JP2008292955A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device equipped with a flare developing system enhancing flare uniformity on an electrode and restraining blowing out of toner to an end part. <P>SOLUTION: In a toner carrying roller 31 of the developing device, electrode shafts 40A and 40B which are rotating shaft members protruding from axial both end faces of a roller part are rotatably supported by a bearing not shown in Figure. In the roller part, an electrode pattern composed of a plurality of electrodes 41, 42 and 43 arranged along a surface movement direction by rotation in a pitch of p[μm] is formed. An odd-numbered electrode group which is an aggregate of odd-numbered electrodes in the electrode pattern is connected to the electrode shaft 40A. An even-numbered electrode group which is an aggregate of even-numbered electrodes in the electrode pattern is connected to the electrode shaft 40B. Pulse voltage output from AC power supply not shown in Figure is applied to the electrodes 40A and 40B through a contact member such as an electrode brush not shown in Figure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus, and more particularly to a developing technique for improving dot reproducibility in a two-component developing system.

  There are a number of development methods including those in practical use. Among them, representative development methods include a two-component development method and a one-component development method. The two-component development method is very suitable for high-speed development, and is the mainstream method for current medium-speed and high-speed output machines. In order to aim for high image quality, it is necessary to make the state of the developer in contact with the electrostatic latent image very dense. For this reason, the carrier particles are now being reduced in diameter, and carriers of about 30 μm are beginning to be used on a commercial level. However, the demand for higher image quality is increasing, and the required dot size of the pixel itself must be equal to or smaller than the current carrier particle size, meaning that isolated dot reproducibility. Then, it is necessary to further reduce the carrier particles. However, as the carrier diameter is reduced, the permeability of the carrier particles decreases, so that the carrier is easily detached from the developing roller. If the detached carrier particles adhere to the latent image carrier, the carrier adheres. Not only does this cause image defects, but it also causes side effects such as scratching the latent image carrier from that point. In order to prevent this carrier detachment, attempts have been made to increase the magnetic permeability of carrier particles from the material surface and to increase the magnetic force of the magnet included in the developing roller. Development is extremely difficult due to this balance.

In addition, due to the downsizing of the developing roller, the developing roller is becoming smaller in diameter, and it becomes difficult to design a developing roller having a strong magnetic field configuration that can completely prevent carrier detachment. Yes. In the first place, the two-component development system is a process of forming a toner image by rubbing the ears of a two-component developer called a magnetic brush against an electrostatic latent image. Unevenness tends to occur in the developability of isolated dots. Therefore, it is possible to improve the image quality by forming an alternating electric field between the developing roller and the latent image carrier, but it is difficult to completely eliminate the fundamental image unevenness such as unevenness of the ears of the developer.
In order to improve transfer efficiency and cleaning efficiency in the process of transferring the developed toner image to the latent image carrier and the process of cleaning the toner remaining on the latent image carrier after the transfer, the latent image carrier It is necessary to reduce the non-electrostatic adhesion force between the body and the toner as much as possible. As a method of reducing the non-electrostatic adhesion force between the latent image carrier and the toner, it is effective to reduce the coefficient of friction on the surface of the latent image carrier, but in this case, the spikes of the two-component developer are smooth. Since the developing portion slips through, the development efficiency and dot reproducibility become very poor.

On the other hand, the one-component development method is the mainstream method of current low-speed output machines because the mechanism is small and light. In this method, in order to form a toner thin layer on the developing roller, a toner regulating member such as a blade or a roller is brought into contact, and at that time, the toner is charged by friction with the developing roller or the toner regulating member. The charged toner layer formed as a thin layer on the developing roller is transported to the developing unit and developed. The developing system here is largely divided into a contact type and a non-contact type, the former is a non-contact between the developing roller and the latent image carrier, and the latter is in contact. In any method, the toner layer thinned on the developing roller is sufficiently pressed, so that the toner responsiveness to the electric field in the developing unit is very poor. Therefore, in order to obtain high image quality, it is usually the mainstream to form a strong alternating electric field between the developing roller and the latent image carrier, but even if this alternating electric field is formed, an electrostatic latent image can be obtained. On the other hand, it is difficult to stably develop a certain amount of toner, and it is difficult to uniformly develop high resolution minute dots.
In addition, in this one-component developing system, a very large stress is applied to the toner when the toner thin layer is formed on the developing roller, so that the toner circulating in the developing device is deteriorated very quickly. As the toner deteriorates, unevenness and the like are likely to occur even in the process of forming a toner thin layer on the developing roller, which is generally not suitable as a developing method for a high-speed and highly durable image forming apparatus.

