JP2749865B2 - Image forming method and image forming apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming method including a step of developing a latent electrostatic image formed in an electrophotographic method, an electrostatic printing method, an electrostatic recording method, or the like using a magnetic toner. The present invention relates to a method and an image forming apparatus therefor,
The latent image is represented by unit pixels, and the unit pixels are turned on.
The present invention relates to an image forming method and an image forming apparatus for visualizing a digital latent image expressed by an OFF binary or finite gradation by a reversal developing method.

(Background technology)

2. Description of the Related Art In recent years, as image forming apparatuses such as electrophotographic copiers have become widespread, their uses have been diversified, and requirements for image quality have become strict. 2. Description of the Related Art In copying images such as ordinary documents and books, it is required to reproduce very finely and faithfully without crushing or breaking even fine characters. In particular, when the latent image on the photoreceptor of the image forming apparatus is a line image of 100 μm or less, thin line reproducibility is generally poor, and the line image is not yet sufficiently sharp. Recently, in an image forming apparatus such as an electrophotographic printer using a digital image signal, a latent image is formed by collecting dots of a constant potential, and a solid portion,
The halftone portion and the light portion are expressed by changing the dot density. However, if the toner particles do not adhere exactly to the dots and the toner particles protrude from the dots, the gradation of the toner image corresponding to the dot density ratio of the black portion and the white portion of the digital latent image cannot be obtained. There is a problem. Furthermore, when the resolution is improved by reducing the dot size in order to improve the image quality, the reproducibility of a latent image formed from minute dots becomes more difficult, and the resolution and gradation are poor, and the sharpness is low. Image tends to be lacking.

In order to faithfully reproduce such a minute latent image, a toner having a small particle size is required, and some toners have been proposed so far.

JP-A-58-129437 discloses that the average particle size is 6 to 10 μm.
Non-magnetic toners having the largest number of particles of 5 to 8 μm have been proposed, but the number of particles of 5 μm or less is as small as 15% by number or less, and an image lacking in sharpness tends to be formed.

According to the study of the present inventors, it has been found that toner particles having a size of 5 μm or less clearly reproduce the outline of the latent image and have a main function of dense toner adhesion to the entire latent image. In particular, in the electrostatic latent image on the photoreceptor, due to the concentration of lines of electric force, the contoured edge portion has a higher electric field intensity than the inside, and the sharpness of the image quality is determined by the quality of the toner particles collected in this portion. According to the study of 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 one-component magnetic toner,
For example, Japanese Patent Application Laid-Open No. 57-66455, etc., there is a toner carrier having a specific uneven surface roughened by sand blasting with irregular shaped particles as a toner carrier. It is an excellent developing device that can maintain a good toner coated state over a long period of time without any uniform unevenness on the body surface. The target surface is an embodiment in which countless fine notches or projections are formed in random directions over the entire area.

However, in a developing device using a toner carrier having such a specific surface state, when a toner having a small particle diameter as described above is used, the toner or a component in the toner may include:
The toner easily adheres to the surface, so that the so-called contamination on the surface of the toner carrier occurs. As a result, if the contamination progresses due to a decrease in the density of the initial image and further due to the durability, the image is lost due to the rotation cycle of the toner carrier. Tends to occur. This is due to the fact that the components in the toner adhere to the inclined surfaces and the concave portions of the convex portions on the surface of the toner carrier, so that poor charging of the magnetic toner particles occurs and the charge amount of the toner layer decreases.

Generally, the components in the magnetic toner are composed of materials such as a binder resin magnetic material, a charge control agent, and a release agent. Materials are designed so as to prevent contamination on the surface of the toner carrier. However, at present, selection of materials is extremely restricted.

As a method of preventing or reducing the contamination of the magnetic toner carrier, it was apparently preferable to make the surface of the toner carrier smoother. However, although the cause is unclear, if the surface of the toner carrier is smooth, the toner coat layer becomes excessively thick, and it is difficult to form a uniform toner coat layer.

As described above, it has been extremely difficult to stably supply an image faithfully reproducing a fine latent image.

[Object of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to uniformly coat a magnetic toner on a toner carrier and to prevent or reduce contamination of the toner carrier surface by the magnetic toner and / or components in the magnetic toner. It is an object of the present invention to provide an image forming method and an image forming apparatus which solve the above problem for a long time.

It is a further object of the present invention to provide an image forming method and an image forming apparatus capable of obtaining a clear, high-quality image with high image density, excellent fine line reproducibility, and no fog for a long period of time.

Still another object of the present invention is to provide an image forming method and an image forming apparatus in which performance does not change due to environmental changes.

[Summary of the Invention]

An image forming method and an image forming apparatus according to the present invention have been devised to achieve the above-described object, and include an electrostatic image holder for holding an electrostatic image and a toner holder for holding a magnetic toner on the surface. Are arranged at a fixed interval in the developing section, and the magnetic toner is conveyed to the developing section while being regulated to a thickness smaller than the gap on the toner carrier, and developed while applying an alternating electric field to the toner in the developing section. In the image forming method, the toner carrier has a surface on which irregularities due to a plurality of spherical trace dents are formed by blasting with regular particles,
The surface condition is such that the diameter R of the spherical trace depression is 20 to 250 μm.
An elastic layer thickness regulating member which satisfies the condition that the pitch P of the unevenness is 2 to 100 μm and the surface roughness d is 0.1 to 5 μm, and the toner layer on the toner carrier comes into contact with the surface of the toner carrier by elastic force. Is transported to the developing unit after being layered as a thin layer, and the charge amount of the magnetic toner is -10 to -20 μc /
g, having a volume average diameter of 6 to 8 μm, and containing 17 to 60% by number of magnetic toner particles having a particle diameter of 5 μm or less,
5 to 5 magnetic toner particles having a particle size of 6.35 to 10.08 μm
0% by volume, magnetic toner particles having a particle size of 12.7 μm or more are contained at 2.0% by volume or less, and a magnetic toner particle group of 5 μm or less is represented by the following formula: [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 represents a positive number of 4.6 to 6.7. . ], And an image forming method characterized by satisfying the following.

