JP2801724B2 - Developing roller - 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 which is suitable for a developing device in which a toner carrier is pressed or brought into contact with an electrostatic latent image by a pressure developing method to perform development, and has a stable volume specific resistance value with respect to the environment.

(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 colorization 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.

Incidentally, coating resin paints more suitable for the configuration of the developing roller include degradation resistance, tensile stress, surface friction fastness, polymer solution stability, ease of application, easy dispersibility of the conductivity imparting agent, and volume. Environmental stability of the specific resistance value (particularly, stability against humidity) is required.

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, frame-shaped metal, etc.).

However, among the above resin coatings, urethane resins are superior in all physical properties such as mechanical strength, abrasion resistance, flexibility, flexibility, and chemical resistance as compared with other resins. It is preferable as a coating material for a developing roller in a developing method. Further, among the conductive fillers, carbon black is widely used as a stable conductive and inexpensive material, and is preferable.

Polyurethane is obtained by reacting a polymer diol with an organic diisocyanate and an active hydrogen compound as a chain extender. For example, when an aromatic organic diisocyanate is used as the organic diisocyanate, the polyurethane obtained has a light deterioration resistance. In particular, it is known that light irradiation causes yellowing and a decrease in strong elongation. By using an aliphatic or alicyclic organic diisocyanate instead of the aromatic diisocyanate, the light deterioration resistance is improved. However, even in this case, of the light deterioration resistance, although yellowing due to light irradiation can be considerably prevented, it is often insufficient to prevent the strong elongation due to light deterioration.

Polyurethanes using aliphatic or alicyclic organic diisocyanates have disadvantages such as low softening temperature, low tensile stress, and poor surface rub fastness. In order to remedy this drawback, a means of increasing the intermolecular cohesion by using a diamine instead of a low molecular weight diol as a chain extender and introducing a urea bond into the chain is generally employed. Furthermore, in order to further improve the improvement effect, a means for increasing the ratio of the organic diisocyanate and the low-molecular-weight organic diamine to the polymer diol may be considered.

However, the means of introducing a urea bond using a diamine as a chain extender, on the other hand, causes serious defects in the solution stability of the polyurethane solution. In other words, the polymer solution tends to be extremely unfavorable, such as thickening during polymerization or during storage after polymerization, or becoming a gel. Even if this phenomenon does not occur in a normal temperature state, it is often observed that the phenomenon occurs when the apparatus is left in a low temperature state, which is a serious problem.

Therefore, the present invention satisfies both light degradation resistance, environmental resistance and polymer solution stability, and furthermore, physical properties such as strong elongation, surface physical properties such as surface rub fastness, and excellent flex resistance. An object of the present invention is to provide a developing roller capable of maintaining a stable volume specific resistance value with respect to changes in temperature and humidity in a conductive resin layer forming an outer peripheral surface and capable of always forming an image of uniform image quality.

[Means for Solving the Problems] The present invention relates to a developing roller in which a conductive resin paint is coated on the outer peripheral surface of an elastic layer formed on the outer peripheral surface of a metal roller base material. Yes, as a coating material,
(A) a polyester-polyisocyanate-based polyurethane binder resin, and (b) an oil absorption of 100 to 350 ml (DB
P) / 100 g, surface area 125~1500m ² / g, more than 90% of the dispersed particles
It is characterized by using a conductive resin comprising carbon black having a particle diameter of 0.3 μm or less.

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.

As the polyester constituting the polyurethane-based conductive composition coated on the developing roller of the present invention, a softening temperature of 150 ° C. or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 200
It may be of the order of ~ 2000 and is produced from a polybasic organic acid (mainly a dicarboxylic acid) and a polyol.

Examples of dicarboxylic acids include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, and saturated fatty acids such as isosebacic acid,
Unsaturated fatty acids such as maleic acid and fumaric acid, and aromatic or anhydrides such as phthalic acid and isophthalic acid are used alone or in combination. Further, dimer acid obtained by dimerization of unsaturated fatty acid can also be used.

