U.S. patent application number 10/322216 was filed with the patent office on 2003-08-07 for ink composition and a method for ink jet recording.
Invention is credited to Kondo, Ai.
Application Number | 20030149130 10/322216 |
Document ID | / |
Family ID | 26625206 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030149130 |
Kind Code |
A1 |
Kondo, Ai |
August 7, 2003 |
Ink composition and a method for ink jet recording
Abstract
A white ink composition for ink jet recording characterized in
comprising at least a white pigment, a polymerizable compound, and
a polymerization initiator and having a viscosity of 10 to 500
Pa.multidot.s at 30.degree. C. A method for ink jet recording
comprising the steps of: heating an ink in an ink-jet head to be
not less than 40.degree. C. and jetting the ink onto an ink-jet
recording medium.
Inventors: |
Kondo, Ai; (Tokyo,
JP) |
Correspondence
Address: |
Cameron Kerrigan
Squire, Sanders & Dempsey L.L.P.
Suite 300
One Maritime Plaza
San Francisco
CA
94111
US
|
Family ID: |
26625206 |
Appl. No.: |
10/322216 |
Filed: |
December 17, 2002 |
Current U.S.
Class: |
523/160 ;
523/161 |
Current CPC
Class: |
C09D 11/30 20130101;
C09D 11/101 20130101 |
Class at
Publication: |
523/160 ;
523/161 |
International
Class: |
C03C 017/00; C09D
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2001 |
JP |
2001-389233 |
Dec 21, 2001 |
JP |
2001-389234 |
Claims
What is claimed is:
1. An ink for ink jet recording comprising at least a pigment, a
polymerizable compound, and a polymerization initiator, wherein the
ink has a viscosity of 10 to 500 Pa.multidot.s at 30.degree. C. and
a viscosity of 7 to 30 mPa.multidot.s when heated to at least
40.degree. C.
2. The ink for ink jet recording of claim 1, wherein the ink is a
white ink and the pigment comprises a white pigment.
3. The ink for ink jet recording of claim 2, wherein the content
ratio of the white pigment is from 1 to 50 percent by weight.
4. The ink for ink jet recording of claim 2, wherein the pigment
comprises a white inorganic pigment, a white organic pigment or
fine hollow polymer particles.
5. The ink for ink jet recording of claim 4, wherein the white
inorganic pigment is a titanium oxide.
6. The ink for ink jet recording of claim 2, wherein the average
particle diameter of the pigment is from 0.1 to 1 .mu.m.
7. The ink for ink jet recording of claim 2, comprising solvent not
more than 7 weight % based on the ink.
8. The ink for ink jet recording of claim 2, comprising the surface
tension of 27 to 50 mN/m.
9. The ink for ink jet recording of claim 2, comprising the surface
tension of 30 to 50 mN/m.
10. The ink for ink jet recording of claim 2, wherein the viscosity
of the ink at 30.degree. C. is 30 to 300 mPa.multidot.s.
11. The ink of claim 2, wherein the ink has a viscosity of 7 to 30
mPa.multidot.s at 70.degree. C.
12. The ink for ink jet recording of claim 3, wherein the white
pigment is a titanium oxide, the viscosity of the ink at 30.degree.
C. is 30 to 300 mPa.multidot.s, and the ink includes a
polymerization inhibitor.
13. An image forming method comprising the steps of: heating an ink
in an ink-jet head so as to be not less than 40.degree. C., and
jetting the ink through an ink-jet head nozzle, wherein the ink has
a viscosity of 10 to 500 mPa.multidot.s at 30.degree. C., and has a
viscosity of 7 to 30 mPa.multidot.s after heating to be not less
than 40.degree. C.
14. The method of claim 13, wherein when recording is carried out
on a recording medium under performing a tone reproduction method
with a white ink and a colored ink, the transmission density of a
white ink layer on the recording medium is at least 0.15 and the L
value thereof is at least 65.
15. The method of claim 14, wherein said tone reproduction method
is an error diffusion method.
16. The method of claim 14, wherein said tone reproduction method
is a dither method.
17. The method of claim 14, wherein said reproduction method are
performed with a plurality of colored inks having the same color at
different densities.
18. The method of claim 14, wherein said tone reproduction method
are performed with a dot diameter which is varied at a plurality of
levels.
19. The method of claim 14, wherein the recording medium is
transparent.
