JPS59222852A - Developing method - Google Patents

Abstract

PURPOSE:To improve sepn. from a carrier with a pulverized developer as well and to enable sharp reproduction of a fine image by developing the image under application of an oscillating electric field thereon by using a two-component developer of the carrier and toner particles consisting of magnetic material particles and a thermoplastic resin. CONSTITUTION:Development is accomplished by using a two-component developer D consisting of insulating carrier particles, more preferably spherical particles, composed of magnetic material particles and a thermoplastic and having <=50mu average grain size and a preferably spherical toner having <=20mu average grain size, making the thickness of the toner layer thinner than the space in a developing region A between an image carrier 1 and a developer conveying carrier 2 and impressing an oscillating electric field by the AC and DC from a power source 10. The image having good reproducibility of fine lines, dots and varying densities is thus always obtd. without troubles by using the carrier and toner which are made more pulverous than in the prior art.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an improvement in an electrostatic image development method in an electrophotographic copying machine or the like or a magnetic image development method for making a magnetic image into a visible image. A developer in which carrier particles and toner particles are mixed is supplied to the surface of the developer transport carrier to form a developer layer on the developer transport carrier, and the developer layer forms an electrostatic image or an image on the image carrier surface. This invention relates to improvements in developing methods for developing magnetic images.

[Prior art]

As an example, an outline of a developing method in an electrophotographic copying apparatus will be described. Regarding this, the magnetic brush development method using a general two-component developer is relatively easy to control triboelectrification of toner particles, prevents agglomeration of toner particles, and allows the magnetic brush to stand up well, resulting in image bearing. Because it has excellent abrasion properties on the body surface and has a sufficient cleaning effect even when used for cleaning, it is often used even though it is necessary to control the amount of toner particles relative to carrier particles. It is being In addition, the developing method is as follows:
Conventionally, developers have been used that are composed of magnetic carrier particles with an average particle size of several tens to hundreds of micrometers and non-magnetic toner particles with an average particle size of tens of micrometers. Furthermore, because the carrier particles are coarse, it is difficult to obtain high-quality images that reproduce delicate lines, dots, and differences in shading. Therefore, in order to obtain high-quality images using this developing method, many efforts have been made in the past, such as resin coating of carrier particles, improvement of the magnet in the developer transport carrier, and study of the bias voltage for the developer transport carrier. However, the reality is that it is still difficult to obtain stable and fully satisfactory images. Therefore, in order to obtain high quality images, it is considered necessary to make toner particles and carrier particles finer. However, toner particles with an average particle size of 20μ
If the toner particles are smaller than 10 μm, especially 10 μm or smaller, the influence of Van der Waals force will appear on the Coulomb force during development, and so-called fog will occur where toner particles will also adhere to the ground area of the image background. Even by applying a DC bias voltage to the developer transport carrier, it becomes difficult to prevent fogging. (2) Frictional charging control of toner particles becomes shorter, making aggregation more likely to occur. Further, as the carrier particles are made finer, (2) 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 force is reduced and the carrier particles adhere to the image bearing member together with the toner particles.

Note that carriers also adhere to the ground portion of the image background (as the Iasumi pressure increases).

A 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. Met.

[Purpose of the invention]

The present invention does not cause the above-mentioned problems even when using a developer in which toner particles and carrier particles are finely divided.
That is, even if toner particles with an average particle diameter of 20 μm or less, or even 10 μm or less, the above-mentioned problems (1) and (2) do not occur, and the average particle diameter is 50 μm or less, or even 30 μm or less.
To provide a developing method that does not cause the above-mentioned trouble (2) even when using carrier particles with a particle size of μm or less, and can therefore obtain a clear, high-quality image that faithfully reproduces delicate lines, dots, shading differences, etc. It is something to do.

[Structure of the invention]

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

That is, the developing method of the present invention uses particles consisting of a resin and magnetic particles as magnetic carrier particles of a two-component developer,
By developing under an oscillating electric field, it is possible to use micronized magnetic carrier particles and toner particles without any trouble. Preferably one that meets the conditions.

First, regarding the carrier, if the average particle size of the magnetic carrier particles is generally large, (1) the developer layer formed on the developer transport carrier will be rough, making it difficult to develop an electrostatic image while applying vibrations by an electric field; However, problems such as unevenness tend to appear in the toner image and the toner concentration in the developer layer becomes low, such that high-density development cannot be performed. In order to solve this problem (2), the average particle size of the carrier particles can be reduced, and as a result of experiments, the effect begins to appear when the particle size is 50 μm or less, and when the particle size is 30 μm or less, the problem (2) actually occurs. It turned out to be gone.

