[0001] The present invention relates to a black toner comprising black non-magnetic composite
particles which are not only excellent in dispersibility in a binder resin due to
a less amount of carbon black desorbed or fallen-off from the surfaces thereof, but
also have more excellent fluidity and blackness; and having more excellent fluidity
and blackness as well as a high resistivity value.
[0002] In conventional electrophotographic developing processes, a black toner prepared
by mixing and dispersing non-magnetic black pigments such as carbon black fine particles
in a binder resin, has been widely used as a developer.
[0003] Recent developing systems have been generally classified into one-component developing
methods and two-component developing methods.
[0004] In the two-component developing methods, the black toner and carrier are brought
into frictional contact with each other to impart an electrostatic charge having a
reverse sign to that of an electrostatic latent image to the black toner, so that
the black toner is attached onto the surface of the electrostatic latent image due
to an electrostatic attracting force therebetween, thereby neutralizing opposite electrostatic
charges on the black toner and the electrostatic latent image.
[0005] On the other hand, in the one-component developing methods, since no carrier is used
therein, it is not necessary to control a density of the black toner. Besides, a developing
apparatus used therefor can be miniaturized due to its simple structure. However,
since the one-component developing methods are inferior in developing performance
or quality to the two-component developing methods, high techniques have now been
required to obtain the same developing performance or quality as those of the two-component
developing methods. As one of the one-component developing methods, there is known
a so-called insulated non-magnetic toner developing method using a high-resistant
or insulated black toner prepared by dispersing carbon black fine particles in a binder
resin without using magnetic particles.
[0006] In the case where the black toners used in the above two-component developing method
and the insulated non-magnetic toner developing method, are applied to a currently
predominant PPC system of copiers, both types of the black toners are required to
exhibit a good insulating property or a high resistance, specifically to have a volume
resistivity as high as not less than 1 × 10
13 Ω·cm.
[0007] Also, it is known that the behavior (movement) of a developer in a developing apparatus
is strongly governed by the fluidity thereof, for example, the fluidity of the developer
has strong influences on the frictional charging properties between the black toner
and the carrier in the case of the two-component developing method, or on the charging
property of the black toner on a sleeve in the case of the one-component developing
method. Recently, with the enhancement in image quality such as image density, or
tone gradation or in developing speed in the developing apparatus, it has been strongly
demanded to increase the fluidity of the black toner.
[0008] With the recent tendency of reducing a particle size of the black toner, it has been
more strongly required to enhance the fluidity thereof.
[0009] With respect to such a fact, in "Comprehensive Data Collection for Development and
Utilization of Toner Materials", published by Japan Scientific Information Co., Ltd.,
page 121, it has been described that "With extensive development of printers such
as IPC, a high image quality has been required. In particular, it has been demanded
to develop high-precision or high-definition printers. In Table 1, there is shown
a relationship between image definitions obtained by using various toners. As is apparent
from Table 1, the smaller the particle size of wet toner, the higher the image definition
becomes. When a dry toner is used, it is also required to reduce the particle size
of the toner for enhancing the image definition. ··· As to toners having a small particle
size, it has been reported that by using toners having a particle size of 8.5 to 11
µm, fogs on a background area as well as toner consumption can be reduced. Further,
it has been proposed that by using polyester-based toners having a particle size of
6 to 10 µm, an image quality, a charging stability and lifetime of the developer can
be improved. However, when such toners having a small particle size are used, it has
been required to solve many problems, e.g., those problems concerning productivity,
sharpness of particle size distribution, improvement in fluidity, etc.".
[0010] Also, the black toner has been required to show a high blackness and a high image
density of line images and solid area images on copies.
[0011] With respect to this fact, on page 272 of the above-mentioned "Comprehensive Data
Collection for Development and Utilization of Toner Materials", it has been described
that "Powder development is characterized by a high image density. However, the image
density as well as the fog density as described hereinafter, have strong influences
on image characteristics".
[0012] As described above, it has been strongly demanded to enhance various properties of
the black toner. It is known that the black toner, especially black pigments exposed
to the surface of the black toner, have large influences on developing characteristics.
There is a close relationship between properties of the black toner and those of the
black pigments mixed and dispersed in the black toner.
[0013] That is, the fluidity of the black toner considerably depends upon the surface condition
of the black pigments exposed to the surface of the black toner. Therefore, the black
pigments themselves have been strongly required to show an excellent fluidity. Further,
the blackness and density of the black toner also considerably depend upon the blackness
and density of the black pigments contained in the black toner.
[0014] At present, as the black pigments for black toner, there may be mainly used carbon
black fine particles (Japanese Patent No. 2715336 and Japanese Patent Application
Laid-Open (KOKAI) No. 10-39546(1998)).
[0015] There have now been most strongly demanded black non-magnetic particles for black
toner which can show not only more excellent fluidity and blackness, but also an excellent
dispersibility in a binder resin. However, such black non-magnetic particles capable
of satisfying all of these properties have not been obtained.
[0016] Namely, in the case where the above-mentioned carbon black fine particles are used
as the black particles for black toner, the amount of the carbon black fine particles
used must be restricted in order to obtain a black toner having a volume resistivity
of not less than 1 × 10
13 Ω·cm. For this reason, there arises a problem that a sufficient blackness and a sufficient
fluidity cannot be obtained.
[0017] The above conventional problems are explained more specifically below.
[0018] Due to the fact that the carbon black fine particles themselves are conductive materials,
when a large amount of the carbon black fine particles are added and mixed in the
black toner in order to enhance the blackness thereof, the volume resistivity of the
black toner is remarkably decreased because the carbon black fine particles having
a specific cluster-like structure are present on the surface of each black toner particle.
As a result, the toner is no longer usable as an insulating or high-resistant toner.
Conversely, when the amount of the carbon black fine particles contained in the black
toner is reduced to increase the volume resistivity value of the black toner, the
obtained black toner tends to be deteriorated in not only blackness but also fluidity.
This is because the carbon black fine particles are buried inside each black toner
particle due to the fineness of the carbon black fine particles having an average
particle size as small as 0.010 to 0.060 µm, and, therefore, the amount of the carbon
black fine particles exposed to the surface of each toner particle is reduced.
[0019] In addition, the carbon black fine particles have a specific gravity as low as 1.80
to 1.85, resulting in poor handing property of the carbon black fine particles. Further,
when such carbon black fine particles are dispersed in a binder resin, the obtained
black toner has merely a low bulk density. Such a black toner tends to be scattered
around and deteriorated in fluidity.
[0020] As a result of the present inventors' earnest studies for solving the above problems,
it has been found that by using as non-magnetic particles for a black toner, black
non-magnetic composite particles having an average particle size of 0.06 to 1.0 µm,
which comprise hematite particles or iron oxide hydroxide particles; a coating layer
formed on the surface of the hematite particles or iron oxide hydroxide particles,
comprising organosilicon compounds; and a carbon black coat formed at least a part
of the surface of the coating layer in an amount of 26 to 55 parts by weight based
on 100 parts by weight of the hematite particles or iron oxide hydroxide particles
, the obtained black toner is not only more excellent in fluidity and blackness, but
also can exhibit a high resistivity value. The present invention has been attained
on the basis of the finding.
[0021] It is an object of the present invention to provide a black toner which is not only
more excellent in fluidity and blackness, but also exhibits a high resistivity value.
[0022] It is an another object of the present invention to provide black non-magnetic composite
particles for black toner, which are not only more excellent in fluidity and blackness,
but also can show an excellent dispersibility in a binder resin.
[0023] To accomplish the aims, in a first aspect of the present invention, there is provided
a black toner comprising:
a binder resin; and
black non-magnetic composite particles having an average particle diameter of 0.06
to 1.0 µm, comprising:
hematite particles or iron oxide hydroxide particles as core particles;
a coating layer formed on the surface of the hematite particles or iron oxide hydroxide
particles, comprising at least one organosilicon compound selected from the group
consisting of:
(1) organosilane compounds obtained from an alkoxysilane compounds, and
(2) polysiloxanes or modified polysiloxanes; and
a carbon black coat formed on the coating layer comprising the organosilicon compound,
in an amount of 26 to 55 parts by weight based on 100 parts by weight of the hematite
particles or iron oxide hydroxide particles.
[0024] In a second aspect of the present invention, there is provided a black toner comprising:
black non-magnetic composite particles having an average particle diameter of 0.06
to 1.0 µm, comprising:
hematite particles or iron oxide hydroxide particles as core particles;
a coat formed on at least a part of the surface of the hematite particles or iron
oxide hydroxide particles and comprising at least one compound selected from the group
consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and
oxides of silicon in an amount of 0.01 to 50 % by weight, calculated as Al or SiO2, based on the total weight of the hematite particles or iron oxide hydroxide particles;
a coating layer formed on the said coat formed the surface of the hematite particles
or iron oxide hydroxide particles, comprising at least one organosilicon compound
selected from the group consisting of:
(1) organosilane compounds obtained from an alkoxysilane compounds, and
(2) polysiloxanes or modified polysiloxanes; and
a carbon black coat formed on the coating layer comprising the organosilicon compound,
in an amount of 26 to 55 parts by weight based on 100 parts by weight of the hematite
particles or iron oxide hydroxide particles.
[0025] In a third aspect of the present invention, there is provided a method of using black
non-magnetic composite particles for production of a black toner, comprising mixing
the black non-magnetic composite particles with a binder resin,
which black non-magnetic composite particles having an average particle diameter
of 0.06 to 1.0 µm, comprising:
hematite particles or iron oxide hydroxide particles as core particles;
a coating layer formed on the surface of the hematite particles or iron oxide hydroxide
particles, comprising at least one organosilicon compound selected from the group
consisting of:
(1) organosilane compounds obtained from an alkoxysilane compounds, and
(2) polysiloxanes or modified polysiloxanes; and
a carbon black coat formed on the coating layer comprising the organosilicon compound,
in an amount of 26 to 55 parts by weight based on 100 parts by weight of the hematite
particles or iron oxide hydroxide particles.
[0026] In a fourth aspect of the present invention, there are provided black non-magnetic
composite particles for a black toner,
which have an average particle diameter of 0.06 to 1.0 µm and a sphericity of from
1 to less than 2, and comprise:
hematite particles or iron oxide hydroxide particles as core particles;
a coating layer formed on the surface of the hematite particles or iron oxide hydroxide
particles, comprising at least one organosilicon compound selected from the group
consisting of:
(1) organosilane compounds obtained from an alkoxysilane compounds, and
(2) polysiloxanes or modified polysiloxanes; and
a carbon black coat formed on the coating layer comprising the organosilicon compound,
in an amount of 26 to 55 parts by weight based on 100 parts by weight of the hematite
particles or iron oxide hydroxide particles.
