JP2646221B2 - Development method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for developing a latent image formed by electrophotography or electrostatic recording.

[Prior Art] The present applicant forms a thin layer of developer on a developer carrier, brings the developer of the thin layer close to a latent image, and applies an alternating electric field to the approaching portion to perform development. Japanese Patent Application Publication Nos. 58-32375 and 58-32377.

This device has a high development efficiency (the ratio of toner that can be consumed for development to the toner present in the developing section), and is very advantageous in terms of miniaturization, but the developer used in this device is a magnetic material. Since it is a one-component magnetic toner which is essential to contain, there are disadvantages such as poor fixability of a developer and poor reproducibility of a color image.

As a device to compensate for this drawback, the applicant has developed a method and a device using a non-magnetic toner and forming a thin layer of only the non-magnetic toner on the developer carrying member. (Japanese Patent Application Laid-Open Nos. 58-143360 and 59-101680).

This is useful because the disadvantages caused by the toner containing a magnetic material are eliminated while maintaining the advantages of the developing device using the magnetic toner, but the density of the developed image is relatively low and the negative Deficiencies in developing characteristics, such as the possibility of exhibiting image characteristics (image density decreases with an increase in latent image potential) were found.

A so-called two-component magnetic brush developing method (for example, JP-A-53-93841) can use a non-magnetic developer. Since the developing efficiency is low because the ratio is small, it is necessary to apply a large amount of developer onto the developing roller with a constant amount and uniform toner concentration every time the developing roller rotates in order to obtain a predetermined sufficient developing density, The configuration of the developing unit must be large and complicated. Further, there is a disadvantage that traces of rubbing by the brush are generated on the developed image like sweeping.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned conventional circumstances, and has a very high developing efficiency and can be downsized to obtain a developed image which is not inferior to the conventional developing system. The purpose is to provide a simple developing method.

Means for Solving the Problems According to the present invention, a toner particle layer and a magnetic brush layer having toner particles and magnetic particles are formed on a developer carrying member, and the developer carrying member and the electrostatic latent image are formed. A developing method for developing a latent electrostatic image by applying a bias electric field having an AC component and a DC component to an electrostatic latent image carrier for carrying the electrostatic latent image, wherein: (a) the magnetic particles are coated with a silicon resin; The coated magnetic particles are further mixed with fluoropolymer fine particles of 1 μm or less, and (b) toner particles are transferred or transferred to the electrostatic latent image carrier facing the developer carrier. (C) the electric field of the AC component is set to a frequency of 1000 to 3000 Hz, the peak-to-peak voltage does not destroy the electrostatic latent image, and In the developing section, the magnetic particles (D) in the developing section, the toner particles of the toner particle layer and the toner particles of the magnetic brush layer on the developer carrying member The present invention relates to a developing method characterized in that the electrostatic latent image is developed by being transferred or supplied to an electrostatic latent image carrier.

Non-magnetic toner here refers to an external magnetic field of 50,000e and 10em
Refers to a toner that exhibits only a magnetization of v / g or less and cannot substantially behave as a magnetic toner.

The present inventors have made extensive studies on the improvement after the applicant proposed Japanese Patent Application Laid-Open No. 58-143360, and as a result, formed a clear developing magnetic pole in the developing section and performed localized concentrated development. In the one-component developing method, the application of frictional charge to the toner mainly increases the surface area of the sleeve, thereby stabilizing the frictional chargeability of the toner, stabilizing the supply of the toner on the sleeve, gradation, and uniformity. It has been found that the improvement of the image quality and the like can be achieved. further,
The magnetic particles used in the present invention have an extremely high efficiency of distributing an appropriate amount of toner to the toner carrier and the magnetic particles when applied to the present developing method, and further improve the stabilization of the triboelectric charging property to the toner. It has been found that it is extremely advantageous for achieving the image forming method of the present invention. In other words, ATR and strong toner
The most important point for achieving a compact image forming method that does not require a magnetic particle mixing device is that the supplied toner is quantitatively distributed between the toner carrier and the magnetic particles, and the toner is uniformly distributed. The object of the present invention is to carry out efficient fly development by using an alternating electric field from both surfaces.
For that purpose, it has been found that the best effect can be obtained by mechanically mixing and using fluorine-containing polymer fine particles of 1 μm or less with the magnetic particles coated with the silicone resin. In other words, the magnetic particles used in the present invention can uniformly control the intake of the toner even in a developing device without an ATR or a strong toner / magnetic particle mixing device, and impart sufficient positive triboelectric charging property to the toner. It has been found that it is possible to provide a clear image without fog and density unevenness.

 Hereinafter, the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a sectional view of one of the developing devices of the present invention.

In FIG. 1, reference numeral 1 denotes an electrostatic latent image carrier for carrying an electrostatic latent image to be developed, and more specifically, a photosensitive drum or belt or a dielectric drum or belt which can move endlessly. The method of forming an electrostatic latent image thereon is not the gist of the present invention, and may be a known method. In FIG. 1, the electrostatic latent image carrier is a photosensitive drum on which an electrostatic latent image is formed by electrophotography, and is rotatable in the direction of arrow a.

The apparatus shown in FIG. 1 includes a developer container 2, a developing sleeve 3 (hereinafter simply referred to as a sleeve) as a developer carrying member, a magnet 4 as a magnetic field generating means, and an amount of developer conveyed to a developing unit on the sleeve 3. Blade 5 (hereinafter simply referred to as a blade) for controlling the electric field, a power source 6 as an alternating electric field forming means, and the like. Hereinafter, each configuration will be described.