Further, in the present invention, an electrostatic image holding member for holding an electrostatic image and a toner holding member for holding a magnetic toner on the surface are arranged with a certain gap in a developing section, and the magnetic toner is placed on the toner holding member. In an image forming apparatus which regulates the thickness to be smaller than the gap and conveys the toner to the developing unit, and develops the toner while applying an alternating electric field to the developing unit, the toner carrier is subjected to a plurality of spherical traces by blasting with fixed particles. The surface condition is such that the diameter R of the spherical trace depression is 20 to 250 μm, the pitch P of the irregularity is 2 to 100 μm, and the surface roughness d is 0.1 to 5 μm. Satisfactory, the toner layer on the toner carrier is layered as a thin layer by an elastic layer thickness regulating member that abuts against the toner carrier surface by elastic force, and is transported to the developing unit. body An insulating one-component magnetic toner containing the charge amount of the toner is -10~-20μc / g
Having 17 to 60% by number of magnetic toner particles having a volume average particle diameter of 6 to 8 μm and a particle diameter of 5 μm or less,
5 to 5 magnetic toner particles having a particle size of 6.35 to 10.08 μm
0% by volume, magnetic toner particles having a particle size of 12.7 μm or more are contained at 2.0% by volume or less, and a magnetic toner particle group of 5 μm or less is represented by the following formula: [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 represents a positive number of 4.6 to 6.7. . Here, N indicates a positive number of 17 to 60. ] Which has a particle size distribution satisfying the following.

[Specific description of the invention]

According to such a configuration, since the surface of the toner carrier has specific irregularities formed by a plurality of spherical trace depressions, it is difficult for toner components to adhere to the surface, thereby preventing contamination over a long period of time. The ability to uniformly coat the magnetic toner on the toner carrier with the magnetic toner is as follows. The toner carrier having an irregular surface in which countless fine cuts or projections are formed in a random direction by sandblasting with irregular shaped particles. Although it is slightly inferior to the body under a specific environment under the specific environment, it is far superior to the toner carrier having a completely smooth surface, and is further applied to the toner and the surface of the toner carrier by using an elastic layer thickness regulating member. And a stable toner layer having a thin coating thickness, a high level of charging characteristics in a dense surface state, and a stable toner layer with respect to environmental changes. Door can be.

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

As a result, a clear, high-quality image with high image density, excellent fine line reproducibility and gradation, and no fog can be obtained for a long period of time.

Hereinafter, the present invention will be described specifically. Hereinafter, the toner carrier is referred to as a sleeve, and the layer thickness regulating member is referred to as a blade.

The sleeve in the present invention has a surface having irregularities formed by a plurality of spherical trace depressions. As a method for obtaining the surface state, a blasting method using shaped particles can be used. As the shaped particles, for example, various hard spheres made of metal such as stainless steel, aluminum, steel, nickel, and brass having a specific particle size or various hard spheres such as ceramic, plastic, and glass beads can be used. By blasting the surface of the sleeve with the regular particles having a specific particle diameter, a plurality of spherical trace depressions having substantially the same diameter R can be formed.

In the present invention, the diameter R of the plurality of spherical trace depressions on the sleeve surface is preferably from 20 to 250 μm, and if the diameter R is less than 20 μm, contamination by the components in the magnetic toner increases, which is not preferable. If it exceeds 250 μm, the uniformity of the toner coat on the sleeve is undesirably reduced. Therefore, it is preferable that the particles having a diameter of 20 to 250 μm are also used in the blasting of the sleeve surface. Also,
In the present invention, the pitch P and the surface roughness d of the surface of the sleeve are measured by using a fine surface roughness meter (a sales agency, Taylor Hopson, Kosaka Laboratory, etc.) to determine the surface roughness. d is JIS 10 point average roughness (RZ) "JIS B
0601 ”.

That is, as shown in FIG. 1, a straight line parallel to the average line of a portion extracted by the reference length 1 from the sectional curve is 3
The distance between two straight lines, which passes through the top of the third peak and the bottom of the third valley from the deepest, is expressed in micrometers (μm), and the reference length 1 is 0.25 mm. Also pitch P
The peaks having a height of 0.1 μm or more with respect to the concave portions on both sides are counted as one peak, and are determined as follows by the number of peaks within a reference length of 0.25 mm.

[250 (μ)] / [Number of peaks included in 250 (μ) (μ)] In the present invention, the pitch P of the unevenness on the sleeve surface is
When P is less than 2μ, sleeve contamination due to components in the magnetic toner is increased, which is not preferable. On the contrary, when P exceeds 100μ, the uniformity of the toner coat on the sleeve is reduced. But not preferred. The surface roughness d of the irregularities on the sleeve surface is preferably 0.1 to 5 μm. When d exceeds 5 μm, an alternating voltage is applied between the sleeve and the latent image holding member to transfer the magnetic toner from the sleeve side to the latent image surface. In the method of developing by flying, the electric field tends to be concentrated on the uneven portion and the image tends to be disturbed. Therefore, when d is less than 0.1 μm, the toner coat on the sleeve is unfavorable. Is undesirably reduced.

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 on the upper side is fixed to the developer container side. The developing sleeve is bent in the forward or reverse direction against the elasticity of the blade on the lower side, and the inner surface of the blade (or the outer surface in the case of the reverse direction) is pressed against the sleeve surface by an appropriate amount of elasticity. To make contact. An example of the image forming apparatus is shown in the schematic diagrams of FIGS. According to such an apparatus, a thin and dense toner layer can be stably obtained even when the environment changes. Although the reason is not always clear, toner particles are forcibly rubbed against the sleeve surface by the elastic blade compared to a device in which a commonly used metal blade is attached with a certain gap from the sleeve. It is presumed that the charging is always performed in the same state regardless of the change in the behavior due to the environmental change.

