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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a water-based ink composition, and an ink-jet
recording process.
2. Description of the Related Art
As ink-jet recording systems, ink ejection systems are known in the art as
exemplified by a system utilizing electrostatic attraction, a system in
which mechanical vibration or displacement is imparted to an ink
composition by the use of a piezoelectric device, and a system in which an
ink composition is heated to cause it bubble and a pressure produced when
it bubbles is utilized. Ink droplets are formed by some of these ink
ejection systems, and part or the whole of the droplets is caused to
adhere to recording mediums such as paper to make a record. When writing
implements such as fountain pens, felt-tip pens and ball-point pens are
used, an ink composition is ejected from capillaries and the ink
composition thus ejected is received on recording mediums to make a
record. As ink compositions used in such ink-jet recording systems or
writing implements, those prepared by dissolving or dispersing a
water-soluble dye or a pigment in water or an aqueous medium comprising
water and a water-soluble organic solvent are known and put into use.
In such conventional ink compositions, they are of course required to have
various performances. In particular, the performance most required is the
liquid stability that the ink composition does not cause clogging of, and
deposits at, nozzles or orifices of recording apparatus or pen points when
recording is being performed using the ink composition, when the recording
is paused and also when the recording is stopped over a long period of
time. Especially in the ink-jet recording systems, the apparatus are
expensive compared with the writing implements, and hence it is important
to prevent ink-jet nozzles or orifices from clogging. Moreover, in the
ink-jet recording systems, if the nozzles or orifices are not even
clogged, faulty images due to curved jets, changes in ink drop quantity
and changes in flying speed which are caused by the deposits formed at the
nozzles or orifices have caused a great problem. Furthermore, among the
ink-jet recording systems, the thermal ink-jet recording system that
utilizes heat energy tends to cause deposition of foreign matter on the
surface of a heating element as a result of temperature changes, and the
problem is more important.
Commercially available dyes or pigments used as materials for ink
compositions also contain many impurities (e.g., organic matter and
inorganic matter such as dispersants and leveling agents). Ink components
other than the dyes or pigments, as exemplified by water and water-soluble
organic solvents, also contain not a little organic or inorganic
impurities. Still also, during the manufacture of ink compositions,
various impurities may be included therein according to containers or
implements used and the environment.
Under such circumstances, it has been attempted to solve the above problems
by controlling the quantity of the impurities in ink compositions that may
cause the deposits.
For example, Japanese Patent Application Laid-open No. 3-48951 discloses a
liquid composition containing a water-soluble dye used in ink-jet
recording and in which iron and silicon contained therein are controlled
to be in a content not more than 9 ppm in total. Japanese Patent
Publication No. 2-2906 also discloses an ink-jet recording ink composition
mainly composed of an aqueous solution containing a water-soluble acid dye
or water-soluble direct dye having been subjected to ion exchange by the
use of a cationic ion-exchange resin.
Japanese Patent Application Laid-open No. 64-4350 also discloses an ink-jet
recording apparatus in which sodium ions in an ink composition are
controlled to be in a content of 0.001% by weight to 0.2% by weight, and
fatty acids and fatty acid derivatives contained in materials constituting
an ink tank, 10 to 100 ppm in total weight.
Japanese Patent Publication No. 60-48552 still also discloses an ink
composition comprising water, a water-soluble dye and a polyhydric alcohol
or polyhydric alcohol derivative and in which a fatty acid ester as an
anti-foaming agent is controlled to be in a content of 0.01% by weight to
5% by weight.
Such conventional impurity-controlled ink compositions are more improved
than ink compositions containing impurities in excess. However, they have
not necessarily been well effective when, for example, even the long-term
storage of ink compositions and the changes in temperature and environment
are taken into account. In particular, they have not perfectly solved the
problems of the curved jets, changes in ink drop quantity and changes in
flying speed in the ink-jet recording systems. In the case of the ink-jet
recording system utilizing heat energy, they have been not able to well
prevent the deposition of foreign matter on the heating element.
The above Japanese Patent Application Laid-open No. 64-4350 does not teach
any control of the quantity of fatty acids or fatty acid esters in ink
compositions.
