JPH11231662A - Conductive belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive belt which causes little permanent elongation even in a long-term use and which has excellent uniformity in the electric resistance and high strength with little changes with time. SOLUTION: This conductive belt to be used for the mechanism of an electrophotographic copying device or a laser printer has a conductive layer which consists of an elastomer having urethane bonds and urea bonds in the molecule with addition of conductive carbon black and an ionic conductive material in the elastomer. The average ratio of urethane bonds to urea bonds in the molecule of the elastomer is preferably (5:95) to (95:5). The conductive belt is formed by a centrifugal forming method. It is preferable that a flocculated layer of the conductive carbon black is preferably formed near the surface of the conductive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive belt used for a belt transfer, a toner image transfer, a paper transporting portion of an electrophotographic copying machine or a laser printer, and more particularly, a aging of an electric resistance even in long-term use. The present invention relates to a conductive belt having little change.

[0002]

2. Description of the Related Art In recent years, with the development of electrophotographic technology, a transfer device such as an electrophotographic copying machine or a laser printer,
Attention has been focused on conductive belts used for paper conveyance and the like. Such a conductive belt must have not only a predetermined electric resistance but also characteristics suitable for various mechanisms.

Conventionally, conductive belts are silicone rubber, N
A general rubber material such as BR, H-NBR, CR, urethane rubber and EPDM is used as a base material, and a filler-based conductivity-imparting substance, for example, general conductive carbon, conductive metal oxide, carbon fiber, etc. is added thereto. The electrical resistance of the conductive layer is adjusted to the desired electrical resistance, but if used for a long period of time, the electrical resistance of the conductive layer is broken in response to the permanent elongation of the rubber and the ozone deterioration, and the electrical resistance increases. And the like. Further, in the conventional conductive belt, there is a problem that the positional deviation of the transferred image is gradually increased at the time of transferring the color image, and the registration is deteriorated such as image blur and fuller. In order to solve such a problem, it has been proposed that the conductive belt be reinforced with Kevlar fiber, polyester fiber, glass fiber, etc., but this belt can suppress the permanent elongation but increases the cost. In addition, there is a drawback that the film thickness adjustment also depends on the thickness and winding method of the core material to be used, and tends to cause belt meandering and pitch contraction / elongation. In addition, it is necessary to make the dispersion state of the conductive filler uniform with the improvement of image quality.However, with the conventional conductive belt, white spots, black spots, and white spots are generated due to uneven resistance, dispersion and aggregation of the filler. It is difficult to control the dispersion state of the conductive filler only by the amount of carbon black added and the size of the secondary aggregate.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been developed to produce a conductive belt having a small permanent elongation even when used for a long period of time, and to have excellent uniformity of electric resistance.
It is an object of the present invention to provide a high-strength conductive belt with little change over time.

[0005]

Means for Solving the Problems That is, the present inventors provide:
As a result of intensive studies on the cause of the increase in the electrical resistance of the conductive layer when the conductive belt is used for a long time, the use of an ionic conductive material in combination with or in addition to the conventional filler-based conductive material has led to a reduction in the electrical resistance. It has been found that by maintaining uniformity and controlling the mechanical strength of the conductive belt by controlling the composition of the elastomer, the permanent elongation is small even when used for a long time, and the change with time can be suppressed.

The present invention has been achieved based on the above findings, and the conductive belt according to claim 1 is
In a conductive belt having a function of transferring a toner image on an image carrier to a sheet, or conveying a sheet, or both of them, the conductive belt is made of an elastomer having an urethane bond and a urea bond in a molecule. A conductive belt having a conductive layer obtained by adding an ion conductive substance and conductive carbon black to a conductive belt. The conductive belt according to claim 2, wherein the elastomer adjusts the mixing ratio of the diamine monomer and the polyol, and crosslinks with diisocyanate so that the average ratio of urethane bonds and urea bonds in the molecule is from 5:95 to 95: 5. <1> is a conductive belt according to <1>. The conductive belt according to claim 3, wherein the conductive belt is formed by a centrifugal molding method, and an aggregated layer of conductive carbon black is formed near the surface of the conductive layer.
A conductive belt according to 1> or <2>. The conductive belt according to a fourth aspect is the conductive belt according to any one of <1> to <3>, wherein a protective layer is provided on the conductive layer. The conductive belt according to claim 5, wherein M100% (1
00% belt elongation modulus) is 20 to 200 kgf /
The conductive belt according to <2>, which is adjusted to cm ² . The conductive belt according to claim 6 is the conductive belt according to <3>, wherein an air surface at the time of centrifugal molding is a conveying surface.

