JPS6088961A - Positive charge type magnetic toner for heat roll fixing - Google Patents

Abstract

PURPOSE:To improve positive chargeability of a magnetic toner and to enable all types of heat roll fixing by constituting a toner of a thermoplastic resin, magnetic powder and nigrosine dye and adding a partly crosslinked styrene-butadiene copolymer, amide wax or ethylene bis-fatty acid amide and low mol.wt. PP thereto. CONSTITUTION:An alpha-methylene aliphat. monocarboxylic acid alkyl ester copolymer contg. methyl methacrylate as an essential component is most preferred for positive chargeability of a toner. A partly crosslinked styrene/butadiene copolymer having about 50,000-100,000mol.wt. and about 10-50wt% gel content is effective as the resin having a releasing characteristics A better effect is obtd. if amide wax having the m.p. ranging 140-150 deg.C or ethylene bis-fatty acid amide and PP having <=50,000mol.wt. are added thereto as a releasing agent. Alloys or compds. contg. elements exhibiting ferromagnetism such as iron, cobalt, nickel, etc. in addition to ferrite and magnetite and various other alloys, etc. which exhibit ferromagnetism when subjected to certain treatment such as heat treatment are used as the magnetic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic developer, and particularly to a magnetic toner for heat roll fixing that has good positive chargeability.

Conventionally, electrophotography uses electrostatic fl! 1M 'a' is formed, and a carrier such as glass beads or iron powder is mixed with insulating colored fine powder toner on the latent image surface, and a developer in which the toner is triboelectrically charged is brought into contact with the electrostatic latent image. Perform development.

Therefore, a method of directly recording the image or transferring the image by stacking transfer sheets and applying an electric field is commonly used.

On the other hand, magnetic toners that do not use the carrier are attracting attention for the purpose of making electrophotographic copying devices simpler and more compact and maintenance-free. Magnetic toner is magnetite)
(J'ts Oa), which has a magnetic powder having strong saturation magnetization and a certain degree of coercive force, dispersed in a resin, has been actively used in developing electrostatic latent images in recent years. In this magnetic toner.

A known method is to add conductive particles such as carbon black to the inside and/or surface of the toner to make it conductive, and to conduct development by inducing an opposite charge to the electrostatic latent image from a grounded developing device. (Refer to Japanese Patent Publication No. 56-2705).

A magnetic toner used in such a system is also known (US Pat. No. 3,639,245). This type of conductive magnetic toner is an electrostatic latent image formed on photosensitive paper or electrostatic recording paper that is directly developed and fixed, and each paper requires special processing and expensive paper. . Therefore, recently, a PPC method using magnetic toner, that is, a method in which an electrostatic latent image formed on a photoreceptor such as selenium, zinc oxide, or an organic photoconductor is developed and then transferred to plain paper is used. As demand has increased, PPC copying machines that partially use magnetic toner have also been put into practical use. In this case, the price of the transfer sheet is also low, and there are many advantages.

In order to use this method, it is necessary to increase the electrical resistance of the magnetic toner in order to improve transferability. However, when the electrical resistance increases, the amount of charge caused by induction charging of the toner decreases, resulting in a decrease in developability and transferability. Therefore, by increasing the charging characteristics of the photoreceptor and devising a developing method.

It is necessary to increase the amount of charge on the toner. A method has already been proposed in which a toner having a small amount of carbon black added to its surface is strongly stirred in a developing device to increase the amount of charge of the toner (Japanese Patent Application Laid-open No. 31136/1983).

On the other hand, a certain kind of dye having a charge control function is added to the toner (% JP-A-56-101150),
By adding a large amount of hydrophobic silica fine powder to the outside of the toner,
There is a method of increasing the triboelectricity of the toner itself (Japanese Patent Application Laid-Open No.
5-118049, 55-135854). According to this method, the toner is frictionally charged with the doctor blade or non-magnetic sleeve of the developer and retains a certain amount of charge, so it exhibits good development and transfer characteristics without being affected by the charging characteristics of the photoreceptor. I know. However, conventional magnetic toners generally have excellent negative triboelectric charging characteristics, and development methods that require positive triboelectric charging characteristics include, for example, a reversal development method using a positively charged selenium photoconductor, and a negatively charged oxidation Application of magnetic toner to regular development methods for zinc or organic photoreceptors has been delayed.

Also, as a fixing method for transferred toner.