[0027] In a fifth aspect of the present invention, there are provided black non-magnetic
composite particles for a black toner,
which have an average particle diameter of 0.06 to 1.0 µm and a sphericity of from
1 to less than 2, and comprise:
hematite particles or iron oxide hydroxide particles as core particles;
a coat formed on at least a part of the surface of the hematite particles or iron
oxide hydroxide particles and comprising at least one compound selected from the group
consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and
oxides of silicon in an amount of 0.01 to 50 % by weight, calculated as Al or SiO2, based on the total weight of the hematite particles or iron oxide hydroxide particles;
a coating layer formed on the said coat formed on the surface of the hematite particles
or iron oxide hydroxide particles, comprising at least one organosilicon compound
selected from the group consisting of:
(1) organosilane compounds obtained from an alkoxysilane compounds, and
(2) polysiloxanes or modified polysiloxanes; and
a carbon black coat formed on the coating layer comprising the organosilicon compound,
in an amount of 26 to 55 parts by weight based on 100 parts by weight of the hematite
particles or iron oxide hydroxide particles.
[0028] The present invention will be described in detail below.
[0029] First, the black non-magnetic composite particles as one constituent of the black
toner according to the present invention, are explained.
[0030] The black non-magnetic composite particles used in the present invention are black
non-magnetic composite particles having an average particle size of 0.06 to 1.0 µm,
which comprise hematite particles or iron oxide hydroxide particles as core particles;
a coating layer formed on the surface of the hematite particles or iron oxide hydroxide
particles, comprising organosilicon compound; and a carbon black coat formed on at
least a part of the surface of the coating layer in a large amount.
[0031] As the core particles used in the present invention, there may be exemplified hematite
particles, iron oxide hydroxide particles or mixed particles thereof. In the consideration
of blackness of the obtained black non-magnetic composite particles, black hematite
particles, black iron oxide hydroxide particles or mixed particles thereof are preferred.
As the iron oxide hydroxide particles, there may be exemplified goethite particles,
lepidocrosite particles.
[0032] As the black hematite particles, there may be exemplified manganese-containing hematite
particles which contain manganese in an amount of 5 to 40 % by weight (calculated
as Mn) based on the weight of the manganese-containing hematite particles. As the
black iron oxide hydroxide particles, there may be exemplified manganese-containing
iron oxide hydroxide particles such as manganese-containing goethite particles, which
contain manganese in an amount of 5 to 40 % by weight (calculated as Mn) based on
the weight of the manganese-containing iron oxide hydroxide particles.
[0033] The core particles may be in the form of either isotropic particles having a sphericity
(ratio of an average particle length to an average particle breadth; hereinafter referred
to merely as "sphericity") of not less than 1.0:1 and less than 2.0:1, such as spherical
particles, granular particles or polyhedral particles, e.g., hexahedral particles
or octahedral particles; or anisotropic particles having an aspect ratio (ratio of
average major axial diameter to average minor axial diameter; hereinafter referred
to merely as "aspect ratio") of not less than 2.0:1, such as acicular particles, spindle-shaped
particles or rice grain-shaped particles. In the consideration of the fluidity of
the obtained black non-magnetic composite particles, the use of the isotropic particles
is preferred, and the use of the spherical particles and the granular particles is
more preferred.
[0034] In the case of the isotropic hematite particles or iron oxide hydroxide particles
as core particles, the average particle size (diameter) thereof is 0.055 to 0.95 µm,
preferably 0.065 to 0.75 µm, more preferably 0.065 to 0.45 µm. The sphericity thereof
is usually not less than 1.0:1 and less than 2.0:1, preferably 1.0:1 to 1.8:1, more
preferably 1.0:1 to 1.6:1.
[0035] In the case of the anisotropic hematite particles or iron oxide hydroxide particles
as core particles, the average major axial diameter thereof is 0.055 to 0.95 µm, preferably
0.065 to 0.75 µm, more preferably 0.065 to 0.45 µm. The aspect ratio thereof is 2.0:1
to 20.0:1, preferably 2.0:1 to 18.0:1, more preferably 2.0:1 to 15.0:1.
[0036] When the average particle size of the hematite particles or iron oxide hydroxide
particles is more than 0.95 µm, the obtained black non-magnetic composite particles
are coarse particles and are deteriorated in tinting strength. On the other hand,
when the average particle size is less than 0.055 µm, the intermolecular force between
the particles is increased due to the reduction in particle diameter, so that agglomeration
of the particles tends to be caused. As a result, it becomes difficult to uniformly
coat the surface of the hematite particles or iron oxide hydroxide particles with
the organosilicon compounds, and uniformly form the carbon black coat on the surface
of the coating layer comprising the organosilicon compounds.
[0037] When the core particles have an anisotropic shape, and the upper limit of the aspect
ratio is more than 20:1, the particles tend to be entangled with each other. As a
result, it is difficult to form a uniform coating layer comprising the organosilicon
compounds on the surfaces of the core particles and uniformly form carbon black coat
onto the surface of the coating layer.
[0038] As to the particle diameter distribution of the hematite particles or iron oxide
hydroxide particles, the geometrical standard deviation value thereof is preferably
not more than 2.0, more preferably not more than 1.8, still more preferably not more
than 1.6. When the geometrical standard deviation value thereof is more than 2.0,
coarse particles are contained therein, so that the particles are inhibited from being
uniformly dispersed. As a result, it also becomes difficult to uniformly coat the
surfaces of the hematite particles or iron oxide hydroxide particles with the organosilicon
compounds, and uniformly form the carbon black coat on the surface of the coating
layer composed of the organosilicon compounds. The lower limit of the geometrical
standard deviation value is 1.01. It is industrially difficult to obtain particles
having a geometrical standard deviation value of less than 1.01.
[0039] The BET specific surface area of the hematite particles or iron oxide hydroxide particles
thereof is not less than 0.5 m
2/g. When the BET specific surface area is less than 0.5 m
2/g, the hematite particles or iron oxide hydroxide particles may become coarse particles,
or the sintering between the particles may be caused, so that the obtained black non-magnetic
composite particles also may become coarse particles and tend to be deteriorated in
tinting strength. In the consideration of the tinting strength of the obtained black
non-magnetic composite particles, the BET specific surface area of the hematite particles
or iron oxide hydroxide particles is preferably not less than 1.0 m
2/g, more preferably 1.5 m
2/g. Further, in the consideration of uniformly coating the surfaces of the hematite
particles or iron oxide hydroxide particles with the organosilicon compounds, and
uniformly forming the carbon black coat on the coating layer composed of the organosilicon
compounds, the upper limit of the BET specific surface area of the hematite particles
or iron oxide hydroxide particles, is usually 190 m
2/g, preferably 140 m
2/g, more preferably 90 m
2/g.
[0040] As to the fluidity of the hematite particles or iron oxide hydroxide particles, the
fluidity index thereof is about 25 to about 42. Among the hematite particles or iron
oxide hydroxide particles having various shapes, the spherical particles are excellent
in fluidity, for example, the fluidity index thereof is about 30 to about 42.
[0041] As to the blackness of the core particles, in the case of the hematite particles,
the lower limit thereof is usually 18.0 when represented by L* value, and the upper
limit thereof is usually 36.0, preferably 34.0 when represented by L* value. In the
case of the iron oxide hydroxide particles such as the goethite particles, the lower
limit thereof is usually 18.0 when represented by L* value, and the upper limit thereof
is usually 38.0, preferably 36.0 when represented by L* value.
[0042] In the case of the black hematite particles such as the manganese-containing hematite
particles, the lower limit thereof is usually 18.0 when represented by L* value, and
the upper limit thereof is usually 28.0, preferably 25.0 when represented by L* value.
In the case of the black iron oxide hydroxide particles such as the manganese-containing
goethite particles, the lower limit thereof is usually 18.0 when represented by L*
value, and the upper limit thereof is usually 30.0, preferably 28.0 when represented
by L* value.
[0043] When the L* value exceeds the above-mentioned upper limit, the lightness of the particles
is increased, so that it is difficult to obtain black non-magnetic composite particles
having a sufficient blackness.
[0044] As the core particle, there may be used hematite particles or iron oxide hydroxide
particles wherein at least a part of the surface of the hematite particle or iron
oxide hydroxide particle is preliminarily coated with at least one compound selected
from the group consisting of hydroxides of aluminum, oxides of aluminum, hydroxides
of silicon and oxides of silicon (hereinafter referred to as "hydroxides and/or oxides
of aluminum and/or silicon"). In this case, the dispersibility of the obtained composite
particles in a vehicle may become improved as compared to those having no undercoat
composed of hydroxides and/or oxides of aluminum and/or silicon, because the percentage
of desorption of carbon black from the black non-magnetic composite particles is lessened.
[0045] The amount of the coat composed of hydroxides and/or oxides of aluminum and/or silicon
is preferably 0.01 to 50 % by weight (calculated as Al, SiO
2 or a sum of Al and SiO
2) based on the weight of the hematite particles or iron oxide hydroxide particles
as core particles.
[0046] When the amount of the hydroxides and/or oxides of aluminum and/or silicon coat is
less than 0.01 % by weight, the effect of enhancing the dispersibility of the obtained
black non-magnetic composite particles in a binder resin upon the production of black
toner may not be obtained, because of failing to achieve the improvement of lessening
the percentage of desorption of carbon black therefrom. On the other hand, when the
amount of the hydroxides and/or oxides of aluminum and/or silicon coat is more than
50 % by weight, the obtained black non-magnetic composite particles can exhibit a
good dispersibility in a binder resin upon the production of black toner by the improvement
of lessening the percentage of desorption of carbon black therefrom. However, the
coating effect is saturated and, therefore, it is meaningless to add such an excess
amount of the hydroxides and/or oxides of aluminum and/or silicon coat.
[0047] The particle shape and particle size of the black non-magnetic composite particles
used in the present invention are considerably varied depending upon those of the
hematite particles or iron oxide hydroxide particles as core particles. The black
non-magnetic composite particles have a similar particle shape to that of the hematite
particles or iron oxide hydroxide particles as core particle, and a slightly larger
particle size than that of the hematite particles or iron oxide hydroxide particles
as core particles.
