JPH06295108A - Electrophotographic recording method - Google Patents

Abstract

(57) [Abstract] [Purpose] A recording method in which only the insulating toner is stably developed in the developer used for the optical backside exposure recording method, and sufficient image density, low fog, and good image quality are obtained. provide. In the optical backside exposure recording method, the developer is a mixture of a conductive magnetic carrier and an insulating toner, and the conductive magnetic carrier is saturated at an average particle size of 15 to 30 μm and an external magnetic field of 10 kOe. An electrophotographic recording method, which is a substantially spherical carrier having a magnetization of 50 emu / g or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording method, and more particularly, to an optical backside recording method for exposing a photosensitive member to a developer and at the same time performing image exposure from the inside of the photosensitive member.

[0002]

2. Description of the Related Art In the Carlson system, which is a general electrophotographic method, a photoconductive photoconductor is uniformly charged with corona ions and then imagewise exposed to form an electrical latent image on the photoconductor. Then, the latent image is developed with toner, the toner image is transferred to a transfer material such as paper, if necessary, and then fixed by means of heating / pressing to obtain a copy.

Normally, a corona charger is used for charging the photosensitive member and electrostatically transferring toner, but the corona charger has a problem that ozone other than corona ions is generated, which adversely affects the human body. Therefore, in recent years, a roller charging method and a roller transfer method have been devised and put into practical use. In this method, a voltage is applied while the conductive roller or the dielectric roller is in contact with the photoconductor, so that there is an advantage that excessive discharge is suppressed and ozone is hardly generated.

Further, the optical backside exposure recording system has been proposed as a system having no special charging device. In this system, the photoconductor is charged by the developing bias applied to the developer in contact with the photoconductor, image exposure is performed by the exposure device installed inside the photoconductor, and the image is developed by the developer described above. And the charging / exposure
Development is performed almost at the same time. For this reason, a charging device such as a charging charger and a charging roller and a high-voltage power supply unit associated therewith are not required, and therefore, not only ozone is not generated, but also the device can be downsized.

However, in this optical backside exposure recording system, since it is necessary to charge the photoconductor by the bias voltage applied to the developer, it is necessary to make the volume resistivity of the developer relatively low. However, if a conductive toner is used for that reason, there are problems that the image density becomes insufficient and the transferability after development is deteriorated.

In order to solve this problem, JP-A-63-1
395969 and Japanese Patent Laid-Open No. 63-214781 disclose that a mixture of a conductive magnetic toner and an insulating magnetic toner is used as a developer to obtain sufficient image density, transferability and good image quality.

However, when the developer having such a structure is used, not only the insulating magnetic toner but also the conductive magnetic toner is developed by electrostatic induction, so that it is necessary to replenish the mixture of both toners. There is also a problem that the mixing ratio of both toners to be consumed changes depending on environmental conditions such as temperature / humidity. Further, the conductive magnetic toner is also developed, so that the transferability to the paper is deteriorated.

In order to solve the above problems, it is effective to make the conductive magnetic toner into a carrier so that it is not developed (only the insulating toner is developed). When the particle diameter is about 5 to 15 μm, the influence of electrostatic induction is stronger than the magnetic force, and the particles are transferred to the photoconductor. Therefore, if the particle diameter of the conductive resin carrier is set to 15 μm or more and the saturation magnetization is increased, the transfer of the carrier to the photoconductor can be prevented.

However, if the particle size of the carrier is increased, the frequency of contact of the carrier particles with the photosensitive member decreases, so that it becomes difficult to uniformly charge the photosensitive member, resulting in deterioration of image quality and increase of fog. It will be.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and in the developer used in the optical backside exposure recording system, only the insulating toner is stably developed, and it is sufficient. An object of the present invention is to provide a recording method capable of obtaining image density, low fog, and good image quality.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, in which a developing sleeve having a magnetic member disposed therein brings a developer into contact with the surface of the photoconductor and, at the same time, the interior of the photoconductor. In an optical backside exposure recording system in which an image is formed by performing image exposure, the developer is a mixture of a conductive magnetic carrier and an insulating toner, and the conductive magnetic carrier has an average particle size of 15 to The electrophotographic recording method is characterized in that the carrier is a substantially spherical carrier having a saturation magnetization of 50 emu / g or more at 30 μm and an external magnetic field of 10 kOe.

