Process for preparing toner or capsule toner for use in electrophotography

A mixture of a colorant, and a binder compound having an aliphatic hydrocarbon long chain and having a relatively low melt viscosity, is kneaded in a molten state in the presence of solid media such as balls or beads to form a uniform mixture in which the colorant particles or aggregates have been disintegrated to a size of 5 .mu. or below. Solid particles which may be used as a toner are formed from the uniform mixture and may be encapsulated, as desired, to provide a capsule toner.

FIELD OF THE INVENTION AND RELATED ART 
This invention relates to a process for preparing a toner or a capsule 
toner to be used in the electrophotography, electrostatic photography, 
magnetic recording, or electrostatic printing, and to a toner or a capsule 
toner to be obtained by the process. 
Heretofore, various developing methods for electrophotography have been 
known, such as the powder cloud method, the fur brush method, the cascade 
developing method, and the magnetic brush developing method. 
The toner used in these developing methods conventionally comprises colored 
fine particles each comprising a natural or synthetic resin and a dye or 
pigment dispersed therein. For example, in the magnetic brush developing 
method which is widely practiced at the present time, a two-component 
developer comprising iron powder called "carrier", and a toner is used. 
Further, a developing method using a one-component developer comprising a 
toner containing magnetic powder such as magnetite powder, has been 
developed and practiced. 
An operation called "fixing" is practiced when a developed toner image is 
desired to be stored. As fixing methods, there are known a method in which 
the toner is attached through melting by heating in a heat chamber, a 
method in which the toner is pressure-bonded onto a surface of a support 
simultaneously with melting by means of hot rollers, a method in which the 
toner is attached by dissolving it in a solvent and thereafter removing 
the solvent, and a method in which the toner is fixed by means of applying 
a fixing agent including a resinous solution onto the toner image. 
From the viewpoints, of economy of energy consumption and harmlessness to 
environment, the pressure-fixing method using rigid rollers, optionally 
with a small amount of heat, has been attracting increasing attention in 
recent years. This pressure fixing method is advantageous in many respects 
such that no fear of scorching of copied sheets is involved, that copying 
operation can be started immediately after turning on the power source and 
without requiring any waiting time, that high speed fixing is possible, 
and that the fixing apparatus is simple. 
However, the pressure fixing method known in the art involves some vital 
problems. One of them is the pressure required for fixing, which is 
generally 130 kg/cm or above in terms of line pressure. For application of 
such a large force, the fixing device is required to have a considerable 
strength, and therefore the fixing device becomes undesirably large and 
heavy. Further it is extremely difficult to apply a pressure as mentioned 
above evenly on the transfer paper, so that the transfer paper tends to 
crease or curl. Another problem is that the image surface will be 
flattened to give rise to luster on the image and lower the quality of 
image, when a large pressure as mentioned above is applied on the image by 
rollers. 
In order to overcome these problems, efforts for development of a toner or 
a capsule toner capable of being fixed with a low fixing pressure and low 
energy consumption, have been exercised. 
More specifically, it has been desired to develop a practical toner or a 
capsule toner of low-energy consumption type, which is excellent in 
fixability with low energy consumption, excellent in anti-offsetting to 
the pressure rollers, stable in developing and fixing performances during 
repeated uses, with little adhesion onto carriers, metal sleeve or the 
surface of a photosensitive member, and also excellent in storage 
stability without agglomeration or caking during storage. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a toner or a microcapsule 
toner which has excellent fixability while requiring low energy 
consumption, and a process for preparing the same. 
Another object of the present invention is to provide a pressure fixable 
toner or microcapsule toner which can be fixed with a low pressure alone 
or optionally with a little heat, and a process for preparing the same. 
Still another object of the present invention is to provide a toner or a 
microcapsule toner which is little influenced by change in fixing speed 
and is suitable for high speed fixing, and a process for preparing the 
same. 
A further object of the present invention is to provide a toner or a 
microcapsule toner with little offsetting to the pressure rollers, with 
little adhesion onto metal sleeve or the surface of a photosensitive 
member, and a process for preparing the same. 
A still further object of the present invention is to provide a toner or a 
microcapsule toner which is stable in developing and fixing performances 
during repeated uses and hardly causes agglomeration or caking during 
storage, and a process for preparing the same. 
According to one aspect of the present invention, there is provided a 
process for preparing a toner for use in electrophotographic development, 
comprising: heating a mixture of 1 to 200 parts by weight of a colorant 
and 100 parts by weight of a binder containing a compound having an 
aliphatic hydrocarbon long chain, the compound having a melt viscosity of 
30 cps (centipoises) or below at 100.degree. C., stirring the heated 
mixture in the presence of a solid media for disintegrating an aggregate 
of the colorant in the mixture, to obtain a uniform mixture, and forming 
toner particles from the uniform mixture. 
According to another aspect of the present invention, there is provided a 
toner obtained by the above mentioned process. 
According to a further aspect of the present invention, there is provided a 
process for preparing a capsule toner for use in electrophotographic 
development, comprising: heating a mixture of 1 to 200 parts by weight of 
a colorant and 100 parts by weight of a binder containing a compound 
having an aliphatic hydrocarbon long chain, the compound having a melt 
viscosity of 30 cps or below at 100.degree. C., stirring the heated 
mixture in the presence of a solid media for disintegrating an aggregate 
of the colorant in the mixture to obtain a uniform mixture, forming solid 
core particles from the uniform mixture, and encapsulating the solid core 
particles. 
According to a still further aspect of the present invention provides a 
capsule toner prepared by the above mentioned process. 
The above mentioned and other objects and features of the invention will be 
better understood upon consideration of the following detailed description 
concluding with specific examples of practice. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides a toner composed of solid particles 
comprising a colorant and a binder resin. The binder resin comprises a 
compound having an aliphatic hydrocarbon long chain and showing a melt 
viscosity of 1 to 30 cps at 100.degree. C. (hereinafter, sometimes simply 
referred to as "long chain compound"). The colorant is uniformly dispersed 
in a particle size of 5.mu. or smaller in the binder resin. The solid 
particles may also be used as solid cores for a capsule toner. The solid 
particles constituting the toner or solid cores of the capsule toner 
according to the present invention should preferably have a penetration of 
15 or below, particularly 5 or below in view of the durability of the 
toner in the developing operation. 
