Ink, ink-jet recording process and apparatus making use of the same

Provided is an ink comprising a compound having at least one carbonyl group and a hydrazide compound selected from the group consisting of a styrene-maleic acid resin having at least two hydrazide groups, a polyacrylic acid having at least two hydrazide groups and a compound represented by the formula ##STR1## wherein R represents (CH.sub.2).sub.n or C.sub.6 H.sub.4, where n is an integer of 0 to 10, or the formula ##STR2##

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an ink suited for ink-jet printers, and 
also to an ink-jet recording process and apparatus that make a record on 
paper by causing ink to fly from orifices of a recording head by the 
action of energy, preferably heat energy. More particularly, it relates to 
an ink-jet recording process and apparatus that make a record on 
non-coated paper such as paper for copying, paper for reporting, 
notepaper, letter paper, bond paper and computer printout paper 
(continuous business forms) commonly used in offices and homes. 
2. Related Background Art 
Ink-jet recording systems have the advantages that they make less noise in 
the course of recording and a recorded image with a high resolution can be 
obtained at a high speed because of use of a highly integrated head. Inks 
used in such ink-jet recording systems are those prepared by dissolving 
various kinds of water-soluble dyes in water or in a mixed solution of 
water and an organic solvent. 
When the water-soluble dyes are used, however, light fastness of recorded 
images is often questioned because such water-soluble dyes have poor light 
fastness by nature. 
Water fastness of recorded images is also often questioned because the dye 
is water-soluble. More specifically, if recorded images become wet with 
rain, sweat, or water from food and drink, they may become blurred or 
disappear. 
Meanwhile, light fastness and water fastness are similarly questioned also 
in writing utensils such as ball-point pens because water-soluble dyes are 
mainly used, and various water-based pigment inks for writing utensils 
have been proposed so that such problems can be settled. Examples of 
studies on dispersion stability, prevention of ink solidification at pen 
points and prevention of ball wear of ballpoint pens for the purpose of 
putting water-based pigment inks into practical use are seen in Japanese 
Patent Application Laid-Open No. 58-80368, No. 61-200182, No. 61-247774, 
No. 61-272278, No. 62-568, No. 62-101671, No. 62-101672, No. 1-249869, No. 
1-301760, etc. Recently, ball-point pens or markers making use of 
water-based pigment inks have become commercially available. 
Also ink-jet recording inks making use of water-based pigment inks, pigment 
inks making use of specific water-soluble solvent and polymeric dispersant 
are proposed in Japanese Patent Application Laid-Open No. 56-147859 and 
No. 56-147860. Inks making use of a pigment and a dye in combination are 
also proposed in Japanese Patent Application Laid-Open No. 4-57859 and No. 
4-57860. 
In ink-jet recording, it is very important for non-volatile components in 
the ink to rapidly cohere after ejection onto the recording paper. When, 
however, the conventional water-based pigment inks are used in ink-jet 
recording, the non-volatile components which have cohered on recording 
paper are kept present on the recording paper as a solid material after 
the ink has been fixed thereon. Hence, there has been the problem that 
print surfaces stain when strongly rubbed or when traced with a 
highlighter pen (fluorescent-ink pen). 
When conventional inks are used to make a record by ink-jet recording on 
plain paper on which no particular ink-receiving layer is formed, there 
also has been the problem that leathering may occur, though it differs 
more or less depending on composition. Accordingly, in order to prevent 
the feathering, it is proposed to add a highly viscous solvent to ink. The 
feathering can be prevented by increasing the ink viscosity. However, a 
highly viscous organic solvent must be added in a large quantity for such 
purpose, so that the ink comes to have an excessively high viscosity, 
which brings about the problem that the ejection of ink may become 
unstable because of a decrease in ejection speed of the ink from nozzles 
or a decrease in surface tension. There still also has been the problem 
that the degree of print density or feathering may differ depending on the 
types of recording paper. 
As an attempt to solve such problems, Japanese Patent Publication No. 
60-500540 and Japanese Patent Application Laid-open No. 63-159485 disclose 
techniques in which iodine or the like is added to ink to improve the 
quality level of prints on a specific recording paper. The techniques 
disclosed in these publications, however, are not effective for a great 
variety of recording paper. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide an ink that 
can be free from any irregular print quality level due to differences in 
the types of recording paper and can satisfy fixing speed and rub-off 
fastness, and also thereby obtain stable recorded images without 
decreasing print density. 
Another object of the present invention is to provide an ink that enables 
blurring-free recording on all sorts of recording paper without 
excessively increasing the viscosity of the ink and also has superior 
recording performances in variety, and an ink-jet recording process and 
apparatus making use of the ink; more specifically, to provide an ink that 
has solved the problems of blurring of ink and slow-drying of recorded 
matter that may occur when recording is performed on non-coated paper, 
what is called plain paper, such as paper for copying, paper for 
reporting, notepaper, letter paper, bond paper and computer printout paper 
commonly used in offices and so forth. 
A still another object of the present invention is to provide an ink that 
is very safe when used in offices and homes. 
The above objects of the present invention can be achieved by the invention 
as described below. 
The present invention is an ink comprising a hydrazide compound selected 
from the group consisting of a compound represented by the following 
Formula (I) or (II), a styrene-maleic acid resin having at least two 
hydrazide groups and a polyacrylic acid having at least two hydrazide 
groups, and a compound having at least one carbonyl group. 
##STR3## 
wherein R represents (CH.sub.2).sub.n or C.sub.6 H.sub.4, where n is an 
integer of 0 to 10. 
##STR4## 
The present invention also provides an ink comprising a water-soluble resin 
having an oxazolyl group or a fine particle having oxazolyl groups 
adsorbed on its outer surface, and a compound having at least one carbonyl 
group. 
The present invention also provides an ink-jet recording process comprising 
ejecting an ink from an orifice according to recording signals to make a 
record on a recording medium, wherein said ink is the ink described above. 
The present invention still also provides a recording unit comprising an 
ink holder that holds an ink, and a head assembly for ejecting the ink in 
the form of ink droplets, wherein said ink is the ink described above. 
The present invention further provides an ink-jet recording apparatus 
comprising a recording head for ejecting ink droplets, an ink cartridge 
having an ink holder that holds an ink, and an ink feeding means for 
feeding the ink to the recording head, wherein said ink is the ink 
described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First Preferred Embodiment: (Embodiment in which a hydrazide compound is 
used) 
The present inventors have discovered that, in a water-based pigment ink, 
use of a compound with a specific structural formula brings about an 
improvement in rub-off fastness of prints and can solve the problems 
previously discussed, while maintaining print quality level, and thus have 
accomplished the present invention. More specifically, a compound 
represented by the formula 
##STR5## 
wherein R represents (CH.sub.2).sub.n or C.sub.6 H.sub.4, where n is an 
integer of 0 to 10, or the formula 
##STR6## 
a styrene-maleic acid resin having two or more hydrazide groups and a 
polyacrylic acid having two or more hydrazide groups (these compounds are 
hereinafter generically called a hydrazide compound) have the properties 
of uniformly dissolving in an aqueous solution and, once water has 
disappeared, reacting with a compound having a carbonyl group. With 
utilization of such properties, this hydrazide compound is added in a 
water-based ink so that it is cross-linked with carbonyl groups of a 
dispersant or the like contained in the ink on recording paper, to form a 
film of non-volatile components, whereby an improvement in rub-off 
fastness of prints can be achieved. Moreover, the cross-linking reaction 
uniformly takes place without regard to the types of paper, and hence any 
dependence of print quality on recording paper can be eliminated. 
