U.S. patent application number 09/250181 was filed with the patent office on 2002-01-10 for ink for ink jet recording and ink jet recording method.
This patent application is currently assigned to FUJI XEROX CO., LTD. Invention is credited to HASHIMOTO, KEN, INOUE, HIROSHI, YAMASHITA, YOSHIRO.
Application Number | 20020002930 09/250181 |
Document ID | / |
Family ID | 12885436 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020002930 |
Kind Code |
A1 |
YAMASHITA, YOSHIRO ; et
al. |
January 10, 2002 |
INK FOR INK JET RECORDING AND INK JET RECORDING METHOD
Abstract
Disclosed is an ink for ink jet recording comprising water, a
pigment that is self-dispersible-in-water, and a water-soluble
organic solvent, wherein said ink for ink jet recording contains a
water-soluble organic compound having an S.P. value of 12 or less
and a surface tension at 25.degree. C. of less than 40 mN/m in an
amount of from 3.0 to 15.0 wt % based on the entire weight of the
ink. Also, disclosed are a method for producing the ink and an ink
jet recording method by using the ink.
Inventors: |
YAMASHITA, YOSHIRO;
(KANAGAWA, JP) ; INOUE, HIROSHI; (KANAGAWA,
JP) ; HASHIMOTO, KEN; (KANAGAWA, JP) |
Correspondence
Address: |
FINNEGAN HENDERSON FARABOW
GARRETT & DUNNER
1300 I STREET NW
WASHINGTON
DC
20005
|
Assignee: |
FUJI XEROX CO., LTD
|
Family ID: |
12885436 |
Appl. No.: |
09/250181 |
Filed: |
February 16, 1999 |
Current U.S.
Class: |
106/31.6 ;
106/31.65; 106/31.86 |
Current CPC
Class: |
C09D 11/322
20130101 |
Class at
Publication: |
106/31.6 ;
106/31.65; 106/31.86 |
International
Class: |
C09D 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 1998 |
JP |
10-051383 |
Claims
What is claimed is:
1. An ink for ink jet recording comprising water, a pigment that is
self-dispersible-in-water, and a water-soluble organic solvent,
wherein said ink contains a water-soluble organic compound having
an S.P. value of 12 or less and a surface tension at 25.degree. C.
of less than 40 mN/m in an amount of from 3.0 to 15.0 wt % based on
the entire weight of the ink.
2. The ink for ink jet recording as claimed in claim 1, wherein the
drying time is less than 5 seconds when a solid image having an
image area ratio of 100% is printed on a plain paper with the
ink.
3. The ink for ink jet recording as claimed in claim 1, wherein the
water self-dispersible pigment has a number average dispersion
particle size of from 15 to 100 nm.
4. The ink for ink jet recording as claimed in claim 1, wherein the
water self-dispersible pigment has a dispersion particle size
distribution of 3.5 or less.
5. The ink for ink jet recording as claimed in claim 1, wherein the
number of particles having a particle size in excess of 0.5 .mu.m
contained in the ink is 6.times.10.sup.10 particles/dm.sup.3 or
less.
6. The ink for ink jet recording as claimed in claim 1, wherein the
water-soluble organic compound has a weight molecular weight of
less than 400.
7. The ink for ink jet recording as claimed in claim 1, wherein the
water-soluble organic compound has an S.P. value of 8 or more.
8. The ink for ink jet recording as claimed in claim 1, wherein the
water-soluble organic compound is a compound represented by
R--O--X.sub.nH, wherein R is a functional group selected from the
group consisting of alkyl, alkenyl, alkynyl, phenyl, alkylphenyl
and cycloalkyl having from 1 to 8 carbon atoms, X represents
oxyethylene or oxypropylene, and n is an integer of from 1 to
8.
9. The ink for ink jet recording as claimed in claim 1, wherein the
ink has a surface tension of from 20 to 40 mN/m.
10. The ink for ink jet recording as claimed in claim 1, wherein
the ink has a viscosity of from 1.8 to 4.0 mPas.
11. The ink for ink jet recording as claimed in claim 1, wherein
the ink has an electric conductivity of from 0.03 to 0.4 S/m.
12. A process for producing an ink for ink jet recording, which
comprises: dispersing a pigment that is dispersible-in-water in
water by using one of an ultrasonic homogenizer and a high-pressure
homogenizer; and mixing the dispersed pigment, a water-soluble
solvent and a water-soluble organic compound having an S.P. value
of 12 or less and a surface tension at 25.degree. C. of less than
40 mN/m.
13. The process for producing an ink for ink jet recording as
claimed in claim 12, which further comprises a step of removing
coarse particles by centrifugal separation.
14. An ink jet recording method comprising ejecting an ink
according to claim 1 from an orifice in response to a recording
signal.
15. The ink jet recording method as claimed in claim 14, wherein
the ink is ejected by the action of heat energy upon the ink.
16. The ink jet recording method as claimed in claim 14, wherein a
plurality of pulses is applied to form and eject one ink
droplet.
17. The ink jet recording method as claimed in claim 14, which
further comprises a step of mixing the ink ejected and a fixing
agent on a recording material.
18. The ink jet recording method as claimed in claim 14, wherein
the amount of ink ejected is from 1 to 20 ng per one drop.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an ink for ink jet
recording for use in ink jet system recording apparatuses (e.g.,
printer, copying machine, facsimile, word processor, plotter), a
method for producing the ink, and an ink jet recording method using
the ink.
BACKGROUND OF THE INVENTION
[0002] Recording apparatuses using a so-called ink jet system in
which a liquid or fused solid ink is ejected from nozzle, slit,
porous film or the like to make recording on a recording material
such as paper, cloth or film are advantageous in that the apparatus
is compact, inexpensive and noiseless. Accordingly, various
investigations are being made thereon. In recent years, a large
number of products are commercially available and predominating in
the field of recording apparatus, where not only black single color
recording but also full color recording with good print quality can
be obtained on a so-called plain paper such as report paper or copy
paper.
[0003] In usual, the ink for use in ink jet recording apparatuses
mainly comprises a solvent, a coloring material and additives. The
ink for ink jet recording is required to have the following
properties:
[0004] (1) that a high-resolution and high-density uniform image
can be obtained without causing blotting or fogging on paper;
[0005] (2) that clogging of a nozzle tip due to drying of the ink
does not occur and ejection responsibility and ejection stability
are always kept in good condition;
[0006] (3) that the ink on paper exhibits good drying property;
[0007] (4) that the image has good fastness; and
[0008] (5) that high stability is ensured in the long-term
storage.
[0009] In order to satisfy these requirements, various techniques
have been proposed. For example, (3) the drying property of the ink
on paper is important for achieving high-speed printing in the
recording apparatus or in the case of color printing, for
preventing color mixing and improvement of this drying property has
been heretofore made by using a solvent having a high permeability
or volatility or by adding a surfactant.
[0010] With respect to (4) the fastness of the image, a large
number of inks have been disclosed where the water resistance is
improved by using a pigment in place of a dye as a coloring
material (see, JP-A-56-147869 (the term "JP-A" as used herein means
an "unexamined published Japanese patent application"),
JP-A-2-255875, U.S. Pat. No. 5,085,698). When a pigmented ink is
used, the water resistance may be improved, however, the ink is
disadvantageously inferior to a dyed ink in the rub resistance.