The image forming method and the image forming apparatus according to the present invention will be described with reference to FIGS. The primary charger 2 charges the photoreceptor surface 15 to a negative polarity, forms an image by performing image scanning by exposure to the laser beam 5, forms a digital latent image, and forms a plurality of spherical surfaces on the surface including the elastic blade 11 and the magnet 14. The latent image is developed with a one-component magnetic toner 10 of a developing device provided with a developing sleeve 4 having irregularities formed by the trace depression.
In the developing section, an alternating electric field and / or a DC bias is applied between the conductive base 16 of the photosensitive drum 1 and the developing sleeve 4 by the bias applying means 12. When the transfer paper P is conveyed to the transfer section, the transfer charger 3 charges the transfer paper with a positive polarity from the back surface (the surface opposite to the photosensitive drum side), thereby forming a negatively charged toner image on the surface of the photosensitive drum. It is electrostatically transferred onto transfer paper. The transfer paper separated from the photosensitive drum 1 is fixed on the toner image on the transfer paper P by the heating / pressing roller fixing device 7.

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

The electrostatic image carrier (photosensitive drum) has a photosensitive layer 15 and a conductive substrate 16, and moves in the direction of the arrow. The developing sleeve 4 of a non-magnetic cylinder, which is a developer carrying member, rotates in the developing section so as to advance in the same direction as the surface of the electrostatic image holding member. Inside the non-magnetic cylinder 4, a multi-pole permanent magnet (magnet roll) 14 as a magnetic field generating means is arranged so as not to rotate. The one-component insulative developer in the developing device 9 is thinly applied on the surface of the developing sleeve by an elastic blade, and the toner particles are charged by the friction.

In the developing section, an alternating electric field is applied between the developer carrier 4 and the electrostatic image holding surface. This AC bias is f 200 ~ 4,0
00Hz and Vpp should be 500-3,000V.

When the toner particles are transferred in the developing portion, the toner particles are transferred to the electrostatic image side by the action of the electrostatic force and the AC bias on the electrostatic image holding surface. The toner container is preferably provided with a toner container agitating means 13, and the toner 10 in the toner container 9 is positively sent to the vicinity of the developing sleeve so that a uniform toner layer can be formed just before the toner runs out. It is effective for

In the magnetic toner according to the present invention, the charge amount is -10 to
-20 μc / g, BET specific surface area by nitrogen gas adsorption method 1.
Having 8~3.5m ² / g, a density 0.4~0.52g / cm ³ apparent loose, having a true specific gravity 1.45~1.8g / cm ^3.

Since the ability of the image forming apparatus of the present invention to impart frictional charge to the toner is very high, the charge amount of the magnetic toner according to the present invention needs to be low, and the range of −10 to −20 μc / g is particularly preferable. By controlling the charge amount of the toner within the above-mentioned range, it is possible to suppress the unnecessary change of the toner particles having a particle diameter of 5 μm or less, which is relatively easy to rise, and the toner layer on the sleeve is always a stable and uniform layer. Is obtained. If the triboelectric charge is less than -10 μc / g, sufficient charge for development on the developer carrier cannot be obtained, the image density is low from the beginning, and the toner on the sleeve is scattered due to the rotation of the sleeve. Occurs.

On the other hand, if it is larger than -20 μc / g, the amount of charge of the developer in the vicinity of the sleeve on the sleeve is increased by repeating image formation, and the so-called charge-up phenomenon that hinders proper charging of the toner on the sleeve. And the image density gradually decreases. This phenomenon is likely to occur when developing a digital latent image, which is a development of a dot latent image, and is remarkable in a low potential contrast reversal developing method using an OPC photosensitive member.

The charge amount of the toner is determined by the internal prescription and the external prescription of the toner.However, the method of controlling the charge amount of the toner according to the present invention to the above-described range includes a method of controlling the magnetic toner particles having a higher charge amount than the above-described range. Any method may be used, such as a method of lowering the charge amount of the entire toner with an external additive to adjust the charge amount to the above range, or a reverse method, or a method of using a toner in the above range before and after mixing the external additive. However, it is preferable that the difference between the charge amounts of the toner before and after the addition of the external additive is not so large.

Further, if the BET specific surface area of the developer of the present invention by a nitrogen gas adsorption method is less than 1.8 m ² / g, it takes time to obtain a sufficient charge amount for development on the developer carrier, and the initial concentration is The image becomes thin and fogged. On the other hand, if it is larger than 3.5 m ² / g, the reflection power with the sleeve is increased, and the development rate is lowered, and as a result, the image density is lowered.

Further, the true specific gravity of the developer of the present invention is 1.45~1.8g / cm ^3, in method of developing by applying an AC bias in the magnetic field is less than 1.45, also prone to fog, the line width is thicker becomes resolution Getting worse. If it is larger than 1.8, line fading is likely to occur, and the image density also decreases.

The loose apparent density of the developer of the present invention is 0.4 to 0.5.
2 (preferably 0.45 to 0.5), which is characteristic in that the loose apparent density is smaller than the true specific gravity. The porosity calculated from the true specific gravity and the loose apparent density is preferably from 62 to 75%.

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

The solid apparent density is preferably in the range of 0.8 to 1.0, and the porosity (εp) at this time is preferably 40 to 50%.

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

When εp is less than 40%, the developer is liable to be jammed inside the developing device, and the developer is not smoothly supplied to the developer carrying member, so that white drop is liable to occur. On the other hand, if it is larger than 50%, a larger developing device capacity is required to contain the same amount of developer, which hinders downsizing of the printer.

The charge amount of the toner in the present invention is 1 g of toner and 200 to 3
9 g of iron powder carrier of mesh mesh is placed in a 50 cc polyethylene bottle, covered, shaken by hand for 20 seconds (about 100 times) in an environment of 23 ° C. and 60% RH for a small amount of the mixture shown in FIG. Take in a container, 250mmH ₂ O for about 1 minute until the potential is saturated
Suction at pressure of.

At this time, the charge amount Q was obtained from the saturation potential V, the condenser capacity C, and the weights W ₁ and W ₂ of the container before and after suction, according to the following equation.

The BET specific surface area of the magnetic toner particles is QUANTACHROM
It was determined by the BET one-point method using a specific surface area meter Autosorb 1 manufactured by Company E.

The loose apparent density in the present invention is Hosokawa Micron Co., Ltd.
The measurement was carried out using a powder tester manufactured by Nippon Kayaku Co., Ltd. and a container attached to the powder tester according to the instruction manual of the powder tester.

