JPH03152557A - Magnetic developer - Google Patents

Abstract

PURPOSE:To improve an offset characteristic and image reproducibility by specifying the volume average grain size of a magnetic toner, the grain size distribution of magnetic toner particle groups and a binder resin constituting the magnetic toner. CONSTITUTION:The volume average grain size of the magnetic toner is 6 to 8 mum. The particles of <=5 mum grain size are incorporated therein at 17 to 60 number %, 6.35 to 10.08 mum at 5 to 50 number %, and >=12.7 mum grain size at <=2.0 vol.%. The magnetic toner particle groups of >=5 mum exhibit the grain size distribution of equation I and the THF-insoluble component of the binder resin is incorporated into the toner at 5 to 70 wt.%. The mol.wt. distribution by GPC of the THF-soluble component has a peak in the region of >=2,000 to < 15,000 mol.wt. and has a peak or shoulder in the region of 15,000 to 100,000 mol.wt. In the equation I, N denotes number % of <=5 mum grain size, V denotes volume % of <=5 mum grain size; K denotes 4.6 to 6.7 positive integer. The high- quality images improved in the offset resistance are obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic developer for developing electrostatic images in electrophotography, etc., and in particular has improved heat roller fixing performance and electrostatic image development performance. The present invention relates to a magnetic developer.

[Prior art] Conventionally, as an electrophotographic method, the U.S. patent cylinder 2.297°69
Although many methods are known, as described in Japanese Patent Publication No. 1, Japanese Patent Publication No. 42-23910, Japanese Patent Publication No. 43-24748, etc., in general, photoconductive materials are utilized and various methods are used. An electrical latent image is formed on the photoreceptor by the following method, and then the latent image is developed using toner, and if necessary, the toner image is transferred to a transfer material such as paper, and then heated, pressured, heated and pressed, or The toner is fixed by solvent vapor or the like to obtain a copy, and the toner remaining on the photoreceptor without being transferred is cleaned by various methods, and the above-mentioned process is repeated.

In recent years, such copying machines have been used not only as office copy machines for copying original documents, but also for copying high-definition images such as digital printers or graphic designs as output from computers. I started.

For this reason, higher reliability has been strictly pursued, and as a result, the performance required of the toner has become more advanced, and it has become impossible to create a superior device unless the performance of the toner can be improved.

Incidentally, the most important performances required of toner in digital printers and high-definition image copying include fine line fixing performance and development reproduction performance.

Regarding the fixing process, various methods and devices have been developed, but the most common method at present is a compression heating method using a heated roller.

The press heating method using a heating roller is a method of fixing by passing the toner image surface of the sheet to be fixed under pressure while contacting the surface of a heating roller whose surface is made of a material that has releasability for toner. . In this method, the surface of the heat roller and the toner image on the sheet to be fixed come into contact with each other under pressure, so the thermal efficiency when fusing the toner image onto the sheet to be fixed is extremely good, and the fixing can be performed quickly. It is very effective in high-speed electrophotographic copying machines.

However, in the above method, since the surface of the heat roller and the toner image contact each other under pressure in a molten state, a portion of the toner image adheres to and transfers to the surface of the fixing roller, and this is transferred again to the next sheet to be fixed, resulting in so-called This may cause an offset phenomenon and stain the fixing sheet. Preventing toner from adhering to the surface of the heat fixing roller is considered to be one of the essential conditions for the heat roller fixed fixing method.

On the other hand, in the latent image portion of the fine image, lines of electric force are concentrated at the boundary between the exposed and non-exposed areas, and the surface potential of the upper photoreceptor appears to increase. In particular, in digital printers, the latent image is composed of binary basic pixels of 0N-OFF, so the electric lines of force are concentrated at the boundary between exposed and non-exposed areas, and the basic pixels are The amount of toner per unit area developed into the composed line latent image is
This is more than the amount of toner on a normal analog image. Therefore, in fixing such images, there is a current demand for toners with better fixing properties and offset properties than ever before.

Further, when used as a printer, the amount of copies to be made is 3 to 5 times that of a copying machine of the same level, and at the same time, high durability of development and high image stability are also required.

As a technique for improving the binder resin of a toner, for example, a toner using a crosslinked polymer as a binder resin has been proposed in Japanese Patent Publication No. 51-23354. If this method is followed, it will be effective in improving offset resistance and wrapping resistance, but on the other hand, increasing the degree of crosslinking will increase the fixing point, and the fixing temperature will be low enough to improve offset resistance and wrapping resistance. However, no one with sufficient fixing properties has been obtained. - In order to improve fixation for boat fishing, it is necessary to lower the molecular weight of the binder resin to lower the softening point, which is contradictory to measures to improve offset resistance, and to lower the softening point. This inevitably causes an undesirable phenomenon in which the glass transition point of the resin decreases and the toner blocks during storage.

Furthermore, regarding a toner that is a blend of a low molecular weight polymer and a crosslinked polymer, for example, a toner that has a low molecular weight polymer and an infusible high molecular weight polymer as main resin components has been proposed in JP-A-58-86558. ing. If that method is followed, fixing properties tend to be improved, but the weight average molecular weight/number average molecular weight (Mw/Mn) of the low molecular weight polymer is 3.
5 or less and the content of the infusible high molecular weight polymer is as large as 40 to 90% by weight, it is difficult to satisfy high performance offset resistance, and in practice, offset prevention liquids are difficult to achieve. It is extremely difficult to produce toner that satisfies fixing properties (especially high-speed fixing) and offset resistance unless the toner is used in a fixing device equipped with a supply device.

Furthermore, in JP-A-60-166958, a low molecular weight polyα-
A toner comprising a resin composition obtained by polymerization in the presence of methylstyrene has been proposed.

In particular, in this publication, the number average molecular weight (Mn) is from 9,000 to
Although it is said that a range of 30.000 is preferable, if Mn is increased in order to further improve offset resistance, fixing performance becomes a practical problem, and therefore it is difficult to satisfy offset resistance with high performance.

