Toner binder for flash fixing, toner, electrostatic photographic printing method and apparatus therefor

A toner binder comprising a crosslinked polyester resin obtained by using 0.1 to 3 mol % of trimellitic acid and 0.1 to 5 mol % of an epi-bis type epoxy in combination as crosslinking components, said binder having a number average molecular weight (Mn) in the chromatogram determined by a gel permeation chromatography on the non-gel portion of the polyester resin, of 2,000 to 4,000, a ratio (Mw/Mn) of the weight average molecular weight to the number average molecular weight of 10 to 25 and a (percent gel) of the residue unsoluble in tetrahydrofuran solvent of 1 wt % or less. A toner composition for flash fixing comprising the above-described binder as an essential constituent component. The toner and the toner binder exhibit good fixability and void resistance upon flash fixing and produce little fixing odor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a binder for toner used in flash fixing, a 
toner, an electrophotographic printing method and an apparatus therefor. 
More specifically, it relates to a toner exhibiting excellent fixability 
and void resistance during flashlight irradiation and having reduced 
fixing odor, an improved binder for the toner, an electrophotographing 
method using the toner and an apparatus therefor, pertaining to the toner 
used in the development of an electrostatic image for an electrophotograph 
and the like. 
2. Description of Related Art 
Electrophotography has been conventionally known to use such a system as 
described in U.S. Pat. No. 2,297,691, where a photoconductive insulator 
(e.g., a photoconductive drum) is commonly used, a uniform electrostatic 
charge is applied to the photoconductive insulator, for example, by corona 
discharge, a light image is irradiated on the photoconductive insulator by 
various means to form an electrostatic latent image, the latent image is 
developed and visualized using fine particles called toner and after the 
toner image is transferred, if desired, to paper or the like, the toner 
image is fixed onto the recording medium such as paper by means of 
pressurization, heating, exposure to solvent vapor or irradiation by light 
to obtain a printed matter. 
The toner used for developing the electrostatic latent image is 
conventionally produced by dispersing a coloring agent such as carbon 
black in a binder resin comprising a natural or synthetic polymer material 
and finely granulating the obtained dispersion into particles 
approximately 5 to 20 .mu.m in size. The toner may be used by itself or as 
a mixture thereof with a carrier such as an iron powder or glass beads in 
the development of an electrostatic latent image as the toner. In the case 
where an iron powder or other ferromagnetic powder is used as the carrier, 
the development is conducted in such a manner that the developing agent 
consisting of a toner and a carrier is mixed and stirred in a developing 
apparatus to charge the toner with frictional electrification, a magnet 
roll in the developing apparatus is rotated to form a magnetic brush, the 
magnetic brush is transported to the electrostatic latent image portion on 
the photoconductive sensitized material by rotation of the magnet roll and 
only the charged toner is adsorbed to the latent image due to the 
electrical attraction force. After the development, the developing agent 
which has reduced in toner density is replenished by new toner to maintain 
the toner density constant and can be repeatedly used. 
On the other hand, the toner powder image formed on the photosensitive drum 
is transferred onto a recording medium (e.g., paper) by corona transfer or 
roller transfer. The toner powder image transferred to the recording 
medium is attached to the paper in the state of powder forming an image, 
where if it is rubbed, for example, by a finger, the powder image is 
damaged. In order to fix the toner powder image on the recording medium, 
the powder image must be melted to fix it to the recording medium and 
various methods are used therefor. Among these methods, the flash fixing 
method, as a representative example of a photofixing method, is conducted 
by flash of light from a discharge tube such as a xenon flash lamp and is 
characterized as follows: 
1) due to non-contact fixing, the resolution of a developed image is not 
deteriorated, 
2) the stand-by time after a power source is turned on is not required and 
a quick start can be realized, 
3) even when jamming of the recording paper is caused in the fixing device 
due to a system failure, ignition is not caused, and 
4) fixing is possible irrespective of material or thickness of the 
recording paper, such as glued paper, preprinted paper or paper of 
different thickness. 
Fixing the toner to the recording paper by flash fixing occurs through the 
following procedure. As described above, the toner image adheres to the 
recording paper as a powder when it is transferred to the recording paper 
and it is readily damaged by rubbing, for example, with a finger. When the 
flash of light from a discharge tube such as a xenon flash lamp is 
irradiated thereto, the toner absorbs the energy of flash light, its 
temperature is raised and thereby the toner is softened and melted to 
tightly adhere to the recording paper. At the end of the flash of 
irradiation, the temperature lowers to solidify the image to form a fixed 
image, thus accomplishing the fixing, and the fixed image firmly adhered 
to the recording paper is not damaged even when it is rubbed, for example, 
with a finger. 
It is important in flash fixing that the toner is melted and firmly adheres 
to the recording paper and therefore, the toner must be thoroughly melted 
by absorbing energy from the flash of light. The total light energy must 
include not only the energy for melting the toner but also the heat energy 
diffusing outside and not contributing to the increase of temperature. 
Accordingly, if the total light energy given is insufficient, the toner 
cannot be melted thoroughly and as a result, the fixing obtained is not 
satisfactory. When the light energy is absorbed by the toner, the toner is 
melted and its viscoelasticity is abruptly lowered. 
