JP4331763B2 - Method for developing conductive particles - Google Patents

Description

The present invention relates to the development of electrostatic printing and electrophotography, and more particularly to a method and apparatus for developing with conductive particles.

The electrophotographic method invented by Carlson in 1983 has spread all over the world due to its resolution and high output speed, and has been improved today.
A developer for developing an electrostatic latent image is called a toner, and it can be said that various improvements have been made in the world of copiers and printers.

General toner is a mixture of pigment and resin particles. In the case of dry type, the electrostatic latent image is developed by using triboelectric charging with magnetic particles or developing sleeve, and in the case of liquid using solvation. It is common.
Since the toner holds the charged electric charge, the toner adheres to the magnetic particles or the developing sleeve, is transported to the vicinity of the electrostatic image carrier, and is developed to adhere to the image carrier by an electric field. Since the undeveloped toner adheres to the magnetic particles or the sleeve, it is collected by a scraping plate, a brush, a roller or the like, mixed with the developer in the toner reservoir, and used again for development. In a system that further requires electrostatic transfer, the toner maintains charge even on the image carrier and is transferred to the transfer target by an electric field at the transfer portion.

In order to realize such a series of operations, at least a part of the surface of the toner must be substantially an insulator in order to maintain charging.
In recent years, there has been a demand for manufacturing a wiring board directly from digital data by taking advantage of the resolution of electrophotography, the speed of output speed, and the advantage of obtaining hard output directly from digital data. Various ideas have been made to enable development.

Examples of patents include the following.
JP 59-189617 A JP 59-202682 A JP-A-60-137886 JP 60-160690 A In these patent examples, a method is disclosed that uses a metal toner that is coated with an insulating resin around conductive particles. These are intended to be developed and transferred by electrophotography by applying a thin insulating film to the metal particles to cause a behavior equivalent to that of insulating toner. Most of the toners referred to as conductive toners and metal toners in the electrostatic printing method and electrophotographic method are of this type, and are not simple conductive particles or metals.

Applying an insulating film to the conductive material or including a resin is a method that is easy to handle for the electrostatic printing method or the electrophotographic method, but is extremely troublesome for the purpose of using the conductive material.
The purpose of electrical conductivity has a large purpose of flowing current therethrough, and no matter how the insulating coating material is devised, the result is an electrode or wiring with high electrical resistance.
For this reason, the current situation is that it is used only for limited applications such as blowing off the insulating coating at a high temperature.

In order to improve the above-mentioned conductivity, Japanese Patent Laid-Open Nos. 58-57883 and 07-254768 have been proposed. In these patents, a method is proposed in which vanadium or the like serving as a base material for initiating plating is included in the surface of the toner, and after patterning, plating is performed thereon to form a conductive pattern. However, in the plating method, another process is added, and it is out of the production of the wiring board directly from the digital data, and the merit is also halved.
In addition to the production of the wiring board, there is a demand for patterning without including any impurities in the conductive material, and there is an increasing demand for handling the conductive material itself.

The reason why a conductive material itself that is not treated with resin or the like in electrophotography or electrostatic printing method cannot be handled well is because it completely contradicts the characteristics required for electrostatic toner.

The toner must first be dispersed into individual particles. It must be transported close to the image carrier. Do not splash when transported. Do not destroy the electrostatic latent image. Be sure to be charged to the desired polarity and not adhere to any part other than the target latent image. Etc. are required.

Ordinary toner is almost an insulator, and when charged by contact charging or the like, the repulsive force acts naturally and disperses into individual particles. In addition, when charged, it electrostatically adheres to a conveying material called magnetic particles and is freely conveyed, and even if it is dynamically swung, it hardly scatters. Further, even if it is in contact with the image carrier, if it is an insulator, it will not destroy the latent image, and will adhere only to the electrostatic attracting area, and will not adhere to the reverse polarity part.
In this way, the toner is devised to ensure that each particle is charged uniformly and reliably to the target polarity.

However, if it is a conductive material, it is difficult to disperse and charge each individual particle, and it is difficult to maintain the charge, so that it is a conductor if it is scattered by conveyance and touches the latent image. As a result, the electric charge leaks and the electrostatic latent image is destroyed.