The "penetration" used herein is measured according to the method as 
defined in JISK-2530. More specifically, it is a value of the depth of 
penetration expressed in terms of 0.1 mm as the unit when a needle having 
a diameter of about 1 mm and a conically shaped tip with an apex angle of 
9.degree. is caused to penetrate the sample material under a certain load. 
The test conditions employed in the present invention were a sample 
temperature of 25.degree. C., a load of 100 g, and a penetration time of 5 
seconds. 
As the long chain compound having a melt viscosity of 1 to 30 cps at 
150.degree. C., there are enumerated compounds of C.sub.12 to C.sub.50 
(i.e., having 12 to 50 carbon atoms), such as hydrocarbons, fatty acids, 
fatty acid esters, metal soaps, fatty alcohols, metal salts of fatty acid, 
fatty acid amides, fatty acid bisamides, and halogenated derivatives of 
the above. 
More specifically, the above mentioned long-chain compounds with a carbon 
chain of C.sub.12 -C.sub.50, include the following compounds. 
(1) Normal- or iso-paraffins having formulas of C.sub.n H.sub.2n+2 
(n=12-50), which can contain unsaturated bonds to such an extent not 
inviting ill effects thereby, as follows: 
C.sub.28 n-octacosane (C.sub.28 H.sub.58), 
C.sub.32 n-dotriacontane (C.sub.32 H.sub.66), 
C.sub.36 n-hexatriacontane (C.sub.36 H.sub.74), 
squalene (C.sub.30 H.sub.50), 
squalane (2.6, 10, 15, 19, 23-hexamethyl-tetracosane (C.sub.30 H.sub.62)). 
(2) Fatty acids having a long chain of the aliphatic hydrocarbons. 
Examples of such compounds are shown in the following Table. 
TABLE 1 
______________________________________ 
Saturated straight-chain fatty acids 
Name Formula m.p. (.degree.C.) 
______________________________________ 
n-heptacosanoic acid 
C.sub.26 H.sub.53 CO.sub.2 H 
87.6 
montanic acid C.sub.27 H.sub.55 CO.sub.2 H 
90.0 
n-nonacosanoic acid 
C.sub.28 H.sub.57 CO.sub.2 H 
90.3 
melissic acid C.sub.29 H.sub.59 CO.sub.2 H 
93.6 
n-hentriacontanoic acid 
C.sub.30 H.sub.61 CO.sub.2 H 
93.1 
n-dotriacontanoic acid 
C.sub.31 H.sub.63 CO.sub.2 H 
96.2 
n-tetracontanoic acid 
C.sub.33 H.sub.67 CO.sub.2 H 
98.4 
ceroplastic acid C.sub.34 H.sub.69 CO.sub.2 H 
98.3-98.5 
n-hexatriacontanoic acid 
C.sub.35 H.sub.71 CO.sub.2 H 
99.9 
n-octatriacontanoic acid 
C.sub.37 H.sub.75 CO.sub.2 H 
101.6 
n-hexatriacontanoic acid 
C.sub.45 H.sub.91 CO.sub.2 H 
106.8 
______________________________________ 
(3) Alcohols having a long chain of the aliphatic hydrocarbons. Examples 
are shown in Table 2 below. 
TABLE 2 
______________________________________ 
Saturated alcohols 
Trivial 
n Name Name Formula m.p. (.degree.C.) 
______________________________________ 
26 hexacosanol ceryl C.sub.26 H.sub.53 OH 
79.3-79.6 
alcohol 
28 octacosanol C.sub.28 H.sub.57 OH 
82.9-83.1 
30 triacontanol melissyl C.sub.30 H.sub.61 OH 
86.3-86.5 
alcohol 
32 dotriacontanol C.sub.32 H.sub.65 OH 
89.3-89.5 
______________________________________ 
(4) Esters formed of the fatty acids and the alcohols having a long chain 
as described above. 
(5) Chlorinated derivatives of the above described compounds, for example, 
chlorinated paraffins. 
(6) Amides and bisamides having a hydrocarbon chain of C.sub.12 to 
C.sub.50. Examples of such compounds are shown in Table 3 below. 
TABLE 3 
______________________________________ 
N,N'--Methylenebisamides 
Number of m.p. 
Name Carbon atoms 
(.degree.C.) 
______________________________________ 
N,N'--methylenebis(myristic acid 
29 151.6 
amide) 
N,N'--methylenebis(palmitic acid 
33 148.1 
amide) 
N,N'--methylenebis(stearic acid 
37 145.7 
amide) 
N,N'--methylenebis(arachidic 
-- -- 
acid amide) 
N,N'--methylenebis(behanic acid 
45 141.9 
amide) 
N,N'--methylenebis(palmitoleic 
-- -- 
acid amide) 
N,N'--methylenebis(oleic acid 
37 118.1 
amide) 
N,N'--methylenebis(eicosenoic 
41 122.3 
acid amide) 
N,N'--methylenebis(erucic acid 
45 123.8 
amide) 
N,N'--methylenebis(elaidic acid 
37 131.2 
amide) 
______________________________________ 
These compounds are used alone or in mixtures. The above described examples 
are commercially available as paraffin wax, microcrystalline wax, montan 
wax, ceresin wax, ozocerite, carnauba wax, rice wax, shellac wax, Sazol 
wax, metal soap, amide wax, lubricants, etc. 
Examples of commercially available products include Paraffin Wax (Nippon 
Sekiyu K.K.), Paraffin Wax (Nippon Seiro K.K.), Microwax (Nippon Sekiyu 
K.K.), Microcrystalline Wax (Nippon Seiro K.K.), Hoechst Wax (Hoechst AG), 
Diamond Wax (Shinnippon Rika K.K.), Santite (Seiko Kagaku K.K.), Panasate 
(Nippon Yushi K.K.). 
Representative grades of paraffin wax for example, are shown in the 
following Table 4 and Table 5. 
TABLE 4 
______________________________________ 
Paraffin Wax and Microwax (produced 
by Nippon Sekiyu K.K.) 
Name Melting point (.degree.C.) 
______________________________________ 
Nisseki No. 1 Candle Wax 
59.7 
Nisseki No. 2 Candle Wax 
62.0 
145.degree. Paraffin 
63.2 
Nisseki Microwax 155 
70.0 
Nisseki Microwax 180 
83.6 
______________________________________ 
TABLE 5 
______________________________________ 
Paraffin Wax (produced by Nippon 
Seiro K.K.) 