The physical properties of the melted toner, such as viscoelasticity and 
surface tension, vary greatly depending on the material and the melting 
temperature of the binder resin constituting the toner and if the surface 
tension of the toner at the time of melting and fixing overpowers the 
viscoelasticity thereof, the toner aggregates and the toner which was 
uniformly present on the image portion moves to cause an image drop-out 
phenomenon called a void (aggregation void) on the fixed image, resulting 
in a reduction in the image density. Further, if an excess amount of 
energy is given, the toner boils and the melted toner is blown off by the 
explosive expansion of gas present in spaces in the toner powder image and 
the gas generated by the toner decomposition, to generate a void 
(explosion void) in the fixed image to thereby cause a reduction in the 
image density. 
Accordingly, the toner must not be hardly susceptible to the generation of 
voids due to aggregation or moving of the toner and in this concern, the 
use of a binder resin having a low surface tension and a high 
viscoelasticity is needed so that the viscoelasticity of toner overpowers 
the surface tension during melting. 
As known from the foregoing, in order to have good fixability, in the flash 
fixing system, the total amount of light energy irradiated must be 
sufficiently large and the toner used or the binder resin constituting the 
toner must have physical properties of a low melting point and a low melt 
viscoelasticity so that it swiftly absorbs the light energy of flash light 
and melts to permeate the recording medium such as paper. On the other 
hand, in order to prevent voids, in the flash fixing system, excessive 
energy must not be applied but the energy must be applied to the toner in 
such a manner that melt properties (e.g., melting temperature) of the 
toner are controlled and the toner used needs to have a melt 
viscoelasticity sufficiently high to prevent movement of the toner causing 
generation of voids. 
The toner for flash fixing must also not generate a bad odor even if it is 
heated to a high temperature during flash fixing. 
The main object of the present invention is to provide a toner and a binder 
for the toner which have excellent fixability and void resistance in flash 
fixing and have a low fixing odor. 
DISCLOSURE OF THE INVENTION 
In order to achieve the above-described object, the present invention 
provides a toner binder comprising a crosslinked polyester resin obtained 
by using in combination 0.1 to 3 mol % of a trimellitic acid and 0.1 to 5 
mol % of an epi-bis type epoxy as crosslinking components, the polyester 
resin having a number average molecular weight (Mn) in the chromatogram 
determined by a gel permeation chromatography on the non-gel portion of 
the polyester resin, of 2,000 to 4,000, a ratio (Mw/Mn) of the weight 
average molecular weight to the number average molecular weight of 10 to 
25 and a residue (gel proportion) not dissolved to the tetrahydrofuran 
solvent of 1 wt % or less. 
Preferably, the essential constituent monomers of the binder acid component 
comprise 80 mol % or more of a terephthalic acid and/or isophthalic acid 
and the alcohol component comprises 15 to 70 mol % of aliphatic diol 
having 5 or less carbon atoms and a methyl side chain and 30 to 85 mol % 
of an etherified bisphenol A. The epi-bis type epoxy used as a 
crosslinking agent preferably has a molecular weight of 1,500 or less. 
The present invention also provides a toner comprising the above-described 
toner binder as an essential constituent and an electrophotographing 
apparatus characterized by using the above-described toner and, after 
developing and transferring the electrostatic image, flash fixing the 
toner image. 
A first gist of the present invention resides in that by employing a 
crosslinked polyester obtained with a specific crosslinkable agent as an 
essential binder resin for the toner, the binder resin can be controlled 
to have a specific configuration of the molecular weight distribution 
which greatly affects the melt viscoelasticity of the toner and can have a 
good permeability to the recording medium. 
In order to provide a toner with high void resistance and excellent 
fixability at the same time, the toner should have melt viscoelasticity in 
high-temperature melting state and melt viscoelasticity in low-temperature 
melting state, as described in Japanese Unexamined Patent Publication 
(kokai) No. 4-56869. 
The present inventors have made intensive investigations to achieve both 
fixability and void resistance at an extremely high level and as a result, 
have found that the desired melt viscoelasticity is about 90 to 130 poise 
at 200.degree. C. and about 35,000 to 65,000 poise at 120.degree. C. 
The desired fixability intended by the present inventors means 95 to 100% 
in terms of fixing ratio determined by the Scotch Mending Tape peeling-off 
test, and the desired void resistance means 90% or more in terms of image 
covering ratio after flash fixing, which will be described later in 
detail. 
As an effective means to impart the viscoelasticity to the toner for flash 
fixing, Japanese Unexamined Patent Application (kokai) Nos. 57-109825 and 
5-107805 propose to introduce a crosslinking structure into the polyester 
by incorporating a trace amount of a multifunctional monomer such as 
trimellitic acid thereinto and Japanese Unexamined Patent Application 
(kokai) No. 4-56869 proposes a means to blend a plurality of binders 
different in the melt viscoelasticity. However, when crosslinking for 
imparting a desired viscoelasticity is obtained only by trimellitic acid, 
the peak molecular weight, in the chromatogram determined by gel 
permeation chromatography, is shifted to the high molecular weight side, 
the amount of the low molecular weight component being reduced, and, 
further, an excessive amount of gel component is formed in many cases. 
Here, inconvenience is caused in that, if the trimellitic acid content is 
increased too much, the void resistance may be ameliorated but the 
fixability is deteriorated, whereas if the addition amount of trimellitic 
acid is reduced too much, a desired viscoelasticity cannot be obtained, 
and the fixability and the void resistance cannot be achieved at the same 
time. 