Furthermore, when a pigmented ink is used, the long-term storage
stability (5) is generally deteriorated as compared with dyed
inks.
[0011] In order to solve these problems with the use of a pigment,
for example, U.S. Pat. No. 5,571,311 discloses a method of coupling
a substituent having a water solubilization group with carbon
black, JP-A-8-81646 discloses a method of polymerizing a
water-soluble monomer or the like to the carbon black surface, and
JP-A-8-3498 discloses a method of oxidation treating carbon
black.
[0012] However, an ink for ink jet recording having good long-term
storage stability and fast drying property on a plain paper and
capable of giving an image having good print quality and excellent
water resistance/rub resistance has not yet been found.
SUMMARY OF THE INVENTION
[0013] Accordingly, the object of the present invention is to solve
these problems in conventional techniques and provide an ink having
good long-term storage stability and fast drying property on a
plain paper and capable of giving an image having good print
quality and excellent water resistance/rub resistance.
[0014] The present inventors have found that when an ink for ink
jet recording comprising water, a water-soluble organic solvent and
a water self-dispersible pigment (i.e., a pigment that is
self-dispersible-in-wat- er) contains a water-soluble organic
compound having an S.P. value of 12 or less and a surface tension
at 25.degree. C. of less than 40 mN/m in an amount of from 3.0 to
15.0 wt % based on the entire weight of the ink, the
above-described object can be obtained. The present invention has
been accomplished based on this finding.
[0015] More specifically, the present invention consists of:
[0016] an ink for ink jet recording comprising water, a water
self-dispersible pigment and a water-soluble organic solvent,
wherein the ink for ink jet recording contains a water-soluble
organic compound having an S.P. value of 12 or less and a surface
tension at 25.degree. C. of less than 40 mN/m in an amount of from
3.0 to 15.0 wt % based on the entire weight of the ink;
[0017] a process for producing an ink for ink jet recording,
comprising a step of dispersing a water self-dispersible pigment in
water using an ultrasonic homogenizer or high-pressure homogenizer
and a step of mixing the pigment dispersed with water, a
water-soluble solvent and a water-soluble organic compound having
an S.P. value of 12 or less and a surface tension at 25.degree. C.
of less than 40 mN/m; and
[0018] an ink jet recording method comprising ejecting the
above-described ink from an orifice in response to a recording
signal.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention is described in detail below.
[0020] The "water self-dispersible pigment" as used in the present
invention means a pigment having a large number of water
solubilization groups on the surface thereof and capable of stable
dispersion even in the absence of a dispersant. The "water
self-dispersible pigment" of the present invention may be any
pigment if the pigment satisfies the condition such that when a
pigment is dispersed in water by means of a dispersing machine such
as ultrasonic homogenizer, nanomizer, microfluidizer or ball mill
without using a dispersant to have a concentration of water/pigment
being 95 wt %/5 wt % and thereafter the dispersion solution placed
in a glass bottle is allowed to stand for 1 day, the pigment
concentration in a supernatant obtained is 98% or more of the
initial pigment concentration measured immediately after the
preparation of the dispersion solution.
[0021] The "water self-dispersible pigment" of the present
invention can be usually produced by applying a surface
modification treatment to a normal pigment, such as acid.cndot.base
treatment, coupling agent treatment, polymer graft treatment,
plasma treatment or oxidation and reduction treatment. The pigment
subjected to such a surface treatment is increased in the number of
water solubilization groups therein than usual and can be dispersed
by itself. Preferred examples of the normal pigment subjected to
the surface modification treatment include carbon black such as
Raven 5250, Raven 3500, Raven 5750, Raven 1080, Regal 330R, Mogul
L, Monarch 1000, Color Black FW2, Black Pearl L, Printex V, Special
Bk 4A and Mitsubishi Chemical No. 25. Other examples of the pigment
which can be used include cyan pigments such as C.I. Pigment Blue
1, C.I. Pigment Blue 3, C.I. Pigment Blue 15, C.I. Pigment Blue
15-3, C.I. Pigment Blue 16 and C.I. Pigment Blue 60; magenta
pigments such as C.I. Pigment Red 5, C.I. Pigment Red 12, C.I.
Pigment Red 48, C.I. Pigment Red 112, C.I. Pigment Red 122, C.I.
Pigment Red 146, C.I. Pigment Red 168 and C.I. Pigment Red 202; and
color pigments such as 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, C.I. Pigment Yellow 73, C.I. Pigment Yellow 83, C.I.
Pigment Yellow 98, C.I. Pigment Yellow 114, C.I. Pigment Yellow 128
and C.I. Pigment Yellow 154.
[0022] Furthermore, a commercially available water self-dispersible
pigment may be used as it is as the "water self-dispersible
pigment" for use in the present invention. Examples of such a
commercially available water self-dispersible include
Cab-o-jet-200, Cab-o-jet-300, IJX-55 (all produced by Cabot Co.)
and Microjet Black CW-1 (produced by Orient Kagaku KK).
[0023] The water solubilization group contained in the water
self-dispersible pigment may be nonionic, cationic or anionic and
predominantly, a sulfonic acid, a carboxylic acid, a hydroxyl
group, a phosphoric acid and the like are preferably added. In the
case of a sulfonic acid, a carboxylic acid or a phosphoric acid,
the free acid as it is may be used but the acid may be formed into
a salt and in this case, the counter ion of the acid in general is
preferably Li.sup.+, Na.sup.+, K.sup.+, NH.sub.4.sup.+ or an
organic amine.
[0024] In the present invention, the water self-dispersible pigment
is preferably contained in an amount of from 0.1 to 20 wt %, more
preferably from 0.5 to 15 wt %, still more preferably from 1 to 10
wt %, based on the entire ink weight. If the pigment content
exceeds 20 wt %, clogging is readily generated at a nozzle tip,
whereas if it is less than 0.1 wt %, a sufficiently high optical
density cannot be obtained.
[0025] The water self-dispersible pigment in the ink preferably has
a number average dispersion particle size of from 15 to 100 nm,
more preferably from 15 to 50 nm. When the number average
dispersion particle size is present in this range, clogging hardly
occurs and excellent storage stability can be attained. If the
number average dispersion particle size is less than 15 nm, the
surface area per the particle unit volume becomes large and
probably because the contact area between particles in the ink
tends to increase, the ink viscosity elevates and clogging is
readily generated, whereas if the average particle size exceeds 100
nm, unstable dispersion is liable to result and this gives rise to
agglomeration and then precipitation of the pigment.
[0026] The water self-dispersible pigment preferably has a
dispersion particle size distribution (a ratio of the volume
average dispersion particle size to the number average dispersion
particle size) of 3.5 or less, more preferably 2.5 or less. If the
dispersion particle size distribution exceeds 3.5, some large
dispersion particles serve as a core and the pigment is liable to
readily undertake agglomeration and then precipitation even if the
number average dispersion particle size falls within the
above-described range. By adding "a water-soluble organic compound
having an S.P. value of 12 or less and surface tension of less than
40 mN/m" for use in the present invention in an amount of from 3.0
to 15.0 wt % based on the entire ink weight, the dispersion
particle size distribution can be settled to be 3.5 or less.