20. A method for producing a material by ink jet apparatus
comprising the step of: jetting an ink onto an ink-jet recording
medium, wherein the ink comprises a viscosity of 10 to 500
Pa.multidot.s at 30.degree. C., and a viscosity of 7 to 30
mPa.multidot.s at a temperature which is same or vicinity of a
temperature of an ink jet head nozzle when jetting.
21. The method for ink jet recording of claim 20, wherein the ink
comprises the viscosity from 7 to 30 mPa.multidot.s at the
temperature of the ink jet head nozzle .+-.2.degree. C. when
jetting.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an ink for ink jet
recording and an ink jet recording method.
[0002] By employing the ink jet recording system, it is possible to
easily and conveniently produce images at low cost. Further, along
with recent improvement in image quality, it has received attention
as a technique which enables high image quality recording which is
sufficiently applicable to various printing fields.
[0003] However, based on the printing system, ink compositions for
ink jet recording are commonly comprised of low viscosity ink
compositions comprising water based solvents or non-water based
solvents as a major component. Therefore, required as recording
media are those which are ink absorptive. In addition, in order to
achieve high image quality, special paper is required.
[0004] On the other hand, proposed as ink compositions capable of
being printed onto non-ink absorptive recording media such as film
and metal, based on adhesion, are, for example, an ink composition
described in Japanese Patent Application Open to Public Inspection
(JP-A) No. 3-216379 which is comprised of components which are
polymerized by ultraviolet radiation exposure, and an ultraviolet
radiation curable ink composition comprising colorants, ultraviolet
radiation curing agents, and photopolymerization initiators
described in U.S. Pat. No. 5,623,001.
[0005] Further, almost all of the inks for ink jet recording are
commonly highly transparent inks which are mainly employed for
printing onto white based recording media. Therefore, when printed
onto, for example, transparent base materials employed in soft
packaging and low lightness base materials, neither the desired
contrast nor bright color is obtained, whereby it becomes difficult
to present images with desired visibility.
[0006] In the case of poor visibility, methods are known in which
visibility is achieved employing white ink with high covering
properties. Proposed as white ink compositions are, for example, a
white ink composition described in JP-A No. 2-45663, which is
comprised of white inorganic pigments, organic solvents, and
binding resins and has a viscosity of 1 to 15 cp from 5 to
40.degree. C., and an ink composition for photocurable ink jet
recording, described in JP-A No. 2000-336395, which is comprised of
titanium oxide, polymerizable compounds, photopolymerization
initiators, and water based solvents.
[0007] However, when these inks are applied onto non-ink absorptive
recording media, ejected ink droplets spread due to their low
viscosity at room temperature. Further, since these inks are
comprised of solvents, thermal drying is required to remove the
residue, whereby they are not suitable for printing onto thermally
shrinkable base materials.
[0008] In ink jet recording, in order to achieve high resolution as
well as high image quality, it is preferable to obtain
multi-density levels. Known as such means are a method in which a
plurality of inks of the same color at different densities is
employed in combination and by modulating dot diameter, recording
dots themselves are multi-valued and a method in which binary image
data are subjected to halftone processing, employing an error
diffusion method or a dither method so that the visible effect is
as if there is a difference in density.
[0009] Further, almost all inks for ink jet recording are commonly
high transparent inks which are mainly employed for printing onto
white based recording media. Therefore, when printed onto, for
example, transparent base materials employed in soft packaging and
low lightness base materials, bright color formation is not
obtained due to the absence of contrast. Ink visibility in the low
density area is especially, degraded, whereby it becomes difficult
to achieve high quality images.
[0010] The foregoing are desired to be resolved.
SUMMARY OF THE INVENTION
[0011] This invention relates to ink for ink jet recording and ink
jet recording method.
[0012] One embodiment of the present invention includes an ink for
ink jet recording which comprises at least a pigment, a
polymerizable compound, and a polymerization initiator and having a
viscosity of 10 to 500 Pa.multidot.s at 30.degree. C.
[0013] One other embodiment includes an ink jet recording method
which has a tone reproduction means, wherein when recording is
carried out on a recording medium employing colored ink and white
ink, the transmission density of the white ink layer is at least
0.15 and the L value thereof is at least 65.
[0014] Another one of embodiments of the present invention includes
an ink jet recording method which comprises the steps of heating an
ink in an ink-jet head to be not less than 40.degree. C. and
jetting the ink onto an ink-jet recording medium.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The ink for ink jet recording, especially white ink
(hereinafter occasionally referred simply to as white ink
composition) is characterized in that the viscosity at 30.degree.
