JPH09288400A - Contact electrifying member and contact electrifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact electrifying member which has improved electrification property and can maintain resistance against spent for a long term, and thereby, which can maintain good electrification, and to provide a contact electrifying device using this contact electrifying member. SOLUTION: This electrifying member has a conductive member and magnetic particles held by the conductive member and is disposed in contact with the body to be electrified. By applying voltage on the conductive member, the objective body is electrified. In this method, the diameter of the magnetic particles corresponding to 50% of the volume distribution is between >=10μm and <=100μm, and the diameter ratio of particles corresponding to 50% volume distribution to 5% volume distribution is >=1.40. The volume resistance of the magnetic particles is controlled to >=1×10<4> Ωcm and <=1×10<11> Ωcm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging member which is disposed in contact with an object to be charged (electrophotographic photoreceptor) to charge the object to be charged by applying a voltage, and a contact member and an object to be charged. The present invention relates to a contact charging device that has a charging member that charges and charges a member to be charged by applying a voltage to the charging member.

[0002]

2. Description of the Related Art The following methods are generally used as conventional electrophotographic methods.

That is, an electrostatic latent image is formed on a photoconductor by a charging means and an image exposing means, and then the latent image is developed by a toner to form a visible image (toner image). After the toner image is transferred onto, the toner image is fixed on the transfer material by heat, pressure or the like to obtain a copy. At this time, toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.

In the electrophotographic photoreceptor, various organic photoconductive substances have been developed as photoconductive substances, and in particular, a function separation type in which a charge generation layer and a charge transport layer are laminated is installed in a copying machine, a printer, a facsimile or the like. Has been done.

As a charging means for such an electrophotographic apparatus, a contact charging means is now widely used from a means utilizing corona discharge.

Contact charging is a method in which a charging member such as a roller or a blade is brought into contact with the surface of a photosensitive member, and a discharge as interpreted by Paschen's law is formed in the vicinity of the contact portion to charge the photosensitive member. Therefore, it is possible to suppress the generation of ozone as much as possible compared with the conventional corona discharge. Among them, the roller charging method using a charging roller as a charging member is preferably used from the viewpoint of charging stability.

Since such contact charging is performed by discharging from the charging member to the body to be charged, it is necessary to apply a voltage higher than a certain threshold voltage.

For example, when a charging roller is brought into contact with a photosensitive body containing an organic photoconductive substance having a photosensitive layer thickness of about 25 μm, the surface potential of the photosensitive body can be increased by applying a voltage of about 640 V or more. Starts to rise, and thereafter, the photosensitive member surface potential increases linearly with an inclination of 1 with respect to the applied voltage (hereinafter, this threshold voltage is defined as the charging start voltage Vth).

That is, a minimum DC voltage of Vd + Vth is required for the charging roller in order to obtain the photoreceptor surface potential Vd. Further, the resistance value of the charging roller may fluctuate due to environmental fluctuations, etc., and an expensive device may be required to keep the potential of the photoconductor at a desired value for a long period of time.

Therefore, in order to make the charging even more uniform, a peak-to-peak voltage of 2 × Vth or more is applied to the DC voltage corresponding to the desired Vd, as disclosed in Japanese Patent Laid-Open No. 63-149669. A DC + AC charging method has been adopted in which a voltage superposed with the AC voltage is applied to the charging roller.

This is for the purpose of leveling the potential by the AC voltage, and the potential of the charged body converges on Vd which is the center of the AC voltage, and is characterized in that it is hardly affected by external disturbances. .

However, even in such a charging method, since the essential charging mechanism uses the discharging phenomenon from the charging member to the photoconductor, as described above, the voltage required for charging is the photoconductor. A value above the surface potential is required. Further, noise (hereinafter referred to as AC charging sound) may be generated between the charging member and the photoconductor due to vibration caused by the electric field of AC voltage. Further, when the photoconductor is used for a long period of time, surface deterioration may occur due to discharge.

Therefore, as a charging method with higher charging efficiency, so-called injection charging in which charges are directly injected into a photosensitive member has been reported in recent years.

This injection charging is a charging method in which a voltage is applied to a contact charging member such as a charging roller, a charging fiber brush, a charging magnetic brush or the like, and charges are injected into the trap level on the surface of the photoconductor. For more information, see Japan Hardcop
y As described in “Contact Charging Characteristics Using Conductive Rollers” in 1992, P287, “Charge Characteristics Using Conductive Roller”, a voltage is applied to a low resistance charging member for a photoconductor having a dark insulating property to perform injection charging. This method is performed on condition that the resistance value of the charging member is sufficiently low and that the conductive material (conductive filler or the like) is sufficiently exposed on the surface of the charging member. For this reason, in the above-mentioned documents, it is said that the charging member is preferably an aluminum foil or an ion conductive charging member having a sufficiently low resistance value in a high humidity environment. According to the study by the present inventors, the resistance value of the charging member capable of sufficiently injecting charge into the photoconductor is 1 × 10 ³ Ωcm or less, and above this, a difference occurs between the applied voltage and the charging potential. It has been found that there is a problem in the convergence of the charging potential at the beginning.

