JP2001005260A - Electroconductive elastic member surface layer for electrophotography, and electrophotographic roller and belt using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface layer of a conductive elastic member for electrophotography, which has good toner separation, a small friction coefficient, and is hardly peeled off from a substrate, and an electrophotographic roller and a belt using the same. SOLUTION: A surface layer 37 provided on the outer surface of a base material 36 made of a conductive elastic member, which is made of a synthetic resin containing polyurethane as a main component and having a fluorine group, and the concentration of the fluorine group is high on the outermost layer surface. A surface layer 37 gradually reduced in the direction of the base material 36, and a cylindrical base material 37 made of a conductive elastic layer are formed concentrically on the outer periphery of the rotating shaft 35, and are formed on the outer periphery of the base material 37. An electrophotographic belt in which a substrate made of a conductive elastic member is formed in a film shape on an electrophotographic roller and a belt-shaped core provided with the surface layer 37, and the surface layer is provided on an outer surface of the film-shaped substrate. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive elastic member surface layer which is disposed around a photosensitive member of an electrophotographic apparatus and is used in contact with the photosensitive member, and a charging roller and a developing roller using the conductive elastic member surface layer. And a belt such as an intermediate transfer belt.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, a developing roller, a transfer roller, a charging roller, an intermediate transfer member, etc. around a photoreceptor are
Since the photoconductor is in contact with the photoconductor, a surface layer is provided on a surface of the substrate made of a conductive elastic member which is in contact with the photoconductor so as not to damage the photoconductor. Conventionally used conductive elastic member surface layers include ethylene propylene rubber (EPDM), epichlorohydrin, acrylonitrile butadiene rubber (NB)
R), silicone rubber, polyurethane rubber and the like. Materials with excellent abrasion resistance have been demanded due to the speeding up of electrophotographic devices, recycling from recent environmental issues, and prolonged life. Polyurethane rubber has been selected as a material that meets this requirement from among the various rubbers. I have.

In recent years, the demand for electrophotographic devices has become higher, and there have been cases where the characteristics of urethane materials do not match the required characteristics. In particular, when used for the above-mentioned rollers and belts, sufficient performance may not be exhibited due to the characteristics of the organic photoconductor and toner of the contacting partner. For example, a developing member that holds and conveys toner to develop an electrostatic latent image, and a color intermediate transfer member that transfers and holds toner on a photoreceptor to the surface and superimposes the toner several times, etc. If the affinity is high, uneven transfer of toner and contamination of the member surface occur, causing serious defects in screen quality. Further, when the friction coefficient between each of the rollers and the belt and a mating material such as a photoconductor in contact with the roller or the belt is large, the life of the rollers, the belt and the mating material is shortened, and the sliding resistance therebetween is increased. Increase the load on the entire device. In order to solve such problems caused by the urethane material itself, the properties of the urethane material are changed by blending other components into the urethane material, or by imparting a functional group to carbon serving as the skeleton of the urethane material. It has been proposed to do so.

[0004]

If another component, for example, a component that lowers the affinity for the toner, is blended into the urethane material, the adhesion to the base material generally deteriorates, and the friction between the urethane material and the mating material is reduced. Therefore, there is a problem in durability such as the surface layer peeling off from the substrate.

In addition, when a functional group having a releasing action is introduced into carbon serving as a skeleton of the urethane material, the physical properties of the urethane material itself are reduced, the desired elasticity cannot be obtained, and the friction coefficient increases. .

[0006] In addition, a method of irradiating the surface of the urethane member with ultraviolet rays, an electron beam or the like to modify the surface is also conceivable, but it is difficult to modify the surface to have the required properties, and special applications are required. Other than that have not been put to practical use.

An object of the present invention is to provide an electrophotographic elastic member surface layer which has good toner separation, excellent abrasion resistance and durability and does not peel off from a substrate, and an electrophotographic roller and belt using the same. That is.

[0008]

According to the present invention, there is provided an electrophotographic member having a surface layer on the outer surface of a substrate made of a conductive elastic member, wherein the surface layer mainly comprises polyurethane,
A conductive elastic member surface layer for electrophotography, comprising a synthetic resin having a fluorine group, wherein the concentration of the fluorine group is high on the outermost layer surface and decreases stepwise in the direction of the base material.

