JPH04274253A - Magnetic toner for electrostatic image development and heat fixing method - Google Patents

Abstract

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

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner for developing electrostatic images in electrophotography, electrostatic recording, electrostatic printing, etc.

0002

[Prior Art] Conventionally, as an electrophotographic method, US Pat.
, 297,691, Japanese Patent Publication No. 42-23910, Japanese Patent Publication No. 43-24748, etc., many methods are known, but in general, they utilize a photoconductive substance, An electrical latent image is formed on the photoreceptor by various means, then the latent image is developed using toner, and if necessary, the toner image is transferred to a transfer material such as paper, followed by heating, pressure, or heating. Copies are obtained by fixing under pressure or solvent vapor, and the toner remaining on the photoreceptor without being transferred is cleaned by various methods, and the above-mentioned steps are repeated.

[0003] In recent years, such copying devices have begun to be used not only as office copy machines for copying original documents, but also as printers for computer output or as personal copies for individuals. .

[0004] Therefore, smaller size, lighter weight, higher speed, and higher reliability are being strictly pursued, and machines are being constructed of simpler elements in various respects. As a result, the performance required of toner has become more advanced, and it has become impossible to create better machines unless the performance of toner can be improved.

For example, various methods and devices have been developed for the process of fixing toner images on sheets such as paper.
The most common method at present is the compression heating method using a heated roller.

[0006] In the pressure heating method using a heated roller, fixing is carried out by passing the toner image surface of the sheet to be fixed under pressure while contacting the surface of a heated roller whose surface is made of a material that has releasability for the toner. It is something. 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 come into contact with each other under pressure in a molten state, a part 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, so-called. This may cause an offset phenomenon and stain the fixing sheet. One of the essential conditions for the heat roller fixing method is to prevent toner from adhering to the surface of the heat fixing roller.

Conventionally, in order to prevent toner from adhering to the surface of the fixing roller, the roller surface is made of a material that has excellent releasability for toner, such as silicone rubber or fluorine resin, and is further coated with anti-offset and other materials. In order to prevent fatigue on the roller surface, the roller surface is coated with a thin film of a liquid having good mold releasability, such as silicone oil. However, although this method is extremely effective in preventing toner offset, it requires a device to supply the offset prevention liquid, resulting in problems such as the complexity of the fixing device. .

[0008] This is in the opposite direction to miniaturization and weight reduction, and moreover, silicone oil and the like may evaporate due to heat and contaminate the inside of the machine. Therefore, instead of using a silicone oil supply device, we proposed a method of adding a release agent such as low molecular weight polyethylene or low molecular weight polypropylene to the toner, with the idea of supplying offset prevention liquid from the toner during heating. has been done. If a large amount of such additives is added in order to obtain a sufficient effect, it may cause filming on the photoreceptor or contaminate the surface of a toner carrier such as a carrier or sleeve, deteriorating the image and causing practical problems. Therefore, a small amount of release agent is added to the toner to the extent that the image does not deteriorate, and a device that cleans the toner by supplying a small amount of release oil or using a device such as a web to take up the offset toner. They are used together.

However, in view of recent demands for smaller size, lighter weight, and higher reliability, it is necessary and desirable to eliminate even these auxiliary devices. Therefore, we cannot respond without further performance improvements such as toner fixation and offset.
That is difficult to achieve without further improvements in toner binder resins.

As a technique for improving the binder resin of a toner, for example, Japanese Patent Publication No. 51-23354 proposes a toner using a crosslinked polymer as a binder resin. If this method is followed, it will be effective in improving offset resistance and clinging resistance, but on the other hand, if the degree of crosslinking is increased, the fixing point will rise, and the fixing temperature will be sufficiently low, resulting in good offset resistance and clinging resistance. However, no one with sufficient fixing properties has been obtained. Generally, in order to improve fixing properties, it is necessary to lower the softening point by lowering the molecular weight of the binder resin, which is contradictory to measures to improve offset resistance. Inevitably, the glass transition point of the resin decreases, and the undesirable phenomenon of blocking of the toner during storage also occurs.

On the other hand, Japanese Patent Application Laid-Open No. 56-158340
A toner made of a low molecular weight polymer and a high molecular weight polymer is proposed in the above publication, but although this binder resin improves fixing properties, it is still insufficient in terms of offset resistance, and offset resistance and It is difficult to achieve a high level of fixability.

JP-A-58-203453 proposes a toner comprising a low temperature softening resin and a high temperature softening resin. Although this binder resin has improved offset resistance, it is still insufficient in fixing properties, and it is difficult to achieve high levels of offset resistance and fixing properties.

[0013] Furthermore, Japanese Patent Publication No. 60-20411 proposes a method for producing a resin composition comprising a low polymerization degree polymer and a high polymerization degree polymer, but this resin is not used as a binder resin for toner. Although there is a tendency for the crushability to be improved in the case where the powder is pulverized, both the fixing performance and anti-offset properties are still insufficient, and there is still much room for improvement.

Furthermore, regarding toners containing a blend of a low molecular weight polymer and a crosslinked polymer, for example, JP-A-58-86
No. 558 proposes a toner containing a low molecular weight polymer and an infusible high molecular weight polymer as main resin components. If the method is followed, fixing properties and crushability tend to be improved, but the weight average molecular weight/number average molecular weight (Mw/Mn) of the low molecular weight polymer is as small as 3.5 or less, and the insoluble and infusible Due to the large content of high molecular weight polymer, 40 to 90 wt%, it is difficult to achieve high performance in both offset resistance and crushability. It is extremely difficult to produce toner that satisfies fixing properties (especially high-speed fixing), anti-offset properties, and pulverizability unless one is very dexterous.

Furthermore, when the amount of insoluble and infusible high molecular weight polymer increases, the melt viscosity becomes extremely high during heat kneading during toner production, so it is necessary to heat knead at a much higher temperature than usual or heat knead with a high shear. As a result, the former has the problem of deterioration of toner properties due to thermal decomposition of other additives, and the latter has the problem that the molecules of the binder resin are excessively cut, making it difficult to achieve the original anti-offset performance.