The following methods are used: a pressure fixing method using only a pressure roll at room temperature, a heat fixing method using oven heating, a flash fixing method using a halogen lamp, etc., and a heat fixing method using a heat roll. Among these, pressure fusing has the advantage of requiring less power consumption and allowing quick start, but has the disadvantage of weak absolute fixing performance, while open fusing and flash fusing have strong fixing performance but are difficult to fix at high speeds. It has the disadvantage of being bad. Against these l-heat roll adhesion-
C has good fixing properties and is effective in high-speed fixing.
・There are advantages.

In heat roll fixing, as the toner comes into pressure contact with the heat roll surface in a heated and molten state, part of the toner adheres to the roll surface and then adheres to the paper again, which tends to cause an offset phenomenon that smears the image, so this should be avoided as much as possible. There is a need to.

There are two types of heat roll fixing methods: 1. For example, there is a type in which a heat roll coated with silicone rubber or fluororesin, which has good mold releasability, is coated with a mold release agent such as silicone oil. There is a type that is used as a heat roll made of impregnated silicone rubber. These devices require an accessory device for supplying silicone oil, and if the supply of silicone oil is stopped, offsets and throats occur, resulting in poor reliability. Therefore, recently, a device in which a metal roll is thinly coated with Teflon has been developed, and a system in which a small amount of silicone oil is supplied or no silicone oil is supplied has been used.

On the other hand, various methods have been proposed from the viewpoint of material composition to prevent toner offset. For example, a method of using a specific m-lipid for toner fixing and increasing its molecular weight distribution (Japanese Patent Publication No. 55-6895);
A liquid or solid resin with mold release properties is mixed with a specific fixing resin.

How to prevent toner from adhering to the heat roll
-15655, 53-21655, 55-25
No. 084, No. 53-25496, No. 55-25655
No. 53-25654 and No. 55-25655).

These methods have been proposed for raw two-component toner, and because magnetic toner contains a large amount of magnetic powder that does not melt at normal fixing temperatures, the above-mentioned prior art cannot be applied as is. there were. Therefore, a
As a method for preventing the 5° offset of a toner, a specific styrene-(meth)acrylic copolymer or a styrene heptadiene copolymer is combined with a diolefin rubber-like substance, a low molecular weight polyalkylene, polyethylene wax, etc. A method of adding a mold release agent was proposed (JP-A-55-130548;
6-37548). According to the study by the inventors,
Although these magnetic toners have excellent anti-offset properties, they are inferior in positive chargeability, so a reversal development method using a positively charged selenium photoreceptor, or a negatively charged zinc oxide or organic photoreceptor is used. It has been found that the regular development method has drawbacks that make it inapplicable.

In view of the above circumstances, the present invention provides excellent reversal and regular developability for positively charged selenium photoreceptors, negatively charged zinc oxide, or organic photoreceptors, respectively.
In addition, we provide magnetic toner for heat roll fixing that is compatible with all types of heat roll fixing, has good high-speed fixing properties, can minimize offset phenomenon, and has excellent positive chargeability and excellent storage stability. The purpose is to

The magnetic toner of the present invention is manufactured by the above-mentioned Japanese Patent Publication No. 56-57548.
The magnetic toner composition proposed in the above publication is further improved, and is composed of a thermoplastic resin, magnetic powder, and nigrosine dye. To improve coalescence and prevent toner offset, partially crosslinked styrene-butadiene copolymer, amide wax or ethylene bis fatty acid amide, and low molecular weight polypropylene are added to 770.
It is characterized by what it did.

The present invention aims to provide a magnetic toner with excellent positive chargeability, but for this purpose, it is necessary to consider the triboelectric chargeability of the toner material itself. As the resin, styrene-acrylic copolymer is suitable from the standpoint of heat roll fixing.

This styrene-acrylic copolymer may include many types of copolymers depending on the monomer composition of the copolymer. already,
Focusing on the positive chargeability of the toner, we developed an acrylic copolymer containing 7 alkylamide groups (% 1989-102635, 54-
Publications No. 124731 and No. 54-145647),
Nitrogen-containing heterocyclic vinyl copolymer (Japanese Patent Application Laid-Open No. 54-15542
No. 54-89640) have been proposed, but these resins have problems in moisture resistance and have not been put into practical use. Therefore. In the present invention, as a result of examining styrene-acrylic copolymers other than those mentioned above, it was found that an α-methylene aliphatic monocarboxylic acid alkyl ester copolymer containing methyl methacrylate as an essential component is the best for positively charging the toner. Understood. This is because conventional styrene-acrylic copolymers contain styrene and polar functional groups with strong electron-attracting properties, which weakens the positive triboelectric charging properties of the resin.