C. is from 10 to 500 mPa.multidot.s, while the viscosity is
preferably from 30 to 300 mPa.multidot.s.
[0016] Further, it is preferable that the composition ratio is
determined so that when heated to at least 40.degree. C., the
resultant viscosity is from 7 to 30 Pa.multidot.s.
[0017] The viscosity of the ink can be controlled by any known
methods. For example, when the ink includes solvent, the viscosity
of the ink can be controlled by adjusting the proportion of the
solvent in the ink. When the ink of the present invention includes
no solvent, the viscosity of the ink can be controlled by selecting
the polymerizable compounds in the ink. Specifically, the viscosity
can be raised by increasing the proportion of the polymerizable
compound comprised of monomers having poly functional group in the
ink.
[0018] By increasing the viscosity at room temperature, it is
possible to minimize the penetration of ink on absorptive recording
media. Further, it is possible to decrease monomers which have not
been cured as well as to decrease unpleasant odors. Still further,
it is possible to minimize bleeding of ejected ink droplets,
whereby image quality is improved. Yet further, even though the
surface tension of base materials differs, similar image quality is
obtained due to the formation of nearly identical dots.
[0019] When the viscosity at 30.degree. C. of said ink composition
is in the range of 10 to 500 mPa.multidot.s, sufficient bleeding
resistant effects are obtained, and the possibility of occurrence
of problems of ink supply is reduced.
[0020] The viscosity of the ink composition by heating not less
than 40.degree. C. is preferably adjusted to the range of 7 to 30
mP.multidot.s in order to obtain stable ejection properties. This
includes the ink having the viscosity of 7 to 30 mP.multidot.s at
any one of the points of the temperature not less than 40.degree.
C.
[0021] It is preferable that the ink has surface tension of 27 to
50 mN/m, more preferably 30 to 50 mN/m.
[0022] Further, hereinafter the white ink composition is explained.
The white ink composition for ink jet recording is comprised of at
least a white pigment, a polymerizable compound, and a
photopolymerization initiator. Each of the materials of this
constitution will now be described.
[0023] (White Pigments)
[0024] Employed as white pigments, which are used in the white ink
composition, may be those which are capable of rendering said ink
composition white. Any of several white pigments, which are
commonly used in this field, may be employed. Employed as such
white pigments may be, for example, white inorganic pigments, white
organic pigments, and fine white hollow polymer particles.
[0025] Listed as white inorganic pigments are sulfates of alkaline
earth metals such as barium sulfate, carbonates of alkaline earth
metals such as calcium carbonate, silica such as fine silicic acid
powder, synthetic silicates, calcium silicate, alumina, alumina
hydrates, titanium oxide, zinc oxide, talc, and clay. Specifically,
titanium oxide is known as a white pigment which exhibits desired
covering properties, coloring (tinting) properties, and desired
diameter of dispersed particles.
[0026] Listed as white organic pigments are organic compound salts
disclosed in JP-A No. 11-129613, and alkylenebismelamine
derivatives disclosed in JP-A Nos. 11-140365 and 2001-234093.
Listed as specific commercially available products of the aforesaid
white pigments are Shigenox OWP, Shigenox OWPL, Shigenox FWP,
Shigenox FWG, Shigenox UL, and Shigenox U (all are commercial
product names, by Hakkoru Chemical Co.).
[0027] Listed as fine white hollow polymer particles are fine
thermoplastic particles comprised substantially of an organic
polymer, which are disclosed in U.S. Pat. No. 4,089,800.
[0028] In the present invention, white pigments may be employed
individually or in combination.
[0029] Pigments may be dispersed employing a ball mill, a sand
mill, an attritor, a roller mill, an agitator, a Henschel mixer, a
colloid mill, an ultrasonic homogenizer, a pearl mill, a wet type
jet mill, and a paint shaker. Further, it is possible to add
dispersing agents during dispersion of said pigments.
[0030] Preferably employed as dispersing agents are polymer
dispersing agents. Listed as said polymer dispersing agents are
Solsperse Series of Zeneca Corp. Further, it is possible to use
synergists corresponding to each type of pigments as a dispersing
aid. It is preferable that these dispersing agents and dispersing
aids are added in an amount of 1 to 50 parts by weight with respect
to 100 parts by weight of the pigment. Dispersion is carried out
employing solvents or polymerizable compounds as a dispersion
medium. However, it is preferable that the amount of solvent in the
white ink composition is not more than 7 weight %, preferably
substantially no solvent. It is more preferable that the white ink
composition comprises no solvent so as to be subjected to reaction
and curing immediately after ink adhesion. When solvents remain in
cured images, solvent resistance degrades and problems with VOC
(Volatile Organic Compound) of the residual solvents occur. As a
result, from the viewpoint of dispersion adaptability, preferably
selected as dispersion media are not solvents but are polymerizable
compounds, of them especially monomers having the lowest
viscosity.
