JPH07146603A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] An image forming apparatus capable of increasing the charging potential of a photosensitive drum of an electrophotographic printer and extending the charging time is preferable because it prevents "fogging" and a decrease in print density. An object of the present invention is to provide an image forming apparatus capable of various printing. [Structure] A photosensitive member 1 in which the surface of a light-transmissive conductive layer 14 and a photoconductive layer 15 sequentially laminated on a light-transmissive substrate 13 moves
And an exposing means 3 for exposing an image on the photoreceptor 1 from the side of the base body 13.
And a developing means 4 arranged on the photoconductive layer 15 side to convey the developer 40 by the magnet roller 41 to bring it into contact with the photoconductor 1, and within the contact width of the photoconductor 1 and the conveyed developer 40. In the image forming apparatus, the voltage V1 is applied to the developer 40 to charge the photoconductor 1, and the exposure and the development are performed almost at the same time. The developer on the surface of the photoconductor 1 is located between the photoconductor 1 and the magnet roller 41. A voltage V2 higher than the voltage V1 by a predetermined voltage is applied to the electrode 16 provided on the upstream side in the moving direction of 40 and having a length substantially equal to that of the photoconductor 1 and in contact with the developer 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic printer, and more particularly to an image forming apparatus capable of increasing a charging potential of a photosensitive drum and extending a charging time. .

With the recent rapid development of computers and communication technologies, the demand for printers as output terminals is increasing. Electrophotographic printers are rapidly becoming popular because of their excellent recording speed and print quality.

However, in the conventionally widely used electrophotographic method (Carlson process), a photosensitive drum is used as a recording medium, and recording is performed by complicated steps of charging, exposing, developing, transferring, fixing, discharging and cleaning. Therefore, there is a limit to downsizing, cost reduction, and maintenance-free of the device, and a device having a simpler process has been desired.

On the other hand, an optical backside recording type electrophotographic printer which is capable of simplifying the process is being developed. In this type, a photosensitive drum is charged by applying a voltage to the developer side. Therefore, the surface potential of the photosensitive drum becomes lower than the applied voltage due to the loss. Therefore, when a general non-magnetic toner is used, "fogging" (dirt on the background of printing) occurs on the entire surface, and the print density decreases.

Therefore, conventionally, by using the magnetic toner, the collection force from the magnet roller has been strengthened to reduce the "fog" and prevent the print density from decreasing. However, the magnetic powder in the toner is often non-uniformly contained, and toner with a small amount of magnetic powder easily causes "fog" and the print density tends to decrease. There is a demand for a method capable of preventing a decrease in the temperature.

[0006]

2. Description of the Related Art FIG. 9 shows an internal side view of an electrophotographic printer of the Carlson process type. In the figure, 1a is a photosensitive drum, 2 is a charger, 3a is an exposure device, 4a is a developing device, 5 is a transfer device, 6 is a static eliminator, 7 is a cleaner, 8 is a fixing device, 9 is a conveying path, and 10 is a use. A sheet feeding unit that accommodates sheets 12 of different sizes, and 11 is a stacker.

With this structure, the photosensitive drum 1a is used as a latent image recording medium, and recording is performed in seven steps of uniform charging, image exposure, development, transfer, fixing, charge removal and cleaning. The charger 2 applies a positive or negative uniform positive charge to the surface of the photosensitive drum 1a having photoconductivity, and the exposure device 3a irradiates optical data obtained by converting print information with a photo diode (LED) or laser light. By erasing the surface charge of a specific portion, an electrostatic latent image according to print information is formed on the photosensitive drum 1a.

Next, the developing device 4a electrostatically develops with the toner 40a to form a visible image with the toner 40a on the photosensitive drum 1a. Finally, the toner image is transferred with the transfer device 5 to the sheet feeding section 10. The sheet 12 is electrostatically transferred onto the sheet 12 that has been fed from the sheet and conveyed in the direction of the arrow in the conveying path 9, and is fixed by heat, light, pressure, etc. by the fixing device 8, and the sheet 12 is sent to the stacker 11.

The photosensitive drum 1a on which the toner image has been transferred is neutralized by the static eliminator 6 and is cleaned by the cleaner 7 to prepare for the next printing. However, in such an electrophotographic printer by the Carlson process method, the means used for each step are generally arranged around the photosensitive drum 1a, and as the apparatus is downsized, the means for each step is changed to the photosensitive drum 1a.
Since they are closely connected to each other, there is a limit to downsizing, and there is a drawback that the toner 40a is scattered from the developing device 4a and the optical system of the exposing device 3a is soiled, which adversely affects printing.

Further, the conventional charging means using the charger 2 is as follows.
Since charging is performed by corona charging, there is a problem that ozone is generated and adversely affects the human body. Therefore, an optical backside recording type electrophotographic printer in which the exposing means is disposed inside the photosensitive drum and the charging means does not use corona charging is disclosed in Japanese Patent Laid-Open Nos. 58-153957 and 57-57.
It is proposed in Japanese Patent No. 119375.