In order to compensate for the drawbacks of the two-component method and the one-component method, several hybrid devices have been proposed as in Patent Document 1. Although such a hybrid increases the size and the number of parts of the developing device itself, some problems are overcome. However, in the developing portion, the same problem as that of one component, that is, difficulty in developing a high-resolution minute uniform dot remains.
For example, Patent Document 2 discloses a method for developing high-resolution minute uniform dots. In contrast to the hybrid configuration described above, by installing a wire to which a high frequency bias is applied to the developing unit, toner clouding is performed in the developing unit, thereby realizing high-resolution dot developability. With this method, the construction of the developing device is complicated, but it is considered that highly stable and high-quality development can be realized. However, in this method, there is no force to bind the clouded toner to the development area, and toner scattering becomes a big problem.

In order to form the most efficient and stable toner cloud, Patent Document 3 and the publicly known example cited therein propose a method of forming an electric field curtain on a rotating roller. This method can be interpreted as being extremely excellent for obtaining a small-sized and high-quality development. However, as a result of intensive studies by the present inventors, in order to obtain an ideal high image quality, It was discovered that conditions such as development must be limited. That is, it has been found that if image formation is performed under conditions other than the appropriate conditions, not only an effect is not obtained, but a poor image quality is provided.
Japanese Patent Laid-Open No. 03-100575 Japanese Patent Laid-Open No. 03-113474 Japanese Patent Laid-Open No. 03-21967

  The present invention has been made in view of the above problems, and in the flare development system, which is a development system capable of realizing higher image quality (high resolution dot reproducibility) than the conventional development system, the flare on the electrode. It is an object of the present invention to provide a developing device having a flare developing system that enhances uniformity and suppresses toner ejection to an end portion.

In order to solve such a problem, the present invention provides an odd-numbered electrode group that is an aggregate of odd-numbered electrodes starting from a predetermined electrode and an even-numbered electrode group that is an aggregate of even-numbered electrodes. In a developing device that is formed on the surface layer of a toner carrier and applies a periodic potential in the opposite phase between the odd-numbered electrode group and the even-numbered electrode group and develops it, it is applied to the odd-numbered electrode group Of the potentials, Vodd_max is the maximum potential applied to the same polarity side as the polarity of the toner, and the maximum potential applied to the same polarity side of the toner as the potential applied to the even-numbered electrode group. When Veven_max is set, the maximum potential V formed on the same polarity side as the polarity of the toner among the potentials formed at the end of the toner carrier is | V |> | Vodd_max |, | V |>. ｜ Vev Characterized in that it satisfies the relationship | n_max.
According to a second aspect of the present invention, electrode ends for collecting the odd-numbered electrode group and the even-numbered electrode group are provided at both ends of the toner carrier.
According to a third aspect of the present invention, an insulating member is provided at both ends of the toner carrier, and the insulating member surface layer is charged to satisfy the relationship of | V |> | Vodd_max | and | V |> | Veven_max |. It is characterized by that.

According to a fourth aspect of the present invention, there is provided a rubbing member for rubbing the insulating member, and the insulating member surface layer is charged by rubbing the insulating member with the rubbing member.
According to a fifth aspect of the present invention, a charging member for charging an electric charge is provided, and the charging member surface layer is charged by rubbing the charging member with the rubbing member.
According to a sixth aspect of the present invention, the surface layer material of the toner carrier is coated with a material capable of giving a regular charge to the toner in friction with the toner.
According to a seventh aspect of the present invention, the surface layer of the toner carrier is coated with a material having a volume resistivity of 10 ⁹ (Ω · cm) to 10 ¹² (Ω · cm).
According to an eighth aspect of the present invention, each electrode end that collects each of the odd-numbered electrode group and the even-numbered electrode group is connected to each end portion of the rotating shaft of the toner carrier that is electrically separated. And
According to a ninth aspect of the present invention, an average potential value at each instant of the periodic potential applied to the odd-numbered electrode group and the periodic potential applied to the even-numbered electrode group is formed on the electrostatic latent image carrier. It is a value between the image portion potential and the non-image portion potential.
A tenth aspect includes the developing device according to any one of the first to ninth aspects, and the developing device forms an image by superimposing at least two kinds of toner images on the electrostatic latent image carrier. It is characterized by that.