However, when such a charging member having a low resistance value is actually used, an excessive leak current flows from the injection charging member to the scratches, pinholes, etc. formed on the surface of the photosensitive member, and charging defects in the periphery and the like occur. It is easy for the pinhole to expand and the charging member to be damaged by electricity.

In order to prevent this, it is necessary that the resistance value of the charging member is about 1 × 10 ⁴ Ωcm or more. However, in the charging member having this resistance value, the charge injection into the photosensitive member is as described above. There is a contradiction that the charge is lowered and charging is not performed.

Therefore, it has been desired to solve the above problems in the contact type charging member or the contact charging device.

Further, the contact charging member brought into contact with the member to be charged may cause stains (spents) on the charging member, resulting in a decrease in chargeability after long-term use, which may cause image defects. The spent toner of the charging member passes through the cleaning member without being removed by the cleaning unit, such as toner that has not been transferred and adheres to the surface of the charging member due to friction with the charging member. It is believed to occur in.

Generally, as a countermeasure against the spent, the charging member is coated with a resin having spent resistance. However, the resin with excellent spent resistance often does not have sufficient adhesion to the charging member as the core material, and the film is peeled off due to durability, and the spent chips are regenerated or the film fragments that have come off are removed from the photoreceptor or the developing device. Sometimes polluted.

Therefore, in contact charging, there is an urgent need to improve the charging property and prevent charging deterioration due to spent for a long period of time.

Similarly, also in charging by injecting charges into the body to be charged, there is an urgent need to improve the charging property and prevent charging deterioration for a long period of time.

[0022]

SUMMARY OF THE INVENTION An object of the present invention is to improve the charging property, and also to provide a contact charging member capable of exhibiting spent resistance for a long period of time and maintaining good charging, and a contact charging device having the same. To provide.

[0023]

In order to achieve the above object,
According to a first aspect of the present invention, there is provided a conductive member and magnetic particles supported by the conductive member, and the magnetic particles are arranged in contact with a member to be charged, and the member to be charged is applied by applying a voltage to the conductive member. In the contact charging member for charging, the 50% diameter of the volume distribution of the magnetic particles is 10 μm or more and 100 μm or less, and the ratio of the 50% diameter of the volume distribution to the 5% diameter of the volume distribution is 1.40 or more. , The volume resistance of the magnetic particles is 1 × 1
It is characterized in that it is not less than 0 ⁴ Ωcm and not more than 1 × 10 ¹¹ Ωcm.

According to a second aspect of the present invention, in the above-mentioned first aspect, the 50% diameter of the volume distribution of the magnetic particles is 1
It is characterized by being 0 μm or more and 60 μm or less.

The invention according to claim 3 is the same as claim 1 or 2 above.
In the invention described above, the ratio of the 50% diameter of the volume distribution of the magnetic particles to the 5% diameter of the volume distribution is 1.55 or more and 5.00 or less.

The invention according to claim 4 is characterized in that, in the invention according to claim 1, the surface layer of the magnetic particles contains a resin having a molecular weight P1 of 10,000 or more at the main peak of the GPC chromatogram. To do.

In the invention according to claim 5, in the invention according to claim 4, the GPC chromatogram of the resin in the surface layer of the magnetic particles has at least one peak or shoulder on the low molecular weight side of the main peak. Is characterized by.

The invention according to claim 6 is the same as claims 4 and 5 above.
In the invention described above, GP of the resin of the surface layer of the magnetic particles
The ratio P of the molecular weight P1 of the main peak of the C chromatogram and the molecular weight P2 of the peak or shoulder on the low molecular weight side
1: P2 is 3: 1 to 100: 1.

The invention according to claim 7 is the same as claim 5 or 6 above.
In the invention described above, GP of the resin of the surface layer of the magnetic particles
The molecular weight of the main peak of C chromatogram is 30,000
Is about 400000, and the molecular weight of at least one peak or shoulder on the low molecular weight side is 3000 to 3000.
It is characterized by being 0.

The invention according to claim 8 is the above-mentioned claim 4,
In the inventions described in 5, 6, and 7, the weight average molecular weight Mw of the resin of the surface layer of the magnetic particles is 50,000 to 70,000.
0, the number average molecular weight Mn is 5,000 to 50,000,
It is characterized in that Mw / Mn is 10 or more.

The invention according to claim 9 is the above-mentioned claim 4,
In the inventions described in 5, 6, 7, and 8, the resin of the surface layer of the magnetic particles is at least a fluorine resin, an acrylic resin,
It is characterized by being one or more kinds of resins selected from silicone resins and polyolefin resins.

The invention according to claim 10 is the above-mentioned claim 4,
In the invention described in 5, 6, 7, 8, and 9, the resin of the surface layer of the magnetic particles is a polyolefin resin.