According to the present invention, a fluorine group is added to a synthetic resin containing polyurethane as a main component. Fluorine groups are hydrophobic and are incompatible with polyols and polyisocyanates (all of which have polarity) constituting polyurethane. Accordingly, even when no special operation is performed at the time of curing, the toner is transferred to the surface, and the surface concentration of the release component becomes higher than the internal concentration.

In order to transfer the release component to the surface more effectively, the reaction curing temperature of the polyol and the polyisocyanate is set to 100 ° C. or higher, preferably 130 ° C. or higher.
When the reaction curing temperature is lower than 100 ° C., particularly at a low temperature of about 50 ° C., since the release component does not sufficiently transfer to the surface, a large amount of an expensive release component must be added to obtain the same release property of the toner. Must. Also, the surface layer may be peeled off from the substrate.

Further, the present invention is characterized in that the fluorine group is carried on a polymer mainly composed of carbon, and forms a copolymer with polyurethane.

According to the present invention, a fluorine group is introduced into a polymer mainly composed of carbon, and the obtained polymer is mixed with a base urethane resin stock solution and then heat-cured to form a copolymer. . The polymer is usually obtained by pendant an oligomer having a side chain of a polymer having a carbon skeleton and carrying fluorine on the side chain. Since the polymer compound having such a form has an affinity for the urethane resin, it is almost uniformly dispersed when mixed with the polyurethane resin stock solution. However, when allowed to stand, the fluorine groups gradually migrate to the surface thereof, particularly when heated, based on the hydrophobicity of the fluorine groups. Thereafter, when the urethane resin cures, entanglement occurs between the fluorine-containing polymer and the urethane resin molecules, and the urethane resin is fixed to the surface of the urethane resin at a high concentration.

Further, the present invention is characterized in that the fluorine group is a copolymer which is supported on a polymer mainly composed of carbon and contains an isocyanate group.

In the present invention, the isocyanate group is preferably
It is a multifunctional blocked isocyanate.

According to the present invention, an isocyanate group reactive with the urethane resin can be introduced into the fluoropolymer, and co-crosslinking with the urethane resin is performed, whereby the holding effect is further enhanced. In particular, by using the blocked isocyanate, the fluorine group is stably maintained during the molding of the isocyanate group, and the holding to the molecular chain becomes more effective.

The present invention is also characterized in that the polymer carrying a fluorine group has an average molecular weight of 500 to 50,000.

According to the present invention, the polymer carrying a fluorine group has an average molecular weight of 500 to 50,000. If the average molecular weight is less than 500, when the urethane resin is cured, sufficient entanglement between the polymer and the urethane resin cannot be obtained, so that toner separation is poor and abrasion resistance is poor. On the other hand, when the average molecular weight exceeds 50,000, the surface transferability of fluorine groups is impaired.

According to the present invention, there is provided a roller for electrophotography, wherein a cylindrical base made of a conductive elastic member is formed concentrically on the outer periphery of a rotating shaft, and the surface layer is provided on the outer periphery of the base. It is.

According to the present invention, an elastic member stock solution containing a conductive material is poured into a mold in which a metal rotating shaft (core bar) is inserted, and the mold is heated to react and harden the elastic member stock solution. After curing, the mold is removed to obtain a roller base material. On a roller substrate, a solution of urethane resin raw material dissolved in a solvent,
An undiluted solution in which a fluorine-containing polymer is dissolved is applied, the solvent is removed with dry air, and the mixture is cured by heating to form a surface layer on the roller base material. Thereby, an electrophotographic roller having a surface layer in which the temperature of the fluorine-containing polymer is fixed particularly high near the surface is obtained.

Further, the present invention provides a method in which a substrate made of a conductive elastic material is formed in a film shape on a belt-shaped core, and the outer surface of the film-shaped substrate is
An electrophotographic belt provided with the surface layer.

According to the present invention, a stock solution of an elastic member to which a conductive material is added is applied to a belt-shaped core body, and the stock solution of the elastic member is reacted and cured by heating to obtain a base material for a belt. An undiluted solution in which a fluorine-containing polymer is dissolved is applied to a solution of a urethane resin raw material in a solvent on a belt base material, the solvent is removed with dry air, and the base material for the belt is cured by heating. A surface layer is formed on the material. As a result, an electrophotographic belt having a surface layer in which the temperature of the fluorine-containing polymer is fixed at a high temperature, particularly near the surface, is obtained.

