U.S. patent number 3,669,886 [Application Number 04/767,031] was granted by the patent office on 1972-06-13 for liquid developer for electrostatography.
This patent grant is currently assigned to Philip A. Hunt Chemical Corporation. Invention is credited to George E. Kosel.
United States Patent |
3,669,886 |
Kosel |
June 13, 1972 |
LIQUID DEVELOPER FOR ELECTROSTATOGRAPHY
Abstract
A liquid electrostatographic image developer composed of the
following five constituents; a petroleum fraction paraffinic
solvent, a solid film-forming fixing agent, a solid dispersant, a
solid charge director, and a submicron solid electroscopic pigment
material. The fixing agent and the dispersant are dissolved in the
solvent. The charge director is carried by the solvent being either
dispersed or dissolved therein. The pigment material is insoluble
in the solvent and is dispersed therein. The solvent evaporates at
least as fast as kerosene and slower than hexane; it has a K.B.
number less than 35, a dielectric constant less than 31/2, a flash
point of at least 100.degree. F, and a room temperature viscosity
of between 0.5 and 2.5 centipoises. The solvent is non-toxic,
practically odorless, highly resistant, and non-polar; it
evaporates rapidly slightly below the char point of paper. The
film-forming fixing agent is non-tacky and forms a tough film; it
has a good solvent release and it forms, upon evaporation of the
solvent, a coherent film that binds the pigment material in place,
and bonds well to an electrostatographic surface.
Inventors: |
Kosel; George E. (Park Ridge,
NJ) |
Assignee: |
Philip A. Hunt Chemical
Corporation (Palisades Park, NJ)
|
Family
ID: |
25078287 |
Appl.
No.: |
04/767,031 |
Filed: |
September 11, 1968 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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397638 |
Sep 18, 1964 |
|
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Current U.S.
Class: |
430/116;
430/115 |
Current CPC
Class: |
G03G
9/125 (20130101); G03G 9/1355 (20130101); G03G
9/132 (20130101); G03G 9/131 (20130101); G03G
9/135 (20130101); G03G 9/122 (20130101); G03G
9/13 (20130101) |
Current International
Class: |
G03G
9/12 (20060101); G03G 9/135 (20060101); G03G
9/125 (20060101); G03G 9/13 (20060101); G03g
009/04 () |
Field of
Search: |
;252/62.1 ;117/37LY |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Brammer; J. P.
Parent Case Text
RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
397,638 filed Sept. 18, 1964.
Claims
Having thus described the invention, I claim as new and desire to
secure by Letters Patent:
1. A liquid electrostatographic image developer for a base sheet
having a coating binder for zinc oxide, said developer essentially
consisting of a petroleum fraction paraffinic solvent which has
less than 2 percent by weight aromatic solvent, a solid
film-forming fixing agent dissolved in said solvent, a solid
dispersant dissolved in said solvent, a solid charge director
carried by said solvent and a sub-micron solid electroscopic
pigment material dispersed and insoluble in said solvent, said
film-forming fixing agent being present in an amount of about 30 to
60 percent by weight of the solid constituents sufficient to bond
to an electrostatographic surface the electroscopic pigment
material electrostatically attracted to said surface, said
dispersant being present in an amount of about 5 to 30 percent by
weight of the solid constituents sufficient to disperse the
electroscopic pigment material in the solvent, said charge director
being present in an amount of about 0.1 to 5 percent by weight of
the solid constituents sufficient to augment the charge direction
of the electroscopic pigment material and said electroscopic
pigment material being present in an amount of from about 5 percent
to about 40 percent by weight of the solid constituents, the
film-forming fixing agent and the dispersant being the major
proportion of the solid constituents, said solvent having an
evaporation rate at least as fast as that of kerosene and slower
than that of hexane, a K.B. number of from about 26 to 35, a
dielectric constant less than 31/2, a flash point of at least
100.degree. F, a viscosity of between 0.5 and 2.5 centipoises at
room temperature and being non-toxic, of low odor, of high volume
resistivity, non-polar, substantially aromatic-liquid-free and