According to the investigation by the present inventors, as the trimellitic 
acid content increases, the fixing odor becomes irritating and thus the 
trimellitic acid content needs to be 3.0% or less, preferably 2.0% or 
less, but with a trimellitic acid content as low as this, a desired 
viscoelasticity cannot be obtained. 
Also, according to the investigation by the present inventors, when high 
levels of fixability and void resistance are intended to become 
concomitant by means such as blending of binders, as described in Japanese 
Unexamined Patent Publication (kokai) No. 4-56869, a binder having an 
extremely high viscosity and a binder having a low viscosity need to be 
blended and the compatibility between two binders is very likely to be 
poor, therefore, binders form a sea/island structure in the toner and are 
not mixed uniformly with each other, resulting in unsatisfactory color 
tone, electrostatic charge characteristics and rupture strength of the 
toner and thus the results obtained are not satisfactory. 
As a result of investigations, the present inventors have found that, in 
order to overcome these problems and to simultaneously achieve fixability 
and void resistance, at a high level, it is essential to optimize the 
molecular weight distribution of the binder, as an item having a great 
effect on the melt viscoelasticity of binder, and also to optimize the 
molecular configuration of the binder in relation to the permeability to 
the recording medium, and have accomplished the present invention. 
First, with respect to optimization in the molecular weight distribution, 
according to the finding of the present inventors, a predetermined amount 
of a low molecular weight component must be present to impart good 
fixability to the toner and the required amount for the low molecular 
weight component can be defined by 4,000 or less in terms of the number 
average molecular weight (Mn) and 25 or less in terms of the ratio (Mw/Mn) 
of the weight average molecular weight (Mw) to the number average 
molecular weight (Mn). In order to have such a content of the low 
molecular weight component and impart a desired viscoelasticity to the 
toner, the present inventors used trimellitic acid and an epi-bis type 
epoxy in combination, as crosslinking agents for the polyester, and 
accomplished the present invention. 
According to the present inventors, the combined use of the above 
crosslinking agents has the following advantages. 
First, when using the trifunctional or higher functional acids such as 
trimellitic acid and pyromellitic acid or trifunctional or higher 
functional alcohols such as glycerine, trimethylolpropane and 
pentaerythritol, which have been conventionally used as a crosslinking 
agent in many cases, the molecular weight of the crosslinking component is 
low and the functional groups as crosslinking points are adjacent, 
therefore, the polymer chains extending from respective crosslinking 
points cannot be extended uniformly due to an effect such as steric 
hindrance. Also, in the case where isocyanates are used as crosslinking 
agents, the polymer chains are susceptible to the same steric hindrance. 
Accordingly, as shown in FIG. 4, the molecular weight distribution takes 
such a configuration that an explicit peak top is present at a specific 
molecular weight value and since the molecular weight at the peak changes 
according to the amount of added crosslinking agent, and if the peak is 
present on the high molecular weight side, the void resistance may be 
ameliorated but the fixability is inferior, whereas if the top peak is 
present on the low molecular weight side, the void resistance stays at an 
unsatisfactory level. 
On the contrary, in the case where an epi-bis type epoxy resin is used as a 
crosslinking chain, the crosslinking points lie at the glycidyl groups 
present at each end of the epoxy resin and at the hydroxyl groups between 
the repeating units such as bisphenol A and therefore, the polymer chain 
can extend uniformly from each crosslinking point due to a sufficient 
distance between respective crosslinking points. As a result, as shown in 
FIG. 3, the molecular weight distribution configuration is relatively 
close to a trapezoid showing a relatively low viscosity at low 
temperatures and a relatively high viscosity at high temperatures and 
thus, the void resistance and fixability of an extremely high level can be 
realized. 
With respect to permeability to the recording medium, in comparing cases 
where polymers having the same molecular weight are produced, using as the 
crosslinking agent trimellitic acid solely or trimellitic acid and an 
epi-bis type epoxy resin in combination, the following can be pointed out. 
In the case of crosslinking by only trimellitic acid, a gel is readily 
formed and the polymer chains extending from the crosslinking points are 
not uniform and therefore, the molecule itself becomes bulky, resulting in 
poor permeability to the recording medium. On the other hand, in the case 
of crosslinking by a combined use of trimellitic acid with an epi-bis type 
epoxy resin, the molecule is relatively less bulky and the molecular 
chains extending from the crosslinking points are not susceptible to 
steric hindrance and are free and, therefore, the crosslinking chains can 
act as a soft segment, so that excellent melt viscoelasticity and 
permeability to the recording medium of the toner binder can be achieved. 
A representative example of the epi-bis type epoxy resin which can be used 
in the present invention is the compound represented by the following 
formula: 
##STR1## 
This resin is produced by the reaction of epichlorohydrin with bisphenol A 
or bisphenol F and representative commercial products thereof are Epicote 
828, 1001 and 1004 produced by Yuka Shell Epoxy KK. 
The molecular weight of the epoxy resin is preferably 1,500 or less because 
if the crosslinking chain of the resin becomes long and exceeds a certain 
level, there arises a problem of reduction in glass transition 
temperature. Also, a graft copolymer of an epi-bis type epoxy resin with 
another copolymer component or a graft polymer obtained by polymerizing a 
functional group of the epi-bis type epoxy with other copolymer component 
may be used as the crosslinking chain, however, according to the finding 
of the present inventors, when using a block copolymer or a graft 
copolymer of the epi-bis type epoxy resin as a crosslinking agent, the 
reduction in glass transition temperature or reduction in fixability is 
caused in many cases and favorable results are often not provided. The 
present inventors assume that this is because block or graft 
copolymerization of the crosslinking molecular chain restricts the steric 
freedom of the crosslinking molecular chain and makes it difficult for the 
crosslinking chain to effectively act as a soft segment. 