The container 2 contains a developer containing magnetic particles 7 and toner particles 8 as a mixture.

The sleeve 3 is made of a non-magnetic material such as aluminum, and is provided in the opening of the container 2, exposes a part of its surface, and projects another surface into the container 2.
The sleeve 3 is rotatably supported around an axis perpendicular to the drawing, and is driven to rotate in a direction indicated by an arrow b. In FIG. 1, the sleeve 3 is a cylindrical sleeve, but it may be an endless belt.

The sleeve 3 is opposed to the photosensitive drum 1 with a minute gap to form a developing section B. The toner and the magnetic particles are transported to the developing section B by the sleeve 3, where the magnetic particles are present in a volume ratio (1.5 to 30%). This will be described later.

The magnet 4 is fixedly fixed inside the sleeve 3 and does not move when the sleeve 3 rotates. The magnet 4 is a blade 5 described later.
N that controls the amount of developer applied on sleeve 3 in cooperation with
It has a magnetic pole 4d, an S magnetic pole 4e as a developing magnetic pole, an N magnetic pole 4f and an S magnetic pole 4g for transporting the developer after passing through the developing section into the container 2. The S pole and the N pole may be reversed. Although this magnet is a permanent magnet in FIG. 1, an electromagnet may be used instead.

The blade 5 can be made of either a magnetic material or a non-magnetic material. In FIG. 1, at least its tip is made of a non-magnetic material such as aluminum, for example. , The base of which is fixed to the container 2, and the distal end side faces the surface of the sleeve 3 with a gap. The gap between the tip of the blade 5 and the surface of the sleeve 3 is 50 to 500 μm, preferably 100 to 350 μm.
In FIG. 1, it is 300 μm. This gap is 50
If it is smaller than μm, the magnetic particles tend to clog the gap, and if it exceeds 500 μm, a large amount of magnetic particles and toner pass through the gap, and a developer layer having an appropriate thickness cannot be formed on the sleeve 3. The thickness of the developer layer is smaller than the gap between the photosensitive drum 1 and the sleeve 3 in a developing section described later (however, the thickness of the developer is the thickness on the sleeve 3 in a state where no magnetic force is applied). is there). In order to form a developer layer having such a thickness, the gap between the blade tip and the sleeve surface is preferably equal to or smaller than the gap between the sleeve surface and the photosensitive drum surface, but may be larger. .

A magnetic particle circulation limiting member 9 is provided on the inside of the vessel 2 of the blade 5, and this restricts a circulation area of the magnetic particles in the vessel 2, which will be described later.

A power source 6 applies a voltage between the photosensitive drum 1 and the sleeve 3 to form an alternating electric field in a gap between them, and the developer on the sleeve 3 is transferred to the toner photosensitive drum 1.
The voltage from the power supply 6 may be a symmetrical alternating voltage having the same peak voltage on the positive side and the negative side, or an asymmetrical alternating voltage in which a DC voltage is superimposed on such an alternating voltage. As a specific voltage value, for example, a dark part potential -600 V, a bright part potential -200 V, as an example, a DC voltage -300 V is superimposed, a peak-to-peak voltage is 500 to 2200 Vpp, and a frequency is 1000. ~
3000Hz alternating voltage is applied to the sleeve 3 side, and the photosensitive drum 1
At the ground potential.

The magnetic particles 7 are put into the container 2. The injected magnetic particles 7 are held on the sleeve 3 by the magnetic poles 4d and 4g,
It adheres over the entire surface of the sleeve 3 facing the inside of the container 2 and forms a magnetic particle layer. Then, the toner 8 is placed in the container 2
To form a toner layer outside the magnetic particle layer. It is preferable that the magnetic particles 7 initially charged contain toner in an amount of 4 to 30% (by weight) based on the magnetic particles.

Once the magnetic particles 7 are adsorbed and held on the surface of the sleeve 3 as a magnetic particle layer, substantially no flow or inclination occurs even by the vibration of the device or a large inclination, and the state of covering the surface of the sleeve 3 is reduced. Will be maintained.

Next, when the sleeve 3 is rotated in the direction of the arrow b, the magnetic particles rise from the lower part of the container 2 in a direction along the surface of the sleeve 3 and reach the vicinity of the blade 5.

Therefore, some of the magnetic particles pass through the gap between the tip of the blade 5 and the surface of the sleeve 3 together with the toner. The magnetic particle layer near the tip of the blade 5 is a sleeve 3
Is rotated in the direction of arrow b, the regulating force based on the effect of gravity and the magnetic force and the presence of the blade 5 and the sleeve 3
Due to the balance with the conveying force in the direction of movement of the sleeve 3, it accumulates at the point 15 on the surface of the sleeve 3 to form a stationary layer that can move somewhat but is slow. When the sleeve 3 is rotated in the direction of the arrow b, the magnetic brush circulates in the direction of the arrow c near the magnetic pole 4g by appropriately selecting the arrangement position of the magnetic poles, the fluidity of the magnetic particles 7, and the magnetic properties. To form In the circulation layer, the magnetic particles relatively close to the sleeve 3 rise from the vicinity of the magnetic pole 4d onto the stationary layer on the downstream side of the rotation of the sleeve due to the rotation of the sleeve 3. That is, it receives the force of pushing up. Since the upper limit of the circulating region is determined by the magnetic particle circulating region limiting member 9 provided on the upper portion of the blade 5, the pushed up magnetic particles fall by gravity without climbing on the blade 5, It returns to the vicinity of the magnetic pole 4g again. In this case, the magnetic particles having a small push-up force, such as being located far from the sleeve surface, may fall before reaching the magnetic particle circulation region limiting member 9. In other words, in the circulating layer, the magnetic brush of the magnetic particles is circulated as indicated by arrow c by the magnetic force and frictional force due to gravity and magnetic poles, and the fluidity (viscosity) of the magnetic particles. The non-magnetic toner 8 is sequentially taken in from the toner layer on the layer, returns to the lower part in the developer supply container 2, and repeats this circulation with the rotation drive of the sleeve 3.

