Toner for developing electrostatic images

A toner for developing an electrostatic image, comprises a binder resin and a colorant. The toner has a glass transition temperature (Tg) of 65.degree. C. or lower. The binder resin comprises a styrene-acrylic copolymer formed from at least a styrenic monomer and a mixture of two or more acrylic monomers. The binder resin contains 10% by weight or more of THF insolubles. The amount of the styrenic monomer remaining in the toner is 0.005 part or less by weight based on 100 parts by weight of the binder resin component in the toner (50 ppm), and the amount of the acrylic monomers remaining in said toner is 0.001 part by weight based on 100 parts by weight or less of the binder resin component in the toner (10 ppm). At least one component of the mixture of acrylic monomers has a Q-value of 0.5 to less than 1.0 and the other has a Q-value of 0.3 to less than 0.5. This toner is excellent in the anti-off-set property to a fixing roller surface, good in fixability, giving high image density and little odor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a toner for developing electrostatic images. 
Further, the present invention relates to a detachable unit freely 
detachable from the main apparatus, comprising a chargeable body and a 
developing means holding a toner to develope electrostatic images. 
Further, the present invention relates to an image forming apparatus 
having a developing means holding the toner for developing electrostatic 
images. Further, the present invention relates to a facsimile apparatus 
using in electrophotographic apparatus as the printer. 
2. Related Background Art 
In the prior art, as the electrophotographic method, there have been known 
a large number of methods as described in U.S. Pat. No. 2,297,691, 
Japanese Patent Publication No. 42-23910, Japanese Patent Publication No. 
43-24748. Generally, the method comprises utilizing a photoconductive 
substance, forming electrical latent images on a photosensitive body by 
various means, subsequently developing the latent images by use of a 
toner, transferring the toner images onto a transfer material such as 
paper, etc. if necessary, then fixing the images by various methods to 
obtain a copied product. As the fixing method, there are the pressure 
fixing system of passing through two or more metal rolls, the oven fixing 
system of passing through the heated atmosphere heated by an 
electrothermal heater, and the currently most popular hot-roll fixing 
system by passing through heated rollers. 
The pressure heating system using heated rollers performs fixing by passing 
the sheet to be fixed through the hot rollers under pressure, where the 
toner image on the sheet is in contact with the roller surface which is 
made of a toner-releasing material. According to this method, since the 
surface of the hot roller contacts the toner image on the sheet to be 
fixed under pressure, heat efficiency during fusion of the toner image 
onto the sheet to be fixed is extremely good and also fixing can be 
effected rapidly, and therefore it is very effective in a high speed 
electrophotographic copying machine. In the above-mentioned method, since 
the hot roller surface comes in contact with the toner image in melted 
state under pressure, a part of the toner image may adhere and transfer 
onto the surface of the fixing roller, which is retransferred onto the 
next sheet to be fixed to give rise to the so-called off-set phenomenon, 
thereby contaminating the sheet to be fixed. It is one of the essential 
conditions of the hot roller fixing system to avoid adhesion of the toner 
onto the hot fixing roller surface. 
For obtaining a toner satisfying the above essential conditions, 
improvements of the toner binder have been attempted. For example, 
Japanese Patent Publication No. 1-15063 proposes a developer by use of a 
resin in which a polyester resin and two kinds of vinyl resins of 
different gel contents (80% or more and less than 10% of THF insolubles) 
are simply blended. Japanese Patent Application Laid-open No. 63-223662 
proposes a developer improved in the anti-off-set property by controlling 
the content of the THF insolubles in the binder resin in the toner. 
As the polymerization method to obtain a resin containing such amount of 
THF insolubles as mentioned above, the suspension polymerization or 
emulsion polymerization method may be preferably employed. 
Since these polymerization methods are carried out generally in aqueous 
solutions, after completion of the reaction, there exists no removal step 
of the solvent and the residual polymerizable monomer from the solution 
polymerization method, and also the temperature of the reaction system is 
limited. A resin containing much THF insolubles is liable to have the 
monomers confined within the resin, whereby the content of the remaining 
monomer in the resin must be larger. When the amount of the remaining 
monomer is large, there exist problems such as (1) generation of odor 
during toner preparation, particularly during melting and kneading 
process, which degrades the working environment, or (2) generation of odor 
during image formation, giving unpleasant feelings. In recent years, 
recording methods using the electrophotographic method are expanding its 
application scope, so that now they are used in ordinary offices and 
homes. As to the developer, it has become necessary to pay attention not 
only to the safety of the substance, of course, but also to odor 
generation during fixing. 
Japanese Patent Application Laid-open No. 55-155632 proposes the 
improvement of the anti-off-set property, storage property and fluidity by 
the use of a polymer as a binder resin for a developer, where the resin 
contains less than 0.1% by weight of the residual solvent or the 
polymerizable monomers used in the polymerization. 
Japanese Patent Application Laid-open No. 53-17737 describes that remaining 
of the polymerizable monomers influences the triboelectric chargeability, 
blocking property and fixability of the developer. Further, as to the 
binder resin for developing, it has been proposed to reduce the remaining 
solvent or the polymerizable monomers used for obtaining the polymer. 
Japanese Patent Application Laid-open No. 64-70765 proposes a resin for a 
developer with a remaining monomer content of 200 ppm or less by 
evaporating the water after polymerization, for overcoming such problems 
as degrading of the working environment particularly caused by the 
generation of odor during melting and kneading, or generation of odor 
during copying to give unpleasant sensations. In such literature, there is 
the description that antiblocking property and resistance to vinyl 
chloride plasticizer become low, or the problem of odor remains if the 
remaining monomer amount exceeds 200 ppm. 
All of the toners obtained according to the methods as mentioned above were 
still not satisfactory in the improvement in both anti-off-set property 
and odor. 
Particularly, in recent electrophotographic apparatus, for the prevention 
of ozone generation by high voltage application during formation of 
electrostatic latent images on the photosensitive body surface, contact 
charging means has been used in place of corona charging. As the result of 
substantial absence of ozone generation, in the electrophotographic 
apparatus by use of the contact charging means, it has become possible to 
eliminate an ozone filter, whereby the problem of odor of the developer 
becomes marked when no ozone filter is mounted. 