  According to the present invention, an odd-numbered electrode group that is an aggregate of odd-numbered electrodes starting from a predetermined electrode and an even-numbered electrode group that is an aggregate of even-numbered electrodes are formed on the surface layer of the toner carrier, In a developing device for developing by applying periodic potentials having opposite phases to each other between the odd-numbered electrode group and the even-numbered electrode group, the same polarity as the polarity of the toner among the potentials applied to the odd-numbered electrode group When the maximum potential applied to the side is Vodd_max and the maximum potential applied to the same polarity as the polarity of the toner among the potentials applied to the even-numbered electrode group is Veven_max, the end of the toner carrier The maximum potential V formed on the same polarity side as the polarity of toner has a relationship of | V |> | Vodd_max | and | V |> | Veven_max |. In, increasing the flare uniformity on the electrode, and can suppress the toner ejection of the end.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
FIG. 1 is an enlarged configuration diagram showing a cross section of a substrate that can perform the same function as the toner carrier of the image forming apparatus according to the present invention. In FIG. 1, an electrode pattern 2 obtained by processing a metal layer formed by vapor deposition of aluminum into a predetermined pattern is formed on a glass substrate 1. The electrode pattern 2 includes a plurality of electrodes 21, 22, 23... Arranged in the substrate surface direction at a pitch of p [μm]. A surface layer 3 made of a resin having a thickness of about 3 [μm] and a volume resistivity of about 10 ¹⁰ [Ω · cm] is formed on the solid surfaces of the electrode pattern 2 and the glass substrate 1.
The surface layer 3 is formed with a toner layer 5 made of a plurality of toner particles charged to a predetermined polarity (in this example, a negative polarity). The toner layer 5 is formed by developing a thin layer of a solid image made of toner on the surface layer 3 by a two-component developing device (not shown). The toner is composed of a plurality of toners made of polyester resin. The particle size of individual toner particles is about 6 [μm]. When the charge amount of the toner of the toner layer 5 developed on the surface layer 3 on the substrate 4 having such a configuration was measured, it was about −22 [μC / g].

FIG. 2 is a schematic view of an experimental machine incorporating this flare substrate. The flare substrate 12 is configured to move along the slide rail 11, and enters the developing area facing the photoconductor 10 in a state where toner is supplied onto the flare substrate 12.
FIG. 3 is a schematic view of a flare substrate. Experiments were conducted by installing electrodes or insulating members (insulating tape) at positions 16a and 16b indicated by broken lines in the figure. FIG. 3 shows a diagram in which the region 17 is divided into nine parts. The uniformity of flare, which is the main object of the present invention, is measured by measuring the toner amount in each of these nine regions and evaluating the unevenness of the adhesion amount. .

FIG. 4 is a diagram showing an experimental result when an electrode is installed at the end. The horizontal axis represents the bias applied to the end electrode, and the vertical axis represents the maximum adhesion amount-minimum adhesion amount value in each region shown in FIG. An AC voltage having a frequency of 1 kHz and Vpp of 400 V is applied to the flare substrate 12. Note that the adhesion amount in the initial state, that is, when the toner is supplied to the flare substrate 12 is 0.45 mg / cm ² . As is apparent from FIG. 4, the unevenness in the amount of adhesion varies greatly depending on the bias applied to the end electrodes. By applying an alternating voltage to the flare electrode, the toner enters a hopping state and forms a toner cloud.
Examples of the force acting on the toner in the cloud state include 1) a force received from an electric field formed by an interelectrode potential difference, and 2) a repulsive force between toners. When the electric field force is uniformly formed on the flare electrode surface, the behavior of the toner is diffused by the repulsive force between the toners. The results show that forming an electric field that repels the toner by the end electrodes pushes the toner back to the electrodes, resulting in in-plane uniformity.

In FIG. 4, the effect appears when the bias applied to the electrode is −200 V or more, that is, the negative maximum voltage applied to the flare electrode is −200 V or more. Even if the voltage is further increased, there is an effect. However, if the voltage is extremely increased, the toner is pushed back, and the toner near the end portion is reduced. In this experiment, in the case where −1 kV or more was applied, adhesion amount unevenness occurred.
Further, by providing insulating members at the end portions 14 and 15 and raising the potential of the surface layer, an effect equivalent to applying a voltage to the electrodes can be obtained. In the experiment, Teflon (registered trademark) tape was affixed to the dotted line portions 14 and 15 in FIG. 3, and the surface of the tape was raised by rubbing the surface moderately, and the same effect as in the case of the electrode was obtained. . In the experiment, the surface of the tape was rubbed, but it has also been confirmed that by installing a charging member, the potential can be increased more reliably and unevenness in the amount of adhesion on the flare electrode can be suppressed.