Furthermore, JP-A No. 56-16144 describes a method containing a binder resin component having at least one maximum value in each region of molecular weight 103 to 8 x 10' and molecular weight 10' to 2 x 10' in the molecular weight distribution by GPC. A toner that does this has been proposed. In this case, offset resistance, fixing properties,
Although the toner has excellent properties in terms of filming and fusing to a photoreceptor, it is desired to further improve the offset resistance and fixing properties of the toner. In particular, it is desired to meet today's strict demands while further improving fixing properties and maintaining or improving various other performances.

Furthermore, JP-A No. 63-223662 discloses that offset resistance can be achieved by using a binder resin containing 10 to 60 parts by weight of THF-insoluble matter and having a peak in molecular weight distribution. However, although it exhibits relatively good anti-offset properties initially, as the number of printing increases, the surface of the heat roller of the fixing device tends to become contaminated and the anti-offset properties tend to deteriorate. Particularly in a developer using a toner with a large specific surface area and a small particle size, this problem has become an obstacle to reducing the particle size of the toner in the developer.

Furthermore, regarding the development reproducibility performance, especially when the latent image on the photoreceptor of the image forming apparatus is a line image of 100 μm or less, fine line reproducibility is generally poor, and the sharpness of the line image is still not sufficient. Recently, in image forming devices such as electrophotographic printers that use digital image signals, a latent image is formed by a collection of dots with a constant potential, and the dot density changes in solid areas, halftone areas, and light areas. It is expressed by. However, if the toner particles do not adhere to the dots faithfully and the toner particles protrude from the dots, the gradation of the toner image that corresponds to the ratio of dot densities in the black and white areas of the digital latent image cannot be obtained. There is a problem. Furthermore, when reducing dot size to improve resolution in order to improve image quality, the reproducibility of latent images formed from minute dots becomes even more difficult.
Images tend to have poor resolution and gradation, and lack sharpness.

Further, although the image quality is good initially, as copying or printing continues, the image quality may deteriorate. This development is thought to occur because, as copying or printing continues, only toner particles that are easily developed are consumed first, and toner particles that are less developable accumulate and remain in the developing machine.

Until now, for the purpose of improving the image quality, I (
Several developers have been proposed. Japanese Patent Publication No. 51-3244
The publication proposes a non-magnetic toner intended to improve image quality by regulating particle size distribution. In the toner,
The toner is mainly composed of toner having a particle size of 8 to 12 Pa+, which is relatively coarse, and according to the studies of the present inventors, it is difficult to uniformly "glue" the latent image with this particle size, and the toner has a particle size of 5 μm or less. is 30% by number or less, and 20 μm or more is 5% by number or less, which means that the particle size distribution is broad, which also tends to reduce uniformity. In order to form clear images using such coarse toner particles and a toner with a broad particle size distribution,
It is necessary to increase the apparent image density by thickly stacking the toner particles to fill the gaps between the toner particles, and there is also the problem that the amount of toner consumption required to achieve a predetermined image density increases.

Furthermore, in JP-A-54-72054, a non-magnetic toner having a sharper distribution than the former has been proposed, but the particle size of intermediate weight particles is coarse, 8.5 to 11.01, and There is still room for improvement as a toner in terms of resolution.

In JP-A No. 58-129437, the average particle size is 6 to 6.
A non-magnetic toner has been proposed in which the particle size is 10 gm and the maximum number of particles is 5 to 8 μm, but the number of particles of 5 μm or less is 15%.
Images with poor sharpness tend to be formed.

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

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

Also, Japanese Patent Publication No. 63-39905 (U.S. Patent No. 4.29
No. 9°900) proposes a jumping development method using a developer containing 10 to 50% by weight of magnetic toner of 20 to 35 .mu.m. That is, magnetic toner is frictionally charged and a toner layer is uniformly and thinly applied on the sleeve.
Further, in order to improve the environmental resistance of the developer, efforts have been made to find a suitable toner particle size. However, considering more stringent requirements such as fine line reproducibility and resolution, further improvements are required.

Furthermore, in Japanese Patent Application Laid-open No. 1-112253, a developer with a volume average particle diameter of 4 to 9 μm with a specific particle size distribution has been proposed, but although this has been a major improvement in analog copiers, the minuteness of the digital latent image is Further improvements are desired in order to faithfully reproduce spots.

As mentioned above, there is a long-awaited toner that can satisfy both fixing performance and development reproducibility, especially a toner that can satisfactorily develop digital latent images.

[Problems to be Solved by the Invention] The present invention has been made to solve the above-mentioned problems, and its purpose is to provide excellent fixing properties and offset properties, good image reproducibility, and reverse fogging. An object of the present invention is to provide a developer having a toner free of toner.

A further object of the present invention is to provide a developer containing toner that does not cause image deterioration even after long-term use.

A further object of the present invention is to provide a developer having a toner that can be fixed at a low temperature, has excellent anti-blocking properties, and can be used satisfactorily even in the high-temperature atmosphere of a small copying machine.

A further object of the present invention is to provide a toner that has excellent anti-offset properties and also has good production efficiency.

Furthermore, the object of the present invention is to achieve high image density, fine line reproducibility,
The present invention provides a magnetic developer with excellent gradation.

A further object of the present invention is to provide a developer that can maintain a stable high image density regardless of the environment.

A further object of the present invention is to provide a developer that can maintain good initial offset resistance without contaminating the surface of the heat roller of the fixing device even after printing out a large number of sheets.

[Means and effects for solving the problem] In order to achieve the above-mentioned object, various materials were intensively studied from various angles. As a result, it has been found that this can be achieved using a magnetic developer having the structure shown below.

