JPH02284163A - Image forming method and image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to an image forming method that includes a step of developing an electrostatic latent image formed by electrophotography, electrostatic printing, electrostatic recording, etc. using magnetic toner. Regarding a method and an image forming apparatus therefor, particularly in an electrophotographic image forming method, a latent image is expressed by a unit pixel, and the unit pixel inverts a digital latent image expressed by binary values of on-off or finite gradation. The present invention relates to an image forming method and an image forming apparatus for visualizing an image using a developing method.

[Background technology]

2. Description of the Related Art In recent years, as image forming apparatuses such as electrophotographic copying machines have become widespread, their uses have expanded to a wide variety of uses, and demands on their image quality have become stricter.

When copying images such as general documents and books, it is required to reproduce extremely finely and faithfully, without being crushed or cut off, even down to the minute characters. Particularly, when the latent image on the photoreceptor of the image forming apparatus is a line image of 100 μm or less, fine line reproducibility is generally poor, and the sharpness of the line image is still not sufficient. Furthermore, in recent image forming apparatuses such as electrophotographic printers that use digital image signals, latent images are formed by a collection of dots with a constant potential, and solid areas, halftone areas, dark areas, and dark areas are It is expressed by changing the dot density. However, if the toner particles do not adhere to the dots faithfully and the toner particles protrude from the dots, the gradation of the toner image that corresponds to the ratio of dot densities in the black and white areas of the digital latent image cannot be obtained. There is a problem. Furthermore, when improving resolution by reducing the dot size in order to improve image quality, it becomes more difficult to reproduce latent images formed from minute dots, resulting in poor resolution and gradation.
Images tend to lack sharpness.

In order to faithfully reproduce such a minute latent image, a toner with a small particle size is required, and several proposals have been made so far.

In JP-A No. 58-129437, the average particle size is 6 to 6.
10 μm, and a non-magnetic toner in which the largest number of particles is 5 to 8 μm has been proposed, but particles with a size of 5 μm or less account for 15% by number.
There is a tendency for images with less sharpness to be formed.

According to studies conducted by the present inventors, it has been found that toner particles of 5 μm or less have the main function of clearly reproducing the outline of a latent image and densely applying the toner to the entire latent image.

In particular, in the electrostatic latent image on the photoreceptor, the electric field strength is higher at the edge part than the inside due to the concentration of electric lines of force.
The quality of the toner particles that collect in this area determines the sharpness of the image quality. According to studies conducted by the present inventors, it has been found that the amount of particles of 5 μm or less is effective in solving the problem of sharpness of image quality.

On the other hand, as a developing device using a -component magnetic toner, there is, for example, Japanese Patent Application Laid-Open No. 57-66455. By using a roughened surface, this is an excellent developing device that can maintain a good toe-coating condition over a long period of time, with uniformity and no unevenness on the surface of the toner carrier. The target surface has numerous fine incisions or protrusions arranged in random directions over the entire area.

However, in a developing device using a toner carrier having such a specific surface condition, when toner with a small particle size as described above is used, the toner or components in the toner tend to adhere to the surface (therefore, When so-called contamination occurs on the surface of the toner carrier, and as a result, the density of the initial image decreases, and the contamination progresses due to durability, there is a tendency for image dropouts to occur during the rotation period of the toner carrier. This is caused by components in the toner adhering to the slopes of the convex portions and concave portions of the surface of the toner carrier, resulting in poor charging of the magnetic toner particles and a decrease in the amount of charge in the toner layer.

In general, components in a magnetic toner include materials such as a binder resin magnetic material, a charge control agent, and a release agent. Although materials are designed to prevent contamination of the surface of the toner carrier, the selection of materials is currently extremely limited.

It is clear that a method for preventing or reducing contamination of the magnetic toner carrier is to make the surface of the toner carrier smoother. However, although the cause is unknown, if the surface of the toner carrier is smooth, the toner coat layer becomes excessively thick, making it difficult to form a uniform toner coat layer.

As described above, it has been extremely difficult to stably supply images that faithfully reproduce minute latent images.

[Purpose of the invention]

An object of the present invention is to uniformly coat a toner carrier with magnetic toner and to prevent or reduce contamination of the surface of the toner carrier by the magnetic toner and/or components in the magnetic toner in the above-mentioned developing method. An object of the present invention is to provide an image forming method and an image forming apparatus that simultaneously solve these problems over a long period of time.

A further object of the present invention is to provide an image forming method and an image forming apparatus that can produce clear, high-quality images with high image density (excellent fine line reproducibility and no fog) over a long period of time.

A further object of the present invention is to provide an image forming method and an image forming apparatus whose performance does not change due to environmental changes.

[Summary of the invention]

The image forming method and image forming apparatus of the present invention were invented to achieve the above-mentioned object, and include an electrostatic image carrier that holds an electrostatic image, and a toner carrier that carries magnetic toner on its surface. are arranged with a certain gap in the developing section, and the magnetic toner is conveyed onto the toner carrier with a thickness thinner than the gap, and the toner is developed in the developing section while applying an alternating electric field to the toner. In the image forming method, the toner carrier has a surface having irregularities formed by a plurality of spherical trace depressions by blasting with regular particles, and the surface condition is such that the diameter R of the spherical trace depressions is 20 to 250 μm.
m, the pitch P of the unevenness is 2 to 100 μm, and the surface roughness d is 0.1 to 5 μm. The magnetic toner is layered as a thin layer by a thickness regulating member and transported to the developing section, and the amount of charge of the magnetic toner is -10 to
-20 μc/g and a volume average diameter of 6 to 8 μm;
17 to 60 magnetic toner particles having a particle size of 5 μm or less
12. 5 to 50 magnetic toner particles having a particle size of 6.35 to 10.08 μm are contained; 12.
Magnetic toner particles having a particle size of 7 μm or more are contained at 2.0% by volume or less, and magnetic toner particles having a particle size of 5 μm or less are contained in the following formula % [where N is magnetic toner particles having a particle size of 5 μm or less] (2) represents the volume % of magnetic toner particles having a particle size of 5 μm or less, and k represents a positive number from 4.6 to 6.7. ] An image forming method characterized by satisfying the following.

