Note: Descriptions are shown in the official language in which they were submitted.
-- ~ 1 2-8976
INK COMPOSITIONS AND PREPARATION PROCESSES THEREOF-
BACKGROUND OF THE INVENTION
The present invention is directed to aqueous ink compositions.
More particularly, the present invention is directed to ink compositions
suitable for use in ink jet printing processes. One embodiment of the
present invention is directed to a process for preparing an ink composition
which comprises admixing water, a colorant, a base, and phosphorous acid,
wherein the pH of the ink is adjusted by a process selected from the group
consisting of (a) adding phosphorous acid to an aqueous solution
containing the base, and tb) adding the base to an aqueous solution
containing phosphorous acid. Another embodiment of the present
invention is directed to a process for preparing an ink composition which
comprises (a) forming a mixture by admixing water and a base; (b) adding a
colorant to the mixture; and (c) adjusting the pH of the mixture by adding
phosphorous acid thereto. Yet another embodiment of the present
invention is directed to a process for preparing an ink composition which
comprises (a) forming a mixture by admixing water and phosphorous acid;
(b) adding a colorant to the mixture; and (c) adjusting the pH of the
mixture by adding a base thereto. The present invention also includes ink
compositions prepared by these processes. One embodiment of the present
invention is directed to an ink composition which comprises water, a
colorant, and phosphorous acid. Another embodiment of the present
invention is directed to an ink composition which comprises water, a
colorant, and a phosphite salt.
Ink compositions for ink jet printing are known. for example,
U.S. Patent 5,062,892 (Halko) discloses ink jet ink compositions containing
oxo anions (phosphates, polyphosphates, phosphate esters, arsenate,
molybdate, sulfate, sulfite, and oxalate) in an amount of from 9 milligrams
per liter to 14 weight percent. The oxo anion additive is included in the ink
to reduce kogation in thermal ink jet printers.
.~ .
2128~7~
In addition, U.S. Patent 4,853,037 (Johnson et al.) discloses an ink
composition for printing on plain paper using a thermal ink jet printer. The
ink composition comprises at least one member selected from the group
consisting of ethylene glycol and diethylene glycol, present in an amount
ranging from about 5 to 10 weight percent, dye, ranging from about 1 to 4
weight percent, and the balance water. A biocide ranging from about 0.01
to 0.3 weight percent and/or a buffering agent, such as sodium borate,
sodium hydrogen phosphate, or sodium dihydrogen phosphate, ranging in
concentration from about 0.05 to 0.5 weight percent may also be included.
U.S. Patent 4,920,361 (Arahara et al.) discloses an image
recording method and an image recording apparatus using an ink which is
substantially non-adhesive but can be imparted with an adhesiveness when
subjected to a pH change. In the image recording method, the ink is
subjected to a pattern of pH change to be provided with an adhesive
pattern, which is then transferred to a recording medium, such as plain
paper, directly or by the medium of an intermediate transfer medium to
form an ink pattern corresponding to the pH change pattern.
U.S. Patent 4,838,940 (Kan et al.) discloses an ink which can be
imparted with an adhesiveness on application of an electric current. The
ink is obtained by impregnating a crosslinked substance such as guar gum
or polyvinyl alcohol compound with a liquid dispersion medium such as
water. The ink is supplied with a pattern of energy to be provided with an
adhesive pattern, which is then transferred to a recording medium, such as
plain paper, directly or by the medium of an intermediate transfer medium
to form an ink pattern corresponding to the energy pattern applied. The
ink further comprises a buffer action-imparting substance and is excellent
in storage stability and stability of performances during a continuous use.
Japanese Patent Publication 53-85626 discloses a water-based
ink composition for ball point pens which comprises an aqueous water-
soluble dye solution and a pH buffer. The pH buffer is either (i) NaOH and
KH2PO4, (ii) KH2PO4 and Na2HPO4, (iii) citric acid and Na2HPO4, (iv) KH2PO4
and borax, (v) borax, or (vi) sodium tripolyphosphate, each providing an
initial pH of 7 to 9.
-2-
21 28976
Japanese Patent Publication 56-36170 discloses a
water-based ink for ink jet printing containing water
soluble dyes, a phosphoric ester type surfactant as a
humectant, and water.
Although known inks are suitable for their intended
purposes, a need remains for improved ink compositions
suitable for use in ink jet printing processes. In
addition, there is a need for ink compositions which
exhibit improved latency and recoverability in ink jet
printers. Further, there is a need for ink compositions
which exhibit improved latency and which also exhibit
acceptable waterfastness, pH, viscosity, and surface
tension and generate high quality images. Additionally,
there is a need for ink compositions with good latency
and acceptable pH for which a wide range of solvents is
available so that the ink composition can be tailored for
compatibility with specific colorants, improved
waterfastness, adjusted viscosity, adjusted surface
tension, or other important ink characteristics. There
is also a need for ink compositions with both improved
latency and improved apparent dry times and/or
penetration rates into substrates. Further, there is a
need for processes for adjusting the pH of aqueous ink
compositions containing dyes wherein no crystallization
of salts is observed in the pH-adjusted ink. In
addition, there is a need for ink compositions for ink
jet printing which are stable at pH values of less than
about 7Ø
SUMMARY OF THE lN ~N'l ION
It is an object of an aspect of the present
invention to provide ink compositions with the above
noted advantages.
-3-
A
21 28q76
-
It is an object of an aspect of the present
invention to provide improved ink compositions suitable
for use in ink jet printing processes.
It is an object of an aspect of the present
invention to provide ink compositions which exhibit
improved latency and recoverability in ink jet printers.
It is an object of an aspect of the present
invention to provide ink compositions which exhibit
improved latency and which also exhibit acceptable
waterfastness, pH, viscosity, and surface tension and
generate high quality images.
An obj-ect of an aspect of the present invention is
to provide ink compositions with good latency and
acceptable pH for which a wide range of solvents is
available so that the ink composition can be tailored for
compatibility with specific colorants, improved
waterfastness, adjusted viscosity, adjusted surface
tension, or other important ink characteristics.