[0027] In the case of using an ink jet recording system
characterized in that the ink is ejected by the action of heat
energy, the number of particles having a particle size of >0.5
.mu.m contained in the ink is preferably controlled to be
.ltoreq.6.times.10.sup.10 particles/dm.sup.3, more preferably
.ltoreq.3.times.10.sup.10 particles/dm.sup.3, so as to prevent
kogation on the heater. In order to control the number of particles
having a particle size of >0.5 .mu.m to fall within the
above-described range, a step for removing coarse particles by
centrifugal separation or filtration is preferably included in the
production process of the ink. If the number of particles having a
particle size of >0.5 .mu.m contained in the ink exceeds
6.times.10.sup.10 particles/dm.sup.3, this may cause clogging or
precipitation of the pigment during the storage or kogation on the
heater may be accelerated to reduce the drop volume. In the case
when a large amount of a surfactant is used so as to reduce the
drying time, the number of particles is liable to increase in the
normal pigment dispersion system, however, by using the
self-dispersible pigment, the number of particles having a particle
size of >0.5 .mu.m can be suppressed from increasing.
[0028] The water-soluble organic compound for use in the present
invention has an S.P. value (solubility parameter) of 12 or less,
preferably from 8 to 12. If the S.P. value exceeds 12, the drying
time is prolonged, whereas if it is less than 8, the solubility in
water readily decreases.
[0029] Also, the water-soluble organic compound for use in the
present invention has a surface tension at 25.degree. C. of less
than 40 mN/m, preferably from 20 to less than 40 mN/m. If the
surface tension is 40 mN/m or more, the wettability to the
recording material turns to worse and the drying property or rub
resistance cannot be improved, whereas if it is less than 20 mN/m,
the ink is excessively wetted to the recording material, as a
result, blotting or strike through is readily generated.
[0030] Furthermore, the water-soluble organic compound for use in
the present invention preferably has a molecular weight of less
than 400. If the molecular weight is 400 or more, the nozzle
disadvantageously exhibits bad clogging property.
[0031] The water-soluble organic compound satisfying these
requirements is preferably, in view of the pigment dispersion
stability, a compound represented by R--O--X.sub.nH (wherein R is a
functional group selected from the group consisting of alkyl having
1 to 8 carbon atoms, alkenyl having 1 to 8 carbon atoms, alkynyl
having 1 to 8 carbon atoms, phenyl, alkylphenyl having 7 to 8
carbon atoms and cycloalkyl having 3 to 8 carbon atoms, X is
oxyethylene or oxypropylene, and n is an integer of from 1 to 8).
In the formula above, R is preferably a functional group having
from 3 to 6 carbon atoms and n is preferably an integer of from 1
to 6. Examples of the compound having a structure represented by
the above-described formula include ethylene glycol monobutyl
ether, ethylene glycol monopropyl ether, diethylene glycol
monobutyl ether, diethylene glycol monohexyl ether, diethylene
glycol monopropyl ether, dipropylene glycol monopropyl ether,
dipropylene glycol monobutyl ether, propylene glycol monobutyl
ether, propylene glycol monopropyl ether, triethylene glycol
monobutyl ether and diethylene glycol monophenyl ether. Of these,
diethylene glycol monobutyl ether, diethylene glycol monohexyl
ether, propylene glycol monobutyl ether and triethylene glycol
monobutyl ether are preferred.
[0032] The ink for ink jet recording of the present invention
contains such a water-soluble organic compound in an amount of from
3.0 to 15.0 wt %, preferably from 3.0 to 10.0 wt %, based on the
entire weight of the ink. If the content is less than 3.0 wt %, the
permeation effect cannot be satisfactorily brought out, then drying
speed becomes lower. If the content is more than 15.0 wt %, there
arise troubles, for example, blotting is easily generated or the
water self-dispersible pigment is reduced in the dispersion
stability.
[0033] The water-soluble organic solvent for use in the present is
not particularly limited as far as it is used for preventing
evaporation of water in the ink for ink jet recording. Examples of
the water-soluble organic solvent which can be used include
polyhydric alcohols such as ethylene glycol, diethylene glycol,
propylene glycol, polyethylene glycol, triethylene glycol,
glycerin, trimethylolpropane, 1,2,6-hexanetriol, 1,5-pentanediol
and dipropylene glycol; saccharides such as glucose, fructose,
galactose, mannose and xylose; sulfur-containing solvents such as
thiodiethanol, 2-mercaptoethanol, thioglycerol, sulfolane and
dimethylsulfoxide; and nitrogen-containing solvents such as
2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone,
monoethanolamine, triethanolamine and diethanolamine. Of these,
ethylene glycol, diethylene glycol, propylene glycol, glycerin,
thiodiethanol, sulfolane, 2-pyrrolidone and N-methyl-2-pyrrolidone
are preferred. These solvents may be used either individually or in
combination of two or more thereof. The content of the
water-soluble organic solvent is preferably from about 1 to about
60 wt %, more preferably from about 3 to about 50 wt %, based on
the entire weight of the ink. If the content exceeds 60 wt %, the
viscosity of the ink increases and in turn the ejection stability
and ejection responsibility decrease, whereas if it is less than 1
wt %, the evaporation of water cannot be satisfactorily prevented
and clogging readily occurs in some cases.
[0034] The water for use in the present invention is not
particularly limited, however, pure water is preferred. The water
is preferably contained in an amount of from 35 to 95 wt % based on
the entire weight of the ink. If the content is less than 35 wt %,
the water self-dispersible pigment may be deteriorated in the
dispersion stability or the viscosity of the ink increases to lower
the ejection stability in some cases, whereas if it exceeds 95 wt
%, the water is liable to evaporate in a large amount at the distal
end of a nozzle and the nozzle may be clogged.
[0035] The ink for ink jet recording of the present invention may
contain an ejection stabilizer such as urea, thiourea, ethylene
urea, ethylene thiourea, methyl urea, dimethyl urea and methyl
thiourea, and these ejection stabilizers may be used individually
or in combination of two or more thereof. The content of the
ejection stabilizer is preferably from about 0.5 to about 15 wt %,
more preferably from 1 to about 10 wt %, based on the weight of the
ink.
[0036] Furthermore, the ink for ink jet recording of the present
invention may contain a surfactant and examples of the surfactant
which can be used include nonionic surfactants such as
polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether,
polyoxyethylene fatty acid ester, sorbitan fatty acid ester,
polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin
fatty acid ester, polyglycerin fatty acid ester, polyoxyethylene
sorbitol fatty acid ester, polyoxyethylene sterol, polyoxyethylene
polyoxypropylene ether, polyoxyethylene fatty acid amide,
polyoxyethylene polyoxypropylene block copolymer,
tetramethyldecynediol and tetramethyldecynediol ethylene oxide
adduct; anionic surfactants such as alkylbenzenesulfonate,
alkylphenylsulfonate, alkylnaphthalenesulfonate- , higher fatty
acid salt, sulfate of higher fatty acid ester, sulfonate of higher
fatty acid ester, sulfate of higher alcohol ether, sulfonate,
higher alkyl sulfosuccinate, formalin condensate of naphthalene
sulfonate, polystyrene-sulfonate, polyacrylate, polyoxyethylene
alkyl ether phosphate, alkyl ether carboxylate, alkylsulfate and
acrylic acid-acrylic acid ester copolymer; silicone-based
surfactants such as polysiloxane polyoxyethylene adduct;
fluorine-based surfactants such as perfluoroalkyl carboxylate,
perfluoroalkyl sulfonate and oxyethylene perfluoroalkyl ether; and
biosurfactants such as spiculisporic acid, rhamnolipid and
lysolecithin. These surfactants may be used individually or in
combination of two or more thereof.