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

A cylinder made of Stellence with an inner diameter of 10 mm and a length of about 5 cm,
A disk (A) having an outer diameter of about 10 mm and a height of 5 mm that can be closely inserted therein and a piston (B) having an outer diameter of about 10 mm and a length of about 8 cm are prepared. The disk (A) is placed at the bottom of the cylinder, then about 1 g of the measurement sample is placed, and the piston (B) is gently pushed. To this was added the force of 400 kg / cm ² by a hydraulic press,
Take out what was compressed for 5 minutes. The weight of the compressed sample is weighed (wg), the diameter (Dcm) and the height (Lcm) of the compressed sample are measured with a micrometer, and the true density is calculated by the following equation.

The magnetic toner according to the present invention has a volume average particle diameter of 6 to 8 μm, contains 17 to 60% by number of magnetic toner particles having a particle diameter of 5 μm or less, and has a magnetic particle diameter of 6.35 to 10.08 μm. 5 to 50% by number of toner particles
2.0% by volume of magnetic toner particles having a particle size of 2.7μm or more
The magnetic toner particles having a particle size of 5 μm or less [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 represents a positive number of 4.6 to 6.7. . Here, N indicates a positive number of 17 to 60. Is one of the characteristics.

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

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

That is, one feature of the magnetic toner of the present invention is that 17 to 60% by number of magnetic toner particles having a particle diameter of 5 μm or less. Conventionally, 5 μm
The following magnetic toner particles are difficult to control the charge amount, impair the fluidity of the magnetic toner, and actively decrease as a component that scatters the toner and stains the machine, as well as a component that causes image fogging. Was thought to be necessary.

However, studies by the present inventors have revealed that magnetic toner particles having a size of 5 μm or less are essential components for forming high-quality images.

For example, using a magnetic toner having a particle size distribution ranging from 0.5 μm to 30 μm, the surface potential on the photoreceptor is changed, and from a large development potential contrast in which a large number of toner particles are easily developed, to a halftone, and further, a very small amount. A latent image with a changed surface potential on the photoreceptor was developed to a small development potential contrast where only toner particles were developed, and the developed toner particles on the photoreceptor were collected. The toner particle size distribution was measured. It has been found that there are many magnetic toner particles, especially magnetic toner particles of 5 μm or less. In other words, when magnetic toner particles having a particle size of 5 μm or less, which are most suitable for development, are smoothly supplied to the development of the latent image on the photoreceptor, the toner is faithful to the latent image and does not protrude from the latent image, and is truly reproducible And excellent images can be obtained.
This development was the same in the case of reversal development of the digital latent image.

Further, in the magnetic toner according to the present invention, 6.35 to 10.0
One feature is that particles in the range of 8 μm are 5 to 50% by number. This is related to the necessity of the presence of magnetic toner particles having a particle size of 5 μm or less as described above.
Magnetic toner particles having the following particle diameters cover the latent image strictly and have the ability to faithfully reproduce the latent image.However, in the latent image itself, the electric field intensity at the edge portion around the latent image is higher than that in the central portion. In some cases, the toner particles become thinner than the edge portion, and the image density may appear to be light. In particular, 5μ
The tendency is strong for magnetic toner particles of m or less. However, the present inventors have found that this problem can be solved and made clearer by containing 5 to 50% by number of toner particles in the range of 6.35 to 10.08 μm.
That is, it is considered that the toner particles having a particle size in the range of 6.35 to 10.08 μm have a moderately controlled charge amount with respect to the magnetic toner particles having a particle size of 5 μm or less.
The toner is supplied to the inner side of the latent image where the electric field intensity is smaller than the edge portion, and a small amount of the toner particles on the edge portion is compensated for, so that a uniform developed image is formed. This provides a sharp image with excellent gradation.

Further, for particles having a particle size of 5 μm or less, between the number% (N) and the volume% (V), N / V = 0.05N + k (where 4.6 ≦ k ≦ 6.7: 17 ≦ N ≦ 60). One of the features is that the relationship is satisfied by the magnetic toner of the present invention. 4th
The range is shown in the figure. Along with other features, the magnetic developer containing the magnetic toner according to the present invention having a particle size distribution satisfying this range has excellent developability with respect to digital latent images formed from minute spots. Can be achieved.

The present inventors have studied the state of the particle size distribution of 5 μm or less and found that there is a state of existence of the fine powder most suitable for achieving the object as shown by the above formula. In other words, for a given value of N, a large N / V means that 5 μm
It indicates that the following particles are widely contained, and N / V
Is small, it is understood that the abundance of particles around 5 μm is high, and that particles having a particle size smaller than 5 μm are small, and the value of N / V is in the range of 1.6 to 5.85; and N is
When the ratio is in the range of 17 to 60 and the above relational expression is further satisfied, good fine line reproducibility and high resolution are achieved.

Further, for magnetic toner particles having a particle diameter of 12.7 μm or more, the content is preferably set to 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 recent severe demands for high image quality.

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

Magnetic toner particles having a particle size of 5 μm or less have a total particle number of 17 to
The number is preferably 60% by number, preferably 25% to 60% by number, and more preferably 30% to 60% by number. When the number of magnetic toner particles having a particle diameter of 5 μm or less is less than 17% by number, the amount of magnetic toner particles effective for high image quality is small. In particular, as the toner is used by continuing printout, the effective magnetic toner particle component is reduced. Decrease, the balance of the particle size distribution of the magnetic toner as shown in the present invention deteriorates,
Image quality gradually decreases. If it exceeds 60% by number, the magnetic toner particles tend to aggregate with each other,
Since the toner mass is larger than the original particle size, the image quality becomes rough, the resolution is reduced, or the density difference between the edge portion and the inside of the latent image is increased, so that the image tends to be slightly hollow.

