁶ Ω, the impedance becomes high, and it tends to be difficult to make the charge amount of the toner on the developing roller uniform. In order to inject charge into the toner, the blade for the developing roller is at -200 V to -600 V above the developing bias.
A DC voltage of V is preferably applied, and for that reason, the electric resistance of the developing roller blade is preferably 10 ⁶ Ω or less. The method for measuring the electric resistance of the blade for the developing roller employs a method of measuring the electric resistance between the corner of the blade where the blade contacts the developing roller and the holder for fixing the blade with an insulation resistance meter (applied voltage 500V). To do.

In order to set the compression set, rebound elastic modulus and Young's modulus of the developing roller blade within the above ranges, the vulcanization conditions such as the addition amount of the vulcanizing agent contained in the rubber elastic body are selected. . For example, in order to obtain a rubber elastic body having a small compression set, it is preferable to increase the addition amount of the crosslinking agent, increase the crosslinking temperature, and lengthen the crosslinking time.
Further, the electric resistance of the developing roller blade preferably used in the present invention is set to 10 ⁶ Ω or less by adjusting the addition amount of carbon black contained in the rubber elastic body.

The rubber elastic material constituting this blade is not particularly limited, but styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber. , Silicone rubber, etc., preferably urethane rubber, NBR, etc. are used.

Developing Roller In the present invention, the developing roller is not particularly limited, but at least the surface is preferably made of a rubber elastic body, and the friction coefficient of the surface is 0.1 to 1.2, preferably 0.1.
It is 5 to 0.8, and more preferably 0.2 to 0.6.

The coefficient of friction of the surface of the developing roller is set to 0.1
By setting to 1.2, it is possible to reduce photoconductor fogging, paper fogging, and the like. Further, by setting the friction coefficient within such a range, even when a virgin developing roller is used, normal printing can be performed without idling. With a developing roller having a friction coefficient of less than 0.1, the surface of the roller may slip too much and the toner layer may not be formed uniformly. If the coefficient of friction is greater than 1.2, the toner layer becomes too thick, and the fog on the photoreceptor and the fog on paper tend to increase.

The rubber elastic material constituting the surface of the developing roller is not particularly limited, but styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber, epichlorohydrin rubber, urethane rubber, A silicone rubber or the like, preferably a blend rubber of epichlorohydrin rubber and an acrylonitrile-butadiene copolymer rubber, or the like is used.

The developing roller preferably used in the present invention is manufactured, for example, by coating the outer circumference of a conductive shaft with a rubber elastic body. The conductive shaft is made of metal such as stainless steel. In order to coat the rubber elastic body on the outer periphery of the conductive shaft, the rubber elastic body may be applied to the outer periphery of the conductive shaft by means such as press molding and extrusion molding. In this case, extrusion molding is particularly preferable. This is because it is suitable for mass production, and unlike press molding, split mold lines are not formed.

As means for making the surface of the developing roller have a friction coefficient within the above range, after the outer peripheral surface of the developing roller is polished by a cylindrical cutting machine or the like, ultraviolet irradiation is performed to crosslink the unsaturated portion of the rubber elastic body. A means for adjusting the friction coefficient within the above range can be adopted. The conditions of UV irradiation are
For example, the conditions are such that a light source of 80 W / cm is used and irradiation is performed for 2 to 3 minutes. In addition, it is preferable that the polishing of the roller is first performed with a coarse cutting file or a grindstone, and finally with a fine file or a grindstone.

When the developing roller preferably used in the present invention is composed of a conductive shaft and a rubber elastic body, the electric resistance between the surface of the rubber elastic body and the surface of the conductive shaft is 10 ⁵ to 10 ^5. It is preferably ⁸ Ω (when a voltage of 500 V is applied) or volume resistivity of 10 ⁷ to 10 ¹⁰ Ω · cm. If the resistance of the rubber elastic body is too low, a current may flow from the developing roller to the latent image carrier (photosensitive drum), and the electric charge of the toner may leak to the developing roller, which is not preferable. Further, if the resistance of the rubber elastic body is too high, the surface may be charged due to friction to adversely affect the development.

The peripheral surface roughness of the developing roller preferably used in the present invention is preferably 10 μm or less, and the axial surface roughness is preferably 10 μm or less. When the surface roughness in the circumferential direction is larger than 10 μm, the fog on the photoreceptor and the paper fogging are likely to occur along the circumferential direction.
If the surface roughness in the axial direction is larger than 10 μm, the fog on the photosensitive member and the fog on the paper tend to occur along the axial direction.

In the present invention, the term "surface roughness" means that the roller surface is traced with a pointer, the movement of the roller is recorded to represent the uneven shape of the surface as a surface roughness curve, and the ten-point average roughness (Rz ) Say. Further, the friction coefficient in the present invention is a coefficient obtained by the Euler belt type friction coefficient measuring method shown in FIG.