[0037] Taking account of the dispersion stability of the pigment,
the surfactant preferably has an HLB of from 5 to 25. The amount of
the surfactant added is preferably from about 0.001 to about 1 wt
%, more preferably about 0.005 to about 0.5 wt %, based on the
entire weight of the ink. The surfactant contributes to the
improvement in the wiper cleaning property of the ink jet head.
[0038] The ink for ink jet recording of the present invention may
contain a pH adjusting agent and examples thereof include acids
such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid,
citric acid, oxalic acid, malonic acid, boric acid, phosphoric
acid, phosphorous acid and lactic acid, and bases such as sodium
hydroxide, potassium hydroxide, lithium hydroxide and ammonia.
Also, the ink for ink jet recording of the present invention may
contain a buffer such as phosphate, oxalate, amine salt or good's
buffer. The pH of the ink for ink jet recording of the present
invention is preferably, in view of the ink storage stability or
erosion of the head or cartridge part, from 4 to 12, more
preferably from 5 to 11.
[0039] The ink for ink jet recording of the present invention may
contain a solubilizing agent such as acetamide and betaine, a
physical property conditioner such as polyethyleneimine, a
polyamine, polyvinyl pyrrolidone, polyethylene glycol or cellulose
derivative, and a clathrate compound such as cyclodextrin,
polycyclodextrin, a large ring amine or a crown ether. Furthermore,
the ink for ink jet recording of the present invention may contain,
if desired, an antimold, an anticorrosion, a microbicide, an
antioxidant, a chelating agent, a dendrimer or a polymer
emulsion.
[0040] The ink for ink jet recording of the present invention is
characterized in that the drying time is less than 5 seconds at the
printing of a solid image having an image area ratio of 100% on a
plain paper. The "solid image having an image area ratio of 100%"
as used in the present invention means a solid image where the ink
amount is approximately from 1.2 to 2.0 mg/cm.sup.2 per the unit
area. The drying time of less than 5 seconds can be achieved by
adding a water-soluble organic compound having an S.P. value of 12
or less and a surface tension at 25.degree. C. of less than 40 mN/m
in an amount of from 3.0 to 15.0 wt % as described above.
[0041] The ink for ink jet recording of the present invention
preferably has a stationary flow viscosity of from 1.8 to 4.0 mPas.
If the stationary flow viscosity is less than 1.8 mPas, the ink
readily falls from the nozzle and at the same time, pigment
particles become free to move and readily agglomerate, whereas if
it exceeds 4.0 mPas, resistance against ejection force
increases.
[0042] The ink for ink jet recording of the present invention
preferably has a surface tension of form 20 to 40 mN/m. If the
surface tension is less than 20 mN/m, blotting and strike through
is generated, whereas if it exceeds 40 mN/m, drying time property
becomes worse.
[0043] The ink for ink jet recording of the present invention
preferably has an electric conductivity of from 0.03 to 0.4 S/m,
more preferably from 0.05 to 0.3 S/m. If the electric conductivity
is less than 0.03 S/m, insufficient dissociation proceeds on the
surface of the self-dispersible pigment and poor dispersibility
results, whereas if it exceeds 0.4 S/m, the electric double layer
formed around the pigment particle has a small thickness and due to
the small distance between particles, the pigment is deteriorated
in the dispersibility. Accordingly, it is preferred to reduce the
electrolyte other than the self-dispersible pigment as much as
possible.
[0044] Incidentally, if the Mg and Fe contents in the ink increase,
agglomeration of the pigment is accelerated and when the ink is
used in the recording system where the ink is ejected by the action
of heat energy, kogation on the heater is liable to increase.
Accordingly, the Mg and Fe contents each is preferably controlled
to be less than 5 ppm. Mg and Fe may be removed by the operation
such as water washing, filtration through reverse osmosis
membrane/ultrafilter or the like, separation by ion exchange resin,
or adsorption to activated carbon/zeolite or the like. These
operations may be used individually or in combination. Mg and Fe
dissolve out mainly from the pigment and accordingly, these may be
removed by an effective and appropriate method in respective stages
of pigment itself, pigment dispersion solution and ink.
[0045] The process for producing an ink for ink jet recording of
the present invention is described below.
[0046] For the purpose of preventing dissolving out of Mg and Fe,
the production process of an ink for ink jet recording of the
present invention preferably includes a step of dispersing the
pigment by an ultrasonic homogenizer or high-pressure homogenizer
without using a dispersion media. Furthermore, the production
process preferably includes a step of removing coarse particles by
centrifugal separation. As described above, if the ink contains a
large number of particles having a particle size of >0.5 .mu.m,
the dispersion becomes unstable or kogation on the heater
increases. When a step of removing coarse particles by centrifugal
separation is provided, the coarse particles can be efficiently
removed. At the time of centrifugal separation, coarse particles
can be more effectively removed as the pigment concentration is
lower.
[0047] Accordingly, the process for producing an ink for ink jet
recording of the present invention preferably comprises a step of
dispersing a water self-dispersible pigment in water by means of an
ultrasonic homogenizer or high-pressure homogenizer without using a
dispersion media and a step of mixing the pigment dispersed and
other materials such as water, a water-soluble organic solvent and
a water-soluble organic compound, and more preferably further
comprises a step of removing coarse particles by centrifugal
separation.
[0048] The ink jet recording method of the present invention is
described below.
[0049] The ink jet recording method of the present invention is
characterized in that the recording is performed on a recording
material by ejecting an ink for ink jet recording of the present
invention in response to a recording signal.
[0050] In a preferred embodiment, the ink is ejected by the action
of heat energy upon the ink, so that kogation on the heater can be
reduced. Furthermore, by applying a plurality of pulses and thereby
forming and ejecting one ink droplet, the drop amount is stabilized
and the ejection stability at the continuous ejection can be
increased. As the drop on printing is made smaller to elevate the
ink jet recording resolution, the effect of improving the image
quality and drying property becomes larger. In particular, the
amount of ink ejected per one drop is preferably 20 ng or less,
more preferably 15 ng or less. This phenomenon seems to occur
because the specific surface area of drops increases and therefore,
the effect on the surface is intensified.
[0051] Moreover, by mixing the ink for ink jet recording of the
present invention and a fixing agent on a recording material, a
high-resolution, high-density and highly fixed image can be
obtained. The fixing agent is a material used for preventing
permeation of a coloring material in the ink. Examples of the
fixing agent which can be used include a polyvalent metal salt, an
organic amine and a salt thereof, a quaternary ammonium salt, a
cationic polymer, a nonionic polymer and an anionic polymer. The
fixing agent in the form of an aqueous solution or the like may be
coated on a recording material before or after the ink recording or
simultaneously with the ink recording. For the coating of the
fixing agent, a method of ejecting the fixing agent from an orifice
in response to a signal and coating it on a recording material is
effective and efficient similarly to the ink.
