U.S. patent number 3,893,934 [Application Number 05/336,158] was granted by the patent office on 1975-07-08 for solid developer for electrostatic latent images.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Robert A. Braun, Robert Mermelstein.
United States Patent |
3,893,934 |
Braun , et al. |
July 8, 1975 |
Solid developer for electrostatic latent images
Abstract
A finely-divided low melting toner comprising a colorant, a
thermoplastic resin comprising a vinyl resin, and at least one
arylsulfonamide formaldehyde adduct. Developer mixtures comprising
said toner electrostatically clinging to the surface of carrier
surfaces and processes of developing electrostatic latent images
therewith are also disclosed.
Inventors: |
Braun; Robert A. (Rochester,
NY), Mermelstein; Robert (Rochester, NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
|
Family
ID: |
23314839 |
Appl.
No.: |
05/336,158 |
Filed: |
February 26, 1973 |
Current U.S.
Class: |
430/108.5 |
Current CPC
Class: |
G03G
9/09775 (20130101) |
Current International
Class: |
G03G
9/097 (20060101); G03g 009/02 () |
Field of
Search: |
;252/62.1P
;260/3.8R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lovering; Richard D.
Claims
What is claimed is:
1. A solid electrostatographic developer material comprising
particles, said particles including finely-divided toner material
having a particle size of up to about 30 microns, a melting point
of at least about 110.degree.F, a melt viscosity of less than about
2.5 .times. 10.sup..sup.-4 poise at temperatures up to about
450.degree.F, said toner material comprising a colorant selected
from the group consisting of pigments, dyes, and mixtures thereof,
a thermoplastic resin consisting essentially of a vinyl polymer
having a melting point of at least about 110.degree.F, and from
about 5 percent to about 55 percent by weight, based on the weight
of said vinyl polymer, of an arylsulfonamide formaldehyde adduct
having a melting point between about 50.degree.F and about
250.degree.F and having the general structure ##SPC2##
wherein R.sub.1 and R.sub.2 are either hydrogen or methyl provided
that where R.sub.1 or R.sub.2 is methyl, the other is hydrogen.
2. A solid electrostatographic developer material according to
claim 1 wherein said vinyl polymer has a weight average molecular
weight between about 3,000 to about 500,000.
3. A solid electrostatographic developer material according to
claim 1 wherein said finely-divided toner particles contain at
least about 25 percent by weight, based on the total weight of said
thermoplastic resin in said toner, of a styrene resin.
4. A solid electrostatographic developer material according to
claim 1 wherein said arylsulfonamide formaldehyde adduct is
selected from the 2-methylbenzene sulfonamide formaldehyde adduct
and the 4-methylbenzene sulfonamide formaldehyde adduct.
5. A solid electrostatographic developer material according to
claim 1 wherein said colorant is present in an amount of from about
1 to about 20% by weight of said toner material.
6. A solid electrostatographic developer material according to
claim 1 wherein said resin is a copolymer of styrene and an alkyl
methacrylate.
7. A solid electrostatographic developer material according to
claim 1 wherein said finely-divided toner particles are
electrostatically coated on the surface of carrier particles having
an average particle diameter between about 50 to about 1,000
microns.
8. A solid electrostatographic developer material according to
claim 7 wherein said developer material comprises about 1 part by
weight of said finely-divided toner particles and from about 10 to
about 200 parts by weight of said carrier particles.
9. A solid electrostatographic developer material comprising
finely-divided toner particles electrostatically coated on a
carrier surface capable of retaining said toner particles by
electrostatic attraction, said toner particles having a particle
size range of up to about 30 microns, a blocking temperature of at
least about 110.degree.F, a melt viscosity less than about 2.5
.times. 10.sup..sup.-4 poise at temperatures up to about
450.degree.F, and comprising a colorant selected from the group
consisting of a pigment and a dye, a thermoplastic resin consisting
essentially of a vinyl polymer having a melting point at least
about 110.degree.F, and from about 5 percent to about 55 percent by
weight, based on the weight of said vinyl polymer, of an
arylsulfonamide formaldehyde adduct having a melting point between
about 50.degree.F and about 250.degree.f and having the general
structure ##SPC3##
wherein R.sub.1 and R.sub.2 are either hydrogen or methyl provided
that where R.sub.1 or R.sub.2 is methyl, the other is hydrogen.
10. A solid electrostatographic developer material comprising
carrier particles and toner particles, said toner particles having
a melting point of at least about 110.degree.F, said toner
particles comprising a colorant selected from the group consisting
of dyes, pigments, and mixtures thereof, a thermoplastic resin
consisting essentially of a vinyl polymer having a melting point of
at least about 110.degree.F, and from about 5 percent to about 55
percent by weight, based on the weight of said vinyl polymer, of an
arylsulfonamide formaldehyde adduct having a melting point between
about 50.degree.F and about 250.degree.F and having the general
structure ##SPC4##
wherein R.sub.1 and R.sub.2 are either hydrogen or methyl provided
that where R.sub.1 or R.sub.2 is methyl, the other is hydrogen.
Description
BACKGROUND OF THE INVENTION
This invention relates to imaging systems, and more particularly,
to improved electrostatographic developing materials, their
manufacture and use.
The formation and development of images on the surface of
photoconductor materials by electrostatic means is well known. The
basic xerographic process, as taught by C. F. Carlson in U.S. Pat.
No. 2,297,691, involves placing a uniform electrostatic charge on a
photoconductive insulating layer, exposing the layer to a light-and
shadow image to dissipate the charge on the areas of the layer
exposed to the light and developing the resulting electrostatic
latent image by depositing on the image a finely divided
electroscopic material referred to in the art as "toner." The toner
will normally be attracted to those areas of the layer which retain
a charge, thereby forming a toner image corresponding to the
electrostatic latent image. This powder image may then be
transferred to a support surface such as paper. The transferred
image may subsequently be permanently affixed to the support
surface as by heat. Instead of latent image formation by uniformly
charging the photoconductive layer and then exposing the layer to a
light-and-shadow image, one may form the latent image by directly
charging the layer in image configuration. The powder image may be
fixed to the photoconductive layer if elimination of the powder
image transfer step is desired. Other suitable fixing means such as
solvent or overcoating treatment may be substituted for the
foregoing heat fixing steps.