The outline will be described below with reference to FIG. In FIG. 10, 1b is a photosensitive drum, 3b is an exposing device, 4b is a developing device, and 5a.
Is a transfer roller, and 6a is a discharge lamp. The same reference numerals as those in FIG. 4 denote the same objects.

In the photosensitive drum 1b, a transparent conductive layer 14a and a photoconductive layer 15a are sequentially laminated on a transparent substrate 13a. The exposure device 3b is disposed inside the photosensitive drum 1b and exposes optical data on the back surface of the conductive layer 14a facing the photosensitive drum 1b in the direction of the developing device 40b.

The developing device 4b is composed of a developing roller 41a facing the photosensitive drum 1b with a gap and an accommodating portion 44 accommodating the developer 40b. The developing roller 41a includes a conductive and non-magnetic sleeve 42 and a magnet disposed inside the sleeve 42.
The magnet 43 is fixed, and the sleeve 42 rotates in the arrow direction. A direct current power source is connected to the sleeve 42, and the developer supplied from the accommodating portion 44 when the sleeve 42 rotates.
40b is conveyed to the opposite surface of the photosensitive drum 1b, and the developer 40b is brought into contact with the surface of the photosensitive drum 1b to form a contact width.
Photosensitive drum grounded by sleeve 42 with medium 40b
The bias voltage applied between 1b and the photosensitive drum
The electrostatic latent image formed on 1b is developed with toner.

The accommodating portion 44 is composed of a stirring screw 45, a feed screw 46, a partition plate 47 and a feed plate 48 which rotate in mutually opposite directions. Developer stored in storage section 44
The rotation of the agitation screw 45 causes the 40b to be agitated by, for example, being screw-conveyed in the vertical direction downward in the drawing, and the conveyed developer 40b makes a U-turn behind the partition plate 47, and the rotation of the supply screw 46 causes a rotation of the drawing. It is conveyed in the upward vertical direction, is fed onto the supply plate 48, and is supplied to the developing roller 41a.

The developer 40b is a one-component developer of a conductive toner, or a two-component developer obtained by mixing an insulating toner and a conductive carrier of 10 ⁵ Ωcm or less (Japanese Patent Laid-Open No. 58-15).
3957).

With this structure, the charging, exposing and developing processes will be described with reference to FIG.
As shown in (a), the sleeve 42 of the developing device 4b and the photosensitive drum 1b are connected to each other via the developer 40b which is brought into contact with the surface of the photosensitive drum 1b.
A bias direct current (DC) voltage is applied to the conductive layer 14a of 1b to uniformly charge the surface of the photosensitive drum 1b. In addition,
This applied voltage is controlled to a constant DC voltage.

Next, as shown in FIG. 11 (b), the photosensitive drum 1b
The optimum position of the contact portion between the developer and the developer 40b is exposed from the conductive layer 14a side by the exposure device 3b to form an electrostatic latent image on the photoconductive layer 15a, and at the same time, as shown in FIG. 11 (c), the latent image is formed. The toner 40A is sucked by the electric attraction of the part, and
A toner image is formed on the surface of 1b. The toner 40A other than the electrostatic latent image is magnetized, and the toner in the sleeve 42 is magnetized.
It is removed together with the carrier 40B by the magnetic force of 43.

Thus, as shown in FIG. 10, the photosensitive drum 1b
The toner image formed on is transferred to the supplied paper 12 by the transfer roller 5a to which a voltage is applied, and is fixed by the fixing device 8. After transferring the toner image to paper 12,
The surface of 1b is neutralized by the static elimination lamp 6a arranged inside, and is prepared for the next printing.

Since printing is performed in this manner, when this method is used, ozone such as corona charging is not generated, the exposure device 3b is inside the photosensitive drum 1b, and the developing device 4b is charged. Since both the means and the developing means are used, the number of steps can be greatly reduced and the apparatus can be easily downsized.

[0020]

According to the above-mentioned conventional method, in the above-mentioned Carlson process method, the photosensitive drum is usually charged by corona discharge (or fur brush, roller, etc.). There is a time allowance to increase the surface potential of the photosensitive drum sufficiently by performing another process before, and since this charging potential is higher than the voltage applied to the developer, theoretically The toner does not adhere to the background portion of the print, and “fog” does not occur.

However, in the above-mentioned optical back surface recording system, since the photosensitive drum is charged by applying a voltage to the developer side, the surface potential of the photosensitive drum is applied from the developer side even if there is no loss due to charging. However, the charging of the photosensitive drum does not become higher than the voltage applied to the developer as in the Carlson process method. Usually, the surface potential of the photosensitive drum is lower than the voltage applied to the developer because it includes some loss due to charging.

