JPH046567A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To maintain a stable function and to prevent deterioration of an electrifying member and a photosensitive body by utilizing the electrifying member with density maintained in the range of 35 deg.C to 55 deg.C. CONSTITUTION:The organic photosensitive body 1 for laser shots, the electrifying member 2 to carry out electrification directly, a developing device 4, a paper feeding roll and a paper feeding guide 5, a transfer electrifying device 6, and a cleaner 7 are provided. Then, the electrifying process where the photosensitive body surface is electrified by impressing voltage by bringing the electrifying member 2 in contact with the electrophotographic photosensitive body 1 is utilized, and this is carried out with the temperature of the electrifying member 2 maintained within the range of 35 deg.C to 55 deg.C. Thus, the stable electrifying characteristic against variation in environment such as the temperature or humidity is maintained and the influence of ozone, etc., is reduced.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic method in which charging is performed by bringing a charging member into contact with an electrophotographic photoreceptor, and more specifically, the present invention relates to an electrophotographic method in which charging is performed by bringing a charging member into contact with an electrophotographic photoreceptor. This invention relates to an electrophotographic method that performs stable charging by maintaining high temperatures.

[Prior Art] Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide are known as photoconductive materials used in electrophotographic photoreceptors. These photoconductive materials have a number of advantages, such as being able to be charged to an appropriate potential in the dark, having little charge dissipation in the dark, or being able to quickly dissipate the charge when irradiated with light. On the other hand, it has various drawbacks. For example, in selenium-based photoreceptors, crystallization easily progresses due to factors such as temperature, humidity, dust, and pressure. Especially when the ambient temperature exceeds 40°C, crystallization occurs significantly, resulting in decreased charging properties and white images. It has the disadvantage of causing spots. Cadmium sulfide photoreceptors have the disadvantage that stable sensitivity cannot be obtained in humid environments. Furthermore, zinc oxide photoreceptors require the sensitizing effect of sensitizing dyes such as rose bengal.
Such sensitizing dyes have the disadvantage that they cannot provide stable images over a long period of time because they cause charging deterioration due to charging and photobonding due to exposure light.

On the other hand, it has been discovered that certain organic compounds exhibit photoconductivity. For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene, and low-molecular organic photoconductor bakaphthalocyanine pigments such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkanes. Organic pigments and dyes such as , azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes, and methine squaric acid dyes are known. In particular, many photoconductive organic pigments and dyes have been proposed because they are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded. . For example, U.S. Patent Nos. 4123270, 4251613, and 4251
No. 614, No. 4256821, No. 4260672
Disazo pigments that exhibit photoconductivity as a charge-generating substance in a photosensitive layer that is functionally separated into a charge-generating layer and a charge-transporting layer, as disclosed in Japanese Patent No. 4268596, No. 4278747, and No. 4293528. Electrophotographic photoreceptors using the same are known.

In the charging process in an electrophotographic process using such an electrophotographic photoreceptor, a high voltage (DC 5 to 8 kV) is applied to a metal wire, and charging is performed using generated corona. However, with this method, when corona occurs, corona products such as ozone and NOx alter the surface of the photoreceptor, causing image blurring and deterioration, and dirty wires affect image quality, resulting in white spots and black lines in the image. There were some problems such as:

On the other hand, in terms of electric power, the current flowing to the photoreceptor is 5 to 30
%, and most of it flowed to the shield plate, making it inefficient as a charging means.

In order to compensate for these drawbacks, direct charging methods have been researched and many proposals have been made (Japanese Patent Laid-Open No. 57-178
No. 267, No. 56-104351, No. 5g-4056
No. 6, No. 58-139156, No. 58-150975
No. etc.).

[Problems to be Solved by the Invention] However, in reality, even when a photoreceptor is charged by the contact charging method as described above, each part of the surface of the photoreceptor is not uniformly charged, resulting in spot-like charging unevenness.

In particular, the charging characteristics change due to changes in the environment, and at low temperatures, uniform charging is not achieved and uneven charging becomes severe. In addition, even in the contact charging method, discharge occurs during charging, which is 1/l O to 1/10 lower than in the case of corona charging.
Ozone, NOx, etc. are generated, although the amount is small (0). Ozone and N
Ox and the like deteriorate the photoreceptor and the charging member.

