JP2000130429A - Semi-conductive silicon rubber roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-conductive silicon roll capable of giving a sufficient electrification capacity relating to a toner by preventing deterioration of an environmental resistance characteristic of silicon rubber as an elastic unit, and having a stable frictional electrification characteristic. SOLUTION: This semi-conductive silicon rubber roll is formed by coating an outer peripheral surface of a conductive shaft unit 1 with a polyurethane resin layer 3 of 0 to 15 (nC) contact electrification capacity, when it is measured by using a cascaded contact electrification measuring device, through a semi- conductive elastic layer 2 consisting of silicon rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic OA.
The present invention relates to a semiconductive silicone rubber roll having excellent charging characteristics, which can be used as a roll around a photosensitive drum in an apparatus, and is particularly useful as a developing roll.

[0002]

2. Description of the Related Art In a developing process of an electrostatic recording apparatus such as a copying machine, an LBP (laser beam printer), a facsimile, etc., which adopts an electrophotographic method in OA equipment, a thin layer of triboelectric toner is formed on a developing roller. Then, the latent image on the photoconductor is developed by bringing the developing roller and the photoconductor into contact with the thin toner layer. In this case, the toner is charged to a predetermined charge amount mainly by frictional charging between the toner and the developing roller and between the toner and the developing blade, and after the layer thickness is regulated by the developing blade pressed against the developing roller, the toner surface is And electrostatically adheres to the electrostatic latent image formed thereon to form a visible image. The properties required of the developing roller include having an appropriate surface roughness, obtaining a uniform layer thickness, being excellent in durability, and having stable charging characteristics.

[0003] As described above, the developing roller has a function of frictionally charging the toner in contact with the surface. Generally, in the triboelectric charging between two substances having different compositions, charges of opposite signs are generated on the surfaces of the contacted and separated substances in equal amounts. Whether the material is positively or negatively charged is a relative relationship between the two materials (contact charging sequence), and the charge capacity is defined by a capacitance inherent to the material. Since the charged state changes depending on the relative relationship between the two substances in contact with each other, the positive charge / negative charge of one substance,
Charging characteristics such as charging amount and charging stability greatly affect the charging characteristics of the other substance. In other words, the charging characteristics of the developing roll include the charging amount of the frictionally charged toner, the toner layer thickness, the toner consumption amount, and the toner releasability inside the developing device, and the black solid density (Macbeth density) and the fog density as the actual image. It is closely related to outbreaks and white spots. At present, the thin toner layer formed on the developing roll, in the case of magnetic one-component development,
0.6~1.2mg / cm ² at a coverage, the layer thickness corresponds to a 30~60μm, 0.5~1.1mg / cm ² at a coverage in the non-magnetic one-component developing,
As a layer thickness, 20 to 30 μm is used as a general value.

[0004]

A developing roll using silicone rubber as a raw material, which is currently used, has excellent environmental resistance as compared with other types of rubber, and has stable characteristics as an elastic body for a long period of time. There are advantages such as that the charge amount distribution of the frictionally charged toner is sharp, and that filming by the toner is less likely to occur on the roll surface. However, with an increase in printing speed in recent years, the amount of toner charge has become insufficient, and fog and insufficient print density have occurred as problems on images. In addition, there is a demand for a thinner toner layer on the surface of the developing roll in order to achieve higher image quality. In contrast, a method of controlling the charge amount of a roll by adding a modified silicone oil to a semiconductive elastic layer made of silicone rubber, or a method of controlling a mechanical toner conveyance force by changing a roll surface roughness In the former, problems such as a decrease in toner fluidity due to bleeding of oil, filming on rolls and photoreceptors, and changes in elastic material properties of silicone rubber occur in the latter. Thus, there is a problem that the toner charge amount distribution is broadened accordingly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductive material which has a stable triboelectric charging characteristic without impairing the environmental resistance characteristics of silicone rubber as an elastic material and which can provide a sufficient amount of charge to a toner. To provide a silicone rubber roll.

[0006]

The semiconductive silicone rubber roll of the present invention uses a cascaded contact charge measuring device via a semiconductive elastic layer made of silicone rubber on the outer peripheral surface of a conductive shaft. The contact charge amount when measured is 0
It is characterized by being coated with a polyurethane resin layer of up to 15 (nC).