The second gist of the present invention resides in the finding, as a 
result of investigation on combinations of various monomers constituting 
the skeleton structure of the polyester, of monomer compositions having a 
high affinity to the recording medium and favored physical properties such 
as melting point and glass transition point suitable for the toner. 
According to the investigation by the present inventors, in order to 
increase the affinity to the recording medium (in particular, paper), it 
is preferred to incorporate a large quantity of soft segment components or 
to incorporate a monomer having a large number of branched chains, 
however, the incorporation of such a component brings about reduction in 
the glass transition temperature of the toner and causes a problem with 
respect to the storage stability of the toner. These contradictory 
propositions are overcome by the finding that a monomer composition can 
have, while retaining a glass transition temperature of 65.degree. C. or 
higher, an excellent affinity (permeability) to the recording medium and 
excellent fixability. The composition comprises 80 mol % or more of a 
terephthalic acid and/or an isophthalic acid in the acid component, and on 
the alcohol component of 15 to 70 mol % of an aliphatic diol having 5 or 
less carbon atoms and a methyl side chain and 30 to 85 mol % of etherified 
bisphenol A. 
The alcohol components may be selected from etherified bisphenol A, 
1,2-propylene glycol, 1,3-butanediol, and neopethyl glycol. The acid 
components may be selected from terephthalic acid and isophthalic acid. 
The etheried bisphenol A which is employed in the present invention is 
obtained by conducting the addition reaction of bisphenol A and an 
alkylene oxide such as ethylene oxide or propylene oxide. Those having an 
added average number of 2 to 10 moles per mole of bisphenol A can suitably 
used. 
As for aliphatic diols having a methyl side chain and 5 or less carbon 
atoms, 1,2-propylene glycol, 1,3-butanediol, and neopentyl glycol are 
examples thereof. 
A small amount (10% or less by mole of all alcohol components) of the other 
alcohols can be used, besides the etherified bisphenol A, aliphatic diols 
mentioned above, and epi-bis type epoxy resin. 
As for the above alcohol components, etylene glycol, diethylene glycol, 
triethylene glycol, 1,3-propylene glycol, 1,4-butanediol, hydrogenated 
bisphenol A and the like can be given as the examples thereof. 
A small amount (17% or less by mole of all acid components) of the other 
acids can be used, besides terephthalic acid, isophthalic acid, and 
trimellitic acid. 
As for the above acid components, phthalic acid, maleic acid, fumaric acid, 
succinic acid, adipic acid, and the like can be given as the examples 
thereof. 
In the toner binder, it is preferred that the ratio of the number of 
carboxyl groups in all acid components to the number of hydroxyl groups in 
all alcohol components is within the range of 0.8 to 1.2. 
The present inventors consider that the methyl side chain has the following 
two effects. First, due to the presence of the side chain, the polyester 
is inhibited from being crystallized and even when it has a molecular 
weight sufficiently high to provide a long chain and a high melt 
viscosity, the melting point thereof is relatively low and therefore, the 
fixability can be easily attained. Secondly, due to the side chain of the 
molecule, tangling of the molecules increases to ensure the melt viscosity 
and also, tangling of the polyester with molecules of the recording medium 
easily occurs to increase the bonding ability. 
The reason why the side chain is limited to the methyl chain is that if the 
side chain is a hydrocarbon chain having 2 or more carbon atoms, the 
degree of freedom of the side chain is increased so that the glass 
transition temperature is conspicuously reduced. 
Further, the reason why the gel proportion is limited to 1.0 wt % or less 
is that, if the gel proportion exceeds this range, the fixability at a 
high level cannot be retained. 
The binder resin for use in the present invention can be produced by 
conventionally known methods. More specifically, it may be produced by 
condensation polymerization of the acid component with the alcohol 
component at a temperature of from 150 to 280.degree. C. and in this case, 
a catalyst such as di-n-butyl tin oxide may be added to accelerate the 
reaction or the reaction may be conducted under reflux of a solvent or 
under reduced pressure. Further, by changing the carboxylic acid group to 
a lower ester such as methyl ester, transesterification may be conducted. 
The toner used in the present invention can be produced by conventionally 
known methods. More specifically, a binder resin, a coloring agent and if 
desired, carbon and an electrostatic charge controlling agent are 
melt-kneaded, for example, in a pressure kneader, a roll mill or an 
extruder to disperse them uniformly, finely ground, for example, by a jet 
mill and then classified by a classifier such as a pneumatic classifier to 
obtain a desired toner. A representative toner composition comprises 
carbon as a pigment or an electroconductivity-imparting agent in an amount 
of from 3 to 10%, preferably from 3 to 5%, an electrostatic charge 
controlling agent in an amount of from 1 to 5% and a lubricant in an 
amount of 1% or less, each based on the binder. Accordingly, the binder is 
mostly present in an amount of approximately from 80 to 95%. The toner 
particle size is typically from 5 to 20 .mu.m. 
The binder for flash fixing and the toner for flash fixing described 
specifically in the foregoing have excellent flash fixability and void 
resistance and exhibit good color tone, electrostatic characteristics and 
storage stability. 
An electrophotographing method using flash fixing and an apparatus therefor 
are described below by referring to the drawings attached. 
In FIGS. 1A, 1B and 1C, a toner 1 in the state of powder is bonded onto a 
recording medium 2 and upon irradiation by a flash of light 3, the surface 
layer portion 1 of the toner is melted and as the heat conduction 
gradually proceeds, the toner on the lower layer portion is melted. In the 
case where the toner of the present invention is not used, the toner 
undergoes coagulation due to the surface tension of toner to generate a 
void 5 in the fixed image. When the toner of the present invention is 
used, no void is generated. 
The toner of the present invention is preferably used, for example, in an 
electrophotographic apparatus as shown in FIG. 2. First, a developing 
agent comprising a mixture of the toner of the present invention and a 
magnetic powder such as iron powder is used. The developing agent 11 is 
mixed and stirred by means of stirring screws 12 to charge the toner with 
frictional electrification. The toner charged with frictional 
electrification is transported by a development roller 13 to a 
photosensitive drum 14 and the charged toner adheres to the photosensitive 
drum according to the electrostatic image pattern on the photosensitive 
drum 14 to provide a visible image. The toner image on the drum is 
transferred to a recording medium 15, for example, paper, and heated and 
melted by a flash of light 17 so that the toner penetrates into the paper 
to provide a fixed image 18. In FIG. 2, the numeral 16 stands for a 
transfer portion, 19 a pre-electrification part and 20 an exposure 
portion. 
The above-described printing method and electrophotographic apparatus are 
excellent owing to the characteristics described below. First, the fixing 
system uses flash fixing and therefore, the following advantages can be 
provided: 
1) due to non-contact fixing, the resolution of a developed image is not 
deteriorated, 
2) the stand-by time after a power source is turned on is not required and 
a quick start can be realized, 
3) even when jamming of the recording paper is caused in the fixing device 
due to a system failure, ignition is not caused, and 
4) printing is possible irrespective of materials or thickness of the 
recording paper, such as pasted paper, preprint paper or papers different 
in thickness. Further, since the toner of the present invention is used, 
excellent flash fixability and superior void resistance can be achieved 
and thereby a high-quality fixed image can be obtained. 
The values of various physical properties set forth in the present 
invention, including those in examples, are determined according to the 
measurement methods described below. 
[Melting Point (Softening Point)] 
A temperature flow test was conducted using a Shimadzu Flow Tester 
(CFT-500, manufactured by Shimadzu Seisakusho) under the following 
measurement conditions and the temperature when the plunger descended 4 mm 
was determined to be the melting point. 
______________________________________ 
Die 1.0 mm.phi. .times. 1.0 mm 
Temperature increase 
6.degree. C./min 
rate 
Sample 1.0 g pellets 
Load 20 kg/cm.sup.2 
Pre-heating temperature 
60.degree. C. 
Pre-heating time 300 sec 
______________________________________ 
[Glass Transition Temperature] 
The temperature rise endothermic curve was measured using a differential 
scanning calorimeter (DSC-3100, manufactured by Mac Science KK) under the 
following conditions and the inflection point was determined by 
extrapolation. 
______________________________________ 
Temperature 20 .degree. C. /min 
increase rate 
Sample 4 mg (crimper die) 
______________________________________ 
[Viscoelasticity] 
A constant temperature flow test was conducted using a Shimadzu Flow Tester 
(CFT-500, manufactured by Shimadzu Seisakusho) under the following 
measurement conditions and the viscoelasticity was determined from the 
flow value. 
______________________________________ 
High temperature measurement 
Die 0.5 mm.phi. .times. 10.0 mm 
Measurement temperature 
200.degree. C. 
Sample 1.0 g pellets 
Load 10 kg/cm.sup.2 
Low temperature measurement 
Die 1.0 mm.phi. .times. 1.0 mm 
Measurement temperature 
120.degree. C. 
Sample 1.0 g pellets 
Load 20 kg/cm.sup.2 
______________________________________ 
[Molecular Weight and Molecular Weight Distribution] 
The chromatogram determined by a gel permeation chromatograph (HLC-8020, 
manufactured by Tosoh Corporation) was calculated in terms of a 
calibration curve formed by a monodispersed polystyrene standard sample. 
______________________________________ 
Column TSK GEL G2000HLX, G3000HLX, G4000HLX 
Solvent tetrahydrofuran 
Column temperature 
40.degree. C. 
Flow rate 1.0 ml/min 
______________________________________ 
[Gel Proportion] 
A polyester resin with no crosslinking component as a monomer was used as a 
reference. The reference was dissolved in a tetrahydrofuran solvent to 
provide a 0.3% solution thereof and the area of the peak was determined by 
the gel permeation chromatography. Separately, a test sample was also 
adjusted to a 0.3% tetrahydrofuran solution for determination of the 
molecular weight and the resulting solution was filtered through a filter 
having a pore size of 0.45 .mu.m to remove the gel content. Thereafter, 
the peak area was determined by gel permeation chromatography. The peak 
areas of these two solutions were compared and calculated. 
According to the present invention, good fixability and void resistance 
during flash fixing can be achieved at the same time and the both toner 
and the toner binder are low in fixing odor.

