JP3024730B2 - Charging member and electrophotographic apparatus - 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 for charging an electrophotographic photosensitive member, such as primary charging, transfer charging and static elimination, and an electrophotographic apparatus having the same.

[0002]

2. Description of the Related Art Recently, in a charging process in an electrophotographic process using an electrophotographic photosensitive member, a contact charging system such as a charging roller, a transfer roller, and a charge removing roller has been devised and put into practical use. This method is characterized in that it has a lower voltage and a lower concentration of corona products such as ozone generated than the conventional corona charging method.

[0003]

However, even though the contact charging member has a lower ozone concentration than the corona charger, about 0.1 to 5 ppm of ozone is generated. Therefore also occur discharge products such as NO _X. The ozone product often adheres to the surface of a contact charging member, for example, a charging roller or a transfer roller, or oxidizes or decomposes a material of a surface layer to alter the quality.
This deterioration of the surface layer has a risk of lowering the function (resistance value, surface roughness, etc.) of the contact charging member, and causes poor charging of the photoconductor. Therefore, in long-term use, there is a risk of causing an image defect due to a decrease in the function of the contact charging member.

In the case of recycling, if such a function is deteriorated, the charging member is reused (used as it is).
Can not do it.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to prevent such a contact charging member from being deteriorated in function due to ozone and discharge products.

[0006] In particular, the discharge products such as ozone and NO _X generated in the discharge generated during the charging, the surface of the contact charging member is to prevent the oxidation and decomposition.

That is, the present invention provides a charging member for charging by contacting the surface of an object to be charged, wherein at least the surface layer of the charging member contains a phenolic compound and a phosphite compound. It is a member.

[0008] Further, the present invention provides a phenolic compound,
The charging member is one kind selected from a monophenol compound, a bispolyphenol compound, a tris polyphenol compound, a thiobisphenol compound, and a hindered phenol compound.

Further, the present invention provides a photosensitive member, a latent image forming means,
In an electrophotographic apparatus having a unit for developing a formed latent image and a unit for transferring a developed image to a transfer material, a charging member used for a primary charging process of a photoreceptor as the latent image forming unit, or a transfer member in the transfer unit. An electrophotographic apparatus characterized in that the charging member is used as a charging member used for processing.

The phenolic compound and the phosphite compound contained in the contact charging member are so-called antioxidants.

Both compounds are dissolved, dispersed or kneaded in the surface layer material of the contact charging member and contained. In order to prevent the functional deterioration of the contact charging member, the combined use of the phenol compound and the phosphite compound is more synergistic than the use of the phenol compound alone.

The addition amount of both compounds is preferably in the range of 0.1% by weight to 30% by weight with respect to the solid content of the surface layer material. Can be determined as appropriate.

When the amount is less than 0.1% by weight, the effect of preventing oxidation deterioration is small, and when the amount exceeds 30% by weight, adverse effects such as deterioration in film formability and moldability of the surface layer material and decrease in mechanical strength of the coating film occur. It will be easier.

Examples of the monophenolic compound include 1-hydroxy-3-methyl-4-isopropylbenzene,
2,6-di-t-butylphenol, 2,6-di-t-
Butyl-4-ethylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-
4-sec-butylphenol, butylhydroxyanisole, 2- (1-methylcyclohexyl) -4,6-
Dimethylphenol, 2,6-t-butyl-α-dimethylamino-p-cresol, and the like.

As the bispolyphenol compound, 2,
2'-methylenebis (4-methyl-6-t-butylphenol), 2,2-methylenebis (4-cyclohexylphenol), 2,2'-methylenebis (4-ethyl-
6-t-butylphenol), 4,4'-methylenebis (2,6-di-t-butylphenol), 2,2'-methylenebis (6-alphamethyl-benzyl-p-cresol), 4,4'-butylidenebis (6-t-butyl-m-cresol), 2,2'-ethylidenebis (4,
6-di-t-butylphenol), 1,1'-bis (4
-Hydroxyphenyl) cyclohexane, 2,2'-dihydroxy-3,3'-di (α-methylclohexyl)
-5,5'-dimethyldiphenylmethane and the like.

