Magnetic toner for developing electrostatic image

A magnetic toner for developing an electrostatic image is disclosed which has a binder resin, a magnetic material and an iron compound of the formula (I). The magnetic toner has a saturation magnetization of 20 to 50 Am.sup.2 /kg and a coercive force of 40 to 200 oersted.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a magnetic toner for developing an electrostatic 
image, used in image forming processes such as electrophotography and 
electrostatic recording, to render electrostatic latent images visible. 
2. Related Background Art 
As electrophotography, various methods are disclosed in U.S. Pat. No. 
2,297,691, Japanese Patent Publication No. 42-23910 and Japanese Patent 
Publication No. 43-24748 and so forth. 
Developing systems applied in such electrophotography are roughly grouped 
into a dry developing method and a wet developing method. The former is 
further grouped into a method making use of one-component developers and a 
method making use of two-component developers. The developing method 
making use of one-component developer has a feature that developing 
apparatus can be made small-sized. This method, however, has difficulty in 
imparting sufficient triboelectricity to the toner and hence it has the 
problem that the allowable scope for designing toners and developing 
systems is narrow. On the other hand, the developing method making use of 
the two-component developer can impart sufficient charges to toners and 
hence has the advantage that it has wider tolerance for designing, but has 
a problem that it requires a means for uniformly controlling the mixing 
ratio of the toner and the carrier, making its apparatus complicated. 
As toners used in these developing methods, fine powders comprising a 
colorant such as a dye or pigment dispersed in a natural or synthetic 
resin are hitherto used. For example, toner particles are prepared by 
pulverizing a dispersion of a colorant in a binder resin such as 
polystyrene to a size of about 1 to 30 .mu.m. As a magnetic toner, toner 
particles containing magnetic material particles such as magnetite are 
used. 
Toners have positive charges or negative charges depending on the polarity 
of electrostatic latent images to be developed. In order to charge toners, 
it is possible to utilize triboelectric chargeability of resins that 
compose toners. In such a method, however, the chargeability of the toner 
is so small that toner images obtained by development tend to be foggy and 
unclear. In order to impart a desired triboelectric chargeability to 
toners, a dye or pigment capable of controlling chargeability and also a 
charge control agent are commonly added. 
However, toners containing such charge control agents tend to contaminate 
the toner carrying members such as the developing sleeve, and hence such 
toners tend to cause a decrease in quantity of triboelectricity as the 
number of copies taken increases, resulting in a decrease in image 
density. Charge control agents of a certain type have a small quantity of 
triboelectricity and tend to be affected by temperature and humidity, and 
hence may cause variations of image density in accordance with 
environmental changes. Certain charge control agents have a poor 
dispersibility in resins, and hence toners making use of such charge 
control agents tend to have uneven triboelectricity between toner 
particles, tending to cause fogging. Certain charge control agents have 
poor storage stability so that toners may undergo a decrease in 
triboelectric performance during long-term storage. 
As a means for solving these problems, Japanese Patent Publication Nos. 
43-17955, 55-42752 and 63-1994 propose various kinds of metal complexes as 
charge control agents. These charge control agents certainly have a good 
negative triboelectric chargeability. Most of them, however, are chromium 
compounds, and more improvement has been sought from the viewpoint of 
environmental safety. 
Japanese Patent Application Laid-open Nos. 61-155464, 61-101558 and 
61-155463 propose iron complexes. 
These publications disclose that the iron complexes have a negative 
triboelectric chargeability and have a very good compatibility with 
resins. However, studies made by the present inventors have revealed that 
only some of them can provide magnetic toners providing a more stable 
image quality in the one-component development system as described later. 
In order to maintain the high image quality obtained at the initial stage, 
without regard to the number of copies taken, it is insufficient to only 
maintain the quantity of triboelectricity. The particle size distribution 
of the toner at the initial stage must also be kept constant. In 
particular, it is important for the toner particles of relatively large 
particle size (coarse powder) to be used in development in a good 
efficiency to prevent their accumulation. For such purpose, the magnetic 
properties and quantity of triboelectricity of magnetic toners must be 
adjusted to proper values. Taking these points into account, the present 
inventors have studied charge control agents to find but the quantity of 
negative triboelectricity becomes smaller when organic ammonium ions are 
used as counter ions. The reason is unclear, but it is presumed to be due 
to a positive triboelectric chargeability inherent in organic ammonium 
ions as generally known in the art. Japanese Patent Application Laid-open 
No. 61-101558 discloses that organic ammonium ions are effective to 
improve the dispersibility of metal complexes in resins. According to the 
studies made by the present inventors, however, in the case of 
one-component developers making use of magnetic toners, the organic 
ammonium ions exert greater influence on a decrease in triboelectric 
chargeability than on the improvement of dispersibility, so that the 
coarse powder in the toner accumulates as developing is repeated many 
times, to cause a slight lowering of image quality. 
Polyvalent inorganic ions disclosed in Japanese Patent Application 
Laid-open No. 63-267793 also have caused accumulation of the coarse powder 
in toners. Negative charge control agents disclosed in Japanese Patent 
Application Laid-open No. 63-267793 have polyvalent ions as counter ions 
to make the molecular structure larger, so that they show more improved 
dispersibility in resins than the negative charge control agent disclosed 
in Japanese Patent Application Laid-open No. 61-155464. As a result, the 
carrier contamination due to the toner can be repressed prolonging the 
life time of the developer from 50,000 to 100,000 sheets copying to 
200,000 sheet or more as so disclosed therein. According to the studies 
made by the present inventors, however, in order to maintain the good 
image quality at the initial stage using a magnetic toner in one-component 
development, it is necessary not only to keep the quantity of 
triboelectricity constant, but as previously stated, also to maintain a 
high quantity of triboelectricity, so that the coarse powder in the toner 
can also participate in the development. From such viewpoints, the iron 
complexes of polyvalent ions as disclosed in Japanese Patent Application 
Laid-open No. 63-267793 are not suited for magnetic toners. The coarse 
powder tends to accumulate also in the case of the iron complexes having a 
substituent such as a nitro group as shown in Japanese Patent Application 
Laid-open No. 61-155463, or those having a sulfonamide group, in Japanese 
Patent Application Laid-open No. 61-155464. 
Meanwhile, with regard to magnetic properties of magnetic toners, proposals 
are made as follows: 
Japanese Patent Application Laid-open Nos. 58-95748, 58-98744 and 3-95578 
report the magnetic properties of magnetic toners. 
According to Japanese Patent Application Laid-open No. 58-95748, saturation 
magnetization has an influence on transport performance of magnetic toner 
particles. Those with a saturation magnetization less than 23 emu/g weaken 
magnetic transport power to tend to cause uneven development. Those with a 
saturation magnetization more than 50 emu/g require a large quantity of 
magnetic powder in magnetic toners to make fixing performance low or 
developing performance poor. Toner particles with a coercive force less 
than 150 oersted greatly lower the developing performance, and those with 
a coercive force more than 350 oersted strengthen agglomeration force of 
toner particles to cause a problem in toner transport performance. 
Japanese Patent Application Laid-open No. 58-98744 discloses that coercive 
force of 150 oersted or more is required in order to obtain fog-free 
images in reversal development. 
Japanese Patent Application Laid-open No. 3-95578 discloses to reduce the 
quantity of a magnetic material so that a color toner with less turbidity 
can be obtained. For this reason, the magnetic toner is made to have a 
saturation magnetization of 40 emu/g or less, and a magnetic roller (a 
developing sleeve) is designed so as to compensate for any lowering of the 
transport power of the magnetic toner. In any case, the saturation 
magnetization is controlled taking into account the transport performance 
of magnetic toners and the coercive force is controlled for developing 
performance. Although the image quality at the initial stage can be 
improved by controlling magnetic properties of the magnetic toner, it is 
difficult to control image deterioration due to changes in toner particle 
size that may occur as developing is repeated many times. In order to 
prevent the magnetic toner from changing particle size, both the quantity 
of triboelectricity of the magnetic toner and the magnetic properties 
thereof must be taken into account. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a magnetic toner for 
developing an electrostatic image, having solved the problems discussed 
above. 
