JP3382386B2 - Contact type charging member and contact type charging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type charging member and a contact type charging device mainly used in an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus such as an electrophotographic copying machine or printer, an electrostatic recording device, etc., is a primary charging means for charging an image carrier, and a transfer for attracting a developer on the image carrier onto a material to be printed. It includes means for uniformly charging the body to be charged, such as means. As a charging method used at that time, a contact charging method, which produces a significantly smaller amount of ozone than the conventional corona charging method, has been studied, and recently it has been partially put into practical use.

The contact charging method is a method in which a charging member to which a voltage is applied is brought into contact with a member to be charged to charge the member to be charged, but the discharge phenomenon that occurs in a minute gap near the contact portion is used. It is common to charge the body to be charged by means of Also,
When the applied voltage is constant, the amount of charge on the member to be charged is determined by the distance between the charging member and the member to be charged, that is, the minute gap amount.

Therefore, in the case of contact charging, either the charging member or the member to be charged must be brought into contact with a predetermined pressing force as an elastic member in order to keep the minute gap constant.
Generally, the charging member is an elastic body. When the charging member is an elastic body, the use of a plasticizer is indispensable in order to give the elastic body a desired hardness. However, when the elastic body is brought into direct contact with the body to be charged, foreign matter (toner, paper dust, etc.) on the body to be charged is transferred to the surface of the charging member due to the adhesiveness of the exuded plasticizer, and the charging is performed. There is a problem that performance is significantly deteriorated. In addition, there is a concern that the exuded additive such as a plasticizer may contaminate the body to be charged.

Therefore, as the contact type charging member, the elastic body is covered with a binding material in order to seal the exudation from the elastic body, that is, at least the elastic layer and the surface layer in contact with the charged body. It is common that the surface layer is composed of layers, and the surface layer is composed of a binding material. As the binding material used for the surface layer, polyurethane, from the viewpoint of economy and versatility,
A resin such as polyamide is often used.

Further, the charging member has its original purpose of maintaining the charged body at a predetermined potential, and therefore, the conductive pigment is dispersed in the binder material of the surface layer to have its electric resistance within a certain range. It is important to control to. For this resistance control, a fine particle type conductive material such as carbon black, tin oxide or titanium oxide is usually used. Regarding carbon black, the powder resistance is 10 ^-2 Ωcm and the particle size is 0.
About 0.2 μm, and for tin oxide, titanium oxide, etc., the powder resistance is 10 ¹ to 10 ² Ωcm, and the particle diameter is 0.2 μm.
In many cases, those of about m are used.

[0007]

However, the contact type charging device using the above-mentioned conductive elastic body with a surface layer as a charging member has the following problems.

When only a DC voltage is applied to the contact type charging member, there is a problem that minute resistance unevenness existing in the surface layer of the charging member directly becomes a slight charging unevenness on the body to be charged.

The surface layer is generally formed by a dry film of a coating material in which the fine particle type conductive material is added to and dispersed in a binder material. However, since the fine particle-type conductive material is likely to cause re-aggregation, sedimentation, etc. after the dispersion treatment and has poor stability in the paint, the fine particle-type conductive material in the surface layer tends to have uneven distribution and density. Uniformity causes uneven resistance of the charging member. Therefore, the superimposed voltage is applied to eliminate the charging unevenness that occurs on the body to be charged. The superimposed voltage is an applied voltage obtained by superimposing an AC voltage having a peak-to-peak voltage that is about twice the charging start voltage when the DC voltage is applied to the charging member on the DC voltage. This is a means for eliminating uneven charging. However, the addition of an AC power source to eliminate the uneven charging causes an increase in the cost of the device.

Further, depending on the temperature and humidity environment in which the contact type charging member is used, there is a problem that the binding material such as polyurethane and polyamide used for the surface layer absorbs moisture and electric characteristics are changed. Therefore, the charging performance may vary greatly depending on the usage environment.Therefore, the applied voltage is changed by a control means such as constant current control to make the charge amount of the charged body constant. The addition of control means and the like increases the cost of the device.

The object of the present invention is to obtain the above resistance unevenness,
An object of the present invention is to provide a contact-type charging member that does not fluctuate in the electrical characteristics of the environment, thereby providing an inexpensive contact-type charging device.

