JPH047506B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in a method for developing an electrostatic latent image or a magnetic latent image in an electrophotographic copying device, etc., and more particularly, the present invention relates to an improvement in a method for developing an electrostatic latent image or a magnetic latent image in an electrophotographic copying apparatus. So-called magnetic brush development, in which a mixed two-component developer is supplied to the surface of a developer transport carrier to form a developer layer on the developer transport carrier, and the latent image on the image carrier surface is developed with the developer layer. Concerning improvements in methods.

[Prior art]

First, as an example, an outline of a developing method in an electrophotographic copying apparatus will be described. Regarding this, the general magnetic brush development method using a two-component developer is relatively easy to control the triboelectrification of toner particles, is less likely to aggregate, and the magnetic brush has good spikes, and image bearing Excellent abrasion properties on the body surface,
Since it has the characteristic of exhibiting a sufficient cleaning effect even when used for cleaning, it is widely used even though it is necessary to control the amount of toner particles relative to carrier particles.
Conventionally, this developing method generally uses a two-component developer consisting of magnetic carrier particles with an average particle diameter of several tens to hundreds of micrometers and toner particles for heat fixing with an average particle diameter of more than ten micrometers. ing. Instead of toner particles for heat fixing, toner particles for pressure fixing, which can be easily fixed on recording paper without the need for a heating means, can be used, and a carrier that triboelectrically charges the toner particles can be used. During agitation with particles, toner particles tend to settle on the surface of carrier particles or toner particles agglomerate together. Since strong rubbing is used, there is a problem in that the adhesion between toner particles and carrier particles becomes even stronger.

Furthermore, because the toner particles and carrier particles of the developer are coarse, it is difficult to obtain high-quality images that reproduce delicate lines, dots, and differences in shading using conventional magnetic brush development methods. That is, in order to obtain high-quality images in this developing method, conventional techniques such as resin coating of carrier particles, etc.
Many efforts have been made to improve the magnets in the developer transport carrier and consider the bias voltage for the developer transport carrier, but it is still not possible to obtain stable and fully satisfactory images. This is the reality. Therefore, in order to obtain high quality images, it is considered necessary to make the toner particles and carrier particles even finer. However, when the toner particles are made into fine particles with an average particle size of 20 μm or less, especially 10 μm or less, the influence of Van der Waals force becomes large relative to the Coulomb force during development, and the background part of the image is affected. So-called fogging, in which toner particles adhere to the toner particles, occurs, and it becomes difficult to prevent fogging even by applying a DC bias voltage to the developer transport carrier. It becomes difficult to control triboelectrification of toner particles, and aggregation becomes more likely to occur. On the other hand, as the carrier particles are made finer, the carrier particles also come to adhere to the electrostatic image portion of the image carrier. The reason for this is thought to be that the magnetic bias force was reduced and the carrier particles adhered to the image carrier side together with the toner particles. Note that as the bias voltage increases, carrier particles will also adhere to the ground portion of the image background. The problem with micronization is that the side effects mentioned above are more noticeable and clear images cannot be obtained, so it is difficult to actually use micronization of toner particles and carrier particles. It was hot.

[Purpose of the invention]

The present invention makes it possible to easily fix toner particles on recording paper, prevent fixation and aggregation of toner particles on carrier particles, and furthermore, it is possible to use fine particle toner and carrier particles and is delicate. The present invention provides a method for developing an electrostatic latent image or a magnetic latent image that can faithfully reproduce lines, points, shading differences, etc.

[Structure of the invention]

The present invention provides a method for forming a two-component developer layer consisting of toner particles and magnetic carrier particles on the surface of a developer carrier, and developing an image on the surface of an image carrier with the developer layer. A developing method characterized in that toner particles for pressure fixing are used and the development is performed under an oscillating electric field.

Hereinafter, the present invention will be described with reference to a case where an electrostatic image formed on an image carrier such as a photoreceptor is developed.