On the other hand, in recent years, accompanying the speed-up of recording 
methods by the electrophotographic method, there have been developed 
various contrivances for improving fixability in the hot-roll fixing 
system. As the method for improving the binder resin, improvements have 
been made to lower the glass transition temperature, thereby enabling low 
temperature fixing of the developer. As the means for controlling the 
glass transition temperature (Tg) of the resin, the method of controlling 
the components of the resin may be employed. In the styrene-acrylic resin 
which has been used most generally as a binder resin, the method of 
increasing the ratio of the acrylic component in the resin has been 
employed. As the acrylic resin, one which has the significant effect of 
lowering the glass transition point (Tg) tends to be used frequently. 
As described above, when the ratio of acrylic monomer of low reactivity as 
compared with styrene monomer is increased, the remaining amount of the 
monomer in the resin after completion of the polymerization will be also 
increased, whereby problems as mentioned above will be brought about. For 
this reason, resin synthesis is carried out by use of an acrylic component 
with higher reactivity. According to this method, although the amount of 
the remaining monomer in the resin is considerably reduced, a large amount 
of an acrylic monomer is required to lower the glass transition 
temperature (Tg). As a result, there is a tendency to reduce charge 
amount, resulting in lower developability, whereby the image density is 
lowered. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a toner for developing 
electrostatic images which is excellent in the anti-off-set property to a 
fixing roller surface, good in fixability, can give high image density and 
has little odor. 
Another object of the present invention is to provide a toner for 
developing electrostatic images having little odor and containing a binder 
resin polymerized in an aqueous medium. 
Still another object of the present invention is to provide a toner for 
developing electrostatic images having a low glass transition temperature 
(Tg) and containing the binder resin with little remaining monomer. 
Still another object of the present invention is to provide a toner for 
developing electrostatic images which generates little odor during toner 
manufacturing and can maintain well the working environment in a good 
condition. 
Still another object of the present invention is to provide a toner 
generating little odor during image formation even when an image forming 
device not equipped with a filter such as an ozone filter, etc. is used. 
Still another object of the present invention is to provide a detachable 
apparatus which can be freely detached from the main device having a 
developing means holding a toner for developing electrostatic images which 
can solve the various problems as mentioned above. 
Still another object of the present invention is to provide an image 
forming apparatus having a developing means holding a toner for developing 
electrostatic images which can solve the various problems as mentioned 
above. 
Still another object of the present invention is to provide a facsimile 
apparatus which uses as a printer an electrophotographic apparatus having 
a developing means holding a toner for developing electrostatic images 
which can solve the various problems as mentioned above. 
Still another object of the present invention is to provide a toner for 
developing electrostatic images, comprising a binder resin and a colorant, 
the toner has a glass transition temperature (Tg) of 65.degree. C. or 
lower, 
the binder resin comprises a styrene-acrylic copolymer made from at least a 
styrenic monomer and a mixture of two or more acrylic monomers and the 
binder resin containing 10% by weight or more of THF insolubles, 
wherein the amount of the residual styrenic monomer in the toner is 0.005 
part by weight or less to 100 of the binder resin component in the toner 
(50 ppm), and the amount of the residual acrylic monomers in the toner is 
0.001 part by weight or less to 100 parts by weight of the binder resin 
component in the toner (10 ppm), at least one of the acrylic monomers has 
a Q-value of 0.5 to less than 1.0 and the other having a Q-value of 0.3 to 
less than 0.5. 
Still another object of the present invention is to provide a detachable 
apparatus comprising: 
(a) a chargeable body for carrying electrostatic images thereon, 
(b) a charging means for charging the chargeable body, 
(c) a developing means for developing the electrostatic images carried on 
the chargeable body, the charging means and developing means being 
integrated together with the chargeable body to form a unit, the unit 
being freely detachable from the main apparatus, 
wherein the developing means holds a toner comprising a binder resin and a 
colorant, 
the toner having a glass transition temperature (Tg) of 65.degree. C. or 
lower, 
the binder resin comprising a styrene-acrylic copolymer formed from at 
least a styrenic monomer and a mixture of two or more acrylic monomers and 
the binder resin containing 10% by weight or more of THF insolubles, 
wherein the amount of the styrenic monomer remaining in the toner is 0.005 
part or less by weight based on 100 parts by weight of the binder resin 
component in the toner (50 ppm), and the amount of the acrylic monomers 
remaining in the toner is 0.001 part or less by weight based on 100 parts 
by weight of the binder resin component in the toner (10 ppm), at least 
one of the acrylic monomers having a Q-value of 0.5 to less than 1.0 and 
the other having a Q-value of 0.3 to less than 0.5. 
Still another object of the present invention is to provide an image 
forming apparatus comprising: 
(a) a chargeable body for carrying static images thereon, 
(b) a charging means for charging the chargeable body, 
(c) a developing means for developing the electrostatic images carried on 
the chargeable body, the charging means and developing means being 
integrated together with the chargeable body to form a unit, the unit 
being freely detachable from the main apparatus. 
(d) a transfer means for transferring the developed images developed by the 
developing means from the chargeable body to a transfer material and 
(e) a fixing means for fixing the unfixed toner images transferred onto the 
transfer material on said transfer material, 
wherein the developing means holds a toner comprising a binder resin and a 
colorant, 
the toner having a glass transition temperature (Tg) of 65.degree. C. or 
lower, 
the binder resin comprising a styrene-acrylic copolymer formed from at 
least a styrenic monomer and a mixture of two or more acrylic monomers and 
the binder resin containing 10% by weight or more of THF insolubles, 
wherein the amount of the styrenic monomer remaining in the toner is 0.005 
part or less by weight to 100 parts by weight of the binder resin 
component in the toner (50 ppm), and the amount of the acrylic monomers 
remaining in said toner is 0.001 part or less by weight to 100 parts by 
weight of the binder resin component in the toner (10 ppm), at least one 
of the acrylic monomers having a Q-value of 0.5 to less than 1.0 and the 
other having a Q-value of 0.3 to less than 0.5. 