That is, the present invention provides a triboelectric magnetic developer having a magnetic toner containing at least a binder resin and a magnetic powder, in which the volume average particle size of the magnetic toner is 6 to 8 μm, and furthermore, a particle size of 5 μm or less. The magnetic toner particles having 17 to 6
0% by number, 5% to 50% by number of magnetic toner particles having a particle size of 6.35 to 10.081 Lm, 2.0% by volume or less of magnetic toner particles having a particle size of 12.7H or more, 51 The following magnetic toner particle groups are represented by the following formula % [In the formula, N represents the number % of magnetic toner particles having a particle size of 5 μm or less, and ■ represents the volume % of magnetic toner particles having a particle size of 3 μm or less. , K represents a positive number from 4.6 to 6.7. However, N represents a positive number from 17 to 60. ] (see Figure 1), and furthermore, the THF-insoluble content of the binder resin constituting the magnetic toner is 5 to 7.
The molecular weight distribution of the THF-soluble portion of the binder resin by GPC has a peak in the molecular weight range of 2,000 or more to less than 15,000, and the molecular weight is 15,000 to 100,000. The present invention relates to a magnetic developer having a peak or shoulder in a region, and characterized in that the binder resin is a copolymer of a monomer containing a carboxylic acid group and another copolymerizable monomer.

The present invention will be explained in detail below.

In order to achieve the above objectives at the same time, we conducted intensive studies from various angles. The fixing properties of the image agent, anti-offset properties, and pulverization properties of the toner are achieved when the proportion of the THF-insoluble part of the binder resin containing acid groups and the molecular weight distribution of the THF-soluble part are set in a specific manner. I found out what I can do. When the binder resin is dissolved in a solvent such as THF, it can be separated into an insoluble component and a soluble component, and the molecular weight distribution of the soluble component can be measured by GPC. Focusing on the peak positions of the molecular weight distribution of THF-insoluble and THF-soluble components, THF
Systems with no or a small amount of insoluble matter are extremely disadvantageous in terms of grindability, and as mentioned above, in order to improve grindability, the peak position of the molecular weight distribution of THF-soluble content is simply shifted to a position with a lower molecular weight. (direction) worsens offset resistance, proving that it is difficult to satisfy both offset resistance and crushability.

From this study, it has been found that it is very effective to contain a specific amount of THF-insoluble matter not only for the purpose of anti-offset properties, as is usually thought, but also for the purpose of improving crushability.

Furthermore, the molecular weight distribution of the THF soluble content, the property of whether the fixable temperature is high or low (hereinafter simply referred to as fixability), offset resistance, crushability, and blocking resistance were investigated. As a result, in the binder resin, basically TH
The F-insoluble content mainly affects offset resistance, coiling properties, and crushability, and the THF-soluble content has a molecular weight of 15.000.
The components below mainly affect the crushing property, blocking property, adhesion to the photoreceptor, filming property, surface contamination of the heat roller, and adhesion to the inner wall of the grinding device. It was found that components having a weight of .000 or more mainly affected offset resistance and fixing properties.

Furthermore, as a result of intensive studies by the present inventors, it is preferable that both the THF-soluble and insoluble components contain carboxylic acid groups, and the amount of carboxylic acid groups in the THF-soluble component is greater than the amount of carboxylic acid groups in the THF-insoluble component. It has been found that it is more preferable for the amount of carboxylic acid groups to be greater than the amount of carboxylic acid groups.

This is due to the interaction between the acid groups in the THF soluble content and the acid groups in the insoluble content due to hydrogen bonds, and the release effect of the acid groups on the surface of the fixing roller, which causes the resin component to adhere to the heat fixing roller ( This is thought to improve offset resistance.

Furthermore, the present inventors have found that the above effect is greater when the carboxylic acid group is present as a dicarboxylic acid. This is thought to be due to the fact that the two carboxylic acid groups are adjacent to each other, thereby improving the releasability from the fixing roller.

Furthermore, if the number of acid groups in the THF-insoluble content is greater than the acid groups in the THF-soluble content, the development characteristics of the developer tend to deteriorate.

To explain the present invention more specifically, the binder resin used in the toner of the present invention preferably has a THF-insoluble content (gel component) of 5 to 70% by weight (based on the binder resin), and preferably 20 to 60% by weight. GPC of THF soluble components
In the chromatogram, the molecular weight is 2000 or more to 1
less than 5,000, preferably less than 1 peak in the region of 3,000 to 12,000, and a molecular weight of 1,500
0 to toooo, preferably 20000 to 70000
has at least one peak or shoulder in the region of

Furthermore, preferably a molecular weight of 2,000 or more to 15,000
Peaks in the region below and molecular weights of 15.000 to 10
The gap between the peak or shoulder in the 0,000 range should preferably have a difference in molecular weight of 5,000 or more (and more preferably a difference of 10,000 or more in molecular weight).

These reasons are because the THF-insoluble component in the resin composition is 70%
If it exceeds % by weight, due to its melting properties, when used in a toner, the fixing temperature will increase, and furthermore, the dispersion of the additive will become worse. Furthermore, the elevated structural components are likely to be cut when the resin cross-wires, causing problems in toner design.

If the gel component is less than 5%, offset is likely to occur, and if the gel component is less than 5% and there are many high molecular weight regions,
Grindability deteriorates significantly. In addition, there is no peak value in the region where the molecular weight of the THF solvent soluble component is 2000 or more and less than 15000 (if the peak value is 15000 or more, the fixing temperature of the prepared toner increases and the fixing temperature range becomes narrow,
Grindability also worsens, leading to a decrease in production efficiency (If the peak molecular weight is less than 2,000, the produced toner is likely to contaminate the heat fixing roller, significantly reducing offset resistance, and causing problems with blocking. The molecular weight of the other peak or shoulder is 15,000 to 100,000.
If the value exceeds 100,000, the dispersibility of the additive will be poor (the fixing temperature will rise significantly, and the crushability will also deteriorate significantly.
oo.

If the amount is less than 100%, the produced toner will have poor offset resistance, which may cause blocking problems.

The THF-insoluble content in the present invention refers to the polymerization ratio of the polymer component (substantially crosslinked polymer) that has become insoluble in the THF solvent in the resin composition in the toner, and refers to the polymerization ratio of the polymer component (substantially crosslinked polymer) in the resin composition in the toner. It can be used as a parameter indicating the degree of crosslinking.

The THF-insoluble content is defined by the value measured as follows.