In the present invention, the toner particles for pressure fixing used in the two-component developer are fixed to the recording paper when applied with a pressure roller for fixing at a linear pressure of about 20 kg/cm. Fusing toner particles are used. Such toner particles include polyolefins, ethylene-vinyl acetate copolymers, polyurethane, adhesive resins such as rubber, or fatty acid waxes such as palmitic acid and stearic acid, with coloring components such as carbon added as necessary. In the case of magnetic toner, metals such as iron, chromium, nickel, and cobalt, or compounds and alloys thereof, such as triiron tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide, Particles containing dispersed fine particles of ferromagnetic or paramagnetic substances such as ferrite, manganese-copper alloy, etc., and the outer side of such particles with good adhesiveness are used as ordinary heat fixing toner particles. There are known microcapsule-type particles coated with a highly chargeable resin (which may contain a coloring component, etc.). Particularly preferred in the present invention are spherical dispersed toner particles and microcapsule toner particles in which the above-mentioned highly adhesive particles are formed into spherical shapes by a spray drying method, a flow coater method, a granulation polymerization method, etc. It will be done. Note that the spheroidizing treatment in the flow coater method may be performed using hot air or hot water. When such spherical toner particles are used, the fluidity of the toner particles is improved, and toner particles are significantly prevented from firmly adhering to carrier particles or agglomerating with each other.
In addition, electrification due to friction with carrier particles has become effective, and for this reason, only toner particles are selectively applied to electrostatic images from a developer layer formed with carrier particles and an appropriate toner concentration. At the same time, the transfer efficiency and fixing performance from the surface of the image carrier to the recording paper are improved. This is due to the spherical shape of the toner particles, which reduces the contact area between the toner particles and the carrier particles and between the toner particles and the image bearing surface, reducing non-uniform forces that are difficult to control, such as van der Waals forces. This is thought to be related to the following factors: acicular protrusions, edges, or elongated shapes that cause charge concentration and discharge neutralization are less likely to occur, and the contact pressure with the recording paper is higher. . For this purpose, the toner particles are preferably spherical so that the ratio of the major axis to the minor axis is at least 3 times or less.

Further, magnetic toner is preferably used in the present invention, and in particular, the amount of magnetic fine particles in the toner particles is
It is preferably used that does not exceed 60 wt%, particularly not exceeding 30 wt%. When the toner particles contain magnetic particles, the toner particles are influenced by the magnetic force of the magnet included in the developer transport carrier, which further improves the uniformity of the developer layer. Furthermore, fogging is prevented from occurring, and toner particles are less likely to scatter. However, if the amount of magnetic material contained is too large, the magnetic force between the carrier particles and the carrier particles becomes too large, making it impossible to obtain a sufficient developing density. As a result, frictional charging control becomes difficult, toner particles are more likely to be damaged, and toner particles are more likely to aggregate with carrier particles.

Further, the toner particles used in the present invention preferably have an average particle diameter of 20 μm or less, particularly 10 μm or less so that high-quality images can be obtained. As the average particle size of the toner increases, as described above, the roughness of the image becomes noticeable. Usually 10 pieces/
Toner with an average particle size of about 20 μm is not a practical problem for developing fine lines lined up at a pitch of about mm, but
However, when a finely divided toner with an average particle diameter of 10 μm or less is used, the resolution is significantly improved, and development can be performed that faithfully reproduces the difference in density and the like.
Such toner particles can be obtained by sorting the toner particles obtained by the method described above, if necessary, by a known average particle size sorting means. However, in general, when the average particle size of toner particles is reduced, it becomes easier to reproduce delicate lines, dots, and differences in shading, but on the other hand, the amount of triboelectric charge qualitatively decreases in proportion to the square of the particle size. On the other hand, adhesion forces such as Van der Waals force become relatively strong, making it difficult for toner particles to separate from carrier particles, or once toner particles adhere to a non-image area of the image carrier surface. This cannot be easily removed by rubbing with a magnetic brush, causing fogging. In conventional magnetic brush development methods, the average particle size of toner particles is
This problem became noticeable when the thickness was less than 10 μm.
This is also true in the conventional magnetic brush development method.
This is one of the reasons why toner particles for pressure fixing are not used as toner particles.

