JPH0264561A - 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. The present invention relates to a method and an image forming apparatus therefor.

[Background technology]

Conventionally, as a developing method using a component magnetic toner, a developing method using a conductive magnetic toner disclosed in U.S. Pat. No. 3,909,258 and the like has been known and used.

However, in such development methods, the toner must be inherently conductive, and the conductive toner uses an electric field to transfer the toner image on the latent image carrier to the final image supporting member (for example, plain paper). However, it has been difficult to transfer it (the reason for this is not fully understood).

The present applicant has previously proposed a new developing method that solves the problems of the conventional developing method using one-component magnetic toner (for example, Japanese Patent Laid-Open No. 55-18656 and Japanese Patent Laid-Open No. 55-18659) Public bulletin). In this method, an insulating magnetic toner is uniformly applied onto a cylindrical toner carrier having a magnet inside, and the toner is developed without coming into contact with the latent image carrier (facing the latent image carrier). There is a method of forming a toner layer on the toner by using a coating blade at the outlet of the toner container. For example, the method shown in FIG.
One magnetic pole N of the fixed magnet 4 built into the toner carrier 2
A blade 1a made of a magnetic material is provided at a position opposite to the magnetic material blade 1a, and the toner is made to stand up along the lines of magnetic force between the magnetic pole and the magnetic material blade, and this is cut with the edge portion of the tip of the blade, thereby utilizing the action of the magnetic force. Thus, the thickness of the toner layer is regulated (see, for example, Japanese Patent Laid-Open No. 43037/1983).

During development, a low-frequency alternating voltage is applied between the toner carrier and the base conductor of the latent image holder to cause the toner to reciprocate between the toner carrier and the latent image holder, thereby eliminating ground force blur. In addition, it has excellent gradation reproduction and can perform good development without thinning at the edges of the image. In this developing method, since the toner is an insulator, electrostatic transfer is easy.

In FIG. 1, 7 is a developing device containing toner 10;
is a latent image holding body (hereinafter referred to as a photoconductor or photoconductor drum) such as a photoconductor drum in electrophotography and an insulating drum in electrostatic recording.

In such a developing method, it is extremely important to: To uniformly coat the toner carrier with the magnetic toner, and to prevent or reduce contamination of the surface of the toner carrier by components in the magnetic toner. It is. However, the problem and the problem (2) are in conflict with each other, and it is difficult to solve both issues simultaneously.

That is, as a method for uniformly coating a toner carrier with magnetic toner, the present applicant has developed a method that can stably form a uniform toner coat layer on a toner carrier for a long period of time in practice. We proposed a developing device (
(Japanese Unexamined Patent Publication No. 57-66455). As shown in FIG. 1, by using a toner carrier whose surface has been sandblasted with amorphous particles to form a roughened surface with a specific unevenness, the surface of the toner carrier can be uniformly distributed. This is an excellent developing device that can always maintain a good toner coating condition over a long period of time without any unevenness.

The target surface is, for example, as seen in the 2000x photograph taken with a scanning electron microscope in Figure 2, where the surface of the stainless steel cylindrical toner carrier has numerous minute incisions or protrusions arranged in random directions over the entire surface. This is an embodiment configured as follows.

However, in a developing device using a toner carrier having such a specific surface condition, depending on the applied magnetic toner, the toner or components in the toner tend to adhere to the surface, resulting in so-called contamination on the surface of the toner carrier. As a result, when the density of the initial image decreases and its contamination progresses due to durability, there is a tendency for the image to fall off during the rotation period of the toner carrier. this is,
Components in the toner adhere to the convex slopes and concave areas on the surface of the toner carrier, resulting in poor charging of magnetic toner particles.
This is caused by a decrease in the amount of charge on the toner layer. The state in which the surface of the toner carrier is contaminated by the components in the toner is shown in a photograph taken at a magnification of 2000 times by a scanning electron microscope in FIG.

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.

Regarding problem (2), as a method to prevent or reduce contamination of the magnetic toner carrier, it can be easily inferred that the tendency is the opposite of that of the problem, but in fact, it is better to make the surface of the toner carrier smoother. It was clear that However, in this method, the volume average particle size of the magnetic toner is 1
It has been experimentally found that if the thickness is 2 μm or more, the toner coat tends to become non-uniform, resulting in unevenness in the visible image, making it impossible to obtain a good image. When the phenomenon causing this toner coating unevenness was observed in detail by idle rotation of the developing device, the following was discovered.

Although the cause is unknown at the beginning of the main rotation, if the toner carrier surface is smooth, the toner coating layer becomes excessively thick. The toner protrudes to the side (section A in Figure 4), as shown in the enlarged cross-sectional view in Figure 4.
A toner pool 10a is generated in the A section. When the toner pool reaches a certain limit, the transfer force of the sleeve 2 is transferred onto the sleeve, causing uneven coating as shown in 3a. If there are toner lumps like 3a in the toner layer 3 coated like -, these will appear unevenly on the image. The unevenness includes dense unevenness, uneven fogging, etc. It was found that the shape of the toner application unevenness 3a includes a rectangular spot pattern, a wavy spot pattern, a wavy pattern, etc.

As described above, with the conventional developing method, it is extremely difficult to solve both the problem and the problem (2) at the same time.

[Purpose of the invention]

An object of the present invention is to uniformly coat a toner carrier with a developer and to prevent or reduce contamination of the surface of the toner carrier by 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 have high image density, excellent fine line reproducibility and gradation, and can provide clear, high-quality images without fog over a long period of time. .

[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 developer that carries a developer on its surface. and the carrier are arranged with a certain gap in the developing section,
In an image forming method in which the developer is regulated to a thickness thinner than the gap on a developer carrier and transported to a developing section, and the toner is developed while being applied with an alternating electric field in the developing section, the developer carrier has a regular shape. By blasting with particles, the magnetic toner particles have a surface with unevenness formed by a plurality of spherical trace depressions, and the magnetic toner particles have a particle size of 5 μm or less.
60% by number, 1 to 33% by number of magnetic toner particles with a particle size of 8 to 12.7 μm, and 2.0% by volume or less of magnetic toner particles with a particle size of 16 μm or more. As a charge softening agent fine powder having a particle size distribution with a volume average particle size of 4 to 11 μm, and further having a frictional charging property with iron powder of 50 μc/g or less and a number average particle size of 0.5 μm or less. The present invention relates to an image forming method characterized by containing a carbon allotrope or a metal oxide.