Furthermore, the present invention provides an electrostatic image carrier that holds an electrostatic image;
A toner carrier carrying magnetic toner on its surface is arranged with a certain gap in the developing section, and the magnetic toner is regulated to a thickness thinner than the gap on the toner carrier and transported to the developing section, where it is developed. In an image forming apparatus that develops an image while applying an alternating electric field to the toner, the toner carrier has a surface with unevenness formed by a plurality of spherical trace depressions by blasting with regular particles, and the surface state is spherical. The diameter R of the trace depression is 20 to 250 μm, the pitch P of the unevenness is 2 to 100 μm, and the surface roughness d is 0.1 to 250 μm.
5 μm, the toner layer on the toner carrier is aligned as a thin layer by an elastic layer thickness regulating member that comes into contact with the surface of the toner carrier with elastic force, and is conveyed to a developing section, and the magnetic toner is at least It is an insulating one-component magnetic toner containing a binder resin and a magnetic material, and the charge amount of the toner is -lO~
- 20 μc/g, a volume average particle size of 6 to 8 μm, and 17 to 6 magnetic toner particles having a particle size of 5 μm or less;
0% by number is contained, 5 to 50% by number of magnetic toner particles having a particle size of 6.35 to 10.08 μm are contained, and 1
Magnetic toner particles having a particle size of 2.7 μm or more are 2.0 μm or more.
The magnetic toner particles contained in the volume percent or less and having a particle size of 5 It m or less are represented by the following formula % [In the formula, N indicates the number % of magnetic toner particles having a particle size of 5 μm or less, and ■ indicates the number of particles having a particle size of 5 μm or less. It represents the volume % of magnetic toner particles having a diameter, and k represents a positive number from 4.6 to 6.7. However, N represents a positive number from 17 to 60. ] An image forming apparatus characterized by having a particle size distribution that satisfies the following.

[Detailed description of the invention]

According to such a configuration, since the surface of the toner carrier has a specific unevenness formed by a plurality of spherical trace depressions, it becomes difficult for toner components to adhere to the surface, and it is possible to prevent or prevent contamination over a long period of time. In addition, the ability to uniformly coat the toner carrier with magnetic toner is achieved by using a toner carrier having an uneven surface with numerous fine incisions or protrusions in random directions by sandblasting with amorphous particles. Although it is slightly inferior under certain environments when compared to a body, it is far superior when compared to a toner carrier that has a completely smooth surface, and an elastic layer thickness regulating member is used to pressure apply the toner onto the surface of the toner carrier. In this way, a toner layer with a thin coating thickness, a dense surface state, a high level of charging characteristics, and a stable toner layer can be stably obtained even under environmental fluctuations.

On the other hand, in magnetic toner, the charge amount is -10 to -20
It has a relatively low charge amount of μc/g and a volume average particle size of 6
~8 μm and has a specific particle size distribution, even if the toner carrier of the present invention is used, the toner coating layer is prevented from becoming excessively thick, and therefore, toner coating unevenness does not occur and the toner coating is uniform over a long period of time. can be coated with toner.

As a result, the image density is high, fine line reproducibility and gradation are excellent, and there is no fog (clear, high-quality images can be obtained over a long period of time).

The present invention will be specifically explained below. Further, the toner carrier will be hereinafter referred to as a sleeve, and the layer thickness regulating member will be referred to as a blade.

The sleeve of the present invention has a surface with an uneven surface formed by a plurality of spherical trace depressions, and a blasting method using regular particles can be used to obtain this surface condition. Examples of fixed particles include stainless steel having a specific particle size, various rigid spheres made of metals such as aluminum, steel, nickel, and brass, ceramics, plastics,
Various rigid spheres such as glass beads can be used.

By blasting the sleeve surface using regular particles having a specific particle size, it is possible to form a plurality of spherical trace depressions with approximately the same diameter R.

In the present invention, the diameter R of the plurality of spherical trace depressions on the sleeve surface is preferably 20 to 250 μm, and the diameter R is 20 μm.
If the diameter R is less than 250 μm, it is undesirable because it increases contamination due to components in the magnetic toner (on the contrary, if the diameter R exceeds 250 μm, the uniformity of the toner coat on the sleeve decreases, which is undesirable. The regular shaped particles used during the blasting process also preferably have a diameter of 20 to 250 μm.

In addition, in the present invention, the pitch P of the unevenness on the sleeve surface is
and surface roughness d, the surface of the sleeve was measured using a micro surface roughness meter (
The surface roughness d is measured using JISIO point average roughness (R
Z) rJIS B 0601J 1m.

In other words, as shown in Figure 1, there are two lines: one that is parallel to the average line of the section cut out by the reference length l from the cross-sectional curve, and that passes through the third peak from the highest one, and one that passes through the bottom of the third valley from the deepest one. , the distance between two straight lines is expressed in micrometers (μm), and the reference length is 1! =0.25mm. In addition, the pitch P is based on a standard length of 0, 25, when the height of the convex part is 0.1μ or more relative to the concave parts on both sides, and is counted as one mountain.
It is calculated as follows based on the number of mountains in mm.

(250 (μ)] / (Number of peaks (μ) included in 250 (μ)) In the present invention, the pitch P of the unevenness on the sleeve surface is preferably 2 to 1OOμ, and when P is less than 2μ, the magnetic This is not preferable because sleeve contamination due to components in the toner increases (on the contrary, if P exceeds 100μ,
This is undesirable because the uniformity of the toner coating on the sleeve deteriorates. In addition, the surface roughness d of the unevenness on the sleeve surface is 0.1 to 5.
μm is preferable, and when d exceeds 5 μm, in a method in which an alternating voltage is applied between the sleeve and the latent image holder to cause magnetic toner to fly from the sleeve side to the latent image surface for development. This is undesirable because the electric field tends to concentrate on the uneven portions, causing image disturbance.On the other hand, if d is less than 0.1μ, the uniformity of the toner coat on the sleeve decreases, which is undesirable.

As the elastic blade in the present invention, a rubber elastic body such as silicone rubber NBR, a synthetic resin elastic body such as polyethylene terephthalate, or a metal elastic body such as stainless steel can be used, and the base, which is the upper side, is fixed to the developer container side. The lower side is bent in the forward or reverse direction of the developing sleeve against the elasticity of the blade, and the inner side of the blade (or outer side in the case of the opposite direction) is pressed against the sleeve surface with appropriate elasticity. Bring it into contact with the FIG. 2 shows an example of an image forming apparatus.

This is shown schematically in FIG. With such an apparatus, a thin and dense toner layer can be stably obtained even under environmental changes.

The reason for this is not necessarily clear, but compared to the normally used device in which a metal blade is attached to the sleeve with a certain gap, the toner particles are forcibly rubbed against the sleeve surface by the elastic blade. It is assumed that this is related to changes in behavior due to environmental changes (because charging is always performed in the same state).

