JPH0798549A - Conductive roller - Google Patents

Abstract

PURPOSE:To stably provide the conductive roller of stable performance under all environmental conditions suitable for a mechanism subjected to constant voltage control without increasing a power source capacity. CONSTITUTION:This conductive roller 1X10<3>OMEGA to 10<12>OMEGA resistance when impressed with 500V at and under ordinary temp. and ordinary humidity of 25'C and 50% relative humidity. The conductive roller described above is so designed that the change rate K of the roller resistance by a negative charge voltage when the roller resistance value is measured under voltage charge conditions of respectively 500V and 2000V under respective environments of 35 deg.C and 85% relative humidity(RH) (hereafter described as H/H environment), 25 deg.C and 15%RH (hereafter described as NUN environment) and 10 deg.C and 15%RH (hereafter described as L/L environment) attains K=(the roller resistance at the time of loading with 500V voltage)/(the roller resistance at the time of loading with 2000V voltage), (K in the H/H environment)<=(K in the N/N environment)<(K in the L/L environment).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roller such as a toner carrying roller, a developing roller, a transfer roller and a cleaning roller in an electrophotographic or electrostatic printer, which electrically controls a contacted object.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic process in which toner prepared in a toner cartridge is supplied to a photosensitive member on which an electrostatic latent image is formed and transferred and fixed on a sheet is generally charged, exposed and developed. It consists of various mechanisms such as transfer, fixing, static elimination, etc., and each mechanism uses various rollers for precisely controlling charged materials, and the required characteristics of the roller materials have become more and more severe in recent years.

Particularly, a roller used in a developing mechanism including a toner conveying roller, a developing roller, a transfer roller, a roller used in a cleaning mechanism, etc. electrically control a contacted object, so that mechanical characteristics and electrical characteristics Both characteristics are required to be more stringent than ever before. Polyurethane resin has traditionally been used for its durability, flexibility, low compression set,
Due to its low stain resistance, it is used as a foam or elastomer for these applications. Urethane resin without the addition of conductive additives has a small amount of conductivity because water and impurities in the resin become carriers, and this conductivity mechanism is considered to be ionic conduction, and its electrical characteristics are also characteristic of ionic conduction. Indicates. A roller using such a general urethane resin has a roller resistance value of 10 ⁷ to 1 under H / H environment.
0 ⁹ Ω, 10 ⁹ to 10 ¹¹ Ω under L / L environment, H /
The resistance changes by about 2 digits or more between the H environment and the L / L environment. These resistance values change little with applied voltage.

When such a roller is used, especially when the roller is used by being connected to a constant current control power source, H
Since the roller resistance is low under the / H environment, the generated voltage is low under the constant current control, and the roller resistance is high under the L / L environment, so the generated voltage is high. The power source of the constant current mechanism used in general electrophotography mechanism is 0.1μ.
Constant current control is often performed at about A to 30 μA, for example, 1 × 10 ⁸ Ω under H / H environment and 2 × under L / L environment.
When a roller of 10 ¹⁰ Ω is used (when constant current control of 1 μA is performed), the generated voltage is 100 V and 2000, respectively.
Since it becomes V, a high voltage is required under the L / L environment, capacity increase of the power supply unit, discharge countermeasures, etc. are required, which is economically and space disadvantageous. When the roller is used by connecting it to a constant-capacity power source with insufficient capacity, L /
In the L environment, the power supply capacity may be insufficient, and the required amount of current may not be obtained, which may cause a defect in an image or the like.

Conventionally, in order to solve these problems, there is known a method of lowering the resistance of the roller by adding a conductivity imparting substance by an ion conduction mechanism or adding a large amount of a conductivity imparting substance by an electron conduction mechanism such as carbon. Has been.