Another object of the present invention is to provide a toner for 
developing an electrostatic image, causing less image deterioration during 
the development of a large number of copying sheets. 
Still another object of the present invention is to provide a magnetic 
toner having a superior environmental stability. 
A further object of the present invention is to provide a magnetic toner 
having a superior stability when left to stand. 
This invention provides a magnetic toner for developing an electrostatic 
image, comprising a binder resin, a magnetic material and an iron compound 
represented by the following formula (I): 
##STR1## 
wherein R.sup.1 and R.sup.2 each represent a hydrogen atom, a sulfonic 
acid group, a carboxylic acid group, a carboxylate group, a hydroxyl group 
or a halogen atom, and may be the same or different; n.sub.1 and n.sub.2 
each represent an integer of to 1 to 4; and X.sup.2 each represent a 
hydrogen atom or a halogen atom; m.sub.1 and m.sub.2 each represent an 
integer of 1 to 3; and A.sup..sym. represents a hydrogen ion, an alkali 
metal ion or an ammonium ion; 
said magnetic toner having a saturation magnetization of from 20 Am.sup.2 
/kg to 50 Am.sup.2 /kg and a coercive force of from 40 oersted to 200 
oersted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
According to the studies made by the present inventors, it is important to 
properly balance the quantity of triboelectricity and magnetic properties 
of a magnetic toner in order to maintain the initial good image quality 
when the magnetic toner is used in one-component developing system. Based 
on such a finding, the present inventors studied various types of charge 
control agents in magnetic toner of various magnetic properties. As a 
result, they discovered that changes in particle size of magnetic 
materials that may occur as developing is repeated many times can be 
inhibited and the initial good image quality can be maintained when a 
specific iron compound is used in a toner for developing electrostatic 
images, where the toner has a saturation magnetization of from 20 to 50 
Am.sup.2 /kg and a coercive force of from 40 to 200 oersted. They have 
thus accomplished the present invention. The unit "Am.sup.2 /kg" is a unit 
in the International System of Units (SI) for measuring saturation 
magnetization in which A is "ampere", "m" is meter and "kg" is kilogram. 
The iron compound used in the present invention is represented by the 
following formula (I). Formula (I) 
##STR2## 
wherein R.sup.1 and R.sup.2 each represent a hydrogen atom, a sulfonic 
acid group, a carboxylic acid group, a carboxylate group, a hydroxyl group 
or a halogen atom, and may be the same or different; n.sub.1 and n.sub.2 
each represent an integer of 1 to 4; X.sup.1 and X.sup.2 each represent a 
hydrogen atom or a halogen atom; m.sub.1 and m.sub.2 each represent an 
integer of 1 to 3; and A.sup..sym. represents a hydrogen ion, an alkali 
metal ion or an ammonium ion; 
A.sup..sym. may preferably be an ammonium ion or be mainly composed of an 
ammonium ion (70 mol % or more). A.sup..sym. may more preferably be a 
mixture of an ammonium ion and an alkali metal ion and/or a hydrogen ion, 
and be mainly composed of an ammonium ion. Still more preferably, in the 
above mixture, the ammonium ion may be in a content of from 80 to 98 mol 
%, and more preferably from 85 to 95 mol %. 
According to the studies made by the present inventors, when the compound 
has ammonium ions and alkali metal ions or hydrogen ions in combination, 
the quantity of triboelectricity of the magnetic toner having been left to 
stand in an environment of high humidity can be restored to the original 
(i.e., before leaving to stand) quantity of triboelectricity, and also can 
be recovered more quickly with a stable image quality. On the other hand, 
when the compound has only protons or alkali metal ions as cations, the 
magnetic toner having been left in an environment of high humidity can be 
triboelectrically charged quickly, but the quantity of triboelectricity 
can not be well restored to the original quantity of triboelectricity, 
tending to cause a decrease in image density. 
According to the studies made by the present inventors, a good compound 
that shows less deterioration even when left to stand over a long period 
of time can be obtained when ammonium ions and alkali metal ions or 
hydrogen ions are present together in the compound. 
In particular, the rate and the level of restoration can be well maintained 
when ammonium ions are in a content of from 80 mol % to 98 mol %. If 
ammonium ions are in a content of less than 80 mol %, the restored level 
of triboelectricity may become a little lower than the original quantity 
of triboelectricity. On the other hand, if they are in a content more than 
98 mol %, the rate of restoration may become lower. When the ammonium ions 
are in a content of from 85 mol % to 95 mol %, the rate of restoration 
preferably become higher. In addition, better results can be obtained also 
on restoration performance in an environment of high humidity. 
The reason therefor is, according to the mechanism of ion conduction 
proposed as one of the mechanisms of triboelectric charging, presumed as 
follows: 
It is presumed that when water content is relatively large as in the 
environment of high humidity, monovalent cations with small ion radii have 
high mobility so that charges once having leaked when the toner is left to 
stand can be quickly restored. 
For that purpose, it is preferable for the alkali metal ions or hydrogen 
ions as the monovalent cations to be in a uniform content of at least 2 
mol %, and more preferably at least 5 mol %. 
In the present invention, the performance of restoration of the quantity of 
triboelectricity is expressed by a proportion of the restored charge to 
the original charge when a triboelectrically charged magnetic toner in an 
environment of high humidity is left to stand for a long period of time 
and thereafter shaken together with an iron powder carrier. 
Stated specifically, 2.5 g of a magnetic toner and 47.5 g of an iron powder 
carrier are collected in a 50 cm.sup.3 polyethylene container, and left to 
stand for 2 days in an environment of a temperature of 30.degree. C. and a 
relative humidity of 80% RH in an uncovered state. These are then shaken 
in a tumbling mixer for 240 seconds, and thereafter about 0.5 g of the 
powdery mixture is collected to measure the quantity of triboelectricity 
of the magnetic toner by blowing-off. The measurement thus obtained is 
regarded as the original quantity of triboelectricity. The powdery mixture 
is further left to stand for 4 days in an uncovered state, followed by 
shaking in the tumbling mixer for 0, 60 or 240 seconds to measure the 
corresponding quantities of triboelectricity of the magnetic toner, and 
its percentage to the quantity of triboelectricity of the original 
magnetic toner is calculated. 
FIG. 2 illustrates an apparatus for measuring the quantity of 
triboelectricity. In a measuring container 2 made of a metal at the bottom 
of which is provided an electroconductive screen 3 of 500 meshes 
(appropriately changeable to the size the screen may not pass the carrier 
particles), the sample is put and the container is covered with a plate 4 
made of a metal. Next, in a suction device 1 (made of an insulating 
material at least at the part coming into contact with the measuring 
container 2), air is sucked from a suction opening 7 and an air-flow 
control valve 6 is operated to control the pressure indicated by a vacuum 
indicator 5 to be 250 mmHg. In this state, suction is sufficiently carried 
out (for about 1 minute). The potential indicated by a potentiometer at 
this time is expressed by V (volt). Reference numeral 8 denotes a 
capacitor, whose capacitance is expressed by C (.mu.F). The charges 
obtained therefrom are divided by the weight (g) of the magnetic toner 
removed by suction to obtain a value which is the quantity of 
triboelectricity (mC/Kg). 
The magnetic toner of the present invention can also effectively prevent 
photosensitive members from being scraped. It can be presumed that, 
because of a good transfer rate of the magnetic toner of the present 
invention, the amount of the magnetic toner remaining on a photosensitive 
member after the step of transfer is sufficiently small to result in a 
small load in the step of cleaning. As can be also considered, the iron 
compound used in the present invention acts on the surface of the magnetic 
material to improve its state of dispersion in a resin, so that the 
magnetic material present on the surfaces of the magnetic toner particles 
has decreased. 
In the present invention, complexes represented by formula (I) may be mixed 
to obtain the iron compound having the mixture of cations. A better shelf 
stability can be obtained when the iron compound is synthesized at one 
time while changing the percentage or pH of cationic components during its 
synthesis. This is presumably because the respective cations can be more 
uniformly dispersed and at the same time different cationic complexes can 
preferably interact, when the compound is synthesized at one time. 