[0031] When pigments are dispersed, it is preferable that the
average particle diameter is adjusted to the range of 0.1 to 1
.mu.m. Pigments, dispersing agents, and dispersing media are
selected, and dispersion conditions as well as filtration
conditions are set so that the maximum particle diameter ranges
from 0.3 to 10 .mu.m, and preferably from 0.3 to 3 .mu.m. By
achieving said particle diameter management, it is possible to
minimize head nozzle clogging, as well as to maintain the storage
stability of ink, ink covering properties, and curing
sensitivity.
[0032] The average particle diameter in the present invention was
determined as follows. A commercially available measurement
apparatus (High Performance Particle Sizer, produced by Malvern
Instruments Ltd.) was used which utilizes the dynamic optical
scattering method as a measurement principle. Dispersed articles
were irradiated with a laser beam and the backward scattered light,
which was the reflected laser beam, was detected and was subjected
to cumulant analysis so as to determine the average particle
diameter. Further, it is preferable that the particle diameter is
as uniform as possible and the dispersion coefficient (being
standard deviation/average particle diameter) is at most 0.5.
[0033] The content ratio of white pigments in the white ink
composition is commonly from 1 to 50 percent by weight with respect
to the total white ink composition, and is preferably from 2 to 30
percent by weight. When the content ratio is in the ratio described
above, desired covering properties and ejection properties from ink
jet are obtainable and the possibility of clogging is reduced.
[0034] (Polymerizable Compounds and Photopolymerization
Initiators)
[0035] Polymerizable Compounds and Photopolymerization
Initiators
[0036] Listed as polymerizable compounds usable in the present
invention may be radically polymerizable compounds as well as
cationic polymerization based photocurable resins.
[0037] As for the radically polymerizable compounds, they are
disclosed for example, such as JP-A No. 7-159983, Japanese Patent
Publication No. 7-31399, JP-A Nos. 8-224982 and 10-863, and
Japanese Patent Application No. 10-231444 (U.S. Pat. No.
5,784,491), and cationic polymerization based photocurable resins
are disclosed, for example, in JP-A Nos. 6-43633 corresponding to
U.S. Pat. No. 5,527,659 and 8-324137.
[0038] Radically polymerizable compounds are compounds having a
radically polymerizable ethylenically unsaturated bond. Any
compounds may be used which have at least one radically
polymerizable ethylenically unsaturated bond in the molecule, and
include those having chemical structures such as monomers,
oligomers, and polymers. Radically polymerizable compounds may be
employed individually or in combination of at least two types at an
optional ratio to enhance targeted characteristics.
[0039] Listed as examples of compounds having a radically
polymerizable ethylenically unsaturated bond are unsaturated
carboxylic acids such as acrylic acid, methacrylic acid, itaconic
acid, crotonic acid, isocrotonic acid, and maleic acid, as well as
salts and esters thereof; urethane, amides and anhydrides thereof,
acrylonitrile, styrene, as well as various radically polymerizable
compounds such as unsaturated polyesters, unsaturated polyethers,
unsaturated polyamides and unsaturated polyurethanes. Listed as
specific examples are acrylic acid derivatives such as 2-ethylhexyl
acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol
acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl
acrylate, bis(4-acryloxypolyethoxyphenyl)propane, neopentyl glycol
diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate,
diethylene glycol diacrylate, triethylene glycol diacrylate,
tetraethylene glycol diacrylate, polyethylene glycol diacrylate,
polypropylene glycol diacrylate, pentaerythritol triacrylate,
pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate,
trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate,
oligoester acrylate, N-methylol acrylamide, diacetone acrylamide
and epoxy acrylate; methacrylic acid derivatives such as methyl
methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate,
lauryl methacrylate, allyl methacrylate, glycidyl methacrylate,
benzyl methacrylate, dimethyl aminomethyl methacrylate,
1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate,
triethylene glycol dimethacrylate, polyethylene glycol
dimethacrylate, polypropylene glycol dimethacrylate,
trimethylolethane dimethacrylate, trimethylolpropane
dimethacrylate, and 2,2-bis(4-methacryloxypolyethoxyphenyl)propane;
as well as derivatives of allyl compounds, such as allyl glycidyl
ether, diallyl phthalate and triallyl trimellitate. Further,
specifically employed are radically polymerizable or crosslinking
monomers, oligomers and polymers, which are commercially available,
or known in the art, described in "Kakyozai Handbook (Handbook of
Crosslinking Agents)", edited by Shinzo Yamashita (1981, Taisei
Sha.), "UV.EB Kohka Handbook (Genryo Hen)(UV.EB Curing Handbook
(Raw Materials Part)", edited by Kiyoshi Kato (1985, Kohbunshi
Kankoh Kai), "UV.EB Kohka Gijutsu no Ohyoh to Shijoh (Application
and Market of UV.EB Curing Technology)", edited by Radotech Kenkyu
Kai, page 79 (1989, CMC), and "Eiichiroh Takiyama, "Polyester Jushi
Handbook (Handbook of Polyester Resins)" (1988, Nikkan Kogyo
Shimbun Co.).
