JPH1115259A - Developing roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roll constituted so that leakage is prevented from occurring from a low resistance layer and excellent image quality is obtained both at the initial time of copying and after the endurance thereof. SOLUTION: The developing roll is obtained by forming a base rubber layer (A) 2 is formed on the outside circumferential surf ace of a core bar 1, forming an intermediate layer 3 on the outside circumference thereof and forming an outermost layer (B) 4 on the outside circumference thereof besides. Then, both left and right end parts 3a of the layer 3 are extended on both left and right end surfaces 2a of the layer (A) 2. The electric resistance of the roll consisting of the core bar 1, the layer (A) 2 and the layer 3 is adjusted to be >=1×10<7> Ωand the electric resistance of the roll consisting of the core bar 1, the layer (A) 2, the layer 3 and the layer 4 is adjusted within the range of 1×10<7> to 1×10<10> Ω. (A) is the base rubber layer whose volume resistivity is adjusted within the range of 1×10<4> to 1×10<10> Ω.cm. (B) is the outermost layer whose volume resistivity is adjusted within the range of 1×10<4> to 1×10<7> Ω.cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing roll used in an electrophotographic apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art Generally, copying by an electrophotographic copying machine is performed as follows. That is, a document image is formed as an electrostatic latent image on a photosensitive drum rotating about an axis, and toner is adhered to the image to form a toner image. Next, copying is performed by transferring the toner image to copy paper.
In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, and a document image is projected on the charged portion through an optical system and irradiated with light. 2. Description of the Related Art An electrostatic latent image is formed by canceling the charge of a part. As a method of charging the surface of the photosensitive drum prior to the formation of the electrostatic latent image, recently, a roll charging method of charging the surface of the photosensitive drum by directly contacting a charging roll with the surface of the photosensitive drum has been adopted. . Further, as a method for forming a toner image on the electrostatic latent image formed on the surface of the photosensitive drum in this manner, a method using a developing roll (contact developing method) is employed. That is, toner adheres to the surface of the frictionally charged developing roll, and the toner is transferred from the developing roll to the electrostatic latent image on the surface of the photosensitive drum, thereby forming a toner image on the surface of the photosensitive drum. Copying is performed by fixing the toner image on copy paper.

As a roll such as a charging roll and a developing roll in the electrophotographic copying machine, for example, as shown in FIG. 5, a base rubber layer (medium resistance layer) 52 is formed along the outer peripheral surface of a cored bar 51, A first coat layer (low resistance layer) 53 is formed on the outer periphery, and a second coat layer (medium resistance layer) 54 and a third coat layer (medium resistance layer) 55 are further formed on the outer periphery.
Is used. However, in such a roll, since the low resistance layer 53 having a lower resistance than the other medium resistance layers 52, 54, and 55 exists in the plurality of resistance layers 52 to 55, the first low resistance layer, which is the low resistance layer, is provided. A current easily flows in the lateral direction (longitudinal direction) from the coat layer 53, and as a result,
There is a problem that a leak occurs.

Therefore, in order to prevent the occurrence of leakage from the first coat layer 53, which is the low resistance layer, as shown in FIG. 6, the left and right ends of a third coat layer (medium resistance layer) 65, which is the outermost layer, are formed. The portion 65a is extended and wrapped around the end surface of the resistance layer to cover the end surface of the first coat layer 53, and between the core metal 51 and the surface of the resistance layer that contacts the member to be charged. A roll has been proposed in which the relationship between the resistance Rs and the resistance Rp between the left and right end faces of the resistance layer is set so as to satisfy the relationship of Rp ≧ Rs (Japanese Patent Application Laid-Open No. 9-26686).

[0005]

However, when the roll having the structure shown in FIG. 6 is used as a developing roll, the third coat layer (medium resistance layer) 65, which is the outermost layer, has a large resistance. The surface of the roll is charged up with the increase of the image quality, and problems such as inferior image quality after copying durability occur. As described above, a developing roll that can prevent the occurrence of leakage from the low-resistance layer and obtain good image quality both at the beginning of copying and after copying has not been obtained yet. Therefore, development of a developing roll having such characteristics is desired.