An object of the present invention is to provide an electrophotographic method that solves the above-mentioned drawbacks, maintains stable charging characteristics even with changes in the environment such as temperature and humidity, and is less susceptible to the effects of ozone, etc. It is in.

[Means for Solving the Problems] The electrophotographic method of the present invention uses a charging process in which the surface of the photoreceptor is charged by bringing a charging member into contact with the electrophotographic photoreceptor and applying a voltage. The method is characterized in that the temperature of the charging member is maintained in the range of 35°C to 55°C.

The method of direct charging in the electrophotographic method of the present invention is not limited to a specific method. The shapes of charging members include rollers, brushes (including magnetic brushes), blades,
It may be of any shape, such as a belt, and can be selected according to the specifications and form of the electrophotographic apparatus. Also, as the material of this charging member, metals such as aluminum, iron, copper;
Conductive polymer materials such as polyacetylene, polypyrrole, and polythiophene; Rubber and artificial fibers treated to be conductive by dispersing carbon, metal, etc.; Or insulating materials such as polycarbonate, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and acrylic resin. A material whose surface is coated with metal or other conductive material can be used. The resistivity of these charging members brought into contact with the electrophotographic photoreceptor is preferably in the range of 10 DEG to 10'2 ΩCm, and optimally 10'' to 10I0 Ω·cm, from the viewpoint of good charging, insulation, and destruction prevention.

In addition, in order to reduce the voltage drop caused by excessive current flowing when the electrophotographic photoreceptor has defects such as dielectric breakdown, the surface layer of the charging member is made of a material with a volume resistivity such as alkoxymethylated nylon. 106~1012Ω・c
It is also possible to have a multilayer structure with about m resin layers. In particular, when a conductive polymer material, alkoxymethylated nylon, or the like is used, charging characteristics tend to deteriorate in a low-temperature environment, so the present invention is effective in preventing this.

In the electrophotographic method of the present invention, the method of installing the charging member that is brought into contact with the electrophotographic photoreceptor is not limited to a specific method, and the charging member may be fixed, or may be placed in the same direction or opposite to the electrophotographic photoreceptor. It may be installed using any method of movement, such as rotation in direction, etc. Furthermore, it is also possible for the charging member to function as a toner cleaning device on the electrophotographic photoreceptor.

The voltage applied to the charging member by direct charging in the electrophotographic method of the present invention may be either direct current or alternating current, or may be applied in the form of superimposing alternating current on direct current. Furthermore, the application method depends on the specifications of each electrophotographic device, but in addition to the method of instantaneously applying the desired voltage, there is also a method of increasing the applied voltage in stages for the purpose of protecting the electrophotographic photoreceptor. If the voltage is applied in the form of direct current and alternating current superimposed, a method can be adopted in which the voltage is applied in the order of direct current-alternating current or alternating current-direct current. In order to uniformly charge each part of the surface of the electrophotographic photoreceptor and to prevent spot-like charging unevenness, it is preferable to apply a superimposed alternating current to a direct current.

When direct current is applied in the form of superimposed alternating current, the current increases and more products such as ozone and NOx are generated than when direct current is applied, resulting in deterioration of the electrophotographic photoreceptor and charging member. The present invention is more effective in preventing this from occurring.

In recent years, copying machines, laser printers, etc. have become faster, and in the case of high process speeds (peripheral speed of the electrophotographic photoreceptor), it is necessary to uniformly charge the surface of the electrophotographic photoreceptor. The current increases, resulting in ozone, N
A large amount of Ox, etc. is generated, which tends to cause deterioration of the electrophotographic photoreceptor and charging member, and also makes it susceptible to changes in the charging characteristics of the charging member. The present invention is effective in preventing this, and is particularly effective when the peripheral speed (process speed) of the electrophotographic photoreceptor is 40 mm/sec or more.

The temperature of the charging member is suitably in the range of 35°C to 55°C. This is because if the temperature is below 35°C, the effect of improving low-temperature properties will be weak, and if it exceeds 55°C, there will be a problem of the developer (toner) that has slipped through the cleaner adhering to the charging member and the electrophotographic photoreceptor. This is because it comes.

