JPH08146710A - Contact electrostatic cahrging member - Google Patents

Abstract

PURPOSE: To prevent deterioration in the lope of time in external evironments and the material and to maintain uniform conductivity for a long time without variation in the resistance by incorporating hydroxides of alkali metals or hydroxides of alkaline earth metals into a contact charging member. CONSTITUTION: The roller type contact electrostatic charging member consists of a core metal 1a and an elastic layer 1b, resistance layer is 1e, conductive layer 1d, and surface layer 1c formed on the core metal 1a. Hydroxides of alkali metals or alkaline earth metals may be added to any layers of this contact electrostatic charging member. In this case, various kinds of additives may be added according to the purpose of the layer to be used. For example, for a conductive layer, carbon black, inorg. oxide, ionic conductive material, or surfactant is added as a conductivity imparting agent to control the resistance. For the resistance layer, insulating pigments or the like is added to stabilize the resistance. For the surface layer, an additive to improve the surface characteristics is added.

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 used in an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art As a charging member for electrophotography, a contact charging member which is charged by directly contacting a photosensitive member recently can be used at a lower applied voltage as compared with a corona charging method which has been conventionally used. It is recognized that it has advantages such as low ozone generation and low ozone generation. Therefore, as described in, for example, JP-A-63-167380 and JP-A-3-59683, many contact charging members using various resins have been proposed. However, when these resins are used as a charging member and a discharge is repeated by applying a DC voltage or a voltage in which an AC voltage is superimposed on a DC voltage, nitrogen oxides are adsorbed on the surface of the charging member, although the amount is smaller than in the corona charging method. Then, it reacts with moisture in the air to produce nitric acid. Therefore, the pH of the surface of the charging member is lowered, the polarity of the surface is strengthened, and a slight change is given to the physical properties of the discharge surface, so that the electric resistance of the charging member becomes unstable, which may cause an image defect. Become.

As described above, at present, there is no charging member which is satisfactory in terms of durability for keeping the conductivity uniform for a long period of time and environmental stability not affected by any environmental conditions.

An object of the present invention is to solve the above problems, and to provide a contact charging member which prevents deterioration of the external environment and materials over time, has no resistance fluctuation, and maintains uniform conductivity for a long period of time. is there.

[0005]

That is, the present invention is a contact charging member containing at least one kind of alkali metal hydroxide or alkaline earth metal hydroxide.

The present invention also provides one or more alkali metal hydroxides or alkaline earth metal hydroxides, and N
The above-mentioned contact charging member containing an alkoxymethylated nylon.

Further, the present invention is the above-mentioned contact charging member containing one or more kinds of alkali metal hydroxides or alkaline earth metal hydroxides, an organic acid, and N-alkoxymethylated nylon.

The present invention will be described in detail below.

The contact charging member of the present invention may have any shape such as a roller, a blade or a belt. Further, even if the contact charging member is in contact with the photoconductor, the gap between the photoconductor and the photoconductor is 100.
You may install in the position which is 0 micrometer or less and what is called non-contact proximity charging is possible.

As the layer structure of the charging member, for example, in the case of a roller, as shown in FIG. 1, an elastic layer, a resistance layer, a conductive layer, a surface layer, etc. are provided around a core metal according to each purpose. , The layers can be combined in any order. 2 shows an example of an image forming apparatus using the charging member of the present invention.

The alkali metal hydroxide or alkaline earth metal hydroxide, organic acid, and N-alkoxymethylated nylon may be used in any of the layers. In that case, depending on the purpose of the layer used, various additives can be added, for example, for resistance adjustment in the case of a conductive layer,
Various carbon blacks, inorganic oxides, ionic conductive substances, surfactants and the like may be used as conductivity-imparting agents, and an insulating pigment or the like may be added as appropriate to stabilize the resistance of the resistance layer. Further, if it is a surface layer, an additive for improving the surface property can be added.