[0048] More specifically, when the isotropic hematite particles or iron oxide hydroxide
particles are used as core particles, the obtained black non-magnetic composite particles
used in the present invention, have an average particle size of usually 0.06 to 1.0
µm, preferably 0.07 to 0.8 µm, more preferably 0.07 to 0.5 µm and a sphericity of
usually from not less than 1.0:1 and less than 2.0:1, preferably 1.0:1 to 1.8:1, more
preferably 1.0:1 to 1.6:1.
[0049] When the anisotropic hematite particles or iron oxide hydroxide particles are used
as core particles, the lower limit of the average particle diameter of the obtained
black non-magnetic composite particles used in the present invention, is usually 0.06
µm, preferably 0.07 µm, and the upper limit of average particle diameter thereof is
usually 1.0 µm, preferably 0.8 µm, more preferably 0.5 µm. In addition, the aspect
ratio of the obtained black non-magnetic composite particles according to the present
invention, is usually 2.0:1 to 20.0:1, preferably 2.0: 1 to 18.0:1, more preferably
2.0:1 to 15.0:1.
[0050] When the average particle size of the black non-magnetic composite particles is more
than 1.0 µm, the obtained black non-magnetic composite particles may be coarse particles,
and deteriorated in tinting strength. On the other hand, when the average particle
diameter thereof is less than 0.06 µm, the black non-magnetic composite particles
tends to be agglomerated by the increase of intermolecular force due to the reduction
in particle size, thereby deteriorating the dispersibility in a binder resin upon
production of the black toner.
[0051] When the aspect ratio is more than 20.0:1, the black non-magnetic composite particles
may be entangled with each other in the binder resin, so that the dispersibility in
binder resin upon the production of the black toner tends to be deteriorated.
[0052] The geometrical standard deviation value of the black non-magnetic composite particles
used in the present invention is preferably not more than 2.0, more preferably not
more than 1.8, still more preferably not more than 1.6. The lower limit of the geometrical
standard deviation value thereof is preferably 1.01. When the geometrical standard
deviation value thereof is more than 2.0, the tinting strength of the black non-magnetic
composite particles is likely to be deteriorated due to the existence of coarse particles
therein. It is industrially difficult to obtain such particles having a geometrical
standard deviation of less than 1.01.
[0053] The BET specific surface area of the black non-magnetic composite particles used
in the present invention, is usually 1.0 to 200 m
2/g, preferably 1.5 to 150 m
2/g, more preferably 2.0 to 100 m
2/g. When the BET specific surface area thereof is less than 1.0 m
2/g, the obtained black non-magnetic composite particles may be coarse, and the sintering
between the particles is caused, thereby deteriorating the tinting strength. On the
other hand, when the BET specific surface area is more than 200 m
2/g, the black non-magnetic composite particles tend to be agglomerated together by
the increase in intermolecular force due to the reduction in particle size, thereby
deteriorating the dispersibility in a binder resin upon production of the black toner.
[0054] As to the fluidity of the black non-magnetic composite particles used in the present
invention, the fluidity index thereof is preferably 48 to 90, more preferably 49 to
90, still more preferably 50 to 90. When the fluidity index thereof is less than 48,
the fluidity of the black non-magnetic composite particles becomes insufficient, thereby
failing to improve the fluidity of the finally obtained black toner. Further, in the
production process of the black toner, there tend to be caused defects such as clogging
of hopper, etc., thereby deteriorating the handling property or workability.
[0055] As to the blackness of the black non-magnetic composite particles used in the present
invention, in the case the hematite particles are used as core particles, the upper
limit of the blackness of the black non-magnetic composite particles is usually 19.5,
preferably 18.8, more preferably 18.3 when represented by L* value. In the case the
iron oxide hydroxide particles such as the goethite particles are used as core particles,
the upper limit of the blackness of the black non-magnetic composite particles is
usually 19.5, preferably 19.3, more preferably 18.8 when represented by L* value.
[0056] In the case the black hematite particles such as the manganese-containing hematite
particles are used as core particles, the upper limit of the blackness of the black
non-magnetic composite particles is usually 19.5, preferably 18.3, more preferably
17.8 when represented by L* value. In the case the black iron oxide hydroxide particles
such as the manganese-containing goethite particles are used as core particles, the
upper limit of the blackness of the black non-magnetic composite particles is usually
19.5, preferably 18.8, more preferably 18.3 when represented by L* value.
[0057] When the L* value thereof is more than 19.5, the lightness of the obtained black
non-magnetic composite particles becomes high, so that the black non-magnetic composite
particles having a sufficient blackness cannot be obtained. The lower limit of the
blackness thereof is 15 when represented by L* value.
[0058] The dispersibility in binder resin of the black non-magnetic composite particles
used in the present invention, is preferably 4th or 5th rank, more preferably 5th
rank when evaluated by the method described hereinafter.
[0059] The percentage of desorption of carbon black from the black non-magnetic composite
particles used in the present invention, is preferably not more than 20 %, more preferably
not more than 10 %. When the desorption percentage of the carbon black is more than
20 %, the desorbed carbon black tend to inhibit the black non-magnetic composite particles
from being uniformly dispersed in the binder resin upon production of the black toner.
[0060] The coating formed on the surfaces of the core particles comprises at least one organosilicon
compound selected from the group consisting of (1) organosilane compounds obtainable
from alkoxysilane compounds; (2) polysiloxanes, and (2') modified polysiloxanes selected
from the group consisting of (A) polysiloxanes modified with at least one compound
selected from the group consisting of polyethers, polyesters and epoxy compounds (hereinafter
referred to merely as "modified polysiloxanes"), and (B) polysiloxanes whose molecular
terminal is modified with at least one group selected from the group consisting of
carboxylic acid groups, alcohol groups and a hydroxyl group (hereinafter referred
to merely as " terminal-modified polysiloxanes").
[0061] The organosilane compounds (1) may be produced by drying or heat-treating alkoxysilane
compounds represented by the formula (I):
R
1 aSiX
4-a (I)
wherein R
1 is C
6H
5-, (CH
3)
2CHCH
2- or n-C
bH
2b+1- (wherein b is an integer of 1 to 18); X is CH
3O- or C
2H
5O-; and a is an integer of 0 to 3.
[0062] The drying or heat-treatment of the alkoxysilane compounds may be conducted, for
example, at a temperature of usually 40 to 200°C, preferably 60 to 150°C for usually
10 minutes to 12 hours, preferably 30 minutes to 3 hours.
[0063] Specific examples of the alkoxysilane compounds may include methyltriethoxysilane,
dimethyldiethoxysilane, phenyltriethyoxysilane, diphenyldiethoxysilane, methyltrimethoxysilane,
dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, isobutyltrimethoxysilane,
decyltrimethoxysilane or the like. Among these alkoxysilane compounds, in view of
the desorption percentage and the adhering effect of carbon black, methyltriethoxysilane,
phenyltriethyoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane and isobutyltrimethoxysilane
are preferred, and methyltriethoxysilane and methyltrimethoxysilane are more preferred.
[0064] As the polysiloxanes (2), there may be used those compounds represented by the formula
(II):
wherein R
2 is H- or CH
3-, and d is an integer of 15 to 450.
[0065] Among these polysiloxanes, in view of the desorption percentage and the adhering
effect of carbon black, polysiloxanes having methyl hydrogen siloxane units are preferred.
[0066] As the modified polysiloxanes (2'-A), there may be used:
(a) polysiloxanes modified with polyethers represented by the formula (III):
wherein R3 is -(-CH2-)h-; R4 is -(-CH2-)i-CH3; R5 is -OH, -COOH, -CH=CH2, -C(CH3)=CH2 or - (-CH2-)j-CH3; R6 is -(-CH2-)k-CH3; g and h are an integer of 1 to 15; i, j and k are an integer of 0 to 15; e is an
integer of 1 to 50; and f is an integer of 1 to 300;
(b) polysiloxanes modified with polyesters represented by the formula (IV):
wherein R7, R8 and R9 are -(-CH2-)q- and may be the same or different; R10 is -OH, -COOH, -CH=CH2, -C(CH3)=CH2 or -(-CH2-)r-CH3; R11 is -(-CH2-)s-CH3; n and q are an integer of 1 to 15; r and s are an integer of 0 to 15; e' is an integer
of 1 to 50; and f' is an integer of 1 to 300;
(c) polysiloxanes modified with epoxy compounds represented by the formula (V):
wherein R12 is -(-CH2-)v-; v is an integer of 1 to 15; t is an integer of 1 to 50; and u is an integer of
1 to 300; or a mixture thereof.
[0067] Among these modified polysiloxanes (2'-A), in view of the desorption percentage and
the adhering effect of carbon black, the polysiloxanes modified with the polyethers
represented by the formula (III), are preferred.
[0068] As the terminal-modified polysiloxanes (2'-B), there may be used those represented
by the formula (VI):
wherein R
13 and R
14 are -OH, R
16OH or R
17COOH and may be the same or different; R
15 is -CH
3 or -C
6H
5; R
16 and R
17 are -(-CH
2-)
y-; y is an integer of 1 to 15; w is an integer of 1 to 200; and x is an integer of
0 to 100.
[0069] Among these terminal-modified polysiloxanes, in view of the desorption percentage
and the adhering effect of carbon black, the polysiloxanes whose terminals are modified
with carboxylic acid groups are preferred.
[0070] The amount of the coating layer composed of the organosilicon compounds is usually
0.02 to 5.0 % by weight, preferably 0.03 to 4.0 % by weight, more preferably 0.05
to 3.0 % by weight (calculated as Si) based on the weight of the hematite particles
or iron oxide hydroxide particles coated with the organosilicon compounds.
[0071] When amount of the coating layer composed of the organosilicon compounds is less
than 0.02 % by weight, it becomes difficult to adhere the carbon black on the surfaces
of the hematite particles or iron oxide hydroxide particles. On the other hand, when
the coating amount of the organosilicon compounds is more than 5.0 % by weight, since
the carbon black coat can be sufficiently formed on the surface of the coating layer
composed of the organosilicon compounds, it is meaningless to coat an excess amount
of the organosilicon compounds.
[0072] A carbon black coat is formed on at least a part of the surface of coating layer
composed of the organosilicon compounds, and is composed of at least two carbon black
layers integrally adhered with each other through an adhesive. If required, 3 or more
carbon black layers are integrally adhered with each other through an adhesive to
form the carbon black coat.
