JPH10141355A - Conductive roller - Google Patents

Abstract

(57) [PROBLEMS] To provide a conductive elastic layer of a conductive roller having a low hardness and a small compression set to prevent contamination of a mating material and to prevent the resulting image unevenness when mounted on an image forming apparatus. SOLUTION: A sponge-like conductive elastic layer is formed by concentrically laminating the outer periphery of a rotating shaft, and the sponge-like conductive elastic layer reacts with a polyol component and an isocyanate component in a conductive roller used in contact with a counterpart material. A polyisocyanate formed from the resulting polyurethane and having an average number of functional groups in which the isocyanate component is greater than 2.0 and less than 3.0 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a conductive roller. In particular, the present invention relates to a conductive roller that can be used in an electrophotographic apparatus or the like and provides excellent image quality.

[0002]

2. Description of the Related Art An electrophotographic apparatus such as a copying machine, a facsimile, and a printer has a photoconductor having a photoconductor layer provided on a surface thereof. In operation, an outer peripheral surface of the photoconductor is uniformly charged. Then, an outer peripheral surface is exposed with a laser beam corresponding to an irradiation reflected light or an electric signal to the copy object to form an electrostatic latent image, and a toner is formed by attaching toner to the electrostatic latent image. After that, the image is transferred to paper or the like and fixed.

In the above process, as shown in FIG. 1, a charging roller 1, a toner 2
, And a developing roller 3 for adhering to the photoreceptor 6
A transfer roller 4 for transferring the toner image from the photoreceptor 6 to the sheet 7; a cleaning roller 5 for assisting a cleaning blade for scraping off the toner remaining on the photoreceptor 6 after the transfer
Various conductive rollers are used.

As such a conductive roller, a roller in which a conductive layer made of an elastic material is concentrically laminated on the outer periphery of a rotating shaft made of metal is usually used, and further, a surface property is imparted. For this reason, a conductive layer formed by laminating a surface layer as necessary and having two or more layers is also used.

The conductive elastic layer has a low hardness and is easily deformed and has excellent deformation recovery in order to secure a constant contact width with a mating material (contacted material) such as a photoconductor. It is desired that the material has extremely low contamination.

It is apparent that the cause of the contamination of the counterpart material is caused by the unreacted substance blooming or bleeding microscopically or macroscopically from the conductive elastic layer, so that the unreacted substance does not remain in the conductive elastic layer. That is, it is necessary to complete the reaction for forming the conductive elastic layer.

A conductive roller having a conductive elastic layer usually made of polyurethane (elastomer or foam) is manufactured by using an injection machine (a casting machine, a foaming machine) that automatically measures and mixes a polyol component and an isocyanate component. Is done.
For the metering of materials with such an injector, a gear pump,
If a plunger pump or the like is used and the viscosity of the polyol component and the isocyanate component is too low, material leakage from the seal portion is likely to occur, and there is a problem that accurate measurement cannot be continuously performed. Further, in order to impart conductivity to the roller, a conductivity-imparting agent such as carbon graphite is added to the polyol component. When these conductivity-imparting agents are added, the viscosity of the polyol component reaches several thousand centipoise (cps) or more. When the isocyanate component is mixed with the mixture, the viscosity of the mixed solution is further increased.

In particular, if the viscosity of the isocyanate component is too high, uniform mixing becomes difficult, and even if uniform mixing is possible, the viscosity of the mixed solution becomes too high, causing air to be trapped during injection or poor injection. That is, if the viscosity of the isocyanate component is too low, the mixing ratio will be incorrect due to poor measurement, and if the viscosity of the isocyanate component is too high, poor mixing of the polyol component and the isocyanate component will occur,
In either case, as a result, the reaction is not completed and causes contamination of the contacting material.

[0009]

In view of the above, the present invention has been made in view of the above, the mixing ratio of a polyol component and an isocyanate component is constant, uniform mixing is possible, low hardness and low compression set obtained by reacting these components, Further, it is another object of the present invention to provide a conductive roller made of a polyurethane foam free of photoconductor contamination.

[0010]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a sponge-like conductive roller which is formed by concentrically laminating a sponge-like conductive elastic layer on the outer periphery of a rotating shaft and which is used in contact with a mating member. The elastic layer is made of polyurethane,
In order to achieve low hardness and low compression set, the number of functional groups is specified for an isocyanate component, which is one of the components forming a polyurethane. That is, according to the present invention, the sponge-like conductive elastic layer is formed by concentrically laminating the sponge-like conductive elastic layer on the outer periphery of the rotating shaft, and the sponge-like conductive elastic layer is formed of a polyol component and an isocyanate. And a polyurethane obtained by reacting the isocyanate component.
A conductive roller comprising a polyisocyanate having an average number of functional groups greater than 0 and less than 3.0.