Examples of the binder resin for the charging member include resins such as polyacetal, polyacrylate, polyamide, polyurethane, polyethylene, polyolefin, polysiloxane, polystyrene, polyvinyl, polybutadiene and fluorine compounds, EPDM, IR, BR and SB.
Examples thereof include rubbers such as R, chloroprene, and nitrile. N-alkoxymethylated nylon is preferable, and methoxymethylated 6 nylon is more preferable.

N-alkoxymethylated nylon is 6-
A compound having a structure in which various polyamides such as nylon, 12-nylon and 6,6-nylon are reacted with formaldehyde and alcohol such as methanol, ethanol, propanol and butanol, and hydrogen of the amide bond is substituted with an alkoxy group. Examples include methylated nylon, ethoxymethylated nylon, propoxymethylated nylon and butoxymethylated nylon. These N-
Alkoxymethylated nylon desorbs alcohol by an acid catalyst to cause a crosslinking reaction to form a three-dimensional structure. If this cross-linking proceeds too much, problems such as a marked increase in resistance and abnormal conductivity due to environmental changes become problems.

When this resin is used as a charging member and a discharge is repeated by applying a DC voltage or a voltage in which an AC voltage is superimposed on a DC voltage, nitrogen oxide is adsorbed on the surface of the charging member,
When an acid is generated by the reaction with water in the air, the pH is lowered like usual resins, the polarity of the surface is strengthened, and the acid acts as a catalyst to promote the crosslinking reaction. for that reason,
The electric resistance is further increased and destabilized, which causes a serious image defect.

Therefore, it is possible to suppress the progress of cross-linking by previously adding a hydroxide of an alkali metal or an alkaline earth metal to the resin to neutralize the acid. Since the other surface properties are constant, there can be provided a charging member having excellent durability and environmental stability.

Further, in the case of forming a surface layer using an alkoxymethylated nylon, it is often the case that if the crosslinking is allowed to proceed uniformly to some extent, the resistance in the surface layer will be uniform, so It is also possible to add a fixed amount of organic acid to stabilize the physical properties. Even in that case, if the above-mentioned metal hydroxide is added, the cross-linking does not proceed too much, and the resistance can be further stabilized. Examples of the organic acid include citric acid, itaconic acid, glutaric acid, adipic acid, azelaic acid, oxalic acid, succinic acid, glycolic acid, malonic acid, crotonic acid, maleic acid, lactic acid, tartaric acid, phosphite, and the like. Preferably citric acid,
Tartaric acid and succinic acid, and more preferably citric acid.

Alkali metal hydroxides or alkaline earth metal hydroxides include LiOH, NaOH and KO.
H, RbOH, CsOH, FrOH, Be (OH) ₂ ,
Mg (OH) ₂ , Ca (OH) ₂ , Sr (OH) ₂ , B
Hydroxides of alkali metals or alkaline earth metals which are usually used such as a (OH) ₂ and Ra (OH) ₂ , and preferably Ca (OH) ₂ , Ba (OH) ₂ and Mg (OH)
₂ The metal of these hydroxides has a low electronegativity and a strong reducing property, so it reacts with the nitric acid generated on the surface of the charging member by the heat at the time of discharge, is oxidized by itself, and removes the acid from the surface of the charging member. It is possible to Furthermore, since this reaction permeates each layer and diffuses into the other layers, the alkali metal or alkaline earth metal hydroxide, organic acid, and N-alkoxymethylated nylon are respectively used in the charging member. Even if it is used as an internal layer, its effect is not impaired.

These metal hydroxides are added to a binder resin and formed into a roller type, a blade type, a belt type or the like by using the same or different arbitrary materials, and the elastic layer of the charging member, preferably the surface layer, The charging member is formed by a method such as spray coating, dipping coating, or printing. The addition amount is preferably 0.1 with respect to the resin solid content.
-20 parts by weight, more preferably 1-10 parts by weight.

At this time, the volume resistance value of the charging member is preferably in the range of 0.1 MΩcm or more and less than 100 MΩcm, more preferably 1 MΩcm or more and less than 10 MΩcm.