The present invention has been made in view of such circumstances, and can prevent the occurrence of a leak from a low-resistance layer, and obtain a good image quality both at the initial stage of copying and after copying. It is an object of the present invention to provide a developing roll capable of performing the above-described operations.

[0007]

In order to achieve the above object, a developing roll of the present invention comprises a core, a base rubber layer (A) formed on the outer peripheral surface of the core, A developing roll comprising at least one intermediate layer formed on the outer periphery of the base rubber layer (A) and the following outermost layer (B) formed on the outer periphery of the intermediate layer, wherein at least one of the intermediate layers The left and right ends extend on the left and right end surfaces of the base rubber layer (A), and the roll composed of the core metal, the base rubber layer (A), and the intermediate layer has an electric resistance of 1 ×.
It is adjusted to 10 ⁷ Ω or more, and the electric resistance of the roll composed of the core metal, the base rubber layer (A), the intermediate layer and the outermost layer (B) is adjusted to a range of 1 × 10 ⁷ to 1 × 10 ¹⁰ Ω. Take the configuration that. (A) A base rubber layer having a volume resistivity adjusted to a range of 1 × 10 ⁴ to 1 × 10 ¹⁰ Ω · cm. (B) The outermost layer having a volume resistivity adjusted to a range of 1 × 10 ⁴ to 1 × 10 ⁷ Ω · cm.

In other words, the present inventors obtain a developing roll which can prevent the occurrence of leakage from the low resistance layer and can obtain good image quality both at the beginning of copying and after copying. I did my utmost research. As a result, the volume resistivity of the base rubber layer (A) and the outermost layer (B) are adjusted and set to specific ranges, respectively, and the electric resistance of the roll before and after the formation of the outermost layer (B) is set to a specific value. It has been found that the desired object can be achieved if the intermediate layer is set so as to be adjusted so that at least one of the left and right end portions of the intermediate layer extends on the left and right end surfaces of the base rubber layer (A). The invention has been reached.

[0009]

Next, embodiments of the present invention will be described in detail.

As shown in FIG. 1, the developing roll of the present invention comprises a cored bar 1, a base rubber layer (medium resistance layer) 2 formed along the outer peripheral surface of the cored bar 1, and the base rubber layer. An intermediate layer (medium resistance layer) 3 formed on the outer periphery of the intermediate layer 2 and an outermost layer (low resistance layer) 4 formed on the outer periphery of the intermediate layer 3.

The core 1 is not particularly limited, and any conventionally known core may be used. For example, a metal core made of a solid metal body, a metal cylindrical body whose inside is hollowed out, and the like are used. Examples of the material include aluminum, stainless steel, and iron plated. The core metal 1 also serves as a power supply electrode.

As shown in FIG. 1, the base rubber layer 2 formed along the outer peripheral surface of the cored bar 1 has beveled left and right ends, and the left and right end faces 2a are chamfered.
The left and right ends 3a of the intermediate layer 3 extend upward. With such a configuration, it is possible to prevent leakage from the outermost layer 4 which is a low resistance layer.

The material for forming the base rubber layer 2 is not particularly limited, and any conventionally known material may be used. For example, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SB
R), silicone rubber, polyurethane elastomers and the like. A conductive agent may be appropriately added to the above materials. Examples of the conductive agent include carbon black, graphite, potassium titanate, iron oxide, c-TiO ₂ , c-ZnO, and c-SnO which have been conventionally used.
₂ , ionic conductive agents (quaternary ammonium salts, borates, surfactants, etc.). Note that the above "c-"
It means that it has conductivity.