In the present invention, the viscosity of the isocyanate component is preferably in the range of 50 to 2,000 cps at room temperature in order to secure a measurement ratio with the polyol component and to perform uniform mixing. Furthermore, in the present invention, the functional group ratio [NCO] / [OH] of the polyisocyanate and the polyol in the polyol component is preferably 0.9 in order to ensure a reaction ratio that does not leave unreacted substances in the sponge-like conductive elastic layer. １．２1.2. As used herein, "low hardness" refers to Asker C hardness of 20.
° to 50 ° hardness. “Conductivity” refers to a level of electric resistance of 10 ³ to 10 ¹⁰ Ω · cm.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, the polyol component that can be used for forming the polyurethane foam is not particularly limited, and examples thereof include a polyether polyol, a polyester polyol, a polybutanediene polyol, ethylene glycol, and butanediol. These mixtures may be used as the polyol component.

In the present invention, a polyisocyanate having an average number of functional groups of more than 2.0 and less than 3.0 is suitable for the isocyanate component which can be used for forming a polyurethane foam. Examples of such polyisocyanates include 2,4'-diphenylmethane diisocyanate (MDI) or a mixture of 4,4'-diphenylmethane diisocyanate (MDI) and polymethylene polyphenylisocyanate (polymeric MDI), and polymeric MDI and toluene range. Isocyanate (TDI)
And modified MDI (adduct, trimer,
And the like, but are not limited to these specific polyisocyanates. As in the case of the polyol, a mixture of the above-mentioned polyisocyanates may be used.

If the average number of functional groups of the polyisocyanate is 2 or less, the polyurethane foam formed has a low hardness, but the compression set becomes extremely large. On the other hand, when the average number of functional groups is 3 or more, although the compression set is excellent, the hardness becomes too high and the deformability is impaired.
Therefore, the average number of functional groups of the polyisocyanate,
It is essential that it be greater than 2.0 and less than 3.0.

[0015] In order to impart conductivity to the polyurethane foam to be formed, a conductivity-imparting agent is usually added to the polyol component in advance, and the resulting mixture is uniformly dispersed before use. Examples of the conductivity-imparting agent include tin oxide particles in addition to carbon black and graphite. A preferred conductive agent is carbon black. The amount used is the polyol component 100
Parts by weight is 0.2 to 3.0 parts by weight, preferably 0.5 part by weight.

The above-mentioned polyol component, isocyanate component, and, if necessary, a chain extender, a cross-linking agent, a catalyst, a foaming agent, a foam stabilizer, and the like are added and reacted according to a conventional method to form a polyurethane foam. Suitable catalysts to be used are tin catalysts (trimethyltin laurate, dibutyltin dilaurate, etc.) and amine catalysts (polyethylenediamine, diazabicycloamine salt, etc.). Used by adding 5 parts by weight.

The polyurethane foam forming reaction is specifically carried out as follows. That is, an appropriate amount of a conductivity-imparting agent is added to the polyol component, and the mixture is kneaded and dispersed. To this, a foaming agent (water or the like), a catalyst, and in some cases, a foam stabilizer are appropriately added and mixed to prepare a polyol component. Heating and foaming in the mold by injecting a reaction mixture obtained by mixing the polyol component with the isocyanate component at a predetermined mixing ratio into a mold for forming a conductive elastic layer in which a rotating shaft that has been subjected to an adhesive treatment is held in advance. After curing, a sponge-like conductive elastic layer is formed on the outer periphery of the rotating shaft. Instead of using a foaming agent, a foam may be mechanically taken in during molding to form a sponge.

As the rotary shaft, a pipe or rod made of metal and processed to support both ends of the rod as described above is used. From the viewpoint of rust prevention, stainless steel or surface-treated steel is preferably used.

These rotating shafts are degreased and cleaned at the outer periphery,
After the adhesive is applied and dried, it is positioned and installed in the conductive elastic layer forming mold and is preheated. The above reaction mixture is poured into this mold to obtain a molded body having a sponge-like conductive elastic layer formed on the outer periphery of the rotating shaft.

The mixing ratio between the isocyanate component and the polyol component is determined by the functional group ratio [NCO] of the polyisocyanate and the polyol in the isocyanate component and the polyol component.
It is adjusted by setting / [OH] in the range of 0.9 to 1.2. If the functional group ratio is out of this range, unreacted substances remain in the formed polyurethane foam (that is, the sponge-like conductive elastic layer), and when used as a conductive roller, contaminate a partner material (for example, a photoreceptor). . Furthermore, even if the functional group ratio is set within the above range, if the mixing is not performed uniformly during blending, the functional group ratio locally deviates from the above range in the mixture, and unreacted substances remain. Therefore, in order to prevent contamination of the counterpart material, it is important to set the functional group ratio in the above range and uniformly mix both isocyanate and polyol components.