Therefore, (a) If a general non-magnetic toner is used, "fogging" will occur on the entire surface. As a countermeasure against this, conventionally, by using a magnetic toner, the collection force from the magnet roller is strengthened to reduce “fog”. However, the magnetic powder contained in toner is often non-uniformly contained, and toner with a small amount of magnetic powder causes "fog".
There is a problem that it becomes easy and the print density is lowered.

This phenomenon is significantly affected by changes in temperature and humidity. That is, when the temperature and humidity are high, the electric resistance of the developer is reduced, the charge amount on the photosensitive drum is reduced, and "fog" occurs. When the temperature and humidity are low, the electric resistance of the developer is increased and the photosensitive drum is It becomes difficult to be charged, and “fog” occurs again, and the print density decreases.

Therefore, in order to eliminate the "fog" of the non-magnetic toner and the toner having the low magnetic property, the potential of the photosensitive drum is brought close to the voltage applied from the developer side, or
Or it needs to be higher.

Further, (b) charging, exposure and development are carried out almost simultaneously within the contact width where the developer is in contact with the photosensitive drum, so the time for charging is short and the surface potential of the photosensitive drum cannot be sufficiently raised. . For this reason, if the process proceeds to the next step as it is, "fog" occurs and the print density decreases. This phenomenon is significantly affected by changes in temperature and humidity.

Therefore, it is necessary to lengthen the charging time so that the surface potential of the photosensitive drum can be sufficiently increased. As a publicly known example for solving similar problems, in order to solve the above problem (a), (1) JP-A-58-145468 "image recording device", (2) JP-A-4-182683 " There is an "image forming apparatus" and (3) JP-A-3-156477, "Developing method and apparatus", but (1) is for solving the drawbacks that the print density becomes thin and "fog" easily occurs. However, this is a method of applying a voltage from the back of the paper in order to form a toner image directly on the paper and print it, which is completely different from the object of the present invention.

In (2), the toner is prevented from scattering by disposing an electrode along the image carrier (photosensitive drum) on the upstream side of the developing device. Need to cover. In the present invention, the charging of the photosensitive drum is targeted.

The method (3) is a method of developing by separating the toner and the carrier by an alternating electric field in order to prevent the development failure due to the aggregation phenomenon of the toner having a small particle size. In the present invention, the charging of the photosensitive drum is targeted.

Therefore, the known examples of (1), (2) and (3) are:
It cannot be a method to solve the problem of (a) above. In addition, with respect to the above problem (b), (4) JP-A-62-17
No. 5772, "Image display device", (5) JP-A-3-13
No. 977, "Developing device" and (6) JP-A-4-1595
Although there is an image recording apparatus disclosed in Japanese Patent Laid-Open No. 65-65, (4) is an apparatus using a magnetic brush as a cleaning mechanism and has a different configuration from the apparatus targeted by the present invention.

In order to prevent toner scattering, (5) is provided with a magnet at the portion where the developer comes out of the developing container.
In the present invention, the upstream side of the photosensitive drum is targeted. (6)
In order to prevent "fogging" and improve print density, a magnetic field generating means is provided in an endless belt that conveys toner, and the configuration is completely different from that of the apparatus of the present invention.

Therefore, the known examples of (4), (5) and (6) are:
It cannot be a method to solve the problem of (b) above. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of performing favorable printing by preventing the occurrence of "fog" and the reduction of print density regardless of temperature and humidity.

[0032]

1 and 2 are principle diagrams of the present invention. FIG. 1 is a principle configuration diagram corresponding to claim 1, and FIG.
[Fig. 4] is a principle configuration diagram corresponding to claim 3.

1) Means corresponding to claim 1 In FIG. 1, 1 is a photoreceptor, 40 is a developer, 1 is a conductive layer 14 and a photoconductive layer 15 are sequentially laminated on a substrate 13, and the surface is moved. A photoconductor, 13 is provided on the photoconductor 1, a substrate formed of a material having light transmittance, and 14 is provided on the photoconductor 1.
A conductive layer formed of a material having a light-transmitting property, 15 a photoconductive layer provided on the photoconductor 1, 3 an exposure means arranged on the base 13 side of the photoconductor 1, and exposing an image on the photoconductor 1. Reference numeral 4 denotes a developing unit which is arranged on the photoconductive layer 15 side of the photoconductor 1 and which has a magnet roller 41 and which conveys the developer 40 to bring it into contact with the photoconductor 1. 41 is provided in the developing unit 4 and 16 is a magnet roller that conveys the photoconductor 1 and the magnet roller 41.
Between the photoconductor 1 and the magnet roller 41 on the upstream side in the moving direction of the developing material 40 on the surface of the photoconductor 1 from the position facing the magnet roller 41 of the photoconductor 1. The electrode is in contact with the developer 40 and has a length substantially equal to the facing length of the.

Therefore, the photoconductor 1 and the magnet roller 41
Within the contact width of the upper developer 40, a voltage V1 is applied to the developer 40 to charge the photoconductor 1 and the electrostatic latent image formed on the photoconductor 1 by exposure and exposure of the photoconductor 1 by the exposure means 3 is performed. An image forming apparatus that develops an image by the developing means 4 almost at the same time, and is configured to apply a voltage V2 higher than the voltage V1 applied to the developer 40 by a predetermined voltage to the electrode 16.