The material constituting the belt-shaped core may be a canvas made of natural yarn or synthetic yarn or metal fiber, and the elastic member constituting the roller base or the belt base may be urethane, NBR, CR ( A known elastomer member such as chloroprene rubber) may be used.

[0023]

FIG. 1 is a cross-sectional view of one embodiment of the vicinity of a photoconductor of an electrophotographic apparatus for color copying. Photoconductor 1
Is uniformly charged by the charging roller 2. The charged photoreceptor 1 is exposed by light reflected from a copy object (not shown). In the case of a color copy, the reflected light is separated into blue, green, and red by a color filter, and is separately exposed. For example, light transmitted through a blue color filter forms an electrostatic latent image on the photoreceptor 1 by yellow light, which is a complementary color of blue. The photoconductor 1 rotates in the arrow 3 direction,
, The yellow toner is supplied from the first developing roller 4Y, and the yellow component of the copy object is developed. The second to fourth developing rollers 4M, 4C, 4B are not in contact with the photoconductor 1, and the photoconductor 1 is in contact with the transfer belt 6 by the first transfer roller 5. Transfer belt 6 is 2
By moving the pulleys 7 and 8 in the direction of arrow 9, the yellow image on the photoconductor 1 is transferred onto the transfer belt 6. The photoreceptor 1 is removed from the remaining yellow toner by a cleaning blade, and is discharged.

When the exposure through the yellow color filter is completed, the color filter is changed to green, and an electrostatic latent image is formed on the photosensitive member 1 by magenta light, which is a complementary color of green. At this time, the first, third, and fourth developing rollers 4
Y, 4C, and 4B do not contact the photoconductor 1, only the second developing roller 4M contacts the photoconductor 1, and a magenta image is developed on the photoconductor 1. When the transfer of the yellow image is completed, the transfer belt 6 separates the first transfer roller 5 from the photoreceptor 1 and is rotated by the pulleys 7 and 8 in the direction opposite to the arrow 9 direction, and returns to the original position. When the magenta image on the photoconductor 1 comes to a position where it contacts the transfer belt 6, the magenta image on the photoconductor 1 is transferred to the transfer belt 6 by the first transfer roller 5.
As a result, the yellow image and the magenta image are superimposed on the transfer belt 6.

Similarly, a cyan image having passed through a red color filter is developed on the photoreceptor 1 and is superposed on the transfer belt 6. Finally, a black image is developed on the photoreceptor 1 and superimposed on the transfer belt 6 by white reflected light without using a color filter. As a result, the same color image as the object to be copied is formed on the transfer belt 6. The color image on the transfer belt 6 is transferred onto the paper 12 supplied between the second transfer roller 11 and the pulley 8. Paper 1
2 is fixed on the paper 12 by a fixing device (not shown). After the transfer belt 6 transfers the color image to the recording paper, the remaining toner is removed by the cleaning blade 13.

FIG. 2 is a sectional view of another embodiment in the vicinity of the photoreceptor of the electrophotographic apparatus for color copying. Photoconductors 1 and 4
The developing rollers 4Y, 4M, 4C, and 4B (collectively indicated by reference numeral 4), the cleaning blade 10, and the charging roller 2 are the same as those in the previous embodiment. In this embodiment, a transfer drum 21 is used instead of the transfer belt 6. The four images separately formed on the photoconductor 1 are
Above, as in the case of the transfer belt 6 described above, a color image is formed. This color image is transferred
The image is transferred and fixed on the paper 12 supplied between the transfer roller 1 and the transfer roller 22.

FIG. 3 is a sectional view showing the vicinity of the photosensitive member of the monochrome electrophotographic apparatus. For monochrome, the developing roller 4 is
It only supplies black toner, and the photoreceptor 1
Since there is no need to superpose the above images, there is no intermediate transfer member such as a transfer belt or a transfer drum. The monochrome image formed on the photoconductor 1 is directly transferred to the paper 12 supplied between the photoconductor 1 and the transfer roller 24. Note that FIG. 3 also illustrates the toner supply device 29 omitted in FIGS. 1 and 2. The toner is stored in a toner box 30, stirred by a stirrer 31, and supplied to a developing roller 4 via a supply roller 32. Excess toner on the developing roller 4 is regulated by the toner regulating blade 33, and the toner having a constant thickness always exists on the developing roller 4 in contact with the photoconductor 1.