evaporating rapidly at slighly below the char point of paper, said
film-forming fixing agent being non-tacky and tough in solid film
form, having a good solvent release and forming a coherent film
that bonds well to an electrostatographic surface, all of said
solid constituents being mutually compatible and chemically inert
to one another at ambient temperatures, the film-forming fixing
agent being selected from the group consisting of hydrogenated
polymerized wood rosin having an acid number of 145-65 and a
softening point of 85.degree. to 93.degree. C by the Hercules drop
method, hydrogenated wood rosin having an acid number of 165 and a
softening point of 76.degree. C by the Hercules drop method,
glycerol ester of modified wood rosin having an acid number of 8
and a softening point of 168.degree. C by the Hercules drop method,
pentaerythritol ester of wood rosin having an acid number of 12 and
a softening point of 111.degree. C by the Hercules drop method,
pentaerythritol ester of polymerized wood rosin having an acid
number of 14 and a softening point of 135.degree. C by the Hercules
drop method, modified pentaerythritol ester of wood rosin having an
acid number of 14 and a softening point of 135.degree. to
159.degree. C by the Hercules drop method, pentaerythritol ester of
hydrogenated wood rosin having an acid number of 13 and a softening
point of 104.degree. C by the Hercules drop method, pentaerythritol
ester of dimeric resin acids having an acid number of 14-15 and a
softening point of 159.degree. to 172.degree. C by the Hercules
drop method, glycerol ester of polymerized wood rosins having an
acid number of 6 and a softening point of 112.degree. C by the
Hercules drop method, and pentaerythritol ester of modified wood
rosin having an acid number of less than 1 and a softening point of
180.degree. to 190.degree. C by the mercury method, the charge
director being selected from the class consisting of aluminum
stearate, aluminum dresinate, vanadium dresinate, tin dresinate,
cobalt salt to 2-ethyl hexoic acid, iron salt of 2-ethyl hexoic
acid, manganese salt of 2-ethyl hexoic acid, manganese linoleate,
1-[2-hydroxyethyl]-2-[mixed pentadecyl and
heptacecyl]-2-imidazoline, and a fatty amide condensate and the
dispersant being selected from the group consisting of a tripolymer
of a weight mixture of 50 parts of octadecenyl methacrylate, 10
parts diethyl aminoethyl methacrylate, and 40 parts styrene,
methacrylate polymer, alkyl methacrylate maleic anhydride polymer,
maleimide polymer, a polymer consisting of the reaction product of
alkyl methacrylate, polyethylene glycol methacrylate and maleic
anhydride, a polymer consisting of the reaction product of alkyl
methacrylate, polyethylene glycol methacrylate and imide of maleic
anhydride and tetraethylene pentamine, polyglycol substituted
polyesters and polyglycol substituted polyamides, all said
film-forming fixing agents being fully soluble in said solvent.
2. A liquid electrostatographic image developer as set forth in
claim 1 wherein the flash point is from about 120.degree. to
152.degree. F.
3. A liquid electrostatographic image developer as set forth in
claim 1 wherein the solvent has an IBP of about 345.degree. to
375.degree. F, a dry end point of about 371.degree. to 482.degree.
F and an aniline point of about 146.degree. to 187.degree. F.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
Electrostatographic liquid developers.
2. Description of the Prior Art
The use of liquid developers for electrostatography, i.e.,
rendering visible as a permanent image a latent image consisting of
a pattern of electrostatic charges, is well known. Advocates
thereof prefer it over the dry method for developing such a pattern
of charges for many reasons, including, for example, sharper and
better defined images, images having a higher degree of and more
delicate gradations of contrast, cleaner whites, more economical
use of the developer, a faster developing cycle, and simpler, less
expensive and more trouble-free developing equipment. However,
although the industry strongly desires an excellent liquid
electrostatographic developer, those which presently are
commercially available or which have been proposed in patent
literature and in publications are subject to sundry deficiencies
that are largely concerned with refinements of commercial demands.