2) Means corresponding to claim 3 In FIG. 2, 1 is a photoconductor, 40 is a developer, 1 is a conductive layer 14 and a photoconductive layer 15 are sequentially laminated on a substrate 13, and the surface is moved. A photoconductor, 13 is provided on the photoconductor 1, a substrate formed of a material having light transmittance, and 14 is provided on the photoconductor 1.
A conductive layer formed of a material having a light-transmitting property, 15 a photoconductive layer provided on the photoconductor 1, 3 an exposure means arranged on the base 13 side of the photoconductor 1, and exposing an image on the photoconductor 1. Reference numeral 4 denotes a developing unit which is arranged on the photoconductive layer 15 side of the photoconductor 1 and which has a magnet roller 41 and which conveys the developer 40 to bring it into contact with the photoconductor 1. 41 is provided in the developing unit 4 and the developer 40 The reference numeral 17 denotes a magnet roller that conveys the photosensitive member 1 to the upstream side in the moving direction of the developer 40 on the surface of the photosensitive member 1 facing the magnet roller 41 and the exposure position of the photosensitive member 1 from the exposure unit 3 on the substrate 13 side of the photosensitive member 1. It is provided at least at one of predetermined positions on the upstream side in the moving direction of the developer 40 on the surface, parallel to the photoconductor 1, and
And a magnet plate having a length substantially equal to the facing length of the magnet roller 41.

Therefore, the photoconductor 1 and the magnet roller 41
Within the contact width of the upper developer 40, a voltage V1 is applied to the developer 40 to charge the photoconductor 1 and the electrostatic latent image formed on the photoconductor 1 by exposure and exposure of the photoconductor 1 by the exposure means 3 is performed. The image is developed by the developing means 4 almost at the same time.

[0037]

[Action]

1) Action corresponding to claim 1 Between the photoconductor 1 and the magnet roller 41, the electrode 16 is provided on the upstream side of the surface of the photoconductor 1 in the moving direction of the developer 40, and the voltage V1 applied to the developer 40 is provided. By applying a voltage V2, which is higher than the predetermined voltage, to the electrode 16, the potential of the photoconductor 1 is increased by the developer 40.
Since it can be made higher than the voltage applied from the side, it is possible to prevent the "fog" of the developer 40 of the photoconductor 1 and the reduction of the print density without affecting the changes of temperature and humidity. Print quality is obtained.

2) Action corresponding to claim 3 The developer on the surface of the photoconductor 1 facing the magnet roller 41.
A magnet plate 17 is provided on at least one of the upstream side in the moving direction of 40 and the predetermined position on the upstream side in the moving direction of the developer 40 on the surface of the photoconductor 1 with respect to the exposure position by the exposure means 3 on the side of the substrate 13 of the photoconductor 1. By installing the developer on the magnet plate 17,
40 is sucked, the contact width of the developer 40 on the photoconductor 1 is expanded to the upstream side, the charging time of the photoconductor 1 by the developer 40 is lengthened, and the surface potential can be sufficiently increased. Also, it is possible to prevent "fog" of the developer 40 of the photoconductor 1 and a decrease in print density without affecting the change in humidity, and obtain good print quality.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first and second embodiments in which the present invention is applied to the electrophotographic printer of the optical backside recording system described in the prior art will be described below.

(1) Description of First Embodiment A first embodiment (corresponding to claim 1 and claim 2) will be described with reference to FIGS. FIG. 3 shows the first of the present invention.
FIG. 4 is a block diagram showing an apparatus (1) of an embodiment of the present invention, FIG.
FIG. 5 is a side view showing the device (2) of the embodiment, and FIG. 5 is a view showing the print evaluation result of the first embodiment. The same reference numerals denote the same objects throughout the drawings.

3 and 4, the photosensitive drum 1b, the exposure device 3b,
The developing device 4b, the charging electrode 16a, and the developing roller 41a are shown in FIG.
Of the photoconductor 1, the exposure means 3, the developing means 4, the electrodes 16, and the magnet roller 41.

1) Device (1) (corresponding to claim 1) As shown in FIGS. 3 (a) and 3 (b), the photosensitive drum 1b is provided between the photosensitive drum 1b and the sleeve 42 of the developing roller 41a. On the upstream side in the moving direction of the developer 40b on the surface of the above, at a position below the contact width of the developer 40b on the surface of the photosensitive drum 1b in the lower part in the figure,
A charging electrode 16a having a length substantially equal to the length of the photosensitive drum 1b in the longitudinal direction is provided parallel to the photosensitive drum 1b. The charging electrode 16a is made of a strip-shaped conductor having a cross section of 1 mm × 0.5 mm, for example, a copper plate.