Still another object of the present invention is to provide a facsimile 
apparatus comprising: 
(i) an electrophotographic imaging means, and 
(ii) a receiving means for receiving image information from remote 
terminals, 
wherein the electrophotographic imaging means comprising: 
(a) a chargeable body for carrying electrostatic images thereon, 
(b) a charging means for charging the chargeable body, 
(c) a developing means for developing the electrostatic images carried on 
the chargeable body, the charging means and developing means being 
integrated together with the chargeable body to form a unit, the unit 
being freely detachable from the main apparatus, 
(d) a transfer means for transferring the developed images developed by the 
developing means from the chargeable body to a transfer material and 
(e) a fixing means for fixing the unfixed toner images transferred onto the 
transfer material on the transfer material, 
wherein the developing means holds a toner comprising a binder resin and a 
colorant, 
the toner having a glass transition temperature (Tg) of 65.degree. C. or 
lower, 
the binder resin comprising a styrene-acrylic copolymer formed from at 
least a styrenic monomer and a mixture of two or more acrylic monomers and 
the binder resin containing 10% by weight or more of THF insolubles, 
wherein the amount of the styrenic monomer remaining in the toner is 0.005 
part or less by weight to 100 parts by weight of the binder resin 
component in the toner (50 ppm), and the amount of the acrylic monomers 
remaining in the toner is 0.001 part or less by weight to 100 parts by 
weight of the binder resin component in the toner (10 ppm), at least one 
of the acrylic monomers having a Q-value of 0.5 to less than 1.0 and the 
other having a Q-value of 0.3 to less than 0.5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the styrene-acrylic binder resin contained in the toner of the present 
invention, the presence of a substantial amount of THF insolubles for 
anti-off-set property improvement and a certain amount of an acrylic 
monomer for fixability improvement is essential. The present inventors 
have mainly investigated the reduction of the remaining monomer in the 
binder resin. As a result, it could be confirmed that by use of an acrylic 
monomer with 0.5 to less than 1.0 of Q-value which is one of the measures 
of copolymerization reactivity, the residual monomer amounts (both 
styrenic and acrylic monomers) after the polymerization reaction could be 
markedly reduced. 
Here, Q-value is a constant indicating reactivity of a monomer proposed by 
Alfrey and Price, and the larger Q-value is, the higher copolymerization 
reactivity. 
We prepared and actually used a developing agent containing a negatively 
chargeable toner having a styrene-acrylic resin as a binder using the 
acrylic component having a Q-value of 0.5 to less than 1.0. The result was 
that, although the remaining monomer amount was reduced to 50 ppm or less 
based on the resin, the charging amount is low as compared with a toner 
comprising a styrene-acrylic binder using the acrylic component having a 
Q-value of 0.3 to less than 0.5, and also only low image density could be 
obtained. 
The present inventors speculated the causes of this result as follows. 
Generally speaking, Q-value is a measure of the resonance stability of 
radicals formed from a monomer, and the high Q-value means the high 
reactivity of formed radicals. That is, the stability of the radicals is 
low and, in other words, they are at a high energy level. For example, a 
methacrylic monomer generally has a higher Q-value than an acrylic 
monomer, which is interpreted as follows: A methacrylic monomer has a 
methyl group adjacent to the double bond of a vinyl group. This methyl 
group acts as an electron donor, and increases the orbital energy of the 
radical electron formed at the double bond position to make the radical 
unstable, whereby the reactivity is increased. Thus, the higher Q-value of 
acrylic monomer is, the higher the electron density on the double bond of 
the vinyl group is. 
In triboelectric charging of the negatively chargeable toner having a 
styrene-acrylic binder, most of the negative charges are considered to 
exist in the .pi..sup.* orbit on the benzene ring of styrene. In that 
case, an electrical field is generated around the benzene ring, whereby 
the groups having a bipolar moment existing therearound must be oriented 
along the electrical field. For example, the carbonyl group in acrylic 
group is oriented in the direction which makes the positively polarized 
carbon atom approach toward the negatively charged benzene ring, and the 
negatively polarized oxygen atom depart from the benzene ring. By the 
oriented bipolar moments, the negative charges on benzene ring are 
stabilized. 
As the Q-value of the acrylic monomer becomes higher, namely the charge 
density on the double bond of vinyl group becomes higher, the charges also 
flow onto the carbon of carbonyl group to weaken the positive charge of 
the carbon. Therefore, the stabilization of negative charges on the 
benzene ring by the carbon becomes weak, and the benzene ring becomes hard 
to be chargeable. In other words, the higher the Q-value of the acrylic 
monomer is, the more the amount of triboelectric charges is reduced 
resulting in the poor developability. This problem also occurs similarly 
in a toner containing a negative charge control agent. 
For the improvement of the developability, a styrene-acrylic binder 
comprising an acrylic monomer with low charge density on the double bond, 
namely of a low Q-value, may be employed, but if a monomer with a low 
Q-value is used, the above-mentioned problem of remaining monomer amount 
will occur. 
As the result of the investigations by the present inventors, by the 
combination use of an acrylic monomer with a Q-value of 0.5 to less than 
1.0 (for suppressing the remaining monomer amount) and an acrylic monomer 
with a Q-value of 0.3 to less than 0.5 (for imparting sufficient 
triboelectric charge amount to the acrylic monomer and the toner) at a 
specific ratio, the Tg of the resin is made 65.degree. C. or lower, 
preferably 45.degree. to 65.degree. C. the amount of resin components 
insoluble in THF are controlled to 10 parts or more, preferably 10 to 70 
parts by weight to 100 parts of the resin. By doing so, it has been found 
that the both problems of the remaining monomer amount contained in the 
binder resin of the toner and the developability of the toner can be 
solved at once, with maintaining the anti-off-set property and good 
fixability of the toner. More specifically, in the present invention, when 
the amount of the acrylic monomer units with a Q-value of 0.5 to less than 
1.0 contained in 100 parts by weight of the resin is defined as n.sub.1 
(part), and the amount of the acrylic monomer units with a Q-value of 0.3 
to less than 0.5 as n.sub.2 (part), preferably the following formulae 
should be satisfied: 
EQU 5.ltoreq.n.sub.1 +n.sub.2 .ltoreq.45, 0.05.ltoreq.n.sub.1 /n.sub.2 
.ltoreq.3.0, 
more preferably the following formulae should be satisfied: 
EQU 10.ltoreq.n.sub.1 +n.sub.2 .ltoreq.38, 0.08.ltoreq.n.sub.1 /n.sub.2 
.ltoreq.2.0. 
and more preferably, the following formulae should be satisfied: 
EQU 25.ltoreq.n.sub.1 +n.sub.2 .ltoreq.35, 0.1.ltoreq.n.sub.1 /n.sub.2 
.ltoreq.2.0. 
