Color ink jet recording method

An ink set and a recording method, especially an ink jet recording method, are provided which can realize a good color image having no significant feathering or bleeding, particularly bleeding derived from color-to-color intermixing. The ink set comprises a yellow ink, a magenta ink, a cyan ink, and optionally a black ink, the cyan ink comprising a resin emulsion, the yellow ink composition and the magenta ink composition comprising a reactant capable of breaking the state of dispersion and/or dissolution of a colorant and the resin emulsion in the cyan ink and the black ink.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an ink jet recording method, wherein two 
ink compositions are deposited onto a recording medium, and an ink set 
used therefor. 
2. Background Art 
An ink jet recording method is a printing method wherein droplets of an ink 
composition are ejected and deposited onto a recording medium such as 
paper. This method has a feature that an image having a high resolution 
and a high quality can be printed at a high speed with a relatively 
inexpensive apparatus. In general, the ink composition used in the ink jet 
recording comprises water as a main component and, added thereto, a 
colorant and a wetting agent such as glycerin added for prevention of 
clogging and other purposes. 
On the other hand, a new ink jet recording method has been recently 
proposed which comprises applying a polyvalent metal salt solution onto a 
recording medium and then applying an ink composition containing a dye 
material having at least one carboxyl group (see e.g., Japanese Patent 
Laid-Open No. 202328/1993). The claimed advantage of this method is that 
polyvalent metal ions combine with the dye to form an insoluble composite 
which can provide an image having water resistance and a high quality free 
from color bleeding. 
Further, an ink jet recording method has been proposed wherein a first ink 
composition containing a pH-sensitive dye is used in combination with a 
second ink composition having such a pH value as will cause precipitation 
of the pH-sensitive dye (Japanese Patent Laid-Open No. 208548/1993). The 
claimed advantage of this method is that use of these two ink compositions 
can realize an image having water resistance and high quality free from 
color bleeding. 
Further, an ink jet recording method has been proposed wherein a color ink 
containing at least a surfactant or a penetrable solvent and a salt for 
imparting a penetrating property is used in combination with a black ink 
which cooperates with the salt to cause thickening or coagulation, thereby 
providing a high-quality color image having a high image density and free 
from color bleeding (Japanese Patent Laid-Open No. 106735/1994). More 
specifically, in this method, two liquids, i.e., a first liquid containing 
a salt and a second liquid of an ink composition, are printed to provide a 
good image. 
Furthermore, other ink jet recording methods wherein two liquids are 
printed have been proposed, for example, in Japanese Patent Laid-Open Nos. 
240557/1991 and 240558/1991. 
SUMMARY OF THE INVENTION 
The present inventors have now found that, in an ink jet recording method 
comprising printing such two liquids, use of in combination two ink 
compositions having specific compositions can realize a color image free 
from feathering or bleeding, particularly not having significant bleeding 
derived from color-to-color intermixing. The present invention has been 
made based on such finding. 
Accordingly, an object of the present invention is to provide an ink set 
which can yield a good color image. 
Another object of the present invention is to provide a recording method 
using this ink set which can realize a good color image. 
According to the first aspect of the present invention, there is provided 
an ink set comprising a yellow ink composition containing a yellow 
colorant, a magenta ink composition containing a magenta colorant, and a 
cyan ink composition containing a cyan colorant, 
the magenta ink composition and the cyan ink composition each comprising a 
resin emulsion and/or an inorganic oxide colloid, 
the yellow ink composition comprising a reactant capable of breaking the 
state of dispersion and/or dissolution of the colorant and the resin 
emulsion in the magenta ink composition and the cyan ink composition. 
According to the second aspect of the present invention, there is provided 
an ink set comprising a yellow ink composition containing a yellow 
colorant, a magenta ink composition containing a magenta colorant, and a 
cyan ink composition containing a cyan colorant, 
the cyan ink composition comprising a resin emulsion and/or an inorganic 
oxide colloid, 
the yellow ink composition and the magenta ink composition each comprising 
a reactant capable of breaking the state of dispersion and/or dissolution 
of the colorant and the resin emulsion in the cyan ink composition. 
According to the third aspect of the present invention, there is provided 
an ink set comprising a yellow ink composition containing a yellow 
colorant, a magenta ink composition having a lower color density 
containing a magenta colorant, a magenta ink composition having a higher 
color density containing a magenta colorant, a cyan ink composition having 
a lower color density containing a cyan colorant, and a cyan ink 
composition having a higher color density containing a cyan colorant, 
the magenta ink composition having a lower color density, and the cyan ink 
composition having a lower color density each comprising a reactant 
capable of breaking the state of dispersion and/or dissolution of the 
colorant in the yellow ink composition, the magenta ink composition having 
a higher color density and the cyan ink composition having a higher color 
density. 
According to the fourth aspect of the present invention, there is provided 
an ink set comprising a yellow ink composition containing a yellow 
colorant, a magenta ink composition having a lower color density 
containing a magenta colorant, a magenta ink composition having a higher 
color density containing a magenta colorant, a cyan ink composition having 
a lower color density containing a cyan colorant, and a cyan ink 
composition having a higher color density containing a cyan colorant, 
the yellow ink composition, the magenta ink composition having a lower 
color density, and the cyan ink composition having a lower color density 
each comprising a reactant capable of breaking the state of dispersion 
and/or dissolution of the colorant in the magenta ink composition having a 
higher color density and the cyan ink composition having a higher color 
density. 
According to the fifth aspect of the present invention, there is provided a 
recording method using the above ink set of the present invention.

DETAILED DESCRIPTION OF THE INVENTION 
Ink Sets According to First and Second Aspects of Invention 
The ink sets according to the first and second aspects of the present 
invention each basically comprise a cyan ink composition. If necessary, it 
may further comprise a black ink composition. The ink compositions 
constituting the ink set according to the present invention each comprise 
at least a colorant, water, and an organic solvent. 
