JP3295783B2 - Developer for developing electrostatic images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing an electrostatic image used in an image forming method such as an electrophotographic method, an electrostatic recording method and an electrostatic printing method.

[0002]

2. Description of the Related Art Conventionally, electrophotography has been disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910.
Numerous methods are known as described in Japanese Patent Application Laid-Open Publication No. Hei. Generally, a photoconductive substance is used to form an electric latent image on a photoreceptor by various means, and then the latent image is developed using toner, and if necessary, a toner image is formed on a transfer material such as paper. Is transferred, and then fixed by heating, pressure, heating and pressurizing, or solvent vapor to obtain a toner image.

Various methods and apparatuses have been developed for fixing the toner image to a sheet such as paper, which is the above-mentioned final step, but the most common method at present is a pressure heating method using a heat roller.

In the pressure heating method using a heating roller, the toner image is fixed by passing the surface of the heat roller having a releasing property to the toner and the toner image surface of the sheet to be fixed while pressing the sheet under pressure. Is performed. In this method, since the surface of the heat roller and the toner image on the sheet to be fixed come into contact with each other under pressure, the thermal efficiency at the time of fusing the toner image onto the sheet to be fixed is extremely good, and the fixing can be performed quickly. And is very effective in high-speed electrophotographic copying machines.

In such a fixing method, use of a binder resin containing an acid component in order to improve fixability has been proposed in JP-A-55-134861. However, a toner using such a binder resin tends to cause insufficient charging under high humidity and excessive charging under low humidity, and is easily affected by environmental fluctuation. Further, fog is likely to occur and the image density may be low.

On the other hand, acid anhydrides have a function of improving the chargeability, and examples of applying a resin containing an acid anhydride are disclosed in JP-A-59-139053 and JP-A-62-280758.
No. 1993. These methods employ a method of diluting a polymer having acid anhydride units at a high density into a binder resin. In these methods, it is necessary to uniformly disperse the acid anhydride-containing resin in the binder resin, and if not dispersed well, the toner particles become non-uniform in charge, fogging is likely to occur, and adversely affects the developability. .

Therefore, dispersing and diluting the units of the acid anhydride into the polymer chains in the binder resin by copolymerization can solve the problem of dispersion and provide toner particles with uniform chargeability. . JP-A-61-123856,
These toners have been proposed in, for example, JP-A-61-123857. These toners have good fixability, offset resistance, and developability.

However, when such a toner is applied to a high-speed copying machine under low humidity, the toner may be excessively charged, causing fog and a decrease in density.

Further, in recent years, digitalization of the copying machine and reduction in the particle size of the toner have been demanded to increase the functions of the copying machine and improve the quality of the copied image.

[0010] However, in the multifunctional copying machine, for example, a part of an image is erased by exposure or the like, and
Then, in a function such as multiplex multicolor copying in which another image is inserted into the portion or a frame around the periphery of the copy paper, fogging occurs in a portion of the image to be removed in white.

That is, when a potential opposite to the latent image potential with respect to the development reference potential is applied by strong light such as an LED or a fuse lamp to erase an image, there is a problem that the fog tends to occur in that portion. .

[0012] Further, even if the resolution and sharpness of an image can be increased by digitization and reduction in the particle diameter of the toner, various problems arise.

The first problem is the fogging problem described above. By reducing the particle size of the toner, the surface area of the toner is increased, and therefore, the width of the charge amount distribution is increased, and fogging is likely to occur. Further, as the toner surface area increases, the charging characteristics of the toner are more likely to be affected by the environment.

Further, when the particle diameter of the toner is reduced, it is apparent that the dispersion state of the polar substance and the colorant greatly affects the chargeability of the toner.

[0015] In recent digital copiers,
In a photographic image containing characters, the characters of the copy image are required to be clear, and the photographic image is required to have a density gradation property faithful to a document. In general, in copying a photographic image containing characters, if the line density is increased to make the characters clear, not only the density gradation of the photographic image is impaired, but also the halftone portion becomes a very rough image. Conversely, if an attempt is made to improve the density gradation of a photographic image, the density of the character line will decrease, and the sharpness will deteriorate.

In recent years, the density gradation has been improved to some extent by reading the image density and converting it into digital data. However, it is still not enough.

This is largely due to the developing characteristics of the developer. That is, the developing potential (difference between the potential of the photosensitive member and the potential of the developer carrying member) does not have a linear relationship with the image density.
As shown in (solid line), a curve with a low developing potential is convex downward, and a curve with a high developing potential is convex upward. Therefore, in the halftone area, a slight change in the development potential causes a very large change in image density. This makes it difficult to obtain a sufficiently satisfactory density gradation.

Normally, in order to copy a line image and maintain its sharpness, since the edge effect is affected, the maximum image density in a solid image portion which is hardly affected by the edge effect is 1.30.
A degree is sufficient.

However, in a photographic image, the maximum density of the photograph itself largely depends on its surface glossiness, which is 1.9.
It is very high, from 0 to 2.00. Therefore, even when the glossiness of the surface is suppressed in copying a photographic image, the image area is large and the density is not increased by the edge effect. Therefore, the maximum image density in the solid image portion is 1.4 to About 1.5 is necessary.

Therefore, the developing potential and the image density are set to a primary (linear) relationship, and the maximum image density is set to 1.4 to
A value of 1.5 is very important for copying photographic images with text.

For this purpose, it is important to control the charge amount of the toner as uniformly as possible.

Japanese Patent Application Laid-Open No. S58-58158 discloses a method for preventing an increase in the charge amount of toner and stabilizing the charge amount by using conductive powder.
-66951, JP-A-59-168458-16
No. 8460, JP-A-59-170847 and the like disclose methods using conductive zinc oxide and tin oxide. According to these methods, the maximum image density is 1.3
In a system using a large amount of conductive powder, the density is 1.4 or more, but the density gradation is poor. It is well known that the charge amount of toner has a charge amount distribution, and the distribution width increases as the charge amount of toner increases. That is, in these methods, the amount of charge is reduced and the distribution of the charge amount is sharpened by attaching conductive powder to the toner having a high charge amount. However, even with these methods, a satisfactory image cannot be obtained in copying a photographic image containing characters.

Further, a non-magnetic toner having a volume average particle diameter of 5 to 20 μm is mixed with a fine powder having a volume average particle diameter of 1/20 to 1/2 to stabilize the toner replenishing property. JP-A-61-183664 discloses a method for forming a uniform toner layer and obtaining a sufficient amount of triboelectric charge.
According to this method, in the color toner, the toner replenishment can be stabilized to form a thin layer on the developer carrier, and the charge amount can be increased. However, in the magnetic toner, as described above,
When the charge amount distribution is sharpened and further copied, a maximum density of 1.4 to 1.5 and a sufficient density gradation cannot be obtained.

Japanese Patent Application Laid-Open No. Sho 60-32060 discloses a method for removing paper powder, ozone adducts and the like generated or adhered to the surface of a photoreceptor by using two kinds of inorganic powders. .

Further, in Japanese Patent Application Laid-Open No. 2-110475, two kinds of inorganic fine powders are used for a toner using a metal-crosslinked styrene acrylic resin to form paper powder, ozone There is disclosed a method for improving removal of adducts and the like and improvement of toner fixability, toner scattering under high temperature and high humidity, image deletion, and image density reduction.

Although these methods can certainly remove the deposits on the photoreceptor, they have not yet solved the various problems described above.

Further, Japanese Patent Application Laid-Open No. 1-112255 discloses a method using organic fine particles and two or more kinds of inorganic fine particles. This method is characterized by having two or more types of inorganic fine particles and organic fine particles having an average primary particle size of 3 μm or less and larger than the average primary particle size of the inorganic fine particles. However, even this method has not solved all of the above-mentioned problems.

As described above, at present, there is no developer that can solve all of the various problems described above.

[0029]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer for developing an electrostatic image used in an image forming method using an organic photoreceptor, which solves the above-mentioned problems.

An object of the present invention is to provide a developer for developing an electrostatic image capable of obtaining a high-density copy image without fogging without impairing the fixing property.

An object of the present invention is to provide a developer for developing an electrostatic charge image which gives a good image even under low humidity and high humidity without being affected by environmental changes.

An object of the present invention is to provide a developer for developing an electrostatic image which gives a good image stably even in a high-speed machine and has a wide range of applicable models.

It is an object of the present invention to provide a developer for developing an electrostatic charge image which is excellent in durability, has a high image density even when used continuously for a long time, and has no fog on a white background and can obtain a copy image. is there.

It is an object of the present invention to provide a photographic image containing characters, which is excellent in resolution and fine line reproducibility, in which the characters of the copied image are clear, and the photographic image has a density gradation faithful to the original. An object of the present invention is to provide a developer for developing a charge image.