Further, in the present invention, by setting the viscosity of the isocyanate component to a predetermined range, the isocyanate component can be continuously measured by an injector and uniformly mixed with the polyol component. If the viscosity of the isocyanate component is less than 50 cps, a leak from the seal portion of the metering pump occurs during the metering, and it becomes difficult to maintain the metering accuracy for a long time. Further, if the viscosity of the polyol component is on the order of several thousand cps, even if mixed and stirred with the isocyanate component, the difference in viscosity is large, and uniform mixing cannot be expected. In particular, if the viscosity of the isocyanate component exceeds 2,000 cps, not only does the compatibility with the polyol component deteriorate, but also the viscosity of the reaction mixture increases, and the viscosity becomes too high when injected into a mold. Problem occurs, and it becomes impossible to stably produce a polyurethane foam. Therefore, in order to measure the isocyanate component, blend with the polyol component, and further stably produce the polyurethane foam, the viscosity of the isocyanate component is set to 50 to 50.
It is preferable to be in the range of 2000 cps.

(Examples) The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

Example 1 Polyether polyol (SBU polyol 0248, manufactured by Sumitomo Bayer Urethane Co., hydroxyl value 28 mg KOH / g) was used as the polyol. To 100 g of this polyol, 2 g of Ketjen Black EC (manufactured by Lion Akzo) as conductive carbon was added and kneaded and dispersed with a three-roll mill. As a reaction modifier (catalyst) to 102 g of this polyol,
Triethylenediamine in dipropylene glycol 33
% Of TEDA-L33 (manufactured by Tosoh Corporation)
g, toycat-ET in which bisdimethylaminoethyl ether is dissolved 70% in dipropylene glycol
(Tosoh Corporation) (0.3 g) and water (0.3 g) as a blowing agent were added and mixed to obtain a polyol component. OH mol of this mixed polyol component is 0.0968 mol / 100 g.
And the viscosity was 5000 cps (25 ° C.). Polymeric MDI Sumidur 44v-20 (Sumitomo Bayer Urethane Co., Ltd., NCO
31.5%). The above mixed polyol component and isocyanate component are supplied to a two-liquid mixing type low pressure foaming machine having a gear pump (manufactured by Takachiho Machinery Co., Ltd.), and after dehydration under reduced pressure, the functional group ratio [NCO] / [O
H] = 1.05 with respect to 100 g of polyol,
3 g of the isocyanate was weighed and mixed, poured into a cylindrical mold having a mirror-finished inner surface, crosslinked at 45 ° C. for 20 minutes, and then released to obtain the conductive roller of the present invention. The cylindrical mold was preheated to 45 ° C. while holding both ends of a stainless steel (SUS303) rotary shaft having an outer periphery coated with an adhesive in advance and fixed.

Example 2 A polyisocyanate (44 V) was added to 100 g of a polyol so that the functional group ratio [NCO] / [OH] = 0.9.
-20) was obtained in the same manner as in Example 1 except that 11.6 g of the conductive roller of the present invention was obtained.

Example 3 A polyisocyanate (44 v) was added to 100 g of a polyol so that the functional group ratio [NCO] / [OH] = 1.2.
-20) was obtained in the same manner as in Example 1 except that 15.5 g of the conductive roller of the present invention was obtained.

Example 4 Instead of the polyisocyanate of Example 1, 10 g of tolylene diisocyanate TDI-80 having 2.0 functional groups (Coronate T-80, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100 g of the above 44v-20 as an isocyanate component.
The added blended isocyanate was used. This blended isocyanate has an average number of functional groups of 2.36 and a viscosity of 1
50 cps (25 ° C.), NCO was 33%. A conductive roller of the present invention was obtained in the same manner as in Example 1, except that 12.9 g of the blended isocyanate was blended with 100 g of the polyol so that the functional group ratio [NCO] / [OH] = 1.05. .

Example 5 Instead of the polyisocyanate of Example 1, as an isocyanate component, Cosmonate M-50 (manufactured by Mitsui Toatsu Chemicals, NCO 31.5%) having a functional group number of 2.1 and a viscosity of 100 cps was used. Using. A conductive roller of the present invention was obtained in the same manner as in Example 1, except that 13.6 g of this was mixed with 100 g of polyol so that the functional group ratio [NCO] / [OH] = 1.05.

