Carrier for developing electrostatic latent image, electrostatic latent image developer, method for forming image and image forming apparatus

A carrier for developing an electrostatic latent image comprising a core material coated with a resin layer, wherein the F/N ratio of the surface of the resin layer ranges from 1 to 20. It is desirable that the resin layer include resin particles containing a nitrogen atom, that the average particle diameter of the nitrogen-atom-containing resin be in a range from 0.1 to 2 .mu.m, that the thickness of the resin layer be in a range from 0.1 to 10 .mu.m, that the resin layer include an electroconductive material which is in a condition to be dispersed in the resin layer, that the electroconductive material be made of carbon black, and that the average particle diameter of the carrier for developing an electrostatic latent image be in a range from 30 to 150 .mu.m. The carrier for developing an electrostatic latent image, which is long-lived, provided with a charging capability unchanged over time, and is capable of effectively preventing fogging are provided.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a carrier for developing an electrostatic latent 
image, an electrostatic latent image developer, a method for forming an 
image, and an image forming apparatus used in an electrophotographic 
process and an electrostatic recording process. 
2. Description of the Related Art 
A method conventionally used in an electrophotographic process comprises 
using various measures to form an electrostatic latent image on a 
photoreceptor or an electrostatic recording medium and allowing detective 
microparticles, called "toner", to stick to the electrostatic latent 
image, thereby developing the electrostatic latent image. In this method, 
carrying particles, called "carrier", are mixed with the toner and both 
the carrier and the toner are subjected to frictional electrification 
together to provide the toner with an appropriate magnitude of positive or 
negative charge. 
Generally, the carrier is roughly divided into a coated carrier having a 
layer on the surface thereof and a non-coated carrier having no layer on 
the surface thereof. The coated carrier is superior in terms of developer 
life so that various coated carriers have been developed and practiced. 
The characteristics required of the coated carrier include a function of 
providing the toner with an appropriate charging capability (charge amount 
or charge distribution) and a function of maintaining the charging 
capability for a long period of time. It is therefore very important that 
the impact resistance and the resistance to friction of the carrier be 
high and that the charging capability of the toner be unchanged regardless 
of the changes in environmental conditions such as temperature, humidity, 
and the like. Because of this, various coated carriers have been proposed. 
According to, for example, Japanese Patent Application Laid-Open (JP-A) 
Nos. 61-80161, 61-80162, and 61-80163, a comparatively long-lived coated 
carrier can be obtained by coating the surface of a carrier core material 
with a copolymer of a nitrogen-containing fluorinated alkyl (meth)acrylate 
and a vinyl-type monomer, or a copolymer of a fluorinated alkyl 
(meth)acrylate and a nitrogen-containing vinyl-type monomer. On the other 
hand, according to Japanese Patent Application Laid-Open (JP-A) Nos. 
5-61263 and 4-175769, a comparatively long-lived coated carrier can be 
obtained by coating the surface of a carrier with a compound containing a 
fluorine-containing block polymer resin and a nitrogen atom in a specific 
proportion. 
However, when the surface of the carrier core material is coated with each 
of these resins, an amount of the fluorine-type resin is present on the 
outside of the surface layer, whereas the compound containing nitrogen is 
maldistributed within the inside of the surface layer. If the carrier 
produced in the above manner is used for a long period of time, the layer 
is worn from the surface of the carrier. As a result, the surface 
composition changes with time and the charging capability also changes 
with time, resulting in a problem that stable formation of an image of 
high quality cannot be maintained for a long period of time. 
SUMMARY OF THE INVENTION 
This invention has been achieved to solve the above problems and has an 
object of providing a carrier for developing an electrostatic latent image 
which is very long-lived and resistant to change in charging capability 
with time. 
Another object of the present invention is to provide an electrostatic 
latent image developer, a method for forming an image, and image forming 
apparatus, which are capable of forming an image of high quality in stable 
condition for a long period of time without changes in the charging 
capability with time. 
This invention is based on the following knowledge of the present 
inventors: Specifically, when the fluorine-to-nitrogen (F/N) ratio of the 
surface of a resin layer in a coated carrier is defined in a specific 
range, the above problems can be solved. Accordingly, a carrier for 
developing an electrostatic latent image, which is long-lived and has a 
continuously stable charging capability lasting a long time, can be 
provided. 
The above objects can be attained in the present invention by a provision 
of a carrier for developing an electrostatic latent image comprising 
coating a core material with a resin layer, wherein the F/N ratio of the 
surface of the resin layer is in a range from 1 to 20. 
In preferred embodiments of the present invention, it is desirable that the 
resin layer may include nitrogen-atom-containing resin particles; 
it is desirable that the average particle diameter of the 
nitrogen-atom-containing resin particles be in a range from 0.1 to 2 
.mu.m; 
it is desirable that the thickness of the resin layer be in a range from 
0.1 to 10 .mu.m; 
it is desirable that the resin layer contain an electroconductive material 
which is in a condition to be dispersed in the resin layer; 
it is desirable that the electroconductive material be carbon black; and 
it is desirable that the average particle diameter of the carrier for 
developing an electrostatic latent image be in a range from 30 to 150 
.mu.m. 
The electrostatic latent image developer of the present invention comprises 
the carrier for developing an electrostatic latent image of the present 
invention and a toner. 
In preferred embodiments of the present invention, it is desirable that, in 
the electrostatic latent image developer, the carrier for developing an 
electrostatic latent image be positively charged and the toner be 
negatively charged; 
it is desirable that the average particle diameter of the toner be in a 
range from 3 to 10 .mu.m; and 
it is desirable that the toner contain a binding resin and that the binding 
resin contain a linear polyester. 
The method of the present invention for forming an image comprising using a 
developer layer on a developer support to develop an electrostatic latent 
image on an electrostatic latent image support, wherein the developer is 
the above-described electrostatic latent image developer of the present 
invention. 
The image forming apparatus of the present invention comprising developing 
an electrostatic latent image on an electrostatic latent image support in 
a developer layer on a carrier for a developer, wherein the developer is 
the above-described electrostatic latent image developer of the present 
invention. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The carrier for developing an electrostatic latent image of the present 
invention comprises coating a core material with a resin layer. 
There are no limitations to the type of the core material, and the core 
material may be optionally selected from, in accordance with objects, for 
example, magnetic metals such as iron, steel, nickel, and cobalt; magnetic 
oxides such as ferrite and magnetite; and particles such as glass beads. 