Several methods are known for applying the electroscopic particles
to the electrostatic latent image to be developed. One development
method, as disclosed by E. N. Wise in U.S. Pat. No. 2,618,552, is
known as "cascade" development. In this method, a developer
material comprising relatively large carrier particles having
finely divided toner particles electrostatically coated thereon is
conveyed to and rolled or cascaded across the electrostatic latent
image bearing surface. The composition of the carrier particles is
so selected as to triboelectrically charge the toner particles to
the desired polarity. As the mixture cascades or rolls across the
image bearing surface, the toner particles are electrostatically
deposited and secured to the charged portion of the latent image
and are not deposited on the uncharged or background portions of
the image. Most of the toner particles accidentally deposited in
the background are removed by the rolling carrier, due apparently,
to the greater electrostatic attraction between the toner and the
carrier than between the toner and the discharged background. The
carrier and excess toner are then recycled. This technique is
extremely good for the development of line copy images.
Another method of developing electrostatic images is the "magnetic
brush" process as disclosed, for example, in U.S. Pat. No.
2,874,063. In this method, a developer material containing toner
and magnetic carrier particles are carried by a magnet. The
magnetic field of the magnet causes alignment of the magnetic
carrier into a brush-like configuration. This magnetic brush is
engaged with the electrostatic image-bearing surface and the toner
particles are drawn from the brush to the latent image
electrostatic attraction.
Still another technique for developing electrostatic latent images
is the "powder cloud" process as disclosed, for example, by C. F.
Carlson in U.S. Pat. No. 2,221,776. In this method a developer
material comprising electrically charged toner particles in a
gaseous fluid is passed adjacent the surface bearing the
electrostatic latent image. The toner particles are drawn by
electrostatic attraction from the gas to the latent image. This
process is particularly useful in continuous tone development.
Other development methods such as "touchdown" development, as
disclosed by R. W. Gundlach in U.S. Pat. No. 3,166,432, may be used
where suitable.
The developed image can then be read or permanently affixed to the
imaging surface of the photoconductive substrate if this imaging
surface is not to be reused. In the event that the imaging surface
is of a reusable material and is to be used in preparation of
subsequent electrostatographic copies, the developed image can be
transferred to another substrate, such as paper, and then
permanently affixed thereto. Various techniques have been devised
to permanently affix this toner image to its substrate including
overcoating the toner image with a transparent film, and solvent or
thermal fusion of the toner particles to the substrate material.
The energy requirements involved in thermal fixation of the toner
are considerable since these thermoplastic toner materials often
require temperatures in the range of 350.degree.-400.degree.F and
higher to fuse them to the substrate. Thus, a substantial reduction
in the fusion temperatures of the toner would result in a
corresponding reduction in energy requirements of such an imaging
process. Any reduction in the fusion temperature of the toner would
also permit lowering the operating temperatures within the copier
and, therefore, reduce the demands placed upon the temperature
control unit within such an apparatus.
Although some of the foregoing development techniques are employed
commercially today, the most widely used commercial
electrostatographic development technique is the technique known as
cascade development. A general purpose office copying machine
incorporating this development process is described in U.S. Pat.
No. 3,099,943. The cascade technique is generally carried out in a
commercial apparatus by cascading a developer mixture over the
upper surface of an electrostatic latent image-bearing drum having
a horizontal axis. The developer is transported from a trough or
sump to the upper portion of the drum by means of an endless belt
conveyor. The developer is cascaded downward along a portion of the
surface of the drum into the sump and is subsequently recycled
through the developing system to develop additional electrostatic
latent images. Small quantities of toner are periodically added to
the developing mixture to compensate for the toner depleted by
development. This process is then repeated for each copy produced
by the machine and is ordinarily repeated many thousands of times
during the usable life of the developer.
Thus, it is apparent from the description presented above, as well
as in other development techniques, that the toner is subjected to
mechanical attrition which tends to break down the particles into
undesirable dust fines. Toner fines are detrimental to machine
operation because they are extremely difficult to remove from
reusable imaging surfaces and also because they tend to drift to
other parts of the machine and deposit on critical machine parts
such as optical lenses. The formation of fines is retarded when the
toner contains a tough, high molecular weight resin which is
capable of withstanding the shear and impact forces imparted to the
toner in the machine. Unfortunately, many high molecular weight
materials cannot be employed in high speed automatic machines
because they cannot be rapidly fused during a powder image heat
fixing step. Attempts to rapidly fuse a high melting point toner by
means of oversized high capacity heating units have been confronted
with the problems of preventing the charring of paper receiving
sheets and of adequately dissipating the heat evolved from the
fusing unit or units. Thus, in order to avoid charring or
combustion, additional equipment such as complex and expensive
cooling units are necessary to properly dispose of the large
quantity of heat generated by the fuser. Incomplete removal of the
heat evolved will result in operator discomfort and damage to
heat-sensitive machine components. Further, the increased space
occupied by and the high operating cost of the heating and cooling
units, often outweigh the advantages achieved by the increased
machine speed. On the other hand, low molecular weight resins which
are easily heat fused at relatively low temperatures are often
undesirable because these materials tend to form thick films on
reusable photoconductor surfaces. These films tend to cause image
degradation and contribute to machine maintenance down time. In
addition, low molecular weight resins tend to form tacky images on
the copy sheet which often offset to other adjacent sheets.
Further, toner particles containing low molecular weight resins
tend to bridge, cake, and block in the shipping container as well
as in the xerographic machine. Also, the toner material must be
capable of accepting a charge of the correct polarity when brought
into rubbing contact with the surface of carrier materials in
cascade, magnetic brush or touch-down development systems. Some
resinous materials which possess many properties which would be
desirable in xerographic toners dispense poorly and cannot be used
in automatic copying and duplicating machines. Other resins
dispense well but form images which are characterized by low
density, poor resolution, or high background. Further, some resins
are unsuitable for processes where electrostatic transfer is
employed. Many thermoplastic materials, such as those presently in
use in electrostatographic toners, have traditionally been
difficult to mold or form because of unfavorable rheological
properties. Probably the most widely accepted technique for
modification of these thermoplastics to facilitate forming of such
materials had been the inclusion of certain additives in said
materials designed to reduce their melt viscosity. These additives,
generally referred to in the art as "plasticizers", include
non-volatile organic liquids or low melting solids, e.g. phthalate,
adipate and sebacate esters and aryl phosphate esters.