[0016] Also, in JP-A-60-166958,
A toner comprising a resin composition obtained by polymerization in the presence of low molecular weight polyα-methylstyrene having a number average molecular weight (Mn) of 500 to 1,500 has been proposed.

In particular, the publication states that the number average molecular weight (Mn) is preferably in the range of 9,000 to 30,000;
If Mn is increased in order to further improve offset resistance, fixing properties and pulverization properties during toner production become practical problems, and therefore it is difficult to satisfy offset resistance and pulverization properties with high performance. In this way, a toner with poor pulverizability during toner production is undesirable because not only does the production efficiency during toner production decrease, but also rough toner tends to be mixed into the toner, which may result in a scattered image.

[0018] Also, in Japanese Patent Application Laid-open No. 56-16144, GP
In the molecular weight distribution according to C, the molecular weight is 103 to 8 x 10
A toner containing a binder resin component having at least one maximum value in each of the molecular weight regions of 4 and 105 to 2.times.106 has been proposed.

Furthermore, JP-A-63-223662 discloses that the THF-insoluble content is 10 to 60% by weight based on the binder resin, and in the molecular weight distribution of the THF-soluble content by GPC, the weight average molecular weight/number average molecular weight ( Mw/Mn)≧
5, has a peak in the molecular weight range of 2 x 103 to 1 x 104, has a peak or shoulder in the molecular weight range of 1.5 x 104 to 1 x 105, and the component with a molecular weight of 1 x 104 or less is a binder resin. A toner containing 10 to 50% by weight has been proposed. In this case, the pulverization properties, fixing properties, filming and fusing to the photoreceptor, image properties, and offset resistance (especially offset resistance on the high temperature side) are excellent, but the offset resistance and fixing properties of the toner are also excellent. There is a need for improvement. In particular, it is difficult for this resin to meet severe conditions in which both fixing properties at low temperatures and anti-offset properties at high temperatures are required.

[0020] As described above, it is extremely difficult to achieve both high performance related to fixing and crushability. In particular, pulverization during toner production is an important factor as the particle size of toner is becoming smaller in response to demands for higher quality, higher resolution, and fine line reproducibility of copied images. Since the process requires a very large amount of energy, improving crushability is also important from the perspective of energy conservation.

[0021]Furthermore, the toner fusion phenomenon on the inner wall of the pulverizing device tends to occur with toner having good fixing performance, which deteriorates the pulverizing efficiency. As a further aspect, in another copying process, there is a process of cleaning the toner remaining on the photoreceptor after transfer. Nowadays, cleaning using a blade (blade cleaning) has become common in view of the miniaturization, weight reduction, and reliability of devices. With the longer lifespan of photoreceptors, the miniaturization of photoreceptor drums, and faster systems,
Toners are required to have higher resistance to adhesion to photoreceptors, anti-filming properties, etc. In particular, amorphous silicon photoreceptors that have recently been put into practical use have extremely high durability, and the lifespan of OPC (organic photoreceptors) is also increasing, so the various performances required of toners are becoming more advanced. There is.

[0022] Furthermore, miniaturization requires that each element be neatly accommodated in a narrow space. As a result, there is less space for air to flow properly, and the heat sources of the fixing device and exposure system are very close to the toner hopper and cleaner, exposing the toner to a high-temperature atmosphere. Therefore, it has become impossible to put toners into practical use unless they have better anti-blocking properties.

[0023] For example, the various performances required of toners, such as fixing properties and anti-blocking properties, are often contradictory, and moreover, it is increasingly desired and researched to satisfy both of them with high performance. However, there is still not enough available.

[0024]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner that solves the above-mentioned problems.

That is, an object of the present invention is to provide a toner that can be fixed at a low temperature and has excellent offset resistance over a wide temperature range from low to high temperatures.

Another object of the present invention is to provide a toner that does not cause fusion or filming on a photoreceptor even in high-speed systems and even after long-term use.

Another object of the present invention is to provide a toner that has excellent anti-blocking properties and can be used satisfactorily even in the high-temperature atmosphere of small machines.

A further object of the present invention is to provide a toner that can be produced efficiently and continuously because the crushed material is not fused to the inner wall of the device during the crushing process during toner production.

[0029]

[Means and effects for solving the problems] The present invention provides a magnetic toner for developing electrostatic images having at least a binder resin and a colorant, in which the THF-insoluble content of the binder resin is less than 10% by weight based on the binder resin. , the weight average molecular weight/number average molecular weight (=Mw/Mn) in GPC (gel permeation chromatography) of the THF soluble portion of the binder resin is ≧8, and the molecular weight is 1.5.
One molecular weight peak value MA between ~40,000, one molecular weight peak value MB between molecular weight 380,000 and 1 million, molecular weight 4
Each has a minimum molecular weight value Md between 10,000 and 380,000, and M
B/MA=10 to 70, and the area of the molecular weight distribution curve from molecular weight 400 to Md is SA, molecular weight Md to 50
When the area of the molecular weight distribution curve up to 00,000 is SB, and the area surrounded by the straight line connecting the apex of the molecular weight peak value MA and the apex of the molecular weight peak value MB and the molecular weight distribution curve is Sd,
SA:SB:Sd=1:0.2-0.5:0.2-0.
5. This is a magnetic toner for developing an electrostatic image, characterized in that:

[0030] In addition, the toner has a number average molecular weight of 3,000 or less, a weight average molecular weight of 12,000 or less, a weight average molecular weight/number average molecular weight (=Mw/Mn)≦4.0, and a melting point of 60 to 150°C. The molding agent is 1 based on the binder resin.
This is a magnetic toner for developing electrostatic images containing up to 10% by weight.

Furthermore, in the above toner, the binder resin is produced by mixing a polymer A having a weight average molecular weight of 20,000 to 60,000 and a polymer B having a weight average molecular weight of 400,000 to 1,500,000 in a solvent, and then removing the solvent. This is a magnetic toner for developing electrostatic images.

Furthermore, in the toner, a visual image of the toner is recorded by a fixedly supported heating body and a pressure member that is in opposing pressure contact with the heating body and brings the recording material into close contact with the heating body through a film. This is a magnetic toner for developing electrostatic images used in a heat fixing method for heat fixing onto materials.