The invention according to claim 11 is the above-mentioned claim 4,
The invention described in 5, 6, 7, 8, 9, and 10 is characterized in that the resin of the surface layer of the magnetic particles contains conductive particles.

According to a twelfth aspect of the present invention, there is provided a charged member, a conductive member, and a charging member having magnetic particles supported by the conductive member and arranged in contact with the charged member. In a contact charging device that charges a body to be charged by applying a voltage to a conductive member, the volume distribution of the magnetic particles is 5
The 0% diameter is 10 μm or more and 100 μm or less, the ratio of the 50% diameter of the volume distribution to the 5% diameter of the volume distribution is 1.40 or more, and the volume resistance of the magnetic particles is 1 × 10 ⁴ Ωcm or more 1. It is characterized in that it is not more than × 10 ¹¹ Ωcm.

The invention according to claim 13 is the above-mentioned claim 12.
In the invention described above, the 50% diameter of the volume distribution of the magnetic particles is 10 μm or more and 60 μm or less.

The invention according to claim 14 is the above-mentioned claim 1.
In the inventions 2 and 13, the ratio of the 50% diameter of the volume distribution of the magnetic particles to the 5% diameter of the volume distribution is 1.55 or more and 5.0.
It is characterized by being 0 or less.

The invention according to claim 15 is the above-mentioned claim 12.
In the invention described above, the surface layer of the magnetic particles has a molecular weight P1 of 10,000 at the main peak of the GPC chromatogram.
It is characterized by containing the above resin.

The invention according to claim 16 is the above-mentioned claim 15.
In the invention described above, GP of the resin of the surface layer of the magnetic particles
The C chromatogram is characterized by having at least one peak or shoulder on the low molecular weight side of the main peak.

The invention according to claim 17 is the above-mentioned claim 1.
In the inventions 5 and 16, the molecular weight P1 of the main peak of the GPC chromatogram of the resin in the surface layer of the magnetic particles
And the molecular weight P2 of the peak or shoulder on the low molecular weight side
Ratio P1: P2 of 3: 1 to 100: 1.

The invention according to claim 18 is the above-mentioned claim 1.
In the inventions described in 5, 16, and 17, the molecular weight of the main peak of the GPC chromatogram of the resin in the surface layer of the magnetic particles is 30,000 to 400,000, and the molecular weight of at least one peak or shoulder on the low molecular weight side is 30.
It is characterized by being in the range of 00 to 30,000.

The invention according to claim 19 is the above-mentioned claim 1.
5, 16, 17, 18, the weight average molecular weight Mw of the resin of the surface layer of the magnetic particles is 50,000 to 7
00000, number average molecular weight Mn is 5,000 to 50,000
And Mw / Mn is 10 or more.

The invention according to claim 20 is the above-mentioned claim 1.
In the inventions described in 5, 16, 17, 18, and 19, the resin of the surface layer of the magnetic particles is at least one resin selected from at least a fluorine resin, an acrylic resin, a silicone resin, and a polyolefin resin. Is characterized by.

The invention according to claim 21 is the above-mentioned claim 1.
In the invention described in 5, 16, 17, 18, 19, and 20, the resin of the surface layer of the magnetic particles is a polyolefin resin.

The invention according to claim 22 is the above-mentioned claim 1.
In the invention described in 5, 16, 17, 18, 19, 20, and 21, the resin of the surface layer of the magnetic particles contains conductive particles.

The invention according to claim 23 is the above-mentioned claim 12.
In the invention described above, the surface layer of the member to be charged is a charge injection layer.

The invention according to claim 24 is the above-mentioned claim 23.
In the invention described above, the charge injection layer contains conductive particles and a binder resin.

The invention of claim 25 is the same as claim 23.
In the invention described above, the charge injection layer is an inorganic semiconductor layer.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION The contact charging member according to the present invention is
A magnetic medium resistance material is magnetically erected, and this magnetic brush is brought into contact with a photoreceptor to be charged.

Therefore, as the magnetic particles contained in the charging member, an alloy or compound containing an element exhibiting ferromagnetism such as iron, cobalt and nickel is used. Such magnetic particles can be adjusted within an arbitrary resistance range, and can be achieved by, for example, an oxidation treatment or a reduction treatment. Specific examples thereof include composition-adjusted ferrite, hydrogen-reduced Zn-Cu ferrite, and oxidized magnetite.

The present invention relates to magnetic particles having a volume distribution diameter of 2.2 μm or more and having a volume distribution 50% diameter of 10 μm or more.
0 μm or less and 50% volume distribution diameter and volume distribution 5
% Ratio (hereinafter referred to as particle size ratio)) is 1.40 or more, and more preferably, the volume distribution 50% size is 10 μm or more and 60 μm or less, and the particle size ratio is 1.
It is 55 or more and 5.00 or less.

In the contact charging, improvement of the contact property with the photoconductor is an important factor for enhancing the charging ability, and it is effective to use magnetic particles having the above-mentioned particle diameter and particle diameter ratio range as a means for achieving this. .