In the present invention, a resin carrier in which magnetic powder is dispersed in resin is applied as an example of the conductive magnetic carrier. The resin carrier is obtained by a so-called spray drying method in which magnetic powder and a binder resin are dispersed in a solvent and then sprayed and dried in hot air. It can also be obtained by dispersing magnetic powder in a resin monomer and carrying out suspension polymerization. Further, the magnetic powder and the binder resin may be melt-kneaded by heat, mechanically crushed, and spheroidized by hot air. Also,
A spherical iron powder or ferrite powder coated with a conductive material may be used. In the carrier particles used in the present invention, a conductive material such as carbon black may be dispersed inside or adhered / fixed to the surface in order to adjust the volume resistivity. In the present invention, in the case of a resin carrier, as a means for increasing the saturation magnetization to 50 emu / g or more,
This can be achieved by 1) increasing the content of magnetic powder, and 2) blending magnetic powder with high saturation magnetization. Further, the iron powder carrier has a saturation magnetization of 50 emu / g or more, and the ferrite carrier can have a saturation magnetization of 50 emu / g or more by selecting the composition.

The insulating toner of the present invention is preferably an insulating non-magnetic toner or an insulating magnetic toner used in a general two-component developing system.

The optical backside exposure recording method used in the present invention is, as shown in FIG. 1, a developing device 2 having a magnetic sleeve 1.
And a photosensitive member 3 having a transparent conductive layer, an exposure unit 4 installed inside the photosensitive member, a developer transfer unit 5, a fixing unit 7, and the like. The developer contained in the developing device 2 is conveyed by the magnetic sleeve 1 and comes into contact with the photoconductor 3 having a transparent conductive layer. At this time, the photoconductor 4 is charged to a predetermined surface potential by the bias voltage applied to the magnetic sleeve 1. Almost at the same time, image exposure is performed from the inside of the photoconductor 3 by the exposure unit 4, and the triboelectrically charged toner is developed on the image portion. The developed toner is transferred to the transfer material (transfer paper) 6 by the developer transfer means 5 and fixed by the fixing means 8 to obtain an image.

[0015]

In the recording method of the present invention, since a substantially spherical carrier is used, the fluidity of the developer is improved and the potential distribution of the photoconductor charged by the developing bias can be made uniform. Further, since the average particle diameter is 15 μm or more and the saturation magnetization is 50 emu / g or more, the carrier is held on the magnetic developing sleeve and does not transfer to the photoreceptor. If the average particle size of the carrier is 15 μm or less, a so-called carrier rising phenomenon occurs in which the carrier is also developed on the photosensitive member by electrostatic induction, while if it exceeds 30 μm, the carrier density on the sleeve surface becomes coarse and the image quality deteriorates. To do. The average particle diameter in the present invention is based on the volume-based 50% diameter measured by the Coulter counter method.

The conductive magnetic carrier used in the recording method of the present invention preferably has a resistance low enough to charge the photosensitive member by a bias voltage. Although it depends on the distance between the developing sleeve and the photoconductor, the proper volume resistivity is about 10 ² to 10 ⁵ Ω · cm. The volume resistivity, the main electrode area under a load of 200 g / cm ² and the sample was placed in a cylindrical electrode of 1.00 cm ^2, measured under a DC electric field. The applied voltage is changed depending on the volume resistivity of the measurement object.

[0017]