The material for forming the intermediate layer 3 formed on the outer peripheral surface of the base rubber layer 2 is not particularly limited, and any conventionally known material may be used. For example, EPDM, SBR, nitrile rubber, hydrogenated nitrile rubber (H-NBR), polyurethane-based elastomer, polyester, polyamide, N-methoxymethylated nylon and the like can be mentioned. The above-mentioned conductive agent may be appropriately added to the above-mentioned material.

The material for forming the outermost layer 4 formed on the outer peripheral surface of the intermediate layer 3 is not particularly limited, and any conventionally known material may be used. For example, urethane resin, silicone resin, acrylic urethane resin, acrylic silicone resin, silicone rubber, fluoro rubber,
Fluororesin, epichlorohydrin rubber (ECO), N-
Examples include methoxymethylated nylon, acrylic resin, polyester resin and the like. These may be used alone or in combination of two or more. The above-mentioned material may further contain the above-mentioned conductive agent as appropriate.

The developing roll of the present invention is manufactured, for example, as follows. That is, first, the components for the base rubber layer 2 forming material are mixed using a kneader or a stirrer such as a kneader to prepare the base rubber layer 2 forming material. Further, respective coating liquids as the material for forming the intermediate layer 3 and the material for forming the outermost layer 4 are prepared. Each of the above coating liquids is
The components are mixed by using a dispersing machine such as a ball mill or a three-roll mill, and an organic solvent is added to the mixture, followed by mixing and stirring.

Examples of the organic solvent include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide,
Examples include ethyl acetate, methyl isobutyl ketone, ethanol, xylene, tetrahydrofuran and the like. These may be used alone or in combination of two or more.

Next, a metal core is prepared, and as shown in FIG. 2, the base rubber layer 2 forming material is placed in a lower lid 21 and a cylindrical mold 22 on which the metal core 1 is set. Then, the upper lid 23 is externally fitted to the cylindrical mold 22. Then
The entire roll mold is heated to vulcanize the compound-like base rubber layer 2 forming material (150 to 220 ° C. × 30).
), And a base rubber layer 2 is formed. Next, the core metal 1 on which the base rubber layer 2 is formed is removed from the mold, and secondary vulcanization is performed as necessary to complete the reaction (80 to 200 ° C. × 4 hours). The left and right ends of the base rubber layer 2 are shown in FIG.
As shown in FIG. 5, the left and right end surfaces 2a are formed by beveling obliquely by a known method. Then, a coating liquid as a material for forming the intermediate layer 3 is applied to the outer periphery of the base rubber layer 2, or the roll on which the base rubber layer 2 has been formed is dipped in the coating liquid and pulled up, followed by drying and heat treatment. As a result, the intermediate layer 3 is formed on the outer periphery of the base rubber layer 2. Further, a coating liquid as a material for forming the outermost layer 4 is applied to the outer periphery of the intermediate layer 3, or a roll on which the intermediate layer 3 has been formed is dipped in the coating liquid and pulled up, followed by drying and heat treatment. Thereby, the outermost layer 4 is formed on the outer periphery of the intermediate layer 3. The method of applying the coating liquid is not particularly limited, and includes a conventionally known dipping method, spray coating method, roll coating method, and the like. Thus, the core metal 1
A base rubber layer 2 is formed along an outer peripheral surface of the base rubber, an intermediate layer 3 is formed on the outer circumference, an outermost layer 4 is further formed on the outer circumference, and left and right ends 3a of the intermediate layer 3 are formed on the base rubber. A developing roll extending on the left and right end surfaces 2a of the layer 2 can be manufactured.

The chamfering of the left and right ends of the base rubber layer 2 is not limited to the case after the vulcanization treatment as described above, but a molding die having the left and right ends chamfered from the beginning is prepared. By casting the material for forming the base rubber layer 2 in a molding die, a configuration similar to the above can be obtained.