Further, in the present invention, an electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries a developer on its surface are arranged with a certain gap in a developing section, and the developer is In an image forming apparatus that develops an electrostatic charge image by transporting toner onto a toner carrier to a thickness thinner than the gap, and applying an alternating electric field to the toner in the developing unit, the toner carrier is By blasting with regular-shaped particles, the magnetic toner has a surface with unevenness formed by a plurality of spherical trace depressions, and the magnetic toner particles have a particle size of 5 μm or less.
0% by number, 1 to 33% by number of magnetic toner particles with a particle size of 8 to 12.7 μm, and 2.0% by volume or less of magnetic toner particles with a particle size of 16 μm or more. having a particle size distribution with a volume average particle diameter of 4 to 11 μm,
Further, the image forming method is characterized in that it contains a carbon allotrope or metal oxide as a charge moderating fine powder having a triboelectric charging property with iron powder of 50 μc/g or less and a number average particle size of 0.5 μm or less. Regarding equipment.

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 toner carrier, it is far superior when compared to a toner carrier having a completely smooth surface.

On the other hand, magnetic toner has a volume average particle size of 4 to 11
μm and has a specific particle size distribution, even when 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 layer remains uniform for a long period of time. can be coated with toner.

As a result, it is possible to obtain clear, high-quality images with high image density, excellent fine line reproducibility and gradation, and no fog over a long period of time.

The present invention will be specifically explained below. Further, the toner carrier is hereinafter referred to as a sleeve.

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 various rigid spheres made of metals such as stainless steel, aluminum, steel, nickel, and brass, ceramics, and plastics having a specific particle size.
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, the contamination due to components in the magnetic toner increases, which is undesirable (on the contrary, if the diameter R is 250 μm or more, the uniformity of the toner coating on the sleeve decreases, which is undesirable. It is preferable that the regular shaped particles used during the blasting process have a diameter of 20 to 250 μm.In addition, in the present invention, the pitch P of the unevenness on the sleeve surface and the surface roughness d are determined by measuring the surface of the sleeve with a micro surface roughness meter ( The surface roughness d is measured using JISIO point average roughness (
RZ) rJls B 0601J.

In other words, as shown in Fig. 5, there are two straight lines parallel to the average line of the section cut out by the standard length l from the cross-sectional curve, one that passes through the third peak from the highest and one that passes through the bottom of the third valley from the deepest. , the distance between two straight lines is expressed in micrometers (μm), and the reference length 1 = 0.25 mm. In addition, the pitch P was determined as follows by counting the height of the convex part with a height of 0.1 μ or more from the concave parts on both sides as one peak and the number of peaks within the standard length of 0.25 mm. It is something.

(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 100μ, and when P is less than 2μ, the magnetic This is not preferable because the sleeve contamination due to components in the toner increases, and conversely, 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 not preferable since the electric field tends to concentrate on the uneven portions and cause image disturbance (on the contrary, if d is less than 0.1 μm, the uniformity of the toner coat on the sleeve decreases, which is not preferable).

As the sleeve used in the present invention, the diameter of 80% or more of the stainless steel sleeve surface is 53 to 62 μm as regular particles.
FIG. 6 shows a 1,000x photograph taken with a scanning electron microscope of the surface of blast-treated glass beads of 500 mm.

In the magnetic toner according to the present invention, the volume average particle diameter is 4
One feature is that it is ~11 μm.

As mentioned above, the sleeve according to the present invention (hereinafter referred to as the present sleeve 2-1) has a specific uneven surface with a plurality of spherical trace depressions, but the magnetic toner is uniformly coated on the sleeve. In terms of the performance, experimental results were obtained that were slightly inferior under specific environments when compared with a sleeve (hereinafter referred to as Comparative Sleeve 2-2) having an uneven surface obtained by sandblasting with irregularly shaped particles. It mainly applies magnetic toner with a volume average particle size of 12 μm or more to a developing device having the main sleeve 2-1 and the comparative sleeve 2-2 under a specific environment of a temperature of 15° C. or less and a humidity of 10% or less. When the rotation is performed, the weight M/S of the toner layer per unit area on the sleeve is 1.6 to 2.3 mg in this sleeve 2-1.
/crrr, 0.6 to 1.5 for comparison sleeve 2-2
mg/crtr, sleeve 2-1 has a thicker toner coat, and if main rotation is continued for a long time, sleeve 2-1 has a thicker toner coat.
-1, it was confirmed that toner coating unevenness may occur as shown in FIG.

However, according to the studies of the present inventors, although the reason is not necessarily clear, when similar experiments were conducted using magnetic toner with a volume average particle size of 4 to 11 μm, it was found that the present sleeve 2-1 did not work. Even if the M/S on the sleeve is 0.7 to 1
．． It was found that the toner coat thickness could be kept low at 5 mg/c rd, and as a result, even though the main rotation was continued for a long time, sleeve coat unevenness did not occur and the toner coat thickness could be reduced for a long time. We discovered a fact that is extremely effective in achieving uniformity.

In the present invention, the volume average particle size of the magnetic toner is 4 to 11
The thickness is preferably .mu.m, more preferably 6 to 10 .mu.m. If the volume average particle size is less than 4 μm, problems such as a small amount of toner on the transfer paper (low image density) may occur in applications with a high image area ratio such as graphic images, etc. If the volume average particle size exceeds 12 μm, As mentioned above, the uniformity effect of the sleeve coat is reduced.