Further, particles in the range of 6.35 to 10.08 μm are 5 to 50% by number.
And preferably 8 to 40% by number. 50
If the amount is more than the number%, the image quality is deteriorated, and the development is performed more than necessary, that is, the toner is excessively applied, the reproducibility of fine lines is reduced, and the toner consumption is increased. On the other hand, if it is less than 5% by number, it becomes difficult to obtain a high image density. The number% (N) of the magnetic toner particles having a particle size of 5 μm or less
%) And volume% (V%), there is a relationship of N / V = −0.05N + k, which indicates a positive number in the range of 4.6 ≦ k ≦ 6.7. Preferably, 4.6 ≦ k ≦ 6.2, and more preferably, 4.6 ≦ k ≦ 5.7. As indicated 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 diameter smaller than 5.0 μm is small, and the image density, resolution, and sharpness are poor. The appropriate presence of fine magnetic toner particles, which was conventionally considered unnecessary, contributes to the closest packing of the toner in development and contributes to the formation of a uniform image without roughness. In particular, by uniformly filling the fine lines and the contours of the image, the sharpness is further enhanced visually.
That is, when k <6.7, these characteristics are inferior due to the lack of the particle size distribution component.

From another aspect, in production, it is necessary to cut a large amount of fine powder by classification or the like to satisfy the condition of k <4.6, which is disadvantageous in terms of yield and toner cost.
Also, at k> 6.7, the presence of more fine powder than necessary
As printout is repeated, the image density tends to decrease. Such development occurs when excessive fine powdered magnetic toner particles having an unnecessary charge are charged and adhered to the developing sleeve, thereby hindering normal magnetic toner from being carried on the developing sleeve and applying charge. Conceivable.

The content of the magnetic toner particles having a particle size of 12.7 μm or more is preferably 2.0% by volume or less, more preferably 1.0% by volume or less, and further preferably 0.5% by volume or less. If it is more than 2.0% by volume, it will hinder the reproduction of fine lines. Further, the volume average diameter of the magnetic toner is 6 to 8 μm, and this value cannot be considered separately from the above-mentioned respective constituent elements. If the volume average particle diameter is less than 6 μm, in the use of digital latent images having a high image area ratio such as graphic images, there is a problem that the amount of applied toner on transfer paper is small and the image density is low. This is considered to be due to the same reason as described above for lowering the density inside the edge portion of the latent image. When the volume average particle diameter exceeds 8 μm, the resolution of fine spots having a size of 100 μm or less is not good, and the image quality is liable to deteriorate if printing is continued at the beginning of printing.

Although the particle size distribution of the toner can be measured by various methods, in the present invention, the measurement was performed using a Coulter counter.

In other words, the Coulter Counter TA is used as a measuring device.
-Type II (manufactured by Coulter, Inc.) is connected to an interface (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) that output the number distribution and volume distribution, and the primary electrolyte is sodium chloride. Prepare 1% NaCl aqueous solution. As a measuring method, a surfactant as a dispersant, preferably 0.1 to 5 ml of an alkylbenzene sulfonate is added to the electrolytic aqueous solution of 100 to 150 ml, and a measurement sample is 2 to 20 mg.
(About 30,000 to about 300,000 particles). The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the Coulter Counter TAII type was used, and a particle size distribution of 2 to 40 μ particles based on the number was measured using a 100 μ aperture as an aperture. Was measured, and then the value according to the present invention was determined.

As the binder resin used in the magnetic toner according to the present invention, when a heating and pressing roller fixing device having an oil application device is used, the following binder resins for toner can be used.

For example, polystyrene, poly-p-chlorostyrene,
Styrenes such as polyvinyltoluene and their substituted homopolymers; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylate copolymer, styrene -Methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone Styrene copolymers such as copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, naturally-modified phenolic resins, and naturally-modified maleic resins Acid resin, Acrylic Resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethane, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resin, coumarone-indene resins, and petroleum resins.

In the heat and pressure roller fixing method in which almost no 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 problems. is there. These problems must be considered at the same time because toners that fix with less heat energy tend to block or cake during storage or in a developing unit. The physical properties of the binder resin in the toner are most greatly involved in these phenomena. However, according to the study of the present inventors, when the content of the magnetic substance in the toner is reduced, the toner image supporting member is fixed at the time of fixing. The adhesion of the toner to the toner is improved, but offset tends to occur, and blocking or caking tends to occur. Therefore, in the present invention, when using the heating / pressing roller fixing method in which almost no oil is applied, the selection of the binder resin is more important. Preferred binders include crosslinked styrenic copolymers or crosslinked polyesters.

Examples of the comonomer for the styrene monomer of the styrene copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, and methacrylic acid. Acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile,
Monocarboxylic acids having a double bond such as methacrylonitrile, acrylamide and the like or substituted products thereof; for example, dicarboxylic acids having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like; Substitutes; vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc .; ethylene olefins such as ethene, propylene, butylene, etc .; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, etc. Vinyl monomers such as vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether; and the like, or two or more vinyl monomers.

Here, as the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene and the like; for example, ethylene glycol diacrylate, ethylene glycol dimethacrylate Double bonds such as 1,3-butanediol dimethacrylate, etc.
Carboxylic acid esters; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone; and compounds having three or more vinyl groups are used alone or as a mixture.

When a pressure fixing method is used, a binder resin for a pressure fixing toner can be used, and examples thereof include polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, and ethylene-vinyl acetate copolymer. Coalescent, ionomer resin, styrene-butadiene copolymer, styrene-isoprene copolymer, linear saturated polyester, paraffin and the like.

In the magnetic toner of the present invention, it is preferable that a charge control agent is blended (internally added) to the toner particles or mixed (externally added) with the toner particles for use. The charge control agent makes it possible to control the optimal charge amount according to the development system. In particular, in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge, and by using the charge control agent The function separation and the complementarity for higher image quality for each particle size range described above can be further clarified.

Examples of the negative charge controlling agent that can be used in the present invention include a metal complex of a monoazo dye or a salt, salicylic acid, alkyl salicylic acid, dialkyl salicylic acid,
Alternatively, a metal complex or salt of naphthoic acid is used.

The above-mentioned charge control agent (having no action as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of the charge control agent is specifically preferably 4 μm or less (more preferably 3 μm or less).

When internally added to the toner, such a charge control agent is used in an amount of 0.1 to 10 parts by weight (more preferably 0.1 to 5 parts by weight) based on 100 parts by weight of the binder resin.
Parts by weight).