[0052] (Mode of Operation)
[0053] As described in the foregoing, according to the present
invention, the ink for ink jet recording comprising water, a
water-soluble organic solvent and a water self-dispersible pigment,
contains a water-soluble organic compound having an S.P. value of
12 or less and a surface tension at 25.degree. C. of less than 40
mN/m in an amount of from 3.0 to 15.0 wt % based on the weight of
the ink. By virtue of this constitution, the ink for ink jet
recording having a drying time of less than 5 seconds at the
printing of a solid image having an image area ratio of 100% on a
plain paper can be obtained. The ink for ink jet recording of the
present invention is advantageous in that drying on a paper is
fast, the water resistance and rub resistance both are excellent,
the long-term storage stability is high, the print quality is good
and problems of clogging and the like are not caused.
[0054] The mechanism of these effects obtained by adding a water
self-dispersible pigment and a water-soluble organic compound
having an S.P. value of 12 or less and a surface tension at
25.degree. C. of less than 40 mN/m in combination is not fully
elucidated but it is presumed as follows. With respect to the
dispersion stability of the ink, although a pigment which is
insoluble in water is usually dispersed and prevented from
agglomeration and precipitation using the action of a dispersant
adsorbed to the pigment in the case of a normal pigment dispersed
ink, the pigment is dispersed by itself without using a dispersant
in the present invention where a water self-dispersible pigment is
used. When a large amount of penetrant is present in the ink and
the interaction between the penetrant and the dispersant is strong,
the dispersant adsorbed to the pigment is considered to gradually
dissociate from the pigment and thereby agglomeration and
precipitation of the pigment is caused. This problem is not
incurred in the case of a water self-dispersible pigment. With
respect to the drying property and print quality, it is considered
that the pigment has a large particle size as compared with a dye
and difficultly passes through voids in the recording material even
with the same penetrant, as a result, excess permeation is
prevented and blotting is reduced despite the fast drying. With
respect to the rub resistance, although the wettability to the
recording material is poor in the case of an ink having a high
surface tension, the surface tension of the ink is 40 mN/m or less
in the present invention and by virtue of this, it is considered
that the contact area between the ink and the recording material is
increased and the fixing property is improved. With respect to the
clogging, as compared with normal pigment dispersed ink, the ink of
the present invention is less subject to the adverse effect by the
interaction between the dispersant and the penetrant at the time of
the penetrant ratio increasing on the nozzle surface and this seems
to work advantageously.
[0055] The present invention is described in greater detail below
by referring to the Examples.
EXAMPLE 1
[0056] Microjet Black CW-1 (produced by Orient KK) was diluted with
water to have a carbon concentration of 10 wt % and then subjected
to centrifugal separation (7,000 r.p.m., 30 minutes) to obtain a
pigment dispersion solution (carbon concentration: 8.3 wt %).
1 Pigment dispersion solution 50 parts by weight obtained above
Glycerin (S.P. value: about 20) 15 parts by weight Diethylene
glycol monobutyl ether 5 parts by weight (S.P. value: about 10.5,
.gamma. (surface tension) = 34 mN/m) N,N-Bis(2-hydroxyethyl)-2- 0.5
parts by weight aminomethylethanesulfonic acid NaOH 0.1 part by
weight Pure water 29.4 parts by weight
[0057] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink.
EXAMPLE 2
[0058] Cab-o-jet-300 (produced by Cabot Co.) was subjected to
centrifugal separation (8,000 r.p.m., 40 minutes) to obtain a
pigment dispersion solution (carbon concentration: 14.4 wt %).
2 Pigment dispersion solution 35 parts by weight obtained above
Ethylene glycol 10 parts by weight (S.P. value: about 18) Propylene
glycol monobutyl ether 7 parts by weight (S.P. value: about 10.5,
.gamma. = 26 mN/m) Urea 5 parts by weight Pure water 43 parts by
weight
[0059] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink.
COMPARATIVE EXAMPLE 1
[0060] An ink was prepared in the same manner as in Example 1
except for omitting diethylene glycol monobutyl ether (S.P. value:
about 10.5, .gamma.=34 mN/m) and changing the amount of pure water
to 34.4 parts by weight. The glycerin has an S.P. value of 20 and
.gamma.=63 mN/m.
COMPARATIVE EXAMPLE 2
[0061] An ink was prepared in the same manner as in Example 2
except for changing the amount of propylene glycol monobutyl ether
(S.P. value: about 10.5, .gamma.=26 mN/m) to 0.5 parts by weight
and the amount of pure water to 50 parts by weight.
COMPARATIVE EXAMPLE 3
[0062]
3 Carbon black (Black Pearl L) 5 parts by weight Styrene-sodium
maleate copolymer 1 part by weight Glycerin (S.P. value: about 20)
15 parts by weight Diethylene glycol monobutyl ether 5 parts by
weight (S.P. value: about 10.5, .gamma. = 34 mN/m)
N,N-Bis(2-hydroxyethyl)-2- 0.5 parts by weight
aminomethylethanesulfonic acid NaOH 0.1 part by weight Pure water
73.4 parts by weight
[0063] A carbon black dispersion solution was prepared from carbon
black, styrene-sodium maleate copolymer and pure water, then
thoroughly mixed with other components shown above and filtered
under pressure to prepare an ink.
COMPARATIVE EXAMPLE 4
[0064]
4 Carbon black (Mitsubishi MA-100) 4 parts by weight Styrene-sodium
maleate copolymer 1 part by weight Glycerin 15 parts by weight
(S.P. value: about 20, .gamma. = 63 mN/m)
N,N-Bis(2-hydroxyethyl)-2- 0.5 parts by weight
aminomethylethanesulfonic acid NaOH 0.1 part by weight Pure water
79.4 parts by weight
[0065] A carbon black dispersion solution was prepared from carbon
black, styrene-sodium maleate copolymer and pure water, then
thoroughly mixed with other components shown above and filtered
under pressure to prepare an ink.
TEST EXAMPLE 1
[0066] Using the inks obtained in Examples 1 and 2 and Comparative
Examples 1 to 4, the following evaluations (1) to (11) were
performed.
[0067] (1) Surface Tension of Ink
[0068] The ink surface tension was measured in an environment of
23.degree. C. and 55% RH using a Wilhelmy's surface balance.
[0069] (2) Viscosity of Ink
[0070] The ink viscosity was measured in an environment of
23.degree. C. and 55% RH at a shear rate of 1,400 S.sup.-1.
[0071] (3) Electric Conductivity of Ink
[0072] The ink electric conductivity was measured in an environment
of 23.degree. C. and 55% RH using a conductivity meter (AOL-40,
manufactured by DKK).
[0073] (4) Number Average Dispersion Particle Size and Dispersion
Particle Size Distribution of Ink
[0074] The number average dispersion particle size and dispersion
particle size distribution of ink were measured at 23.degree. C.
using Microtrup UPA (manufactured by Leeds & Northrup).
[0075] (5) Number of Particles of >0.5 .mu.m Contained in
Ink
[0076] Particles having a particle size in excess of 0.5 .mu.m were
counted at 23.degree. C. using Accusizer 770A Optical Particle
Sizer (manufactured by Particle Sizing Systems) and the value
obtained was calculated in terms of a value per 1 dm.sup.3.