In the present invention, the charge amount of the toner layer per unit area on the carrier and the weight of the toner layer were determined using the so-called suction type Faraday cage method. In this suction type Faraday cage method, the outer cylinder is pressed against the toner carrier to suck all the toner on a certain area on the carrier, and the toner is collected in a filter in the inner cylinder. The weight of the toner layer per unit area above can be calculated. At the same time, this method allows the amount of charge per unit area on the toner carrier to be determined by measuring the amount of charge accumulated in an inner cylinder that is electrostatically shielded from the outside.

One of the characteristics of the magnetic toner according to the present invention is that magnetic toner particles having a particle size of 5 μm or less account for 12 to 60% by number.

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 stabilizing the volume average particle size of the magnetic toner on the sleeve during image printing.

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 of 8 μm or less (in particular, there were many magnetic toner particles of 5 μm or less. In other words, the image output durability If this is done, a large amount of magnetic toner particles with a particle size of 5 μm or less, which is the most suitable for development, will be consumed.If this amount is small, the volume average particle size on the sleeve will gradually become large, resulting in a large amount of magnetic toner particles on the sleeve. S increases,
This tends to make uniformity of the sleeve coat difficult. Therefore, it is preferable that magnetic toner particles with a particle size of 5 μm or less account for 12 to 60% of the total number of particles.If the amount is less than 12% by number, there is no effect, and if it exceeds 60% by number, magnetic toner particles Toner particles tend to aggregate with each other, resulting in toner clumps that are larger than the original particle size, resulting in poor image quality.
The resolution may be lowered, or the difference in density between the edges and the inside of the latent image may become large, resulting in a hollow image.

Further, in the magnetic toner of the present invention, 8 to 12.7μ
One of the characteristics is that the number of particles in the range of m is 1 to 33% by number. This is related to the developability of magnetic toner particles with a particle size of 5 μm or less. Magnetic toner particles with a particle size of 5 μm or less have the ability to strictly cover the latent image and reproduce it faithfully, but the latent image itself In this case, the electric field strength at the peripheral edge portion is higher than that at the center portion, and therefore, the toner particles tend to adhere more tightly inside the latent image than at the edge portion, and the image density may appear to be thinner. In particular, magnetic toner particles with a diameter of 5 μm or less have a strong tendency to do so.

However, the present inventors have found that this problem can be solved and the image can be made even clearer by containing toner particles in the range of 8 to 12.7 μm in an amount of 1% to 33% by number. In other words, it is thought that this is because toner particles in the particle size range of 8 to 12.7 μm have a suitably controlled amount of charge compared to magnetic toner particles with a particle size of 5 μm or less; The toner is supplied to the inner side, where the electric field strength is lower, and compensates for the less adhesion of toner particles on the inner side to the edge areas, forming a uniformly developed image.As a result, the toner has a high density and excellent resolution and gradation. This provides sharp images.

Therefore, it is preferable that the number of particles in the range of 8 to 12.7 μm is 1 to 33% by number; if it exceeds 33% by number, the image quality will deteriorate and more development than necessary, that is, too much toner will be applied. , mimics the increase in toner consumption4゜Meanwhile,
If it is less than 1% by number, it becomes difficult to obtain high image density. Furthermore, for particles with a particle size of 5 μm or less, the relationship between number % (N) and volume % (V) is N/V=-0,04N+k (however, 4.5≦≦6.5; 12 It is preferable that the magnetic toner of the present invention satisfies the following relationship: ≦N≦60).

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 5 μm
It shows that it contains a wide range of particles, including N/
It is understood that a small v value indicates that the abundance of particles around 5 μm is high, and that there are few particles with a particle size smaller than that, and the value of N/V is in the range of 2.1 to 6.02. and N is in the range of 12 to 60, and the above relational expression is further satisfied, it is possible to further stabilize the volume average particle diameter of the magnetic toner on the sleeve during image printing durability. can.

Further, it is preferable that the amount of magnetic toner particles having a particle size of 16 μm or more is 2.0% by volume or less, and is as small as possible.

In the magnetic toner of the present invention, it is preferable that magnetic toner particles having a particle size of 16 μm or more account for 2.0% by volume or less. 16
Contrary to magnetic toner particles with a particle size of 5 μm or less, magnetic toner particles with a particle size of 1 μm or more are relatively consumed even after image printing durability. Since the volume average particle size on the sleeve gradually becomes larger, the M/S on the sleeve increases, which is undesirable.

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 the electrolyte is 1% NaCJ! using primary sodium chloride. Prepare an aqueous solution. As a measurement method, the electric field aqueous solution 100~
Into 150 mJF, 0.1 to 5 mIt of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant, and 2 to 20 mg of the measurement sample is further added. The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and then dispersed using the Coulter Counter TA-II model.
Using a 100μ aperture as an aperture, the particle size distribution of particles of 2 to 40μ based on number was measured, and the values according to the present invention were determined therefrom.

As described above, the present inventors have made it possible to achieve high image quality and high density to some extent by making the magnetic toner have a specific particle size distribution.

However, if higher speed copying machines are required, the problems faced by the present invention become even more severe. In other words, as the copying speed increases, the fuser, photoreceptor drum, etc. of the copying machine will rotate faster than before, and the developing sleeve, which carries toner for development, will also rotate at a much faster speed than before. It will rotate. The chances of contact between the toner particles and the sleeve surface increase, the amount of charge increases, and the charge tends to gradually become excessive. In particular, under low temperature conditions, the amount of charge increases further, which may cause increased fogging, roughness, scattering, and a decrease in image density. In addition, under such severe conditions such as high speed and low humidity conditions, it is necessary to use a small particle size magnetic toner such as the one of the present invention, which has a thin toner coat (and is uniform, and is advantageous against sleeve coat unevenness). Even if a developing sleeve is used and has a surface with an uneven surface formed by a plurality of specific spherical trace depressions that suppress the toner coat thickness and stabilize it uniformly, under such severe conditions, the sleeve coat Unevenness may occur.

