JPH10260568A - Electrifying member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent residual toner particles from being fixed to an electrifying member, to uniformly electrify the surface of a photoreceptor and to prevent the quality of an output image from degrading. SOLUTION: An elastic layer 102 essentially consisting of epichlorohydrin rubber is formed on a conductive base body 101, and a surface layer 103 containing isocyanurate essentially consisting of hexamethylene diisocyanate is formed on the elastic layer 102. The polymer acts as a nonadhesive coating film giving a good effect on the surface layer 103 of the electrifying member 100. Namely, the polymer gives an excellent preventing effect against fixing of a toner to the surface of the electrifying member 100 and gives stable electrification characteristics. Therefore, good image quality can be maintained for a long time. The epichlorohydrin rubber is preferably a terpolymer of epichlorophydrin, ethylene oxide and allylglycidylether.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member in an electrophotographic system, and more particularly, to a charging member which is brought into contact with an image carrier and a direct current voltage is applied between the member and the image carrier. The present invention relates to a charging member for charging a body.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a corona discharger has been widely used as a charging method for uniformly charging the entire surface of an image carrier (hereinafter, referred to as a photosensitive member). Was. However, corona dischargers generate harmful substances such as ozone. For this reason, harmful substances are collected by a filter or the like. However, if used for a long time, the collection efficiency of the filter decreases. In addition, it is necessary to replace the filter periodically.

In order to avoid such a problem, a charging method (contact charging method) that does not use a corona discharger has been proposed. For example, JP-A-58-1391
In the method described in Japanese Patent Application Laid-Open No. 56-178267 and Japanese Patent Application Laid-Open No. 57-178267, charging is performed by bringing a brush-shaped charger into contact with the surface of the photoreceptor. Also, Japanese Patent Application Laid-Open No. Sho 56-10435
In the system described in Japanese Patent Application Publication No. 1 (1999), a charging belt is employed, and charging is performed by bringing the charging belt into contact with a photosensitive member. Further, in the method described in Japanese Patent Application Laid-Open No. 58-40566, a fibrous electrode is used in order to further suppress ozone generation.

In this type of contact charging system, the applied voltage can be reduced as compared with the corona charging system (1 to 2).
KV), the generation of ozone can be suppressed.

[0005]

However, according to the above-mentioned prior art, when the toner is continuously charged in a copying machine or the like, the toner particles pass through the cleaning unit and remain on the photoreceptor, and remain on the photoreceptor. This adheres to the surface of the charging roller to cause a filming phenomenon. When the residual toner particles adhere to the surface of the charging roller, the surface of the charging roller is electrically insulated, so that the charging of the surface of the photoreceptor becomes uneven, and the quality of an output image is significantly reduced. was there.

In particular, in the case of regular development, white streak-like image unevenness occurs in an output image, and in the case of reversal development generally used in laser printers and the like, black streak-like image unevenness occurs in an output image. Was.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and prevents the residual toner particles from sticking to the charging member, uniformly charges the surface of the photoreceptor, and prevents the quality of the output image from deteriorating. The purpose is to:

[0008]

In order to achieve the above object, in the charging member according to the first aspect, the charging member is brought into contact with an image carrier and a DC voltage is applied between the image carrier and the image carrier. Thus, in the charging member for charging the image carrier,
An elastic layer mainly composed of epichlorohydrin rubber is provided on a conductive support, and a surface layer containing an isocyanurate containing hexamethylene diisocyanate as a main component is provided on the elastic layer.

The charging member according to a second aspect of the present invention is the charging member according to the first aspect, wherein the epichlorohydrin rubber comprises epichlorohydrin, ethylene oxide,
It is a ternary copolymer of allyl glycidyl ether.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The charging member of the present invention will be described below with respect to [Example of shape and configuration of charging member of the present invention], [Configuration example of electrophotographic apparatus], [First Embodiment], [Embodiment 1] Embodiment 2] and [Comparative Examples 1 to 3] will be described in detail with reference to the drawings. The present invention is not limited by the embodiment.

