JP3438505B2 - Charging member - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member such as a charging roll that contacts a surface of a member to be charged to charge the surface of the member.

[0002]

2. Description of the Related Art A corona charging method has been most widely put into practical use as a charging means for a member to be charged such as a photoconductor in an image forming apparatus such as an electrophotographic recording method and an electrostatic recording method. However, this method, because it uses the corona discharge, discharge products such as ozone and NO _X a large amount of generated, they are, there is a problem such that may cause degradation of the electrostatic latent image holding member . In addition, since a high voltage of about 5 kV is required as the corona voltage, increasing the size of the power supply device and increasing the current capacity has been an unavoidable problem.

On the other hand, in the contact charging system in which a charging member is brought into contact with the electrostatic latent image holding member and a voltage is applied from the charging member to charge the electrostatic latent image holding member, discharge products are generated. It has advantages that it hardly occurs and a relatively low applied voltage of about 400 V can be used as the power supply voltage.

As the charging member, a charging roll having a structure in which a conductive elastic layer is formed on the outer circumference of a metal core material is used. This charging roll is required to have a function of holding the body to be charged at a predetermined potential, and therefore it is important to control the electric resistance of the charging roll within a certain range. Conductive fillers such as carbon black, tin oxide, and titanium oxide are generally widely used for this resistance control.

The preferable resistance of the entire charging roll is 1.0 × 10 ^{3 to} 1.0 × 10 ⁹ Ω · cm.
However, since the resistance value in this region largely changes due to slight fluctuations in the amount of filler added, resistance adjustment is performed using only the conductive filler described above, thereby stably producing the charging roll. It's difficult.

Therefore, for the purpose of preventing the above problems, a charging roll characterized by adjusting the resistance value by, for example, containing a conductive filler and an insulating metal oxide is proposed. Has been done. (JP-A-7-20
(685 publication)

Since this charging roll directly applies a voltage to the electrostatic latent image holding member, there is a problem that discharge dielectric breakdown of the electrostatic latent image holding member is likely to occur. In the case of one breakdown point due to this discharge insulation breakdown, for example, in the case of a cylindrical electrostatic latent image holder, the charge in the entire axial direction may flow to that breakdown point, and the electrostatic latent image holder may not be charged.

Therefore, for the purpose of preventing the above problems, there has been proposed a charging roll characterized by having a resin layer containing an alkyd resin on the conductive elastic layer. (JP-A-4-67067)

However, in the case of using the charging member as described above, there is no problem in the initial use, but the toner adheres to the charging member in a volume during durable use, and the effect of the fixed toner However, there is a problem that an image abnormality such as fogging occurs.

Therefore, for the purpose of preventing the problem of toner sticking as described above, there has been proposed a charging member characterized in that, for example, the surface layer is formed of a soluble fluororesin mixed with a conductive material. . (JP-A-6-17547
0)

However, since the fluororesin is generally expensive, the cost of the charging member becomes high if the surface layer is formed of only the soluble fluororesin. Further, since the fluororesin has a very strong polarity, it is very difficult to uniformly disperse the conductive material, especially carbon black in the fluororesin, and therefore, the resistance value of the charging roll is controlled within a certain range. It is very difficult to do.

For the purpose of preventing the problem of toner sticking as described above, there has been proposed a charging roll characterized by arranging insoluble fluororesin fine powder having a particle diameter of 30 μm, for example. (JP-A-8-123143)

However, if the blending amount of the fluororesin fine powder is too small, the effect of preventing toner sticking or the like is not exhibited, and if it is too large, the resistance value of the charging roll becomes high and good charging cannot be performed. On the other hand, when the blending amount of the fluororesin fine powder is adjusted so that the resistance value of the charging roll is in a preferable range, the fluororesin fine powder does not sufficiently appear on the charging roll surface, and the effect of preventing toner sticking is not exhibited. was there.

Therefore, for the purpose of preventing the above problems, the conductive substrate contains fluoride particles and a metal,
A charging member has been proposed, which is characterized in that a composite layer having a contact angle to pure water of 130 degrees or more is formed. (Japanese Patent Laid-Open No. 8-76557)

However, since the charging member is formed by electroplating on a metal hollow cored bar, it has high hardness and becomes hard. For this reason, when the contact charging device as described above is used, since the charging member and the electrostatic latent image holding member are in contact with each other, vibration noise is likely to be generated, and noise during operation of a printer or the like is reduced. In order to reduce it, there arises a problem of being extremely inconvenient.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to obtain stable charging without uneven resistance and good discharge dielectric breakdown resistance, and even after long-term use, image abnormality due to toner sticking does not occur. It is an object of the present invention to provide a low-cost charging member with a simple layer structure capable of performing the above.