The image forming method and image forming apparatus of the present invention will be explained with reference to FIGS. 2 and 3. - Charge the photoreceptor surface 15 to negative polarity with the blower 2, perform image scanning by exposure with the laser beam 5 to form a digital latent image, and form a plurality of spherical shapes on the surface containing the elastic blade 11 and the magnet 14. The latent image is developed with a one-component magnetic toner 10 of a developing device equipped with a developing sleeve 4 having unevenness formed by trace depressions. In the developing section, the conductive substrate 16 of the photosensitive drum l,
An alternating electric field and/or DC bias is applied between the developing sleeve 4 and the developing sleeve 4 by a bias applying means 12 . When the transfer paper P is conveyed and reaches the transfer section, the transfer charger 3 charges the transfer paper with positive polarity from the back side (the opposite side to the photosensitive drum side), so that the negatively charged toner image on the surface of the photosensitive drum is charged. Electrostatically transferred onto transfer paper. The transfer paper separated from the photosensitive drum 1 is transferred to a transfer paper P by a heating and pressure roller fixing device 7.
The upper toner image is fused.

The one-component developer remaining on the photosensitive drum after the transfer process is
It is removed by a cleaning device 8 having a cleaning blade. After cleaning, the photosensitive drum 1 is neutralized by erase exposure 6, and the process starting from the charging process by the negative charger 2 is repeated again.

The electrostatic image holder (photosensitive drum) has a photosensitive layer 15 and a conductive substrate 16, and moves in the direction of the arrow. A non-magnetic cylindrical developing sleeve 4 serving as a developer carrier rotates in the developing section so as to move in the same direction as the surface of the electrostatic image holder. Non-magnetic cylinder 4
Inside, a multipolar permanent magnet (magnet roll) 14, which is a magnetic field generating means, is arranged so as not to rotate. The one-component insulating developer in the developing device 9 is thinly applied onto the surface of the developing sleeve by an elastic blade, and the toner particles are charged by the friction thereof.

In the developing section, an alternating electric field is applied between the developer carrier 4 and the electrostatic image holding surface. This AC bias has f of 200 to 4
, OOOHHz, Vpp is 500-3,0OO
V Te is good.

When the toner particles are transferred in the developing area, the toner particles are transferred to the electrostatic image side by the action of the electrostatic force of the electrostatic image holding surface and the alternating current bias. It is preferable that the toner container is provided with a toner container stirring means 13, which actively sends the toner 10 in the toner container 9 to the vicinity of the developing sleeve to form a uniform toner layer until the toner is about to run out. It is effective for

In the magnetic toner according to the present invention, the charge amount is -10 to
-20μc/g, BET specific surface area 1.8-3.5n (7g) by nitrogen gas adsorption method, apparent loose density 0.4-Q, 52g/crrf, true specific gravity 1 .4
It has 5 to 1.8 g/c-.

Since the image forming apparatus of the present invention has a very high ability to impart triboelectric charge to the toner, the amount of charge of the magnetic toner according to the present invention must be low (need to be low, and is particularly preferably in the range of -10 to -20 μc/g). By controlling the amount of charge on the toner within the above range, it is possible to suppress the unnecessary charge-up of toner particles with a particle size of 5 μm or less, which tend to charge up relatively easily, and the toner layer on the sleeve is always stable and uniform. If the amount of triboelectric charge is less than 11 Oμc/g, it will not be possible to obtain a sufficient amount of charge for development on the developer carrier,
The image density is low from the beginning (and a phenomenon occurs in which the toner on the sleeve scatters due to the rotation of the sleeve).

On the other hand, if it is larger than -20 μc/g, the amount of charge of the developer near the sleeve on the sleeve becomes large and increases due to repeated image formation (which inhibits proper charging of the toner on the sleeve, so-called A charge-up phenomenon occurs, causing a gradual decrease in image density.This phenomenon tends to occur when developing a digital latent image, which is the development of a dot latent image.
This is noticeable in a low potential contrast reversal development system using a C photoreceptor.

The amount of charge of a toner is determined by the internal and external additive formulations of the toner, and the method of controlling the amount of charge of a toner according to the present invention within the above range is based on magnetic toner particles having a charge amount higher than the above range. The charge amount of the entire toner may be lowered by using an external additive to bring it within the above range, or vice versa, or the method may be by using an external additive that is within the above range both before and after mixing. However, it is preferable that the difference in the amount of charge of the toner before and after adding the external additive is not too large.

In addition, if the BET specific surface area of the developer of the present invention determined by the nitrogen gas adsorption method is less than 1.8 rrf/g, it will take time to obtain a sufficient amount of charge for development on the developer carrier, and the initial concentration will decrease. The image will be thin and have a lot of fog.

On the other hand, if it is larger than 3.5 rrr/g, the mirroring force with the sleeve becomes large, resulting in a decrease in development rate and, as a result, a decrease in image density.

Further, the true specific gravity of the developer of the present invention is 1.45 to 1.8 g/
crd, and if l is less than 45, fog is likely to occur in a developing method in which an alternating current bias is applied in a magnetic field, and the line width becomes thicker, resulting in poor resolution. When it is larger than 1.8, lines tend to fade and image density decreases.

In addition, the apparent density of the developer of the present invention is 0.4 to 0.
．． 52 (preferably 0.45 to 0.5), and is characterized by a small loose apparent density compared to the true specific gravity. The porosity calculated from true specific gravity and loose apparent density is preferably 62 to 75%.

The porosity (εa) is calculated by the following formula.

Moreover, the solidified apparent density is preferably in the range of 0.8 to 1.0, and the porosity (εp) in this case is preferably 40 to 50%.

When εa is less than 62%, the toner is not loosened sufficiently by stirring inside the developing device, and when it is more than 75%, toner scattering and toner leakage are likely to occur.

When εp is less than 40%, developer clogging is likely to occur inside the developing device, the developer is not smoothly supplied to the developer carrier, and white spots are likely to occur. Moreover, if it is larger than 50%, a larger capacity of the developer is required to contain the same amount of developer, which becomes an obstacle to downsizing the printer.

The amount of charge of the toner in the present invention is 1 g of toner and 200 g of toner.
9 g of ~300 mesh iron powder carrier was placed in a 50 cc polyethylene bottle, covered with a lid, and heated to 23°C.

A small amount of the mixture, which has been shaken by hand for 20 seconds (approximately 100 times) in a 60% RH environment, is placed in a container of the apparatus shown in Figure 4, and suctioned at a pressure of 250 mmH2O for approximately 1 minute until the potential is saturated.

The charge flQ was determined from the saturation potential v1, capacitance C1, weight W2 of the container before and after suction at this time, using the following formula.

In addition, the BET specific surface area of the magnetic toner particles is QUANT
It was determined by the BETI point method using a specific surface area meter Autosorb I manufactured by ACHROME.

The loose apparent density in the present invention was measured using a powder tester manufactured by Wire Micron Co., Ltd. and the container attached to the powder tester according to the procedure in the instruction manual of the powder tester.

In the measurement of true density in the present invention, the following method was adopted as an accurate and simple method when measuring fine powder.

A stainless steel cylinder with an inner diameter of 10 mm and a length of about 5 cm, and an outer diameter of about 10 mm that can be inserted tightly into the cylinder.