The present invention will be described below in greater detail with 
reference to the examples but the present invention should not be 
construed as being limited thereto. 
EXAMPLES 
Example 1 
632 g (1.8 mol) of polyoxypropylene (2)-2,2-bis(4-hydroxyphenyl)propane, 
490 g (1.5 mol) of polyoxyethylene (2)-2,2-bis(4-hydroxyphenyl)propane, 
221 g (2.46 mol) of 1,3-butanediol, 108 g (0.12 mol) of Epicote 1001, 598 
g (3.6 mol) of terephthalic acid, 299 g (1.8 mol) of isophthalic acid, 
23.0 g (0.12 mol) of trimellitic acid anhydride and 2.3 g of di-n-butyl 
tin oxide were poured in a four-neck 3-liter flask made of glass and after 
furnishing the flask equiped with a thermometer, a stirrer, a flow 
down-type condenser and a nitrogen-introducing tube, the ingredients were 
reacted under a nitrogen stream at 220.degree. C. while stirring in an 
electrothermic mantle. When the temperature reached the softening point, 
namely, 118.degree. C., the condensation polymerization was terminated. 
The resulting polyester resin was a light yellow, transparent solid having 
the physical properties as shown in Table 2. 
92 parts by weight of the polyester obtained above as a binder resin, 5 
parts by weight of carbon black (Black Pearls L, produced by Cabot KK) as 
a coloring agent and 3 parts by weight of a nigrosine dye (Bontron N-04, 
produced by Orient Kagaku Kogyo KK) as an electrostatic charge controlling 
agent were mixed and melt-kneaded in a pressure kneader at 130.degree. C. 
for 30 minutes to obtain a toner lump. After cooling, the toner lump was 
finely ground using a Lawtoplex grinder and a jet mell (PJM Grinder, 
manufactured by Nippon Pneumatic Kogyo KK) and the crushed matter was 
classified by a pneumatic classifier (manufactured by Alpine KK) to obtain 
a positively chargeable toner having a particle size of from 5 to 20 
.mu.m. The manufacturability of the toner was good. 
Then, a developing agent consisting of 5 parts by weight of the toner and 
95 parts by weight of an irregular-shape iron powder TSSV100/200 (produced 
by Powdertec KK) as a carrier was prepared. 
In order to evaluate the flash fixability of the toner, a 1 inch.times.1 
inch solid image was printed using a laser printer (F-6715E, manufactured 
by Fujitsu KK) employing a flash fixing system and a tape peeling test was 
conducted thereon. The fixing device conditions were such that a 160 .mu.F 
condenser was used and the charging voltage of 2,050 V was applied to the 
flash lamp. The toner layer amount of the solid image on the recording 
medium was about 9 mg/cm.sup.2. The tape peeling test was conducted in 
such a manner that a pressure sensitive adhesive tape (Scotch Mending 
Tape, produced by Sumitomo 3M KK) was lightly affixed to the solid image 
portion, an iron-made cylindrical block having a diameter of 100 mm and a 
thickness of 20 mm was rolled at a constant speed in contact with the 
recording medium on the tape and then the tape was peeled off from the 
recording medium. As the index for fixability, excellency of the 
fixability was determined based on the ratio (percentage) of the optical 
image density (OD) after to before the peeling off of the tape. When the 
ratio is 95% or more, the fixability rated good. The result of the above 
evaluation on fixability was 96% as shown in Table 3 and good. 
The optical image density was then measured using a PCM Meter (manufactured 
by Macbeth KK). The result was 1.35 of OD as shown in Table 3 and good. 
The amount of void formed in the fixed image was determined as the ratio 
(covering ratio) of area where the toner was attached to the total area in 
a microphotograph of the fixed image, analyzed by an image analyzer (Ruzex 
2000, manufactured by Nireco KK), and the void resistance was rated good 
when the ratio was 90% or more. The result of the void resistance in this 
example was good and provided a covering ratio of 95% as shown in Table 3. 
The heat stability of the toner was evaluated by the weight of toner left 
after the removal of toners with a size 200 mesh (75 .mu.m) or less from 
the toner, which was taken out from a polyester-made bottle where 20 g of 
toner had been charged and exposed to the environment of 60.degree. C. and 
30% RH for 12 hours. When the toner weight left was 10 wt % or less, the 
heat stability rated good. 
In this example, the amount of the toner left on the mesh was 5 wt % and 
the heat stability was satisfactory. 
The fixing odor was evaluated, in a sensory manner, on the odor generated 
during a continuous printing test for 10 minutes. When 90% or more of 
panelists determined, the odor to be less odorous, the fixing odor rated 
good. In this example, all panelists found to be no problem with the odor. 
From the foregoing, it is understood that the toner and the toner binder in 
Example 1 had fixability and void resistance at extremely high levels and 
also that it was very satisfactory in physical properties such as storage 
stability. 
Example 2 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
the resulting toner had fixability and void resistance at extremely high 
levels such that the fixability according to the tape peeling test was 
100% and the covering ratio was 93% and the physical properties of the 
toner such as storage stability were very satisfactory. 
Example 3 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
the resulting toner had fixability and void resistance at extremely high 
levels such that the fixability according to the tape peeling test was 95% 
and the covering ratio was 92% and the physical properties of the toner 
such as storage stability were very satisfactory. 
Example 4 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
the resulting toner had fixability and void resistance at extremely high 
levels such that the fixability according to the tape peeling test was 
100% and the covering ratio was 88% and the physical properties of the 
toner such as storage stability were very satisfactory. 