The trispolyphenol compounds include:
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate,
2-tert-butyl-3,5,6-tris (3'-tert-butyl-5'-methyl-2'-hydroxybenzyl) -4-
Methylphenyl acrylate and the like can be mentioned.

As the thiobisphenol-based compound,
4,4'-thiobis (6-t-butyl-3-methylphenol), 4,4'-thiobis (6-t-butyl-O-
Cresol), 4,4'-dithiobis (2,6-di-t
-Butylphenol), 4,4'-trithiobis (2,
6-di-t-butylphenol), bis (3,5-di-
t-butyl-4-hydroxybenzyl) sulfide and the like.

The hindered phenol compounds include:
1,1,3-tris (2-methyl-4-hydroxy-5
-T-butylphenyl) butane, 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 2,
2-thiobis (4-methyl-6-t-butylphenol), n-octadecyl-3- (4'-hydroxy-
3 ', 5'-di-t-butylphenyl) propionate, tetrakis [methylene-3- (3', 5'-di-t
-Butyl-4'-hydroxyphenyl) propionate] methane, triethylene glycol-bis [3- (3
-T-butyl-5-methyl-4-hydroxyphenyl)
Propionate], 6- (4-hydroxy-3,5-di-t-butylanilino) -2,4-bisoctyl-
Thio-1,3,5-triazine, tris (3,5-di-
(t-butyl-4-hydroxybenzyl) isocyanurate and the like.

The above-mentioned phenol compound alone has an effect on the change in the function of the contact charging member such as the shape of a roller, but the effect is synergistically improved when the following phosphite-based compounds are simultaneously added. .

Examples of the phosphite compound include tris (nonylphenyl) phosphite, phenyldiisodecyl phosphite, diphenyl mono (2-ethylhexyl) phosphite, diphenyl monotridecyl phosphite, diphenyl isodecyl phosphite, and diphenyl isophenyl. Octyl phosphite, diphenyl nonyl phenyl phosphite, triphenyl phosphite, tris (tridecyl) phosphite, triisodecyl phosphite, tris (2-ethylhexyl) phosphite, tris (2,4-di-t-butylphenyl) Phosphite,
Tetraphenyldipropylene glycol diphosphite, tetraphenyltetra (tridecyl) pentaerythritol tetraphosphite, 1,1,3-tris (2
-Methyl-4-di-tridecylphosphite-5-t-
Butylphenyl) butane, 4,4'-butylidenebis (3-methyl-6-t-butyl-di-tridecylphosphite), 2,2'-ethylidenebis (4,6-t-butylphenol) fluorophosphite, 4,4'-isopropylidene - diphenol alkyl (C ₁₂ ~C ₁₅₎
Phosphite, cyclic neopentanetetraylbis (2,
4-di-t-butylphenylphosphite), cyclic neopentanetetraylbis (2,6-di-t-butylmethylphenylphosphite), cyclic neopentanetetraylbis (nonylphenylphosphite), bis (nonyl) (Phenyl) pentaerythritol diphosphite, dibutyl hydrogen phosphite, distearyl pentaerythritol diphosphite and the like.

Examples of the surface layer material of the contact charging member include conductive polymer materials such as polyacetylene, polypyrrole, polyaniline, and polythiophene, and synthetic resins and synthetic rubbers containing conductive powder and metal powder.

For example, as the synthetic resin, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyamide, polyurethane, polyester and the like can be used. In addition, thermoplastic elastomers such as polyolefin, polyester, polyurethane, polyamide, and polystyrene can be used. Further, examples of the synthetic rubber include SBR, BR, chloroprene rubber, hydrin rubber, acrylic rubber, silicone rubber, EPDM, and the like.

On the other hand, conductive powders such as conductive carbon, carbon graphite, conductive titanium oxide, conductive tin oxide, and conductive silicon oxide are used as the conductive powder, and gold, silver, copper, nickel, aluminum, and the like are used as the metal powders. chromium,
Tin and the like.

The contact charging member can be manufactured by providing a single layer of the synthetic resin or synthetic rubber containing the additive on a conductive substrate. It may be possible to produce an inner layer made of a plastic elastomer and a surface layer made of the synthetic resin or synthetic rubber containing the additive into two or three layers.