The present invention will be explained in detail below.

In order to achieve the above-mentioned object, the inventors of the present invention have made extensive studies and found that the THF-insoluble content of the binder resin contained in the toner is less than a specific weight %, and the THF-soluble content is GPC It has been found that a molecular weight distribution of 100% is achieved with a specific configuration.

Furthermore, it has been found that this becomes noticeable when an anti-offset agent having a specific molecular weight and molecular weight distribution and a specific melting point is contained.

It has also been found that this is particularly well achieved when the binder resin is prepared by mixing a low molecular weight polymer and a high molecular weight polymer in a solvent and then removing the solvent.

[0037] In addition to the conventional heat roll fixing machine, in order to heat and fix the toner image on the recording material,
A heating element that is fixedly supported and a pressure member that is in pressure contact with the heating element and brings the recording material into close contact with the heating element via a film are used to heat and fix the visible image of the toner onto the recording material. It has been found that this toner is suitable for fixing systems.

T of the binder resin constituting the toner
The HF-insoluble content is less than 10% by weight, preferably 5% by weight or less, based on the binder resin. If THF-insoluble matter is contained in an amount of 10% by weight or more, the anti-offset property will improve, but the fixing property will tend to deteriorate, and it is difficult to satisfy both requirements to a high degree, which is not preferable.

[0039] In addition, the THF-insoluble portion of the binder resin has a weight average molecular weight/number average molecular weight (Mw/Mn) ≧8 according to molecular weight measurement by GPC, and has a molecular weight of 15,000 to 4
Molecular weight peak value MA between 10,000 and 1,000, molecular weight 380,000 to 1
One molecular weight peak value MB in 1,000,000, molecular weight 40,000 ~
Each has a molecular weight minimum value Md between 380,000 and MB/
MA=10-70, and as shown in Figure 1, the molecular weight is 4
The area of the molecular weight distribution curve from 00 to Md is SA, and the area of the molecular weight distribution curve from molecular weight Md to 5 million is SB.
, the area surrounded by the straight line connecting the apex of molecular weight peak value MA and the apex of molecular weight peak value MB and the molecular weight distribution curve is S.
When d, SA:SB:Sd=1:0.2~0.5
: The case where it is 0.2-0.5 is preferable. If even one of the above conditions is not satisfied, the object of the present invention cannot be achieved.

Weight average molecular weight/number average molecular weight (Mw/M
n) ≧8 or more, preferably 12 or more, more preferably 18-30. If Mw/Mn is less than 8, fixing properties tend to be improved, but offset resistance becomes poor, and toner deterioration causes fogging, scattering, and decreased density.

[0041] Molecular weight 15,000-40,000 and molecular weight 380,000-380,000.
One molecular weight peak value each (MA and M
B) and has a minimum molecular weight of 40,000 to 380,000, preferably MB/MA = 10 to 70, more preferably a molecular weight of 18,000 to 30,000 and a molecular weight of 400,000 to 400,000.
each having one molecular weight peak value between 700,000 and
Has a minimum molecular weight between 100,000 and 250,000, MB/MA=1
5 to 50. If these conditions are not satisfied, for example, if the molecular weight peak value MA is less than 15,000, the blocking resistance will be poor and filming or fusion to the photoreceptor will occur, and if the MA exceeds 40,000. In some cases, the fixing performance may be poor. Furthermore, if the molecular weight peak value MB is less than 380,000, the offset resistance may be poor, and fused substances may be generated in the device during the crushing process, and if it exceeds 1,000,000, the fixing property may be poor. At the same time, the crushability becomes poor and the productivity is also poor.

[0042] Molecular weight peak value ratio MB/MA=10~
70, preferably 15-50, and more preferably 30-100.

If MB/MA is less than 10 or more than 70, it becomes difficult to achieve both high fixing properties and anti-offset properties.

Area ratio of molecular weight distribution curve SA:SB:Sd
=1:0.2-0.5:0.2-0.5, preferably SA:SB:Sd=1:0.25-0.4:0.2
It is 5 to 0.4. If SB is less than 0.2, the anti-offset property tends to be poor, and if it exceeds 0.5, the fixing property tends to be poor and the crushability also tends to be poor. Sd
If it is less than 0.2, the fixing properties and/or anti-offset properties tend to be poor, and when it exceeds 0.5, the anti-offset properties tend to be poor.

The release agent preferably used in the toner of the present invention has a number average molecular weight of 3,000 or less, a weight average molecular weight of 12,000 or less, and a weight average molecular weight/number average molecular weight (Mw/
Mn)≦40, the melting point is 60 to 150°C, and the content is 0.1 to 20% by weight based on the binder resin. More preferably, number average molecular weight≦2500, weight average molecular weight≦7000, Mw/Mn≦3.0, melting point 60-120
℃, and the mold release agent has a temperature of 1 to
This is the case where the content is 10% by weight.

If the release agent used in the toner of the present invention does not satisfy these conditions, for example, if the melting point exceeds 150°C, the fixing properties will be adversely affected, and if the melting point is below 60°C, the offset resistance and toner has a negative effect on the blocking performance of Furthermore, if the content of the release agent exceeds 20% by weight, it will have a negative effect on blocking and fixing properties when the toner is left at high temperatures, and if it is less than 0.1% by weight, the toner offset prevention effect will be poor. It may be insufficient.

The binder resin used in the toner of the present invention is prepared by mixing a polymer A having a weight average molecular weight of 20,000 to 60,000 and a polymer B having a weight average molecular weight of 400,000 to 1,500,000 in a solvent.
It is produced by solvent removal. Preferably, it is produced by mixing a polymer A having a weight average molecular weight of 25,000 to 50,000 and a polymer B having a weight average molecular weight of 450,000 to 1,000,000 in a solvent, and then removing the solvent. Any solvent may be used as long as it dissolves the polymer A and the polymer B, such as toluene, xylene, 2-propanone, and the like.

In the production of the binder resin used in the toner of the present invention, Polymer A is produced by a solution polymerization method or suspension polymerization method, and Polymer B is produced by a suspension polymerization method or an emulsion polymerization method. Preferably, the polymer A is produced by a solution polymerization method and the polymer B is produced by a suspension polymerization method.