The sleeve 42 has a DC voltage V _DC (= -650).
V) is applied. That is, it is applied to the developer 40b. In this case, the gap between the photosensitive drum 1b and the sleeve 42 is 0.3 mm.

The charging electrode 16a has an absolute value higher than the DC voltage V _DC applied to the sleeve 42 by 10 to 500 V (for example, −2).
Apply a voltage (00V higher). That is, DC voltage (= -850
V) is applied.

In each case, constant voltage control is performed as a voltage driving method for applying. With such a configuration, the voltage applied to the charging electrode 16a is higher than the voltage applied to the sleeve 42, so that the potential of the photosensitive drum 1b can be made higher than the voltage applied from the developer 40b side. It is possible to prevent "fog" of the developer 40b on the photosensitive drum 1b and a decrease in print density, and it is possible to obtain good print quality.

2) Device (2) (corresponding to claim 2) FIG. 4 shows the position of the device (1) and the charging electrode 16a described in FIG.
The gap between the photosensitive drum 1b and the sleeve 42 is the same, and the voltage application method is different. That is, as shown in FIG. 4, an alternating voltage in which a DC voltage is superimposed on an AC voltage is applied to the sleeve 42 and the charging electrode 16a, respectively.

That is, an alternating voltage in which the AC voltage V _AC is a peak voltage V _PP (= 1200 V, frequency 600 Hz) and the DC voltage V _DC (= −650 V) is applied to the sleeve 42. In this case, the gap between the photosensitive drum 1b and the sleeve 42 is 0.3mm.
I am trying.

In the charging electrode 16a, the AC voltage V _AC is higher than the peak-to-peak voltage V _PP (= 1200 V, frequency 600 Hz) and the DC voltage V _DC applied to the sleeve 42 by 10 to 500 V in absolute value (for example, -200 V higher). ) Apply voltage (= -850V).

In each case, constant voltage control is performed as a voltage driving method for applying. With such a configuration, the voltage applied to the charging electrode 16a is higher than the voltage applied to the sleeve 42, so that the potential of the photosensitive drum 1b can be made higher than the voltage applied from the developer 40b side. By applying an alternating voltage in which a direct current voltage is superimposed on an alternating current voltage, the environmental dependence becomes stronger, the potential of the photosensitive drum 1b becomes more stable, and the "fog" and print density of the developer 40b on the photosensitive drum 1b Can be prevented, and good print quality can be obtained.

Below, the photosensitive drum 1 of the devices (1) and (2)
An example of creating the b and the developer 40b will be described. a) Example of making photosensitive drum Since the photosensitive drum 1b used is exposed and developed almost at the same time, it is required to have high mobility (the holes generated during exposure reach the surface quickly). ing.

However, in the photosensitive drum 1b using the inorganic material for the photoconductive layer 15a, although the mobility is very fast, the dark resistance (the resistance in a place not exposed to light) is lower than that of the organic material, Sufficient charging cannot be provided unless the resistance of the developer 40b used is low, and it is difficult to use inorganic materials.

On the other hand, it has been found that the photosensitive drum 1b using an organic material for the photoconductive layer 15a has a high dark resistance, and thus can be sufficiently charged without imparting conductivity to the developer 40b. Therefore, the photosensitive drum 1b using an organic material for the photoconductive layer 15a uses a glass cylinder for the base body 13a, and the conductive layer 14a is formed of ITO (indium tin oxide) with a film thickness of 100 Å by vacuum deposition. . Next, cyanoethylated pullulan 1 was dissolved in acetone 10 in a weight ratio, and this was coated on the conductive layer 14a by dip coating and dried at 100 ° C. for 1 hour to obtain a film thickness of 1
A μm intermediate layer is formed.

Further, a mixture of α-type oxotital phthalocyanine 1, polyester 1,1,1,2-trichloroethane 20 in a weight ratio, dispersed and mixed for 24 hours using a hard glass pot, was applied on the above-mentioned intermediate layer, Film thickness after drying at 100 ℃ for 1 hour
A 0.3 μm charge generation layer was formed. To form the charge transport layer, the weight ratio of butadiene derivative 1 and polycarbonate 1 is 1
Was dissolved in dichloromethane 17 to prepare a coating solution, which was applied onto the above charge generating layer by dip coating and dried at 90 ° C. for 1 hour to form a charge transporting layer having a thickness of about 15 μm. That is, the photoconductive layer 15a is formed.

B) Preparation Example of Developer Toner (1) Preparation As a binder resin, polyester resin (NE
-2150, Kao Corporation 60 and carbon black as a colorant (Black Pearls L: average particle size 2.4 μm, specific surface area 138 m ² / g: manufactured by Cabot) 5, azo dye (Bontron S-34, manufactured by Orient Chemical Co., Ltd.) ) 1, magnetic powder (MTZ-703, manufactured by Toda Kogyo Co., Ltd.) 30, propylene wax (Viscole 55)
0P Sanyo Kasei Co., Ltd.) 4 was added, and pressure kneader 160
Melt and knead at 30 ° C. for 30 minutes to obtain a toner mass.