The above Japanese Patent Publication No. 60-48552 teaches control of the
quantity of a fatty acid ester intentionally added as an anti-foaming
agent, but does not teach any control of the quantity of fatty acid esters
as well as impurities that are actually present in ink compositions.
SUMMARY OF THE INVENTION
The present invention was made in order to solve the problems discussed
above. Accordingly, an object of the present invention is to provide a
water-based ink composition that may cause no clogging of nozzles or
orifices in the heads of ink-jet printers or the like, and may cause no
faulty prints due to curved jets, changes in ink drop quantity and changes
in flying speed, when used, when stored for a long term and even when
undergoes changes in temperature and environment.
To achieve the above object, the present inventors made extensive studies.
Since the impurities contained in inks cause the above problems, they
studied various effects or influences of such impurities. As the result,
they have discovered that the clogging of nozzles or orifices in the
ink-jet heads, the formation of deposits on the heating elements, the
curved jets, the changes in ink drop quantity, the changes in flying speed
and the deposits formed during the storage of inks are greatly caused by
fatty acids or fatty acid esters contained in ink compositions, and that
the above various problems can be solved when an ink composition is used
whose quantity of such impurities has been controlled to be not more than
a certain value is used. Thus, they have accomplished the present
invention.
The present invention provides a water-based ink composition comprising a
dye or a pigment, dissolved or dispersed in an aqueous medium, wherein the
water-based ink composition has fatty acids in a total content not more
than 0.3% by weight or fatty acid esters in a total content not more than
0.6% by weight.
The present invention also provides an ink-jet recording process carried
out by jetting a water-based ink composition to a recording medium in the
form of droplets to make a record, wherein the water-based ink composition
comprises a dye or a pigment, dissolved or dispersed in an aqueous medium,
and has fatty acids in a total content not more than 0.3% by weight or
fatty acid esters in a total content not more than 0.6% by weight.
In the present invention, the water-based ink composition may fulfill
either the condition that the fatty acids are in a total content not more
than 0.3% by weight or the condition that the fatty acid esters are in a
total content not more than 0.6% by weight. It is preferable for the
water-based ink composition to fulfill both the conditions at the same
time.
These and other features and advantages of the present invention are
described in or will become apparent from the following detailed
description of the preferred embodiments.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The water-based ink composition of the present invention is characterized
in that the total content of fatty acids is controlled to be not more than
0.3% by weight or the total content of fatty acid esters is controlled to
be not more than 0.6% by weight. This makes it possible to prevent
clogging of nozzles or orifices in the heads of ink-jet printers or the
like, and prevent curved jets, so that faulty prints due to changes in ink
drop quantity and changes in flying speed can be prevented, when the ink
composition is used, when stored for a long term and when undergoes
changes in temperature and environment.
The reason why the content of the fatty acids or fatty acid esters is set
not more than the stated value in this way is as follows:
According to the studies made by the present inventors, as a result of
analyses of the deposits formed during a long-term storage of water-based
ink compositions and the deposits formed at nozzles or orifices of ink-jet
heads having caused curved jets or non-ejection and also as result of
analyses of the deposits formed on the surfaces of heating elements, it
has been found that these phenomena are chiefly caused by fatty acids or
fatty acid esters and also that the frequencies of the curved jets,
changes in ink drop quantity and changes in flying speed that may occur in
ink-jet recording systems distinctively correlate with the content of the
fatty acids or fatty acid esters in water-based ink compositions.
The mechanism by which the fatty acids or fatty acid esters cause the
problems as stated above is unclear, and is presumed as follows:
The fatty acids or fatty acid esters present in ink compositions are in the
state they are completely dissolved or dispersed in the water-based ink
composition available immediately after it has been prepared through the
step of precision filtration. Thereafter the water-based ink composition
undergoes environmental changes such as changes in temperature, humidity,
pH and so forth, whereupon the fatty acids or fatty acid esters react with
cations as typified by alkali metal ions present in the water-based ink
composition, to form insoluble salts. The insoluble salts cause the
clogging of nozzles or orifices of the ink-jet heads and the formation of
deposits on the heating elements. In particular, the salts of the fatty
acids or fatty acid esters with the cations are remarkably produced at low
temperatures, and are remarkably produced also when ink compositions have
a high pH.