Further, conventionally known dyes and pigments can be used as other coloring materials, and usually 0.5 to 20 parts by weight based on 100 parts by weight of the binder resin can be used.

The magnetic tonneau of the present invention has a 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 used in an amount of 0.1 to 10 parts by weight (more preferably 0.1 to 5 parts by weight) based on 100 parts by weight of the binder resin.
Parts by weight). Dyes and pigments conventionally known as other coloring materials can be used. Usually, the magnetic binder developer of the present invention has hydrophobic silica fine powder. The magnetic toner having a particle size distribution as a feature of the present invention has a larger specific surface area than a conventional tonneau. When magnetic toner particles are brought into contact with the surface of a cylindrical conductive sleeve having a magnetic field generating means inside due to triboelectric charging, the number of times of contact between the surface of the toner particles and the sleeve increases compared to conventional magnetic toner, and the toner Particle wear and contamination of the sleeve surface are likely to occur. When the magnetic toner according to the present invention is combined with silica fine powder, wear is significantly reduced because the silica fine powder is interposed between the toner particles and the sleeve surface. As a result, the life of the magnetic toner and the sleeve can be prolonged, and a stable chargeability can be maintained, and a developer having a magnetic toner that is more excellent for long-term use can be obtained. Furthermore, the magnetic toner particles having a particle diameter of 5 μm or less, which play a major role in the present invention, exhibit more effects in the presence of the silica fine powder, and can stably provide high-quality images.

As the silica fine powder, any of 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 of a dry method.

The dry method referred to here is a method for producing silica fine powder generated by vapor phase oxidation of a silicon halide. For example, in a method utilizing the thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen-hydrogen, the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl In this manufacturing process, for example, by using another metal halide such as aluminum chloride or titanium chloride together with a silicon halide, a fine composite powder of silica and another metal oxide can be obtained. It is also possible to obtain and include that.

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

AEROSIL 130 (Nippon Aerosil) 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL M-5 (CABOTO Co.) MS-7 MS-75 HS-5 EH-5 Wacker HDK N20 V15 (WACKER-CHEMIE GMBH N20E T30 T40 DC Fine Silica (Dow Corning Co.) Fransol (Fransil) On the other hand, as a method for producing the silica fine powder used in the present invention by a wet method, various conventionally known methods can be applied. For example, the decomposition of sodium silicate with an acid is represented by the following general reaction formula.

Na ₂ O ・ XSiO ₂ + HCl + H ₂ O → SiO ₂・ nH ₂ O + NaCl In addition, decomposition of sodium silicate with ammonium salts or alkali salts, formation of alkaline earth metal silicate from sodium silicate, and decomposition with acid Silicate, a method in which a sodium silicate solution is converted into silicate using an ion exchange resin, a method in which natural silicate or silicate is used, and the like.

Silica such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, zinc silicate, etc. can be applied to the silica fine powder here, in addition to anhydrous silicon dioxide (silica).

Among the above silica fine powders, those having a specific surface area of 70 to 300 m ² / g by nitrogen adsorption measured by the BET method give good results. The fine silica powder is used in an amount of 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the magnetic toner.

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

The hydrophobic silica fine powder used in the present invention has a charge amount of -10.
Those having a concentration of -300 [mu] c / g are preferably used. When the charge amount of silica is less than -10 μc / g, the charge amount of the toner itself is reduced, and the humidity characteristics are reduced. Also, -300
When the one exceeding μc / g is used, it promotes sleeve memory and is susceptible to silica deterioration, which hinders durability characteristics. In addition, those finer than 300 m ² / g have no effect of adding to the developer, and those larger than 70 m ² / g have a large probability of being present as free matter, causing black spots due to uneven deposition of silica and suspicious matter. Cheap.

The charge amount of the negatively chargeable silica fine powder is the same as in the case of the charge amount measurement 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 a so-called dry method produced by vapor phase oxidation of a silicon halide compound or a so-called wet silica produced from water glass or the like, and dry silica called fumed silica can be used. , Few silanol groups on the surface and inside,
Dry silica without production residue is preferred.

The hydrophobizing treatment is applied by chemically treating with an organic silicon compound or the like which reacts or physically adsorbs with the silica fine powder. As a preferred method, the dry silica fine powder produced by the vapor phase oxidation of the silicon halide is treated with a silane coupling agent or simultaneously with the silane coupling agent and treated with an organosilicon compound such as silicone oil.

Examples of the silane coupling agent used in the hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, and allylphenyldichloro. Silane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane , Dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltet Disiloxane, 1,3
Diphenyltetramethyldisiloxane.

Examples of the organosilicon compound include silicone oil. Preferred silane coupling agents include hexamethyldisilazane (HMDS). In addition, preferred silicone oils have a viscosity at 25 ° C. of about
Those having 30 to 1,000 centistokes are used, and preferred examples thereof include dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil. For the purposes of the present invention, -OH groups, -COOH groups,
Silicon oil containing a large amount of —NH ₂ groups and the like is not preferred.

For the method of silicon oil treatment, for example, silica fine powder treated with a silane coupling agent and silicon oil may be directly mixed using a mixer such as a Hensiel mixer, or silica as a base may be sprayed with silicon oil. It is good depending on the method. Alternatively, it may be prepared by dissolving or dispersing silicon oil in an appropriate solvent, mixing with a base silica fine powder, and removing the solvent.

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

100 ml of ion-exchanged water and 0.1 g of a sample are placed in a sealed stopper 200 ml separatory funnel, and shaken at 90 rpm for 10 minutes with a shaker (Tarbrush acre mixer T2C type). After shaking, the mixture was allowed to stand for 10 minutes.After the silica powder layer and the aqueous layer were separated, 20-30 ml of the lower aqueous layer was sampled, placed in a 10 mm cell, and charged with a blank ion containing no silica fine powder at a wavelength of 500 nm. The transmittance is measured based on the exchanged water, and the value of the transmittance is used as the hydrophobicity of silica.

The 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, it is difficult to obtain a high-quality image due to moisture adsorption of the silica fine powder under high humidity.

The magnetic toner of the present invention may optionally contain an external additive other than silica fine powder.