For example, the liquid developers heretofore proposed have not
given sufficiently good resolution or sufficiently dense or sharp
images. Where the final image was black, it was not black enough,
nor was the background sufficiently clear. Moreover, as to many
developers, there has been a serious complaint that the shelf life
was not long enough in that some solids suspended within the liquid
developer tended to settle and agglomerate too quickly, making it
necessary to redisperse them prior to use. This sometimes could be
accomplished by vigorous hand shaking, but was not too
satisfactory. Other solids settled in the form of a cake which
could not be redispersed by manual or even machine shaking and
which had to be resuspended by passing the ingredients of the
developer through a milling machine or the like, e.g., a ball mill
or pebble mill. Still further, other liquid developers have tended
to gel and thereby become ineffective when subjected in bulk to
mild temperatures, e.g., in the order of 125.degree. F, such as
might be encountered in electrostatographic developing
equipment.
SUMMARY OF THE INVENTION
It is a principal object of the present invention to provide a
liquid electrostatographic image developer which overcomes the
aforesaid deficiencies and drawbacks, effecting through its use a
consistently and commercially acceptable developed electrostatic
image.
More particularly, it is an object of the present invention to
provide a liquid electrostatographic image developer which will
secure a dense image of good resolution, an image which, when black
and white copy is to be made, is composed of blacks that are of a
deep jet hue.
It is another object of the invention to provide a liquid
electrostatographic image developer which will create a visible
image that is bonded firmly to the sheet on which the electrostatic
pattern of charges was present, for example, which will bond well
to a sheet coated with a photoconductive material such as zinc
oxide or zinc sulfide or to a sheet of a non-photosensitive
insulating material.
It is another object of the invention to provide a liquid
electrostatographic image developer which will form a fast-drying
non-tacky, non-smearing and non-offsetting image, and which will
enable an apparatus utilizing the same to have a rapid developing
and drying cycle.
It is another object of the invention to provide a liquid
electrostatographic image developer, which, in addition to its many
desirable attributes, is inexpensive and easy to produce.
Bearing in mind that equipment employing a liquid
electrostatographic image developer may be run in an enclosed area
under the supervision of an operator, it is another object of the
invention to provide a liquid electrostatographic image developer
which is odorless, non-toxic and non-flammable under the conditions
of use.
It is another object of the invention to provide a liquid
electrostatographic image developer which will not settle or
separate upon standing for extended periods and which will not gel
in a developing machine under normal conditions of use.
Other objects of the invention in part will be obvious and in part
will be pointed out hereinafter.
The invention accordingly consists in the compositions of matter
which will be exemplified in the materials hereinafter described
and of which the scope of application will be indicated in the
appended claims.
In general, the several objects of the invention are accomplished
by providing a liquid electrostatographic image developer which
essentially consists of an organic liquid carrier constituting a
petroleum fraction in which there are dissolved a solid
film-forming fixing agent, i.e., a binder, and a solid dispersant,
in which a solid charge director is dissolved or dispersed, and in
which a finely divided solid opaque electroscopic material that
functions as a pigment is dispersed. The film-forming agent and the
dispersant constitute the major proportion of the solid
constituents of the liquid electrostatographic image developer and
since they are fully dissolved in the organic liquid carrier, they
will not settle out upon standing. However, even though present in
dissolved form, they perform their primary functions efficiently,
that is to say, the dispersant will maintain the pigment and also
the charge director, if the latter is dispersed, in suspended state
despite the fact that the dispersant is in solution, and the
film-forming fixing agent will act to bind the electrostatically
attracted pigment to an electrostatic electrophotographic or an
electrostatic electrographic base sheet after the carrier has
evaporated. The solid charge director and the solid pigment are
present in minor proportions and will remain in suspension
indefinitely.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The organic liquid carrier is, as mentioned above, a petroleum
fraction, it having been discovered that this particular class of
carriers is uniquely capable of effecting the present invention by
virtue of the following attributes: (a) quick evaporation, e.g., a
thin film of the carrier will evaporate in a few seconds at a
temperature below the char point of paper, so as to permit fast
drying; (b) non-toxicity; (c) low odor; (d) the characteristic that
when employed with soluble solid film-forming agents it will fully
escape therefrom so as to leave the solid film deposited by such
agent tack-free and not subject to evaporation over protracted
periods of time after the deposited image is seemingly dry; (e)
sufficient fluidity to allow the particles of pigment to migrate
therethrough with ease so that the pigment is capable of being
quickly electrostatically attracted to and coupled with the pattern
of electrostatic charges which is to be developed; (f) not
attacking the coating binders on a base sheet and not attacking
other ingredients of the sheet; (g) not bleeding the electrostatic
charges before the pigment is deposited so as to maintain any
desired degree of contrast; and (h) inexpensiveness.