The elastomer constituting the base material of the conductive layer is
An elastomer having a urethane bond and a urea bond in the molecule. By adjusting the average ratio of these, it is possible to maintain the flexibility of the belt and to adjust the strength to a low permanent elongation even after long-term use. The ion conductive substance added to such an elastomer is successively uniformly mixed and dissolved in the diamine or polyol raw material of the elastomer, and the conductive carbon black is uniformly dispersed. The raw material obtained by dissolving and dispersing the ion conductive substance and the conductive carbon black in the elastomer raw material, for example, when a centrifugal molding method is formed, to form an aggregated layer of the conductive carbon black on the mold side during centrifugal molding. By forming the lower resistance layer more uniformly, the conductive carbon black of the same amount was adjusted by adjusting the liquid viscosity by adjusting the blend ratio of the ion conductive substance and the conductive carbon black, the number of rotations of the mold during centrifugal formation, and the discharge amount. Also, the resistance of the conductive belt can be controlled.
Therefore, a conductive belt having the same electric resistance can be formed with a lower addition amount of the conductive carbon black. Even if this conductive belt is used for a long period of time under a tension of about 3 to 20 kg, there is very little change in the strength, elongation, elastic modulus and the like of the belt with time. It is considered that the permanent elongation of the segment does not change.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the conductive belt of the present invention will be described in more detail. FIG. 1 shows a mounting example of the conductive belt of the present invention. In FIG. 1, reference numeral 1 denotes a photosensitive drum, 2 denotes a charging electrode, 3 denotes an exposure device, 4 denotes a developing device, 5 denotes a conductive belt, 6 denotes a conveying roller, 7 denotes a transfer roller, and 8 denotes a peeling roller. The belt 5 is supported by rollers (6, 7, 8), and a tension of about 3 to 10 kg is applied.

FIG. 2 shows an example of the configuration of the conductive belt 5. Here, 101 is a conductive layer, 102 is a protective layer, and the conductive belt of the present invention is based on an elastomer having a urethane bond and a urea bond, and a conductive layer obtained by adding an ion conductive substance and conductive carbon black to the base. 101
The protective layer 102 may be provided on one side or both sides of the conductive layer 101 according to the purpose. In addition, the inner surface of the conductive belt 5 and the conveying roller may be processed on various back surfaces and edges, for example, by providing irregularities so that they do not idle or meander.

The conductive layer 101 of the conductive belt 5 has an electric resistance of 10 ⁴ to 10 ¹² ohmcm and a surface resistance of 10 ⁴ to 10 ⁴ ohmcm.
10 ¹⁵ ohm ports, hardness JIS-A hardness is preferably about 70 to 80 degrees. The thickness of the conductive layer 101 is preferably 10 to 3000 μm, more preferably 100 μm.
１０００1000 μm. When the thickness is <10 μm, the conductive belt is easily stretched, and when the thickness is 3000 μm or more, the shape following property is lost when the belt tension is applied, the belt driving torque is increased, and the habit in the pulley portion is easily generated. It is difficult to form a uniform nip with the photosensitive drum due to deformation, dent, elongation, and the like.

The resistance of the protective layer 102 is not particularly limited, and the electric resistance of the conductive belt itself is 10 ⁴ to 10 ¹² o.
hmcm, and preferably has a higher electric resistance than the conductive layer 101. With such a conductive belt, it is possible to maintain the dielectric strength when a high voltage is applied.