Examples of the iron compound represented by formula (I) are shown below. 
##STR3## 
In the above exemplary iron compounds (1) to (10), a.sub.1 through a.sub.10 
may preferably be 0.80 to 0.98; b.sub.1 through b.sub.10, 0.01 to 0.20; 
and c.sub.1 through c.sub.10, the balance. More preferably, a.sub.1 
through a.sub.10 may be 0.85 to 0.95; b.sub.1 through b.sub.10, 0.01 to 
0.05; and c.sub.1 through c.sub.10, the balance. 
In the above iron compound (1), a.sub.1 may preferably be 0.80 to 0.98; 
b.sub.1, 0.01 to 0.19; and c.sub.1, 0.01 to 0.19. More preferably, a.sub.1 
may be 0.85 to 0.95; b.sub.1, 0.01 to 0.14; and c.sub.1, 0.0.1 to 0.14. 
##STR4## 
The iron compound can be incorporated into the toner by a method in which 
it is internally added to the inside of magnetic toner particles or 
externally added to the particles. The iron compound may preferably be 
used in an amount ranging from 0.1 part to 10 parts by weight, and more 
preferably from 0.1 part to 5 parts by weight, based on 100 parts by 
weight of the binder resin. When it is externally added, it may preferably 
be in an amount of from 0.01 part to 10 parts by weight, and more 
preferably from 0.01 part to 3 parts by weight, based on 100 parts by 
weight of the binder resin. In particular, it is preferred for iron 
compound particles to be mechanochemically fixed on the surfaces of the 
magnetic toner particles. 
The iron compound used in the present invention may be used in combination 
with any conventionally known charge control agents so long as the effect 
of the iron compound is not damaged. 
According to the studies made by the present inventors, in order to prevent 
the changes in particle size of magnetic toners that may occur during 
repeated developing, for the purpose of maintaining the initial high image 
quality, it is important to use the iron compound of the present invention 
and also make the saturation magnetization from 20 to 50 Am.sup.2 /kg and 
a coercive force of from 40 to 200 oersted. In particular, it is 
preferable for the magnetic toner to have a saturation magnetization of 
from 25 to 40 Am.sup.2 /kg and a coercive force of from 50 to 150 oersted. 
As conventionally pointed out, magnetic toners come to have a low transport 
performance if their saturation magnetization is less than 20 Am.sup.2 
/kg. In particular, the transport performance of coarse powder in a 
magnetic toner to a developing zone may become poor, tending to cause the 
coarse powder in the magnetic toner to accumulate in a developing assembly 
as developing is repeated many times. If the saturation magnetization is 
more than 50 Am.sup.2 /kg, the magnetic binding force on a developing 
sleeve increases, resulting, in particular, in a lowering of developing 
performance of the coarse powder. The cause thereof is not necessarily 
clear, but it is presumed as follows: The quantity of triboelectricity of 
a magnetic toner is considered proportional to the square of a particle 
diameter of the magnetic toner, and on the other hand the saturation 
magnetization is proportional to the cube of the same. Hence, particularly 
in the coarse powder of the magnetic toner, the magnetic binding force on 
the developing sleeve becomes larger than the quantity of 
triboelectricity, causing a lowering of developing performance and causing 
the coarse powder to accumulate. 
As for the coercive force of the magnetic toner, the coarse powder tends to 
accumulate when it is more than 200 oersted. 
For the measurement of magnetizing force, values at a magnetic field of 1 k 
oested are measured using, e.g., VSM, manufactured by Toei Kogyo K.K. 
The magnetic material contained in the magnetic toner of the present 
invention may include iron oxides such as magnetite, .gamma.-iron oxide, 
ferrite and iron-excess ferrite; metals such as iron, cobalt and nickel, 
or alloys of any of these with a metal such as aluminum, cobalt, copper, 
lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, 
calcium, manganese, selenium, titanium, tungsten or vanadium, and mixtures 
of any of these. 
These magnetic materials may preferably be those having an average particle 
diameter of from 0.1 to 1 .mu.m, and preferably from 0.1 to 0.5 .mu.m. 
The magnetic material may preferably be contained in the magnetic toner in 
an amount that may satisfy the following expression. 
EQU MT=-(10/3).times.d+(70.+-.15) 
wherein MT represents a content (% by weight) of the magnetic material, and 
d represents a weight average particle diameter (.mu.m) of the magnetic 
toner, provided that d is not more than 9 .mu.m. 
Use of the magnetic material in an amount less than the above limit may 
generally result in a low saturation magnetization of the magnetic toner, 
tending to cause lowering of the transport performance of the magnetic 
toner. As a result, the magnetic toner can not be fed to the developing 
zone in a sufficient quantity and hence only toner images with a low 
density can be obtained. On the other hand, if a magnetic material with a 
higher saturation magnetization is used in an amount less than the above 
limit to obtain a magnetic toner with a good transport performance, the 
toner has a high electrical resistivity because of the decrease of the 
magnetic material. As a result, when the iron compound of formula (I) is 
used, the quantity of triboelectricity becomes higher than the proper 
value tending to cause lowering of developing performance. 
On the other hand, the use of the magnetic material in an amount more than 
the foregoing limit makes the saturation magnetization or coercive force 
of the magnetic toner excessively large, so that the fluidity of the 
magnetic toner may decrease or the magnetic binding force on the 
developing sleeve may increase. As a result, the developing performance of 
the magnetic toner may be lowered or the coarse powder of the magnetic 
toner may accumulate as developing is repeated many times, tending to 
cause lowering of image quality. An increase in the quantity of the 
magnetic material also result in a decrease in the quantity of 
triboelectricity of the magnetic material. Hence, this also can be the 
cause of a lowering of the developing performance of the magnetic 
tonerial. 
Thus, in order to prevent the accumulation of the coarse powder as 
developing is repeated many times and to maintain the initial high image 
quality, it is important to control both the magnetic properties and the 
quantity of triboelectricity of the magnetic toner as described above. For 
that purpose, the quantity of triboelectricity of the magnetic toner must 
be controlled using the specific iron compound of formula (I) as a charge 
control agent, and on that occasion the amount of the magnetic material 
may preferably be within the range set out above. 
In the magnetic toner of the present invention, the magnetic toner may 
preferably have a weight average particle diameter of from 3 to 9 .mu.m. 
In particular, a magnetic toner having a weight average particle diameter 
of from 5 to 9 .mu.m is preferred. 
The particle size distribution of the magnetic toner can be measured by 
various methods. In the present invention, it is suitable to measure it 
using a Coulter counter. 
A Coulter counter Type TA-II (manufactured by Coulter Electronics, Inc.) is 
used as a measuring device. The volume distribution and number 
distribution of particles of 2 .mu.m to 40 .mu.m are calculated by 
measuring the volume and number distribution of the toner particles, using 
an aperture of 100 .mu.m as its aperture. Then the weight-based, weight 
average particle diameter D.sub.4 is calculated from the volume 
distribution of the present invention (representative value of each 
channel is the median of each channel) and the weight-based, coarse-powder 
content is calculated from the volume distribution. 
In the magnetic toner of the present invention, it is preferable to use a 
fine inorganic oxide powder by its external addition. 
As the fine inorganic oxide powder, various materials can be used, as 
exemplified by silica, titanium oxide, aluminum oxide, cerium oxide and 
strontium titanate. In particular, those having metal ions with an 
electronegativity of from 10 to 15 are preferred in view of charging rate 
and environmental stability. 
For the purpose such as imparting fluidity to the magnetic toner of the 
present invention, it is very preferable to externally add fine silica 
powder or fine titanium oxide powder. 
The fine silica powder may include anhydrous silicon dioxide (silica), as 
well as silicates such as aluminum silicate, sodium silicate, potassium 
silicate, magnesium silicate and zinc silicate, any of which can be used. 