The surface layer of the present invention is used as the surface layer of the charging roller 2, the developing roller 4, the intermediate transfer member (the transfer belt 6 and the transfer drum 21), and the transfer rollers 5, 11, 22, and 24 shown in FIGS. Used. FIG. 4 is a longitudinal sectional view and a transverse sectional view of these rollers. The roller has a configuration in which a cylindrical base material 36 made of a conductive elastic member is formed concentrically on the outer periphery of a metal rotating shaft 35, and a surface layer 37 of the present invention is provided on the base material 36. As a result, it rotates in contact with a partner member such as the photoconductor 1. FIG. 5 is a sectional view of the transfer belt 6. A belt-like base material 39 made of a conductive elastic member is formed in a film shape on a belt-like core body 38, and a surface layer 40 of the present invention is provided on a surface of the film-like base material 39 in contact with the photoreceptor 1 or the like. is there.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

Examples 1 to 4 and Comparative Examples 1 to 5 A polymer having a fluorine group shown in Table 1 was mixed and dissolved in a urethane resin solution obtained by dissolving a raw material of a thermoplastic urethane resin in a mixed solvent of MEK25: DMF10. A stock solution was prepared. This undiluted solution was applied on a PET film so as to obtain a coating having a thickness of 30 μm, and dried at 150 ° C. for 15 minutes to obtain a fluorine-containing urethane resin coating, and its physical properties were examined.
Table 1 shows the results.

[0031]

[Table 1]

Fluorine group-containing polymer: molecular weight: 8,000 Fluorine group-containing polymer: molecular weight: 4,000 Fluorine group-containing polymer: molecular weight 350 The surface condition was determined to be good if there was no problem in film-forming properties and no defects were observed. Roughness is determined according to JIS B 0601-1982

The maximum static friction coefficient was measured using a Haydon 14 type testing machine shown in FIG. 6 and a value measured with a 100 kg weight (vertical load) and a SUS304 contact element of 10 × 10 (mm). Is a measured value under the same conditions and a sliding speed of 100 mm / min.

The contact angle of water after immersion in IPA and n-hexane was as follows: after leaving in IPA (2-propanol) and n-hexane for 96 hours at room temperature, wiping IPA and N-hexane, and then contacting water after drying. Is the corner.

The test after abrasion is each test after rubbing with the tester.

From the results shown in Table 1, the surface layer of the present invention has a large water contact angle of 110 ° or more and a low friction coefficient of 0.9 or less, and its physical properties are as follows after IPA or n-hexane immersion. It can be seen that there is almost no change even after abrasion, and it satisfies the requirements as the surface layer of the electrophotographic roller or belt. On the other hand, Comparative Examples 1, 3, and 5, which do not contain a fluorine group, and Comparative Examples 2, 4, which contain a fluorine group and have a low molecular weight of a polymer, have low measured values and are sufficiently required. not filled.

Examples 5 and 6 and Comparative Examples 6, 7, and 8 The stock solutions obtained in Examples 3 and 4 and Comparative Examples 3, 4, and 5 were coated on the surface of a urethane roller base material by a dipping method, and were placed in a hot air oven. At 80 ° C. for 15 minutes and at 150 ° C. for 10 minutes to form a surface layer having a thickness of 30 μm on the surface of the roller substrate, thereby obtaining a developing roller. This developing roller is a non-magnetic 1
The image was evaluated after being incorporated in a developing machine using a component contact toner and passing the initial and continuous 10,000 sheets (3,000 sheets and 6,500 sheets in Comparative Examples). Table 2 shows the results.

[0038]

[Table 2]