A disk (A) with a height of 5 mm and a piston (B) with an outer diameter of about 10 mm and a length of about 8 cm are prepared. Place the disk (A) at the bottom of the cylinder, then about 1 g of the sample to be measured, and gently push the piston (B). A force of 400 kg/crrr was applied to this using a hydraulic press, and the product was compressed for 5 minutes and taken out. Weigh the compressed sample (
wg) L/diameter of compressed sample in micrometer (D
cm ) and height (L cm ), and calculate the true density using the following formula.

In the magnetic toner according to the present invention, the volume average particle diameter is 6
~8 μm, containing 17 to 60 number % of magnetic toner particles having a particle size of 5 μm or less, and 6.35 to 10.0 μm.
5 to 50 number % of magnetic toner particles having a particle size of 8 μm
Magnetic toner particles having a particle size of 12.7 μm or more are contained in an amount of 2.0% by volume or less, and magnetic toner particles having a particle size of 5 μm or less are represented by the following formula % [where N is a particle size of 5 μm or less]. represents the number % of magnetic toner particles having a particle size of 5 μm or less, ■ represents the volume % of magnetic toner particles having a particle size of 5 μm or less, and k represents a positive number from 4.6 to 6.7. However, N represents a positive number from 17 to 6o. ] One of the characteristics is that it has a particle size distribution that satisfies the following.

The insulating magnetic toner having a specific particle size distribution as described above has particularly excellent resolution of digital latent images due to the synergistic effect with the image forming method and image forming apparatus of the present invention, and is also excellent in image density.

The reason why such an effect is obtained in the magnetic toner according to the present invention is not necessarily clear, but it is presumed as follows.

That is, one of the characteristics of the magnetic toner of the present invention is that magnetic toner particles having a particle size of 5 μm or less account for 17 to 60% by number. Conventionally, in magnetic toner, 5μ
Magnetic toner particles with a size of less than m are difficult to control the amount of charge, impair the fluidity of the magnetic toner, and are actively used as components that cause toner scattering and stain machines, and as components that cause image fogging. It was considered necessary to reduce

However, according to studies conducted by the present inventors, it has been found that magnetic toner particles of 5 μm or less are an essential component for forming high-quality images.

For example, changing the surface potential on the photoreceptor using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm,
Developing a latent image by changing the surface potential on the photoreceptor, from a large development potential contrast in which a large number of toner particles are easily developed, to a halftone, to a small development potential contrast in which only a few toner particles are developed,
When the developed toner particles on the photoreceptor were collected and the toner particle size distribution was measured, it was found that there were many magnetic toner particles with a diameter of 8 μm or less, and particularly a large number of magnetic toner particles with a diameter of 5 μm or less. In other words, when magnetic toner particles with a particle size of 5 μm or less, which is the most suitable for development, are smoothly supplied to develop the latent image on the photoreceptor, the latent image is faithful to the latent image and does not protrude from the latent image (true reproduction). It is possible to change the image with excellent quality.

This development was similar to the case of reversal development of the digital latent image.

In addition, in the magnetic toner according to the present invention, 6.35 to 1
One of the characteristics is that the number of particles in the range of 0.08 μm is 5 to 50% by number. As mentioned above, this is related to the necessity of the presence of magnetic toner particles with a particle size of 5 μm or less, and magnetic toner particles with a particle size of 5 / Z m or less strictly cover the latent image and reproduce it faithfully. However, in the latent image itself, the electric field strength at the edges around it is higher than at the center, and as a result, the toner particles inside the latent image are thinner than at the edges, and the image density appears thinner. In particular, magnetic toner particles with a diameter of 5 μm or less have a strong tendency to do so.
It has been found that this problem can be solved and further clarity can be achieved by containing toner particles in the range of 0.08 μm in an amount of 5% to 50% by number.

In other words, this is thought to be because toner particles with a particle size in the range of 6.35 to io, os μm have a suitably controlled amount of charge compared to magnetic toner particles with a particle size of 5 μm or less, but the edge of the latent image The toner is supplied to the inner side, where the electric field strength is lower than the edge area, to compensate for the lack of adhesion of the inner toner particles to the edge area, and a uniform developed image is formed, resulting in high density, resolution and gradation. It provides excellent sharp images.

Furthermore, for particles with a particle size of 5 μm or less, the number %
(N) and volume % (V), N/V=0.05N+
k (However, 4.6≦≦6.7: 17≦N≦60
) is also one of the characteristics of the magnetic toner of the present invention. This range is shown in FIG. 4, and the magnetic developer containing the magnetic toner according to the present invention having a particle size distribution that satisfies this range, as well as other features, is effective against digital latent images formed from minute spots. Achieves excellent developability.

While studying the state of particle size distribution of 5 μm or less, the present inventors found that there is a state of existence of fine powder most suitable for achieving the purpose as shown in the above formula. In other words, for a certain value of N, a large N/V means that 5 μm
It shows that it contains a wide range of particles, including N/
A small V is understood to indicate that the abundance of particles around 5 μm is high (and that there are few particles with a particle size smaller than that). If N is within the range, N is in the range of 17 to 60, and the above relational expression is further satisfied, good fine line reproducibility and high resolution can be achieved.

Further, it is preferable that the amount of magnetic toner particles having a particle size of 12.7 μm or more be 2.0% by volume or less, and as small as possible.

The magnetic developer of the present invention solves the conventional problems and can withstand the recent strict demands for high image quality.

The configuration of the present invention will be explained in more detail.

Magnetic toner particles with a particle size of 5 μm or less account for 17 to 17 of the total number of particles.
The content is preferably 60% by number, preferably 25 to 60% by number, and even more preferably 30 to 60% by number. If the number of magnetic toner particles with a particle size of 5 μm or less is less than 17%, the number of magnetic toner particles effective for high image quality will be small (particularly, as the toner is used for continuous printing, the effective magnetic toner particle component will decrease). decreases,
The balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates, and the image quality gradually deteriorates. If it exceeds 60% by number, magnetic toner particles tend to aggregate with each other, resulting in toner lumps larger than the original particle size, resulting in rough image quality, lowering resolution, or causing the edges of the latent image to The density difference between the area and the inside becomes large, and the image tends to look hollow.

In addition, particles in the range of 6.35 to 10.08 μm are 5 to 5
It is good that it is 0% by number, preferably 8 to 40% by number.
is good. If the number is more than 50%, the image quality deteriorates, and more development than necessary occurs, that is, too much toner is applied, resulting in a decrease in fine line reproducibility and an increase in toner consumption. On the other hand, if it is less than 5% by number, high image density cannot be obtained. , N/V=-
There is a relationship of 0.05N0, which indicates a positive number in the range of 4.6≦ and ≦6.7. Preferably 4.6≦≦6.2, more preferably 4.6≦≦5.7. As shown above, 17≦N≦60. Preferably 25≦N≦60,
More preferably, 30≦N≦60.