[0006]

The method of adding the conductivity-imparting substance by the ionic conduction mechanism lowers the resistance under the L / L environment and at the same time lowers the resistance under the H / H environment. Generated electricity under / H environment is very small,
Images and other defects (transfer defects, development defects, etc.) may occur. Further, in the method of lowering the resistance of the roller by adding a conductivity-imparting substance such as carbon by an electronic conduction mechanism, in order to reduce the resistance value in each environment of H / H, N / N and L / L to the target resistance. However, it is necessary to add a large amount of electronic conductive material. Most of the substances that give conductivity by the electron conduction mechanism are powders or fibrous substances that are insoluble in urethane resin raw materials such as carbon, metal, and metal oxides. By mixing a large amount of these into the raw materials, the viscosity of the raw material system is increased. As a result, process problems occur in resin production and molding. Especially in the case of foaming, it becomes very difficult to control bubbles. Also, by mixing a large amount of powder,
The hardness of the cured resin becomes high and the flexibility is impaired. As a roller material used in a mechanism such as electrophotography, there is a rubber roller such as EPDM or silicon in which a conductivity imparting substance such as carbon is kneaded in addition to urethane resin. There are many problems caused by the rubber material itself, such as the fact that the material is often altered by contamination or chemical reaction, and the compression set is large.

Therefore, an object of the present invention is to stably provide a conductive roller which is suitable for a mechanism controlled by a constant current without increasing the power source capacity and can obtain stable performance under all environmental conditions. To do.

[0008]

In order to achieve the above object, the present invention has a resistance of 1 × 10 ³ Ω at a temperature of 25 ° C. and a relative humidity of 50% RH at room temperature and normal humidity when 500 V is applied.
With a conductive roller having a resistance of -10 ¹² Ω, a temperature of 35 ° C
Relative humidity 85% RH (H / H environment), temperature 2
5 ℃, relative humidity 50% RH (hereinafter referred to as N / N environment),
When the roller resistance value was measured under the conditions of a temperature of 10 ° C. and a relative humidity of 15% RH (hereinafter referred to as L / L environment) under voltage load conditions of 500 V and 2000 V, respectively, the roller resistance change rate K due to the load voltage was K. = (Roller resistance at 500V voltage load) / (roller resistance at 2000V voltage load), K _HH (H
/ H environment K) ≤ K _NN (N / N environment K) <K
_LL (K in L / L environment).

[0009]

In the present invention, since the current value under the L / L environment can be secured at a low voltage, a large capacity voltage generator is not required. Also, by using the conductive roller designed in this way with a mechanism such as electrophotography controlled by constant current, it is possible to reduce the change in generated voltage due to environmental changes, and to stabilize the voltage in all environments. The current can be secured and a good image can be obtained.

In a general polyurethane resin, the resistance becomes high under the L / L environment, and when it is used under the constant current control, the generated voltage becomes high, which causes a problem. The rate of resistance change due to the load voltage in this case was as shown in the following equation.

[0011]

[Equation 1]

In the urethane resin to which the conductivity-imparting substance by the ion conduction mechanism is added in order to reduce the overall resistance, the environmental change of the resistance value is large and a problem occurs in either H / H or L / L. The rate of resistance change due to the load voltage in this case was as shown in the following equation.

[0013]

[Equation 2]

Further, in order to reduce the overall resistance, a urethane resin containing a large amount of a conductivity-imparting substance by an electron conduction mechanism has many problems in the process of resin molding. When trying to obtain a low hardness one, the cell became rough and only a high density and high hardness was obtained, which caused a problem. In the case of the elastomer, the hardness of the resin itself becomes high, which causes a problem. The rate of resistance change due to the load voltage in this case was as shown in the following equation.

[0015]

[Equation 3]

As a result of intensive studies, it has been found that all the above-mentioned problems can be solved by designing the resistance change rate according to the load voltage so that K _HH ≤K _NN <K _LL . From the viewpoint of processability, resin hardness, etc., preferably 0.9 ≦ K _HH <2,2 ≦ K _LL ≦ 50, and particularly preferably 0.9 ≦ K _HH <2,2 ≦ K _LL ≦ 20. A stable product is obtained.