Of the above fine silica powders, those having a specific surface area, as 
measured by the BET method using nitrogen absorption, of not less than 30 
m.sup.2 /g, and particularly from 50 to 400 m.sup.2 /g, are preferred as 
base material silica. 
Any of these fine silica powder, or those treated as described below, may 
preferably be used in an amount of from 0.01 part to 20% by weight, and 
particularly preferably from 0.03 part to 5% by weight, based on the 
weight of the magnetic toner. 
The fine silica powder may be optionally treated with a treatment agent 
such as a silane coupling agent or an organic silicon compound, or with 
silicone oil or the like. 
Such a treatment agent can be exemplified by hexamethyldisilazane, 
trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, 
dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, 
allylphenyldichlorosilane, benzyldimethylchlorosilane, 
bromomethyldimethylchlorosilane, .alpha.-chloroethyltrichlorosilane, 
.beta.-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, 
triorganosilyl mercaptan, trimethylsilyl mercaptan, triorganosilyl 
acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, 
dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 
1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and a 
dimethylpolysiloxane having 2 to 12 siloxane units in its molecule and 
containing a hydroxyl group bonded to each Si in its units positioned at 
the terminals. Any of these may be used alone or in the form of a mixture 
of two or more kinds. 
When the treated fine silica powder has been made hydrophobic to such 
degree that it shows a hydrophobicity of a value ranging from 30 to 80 as 
measured by methanol titration, a magnetic toner containing such a fine 
silica powder is preferred since its quantity of triboelectricity comes to 
show a sharp and uniform positive chargeability. Here, the methanol 
titration is a test method to determine the hydrophobicity of fine silica 
powder whose surfaces have been made hydrophobic. 
In order to evaluate the hydrophobicity of the treated fine silica powder, 
the "methanol titration" as defined in the present specification is 
carried out in the following way: 0.2 g of fine silica powder is added to 
50 ml of water contained in a 250 ml Erlenmeyer flask. Methanol is 
dropwise added from a buret until the whole fine silica powder has been 
wetted. Here, the solution inside the flask is continually stirred using a 
magnetic stirrer. The end point can be observed upon suspension of the 
whole fine silica powder in the solution. The hydrophobicity is expressed 
as the percentage of the methanol present in the liquid mixture of 
methanol and water when the reaction has reached the end point. 
The binder resin used in the present invention may include polystyrene; 
homopolymers of styrene derivatives such as poly-p-chlorostyrene and 
polyvinyltoluene; styrene copolymers such as a styrene/p-chlorostyrene 
copolymer, a styrene/vinyltoluene copolymer, a styrene/vinylnaphthalene 
copolymer, a styrene/acrylate copolymer, a styrene/methacrylate copolymer, 
a styrene/methyl .alpha.-chloromethacrylate copolymer, a 
styrene/acrylonitrile copolymer, a styrene/methyl vinyl ether copolymer, a 
styrene/ethyl vinyl ether copolymer, a styrene/methyl vinyl ketone 
copolymer, a styrene/butadiene copolymer, a styrene/isoprene copolymer and 
a styrene/acrylonitrile/indene copolymer; polyvinyl chloride, phenol 
resins, natural resin modified phenol resins, natural resin modified 
maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, 
silicone resins, polyester resins, polyurethane resins, polyamide resins, 
furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene 
resins, cumarone indene resins, and petroleum resins. 
Cross-linked styrene copolymers are also preferable binder resins. 
Comonomers copolymerizable with styrene monomers in styrene copolymers may 
include monocarboxylic acids having a double bond and derivatives thereof 
such as acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 
dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, 
methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl 
methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile and 
acrylamide; dicarboxylic acids having a double bond and derivatives 
thereof such as maleic acid, butyl maleate, methyl maleate and dimethyl 
maleate; vinyl esters such as vinyl acetate and vinyl benzoate; olefins 
such as ethylene, propylene and butylene; vinyl ketones such as methyl 
vinyl ketone and hexyl vinyl ketone; and vinyl ethers such as methyl vinyl 
ether, ethyl vinyl ether and isobutyl vinyl ether. Any of these vinyl 
monomers may be used alone or in combination of two or more. 
As a cross-linking agent, compounds having at least two polymerizable 
double bonds are mainly used, which include, for example, aromatic divinyl 
compounds such as divinyl benzene and divinyl naphthalene; carboxylic acid 
esters having two double bonds such as ethylene glycol diacrylate, 
ethylene glycol dimethacrylate and 1,3-butanediol dimethacrylate; divinyl 
compounds such as divinyl apiline, divinyl ether, divinyl sulfide and 
divinyl sulfone; and compounds having at least three vinyl groups. Any of 
these may be used alone or in the form of a mixture. In particular, 
styrene copolymers having at least one peak of molecular weight 
distribution in the region of from 3.times.10.sup.3 to 5.times.10.sup.4 
and at least one peak or shoulder in the region of 10.sup.5 or more as 
measured by gel permeation chromatography (GPC) are preferred. 
The molecular weight distribution is measured by GPC under the following 
conditions. 
Columns are stabilized in a heat chamber of 40.degree. C. To the columns 
kept at this temperature, THF as a solvent is flowed at a flow rate of 1 
ml per minute, and 100 .mu.l of THF sample solution is injected thereinto 
to make measurement. In measuring the molecular weight of the sample, the 
molecular weight distribution of the sample is calculated from the 
relationship between the logarithmic value of the molecular weight and the 
count number of the eluate (a calibration curve) prepared using several 
kinds of monodisperse polystyrene standard samples. As the standard 
polystyrene samples used for the preparation of the calibration curve, it 
is suitable to use samples with molecular weights of from 10.sup.2 to 
10.sup.7, which are available from Toso Co., Ltd. or Showa Denko KK., and 
to use at least about 10 standard polystyrene samples. An RI (refractive 
index) detector is used as a detector. Columns should be used in 
combination of a plurality of commercially available polystyrene gel 
columns. For example, they may preferably comprise a combination of Shodex 
GPC KF-801, KF-802, KF-803, KF-804, KF-805, KF-806, KF-807 and KF-800P, 
available from Showa Denko K.K.; or a combination of TSKgel 
G1000H(H.sub.XL), G2000H(H.sub.XL), G3000H(H.sub.XL), G4000H(H.sub.XL), 
G5000H(H.sub.XL), G6000H(H.sub.XL), G7000H(H.sub.XL) and TSK guard column, 
available from Toso Co., Ltd. 
The sample is prepared in the following way: 
The binder resin or the magnetic toner is put in THF, and is left to stand 
for several hours, followed by thorough shaking so as to be well mixed 
with the THF until coelescent matters of the sample has disappeared, which 
is further left to stand for at least 12 hours. At this time, the sample 
is so left as to stand in THF for at least 24 hours. Thereafter, the 
solution having been passed through a sample-treating filter (pore size: 
0.45 to 0.5 .mu.m; for example, MAISHORI DISK-25-5, available from Toso 
Co., Ltd. or EKICHRO DISK 25CR, available from German Science Japan, Ltd., 
can be utilized) is used as the sample for GPC. The sample is so adjusted 
to have resin components in a concentration of from 0.5 to 5 mg/ml. 
When a pressure fixing system is employed, a pressure-fixable resin can be 
used. It may include, for example, polyethylenes, polypropylene, 
polymethylene, polyurethane elastomers, an ethylene/ethyl acrylate 
copolymer, an ethylene/vinyl acetate copolymer, ionomer resins, a 
styrene/butadiene copolymer, a styrene/isoprene copolymer, linear 
saturated polyesters, and paraffin. 
The magnetic toner of the present invention may be optionally mixed with 
additives. The additives may include, for example, lubricants such as zinc 
stearate, abrasives such as cerium oxide and silicon carbide, 
fluidity-providing agents such as aluminum oxide, anti-caking agents, and 
conductivity-providing agents such as carbon black and tin oxide. 
Fine fluorine-containing polymer powders such as fine polyvinylidene 
fluoride powder are also preferable additives in view of fluidity, 
abrasion and static charging stability. 