In the water-based ink composition of the present invention, the fatty acid
are controlled to be in a total content not more than 0.3% by weight as
previously stated, and preferably not more than 0.09% by weight. The fatty
acid esters are controlled to be in a total content not more than 0.6% by
weight, and preferably not more than 0.3% by weight. It is also preferable
for the water-based ink composition to fulfill at the same time both the
condition that the fatty acids are in a total content not more than 0.3%
by weight, and preferably not more than 0.09% by weight, and the condition
that the fatty acid esters are in a total content not more than 0.6% by
weight, and preferably not more than 0.3% by weight.
Here, the fatty acids, which are contained in dust or dirt present in the
atmosphere or contained in dyes, surface active agents and so forth as
impurities, include fatty acids ranging from lower fatty acids up to
higher fatty acids having 22 or more carbon atoms. As fatty acids that are
present in relatively a large quantity and also form the insoluble salts,
it is preferable to take note of palmitic acid and stearic acid. In such
an instance, the palmitic acid in the water-based ink composition may
preferably be controlled to be in a content not more than 0.1% by weight,
and more preferably 0.03% by weight. The stearic acid may preferably be
controlled to be in a content not more than 0.2% by weight, and more
preferably not more than 0.06% by weight.
The fatty acid esters, which are contained in dust or dirt present in the
atmosphere or contained in dyes, surface active agents and so forth as
impurities, include lower alkyl esters or glycerides of fatty acids
ranging from lower fatty acids up to higher fatty acids having 22 or more
carbon atoms. As fatty acid esters that are present in relatively a large
quantity and also form the insoluble salts, it is preferable to take note
of methyl palmitate and methyl stearate. In such an instance, the methyl
palmitate in the water-based ink composition may preferably be controlled
to be in a content not more than 0.2% by weight, and more preferably 0.1%
by weight. The methyl stearate may preferably be controlled to be in a
content not more than 0.4% by weight, and more preferably not more than
0.2% by weight.
Basic components that make up the water-based ink composition of the
present invention will be described below.
As basic components that make up the water-based ink composition of the
present invention, those conventionally used in water-based ink
compositions may be used.
For example, the dye includes water-soluble dyes as typified by direct
dyes, acid dyes, basic dyes and reactive dyes. In particular, as those
preferable for inks used in the ink-jet recording systems and satisfying
sharpness, water-solubility, stability, light-fastness and other required
performances, the dye includes, for example, C.I. Direct Black 17, 19, 32,
51, 71, 108, 146, 154, 168; C.I. Direct Blue 6, 22, 25, 71, 86, 90, 106,
199; C.I. Direct Red 1, 4, 17, 28, 83, 227; C.I. Direct Yellow 12, 24, 26,
86, 98, 142; C.I. Direct Orange 34, 39, 44, 46, 60; C.I. Direct Violet 47,
48; C.I. Direct Brown 109; C.I. Direct Green 59; C.I. Acid Black 2, 7, 24,
26, 31, 52, 63, 112, 118; C.I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 113,
117, 120, 167, 229, 234; C.I. Acid Red 1, 6, 32, 37, 51, 52, 80, 85, 87,
92, 94, 115, 181, 256, 289, 315, 317; C.I. Acid Yellow 11, 17, 23, 25, 29,
42, 61, 71; C.I. Acid Orange 7, 19; C.I. Acid Violet 49; C.I. Basic Black
2; C.I. Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28, 29; C.I. Basic Red 1, 2,
9, 12, 13, 14, 37; C.I. Basic Violet 7, 14, 27; and C.I. Food Black 1, 2.
The foregoing examples of the dye are examples particularly preferred for
the water-based ink composition of the present invention. In the present
invention, examples are by no means limited to these dyes.
As the pigment, carbon black and besides many inorganic pigments and
organic pigments may be used. For example, it may include azo pigments
such as azo lakes, insoluble azo pigments, condensed azo pigments and
chelate azo pigments, polycyclic pigments such as phthalocyanine pigments,
perylene and perynone pigments, anthraquinone pigments, quinacridone
pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments
and quinophthalone, dye lakes such as basic dye lakes and acid dye lakes,
organic pigments such as nitro pigments, nitroso pigments and aniline
black daylight fluorescent pigments, and inorganic pigments such as
titanium oxide, iron oxide type ones and carbon black type ones. Other
pigments may also be used so long as they are dispersible in an aqueous
phase. Those obtained by surface-treating these pigments with a surface
active agent or a polymeric dispersant, as exemplified by graft carbon,
may also be used.
The foregoing examples of the pigment are examples particularly preferred
for the water-based ink composition of the present invention. In the
present invention, examples are by no means limited to these dyes.
When the above pigment is used as a colorant of the present invention, it
is dispersed by a conventionally known method together with a suitable
dispersant, a solvent, pure water and optionally other additives.
As the dispersant, polymeric dispersants or surface active agents as
disclosed in, for example, Japanese Patent Application Laid-open No.
62-101672 may be used. The polymeric dispersants include anionic polymeric
dispersants as exemplified by proteins such as gelatin and albumin,
natural rubbers such as gum arabic and tragacanth rubber, glucosides such
as saponin, cellulose derivatives such as methyl cellulose, carboxyl
cellulose and hydroxymethyl cellulose, natural polymers such as lignin
sulfonate and shellac, polyaclyrates, salts of a styrene-acrylic acid
copolymer, salts of a vinylnaphthalene-acrylic acid copolymer, salts of a
styrene-maleic acid copolymer, salts of a vinylnaphthalene-maleic acid
copolymer, sodium salt of a formalin condensate with
.beta.-naphthalenesulfonic acid, and phosphates; and nonionic polymeric
dispersants such as polyvinyl alcohol, polyvinyl pyrrolidone and
polyethylene glycol. The surface active agents include anionic surface
active agents such as higher alcohol sulfuric acid ester salts, liquid
fatty oil sulfuric acid ester salts and alkylallylsulfonic acid salts, and
nonionic surface active agents such as polyoxyethylene alkyl ethers,
polyoxyethylene alkyl esters, sorbitan alkyl esters and polyoxyethylene
sorbitan alkyl esters. One or more kinds of these may be used under
appropriate selection. The dispersant may preferably be used in an amount
of usually from 1 to 20% by weight based on the total weight of the ink
composition.
Meanwhile, the dispersion machine used to disperse the pigment may include
any of those commonly available as dispersion machines, as exemplified by
ball mills, roll mills and sand mills. In particular, high-speed sand
mills are especially preferred.
The dye and the pigment may each be used alone, or may be used as a mixture
of two or more kinds of dyes, pigments, or dyes and pigments in
combination.
The dye and the pigment may be used in an amount of usually from 0.1 to 20%
by weight, and preferably from 0.3 to 15% by weight, based on the weight
of the water-based ink composition of the present invention.
The aqueous medium used in the water-based ink composition of the present
invention and used in the recording process of the present invention may
be water, or a mixed solvent of water and a water-soluble organic solvent.
Particularly preferably, it may be a mixed solvent of water and a
water-soluble organic solvent. The water-soluble organic solvent includes
those having a drying-preventive (wetting) effect. As the water, it is
preferable to use not commonly available water containing various ions but
deionized water.
The water-soluble organic solvent used as its 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 and isobutyl
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 glycol; alkylene glycols whose alkylene group has
2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, butylene
glycol, diethylene glycol, dipropylene glycol, triethylene glycol,
tripropylene glycol, 1,2,6-hexanetriol, thiodiglycol, 1,3-butanediol,
1,5-pentanediol and hexylene glycol; glycerol; lower alkyl ethers of
polyhydric alcohols, such as ethylene glycol methyl (or ethyl or n-propyl
or isopropyl or n-butyl or isobutyl) ether, propylene glycol methyl (or
ethyl or n-propyl or isopropyl or n-butyl or isobutyl) ether, diethylene
glycol methyl (or ethyl or n-propyl or isopropyl or n-butyl or isobutyl)
ether, dipropylene glycol methyl (or ethyl or n-propyl or isopropyl or
n-butyl or isobutyl) ether, triethylene glycol methyl (or ethyl or
n-propyl or isopropyl or n-butyl or isobutyl) ether, and tripropylene
glycol methyl (or ethyl or n-propyl or isopropyl or n-butyl or isobutyl)
ether; pyrrolidones such as 2-pyrrolidone and N-methyl-2-pyrrolidone; and
1,3-dimethyl-2-imidazolidinone. Of these many water-soluble organic
solvents, polyhydric alcohols such as diethylene glycol and glycerol, and
lower alkyl ethers of polyhydric alcohols, such as triethylene glycol
monomethyl (or ethyl or n-propyl or isopropyl or n-butyl or isobutyl)
ether are preferred.
The water-soluble organic solvent may be contained in the ink composition
in an amount of usually from 0 to 95% by weight, preferably from 10 to 80%
by weight, and more preferably from 20 to 50% by weight, based on the
total weight of the ink composition.
When this water-soluble organic solvent is used, the content of the water
may be determined within a vast range, depending on the type of component
of the water-soluble organic solvent, the composition thereof and the
desired properties of ink, and may be within the range of usually from 10
to 95% by weight, preferably from 10 to 75% by weight, and more preferably
from 20 to 70% by weight, based on the total weight of the ink
composition.
The process for preparing the water-based ink composition of the present
invention, containing the fatty acids or fatty acid esters controlled to
be in the content not more than the stated, will be described below.
First, the materials for the ink composition are mixed by a commonly
available method, followed by precision filtration to obtain a filtrate.
The filtrate obtained is left to stand for a day after its temperature has
been raised to above normal temperature, preferably 40.degree. C. or
above. Thereafter, the filtrate is further left to stand for a day after
its temperature has been lowered preferably to normal temperature or
below, and more preferably 10.degree. C. or below. The filtrate having
been subjected to such aging is again precision-filtered in a temperature
environment of normal temperature or below, and preferably 10.degree. C.
or below. Thus, the water-based ink composition of the present invention
is obtained.
In the above preparation process, the temperature of the ink composition is
raised to above normal temperature in order to accelerate the reaction of
the fatty acids or fatty acid esters contained in the filtrate, with the
cations typified by alkali metals to convert the former into insoluble
fatty acid salts. The temperature of the filtrate thus treated is lowered
to normal temperature or below in order to accelerate the precipitation of
the insoluble fatty acid salts. The precision filtration thereafter
carried out at a temperature of normal temperature or below is in order to
remove the insoluble fatty acid salts without allowing the precipitated
insoluble fatty acid salts to again dissolve in the ink composition.
In the ink composition thus obtained, the quantity of fatty acid or fatty
acid esters can be greatly smaller than that before the treatment and also
the quantity of metal cations such as alkali metals contained in the ink
composition can be greatly smaller, so that an ideal state of ink as the
ink composition for ink-jet recording can be achieved, having very less
impurities.
In the foregoing, a method for controlling the content of the fatty acids
or fatty acid esters in the ink composition is shown. Methods for such
control are by no means limited to this method, and all methods by which
the fatty acids or fatty acid esters or fatty acid salts can be removed
can be effectively used.
In practice, together with the removal of such fatty acid or fatty acid
ester matter, it is preferable to also remove various inorganic salts such
as sodium chloride, sulfates and sodium salts, as well as calcium,
magnesium and so forth.
The water-based ink composition used in the present invention is basically
constituted as described above. Besides, various dispersants, surface
active agents, viscosity modifiers, surface tension modifiers, pH
adjusters, anticeptic antifungal agents known in the art may be optionally
added.
When an ink composition is prepared which is used in an ink-jet recording
process of the type a recording solution is charged, a specific resistance
modifier including inorganic salts such as lithium chloride, ammonium
chloride and sodium chloride is added.
When the ink composition is used in the ink-jet recording of the type the
ink is ejected by the action of heat energy, thermal properties (e.g.,
specific heat, coefficient of thermal expansion, and thermal conductivity)
are controlled in some cases.
The water-based ink composition used in the present invention, obtained in
the manner as described above, has well solved the problems involved in
the prior art, and is for itself advantageous as having well balanced
performances in respect of all of recording performances in ink-jet
recording (e.g., signal response, stability in droplet formation,
long-time continuous recording performance, and ink ejection stability
after long-time pause), storage stability, fixing performance to recording
mediums, recorded image light-fastness, water resistance and so forth. It
can be useful as water-based ink compositions for ink-jet recording of
various systems, can be preferable as a water-based ink composition
especially for the ink-jet recording system in which the water-based ink
composition is jetted in the form of droplets by utilizing the vibration
of a piezoelectric device and for the ink-jet recording system in which
the water-based ink composition is jetted in the form of droplets by
utilizing the action of heat energy, the latter being the ink-jet
recording system easily affected by the formation of deposits. The present
water-based ink composition can also enjoy superior recording.
EXAMPLES
Examples in which the present invention is embodied will be given below.
In the following description, "%" and "parts" are by weight.
Example A1
Composition of liquid:
______________________________________
Acid Yellow 23 (Acid Yellow XX-SF; trade name;
1%
available from Hoechst Japan, Ltd.)
Diethylene glycol 10%
Glycerol 2%
Pure water 87%
______________________________________
The above materials were thoroughly mixed and stirred, followed by
filtration with a 0.8 .mu.m membrane filter to obtain a filtrate. This
filtrate was heated to 40.degree. C. and left to stand overnight (heat
aging). Thereafter, the resulting filtrate was cooled to 5.degree. C. and
left to stand overnight (cold aging). After such aging, while being
maintained at 5.degree. C., the filtrate was further again filtered with
the 0.8 .mu.m membrane filter to form an ink composition.
Fatty acid content in this ink composition was measured using a gas
chromatography mass spectrometer to reveal that it was 0.08%. Of the fatty
acids, palmitic acid was in a content of 0.02%, and stearic acid, 0.05%.
Fatty acids such as behenic acid and myristic acid other than palmitic
acid and stearic acid were in a content of 0.01% in total.
Using this ink composition, the following T1 to T5 were examined on a
recording apparatus having an on-demand type multi-head that performs
recording by imparting heat energy to the ink in the recording head to
produce ink droplets (ejection orifice diameter: 35 .mu.m; heating
resistor resistance value: 150 ohms; drive voltage: 30 volts; frequency: 2
KHz) and a recording apparatus having an on-demand type multi-head that
performs recording by imparting pressure produced by piezoelectric
vibration, to the ink in the recording head to produce ink droplets
(ejection orifice diameter: 40 .mu.m; drive voltage: 30 volts; frequency:
10 KHz), to find that good results were obtained in all the cases as noted
below together.
(T1) Long-term stability: The ink composition was hermetically enclosed in
a bag made of plastic film, and stored at -30.degree. C. or 60.degree. C.
for 6 months. Even after such storage, deposition of insoluble matter was
not seen, and any changes in liquid properties and color tones were also
not seen.
(T2) Ejection stability: The ink composition was continuously ejected in an
atmosphere of room temperature, 5.degree. C. or 40.degree. C., for 24
hours for each. Always stable, high-quality recording was performed in all
atmospheres.
(T3) Ejection response: Ejection intermittently carried out at intervals of
2 seconds and ejection after leaving for 2 months were examined. In both
instances, no clogging occurred at the orifice tips, and stable and
uniform recording was performed.
(T4) Quality of recorded images: Images recorded on the recording mediums
shown below had a high density and were sharp. After the images were
exposed to room light for 6 months, their densities decreased by 1% or
less.
Recording mediums:
Woodfree paper GINKAN, trade name, available from Sanyo Pulp Co., Ltd.
Woodfree paper SEVEN STAR, trade name, available from Hokuetsu Paper Co.,
Ltd.
Mechanical woodpulp paper HAKUBOTAN, trade name, available from Honshu
Paper Co., Ltd.
Non-size paper TOYO ROSHI No. 4, trade name, available from Toyo Roshi Co.,
Ltd.
(T5) Fixing performance on each kind of recording medium: Five seconds
after printing on the recording medium shown in the above (T4), print
areas were rubbed with fingers to examine whether or not images were
rubbed off or blurred. As the result, images were neither rubbed off nor
blurred in all instances, showing a superior fixing performance.
Examples A2 to A4
Ink compositions were prepared in the same manner as in Example A1 except
that the following commercially available dyes were used, and T1 to T5 of
the respective ink compositions were examined in the same manner as in
Example A1. Like those in Example A1, these ink compositions showed good
results.
Example
______________________________________
Acid Blue 9 (Acid Blue AE-SF; trade name; available from
2%
Hoechst Japan, Ltd.)
Diethylene glycol 12%
Pure water 86%
______________________________________
Fatty acid content in the ink composition, controlled to 0.06%; palmitic
acid. 0.01%, and stearic acid, 0.03%.
Example A3:
______________________________________
Acid Red 52 (Acid Rhodamine B-SF; trade name; available
1%
from Hoechst Japan, Ltd.)
Diethylene glycol 10%
Triethanolamine 3%
Pure water 86%
______________________________________
Fatty acid content in the ink composition, controlled to 0.04%; palmitic
acid, 0.01%, and stearic acid, 0.02%.
Example A4:
______________________________________
Direct Black 168 (Direct Black HEF-SF; trade name;
3%
available from Hoechst Japan, Ltd.)
Glycerol 10%
Ethanol 5%
Pure water 82%
______________________________________
Fatty acid content in the ink composition, controlled to 0.09%; palmitic
acid, 0.03%, and stearic acid, 0.05%.
Example A5
Using respectively the ink composition of Example A1 as cyan ink, the ink
composition of Example A2 as magenta ink, the ink composition of Example
A3 as yellow ink and the ink composition of Example A4 as black ink,
full-color photographic images were reproduced on the same ink-jet
recording apparatus as used in Examples A1 to A4. Images obtained were
very sharp and their colors were well reproduced.
Examples A6 to A9
Using the same commercially available dyes as used in Examples A1 to A4,
ink compositions were prepared in the same manner as in Example A1 except
that in the preparation of the ink compositions the high-temperature aging
was carried out at a temperature of 35.degree. C., and the low-temperature
aging and the re-filtration, at 10.degree. C. (Examples A6 to A9). T1 to
T5 of the respective ink compositions thus prepared were examined in the
same manner as in Example A1. As the result, like those in Example A1,
these ink compositions showed good results in respect of T1, T2, T4 and
T5. In respect of T3, curved Jets and changes in flying speed were
slightly observed at the ejection after leaving for 2 months, but the
original state was restored immediately after the printing was started.
Example A6:
The same composition of liquid as Example A1.
Fatty acid content in the ink composition, controlled to 0.25%; palmitic
acid, 0.08%, and stearic acid, 0.15%.
Example A7:
The same composition of liquid as Example A2.
Fatty acid content in the ink composition, controlled to 0.20%; palmitic
acid, 0.06%, and stearic acid, 0.12%.
Example A8:
The same composition of liquid as Example A3.
Fatty acid content in the ink composition, controlled to 0.17%; palmitic
acid, 0.05%, and stearic acid, 0.11%.
Example A9:
The same composition of liquid as Example A4.
Fatty acid content in the ink composition, controlled to 0.29%; palmitic
acid, 0.09%, and stearic acid, 0.18%.
Example A10
Pigment carbon black and a 100-fold amount of pure water were stirred for 1
hour, and the mixture was filtered three times, followed by drying. Using
this product, a liquid composition having the composition shown below was
prepared, and was subjected to dispersion by means of a dispersion machine
PEARL MILL (trade name, manufactured by Ashizawa K. K.) to obtain a
dispersion.
As grinding media put in the dispersion machine, zirconia beads were used.
At the parts coming in contact with liquid in the dispersion machine,
those subjected to ceramic coating were used.
Liquid composition:
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Carbon black (MA-7, available from Mitsubishi Chemical
10%
Industries Limited)
Styrene-maleic anhydride copolymer (molecular weight:
7%
10,000; acid value: 175)
Glycerol 5%
NIKKOL TS-30 (trade name; available from Nikko
2%
Chemicals Co., Ltd.)