Based on the above findings, the developer of the present invention has a magnetic toner having the particle size distribution and material composition described above, has a triboelectric charging property with iron powder of 50 μc/g (absolute value) or less, and has a number average particle size of 0.
．． This method is characterized in that a fine charge moderating agent powder having a particle size of 5 .mu.m or less or a mixture thereof is blended with the magnetic toner particles (internal addition) or mixed with the magnetic toner particles (external addition).

The content of the fine charge softening agent powder used in the present invention is 0.1 to 50 parts by weight, preferably 0.2 to 30 parts by weight, based on 100 parts by weight of the binder resin when added internally, and preferably 0.2 to 30 parts by weight when added externally. for,
0.01 to 10 parts by weight per 100 parts by weight of magnetic toner,
Preferably it is 0.02 to 5 parts by weight.

Specific examples of the above-mentioned charge mitigating agent include the following substances. Carbon allotropes consisting mainly of carbon atoms such as carbon black, graphite, etc., magnesium oxide,
Mainly composed of metal atoms (one or more) and oxygen atoms, such as alumina, titanium oxide, iron oxide, nickel oxide, chromium oxide, copper oxide, zinc oxide, tin oxide, cerium oxide, cobalt oxide, zirconium oxide, etc. Examples include metal oxides. It is thought that these substances are easily charged (or exposed to moisture in the air, causing charge emission).In fact, the amount of charge of these substances on iron powder is 50 μc/g (absolute value ) or less, preferably 20 μc/g (absolute value) or less.

By containing an appropriate amount of fine powder of these substances in a magnetic toner, excessive frictional electrification can be suppressed and excessively charged charges can be released.

In other words, these fine powders are considered to function as a charge moderating agent that reduces the amount of triboelectric charge of the magnetic toner to an appropriate level.

On the other hand, the magnetic toner of the present invention has a small particle size, so the amount of charge tends to increase, and the average particle size is small (as it increases, it becomes more difficult to control the charge).

When these magnetic toners are overcharged, image defects such as roughness, scattering, and decreased density occur.

In addition, small particles in the magnetic toner become overcharged and have a strong mirroring force with the sleeve, adhering to the sleeve surface, interfering with the frictional charging of the developer, generating poorly charged particles, and causing fogging. This may cause an increase in image density, a decrease in image density, and even cause uneven sleeve coating.

Therefore, the effect of the developer of the present invention is more significant as the particle size becomes smaller.

Further, the magnetic toner of the present invention has many particles of 5 μm or less,
The developer of the present invention is preferable in order to prevent excessive charging of these particles and to control the amount of charge of the magnetic toner.

There are two ways to incorporate the fine powder of the charge softener into the developer of the present invention: an internal addition method and an external addition method. However, the external addition method is better because it is present in a larger amount on the surface of the magnetic toner. A large effect can be expected.Also, if the effect is achieved with a very small amount, or if the toner easily detaches from the surface of the magnetic toner, the amount added can be increased to ensure good dispersion in the developer, or if it is fixed to the surface of the magnetic toner. A method of internal addition is also effective.Furthermore, in the case where the fine powder in the developer of the present invention is magnetic, a method of internal addition can be used as long as the magnetic properties are within the range of the desired magnetic properties required for a magnetic toner.

However, if it affects the magnetic properties of the magnetic toner, the amount added can be reduced by external addition to achieve the objective.

When the triboelectric charging property is 50 μc/g or more in absolute value, the charging is not sufficiently relaxed (sometimes this occurs, and when the polarity is opposite to that of the magnetic toner, the developing property may be affected by increased fogging or decreased density). may have a negative impact.

If the number average particle size exceeds 0.5 μm, the dispersibility in the developer will be poor, and variations will occur between particles, which will adversely affect developability and increase fog, making it difficult to produce good images. The average particle size of the magnetic toner of the present invention is small (the more the effect becomes greater).

If the content exceeds the specified value, the amount of charge decreases greatly under conditions such as high humidity, resulting in image defects such as poor image density. It is not possible to fully exert the mitigation effect of the coating, and it tends to become overcharged, which may result in a decrease in density and uneven sleeve coating.

Here, the method for measuring the amount of charge of the developer and the charge moderator fine powder in the present invention will be described in detail with reference to the drawings.

FIG. 5 is an explanatory diagram of an apparatus for measuring the amount of electric charge.

First, a metal measurement container 32 with a 400-mesh screen 33 at the bottom is placed in a sample whose charge amount is to be measured and a developer consisting of an iron powder carrier (200 to 300 meshes) at a weight ratio of 10:90, with a small amount of charge softening agent. For powder, 1 g of a mixture with a weight ratio of 2:98 is added and a metal lid 34 is placed. Weigh the entire weight of the measurement container 32 at this time, W+(g
). Next, with the suction device 31 (the part that comes into contact with the measurement container 32 is small (both are insulators), suction is performed from the suction port 37, and the air volume control valve 36 is adjusted to raise the pressure of the vacuum gauge 35 to 250.
Let it be mmH20. In this state, perform sufficient suction to remove the sample. The potential of the electrometer 39 at this time is assumed to be V (volt). Here, 38 is a capacitor, and the capacitance is C (μF). In addition, the weight of the entire measurement container after suction is weighed and is defined as Wz (g). The amount of charge of this sample (μc
/g) is calculated as shown below.

However, the measurement conditions are 23° C. and 60% RH.

In addition, the carrier (iron powder) used for measurement is 200 to 30
0 mesh, but in order to avoid any errors, the carrier was sufficiently suctioned using the suction device mentioned above, and the carrier that passed through the 400 mesh screen was removed before being mixed with the sample.

In the present invention, fine line reproducibility was measured by the following method. In other words, an image of an original manuscript with thin lines exactly 100 μm in width was copied under appropriate copying conditions as a sample for measurement, and a Luzetx 450 Particle Analyzer was used as the measurement device to measure the line width using an indicator from the enlarged monitor image. Perform measurements. At this time, since the line width measurement position has irregularities in the width direction of the fine line image of the toner, the average line width of the irregularities is taken as the measurement point. From this, the value (%) of fine line reproducibility is calculated using the following formula.