That is, in the case of the magnetic particles having the above particle size distribution, the magnetic particles having a particle size smaller than the 50% volume distribution can move between the magnetic particles as auxiliary particles to be attached (constrained by magnetic force). The following effects can be obtained. 1) The contact surface between the magnetic particles and the photoconductor is brought into closer contact. 2) Make the magnetic particles dense and make the resistance in the magnetic brush uniform. 3) It is possible to prevent the spent of the developer and the like adhering to the surface of the magnetic particles.

Here, if the particle size ratio is less than 1.40, the effect as auxiliary particles decreases, and charging failure may occur under low temperature and low humidity conditions. On the small particle size side of the volume distribution, magnetic particles having a volume distribution diameter of less than 2.2 μm may adhere to the photoconductor, and in such a case, it may cause abrasion of the photoconductor.

Here, the volume distribution diameter of the magnetic particles is measured by a laser diffraction type particle size distribution measuring device HEROS (JEOL Ltd.).
Manufactured), and a range of 0.05 μm to 200 μm is set to 32.
The measurement was performed by logarithmic division.

The magnetic particles used in the present invention have a volume resistance
The value is l × 10^Four Ωcm or more l × l0 ¹¹Ωcm or less
You. Resistance value is l × 10^Four Pinholey below Ωcm
Is likely to occur, l × 10¹¹If it exceeds Ωcm, it will
Good charging becomes difficult under humidity conditions.

Here, the volume resistance value of the magnetic particles was calculated from the value of current flowing at the time when a voltage was applied between the electrodes after the particles were filled in a cell in which two electrodes were arranged. The measurement conditions were 23 ° C. and 65%, the contact area between the filling particles and the cell S = 2 cm ² , the thickness d = 1 mm, and the load 10 of the upper electrode.
kg, applied voltage 100V.

In the present invention, it is preferable to coat the surface of the magnetic particles with a resin having a specific molecular weight distribution.

That is, the coating resin used in the present invention is G
It is preferable that the main peak of the PC chromatogram has a molecular weight (P1) of 10,000 or more, and at least one peak or shoulder is on the low molecular weight side of the main peak. The main peak on the high molecular weight side improves the abrasion resistance of the resin and prevents the surface from being spent by toner or the like. The sub-peak or shoulder on the low molecular weight side has the effect of improving the adhesion between the magnetic particle core and the resin and preventing the coating resin from peeling off from the magnetic particles. Even when the magnetic particles of the charging member are likely to have a large share due to the synergistic effect, the deterioration of the magnetic particles is small, uniform charging can be obtained even by long-term durability, and a good image can be obtained.

Specifically, the molecular weight of the main peak (P
1) is 30,000 to 400,000, and at the same time the adhesion (peel) of the coating resin under long-term shear conditions
From the standpoint of, the molecular weight of at least one peak or shoulder on the low molecular weight side is preferably 3,000 to 30,000. Here, the inflection point of the differential curve of the GPC chromatogram was defined as the peak / shoulder position.

The weight average molecular weight Mw is 50,000-
700,000, number average molecular weight Mn is 5000 to 5000
0, the Mw / Mn is 10 or more, and the Z-average molecular weight Mz is 1,000,000 to 50,000.
It is preferably in the range of 00.

A resin having a peak or shoulder on the low molecular weight side of less than 3,000 may have a reduced effect on abrasion resistance, while a resin having a peak or shoulder of less than 3,000 tends to cause the coating resin to easily peel off (release) from the surface of the magnetic particles. is there.

Similarly, when the number average molecular weight Mn, the weight average molecular weight Mw, the Z average molecular weight Mz, and Mw / Mn are in the above ranges, it is very useful for abrasion resistance of the resin, prevention of peeling, and prevention of spent of toners. Effective, but more preferably
The main peak has a molecular weight of 50,000 to 300,000, and the low molecular weight peak or shoulder has a molecular weight of 3,000.
˜15,000, weight average molecular weight Mw is 100,000 to 5
00000, number average molecular weight Mn is 7,000 to 4,000
0, Mw / Mn is 20 or more.

Further, the ratio of the molecular weight P1 of the main peak to the molecular weight P2 of the peak or shoulder on the low molecular weight side is 3: 1 to 100: 1 so that the adhesion of the resin to the magnetic particles and the abrasion resistance can be improved. It is preferable from the viewpoint of compatibility and is preferably 5: 1 to 50: 1 in order to exert a long-term effect.

Examples of the coating resin used in the present invention include nylon-6, nylon-12, nylon-46,
Polyamide resin such as aramids, polyester resin such as PET, polyolefin resin such as PE and PP, epoxy resin, methyl silicone, methylphenyl silicone, silicone resin such as silicone acryl, vinyl chloride resin, polyurethane resin Resin, polytetrafluoroethylene, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer, fluorine resin such as polyvinylidene fluoride, polycarbonate resin,
Melamine resin, styrene resin, acrylic resin such as polymethacrylic acid ester, polyacetal resin,
Examples thereof include vinyl acetate resin and phenol resin.