By circulating in this manner with the rotation of the sleeve 3, the toner 8 is charged by friction between the magnetic particles 7 and the surface of the sleeve 3. At this time, the state of the magnetic brush is an important factor in controlling the toner concentration of the developer and the triboelectric charge amount in the developing section of the sleeve 3. That is, by applying the magnetic particles used in the present invention, the movement of the circulating layer of the magnetic brush becomes gentle and uniform, and the toner can be carried out to the developing section of the sleeve 3 in a small amount and evenly. Become. Further, it is possible to give a sufficient amount of triboelectric charge to the toner in any circulation.

In the vicinity of the blade 5, the magnetic particles 7 near the surface of the sleeve 3 are attracted to the surface of the sleeve 3 by the magnetic pole 4 d, and pass through the lower part of the blade 5 and out of the container 2 as the sleeve 3 rotates. In this case, the magnetic particles 7 carry out the toner attached to the surface together. In addition, a part of the charged toner particles 8 goes out of the container on the sleeve 3 while being adhered to the surface of the sleeve 3 by a reflection force. The blade 5 regulates the amount of developer applied on the sleeve 3.

At this time, the toner amount ratio between the sleeve and the magnetic particles according to the present invention is preferably set so that the flying developability from both is best. Is desirably within the range. If the ratio is larger than this ratio, the effect of increasing the surface area on the sleeve is small because the toner of the magnetic particles is too small. Conversely, if the ratio is smaller than this ratio, development is performed only from the magnetic particles, resulting in a rough image.

The method for measuring the toner amount will be described below. First, a magnetic brush made of a mixture of magnetic particles and toner is formed on a sleeve, the magnetic brush is attracted by a fixed magnet, and the toner is washed away with a surfactant to remove the toner weight T.
₂ (mg) was measured. Next, the toner remaining on the sleeve from which the magnetic brush was removed was sucked using a smooth filter as a filter, and the toner weight T ₁ (mg) on the sleeve was calculated.

The toner concentration T ₃ (% by weight) of the developer in the developing section is determined by (T ₁ + T ₂ ) / CC: the amount of magnetic particles on the sleeve, and is preferably 4 to 30% by weight.

The developer layer (mixture of magnetic particles 7 and toner 8) thus formed on the surface of the sleeve 3
With the rotation of, the photosensitive drum 1 reaches the developing section.
Here, the toner is transferred from the surface of the sleeve 3 and the surface of the magnetic particles onto the latent image by the alternating electric field applied between the photosensitive drum 1 and the sleeve 3, and the latent image is developed.

Next, the behavior of the toner and the magnetic particles in the developing section will be described with reference to FIG. In FIG. 2, since the electrostatic latent image is constituted by negative charges (image dark portions), the electric field due to the electrostatic latent image is in the direction indicated by arrow a. The toner particles and the magnetic particles are mutually rubbed in the developing device or /
The toner is positively charged and the magnetic particles are negatively charged by the toner and the sleeve. Charges are injected into the magnetic particles according to the charge / discharge time constant of the charges determined by the material, shape, and the like, and the charge polarity can change depending on the electric field.

In FIG. 1, the photosensitive drum 1 and the sleeve 3 rotate as indicated by arrows so as to move in the same circumferential direction. The aforementioned alternating voltage is applied by the power source 6 to the space between these, and an alternating electric field is formed. On the other hand, there is a magnetic pole 4e of the magnet 4 inside the sleeve 3 corresponding to the closest portion between the photosensitive drum 1 and the sleeve 3.

In this space, there is a developer that is a mixture of the magnetic particles 7 and the toner 8 that have been conveyed by the rotation of the sleeve 3 as described above. The point that the magnetic particles 7 are present here is essentially different from the case of the so-called one-component non-magnetic developer thin layer developing method (JP-A-58-143360 and JP-A-59-101680). I have. Also, from the relation of the volume ratio of the magnetic particles in this portion (described later), the amount of the magnetic particles present is much smaller than that of a normal so-called magnetic brush developing method. Different. The small number of the magnetic particles 7 form the chain-like magnetic brush 14 in a rough state, that is, a sparse state by the action of the magnetic pole 4d.

The behavior of the magnetic particles 7 in the developing section is special because the degree of freedom is increased.

In other words, the sparse magnetic particle magnetic brush can form a uniform distribution in the direction of the magnetic force and open both the sleeve surface and the magnetic particle surface, so that the toner attached to the magnetic particle surface is impeded by the magnetic brush. The toner adhered to the surface of the sleeve can fly from the surface of the sleeve to the surface of the photosensitive drum with an alternating electric field by forming a uniform open surface on the surface of the sleeve.

Here, the volume ratio of the magnetic particles in the developing section will be described. The “development section” means the area from the sleeve 3 to the photosensitive drum 1
This is a portion where the toner is transferred or supplied, and specifically, as shown in I and II in FIG. 2, indicates a region where the magnetic brush is in contact with the electrostatic latent image carrier. The "volume ratio" is the percentage of the volume occupied by the magnetic particles present therein relative to the volume of the developing section. As a result of various experiments and considerations, the present inventors have found that this volume ratio has an important effect in the above-mentioned developing device, and that the volume ratio has a
It has been found that it is extremely preferable to set the content to 2.6 to 26%.