[0017]

The charging member of the present invention comprises:
In a charging member having a structure in which a conductive elastic body layer and a surface layer in which a conductive substance is dispersed in a core material are sequentially laminated, the surface layer is an aliphatic polyester resin, a melamine resin,
And a fluorine-containing polymer compound.

The compounding ratio of the aliphatic polyester resin and the melamine resin is preferably 30 to 70 parts by weight with respect to 100 parts by weight of the aliphatic polyester resin, and the fluoropolymer compound is an aliphatic polyester resin. And 10 to 100 parts by weight of melamine resin in total
It is preferably contained in an amount of 0 part by weight.

Further, the conductive substance is made of carbon black, and the carbon black is 5 to 5 with respect to 100 parts by weight of the total amount of the aliphatic polyester resin and the melamine resin.
It is preferably contained in an amount of 0 part by weight. Further, the fluorine-containing polymer compound is preferably fine powder of fluorine-containing polymer compound having a particle diameter of 15 μm or less. Furthermore, the contact angle of water of the surface layer is 100 degrees or more, and the particle diameter is 15 μm.
It is preferable that the ratio (surface occupancy) of the surface of the surface layer of the fine fluorinated polymer compound powder having a particle size of m or less is 40% or more.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The charging member of the present invention may be any member that comes into contact with a member to be charged and charges the member, and examples thereof include a charging roll, a charging plate, a charging brush, and a charging plate. .

FIG. 1 shows an embodiment of a charging roll as a charging member of the present invention and a usage pattern of this charging roll. In this charging roll 1, a conductive elastic body layer 3 is provided on the outer peripheral surface of a core material 2, and carbon black is contained in a resin composed of an aliphatic polyester resin and a melamine resin on the outer peripheral surface of the conductive elastic body layer 3. It has a three-layer structure in which a surface layer 4 formed of a coating film containing a finely divided fluororesin in a dispersed state is provided.

In the present invention, the aliphatic polyester resin contained in the surface layer has a methylene chain of the main chain portion bound in a chain form and has a molecular weight of 10,000 to 30,000.
Any polyester resin of 0 can be used, but among them, linear saturated polyester resin (trade name: Byron 200, manufactured by Toyobo, trade name: Byron 300, manufactured by Toyobo) is particularly preferable. .

In the present invention, examples of the melamine resin contained in the surface layer include n-butyl alcohol-modified melamine resin, iso-butyl alcohol-modified melamine resin and methyl alcohol-modified melamine resin. In particular, an n-butyl alcohol-modified melamine resin or an iso-butyl alcohol-modified melamine resin is suitable.

In the present invention, the compounding ratio of the aliphatic polyester resin and the melamine resin is preferably 30 to 70 parts by weight with respect to 100 parts by weight of the aliphatic polyester resin. When the content of the melamine resin is less than 30 parts by weight, the uncrosslinked part remains, and the resulting surface layer is tacky and easily tacks with the adherend. On the other hand, when it exceeds 70 parts by weight, highly crosslinked. The surface layer obtained becomes brittle and hard, and cracks easily occur, which is not preferable.

As the fluorine-based polymer compound used in the present invention, as a fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),
Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-
Ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PV
F) and the like. Further, as the fluororubber, vinylidene fluoride-3 fluorochloroethylene copolymer, vinylidene fluoride-6 fluoropropylene copolymer vinylidene fluoride-6 fluoropropylene-4 fluoroethylene terpolymer, etc. are available. Can be mentioned.

The content of the fluorine-containing polymer compound is preferably 1 to 100 parts by weight, more preferably 20 to 60 parts by weight, based on 100 parts by weight of the total amount of the aliphatic polyester resin and the melamine resin. If the content of the fluorine-containing polymer compound is less than 1 part by weight, the effect of preventing toner sticking is small, while if it exceeds 100 parts by weight, the surface layer occupancy becomes high and the resistance value is 10 ⁹ Ω.・ It is not preferable because it exceeds cm and the coating processability is significantly reduced. The particle size of the fluorine-based polymer compound is 15 μm or less, preferably 6 μm or less, and more preferably 3 μm or less. When the particle diameter of the fluorine-based polymer compound exceeds 15 μm, the smoothness of the surface layer after coating is deteriorated, and conversely, paper powder, abrasion material, etc. are likely to occur, which is not preferable.