This semiconductive silicone rubber roll also has a roll resistance R ₁ before coating with a polyurethane resin layer and a roll resistance R ₂ after coating with a polyurethane resin layer having the formula: 3.0 <Lo
It is preferable that g (R ₂ / R ₁ ) <6.0 is satisfied, and the surface of the semiconductive elastic layer is modified by irradiation with ultraviolet rays.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the semiconductive silicone rubber roll of the present invention will be described below in detail with reference to FIG. FIG. 1A is a perspective view of a semiconductive silicone rubber roll of the present invention, and FIG. 1B is a longitudinal sectional view thereof. 1 is a conductive shaft body, 2 is a semiconductive elastic layer (hereinafter simply referred to as a semiconductive elastic layer) made of silicone rubber formed on the outer peripheral surface thereof, and 3 is a coating of the semiconductive elastic layer 2. The above-mentioned polyurethane resin layer (hereinafter, simply referred to as a polyurethane resin layer).

In the above semiconductive silicone rubber roll, the conductive shaft 1 is made of a so-called "core metal" made of iron, aluminum, SUS, brass or the like, or a thermoplastic resin, a thermosetting resin or the like. Conductive by plating on the surface of the insulating core, or thermoplastic resin, carbon black as a conductivity-imparting agent on a thermosetting resin,
For example, a resin molded with a conductive resin containing a metal powder or the like is used. These conductive shafts 1 are grounded at one end or applied with a bias voltage to charge the latent image carrier, inject charge into the toner, and transport the toner from the latent image carrier to form an electrostatic latent image. Exhibits functions such as image development.

For forming the semiconductive elastic layer 2, for example, at least one kind of polyorganosiloxane raw rubber such as dimethylsilicone raw rubber or methylphenylsilicone raw rubber, and, if necessary, reinforcement such as fumed silica or precipitated silica. Conductive carbon black as a conductivity-imparting agent; a metal powder such as nickel, aluminum, and copper; a metal oxide such as zinc oxide and tin oxide; a barium sulfate; Silicone rubber composition obtained by mixing at least one kind such as one obtained by coating a conductive substance such as tin oxide on an insulating core material such as titanium oxide and potassium titanate, and further adding a vulcanizing agent or a bulking agent. Object is used.

As the vulcanizing agent, for example, benzoyl peroxide, bis 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis ( t-
Peroxides such as butylperoxy) hexane, and 1
Examples thereof include those in which an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in a molecule and a catalytic amount of a platinum-based catalyst are added. When mixing these components, a pressure kneader, a Banbury mixer,
It may be carried out by a conventional silicone rubber compound kneading method using a mixing roll, a planetary mixer or the like.

As described above, the polyurethane resin used to form the polyurethane resin layer 3 has a contact charge amount of 0 when measured using a cascade-type contact charge measurement device.
~ 15 (nC). Here, the contact charge amount is a value measured using a cascade-type contact charge measuring device: TS-100AT (trade name, manufactured by Toshiba Chemical Corporation) under the following conditions.

FIG. 2 schematically shows this apparatus. This device uses a spherical reference contact powder 11 and removes it from the hopper 12.
A contact charge measuring device which is poured onto a 60 ° inclined plate (sample plate) 13 and received in a metal container 15 on an insulating plate 14, 16 is a capacitor, and 17 is an electrometer for measuring a contact charge. This measuring instrument is capable of high-precision measurement and uses ESCA (Electron
An abbreviation of Spectroscopy for Chemical Analysis, a type of electron spectroscopy that analyzes the surface of a solid or the state of chemical bonding. In this measurement, spherical ferrite powder (particle diameter 100 μm) whose surface was treated with a silicone resin was used as a reference contact powder, and SU
Each polyurethane resin is 20μm thick on S board (75 × 100mm)
Use the one coated with. The pouring time is 5 seconds, and the measurement is performed three times on the same sample plate while taking care that the powder flows to a new portion of the sample surface for each measurement, and the average value is defined as the contact charge amount on the coating resin surface. These measurements are at 25 ° C, 60%
This is performed in an atmosphere of RH.