In order to solve these problems, the inventors proposed in Japanese Patent Application No. 2005-214192 a method of developing conductive particles not containing a resin. It mixes conductive particles with magnetic materials such as ferrite particles or iron particles, and transports them to the vicinity of the image carrier by holding them in a magnetic material carried in a conductive nonmagnetic sleeve containing a magnetic aggregate, and by an electric field This is a developing method in which the conductive particles are developed by flying onto an image carrier. As a result, compared to the system disclosed in Japanese Patent Laid-Open No. 63-88893, a relatively free system configuration can be achieved as in the case of a conventional developing device, such as being arranged laterally with respect to the photoreceptor.

However, in the developing device according to the invention, since the conductive powder is only held in the magnetic powder and has no adhesion, when the developing sleeve is rotated at a high speed, the conductive powder is scattered by centrifugal force and adheres to the background. There is a limitation that it can only be used on low-speed systems.

The present invention provides a method of developing conductive particles that do not contain a resin that can be applied to a high-speed system.

The basic configuration of the present invention will be described with reference to FIG.
The conductive particles 1 supplied from the toner hopper 9 are mixed by the rotation of the magnetic particles 2 and the paddle 5 and mechanically dispersed. The magnetic roll is composed of a conductive non-magnetic sleeve 3 and a magnetic assembly 4, and the magnetic particles 2 hold the conductive particles 1 and are attracted to the magnetic force of the magnetic assembly 4 to be attached to the sleeve 3. The sleeve 3 is rotating and tries to carry a large amount of the magnetic particles 2 holding the conductive particles 1 by the magnetic force of the magnetic aggregate 4. Keep the thickness constant. This is because a gap is formed so that the magnetic particles 2 and the conductive particles 1 on the sleeve 3 do not come into contact with the developing roller 12 spaced apart from the magnetic roller.

A developing bias power source 7 is connected to the developing roller 12, and an auxiliary power source 8 is connected to the sleeve 3, and the conductive particles 1 fly through the gap due to a voltage difference applied to each, and adhere to the developing roller 12. Then, it is carried to the vicinity of the image carrier 10.

If the magnetic particles 2 and the conductive particles 1 on the developing roller 12 and the sleeve 3 are in contact with each other, the developing roller 12 and the sleeve 3 are short-circuited, and a voltage difference between the developing roller 12 and the sleeve 3 does not occur. The conductive particles 1 cannot fly and cannot adhere to the developing sleeve 12.

The developing roller 12 is arranged with a gap so that the conductive particles 1 attached to the surface do not come into contact with the image carrier 10. The image carrier is composed of a conductive substrate 11 and an insulating coating or a photoreceptor 10 to form an electrostatic latent image. Development is performed by supplying an electric field by the developing bias power source 12 so that the conductive particles 1 fly from the developing roller only to the signal latent image but not to the background.
When the magnetic roller rotates at a high speed, the conductive particles are scattered. However, as shown in FIG. 1, the conductive particles are surrounded by the developing roller 12, the scraper 13, and the case and are not scattered outside, so that high speed development is possible.

The configuration of FIG. 1 is similar to the configuration of a developing device that performs resin-toning development at first glance, but the working mechanisms are completely different. The different points will be described in detail.

First, in the dispersed portion, the conductive particles are not charged and dispersed by stirring with the magnetic particles, but the magnetic particles are mechanically ground to disperse the conductive particles into fine particles. For example, when ferrite particles are used as magnetic particles and copper powder is used as conductive particles, and the mixed particles obtained by stirring these particles are observed with a microscope, the ferrite particles and the copper powder are separated, and there is no appearance that they are adhered to each other.
The magnetic particles are attracted by the magnetic force of the magnetic assembly 4 of the magnetic roll and are attached to the sleeve 3. Also at this time, the conductive particles 1 are not charged by the stirring with the magnetic particles 2 and attached to the magnetic particles 2 or the sleeve 3 but are caught between the magnetic particles, held and conveyed.

There are a method of fixing the magnetic assembly 4 so as not to rotate and a method of rotating in the direction opposite to the rotation of the sleeve 3. Each has its own characteristics, and which is selected depends on the size and shape of the magnetic particles and conductive particles used.

FIG. 2 shows the state of one magnetic particle on the moving sleeve by fixing the magnetic assembly so that the movement of the magnetic particle 2 when the magnetic assembly 4 and the sleeve 3 move relatively can be easily understood. is doing. Since the magnetic particles change their direction while being pulled along the magnetic force lines of the magnetic assembly 4, they roll on the sleeve. If the sleeve 3 and the magnetic assembly 4 are rotated in the opposite directions, the magnetic particles will rotate at a higher speed, and the conductive particles held in the back will come out to the surface evenly and fly in the next stage. Increase efficiency.