That is, weigh out 0.5 to 1.0 g of the toner sample.
ag) Cylindrical filter paper (for example, Toyo Roshi N (L86R))
in a Soxhlet extractor, using T H as a solvent.
F 100~200o+j! 7, in which the soluble components extracted with the solvent were evaporated.
1. Vacuum dry at 100°C for several hours, weigh the amount of THF-soluble resin component (Wz g), take the weight of components other than the resin component such as magnetic material or pigment in the toner (Wsg), and THF-insoluble. The minutes can be calculated from the formula below.

In the present invention, the molecular weight of the peak and/or shoulder 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 flowed as a solvent through the column at this temperature at a flow rate of 1 flll/min to adjust the sample concentration to 0.05 to 0.6% by weight. Inject 50-200+J+ of THF sample solution of resin and measure. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithm value and the count number of a calibration curve prepared using several types of monodisperse polystyrene standard samples. Standard polystyrene samples for preparing the calibration curve include, for example, Molecular Weight 6 x 10'', 2.I manufactured by Pressure Chemical Co., or Toyo Tsudani Gyakusha.
X 10', 4 X 10', 1.75 X 10'
.

5, I X 10', 1. IX 10', 3
．． 9X 10', 8.6X lo'.

It is appropriate to use a standard polystyrene sample with dimensions of 2 x 10', 4.48 x 10'' and at least the 1O point. Also, an RI (refractive index) detector is used as the detector.

As a column, in order to accurately measure the molecular weight range of 10s to 4 x 10'', it is recommended to combine multiple commercially available polystyrene gel columns (for example, μmm styrag manufactured by Waters).
el) 500.10", 10', 10' combination, Showa Denko's Showa Denko (5hodex)
) K F -80M, K F -802, 803, 8
04,805 combination or TSKgel manufactured by Toyo Soda
GloooH.

G2000H, G2500H, G3000H, G400
0H.

A combination of G5000H, G6000H, G7000H, and GMH is preferred.

The weight percent of the binder resin of the present invention having a molecular weight of less than 15,000 is 15% by weight in the chromatogram determined by GPC.
,000, the weight ratio with the cutout having a molecular weight of 15,000 or more is calculated, and the weight % of the THF-insoluble content is used to calculate the weight % with respect to the entire binder resin.

In the magnetic toner according to the present invention, the volume average particle diameter is 6
~8 μm, 17 to 60 number % of magnetic toner particles having a particle size of 5 μm or less, 6.35 to IO, 0 g μm
5 to 50 number % of magnetic toner particles having a particle size of 12
．． Magnetic toner particles having a particle size of 7 μm or more are contained at 2.0% by volume or less, and magnetic toner particles having a particle size of 5 μm or less are contained in the following formula % [where N is magnetic toner particles having a particle size of 5 μm or less] (2) represents the volume % of magnetic toner particles having a particle size of 5 μm or less, and K represents a positive number from 4.6 to 6.7. However, N represents a positive number from 17 to 60. ] It has a particle size distribution that satisfies the following.

If the volume average particle diameter is less than 6 μm, the amount of toner on the transfer paper will be small and the image density will be low (easily) in applications with a high image area ratio such as graphic images. It is thought that this is due to the same reason as the reason why the concentration of
If it exceeds 100 μm, the resolution of the digital latent image formed from minute spots of 100 μm or less will not be good, and the image will likely deteriorate due to durability.

In addition, if the number of magnetic toner particles with a particle size of 5 μm or less is less than 17%, there are few magnetic toner particles effective for high image quality, and in particular, as the toner is used for continuous printouts, the effective magnetic toner particle component decreases. As a result, the variation in the particle size distribution of the magnetic toner as shown in the present invention worsens, and the image quality gradually deteriorates. Also, 60%
If the magnetic toner particles exceed the above range, agglomeration of magnetic toner particles tends to occur, resulting in toner lumps larger than the original particle size, resulting in rough image quality, lowering resolution, or causing interference between the edges and the inside of the latent image. The density difference is large (the image tends to be hollow).

In addition, particles in the range of 6.35 to 10.08 μm are 5 to 5
It is good that it is 0% by number, preferably 8 to 40% by number.
is good. If the number is more than 50%, the image quality deteriorates and more development than necessary occurs, that is, too much toner is applied.
Thin line reproducibility decreases, leading to increased toner consumption (on the other hand,
If it is less than 5% by number, it becomes difficult to obtain high image density. In addition, between the number % (N%) and volume % (V%) of magnetic toner particle groups with a particle size of 5#LI11 or less, N/V=-0,
05N+, and indicates a positive number in the range of 4.6≦ and ≦6.7. Preferably 4.6≦≦6.2, more preferably 4.6≦≦5.7. As shown above, 17≦N≦60, preferably 25≦N≦60, more preferably 30≦N≦60.

When k<4.6, the number of magnetic toner particles with a particle size smaller than 5.0 μm is small (image density, resolution, and sharpness are inferior. The presence of an appropriate amount of magnetic toner particles contributes to achieving close packing of toner during development and forming a uniform image without roughness.In particular, by uniformly filling in fine lines and image contours, This further promotes visual novelty.That is, when k<4.6, these properties are inferior due to the lack of this particle size distribution component.

From another point of view, in terms of production, it is necessary to cut a large amount of fine powder by classification or the like in order to satisfy the condition of k<4.6, which is disadvantageous in terms of yield and toner cost.

Also, when k>6.7, due to the presence of more fine powder than necessary,
As printouts continue, the image density tends to decrease. It is thought that this phenomenon occurs because excessive fine magnetic toner particles with more charge than necessary adhere to the developing sleeve and prevent the normal magnetic toner from being carried and charged on the developing sleeve. It will be done.

In addition, magnetic toner particles having a particle size of 12.7 μm or more are 2.
It is preferably 0% by volume or less, more preferably 1.0% by volume.
It is not more than 0.5% by volume, more preferably not more than 0.5% by volume. If it is more than 2.0% by volume, it will hinder fine line reproduction.

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

That is, the measuring device is Coulter counter TA-U.
Distribute the number of pieces using a mold (manufactured by Coulter).