In addition, the problem @ can be solved by making the magnetic carrier finer particles, which increases the toner concentration in the developer layer, thereby allowing high-density development to be carried out. but,
If the carrier particles are too fine, they may adhere to the surface of the image carrier together with the zero toner particles, or they may easily scatter. These phenomena are also related to the strength of the magnetic field acting on the carrier particles and the resulting magnetization strength of the carrier particles, but in general, when the average particle size of the carrier particles is 15μ
A tendency gradually begins to appear when the thickness is less than 5 μm, and becomes noticeable when the thickness is less than 5 μm. A portion of the carrier particles adhering to the image bearing surface is transferred onto the recording paper together with the toner, and the remaining part is removed from the image bearing surface along with the residual toner by a cleaning device such as a blade or fur brush. With carrier particles made only of magnetic material, there is a problem that (1) the carrier particles that have migrated onto the recording paper are not fixed on the recording paper by themselves and are likely to fall off; There is a problem in that the surface of the image carrier made of a photoreceptor is easily damaged when it is removed by the apparatus. These problems (1) and (2) can be solved by using thermoplastic resin for the magnetic carrier particles. That is, by using a thermoplastic resin for the magnetic carrier particles, the carrier particles attached to the recording paper are fixed by heat and pressure, and also when removed from the image bearing surface by the cleaning device. There is no possibility of damaging the surface of the image carrier. If carrier adhesion occurs, it is effective to provide a recycling mechanism.

By using a thermoplastic resin for the magnetic carrier particles, the problem of θ does not cause any practical trouble even if the carrier particles have an average particle size K of 5 to 15 μm. Furthermore, by making the carrier particles spherical, it improves the agitation performance of the toner and carrier and the transportability of the developer, and also improves the charge controllability of the toner, making it difficult for toner particles to coagulate with each other or toner particles and carrier particles to aggregate. do. Therefore, the problem of O is also reduced, and accordingly, the problem of O is also reduced.

In addition to the spherical shape of the carrier particles, this effect of improving the agitation and transportability of the developer is also related to the fact that the specific gravity is reduced by the resin and that the magnetizing force is appropriately weakened. It is thought that there are.

From the above, the magnetic carrier particles of the two-component developer used in the present invention are particles consisting of magnetic particles and resin, such as a resin dispersion system of magnetic powder and resin, or resin-coated magnetic particles, and are more preferably spherical. The average particle size is preferably 50 μm or less, particularly preferably 30 μm.
Particles with a diameter of 5 μm or less are suitable.

Such magnetic carrier particles are magnetic, similar to those in conventional magnetic carrier particles, such as iron.

Metals such as chromium, nickel, and cobalt, or their compounds and alloys; ferromagnetic materials such as triiron tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite, and manganese-copper alloys; Or, using paramagnetic particles, the surfaces of these particles are coated with resin such as styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, etc. Alternatively, it can be obtained by making particles from a resin containing fine magnetic particles dispersed therein, and then selecting the particle size of the obtained particles using a conventionally known average particle size selection means. In order to obtain spherical magnetic carrier particles, resin-coated carrier particles should be as spherical as possible and coated with resin. It is manufactured by using fine particles and performing a spheroidizing treatment using hot air or hot water after forming dispersed resin particles, or directly forming spherical dispersed resin particles by a spray drying method.

In addition to the above-mentioned effects, the magnetic carrier particles sphericalized by such a resin make the developer layer formed on the developer transport carrier uniform, and also apply a high bias voltage to the developer transport carrier. It also has the effect of making it possible. That is, the fact that the carrier particles are spherical with resin is because (1) Generally, carrier particles tend to be magnetized and attracted in the long axis direction, but by sphericalization, this directionality is lost, and therefore, the developer layer is (2) Formed uniformly to prevent localized areas of low resistance and uneven layer thickness from occurring.
As the resistance of the carrier particles increases, the edge portions seen in conventional carrier particles disappear, and the electric field no longer concentrates on the edge portions.As a result, a high bias voltage is applied to the developer transport carrier. This also provides the effect that discharge on the surface of the image carrier will not disturb the electrostatic latent image or breakdown of the bias voltage will 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 effects described below cannot be fully exhibited. That means it can be done.