Of these, from the standpoint of preventing the spent for a longer period of time, it is preferable that at least one selected from the group consisting of fluorine-based resins, acrylic resins, silicone-based resins and polyolefin-based resins is used. It is a polyolefin resin with excellent abrasion resistance.

The surface layer of the magnetic particles used in the present invention does not necessarily have to completely cover the surface layer of the core material of the magnetic particles, and the core material may be exposed to the extent that the above effects can be obtained. That is, the surface layer may be formed discontinuously.

The resin for coating the magnetic particles used in the present invention can disperse the conductive particles within a range satisfying the resistance region of the magnetic particles.

Examples of such conductive particles include metal powder of iron, copper, silver, etc., composite metal powder of zinc oxide, tin oxide, titanium oxide, copper sulfide, etc., conductive carbon such as carbon black, polypyrrole. And the like, electron-conjugated polymers and the like. Of these, conductive carbon such as carbon black is preferable.

The resin coating layer in the present invention preferably has a coating layer solid content of 0.1 to 20% by weight based on the amount of the core material. If it is less than 0.1% by weight, the coating effect is not sufficient, and if it exceeds 20% by weight, the fluidity and the adhesive force with the electrode sleeve are lowered, and it may be difficult to obtain long-term uniform charging property. It also leads to higher costs.

The molecular weight of the polyolefin resin of the present invention was measured by the following method.

The apparatus is a gel permeation chromatography (GPC) measuring apparatus manufactured by Waters, GPC-
Using 150C, the measurement was performed under the following conditions.

Column: Shodex HT-806M 2 pieces (pre-column Shodex HT-800P 1 piece) Temperature: In the case of polyethylene resin 145 ° C. Other resin 40 ° C. Solvent: In case of polyethylene resin o-dichlorobenzene (addition of 0.1% ionol) ) Other resins Tetrahydrofuran Flow rate: 1.0 ml / min Sample: 0.4 ml of 0.15% sample injected

In the case of measuring the molecular weight of the resin coated with magnetic particles, Soxhlet extraction of magnetic particles was carried out for 20 hours using a xylene solvent, xylene was removed from the extract by an evaporator, etc., and the solid content obtained was dried. Was used as a sample.

The molecular weight of the sample was calculated by using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample.

[Production Example of Magnetic Particles] (Magnetic Particle Production Examples 1 to 5) Cu—Zn ferrites having the following volume distributions of 50% diameter and 5% diameter were prepared.

[0076]

(Magnetic Particle Production Example 6) Hot xylene solvent 10
0.1 part by weight of a polyethylene resin having a peak molecular weight of 4000 and 0.9 part by weight of a polyethylene resin having a peak molecular weight of 100,000 were added and mixed in 0 part by weight to prepare a magnetic particle coating solution. Mn = 1300 for the entire mixed resin
0, Mw = 370,000 and Mw / Mn = 28.5. This coating solution was applied to the above-mentioned magnetic particles 1 by a spir coater so that the resin coating amount was 1 part by weight with respect to the magnetic particles to obtain magnetic particles 6 having a volume resistance value of 8 × 10 ⁷ Ωcm.

Here, the volume distribution is as follows: volume distribution 50% diameter (D50) = 25.51, volume distribution 5% diameter (D5) = 1.
6.06 and D50 / D5 = 1.59.

(Magnetic Particle Production Example 7) A polyethylene resin having the following molecular weight distribution was coated on the magnetic particles 2 in the same manner as in the above-mentioned magnetic particle production example 6, and the volume resistance was 9 × 10 ^7.
Magnetic particles 7 of Ωcm were obtained.

The molecular weight distribution is 500 for the main peak molecular weight.
00, Mn = 9000, Mw = 140,000, Mw / M
At n = 15.6. Here, the volume distribution is D50 = 27.7.
7, D5 = 14.21, and D50 / D5 = 1.95.

(Magnetic Particle Production Example 8) By the same method as in the above-mentioned magnetic particle production example 6, 0.1 part by weight of a polyethylene resin having a peak molecular weight of 4000, 0.9 part by weight of a polyethylene resin having a peak molecular weight of 100,000 and conductive carbon of 0.1. Two
Parts were mixed and coated on the magnetic particles 3 to obtain magnetic particles 8.

Here, Mn = 130 as the whole mixed resin.
00, Mw = 370000, Mw / Mn = 28.5, volume resistance value is 5 × 10 ⁷ Ωcm, and volume distribution is D50 =
29.97, D5 = 18.68, D50 / D5 = 1.6
0.

(Magnetic Particle Production Example 9) Polyperfluoroalkylmethacrylate-polymethylmethacrylate copolymer and methylmethacrylate-having the following molecular weight distributions:
5 parts by weight of each of the butyl acrylate copolymers were mixed in a toluene-methylethylketone (1: 1) mixed solvent, and the magnetic particles 1 were coated with a spira coater to obtain magnetic particles 9 having a volume resistance of 9 × 10 ⁷ Ωcm. Obtained. Molecular weight distribution: Main peak molecular weight 28,000 polyperfluoroalkylmethacrylate-polymethylmethacrylate copolymer and peak molecular weight 3800 methylmethacrylate-butylacrylate copolymer, mixed resin Mn = 6000, Mw = 40,000, Mw / Mn =
6.7.