Examples of the polyol include diols such as ethylene glycol, diethylene glycol, triethylene glycol, polytetramethylene glycol, polypropylene glycol, polyethylene glycol, polyester glycols, polyacetal glycol, polycarbonate glycol, polybutadiene glycol, butylene glycol, and neopentyl glycol, and trimethylolpropane. And triols such as trimethylolethane, hexanetriol and glycerin, and hexaols such as sorbitol.

The polyurethane composition coated on the developing roller of the present invention is sufficiently resistant to practical use in light deterioration resistance and oxidation deterioration resistance, but when more excellent performance is required, it is used as a polymer diol. In particular, it is preferable to use a diol mainly composed of a polyester chain or a polycarbonate chain.

Polyesters obtained from various combinations of such polybasic organic acids and polyols, or combinations of various compositions can be used as raw materials for polyurethane, and polyesters obtained from lactones or derivatives thereof, which are intramolecular esters, are also used for urethanes. Used as raw material.

When producing a polyurethane using the polyester exemplified above as one raw material component, the polyisocyanate used as the other raw material component is tolylene diisocyanate, 3,3′-ditolylene-4,4′-diisocyanate, diphenylene methane. -4,4'-diisocyanate,
3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 2,4-tolylenediisocyanate dimer, isophoronediamine, 4,4'-diaminodicyclohexylmethane, 4,4'-diamino-3,3'-dimethyldicyclohexyl Methane, cyclohexylenediamine, isophorone diisocyanate, dicyclohexylmethane-4,4'-
Diisocyanate, 4,4'-isopropylidene dicyclohexane diisocyanate, cyclohexylene diisocyanate and the like.

As a raw material component of the polyurethane-based conductive composition to be coated on the developing roller of the present invention, as the carbon black to be added and dispersed, various commercially available carbon blacks can be used. Among them, furnace black, acetylene black, Conductive carbon black, such as Ketjen Black, is recommended, but thermal black, channel black, process black, etc. can also be used.

The carbon black has an oil absorption of 100-350ml
(DBP) / 100g, surface area of 125~1500m ² / g, 90 of the dispersed particles
% Or more and 0.3 μm or less. In this case, the surface layer having a coating film formed on the surface of the developing roller exhibits a state in which there is no unevenness in resistance value.

In kneading and dispersing the conductive filler in the urethane-based binder resin, various kneading machines can be used. For example, a three-roll mill, a ball mill, a bebble mill, a sand grinder, a high-speed stone mill, a high-speed impact mill, a disper, a kneader, a high-speed mixer, a homogenizer, an ultrasonic disperser and the like can be used alone or in combination.

Examples of the solvent constituting the polyurethane-based conductive composition coated on the developing roller of the present invention include dimethylformamide, diethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, N, N-tetramethylurea, Aprotic polar solvents such as hexamethylene phosphoamide and tetramethyl sulfone; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; ester solvents such as methyl acetate, ethyl acetate and butyl acetate; acetone and methyl ethyl ketone; Ketone solvents such as methyl isobutyl ketone and cyclohexanone; chlorinated hydrocarbon solvents such as trichlene and dichloroethane; alcohol solvents such as isopropanol; ether solvents such as tetrahydrofuran and dibutyl ether Etc. is used.

The polyurethane-based conductive composition coated on the developing roller of the present invention may contain, if necessary, other components such as various types of face dyes, fillers, plasticizers, antioxidants, and interface components in addition to the above-mentioned components. Activators and other additives can be used.

In the present invention, a polyisocyanate may be added in order to improve the ease of coating, the adhesion to the base, and the characteristics of the obtained dried coating film. At this time, an aliphatic polyisocyanate is suitable for maintaining the stability of the coating solution after blending for a long time.

The coating liquid prepared above 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 a line, and is applied. Then, a required conductive layer is formed by leaving the substrate at room temperature or drying by heating.
The heating and drying conditions are generally at 50 to 150 ° C. for 10 to 60 minutes,
In heating and drying, a curing catalyst can be added as necessary. In this case, drying can be performed at a lower temperature and in a shorter time than the above conditions.