In relation to the fact that this high bias voltage can be applied, the magnetic carrier particles using resin in the present invention are
It is preferable that the resistivity is 10 8 Ω or more, particularly 10 13 Ω α or more. This resistivity is determined by placing the particles in a container with a cross-sectional area of 0.5012, tapping them, applying a load of I Ky/cm2 on the packed particles, and applying a load of 100OV/α between the load and the bottom electrode. This value is obtained by reading the current value when a voltage that generates an electric field is applied. If this resistivity is low, when a bias voltage is applied to the developer transport carrier, charges will be injected into the carrier particles.
Carrier particles tend to adhere to the surface of the image carrier, or breakdown of the bias voltage tends to occur.

From the above, magnetic carrier particles have a resin component, are spherical so that the ratio of the long axis to the short axis is at least 3 times or less, have no protrusions such as needles or edges, and have resistivity. is 10
It is preferable that the resistance is 8Ω or more, particularly 1015Ωm or more.

Next, regarding toner, in general, as the average particle size of toner particles decreases, the amount of charge qualitatively decreases in proportion to the square of the particle size, and the adhesion force such as van der Waals force increases relatively. Therefore, it becomes difficult for the toner particles to separate from the carrier particles, and once the toner particles adhere to the non-image area of the image carrier surface, they cannot be easily removed by rubbing with a conventional magnetic brush, causing fogging. become. In the conventional magnetic brush development method, such problems became noticeable when the average particle size of toner particles became 10 μm or less.The development method of the present invention solves this problem by performing development with a developer layer under an oscillating electric field. In other words, the toner particles in the developer layer are separated from the developer layer and transferred to the image area and non-image area on the image carrier surface by the electrically applied motion. If the surface of the image carrier is rubbed with the developer layer, the toner particles attached to the non-image area of the image carrier can be easily removed or removed from the electrostatic image area. If the thickness of the developer layer is made thinner than the gap between the image carrier surface and the developer transport carrier surface, toner particles with a low charge amount may migrate to the image area or non-image area. Since the toner particles are almost completely eliminated and are not rubbed against the surface of the image carrier, they do not adhere to the image carrier due to frictional charging, and toner particles with a particle size of about 1 μm are now used. It is possible to obtain a clear toner image with good reproducibility that faithfully develops an electrostatic latent image.Furthermore, since the oscillating electric field weakens the bond between toner particles and carrier particles, the carrier particles accompanying the toner particles are prevented from reaching the image bearing surface. Adhesion is also reduced. In particular, when the developer layer thickness is made thinner than the gap between the image carrier surface and the developer transport carrier surface, toner particles with a large amount of charge in the image area and non-image area vibrate under the oscillating electric field. However, depending on the strength of the electric field, the carrier particles also vibrate, causing the toner to selectively migrate to the electrostatic image area on the image carrier surface, which greatly reduces the adhesion of the carrier to the image carrier surface. Reduced.

On the other hand, as the average particle size of the toner increases, as described above, the roughness of the image becomes noticeable.

Normally, toner with an average particle size of about 20 μm has no practical problem for developing fine lines lined up at a pitch of about 10 lines per minute, but in practice, if a fine toner with an average particle size of 10 μm or less is used, The resolution has been significantly improved, providing clear, high-quality images that faithfully reproduce the differences in shading. For the above reasons, the average particle size of toner is 20μ.
A suitable condition is less than m, preferably less than 10 μm. In addition, 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/fl (preferably 3 to 3 μc/fl).
300μC/y) is desirable. Particularly when the particle size is small, a high amount of charge is required.

Such toner can be obtained in the same manner as conventional toner. That is, it is possible to use a toner in which spherical or amorphous nonmagnetic or magnetic toner particles in conventional toners are sorted by an average particle size sorting means.

Among these, it is preferable that the toner particles are magnetic particles containing fine magnetic particles, and in particular, the amount of fine magnetic particles is 60%.
It is preferably less than □ wt%, especially 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. , fogging is prevented from occurring, and toner particle scattering is also less likely to occur. 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. Buttons appear on the surface, making it difficult to control triboelectric charging, and toner particles becoming more easily damaged.
They tend to aggregate with carrier particles.