Name m.p. Name m.p. Name 
______________________________________ 
155 70 SP-0145 62 NCw-60 
150 66 SP-1035 58 NCW-110 
140 60 SP-1030 56 NCW-120 
SP-3040 63 NCW-125 
SP-3035 60 
______________________________________ 
Other examples are: 
Hoechst Wax OP (partially saponified ester wax of montanic acid, produced 
by Hoechst AG): 
Hoechst Wax E (ester wax of montanic acid, produced by Hoechst AG): 
Hoechst Wax GL3 (partially saponified synthetic wax, produced by Hoechst 
AG). 
If necessary, vinyl resins or other polymeric materials may be used in 
combination with the above-mentioned compounds. Further, derivatives to be 
obtained by graft copolymerizing the above-mentioned compounds with vinyl 
monomers are preferably used. Specific examples of such derivatives 
include products obtained by graft copolymerizing the waxes with 
dimethylaminoethyl methacrylate. 
In the present invention, the compounds with an aliphatic long chain having 
a melt viscosity of 1 to 30 cps at 100.degree. C., are used in an amount 
of 30% or more, preferably 50% or more, with respect to the total amount 
of the binder component in the toner or the core particles of the capsule 
toner. 
As a result of our further studies on pressure-fixable toners which can be 
fixed under a low pressure or with a little energy consumption, it has 
been discovered that a pressure-fixable toner or capsule toner capable of 
being fixed under a low-fixing pressure must contain a solid material in 
the vicinity of room temperature, and showing a low melt viscosity on 
heating, as a binder component. In the case of using such solid material, 
it has been found very difficult to disperse a colorant evenly in the 
binder because of aggregation of the colorant by the conventional method 
for dispersing a colorant which is widely used for preparing a toner. When 
a kneaded mixture obtained by the conventional method is cooled and 
thereafter pulverized into fine particles, some toner particles are found 
to contain no colorant therein, or to contain an aggregate of the colorant 
in a particle size of 5.mu. or larger. In the case where such a toner is 
used, it has been observed that ill effects are produced on toner 
performances such as developing property, antiadhering property, 
fixability, anti-offsetting property and durability. 
On the contrary, the present invention can provide toner particles wherein 
aggregates of a colorant have been reduced into a size of 5.mu. or 
smaller, preferably 2.mu. or smaller. 
As methods of evaluating dispersion states of colorants in a toner, there 
are known a method wherein toner particles are embedded in a mass of resin 
such as epoxy resin, sliced into a thin film by a device such as a 
microtome and the resultant film sample is observed through a 
transmission-type microscope or electron microscope; and a method wherein 
melt-kneaded toner material in which a colorant has been dispersed is 
melted and applied in a thin layer on a glass plate, and then observed 
through a microscope. 
As the melted mixture of the long chain compound having a melt viscosity of 
1-30 cps at 100.degree. C. and the colorant for producing the toner 
according to the present invention has a low melt viscosity, a 
sufficiently large shearing force as required for effective dispersion can 
not be exerted to the melted mixture if the conventional dispersion method 
such as the three roll mill method or the biaxial extruder-type kneader is 
used, whereby colorant particles or aggregates having a size of 5.mu. or 
larger can frequently remain in toner particles. In such toner particles, 
the colorant is localized or not evenly present and the content thereof is 
different, particle to particle or even in a single toner particle. 
Because of this ununiformity of colorant distribution, the physical 
properties of the toner particles such as triboelectric characteristic, 
magnetic property, color property and smoothness become ununiform or 
unbalanced among toner particles, whereby several difficulties are 
encountered such as a color difference among toner particles due to 
insufficient dispersion of the colorant and a difference in hue or density 
between the initial stage and the final stage of repeating image-formation 
operations by using a copying machine. Furthermore, extreme localization 
or different contents of the colorant in toner particles can result in 
different strengths among toner particles, whereby further difficulties 
are encountered such that several types of adhesion or aggregation of the 
toner can occur or the fixing characteristic of the toner become ununiform 
to result in undesirable phenomena such as fixing insufficiency or 
offsetting. 
Similarly, the localization or different contents of the colorant in toner 
particles lead to ununiformity in electrostatic property or magnetic 
property of respective toner particles, i.e., ununiformity or instability 
of developing characteristic or transfer characteristic of toner 
particles, so that undesirable phenomena such as deterioration of imaging 
characteristic or instability during a long run of operation, e.g., change 
in image density, are likely to occur. 
According to the present invention, these problems are obviated through 
improved dispersion of the colorant, so that the toner performances are 
improved. 
According to the process of the present invention, the mixture of a binder 
and a colorant is heated so that it will have a low melt viscosity of 40 
ps (poises) or below, preferably 5 to 20 ps, and stirring the heated 
mixture while retaining its low viscosity state in the presence of solid 
media. 
Mixing apparatus using solid media are known, such as ball mills, sand 
mills and attritors. With respect to these apparatus, the condition or 
intensity of dispersion can be changed by appropriately selecting the 
revolution speed, and the kind and the amount of the solid media. 
The solid media to be used in the present invention for dispersion or 
disintegration of the colorant may preferably comprise beads or particles 
with a single particle size in the range of 0.5 to 20 mm, or a mixture of 
such beads or particles with various particle sizes. The solid media 
should take any shapes including spheres and irregularly shaped beads or 
particles. 
The solid media may comprise glass beads; steel balls; siliceous sand, 
alumina, zirconia; plastics; ceramics; etc. 
The solid media may preferably be used in a proportion of 5 to 200 parts by 
volume, particularly 10 to 100 parts by volume with respect to 10 parts by 
volume of the melt mixture. 
The colorant used in the present invention may be any of known colorants 
used for toner production such as, for example, carbon black of various 
species, Aniline Black, Naphthol Yellow, Molybdenum Orange, Rhodamine 
Lake, Alizarin Lake, Methyl Violet Lake, Phthalocyanine Blue, Nigrosine, 
Methylene Blue, Rose Bengal, Quinoline Yellow and others. Such 
substantially nonmagnetic colorant may be used in an amount of 1 to 200 
parts by weight, preferably 1 to 50 parts by weight with respect to 100 
parts by weight of the binder. 