If the density is less than 1.5%, a decrease in the density of the developed image is observed, a sleeve ghost is generated, a remarkable density difference is generated between a portion where the magnetic brush 14 is present and a portion where the magnetic brush 14 is not present, It is not preferable in that the thickness of the formed developer layer becomes non-uniform as a whole.

If it exceeds 30%, the degree of closing the sleeve surface increases, which is not preferable in that fogging occurs.

In particular, the present invention does not monotonously degrade or increase the image quality as the volume ratio increases or decreases.
Sufficient image density can be obtained in the range of 30% to 30%, and even if it is less than 1.5% or more than 30%, image quality is reduced, and if the image quality is in the above range, sleeve ghost and fog do not occur. It is based on facts. The former is considered to be caused by the negative characteristic, and the latter is caused by the fact that the amount of the magnetic particles becomes large and the surface of the sleeve 3 cannot be opened, so that the toner supply amount from the surface of the sleeve 3 is greatly reduced. Can be

If it is less than 1.5%, the reproducibility of the line image is inferior, and the image quality density is remarkably reduced. On the other hand, when it exceeds 30%, there is a problem that the magnetic particles damage the surface of the photosensitive drum, and there is a problem of transfer and fixing that occurs because the magnetic particles adhere as a part of the image.

When the presence of magnetic particles is close to 1.5%, when reproducing a large-area uniform high-density image (solid black), "Arabi"
In some cases (particular environment or the like), there is a case where a partial development unevenness referred to as “development unevenness” occurs. This value is more preferable because the volume ratio of the magnetic particles to the developing part is 2.6% or more. If the presence of magnetic particles is close to 30%, toner replenishment from the sleeve surface may be delayed around the area where the magnetic brush contacts the magnetic particles (at high development speed, etc.). Density unevenness may occur. As a certain range for preventing this, the above volume ratio of the magnetic particles is more preferably 26% or less.

When the volume ratio is in the range of 1.5 to 30%, the magnetic brush 14 is formed on the surface of the sleeve 3 in a sparse state to a desirable extent, and both toner on the sleeve 3 and the magnetic brush 14 Since the toner on the sleeve is sufficiently opened and the toner on the sleeve also flies and transfers by the alternating electric field, almost all the toner can be consumed for development. Therefore, high developing efficiency (the toner existing in the developing unit can be consumed for development) Toner) and a high image quality density. Preferably causing a small but intense brush vibration,
Thereby, the magnetic particles and the toner adhering to the sleeve 3 are loosened. In any case, it is possible to prevent the occurrence of uneven sweep and ghost images as in the case of a magnetic brush.
Further, the magnetic particles 7 and the toner 8 are
The frictional contact with the toner 8 becomes active, so that the frictional charging of the toner 8 can be improved and the occurrence of fog can be prevented. The high developing efficiency is suitable for downsizing the developing device.

The volume ratio of the magnetic particles 7 present in the developing section can be obtained by (M / h) × (1 / ρ) × [(C / (T + C)], where M is per unit area of the sleeve. Coating amount of developer (mixture: when not standing) (g / c
m ² ), h is the distance (cm) between the electrostatic latent image carrier and the developer carrying member in the developing section, and ρ is the true density of magnetic particles g / cm ³ , C /
(T + C) is the weight ratio of the magnetic particles in the developer on the sleeve.

The ratio of the toner to the magnetic particles in the developing section as defined above is preferably 3 to 30% by weight.

In a phase where the electrostatic latent image is a dark portion, for example, −600 V, and the positive component of the alternating electric field is applied to the sleeve 3 side, the direction of the electric field due to this coincides with the direction of the electric field due to the latent image.
At this time, the amount of electric charge of the magnetic particles injected into the magnetic brush 14 by the electric field is maximized, the magnetic particles are positively charged, and the magnetic brush 14 is in the maximum standing state as shown in FIG. The magnetic brush extends to the surface of the photosensitive drum I, and the short magnetic brush flies to the surface of the photosensitive drum 1 by the action of an electric field.

On the other hand, since the toner is insulative and has a small charge injection effect and is always positively charged, the toner on the surface of the sleeve 3 and the magnetic particles is transferred to the photosensitive drum 1 by the electric field formed in this space. At this time, the magnetic brush 14
Is standing in a rough state, the surface of the sleeve 3 is exposed, and the toner 8 is applied to the surface of the sleeve 3 and the magnetic brush.
Desorbs from both of the 14 surfaces. In addition, since the magnetic brush 14 has a charge of the same polarity as the toner 8, the magnetic brush 14
14 The toner 8 on the surface is more easily moved by the electric repulsion.

In the phase in which the negative component of the alternating voltage component is applied to the sleeve 3, the electric field (arrow b) due to the alternating voltage is in the opposite direction to the electric field (arrow a) due to the electrostatic latent image. Therefore, the electric field in this space becomes stronger in the opposite direction, the magnetic particles bearing positive charges are drawn toward the sleeve 3, the long magnetic brush shrinks, and the short magnetic brush flies to the surface of the sleeve 3.

On the other hand, since the toner 8 on the photosensitive drum 1 is charged to the positive polarity as described above, the toner 8 is reversely transferred to the sleeve 3 or the magnetic particles 7 by the electric field formed in this space.
In this manner, the toner 8 reciprocates between the photosensitive drum 1 and the surface of the sleeve 3 or the surface of the magnetic particles 7, and the electric field weakens as the space between the photosensitive drum 1 and the sleeve 3 expands due to the rotation of the photosensitive drum 1 and the sleeve 3. At the same time, the developing operation is completed.