[0012]

The contact type charging member of the present invention is configured to have at least a conductive substrate, a conductive elastic layer and a surface layer in contact with the charged body, and to apply a voltage to the charged body. In a contact-type charging member that charges an object to be charged by applying a voltage, the binding material of the surface layer is a hydrophobic sheet.
A recone based binder material, the surface layer is at least
A layer provided by applying a coating material containing the silicone- based binder material and a particulate conductive material onto the conductive elastic layer, wherein the silicone-based binder material contains a silicone resin.
The fine particle-type conductive material has an average primary particle size of 0.5 μm or more and 5 μm or less and a powder resistance of 10 ⁻² Ωcm or more.
^{6 Ωcm} I der below, as a core material of barium sulfate
A contact charging member, characterized in Rukoto such from those forming a conductive film on the surface.

The contact type charging device of the present invention is a contact type charging device in which a voltage is applied to a conductive substrate of a charging member to charge an object to be contacted with the charging member, wherein the charging member is the above-mentioned one. It is a contact type charging device having a configuration and features.

FIG. 1 is a schematic configuration diagram of an image forming apparatus (copier) using the charging device according to the present invention. A sectional view of an example of the charging member used in the present invention is shown in FIG.

The charging member (2) is a cored bar (2a) which is a conductive substrate to which an oscillating voltage such as a DC voltage or a superimposed voltage of a DC voltage and an AC voltage is applied from a power source (3), and a conductive member which imparts elasticity. Elastic layer (2b), a coating layer (2d) which is a surface layer in contact with the body to be charged, and the resistance control layer (2c) for controlling the resistance of the charging member is an elastic layer (2).
It is provided outside of b). The charging member (2) is in contact with the body to be charged (1) with a predetermined contact force by a pressing means (not shown). In the image forming apparatus of FIG.
The charging member (2) and the member to be charged (1) rotate in the directions of the respective arrows, and the photosensitive layer (1a) of the member to be contacted by the charging member (2) is charged by the voltage applied by the power source (3). Then, it becomes an image on the photosensitive layer (1a) through the exposure step (4) and the developing step (5), and the transferred image is formed on the printing object (7) in the transfer step (6). (8) shows a cleaning step of the photosensitive layer (1a).

As the silicone-based binder material contained in the surface layer, any of condensation reaction type, addition reaction type and peroxide curing reaction type silicone resins can be used. If necessary, alkyd or polyester may be used in the reaction. , Epoxy,
A modified resin copolymerized with an organic resin such as urethane or acrylic may be used. Of course, these resins may be used alone or in combination of two or more kinds. These silicone-based binder materials are hydrophobic, and the environmental stability of the charging member using such a material is extremely good. Also,
It has a large contact angle with water, and is characterized in that contaminants such as paper powder and toner hardly adhere to it.

The conductive material added to and dispersed in the silicone-based binder material and contained in the surface layer has an average primary particle diameter of 0.5 μm or more and 5 μm or less, preferably 0.5 μm or more and 3 μm or less, and powder. Resistance is 10 ^-2 Ωcm or more 10
⁶ [Omega] cm or less, preferably 10 ⁰ [Omega] cm or more 10 ³ .omega.c
A particulate conductive material having a particle size of m or less can be used. The primary particle size refers to the particle size of the conductive material particles added before being dispersed in the silicone binder.

As the fine particle type conductive material, there are conductive materials made of metal oxides such as titanium oxide, tin oxide and zinc oxide, conductive materials made of spherical carbon material, etc., which may be used alone or in combination of two or more kinds. Good. Further, in order to stabilize the particle diameter, it is also possible to use a fine particle type conductive material having a core material of barium sulfate or the like and a conductive coating film of tin oxide or the like formed on the surface thereof. When the average primary particle diameter is 0.5 μm or less, secondary aggregation after dispersion treatment occurs and resistance unevenness is likely to occur. When the average primary particle size is 5 μm or more, contact failure due to surface roughness occurs, and uneven charging of the body to be charged easily occurs. In addition, deterioration of image quality due to uneven charging due to discharge concentration is likely to occur.
When a conductive material having a powder resistance of 10 ^-2 Ωcm or less, for example, a metal powder such as nickel, copper, or zinc is used, the resistance unevenness due to the resistance difference with the resin becomes large and the image quality is deteriorated due to the charging unevenness. Easy to invite. When the powder resistance is 10 ⁶ Ωcm or more, the effect of addition is small and it becomes difficult to adjust the resistance.
Therefore, the average primary particle size of 0.5μm or more 5μm or less, preferably and at 0.5μm or more 3μm or less, the powder resistance, 10 ^-2 [Omega] cm or more 10 ⁶ [Omega] cm or less, preferably 10 ⁰ [Omega] cm or more 10 ³ [Omega] cm or less The surface layer obtained by adding and dispersing the fine particle-type conductive material to the silicone-based binder provides a contact type charging member with less resistance unevenness due to secondary aggregation after the dispersion treatment and resistance unevenness due to the resistance difference with the resin. It became possible to do. Further, when the contact type charging member is brought into contact with the body to be charged (1) with a predetermined pressing force and a voltage is applied from the core metal (2a), the contact type charging member has a contact failure due to surface roughness. It has become possible to provide a contact-type charging device capable of charging the charged body (1) with less charging unevenness due to the above and less charging unevenness due to discharge concentration.