As the conductive substance used in the present invention, carbon black is particularly preferable, and as the carbon black, furnace blacks such as SAF, HAF,
Examples thereof include hard carbon and soft carbon such as GPF and SRF, acetylene black, Ketchin black, and channel black. The content of carbon black as the conductive material is 1 to 5 with respect to 100 parts by weight of the total amount of the aliphatic polyester resin and the melamine resin.
0 parts by weight, particularly 5 to 20 parts by weight are preferred. If the content of carbon black is less than 1 part by weight, the resistance value may vary, and the manufacturing stability tends to deteriorate.
If it exceeds 50 parts by weight, the viscosity is increased during the production of the coating composition, which is liable to cause poor dispersion and the workability is deteriorated, which is not preferable.

The surface layer 4 has a contact angle with water of 1
The surface layer is formed so that the surface occupancy of the fine particles of the fluoropolymer compound is 40% or more so that the surface occupancy rate is 00 ° or more, preferably 110 ° or more. The larger the contact angle of the surface layer 4 with water, the higher the effect of preventing toner sticking. For this reason, the larger the surface occupancy rate of the fine particles of the fluoropolymer compound, the higher the effect of preventing toner sticking. However, surface layer 4
When the contact angle with respect to water is less than 100 degrees and the surface occupancy rate of the fluorine-based polymer fine powder is less than 40%, it becomes difficult to obtain the desired toner adhesion preventing effect.

The surface layer of the present invention can be formed by coating such as spray coating, dip coating, wire bar coating and blade coating. At this time, the type and blending amount of the diluting solvent, coating conditions, drying conditions, etc. Or by polishing the surface layer after forming the surface layer to expose the fluorine-based polymer compound fine powder to the surface of the charging member so that the contact angle with water becomes 100 degrees or more. The surface layer is formed so that the surface occupancy of the fine particles of the fluororesin compound is 40% or more.

The resistance value of the surface layer 4 is 10 ³ to 10 ⁹ Ω.
A range of cm is preferred. The thickness of the surface layer 4 is
It is preferably 100 μm or less, particularly 30 to 60 μm. The blending ratio of the carbon black and the fluorine-based polymer compound fine powder is adjusted to fall within this resistance value range.

Further, in the present invention, the conductive elastic layer 3
Is a material in which carbon black is added to the elastic material to impart conductivity, and its volume resistance is 10 ⁻⁰ 0 to ^{10 −10} Ω · cm,
The hardness is preferably set to 45 to 55 degrees (JIS A hardness).

As the elastic material, polybutadiene, natural rubber, polyisoprene, butyl rubber, SBR (styrene butadiene rubber), CR (chloroprene), NBR
(Nitrile butadiene rubber), silicone rubber, epichlorohydrin and other rubbers, BR (butadiene rubber), SB
Polystyrene type such as S (styrene-butadiene-styrene elastomer), polyolefin type, polyester type polyurethane type, thermoplastic elastomer such as PVC (polyvinyl chloride), nitrile rubber, polyurethane, polystyrene, polyethylene, polypropylene, PVC, acrylic type A resin, an elastomer material such as a styrene-vinyl acetate copolymer, or the like can be used. Urethane rubber, EPDM, etc. are used as the rubber having good ozone resistance.

The carbon black used for the conductive elastic layer 3 may be the same as that used for the surface layer 4 described above. The content of carbon black is preferably 1 to 100 parts by weight with respect to 100 parts by weight of the elastic material,
If the content is more than 100 parts by weight, the rubber becomes too hard, and if less than 1 part by weight, it becomes difficult to adjust the volume resistance. The conductive elastic layer 3 is formed by a conventional method such as an extrusion forming method, a casting method, and an injection forming method.

When the surface layer is formed, the aliphatic polyester resin, the melamine resin, the fluoropolymer compound and the conductive substance are sufficiently mixed and dispersed in predetermined amounts, respectively, and the obtained mixed dispersion is used as a solvent. A surface layer having a predetermined thickness is formed by applying the dissolved coating material to the conductive elastic layer 3 and drying the coating at a predetermined temperature for a predetermined time. In this method, the surface layer can be formed easily and with a constant thickness, and by forming the surface layer by painting, absorption unevenness such as molding unevenness and seam lines in the lower conductive elastic layer is hidden. As a result, it is possible to obtain a surface layer having extremely excellent surface smoothness, and to prevent charging failure due to molding unevenness, seam lines, etc., and eventually image deterioration.