When the amounts of monomer units satisfy the above range, the amounts of 
the remaining monomers, analyzed by gas chromatography, were found to be 
100 ppm or less of the styrenic monomer and 50 ppm or less of the acrylic 
monomer in the binder resin, and 50 ppm or less of the styrenic monomer 
and 10 ppm or less of the acrylic monomer in the toner based on the binder 
resin in the toner. 
As a result, even when filters such as an ozone filter are removed from an 
image forming apparatus not using corona charging, there is little 
generation of odor and also the temperature elevation within the apparatus 
can be prevented. 
If the amounts of remaining monomers in the toner, exceed 0.005 part by 
weight (namely 50 ppm) for the styrenic monomer, and 0.001 part by weight 
(namely 10 ppm) for the acrylic monomer based on 100 parts by weight of 
the binder resin, odor is increased, whereby unpleasant sensations become 
obvious as the printing speed and the printing area (particularly solid 
black) are increased. 
Quantitation of amounts of remaining monomers was conducted specifically 
according to the method as described below using Gas Chromatography 
Shimazu GCG-15A (Shimazu). 
With 2.55 mg of DMF as an internal reference, an internal reference 
containing solvent is prepared by addition of 100 ml of acetone. 
An amount 200 mg of a binder resin for toner is made up to 10 ml with the 
internal reference solution. 
The above solution is applied to a UW-25 sonication vibrator (TAGA ELECTRIC 
K.K.) for 30 minutes, and then left to stand for one hour. 
After one hour standing the solution is filtered by a filter (0.5 .mu.m). 
The injection volume of the sample is 4 .mu.l. 
The following conditions of gas chromatography are used: 
capillary column (50 m.times.0.25 mm, ULBON HR-1, manufactured by Shinwa 
Kako K.K.); 
detector: FID, nitrogen pressure: 0.45 kg/cm.sup.2 ; 
injection temperature: 200.degree. C., detector temperature 200.degree. C., 
and column temperature elevated from 50.degree. C. at a rate of 5.degree. 
C./min. for 30 minutes; 
preparation of calibration curve. 
For the standard sample, the known amounts of styrene monomer and the 
acrylic monomer to be measured are added to an acetone solution (the 
internal reference solution) containing the same amount of DMF as the 
sample solutions. Gas chromatographic measurement is conducted, and the 
weight ratio/area ratio of the styrenic monomer to the internal reference 
DMF and the weight ratio/area ratio of the acrylic monomer to the internal 
reference DMF are respectively determined. 
In the present invention, the glass transition temperature (Tg) of the 
toner should be controlled to come below 65.degree. C., more preferably 
within 50.degree. to 62.degree. C. 
In the present invention, the glass transition temperature Tg of the resin 
and the toner was measured according to the ASTM-D3418-82 method using a 
differential scanning calorimetric measuring device (DSC measuring 
device), DSC-7 (Perkin Elmer). 
The sample to be measured is weighed accurately in an amount of 5 to 20 mg, 
preferably 10 mg. 
The weighed sample to be measured is placed in an aluminum pan, and after 
once elevated to 200.degree. C. and quenched, the measurement is carried 
out under normal temperature and normal humidity at a temperature 
elevation rate of 10.degree. C./min. at a measurement temperature range 
from 30.degree. C. to 200.degree. C. using an empty pan as a control. 
In the temperature elevation process, a heat absorption peak in the range 
of temperature from 40 to 100.degree. C. is obtained. 
The intersecting point of a vertical line passing the middle point of the 
base line before and after advent of the heat absorption peak and the 
differential thermal curve is defined as the glass transition temperature 
(Tg). 
The THF insolubles in the present invention is defined as the gel 
components which have become insoluble in THF by crosslinking in the resin 
composition contained in the toner. The weight ratio of the THF insolubles 
can be used as a parameter indicating the extent of crosslinking of the 
resin composition which contains highly crosslinkable components. The THF 
insolubles are defined by the value measured as described below. 
When the toner is a non-magnetic toner, the contents of the THF insolubles 
other than the resin such as pigment. etc., are measured previously 
according to known methods, while for a magnetic toner, the contents of 
the THF insolubles other than the resin, such as pigment and magnetic 
material are measured. Next, a certain amount (W.sub.1 g) ranging from 0.5 
to 1.0 g of the toner or the developing agent is weighed, placed in a 
cylindrical filter paper (Toyo Roshi No. 86 R) and extracted by a 
Soxhlet's extractor with 100 to 200 ml of THF as a solvent for 6 hours. 
The solubles extracted with the solvent are evaporated, then dried under 
vacuum at 100 .degree. C. for several hours and the amount of the soluble 
resin components is weighed (W.sub.2 g). Of the pigments and magnetic 
materials contained in the predetermine amount of the toner or the 
developing agent, the weight of the components soluble in THF is defined 
as W.sub.3 g and the weight of the components insoluble in THF as W.sub.4 
g, and then the THF insolubles in the resin composition can be calculated 
according to the formula shown below: 
Content of 
THF insolubles=[(W.sub.1 -W.sub.2 -W.sub.4)/(W.sub.1 -W.sub.3 
-W.sub.4)].times.100(%). 
Of the copolymers constituting the binder resin in the toner of the present 
invention, as the styrene monomers in the styrene-acrylic copolymer of the 
present invention, there can be used styrene, o-methylstyrene, 
m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, 
p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, 
p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, 
p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, and derivatives 
thereof. 
As the acrylic monomers with a Q-value of 0.3 to less than 0.5 in the 
present invention, there can be used acrylic acid esters such as methyl 
acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl 
acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, 
stearyl acrylate, 2-chloroethyl acrylate and the like. 
Further, as the acrylic monomers with a Q-value of 0.5 to less than 1.0, 
there can be used methacrylic acid esters such as methyl methacrylate, 
ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl 
methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl 
methacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, 
diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate and the like. 
The Q-values of the monomers are generally described in various 
literatures, and reference can be made to the values as described in 
"Copolymerization" (published by Baihukan). 
A monomer with a Q-value less than 0.3 and a monomer with a Q-value of 1.0 
or more can be also used in combination to carry out Copolymerization, 
provided that the amount is less than the styrenic monomer and the acrylic 
monomer. 