For the purpose of improving releasability at the time of heat-roll fixing, 
it is one of preferred embodiments of the present invention to add to the 
toner a waxy material such as a low-molecular weight polyethylene, a 
low-molecular weight polypropylene, microcrystalline wax, carnuba wax, 
sasol wax and paraffin wax in an amount of from 0.5 to 5% by weight. In 
particular, sasol wax is one of preferred release agents. 
The magnetic toner of the present invention may preferably be produced by a 
process comprising the steps of thoroughly mixing the magnetic toner 
component materials in a mixing machine such as a ball mill, well mixing 
the mixture by means of a heat kneading machine such as a heat roll 
kneader and an extruder, cooling the kneaded product to solidify, 
thereafter mechanically pulverizing the solidified product, and 
classifying the pulverized product to obtain a magnetic toner. 
Alternatively, the magnetic toner can also be produced by a method in 
which the component materials are dispersed in a binder resin solution, 
followed by spray drying to obtain a toner; a method in which given 
materials are mixed in monomers that constitute a binder resin to make up 
an emulsion dispersion, followed by polymerization to obtain a toner; and 
a method in which, in a microcapsule toner comprised of a core material 
and a shell material, given materials are incorporated into the core 
material or the shell material or into both of them. The magnetic toner 
can also be produced by a method in which desired additives and the 
magnetic toner are optionally further thoroughly blended by means of a 
mixing machine such as a Henschel mixer to obtain a magnetic toner. 
The magnetic toner of the present invention can be well used to for 
development, to convert electrostatic images into visible images in 
electrophotography, electrostatic recording, electrostatic printing and so 
forth. 
FIG. 1 shows an embodiment of a developing assembly in which the magnetic 
toner of the present invention can be applied. 
An electrostatic image bearing member 1 is rotated in the direction of an 
arrow. A non-magnetic cylinder (a developing sleeve) 4 serving as a toner 
carrier member is rotated in the same direction as the electrostatic image 
bearing member 1 at a developing zone. The developing sleeve 4 is provided 
in its inside with a multi-polar permanent magnet 9. A magnetic toner 11 
delivered from a toner container 12 is spread on the developing sleeve 4, 
and a magnetic blade 10 control the magnetic toner layer in a small and 
uniform thickness. In the developing zone, a DC bias voltage is applied to 
the developing sleeve 4 through a bias applying means 13. At this time, an 
AC bias may also be applied simultaneously. The AC bias when applied may 
preferably have a frequency of from 200 to 4,000 Hz and a potential 
difference between peaks, of from 3,000 to 5,000 V. In FIG. 1, the 
magnetic blade 10 is not in touch with the developing sleeve 4, but a 
blade made of an elastic material such as plastic or rubber may be in 
touch with it so that the magnetic toner layer thickness can be 
controlled. 
EXAMPLES 
The present invention will be described below in greater detail by giving 
Examples. These by no means limit the present invention. In the following 
formulation, "part(s)" refers to "part(s) by weight" in all occurrences. 
Example 1 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 250,000; 
first peak (peak 1): molecular weight 10,000; 
second peak (peak 2): molecular weight 70,000) 
Magnetic material 80 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 90 oersted) 
Sasol wax 3 parts 
Iron compound (1) 2 parts 
(molar ratio of NH.sub.4.sup..sym. to Na.sup..sym. to H.sup..sym. : 
0.9:0.05:0.05) 
______________________________________ 
The above materials were thoroughly premixed using a blender, and then 
kneaded using a twin-screw kneading extruder set to 130.degree. C. The 
resulting kneaded product was cooled, and then crushed. Thereafter, the 
crushed product was finely pulverized using a fine grinding mill utilizing 
a jet stream. The resulting finely pulverized product was further put in a 
multi-division classifier utilizing the Coanda effect (Elbow Jet 
Classifier, manufactured by Nittetsu Kogyo Co.) to strictly classify and 
remove ultrafine powder and coarse powder at the same time. Thus, a black 
fine powder (a negatively chargeable magnetic toner) with a weight average 
particle diameter of 8.5 .mu.m was obtained. 
Then, 100 parts of the negatively chargeable magnetic toner thus obtained, 
0.6 part of hydrophobic fine silica powder (average particle diameter: 15 
nm) and 0.3 part of fine strontium titanate powder (average particle 
diameter: 1 .mu.m) were mixed using a Henschel mixer to obtain a 
one-component magnetic toner. This magnetic toner had a saturation 
magnetization of 28 Am.sup.2 /kg and a coercive force of 90 oersted. 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and latent images were formed, followed by 
developing, transferring and fixing to make copying tests. 
Copies were taken on 20,000 copy sheets in an environment of normal 
temperature and normal humidity, a temperature of 23.degree. C. and a 
humidity of 60% RH. As a result, sharp images with an image density of 
1.40.+-.0.03 were obtained at the initial and following stages. With 
regard to resolution of images also, a resolution of 6.3 lines/mm at the 
initial stage was maintained. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.40.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.35.+-.0.03 
were obtained at the initial and following stages. After the toner in the 
copying machine was left to stand for 4 days in the environment of high 
temperature and high humidity, copies were taken on 10,000 copy sheets. 
Good images with a density of 1.35.+-.0.03 were obtained on the first and 
following copy sheets after copying was again started. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 2 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 250,000; 
first peak: molecular weight 10,000; second 
peak: molecular weight 70,000) 
Magnetic material 80 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 90 oersted) 
Sasol wax 3 parts 
Iron compound (1) 2 parts 
(molar ratio of NH.sub.4.sup..sym. to Na.sup..sym. to H.sup..sym. : 
0.98:0.01:0.01) 
______________________________________ 
A one-component magnetic toner was obtained in the same manner as in 
Example 1 except that the above materials were used. This magnetic toner 
had a saturation magnetization of 28 Am .sup.2 /kg and a coercive force of 
90 oersted. 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and copying tests were made in the same 
manner as in Example 1. 
Copies were taken on 20,000 copy sheets in an environment of a temperature 
of 23.degree. C. and a humidity of 60% RH. As a result, sharp images with 
an image density of 1.40.+-.0.03 were obtained at the initial and 
following stages. With regard to resolution of images also, a resolution 
of 6.3 lines/mm at the initial stage was maintained. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.40.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.35.+-.0.03 
were obtained at the initial and following stages. After the toner in the 
copying machine was left to stand for 4 days in the environment of high 
temperature and high humidity, copies were taken on 10,000 copy sheets. On 
the first sheet after copying was again started, images had an image 
density of 1.30 which was a little lower than that obtained before the 
toner had been left, but good images with a density of 1.35.+-.0.03 were 
obtained on the 10th and following copy sheets. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 3 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 250,000; 
first peak: molecular weight 10,000; second 
peak: molecular weight 70,000) 
Magnetic material 80 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 90 oersted) 
Sasol wax 3 parts 
Iron compound (1) 2 parts 
(molar ratio of NH.sub.4.sup..sym. to Na.sup..sym. to H.sup..sym. : 
0.8:0.15:0.05) 
______________________________________ 
A one-component magnetic toner was obtained in the same manner as in 
Example 1 except that the above materials were used. This magnetic toner 
had a saturation magnetization of 28 Am .sup.2 /kg and a coercive force of 
90 oersted. 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and copying tests were made in the same 
manner as in Example 1. 
Copies were taken on 20,000 copy sheets in an environment of a temperature 
of 23.degree. C. and a humidity of 60% RH. As a result, sharp images with 
an image density of 1.40.+-.0.03 were obtained at the initial and 
following stages. With regard to resolution of images also, a resolution 
of 6.3 lines/mm at the initial stage was maintained. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.40.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.35.+-.0.03 
were obtained at the initial and following stages. After the toner in the 
copying machine was left to stand for 4 days in the environment of high 
temperature and high humidity, copies were taken on 10,000 copy sheets. On 
the first sheet after copying was again started, images had an image 
density of 1.28 which was a little lower than that obtained before the 
toner had been left, but good images with a density of 1.35.+-.0.03 were 
obtained on the 30th and following copy sheets. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 4 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 250,000; 
first peak: molecular weight 10,000; second 
peak: molecular weight 70,000) 
Magnetic material 80 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 90 oersted) 
Sasol wax 3 parts 
Iron compound (1) 2 parts 
(molar ratio of NH.sub.4.sup..sym. to Na.sup..sym. to H.sup..sym. : 
0.5:0.2:0.3) 
______________________________________ 
A one-component magnetic toner was obtained in the same manner as in 
Example 1 except that the above materials were used. This magnetic toner 
had a saturation magnetization of 28 Am.sup.2 /kg and a coercive force of 
90 oersted. 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and copying tests were made in the same 
manner as in Example 1. 