In the ink set according to the first aspect of the present invention, the 
magenta ink composition and the cyan ink composition comprise a resin 
emulsion and/or an inorganic oxide colloid. When the black ink composition 
is contained in the ink set, the black ink composition also preferably 
comprises a resin emulsion and/or an inorganic oxide colloid. Further, in 
the ink set according to this aspect of the present invention, the yellow 
ink composition comprises a reactant capable of breaking the dispersion 
and/or dissolution of the colorant and the resin emulsion and/or the 
inorganic oxide colloid in the magenta ink composition and the cyan ink 
composition. 
In the ink set according to the second aspect of the present invention, the 
cyan ink composition comprises a resin emulsion and/or an inorganic oxide 
colloid. When the black ink composition is contained in the ink set, the 
black ink composition also preferably comprises a resin emulsion and/or an 
inorganic oxide colloid. Further, in this aspect of the present invention, 
the yellow ink composition and the magenta ink composition comprise a 
reactant capable of breaking the dispersion and/or dissolution of a 
colorant and the resin emulsion and/or the inorganic oxide colloid in the 
cyan ink composition. 
The ink sets according to the present invention can realize a good color 
image. A major cause of a deterioration in quality of a color image is 
uneven color mixing at boundary areas between different colors, i.e., 
color bleeding. According to the ink composition of the present invention, 
the color bleeding can be effectively prevented. The ink composition 
containing a reactant, upon contact on a recording medium with the ink 
composition containing a colorant and a resin emulsion of which the state 
of dispersion and/or dissolution is broken by the reactant, agglomerates 
the colorant and the resin emulsion and the inorganic oxide colloid, after 
which color mixing caused by flow of the ink composition is prevented. 
The ink compositions containing a reactant in the ink set according to the 
present invention, i.e., the yellow ink composition in the first aspect of 
the present invention and the yellow and magenta ink compositions in the 
second aspect of the present invention, each basically comprise a 
colorant, water, a water-soluble organic solvent, and a reactant. 
As described above, the reactant according to the present invention is not 
particularly limited so far as it can break the state of dispersion and/or 
dissolution of the colorant and the resin emulsion and/or the inorganic 
oxide colloid in the ink composition free from the reactant. However, 
specific examples of preferred reactants usable herein include polyvalent 
metal salts, polyallylamine, and polyallylamine derivatives. 
Preferred examples of a polyvalent metal salt as a reactant include salts 
which are constituted by divalent or higher polyvalent metallic ions and 
anions bonded to the polyvalent metallic ions and are soluble in water. 
Specific examples of polyvalent metallic ions include divalent metallic 
ions, such as Ca.sup.2+, Cu.sup.2+, Ni.sup.2+, Mg2+, Zn.sup.2+, and 
Ba.sup.2+, trivalent metallic ions, such as Al.sup.3+, Fe.sup.3+, and 
Cr.sup.3+. Anions include Cl.sup.-, NO.sub.3.sup.-, I.sup.-, Br.sup.-, 
ClO.sub.3.sup.-, and CH.sub.3 COO.sup.-. 
In particular, a metal salt constituted by Ca.sup.2+ or Mg.sup.2+ 
provides favorable results in terms of pH of the first solution and the 
quality of prints. 
The concentration of the polyvalent metal salt in the ink composition may 
be suitably determined so as to attain the effect of providing a good 
print quality and preventing clogging. It, however, is preferably about 
0.1 to 40% by weight, more preferably about 5 to 25% by weight. 
According to a preferred embodiment of the present invention, the 
polyvalent metal salt is constituted by divalent or higher polyvalent 
metallic ions and nitrate ions or carboxylate ions bonded to the 
polyvalent metallic ions and is soluble in water. 
The carboxylate ions are preferably derived from a saturated aliphatic 
monocarboxylic acid having 1 to 6 carbon atoms and a carbocyclic 
monocarboxylic acid having 7 to 11 carbon atoms. Preferred examples of the 
saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms include 
formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, 
valeric acid, isovaleric acid, pivalic acid, and hexanoic acid. Among 
them, formic acid and acetic acid are particularly preferred. 
A hydrogen atom(s) on the saturated aliphatic hydrocarbon residue in the 
monocarboxylic acid may be substituted by a hydroxyl group. Preferred 
examples of such carboxylic acids include lactic acid. 
Preferred examples of the carbocyclic monocarboxylic acid having 6 to 10 
carbon atoms include benzoic acid and naphthoic acid with benzoic acid 
being more preferred. 
The polyallylamine and polyallylamine derivative, which may be preferably 
used as the reactant, are cationic polymers which are soluble in water and 
can be positively charged in water. Such polymers include, for example, 
those represented by the following formulae (a), (b), and (c): 
##STR1## 
wherein X.sup.- represents chloride, bromide, iodide, nitrate, phosphate, 
sulfate, acetate or other ion. 
In addition, a copolymer of an allylamine with a diallylamine and a 
copolymer of diallylmethylammonium chloride with sulfur dioxide may also 
be used. 
The content of the polyallylamine and the polyallylamine derivative is 
preferably 0.5 to 10% by weight based on the ink composition. 
Various colorants may be used as the colorant contained in the ink 
composition containing a reactant in the ink set according to the present 
invention so far as they are not agglomerated by the reactant. The 
colorant used in these ink compositions may be either a dye or a pigment. 
According to a preferred embodiment of the present invention, the above 
pigment is preferably added, to the ink, in the form of a pigment 
dispersion prepared by dispersing the pigment in an aqueous medium with 
the aid of a dispersant or a surfactant. Preferred dispersants include 
those commonly used in the preparation of a dispersion of a pigment, for 
example, polymeric dispersant. 