As the crosslinking agent to be used in the resin for the toner of the 
present invention, polyfunctional crosslinking agents can be used. 
Examples of a bifunctional crosslinking agent may include divinyl benzene, 
bis (4-acryloxypolyethoxyphenyl)propane, ethylene glycol diacrylate, 
1,3-butylene glycol diacrylate, 1,4-butane diol diacrylate, 1,5-pentane 
diol diacrylate, 1,6-hexane diol diacrylate, neopentyl glycol diacrylate, 
diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene 
glycol diacrylate, respective diacrylates of polyethylene glycol #200, 
#400, #600, dipropylene glycol diacrylate, polypropylene glycol 
diacrylate, polyester type diacrylate (MANDA Nippon Kayaku) and those as 
mentioned above in which acrylates are changed to methacrylates. 
Examples of trifunctional or more polyfunctional crosslinking agents may 
include pentaerythritol triacrylate, trimethylolethane triacrylate, 
trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, 
oligoester acrylate and methacrylate thereof, 2,2-bis(4-methacryloxy, 
triethoxyphenyl)propane, diallyl phthalate, triallyl cyanurate, triallyl 
isocyanurate, triallyl trimellitate, diaryl chlorendate. 
In the present invention, the amount of the crosslinking agent used in the 
resin for the toner may be 0.01 to 10 parts by weight, preferably 0.05 to 
5 parts by weight, to 100 parts by weight of the monomers. 
In the toner using the resin according to the present invention, for the 
purpose of improving various electrophotographic properties, in addition 
to the above binder resin components, compounds as mentioned below may be 
also contained within the range which does not harmfully affect the 
effects of the present invention, and at a ratio less than the content of 
the binder resin components. 
As such compounds, for example, there may be included silicon resin, 
polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, rosin, 
modified rosin, terpene resin, phenol resin, aliphatic or alicyclic 
hydrocarbon resin such as low molecular weight polyethylene or low 
molecular weight polypropylene, aromatic petroleum resin, chlorinated 
paraffin, paraffin wax, etc. 
In the toner according to the present invention, generally known dyes, 
pigments and charge control agents can be formulated. 
Particularly, in the toner of the present invention, an ethylenic olefin 
polymer may be also used together with the binder resin as an auxiliary 
fixing agent. 
As the ethylenic olefin homopolymer or ethylenic olefin copolymer, there 
are polyethylene, polypropylene, ethylene-propylene copolymer, 
ethylenevinyl acetate copolymer, ethylene-ethyl acrylate copolymer, 
ionomer having a polyethylene skelton, and in the above-mentioned 
copolymers, those containing 50 mole % or more of olefin monomer (more 
preferably 60 mole % or more) are preferred. 
Because the binding resin used in the present toner requires not less than 
10 parts of THF insolubles to 100 parts of the binding resin by weight a 
polymerization method conducted in a solution such as suspension 
polymerization or emulsion polymerization is preferred. In addition, 
treatment of the resin for a few hours under reduced pressure at 
70.degree.-90.degree. C. after the completion of the polymerization can 
remove the residual monomer and low-molecular components, so that the 
amount of the residual monomer in the binding resin can be reduced. 
In the toner for developing electrostatic images of the present invention, 
a magnetic material can be contained and the toner can be used as the 
magnetic toner. As the magnetic material to be contained, a substance 
which can be magnetized when placed in a magnetic field, that is, a powder 
of a ferromagnetic metal such as iron, cobalt, nickel or an alloy or 
compound such as magnetite, .gamma.-Fe.sub.2 O.sub.3, ferrite, can be 
used. 
The fine particles of these magnetic materials should be preferably 
magnetic powders having a BET specific surface area of 2 to 20 m.sup.2 /g, 
particularly 2.5 to 12 m.sup.2 /g (nitrogen absorption method), and 
further a Mohs hardness of 5 to 7. The content of the magnetic powder 
should be preferably 70 to 120 parts by weight to 100 parts by weight of 
the binder resin. 
The toner of the present invention as described above has the following 
effects. 
(1) Since the amounts of remaining monomers are small, generation of odor 
during toner preparation is small and the working environment can be 
maintained in a good condition. 
(2) Since the amounts of remaining monomers are small, odor generated 
during image formation is very small causing a few unpleasant sensations. 
(3) Since the glass transition temperature (Tg) is low, anti-off-set 
property to the fixing roller is excellent. 
(4) Since the acrylic monomer consists of at least two kinds of monomers 
having a Q-value of 0.5 to less than 1.0 and a Q-value of 0.3 to less than 
0.5, even when the amounts of the acrylic monomers may be increased in 
order to lower the glass transition temperature (Tg), so that the amount 
of charging is not lowered, and developability is excellent, and image 
density is not lowered, giving an image of high quality. 
(5) Even when the toner of the present invention is used in an image 
forming apparatus having no ozone filter, very little odor is generated. 
Referring now to FIG. 1, the image forming apparatus of the present 
invention is described. 
The numeral 102 is a charging roller which is a charging member brought 
into contact with the above-mentioned photosensitive drum 101 under a 
predetermined pressure, where the roller consists of the metal core 102a 
provided with an electroconductive rubber layer 102b, and a surface layer 
102c (a releasable coating) on the peripheral surface of 102b. The 
electroconductive rubber layer should preferably have a thickness of 0.5 
to 10 mm (more preferably 1 to 5 mm). The surface layer is a coating for 
improving releasability (releasable coating), and provision of a 
releasable coating is preferable in matching with the toner for developing 
electrostatic images according to the present invention. However, if the 
releasable coating has too great resistance, the photosensitive drum 101 
will not be charged, while if the resistance is small, too excess voltage 
is applied on the photosensitive drum 101 causing damage to the drum or 
the generation of pinholes. Hence, it is preferable to have an adequate 
resistance value (preferably a volume resistivity of 10.sup.9 to 10.sup.14 
ohm.multidot.m). The thickness of the releasable coating may be preferably 
within 30 .mu.m (preferably 10 to 30 .mu.m). The lower limit of the 
releasable coating may be reduced as far as there is no peeling or 
tear-up, probably about 5 .mu.m. 