An object of an aspect of the present invention is
to provide ink compositions with both improved latency
and improved apparent dry times and/or penetration rates
into substrates.
An object of an aspect of the present invention is
to provide processes for adjusting the pH of aqueous ink
compositions containing dyes wherein no crystallization
of salts is observed in the pH-adjusted ink.
It is an object of an aspect of the present
invention to provide ink compositions for ink jet
printing which are stable at pH values of less than
about 7Ø
These and other objects of the present invention
(or specific embodiment thereof) can be achieved by
providing an ink composition which comprises water, a
colorant, and phosphorous acid. Another embodiment of
the present invention is directed to an ink composition
- 212897~
which comprises water, a colorant, and a phosphite salt. Another
embodiment of the present invention is directed to a process for preparing
an ink composition which comprises admixing water, a colorant, a base,
and phosphorous acid, wherein the pH of the ink is adjusted by a process
selected from the group consisting of (a) adding phosphorous acid to an
aqueous solution containing the base, and (b) adding the base to an
aqueous soiution containing phosphorous acid. Yet another embodiment
of the present invention is directed to a process for preparing an ink
composition which comprises (a) forming a mixture by admixing water and
a base; (b) adding a colorant to the mixture; and (c) adjusting the pH of the
mixture by adding phosphorous acid thereto. Still another embodiment of
the present invention is directed to a process for preparing an ink
composition which comprises (a) forming a mixture by admixing water and
phosphorous acid; (b) adding a colorant to the mixture; and (c) adjusting
the pH of the mixture by adding a base thereto.
DETAILED DESCRIPTION OF THE INVENTION
The liquid vehicle of the inks of the present invention may
consist of water, or it may comprise a mixture of water and a miscible
organic component, such as ethylene glycol, propylene glycol, diethylene
glycols, glycerine, dipropylene glycols, polyethylene glycols, polypropylene
glycols, amides, ethers, carboxylic acids, esters, alcohols, organosulfides,
organosulfoxides, suifones, such as sulfolane, alcohol derivatives, carbitol,
butyl carbitol, cellusolve, ether derivatives, amino alcohols, ketones,
N-methylpyrrolidinone, 2-pyrrolidone, cyclohexylpyrrolidone,
hydroxyethers, amides, sulfoxides, lactones, and other water miscible
materials, as well as mixtures thereof. When mixtures of water and water
miscible organic liquids are selected as the liquid vehicle, the water to
organic ratio may be in any effective range, and typically is from about
100:0 to about 30:70, preferably from about 97:3 to about 50:50, although
the ratio can be outside this range. The non-water component of the liquid
vehicle generally serves as a humectant which has a boiling point higher
than that of water (100~C). In the inks of the present invention, the liquid
vehicle (comprising water plus humectant) is generally present in an
21289~ ~.
amount of from about 60 to about 99.5 percent by weight, and preferably
from about 75 to about 99 percent by weight, although the amount can be
outside of this range. In a particularly preferred embodiment of the
present invention, the liquid vehicle comprises a mixture of water, 2-
pyrrolidinone or N-methyl pyrrolidinone, and sulfolane, of the formula
~S~
Preferably, the liquid vehicle comprises water in an amount of from about
80 to about 90 parts by weight, sulfolane in an amount of from about 5 to
about 10 parts by weight, and 2-pyrrolidinone or N-methyl pyrrolidinone in
an amount of from about 5 to about 10 parts by weight, although the
relative amounts can be outside this range.
Inks of the present invention contain a colorant. Generally, the
colorant is a dye. Preferred dyes are the anionic dyes. Specific examples
include Bernacid Red 2BMN, Pontamine Brilliant Bond Blue A, BASF X-34,
Pontamine, Food Black 2, Carodirect Turquoise FBL Supra Conc. (Direct Blue
199), available from Carolina Color and Chemical, Special Fast Turquoise
8GL Liquid (Direct Blue 86), available from Mobay Chemical, Intrabond
Liquid Turquoise GLL (Direct Blue 86), available from Crompton and
Knowles, Cibracron Brilliant Red 38-A (Reactive Red 4), available from
Aldrich Chemical, Drimarene Brilliant Red X-2B (Reactive Red 56), available
from Pylam, Inc., Levafix Brilliant Red E-4B, available from Mobay Chemical,
Levafix Brilliant Red E-6BA, available from Mobay Chemical, Procion Red
H8B ~Reactive Red 31), available from ICI America, Pylam Certified D&C Red
~28 (Acid Red 92), available from Pylam, Direct Brill Pink B Ground Crude,
available from Crompton & Knowles, Cartasol Yellow GTF Presscake,
available from Sandoz, Inc., Tartrazine Extra Conc. (FD&C Yellow #5, Acid
Yellow 23), available from Sandoz, Carodirect Yellow RL (Direct Yellow 86),
available from Carolina Color and Chemical, Cartasol Yellow GTF Liquid
Special 110, available from Sandoz, Inc., D&C Yellow #10 (Acid Yellow 3),
available from Tricon, Yellow Shade 16948, available from Tricon, Basacid