Conversely, when the electrostatic latent image is a bright portion, for example, −100 V, even in the phase in which the positive component of the alternating electric field is applied to the sleeve 3 side, there is almost no charge injected into the magnetic particle brush by the electric field, As described later, the magnetic particles are injected during the phase when the negative component is applied to the sleeve and remain negatively charged. The long magnetic brush shrinks due to the electric field, and the short magnetic brush flies to the surface of the sleeve 3.

The toner is transferred to the photosensitive drum 1 by the electric field formed in this space. At this time, the magnetic brush 14 is shrunk, the surface of the sleeve 3 is covered, and the detachment of the toner from the sleeve 3 is suppressed. In addition, since the magnetic brush 14 has a charge having a polarity opposite to that of the toner, the toner 8 on the surface of the magnetic brush 14 suppresses the separation of the toner by an electric attraction force.

In the phase in which the negative component of the alternating voltage component is applied to the sleeve 3, the electric field in the direction of the reverse arrow b becomes maximum, the amount of electric charge injected into the magnetic brush of the magnetic particles increases, and the magnetic particles discharge more negative charges. The magnetic brush 14 is in the maximum standing state, the long magnetic brush extends to the surface of the photosensitive drum, and the short magnetic brush flies to the surface of the photosensitive drum by the action of an electric field.

On the other hand, the toner on the photosensitive drum is transferred to the sleeve 3 or the magnetic particles by the electric field formed in this space. At this time, since the magnetic brush 14 stands up in a rough state, the surface of the sleeve 3 is exposed, the toner is easily returned, and the toner and the magnetic particles charged to the opposite polarity are close to each other. The toner is further easily separated from the photoreceptor surface by the electric attraction force.

The magnetic brush 14 has a triboelectric charge or a mirror charge with the toner 8, an electrostatic latent image charge on the photosensitive drum 1, and a charge injected by an alternating electric field between the photosensitive drum 1 and the sleeve 3. The state changes depending on the charge / discharge time constant of the charge determined by the material of the magnetic particles 7 and the like.

In general, the lower the resistance value of the magnetic particles, the more charge injection, the more the magnetic particles are developed in the dark and light portions of the image by the injection of charge. Conversely, when the resistance is extremely high, the magnetic particles always retain the charge of the opposite polarity to the toner, so that the magnetic particles on the background are likely to fog, and by appropriately selecting the shape of the resistance material of the magnetic particles, etc. Can be prevented from adhering.

To ensure the behavior of the magnetic particles described above,
Dark portion potential of the developing sleeve and the bias electric field potential applied between the photosensitive member (AC component and a DC component obtained by superimposing a) the peak value V _P and the photosensitive member of waveform components of the toner from the photoreceptor to the developing sleeve direction It is preferable that the value of V _D becomes | V _P |> | V _D |, and that the voltage due to the alternating voltage exceeds the electric field due to the electrostatic latent image.

As described above, the brush of magnetic particles is in a small but intense vibration flying state by the above-mentioned alternating electric field.

By applying an alternating electric field to the developing unit and causing the toner and the magnetic particles to fly by vibration, the following effects are produced.

Since the toner flies from the magnetic brush and the surface of the sleeve and is developed, the developing efficiency becomes extremely high. Therefore, the amount of the applied developer is relatively small, and the resolution of the developed image is increased. In addition, since the developing efficiency is high, the relative speed between the developing sleeve and the photosensitive member can be made substantially the same, and sweeping of the solid developing portion caused by setting the relative speed does not occur. Further, even if the relative speed is increased, there is an effect of reducing sweeping.

Further, since the magnetic particles are vibrated by the alternating electric field, no trace of each magnetic brush is generated, and a very high-quality developed image can be obtained.

Further, by applying an alternating electric field enough for the magnetic particles to move in the space between the sleeve and the photoreceptor, when the magnetic particles fly as described above, they behave together with the toner in the dark area to promote development, and in the light area, It exhibits the opposite behavior to toner and has the effect of separating toner adhering to the photoreceptor surface, thus preventing fogging.

Furthermore, the magnetic particles attached to the photoreceptor surface will eventually
The magnetic particles and the moving force due to the electric field are pulled back to the developing sleeve side, so that the amount of magnetic particles attached to the photoreceptor can be reduced.

Furthermore, even when the magnetic particle brushes are unevenly distributed, the brush is partially collapsed when the magnetic particles fly, and there is also an effect of smoothing out the magnetic particles.

When the magnetic particles 7 having a relatively low resistance value are used, the alternating voltage applied between the photosensitive drum 1 and the sleeve 3 causes a gap discharge in both the dark portion and the bright portion of the latent image at the peak value. It must be set so that it does not occur. On the other hand, when the magnetic brush 14 having a relatively high resistance value is used, the gap voltage does not reach the discharge starting voltage by appropriately selecting the frequency of the alternating voltage and the charging / discharging time constant of the magnetic brush 14. Is preferred.

In consideration of these, the resistance of the magnetic brush 14 in the height direction of the magnetic brush 14 in a state where the developing brush is in contact with the photosensitive drum 1 is preferably about 10 ¹⁵ to 10 ⁶ Ωcm.