Copies were taken on 20,000 copy sheets in an environment of a temperature 
of 23.degree. C. and a humidity of 60% RH. As a result, sharp images with 
an image density of 1.40.+-.0.03 were obtained at the initial and 
following stages. With regard to resolution of images also, a resolution 
of 6.3 lines/mm at the initial stage was maintained. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.40.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.35.+-.0.03 
were obtained at the initial and following stages. After the toner in the 
copying machine was left to stand for 4 days in the environment of high 
temperature and high humidity, copies were taken on 10,000 copy sheets. On 
the first sheet after copying was again started, images had an image 
density of 1.25 which was a little lower than that obtained before the 
toner had been left, but good images with a density of 1.30.+-.0.03 were 
obtained on the 30th and following copy sheets. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 5 
A one-component magnetic toner was obtained in the same manner as in 
Example 1 except that the amount of the magnetic material was changed to 
120 parts. This magnetic toner had a saturation magnetization of 42 
Am.sup.2 /kg and a coercive force of 90 oersted. 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and copying tests were made in the same 
manner as in Example 1. 
Copies were taken on 20,000 copy sheets in an environment of a temperature 
of 23.degree. C. and a humidity of 60% RH. As a result, sharp images with 
an image density of 1.35.+-.0.03 were obtained at the initial and 
following stages. With regard to resolution of images also, a resolution 
of 6.3 lines/mm at the initial stage was maintained. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.40.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.30.+-.0.03 
were obtained at the initial and following stages. After the toner in the 
copying machine was left to stand for 4 days in the environment of high 
temperature and high humidity, copies were taken on 10,000 copy sheets. 
Good images with a density of 1.30.+-.0.03 were obtained on the first and 
following copy sheets after copying was again started. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 6 
A one-component magnetic toner was obtained in the same manner as in 
Example 1 except that the iron compound (1) was replaced with 3 parts of 
an iron compound represented by formula (17) shown below. This magnetic 
toner had a saturation magnetization of 28 Am.sup.2 /kg and a coercive 
force of 90 oersted. 
##STR5## 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and copying tests were made in the same 
manner as in Example 1. 
Copies were taken on 20,000 copy sheets in an environment of a temperature 
of 23.degree. C. and a humidity of 60% RH. As a result, sharp images with 
an image density of 1.35.+-.0.05 were obtained at the initial and 
following stages. With regard to resolution of images also, a resolution 
of 6.3 lines/mm at the initial stage was maintained. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.40.+-.0.05 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.25.+-.0.05 
were obtained at the initial and following stages. After the toner in the 
copying machine was left to stand for 4 days in the environment of high 
temperature and high humidity, copies were taken on 10,000 copy sheets. 
However, on the first sheet after copying was again started, images had an 
image density of 1.05 which was lower than that obtained before the toner 
had been left. Also after copying on the 100th sheet, images had an image 
density of 1.20.+-.0.05, which was inferior to the images obtained before 
the toner had been left. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high temperature and high humidity is shown in 
Table 1. 
Example 7 
A one-component magnetic toner was obtained in the same manner as in 
Example 1 except that the styrene/butyl methacrylate copolymer was 
replaced with polyester resin (weight average molecular weight: 20,000) 
was used. This magnetic toner had a saturation magnetization of 28 Am 
.sup.2 /kg and a coercive force of 90 oersted. 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and copying tests were made in the same 
manner as in Example 1. 
Copies were taken on 20,000 copy sheets in an environment of a temperature 
of 23.degree. C. and a humidity of 60% RH. As a result, sharp images with 
an image density of 1.40.+-.0.03 were obtained at the initial and 
following stages. With regard to resolution of images also, a resolution 
of 6.3 lines/mm at the initial stage was maintained. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.40.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.35.+-.0.03 
were obtained at the initial and following stages. After the toner in the 
copying machine was left to stand for 4 days in the environment of high 
temperature and high humidity, copies were taken on 10,000 copy sheets. 
Good images with a density of 1.35.+-.0.03 were obtained on the first and 
following copy sheets after copying was again started. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high temperature and high humidity is shown in 
Table 1. 
Example 8 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 300,000; 
first peak: molecular weight 6,000; second 
peak: molecular weight 100,000) 
Magnetic material 100 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 90 oersted) 
Low-molecular weight polypropylene wax 
3 parts 
Iron compound (1) 2 parts 
(molar ratio of NH.sub.4.sup..sym. to Na.sup..sym. to H.sup..sym. : 
0.92:0.04:0.04) 
______________________________________ 
The above materials were thoroughly premixed using a blender, and then 
kneaded using a twin-screw kneading extruder set to 130.degree. C. The 
resulting kneaded product was cooled, and then crushed. Thereafter, the 
crushed product was finely pulverized using a fine grinding mill utilizing 
a jet stream. The resulting finely pulverized product was further put in a 
multi-division classifier utilizing the Coanda effect (Elbow Jet 
Classifier, manufactured by Nittetsu Kogyo Co.) to strictly classify and 
remove ultrafine powder and coarse powder at the same time. Thus, a black 
fine powder (a negatively chargeable magnetic toner) with a weight average 
particle diameter of 6.5 .mu.m was obtained. This magnetic toner had a 
saturation magnetization of 28 Am.sup.2 /kg and a coercive force of 90 
oersted. 
Then, 100 parts of the magnetic toner thus obtained and 1 part of 
hydrophobic fine silica powder (average particle diameter: 15 nm) were 
mixed using a Henschel mixer to obtain a one-component magnetic toner. 
The one-component magnetic toner obtained was applied in a commercially 
available laser beam printer LBP-KT (trade name; manufactured by Canon 
Inc.) to make printing tests. 
Prints were obtained on 6,000 copy sheets in an environment of a 
temperature of 23.degree. C. and a humidity of 60% RH. As a result, sharp 
images with an image density of 1.40.+-.0.03 were obtained at the initial 
and following stages. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 6,000 sheet printing test was 
made. As a result, good images with an image density of 1.40.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 3,000 sheet printing test was 
also made. As a result, good images with an image density of 1.35.+-.0.03 
were obtained at the initial and following stages. After the toner in the 
printer was left to stand for 4 days in the environment of high 
temperature and high humidity, prints were obtained on 3,000 copy sheets. 
Good images with a density of 1.35.+-.0.03 were obtained on the first and 
following copy sheets after printing was again started, where no decrease 
in image density due to the toner having been left to stand was seen. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high temperature and high humidity is shown in 
Table 1. 
Example 9 
A one-component magnetic toner was obtained in the same manner as in 
Example 8 except that the iron compound (1) was replaced with 1 part of 
the iron compound (2) (molar ratio of NH.sub.4.sup..sym. to Na.sup..sym. 
to H.sup..sym. : 0.93:0.04:0.03). This magnetic toner had a saturation 
magnetization of 28 Am.sup.2 /kg and a coercive force of 90 oersted. 
The one-component magnetic toner obtained was applied in a commercially 
available laser beam printer LBP-KT (trade name; manufactured by Canon 
Inc.) to make printing tests. 
Prints were obtained on 6,000 copy sheets in an environment of a 
temperature of 23.degree. C. and a humidity of 60% RH. As a result, sharp 
images with an image density of 1.40.+-.0.05 were obtained at the initial 
and following stages. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 6,000 sheet printing test was 
made. As a result, good images with an image density of 1.40.+-.0.05 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 3,000 sheet printing test was 
also made. As a result, good images with an image density of 1.35.+-.0.05 
were obtained at the initial and following stages. After the toner in the 
printer was left to stand for 4 days in the environment of high 
temperature and high humidity, prints were obtained on 3,000 copy sheets. 