For production of a magnetic toner or magnetic capsule toner, magnetic 
powder per se may be used as a colorant. The magnetic powder may be powder 
having a particle size of 1.mu. or below of, for example, a ferromagnetic 
element such as iron, cobalt, nickel or manganese, alloy or compounds 
containing such ferromagnetic elements. The magnetic powder may be used in 
combination with another colorant. The magnetic powder may be used in an 
amount of 1 to 200 parts by weight, preferably 15 to 70 parts by weight 
with respect to 100 parts by weight of the binder. 
It is possible to add or mix optional additives to the toner or the capsule 
toner according to the present invention. Such optional additives may 
include carbon black, various dyes or pigments, hydrophobic colloidal 
silica, etc., to be used as, for example, charge controllers, flowability 
improvers and agents for color modification. 
The average particle size of the toner or capsule toner should preferably 
be within the range of 3 to 20.mu., preferably 5 to 10.mu.. It is further 
preferred that 50% or more of the toner particles are within the range of 
.+-.4.mu. from the average particle size. The capsule toner should 
preferably have a structure where the solid cores containing about 1 to 30 
wt. %, preferably 5 to 15 wt. %, of the colorant or the magnetic solid 
cores as described above are coated with a relatively hard material in a 
thickness of 0.01 to 2.mu., preferably 0.1 to 0.3.mu.. 
After uniformly melt-mixing the binder and the colorant as described above 
while disintegrating the aggregates of the colorant, the mixture is formed 
into fine particles by a method wherein the mixture is first cooled and 
then comminuted by means of a so-called pulverizer, or a method wherein 
the mixture is comminuted as it is in the molten state and then cooled. 
In the mixture of the long chain compound having a melt viscosity of 1-30 
cps at 100.degree. C. and the colorant, even if the latter is uniformly 
dispersed in the former, the colorant is liable to cause re-aggregation 
because of the low viscosity of the long chain compound. Accordingly, when 
the former method is used for comminution of the mixture, rapid cooling is 
required so as to solidify the mixture before the re-aggregation occurs. 
After the mixing, the mixture should preferably be dropped on a solid 
cooling medium or poured into a liquid cooling medium. The necessary 
cooling speed depends on the materials used, desired particle size or 
properties of the toner and the modes of mixing. 
In a preferred embodiment of the present invention, the mixture of the 
binder and the colorant is heated to 100.degree. C. or above so that the 
mixture will have a melt viscosity of 30 ps or below. The thus heated 
mixture at 100.degree. C. or above is required to be cooled in a short 
time to reach such a state where the colorant no longer causes 
re-aggregation, or to be solidified. For this purpose, in a preferred 
embodiment, the mixture above the melt mixture at 100.degree. C. or above 
is poured into crushed ice to be solidified. 
Another preferred method for producing fine particles is one wherein the 
mixture is comminuted as it is molten and then cooled into solid 
particles. 
In order to effect the comminution under molten state, the molten mixture 
is comminuted under the action of a dispersing force in various gaseous or 
liquid medium. More specifically, for example, the molten mixture may be 
dispersed in a hot gaseous stream under the action of an effluent pressure 
or another hot gaseous stream and recovered after cooling the gaseous 
stream. In another method, the molten mixture may be comminuted in a 
liquid medium such as hot water under the action of a stirring force, an 
emulsifier or a dispersion aid, and the mixture including the liquid 
medium may be cooled and subjected to various solid-liquid separation 
means to recover solid particles which may be subjected to optional 
treatment such as drying. 
In a preferred embodiment, the molten mixture comprising a binder and a 
colorant which has been disintegrated into a size of 5.mu. or less, 
preferably 2.mu. or less and dispersed in the binder, is subjected to 
suspension particulation by dispersing it into hot water containing an 
inorganic dispersant, whereby solid particles having a narrow particle 
size distribution may be formed in a short time. 
In another preferred embodiment, the molten mixture is dispersed in water 
in the presence of an inorganic dispersant while being charged (a) 
cationically by adding thereto a cationic compound or a hardly 
water-soluble or substantially water-insoluble organic amine compound or 
(b) anionically by the addition of an anionic compound. The inorganic 
dispersant is charged to a polarity opposite o that of the dispersed 
molten mixture particles, so that the dispersed particles are dispersed 
while being uniformly coated with the inorganic dispersant through ionic 
bonding or interaction and recovered as toner particles with a uniform 
particle size distribution. 
According to a conventional method, a molten mixture is dispersed in hot 
water containing a surfactant to be recovered as particles. It is possible 
to obtain fine particles by this method but particles having a size much 
larger than and particles having a size much smaller than the desired size 
are also produced according to this method, so that a classification 
operation such as sieving is required for selectively recovering the 
desired size of particles. It is also difficult to remove the surfactant 
from the surface of the particles. 
The inorganic dispersant is a hardly watersoluble or substantially 
water-insoluble inorganic compound in finely pulverized form, including 
hardly water-soluble salts such as BaSO.sub.4, CaSO.sub.4, BaCO.sub.3, 
CaCO.sub.3, MgCO.sub.3 and Ca.sub.3 (PO.sub.4).sub.2, inorganic 
macromolecular compounds such as talc, colloidal silica (SiO.sub.2) 
bentonite (SiO.sub.2 /Al.sub.2 O.sub.3), silicic acid, diatomaceous earch, 
clay and SiO.sub.2, powder of metals or metal oxides such as aluminum 
oxide (Al.sub.2 O.sub.3). Among these, for example, colloidal silica and 
bentonite are anionic inorganic dispersants, and aluminum oxide is a 
cationic inorganic dispersant. The inorganic dispersant shows a sufficient 
effect in a smaller quantity, if it is in a smaller particle size. 
For example, colloidal silica having a mean primary particle size of about 
40 m.mu. to 7 m.mu. exhibits a pH value of 3.6 to 4.3 at a concentration 
of 4% in water. Aluminum Oxide C which is an aluminum oxide product 
available from Degussa Co., West Germany, is very fine with a mean size of 
primary particles of 20 m.mu. and of high purity. Aluminum Oxide C 
exhibits an isoelectric point of about pH 9 and it is used in a neutral or 
acidic dispersing medium. 