[0049] Polymer A and polymer B are mixed in a solvent and then removed in order to produce a binder resin having a uniform composition and molecular weight distribution. With other mixing methods, such as heating and melt-mixing using a kneader, it is difficult to obtain a binder resin with a uniform composition and molecular weight distribution. It is difficult to satisfy offset characteristics,
This is undesirable because the fused material is likely to form on the photoreceptor or the pulverized material is likely to be fused to the inner wall of the apparatus during the pulverization process.

If the weight average molecular weight of the polymer A is less than 20,000, the offset resistance will be poor and the crushability will also be poor. Furthermore, if the weight average molecular weight exceeds 60,000, the fixing performance will be poor.

When the weight average molecular weight of the polymer B is less than 400,000, it tends to have poor crushability, and at the same time, it causes a decrease in offset resistance, poor blocking properties, and the formation of fused substances on the photoreceptor, which is undesirable. .

[0052] If the weight average molecular weight exceeds 1,500,000, the crushability will be significantly deteriorated.

Even if Polymer A and Polymer B are used alone as a binder resin for toner, it is difficult to achieve the object of the present invention.
It is difficult to achieve the object of the present invention using a manufacturing method that involves melt-mixing. This is suitably achieved by a manufacturing method in which the solvent is removed after mixing in a solvent. By using the manufacturing method of the toner of the present invention, Polymer B can suitably satisfy contradictory properties such as anti-offset properties, fixing properties at low temperatures, and crushability.

[0054] The THF-insoluble content in the present invention refers to the weight percentage of the polymer component (substantially crosslinked polymer) that has become insoluble in the THF solvent in the resin composition of the toner. The THF-insoluble content is defined by the value measured as follows.

That is, toner sample 0.5 to 1.0
Weigh 1 g (W 1 g), and use a cylindrical filter paper (for example, N manufactured by Toyo Roshi Co., Ltd.).
o. 86R) and subjected to a Soxhlet extractor, extracted for 6 hours using 100 to 200 ml of THF as a solvent, evaporated the soluble components extracted by the solvent, and vacuum-dried at 100°C for several hours to extract the THF-soluble resin components. Weigh the amount (W2g). The weight of components other than resin components such as magnetic substances or pigments in the toner is assumed to be (W3 g). The THF-insoluble content is calculated from the following formula.

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 ml per minute to give a sample concentration of 0.05 to 0.6 weight. Measurement is performed by injecting 50 to 200 μl of a THF sample solution of the resin adjusted to %. 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. As a standard polystyrene sample for creating a calibration curve, for example, Pressure Chemical
Co. or manufactured by Toyo Soda Kogyo Co., Ltd. with a molecular weight of 6×1
02, 2.1×103, 4×103, 1.75×104
,5.1×104,1.1×105,3.9×105,
It is appropriate to use at least 10 standard polystyrene samples of 8.6×10 5 , 2×10 6 , and 4.48×10 6 . Further, an RI (refractive index) detector is used as a detector.

[0058] As a column, 103 to 2 x 10
In order to accurately measure the molecular weight range of 6, it is recommended to combine multiple commercially available polystyrene gel columns.
μ-styragel 500,10 manufactured by TERS
3,104,105 combination and Showa Denko's s
hodex KF-801, 802, 803, 804
, 805, 806, 807, or TSKgel G1000H, G2000 manufactured by Toyo Soda.
H, G2500H, G3000H, G4000H, G5
A combination of 000H, G6000H, G7000H, and GMH is preferred, and in the present invention, shodex KF801
Seven series of ~807 were used.

On the other hand, SA, SB and Sd of the molecular weight distribution curve of the binder resin used in the toner of the present invention are GP
Cut out the chromatogram by C, calculate the weight ratio, and
The weight percent of the HF-insoluble content was subtracted and the area ratio was calculated.

In the present invention, the molecular weight distribution of the mold release agent is G
Measured by PC under the following conditions.

<GPC measurement conditions> Equipment: GPC-150C (Waters) Column: Showdex KF-80M 2 series (Showa Denko) Temperature: 135°C Solvent: O-dichlorobenzene (0.1% ionol added) Flow rate : 1.0 ml/min Sample: A 0.15% sample is measured under conditions of injection of 0.4 ml or more, and a molecular weight calibration curve prepared using a monodisperse polystyrene standard sample is used to calculate the molecular weight of the sample.

In the present invention, the melting point of the mold release agent is determined by DSC-
7 (manufactured by Perkin Elmer) using a differential scanning calorimeter at a heating temperature of 10°C/min.
Measurement is carried out according to the temperature setting pattern of 18-82),
The temperature was defined as the peak top of the highest melting temperature.

The resin composition in the toner of the present invention is preferably one obtained by polymerizing one or more monomers selected from styrenes, acrylic acids, methacrylic acids, and derivatives thereof from the viewpoint of developing characteristics, charging characteristics, etc. Examples of monomers that can be used include styrene,
Examples include α-methylstyrene, vinyltoluene, and chlorostyrene. Acrylic acids, methacrylic acids and their derivatives include acrylic acid, methyl acrylate,
Ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, n-tetradecyl acrylate, n-hexadecyl acrylate, lauryl acrylate, cyclohexyl acrylate, diethylaminoethyl acrylate, dimethyl acrylate Examples include acrylic esters such as aminoethyl, as well as methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, and octyl methacrylate. , decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, glycidyl methacrylate, stearyl methacrylate, etc. Examples include methacrylic acid esters. In addition to the above-mentioned monomers, small amounts of other monomers may be used as long as the objects of the present invention can be achieved, such as acrylonitrile, 2-vinylpyridine, 4-vinylpyridine, vinyl carbazole, vinyl methyl ether, butadiene, isoprene, maleic anhydride, Maleic acid, maleic monoesters, maleic diesters, vinyl acetate, etc. may also be used.

The monomers mentioned above can be polymerized in the presence of an initiator and in the presence or absence of a crosslinking agent.