In the present invention, the resolution was measured by the following method. In other words, it is a pattern consisting of five thin lines with equal line width and spacing, with a width of 2.8 mm per 1 mm. 3.2.3
．． 6.4.0.4, 5.5.0.5.6.6.3゜7.
An original image drawn as if there were 1 or 8.0 line images is taken.The original document with these 10 types of line images is copied under appropriate copying conditions, and observed with a magnifying glass, and the gaps between thin lines are The number of images with clearly separated images (images/
m m ) is taken as the value of resolution.

The larger this number, the higher the resolution.

As the binder resin used in the magnetic toner of the present invention, the following toner binder resins 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 Styrenic copolymers such as ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol Resin, natural 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, Coumarone indene resin, petroleum-based resin, etc. can be used.

In the heating and pressure roller fixing method that does not apply much oil, 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 important (involved in 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 deteriorate during fixing. Although the adhesion of the toner to the support member is improved, offset is likely to occur, and blocking or caking is also likely to occur.Therefore, in the present invention, when using a heated pressure roller fixing method that does not apply much oil, The selection of the binder resin is more important. Preferred binder materials include crosslinked styrenic copolymers or 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 methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrinitrile, acrylamide, etc., or substituted products thereof; for example, maleic acid, butyl maleate, Dicarboxylic acids with double bonds such as methyl maleate, dimethyl maleate, etc. and substituted products thereof; e.g. vinyl chloride, vinyl acetate,
Vinyl esters such as vinyl benzoate; ethylene olefins such as ethylene, propylene, butylene; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone; vinyl methyl ether, vinyl ethyl ether, Vinyl monomers such as vinyl ethers such as vinyl isobutyl ether may be used alone or in combination of two or more.

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,
Ethylene glycol dimethacrylate! , 3-butanediol dimethacrylate, etc.; carboxylic acid esters having two double bonds; divinyl compounds such as divinyl aniline, divinyl ether, divinyl sulfide, divinyl sulfone; and compounds having three or more vinyl groups; Used alone or in mixtures.

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 (internal addition) or mixing it with the toner particles (external addition). The charge control agent makes it possible to optimally control the amount of charge depending on the developing system, and in particular, in the present invention, it is possible to further stabilize the balance between particle size distribution and charge. As a positive charge control agent, modified products with nigrosine and fatty acid metal salts; tributylbenzylammonium-1-hydroxy-
Quaternary ammonium salts such as 4-naphthosulfonate, tetrabutylammonium tetrafluoroborate; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyltinborate, dioctyltinborate, dicyclohexyltinborate, etc. These diorganostin borates can be used alone or in combination of two or more.

Among these, charge control agents such as nigrosine and quaternary ammonium salts are particularly preferably used.

In addition, the general formula [wherein R1 represents H or CHa, R2 and R3
is a substituted or unsubstituted alkyl group (preferably Cl-
04). ] A homopolymer of the monomer represented by; or a copolymer with a polymerizable monomer such as styrene, acrylic acid ester, or methacrylic acid ester as described above can be used as a positive charge control agent. The charge control agent also functions as (all or part of) a binder resin.

As negative chargeability control agents that can be used in the present invention, for example, organic metal complexes and chelate compounds are effective; examples thereof include aluminum acetylacetonate, iron (n
) acetylacetonate, chromium 3,5-ditertiary-butylsalicylate, etc., and acetylacetone metal complexes, salicylic acid metal complexes or salts are particularly preferred, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferred.

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:
The thickness 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 20 parts by weight (or even 0.1 to 20 parts by weight) per 100 parts by weight of the binder resin.
．． 2 to 10 parts by weight) is preferably used.

Various additives may be added internally or externally to the magnetic toner according to the present invention, if necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight may be used per 100 parts by weight of the binder resin. Other additives include, for example, lubricants such as zinc stearate; abrasives such as silicon carbide.

In addition, in order to improve mold releasability during hot roll fixing, waxy substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, Sasol wax, paraffin wax, etc. are added to the binder resin. It is also one of the preferred embodiments of the present invention to add about 0.5 to 5 wt% to the magnetic toner.

Further, the magnetic toner according to the present invention contains a magnetic material, although it may also serve as a colorant. Magnetic materials contained in the magnetic toner of the present invention include magnetite, γ
- Iron oxides such as iron oxide rougherite iron-rich ferrite; metals such as iron, cobalt, and nickel, or these metals and aluminum.

Cobalt, copper, lead, magnesium, tin, zinc.

antimony, beryllium, bismuth, cadmium.

Calcium, manganese, selenium9. Examples include alloys with metals such as titanium, tungsten, and vanadium, and mixtures thereof.

These ferromagnetic materials preferably have an average particle size of 0.1-1 μm, preferably 0.1-0.5 μm, and are contained in the magnetic toner in an amount of 60-200 parts by weight per 100 parts by weight of the resin component. parts, preferably 60 to 150 parts by weight per 100 parts by weight of the resin component, and more preferably 65 to 110 parts by weight per 100 parts by weight of the resin component.

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, niegu, or extruder to make the resins compatible with each other. The 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.

Further, fine silica powder may be added internally or externally to the magnetic toner of the present invention, but it is more preferable to mix it externally. 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 triboelectrification, the number of times the toner particle surface contacts the sleeve increases compared to conventional magnetic toner, and the toner particles Particle wear is more likely to occur. 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. This not only extends the lifespan of the magnetic toner, but also
It is also possible to maintain stable charging properties, and it is possible to obtain a developer having a magnetic toner that is more excellent even in long-term use.

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.

On the other hand, various conventionally known methods can be applied to produce the silica fine powder used in the present invention by a wet method.

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 silica fine powders mentioned above, the specific surface area due to nitrogen adsorption measured by the BET method is 30rd/g or more (especially 50 to 40rd/g).
0 rrf/g) gives good results. Silica fine powder 0.0 per 100 parts by weight of magnetic toner
It is good to use 1 to 8 parts by weight, preferably 0.1 to 5 parts by weight.