In order to obtain these beneficial attributes, the petroleum
fraction, i.e., paraffinic solvent, should have an evaporation rate
at least as fast as that of kerosene, but slower than that of
hexane. Thereby, the evaporation of the liquid from a film will be
rapid, e.g., 2 seconds, at a temperature slightly below the char
point of paper, it being customary to raise the temperature of the
film of liquid developer to this level for the purpose of
evaporating the developer after the opaque electroscopic particles
of pigment have been deposited by attraction on the
electrostatically charged pattern. The petroleum fraction should
have a low K.B. (Kauri-butanol) number, to wit, less than 35, and
preferably between 26 and 35. This low K.B. number minimizes the
possibility that the petroleum fraction will attack the coating
binder, e.g., the binder for the zinc oxide, or will attack any
sizing on the sheet, e.g., paper, upon which the coating is
applied. The petroleum fraction also should be substantially free
of aromatic liquid constituents, i.e., it should be substantially
aromatic-liquid-free. This term, as used herein, connotes that the
proportion of aromatic liquids in the organic liquid carrier should
not be in excess of two per cent by weight. The aromatic liquids
have a strong tendency to attack the coating binders, e.g., the
coating binders for zinc oxide, but in concentrations of less than
two per cent this tendency is so negligible as to be unnoticeable.
The petroleum fraction must have a high electrical resistivity,
e.g., in the order of at least 10.sup.9 ohm centimeters, and a
dielectric constant of less than 31/2, so that the liquid carrier
will not dissipate the pattern of electrostatic charges which are
to be developed. The TCC (Tagliabue closed cup) flash point of the
liquid carrier should be at least 100.degree. F and preferably
about 120.degree. F to 152.degree. F, whereby under the conditions
of use the liquid is considered non-flammable. The paraffinic
solvent also is non-toxic. It possesses no objectionable odor and
preferably is odor-free, this being denoted by the term "low odor."
Consonant with its low dielectric constant and high resistivity,
the liquid carrier is non-polar. The liquid carrier should have low
viscosity for the purpose, as indicated above, of permitting rapid
migration therethrough of opaque electroscopic charged pigment
particles which are to be attracted in large number to the
electrostatically charged image which is to be developed. Such
viscosity should be between 0.5 and 2.5 centipoises at room
temperature. The petroleum fraction also is inexpensive.
Examples of petroleum fraction organic liquid carriers having
physical characteristics which fall within the foregoing criteria
are Shell Sol 71, manufactured by Shell Oil Company; Isopar H,
Isopar K, and Isopar L, manufactured by Humble Oil and Refining
Company; Amsco OMS, Amsco 460 Solvent and Amsco Odorless
Insecticide Base manufactured by American Mineral Spirits Company;
and odorless kerosene. All of the foregoing are low odor paraffinic
solvents. The dielectric constant of Shell Sol 71 is 2.06 at room
temperatures. The other solvents have dielectric constants of the
same order of magnitude. Other physical characteristics of Shell
Sol 71, Isopar H, Isopar K, Isopar L, Amsco OMS, Amsco 460 Solvent
and Amsco Odorless Insecticide Base which fingerprint these
solvents and denote the presence of several of the above listed
attributes are set forth below: ##SPC1##
The pigment employed can be any one of the many now known to the
art in connection with liquid electrostatographic developers. As is
well-known, these pigments essentially constitute very fine solid
particles the size of which is in the submicron range, which are
opaque in mass and which are capable of acquiring an electroscopic
charge. They are insoluble in the liquid carrier. So many different
kinds and species of pigments are known that only typical
representative examples will be mentioned. These are: powdered
metals, e.g., powdered aluminum; powdered metal oxides, e.g.,
powdered magnetic iron oxide; powdered metal salts, e.g., powdered
cadmium selenide (CdSe), powder lead iodide (PbI.sub.2), powdered
lead chromate (PbCrO.sub.4); Cyan Blue G.T. 55-3295 (American
Cyanamid Company, Pigments Division)*(material in first parentheses
indicates name of manufacturer.) (74160)**(**material in second
parentheses indicates color index number.) described in United
States Letters Patent No. 2,486,351; Cibacron Black BG (Ciba
Company, Inc.); Cibacron Turquoise Blue G (Ciba); Cibalon Black BGL
(Ciba); Orasol Black BRG (Ciba); Orasol Black RBL (Ciba); Acetamine
Black CBS (E. I. du Pont de Nemours and Company, Inc.); Crocein
Scarlet N Ex (duPont) (27290); Fiber Black VF (duPont) (30235);
Luxol Fast Black L (duPont) (Solv. Black 17); Nigrosine Base No.
