JPS60107040A - Magnetic toner - Google Patents

Abstract

PURPOSE:To improve developing performance, etc., by reacting a compd. having isocyanate groups with a magnetic material. CONSTITUTION:A compd. having isocyanate groups and a weight average mol. wt. of 200-10,000 with a magnetic material to cover its surface. When a toner is prepared by the suspension polymn. method, since the suspended toner particles are formed in an aq. dispersion medium, and when OH groups remain on the surface of the magnetic material, it concentrates on the surface, and adhesion of the magnetic material to the toner particles is made unfavorable, and the material is also released from the surfaces of the toner particles by mechanical shearing stress in a developing machine. Said coated magnetic material is used for the toner to be prepared by the suspension polymn. method, the magnetic material is contained in the inside of the toner particles to raise insulation property, and this toner can be used as te insulating toner as it is. It can also be made to a conductive toner by adding a fine condutive powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic toner used in electrophotography, electrostatic recording, and the like.

As a conventional electrophotographic method, U.S. Patent No. 2,297,691
specification, Japanese Patent Publication No. 42-23910 (U.S. Patent No. 3,666.363) and Japanese Patent Publication No. 43-247
Publication No. 48 (U.S. Patent No. 4,071,361)
Although a number of methods are known, such as those described in J.D. After developing the toner image into a visible image and transferring the toner image to a transfer material such as paper as necessary, heating is performed. It is fixed by pressure or the like to obtain copies.

Various methods for visualizing electrostatic latent images using toner are also known. For example, the magnetic brush method described in U.S. Pat. No. 2,874,063;
A large number of development methods are known, such as the cascade development method described in Specification No. 2, the powder cloud method, fur brush development method, and liquid development method described in Specification No. 2221776. Among these developing methods, a magnetic brush method, a cascade method, a liquid developing method, and the like, which use a developer in which toner and carrier are living organisms, have been widely put into practical use. All of these methods are excellent methods in which good images can be obtained relatively stably, but on the other hand, they have common drawbacks associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier.

In order to avoid such drawbacks, various development methods using a one-component developer made only of toner have been proposed, but among them, many methods using a developer made of magnetic toner particles are superior.

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. In this method, conductive magnetic toner is supported on a cylindrical conductive sleeve having magnetism inside, and is brought into contact with an electrostatic image to be developed. At this time, in the developing section, a conductive path is formed by the toner particles between the recording body surface and the sleeve surface, and charges are guided to the toner particles from the C sleeve through this conductive path, and the electrostatic image is connected to the image area. Due to the Coulomb force between the images, toner particles adhere to the image area and are developed. This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with conventional two-component developing methods.

Furthermore, as a developing method using a high-resistance magnetic toner, there is a developing method that utilizes dielectric polarization of toner particles.

Other developing methods using high-resistance magnetic toner include
A known method is to triboelectrically charge toner particles by friction between toner particles, friction between toner particles and a sleeve, etc., and develop the toner particles by contacting them with an electrostatic force holding member.

Further, in Japanese Patent Application Laid-Open No. 55-18656, etc., a new developing method which eliminates the above-mentioned drawbacks has been proposed. This involves applying a very thin layer of magnetic toner onto the sleeve, triboelectrically charging it, and then placing it in close proximity to the electrostatic image. This method increases the chances of contact between the sleeve and the toner by applying an extremely thin layer of magnetic toner onto the sleeve, enabling sufficient frictional charging, supporting the toner by magnetic force, and moving the magnet and toner relative to each other. By moving the toner particles to the surface, the agglomeration of the toner particles is eliminated, and the toner particles are sufficiently rubbed against the sleeve.The toner is supported by magnetic force and is caused to face the electrostatic image without coming into contact with it. The magnetic toner used in this type of -component development method is mainly composed of a binder resin and a magnetic material, and contains a colorant, a charge control agent, and a release agent. Additives such as these are added to bring out the characteristics necessary for the toner. The biggest problem with this magnetic toner is the dispersion and adhesion of the binder resin and the magnetic material. If the magnetic material is poorly dispersed, the transferability will be poor, and the content of the magnetic material will vary depending on the toner particles, resulting in differences in appearance. In particular, when used as an insulating magnetic toner, a toner with a small amount of magnetic material has a high resistance and therefore a large amount of band, while a toner with a large amount of magnetic material has a low resistance and therefore a small amount of charge.