For example, the toner charge amount positive polymethyl methacrylate and fluorine resin or the like for controlling the range or high resistance (10 ¹⁰ or Omega) having a negative charging property, or medium resistance ^{(10 6} Ω~10 10 Ω ) Resin fine particles and conductivity-imparting agents such as carbon black and tin oxide. In addition, for example, a lubricant such as zinc stearate, a polishing agent such as cerium oxide or silicon carbide, a fluidity imparting agent such as alumina, a caking inhibitor, a low molecular weight compound for the purpose of improving the releasability at the time of hot roll fixing. Polyethylene or polypropylene may be added.

To prepare the magnetic toner for developing an electrostatic image according to the present invention, a magnetic powder and a vinyl-based or non-vinyl-based thermoplastic resin, a pigment or a dye as a colorant as needed, a charge control agent,
After the other additives and the like are sufficiently mixed by a mixer such as a ball mill, the resins are melted, kneaded, and kneaded using a hot kneader such as a heating roll, kneader, or extruder to make the resins compatible with each other. In the present invention, the pigment or dye is dispersed or dissolved, and after cooling and solidification, pulverization and strict classification are performed to obtain the insulating magnetic toner according to the present invention.

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

The triboelectric charge of the magnetic toner and the magnetic developer of the present invention is almost the same as that of the above-mentioned silica fine powder, but the ratio is different, and 2.0 g of magnetic developer or magnetic toner and 9.0 g of carrier iron powder are precisely weighed. The measurement is performed in the same manner.

Hereinafter, the present invention will be described specifically with reference to Examples, but this does not limit the present invention in any way. All parts in the following formulations are parts by weight.

Example 1 80% or more of glass beads having a diameter of 53 to 62 μm as regular particles were blasted on the surface of a cylindrical stainless steel sleeve having a diameter of 20φ, and a plurality of spherical trace depressions had a diameter R of 53 to 62 μm. Irregularities were formed. The pitch P of the irregularities on the sleeve surface is 33μ and the surface roughness d is
2.0μ. The surface-treated sleeve is referred to as a sleeve A, and the rubber elastic blade is referred to as a blade A.
A developing device as shown in the figure was prepared.

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

After the above materials were mixed well in a blender, they were kneaded with a biaxial kneading extruder set at 150 ° C. The obtained kneaded material was cooled, coarsely pulverized by a cutter mill, and then finely pulverized by using a fine pulverizer using a jet stream, and the obtained finely pulverized powder was classified by a fixed wall type air classifier to classify. A powder was produced. Further, the obtained classified powder is strictly classified and removed simultaneously by a multi-division classifier utilizing a Coanda effect (an elbow jet classifier manufactured by Nittetsu Mining Co., Ltd.) to simultaneously remove the fine powder and coarse powder.
A fine black powder (magnetic toner) of 5 μm was obtained.

The multi-segment classifier used in the present embodiment and the classification process by the classifier will be described with reference to FIGS. 5 and 6. FIG. 5 and 6, the multi-segment classifier 40 has a side wall having a shape indicated by 52 and 54, a lower wall has a shape indicated by 55, and a side wall 53 and a lower wall 55 respectively. Knife edge type classification edges 47, 48 are provided, and the classification zones are divided into three by these classification edges 47, 48. Provided below the side wall 52 is a raw material supply nozzle 46 that opens into the classification chamber, and a Coanda block 56 that is bent downward in the direction of extension of the tangent at the bottom of the nozzle to form an elliptical arc is provided. Classification room upper wall
57 is a knife edge type inlet edge to the lower part of the classification chamber.
In addition to the above, the air intake pipe that opens to the classification chamber
44, 45 are provided. The inlet pipes 44, 45 are provided with first and second gas introduction adjusting means 50, 51 such as dampers, and static pressure gauges 58, 59, respectively. Discharge pipes 41, 42, and 43 having discharge ports that open into the room are provided on the lower surface of the classifying chamber so as to correspond to the respective dividing areas. The classified powder is introduced under reduced pressure from the supply nozzle 46 into the classification region, and moves along the curved line 60 due to the action of the Coanda effect of the Coanda block 56 due to the Coanda effect and the action of the high-speed air flowing in at that time. The particles were classified into black fine powder (magnetic toner) 42 and ultrafine powder 43 having a predetermined volume average particle size and particle size distribution. Table 1 below shows data obtained by measuring the obtained magnetic toner, which is a black fine powder made of negative charge, using a Coulter Counter TAII type having an aperture of 100 μ as described above.

0.8 parts by weight of the obtained magnetic toner A was negatively charged hydrophobic dry silica A (BET specific surface area: 200 m ² / g, charge amount: −200 μc / g) 0.8
Parts and further 0.3 parts of positively chargeable polymethyl methacrylate resin fine particles (average particle diameter 0.4 μm, charge amount + 500 μc / g) having a polarity opposite to that of the toner particles, and mixed with a Hensiel mixer to form a negatively chargeable component magnetic development. Agent A.

Table 2 shows the particle size distribution, charge amount, BET specific surface area, loose apparent density, and true specific gravity of this developer.

Using the above-mentioned developing device and developer, the closest gap between the organic photoconductor (OPC) photosensitive drum and the developing sleeve was set to 300 μm in a stacked type using a modified laser beam printer LBP-8AJ1 made by Canon Inc. -700 V on the surface of the photosensitive drum
A primary latent charge is performed to form a digital latent image with the potential of the laser beam exposed portion at -100 V, and a DC bias of -500 V and an AC bias (1800 Hz, peak to peak 1600 V) are applied between the photosensitive drum substrate and the developing sleeve. And normal temperature and humidity (25 ° C, 60% RH), high temperature and high humidity (30 ° C,
3,000 images were printed in three environments of 90% RH) and low temperature and low humidity (15 ° C, 10% RH). The results are shown in Table 3. In Table 3, Dmax is the density minute dot reproducibility of a solid black square having a side of 5 mm.
= Reproducibility of an image obtained by developing a checker pattern of 80 μm or 50 μm under low temperature and low humidity was observed and evaluated with a microscope.