An object of the present invention is to simultaneously achieve a uniform coating of the toner on the developer carrying member and a stable and uniform charging of the toner on the developer carrying member for a long period of time. An object of the present invention is to provide a developer for developing an electrostatic image that makes flying more efficient.

[0036]

According to the present invention, the weight average particle diameter (t-D4) is ₄ to 12 m, the length average particle diameter (t-D1) is ₁ to 10 m, (t-D ₄₎
An insulating toner having a value of / (t-D ₁ ) of 1.01 to 2,

A fluidizing agent having a specific surface area of at least 30 m ² / g by the BET method, which is charged to the same polarity as the insulating toner and adsorbs N ₂ ,

The toner is charged in the opposite polarity to the insulating toner, has a weight average particle diameter (m-D ₄ ) of 0.6 to 5 μm, and a length average particle diameter (m-D ₁ ) of 0.5 to 4 μm. Yes, (m-D ₄₎
/ (M−D ₁ ) is 1.0 to 2.4, and (m−D
₄ ) / (m-D ₁ ) is the same or larger than the value of (t-D ₄ ) / (t-D ₁ );

A developer for developing an electrostatic image, characterized by containing an organic fine powder which is charged in the opposite polarity to the insulating toner and has a length average particle diameter (p-D ₁ ) of 0.8 μm or less. is there.

As described above, it is well known that a charge amount distribution also exists in the charge amount of a toner. This distribution state is affected by the distribution state of the material constituting the toner, for example, a magnetic substance and a colorant, and the particle size distribution of the toner. When the materials constituting the toner are uniformly dispersed, the charge amount distribution is mainly affected by the particle size distribution of the toner. Generally, a toner having a small particle size has a large charge amount, and a toner having a large particle size has a small charge amount. Also, the distribution width of the toner having a larger charge amount is generally wider as the charge amount of the toner is larger, and narrower as the charge amount of the toner is small.

As a method of sharpening the charge amount distribution by using a toner having a high charge amount, as described above, there is a method of attaching a conductive powder to the toner to reduce the charge amount. Although the properties are good, the concentration is not sufficient at the maximum concentration. The present inventors considered the reason for this as follows.

In the method of lowering the charge amount by attaching the conductive powder to the toner, the conductive powder itself is slightly charged, but does not uniformly adhere to the toner. It is thought that more adherence is caused by the mechanical force.

In charging by friction between toners, since the surfaces of the toners in contact with each other are charged, the oppositely charged charges are distributed on the same toner surface. Therefore, it is considered that the toner having a small particle diameter has a larger surface area, and thus easily adheres regardless of the charging polarity of the conductive powder. Further, the toner having a smaller particle diameter has a larger surface area, and the amount of charge per unit weight increases. Therefore, when charged with the opposite polarity, fog appears as a white background portion when copied. Therefore, fog is improved by putting the conductive powder into the toner and attaching it to the opposite polarity toner having a small particle size.

However, a toner having a small particle diameter to which conductive powder having a large effect of lowering the charge amount adheres is selectively developed because the charge amount has decreased. Therefore, although the density gradation is improved, the maximum image density is small because the toner having a small particle size is melted and spread by fixing and the area covering the fixing support is smaller than that of the toner having a large particle size. Is slightly inferior to that of the toner having a large particle size.

Furthermore, since only toner having a small particle size is selectively developed, halftone roughness is good at the beginning, but if copying is continued, the toner particle size in the developing device becomes large and deteriorates.

As a result of intensive studies, the present inventors have found that, contrary to the reduction of the charge amount of the toner, the toner is charged to the opposite polarity to the toner.
In addition, a method has been found to increase the charge amount of a toner having a low charge amount in the charge amount distribution by contacting the toner with an inorganic fine powder having a weight average particle diameter of 0.6 to 5 μm. In other words, instead of attaching the inorganic fine powder to the toner for development, the toner and the inorganic fine powder are contact-frictionally charged in a developing device to obtain a uniformly charged toner.

With respect to a toner having a certain particle size, an extremely small inorganic fine powder has a very large image repelling force on the toner itself, so that it is agitated in a developing device and rotated by a developer carrier. Even if a shear force is applied, the toner remains attached to the toner, and thus has an effect of reducing the charge amount of the toner as described above. However, an inorganic fine powder having a certain size for a toner having a certain particle size adheres to the toner,
Due to the shearing force received in the developing device, the number of times of contact with the toner increases due to separation, and accordingly, the charge amount of the toner increases.

The present inventors have conducted detailed studies based on this concept and have ascertained the following.

The width of the particle size distribution of the inorganic fine powder [(m-D ₄ )
/ (M−D ₁ )] is the width [t−D ₄ ) of the particle size distribution of the toner.
/ (T-D ₁ )], or a wider one can obtain uniform charging properties. This is because, for a toner having a certain particle size, an inorganic fine powder having a particle size within a certain range has an ability to significantly increase the charge amount of the toner. Therefore, the width of the particle size distribution of the inorganic fine powder is preferably wider than the width of the particle size distribution of the toner.

Further, it has been found that it is important that the developer satisfies the following constitutional requirements.

The toner has a weight average diameter of 4 to 12 μm, a length average diameter of 1 to 10 μm, and a distribution width [(t−D ₄ ) / (t−D ₁ )] of 1.01 to 2. That.

Use of a fluidizing agent which is charged to the same polarity as the toner and has a specific surface area of 30 m ² / g or more by the BET method.

The toner is charged in the opposite polarity to the toner, has a weight average particle diameter of 0.6 to 5 μm, and a length average particle diameter of 0.5 to 5 μm.
4 μm, and the distribution width [(m−D ₄ ) / (m−D
₁ )] Use an inorganic fine powder having a value of 1.1 to 2.4.

Use is made of an organic fine powder which is charged in the opposite polarity to the toner and has a length average particle size (p-D ₁ ) of 0.5 μm or less.

These are due to the following reasons.

If the weight-average particle diameter of the toner exceeds 12 μm, the halftone image becomes a rough half-tone image.
If it is less than μm, fog on a white background portion is poor.

If the toner particle size exceeds 12 μm, an inorganic fine powder having a large particle size is required to increase the charge amount of the toner. The inorganic fine powder having a large particle size is not developed and is accumulated in the vicinity of the developer carrier.
Therefore, a large amount of inorganic fine powder having a large particle size is present on the developer carrying member, and the amount of toner to be developed is reduced, so that white streaks appear on an image, a reduction in image density, and roughness of a halftone image. It gets worse.

When the particle diameter of the toner is less than 4 μm, in order to increase the charge amount of the toner, in terms of the particle diameter,
What is necessary is just to make the particle diameter of an inorganic fine powder small. However, at such a particle size, the surface area of the toner increases,
Unless a large amount of inorganic fine powder is used, the chargeability of the toner cannot be kept uniform. When a large amount of inorganic fine powder having a small particle diameter is used, the fine particles pass through the cleaning blade, that is, cleaning failure occurs, or the inorganic fine powder gradually removes the resin layer of the organic photoreceptor so that the photosensitive layer is exposed. This degrades the sensitivity of the body and causes deterioration of the copied image such as a decrease in image density.

The width of the particle size distribution of the toner [(t−D ₄ ) /
When (t−D ₁ )] is larger than 2, the spread of the charge amount distribution due to the particle size distribution increases as described above, so that sufficient uniform chargeability can be obtained even when the inorganic fine powder according to the present invention is used. I can't.

Further, in the absence of a fluidizing agent, the fluidity of the toner used in the present invention is remarkably reduced, which causes poor charging. In the absence of a fluidizing agent, the fluidity of the waste developer in the cleaning unit is significantly reduced, so that the amount of scraping of the photoconductor surface layer resin is increased or the image is deteriorated by being damaged. .

When an inorganic fine powder having a weight average particle size of more than 5 μm is used, the chargeability of the toner is improved to some extent. However, since the toner is large, the inorganic fine powder is not developed in the inverted portion of the white background and is not consumed. In addition, the fine particles are accumulated in the developing device, so that the amount of the inorganic fine powder on the developer carrier increases, and the image quality of the copied image gradually decreases. When the weight average diameter is smaller than 0.6 μm, the chargeability of the toner is reduced as described above, which does not meet the purpose of the present invention.
Further, the ratio of _{(m-D 4) / (} m-D 1) is larger than 2.4, the particle size distribution is too wide, that too fine particle size and, most things too coarse particle size To include
Not preferred.

Further, in the toner and the inorganic fine powder according to the present invention, it is preferable that the inorganic fine powder is charged to a polarity opposite to that of the toner. In the present invention, instead of using inorganic fine powder attached to the toner, by frictional charging, since the purpose is to increase the charge, if the same polarity is used,
Not only does the charge amount of the toner decrease, but also the frictional charging speed decreases, and the copy initial density is low. As copying continues, the density gradually increases, a so-called rising phenomenon occurs.