(Function) The present invention is 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, and the coating material is made of polyester-polyisocyanate. The coating material is applied to the outer peripheral surface of the elastic layer and is coated as a dry film using a polyurethane-based binder resin and a conductive resin made of carbon black. Then
The polyurethane-based binder resin satisfies both light deterioration resistance, environmental resistance and polymer solution stability, and furthermore, physical properties such as high elongation, surface physical properties such as surface rub fastness, bending resistance and the like. The carbon black dispersed as a conductive filler in the conductive resin layer forming the outer peripheral surface has an oil absorption of 100 to 350 ml (DBP) / 10
0 g, surface area 125~1500m ² / g, more than 90% of the dispersed particles 0.3μ
When the particle size is selected to be not more than m, not only a paint or a conductive layer having a target resistance value can be more easily obtained, but also a change in temperature and humidity when a coating film is formed on the surface of the developing roller. Exhibits a stable volume resistivity,
Also, there is no unevenness in the resistance value of the surface layer, and an image of uniform image quality can always be obtained over a long period of time.

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 source, and a toner supply roller (not shown) is provided in addition to the toner thin layer forming member 5. It may be attached.

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 into a thin layer having a predetermined thickness, and to transfer electric charges. It is configured to give.

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,
Diameter φ = 6) Ethylene propylene (EPD)
M) An elastic roller (length = 220, diameter φ = 18) provided with an elastic layer 1b made of rubber (hardness 30 degrees Shore A, strain rate <10%) 1b was prepared.

Preparation of conductive paint Pre-dispersion of conductive carbon black Conductive carbon black (Ketjen Black EC) with an oil absorption of 340 ml (DBP) / 100 g, a surface area of 1000 m ² / g, and a particle diameter of 90% or more of the dispersed particles of 0.3 μm or less 40 parts by weight, manufactured by Lion Akzo Co., Ltd.) and 100 parts by weight of a polyurethane-based binder resin clear (Z-279, manufactured by Taitai Kako Co.) were mixed and dispersed using a three-roll mill to prepare a premixed fine dispersion.

Preparation of conductive paint 40 parts by weight of the conductive carbon black pre-dispersion liquid, 100 parts by weight of a polyester-polyisocyanate-based polyurethane resin (N-5120, manufactured by Nippon Polyurethane), 150 parts by weight of a mixed solvent of toluene, ethyl acetate and methyl ethyl ketone Parts and 2 parts by weight of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) were mixed to obtain a conductive paint.

Creation of a developing roller By a spray coating method on the outer peripheral surface of the elastic roller,
The conductive paint was applied to a thickness of 60 μm. Dry in an oven at 80 ° C for 10 minutes, cool and cool the conductive resin layer on the outer surface
The conductive elastic developing roller 1 provided with 1a was obtained. The volume resistivity measured immediately after application by the method described below is 8 ×
It was 10 ⁵ Ω · cm.

Image Output A commercially available copying machine (trade name: RheoDry 3301,
(Manufactured by Toshiba Corp.), and the toner image was developed so that the toner image could be developed.

For development, a toner prepared as follows was used. That is, 93 parts by weight of a polyester resin (NE-2155, manufactured by Kao Corporation), 3 parts by weight of carbon black (MA-100, manufactured by Mitsubishi Kasei), polypropylene wax (660P, manufactured by Sanyo Chemical)
2 parts by weight and 2 parts by weight of a charge control agent (E-88, manufactured by Orient Chemical Co., Ltd.) are heated and melt-kneaded by a pressure kneader, coarsely pulverized by a hammer mill, and then hydrophobic silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) One part by weight was added, 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 classified by an air classifier to obtain a volume average diameter of 9.0.
μm, black negative polarity toner was used.

Then, the black negative polarity toner is put into the toner hopper 4 of the modified non-magnetic one-component developing device, and the silicone blade 5 is pressed against the peripheral surface of the developing roller 1 so that the electrostatic latent image holder (photoreceptor) 2 The contact width between the developing roller 1 and the developing roller 1 is set to 1 mm, the developing roller 1 is rotated at a rotational peripheral speed of 188 mm / sec, and the photosensitive member 2 is rotated at a peripheral speed of 47 mm / sec. Developing was performed under the developing conditions of developing bias applied to 1 and -200V.