It is thought that the positive chargeability of the toner is reduced.

The above-mentioned (meth)acrylic copolymer is required to have resin physical properties within a specific range in order to improve toner storage stability, fixing properties during heat roll fixing, and offset resistance. Generally in heat roll fixing.

The temperature of the roll is in the range of 150 to 180[deg.] C., and resin properties that provide good fixing properties and anti-offset properties must be selected within this range. As a result of examining the melt index (Ml) value and reduced viscosity as resin physical properties, the inventors found that the melt index (Ml) value (founded value at a load of 5 to 9 and a temperature of 150 t! based on ASTM D125B) was 15.
~25 f/10 mtn, reduced viscosity (0,5 f/
dl chloroform solution, sub-determinant value at 20υ) is 0.6~
It has been found that a resin suitable for all types of heat roll fixing can be obtained when D and Bdt/f are within the range.

Further, in order to improve the storage stability of the toner (the property that the toner does not cause blocking phenomenon during storage or in the developing box), the glass transition temperature of 9 gB fat needs to be 60 fat or higher. However, if the glass transition temperature of fat 11 is too high, the melt viscosity of the toner increases.

The upper limit of the glass transition temperature of 41 fat and fat can be set to 7011+ since the fixing properties are lowered.

Through the above studies, the main resin of the present invention can be obtained. Representative examples of the monomer components constituting the main resin of the present invention are as follows. For example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, furovir acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, ethylhexyl acrylate, stearyl acrylate, methacrylate! /rR ethyl, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,
Examples include n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, and methyl methacrylate.

For the synthesis of the copolymer of the present invention, ordinary polymerization methods applicable to (meth)acrylic copolymers, such as solution polymerization, suspension polymerization, and bulk polymerization, are employed. This is carried out using an initiator with sufficient initiator function, such as oxide, azobisisobutyronitrile, etc.

In addition, the melt index value, glass transition temperature, and ring base viscosity of the copolymer can be adjusted by the type of monomer, blending ratio, and amount of initiator, but if desired, they can also be adjusted by using a suitable chain transfer agent. can.

The magnetic toner of the present invention can almost achieve the above-mentioned purpose by using a methanoacrylic copolymer, but as a magnetic toner for heat roll fixing, it can be used at a wide range of fixing speeds as possible for any type of fixing roll. There is a need for a toner that is effective in preventing offset in the range of fixation temperature and fixing temperature.The present inventors therefore developed a magnetic toner containing the above-mentioned (meth)acrylic copolymer that further improves release properties. As a result of considering the addition of a resin with a molecular weight of approximately s
o, o o o~100,000. Gel content is approximately 1
Partially crosslinked styrene-butadiene copolymer weighing 0 to 50% by weight is effective.

It turns out that there is a fruit. Also, the melting point is 140-150
It has been found that it is effective to add amide wax or ethylene bis fatty acid amide in the range of υ and polypropylene with a molecular weight of less than so, o o as a mold release agent.

Styrene-butadiene copolymer is a thermoplastic rubber with high tensile strength, and when added to the above-mentioned (meth)acrylic copolymer, it has the effect of increasing the tensile strength of the toner and preventing offset. however.

A partially crosslinked styrene-butadiene copolymer is preferred because it has a low glass transition temperature and has rubber elasticity, which reduces the pulverization efficiency during toner production, toner storage stability, and agglomeration resistance. The molecular weight and gel content of the styrene-butadiene copolymer are required to be in an appropriate range from the viewpoint of toner fixing properties and anti-offset properties, and in the present invention, the weight average molecular weight - about so, ooo to 100,000. A gel content range of about 10 to 50 parts by weight is suitable.

On the other hand, amide wax or ethylene bis fatty acid amide added as a mold release agent has a positive triboelectric charge.

It is a resin that has a strong positive charging property for toner.

It is effective in promoting In addition, by setting the melting point of the resin to be below the fixing temperature of the heat roll, i.e., i50, it is eluted from the toner during fixing and coats the surface of the heat roll.
It is possible to prevent the toner from being offset from the roll. However, if the melting point of the resin becomes too low, the melt viscosity of the toner will decrease.