[0073] In the present invention, the amount of carbon black coat is 26 to 55 parts by weight
based on 100 parts by weight of the core particles.
[0074] When the amount of the carbon black coat is less than 26 parts by weight, it is difficult
to obtain the aimed black non-magnetic composite particles having more excellent fluidity
and blackness. When the amount of the carbon black coated is more than 55 parts by
weight, the desorption percentage of the carbon black is increased, resulting in poor
dispersibility in a binder resin upon production of the black toner.
[0075] The thickness of the carbon black coat is preferably not more than 0.06 µm, more
preferably not more than 0.05 µm, still more preferably 0.04 µm. The lower limit thereof
is more preferably 0.0001 µm.
[0076] In the black non-magnetic composite particles used in the present invention, at least
a part of the surface of the hematite particle or iron oxide hydroxide particle as
core particle may be preliminarily coated with hydroxides and/or oxides of aluminum
and/or silicon. In this case, the obtained black non-magnetic composite particles
can show a higher dispersibility in a binder resin as compared to in the case where
the hematite particles or iron oxide hydroxide particles are uncoated with hydroxides
and/or oxides of aluminum and/or silicon, because of achieving the improvement of
lessening the percentage of desorption of carbon black therefrom.
[0077] The black non-magnetic composite particles using as core particles the hematite particle
or iron oxide hydroxide particle having the coat composed of the hydroxides and/or
oxides of aluminum and/or silicon may be substantially identical in a particle size,
a geometrical standard deviation, a BET specific surface area, a blackness (L* value),
a fluidity and a magnetic property, to those having no hydroxides and/or oxides of
aluminum and/or silicon coat.
[0078] By coating the core particle with the hydroxides and/or oxides of aluminum and/or
silicon, the percentage of desorption of carbon black from the obtained black non-magnetic
composite particles of the present invention is preferably not more than 10 %, more
preferably not more than 5 %.
[0079] Next, the black toner according to the present invention is described.
[0080] The black toner according to the present invention comprises the black non-magnetic
composite particles, and a binder resin. The black toner may further contain a mold
release agent, a colorant, a charge-controlling agent and other additives, if necessary.
[0081] The black toner according to the present invention has an average particle size of
usually 3 to 25 µm, preferably 4 to 18 µm, more preferably 5 to 15 µm.
[0082] The amount of the binder resin used in the black toner is usually 50 to 3500 parts
by weight, preferably 50 to 2000 parts by weight, more preferably 50 to 1000 parts
by weight based on 100 parts by weight of the black non-magnetic composite particles.
[0083] As the binder resins, there may be used vinyl-based polymers, i.e., homopolymers
or copolymers of vinyl-based monomers such as styrene, alkyl acrylates and alkyl methacrylates.
As the styrene monomers, there may be exemplified styrene and substituted styrenes.
As the alkyl acrylate monomers, there may be exemplified acrylic acid, methyl acrylate,
ethyl acrylate, butyl acrylate or the like.
[0084] It is preferred that the above copolymers contain styrene-based components in an
amount of usually 50 to 95 % by weight.
[0085] In the binder resin used in the present invention, the above-mentioned vinyl-based
polymers may be used in combination with polyester-based resins, epoxy-based resins,
polyurethane-based resins or the like.
[0086] As to the fluidity of the black toner according to the present invention, the fluidity
index is usually 78 to 100, preferably 79 to 100, more preferably 80 to 100. When
the fluidity index is less than 78, the black toner may not show a sufficient fluidity.
[0087] The blackness of the black toner according to the present invention is usually not
more than 19.0, preferably not more than 18.8, more preferably not more than 18.5
when represented by L* value. When the blackness thereof is more than 19.0, the lightness
of the black toner may be increased, resulting in insufficient blackness. The lower
limit of the blackness of the black toner is usually about 15 when represented by
L* value.
[0088] The volume resistivity of the black toner according to the present invention, is
usually not less than 1.0 × 10
13 Ω·cm, preferably not less than 3.0 × 10
13 Ω·cm, more preferably not less than 5.0 × 10
13 Ω·cm. When the volume resistivity is less than 1.0 x 10
13 Ω·cm, the charge amount of the black toner tends to vary depending upon environmental
conditions in which the toner is used, resulting in unstable properties of the black
toner. The upper limit of the volume resistivity thereof is 1.0 × 10
17 Ω·cm.
[0089] The black non-magnetic composite particles according to the present invention can
be produced by the following method.
[0090] The granular hematite particles as the isotropic core particles used in the present
invention can be produced by heating, in air at a temperature of 750 to 1,000°C, granular
magnetite particles which are obtained by a so-called wet oxidation method, i.e.,
by passing an oxygen-containing gas through a suspension containing a ferrous hydroxide
colloid obtained by reacting an aqueous ferrous salt solution with alkali hydroxide.
[0091] The granular manganese-containing hematite particles as the isotropic core particles
used in the present invention, can be produced by heating, in air at a temperature
of 750 to 1,000°C, (a) coated magnetite particles which are obtained by first producing
granular magnetite particles by a so-called wet oxidation method, i.e., by passing
an oxygen-containing gas through a suspension containing a ferrous hydroxide colloid
obtained by reacting an aqueous ferrous salt solution with alkali hydroxide, and then
coating the obtained granular magnetite particles with a manganese compound in an
amount of 8 to 150 atm % (calculated as Mn) based on whole Fe, or (b) magnetite particles
containing manganese in an amount of 8 to 150 atm % (calculated as Mn) based on whole
Fe, which are obtained by conducting the above wet oxidation method in the presence
of manganese. In the consideration of blackness of the obtained manganese-containing
hematite particles, it is preferred to use the manganese-containing magnetite particles
(b).
[0092] The acicular or spindle-shaped hematite particles as the anisotropic core particles
used in the present invention, can be produced by heating acicular or spindle-shaped
iron oxide hydroxide particles obtained by the method described hereinafter, in air
at a temperature of 400 to 800°C.
[0093] The acicular or spindle-shaped iron oxide hydroxide particles as the anisotropic
core particles used in the present invention, can be produced by passing an oxygen-containing
gas through a suspension containing either ferrous hydroxide colloid, iron carbonate
or iron-containing precipitates obtained by reacting an aqueous ferrous salt solution
with alkali hydroxide, alkali carbonate or both of alkali hydroxide and alkali carbonate,
and then subjecting the obtained iron oxide hydroxide particles to filtration, washing
with water and drying.
[0094] The acicular or spindle-shaped manganese-containing hematite particles as the anisotropic
core particles used in the present invention, can be produced by heating, in air at
a temperature of 400 to 800°C, acicular or spindle-shaped iron oxide hydroxide particles
containing manganese in an amount of 8 to 150 atomic % based on whole Fe, which are
obtained by the method described hereinafter.
[0095] The acicular or spindle-shaped manganese-containing iron oxide hydroxide particles
as the anisotropic core particles used in the present invention, can be produced by
passing an oxygen-containing gas through a suspension containing either ferrous hydroxide
colloid, iron carbonate or iron-containing precipitates obtained by reacting an aqueous
ferrous salt solution with alkali hydroxide, alkali carbonate or both of alkali hydroxide
and alkali carbonate, in the presence of manganese in an amount of 8 to 150 atm %
(calculated as Mn) based on whole Fe, and then subjecting the obtained iron oxide
hydroxide particles to filtration, washing with water and drying.
[0096] The coating of the hematite particles or iron oxide hydroxide particles with the
alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes or the terminal-modified
polysiloxanes, can be conducted (i) by mechanically mixing and stirring the hematite
particles or iron oxide hydroxide particles together with the alkoxysilane compounds,
the polysiloxanes, the modified polysiloxanes or the terminal-modified polysiloxanes;
or (ii) by mechanically mixing and stirring both the components together while spraying
the alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes or the terminal-modified
polysiloxanes onto the hematite particles or iron oxide hydroxide particles. In these
cases, substantially whole amount of the alkoxysilane compounds, the polysiloxanes,
the modified polysiloxanes or the terminal-modified polysiloxanes added can be applied
onto the surfaces of the hematite particles or iron oxide hydroxide particles.
[0097] In order to uniformly coat the surfaces of the hematite particles or iron oxide hydroxide
particles with the alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes
or the terminal-modified polysiloxanes, it is preferred that the hematite particles
or iron oxide hydroxide particles are preliminarily diaggregated by using a pulverizer.
[0098] As apparatuses used for (a) mixing and stirring the core particles with alkoxysilane
compounds, the polysiloxanes, the modified polysiloxanes or the terminal-modified
polysiloxanes; (b) mixing and stirring the carbon black fine particles with the particles
surface-coated with alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes
or the terminal-modified polysiloxanes; (c) mixing and stirring the adhesive with
the particles having a first carbon black coat formed onto the surface-coating composed
of alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes or the terminal-modified
polysiloxanes (hereinafter referred to as "composite particles"); and (d) mixing and
stirring the carbon black fine particles with the composite particles coated with
the adhesive, there may be preferably used apparatus capable of applying a shearing
force to a layer of the particles to be treated, more preferably those capable of
conducting shearing, spatula-stroking and compression at the same time, for example,
wheel-type kneader, ball-type kneader, blade-type kneader, roll-type kneader or the
like. Among these apparatuses, the wheel-type kneader is more effective for the practice
of the present invention.
[0099] Specific examples of the wheel-type kneaders may include an edge runner (equal to
a mix muller, a Simpson mill or a sand mill), a multi-mull, a Stotz mill, a wet pan
mill, a Conner mill, a ring muller, or the like. Among them, an edge runner, a multi-mull,
a Stotz mill, a wet pan mill and a ring muller are preferred, and an edge runner is
more preferred.
[0100] Specific examples of the ball-type kneaders may include a vibrating mill or the like.
Specific examples of the blade-type kneaders may include a Henschel mixer, a planetary
mixer, a Nawter mixer or the like. Specific examples of the roll-type kneaders may
include an extruder or the like.