The resistance value of the contact charging member is 1 × 10
^The resistance is preferably ⁴ Ω to 1 × 10 ¹⁰ Ω. 1 × 10 ⁴
If it is less than Ω, when damage such as pinholes occurs on the surface of the photoconductor, current concentrates on that portion, and so-called “charge loss” may occur.

On the other hand, if it exceeds 1 × 10 ¹¹ Ω, the applied voltage may drop, and the discharge may not be performed uniformly, making it difficult to uniformly charge the surface of the photoreceptor.

The shape of the charging member may be a roller shape, a blade shape, a flat plate shape, or the like.

Examples of the conductive substrate include iron, copper, stainless steel, etc., and the surface may be plated for the purpose of rust prevention.

The resistance value of the contact charging member is measured as follows. As shown in FIG. 2, an aluminum foil 50 having a width of 1 cm was wound on the surface layer 2b of the contact charging member, and 250 V was applied using the cored bar 2a and the aluminum foil as electrodes, and the current value after one minute was applied. Is measured by the ammeter 51 to calculate the resistance value.

As the applied voltage in the present invention, a DC voltage or a voltage obtained by superimposing an AC voltage on a DC voltage is used. When an AC voltage is superimposed on a DC voltage, an AC peak-to-peak voltage (V _pp ) twice or more the DC voltage value is used. Thereby, the surface of the photoconductor can be stably charged.

An electrophotographic photosensitive member has a basic configuration in which a photosensitive layer is provided on a conductive support. As the conductive support, a support having conductivity itself, for example, aluminum, an aluminum alloy, stainless steel, chromium, titanium, or the like can be used. In addition, aluminum, an aluminum alloy, an indium oxide-tin oxide alloy, or the like can be used. The above-mentioned conductive support having a layer formed by vacuum evaporation, plastic, a support obtained by impregnating plastic or paper with conductive particles (eg, carbon black, tin oxide particles, etc.) together with an appropriate binder, conductive Plastic having a binder or the like can be used.

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer. The undercoat layer is casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide,
It can be formed of polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is 5 μm or less, preferably 0.5 to 3 μm. The undercoat layer desirably has a resistivity of 10 ⁷ Ω · cm or more in order to exhibit its function.

The photosensitive layer is formed, for example, by coating a photoconductor such as an organic photoconductor, amorphous silicon, or selenium together with a binder, if necessary, by coating or vacuum deposition. When an organic photoconductor is used, a photosensitive layer composed of a combination of a charge generation layer that generates charge carriers by exposure and a charge transport layer that has the ability to transport the generated charge carriers can be effectively used.

The charge generation layer is formed by depositing one or more charge generation materials such as azo pigments, quinone pigments, quinocyanine pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, phthalocyanine pigments, and quinacdrine pigments. Alternatively, it can be formed by dispersing with a suitable binder (or even without a binder) and coating.

The binder can be selected from a wide range of insulating resins or organic photoconductive polymers. For example, as the insulating resin, polyvinyl butyral, polyarylate (condensed polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, acrylic resin, polyacrylamide resin, polyamide, cellulose resin, urethane resin, epoxy resin, Casein, polyvinyl alcohol and the like can be mentioned. Examples of the organic photoconductive polymer include carbazole, polyvinyl anthracene, and polyvinyl pyrene.

The thickness of the charge generation layer is 0.01 to 15 μm,
It is preferably 0.05 to 5 μm, and the weight ratio of the charge generation layer to the binder is 10: 1 to 1:20.

The solvent used for the coating for the charge generating layer is selected from the solubility and dispersion stability of the resin and the charge transporting material used. Examples of the organic solvent include alcohols, sulfoxides, ethers, esters, and fatty acids. An aromatic halogenated hydrocarbon or an aromatic compound can be used.

The coating can be performed by a coating method such as a dip coating method, a spray coating method, a Meyer bar coating method and a blade coating method.

The charge transport layer is formed by dissolving a charge transport material in a resin having a film forming property. Examples of the organic charge transporting material used in the present invention include a hydrazone compound,
Examples include stilbene compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, and triarylmethane compounds. These charge transport materials are 1
They can be used alone or in combination of two or more.