Further, when inorganic fine powder charged to the opposite polarity to the toner is used, the toner having a small particle size and the inorganic fine powder having a small particle size interact when mixed. That is, those having a large charge amount per unit weight and having a large action surface area act on each other because of opposite polarities. Therefore, the toner having a large particle size and the inorganic fine powder having a large particle size interact with each other. In the same developing device, the combination of the toner having a small particle diameter and the inorganic fine powder is less susceptible to frictional charging due to stirring than the combination of the large toners. This is because when subjected to shearing force due to agitation, small ones often slip through without receiving the shearing force. In addition, the amount of charge given to the toner having a small particle size by the inorganic fine powder having a small particle size is small because the total charge amount of the inorganic fine powder is small. Conversely, in the case of a combination of an inorganic fine powder having a large particle diameter and a toner having a large particle diameter, the charge amount of the inorganic fine powder is also large due to the influence of contact charging due to stirring.
The charge amount of the toner having a large particle diameter, which was low depending on the particle diameter, became large, and the difference in the toner particle diameter in the developing ability disappeared, that is, the phenomenon of the selective development described above did not occur.

From the above, it is important for each of the toner particle size and the inorganic fine powder particle size. However, considering the charging mechanism by the interaction, the particle size distribution width of the toner and the particle size distribution width of the inorganic fine powder are considered. And the relationship between the particle size of the toner and the particle size of the inorganic fine powder become very important.

As a result of a detailed study, it is preferable that the toner and the inorganic fine powder satisfy the relationship of the following formula with respect to the above, since they can exhibit more effectively.

[0066]

(Equation 1)

[0067]

(Equation 2)

The organic fine powder charged to the opposite polarity to the toner and having a length average particle diameter (p-D ₁ ) of 0.8 μm or less adheres to the toner and is partially fluidized on the toner surface. This prevents the toner from being charged up by the agent and plays a role in uniform charging of the toner. In addition, the presence of the organic fine powder makes it possible to adjust the height of the spike of the developer on the developer carrier, thereby mitigating the edge effect and reducing the density change of the edge portion in a solid image. be able to. Therefore, the quality of a photographic image is excellent. Also, by mitigating the edge effect, for example,
In a roller transfer device used in printers and the like in recent years, it is possible to prevent a phenomenon in which only a portion of the toner with a large amount of toner applied is whitened without being transferred. Furthermore, when an organic photoreceptor is used, the amount of the organic photoreceptor scraped by the toner or the inorganic fine powder can be greatly reduced due to the presence of the organic fine powder, and therefore, a high quality copy image can be obtained over a long period of time. Further, the presence of the organic fine powder can also prevent toner scattering. When the length average particle diameter (p-D ₁ ) of the organic fine powder is larger than 0.8 μm, the organic fine powder is present in a free state without adhering to the toner. , The quality of the copied image gradually deteriorates.

Only when the developer satisfies the above-mentioned constitutional requirements can the above-mentioned various problems be solved. Further, in the developer of the present invention, it is possible to prevent the phenomenon that only the toner having a small particle diameter described above is selectively developed and consumed, so that even if copying is continued, halftone There is no roughness, excellent fine line reproducibility, satisfactory density gradation, maximum image density, satisfactory development characteristics of developer, and suppression of selective development. can get.

Further, the constitution of a developer which is preferable for achieving the object in the present invention will be described in detail below.

The following are examples of the monomer of the vinyl copolymer.

For example, styrene, o-methylstyrene, m
-Methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene,
2,4-dimethylstyrene, pn-butylstyrene,
styrene and its derivatives such as p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene; ethylene; Ethylenically unsaturated monoolefins such as propylene, butylene and isobutylene; unsaturated polyenes such as butadiene;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; vinyl ester acids such as vinyl acetate, vinyl propionate and vinyl benzoate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid α-methylene aliphatic monomers such as n-butyl, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate Carboxylic esters;
Methyl acrylate, ethyl acrylate, acrylic acid n-
Butyl, isobutyl acrylate, propyl acrylate,
Acrylic esters such as n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate and phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N
N- such as vinylindole and N-vinylpyrrolidone
Vinyl compounds; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; esters of the above-mentioned α, β-unsaturated acids and diesters of dibasic acids.

Also, unsaturated dibasic acids such as maleic acid, citraconic acid, itaconic acid, alkenyl succinic acid, fumaric acid and mesaconic acid; maleic anhydride, citraconic anhydride, itaconic anhydride, alkenyl succinic anhydride Unsaturated dibasic acid anhydrides such as those; methyl maleate half ester, maleic acid ethyl half ester, maleic acid butyl half ester, citraconic acid methyl half ester, citraconic acid ethyl half ester, citraconic acid butyl half ester, methyl itaconate Half esters of unsaturated dibasic acids such as half ester, methyl alkenyl succinate half ester, methyl fumarate half ester and methyl half mesaconic acid; unsaturated dibasic acid esters such as dimethyl maleic acid and dimethyl fumaric acid; Acid, methacrylic acid, crotonic acid, such as cinnamic acid alpha, beta-unsaturated acid; crotonic acid anhydride, such as alpha of cinnamic acid anhydride, beta-unsaturated acid anhydride, the alpha, beta
-Anhydrides of unsaturated acids and lower fatty acids; and monomers having a carboxyl group such as alkenyl malonic acid, alkenyl glutaric acid, alkenyl adipic acid, acid anhydrides and monoesters thereof.

Among these, a combination of monomers that results in a styrene-based copolymer or a styrene-acrylic-based copolymer is preferred.

If necessary, the polymer may be cross-linked with a cross-linkable monomer as exemplified below.

Examples of aromatic divinyl compounds include divinylbenzene and divinylnaphthalene; examples of diacrylate compounds linked by an alkyl chain include:
Ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol acrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and the above compounds Diacrylate compounds linked by an alkyl chain containing an ether bond, for example, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 400 diacrylate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, and methacrylate Include those obtained by changing the over preparative; e.g. diacrylate compounds linked with a chain containing an aromatic group and an ether bond, polyoxyethylene (2)
-2,2-bis (4-hydroxyphenyl) propane diacrylate, polyoxyethylene (4) -2,2-bis (4-hydroxyphenyl) propane diacrylate, and acrylates of the above compounds were replaced with methacrylates. And polyester-type diacrylate compounds, for example, trade name MANDA (Nippon Kayaku). Examples of polyfunctional crosslinking agents include pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylol methanetetraacrylate,
Oligoester acrylates and those obtained by replacing the acrylates of the above compounds with methacrylates; triallyl cyanurate, triallyl trimellitate;

These cross-linking agents can be used in combination with other monomer components 10
0.01 to 5% by weight (more preferably 0.03 to 3% by weight) can be used with respect to 0% by weight.

Among these crosslinkable monomers, those which are preferably used from the viewpoint of fixability and offset resistance to the resin for toner include aromatic divinyl compounds (particularly divinylbenzene), chains containing an aromatic group and an ether bond. Diacrylate compounds tied together.

In the present invention, a vinyl monomer homopolymer or copolymer, polyester, polyurethane, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic carbon A hydrogen resin, an aromatic petroleum resin, or the like can be used by being mixed with the binder resin described above as necessary.

When two or more resins are mixed and used as a binder resin, as a more preferred form, those having different molecular weights are preferably mixed at an appropriate ratio.

The glass transition temperature of the binder resin is 45 to 8
0 ° C., preferably 55-70 ° C., and a number average molecular weight M
n2,500-50,000, weight average molecular weight Mw1
It is preferably from 000 to 1,000,000.

The method for synthesizing the vinyl binder resin according to the present invention includes a bulk polymerization method, a solution polymerization method, a suspension polymerization method,
A polymerization method such as an emulsion polymerization method can be used. When a carboxylic acid monomer or an acid anhydride monomer is used, it is preferable to use a bulk polymerization method or a solution polymerization method due to the nature of the monomer.

The composition of the polyester resin used in the present invention is as follows.

The polyester resin used in the present invention comprises:
45 to 55 mol% of all components are alcohol components,
55 to 45 mol% is an acid component.

As the alcohol component, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol,
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, and a bisphenol derivative represented by the formula (a);

[0086]

Embedded image

Diols represented by the formula (b):

[0088]

Embedded image And polyhydric alcohols such as glycerin, sorbit, and sorbitan.

Examples of the divalent carboxylic acid containing 50 mol% or more of the total acid component include benzenedicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and phthalic anhydride or anhydrides thereof; succinic acid, adipic acid and sebacine Alkyl dicarboxylic acids such as acid and azelaic acid or anhydrides thereof, and succinic acid or anhydrides further substituted with an alkyl group having 6 to 18 carbon atoms; non-succinic acids such as fumaric acid, maleic acid, citraconic acid and itaconic acid; Saturated dicarboxylic acids or anhydrides thereof and the like, and as the trivalent or higher carboxylic acid, trimellitic acid, pyromellitic acid,
Benzophenone tetracarboxylic acid and its anhydride are exemplified.