Preferred example of dispersant include cationic dispersants, anionic 
dispersants, and nonionic dispersants. Preferred examples of anionic 
dispersants usable herein include polyacrylic acid, polymethacrylic acid, 
acrylic acid/acrylonitrile copolymer, vinyl acetate/acrylic ester 
copolymer, acrylic acid/alkyl acrylate copolymer, styrene/acrylic acid 
copolymer, styrene/methacrylic acid copolymer, styrene/acrylic acid/alkyl 
acrylate copolymer, styrene/methacrylic acid/alkyl acrylate copolymer, 
styrene/.alpha.-methylstyrene/acrylic acid copolymer, 
styrene/.alpha.-methylstyrene/acrylic acid/alkyl acrylate copolymer, 
styrene/maleic acid copolymer, vinylnaphthalene/maleic acid copolymer, 
vinyl acetate/ethylene copolymer, vinyl acetate/fatty acid/vinylethylene 
copolymer, vinyl acetate/maleic ester copolymer, vinyl acetate/crotonic 
acid copolymer, and vinyl acetate/acrylic acid copolymer. Preferred 
examples of the anionic dispersant include sodium dodecylbenzenesulfonate, 
sodium laurate and an ammonium salt of a polyoxyethylene alkyl ether 
sulfate. Further, preferred examples of the nonionic dispersant include a 
polyoxyethylene alkyl ether, a polyoxyethylene alkyl ester, a 
polyoxyethylene sorbitan fatty acid ester, a polyoxyethylene alkyl phenyl 
ether, a polyoxyethylene alkylamine, and a polyoxyethylene alkylamide. 
They may be used alone or as a mixture of two or more. Further, it is also 
possible to use commercially available nonionic dispersants such as OLFINE 
Y and Surfynol 82, 104, 440, 465, 485 and TG (all the above products being 
acetylene glycol and manufactured by Air Products and Chemicals Inc.) and 
Solsperse 27000 (manufactured by Zeneca Co., Ltd. 
According to a preferred embodiment of the present invention, the nonionic 
dispersant is preferable, especially when a polyvalent metal salt is used 
as a reactant. The use of the nonionic dispersant can realize a good 
storage stability of the ink composition. Furthermore, the use of the 
nonionic dispersant can realize a stable printing for long time in ink Jet 
printing with a piezoelectric recording head. 
According to a further preferred embodiment of the present invention, when 
the ink composition that contains a reactant include a nonionic 
dispersant, the ink composition that is free from a reactant preferably 
include an anionic dispersant. 
Specific examples of organic solvents usable herein include high-boiling 
organic solvents. The high-boiling organic solvent serves to prevent the 
ink composition from being concentrated due to evaporation, thus 
preventing clogging of a recording head. Preferred examples of 
high-boiling organic solvents include polyhydric alcohols such as ethylene 
glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 
polypropylene glycol, propylene glycol, butylene glycol, 
1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, 
trimethylolethane, and trimethylolpropane; alkyl ethers of polyhydric 
alcohols, such as ethylene glycol monoethyl ether, ethylene glycol 
monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol 
monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol 
monomethyl ether, triethylene glycol monoethyl ether, and triethylene 
glycol monobutyl ether; urea, 2-pyrrolidone, N-methyl-2-pyrrolidone, 
1,3-dimethyl-2-imidazolidinone, and triethanolamine. 
Although the amount of the high-boiling organic solvent added is not 
particularly limited, it is preferably about 0.5 to 40% by weight, more 
preferably about 2 to 20% by weight. 
The reactant-containing ink composition may contain a low-boiling organic 
solvent as the organic solvent. Preferred examples of low-boiling organic 
solvents usable herein include methanol, ethanol, n-propyl alcohol, 
isopropyl alcohol, n-butanol, sec-butanol, tert-butanol, isobutanol, and 
n-pentanol. Monohydric alcohols are particularly preferred. The 
low-boiling organic solvent has the effect of shortening the time taken 
for drying the ink. The amount of the low-boiling organic solvent added is 
preferably in the range of from 0.5 to 10% by weight, more preferably in 
the range of from 1.5 to 6% by weight. 
According to a preferred embodiment of the present invention, the 
reactant-containing ink composition may contain a penetrating agent. 
Penetrating agents usable herein include various surfactants such as 
anionic, cationic, and amphoteric surfactants; alcohols such as methanol, 
ethanol, and iso-propyl alcohol; and lower alkyl ethers of polyhydric 
alcohols, such as ethylene glycol monomethyl ether, diethylene glycol 
monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol 
monobutyl ether, propylene glycol monobutyl ether, and dipropylene glycol 
monobutyl ether. 
The ink compositions, containing a resin emulsion and/or an inorganic oxide 
colloid, constituting the ink set according to the present invention, that 
is, the magenta and cyan ink compositions in the first aspect of the 
present invention and the cyan ink compositions in the second aspect of 
the present invention, each basically comprise a colorant, water, a 
water-soluble organic solvent, and a resin emulsion and/or an inorganic 
oxide colloid. 
The colorant used in these ink compositions may be either a dye or a 
pigment so far as the state of the dispersion and/or dissolution can be 
broken by the reactant. The pigment, however, is preferred. 
Dyes usable herein include various dyes commonly used in ink compositions, 
especially ink jet recording, such as direct dyes, acid dyes, foodstuff 
dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat 
dyes, and reactive disperse dyes. 