Examples of the binder used for the charge transport layer include:
Phenoxy resin, polyacrylamide, polyvinyl butyral, polyarylate, polysulfone, polyamide,
Acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenolic resin, epoxy resin, polyester, alkyd resin, polycarbonate, polyurethane or a copolymer containing two or more of repeating units of these resins, for example Styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and the like can be mentioned. It can also be selected from organic photoconductive polymers such as -N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene.

The charge transport layer has a thickness of 5 to 50 μm, preferably 8 to 20 μm, and the weight ratio of the charge transport material to the binder is 5: 1 to 1: 5, preferably 3: 1 to 1: 5. It is about 3. The coating can be performed by the coating method as described above.

Further, dyes, pigments, organic charge transporting substances and the like are generally stained by ultraviolet rays, ozone, oil, etc.
A protective layer may be provided as necessary because it is weak against metals and the like. In order to form an electrostatic latent image on the protective layer, the surface resistivity is desirably 10 ¹¹ Ω or more.

The protective layer that can be used in the present invention includes polyvinyl butyral, polyester, polycarbonate,
Acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer and the like dissolved in a suitable organic solvent to apply a liquid on the photosensitive layer, It can be formed by drying. At this time, the thickness of the protective layer is generally in the range of 0.05 to 20 μm. The protective layer may contain an ultraviolet absorber or the like.

The charging member of the present invention can be applied to, for example, an electrophotographic apparatus as shown in FIG. In this apparatus, a roller-shaped charging member 2, an image exposure unit 3, a developing unit 4, a transfer charging unit 6, a separation charging unit 7, a cleaning unit 8, and a pre-exposure unit 10 are arranged on a peripheral surface of an electrophotographic photosensitive member 1. ing.

A voltage (for example, 200 V) is applied from an external power supply 11 to the charging member 2 in contact with the electrophotographic photosensitive member 1.
DC voltage of 2000 V or less and peak-to-peak voltage 4000
The surface of the electrophotographic photosensitive member 1 is charged, and the image on the original is image-exposed on the photosensitive member by the image exposure means 3 to form an electrostatic latent image. Next, the electrostatic latent image on the photoconductor is developed (visualized) by attaching the developer in the developing unit 4 to the photoconductor, and the developer on the photoconductor is transferred by the transfer charging unit 6. The developer is transferred to a transfer member such as paper that has passed through the paper feed roller and the paper feed guide 5, and the developer remaining on the photoconductor without being transferred at the time of transfer by the cleaning unit 8 is collected. On the other hand, the member to be transferred is separated by the separating and charging means 7 and sent to a fixing unit (not shown) by the transport unit 9.

An image can be formed by such an electrophotographic process. However, if residual charge remains on the photosensitive member, the photosensitive member is exposed to light by the pre-exposure means 10 before primary charging. It is better to remove the charge.

[0047]

The present invention will be described below with reference to examples. (Example 1) EPDM compound 100 parts by weight Carbon black (Ketjen black) 5 parts by weight Paraffin oil 10 parts by weight Dicumyl peroxide 2 parts by weight The above materials were kneaded with two rolls for 30 minutes (roll temperature 20 ° C). ), A raw material compound was prepared.

Using this compound, a conductive rubber layer was formed around a stainless steel core (outer diameter 6 mm) by transfer molding. Then, the roller was heated at 160 ° C. for 3 hours.
Vulcanized by heating for hours. (Roller outer diameter 12 mm, rubber length 225 mm, conductive rubber layer, resistance value 1 × 10 ⁴ Ω,
(23 ° C., 55% RH) On this conductive rubber layer, the following resin solution was applied to form a surface layer. (Drying conditions, 120 ° C., 1 hour, film thickness after drying 10 μm) N-methoxymethylated polyamide 10 parts by weight Ketjen black 0.2 part by weight Phenol compound A 0.1 part by weight Tris (2 0.1 parts by weight of 4-di-t-butylphenyl) phosphite 90 parts by weight of methanol At this time, the phenolic compound A was variously changed to produce a roller. The rollers were 1, 2, 3, 4, and 5, respectively.