The specific volume resistivity of the contact type charging member of the present invention is preferably in the range of 10 ² Ωcm to 10 ¹⁰ Ωcm. If the volume resistivity is less than 10 ² Ωcm, pinhole leakage occurs due to dielectric breakdown. If it exceeds 10 ¹⁰ cm, the discharge point is decreased due to the increase in surface resistance, and sandy-like charging failure occurs.

The shape of the contact type charging member is preferably a roller shape for practical use.

In the contact type charging device of the present invention, since the charging member is constructed as described above and brings about the effects as described above, the voltage applied to the conductive substrate is a DC voltage or an AC voltage. It may be an oscillating voltage such as a superposed voltage of DC voltage and DC voltage, and in any case, the excellent effect of the present invention can be exhibited. Even if only the DC voltage for which the AC power supply is abolished, an image having the same level of uniformity as in the past can be obtained, so that the cost can be reduced. When the weight voltage is used, a higher definition image can be obtained as compared with the conventional one.

[0022]

EXAMPLES The contact type charging member and the contact type charging device of the present invention will be described in detail below with reference to examples.

Example 1 I. Creation of elastic layer: silicone rubber (100 parts by weight),
Zinc oxide (5 parts by weight), conductive carbon black (7 parts by weight) and industrial paraffin (20 parts by weight) were thoroughly mixed and kneaded using a closed mixer, and then dicumyl peroxide (2 (Parts by weight) was added to prepare an elastic layer compound. This elastic layer compound is placed on a stainless steel core bar with a diameter of 10 mm at 150 ° C.
Was vulcanized by heating for 15 minutes to prepare a silicone rubber roller having an elastic layer with a thickness of 3 mm.

II. Preparation of coating material for coating layer: condensation reaction type silicone resin (100 parts by weight), catalyst (6 parts by weight), tin oxide-coated barium sulfate (primary particle size = 0.7 μm)
m, powder resistance = 10 ¹ Ωcm, 120 parts by weight) and DM
F (420 parts by weight) was kneaded using a small bead mill to prepare a coating material for the coating layer.

III. Preparation of charging member: The coating material for the coating layer was applied by dipping onto the silicone rubber roller and left to dry at room temperature for 1 day to obtain a charging member having a coating layer with a thickness of 10 μm. The volume resistivity of this charging member was measured and found to be 1.5 × 10 ⁶ Ωcm.

IV. Evaluation of charging member: The charging member was attached to the position of the primary charger of an analog copying machine (NP2020, manufactured by Canon Inc.), and the initial image evaluation and durability test were performed at 23 ° C / 5% and 23 ° C at an applied voltage of -1800 VDC. / 60
% And 30 ° C./80% RH. In addition, the leak test was performed in an environment of 30 ° C./80% RH. The results are shown in Table 1.

Comparative Example 1 I. Preparation of elastic layer: Same as in Example 1.

II. Preparation of coating material for coating layer: polyamide resin (100 parts by weight), catalyst (6 parts by weight), tin oxide-coated barium sulfate (primary particle size = 0.7 µm, powder resistance = 10 ¹ Ωcm, 30 parts by weight) , Methanol (100 parts by weight) and toluene (300 parts by weight) were kneaded using a small bead mill to prepare a coating material for the coating layer.