As shown in FIG. 7, first, a measurement paper (usually a copy paper) 40 is fixed in width (for example, about 20 m).
Cut to m). Next, the measurement paper is wound around the developing roller 8 (measuring roller) at about 90 degrees, and a weight 42 having a predetermined weight is attached to one end of the measurement paper and a tension gauge 44 is attached to the other end. Next, the measurement paper 40 on the surface of the roller 8 without the fluctuation of the weight 42.
Is pulled at a constant speed (about 100 ± 20 mm / min). Then, the scale of the tension gauge 44 at the moment when the measurement paper 40 starts to move on the roller surface is read.

The value obtained by substituting the measured value F read by the tension gauge 44 and the weight W of the weight 42 into the following mathematical formula is the friction coefficient μ _s in the present invention.

[0032]

[Equation 1]

Developing Device The developing device according to the present invention has a developing roller blade and a developing roller. In the present invention, the blade is brought into contact with the developing roller such that the tip of the free end is on the outer periphery of the developing roller, and the free end is bent in the direction opposite to the rotating direction of the developing roller with respect to the base end. In the present invention, the bending amount of the blade tip due to bending of the free end of the blade is 2 to 4 mm as compared with the blade tip before bending.

If the bending amount of the tip of the blade is less than 2 mm, the linear pressure of the blade is insufficient and the toner layer on the developing roller tends to be too thick. If it is more than 4 mm, the linear pressure becomes excessive. As a result, excessive stress is applied to the toner and a so-called jitter phenomenon may occur. In the present invention, the linear pressure when the blade is attached to the developing roller is preferably 0.7 to 2 g / m.
m, more preferably 1 to 1.5 g / mm.

If the linear pressure is too low, the toner layer on the developing roller tends to be too thick, and if the linear pressure is too high, the toner on the developing roller is excessively stressed and the toner layer is thin. Tends to be too much. In addition,
The linear pressure f is defined by the following mathematical formula.

F = t ³ · δ · E / 4l ^{3 In} this equation, t is the thickness of the blade, δ is the deflection of the blade, E is the Young's modulus of the blade, and l is the free end length of the blade. In the present invention, the contact angle of the blade with the developing roller is not particularly limited, but is preferably 75 to 85 degrees, more preferably 80 to 85 degrees.

If the contact angle is less than 75 degrees, the toner layer formed on the surface of the developing roller tends to be too thin, and if the contact angle becomes smaller, the blade may be turned up by the rotation of the developing roller. is there. When the contact angle is larger than 85 degrees, the toner layer becomes too thick, and when the contact angle becomes too large, the abdomen of the blade comes into contact with the outer peripheral surface of the developing roller, and the toner layer becomes extremely thick. . The contact angle is an angle formed by the tangent line of the outer periphery of the developing roller that passes through the point where the developing roller blade contacts the developing roller, and the tip surface of the blade.

In the casing of the developing device, a toner supply roller for assisting good adhesion of the toner to the outer peripheral surface of the developing roller may be rotatably arranged near the developing roller. A bias voltage is preferably applied to the conductive shaft of the developing roller.
In the case of reversal development, a voltage having the same polarity as that of the electrostatic latent image on the latent image carrier is applied to the conductive shaft of the developing roller.

Image Forming Apparatus In the image forming apparatus according to the present invention, the developing device and a part of the toner attached to the outer periphery of the developing roller are selectively moved in a predetermined pattern corresponding to a latent image. The toner image is formed, and the latent image carrier that transfers the toner image to the transfer material is included.

The latent image carrier is composed of, for example, a photosensitive drum. The transfer material is, for example, transfer paper. The image forming apparatus according to the present invention includes a charging device that charges the surface of the latent image carrier uniformly and uniformly around the latent image carrier, and an electrostatic latent image on the surface of the uniformly charged photoreceptor. It is preferable to have a latent image forming device such as a writing laser device, the developing device, and a portion for transferring the developed toner image onto a transfer paper or the like. A cleaning device for removing excess toner and the like adhering to the surface of the latent image holding member may be arranged between the transfer portion and the charging device. Note that this cleaning device is not always necessary when cleaning is performed at the same time as development.

Toner The toner that can be used in the present invention is not particularly limited, but the following spherical toner is preferable. The spherical toner preferably used in the present invention is a spherical toner having a volume average particle size (dv) of 3 to 15 μm, particularly 5 to 10 μm, and more preferably a volume average particle size (dv) and a number average particle. The ratio (dv / dn) of the diameters (dn) is in the range of 1.00 to 1.40, and the area (Sc) of a circle whose diameter is the absolute maximum length of the particle is the substantial projected area (S) of the particle.
The value (Sc / Sr) divided by r) is in the range of 1.00 to 1.30 and the specific surface area (A) (m ² /
g), the number average particle diameter (dn) (μm) and the true specific gravity (D) (A × dn × D) are substantially spherical in the range of 5 to 10, and the charge amount (Q) (μc) / G) to the specific surface area (A) (Q / A) is in the range of 80 to 150.