[0040] The addition amount of the aforesaid radically polymerizable
compounds is preferably from 1 to 97 percent by weight, and is more
preferably from 30 to 95 percent by weight.
[0041] Listed as cationically polymerizable photocurable resins may
be UV curable prepolymers of such a type (mainly an epoxy type)
which results in polymerization via cationic polymerization, and
prepolymers in which the monomers have at least two epoxy groups in
one molecule. Listed as such prepolymers may be, for example,
alicyclic polyepoxides, polyglycidyl esters of polybasic acids,
polyglycidyl ethers of polyhydric alcohols, polyglycidyl ethers of
polyoxyalkylene glycol, polyglycidyl ethers of aromatic polyols,
hydrogenated compounds of polyglycidyl ethers of aromatic polyols,
and polyoxylated butadienes. These prepolymers may be employed
individually or in combination of at least two types.
[0042] Other than those above, listed as cationically polymerizable
compounds incorporated in cationic polymerization based
photocurable resins may be, for example, (1) styrene derivatives,
(2) vinylnaphthalene derivatives, (3) vinyl ethers, and (4) N-vinyl
compounds.
[0043] (1) Styrene Derivatives
[0044] For example, styrene, p-methylstyrene, p-methoxystyrene,
.beta.-methylstyrene, p-methyl-.beta.-methylstyrene,
.alpha.-methylstyrene, and
p-methoxystyrene-.beta.-methylstyrene
[0045] (2) Vinylnaphthalene Derivatives
[0046] For example, 2-vinylnaphthalene,
.alpha.-methyl-2-vinylnaphthalene,
.beta.-methyl-2-vinylnaphthalene, 4-methyl-2-vinylnaphthalene, and
4-methoxy-2-vinylnaphthalene
[0047] (3) Vinyl Ethers
[0048] For example, isobutyl vinyl ether, ethyl vinyl ether, phenyl
vinyl ether, p-methylphenyl vinyl ether, p-methoxyphenyl vinyl
ether, .alpha.-methylphenyl vinyl ether, .beta.-methylisobutyl
vinyl ether, and .beta.-chloroisobutyl vinyl ether
[0049] (4) N-vinyl Compounds
[0050] For example, N-vinylcarbazole, N-vinylpyrrolidone,
N-vinylindole, N-vinylpyrrole, N-vinylphenothiazine,
N-vinylacetoanilide, N-vinylethylacetoamide, N-vinylsuccinimide,
N-vinylphthalimide, N-vinylcaprolactam, and n-vinylimidazole
[0051] The content ratio of aforesaid cationic polymerization based
photocurable resins in the cationically polymerizable compositions
is preferably from 1 to 97 percent by weight, and is more
preferably from 30 to 97 percent.
[0052] Listed as radical polymerization initiators are, for
example, triazine derivatives described in Japanese Patent
Publication Nos. 59-1281, and 61-9621 and JP-A No. 61-60104;
organic peroxides described in JP-A Nos. 59-1504 and 61-243807;
diazonium compounds described Japanese Patent Publication Nos.
43-23684, 44-6413, and 47-1604, and U.S. Pat. No. 3,567,453;
organic azides described in U.S. Pat. Nos. 2,848,328, 2,852,379,
and 2,940,853; ortho-quinone diazides described in Japanese Patent
Publication Nos. 36-22062, 37-13109, 38-18015, and 45-9610; various
onium compounds described in Japanese Patent Publication No.