The melting point of the amide wax or fatty acid amide is suitably in the range of 140 V or more and less than 150 C, since there is a risk that the adhesive strength will decrease and the toner's fluidity, printing durability, and abrasion resistance will decrease.

Furthermore, it is conceivable to add low molecular weight i-polypropylene having a molecular weight of not more than so, o o o as a mold release agent, and by adding polypropylene, it is possible to completely prevent the toner offset phenomenon. As a result, in all types of heat roll fixing, a magnetic toner can be obtained that exhibits good fixing properties 2 and 7 resistance over a wide range of fixing speeds and fixing temperatures.

When preparing toner by blending each of the above resins.

It is necessary to consider the temperature, pressure, etc. during heat roll fixing.1 In normal cases, if the resin composition is selected so that the melt viscosity of the magnetic toner at 160V is in the range of i,ooo to 10,000 voise, fixing will be possible. A magnetic toner having good properties and excellent anti-offset properties can be obtained.

First, the amount of the (meth)acrylic copolymer added may be 20 to 500 to 50% by weight based on the total amount of the toner. This is because if the amount is less than 20% by weight, the image will be poor, and if it exceeds 500% by weight, the transportability and image quality will be poor. Further, the amount of the partially crosslinked styrene-butadiene copolymer added is based on the total amount of the toner.

A range of 5 to 20 weight ratios is suitable. If it is less than 5% by weight, there is no offset prevention effect, and if it exceeds 20% by weight, the pulverization efficiency, storage stability, and agglomeration resistance of the toner will decrease.

Next, the amount of amide wax, ethylene bis fatty acid amide, and polypropylene added is 0.000000000000000000000000000 with respect to the total amount of toner.
The content may be in the range of 5 to 5% by weight. This is 0
．． If it is less than 5% by weight, the effect of preventing offset is small;
If the weight percentage is exceeded, image characteristics, storage stability, fluidity,
This is because printing durability and abrasion resistance decrease.

The magnetic toner of the present invention is prepared by adding magnetic powder and a nigrosine dye as a positive charge control agent to the above resin. As magnetic powder, alloys or compounds containing ferromagnetic elements such as ferrite, magnetite, iron, cobalt, nickel, etc., and various alloys that exhibit ferromagnetism through some kind of treatment such as low heat treatment are used. . A specific example is magnetite (F
esυa), C, added magnetite, spinel type ferrite, magnet brambite type ferrite, etc. The smaller the amount of these magnetic powders added, the better from the viewpoint of fixing performance, but if the amount of fB magnetic powder is small, the toner conveyance force by the magnet will decrease, toner scattering problems will occur, and , an offset phenomenon occurs during fixing, resulting in poor quality. Therefore, the total amount of toner is 40 to 600.
~60% by weight is appropriate.

Nigrosine dyes are listed in the “Dye Handbook” (edited by the Society of Organic Synthetic Chemistry).
C.I. Solvent Black s (C, I. published by Maruzen Co., Ltd.) listed in No. 875R.

5olvent Black 5) and Sea and Eye
Solvent Curve Black 7 (C,1,5olvtnt
It represents a dye classified as Black 7) and is a commonly used material as a positive charge control agent. Also based on nigrosine dye.

Aliphatic-reactants with basic acids and/or dibasic acids.

In addition, reactants of nigrosine dyes and carboxyl group-containing resins have been developed, and since these dyes have good dispersibility in toner resins, they can be used particularly effectively in terms of charge stabilization. The amount of these nigrosine dyes added is suitably in the range of 1 to 7% by weight based on the total amount of the toner. If the amount is less than 1% by weight, the charge control effect will be small, and if it exceeds 7% by weight.

The fluidity and agglomeration resistance of the toner are reduced, resulting in poor image quality.As for the electrical properties of the toner, in order to improve the toner's triboelectric charging properties and the transfer efficiency to plain paper, an electrical resistance bar, C, 4O, etc.
oo V 1014Ω・α when applying an electric field of 7cm
Above, the relative permittivity is 5 at a frequency of 100 Kll z
．． A range of less than 0 is desirable.

The magnetic toner of the present invention can be spread, for example, as follows. Magnetic powder and nigrosine dye are premixed using a mixer such as a ball mill or a super mixer, and then a (meth)acrylic copolymer and partially crosslinked styrene-butadiene copolymer are prepared.

Add amide wax or ethylene bis fatty acid amide low molecular weight polypropylene and premix.