Black X34, available from BASF, Carta Black 2GT, available from Sandoz,
- 2128~-~",P
Inc., Neozapon Red 492 (BASF), Orasol Red G (Ciba-Geigy), Direct Brilliant
Pink B (Crompton-Knolls), Aizen Spilon Red C-BH (Hodagaya Chemical
Company), Kayanol Red 3BL (Nippon Kayaku Company), Levanol Brilliant
Red 3BW (Mobay Chemical Company), Levaderm Lemon Yellow (Mobay
Chemical Company), Spirit Fast Yellow 3G, Aizen Spilon Yellow C-GNH
(Hodagaya Chemical Company), Sirius Supra Yellow GD 167, Cartasol
Brilliant Yellow 4GF (Sandoz), Pergasol Yellow CGP (Ciba-Geigy), Orasol
Black RL (Ciba-Geigy), Orasol Black RLP (Ciba-Geigy), Savinyl Black RLS
(Sandoz), Dermacarbon 2GT (Sandoz), Pyrazol Black BG (ICI), Morfast Black
Conc A (Morton-Thiokol), Diazol Black RN Quad (ICI), Orasol Blue GN (Ciba-
Geigy), Savinyl Blue GLS (Sandoz), Luxol Blue MBSN (Morton-Thiokol),
Sevron Blue 5GMF (ICI), Basacid Blue 750 (BASF), Levafix Brilliant Yellow
E-GA, Levafix Yellow E2RA, Levafix Black EB, Levafix Black E-2G, Levafix
Black P-36A, Levafix Black PN-L, Levafix Brilliant Red E6BA, and Levafix
Brilliant Blue EFFA, available from Bayer, Procion Turquoise PA, Procion
Turquoise HA, Procion Turquoise H-5G, Procion Turquoise H-7G, Procion
Red MX-SB, Procion Red MX 8B GNS, Procion Red G, Procion Yellow MX-8G,
Procion Black H-EXL, Procion Black P-N, Procion Blue MX-R, Procion Blue
MX-4GD, Procion Blue MX-G, and Procion Blue MX-2GN, available from ICI,
Cibacron Red F-B, Cibacron Black BG, Lanasol Black B, Lanasol Red 5B,
Lanasol Red B, and Lanasol Yellow 4G, available from Ciba-Geigy, Basilen
Black P-BR, Basilen Yellow EG, Basilen Brilliant Yellow P-3GN, Basilen
Yellow M-6GD, Basiien Brilliant Red P-3B, Basilen Scarlet E-2G, Basilen Red
E-B, Basilen Red E-7B, Basilen Red M-5B, Basilen Blue E-R, Basilen Brilliant
Blue P-3R, Basilen Black P-BR, Basilen Turquoise Blue P-GR, Basilen
Turquoise M-2G, Basilen Turquoise E-G, and Basilen Green E-6B, available
from BASF, Sumifix Turquoise Blue G, Sumifix Turquoise Blue H-GF, Sumifix
Black B, Sumifix Black H-BG, Sumifix Yellow 2GC, Sumifix Supra Scarlet 2GF,
and Sumifix Brilliant Red 5BF, available from Sumitomo Chemical Company,
Intracron Yellow C-8G, Intracron Red C-8B, Intracron Turquoise Blue GE,
Intracron Turquoise HA, and Intracron Black RL, available from Crompton
and Knowles, Dyes and Chemicals Division, and the like. Particularly
preferred are dyes available from ICI Americas, Inc. of the chemical
structure:
212~
~N
NH2
~N~ ~ ~N~
H~2 H03S
and those of the chemical structure
HO~ HO S
' S03Na
NH2
,~N ~ ~ N--
03Na
2 12 8 ~
Also particularly preferred are BASF X-34 black dye (available from BASF)
and Duasyn Brilliant Red F3B SF VP 218 (high purity solid, obtained from
Hoechst, Coventry, Rl). Dyes that are invisible to the naked eye but
detectable when exposed to radiation outside the visible wavelength range
(such as ultraviolet or infrared radiation), such as dansyl-lysine, N-(2-
aminoethyl)-4-amino-3,6-disulfo-1,8-dinaphthalimide dipotassium salt, N-
(2-aminopentyl)-4-amino-3,6-disulfo-1,8-dinaphthalimide dipotassium salt,
Cascade Blue ethylenediamine trisodium salt (available from Molecular
Proes, Inc.), Cascade Blue cadaverine trisodium salt (available from
Molecular Proes, Inc.), bisdiazinyl derivatives of 4,4'-diaminostilbene-2,2'-
disulfonic acid, amide derivatives of 4,4'-diaminostilbene-2,2'-disulfonic
acid, phenylurea derivatives of 4,4'-disubstituted stilbene-2,2'-disulfonic
acid, mono- or di-naphthyltriazole derivatives of 4,4'-disubstituted stilbene
disulfonic acid, derivatives of benzithiazole, derivatives of benzoxazole,
derivatives of benziminazole, derivatives of coumarin, derivatives of
pyrazolines containing sulfonic acid groups, 4,4'-bis(triazin-2-
ylamino)stilbene-2,2'-disulfonic acids, 2-(stilben-4-yl)naphthotriazoles, 2-(4-
phenylstilben-4-yl)benzoxazoles, 4,4-bis(triazo-2-yl)stilbene-2,2'-disulfonic
acids, 1,4-bis(styryl)biphenyls, 1,3-diphenyl-2-pyrazolines, bis(benzazol-2-yl)
derivatives, 3-phenyl-7-(triazin-2-yl)coumarins, carbostyrils,
naphthalimides, 3,7-diaminodibenzothiophen-2,8-disulfonic acid-5,5-
dioxide, other commerciaily available materials, such as C.l. Fluorescent
Brightener No. 28 (C.l. 40622), the fluorescent series Leucophor B-302, BMB
(C.l. 290), BCR, BS, and the like (available from Leucophor), and the like, are
also suitable. The dye is present in the ink composition in any effective
amount, typically from about 1 to about 20 percent by weight, and
preferably from about 2 to about 10 percent by weight (wherein the
amount refers to the amount of dye molecules present in the ink), although
the amount can be outside of this range. A mixture of dyes in the
proportions desired to obtain a specific shade may also be employed.
In addition, the colorant for the ink compositions of the present
invention can be a pigment, or a mixture of one or more dyes and/or one or
more pigments. The pigment can be black, cyan, magenta, yellow, red,
blue, green, brown, mixtures thereof, and the like. Examples of suitable
- 2128~7-i
black pigments include various carbon blacks such as channel black, furnace
black, lamp black, and the like. Colored pigments include red, green, blue,
brown, magenta, cyan, and yellow particles, as well as mixtures thereof.