As the initiator, di-t-butyl peroxide, benzoyl peroxide, lauroyl peroxide, t-butyl peroxylaurate, 2,2'
-Azobisisobutyronitrile, 1,1'-bis(t-
butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,4-bis(t-butylperoxycarbonyl)cyclohexane, 2,2-bis(t- butylperoxy)octane, n-butyl 4,4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane, 1,3-bis(t-butylperoxy-isopropyl) ) benzene, 2,5-dimethyl-2,
5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 2,5-dimethyl-2,5-di(benzoylperoxy) Hexane, di-t-butyldiperoxyisophthalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, di-t-butylperoxyα-methylsuccinate, di-t-butylperoxycyclohexyl -butylperoxydimethylglutarate, di-t-butylperoxyhexahydroterephthalate, di-t-butylperoxyazelate, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, Diethylene glycol
Bis(t-butylperoxycarbonate), di-t-
Butyl peroxytrimethyl adipate, tris(t-
butylperoxy)triazine, vinyltris(t-butylperoxy)silane, etc., and these can be used alone or in combination.

Next, as a crosslinking agent, a compound having two or more polymerizable double bonds can be mainly used. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; carboxylic acid esters with two double bonds such as ethylene glycol diacrylate, triethylene glycol diacrylate, and bisphenol diethylene glycol diacrylate; divinyl ether, divinyl sulfide , divinyl compounds such as divinyl sulfone, and compounds having three or more vinyl groups may be used alone or as a mixture.

[0067] These crosslinking agents are preferably not included at all in order to keep the THF-insoluble matter to less than 10% by weight, but if they are included, the amount is less than 1% by weight, preferably 0.5% by weight or less, based on the binder resin. , more preferably 0.
The content is 2% by weight or less.

The toner used in the present invention has a number average molecular weight Mn of 3.0×10 3 or less, a weight average molecular weight Mw
is 1.2 x 104 or less, Mw/Mn 4.0 or less, melting point m
At least one type of release agent having p in the range of 60 to 150° C. is used in an amount of 0.1 to 20% by weight based on the toner.

Examples of release agents preferably used in the toner of the present invention include paraffin wax, low molecular weight polyethylene wax, and polyolefin wax graft-modified with unsaturated fatty acids, styrene derivatives, or unsaturated fatty acid esters. Among these, graft-modified polyolefin waxes are particularly preferred from the viewpoint of prolonging the life of the developer and machines such as copying machines that use the developer and being free from service and maintenance.

The unsaturated fatty acids or unsaturated fatty acid esters used to synthesize the graft-modified polyolefin include methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate,
n-Butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, staryl methacrylate, dodecyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, methacrylic acid-2
-Methacrylates such as hydroxyethyl, 2,2,2-trifluoroethyl methacrylate, glycidyl methacrylate, acrylic acid and methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, lauryl acrylate , stearyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, 2-chloroethyl acrylate, 2-hydroxyethyl acrylate, cyclohexyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dibutylaminoethyl acrylate, 2-ethoxy acrylate, Acrylates such as 1,4-butanediol diacrylate, maleic acid, fumaric acid, itaconic acid, citraconic acid and monoethyl maleate, diethyl maleate, monopropyl maleate, dipropyl maleate, monobutyl maleate, Dibutyl maleate, di-2-ethylhexyl maleate, monoethyl fumarate, diethyl fumarate, dibutyl fumarate, di-2-ethylhexyl fumarate, monoethyl itaconate, diethyl itaconate, monoethyl citraconate, diethyl citraconate Examples include unsaturated dibasic acid esters such as esters of unsaturated dibasic acids, and one type or two or more types of these can be used simultaneously.

The aromatic vinyl monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, 2,4 dimethylstyrene, p-ethylstyrene, p-n-butylstyrene, Examples include p-tert-butylstyrene, p-n-dodecylstyrene, p-phenylstyrene, and p-chlorostyrene, and one or more of these can be used simultaneously.

[0072] As a method for graft modification, conventionally known methods can be used. For example, the polyolefin, an aromatic vinyl monomer, and an unsaturated fatty acid or an unsaturated fatty acid ester are dissolved in a molten state or a solvent and heated in the atmosphere or under pressure in the presence or absence of a radical initiator to react. A graft-modified polyolefin is obtained. Grafting with an aromatic vinyl monomer and an unsaturated fatty acid or an unsaturated fatty acid ester may be carried out simultaneously or individually.

[0073] As the initiator used for the grafting reaction,
For example, benzoyl peroxide, dichlorobenzoyl peroxide, di-tert-butyl peroxide, lauroyl peroxide, tert-butyl perphenylacetate, cumin perpivalate, azobis-isobutyronitrile, dimethylazoisobutyrate,
Dicumyl peroxide and the like can be mentioned.

The toner used in the present invention is made of the above-mentioned constituent materials, has a number average molecular weight Mn of 3.0×10 3 or less,
Weight average molecular weight Mw is 1.2 x 104 or less, Mw/Mn
4.0 or less, melting point mp. In addition to the mold release agent having a temperature in the range of 60 to 150°C, one or more mold release agents similar to those of the above constituent materials having a melting point of over 150°C may be mixed and used.

As the charge control agent used in the toner of the present invention, conventionally known positive or negative charge control agents can be used. Charge control agents known in the art today include the following:

(1) The following substances can be used to control the toner to be positively charged.

Nigrosine, azine dyes containing an alkyl group having 2 to 16 carbon atoms (Japanese Patent Publication No. 1627/1983), basic dyes (for example, C.I. Basic Yellow
w 2 (C.I.41000), C.I. I. Bas
ic Yellow 3,C. I. Basic
Red 1 (C.I. 45160),
C. I. Basic Red 9 (C.
I. 42500), C. I. BasicVio
let 1 (C.I.42535), C. I
．． Basic Violet3 (C.I.4
2555), C. I. Basic Viol
et 10 (C.I. 45170), C. I
．． Basic Violet 14 (C.
I. 42510), C. I. Basic B
lue 1 (C.I.42025), C. I
．． Basic Blue 3 (C.I.5
1005), C. I. Basic Blue
5 (C.I. 42140), C. I.
Basic Blue 7 (C.I.4259
5), C. I. Basic Blue 9
(C.I.52015), C. I. Basic
Blue24 (C.I.52030), C. I
．． Basic Blue 25 (C.I.52
025), C. I. Basic Blue
26 (C.I.44025), C. I. Basi
c Green 1 (C.I.42040),
C. I. Basic Green 4
(C.I.42000), these basic dye lake pigments (as lake agents, phosphotungstic acid,
Phosphormolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide,
ferrocyanide, etc.), C. I. Sovent Bla
ck 3 (C.I.26150), Hansa Yellow G (C.I.11680), C.I. I. Mor
dlant Black 11, C. I. Pi
gment Black 1st prize.