The non-magnetic one-component spherical toner can be obtained by polymerizing a homogeneous mixed liquid containing a vinyl monomer and a colorant by a suspension polymerization method. As a specific suspension polymerization method, for example, a mixture containing a vinyl-based monomer, a colorant, a radical polymerization initiator, and optionally various additives is uniformly dispersed in a ball mill or the like to prepare a uniform mixed solution. Then, a method of suspension polymerization at a temperature of 30 to 200 ° C. is usually used as an aqueous dispersion obtained by finely dispersing this homogeneous mixed solution in water by high shear stirring.

Examples of vinyl monomers used here include aromatic vinyl such as styrene, vinyltoluene, and α-methylstyrene; acrylic acid, methacrylic acid,
Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate,
Derivatives of acrylic acid or methacrylic acid such as dimethylaminoethyl methacrylate, acrylonitrile and acrylamide; olefins such as ethylene, propylene and butylene; vinyl halides such as vinyl chloride, vinylidene chloride and vinyl fluoride; vinyl acetate, vinyl propionate, etc. Vinyl ester; vinyl methyl ether, vinyl ethyl ether and other vinyl ethers; vinyl methyl ketone, methyl isopropenyl ketone and other vinyl ketones; 2
-Nitrogen-containing vinyl compounds such as -vinyl pyridine, 4-vinyl pyridine, and N-vinyl pyrrolidone are listed. These vinyl monomers can be used alone or in combination of two or more kinds.

Any cross-linking agent can be used with these vinyl monomers. As the crosslinking agent, for example,
Aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and its derivatives; Diethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-
Examples thereof include divinyl compounds such as divinylaniline and divinylether, and compounds having 3 or more vinyl groups. These crosslinking agents can be used alone or in combination of two or more kinds.

Examples of the colorant used in the present invention include pigments and dyes such as carbon black, aniline black, crystal violet, rhodamine B, malachite green, ligrosin, copper phthalocyanine and azo dyes. These colorants may be used alone or in combination of two or more.

Further, nigrosine dye, monoazo dye,
Metal-containing dye, zinc hexadecyl succinate, alkyl ester or alkylamide of naphthoic acid, nitrohumic acid, N, N'-tetramethyldiaminebenzophenone, N, N'-tetramethylbenzidine, triazine,
One or more substances having a strong polarity called a charge control agent in this field, such as a salicylic acid metal complex, may be contained.

Further, the non-magnetic one-component spherical toner which can be used in the present invention is internally added with an additive for controlling the charging property, the conductivity, the fluidity, or the adhesion property to the photoconductor or the fixing roller. Alternatively, it can be externally added. Such additives include, for example, low molecular weight polypropylene, low molecular weight polyethylene, various waxes, release agents such as silicone oil, carbon black, silica, alumina, titanium oxide, zinc oxide, cerium oxide, calcium carbonate and other inorganic materials. Examples include fine powder.

[0048] In the developing apparatus and an image forming apparatus according to the action the present invention, the developing roller blade made of a rubber elastic body, with respect to the developing roller, the amount of deflection is mounted so that 2-4 mm. Therefore, an appropriate linear pressure can be obtained, excessive stress on the toner can be suppressed, and a jitter phenomenon can be suppressed mechanically, and a substantially single-layer toner layer can be formed on the outer periphery of the developing roller. This makes it possible to stabilize the toner charge amount and toner adhesion amount, and it is difficult for the photoconductor fog, the paper fog, and the increase or decrease in print density to occur.

In particular, by using the above-mentioned preferable spherical toner, the preferable developing roller and the blade for the developing roller preferably used in the present invention in combination, the spherical toner layer around the roller is substantially a single layer (of the roller surface). The packing density of the toner becomes 0.2 to 0.4 mg / cm ² ) and a more stable image can be obtained. Further, even when a virgin developing roller is used, normal printing can be performed without idling.

[0050]

BEST MODE FOR CARRYING OUT THE INVENTION An image forming apparatus according to the present invention will be described below in detail with reference to the embodiments shown in the drawings. First Embodiment As shown in FIG. 1, an image forming apparatus according to an embodiment of the present invention has a photosensitive drum 1 as a latent image holder. The photosensitive drum 1 is mounted rotatably in the direction of arrow A.
The photosensitive drum 1 has a photoconductive layer provided on a conductive support drum body, and the photoconductive layer is composed of, for example, an organic photoconductor, a selenium photoconductor, a zinc oxide photoconductor, an amorphous silicon photoconductor, or the like. To be done.

Around the photosensitive drum 1, a charging device 3, a latent image forming device 4, a developing device 5, a transfer device 6 and a cleaning device 2 are arranged along the circumferential direction. The charging device 3 is for uniformly charging the surface of the photosensitive drum 1 positively or negatively, and is composed of, for example, a corona discharge device, a charging drum, a charging blade, and the like.

The latent image forming device 4 irradiates the surface of the photosensitive drum with light corresponding to an image signal, irradiates the surface of the uniformly charged drum with light in a predetermined pattern, and the light is irradiated. It is for forming an electrostatic latent image on a portion (in the case of reversal development) or for forming an electrostatic latent image on a portion not irradiated with light (in the case of regular development). For example, a laser device and an optical system are used. Composed. Alternatively, the LED array and the optical system may be used.