Among these, the magnetic metals and magnetic oxides are preferable in the 
case where a magnetic brushing method is used. 
The average particle diameter of the core material is usually from 10 to 
500 .mu.m, preferably from 30 to 100 .mu.m. 
The F/N ratio of the surface of the resin layer is in a specific range. 
The F/N ratio means the ratio by atomic percent of fluorine atoms to 
nitrogen atoms contained in the surface of the carrier for developing an 
electrostatic latent image. 
The F/N ratio of the surface of the resin layer is from 1 to 20 , 
preferably from 2 to 20 , and more preferably from 3 to 20 . Also, the F/N 
ratio is preferably in the range which may be defined by either any one of 
the above-described lower limits or any one of the lower limits of the F/N 
ratio to be defined in the examples described below and by either any one 
of the above-described upper limits or any one of the upper limits of the 
F/N ratio to be defined in the examples described below. 
If the F/N ratio is less than one, the critical surface tension of the 
carrier surface becomes high, which causes the occurrence of contamination 
of the carrier surface with the toner, leading to a reduction in the 
charging capability to the toner and changes in the charging capability 
with time. On the other hand, if the F/N ratio exceeds 20, there is a 
tendency that the capability of providing the toner with a charge is 
insufficient. In any case, when the F/N ratio is outside of the range of 
1-20, the charging capability greatly changes with time so that the 
capability of providing the toner with a charge changes remarkably with 
time. Therefore, there is often a case where the formation of an image of 
high quality cannot be maintained in a stable condition for a long period 
of time. On the other hand, when the F/N ratio ranges from 1 to 20, the 
above drawbacks are eliminated so that the charging capability remains 
unchanged over time and an image of high quality can be formed in a stable 
condition for a long period of time. An F/N ratio ranging from 2 to 20 is 
preferable to promote the above effects and an F/N ratio ranging from 3 to 
20 is more preferable to further promote these effects even more. 
In this invention, it is desirable that the F/N ratio of the inside of the 
resin layer be in the above F/N ratio range defined for the surface of the 
carrier. In this case, even if the film is worn from the surface of the 
carrier, the F/N ratio is kept almost in a fixed range so that a high 
capability of providing the toner with a charge can be maintained, which 
is advantageous. 
The F/N ratio of the surface of the carrier for developing an electrostatic 
latent image can be measured by inspecting the surface using an XPS (JPS 
80, manufactured by JEOL Ltd.) in the following conditions: X-ray source: 
MgK.alpha.; acceleration voltage: 10 kV; emission current: 30 mA; and 
repetitive measuring number: 5 times. The F/N ratio in this invention was 
measured in this manner. 
The resin layer includes a fluorine atom (F) and a nitrogen atom (N), and 
also an electroconductive material as required. 
The resin layer can be formed using, for example, a 
fluorine-atom-containing resin and a nitrogen-atom-containing resin, or a 
resin containing both a fluorine atom and a nitrogen atom. The resin layer 
is produced, for example, by polymerizing a monomer containing a fluorine 
atom and a monomer containing a nitrogen atom, and, as required, using 
other resins, electroconductive materials, and the like. 
The fluorine-atom-containing resin has preferably a critical surface 
tension of 35 dyn/cm or less, and more preferably 30 dyn/cm or less. Also, 
the critical surface tension is preferably in the range which may be 
defined by either any one of the above-described upper limits or anyone 
the upper limits of the critical surface tension to be defined in the 
examples described below. In addition, the critical surface tension is 
preferably in the range which may be defined by either any one of the 
above-described upper limits or any one of the upper limits defined in the 
examples below and by any one of the lower limits to be defined in the 
examples described below. 
The critical surface tension exceeding 35 dyn/cm is undesirable because 
contamination of the surface of the carrier for developing an 
electrostatic latent image cannot be restrained so that the charging 
capability is reduced and changes in the charging capability with time 
tend to increase. On the other hand, if the critical surface tension is 35 
dyn/cm or less, the above drawbacks are eliminated so that the surface 
contamination of the carrier for developing an electrostatic latent image 
can be effectively controlled. Further, the critical surface tension of 30 
dyn/cm or less is even more preferable to promote the above effects. 
Examples of such a fluorine-atom-containing resin include polyvinyl 
fluoride (.gamma.c=28 dyn/cm), polyvinylidene fluoride (.gamma.c=25 
dyn/cm), polytrifluoroethylene (.gamma.c=22 dyn/cm), 
polytetrafluoroethylene (.gamma.c=18 dyn/cm), and polyhexafluoropropylene 
(.gamma.c=16 dyn/cm). Other than these compounds, a copolymer of 
vinylidene fluoride and an acryl monomer, a copolymer of vinyidene 
fluoride and vinyl fluoride, fluoroterpolymers such as a terpolymer of 
tetrafluoroethylene, vinylidene fluoride, and a nonfluorinated monomer, 
perfluoroacrylate copolymers, perfluoroacrylate-hydroxyethyl methacrylate 
(hereinafter abbreviated as HEMA as the case may be) copolymers, 
perfluorosulfonylamide copolymers, and the like, which have a critical 
surface tension of 35 dyn/cm or less. 
These compounds may be used either singly or in combinations of two or 
more. Also, compounds appropriately synthesized or commercially available 
compounds may be used. Among these, perfluoroacrylate copolymers, 
perfluoroacrylate-hydroxyethyl methacrylate copolymers, 
perfluorosulfonylamide copolymers, resins produced by grafting an alkyl 
acrylate or the like in the above resins, or resins produced by providing 
the above resin with a reactive group such as a hydroxyl group or the like 
and cross-linking the resulting resin using a coupling agent, isocyanate, 
or the like are preferably used in consideration of the compatibility of 
the resistance to contamination of the carrier surface with the adhesion 
to the core material. 
Though either thermoplastic resins or heat-curable resins can be used as 
the resin containing a nitrogen atom, the heat-curable resins are 
preferably used in view of hardness. Examples of the resins containing a 
nitrogen atom include polyacrylonitrile, polyvinylcarbazole, polyurethane, 
amino resins, urea-formaldehyde resin, melamine resin, benzoguanamine 
resins, urea resins, polyamide resins, and styrene-dimethylamino acrylate 
copolymers (hereinafter abbreviated as St/DMAA as the case may be). 
These compounds may be used either singly or in combinations of two or 
more. Also, compounds appropriately synthesized or commercially available 
compounds may be used. Among these, melamine resins, styrene-dimethylamino 
acrylate colpolymers, benzoguanamine resins, urea resins, and polyurethane 
are preferable in view of wear resistance, and melamine resins and 
benzoguanamine resins are particularly preferable. 