[Example of shape and configuration of charging member of the present invention] The charging member of the present invention comprises a medium-resistance elastic layer mainly composed of epichlorohydrin rubber on the outer periphery of a conductive support, and a layer above the elastic layer. In addition, a film containing an isocyanurate body containing hexamethylene diisocyanate (hereinafter referred to as HDI) as a main component is formed as a surface layer.

FIG. 1 is a sectional view of the charging member of the present invention. The charging member 100 is in the form of a roller, and has a conductive support 101 in the form of a metal core, and a medium-resistance elastic layer 102 provided on the outer periphery of the conductive support 101.
And a surface layer 103 formed on the outer peripheral surface of the elastic layer 102.
And a two-layer structure composed of

In FIG. 1, a primer layer or the like for improving the adhesion between the layers may be provided. For example,
The surface of the conductive support 101 may be treated with a conductive primer such as synthetic rubber mixed with a conductive substance such as carbon black.

Further, as the conductive support 101, iron,
Metals such as stainless steel and aluminum, and conductive resins such as carbon black dispersed resin and metal particle dispersed resin can be used.

The elastic layer 102 has an electric resistance of 10 ⁷ to
Good results can be obtained with a range of 10 ⁹ Ω · cm.
As a material for the medium resistance elastic layer 102, polar rubbers such as epichlorohydrin rubber, urethane rubber, chloroprene rubber, and acrylic rubber can be used as a raw material rubber. Epichlorohydrin rubber is preferred because of its low environmental dependency.

The raw rubber for epichlorohydrin includes homopolymers of epichlorohydrin, copolymers of epichlorohydrin and ethylene oxide, copolymers of epichlorohydrin and allyl glycidyl ether, and ternary copolymers of epichlorohydrin, ethylene oxide and allyl glycidyl ether. Although there is a polymer (hereinafter referred to as GECO), GECO is preferred because it has a relatively low electric resistance, has little environmental dependence of electric resistance, and has a very small increase in electric resistance due to energization.

The surface layer 103 is made of a polymer composed of an isocyanurate containing HDI (hexamethylene diisocyanate) as a main component. The present inventor has found that this polymer can act as a non-adhesive film that works well on the surface layer 103 of the charging member 100. That is, the toner is excellently prevented from sticking to the surface of the charging member 100, and stable charging characteristics are obtained, so that good image quality can be maintained over a long period of time.

The polymer of the surface layer 103 is a trimer of an aliphatic diisocyanate, as shown by the chemical formula 1, which has flexibility and excellent non-adhesion to toner.
Moreover, it has excellent durability and environmental resistance.

[0019]

Embedded image

This polymer has an electric resistance of 10 ⁹ Ω · cm.
And a medium resistance region. Therefore, the applied DC voltage can be made to work efficiently without adding a resistance adjusting material such as conductive particles, and the unevenness of the electric resistance in the surface layer 103 can be suppressed to a very small level. Therefore, charging unevenness can be minimized.

Also, for example, by using a surface layer 103 having a curing agent of polyvinyl butyral resin and HDI isocyanurate having a very good non-adhesiveness to toner, non-adhesiveness and durability to toner can be improved. It can be further improved. However, since the electrical resistance of polyvinyl butyral resin is relatively high at 10 ¹² to 10 ¹³ Ω · cm, the NCO of HDI and isocyanurate
It is desirable that the / OH molar ratio be modified at a ratio of 2: 1 to 10: 1.

[Configuration Example of Electrophotographic Apparatus] FIG. 2 is a configuration diagram showing an electrophotographic apparatus 200 using the charging member 100 of the present invention. Conductive support 101 of charging member 100
Has a DC voltage power supply 20 for applying a bias voltage.
2 are connected to form a charging device. The charging member 100 is arranged in contact with a drum-shaped electrophotographic photosensitive member 203 which is an organic photosensitive member (OPC).

On the peripheral surface of the electrophotographic photosensitive member 203, a charging member 100, an image exposure device (not shown),
A developing unit 204, a transfer charging device 205, a cleaning device 206, and a pre-exposure device (not shown) are arranged. In the drawing, reference numeral 207 denotes exposure light emitted from the image exposure device, 208 denotes pre-exposure light of the pre-exposure device, and 209 denotes a member to be transferred such as paper.