To summarize the above, the preferred toner in the developing method of the present invention uses the resin described above for the carrier and furthermore fine particles of magnetic material, and also contains a coloring component such as carbon and a charge control agent, etc. as necessary. In addition, it consists of particles having an average particle diameter of 20 μm or less, particularly preferably 10 μm or less, which can be produced by a method similar to a conventionally known method for producing toner particles.

In the developing method of the present invention, a developer in which carrier particles and toner particles as described above are mixed in the same ratio as in a conventional two-component developer is preferably used.
If necessary, a fluidizing agent to improve the fluidity and sliding of the particles and a cleaning agent to clean the surface of the image bearing member are mixed therein. As a fluidizing agent, colloidal silica, silicon face, metal soap, or a nonionic surfactant can be used, and as a cleaning agent, a fatty acid metal salt, organic group-substituted silicon, or a surfactant such as fluorine can be used. I can do it.

The above are the conditions for the developer, and next, the conditions for the developer transport carrier that forms such a developer layer and develops the electrostatic image on the image carrier will be described.

A developer transport carrier similar to that used in conventional development methods to which a bias voltage can be applied is used as the developer transport carrier, but in particular, a developer transport carrier having a plurality of magnetic poles inside the sleeve on which developer spikes are formed is used. A structure in which a rotating magnet body is provided is preferably used. In such a developer transport carrier, the rotation of the rotating magnet causes the developer layer formed on the surface of the sleeve to move on the surface in a wave-like manner, so that new developer is continuously supplied. In addition, non-uniformity in the thickness of the developer layer is no longer a problem in practice. The conveyance speed of the developer layer due to the rotation of the rotating magnet or the rotation of the sleeve is preferably almost the same as or faster than the moving speed of the image carrier. In fact, it is preferable that the rotation of the rotating magnet body and the rotation of the sleeve be carried in the same direction. Image reproducibility is better in the same direction than in the opposite direction. However, it is not limited to these.

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 gap between the transport carrier and the image carrier is several 10 to 200
0 μm is preferable. If the surface gap between the developer transport carrier and the image carrier is too narrow, less than several tens of micrometers, it will be difficult to form a developer layer that acts uniformly, making it impossible to supply sufficient toner particles to the developing section. As a result, stable development cannot be performed. Also, the surface gap is 2000μ
If it exceeds m, the effect of the opposing electrode decreases, making it impossible to obtain sufficient development density, and the edge of the electrostatic image or magnetic image is more likely to adhere to the contours than the center. The effect will also be greater. In this way, when the surface gap between the developer transport carrier and the image carrier becomes extreme, the
- However, it is difficult to make the thickness of the developer layer on the developer transport carrier appropriate, but the surface gap is from several tens of micrometers to 2,000 micrometers.
When m is within the range, the thickness of the developer layer can be formed appropriately. Therefore, it is particularly preferable to set the surface gap and the thickness of the developer layer to conditions such that the developer layer does not come into contact with the surface of the image carrier, but is as close to it as possible. This prevents scratches and fog from occurring due to rubbing of the developer layer in toner development of an electrostatic or magnetic image.

In the present invention, development under an oscillating electric field is preferably carried out by applying an oscillating bias voltage to the sleeve of the developer transport carrier. 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. 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 voltage of DC and AC.

The developing method of the present invention as described above is shown in FIGS.
This is implemented by a device such as that illustrated in the figure.

In FIGS. 1 to 3, 1 is 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 and light-opening device (not shown); 2 is an aluminum image carrier; A sleeve made of a non-magnetic material such as 3-piece sleeve 2, and a magnet body having a plurality of N and S magnetic poles in the circumferential direction on the surface, and this sleeve 2 and magnet body 3 form a developer transport carrier. It consists of 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. Also,
The N and S magnetic poles of the magnet body 3 are normally magnetized to a magnetic flux density of 500 to 1500 Gauss, and the magnetic force forms a layer of developer as described above, a so-called 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 pool in the developer reservoir 6, the developer reservoir is thereby supplied, and the developer reservoir 7 stirs the developer reservoir to make the components uniform. It is a stirring screw. Since the toner particles in the developer reservoir 6 are consumed when the phenomenon 1 is performed, 8 is a toner hopper for replenishing the toner particles T'5f as described above. , 9 is 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. While the magnetic flux densities of the magnetic poles are approximately equal, in the device shown in FIG. 2, the sleeve 2 rotates in the direction of the arrow;
The magnet body 3 is fixed, and in the apparatus shown in FIG. N.