Alternatively, for example, benzolmethyl-hexadecyl ammonium chloride, decyl-trimethyl ammonium chloride, dialkyltin compounds such as dibutyl and dioctyl, metal salts of higher fatty acids, inorganic fine powders such as glass, mica, and zinc oxide, EDTA, acetylacetone, etc. Polyamine resins such as metal complexes, vinyl polymers containing amino groups, condensation polymers containing amino groups, etc. In particular, from the viewpoint of dispersibility, nigrosine, metal salts of higher fatty acids, vinyl polymers having amino groups, etc. are preferable.

(2) The following substances can be used to control the negative chargeability of toner. Special Publication No. 41-20153, No. 4
No. 2-27596, No. 44-6397, No. 45-26
Examples include metal compounds of monoazo dyes such as those described in No. 478.

[0080] Nitrohumic acid and its salts or C.I. I. 1464
Dye and pigments such as 5, Special Publication No. 55-42752, Special Publication No. 5 of the 1970s
No. 8-41508, Special Publication No. 58-7384, Special Publication No. 58
Zn, Al, Co, Cr, F of salicylic acid, naphthoic acid, dicarboxylic acid described in No. 9-7384 etc.
metal compounds such as e, sulfonated copper phthalocyanine pigments, nitrile groups, halogen-introduced styrene oligomers, chlorinated paraffins, etc. In particular, from the viewpoint of dispersibility, metal compounds of monoazo dyes, metal compounds of salicylic acid, alkylsalicylic acid, naphthoic acid, and dicarboxylic acid are preferred.

Good results can also be obtained with the toner of the present invention when additives are mixed therein as required. Examples of additives include lubricants such as Teflon, zinc stearate, and polyvinylidene fluoride, with polyvinylidene fluoride being preferred. Alternatively, abrasives such as cerium oxide, silicon carbide, and strontium titanate, among which strontium titanate is preferred. Alternatively, fluidity imparting agents such as colloidal silica and aluminum oxide, particularly hydrophobic colloidal silica, are preferred. Caking inhibitors, conductivity imparting agents such as carbon black, zinc oxide, antimony oxide, tin oxide, fixing aids such as conventionally used low molecular weight polyethylene, low molecular weight polypropylene, various waxes, etc. There are offset agents. Further, a small amount of white fine particles and black fine particles of opposite polarity can be used as a developing property improving agent.

The magnetic materials used 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 iron cobalt and nickel; or these metals and aluminum; cobalt, copper, lead, magnesium, tin, zinc, antimony,
Examples include alloys with metals such as beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures thereof. These ferromagnetic materials have an average particle diameter of about 0.1 to 2 μm, preferably about 0.1 to 0.5 μm, and are contained in the toner in an amount of 20 to 200 parts by weight, preferably 20 to 200 parts by weight per 100 parts by weight of the resin component. is 40 to 1 per 100 parts by weight of the resin component.
It is 20 parts by weight.

To prepare the magnetic toner for developing electrostatic images according to the present invention, the resin composition and magnetic powder according to the present invention,
If necessary, charge control agents, pigments or dyes as colorants, additives, etc. are thoroughly mixed using a ball mill or other mixer, and then melted, kneaded, and mixed using a heat kneader such as a heated roll, kneader, or extruder. Pigments or dyes are dispersed or dissolved in the mixture, which is kneaded to make the resins compatible with each other, cooled and solidified, and then pulverized and classified to obtain a toner having an average particle size of 3 to 20 μm.

[0084]

[Examples] The present invention will be specifically explained below using Examples, but these are not intended to limit the invention in any way. Note that the parts in the following formulations are parts by weight.

Synthesis Example 1 200 parts of toluene was placed in a reactor and heated to reflux temperature. A mixture of 84 parts of styrene monomer, 16 parts of butyl acrylate, and 5 parts of di-tert-butyl peroxide was added dropwise to this at 100° C. over 4 hours. Furthermore, solution polymerization was completed under refluxing of toluene, and toluene was removed. The obtained styrene-butyl acrylate copolymer had a weight average molecular weight of 32,000, and a peak molecular weight (MA) of 3.05.
It was 10,000. This is referred to as polymer a-1 of the binder resin related to the toner of the present invention.

Synthesis Examples 2 to 5 Solution polymerization was carried out in the same manner as in Synthesis Example 1 using the monomer composition, polymerization initiator, and solvent shown in Table 1 to obtain binder resin polymers a-2 to 1 according to the present invention. A-5 was obtained.

[0087]

[Table 1]

Synthesis Example 6

[0089]

[Table 2] 200 parts of degassed water in which 0.1 part of partially saponified polyvinyl alcohol was dissolved was added to a reactor, and the monomer composition shown in Table 2 was added to form a suspension dispersion. The above suspension dispersion is heated to 80° C. under a nitrogen atmosphere. At that temperature 2
The polymerization reaction was completed by holding for 4 hours. After cooling to room temperature,
The spherical polymer particles produced by the polymerization reaction were filtered, thoroughly washed with water, dehydrated, and dried to obtain a binder resin polymer b-1 for the toner of the present invention. still,
The weight average molecular weight was 825,000, the peak molecular weight was 807,000, and Tg was 65°C.

Synthesis Examples 7 to 10 Synthesis Example 7 was carried out using the monomer composition and polymerization initiator shown in Table 3.
Suspension polymerization was carried out in the same manner as above to obtain binder resin polymers b-2 to b-5 for the toner of the present invention.