The charging roller 102 has an outer diameter of 12 mm.phi.. The 
electroconductive rubber layer 2b having a thickness of about 3.5 mm is 
made of an ethylene-propylene-diene ternary copolymer (EPDM). The surface 
layer 2c is made of a nylon resin (specifically methoxymethylated nylon) 
with a thickness of 10 .mu.m. The charging roller 102 has a hardness of 
54.5.degree. (ASKER-C). 115 is a power source portion for applying a 
voltage on the charging roller 102, and supplies a predetermined voltage 
to the core metal 102a (diameter 5 mm) of the charging roller 102. 
The numeral 103 is a transfer roller having a core metal 103a and an 
electroconductive elastic layer 103b. The electroconductive elastic layer 
103b is made of an elastic material with a volume resistivity of 10.sup.6 
to 10.sup.10 ohm.multidot.cm such as polyurethane resin or 
ethylene-propylene-diene ternary copolymer (EPDM) containing an 
electroconductive material such as carbon dispersed therein. On the core 
metal 103a is applied a bias by the constant voltage power source 114. As 
the bias conditions, a current value of 0.1 to 50 .mu.A, a voltage 
(absolute value) of 100 to 5000 V (preferably 500 to 4000 V) are 
preferred. 
In the following, the flow of forming an image is described. 
At the charging roller (charging means) 102 having the power source unit 
(voltage applying means) 115, the photosensitive surface (chargeable body) 
is negatively charged, and a digital latent image is formed by image 
scanning by exposure 105 with a laser beam. The latent image is subjected 
to reversal developing with a negatively chargeable magnetic developing 
agent of one-component system (developing means) (110) containing the 
toner of the present invention, in the developing instrument 109 equipped 
with the developing sleeve 104 including the magnetic blade 111 and the 
magnet therein. At the developing section, between the electroconductive 
substrate of the photosensitive drum 101 and the developing sleeve 104, an 
alternate bias, a pulse bias and/or a direct current bias is applied by 
the bias applying means 112. When the transfer paper P is conveyed and 
comes to the transfer section, by charging from the back surface of the 
transfer paper P (the opposite surface to the photosensitive drum side) by 
the transfer roller (transfer means) 103 by the voltage applying means 
114, the developed image (toner image) on the photosensitive drum surface 
is electrostatically transferred onto the transfer paper P. The transfer 
paper P separated from the photosensitive drum 101 is subjected to the 
fixing treatment for fixing the toner image on the transfer paper P by the 
heating and pressurizing roller fixer 107. 
The one-component system developer remaining on the photosensitive drum 
after the transfer step is removed by a cleaner 108 having a cleaning 
blade. The photosensitive drum 101 after cleaning is deelectrified by 
erase exposure 106, and again the steps starting from the charging step 
with the charger 102 are repeated. 
The electrostatic image holding body (photosensitive drum) 101 as the 
chargeable body has a photosensitive layer and an electroconductive 
substrate, and moves toward the arrowhead direction. The non-magnetic 
cylindrical developing sleeve 104 as a toner carrying body rotates at the 
developing section so as to progress in the same direction as the 
electrostatic image holding body. In the non-magnetic sleeve 104 is 
arranged a multi-pole permanent magnet (magnet roll) which is the magnetic 
field generating means so that it may not be rotated. The one-component 
system insulating magnetic developer 110 within the developing apparatus 
109 is applied on the surface of the non-magnetic cylinder, and through 
friction between the surface of the sleeve 104 and the toner particles, 
the toner particles get, for example, negative triboelectric charges. 
Further, by arrangement of a magnetic doctor blade 111 made of iron close 
by the cylindrical surface (gap 50 .mu.m-500 .mu.m) in the opposite 
direction from one magnet pole position of the multi-pole permanent 
magnet, the thickness of the developer layer can be regulated thinly (30 
.mu.m-300 .mu.m) and uniformly to make the developer layer thinner than 
the gap between the electrostatic image holding body 101 and the toner 
carrying body (non-magnetic cylindrical sleeve) 104 at the developing 
section so as to become non-contacting. By controlling the image speed of 
the toner carrying body 104, the speed of the sleeve surface is made 
substantially equal or approximate to the speed of the electrostatic image 
holding surface. The opposed magnet pole may be also formed by use of a 
permanent magnet in place of iron as the magnetic doctor blade 111. An 
alternate bias or pulse bias may be also applied by the bias means 512 
between the toner carrying body 104 and the electrostatic image holding 
surface at the developing section. 
During the transfer of the toner particles at the developing section, the 
toner particles are transferred through the action of the electrostatic 
force on the electrostatic image holding surface and the alternate bias or 
pulse bias. 
In place of the magnetic doctor blade 111, an elastic blade formed on an 
elastic material such as silicone rubber may be also used to regulate the 
layer thickness of the developer layer by pressing pressure, thereby 
coating the developer on the developer carrying body. 
For the charging means 102 for charging the surface of the photosensitive 
body negative, a charger which charges the surface of the photosensitive 
body by general corona charging may be employed in place of the charging 
roller in contact with the photosensitive body surface. 
For the transfer means 103 for electrostatioally transferring the developed 
image on the photosensitive body surface onto the transfer paper P, a 
transfer means which transfers the developed image by corona charging onto 
the transfer paper may be employed instead of the transfer roller which 
comes into contact with the transfer paper. 
In the case when either one of the means which performs corona charging as 
mentioned above, more ozone is generated and therefore it is preferable to 
mount an ozone filter, etc. 
As the image forming apparatus, of the constituent elements such as 
photosensitive body (chargeable body), developing means, charging means, 
etc., more than one constituent may be integrated into a unit to 
constitute a detachable apparatus, which is freely detachable from the 
main apparatus. For example, at least one selected from the charging 
means, developing means and cleaning means may be supported together with 
the photosensitive body to form a unit apparatus freely detachable from 
the main apparatus, where the detachability may be conducted by use of a 
guide means such as rails on the main apparatus, etc. In this case, the 
charging means and/or the developing means can be integrated into the 
above-mentioned detachable apparatus. 
In the case when the image forming apparatus of the present invention is 
used as the printer of facsimile, the photoimage exposure 105 is the 
exposure for printing the received data. FIG. 2 shows an example of this 
case by a block diagram. 
The controller 211 controls the image reading section 210 and the printer 
219. The whole controller 211 is controlled by CPU 217. The data read from 
the image reading section are sent through the sending circuit 213 to the 
partner. The data received from the partner are sent through the receiving 
circuit 212 to the printer 219. In the image memory, given image data are 
memorized. The printer controller 218 controls the printer 219. 214 is a 
telephone. 