The present invention mainly performs development under an oscillating electric field, thereby solving the above-mentioned problems caused by using toner particles for pressure fixing as toner particles of a two-component developer, and the above-mentioned problems when toner particles are made into fine particles. I'm trying to solve the problem. That is, the toner particles attached to the developer layer are easily transferred from the developer layer to the image area or non-image area of the image bearing member surface by the electrically applied vibrations, and are easily separated from the developer layer. When the surface of the image carrier is rubbed with the developer layer, toner particles attached to the non-image area of the image carrier can be easily removed or moved to the electrostatic image area, and the developer layer can be easily removed or moved to the electrostatic image area. If the thickness of the layer is made thinner than that between the image carrier surface and the developer transport carrier, the migration of toner particles with a low charge amount to image areas and non-image areas will be significantly reduced, and Since toner particles are not rubbed against the toner particles, they do not adhere to the image carrier due to frictional electrification, and toner particles of about 1 μm can now be used. Therefore, it is possible to obtain a clear toner image with good reproducibility in which the electrostatic latent image is faithfully developed. Furthermore, since the oscillating electric field weakens the bond between the toner particles and the carrier particles, the adhesion of the carrier particles associated with the toner particles to the image carrier surface is also reduced. The effect of development under an oscillating electric field becomes even more remarkable when spherical toner particles are used as the toner particles. In particular, when the thickness of the developer layer is made thinner than the thickness between the image carrier surface and the developer transport carrier surface, toner particles with a large amount of charge will be exposed to the oscillating electric field in the image area and non-image area. The carrier particles vibrate and, depending on the strength of the electric field, the toner particles selectively move to the electrostatic image area on the image bearing surface, which greatly reduces the adhesion of the carrier to the image bearing surface. will be reduced to Furthermore, in order for the toner particles to follow the electric field, the amount of charge of the toner particles should be greater than 1 to 3 μC/g (preferably 3 to 300 μC/g).
Particularly when the particle size is small, a high amount of charge is required.

Before describing specific preferable development conditions, preferable conditions for the carrier particles of the developer used in the present invention will be described.

In general, when the carrier of a two-component developer has a large average particle size of magnetic carrier particles, the condition of the developer layer formed on the developer transport carrier becomes rough. Even when developed, unevenness tends to appear in the toner image, and the toner concentration in the developer layer becomes low, causing problems such as high-density development is no longer possible. In order to solve this problem, the average particle size of the carrier particles needs to be reduced, and as a result of experiments, the effect begins to appear at 50 μm or less, and when it becomes 30 μm or less, the above problem in It was found that this does not occur. Also,
The above-mentioned problems in ◯ and ② can also be solved by making the magnetic carrier particles finer, thereby increasing the toner concentration in the developer layer, allowing high-density development to be performed. On the other hand, if the carrier particles are too fine, they tend to adhere to the surface of the image carrier together with the toner particles, or they tend to scatter. These phenomena are also related to the strength of the magnetic field acting on the carrier particles and the resulting magnetization of the carrier particles, but in general, a tendency gradually begins to appear when the average particle size of the carrier particles becomes 15 μm or less. , becomes noticeable below 5 μm. A portion of the carrier particles adhering to the image carrier surface transfers onto the recording paper together with the toner, and is removed from the image carrier surface together with the remaining toner. However, with conventional carrier particles made only of magnetic material, There is a problem in that the carrier particles that have migrated onto the recording paper are not fixed on the recording paper by themselves, so they easily fall off. However, there is a problem in that the surface of an image carrier made of a photoreceptor is easily damaged.

The above-mentioned problems ◯◯◯◯◯ that occur when using particularly finely divided carrier particles can be solved by forming magnetic carrier particles from resin or the like and magnetic particles. The magnetic carrier particles are formed with a resin or the like that can be fixed to the recording paper together with the toner particles, so that even if they adhere to the recording paper, they are fixed together with the toner particles by pressure. To become. Furthermore, since the magnetic carrier particles contain a resin or the like, the surface of the image carrier will not be damaged when the magnetic carrier particles are removed from the surface of the image carrier together with residual toner by a cleaning device. Therefore, even if the carrier particles have an average particle size of 15 to 5 .mu.m or less, the above-mentioned problem (C) does not actually cause any trouble. In addition, if carrier adhesion occurs, it is effective to provide a recycling mechanism. Furthermore, the fact that the carrier particles are spherical improves the agitation performance of the toner and carrier and the transportability of the developer, and makes it difficult for toner particles to coagulate among themselves or toner particles and carrier particles to coagulate.