[0091]

[Table 3]

Comparative synthesis example 1

[0093]

[Table 4] Comparative Polymer 1 was obtained in the same manner as Synthesis Example 1 except that the monomer composition shown in Table 4 was used. In addition, the weight average molecular weight is 70
00, the peak molecular weight was 6500, and Tg=64°C.

Comparative synthesis example 2

[0095]

[Table 5] Comparative Polymer 2 was obtained in the same manner as Synthesis Example 6 except that the monomer composition shown in Table 5 was used. Furthermore, the weight average molecular weight is 27
The peak molecular weight was 252,000, and Tg was 60°C.

Next, an example of manufacturing the binder resin for the toner of the present invention will be described.

Production Example 1 70 parts of polymer a-1 and 30 parts of polymer b-4 are added to 200 parts of xylene with stirring. Next 6
Heat to 0°C to completely dissolve added polymers a-1 and b-4. After continued stirring for about 2 hours, the xylene was removed. This is used as binder resin 1 for the toner of the present invention.
shall be.

Production Examples 2 to 7 Binder resins 2 to 7 for toners of the present invention were obtained in the same manner as Production Example 1 except that the polymers shown in Table 6 were used.

Comparative Binder Resin Production Examples 1 and 2 Comparative binder resin 1 was produced in the same manner as Production Example 1 except that 90 parts of comparative polymer a-1 and 10 parts of b-2 were used.
I got it. Production Example 1 except that the polymer shown in Table 6 was further used.
Comparative binder resin 2 was obtained in the same manner as above.

[0100]

[Table 6]

Example 1 Binder resin 1
10
Part 0 Magnetic material

80 parts Negative charge control agent

2 parts low molecular weight polyethylene
4 parts The above materials were premixed in a Henschel mixer, and then kneaded for 20 minutes in a two-roll mill heated to 150°C. After cooling the kneaded material, it was roughly pulverized using a cutter mill, then pulverized using a pulverizer using a jet stream, and further classified using an air classifier to obtain a black fine powder with a weight average particle size of 8.5 μm. I got it.

[0102] 0.4 parts of colloidal silica fine powder is dry mixed with 100 parts of the black fine powder, and a developer (toner) is prepared.
I got it. This is referred to as toner 1 of the present invention.

[0103] The pulverizability of toner can be expressed as the amount of toner that can be pulverized per unit time.
Met. Furthermore, no fusion occurred inside the crusher.

[0104] The blocking property was also examined by looking at the change in the degree of aggregation when about 10 g of toner was placed in a 100 cc polycup and left at 50°C for one day. The degree of aggregation was measured using a powder tester manufactured by Hosokawa Micron. The product left at room temperature and the product left at 50° C. for one day showed almost the same values at 9% by weight and 12% by weight, and the difference (ΔG) was 3%, confirming that there was no substantial blocking.

Regarding fixing properties, offset properties, wrapping properties, image quality, and durability, Canon's copying machine NP-1
The investigation was conducted using a modified 215 aircraft.

In particular, the offset property was evaluated by removing the cleaning mechanism of the fixing roller and determining the number of copies it took to stain the image or stain the roller based on the number of copies that could be made.

A test was conducted by lowering the set temperature of the fixing device by 5°C. The fixing property is approximately 100g by moving the image back and forth 10 times on Silvon C paper.
Rubbing with load, reflecting peeling of image Density reduction rate (%)
It was expressed as The evaluation image is 200 when 200 consecutive images are taken.
I saw it for the first time.

[0108] The wrapping property was determined by producing three completely black images and checking the appearance of the marks left by the peeling tabs of the fixing roller on the images, and how much the film relied on the tabs.

As a result, the fixing performance was very good with a reduction rate of 3%, the offset performance was good with no roller stains on the image even after printing 50,000 sheets, and the wrapping performance was also good with no traces caused by the claws on the image. Although it was slightly attached, it was very good.

[0110] Furthermore, a durability test was carried out on about 10,000 sheets using images with an image area ratio of about 5%, and the images were found to be good.

[0111] The low molecular weight polyethylene used in this example had a number average molecular weight of 880, a weight average molecular weight of 2500, a weight average molecular weight/number average molecular weight = 2.8, and a melting point of 97.
It was ℃.

[0112] Furthermore, the THF-insoluble content of this toner is 4% by weight.
The weight average molecular weight by GPC of the THF soluble portion/
Number average molecular weight = 23.8, molecular weight peak MA = 29,000, molecular weight peak MB = 823,000, MB/MA = 28.
4. Area of molecular weight distribution curve SA:SB:Sd=1:0.
36:0.33.

Example 2 Binder resin 2
10
Part 0 Magnetic material

80 parts Positive charge control agent

Part 2 Graft modified wax
4 parts The above materials were premixed in a Henschel mixer, and then kneaded for 20 minutes in a two-roll mill heated to 150°C. After cooling the kneaded material, it was roughly pulverized using a cutter mill, then pulverized using a pulverizer using a jet stream, and further classified using an air classifier to obtain a black fine powder with a volume average particle size of 8.7 μm. I got it.

[0114] 0.6 parts of colloidal silica fine powder is dry mixed with 100 parts of the black fine powder, and a developer (toner) is prepared.
I got it. This is referred to as toner 2 of the present invention.

[0115] The pulverizability of toner can be expressed as the amount of toner that can be pulverized per unit time.
And it was very good. Furthermore, no fusion occurred inside the crusher.

[0116] The blocking property was also examined by looking at the change in the degree of aggregation when about 10 g of toner was placed in a 100 cc polycup and left at 50°C for one day. The degree of aggregation was measured using a powder tester manufactured by Hosokawa Micron. The product left at room temperature and the product left at 50° C. for one day showed almost the same values at 17% by weight and 21% by weight, and the difference (ΔG) was 4%, confirming that there was no substantial blocking.

Regarding fixing properties, offset properties, wrapping properties, image quality, and durability, Canon's copying machine NP-4
The investigation was conducted using a modified 835 machine (fixing temperature set at 200° C.).

In particular, the offset property was evaluated by removing the cleaning mechanism of the fixing roller and determining the number of copies it took to stain the image or stain the roller.

A test was conducted by lowering the set temperature of the fixing device by 10°C. The fixability is approximately 100% when the image is transferred back and forth 10 times on Silvon C paper.
Rub the image with a load of
).