The developing device 5 is for adhering toner to the electrostatic latent image on the photosensitive drum 1. In the reversal development, the toner is attached only to the light irradiation portion, and in the regular development, the light non-irradiation portion. A bias voltage is applied between the developing roller 8 and the photosensitive drum 1 so that the toner adheres only to the. Details of this developing device will be described later.

The transfer device 6 is for transferring the toner image on the surface of the photosensitive drum formed by the developing device 5 onto the transfer paper 7, and is composed of, for example, a transfer device or a transfer roller. The cleaning device 2 is the photosensitive drum 1.
Is for cleaning the toner remaining on the surface of the
For example, it is composed of a cleaning blade. This cleaning device is not always necessary in the case of a system in which a cleaning action is performed simultaneously during development.

Next, the developing device 5 according to this embodiment will be described. The developing device 5 has a developing roller 8 and a supply roller 12 in a casing 11 that accommodates the spherical toner 10. The developing roller 8 is arranged close to the photosensitive drum 1 so as to partially contact the photosensitive drum 1, and rotates in the direction B opposite to the photosensitive drum 1. Supply roller 12
Contacts the developing roller 8 and is in the same direction C as the developing roller 8.
It rotates so that the spherical toner 10 is supplied to the outer periphery of the developing roller 8.

As shown in FIG. 2, the developing roller 8 is
It is manufactured by coating the outer circumference of the conductive shaft 20 with a rubber elastic body 22. The conductive shaft 20 is made of metal such as stainless steel. In order to coat the rubber elastic body 22 on the outer periphery of the conductive shaft 20, the rubber elastic body 22 may be attached to the outer periphery of the conductive shaft 20 by means such as press molding and extrusion molding. In this case, extrusion molding is particularly preferable. This is because it is suitable for mass production, and unlike press molding, split mold lines are not formed.

Surface of rubber elastic body 22 and conductive shaft 2
The electrical resistance between the surface of 0 and 10 ^Five -10⁸ Ω (50
It is preferable that the voltage is 0 V). Rubber elastic body 2
If the resistance of No. 2 is too low, the developing roller 8 moves to the photosensitive drum.
There is a risk that current will flow to the
The load may leak to the developing roller 8, which is preferable.
Not good. Further, the resistance of the rubber elastic body 22 is too high.
And the surface may become charged due to friction and adversely affect development.
It is not preferable because it exists.

In this embodiment, the friction coefficient of the surface of the rubber elastic body 22 is 0.1 to 1.2, preferably 1.5 to 0.
8, more preferably 0.2 to 0.6. By setting the friction coefficient of the surface of the rubber elastic body 22 in such a range, the toner layer on the roller surface is stably formed by the layer thickness regulating blade 9 to have a density of 0.2 to 0.4 mg / cm ^2. It becomes easier, and spherical toner can be uniformly triboelectrically charged,
It is possible to reduce photoconductor fogging and paper fogging.

The surface roughness of the rubber elastic body 22 in the circumferential direction is preferably 10 μm or less, and the surface roughness in the axial direction of the surface is preferably 10 μm or less. In this embodiment,
The surface roughness in the circumferential direction and the surface roughness in the axial direction may be as close as possible to 0 as long as they are 10 μm or less, but considering mass productivity and economical efficiency, it is preferably about 6 to 8 μm.

Surface roughness in the circumferential and axial directions of 10 μm
By the following, as shown in FIG. 3, the layer of the toner 10 becomes uniform, and the photoconductor fogging and the paper fogging can be further reduced. In order to set the surface roughness within the above range, the outer peripheral surface of the rubber elastic body 22 may be polished with a cylindrical grinder or the like. Further, in order to keep the friction coefficient within the above range,
Ultraviolet irradiation may be performed after polishing the outer peripheral surface of the developing roller. The ultraviolet irradiation conditions are, for example, a light source of 80 W / cm ² and irradiation for 2 to 3 minutes.

In this embodiment, as shown in FIG. 1, it is preferably used in the present invention around the developing roller 8 at a position between the contact point with the supply roller 12 and the contact point with the photosensitive drum 1. A layer thickness regulating blade 9 as a developing roller blade is arranged. The blade 9 is made of, for example, a conductive rubber elastic body, and its compression set is preferably 10% or less.

By setting the compression set to 10% or less, the permanent set that occurs in the blade in pressure contact with the developing roller is reduced, and it is possible to prevent the linear pressure of the blade against the roller from decreasing with time, and to maintain the proper setting. It becomes possible to form a toner layer. The repulsion elastic modulus of the developing roller blade 9 is 30 to
Preferably it is 50%. Impact resilience of 30-50
When it is set to%, it becomes easy to make the thickness of the toner layer substantially a single layer.

[0063] The Young's modulus of the layer thickness regulating blade 9 is preferably 80~120kg / cm ^2, more preferably 90~110kg / cm ^2. In the present embodiment, the blade 9 has a strip plate shape as shown in FIG.
The base end is held by the holder 50. Holder 5
0 is made of a conductive material such as metal.