The drying condition for forming the surface layer is 100 to 180 ° C., preferably 140 to 170 ° C., and time is 10 to 200 minutes, preferably 20 to 6 minutes.
0 minutes is preferred. If the temperature is too low and the time is too short, the solidification of the surface layer is not sufficient and toner sticking easily occurs.

In charging using the charging roll 1, a voltage of 100 to 5000 V is applied to the photosensitive member 5 via the power source 6 to charge the photosensitive member 5. Further, in the present invention,
For the processes such as image exposure, development and cleaning, any method known in the field of electrostatic photography can be adopted, and the kind of developer is not limited to a particular one.
The charging roll of the present invention can be used not only in copying machines, but also in electrophotographic application fields such as laser printers, CRT printers and fax machines.

[0037]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. "Part" in the text is "part by weight"
Indicates. [Example 1] EPDM raw material rubber (Mooney viscosity 20) 1
To 00 parts, 1 part of a vulcanizing agent (dicumyl peroxide), 3 parts of methacrylic acid ester, 1 part of zinc oxide, and 10 parts of Ketchin black and 20 parts of furnace black SAF were added and kneaded on a two-roll for 30 minutes. , And mixed to prepare a rubber raw material.

This is weighed in a mold having an SUS core material having an outer diameter of 6 mm (stainless steel bar, iron bar plated with nickel, etc.), and press-molded 16
After heating at 0 ° C. for 30 minutes to perform primary vulcanization,
It was taken out of the mold and heated at a temperature of 160 ° C. for 30 minutes for secondary vulcanization to form a conductive rubber layer as a conductive elastic body layer around a SUS core material (thickness: 3 mm). The conductive rubber layer has a rubber hardness of 55 degrees (JIS.A hardness),
The resistance value in the layer thickness direction is 1.0 × 10 ⁴ Ω · cm (22
C., 55% RH).

Next, 80 parts of a linear polyester resin (trade name: Byron 30SS, manufactured by Toyobo) and 20 parts of a melamine resin (trade name: Super Beckamine G-821-60 manufactured by Dainippon Ink and Chemicals, Inc.) were electrically conductive. Carbon (Product name: F
W200, manufactured by Degussa) and 5 parts of fluororesin fine powder (trade name: Lubron L-5, manufactured by Daikin Industries, Ltd.) were mixed and dispersed using a sand mill to prepare a coating for forming a surface layer.

Then, the surface layer-forming coating material was diluted at a ratio of 150 parts of xylene to 100 parts of the surface layer-forming coating material to adjust the viscosity, and then a bell-type electrostatic coating machine (Landsburg Industry Co., Ltd.) was used. Manufactured), a surface layer is formed on a conductive rubber roll so that the film thickness when dried is 35 μm, and then the surface layer is dried at 160 ° C. for 30 minutes,
A charging roll as shown in FIG. 1 was prepared. In the figure, 2 is a core material, 3 is a conductive elastic body (rubber) layer, and 4 is a surface layer made of an electrostatic coating film. The volume resistance of this charging roll is 1
Indicates 0 ^5.2 Ω · cm, were measured voltage causing discharge breakdown was 2200 V. The contact angle between this surface layer and water was 110 °, and the surface occupancy of the fluororesin fine powder was 45%.

As shown in FIG. 1, this charging roll is installed so as to rotate in contact with the photoconductor 5 in the copying machine, and the core material 2 is provided with a DC power source of 500 V from a power source 6 to 2 k.
Applying a 2kHZ AC power supply superimposed on V,
When a charging test of 40,000 sheets was continuously conducted in an environment of 23 degrees and 55% RH, toner was not fixed and uniform and good charging was performed. At this time, when the surface of the photoconductor 5 was examined for contamination, it was found that there was no stain due to the exuding component. Further, the charging roll is brought into contact with the photoconductor,
When a storage test was carried out at 0 ° C. and 95% RH for 30 days, contamination of the photoreceptor by bleeding did not occur.