424 (duPont) (50415 B); Oil Black BG (duPont) (Solv. Black 16);
Rotalin Black RM (duPont); Sevron Brilliant Red 3 B (duPont); Basic
Black DSC (Dye Specialties, Inc.); Hectolene Black (Dye
Specialties); Azosol Brilliant Blue B (General Aniline and Film
Corporation, Dyestuff and Chemical Division) (Solv. Blue 9); Azosol
Brilliant Green BA (General Aniline) (Solv. Green 2); Azosol Fast
Brilliant Red B (General Aniline); Azosol Fast Orange RA Conc.
(General Aniline) (Solv. Orange 20); Azosol Fast Yellow GRA Conc.
(General Aniline) (13900 A); Basic Black KMPA (General Aniline);
Benzofix Black CW-CF (General Aniline) (35435); Cellitazol BNFV Ex
Soluble CF (General Aniline) (Disp. Black 9); Celliton Fast Blue AF
Ex Conc (General Aniline) (Disp. Blue 9); Cyper Black IA (General
Aniline) (Basic Blk. 3); Diamine Black CAP Ex Conc (General
Aniline) (30235); Diamond Black EAN Hi Conc. CF (General Aniline)
(15710); Diamond Black PBBA Ex (General Aniline) (16505); Direct
Deep Black EA Ex CF (General Aniline) (30235); Hansa Yellow G
(General Aniline) (11680); Indanthrene Black BBK Powd. (General
Aniline) (59850); Indocarbon CLGS Conc. CF (General Aniline)
(53295); Katigen Deep Black NND Hi Conc. CF (General Aniline)
(53190); Nyliton Black B (General Aniline); Palatine Fast Black
WANA Conc. CF (General Aniline) (15711); Rapidogen Black 3 G
(General Aniline) (Azoic Blk. 4); Sulphon Cyanine Black BA-CF
(General Aniline) (26370); Zambezi Black VD Ex Conc. (General
Aniline) (30015); Azo Oil Black (National Aniline Division of
Allied Chemical and Dye Corporation) (Solv. Blk. 12); Iosol Blue 6
G (National Aniline) (Solv. Blue 30); Spirit Nigrosine SSB
(National Aniline) (50415); Methyl Violet T Lake (N.Y. Color and
Chemical Co.) (42535); Rubanox Red CP-1495 (The Sherwin-Williams
Company) (15630); Victoria Blue Molybdate Lake (Standard
Ultramarine and Color Co.) (42595); Toner 8100 (Paul Ulich and
Company, Inc.) a mixture of carbon black and black dye precipitated
on a lake; Raven 11 (Columbian Carbon Company) carbon black
aggregates with a particle size of about 25 .mu., and chrome
green.
The solid film-forming fixing agent, in addition to being fully
soluble in the liquid carrier must have a good solvent release
characteristic, that is to say, must permit the solvent to
evaporate completely and quickly through a solid coherent film-like
deposit left as a residue by solvent evaporation. The film thus
deposited must be tack-free, tough and coherent, whereby the final
image that is formed will not smear or shred. The film-forming
agent must be compatible with the binder for the
electrostatographic coating, e.g., with the binder for a
photoconductive zinc oxide coating, and should bond well to said
coating in order to avoid any tendency of the finished image to
separate or peel from the coated sheet.
An excellent film-forming agent having the foregoing
characteristics is a hydrogenated polymerized rosin, a typical
example being Resin NC 11, manufactured by Hercules Powder Company.
This is a pale thermoplastic acidic wood rosin resin that has been
both polymerized and hydrogenated. It has a softening point of
85.degree.C to 93.degree.C by the Hercules drop method and an acid
number of 145-65. Its density at 20.degree. C is 1.065. It has a
saponification number of 155-165. Its degree of hydrogenation is
about 90 percent and it has an average molecular weight of 360.
About 20 percent of the rosin acids are polymerized.
Other useful film-forming agents are: ##SPC2##
+A thermoplastic petroleum hydrocarbon resin in which the units in
the polymer are predominantly aromatic or cyclic in structure. It
is prepared by the polymerization of unsaturated hydrocarbon
fractions boiling between about 125.degree. C and about 250.degree.
C, having a Sp. Gr. (15.6/15.6.degree. C) of between 0.90 and 0.95.
The polymerizable constituents comprise between about 30 and 90
percent by weight and the principal polymerizable monomers are:
cyclodiene dimers** 5-30% indene 5-20% vinyl toluene 5-25% styrene
0-10%
the balance dry weight of the hydrocarbon fraction is constituted
of essentially umpolymerizable paraffins, napthenes and aromatics
containing eight or more carbon atoms per molecule and boiling
within the aforementioned range, i.e., between about 125.degree.
and 250.degree. C.
The unsaturated hydrocarbon fractions from which the resin is
obtained come from high temperature and low pressure pyrolysis of
normally liquid or gaseous hydrocarbons having two or more carbon
atoms per molecule. The cracking operation may be by-products of
pyrolytic processes in which the principal products sought are low
boiling olefines and dienes such as ethylene, propylene, butenes,
butadiene, etc. which are widely used base hydrocarbons in the
petrochemical and plastics fields including elastomers. Pyrolysis
of both liquid and gaseous hydrocarbons for such purposes is well
known and need not be described in detail.
Test Property Nevchem 100 (Typical properties)
__________________________________________________________________________
1. Soft Point (R&B) .degree.C. 100 2. Molecular Weight (No.
Ave) 800 3. C/H Weight ratio 10.5
__________________________________________________________________________
Test Property Nevchem 100 (Typical properties)
__________________________________________________________________________
4. Sp. Gr. 25/25.degree.C 1.090 5. Refr. Index 25.degree.C/D 1.602
6. Iodine Number 65 7. Acid Number <1 List of Test Methods: 1.
ASTM E-28-58T 2. Osmotic 3. Combustion Analysis 4. ASTM D-71-52 5.
Neville Method (toluene solution, extrapolated to solid resin) 6.
ASTM D-555
__________________________________________________________________________
the solid dispersant, like the solid film-forming agent, is
characterized by its full solubility in the paraffinic solvent
carrier. It must disperse solid pigments of sub-micron range in a
non-polar solvent. It must be compatible in solid form with the
solid film-forming agent and desirably is a film-forming agent in
its own right. Desirably, likewise, it will augment the charge
direction of the solid submicron pigment particles.
Examples of solid dispersants having the foregoing physical
characteristics are: Lube Oil 564 and FOA 2. Lube oil 564 is
manufactured by du Pont and is composed of 40 percent of
methacrylate polymer and 60 percent of light neutral petroleum oil.
FOA2 is manufactured by du Pont and is composed of 50 percent of
methacrylate polymer and 50 percent of kerosene. Insofar as the
above examples of dispersants are concerned, it is the solid
constituent that constitutes the dispersant, the liquid carrier
merely forming a convenient vehicle therefor. Other dispersants
include: an oil additive constituting a tripolymer prepared from a
weight mixture of 50 parts of octadecenyl methacrylate, 10 parts
diethylaminoethyl methacrylate, and 40 parts styrene, the same
being polymerized by conventional bulk, solution or dispersion
polymerization methods involving known initiators including
oxygen-yielding compounds, such as benzoyl peroxide, and azo
compounds such as alpha, alpha' azodiisobutyronitrile. The
polymerization process preferably is carried out in an inert
atmosphere, for example, nitrogen or carbon dioxide, at
conventional temperatures ranging, as is well known, from
30.degree. to 150.degree. C, depending on the catalyst used, and
generally between 50.degree. to 70.degree. C where the catalyst is
alpha, alpha' azodiisobutyronitrile. The polymerization is carried
substantially to completion to eliminate substantially all of the
unpolymerized monomers, it being understood that "substantially to
completion" as used herein denotes that there is a remainder of
from 0 to 15 percent of total monomers. The aforesaid tripolymer is
dissolved in kerosene in proportions of 50 percent by weight of the
tripolymer to 50 percent by weight of kerosene. The tripolymer
constitutes, as is seen, several completely organic compounds
combined in proportions to effect the optimum balance between
polar-active and oil-soluble groups. The said tripolymer is large
and has an average molecular weight of 50,000.