The alcohol component of the polyester resin particularly preferred in the practice of the present invention is a bisphenol derivative represented by the above formula (a), and the acid component is phthalic acid, terephthalic acid, isophthalic acid or its anhydride, or succinic acid. And dicarboxylic acids such as n-dodecenylsuccinic acid or anhydride thereof, fumaric acid, maleic acid and maleic anhydride; and trimellitic acid or tricarboxylic acids of anhydride thereof.

This is because the polyester resin obtained with these acids and alcohols has a good fixing property as a toner for fixing with a heat roller, and has an excellent offset resistance.

The acid value is 90 or less, preferably 50 or less.
Hereinafter, the OH value is desirably 50 or less, preferably 30 or less. This is because when the number of terminal groups in the molecular chain increases, the toner has a large environmental dependency in the charging characteristics of the toner.

Further, the glass transition temperature of the polyester resin obtained here is 50 to 75 ° C., preferably 55 to 65 ° C.
° C, and further, a number average molecular weight Mn of 1,500 to 50,000.
Preferably 2,000 to 20,000, weight average molecular weight Mw 6,000 to 100,000, preferably 10,000
It is preferably from 0 to 90,000.

In the toner for developing an electrostatic image of the present invention, a charge control agent can be used if necessary in order to further stabilize the chargeability. The charge control agent is a binder resin 100
0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight
It is preferred to use parts by weight.

The charge control agents known in the art today include the following:

To control the toner to be negatively charged,
For example, organic metal complexes and chelate compounds are effective. Examples thereof include a monoazo metal complex, an aromatic hydroxycarboxylic acid, a metal complex, and an aromatic dicarboxylic acid-based metal complex. Others include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters,
Phenol derivatives of bisphenol are mentioned.

When a positively chargeable toner is prepared, nigrosine, a triphenylmethane compound, a rhodamine dye, polyvinyl pyridine, or the like may be used as a charge control agent having a positive charge. In the case of producing a color toner, an aminocarboxylic acid ester such as dimethylaminomethyl methacrylate having positive chargeability is used as a monomer in an amount of 0.1 to 40 mol%, preferably 1 to 40 mol%.
Use a binder resin containing 0 mol%, or
A colorless or light-colored positive charge control agent that does not affect the color tone of the toner may be used. Examples of the positive charge control agent include quaternary ammonium salts represented by the structural formulas (A) and (B).

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Among the quaternary ammonium salts represented by the structural formulas (A) and (B), the positive charge control agents represented by the structural formulas (A) -1, -2 and (B) -1 are used. Is preferable because it shows good chargeability with little dependence on the environment.

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In the case where an aminocarboxylic acid ester such as dimethylaminomethyl methacrylate having a positive charge characteristic is used as a resin component of the binder resin in the positively chargeable toner, a positive charge control agent or a negative charge control agent is used. Use as needed.

In the case where a positively chargeable toner does not use an aminocarboxylic acid ester such as dimethylaminomethyl methacrylate showing a positive charge characteristic as a resin component, a positive charge control agent is added to 100 parts by weight of the binder resin. 0.1 to 15
It is desirable to use parts by weight, preferably 0.5 to 10 parts by weight. When aminocarboxylic acid esters are used, a positive charge control agent and / or a negative charge control agent may be added to 100 parts by weight of the binder resin, if necessary, for the purpose of providing good chargeability with little environmental dependency. 0 to 10 parts by weight, preferably 0 to 8 parts by weight.

When the toner of the present invention is used as a magnetic toner, the magnetic material contained in the magnetic toner includes iron oxides such as magnetite, maghemite, and ferrite, and iron oxides containing other metal oxides; Or a metal such as Al, Co, Cu, P
b, Mg, Ni, Sn, Zn, Sb, Be, Bi, C
Alloys with metals such as d, Ca, Mn, Se, Ti, W, and V, and mixtures thereof, and the like.

Conventionally, as a magnetic material, triiron tetroxide (F
e_Three O_Four ), Iron sesquioxide (γ-Fe_Two O_Three ), Iron oxide
Lead (ZnFe_Two O_Four ), Yttrium iron oxide (Y_Three Fe
_Five O ₁₂), Cadmium iron oxide (CdFe_Two O_Four ), Oxidation
Iron gadolinium (Gd_Three Fe_Five -O₁₂), Iron oxide copper (C
uFe_Two O_Four ), Lead iron oxide (PbFe₁₂-O₁₉), Oxidation
Iron nickel (NiFe_Two O_Four ), Iron neodymium oxide (Nd
Fe_Two O_Three ), Barium iron oxide (BaFe)₁₂O₁₉),
Magnesium iron oxide (MgFe_Two O_Four ), Iron oxide manga
(MnFe_Two O_Four ), Iron oxide lanthanum (LaFeO)
_Three ), Iron powder (Fe), cobalt powder (Co), nickel powder
(Ni) and the like are known, but according to the present invention,
Magnetic materials used alone or in combination of two or more
I do. A particularly preferred magnetic material for the purposes of the present invention is triiron tetroxide.
Or a fine powder of γ-iron sesquioxide.

These ferromagnetic materials have an average particle size of 0.1 to 2
about 10 μm, the magnetic characteristics when a 10K Oersted is applied show a coercive force of 20 to 150 Oersted saturation magnetization of 50 to 200 e
mu / g (preferably 50 to 100 emu / g) and a residual magnetization of 2 to 20 emu / g are desirable.

The magnetic material 1 was added to 100 parts by weight of the binder resin.
It is preferable to use 0 to 200 parts by weight, preferably 20 to 150 parts by weight.

As the colorant irrespective of one component or two components, carbon black, titanium white, and any other pigments and / or dyes can be used. For example, when the toner of the present invention is used as a magnetic color toner, C.I. I. Direct Red 1,
C. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modant Red 30, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I.
I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modant Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic Green 6 and the like. Examples of pigments include: graphite, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, Hansa yellow G, permanent yellow NCG, tartrazine lake, red-mouthed graphite, molybdenum orange, permanent orange GTR, pyrazolone orange, benzidine orange G , Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Navy Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue,
First Sky Blue, Indanthrene Blue BC,
Chrome green, chromium oxide, pigment green B,
Malachite Green Lake, Final Yellow Green G, etc.

When the toner of the present invention is used as a two-component full-color toner, the following may be mentioned. Examples of the magenta coloring pigment include C.I. I. Pigment Red 1,2,3,4,5,6,7,8,9,1
0, 11, 12, 13, 14, 15, 16, 17, 1
8, 19, 21, 22, 23, 30, 31, 32, 3
7, 38, 39, 40, 41, 48, 49, 50, 5
1,52,53,54,55,57,58,60,6
3,64,68,81,83,87,88,89,9
0, 112, 114, 122, 123, 163, 20
2,206,207,209, C.I. I. Pigment Violet 19, C.I. I. Butt Red 1,2,10,1
3, 15, 23, 29, 35 and the like.

Although such a pigment may be used alone, it is more preferable to improve the sharpness of the pigment in combination with the dye and the pigment from the viewpoint of the image quality of a full-color image. Examples of such magenta dyes include C.I. I. Solvent Red 1,
3, 8, 23, 24, 25, 27, 30, 49, 81,
82, 83, 84, 100, 109, 121, C.I. I.
Disperse Red 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as Disperse Violet 1, C.I. I. Basic Red 1,2,9,12,13,14,15,17,18,
22, 23, 24, 27, 29, 32, 34, 35, 3
6, 37, 38, 39, 40, C.I. I. Basic Violet 1,3,7,10,14,15,21,25
And basic dyes such as 26, 27 and 28.

Other coloring pigments include cyan coloring pigments such as C.I. I. Pigment Blue 2, 3, 15,
16, 17, C.I. I. Bat Blue 6, C.I. I. Acid Blue 45 or a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on a phthalocyanine skeleton having a structure represented by Chemical Formula 3.

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Examples of the coloring pigment for yellow include C.I. I. Pigment Yellow 1,2,3,4,5,6,7,10,
11, 12, 13, 14, 15, 16, 17, 23, 6
5, 73, 83, C.I. I. Bat Yellow 1,3,20
And the like.

The amount of the colorant used is 0.1 to 60 parts by weight, preferably 0.5 to 5 parts by weight, per 100 parts by weight of the binder resin.
0 parts by weight.

In the present invention, one or more release agents may be contained in the toner, if necessary.