EXAMPLES Examples of the present invention will be described below. Example 1 Epoxy resin 20 parts by weight (Epicoat 1004: Yuka Shell Co., Ltd.) Magnetite 76 parts by weight (EPT-500: Toda Kogyo Co., Ltd.) Carbon black 4 parts by weight (# 40: Mitsubishi Kasei Kogyo Co., Ltd.) The material was dispersed / dissolved in toluene, and carrier particles were obtained by a spray drying method. The carrier particles were classified to obtain a spherical conductive magnetic carrier having an average particle diameter of 20 μm. The saturation magnetization of this carrier is 65 emu /
g, volume resistivity was 3.0 × 10 ³ Ω · cm. Furthermore, 90 parts by weight of styrene-acrylic copolymer resin (Mw = 120,000, Mn = 6,000, Mw / Mn = 20) 3 parts by weight of polypropylene (Viscor 660P: manufactured by Sanyo Chemical Industry Co., Ltd.) 5 parts by weight of carbon black ( MA-100: manufactured by Mitsubishi Kasei Co., Ltd. 2 parts by weight of chromium-containing dye (Bontron S-44: manufactured by Orient Chemical Co., Ltd.) The materials having the above-mentioned composition were mixed, melt-kneaded by a kneader, and ground by a jet mill. After that, classification was performed to obtain toner particles having an average particle diameter of 8 μm. Carbon black (MA-100: manufactured by Mitsubishi Kasei Co., Ltd.) based on 100 parts by weight of the toner particles
0.5 parts by weight was added and mixed with a Henschel mixer (manufactured by Mitsui Miike Chemical Industry Co., Ltd.) to obtain an insulating non-magnetic toner. The conductive magnetic carrier and the insulating non-magnetic toner are mixed in a ratio of 95 parts by weight: 5 parts by weight and used in the present invention.
To obtain a developer.

Example 2 Styrene / acrylic copolymer resin 66 parts by weight (Mw = 120,000, Mn = 6,000, Mw / Mn = 20) Polypropylene 2 parts by weight (Viscole 660P: manufactured by Sanyo Kasei Co., Ltd.) Magnetite 30 Parts by weight (EPT-500: manufactured by Toda Kogyo Co., Ltd.) 2 parts by weight of chrome-containing dye (Bontron S-44: manufactured by Orient Chemical Industry Co., Ltd.) The materials having the above composition are mixed, melt-kneaded by a kneader, and then jet-milled. After pulverization, the particles were classified to obtain toner particles having an average particle diameter of 8 μm. Carbon black (MA-100: manufactured by Mitsubishi Kasei Co., Ltd.) based on 100 parts by weight of the toner particles
0.4 parts by weight was added and mixed with a Henschel mixer (manufactured by Mitsui Miike Chemical Industry Co., Ltd.) to obtain an insulating magnetic toner. The conductive magnetic carrier of Example 1 and the above-mentioned insulating magnetic toner were mixed with each other.
The developer of Example 2 used in the present invention was obtained by mixing in a ratio of 2 parts by weight: 8 parts by weight.

Example 3 Epoxy resin 25 parts by weight (Epicoat 1004: manufactured by Yuka Shell Co., Ltd.) Magnetite 75 parts by weight (EPT-500: manufactured by Toda Kogyo Co., Ltd.) The above-mentioned materials were mixed and melt-kneaded with a kneader. After crushing with a jet mill, spheronization was performed in a hot air stream, and the treated product was classified to obtain carrier particles having an average particle size of 25 μm. Further, 100 parts by weight of the carrier particles and 1 part by weight of carbon black (# 40: manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) were mixed, and then charged into a mechanofusion system (manufactured by Hosokawa Micron Co., Ltd.) and treated for 30 minutes to obtain a spherical shape. A conductive magnetic carrier was obtained. The carrier has a saturation magnetization of 64 emu / g and a volume resistivity of 5.5 × 10 ² Ω · c.
It was m. The conductive magnetic carrier and the insulating non-magnetic toner of Example 1 were mixed at a ratio of 95 parts by weight: 5 parts by weight to obtain a developer of Example 3 used in the present invention.

Comparative Example 1 A material having the same composition as the carrier of Example 1 was dispersed / dissolved in toluene to obtain magnetic carrier particles by a spray drying method. The carrier particles are classified to have an average particle diameter of 12μ.
m spherical spherical conductive magnetic carrier was obtained. The carrier has a saturation magnetization of 65 emu / g and a volume resistivity of 7.2 × 10.
It was ³ Ω · cm. The conductive magnetic carrier and the insulating non-magnetic toner of Example 1 were mixed at a ratio of 95 parts by weight: 5 parts by weight to obtain a developer of Comparative Example 1.