[0017]

The preferred embodiments of the present invention will be described below.

As the polyurethane resin, a polyhydroxyl compound, an organic polyisocyanate compound, a catalyst, a cross-linking agent, etc. are used.
Although a foam stabilizer is used, it is made into a resin mainly by the reaction of a polyisocyanate and a polyhydroxyl compound.

The polyhydroxyl compound is a polyol used in the production of general flexible urethane foams and urethane elastomers, that is, a polyether polyol having a hydroxyl group at the terminal, a polyester polyol, and a polyether polyester polyol which is a copolymer of the two. Also, general polyols such as so-called polymer polyols obtained by polymerizing an ethylenically unsaturated monomer in a polyol can be used. As the polyisocyanate compound, similarly, general soft urethane foam and polyisocyanate used for producing urethane elastomer can be used. That is, tolylene diisocyanate (TDI) crude TDI, 4,4'-diphenylmethane diisocyanate (MDI), crude MDI, C2-C18 aliphatic polyisocyanate, C4-C15 aliphatic polyisocyanate, C8 .About.15 aromatic polyisocyanates and mixtures and modified products of these polyisocyanates, for example, prepolymers obtained by partially reacting with polyols are used. A general organometallic compound as a catalyst,
For example, dibutyl tin dilaurate, tin octylate, octyl zinc, sodium acetate, etc., alkoxides and phenoxides of alkali and alkaline earth metals, tertiary amines such as triethylamine, triethyldiamine, N-methylmorpholine, dimethylaminomethylphenol, etc.,
Examples thereof include quaternary ammonium salts, imidazoles, and the like, and nickel acetylacetonate, diacetylacetonate nickel, etc. disclosed in JP-B-53-8735 can also be used. As the foam stabilizer, a known foam stabilizer used for foaming polyurethane foam can be used, and there is no particular limitation. As the other additives used in the present invention, known pigments, dyes, organic / inorganic fillers and the like used in the production of urethane foams and elastomers can be used as required.

An elastomer is produced by mixing and dispersing a conductivity-imparting substance having an electron-conducting mechanism and a conductivity-imparting substance having an ionic-conducting mechanism in the polyurethane resin as described above to prepare an elastomer. And foamed by mechanical stirring to produce a polyurethane foam.

A roller having a shape as shown in FIG. 1 is obtained by using these elastomers or polyurethane foams. For rollers used in mechanisms such as electrophotography,
When an elastomer is used, if the hardness becomes high, the contact with the abutting member becomes poor. Therefore, the Asker C hardness is preferably 80 ° or less, particularly 75 ° or less. In the case of a roller using polyurethane foam, the Asker C hardness is preferably 65 ° or less, particularly 60 ° or less for the same reason, and the cell diameter is 500 μm in average cell diameter.
It is particularly preferable that the thickness be 300 μm or less.

As the conductivity-imparting substance by the electron conduction mechanism, general conductive carbon, graphite powder, or single fiber thereof, or conductive metal powder of copper, nickel, silver or the like or fiber thereof. Substances, metal oxides such as tin oxide, titanium oxide, and indium oxide, or substances in which various fillers are metal-plated to give conductivity, organic conductive fine powders such as polyaniline, polypyrrole, and polyacetylene is there. The number of parts to be added can be adjusted depending on the target resistance value and the kind of the conductivity-imparting substance by the electron conduction mechanism, but normally 2000 V under L / L environment.
When the roller resistance when applied is in the range of 1 × 10 ⁴ to 1 × 10 ⁹ Ω, preferably 1 × 10 ⁸ to 1 × 10 ¹⁰ , the roller resistance change rate K depending on the load voltage is (roller resistance at 500 V voltage load). / (Roller resistance at 2000V voltage load), and 0.
9 ≦ (K in H / H environment) ≦ (K in N / N environment) <
Adjust so that (K in L / L environment) <100.