The following are examples of the release agent used in the present invention. Aliphatic hydrocarbon-based waxes such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, microcrystalline wax, and paraffin wax; and aliphatic hydrocarbon-based waxes such as oxidized polyethylene wax, or block copolymers thereof; Examples of the wax include waxes mainly containing a fatty acid ester such as wax, sasol wax and montanic acid ester wax, and those obtained by partially or entirely deoxidizing fatty acid esters such as deoxidized carnauba wax.
Furthermore, saturated straight-chain fatty acids such as palmitic acid, stearic acid, and montanic acid, unsaturated fatty acids such as brandinic acid, eleostearic acid, and vinaric acid, stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubivir alcohol, and seryl Alcohols, saturated alcohols such as melisyl alcohol, polyhydric alcohols such as sorbitol, fatty acid amides such as linoleic acid amide, oleic acid amide, lauric acid amide, methylenebisstearic acid amide, ethylenebiscapric acid amide, ethylenebis Saturated fatty acid bisamides such as lauric amide, hexamethylene bisstearic acid amide, ethylene bisoleic acid amide, hexamethylene bis oleic acid amide, N, N'-dioleyl adipamide, N, N ' Unsaturated fatty acid amides such as dioleyl sebacamide, aromatic bisamides such as m-xylene bisstearic acid amide, N, N'-distearylisophthalic acid amide, calcium stearate, calcium laurate, zinc stearate; Fatty acid metal salts such as magnesium stearate (commonly referred to as metallic soaps), waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid, and behenin Examples thereof include a partially esterified product of a fatty acid such as acid monoglyceride and a polyhydric alcohol, and a methyl ester compound having a hydroxyl group obtained by hydrogenation of a vegetable oil or the like.

The amount of the release agent used in the present invention is desirably 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, per 100 parts by weight of the binder resin.

These release agents are usually contained in the binder resin by dissolving the resin in a solvent, increasing the temperature of the resin solution and adding and mixing while stirring, or mixing at the time of kneading.

As the negatively chargeable fluidizing agent used in the present invention, any material can be used as long as it can be added to the colorant-containing resin particles so that the fluidity can be increased before and after the addition. It is possible. For example, fluorine-based resin powders such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder, fine powder silica such as wet-process silica, dry-process silica, and the like, silane coupling agent, titanium coupling agent, silicon oil, etc. And the like, surface-treated silica.

Preferred fluidizing agents are fine powders produced by vapor phase oxidation of silicon halide compounds.
It is what is called dry silica or fumed silica, and is manufactured by a conventionally known technique. For example, it utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, and the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl Further, in this production step, by using another metal halide such as aluminum chloride or titanium chloride together with the silicon halide, a composite fine powder of silica and another metal oxide can be obtained. It is also possible to obtain bodies, including them. The particle size is 0.0 as an average primary particle size.
It is desirable to be within the range of 01 to 2 μm, and it is particularly preferable to use silica fine powder within the range of 0.002 to 0.2 μm.

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

AEROSIL (Nippon Aerosil) 130 200 300 380 TT600 MOX170 MOX80 COK84 Ca-O-SiL (CABOT Co.) M-5 MS-7 MS-75 HS-5 EH-5 Wacker HDK N20 V15 WAC -CHEMIE GMBH) N20E T30 T40 DC Fine Silica (Dow Corning Co.) Fransol (Fransil)

Further, it is more preferable to use a treated silica fine powder obtained by subjecting a silica fine powder produced by the gas phase oxidation of the silicon halide compound to a hydrophobic treatment. It is particularly preferable that the treated silica fine powder is obtained by treating the silica fine powder such that the degree of hydrophobicity measured by a methanol titration test shows a value in the range of 30 to 80.

The method for imparting hydrophobicity is provided by chemically treating an organic silicon compound or the like which reacts with or physically adsorbs silica fine powder. As a preferred method, silica fine powder produced by vapor phase oxidation of a silicon halide is treated with an organosilicon compound.

Examples of such organosilicon compounds include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyl Dimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, ρ-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxy Silane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyl Disiloxane, 1,3-diphenyltetramethyldisiloxane and 2 to 12 per molecule
For example, dimethylpolysiloxane having a hydroxyl group bonded to Si and having one siloxane unit as a terminal unit may be used. These are used alone or as a mixture of two or more.

As the positively chargeable fluidizing agent used in the present invention, those obtained by treating the above-mentioned dry process silica with the following coupling agent having an amino group or silicone oil are used.

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[0131]

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As the silicone oil, an amino-modified silicone oil having a partial structure having an amino group in a side chain represented by the following formula is generally used.

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(Where R ₁ represents hydrogen, an alkyl group, an aryl group or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, and R ₃ and R ₄ represent a hydrogen, an alkyl group or an aryl group. However, the alkyl group, the aryl group, the alkylene group, and the phenylene group may contain an amine, or may have a substituent such as halogen as long as the chargeability is not impaired. A positive integer is shown.) Examples of the silicone oil having such an amino group include the following.

Viscosity at 25 ° C. Amine Equivalent Trade name (cps) SF8417 (manufactured by Toray Silicone Co., Ltd.) 1200 3500 KF393 (manufactured by Shin-Etsu Chemical Co., Ltd.) 60 360 KF857 (manufactured by Shin-Etsu Chemical Co., Ltd.) 70 830 KF860 (manufactured by Shin-Etsu Chemical Co., Ltd.) 250 7600 KF861 (Shin-Etsu Chemical Co., Ltd.) 3500 2000 KF862 (Shin-Etsu Chemical Co., Ltd.) 750 1900 KF864 (Shin-Etsu Chemical Co., Ltd.) 1700 3800 KF865 (Shin-Etsu Chemical Co., Ltd.) 90 4400 KF369 (Shin-Etsu Chemical Co., Ltd.) 20 320 KF383 (Shin-Etsu Chemical Co., Ltd.) 20 320 X-22-3680 (Shin-Etsu Chemical Co., Ltd.) 90 8800 X-22-380D (Shin-Etsu Chemical Co., Ltd.) 2300 3800 X-22-3801C (Shin-Etsu Chemical Co., Ltd.) 3500 3800 X-22-3810B (Shin-Etsu Chemical Co., Ltd.) Shinetsu Gakusha, Ltd.) 1300 1700

The amine equivalent is a value obtained by dividing the molecular weight by the number of amines per molecule in terms of the equivalent per amine (g / equiv).

The fluidizing agent used in the present invention has good results when it has a specific surface area of 30 m ² / g or more, preferably 50 m ² / g or more measured by nitrogen adsorption according to the BET method. Fluidizer 0.01 for 100 parts by weight of toner
To 8 parts by weight, preferably 0.1 to 4 parts by weight.

Examples of the positively chargeable inorganic fine powder used in the present invention include metal oxides such as magnesium, zinc, aluminum, cobalt, copper, cerium, yttrium, manganese, bismuth and strontium; calcium titanate, barium titanate; Composite metal oxides such as strontium titanate; and others, such as calcium carbonate and barium sulfate. Among them, zinc oxide, aluminum oxide, cobalt oxide, cerium oxide, strontium titanate, bismuth oxide, and calcium carbonate are preferable because the effects of the present invention can be further exhibited.

Examples of the negatively chargeable inorganic fine powder used in the present invention include metal oxides such as molybdenum, tungsten, tantalum, niobium, germanium, vanadium, silicon, titanium, tin, iron, chromium, and zirconium; titanium, zirconium, Metal silicides such as niobium, tantalum, molybdenum, tungsten; titanium, zirconium,
Metal nitrides such as vanadium, niobium, and tantalum; and metal carbides such as titanium, zirconium, vanadium, niobium, tantalum, molybdenum, and tungsten. Among them, molybdenum trioxide, tungsten trioxide, zirconium oxide, titanium silicide, and titanium carbide are preferable because the effects of the present invention can be further exhibited.

The inorganic fine powder used in the present invention, in the case of a metal oxide, is produced by, for example, a sintering method, mechanically pulverized, then classified by air classification, and has a desired particle size and particle size distribution. .

The inorganic fine powder according to the present invention is a toner 100
0.01 to 20 parts by weight, preferably 0.1 to 20 parts by weight, per part by weight.
It is preferable to use 1 to 10 parts by weight.

As the negatively chargeable organic fine powder used in the present invention, negatively chargeable resin fine particles are preferably used. Examples of the negatively chargeable resin include the vinyl resins and polyester resins described above as the binder resin for the toner, as well as epoxy resins, phenol resins, fluororesins, and silicon resins.

In the present invention, a negative charge controlling agent used for toner can be used for the purpose of improving the negative chargeability of the resin in order to sufficiently exert the effect. It is desirable that the amount of the negative charge control agent be 20 parts by weight or less per 100 parts by weight of the negatively chargeable resin.