As is clear from Table 3, in each environment, images with high density and excellent fine dot reproducibility were stably obtained up to 3000 sheets.
In addition, there is no contamination of the sleeve and no uneven toner coat after 3,000 images are output, and the toner coat amount on the sleeve is 1.
At about 2 mg / cm ² , there was almost no change from the initial stage.

Comparative Example 1 Instead of the glass beads used in Example 1, a sleeve B made of # 300 carborundum, which is an irregular shaped particle, was used. Evaluation was performed in the same manner as in Example 1 except that B was used with a gap of 250 μm from the sleeve. As shown in Table 3, the sleeve after 3,000 sheets was very contaminated, and the image density was large compared to the initial level. The width has dropped.

Comparative Example 2 Blade B instead of blade A used in Example 1
Was evaluated in the same manner as in Example 1 except for using a gap of 250 μm with the sleeve. As shown in Table 3, toner coat unevenness occurred at the end of the sleeve in a low-temperature and low-humidity environment. The amount of toner coating on the sleeve is increased, resulting in poor environmental stability.

Example 2 Instead of the developer A used in Example 1, an external additive was hydrophobic silica B (BET specific surface area: 300 m ² / g, charge amount: −30 μc / g)
Evaluation was performed in the same manner as in Example 1 except that the developer B was changed to 1.2 parts, and good results were obtained as in Example 1. The physical properties of the developer B are shown in Table 2 and the 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 further, 0.6 parts of hydrophobic silica A and 0.3 parts of positively chargeable polymethyl methacrylate were mixed to obtain developer C. 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. As a result, good results were obtained as in Example 1.

The other physical properties of the developer C are shown in Table 2 and the evaluation results are shown in Table 3.

Comparative Example 3 A developer D 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. Developer D in place of Developer A of Example 1
The evaluation was performed in the same manner as in Example 1 except for using, and the results are shown in Table 3. As a result, the density becomes thinner and the line becomes thinner as the number of output images advances. Further, the amount of toner coat after 3,000 sheets was smaller than the initial amount.

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 iron trioxide was changed to 60 parts. Hydrophobic silica A
Developer E was obtained by mixing 0.4 part and 0.3 part of positively chargeable polymethyl methacrylate. Evaluation was performed 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 coat condition was good,
The reproducibility of the minute dots was poor, and the images were noticeable, and no satisfactory results were obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the definition of surface roughness and pitch. FIG. 2 is a schematic explanatory view of the image forming apparatus according to the present invention, and FIG. 3 is an enlarged view of the developing unit in FIG. FIG. 4 is a schematic diagram of a toner charge amount measuring device according to the present invention. FIG. 5 and FIG. 6 are schematic illustrations of a multi-segment classifier used in the embodiment for classifying toner. FIG. 7 is a partial view showing an image pattern used in Examples and Comparative Examples. FIG. 8 is a diagram showing a range of a content ratio of particles of 5 μm or less in the toner according to the present invention.

Continuation of front page (72) Inventor Motoki Hisagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-58-57165 (JP, A) JP-A-60-87345 (JP, A) JP-A-57-86869 (JP, A)

Claims (2)

(57) [Claims] An electrostatic image holding member for holding an electrostatic charge image and a toner holding member for holding a magnetic toner on the surface are arranged at a fixed gap in a developing section, and the magnetic toner is placed on the toner holding member. In the image forming method in which the toner carrier is conveyed to the developing unit while being regulated to a thickness smaller than the gap, and is developed while applying an alternating electric field to the toner in the developing unit, the toner carrier is subjected to a plurality of spherical traces by blasting with regular particles. It has a surface with irregularities formed by depressions, and the surface condition is such that the diameter R of the spherical trace depression is 20 to 250 μm, the pitch P of the irregularities is 2 to 100 μm, and the surface roughness d is 0.1 to 5 μm. Is satisfied, the toner layer on the toner carrier is layered as a thin layer by an elastic layer thickness regulating member that abuts on the toner carrier surface by elastic force and transported to the developing unit, and the magnetic toner is at least a binder resin, Magnetic material Having a charge amount of −10 to −20 μc / g, a volume average particle diameter of 6 to 8 μm, and 17 μm or less of magnetic toner particles having a particle diameter of 5 μm or less. ~ 60% by number, 6.35
5 to 50% by number of magnetic toner particles having a particle diameter of about 10.08 μm, 2.0% by volume or less of magnetic toner particles having a particle diameter of 12.7 μm or more, and a group of magnetic toner particles of 5 μm or less are represented by the following formula: [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 represents a positive number of 4.6 to 6.7. . Here, N indicates a positive number of 17 to 60. ] The image forming method characterized by having a particle size distribution satisfying the following. 2. An electrostatic image carrier for holding an electrostatic image and a toner carrier for carrying a magnetic toner on the surface thereof are arranged at a fixed gap in a developing section, and the magnetic toner is placed on the toner carrier. In an image forming apparatus which regulates the thickness to be smaller than the gap and conveys the toner to the developing unit, and develops the toner while applying an alternating electric field to the developing unit, the toner carrier is subjected to a plurality of spherical traces by blasting with fixed particles. It has a surface with irregularities formed by depressions, and the surface condition is such that the diameter R of the spherical trace depression is 20 to 250 μm, the pitch P of the irregularities is 2 to 100 μm, and the surface roughness d is 0.1 to 5 μm. Is satisfied, the toner layer on the toner carrier is layered as a thin layer by an elastic layer thickness regulating member that abuts on the toner carrier surface by elastic force and transported to the developing unit, and the magnetic toner is at least a binder resin, Magnetic material Having a charge amount of −10 to −20 μc / g, a volume average particle diameter of 6 to 8 μm, and 17 μm or less of magnetic toner particles having a particle diameter of 5 μm or less. ~ 60% by number, 6.35
5 to 50% by number of magnetic toner particles having a particle diameter of about 10.08 μm, 2.0% by volume or less of magnetic toner particles having a particle diameter of 12.7 μm or more, and a group of magnetic toner particles of 5 μm or less are represented by the following formula: [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 represents a positive number of 4.6 to 6.7. . Here, N indicates a positive number of 17 to 60. An image forming apparatus having a particle size distribution satisfying the following.