The resin layer may contain the above resins containing a nitrogen atom in 
any shape to the extent that the F/N ratio of the surface of the resin 
layer ranges from 1 to 20. However, it is preferable that the resin layer 
contain resin particulates. 
Generally, the nitrogen-atom-containing resin has less mutual solubility 
with the fluorine-atom-containing resin and tends to localize inside the 
resin layer. When the nitrogen-atom-containing resin has a particulate 
shape, the resin disperses in the resin layer uniformly both in the 
direction of the thickness of the resin layer and in the direction of the 
tangential line of the surface of the carrier for developing an 
electrostatic latent image. Therefore, even if the resin layer is worn 
from the surface as it is used for a long period of time, a fixed surface 
composition can be always kept, thereby maintaining a high capability of 
providing the toner with a charge, which is advantageous. 
The nitrogen-atom-containing resin particulates are resin particulates 
prepared by cross-linking a nitrogen-atom-containing resin. 
There are no limitations to a method for manufacturing the particulate 
nitrogen-atom-containing resin and the method may be appropriately 
selected from known methods according to the object. As the method for 
manufacturing the particulate nitrogen-atom-containing resin, a suspension 
polymerization method and an emulsion polymerization method can be used. 
Other than these methods, included as the method for manufacturing the 
resin particulates in which a monomer or an oligomer is dispersed into a 
bad solvent and granulated due to the surface tension thereof while a 
cross-linking reaction is carried out and a method in which a low 
molecular component and a cross-linking agent are mixed and reacted by 
melting and kneading or the like and then pulverized to a specific 
particle size using wind force, mechanical force, or the like. 
The average particle diameter of the particulates of the 
nitrogen-atom-containing resin is in a range from 0.1 to 2 .mu.m, 
preferably from 0.2 to 1 .mu.m. Also, the average particle diameter is 
preferably in the range which may be defined by either anyone of the 
above-described lower limits or any one of the lower limits of the average 
particle diameter to be defined in the examples described below and by 
either any one of the above-described upper limits or any one of the upper 
limits of the average particle diameter to be defined in the examples 
described below. 
If the average particle diameter is less than 0.1 .mu.m, the dispersibility 
of the particulates in the resin layer is greatly impaired, whereas if the 
average particle diameter exceeds 2 .mu.m, the resin particulates tend to 
fall away from the resin layer so that its primary functions cannot be 
maintained. On the other hand, when the average particle diameter is in 
the above-defined ranges, the above drawbacks are eliminated so that the 
resin particulates can be uniformly dispersed in the resin layer with 
ease. When the average particle diameter is in the above preferred range, 
the resin particulates falls away hardly at all, especially when 
mechanically stressed in a copying operation, which is advantageous. 
In addition, given as preferred examples of the combination of the 
fluorine-atom-containing resin and the nitrogen-atom-containing resin are 
a combination of a perfluoroacrylate copolymer and a melamine resin, 
benzoguanamine resin, urea resin, or styrene-dimethylacrylic acid 
copolymer; a combination of perfluoroacrylate-hydroxyethyl methacrylate 
copolymer and a melamine resin; and a combination of a perfluoroacrylate 
copolymer and an acrylamide resin. 
Examples of the fluorine-atom-containing resin and a 
nitrogen-atom-containing resin include perfluorosulfonylamide copolymer, 
perfluorinated alkylsulfonylaminoalkyl methacrylate copolymer, and 
perfluoroacrylate-dimethylacrylamide copolymer. These compounds may be 
used either singly or in combinations of two or more. Also, compounds 
appropriately synthesized or commercially available compounds may be used. 
Examples of the above other resins include polyolefin type resins such as 
polyethylene and polypropylene; polyvinyl and polyvinylidene type resins; 
polystyrene, acryl resins, polyvinyl acetate, polyvinyl alcohol, polyvinyl 
butyral, polyvinyl chloride, polyvinylcarbazole, polyvinyl ether, and 
polyvinyl ketone; vinyl chloride-vinyl acetate copolymers; styrene-acrylic 
acid copolymers; straight silicon resins formed by organosiloxane bonding 
or modified products of them; polyesters, polycarbonates, phenol resins, 
and epoxy resins. 
These compounds may be used either singly or in combinations of two or 
more. Also, compounds appropriately synthesized or commercially available 
compounds may be used. Among these, polystyrene, silicon resins, 
polycarbonate resins, phenol resins, epoxy resins, and the like are 
preferable because these compounds have a relatively lower critical 
surface tension. 
There are no limitations to the type of electroconductive materials and 
their type may be appropriately selected according to the object. Examples 
of the electroconductive material include metals such as gold, silver, 
copper, and the like; semiconductive oxides such as carbon black, titanium 
oxide, zinc oxide, and the like; and materials produced by coating the 
surface of a compound such as titanium oxide, zinc oxide, barium sulfate, 
aluminum borate, and potassium titanate powder with tin oxide, carbon 
black, a metal, or the like. 
It is advantageous that the resin layer contain the electroconductive 
material, which is in a condition so as to be uniformly dispersed in the 
resin layer, since reproductivity of a solid can be improved and the toner 
can be electrically charged in a short time. 
These compounds may be used either singly or in combinations of two or 
more. Also, compounds appropriately synthesized or commercially available 
compounds may be used. Among these, carbon black is preferable in view of 
the stability in production cost, electroconductivity, and the like. 
There are no limitations to the above-mentioned carbon black and known 
carbon blacks maybe used as the carbon black. It is desirable to use 
carbon blacks with a DBP oil absorbing rate ranging from 50 to 250 ml/100 
g. 
The method for forming the resin layer may be appropriately selected from 
known methods. Examples of the method for forming the resin layer include 
a dipping method in which the core material is dipped into a resin layer 
forming liquid, a spraying method in which a resin layer forming liquid is 
sprayed on the surface of the core material, a fluidized-bed method in 
which a resin layer forming liquid is sprayed on the core material floated 
by an air flow, and a kneader coater method in which the core material and 
a resin layer forming liquid are mixed in a kneader coater followed by the 
removal of a solvent. 
Among these methods, the kneader coater method is preferable. In addition, 
after the resin layer forming liquid is applied on the core material and 
the solvent is removed to form the resin layer, the 
nitrogen-atom-containing resin may be cross-linked to improve the strength 
and hardness of the resin layer. 