The magnetic flux density is larger than that of the S magnetic pole. Note that as the magnetic poles facing the image carrier 1, N magnetic poles may be arranged and facing each other as shown in FIG.

The S magnetic poles may be arranged 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 surface gap with 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 sleeve 2
Alternatively, since the magnetic flux density on the surface of the magnet 3 changes as it rotates, it moves on the sleeve 2 while vibrating, thereby stably and smoothly passing through the gap with the image carrier 1. At this time, a uniform developing effect is imparted to the surface of the image carrier 1, making it possible to stably develop with a high toner density. In order to prevent fogging and to improve the developing effect, an oscillating bias voltage is applied to the sleeve 2 by a bias power supply 10. As mentioned earlier, a preferable superimposed voltage of DC voltage and AC voltage is used for this bias voltage,
The DC component prevents fogging, and the AC component vibrates the magnetic brush to improve the developing effect. Incidentally, a voltage of 50 to 600 µ which is approximately equal to or higher than the non-image area potential is normally used for the DC voltage component, and a voltage of 100 Hz to 10 KHz, preferably 1 to 5 kHz is used for the AC voltage component.
frequency is used. Note that when the toner particles contain a magnetic material, the DC voltage component may be lower than the potential of the non-image area. If the frequency of the AC voltage component is too low,
There is a tendency that the effect of providing imaging cannot be obtained, and even if the electric field is too high, the developer cannot follow the vibrations of the electric field, the developed density decreases, and a clear high-quality image cannot be obtained. In addition, the voltage value of the AC voltage component is also related to the frequency, but the higher the voltage value, the more the magnetic brush will vibrate and the more effective it will be. It also makes dielectric breakdown more likely to occur. However, the fact that the carrier particles in the developer contain resin and are spherical prevents dielectric breakdown, and the occurrence of fog 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 coated with an insulating or semi-insulating coating 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. It is also possible to improve the developing effect by providing vibration to the magnetic brush by extending several electrode wires and applying an oscillating voltage to them. 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. Also,
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.

〔Example〕

Next, the present invention will be explained using specific examples.

Example 1 As the carrier particles, ferrite particles with an average particle diameter of 25 μm were suspended in hot air, and the same styrene-acrylic resin used for the toner particles dissolved in a solvent was attached to the carrier particles by spraying from a nozzle. The average particle size obtained by drying is 30 μm 1 magnetization is 5 Q em
U/f, resin-coated spherical carrier particles with a resistivity of 1014 Ωα or more are used, and the toner particles are styrene/acrylic resin (Himar UP manufactured by Sanyo Chemical Co., Ltd.).
110) Non-magnetic particles obtained by pulverizing and granulating particles with an average particle size of 10 μm and spheroidizing them with hot air, consisting of 100 parts by weight, 10 parts by weight of carbon black (Mitsubishi Kasei MA-100), and 5 parts by weight of nigrosine. Using the apparatus shown in FIG. 1, the ratio of toner particles in the developer reservoir 6 to the carrier particles is 10 wt%.
Development was carried out under the following conditions. The average charge amount of the toner at this time is 15μC/? Met.

In this case, the image carrier 1 is an OdS 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 fins, and its rotation is Number 10 Orpm, the magnetic flux density of the N and S magnetic poles of the magnet body 3 is 900 Gauss, and its rotation speed is 11000
rp, the thickness of the developer layer in the development area A is 0.6 m, the gap between the sleeve 2 and the image carrier 1 is 0.5 fflfilJ, 500 μm1, and the bias voltage applied to the sleeve 2 is a DC voltage component of −250 V and an AC voltage. component 1.5 kHz,
It was set at 500■.

The image was developed under the above conditions, transferred to plain paper using a corona discharge transfer device, and fixed by a heat roller fixing device with a surface temperature of 140°C. The images were extremely clear, free of dark spots, and of high density.I subsequently produced 50,000 sheets of recording paper, and was able to obtain stable and unchanging images from beginning to end.

Example 2゜As carrier particles, the same styrene/acrylic resin as in Example 1 containing 50 wt% of dispersed fine ferrite particles with an average particle size of 0.2 μm was pulverized and then treated with hot air.The average particle size was 20 μm1 and the magnetization was 30 emu. / ? , using spherical particles with a resistivity of 1014 Ω or more, and using spherical nonmagnetic particles with an average particle size of 5 μm obtained by the flow coater method with the same composition as in Example 1 as toner particles, as shown in FIG. 3. With the shown apparatus, the ratio of toner particles in the developer reservoir 6 to the carrier particles is 5wt.
%. The average charge amount of toner is 3
It was 0μc/f.