An interface that outputs volume distribution (manufactured by Nikkaki) and a CX-1 personal computer (manufactured by Canon) are connected, and the electrolyte is approximately 1% NaC using first grade sodium chloride.
1) Prepare an aqueous solution. As a measurement method, a surfactant, (
Preferably alkylbenzene sulfonate) from 0.1 to
5-Add and further add 2 to 20 mg of the measurement sample. The electrolytic solution in which the sample was suspended was dispersed for about 1 to 3 minutes using an ultrasonic disperser, and then dispersed using the Coulter Counter Model TA-II, using a 100μ aperture as an aperture, to disperse particles with a size of 2 to 40μ based on the number of particles. Measure the particle size distribution of
Then, the values related to the present invention were determined.

Furthermore, the binder resin of the present invention contains THF-insoluble matter and/or THF
It is preferable that the soluble content has an acid value of 1 to 70 in order to further improve blocking resistance and offset resistance.

Examples of polymerizable monomers containing a carboxylic acid value that can be used in the present invention include the following.

α, β-unsaturated carboxylic acids such as acrylic acid and methacrylic acid; α, β-unsaturated dicarboxylic acids such as maleic acid and fumaric acid; n-butenylsuccinic acid, n-octenylsuccinic acid, butyl n-butenylsuccinate; Alkenyldicarboxylic acids such as lobetenylmalonic acid, n-butenyladipic acid, etc.

Examples of dicarboxylic acid half ester monomers that can be used in the present invention include monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, monoallyl maleate, monophenyl maleate, monomethyl fumarate, and fumaric acid. Half esters of α,β-unsaturated dicarboxylic acids such as monoethyl, monobutyl fumarate, monophenyl fumarate, etc.; monobutyl n-butenylsuccinate, monomethyl n-octenylsuccinate, monoethyl n-butenylmalonate, n-dodecyl Alkenyldicarboxylic acid half esters such as monomethyl nylglutarate, monobutyl n-butenyladipate, etc.; octa-vanisters of aromatic dicarboxylic acids such as monomethyl phthalate, monoethyl phthalate, monobutyl phthalate, etc. etc.

Preferred are dicarboxylic acids and derivatives thereof that can be anhydrified.

In this case, the amount of the polymerizable monomer containing an acid group is preferably 1 to 30 parts by weight based on the total amount of the binder resin, and the acid value of the entire binder resin is 1 to 70, more preferably 5 to 50. .

The reason why the above dicarboxylic acid half ester monomer is selected is that suspension polymerization is preferred as a method for producing the resin, as will be described in detail later. This is because, in the suspension polymerization, it is not appropriate to use an acid monomer with high solubility in an aqueous suspension, and it is preferable to use an ester with low solubility.

Examples of comonomers other than the polymerizable monomer containing a carboxylic acid group for obtaining the binder resin of the present invention include the following.

Styrene, 0-methylstyrene, m-methylstyrene,
p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4 dimethylstyrene, p-n-butylstyrene, p-tert- Styrene and its derivatives such as butylstyrene, p-n-hexylstyrene, p-n-nonylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene; ethylene, propylene, Ethylenically unsaturated monoolefins such as butylene and isobutylene; unsaturated polyenes such as butadiene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl slag;
Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-methacrylate
α-Methylene aliphatic monocarbons such as butyl, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc. Acid esters; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate,
Dodecyl acrylate, 2-ethylhexyl acrylate,
stearyl acrylate, 2-chloroethyl acrylate,
Acrylic esters such as 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
- N-vinyl compounds such as vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone; vinylnaphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; Used above.

Among these, combinations of monomers that result in styrene copolymers and styrene-acrylic copolymers are preferred.

As the crosslinking monomer, monomers having two or more polymerizable double bonds are mainly used.

In order to achieve the purpose of the present invention, the binder resin used in the present invention needs to be a polymer crosslinked with a crosslinkable monomer as exemplified below.

Aromatic divinyl compounds, such as divinylbenzene, divinylnaphthalene, etc.; diacrylate compounds linked with an alkyl chain, such as ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1
．． 4-butanediol diacrylate, 1.5-bentanediol diacrylate, 1.6-hexanediol diacrylate, neopentyl glycol diacrylate, and the above compounds in which the acrylate is replaced with methacrylate; alkyl containing an ether bond Chained diacrylate compounds, such as diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate,
Polyethylene glycol #400 diacrylate, polyethylene glycol #600 diacrylate, dipropylene glycol diacrylate, and the above compounds in which the acrylate is replaced with methacrylate; diacrylate compounds connected by a chain containing an aromatic group and an ether linkage such as polyoxyethylene (2)-2,2-
Bis(4-hydroxyphenyl)propane diacrylate, polyoxyethylene (4)-2,2-bis(4-hydroxyphenyl)propane diacrylate, and compounds in which the acrylate of the above compounds is replaced with methacrylate; Polyester type diacrylate compounds,
For example, the product name MANDA (Nippon Kayaku) is listed. Examples of polyfunctional crosslinking agents include pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, oligoester acrylate, and compounds in which the acrylate of the above compounds is replaced with methacrylate; allyl cyanurate,
Triallyl trimellitate: etc.

These crosslinking agents are preferably used in an amount of 0.01 to 5 parts by weight (more preferably 0.03 to 3 parts by weight) based on 100 parts by weight of other monomer components.

Among these crosslinking monomers, aromatic divinyl compounds (particularly divinylbenzene),
Mention may be made of chain diacrylate compounds containing aromatic groups and ether linkages.

The method of synthesizing the binder resin according to the present invention is basically preferably a method of synthesizing two or more types of polymers.

That is, it is a method of obtaining a resin composition by dissolving a low molecular weight polymer having a small amount of THF-insoluble matter and being soluble in a polymerization monomer, and polymerizing the monomer. In this case, a composition is formed in which the former and latter polymers are uniformly mixed. The low molecular weight polymer in the binder resin composition used in the present invention can be obtained by a commonly used polymerization method such as a bulk polymerization method or a solution polymerization method.

More preferably, a low molecular weight polymer containing an acid anhydride is produced by solution polymerization, and then this polymer is dissolved in a polymerizable polymer, and then suspended or emulsion polymerized in an aqueous system to produce a dicarboxylic acid. good.