By heating the charging member to a temperature of 35° C. to 55° C., charging failures can be prevented in low-temperature, low-humidity environments, and stable performance can be maintained even under environmental changes. In addition, by heating the temperature between 35°C and 55°C, ozone and NOx generated by discharge can be prevented from adhering to the belt and heavy-duty parts, promoting decomposition, and contaminating charging parts and electrophotographic photoreceptors. , deterioration can be prevented.

In the electrophotographic method of the present invention, any means can be used to heat the charging member as long as the temperature can be kept within the above range. For example, near the charging member,
Alternatively, a method of providing a heat source inside the charging member, or a means of heating the charging member using heat from a heat fixing device or the like as a heat source may be adopted. The temperature may be adjusted using a known temperature adjusting member such as a thermostat.

The electrophotographic photoreceptor in the electrophotographic method of the present invention is Se,
It may be an inorganic photoreceptor such as CdS or amorphous silicon, or an organic photoreceptor. For example, in the case of an organic photoreceptor, a metal such as aluminum, aluminum alloy, or stainless steel is used as the conductive support; a metal coated with a conductive substance alone or with an appropriate binder to form a conductive layer; Any conventionally known material can be used, such as a drum-shaped or sheet-shaped material made of plastic or paper.

The charge generation layer contains a charge generation substance such as an azo pigment, a quinone pigment, a quinocyanine pigment, a perylene pigment, an indigo pigment, or a phthalocyanine pigment, and a binding resin such as polyvinyl butyral, polystyrene, acrylic resin, polyester, polyvinyl acetate, or polycarbonate. It can be formed by dispersing and containing the film, or it can also be formed as a vacuum deposited film using a vacuum deposition apparatus. The thickness of the charge generation layer is preferably 0.01 to 3 μm.

The charge transport layer contains charge transport substances such as styryl compounds, hydrazone compounds, triarylamine compounds, carbazole compounds, oxazole compounds, and pyrazoline compounds, and polyarylates, polystyrene, acrylic resins, polyesters, polycarbonates, etc. It can be formed by being dispersed in a binding resin. The preferred thickness of the charge transport layer is 10 to 30 μm.

Further, the structure of the photosensitive layer is such that the charge generation layer and the charge transport layer are laminated in this order, or vice versa. Alternatively, it may be a single layer type in which the charge generating material and the charge transporting material described above are contained together. Furthermore, an intermediate layer such as a subbing layer may be provided between the conductive support and the photosensitive layer in order to improve adhesiveness and barrier properties.

Furthermore, dyes, pigments, organic charge transport substances, and the like are generally susceptible to ultraviolet rays, ozone, stains caused by oil, and metals, so a protective layer may be provided as necessary. In order to form an electrostatic tide image on this protective layer, the surface resistivity must be IQIIΩ・
It is desirable that the value is 0111 or more.

The protective layer used in the present invention is made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-
The photosensitive layer can be formed by applying a solution prepared by dissolving a resin such as an acrylic acid copolymer or a styrene-acrylonitrile copolymer in a suitable organic solvent onto the photosensitive layer and drying it. At this time, the thickness of the protective layer is generally 0.05 to 20 μm.
is within the range of This protective layer may contain an ultraviolet absorber or the like.

Organic photoreceptors produce less ozone and NOx than inorganic photoreceptors.
The present invention is particularly effective in preventing this.

The electrophotographic method of the present invention can be widely used not only in copying machines but also in electrophotographic application fields such as laser printers, LED printers, CRT printers, and electrophotographic plate making systems.

[Examples] Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Examples 1, 2.3 and Comparative Example 1.2 Canon laser beam printer [Laser Shot LB
P-A408] was modified as shown in FIG. In FIG. 1, 1 is an organic photoreceptor for laser shot, 2 is a charging member for direct charging, 3 is a semiconductor laser exposure member,
4 is a developing device, 5 is a paper feed roller and a paper feed guide, 6 is a transfer charger, 7 is a cleaner, and 8 is a pre-exposure.