When k < 4.6, the number of magnetic toner particles having a particle size smaller than 5.0 μm is small, resulting in poor image density, resolution, and sharpness. The presence of an appropriate amount of fine magnetic toner particles, which were conventionally thought to be unnecessary, contributes to achieving close packing of toner during development and forming a uniform image without roughness. In particular, by uniformly filling in thin lines and image contours, visual sharpness is further enhanced. That is, when k < 8.7, these properties are inferior due to the lack of this particle size distribution component.

From another point of view, in terms of production, it is necessary to cut a large amount of fine powder by classification or the like in order to satisfy the condition of k < 4.6, which is disadvantageous in terms of yield and toner cost. In addition, when k > 6.7, due to the presence of more fine powder than necessary (while continuing to print out
Image density tends to decrease.

This phenomenon occurs when excessive fine powder magnetic toner particles with more charge than necessary adhere to the developing sleeve and prevent the normal magnetic toner from being carried and charged on the developing sleeve. Conceivable.

In addition, magnetic toner particles having a particle size of 12.7 μm or more are 2.
It is preferably 0% by volume or less, and more preferably 1.
The content of O is not more than 0.5% by volume, more preferably not more than 0.5% by volume. If it is more than 2.0% by volume, it will hinder fine line reproduction. In addition, the volume average diameter of the magnetic toner is 6 to 8 μm.
m, and this value cannot be considered separately from each component mentioned above. Volume average particle size 6μ
If it is less than m, in applications of digital latent images with a high image area ratio such as graphic images, the amount of toner on the transfer paper is small, which tends to cause the problem of low image density. This is considered to be due to the same reason as the reason why the density inside the edge portion of the latent image decreases as described above. When the volume average particle diameter exceeds 8 μm, the resolution of minute spots of 100 μm or less is not good, and even if the printout is good at the beginning, the image quality tends to deteriorate with continued use.

The particle size distribution of toner can be measured by various methods.
In the present invention, a Coulter counter was used.

In other words, the measuring device is Coulter counter TA.
- An interface (manufactured by Nikkaki) that outputs number distribution and volume distribution using type II (manufactured by Coulter) and CX-
1 A personal computer (manufactured by Canon) is connected, and a 1% NaCl aqueous solution is prepared using primary sodium chloride as an electrolyte. As a measurement method, the electrolytic aqueous solution 100-1
Add 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, as a dispersant to 50 mf, and add 2 to 20 mg of the measurement sample (approximately 30,000 to approximately 300,000 particles). The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and the particle size of the particles was 2 to 40 μ based on the number of particles using a 100 μ aperture as an aperture using the Coulter Counter TAU type. The distribution was measured and the values according to the invention were determined therefrom.

As the binder resin used in the magnetic toner according to the present invention, the following binder resins for toners can be used when a heated pressure roller fixing device having an oil coating device is used.

For example, monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers , styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl chloromethacrylate 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- Styrenic copolymers such as indene copolymers; polyvinyl chloride, phenolic resin, naturally modified phenolic resin, natural resin-modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide Resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumaron indene resin, petroleum resin, etc. can be used.

In the heating and pressure roller fixing method in which little oil is applied, the so-called offset phenomenon, in which a part of the toner image on the toner image support member is transferred to the roller, and the adhesion of the toner to the toner image support member are important issues. be. Toners that are fixed with less thermal energy usually tend to block or cake during storage or in a developing device, so these problems must also be taken into consideration. The physical properties of the binder resin in the toner are most responsible for these phenomena, but according to the research of the present inventors, reducing the content of magnetic material in the toner causes the toner image to become weaker on the toner image supporting member during fixing. Although this improves the adhesion of the toner to the toner, offset is more likely to occur, and blocking or caking is also more likely to occur.Therefore, in the present invention, when using a heated pressure roller fixing method that does not apply much oil, the binder resin The selection of the binder is more important. Preferred binding materials include crosslinked styrenic copolymers and crosslinked polyesters.

Examples of comonomers for the styrene monomer in the styrenic copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, and methacrylate. acids, monocarboxylic acids having a double bond such as methyl methacrylate, ethyl methacrylsanoate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrinitrile, acrylamide, etc., or substituted products thereof; for example,
Dicarboxylic acids with double bonds and substituted products thereof such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate, etc.; vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc.; e.g. ethylene , propylene, butylene, etc.; vinyl ketones, such as vinyl methyl ketone, vinyl hexyl ketone, etc.; vinyl ethers, such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc.; A single monomer or two or more monomers may be used.

As the crosslinking agent, compounds having two or more polymerizable double bonds are mainly used, such as aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate,
Carboxylic acid esters having two double bonds such as ethylene glycol dimethacrylate and 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone; and three or more vinyl Compounds having groups can be used alone or as a mixture.

In addition, when using a pressure fixing method, it is possible to use a binder resin for pressure fixing toner, such as polyethylene,
Examples include polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, and paraffin.

Further, in the magnetic toner of the present invention, it is preferable to use a charge control agent by blending it into the toner particles (internally adding it) or mixing it with the toner particles (externally adding it). The charge control agent makes it possible to control the amount of charge optimally depending on the development system.
In particular, in the present invention, it is possible to further stabilize the balance between particle size distribution and charge, and by using a charge control agent, it is possible to separate functions for high image quality according to the particle size range as described above. and mutual complementarity can be made clearer.

Negative charge control agents that can be used in the present invention include:
For example, metal complexes or salts of monoazo dyes, metal complexes or salts of salicylic acid, alkylsalicylic acid, dialkylsalicylic acid or naphthoic acid are used.

The above-mentioned charge control agent (one that does not function as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of this charge control agent is specifically 4
The thickness is preferably .mu.m or less (more preferably 3 .mu.m or less).

When internally added to the toner, such a charge control agent is added in an amount of 0.1 to 10 parts by weight (or even 0.1 to 10 parts by weight) per 100 parts by weight of the binder resin.
．． 1 to 5 parts by weight) is preferably used.

In addition, conventionally known dye pigments can be used as other coloring materials, and are usually used in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder resin.

The magnetic tonneau of the present invention contains hydrophobic silica fine powder. Specifically, the particle size is preferably 4 μm or less (more preferably 3 μm or less).

When internally added to the toner, such a charge control agent is added in an amount of 0.1 to 10 parts by weight (or even 0.1 to 10 parts by weight) per 100 parts by weight of the binder resin.
．． 1 to 5 parts by weight) is preferably used. Also, dyes that are conventionally known as other coloring agents.