First, the conductive support 1 of the charging member 100
01, a voltage (for example, −14) by the DC voltage power supply 202.
00V), the surface of the electrophotographic photosensitive member 203 is charged, and then the image on the original is image-exposed on the electrophotographic photosensitive member 203 by an image exposure device to form an electrostatic latent image.

Next, the electrostatic latent image on the electrophotographic photosensitive member 203 is developed by attaching the developer in the developing unit 204 to the electrophotographic photosensitive member 203. Subsequently, the developer on the electrophotographic photosensitive member 203 is transferred to a transfer member 209 such as paper by the transfer charging device 205. The cleaning device 206 does not transfer the image onto the paper at the time of the transfer.
The developer remaining in 03 is collected. If residual charge remains on the electrophotographic photosensitive member 203, the charging member 1
It is better to remove the residual charges by a pre-exposure device before performing the primary charging by 00.

[Embodiment 1] In Embodiment 1, the charging member 100 is manufactured by the following method. Conductive support 1
A stainless steel core of φ8 mm was used as 01, and the elastic layer 102 having a medium resistance was formed by the following composition and processing method.

GECO-based epichlorohydrin raw rubber (trade name: Epichroma CG102, manufactured by Daiso) 100 parts by weight Calcium carbonate (trade name: Tamapearl TR-222H, manufactured by Okutama Kogyo) 30 parts by weight Sub (trade name: Neofactis U-8, Temma) 10 parts by weight Stearic acid (trade name: fatty acid SA-200, manufactured by Asahi Denka) 0.5 part by weight Vulcanization accelerator (trade name: Noxera TT, manufactured by Ouchi Shinko Chemical) 1.0 part by weight 1.5 parts by weight of vulcanization accelerator (trade name: Noxera DM, manufactured by Ouchi Shinko Chemical) 1.0 part by weight of vulcanization accelerator (trade name: Barnock R, manufactured by Ouchi Shinko Chemical) Sulfax, Tsurumi Chemical) 0.25 parts by weight

The composition ratio of Epichroma CG102 is as follows:
Epichlorohydrin 40 mol%, ethylene oxide 5
6 mol% and allyl glycidyl ether 4 mol%.

After kneading the above compound to form a compound having a uniform composition, a primary vulcanization (steam can, 4.5 × 10 ² ) was placed on a φ8 mm stainless steel core (conductive support 101).
kpa, 150 ° C. × 1 hour) and secondary vulcanization (155 ° C. × 7 hours) to form a roller-shaped medium-resistance elastic layer 102 having an outer diameter of 14 mm × 310 mm.
The electric resistance of this medium resistance elastic roller is 2 × 10 ⁷ Ω · c
m, roller rubber hardness was 38 degrees (JisA).

The electric resistance of the medium-resistance elastic roller was measured by measuring the medium-resistance elastic roller at 20.degree. H. After being left in the environment for 16 hours, a copper foil tape (trade name: Scotch No. 1181, manufactured by 3M) having a width of 25.4 mm was wound around the circumference of the medium resistance elastic roller to form an electrode. A DC voltage of 500 V was applied between the metal core and the electrode, and a current value one minute after the application was measured to determine a volume resistance value. The rubber hardness of the medium resistance elastic roller was measured by JisK.
Using a hardness meter JisA described in No. 6301, measurement was performed by applying pressure perpendicular to the center axis direction of the medium resistance elastic roller.

Next, the surface layer 1 is placed on the medium resistance elastic roller.
03 was formed as follows. First, the paint for the surface layer was prepared as follows. HDI isocyanurate (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry)
10 parts by weight were diluted with 45 parts by weight of toluene and 45 parts by weight of xylene to obtain a coating liquid. The nonvolatile content of Coronate HX is 100 wt% and the NCO content is 21.3 wt%.

This surface layer paint was applied on the medium resistance elastic roller by dip coating, and then cured at 110 ° C. for 1 hour to form a surface layer 103 having a thickness of 7 μm. This surface layer 103
Had an electric resistance of 8 × 10 ⁹ Ω · cm.

The electric resistance of the surface layer 103 was measured on an aluminum plate (thickness 0.2 mm) with a paint for the surface layer having a thickness of about 100 μm.
m, a sample coated at 20 ° C., 60% R.M. 1 in H environment
After standing for 6 hours, a resistance measuring cell (trade name: 16008)
A, manufactured by YHP) and a resistance meter (trade name: R8340A, manufactured by Advantest) at an applied voltage of 100 V.