In addition, when the magnetic toner according to the present invention is used as a positively charged magnetic toner, as the silica fine powder added to prevent toner wear, positively charged silica fine powder is used rather than negatively charged silica fine powder. It is preferable to use it without impairing charging stability.

As a method for obtaining positively chargeable silica fine powder, the above-mentioned untreated silica fine powder is mixed with fewer nitrogen atoms in the side chain (both 1 and 1).
There is a method of treatment with a silicone oil having more than one organo group, a method of treatment with a nitrogen-containing silane coupling agent, or a method of treatment with both.

In the present invention, positively charged silica refers to silica that has a positive triboelectric charge relative to the iron powder carrier when measured by a plow-off method.

As the silicone oil having a nitrogen atom in the side chain used in the treatment of silica fine powder, a silicone oil having at least a partial structure represented by the following formula can be used.

(In the formula, R1 represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R2 represents an alkylene group or a phenylene group, R3 and R4 represent hydrogen, an alkyl group, or an aryl group, and R6 represents a nitrogen-containing heterocyclic ring. Note that the alkyl group, aryl group, alkylene group, and phenylene group described above may have an organo group having a nitrogen atom, or may have a substituent such as a halogen within a range that does not impair chargeability. It's okay to do so.

Furthermore, the nitrogen-containing silane coupling agent used in the present invention is
It generally has a structure shown by the following formula.

Rm-8i-Yrt (R represents an alkoxy group or a halogen, Y represents an amino group or an organo group having one or more nitrogen atoms, m and n are integers of 1 to 3, and m +
n = 4. ) Examples of the organo group having one or more nitrogen atoms include an amino group having an organic group as a substituent, a nitrogen-containing heterocyclic group, or a group having a nitrogen-containing heterocyclic group.Nitrogen-containing heterocyclic group Examples of the unsaturated heterocyclic group include unsaturated heterocyclic groups and saturated heterocyclic groups, and known ones are applicable. Examples of the unsaturated heterocyclic group include the following.

Examples of the saturated heterocyclic group include the following.

The heterocyclic group used in the present invention is preferably a five-membered ring or a six-membered ring in consideration of stability.

Examples of such treatment agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, Monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ
-Propylphenylamine, trimethoxysilyl-γ-
Propylbenzylamine, etc. Furthermore, as the nitrogen-containing heterocycle, those having the above-mentioned structure can be used. Examples of such compounds include trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, Examples include trimethoxysilyl-γ-propylimidazole.

The application amount of these treated positively charged silica fine powders is
0.01 to 100 parts by weight of positively charged magnetic toner
The effect is exhibited when the amount is 8 parts by weight, particularly preferably 0.1
When added in an amount of up to 5 parts by weight, it exhibits positive chargeability with excellent stability. Regarding the form of addition, the preferred form is 0.1 to 100 parts by weight of positively charged magnetic toner.
It is preferable that 3 parts by weight of the treated silica fine powder be attached to the surface of the toner particles. Note that the untreated fine silica powder described above can also be used in the same amount.

Furthermore, the silica fine powder used in the present invention may be treated with a silane coupling agent or a treatment agent such as an organosilicon compound for the purpose of hydrophobization, if necessary, to react with or physically adsorb to the silica fine powder. Treated with the above-mentioned processing agent. Examples of such treatment agents include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane,
Trimethylethoxysilane, dimethyldichlorosilane,
Methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-
Chlorethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane, hexa Methyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and siloxane units having 2 to 12 siloxane units per molecule, with one unit per molecule at each end. Examples include dimethylpolysiloxane containing a hydroxyl group bonded to St. These can be used alone or in a mixture of two or more.

Further, in the magnetic toner according to the present invention, a fine powder of a fluorine-containing polymer may be added internally or externally. Examples of fine fluorine-containing polymer powders include fine powders of polytetrafluoroethylene, polyvinylidene fluoride, etc., and fine powders of tetrafluoroethylene-vinylidene fluoride copolymers. It is preferable from the viewpoint of hardness and abrasiveness. The amount added to the toner is 0.01 to 2. Owt%, especially 0.
02 to 1.0 wt% is preferable.

In particular, in magnetic toners in which fine silica powder is mixed with the above-mentioned fine powders and externally added, for reasons that are not clear, the state of the silica attached to the toner is stabilized, and for example, the attached silica is released from the toner. Therefore, the effect on toner abrasion and sleeve staining does not decrease, and it is possible to further increase charging stability.

The developer of the present invention can be used for one-component development for visualizing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc. by conventionally known means.

Further, the developer of the present invention is preferably applied to an image forming method in which a latent image is developed while flying toner from a toner carrier such as a cylindrical sleeve to a latent image carrier such as a photoreceptor. That is, the developer is given a triboelectric charge mainly through contact with the sleeve surface, and is coated in a thin layer on the sleeve surface. The thickness of the thin layer of developer is formed to be thinner than the gap between the photoreceptor and the sleeve in the development area. When developing a latent image on the photoreceptor, it is preferable to apply an alternating electric field between the photoreceptor and the sleeve, and then allow the tribocharged developer to fly from the sleeve to the photoreceptor.

Examples of the alternating electric field include a pulsed electric field, an alternating current bias, or a combination of alternating current and direct current bias.

EXAMPLES The present invention will be specifically explained below with reference to 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 The developing conditions and device conditions of the present invention will be described with reference to the developing device shown in FIG. 1 of the accompanying drawings.