Pigments can be used, and the magnetic binder developer of the present invention usually contains hydrophobic silica fine powder. A magnetic toner having a particle size distribution characteristic of the present invention has a larger specific surface area than conventional toners. When magnetic toner particles are brought into contact with the surface of a cylindrical conductive sleeve that has a magnetic field generating means inside for triboelectric charging, the number of times the toner particle surface contacts the sleeve increases compared to conventional magnetic toner.
Abrasion of toner particles and contamination of the sleeve surface are likely to occur (
Become. When the magnetic toner according to the present invention is combined with fine silica powder, wear is significantly reduced due to the presence of the fine silica powder between the toner particles and the sleeve surface. As a result, the life of the magnetic toner and the sleeve can be extended, and stable charging properties can also be maintained, making it possible to obtain a developer having a magnetic toner that is better for long-term use. Furthermore, 5μ, which plays a major role in the present invention,
In the presence of fine silica powder, magnetic toner particles having a particle size of m or less exhibit more effects and can stably provide high-quality images.

As the silica fine powder, both silica fine powder produced by a dry method and a wet method can be used, but from the viewpoint of filming resistance and durability, it is preferable to use a silica fine powder produced by a dry method.

The dry method mentioned here is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halide compound. For example, this method utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the basic reaction formula is as follows.

S+C1' 4 + 2H2+ 02 →S+02 +
4HCfAlso, it is also possible to obtain a composite fine powder of silica and other metal oxides by using other metal halide compounds such as aluminum chloride or titanium chloride together with silicon halide compounds in this manufacturing process. Also includes.

Commercially available fine silica powder produced by vapor phase oxidation of a silicon halogen compound used in the present invention includes, for example, those commercially available under the following trade names.

AERO3IL 130 (Japan Aerosil Co., Ltd.) 200X50 T600 0X80 0X170 0K84 Ca -0-S i L M -5
(CABOTOCo, Inc.) MS-7 S-5 H-5 Wacker HDK N20
V15 (WACKER-CHEMIE GMBH) N20Ep-Cpiyle 5ili
ca (Dow Corning Co., Ltd.) Fransol (Fransil Company) On the other hand, various conventionally known methods can be applied to the method of producing the silica fine powder used in the present invention by a wet method.

For example, the general reaction formula for the decomposition of sodium silicate with an acid is shown below.

Na2O・XSiO2+HCf+H2O−+SiO2・
nH20+NaCf Other methods include decomposition of sodium silicate with ammonia salts or alkali salts, a method of generating alkaline earth metal silicate from sodium silicate and then decomposing it with acid to form silicic acid, and a method of converting sodium silicate solution to ion exchange resin. There are methods such as using silicic acid, and using natural silicic acid or silicate.

The silica fine powder referred to herein can be any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate.

Among the above-mentioned silica fine powders, those having a specific surface area due to nitrogen adsorption measured by the BET method within the range of 70 to 300 d/H give good results. 0.01 to 8 parts by weight of fine silica powder, preferably 0.01 to 8 parts by weight, per 100 parts by weight of magnetic toner.
It is preferable to use 1 to 5 parts by weight.

As the hydrophobic silica fine powder, negatively charged hydrophobic silica fine powder is preferable.

The hydrophobic silica fine powder used in the present invention has a charge amount of -10
Those having ~-300 μc/g are preferably used. If the amount of charge of silica is less than 110 μc/g, the amount of charge of the toner itself will decrease, and the humidity characteristics will deteriorate. In addition, if it exceeds -300 μc/g, it will promote sleeve memory and be susceptible to silica deterioration (which will impede the durability characteristics.
If it is finer than /g, it will have no effect when added to the developer (7 oi
/g, the probability of existence of coarse particles as free substances is high, and they are likely to cause black spots due to uneven accumulation of silica and aggregates.

The amount of charge of the negatively chargeable silica fine powder is the same as in the case of measuring the amount of charge of the toner described above, but the weight ratio of silica to iron powder carrier is 2:98.

As the silica fine powder used in the present invention, both so-called dry silica produced by vapor phase oxidation of a silicon halide compound, dry silica called fumed silica, and so-called wet silica produced from water glass etc. can be used. It is preferable to use dry silica, which has fewer silanol groups on the surface and inside and has no production residue.

The hydrophobic treatment is applied by chemically treating with an organosilicon compound that reacts with or physically adsorbs the silica fine powder. A preferred method is to treat fine dry silica powder produced by vapor phase oxidation of a silicon halide with an organosilicon compound such as silicone oil after or simultaneously with a silane coupling agent.

Examples of silane coupling agents used for hydrophobization include hexamethyldisilazane, trimethylsilane,
trimethylchlorosilane, trimethylethoxysilane,
Dimethyldichlorosilane.

Methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-
Chlorethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan.

Triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane.

Examples include dimethyldimethoxysilane, diphenyljethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, and 1,3-diphenyltetramethyldisiloxane.

Examples of organosilicon compounds include silico-oil. A preferred silane coupling agent includes hexamethyldisilazane (HMDS). Preferred silicone oils include those having a viscosity of approximately 30 to 1,000 centistokes at 25°C, such as dimethyl silicone oil and methylphenyl silicone oil.

Preferred are α-methylstyrene-modified silicone oil, chlorphenyl silicone oil, fluorine-modified silicone oil, and the like. For the purpose of the present invention, silicone oil containing a large amount of -○H groups, -COOH groups, -NH2 groups, etc. is not preferred.

The method of silicone oil treatment may be, for example, by directly mixing silica fine powder treated with a silane coupling agent and silicone oil using a mixer such as a Henschel mixer, or by spraying silicone oil on the base silica. It depends on the method.

Alternatively, it may be prepared by dissolving or dispersing silicone oil in a suitable solvent, mixing it with the base silica fine powder, and removing the solvent.

The degree of hydrophobicity of fine silica powder in the present invention uses a value measured by the following method. Of course, other measurement methods can also be applied while referring to the measurement method of the present invention.

Sealed 200 m I! Put 100 ml of ion-exchanged water and 0.1 g of the sample into a separating funnel, and shake for 10 minutes at 9 rpm using a shaker (Targra shaker mixer T2C type). After shaking, let stand for 10 minutes to separate the silica powder layer and water layer, and then remove the lower water layer from 20 to 30
ml was collected, placed in a 10 mm cell, and exposed to 500 nm.
The transmittance is measured using blank ion-exchanged water containing no silica fine powder as a standard at a wavelength of

The degree of hydrophobicity of the hydrophobic silica fine powder in the present invention is 90
% or more (more preferably 93% or more). If the degree of hydrophobicity is less than this, high-quality images cannot be obtained due to moisture adsorption of the silica fine powder under high humidity.

The magnetic toner of the present invention may contain external additives other than fine silica powder, if necessary.