When the magnetic assembly 4 is fixed, the magnetic particles stand perpendicular to the sleeve at the magnetic pole portion, so that the conductive particles near the sleeve are free. Become. That is, it is easy to fly if exposed to an electric field without being shielded by magnetic particles.

Then, if only the sleeve is rotated without flying as it is, the conductive particles 1 will spill downward. This is the same for a metal particle such as copper powder having a high specific gravity, but also for a carbon particle having a low specific gravity. This phenomenon also indicates that the conductive particles 1 hardly adhere to the magnetic particles 2 and the sleeve 3.
Since the magnetic particles 2 are only used for transporting the conductive particles 1 by a magnetic roller, they are not affected by the type of magnetic particles. An electrically insulating material such as a ferrite particle or a metal magnetic particle may be used. Also, those containing resin, such as those obtained by binding them with a resin, those obtained by coating those magnetic particles on the surface of the resin, and those obtained by coating the surface of the magnetic particles with a resin are also acceptable.

The resin particles coated on the surfaces of the magnetic particles are likely to be charged due to friction between the resin and the metal particles, but are unlikely to adhere unless the metal particles are very fine. The inventors have confirmed that ferrite particles are coated with acrylic resin, polytetrafluoroethylene resin, etc., and when carbon or copper powder having a particle size of about 5 to 20 microns is mixed, most of the appearance is attached. There was no. Even if there is a slight frictional charge, it is considered that a force sufficient to adhere cannot be obtained.

The developing bias power source 7 connected to the developing roller 12 and the auxiliary power source 8 connected to the sleeve 3 provide an electric field for the conductive particles 1 held in the magnetic particles 2 to fly to the developing roller 12. When the magnetic particles 2 are insulative, the conductive particles 1 are injected with charge from the sleeve 3 when they contact the sleeve 3, and then charge or fly, or are polarized according to the electric field, and are charged according to the strength of the electric field. Release, charge and fly. When the magnetic particles 2 are conductive, the conductive particles 1 are charged from the magnetic particles 2 and charged and fly. In addition, it is considered that the magnetic particles 2 in contact with the conductive particles 1 should also be polarized in order to facilitate the discharge of charges. Therefore, when the magnetic particles 2 are electrically insulating like ferrite, the flying efficiency will increase if the surface is conductively treated.
The flying conductive particles 1 adhere to the developing roller 12 and are carried to the vicinity of the image carrier 10. The developing roller 12 is usually made of an aluminum drawing material or stainless steel, and it has been confirmed that the same can be used in the present invention. Here, it becomes a question why the conductive particles adhere to the developing roller which is a very low conductor.

As described above, the flying conductive particles 1 are charged and reach the developing roller 12. At this time, since the developing roller 12 is a conductor, the charged electric charge should be lost and the adhesion due to electrostatic force should be lost. In fact, even if measured with a surface electrometer, the potential is hardly displayed. In this case, the dominant adhesion is considered to be van der Waals force. The adhesion force due to the van der Waals force increases as the developing roller 12 and the conductive particles 1 come into close contact with each other, and increases as the contact area increases. If this force is greater than the centrifugal force and guidance of the developing roller 12 and the gravity of the electroparticles 1 themselves, they will continue to adhere. It is considered that the phenomenon of increasing the adhesion and the contact area is obtained by causing the conductive particles 1 to adhere to the surface of the developing roller 12 by flying. And once attached, since there is no external force which peels off the attachment, it is thought that it can continue adhering. Such a situation can hardly be obtained by other means.

When organized, the adhesive force is considered to depend on the contact area, that is, the number of contact points. The force acting in the peeling direction is thought to depend on gravity, centrifugal force, kinetic energy of the particles themselves, and impact energy received from the outside.
If the adhesion principle is as described above, the adhesion situation depends on the shape and weight of the conductive particles 1.
Although detailed experiments have not been conducted, it is confirmed that the probability of adhesion is extremely reduced when the particle size is about 100 microns or more with copper particles having an irregular shape, and that even when the particle size is spherical, it cannot be adhered even with a particle size of 80 microns. It was done. Although other materials such as iron powder and carbon particles have not been confirmed, it is considered that a particle size that can be adhered is probably required in proportion to the specific gravity of the copper particles.