As the material of the core material of the magnetic particles used in the present invention, general materials can be used, for example, metals such as iron, nickel, cobalt, manganese, chromium, rare earth and the like, whose surface is oxidized or not oxidized, and alloys thereof. Alternatively, an oxide or the like can be used, but preferably a metal oxide, more preferably a ferrite particle can be used. There is no particular restriction on the manufacturing method. Magnetic particles generally have an average particle size of 30 to 70μ.
m, preferably 35 to 65 μm. When the particle size is smaller than 30 μm, the magnetic particles are easily developed on the latent image holding member,
The latent image holder and the cleaning blade are easily damaged. On the other hand, if the particle diameter is larger than 70 μm, the toner retaining ability of the magnetic particles is reduced, causing unevenness of the leveled image, toner scattering, fogging and the like. The magnetic particle core material may be composed of only a magnetic material, may be a combination of a magnetic material and a magnetic attraction material, or may be a mixture of two or more magnetic particles.

Further, as a method of coating the surface of the magnetic particles with a resin, the resin is dissolved or suspended in a solvent and applied.
A method of attaching to magnetic particles is preferred.

The coating amount of the magnetic particle-coated silicone resin used in the present invention is 0.1 to 30% by weight based on the total amount of the magnetic particles of the present invention.
(Preferably 0.5 to 20% by weight).

In addition, as a method of coating with a silicon resin, a method of mixing with a powder, melting or softening with heat and attaching to magnetic particles, a method of dissolving or suspending in a solvent and applying and attaching to magnetic particles, etc. Any of the known methods can be applied.

As the silicone resin used in the present invention, conventionally known polysiloxanes such as dimethylpolysiloxane and phenylmethylpolysiloxane are all used, and alkyd-modified silicon, epoxy-modified silicon, polyester-modified silicon, and urethane-modified silicon are also used. A modified resin such as acrylic-modified silicon can also be used.

As the modified form, any of a block copolymer, a graft copolymer, a comb-shaped graft polysiloxane and the like can be used.

When applying the magnetic particles to the actual magnetic particle surface, the silicone resin is varnished such as solid methyl silicon varnish, solid phenyl silicon varnish, solid methyl phenyl silicon varnish, solid ethyl silicon varnish, and various modified silicon varnishes. A method of dispersing the varnish therein, a method of spraying a varnish onto the magnetic particles, and the like are employed.

On the other hand, the fluoropolymer fine particles used in the present invention preferably have a primary particle diameter of 1 μ or less. If the primary particle diameter of the fluorinated polymer fine particles is larger than 1 μm, the fluorinated polymer fine particles cannot be uniformly dispersed and adhered to the surface of the magnetic particles, and the toner cannot be sufficiently positively charged, causing fogging. Further, the circulation of the magnetic brush composed of the magnetic particles becomes uneven, causing unevenness in taking in the toner, which causes unevenness in the density of the image.

The above-mentioned fluoropolymer fine particles have a triboelectric charge with a magnetic particle coated with a resin containing a fluoropolymer having a value of −10 μg / g or more, preferably by a blow-off powder charge measurement device (manufactured by Toshiba Chemical Corporation). Is preferably −30 μg / g or more.

Further, as the above-mentioned fluorine-containing polymer fine particles, a polymer having a fluorine content of 30 to 75% by weight is preferable because the chargeability of the toner and the circulation of the magnetic brush are controlled. For example, polyvinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, and the like are preferable.

The amount of the fluoropolymer particles added is 0.01 to 1% by weight (preferably 0.05 to 0.
5% by weight).

When the magnetic particles to which the addition amount of the fluoropolymer fine particles is 0.01% by weight or less are applied to the present developing method, the environment of the magnetic brush composed of the magnetic particles becomes uneven in a certain environment, and the toner concentration on the sleeve 3 is reduced. It will not be constant, and fog and shading will occur. Conversely, if the addition amount of the fluoropolymer fine particles is 1.0% by weight or more, the positive charging property of the toner becomes too high, the circulation of the magnetic brush is slowed down, the toner density on the sleeve 3 is reduced, and the image density is reduced. This will cause a drop.

The treatment of the resin-coated magnetic particles with the fluoropolymer fine particles is performed by mechanical mixing, and a known method can be applied.
For example, commercially available devices such as a V-type mixer, a Nauter mixer, a tumbler mixer, a cone blender, and a Henschel mixer can be applied. Although the detailed mechanism when the magnetic particles used in the present invention are applied to the present developing system has not been completely elucidated yet, it is estimated as follows from the experimental facts so far.
That is, since the fluorine-containing polymer covering the magnetic particle core material has the opposite chargeability to the toner, it has a role of imparting the original charge to the toner, and the second polymer blended with the fluorine-containing polymer is: It has a role of improving the coating property of the fluorine-containing polymer on the carrier core material rather than the charge-imparting ability. Therefore, by blending the second polymer, the ratio of the fluoropolymer occupying the magnetic particle surface is reduced, and the ability to impart triboelectric charging to the toner is also reduced. Therefore, by appropriately controlling the mixing ratio between the fluoropolymer and the second polymer, the balance between the triboelectrification characteristics of the toner and the magnetic particles and the adhesiveness of the fluoropolymer to the magnetic particle core material can be controlled to some extent. However,
Under special conditions such as fluctuations in environmental conditions and fluctuations in toner density, the chargeability between the toner and the magnetic particles may change slightly, causing problems such as slight fluctuations in image reflection density and increase in fog. is there. Therefore, fluoropolymer fine particles that act similarly to the fluoropolymer coating material in charge,
When dispersed on the surface of the resin-coated magnetic particles containing the fluoropolymer, a part of the fluoropolymer fine particles strongly adheres to the second polymer blend, and plays a role of enhancing the charge of the toner. The polymer particles adhere weakly to the surface of the coated magnetic particles, and also play a role in enhancing the charge of the toner in one environment, and in another environment, they are closely attached to the toner matrix and thus contribute to the chargeability of the toner. It is considered that a suitable charge control agent exists between the toner and the surface of the magnetic particles.