[0101] In order to coat the surfaces of the core particles with the alkoxysilane compounds,
the polysiloxanes, the modified polysiloxanes or the terminal-modified polysiloxanes
as uniformly as possible, the conditions of the above mixing or stirring treatment
may be appropriately controlled such that the linear load is usually 19.6 to 1960
N/cm (2 to 200 Kg/cm), preferably 98 to 1470 N/cm (10 to 150 kg/cm), more preferably
147 to 980 N/cm (15 to 100 kg/cm); and the treating time is usually 5 to 120 minutes,
preferably 10 to 90 minutes. It is preferred to appropriately adjust the stirring
speed in the range of usually 2 to 2,000 rpm, preferably 5 to 1,000 rpm, more preferably
10 to 800 rpm.
[0102] The amount of the alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes
or the terminal-modified polysiloxanes added, is preferably 0.15 to 45 parts by weight
based on 100 parts by weight of the hematite particles or iron oxide hydroxide particles.
When the amount of the alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes
or the terminal-modified polysiloxanes added is less than 0.15 part by weight, it
may become difficult to form the carbon black coat on the coating layer.
[0103] On the other hand, when the amount of the alkoxysilane compounds, the polysiloxanes,
the modified polysiloxanes or the terminal-modified polysiloxanes added is more than
45 parts by weight, a sufficient amount of the carbon black coat can be formed on
the surface of the coating, and therefore, it is meaningless to add such an excess
amount of the alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes
or the terminal-modified polysiloxanes.
[0104] Meanwhile, a part of the alkoxysilanes coated on the surfaces of the core particles
may be converted into the organosilane compounds via the coating step thereof. Even
in such a case, the subsequent adhesion step with carbon black is not adversely affected.
[0105] Next, the carbon black fine particles are added to the hematite particles or iron
oxide hydroxide particles coated with the polysiloxanes, the modified polysiloxanes
or the terminal-modified polysiloxanes, and the resultant mixture is mixed and stirred
to form a first carbon black coat on the surfaces of the coating composed of the polysiloxanes,
the modified polysiloxanes or the terminal-modified polysiloxanes added.
[0106] As the carbon black fine particles used in the present invention, there may be exemplified
commercially available carbon blacks such as furnace black, channel black or the like.
Specific examples of the commercially available carbon blacks usable in the present
invention, may include #3050, #3150, #3250, #3750, #3950, MA100, MA7, #1000, #2400B,
#30, MA77, MA8, #650, MA11, #50, #52, #45, #2200B, MA600, etc. (tradename, produced
by Mitsubishi Chemical Corp.), SEAST 9H, SEAST 7H, SEAST 6, SEAST 3H, SEAST 300, SEAST
FM, etc. (tradename, produced by Tokai Carbon Co., Ltd.), Raven 1250, Raven 860 ULTRA,
Raven 1000, Raven 1190 ULTRA, etc. (tradename, produced by Colombian Chemicals Company),
Ketchen black EC, Ketchen black EC600JD, etc. (tradename, produced by Ketchen Black
International Co., Ltd.), BLACK PEARLS-L, BLACK PEARLS 1000, BLACK PEARLS 4630, VULCAN
XC72, REGAL 660, REGAL 400, etc. (tradename, produced by Cabott Specialty Chemicals
Ink Co., Ltd.), or the like.
[0107] In the consideration of uniformly forming the carbon black coat onto the coating
composed of the alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes
or the terminal-modified polysiloxanes, or the dimethylpolysiloxane coating layer,
the use of carbon black fine particles having a DBP oil absorption of not more than
150 ml/100g is preferred. Specific examples of the commercially available carbon blacks
usable in the present invention, may include MA100, MA7, #1000, #2400B, #30, MA77,
MA8, #650, MA11, #50, #52, #45, #2200B, MA600, etc. (tradename, produced by MITSUBISHI
CHEMICAL CORP.), SEAST 9H, SEAST 7H, SEAST 6, SEAST 3H, SEAST 300, etc. (tradename,
produced by TOKAI CARBON CO., LTD.), Raven 1250, Raven 860 ULTRA, Raven 1000, Raven
1190 ULTRA, etc. (tradename, produced by COLOMBIAN CHEMICALS COMPANY), BLACK PEARLS-L,
BLACK PEARLS 1000, BLACK PEARLS 4630, REGAL 660, REGAL 400, etc. (tradename, produced
by CABOTT SPECIALTY CHEMICALS INK CO., LTD.).
[0108] The average particle size of the carbon black fine particles used is usually 0.002
to 0.05 µm, preferably 0.002 to 0.035 µm. When the average particle size of the carbon
black fine particles used is less than 0.002 µm, the carbon black fine particles used
are too fine to be well handled.
[0109] On the other hand, when the average particle size thereof is more than 0.05 µm, since
the particle size of the carbon black fine particles used is much larger, it is necessary
to apply a larger mechanical shear force for forming the uniform carbon black coat
on the coating layer composed of the organosilicon compounds, thereby rendering the
coating process industrially disadvantageous.
[0110] It is preferred that the carbon black fine particles are added little by little and
slowly, especially about 5 to 60 minutes.
[0111] In order to form the first carbon black coat onto the coating layer composed of the
alkoxysilane compounds, the polysiloxanes, the modified polysiloxanes or the terminal-modified
polysiloxanes as uniformly as possible, the conditions of the above mixing or stirring
treatment can be appropriately controlled such that the linear load is usually 19.6
to 1960 N/cm (2 to 200 Kg/cm), preferably 98 to 1470 N/cm (10 to 150 Kg/cm), more
preferably 147 to 980 N/cm (15 to 100 Kg/cm); and the treating time is usually 5 to
120 minutes, preferably 10 to 90 minutes. It is preferred to appropriately adjust
the stirring speed in the range of usually 2 to 2,000 rpm, preferably 5 to 1,000 rpm,
more preferably 10 to 800 rpm.
[0112] The amount of the carbon black fine particles added for forming the first carbon
black layer is usually 1 to 25 parts by weight, preferably 5 to 25 parts by weight
based on 100 parts by weight of the core particles. When the amount of the carbon
black fine particles added is less than 1 part by weight, a satisfactory first carbon
black layer may not be formed, so that the amount of the adhesive capable of adhering
to the first carbon black layer may become insufficient. In such a case, when the
carbon black fine particles for forming the second carbon black layer is subsequently
added in such a large amount that a total amount of carbon black adhered is not less
than 26 parts by weight based on 100 parts by weight of the core particles, it may
be difficult to adhere a sufficient amount of carbon black thereonto. In addition,
the desorption percentage of carbon black may be increased, resulting in poor dispersibility
of the obtained black non-magnetic composite particles in a binder resin upon production
of the black toner. On the contrary, when the amount of the carbon black fine particles
added for forming the first carbon black layer is more than 25 parts by weight, the
carbon black fine particles may tend to be desorbed or fallen-off from the surfaces
of the core particles and, as a result, from the surfaces of the obtained black non-magnetic
composite particles.
[0113] Then, a second carbon black coat is formed onto the first carbon black coat through
an adhesive such as dimethylpolysiloxanes.
[0114] The first and second carbon black coats can be bonded to each other by adhering the
carbon black themselves through the adhesive, thereby obtaining a carbon black coat
wherein the first and second carbon black coats are integrated. In order to obtain
black non-magnetic composite particles exhibiting excellent fluidity and blackness,
in which the two carbon black coats are firmly and uniformly bonded together, dimethylpolysiloxanes
represented by the following formula is preferably used as the adhesive.
wherein v' is a is an integer of 15 to 450.
[0115] The amount of the adhesive added is 0.1 to 5.0 parts by weight, preferably 0.2 to
4.0 parts by weight, more preferably 0.3 to 3.0 parts by weight based on 100 parts
by weight of the core particles.
[0116] When the amount of the adhesive is less than 0.1 part by weight, it may be difficult
to sufficiently bond the second carbon black coat onto the first carbon black coat,
thereby failing to obtain black non-magnetic composite particles exhibiting a more
excellent fluidity and a more excellent blackness.
[0117] When the amount of the adhesive adhered is more than 5.0 part by weight, the carbon
black can be adhered thereon in such an amount enough to achieve the more excellent
fluidity and blackness of the obtained black non-magnetic composite particles. However,
since the effect is already saturated, it is unnecessary to use such a large amount
of the adhesive.
[0118] The amount of the adhesive is usually 0.04 to 1.89 % by weight, preferably 0.08 to
1.51 % by weight, more preferably 0.11 to 1.13 % by weight (calculated as Si) based
on the weight of the non-magnetic acicular black iron-based composite particles.
[0119] After the adhesive is added to, and then mixed and stirred with the composite particles
on which the first carbon black coat is formed, the carbon black fine particles are
added to, and then mixed and stirred with the resultant mixture to form the second
carbon black coat onto the first carbon black coat through the adhesive, thereby integrating
the carbon black coats. The thus obtained composite particles may be dried and heat-treated,
if required.
[0120] The mixing and stirring conditions for adhering the adhesive onto the composite particles
on which the first carbon black coat is formed, may be appropriately selected such
that the adhesive can be uniformly coated onto the first carbon black coat of each
composite particle. More specifically, the linear load used for the mixing and stirring
is usually 19.6 to 1,960 N/cm (2 to 200 kg/cm), preferably 98 to 1,470 N/cm (10 to
150 kg/cm), more preferably 147 to 980 N/cm (15 to 100 kg/cm); the treating time is
5 to 120 minutes, preferably 10 to 90 minutes; and the stirring speed is usually 2
to 2,000 rpm, preferably 5 to 1,000 rpm, more preferably 10 to 800 rpm.
[0121] The amount of the carbon black fine particles added for forming the second carbon
black coat is 1 to 30 parts by weight based on 100 parts by weight of the hematite
particles or iron oxide hydroxide particles. When the amount of the carbon black fine
particles added is less than 1 part by weight, the total amount of carbon black adhered
becomes insufficient, so that it may be difficult to obtain aimed black non-magnetic
composite particles which are more excellent in fluidity and blackness. On the contrary,
when the amount of the carbon black fine particles added is more than 30 part by weight,
the carbon black tends to be desorbed or fallen-off from the surfaces of the obtained
black non-magnetic composite particles, resulting in deteriorated dispersibility in
a binder resin upon production of the black toner.
[0122] The mixing and stirring conditions for forming the second carbon black coat onto
the first carbon black coat through the adhesive, may be appropriately selected such
that the second carbon black coat can be uniformly coated onto the first carbon black
coat through the adhesive. More specifically, the linear load used for the mixing
and stirring is usually 19.6 to 1,960 N/cm (2 to 200 kg/cm), preferably 98 to 1,470
N/cm (10 to 150 kg/cm), more preferably 147 to 980 N/cm (15 to 100 kg/cm); the treating
time is 5 to 120 minutes, preferably 10 to 90 minutes; and the stirring speed is usually
2 to 2,000 rpm, preferably 5 to 1,000 rpm, more preferably 10 to 800 rpm.