From the above, the appropriate conditions for the carrier are that the average particle diameter of the magnetic carrier particles is preferably 50 μm or less, particularly preferably 30 μm or less, and that the magnetic carrier particles are formed together with a substance such as a resin that can be fixed on the recording paper. Furthermore, it is spherical.

For such magnetic carrier particles, spherical magnetic particles with the same resistance as in magnetic toners are selected, or spherical magnetic particles are selected from resins or waxes similar to those in toners, in particular, Conventional coating materials such as styrene resin, vinyl resin, ethyl resin,
Resins such as rosin modified resins, acrylic resins, polyamide resins, epoxy resins, polyester resins,
Alternatively, it can be obtained by coating it in a spherical shape with a resin to which a charge control agent is added as necessary, or by making spherical particles of resin or wax containing dispersed magnetic particles. A method using hot air or hot water similar to that described above can be applied, and in the case of a dispersed type, a spray drying method can also be used. As for the average particle size, a preferable carrier can be obtained by selecting the average particle size using a conventionally known average particle size selection means, if necessary.

In addition to the above-mentioned effects, making the carrier particles spherical with a resin or the like as described above makes the developer layer formed on the developer transport carrier uniform, and also makes the developer layer more uniform. It also has the effect of making it possible to apply a high bias voltage to the carrier. That is, the fact that the carrier particles are made spherical by resin or the like is because: (1) Generally, carrier particles tend to be magnetized and attracted in the long axis direction, but by sphericalization, this directionality is lost; The developer layer is formed uniformly, preventing the occurrence of locally low resistance areas and uneven layer thickness. As a result, even if a high bias voltage is applied to the developer transport carrier, the electric field will not be concentrated on the edge portion, and as a result, even if a high bias voltage is applied to the developer transport carrier, it will discharge to the image bearing surface and disturb the electrostatic latent image. This provides the effect that voltage breakdown does not occur. The fact that this high bias voltage can be applied means that when the development under an oscillating electric field in the present invention is performed by applying an oscillating bias voltage, the effect can be fully exhibited. That's what I'm saying. Furthermore, as mentioned above, wax can be used to make the carrier particles spherical, which produces such an effect, but from the viewpoint of the durability of the carrier, it is preferable to use resin ^. It is preferable to form insulating magnetic particles so that the resistance is Ωcm or more, particularly 10 ¹³ Ωcm or more. This resistivity is
After placing the particles in a container with a cross-sectional area of 0.50 cm ² and tapping them, a load of 1 Kg/cm ² is applied to the packed particles, and a voltage is applied to generate an electric field of 1000 V/cm between the load and the bottom electrode. This value is obtained by reading the current value when applied, and if this value is low,
When a bias voltage is applied to the developer transport carrier, charge is injected into the carrier particles, making it easier for the carrier particles to adhere to the surface of the image carrier, or for bias voltage breakdown to occur more easily.

In summary, the magnetic carrier particles are spherical so that the ratio of the major axis to the minor axis is at least 3 times or less, and therefore cause charge concentration and discharge at needle-shaped parts and edge parts. Appropriate conditions are that there are no protrusions that easily occur, and that the resistivity is 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm or more, and such magnetic carrier particles can be obtained by the method described above. .

In the developing method of the present invention, a developer in which spherical toner particles and carrier particles, particularly preferably spherical carrier particles, as described above are mixed in the same proportion as in a conventional two-component developer is preferably used. However, if necessary, a fluidizing agent for improving the fluidity and sliding of the particles and a cleaning agent for cleaning the surface of the image bearing member are mixed therein.
As the fluidizing agent, colloidal silica, silicone varnish, metal soap or nonionic surfactant can be used, and as the cleaning agent,
Surface active agents such as fatty acid metal salts, organic group-substituted silicones, and fluorine can be used.