In the developing roll of the present invention thus obtained, the volume resistivity of the base rubber layer 2 is 1 × 1.
0 ⁴ it is necessary to adjusted to a range of ~1 × ¹⁰ 10 Ω · cm, preferably ^{1 × 10 5 ~1 × 10 8} Ω
・ It is in the range of cm. That is, if the volume resistivity of the base rubber layer 2 is out of the range of 1 × 10 ⁴ to 1 × 10 ¹⁰ Ω · cm, the image quality at the beginning of copying and after copying is inferior. The volume resistivity of the intermediate layer 3 is 1 × 1
0 ⁶ to 1 × 10 is preferably adjusted to a range of ^{10 Ω} · cm, particularly preferably ^{1 × 10 6 ~1 × 10 8} Ω · cm
Range. The electric resistance of the roll (before the outermost layer 4 is formed) composed of the metal core 1, the base rubber layer 2, and the intermediate layer 3 needs to be adjusted to 1 × 10 ⁷ Ω or more, and is preferably The range is from 1 × 10 ⁷ to 1 × 10 ¹¹ Ω. That is, if the electric resistance of the roll (before the outermost layer 4 is formed) is less than 1 × 10 ⁷ Ω, the resistance is too low and a leak occurs.

The volume resistivity of the outermost layer 4 is 1 ×
10^Four~ 1 × 10⁷It is necessary to adjust the
It is important. That is, the volume resistivity of the outermost layer 4 is 1 ×
10 ^FourIf it is less than Ω · cm, a leak will occur and
Poor quality, 1 × 10⁷If it exceeds Ωcm, roll surface
Charge up during copying endurance, and image quality after copying endurance
Because it is inferior. Then, the core metal 1 and the base rubber layer 2
Of a roll (developing roll) composed of the intermediate layer 3 and the outermost layer 4
Electric resistance is 1 × 10⁷~ 1 × 10^TenAdjust to Ω range
And preferably 1 × 10⁷~ 1 × 10
⁹Ω range. That is, the electric resistance of the developing roll
Anti 1 × 10⁷~ 1 × 10^TenIf it is outside the range of Ω,
This is because the image quality in the initial stage of the copying and after the copying operation is inferior.

The above electric resistance and volume resistivity are as follows:
DC voltage 1 according to the method described in JIS K 6911
It is a value measured at 0V.

In the developing roll, the base rubber layer 2
Is preferably set in the range of 2 to 10 mm, and particularly preferably in the range of 3 to 6 mm. The thickness of the intermediate layer 3 is preferably set in the range of 1 to 150 μm, particularly preferably in the range of 5 to 30 μm. The thickness of the outermost layer 4 is preferably set in the range of 3 to 100 μm, particularly preferably 5 to 30 μm.
It is in the range of μm.

FIG. 3 shows another example of the developing roll of the present invention.
Shown in In the developing roll shown in FIG. 3, the same portions as those in the developing roll of FIG. 1 are denoted by the same reference numerals. This developing roll comprises a low resistance layer 5 between the base rubber layer 2 and the intermediate layer 3.
The feature is that it is provided. The volume resistivity of the low-resistance layer 5 is 1 ×, like the volume resistivity of the outermost layer 4.
It is necessary to adjust so as to be in the range of 10 ⁴ to 1 × 10 ⁷ Ω · cm. As the material for forming the low resistance layer 5, the same material as the material for forming the outermost layer 4 can be used. The thickness of the low resistance layer 5 is 3 to 100 μm.
m, particularly preferably 5
３０30 μm.

FIG. 4 shows still another example of the developing roll of the present invention. This developing roll is characterized in that the left and right ends of a base rubber layer (medium resistance layer) 12 formed along the outer peripheral surface of the cored bar 1 are not beveled. The developing roll has an intermediate layer (medium resistance layer) 13 formed on the outer peripheral surface of the base rubber layer 12 and an outermost layer (low resistance layer) 14 formed on the outer periphery thereof. On the left and right end surfaces of the base rubber layer 12, left and right end portions 13a of the intermediate layer 13 extend. With such a configuration, it is possible to prevent leakage from the outermost layer 14 which is a low resistance layer. The material, volume resistivity and thickness of the base rubber layer 12 and the intermediate layer 13 are the same as those of the base rubber layer 2 and the intermediate layer 3 in FIG. Also, the material, volume resistivity and thickness of the outermost layer 14 formed on the outer periphery of the intermediate layer 13 are shown in FIG.
Is the same as the outermost layer 4.