In addition, some of the fluoropolymer microparticles adhere away from the surface of the magnetic particles onto the sleeve, which enhances the effect of successfully dividing the toner on the sleeve and the carrier surface, and the toner particles from both the magnetic particles and the sleeve surface It is considered that the toner plays a role of efficiently developing the toner.

Furthermore, by mixing the fluorine-containing polymer fine particles with the magnetic particles, the toner particles can easily adhere to the magnetic particle surfaces one by one, whereby the movement of the magnetic brush of the magnetic particles can be performed uniformly and slowly. It is considered that the incorporation of the toner particles from the toner layer was stabilized, and as a result, the toner concentration on the sleeve was well controlled.

On the other hand, there is also a method of adding a fluorine-containing polymer to the toner. However, since the fluorine-containing polymer fine particles strongly adhere to the toner base, the role of enhancing the chargeability of the toner is larger than that of the magnetic particles used in the present invention. Inferior. Further, if the fluorine-containing polymer particles are added so as to have sufficient charge controllability to the toner, the fluidity of the toner is remarkably deteriorated, and it becomes difficult to take the toner into a magnetic brush made of magnetic particles. As a result, the toner density on the sleeve decreases, resulting in a low image density.

On the other hand, as the binder resin of the toner used in the present invention, styrene such as polystyrene, poly p-chlorostyrene, polyvinyltoluene and a homopolymer of a substituted product thereof;
Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-
Methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Coalesce, styrene-butyl methacrylate copolymer,
Styrene-acryl-aminoacrylic copolymer, styrene-aminoacrylic copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl Ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid Styrene copolymers such as ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral , Polyacrylic acid resin, rosin, modified rosin, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffin, and paraffin wax may be used alone or in combination.

In the toner, any suitable pigment or dye can be used as a colorant. For example, there are known dyes and pigments such as carbon black, iron black, phthalocyanine blue, ultramarine, quinacridone, and benzidine yellow.

Further, as a charge control agent, an amino compound, a quaternary ammonium compound and an organic dye, particularly a basic dye and a salt thereof, benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethyl ammonium chloride,
Nigrosine base, nigrosine hydrochloride, safranin γ and crystal violet may be added. At this time, the charge amount between the magnetic particles and the toner used in the present invention is desirably 3 to 50 μC / g (preferably 6 to 40 μC / g). If the absolute value of the charge amount is greater than 50 μC / g, the separation between the toner and the magnetic particles is poor, and the developability is reduced.
If the density is lower than 3 μC / g, the toner is less restrained by the magnetic particles, causing toner scattering and fogging.

In the above-described toner composition, a toner obtained by a commonly used mixing and pulverizing method may be used, or a wall material and / or a core material of a microcapsule toner may be used.

The mixing method of the toner and the magnetic particles used in the present invention,
A commonly used mixing method can be applied. If the toner concentration is 3 to 30 parts by weight (preferably 5 to 25 parts by weight) with respect to 100 parts by weight of the developer, the image density is high and sharp. An image is obtained.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.
The parts shown in the examples are parts by weight.

The developing device shown in FIG. 1 was used. In the embodiment, the photosensitive drum 1 is 60 mm /
Rotates at a peripheral speed of seconds. Reference numeral 3 denotes a stainless steel (SUS) having an outer diameter of 32 mm and a thickness of 0.8 mm that rotates in the direction of arrow b at a peripheral speed of 66 mm / sec.
304) sleeve, the surface of which was subjected to irregular sandblasting using # 600 alundum abrasive grains to make the circumferential surface roughness 0.8 μm (R ₂ =). On the other hand, a ferrite sintered type magnet 4 is fixed and disposed in the rotating sleeve 3, and the maximum magnetic flux density is about 800 gauss as shown in FIG.

The blade 5 is made of a non-magnetic stainless steel having a thickness of 1.2 mm, so that the volume ratio of the magnetic particles in the developing unit B is 20%.
The distance between the blade and the sleeve was 350 μm. On the surface of the photoreceptor drum 1 opposed to the sleeve 3, a charge pattern of a dark area of -600V and a light area of -150V was formed as an electrostatic latent image, and the distance from the sleeve surface was set to 350 µm. Then, a voltage having a frequency of 1000 Hz, a peak-to-peak value of 1.4 KV, and a center value of -300 V was applied to the sleeve from a power source 6 to perform development.

Example 1 0.8% by weight of colloidal silica was added to a fine red powder having an average particle diameter of 11 μm to prepare a toner. Next, the particle size is 40-6
1 kg of 0 μm ferrite particles were impregnated with a xylene solution prepared by diluting 50 ml of a silicon varnish SR2410 (manufactured by Toray Silicon Co., Ltd.) and heated and dried while stirring. This is referred to as magnetic particles A _1. Further, polyvinylidene fluoride fine particles (primary particle diameter of about 0.3 μm) 0.1 _per 100 parts by weight of the magnetic particles A ₁
The parts by weight dispersing by using a V-type mixer to obtain magnetic particles A _2. The polyvinylidene fluoride fine particles at this time are magnetic particles
Triboelectric charge quantity of the A ₁ was -9.7μC / g.

Constant temperature and humidity (23 ℃, 60% RH) in an environment, and the toner and the magnetic particles A ₂ were mixed in a weight ratio of 15:85 was applied to the developing device, very good images obtained without fog Was done. At that time, the ratio (T ₁ / T ₂ ) of the amount of toner on the sleeve to the amount of toner on the magnetic particles in the developing unit was 1/8, and the distribution of the toner to both was smooth.