The present inventors also made extensive studies on a variety of ink 
compositions so that blurring-free properties, drying performance and 
penetrability of ink on plain paper can be improved. As a result, they 
have discovered that the above hydrazide compounds bring about good 
results against blurring, also have no ill effect on the prevention of 
clogging and also have no safety problem, promising high reliability. They 
have thus accomplished the present invention. 
More specifically, according to research made by the present inventors, the 
use of surface active agents employed in conventional inks makes it 
difficult to perform stable recording with regard to the blurring and 
penetrability of ink on plain paper, because of mingled results some of 
which are good and some not. On the other hand, the use of the hydrazide 
compound can bring about very good results such that stable recording with 
less difference in quality depending on the types of recording paper can 
be achieved also when used in combination with a penetrant such as a 
surface active agent. 
The reason therefor is that the hydrazide compounds have the properties of 
uniformly dissolving in an aqueous solution and, once water has 
disappeared, reacting with a dye having a carbonyl group. With utilization 
of such properties, the hydrazide compound is added in a water-based ink 
so that it is cross-linked with the dye on the recording paper, whereby 
any dependence of print quality level on recording paper can be eliminated 
and also fixing speed can be improved. 
Components that constitute the ink of the present invention will be 
described below. 
As a first ink according to the first embodiment of the ink of the present 
invention, the ink comprises a hydrazide compound, a pigment, an aqueous 
medium, and a water-soluble resin having a carbonyl group as the compound 
having at least one carbonyl group. 
There are no particular limitations on the pigment so long as it can 
satisfy the functions required in conventional ink-jet recording inks. 
Particularly preferred examples thereof are shown below. 
Carbon black used in black inks may preferably be carbon black produced by 
the furnace process or the channel process, having a primary particle 
diameter of from 15 to 40 m.mu., a specific surface area of from 50 to 300 
m.sup.2 /g as measured by the BET method, a DBP oil absorption of from 40 
to 150 ml/100 g, a volatile component of from 0.5 to 10% and a pH value of 
from 2 to 9. For example, it is preferable to use commercially available 
products such as No.2300, No.900, MCF88, No.33, No.40, No.45, No.52, MA7, 
MA8, No.2200B (trade names; available from Mitsubishi Chemical Industries 
Limited), RAVEN1255 (trade name; available from Columbian Chemicals), 
REGAL400R, REGAL330R, REGAL660R, MOGUL L (trade names; available from 
Cabot Corp.), and Color Black FW1, Color Black FW18, Color Black S170, 
Color Black S150, Printex-35, Printex-U (trade names; available from 
Degussa, Inc.). 
Pigments used in yellow inks may include C.I. Pigment Yellow 1, C.I. 
Pigment Yellow 2, C.I. Pigment Yellow 3, C.I. Pigment Yellow 13, C.I. 
Pigment Yellow 16 and C.I. Pigment Yellow 83, which can be preferably 
used. 
Pigments used in magenta inks may include C.I. Pigment Red 5, C.I. Pigment 
Red 7, C.I. Pigment Red 12, C.I. Pigment Red 48(Ca), C.I. Pigment Red 
48(Mn), Pigment Red 57(Ca), C.I. Pigment Red 112 and C.I. Pigment Red 122, 
which can be preferably used. 
Pigments used in cyan inks may include C.I. Pigment Blue 1, C.I. Pigment 
Blue 2, C.I. Pigment Blue 3, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, 
C.I. Pigment Blue 22, C.I. Vat Blue 4 and C.I. Vat Blue 6, which can be 
preferably used. 
The pigment of the first ink of the present invention is by no means 
limited to the above commercially available products, and those newly 
produced may also be used. 
The water-soluble resin having carbonyl groups functions as a dispersant of 
the pigment. Characteristic groups comprising the carbonyl group may 
include the carbonyl group itself, as well as carboxyl groups, ester 
bonds, amide bonds, ketone groups and urethane groups. Any water-soluble 
resins can be used so long as they have a --C.dbd.O bond. Those having a 
weight average molecular weight of from 1,000 to 30,000 are preferred. 
Those of from 3,000 to 15,000 are more preferred. They specifically 
include block copolymers, random copolymers and graft copolymers, and 
salts thereof, comprised of at least two monomers (at least one of which 
is a hydrophilic monomer) selected from the group consisting of styfane, 
styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, 
aliphatic alcohol esters of .alpha.,.beta.-ethylenically unsaturated 
carboxylic acids, as well as acrylic acid, acrylic acid derivatives, 
maleic acid, maleic acid derivatives, itaconic acid, itaconic acid 
derivatives, fumaric acid, fumaric acid derivatives, vinyl acetate, 
vinylpyrrolidone, acrylamide and derivatives of these. Natural resins such 
as rosin, shellac and starch may also be used. These natural resins are 
alkali-soluble resins capable of being dissolved in an aqueous solution 
comprising a base dissolved therein. 
The water-soluble resin described above may preferably be contained in an 
amount ranging from 0.1 to 5% by weight based on the total weight of the 
ink. It is more preferable for the ink to be prepared in neutrality or 
alkalinity as a whole. This is preferable for improving the solubility of 
the water-soluble resin and providing an ink having much superior 
long-term storage stability. In this instance, however, such an ink may 
cause corrosion of various members used in an ink-jet recording apparatus, 
and hence it should be adjusted in a pH range of from 7 to 10. 
A pH adjustor used for such purpose may include, for example, various 
organic amines such as diethanolamine and triethanolamine, inorganic 
alkali agents including alkali metal hydroxides such as sodium hydroxide, 
lithium hydroxide and potassium hydroxide, organic acids and mineral 
acids. 
The pigment and water-soluble resin as described above are dispersed or 
dissolved in an aqueous medium. 
The aqueous medium may preferably include mixed solvents of water and 
water-soluble organic solvents. 
The water should not be tap water containing various ions, and may 
preferably be ion-exchanged water (deionized water). 
The water-soluble organic solvent used in mixture with water may include, 
for example, alkyl alcohols having 1 to 4 carbon atoms, such as methyl 
alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl 
alcohol, sec-butyl alcohol, tert-butyl alcohol; amides such as 
dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as 
acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; 
polyalkylene glycols such as polyethylene glycol and polypropylene 
glycols; alkylene glycols the alkylene group of which has 2 to 6 carbon 
atoms, such as ethylene glycol, propylene glycol, butylene glycol, 
triethylene glycol, thiodiglycol, hexylene glycol and diethylene glycol; 
1,2,6-hexanetriol; glycerol; lower alkyl ethers of polyhydric alcohols, 
such as ethylene glycol monomethyl or -ethyl ether, diethylene glycol 
methyl or ethyl ether and triethylene glycol monomethyl or -ethyl ether; 
N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. 
Of these many water-soluble organic solvents, polyhydric alcohols such as 
diethylene glycol and lower alkyl ethers of polyhydric alcohols such as 
ethylene glycol monomethyl or -ethyl ether are particularly preferred. 
The water-soluble organic solvent in the ink of the present invention may 
usually be contained in an amount ranging from 3 to 50% by weight, and 
preferably in an amount ranging from 3 to 40% by weight, based on the 
total weight of the ink. The water may be in an amount ranging from 10 to 
90% by weight, and preferably in an amount ranging from 30 to 80% by 
weight, based on the total weight of the ink. 
In the present invention, the hydrazide compound incorporated into the ink 
for cross-linking it with carbonyl groups of the dispersant to form a film 
of non-volatile components may specifically include adipic acid 
dihydrazide, oxalic acid dihydrazide, carbohydrazide, polyacrylic acid 
hydrazide (which are available from Otsuka Chemical Co., Ltd.), and 
ACRONAL (trade name; available from Mitshbishi Yuka Badische Co., Ltd.). 