The polyurethane resin having the above-mentioned contact charge applied to the present invention is a resin obtained by reacting a polyether polyol or polyester polyol with an aromatic polyisocyanate or an aliphatic polyisocyanate, and is dissolved and dispersed in an organic solvent. And a self-emulsifying aqueous type having a urethane skeleton having a hydrophilic functional group. When selecting the polyol and the polyisocyanate, it is desirable to select a polyisocyanate having high solubility in an organic solvent and high compatibility with the polyol. In addition, since the charging characteristics of the formed urethane resin are mainly changed by the functional group in the side chain, it is necessary to pay attention when selecting the polyol whether the functional group is electron-accepting or electron-donating.

As the polyether polyol, alkylene oxides such as ethylene oxide and propylene oxide are added to low molecular weight polyols such as ethylene glycol, propylene glycol and glycerin, amines such as ethylene diamine, diethylene triamine and tolylene diamine, and polyphenols. Examples thereof include polypropylene glycol, polytetramethylene ether glycol, and the like.Examples of the polyester polyol include the low-molecular-weight polyols and adipic acid,
Examples thereof include polycaprolactone and polycarbonate polyol obtained by a dehydration condensation reaction with a dicarboxylic acid such as phthalic acid.

On the other hand, examples of the aromatic polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, tolidine diisocyanate, and naphthalene diisocyanate. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate. Isophorone diisocyanate, xylylene diisocyanate,
Examples include hydrogenated xylylene diisocyanate, dimer acid diisocyanate, tetramethylhexamethylene diisocyanate, and lysine diisocyanate methyl ester.

The thickness of the polyurethane resin layer covering the surface of the semiconductive elastic layer 2 is preferably in the range of 5 μm to 100 μm. If this is less than 5 μm, sufficient mechanical strength cannot be maintained,
Peeling of the polyurethane resin layer occurs, and the charge amount of the toner becomes non-uniform, resulting in image defects such as fog and white spots. If it is larger than 100 μm, the charge amount becomes non-uniform,
It is not preferable because the toner is damaged due to a decrease in surface elasticity.

The triboelectric charging property, that is, the toner charging property, developed on the surface of the semiconductive silicone rubber roll of the present invention is as follows.
Not only the charging characteristics of the coated polyurethane resin layer,
It also changes depending on the relationship between the volume resistance of the semiconductive elastic layer made of silicone rubber and the volume resistance of the polyurethane resin layer. That is, the roll resistance R ₁ before coating the polyurethane resin layer and the roll resistance R ₂ after coating the polyurethane resin layer.
Preferably satisfies the formula: 3.0 <Log (R ₂ / R ₁ ) <6.0.

In forming the semiconductive silicone rubber roll of the present invention, a press molding method for simultaneously heating and pressing a conductive shaft and a silicone rubber composition for forming a semiconductive elastic layer in a mold, After extruding the body and the above-mentioned composition integrally using an extruder using a crosshead, an extrusion molding method of primary vulcanization in a gear oven or an IR (infrared) furnace, and a conductive shaft were set in a molding die. Thereafter, an injection molding method or the like in which the composition is injected into the mold and heated is used. Thereafter, secondary vulcanization can be performed using a gear oven or the like to stabilize the physical properties. In this case, the secondary vulcanization temperature is usually preferably in the range of 100 to 225 ° C.

In order to obtain a developing roller having a lower hardness,
What is necessary is just to prepare what added the organic foaming agent to the said composition, and to provide the non-foaming elastic body layer on the outer peripheral surface of the foaming elastic body layer obtained by carrying out heat hardening and foaming by the above-mentioned method. As this organic foaming agent, azobisisobutyronitrile (AIBN), azodicarboxylic amide (ADCA) and the like are suitable.
The addition amount is preferably in the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the composition. If the amount is less than 0.5 part by weight, the foaming is not sufficient, and if it is added in excess of 5 parts by weight, the mechanical strength is reduced. It is not preferable.