As a result, those with less magnetic material are easier to develop,
If development is carried out for a long time, only toner containing a large amount of magnetic material and having poor developability will remain in the developing machine, resulting in an extremely low image density, and furthermore, the high humidity characteristics will deteriorate, resulting in the worst situation. In addition, if the adhesion between the binder resin and the magnetic material deteriorates, the magnetic material will fall off from the toner particles and contaminate the image.
It can scratch the latent image carrier, causing filming, poor cleaning, etc.Furthermore, it can scratch the roller in the case of fixing with heat rollers and pressure rollers, which are most commonly used in fixing machines. , toner tends to adhere to the roller, causing offset phenomenon, clinging phenomenon, etc. Furthermore, the more the development is repeated, the more the magnetic material that falls off remains in the developing machine, resulting in an extreme decrease in image density and deterioration in high-humidity characteristics.

Therefore, several methods have been proposed to improve the adhesiveness and dispersibility between the binder resin and the magnetic material. JP-A-54-84731 discloses a method of treating and using a magnetic material with a silane coupling agent, JP-A-55-26519.
JP-A-54-122129, JP-A-54-130130, and JP-A-55-6344 disclose a method of treating and using a magnetic material with a titanium-based coupling agent. , No. 55-11218 describes a method of using a magnetic material by coating it with a suitable magnetic material.

However, although these methods achieve some results, they are not fully satisfactory in all respects. In particular, it is still not sufficient for long-term use and adaptation to high-speed phenomena.

Therefore, an object of the present invention is to provide a magnetic toner that can be used for a long period of time.

Furthermore, the present invention provides a magnetic toner for developing electrostatic images in which image density does not decrease even after repeated development.

Furthermore, the present invention provides a magnetic toner for developing electrostatic images that retains good images even in repeated phenomena.

Furthermore, the present invention provides a magnetic toner for electrostatic charge development which does not damage or contaminate the latent image carrier even during repeated development.

Furthermore, the present invention provides a magnetic toner for developing electrostatic images whose high-humidity properties do not deteriorate even after repeated development.

Furthermore, the present invention provides a magnetic toner for developing electrostatic images that is suitable for high-speed development.

Furthermore, the present invention provides a magnetic toner for developing electrostatic images with good transferability.

That is, the present invention can be achieved by using a magnetic material reacted with a compound containing an incyanate group and having a weight average molecular weight of 200 to 10,000. Further, it is preferably used in toners produced by suspension polymerization.

When the magnetic material is reacted with the compound, the -OH groups on the surface of the magnetic material completely react with the compound and become hydrophobic. It can be said that coatings using conventional silane coupling agents, titanium thread coupling agents, and coating materials have not sufficiently rendered the toner hydrophobic in view of the toner properties. When the magnetic material produced in this way is used in magnetic toner, it exhibits sufficiently satisfactory performance.

The magnetic toner referred to here is, for example, produced by a pulverization method. That is, a magnetic material, a binder resin, a colorant, other additives, etc. are mixed together, the mixture is kneaded with heat, and after cooling, it is coarsely pulverized.
This is a method of obtaining toner with a desired particle size and particle size distribution by finely pulverizing and, if necessary, classifying.Other methods include the capsule method, emulsion polymerization method, and spray drying method.

In contrast, a suspension polymerization method is known. This is a method in which a polymerizable monocap, an initiator, and the like are dispersed in a dispersion medium to form suspended particles having the required particle size and particle size distribution, and the particles are polymerized to obtain a toner. The magnetic material used in the present invention is particularly suitable for this suspension polymerization toner. Turbid polymerization creates suspended particles in a mostly aqueous dispersion medium. Therefore, if even a small amount of hydrophilic groups, such as 10H groups, remain on the surface of the magnetic material, that portion will be released into the aqueous dispersion medium, causing the magnetic material to gather on the particle surface. For this reason, the resistance of the toner is reduced due to the conductive portion exposed on the surface, that is, the magnetic material. In the case of conductive magnetic toner, it seems that it can be used as a toner, but in reality, magnetic materials with hydrophilic groups have poor adhesion with binder resins, and most magnetic materials As the toner particles collect on the surface, the magnetic material falls off from the toner surface due to mechanical shear in the developing machine. Furthermore, such magnetic materials have poor dispersibility (1), resulting in non-uniformity of the toner and poor developability. This tendency is greater than the previous pulverization method toner because there is no process of kneading the binder resin and magnetic material at high temperature, high viscosity, and high shear like in the pulverization method toner. The advantages and disadvantages are that it is an energy-saving and low-cost manufacturing method.

When this suspension polymerization toner is made of a magnetic material reacted with the above-mentioned reactant, the magnetic material is internally contained within the toner and almost never appears on the surface of the toner. In addition, the magnetic material is better dispersed in each toner particle, making the toner homogeneous and developing properties significantly improved. This toner has almost no magnetic material on the toner surface, so it has the same resistance.
Therefore, it can be used as an insulating toner as it is, and its resistance can be adjusted freely by adding conductive fine powder such as carbon black, making it suitable as a conductive magnetic toner.

The compound containing an incyanate group may be one in which an appropriate number of incyanate groups are introduced into the polymer chain or side chain.
For example, the reaction mechanism is as follows.

Any of a wide variety of incyanate compounds may be used to treat magnetic materials. The isocyanate compound can be used in liquid or gaseous form or as a non-aqueous solution.

Generally, an incyanate compound and a magnetic material are brought into contact with each other, and a chemical bond is formed by addition reaction with the OH group on the surface of the magnetic material as shown in formula (1).

When this treatment is performed using a gaseous incyanate compound, the dry magnetic particles are treated at a high temperature of 100 to 200°C for about 1 hour in a saturated incyanate compound atmosphere2, or at 15 to 30°C. There are methods such as milling for 1 to 4 hours in a non-aqueous solution of a preserved incyanate compound. Generally, the higher the temperature of the solution, the faster the reaction rate. However, if the reaction is too rapid, the magnetic particles will agglomerate. In order to achieve uniform dispersion without agglomeration, it is important to maintain an appropriate temperature and reduce agglomerates by milling, and for this reason, it is desirable to mill continuously until the processing is completed.

If the weight average molecular weight is less than 200, the magnetic material may not be sufficiently dispersed due to poor compatibility with the binder resin, and if it exceeds 10,000, the 10H groups on the surface of the magnetic material may There may be cases where the reaction does not occur completely. This seems to be because the molecular weight is so large that the molecules that reacted first with the -OH group interfere with the molecules that are about to react next.

The compound containing an isocyanate group is selected from aromatic and aliphatic diisocyanate compounds, or compounds partially containing them.

For example, phenyl isocyanate, dodecyl isocyanate, m-phenylene diisocyanate.

1.6-hexamethylene diisocyanate), 1.4-cyclohexylene diisocyanate, 4-chloro-1,3-
phenylene diisocyanate), urethane-modified polybutadiene, etc.

The magnetic powder used is a substance that becomes magnetized when placed in a magnetic field, and includes powders of ferromagnetic metals such as iron, cobalt, and nickel, and alloys and compounds such as magnetite, hematite, and ferrite. The content of this magnetic powder is preferably 15>70% by weight based on the weight of the toner.