[0020]

EXAMPLES Examples of the present invention will be shown below, but the conditions such as the combination of materials, the constitution and the evaluation method are not limited to the following. (Example 1) As a charging member, 100 parts by weight of SBR rubber was melt-kneaded with 5 parts by weight of conductive carbon black, and a stainless steel shaft having a diameter of 6 mm x 260 mm was formed at the center to form a charging member base layer. Next, a resin solution was prepared by adding 2 parts by weight of calcium hydroxide and 20 parts by weight of titanium oxide to 15 parts by weight of methoxymethylated 6 nylon and 85 parts by weight of methanol. The solution was applied onto the charging member base layer by dipping and dried to form a surface layer having a film thickness of 100 μm, and a roller-shaped charging member was manufactured.

As an evaluation method, a laser beam printer (trade name: Laser Shot A408, manufactured by Canon Inc.) was used, and the developing DC bias of the printer body was set to -4.
00V, a DC voltage of -550V for setting the surface potential of the drum to -700V, and an AC voltage of -1.2Kvpp were applied, and 4000 durable images were printed. The results are shown in Table 1.

(Example 2) A surface layer of a charging member was prepared by adding 100 parts by weight of an ether urethane prepolymer, 20 parts by weight of TDI and a necessary amount of piperazine to a resin solution containing 3 parts by weight of sodium hydroxide and 10 parts by weight of carbon black. A charging member was manufactured in the same manner as in Example 1 except that the charging member was formed.

As an evaluation method, a monocolor copying machine (trade name: NP6030, manufactured by Canon Inc.) was used, and the developing DC bias of the copying machine main body was -250V and the surface potential of the drum was -680V DC voltage -1400V. As a result, 60,000 durable images were printed. The results are shown in Table 1.

Example 3 The same as Example 1 except that the charging member surface layer was formed by a resin solution in which 3 parts by weight of barium hydroxide and 30 parts by weight of tin oxide were added to 100 parts by weight of dimethylpolysiloxane. A charging member was manufactured and evaluated in the same manner as in Example 2. The results are shown in Table 1.

Example 4 A charging member was manufactured in the same manner as in Example 1 except that the charging member surface layer was formed by adding 2 parts by weight of citric acid to prepare a resin solution. The same evaluation was performed. The results are shown in Table 1.

(Comparative Example 1) A charging member was manufactured in the same manner as in Example 1 except that calcium hydroxide was not added to the resin solution, and evaluation was carried out under the same conditions as in Example 1. The results are shown in Table 1.

(Comparative Example 2) A charging member was manufactured in the same manner as in Example 2 except that sodium hydroxide was not added to the resin solution, and evaluation was performed under the same conditions as in Example 2. The results are shown in Table 1.

[0028] Evaluation: 〇 No abnormality × Fogging (impossible)

[0029]

EFFECTS OF THE INVENTION The contact charging member of the present invention can prevent changes in the physical properties of the surface due to the formation of a trace amount of nitrogen oxide, and can maintain uniform conductivity and environmental stability. An image is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a roller-type contact charging member of the present invention.

FIG. 2 is a schematic configuration diagram of an image forming apparatus using the contact charging member of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contact charging member 1-a Core metal 1-b Elastic layer 1-c Surface layer 1-d Conductive layer 1-e Resistance layer 2 Photoconductor 3 Developing unit 4 Transfer unit 5 Cleaning unit 6 Power supply 7 Transfer material

Claims (3)

[Claims] 1. A contact charging member comprising one or more alkali metal hydroxides or alkaline earth metal hydroxides. 2. The contact charging member according to claim 1, which contains one or more kinds of alkali metal hydroxides or alkaline earth metal hydroxides and N-alkoxymethylated nylon. 3. The contact charging member according to claim 1, which contains one or more kinds of alkali metal hydroxides or alkaline earth metal hydroxides, an organic acid, and N-alkoxymethylated nylon.