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 3Q++++++, but the number of rotations is 15.
0 rpms The magnetic flux density of the magnetic pole facing the development area A of the magnet body 3 is 1200 Gauss, and the thickness Q of the developer layer is 5 mm.

Between sleeve 2 and image carrier 1 @Q, 7mm, i.e. 700
The bias voltage applied to μm1 sleeve 2 has a DC voltage component of -200 V and an AC voltage component of 2 kHz, 1000 V.
■It was.

The image was developed under the above conditions, transferred to plain paper by corona discharge, and fixed by a heat roller fixing device with a surface temperature of 140°C. The resulting image on the recording paper was free from edge effects and fog. It was extremely clear, with high density, and although 50,000 sheets of recording paper were subsequently obtained, it remained stable from the beginning to the last dimension.

I was able to obtain an image that did not change.

Example 3 Using a developer reservoir in which the carrier particles and toner particles are the same as those in Example 2, the toner particle ratio of the developer reservoir in the developer reservoir 6 is changed to carrier particles using a developing device having substantially the same configuration as shown in the first figure. Development was carried out under conditions where the amount was 5 wt%. In this case as well, the average charge amount of the toner was 30 μc/S'.

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 30mm, but the rotation speed is 100 rpm.
The magnetic flux density of the XN S pole is 700 Gauss, and its rotation speed is 5
00 rpm, the thickness of the developer layer is 0.6, the gap Q between the sleeve 2 and the image carrier 1 is 7 mm, that is, 700 μm, and the bias voltage applied to the sleeve 2 is a DC voltage component of −200 V.
The AC voltage component was 2 kHz and 1000 V.

As a result of developing under the above conditions, corona-transferring the image onto plain paper, and fixing it through a heat roller fixing device with a surface temperature of 140°C, the resulting image on the recording paper has no edge effects or fog, and The image was very clear with high density, and was superior to the image in 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 unchanging images from beginning to end.

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 in which 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 several dots is a range where uneven development occurs due to the 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〕

As is clear from the above examples, according to the present invention, carriers with an average particle size of 30 μm or less and carriers with an average particle size of 10 μm
Using the following toners, an excellent effect can be obtained in that clear, fog-free recorded images can be obtained without any trouble.

[Brief explanation of the drawing]

1 to 3 are partial cross-sectional views of a developing device used in the present invention, and FIGS. 4 and 5 are graphs showing the influence of the frequency and voltage of an alternating current voltage component that generates an alternating electric field. ■...Image carrier, 2...Sleeve, 3...
Magnet, 4... Regulating blade, 5... Cleaning blade, 6... Developer reservoir, 7... Stirring screw, 8... Toner hopper, 9... Supply roller, 1
0...Bias power supply, 11...Protection resistor, A.
...Development area, D...Developer, T...Toner particles, N, S...Magnetic pole. Figure 1 Figure z Figure 4 01234567 ■Multiple skin number (Kl-(,) Figure 5 Frequency #, (to H2)

Claims (1)

[Scope of Claims] (1) A two-component developer layer consisting of magnetic carrier particles and toner particles is formed on the surface of a developer transport carrier, and the image on the image carrier surface is developed by the developer on the surface of the transport carrier. A developing method, characterized in that the magnetic carrier particles are particles composed of magnetic particles and a thermoplastic resin, and the development is performed under an oscillating electric field. (2) The developing method according to claim 1, wherein the oscillating electric field is formed between the developer transport carrier and the image carrier. (5) The thermoplastic resin of the magnetic carrier particles is a resin having substantially the same softening temperature as the thermoplastic resin constituting the toner particles, and the layer thickness is formed to be thinner than the gap between the carrier surfaces. A developing method according to claims 1 to 5. (5) The developing method according to any one of claims 1 to 4, wherein the magnetic carrier particles are insulating particles. (6) The developing method according to any one of claims 1 to 5, wherein the magnetic field is temporally varied in a region where the developer is vibrated by an oscillating electric field. (7) The developing method according to any one of claims 1 to 6, wherein the magnetic carrier particles are resin-dispersed particles. (8) The developing method according to any one of claims 1 to 7, wherein the magnetic carrier particles are spherical.