The roll-shaped molded product formed under such conditions is coated with the polyurethane resin layer as it is or after the outer peripheral surface of the roll-shaped molded product is polished by a cylindrical grinder. At that time, in order to enhance the adhesiveness between the semiconductive elastic layer and the polyurethane resin layer, a primer is applied to the surface of the semiconductive elastic layer, or the surface is irradiated with ultraviolet rays, so that the size of the irregularities on the surface is reduced. The density can also be adjusted. The polyurethane resin layer may be formed by a method suitable for the form of the material, for example, a solvent-based material may be formed by a spray coating method or a dipping method, and a film-shaped product may be formed by covering a film tube with a roll. .

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the description of these examples.

(Example 1) SUM2 was used as the conductive shaft.
Use a 10 mm diameter, 400 mm long shaft made of electroless nickel plated for silicone primer No. 101A
And No.101B (both manufactured by Shin-Etsu Chemical Co., Ltd., trade name) in a ratio of 1: 1 and applied in a gear oven.
A baking treatment was performed at 50 ° C. for 10 minutes. As a silicone rubber composition for forming a semiconductive elastic layer, 100 parts by weight of organic peroxide-reactive silicone raw rubber, KE-78VBS (same as above), carbon black and thermal black (trade name, manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, 25 parts by weight of fumed silica filler Aerosil 200 (trade name, manufactured by Nippon Aerosil Co., Ltd.) are added, and after kneading with a pressure kneader, an organic peroxide-based vulcanizing agent C-8 (Shin-Etsu Chemical Co., Ltd., trade name) 2.0 parts by weight was prepared. This was vulcanized and adhesive-molded with the shaft at 175 ° C. for 10 minutes in a compression mold having a cylindrical cavity having an inner diameter of 20 mm. After that, secondary vulcanization is performed in a gear oven at 200 ° C for 7 hours, polished with a cylindrical grinder, and has a diameter of 18 mm, a rubber part length of 320 mm, and a solid semiconductive material on the outer peripheral surface of the conductive shaft. A roll-shaped molded article provided with a flexible elastic layer was obtained.

Next, after applying the primer KBP-40 to the surface of the roll-shaped molded product, a two-pack type urethane-based paint: Daiplacoat Soft SO (trade name, manufactured by Dainichi Seika Kogyo Co., Ltd.) is applied to the surface. Coating was performed with a spray coating machine to a film thickness of 20 μm, and dried and cured in a gear oven at 200 ° C. for 30 minutes to form a polyurethane resin layer, thereby obtaining a semiconductive silicone rubber roll of the present invention. At the same time, the above urethane-based paint is applied to a SUS plate (75 × 100 mm) whose surface has been polished for contact charge measurement at a thickness of 20 μm using a spray coater, and dried and cured at 200 ° C. for 30 minutes in a gear oven. A sample plate was also prepared and measured and evaluated by the following methods.

<Measurement of Contact Charge Amount of Coating Film> A spherical ferrite powder (particle diameter: 100 μm) whose surface was treated with a silicone resin as a reference contact powder, and SU whose surface was polished as a sample plate
Each polyurethane resin is 20μm thick on S board (75 × 100mm)
Was used. The pouring time was 5 seconds, and the measurement was performed three times on the same sample plate while paying attention to the flow of the powder to a new portion of the sample surface for each measurement, and the average value was defined as the contact charge amount on the coated resin surface. These measurements were taken at 25 ° C, 60% R
The test was performed under an atmosphere of H.

<Initial and post-durability Macbeth density> A 500-sheet continuous printing test (using a continuous printing pattern) was performed using an electrophotographic printer, and when the fifth and 500th printing were completed, the evaluation pattern was evaluated. (One set of a series of printing patterns such as solid black, halftone dot, 5% duty, white background printing, etc.) is printed, and the Macbeth density of the black cell portion of each 5% duty image is measured using a Macbeth densitometer. The measured value was 1.3 or more.

<Initial and endurance fog> A 500-sheet continuous printing test (using a continuous printing pattern) was performed using an electrophotographic printer, and when the fifth and 500th printing were completed, the evaluation pattern ( One set consists of a series of print patterns such as solid black, halftone dots, 5% duty, white background printing, etc.), and the fog point in the 0.5 × 1 mm area under the black square on the 5% duty image is calculated as CC.
Enlargement and measurement were performed with a D camera (200 times), and those whose number was 15 or less were accepted.