In addition, low molecular weight polymers are polymerized again together with monomers that give high molecular weight polymers, but emulsion polymerization and suspension polymerization are also used as polymerization methods to obtain gel components in the crosslinked region until they become solvent-insoluble components. Preferably legal.

In the toner of the present invention, conventionally known charge control agents may be used, but depending on the polarity of the potential of the photoreceptor, a control agent that is positively chargeable or negatively chargeable can be used to develop either positive or negative chargeability. It is also possible to prepare agents.

The amount of the charge control agent added is 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight, per 100 parts by weight of the binder resin.

The magnetic toner of the present invention may contain additives if necessary. As the colorant, conventionally known dyes and pigments can be used, and usually 0.5 to 20 parts by weight may be used per 100 parts by weight of the binder resin. Additives (external additives) used in combination with the toner include lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide, anti-caking agents, and carbon black and tin oxide. There are conductivity imparting agents such as

In addition, in order to improve mold release properties during hot roll fixing, waxy substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, Sasol wax, paraffin wax, etc.
Adding (internally adding) about 5% by weight to the magnetic toner is also one of the preferred embodiments of the present invention.

Furthermore, the magnetic toner of the present invention may also serve as a colorant, but it contains a magnetic material. The magnetic materials contained in the magnetic toner of the present invention include iron oxides such as magnetite, γ-iron oxide, ferrite, and iron-rich ferrite;
Metals such as cobalt, nickel or these metals with aluminum, cobalt, copper, lead, magnesium, tin,
Examples include alloys with metals such as zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, molene, titanium, tungsten, and vanadium, and mixtures thereof.

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

Furthermore, in the developer of the present invention, in order to improve charging stability, developability, fluidity, and durability, it is preferable to mix fine silica powder with the toner and add it externally.

The silica fine powder used in the present invention has a specific surface area of 30 m" or more than 1 g (especially 5
0 to 400 m"/g) gives good results. 0.0 to 400 m"/g of fine silica powder per 100 parts by weight of toner.
It is preferable to use 6 to 1.6 parts by weight.

Furthermore, the silica fine powder used in the present invention may contain silicone oil, various modified silicone oils, silicone oil, various modified silicone oils, a silane coupling agent, and a functional group for the purpose of hydrophobization, chargeability control, etc., as necessary. It is also preferable that the material be treated with a treatment agent such as a silane coupling agent or other organosilicon compound, or a combination of various treatment agents.

[Example] The basic configuration and features of the present invention have been described above, but
The present invention will be specifically described below based on Examples.

Synthesis Example 1 200 parts by weight of cumene was placed in a reactor, and the temperature was raised to reflux temperature. The above mixture was added dropwise to the cumene over 4 hours under reflux.

Furthermore, polymerization was completed under cumene reflux (146 to 156°C), and cumene was removed. The obtained styrene-n-butyl acrylate-monobutyl maleate copolymer has a main peak at a molecular weight of 9000 and a glass transition point (
Tg) was 62°C. The above styrenic copolymer 30
Parts by weight were dissolved in the following monomer mixture to prepare a mixture.

45 parts by weight of styrene monomer 170 parts by weight of water in which 0.1 part by weight of partially saponified polyvinyl alcohol was dissolved was added to the above mixture to form a suspension dispersion.Water 1
The above dispersion was added to a reactor containing 5 parts by weight and purged with nitrogen, and a suspension polymerization reaction was carried out at a reaction temperature of 70 to 95°C for 6 hours. After finishing, the mixture was separated in a furnace, dehydrated, and dried to obtain a composition of styrene-n-butyl acrylate-monobutyl maleate copolymer. The molecular weight distribution of the obtained resin had peaks at molecular weights of 0.95 million and 40 thousand, and THF insoluble matter was 45% by weight.
, Tg=53°C, and acid value was 17.0.

In the present invention, the glass transition point Tg of the resin was measured using a differential thermal analysis measuring device (DSC measuring device), DSC-7 (manufactured by PerkinElmer).

The sample to be measured is accurately weighed in an amount of 5 to 20 mg, preferably 10 mg.

This is placed in an aluminum pan, and the measurement is carried out at room temperature and humidity using an empty aluminum pan as a reference within the measurement temperature range of 30° C. to 200° C. at a heating rate of 10° C./win.

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

The intersection point between the line at the midpoint of the baseline before and after the endothermic peak appeared and the differential thermal curve was defined as the intersection point.

Furthermore, the acid value of the resin was measured by the following method according to JIS K-0070.

Weigh 2 to 10 g of the sample into a 200 to 300 mm Erlenmeyer flask, and add about 50 g of a mixed solvent of ethanol:benzene = 1:2 to dissolve the resin. If the solubility is poor, a small amount of acetone may be added. Using a phenolphthalene indicator, titration was performed with a pre-standardized N710 potassium-alcohol solution, and the acid value was determined from the consumption amount of alcoholic potassium solution using the following formula (3).

Acid value = KO)l (number of ml) X N X 56
．． 1/Amount of paper sample...(3) (N is a factor of N/10 KOH) 4 parts by weight of each of the above components in 200 parts by weight of cumene heated to reflux temperature.
It dripped over time. Furthermore, under cumene reflux (146-1
Solution polymerization was completed at 56° C.) and cumene was removed. The obtained styrenic copolymer had a molecular weight of 5000 at the main peak of GPC and a Tg of 65°C.

30 parts by weight of the styrene copolymer was dissolved in the following monomer mixture to prepare a mixed solution.

Add 0% of the partially saponified polyvinyl alcohol to the above mixed solution.
170 parts by weight of water in which 1 part by weight was dissolved was added to form a suspension dispersion. The above suspension dispersion was added to a reactor containing 15 parts by weight of water and purged with nitrogen, and a suspension polymerization reaction was carried out at a reaction temperature of 70 to 95°C for 6 hours. After the reaction was completed, the mixture was separated in a furnace, dehydrated, and dried to obtain a composition of styrene-n-butyl acrylate-acrylic acid copolymer and styrene-n-butyl acrylate-monobutyl maleate copolymer. In this composition, the THF-insoluble and THF-soluble components are uniformly mixed, and the styrene-n-butyl acrylate copolymer and the styrene-n-butyl acrylate-monobutyl maleate copolymer are uniformly mixed. It was mixed. The THF-insoluble content of the obtained resin composition (
24 mesh passes and 60 mesh passes) was 40% by weight.