The cooled toner mass is made into a coarse toner of about 2 mm or less by a Rotoplex grinder. Next, the coarse toner is finely pulverized by using a jet mill (PJM pulverizer, manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and the pulverized product is classified by an air classifier (produced by Alpine Co., Ltd.), and a toner having an average particle diameter of 10 μm To get

Toner (2) Preparation As a binder resin, a polyester resin (NE
-2150, Kao Co., Ltd. 90, and carbon black as a colorant (Plac Pearls: average particle size 2.4 μm, specific surface area 138 m ² / g: manufactured by Cabot) 5, azo dye (Bontron S-34, manufactured by Orient Chemical Co., Ltd.) ) 1 and propylene wax (Viscole 550P, manufactured by Sanyo Kasei) 4 are added, and the mixture is melt-kneaded with a pressure kneader at 160 ° C. for 30 minutes to obtain a toner mass.

The cooled toner mass is made into a coarse toner of about 2 mm or less by a Rotoplex grinder. Next, the coarse toner is finely pulverized by using a jet mill (PJM pulverizer, manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and the pulverized product is classified by an air classifier (produced by Alpine Co., Ltd.), and a toner having an average particle diameter of 10 μm To get

Preparation of carrier Styrene acrylic resin (BR-85, Mitsubishi Rayon by weight ratio)
85) and carbon (Ketchin Black) 15 are dissolved or dispersed in a dimethylkent solution to prepare a coating solution. Magnetite (Kanto Denka Co., Ltd.) 3000, which is the core material of the carrier, is coated with this coating solution using a universal stirrer. The electrical resistance of the created carrier is
It is 10 ⁸ Ωcm.

The electric resistance was measured by the following method. 1
A carrier of cm ³ is placed between 1 cm ³ of parallel electrodes (interelectrode distance 1 cm) where a constant magnetic field (magnetic flux density 950 gauss, magnetic field strength 3400e) is working, and a current value i (A ) Was measured and the value of electric resistance was calculated from the equation of R = 100 / i.

Preparation of developer (1) Toner (1) 25 and carrier 75 are mixed in a weight ratio to prepare a developer.
Get (1). Preparation of developer (2) Mix toner (2) 25 and carrier 75 in a weight ratio and
(2) is obtained.

Using the developer 40b (developer (1) and (2)) thus prepared, the above-mentioned devices (1) and (2) and the device described in the conventional example are subjected to "fogging" in printing. The results of evaluation of the print density and the print density are shown in FIG. In the evaluation of ○ in the figure, the density difference ΔOD due to "fog" on the photosensitive drum is 0.
A value of 05 or less was evaluated as ○, and a print density of OD of 1.35 or more on the paper 12 was evaluated as ○. OD (Optical Density) is a unit of print density.

Therefore, the charging electrode 16a is provided, and the sleeve
A voltage higher than the voltage applied to 42 by a specified voltage.
It is clear that the result obtained by applying the voltage to 16a is superior to the conventional method not only in the case of normal temperature and normal humidity but also in the case of high temperature high humidity and low temperature low humidity. (2) Description of Second Embodiment A second embodiment (corresponding to claim 3) will be described with reference to FIGS. 6 to 8. FIG. 6 shows an apparatus according to the second embodiment of the present invention.
FIG. 7 is a side view showing (1), and FIG. 7 is an apparatus according to a second embodiment of the present invention.
FIG. 8 is a configuration diagram showing (2), and FIG. 8 is a diagram showing a print evaluation result of the example. The same reference numerals denote the same objects throughout the drawings.

The photosensitive drum 1b and the exposure device 3b shown in FIGS.
The developing unit 4b and the developing roller 41a correspond to the photoconductor 1, the exposure unit 3, the developing unit 4, and the magnet roller 41 of FIG. 2, respectively.

1) Device (1) As shown in FIG. 6, between the photosensitive drum 1b and the sleeve 42 of the developing roller 41a, on the upstream side in the moving direction of the developer 40b on the surface of the photosensitive drum 1b, in the lower part of the drawing. At a position below the contact width of the developer 40b on the surface of the photosensitive drum 1b, a magnet plate 17a having a length substantially equal to the length in the longitudinal direction of the photosensitive drum 1b.
(For example, the cross section is 1 mm × 0.5 mm) is provided parallel to the photosensitive drum 1b.

An alternating voltage, in which the AC voltage V _AC is a peak-to-peak voltage V _PP (for example, V _PP = 1200 V, frequency 600 Hz) and a DC voltage V _DC (for example, -650 V), is applied to the sleeve 42. That is, it is applied to the developer 40b. In this case, the gap between the photosensitive drum 1b and the sleeve 42 is 0.3 mm.