<Initial and post-durability black solid followability> A 500-sheet continuous printing test (using a continuous printing pattern) was performed with an electrophotographic printer, and evaluation was performed at the end of printing the fifth and 500th sheets. Pattern (one set of a series of printing patterns such as solid black, halftone dot, 5% duty, white background printing, etc.) is printed, and the Macbeth density of each solid black image is determined for each roll cycle (6 per image). Point) measurement, 1
Calculate the density change rate at the dot and the sixth point, and find that the value is 0.98
The above were accepted.

(Example 2) The same procedure as in Example 1 was carried out except that 10% by weight of oplite (crystalline silica) was added to the urethane-based coating instead of Daiplacoat Soft SO (described above). Similarly, a semiconductive silicone rubber roll and a sample plate of the present invention were produced. A test was performed in the same manner as in Example 1 using these two.

(Example 3) As a urethane-based paint, 10% by weight of crystallite (trade name, crystalline silica, manufactured by Tatsumori Co., Ltd.) was added to this in place of Daiplacoat Soft SO (described above). Except for using, in the same manner as in Example 1,
A semiconductive silicone rubber roll and a sample plate were obtained. A test was performed in the same manner as in Example 1 using both of them.

(Comparative Example 1) In the same manner as in Example 1 except that a one-pack type urethane-based paint: Daiplacoat Soft MH (the same as above) was used instead of Daiplacoat Soft SO (described above), A semiconductive silicone rubber roll and a sample plate were obtained. When a test was conducted using these two in the same manner as in Example 1, as shown in Table 1, the number of fog points and black solid followability were rejected.

(Comparative Example 2) A semiconductive material was prepared in the same manner as in Example 1 except that a fluoroplastic paint: GLS213 (trade name, manufactured by Daikin Industries, Ltd.) was used instead of the die plastic coat software SO (described above). A silicone rubber roll and a sample plate were obtained. When a test was performed using these two in the same manner as in Example 1, as shown in Table 1, the Macbeth density, fog score, and black solid followability of the black mass part were rejected.

[0033]

[Table 1]

[0034]

According to the semiconductive silicone rubber roll of the present invention, the silicone rubber as an elastic body has a stable frictional charging property without impairing the environmental resistance property of the silicone rubber, and provides a sufficient charge amount to the toner. Can be granted. As a result, a uniform toner layer can be formed on the roll surface, and an excellent image without fogging or blurring can be obtained.

[Brief description of the drawings]

FIG. 1A is a perspective view and FIG. 1B is a longitudinal sectional view of a semiconductive silicone rubber roll according to the present invention.

FIG. 2 is a perspective view of an apparatus for measuring a contact charge amount used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conductive shaft body, 2 ... Semiconductive elastic layer, 3 ... Polyurethane resin layer, 11 ... Reference contact powder, 12 ... Hopper, 13 ... Inclined plate (sample plate), 14 ... Insulating plate, 15 ... Metal container , 16… Condenser, 17… Electrometer for contact charge measurement.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) C08J 7/00 304 C08J 7/00 304 G03G 15/02 101 G03G 15/02 101 15/08 501 15/08 501B 504 504D // C08L 77:00 F term (reference) 2H003 BB11 BB14 CC05 2H077 AD06 AD12 AD35 AE02 FA13 FA14 FA22 FA25 3J103 AA02 AA13 AA23 BA41 FA23 GA02 GA57 GA58 GA60 HA02 HA12 HA48 HA53 4F073 AA03 BA0345 JG01 JG03

Claims (3)

[Claims] A contact charge amount of 0 to 15 when measured using a cascade-type contact charge measuring device is provided on the outer peripheral surface of a conductive shaft body via a semiconductive elastic layer made of silicone rubber.
A semiconductive silicone rubber roll coated with a polyurethane resin layer (nC). 2. The semi-conductive silicone rubber roll according to claim 1, wherein the roll resistance R ₁ before coating the polyurethane resin layer and the roll resistance R ₂ after coating the polyurethane resin layer are:
_{Formula: 3.0 <Log (R 2 /} R 1) < semiconductive silicone rubber roll and satisfying 6.0. 3. The semiconductive silicone rubber roll according to claim 1, wherein the surface of the semiconductive elastic layer made of silicone rubber is modified by irradiation with ultraviolet rays.