As the binder resin for the toner, homopolymers of styrene and its substituted products such as polystyrene, polyp-chlorostyrene, polyvinyltoluene, styrene-pchlorostyrene copolymer, styrene vinyl tzy+ene copolymer, and their substituted products are used. Copolymer: Copolymer of styrene and acrylic ester such as styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-n-butyl acrylate copolymer; styrene-meccrylic acid Copolymers of styrene and methacrylic acid esters, such as methyl copolymer, styrene-ethyl methacrylate copolymer, and styrene-n-butyl methacrylate copolymer; Polymers: Other styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-butadiene copolymer, styrene-vinyl methyl ketone copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid ester Styrenic copolymers of styrene and other vinyl monomers such as copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid, phenolic resin, fat Group or alicyclic hydrocarbon resins, petroleum resins, chlorinated paraffins, etc. can be used alone or in combination.

In particular, binder resins for toners used in pressure fixing systems include low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymers, ethylene-acrylic acid ester copolymers, higher fatty acids, polyamide resins, polyester resins, etc. can be made singly or in combination.

Monomers used when creating toner by suspension polymerization include:
The following can be applied to the present invention.

Styrene, 0-methylstyrene, m-methylstyrene,
p-Methylstyrene, p-methoxystyrene, R-phenylstyrene, p-restyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, P- Styrene and derivatives thereof such as tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene; ethylene, propylene, butylene,
Ethylenically unsaturated monoolefins such as isobutylene;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl foam, vinyl esters of vinyl acetate, vinyl propionate, vinylbenzoate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n methacrylate - α-methylene aliphatic monomers such as butyl, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, -2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc. Carboxylic acid esters methyl acrylate, ethyl acrylate, acrylic acid n
- Acrylic acid esters such as butyl, inbutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; vinyl methyl ether , vinyl ethers such as vinyl ethyl ether, vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; N-vinyl pyrrol, N-vinyl carbazole,
N such as N-vinylindole and N-vinylpyrrolidone
- Vinyl compounds; vinylnaphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylaterile, acrylamide, etc.

During polymerization, polymerization is carried out in the presence of the following crosslinking agent,
It may also be a crosslinked polymer.

Dipinylbenzene, divinylnaphthalene, divinyl ether, sivinyl sulfone, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol dimethacrylate), 1
．． 6 hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate V-), 2.2'bis(4-methacryloxyjethoxyphenyl)propane, 2.2'bis(4-) General crosslinking agents such as acryloxyjetoxyphenyl)propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetrametherolmethanetetraacrylate, dibromneopentyl glycol dimethacrylate, and phthalate are used as appropriate. I can do it.

If these crosslinking agents are used in large amounts, they will not dissolve, resulting in poor fixing properties. Also, if the amount used is small, properties such as blocking resistance and durability required for toner will deteriorate, and during hot roll fixing, some of the toner will not completely adhere to the paper and will stick to the roller surface and be transferred to the next paper. It becomes difficult to prevent the offset phenomenon of metastasis. Therefore, the amount of these crosslinking agents used is 0 based on the total amount of monomers.
．． 0.001 to 15% by weight (more preferably 0.1 to 10% by weight).

The polymerization initiator may be any suitable polymerization initiator, such as azobisisobutyronitrile (AIBN), benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate, cumene hydroperoxide, 2,4-dichlorylbenzoyl. Polymerization of monomers can be carried out using peroxide, lauroyl peroxide, and the like.

Generally about 0.5 to 5% initiator by weight of monomer is sufficient.

Suitable dispersion media used in the present invention include, for example, any suitable stabilizer, such as polyvinyl alcohol,
Gelatin, methyl cellulose, methyl hydropropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, polyacrylic acid and their salts, starch, gum alginate, zein, casein,
Tricalcium phosphate, talc, barium acetate, bentonite, aluminum hydroxide, ferric hydroxide, titanium hydroxide, thorium hydroxide, and the like can be incorporated into the aqueous phase.

The stabilizer is used in a stabilizing amount in the continuous phase, preferably in the range of about 01 to 10% by weight.