[0077] (6) Ink Drop Amount
[0078] Ink was ejected three times in an environment of 23.degree.
C. and 55% RH using a prototype head (400 dpi) at a frequency of 6
kHz and 1/4 tone (2035.times.128 pulse) and received in a small
piece ink absorber. The weight was determined and the amount of ink
ejected in one drop was calculated.
[0079] (7) Drying Time Test
[0080] A solid image of 10 mm.times.50 mm having an image area
ratio of 100% was printed on a representative plain paper FX-L
(produced by Fuji Xerox Co., Ltd.) in an environment of 23.degree.
C. and 55% RH using a thermal ink jet printer having a resolution
of 600 dpi manufactured as a prototype for evaluation. The time
period from the printing until the droplet was not visually
observed on the paper was determined.
[0081] (8) Image Quality Test
[0082] A 1 dot-line solid image was test printed on a
representative plain paper FX-L (produced by Fuji Xerox Co., Ltd.)
using a thermal ink jet printer having a resolution of 400 dpi
manufactured as a prototype for evaluation. The image quality was
evaluated by examining blotting of lines and uniformity of edges in
the solid image according to the following criteria.
[0083] a) Blotting of Lines
[0084] .smallcircle.: No blotting.
[0085] .DELTA.: Slightly blotted.
[0086] .times.: Blotted like barb in many portions.
[0087] b) Solid Uniformity
[0088] .smallcircle.: No disorder.
[0089] .DELTA.: Slightly disordered.
[0090] .times.: Indented and no smoothness.
[0091] (9) Rub Resistance Test
[0092] An image was printed using a thermal ink jet printer having
a resolution of 400 dpi manufactured as a prototype for evaluation.
One day after the printing, the image area was rubbed with a finger
and the degree of color falling and staining on the non-image area
were evaluated according to the following criteria:
[0093] .smallcircle.: No reduction in the image density and
completely no staining on the non-image area.
[0094] .DELTA.: Almost no reduction in the image density but the
non-image area was slightly stained.
[0095] .times.: Image density was reduced and staining on the
non-image area was conspicuous.
[0096] (10) Clogging Resistance Test
[0097] After stopping ejection in a thermal ink jet printer having
a resolution of 400 dpi manufactured as a prototype for evaluation,
the ink in an uncapped state was left standing in an environment of
23.degree. C. and 55% RH and then the ejection was restarted. How
long the ink was left standing until the image disorder occurred on
restarting of the ejection was determined. The evaluation was made
according to the following criteria:
[0098] .smallcircle.: 1 minute or more
[0099] .DELTA.: from 0.5 to 1 minute
[0100] .times.: less than 0.5 minute
[0101] (11) Ink Storage Stability Test
[0102] After storage at 60.degree. C. or -20.degree. C. for one
month, the ink was again filtered through a 1-.mu.m filter and then
used for printing in a thermal ink jet printer having a resolution
of 400 dpi. The evaluation was made according to the following
criteria:
[0103] .smallcircle.: No change in the filterability after storage
and also no change in the image density.
[0104] .DELTA.: The filtration rate was slightly reduced after
storage but no change in the image density.
[0105] .times.: After storage, the ink heavily caused filter
clogging and the image density was greatly reduced.
5 TABLE 1 Examples Comparative Examples 1 2 1 2 3 4 Surface Tension
of Ink 37 34 60 37 37 57 (mN/m) Viscosity of Ink (mPas) 3.0 2.8 2.3
2.3 3.4 2.5 Electric Conductivity of Ink 0.12 0.18 0.16 0.22 0.15
0.15 (S/m) Number Average Dispersion 27 41 25 40 37 48 Particle
Size of Ink (nm) Particle Size Distribution 1.8 2.2 1.8 2.0 2.7 2.3
Number of Particles of >0.5 0.4 2.4 0.5 2.0 12.5 2.5 .mu.m
(.times. 10.sup.10) Ink Drop Amount (ng) 48 52 51 49 46 49 Drying
Time Test (sec) 2 1 40 15 2 40 Image Quality Test a) .largecircle.
.largecircle. .largecircle. X .largecircle. .largecircle. Image
Quality Test b) .largecircle. .largecircle. .largecircle. X
.largecircle. .largecircle. Rub Resistance Test .largecircle.
.largecircle. X .DELTA. .largecircle. X Clogging Resistance Test
.largecircle. .largecircle. .largecircle. .largecircle. X
.largecircle. Ink Storage Stability Test .largecircle.
.largecircle. .largecircle. .largecircle. X .largecircle.
EXAMPLE 3
[0106] Microjet Black CW-1 (produced by Orient KK) was subjected to
centrifugal separation (8,000 r.p.m., 20 minutes) and filtered
under pressure through a 5-.mu.m filter and then through a 2-.mu.m
filter to obtain a pigment dispersion solution (carbon
concentration: 15.7 wt %).
6 Carbon black dispersion solution 25 parts by weight obtained
above Triethylene glycol monobutyl ether 4 parts by weight (S.P.
value: about 10, .gamma. = 34 mN/m) Propylene glycol 10 parts by
weight (S.P. value: about 16) SURFYNOL 440 (HLB: about 6) 0.3 parts
by weight Urea 3 parts by weight Pure water 57.7 parts by
weight
[0107] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 2.6 mPas, 29 mN/m, 0.09 s/m, 24 nm, 1.9 and
1.1.times.10.sub.10 particles, respectively. The drop amount was 51
ng, the drying time was 3 seconds and the test results on the image
quality, rub resistance, clogging resistance and ink storage
stability all were .smallcircle..
EXAMPLE 4
[0108] Cab-o-jet-300 (produced by Cabot Co.) was treated in an
ultrasonic homogenizer for 30 minutes, diluted with water to a
concentration of 10% and then subjected to centrifugal separation
(7,000 r.p.m., 20 minutes) to obtain a pigment dispersion solution
(carbon concentration: 8.8 wt %).
7 Carbon black dispersion solution 50 parts by weight obtained
above Diethylene glycol 10 parts by weight (S.P. value: about 15)
N-Methyl-2-pyrrolidone 5 parts by weight (S.P. value: about 11,
.gamma. = 48 mN/m) Dipropylene glycol monobutyl ether 5 parts by
weight (S.P. value: about 10, .gamma. = 29 mN/m) Pure water 30
parts by weight
[0109] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 2.5 mPas, 33 mN/m, 0.18 S/m, 25 nm, 2.1 and
1.6.times.10.sup.10 particles, respectively. The drop amount was 49
ng, the drying time was 1.5 seconds and the test results of the
image quality, rub resistance, clogging resistance and ink storage
stability all were .smallcircle..
EXAMPLE 5
[0110] Carbon black (Raven 5750) was subjected to surface oxidation
treatment with sodium hypochlorite, desalted, adjusted to have a pH
of 7.5 and dispersed in pure water as a solvent using an ultrasonic
homogenizer. After the dispersion, the solution was subjected to
centrifugal separation (7,000 r.p.m., 20 minutes) to obtain a
pigment dispersion solution (carbon concentration: 11 wt %).