As the positively chargeable organic fine powder used in the present invention, positively chargeable resin fine particles are preferably used. As the positively chargeable resin, a polymethyl methacrylate resin or dimethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, a vinyl resin obtained by polymerizing a monomer having an amino group such as p-dimethylaminostyrene, partially or entirely, And polyamide-based resins.

In this case, similarly to the above, a positive charge control agent used in the toner for improving the positive charge property can be used. When a positive charge control agent is used, a vinyl resin made of a monomer having no amino group may be used. The amount of the positive charge control agent used is resin 1
It is desirable that the amount be 20 parts by weight or less per 00 parts by weight.

The production method of the organic fine powder used in the present invention is as follows.
Either adjust the particle size by emulsion polymerization, suspension polymerization, spray drying, etc., or pulverize and classify the resin obtained by emulsion polymerization, solution polymerization, condensation polymerization, etc. And the like.

To prepare the toner for developing an electrostatic image of the present invention, a binder resin, a colorant and / or a magnetic substance, a charge control agent or other additives are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill. Then, using a heat kneader such as a heating roll, a kneader, an extruder, melt, knead and knead the meat to make the resins compatible with each other, cool and solidify the melt-kneaded material, pulverize the solidified material, and pulverize the pulverized material. After classification, the toner of the present invention can be obtained.

Further, a fluidizing agent charged to the same polarity as the toner, an inorganic fine powder and an organic fine powder charged to the opposite polarity to the toner, and the toner are sufficiently mixed by a mixer such as a Henschel mixer, and the mixture is added to the surface of the toner particles. The developer for developing an electrostatic image of the present invention having an additive can be obtained.

(1) Measurement of Particle Size Distribution The particle size distribution can be measured by various methods. In the present invention, the measurement was carried out using a Coulter counter multisizer.

That is, as a measuring device, a Coulter counter Multisizer II (manufactured by Coulter) was used, and an interface (manufactured by Nikkaki) for outputting the number distribution and volume distribution and a CX-1 personal computer (manufactured by Canon) were connected. Then, a 1% NaCl aqueous solution is prepared using a special grade or primary grade sodium chloride as an electrolytic solution. As a measurement method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersing agent to 100 to 150 ml of the electrolytic aqueous solution, and the measurement sample is added to 2 to 100 ml.
Add ~ 20 mg. The electrolytic solution in which the sample is suspended is subjected to dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and a multi-sizer type II of the Coulter counter uses a 100 μm aperture when measuring the toner particle size as an aperture. 13μ when measuring the particle size of inorganic fine powder
Measure using an m aperture. The volume and the number of the toner and the inorganic fine powder were measured, and the volume distribution and the number distribution were calculated. Then, the weight-based weight average diameter determined from the volume distribution according to the present invention is determined from the volume distribution.

The particle size of the organic fine powder was observed with an optical microscope equipped with a CCD camera at a magnification of × 1000 to × 4000.
The particle size of 00 or more particles was determined and the average value was defined as the length average particle size.

(2) Measurement of triboelectric charge: FIG. 3 is an explanatory view of a triboelectric charge measuring device.

Measurement of the triboelectric charge of the magnetic toner: The toner passed through 200 mesh and did not pass through 300 mesh.
The sieved iron powder and the magnetic toner were weighed at a weight ratio of 95: 5, left in a measurement environment at a temperature of 23 ° C. and a humidity of 60% for 12 hours or more, and then placed in a polyethylene bottle, thoroughly mixed and stirred. I do.

Next, a conductive screen 3 of 500 mesh (which can be appropriately changed to a size that does not allow magnetic particles to pass) is provided on the bottom.
A measurement sample is put in a metal measurement container 2 having a metal cover 4. At this time, the weight of the entire measurement container 2 is weighed and set as W ₁ (g). Next, in the suction device 1 (at least a portion in contact with the measurement container 2 is an insulator), the pressure of the vacuum gauge 5 is adjusted to 250 by adjusting the air volume control valve 6 by suctioning from the suction port 7.
mmAq. In this state, suction is sufficiently performed (about 2 minutes) to remove toner by suction. The potential of the electrometer 9 at this time is set to V (volt). Here, reference numeral 8 denotes a capacitor, whose capacity is C (μF). Further, the weight of the whole measurement container after suction is weighed to be W ₂ (g). This frictional charge amount T (μ
C / g) is calculated as follows.

T (μC / g) = (C × V) / (W ₁ −W ₂ )

In the measurement of the triboelectric charge of the fluidizing agent and the organic fine powder, the iron powder was mixed with the fluidizing agent or the organic fine powder in a ratio of 98: 2.
The charge amount was determined in the same manner as described above, except that the weight ratio was changed.

Measurement of triboelectric charge of inorganic fine powder The kneaded product obtained by cooling and solidifying the kneaded material during the production of the magnetic toner is crushed to obtain a sieved kneaded product that has passed through 200 mesh and has not passed through 300 mesh. The charge amount was determined in the same manner as in the preparation of the measurement sample except that the kneaded and crushed material and the inorganic fine powder were prepared in a weight ratio of 95: 5. However, the charge amount was calculated as a volume conversion value calculated from the specific gravity.

(3) Glass transition temperature Tg In the present invention, the glass transition temperature is measured using a differential thermal analyzer (DSC measuring device), DSC-7 (manufactured by PerkinElmer).

The measurement sample is 5 to 20 mg, preferably 10
Weigh the mg precisely.

This was put in an aluminum pan, and an empty aluminum pan was used as a reference.
The measurement is performed at a temperature rising rate of 10 ° C./min and at normal temperature and normal humidity between 0 ° C.

In this heating process, an endothermic peak of a main peak in a temperature range of 40 to 100 ° C. is obtained.

The intersection between the line of the midpoint of the baseline before and after the endothermic peak appears and the differential heat curve is defined as the glass transition temperature Tg in the present invention.

(4) Measurement of Molecular Weight In the present invention, the molecular weight of a chromatogram by GPC (gel permeation chromatography) is measured under the following conditions.

That is, the column was stabilized in a heat chamber at 40 ° C., and THF (tetrahydrofuran) was passed through the column at this temperature as a solvent at a flow rate of 1 ml per minute, and the sample concentration was 0.05 to 0.6% by weight. % Of the THF sample solution of the resin adjusted to 50% to 200 μl is measured. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the count number. As a standard polystyrene sample for preparing a calibration curve, for example, Pressure Chemical
Co. Or Toyo Soda Kogyo Co., Ltd. with a molecular weight of 6
× 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 1
0 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9 × 10
⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ , and at least about 10 standard polystyrene samples are suitable. Also, the detector uses RI
A (refractive index) detector is used.

The column used is 10 ³ to 2 × 10
^In order to accurately measure the molecular weight region of ^6, a plurality of commercially available polystyrene gel columns are preferably combined.
μ-styragel 500, 10 manufactured by Aters
Combination of ³ , 10 ⁴ and 10 ⁵ and Showa Denko sho
dex KF-80M, KF-801, 803, 80
4, 805, KA-802, 803, 804,
805 combination or TSKgel manufactured by Toyo Soda
G1000H, G2000H, G2500H, G300
0H, G4000H, G5000H, G6000H, G
A combination of 7000H and GMH is preferred.

[0166]

The present invention will be described below with reference to production examples and examples.

[Production Example of Strontium Titanate] 600 g of strontium carbonate and 320 g of titanium oxide were wet-mixed in a ball mill for 8 hours and then filtered and dried. This mixture was molded at a pressure of 5 kg / cm ² and calcined at a temperature of 1100 ° C. for 8 hours.

Thereafter, the mixture was mechanically pulverized to a weight average diameter of 1.8 μm.
m, length average diameter 0.7 μm, particle size distribution [(m−D ₄ ) /
(M-D ₁ )] to obtain strontium titanate fine powder of 2.6. This is designated as strontium titanate A. FIG. 5 shows the volume distribution and the number distribution of strontium titanate A. The coarse powder and the fine powder were simultaneously removed by an elbow jet classifier utilizing the Coanda effect, and the weight average diameter was 1.4 μm, the length average diameter was 1.0 μm, and the particle size distribution [(m−
_{D 4) / (m-D} 1)] to give a strontium titanate I 1.4. FIG. 4 shows the volume distribution and the number distribution of strontium titanate I. The charge amount of the strontium titanate I was +4.5 μC / cm ³ .

[Production Example of Aluminum Oxide] Aluminum hydroxide was molded at a pressure of 1000 kg / cm ² ,
Sintering was performed at a temperature of 00 ° C. for 2 hours. Thereafter, by mechanical pulverization and classification by an elbow jet classifier, a weight average diameter of 4.0 μm, a length average diameter of 2.5 μm, and a particle size distribution [(m−
_{D 4) / (m-D} 1)] to give 1.6 aluminum oxide. The charge amount of this aluminum oxide is +5.6 μC / c
m ³ .