The image received through the circuit wire 215 (image information from the 
remote terminal connected through the circuit wire) is modulated again by 
the receiving circuit 212, then subjected to signal restoration processing 
of the image information by CPU 217 and successively housed in the image 
memory 216. When at least one page of image is housed in the memory 216, 
image recording of that page is performed. CPU 217 sends out the 
signal-restored image information of one page read from the memory 216 to 
the printer controller 218. The printer controller 218 on receipt of the 
image information of one page from CPU 218 controls the printer 219 so as 
to perform image information recording of that page. 
CPU 217 is performing receipt of the next page during recording by the 
printer 219. 
As described above, receiving and recording of the image are performed. 
The present invention is described in detail below by referring to 
examples, but these are not limitative of the present invention at all. 
In the examples, parts and % all represent parts by weight and % by weight. 
Synthesis example 1 
Into a reactor were charged and mixed 63 parts of styrene monomer 
(Q-value=1.0), 22 parts of n-butyl acrylate monomer (Q-value=0.43), 13 
parts of n-butyl methacrylate monomer (Q-value=0.67). 0.6 part of 
divinylbenzene and 2 parts of benzoyl peroxide, and then 170 parts of 
water were added to form a suspension, followed by suspension 
polymerization reaction at a reaction temperature of 70.degree. to 
95.degree. C. for 8 hours. After completion of the reaction, the 
reduced-pressure treatment was carried out at 80.degree. C. for two hours 
to remove the residual monomer and low-molecular compounds. After that the 
mixture was filtered to obtain a copolymer composition. The thus obtained 
resin composition had THF insolubles of 54% and a glass transition point 
Tg of 59.degree. C. 
THF insolubles of the resin composition were measured as described below. 
About 0.5 g (W.sub.1) of the resin composition was weighed, placed in a 
cylindrical filter (Toyo Roshi, No. 86 R: 28.times.100 mm), and extracted 
by a Soxhlet's extractor using 200 ml of THF as a solvent for 6 hours. The 
extraction cycle of THF in the Soxhlet's extractor was once per about 4 
minutes. 
After THF solubles extracted with THF were evaporated, the residue was 
dried under reduced pressure at a temperature of 100.degree. C., and the 
weight (W.sub.2) of THF solubles was measured. 
THF insolubles (%)=[(W.sub.1 -W.sub.2)/W.sub.1 ].times.100 
Synthesis example 2 
Into a reactor were charged and mixed 68 parts of styrene monomer 
(Q-value=1.0). 1.0 parts of n-butyl acrylate monomer (Q-value=0.43), 20 
parts of n-butyl methacrylate monomer (Q-value=0.67), 0.55 part of 
divinylbenzene and 1.8 parts of benzoyl peroxide, and then 170 parts of 
water were added to form a suspension, followed by suspension 
polymerization reaction at a reaction temperature of 70.degree. to 
85.degree. C. for 8 hours. After completion of the reaction, the 
reduced-pressure treatment was carried out at 80.degree. C. for two hours 
to remove the residual monomer and low-molecular compounds. After that, 
the mixture was filtered to obtain a copolymer composition. The resin 
composition obtained had a glass transition point Tg of 62.degree. C. and 
THF insolubles of 46%, measured according to the same method as described 
in Synthesis example 1. 
Synthesis example 3 
Into a reactor were charged and mixed 65 parts of styrene monomer 
(Q-value=1.0), 28 parts of n-butyl acrylate monomer (Q-value=0.43). 3 
parts of methyl methacrylate monomer (Q-value=0.74), 2 parts of 
2-hydroxyethyl methacrylate monomer (Q-value=0.80), 0.5 part of 
divinylbenzene and 2 parts of benzoyl peroxide, and then 170 parts of 
water were added to form a suspension, followed by suspension 
polymerization reaction at a reaction temperature of 70.degree. to 
95.degree. C. for 8 hours. After completion of the reaction, the 
reduced-pressure treatment was carried out at 80.degree. C. for two hours 
to remove the residual monomer and low-molecular compounds. After that, 
the mixture was filtered to obtain a copolymer composition. The resin 
composition obtained had THF insolubles of 38% as measured according to 
the same method as described in Synthesis example 1 and a glass transition 
point Tg of 60.degree. C. 
Comparative synthesis example 1 
Into a reactor were charged and mixed 63 parts of styrene monomer, 35 parts 
of n-butyl methacrylate monomer, 0.1 part of divinylbenzene and 2.0 parts 
of benzoyl peroxide, and then 170 parts of water were added to form a 
suspension, followed by suspension polymerization reaction at a reaction 
temperature of 70.degree. to 95.degree. C. for 5 hours. After completion 
of the reaction, the mixture was filtered to obtain a copolymer 
composition. The resin composition obtained had a glass transition point 
Tg of 59.degree. C. and THF insolubles of 4% measured according to the 
same method as described in Synthesis example 1. 
Comparative synthesis example 2 
Into a reactor were charged and mixed 73 parts of styrene monomer, 25 parts 
of methyl acrylate monomer, 2 parts of divinylbenzene and 1.4 parts of 
benzoyl peroxide and then 170 parts of water were added to form a 
suspension, followed by suspension polymerization reaction at a reaction 
temperature of 80.degree. to 95.degree. C. for 5 hours. After completion 
of the reaction, the mixture was filtered to obtain a copolymer 
composition. The resin composition obtained had THF insolubles of 82% 
measured according to the same method as described in Synthesis example 1 
and a glass transition point Tg of 67.degree. C. 
TABLE 1 
______________________________________ 
Residual monomers 
Glass (ppm) 
THF transition Acrylic 
insolubles 
point Styrene 
monomer 
Resin (%) (.degree.C.) 
monomer 
(total) 
______________________________________ 
Synthesis Example 1 
54% 59.degree. C. 
67 41 
Synthesis Example 2 
46 62 50 27 
Synthesis Example 3 
38 60 95 48 
Comparative 4 59 43 40 
Synthesis Example 1 
Comparative 82 67 235 176 
Synthesis Example 2 
______________________________________ 
EXAMPLE 1 
______________________________________ 
Resin of Synthesis example 1 
100 parts 
Magnetite particles 60 parts 
(particle size 0.3.mu.) 
Negatively chargeable control 
1 part 
agent (monoazo dye type 
chromium complex) 
Low molecular weight 3 parts. 
polypropylene (Mw = 6000) 
______________________________________ 
The above mixture was melted and kneaded by a twin screw extruder heated to 
140.degree. C., the cooled kneaded product was coarsely crushed and the 
coarsely crushed product was finely pulverized by a jet mill. The fine 
powder obtained was classified by wind force to obtain a magnetic toner 
(I) (Tg 57.degree. C.) with a volume average particle size of 11.5 .mu.m). 
EXAMPLE 2 
______________________________________ 
Resin of Synthesis example 2 
100 parts 
Magnetite particles 60 parts 
(particle size 0.3.mu.) 
Negatively chargeable control 
1 part 
agent (monoazo dye type 
chromium complex) 
Low molecular weight 3 parts. 
polypropylene (Mw = 6000) 
______________________________________ 
The above mixture was subjected to the same procedures as in Example 1 to 
obtain a toner (II) (Tg 59.degree. C.). 
EXAMPLE 3 
______________________________________ 
Resin of Synthesis example 3 
100 parts 
Magnetite particles 60 parts 
(particle size 0.3.mu.) 
Negatively chargeable control 
1 part 
agent (monoazo dye type 
chromium complex) 
Low molecular weight 3 parts. 
polypropylene (Mw = 6000) 
______________________________________ 
The above mixture was subjected to the same procedures as in Example 1 to 
obtain a toner (III) (Tg 58.degree. C.). 
COMATIVE EXAMPLE 1 
______________________________________ 
Resin of Comparative synthesis 
100 parts 
example 1 
Magnetite particles 60 parts 
(particle size 0.3.mu.) 
Negatively chargeable control 
1 part 
agent (monoazo dye type 
chromium complex) 
Low molecular weight 3 parts. 
polypropylene (Mw = 6000) 
______________________________________ 
The above mixture was subjected to the same procedures as in Example 1 to 
obtain a toner (IV) (Tg 57.degree. C.). 
COMATIVE EXAMPLE 2 
______________________________________ 
Resin of Comparative synthesis 
100 parts 
example 2 
Magnetite particles 60 parts 
(particle size 0.3.mu.) 
Negatively chargeable control 
1 part 
agent (monoazo dye type 
chromium complex) 
Low molecular weight 3 parts. 
polypropylene (Mw = 6000) 
______________________________________ 
The above mixture was subjected to the same procedures as in Example 1 to 
obtain a toner (V) (Tg 61.degree. C.). 
To each of the thus obtained magnetic toners (I) to (V) was added a 
colloidal silica fine powder, and the mixture was mixed by a Henschel 
mixer to obtain magnetic toners (A) to (E) externally added with a 
colloidal silica fine powder. 
The individual magnetic toners (A) to (E) were subjected to the real 
printing tests of continuously forming solid black images by the reversal 
developing system using an image forming device (Canon, modified LBP-8II 
machine) at an modified printing speed of 16 sheets (A$)/min. under normal 
temperature/normal humidity (25.degree. C./60% RH), and the printout 
images were evaluated. The developing conditions here were made as 
follows: 
[the minimum gap between the lamination type OPC photosensitive drum and 
the coated developing sleeve coated with a phenolic resin containing fine 
carbon graphite particles (including fixed magnet): about 300 .mu.m, the 
gap between the magnetic blade and the coated developing sleeve: about 250 
.mu.m, the thickness of the magnetic toner layer on the coated developing 
sleeve: about 130 .mu.m, the developing bias: alternate current bias (Vpp 
1600 V, frequency 1800 Hz) and direct current bias (-390 V)]. 
The conditions of the transfer roller were made as follows: 
[surface rubber hardness of transfer roller: 27.degree., transfer current: 
1 .mu.A, transfer voltage: +2000 V, contact pressure: 50 [g/cm], 
electroconductive elastic layer of transfer roller: EPDM having 
electroconductive carbon dispersed therein, volume resistivity of 
electroconductive elastic layer: 10.sup.8 ohm.multidot.cm]. 
The conditions of the charging roller were made as follows: 
[roller diameter: 12 mm, core diameter: 5 mm, electroconductive rubber 
layer thickness of the charging roller: 3.5 mm, mold release coating: 
methoxymethylated nylon, thickness 20 .mu.m, contact pressure with OPC 
photosensitive member: total pressure 1.2 kg]. 
In addition to the evaluations of the printout images, also the odor at the 
exhaust outlet of the device was evaluated under the state where the ozone 
filter was removed. 
Under the state where the surface temperature of the roller on the fixer is 
maintained at 200.degree. C., anti-off-set property and fixability were 
evaluated. Anti-off-set property was evaluated after removing the cleaning 
device of the fixing roller, by evaluating the back contamination of the 
second sheet of the solid black passing papers under the state where no 
oil was coated. Fixability was evaluated for the first sheet immediately 
after weight-up. Further the triboelectric charge of the toner was 
measured. 
TABLE 2 
__________________________________________________________________________ 
Residual monomers Solid black 
(ppm) *.sup.2 density 
Magnetic Acrylic Anti- 
Charge 
(average from 
Toner 
Styrene 
monomer 
*.sup.1 
Fix- 
off-set 
of toner 
initiation to 
No. monomer 
(total) 
Odor 
ability 
property 
(.mu.c/g) 
100 sheets) 
__________________________________________________________________________ 
Example 1 
(A) 39 .ltoreq.10 
.largecircle. 
.largecircle. 
.largecircle. 
-10 1.25 
Example 2 
(B) 26 .ltoreq.10 
.largecircle. 
.largecircle. 
.largecircle. 
-9 1.25 
Example 3 
(C) 48 .ltoreq.10 
.largecircle. 
.largecircle. 
.largecircle. 
-11 1.3 
Comparative 
(D) 13 .ltoreq.10 
.largecircle. 
.largecircle. 
X -6 1.0 
Example 1 
Comparative 
(E) 105 87 X X .largecircle. 
-11 1.3 
Example 2 
__________________________________________________________________________ 
*.sup.1 Evaluation of odor: 
.largecircle. Extremely small odor 
.DELTA. slight odor 
X Considerable odor (panel: 5) 
*.sup.2 Charge amount of toner: Toner on the sleeve is recovered and 
measured by blow off method.