Example 2 The same charging roll as in Example 1 except that the amount of the fluororesin fine powder (trade name: Lubron L-5, manufactured by Daikin Industries, Ltd.) in Example 1 was 6.5 parts. It was created. Next, the surface layer of this charging roll was polished by 1 to 5 μm using # 1000 sandpaper, and the same test as in the example was conducted. The volume resistance of this charging roll was 10 ^6.4 Ω · cm, and the voltage causing discharge dielectric breakdown was measured and found to be 2200V. The contact angle with water was 112 degrees, and the surface occupancy of the fluororesin fine powder (trade name: Lubron L-5, manufactured by Daikin Industries, Ltd.) was 45%. Using this charging roll, a continuous 40,000-sheet charging test was carried out. As a result, the toner was hardly fixed, and uniform and good charging was performed. At this time, when the surface of the photoconductor 5 was examined for contamination, it was found that there was no stain due to the exuding component.

[Comparative Example 1] The carbon black content in the example was 4 parts, and instead of the fluororesin fine powder,
A charging roll similar to that of Example 1 was prepared except that 2.5 parts of silica fine powder (Aerosil R972; manufactured by Nippon Aerosil Co., Ltd.) was blended, and the same test was performed. The volume resistance of this charging roll shows 10 ^5.0 Ω · cm, and the voltage causing discharge dielectric breakdown was measured to be 2200 V.
Met. The contact angle between this surface layer and water was 70 degrees. When this charging roll was subjected to a charging test in the same manner as in Example 1, image defects due to toner sticking were remarkable,
Further, the roller surface was considerably soiled with toner. [Comparative Example 2] A charging roll was prepared in the same manner as in Example 1 except that the carbon black content in the example was 4 parts and the fluororesin fine powder content was 0 part. I did it. The volume resistance of this charging roll was 10 ^4.5 Ω · cm, and it was 1700 V when the voltage causing discharge dielectric breakdown was measured. The contact angle between this surface layer and water was 60 degrees. When this charging roll was subjected to a charging test in the same manner as in Example 1,
A charging failure occurred due to the occurrence of insulation discharge breakdown.

As described above, the charging roll of the present invention has a surface in which a conductive resin and a fluorine-containing polymer fine powder are dispersed in a binder resin containing an aliphatic polyester resin and a melamine resin. A layer is provided, and such a surface layer can be easily manufactured with stable electric resistance of the charging member within a certain range by optimizing the blending amount of the conductive substance and the fluoropolymer compound. can do. In addition, since the fluorine-based polymer compound fine powder, which is an insulating material, is blended, electric charges can be prevented from flowing along the surface of the surface layer, and at the breakdown point due to discharge dielectric breakdown,
It has become possible to prevent the problem that the charge in the entire axial direction of the charging member flows in and the charge is no longer charged. In addition, this charging roll has a simple layer structure of two layers, and since its surface layer can be easily formed in one coating step, the number of manufacturing steps is short, and the cost is low and the cost is low. Can be manufactured in.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a sectional structure of a charging roll as a charging member of the present invention and a usage pattern of the charging roll.

[Explanation of symbols]

1 Charging roll 2 core material 3 Conductive elastic layer 4 surface layer 5 photoconductor 6 power supply

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-10-148995 (JP, A) JP-A-8-227206 (JP, A) JP-A-4-184370 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103 G03G 15/08 501

Claims (7)

(57) [Claims] 1. A charging member having a structure in which a conductive elastic layer and a surface layer in which a conductive substance is dispersed are sequentially laminated on a core material, wherein the surface layer is an aliphatic polyester resin,
A charging member comprising a melamine resin and a fluoropolymer compound. 2. The charging member according to claim 1, wherein the melamine resin is contained in an amount of 30 to 70 parts by weight based on 100 parts by weight of the aliphatic polyester resin. 3. The charging composition according to claim 1, wherein the fluoropolymer compound is contained in an amount of 1 to 100 parts by weight based on 100 parts by weight of the total amount of the aliphatic polyester resin and the melamine resin. Element. 4. The electrically conductive substance is composed of carbon black, and the carbon black is contained in an amount of 5 to 50 with respect to a total of 100 parts by weight of the aliphatic polyester resin and the melamine resin.
The charging member according to any one of claims 1 to 3, wherein the charging member is contained by weight. 5. The fluorine-based polymer compound has a particle diameter of 15 μm.
The charging member according to claim 3, which is a fine powder of a fluorine-based polymer compound having a particle size of m or less. 6. The contact angle of the surface layer with water is 100.
The charging member according to claim 1, wherein the charging member has a temperature of not less than 100 degrees. 7. The charging member according to claim 1, wherein the surface occupancy of the fluorine-based polymer fine powder in the surface layer is 40% or more.