Illustrative examples of magenta pigments include 2,9-dimethyl-substituted
quinacridone and anthraquinone dye, identified in the Color Index as Cl
60710, Cl Dispersed Red 15, a diazo dye identified in the Color Index as Cl
26050, Cl Solvent Red 19, and the like. Illustrative examples of suitable cyan
pigments include copper tetra-4-(octadecyl sulfonamido) phthalocyanine,
X-copper phthalocyanine pigment, listed in the Color Index as Cl 74160, Cl
Pigment Blue, and Anthradanthrene Blue, identified in the Color Index as Cl
69810, Special Blue X-2137, and the like. Illustrative examples of yellow
pigments that can be selected include diarylide yellow 3,3-
dichlorobenzidene acetoacetanilides, a monoazo pigment identified in the
Color Index as Cl 12700, Cl Solvent Yellow 16, a nitrophenyl amine
sulfonamide identified in the Color Index as Foron Yellow SE/GLN, Cl
Dispersed Yellow 33, 2,5-dimethoxy-4-sulfonanilide phenylazo-4'-chloro-
2,5-dimethoxy acetoacetanilide, Permanent Yellow FGL, and the like.
Additional examples of pigments include Normandy Magenta RD-2400
(Paul Uhlich), Paliogen Violet 5100 (BASF), Paliogen Violet 5890 (BASF),
Permanent Violet VT2645 (Paul Uhlich), Heliogen Green L8730 (BASF),
Argyle Green XP-11 1-S (Paul Uhlich), Brilliant Green Toner GR 0991 (Paul
Uhlich), Heliogen Blue L6900, L7020 (BASF), Heliogen Blue D6840, D7080
(BASF), Sudan Blue OS (BASF), PV Fast Blue B2G01 (American Hoechst),
Irgalite Blue BCA (Ciba-Geigy), Paliogen Blue 6470 (BASF), Sudan lll
(Matheson, Coleman, Bell), Sudan ll (Matheson, Coleman, Bell), Sudan IV
(Matheson, Coleman, Bell), Sudan Orange G (Aldrich), Sudan Orange 220
(BASF), Paliogen Orange 3040 (BASF), Ortho Orange OR 2673 (Paul Uhlich),
Paliogen Yellow 152, 1560 (BASF), Lithol Fast Yellow 0991 K (BASF), Paliotol
Yellow 1840 (BASF), Novoperm Yellow FG1 (Hoechst), Permanent Yellow YE
0305 (Paul Uhlich), Lumogen Yellow D0790 (BASF), Suco-Gelb L1250 (BASF),
Suco-Yellow D1355 (BASF), Hostaperm Pink E (American Hoechst), Fanal
Pink D4830 (BASF), Cinquasia Magenta (DuPont), Lithol Scarlet D3700
(BASF), Tolidine Red (Aldrich), Scarlet for Thermoplast NSD PS PA (Ugine
Kuhlmann of Canada), E. D. Toluidine Red (Aldrich), Lithol Rubine Toner
-10-
2 ~
(Paul Uhlich), Lithol Scarlet 4440 (BASF), Bon Red C (Dominion Color
Company), Royal Brilliant Red RD-8192 (Paul Uhlich), Oracet Pink RF (Ciba-
Geigy), Paliogen Red 3871K (BASF), Paliogen Red 3340 (BASF), and Lithol
Fast Scarlet L4300 (BASF) Other pigments can also be selected. Preferably,
the pigment particle size is as small as possible to enable a stable colloidal
suspension of the particles in the liquid vehicle and to prevent clogging of
the ink channels when the ink is used in a thermal ink jet printer. Preferred
particle average diameters are generally from about 0.001 to about 0.1
micron. The pigment is present in the ink composition in any effective
amount, generally from about 1 to about 7 percent by weight and
preferably from about 2 to about S percent by weight, although the
amount can be outside of this range.
Ink compositions of the present invention are buffered to the
desired pH by the addition of phosphorous acid and a base. Phosphorous
acid is of the formula H3PO3 (often written HPO(OH)2), and is a dibasic acid
which dissociates in water, under the appropriate pH conditions, to form
the phosphite ions dihydrogen phosphite and monohydrogen phosphite, as
fol lows:
H H - H 2-
HO P OH , O~~-P---o + H+ O~~~P---o + 2H
O _ OH _ _ O
Neutralization of phosphorous acid by bases produces two series of salts,
the dihydrogen phosphites, of the formula H2PO3-, and the
monohydrogen phosphites, of the formula HPO32-. For example, if
phosphorous acid is neutralized by an alkali metal hydroxide, such as
sodium hydroxide, lithium hydroxide, potassium hydroxide, or the like,
dihydrogen phosphite salts such as NaH2P03, LiH2PO3, KH2PO3, or the like,
as well as monohydrogen phosphite saits, such as Na2HPO3, Ll2HPO3,
K2HPO3, or the like, can be formed. For the purposes of the present
invention, the term "phosphite salts~' refers both to monohydrogen
phosphites and dihydrogen phosphites. Phosphorous acid is commercially
available from a number of suppliers, such as Aldrich, Milwaukee, Wl. The
phosphorous acid is added to the ink composition in an amount of at least
212 8 9 L: ~J
about 0.1 percent by weight of the ink, preferably from about 0.1 to about
l O percent by weight, and more preferably from about 1 to about 2 percent
by weight, although the amount can be outside these ranges.
The base can be any suitable base which forms an effective
buffer system in the ink in combination with the phosphorous acid.
Preferably, the base is sufficiently volatile to leave the liquid vehicle as theink dries. Examples of suitable bases include ammonia, ammonium
hydroxide, methylamine, dimethylamine, trimethylamine, ethylamine,
diethylamine, triethylamine, ethylene diamine, and the like, as well as
mixtures thereof. The base is added to the ink composition in any effective
amount. For example, for a base which is an ammonium hydroxide solution
in water (61% NH40H), typical amounts are at least about 0.1 percent by
weight of the ink, preferably from about 0.1 to about 10 percent by weight,
and more preferably from about 1 to about 2 percent by weight, although
the amount can be outside these ranges. For bases of higher molecular
weight, proportionally greater amounts can be used. The amount of base
present can also be expressed in terms of the number of molar equivalents
of base per molar equivalent of dye in the ink. Typically, the amount of
base is from about 0.5 to about 25 molar equivalents of base per molar
equivalent of dye, preferably from about 2 to about 10 molar equivalents
of base per molar equivalent of dye, although the amount can be outside
these ranges.