The photosensitive drum 1b is the same as that described in the first embodiment. The charging electrode 16a has an absolute value higher by 10 to 500 V than the DC voltage applied to the sleeve 42 (for example,
-200 V higher) is applied. That is, AC voltage (= 12
Apply an alternating voltage with a DC voltage (= -850V) superimposed on 00V: 600Hz.

In each case, constant voltage control is performed as a voltage driving method for applying. With such a configuration, the developer 40b between the photosensitive drum 1b and the photosensitive drum 1b is attracted by the magnet plate 17a, the contact width of the developer 40b spreads upstream, and the charging time of the photosensitive drum 1b by the developer 40b increases. Getting longer,
Since the surface potential of the photosensitive drum 1b can be sufficiently increased, it is possible to prevent the occurrence of "fog" from high temperature and high humidity to low temperature and low humidity, and to obtain a desired print density and obtain good print quality. Obtainable.

2) Device (2) As shown in FIG. 7, inside the base 13a of the photosensitive drum 1b,
At a position facing the lower side of the contact width of the developer 40b on the upstream side in the moving direction of the developer 40b on the surface of the photosensitive drum 1b from the exposure position by the exposure device 3b, the length substantially equal to the length of the photosensitive drum 1b in the longitudinal direction. The magnet plate 17b is provided parallel to the photosensitive drum 1b.

The other structure and the voltage applied to the sleeve 42 are the same as those of the device (1). With such a configuration, the developer 40b between the photosensitive drum 1b and the photosensitive drum 1b is attracted by the magnet plate 17b, and the developer 40b is provided upstream.
The contact width of the photosensitive drum 1b becomes wider, the charging time of the photosensitive drum 1b with the developer 40b becomes longer, and the potential of the surface of the photosensitive drum 1b can be sufficiently increased. It is possible to prevent the occurrence of "fog", obtain a desired print density, and obtain good print quality.

Developer used in the above devices (1) and (2)
In 40b, the toner (1) and the carrier described in the first embodiment were mixed with the toner (1) 25 and the carrier 75 in a weight ratio. Using the developer 40b created in this way, the "fogging" of printing was performed on the devices (1) and (2) described above and the device described in the conventional example (this was used as a comparative example as the device (3)).
FIG. 8 shows the result of evaluating the print density. ○ × in the figure
Is evaluated in the same manner as in the first embodiment.

Therefore, by providing the magnet plate 17a or the magnet plate 17b to widen the contact width of the developer 40b on the surface of the photosensitive drum 1b, as compared with the conventional method, room temperature and normal humidity, high temperature and high humidity and low temperature and low humidity are provided. It is shown that both cases are excellent.

In the first embodiment, the voltage is applied to the sleeve 42.
AC voltage V_ACIs the peak-to-peak voltage V _PP= 1200V, frequency
600Hz, DC voltage V_DC== − 650V is explained
However, peak-to-peak voltage V_PP= 10 to 5000 V, frequency 10 to 1000
0Hz, DC voltage V_DC= -150 to 1000V can be set
It

In the first embodiment, the charging electrode 16a is used.
The voltage applied to the AC voltage V _AC is the peak-to-peak voltage V _PP =
The case where the voltage is set to 1200 V, the frequency 600 Hz, and the DC voltage V _DC = −850 V has been described, but the peak-to-peak voltage V _PP = 10 to 5000 V,
Frequency 10 to 10000 Hz, DC voltage V _DC = -150 to -1000V
Can be set.

Further, in the above first embodiment, the case of the so-called two-component developing method in which the toner and the carrier are present in the entire developing device has been described. The same can be applied to the case of a developing method which exists only.

In the second embodiment, the case where the alternating voltage in which the direct current voltage is superimposed on the alternating current voltage is applied to the sleeve 42 has been described, but only the direct current voltage may be applied, and the constant voltage control is performed. Although the case has been described, constant current control may be performed.

In the second embodiment, the case where the magnet plate 17a is provided in the device (1) and the magnet plate 17b is provided in the device (2) has been described, but the device (1) and the device (2) are not provided. The method may be combined with the magnet 17a and the magnet 17b, and the effect can be further ensured.

[0077]

As described above, according to the present invention, in claim 1, the electric potential of the photoconductor can be made higher than the voltage applied from the developer side, and therefore, even when the temperature and humidity are changed. It is possible to prevent "fog" of the developer on the photoconductor and a decrease in print density without affecting, and it is possible to obtain good print quality.

According to a second aspect of the present invention, by applying an alternating voltage in which a DC voltage higher than the DC voltage applied to the developer by a predetermined voltage to the AC voltage is applied to the electrodes, the environmental dependence becomes stronger and the potential of the photoconductor is increased. It is more stable and the effect of claim 1 can be further enhanced.

In the third aspect, the developer is attracted to the magnet plate, the contact width of the developer on the photosensitive member is expanded to the upstream side, the charging time of the photosensitive member by the developer is lengthened, and the surface potential is sufficiently increased. Since it can be raised, it does not affect the changes in temperature and humidity, and the "fog" of the developer on the photoconductor
Also, it is possible to prevent a decrease in print density and obtain good print quality. There is an effect.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram corresponding to claim 1 of the present invention.