The resin layer forming liquid may be a liquid comprising the 
fluorine-atom-containing resin and the nitrogen-atom-containing resin, 
and, as required, further the other resin and the electroconductive 
material, which are dissolved and dispersed in a solvent. 
As examples of the solvent, aromatic hydrocarbons such as toluene, xylene, 
and the like; ketones such as acetone, methyl ethyl ketone, and the like; 
and ethers such as tetrahydrofuran, dioxane, and the like can be given, 
although there are no limitations as to the type of the solvent, to the 
extent that the solvent can dissolve each of the above resins. 
The amount of the fluorine-atom-containing resin in the resin layer forming 
liquid is around 0.5 to 5 parts by weight in 100 parts by weight of the 
core material, although the amount is different depending on the types and 
mutual solubility with the nitrogen-atom-containing resin, the film 
thickness of a coating layer, and the like, so that it is not defined in 
general. 
If the amount of the fluorine-atom-containing resin is less than 0.5 parts 
by weight, the surface energy of the carrier for developing an 
electrostatic latent image increases so that the capability of providing 
the toner with a charge decreases, which is often the cause of fogging, 
scattering of the toner, and the like. If the amount exceeds 5 parts by 
weight, carrier particles tend to agglomerate so that a manufacturing 
yield often tends to decrease. On the other hand, if the amount of the 
fluorine-atom-containing resin is in the above defined range, the above 
drawbacks are eliminated, which is advantageous. 
The amount of the nitrogen-atom-containing resin in the resin layer forming 
liquid is around 0.5 to 5 parts by weight in 100 parts by weight of the 
core material, although the amount is different depending on the types and 
mutual solubility with the fluorine-atom-containing resin, the charging 
capability of the toner, the electric charging rate, and the like, so that 
it is not defined in general. 
If the amount of the nitrogen-atom-containing resin is less than 0.5 part 
by weight, there is a case where the carrier for developing an 
electrostatic latent image has an insufficient charging capability. On the 
other hand, if the amount exceeds 5 parts by weight, the F/N ratio of the 
surface of the carrier is often less than one. Yet further, on the other 
hand, if the amount of the nitrogen-atom-containing resin is in the above 
defined range, the above drawbacks are eliminated, which is advantageous. 
The amount of the other resin in the resin layer forming liquid is 
preferably in a range from 0 to 2 parts by weight in 100 parts by weight 
of the above core material. When the amount of the other resin exceeds 2 
parts by weight, the carrier particles tend to agglomerate so that 
manufacturing yield often tends to be reduced. 
The amount of the electroconductive material in the resin layer forming 
liquid is in a range from 0 to 1.0 parts by weight, more preferably from 0 
to 0.4 parts by weight in 100 parts by weight of the above core material. 
The thickness of the resin layer is usually in a range from 0.1 to 10 
.mu.m, preferably 0.2 to 3 .mu.m. Also, the thickness is preferably in the 
range which may be defined by either any one of the above-described lower 
limits or any one of the lower limits of the thickness to be defined in 
the examples described below and by either any one of the above-described 
upper limits or any one of the upper limits of the thickness to be defined 
in the examples described below. If the thickness of the resin layer is 
less than 0.1 .mu.m, it is often the cause of flaking of a coating layer 
due to mechanical stress and separation of the particulates of the 
nitrogen-atom-containing resin. If the thickness of the resin layer 
exceeds 10 .mu.m, the carrier particles tend to agglomerate so that 
manufacturing yield often tends to decrease. 
The average particle diameter of the carrier for developing an 
electrostatic latent image is in a range from 30 to 150 .mu.m, preferably 
from 30 to 100 .mu.m. 
The carrier for developing an electrostatic latent image is positively 
charged due to a nitrogen atom contained in the resin layer. Because of 
this, when the carrier for developing an electrostatic latent image of the 
present invention is combined with a toner to prepare an electrostatic 
latent image developer, it is desirable that the toner be negatively 
charged. The carrier for developing an electrostatic latent image of the 
present invention can be suitably used as a carrier for the electrostatic 
latent image developer of the present invention. 
The electrostatic latent image developer comprises the carrier for 
developing an electrostatic latent image of the present invention and a 
toner. 
There are no limitations as to the types of toner, and the toner may be 
appropriately selected from toners according to the object. For example, 
known toners including a binding resin and coloring material, and, as 
required, further including additives such as a charge controlling agent, 
fixing adjuvant, or the like can be used. 
Examples of the binding resins include monopolymers or copolymers of 
styrenes such as styrene, chlorostyrene, and the like; mono-olefin such as 
ethylene, propylene, butylene, isoprene, and the like; vinyl esters such 
as vinyl acetate, vinyl propionate, vinyl benzoate, and the like; 
.alpha.-methylene aliphatic monocarboxylates such as methyl acrylate, 
ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl 
acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 
dodecyl methacrylate, and the like; vinyl ethers such as vinylmethyl 
ether, vinylethyl ether, vinylbutyl ether, and the like; and vinyl ketones 
such as vinylmethyl ketone, vinylhexyl ketone, vinylisopropyl ketone, and 
the like. Among these, especially typical examples of the binding resins 
are polystyrene, styrene-alkylacrylate copolymer, 
styrene-alkylmethacrylate copolymer, styrene-acrylonitril copolymer, 
styrene-butadiene copolymer, styrene-maleic anhydride copolymer, 
polyethylene, and polypropylene. Further, polyester, polyurethane, epoxy 
resin, silicon resin, polyamide, modified rosin, paraffin, waxes, and the 
like may be used as the binding resin. 
Among these, polyesters are preferable. Preferred examples of the 
polyesters are a linear polyester resin including, as a main monomer 
component, a condensation polymerization compound composed of bisphenol A 
and polyvalent aromatic carboxylic acid, and the like. 
As the binding resin, resins having the following specifications are 
desirable: softening point: 90.degree.-150.degree. C.; glass transition 
point: 50.degree.-70.degree. C.; number average molecular weight: 
2,000-6,000; weight-average molecular weight: 8,000-150,000; acid value: 
5-30; and hydroxyl value: 5-40. 
Examples of the coloring material include carbon black, nigrosine, aniline 
blue, calcoyl blue, chrome yellow, ultramarine blue, Du Pont oil red, 
quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite 
green-oxalate, lamp black, Rose Bengale, C.I. Pigment Red 48:1, C.I. 
Pigment Red 122, C.I. Pigment Red 57:1, C.I. Pigment Yellow 97, C.I. 
Pigment Yellow 12, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:3, and the 
like. 