The inorganic dispersant, including both anionic and cationic inorganic 
dispersants as mentioned above, may be used in an amount of from 0.001 to 
0.1 wt. phr., preferably 0.01 to 0.05 phr of the molten mixture. 
Use of an inorganic dispersant having a charging characteristic opposite to 
that of the molten mixture according to a preferred embodiment of the 
present invention as described above is preferred for the following 
reason. Thus, in this system, the particles of the molten mixture are 
charged cationically or anionically at their interfaces to form stable 
agglomerates through interaction with the above-mentioned inorganic 
dispersant. In other words, the surfaces of the suspended or dispersed 
particles are coated completely uniformly with the inorganic dispersant 
firmly bonded thereto due to ionic bonding, whereby coalescence between 
particles can be prevented. 
More specifically, for example, bentonite (SiO.sub.2 /Al.sub.2 O.sub.3) and 
colloidal silica contain a small amount of silanol groups (--SiOH), which 
are dissociated in water to form SiO.sup..sym. H.sup..sym. and provide a 
negative charge. Thus, these inorganic dispersants are anionically charged 
in water and firmly bonded with cationically charged molten mixture 
particles so as to coat the surface of the molten mixture particles, 
whereby the re-agglomeration of the particles may be effectively avoided. 
In the case of the inorganic dispersant thus firmly bonded through ionic 
bonding, outstanding superiority can be seen as compared with ordinary 
methods using a dispersant, wherein the dispersant is merely adsorbed onto 
the polymer particles or dispersed between particles to prevent 
coalescence. 
For effective suspension, stirring is another important factor, and an 
appropriate condition for stirring is important and selected depending on 
the purpose, because the sizes of the particles and stability of the 
particles are determined thereby. More specifically, control of the 
particle sizes is greatly influenced by the intensity of stirring and the 
kind of the stirring blade amployed. Generally speaking, as the stirring 
is made more vigorous, particles with smaller sizes can be obtained. 
However, there is a lower limit with respect to the size attainable in 
industrial application and yield is also lowered due to entrainment of air 
into the stirring device. 
We have made extensive studies to obtain minute particles, and consequently 
found that, in order to form such minute particles, it is very effective 
to use a dispersing device, comprising a rotary blade (turbine) having a 
high shearing force and rotatable at a high speed and a fixed blade 
(stator), which effects dispersion through powerful shearing force created 
between minute gaps which are precise and uniform. As examples of such a 
device, there are TK homomixer, TK pipeline homomixer (mfd. by Tokushu 
Kika Kogyo K.K.) and Microagitor (mfd. by Shimazu Seisakusho K.K.). 
When the above mentioned method is used, the molten mixture is formed into 
particles while retaining the dispersion state attained during the melt 
mixing, whereby uniform particles in which the colorant is evenly 
dispersed may be obtained. The thus obtained solid particles have 
excellent properties as a toner for themselves or cores for a capsule 
toner. 
The above mentioned effects are pronounced, especially when a colorant 
having a relatively large particle size is added in a large amount, for 
example, when a magnetic material or titanium white is used as the 
colorant. 
We have further discussed that the above mentioned method provides solid 
particles with less colorant particles appearing on the surfaces thereof. 
This is advantageous for providing uniformization of physical properties 
such as electric properties, surface smoothness and chemical properties of 
the solid particles. Therefore, the solid particles may be effectively 
used not only as a toner by themselves but also cores for a capsule toner, 
since they can be easily encapsulated. 
Thus, the solid particles as produced above may be coated with a 
shell-forming resin to provide a microcapsule toner. In this instance, as 
the solid particles have uniform surfaces, a uniform coating can be 
provided to form an excellent microcapsule toner. 
As the shell material for the microcapsule toner according to the present 
invention, known resins may be available, including homopolymers of 
styrene and substituted derivative thereof such as polystyrene, 
poly-p-chlorostyrene, polyvinyltoluene and the like; styrene copolymers 
such as styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, 
styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, 
styrenemethyl methacrylate copolymer, styrene-ethyl acrylate copolymer, 
styrene-butyl acrylate copolymer, styreneoctyl acrylate copolymer, 
styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate 
copolymer, styrenebutyl methacrylate copolymer, 
styrene-.alpha.-chloromethyl methacrylate, styrene-acrylonitrile 
copolymer, styrenevinyl methyl ether copolymer, styrene-vinyl ethyl ether 
copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene 
copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene 
copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester 
copolymer and the like; polymethyl methacrylate, polybutyl methacrylate, 
polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, 
polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, 
modified rosin, terpene resin, phenol resin, aliphatic or alicyclic 
hydrocarbon resin, aromatic petroleum resin, urea resin, melamine resin, 
and so on. These resins may be used either singly or as a mixture. 
The shell-forming resin should preferably have a molecular weight 
(number-average molecular weight) of not less than 5000, preferably 10,000 
to 50,000 in view of required strength. Further, it is desirable to use a 
resin from which a lower molecular weight fraction has been removed, in 
view of storage stability under heat. 
Any microencapsulation method known in the art may be applicable. For 
example, there may be employed the spray drying method, the 
drying-in-liquid method, the phase separation method and the in-situ 
polymerization method. A multi-layer sheel structure may also be provided 
in order to impart insulating property and appropriate triboelectric 
charging characteristic to the toner of the present invention. 
In a preferred embodiment of the microencapsulation, the core material is 
dispersed in a solution of the shell material in a solvent, and the shell 
material is precipitated or deposited on the core particles to form a 
capsule toner comprising the core particles coated with the shell 
material, wherein a polymer having an ethylenically polymerized main chain 
and branches of a long alkyl group and an acid anhydride or its derivative 
unit is dissolved in the solution. The precipitation or deposition of the 
shell material is effected by removing the solvent by the spray drying 
method or by the drying-in-liquid method; or by changing the dissolving 
power of the solvent by way of adding a poor solvent having a poor 
capability of dissolving the shell material into the solution of the shell 
material, adding a phase separation-inducing material into the solution or 
changing the temperature of the system. 
It has been observed that a compound having both a hydrophobic group and a 
polar group has some effect on the microencapsulation when it is 
co-present in the microencapsulation system. The use of an ordinary 
surfactant, however, rather binders the coating of the core material with 
the shell material, invites the formation of free fine particles of the 
shell material, or deteriorates the charging characteristic of the 
resultant microcapsule toner in many cases and therefore cannot be 
employed in the production of capsule toners. 