Still other dispersants that may be used are those disclosed in
U.S. Pat. No. 3,048,544, namely alkyl methacrylate maleic anhydride
polymer, maleimide polymer, a polymer constituting the reaction
product of alkyl methacrylate, polyethylene glycol methacrylate and
maleic anhydride, and a polymer constituting the reaction product
of alkyl methacrylate, polyethylene glycol methacrylate and imide
of maleic anhydride, and tetraethylene pentamine; the polyglycol
substituted polyesters disclosed in U.S. Pat. No. 3,083,187; and
the polyglycol substituted polyamides disclosed in U.S. Pat. No.
3,083,188. The methods of preparation of these latter dispersants
are detailed in said patents.
The charge directors which are per se well known in the field of
liquid electrostatographic image developers must be soluble or
dispersible in the paraffinic solvent and must create or augment an
electrostatic charge on the sub-micron pigment particles. Examples
of useable charge directors pursuant to this invention are:
aluminum stearate; aluminum dresinate; vanadium dresinate; tin
dresinate; cobalt salt of 2-ethyl hexoic acid; iron salt of 2-ethyl
hexoic acid; manganese salt of 2-ethyl hexoic acid; manganese
linoleate 1-[2-hydroxyethyl]-2-[mixed pentadecyl and
heptadecyl]-2-imidazoline; and Nopco FOA 2, manufactured by Nopco
Chemical Company, a fatty amide condensate.
The dresinates are prepared by adding a solution of the
corresponding metallic sulfate, e.g., Al.sub.2 [SO.sub.4 ].sub.3,
Sn[SO.sub.4 ].sub.2 or V.sub.2 O.sub.4 [SO.sub.3 ].sub.3. 16H.sub.2
O to a solution of the sodium salt of a processed rosin, to wit,
Dresinate 731, manufactured by Hercules Powder Company.
As has been mentioned earlier herein, the major proportion of the
solid constituents of a liquid electrostatographic image developer
pursuant to the present invention are soluble in the petroleum
fraction organic liquid carrier. These constituents are the
film-forming fixing agent and the dispersant. The minor proportion
or the solids need not be soluble in the liquid carrier, such
constituents constituting the necessarily nonsoluble submicron
pigment particles and the charge director, the latter optionally
being soluble. Thereby, even in concentrated forms of the liquid
electrostatographic image developer, prior to dilution, the
dispersed particulate solids will not settle upon standing.
The various constituents of the liquid electrostatographic image
developer are chemically inert to one another at ambient
temperatures, all said constituents being selected and admixed
solely for their physical characteristics and not for chemical
interaction. Moreover, all of the constituents are heat stable
under ambient conditions and a developer made of the foregoing
constituents will not gel under the operating conditions prevailing
in a liquid electrostatographic developing apparatus, that is to
say, at temperatures up to as high as 125.degree. F.
Satisfactory results are obtained when the total of solid
constituents is composed of the four individual solid constituents
present in the following ranges of percentages by weight: fixing
agent from about 30 to 60 percent, dispersant from about 5 to 30
percent, charge director from about 0.1 to 5 percent, and pigment
from about 5 to 40 percent. The fixing agent and dispersant jointly
are in excess of 50 percent by weight of the total solid
constituents and the charge director and pigment jointly are less
than 50 percent.