In Japanese Patent Application Laid-Open No. 07-333980, a conductive toner is mixed with a magnetic carrier, conveyed by a magnetic roll generally used in electrophotography, only the magnetic carrier is blocked by a regulating blade, and only the conductive toner is a sleeve. An embodiment is described in which it is deposited on top and conveyed to the vicinity of the image carrier. In this method, the magnetic carrier blocked by the regulating blade against the conductive toner adhering to the sleeve collides with the conductive toner adhering to the sleeve and works in the direction of peeling the conductive toner from the sleeve. The conductive toner cannot be adhered.

As described above, according to the present invention, adhesion and conveyance are performed based on a completely different principle from the operation of toner that is charged and adhered. Since the conductive particles are not charged, the presence or absence of flight is determined only by the magnitude of the potential difference regardless of the direction of the electric field (voltage polarity).
Thus, the charging polarity of the conductive particles can be freely controlled by the polarity of the developing bias voltage supplied. Further, the voltage of the developing bias power source 7 may be only DC, but if the AC component is superimposed, the flying effect is further improved. These are illustrated in the following examples.

In the configuration of FIG. 1, carbon particles having an average particle size of 5 cron were used as the conductive particles 1, and iron powder having an average particle size of 100 microns was used as the magnetic particles 2. Both the sleeve 3 and the developing roll 12 are made of aluminum, the narrowest gap between the surface of the sleeve 3 and the developing roll 12 is 4 mm, the gap between the sleeve 3 and the regulating blade 6 is 1 mm, the surface of the developing roll 4 and the image carrier The narrowest gap on the surface of the body was 1 mm. When the signal potential of the electrostatic latent image on the image carrier is plus 100 V, the background is plus 700 V, and the surface speed of the image carrier is 100 mm / sec, the developing bias power source 7 is plus 800 V, and the auxiliary power source 8 is 0 V. Alternatively, by applying plus 1600 V, development with no fogging and a certain degree of contrast has been achieved.

The potential difference between the auxiliary power supply 8 and the developing bias power supply 7 is also 800 V, and when the auxiliary power supply 8 is set to 0 V, the copper particles are negatively charged from above the sleeve 3 according to the direction of the electric field and fly to the developing roller. When the power source 8 is set to plus 1600 V, the carbon particles are charged plus and fly to the developing roller. Regardless of the polarity of the carbon particles, the charge is lost when the carbon particles are attached to the developing roller, so the flying condition from the developing roller does not change. In either case, the signal latent image is positively charged plus 100V. Fly to the part. The signal latent image portion flies with a potential difference of 700 V, and does not fly with a potential difference of 100 V from the background.

In the configuration of FIG. 1, as in Example 1, carbon particles having an average particle size of 5 microns were used as the conductive particles 1, and iron powder having an average particle size of 100 microns was used as the magnetic particles 2. Both the sleeve 3 and the developing roll 12 are made of aluminum, the narrowest gap between the surface of the sleeve 3 and the developing roll 12 is 3 mm, the gap between the sleeve 3 and the regulating blade 6 is 1 mm, and the surface of the developing roll 4 and the image carrier The narrowest gap on the surface of the body was 1 mm. When the electrostatic latent image on the image carrier has a signal potential of +700 V, a background of +100 V, and the surface speed of the image carrier is 100 mm / sec, contrary to the first embodiment, the developing bias power supply 7 has 0 V. By applying plus 800V or minus 800V to the auxiliary power source, development with no fogging and some contrast could be achieved.

The carbon particles are negatively charged and fly from the developing roller to the latent image, which is different from that in the first embodiment, but the conditions for the presence or absence of the flight are exactly the same as those in the first embodiment, and the signal latent image portion has 700V. It flies due to a potential difference, and does not fly when the potential difference from the background is 100V. In this way, whether the latent image is positive or negative, it can be established without changing any other components by adjusting only the power supply conditions.

In the configuration of FIG. 1, copper particles having an average particle size of 10 microns were used as the conductive particles 1, and ferrite particles having an average particle size of 100 microns were used as the magnetic particles 2. Both the sleeve 3 and the developing roll 12 are made of aluminum, the narrowest gap between the surface of the sleeve 3 and the developing roll 12 is 4 mm, the gap between the sleeve 3 and the regulating blade 6 is 1 mm, the surface of the developing roll 4 and the image carrier The narrowest gap on the surface of the body was 1 mm. When the electrostatic latent image of the image carrier has a signal potential of plus 100 V, the background is plus 700 V, and the surface speed of the image carrier is 100 mm / sec, the development bias power supply 7 is supplied with DC 400 V and 500 Hz AC 400 VP-P. When 0V was applied to the superposed voltage 8 and the auxiliary power source 8, there was no fog and development with high density and high contrast was achieved.