Further, as the conductivity-imparting substance by the ionic conduction mechanism, a cationic surfactant such as a quaternary ammonium salt, an aliphatic sulfonate, a higher alcohol sulfate ester salt, a higher alcohol ethylene oxide addition sulfate ester salt. , Higher alcohol phosphoric acid ester salts, higher alcohol ethylene oxide-added phosphoric acid ester salts and other anionic surface active agents, betaine and other amphoteric surface active agents, higher alcohol ethylene oxide, polyethylene glycol fatty acid esters, polyhydric alcohol fatty acid esters, etc. General antistatic agents such as ionic surfactants, and these antistatic agents have at least one or more hydroxyl group, carboxyl group, group having active hydrogen that reacts with isocyanate such as primary or secondary amine group. There are some. Further, a conductive material having the following ionic conduction mechanism can be used. That is, LiCF ₃ SO
₃ , NaClO ₄ , LiClO ₄ , LiAsF ₆ , Li
BF ₄ , NaSCN, KSCN, Li ⁺ such as NaCl,
Na ⁺ , K ⁺ Periodic Table 1 Group 1 metal salt or NH
Electrolytes such as ₄ ⁺ salts, and Ca such as Ca (ClO ₄ ) ₂
Periodic table such as ⁺⁺ , Ba ^++, etc., metal salts of Group 2 and the like, and 1.
Examples thereof include complexes of polyhydric alcohols such as 4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol, and polyethylene glycol and their derivatives, and complexes with monools such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. The number of parts to be added can be adjusted depending on the target resistance value and the kind of the conductivity-imparting substance by the ion conduction mechanism, but normally the roller resistance when 500 V is applied in an H / H environment is 1 × 10 ⁴ to 1 × 10 ^9. Ω, preferably 1 × 10 ⁵
The roller resistance change rate K due to the load voltage is adjusted within the range of up to 1 × 10 ⁸ so as to be the main characteristic. If the target resistance value is relatively high (1 × 10 ⁷ Ω or more), the ion conductivity due to the water and impurities in the polyurethane resin will not cause any special addition of the conductivity-imparting substance due to the ion conduction mechanism. Sometimes you get a feature.

[Comparative Example 1] 100 parts of polyether polyol (OH number 33) (Exenol (registered trademark) 828 manufactured by Asahi Glass Co., Ltd.) having a molecular weight of 5000 by adding propylene oxide and ethylene oxide to glycerin・ Urethane-modified MDI NCO% = 23% (Sumijour (registered trademark) PF manufactured by Sumitomo Bayer Urethane Co., Ltd.) 25.0 parts ・ 1.4 butanediol 2.5 parts ・ Silicone surfactant (Japan Unica ( L-520) 1.5 parts-Dibutyltin dilaurate 0.01 parts

These were placed in a 1-liter plastic container and stirred for 2 minutes with a home-use whisk to obtain a foam having fine uniform cells. This foam is 250mm (length) x 30
Pour into a mold of mm (width) x 30 mm (depth), 2 at 140 ° C
Heated for 0 minutes to cure. Foam 2 obtained as a result
Has an Asker C hardness of 44 °, a density of 0.56 g / cm ³ , and a cell diameter of 120 μm. Using this foam 2, a conductive roller 1 as shown in FIG. 1 was prepared. This roller 1 is shown in FIG.
As shown in Fig. 3, a load of 500 g is applied to both ends of the shaft 3, and 500 V is applied in the L / L environment, N / N environment, and H / H environment, and the resistance value of each resistance value (Ω ) Is shown in Table 1. The diameter of the foam 2 is 20 mm, the length is 210 mm, and the diameter of the shaft 3 is 6 m.
m and length 270 mm.

[0026]

[Table 1]

When this roller was set and evaluated as a transfer roller used for constant current control in a commercially available laser beam printer, a good image was obtained under N / N and H / H environment, but L / N Image defects occurred in the L environment. The cause was judged to be insufficient capacity of the voltage generator.