By setting the Young's modulus of the blade 9 in the above range, the thickness of the toner layer can be made substantially easy to approach a single layer. Further, if the Young's modulus is too large, the rotational torque to the developing roller increases, and a phenomenon such as jitter (horizontal stripes corresponding to the number of teeth of the gear for driving the developing roller) may occur.

Further, in this blade 9, the electric resistance between the portion of the blade that comes into contact with the developing roller and the holder portion that fixes the blade is 10 ⁶ Ω or less, and practically 10 ⁴
It is preferably 10 ⁶ Ω. Layer thickness control blade 9
In order to inject charge into the toner,
A voltage of 600 V is preferably applied, and for that reason, the electric resistance of the layer thickness regulating blade 9 is preferably 10 ⁶ Ω or less. The method for measuring the electric resistance of the layer thickness regulating blade 9 is as follows. As shown in FIG. 5, the tip of the corner of the blade 9 where the blade 9 contacts the developing roller 8 is brought into contact with the conductive plate 52, and the electrical resistance between the blade 9 and the holder 50 for fixing the blade 9 is measured by an insulation resistance meter 54 (applied voltage). 500 V).

In order to set the compression set, the repulsion elastic modulus and the Young's modulus of the layer thickness regulating blade 9 according to the present embodiment to the above ranges, the amount of the vulcanizing agent contained in the rubber elastic body constituting the blade 9 is added. It is performed by selecting the vulcanization conditions of. For example, when the rubber elastic body forming the blade is made of urethane rubber, the total amount of the rubber elastic body is 100% by weight, the addition amount of the vulcanizing agent is 1.6 to 3.2% by weight, and the vulcanization temperature is 150 to By setting the temperature to 170 ° C. and the vulcanization time to 20 to 50 minutes, the compression set, the impact resilience and the Young's modulus can be set within the above ranges.

Further, in order to reduce the electric resistance of the layer thickness regulating blade 9 according to the present embodiment to 10 ⁶ Ω or less, the content of conductive particles such as carbon black contained in the rubber elastic body constituting the blade 9 should be set. It is done by adjusting. For example, when the rubber elastic body forming the blade is made of urethane rubber, the total amount of the rubber elastic body is 100% by weight, and the addition amount of carbon black having an average particle diameter of 40 nm is 7.2 to 30% by weight. Thus, the electric resistance can be set within the above range.

In the developing device 5 according to this embodiment, as shown in FIG.
As shown in (A) and (B), the layer thickness regulating blade 9 made of a rubber elastic body is arranged so that the free end is bent with respect to the developing roller 8 in the direction opposite to the rotation direction B of the developing roller 8. ,
In addition, the tip of the free end is attached so that the amount of flexure δ is 2 to 4 mm. Moreover, in the present embodiment, it is preferable that the blade 9 is attached so that the contact angle θ is 75 to 85 degrees.

As shown in FIG. 4 (B), the amount of deflection δ is determined from the position of the tip of the blade 9 before the tip of the blade 9 comes into contact with the developing roller 8, that is, before the tip of the blade 9 bends. It is the amount of displacement up to the displacement position of the tip when the free end is bent by abutting. The contact angle θ is shown in FIG.
As shown in, the angle between the tangent line T of the outer periphery of the developing roller passing the point where the blade 9 comes into contact with the developing roller 8 and the tip surface S of the blade 9 is shown. If the tip surface of the blade 9 is a flat surface or a curved surface other than a right angle to the blade belly surface, the tip surface S of the blade 9 means the blade 9
Is defined as a surface substantially perpendicular to the bending line U along the free end of the.

In this embodiment, the layer thickness regulating blade 9 is preferably attached to the developing roller 8 so that the linear pressure is 0.7 to 2 g / mm. The spherical toner 10 accommodated in the developing device 5 according to the present embodiment has a volume average particle diameter (dv) of 3 to 15 μm, particularly 5 to 10.
those in the range of μm, preferably the volume average particle diameter (d
v) and the number average particle diameter (dn) ratio (dv / dn) is 1.
The area (Sc) of a circle whose diameter is the absolute maximum length of the particle is in the range of 00 to 1.40, and the actual projected area (Sr) of the particle is
The value (Sc / Sr) divided by 1.00 is in the range of 1.00 to 1.30, and the specific surface area (A) by BET method (m ² / g),
The product of the number average particle diameter (dn) (μm) and the true specific gravity (D) (A × dn × D) is substantially spherical in the range of 5 to 10,
Further, the non-magnetic one-component spherical toner has a ratio (Q / A) of the charge amount (Q) (μc / g) to the specific surface area (A) in the range of 80 to 150.