III. Preparation of charging member: The coating material for the coating layer was dip-coated on the silicone rubber roller, and
By heating and drying at 0 ° C. for 2 hours, a charging member having a coating layer with a thickness of 10 μm was obtained. The volume resistivity of this charging member was measured and found to be 2.5 × 10 ⁶ Ωcm.

IV. Evaluation of charging member: The above charging member was subjected to initial image evaluation, durability test and leak test under the same conditions as in Example 1. The results are shown in Table 1.

Example 2 I.D. Preparation of elastic layer: Same as in Example 1.

II. Preparation of coating material for coating layer: addition reaction type silicone resin (100 parts by weight), catalyst (10 parts by weight), tin oxide-coated barium sulfate (primary particle size = 0.7 μm)
m, powder resistance = 10 ¹ Ωcm, 200 parts by weight) and DM
F (420 parts by weight) was kneaded using a small bead mill to prepare a coating material for the coating layer.

III. Preparation of charging member: The coating material for the coating layer is applied by dipping onto the silicone rubber roller, and
A charging member having a coating layer having a thickness of 11 μm was obtained by heating and drying at 0 ° C. for 20 minutes. The volume resistivity of this charging member was measured and found to be 2.8 × 10 ⁶ Ωcm.

IV. Evaluation of charging member: The above charging member was subjected to initial image evaluation, durability test and leak test under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Example 2 I.D. Preparation of elastic layer: Same as in Example 1.

II. Preparation of coating material for coating layer: condensation reaction type silicone resin (100 parts by weight), catalyst (6 parts by weight), titanium oxide (primary particle size = 0.04 µm, powder resistance = 10 ¹ Ω)
cm, 120 parts by weight) and DMF (420 parts by weight) were kneaded using a small bead mill to prepare a coating material for the coating layer.

III. Preparation of charging member: The coating material for the coating layer was applied by dipping onto the silicone rubber roller and left to dry at room temperature for 1 day to obtain a charging member having a coating layer with a thickness of 10 μm. The volume resistivity of this charging member was measured and found to be 1.8 × 10 ⁶ Ωcm.

IV. Evaluation of charging member: The above charging member was subjected to initial image evaluation, durability test and leak test under the same conditions as in Example 1. The results are shown in Table 1.

[0039]

[0040]

[0041]

[0042]

Comparative Example 3 I. Preparation of elastic layer: Same as in Example 1.

II. Preparation of coating material for coating layer: condensation reaction type silicone resin (100 parts by weight), catalyst (6 parts by weight), carbon black (primary particle size = 0.02 μm, powder resistance = 1)
0 ⁻² Ωcm, 5 parts by weight) and DMF (420 parts by weight) were kneaded using a small bead mill to prepare a coating material for the coating layer.

III. Preparation of charging member: The coating material for the coating layer was applied by dipping onto the silicone rubber roller and left to dry at room temperature for 1 day to obtain a charging member having a coating layer with a thickness of 10 μm. The volume resistivity of this charging member was measured and found to be 1.1 × 10 ⁶ Ωcm.

IV. Evaluation of charging member: The above charging member was subjected to initial image evaluation, durability test and leak test under the same conditions as in Example 1. The results are shown in Table 1.

Example 3 I.D. Preparation of elastic layer: Same as in Example 1.

II. Preparation of paint for resistance control layer: hydrin rubber (100 parts by weight), ethylenethiourea (2 parts by weight), lead oxide (5 parts by weight), fatty acid metal salt (2.5 parts by weight) and titanium oxide (primary particle size = 0) 0.02 μm, powder resistance = 10 ¹ Ωcm, 60 parts by weight) was kneaded for 20 minutes while cooling with an open roll to prepare a compound. This compound was diluted with toluene and dissolved to prepare a hydrin rubber paint having a solid content of 5% as a paint for the resistance control layer.

II '. Preparation of coating material for coating layer: Same as in Example 1.

III. Preparation of charging member: The resistance control layer coating material (hydrin rubber coating material) was dip-coated on the silicone rubber roller and heated and dried at 160 ° C. for 1 hour to obtain a charging member having a resistance control layer having a thickness of 105 μm. It was Next, the coating material for coating layer (silicone resin coating material) was applied onto the charging member by dip coating, and left to dry at room temperature for 1 day to obtain a charging member having a coating layer with a thickness of 10 μm. When the volume resistivity of this charging member was measured, it was 1.4 × 10 ⁶ Ωcm.