Next, it is melted and kneaded using a kneading machine such as a two-roll or kneader, then cooled and solidified, and then pulverized using a die-cut mill.
Classified using a zigzag classifier, with an average particle size of 3 to 44 μm
Get the toner. If the average particle size is less than 3 μm, image fog will increase, and if it exceeds 44 μm, the roughness of the image will become severe, so the average particle size should be in the range of 3 to 44 μm, preferably 5 μm.
A range of 50 μm is preferable.

It is effective to add a small amount of carbon black and/or hydrophobic silica fine powder to the outside of the toner in order to improve the magnetic resistance against static motion and image damage. The amount of carbon black to be added is 0.1% by weight or less, and the amount of hydrophobic silica powder is 0.05% by weight based on the total amount of toner.
A range of 0.5% by weight is suitable.

When the amount is less than the above range, the addition has no effect.

If the amount exceeds the above range, the positive triboelectric charging properties of the toner will decrease and the gR characteristics per image will deteriorate.

The fixing properties and anti-offset properties of the magnetic toner of the present invention were evaluated using a metal heat roll coated with Teflon (trade name) and an RTV silicone rubber roll.After fixing, the toner image was passed between the two. , evaluated by cellophane tape peel test and visual inspection.

The present invention will be specifically explained below using examples.

Example 1 60 parts by weight of methyl methacrylate and 40 parts by weight of butyl methacrylate were copolymerized to obtain a melt index value of C.
ASTM D 1238 method/load 5, temperature i5°) is 209710 m1n, glass transition temperature (DSC method) is 60°C, reduced viscosity (o, s t /lit chloroform solution.

A copolymer with 20υ) of 0.67 dl 7 y was obtained.

29 parts by weight of the above copolymer 1 molecular weight 6o, ooo, gel-containing 30% partially crosslinked styrene-butadiene copolymer (manufactured by Nippon Zeon, 5226) 10 parts by weight, melting point 14
Amide wax (Wax C manufactured by Hoechst, West Germany) in 2.

2 parts by weight 1 part by weight of polypropylene with a molecular weight of 14,600 (Viscol 550 P manufactured by Sanyo Chemical Co., Ltd.), 55 parts by weight of magnetic powder (KN-520 manufactured by Toda Kogyo Co., Ltd.), nigrosine dye (
A mixture consisting of 5 parts by weight of Bontron #-01) manufactured by Orient Chemical Co., Ltd. was heated and kneaded, cooled, and then ground to obtain a fine powder.

After classifying this into 5 to 30 μm, 0.05 weight ratio of carbon black (Mitsubishi Kasei-844) to the total amount of fine powder,
0.3% by weight of hydrophobic silica fine powder (R-972 manufactured by Nippon Aerosil Co., Ltd.) was added to prepare an a-type toner.

This toner had an electrical resistance of 6×10 14 Ω·α and a relative dielectric constant of 2.06, which was found to be an insulating property. This toner was used in the reversal development experiment described below to produce a 1 m7 image.

Selenium drum (Yamanashi Denshi!lIlist-Tg) on the photoconductor
system drum, outer diameter 12 om), semiconductor laser as Yt source (Hitachi PJr 11L-1400, oscillation wavelength BO7n)
In a laser beam printer using a rated output power of 5 mW.

A developing roller made of a non-magnetic conductive material and having a strength of about 1000 Gauss for tapping onto a developing sleeve (outer diameter 32111116) with a built-in magnet, and a so-called dual rotation system in which the magnet and sleeve can be rotated independently. The above-mentioned magnetic toner is layered on top with a spacing of 0.2+a between the non-magnetic cutting plate and the sleeve, and the magnetic toner is arranged so that it can be supplied from the hopper to the developing roller section, and the magnetic toner is placed between the surface of the photoreceptor and the developing roller. The interval of 0.4. Close,
The developing sleeve and photoconductor rotate in opposite directions, and the magnet rotates in the same direction as the sleeve, allowing the photoconductor to be rotated 2-Orp.
m, developing sleeve 40Orpm, magnet 150
Orpm was used to develop the photoreceptor. The image production conditions were: selenium photoconductor charge voltage 7oo J/, divided exposure of character patterns t5mJF using a semiconductor laser, reversal development method in which a DC bias voltage of ω650 to 700V was applied to the conductive sleeve, and a transfer voltage of e5.5KV. An image was created on plain paper. When the printed image was fixed using a Teflon heat roll heated to 160υ, it was possible to obtain a high-quality printer image with good fixing properties and offset resistance.