It is desirable that the toner be negatively charged. It is advantageous to 
use the negatively charged toner since the toner is capable of keeping 
more stable negative charge due to a nitrogen atom contained in the resin 
layer of the carrier for developing an electrostatic latent image. 
The average particle diameter of the toner is usually in a range from 3 to 
10 .mu.m, preferably from 4 to 9 .mu.m. 
The method of the present invention for forming an image itself comprises 
known image forming steps, specifically, a step of forming a latent image 
on a latent image support, a step of developing the electrostatic latent 
image on the electrostatic latent image support using a developer layer on 
a carrier for a developer, a step of transferring the developed toner 
image on a transferring member, a step of fixing the toner image on the 
transferring member, and the like. In this method, the electrostatic 
latent image developer of the present invention is used as the developer. 
The method of the present invention for forming an image can be carried out 
using, for example, the image forming apparatus of the present invention. 
Incidentally, the above fixing itself can be performed using a known 
fixing apparatus. 
The image forming apparatus of the present invention comprises a means for 
forming a latent image on a latent image support, a means for developing 
the electrostatic latent image on the electrostatic latent image support 
using a developer layer on a carrier for a developer, a means for 
transferring the developed toner image on a transferring member, a means 
for fixing the toner image on the transferring member, and the like. In 
this apparatus, the electrostatic latent image developer of the present 
invention is used as the developer. 
As the image forming apparatus of the present invention, known equipment 
such as a copy machine, a facsimile machine, or the like essentially using 
the electrostatic latent image developer of the present invention as the 
developer may be used.

EXAMPLES 
The present invention will be explained in more detail by way of examples, 
which are not intended to be limiting of the present invention. 
Examples 1 
______________________________________ 
Manufacturing of carrier A for developing an electrostatic 
latent image 
Parts by weight 
______________________________________ 
Ferrite particles 100 
Average particle diameter: 50 .mu.m 
Toluene 14 
Perfluoroacrylate copolymer 
1.6 
Critical surface tension: 28 dyn/cm, 
perfluorooctylethyl acrylate/methyl 
methacrylate copolymer, copolymerization ratio: 
60:40, weight-average molecular weight M.sub.w : 70,000 
Cross-linked melamine resin particles 
0.25 
Average particle diameter: 0.3 .mu.m, insoluble in 
toluene 
Carbon black 0.12 
VXC 72, manufactured by Cabot Co., Ltd., oil 
absorbing rate: 178 ml/100 g 
______________________________________ 
The above-described components excluding the ferrite particles as the core 
material were dissolved and dispersed for 10 minutes using a stirrer to 
prepare a resin layer forming liquid. The resin layer forming liquid and 
the ferrite particles were placed in a vacuum deaerator type kneader and 
agitated at 60.degree. C. for 30 minutes according to a kneader-coater 
method. Toluene was distilled away under reduced pressure in the kneader, 
thereby forming a resin layer on the ferrite particles to prepare carrier 
A for developing an electrostatic latent image. Incidentally, in this 
example, the carbon black diluted in toluene was dispersed in 
perfluoroacrylate copolymer using a sand mill in advance. 
This carrier A for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 51 .mu.m, the thickness of 
a resin layer was 1.0 .mu.m, and the F/N ratio of the surface of the resin 
layer was 14.7. Also, it was observed that the cross-linked melamine resin 
was dispersed in the resin layer of carrier A for developing an 
electrostatic latent image uniformly both in the direction of the 
thickness of the resin layer and in the direction of the tangential line 
of the surface of carrier A for developing an electrostatic latent image. 
Example 2 
______________________________________ 
Manufacturing of carrier B for developing an electrostatic 
latent image 
Parts by weight 
______________________________________ 
Ferrite particles 100 
Average particle diameter: 50 .mu.m 
Toluene 14 
Perfluoroacrylate/HEMA copolymer 
1.6 
Critical surface tension: 30 dyn/cm, 
perfluorooctylethyl acrylate/HEMA copolymer, 
copolymerization ratio: 10:1, weight-average 
molecular weight M.sub.w : 50,000 
Butylated melamine 0.4 
Carbon black 0.10 
R330R, manufactured by Cabot Co., Ltd., oil 
absorbing rate: 70 ml/100 g 
______________________________________ 
The above-described components excluding the ferrite particles as the core 
material were dissolved and dispersed for 10 minutes using a homogenizing 
mixer to prepare a resin layer forming liquid. The resin layer forming 
liquid and the ferrite particles were placed in a vacuum deaerator type 
kneader and agitated at 60.degree. C. for 30 minutes according to a 
kneader-coater method. Toluene was distilled away under reduced pressure 
in the kneader, thereby forming a resin layer on the ferrite particles. 
The resulting product was agitated at 150.degree. C. for 60 minutes to 
cross-link the butylated melamine to prepare carrier B for developing an 
electrostatic latent image. Incidentally, in this example, the carbon 
black diluted in toluene was dispersed in perfluoroacrylate copolymer 
using a sand mill in advance. 
This carrier for developing an electrostatic latent image B was positively 
charged, having an average particle diameter of 51 .mu.m, the thickness of 
a resin layer was 1.0 .mu.m, and the F/N ratio of the surface of the resin 
layer was 8.61. 
Example 3 
______________________________________ 
Manufacturing of carrier C for developing an electrostatic 
latent image 
Parts by weight 
______________________________________ 
Ferrite particles 100 
Average particle diameter: 45 .mu.m 
Toluene 14 
Perfluoroacrylate copolymer 
0.1 
Critical surface tension: 28 dyn/cm, 
perfluorooctylethyl acrylate/methyl 
methacrylate copolymer, copolymerization ratio: 
40:60, weight-average molecular weight M.sub.w : 70,000 
St/DMAA copolymer (St/DMAA = 6/4) 
0.7 
______________________________________ 
The above-described components excluding the ferrite particles as the core 
material were dissolved and dispersed for 10 minutes using a stirrer to 
prepare a resin layer forming liquid. The resin layer forming liquid and 
the ferrite particles were placed in a vacuum deaerator type kneader and 
agitated at 60.degree. C. for 30 minutes according to a kneader-coater 
method. Toluene was distilled away under reduced pressure in the kneader, 
thereby forming a resin layer on the ferrite particles to prepare carrier 
C for developing an electrostatic latent image. 
This carrier C for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 46 .mu.m, the thickness of 
a resin layer was 0.5 .mu.m, and the F/N ratio of the surface of the resin 
layer was 2.32. 
