JP2989873B2 - Developing roller, developing device and copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a developing roller used in a developing device for visualizing an electrostatic latent image in an electrophotographic apparatus or an electrostatic recording apparatus. More particularly, the present invention relates to a developing roller suitable for a developing device that performs development by pressing or contacting a toner carrier with an electrostatic latent image by a pressure developing method.

(Prior Art) As one of developing means using a one-component developer, a pressure developing method is known. This method visualizes the electrostatic latent image by pressing or contacting a toner carrier having a required toner on the surface with an electrostatic latent image surface, and the magnetic material powder is contained in the toner. Since it is not necessary to contain the toner, the developing device can be simplified and downsized, and has many advantages such as easy color of the toner.

Thus, in the above-mentioned pressure development method, it is necessary to use a developing roller having elasticity and conductivity as a toner carrier. In particular, in order to prevent the electrostatic latent image holder from being damaged, it is essential that the developing roller be made of an elastic material.

On the other hand, as is well known, in order to obtain a developing electrode effect and a developing bias effect, it is desirable to provide a conductive layer on or near the surface of the developing roller and to apply a bias voltage to this conductive layer as necessary. It is rare.

(Problem to be Solved by the Invention) As a specific example of the developing roller having the above configuration, an elastic layer is formed coaxially on the outer peripheral surface of a metal roller base material, and the outer peripheral surface is further provided with conductivity. And a developing roller formed by coating with a resin paint.

As a conductive resin paint, lacquer, vinyl, amino alkyd, amino acryl, phenol, alkyd, epoxy, polyester, silicone, acrylic urethane, vinyl urethane, polyurethane as a conductive filler in a resin, such as carbon black, Graphite, metal oxide semiconductors (tin oxide, zinc oxide, titanium oxide, etc.), conductive surfactants, fine metal particles (copper, nickel, silver, iron, etc.), composite materials with metal attached to the carrier surface (metal plating) Glass fiber, fibrous metal, flake metal, etc.).

However, in the developing roller having the above configuration, when the conductive layer is formed by coating the resin coating containing the conductive filler, the following problem is observed.

(1) When carbon black is used as the conductive filler.

When a dry coating film is formed on the outer peripheral surface of the elastic layer by using this conductive resin paint to form a required conductive layer, the surface roughness of the coating film is 5 μm or less. For this reason, the toner conveyance performance becomes insufficient, and the toner charge amount per unit weight becomes large. Therefore, for example, when a solid image is output, the toner is not sufficiently conveyed from the second and third rounds of the developing roller, and phenomena such as unevenness and blurring tend to occur in the latter half of the image.

(2) When a metal oxide semiconductor is used as the conductive filler.

In order to obtain the required conductivity, it is necessary to increase the content of the conductive filler. Therefore, when a dry coating film is formed by coating the outer peripheral surface of the elastic layer using the conductive resin paint, and the required conductive layer is formed, the surface roughness of the coating film becomes 20 μm or more. Therefore, although the toner transport performance is sufficient, the unevenness of the surface appears as an image, which leads to a reduction in image quality. This phenomenon is particularly remarkable when a solid image is output.

(3) A case where a composite material in which metal is attached to a metal fine particle or a carrier surface as a conductive filler is used.

Since the specific gravity of the conductive filler is large, in the step of forming a dry coating film on the outer peripheral surface of the elastic layer by using this conductive resin paint, the conductive filler is biased by the time it is dried until it is dried. This causes unevenness in the properties and causes uneven development during development.

The present invention has been made in view of the above circumstances, and provides a developing roller which includes a conductive layer having a desired surface roughness, exhibits good transportability, and can always form an image of uniform image quality. Aim.

[Constitution of the Invention] (Means for Solving the Problems) The present invention relates to a developing roller in which an outer peripheral surface of an elastic layer formed on an outer peripheral surface of a metal roller base material is coated with a conductive resin paint. Wherein the coating film is
A mixture comprising at least a carbon black and a metal oxide semiconductor is dispersed in a binder resin and has a surface roughness (Rz) of 5 to 20 μm.

Thus, the binder resin (solid content) is a, the carbon black is b, and the metal oxide semiconductor is c,
And when the paint is 100g, And the surface roughness of the formed conductive film (layer) is desirably set to 5 to 20 μm.

In the present invention, as the elastic layer formed on the outer peripheral surface of the metal roller base material, a layer made of rubber or foam such as urethane, EPDM, silicone, NBR, SBR, natural rubber, polyethylene, and polypropylene is used. No.

In the developing roller of the present invention, as the binder resin of the conductive paint which is coated on the outer peripheral surface to form the conductive layer, lacquer, vinyl, aminoalkyd, aminoacryl, phenol, alkyd, epoxy, polyester, silicone, acrylic urethane , Vinyl urethane, polyurethane and the like, and these may be used alone or in a mixture of two or more.

In the developing roller of the present invention, various types of commercially available carbon black that can be added and dispersed as a component of the conductive paint constituting the conductive layer can be used. Among them, conductive carbon black such as furnace black, acetylene black, and Ketjen black is recommended, but thermal black, channel black, and process black can also be used.

In the developing roller of the present invention, as a component of the conductive paint constituting the conductive layer, and as a metal oxide semiconductor to be added and dispersed, zinc oxide, tin oxide, titanium oxide, barium oxide, antimony oxide, zirconium oxide, and aluminum oxide , Zinc sulfide, barium sulfide and the like. Thus, the metal oxide semiconductor preferably has a specific resistance of about 100 Ω · cm or less. That is, when a metal oxide semiconductor having a large specific resistance value is used, it is necessary to increase the mixing ratio in order to obtain required conductivity, which adversely affects the adhesive strength to the elastic layer as a base.

In kneading and dispersing the binder resin, carbon black and the metal oxide semiconductor, various kneaders can be used. For example, three roll mill, ball mill, bebble mill, sand grinder, high speed stone mill, high speed impact mill, disper, kneader, high speed mixer,
Homogenizers, ultrasonic dispersers and the like can be mentioned, and these may be used alone or in combination.

Solvents constituting the conductive paint coated on the developing roller of the present invention include dimethylformamide, diethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, N, N-tetramethylurea, hexamethylenephosphamide , Aprotic polar solvents such as tetramethyl sulfone, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, ester solvents such as methyl acetate, ethyl acetate and butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, Ketone solvents such as cyclohexanone, chlorinated hydrocarbon solvents such as trichlene and dichloroethane, alcohol solvents such as isopropanol, and ether solvents such as tetrahydrofuran and dibutyl ether are used.

The conductive paint or composition coated on the developing roller of the present invention may contain various types of facial dyes, fillers, plasticizers, antioxidants, if necessary, in addition to the components described above.
Surfactants and other additives can be used.

The above prepared coating liquid (paint) is applied to the required elastic roller surface by hand coating or continuous or semi-continuous dip, spray, curtain flow, brush coating or other methods in the line. After the application, the conductive layer is left at room temperature or dried by heating to form a required conductive layer. In this coating step, the surface of the elastic layer may be previously subjected to a primer treatment in order to increase the adhesive strength to the elastic layer.

(Function) The present invention is a developing roller in which an outer peripheral surface of an elastic body layer formed on an outer peripheral surface of a metal roller base material is coated with a conductive resin paint, and a coating film (conductive layer) is provided. ,
It is composed of a mixed dispersion of at least a binder resin, carbon black and a metal oxide semiconductor. Thus, the conductive layer has a required conductivity that contributes to the development bias effect during development and has a surface roughness of 5 to 20.
A good toner conveying function is maintained at about μm. Therefore, it is possible to always develop an image having a uniform image quality including a solid image.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

First, the manner in which the developing roller according to the present invention is used, development evaluation, and the like will be generally described.

The developing roller is used, for example, in a developing device whose main part is shown in cross section in FIG. In this developing device, a developer (toner) is carried on an outer peripheral surface of a developing roller 1 having a conductive resin layer 1a, and is sent to an electrostatic latent image holding member (photoconductor) 2 to form an electrostatic latent image. In a non-magnetic-component developing device for developing a visual image, a toner thin layer forming member 5 is attached to an opening of a toner hopper 4 storing toner 3, and a developing roller for carrying the toner 3 is provided below the hopper 4. 1 is provided. Further, the front end of the thin toner layer forming member 5 is in contact with the peripheral surface of the developing roller 1, and an electrostatic latent image holding member 2 that holds the electrostatic latent image facing the peripheral surface of the developing roller 1 is arranged. The developing roller 1 and the electrostatic latent image holder 2 are in contact with each other. In the drawing, 1b is an elastic layer of the developing roller 1, 1c
Indicates a metal roller base material. Thus, a DC voltage and / or an AC voltage is applied to the developing roller 1 from a bias power supply. In addition to the toner thin layer forming member 5, a toner supply roller (not shown) ) May be added.

In the evaluation of the development, the toner 3 may include various kinds of thermoplastic resins such as a styrene resin, an acrylic resin, a polyester resin, and an epoxy resin, a colorant such as carbon and a face dye, and a polarity control such as a metal-containing azo dye. , A wax such as polyethylene, polypropylene and the like are dispersed, crushed and classified to have a volume average diameter of 9 to 11 μm, and in some cases, in order to enhance fluidity, in a range of 0.5 to 2 parts by weight based on toner particles. And a non-magnetic-component toner to which a fluidizing agent such as hydrophobic silica is added.

Further, the toner thin layer forming member 5 is made of silicon resin or the like, and is brought into contact with a predetermined magnitude of contact pressure to form the toner 3a carried on the surface of the developing roller 1 into a thin layer of a predetermined thickness. Is provided.

Next, specific examples of the present invention will be described, but the present invention is not limited thereto.

Preparation of elastic roller Metal roller base material (stainless steel, length l = 260,
Elastic roller (length l = 220, diameter φ = 18) provided with an elastic layer (hardness 30 degrees Shore A, distortion rate <10%) 1b made of urethane rubber on the outer peripheral surface of 1c It was created.

Preparation of conductive paint (a) Preliminary dispersion of conductive carbon black Conductive carbon black (Ketjen Black EC, manufactured by Lion Akzo Co., Ltd.) 20 parts by weight of urethane-modified acrylic binder resin clear (D-4256E, resin solid content) 50
%, Manufactured by Shinto Chemitron Co., Ltd.) and mixed and dispersed using a three-roll mill with 100 parts by weight to obtain a premixed fine dispersion.

(B) Pre-dispersion of metal oxide semiconductor 100 parts by weight of conductive titanium oxide (ECT-62, manufactured by Titanium Industry Co., Ltd.) is urethane-modified acrylic binder resin clear (D-4256E, resin solid content 50%, Shinto Chemitron Co., Ltd.) And 50 parts by weight, and mixed and dispersed using a three-roll mill to obtain a premixed fine dispersion.

(C) Preparation of conductive paint The conductive carbon black pre-dispersion of (a),
(B) Preliminary dispersion of metal oxide semiconductor, urethane-modified acrylic binder resin clear (D-4256E, resin solid content 50%, manufactured by Synto Chemitron), isopropyl alcohol-ethyl alcohol mixed solution and polyisocyanate (Coronate L , Manufactured by Nippon Polyurethane Co., Ltd.) at a composition ratio (parts by weight) shown in Table 1 to prepare five types of conductive paints including Comparative Examples.

In Table 1, the F value is defined as: Is shown. Here, a is a binder resin (solid content), b is carbon black, and c is the amount of the metal oxide semiconductor.

Creation of a developing roller By a spray coating method on the outer peripheral surface of the elastic roller,
The conductive paint of (c) was applied in a thickness of 60 μm. After air-drying at room temperature for 30 minutes, it was dried in an oven at 80 ° C. for 10 minutes, and cooled to obtain a conductive elastic developing roller 1 having a conductive resin layer 1a on the outer surface. The volume resistivity measured immediately after coating by the method described later was 10 ⁵ to 10 ⁶ Ω · cm.

Table 2 shows the results of measuring the roughness of the conductive resin layer 1a formed by coating with a surface roughness meter (Surtronic 10, manufactured by Rank Taylor Hobson).

Image Retrieval The developing roller 1 prepared above is used as a commercially available copier (trade name: Rheodry 330) which is a modification of the non-magnetic one-component developing device.
(1. Toshiba Corp.) and developed the toner image so that the image could be developed.

For development, a toner prepared as follows was used. That is, 95.5 parts by weight of a polyester resin (NE-2155, manufactured by Kao Corporation) and a red pigment (Pigment Red-31; Fuji Carmine # 547)
2.5 parts by weight of Fuji Dye Co., Ltd. and 2 parts by weight of polypropylene wax (660P, manufactured by Sanyo Chemical Co., Ltd.) are heated and melted and kneaded by a pressure kneader, coarsely pulverized by a hammer mill, and the coarsely pulverized product is obtained.
One part by weight of hydrophobic silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts by weight, and the mixture obtained by mixing for 30 minutes with a V-type blender was further finely pulverized by an air jet mill, and then by a wind classifier A magenta color negative toner having a volume average diameter of 9.0 μm obtained by classification was used.

Then, the magenta negative toner is put into the toner hopper 4 of the modified non-magnetic one-component developing device,
A silicon blade (toner thin layer forming member) 5 is pressed against the peripheral surface of the developing roller 1 so that the contact width between the electrostatic latent image holding member (photoconductor) 2 and the developing roller 1 is 1 mm, and the rotational speed of the developing roller 1 is 1 mm.
The photosensitive drum 2 was rotated at 88 mm / sec and the peripheral speed of the photosensitive drum 2 at 47 mm / sec.
The development was performed under a development condition of a developing bias of −200 V applied to the substrate.

Evaluation Results Table 3 shows the results of the image density of the leading edge and the trailing edge of the original when the image was developed under the above-mentioned developing conditions and a solid black image was output. Table 4 shows the evaluation results of the toner charge amount and the toner transport amount per unit area on the developing roller surface. The measurement of the image density is a value obtained by measuring the reflection density of a fixed image using a Macbeth densitometer.

As is apparent from Table 3, in the case of Examples 1 to 3,
Even after the output of 10,000 sheets, there was no difference in density between the leading edge and the trailing edge of the image, and good toner conveyance performance was recognized. A difference in density between the image and the rear end (image blurring) was observed, and a decrease in the density at the front end was also observed.

Further, as is apparent from Table 4, in the case of Comparative Example 1, the amount of toner transported on the developing roller per unit area is low, and it is difficult to perform required development. In the case of Comparative Example 2, since the surface roughness of the developing roller was as large as 24.4 μm, the toner conveyance amount was sufficient. However, the surface roughness (irregularities) of the developing roller appeared in the image, and the image quality was reduced. Had been lowered.

[Effects of the Invention] As is apparent from the above description, the developing roller according to the present invention has a binder resin, carbon black, and a metal on the outer peripheral surface of an elastic layer formed on the outer peripheral surface of a metal roller base material. It has a configuration in which a conductive resin layer (film) including an oxide semiconductor as an essential component is covered. Thus, by selecting the composition ratio of the binder resin, carbon black, and the metal oxide semiconductor, which are the essential components constituting the conductive resin layer, the conductive resin layer has the required conductivity without resistance value unevenness, and has a surface of 5 to 20 μm. It exhibits roughness and exhibits good toner transportability. That is, since the toner has both conductivity without resistance value unevenness and good toner transportability, it is possible to obtain an effect that a uniform and high-quality image can always be easily formed. Thus, it can be said that the industrial value of the developing roller according to the present invention is great.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of a non-magnetic-component developing device equipped with a developing roller according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Development roller 1a ... Conductive resin layer 1b ... Elastic layer 1c ... Metal roller base material 2 ... Electrostatic latent image holding body (photoreceptor) 3 ... Toner (developer) 3a ... Toner carried on developing roller surface 4 Toner hopper 5 Toner thin layer forming member

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Takano 1 Toshiba-cho, Komukai, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Masahiro Hosoya 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Address Toshiba Research Institute, Inc. (56) References JP-A-64-581 (JP, A) JP-A-63-183469 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08-15/09 101

Claims (3)

(57) [Claims] A metal roller base material, an elastic layer formed on an outer surface of the roller base material, and a conductive resin layer formed on an outer peripheral surface of the elastic layer. In the developing roller, the conductive resin layer is a coating film having at least a mixture of carbon black and a metal oxide semiconductor dispersed in a binder resin, and having a surface roughness (Rz) of 5 to 20 μm. Developing roller. 2. A developing device comprising: a toner container for storing toner; an electrostatic latent image holding member; and a developing roller for conveying toner to the electrostatic latent image holding member, wherein the developing roller is made of metal. Roller base material, an elastic layer formed on the outer surface of the roller base material, and a mixture comprising at least carbon black and a metal oxide semiconductor formed on the outer peripheral surface of the elastic body layer as a binder resin. And a conductive resin layer having a surface roughness (Rz) of 5 to 20 μm dispersed therein. 3. A copying machine having a toner container for storing toner, an electrostatic latent image holding member, and a developing toner for conveying toner to the electrostatic latent image holding member, wherein the developing roller is made of metal. Roller base material, an elastic layer formed on the outer surface of the roller base material, and a mixture comprising at least carbon black and a metal oxide semiconductor formed on the outer peripheral surface of the elastic body layer as a binder resin. A copying machine, comprising: a conductive resin layer dispersed and having a surface roughness (Rz) of 5 to 20 μm.