The following are examples of liquid electrostatographic image
developers in concentrated form:
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EXAMPLE I
25 gs. Picco 6120-3 9 gs. Toner 8100 9 gs. Spirit Nigrosine SSB 120
gs. Amsco 460 Solvent 0.25gs. Aluminum Dresinate 17.5 gs. 50% by
weight of a tripolymer of 50 parts by weight of octadecenyl
methacrylate, 10 parts by weight of diethyl aminoethyl methacrylate
and 40 parts by weight of styrene dissolved in 50% by weight of
kerosene
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EXAMPLE II
40 gs. Krumbhaar 484 15 gs. Toner 8100 15 gs. Spirit Nigrosine SSB
5 gs. Raven 11 50 gs. 50% by weight of a tripolymer of 50 parts by
weight of octadecenyl methacrylate, 10 parts by weight of diethyl
aminoethyl methacrylate and 40 parts by weight of styrene dissolved
in 50% by weight of kerosene 150 mls. Shell Sol 71 2 gs. Manganese
linoleate 2 gs. Aluminum stearate
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EXAMPLE III
25 gs. Nevchem 100 9 gs. Toner 8100 9 gs. Spirit Nigrosine SSB 120
gs. Shell Sol 71 0.25gs. Aluminum Dresinate 17.5 gs. 50% by weight
of a tripolymer of 50 parts by weight of octadecenyl methacrylate,
10 parts by weight of diethyl aminoethyl methacrylate and 40 parts
by weight of styrene dissolved in 50% by weight of kerosene 1 g.
Nopco FOA 2
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EXAMPLE IV
55 gs. Resin NC-11 17.5 gs. Lube Oil 564 1 g. Aluminum Stearate 182
gs. Shell Sol 71 30 gs. Cadmium Selenide
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EXAMPLE V
55 gs. Resin NC-11 17.5 gs. 50% by weight of a tripolymer of 50
parts by weight of octadecenyl methacrylate, 10 parts by weight of
diethyl aminoethyl methacrylate and 40 parts by weight of styrene
dissolved in 50% by weight of kerosene 182 gs. Shell Sol 71 0.5 gs.
Aluminum stearate 28 gs. Cyan Blue GT 55-3295
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each of the foregoing concentrated liquid electrostatographic
developers is formed by introducing all of the recited ingredients
into a ball mill and milling the same therein at room temperature
for at least 24 hours.
For use in a liquid electrostatographic developing apparatus any
one of the concentrated developers of which examples are given
above and in which the solid-to-liquid ratio is about one-to-one to
about one-to-two are diluted in a ratio of about 2 to 12 grams of
concentrated developer to one liter of organic liquid carrier. The
original solids concentration is not critical but rather is
controlled by economics. The developing concentration depends upon
the developing equipment used, the method parameters and the
contrast desired so that it is widely variable and is not a
critical aspect of the invention. Preferably, when carrying out
this dilution the same organic liquid carrier is used as was
employed in the concentrated developer.
Any of said diluted developers can be used in a liquid
electrostatographic printing process and will achieve the
successful results described at length above. Pursuant to the
present invention such developers are used by applying the liquid
image developer composition to a latent image consisting of a
pattern of electrostatic charges created, for example, in a
photoconductive zinc oxide coating applied to a sheet of paper. The
liquid developer is applied to such latent image in any well known
manner as by spraying or rolling, or by immersing the sheet
carrying the image in a receptacle containing the liquid developer.
As soon as the image has been developed by electrostatic coupling
the sheet is dried, as by subjecting it to an elevated temperature
below the char point of the paper, whereupon the liquid carrier
will rapidly evaporate and leave a clear image the contrast of
which will be controlled only by the developing parameters (time,
pigment concentration, etc.).
The said liquid electrostatographic developers in addition to being
useful as developers in electrophotography wherein the latent
electrostatic image is produced in a photoresponsive medium, such
as a zinc oxide or zinc sulfide coating on a surface, also are
useful as developers in electrography wherein the latent image is
produced in a non-photosensitive dielectric medium on a surface.
Moreover said developers can be used in processes wherein the
developed image is used as the final image for optical scanning,
e.g., reading, or as a copy that is used as a master in a
duplicating process, e.g., lithography or offset printing.
It thus will be seen that there are provided liquid
electrostatographic image developers which achieve the several
objects of the invention and which are well adapted to meet the
conditions of practical use.
As various possible embodiments might be made of the above
invention and as various changes might be made in the embodiments
above set forth, it is to be understood that all matter herein
described is to be interpreted as illustrative and not in a
limiting sense.
* * * * *