In addition, when we measured the molecular weight distribution of THF-soluble components, we found that GP
In the chart of C, there are peaks at approximately 45,000 and 34,000 positions, the Tg of the resin is 58°C, and the acid value is 14.
It was 0.

Synthesis Example 3 150 parts by weight of cumene was placed in a reactor, and the temperature was raised to reflux temperature. Further, the above mixture was added dropwise to the cumene over 4 hours under reflux. Then, the polymerization was completed under cumene reflux (146 to 156°C), and cumene was removed. The obtained polystyrene has a main peak at a molecular weight of 4500 and Tg = 7
It was 0°C. 40 parts by weight of the above polystyrene was dissolved in the following monomer mixture to form a mixed solution.

Add 0.1% of partially saponified polyvinyl alcohol to the above mixture.
A suspended dispersion was prepared by adding 170 parts by weight of water in which parts by weight were dissolved. The above dispersion was added to a reactor containing 15 parts by weight of water and purged with nitrogen, and reacted at a reaction temperature of 70 to 95°C for 6 hours. After the reaction was completed, the mixture was separated in a furnace, dehydrated, and dried to obtain a composition of polystyrene and styrene-n-butyl acrylate-monobutyl maleate copolymer. T of the obtained copolymer composition
The HF-insoluble content was 30% by weight, and the THF-soluble content had a molecular weight of 0.47 million and a peak at approximately 50.000 in the GPC chart, and the Tg of the resin was 50°C and the acid value was 40.0. .

Synthesis Example 4 200 parts by weight of xylene was placed in a reactor, and the temperature was raised to reflux temperature.

The following mixture was added dropwise over 4 hours under reflux of xylene.

Further, the polymerization was completed under xylene reflux (138 to 144°C), and xylene was removed. The obtained copolymer had a main beak at a molecular weight of 4.000 and had a weight of 7g and a temperature of 63°C. 30 parts by weight of the above copolymer was dissolved in the following monomer mixture to prepare a mixture.

Add 0.1% of partially saponified polyvinyl alcohol to the above mixture.
A dispersion liquid was prepared by adding 170 parts by weight of water in which parts by weight were dissolved.

The above dispersion was added to a reactor containing 15 parts by weight of water and purged with nitrogen, and reacted at a reaction temperature of 70 to 95°C for 6 hours. After completion, the mixture was dehydrated and dried to obtain a composition of styrene-monobutyl acrylate copolymer. The molecular weight distribution of the obtained resin had peaks at 45,000 and 29,000, and TH
The F insoluble matter was 40% by weight, Tg = 60°C, and acid value was 3.5.

Comparative Synthesis Example 1 150% by weight of cumene was placed in a reactor and heated to reflux temperature. The following mixture was added dropwise to the cumene over 4 hours under reflux.

Furthermore, polymerization was completed under cumene reflux (138 to 143°C), and cumene was removed. The obtained polystyrene has a main beak at a molecular weight of 11,000, and has a Tg of 82.
It was ℃.

30 parts by weight of the above polystyrene was dissolved in the following monomer mixture to prepare a mixed solution.

The resin had a Tg of 65°C.

Comparative Synthesis Example 2 170 parts by weight of water in which 0.1 part by weight of partially saponified polyvinyl alcohol was dissolved was added to the following monomer mixture to prepare a suspension dispersion.

The above mixture was subjected to suspension polymerization in the same manner as in Synthesis Example 1 to obtain a composition of polystyrene and styrene-n-butyl acrylate-monobutyl aleate copolymer. Acid value is 0.5
Met. The THF-insoluble content of this copolymer composition was 15% by weight, and when the molecular weight distribution of the THF-soluble content was measured, it was found that the molecular weight distribution of this dispersion was about 19,000 and 42,000 on the GPC chart. The above dispersion was added to a reactor containing 15 parts by weight and purged with nitrogen, and the reaction temperature was 70 to 95°C for 6 hours.
A suspension polymerization reaction was carried out for a period of time. After the reaction is complete, separate the furnace.

After dehydration and drying, a styrene-n-butyl acrylate-monobutyl maleate copolymer was obtained.

This copolymer has a main peak with a molecular weight of 17.000.
There was virtually no peak at molecular weights below 15,000.

Also, Tg = 60°C, acid value is 20.5, THF insoluble content is 3
It was 0% by weight.

Example 1 The above materials were thoroughly mixed in a blender and then kneaded in a twin-screw kneading extruder set at 130°C. The obtained mixed material is cooled and coarsely pulverized using a cutter mill, then finely pulverized using a pulverizer using a jet stream, and the resulting pulverized powder is classified using a fixed wall type wind classifier. A classified powder was produced. Furthermore, the obtained classified powder is strictly classified and removed at the same time to remove ultrafine powder and coarse powder using a multi-division classifier that utilizes the Coanda effect (elbow jet classifier manufactured by Nippon Steel Mining Co., Ltd.) to obtain a volume average particle size of 6.
A 3 μm magnetic toner was obtained.

Table 1 shows the data obtained by measuring the obtained magnetic toner using a Coulter counter type TAII equipped with an aperture of <100 .mu. as described above.

Further, 1.0 parts by weight of colloidal silica fine powder was dry mixed with 100 parts by weight of the magnetic toner obtained here to obtain a magnetic developer.

Next, an image reproduction test was conducted using the magnetic developer obtained here. The test results are shown in Table 2. For image production, a part of the scanner of a small laser beam printer (Canon LBP-811) was improved to create a latent image with a minute spot of up to 50μ, improving initial image quality, fixation, and
After printing 00 sheets, offset resistance and staining of the fixing roller were evaluated.