The charging member 10 manufactured as described above
No. 0 (charging roller) was attached in place of the primary corona charger of a regular development type copying machine (trade name: Ricoh FT3350, manufactured by Ricoh Co., Ltd.), and was brought into contact with the surface of a photoreceptor (OPC) drum to be driven to rotate. A DC voltage of -1400 V is applied as a primary charging voltage, 24 ± 1 ° C., 50 to 55
% R. Run continuously in H environment, start, 1000
0, 20,000, 30,000, 40000 (A
The potential measurement of the charging potential (dark potential) of the photosensitive drum for each of the three sizes), the contamination state of the charging roller surface, and the image quality were evaluated.

Table 1 shows the results of the evaluation. The state of contamination of the surface of the charging roller with toner and the like was evaluated according to the following criteria. : Slight toner and the like adhered, but the adhered matter on the roller surface can be easily wiped off with a cloth or the like. : A slight amount of toner or the like remains on the roller surface after wiping. : Complete wiping was not possible, and a thin film of toner remained on the roller surface. : The toner and the like are strongly adhered to the roller surface.

[0036]

[Table 1]

[Second Embodiment] In the second embodiment, the elastic layer 102 is formed on the conductive support 101 in the same manner as in the first embodiment.
The surface layer 103 was formed on the roller provided with as follows.

The coating material for the surface layer 103 was prepared as follows. 8.5 parts by weight of a polyvinyl butyral resin (trade name: Denka butyral ^# 3000-K, manufactured by Denki Kagaku Kogyo) is dissolved in 120 parts by weight of toluene and 120 parts by weight of xylene, and then the coronate HX (14.5 parts by weight) is dissolved. In addition, it was a paint.

The composition of Denka Butyral ^# 3000-K is such that polyvinyl butyral is 78 wt% or more, polyvinyl alcohol is 9 to 13 wt%, and polyvinyl acetate is 2.0 wt%.
８8.4 wt%.

Next, using this paint, a surface layer 1 having a thickness of 8 μm was formed on the medium resistance elastic roller in the same manner as in the first embodiment.
03 was formed. The electric resistance of the surface layer 103 is 3 × 1
It was 0 ¹⁰ Ω · cm.

Table 1 shows the evaluation results of the charging roller manufactured as described above in the same manner as in the first embodiment.

[Comparative Example 1] As Comparative Example 1, a medium-resistance elastic roller in which the surface layer 103 of Embodiment 1 was not applied was manufactured. Table 1 shows the results of evaluation of this medium resistance elastic roller in the same manner as in Embodiment 1.

[Comparative Example 2] As Comparative Example 2, a medium-resistance elastic roller was used. Among the material combinations of the medium-resistance elastic layer 102 of the first embodiment, the product name: Epichroma CG102 was changed to the product name: Epichroma H (Daiso H). )
It was manufactured in the same manner as in the first embodiment.

The electric resistance of this medium resistance elastic roller is 8 × 1
It was 0 ¹⁰ Ω · cm.

Next, the surface layer 1 is placed on the medium resistance elastic roller.
03 was formed in the same manner as in the first embodiment. This surface layer 10
The thickness of No. 3 was 7 μm.

Table 1 shows the evaluation results of the charging roller manufactured as described above in the same manner as in the first embodiment.

[Comparative Example 3] As Comparative Example 3, a medium-resistance elastic roller was made of the material mixture of the medium-resistance elastic layer 102 of the first embodiment, and the product name: Epichroma CG102 was replaced by the product name: Epichroma C (Daiso C). )
It was manufactured in the same manner as in the first embodiment. The composition ratio of this epichroma C is 49 mol% of epichlorohydrin and 51 mol% of ethylene oxide.

The electric resistance of the medium resistance elastic roller was 1 × 10 ⁹ Ω · cm.

Next, the surface layer 1 is placed on the medium resistance elastic roller.
03 was formed in the same manner as in the first embodiment. The thickness of the surface layer was 8 μm.