Next, preferred developing conditions for forming such a developer layer on a developer transport carrier and developing an electrostatic image on an image carrier will be specifically described.

The developer transport carrier that forms the developer layer is the same developer transport carrier used in conventional development methods to which a bias voltage can be applied. A structure in which a rotating magnet body having a plurality of magnetic poles is provided inside is preferably used. In such a developer transport carrier, the developer layer formed on the surface of the sleeve moves in a wave-like manner due to the rotation of the rotating magnet, so new developer is continuously supplied. Therefore, even if there is some unevenness in the thickness of the developer layer on the surface of the sleeve, its influence is sufficiently covered by the wave-like movement so that it does not become a problem in practice. The developer transport speed due to the rotation of the rotating magnet or the rotation of the sleeve is almost the same as the moving speed of the image carrier.
It is preferable that it be earlier than that. Note that it is preferable that the rotating magnet body and the sleeve be conveyed by rotating in the same direction. In the case of the same direction, image reproducibility is better than in the opposite direction. However, it is not limited to these.

Further, the thickness of the developer layer formed on the developer transport carrier is preferably such that the adhered developer is sufficiently scraped off by a thickness regulating blade to form a uniform layer. The distance between the developer transport carrier and the image carrier is preferably several 10 to 2000 μm.
The distance between the surfaces of the developer transport carrier and the image carrier is several tens of μm.
If the width is too narrow, it will be difficult to form magnetic brush ears that will uniformly develop the area, and it will also be impossible to supply sufficient toner particles to the developing area, resulting in stable development. If the gap greatly exceeds 2000 μm, the opposing electrode effect will decrease and sufficient development density will not be obtained, resulting in toner adhesion at the contours of the electrostatic image compared to the center. As the number increases, the edge effect also increases. In this way, when the distance between the developer transport carrier and the image carrier becomes extreme, it becomes impossible to make the thickness of the developer layer on the developer transport carrier appropriate; 10μm～2000μm
Within this range, the developer layer can be formed with an appropriate thickness. Therefore, it is particularly preferable to set the distance and the thickness of the developer layer to conditions such that the developer layer does not come into direct contact with the surface of the image carrier, but comes as close as possible. This prevents scratches and fog from occurring due to rubbing of the developer layer in toner development of an electrostatic image.

Furthermore, development under an oscillating electric field is preferably carried out by applying an oscillating bias voltage to the sleeve of the developer transport carrier without providing a new electrode member. Further, it is preferable to use a bias voltage that is a combination of a direct current voltage that prevents toner particles from adhering to non-image areas and an alternating current voltage that makes it easier for the toner particles to separate from the carrier particles. An oscillating electric field is formed between the grounded image carrier substrate and the sleeve. However, the present invention is not limited to the method of applying an oscillating voltage to the sleeve or the method of applying a superimposed DC and AC voltage.

The developing method of the present invention as described above is carried out by an apparatus as illustrated in FIGS. 1 to 3.

1 to 3, reference numeral 1 denotes a drum-shaped image carrier made of a photoreceptor such as Se, which rotates in the direction of the arrow and has an electrostatic image formed on its surface by a charging exposure device (not shown); 2; 3 is a sleeve made of a non-magnetic material such as aluminum, and 3 is a magnet body that is provided inside the sleeve 2 and has a plurality of N and S magnetic poles on its surface in the circumferential direction. It constitutes a carrier. The sleeve 2 and the magnet body 3 can rotate relative to each other, and the figure shows that the sleeve 2 rotates in the direction of the arrow. In addition, the N and S magnetic poles of the magnet body 3 are usually 500~
It is magnetized to a magnetic flux density of 1500 Gauss, and its magnetic force forms a layer of the developer D as described above, that is, a magnetic brush, on the surface of the sleeve 2. 4 is a regulating blade made of magnetic or non-magnetic material that regulates the height and amount of the magnetic brush; 5 is a cleaning blade that removes the magnetic brush that has passed through the developing area A from above the sleeve 2; Since the surface of the sleeve 2 comes into contact with the developer D in the developer reservoir 6, the developer D is supplied thereby, and the developer 7 stirs the developer D in the developer reservoir 6 to make the components uniform. This is a stirring screw. Since the toner particles in the developer D in the developer reservoir 6 are consumed when development is performed, 8 is a toner hopper for replenishing the toner particles T as described above;
Reference numeral 9 denotes a supply roller having a concave portion on its surface that drops the toner particles T into the developer reservoir 6 . 10 is protection resistance 1
1 is a bias power supply that applies a bias voltage to the sleeve 2 through the sleeve 2.