However, when a polymer having an ethylenically polymerized main chain and 
branches of a long alkyl group and an acid anhydride group is used, 
difficulties as encountered when an ordinary surfactant is used are 
obviated, and the microencapsulation proceeds very smoothly. 
The acid anhydride may preferably be cyclic acid anhydrides such as those 
of succinic acid and maleic acid. A part of the cyclic structure may be 
incorporated in the ethylenic main chain or the cyclic structure may form 
a pendant group. 
An example of the polymer having a cyclic acid anhydride group incorporated 
in or directly connected to the ethylenic chain is an 
.alpha.-olefin-maleic anhydride copolymer represented by the general 
formula (I) below, and an example of the pendant type polymer is a 
polyalkenylsuccinic anhydride represented by the general formula (II) 
below. 
##STR1## 
R: alkyl group having 4 to 28 carbon atoms (C.sub.4 -C.sub.28) n: 
polymerization degree 
##STR2## 
(R, n: the same as above) 
The above described polymer has a hydrophobic alkyl group and an acid 
anhydride group with a strong polarity in combination, and therefore has a 
surface activity as well as a unique solubility characteristic. Those 
polymers having a molecular weight of the order of 8000 to 50,000 may be 
readily available and may suitably be used. Such a polymer having a long 
chain alkyl group and an anhydride group, when it is present in a solution 
of a shell material for microcapsulation, is capable of suppressing the 
thickening of the solution when the solution is condensed by removal of 
the solvent or phase-separation, and also capable of remarkably improving 
the wetting of the core material with the shell material. The thus 
obtained microencapsulated toner particles have uniformly smooth surfaces 
and are also free of agglomerates thereof or, even if some are present, 
they can be easily disintegrated with a small force and without causing 
such a difficulty that the shell material is localized onto some particles 
and cores of some other particles are exposed. 
The effect of adding the polymer having a long chain alkyl group and an 
acid anhydride group appears if the polymer is used in an amount of 0.5 
wt. % or more of the shell material. Excessive amount of the polymer is 
not desirable as fine particles formed of only the shell material are 
produced if the amount exceeds 30 wt. %. 
The maleic anhydride group of the .alpha.-olefin-maleic anhydride copolymer 
is reactive with a functional group such as hydroxyl, amino and glycidyl 
and may cause partial reaction with a polymer having such a functional 
group. Accordingly, the .alpha.-olefin-maleic anhydride copolymer shows a 
more pronounced effect when a polymer having a polar functional groups is 
used as a shell-forming material. 
Examples of the derivative of the .alpha.-olefin-maleic anhydride copolymer 
include the reaction products of the copolymer and amino compounds, epoxy 
compounds, alcohols and bases which react with the maleic anhydride 
portion of the copolymer. These derivatives show similar effects to those 
of the anhydride copolymer but the degree is somewhat weaker. Hydrolyzed 
products of these derivative exhibit intermediate effects between the 
anhydride copolymer and the above derivatives. 
The optimum alkyl chain length of the .alpha.-olefin portion can vary 
depending on the properties of the core material and the shell material 
affecting the interfacial energy and the solvent used. When the alkyl 
chain is too long, the copolymer loses its solubility in ordinary 
solvents, and the affinity thereof with the core and shell materials is 
impaired. On the other hand, if the alkyl chain is too short, the polymer 
will lose its surface activity. While the length of C.sub.8 -C.sub.26 may 
suitably be used regardless of the core, shell and solvent materials, the 
length of C.sub.4 -C.sub.28 may also be suitably used when appropriate 
materials are used for the above components. 
The toner or capsule toner according to the present invention, when it 
contains magnetic powder, may be used as a one-component magnetic toner. 
Further, the toner or capsule toner according to the present invention may 
be admixed with carrier particles such as iron powder, glass beads, nickel 
powder, and ferrite powder to form a two-component developer for 
developing latent images. Also, the toner can be mixed with negative or 
positive hydrophobic colloided silica powder for the purpose of improving 
free flowability, or can be mixed with abrasive particles such as cerium 
oxide for preventing the toner from sticking on a latent image-bearing 
member. Further the toner or capsule toner according to the present 
invention may be applicable to a developing process of a microtoning 
system. 
The toner or capsule toner according to the present invention may be 
adapted for various modes of low energy fixation systems including a 
pressure fixation apparatus requiring a low pressure, a low-duty thermal 
fixation system capable of effecting fixation at lower energy consumption 
then before, and a low-pressure and low-heat duty fixation apparatus. 
The present invention will be explained more specifically by way of working 
examples, wherein "part" are "parts by weight".

EXAMPLE 1 
______________________________________ 
Paraffin wax (Melt viscosity at 100.degree. C.: 
70 parts 
10 cps, m.p.: 70.degree. C.) 
Polyethylene (Melt viscosity at 100.degree. C.: 
30 parts 
100 cps) 
Dodecylamine 0.5 parts 
Magnetite (primary particle size: 0.3.mu.) 
60 parts 
______________________________________ 
The above ingredients were heat-melted and mixed with a mixer rotating at 
100 rpm for 10 minutes. The mixture was then charged into an attritor 
mixer (MITSUIMIKE Attritor MAISD-type) in which steel balls of 2 mm in 
diameter had been charged in a volume 8 times that of the mixture, and the 
mixture was stirred for 3 hours under the conditions of a temperature of 
200.degree. C., a melt viscosity of 18 ps, and a rotational speed of 360 
rpm. After confirming that aggregates of the magnetite having a size of 
5.mu. or above had substantially disappeared, 100 g of the thus obtained 
mixture after stirring was thrown into a vessel provided with a TK 
Homomixer and containing 3 g of Aerosil 300 and 2000 ml of water 
maintained at 95.degree. C. The content of the vessel was stirred for 60 
minutes by rotating the TK Homomixer at 7000 rpm initially and with 
gradually increasing rotational speeds. The resultant dispersion 
containing fine particles was thrown into 3 kg of crused ice for cooling. 
The fine particles were then washed with an alkaline liquid, subjected to 
repetition of filtration and washing and recovered after drying as fine 
particles to be used as a toner. The fine particles were found to have an 
average particle size of 13.mu. and 56% thereof was within the range of 
from 9 to 17.mu.. 