Table 1 shows the evaluation results of the charging roller manufactured as described above in the same manner as in the first embodiment.

Consideration is made from Table 1 above. First, there is a marked difference between the first embodiment and the comparative example 1 in the state of contamination on the surface of the charging roller depending on whether or not the surface layer 3 is provided. When the surface layer 103 is provided, in the range from the start to 40,000 sheets, the level is such that "a slight amount of toner or the like adheres to the surface of the charging roller, but the attached matter on the roller surface can be easily wiped off with a cloth or the like." (Reference). However, when the surface layer 103 was not provided, in the same range, the level (reference) was lower than the reference, and "the toner or the like was strongly fixed to the roller surface".

Next, the charging potential is compared between the first embodiment and the first comparative example. In Comparative Example 1, the charging potential decreased as the number of sheets increased, and the charging became completely insufficient from 20,000 sheets. On the other hand, in Embodiment 1, the charging potential was stable even when the number of sheets was increased. This indicates that if the surface of the charging roller is extremely contaminated (Comparative Example 1), the charging becomes insufficient.

Next, regarding the presence / absence of an abnormal image, it does not occur in the first embodiment.
From the time of 000 sheets, the image density became low, and streaky unevenness increased.

From this, it can be seen that the surface layer 103 containing the isocyanurate of HDI works effectively to prevent contamination of the surface of the charging roller and generation of abnormal images.

(2) Next, when the first and second embodiments are compared with the comparative examples 2 and 3, first, in the first and second embodiments, the elastic layer 10
2 as epichroma CG102 (epichlorohydrin
Ethylene oxide / allyl glycidyl ether terpolymer).

On the other hand, the elastic layer 102 of Comparative Example 2
Uses epichroma H (epichlorohydrin homopolymer), and the elastic layer 102 of Comparative Example 3 is made of epichroma C.
(Epichlorohydrin / ethylene oxide copolymer)
Is used.

According to the comparison results, the contamination state of the charging roller surface is good in any case. Further, with respect to the charging potential, the comparative examples 2 and 3 have some variation.

However, looking at the presence or absence of an abnormal image,
In the first and second embodiments, no abnormal image is generated, whereas in the comparative examples 2 and 3, the image density is reduced from the beginning. From this, it is clear that it is desirable that the epichlorohydrin rubber is a terpolymer of epichlorohydrin / ethylene oxide / allyl glycidyl ether as in the embodiment.

[0059]

As described above, according to the charging member of the present invention (claim 1), the image is formed by bringing the charging member into contact with the image carrier and applying a DC voltage to the image carrier. In a charging member for charging a carrier, an elastic layer mainly composed of epichlorohydrin rubber is provided on a conductive support, and a surface layer containing an isocyanurate mainly composed of hexamethylene diisocyanate on the elastic layer. Is provided, the non-adhesiveness to the toner on the surface of the charging member increases, and the toner hardly remains on the surface of the charging member. As a result, the photosensitive member surface can be uniformly charged,
Deterioration of the quality of the output image is prevented. In other words, it is possible to prevent the residual toner particles from sticking to the charging member, uniformly charge the surface of the photoconductor, and prevent the quality of the output image from deteriorating.

Further, the charging member of the present invention (Claim 2)
Is epichlorohydrin rubber, epichlorohydrin,
Since it is a ternary copolymer of ethylene oxide and allyl glycidyl ether, the charging characteristics of the elastic layer can be improved, and good image quality can be maintained over a long period of time.

[Brief description of the drawings]

FIG. 1 is a sectional configuration view of a charging member of the present invention.

FIG. 2 is a configuration diagram illustrating an electrophotographic apparatus using the charging member of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 charging member 101 conductive support 102 elastic layer 103 surface layer

Claims (2)

[Claims] 1. A charging member for charging an image carrier by applying a DC voltage between the image carrier and an image bearing member, the charging member mainly comprising epichlorohydrin rubber. A charging member, comprising: an elastic layer provided on a conductive support; and a surface layer containing an isocyanurate containing hexamethylene diisocyanate as a main component is provided on the elastic layer. 2. The charging member according to claim 1, wherein the epichlorohydrin rubber is a ternary copolymer of epichlorohydrin, ethylene oxide, and allyl glycidyl ether.