Example 4 
______________________________________ 
Manufacturing of carrier D for developing an electrostatic 
latent image 
Parts by weight 
______________________________________ 
Ferrite particles 100 
Average particle diameter: 45 .mu.m 
Toluene 14 
Perfluoroacrylate copolymer 
0.5 
Critical surface tension: 28 dyn/cm, 
perfluorooctylethyl acrylate/n-butyl 
methacrylate/methyl methacrylate copolymer, 
copolymerization ratio: 4:3:3, weight-average 
molecular weight M.sub.w : 95,000 
Benzoguanamine 0.2 
Polymethyl methacrylate 0.3 
______________________________________ 
The above-described components excluding the ferrite particles as the core 
material were dissolved and dispersed for 10 minutes using a stirrer to 
prepare a resin layer forming liquid. The resin layer forming liquid and 
the ferrite particles were placed in a vacuum deaerator type kneader and 
agitated at 60.degree. C. for 30 minutes according to a kneader-coater 
method. Toluene was distilled away under reduced pressure in the kneader, 
thereby forming a resin layer on the ferrite particles to prepare carrier 
D for developing an electrostatic latent image. 
This carrier D for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 46 .mu.m, the thickness of 
a resin layer was 0.3 .mu.m, and the F/N ratio of the surface of the resin 
layer was 3.02. 
Example 5 
______________________________________ 
Manufacturing of carrier E for developing an electrostatic 
latent image 
Parts by weight 
______________________________________ 
Ferrite particles 100 
Average particle diameter: 45 .mu.m 
Toluene 14 
Perfluorosulfonylamide copolymer 
2.0 
Critical surface tension: 28 dyn/cm, 
perfluorooctylsulfonylaminoethyl 
methacrylate/methyl methacrylate copolymer, 
copolymerization ratio: 50:50, weight-average 
molecular weight M.sub.w : 65,000 
Carbon black 0.15 
VXC 72, manufactured by Cabot Co., Ltd., oil 
absorbing rate: 178 ml/100 g 
______________________________________ 
The above-described components excluding the ferrite particles as the core 
material were dissolved and dispersed for 10 minutes using a stirrer to 
prepare a resin layer forming liquid. The resin layer forming liquid and 
the ferrite particles were placed in a vacuum deaerator type kneader and 
agitated at 60.degree. C. for 30 minutes according to a kneader-coater 
method. Toluene was distilled away under reduced pressure in the kneader, 
thereby forming a resin layer on the ferrite particles to prepare carrier 
E for developing an electrostatic latent image. Incidentally, in this 
example, the carbon black diluted in toluene was dispersed in 
perfluoroacrylate copolymer, which was a resin layer forming resin, using 
a sand mill in advance. 
This carrier E for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 46 .mu.m, the thickness of 
a resin layer was 1.2 .mu.m, and the F/N ratio of the surface of the resin 
layer was 7.69. 
Comparative Example 1 
______________________________________ 
Manufacturing of carrier F for developing an electrostatic 
latent image 
Parts by weight 
______________________________________ 
Ferrite particles 100 
Average particle diameter: 45 .mu.m 
Toluene 14 
Perfluoroacrylate copolymer 
1.5 
Critical surface tension: 28 dyn/cm, 
perfluorooctylethyl acrylate/methyl 
methacrylate copolymer, copolymerization ratio: 
40:60, weight-average molecular weight M.sub.w : 70,000 
Butylated melamine 0.1 
Carbon black 0.4 
VXC 72, manufactured by Cabot Co., Ltd., oil 
absorbing rate: 178 ml/100 g 
______________________________________ 
The above-described components excluding the ferrite particles as the core 
material were dissolved and dispersed for 10 minutes using a stirrer to 
prepare a resin layer forming liquid. The resin layer forming liquid and 
the ferrite particles were placed in a vacuum deaerator type kneader and 
agitated at 60.degree. C. for 30 minutes according to a kneader-coater 
method. Toluene was distilled away under reduced pressure in the kneader, 
thereby forming a resin layer on the ferrite particles to prepare carrier 
F for developing an electrostatic latent image. Incidentally, in this 
example, the carbon black diluted in toluene was dispersed in 
perfluoroacrylate copolymer, which was a resin layer forming resin, using 
a sand mill in advance. 
This carrier F for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 46 .mu.m, the thickness of 
a resin layer was 1.0 .mu.m, and the F/N ratio of the surface of the resin 
layer was 23.6. 
Comparative Example 2 
______________________________________ 
Manufacturing of carrier G for developing an electrostatic 
latent image 
Parts by weight 
______________________________________ 
Ferrite particles 100 
Average particle diameter: 45 .mu.m 
Toluene 14 
Perfluoroacrylate copolymer 
0.5 
Critical surface tension: 28 dyn/cm, 
perfluorooctylethyl acrylate/methyl 
methacrylate copolymer, copolymerization ratio: 
40:60, weight-average molecular weight M.sub.w : 70,000 
Urea resin 1.0 
Average particle diameter: 0.3 .mu.m, insoluble in 
toluene 
Carbon black 0.4 
VXC 72, manufactured by Cabot Co., Ltd., oil 
absorbing rate: 178 ml/100 g 
______________________________________ 
The above-described components excluding the ferrite particles as the core 
material were dissolved and dispersed for 10 minutes using a stirrer to 
prepare a resin layer forming liquid. The resin layer forming liquid and 
the ferrite particles were placed in a vacuum deaerator type kneader and 
agitated at 60.degree. C. for 30 minutes according to a kneader-coater 
method. Toluene was distilled away under reduced pressure in the kneader, 
thereby forming a resin layer on the ferrite particles to prepare carrier 
G for developing an electrostatic latent image. Incidentally, in this 
example, the carbon black diluted in toluene was dispersed in 
perfluoroacrylate copolymer, which was a resin layer forming resin, using 
a sand mill in advance. 
This carrier G for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 46 .mu.m, the thickness of 
a resin layer was 1.0 .mu.m, and the F/N ratio of the surface of the resin 
layer was 0.22. 
Example 6 
Carrier H for developing an electrostatic latent image 
Carrier H for developing an electrostatic latent image was produced in the 
same manner as in Example 1 except that a cross-linked melamine resin with 
an average particle diameter of 0.05 .mu.m was used instead of the 
cross-linked melamine resin used in Example 1. The manufacture of carrier 
H was more difficult than that of cross-linked melamine resin A in Example 
1, because the dispersibility of the cross-linked melamine resin in the 
resin layer forming liquid was low. 