The difference between the devices shown in FIGS. 1 to 3 is that
In the device shown in FIG. 1, the sleeve 2 rotates in the direction of the arrow, and the magnet body 3 rotates in the opposite direction of the arrow, so that the magnetic flux densities of the N and S magnetic poles are approximately equal. In the device shown in Figure 2,
The sleeve 2 rotates in the direction of the arrow, but the magnet 3 is fixed, and in the device shown in FIG. 3, the magnetic flux densities of the N and S magnetic poles of the fixed magnet 3 are not the same;
The magnetic flux density of the N magnetic pole facing the image carrier 1 is larger than the magnetic flux density of the other N and S magnetic poles. Note that the magnetic pole facing the image carrier 1 is as follows:
Of course, the N magnetic poles may be arranged side by side and facing each other as shown in the third figure, or the N and S magnetic poles may be arranged side by side and opposed to each other. By arranging a plurality of magnetic poles to face each other in this manner, it is possible to obtain the effect that development is more stable than when a single pole is posed to face each other.

In the apparatus described above, when the sleeve 2 is set so that the distance between the surfaces of the image carrier 1 is in the range of several tens to 2000 μm, and the electrostatic image on the image carrier 1 is developed, the sleeve 2 The magnetic brush formed on the surface of the sleeve 2 changes its magnetic flux density as the sleeve 2 or the magnet 3 rotates, so the magnetic brush moves on the sleeve 2 while vibrating. The toner passes stably and smoothly between the toner body 1 and the toner body 1, thereby imparting a uniform developing effect to the surface of the image carrier 1, thereby making it possible to stably develop with a high toner density. To do this, in order to prevent the occurrence of fog and to improve the developing effect, an oscillating bias voltage is applied to the sleeve 2 by a bias power supply 10, and the base 1 of the image carrier 1 is
A is grounded to form an oscillating electric field between the sleeve 2 and the image carrier 1. As mentioned earlier, this bias voltage uses a preferable superimposed voltage of DC voltage and AC voltage.The DC component prevents fogging, and the AC component vibrates the magnetic brush to improve the developing effect. improves. Note that for the DC voltage component, a voltage of 50 to 600 V that is approximately equal to or higher than the non-image area potential is usually used, and for the AC voltage component, a frequency of 100 Hz to 10 kHz, preferably 1 to 5 kHz is used. . Note that if the toner particles contain a magnetic material, the DC voltage component may be lower than the non-image area potential. If the frequency of the AC voltage component is too low, the effect of imparting vibration cannot be obtained, and if it is too high, the developer will not be able to follow the vibrations of the electric field, resulting in a decrease in developer density and the ability to obtain clear, high-quality images. There is a tendency to disappear. Also,
The voltage value of the AC voltage component is also related to the frequency, but
The higher the height, the more the magnetic brush is vibrated, which increases the effect accordingly, but on the other hand, the higher it is, the more likely it is that fogging will occur, and the more likely it is that dielectric breakdown such as that caused by lightning strikes will occur. However, if the carrier particles of the developer D are made spherical by resin or the like, dielectric breakdown can be prevented, and fogging can also be prevented by using the DC voltage component. Note that the surface of the sleeve 2 to which this AC voltage is applied may be insulated or semi-insulated covered with a resin or oxide film.