In the developing roll of the present invention, the intermediate layer formed on the outer periphery of the base rubber layer is not necessarily limited to one layer, but an appropriate number of layers may be formed. In this case, in order to prevent the occurrence of leakage from the outermost low resistance layer, at least the left and right ends of at least one of the plurality of intermediate layers do not extend on the left and right end faces of the base rubber layer. No.

Next, examples will be described together with comparative examples.

[0028]

Examples 1-4, Comparative Examples 1-6

First, a SUS303 core metal (diameter 8 mm)
Was prepared. In addition, the components shown in Tables 1 and 2 described below were blended in the proportions shown in the same table to prepare materials for forming each layer. In Table 1 below, the acrylic silicone resin * 4 as the outermost layer forming material is represented by the following structural formula (1)
Was used.

[0030]

Embedded image

Next, the compound as the base rubber layer forming material was poured into a cylindrical mold having the core metal set with the adhesive applied to the periphery (see FIG. 2), and heated and vulcanized (1).
(50-220 ° C. × 30 minutes), and then demolded and further subjected to a secondary vulcanization treatment (80-200 ° C. × 4 hours) to form a base rubber layer along the outer peripheral surface of the cored bar. Then, both left and right end faces of the base rubber layer were chamfered obliquely. Next, the intermediate layer A and the outermost layer were formed on the outer peripheral surface of the base rubber layer by a roll coating method using the intermediate layer forming material and the outermost layer forming material, thereby producing a target developing roll. The left and right ends of the intermediate layer A in each developing roll extend on the left and right ends of the base rubber layer. The developing rolls of Example 3, Example 4, and Comparative Example 6 had a configuration in which another intermediate layer B was formed along the outer peripheral surface of the intermediate layer A.

[0032]

[Table 1]

[0033]

[Table 2]

The thickness and volume resistivity of each layer of the developing roll thus obtained are shown in Tables 3 and 4 below. Further, each developing roll was incorporated in an electrophotographic copying machine of a system in which a potential difference was provided between development and a metal blade using a contact developing method, and copying was actually performed. Then, image evaluation was performed according to the following criteria. The results are shown in Tables 3 and 4 below. Comparative Example 2
The endurance copy test was not performed on the developing rolls of Nos. 6 to 6 due to poor initial image quality.

[Leak] The presence or absence of a leak at the beginning of copying and after copying 3,000 sheets was observed. That is, the value of the current flowing through the roll 71 was measured by a method as shown in FIG. 7, and a case where the maximum current value at the time of applying a voltage exceeded 1 mA even at one location was determined to be leakage. Then, those in which no leak occurred were indicated by ○, and those in which leak occurred were indicated by x. In the drawing, reference numeral 72 denotes a metal core, 73 denotes a metal roll, 74 denotes an ammeter, and the load is 700 g on one end.
It is.

[Image Quality] The image quality of the copied image at the beginning of copying and after copying 3,000 sheets was visually evaluated. That is, a character was copied, and the copied image had no problem, and a fine line was clearly copied. Respectively. In addition, the blur refers to an image in which a thin line is interrupted, and the fog refers to an image in which toner has flown to a place where there is no image.

[0037]

[Table 3]

[0038]

[Table 4]

From the results shown in Tables 3 and 4, the developing roll of the product of the present invention has a specific range in which the volume resistivity of the base rubber layer, the outermost layer, and the electric resistance of the roll before and after the outermost layer are formed are all specified ranges. Therefore, leakage is prevented both at the beginning of copying and after copying, and
It can be seen that the image quality is good both at the beginning of copying and after copying.