The hydrazide compound may preferably be contained in the ink in an amount 
of from 0.1 to 10% by weight, and more preferably from 0.5 to 5% by 
weight. Any of these compounds used in an amount less than 0.1% by weight 
can not bring about an improvement in rub-off fastness of prints as 
intended in the present invention. On the other hand, its use in an amount 
more than 10% by weight may tend to cause ill effects such as clogging of 
the ejection orifices because of an increase in viscosity of the ink. 
In addition to the components described above, a surface active agent, a 
defoamer, an antiseptic and so forth may be optionally added to the ink of 
the present invention so that the ink can have the desired values of 
physical properties. A commercially available water-soluble dye also may 
be added. 
The ink of the present invention can be prepared in the following way: 
First, the pigment is added to an aqueous solution comprised of at least 
the water-soluble resin having carbonyl groups and water, followed by 
stirring. Thereafter, the pigment is dispersed in the solution by a 
dispersion means described later, optionally followed by centrifugal 
separation to obtain a desired dispersion. Next, to the resulting 
dispersion, the hydrazide compound described above is added, followed by 
stirring to provide ink. In instances in which the alkali-soluble resin 
such as natural resin is used, it is necessary to add a base in order to 
dissolve the resin. 
The base added to the dispersion when the alkali-soluble resin is used may 
preferably include organic amines such as monoethanolamine, 
diethanolamine, triethanolamine, aminomethylpropanol and ammonia or 
inorganic bases such as potassium hydroxide and sodium hydroxide. 
It is also effective to carry out premixing for 30 minutes or more before 
the aqueous solution containing the pigment is dispersed. This premixing 
enables improvement in wettability of the pigment surface to promote 
adsorption of resin on the pigment surface. 
As for the dispersion means used in the present invention, it may be any of 
dispersion machines commonly used, including, for example, a ball mill, a 
roll mill and a sand mill. In particular, a high-speed sand mill is 
preferred, as exemplified by Super mill, Sand grinder, Beads mill, 
Agitator mill, Grain mill, Dyno mill, Pearl mill and Coball mill (all 
trade names). 
In the present invention, a pigment with a desired particle size 
distribution can be obtained by a method in which a tumbling medium of the 
dispersion machine is made to have a small size, the tumbling medium is 
used in a large packing fraction, the dispersion is carried out for a long 
time, treated products are slowly discharged, or, after being pulverized, 
they are classified using a filter or a centrifugal separator. Any of 
these methods may also be used in combination. 
As a second ink according to the first embodiment of the ink of the present 
invention, the ink comprises the hydrazide compound, an aqueous medium, 
and a dye having at least one carbonyl group as the compound having at 
least one carbonyl group. 
The dye having at least one carbonyl group may include dyes having a 
carbonyl group, a carboxyl group, an ester bond, an amide bond, a ketone 
group, a urethane bond or the like, as exemplified by various dyes such as 
direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse 
dyes, vat dyes, soluble vat dyes, reactive disperse dyes and oil dyes. Of 
these dyes, water-soluble dyes are particularly preferred in view of 
performances of the ink. 
The content of the dye in the ink depends on the types of liquid medium 
components, the properties required for the ink, and so forth. In usual 
instances, the dye may be contained in an amount of approximately from 0.2 
to 20% by weight, preferably from 0.5 to 10% by weight, and more 
preferably from 1 to 5% by weight, based on the total weight of the ink. 
As the aqueous medium, the same one as that in the first ink previously 
described may be used. In the second ink, the most preferable aqueous 
medium is composed of water and at least one organic solvent, where the 
organic solvent is at least one water-soluble organic solvent with a high 
boiling point as exemplified by polyhydric alcohols such as diethylene 
glycol, triethylene glycol, glycerol, 1,2,6-hexanetriol and thiodiglycol, 
and 2-pyrrolidone. 
The water-soluble organic solvent and the water may be contained in the ink 
each in the same amount as in the case of the first ink. 
As the hydrazide compound, the same compounds as those in the first ink can 
be used. 
In addition to the components described above, various kind of dispersant, 
surface active agent, viscosity modifier, surface tension modifier, 
fluorescent brightener and so forth may be optionally added to the second 
ink of the present invention. 
As the viscosity modifier, polyvinyl alcohol, celluloses, water-soluble 
resins or the like are suitable. As the surface active agent, all sorts of 
surface active agents of cationic, anionic and nonionic types can be used. 
As the surface tension modifier, diethanolamine and triethanolamine are 
suitable. Besides, pH adjustors using buffers, antifungal agents, and so 
forth may also be used. 
In the case of inks applied in ink-jet recording in which the ink is 
electrostatically charged, a resistivity regulator including inorganic 
bases such as lithium chloride, ammonium chloride or sodium chloride is 
added. 
In order to solve the problems of feathering and drying performance of 
recorded matter and penetrability and at the same time improve 
compatibility with ink-jet recording heads, the second ink of the present 
invention may preferably be adjusted to have, as physical properties of 
the ink itself, a surface tension of from 30 to 68 dyne/cm and a viscosity 
of 15 cP or less, and more preferably 5 cP or less, at 25.degree. C. 
Second Preferred Embodiment: (Embodiment in which a compound having 
oxazolyl groups is used) 
The ink of the present invention may also comprise a component having an 
oxazolyl group and a compound having at least one carbonyl group. 
Use of the ink of the present embodiment makes it possible to obtain stable 
recorded images having a superior fixing speed or rub-off fastness and 
which are free from a decrease in print density. This is presumably 
because the compound having oxazolyl groups has the properties of 
uniformly dissolving in an aqueous solution and, once water has 
disappeared, reacting with the compound having at least one carbonyl 
group. More specifically, it is presumed that component (a) (the compound 
having oxazolyl groups) in the ink of the present embodiment is uniformly 
dissolved in the ink, and, once this ink has been ejected from an ink-jet 
recording head onto recording paper and has dried, the oxazolyl group 
possessed by component (a) and the carboxyl group possessed by component 
(b) (the compound having at least one carbonyl group) combine to form a 
cross-linked structure, which brings about a formation of a film of 
non-volatile components, whereby an improvement in rub-off fastness of 
prints can be achieved. It is also presumed that the cross-linking 
reaction uniformly takes place without regard to the types of paper, and 
hence any dependence of print quality on recording paper can be 
eliminated. 
The component (a) used in the ink of the present embodiment comprises 
(a-1): a water-soluble resin having an oxazolyl group or (a-2): a fine 
particle having oxazolyl groups adsorbed on its outer surface. The 
component (a) may include oxazoline type reactive polymers. The oxazoline 
type reactive polymers are commercially available, including, for example, 
K-1000 series and K-2000 series acryl-styrene resins, RPS series styrene 
resins and RAS series acrylonitrile-styrene resins, produced by Nippon 
Shokubai Kagaku Kogyo Co., Ltd. 
The water-soluble resin (a-1) refers to, for example, an oxazoline type 
reactive polymer having one or more oxazolyl groups represented by the 
formula 
##STR7## 
The fine particle (a-2) used in the present embodiment may include organic 
particles and inorganic particles without any particular limitations. 
Those insoluble in water and capable of being stably dispersed therein are 
preferred. There are also no particular limitations on particle diameter. 
Spherical particles may preferably be used. Stated specifically, the 
organic fine particles may include particles of polystyrene, 
styrene-acrylate copolymers, polymethyl methacrylate, melamine resins, 
epoxy resins, silicone resins, benzoguanamine resins, polyamide resins, 
fluorine resins, and polymers obtained by emulsion polymerization of 
.alpha.,.beta.-unsaturated ethylenic monomers. The inorganic fine 
particles may include a large number of materials such as titanium dioxide 
particles, silica particles and alumina particles. As commercially 
available products, the organic fine particles may include MUTICLE series 
products, available from Mitsui Toatsu Chemicals, Inc. ME series products, 
available from Soken Chemical & Engineering Co., Ltd.; JULIMER MB series 
products, available from Nihon Junyaku Co., Ltd.; TOSPEARL series 
products, available from Toshiba Silicone Co., Ltd.; EPOSTAR series 
products, available from Nippon Shokubai Kagaku Kogyo Co., Ltd.; MICROGEL 
series products, available from Nippon Paint Co., Ltd.; and FLUON series 
products, available from Asahi Glass Co., Ltd. The inorganic fine 
particles may include titania series products, available from Indemitsu 
Kosan Co., Ltd.; and aluminum oxide C, available from Nippon Aerosil Co., 
Ltd. Their particle diameter may, depending on the nozzle diameter of a 
printer head used, be approximately from 0.01 to 5 .mu.m, and preferably 
from 0.05 to 1.0 .mu.m. 
The fine particle (a-2) refers to a fine particle having at least one 
oxazolyl group adsorbed on its outer surface, as diagrammatically 
represented by the formula 
##STR8## 
This component (a) should preferably be contained in the ink in an amount 
of from 0.1 to 10% by weight, and more preferably from 0.5 to 5% by 
weight. Its use in a content less than 0.1% by weight tends to result in 
an unsatisfactory improvement in rub-Off fastness of prints. On the Other 
hand, its use in a content more than 10% by weight tends to slightly cause 
clogging of ejection orifices because of an increase in viscosity of ink. 
The compound (b) having at least one carbonyl group includes (b-1): a 
water-soluble resin having a carbonyl group and (b-2): a dye having a 
carbonyl group. Of these, the water-soluble resin (b-1) having a carbonyl 
group, mainly used in the case of a water-based pigment ink, acts as a 
dispersant. As the water-soluble resin (b-1), the same ones as those 
described in the first embodiment may be used. This water-soluble resin 
(b-1) should preferably be contained in the ink in an amount ranging from 
0.1 to 5% by weight. 
Of the compound (b) having a carbonyl group, used in the ink of the present 
embodiment, the dye (b-2) having a carbonyl group may include those having 
a carbonyl group without any particular limitations, as exemplified by 
direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse 
dyes, vat dyes, soluble vat dyes, reactive disperse dyes and oil dyes. Of 
these dyes, water-soluble dyes are particularly preferred in view of the 
performance of the ink. 
The content of the dye (b-2) in the ink depends on the properties required 
for the ink, and so forth. In usual instances, the dye should be contained 
in an amount of approximately from 0.2 to 20% by weight, preferably from 
0.5 to 10% by weight, and more preferably from 1 to 5% by weight, based on 
the total weight of the ink. 
Pigment (c) is used when the ink of the present embodiment comprises a 
water-based pigment ink. As the pigment (c), the same ones as those 
previously described in the first embodiment may be used. It may be 
contained in the ink in an amount ranging from 1 to 20% by weight, and 
preferably from 2 to 12% by weight. 
The ink of the present embodiment should preferably be an ink comprising 
the components (a), (b) and (c) detailed above which are dispersed or 
dissolved in a mixed solvent of water (d) and water-soluble organic 
solvent (e). The water (d) and the water-soluble organic solvent (e) may 
be the same ones as those described in the first embodiment. 
The water (d) should preferably be contained in the ink in an amount of 
from 10 to 90% by weight, and preferably from 30 to 80% by weight. The 
water-soluble organic solvent (e) should preferably be contained in the 
ink in an amount of from 3 to 50% by weight, and preferably from 3 to 40% 
by weight. 
It is more preferable for the ink to be prepared in neutrality or 
alkalinity as a whole. This is preferable, for example, for improving the 
solubility of the water-soluble resin (c) and providing an ink having much 
superior long-term storage stability. In this instance, however, such an 
ink may cause corrosion of various members used in ink-jet recording 
apparatus, and hence it should be adjusted in a pH range of from 7 to 10. 
A pH adjustor used therefor may include, for example, various organic 
amines such as monoethanolamine, diethanolamine and triethanolamine, 
inorganic bases such as sodium hydroxide, lithium hydroxide and potassium 
hydroxide, and other organic acids and mineral acids. 
In addition to the components (a) to (e) described above, various optional 
components may be added to the ink of the present embodiment as occasion 
calls. For example, a surface active agent, a defoamer, an antiseptic, a 
dispersant, a viscosity modifier, a surface tension modifier, a 
fluorescent brightener, a water-soluble dye (including dyes having no 
carboxyl group) and so forth may be added. The viscosity modifier may 
include polyvinyl alcohol, celluloses and water-soluble resins. The 
surface active agent may include all sorts of surface active agents of 
cationic, anionic and nonionic types. The surface tension modifier may 
include diethanolamine and triethanolamine. Besides, pH adjustors using 
buffers, antifungal agents, and so forth may also be used. In order to 
prepare inks applied in ink-jet recording in which the ink is 
electrostatically charged, a resistivity regulator including inorganic 
bases such as lithium chloride, ammonium chloride or sodium chloride may 
be added. 
In order to solve the problems of feathering and drying performance of 
recorded matter and penetrability and at the same time improve 
compatibility with ink-jet recording heads, the ink of the present 
embodiment may preferably be adjusted to have, as physical properties of 
the ink itself, a surface tension of from 30 to 68 dyne/cm and a viscosity 
of 15 cP or less, and more preferably 5 cP or less, at 25.degree. C. 
The ink of the present embodiment can be prepared by a method in which, in 
the case of, for example, the dye ink, the respective components are well 
mixed and thereafter the pH is optionally adjusted, followed by filtration 
under pressure. 
In the case of, for example, the water-based pigment ink, it can be 
prepared in the following way: The pigment (c) is added to an aqueous 
solution comprised of at least the water-soluble resin (b-1) and water, 
followed by stirring. Thereafter, the pigment is dispersed in the solution 
by a dispersion means described later, optionally followed by centrifugal 
separation to obtain a desired pigment dispersion. Next, to the resulting 
dispersion, the resective components described above are added, followed 
by stirring. It is also effective to carry out premixing for 30 minutes or 
more before the aqueous solution containing the pigment (c) is dispersed. 
This premixing enables improvement in wattability of the pigment surface 
to promote adsorption of resin on the pigment surface. As the dispersion 
means used for dispersion, any of dispersion machines commonly used can be 
used, including, for example, a ball mill and a sand mill. In particular, 
a high-speed sand mill is preferred, as exemplified by Super mill, Sand 
grinder, Beads mill, Agitator mill, Grain mill, Dyno mill, Pearl mill and 
Coball mill (all trade names). 
A pigment (c) with a desired particle size distribution can be obtained by 
a method in which a tumbling medium of the dispersion machine is made to 
have a small size, the tumbling medium is used in a large packing 
fraction, the dispersion is carried out for a long time, treated products 
are slowly discharged, or, after being pulverized, they are classified 
using a filter or a centrifugal separator. Any of these methods may also 
be used in combination. 
When ink-jet recording is carried out using the ink of the present 
invention, it is suitable to use an apparatus in which heat energy 
corresponding to recording signals is imparted to the ink in a recording 
head so that ink droplets are generated by the action of the heat energy. 
FIGS. 1A, 1B and 2 show examples of the construction of the head, which is 
a main component of such an ink-jet recording apparatus. FIG. 1A is a 
partial cross section of a recording head 13 along its ink flow path, and 
FIG. 1B is a partial cross section along the line A-B in FIG. 1A. The 
recording head 13 is formed by bonding a glass, ceramic or plastic plate 
or the like having a channel 14 through which ink is passed, to a heating 
head 15 used in thermal recording (the drawing shows a thin-film head, to 
which, however the invention, is not limited). 
The heating head 15 is comprised of a protective film 16 formed of silicon 
oxide or the like, aluminum electrodes 17-1 and 17-2, a heating resistor 
layer 18 formed of nichrome or the like, a heat accumulating layer 19, and 
a substrate 20 with good heat dissipation properties. The ink 21 reaches 
an ejection orifice (a minute opening) 22 and a meniscus 23 is formed 
there by a pressure P. Upon application of electric signals to the 
electrodes 17-1 and 17-2, heat is abruptly generated at the region denoted 
by n in the thermal head 15, so that bubbles are generated in the ink 21 
coming into contact with this region. The pressure thus produced thrusts 
out the meniscus 23 and the ink 21 is ejected from the orifice 22 in the 
form of minute recording drops 24 to fly against a recording medium 25. 
FIG. 2 is a partial perspective view of a multi-head comprising the head 
as shown in FIGS. 1A and 1B, arranged in a large number. The multi-head is 
prepared by bonding a glass plate 27 having a multi-channel 26, to a 
heating head 28 similar to the head as illustrated in FIG. 1A. 
FIG. 3 is a perspective view to show an example of an ink-jet recording 
apparatus in which such a head has been incorporated. In FIG. 3, reference 
numeral 61 denotes a blade serving as a wiping member in the form of a 
cantilever, one end of which is a stationary end retained by a 
blade-retaining member. The blade 61 is provided at the position adjacent 
to the region in which a recording head makes a record. In the present 
example, the blade is retained in such a form that it projects to 1 the 
course through which the recording head is moved. Reference numeral 62 
denotes a cap, which is provided at the home position adjacent to the 
blade 61, and is so constituted that it moves in the direction 
perpendicular to the direction in which the recording head is moved and 
comes into contact with the face of ejection openings to carry out 
capping. Reference numeral 63 denotes an ink absorber provided adjoiningly 
to the blade 61, and, similar to the blade 61, is retained in such a form 
that it projects to the course through which the recording head is moved. 
The above blade 61, cap 62 and absorber 63 constitute an ejection 
restoration assembly 64, where the blade 61 and the absorber 63 remove the 
water, dust or the like from the ink ejection opening face. Reference 
numeral 65 denotes the recording head having an ejection energy generating 
means and ejects ink to the recording medium set opposite to the ejection 
opening face provided with ejection openings, to carry out recording. 
Reference numeral 66 denotes a carriage on which the recording head 65 is 
mounted so that the recording head 65 can be moved. The carriage 66 is 
slidably associated with a guide shaft 67. Part of the carriage 66 is 
connected (not shown) with a belt 69 driven by a motor 68. Thus, the 
carriage 66 can be moved along the guide 67 and hence the recording head 
65 can be moved from a recording region to a region adjacent thereto. 
Reference numeral 51 denotes a paper feeding part from which recording 
mediums are inserted, and 52, a paper feed roller driven by a motor (not 
shown). With such construction, the recording medium is fed to the 
position opposite to the ejection opening face of the recording head, and, 
with the progress of recording, is outputted from a paper output section 
provided with a paper output roller. 
In the above constitution, the cap 62 of the head restoration assembly 64 
is receded from the moving course of the recording head 65 when the 
recording head 65 is returned to its home position, e.g., after completion 
of recording, and the blade 61 stands projected to the moving course. As a 
result, the ejection opening face of the recording head 65 is wiped. When 
the cap 62 comes into contact with the ejection opening face of the 
recording head 65 to carry out capping, the cap 62 is moved in such a way 
that it projects to the moving course of the recording head. 
When the recording head 65 is moved from its home position to the position 
at which recording is started, the cap 62 and the blade 61 are at the same 
position as the position where the ejection opening face is wiped. As a 
result, the ejection opening face of the recording head 65 is wiped also 
at the time of this movement. 
The above movement of the recording head to its home position is made not 
only at the time of the completion of recording or restoration of 
ejection, but also when the recording head is moved between recording 
regions for the purpose of recording, during which it is moved to the home 
position adjacent to each recording region at given intervals, where the 
ejection opening face is wiped in accordance with this movement. 
FIG. 4 is a cross-sectional view to show an example of an ink cartridge, 
denoted as 45, that has held the ink being fed to the head through an 
ink-feeding tube. Herein reference numeral 40 denotes a bag that has held 
the feeding ink. The top thereof is provided with a stopper 42 made of 
rubber. A needle (not shown) may be inserted into this stopper 42 so that 
the ink in the ink holder 40 can be fed to the head. Reference numeral 44 
denotes an absorber that receives a waste ink. 
The ink-jet recording apparatus used in the present invention is not 
limited to the apparatus as described above in which the head and the ink 
cartridge are separately provided, and a device can also be preferably 
used in which these are integrally formed as shown in FIG. 5. In FIG. 5, 
reference numeral 70 denotes an ink cartridge (a recording unit), in the 
interior of which an ink absorber impregnated with ink is held. The ink 
cartridge is so constructed that the ink in such an ink absorber is 
ejected in the form of ink droplets from a head 71 having a plurality of 
orifices. Reference numeral 72 denotes an air path opening through which 
the interior of the cartridge is made to communicate with the atmosphere. 
This ink cartridge 70 can be used in place of the recording head 65 shown 
in FIG. 3, and is detachably mounted to the carriage 66. 
EXAMPLES 
The present invention will be described below by giving Examples and 
Comparative Examples. In the following, "part(s)" indicates "part(s) by 
weight" unless particularly noted. 
First Embodiment 
Example 1 
(1) Preparation of ink: 
a. Preparation of pigment dispersion: 
______________________________________ 
Styrene/acrylic acid/ethyl acrylate copolymer 
1.5 parts 
(acid value: 140; weight average molecular 
weight: 5,000) 
Monoethanolamine 1 part 
Ion-exchanged water 81.5 parts 
Diethylene glycol 5 parts. 
______________________________________ 
The above components were mixed, and the mixture was heated to 70.degree. 
C. on a water bath to completely dissolve the resin component. To the 
resulting solution, 10 parts of carbon black (MCF88, available from 
Mitsubishi Chemical Industries Limited) and 1 part of isopropyl alcohol 
were added, followed by premixing for 30 minutes, and thereafter the 
mixture obtained was dispersed under conditions shown below. 
Dispersion machine: Sand grinder (manufactured by Igarashi Kikai K.K.) 
Tumbling media: Zirconium beads of 1 mm diameter 
Tumbling media packing fraction: 50% (by volume) 
Pulverizing time: 3 hours. 
Centrifugal separation was further carried out (12,000 rpm; for 20 minutes) 
to remove coarse particles. Thus, dispersion 1 was formed. 
b. Preparation of ink: 
______________________________________ 
Dispersion 1 30 parts 
Glycerol 10 parts 
Ethylene glycol 5 parts 
N-methylpyrrolidone 5 parts 
Ethyl alcohol 2 parts 
Adipic acid dihydrazide (available from Otsuka 
2 parts 
Chemical Co., Ltd.) 
Ion-exchanged water 46 parts. 
______________________________________ 
The above components were mixed to obtain an ink. 
(2) Recording: 
The ink formulated as shown above was tested using an ink-jet recording 
apparatus having an on-demand type multi-recording head capable of 
imparting heat energy corresponding to recording signals to thereby eject 
ink droplets. 
Example 2 
(1) Preparation of ink: 
a. Preparation of pigment dispersion: 
______________________________________ 
Styrene/maleic acid/maleic acid half ester 
4 parts 
copolymer (acid value: 70; weight average molecular 
weight: 12,000) 
Aminomethyl propanol 2 parts 
Ion-exchanged water 74 parts 
Diethylene glycol 5 parts. 
______________________________________ 
The above components were mixed, and the mixture was heated to 70.degree. 
C. on a water bath to completely dissolve the resin component. To the 
resulting solution, 15 parts of carbon black (MCF88, available from 
Mitsubishi Chemical Industries Limited) was added, followed by premixing 
for 30 minutes, and thereafter the mixture obtained was dispersed under 
conditions shown below. 
Dispersion machine: Pearl mill (manufactured by Ashizawa K.K.) 
Tumbling media: Glass beads of 1 mm diameter 
Tumbling media packing fraction: 50% (by volume) 
Discharge rate: 100 ml/min. 
Centrifugal separation was further carried out (12,000 rpm; for 20 minutes) 
to remove coarse particles. Thus, dispersion 2 was formed. 
b. Preparation of ink: 
______________________________________ 
Dispersion 2 30 parts 
Glycerol 8 parts 
Ethylene glycol 5 parts 
Ethanol 5 parts 
Oxalic acid dihydrazide (available from Otsuka 
1 part 
Chemical Co., Ltd.) 
Ion-exchanged water 51 parts. 
______________________________________ 
The above components were mixed, and aminomethyl propanol was added to 
adjust the pH value to 8 to 10. 
(2) Recording: 
The ink thus formulated was tested in the same manner as in Example 1. 
Example 3 
(1) Preparation of ink: 
a. Preparation of pigment dispersion: 
______________________________________ 
.alpha.-Methylstyrene/methyl acrylate/acrylic acid 
2.0 parts 
copolymer (acid value: 95; weight average 
molecular weight: 8,000) 
Ion-exchanged water 81.0 parts 
Ethylene glycol 5 parts. 
______________________________________ 
The above components were mixed, and the mixture was heated to 70.degree. 
C. on a water bath to completely dissolve the resin component. To the 
resulting solution, 11 parts of carbon black (S170, available from 
Degussa, Inc.) and 1 part of isopropyl alcohol were added, followed by 
premixing for 60 minutes, and thereafter the mixture obtained was 
dispersed under conditions shown below. 
Dispersion machine: Sand grinder (manufactured by Igarashi Kikai K.K.) 
Tumbling media: Zirconium beads of 0.5 mm diameter 
Tumbling media packing fraction: 70% (by volume) 
Pulverizing time: 10 hours. 
Centrifugal separation was further carried out (12,000 rpm; for 20 minutes) 
to remove coarse particles. Thus, dispersion 3 was formed. 
b. Preparation of ink: 
______________________________________ 
Dispersion 3 30 parts 
Glycerol 12 parts 
Diethylene glycol 10 parts 
2-Pyrrolidone 5 parts 
ACRONAL YJ-6380D (trade name; available 
0.5 part 
from Mitshbishi Yuka Badische Co., Ltd.) 
Ion-exchanged water 42.5 parts. 
______________________________________ 
The above components were mixed to obtain an ink. 
(2) Recording: 
The ink thus formulated was tested in the same manner as in Example 1. 
Comparative Examples 1 to 3 
Examples 1 to 3 were respectively repeated to prepare inks, except that no 
hydrazide compound was added and ion-exchanged water was instead added. 
Using inks thus obtained, recording tests were carried out in the same 
manner as in Examples 1 to 3. 
Evaluation of ink and prints: 
Prints obtained by printing characters on Canon NP-DRY copy paper according 
to the above method were evaluated in the following way. Results obtained 
are shown in Table 1. 
(1) Print density of prints: 
Print density of prints was measured using a Macbeth densitometer (TR918). 
(2) Ink drying time: 
Printed areas were rubbed with filter paper (trade name: No.5C; available 
from Toyo Roshi K.K.), and the time taken until the printed areas no 
longer blurred was measured. 
(3) Rub-off fastness: 
Prints were rubbed with a highlighter pen. An instance in which no prints 
blurred when rubbed 5 times was evaluated as "A"; an instance in which 
prints blurred in 5 times but no print blurred when rubbed 3 times, as 
"B"; and an instance in which prints blurred when rubbed once, as "C". 
TABLE 1 
______________________________________ 
Print Drying time (sec) 
Rub-off 
density 
Solid print 
Characters 
fastness 
______________________________________ 
Example: 
1 1.40 30 10 A 
2 1.38 32.5 12.5 A 
3 1.37 35 15 A 
Comparative 
Example: 
1 1.30 60 35 C 
2 1.29 65 40 C 
3 1.29 75 45 C 
______________________________________ 
Examples 4 to 9 
To prepare inks A to F, components as respectively shown below were mixed 
and stirred for 5 hours. Thereafter, an aqueous 0.1% sodium hydroxide 
solution was added to adjust the pH to 7.5, followed by filtration under 
pressure using a membrane filter with a pore size of 0.22 .mu.m (trade 
name: Fluoro pore filter; available from Sumitomo Electric Industries, 
Ltd.). Thus, inks A to F of the present invention were obtained. 
Composition of ink A: 
______________________________________ 
C.I. Direct Yellow 44 2 parts 
Diethylene glycol 15 parts 
Adipic acid dihydrazide 3 parts 
(available from Otsuka Chemical Co., Ltd.) 
Water 80 parts. 
Composition of ink B: 
C.I. Direct Red 26 2 parts 
Glycerol 10 parts 
Ethylene glycol 5.5 parts 
Oxalic acid dihydrazide 2 parts 
(available from Otsuka Chemical Co., Ltd.) 
Water 80.5 parts. 
Composition of ink C: 
C.I. Food Black 1 3 parts 
Triethylene glycol 10 parts 
N-methyl-2-pyrrolidone 3 parts 
Carbohydrazide 1 part 
(available from Otsuka Chemical Co., Ltd.) 
Water 83 parts. 
Composition of ink D: 
C.I. Direct Blue 149 2.5 parts 
1,2,6-Hexanetriol 5 parts 
Diethylene glycol 10 parts 
ACRONAL YJ-63680D 3 parts 
(trade name; available from Mitshbishi Yuka 
Badische Co., Ltd.) 
Water 79.5 parts. 
Composition of ink E: 
HI12286 (available from ICI) 
2 parts 
Thiodiglycol 6 parts 
Diethylene glycol 9 parts 
Adipic acid dihydrazide 3 parts 
(available from Otsuka Chemical Co., Ltd.) 
ACETYLENOL EH 0.5 part 
(trade name; available from Kawaken Fine 
Chemicals Co., Ltd.) 
Water 79.5 parts. 
Composition of ink F: 
C.I. Acid Green 34 3 parts 
Ethylene glycol 8 parts 
Diethylene glycol 7 parts 
Oxalic acid dihydrazide 1 part 
(available from Otsuka Chemical Co., Ltd.) 
Ethylene glycol monobutyl ether 
1 part 
Water 80 parts. 
______________________________________ 
Comparative Examples 4 to 9 
Inks G to L were prepared in the same manner as in Examples 4 to 9, 
respectively, except that no hydrazide compound was used. 
Using the inks prepared in Examples 4 to 9 and Comparative Examples 4 to 9, 
recording was carried out to obtain prints, which were then evaluated in 
the following way. Results obtained are shown together in Table 2. 
(1) Evaluation of drying time: 
Characters were printed on commercially available copy paper and bond 
paper, and the printed areas were rubbed with filter paper (trade name: 
No.5C; available from Toyo Roshi K.K.) after 5 seconds, 10 seconds, 20 
seconds and 30 seconds. Evaluation was made in the following way. The 
evaluation was made in an environment of 25.degree. C., 60% RH. 
AA: No blur when rubbed after 5 seconds 
A: No blur when rubbed after 10 seconds 
B: No blur when rubbed after 20 seconds 
C: Blurred when rubbed after 30 seconds 
(2) Occurrence of blurring: 
To examine the occurrence of blurring, 300 dots were continuously printed 
using a printer on commercially available copy paper and bond paper in a 
manner such that they did not touch one another, and were left to stand 
for 1 hour or more. Thereafter, the number of dots having caused blurring 
was counted on a microscope, and its proportion to the whole dot number 
was indicated in % to make an evaluation in the following way. The 
evaluation was made in an environment of 25.degree. C., 60% RH. 
A: 10% or less 
B: 11 to 30% 
C: 31% or more 
(3) Anti-clogging: 
Anti-clogging refers to the lack of clogging of ejection orifices that may 
occur when printing is again started after a pause. The ink holder of a 
printer was filled with a given ink and alphabet and numeral characters 
were continuously printed for 10 minutes. Thereafter, printing was stopped 
and the printer was left to stand for 10 minutes in an uncapped state and 
thereafter alphabet and numeral characters were printed, where any faulty 
prints such as blurred or broken characters were examined to make an 
evaluation. The evaluation was made in an environment of 25.degree. C., 
60% RH. 
A: No faulty prints occur on the first and subsequent characters. 
B: Characters partly blur or break from the first. 
C: Characters can not be printed at all from the first. 
(4) Frequency response: 
Resulting prints were observed with the naked eye to examine the state of 
prints, i.e., any blurs or blank areas and defective ink-droplet impact 
such as a splash or slippage, and an evaluation was made in the following 
way. 
AA: Ink continuity to frequencies is good, and no blurs or white areas and 
defective ink-droplet impact are seen in both solid prints and character 
prints. 
A: Ink continuity to frequencies is substantially good, and no blurs or 
white areas and defective ink-droplet impact are seen in character prints, 
but blurs are slightly seen in solid prints. 
B: No blurs or white areas are seen in character prints, but a defective 
ink-droplet impact is partly seen. In solid prints, blurs or white areas 
are seen in about 1/3 of the solid prints. 
C: Many blurs or white areas are seen in solid prints, and blurs or 
defective ink-droplet impact are seen in a large number in character 
prints. 
TABLE 2 
______________________________________ 
Fre- 
Drying time 
Blurring Anti- quency 
Copy Bond Copy Bond clog- 
re- 
Ink paper paper paper paper ging sponse 
______________________________________ 
Example: 
4 (A) A A A A A A 
5 (B) A A A A A A 
6 (C) A A A A A A 
7 (D) A A A A A A 
8 (E) AA AA A A A A 
9 (F) AA AA A A A A 
Com- 
parative 
Example: 
4 (G) C B B B B B 
5 (H) B B B B B B 
6 (I) B B B B B B 
7 (J) B B B B B B 
8 (K) AA AA C C A A 
9 (L) AA AA C C A A 
______________________________________ 
As described above, the use of the ink according to the present invention 
brings about an improvement in rub-off fastness of prints and fixing 
speed, and also can eliminate any uneven print densities ascribable to the 
types of recording paper, making it possible to obtain stable recorded 
images. The ink is also effective for solving various problems without 
causing the deterioration of performances such as ejection stability of 
the ink, anti-clogging at head tips and maintenance of print quality. 
The ink of the present invention enables good recording free from blurring, 
with a superior quality level and with a good fixing performance also on 
plain paper such as paper for copying, paper for reporting, notepaper, 
letter paper, bond paper and computer printout paper commonly used in 
offices and so forth. 
The present invention also makes it possible to obtain an ink with good 
safety even in its use in offices and homes. 
Second Embodiment 
The second embodiment will be described below by giving Examples 10 to 12 
and Comparative Examples 10 to 12 relating to water-based pigment inks. 
Example 10 
Preparation of pigment dispersion: 
______________________________________ 
Styrene/acrylic acid/ethyl acrylate copolymer 
1.5 parts 
(acid value: 140; weight average molecular weight: 
5,000) 
Monoethanolamine 1 part 
Ion-exchanged water 81.5 parts 
Diethylene glycol 5 parts. 
______________________________________ 
The above components were mixed, and the mixture was heated to 70.degree. 
C. on a water bath to completely dissolve the resin component. To the 
resulting solution, 10 parts of carbon black (MCF88, available from 
Mitsubishi Chemical Industries Limited) and 1 part of isopropyl alcohol 
were added, followed by premixing for 30 minutes, and thereafter the 
mixture obtained was dispersed. In this dispersion treatment, Sand grinder 
(manufactured by Igarashi Kikai K.K.) was used as a dispersion machine, 
where zirconium beads of 1 mm diameter were used as the tumbling media in 
a tumbling media packing fraction of 50% by volume, and pulverization was 
carried out for 3 hours. Centrifugal separation was further carried out at 
12,000 rpm for 20 minutes to remove coarse particles. Thus, a dispersion 
was formed. 
Preparation of ink: 
______________________________________ 
Pigment dispersion shown above 
30 parts 
Glycerol 10 parts 
Ethylene glycol 5 parts 
N-methylpyrrolidone 5 parts 
Ethyl alcohol 2 parts 
K-1010E (trade name; available from Nippon 
2 parts 
Shokubai Kagaku Kogyo Co., Ltd.) 
Ion-exchanged water 46 parts. 
______________________________________ 
The above components were mixed to obtain an ink. 
Example 11 
Preparation of pigment dispersion: 
______________________________________ 
Styrene/maleic acid/maleic acid half ester 
4 parts 
copolymer (acid value: 70; weight average molecular 
weight: 1,200) 
Aminomethyl propanol 2 parts 
Ion-exchanged water 74 parts 
Diethylene glycol 5 parts. 
______________________________________ 
The above components were mixed, and the mixture was heated to 70.degree. 
C. on a water bath to completely dissolve the resin component. To the 
resulting solution, 15 parts of carbon black (MCF88, available from 
Mitsubishi Chemical Industries Limited) was added, followed by premixing 
for 30 minutes, and thereafter the mixture obtained was dispersed. In this 
dispersion treatment, Pearl mill (manufactured by Ashizawa K.K.) was used 
as a dispersion machine, where glass beads of 1 mm diameter were used as 
tumbling media in a tumbling media packing fraction of 50% by volume under 
a discharge rate of 100 ml/min. Centrifugal separation was further carried 
out at 12,000 rpm for 20 minutes to remove coarse particles. Thus, a 
dispersion was formed. 
Preparation of ink: 
______________________________________ 
Pigment dispersion shown above 
30 parts 
Glycerol 8 parts 
Ethylene glycol 5 parts 
Ethanol 5 parts 
RPS-1001 (trade name; available from Nippon 
1 part 
Shokubai Kagaku Kogyo Co., Ltd.) 
Ion-exchanged water 51 parts. 
______________________________________ 
The above components were mixed, and aminomethyl propanol was added to 
adjust the pH value to 8 to 10. Thus, an ink was obtained. 
Example 12 
Preparation of pigment dispersion: 
______________________________________ 
Preparation of pigment dispersion: 
______________________________________ 
.alpha.-Methylstyrene/methyl acrylate/acrylic acid 
2.0 parts 
copolymer (acid value: 95; weight average 
molecular weight: 8,000) 
Ion-exchanged water 81.0 parts 
Ethylene glycol 5 parts. 
______________________________________ 
The above components were mixed, and the mixture was heated to 70.degree. 
C. on a water bath to completely dissolve the resin component. To the 
resulting solution, 11 parts of carbon black (S170, available from 
Degussa, Inc.) and 1 part of isopropyl alcohol were added, followed by 
premixing for 60 minutes, and thereafter the mixture obtained was 
dispersed. In this dispersion treatment, Sand grinder (manufactured by 
Igarashi Kikai K.K.) was used as a dispersion machine, where zirconium 
beads of 0.5 mm diameter were used as tumbling media in a tumbling media 
packing fraction of 70% by volume, and pulverization was carried out for 
100 hours. Centrifugal separation was further carried out at 12,000 rpm 
for 20 minutes to remove coarse particles. Thus, a dispersion was formed. 
Preparation of ink: 
______________________________________ 
Pigment dispersion shown above 
30 parts 
Glycerol 12 parts 
Diethylene glycol 10 parts 
2-Pyrrolidone 5 parts 
CX-K2010E (trade name; available from Nippon 
0.5 part 
Shokubai Kagaku Kogyo Co., Ltd.) 
Ion-exchanged water 42.5 parts. 
______________________________________ 
The above components were mixed to obtain an ink. 
Comparative Examples 10 to 12 
Examples 10 to 12 were respectively repeated to prepare inks, except that 
no compound having an oxazolyl group was added and ion-exchanged water was 
instead added in the same amount. 
Evaluation of ink: 
Using each ink, characters were printed on copy paper (NP-DRY copy paper, 
available from Canon Inc.) using an ink-jet recording apparatus having an 
on-demand type multi-recording head capable of imparting heat energy 
corresponding with recording signals to thereby eject ink droplets. The 
print density, drying time and rub-off fastness of prints were evaluated 
in the same manner as in Examples 1 to 3. Results obtained are shown in 
Table 3. 
TABLE 3 
______________________________________ 
Print Drying time (sec) 
Rub-off 
density 
Solid print 
Characters 
fastness 
______________________________________ 
Example: 
10 1.40 30 10 A 
11 1.38 32.5 12.5 A 
12 1.39 32.5 12.5 A 
Comparative 
Example: 
10 1.30 60 35 C 
11 1.29 70 40 C 
12 1.29 75 45 C 
______________________________________ 
As is seen from the results shown in Table 3, the inks of Examples 10 to 
12, compared with the inks of Comparative Examples 10 to 12, show superior 
print density, drying time and rub-off fastness because of the compound 
having oxazolyl groups contained therein. 
The second embodiment will be further described below by giving Examples 13 
to 18 and Comparative Examples 13 to 18 relating to dye inks. 
Examples 13 to 18 
Components respectively shown below were mixed and stirred for 5 hours. 
Thereafter, a 0.1% sodium hydroxide aqueous solution was added to adjust 
the pH value to 7.5, followed by filtration under pressure using a 
membrane filter with a pore size of 0.22 .mu.m (trade name: Fluoro pore 
filter; available from Sumitomo Electric Industries, Ltd.). Thus, inks of 
the present invention were obtained. 
______________________________________ 
(Example 13) 
C.I. Direct Yellow 41 2 parts 
Diethylene glycol 15 parts 
K-1010E 3 parts 
(trade name; available from Nippon Shokubai 
Kagaku Kogyo Co., Ltd.) 
Ion-exchanged water 80 parts. 
(Example 14) 
C.I. Direct Black 51 3 parts 
Triethylene glycol 10 parts 
N-methyl-2-pyrrolidone 3 parts 
RPS-1001 1 part 
(trade name; available from Nippon Shokubai 
Kagaku Kogyo Co., Ltd.) 
Ion-exchanged water 83 parts. 
(Example 15) 
C.I. Direct Blue 149 2.5 parts 
1,2,6-Hexanetriol 5 parts 
Diethylene glycol 10 parts 
CX-K2010E 3 parts 
(trade name; available from Nippon Shokubai 
Kagaku Kogyo Co., Ltd.) 
Ion-exchanged water 79.5 parts. 
(Example 16) 
HI12286 (available from ICI Co.) 
2 parts 
Thiodiglycol 6 parts 
Diethylene glycol 9 parts 
K-1020E 3 parts 
(trade name; available from Nippon Shokubai 
Kagaku Kogyo Co., Ltd.) 
ACETYLENOL EH 0.5 parts 
(trade name; available from Kawaken Fine 
Chemicals Co., lTd.) 
Ion-exchanged water 79.5 parts. 
(Example 17) 
C.I. Direct Black 174 3 parts 
Ethylene glycol 8 parts 
Diethylene glycol 7 parts 
RAS-1005 1 part 
(trade name; available from Nippon Shokubai 
Kagaku Kogyo Co., Ltd.) 
Ethylene glycol monobutyl ether 
1 part 
Ion-exchanged water 80 parts. 
(Example 18) 
C.I. Acid Green 34 3 parts 
Ethylene glycol 8 parts 
Triethylene glycol 7 parts 
K-10120E 3 parts 
(trade name; available from Nippon Shokubai 
Kagaku Kogyo Co., Ltd.) 
Triethylene glycol monobutyl ether 
1 part 
Ion-exchanged water 78 parts. 
______________________________________ 
Comparative Examples 13 to 18 
Examples 13 to 18 were respectively repeated to prepare inks, except that 
no compound having an oxazolyl group was added and ion-exchanged water was 
instead added in the same amount. 
Evaluation of ink: 
Each ink was poured into an ink cartridge for an ink-jet printer (trade 
name: BJ-10V, manufactured by Canon Inc.) making use of a heating element 
as an energy source for ink ejection. Using this printer, recording was 
carried out on commercially available copy paper and bond paper. Drying 
time of prints, occurrence of blurring, anti-clogging and frequency 
response were evaluated in the same manner as in Examples 4 to 9. Results 
obtained are shown in Table 4. 
TABLE 4 
______________________________________ 
Drying time 
Blurring Anti- Fre- 
Copy Bond Copy Bond clog- 
quency 
paper paper paper paper ging response 
______________________________________ 
Example: 
13 A A A A A A 
14 A A A A A A 
15 A A A A A A 
16 AA AA A A A A 
17 AA AA A A A A 
18 AA AA A A A A 
Comparative 
Example: 
13 C B B B B B 
14 B B B B B B 
15 B B B B B B 
16 AA AA C C B B 
17 AA AA C C A A 
18 AA AA C C A A 
______________________________________ 
As is seen from the results shown in Table 4, the inks of Examples 13 to 
18, compared with the inks of Comparative Examples 13 to 18, show superior 
drying time, occurrence of blurring, anti-clogging and frequency response 
because of the compound having an oxazolyl group contained therein. As 
described above, ink-jet recording carried out using the ink of the 
present invention can bring about recorded images free from uneven print 
quality level due to differences in recording paper, having superior 
drying time and rub-off fastness and free from a decrease in print density 
and blurring. Since also it is unnecessary to add highly viscous organic 
solvents as in the prior art, stable recording can be performed without 
causing the problems of ink ejection stability and solidification at head 
tips. 
Thus, the ink of the present invention enables good recording also on plain 
paper such as paper for copying, paper for reporting, notepaper, letter 
paper, bond paper and computer printout paper commonly used.