The various ink ingredients can be admixed with each other in
any desired order. For example, the base can be admixed with water,
followed by addition of phosphorous acid, followed by addition of the
colorant. Or, the base and the colorant can be admixed with water,
followed by addition of phosphorous acid. Or, phosphorous acid can be
admixed with water, followed by addition of the base, followed by
addition of the colorant. Or, phosphorous acid and the colorant can be
admixed with water, followed by addition of the base. Any additional ink
ingredients, such as solvents, humectants, biocides, or the iike, can be
added at any desired stage of the ink preparation process.
The buffer system comprising the phosphorous acid and the base
enablesthe ink composition to be adjusted to a stable desired pH, generally
2 1 2 8 9 ~ ~
within a range of from about 6.5 to about 10.0 and preferably from about
7.5 to about 9.0, although the pH can be outside these ranges. Buffering
the pH within these ranges is generally preferred to prevent possible
precipitation of the dyes from the ink at pH values lower than about 6.5
and to prevent possible loss of waterfastness and sharp print quality at pH
values higher than about 10Ø
The inks of the present invention, buffered with a combination
of phosphorous acid and a base, exhibit improved latency compared to inks
buffered with other acids. Latency is the period during which the ink jet
printer may stop printing while it contains the ink and subsequently be
restarted without clogging of the nozzle. Latency in general should be as
high as possible to enable restarting of the ink jet printer after extended
idle periods. In most thermal ink jet inks, the choice of ink components in
addition to water and colorant, such as glycols or other humectants,
determines the latency of the ink. In the inks of the present invention,
however, the buffer system enables improved latency; thus, the other ink
ingredients can be selected to optimize other important ink characteristics
such as waterfastness, viscosity, surface tension, or the like, all of which
affect print quality. While not being limited to any particular theory, it is
believed that some latency difficulties can arise when salts from an ink
buffer system crystallize in or over the nozzles in an ink jet printhead.
Crystallization can be reduced or eliminated by selecting ink components
which will maintain these crystals in solution, but these ink components
may eventually evaporate, leaving the crystals behind to block the nozzles.
The combination of phosphorous acid and base in the present invention,
however, exhibits minimal tendencies to dry up or crystallize, and enables
ink jet printers containing the ink which have been idle for extended
periods to restart and jet acceptably with the first pulse. In addition, the
combination of phosphorous acid and base in the present invention
enhances the waterfastness of the ink. Again, while not being limited to
any particular theory, it is believed that the phosphorous acid component
in the ink resists crystallization because of the difficulty it would encounter
in obtaining the proper geometry for crystal lattice packing. Ammonium
212 8 9 9~ ~
phosphite is a highly hygroscopic material which will crystallize if placed in
a desiccating oven at 60~C, but will return to liquid at ambient conditions.
Other additives can also be present in the inks of the present
invention. For example, one or more surfactants or wetting agents can be
added to the ink. These additives may be of the cationic, anionic, or
nonionic types. Suitable surfactants and wetting agents include sodium
lauryl sulfate, Tamol~ SN, Tamol~ LG, those of the Triton~ series available
from Rohm and Haas Company, those of the Marasperse~ series, those of
the Igepal~ series available from GAF Company, those of the Tergitol~
series, and other commercially available surfactants. These surfactants and
wetting agents are present in effective amounts, generally from O to about
15 percent by weight, and preferably from about 0.01 to about 8 percent by
weight, although the amount can be outside of this range.
Polymeric additives can also be added to the inks of the present
invention to enhance the viscosity of the ink and the stability of the
pigment particles and to reduce the rate of agglomeration and
precipitation of the particles. Water soluble polymers such as Gum Arabic,
polyacrylate salts, polymethacrylate salts, polyvinyl alcohols, hydroxy
propylcellulose, hydroxyethylcellulose, polyvinylpyrrolidinone,
polyvinylether, starch, polysaccharides, and the like are particularly useful
for stabilizing pigment particles in a water based liquid vehicle such as
water or a mixture of water and a water miscible organic liquid. Polymeric
stabilizers may be present in the ink of the present invention in amounts of
from O to about 10 percent by weight, and preferably from about 0.01 to
about 5 percent by weight, although the amount can be outside of this
range.
One preferred additive to the inks of the present invention is a
polymeric additive consisting of two polyalkylene oxide chains bound to a
central bisphenol-A moiety. This additive is of the formula
H--(OR~ --o ~ ~o--(R30)y--H
-14-
21 28~76
wherein R1 and R2 are independently selected from the group consisting of
hydrogen, alkyl groups with from 1 to about 8 carbon atoms, such as
methyl, ethyl, propyl, and the like, and alkoxy groups with frorn 1 to about
8 carbon atoms, such as methoxy, ethoxy, butoxy, and the like, R3 and R4
are independently selected from the group consisting of alkyl groups with
from 1 to about 4 carbon atoms, and x and y are each independently a
number of from about 100 to about 400, and preferably from about 100 to
about 200. Generally, the molecular weight of the polyalkylene
oxidelbisphenol-A polymer is from about 14,000 to about 22,000, and
preferably from about 15,000 to about 20,000, although the molecular
weight can be outside this range. Materials of this formula are
commerciaily available; for example, Carbowax M20, a polyethylene
oxide/bisphenol-A polymer of the above formula with a molecular weight
of about 18,000, available from Union Carbide Corporation, Danbury, CT, is
a suitable.polymeric additive for the inks of the present invention. In
addition, compounds of the above formula can be prepared by the
methods disclosed in Polyethers, N. G. Gaylord, John Wiley & Sons, New
York (1963) and "Laboratory Synthesis of Polyethylene Glycol Derivatives,"
J. M. Harris, J. Molecular Science - Rev. Macromol. Chem. Phys., C25(3), 325-
373 (1985) j rhe polyalkylene oxide/bisphenol-A additive is generally
present in the ink in an amount of at least about 1 part per million.