Example 1 Asahi Thermal FT Class (manufactured by Asahi Carbon Co., Ltd.) was added to the compounding system of Comparative Example 1 while paying attention to the rate of change in resistance under load of 500 V and 2,000 V under an L / L environment. A roller similar to Comparative Example 1 was prepared by increasing the amount and adding 5.0 parts as a result, and the same evaluation as in Comparative Example 1 was performed. The resistance value was shown in Table 2, and the density was 0.5.
6g / cm ³ , Asker C hardness 45 °, average cell diameter 150
The image quality under the L / L environment was good. At this time, there was no problem with images under N / N and H / H environments.

[0029]

[Table 2]

[Comparative Example 2] In the compounding system of Comparative Example 1, a quaternary ammonium salt (Kao KS-55 as an ion conductivity imparting substance)
When 0.05 part of 5) is added, the results are shown in Table 3 and the density is 0.
56g / cm ³ , Asker C hardness 44 °, average cell diameter 12
It was 0 μm, and an image defect occurred in the L / L environment.

[0031]

[Table 3]

[Example 2] When Asahi Thermal FT Class was added to the compounding system of Comparative Example 2 in an amount of 5.0 parts by weight, the results are shown in Table 4, with a density of 0.56 g / cm ³ , Asker C hardness of 45 °, and an average cell. The diameter was 150 μm, and good images were obtained in all environments.

[0033]

[Table 4]

[Comparative Example 3] When 0.25 parts of the above-mentioned KS-555 was added to the compounding system of Example 1 as an ion conductive material, the results are as shown in Table 5. In this case, L / L conditions were applied. However, the image under H / H conditions was poor. This roller has a density of 0.56 g / cm ³ , an Asker C hardness of 44 °, and a cell diameter of 120 μm.

[0035]

[Table 5]

Example 3 10 parts of Asahi Thermal FT grade of Example 1 was added to obtain a roller having a density of 0.56 g / cm ³ , an Asker C hardness of 46 ° and a cell diameter of 180 μm. When the same evaluation as in Comparative Example 1 was performed, the resistance value
And good images were obtained under all environments.

[0037]

[Table 6]

[Embodiment 4] In Embodiment 3, KS-5
0.05 part of 55 was added and the ion conduction mechanism and the electron conduction mechanism were used together to obtain a roller having a density of 0.56 g / cm ³ , an Asker C hardness of 46 ° and a cell diameter of 180 μm. When the same evaluation as in Comparative Example 1 was performed, the resistance value was as shown in Table 7, and good images were obtained under all environments.

[0039]

[Table 7]

[Comparative Example 4] The addition number of Asahi Thermal FT grade in Example 1 was 20 parts, and the density was 0.56 g /
When a roller of cm ³ was created, the foam cell was not stable due to the increase in the viscosity of the raw material, and the cell diameter was 200 μm to 800 μm.
m, Asker C hardness was 44 to 48 °, and the variation was large. The average cell diameter was 600 μm. When the same evaluation as in Comparative Example 1 was carried out, the resistance value was as shown in Table 8, and the image had unevenness which is considered to be caused by the roughening of the cell diameter in all environments.

[0041]

[Table 8]

[Comparative Example 5] In Comparative Example 4, the density was 0.
When a roller having a weight of 88 g / cm ³ was prepared, cell roughness was eliminated, and a roller having a cell diameter of 150 μm and an Asker C hardness of 70 ° was obtained. When the same evaluation as in Comparative Example 1 was performed, the resistance value was as shown in Table 9, and in the image, bleeding occurred in the printing of dots and lines.