The alternating electric field is considered to have an effect of vibrating the conductive particles to dissolve the particles and to facilitate the flight. According to the paper, in the conventional toner flying, it is explained that the toner once flies over the entire surface of the image carrier and the background is pulled back at the time of the reverse electric field of the AC, but does not include the resin targeted by the present invention. Since the conductive particles have low resistance, the latent image charge distribution is destroyed when the particles are returned to the entire surface and pulled back, and a normal image is not obtained. It is necessary to give the background a condition not to fly, which is different from the conventional superposition action.

An attempt was made to develop copper particles having a particle size of 100 microns close to a true sphere under the conditions of Example 3, but the copper particles did not adhere to the developing roller 12 made of aluminum and could not be developed. When the surface of the developing roller 12 was covered with an insulating film tube, it adhered to the developing roller 12 but it was very difficult to fly to the image carrier. When the surface of the developing roller 12 was covered with a semiconductive film tube, the copper particles adhered under the electric field conditions of Example 3 and could be developed. Other effects such as winding a semiconductive rubber around the surface of the developing roller 12 and applying a semiconductive resin obtained by kneading resin and carbon were effective. The semiconductive resistance value was measured by comparing the nip width obtained by pressing a conductive plate on the surface of the developing roller with a constant pressure and the current when a voltage was applied. From these calculated values, it was concluded that sufficiently good development can be achieved if it is about 10 9 Ω · cm or less.

The adhesion effect by making the developing roller 12 semiconductive is not logically clear. Real materials are not like those handled by pure semiconductor physics, but most are handled with an average resistance value by mixing conductive materials and insulators, so in reality there are parts that can be charged and held in minute parts, It is considered that a slight electrostatic charge remains on the adhered conductive particles, and the adhesion force is increased by the electrostatic force. In addition, since the material that is a mixture with the resin is lower in hardness than the metal, the conductive particles have a buffering effect when flying and colliding, the contact area and adhesion are larger than the metal, due to van der Waals force It is thought that the adhesion force increases. Alternatively, the above two phenomena may occur together, resulting in stronger adhesion.

Various conditions such as applied voltage and distance in the above embodiment are representative examples, and appropriate conditions differ depending on the material, particle diameter, specific gravity, etc. of the conductive particles, and do not limit the present invention.

Illustration of the basic configuration of the present invention Illustration of the behavior of magnetic particles on the sleeve

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 2 ... Magnetic particle 3 ... Conductive nonmagnetic sleeve 4 ... Magnetic assembly 5 ... Paddle 6 ... Regulating blade 7... Development bias power supply 8... Auxiliary power supply 9... Toner hopper 10... Electrostatic image carrier 11. Developing roller 13 ··· Scraper

Claims (5)

In an apparatus comprising an electrostatic image carrier and a developing device, the developer is a conductive particle containing no resin, and the developing device has a mechanism and magnetic assembly for stirring and mixing the conductive particle and the magnetic particle. A magnetic roller having a conductive nonmagnetic sleeve enclosing the magnetic roller, a regulating blade for regulating the thickness of the magnetic particles on the magnetic roller, and a nonmagnetic developing roller, and the conductive particles on the magnetic roller and the developing The roller is disposed in a non-contact manner, and the conductive particles on the developing roller and the electrostatic image carrier are disposed in a non-contact manner, and the conductive particles are caused to fly from the magnetic roller to the developing roller by an electric field. A developing method characterized in that development is performed by causing an electric field to fly from the developing roller to the image carrier. 2. The developing method according to claim 1, wherein the developer is carbon particles or metal particles. 2. The developing method according to claim 1, wherein the magnetic particles are ferrite particles or magnetic metal particles, or the particles include a resin. 2. The developing method according to claim 1, wherein the surface of the developing roller is made of a metal or a semiconductive material and has an electric resistance of 10 <9> [Omega] .cm or less. 2. The developing method according to claim 1, wherein the electric field for causing the conductive particles to fly is a superposition of a DC electric field and an alternating electric field.

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