In addition, for fine dispersion of the inorganic dispersant, 0.001 to
Surfactants in the range of 0.1% by weight may also be used. This is to promote the intended action of the above-mentioned dispersion stabilizer, and specific examples thereof include sodium dodecylbenzenesulfonate, sodium tetradecylsulfate, sodium pentadecylsulfate, and sodium octylsulfate.
')um, '7'), sodium rualkyl-polyether sulfonate, sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate, 3.3- Disulfone diphenyl urea 414-diazo-bis-amino-8-nando-ru6
-sulfonate sodium, ortho-carboxybenzene-azo-dimethylaniline, 2,2.5゜5-tetramethyl-triphenylmethane-4゜4-diazo-bis-β
- sodium naphthol disulfonate, and others.

In addition, monomers that are easily soluble in water cause emulsion polymerization in water at the same time, and the resulting suspended polymer is contaminated with small emulsion polymer particles, so it is necessary to add a water-soluble polymerization inhibitor, such as a metal salt, to emulsify it in the aqueous phase. It is also good to prevent polymerization. In addition, to prevent particles from coalescing in addition to the clay medium, it is also recommended to add glycerin, glycol, etc. to the water. .

It is also possible to use salts such as Na, So, and the like.

Known pigments or dyes can be used as the toner colorant.

Examples of dyes include C,1, Direct Red 1, C.
,1, Direct Green 4, C,1, Acid Red 1, C,1, Basic Red 1, C,1, Modern Tread 30, C,I. Direct Blue 1, C, 1, Direct Blue'! ,C,1,Acid Plu9,C
,1, Acid Blue 15, C,1, Basic Blue 3, C,1, Basic Blue 5, C,1, Mordand Blue, C,1, Direct Green 6, C,1,
There are basic green 4, C, L basic green 6, etc.

Pigments include yellow lead, cadmium yellow, mineral fast yellow, navel yellow, Chintol Yellow S1 Hansa Yellow G, and permanent yellow NCG.
, tartrazine lake, red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange,
Benzidine Orange G1 Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Eosin Lake, Brilliant Carmino 3B, -? Ngan Purple, Fast Violet B1 Methyl Violet Lake, Deep Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Indan Stremburu-BC, Chrome Green, Chromium Oxide, Pigment Green B1 Malachite Green Lake, There are Final Yellow Green G, etc.

A charge control agent and a fluidity modifier may be added to the toner as necessary, and the charge control agent and fluidity modifier may be mixed (externally added) with the toner particles. . Examples of the charge control agent include metal-containing dyes and nigrosine, conventionally known dyes and pigments can be used as the colorant, and examples of the fluidity modifier include co-tetraidal silica and fatty acid metal salts. and so on. In addition, for the purpose of increasing the amount, fillers such as calcium carbonate and finely powdered silica are added at 0.5 to 2 J)wt%.
It can also be blended into the toner within the range of . Furthermore, in order to prevent mutual aggregation of toner particles and improve their fluidity, a fluidity improver such as fine Teflon powder may be added, and this is for the purpose of improving mold releasability during hot roll fixing. It is also possible to add about 0.5 to 5 wt % of a waxy substance such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, and Sasol wax.

In the suspension method, a monomer system in which a polymerization initiator, magnetic material, monomer, and additives are uniformly dissolved or dispersed is added to a conventional aqueous phase, that is, a continuous phase containing a suspension stabilizer. Disperse using a stirrer, homomixer, homogenizer, etc.

Preferably, the monomer droplets have the desired toner particle size,
In general, the stirring speed and time should be adjusted so that the particles have a size of 30μ or less, and after that, the stirring should be carried out to the extent that this state is maintained by the action of the dispersion stabilizer and that the particles are prevented from settling. . Polymerization temperature is 50℃ or higher, generally 7
Polymerization is carried out at a temperature of 0 to 90"C. After the reaction is completed, the produced toner particles are collected by a suitable method such as washing, filtration, decantation, centrifugation, etc. and dried.

[Example 1] 200 g of xylene BL-200 (manufactured by Titan Ei) was put into a 41 reaction container, stirred vigorously, and B'L
-200 was dispersed. Thereafter, 10 g of urethane polymer (Sirione MR-100, manufactured by Nippon Polyurethane) was added, and the mixture was stirred at room temperature for 4 hours. Thereafter, this mixed solution was filtered, washed, dried, and then lightly crushed to loosen agglomerates. A toner was made using this magnetite powder. The composition was as follows.