[0043]

[Table 9]

Examples of the polyurethane elastomer will be shown below. [Comparative Example 6] A raw material having the same composition as that of Comparative Example 1 was placed in a separable flask, stirred for 3 minutes while degassing under vacuum, and then poured into a mold having an inner diameter of 25 mm and a length of 250 mm.
It was cured by heating at 40 ° C. for 20 minutes. A conductive roller 1 as shown in FIG. 1 was prepared using this urethane elastomer. The elastic part 2 of the roller has a diameter of 20 mm and a length of 2
31 mm, the diameter of the shaft 3 was 6 mm, and the length was 262 mm.
Install this roller on both ends of the shaft 3 as shown in FIG.
With 0g load applied, 500V applied in L / L environment, N / N environment, H / H environment, resistance measuring instrument 4 under 2000V applied condition
Table 10 shows the results of measuring the respective resistance values with. The roller hardness was 70 ° as Asker C hardness. When this roller was set as a developing roller used for constant current control using a commercially available laser beam printer and evaluated, a good image was obtained under the H / H environment, but especially under the L / L environment. Caused a defect.

[0045]

[Table 10]

Example 5 A roller was obtained in the same manner as in Comparative Example 6 except that 3.0 parts of carbon black (Dia Black H: Mitsubishi Kasei Co., Ltd.) was added to the composition.
The resistance values are shown in Table 11, and the roller hardness is Asker C hardness 7
It was 3 °. The image was also good in all environments.

[0047]

[Table 11]

[Comparative Example 7] In Comparative Example 6, diethylene glycol monomethyl ether [CH ₃ OCH ₂ C] of sodium perchlorate [Ca (ClO ₄ ) ₂ ] was added to the composition.
H ₂ OCH ₂ OH] complex compound (MP-100E: Akishima Chemical Industry Co., Ltd.) was added in an amount of 0.01 part to obtain a roller in the same manner. The roller hardness was 70 ° Asker C hardness. The resistance values are shown in Table 12, and good images were obtained in the N / N and H / H environments, but image defects occurred in the L / L environment.

[0049]

[Table 12]

Example 6 A roller was obtained in the same manner as in Comparative Example 7 except that 3.0 parts of Diamond Black H was added to the composition. The roller hardness was Asker C hardness 73 °.
The resistance values are shown in Table 13, and the image was good in all environments.

[0051]

[Table 13]

Comparative Example 8 A roller was obtained in the same manner as in Comparative Example 6, except that 8.0 parts of Diamond Black H was added to the formulation. The roller hardness was Asker C hardness 83 °. The resistance values are shown in Table 14. In the image, the roller hardness is hard and the contact between the developing roller and the photoconductor roller is non-uniform, so that partial unevenness occurs in the entire environment.

[0053]

As described above, according to the present invention, it is possible to obtain stable performance under all environmental conditions, suitable for use in a constant current control mechanism without increasing the power supply capacity.

[Brief description of drawings]

FIG. 1 is a perspective view of a conductive roller.

FIG. 2 is a diagram showing a method of measuring a resistance value.

[Explanation of symbols]

 1 Conductive roller 2 Foam 3 Shaft

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G03G 15/08 A 8530-2H 21/10

Claims (4)

[Claims] 1. A resistance at a temperature of 25 ° C. and a relative humidity of 50% RH at room temperature and normal humidity when 500 V is applied is 1 × 10 ³ Ω to
In a conductive roller of 10 ¹² Ω, a temperature of 35 ° C., a relative humidity of 85% RH (hereinafter referred to as H / H environment), a temperature of 25 ° C., a relative humidity of 50% RH (hereinafter referred to as N / N environment), a temperature of 10 RH relative humidity 15% RH (hereinafter L /
500V and 2000V under each environment (referred to as L environment)
When the roller resistance value is measured under the voltage load condition of, the roller resistance change rate K due to the load voltage is K = (roller resistance at 500V voltage load) / (roller resistance at 2000V voltage load), (H / H environment K) ≦ (K in N / N environment) <(L /
The conductive roller is designed to be K) in an L environment. 2. The conductive roller according to claim 1, comprising a polyurethane elastomer having an Asker C hardness of 80 ° or less. 3. The conductive roller according to claim 1, comprising a polyurethane foam having an Asker C hardness of 65 ° or less and an average cell diameter of 500 μm or less. 4. The conductive roller according to claim 1, which is used in a mechanism such as electrophotography under constant current control.