55-39162, JP-A No. 59-14023, and in "Macromolecules", Volume 10,
page 1307 (1977); azo compounds described in JP-A No. 59-142205;
metal allene complexes described in JP-A No. 1-54440, European
Patent Nos. 109,851 (U.S. Pat. Nos. 5,089,536, 5,191,101,
5,385,954), and 126,712 (U.S. Pat. No. 5,073,476), and in Journal
of Imaging Science, Volume 30, page 174 (1986); (oxo)sulfonium
organic boron complexes described in JP-A Nos. 5-213861, and
5-255347; titanocenes described in JP-A No. 61-151197; transition
metal complexes, containing transition metals such as ruthenium,
described in "Coordination Chemistry Review"Volume 85, pages 85
through 277 (1988) and JP-A No. 2-182701 (U.S. Pat. No. 4,954,414);
2,4,5-triarylimidazole dimer described in JP-A No. 3-209477 (U.S.
Pat. No. 5,532,373); and organic halogen compounds such as carbon
tetrabromide described in JP-A No. 59-107344. These polymerization
initiators are preferably contained in the range of 0.01 to 10
parts by weight based on 100 parts of the compound having a
radically polymerizable ethylenic unsaturated bond.
[0053] Employed as radical polymerization initiators employed in
the present invention may be conventional initiators, known in the
art, such as aryl alkyl ketones, oxime ketones, acylphosphine
oxides, acyl phosphonates, thiobenzoic acid S-phenyl, titanocene,
aromatic ketones, thioxanthone, derivatives of benzyl and quinone,
or ketocoumarin. Of these, since acylphosphine oxides and acyl
phosphonates exhibit high sensitivity and result in a decrease in
absorption due to photodecomposition of the initiators, they are
particularly effective for internal curing of ink images having a
thickness of 5 to 15 .mu.m per color as is seen in an ink jet
system.
[0054] Specifically preferred are
bis(2,4,6-trimethylbenzoyl)-phenylphosph- ine oxide and
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine
oxide.
[0055] When selection is made, taking into account high
sensitivity, safety, and minimized unpleasant odor, preferably
selected and employed are 1-hydroxy-cyclohexyl phenyl ketone,
2-methyl-1[4-(methylthiophenyl)-2- -morpholinopropane-1-one,
2-hydroxy-2-methyl-1-phenyl-propane-1-one, and
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1.
[0056] When initiators are combined taking into account the
minimization of polymerization hindrance due to oxygen and
sensitivity, a combination of
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 and
1-hydroxy-cyclohexyl-phenyl-ketone, a combination of
1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone, a combination
of 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropane-1-one and
diethylthioxanthone or isopropylthioxanthone, and a combination of
benzophenone and an acrylic acid derivative having a tertiary amino
group are effectively employed. Further, the addition of tertiary
amines is effective.
[0057] The added amount of initiators is preferably from 1 to 10
percent by weight with respect to the total weight of ink, and is
more preferably from 1 to 6 percent by weight. In the present
invention, it is preferable that two-stage irradiation is
preferably employed while varying either the wavelength or the
intensity. With regard to initiators, it is preferable that they
are employed in combination of at least two types.
[0058] Further, initiators are detailed in "UV.EB Kohka Gijutsu no
Ohyoh to Shijoh (Application and Market of UV.EB Curing
Technology)", (CMC Shuppan, compiled under the supervision of
Yoneho Tabata/edited by Radotech Kenkyu Kai,).
[0059] Listed as polymerization initiators employed in the cationic
polymerization system of the present invention are photo-acid
generators.
[0060] Employed as the photo-acid generating agents are compounds
which are utilized in chemical amplification type photoresists as
well as photo-cationic polymerization (refer to pages 187 through
192 of "Imaging yoh Yuhki Zairyo (Organic Materials for Imaging)",
edited by Yuhki Electronics Zairyo Kenkyukai, Bunshin Shuppan,
1993).
[0061] First listed may be (C.sub.6F.sub.5).sub.4.sup.-,
PF.sub.6.sup.-, SbF.sub.6.sup.-, and CF.sub.3SO.sub.3.sup.-salts of
aromatic onium compounds such as diazonium, ammonium, iodonium,
sulfonium, and phosphonium.
[0062] Specific examples of onium compounds usable in the present
invention are listed below. 1
[0063] Secondly, it is possible to list sulfonated compounds which
generate sulfonic acid. Specific compounds are exemplified below.