For example, in order to control the toner charge amount within the above range, fine resin particles such as polymethyl methacrylate or fluororesin having positive or negative chargeability with high resistance (1010 Ω or more) or medium resistance (106 Ω to 1010 Ω), carbon Conductivity imparting agents such as black and tin oxide.

Other examples include lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide, fluidizers such as alumina, anti-caking agents, and low-molecular weight agents to improve mold release during hot roll fixing. Polyethylene, polypropylene, etc. may also be added.

To prepare the magnetic toner for developing electrostatic images according to the present invention, magnetic powder, vinyl or non-vinyl thermoplastic resin, pigment or dye as a coloring agent, charge control agent, and other additives are used as necessary. etc. are thoroughly mixed using a mixer such as a ball mill, and then melted, kneaded, and kneaded using a heat kneader such as a heated roll, kneader, or extruder to mix the resins with each other. Alternatively, the insulating magnetic toner according to the present invention can be obtained by dispersing or dissolving the dye, cooling and solidifying it, and then pulverizing and strictly classifying it.

Furthermore, the magnetic developer of the present invention can be prepared by mixing an insulating magnetic toner having a predetermined particle size and particle size distribution with a predetermined amount of hydrophobic silica fine powder.

The amount of triboelectric charging of the magnetic toner and magnetic developer of the present invention is carried out in almost the same way as in the case of the silica fine powder described above, but the ratio of amounts is different: 2.0 g of the magnetic developer or magnetic toner and 9.0 g of the carrier iron powder are finely charged. Weigh and measure in the same way.

EXAMPLES Hereinafter, the present invention will be specifically explained using Examples, but these are not intended to limit the present invention in any way.

Note that all parts in the following formulations are parts by weight.

Example 1 Plast treatment was performed on the surface of a cylindrical stainless steel sleeve with a diameter of 20φ using 80% or more of glass beads having a diameter of 53 to 62 μm as regular particles, and the diameter R of a plurality of spherical trace depressions was 53 to 62 μm. Irregularities were formed. The pitch P of the unevenness on the surface of this sleeve was 33μ, and the surface roughness d was 2.0μ. This surface-treated sleeve was designated as sleeve A, and the elastic blade made of rubber was designated as blade A, and a developing device as shown in FIG. 3 was prepared.

On the other hand, as the negatively charged insulating magnetic toner, the following was used.

After thoroughly mixing the above materials in a blender, they were kneaded in a twin-screw kneading extruder set at 150°C. The obtained kneaded material was cooled and coarsely pulverized using a cutter mill, then finely pulverized using a pulverizer using a jet stream, and the obtained pulverized powder was classified using a fixed wall type wind classifier. A classified powder was produced. Furthermore, the obtained classified powder is strictly classified and removed at the same time to remove ultrafine powder and coarse powder using a multi-division classifier that utilizes the Coanda effect (elbow jet classifier manufactured by 8 Iron Mining Co., Ltd.), and the volume average particle size is 6.
．． A black fine powder (magnetic toner) of 5 μm was obtained.

The multi-division classifier used in this example and the classification process using the classifier will be explained with reference to FIGS. 5 and 6. In the multi-segment classifier 40, in FIGS. 5 and 6, the side wall has a shape indicated by 52.54, the lower wall has a shape indicated by 55, and the side wall 53 and the lower wall 55 each have a shape indicated by 52. A knife-type classification edge 47, 48 is provided, and the classification zone is divided into three parts by this classification edge 47, 48. A raw material supply nozzle 46 opening into the classification chamber is provided below the side wall 52, and a Coanda block 56 is provided which is bent downward in the direction of extension of the bottom tangent of the nozzle to draw an elongated arc. The upper wall 57 of the classification chamber is provided with a knife-shaped edge 49 toward the bottom of the classification chamber, and furthermore, the upper portion of the classification chamber is provided with tubes 44 and 45 that open into the classification chamber. Also, popular pipes 44 and 45 have a damper-like first. Second
Gas introduction adjustment means 50.51 and static pressure gauges 58.59 are provided. The lower surface of the classification chamber has exhaust pipes 41, 42, which have exhaust ports opening into the chamber, corresponding to the respective fractionation areas.
43 is provided. The classified powder is introduced into the classification area from the supply nozzle 46 under reduced pressure, and moves in a curved line 60 due to the Coanda effect of the Coanda block 56 and the action of the high-speed air flowing in at that time, and the coarse powder 41, The powder was classified into black fine powder (magnetic toner) 42 and ultrafine powder 43 having a predetermined volume average particle size and particle size distribution. The obtained magnetic toner, which is a negatively charged black fine powder, was measured using the Coulter counter TAU type having an aperture of 100 .mu. as described above, and the data is shown in Table 1 below.

100 parts by weight of the obtained magnetic toner A was mixed with negatively charged hydrophobic dry silica A (BET specific surface area 200 d/g).

Charge fi - 200 μc/g) 0.8 part and positively chargeable polymethyl methacrylate resin fine particles having opposite polarity to the toner particles (average particle size 0.4 μm charge amount + 500 μc/g)
g) 0.3 part was added and mixed using a Henschel mixer to obtain a negatively chargeable component magnetic developer A.

The particle size distribution, charge amount, and BET specific surface area of this developer.

The loose apparent density and true specific gravity are shown in Table 2.

Using the above-described developer and developer, a modified Canon laser beam printer LBP-8AJ1 was used, and the closest gap between the stacked organic photoconductor (OPC) photosensitive drum and the developing sleeve was set to 300 μm. Then, a digital latent image is formed by primary charging the surface of the photosensitive drum to -700V and setting the potential at the exposed part of the laser beam to -100V.
DC bias between the photosensitive drum base and the developing sleeve
500V, AC bias (1800Hz, peak to beak 1600V) was applied and reverse development was performed at normal temperature and humidity (25°C, 160% RH), high temperature and high humidity (30°C, 19% RH).
0%RH) and low temperature and low humidity (15°C, 10%RH).
In the environment, 3000 images were taken. The results are shown in Table 3.

In Table 3, Dmax is the density minute dot reproducibility of a solid black square with a side of 5 mm. Reproducibility was observed and evaluated using a microscope.

As is clear from Table 3, images with high density and excellent minute tod reproducibility were stably obtained in each environment up to 3,000 sheets, and there was no contamination of the sleeve or uneven toner coating after printing 3,000 sheets. The amount of toner coated on the sleeve was approximately 1.2 mg/cm in each environment, which was almost unchanged from the initial state.

Comparative Example 1 Instead of the glass beads used in Example 1, a sleeve B made of #300 carporundum, which is an amorphous particle, was used, and a non-elastic iron blade was used instead of the rubber elastic plate A. An evaluation was conducted in the same manner as in Example 1 except that B was used with a gap of 250 μm between the sleeve and the sleeve. As shown in Table 3, the sleeve was very contaminated after 3,000 sheets, and the image density was also much higher than at the initial stage. It dropped drastically.