Specifically, of the potentials applied to the odd-numbered electrode group, Vodd_max is the maximum potential applied to the same polarity as the polarity of the toner, and the toner has the potential applied to the even-numbered electrode group. The maximum potential V formed on the same polarity side as the polarity of the toner among the potentials formed on the end portions 14 and 15 of the toner carrying member when the maximum potential applied to the same polarity side as the polarity is Veven_max. But,
| V |> | Vodd_max |
| V |> | Veven_max |
It is necessary to satisfy this relationship.
Although the main object of the present invention is to make the flare generation state uniform, it is necessary to stably generate the flare as a premise. For this purpose, the surface characteristics of the substrate are very important. In order to examine the influence of the electrical characteristics of the substrate surface, the volume resistivity of the surface layer was varied to confirm the same flare activity. The material used for the surface layer is a silicone-based resin. By changing the amount of carbon fine particles dispersed therein, a protective layer having a volume resistivity of 10 ⁷ to 10 ¹⁴ [Ω · cm] (thickness is about 5 [ μm]).

From the results shown in FIG. 5, it can be said that the volume resistivity of the surface layer 3 is in the range of 10 ⁹ to 10 ¹² [Ω · cm]. This is probably because the reason why this range is appropriate is as follows. That is, when the surface layer 3 having a very high volume resistivity is used, the surface of the substrate 4 remains charged due to friction between the surface layer 3 and the toner that repeats hopping. Due to this charging, the surface potential of the substrate fluctuates and the electric field contributing to development becomes unstable. On the contrary, if the volume resistivity of the surface layer 3 is too low, charge leakage (short circuit) occurs between the electrodes 21, 22, 23..., And an effective electric field is formed on the substrate 4. It will not be done. For these reasons, the volume resistivity of the surface layer 3 is such that excessive charges generated in the surface layer 3 can be released to the electrode groups 21, 22, 23. It is thought that it is necessary to be a large value (10 ⁹ to 10 ¹² [Ω · cm] in volume resistivity).

FIG. 6 is a perspective view showing a toner carrying roller 31 as a toner carrying body of the image forming apparatus according to the present embodiment. In the toner carrying roller 31, an electrode shaft 40A and an electrode shaft 40B, which are rotating shaft members protruding from both end surfaces in the axial direction of the roller portion, are rotatably supported by a bearing (not shown). The roller portion is formed with an electrode pattern including a plurality of electrodes 41, 42, 43... Arranged at a pitch of p [μm] along the surface movement direction by rotation. An odd-numbered electrode group that is an aggregate of odd-numbered electrodes in this electrode pattern is connected to the electrode axis A. In addition, an even-numbered electrode group that is an aggregate of even-numbered electrodes in the electrode pattern is connected to the electrode shaft 40B. A pulse voltage output from an AC power source (not shown) is applied to the electrode shafts 40A and 40B via a contact member such as an electrode brush (not shown).
As shown in FIG. 7A, the toner carrier roller is formed of stainless steel in the shaft hole 52 of the cylinder 51 made of acrylic resin, which is an insulator provided with the shaft hole 52, as shown in FIG. The electrode shafts 40A and 40B are press-fitted, so that the electrode shafts 40A and 40B are connected to the odd-numbered electrode groups 41, 43..., The even-numbered electrode groups 42.

In the example shown in FIG. 8, metal flange-shaped electrode shafts 40A and 40B are provided at both ends in the axial direction of the toner carrying roller 31, and the flange-shaped electrode shafts 40A and 40B and the longitudinal direction of each electrode are provided. An example in which one end is connected is shown.
Each electrode of the cylinder 51 is formed by each process shown in FIGS. FIG. 9 shows the surface of the toner carrying roller 31 from the direction along the rotation axis. In the process shown in FIG. 9, first, the surface of the roller is finished smoothly by peripheral turning (FIG. 9A). Next, the grooves 53 are cut so that the pitch is 100 [μm] and the width is 50 [μm] (FIG. 9B). Then, after electroless nickel 54 is plated from above (FIG. 9C), unnecessary conductor film is removed by cutting the plated outer periphery (FIG. 9D). At this time, the electrodes 41, 42, 43,... Thereafter, the roller surface is smoothed by coating with a silicone resin, or a surface layer (thickness of about 5 [μm], volume resistivity of about 10 ¹⁰ [Ω · cm]) 55 is formed (FIG. 9E). . In this way, the toner carrying roller 31 having the electrode configuration as shown in FIG. 6 is formed.