2
[0064] Thirdly, it is possible to employ halides which
photo-generate hydrogen halides. The specific compounds are
exemplified below. 3
[0065] Fourthly, it is possible to list iron arene complexes. 4
[0066] Preferably employed as initiators of cationic polymerization
based radiation curable resins may be aromatic onium salts.
Further, listed as said aromatic onium salts may be salts of
elements of group Va in the Periodic Table such as phosphonium
salts (for example, hexafluorophosphoric acid
triphenylphenacylphosphnium), and salts of elements of group VIa
such as sulphonium salts (for example, tetrafluoroboric acid
triphenylsulfonium, hexafluorophosphoric acid triphenylsulfonium,
hexafluorophosphoric acid tris(4-thiomethoxyphenyl), and sulfonium
and hexafluoroantimonic acid triphenylsulfonium), and salts of
elements of group VIIa such as iodonium salts (for example,
diphenyliodonium chloride).
[0067] The use of such aromatic onium salts as the cationic
polymerization initiator in polymerization of epoxy compounds is
described in U.S. Pat. Nos. 4,058,401, 4,069,055, 4,101,513, and
4,161,478.
[0068] Listed as preferable cationic polymerization initiators are
sulfonium salts of elements of group VIa. Of these, from the
viewpoint of UV curability and storage stability of UV curable
compositions, hexafluoroantimonic acid triarylsulfonium is
preferred. Further, it is possible to optionally employ
photopolymerization initiators, known in the art, which are
described on pages 39 through 56 of "Photopolymer Handbook" (edited
by Photopolymer Konwa Kai, published by Kogyo Chosa Kai, 1989), and
compounds described in JP-A Nos. 64-13142 and 2-4804.
[0069] Preferably employed as polymerizable compounds are acryl or
methacryl based monomers or prepolymers, epoxy based monomers or
prepolymers, and urethane based monomers or prepolymers. More
preferably employed compounds are the following:
[0070] 2-ethylhexyl-diglycol acrylate, 2-hydroxy-3-phenoxypropyl
acrylate, 2-hydroxybutyl acrylate, hydroxypivalic acid neopentyl
glycol diacrylate, 2-acryloyoxyethylphthalic acid,
methoxy-polyethylene glycol acrylate, tetramethylolmethane
triacrylate, 2-acryloyoxyethyl-2-hydroxyethylphthali- c acid,
dimethyloltricyclodecane diacrylate, ethoxylated phenyl acrylate,
2-acryloyoxyethylsuccinic acid, nonylphenol EO addition product
acrylate, modified glycerin triacrylate, bisphenol A
diglycidylether acrylic acid addition products, modified bisphenol
A diacrylate, phenoxy-polyethylene glycol acrylate,
2-acryloyloxyethylhexahydrophthalic acid, bisphenol A PO addition
product diacrylate, bisphenol A EO addition product diacrylate,
dipentaerythritol hexaacrylate, pentaerythritol triacrylate
tolylenediisocyanate urethane polymers, lactone modified flexible
acrylate, butoxyethyl acrylate, propylene glycoldiglycidyl ether
acrylic acid addition products, pentaerithritol triacrylate
hexamethylene diisocyanate urethane prepolymers, 2-hydroxyethyl
acrylate, methoxydipropylene glycol acrylate, ditrimethylolpropane
tetraacrylate, pentaerithritol triacrylate hexamethylene
diisocyanate urethane polymers, stearyl acrylate, isoamyl acrylate,
isomyristyl acrylate, and isostearyl acrylate.
[0071] Compared to polymerizable compounds employed in conventional
UV curable ink, these acrylates result in less skin stimulus as
well as less eruption on the skin, and make it possible to decrease
viscosity to a relatively low level. As a result, it is possible to
achieve stable ink ejection. In addition, these acrylates result in
desired polymerization sensitivity as well as excellent adhesion to
recording media. The content ratio of the aforesaid compounds is
commonly from 20 to 95 percent by weight of the ink, is preferably
from 50 to 95 percent, and is more preferably from 70 to 95
percent.
[0072] Monomers listed as the aforesaid polymerizable compounds
result in minimal eruption on the skin, even though their molecular
weight is low. In addition, said monomers results in high
reactivity as well as low viscosity, and thereby tight adhesion
onto recording media is obtained.
[0073] In order to increase sensitivity, to minimize bleeding, and
to improve adhesion properties, it is preferable that the aforesaid
monoacrylates are employed in combination with polyfunctional
acrylate monomers with a molecular weight of at least 400, or
preferably at least 500, or polyfunctional acrylate oligomers.