The elastomer used as the base material of the conductive layer in the conductive belt of the present invention contains a urethane bond (-NHCOO-) and a urea bond (-NHCONH) in the molecule.
−). Such an elastomer is produced by blending at least a catalyst in addition to a polyol, an isocyanate compound and a polyamine compound. Examples of the polyol include a polyol at a terminal, for example, a polyether polyol having a polyhydroxyl group at a terminal, a polyester polyol, and a polyether polyol which is a copolymer of both. In addition, general polyols such as polyolefin polyols such as polybutadiene polyol and polyisoprene polyol, and polyol prepolymers obtained by polymerizing ethylenically unsaturated monomers in the polyol can be used.

Examples of the polyamine compound include aliphatic amines such as hexamethylenediamine, 2,5-dimethylpiperazine, and triethylenediamine; biphenyldiamine;
Aromatic diamines such as 3,3'-dichlorobenzidine, bis (aminophenyl) ether and p-amino-aniline can be used.

As the polyisocyanate compound, toluene diisocyanate (TDI), crude TDI,
4-diphenylmethane diisocyanate (MDI), crude MDI, isophorone diisocyanate, various modified MD
I, aliphatic isocyanate having 2 to 18 carbon atoms, 4 carbon atoms
To alicyclic polyisocyanates, and mixtures and modified products of these polyisocyanates, such as prepolymers obtained by partially reacting with polyols or diamines.

The catalyst is generally a post-metal compound such as butyl tin laurate, octyl zinc, sodium acetate, etc., alkoxides and phenoxides of alkali metals and alkaline earth metals, tertiary amines such as triethylamine, triethyldiamine, N -Methylmorpholine, dimethylaminomethylphenol, and the like, quaternary ammonium salts, imidazoles, Ni acetyl acetate, diacetyl acetonate Ni, and the like.

Ionic conductivity compounded in elastomer
The substance is not particularly limited.
Monium, stearyltrimethylammonium, octa
Decyltrimethylammonium, dodecyltrimethyla
Ammonium, alcohol-modified fatty acid, dimethyl ammonium
Perchlorate, halogen salt, borofluoric acid
4 such as salt, sulfate, sulfonate and ethosulfate
Cationic surfactants such as quaternary ammonium salts,
Sulfonic acid, higher alcohol sulfate, higher alcohol
Ethylene oxide addition sulfate ester, higher alcohol
Chol phosphate ester, higher alcohol ethylene oxide
Anionic surfactants such as side-added phosphate esters,
Nonionic surfactants such as betaines, higher alcohols
Ethylene oxide, polyethylene glycol fatty acid
Non-ionic, such as steles and polyhydric alcohol fatty acid esters
Antistatic agent such as antistatic agent, LiClO_Four, LiCF_Three
SO _Three, NaClO_Four, LiAsF₆, LiBF_Four, N
a A metal salt such as SCN, KSCN, NaCl, or
Examples include electrolytes such as ammonium salts and phosphates. Conductivity
Carbon black is Ketchen Black, furnace
Racks, known conductive carbons such as acetylene black
And the like.

The average ratio of urethane bonds to urea bonds in the elastomer is preferably from 5:95 to 95: 5, more preferably from 30:70 to 70:30,
The urethane bond can be adjusted by adjusting the blending amount of the polyol and the isocyanate, and the urea bond can be adjusted by adjusting the blending amount of the polyamine compound and the isocyanate. Therefore, the average ratio of urethane bonds to urea bonds in the obtained elastomer can be adjusted by selecting the amounts of the polyol, isocyanate, polyamine compound and the like. In particular, using diisocyanate as a curing agent for the polyol or diamine component, the reactivity ratio is 0.95 to 1.10, preferably 1.03 to 1.10.
It is desirable to adjust to 07 and co-crosslink.