Here, the volume distribution is D50 = 26.11,
D5 = 16.54 and D50 / D5 = 1.57.

(Magnetic Particle Production Example 10) Magnetic particles 2 were coated with a fluororesin (polyperfluoroalkylmethacrylate-polymethylmethacrylate copolymer) having the following molecular weight distribution in the same manner as in the above-mentioned magnetic particle production example 8. ,
Magnetic particles 10 having a volume resistance of 1 × 10 ⁸ Ωcm were obtained.

Here, the molecular weight distribution is as follows: molecular weight of main peak 28,000, Mn = 6000, Mw = 65,000,
Mw / Mn = 10.8, volume distribution is D50 = 2
8.72, D5 = 17.66, D50 / D5 = 1.62
It is.

(Magnetic Particle Production Example 11) Magnetic Particle Production Example 6
In the above, except that a polyethylene resin having a peak molecular weight of 15,000 was used, the same procedure as in magnetic particle production example 6 was carried out to obtain magnetic particles 11.

Here, the volume resistance value is 8 × 10 ⁷ Ωcm, and the volume distribution is D50 = 25.35, D5 = 15.9.
2, D50 / D5 = 1.59.

(Magnetic Particle Production Example 12) A polyethylene resin having the following molecular weight distribution was coated on the magnetic particles 1 in the same manner as in the above-mentioned magnetic particle production example 6, and the volume resistance was 9 × 10.
Magnetic particles 12 having a resistance of ⁷ Ωcm were obtained.

The molecular weight distribution has a peak molecular weight of 4000, M
n = 3000, Mw = 12000, Mw / Mn = 4.0
It is.

Here, the volume distribution is D50 = 26.01,
D5 = 16.62 and D50 / D5 = 1.56.

(Magnetic Particle Production Examples 13 to 16) Cu-Zn ferrites having the following volume distribution of 50% diameter and 5% diameter were prepared.

[0093] [Production Example of Photoreceptor] (Photoreceptor Production Example 1) The photoreceptor is a photoreceptor using an organic photoconductive substance for negative charging, and each functional layer was provided on a cylinder made of aluminum having a diameter of 30 mm.

The first layer is a conductive layer and is a conductive particle-dispersed resin layer having a thickness of about 20 μm, which is provided to smooth defects such as aluminum cylinders and to prevent moire due to reflection of laser exposure. Is.

The second layer is a positive charge injection preventing layer (undercoat layer), which plays a role of preventing the positive charges injected from the aluminum support from canceling out the negative charges charged on the surface of the photoconductor, and serves as a methoxy layer. 10 ⁶ Ωc by methylated nylon
This is a middle resistance layer having a thickness of about 1 μm, the resistance of which is adjusted to about m.

The third layer is a charge generation layer, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs by being exposed to laser.

The fourth layer is a charge transport layer, which is a layer having a thickness of about 25 μm in which hydrazine is dispersed in a polycarbonate resin and is a P-type semiconductor. Therefore, the negative charges charged on the surface of the photoconductor cannot move in this layer, and only the positive charges generated in the charge generation layer can be transferred to the surface of the photoconductor.

Photosensitive material 1 (volume resistance: 2 × 10 ¹⁵ Ω
cm).

(Photoreceptor Production Example 2) In the photoreceptive production example 1, as the charge injection layer on the surface of the fourth layer, a photocurable acrylic resin, SnO ₂ ultrafine particles, and a particle size of about 0.25 μm are used.
Of the tetrafluoroethylene resin particles were dispersed.

Specifically, antimony-doped SnO ₂ particles having a resistance of about 0.03 μm and reduced in resistance are 100% by weight based on the resin, and tetrafluoroethylene resin particles are added in an amount of 2%.
0% by weight, dispersant: 2% by weight dispersed. The coating solution prepared in this way was spray coated to a thickness of about 2.5.
It was applied to a thickness of μm to form a charge injection layer.

As a result, the volume resistance value of the surface layer of the photoconductor is 4
It became × 10 ¹² Ωcm.

This is referred to as a photoconductor 2.

(Photoreceptor Manufacturing Example 3) Φ3 mirror-finished
An amorphous silicon photosensitive member including a blocking layer, a photoconductive layer, and a surface layer was prepared by using a glow discharge method in a 0 mm aluminum cylinder.

First, the reaction chamber was evacuated to about 5 × 10 ⁻³ Pa, and then various gases such as SiH ₄ , B ₂ H ₆ , NO and H ₂ were flow type on the surface of the aluminum cylinder tuned to 250 ° C. I sent it to the reaction chamber. When the internal pressure reached about 30 Pa, glow discharge was generated to form a 5 μm blocking layer.