[Production Example of Calcium Carbonate] A precipitate formed by blowing carbon dioxide into lime milk is filtered, dried and pulverized, and then classified by an elbow jet classifier to obtain a weight average particle size of 3.5 μm and a length of 3.5 μm. Calcium carbonate having an average particle size of 1.7 μm and a particle size distribution of [(m-D ₄ ) / (m-D ₁ )] 2.1 was obtained. The charge amount of this calcium carbonate is +
It was 2.5 μC / cm ³ .

[Production Example of Molybdenum Trioxide] Molybdenum oxide was obtained by heating ammonium molybdate with nitric acid. This was filtered, washed with water, dried, and calcined in air at 400 ° C. for 6 hours to obtain molybdenum trioxide powder.
Thereafter, it is mechanically pulverized, and has a weight average diameter of 2.3 μm, a length average diameter of 0.8 μm, and a particle size distribution [(m−D ₄ ) / (m−D ₁ )].
2.9 molybdenum trioxide fine powder was obtained. The coarse powder and the fine powder were simultaneously removed by an elbow jet classifier utilizing the Coanda effect, and the weight average diameter was 1.8 μm, the length average diameter was 1.0 μm, and the particle size distribution [(m−D ₄ ) / (m -D
₁ )] Molybdenum trioxide Mo-I of 1.8 was obtained.

The amount of charge of this molybdenum trioxide Mo-I was -21 μC / cm ³ .

[Production Example of Tungsten Trioxide] Tungsten trioxide was obtained by firing metal tungsten in oxygen at 700 ° C. for 10 hours. Thereafter, the mixture was mechanically pulverized to obtain a weight average diameter of 4.0 μm, a length average diameter of 1.0 μm, and a particle size distribution of [(m
−D ₄ ) / (m−D ₁ )] to obtain 4.0 tungsten trioxide fine powder. The coarse powder and the fine powder were simultaneously removed by an elbow jet classifier utilizing the Coanda effect, and the weight average diameter was 3.0 μm, the length average diameter was 2.0 μm, and the particle size distribution [(m−D ₄ ) / (m -D ₁ )] 1.5 was obtained.

The charge amount of the tungsten trioxide Wo-I was -9 μC / cm ³ .

[Production Example of Organic Fine Powder] [Production Example 1 of Positively Chargeable Organic Fine Powder] 75 parts by weight of styrene 10 parts by weight of butyl acrylate 15 parts by weight of dimethylaminomethyl methacrylate 3 parts by weight of benzoyl peroxide

The above materials were dissolved in toluene,
The polymerization was carried out for 16 hours. Remove toluene, dry, pulverize,
After classification, an organic fine powder I having a length average particle diameter (p-D ₁ ) of 0.6 μm was obtained. The charge amount of this organic fine powder I is +70 μC
/ G.

[Production Example 2 of Positively Chargeable Organic Fine Powder] 90 parts by weight of styrene 10 parts by weight of n-butyl acrylate 4 parts by weight of benzoyl peroxide

The above materials were dissolved in toluene,
The polymerization was carried out for 6 hours. After removing and drying the toluene, the positive charge control agent represented by the structural formula (A) -1 was kneaded, crushed and classified at 130 ° C. using 10 parts by weight with respect to 100 parts by weight of the resin, and the length was measured. Organic fine powder II having an average particle size (p-D ₁ ) of 0.2 μm was obtained. The charge amount of this organic fine powder is +35
μC / g.

[Production Example 1 of negatively chargeable organic fine powder] 75 parts by weight of styrene 10 parts by weight of n-butyl acrylate 15 parts by weight of monobutyl malate 4 parts by weight of benzoyl peroxide

The above materials were dissolved in toluene,
The polymerization was carried out for 16 hours. Remove toluene, dry, pulverize,
After classification, an organic fine powder III having a length average particle size (p-D ₁ ) of 0.7 μm was obtained. The charge amount of this organic fine powder is -50 μm.
C / g.

[Production Example 2 of Negatively Chargeable Organic Fine Powder] A resin was obtained in the same manner as in the case of the organic fine powder II, and 5 parts by weight of a monoazo metal complex (negative charge controlling agent) was added to 100 parts by weight of the resin. The mixture was kneaded, pulverized and classified at 130 ° C. to obtain an organic fine powder IV having a length average particle diameter (p-D ₁ ) of 0.1 μm.
The charge amount of this organic fine powder was -45 C / g.

[Preparation Example 1 of Binder Resin] Styrene 85.0 parts by weight Butyl acrylate 15.0 parts by weight Di-tert-butyl peroxide 6.0 parts by weight

The above materials were added dropwise to 200 parts by weight of xylene heated to the reflux temperature over 4 hours. Further, the polymerization was completed under xylene reflux (138 to 144 ° C.), and xylene was removed while heating to 200 ° C. under reduced pressure. The resin thus obtained is referred to as resin A.

Resin A 40.0 parts by weight Styrene 45.0 parts by weight Butyl acrylate 15.0 parts by weight Divinylbenzene 0.5 parts by weight Benzoyl peroxide 1.5 parts by weight

170 parts by weight of water in which 0.12 parts by weight of a partially saponified polyvinyl alcohol was dissolved was added to the above mixed solution, and the mixture was vigorously stirred to obtain a suspension dispersion. The suspension dispersion was added to a reactor which was charged with 50 parts by weight of water and purged with nitrogen, and subjected to a suspension polymerization reaction at a reaction temperature of 80 ° C. for 8 hours. After completion of the reaction, the resultant was washed with water, dehydrated and dried to obtain a resin B.

The binder resin B had a glass transition point of 61 ° C., a gel content of 27%, a number average molecular weight Mn of 12,000 and a weight average molecular weight Mw of 100,000. Using a Soxhlet extractor, 0.5 to 1.0 g of the binder resin was weighed, and the gel content was determined from the dry weight of the insoluble matter after extraction for 6 hours. The molecular weights Mw and Mn were measured using those excluding the gel component.

[Production Example 2 of Binder Resin] Bisphenol derivative represented by formula (A) 1320 parts by weight Fumaric acid 100 parts by weight Terephthalic acid 200 parts by weight Trimellitic acid 300 parts by weight

The above materials were placed in a three-liter four-necked round-bottomed flask equipped with a thermometer, a stainless steel stirrer, a glass nitrogen inlet tube, and a falling condenser. The flask was then placed in a heating mantle,
Nitrogen gas was introduced from the glass inlet tube to keep the inside of the reactor in an inert atmosphere, and the temperature was raised to perform dehydration condensation at 220 to 250 ° C. The relationship between the viscosity and the molecular weight was grasped in advance, and when the viscosity reached a predetermined value, the resin was cooled and solidified to obtain a binder resin C.

The glass transition point Tg of the binder resin C is 60
° C, number average molecular weight Mn 7,800, weight average molecular weight M
w was 22,000.

Example 1 100 parts by weight of resin B (binder resin) 80 parts by weight of magnetic iron oxide (average particle size: 0.15 μm, Hc115 Oersted, σs80 emu / g, σr11 emu / g) Low molecular weight ethylene-propylene copolymer 4 Parts by weight Monoazo metal complex (negative charge control agent) 2 parts by weight

After the above materials were premixed with a Henschel mixer, melt kneading was performed at 130 ° C. using a twin screw kneading extruder. After allowing the kneaded material to cool, coarsely pulverized with a cutter mill,
The powder is pulverized using a fine pulverizer using a jet stream and further classified using an air classifier to obtain a weight average particle size (t-D ₄ ).
9.0 μm, average length of length (t-D ₁ ) 7.0 μm, distribution [(t-D ₄ ) / (t-D ₁ )] 1.3 black fine powder (negative triboelectrification magnetic toner) I got FIG. 6 shows the volume distribution and number distribution of the obtained magnetic toner.

With respect to 100 parts by weight of this magnetic toner, 0.6 parts by weight of hydrophobic dry silica (BET 150 m ² / g), 3.0 parts by weight of strontium titanate I, and organic fine powder I
0.3 parts by weight was externally added using a Henschel mixer to prepare a developer.

Using the obtained developer, the photosensitive drum of a Canon NP9330 laser copying machine was converted to an OPC photosensitive drum, and after charging with a negative corona, a latent image was formed with a laser, and the system was changed to a reversal developing method. Evaluation of image output was performed using a modified machine.

As a result, there was no fog on the white background, and the maximum image density was 1.46.
The density gradation was good. In addition, linearity that was almost satisfactory was obtained in the relationship between the development potential and the image density (FIG. 2). In addition, the edge effect could be reduced, and the density change of the edge portion in the solid image was slight.