Incidentally, the mixture constituting the fine particles was found to have 
a penetration of 1. EXAMPLE 2 
A capsule toner was produced in the following manner. 
Thus, 100 g of the fine particles produced in the manner described in 
Example 1 was used as the core material of the capsule and dispersed in a 
solution having the following composition: 
______________________________________ 
Styrene-dimethylaminoethyl methacrylate 
20 g 
copolymer (copolymerization ratio: 90/10 
number-average molecular weight: about 
35000) 
.alpha.-Olefin-maleic anhydride copolymer (C.sub.16) 
1.5 g 
(molecular weight: about 50,000) 
DMF (dimethylformamide) 400 ml 
______________________________________ 
Then, water was gradually added dropwise into the dispersion to cause 
phase-separation of the styrenedimethylaminoethyl methacrylate and the 
.alpha.-olefin-maleic anhydride copolymer and have them coat the core 
material as a shell material. Then, water was further added dropwise to 
solidify the shell. The thus obtained capsule toner was found to have a 
uniform coating with a smooth surface. 
The triboelectric charge of the capsule toner was measured to be +25.3 
.mu.c/g. No blocking was observed after storage for 1 week at 50.degree. 
C., whereby the toner was found to have an excellent thermal stability. 
The capsule toner was used for imaging by means of an electrophotographic 
copier (PC-10, mfd. by Canon K.K.) to obtain a clear toner image was 
obtained without fog on a copy paper. The thus obtained toner image on the 
paper was passed through a pair of pressure rollers having a line pressure 
of 25 kg/cm to be well fixed onto the paper. EXAMPLE 3 
______________________________________ 
Paraffin (Viscosity at 100.degree. C.: 10 cps, 
70 parts 
m.p.: 70.degree. C.) 
Polyethylene wax (Viscosity at 100.degree. C.: 
30 parts 
100 cps) 
Phthalocyanine blue 10 parts 
______________________________________ 
The above ingredients were heat-melted and mixed with a mixer of 100 rpm 
for 10 minutes. The mixture was then kneaded for 1 hour in a sand mill in 
which glass beads of 2 mm in diameter had been charged. During the 
kneading, the mill was heated at 110.degree. C. on an oil bath and the 
mixture showed a melt viscosity of 30 ps. 
The kneaded mixture was withdrawn and supplied to a two-fluid nozzle heated 
at 200.degree. C. and provided with a feeder of compressed air of 4 
kg/cm.sup.2, thereby to be atomized. The atomized product was rapidly 
cooled in air and collected by a cyclone. The thus obtained particles were 
spherical particles having an average particle size of about 12.mu.. Some 
of the particles were embedded in a mass of an epoxy resin and were sliced 
by a microtome into a very thin film, which was then observed through a 
transmission electron microscope, whereby the colorant particles were 
found to have a size of 1.5.mu. even with respect to the largest one. 
The fine particles were encapsulated with a styrene-acrylic copolymer resin 
by the spraying method to form capsules with an average wall thickness of 
0.2.mu.. 
The thus obtained capsule particles were subjected to measurement of 
particle size distribution by a Coulter Counter, TA-II type, whereby the 
average particle size was 11.66.mu. and 52.2% of the particle were found 
to have particle sizes within a range of .+-.4.mu. from the average 
particle size based on the volumetric particle size distribution. 
The thus obtained capsule toner was mixed with carrier iron powder with an 
average particle size of 200.mu. and was used to develop a positive 
electrostatic latent image, whereby a clear image was obtained. The 
developed toner image was transferred onto a copy paper and passed through 
pressure rollers having a line pressure of 25 kg/cm, whereby a well fixed 
toner image was obtained. COMATIVE EXAMPLE 1 
Core particles were prepared in the same manner as in Example 3 except that 
the paraffin was replaced by the polyethylene wax having a viscosity of 
100 cps at 100.degree. C. so that the whole wax was constituted thereby. 
The thus obtained core particles were spheric particles with an average 
particle size of about 25.mu., wherein a large number of phthalocyanine 
blue aggregates having a size of 5.mu. or larger were found to be present 
therein. 
A capsule toner was produced by using the core particles in the same manner 
as in Example 3. The Coulter Counter measurement of the capsule toner 
particles thus obtained gave an average particle size of 25.3.mu. and 
showed that 43.2% of the particles fell within a particle size range of 
.+-.4.mu. from the average particle size based on the volumetric 
distribution. The imaging test gave only an unclear image and the fixed 
image thereof gave such a poor fixability that the toner image was lost by 
soft rubbing by a hand. After several sheets of imaging, the developing 
performance of the toner was rapidly deteriorated. EXAMPLE 4 
______________________________________ 
Paraffin (Viscosity at 100.degree. C. 10 cps, 
40 parts 
m.p.: 70.degree. C.) 
Carnauba wax (Viscosity at 100.degree. C.: 
60 parts 
25 cps) 
Magnetite (0.3 .mu.) 60 parts 
______________________________________ 
The above ingredients were heat-melted and mixed with a mixer of 100 rpm 
for 10 minutes. The mixture was then kneaded for 1 hour in a sand mill in 
which glass beads of 1.5 mm in diameter had been charged. During the 
kneading, the mill was heated at 120.degree. C. on an oil bath and the 
mixture showed a melt viscosity of 25 ps. 
The kneaded mixture was then withdrawn and charged into hot water heated at 
95.degree. C. to be dispersed therein under the action of a high-speed 
stirrer. The resultant dispersion was then quenched in crushed ice, and 
subjected to centrifugal filtration and drying to obtain solid particles. 
The thus obtained particles were encapsulated by the phase separation using 
DMF and water as used in Example 2 to form capsules having a wall of 
styreneacrylic copolymer resin with an average thickness of about 
0.18.mu.. 
The Coulter Counter measurement of the capsule toner particles thus 
obtained gave an average particle size of 10.58.mu. and showed that 65% of 
the particles fell with a particle size range of .+-.4.mu. from the 
average particle size based on the volumetric distribution. 
The capsule toner was applied to a developing apparatus using a magnetic 
sleeve, whereby a clear image was obtained. The developed toner image was 
transferred onto a copy paper and passed through pressure rollers having a 
line pressure of 17 kg/cm, whereby a well fixed image was obtained. 