[0123] In the case where the alkoxysilane compounds are used as the coating compound, the
resultant black non-magnetic composite particles may be dried or heat-treated, for
example, at a temperature of usually 40 to 200°C, preferably 60 to 150°C for usually
10 minutes to 12 hours, preferably 30 minutes to 3 hours, thereby forming a coating
layer composed of the organosilane compounds. By the drying or heat-treatment, the
alkoxysilane compounds on the surface of the core particle is converted to the organosilane
compounds.
[0124] At least a part of the surface of the hematite particles or iron oxide hydroxide
particles may be coated with at least one compound selected from the group consisting
of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of
silicon, if required, prior to mixing and stirring with the alkoxysilane compounds,
the polysiloxanes, the modified polysiloxanes or the terminal-modified polysiloxanes.
[0125] The coating of the hydroxides and/or oxides of aluminum and/or silicon may be conducted
by adding an aluminum compound, a silicon compound or both the compounds to a water
suspension in which the hematite particles or iron oxide hydroxide particles are dispersed,
followed by mixing and stirring, and further adjusting the pH value of the suspension,
if required, thereby coating the surfaces of the hematite particles or iron oxide
hydroxide particles with at least one compound selected from the group consisting
of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of
silicon. The thus obtained particles coated with the hydroxides and/or oxides of aluminum
and/or silicon are then filtered out, washed with water, dried and pulverized. Further,
the particles coated with the hydroxides and/or oxides of aluminum and/or silicon
may be subjected to post-treatments such as deaeration treatment and compaction treatment,
if required.
[0126] As the aluminum compounds, there may be exemplified aluminum salts such as aluminum
acetate, aluminum sulfate, aluminum chloride or aluminum nitrate, alkali aluminates
such as sodium aluminate or the like.
[0127] The amount of the aluminum compound added is 0.01 to 50 % by weight (calculated as
Al) based on the weight of the hematite particles or iron oxide hydroxide particles.
When the amount of the aluminum compound added is less than 0.01 % by weight, it may
be difficult to sufficiently coat the surfaces of the hematite particles or iron oxide
hydroxide particles with hydroxides and/or oxides of aluminum, which can achieve the
improvement of lessening the percentage of desorption of carbon black therefrom, thereby
failing to achieve the improvement of the dispersibility in the binder resin upon
the production of the black toner. On the other hand, when the amount of the aluminum
compound added is more than 50 % by weight, the coating effect is saturated and, therefore,
it is meaningless to add such an excess amount of the aluminum compound.
[0128] As the silicon compounds, there may be exemplified #3 water glass, sodium orthosilicate,
sodium metasilicate, colloidal silica or the like.
[0129] The amount of the silicon compound added is 0.01 to 50 % by weight (calculated as
SiO
2) based on the weight of the hematite particles or iron oxide hydroxide particles.
When the amount of the silicon compound added is less than 0.01 % by weight, it may
be difficult to sufficiently coat the surfaces of the hematite particles or iron oxide
hydroxide particles with hydroxides and/or oxides of silicon, which can achieve the
improvement of lessening the percentage of desorption of carbon black therefrom, thereby
failing to achieve the improvement of the dispersibility in the binder resin upon
the production of the black toner. On the other hand, when the amount of the silicon
compound added is more than 50 % by weight, the coating effect is saturated and, therefore,
it is meaningless to add such an excess amount of the silicon compound.
[0130] In the case where both the aluminum and silicon compounds are used in combination
for the coating, the total amount of the aluminum and silicon compounds added is preferably
0.01 to 50 % by weight (calculated as a sum of Al and SiO
2) based on the weight of the hematite particles or iron oxide hydroxide particles.
[0131] Next, the process for producing the high-resistant black toner according to the present
invention is described.
[0132] The high-resistant black toner may be produced by mixing and kneading a predetermined
amount of a binder resin and a predetermined amount of the black non-magnetic composite
particles together, and then pulverizing the mixed and kneaded material into particles.
More specifically, the black non-magnetic composite particles and the binder resin
are intimately mixed together with, if necessary, a mold release agent, a colorant,
a charge-controlling agent or other additives by using a mixer. The obtained mixture
is then melted and kneaded by a heating kneader, thereby dispersing the black non-magnetic
composite particles in the binder resin. Successively, the molten mixture is cooled
and solidified to obtain a resin-kneaded product. The obtained resin-kneaded product
is then pulverized and classified, thereby producing a black toner having an aimed
particle size.
[0133] As the mixers, there may be used a Henschel mixer, a ball mill or the like. As the
heating kneaders, there may be used a roll mill, a kneader, a twin-screw extruder
or the like. The pulverization of the resin mixture may be conducted by using pulverizers
such as a cutter mill, a jet mill or the like. The classification of the pulverized
particles may be conducted by known methods such as air classification, etc., as described
in Japanese Patent No. 2683142 or the like.
[0134] As the other method of producing the black toner, there may be exemplified a suspension
polymerization method or an emulsion polymerization method. In the suspension polymerization
method, polymerizable monomers and the black non-magnetic composite particles are
intimately mixed together with, if necessary, a colorant, a polymerization initiator,
a cross-linking agent, a charge-controlling agent or the other additives and then
the obtained mixture is dissolved and dispersed together so as to obtain a monomer
composition. The obtained monomer composition is added to a water phase containing
a suspension stabilizer while stirring, thereby granulating and polymerizing the composition
to form black toner particles having an aimed particle size.
[0135] In the emulsion polymerization method, the monomers and the black non-magnetic composite
particles are dispersed in water together with, if necessary, a colorant, a polymerization
initiator or the like and then the obtained dispersion is polymerized while adding
an emulsifier thereto, thereby producing black toner particles having an aimed particle
size.
[0136] A point of the present invention lies in that the black non-magnetic composite particles
comprising the hematite particles or iron oxide hydroxide particles as the core particles,
which are obtained by firmly adhering carbon black onto the surfaces of the hematite
particle or iron oxide hydroxide particle in an amount of 26 to 55 parts by weight
based on 100 parts by weight of the hematite particle or iron oxide hydroxide particle,
are not only more excellent in fluidity and blackness, but also have a less amount
of carbon black desorbed or fallen-off from the surface of each particle.
[0137] The reason why the amount of the carbon black desorbed (or fallen-off) from the surfaces
of the black non-magnetic composite particles according to the present invention,
is small, is considered as follows. That is, the surfaces of the hematite particles
or iron oxide hydroxide particles as the core particles and the organosilicon compounds
are strongly bonded to each other, so that the carbon black bonded to the surfaces
of the hematite particles or iron oxide hydroxide particles through the organosilicon
compounds can be prevented from being desorbed from the hematite particles or iron
oxide hydroxide particles.
[0138] In particular, in the case of the alkoxysilane compounds, metalloxane bonds (≡Si-O-M
wherein M represents a metal atom contained in the hematite particles or iron oxide
hydroxide particles as the core particles, such as Si, Al, Fe or the like) are formed
between the surfaces of the hematite particles or iron oxide hydroxide particles and
alkoxy groups contained in the organosilicon compounds onto which the carbon black
coat is formed, thereby forming a stronger bond between the organosilicon compounds
on which the carbon black coat is formed, and the surfaces of the hematite particles
or iron oxide hydroxide particles.
[0139] In addition, it is considered that when polysiloxane is used, various functional
groups of the polysiloxane on which the carbon black is adhered, are firmly bonded
to the surfaces of the hematite particles or iron oxide hydroxide particles.
[0140] In accordance with the present invention, due to the less amount of carbon black
desorbed or fallen-off from the surfaces of the black non-magnetic composite particles,
it is assured to sufficiently disperse the black non-magnetic composite particles
in a binder resin without any disturbance by desorbed carbon black. Further, since
the carbon black adhered on the surfaces of the core particles form irregularities
thereon, the obtained black non-magnetic composite particles are prevented from contacting
with each other, resulting in excellent dispersibility in a binder resin upon production
of the black toner.
[0141] The reason why the black non-magnetic composite particles used in the present invention
can show a more excellent fluidity, is considered as follows. That is, the carbon
black coat is allowed to be uniformly and densely formed on the surfaces of the hematite
particles or iron oxide hydroxide particles as the core particles, so that many fine
irregularities are formed on the surfaces of the hematite particles or iron oxide
hydroxide particles.
[0142] The reason why the black non-magnetic composite particles used in the present invention
can show a more excellent blackness, is considered such that since the carbon black
coat is uniformly and densely formed on the surfaces of the hematite particles or
iron oxide hydroxide particles as the core particles, the color tone of the core particles
is hidden behind the carbon black, so that an inherent color tone of carbon black
can be exhibited.
[0143] The black toner of the present invention obtained by using the above black non-magnetic
composite particles on which a large amount of carbon black is adhered, not only maintains
a resistivity as high as not less than 1 × 10
13 Ω·cm, but also exhibits more excellent fluidity and blackness.
[0144] The reason why the black toner according to the present invention can show a more
excellent fluidity, is considered as follows. That is, the black non-magnetic composite
particles on which a large amount of the carbon black are uniformly formed, are blended
in the black toner, so that many fine irregularities are formed on the surface of
the black toner.
[0145] The reason why the black toner according to the present invention can show a more
excellent blackness, is considered such that the black non-magnetic composite particles
having a more excellent blackness is blended in the black toner.
[0146] Further, the reason why the black toner according to the present invention can maintain
a high volume resistivity value irrespective of a large amount of carbon black adhered,
is considered as follows.
[0147] That is, in general, carbon black is present in the form of aggregated particles
constituted from parallel-stacked crystallites each having a pseudo-graphite structure.