FIG. 2 is a principle configuration diagram corresponding to claim 3 of the present invention.

FIG. 3 is a configuration diagram showing a device (1) according to a first embodiment of the present invention.

FIG. 4 is a side view showing the device (2) of the first embodiment of the present invention partially cut away.

FIG. 5 is a diagram showing a print evaluation result of the first embodiment.

FIG. 6 is a side view showing the device (1) of the second embodiment of the present invention.

FIG. 7 is a side view showing the device (2) of the second embodiment of the present invention.

FIG. 8 is a diagram showing a print evaluation result of the second embodiment.

FIG. 9 is a side view of the inside of an electrophotographic printer using the Carlson process method.

FIG. 10 is an internal side view of an electrophotographic printer showing a conventional example.

FIG. 11 is an explanatory diagram of a conventional printing method.

[Explanation of symbols]

1 is a photoconductor, 1a and 1b are photoconductor drums, 3 is exposure means, 3a and 3b are exposure devices, 4 is development means,
4a and 4b are developing units, 13 and 13a are bases, 14 and 14a are conductive layers, 15 and 15a are photoconductive layers, 16 are electrodes,
16a is a charging electrode, 17a and 17b are magnet plates, 4
0 and 40b are developers, 41 is a magnet roller, 41a is a developing roller, 40a and 40A are toners, and 40B is a carrier.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuneo Watanuki 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited (72) Inventor Yoshiya Ishiyama 1015, Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa Within Fujitsu Limited ( 72) Inventor Norio Saruwatari 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (3)

[Claims] 1. A substrate formed of a material having optical transparency.
(13) a conductive layer formed of a material having a light transmitting property (14)
And a photoconductive layer (15) are sequentially laminated to form a photosensitive member (1) whose surface moves, and the photosensitive member (1) is arranged on the side of the base body (13) of the photosensitive member (1).
An exposing means (3) for exposing an image on the photoconductor, and a developer (4) disposed on the photoconductive layer (15) side of the photoconductor (1).
0) has a magnet roller (41) for carrying the developer (4)
And a developing means (4) for bringing the photoconductor (1) into contact with the photoconductor (1), and the developer (4) on the photoconductor (1) and the magnet roller (41).
Within the contact width of 0), a voltage (V1) is applied to the developer (40) to charge the photoconductor (1), and the photoconductor by the exposing means (3) is charged.
An image forming apparatus which performs exposure to (1) and development of an electrostatic latent image formed on the photoconductor (1) by the exposure by the developing means (4) at substantially the same time, wherein the photoconductor (1) and Between the magnet roller (41), the developer (4) is provided on the upstream side in the moving direction of the developer (40) from the position on the surface of the photoconductor (1) facing the magnet roller (41).
0) parallel to the photoconductor (1) at a position in contact with
An electrode (16) having a length substantially equal to the facing length of (1) and the magnet roller (41) and in contact with the developer (40) is provided, and the voltage (V1) applied to the developer (40) is provided. An image forming apparatus characterized by applying a voltage (V2) higher than the above voltage by a predetermined voltage to the electrode (16). 2. The voltage applied to the electrode (16) is an alternating voltage in which a DC voltage higher than the voltage (V1) applied to the developer (40) by a predetermined voltage is superimposed on the AC voltage. The image forming apparatus according to claim 1. 3. A substrate formed of a material having a light transmitting property.
(13) a conductive layer formed of a material having a light transmitting property (14)
And a photoconductive layer (15) are sequentially laminated to form a photosensitive member (1) whose surface moves, and the photosensitive member (1) is arranged on the side of the base body (13) of the photosensitive member (1).
An exposing means (3) for exposing an image on the photoconductor, and a developer (4) disposed on the photoconductive layer (15) side of the photoconductor (1).
0) has a magnet roller (41) for carrying the developer (4)
And a developing means (4) for bringing the photoconductor (1) into contact with the photoconductor (1), and the developer (4) on the photoconductor (1) and the magnet roller (41).
Within the contact width of 0), a voltage (V1) is applied to the developer (40) to charge the photoconductor (1), and the photoconductor by the exposing means (3) is charged.
(1) An image forming apparatus for performing exposure to (1) and development of the electrostatic latent image formed on the photoconductor (1) by the exposure by the developing means (4) at substantially the same time, wherein the magnet roller (41) The developer (4) is provided at the upstream side of the surface of the photoconductor (1) facing the developer (40) in the moving direction.
0) and the moving direction of the developer (40) on the surface of the photoconductor (1) from the exposure position by the exposure means (3) on the substrate (13) side of the photoconductor (1). A magnet plate (17) provided at at least one of the predetermined positions on the upstream side, parallel to the photoconductor (1) and having a length substantially equal to the facing length of the photoconductor (1) and the magnet roller (41). An image forming apparatus comprising: