Process for producing toner

A process for producing a toner includes melt-blending at least a colorant and a polymer and finely pulverizing the resulting blend after cooling, wherein the polymer is a crosslinked resin having a ratio of weight-average molecular weight to number-average molecular weight (Mw/Mn) exceeding 4.0 and a melt index of 0.01-10 g/10 min. at 110.degree. C. under a load of 10 Kg and the polymer is further crosslinked to form gel during the melt-blending. The toner thus obtained exhibits a good fixability without offset phenomenon over a wide temperature range.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for producing a toner to be used for 
developing electrostatic images in electrophotography, electrostatic 
recording, electrostatic printing, and the like. More particularly, this 
invention relates to a process for producing a toner which is suited for 
hot-roller fixing. 
2. Description of the Prior Art 
As described in U.S. Pat. Nos. 2,297,691, 3,666,363, and 4,071,361 and in 
other documents, various electrophotographic processes have so far been 
known. Electrophotographic processes, however, generally comprise forming 
an electrostatic latent image on a photosensitive member by a suitable 
method, developing the latent image with a toner, and if necessary, 
transferring the toner image onto an image receiving member such as paper 
or the like, followed by fixing the transferred image with heat, pressure, 
or a solvent vapor, to obtain a duplicate of the latent image. 
As regards the last step of the above process, i.e. the step of fixing a 
toner image on paper or the like, various techniques and devices have been 
developed. The most common technique thereof practiced today is the hot 
press method by a heated roller. In this hot press method, a toner image 
is fixed by passing the toner-image-bearing sheet over a heated roller, 
the surface of which has a good toner-releasing property, so that the 
toner-image-bearing surface will contact the roller surface under 
pressure. Since the toner image is brought into contact with the heated 
roller surface under pressure, this method is excellent in heat efficiency 
and permits quick fixing, thus being applicable very effectively to 
high-speed electrophotographic copying machines. 
According to this method, however, because of the contact of the toner in a 
molten state with a heated roller surface under pressure, a so-called 
offset phenomenon is liable to occur, that is, the toner image often 
partially adheres or transfers to the heated roller surface and the 
adhered toner in turn transfers to the incoming fixing medium, e.g. the 
toner image-bearing paper subsequently subjected to fixing, thus staining 
it. It is therefore one of the essential requirements for the hot roller 
fixing technique to prevent the toner from adhering to the heated fixing 
roller surface. 
This offset is apt to occur particularly when a low molecular weight resin 
is used in the toner as the binder resin. It is conceivable in consequence 
that the offset phenomenon is possibly prevented by using a crosslinked 
resin. However, investigations by the present inventors revealed that the 
use of a simply crosslinked resin does not always give a good result. In 
particular, with an increase in the degree of crosslinking, the required 
fixing temperature rises and in the case of magnetic toner the anti-offset 
property becomes inferior. 
Practice has been made with a view to prevent the toner from adhering to 
the fixing roller surface; for instance, the roller surface is coated with 
a material excellent in toner-releasing property, such as a silicone 
rubber or fluoroplastic and this coating is further covered with a thin 
film of liquid, such as a silicone oil, excellent in releasing property, 
so as to prevent the offset phenomenon and the deterioration of the 
coating. Although very effective in preventing the offset phenomenon, this 
practice has problems such that the offset-preventing liquid evaporates 
off upon heating and smells unpleasant for the operators and that the 
fixation apparatus is complicated because of a device for supplying the 
offset-preventing liquid. Accordingly, a desirable approach to the 
prevention of the offset phenomenon is not to supply such a releasing 
liquid but to develop a toner which is fixable over a wide temperature 
range and excellent in anti-offset property. 
While it is a matter of course that the toner is required to be good in not 
only fixability but also the anti-blocking property, developing ability, 
transferability, cleanability, etc. The existing toners have one or more 
drawbacks like the following. Many toners fusible at relatively low 
temperatures tend to cake or agglomerate during storage or standing in a 
copying machine. Most toners become worse in triboelectric property and 
flow property with the variation of environmental humidity. At repeated 
and continuous image development, most toners, carriers and photoconductor 
surfaces usually deteriorate due to the mutual collision and adhesion. 
This results in variation of developed image density and increased 
background optical density, thus degrading image quality. Moreover, if 
amounts of most toners adhering to the latent-image-bearing photosensitive 
member surface are increased for the purpose of increasing developed image 
density, the background optical density usually increases, that is, the 
so-called fogging occurs. Such being the case, a toner is desired which is 
excellent in those various properties as well as suitable for fixation 
with a hot roller. 
SUMMARY OF THE INVENTION 
The primary object of this invention is to provide a process for producing 
a toner surmounting the above stated drawbacks and having superior 
physical and chemical properties. 
Another object of this invention is to provide a process for producing a 
toner which is successfully fixable with a hot roller and in particular is 
good in anti-offset property. 
Still another object of this invention is to provide a process for 
producing a toner which is suited for fixing with a hot roller and 
exhibits a good and stable chargeability throughout operating time, giving 
clear, fog-free images. 
Another object of this invention is to provide a process for producing a 
toner which is suited for hot-roller fixing, superior in flowability and 
in impact resistance, and which does not agglomerate. 
Another object of this invention is to provide a process for producing a 
toner which is suited for hot-roller fixing and leaves the least amount of 
staining substance on the toner-carrying member surface or on the 
latent-image-bearing photoconductor surface. 
Another object of this invention is to provide a process for producing a 
magnetic toner which is suited for hot-roller fixing and serves as a 
magnetic developer exhibiting adequate magnetism uniformly distributed in 
all its particles. 
With these and other objects in view, the invention consists of a process 
for producing a toner by melt-blending at least a colorant and a polymer 
and finely pulverizing the resulting mixture after cooling, characterized 
in that the polymer is a crosslinked resin having a ratio of 
weight-average molecular weight to number-average molecular weight (Mw/Mn) 
exceeding 4.0 and a melt index of 0.01-10 g/10 min. at 110.degree. C. 
under a load of 10 Kg and the polymer is further crosslinked during the 
melt-blending. 
The toner for hot-roller fixing produced according to the process of the 
present invention is superior in physical and chemical properties. By 
using this toner, good hot-roller fixing can be accomplished without 
causing the offset phenomenon even when no offset-preventing liquid is 
applied on the fixing roller surface, whereby fixing devices employed can 
be made more simple and lightweight. Moreover, since the toner has stable 
and excellent developing ability, the stability and reliability of copying 
machines employed can be markedly improved. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present inventors have found that a toner exhibiting a good fixability 
over a wide temperature range without accompanying offset can be obtained 
by using, as a binder resin for toners fixable with a hot roller, a 
gel-containing polymer, in which the soluble portion has a Mw/Mn exceeding 
4.0 and which has a melt index of 0.01-10 g/10 min., in particular 0.1-6 
g/10 min., at 110.degree. C. under a load of 10 Kg, and further 
crosslinking the polymer to form gel. It has also been found that, when 
the gel content in the melt-blended polymer exceeds 50% by weight, the 
crosslinking is excessive, the softening point of the polymer becomes 
markedly high, and the preparation of a toner therefore becomes difficult. 
Accordingly, the gel content in the melt-blended crosslinked polymer is 
desired to be not exceeding 50% by weight. In particular, when the gel 
content is less than 35% by weight, the toner can be fixed at nearly the 
same temperature as that comprising an uncrosslinked polymer of the same 
type, and very favorable results are obtained. 
A crosslinked polymer having the characteristics mentioned above is 
superior in mechanical properties at a normal temperature, particularly in 
impact resistance and in toughness, and is not liable to adhere to the 
surface of the toner-carrying member or the photosensitive member, thereby 
markedly reducing the deterioration of the toner and the photosensitive 
member. 
Among crosslinked polymers obtained by melt-blending, those having a glass 
transistion temperature of 50.degree. C. or higher are excellent in 
avoiding trouble such as agglomeration of the toner in the development 
device or adhesion of the toner onto the surface of the photosensitive 
member. Particularly preferred polymers have a glass transition 
temperature of 50.degree.-80.degree. C. The glass transition temperatures 
of polymers can be determined with ease by means of a differential 
scanning calorimeter. 
The soluble portion of the polymer used in this invention has a value of 
Mw/Mn exceeding 4.0, preferably exceeding 10, and particularly a 
weight-average molecular weight of 100,000 or more. A polymer having a 
desired melt viscosity can be readily prepared under mild conditions by 
reacting the above defined polymer with a crosslinking agent. With the 
resulting polymer, a toner having the desired fixability can be produced 
steadily. 
In a process for producing a toner of this invention, since a thermal 
crosslinking reaction of the polymer proceeds slowly, the crosslinking 
reaction is easy to control and a toner having a desired melt-viscosity 
can be obtained with ease. 
In a preferred embodiment of this invention, toner components such as a dye 
or pigment and a charge-controlling agent are dispersed in the polymer 
before the cross-linking reaction practically begins at the melt blending. 
Accordingly, the dispersion in this case is more uniform than that in the 
highly crosslinked polymer. Thereafter, the polymer is crosslinked to a 
desired gel content by a mild reaction with a thermal crosslinking agent. 
The toner thus produced has stable electric properties such as 
resistivity, as well as stable chargeability, and markedly improved 
development characteristics since components such as a dye or pigment, 
magnetic powder, and charge controlling agent are homogenously dispersed 
in the toner. 
As will be illustrated later, when a polymer of Mw/Mn&lt;4.0 and Mw&lt;100,000 is 
used, the amount of crosslinking agent and reaction conditions shall be 
decided so that the crosslinking reaction may occur more vigorously than 
when a polymer of Mw/Mn.gtoreq.4.0 is used, in order to obtain a toner of 
desired fixability by crosslinking. Under such conditions, it is very 
difficult to stop the reaction in its optimum stage to provide a 
satisfactory anti-offset property to the resulting toner; it is 
practically impossible to produce steadily a toner of desired fixability 
with good reproducibility. 
On the other hand, when a polymer of Mw/Mn&gt;4.0 and Mw&gt;100,000 is used, a 
toner having a good anti-offset property can be obtained by crosslinking 
the polymer to a moderate extent under mild conditions to form gel. Thus, 
the reaction can be easily controlled and a toner superior in fixability 
can be produced steadily. Moreover, the polymer of Mw/Mn&gt;4.0 and 
Mw&gt;100,000, when crosslinked moderately, will have a further broader 
molecular weight distribution, permitting the resulting toner to have a 
good anti-offset property, with the lowest fixing temperature being 
maintained at a low level. 
Important properties that the toner for electrophotography purposes should 
possess include triboelectric chargeability as well as the above 
development and fixing performance characteristics and mechanical 
properties. For improvement of the chargeability, a charge controlling 
agent is generally added to the toner. If such additives including a 
charge controlling agent are not dispersed uniformly in the toner, its 
triboelectric chargeability will be decreased remarkably, making it 
difficult to obtain a clear image. 
Accordingly, for the purpose of dispersing uniformly the additives 
including a charge controlling agent, colorant, etc. in the polymer used, 
raw materials are generally melt-blended at a temperature around the 
softening point of the polymer, where it exhibits a high melt viscosity. 
The melt-blending in such a high melt viscosity region results in a 
uniform dispersion of the additives in the polymer by the action of 
effective shearing stress due to a high internal friction of the polymer, 
thus giving a toner having a desired uniform color and chargeability. 
However, when such a polymer of Mw/Mn&gt;4.0 and Mw&gt;100,000 is melt-blended in 
the high melt viscosity region around its softening point, the internal 
friction of the polymer is exceedingly high and hence the shearing stress 
is too great, thus causing molecular chain scission, leading to the 
reduction of the melt viscosity, and adversely affecting the anti-offset 
property. For example, when a slightly crosslinked polymer having a melt 
index of about 8 g/10 min. is melt-blended on a roll mill at a temperature 
(about 120.degree. C.) slightly lower than its softening point (about 
135.degree. C.) as measured by the ball and ring method, its melt index 
remarkably increases, to nearly double, whereby the offset-free 
temperature range of the resulting toner becomes much narrower than that 
of a toner prepared by melt-blending at temperatures (about 180.degree. 
C.) considerably higher than the softening point. 
The present inventors have found that the problem of the anti-offset 
property relating to the dispersion of additives can be solved by further 
crosslinking somewhat a slightly crosslinked polymer when it is 
melt-blended, thereby compensating for the reduction of the viscosity due 
to the molecular chain scission. 
According to this method, since the melt-blending is carried out in a high 
melt viscosity region around the softening point of the polymer, the 
additives are dispersed very uniformly in the polymer, the chargeability 
is stabilized, and a wider range of offset-free temperature is obtained. 
Polymers having a Mw/Mn ratio exceeding 4.0 and a Mw of at least 100,000 
can be synthesized by well-known polymerization processes such as solution 
polymerization, suspension polymerization, emulsion polymerization, and 
bulk polymerization processes. Methods for controlling the Mw/Mn ratio 
include: mixing together a plurality of resins different in molecular 
weight in the form of solution or melt; varying the reaction temperature 
in the course of the polymerization; conducting the polymerization by 
proper use of an initiator and chain transfer agent; and suitably 
increasing the Mw/Mn ratio and Mw by crosslinking a polymer in some degree 
during its polymerization. Of these methods, the control of Mw/Mn by 
slight crosslinking is the most suitable in this invention; the 
crosslinking is carried out, for instance, by adding a minute amount of a 
polyfunctional monomer to the polymerization system. 
The above type of polymer is best synthesized by solution polymerization. 
The reason is that the emulsion polymerization or suspension 
polymerization is carried out with a monomer emulsified or dispersed in 
water, which is the continuous phase, in the presence of an additive such 
as a surfactant or dispersion stabilizer and then the product polymer is 
recovered by adding a salt, so that the polymer obtained contains the 
above hydrophilic additives; toners containing such hydrophilic additives 
will adsorb moisture under high humidity conditions; this often adversly 
affects electric properties of toners, e.g. results in the reduction of 
the resistivity. Bulk polymerization becomes difficult to control with 
increasing polymerization degree on account of the gel effect. 
On the other hand, in solution polymerization, because it is carried out 
generally in an organic hydrophobic solvent, no hydrophilic additive is 
necessary and the control of polymerization is relatively easy owing to 
the presence of the solvent. However, when the crosslinking degree is 
raised, solvent-insoluble gels are formed, and this makes difficult the 
reaction control and the polymer recovery after polymerization. It is 
therefore desirable, to synthesize a polymer by the solution 
polymerization process while controlling the crosslinking degree within 
the range where no difficulty as noted above is involved; and to crosslink 
further the resulting slightly crosslinked polymer during preparation of a 
toner therefrom, until the polymer has such a melt viscosity as to give a 
toner of desired fixability. The polymer thus prepared by solution 
polymerization having excellent properties can be applied more easily to a 
toner suited for hot-roller fixing. 
The melt index in this invention was measured by using an apparatus as 
described in JIS K-7210 (test method for flow of thermoplastics) with 
manual cutting of the discharged polymer strand. 
The Mw/Mn ratio was calculated from the data obtained by gel permeation 
chromatography. The gel permeation chromatography was conducted at 
25.degree. C. by passing 0.5 ml of a 8 mg/ml solution of the specimen in 
tetrahydrofuran and eluting with tetrahydrofuran at a flow rate of 1 
ml/min. For the purpose of measuring accurately molecular weights ranging 
from 1.times.10.sup.3 to 2.times.10.sup.6, it is desirable to combine a 
plurality of commercial polystyrene columns; for example, a combination of 
.mu.-Styragels 500, 10.sup.3, 10.sup.4, and 10.sup.5 supplied by Waters 
Co. and a combination of Shodexes A-802, 803, 804, and 805 supplied by 
Showa Denko Co., Ltd. are advisable. The molecular weight of the specimen 
is calculated from the elution curve referring to the calibration curve 
showing the dependence of the logarithm of the molecular weight on the 
count number (elution volume) prepared from several standard monodispersed 
polystyrenes of different molecular weight. Standard polystyrene samples 
suitable for the preparation of calibration curves are, for example, those 
of molecular weights 6.times.10.sup.2, 2.1.times.10.sup.3, 
4.times.10.sup.3, 1.75.times.10.sup.4, 5.1.times.10.sup.4, 
1.1.times.10.sup.5, 3.9.times.10.sup.5, 8.6.times.10.sup.5, 
2.times.10.sup.6, and 4.48.times.10.sup.6 supplied by Pressure Chemical 
Co. or Toyo Soda Manufacturing Co., Ltd. It may be desirable to use at 
least 10 standard polystyrene samples of different molecular weights. A 
refractive index detector may be suitable for the detection of the 
polymer. 
The gel content of a polymer is the crosslinked, solvent-insoluble fraction 
(% by weight) of the polymer, namely an indication of the crosslinking 
degree of the polymer. The gel content in this invention is determined as 
follows: a weighed polymer sample (W.sub.1 g) is subjected to solvent 
extraction on a G-3 glass filter in a Soxhlet extractor for about 50 hours 
to remove the soluble portion of the polymer; the unextracted polymer is 
dried and weighed (W.sub.2 g). The gel content is defined as (W.sub.2 
/W.sub.1).times.100 (%). A solvent suitable for this extraction is, for 
example, toluene. 
The crosslinking reaction at the melt blending is a well-known thermal 
crosslinking reaction. 
There may be mentioned as an example of crosslinking or thermal curing, 
crosslinking reactions of reactive resin itself like acrylic resins and 
polyester resins, and polymers having more than one functional group in 
one monomer unit, or reactions using low molecular crosslinking agents. 
Preferred resins for this purpose are thermosetting acrylic resins and 
thermosetting polyester resins. 
As suitable thermosetting acrylic resins, there may be mentioned vinyl 
copolymers which become reactive on heating, including copolymers of 
acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl 
acrylate, glycidyl methacrylate, glycidyl acrylate, or 
alkoxymethylolacrylamide. 
Thermosetting polyester resins suitable are those prepared from dihydric or 
polyhydric alcohols and unsaturated or saturated dibasic carboxylic acids. 
The dihydric alcohols include, for example, ethylene glycol, triethylene 
glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol 
neopentyl glycol, 1,4-butenediol, 1,4-bis(hydroxymethyl)cyclohexane, 
bisphenol A, hydrogenated bisphenol A, polyoxyethylenated of bisphenol A, 
and polyoxypropylenated bisphenol A. The unsaturated dibasic acids 
include, for example, maleic acid, fumaric acid, mesaconic acid, 
citraconic acid, itaconic acid, and glutaconic acid. The saturated dibasic 
acids usable include, for example, phthalic acid, isophthalic acid, 
terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic 
acid, sebacic acid, and malonic acid. Polyhydric alcohols such as 
glycerol, trimethylolpropane, and pentaerythritol, anhydrides of the above 
cited dibasic acids, and polybasic acids such as trimellitic acid and 
pyromellitic acid may also be used as constituents of the polyester resin. 
The ratio of the reactive monomers constituting the thermosetting resins is 
preferably in the range of from 0.1 to 30% by weight, and more preferably 
from 0.5 to 20% by weight. 
Crosslinking agents used for crosslinking the above thermosetting resins 
are low molecular weight and high molecular weight compounds which have 
two or more reactive functional groups in each molecule; for example, the 
high molecular weight hardeners include epoxy resins, polyamide resins, 
polysulfide resins, urea-formaldehyde resins, phenol-formaldehyde resins, 
melamine resins, aniline resins, toluenesulfonic amide resins, isocyanate 
resins, alkyd resins, furfural resins, and silicone resins; and the low 
molecular weight crosslinking agents include ethylenediamine, 
diethylenetriamine, triethylenetetramine, diethylaminopropylamine, 
m-phenylenediamine, naphthylenediamine, menthane diamine, other 
polyamines, diisocyanates, succinic acid, and phthalic acid. 
The amount of the hardener added may be less than 1/2 mole, preferably 
1/5-1/30 mole, per mole of the functional group of the thermosetting resin 
to be hardened. 
Besides the above thermosetting resin, which is the main polymer component 
of the toner of this invention, another polymer can be incorporated, if 
necessary, in the toner so far as it does not affect adversely the 
anti-offset property and chargeability. Polymers which may be incorporated 
include vinyl polymers constituted of a monomer containing no carboxyl 
group and polymers containing no vinyl monomer; for example, homopolymers 
of styrene and substituted products thereof, such as polystyrene, 
poly-p-chlorostyrene, and polyvinyl toluene; styrene copolymers such as 
styrene-p-chlorostyrene, styrene-vinyltoluene, styrene-vinylnaphthalene; 
styrene-acrylate, styrene-methacrylate, styrene-methyl 
.alpha.-chloromethacrylate, styrene-acrylonitrile, styrene-vinyl methyl 
ether, styrene-vinyl ethyl ether, styrene-vinyl methyl ketone, 
styrene-butadiene, styrene-isoprene, and styrene-acrylonitrile-indene 
copolymers, and other resins such as polyethylene, polypropylene, 
polyvinyl chloride, phenolic resins, natural resin-modified phenolic 
resins, natural resin-modified maleic acid resins, acrylate resins, 
methacrylate resins, polyvinyl acetate, silicone resins, saturated 
polyester resins, polyurethanes, polyamide resins, furan resins, epoxy 
resins, xylene resins, polyvinylbutyral, terpene resins, cumarone-indene 
resins, and petroleum resins. 
In particular, the addition of an ethylenic olefin homopolymer or copolymer 
having a melt viscosity of 10-10.sup.6 cps at 140.degree. C. in amounts of 
0.1-10%, preferably 0.2-5%, by weight, to the toner improves the 
dispersibility and compatibility of colorant and magnetic fine particles 
in the toner and suppresses unfavorable effects of these particles on the 
photoconductor surface, cleaning members, and other parts of the copying 
machine employed. Suitable ethylenic olefin homopolymers and copolymers 
applied herein are, for example, polyethylene, polypropylene, 
ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, and 
ethylene-ethyl acrylate copolymer. These copolymers may be constituted by 
preferably 50-100 mole %, and more preferably 60-100 mole %, of an olefin 
monomer. 
The melt viscosity was measured by the Brookfield method with a B-type 
viscometer equipped with a small-sample adaptor. 
For the toner of this invention, suitable dyes or pigments can be blended 
as colorants. Such dyes or pigments include well known ones, for example, 
carbon black, iron black, phthalocyanine blue, ultramarine blue, 
quinacridone, and benzidine yellow. 
When a magnetic toner is prepared according to the process of this 
invention, a magnetic powder is mixed with other components, which can 
serve also as a colorant. Known magnetic materials can be used for this 
purpose, including ferromagnetic metals such as iron, cobalt, and nickel; 
alloys or compounds of these metals, such as magnetite, hematite, and 
ferrite; and other ferromagnetic alloys. For the purpose of controlling 
the chargeability and preventing agglomeration, some powder additives may 
also be incorporated, such as carbon black, nigrosine, metal complex salt 
powder, colloidal silica, and fluoro-resin powder. 
The toner of this invention may be used with various development processes, 
for example, the magnetic brush process, cascade process, the process 
disclosed in U.S. Pat. No. 3,909,258 wherein a conductive magnetic toner 
is used, the process disclosed in Japanese Patent Laid-Open No. 53-31136 
wherein a high resistivity magnetic toner is used, the process disclosed 
in Japanese Pat. Laid-Open Nos. 54-42141 and 55-18656, fur brush process, 
powder cloud process, impression process, etc. 
Images developed with the toner of this invention and transferred onto a 
fixing member such as paper can be fixed with a hot roller the surface of 
which is not supplied with offset-preventing liquid, without causing the 
offset. The fixing roller used may be coated with a fluoro-resin such as 
Teflon (manufactured by Du Pont Co.), Fluon (manufactured by I.C.I. Co.), 
or Kel-F (manufactured by 3M Co.); or silicone rubbers or silicone resins, 
which form a smooth surface. A fixing roller having a metallic face may 
also used.

EXAMPLE 1 
The following ingredients were melt-blended on a roll mill at about 
130.degree. C.: 
Ratio of the ingredient to be blended: 
______________________________________ 
(1) Styrene-butyl acrylate-glycidyl meth- 
100 wt. parts 
acrylatedivinylbenzene copolymer 
(monomer weight ratio = 75:20:5:0.7) 
(Mw/Mn = 43, gel content = 3%, melt 
index = 2.62.) 
softening point 140.degree.C. 
(2) Xylene resin modified with alkylphenol 
5 wt. parts 
(Nikanol HP-120 supplied by 
Mitsubishi Gas Chemicals Co., Inc.) 
(3) Magnetite powder 60 wt. parts 
(4) Metal complex salt dye 2 wt. parts 
(Zapon Fast Black B supplied by 
BASP A.G.) 
(5) Polypropylene wax (melt viscosity ca. 
5 wt. parts 
400 cps at 140.degree. C.) 
______________________________________ 
The resulting mixture cooled was finely pulverized in an air jet mill and 
classified to give a toner having particle sizes of 5-20.mu.. A developer 
was prepared by mixing 0.5 wt. part of a hydrophobic colloidal silica to 
100 wt. parts of the toner, where the silica powder was attached to the 
outsides of toner particles. 
An image forming test of this developer was conducted by using a commercial 
copying machine (NP-400RE of Canon K.K.). As a result, the lowest fixing 
temperature was 150.degree. C. and no offset phenomenon was observed 
within the fixing temperature range from 150.degree. to 200.degree. C. 
Further, a durability test of 50,000 continuous duplications was conducted 
on the toner at the fixing roller set temperature of 170.degree. C. During 
the 50,000 duplications, the image density was kept at a nearly constant 
value of about 1.0. After the 50,000 duplications, there occurred none of 
the troubles such as the offset phenomenon on the fixing roller, adhesion 
of developer particles onto the photosensitive drum surface, and 
agglomeration of developer particles in the developing device. 
COMATIVE EXAMPLE 1 
A developer was prepared in the same manner as in Example 1 except that the 
xylene resin modified with an alkylphenol was not added. 
Although the lowest fixing temperature of this developer was about 
150.degree. C., the same as of the developer of Example 1, the offset 
phenomenon became notable with increasing fixing temperature and distinct 
marks of transferred images were observed on the fixing roller surface at 
180.degree. C. 
While a durability test was tried in the same manner as in Example 1, the 
offset phenomenon began at about the 500th duplication and the test was 
therefore stopped after 1000 duplications. 