Further, the carbon black particles are chemically and physically bonded with each
other to form a cluster-like (grape-like cluster) structure. It is known that the
larger the cluster-like structure, the higher the electrical conductivity of carbon
black becomes. In the case where the carbon black fine particles having such a cluster-like
structure are added to and mixed with a binder resin, those exposed to the surface
of the black toner also have the cluster-like structure, thereby increasing a conductivity
of the black toner. As a result, it is difficult to obtain a black toner having a
high volume resistivity value. On the contrary, in the case of the black non-magnetic
composite particles used the present invention, the carbon black coat is formed onto
the surface of each core particle without forming the cluster-like structure. Therefore,
since the black toner using such black non-magnetic composite particles are also free
from carbon black having the cluster-like structure, thereby enabling to maintain
a high volume
[0148] As described above, since the black non-magnetic composite particles used in the
present invention, are more excellent not only in fluidity and blackness, but also
in dispersibility in a binder resin due to less amount of the carbon black desorbed
or (fallen-off) from the surfaces thereof, the black non-magnetic composite particles
used in the present invention, are suitable as black non-magnetic composite particles
for black toner capable of attaining a high image quality and a high copying speed.
[0149] In addition, since the black non-magnetic composite particles used in the present
invention, are excellent in dispersibility in a binder resin, the particles can show
excellent handling property and workability and, therefore, are preferable from an
industrial viewpoint.
[0150] Further, the black toner produced from the above black non-magnetic composite particles
which are more excellent in fluidity and blackness, can also show more excellent fluidity
and blackness. Accordingly, the black toner is suitable as black toner capable of
attaining a high image quality and a high copying speed.
[0151] The black toner according to the present invention can maintain a high resistivity
value irrespective of using such black non-magnetic composite particles containing
a large amount of carbon black adhered thereonto. Therefore, the black toner of the
present invention is suitable as a high resistant or insulating toner.
EXAMPLES
[0152] The present invention is described in more detail by Examples and Comparative Examples,
but the Examples are only illustrative and, therefore, not intended to limit the scope
of the present invention.
[0153] Various properties were measured by the following methods.
(1) The average particle size, the average major axial diameter and average minor axial
diameter of hematite particles or iron oxide hydroxide particles, composite particles, black
non-magnetic composite particles and carbon black fine particles were respectively
expressed by the average of values (measured in a predetermined direction) of about
350 particles which were sampled from a micrograph obtained by magnifying an original
electron micrograph (× 20,000) by four times in each of the longitudinal and transverse
directions.
(2) The aspect ratio of the particles was expressed by the ratio of average major axial diameter to average
minor axial diameter thereof. The sphericity of the particles was expressed by the ratio of an average particle length to an average
particle breadth thereof.
(3) The geometrical standard deviation of particle size was expressed by values obtained by the following method.
That is, the particle diameters (or major axial diameters) were measured from the
above magnified electron micrograph. The actual particle diameters (or major axial
diameters) and the number of the particles were calculated from the measured values.
On a logarithmic normal probability paper, the particle diameters (or major axial
diameters) were plotted at regular intervals on the abscissa-axis and the accumulative
number (under integration sieve) of particles belonging to each interval of the particle
diameters (or major axial diameters) were plotted by percentage on the ordinate-axis
by a statistical technique.
The particle sizes (or major axial diameters) corresponding to the number of particles
of 50 % and 84.13 %, respectively, were read from the graph, and the geometrical standard
deviation was calculated from the following formula:
The closer to 1 the geometrical standard deviation value, the more excellent the particle
diameter distribution.
(4) The specific surface area was expressed by the value measured by a BET method.
(5) The amount of Mn which was present within hematite particles or iron oxide hydroxide particles or
on surfaces thereof, the amounts of Al and Si which were present within black non-magnetic composite particles or on surfaces thereof,
and the amount of Si contained in the organosilicon compounds and the amount of Si contained in dimethylpolysiloxanes used for adhering the carbon black, were measured
by a fluorescent X-ray spectroscopy device 3063 M (manufactured by Rigaku Denki Kogyo
Co., Ltd.) according to JIS K0119 "General rule of fluorescent X-ray analysis". ,
(6) The amount of carbon black coat formed on the surface of the hematite particles or iron oxide hydroxide particles
was measured by "Horiba Metal, Carbon and Sulfur Analyzer EMIA-2200 Model" (manufactured
by Horiba Seisakusho Co., Ltd.).
(7) The thickness of carbon black coat formed onto the hematite particles or iron oxide hydroxide particles is expressed
by the value which was obtained by first measuring an average thickness of carbon
black coat formed onto the surfaces of the particles on a photograph (× 5,000,000)
obtained by magnifying (ten times) a micrograph (× 500,000) produced at an accelerating
voltage of 200 kV using a transmission-type electron microscope (JEM-2010, manufactured
by Japan Electron Co., Ltd.), and then calculating an actual thickness of carbon black
coat formed from the measured average thickness.
(8) The fluidity of hematite particles or iron oxide hydroxide particles, composite particles, black
non-magnetic composite particles and black toner was expressed by a fluidity index
which was a sum of indices obtained by converting on the basis of the same reference
measured values of an angle of repose, a degree of compaction (%), an angle of spatula
and a degree of agglomeration as particle characteristics which were measured by a
powder tester (tradename, produced by Hosokawa Micron Co., Ltd.). The closer to 100
the fluidity index, the more excellent the fluidity of the particles.
(9) The blackness of hematite particles or iron oxide hydroxide particles, composite particles, black
non-magnetic composite particles and black toner was measured by the following method.
That is, 0.5 g of sample particles and 1.5 ml of castor oil were intimately kneaded
together by a Hoover's muller to form a paste. 4.5 g of clear lacquer was added to
the obtained paste and was intimately kneaded to form a paint. The obtained paint
was applied on a cast-coated paper by using a 6-mil (150 µm) applicator to produce
a coating film piece (having a film thickness of about 30 µm). The thus obtained coating
film piece was measured according to JIS Z 8729 by a multi-light source spectrographic
colorimeter MSC-IS-2D (manufactured by Suga Testing Machines Manufacturing Co., Ltd.)
to determine an L* value of colorimetric indices thereof. The blackness was expressed
by the L* value measured.
Here, the L* value represents a lightness, and the smaller the L* value, the more
excellent the blackness.
(10) The desorption percentage of carbon black desorbed from the composite particles and black non-magnetic composite
particles was measured by the following method. The closer to zero the desorption
percentage, the smaller the amount of carbon black desorbed from the surfaces of the
composite particles and black non-magnetic composite particles.
That is, 3 g of the sample particles and 40 ml of ethanol were placed in a 50-ml precipitation
pipe and then were subjected to ultrasonic dispersion for 20 minutes. Thereafter,
the obtained dispersion was allowed to stand for 120 minutes, and the carbon black
desorbed was separated from the sample particles on the basis of the difference in
specific gravity between both the particles. Next, the sample particles from which
the desorbed carbon black were separated, were mixed again with 40 ml of ethanol,
and the obtained mixture was further subjected to ultrasonic dispersion for 20 minutes.
Thereafter, the obtained dispersion was allowed to stand for 120 minutes, thereby
separating the sample particles and the carbon black desorbed from each other. The
thus obtained particles were dried at 100°C for one hour, and then the carbon content
thereof was measured by the "Horiba Metal, Carbon and Sulfur Analyzer EMIA-2200 Model"
(manufactured by Horiba Seisakusho Co., Ltd.). The desorption percentage of the carbon
black was calculated according to the following formula:
wherein Wa represents an amount of carbon black initially formed on the composite particles
or the black non-magnetic composite particles; and We represents an amount of carbon black fine particles still adhered on the composite
particles or the black non-magnetic composite particles after desorption test.
(11) The dispersibility in a binder resin of the black non-magnetic composite particles was evaluated by
counting the number of undispersed agglomerated particles on a micrograph (× 200)
obtained by photographing a sectional area of the obtained black toner particle using
an optical microscope (BH-2, manufactured by Olympus Kogaku Kogyo Co., Ltd.), and
classifying the results into the following five ranks. The 5th rank represents the
most excellent dispersing condition.
Rank 1: not less than 50 undispersed agglomerated particles per 0.25 mm2 were recognized;
Rank 2: 10 to 49 undispersed agglomerated particles per 0.25 mm2 were recognized;
Rank 3: 5 to 9 undispersed agglomerated particles per 0.25 mm2 were recognized;
Rank 4: 1 to 4 undispersed agglomerated particles per 0.25 mm2 were recognized;
Rank 5: No undispersed agglomerated particles were recognized.
(12) The volume resistivity of the black toner was measured by the following method.
That is, first, 0.5 g of a sample particles to be measured was weighted, and press-molded
at 1.372 × 107 Pa (140 Kg/cm2) using a KBr tablet machine (manufactured by Simazu Seisakusho Co., Ltd.), thereby
forming a cylindrical test piece.
Next, the thus obtained cylindrical test piece was exposed to an atmosphere maintained
at a temperature of 25°C and a relative humidity of 60 % for 12 hours. Thereafter,
the cylindrical test piece was set between stainless steel electrodes, and a voltage
of 15V was applied between the electrodes using a Wheatstone bridge (TYPE2768, manufactured
by Yokogawa-Hokushin Denki Co., Ltd.) to measure a resistance value R (Ω).
The cylindrical test piece was measured with respect to an upper surface area A (cm2) and a thickness t0 (cm) thereof. The measured values were inserted into the following formula, thereby
obtaining a volume resistivity (Ω·cm).
(13) The average particle size of the black toner was measured by a laser diffraction-type particle diameter distribution-measuring
apparatus (Model HELOSLA/KA, manufactured by Sympatec Corp.).
Example 1:
<Production of black non-magnetic composite particles>
[0154] 20 kg of granular-shaped Mn-containing hematite particles (average particle size:
0.30 µm; sphericity: 1.3; geometrical standard deviation value: 1.46; BET specific
surface area value: 3.6 m
2/g; Mn content: 13.3 % by weight (calculated as Mn) based on the weight of the particle;
fluidity index: 36; blackness (L* value): 22.6), were deagglomerated in 150 liters
of pure water using a stirrer, and further passed through a "TK pipeline homomixer"
(tradename, manufactured by Tokushu Kika Kogyo Co., Ltd.) three times, thereby obtaining
a slurry containing the granular-shaped Mn-containing hematite particles.
[0155] Successively, the obtained slurry containing the granular-shaped Mn-containing hematite
particles was passed through a transverse-type sand grinder (tradename "MIGHTY MILL
MHG-1.5L", manufactured by Inoue Seisakusho Co., Ltd.) five times at an axis-rotating
speed of 2,000 rpm, thereby obtaining a slurry in which the granular-shaped Mn-containing
hematite particles were dispersed.