The interaction of the plasticizer and the resin in the melt
results in a marked improvement in the composition's rheological
properties by affecting a shift in both the glass transition
temperature and fusion points of the composition to lower
temperatures. This shift in the glass transition temperature of the
thermoplastic materials used as electrostatographic toners, is
substantial, can cause these discrete, finely-divided toner
particles to form larger agglomerates. This agglomeration, more
commonly referred to in the electrostatographic art as "blocking",
adversely affects the free flow characteristics of the toner. For
example, in cascade-type development systems, the momentum of these
larger toner particles as they tumble over the imaging member can
exceed the attractive forces of the latent image and, therefore,
result in failure of development of the latent image by these
larger toner particles. Since most thermoplastic materials are
deficient in one or more of the above areas, there is continuing
need for improved toners and developers.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to provide a toner
overcoming the above noted deficiencies.
It is another object of this invention to provide a toner which is
resistant to film formation when employed in conventional
xerographic copying and duplicating devices.
It is another object of this invention to provide a xerographic
toner which forms images having reduced background.
It is another object of this invention to provide a free flowing
toner which is resistant to agglomeration.
It is another object of this invention to provide a xerographic
toner which can be fused at higher rates with less heat energy.
It is another object of this invention to provide a xerographic
toner which forms high resolution images.
It is another object of this invention to provide a xerographic
toner which is resistant to mechanical attrition during the
development process.
It is another object of this invention to provide a xerographic
toner having improved dispensing characteristics.
It is another object of this invention to provide a modified toner
composition which has a fusion temperature substantially less than
that of its unmodified counterpart and which yet remains relatively
unchanged with respect to its glass transition temperature.
It is another object of this invention to provide improved imaging
processes employing one of the modified toner compositions of this
invention.
It is another object of this invention to provide a toner and
developer having physical and chemical properties superior to those
of known toners and developers.
The above objects and others are accomplished by providing a
finely-divided low melting toner comprising a colorant, a
thermoplastic resin comprising a vinyl resin, and at least one
arylsulfonamide formaldehyde adduct having the general structure
##SPC1##
wherein R.sub.1 and R.sub.2 are either hydrogen or methyl provided
that where R.sub.1 or R.sub.2 is methyl, the other is hydrogen.
This invention also embraces imaging processes in which said
improved toner compositions are employed and a method for the
reduction of the fusion temperature of thermoplastic materials,
while at the same time having such materials remain relatively
unchanged with respect to their glass transition temperature.
For optimum operation in high speed electrostatographic machines
employing paper receiving webs, the toner should have a melting
range between about 110.degree.F to about 300.degree.F and a melt
viscosity of less than about 2.0 .times. 10.sup..sup.-4 poise up to
temperatures of about 300.degree.F. Toner melting temperatures
below about 300.degree.F are preferred because heat dissipation and
paper degradation problems are avoided. The developers of this
invention containing said improved toner compositions are
characterized by outstanding fusing rates, high cleanability from
electrostatic imaging surfaces, greater triboelectric stability,
denser toner images, and increased resistance to mechanical
attrition. Unexpectedly, both the fire hazard and excessive power
consumption problems encountered in high speed electrostatographic
development processes are obviated when toners containing the
above-described arylsulfonamide formaldehyde adducts are
employed.
Any suitable vinyl resin having a melting point of at least about
110.degree.F may be employed in the toners of this invention. The
vinyl resin may be a homopolymer or a copolymer of two or more
vinyl monomers. Typical monomeric units which may be employed to
form vinyl polymers include: styrene, p-chlorostyrene; vinyl
naphthalene; ethylenically unsaturated mono-olefins such as
ethylene, propylene, butylene, isobutylene and the like; vinyl
esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl
acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and the
like; esters of alphamethylene aliphatic monocarboxylic acids such
as methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl
acrylate, dodecyl acrylate, n-octyl acrylate, 2 chloroethyl
acrylate, phenyl acrylate, methyl-alpha-chloroacrylate, methyl
methacrylate, ethyl methacrylate, butyl methacrylate and the like;
acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as
vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, and
the like; vinyl ketones such as vinyl methyl ketone, vinyl hexyl
ketone, methyl isopropenyl ketone and the like; vinylidene halides
such as vinylidene chloride, vinylidene chlorofluoride and the
like; and N-vinyl compounds such as N-vinyl pyrrole, N-vinyl
carbazole, N-vinyl indole, N-vinyl pyrrolidene and the like, and
mixtures thereof. Generally, suitable vinyl resins employed in the
toner have a weight average molecular weight between about 3,000 to
about 500,000.
Toner resins containing relatively high percentages of a styrene
resin are preferred. The presence of a styrene resin is preferred
because a greater degree of image definition is achieved with a
given quantity of adduct material. Further, denser images are
obtained when at least about 25 percent by weight, based on the
total weight of resin in the toner, of a styrene resin is present
in the toner. The styrene resin may be a homopolymer of styrene or
styrene homologues or copolymers of styrene with other monomeric
groups containing a single methylene group attached to a carbon
atom by a double bond. Thus, typical monometric materials which may
be copolymerized with styrene by addition polymerization include:
p-chlorostyrene; vinyl naphthalene; ethylenically unsaturated
mono-olefins such as ethylene, propylene, butylene, isobutylene and
the like; vinyl esters such as vinyl chloride, vinyl bromide, vinyl
fluoride vinyl acetate, vinyl propionate, vinyl benzoate, vinyl
butyrate and the like; esters of alpha-methylene aliphatic
monocarboxylic acids such as methyl acrylate, ethyl acrylate,
n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl
acrylate, 2-chloroethyl acrylate, phenyl acrylate,
methyl-alpha-chloroacrylate methyl methacrylate, ethyl
methacrylate, butyl methacrylate and the like; acrylonitrile,
methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl
ether, vinyl isobutyl ether, vinyl ethyl ether, and the like, vinyl
ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl
isopropenyl ketone and the like; vinylidene halides such as
vinylidene chloride, vinylidene chlorofluoride and the like; and
N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole,
N-vinyl indole, N-vinyl pyrrolidene and the like; and mixtures
thereof. The styrene resins may also be formed by the
polymerization of mixtures of two or more of these unsaturated
monomeric materials with a styrene monomer. The expression
"addition polymerization" is intended to include known
polymerization techniques such as free radical, anionic and
cationic polymerization processes.