[0018] 0.001 to 5 parts by weight per 100 parts by weight of an elastomer having a urethane bond and a urea bond in the molecule.
Parts by weight of the ionic conductive material, especially 0.01 to 2 parts by weight, so that the electric resistance of the conductive layer is 10 ⁴ to 10 ⁴ parts by weight.
It can be adjusted to 10 ¹² ohmcm, and the conductive carbon black is blended in an amount of 0.01 to 50 with respect to 100 parts by weight of the elastomer having a urethane bond and a urea bond in the molecule.
By weight, preferably 0.1 to 20 parts by weight, the surface resistance of the conductive layer can be lowered to provide a uniform and stable electric resistance.

In the conductive belt conductive layer, an ion conductive substance is added together with the conductive carbon black, but the ion conductive substance may be used alone or in combination. In the present invention, for example, 0.001% by weight of an ionic electrolyte such as an alkylammonium salt and Ketjen black, lithium perchlorate and furnace black, sodium perchlorate and acetylene black, and 0.1% of conductive carbon black are used. Using 1 to 50 parts by weight, polyol,
A combination in the case of mixing and dissolving in a diamine or the like is preferable.

The belt manufacturing method of the present invention is manufactured by a method of forming into a cylindrical shape by a centrifugal molding machine, removing the molded product, and cutting the formed product into a predetermined length. A cohesive layer is formed near the surface, so that it is possible to maintain a more environmentally stable resistance than a product using only an ion conductive substance.The belt of the present invention is processed into a sheet shape, which is subjected to high-frequency heating, an adhesive, It can be joined to a predetermined size by pressing, ultrasonic welding or the like. When the conductive belt is manufactured by the centrifugal molding method, the air surface is a mirror surface (surface roughness: Ra <1 μm). A suitable air surface can be used as a transfer surface, and if the transfer surface is used without polishing, a conductive belt having excellent transferability and suction properties can be obtained. Further, the conductive belt of the present invention has M100% (100% belt elongation modulus).
Is desirably adjusted to ²⁰ to 200 kgf / cm ² .

By subjecting the protective layer to surface treatment or polishing by dip coating, spray coating, electrostatic coating, roll coater or the like, releasability, conductivity, abrasion resistance and surface cleaning properties can be imparted. The material of the protective layer 102 of the present invention is not particularly limited, and fluorine (PTFE or the like) is used for the purpose of reducing frictional resistance, preventing contamination of the photoreceptor, abrasion by reducing the surface roughness, and stabilizing the electrical characteristics of the environment. A paint in which a resin of nylon, silicone, urethane or the like is dispersed and dissolved in water or a solvent can be used.

[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 following examples. <Example 1> 100 parts by weight of polyether polyol obtained by adding propylene oxide and ethylene oxide to glycerin (molecular weight 5000, Exenol 8281 manufactured by Asahi Glass Co.) 18 parts by weight of urethane-modified MDI (Sumidur PF manufactured by Sumitomo Bayer) 2 parts by weight of hexamethylene diamine 1,4 butanediol 1 part by weight Dibutyltin laurate 0.01 part by weight Tetrabutylammonium perchlorate 0.5 part by weight Ketjen black (manufactured by Lion Akzo) 0.2 part by weight These are stirred for 2 minutes to remove in vacuum. Foam was obtained to obtain a reactive mixed solution.

Next, this reactive mixed solution was filled with an inner diameter of 15 cm,
It was put into a centrifugal molding machine having a depth of 40 cm, rotationally molded at 3000 rpm, and baked at 130 ° C. for 30 minutes to obtain an endless belt having a thickness of 0.5 mm. The obtained endless belt was demolded and aged at 110 ° C. for 12 hours to complete the reaction.
The average ratio of urethane bonds to urea bonds in the molecule of the elastomer of the belt is 30:70, and the electric resistance value of the belt is JIS using a Hiresta HRS manufactured by Mitsubishi Chemical Corporation.
25 degrees, 55% measured according to -K6911
5 × 10 ⁸ ohmcm under RH relative humidity conditions (film thickness: 5
50 μm). The surface resistance using Hyresta HA was 6 × 10 ⁷ ohm / port on the mold surface side and 7 × 10 ⁹ ohm / port on the air surface side. The obtained endless belt was cut to 330 mm, set on the transport roller shown in FIG. 1 and 26 cm / s under a tension of 6 kg.
After rotating at an applied voltage of 2 kV for 48 hours at ec and left once, the electric resistance value and the surface resistance value were not changed by the above measurement method.