Example 5 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
the resulting toner had fixability and void resistance at extremely high 
levels such that the fixability according to the tape peeling test was 90% 
and the covering ratio was 95% and the physical properties of the toner 
such as storage stability were very satisfactory. 
Example 6 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
the resulting toner had fixability and void resistance simultaneously at 
extremely high levels such that the fixability according to the tape 
peeling test was 98% and the covering ratio was 95% but the glass 
transition temperature of the toner was low as 55.degree. C. and, as a 
result, the toner could not be stored at a high temperature and thus the 
toner performance was slightly unsatisfactory in view of storage stability 
though it caused no problem in normal use. 
Example 7 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the covering ratio was 92%, the fixability was slightly 
unsatisfactory in performance at 82%. Also, the grinding efficiency in 
producing the toner was a little low. The present inventors assume that 
this phenomenon was caused by the use of a monomer component having no 
methyl side chain, the crystallinity of binder was increased and when the 
molecular weight was increased sufficiently high to provide the melt 
viscosity necessary to maintain the void resistance, the melting 
temperature rose to as high as 130.degree. C., therefore, the toner melted 
insufficiently during light irradiation on the surface where the lower 
portion of the toner powder image was in contact with the recording 
medium. 
Example 8 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the fixability was at a high level at 95%, the covering ratio 
stayed at about 50% due to generation of voids and therefore, the optical 
print density could be increased only to 1.10, failing to show 
satisfactory performance. The present inventors assume that this result 
was because, since crosslinking of the binder resin proceeded 
insufficiently, the melt viscosity at 200.degree. C. was as low as 65 
poises and the melt viscosity of toner was insufficient in comparison with 
the cohesion of toner at the time of melting for fixing of the toner, 
which results in the generation of voids. 
Example 9 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the fixability and the void resistance were in a good balance 
such that the fixability was 80% and the covering ratio was 70%, they were 
low and far from a satisfactory level. Also, there arose a problem of 
generation of an irritating fixing odor. 
Example 10 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the covering ratio was from 90 to 95%, the fixability was weak at 
60% or lower and also the fixing odor was increased as compared with that 
of Example 9. The present inventors assume that this result was because 
the crosslinking of the binder resin proceeded excessively to raise the 
melt viscosity at 120.degree. C. to 98,000 poises and as a result, the 
toner did not permeate sufficiently into the recording medium surface. In 
Examples 8 to 10, as the blending ratio of trimellitic acid anhydride was 
increased, the odor was markedly intensified and from this, it was 
confirmed that to suppress the amount of trimellitic acid anhydride to 3 
mol % or less was important in view of a reduction in fixing odor. 
Example 11 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the covering ratio was from 90 to 95%, the fixability was at an 
unsatisfactory level of 80%. Further, the fixing odor was remarkably 
increased as compared with that of Example 9 and thus the performance as a 
toner was insufficient. 
Example 12 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the fixability was at a high level as 95%, the covering ratio 
stayed low at about 30% and therefore, the performance as a toner was not 
satisfactory. The present inventors assume that this phenomenon was caused 
because the melt viscosity at 200.degree. C. was as low as 70 poises the 
same as the toner in Example 8 and accordingly, the melt viscosity of 
toner was insufficient in comparison with the cohesion of toner, which 
results in the generation of voids. 
Example 13 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the fixability and the void resistance was on a high level such 
that the fixability in tape peeling test was 92% and the covering ratio 
was 92%, the glass transition temperature of toner was as low as 
52.degree. C. and as a result thereof, the toner suffered from impractical 
performance in view of storage stability. 
Example 14 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the covering ratio was at a reasonable level at from 85 to 95%, 
the fixability was extremely low at 45% and the performance as a toner was 
not satisfactory. The present inventors assume that this phenomenon was 
affected by the absence of a soft segment having a methyl side chain in 
the molecular structure and also by the large molecular weight. 
Example 15 
A polyester resin was produced in the same manner as in Example 1 using the 
monomer blend shown in Table 1 and the polyester resin obtained had 
physical properties as shown in Table 2. The polyester resin was 
formulated into a toner in the same manner as in Example 1 and then 
subjected to the same evaluation as in Example 1. As seen from Table 3, 
although the fixability and the void resistance were in a good balance 
such that the fixability was 82% and the covering ratio was 74%, they were 
too low to be satisfactory. The present inventors assume that this was 
ascribable to the use of a monomer having a long side chain, however, the 
glass transition temperature was low for the binder having a high 
molecular weight and as a result, the storage stability was bad. Also, the 
binder generated an irritating fixing odor. 
As described in the foregoing, toners using each of binders prepared in 
Examples 1 to 7 which fulfill the constituent factors described in claim 1 
can show a performance favored with void resistance (covering ratio) and 
fixability at the same time. Further, the toners using each of binders 
prepared in Examples 1 to 5 which fulfill the constituent factors 
described in claims 1 to 3 can have both void resistance (covering ratio) 
and fixability at a higher level and also, show excellent performance with 
respect to storage stability, fixing odor and grinding efficiency in 
production. 