This carrier H for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 51 .mu.m, the thickness of 
a resin layer was 1.0 .mu.m, and the F/N ratio of the surface of the resin 
layer was 14.0. 
Also, it was observed that the cross-linked melamine resin was dispersed 
uniformly in the resin layer of carrier H for developing an electrostatic 
latent image both in the direction of the thickness of the resin layer and 
in the direction of the tangential line of the surface of carrier H for 
developing an electrostatic latent image. 
Example 7 
Carrier I for developing an electrostatic latent image 
Carrier I for developing an electrostatic latent image was produced in the 
same manner as in Example 1 except that a cross-linked melamine resin with 
an average particle diameter of 2.2 .mu.m was used instead of the 
cross-linked melamine resin used in Example 1 and the amount of the 
perfluoroacrylate resin was altered to 3.2 parts by weight. 
This carrier I for developing an electrostatic latent image was positively 
charged, having an average particle diameter of 51 .mu.m, the thickness of 
a resin layer was 2.0 .mu.m, and the F/N ratio of the surface of the resin 
layer was 15.3. 
Also, it was observed that the cross-linked melamine resin was dispersed 
uniformly in the resin layer of carrier I for developing an electrostatic 
latent image both in the direction of the thickness of the resin layer and 
in the direction of the tangential line of the surface of carrier I for 
developing an electrostatic latent image. 
One hundred parts by weight of each of the carriers for developing an 
electrostatic latent image produced in Examples 1-5 and 7, and Comparative 
Examples 1 and 2, and 6 parts by weight of a toner were mixed to prepare 7 
types of electrostatic latent image developers, which were shown as 
electrostatic latent image developers 1-7 and 1-a corresponding 
respectively to carriers A-G and I for developing an electrostatic latent 
image. 
In addition, the toner used in these examples was a magenta toner (toner A) 
of 8 .mu.m particle diameter, which was prepared by the process described 
below using the following components: 
______________________________________ 
Manufacturing of toner A 
Parts by weight 
______________________________________ 
Linear polyester resin 100 
Linear polyester prepared from terephthalic 
acid/ethylene oxide adduct of bisphenol 
A/cyclohexane dimethanol; T.sub.g : 62.degree. C.; M.sub.n : 4,000; 
M.sub.w : 
35,000; acid value: 12; hydroxyl value: 25 
Magenta pigment 3 
C.I. Pigment Red 57 
______________________________________ 
A mixture of the above components was kneaded using an extruder, pulverized 
using a jet mill, and then dispersed using a pneumatic classifier to 
prepare magenta toner particles (d50: 8 .mu.m). 0.4 parts by weight of R 
972 (silica, manufactured by Japan Aerosil Co., Ltd.) was added to and 
mixed with the magenta toner particles using a Henshell mixer to obtain a 
magenta toner (toner A) which was negatively charged. 
These electrostatic latent image developers 1-7 and 1-a were tested in 
taking 10,000 copies using an electrophotographic copying machine (A-Color 
630, manufactured by Fuji Xerox Co., Ltd.) at an intermediate temperature 
under an intermediate humidity (22.degree. C., 55% RH) The charge quantity 
and the solid densitly were measured at the start of the copying test and 
after taking 3,000 copies and 10,000 copies to evaluate the fog on the 
background according to the standard illustrated below. The results are 
shown in Table 1. 
In Table 1, the charge quantity (.mu.C/g) was a value measured by an image 
analysis using a charge spectrograph (CSG) method. The fog on the 
background was measured by visual inspection and rated as follows: 
.largecircle.: No fogging, good image condition. 
.DELTA.: A slight rate of fogging, practically no problem in image 
condition. 
X: An observable rate of fogging. 
XX: Considerable fogging, remarkably coarse image condition. 
The solid density was measured by a densitometer (X-rite) and was rated 
according to the standard below. A solid density of 1.10 or more ensures 
practical application. 
.largecircle.: The solid density ranged from 1.30 to 1.49. 
.DELTA.: The solid density ranged from 1.10 to 1.29. 
X: The solid density ranged from 0.90 to 1.09. 
XX: The solid density was 0.89 or less. 
TABLE 1 
__________________________________________________________________________ 
Start 
Resin Carrier Charge Fog on 
coated F/N Developer 
amount 
Solid density 
back- 
carrier 
ratio 
Toner 
No. (.mu.C/g) 
Density 
Judgment 
ground 
__________________________________________________________________________ 
Ex. 1 
A 14.70 
A 1 -20.5 
1.43 
.largecircle. 
.largecircle. 
Ex. 2 
B 8.61 
A 2 -23.5 
1.44 
.largecircle. 
.largecircle. 
Ex. 3 
C 2.32 
A 3 -18.2 
1.38 
.largecircle. 
.largecircle. 
Ex. 4 
D 3.02 
A 4 -25.5 
1.32 
.largecircle. 
.largecircle. 
Ex. 5 
E 7.69 
A 5 -22.0 
1.42 
.largecircle. 
.largecircle. 
Comp. 
F 23.60 
A 6 -17.0 
1.38 
.largecircle. 
.largecircle. 
Ex. 1 
Comp. 
G 0.22 
A 7 -28.9 
1.28 
.DELTA. 
.largecircle. 
Ex. 2 
Ex. 7 
I 15.30 
A 1-a -20.5 
1.42 
.largecircle. 
.largecircle. 
__________________________________________________________________________ 
After 3,000 copies After 10,000 copies 
Charge Fog on 
Charge Fog on 
amount Solid density 
back- 
amount 
Solid density 
back- 
(.mu.C/g) 
Density 
Judgment 
ground 
(.mu.C/g) 
Density 
Judgment 
ground 
__________________________________________________________________________ 
Ex. 1 
-22.5 
1.40 
.largecircle. 
.largecircle. 
-21.8 
1.41 
.largecircle. 
.largecircle. 
Ex. 2 
-22.8 
1.45 
.largecircle. 
.largecircle. 
-23.4 
1.46 
.largecircle. 
.largecircle. 
Ex. 3 
-17.5 
1.40 
.largecircle. 
.largecircle. 
-16.7 
1.41 
.largecircle. 
.largecircle. 
Ex. 4 
-26.2 
1.30 
.largecircle. 
.largecircle. 
-26.7 
1.31 
.largecircle. 
.largecircle. 
Ex. 5 
-19.4 
1.46 
.largecircle. 
.largecircle. 
-17.2 
1.38 
.largecircle. 