80% of shaped particles are placed on the surface of a cylindrical stainless steel sleeve (SUS 304) with a fixed magnet 4 inside.
Using glass beads with a diameter of 53 to 62 μm, blasting was performed under the conditions of a blowing nozzle diameter of 7φ, a distance of 100 mm, an air pressure of 4 kg/crrr, and a duration of 2 minutes, and the diameter R of the multiple spherical trace depressions was An unevenness having a size of 53 to 62 μm was formed. The pitch P of the unevenness on the surface of this sleeve was 33μ, and the surface roughness d was 2.0μ. −
The component developer 10 is applied in a thin layer via a magnetic blade 1a onto the surface of a stainless steel cylindrical sleeve 7 rotating at a circumferential speed of 390 mm/7 seconds in the direction of the arrow.
The gap between the blade 1a and the blade 1a was set to about 250 μm. The sleeve 2 has a fixed magnet 4 as a magnetic field generating means, and the fixed magnet generates a magnetic field of 950 Gauss in the vicinity of the sleeve surface in the developing area adjacent to the OPC photosensitive drum 9 comprising an organic photoconductive layer having a negatively charged latent image. was forming. 260
The closest distance between the OPC photosensitive drum 9, which rotates in the direction of the arrow at a circumferential speed of 7 seconds, and the sleeve 2 was set to about 300 μm. In addition, between the OPC photosensitive drum 9 and the sleeve 2, the frequency of 2000 Hz, which is a combination of AC bias and DC bias, is
A bias of /1350 Vpp was applied.

On the other hand, as the magnetic toner, use the following.The above materials were mixed in a blender (after mixing, the temperature was set at 150°C).
The mixture was kneaded using a axial kneading extruder. Cool the resulting crosstalk,
After coarsely pulverizing it with a cutter mill, it was finely pulverized using a pulverizer using a jet stream, and the obtained pulverized powder was classified with a fixed wall type wind classifier to produce classified powder. Furthermore, the obtained classified powder was strictly classified and removed at the same time to remove ultra-fine powder and coarse powder using a multi-division classifier (elbow jet classifier manufactured by 8 Iron Mining Co., Ltd.) using the Coanda effect to obtain a volume average particle size of 8.2 μm.
A black fine powder (magnetic toner) of m was obtained.

The obtained magnetic toner, which is a positively charged black fine powder, was measured using the Coulter Counter TA II type equipped with an aperture of <100 μm as described above, and the data is shown in Table 1 below.

Table 1: Adding 100 parts by weight of the obtained black fine powder magnetic toner to dry aluminum oxide/titanium oxide mixed fine powder (weight ratio 4.
: 96. Number average particle size 0.08 μm, charge amount +4.
0.5 parts by weight of 1 μc/g) were strongly mixed in a turbo mill mixer to make them adhere, and then 0.5 parts by weight of positively charged hydrophobic silica (BET specific surface area 200 m''/g) was added. Toner A is a magnetic toner mixed with a Henschel mixer.
And so. The particle size distribution of this toner A was as shown in Table 2.

Toner A was put into a high-speed electrophotographic copying machine equipped with the above-mentioned sleeve, and an image reproduction test was carried out. Especially the image output test.
Under low temperature and low humidity conditions (15
Table 3 shows the results of 5,000 consecutive tests at 10% (°C, 10%). As is clear from Table 3, in the initial stage, the weight of the toner layer per unit area on the sleeve M/S
shows a moderate value at 1.0 mg/ctrr,
M/S=1.0mg/c even after 5000 sheets of durability
nf and was stable, and the toner coating on the sleeve was also extremely uniform. In addition, the surface of the sleeve after being used for 5,000 sheets was observed using a scanning electron microscope after air cleaning.
No toner components were attached to the surface irregularities, and virtually no sleeve contamination occurred. Therefore, both the initial image and the 5,000-sheet durable image had an image density Dma of
The x was high and there was no fog (clear, high quality image).

Example 2 Using the above materials, black fine powder with a volume average particle diameter of 4.5 μm was obtained in the same manner as in Example 1.

0.5 parts by weight of hydrophobic dry silica was added to 100 parts by weight of black fine powder magnetic toner and mixed in a Henschel mixer to obtain a one-component magnetic developer.

Using the same developing device as in Example 1, evaluation was performed in the same manner as in Example 1 under severe low humidity conditions of 15° C. and 10%.

As is clear from Table 3, both the initial image and the image after 5,000 sheets had high image density (no fog, clear, high quality images were obtained, and there was no sleeve contamination. No unevenness was observed.

Also, the weight of the toner layer per unit area on the sleeve is
Both initial and after durability 1.1mg/cm", 1.2mg/cm
Furthermore, the charge amount Q/S of the toner on the sleeve at this time was 8.0 μc/g, which was appropriate.

Example 3 The same material composition and manufacturing method as in Example 2 were used, except that carbon black was excluded from the raw materials used in Example 2, and the volume average particle size was 1.
A 0.3 μm magnetic toner was obtained. The particle size distribution is shown in Table 1. The amount of frictional electrification with the iron powder carrier was +14 μc/g. The following materials were mixed with 100 parts by weight of the obtained magnetic toner using a Henschel mixer to prepare a one-component developer.

The properties of this developer were as shown in Table 2.

This developer was subjected to the same 5,000 copy test as in Example 1, and the results are shown in Table 3.

As is clear from Table 3, excellent images were obtained.

Example 4 Using the above materials, a magnetic toner having a volume average particle diameter of 9.2 μm was obtained in the same manner as in Example 1.

Add 100 parts by weight of this magnetic toner to dry titanium oxide fine powder (
Number average particle size 0.02μm, charge amount -2, sμc/g)
0.8 parts by weight was added and mixed in a Henschel mixer to prepare a negatively chargeable one-component magnetic developer.

A high-speed copying machine (A4 size 70 sheets/min) equipped with an amorphous silicon photosensitive drum that forms a positively charged electrostatic image, and a developing machine equipped with a developing sleeve subjected to the same blasting process as in Example 1 (sleeve circumferential speed 410 mm/sec), the above-mentioned -component magnetic developer was applied, and evaluation was conducted in the same manner as in Example 1. As shown in Table 3, clear, stable, and high-quality images were obtained, and no unevenness occurred.

Comparative Example 1 Using the apparatus of Example 1, hydrophobic silica (BET 200m") was added to 100 parts by weight of the black fine powder magnetic toner of Example 1.
A one-component developer obtained by mixing 0.5 parts by weight of 7g) in a Henschel mixer was evaluated in the same manner as in Example 1.