Typlcally, the polyalkylene oxide/bisphenol-A additive is present in
amounts of up to 1 percent by weight of the ink, and preferably in amounts
of up to O.S percent by weight of the ink; larger amounts of the additive
may increase the viscosity of the ink beyond the desired level, but larger
amounts can be used in applications wherein increased ink viscosity is not a
problem. Inks containing these additives are disclosed in U.S. Patent
5,207,82S (Schwarz) .
Ink compositions of the present invention can also contain as
optional additives polyamine compounds. Examples of suitable polyamine
additives include N,N'-bis(3-aminopropyl)-1,2-ethylenediamine, 1,4-bis(3-
aminopropyl)piperazine, N,N'-bis(3-aminopropyl)-1,3-propanediamine,
-
21 28976
N,N'-bis(2-aminoethyl)- 1 ,3-propanediamine, N,N'-bis(3-aminopropyl)- 1,4-
butanediamine, ethylenediamine, diethylenetriamine,
triethylenetetramine, tetraethylenepentamine, nitrilotrisethylamine, N,N'-
(diamlnoethyl)piperazine, piperazinylethylethylenediamine,
a m i n o e t h y I t r i e t h y I e n e t e t r a m i n e,
aminoethylpiperazinylethylethylenediamine,
piperazinylethyldiethylenetriamine, pentaethylenehexamine, and the like,
as well as mixtures thereof. These materials are commercially available
from a variety of sources, including Aldrich Chemical Company, Milwaukee,
Wl, Texaco, Inc., Houston, TX, and Bayer tCanada) Inc., Point Claire, PQ. The
polyamine or mixture of polyamines can be present in any effective or
desired amount, typically from about 0.001 to about 5 percent by weight of
the ink composition, preferably from about 0.01 to about 3 percent by
weight of the ink composition, and more preferably from about 0.4 to
about 2.0 percent by weight, although the amount can be outside of these
ranges.
Other optional additTMes to the inks of the present invention
include biocides such as Dowicil 150, 200, and 75, benzoate salts, sorbate
salts, and the like, present in an amount of from about 0.0001 to about 4
percent by weight, ant preferably from about 0.01 to about 2.0 percent by
weight, additional pH controlling agents such as acids or bases, phosphate
salts, carboxylates salts, sulfite salts, amine salts, and the like, present in an
amount of from 0 to about 1 percent by weight and preferably from about
0.01 to about 1 percent by weight, orthe like.
The ink compositions of the present invention are generally of a
viscosity suitable for use in thermal ink jet printing processes. Typically, theink viscosity is no more than about 5 centipoise, and preferably is from
about 1 to about 2.5 centipoise.
Ink compositions of the present invention can be prepared by
any suitable process. Typically, the inks are prepared by simple mixing of
the ingredients. One process entails mixing all of the ink ingredients
together and filtering the mixture to obtain an ink. Inks of the present
invention can be prepared by preparing a conventional ink composition
according to any desired process, such as by mixing the ingredients, heating
1 , ,.
2128~7 6
if desired, and filtering, followed by adding the acid and base pH adjusting
components of the present invention to the mixture and mixing at room
temperature with moderate shaking until a homogeneous mixture is
obtained, typically from about 5 to about 10 minutes. Alternatively, the ink
additives of the present invention can be mixed with the other ink
ingredients during the ink preparation process, which takes place according
to any desired procedure, such as by mixing all the ingredients, heating if
desired, and filtering.
The present invention is also directed to a process which entails
incorporating an ink composition of the present invention into an ink jet
printing apparatus and causing droplets of the ink composition to be
ejected in an imagewise pattern onto a substrate. In a particularly
preferred embodiment, the printing apparatus employs a thermal ink jet
process wherein the ink in the nozzles is selectively heated in an imagewise
pattern, thereby causing droplets of the ink to be ejected in imagewise
pattern. Any suitable substrate can be employed, including plain papers
such as Xerox3 4024 papers, ruled notebook paper, bond paper, silica
coated papers such as Sharp Company silica coated paper, JuJo paper, and
the like, transparency materials, fabrics, textile products, plastics, polymericfilms, inorganic substrates such as metals and wood, and the like. In a
preferred embodiment, the process entails printing onto a porous or ink
absorbent substrate, such as piain paper.
Specific embodiments of the invention wiil now be described in
detail. These examples are intended to be illustrative, and the invention is
not limited to the materials, conditions, or process parameters set forth in
these embodiments. All parts and percentages are by weight unless
otherv~rise indicated.
EXAMPLE I
An ink composition was prepared as follows. To 60.2 grams of
deionized water was added 1.03 grams of N,N'-bis(3-aminopropyl)-1,2-
ethylenediamine (obtained from BASF) and 2 grams of ammonium
hydroxide. The resulting mixture was roll milled for 5 minutes, after which
the pH of the mixture was 11 74. Thereafter, 2.91 grams of a 50 percent by
weight solution of phosphorous acid (obtaineci from Rhone-Poulenc) was
21 28976
added to the mixture, which was then roll milled for another S minutes,
after which the pH was 8.81. Subsequently, to the mixture was added S
grams of betaine (hygroscopic, obtained from Aldrich Chemical Co.), 12.31
grams of 97 percent by weic~t sulfolane (obtained from Phillips 66
Company), 10.58 grams of BASF X-34 black dye (obtained from BASF), and
1.93 grams of a solution containing 16.0 percent by weight Direct Red 227
dye (obtained from Tricon Colors), followed by roll milling the mixture for
10 minutes. Thereafter, to the mixture was added O.OS grams of
polyethylene oxide (obtained from Polyscience), followed by roll milling
the mixture for 30 minutes. The resulting mixture had a pH of 8.42. rO this
mixture was added an additional 0.14 grams of a S0 percent by weight
solution of phosphorous acid, bringing the pH to 8.18. An additional 4.17
grams of deionized water was added, followed by roll milling for 30
minutes and subsequent filtering to yield an ink composition.
EXAMPLE II
An ink composition was prepared as follows. To 69.76 grams of
deionized water was added 1.01 grams of N,N'-bis(3-aminopropyl)-1,2-
ethylenediamine (obtained from BASF) and 2.06 grams of ammonium
hydroxide. The resulting mixture was roll milled for S minutes, after which
the pH of the mixture was 11.62. Thereafter, 3.62 grams of a 50 percent by
weight solution of phosphorous acid (obtained from Rhone-Poulenc) was
added to the mixture, which was then roll milled for another S minutes,
after which the pH was 8.75. Subsequently, to the mixture was added 8.31
grams of 97 percent by weight sulfolane (obtained from Phillips 66
Company), 10.66 grams of BASF X-34 black dye (obtained from BASF), 1.93
grams of Duasyn Brilliant Red F3B SF VP218 dye (obtained from Hoechst),
O.OS grams of po~ethylene oxide (obtained from Polysciences), and 0.099
grams of Dowicil 200 biocide (obtained from l~ow Chemical), followed by
roll milling the mixture for 15 minutes. The resulting mixture had a pH of
8.47. To this mixture was added an additional 0.19 grams of a S0 percent by
weight solution of phosphorous acid, bringing the pH to 8.20. An
additional 10.29 grams of deionized water was added, followed by roll
milling for 10 minutes and subsequent filtering to yield an ink composition.
212~97~
For comparison purposes, an ink composition was prepared by
adding to 60.87 grams of deionized water 1.01 grams of of N,N'-bis(3-
aminopropyl)-1,2-ethylenediamine (obtained from BASF) and 2.01 grams of
ammonium hydroxide. The resulting mixture was roll milled for S minutes,
after which the pH of the mixture was 11.94. Thereafter, 3.67 grams of a 37
percent by weight solution of hydrochloric acid (obtained from Aldrich
Chemical Company) was added to the mixture, which was then roll milled
for another 5 minutes, after which the pH was 8.59. Subsequently, to the
mixture was added 8.27 grams of 97 percent by weight sulfolane (obtained
from Phillips 66 Company), 10.62 grams of BASF X-34 black dye (obtained
from BASF), 0.29 grams of Duasyn Brilliant Red F3B SF VP218 dye (obtained
from Hoechst), 0.05 grams of polyethylene oxide (obtained from
Polysciences), and 0.102 grams of Dowicil 200 biocide (obtained from Dow
Chemical), followed by roll miiling the mixture for 15 minutes. The
resulting mixture had a pH of 8.46. To this mixture was added an additional
0.57 grams of 3 Molar hydrochloric acid, bringing the pH to 8.20. An
additional 12.66 grams of deionized water was added, followed by roll
milling for 10 minutes and subsequent filtering to yield an ink composition.
The ink compositionsthus prepared were each incorporated into
a Hewlett-Packard DeskJet 500 thermal ink jet printer and prints were
generated on paper. Latency and recoverability were tested by operating
the printer in the "de-cap" mode, in which the built-in maintenance
procedures of maintaining the ink jet nozzles capped in a high humidity
environment, were circumvented. After generating prints, the printer was
stopped for a 24 hour period, followed by again generating prints without
any prior maintenance or priming of the nozzles. The ink composition
prepared with phosphorous acid began generating high quality images
after 1.5 pages of printing had been generated under these conditions. In
contrast, the ink prepared with hydrochloric acid began generating high
quality images after 6 pages of printing had been generated under these
cond itions.
EXAMPLE III
_19_
2 1 ~ ~ ~ 7 ~-~
An ink composition was prepared as foilows. To 17.97 grams of
deionized water was added 0.52 grams of N,N'-bis(3-aminopropyl)-1,2-
ethylenediamine (obtained from BASF) and 1 gram of ammonium
hydroxide. The resulting mixture was roll milled for 5 minutes, after which
the pH of the mixture was 12.00. Thereafter, 1.34 grams of a 70 percent by
weight solution of phosphorous acid (obtained from Aldrich Chemical
Company) was added to the mixture, bringing the pH to 8.1û. An
additional 0.19 gram of ammonium hydroxide was added, followed by roll
milling for another 5 minutes, after which the pH was 8.62. Subsequently,
to the mixture was added 12.5 grams of dimethyl sulfoxide (DMSO)
(obtained from Baker Chemical Company), 13 grams of Direct Red 227 dye
(containing 13.4 percent by weight dye solids, obtained from Tricon Colors),
0.0246 grams of polyethylene oxide (obtained from Polysciences), and
0.0494 grams of Dowicil 200 biocide (obtained from Dow Chemical),
followed by roll milling the mixture for 15 minutes. The resulting mixture
had a pH of 8.81. To this mixture was added an additional 0.17 grams of a
70 percent by weight solution of phosphorous acid, bringing the pH to 8.19.
An additional 3.39 grams of deionized water was added, followed by roll
milling for 10 minutes and subsequent filtering to yield an ink composition.
The ink composition thus prepared was incorporated into a
Hewlett-Packard DeskJet 500 thermal ink jet printer and prints were
generated on paper. Latency and recoverability were tested by operating
the printer in the "de-cap" mode, in which the built-in maintenance
procedures of maintaining the ink jet nozzles capped in a high humidity
environment, were circumvented. After generating prints, the printer was
stopped for a 24 hour period, followed by again generating prints without
any prior maintenance or priming of the nozzles. The ink composition
began generating high quality images after 1 page of printing had been
generated under these conditions.