Next, by the same method as the formation of the blocking layer, Si
₂ using H ₄ and H ₂ gas under an internal pressure of about 50 Pa
A 0 μm photoconductive layer was formed.

Further, a glow discharge was carried out using SiH ₄ , CH ₄ , and H ₂ gas under an internal pressure of about 60 Pa to form a surface layer of Si and C having a film thickness of 0.5 μm. The body was made. The surface resistance of the photoconductor is 8 × 10 ¹² Ωcm. This is designated as Photoconductor 3.

[Production Example of Toner] Styrene-butyl acrylate copolymer (copolymerization mass ratio 80:20) 100 parts by weight Magnetite 100 parts by weight Metal azo pigment 2 parts by weight Low molecular weight polypropylene 3 parts by weight The above materials are used in a Henschel mixer. After mixing in 130
The mixture was kneaded in an extruder set at ℃. The obtained kneaded product is cooled, and after roughly crushing with a cutter mill,
The mixture was finely pulverized with a jet mill using a jet stream and subjected to air classification to obtain a black fine powder (magnetic toner particles) having a weight average particle diameter of 7 μm. To 100 parts by weight of this black fine powder, 1.0 part by weight of silica powder hydrophobized with silicone oil was externally added using a Henschel mixer to obtain a magnetic toner.

[0108]

EXAMPLE In this example, the contact charging device of the present invention was incorporated in an electrophotographic apparatus equipped with a cleaning device of a reversal development system with a process speed of 100 mm / sec, and an image was formed using the toner prepared in the toner manufacturing example. The durability evaluation was performed.

Here, the electrode sleeve (φ16) as the contact charging member is made of aluminum and has a magnetic flux density of 10
A magnet roller of 00 × 10 ⁻⁴ T (Tesla) is included and rotated at a peripheral speed difference of −150% (opposing) with respect to the photoconductor (φ30 mm). The gap between the electrode sleeve and the photosensitive member was adjusted to 500 μm, and the nip width of the magnetic brush was adjusted to about 5 mm.

The voltage applied to the electrode sleeve is AC superposition (DC
-700V, 1.6kVpp), weak AC superposition (DC-7)
00V, 1.0 kVpp), injection DC (DC-700
It carried out on 3 conditions of V).

The following evaluations were performed under these conditions.

Evaluation 1 Normal image output durability (5000 sheets)
Then, the potential difference (ΔV) before and after the durability test was measured. here,
The potential difference (ΔV) is the difference between the charging saturation potential (corresponding to Vd) and the first-round charging potential, and it can be said that the smaller ΔV is with respect to the target potential Vd, the better the charging. The evaluation level was four levels.

[0113]

Evaluation 2 The durable magnetic particles of Evaluation 1 were washed with water,
The surface was magnified (electron microscope) to evaluate the spent by the developer. The evaluation was performed in four stages.

[0115]

Evaluation 3 A drum made of SUS was used in place of the photoconductor to perform idle rotation durability (no development, 10 hours).
The surface of the resin-coated magnetic particles before and after the durability test was magnified (electron microscope) to evaluate the adhesion (peel). There are four evaluation levels.

[0117]

(Examples 1 to 12) Magnetic particles shown in Table 6,
Evaluations 1, 2, and 3 were carried out based on the combination of the photoconductor and the application conditions.

[0119]

In this example, the decrease in the potential difference (ΔV) due to the durability was suppressed, and good charging could be maintained. Peeling from the magnetic particles was prevented by coating with the resin of the present invention, and among them, the magnetic particles coated with polyolefin showed the best results.

Also, good spent resistance was obtained except for Example 12 (magnetic particles 12) coated with a resin having a molecular weight (P1) outside the range of the present invention.

(Comparative Examples 1 to 4) Evaluation was made in the same manner as in Example 1 with the combinations of magnetic particles, photoconductors and application conditions shown in Table 7.
Was examined.

[0123]

In this comparative example, ΔV increases with durability,
Image fog has occurred.

[0125]

According to the present invention, a good charging potential can be obtained, and at the same time, it is possible to prevent the spent on the magnetic particles and the resin film from peeling off, so that stable image quality can be maintained for a long period of time. did it.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Fumihiro Arahira 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yoshifumi Hino 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Motoki Hisagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yuji Ishihara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. In the company

Claims (25)

[Claims] 1. A conductive member and magnetic particles supported by the conductive member, which are arranged in contact with an object to be charged, and a voltage is applied to the conductive member to charge the member to be charged. In the contact charging member, the 50% diameter of the volume distribution of the magnetic particles is 10 μm or more and 100
μm or less, the ratio of the 50% diameter of the volume distribution to the 5% diameter of the volume distribution is 1.40 or more, and the volume resistance of the magnetic particles is 1 × 10 ⁴ Ωcm or more and 1 × 10.
A contact charging member having a resistance of ¹¹ Ωcm or less. 2. The 50% diameter of the volume distribution of the magnetic particles is 10
The contact charging member according to claim 1, wherein the contact charging member has a size of not less than μm and not more than 60 μm. 3. The contact charging member according to claim 1, wherein the ratio of the 50% diameter of the volume distribution of the magnetic particles to the 5% diameter of the volume distribution is 1.55 or more and 5.00 or less. 4. The contact charging member according to claim 1, wherein the surface layer of the magnetic particles contains a resin having a main peak molecular weight P1 of a GPC chromatogram of 10,000 or more. 5. The contact charging member according to claim 4, wherein the GPC chromatogram of the resin in the surface layer of the magnetic particles has at least one peak or shoulder on the low molecular weight side of the main peak. 6. The ratio P1: P2 of the molecular weight P1 of the main peak of the GPC chromatogram of the resin of the surface layer of the magnetic particles and the molecular weight P2 of the peak or shoulder on the low molecular weight side.
Is 3: 1 to 100: 1, The contact charging member according to claim 4 or 5. 7. The molecular weight of the main peak of the GPC chromatogram of the resin of the surface layer of the magnetic particles is 30,000 to 40.
The contact charging member according to claim 4, 5, or 6, wherein the peak or shoulder on the low molecular weight side has a molecular weight of 3,000 to 30,000. 8. The weight average molecular weight Mw of the resin of the surface layer of the magnetic particles is 50,000 to 700,000, and the number average molecular weight M is
The contact charging member according to claim 4, 5, 6 or 7, wherein n is 5,000 to 50,000 and Mw / Mn is 10 or more. 9. The resin of the surface layer of the magnetic particles is at least one resin selected from at least fluorine resin, acrylic resin, silicone resin and polyolefin resin. 8. The contact charging member according to item 8. 10. The resin of the surface layer of the magnetic particles is a polyolefin resin, 4, 5, 6, 7, 8 or 9.
The contact charging member described. 11. The contact charging member according to claim 4, wherein the resin of the surface layer of the magnetic particles contains conductive particles. 12. A charging member, which has a member to be charged, a conductive member, and magnetic particles supported by the conductive member, and is placed in contact with the member to be charged, and a voltage is applied to the conductive member. In a contact charging device for charging the body to be charged by applying a magnetic field, the 50% diameter of the volume distribution of the magnetic particles is from 10 μm to 100 μm.
μm or less, the ratio of the 50% diameter of the volume distribution to the 5% diameter of the volume distribution is 1.40 or more, and the volume resistance of the magnetic particles is 1 × 10 ⁴ Ωcm or more and 1 × 10.
A contact charging device characterized by being ¹¹ Ωcm or less. 13. The 50% diameter of the volume distribution of the magnetic particles is 1
The contact charging device according to claim 12, having a size of 0 μm or more and 60 μm or less. 14. The contact charging device according to claim 12, wherein the ratio of the 50% diameter of the volume distribution of the magnetic particles to the 5% diameter of the volume distribution is 1.55 or more and 5.00 or less. 15. The contact charging device according to claim 12, wherein the surface layer of the magnetic particles contains a resin having a main peak molecular weight P1 of a GPC chromatogram of 10,000 or more. 16. The contact charging device according to claim 15, wherein the GPC chromatogram of the resin of the surface layer of the magnetic particles has at least one peak or shoulder on the low molecular weight side of the main peak. 17. The ratio P1: P of the molecular weight P1 of the main peak of the GPC chromatogram of the resin of the surface layer of the magnetic particles and the molecular weight P2 of the peak or shoulder on the low molecular weight side.
The contact charging device according to claim 15 or 16, wherein 2 is 3: 1 to 100: 1. 18. The molecular weight of the main peak of the GPC chromatogram of the resin of the surface layer of the magnetic particles is 30,000 to 4
18. The contact charging device according to claim 15, 16, or 17, wherein the peak or shoulder has a molecular weight of 3000 to 30,000 at least on the low molecular weight side. 19. The weight average molecular weight Mw of the resin of the surface layer of the magnetic particles is 50,000 to 700,000, the number average molecular weight Mn is 5,000 to 50,000, and Mw / Mn is 10.
The contact charging device according to claim 15, 16, 17 or 18, which is as described above. 20. The resin of the surface layer of the magnetic particles is at least one resin selected from at least a fluorine resin, an acrylic resin, a silicone resin and a polyolefin resin, 15, 16, 17, 18 or 19. The contact charging device described in 19. 21. The resin of the surface layer of the magnetic particles is a polyolefin resin, 15, 16, 17, 18, 1
The contact charging device as described in 9 or 20. 22. The resin of the surface layer of the magnetic particles contains conductive particles.
The contact charging device according to 9, 20, or 21. 23. The contact charging device according to claim 12, wherein the surface layer of the member to be charged is a charge injection layer. 24. The contact charging device according to claim 23, wherein the charge injection layer contains conductive particles and a binder resin. 25. The contact charging device according to claim 23, wherein the charge injection layer is an inorganic semiconductor layer.