Comparative Example 2 Evaluation was performed in the same manner as in Example 1 except that blade B was used in place of blade A used in Example 1 with a gap of 250 μm between the sleeve and the sleeve. Toner coating unevenness occurs at the end of the sleeve, and the amount of toner coating on the sleeve increases even in other environments, resulting in a lack of environmental stability.

Example 2 Developer B used in Example 1 was replaced with 1.2 parts of hydrophobic silica B (BET specific surface area 300 rr?/g charge amount -30 μc/g) as an external additive. When evaluated in the same manner as in Example 1 except for using , good results were obtained as in Example 1. The physical property value of developer B is the second
The table and evaluation results are shown in Table 3.

Example 3 In the same manner as in Example 1, the volume average particle size was 7.8 μm.
Toner C having a particle size distribution as shown in the table was prepared, and developer C was obtained by further mixing 0.6 parts of hydrophobic silica A and 0.3 parts of positively chargeable polymethyl methacrylate. Example 1
Evaluation was performed in the same manner as in Example 1 except that developer C was used instead of developer A used in Example 1, and good results were obtained as in Example 1.

Other physical property values of developer C are shown in Table 2, and evaluation results are shown in Table 3.

Comparative Example 3 A developer was obtained in the same manner as in Example 1, except that the positively chargeable polymethyl methacrylate resin fine particles used in Example 1 were not added. The results are shown in Table 3 and evaluated in the same manner as in Example 1 except that developer A was used instead of developer A in Example 1. As a result, as the number of images printed increased, the density became thinner and the lines became thinner.Furthermore, the amount of toner coated after 3000 sheets was smaller than that at the beginning.

Comparative Example 4 A toner E having a volume average particle diameter of 11.4 μm and a particle size distribution as shown in Table 2 was prepared in the same manner as in Example 1 except that the amount of triiron tetroxide in Example 1 was changed to 60 parts, Furthermore, 0.4 part of hydrophobic silica A, positively charged polymethyl methacrylate 0
．． Developer E was obtained by mixing three parts. Evaluations were made in the same manner as in Example 1- except that developer E was used instead of developer A, and the results are shown in Table 3. As a result, the image density was high and the coating condition was good, but the reproducibility of minute dots was poor, and the image had noticeable scratches and fog, so that satisfactory results could not be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of definitions of surface roughness and pitch. FIG. 2 is a schematic explanatory diagram of the image forming apparatus according to the present invention, and FIG. 3 is an enlarged view of the developing section in FIG. 2. FIG. 4 is a schematic diagram of a toner charge amount measuring device according to the present invention. FIGS. 5 and 6 are schematic illustrations of a multi-division classifier used for classifying toner in an embodiment. FIG. 7 is a partial diagram showing an image pattern used in Examples and Comparative Examples. FIG. 8 is a diagram showing the range of the content ratio of particles of 5 μm or less in the toner according to the present invention. Zuke 2ri 4Q Father matebr r-J (9mm peach C Fukiku paddy%) IC)≦n

Claims (2)

[Claims] (1) An electrostatic image carrier that holds an electrostatic charge image and a toner carrier that carries magnetic toner on the surface are arranged with a certain gap in the developing section, and the magnetic toner is placed on the toner carrier in the gap between the toner carrier and the toner carrier. In an image forming method in which the toner is transported to a developing section with a thickness that is regulated to be thinner than the toner, and developed while applying an alternating electric field to the toner in the developing section, the toner carrier is blasted with regular particles to form a plurality of spherical trace depressions. It has an uneven surface, and the surface condition is such that the diameter R of the spherical trace depression is 20 to 250 μm and the pitch P of the unevenness is 2.
~100 μm, and the surface roughness d satisfies the condition of 0.1 to 5 μm, and the toner layer on the toner carrier is aligned as a thin layer by an elastic layer thickness regulating member that contacts the surface of the toner carrier with elastic force. The magnetic toner is an insulating one-component magnetic toner containing at least a binder resin and a magnetic material, and the toner has a charge amount of -10 to -20 μc.
/g, has a volume average particle size of 6 to 8 μm, contains 17 to 60 number % of magnetic toner particles having a particle size of 5 μm or less, and has a particle size of 6.35 to 10.08 μm. Particles are contained in an amount of 5 to 50% by number, magnetic toner particles having a particle size of 12.7 μm or more are contained in an amount of 2.0% by volume or less, and a group of magnetic toner particles having a particle size of 5 μm or less is expressed by the following formula N/V=-0. 05N+k [wherein, N represents the number % of magnetic toner particles having a particle size of 5 μm or less, V represents the volume % of magnetic toner particles having a particle size of 5 μm or less, and k is 4.6 to 6.7 indicates a positive number. However, N represents a positive number from 17 to 60. ] An image forming method characterized by having a particle size distribution that satisfies the following. (2) An electrostatic image carrier that holds an electrostatic charge image and a toner carrier that carries magnetic toner on the surface are arranged with a certain gap in the developing section, and the magnetic toner is placed on the toner carrier in the gap between the toner carrier and the toner carrier. In an image forming apparatus in which the toner is transported to a developing section with a thickness that is regulated to be thinner than the toner, and developed while applying an alternating electric field to the toner in the developing section, the toner carrier is blasted with regular particles to form a plurality of spherical trace depressions. It has an uneven surface, and the surface condition is such that the diameter R of the spherical trace depression is 20 to 250 μm and the pitch P of the unevenness is 2.
~100 μm, and the surface roughness d satisfies the condition of 0.1 to 5 μm, and the toner layer on the toner carrier is aligned as a thin layer by an elastic layer thickness regulating member that contacts the surface of the toner carrier with elastic force. The magnetic toner is an insulating one-component magnetic toner containing at least a binder resin and a magnetic material, and the toner has a charge amount of -10 to -20 μc.
/g, has a volume average particle size of 6 to 8 μm, contains 17 to 60 number % of magnetic toner particles having a particle size of 5 μm or less, and has a particle size of 6.35 to 10.08 μm. Particles are contained in an amount of 5 to 50% by number, magnetic toner particles having a particle size of 12.7 μm or more are contained in an amount of 2.0% by volume or less, and a group of magnetic toner particles having a particle size of 5 μm or less is expressed by the following formula N/V=-0. 05N+k [wherein, N represents the number % of magnetic toner particles having a particle size of 5 μm or less, V represents the volume % of magnetic toner particles having a particle size of 5 μm or less, and k is 4.6 to 6.7 indicates a positive number. However, N represents a positive number from 17 to 60. ] An image forming apparatus characterized by having a particle size distribution that satisfies the following.