Regarding the pigment, inorganic and organic pigments are usable without 
any particular limitation. Examples of the inorganic pigment include, in 
addition to titanium oxide and iron oxide, carbon blacks produced by known 
processes, such as contact, furnace, and thermal processes. Examples of 
the organic pigment include azo pigments (including azo lake, insoluble 
azo pigment, condensed azo pigment, and chelate azo pigment), polycyclic 
pigments (for example, phthalocyanine, perylene, perinone, anthraquinone, 
quinacridone, dioxazine, thioindigo, isoindolinone, and quinophthalone 
pigments), dye chelates (for example, basic dye chelates and acid dye 
chelates), nitro pigments, nitroso pigments, and aniline black. 
According to a preferred embodiment of the present invention, the above 
pigment is preferably added, to the ink, in the form of a pigment 
dispersion prepared by dispersing the pigment in an aqueous medium with 
the aid of a dispersant or a surfactant. Preferred dispersants include 
those commonly used in the preparation of a dispersion of a pigment, for 
example, polymeric dispersant. Preferred examples of the dispersant may 
include dispersants listed in connection with the ink composition 
containing a reactant. 
According to a preferred embodiment of the present invention, as described 
above, the ink composition that is free from a reactant preferably 
includes an anionic dispersant when the ink composition that contains a 
reactant includes a nonionic dispersant. 
Preferred examples of the anionic dispersant usable herein include 
polyacrylic acid, polymethacrylic acid, acrylic acid/acrylonitrile 
copolymer, vinyl acetate/acrylic ester copolymer, acrylic acid/alkyl 
acrylate copolymer, styrene/acrylic acid copolymer, styrene/methacrylic 
acid copolymer, styrene/acrylic acid/alkyl acrylate copolymer, 
styrene/methacrylic acid/alkyl acrylate copolymer, 
styrene/a-methylstyrene/acrylic acid copolymer, 
styrene/.alpha.-methylstyrene/acrylic acid/alkyl acrylate copolymer, 
styrene/maleic acid copolymer, vinylnaphthalene/maleic acid copolymer, 
vinyl acetate/ethylene copolymer, vinyl acetate/fatty acid/vinylethylene 
copolymer, vinyl acetate/maleic ester copolymer, vinyl acetate/crotonic 
acid copolymer, and vinyl acetate/acrylic acid copolymer. 
According to a preferred embodiment of the present invention, the weight 
average molecular weight of the copolymer is preferably about 3,000 to 
50,000, more preferably about 5,000 to 30,000, most preferably about 7,000 
to 15,000. 
The dispersant added may be added in any amount so far as the pigment can 
be stably dispersed and the other effects of the present invention are not 
lost. According to a preferred embodiment of the present invention, the 
amount of the dispersant added is preferably in the range of from about 
1:0.06 to 1:3, more preferably in the range of from about 1:0.125 to 1:3, 
in terms of the ratio of the pigment to the dispersant. 
In this connection, that the dispersant and the surfactant contained in the 
dispersion of the pigment function also as the dispersant and the 
surfactant for the ink composition will be apparent to a person having 
ordinary skill in the art. 
The amount of the pigment added to the ink is preferably about 0.5 to 25% 
by weight, more preferably about 2 to 15% by weight. 
The resin emulsion contained in the ink composition refers to an emulsion 
comprising water as a continuous phase and the following resin component 
as a dispersed phase. Resin components as the dispersed phase include 
acrylic resin, vinyl acetate resin, styrene/butadiene resin, vinyl 
chloride resin, (meth)acrylate/styrene resin, butadiene resin, styrene 
resin, crosslinked acrylic resin, crosslinked styrene resin, 
benzoguanamine resin, phenolic resin, silicone resin, and epoxy resin. 
According to a preferred embodiment of the present invention, the resin is 
a polymer having a combination of a hydrophilic segment with a hydrophobic 
segment. The particle diameter of the resin component is not particularly 
limited so far as the resin component can form an emulsion. It, however, 
is preferably not more than about 150 nm, more preferably about 5 to 100 
nm. 
The resin emulsion may be prepared by dispersion polymerization of a resin 
monomer, optionally together with a surfactant, in water. For example, an 
emulsion of an acrylic resin or a styrene/acrylic resin may be prepared by 
subjecting an ester of (meth)acrylic acid or alternatively an ester of 
(meth)acrylic acid in combination with styrene to dispersion 
polymerization in water in the presence of a surfactant. In general, the 
mixing ratio of the resin component to the surfactant is preferably about 
10:1 to 5:1. When the amount of the surfactant used falls within the above 
range, it is possible to provide an ink which has good water resistance in 
the form of an image and good penetrability. The surfactant is not 
particularly limited. Preferred examples thereof include anionic 
surfactants (for example, sodium dodecylbenzenesulfonate, sodium laurate 
and an ammonium salt of a polyoxyethylene alkyl ether sulfate); nonionic 
surfactants (for example, a polyoxyethylene alkyl ether, a polyoxyethylene 
alkyl ester, a polyoxyethylene sorbitan fatty acid ester, a 
polyoxyethylene alkyl phenyl ether, a polyoxyethylene alkylamine, and a 
polyoxyethylene alkylamide). They may be used alone or as a mixture of two 
or more. Further, it is also possible to use acetylene glycol (OLFINE Y 
and Surfynol 82, 104, 440, 465, 485 and TG (all the above products being 
manufactured by Air Products and Chemicals Inc.). 
The ratio of the resin as the component constituting the dispersed phase to 
water is suitably 60 to 400 parts by weight based on 100 parts by weight 
of the resin with 100 to 200 parts by weight, based on 100 parts by weight 
of the resin, of water being preferred. 
Known resin emulsions may also be used as the above resin emulsion. For 
example, resin emulsions described in Japanese Patent Publication No. 
1426/1987 and Japanese Patent Laid-Open Nos. 56573/1991, 79678/1991, 
160068/1991, and 18462/1992 as such may be used as the resin emulsion in 
the present invention. 