[0120] The wrapping property was determined by producing three completely black images and checking the appearance of the marks left by the peeling tabs of the fixing roller on the images, and how much the film relied on the tabs.

[0121] As a result, the fixing property was very good with a reduction rate of 4%, the offset property was good with no roller stains on the image even after printing 1,000 sheets, and the wrapping property was also good with no marks on the image due to the dependence on the claws. Although it was slightly attached, it was very good.

[0122] Furthermore, a durability test was carried out on about 30,000 sheets using images with an image area ratio of about 5%, and the images were good, with no fusion or filming on the photoreceptor, etc.

[0123] The graft-modified wax used in this example was a styrene-modified polyethylene wax with a number average molecular weight of 530, a weight average molecular weight of 820, a weight average molecular weight/number average molecular weight = 1.5, and a melting point of 91°C. .

[0124] Furthermore, the THF-insoluble content of this toner is 2% by weight.
The weight average molecular weight by GPC of the THF soluble portion/
Number average molecular weight = 24.7, molecular weight peak MA = 3120
0, molecular weight peak MB=623,000, MB/MA=20
．． 0, area of molecular weight distribution curve SA:SB:Sd=1:0
．． 35:0.31.

Example 3 Using the toner produced in Example 2, an unfixed image was obtained using a modified Canon FC-5 copying machine.

The fixing test for unfixed images was carried out using an external fixing device as shown in FIG. 2, which comprises a pressure member that is in pressure contact with a heating body and brings the recording material into close contact with the heating body through a film. Ta. As the material of the fixing film 5, a release layer made of polyimide film added with a fluororesin and a conductive material is used.
An endless film coated with 0 μm was used. As the pressure roller 8, silicone rubber is used, and the nip 3
．． 5 mm, and the process speed was 50 mm/sec. The film is driven by the drive and tension of the drive roller 6 and the driven roller 7 to move the film in the direction of the arrow without wrinkles. (The heating element 1 is a linear heating element with a low heat capacity, and the temperature is regulated by applying energy in a pulsed manner.) The temperature control temperature is the fuser of a modified Canon copier FC-5 (fixing set temperature 180).
The test was carried out at the same temperature (15°C) and at a temperature lowered by 15°C. As a result, the fixability was good, with a decrease rate of 2% and no stains on both the image and the fixing film even after 3,000 sheets.

Examples 4 to 8 Toners 3 to 7 of the present invention were obtained in the same manner as in Example 1 except that the binder resin was changed to those shown in Table 7. Table 8 shows the evaluation results of these toners. Ta.

Comparative Example 1 Comparative Toner 1 was obtained in the same manner except that Binder Resin 2 used in Example 2 was replaced with Comparative Binder Resin 1.

Using a modified FC-5 machine, fixing properties, offset properties, wrapping properties, image quality, durability, etc. were investigated.

As a result, although the fixing performance was good, stains occurred on both the image and the roller from the first sheet. As for the wrapping property, traces from the claws were left on the image, and in some cases, the paper was not ejected from the fixing machine.

[0131] The THF soluble content of this toner is 2% by weight, the weight average molecular weight/number average molecular weight of the THF soluble content by GPC = 38.2, molecular weight peak MA = 6500,
MB=65.7, MB/MA=100, SA:SB:S
d=1:0.12:0.48.

Comparative Example 2 Comparative toner 2 was obtained in the same manner except that binder resin 2 used in Example 2 was replaced with comparative binder resin 2 (see Table 7), and evaluated in the same manner as in Examples 4 to 8. The results are shown in Table 8.

[0133]

[Table 7]

[0134]

[Table 8]

[0135]

Effects of the Invention The present invention focuses on the amount of THF-insoluble components of the binder resin contained in the toner and the molecular weight distribution of the THF-soluble components in GPC. It has excellent offset resistance over a wide temperature range, does not adhere to photoreceptors, etc., has excellent crushability, and can provide stable and good developed images even after long-term use.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a molecular weight distribution curve determined by GPC.

FIG. 2 is an explanatory diagram of a fixing device used in a fixing test for unfixed images.

Claims (4)

[Claims] 1. A magnetic toner for developing electrostatic images comprising at least a binder resin and a magnetic material, wherein the THF-insoluble content of the binder resin is less than 10% by weight based on the binder resin, and the THF-soluble content of the binder resin is GPC
Weight average molecular weight/number average molecular weight (Mw/Mn) in gel permeation chromatography (gel permeation chromatography) ≧8, one molecular weight peak value MA between 15,000 and 40,000, and one molecular weight peak value MA between 380,000 and 1,000,000. One molecular weight peak value MB between them, and one molecular weight minimum value Md between 40,000 and 380,000 molecular weights.
MB/MA=10 to 70, and the area of the molecular weight distribution curve from molecular weight 400 to Md is SA,
The area of the molecular weight distribution curve from molecular weight Md to 5 million is SB, the peak of molecular weight peak value MA and the molecular weight peak value MB
When the area surrounded by the straight line connecting the vertices of and the molecular weight distribution curve is Sd, SA:SB:Sd=1:0.2~0
．． 5: A magnetic toner for developing an electrostatic image, characterized in that the ratio is from 0.2 to 0.5. Claim 2: Number average molecular weight 3000 or less, weight average molecular weight 12,000 or less, weight average molecular weight/number average molecular weight (
2. The magnetic toner for developing electrostatic images according to claim 1, which contains a release agent having a melting point of 60 to 150[deg.] C. in an amount of 0.1 to 20% by weight based on the binder resin. [Claim 3] The binder resin is produced by mixing a polymer A having a weight average molecular weight of 20,000 to 60,000 and a polymer B having a weight average molecular weight of 400,000 to 1,500,000 in a solvent, and then removing the solvent. The magnetic toner for electrostatic image development according to claim 1 or 2. 4. The toner image is heated and fixed on the recording material by a fixedly supported heating body and a pressure member that is in opposing pressure contact with the heating body and brings the recording material into close contact with the heating body through a film. 4. The magnetic toner for developing electrostatic images according to claim 1, wherein the magnetic toner is used in a heat fixing method.