Example 6 Instead of the polyisocyanate of Example 1, an isocyanate component was used as an isocyanate component, having 2.8 functional groups and a viscosity of 700 cps (25 cps).
° C) polymeric MDI-based Sumidule 44v-7
0 (manufactured by Sumitomo Bayer Urethane Co., NCO 30.8%) was used. A conductive roller of the present invention was obtained in the same manner as in Example 1, except that 13.9 g of this was mixed with 100 g of polyol so that the functional group ratio [NCO] / [OH] = 1.05.

Comparative Example 1 Instead of the polyisocyanate of Example 1, an isocyanate component was used as an isocyanate component having a number of functional groups of 3.0 and a viscosity of 2500 cps (2
5 ° C) polymeric MDI death module 44v
-200 (manufactured by Sumitomo Bayer Urethane, NCO 30.8
%). A conductive roller was obtained in the same manner as in Example 1, except that 13.9 g of this was mixed with 100 g of polyol so that the functional group ratio [NCO] / [OH] = 1.05.

Comparative Example 2 Instead of the polyisocyanate of Example 1, the isocyanate component was 2.0 as a functional group and had a viscosity of 12 cps (25 cps).
° C), a mixture of 2.4 'MDI / 4.4' MDI (NCO 33.5% by BASF)
Was used. A conductive roller was obtained in the same manner as in Example 1 except that 12.7 g of this was mixed with 100 g of polyol so that the functional group ratio [NCO] / [OH] = 1.05.

Roller Characteristics For each roller obtained from the above Examples and Comparative Examples, the roller was incorporated into a charging device of an electrophotographic apparatus, and was brought into contact with the photoreceptor at a temperature and humidity of 40 ° C. and 85% for 5 days. After the image was stored as it was, an image was displayed. Furthermore, the state of liquid leakage from the pump one month after the continuous operation of the injection device was confirmed. Table 1 shows the results and other physical properties of the roller.

[0032]

[Table 1]

As is clear from the results shown in Table 1, the conductive roller of the present invention did not cause photoconductor contamination, had excellent moldability of the roller, and formed a good image. On the other hand, the conductive roller of the comparative example caused contamination of the photoreceptor, and had a problem in the moldability of the roller, and furthermore, the formed image was blurred.

The [NCO] / [OH] ratio of the conductive rollers of Comparative Examples 1 and 2 was confirmed by 1R analysis for the unevenness in the partial hardness (fogging portion) and the adhesive portion.
In the case of, the soft part is [NCO] / [OH] at 0.8
And the hard part was 1.3. [NCO] / [OH] of the conductive roller of Comparative Example 2
Decreased to 0.75. Further, when the photosensitive member contact portion with the roller of Comparative Example 2 was observed, a dent due to permanent distortion was confirmed in the contact portion.

[0035]

As described above, according to the present invention, a polyurethane obtained by using a polyisocyanate having an average number of functional groups greater than 2.0 and less than 3.0 as an isocyanate component and reacting with a polyol component. Since the sponge-like conductive elastic layer is formed from, a conductive roller having low hardness and small compression set can be obtained.

Further, according to the present invention, since the viscosity of the isocyanate component is adjusted to a predetermined range and used, the compatibility between the isocyanate component and the polyol component is improved, and the isocyanate component is continuously measured and measured with an injector. Since it can be blended with a polyol component, and the reaction mixture of both has an appropriate viscosity, injection into a mold becomes easy, and a sponge-like conductive elastic layer can be stably manufactured for a long period of time.

In addition, according to the present invention, since the functional group ratio [NCO] / [OH] of the polyisocyanate in the isocyanate component and the polyol in the polyol component is adjusted to a predetermined range, the reaction is carried out. Does not remain in the polyurethane. Therefore, when such a polyurethane is used as the sponge-like conductive elastic layer, unreacted materials do not ooze out of the roller, contamination of the photoreceptor as a mating material does not occur, and image unevenness is prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an example of an electrophotographic apparatus to which a conductive roller according to the present invention is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging roller 2 Toner 3 Developing roller 4 Transfer roller 5 Cleaning roller 6 Photoconductor 7 Paper

Claims (3)

[Claims] 1. A conductive roller which is formed by concentrically laminating a sponge-like conductive elastic layer on the outer periphery of a rotating shaft and which is used in contact with a counterpart material, wherein the sponge-like conductive elastic layer comprises a polyol component and an isocyanate component. A conductive roller comprising a polyurethane obtained by a reaction, and a polyisocyanate having an average number of functional groups in which the isocyanate component is greater than 2.0 and less than 3.0. 2. The method according to claim 1, wherein the viscosity of the isocyanate component is 50 to 2000 cps at room temperature.
The conductive roller as described in the above. 3. The functional group ratio [NCO] / [O] of the polyisocyanate and the polyol in the polyol component.
H] is 0.9 to 1.2.
The conductive roller as described in the above.