[0156] The particles in the obtained slurry which remained on a sieve of 325 meshes (mesh
size: 44 µm) was 0 %. The slurry was filtered and washed with water, thereby obtaining
a filter cake containing the granular-shaped Mn-containing hematite particles. After
the obtained filter cake containing the granular-shaped Mn-containing hematite particles
was dried at 120°C, 11.0 kg of the dried particles were then charged into an edge
runner "MPUV-2 Model" (tradename, manufactured by Matsumoto Chuzo Tekkosho Co., Ltd.),
and mixed and stirred at 294 N/cm (30 Kg/cm) and a stirring speed of 22 rpm for 30
minutes, thereby lightly deagglomerating the particles.
[0157] 110 g of methyltriethoxysilane (tradename, "TSL8123", produced by GE Toshiba Silicone
Co., Ltd.) was mixed and diluted with 200 ml of ethanol to obtain a methyl triethoxysilane
solution. The methyl triethoxysilane solution was added to the deagglomerated granular-shaped
Mn-containing hematite particles under the operation of the edge runner. The granular-shaped
Mn-containing hematite particles were continuously mixed and stirred at a linear load
of 392 N/cm (40 Kg/cm) and a stirring speed of 22 rpm for 60 minutes.
[0158] Next, 1650 g of carbon black fine particles A (particle shape: granular shape; average
particle size: 0.022 µm; geometrical standard deviation value: 1.68; BET specific
surface area value: 134 m
2/g; DBP oil absorption: 89 ml/100 g; and blackness (L* value): 16.6) were added to
the granular-shaped Mn-containing hematite particles coated with methyltriethoxysilane
for 10 minutes while operating the edge runner. Further, the mixed particles were
continuously stirred at a linear load of 392 N/cm (40 Kg/cm) and a stirring speed
of 22 rpm for 60 minutes to form the carbon black coat on the coating layer composed
of methyltriethoxysilane, thereby obtaining composite particles.
[0159] In order to determine the coating amount of methyltriethoxysilane and the amount
of carbon black adhered, a part of the thus obtained composite particles was sampled,
and heat-treated at 105°C for 60 minutes using a drier. As a result, it was confirmed
that the coating amount of methyltriethoxysilane was 0.15 % by weight (calculated
as Si), and the amount of carbon black adhered was 13.00 % by weight (equivalent to
15 parts by weight based on 100 parts by weight of the granular-shaped Mn-containing
hematite particles). Further, as a result of the observation of electron micrograph,
it was confirmed that almost a whole amount of carbon black added was adhered onto
the coating layer of an organosilane compound produced from the methyltriethoxysilane.
[0160] Next, 220 g of dimethylpolysiloxane (tradename: "TSF451", produced by GE Toshiba
Silicone Co., Ltd.) was added to the above composite particles while operating an
edge runner, and the obtained mixture was then mixed and stirred together at a linear
load of 588 N/cm (60 Kg/cm) and a stirring speed of 22 rpm for 30 minutes, thereby
obtaining composite particles on which dimethylpolysiloxane was uniformly adhered.
[0161] Next, 1,650 g of the above carbon black fine particles A were added to the above
obtained particles for 10 minutes while operating the edge runner, and then mixed
and stirred together at a linear load of 588 N/cm (60 Kg/cm) and a stirring speed
of 22 rpm for 30 minutes, thereby bonding the second carbon black coat onto the first
carbon black coat through the dimethylpolysiloxane as an adhesive. Thereafter, the
obtained particles were heat-treated at 105°C for 60 minutes using a drier, thereby
obtaining black non-magnetic composite particles.
[0162] The obtained black non-magnetic composite particles had an average particle size
of 0.31 µm, and a sphericity of 1.3:1 as shown in the electron photograph. In addition,
the black non-magnetic composite particles showed a geometrical standard deviation
of 1.46, a BET specific surface area value of 11.9 m
2/g, fluidity index of 56, a blackness (L* value) of 17.1, and a desorption percentage
of carbon black: 7.3 %. The amount of the carbon black coat formed on the coating
layer composed of the organosilane compound produced from methyltriethoxysilane is
25.59 % by weight (calculated as C) based on the weight of the black non-magnetic
composite particles (corresponding to 30 parts by weight based on 100 parts by weight
of the granular-shaped Mn-containing hematite particles). The thickness of the carbon
black coat formed was 0.0027 µm. The amount of dimethylpolysiloxanes adhered was 0.69
% by weight (calculated as Si). Since no carbon black were recognized on the electron
photograph, it was confirmed that a whole amount of the carbon black used contributed
to the formation of the carbon black coat.
<Production of black toner containing black non-magnetic composite particles>
[0163] 400 g of the black non-magnetic composite particles obtained in the above, 600 g
of styrene-butyl acrylate-methyl methacrylate copolymer resin (molecular weight =
130,000, styrene/butyl acrylate/methyl methacrylate = 82.0/16.5/1.5), 60 g of polypropylene
wax (molecular weight: 3,000) and 15 g of a charge-controlling agent were charged
into a Henschel mixer, and mixed and stirred therein at 60°C for 15 minutes. The obtained
mixed particles were melt-kneaded at 140°C using a continuous-type twin-screw kneader
(T-1), and the obtained kneaded material was cooled, coarsely pulverized and finely
pulverized in air. The obtained particles were subjected to classification, thereby
producing a black toner.
[0164] The obtained black toner had an average particle size of 10.0 µm, a dispersibility
of 5th rank, a fluidity index of 86, a blackness (L* value) of 18.0, a volume resistivity
of 8.6 × 10
14 Ω·cm.
Core particles 1 to 4:
[0165] Various hematite particles or iron oxide hydroxide particles, were prepared by known
methods. The same procedure as defined in Example 1 was conducted by using the thus
prepared particles, thereby obtaining deagglomerated hematite particles or iron oxide
hydroxide particles as core particles.
[0166] Various properties of the thus obtained hematite particles or iron oxide hydroxide
particles as core particles are shown in Table 1.
Core particles 5:
[0167] The same procedure as defined in Example 1 was conducted by using 20 kg of the deagglomerated
granular-shaped Mn-containing hematite particles (core particles 1) and 150 liters
of water, thereby obtaining a slurry containing the granular-shaped Mn-containing
hematite particles. The pH value of the obtained re-dispersed slurry containing the
granular-shaped Mn-containing hematite particles was adjusted to 10.5 by adding an
aqueous sodium solution, and then the concentration of the slurry was adjusted to
98 g/liter by adding water thereto. After 150 liters of the slurry was heated to 60°C,
5444 ml of a 1.0 mol/liter sodium alminate solution (equivalent to 1.0 % by weight
(calculated as Al) based on the weight of the granular-shaped Mn-containing hematite
particles) was added to the slurry. After allowing the slurry to stand for 30 minutes,
the pH value of the slurry was adjusted to 7.5 by adding an acetic acid solution.
After allowing the slurry to stand for 30 minutes, the slurry was subjected to filtration,
washing with water, drying and pulverization, thereby obtaining the granular-shaped
Mn-containing hematite particles coated with hydroxides of aluminum.
[0168] Main production conditions are shown in Table 2, and various properties of the obtained
granular-shaped Mn-containing hematite particles coated with hydroxides of aluminum
are shown in Table 3.
Core particles 6 to 8:
[0169] The same procedure as defined in the production of the core particles 5 above, was
conducted except that kind of core particles, and kind and amount of additives used
in the surface treatment were varied, thereby obtaining surface-treated hematite particles
or iron oxide hydroxide particles.
[0170] Main production conditions are shown in Table 2, and various properties of the obtained
surface-treated hematite particles or iron oxide hydroxide particles are shown in
Table 3.
Examples 2 to 13 and Comparative Examples 1 to 4:
<Production of composite particles>
[0171] The same procedure as defined in Example 1 was conducted except that kind of hematite
particles or iron oxide hydroxide particles to be treated, addition or non-addition
of an alkoxysilane compound or polysiloxane in the coating treatment with alkoxysilane
compound or polysiloxane, kind and amount of the alkoxysilane compound or polysiloxane
added, treating conditions of edge runner in the coating treatment, kind and amount
of first carbon black coat formed, and treating conditions of edge runner used in
the forming process of the first carbon black coat, were varied, thereby obtaining
composite particles. The composite particles obtained in Examples 2 to 13 were observed
by an electron microscope. As a result, almost no independent carbon black was recognized.
Therefore, it was confirmed that a substantially whole amount of the carbon black
contributed to the formation of the first carbon black coat on the coating layer composed
of organosilane compound produced from the alkoxysilane compound, or polysiloxane.
[0172] Various properties of the carbon black fine particles A to C are shown in Table 4.
[0173] Main production conditions are shown in Table 5, and various properties of the obtained
composite particles are shown in Table 6.
[0174] Meanwhile, all the additives used in Examples 11 to 13 were polysiloxanes. Specifically,
"TSF484" (tradename, produced by GE Toshiba Silicone Co., Ltd.) was methyl hydrogen
polysiloxane; "BYK-080" (tradename, produced by BYK-Chemie Japan Co., Ltd.) was modified
polysiloxane; and "TSF-4770" (tradename, produced by GE Toshiba Silicone Co., Ltd.)
was carboxylic acid-terminal-modified polysiloxane.
Examples 14 to 25 and Comparative Examples 5 to 11:
<Production of black non-magnetic composite particles>
[0175] The same procedure as defined in Example 1 was conducted except that kind of composite
particles, kind and amount of adhesive added, edge runner treatment conditions used
in the adhesive-treating step, kind and amount of carbon black fine particles added
in the second carbon black coat-adhering step, and edge runner treatment conditions
used in the second carbon black coat-adhering step, were changed variously, thereby
obtaining black non-magnetic composite particles.
[0176] Meanwhile, as a result of observing the black non-magnetic composite particles obtained
in Examples 14 to 25 by an electron microscope, no liberated carbon black was recognized.
Therefore, it was confirmed that almost a whole amount of carbon black added was adhered
onto the first carbon black coat.
[0177] Main treatment conditions are shown in Table 7, and various properties of the obtained
black non-magnetic composite particles are shown in Table 8.
Examples 26 to 37, Comparative Examples 12 to 26 and Reference Example 1:
<Production of black toner>
[0178] The same procedure as defined in Example 1 was conducted by using the black non-magnetic
composite particles obtained in Examples 14 to 25, and the composite particles obtained
in Example 4, Core particles 1 to 4, carbon black B to D and the particles obtained
in Comparative Examples 3 and 5 to 11, and kind and amount of the binder resin, thereby
obtaining black toners.