[0001] This invention relates to an electrophotographic toner composition which comprises
a colorant and a resin.
[0002] The electrophotographic process and more specifically the xerographic process is
fully described in U. S. Patent 3,635,704. In summary, in the xerographic process
a plate generally comprising a conductive backing upon which is placed a photoconductive
insulating surface is uniformly charged and subsequently the photoconductive surface
is exposed to a light image of the original to be reproduced. The photoconductive
surface is prepared in such a manner so as to cause it to become conductive under
the influence of the light image in order that the electrostatic charge contained
thereon can be selectively dissipated to produce a latent image which is developed
by means of a variety of pigmented resin materials especially made for this purpose
such as toner. It is this toner material that is electrostatically attracted to the
latent image areas on the plate in proportion to the charge concentration thereof,
thus in areas of high charge
[0003] concentration high attraction of toner results while in areas of low charge concentration
substantially no toner is attracted. This developed image can then be transferred
to a final support material such as paper and affixed thereto.
[0004] There are many methods that are known for developing and fixing the resulting images,
some of which are disclosed in U. S. Patent No. 3,635,704 and include for example,
cascade development as described in U. S. Patent No. 2,618,552; magnetic brush development
as described in U. S. Patents 2,874,063; 3,251,706; and 3,357,402; powder cloud development
as described in U.S. Patent No. 2,221,776; and touchdown development as described
.::in U. S. Patent No. 3,166,432. The fixing can be either vapor fixing, heat fixing,
pressure fixing or combinations thereof as described in U.S. Patent No. 3,539,161.
Modern electrostatographic reproducing apparatuses which are capable of producing
copies at extremely high rates can employ radiant flash fusing as this seems to be
the best method for affixing images in such environments. The energy which is emitted
in the form of electromagnetic waves is instantly available and requires no intervening
medium for its propogation.
[0005] The type of toner material_ that is used in a development system is very important
as not only is the image quality a consideration, but cleaning and damage to machine
components is a factor that must be contended with. After forming a powder image on
the electrostatic latent image during the development step as explained herein, the
powder image can be electrically transferred to the support surface by means of a
corona generating device as described for example in U.S. Patent No. 2,777,957. Specifically,
transfer is effected by such a device by imparting an electrostatic charge to attract
the powder image from the drum to the support surface. The polarity of the charge
required to affect the transfer of the image depends upon the visual form of the original
copy relative to the reproduction as well as the electroscopic characteristics of
the developing.material employed to accomplish development. Thus, when a positive
reproduction is to be obtained from a positive original it is conventional to employ
a positive polarity corona 'to affect the transfer of a negatively charged toner image
to a support surface. When a positive reproduction from a negative original is desired
normally there is used a positively charged developing material which is repelled
by the charged areas on the plate to the discharged areas thereon to form a positive
image which may be transferred by negative polarity corona. Additionally, of course,
the type of charge that. is to be imparted to the toner material will depend on the
charge on the photoconductive surface, thus if such charge is negative one would want
a positive charge on the resulting toner or if such a charge is positive one would
want a negative charge on the resulting toner.
[0006] It is known to modify the developer composition containing toner so-as to achieve
optimum copy quality consistently without adversely affecting the imaging system involved.
For example, it has been found to be an advantage to modify the properties of the
toner so that a uniform stable high net electrical charge may be imparted to the toner
powder material. Numerous methods and materials for modifying the surface properties
of toner have been proposed including for example the addition of various dyes, amines,
quaternary ammonium compounds, all of which have been used as charge controlling agents
in electrophotographic toners. While these additives are somewhat effective in controlling
the toner charges, the additives used can adversely affect the system in that, for
example, charge could migrate from the interior of the toner to the surface due to
energy differences which results in causing the toner to change its charge property
and to be less attracted to the electrophotographic latent images in some situations.
Also, these additives are either water soluble or moisture sensitive; thus adversely
affecting the toner and the quality of the image. Further, such additives are difficult
to disperse or dissolve uniformly in the toner which results in particle to particle
non-uniformity and wide distribution of electrical charges.
[0007] The invention as claimed is intended to provide a toner composition which is positively
charged and which does not require the use of an additive to obtain such a charge.
This toner composition is characterised by the inclusion of a resin which is in an
amine copolymer or terpolymer having the formula:
or
wherein M
1 is a monomeric unit, M
2 is a monomeric unit different from M
1, R
1 and R
2 are independently selected from hydrogen, carbon containing radicals, hydrocarbon
and substituted hydro- carbon radicals, R
3 is hydrogen or a hydrocarbon group, n is an integer between 50 and 100,000 and Y
is an integer between 1 and 5, said copolymer or terpolymer being prepared by vinyl
or addition polymerization.
[0008] The toner compositions of the invention have the advantages that they provide improved
toners having the desired charge characteristics that are permanently retained and
which allow the development of images of high quality especially when a negative charge
is present on the photoreceptor used.
[0009] Toner composition in accordance with the invention will now be described in more
detail.
[0010] Generally the colorant which can be a carbon black, magnetite or colorant pigment
is present in amounts of from about 1 to about 70 percent by weight while the resin
is present in amounts of from about 30 to 99 percent by weight. In order to achieve
optimum results it is preferred that the colorant be present in amounts of from 4
to about 50 percent based on the weight of toner and the resin be present in amounts
of from 50 to about 96 percent by weight.
[0011] Any suitable pigment or dye may be employed as the colorant including for example
carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow, ultramarine
blue, DuPont Oil Red, methylene blue chloride, phthalocyanine blue, Rose Bengal, iron
oxides such as Mapico Black, Mapico Yellows, Mapico Reds, Mapico Browns, Mapico Tans,
and mixtures thereof. The pigment or dye should be present in the toner in a sufficient
quantity to render it colored so that it will form a clearly visible image on the
recording surface and generally as indicated above the percent of colorant present
varies from about 1 to about 70 percent. Thus for example where conventional xerographic
copies of typed documents are desired the toner may comprise a black pigment such
as carbon black or magnetite.
[0012] Numerous types of resin materials may be used for preparing toner compositions of
the present invention with the provision that the resulting product contains an amino
group which causes the toner to be positively charged in one preferred embodiment
thus allowing it to be used in those situations where the photoreceptor, especially
an organic photoreceptor, is negatively charged.
[0013] The resin of the invention may be illustrated by an amine copolymer having the following
structure:
wherein M
1 is a monomeric unit such as styrene methyl methacrylate, n-butyl methacrylate, isobutyl
styrene; R
1 and R
2 are as defined below; R
3 is hydrogen or a hydrocarbon group, such group containing from about 1 to about 8
carbon atoms and including for example, methyl, ethyl, propyl, isopropyl, hexyl, octyl;
n is an integer of from about 50 to 100,000; and y is an integer of from about 1 to
5. The terpolymer would be of similar structure with the addition of an M
2 grouping, -M
1-M
2-CH
2 wherein M
2 is usually a different monomeric unit such as n-butyl methacrylate.
[0014] The resin contains an amino group such as a primary, second or tertiary group of
the formula
wherein R
1 and R
2 are independently selected from hydrogen, carbon containing radicals, hydrocarbon
and substituted hydrocarbon groups. R
1 and R
2 could be bonded to the nitrogen-N through the same carbon atom (=CH
2) or through different carbon atoms (N
). The hydrocarbon or substituted hydrocarbon can be aliphatic or aromatic with the
aliphatic group containing from 1 to about 8 carbon atoms including for example, methyl,
ethyl, propyl, isopropyl, hexyl, and octyl. Examples of substituents in the hydro-
carbon group include hydroxyl, halo chloride, bromide, nitro, amino, sulfonyl, while
examples of aromatic groups include phenyl, benzyl phenyl, and heterocyclic such as
nitrogen containing aromatics.