8 Pigment dispersion solution 40 parts by weight obtained above
Triethylene glycol 10 parts by weight (S.P. value: about 14)
Propylene glycol monopropyl ether 8 parts by weight (S.P. value:
about 11, .gamma. = 26 mN/m) Polyoxyethylene alkyl ether 0.3 parts
by weight Pure water 41.7 parts by weight
[0111] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 2.5 mPas, 36 mN/m, 0.17 S/m, 59 nm, 2.1 and
2.8.times.10.sup.10 particles, respectively. The drop amount was 47
ng, the drying time was 2 seconds and the test results of the image
quality, rub resistance, clogging resistance and ink storage
stability all were .smallcircle..
EXAMPLE 6
[0112] Carbon black (Mitsubishi MA-100) was graft polymerized by
sodium styrene sulfonate, dispersed in pure water as a solvent
using an ultrasonic homogenizer, and then subjected to centrifugal
separation (8,000 r.p.m., 40 minutes) to obtain a pigment
dispersion solution (carbon concentration: 7.8 wt %).
9 Pigment dispersion solution 60 parts by weight obtained above
Thiodiethanol 20 parts by weight Polyoxyethylene polyoxypropylene
0.1 part by weight block copolymer Diethylene glycol monohexyl
ether 3 parts by weight (S.P. value: about 10, .gamma. = 29 mN/m)
Pure water 16.9 parts by weight
[0113] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 2.6 mPas, 33 mN/m, 0.15 S/m, 47 nm, 2.4 and
2.4.times.10.sup.10 particles, respectively. The drop amount was 53
ng, the drying time was 1 second and the test results of the image
quality, rub resistance, clogging resistance and ink storage
stability all were .smallcircle..
EXAMPLE 7
[0114] Carbon black (Special Bk 4A) was plasma treated, dispersed
in pure water as a solvent to have a carbon concentration of 20%
using a high-pressure homogenizer, and then subjected to
centrifugal separation (7,000 r.p.m., 30 minutes) to obtain a
pigment dispersion solution (carbon concentration: 15.6 wt %).
10 Pigment dispersion solution 5 parts by weight obtained above
Trimethylolpropane 15 parts by weight Glycerin (S.P. value: about
20) 5 parts by weight Propylene glycol monobutyl ether 5 parts by
weight (S.P. value: about 10.5, .gamma. = 26 mN/m) Polyoxyethylene
perfluoroalkyl 0.01 part by weight ether (HLB: about 13) Pure water
70 parts by weight
[0115] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 3.3 mPas, 23 mN/m, 0.14 S/m, 44 nm, 2.3 and
1.7.times.10.sup.10 particles, respectively. The drop amount was 44
ng, the drying time was 2 seconds and the test results of the image
quality, rub resistance, clogging resistance and ink storage
stability all were .smallcircle..
EXAMPLE 8
[0116]
11 Pigment dispersion solution 30 parts by weight used in Example 2
1,5-Pentanediol 10 parts by weight (S.P. value: about 12.5)
Dipropylene glycol monoethyl ether 8 parts by weight (S.P. value:
about 10.5, .gamma. = 28 mN/m) Isopropyl alcohol 3 parts by weight
Silicone polyoxyethylene adduct 0.1 part by weight (HLB: about 7)
Polyoxyethylene oleyl ether 0.3 parts by weight (HLB: about 12)
Pure water 48.6 parts by weight
[0117] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 3.0 mPas, 33 mN/m, 0.16 S/m, 40 nm, 2.4 and
1.3.times.10.sup.10 particles, respectively. The drop amount was 31
ng, the drying time was 4 seconds and the test results of the image
quality, rub resistance, clogging resistance and ink storage
stability all were .smallcircle.. With respect to the drop amount,
the amount of ink ejected was measured using a prototype head of
600 dpi under the same conditions as in Example 1.
EXAMPLE 9
[0118]
12 Pigment dispersion solution 50 parts by weight used in Example 1
Dipropylene glycol 15 parts by weight (S.P. value: about 13)
Diethylene glycol monobutyl ether 5 parts by weight (S.P. value:
about 10.5, .gamma. = 34 mN/m) Sodium benzoate 0.5 parts by weight
Styrene-acrylic acid ester-acrylic 1.0 part by weight acid emulsion
(average molecular weight: 12,000, acid value: about 20) Pure water
28.5 parts by weight
[0119] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 3.2 mPas, 36 mN/m, 0.22 S/m, 40 nm, 2.4 and
1.5.times.10.sup.10 particles, respectively. The drop amount was 31
ng, the drying time was 1.5 seconds and the test results of the
image quality, rub resistance, clogging resistance and ink storage
stability all were .smallcircle.. With respect to the drop amount,
the amount of ink ejected was measured using a prototype head of
600 dpi under the same conditions as in Example 1.
EXAMPLE 10
[0120]
13 Pigment dispersion solution 30 parts by weight used in Example 3
Glucose 10 parts by weight 1,5-Pentanediol 10 parts by weight (S.P.
value: about 12.5) Dipropylene glycol monopropyl ether 12 parts by
weight (S.P. value: about 10.5, .gamma. = 28 mN/m) SURFYNOL 104 0.1
part by weight N-(2-Acetamido)iminodiacetic acid 0.5 parts by
weight LiOH 0.1 part by weight Pure water 37.3 parts by weight
[0121] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 3.4 mPas, 30 mN/m, 0.22 S/m, 25 nm, 2.1 and
3.9.times.10.sup.10 particles, respectively. The drop amount was 45
ng, the drying time was 1 second and the test results of the image
quality, rub resistance and clogging resistance were .smallcircle..
The ink storage stability was .DELTA..
EXAMPLE 11
[0122] A plasma treated phthalocyanine pigment was dispersed in
water as a solvent to have a pigment concentration of 20% using a
high-pressure homogenizer, subjected to centrifugal separation
(7,000 r.p.m., 30 minutes), adsorbed to activated carbon and then
filtered through a 5-.mu.m filter to obtain a pigment dispersion
solution (phthalocyanine pigment concentration: 14.7%).
14 Pigment dispersion solution 25 parts by weight obtained above
Glycerin (S.P. value: about 20) 15 parts by weight Dipropylene
glycol monobutyl ether 5 parts by weight (S.P. value: about 10,
.gamma. = 29 mN/m) Polyoxyethylene polyoxypropylene 0.3 parts by
weight block copolymer (HLB: about 10) PROXEL GXL 0.03 parts by
weight Pure water 53.7 parts by weight
[0123] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 2-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 2.8 mPas, 32 mN/m, 0.22 S/m, 87 nm, 2.4 and
5.7.times.10.sup.10 particles, respectively. The drop amount was 46
ng, the drying time was 1.5 seconds and the test results of the
image quality, rub resistance and clogging resistance were
.smallcircle.. The ink storage stability was .DELTA..
EXAMPLE 12
[0124] An ink was prepared using the same composition in the same
manner as in Example 11 except for omitting centrifugal separation
and adsorption to activated carbon in Example 11. The viscosity of
the ink was 2.8 mPas, the surface tension was 32 mN/m, the electric
conductivity, number average dispersion particle size, particle
size distribution and number of particles having a particle size of
>0.5 .mu.m were 0.24 S/m, 110 nm, 3.2 and 9.0.times.10.sup.10
particles, respectively, and the Fe and Mg contents were 15 ppm and
10 ppm, respectively. The drop amount was 46 ng and the drying time
was 1.5 seconds. The test results of the image quality was
.smallcircle. and the rub resistance, ink storage stability and
clogging resistance were .DELTA..
