Toners for developing electrostatic images

A toner for electrostatic image developing is disclosed. It is prepared by giving a mechanical impact force to radically polymerized particles containing a colorant and a low molecular weight polyolefine so as to have the low molecular weight polyolefine exist at a ratio of 5 to 40% by number on a surface of the particles. The toner has a uniform and good electrification property, high fixability and no offsetting property.

The present invention relates to a toner used in developing electrostatic 
images, particularly to the constitution of toner particles. 
Preparation of a toner by the polymerization method is known in the art. In 
the polymerization method, a toner is generally prepared by suspending a 
material to form the toner in water and forming particles by suspension 
polymerization. On the other hand, there is disclosed in Japanese Patent 
O.P.I. Publication No. 153944/1980 that use of low molecular weight 
polyolefins is effective in improving the fixability of a toner prepared 
by the pulverization method. Following this instance, there has been tried 
addition of low molecular weight polyolefins to a toner prepared by the 
polymerization method for the purpose of improving fixability. But, as 
described in Japanese Patent O.P.I. Publication No. 230664/1985, low 
molecular weight polyolefins can hardly contribute to the improvement of 
fixability, because they are generally liable to be buried inside of a 
polymer composition and cannot be present at the surface of polyolefin 
particles for their low surface energy and hydrophilicity. Under such 
circumstances, various studies are being made to solve this problem. 
For example, Japanese Patent O.P.I. Publication Nos. 230644/1985 and 
238843/1985 disclose attempts to have these low molecular weight 
polyolefins present at the particle surface by adding hydrophilic 
polyolefins in order to enhance the compatibility with water. However, 
this has a drawback to impair the electrification property in a high 
temperature and high humidity environment, since the surface of polyolefin 
particles turns to hydrophilicity with the addition to hydrophilic 
polyolefins. 
Further, Japanese Patent O.P.I. Publication No. 93749/1989 describes an 
attempt to aggregate particles by steps of adding and dispersing low 
molecular weight polyolefins in a polymerization system to associate them 
with emulsion-polymerized particles, and then giving a mechanical impact 
force to the particles formed through association. However, these low 
molecular weight polyolefins cannot be dispersed so finely as 
emulsion-polymerized particles; therefore, it is difficult to have them 
exist uniformly in toner particles. 
As stated above, use of polyolefins has been proposed in many ways as a 
means to improve the electrification property, fixability and 
anti-environmental property of toners prepared by the polymerization 
method, but none of them are satisfactory. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a toner for an 
electrophotographic developer prepared by the polymerization method and 
containing a polyolefin and a colorant, which has a uniform and good 
electrification property, high fixability and no offsetting property. 
The toner of the invention is a toner for electrostatic image developing, 
prepared by steps of suspending a radically polymerizable monomer, low 
molecular weight polyolefin, colorant and radical polymerization initiator 
in a suspending medium, allowing the suspended matter to undergo radical 
polymerization, and then giving a mechanical impact force to the colored 
and polymerized particles having a volume-average particle size of 3 to 12 
.mu.m in order to have the low molecular weight polyolefin exist at a 
ratio of 5 to 40% by number on the surface of the colored particles. 
In the invention, the low molecular weight polyolefin existing "at the 
surface" means that said polyolefin is present in a surface layer up to a 
depth of 0.1 .mu.m. 
A mechanical impact force, repetitively given to colored particles 
containing a low molecular weight polyolefin prepared by the 
polymerization method, grinds the surface of the colored particles and 
allows the low molecular weight polyolefin to come out to the particle 
surface. 
It is preferable that the radical-polymerizable monomer be selected so as 
to give a polymer having a softening point of 100.degree. to 200.degree. 
C. and glass transition point of 50.degree. to 70.degree. C. The 
weight-average molecular weight of the polymer to be prepared is 
preferably 5.times.10.sup.4 to 1.times.10.sup.6 ; the number-average 
molecular weight of the polymer is preferably 1.times.10.sup.3 to 
1.times.10.sup.5. 
Preferred examples of the radical-polymerizable monomer used in the 
invention include styrene monomers such as styrene, o-methylstyrene, 
m-methylstyrene, p-methylstyrene, .alpha.-methylstyrene, p-ethylstyrene, 
2,4-dimethylstyrene, p-butylstyrene, p-t-butylstyrene, p-hexylstyrene, 
p-octylstyrene, p-nonylstyrene, p-decylstyrene, p-dodecylstyrene, 
p-methoxystyrene, p-phenylstyrene, p-chlorostyrene and 
3,4-dichlorostyrene. Other examples include olefins such as ethylene, 
propylene, butylene, isobutylene; vinyl halides such as vinyl chloride, 
vinylidene chloride, vinyl bromide, vinyl fluoride; vinyl esters such as 
vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate; 
.alpha.-methylene aliphatic monocarboxylates such as ethyl acrylate, butyl 
acrylate, isobutyl acrylate, propyl acrylate, octyl acrylate, dodecyl 
acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 
2-chloroethyl acrylate, phenyl acrylate, methyl-.alpha.-chloroacrylate, 
methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl 
methacrylate, isobutyl methacrylate, octyl methacrylate, dodecyl 
methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl 
methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, 
diethylaminoethyl methacrylate; derivatives of acrylic acid or methacrylic 
acid such as acrylonitrile, methacrylonitrile, acrylamide; vinyl ethers 
such as vinylmethyl ether, vinylethyl ether, vinylisobutyl ether; 
vinylketones such as vinylmethyl ketone, vinylheyl ketone, 
methylisopropenyl ketone;N-vinyl compounds such as N-vinylpyrrole, 
N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone; and vinyl 
naphthalenes. These monomers may be used singly or in combination of two 
or more to give a copolymer. 
In polymerizing these monomers, a radical polymerization initiator is 
generally used in an amount ranging from 0.1 to 10% by weight of monomer. 
An appropriate addition amount is determined by a final polymerization 
degree. 
Typical examples of the polymerization initiator include peroxide type 
initiators such as acetylcyclohexylsulfonyl peroxide, isodibutyl peroxide, 
diisopropylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, 
2,4-dichlorobenzoyl peroxide, t-butylperoxypivalate, 
3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, decanoyl peroxide, 
lauroyl peroxide, stearoyl peroxide, propionyl peroxide, succinic acid 
peroxide, acetyl peroxide, t-butyl peroxy-2-ethylhexanoate, benzoyl 
peroxide, p-chlorobenzoyl peroxide, t-butyl peroxyisobutylate, 
t-butylperoxymaleic acid, t-butylperoxylaurate, cyclohexanone peroxide, 
t-butyl peroxyisopropylcarbonate, 2,5-dimethyl-2,5-dibenzoyl peroxyhexane, 
t-butylperoxyacetate, t-butyl peroxybenzoate, diisobutyl 
diperoxyphthalate, methyl ethyl ketone peroxide, dicumyl peroxide, 
2,5-dimethyl-2,5-di-t-butyl peroxyhexane, t-butylcumyl peroxide, t-butyl 
hydroperoxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butyl 
peroxyhexane, diisopropylbenzene hydroperoxide, p-methane hydroperoxide, 
pinane hydroperoxide, 2,5-dimetylhexane-2,5-dihydroperoxide, cumene 
hydroperoxide; and azo type initiators such as 
2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 
2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, 
2,2'-azobis-2,4-dimethylvaleronitrile. 
A crosslinking agent may be used in the polymerization system to obtain a 
crosslinked polymer. Preferred crosslinking agents are those compounds 
which have two or more polymerizable double bonds. Examples thereof 
include diethylenic carboxylates such as ethylene glycol dimethacrylate, 
diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 
trimethylolpropane triacrylate, allyl methacrylate, tetraethylene glycol 
dimethacrylate, 1,3-butane diol dimethacrylate; divinyl compounds such as 
N,N-divinyl aniline, divinyl ether, divinyl benzene, divinyl sulfide, 
divinyl sulfone; and compounds having three or more vinyl groups. These 
may be used singly or in combination. 
The addition amount of such crosslinking agents to a monomer is generally 
0.005 to 20% by weight, preferably 0.1 to 5% by weight. An excessive 
addition amount raises the softening point and eventually loses the 
fixability. When the addition amount is too small, toner properties such 
as durability, preservability and abrasion resistance can be hardly 
imparted, particularly an anti-offsetting property in the fixing process 
is lowered when used in hot roll fixing type copying machines. 
Suspension polymerization is carried out by suspending a polymerization 
composition, through mechanical stirring, in a suspension medium such as 
water as fine particles of desired sizes. Suspension stabilizers are used 
to prevent association of suspended particles, since the suspended 
particles come to be cohesive and associate with one another to form large 
particles as the polymerization proceeds. 
Water is used as a suspension medium, and an organic solvent such as 
methanol may be further added according to a specific requirement. 
Compounds used as a suspension stabilizer are generally classified into two 
main groups, namely water-soluble polymeric substances and sparingly 
soluble inorganic compounds. The former includes gelatin, starch, 
polyvinyl alcohol, etc. The latter includes sparingly soluble salts such 
as barium sulfate, calcium sulfate, barium carbonate, calcium carbonate 
and calcium phosphate; combinations of the sparingly soluble salts and 
surfactants such as sodium dodecylbenzene sulfonate and sodium dodecyl 
sulfate; inorganic polymeric metal oxides such as talc, clay, silicic acid 
and diatomaceous earth; and other powders. When a polymerization 
composition contains an ionic substance (for example, a cationic substance 
such as nitrogen-containing polymerizable monomer or sparingly 
water-soluble amine, or an anionic substance) and thereby its suspended 
particles in water are charged with either of negative and positive 
polarities, an ionic dispersant which disperses in water with a polarity 
opposite to that of suspended polymer particles can be effectively 
utilized as a suspension stabilizer. Examples thereof include negatively 
electrifiable colloidal silica and positively electrifiable aluminum 
oxide. 
The low molecular weight polyolefin may be a homopolymer obtained from a 
single kind of olefin monomer or a copolymer obtained by copolymerization 
of an olefin monomer and another copolymerizable monomer. 
Examples of the olefine monomer include ethylene, propylene, butene-1, 
pentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1; their 
isomers different in positions of unsaturated bond; olefins having a 
branched chain consisting of alkyl group such as 3-methyl-1-butene, 
3-methyl-2-pentene, 3-propyl-5-methyl-2-hexene; all other olefins. Of 
them, ethylene and propylene are particularly preferred. 
Other monomers copolymerizable with an olefin monomer include, besides 
other olefine monomers, vinyl ethers, vinyl esters, halogenated olefins, 
acrylates, methacrylates, acrylic acid derivatives and organic acids such 
as itaconic acid. 
Further, there may be also used a modified polyolefin which is blocked or 
grafted with another component. 
It is preferable that such a polyolefin have a weight-average molecular 
weight of 6,000 to 70,000 and a number-average molecular weight of 1,500 
to 20,000. 
Next, examples of preferable polyolefins used in the invention are shown; 
namely, Viscol 330-P, Viscol 550-P, Viscol 660-P (polypropylenes made by 
Sanyo Chemical), 320 P, Hiwax 310 P, Hiwax 410 P, Hiwax 405 P, Highwax 400 
P, Hiwax 200 P (polyethylenes made by Mitsui Petrochemical), Sanwax 131-P, 
Sanwax 151-P, Sanwax 161-P, Sanwax 165-P, Sanwax 171-P (polyethylenes made 
by Sanyo Chemical), Polywax 400, Polywax 500, Polywax OH-465, Polywax 1040 
(polyethylenes made by Toyo Petrolite). 
These polyolefins may be used singly or in combination. The addition amount 
of these polyolefins is preferably 1 to 10% by weight and especially 2 to 
7% by weight of polymerizable monomer. 
As a colorant, there may be used magnetite, carbon black, Niglosin dye 
(C.I. No.50415B), aniline blue (C.I. No.50405), Calco oil blue (C.I. No. 
azoic Blue 3), chrome yellow (C.I. No.14090), ultramarine blue (C.I. 
No.77103), Du pont Oil Red (C.I. No.26105), quinoline yellow (C.I. 
No.47005), methylene blue chloride (C.I. No.52015), phthalocyanine blue 
(C.I. No.74160), malachite green oxalate (C.I. No.42000), lamp black (C.I. 
No.77266), rose Bengal (C.I. No.45435), and mixtures thereof. These 
colorants have to be used at a concentration sufficient to form visual 
images of adequate density; its addition amount is generally 1 to 20% by 
weight of a binder resin obtained by the radical polymerization. The toner 
of the invention may contain additives such as a UV absorbent and 
fluorescence dye according to a specific requirement. 
The colored particles according to the invention can be prepared by steps 
of adding a prescribed amount of a colorant, low molecular weight 
polyolefin, polymerization initiator and other additives to a 
polymerizable monomer, mixing them thoroughly to form a uniformly 
dispersed polymerization composition with a stirrer such as sand stirrer, 
adding it to a water-based suspension medium containing a suspension 
stabilizer, dispersing the polymerization composition into oil droplets 
having a particle size appropriate for toner, and then allowing the 
polymerization composition dispersed into fine oil droplets in the 
suspension medium to polymerize. Colored particles consisting of a 
colorant and polyolefin fine particles are thus obtained. Since the size 
of these colored particles is determined by the dispersing state of the 
polymerization composition, the colored particles can be polymerized to a 
necessary size, namely a volume-average particle size of 3 to 12 .mu.m, by 
adjusting dispersing conditions. Consequently, after the resulting colored 
particles are separated from the suspension medium, they can be subjected 
to a mechanical impact treatment as they are. 
As a surface-treating apparatus which exerts a mechanical impact force to 
have the necessary amount of a low molecular weight polyolefin existing at 
the surface of the colored particles obtained as above, a free-mill, 
hybridizer (product of Nara Kikai Seisakusho), Angmill (product of 
Hosokawa Micron) and Kryptron (product of Kawasaki Heavy Ind.) can be 
used. 
As a treating intensity in a system having high-speed rotation blades like 
a hybridizer, for example, it is preferable that the peripheral speed of 
such blades be about 50 to 100 m/sec. A low peripheral speed does not 
produce a noticeable grinding effect, and thereby the amount of a low 
molecular weight polyolefin existing at the surface cannot increase 
adequately; a high peripheral speed tends to exert an excessive mechanical 
energy, and thereby the toner itself is crushed up to yield fine 
particles. 
The surface treatment may be carried out at the normal temperature or under 
heating. But it is preferable that the temperature of colored particles 
determined by the following method be 50.degree. to 110.degree. C. and 
lower than the glass transition point of said colored particles. 
The temperature of colored particles mentioned here means an average of 
approximate surface temperatures of the colored particles obtained by 
inserting a temperature measuring probe into a stream of particles flowing 
under the application of impact force so as to have the particles contact 
the probe at random. 
The temperature measuring probe is composed of a thermocouple, temperature 
measuring resistor, etc. And temperatures can be determined by measuring 
electrically its electromotive force, resistance value, etc. 
A typical example of the thermocouple is a chromel-alumel thermocoupler. 
In the invention, the temperature of colored particles is measured with a 
chromel-alumel thermocoupler covered with a stainless steel (SUS 304) 
shield having a length of 10 cm and a diameter of 6.4 mm (product of 
Hayashi Denko). Measurement is carried out by inserting its head by 5 cm. 
In the invention, the quantity of a low molecular weight polyolefin 
existing at the surface can be measured by the ESCA. Measuring conditions 
of the ESCA are shown below. The definition of percentage by number is 
also described below. 
Measuring apparatus: PHI Model 560 ESCA/SAM made by Perkin-Elmer Co. 
Measuring conditions: X-ray output=15 kV, 26.7 mA 
Sample preparation: particles are scattered on a strip of double coated 
adhesive tape, then the strip is fastened on a sample stand. 
Quantitative calculation is carried out from peak areas of respective 
elements, using peaks of 
carbon=Cls, 
oxygen=Ols, and 
nitrogen=Nls. 
Since the sensitivity varies by elements, area intensities obtained by 
measurement are subjected to sensitivity correction according to "Handbook 
of X-ray Photoelectron Spectroscopy" prepared by Perkin-Elmer Co. Using 
intensity ratios obtained in this way, the percentage by number is 
determined from the ratio of elements existing at the particle surface and 
the ratio of elements of a material used. That is, since the ratio of 
elements existing at the surface is determined by the ratio of used 
materials existing at the surface, the existing quantities can be 
determined by solving the following simultaneous equations. 
EQU k=xa1+xb1+xc1 
EQU l=ya2+yb2+yc2 
EQU m=za3+zb3+zc3 
where x, y, z show existing amounts (%) of constituent compounds A, B and 
C, respectively; a1, a2 and a3 show a ratio of elements 1, 2 and 3 which 
constitute compound A; b1, b2 and b3 show a ratio of elements 1, 2 and 3 
which constitute compound B; c1, c2 and c3 show a ratio of elements 1, 2 
and 3 which constitute compound C; and k, l and m represent a ratio of 
particle-constituting elements 1, 2 and 3. In the invention, x, y and z 
are respectively defined as percentages by number of constituent compounds 
A, B and C. 
As an apparatus for the ESCA, there may be used ones other than the above 
apparatus. Examples of such include Shimadzu's ESCA-1000 and JEOL's 
JPS-90SX. 
When the colored particles are prepared by polymerization, a low molecular 
weight polyolefin is scarcely present at the surface of the colored 
particles. Said polyolefin comes out to the surface of the colored 
particles only when a mechanical impact force is given to the particles. 
In other words, the low molecular weight polyolefin exists uniformly in 
the colored particles, and when the surface of the particles are ground by 
a mechanical impact force, the low molecular weight polyolefin comes out 
to the surface. Therefore, the quantity of the low molecular weight 
polyolefin existing at the surface can be controlled by varying the 
mechanical impact force as described above. 
When the quantity of the low molecular weight polyolefin existing at the 
surface is more than 40% by number, frictional electrification between 
toner particles increases, thereby the transfer ratio comes to be lowered, 
and moreover, the anti-environmental dependency is deteriorated. On the 
contrary, when the quantity of the low molecular weight polyolefin 
existing at the surface is less than 5% by number, the fixing property is 
lowered and the offsetting property is eventually deteriorated. 
The toner of the invention may contain a magnetic material, charge 
controlling agent and dispersant according to a specific requirement. 
As magnetic materials, there may be used ferromagnetic metals such as iron, 
cobalt, nickel, and their alloys and compounds containing these elements 
such as ferrite, magnetite; alloys which contain no ferromagnetic 
materials but come to be ferromagnetic when subjected to a proper heat 
treatment, examples of which include Heusler's alloys containing copper 
and manganese such as manganese-copper-aluminum alloy and 
manganese-copper-tin alloy; and chromium dioxide and others.

EXAMPLES 
The present invention is hereunder described in detail with the examples. 
In the following description, "part" means a relative weight in the same 
weight unit, unless otherwise specified. 
Particle preparation 1 
______________________________________ 
Styrene 80 parts 
Butyl acrylate 20 parts 
S-34 (product of Orient Chemical) 
1 part 
Viscol 660-P 3 parts 
(polypropylene made by Sanyo Chemical) 
______________________________________ 
The above compounds were mixed and then heated to 80.degree. C. under 
stirring to dissolve Viscol 660-P. After cooling it to room temperature, 
______________________________________ 
Azobisisobutyronitrile 1 part 
Mogul L (carbon black) 5 parts 
______________________________________ 
the above compounds were mixed therein and dispersed with a sand grinder 
rotating at 2,000 rpm to obtain a polymerization composition. 
Subsequently, the polymerization composition was added to a concentration 
of 20% by weight to a water containing colloidal tricalcium phosphate in 
an amount of 3% by weight of the polymerization composition and sodium 
dodecylbenzene sulfonate in an amount of 0.04% by weight of the 
polymerization composition. Then, a high speed shearing force (about 8,000 
rpm) was applied thereto with a TK homo-jetter so as to disperse the 
polymerization composition in the water into particles of about 10 .mu.m 
size, so that a suspension of the polymerization composition was obtained. 
The particle size was determined by microscopic observation. Next, the 
suspension was allowed to polymerize for 8 hours at 65.degree. C. under 
stirring, in a flask equipped with a cooling tube, thermometer and 
nitrogen-gas-introducing tube. After completion of polymerization, 
hydrochloric acid was added to remove the colloidal tricalcium phosphate 
used as a suspension stabilizer, and the polymerization product was 
further washed with water. Colored particles having an average particle 
size of 10.1 .mu.m were thus obtained. These colored particles are 
referred to as polymerized particle 1. Then, 130 g of polymerized particle 
1 was subjected to surface grinding with a hybridizer model 1 (product of 
Nara Kikai Seisakusho) by applying a mechanical impact force for 3 minutes 
at a peripheral speed of 75 m/sec and at a particle temperature of 
approximately 45.degree. C. The particles obtained had an average particle 
size of 10.0 .mu.m. These particles are referred to as treated particle 1. 