EXAMPLE IV
An ink composition was prepared as follows. To 15.92 grams of
deionized water was added 0.52 grams of N,N'-bis(3-aminopropyl)-1,2-
ethylenediamine (obtained from BASF) and 1 gram of ammonium
-20-
212~97 ''-.''J
hydroxide. The resulting mixture was roll milled for 5 minutes, after which
the pH of the mixture was 11.60. Thereafter, 1.23 grams of a 70 percent by
weight solution of phosphorous acid (obtained from Aldrich Chemical
Company) was added to the mixture, followed by roll milling for 5 minutes,
bringing the pH to 8.64. Subsequently, to the mixture was added 12.52
grams of dimethyl sulfoxide (DMSO) (obtained from Baker Chemical
Company), 15.03 grams of Projet Cyan 1 Liquid dye (containing 10 percent
by weight dye solids, obtained from ICI), 0.0255 grams of polyethylene
oxide (obtained from Polysciences), and 0.0518 grams of Dowicil 200
biocide (obtained from Dow Chemical), followed by roll milling the mixture
for 15 minutes. The resulting mixture had a pH of 8.85. To this mixture was
added an additional 0.18 grams of a 70 percent by weight solution of
phosphorous acid, bringing the pH to 8.20. An additional 3.61 grams of
deionized water was added, followed by roll milling for 10 minutes and
subsequent filtering to yield an ink composition.
The ink composition thus prepared was incorporated into a
Hewlett-Packard DeskJet 500 thermal ink jet printer and prints were
generated on paper. Latency and recoverability were tested by operating
the printer in the "de-cap" mode, in which the built-in maintenance
procedures of maintaining the ink jet nozzles capped in a high humidity
environment, were circumvented. After generating prints, the printer was
stopped for a 24 hour period, followed by again generating prints without
any prior maintenance or priming of the nozzles. The ink composition
began generating high quality images after 1.5 pages of printing had been
generated under these conditions.
EXAMPLE V
An ink composition was prepared as follows. To 29.94 grams of
deionized water was added 0.52 grams of N,N'-bis(3-aminopropyl)-1,2-
ethylenediamine (obtained from BASF) and 1.02 gram of ammonium
hydroxide. The resulting mixture was roll milled for 5 minutes, after which
the pH of the mixture was 11.43. Thereafter, 1.23 grams of a 70 percent by
weight solution of phosphorous acid (obtained from Aldrich Chemical
Company) was added to the mixture, followed by roll milling for 5 minutes,
2 ~ 7 '
bringing the pH to 8.65. Subsequently, to the mixture was added 12.5
grams of dimethyl sulfoxide (DMSO) (obtained from Baker Chemical
Company), 1.5 grams of Carolina Direct Yellow 86 dye (obtained from
Carolina),0.0244 grams of polyethylene oxide (obtained from Polysciences),
and 0.0503 grams of Dowicil 200 biocide (obtained from Dow Chemical),
followed by roll milling the mixture for 15 minutes. The resulting mixture
had a pH of 8.87. To this mixture was added an additional 0.17 grams of a
70 percent by weight solution of phosphorous acid, bringing the pH to 8.22.
An additional 4.21 grams of deionized water was added, followed by roll
milling for 10 minutes and subsequent filtering to yield an ink composition.
The ink composition thus prepared was incorporated into a
Hewlett-Packard DeskJet 500 thermal ink jet printer and high quality prints
were generated on paper.
EXAMPLE VI
An ink composition was prepared as follows. To 56.53 grams of
deionized water was added 1.02 grams of N,N'-bis(3-aminopropyl)-1,2-
ethylenediamine (obtained from BASF) and 2.02 grams of ammonium
hydroxide. The resulting mixture was roll milled for S minutes, after which
the pH of the mixture was 11.62. Thereafter,2.77 grams of a 70 percent by
weight solution of phosphorous acid (obtained from Aldrich Chemical
Company) was added to the mixture, followed by roll milling for 5 minutes,
bringing the pH to 7.94. Subsequently, to the mixture was added 18.55
grams of 97 percent by weight sulfolane (obtained from Phillips 66
Company), 0.3 gram of Duasyn Brilliant Red dye (obtained from Hoechst),
10.64 grams of BASF X-34 black dye (obtained from BASF), 0.0505 grams of
polyethylene oxide (obtained from Polysciences), and 0.0996 grams of
Dowicil 200 biocide (obtained from Dow Chemical), followed by roll milling
the mixture for 15 minutes. The resulting mixture had a pH of 7.95. To this
mixture was added an additional 0.61 grams of a 70 percent by weight
solution of phosphorous acid, bringing the pH to 6.98. An additional 7.59
grams of deionized water was added, followed by roll milling for 10
minutes and subsequent filtering to yield an ink composition.
2 12 ~
The ink composition thus prepared was incorporated into a
Hewlett-Packard DeskJet 500 thermal ink jet printer and high quality prints
were generated on paper. Latency and recoverability were tested by
operating the printer in the "de-cap" mode, in which the built-in
maintenance procedures of maintaining the ink jet nozzles capped in a
high humidity environment, were circumvented. After generating prints,
the printer was stopped for a 24 hour period, followed by again generating
prints without any prior maintenance or priming of the nozzles. The ink
composition began generating high quality images after 1.5 pages of
printing had been generated under these conditions.
To 20.43 grams of the ink thus prepared was then added an
additional 0.1 gram of a 70 percent by weight solution of phosphorous
acid, followed by roll milling for 15 minutes and filtering, bringing the pH
of the ink composition to 6.53. The ink composition thus prepared was
incorporated into a Hewlett-Packard DeskJet 500 thermal ink jet printer
and high quality prints were generated on paper. Latency and
recoverability were tested by operating the printer in the "de-cap" mode,
in which the built-in maintenance procedures of maintaining the ink jet
nozzles capped in a high humidity environment, were circumvented. After
generating prints, the printer was stopped for a 24 hour period, followed
by again generating prints without any prior maintenance or priming of
the nozzles. The ink composition began generating high quality images
after l page of printing had been generated underthese conditions.
Other embodiments and modifications of the present invention
may occur to those skilled in the art subsequent to a review of the
information presented herein, these embodiments and modifications, as
well as equivalents thereof, are also included within the scope of this
invention .