Further, commercially available resin emulsions may also be used, and 
examples thereof include Microgel E-1002 and E-5002 (styrene/acrylic resin 
emulsion, manufactured by Nippon Paint Co., Ltd.), Voncoat 4001 (acrylic 
resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.), 
Voncoat 5454 (styrene/acrylic resin emulsion, manufactured by Dainippon 
Ink and Chemicals, Inc.), SAE-1014 (styrene/acrylic resin emulsion, 
manufactured by Nippon Zeon Co., Ltd.), and Saivinol SK-200 (acrylic resin 
emulsion, manufactured by Saiden Chemical Industry Co., Ltd.). 
According to a preferred embodiment of the present invention, the amount of 
the resin emulsion incorporated therein is preferably such that the amount 
of the resin component is in the range of from 0.1 to 40% by weight, more 
preferably in the range of from 1 to 25% by weight. 
The resin emulsion, by virtue of interaction with the reactant, has the 
effect of preventing the creation of color bleeding and, at the same time, 
inhibiting the penetration of a coloring component and, further, 
accelerating the fixation on the recording medium. Further, some resin 
emulsions have an additional effect that they form a film on the recording 
medium to improve the rubbing resistance of the resultant print. 
The ink composition used in the present invention may contain an inorganic 
oxide colloid. Preferred examples of inorganic oxide colloids usable 
herein include colloidal silica and alumina colloid. These are generally a 
colloidal solution of ultrafine particles of SiO.sub.2, Al.sub.2 O.sub.3 
or the like in water or an organic solvent. Commercially available 
inorganic oxide colloids are generally such that the dispersion medium is 
water, methanol, 2-propanol, n-propanol, xylene or the like and the 
diameter of SiO.sub.2, Al.sub.2 O.sub.3 and other particles is 5 to 100 
nm. Further, pH of the colloidal solutions of inorganic oxide is, in many 
cases, adjusted to the acidic or alkaline side rather than the neutral 
region. This is because the stable dispersion region of the inorganic 
oxide colloid is present on the acidic side or the alkaline side. In 
adding the colloidal solution to the ink composition, pH of the stable 
dispersion region of the inorganic oxide colloid and pH of the ink should 
be taken into consideration. 
The amount of the inorganic oxide colloid added to the ink composition is 
preferably 0.1 to 15% by weight, and addition of two or more inorganic 
oxide colloids is also possible. 
According to a preferred embodiment of the present invention, the ink 
composition comprising a resin emulsion and/or an inorganic oxide colloid 
preferably comprises an alginic acid derivative. Preferred examples of 
alginic acid derivatives include alkali metal salts (for example, sodium 
salt and potassium salt) of alginic acid, organic acid salts (for example, 
triethanolamine salt) of alginic acid, and ammonium alginate. 
The amount of the alginic acid derivative added to the ink composition is 
preferably about 0.01 to 1% by weight, more preferably about 0.05 to 0.5% 
by weight. 
Although the reason why a good image can be formed by the addition of an 
alginic acid derivative has not been elucidated yet, it is considered that 
the reactant, particularly the polyvalent metal salt, reacts with the 
alginic acid derivative in the ink composition to vary the dispersed state 
of the colorant, promoting the agglomeration and fixation of the colorant 
onto the recording medium. 
According to a preferred embodiment of the present invention, the ink 
composition comprising a resin emulsion and/or an inorganic oxide colloid 
preferably contains an organic solvent. The organic solvent is preferably 
a low-boiling organic solvent, and preferred examples thereof include 
methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, 
sec-butanol, tert-butanol, iso-butanol, and n-pentanol. Monohydric 
alcohols are particularly preferred. The low-boiling organic solvent has 
the effect of shortening the time taken for drying the ink. 
Further, according to a preferred embodiment of the present invention, the 
ink composition comprising a resin emulsion and/or an inorganic oxide 
colloid further comprises a wetting agent comprising a high-boiling 
organic solvent. Preferred examples of high-boiling organic solvents 
usable herein include polyhydric alcohols such as ethylene glycol, 
diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene 
glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, 
hexylene glycol, glycerin, trimethylolethane, and trimethylolpropane; 
alkyl ethers of polyhydric alcohols, such as ethylene glycol monoethyl 
ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl 
ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl 
ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl 
ether, and triethylene glycol monobutyl ether; urea; 2-pyrrolidone; 
N-methyl-2-pyrrolidone; 1,3-dimethyl-2-imidazolidinone; and 
triethanolamine. 
The amount of the wetting agent added is preferably in the range of from 
0.5 to 40% by weight, more preferably in the range of from 2 to 20% by 
weight, based on the ink. The amount of the low-boiling organic solvent 
added is preferably 0.5 to 10% by weight, more preferably in the range of 
from 1.5 to 6% by weight, based on the ink. 
According to a preferred embodiment of the present invention, the ink 
composition comprising a resin emulsion and/or an inorganic oxide colloid 
contains a saccharide. Examples of saccharides usable herein include 
monosaccharides, disaccharides, oligosaccharides (including trisaccharides 
and tetrasaccharides), and other polysaccharides, preferably glucose, 
mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, 
glucitol, sorbitol, maltose, cellobiose, lactose, sucrose, trehalose, and 
maltotriose. The term "polysaccharide" used herein refers to saccharides, 
in a broad sense, including substances which widely exist in the natural 
world, such as alginic acid, a-cyclodextrin, and cellulose. 
Derivatives of these saccharides include reducing sugars of the above 
saccharides (for example, sugar alcohols represented by the general 
formula HOCH.sub.2 (CHOH).sub.n CH.sub.2 OH wherein n is an integer of 2 
to 5), oxidized sugars (for example, aldonic acid and uronic acid), amino 
acid, and thiosugars. Sugar alcohols are particularly preferred, and 
specific examples thereof include maltitol and sorbitol. 