COMPARATIVE EXAMPLE 5
[0125]
15 Pigment dispersion solution 50 parts by weight used in Example 1
Diethylene glycol 15 parts by weight Tetraethylene glycol
monomethyl ether 5 parts by weight (S.P. value: about 10.5, .gamma.
= 50 mN/m) Thiourea 5 parts by weight Pure water 25 parts by
weight
[0126] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1 .mu.m filter to prepare an
ink. The viscosity of the ink was 2.7 mPas, the surface tension was
47 mN/m, the electric conductivity, number average dispersion
particle size, particle size distribution and number of particles
having a particle size of >0.5 .mu.m were 0.14 S/m, 28 nm, 1.9
and 0.8.times.10.sup.10 particles, respectively. The drop amount
was 53 ng and the drying time was 30 seconds. The test results of
the image quality, clogging resistance and ink storage stability
were .smallcircle. and the rub resistance was .times..
COMPARATIVE EXAMPLE 6
[0127]
16 Pigment dispersion solution 35 parts by weight used in Example 2
Diethylene glycol 5 parts by weight Propylene glycol monobutyl
ether 20 parts by weight (S.P. value: about 10.5, .gamma. = 26
mN/m) Pure water 40 parts by weight
[0128] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 3.2 mPas, 33 mN/m, 0.16 S/m, 44 nm, 2.8 and
7.5.times.10.sup.10 particles, respectively. The drop amount was 48
ng and the drying time was 1 second. The test results of the rub
resistance and clogging resistance were .smallcircle. and the image
quality and ink storage stability were .times..
EXAMPLE 13
[0129]
17 Pigment dispersion solution 50 parts by weight used in Example 4
1,2,6-Hexanetriol 10 parts by weight (S.P. value: about 15)
Ethylene glycol monopropyl ether 10 parts by weight (S.P. value:
about 11, .gamma. = 32 mN/m) Oxyethylene oleyl ether 0.2 parts by
weight (HLB: about 10) Pure water 29.8 parts by weight
[0130] Respective components shown above were thoroughly mixed and
then filtered under pressure through a 1-.mu.m filter to prepare an
ink. The viscosity, surface tension, electric conductivity, number
average dispersion particle size, particle size distribution and
number of particles having a particle size of >0.5 .mu.m of the
ink were 2.5 mPas, 39 mN/m, 0.13 S/m, 20 nm, 2.1 and
1.2.times.10.sup.10 particles, respectively. The drop amount was 27
ng. With respect to the drop amount, the amount of ink ejected was
measured using a prototype head of 600 dpi under the same
conditions as in Example 1. The image quality, rub resistance,
clogging resistance, drying time and ink storage stability were
tested using a thermal ink jet printer having a resolution of 600
dpi manufactured as a prototype for evaluation where one droplet is
formed by applying a driving signal constituted of a main pulse, a
prepulse and a quiescent time between the prepulse and the main
pulse. The drying time was 4 seconds and the tests results of all
other items were .smallcircle..
EXAMPLE 14
[0131] An ink having the following composition was prepared.
[0132] Cyan Ink
18 Projet Fast Cyan 2 4 parts by weight (produced by ZENECA) Butyl
carbitol 5 parts by weight Thiodiethanol 15 parts by weight Pure
water 76 parts by weight
[0133] Respective components shown above were thoroughly mixed and
dissolved and filtered under pressure through a 0.45-.mu.m filter
to prepare an ink.
[0134] Magenta Ink
[0135] An ink was prepared using the same composition as above by
thoroughly mixing and dissolving respective components and
filtering under pressure the mixed solution through a 0.45-.mu.m
filter except for using Projet Fast Magenta 2 in place of Projet
Fast Cyan 2 (produced by ZENECA).
[0136] Yellow Ink
[0137] An ink was prepared using the same composition as above by
thoroughly mixing and dissolving respective components and
filtering under pressure the mixed solution through a 0.45-.mu.m
filter except for using Projet Fast Yellow 2 in place of Projet
Fast Cyan 2 (produced by ZENECA).
TEST EXAMPLE 2
[0138] (12) Overprinted Image Quality Test
[0139] Using the ink of Example 1 and the cyan, magenta and yellow
inks obtained in Example 14, the following evaluation was made.
[0140] A solid image pattern having black 1-dot lines and
respective colors adjacent thereto on a color background was test
printed on a representative plain paper FX-L (produced by Fuji
Xerox Co.) using a thermal ink jet printer having a resolution of
400 dpi manufactured as a prototype for evaluation. Blotting of
lines and uniformity of areas adjacent to the solid image were
examined and evaluated according to the following criteria.
[0141] a) Blotting of Lines
[0142] .smallcircle.: No blotting.
[0143] .DELTA.: Slightly blotted.
[0144] .times.: Blotted like barb in many portions.
[0145] b) Solid Uniformity
[0146] .smallcircle.: No disorder.
[0147] .DELTA.: Slightly disordered.
[0148] .times.: Indented and no smoothness.
[0149] The results of evaluations a) and b) were .smallcircle. in
all inks.
TEST EXAMPLE 3
[0150] Using the ink of Example 1 and a fixing agent having a
composition shown below, the following evaluation was made.
[0151] Fixing Agent A
19 Styrene-lithium maleate copolymer 5 parts by weight Ethylene
glycol 15 parts by weight Polyoxyethylene oleyl ether 0.2 parts by
weight Isopropyl alcohol 3 parts by weight Pure water 76.8 parts by
weight
[0152] Fixing Agent A was ejected on a representative plain paper
FX-L (produced by Fuji Xerox Co.) using a thermal ink jet printer
having a resolution of 400 dpi manufactured as a prototype for
evaluation and after 5 seconds, the ink of Example 1 was
overprinted. Thereafter, the image quality test in (9) above was
performed. The result of the image quality test was .smallcircle.
and the image density was higher than that in Example 1.
TEST EXAMPLE 4
[0153] Using the ink of Example 2 and a fixing agent having a
composition shown below, the following evaluation was made.
[0154] Fixing Agent B
20 Benzalkonium chloride 1 part by weight Polyallylamine
hydrochloride 5 parts by weight Glycerin 15 parts by weight Pure
water 79 parts by weight
[0155] An image quality test was performed in the same manner as in
Test Example 3. The result of the image quality test was
.smallcircle. and the image density was higher than that in Example
2.
TEST EXAMPLE 5
[0156] Using the ink of Example 1, the following evaluation was
made.
[0157] The amount of ink ejected per one drop and the drying time
were determined in the same manner as in (6) and (7) of Test
Example 1 except for using an ink jet printer of 800 dpi
manufactured as a prototype for evaluation. Furthermore, 8 point
letters were printed on a representative plain paper FX-L (produced
by Fuji Xerox Co.) using the same printer. The amount of ink
ejected per one drop was 13 ng, the drying time was 1 seconds and
the appearance quality of letters was higher than that obtained by
the printing in a printer used in (8) of Test Example 1.
[0158] The ink for ink jet recording of the present invention is
dried at a high rate on a plain paper, assures excellent properties
in the print quality, water resistance/rub resistance and long-term
storage stability, and does not cause clogging and the like.
* * * * *