FIG. 10 shows an example of a developing device using the toner carrying roller of FIG. A toner carrying roller is installed at the position of the developing roller of a normal one-component developing device, the amount of toner is regulated by the doctor blade, and an AC voltage having a higher Vpp is applied to the doctor blade than between the flare electrodes of the present invention. By doing so, the flare activity is increased and sent to the development area. In the development area, a toner image is formed by the difference between the average potential on the surface of the toner carrying roller and the potential of the latent image carrier, and unnecessary toner that has not contributed to development returns to the toner reservoir again. Since the flare is formed, the adhesion force of the toner to the toner carrying roller is very low, and the toner returned from the developing unit by the toner carrying roller is easily scraped by the rubbing between the toner in the toner reservoir. Or get used to. By repeating this, a substantially constant amount of toner flare is always formed on the toner carrying roller.
FIG. 11 shows an example of the color superimposing system on the photoconductor configured by using the developing device of FIG. 10. By using such a system, writing for four colors is performed on the same photoconductor. Compared with the four-tandem tandem system, in principle there is almost no displacement. Further, by using the developing device according to the present invention, since there is no influence on the toner image once formed on the photosensitive member, there is no problem such as scavenging or color mixing, and high-quality image formation is possible. The process can be performed stably over the long term.

FIG. 3 is an enlarged configuration diagram showing a cross section of a substrate that can perform the same function as the toner carrier of the image forming apparatus according to the present invention. It is the schematic of the experimental machine incorporating this flare board | substrate. It is the schematic of a flare board | substrate. It is a figure which shows the experimental result at the time of installing an electrode in an edge part. It is a figure which shows the relationship between the volume resistivity of a surface layer of a board | substrate, and flare activity. FIG. 3 is a perspective view illustrating a toner carrying roller of the image forming apparatus according to the embodiment. (A)-(c) is sectional drawing which shows a part of manufacturing process of the toner carrying roller, respectively. FIG. 3 is an enlarged schematic plan view showing a toner carrying roller. (A)-(e) is sectional drawing which shows another part of the manufacturing process in a toner carrying roller. FIG. 10 is a diagram illustrating an example of a developing device using the toner carrying roller of FIG. 9. FIG. 11 is a diagram of a color overlay system on a photoconductor configured using the developing device of FIG. 10.

Explanation of symbols

  31 toner carrier roller (toner carrier), 40A, 40B electrode shaft, 41, 42, 43 electrode,

Claims (10)

An odd-numbered electrode group that is an aggregate of odd-numbered electrodes starting from a predetermined electrode and an even-numbered electrode group that is an aggregate of even-numbered electrodes are formed on the surface layer of the toner carrier. In the developing device for developing by applying periodic potentials of opposite phases between the number of electrode groups,
Of the potentials applied to the odd numbered electrode group, Vodd_max is the maximum potential applied to the same polarity as the polarity of the toner, and among the potentials applied to the even numbered electrode group, the same as the polarity of the toner When the maximum potential applied to the polarity side is Veven_max, the maximum potential V formed on the same polarity side as the polarity of the toner among the potentials formed at the end of the toner carrier is:
| V |> | Vodd_max |
| V |> | Veven_max |
A developing device satisfying the relationship:   2. The developing device according to claim 1, wherein electrode ends for collecting the odd-numbered electrode groups and the even-numbered electrode groups are provided at both ends of the toner carrier. By providing an insulating member at both ends of the toner carrier, and charging the insulating member surface layer,
| V |> | Vodd_max |
| V |> | Veven_max |
The developing device according to claim 1, wherein the developing device is configured to satisfy the above relationship.   The developing device according to claim 3, wherein a rubbing member that rubs the insulating member is provided, and the insulating member surface layer is charged by rubbing the insulating member with the rubbing member.   The developing device according to claim 3, wherein a charging member that charges electric charges is provided, and the charging member surface layer is charged by rubbing the charging member with the rubbing member.   6. The surface layer material of the toner carrier is coated with a material capable of giving a regular charge to the toner in friction with the toner. 6. Development device. 7. The surface layer of the toner carrier is coated with a material having a volume resistivity of 10 ⁹ (Ω · cm) to 10 ¹² (Ω · cm). The developing device according to one item.   2. The electrode ends for gathering the odd-numbered electrode group and the even-numbered electrode group, respectively, are connected to respective end portions of the rotating shaft of the toner carrier that is electrically separated. The developing device according to claim 1.   An image portion in which a potential average value at each instant of the periodic potential applied to the odd-numbered electrode group and the periodic potential applied to the even-numbered electrode group is formed on the electrostatic latent image carrier. The developing device according to claim 1, wherein the developing device has a value between a potential and a non-image portion potential.   A developing device according to claim 1, wherein the developing device forms an image by superposing at least two types of toner images on an electrostatic latent image carrier. Image forming apparatus.

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