The content of the above saccharide is suitably in the range of from 0.1 to 
40% by weight, preferably 0.5 to 30% by weight, based on the ink. 
Further, the ink compositions constituting the ink set according to the 
present invention may, if necessary, contain pH adjustors, preservatives, 
antimolds and the like. 
Ink Set According to Third and Fourth Aspects of Invention 
The ink set according to the third or fourth aspect of the present 
invention comprises a yellow ink composition, two magenta ink compositions 
different from each other in color density, two cyan ink compositions 
different from each other in color density, and optionally a black ink 
composition. 
In the third aspect of the present invention, a reactant is added to the 
magenta ink having a lower color density (hereinafter often referred to as 
"light-colored magenta ink") and the cyan ink composition having a lower 
color density (hereinafter often referred to as "light-colored cyan ink"). 
Further, the fourth aspect of the present invention, a reactant is added 
to the yellow ink composition, a light-colored magenta ink and a 
light-colored cyan ink. In the ink set of the third or fourth aspect of 
the present invention, what is required of the reactant is to break the 
state of dispersion and/or dissolution of the colorant contained in at 
least the magenta ink composition having a higher color density, a cyan 
ink composition having a higher color density, and, the yellow ink 
composition in the case of the fourth aspect of the present invention, and 
optionally, the black ink composition. 
According to a preferred embodiment of the present invention, in the third 
and fourth aspects of the present invention, the ink composition that is 
free from a reactant may include a resin emulsion and/or an inorganic 
oxide colloid, and the reactant can break the state of dispersion and/or 
dissolution of the resin emulsion and/or the inorganic oxide colloid. In 
particular, in the third aspect of the present invention, the yellow ink 
composition, the magenta ink composition having a higher color density, 
the cyan ink composition having a higher color density, and, if necessary, 
the black ink composition comprise a resin emulsion and/or an inorganic 
oxide colloid. In the fourth aspect of the present invention, the magenta 
ink composition having a higher color density, the cyan ink composition 
having a higher color density, and, if necessary, the black ink 
composition comprise a resin emulsion and/or an inorganic oxide colloid. 
As with the ink sets according to the first and second aspects of the 
present invention, the ink set according to the third and fourth aspects 
of the present invention can provide a good color image. 
Components of the ink compositions constituting the ink set according to 
the third and fourth aspects of the present invention may be substantially 
the same as those of the ink compositions constituting the ink sets 
according to the first and second aspects of the present invention. The 
difference in color density between ink compositions different from each 
other in color density may be created by making the dye concentration of 
one ink composition lower or higher than that of the other ink composition 
or alternatively by suitably selecting the kind of the colorant used. 
Ink Set According to Fifth Aspect of Invention 
The ink set according to the fifth aspect of the present invention 
comprises a yellow ink composition, a magenta ink composition, a cyan ink 
composition and a black ink composition. Further, the black ink 
composition comprises a resin emulsion and/or an inorganic oxide colloid, 
and the yellow ink composition, the magenta ink composition, and cyan ink 
composition each comprises a reactant capable of breaking the state of 
dispersion and/or dissolution of the colorant and the resin emulsion in 
the black ink composition. 
As with the ink sets according to the first and second aspects of the 
present invention, the ink set according to the fifth aspect of the 
present invention can provide a good color image. 
Components of the ink compositions constituting the ink set according to 
the fifth aspect of the present invention may be substantially the same as 
those of the ink compositions constituting the ink sets according to the 
first and second aspects of the present invention. 
Ink Jet Recording Method 
The ink sets according to the present invention are used in recording 
methods using an ink composition. Recording methods using an ink 
composition include, for example, an ink jet recording method, a recording 
method using writing utensils, such as pens, and other various printing 
methods. Particularly preferably, the ink compositions according to the 
present invention are used in the ink jet recording method. 
Thus, according to another aspect of the present invention, there is 
provided an ink jet recording method using the ink set of the present 
invention. According to the ink jet recording method, the sequence of 
printing of the ink compositions is not particularly limited. 
Specifically, the ink composition containing a reactant may be first 
printed onto a recording medium followed by printing of the ink 
composition containing a colorant and a resin emulsion which can be 
agglomerated by the reactant, or vice versa. 
According to a preferred embodiment of the present invention, the mass of 
the droplet of the ink composition ejected is regulated so that the size 
of a pixel formed by the ink composition that contains a reactant is 
smaller than a pixel formed by the ink composition that is free from a 
reactant. More specifically, the mass of the droplet of the ink 
composition that contains a reactant is preferably less than 30 to 100% by 
weight of the mass of the droplet of the ink composition that is free from 
a reactant. This can realize a better image, especially an image with 
minimized feathering or color bleeding. 
EXAMPLES 
The present invention will be described in more detail with reference to 
the following examples, though it is not limited to these examples only. 
The following ink compositions were prepared according to a conventional 
method. Specifically, a colorant component, together with a dispersant 
component, was dispersed. After other components were added thereto, they 
were mixed together. Insolubles having a given size or larger were removed 
by filtration to give an ink composition. 
______________________________________ 
Yellow ink 1 
C.I. Pigment Yellow 17 2 wt % 
Solsperse 27000 1 wt % 
(nonionic dispersant, manufactured by 
Zeneca Co., Ltd.) 
Sucrose 0.7 wt % 
Maltitol 6.3 wt % 
Glycerin 10 wt % 
2-Pyrrolidone 2 wt % 
Surfynol TG 1 wt % 
Magnesium nitrate hexahydrate 5 wt % 
(reactant) 
Pure water Balance 
Yellow ink 2 
C.I. Acid Yellow 23 3 wt % 
Diethylene glycol 10 wt % 
Surfynol TG 1 wt % 
Polyallylamine PAA-10C 30 wt % 
(reactant, resin component 10%, 
manufactured Nitto Boseki Co., Ltd.) 