The fixing performance was evaluated under a normal temperature environment (23.5℃ 60%).After the machine was adapted to the environment, the power was turned on and a 200μ wide horizontal line pattern (line width 200μ9 interval 200μm) was printed out on an A4 sheet of paper. Vertical), the first printed image was used for evaluation of fixability. The fixability was evaluated by rubbing the image with Silbon paper 5 times back and forth under a load of 10 g, and the peeling of the image was evaluated by the rate of decrease in reflection density (%).

The stains on the fixing roller were visually observed after 5,000 consecutive sheets (A4 size) of character patterns with a dot ratio of 4% were printed out using a new fixing pad.

Further, after the above observation, the 100μ horizontal line pattern was continuously printed on 300 sheets (A4 size), paused for 30 seconds, and then printing was restarted, and the offset resistance was evaluated based on the degree of staining on the back of the first sheet immediately after.

The reproducibility of minute dots was measured by observing the reproducibility of images of checker patterns with square sides of 80 μm and 50 μm as shown in Figure 2 using a microscope, focusing on the sharpness of the images and the scattering of particles into non-image areas. It was evaluated. Note that bond paper with a surface smoothness of 10 [sec] or less was used for the evaluation.

The evaluation criteria are shown below. (1) Fixability O... Good △ ... Slightly poor but usable for practical use・・・ is dirt that is barely noticeable Δ ・・・
Dirty but usable (no offset)
Not practical due to conspicuous dirt (Offset occurs) (3) Offset resistance (stains on the back after resting) ○ ... Total (No dirt ○△ ... is hardly noticeable △ ... Dirty but practical × . . . Impractical due to conspicuous dirt Example 2 The above material was used in the same manner as in Example 1 to obtain a magnetic toner C whose particle size distribution is shown in Table 1. Furthermore, 0.8 parts of colloidal silica fine powder is added to 100 parts by weight of this magnetic toner.
Parts by weight were dry mixed to obtain a magnetic developer.

Next, using the magnetic developer obtained here, Example 1
An image output test was conducted in the same manner as above.

The test results are shown in Table 2.

Example 3 [Copolymer of Synthesis Example 3] 100 parts by weight The above material was used in the same manner as in Example 1 to obtain a magnetic toner (particle size distribution shown in Table 1). Further, 1.1 parts by weight of colloidal silica fine powder was dry mixed with 100 parts by weight of this magnetic material to obtain a magnetic developer.

Next, using the magnetic developer obtained here, Example 1
An image output test was conducted in the same manner as above.

The test results are shown in Table 2.

Example 4 A magnetic toner (particle size distribution shown in Table 1) was obtained using the above materials in the same manner as in Example 1. Further, 1.0 parts of colloidal silica fine powder was added to 100 parts by weight of this magnetic toner.
1 part by weight was dry mixed to obtain a magnetic developer.

Next, using the magnetic developer obtained here, Example 1
An image output test was conducted in the same manner as above.

The test results are shown in Table 2.

Example 5 A magnetic toner (
The particle size distribution was as shown in Table 1). Furthermore, this magnetic toner 1
1.1 parts by weight of aminosilane-treated colloidal silica fine powder was dry mixed with 00 parts by weight to obtain a magnetic developer.

An image reproduction test was conducted using this developer using a digital copying machine (NP-9330 manufactured by Canon) using laser light.

The test results are shown in Table 2.

Comparative Example 1 f Copolymer of Comparative Synthesis Example 1 100 parts by weight The above material was used in the same manner as in Example 1 to obtain a magnetic toner (particle size distribution shown in Table 1). Furthermore, this magnetic toner 1
00 parts by weight and 1.0 parts by weight of colloidal silica fine powder were dry mixed to obtain a magnetic developer.

Next, using the magnetic developer obtained here, Example 1
An image output test was conducted in the same manner as above.

The test results are shown in Table 2.

Comparative Example 2 A magnetic toner (particle size distribution shown in Table 1) was obtained using the above materials in the same manner as in Example 1. Furthermore, 0.5 parts of colloidal silica fine powder is added to 100 parts by weight of this magnetic toner.
Parts by weight were dry mixed to obtain a magnetic developer.

Next, using the magnetic developer obtained here, Example 1
An image output test was conducted in the same manner as above.

The test results are shown in Table 2.

Comparative Example 3 The above material was made into a magnetic toner (particle size distribution shown in Table 1) using the same method as in Example 1. Further, 1.1 parts of colloidal silica fine powder was added to 100 parts by weight of this magnetic toner.
Parts by weight were dry mixed to obtain a magnetic developer.

Next, using the magnetic developer obtained here, Example 1
An image output test was conducted in the same manner as above.

The test results are shown in Table 2.

(Hereinafter referred to as a margin) [Effects of the Invention] As explained above, according to the present invention, the conventional problems of offset resistance and staining of the roller of the fixing device are improved, and high-quality images can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the particle size distribution of toner particles in the developer of the present invention, and FIG. 2 is a diagram showing a checker pattern used in evaluating the reproducibility of minute dots in the present invention. Figure 1

Claims (1)

[Claims] (1) In a triboelectric magnetic developer having a magnetic toner containing at least a binder resin and a magnetic powder, the volume average particle diameter of the magnetic toner is 6 to 8 μm, and further 5 μm.
17 to 60% by number of magnetic toner particles having the following particle diameters:
, 5 to 50% by number of magnetic toner particles having a particle size of 6.35 to 10.08 μm, 2.0% by volume or less of magnetic toner particles having a particle size of 12.7 μm or more, and 5 μm
The group of magnetic toner particles with a diameter of 5 μm or less is expressed by the following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ N / V = -0.05N + K [In the formula, N indicates the number % of magnetic toner particles with 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 from 4.6 to 6.7. However, N represents a positive number from 17 to 60. ] exhibiting a particle size distribution satisfying the following, and further constituting the magnetic toner:
The binder resin contains 5 to 70% by weight of the THF-insoluble part, and the molecular weight distribution of the THF-soluble part of the binder resin by GPC is from 2,000 or more to 15,00% by weight.
Has a peak in the region less than 0, and has a molecular weight of 15,000
A magnetic developer having a peak or shoulder in the region of ~100,000, wherein the binder resin is a copolymerization of a monomer containing a carboxylic acid group and another copolymerizable monomer. .