This roller was used as a charging roller and incorporated into a laser printer (Laser Shot A404, manufactured by Canon) to endure 10K sheets of image at 15 ° C. and 10% environment. Was evaluated. The image was evaluated for the presence or absence of a “fog image” caused by poor charging due to an increase in the resistance value of the charging roller. Table 1 shows the results.

[0050]

[Table 1]

Example 2 A roller was manufactured in the same manner as in Example 1 except that the composition of the surface layer was changed as follows.

N-methoxymethylated polyamide 10 parts by weight Ketjen black 0.2 part by weight 1-oxy-3-methyl-4-isopropylbenzene 0.1 part by weight Phosphite compound B 1 part by weight-90 parts by weight of methanol At this time, a roller was manufactured by variously changing the phosphite-based compound B. The rollers were 6, 7, 8, and 9, respectively.

In the same manner as in Example 1, an image durability test was performed at 15 ° C. in a 10% environment, and resistance value measurement and image evaluation were performed. Table 2 shows the results.

[0054]

[Table 2]

Comparative Example 1 A roller was produced in the same manner as in Example 1 except that the composition of the surface layer was changed as follows.

N-methoxymethylated polyamide 10 parts by weight Ketjen black 0.2 part by weight Phenol compound C 0.2 part by weight Methanol 90 parts by weight A roller was manufactured by shaking the phenolic compound. The rollers were 10, 11, 12, 13, 14, and 15, respectively.

In the same manner as in Example 1, an image durability test was performed under an environment of 15 ° C. and 10% RH to measure a resistance value and evaluate an image. Table 3 shows the results.

[0058]

[Table 3]

Comparative Example 2 A roller was produced in the same manner as in Example 1 except that the composition of the surface layer was changed as follows.

10 parts by weight of N-methoxymethylated polyamide 0.2 parts by weight of Ketjen black 0.2 parts by weight of phosphite compound D 90 parts by weight of methanol As in Example 1, 15 ° C. An image durability test was performed in a 10% RH environment, and a resistance value measurement and an image evaluation were performed.
Table 4 shows the results.

Rollers were manufactured by variously changing the phosphite compound D. Rollers 16, 17, 1
8, and 19.

[0062]

[Table 4]

[0063]

As shown in the present invention, by containing a phenolic compound and a phosphite compound in the surface layer of the charging member, deterioration (resistance change) due to ozone generated during discharge and discharge products. Can be suppressed,
A stable image can be obtained. Therefore, the service life of the charging member can be extended, and the charging member can be reused.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electrophotographic apparatus.

FIG. 2 is a schematic diagram illustrating a method for measuring a resistance value of a charging roller.

DESCRIPTION OF SYMBOLS 1 Photoconductor (electrophotographic photoconductor) 2 Charging roller (charging member) 3 Image exposure unit 4 Developing unit 5 Feed guide 6 Transfer charging unit 7 Separation charging unit 8 Cleaning unit 9 Conveying unit 10 Pre-exposure unit 11 Power supply

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-86765 (JP, A) JP-A-4-866764 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02-15/02 103 G03G 15/16-15/16 103 G03G 21/06 F16C 13/00

Claims (4)

(57) [Claims] 1. A charging member for charging by contacting a surface of an object to be charged, wherein at least a surface layer of the charging member contains a phenol compound and a phosphite compound. 2. The charging member according to claim 1, wherein the phenolic compound is one selected from a monophenolic compound, a bispolyphenolic compound, a trispolyphenolic compound, a thiobisphenolic compound, and a hindered phenolic compound. . 3. An electrophotographic apparatus comprising a photosensitive member, a latent image forming unit, a unit for developing the formed latent image, and a unit for transferring the developed image to a transfer material, wherein the latent image forming unit includes a primary charging unit for the photosensitive member. 2. A charging member used for a process, or a charging member used for a transfer charging process in the transfer unit.
An electrophotographic apparatus using the charging member according to any one of the preceding claims. 4. An electrophotographic apparatus having a photosensitive member, a latent image forming unit, a unit for developing a formed latent image, and a unit for transferring a developed image to a transfer material, wherein the latent image forming unit includes a primary charging unit for the photosensitive member. 3. A charging member used for the processing, or a charging member used for the transfer charging process in the transfer unit.
An electrophotographic apparatus using the charging member according to any one of the preceding claims.