Pure water Balance 
Yellow ink 3 
C.I. Pigment Yellow 74 2 wt % 
Styrene/acrylic copolymer 1 wt % 
ammonium salt 
(nonionic dispersant) 
Grandoll Pp-1000 5 wt % 
(styrene/acrylic resin emulsion, 
resin component 45%, manufactured by 
Dainippon Ink and Chemicals, Inc.) 
Alumina Sol 200 5 wt % 
(Al.sub.2 O.sub.3 content 10%, manufactured by 
Nissan Chemical Industry Ltd.) 
Maltitol 10 wt % 
Glycerin 10 wt % 
2-Pyrrolidone 2 wt % 
Surfynol TG 1 wt % 
Pure water Balance 
Magenta ink 1 
C.I. Pigment Red 57:1 2 wt % 
Solsperse 27000 1 wt % 
(nonionic dispersant) 
Sucrose 10 wt % 
Glycerin 5 wt % 
Triethanolamine 2 wt % 
Surfynol TG 1 wt % 
Calcium chloride 8 wt % 
(reactant) 
Pure water Balance 
Magenta ink 2 
C.I. Direct Red 9 3 wt % 
Diethylene glycol 10 wt % 
Surfynol TG 1 wt % 
Polyallylamine PAA-10C 30 wt % 
(reactant) 
Pure water Balance 
Magenta ink 3 
C.I. Pigment Red 122 3 wt % 
Styrene/acrylic copolymer 1 wt % 
ammonium salt 
(anionic dispersant) 
Microgel E-5002 3.5 wt % 
(styrene/acrylic resin emulsion, 
resin component 29.2%, MFT = about 80.degree. C., 
manufactured by Nippon Paint Co., Ltd.) 
Sucrose 0.7 wt % 
Maltitol 6.3 wt % 
Glycerin 10 wt % 
2-Pyrrolidone 2 wt % 
Surfynol TG 1 wt % 
Pure water Balance 
Light-colored magenta ink 1 
C.I. Pigment Red 122 0.5 wt % 
Solsperse 27000 0.3 wt % 
(nonionic dispersant) 
Diethylene glycol 10 wt % 
Surfynol TG 1 wt % 
Ammonium hydroxide 1 wt % 
Magnesium sulfate tetrahydrate 10 wt % 
(reactant) 
Pure water Balance 
Cyan ink 1 
C.I. Direct Blue 199 3 wt % 
Snowtex S 5 wt % 
(colloidal silica, SiO.sub.2 content 30%, 
manufactured by Nissan Chemical Industry Ltd.) 
Diethylene glycol 10 wt % 
Surfynol TG 1 wt % 
Pure water Balance 
Cyan ink 2 
C.I. Direct Blue 199 3 wt % 
Diethylene glycol 10 wt % 
Surfynol TG 1 wt % 
Danfix 723 3 wt % 
(reactant, resin component 35%, 
manufactured Nitto Boseki Co., Ltd.) 
Potassium hydroxide 1 wt % 
Pure water Balance 
Cyan ink 3 
C.I. Pigment Blue 15:3 2 wt % 
Styrene/acrylic copolymer 1 wt % 
ammonium salt 
(anionic dispersant) 
Microgel E-5002 3.5 wt % 
Sucrose 0.7 wt % 
Maltitol 6.3 wt % 
Glycerin 10 wt % 
2-Pyrrolidone 2 wt % 
Surfynol TG 1 wt % 
Pure water Balance 
Cyan ink 4 
C.I. Pigment Blue 15:3 2 wt % 
Solsperse 27000 1 wt % 
(nonionic dispersant, manufactured by 
Zeneca Co., Ltd.) 
Magnesium acetate tetrahydrate 5 wt % 
(reactant) 
Sucrose 0.7 wt % 
Maltitol 6.3 wt % 
Glycerin 10 wt % 
2-Pyrrolidone 2 wt % 
Surfynol 465 1 wt % 
Ethanol 3 wt % 
Pure water Balance 
Light-colored cyan ink 1 
C.I. Pigment Blue 15:3 0.3 wt % 
Solsperse 27000 0.2 wt % 
(nonionic dispersant) 
Diethylene glycol 10 wt % 
Surfynol TG 1 wt % 
Ammonium hydroxide 1 wt % 
Magnesium sulfate tetrahydrate 10 wt % 
(reactant) 
Pure water Balance 
Black ink 1 
Carbon black Raven 1080 5 wt % 
(manufactured by Columbian Carbon) 
Styrene/acrylic acid copolymer ammonium salt 1 wt % 
(anionic dispersant) 
Voncoat 4001 4 wt % 
(acrylic resin emulsion, resin component 50%, 
MFT = 5.degree. C., manufactured by Dainippon Ink and 
Chemicals, Inc.) 
Sucrose 0.7 wt % 
Maltitol 6.3 wt % 
Glycerin 10 wt % 
2-Pyrrolidone 2 wt % 
Surfynol TG 1 wt % 
Pure water Balance 
Black ink 2 
Carbon black MA 7 5 wt % 
(manufactured by Mitsubishi Kasei Corp.) 
Solsperse 27000 1 wt % 
(nonionic dispersant) 
Glycerin 15 wt % 
Surfynol TG 1 wt % 
Dan fix 723 3 wt % 
(reactant) 
Potassium hydroxide 1 wt % 
Pure water Balance 
______________________________________ 
Print Evaluation Test 1 
Printing was carried out using ink sets 1 and 2 shown in the following 
table with ink jet printer MJ700V2C (manufactured by Seiko Epson Co., 
Ltd.) onto the following papers. In the printing, a solid image (100% 
duty) of a cyan ink, a magenta ink, or a yellow ink was printed, and, 
immediately after that, a letter was printed on the solid image using a 
black ink. In this case, simultaneous deposition of a yellow ink was 
always performed on a dot to which the black ink was to be deposited. 