Such a relatively uniform particle size, especially 5 to 1
A spherical toner having a diameter of about 0 μm is used, and the blade 9 made of a rubber elastic body is bent with respect to the developing roller 8 by a bending amount δ.
By mounting so as to be 2 to 4 mm, an appropriate linear pressure can be obtained, and excessive stress to the toner on the developing roller can be suppressed and the jitter phenomenon can be suppressed.
Further, it becomes possible to form a substantially single toner layer on the outer circumference of the developing roller, the charge amount and the adhesion amount of the toner are stabilized, and the photoconductor fog, the paper fog, and the increase or decrease of the print density occur. It will be difficult.

Second Embodiment In this embodiment, the device shown in the first embodiment (however,
This is an example of a case in which the cleaning device 2 is not provided) and the reversal development is performed to perform the simultaneous development cleaning.

In order to perform reversal development, in this embodiment,
By the charging device 3 shown in FIG. 1, the surface of the photosensitive drum 1 is
As shown in FIG. 6A, for example, Vc = −500V is uniformly charged. Next, the latent image forming device 4 shown in FIG. 1 irradiates light in a predetermined pattern to partially release the charged surface of the photosensitive drum 1 to form an electrostatic latent image in a predetermined pattern. . The potential of the area where the electrostatic latent image is formed is a voltage close to 0V, for example.

Next, in the developing device 5 shown in FIG. 1, the electrostatic latent image on the surface of the photosensitive drum 1 is developed. One layer of spherical toner 10 is formed on the surface of the developing roller 8 of the developing device 5 by the action of the layer thickness regulating blade 9 of the first embodiment. Further, as shown in FIG. 6B, a bias voltage is applied between the developing roller 8 and the photosensitive drum 1 so that the surface potential VD of the developing roller 8 becomes -200V. Therefore, the negatively charged toner 10 attached to the peripheral surface of the developing roller 8 moves to the surface of the photosensitive drum 1 in the pattern of the electrostatic latent image which is the light irradiation portion, and the surface of the photosensitive drum 1 6C, a toner image is formed in the pattern of the electrostatic latent image, as shown in FIG.

As shown in FIG. 6B, the negative residual toner 10a adhering to the area other than the electrostatic latent image on the photosensitive drum 1 is the surface potential of the photosensitive drum and the surface potential of the developing roller 8. Is moved to the developing roller 8 side by the electric field based on. As a result, the surface of the photosensitive drum 1 can be cleaned simultaneously with the development.

In the image forming apparatus according to this embodiment, as shown in FIG.
The cleaning device 2 shown in 1 becomes unnecessary. In the present embodiment, the conditions for performing simultaneous cleaning at the time of development are that the charging potential of the surface of the photosensitive drum 1 is Vc,
When the surface potential of the developing roller 8 is VD, Vc-
It is sufficient if the absolute value of VD is 50 V or more. Also, preferably, the potential at the tip of the layer thickness regulating blade shown in FIG.
When the surface potential of the supply roller 12 is Vs, it is preferable that VD ≧ VBL ≧ Vs. When the charging polarity of the toner 10 and the polarity of the surface potential of the photosensitive drum 1 are positive, the absolute value of Vc-VD is 50 V or more, and the absolute value of VD ≤ the absolute value of VBL ≤ the absolute value of Vs. It would be nice to have a relationship. This relationship is the same in the case of simultaneous development cleaning in regular development.

Other configurations and operations of this embodiment are as follows.
This is the same as the first embodiment. Note that the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

[0078]

EXAMPLES The present invention will be described below based on more specific examples, but the present invention is not limited to these examples. In the following examples, parts and% are based on weight unless otherwise specified.

Example 1 As shown in FIG. 2, a rubber elastic body 22 composed of a blended rubber of epichlorohydrin rubber and acrylonitrile-butadiene copolymer rubber was extruded on the outer circumference of a stainless steel shaft 20 having a diameter of 10 mm. It was formed by molding to have a thickness of 3.9 mm. After that, the outer peripheral surface of the rubber elastic body 22 was polished by a cylindrical cutting machine so that the surface roughness of the outer peripheral surface was set to 4 μm in the axial direction and the circumferential direction.

Next, while rotating the rubber elastic body,
Use a lamp of 80 W / cm for ultraviolet rays on the surface, and
Irradiation was performed for 1 minute. As a result, the coefficient of friction of the surface of the rubber elastic body was 0.4. As shown in FIG. 1, the developing roller 8 was placed in contact with the photosensitive drum 1 so as to have a contact width of about 2 mm.

An organic photosensitive drum was used as the photosensitive drum 1, and its outer diameter was 30 mm. As the charging device 3, a charging roller is used so that the surface potential of the photosensitive drum 1 becomes uniform at Vc = -650V. As the electrostatic latent image forming device 4, a combination of a laser device and an optical system was used. The supply roller 12 has an outer diameter of 12.
A 5 mm urethane rubber sponge roller was used. The supply roller 12 was brought into contact with the developing roller 8 so that the contact width was about 2 mm.

The layer thickness regulating blade 9 is made of a urethane rubber elastic body, has a compression set of 6%, a Young's modulus of 92 kg / cm ² , and a repulsion elastic modulus of 34%.
Then, a flat blade having a size of 11.5 mm × 220 mm × 1.5 mm was used. The electric resistance of this blade was 5 × 10 ⁴ Ω when measured by the measuring method shown in FIG.
As shown in FIGS. 4 (A) and 4 (B), this blade 9 is
The developing roller 8 was attached in contact with the outer periphery of the developing roller 8 so that the amount of flexure δ was 2.1 mm. At that time, the linear pressure F against the developing roller 8 was about 1.07 g / mm, and the contact angle θ was 76 degrees.

As the spherical toner 10 housed inside the developing device 5, a toner obtained by the following manufacturing method was used. 90 parts of styrene, 10 stearyl methacrylate
Parts, low molecular weight polypropylene 4 parts, carbon black (trade name Black Pearl 130) 7 parts, chromium dye (trade name Bontron S-34) 0.5 parts and 2,2 '
-Azobis (2,4-dimethylvaleronitrile) (2 parts) was ball-milled to obtain a uniform mixture.

Next, the above mixture was added to 400 parts of pure water in which 4.5 parts of calcium phosphate was finely dispersed to obtain an aqueous dispersion. This aqueous dispersion was subjected to high-shear agitation with a rotor-stator homomixer under a condition of pH 9 or higher to finely disperse the above mixed solution in water. This water dispersion was placed in a reactor equipped with a stirring blade and heated at 65 ° C for 4 hours.
Polymerization was carried out with stirring for a time.

The polymer-containing dispersion thus obtained was thoroughly washed with acid and water, then separated and dried to obtain a toner material. To 100 parts of the above toner material, 0.3 part of hydrophobic silica as a fluidizing agent was externally added to obtain a non-magnetic one-component toner. The resulting non-magnetic one-component toner was substantially spherical particles. The volume average particle diameter (d
v) is 6.5 μm, the ratio (dv / dn) of the volume average particle diameter (dv) to the number average particle diameter (dn) is 1.18, and the area of a circle whose diameter is the absolute maximum length of the particle. A value (Sc / Sr) obtained by dividing (Sc) by the substantial projected area (Sr) of the particles.
Is 1.07 and the specific surface area (A) according to the BET method
(M ² / g), number average particle diameter (dn) (μm) and true specific gravity (D) product (A × dn × D) is 5.6, and
Ratio of charge amount (Q) (μc / g) and specific surface area (A) (Q /
A) was 120.

Further, in this embodiment, the surface potential VD of the developing roller 8 is -2 in order to carry out the cleaning simultaneous development by the reversal development.
A bias voltage was applied between the developing roller 8 and the photosensitive drum 1 so that the voltage would be 00V. Further, a bias voltage is applied so that the potential at the tip of the layer thickness regulating blade 9 becomes VBL = -400V, and the surface potential Vs of the supply roller 12 is Vs = -4.
A bias voltage is applied so that the voltage becomes 00V. In this embodiment, since the cleaning is performed at the same time as the development, the cleaning device shown in FIG. 1 is unnecessary.

In the image forming apparatus according to this embodiment, the photosensitive drum 1 is rotated in the direction of arrow A at a peripheral speed of 47.6 mm / sec, and the developing roller 8 is rotated in the direction of arrow B at a peripheral speed of 105 mm / sec to supply the toner. The roller 12 was rotated at a peripheral speed of 92 mm / sec in the direction opposite to the arrow C direction, and was transferred onto the paper 7 10 times.

As a result of observing the photoconductor fog, the quantified numerical values for the photoconductor fog and the paper fog are:
The values were 0.2% and 0.1%, respectively, which were confirmed to be small. Further, as a result of observing the print density, the quantified numerical value regarding the print density was 1.40, which was in the appropriate density range (1.2 to 1.4).

For the observation of the photoconductor fog, the toner in the fog portion on the photoconductor drum was transferred to paper with a mending tape, and the reflectance value measured by a whiteness meter (manufactured by Nippon Denshoku) was used. It was carried out by comparing the values obtained by subtracting the reflectance when only No. 1 was attached to the paper from the values measured by the whiteness meter.
The larger this value, the more the fog on the photoreceptor.

Further, for the observation of the paper fog, the reflectance value obtained by measuring the fog portion of the non-image area of the paper after fixing with a whiteness meter and the reflectance value of the paper before printing with the whiteness meter were measured. It was done by comparing the values subtracted from. The observation of the print density was performed by measuring the "black solid part" using a Macbeth densitometer.

Further, when printing was performed using the developing device according to this embodiment, normal printing was possible from the initial stage without idle operation for accommodating the toner. Also, so-called jitter did not occur. Example 2 As shown in FIG. 4 (A), the bending amount δ of the layer thickness regulating blade 9 with respect to the developing roller 8 is 3.0 mm (contact angle θ = 85.
The developing device and the image forming apparatus were configured in the same manner as in Example 1 except that the blade was brought into contact with the developing roller so that the linear pressure was 1.53 g / mm.