Comparative Example 2 Carrier particles having the same composition as the carrier of Example 1 were dispersed / dissolved in toluene and spray-dried to obtain carrier particles. The carrier particles were classified to obtain a spherical conductive magnetic carrier having an average particle diameter of 40 μm. The carrier has a saturation magnetization of 65 emu / g and a volume resistivity of 2.1 × 10 ³ Ω.
・ It was cm. The conductive magnetic carrier and the insulating non-magnetic toner of Example 1 were mixed at a ratio of 95 parts by weight: 5 parts by weight to obtain a developer of Comparative Example 1.

Comparative Example 3 Materials having the same composition as the carrier of Example 3 were melt-kneaded by a kneader and pulverized by a jet mill, and then the treated product was classified to obtain carrier particles having an average particle diameter of 25 μm. further,
100 parts by weight of the carrier particles and carbon black (#
40: Mitsubishi Kasei Co., Ltd.) 1 part by weight was mixed with a Henschel mixer (manufactured by Mitsui Miike Chemical Co., Ltd.) to obtain an amorphous conductive magnetic carrier. The saturation magnetization of this carrier is 64 emu.
/ G and the volume resistivity was 2.0 × 10 ² Ω · cm.
The conductive magnetic carrier and the insulating non-magnetic toner of Example 1 were mixed at a ratio of 95 parts by weight: 5 parts by weight to obtain a developer of Comparative Example 3.

Comparative Example 4 Epoxy resin 45 parts by weight (Epicoat 1004: Yuka Shell Co., Ltd.) Magnetite 50 parts by weight (EPT-500: Toda Kogyo Co., Ltd.) Carbon black 5 parts by weight (# 40: Mitsubishi Kasei Kogyo Co., Ltd.) The materials having the above composition were dispersed / dissolved in toluene to obtain carrier particles by a spray dry method. The carrier particles were dispersed to obtain a spherical conductive magnetic carrier having an average particle diameter of 20 μm. The saturation magnetization of this carrier is 43 emu /
g, volume resistivity was 5.7 × 10 ³ Ω · cm. The conductive magnetic carrier and the insulating nonmagnetic toner of Example 1 were mixed at a ratio of 95 parts by weight: 5 parts by weight to obtain a developer of Comparative Example 4.

Tests were carried out by applying the developers of Examples and Comparative Examples to the optical back surface recording system as shown in FIG. The photoconductor is a transparent glass tube provided with a conductive layer and a photoconductive layer (amorphous silicon), and an LED is used for exposure. The developing bias is -100V, and the transfer bias applied to the transfer roller is + 800V.

The test results are shown in Table 1. The image densities in the table are the values measured with a Macbeth RD914 densitometer, and the fog is measured from the whiteness value of the paper before transfer using the Nippon Denshoku colorimeter and the whiteness of the paper after transfer / fixing is performed. It is the value obtained by subtracting the value of.

[0026]

[Table 1]

As is clear from the examples and comparative examples, the recording method of the present invention consumes only the insulating toner, and is capable of obtaining good image quality without sufficient image density and fog.

[0028]

According to the present invention, in the optical back exposure recording system, since only the insulating toner is developed, good transferability can be obtained, and sufficient image density and fog-free image quality can be obtained. In addition to being able to do so, the device can be downsized.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of an optical backside exposure recording system used in the present invention.

[Explanation of symbols]

 1 Magnetic Sleeve 2 Developing Device 3 Photosensitive Member 4 Exposure Means 5 Developer Transfer Means 6 Transfer Material 7 Fixing Means

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Claims (2)

[Claims] 1. An optical backside exposure recording method for forming an image by bringing a developer into contact with the surface of a photoconductor by a developing sleeve having a magnetic member arranged therein, and at the same time performing image exposure from the inside of the photoconductor. The developer is a mixture of a conductive magnetic carrier and an insulating toner, and the conductive magnetic carrier has an average particle diameter of 15 to 30 μm and an external magnetic field of 10 kOe.
The electrophotographic recording method is a substantially spherical carrier having a saturation magnetization of 50 emu / g or more. 2. The volume resistivity of the conductive magnetic carrier is 10
An electrophotographic recording method, which is ² to 10 ⁵ Ω · cm.