Further, a copy test of 30,000 sheets was performed. As a result, good results were obtained in terms of fixability without toner scattering. The copy image was of good quality with little change from the initial image described above. Also,
No scratch on the surface of the organic photoreceptor was observed, and the result of measurement of the thickness of the photoreceptor surface layer by the quiescent current showed that the shaved amount of the photoreceptor surface layer was 1.6
μm / 10,000 sheets. When the particle size of the developer on the developer carrier was measured, the weight average particle size was 9.5.
μm, length average particle size 7.3 μm (initial weight average particle size 9.
(0 μm, length average particle size: 6.8 μm), there was almost no change in the particle size and distribution, and good results were also obtained in the selective developability.

Further, the carrier memory was also insignificant.

Further, a copy test was conducted at low temperature and low humidity (5 ° C., 10%) and high temperature and high humidity (30 ° C., 80%), and good results were obtained as in the initial stage. A long-term (one week) test was conducted at high temperature and high humidity, and good results were obtained without any decrease in concentration.

Examples 2 and 3 A developer was prepared in the same manner as in Example 1 except that the material composition shown in Table 1 and the toner particle diameter were changed, and the same evaluation as in Example 1 was carried out. And the good results shown in FIG.

[0199]

[Table 1]

[0200]

[Table 2]

Example 4 The procedure of Example 1 was repeated, except that the monoazo metal complex was replaced by 2 parts by weight of nigrosine, to obtain a weight average particle size (t-D ₄ ) of 9.0 μm and a length of 9.0 μm. Average particle size (t-D ₁ )
A positively chargeable magnetic toner having a particle size of 7.0 μm and a distribution (t−D ₄ ) / (t−D ₁ ) of 1.3 was obtained.

An amino group-containing silicone oil (trade name KF8) was added to 100 parts by weight of the positively chargeable magnetic toner.
57) treated with AEROSIL 130 (treated with 13 wt% oil based on silica, BET 120 m ² /
g, the charge amount was +120 [mu] C / g), 3.0 parts by weight of molybdenum trioxide Mo-I, and 0.3 parts by weight of organic fine powder III were externally added using a Henschel mixer. A developer was used.

Using the obtained developer, image output was evaluated by a machine in which the transfer section of a Canon NP4835 copying machine was modified to roller transfer.

As a result, there was no fog on the white background, and the maximum image density was 1.45.
The density gradation was good. In addition, linearity that can be almost satisfied in the relationship between the development potential and the image density was obtained.

The edge effect was reduced, the change in the density of the edge portion in the solid image was slight, and there was no hollowing-out phenomenon in the transfer.

Further, a copy test of 30,000 sheets was performed. As a result, good results were obtained in terms of fixability without toner scattering. The copy image was of good quality with little change from the initial image described above. Further, no scratch on the surface of the organic photoreceptor was observed, and the thickness of the surface layer of the photoreceptor was measured by the quiescent current.
m / 10,000 sheets. When the particle size of the developer on the developer carrier was measured, the weight average particle size was 9.6 μm.
m, length average particle diameter 7.8 μm (initial weight average particle diameter 9.0)
.mu.m, average length particle size of 7.0 .mu.m), and there was almost no change in the particle size and distribution, and good results were also obtained in the selective developability.

Further, the carrier memory was also insignificant.

Further, a copy test was carried out at a low temperature and a low humidity (5 ° C., 10%) and at a high temperature and a high humidity (30 ° C., 80%), and good results were obtained as in the initial stage. A long-term (one week) test was conducted at high temperature and high humidity, and good results were obtained without any decrease in concentration.

Example 5 The same procedure as in Example 4 was carried out except that the molybdenum trioxide and the organic fine powder III were changed to 3 parts by weight of tungsten trioxide and the organic fine powder IV using the positively chargeable magnetic toner of Example 4. As a result, good results as shown in Table 3 were obtained.

The initial particle size of the developer used at this time was 9.0 μm in weight average particle size (t−D ₄ ) and 9.0 μm in length average particle size (t−D ₄ ).
D ₁ ) was 6.9 μm.

[0211]

[Table 3]

Example 6 Resin B 100 parts by weight Monoazo metal complex (negative charge controlling agent) 4 parts by weight The same procedure as in Example 1 was carried out except that 5 parts by weight of copper phthalocyanine represented by the structural formula I was used. (TD
₄ ) 8.0 μm, length average particle diameter (t-D ₁ ) 6.0 μm
m, a negatively chargeable toner having a distribution (t-D ₄ ) / (t-D ₁ ) of 1.3 was obtained.

Using this toner, an external additive was added in the same manner as in Example 1. Further, as a carrier, a Cu—Zn—Fe-based ferrite carrier coated with 0.5% by weight of styrene-acryl 2-ethylhexyl-methyl methacrylate (copolymer weight ratio: 50:20:30) (average particle size: 45%) was used.
μm, 250 mesh pass, 400 mesh on 87% by weight), and a developer was prepared so that the toner concentration was 6.0% by weight.

Using these developers, image formation was evaluated using a full color copying machine CLC-500 made by Canon.

As a result, there was no fog on the white background, and the maximum image density was 1.48.
The density gradation was good. In addition, linearity that can be almost satisfied in the relationship between the development potential and the image density was obtained.

The edge effect was also reduced, and the change in density at the edge of the solid image was slight.

Further, a copy test of 20,000 sheets was performed. As a result, there was no toner scattering and the toner transportability in the copying machine was good and stable. Further, good results were also obtained in the fixing property. The copy image was of good quality with little change from the initial image described above. Further, no scratch on the surface of the organic photoreceptor was observed, and the thickness of the surface layer of the photoreceptor was measured by using a quiescent current. When the particle size of the developer on the developer carrier was measured, the weight average particle size was 8.4 μm and the length average particle size was 6.2 μm (the initial weight average particle size was 8.0 μm, and the length average particle size was 5.9 μm). And there was almost no change in the particle size and distribution, and good results were also obtained in the selective developability.

The carrier memory was also good.

Further, a copy test was carried out at a low temperature and a low humidity (5 ° C., 10%) and at a high temperature and a high humidity (30 ° C., 80%), and good results were obtained as in the initial stage. A long-term (one week) test was conducted at high temperature and high humidity, and good results were obtained without any decrease in concentration.

Comparative Examples 1 to 3 A developer was prepared in the same manner as in Examples 1 and 4 except that the material composition shown in Table 4 and the toner particle diameter were changed, and the same evaluation as in Examples 1 and 4 was carried out. And the results shown in Table 5 were obtained.

[0221]

[Table 4]

[0222]

[Table 5]

[0223]

The developer for developing an electrostatic image of the present invention has excellent development characteristics, and particularly has an excellent effect of suppressing selective development. Further, it is suitable as a developer for developing a latent image formed on an OPC photosensitive member using an organic photoconductive substance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a developing potential and a copy image density when a developer other than the present invention is used. In the figure, a solid line indicates a case where the maximum image density is 1.4 or more, and a broken line indicates This shows a case where the density gradation is improved.

FIG. 2 is a diagram showing a relationship between a development potential and a copy image density when a developer according to the present invention is used.

FIG. 3 is an explanatory diagram of an apparatus for measuring a triboelectric charge amount of toner.

FIG. 4 is a particle size distribution chart (13 μm) of the inorganic fine powder according to the present invention.
m aperture).

FIG. 5 is a particle size distribution diagram (13 μm aperture) of the inorganic fine powder before classification.

FIG. 6 is a particle size distribution diagram (100 μm aperture) of the insulating positive toner.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-19527 (JP, A) JP-A-4-291354 (JP, A) JP-A-1-1133761 (JP, A) JP-A-4-19764 44051 (JP, A) JP-A-5-2284 (JP, A) JP-A-2-139575 (JP, A) JP-A 1-1121863 (JP, A) JP-A-3-177848 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] A weight average particle size (tD ₄ ) of ₄ to 12 μm.
m, the length average particle diameter (t-D ₁ ) is ₁ to 10 μm, and the value of (t-D ₄ ) / (t-D ₁ ) is 1.01 to 2
Insulating toner, BE that is charged to the same polarity as the insulating toner and adsorbs N ₂
A fluidizing agent having a specific surface area of 30 m ² / g or more according to the T method, charged in the opposite polarity to the insulating toner, and having a weight average particle diameter (m-D
₄ ) is 0.6 to 5 μm, and the length average particle size (m−
D ₁ ) is 0.5 to ₄ μm, and (m−D ₄ ) / (m−
D ₁ ) is 1.0 to 2.4, and (m−D ₄ ) /
(M−D ₁ ) is charged to have the same polarity as or larger than the value of (t−D ₄ ) / (t−D ₁ ), and to the opposite polarity to the insulating toner, and has an average length. Particle size (p-D
₁ ) A developer for developing an electrostatic image, comprising an organic fine powder having a particle size of 0.8 μm or less.