Further, the aggregates of the magnetite in the toner were found to have a 
size of 2.0.mu. at the maximum. COMATIVE EXAMPLE 2 
A capsule toner was obtained in the same manner as in Example 4 except that 
the kneading by means of the sand mill was omitted. 
The thus obtained toner particles were found to have an average size of 
20.5.mu., and 23% of the particles fell within a range of .+-.4.mu. from 
the average particle size. Further, the aggregates of magnetite in the 
capsule toner showed a size of 7.8.mu. at the maximum. 
When the capsule toner was used for development in the same manner as in 
Example 4, only unclear images were obtained and the developing 
performance was rapidly deteriorated after several sheets of copying. 
COMATIVE EXAMPLE 3 
A capsule toner was obtained in the same manner as in Example 4 except that 
the paraffin and carnauba wax were replaced by paraffin having a viscosity 
at 100.degree. C. of 0.8 cps. 
The obtained toner particles were found to have an average size of 8.2.mu., 
and 35% of the particles fell within a range of .+-.4.mu. from the average 
particle size. 
When this toner was applied to imaging, only unclear images were obtained 
and, after several tens of sheets of imaging, the developing performance 
of the toner was rapidly deteriorated and fusion sticking of the toner was 
observed on the sleeve EXAMPLE 5 
______________________________________ 
Paraffin (Viscosity at 100.degree. C: 10 cps, 
80 parts 
m.p.: 70.degree. C.) 
Polyethylene wax (Viscosity at 100.degree. C.: 
20 parts 
100 cps) 
Raven 3500 (carbon black) 10 parts 
______________________________________ 
The above ingredients were heat-melted and mixed with a mixer of 120 rpm 
for 10 minutes. The mixture was then kneaded for 1 hour in a ball mill not 
in which ceramic balls of 5 to 15 mm in diameter were charged. During the 
kneading, the pot was heated at 110.degree. C. on an oil bath. 
The kneaded mixture withdrawn was supplied to a two-fluid nozzle heated at 
200.degree. C. and provided with a feeder of compressed air, thereby to be 
atomized. The atomized product was rapidly cooled in air and collected. 
The thus obtained particles were spherical particles having an average 
particle size of 12.mu.. Some of the particles were embedded in a mass of 
an epoxy resin and were sliced by a microtome into a very thin film, which 
was then observed through a transmission electron microscope, whereby the 
carbon black particles were found to have a size of 1.5.mu. even with 
respect to the largest one. 
The thus obtained particles were mixed with carrier iron powder with an 
average particle size of 100.mu. and was used to develop positive 
electrostatic latent image, whereby a clear image was obtained. The 
developed toner image was transferred onto a copy paper and passed through 
pressure rollers having a line pressure of 25 kg/cm, whereby a well fixed 
toner image was obtained. EXAMPLE 6 
______________________________________ 
Paraffin wax (Melt viscosity at 100.degree. C.: 
70 parts 
10 cps, m.p.: 65.degree. C.) 
Carnauba wax 30 parts 
Magnetite (particle size: 0.3.mu.) 
60 parts 
______________________________________ 
The above ingredients were heat-melted and mixed with a mixer of 120 rpm 
for 10 minutes. The mixture was then kneaded in a sand mill in which glass 
beads of 2 mm in diameter had been charged During the kneading, the mill 
was heated at 120.degree. C. by an electric heater. 
The kneaded product was thrown into 2000 parts by water heated at 
95.degree. C. and containing 2 g of sodium dodecylbenzenesulfonate and 
dispersed under stirring at 8500 rpm. The dispersion was then quenched, 
subjected to repetition of filtration and washing and recovered after 
drying as toner particles. 
The thus obtained fine particles were mixed with 0.3 part of hydrophobic 
colloidal silica to form a developer, which was then applied to a 
electrophotographic copier (NP-120, mfd. by Canon K.K.) to provide a clear 
image. The fixing of the toner image was also satisfactorily effected. 
Further, a fixing test was conducted by replacing the fixer of the copier 
with an experimental fixing device providing an average line pressure of 
15 kg/cm, whereby equally satisfactory results were obtained. COMATIVE 
EXAMPLE 4 
A toner was obtained in the same manner as in Example 5 except that the 
ball milling was omitted. The toner particles thus obtained were spherical 
particles having an average size of 15.mu., in which aggregates of carbon 
black particles in the toner were found to have a size of the order of 
7.mu. at the maximum. 
When this toner was used for development, only unclear images were obtained 
and, during a 30-sheet continuous copying test, the image density was 
gradually lowered to reach a state wherein almost no image was observed. 
COMATIVE EXAMPLE 5 
A toner was obtained in the same manner as in Example 6 except that 
polyethylene wax having a viscosity at 100.degree. C. of 140 cps was used 
in place of the paraffin and the carnauba wax. 
When this toner was used for imaging, only a low density of image was 
obtained and the toner image fixed under a pressure of 15 kg/cm was easily 
removed by rubbing with fingers. EXAMPLE 7 
______________________________________ 
Paraffin (Viscosity at 100.degree. C. 8 cps) 
70 parts 
Rice wax 30 parts 
Phthalocyanine blue 10 parts 
______________________________________ 
The above ingredients were heat-melted and mixed with a mixer of 120 rpm 
for 15 minutes. The mixture was then kneaded in a sand mill in which glass 
beads of 1 mm in diameter had been charged. During the kneading, the mill 
was heated at 120.degree. C. by an electric heater. 
The kneaded product was thrown into 1000 parts of water heated at 
95.degree. C. and containing 1.8 g of silica and dispersed under 
high-speed stirring at 8500 rpm. The dispersion was then quenched, 
subjected to repetition of filtration and washing and recovered after 
drying as toner particles. 
The thus obtained toner particles were mixed with carrier particles and 
used as a developer. The toner showed good developing and fixing 
performances and the particles of the phthalocyanine blue in the toner 
showed particle sizes below 3.mu.. COMATIVE EXAMPLE 6 
The procedure of Example 7 was repeated by using paraffin wax having a 
viscosity of 0. 8 cps at 100.degree. C. was used in place of the paraffin 
was (8 cps) and the rice wax. The particles of the phthalocyanine blue in 
the toner showed a particle size of 3.mu. at the maximum, whereas the 
developing performance was insufficient and sticking of the toner onto the 
carrier particles was extensively observed.