The vinyl resins, including styrene type resins, may also be
blended with one or more other resins if desired. When the vinyl
resin is blended with another resin, the added resin is preferably
another vinyl resin because the resulting blend is characterized by
especially good triboelectric stability and uniform resistance
against physical degradation. The vinyl resins employed for
blending with the styrene type or other vinyl resin may be prepared
by the addition polymerization of any suitable vinyl monomer such
as the vinyl monomers described above. Other thermoplastic resins
may also be blended with the vinyl resins of this invention.
Typical non-vinyl type thermoplastic resins include: rosin modified
phenol formaldehyde resins, oil modified epoxy resins, polyurethane
resins, cellulosic resins, polyether resins and mixtures thereof.
When the resin component of the toner contains styrene
copolymerized with another unsaturated monomer or a blend of
polystyrene and another resin, a styrene component of at least
about 25 percent by weight based on the total weight of the resin
present in the toner is preferred because denser images are
obtained and a greater degree of image definition is achieved with
a given quantity of adduct material.
The combination of the resin component, colorant, and adduct,
whether the resin component is a homopolymer, copolymer, or blend,
should have a blocking temperature of at least about 110.degree.F
and a melt viscosity of less than about 2.5 .times. 10.sup..sup.-4
poise temperatures up to about 450.degree.F. When the toner is
characterized by a blocking temperature less than about
110.degree.F, the toner particles tend to agglomerate during
storage and machine operation and also form undesirable films on
the surface of reusable photo-receptors which adversely affect
image quality. If the melt viscosity of the toner is greater than
about 2.5 .times. 10.sup..sup.-4 poise at temperatures above about
450.degree.F, the toner material of this invention generally does
not adhere properly to a receiving sheet even under conventional
electrostatographic machine fusing conditions and may easily be
removed by rubbing.
The arylsulfonamide formaldehyde adducts in the preferred
embodiments of this invention may be selected from the
2-methylbenzene sulfonamide formaldehyde adduct, the
4-methylbenzene sulfonamide formaldehyde adduct, and mixtures
thereof. In addition, suitable sulfonamide formaldehyde adducts may
be derived from N-cyclohexyl p-toluene sulfonamide, N-ethyl
p-toluene sulfonamide, o-toluene sulfonamide, p-toluene
sulfonamide, N,N-di-p-hydroxyethyl-p-toluene sulfonamide,
N,N-dimethyl benzene sulfonamide, N-cyclohexyl benzene sulfonamide,
N-cyclohexyl-3,4-dichlorobenzene sulfonamide, N-allyl p-toluene
sulfonamide, N,N-di-p-hydroxyethyl p-toluene sulfonamide,
N-cyclohexyl p-toluene sulfonamide and the like. These adducts are
formed by condensation of arylsulfonamides with formaldehyde and
generally have a melting point between about 50.degree.F and about
250.degree.F. Some of these adducts are sold under the "Santolite"
trademark by the Monsanto Company, St. Louis, Missouri, for
example, Santolite MHP and Santolite MS-80%. Generally, the adduct
is employed in an amount from about 5 percent to about 55 percent
by weight based on the total weight of the resinous component of
the toner. Preferably, the adduct is employed in an amount from
about 10 percent to about 40 percent by weight based on the total
weight of the resinous component of the toner because as the
relative quantity of adduct in the toner is increased above about
60 percent, the mechanical strength, creep resistance, and
permanency of the ultimate fused toner image begins to decrease
rapidly. Thus, when brittle, non-polymeric compounds such as
compounds disclosed in U.S. Pat. No. 3,272,644 are employed in
automatic copying and duplicating machines, extensive toner dust is
formed and the fused toner images tend to crumble and flake off
receiving sheets when the sheets are folded. Further, some solid
non-polymeric materials tend to vaporize or sublime and form toxic
or flammable fumes. When less than about 3 percent of the adduct is
employed in the toner, the toner fusing, flow, and triboelectric
properties are substantially the same as a toner which does not
contain the adduct. If desired, mixtures of adduct may be employed
in the toner. An increase in the relative quantity of adduct tends
to reduce the melt viscosity of the ultimate toner. It has been
found that the fusing point of toner composition is generally
correlative with the melt viscosity of polymer-toner compositions.
In accordance with this invention, the melt viscosity of a
polymer-toner composition may be lowered by the addition of a
relatively low melting arylsulfonamide formaldehyde adduct thereto
wherein said adduct does not significantly affect the glass
transition temperature of the polymer-toner composition and hence
the blocking temperature of the toner is not influenced. Thus, due
to the substantial reduction in the fusion temperature of the toner
compositions of this invention, imaging processes employing said
toner compositions will have markedly reduced energy requirements
with respect to the thermal fixation of developed toner images. In
addition, the maintenance of relatively constant glass transition
temperatures in said toner compositions also prevents agglomeration
or "blocking" of the discrete, finely-divided toner particles in
developer reservoirs. Although Applicant does not wish to be bound
by any theory for the unexpected findings of this invention, it is
hypothesized that that there may be two possible mechanisms for the
results discovered. It is initially envisioned that the
arylsulfonamide formaldehyde adduct functions as a solvent for the
polymer-toner in the liquid state at elevated temperature but not
in the solid state at ambient temperature. Alternatively, the
adduct above its melting point and above the glass transition
temperature of the toner resin permits sufficient deformation of
the polymer to permit fixation at lower temperatures.
It is to be understood that the specific formulas given for the
units contained in the adducts and resins of this invention
represent the vast majority of the units present, but do not
exclude the presence of other monomeric units or reactants than
those which have been shown. For example, some commercial materials
such as polystyrenes, and polychlorinated polyphenyl compounds
contain trace amounts of homologues or unreacted or partially
reacted monomers. Any minor amount of such substituents may be
present in the materials of this invention.
Any suitable pigment of dye may be employed as the colorant for the
toner particles. Toner colorants are well known and include, for
example, carbon black, nigrosine dye, aniline blue, Calco Oil Blue,
chrome yellow, ultra marine blue, duPont Oil Red, Quinoline Yellow,
methylene blue chloride, phthalocyanine blue, Malachite Green
Oxalate, lamp black, Rose Bengal and mixtures thereof. The pigment
or dyes should be present in the toner in a sufficient quantity to
render it highly colored so that it will form a clearly visible
image on a recording member. Thus, for example, where conventional
electrostatographic copies of typed documents are desired, the
toner may comprise a black pigment such as carbon black or a black
dye such as Amaplast Black dye, available from the National Aniline
Products, Inc. Generally, the pigment is employed in an amount from
about 1 percent to about 20 percent by weight based on the total
weight of the colored toner. If the toner colorant employed is a
dye, substantially smaller quantities of colorant may be used.
However, since a number of the above pigments used in
electrostatographic toner compositions may affect both the glass
transition and fusion temperatures of the toner compositions of
this invention, their concentration preferably should not exceed
about 10 percent by weight of the colored toner.
The toner compositions of the present invention may be prepared by
any well-known toner mixing and comminution technique. For example,
the ingredients may be thoroughly mixed by blending, mixing and
milling the components and thereafter micropulverizing the
resulting mixture. Another well-known technique for forming toner
particles is to spray-dry a ball-milled toner composition
comprising a colorant, a resin, and a solvent.
Generally, the degree of quality of toner fix at a given fuser
temperature decreases with an increase in toner melt viscosity. As
discussed above, if the melt viscosity of the toners of this
invention is greater than about 2.5 .times. 10.sup..sup.-4 poise at
temperatures above about 450.degree.F, the toner materials do not
adhere properly to a receiving sheet even under conventional
electrostatographic machine fusing conditions. Thus, the melt
viscosity value of the toners of this invention aids in the
determination of the degree of flow and penetration of the toner
into the surface of a receiving substrate such as paper during the
heat fixing step. The expression "melt viscosity", as employed
herein, is a measure of the ratio of shear stress to shear rate in
poise at a given temperature. All viscosity measurements are
determined using a Ferronti-Shirley Cone Anol Plate Viscometer.
When the toner mixtures of this invention are to be employed in a
cascade development process, the toner should have an average
particle size less than about 30 microns and preferably between 4
and about 20 microns for optimum results. For use in powder cloud
development methods, particle diameters of slightly less than 1
micron are preferred.
Suitable coated and uncoated carrier materials for cascade
development are well known in the art. The carrier particles
comprise any suitable solid material, provided that the carrier
particles acquire a charge having an opposite polarity to that of
the toner particles when brought in close contact with the toner
particles so that the toner particles adhere to and surround the
carrier particles. When a positive reproduction of the
electrostatic images is desired, the carrier particle is selected
so that the toner particles acquire a charge having a polarity
opposite to that of the electrostatic image. Alternatively, if a
reversal reproduction of the electrostatic image is desired, the
carrier is selected so that the toner particles acquire a charge
having the same polarity as that of the electrostatic image. Thus,
the materials for the carrier particles are selected in accordance
with their triboelectric properties in respect to the electroscopic
toner so that when mixed or brought into mutual contact, one
component of the developer is charged positively if the other
component is below the first component in the triboelectric series
and negatively if the other component is above the first component
in a triboelectric series. By proper selection of materials in
accordance with their triboelectric effects, the polarities of
their charge, when mixed, are such that the electroscopic toner
particles adhere to and are coated on the surfaces of carrier
particles and also adhere to that portion of the electrostatic
image-bearing surface having a greater attraction for the toner
than the carrier particles. Typical carriers include sodium
chloride, ammonium chloride, aluminum potassium chloride, Rochelle
salt, sodium nitrate, aluminum nitrate, potassium chlorate,
granular zircon, granular silicon, methyl methacrylate, glass,
silicon dioxide, nickel, steel, iron, ferrites, and the like. The
carriers may be employed with or without a coating. Many of the
foregoing and other typical carriers are described by L. E. Walkup
et al. in U.S. Pat. No. 2,638,416 and E. N. Wise in U.S. Pat. No.
2,618,552. An ultimate coated carrier particle diameter between
about 50 microns to about 1,000 microns is preferred because the
carrier particles then possess sufficient density and inertia to
avoid adherence to the electrostatic images during the cascade
development process. Adherence of carrier beads to
electrostatographic drums is undesirable because of the formation
of deep scratches on the surface during the imaging transfer and
drum cleaning steps, particularly where cleaning is accomplished by
a web cleaner such as the web disclosed by W. P. Graff, Jr., et al
in U.S. Pat. No. 3,186,838. Also print deletion occurs when carrier
beads adhere to electrostatographic imaging surfaces. Generally
speaking, satisfactory results are obtained when about 1 part toner
is used with about 10 to 200 parts by weight of carrier.
The toner compositions of the instant invention may be employed to
develop electrostatic latent images on any suitable electrostatic
latent image-bearing surface including conventional photoconductive
surfaces. Well-known photoconductive materials include vitreous
selenium, organic or inorganic photoconductors embedded in a
non-photoconductive matrix, organic or inorganic photoconductors
embedded in a photoconductive matrix, or the like. Representative
patents in which photoconductive materials are disclosed include
U.S. Pat. No. 2,803,542 to Ullrich, U.S. Pat. No. 2,970,906 to
Bixby, U.S. Pat. No. 3,121,006 to Middleton, U.S. Pat. No.
3,121,007 to Middleton, and U.S. Pat. No. 3,151,982 to Corrsin.
DESCRIPTION OF PREFERRED EMBODIMENTS
The following examples further define, describe, and compare
methods of preparing the toner materials of the present invention
and of utilizing them to develop electrostatic latent images. Parts
and percentages are by weight unless otherwise indicated.
EXAMPLE I
A control sample of about 1 part of a conventional toner
composition comprising a mixture of styrene/n-butyl methacrylate
copolymer, polyvinyl butyral, and carbon black as the colorant as
disclosed in U.S. Pat. No. 3,079,342 is mixed with about 99 parts
by weight of coated carrier beads as disclosed in U.S. Pat. No.
3,526,533 to form a developer mixture. The toner has a blocking
temperature of about 130.degree.F. Copies of a standard test
pattern are made with the developer mixture in a modified Xerox
3600-III copying machine which are then passed through a standard
Xerox 4000 fuser unit mounted externally to the Xerox 3600 -III
machine. The fuser temperature is regulated with a proportional
temperature controller and is monitored by means of a thermocouple
wherein the fuser temperature is varied in 10.degree.F increments
to determine the fix temperature for minimum acceptable fix and hot
offset. The minimum fix level is established at 10 .+-. 2 "Taber
Cycles". The term Taber Cycles represents the degree of fix
obtained using a test method based on the resistance of a fixed
toner image to abrasion with a Taber Abrader, Model 174, available
from Welch Scientific Co. After passage through the fuser, the copy
sheets are mounted on a specimen card having a diameter of about
4.25 inches and abraded using a standard CS-10 test wheel. The
number of cycles required to result in about a 20 percent decrease
in image density is recorded. A minimum fuser temperature is
established when about a 20 percent decrease in image density is
observed. Generally, an abrasion run of 10 .+-. 2 revolutions of
the abrading wheel constitutes acceptable fusing. The minimum fuser
temperature at which legible copies are obtained with this toner is
found to be about 380.degree.F. The maximum fuser temperature at
which hot offset to the fuser roll occurs is found to be about
430.degree.F.
EXAMPLE II
A toner composition is prepared comprising about 81 parts by weight
of a copolymer of about 65 parts by weight of styrene and 35 parts
by weight of butyl methacrylate, about 9 parts by weight of carbon
black (Neo Spectra Mark II, available from Columbian Carbon Co.),
and about 10 parts by weight of arylsulfonamide formaldehyde adduct
(Santolite MHP, available from Monsanto Co.). After melting and
preliminary mixing, the toner composition is fed to a rubber mill
and thoroughly milled to yield a uniformly dispersed composition of
the carbon black in the resin body. The resulting mixture is then
cooled and finely subdivided in a jet pulverizer to yield toner
particles having an average particle size ranging between about 10
to about 20 microns. The toner has a blocking temperature of about
130.degree.F. About 1 part of the pulverized toner particles are
mixed with about 99 parts by weight of the carrier beads of Example
I and substituted for the developer in the testing machine
described in Example I. Under substantially identical test
conditions, it is found that the minimum fuser temperature at which
legible copies are obtained with this toner is about 325.degree.F.
The maximum fuser temperature at which hot offset to the fuser roll
occurs is found to be about 410.degree.F. These results clearly
indicate that this toner enables a reduction of about 55.degree.F
from the fuser temperature required for the control sample of
Example I. The toner dispenses well and high resolution images
substantially free from background are obtained.
EXAMPLE III
A toner composition is prepared comprising about 71 parts by weight
of a copolymer of about 65 parts by weight of styrene and 35 parts
by weight of butyl methacrylate, about 9 parts by weight of carbon
black (Neo Spectra Mark II, available from Columbian Carbon Co.),
and about 20 parts by weight of arylsulfonamide formaldehyde adduct
(Santolite MHP, available from Monsanto Co.). After melting and
preliminary mixing, the toner composition is fed to a rubber mill
and thoroughly milled to yield a uniformly dispersed composition of
the carbon black in the resin body. The resulting mixture is then
cooled and finely subdivided in a jet pulverizer to yield toner
particles having an average particle size ranging between about 10
to about 20 microns. The toner has a blocking temperature of about
130.degree.F. About 1 part of the pulverized toner particles are
mixed with about 99 parts by weight of the carrier beads of Example
I and substituted for the developer in the testing machine
described in Example I. Under substantially identical test
conditions, it is found that the minimum fuser temperature at which
legible copies are obtained with this toner is about 315.degree.F.
The maximum fuser temperature at which hot offset to the fuser roll
occurs is found to be about 410.degree.F. These results clearly
indicate that this toner enables a reduction of about 65.degree.F
from the fuser temperature required for the control sample of
Example I. The toner dispenses well and high resolution images
substantially free from background are obtained.
EXAMPLE IV
A toner composition is prepared comprising about 61 parts by weight
of a copolymer of about 65 parts by weight of styrene and 35 parts
by weight of butyl methacrylate, about 9 parts by weight of carbon
black (Neo Spectra Mark II, available from Columbian Carbon Co.),
and about 30 parts by weight of arylsulfonamide formaldehyde adduct
(Santolite MHP, available from Monsanto Co.). After melting and
preliminary mixing, the toner composition is fed to a rubber mill
and thoroughly milled to yield a uniformly dispersed composition of
the carbon black in the resin body. The resulting mixture is then
cooled and finely subdivided in a jet pulverizer to yield toner
particles having an average particle size ranging between about 10
to about 20 microns. The toner has a blocking temperature of about
130.degree.F. About 1 part of the pulverized toner particles are
mixed with about 99 parts by weight of the carrier beads of Example
I and substituted for the developer in the testing machine
described in Example I. Under substantially identical test
conditions, it is found that the minimum fuser temperature at which
legible copies are obtained with this toner is about 310.degree.F.
The maximum fuser temperature at which hot offset to the fuser roll
occurs is found to be about 405.degree.F. These results clearly
indicate that this toner enables a reduction of about 70.degree.F
from the fuser temperature required for the control sample of
Example I. The toner dispenses well and high resolution images
substantially free from background are obtained.
EXAMPLE V
A toner composition is prepared comprising about 51 parts by weight
of a copolymer of about 65 parts by weight of styrene and 35 parts
by weight of butyl methacrylate, about 9 parts by weight of carbon
black (Neo Spectra Mark II, available from Columbian Carbon Co.),
and about 40 parts by weight of arylsulfonamide formaldehyde adduct
(Santolite MHP, available from Monsanto Co.). After melting and
preliminary mixing, the toner composition is fed to a rubber mill
and thoroughly milled to yield a uniformly dispersed composition of
the carbon black in the resin body. The resulting mixture is then
cooled and finely subdivided in a jet pulverizer to yield toner
particles having an average particle size ranging between about 10
to about 20 microns. The toner has a blocking temperature of about
130.degree.F. About 1 part of the pulverized toner particles are
mixed with about 99 parts by weight of the carrier beads of Example
1 and substituted for the developer in the testing machine
described in Example I. Under substantially identical test
conditions, it is found that the minimum fuser temperature at which
legible copies are obtained with this toner is about 300.degree.F.
The maximum fuser temperature at which hot offset to the fuser roll
occurs is found to be about 390.degree.F. These results clearly
indicate that this toner enables a reduction of about 80.degree.F
from the fuser temperature required for the control sample of
Example I. The toner dispenses well and high resolution images
substantially free from background are obtained.
EXAMPLE VI
A control toner composition is prepared comprising about 91 parts
by weight of a copolymer of about 80 parts by weight of styrene and
20 parts by weight of isobutyl methacrylate and about 9 parts by
weight of carbon black (Black Pearls L, available from Cabot Corp.,
Boston Mass.) After melting and preliminary mixing, the toner
composition is fed to a rubber mill and thoroughly milled to yield
a uniformly dispersed composition of the carbon black in the resin
body. The resulting mixture is then cooled and finely subdivided in
a jet pulverizer to yield toner particles having an average
particle size ranging between about 10 to about 20 microns. The
toner has a blocking temperature of about 140.degree.F. About 1
part of the pulverized toner particles are mixed with about 99
parts by weight of the carrier beads of Example I and substituted
for the developer in the testing machine described in Example I.
Under substantially identical test conditions, it is found that the
minimum fuser temperature at which legible copies are obtained with
this toner is about 400.degree.F. The maximum fuser temperature at
which hot offset to the fuser roll occurs is found to be about
460.degree.F.
EXAMPLE VII
A toner composition is prepared comprising about 81 parts by weight
of a copolymer of about 80 parts by weight of styrene and 20 parts
by weight of isobutyl methacrylate, about 9 parts by weight of
carbon black (Black Pearls L, available from Cabot Corp, Boston,
Mass.), and about 10 parts by weight of arylsulfonamide
formaldehyde adduct (Santolite MHP, available from Monsanto Co.).
After melting and preliminary mixing, the toner composition is fed
to a rubber mill and thoroughly milled to yield a uniformly
dispersed composition of the carbon black in the resin body. The
resulting mixture is then cooled and finely subdivided in a jet
pulverizer to yield toner particles having an average particle size
ranging between about 10 to about 20 microns. The toner has a
blocking temperature of about 140.degree.F. About 1 part of the
pulverized toner particles are mixed with about 99 parts by weight
of the carrier beads of Example I and substituted for the developer
in the testing machine described in Example I. Under substantially
identical test conditions, it is found that the minimum fuser
temperature at which legible copies are obtained with this toner is
about 340.degree.F. The maximum fuser temperature at which hot
offset to the fuser roll occurs is found to be about 430.degree.F.
These results clearly indicate that this toner enables a reduction
of about 60.degree.F from the fuser temperature required for the
control sample of Example VI. The toner dispenses well and high
resolution images substantially free from background are
obtained.
EXAMPLE VIII
A toner composition is prepared comprising about 71 parts by weight
of a copolymer of about 80 parts by weight of styrene and 20 parts
by weight of isobutyl methacrylate, about 9 parts by weight of
carbon black (Black Pearls L, available from Cabot Corp., Boston
Mass.), and about 20 parts by weight of arylsulfonamide
formaldehyde adduct (Santolite MHP, available from Monsanto Co.).
After melting and preliminary mixing, the toner composition is fed
to a rubber mill and thoroughly milled to yield a uniformly
dispersed composition of the carbon black in the resin body. The
resulting mixture is then cooled and finely subdivided in a jet
pulverizer to yield toner particles having an average particle size
ranging between about 10 to about 20 microns. The toner has a
blocking temperature of about 140.degree.F. About 1 part of the
pulverized toner particles are mixed with about 99 parts by weight
of the carrier beads of Example I and substituted for the developer
in the testing machine described in Example I. Under substantially
identical test conditions, it is found that the minimum fuser
temperature at which legible copies are obtained with this toner is
about 330.degree.F. The maximum fuser temperature at which hot
offset to the fuser roll occurs is found to be about 420.degree.F.
These results clearly indicate that this toner enables a reduction
of about 70.degree.F from the fuser temperature required for the
control sample of Example VI. The toner dispenses well and high
resolution images substantially free from background are
obtained.
EXAMPLE IX
A toner composition is prepared comprising about 61 parts by weight
of a copolymer of about 80 parts by weight of styrene and 20 parts
by weight of isobutyl methacrylate, about 9 parts by weight of
carbon black (Black Pearls L, available from Cabot Corp., Boston,
Mass.), and about 30 parts by weight of arylsulfonamide
formaldehyde adduct (Santolite MHP, available from Monsanto Co.).
After melting and preliminary mixing, the toner composition is fed
to a rubber mill and thoroughly milled to yield a uniformly
dispersed composition of the carbon black in the resin body. The
resulting mixture is then cooled and finely subdivided in a jet
pulverizer to yield toner particles having an average particle size
ranging between about 10 to about 20 microns. The toner has a
blocking temperature of about 140.degree.F. About 1 part of the
pulverized toner particles are mixed with about 99 parts by weight
of the carrier beads of Example I and substituted for the developer
in the testing machine described in Example I. Under substantially
identical test conditions, it is found that the minimum fuser
temperature at which legible copies are obtained with this toner is
about 320.degree.F. The maximum fuser temperature at which hot
offset to the fuser roll occurs is found to be about 410.degree.F.