Pure water 75%
Triethanolamine 1%
______________________________________
Next, this dispersion was treated by a centrifugal separator to remove
coarse particles, and then the resulting dispersion was pressure filtered
with a membrane filter of 1 .mu.m in average pore diameter. Thereafter the
filtrate formed was heated to 40.degree. C. and left to stand for a day.
Then, the resulting filtrate was cooled to 5.degree. C., left to stand for
a day and again filtered with a membrane filter of 1 .mu.m in an
environment of 5.degree. C. to obtain an ink composition. Fatty acid
content in the ink composition thus prepared was measured in the same
manner as in Example A1 to reveal that it was 0.06%. Of the fatty acids,
palmitic acid was in a content of 0.01%, and stearic acid, 0.03%. T1 to T5
of this ink composition were examined in the same manner as in Example A1.
Like those in Example A1, the ink composition showed good results.
Comparative Examples A1 to A4
Using the same commercially available dyes as used in Examples A1 to A4,
ink compositions were prepared in the same manner as in Example A1 except
that the heat aging, cool aging and re-filtration were not carried out
(Comparative Examples A1 to A4). T1 to T5 of the respective ink
compositions thus prepared were examined in the same manner as in Example
A1. As the result, deposition of insoluble matter was seen in respect of
T1. In respect of T2 and T3, clogging, curved jets and changes in flying
speed were frequently observed, and the original state was not restorable.
Comparative Example A1:
The same composition of liquid as Example A1.
Fatty acid content in the ink composition, 1.10%; palmitic acid, 0.35%, and
stearic acid, 0.61%.
Comparative Example A2:
The same composition of liquid as Example A2.
Fatty acid content in the ink composition, 0.95%; palmitic acid, 0.31%, and
stearic acid, 0.57%.
Comparative Example A3:
The same composition of liquid as Example A3.
Fatty acid content in the ink composition, 0.90%; palmitic acid, 0.25%, and
stearic acid, 0.54%.
Comparative Example A4:
The same composition of liquid as Example A4.
Fatty acid content in the ink composition, 1.45%; palmitic acid, 0.46%, and
stearic acid, 0.92%.
As is clear from the foregoing description, in the case of the ink
compositions of Example A1 to A10 and the ink-jet recording carried out
using them, fatty acids contained in the ink compositions are in a content
not more than 0.3% by weight, and preferably not more than 0.09% by
weight, as so characterized in the present invention. Hence, good printing
can be enjoyed without causing the clogging of nozzles or orifices and the
faulty prints due to curved jets, changes in ink drop quantity and changes
in flying speed, when the ink composition are used, when stored for a long
term and even when undergo changes in temperature and environment. Also,
when the ink compositions of the present invention are used in the ink-jet
recording system utilizing heat energy, the deposits on the surface of the
heating element may be hardly formed, bringing about the advantage that
the durability of the head can be improved.
Example B1
Composition of liquid:
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Acid Yellow 23 (Acid Yellow XX-SF; trade name;
1%
available from Hoechst Japan, Ltd.)
Diethylene glycol 10%
Glycerol 2%
Pure water 87%
______________________________________
The above materials were thoroughly mixed and stirred, followed by
filtration with a 0.8 .mu.m membrane filter to obtain a filtrate. This
filtrate was heated to 40.degree. C. and left to stand overnight (heat
aging). Thereafter, the resulting filtrate was cooled to 5.degree. C. and
left to stand overnight (cold aging). After such aging, while being
maintained at 5.degree. C., the filtrate was further again filtered with
the 0.8 .mu.m membrane filter to form an ink composition.
Fatty acid ester content in this ink composition was measured using a gas
chromatography mass spectrometer to reveal that it was 0.17%. Of the fatty
acid esters, methyl palmitate was in a content of 0.05%, and methyl
stearate, 0.10%. Fatty acid esters such as methyl behenate and methyl
myristate other than methyl palmitate and methyl stearate were in a
content of 0.02% in total.
Using this ink composition, like Example B1, the following T1 to T5 were
examined on a recording apparatus having an on-demand type multi-head that
performs recording by imparting heat energy to the ink in the recor | | |