On the other hand, since the volume resistivity of the outermost layer of the developing roll of Comparative Example 1 exceeds a specific range, the roll surface is charged up during copying durability, and the image quality after copying durability is poor. I understand. In the developing roll of Comparative Example 2, since the electric resistance of the roll before forming the outermost layer was lower than a specific range, and the volume resistivity of the outermost layer exceeded a specific range, a leak occurred, and the image quality at the beginning of copying was improved. Is inferior. In the developing rolls of Comparative Example 3 and Comparative Example 5, since the volume resistivity of the base rubber layer and the electric resistance of the rolls before and after the outermost layer were all below specific ranges, a leak occurred, and the image quality at the beginning of copying was deteriorated. Is inferior. In the developing roll of Comparative Example 4, the volume resistivity of the outermost layer and the electric resistance of the roll after the outermost layer were formed exceeded the specific ranges, so that the image quality at the beginning of copying was inferior. Since the volume resistivity of the base rubber layer exceeds the specific range, the image quality of the developing roller of Comparative Example 6 is inferior both at the beginning of copying and after the endurance of copying. Comparative Examples 2, 3,
The leakage of the five developing rolls occurred at the initial stage of copying, so that none of the developing rolls could be evaluated for image output after copying 3,000 sheets.

[0041]

As described above, the developing roll of the present invention
The base rubber layer, the volume resistivity of the outermost layer, and the electric resistance of the roll before and after the outermost layer are formed are each adjusted to a specific range, and the left and right ends of at least one layer of the intermediate layer are left and right of the base rubber layer. Since it extends on both end surfaces, it is possible to prevent the occurrence of leakage from the outermost layer, which is a low resistance layer, and to obtain good image quality both at the beginning of copying and after copying.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure of an example of a developing roll of the present invention.

FIG. 2 is a cross-sectional view schematically showing one example of a method for producing a developing roll of the present invention.

FIG. 3 is a cross-sectional view schematically showing the structure of another example of the developing roll of the present invention.

FIG. 4 is a cross-sectional view schematically showing the structure of another example of the developing roll of the present invention.

FIG. 5 is a cross-sectional view schematically showing a structure of a conventional developing roll.

FIG. 6 is a cross-sectional view schematically showing a structure of a conventional developing roll.

FIG. 7 is an explanatory diagram for observing the presence or absence of a leak.

[Explanation of symbols]

 Reference Signs List 1 core metal 2 base rubber layer 2a left and right end surfaces of base rubber layer 3 middle layer 3a left and right end portions of middle layer 4 outermost layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenichi Ohoe 3600 Gezu, Kokugaiyama, Komaki City, Aichi Prefecture Inside Tokai Rubber Industries Co., Ltd.

Claims (2)

[Claims] 1. A core metal, a base rubber layer (A) formed on an outer peripheral surface of the core metal, and the base rubber layer (A)
A developing roll comprising at least one intermediate layer formed on the outer periphery of the intermediate layer and the following outermost layer (B) formed on the outer periphery of the intermediate layer. The electric resistance of a roll extending on both left and right end surfaces of the base rubber layer (A) and comprising the core metal, the base rubber layer (A) and the intermediate layer is adjusted to 1 × 10 ⁷ Ω or more, The electric resistance of the roll composed of the core metal, the base rubber layer (A), the intermediate layer and the outermost layer (B) is 1 × 10 ⁷ -1.
A developing roll adjusted to a range of × 10 ¹⁰ Ω. (A) A base rubber layer having a volume resistivity adjusted to a range of 1 × 10 ⁴ to 1 × 10 ¹⁰ Ω · cm. (B) The outermost layer having a volume resistivity adjusted to a range of 1 × 10 ⁴ to 1 × 10 ⁷ Ω · cm. 2. The intermediate layer having a volume resistivity of 1 × 10 ⁶ to 1 ×.
¹⁰ 10 Ω · cm developing roll according to claim 1, wherein is adjusted to a range of.