These results clearly indicate that this toner enables a reduction
of about 80.degree.F from the fuser temperature required for the
control sample of Example VI. The toner dispenses well and high
resolution images substantially free from background are
obtained.
EXAMPLE X
A toner composition is prepared comprising about 51 parts by weight
of a copolymer of about 80 parts by weight of styrene and 20 parts
by weight of isobutyl methacrylate, about 9 parts by weight of
carbon black (Black Pearls L, available from Cabot Corp., Boston
Mass.), and about 40 parts by weight of arylsulfonamide
formaldehyde adduct (Santolite MHP, available from Monsanto Co.).
After melting and preliminary mixing, the toner composition is fed
to a rubber mill and thoroughly milled to yield a uniformly
dispersed composition of the carbon black in the resin body. The
resulting mixture is then cooled and finely subdivided in a jet
pulverizer to yield toner particles having an average particle size
ranging between about 10 to about 20 microns. The toner has a
blocking temperature of about 140.degree.F. About 1 part of the
pulverized toner particles are mixed with about 99 parts by weight
of the carrier beads of Example I and substituted for the developer
in the testing machine described in Example I. Under substantially
identical test conditions, it is found that the minimum fuser
temperature at which legible copies are obtained with this toner is
about 310.degree.F. The maximum fuser temperature at which hot
offset to the fuser roll occurs is found to be about 400.degree.F.
These results clearly indicate that this toner enables a reduction
of about 90.degree.F from the fuser temperature required for the
control sample of Example VI. The toner dispenses well and high
resolution images substantially free from background are
obtained.
EXAMPLE XI
Samples of the developer compositions of Examples I-V are employed
in the copying machine described in Example I to make copies of a
standard test image. The standard test patterns are printed to
provide an integrated optical density as determined with a Welch
Densitometer, Model 3834, of 1.2 .+-. 0.1. The degree of fix at
various temperatures employing the fuser unit described in Example
I is evaluated. The results are reported in Taber Cycles required
to reduce the initial density by 20 percent. The results are as
indicated below in Table I.
Table I ______________________________________ Average Taber Cycles
Temp. .degree.F Example 1 2 3 4 5
______________________________________ 290 -- -- 5 7 6 300 -- 3 8 8
12 310 -- 5 9 12 15 320 2.0 8 14 18 18 330 3.0 16 17 22 21 350 3.5
20 23 29 27 360 4.5 24 31 37 30 370 6.0 29 31 37 34 380 8.0 31 33
39 38 390 14.0 32 32 38 45 400 17.0 40 30 35 -- 410 19.5 43 41 50
-- 420 20.5 -- -- -- -- ______________________________________
From the above results, it is readily apparent that the minimum
acceptable fix level of 10 .+-. 2 Taber Cycles may be obtained with
the toner compositions of this invention at a reduction of about
60.degree.F to about 80.degree.F. In addition, at comparable fixing
temperatures, the average number of Taber Cycles obtained is
significantly higher.
EXAMPLE XII
The glass transition temperature of a copolymer resin comprising
about 65 parts by weight of styrene and about 35 parts by weight of
butyl methacrylate was determined using a Differential Scanning
Calorimeter, 10.degree.C/min. heating rate, and 4 mcal./sec.
sensitivity. Measurements were made in a flowing Nitrogen
atmosphere and the dial temperatures were converted for thermal lag
using the melting point of those crystalline substances as
references (octadecone, naphthalene, and p-nitrotoluene). The glass
transition temperature of the aforementioned copolymer resin was
found to be about 56.6.degree.C. After mixing about 10 parts by
weight and about 25 parts by weight, respectively, of an
arylsulfonamide formaldehyde adduct (Santolite MHP) based on the
total weight of the mixture with the aforementined copolymer resin,
the glass transition temperature of the mixtures was found to be
about 58.9.degree.C and 57.5.degree.C, respectively, indicating
within experimental error that the addition of the adduct does not
significantly affect the glass transition temperature of the
copolymer resin and hence the blocking temperature of such a
resin-based toner composition is not adversely influenced.
EXAMPLE XIII
The melt viscosity of a copolymer resin comprising about 65 parts
by weight of styrene and about 35 parts by weight of butyl
methacrylate was determined by using a Ferranti-Shirley Cone and
Plate Viscometer. Data are cited at 30 sec.sup..sup.-1 shear rate.
The melt viscosity of the aformentioned copolymer resin at various
temperatures was found to be about 8.0 .times. 10.sup.3 poise at
140.degree.C; 3.6 .times. 10.sup.3 poise at 150.degree.C; 1.9
.times. 10.sup.3 poise at 160.degree.C; and 1.1 .times. 10.sup.3
poise at 170.degree.C. After mixing about 25 parts by weight of an
arylsulfonamide formaldehyde adduct (Santolite MHP) with the
aforementioned copolymer resin, the melt viscosity of the resultant
mixture was found to be about 4.9 .times. 10.sup.3 at 130.degree.C;
2.8 .times. 10.sup.3 poise at 140.degree.C; 1.1 .times. 10.sup.3
poise at 150.degree.C; 8.2 .times. 10.sup.2 poise at 160.degree.C;
and 4.1 .times. 10.sup.2 poise at 170.degree.C, respectively,
indicating, within experimental error, that the addition of the
adduct results in between about three to four fold lowerings of the
melt viscosity of the copolymer resin. In turn, the melt viscosity
change is reflected in substantially lower fusing temperatures of
the toner compositions.
The expression "developer material" as employed herein is intended
to include electroscopic toner material or combinations of toner
material and carrier material.
Although specific materials and conditions are set forth in the
foregoing examples, these are merely intended as illustrations of
the present invention. Various other suitable thermoplastic toner
resin components, additives, colorants, and development processes
such as those listed above may be substituted for those in the
examples with similar results. Other materials may also be added to
the toner or carrier to sensitize, synergize, or otherwise improve
the fusing properties of other desirable properties of the
system.
Other modifications of the present invention will occur to those
skilled in the art upon a reading of the present disclosure. These
are intended to be included within the scope of this invention.
* * * * *