(Note) Background fog is measured with a white reflection densitometer. Image density is measured with a Macbeth reflection densitometer. From Table 2, it can be seen that the developing roller having the surface layer of the present invention has a capacity of 10,000 sheets at the initial stage. Good images were obtained even after paper.
On the other hand, in the developing roller having a surface layer made of polyurethane containing no fluorine group (Comparative Example 6), unevenness due to non-uniformity of toner transfer was observed even at the initial stage of paper feeding, and 3,000 sheets of paper were not printed. After the paper, image formation became difficult. Further, after 3,000 sheets were passed, toner adhesion was remarkable on the surface of the developing roller. The developing roller (Comparative Example 7) having a surface layer made of a polyurethane copolymer containing a fluorine group but having a polymer molecular weight as small as 350 (Comparative Example 7) provided a good image at the initial stage of paper passing. As the number of sheets increased, background fogging occurred over the entire surface, and in some places, the image density also decreased. After passing 6,500 sheets, image formation became difficult. After 6,500 sheets were passed, toner adhesion was remarkable on the surface of the developing roller. A developing roller (Comparative Example 8) having a surface layer composed of a commercially available fluorine-based coating agent JISLON EC-06 Black (trade name, manufactured by Teikoku Chemicals Co., Ltd.) did not form an image in some places at the beginning of paper feeding, or had a wrinkled pattern Was formed on the paper, and a good image could not be obtained. Therefore, the continuous paper passing test was not performed. In addition, wrinkles and peeling from the roller base material were observed on the surface layer of the developing roller when the number of sheets passed was 1.000 or less, and the surface layer was partially broken.

[0040]

As described above, according to the present invention, a high concentration of fluorine groups is present on the outermost surface of the surface layer of a roller or belt used in contact with a photoreceptor of an electrophotographic apparatus. A surface layer with good separation, a small coefficient of friction with a photoreceptor or the like, and excellent durability can be obtained. Further, the portion contacting with the base material has few fluorine groups, and the base material and the surface layer do not peel off.

Such a surface layer is provided on a substrate made of a conductive elastic member, and is suitably used for a developing roller, a transfer roller, a charging roller, a roller such as a transfer drum, and a belt such as a transfer belt.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment in the vicinity of a photoconductor of an electrophotographic apparatus for color copying.

FIG. 2 is a cross-sectional view of another embodiment in the vicinity of a photoconductor of an electrophotographic apparatus for color copying.

FIG. 3 is a cross-sectional view of the vicinity of a photoconductor of a monochrome electrophotographic apparatus.

FIG. 4 is a cross-sectional view of an electrophotographic roller according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view of the electrophotographic belt according to one embodiment of the present invention.

FIG. 6 is a schematic diagram of a Haydon 14 tester.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 charging roller 4 developing roller 5 first transfer roller 6 transfer belt 11 second transfer roller 12 paper 21 transfer drum 22, 24 transfer roller 35 rotating body 36 roller base material 37 roller surface layer 38 belt-shaped core 39 Belt base material 40 Belt surface layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 G03G 15/16 // C09D 175/04 C09D 175/04 F term (Reference) 2H003 BB11 CC05 2H032 AA05 BA08 BA09 BA23 2H077 AC04 AD02 AD06 AD13 FA13 FA21 GA03 GA13 4J002 BD12X CK02W GM01 GQ00 4J038 CD092 DG001 DG302 GA11 GA12 NA09 NA11 NA12 NA20 PB08 PC07

Claims (7)

[Claims] 1. An electrophotographic member comprising a substrate made of a conductive elastic member and a surface layer provided on an outer surface thereof, wherein the surface layer is made of a synthetic resin containing polyurethane as a main component and having a fluorine group. The concentration is high on the outermost layer,
A conductive elastic member surface layer for electrophotography, wherein the surface layer gradually decreases in the direction of the substrate. 2. The electroconductive elastic member surface layer for electrophotography according to claim 1, wherein said fluorine group is carried by a polymer mainly composed of carbon, and forms a copolymer with polyurethane. 3. The electroconductive elastic member surface layer for electrophotography according to claim 1, wherein the fluorine group is a copolymer supported on a polymer mainly composed of carbon and containing an isocyanate group. 4. The electroconductive elastic member surface layer for electrophotography according to claim 3, wherein the isocyanate group is a polyfunctional blocked isocyanate. 5. The electroconductive elastic member surface layer for electrophotography according to claim 2, wherein the polymer carrying the fluorine group has an average molecular weight of 500 to 50,000. 6. A columnar base made of a conductive elastic member is formed concentrically on the outer periphery of the rotating shaft, and is formed on the outer periphery of the base.
5. An electrophotographic roller provided with the surface layer according to any one of 5. 7. A substrate made of a conductive elastic material is formed in a film shape on a belt-shaped core, and an outer surface of the film-shaped substrate is formed on the outer surface of the film-shaped substrate.
An electrophotographic belt provided with the surface layer according to any one of the above.