COMATIVE EXAMPLE 2 
A developer was prepared in the same manner as in Example 1 except that the 
xylene resins modified with an alkylphenol was not added and the melt 
blending was conducted at 180.degree. C. 
The lowest fixing temperature and offset-free temperature range of this 
developer were the same as those of the developer of Example 1. But, as a 
result of the durability test, the image density was found to begin 
lowering at about the 10,000th duplication and reached 0.7 at the 20,000th 
duplication, where the test was stopped. 
Further, resistance to temperature and humidity was compared between this 
developer and the developer of Example 1 under high temperature and 
humidity conditions (35.degree. C., 85% R.H.). While the developer of 
Example 1 maintained the image density at 0.85 or more, this developer 
lowered the image density to 0.7 or less, thus being markedly inferior in 
humidity resistance. This seems to be attributable to a poor dispersion of 
the charge controlling agent metal complex salt dye. 
EXAMPLE 2 
The ingredients shown below were melt-blended in a midget pressure kneader 
at temperature up to 130.degree. C. to prepare and evaluate a developer in 
the same manner as in Example 1. 
Ratio of the ingredient to be blended: 
______________________________________ 
(1) Polyester resin having carboxyl groups 
100 wt parts 
(gel content 16 wt %, melt index 3.84, 
softening point 135.degree. C.) 
(2) Epoxy resin 6 wt parts 
(3) Magnetite 60 wt parts 
(4) Metal complex salt dye 4 wt parts 
(same as of Example 1) 
(5) Polyethylene wax 4 wt parts 
______________________________________ 
The lowest fixing temperature of this developer was 150.degree. C., no 
offset phonomenon occurred between 150.degree. and 200.degree. C. or more; 
and the durability was also good. 
EXAMPLE 3 
The monomer mixture of styrene-butyl acrylate-methacrylic 
acid-diallylphthalate (monomer weight ratio=75:22:3:0.4) was polymerized 
at 85.degree. C. in toluene. The resulting copolymer had a Mw/Mn value of 
28 and melt index of 5.34. There were melt-blended at about 140.degree. C. 
with a roll mill 100 weight parts of the copolymer, 2 weight parts of 
diphenylmethane-4,4'-diisocyanate, 60 weight parts of magnetite, 4 parts 
of the metal complex dye of Example 1, and 4 weight parts of polyethylene 
wax to prepare a toner, and it was evaluated in the same manner as in 
Example 1. The fixing was done at 155.degree. C. The offset was not 
observed from this temperature up to 240.degree. C. 
EXAMPLE 4 
The monomer mixture of styrene-butyl acrylate-monobutyl maleate-ethylene 
glycol diacrylate (monomer weight ratio=75:20:5:0.2) was polymerized in 
toluene. The resulting polymer had a Mw/Mn ratio of 13 and a melt index of 
8.74. A toner was prepared in the same manner as in Example 1 by melt 
blending 100 weight parts of the copolymer prepared above, 10 weight parts 
of an epoxy resin, 60 weight parts of magnetite, 4 weight parts of metal 
complex dye of Example 1, and it was evaluated. Its fixing characteristics 
were excellent. 
EXAMPLE 5 
One hundred weight parts of the copolymer used in Example 3, 6 weight parts 
of carbon black, 4 weight parts of metal complex dye of Example 1, and 5 
weight parts of menthanediamine were melt-blended at 150.degree. C. with a 
roll mill. After the blend was cooled, it was pulverized and classified to 
obtain the particles of the size of 5-20.mu. for a toner. 
A developer was prepared by mixing 10 weight parts of the toner and 90 
weight parts of carrier iron powder (trade name: EFV 250/400, supplied by 
Nippon Teppun Co.). The developer was applied to a commercial copier 
(trade name: NP-5000, manufactured by Canon K.K.) The fixing could be made 
at 150.degree. C., and offset was not observed up to 220.degree. C., and 
the durability was excellent.