(1) Xerox P Paper (Xerox Corp.) 
(2) Ricopy 6200 Paper (Ricoh Co. Ltd.) 
(3) Xerox 4024 Paper (Xerox Corp.) 
(4) Neenah Bond Paper (Kimberly-Clark) 
(5) Xerox R Paper (Xerox Corp., recycled paper) 
(6) Yamayuri (Honshu Paper Co., Ltd., recycled paper) 
The letter with the black ink for each print was examined for uneven color 
mixing at its boundary areas. The results were evaluated according to the 
following criteria. 
No color mixing with clear boundaries for all the test paper: excellent (A) 
Color mixing in a feather form for any test paper: good (B) 
Color mixing, for all the test papers, to such an extent that the outline 
of the letter is blurred: unacceptable (NG) 
The results are summarized in the following table. 
TABLE 1 
______________________________________ 
Ink Reactant Bleeding 
______________________________________ 
Ink set 1 Yellow ink 1 
Polyvalent metal 
A 
salt 
Magenta ink 1 Polyvalent metal A 
salt 
Cyan ink 3 -- A 
Black ink 1 -- -- 
Ink set 2 Yellow ink 3 -- A 
Magenta ink 3 -- A 
Cyan ink 2 Polyallylamine A 
Black ink 2 Polyallylamine -- 
______________________________________ 
Print Evaluation Test 2 
Printing was carried out using ink sets 3, 4, 5, and 6 shown in the 
following table with ink jet printer MJ700V2C. A solid image (100% duty) 
of a cyan ink, a magenta ink, or a yellow ink was printed in the same 
papers as used in the print evaluation test 1. Further, immediately after 
that, a black letter was formed thereon by overprinting an cyan ink, a 
magenta ink, and a yellow ink. The black letter for each print was 
examined for uneven color mixing at its boundary areas. The results were 
evaluated according to the same criteria as used in the print evaluation 
test 1. The results are summarized in the following table. 
TABLE 2 
______________________________________ 
Ink Reactant Bleed 
______________________________________ 
Ink set 3 Yellow ink 1 Polyvalent metal 
A 
salt 
Magenta ink 3 -- A 
Cyan ink 3 -- A 
Ink set 4 Yellow ink 2 Polyallylamine A 
Magenta ink 2 Polyallylamine A 
Cyan ink 1 -- A 
Ink set 5 Yellow ink 3 -- B 
Magenta ink 2 Polyallylamine A 
Cyan ink 2 Polyallylamine A 
Ink set 6 Yellow ink 3 -- B 
Magenta ink 3 -- A 
Cyan ink 2 Polyallylamine A 
______________________________________ 
Print Evaluation Test 3 
Printing was carried out using an ink set 7 shown in the following table 
with ink Jet printer MJ700V2C in the same manner as in the print 
evaluation test 1, except that a solid image of magenta was formed by 
overprinting a light-colored magenta ink and a magenta ink, a solid image 
of cyan was formed by overprinting a light-colored cyan ink and a cyan 
ink. Further, simultaneous deposition of a light-colored magenta ink was 
always performed on a dot to which the black ink was to be deposited. For 
each print, the letter formed using the black ink composition was examined 
for uneven color mixing at its boundary areas. The results were evaluated 
according to the same criteria as used in the print evaluation test 1. The 
results are summarized in the following table. 
TABLE 3 
______________________________________ 
Ink Reactant Bleeding 
______________________________________ 
Ink set 7 Light-colored 
Polyvalent metal 
A 
magenta ink 1 salt 
Light-colored Polyvalent metal A 
cyan ink 1 salt 
Yellow ink 3 -- A 
Magenta ink 3 -- A 
Cyan ink 3 -- A 
Black ink 1 -- -- 
______________________________________ 
Print Evaluation Test 4 
Printing was carried out using an ink set 8 shown in the following table 
with ink jet printer MJ700V2C in the same manner as in the print 
evaluation test 1, except that a solid image of magenta was formed by 
overprinting a light-colored magenta ink and a magenta ink and a blotted 
image of cyan was formed by overprinting a light-colored cyan ink and a 
cyan ink. Further, deposition of a yellow ink was not performed on a dot 
to which the black ink was to be deposited. For each print, the letter 
formed using the black ink composition was examined for uneven color 
mixing at its boundary areas. The results were evaluated according to the 
same criteria as used in the print evaluation test 1. The results are 
summarized in the following table. 
TABLE 4 
______________________________________ 
Ink Reactant Bleeding 
______________________________________ 
Ink set 8 Light-colored 
Polyvalent metal 
A 
magenta ink 1 salt 
Light-colored Polyvalent metal A 
cyan ink 1 salt A 
Yellow ink 1 Polyvalent metal A 
salt 
Magenta ink 3 -- A 
Cyan ink 3 -- A 
Black ink 1 -- -- 
______________________________________ 
Print Evaluation Test 5 
An ink set 9 specified in the following table was evaluated in the same 
manner as in the print evaluation test 1. The results are summarized in 
the following table. 
TABLE 5 
______________________________________ 
Ink Reactant Bleeding 
______________________________________ 
Ink set 9 Yellow ink 1 
Polyvalent metal 
A 
salt 
Magenta ink 1 Polyvalent metal A 
salt 
Cyan ink 4 Polyvalent metal A 
salt 
Black ink 1 -- -- 
______________________________________ 
Test on Storage Stability of Inks 
The ink compositions prepared above were placed in respective sample 
bottles, and the bottles were hermetically sealed and stored under an 
environment of 50.degree. C. Three months after the initiation of the 
storage, the viscosity, the surface tension and PH of the inks were 
measured and found to be substantially the same as those before the 
storage.