Measurement of Surface Specific Resistance A metal surface having a length of 220 and a width of 2 is brought into contact with the surface of the developing roller 1, and the developing roller shaft (roller base material) 1 c and the contact metal are sandwiched by metal clips, respectively, and a variable DC constant is measured. Apply a constant voltage of 10V with a voltage / current power supply (Metronics model 544B). The resistance value during this period is read by a microelectrometer (manufactured by Kesley, model 610C), and the volume specific resistance value is calculated.

Measurements under different environmental conditions were performed in an environmental test room where the temperature and humidity could be freely controlled.

Evaluation Results FIG. 2 shows the results of measuring the volume specific resistance value while changing the temperature and humidity of the developing roller 1.

Table 1 shows the evaluation results of the original image density and the toner transport amount per unit area on the developing roller surface when the development was performed under the above-described development conditions and a black solid image was output. Table 2 shows the results when the values were changed.

Table 1 Number of output images Image density Transport amount (sheets) (mg / cm ² ) 0 1.38 0.875 1000 1.36 0.864 5000 1.37 0.904 Table 2 Environmental conditions Image density transport amount (mg / cm ² ) 20 ° C, 50% RH 1.38 0.875 10 ° C., 20% RH 1.33 0.843 35 ° C., 80% RH 1.35 0.862 [Effect of the Invention] As is clear from the above description, the developing roller according to the present invention is formed on the outer peripheral surface of the metal roller base material. The outer peripheral surface of the elastic layer thus formed is covered with a conductive resin layer (film) made of a polyurethane binder resin and carbon black. Thus, the polyurethane-based binder resin as the coating agent can satisfy both light degradation resistance, environmental resistance, and stability of the polymer solution, and further has physical properties such as high elongation, surface rub fastness and the like. Excellent surface properties and flex resistance. Also,
In the conductive resin layer forming the outer peripheral surface of the developing roller, carbon black dispersed as a conductive filler is preliminarily dispersed in a binder resin of the same or different kind from the polyurethane resin before being dispersed with the polyurethane binder resin. When the required conductive paint is prepared, further select carbon black having an oil absorption of 100 to 350 ml (DBP) / 100 g, a surface area of 125 to 1500 m ² / g, and a particle size in which 90% or more of the dispersed particles are 0.3 μm or less. In this case, a paint having a target resistance value can be easily obtained. In addition, it has a stable volume specific resistance value against changes in temperature and humidity when a coating film is formed on the surface of the developing roller, and has a uniform resistance value of the surface layer, so that a high-quality image can be easily formed. The effect of obtaining is obtained. 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 explanatory view of a non-magnetic-component developing device equipped with a developing roller according to the present invention, and FIG. FIG. DESCRIPTION OF SYMBOLS 1 ... Development roller 1a ... Conductive resin layer 1b ... Elastic body layer 1c ... Metal roller base material 2 ... Electrostatic latent image holding body (photoreceptor) 3 ... Toner (developer)

Continuing from the front page (72) Inventor Masahiro Hosoya 1 Toshiba Research Institute, Komukai, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Koji Endo 2-6-13 Nakameguro, Meguro-ku, Tokyo Tokyo Inside Electric Co., Ltd. (72) Inventor Yoshimitsu Otaka 2-6-13 Nakameguro, Meguro-ku, Tokyo Tokyo Electric Power Company Inc. (56) References JP-A-64-581 (JP, A) JP-A-63 JP-A-183470 (JP, A) JP-A-1-191880 (JP, A) JP-A-2-37378 (JP, A) JP-A-2-284157 (JP, A) JP-A-3-187732 (JP, A) JP-A-3-20763 (JP, A) JP-A-1-109376 (JP, A) JP-A-1-102484 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08

Claims (1)

(57) [Claims] A metal roller base material; an elastic layer formed on an outer peripheral surface of the roller base material; and a conductive resin layer formed on the outer peripheral surface of the elastic layer. The conductive resin layer comprises at least (a) a polyurethane-based binder resin comprising polyester and polyisocyanate; and (b) an oil absorption of 100 to 350 ml (DBP) / 100 g, and a surface area of 125 to 1500 m ² / g, a developing roller characterized in that 90% or more of the dispersed particles are a coating film of a mixture with a conductive filler made of carbon black having a particle size of 0.3 μm or less.