Good images with a density of 1.35.+-.0.05 were obtained on the first and 
following copy sheets after printing was again started, where no decrease 
in image density due to the toner having been left to stand was seen. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high temperature and high humidity is shown in 
Table 1. 
Example 10 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 250,000; 
first peak: molecular weight 10,000; second 
peak: molecular weight 70,000) 
Magnetic material 80 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 140 oersted) 
Sasol wax 3 parts 
Iron compound (11) 2 parts 
______________________________________ 
The above materials were thoroughly premixed using a blender, and then 
kneaded using a twin-screw kneading extruder set to 130.degree. C. The 
resulting kneaded product was cooled, and then crushed. Thereafter, the 
crushed product was finely pulverized using a fine grinding mill utilizing 
a jet stream. The resulting finely pulverized product was further put in a 
multi-division classifier utilizing the Coanda effect (Elbow Jet 
Classifier, manufactured by Nittetsu Kogyo Co.) to strictly classify and 
remove ultrafine powder and coarse powder at the same time. Thus, a black 
fine powder (a negatively chargeable magnetic toner) with a weight average 
particle diameter of 8.5 .mu.m was obtained. 
This magnetic toner had a saturation magnetization of 28 Am /kg and a 
coercive force of 140 oersted. 
Then, 100 parts of the magnetic toner thus obtained and 0.6 part of 
hydrophobic fine silica powder (BET specific surface area: 200 m.sup.2 /g) 
were mixed using a Henschel mixer to obtain a one-component magnetic toner 
with an average particle diameter of 8.5 .mu.m, having the hydrophobic 
fine silica powder. 
The one-component magnetic toner obtained was applied in a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.), and a 20,000 sheet copying test was made in 
an environment of normal temperature and normal humidity. 
Sharp images with an image density of 1.40 were obtained at the initial and 
following stages. Images after 20,000 sheet copying also had sharp images 
with a density of 1.39. With regard to resolution of images also, a 
resolution of 6.3 lines/mm at the initial stage was maintained. 
The quantity of triboelectricity of the magnetic toner was measured by 
blowing-off to ascertain that it was -10.8 .mu.c/g. The coarse powder with 
a particle diameter larger than 10.8 .mu.m was in a quantity of 25% by 
weight before copying, and 28% by weight after the copying, between which 
there was little change. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.38.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.32.+-.0.03 
were obtained at the initial and following stages. Subsequently, after the 
toner in the copying machine was left to stand for 4 days in the 
environment of high temperature and high humidity, copies were taken on 
10,000 copy sheets. Good images with a density of 1.32.+-.0.03 were 
obtained on the first and following copy sheets after copying was again 
started. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 11 
Example 1 was repeated to obtain a magnetic toner with a weight average 
particle diameter of 8.5 .mu.m, except that a magnetic material (average 
particle diameter: 0.2 .mu.m; coercive force: 180 oersted) with a higher 
coercive force than that in Example 10 was used. The magnetic toner 
obtained had a saturation magnetization of 33 Am.sup.2 /kg and a coercive 
force of 180 oersted. 
On the magnetic toner thus obtained, copying tests were made in the same 
manner as in Example 10. 
As a result, sharp images with an image density of 1.41 were obtained at 
the initial and following stages. Images after 20,000 sheet copying also 
had sharp images with a density of 1.37. With regard to resolution of 
images, however, it was 6.3 lines/mm at the initial stage, but lowered to 
5.6 lines/mm after 20,000 sheet copying. 
The quantity of triboelectricity of the magnetic toner was measured by 
blowing-off to ascertain that it was -11.3 .mu.c/g. The coarse powder with 
a particle diameter larger than 10.8 .mu.m was in a quantity of 23% by 
weight before copying, and 30% by weight after 20,000 sheet copying, 
between which there was a little increase. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, good images with an image density of 1.35.+-.0.03 were 
obtained at the initial and following stages. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, good images with an image density of 1.31.+-.0.03 
were obtained at the initial and following stages. Subsequently, after the 
toner in the copying machine was left to stand for 4 days in the 
environment of high temperature and high humidity, copies were taken on 
10,000 copy sheets. Good images with a density of 1.31.+-.0.03 were 
obtained on the first and following copy sheets after copying was again 
started. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Comparative Example 1 
A one-component magnetic toner was obtained in the same manner as in 
Example 10 except that the iron compound (11) was replaced with the iron 
compound (18) of the formula: 
##STR6## 
This one-component magnetic toner had a saturation magnetization of 28 Am 
.sup.2 /kg and a coercive force of 140 oersted. 
The obtained magnetic toner was used to conduct a copying test in the same 
manner as in Example 11. 
Sharp images with an image density of 1.37 were obtained at the initial 
stage of copying, but images after 20,000 sheet copying had a lowered 
image density of 1.25. With regard to resolution of images also, it was 
6.3 lines/mm at the initial stage, but it was lowered to 4.5 lines/mm 
after 20,000 sheet copying. The quantity of triboelectricity of the 
magnetic toner was measured by blowing-off to ascertain that it was -9.3 
.mu.c/g. The coarse powder with a particle diameter larger than 10.8 .mu.m 
was in a quantity of 25% by weight before copying, and it increased to 39% 
by weight after 20,000 sheet copying. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, an initial image density of 1.35 decreased to 1.21. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, an initial image density of 1.25 lowered to 1.1. 
Restoration performance of the quantity of triboelectricity of the 
magnetic toner in the environment of high humidity is shown in Table 1. 
Comparative Example 2 
A one-component magnetic toner was obtained in the same manner as in 
Example 10 except that the iron compound (11) was replaced with the iron 
compound (19) of the formula: 
##STR7## 
This magnetic toner had a saturation magnetization of 28 Am.sup.2 /kg and a 
coercive force of 140 oersted. 
The obtained magnetic toner was used to conduct a copying test in the same 
manner as in Example 10. 
Sharp images with an image density of 1.35 were obtained at the initial 
stage of copying, but after 20,000 sheet copying, the image density 
lowered to 1.21. With regard to resolution of images also, it was 6.3 
lines/mm at the initial stage, but it was lowered to 4.0 lines/mm after 
20,000 sheet copying. The quantity of triboelectricity of the magnetic 
toner was measured by blowing-off to ascertain that it was -8.8 .mu.c/g. 
The coarse powder with a particle diameter larger than 10.8 .mu.m was in a 
quantity of 27% by weight before copying, and it increased to 43% by 
weight after 20,000 sheet copying. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, an initial image density of 1.35 decreased to 1.23. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, an initial image density of 1.15 lowered to 1.00. 
Restoration performance of the quantity of triboelectricity of the 
magnetic toner in the environment of high humidity is shown in Table 1. 
Comparative Example 3 
A one-component magnetic toner was obtained in the same manner as in 
Example 10 except that a magnetic material having a coercive force (300 
oersted) higher than in Example 11. The one-component magnetic toner had a 
saturation magnetization of 31 Am.sup.2 /kg and a coercive force of 300 
oersted. 
The obtained one-component magnetic toner was used to conduct a copying 
test in the same manner as in Example 10. 
Sharp images with an image density of 1.39 were obtained at the initial 
stage of copying, but after 20,000 sheet copying, the image density 
lowered to 1.22. With regard to resolution of images, it was 6.3 lines/mm 
at the initial stage, but it was lowered to 4.5 lines/mm after 20,000 
sheet copying. The quantity of triboelectricity of the magnetic toner was 
measured by blowing-off to ascertain that it was -10.1 .mu.c/g. The 
coarse powder with a particle diameter larger than 10.8 .mu.m was in a 
quantity of 26% by weight before copying, and it increased to 44% by 
weight after 20,000 sheet copying. 
Next, in an environment of low temperature and low humidity, a temperature 
of 15.degree. C. and a humidity of 10% RH, a 20,000 sheet copying test was 
made. As a result, an initial image density of 1.39 decreased to 1.25. 