When the photoconductor fog, the paper fog and the print density were observed in the same manner as in Example 1, the quantified numerical values of the photoconductor fog and the paper fog were 0.4% and 0.1%, respectively. It was confirmed that the photoconductor fogging and the paper fogging were small, and the print density was 1.34, which was in an appropriate density range. Further, when printing was performed using the developing device according to this example, normal printing was possible from the initial stage without performing idle operation for accommodating the toner. Furthermore, so-called jitter did not occur.

Embodiment 3 As shown in FIG. 4 (A), the bending amount δ of the layer thickness regulating blade 9 with respect to the developing roller 8 is 3.8 mm (contact angle θ = 77).
The developing device and the image forming apparatus were configured in the same manner as in Example 1 except that the blade was brought into contact with the developing roller so that the linear pressure was 1.94 g / mm).

When the photoconductor fog, the paper fog and the print density were observed in the same manner as in Example 1, the quantified numerical values of the photoconductor fog and the paper fog were 0.2% and 0.1%, respectively. It was confirmed that the photoconductor fogging and the paper fogging were small, and the print density was 1.30, which was in an appropriate density range. Further, when printing was performed using the developing device according to this example, normal printing was possible from the initial stage without performing idle operation for accommodating the toner. Furthermore, so-called jitter did not occur.

Comparative Example 1 As shown in FIG. 4 (A), the bending amount δ of the layer thickness regulating blade 9 with respect to the developing roller 8 is 1.8 mm (contact angle θ = 74).
The developing device and the image forming apparatus were configured in the same manner as in Example 1 except that the blade was brought into contact with the developing roller so that the linear pressure was 0.92 g / mm.

When the photoconductor fog, the paper fog and the print density were observed in the same manner as in Example 1, the quantified numerical values of the photoconductor fog and the paper fog were 1.2% and 1.1%, respectively. , Increase in photoreceptor fog and paper fog, and increase in print density (1.
44) was also observed. Further, from the initial stage of the start of printing, photoconductor fogging, paper fogging, and an increase in print density were observed.

Comparative Example 2 As shown in FIG. 4A, the amount of flexure δ of the layer thickness regulating blade 9 with respect to the developing roller 8 is 4.5 mm (contact angle θ = 76.
The developing device and the image forming apparatus were constructed in the same manner as in Example 1 except that the blade was brought into contact with the developing roller so that the linear pressure was 2.30 g / mm.

When the photoconductor fog, the paper fog and the print density were observed in the same manner as in Example 1, the quantified numerical values of the photoconductor fog and the paper fog were 8.4% and 2.1%, respectively. It was confirmed that there was a large amount of photoconductor fogging and paper fogging, and a decrease in print density (1.17) was also observed. Further, from the beginning of printing, fog on the photoreceptor, fog on paper, and a decrease in print density were observed. Furthermore, a so-called jitter phenomenon was also observed.

[0099]

As described above, according to the present invention, by setting the amount of deflection of the tip of the developing roller blade to 2 to 4 mm, excessive stress on the toner can be suppressed,
It is possible to suppress the jitter phenomenon on the mechanism, and it becomes possible to form an appropriate toner layer thickness (substantially a single layer) on the outer periphery of the developing roller, and the toner charge amount and adhesion amount are stabilized, It becomes difficult for photoconductor fogging, paper fogging, and increase or decrease in print density.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view of the developing roller shown in FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of the developing roller shown in FIG.

4 (A) is a schematic view showing the positional relationship between the layer thickness regulating blade and the developing roller shown in FIG. 1, and FIG. 4 (B) is a main part schematic view for explaining the amount of bending.

FIG. 5 is a conceptual diagram showing a method for measuring electric resistance.

FIGS. 6A to 6C are schematic views showing the action of simultaneous development cleaning in reversal development.

FIG. 7 is a conceptual diagram showing a method of measuring a friction coefficient of a developing roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 2 ... Cleaning device 3 ... Charging device 4 ... Latent image forming device 5 ... Developing device 6 ... Transfer device 7 ... Transfer paper 8 ... Developing roller 9 ... Layer thickness regulating blade (developing roller blade) 10 ... Toner 12 Supply roller 20 Conductive shaft 22 Rubber elastic body

Claims (2)

[Claims] 1. A developing roller that selectively moves a part of the toner adhered to the outer periphery on the outer peripheral surface of the latent image holding member in a predetermined pattern corresponding to the latent image to perform development, and the developing roller. A developing roller blade that contacts the outer circumference of the developing roller and adjusts the thickness of the layer of toner formed on the outer circumference of the developing roller, wherein the roller blade is a strip-shaped rubber elastic body. Consists of a blade, the base end of the blade is supported by a holder, the free end of the blade on the outer periphery of the developing roller,
A developing device in which a free end of the developing roller comes into contact with the base end so as to bend in a direction opposite to a rotation direction of the developing roller, and a bending amount of the free end is 2 to 4 mm. 2. The developing device according to claim 1, wherein a part of the toner attached to the outer periphery of the developing roller is selectively moved in a predetermined pattern corresponding to the latent image to form a toner image. An image forming apparatus having a latent image carrier that transfers the toner image onto a transfer material.