As described above, FIGS. 1 to 3 show an example in which an oscillating bias voltage is applied to the developer transport carrier, but the developing method of the present invention is not limited thereto. Even if several electrode wires are stretched and a vibrating voltage is applied thereto, the developer layer on the developer transport carrier is vibrated and the developing effect can be improved. In that case as well, a DC bias voltage may be applied to the developer transport carrier, or oscillating voltages of different frequencies may be applied. Furthermore, the method of the present invention can be similarly applied to reversal development and the like. In that case, the DC voltage component is set to a voltage approximately equal to the reception potential in the non-image background portion of the image carrier. Furthermore, the method of the present invention is equally applicable to the development of magnetic latent images when using magnetic toner particles.

The present invention uses a two-component developer consisting of toner particles for pressure fixing and carrier particles as described above, and performs development under an oscillating electric field under the above-mentioned development conditions. This eliminates the drawback that carrier particles of toner particles for pressure fixing tend to stick or aggregate, and furthermore, it makes it possible to make toner particles and carrier particles finer, making it easier to fix toner images on recording paper. This not only made it possible to achieve high quality recorded images.

Next, specific embodiments of the present invention will be shown.

〔Example〕

Example 1 Ethylene vinyl acetate copolymer 100 in toner particles
Using nonmagnetic particles with an average particle size of 10 μm, which were formed into spherical shapes by a flow coater method after pulverization and granulation, the carrier particles had an average particle size of 10 μm. 30μm,
Using spherical ferrite particles coated with styrene-acrylic resin having a magnetization of 50 emu/g and a resistivity of about 10 ¹⁴ Ωcm, the developer D in the developer reservoir 6 was developed using the developing device shown in FIG. Development was carried out under conditions where the toner ratio was 10 wt% to the carrier. The average charge amount of toner is
It was 15μC/g.

In this case, the image carrier 1 is a CdS photoreceptor, its peripheral speed is 180 mm/sec, the highest potential of the electrostatic image formed on the image carrier 1 is -500 V, the outer diameter of the sleeve 2 is 30 mm, its rotation speed is 100 rpm, and the magnet The magnetic flux density of the N and S magnetic poles of the body 3 is 900 Gauss, the rotation speed is 1000 rpm, the thickness of the developer layer is 0.6 mm, the distance between the sleeve 2 and the image carrier 1 is 0.5 mm, that is, 500 μm, and the magnetic flux is applied to the sleeve 2. Bias voltage is DC voltage component -250V, AC voltage component
1.5kHz, 500V.

Developed under the above conditions, transferred to plain paper using a corona discharge transfer device, and fixed by passing through a pressure fixing device using a calendar roller with a linear pressure of 20 kg/cm, resulting in a recording paper. The toner image had good fixing properties, no edge effect or fog, and was very clear with high density.Even after 50,000 sheets of recording paper were obtained, the image remained stable from beginning to end. I was able to get

Example 2 The same non-magnetic particles as in Example 1 were used except that the toner particles had an average particle size of 5 μm, and the carrier particles contained 50 wt% of fine particle ferrite with an average particle size of 0.2 μm in the same resin as the toner. dispersed,
After kneading and crushing, the average particle size is 20 μm, magnetization is 30 emu/g, and resistivity is 10 ¹⁴ Ω.
Using particles larger than cm, development was carried out using the developing device shown in FIG. 3 under conditions where the toner ratio of the developer D in the developer reservoir 6 to the carrier was 5WT%. The average charge amount of the toner was 30 μC/g.

In this case, the conditions of the image carrier 1 are the same as in Example 1, and the outer diameter of the sleeve 2 is also 30 mm, but the rotation speed is
150 rpm, the magnetic flux density of the magnetic pole facing the development area A of the magnet body 3 is 1200 Gauss, the thickness of the developer layer is 0.6 mm,
Between sleeve 2 and image carrier 1 = 0.7mm, i.e.
700μm, bias voltage applied to sleeve 2 is DC voltage component -200V, AC voltage component 2kHz, 1000V
And so.

The image on the recording paper obtained was developed under the above conditions, transferred to plain paper by corona discharge, and fixed under the same conditions as in Example 1.
It had good fixing properties, no edge effect or fog, and was extremely clear with high density.After producing 50,000 sheets of recording paper, we were unable to obtain a stable and unchanged image from beginning to end. did it.