[0015] Illustrative examples of copolymers and terpolymers containing the amino group include
styrene t-butyl amino ethyl methacrylate, styrene n-butyl methacrylate, t-butyl amino
ethyl methacrylate, dimethylamino ethyl methacrylate.
[0016] The resins of the invention are vinyl or addition type copolymers or terpolymers
containing amino groups. Typical of such vinyl monomeric units include the following
monomers and monomers containing amino groups: styrene; p-chlorostyrene; vinyl naphthalene;
ethylenecally 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 pyrrol, N-vinyl
carbazole, N-vinyl indole, N-vinyl pyrrolidone, N-vinyl pyridine, n-butylamino ethyl
methacrylate, t-butylamino ethyl methacrylate, dimethyl amino ethyl methacrylate,
and the like; and mixtures thereof.
[0017] The addition polymerization technique employed embraces known polymerization techniques
such as free radical, anionic and cationic polymerization processes. Any of these
vinyl resins may be blended with one or more other resins if desired, preferably other
vinyl resins which insure good triboelectric stability and uniform resistance against
physical degradation.
[0018] Where carrier materials are employed with the toner compositions of the present invention
in cascade and magnetic brush development, the carrier particles employed may be electrically
conductive, insulating, magnetic or non-magnetic, as long as the carrier particles
are capable of triboelectrically obtaining a charge of opposite polarity to that of
the toner particles so that the toner particles adhere to and surround the carrier
particles. In developing a positive reproduction of an electrostatic image, the carrier
particle is selected so that the toner particles acquire a charge having a polarity
opposite to that of the electrostatic latent image so that toner deposition occurs
in image areas. Alternatively, in reversal reproduction of an electrostatic latent
image, the carriers are selected so that the toner particles acquire a charge having
the same polarity as that of the electrostatic latent image resulting in toner deposition
in the non-image areas. Typical carrier materials include: sodium chloride, ammonium
chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, aluminum nitrate,
potassium chlorate, granular zircon, granular silicon, methyl methacrylate, glass,
steel, nickel, iron, ferrites, ferromagnetic materials, silicon dioxide and the like.
The carriers may be employed with or without a coating. Many of the foregoing and
typical carriers are disclosed in U. S. Patents 2,618,441; 2,638,552; 3,591,503 and
3,533,835 directed to electrically conductive carrier coatings, and U. S. Patent 3,525,533
directed to methyl terpolymer coating carriers which are the reaction products or
organo silanes, silanols or siloxanes with unsaturated polymerizable organic compounds
{optimum among those disclosed are terpolymer coatings achieved with a terpolymer
formed from the addition polymerization reaction between monomers or prepolymers of:
styrene, methylmethacrylate and unsaturated organo silanes, silanols or siloxanes);
and nickel berry carriers as disclosed in U. S. Patents 3,847,604 and 3,767,598. Nickel
berry carriers are modular carrier beads of nickel characterized by a surface of recurring
recesses and protrusions giving the particles a relatively large external surface
area. An ultimate coated carrier particle diameter between about 50 microns to about
1000 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. The carrier may be employed with the toner composition in any suitable combination,
generally satisfactory results have been obtained when about 1 part toner is used
with about 10 to about 200 parts by weight of carrier.
[0019] The toners of the present invention may be utilized in systems such as powder cloud
development, cascade development, single component touchdown development and other
types of development systems.
[0020] The toner compositions of the present invention can be prepared by any well known
toner mixing and combination 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. The toner compositions of the present invention can be used to develop electrostatic
latent images on any suitable electrostatic surface capable of retaining charge including
conventional photoconductors such as inorganic or organic photoconductive materials.
Some typical materials include sulfur, selenium, zinc sulfide, zinc oxide, cadmium
sulfide, polyvinyl carbazole, 4 dimethyl amino benzylidene, 3 amino carbazole, polyvinyl
carbazole, tri-nitrofluoronone, charge transfer complexes, phthalocyanines, and the
like.