In an environment of high temperature and high humidity, a temperature of 
30.degree. C. and a humidity of 80% RH, a 10,000 sheet copying test was 
also made. As a result, an initial image density of 1.35 lowered to 1.21. 
Restoration performance of the quantity of triboelectricity of the 
magnetic toner in the environment of high humidity is shown in Table 1. 
Comparative Example 4 
A one-component magnetic toner was obtained in the same manner as in 
Example 10 except that a magnetic material was used which had an average 
particle diameter of 0.2 .mu.m, a saturation magnetization of 30 Am.sup.2 
/kg and a coercive force of 140 oersted, and the amount of the magnetic 
material was changed to 150 parts. This one-component magnetic toner had a 
saturation magnetization of 18 Am.sup.2 /kg and a coercive force of 140 
oersted. 
The obtained one-component magnetic toner was used to conduct a copying 
test in the same manner as in Example 10. 
The initial image density was 1.12, and the density after 20,000 sheet 
copying further decreased to 0.91. The images were not sharp with much 
fog. With regard to the resolution of the images, the initial one was 4.5 
lines/mm, and after 20,000 sheet copying, it was further lowered to 3.2 
lines/mm. 
The quantity of triboelectricity of the magnetic toner was measured by 
blowing-off to ascertain that it was -5.4 .mu.c/g. The coarse powder with 
a particle diameter larger than 10.8 .mu.m was in a quantity of 25% by 
weight before copying, and it increased to 48% by weight after 20,000 
sheet copying. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 12 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 250,000) 
Magnetic material 100 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 120 oersted) 
Low-molecular weight polypropylene wax 
3 parts 
Iron compound (12) 1 part 
______________________________________ 
A black fine powder (magnetic toner) with a weight average particle 
diameter of 6.5 .mu.m was obtained by using the above materials in the 
same manner as in Example 10. 
The magnetic toner had a saturation magnetization of 32 Am.sup.2 /kg and a 
coercive force of 120 oersted. 
100 parts of the obtained magnetic toner and 1.0 part of hydrophobic silica 
(BET specific surface area: 200 m.sup.2 /g) were mixed using a Henschel 
mixer to obtain a one-component magnetic toner. 
The one-component magnetic toner obtained was applied to a commercially 
available laser beam printer LBP-KT (trade name; manufactured by Canon 
Inc.) to make 6,000 sheet printing test. 
Sharp images with an image density of 1.42 were obtained from the initial 
stage of printing. Even images after 6,000 sheet printing were sharp with 
a density of 1.45. With regard to the resolution of the images also, an 
initial value of 7.1 lines/mm was maintained. 
The quantity of triboelectricity of the magnetic toner was measured by 
blowing-off to ascertain that it was -16.3 .mu.c/g. The coarse powder with 
a particle diameter larger than 8.0 .mu.m was in a quantity of 10% by 
weight before printing, and 12% by weight after 6,000 sheet printing so 
that there was little change. Restoration performance of the quantity of 
triboelectricity of the magnetic toner in the environment of high humidity 
is shown in Table 1. 
Example 13 
A one-component magnetic toner was obtained in the same manner as in 
Example 12 except that the amount of the magnetic material was changed to 
150 parts. This one-component magnetic toner had a saturation 
magnetization of 42 Am.sup.2 /kg and a coercive force of 120 oersted. 
The obtained one-component magnetic toner was used to conduct a printing 
test in the same manner as in Example 12. 
As a result, sharp images with an image density of 1.34 were obtained from 
the initial stage of printing. Images after 6,000 sheet printing were 
sharp with a density of 1.32. On the other hand, as to the resolution of 
the images, it was 7.1 lines/mm at the initial stage, but it lowered to 
5.6 lines/mm after 6,000 sheet printing. 
The quantity of triboelectricity of the magnetic toner was measured by 
blowing-off to ascertain that it was -12.1 .mu.c/g. The coarse powder with 
a particle diameter larger than 8.0 .mu.m was in a quantity of 12% by 
weight before printing, and it increased to 17% by weight after 6,000 
sheet printing, between which there was a little increase. 
Restoration performance of the quantity of triboelectricity of the magnetic 
toner in the environment of high humidity is shown in Table 1. 
Example 14 
______________________________________ 
Styrene/butyl methacrylate copolymer 
100 parts 
(weight average molecular weight: 350,000) 
(peak 1: molecular weight 8,000; peak 2: 
molecular weight 150,000) 
Magnetic material 80 parts 
(average particle diameter: 0.2 .mu.m; coercive 
force: 110 oersted) 
Sasol wax 3 parts 
Iron compound (13) 3 parts 
______________________________________ 
A black fine powder (negatively chargeable magnetic toner) with a weight 
average particle diameter of 7.5 .mu.m was obtained by using the above 
materials in the same manner as in Example 10. 
The magnetic toner had a saturation magnetization of 30 Am.sup.2 /kg and a 
coercive force of 110 oersted. 
100 parts of the obtained magnetic toner and 0.8 part of hydrophobic silica 
(BET specific surface area: 200 m.sup.2 /g) were mixed using a Henschel 
mixer to obtain a one-component magnetic toner. 
The one-component magnetic toner obtained was applied to a commercially 
available electrophotographic copying machine NP-6060 (trade name; 
manufactured by Canon Inc.) to make 20,000 sheet copying test. 
As a result, sharp images with an image density of 1.38 were obtained from 
the initial stage. Images after 20,000 sheet copying were also sharp with 
a density of 1.40. With regard to the resolution of the images also, an 
initial value of 6.3 lines/mm was maintained. 
The quantity of triboelectricity of the magnetic toner was measured by 
blowing-off to ascertain that it was -11.2 .mu.c/g. The coarse powder with 
a particle diameter larger than 10.8 .mu.m was in a quantity of 33% by 
weight before printing, and 35% by weight after 20,000 sheet copying, so 
that there was little change. Restoration performance of the quantity of 
triboelectricity of the magnetic toner in the environment of high humidity 
is shown in Table 1. 
TABLE 1 
______________________________________ 
Tribo- 
Triboelectricity (2) 
elec. Shaken for 
Shaken for Shaken for 
(1) 0 sec. 60 sec. 240 sec. 
mC/kg mC/kg % mC/kg % mC/kg % 
______________________________________ 
Example 
1 -11.0 -9.9 90 -11.0 100 -11.0 100 
2 -10.2 -9.2 90 -10.0 98 -10.2 100 
3 -10.4 -9.4 90 -10.2 98 -10.4 98 
4 -10.3 -8.8 85 -9.6 93 -9.9 96 
5 -9.4 -7.8 83 -9.4 100 -9.4 100 
6 -9.2 -7.5 81 -8.2 90 -8.6 93 
7 -9.6 -8.6 90 -9.6 100 -9.6 100 
8 -12.5 -11.4 91 -12.5 100 -12.5 100 
9 -11.2 -10.2 91 -11.2 100 -11.2 100 
10 -10.0 -8.3 83 -9.2 92 -9.5 95 
11 -10.2 -8.5 83 -9.4 92 -9.7 95 
12 -13.0 -10.4 80 -11.3 87 -12.0 92 
13 -9.6 -7.5 78 -8.2 85 -8.8 92 
14 -8.9 -7.2 81 -7.8 88 -8.3 93 
Comparative 
Example 
1 -6.8 -5.1 75 -5.6 82 -6.1 89 
2 -6.2 -4.3 70 -4.7 75 -5.1 82 
3 -8.5 -7.0 82 -7.7 90 -7.9 93 
4 -4.2 -3.3 78 -3.7 88 -3.9 92 
______________________________________ 
Triboelectricity (1): Quantity of triboelectricity of magnetic toner whic 
was allowed to stand for 2 days at high temperature and high humidity in 
an uncovered polyethylene container and thereafter shaken in a tumbling 
mixer for 240 seconds. 
Triboelectricity (2): Quantity of triboelectricity of magnetic toner whic 
was further allowed to stand for 4 days at high temperature and high 
humidity and thereafter shaken in a tumbling mixer.