TABLE 1 
__________________________________________________________________________ 
Example 1 2 3 4 5 6 7 8 9 10 
11 12 
13 
14 
15 
__________________________________________________________________________ 
Bis-phenol A polypropylene 
30 
20 
12 
30 
30 
30 
40 
30 
30 
30 
-- 30 
20 
60 
70 
oxide 2-mol adduct 
Bis-phenol A polyethylene 
25 
26 
26 
25 
20 
25 
26 
25 
25 
30 
-- 24 
19 
40 
30 
oxide 
2-mol adduct 
Neopentyl glycol 
-- 
50 
-- 
-- 
-- 
-- 
-- 
-- 
-- 
-- 
100 
-- 
-- 
-- 
-- 
1,3-butanediol 
41 
-- 
-- 
43 
40 
41 
-- 
45 
45 
45 
-- 45 
45 
-- 
-- 
1,2-propylene glycol 
-- 
-- 
60 
-- 
-- 
-- 
-- 
-- 
-- 
-- 
-- -- 
-- 
-- 
-- 
1,4-butanediol 
-- 
-- 
-- 
-- 
-- 
-- 
30 
-- 
-- 
-- 
-- -- 
-- 
-- 
-- 
Epi-bis type epoxy 
2 2 1 0.7 
5 -- 
2 -- 
-- 
-- 
-- 0.5 
5 -- 
-- 
(Epicote 1001) 
Epi-bis type epoxy 
-- 
-- 
-- 
-- 
-- 
2 -- 
-- 
-- 
-- 
-- -- 
-- 
-- 
-- 
(Epicote 1007) 
Terephthalic acid 
60 
70 
65 
60 
60 
60 
60 
60 
60 
60 
45 63 
63 
85 
60 
Isophthalic acid 
30 
23 
25 
33 
28 
30 
30 
32 
25 
18 
45 30 
30 
-- 
-- 
Dodecenylsuccinic acid 
-- 
-- 
-- 
-- 
-- 
-- 
-- 
-- 
-- 
-- 
-- -- 
-- 
-- 
15 
Trimellitic acid anhydride 
2 1 2 0.5 
3 2 2 0.5 
3 10 
10 -- 
-- 
7 5 
__________________________________________________________________________ 
TABLE 2 
__________________________________________________________________________ 
Example 1 2 3 4 5 6 7 8 
__________________________________________________________________________ 
Melt viscosity 
52000 
48000 
42000 
37000 
64000 
49000 
65000 
25000 
(at 120 C.) 
Melt viscosity 
120 110 100 90 130 120 130 65 
(at 200 C.) 
Peak top 
5900 
11400 
6300 
13200 
5400 
5900 
12000 
21000 
molecular weight 
Number average 
molecular weight 
2500 
2800 
2700 
2900 
3200 
2400 
3000 
4200 
(Mn) 
Weight average 
molecular weight 
42500 
50400 
48600 
34700 
73600 
36000 
69000 
25200 
(Mw) 
Mw/Mn 17 18 18 12 23 15 23 6 
Glass transition 
point (Tg) 
66 69 67 71 66 56 81 75 
Melting point 
118 116 113 112 120 118 130 105 
(Tm) 
Acid value (Av) 
9 10 6 5 11 6 11 3 
Gel proportion 
0 0 0 0 0 0 0 0 
__________________________________________________________________________ 
Example 9 10 11 12 13 14 15 
__________________________________________________________________________ 
Melt viscosity 
61000 
98000 
72000 
28000 
6500 
67000 
63000 
(at 120.degree. C.) 
Melt viscosity 
160 330 140 70 130 140 100 
(at 200 C.) 
Peak top 21000 
21000 
23000 
14000 
4800 
21000 
14200 
molecular weight 
Number average 
4400 
4000 
4200 
3000 
2200 
4000 
3100 
molecular weight 
(Mn) 
Weight average 
88000 
124000 
138600 
27000 
44000 
124000 
65100 
molecular weight 
(Mw) 
Mw/Mn 20 31 33 9 20 31 21 
Glass transition 
75 67 65 67 55 67 57 
point (Tg) 
Melting point 
125 132 127 104 123 132 112 
(Tm) 
Acid value (Av) 
7 12 17 5 4 2 9 
Gel proportion 
0 7 4 0 0 6 0 
__________________________________________________________________________ 
TABLE 3 
__________________________________________________________________________ 
Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 
__________________________________________________________________________ 
Fixing ratio (%) 
96 100 
95 100 
90 98 88 95 80 60 or 
80 95 92 45 or 
82 
less 
Covering ratio 
95 93 92 88 95 95 92 50 70 90-95 
92 30 92 85-95 
74 
(void resistance) 
(%) 
Optical Image 
1.35 
1.30 
1.30 
1.30 
1.40 
1.30 
1.30 
1.10 
1.15 
1.25 
1.30 
0.33 
1.30 
1.25 
1.23 
density 
Storage stability 
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Grindability 
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Fixing odor 
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Evaluation 
__________________________________________________________________________ 
FIGS. 3, 4 and 5 each show the molecular weight distribution of the toner 
binder produced in Example 1, Example 8 or Example 13, respectively. In 
Example 1, trimellitic acid and an epi-bis type epoxy are used in 
combination as crosslinking agents, in Example 8, trimellitic acid only is 
used as a crosslinking agent and in Example 13, an epi-bis type epoxy only 
is used as a crosslinking agent. It can be seen from these figures that, 
by using a trimellitic acid and an epi-bis type epoxy in combination as 
crosslinking agents, the molecular weight distribution can be freely 
controlled.