Polymerized particle 1 and treated particle 1 were subjected to 
measurement by the ESCA to determine the quantity of polypropylene 
existing at the surface. The measuring conditions were as follows: 
Measuring apparatus: PHI Model 560 ESCA/SAM made by Perkin-Elmer Co. 
Measuring conditions: X-ray output=15 kV, 26.7 mA 
Sample preparation: particles are scattered on a strip of double coated 
adhesive tape, then the strip is fastened on a sample stand. 
Sensitivity correction: "Handbook of X-ray Photoelectron Spectroscopy" 
prepared by Perkin-Elmer Co. 
The quantities of polypropylene existing at the surfaces were calculated 
from the measured results. The calculation results were 1% by number for 
polymerized particle 1 and 28% by number for treated particle 1. 
Particle preparation 2 
Treated particles having an average particle size of 10.0 .mu.m were 
prepared in the same manner as in particle preparation 1, except that 
treating conditions were changed to a peripheral speed of 100 m/sec, a 
particle temperature of approximately 50.degree. C. and a treating time of 
3 minutes. These treated particles are referred to as treated particle 2. 
The quantity of polypropylene existing at the surface of treated particle 
2 was 35% by number. 
Particle preparation 3 
Treated particles having an average particle size of 10.1 .mu.m were 
prepared in the same manner as in particle preparation 1, except that 
treating conditions were changed to a peripheral speed of 60 m/sec, a 
particle temperature of approximately 50.degree. C. and a treating time of 
3 minutes. These treated particles are referred to as treated particle 3. 
The quantity of polypropylene existing at the surface of treated particle 
3 was 20% by number. 
Particle preparation 4 
Colored particles having an average particle size of 10.6 .mu.m were 
prepared in the same manner as in particle preparation 1, except that the 
polymerization was carried out at 75.degree. C. using 1 part of lauryl 
peroxide instead of azobisisobutyronitrile, 6 parts of Viscol 660-P, 60 
parts of EPT-1000 (product of Toda Kogyo) instead of Mogul L, and 0.1 part 
of lecithin. These colored particles are referred to as polymerized 
particle 2. Treated particles having an average particle size of 10.4 
.mu.m were prepared by giving a mechanical impact force to polymerized 
particle 2 in the same manner as in particle preparation 1. These treated 
particles are referred to as treated particle 4. The quantity of 
polypropylene existing at the surface of treated particle 3 was 35% by 
number. The quantities of polypropylene existing at the surface were 
calculated as in particle preparation 1; the results were 1% by number for 
polymerized particle 2 and 25% by number for treated particle 4. 
Particle preparation 5 
Treated particles having an average particle size of 10.5 .mu.m were 
prepared in the same manner as in particle preparation 4, except that 
conditions of the mechanical impact force were changed to those in 
particle preparation 2. These treated particles are referred to as treated 
particle 5. The quantity of polypropylene existing at the surface of 
treated particle 5 was 38% by number. 
Particle preparation 6 
Treated particles having an average particle size of 10.5 .mu.m were 
prepared in the same manner as in particle preparation 4, except that 
conditions of the mechanical impact force were changed to those in 
particle preparation 3. These treated particles are referred to as treated 
particle 6. The quantity of polypropylene existing at the surface of 
treated particle 6 was 18% by number. 
Toner and developer preparation 
Electrophotographic properties were evaluated using the above treated 
particles. In the evaluation, toners 1, 2 and 3 were prepared by adding 
0.5% each of hydrophobic silica R-972 to treated particles 1, 2 and 3, and 
treating the particles for 10 minutes with a tabular mixer. Toners 4, 5 
and 6 were prepared by adding 0.4% each of hydrophobic silica R-972 to 
treated particles 4, 5 and 6, and treating the particles for 10 minutes 
with a tabular mixer. Further, comparative toner 1 was prepared by adding 
0.5% of silica R-972 to polymerized particle 1 and treating particle for 
10 minutes with a tabular mixer. Comparative toner 2 was prepared by 
adding 0.4% of silica R-972 to polymerized particle 2 and treating the 
particle for 10 minutes with a tabular mixer. 