IV. Evaluation of Charging Member: The charging member was subjected to initial image evaluation, durability test and leak test under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Example 4 I. Preparation of elastic layer: Same as in Example 1.

II. Preparation of paint for resistance control layer: Same as in Example 3.

II '. Preparation of coating material for coating layer: Same as Comparative Example 2.

III. Preparation of charging member: The resistance control layer coating material (hydrin rubber coating material) was dip-coated on the silicone rubber roller and heated and dried at 160 ° C. for 1 hour to obtain a charging member having a resistance control layer having a thickness of 105 μm. It was Next, the coating material for coating layer (silicone resin coating material) was applied onto the charging member by dip coating, and left to dry at room temperature for 1 day to obtain a charging member having a coating layer with a thickness of 10 μm. The volume resistivity of this charging member was measured and found to be 2.1 × 10 ⁶ Ωcm.

IV. Evaluation of Charging Member: The charging member was subjected to initial image evaluation, durability test and leak test under the same conditions as in Example 1. The results are shown in Table 1.

Example 4 The charging member prepared in Example 3 was used as an analog copying machine (NP).
Installed at the position of the primary charger of 2020, manufactured by Canon Inc., DC voltage -750VDC, AC voltage 1500Vpp
23 ° C / 5 for initial image evaluation and durability test with applied voltage of
%, 23 ° C./60% and 30 ° C./80% RH. Also. The leak test was conducted in an environment of 30 ° C./80% RH. The results are shown in Table 1.

Comparative Example 5 The charging member prepared in Comparative Example 4 was subjected to the initial image evaluation, durability test and leak test under the same conditions as in Example 4. The results are shown in Table 1.

[0059]

[Table 1]

[0060]

Since the contact type charging member of the present invention is excellent in environmental stability, it is possible to provide an inexpensive contact type charging device which does not require correction means such as current detection means and voltage control means. Further, since the contact type charging member of the present invention can suppress resistance unevenness to be small, it is possible to provide an inexpensive contact type charging device that does not require a charge leveling means such as an AC power source.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus using a contact type charging device according to the present invention.

FIG. 2 is a sectional view showing an example of a contact type charging member of the present invention.

[Explanation of symbols] 1 Charged member (image bearing member) 1a conductive substrate 1b Photosensitive layer 2 charging member 2a conductive substrate 2b elastic layer 2c Resistance control layer 2d coating layer 3 power supplies 4 exposure process 5 Development process 6 Transfer process 7 Printed material 8 cleaning process

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-6-250437 (JP, A) JP-A-64-66675 (JP, A) JP-A-3-101766 (JP, A) JP-A-6- 221321 (JP, A) JP-A-6-186825 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 103

Claims (7)

(57) [Claims] 1. A contact type having at least a conductive substrate, a conductive elastic layer, and a surface layer in contact with a body to be charged, which contacts the body to be charged and applies a voltage to charge the body to be charged. In the charging member, the binding material for the surface layer is a hydrophobic silicone-based binding material.
A is, the surface layer is a layer provided by coating at least a coating material containing a microparticles based conductive material of the silicone-based binder material on the conductive elastic layer, the silicone-based binder material , A silicone resin, and the fine particle-based conductive material has an average primary particle size of 0.5 μm or more 5
μm or less and powder resistance of 10 ^-2 Ωcm or more and 10 ⁶ Ω
cm it der below, its surface as a core material of barium sulfate
Contact charging member, characterized in Rukoto such from those forming a conductive film on. 2. The contact type charging member according to claim 1, wherein the volume resistivity of the contact type charging member is 10 ² Ωcm or more and 10 ¹⁰ Ωcm or less. 3. The contact type charging member according to claim 1, wherein the contact type charging member has a roller shape. 4. A contact type charging device according to claim 1, wherein in the contact type charging device for applying a voltage to the conductive substrate of the charging member to charge the charged body with which the charging member contacts. A contact type charging device characterized in that 5. The contact type charging device according to claim 4, wherein the means for applying the voltage is means for applying only a DC voltage. 6. The contact type charging device according to claim 4, wherein the means for applying the voltage is means for applying an oscillating voltage. 7. The contact type charging device according to claim 4, wherein the means for applying the voltage is means for applying a superimposed voltage of an AC voltage and a DC voltage.