Embodiment 3 Using the same toner and carrier as in Embodiment 2, a developing device similar to that shown in FIG. Development was carried out under conditions such that the toner particle ratio of developer D was 5 wt % relative to the carrier particles. The average charge amount of the toner was 30 μC/g.

In this case, the conditions of the image carrier 1 are the same as in Example 1, and the outer diameter of the sleeve 2 is also 30 mm, but the rotation speed is
100 rpm, the magnetic flux density of the N and S poles is 700 Gauss, the rotation speed is 500 rpm, the thickness of the developer layer is 0.6 mm, the distance between the sleeve 2 and the image carrier 1 is 0.7 mm or 700 μm, and the bias applied to the sleeve 2 is The voltages were a DC voltage component of -200V and an AC voltage component of 2kHz and 1000V.

The image was developed under the above conditions, transferred to plain paper by corona discharge, and fixed under the same conditions as in Example 1. The image was extremely clear, free of blemishes, and of high density, and was superior to the image of Example 2 in terms of higher resolution and higher density. Subsequently, we obtained 50,000 sheets of recording paper, but were able to obtain stable and unchanged images from beginning to end.

In addition, in the above embodiment, the results of changing the frequency and voltage of the AC voltage component applied to the sleeve 2 are shown in FIGS. 4 and 5. FIG. 4 shows the case of Example 1, and FIG. 5 shows the case of Example 2 and Example 3.

In Figures 4 and 5, the area shaded with horizontal lines is the area where fogging is likely to occur, the area shaded with vertical lines is the area where dielectric breakdown is likely to occur, and the area shaded with diagonal lines is the area where image quality deteriorates. The non-shaded range is the preferred range where stable and clear images can be obtained. As is clear from the figure, the range where fogging is likely to occur changes depending on changes in the AC voltage component. The waveform of the AC voltage component is
The waveform is not limited to a sine wave, but may be a rectangular wave or a triangular wave. Furthermore, in FIGS. 4 and 5, the low frequency region shaded with scattered dots indicates the range where uneven development occurs due to low frequency.

In the above embodiments, if the toner in the two-component developer has magnetism, it goes without saying that the magnetic latent image can also be visualized under the same developing conditions.

〔Effect of the invention〕

According to the present invention, since development is performed while applying an oscillating electric field to the developer layer of the two-component developer within the development area, it is possible to use a pressure fixing toner as the toner. Compared to conventional developing methods, the toner image is easily fixed on the recording paper, and a recorded image with no fog and excellent clarity can be obtained.

[Brief explanation of drawings]

FIGS. 1 to 3 are partial schematic cross-sectional views showing an example of an apparatus for carrying out the present invention, and FIGS. 4 and 5 respectively.
Each figure is a graph showing the development state when the AC voltage component of the bias voltage is changed in the embodiments of the present invention. DESCRIPTION OF SYMBOLS 1... Image carrier, 2... Sleeve, 3... Magnet, 4... Regulation blade, 5... Cleaning blade, 6... Developer reservoir, 7... Stirring screw, 8... Toner hopper, 9... ...supply roller,
10...Bias power supply, 11...Protection resistor, A...
...Development area, D...Developer, T...Toner particles,
N, S...magnetic pole.

Claims (1)

[Scope of Claims] 1. A method of forming a two-component developer layer consisting of toner particles and magnetic carrier particles on the surface of a developer transporting member, and developing an image on the surface of the image carrier with the developer layer, comprising: A developing method, characterized in that toner particles for pressure fixing are used as toner particles, and the development is performed under an oscillating electric field. 2. The developing method according to claim 1, wherein the thickness of the developer layer is formed to be thinner than the thickness between the image carrier surface and the developer transport carrier surface. 3. The developing method according to claim 1 or 2, wherein the toner particles are spherical toner particles. 4. The developing method according to any one of claims 1 to 3, wherein the oscillating electric field is formed between the developer transport carrier and the image carrier. 5. The developing method according to claim 1, wherein the magnetic field is temporally varied in the region where the developer layer is vibrated by the oscillating electric field. 6. The developing method according to any one of claims 1 to 5, wherein the magnetic carrier particles are formed from a magnetic material and a resin.