[0021] It is important to note that no additives are being supplied in or to the toner of
the present invention, that is no material is being supplied to the developer rather
the resin is prepared in such a manner so as to contain amino functionality which
results in the property desired. The results as demonstrated by the working examples
will aid as will be more fully established in the working examples that follow.
[0022] The following examples are being supplied to ..further illustrate the invention.
Parts and percentages are by weight unless otherwise indicated.
[0023] The triboelectric charge of the developer was measured by the following procedure.
One hundred (100) parts of the coated carrier and 3 parts of the toner were placed
in an 8 oz. glass jar. The jar containing the developer was roll mixed at a linear
speed of 90 ft/min for a specific time. The developer was placed in a stainless steel
Faraday cage with a 35 micron screen. The triboelectric charge was measured by blowing
off the toner from the developer, using an electrometer which is connected to the
Faraday cage.
EXAMPLE I
[0024] Toner A comprised of 6 percent Regal 330. carbon black from Cabot Corporation and
94 percent of a copolymer resin was prepared by Banbury blending followed by mechanical
attrition. The copolymer resin was prepared by polymerizing 65 percent styrene and
35 percent n-butyl methacrylate using benzyl peroxide as an initiator. The triboelectric
charge of this toner against a 0.35 percent PFA (perfluor alkoxy fluoro polymer from
duPont Co.) coated Hoeganaes carrier was measured by the procedure outlined above
with the following results. The word 'tribo' is used hereafter to denote triboelectric
charge.
The tribo decreased rapidly as the mixing time was increased. After 4 hours of mixing,
the charge of the toner changed from positive to negative, indicating it was not a
stable developer.
EXAMPLE II
[0025] Toner B which is comprised of 6 percent Regal 330 carbon black and 94 percent of
Terpolymer 1 resin was prepared by Banbury/jetting. The Terpolymer 1 resin of this
toner was prepared by polymerizing 60 percent styrene, 38 percent n-butyl methacrylate,
and 2 percent t-butylamino ethyl methacrylate using benzoyl perioxide as an initiator.
The triboelectric measurements of this toner against a 0.35 percent PFA (perfluoro
alkoxy fluoro polymer from DuPont Co.) coated Hoeganaes carrier were as shown in the
following table:
The charging rate of this toner was rapid and the tribo was rather high and stable.
EXAMPLE III
[0026] Toner C comprising 6 percent Regal'330 carbon black and 94 percent Terpolymer 2 resin
was prepared by Banbury/jetting. The Terpolymer 2 resin of this toner was prepared
by polymerizing 60 percent styrene, 36 percent n-butyl methacrylate, and 4 percent
t-butylamino ethyl methacrylate using benzoyl peroxide as initiator. The tribos of
this toner against a 0.35 percent PFA (perfluoro alkoxy fluoro polymer from duPont
Co.) coated Hoeganaes carrier were as shown in the following table:
The toner displayed fast charging rate and high and stable tribo.
EXAMPLE IV
[0027] Toner D comprising 6 percent Regal 330 carbon black and 94 percent Terpolymer 3 resin
was prepared by Banbury/jetting. The Terpolymer 3 resin of this toner was prepared
by polymerizing 60 percent styrene, 34 percent n-butyl methacrylate and 6 percent
t-butyl amino ethyl methacrylate using benzoyl peroxide as initiator. The tribo of
this toner against a 0.35 percent PFA (perfluoro alkoxy fluoro polymer from duPont
Co.) coated Hoeganaes carrier were as shown in the following table:
The toner displayed fast charging rate, high and stable tribo.
EXAMPLE V
[0028] Toner E comprising 6 percent Regal 330 carbon black and 94 percent Terpolymer 4 resin
was prepared by Banbury/jetting. The Terpolymer 4 resin of this toner was prepared
by polymerizing 50 percent methyl methacrylate, 45 percent n-butyl methacrylate, and
5
The toner displayed fast charging rate, high and stable tribo against uncoated steel
carrier.