Styrene-butyl acrylate copolymer 100 parts (ratio 8:2.Mw=200,000) Above-treated magnetite powder 5 parts Carbon plastic 5 parts Bontron E-81 (Orient Chemical Exhibition) 2 parts Formula used here Ratios are parts by weight, and the same applies hereinafter. - After premixing these materials, they were kneaded at 150°C using a roll mill, cooled, and then coarsely pulverized, finely pulverized, and classified to obtain a toner. The obtained toner had a number average particle size of 108 μm and a weight average particle size of 147 μm. (Coulter counter type■,
(Using an aperture diameter of 100 μm) This toner was placed in a Canon NP-500RE high-speed copying machine, and a 50,000-sheet image reproduction durability test was conducted.

In addition, as a comparative example, untreated magnetite BL-20
0 was made into a toner using the same blending ratio as above. The particle size of this toner is a number average diameter of 11.5 μm and a weight average diameter of 5.5 μm.
It was μ. The results are as follows, showing that the toner of the example was particularly excellent. Also, with the toner of the comparative example, scratches appeared on the photoreceptor drum from about 40,000 sheets onwards, but such problems did not occur in the example. (There wasn't.

Evaluation: 5-very good, 4-2 good, 3=practically usable.

22 Practically Bad, 1- Bad [Example 2] 60 parts of the treated magnetite prepared in Example 1 was added to the following mixture.

Styrene monomer 85 parts Butyl acrylate monomer 15 parts Initiator (V-65: Wako Tsumugi) 0.5 parts Paraffin 15
5F 3 parts Dimethylaminoethyl methacrylate monomer 5 parts The mixture was kept at 60°C and stirred and dispersed for 5 minutes using a TK homomixer (Tokushu Kika ■). In a separate container, 1500 parts water, 2.5 parts tricalcium phosphate
The above-mentioned monomer mixture was introduced into the dispersed solution under stirring, and suspension polymerization was carried out. Tricalcium phosphate of this polymer was dissolved and removed with acid, further washed with water and dried to obtain a toner powder. The obtained toner had a number average particle size of 105μ,
The weight average particle size was 165μ.

This toner was subjected to an image reproduction durability test using a copying machine PC-20 manufactured by Canon.

As a comparative example, a toner was prepared and tested in the same manner as in Example 2 using KBL-200 magnetic material treated with 1% titanium coupling instead of the magnetite treated in Example 1.

The evaluation criteria were the same as in Example 1. In addition, the comparative toner had many scratches on the drum.

In the durability test of the toner of the comparative example, it was found by microscopic tablet observation that the magnetite powder had fallen off from the toner. It is considered that this caused the toner properties to deteriorate and also to cause scratches on the drum. No such problem occurred with the toner of Example 2.

[Example 3] A container containing 200 g of BL-250 (manufactured by Titan Industries) is evacuated to a mercury column height of 0.5 m, and the temperature is raised to about 160°C. Separate the container from the vacuum system and place about 8 g of diphenylmethane isocyanate (MR-2 manufactured by Nippon Polyurethane) in it.
00) so that when it evaporates it creates a substantially saturated atmosphere. The container, which remains disconnected from the vacuum system, is heated to approximately 180° C. for 3 hours. This container is then 180
The isocyanate compounds are removed by evacuation for approximately 1 hour until a pressure of 0.5 tnm of mercury is reached.

Thereafter, the container is cooled to room temperature and the treated magnetite is removed.

This treated magnetic material was polymerized in the same manner as in Example 2 to obtain a toner. The same effects as in Example 2 were obtained.

Applicant Canon Co., Ltd.

Claims (1)

[Claims] <11 Contains an incyanate group and has a weight average molecular weight of 2
A magnetic toner containing a magnetic material reacted with a compound of 00 to io, ooo. (2) The magnetic toner according to claim 1, which is produced by a suspension polymerization method.