<Example 2> Soluble nylon (CM8000, manufactured by Toray) was applied on one side of the endless belt obtained in Example 1.
After spray coating with a 0 wt% methanol solution and drying, a protective layer having a thickness of 20 μm was obtained. The electric resistance of the obtained belt was 8 × 10 ⁸ ohmcm. When a belt was stretched over the transport roller in the same manner as in Example 1, and the change with time was measured in the same manner, no change was observed.

Example 3 10 wt% of a soluble fluororesin (Nippon Oil & Fat, Belflon 1000) dissolved in toluene
% Solution of conductive carbon black FW200 (manufactured by Degussa Co., Ltd.), mixed and stirred, and the endless belt obtained in Example 1 was coated on one surface of the endless belt with a bell-type electrostatic coating machine at 35 μm.
When a protective layer was formed by electrostatic coating to a film thickness of, and the electric resistance of the belt was measured, it was 7 × 10 ⁸ ohmcm. When the belt was stretched around the conveying roller and the change with time was measured in the same manner as in Example 1, no change was observed.

<Comparative Example> Example 1 was repeated except that the ionic conductive substance was removed from the reactive mixed solution of Example 1 and 1 part by weight of conductive carbon black (Denka Black manufactured by Denki Kagaku) was added. An endless belt was produced in the same manner as described above. The electric resistance of the obtained belt was 5 × 10 ⁷ ohmc.
m. Further, when rotated for 48 hours in the same manner as in Example 1, the electric resistance increased to 8 × 10 ⁹ ohmcm,
Even when the belt tension load was released, it did not recover to the initial resistance.

[0027]

As described above, the conductive belt of the present invention can prevent permanent elongation of the belt due to the characteristics of the elastomer, and can use the ionic substance and the conductive carbon black as the charge transfer carrier of the conductive layer. By stabilizing the transfer of electric charge in the film thickness direction, the bias of the ion conductive substance can be reduced, and the deterioration of the transfer performance due to the aging of the electric resistance and the environmental fluctuation can be reduced by the hybrid resistance carrier. Eliminates deterioration in workability due to thickening due to the use of a large amount of carbon black. It is possible to provide a conductive belt having little change in electric resistance even when used for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an electrophotographic copying apparatus equipped with a conductive belt of the present invention.

2A is a sectional view showing an embodiment of a conductive belt in the electrophotographic copying apparatus of FIG. 1, and FIG. 2B is another embodiment of the conductive belt in the electrophotographic copying apparatus of FIG. It is sectional drawing which shows a form.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 charging device 3 exposure 4 developing device 5 conductive belt 6 transport roller 7 transfer roller 8 peeling roller 101 conductive layer 102 protective layer

Claims (6)

[Claims] 1. A conductive belt having a function of transferring a toner image on an image carrier to a sheet, or conveying the sheet, or both functions, wherein the conductive belt has a urethane bond and a urea bond in a molecule. Conductive belt having a conductive layer obtained by adding an ion conductive substance and conductive carbon black to a base material comprising an elastomer having the same 2. The elastomer is characterized in that the average ratio of urethane bonds to urea bonds in the molecule is adjusted from 5:95 to 95: 5 by adjusting the mixing ratio of diamine monomer and polyol and crosslinking with diisocyanate. The conductive belt according to claim 1. 3. The conductive belt according to claim 1, wherein the conductive belt is formed by a centrifugal molding method, and an agglomerated layer of conductive carbon black is formed near a mold surface of the conductive layer.
Or the conductive belt according to claim 2. 4. The conductive belt according to claim 1, wherein a protective layer is provided on the conductive layer. 5. The conductive belt according to claim 2, wherein M100% (100% belt elongation modulus) is adjusted to ²⁰ to 200 kgf / cm ² . 6. The conductive belt according to claim 3, wherein an air surface at the time of the centrifugal molding is a conveying surface.