Example 2 70 parts by weight of methyl methacrylate and 30 parts by weight of butyl acrylate were copolymerized to give a melt index value of 1.
A copolymer having 7.5P710 mtn, a glass transition temperature of 65υ9, and a reduced viscosity of 0.72 dt/f was obtained.

30 parts by weight of the above copolymer, Example 1. 15 parts by weight of the partially crosslinked styrene-butadiene copolymer used in .

Ethylene bisstearamide with M point 144 v (
Chemical soap wax Bu-F) i car weight part 1 molecular weight 8,6
00 polypropylene (Viscol 660 manufactured by Sanyo Chemical Co., Ltd.
p) 1 quintillion parts, magnetic powder (Titan Kogyo RB-4L)
A magnetic toner was prepared in the same manner as in Example 1 using a mixture of 50 parts of stearic acid and 5 parts of a synthetic nigrosine dye (Hontron NN-02 manufactured by Orient Chemical Co., Ltd.).

This toner had an electrical resistance of 4×10 14 Ω·flaws and a relative dielectric constant of 197, indicating that it had high insulation properties.

When this toner was evaluated in the same manner as in Example 1, the developability,
The transfer properties were good, the fixing properties were good, and a high-quality printer image without offset could be obtained.

Example 3 Organic photoconductor sheet (Ricoh Hpr-4700
Organic photoreceptor) In a copying machine using a halogen lamp as a single source, using the magnetic toner described in Example 1 or Example 2, the electrostatic charge voltage of the photoreceptor was 0650 V, and the reflection exposure of an FA document using white light was performed. Example 1 in which the 201X conductive sleeve was grounded. Regular development method with the same rotation conditions as (-7
) A copy image was made on plain paper with a transfer voltage of 5.5 KV. When the obtained image was fixed with a Teflon heat roll heated to 170° C., it was possible to obtain a high quality copy image with good fixing properties and offset resistance.

Example 4 In a copying machine using a zinc oxide sheet as a photoreceptor (zinc oxide photoreceptor for 5F-730 manufactured by Six River Paper Industries) and a halogen lamp as a light source, Example 1. Or Example 2. Example 1. Using the magnetic toner described in 1., the charged voltage of the photoconductor was 500 V, and the original was reflected by a white light source. Regular development method with the same rotation conditions as 05
．． A copy image was produced on plain paper using a transfer voltage of sKV.

When the obtained image was fixed with a Teflon heat roll heated to 170°C, it had good fixing properties and offset resistance.
I was able to obtain a high quality copy image.

According to the present invention, the positive chargeability of magnetic toner, which was insufficient in the past, has been greatly improved, and all types of heat roll fixing are possible, so a reversal development system using a selenium photoreceptor , zinc oxide, and organic photoreceptors are expected to greatly improve the image quality, and promote the simplification, miniaturization, and high reliability of various printers, copiers, facsimile machines, etc. that apply electrophotographic technology. This will lead to a major leap forward in information processing terminal equipment.

Claims (3)

[Claims] (1) A positively charged heat roll fixable magnetic toner comprising at least a thermoplastic resin, a magnetic powder, and a nigrosine dye, the thermoplastic resin comprising: It is composed of methyl methacrylate and a-methylene aliphatic monocarboxylic acid alkyl esters and a partially crosslinked styrene-butadiene copolymer with a gel content of 10 to 50% by weight, and an amide wax or ethylene bis fatty acid amide and a low molecular base. A positively charged magnetic toner for heat roll fixing, characterized in that it contains polypropylene as a release agent. (2) The (meth)acrylic copolymer is contained in a proportion of 20 to 50% based on the total amount of the toner, and partially crosslinked styrene-
Contains 5 to 20% by weight of butadiene copolymer based on the total amount of the toner, and 40 to 60% of amide wax or ethylene bis fatty acid amide and polypropylene based on the total amount of the toner.
Including breath volume, 1 nigrosine dye per total amount of toner
7. The positively charged magnetic toner for heat roll fixing according to claim 1, wherein the amount is added in a range of 7 to 7 weight. (3) Add 0.1 carbon black to the total amount of toner.
Positive charge according to claim 1 or 2, characterized in that hydrophobic silica fine powder is added and mixed in a range of 0.05 to 0.5% by weight based on the total amount of the toner. Magnetic toner for heat roll fixing.