As the durability progressed, the image density decreased from 1.42 to 1.28 at 5,000 sheets under low temperature and low humidity conditions of 15° C. and 10%, and image quality deterioration due to roughness and sputtering was observed. In addition, the patchy sleeve unevenness gradually increased. At this time, the toner charge amount Q/S on the sleeve is initially 13 nc/cm", and when a block occurs, it is 17 to 19 nc/cm".
It was as high as “c/cm”.

Comparative Example 2 In Example 1, the sleeve surface was not blasted with regular particles, but was rubbed using fine powder of cerium oxide as an abrasive to give it a smooth mirror surface. This sleeve was designated as Sleeve B, and evaluation was performed in the same manner as in Example 1 except that Sleeve B was used in place of Sleeve A used in Example 1 under high-speed machine, low temperature, and low humidity conditions.

The initial image was high density and clear with no fog, but the M/S on the sleeve was as large as 2.3 mg/ctrr, and after printing 5,000 images, the sleeve toner was leaking from both ends of the sleeve. Coat unevenness occurred, and the obtained image had defects at both ends, and uneven fogging was observed.

Furthermore, the M/S on the sleeve was as high as 3.8 mg/crrr because it included the uneven toner coating area.

Comparative Example 3 Sleeve C was obtained by surface treatment of the sleeve in the same manner as in Example 1 except that #300 carborundum, which is an amorphous particle, was used instead of the glass beads used in Example 1. . The same evaluation as in Example 1 was performed except that Sleeve C was used instead of Sleeve A used in Example 1.

The initial image was a clear image with high density and no fog, but after printing 5000 images, the image density was 0.4.
2, a significant decrease in image density was observed.

Furthermore, when the sleeve was cleaned with air after the durability test and observed under a scanning electron microscope, a large amount of toner components was observed on the sleeve surface, indicating that the sleeve was contaminated.

Comparative Example 4 A magnetic toner having a volume average particle diameter of 12.5 μm was obtained in the same manner as in Example 1 using the above materials. The particle size distribution is shown in Table 2. 0 parts by weight of hydrophobic silica in 100 parts by weight of this magnetic toner.
．． 5 parts by weight were added and mixed in a Henschel mixer to prepare a developer.

Evaluation was performed in the same manner as in Example 1 using the same developing device as in Example 1. Immediately after the start of image printing, toner coating unevenness occurred on the sleeve, and after several dozen sheets, unevenness appeared on the entire surface of the image. The amount of charge Q/S on the sleeve is 21nc/c
m”, which was extremely high.

No. table

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a developing device using a magnetic blade, FIG. 2 shows a scanning electron micrograph of the surface of the metal structure of a sleeve sandblasted with irregularly shaped particles, and FIG. This is a scanning electron micrograph of the surface of the metal structure of a sleeve that has been sandblasted with irregularly shaped particles and is contaminated by magnetic toner components during development. , FIG. 5 shows an explanatory view of the definition of surface roughness and pitch, and FIG. 6 shows a scanning electron micrograph of the surface of the metal structure of a sleeve that has been blasted with regular particles according to the present invention. FIG. 7 shows a schematic diagram of an apparatus for measuring the amount of triboelectrification of fine powder. la・・・・・・・・・・・・ Magnetic blade 2・・・・・・・・・・・・・・・・・・
・・・・・・・・・・Sleeve 3・・・・
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・・
...Fixed magnet roller 7...
・・・・・・・・・・・・・・・ Developer container 9・・・・・・・・・・・・ ・・・・
・・・・・・・・・・・・・・・・・・ Photosensitive drum Magnetic toner Alternating voltage power supply measuring container ・・・・・・・・・・・・・・・・・・・・・・・・・Screen (400 mesh) suction port electrometer

Claims (4)

[Claims] (1) An electrostatic image carrier that holds an electrostatic image and a developer carrier that carries developer on its surface are arranged with a certain gap in the developing section, and the developer is placed on the developer carrier. In an image forming method in which the developer is conveyed to a developing section with a thickness regulated to be thinner than the gap and developed while applying an alternating electric field to the developer in the developing section, the developer carrier is blasted with a plurality of particles by blasting with regular particles. The developer has a surface with unevenness formed by spherical trace depressions, and the developer contains 12 to 60% by number of magnetic toner particles with a particle size of 5 μm or less, and 8 to 12.7 μm.
Contains 1 to 33% by number of magnetic toner particles with a particle size of 16
Contains 2.0% by volume or less of magnetic toner particles with a particle size of μm or more, the volume average particle size of the magnetic toner is 4 to 11 μm, and the frictional charging property with iron powder is 50 μc/g or less. . An image forming method characterized in that a carbon allotrope or a metal oxide is contained as a charge moderating fine powder having a number average particle size of 0.5 μm or less. (2) The surface condition of the developer carrier 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 to 1
00 μm, and the surface roughness d is 0.1 to 5 μm. (3) An electrostatic image carrier that holds an electrostatic charge image and a developer carrier that carries developer on its surface are arranged with a certain gap in the developing section, and the developer is placed on the developer carrier. In an image forming apparatus in which the electrostatic charge image is developed by regulating the thickness to be thinner than the gap and conveying the electrostatic charge image to a developing section while applying an alternating electric field to the developer in the developing section, the developer carrier is blasted with regular particles. The magnetic toner has a surface having an uneven surface formed by a plurality of spherical trace depressions through treatment, and the magnetic toner contains 12 to 60 number % of magnetic toner particles having a particle size of 5 μm or less,
Contains 1 to 33% by number of magnetic toner particles with a particle size of 8 to 12.7 μm, and contains 2% of magnetic toner particles with a particle size of 16 μm or more.
．． The volume average particle size of the magnetic toner is 4 to 11 μm, and the triboelectric charging property with iron powder is 50 μc/g or less, and the number average particle size is 0.5 μm or less. An image forming apparatus characterized by containing a carbon allotrope or a metal oxide as a fine charge moderating powder. (4) The surface condition of the developer carrier 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 to 1
00μ, and the surface roughness d is 0.1 to 5μ.