2 is a charging member used for direct charging in the electrophotographic method of the present invention, which is made by melting and kneading 100 parts by weight of chloropyrene rubber with 5 parts by weight of conductive carbon, passing a stainless steel shaft through the center, and molding. It was used as a charging member. Further, a heat source 9 was provided near the charging member. The process speed of the laser beam printer was 47 mm/see.

The temperature of the charging member was changed to 35°C, 40°C, and 50°C. Table 1 shows the initial potentials, initial images, and images after 5000 sheets in various temperature environments. Comparative example 1
Similar evaluations were made for those that did not use heating means.

As shown in Table 1, when the charging member was heated to 35 DEG C. to 50 DEG C., good initial images and 5,000-sheet durable images were obtained in each environment.

On the other hand, the one shown as Comparative Example 1 without the heating means had poor charging ability at low temperature and low humidity, resulting in poor charging.
Sand-like black spots appeared on the image.

Even in an environment of 23° C. and 60%, the charging property deteriorates due to durability.

Comparative Example 2, in which the charging member was heated to 60° C., was similarly evaluated, but the toner that had slipped through the cleaner was fused onto the charging member and the electrophotographic photoreceptor from the beginning.

Example 4 and Comparative Example 3 Evaluation was carried out in the same manner as in Example 1, except that the charging member used in Example 1 was replaced with the one below and the temperature of the charging member was heated to 40°C. Ta.

As a charging member, 100 parts by weight of chloroprene rubber and 10 parts by weight of conductive carbon were melt-kneaded, and a stainless steel shaft was passed through the center to form the base layer. Next, 10 parts by weight of methoxymethylated nylon was mixed with methanol. Dissolved in 90 parts by weight and dip coated on the base layer,
The film used was dried to a film thickness of 100 μm.

As Comparative Example 3, a sample was evaluated in which a similar charging member was used but no heating means was used.

As shown in Table 2, in Example 4, good performance was obtained in each environment both at the initial stage and in the 5,000-sheet durability test, but in Comparative Example 3, in which no heating means was provided, charging performance was poor at low temperature and low humidity. () Due to charging failure, sandy black spots appeared on the image.The level of this was worse than that of Comparative Example 1.

Example 5.6 and Comparative Example 4.5 Canon laser beam printer used in Example 1 [
Lasershot LBP-A408] was modified to increase the process speed to 2 OrIrn/sec, 90+am/s
ec was used, and the same evaluation as in Example 4 was carried out, resulting in Examples 5 and 6, respectively. Further, comparative examples 4 and 5 were prepared without a heating means, respectively.

As shown in Table 3, it can be seen that the effect of the present invention is even greater when the process speed is high. That is, when the process speed is 90 mm/see, the charging characteristics at low temperatures in Comparative Example 5 become worse, and even in high-temperature environments, under conditions outside the range of the present invention, the photoreceptor deteriorates and the density decreases. The image flow is getting worse. Further, even in a 23° C., 60% environment, the deterioration of the charging member due to durability and the deterioration of charging characteristics are worse as the process speed is faster. On the other hand, in Examples 5 and 6 according to the present invention, good images were obtained in each environment and even at high process speeds.

[Effect of the invention] As explained above, the concentration of the charging member is set at 35°C to 55°C.
Stable performance can be maintained if the temperature is maintained within the temperature range. Further, deterioration of the charging member and the photoreceptor can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus used in the electrophotographic method of the present invention. In the figure, l is an organic photoreceptor for laser shots, 2 is a charging member, 3 is a semiconductor laser exposure, 4 is a developing device, 5 is a paper feed roller and paper feed guide, 6 is a transfer charger, 7 is a cleaner, 8 is pre-exposure, and 9 is a heat source.

Claims (2)

[Claims] (1) In an electrophotographic method that uses a charging process in which a charging member is brought into contact with an electrophotographic photoreceptor and a voltage is applied to charge the surface of the photoreceptor, the temperature of the charging member is set at 35°C to 55°C. An electrophotographic method characterized by maintaining and performing within a range. (2) The electrophotographic method according to claim 1, wherein the charging process is carried out at a peripheral speed of the electrophotographic photoreceptor of 40 mm/sec or more.