.largecircle. 
Comp. 
-20.0 
1.32 
.largecircle. 
X -12.6 
1.35 
.largecircle. 
XX 
Ex. 1 
Comp. 
-34.5 
1.08 
X .largecircle. 
-40.8 
0.95 
X .largecircle. 
Ex. 2 
Ex. 7 
-18.2 
1.45 
.largecircle. 
.largecircle. 
-15.0 
1.43 
.largecircle. 
.largecircle. 
__________________________________________________________________________ 
Ex.: Example 
Comp. Ex.: Comparative Example 
As is clear from the results shown in Table 1, electrostatic latent image 
developers 1-5 and 1-a were characterized in that the charge amount was 
substantially unchanged with time, exhibiting stable charge amounts and 
stable densities. Also, a good-condition image could be formed without any 
fog on the background. On the other hand, electrostatic latent image 
developers 6 and 7 had the drawbacks that the amounts of charge greatly 
changed with time and the image density changed. Also, fog on the 
background occurred and toner contamination in the apparatus was 
observable, exhibiting a remarkably coarse image. 
With respect to the electrostatic latent image developers 1, 2, and 5 
respectively containing electrostatic latent image developing toners A, B, 
and E containing carbon black, the reproducibility of solid was high and a 
toner could be charged in a short time. 
With respect to electrostatic latent image developer 1-a, there was little 
fogging and a good-condition image could be formed. However, the change in 
the amount of charge with time was slightly greater than that of 
electrostatic latent image developer 1. It was observed that the 
cross-linked melamine resin particles had fallen away from the resin 
layer, which was thought to be the cause of the slightly greater change in 
the amount of charge. 
One hundred parts by weight of each of carriers A-E for developing an 
electrostatic latent image produced in Examples 1-5 and 6 parts by weight 
of the toner below were mixed to prepare 5 types of electrostatic latent 
image developers, which were shown as electrostatic latent image 
developers 8-12 corresponding respectively to carriers A-E for developing 
an electrostatic latent image. 
In addition, the toner used in these examples was a black toner (toner B) 
of 9 .mu.m particle diameter, which was prepared by the process described 
below using the following components: 
______________________________________ 
Manufacturing of toner B 
Parts by weight 
______________________________________ 
Linear polyester resin 100 
Linear polyester prepared from terephthalic 
acid/ethylene oxide adduct of bisphenol 
A/cyclohexane dimethanol; Tg: 62.degree. C.; Mn: 4,000; 
Mw: 35,000; acid value: 12; hydroxyl value: 25 
Carbon black 6 
Mogul L, manufactured by Cabot Co., Ltd. 
______________________________________ 
A mixture of the above components was kneaded using an extruder, pulverized 
using a crusher of a bulk crushing type, and then dispersed using a 
pneumatic classifier to prepare black toner particles (d50:9 .mu.m). 0.4 
part by weight of R 972 (silica, manufactured by Japan Aerosil Co., Ltd.) 
was added to and mixed with the black toner particles using a henshel 
mixer to obtain a black toner (toner A) which was negatively charged. 
These electrostatic latent image developers 8-12 were tested in taking 
10,000 copies using an electrophotographic copying machine (A-Color 630, 
manufactured by Fuji Xerox Co., Ltd.) at an intermediate temperature under 
an intermediate humidity (22.degree. C., 55% RH). The charge amount and 
the solid density were measured at the start of the copying test and after 
taking 3,000 copies and 10,000 copies to evaluate the fog on the 
background according to the standard illustrated above. The results are 
shown in Table 2. 
In Table 2, the charge amount (.mu.C/g), the solid density, and the fog on 
the background are the same as in Table 1. 
TABLE 2 
__________________________________________________________________________ 
Start 
Resin Carrier Charge Fog on 
coated F/N Developer 
amount 
Solid density 
back- 
Ex. 
carrier 
ratio 
Toner 
No. (.mu.C/g) 
Density 
Judgment 
ground 
__________________________________________________________________________ 
1 A 14.70 
B 8 -20.5 
1.43 
.largecircle. 
.largecircle. 
2 B 8.61 
B 9 -25.8 
1.42 
.largecircle. 
.largecircle. 
3 C 2.32 
B 10 -18.8 
1.42 
.largecircle. 
.largecircle. 
4 D 3.02 
B 11 -22.8 
1.38 
.largecircle. 
.largecircle. 
5 E 7.69 
B 12 -23.0 
1.41 
.largecircle. 
.largecircle. 
__________________________________________________________________________ 
After 3,000 copies After 10,000 copies 
Charge Fog on 
Charge Fog on 
amount Solid density 
back- 
amount 
Solid density 
back- 
Ex. 
(.mu.C/g) 
Density 
Judgment 
ground 
(.mu.C/g) 
Density 
Judgment 
ground 
__________________________________________________________________________ 
1 -21.3 
1.40 
.largecircle. 
.largecircle. 
-23.4 
1.42 
.largecircle. 
.largecircle. 
2 -22.4 
1.41 
.largecircle. 
.largecircle. 
-20.5 
1.38 
.largecircle. 
.largecircle. 
3 -17.4 
1.38 
.largecircle. 
.largecircle. 
-17.0 
1.35 
.largecircle. 
.largecircle. 
4 -23.9 
1.37 
.largecircle. 
.largecircle. 
-22.0 
1.40 
.largecircle. 
.largecircle. 
5 -22.8 
1.40 
.largecircle. 
.largecircle. 
-20.2 
1.35 
.largecircle. 
.largecircle. 
__________________________________________________________________________ 
Ex.: Example 
As is clear from the results shown in Table 2, electrostatic latent image 
developers 8-12 were characterized in that the charge amount was 
substantially unchanged with time, exhibiting stable charge amounts and 
stable solid densities with time. Also, a good-condition image could be 
formed without any fog on the background. 
With respect to electrostatic latent image developers 1, 2, and 5 
respectively containing electrostatic latent image developing toners A, B, 
and E containing carbon black, the reproducibility of solid was high and a 
toner could be charged in a short time. 
Use of the carrier for developing an electrostatic latent image of the 
present invention ensures forming of a stable and good-condition image for 
a long period of time, since the carrier for developing an electrostatic 
latent image of the present invention is long-lived and its charging 
capability remains unchanged over time. By using the electrostatic latent 
image developer, the method for forming an image, and the image forming 
apparatus of the present invention, which use the carrier for developing 
an electrostatic latent image of the present invention, an image of high 
quality can be formed in a stable manner over a long period of time.