Further, toners 1, 2 and 3 and comparative toner 1 were respectively mixed 
with an iron powder carrier (approximately 100 .mu.m) surface-coated with 
a styrene-acrylic resin to prepare developers having a toner concentration 
of 3%. 
Evaluation of electrophotographic properties 
(1) Electrification quantity: The iron powder carrier was added to each of 
toners 1 to 6 and comparative toners 1 and 2, and electrification quantity 
in a high temperature and high humidity environment was evaluated on each 
toner by the blowoff method. Ratings corresponding to shaking times with 
the iron powder are shown in the table below. 
Evaluation results of electrification quantity 
______________________________________ 
1-minute 10-minute 30-minute 
Sample shaking shaking shaking 
______________________________________ 
Toner 1 -17.1 .mu.c/g 
-16.7 .mu.c/g 
-15.9 .mu.c/g 
Toner 2 -18.3 .mu.c/g 
-17.8 .mu.c/g 
-16.8 .mu.c/g 
Toner 3 -16.1 .mu.c/g 
-15.7 .mu.c/g 
-14.9 .mu.c/g 
Toner 4 -25.3 .mu.c/g 
-24.5 .mu.c/g 
-24.1 .mu.c/g 
Toner 5 -23.9 .mu.c/g 
-22.7 .mu.c/g 
-22.0 .mu.c/g 
Toner 6 -24.5 .mu.c/g 
-23.8 .mu.c/g 
-22.9 .mu.c/g 
Comparative toner 1 
-18.5 .mu.c/g 
-13.5 .mu.c/g 
-11.5 .mu.c/g 
Comparative toner 2 
-23.7 .mu.c/g 
-21.5 .mu.c/g 
-18.3 .mu.c/g 
______________________________________ 
(2) To evaluate the fixability, the winding property and offsetting 
property were examined. In examining these properties, the U-Bix 1550 
(product of Konica Corp.) was used to form images respectively containing 
toners 1, 2, 3 LP-3015 was used to form images respectively containing 
toners 4, 5, 6 and comparative toner 2. 
Winding property 
Using a transferred image (unfixed) having a solid black head, the winding 
property was evaluated by determining a temperature at which a transfer 
paper began to wind around a fixing roller (winding temperature) while the 
set temperature of the fixing roller was changed 5.degree. C. at a time 
from 230.degree. C. As the fixing apparatus, a fixing unit of the U-Bix 
1550 (product of Konica Corp.) was modified and used. The surface layers 
of the fixing roller and pressing roller were respectively formed from 
Teflon-silicone rubber KE-1300R-TV. The passing speed of the transfer 
material was 120 mm/sec, and no silicone oil was fed to the surface of the 
fixing roller. 
Offsetting property 
Using the fixing apparatus mentioned above, fixing was carried out by 
passing a transfer paper carrying an unfixed toner image at a linear speed 
of 120 mm/sec and then passing a blank transfer paper at the same 
condition, while the set temperature was raised by 5.degree. C. in stages. 
While the fixing was carried on as stated above, whether a toner stain 
occurs or not was visually checked, and the lowest temperature which 
caused a roller stain was taken as an offset generation temperature. 
The results of the above evaluations are shown in the table below. 
______________________________________ 
Winding Offset generation 
Sample temperature 
temperature 
______________________________________ 
Toner 1 175.degree. C. 
More than 230.degree. C. 
Toner 2 165.degree. C. 
More than 230.degree. C. 
Toner 3 180.degree. C. 
More than 230.degree. C. 
Toner 4 175.degree. C. 
More than 230.degree. C. 
Toner 5 165.degree. C. 
More than 230.degree. C. 
Toner 6 180.degree. C. 
More than 230.degree. C. 
Comparative toner 1 
225.degree. C. 
230.degree. C. 
Comparative toner 2 
225.degree. C. 
230.degree. C. 
______________________________________ 
As apparent from the table, the toners according to the invention are high 
in fixing properties and low in environmental dependency.