The toner concentration (T ₃ ) of the developer and the charge amount (Q) of the toner in the developing section on the sleeve are 16% by weight and 14 μC /
g. In addition, 3000 to check the durability of the developer
When the sheet was durable, a clear image free of fog and density unevenness was obtained as in the initial stage. Also, T ₁ / T at that time
₂ , T ₃ , Q are almost unchanged from the initial stage, 1/8, 15% by weight, 15μC
/ g was stable.

Next, an experiment similar to the above was performed in a low-temperature and low-humidity (15 ° C., 10% RH) environment. At the initial stage of image formation, T ₁ / T ₂ = 1/7, T ₃ = 18% by weight, Q = 12 μC / g, and an extremely good image free from fog and density unevenness was obtained. In addition, a clear image can be obtained after the end of 3000 sheets, as in the initial stage, and T ₁ / T ₂ , T ₃ , Q at that time are also 1 /
It was stable at 7,19% by weight and 11μC / g with little change from the initial stage.

The toner used in Comparative Example 1 Example 1 and the magnetic particles A ₁ prepared in Example 1 were mixed in a mixing ratio of 15:85 was evaluated similarly image formation as in Example 1, in particular, low temperature and low humidity (15 ℃, 10% R
H) Shading unevenness and fog occurred in the environment. At that time, T ₁ / T ₂ = 4/1, T ₃ = 40% by weight, and the distribution of the toner between the sleeve and the magnetic particles in the developing section and the control of the toner concentration were not controlled. Further, the charge amount Q of the toner in the developing section was as low as 2.0 μC / g.

Example 2 Using a phenylmethylpolysiloxane varnish (solid content is equivalent to 1.5 parts with respect to 100 parts of ferrite particles) as a magnetic particle code resin, 5 kg of magnetic particles coated with ferrite particles in the same manner as in Example 1 were obtained. This is a magnetic particle B ₁
And Next, polyvinylidene fluoride relative to the magnetic particles B ₁ 100 parts by weight - tetrafluoroethylene copolymer (80: 2
0) 0.2 parts by weight of fine particles (primary particle size about 0.7 [mu] m), and dispersed by using a V-type mixer to obtain a magnetic particle B _2. Polyvinylidene fluoride tetrafluoroethylene copolymer particles at this time, quantity of triboelectricity of the magnetic particles B ₁ is was -8.8μC / g.

When mixing the toner and magnetic particles B ₂ of Example 1 in a weight ratio of ten ninety it was repeated except image unloading Example 1, likewise constant temperature and humidity as in Example 1 (20 ℃, 60% RH ) , Low temperature and low humidity (15 ℃,
Good results were obtained in an environment of 10% RH). Also,
The toner distribution T ₁ / T ₂ and toner concentration in the developing section at that time
T ₃ and the charge amount Q of the toner were all in a good state.

Comparative Example 2 1.0 part by weight of colloidal silica and polyvinylidene fluoride-tetrafluoroethylene copolymer fine particles (primary particle diameter of about 0.7%) were added to 100 parts of the red fine powder having an average particle diameter of 11 μm of Example 1.
μm) of 1.0% by weight to obtain a toner. When the toner and the magnetic particles B ₁ prepared in Example 2 were mixed in a weight ratio of 10:90 was performed edetate in the same manner as in Example 2,
The initial image was good under a constant temperature and humidity environment,
Since the toner intake deteriorated from the durability of 100 sheets, the toner concentration of the developer in the developing section on the sleeve decreased, and as a result, the image density decreased. Further, even under a low temperature and a low humidity, the deterioration of the image density, the unevenness of the density, and the fogging due to the poor toner take-in became worse from the durability of about 60 sheets.

[Effects of the Invention] As described above, according to the present invention, in a manufacturing apparatus that uses magnetic particles with a simple configuration, a small amount of magnetic particles is interposed in a development area to eliminate fog, thereby improving gradation. Good and good image quality without negative characteristics could be obtained in various environments.

Further, by controlling the toner concentration and the toner charge amount in the developing section, and further efficiently distributing the toner on the sleeve and the magnetic particles, and performing flying development from both of them, the development is almost 100% in an alternating electric field. Efficiency could be achieved. This makes it possible to reduce the size and simplify the configuration of the developing device.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view of a developing device according to the developing method according to the present invention, and FIG. 2 is an enlarged explanatory view of a developing unit according to the developing method according to the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Taya 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masayoshi Shimamura 3-30-2 Shimomaruko, Ota-ku, Tokyo (56) References JP-A-62-75686 (JP, A) JP-A-55-127569 (JP, A)

Claims (1)

(57) [Claims] An electrostatic latent image bearing member for forming a toner particle layer and a magnetic brush layer having toner particles and magnetic particles on a developer carrying member and carrying the electrostatic latent image with the developer carrying member. A developing method for developing the electrostatic latent image by applying a bias electric field having an AC component and a DC component to a body, wherein (a) the magnetic particles are coated with a silicone resin, and (B) magnetic particles in a developing section where toner particles are transferred or supplied to the electrostatic latent image carrier facing the developer carrying member; (C) an electric field of an AC component is set to a frequency of 1000 to 3000 Hz, a peak-to-peak voltage is maintained without destroying the electrostatic latent image, and the magnetic particles are developed in a developing unit. Agent carrying member and the electrostatic latent image (D) transferring or supplying the toner particles of the toner particle layer and the toner particles of the magnetic brush layer on the developer carrying member to the electrostatic latent image carrier in the developing section; And developing the electrostatic latent image.