Further, it is preferable that any of the monofunctional,
bifunctional, trifunctional, and polyfunctional monomers are
employed together. By so doing, while maintaining safety, it is
possible to further increase sensitivity, to further minimize
bleeding, and to further improve adhesion properties. Particularly
preferred oligomers include epoxyacrylate oligomers as well as
urethane acrylate oligomers. It is preferable to use the
above-described monoacrylate in combination with multifunctional
acrylate monomer or multifunctional acrylate oligomer. It is
further preferable to use monofunctional, difunctional and three or
more functional acrylate monomers in the same time.
[0074] When flexible media such as PET film and PP film are
employed for recording, monoacrylates selected from the aforesaid
group of compounds are preferably employed in combination with
polyfunctional acrylate monomers or polyfunctional acrylate
oligomers so as to provide flexibility to the resultant layer,
enhance adhesion, and increase layer strength. of monoacrylates,
stearyl acrylate, isoamyl acrylate, isomyristyl acrylate, and
isostearyl acrylate are preferred which result in high sensitivity,
are capable of minimizing curling due to low contraction, minimize
bleeding as well as unpleasant odor of printed matter, and decrease
cost of the exposure apparatus.
[0075] Incidentally, methacrylates result in less skin stimulus
than acrylates, while there is no difference among them in eruption
of the skin. Further, methacrylates are generally inferior to
acrylates due to a decrease in sensitivity. However, methacrylates
exhibit higher reactivity. As results, any of the methacrylates,
which result in minimal eruption of the skin, may be suitably
employed.
[0076] Incidentally, of the aforesaid compounds, alkoxyacrylates
result in low sensitivity and cause problems with bleeding,
unpleasant odor, and exposure light sources. Therefore, it is
preferable that the content ratio of said alkoxyacrylates should be
adjusted to less than 70 percent by weight and the rest is filled
with other acrylates.
[0077] (Other Components)
[0078] If desired, other components may be incorporated in the
white ink composition.
[0079] When electron beams and X-rays are employed as exposure
radiation, initiators are unnecessary. On the other hand, when UV
radiation, visible light, and infrared radiation are employed,
radical polymerization initiators, initiation aids, and sensitizing
dyes, which correspond to each wavelength, are incorporated. The
amount of these compounds is from 1 to 10 parts by weight. Employed
as said radical polymerization initiators, as well as initiation
acids, may be various compounds known in the art. However, in the
present invention, those are selected from compounds which are
soluble in the aforesaid polymerizable compounds. Listed as
specific initiators are xanthone based or thioxanthone based
compounds, benzophenone based compounds, quinone based compounds,
and phosphine oxide based compounds.
[0080] Further, in order to improve retention properties, it is
possible to add polymerization inhibitors in an amount of 200 to
200,000 ppm. It is preferable that the white ink composition is
ejected while heated to the range of 40 to 80.degree. C. so as to
result in a lower viscosity. Therefore, in order to minimize head
clogging, it is preferable that said polymerization inhibitors are
incorporated.
[0081] Polymerization Inhibitors
[0082] In the present invention, when generated species are
radicals, employed as compounds which inhibit polymerization during
storage as well as thermal polymerization are radical quenching
agents such as hindered amine based compounds, thiol, thio acid,
dithio acid, phosphates, thiophosphates, hydroquinone,
p-methoxyphenol, dinitrobenzene, p-quinone, Methylene Blue,
.beta.-naphtol, N-nitrosoamine, nitrosodiphenylamine,
phenothiazine, phosphonic acid esters, triphenyl phosphite, and
salts, especially alkali and aluminum salts of
N-nitroso-cyclohexyl-hydroxylamin- e.
[0083] When generated species are acids, compounds, which can
quench the resulting acid, may be employed. The compounds include,
for example, aromatic amines, amines having an aromatic group,
cyclic amine based compounds such as piperidine, urea based
compounds such as tolylthiourea, sulfur compounds such as sodium
diethylthiophosphate or soluble salts of aromatic sulfonic acid,
and nitrogen compounds including nitrile compounds such as N,
N'-di-substituted-p-aminobenzonitrile, phosphorous compounds such
as tri-n-butylphosphine or sodium diethyldithiophosphide,
tri-Michler's ketone, N-nitrosohydroxylamine derivatives,
oxazolidine compounds, tetrahydro-1,3-oxazine compounds, and
condensation products of formaldehyde or acetaldehyde with diamine.
Further, preferably employed as thermal base generating agents are,
for example, salts of bases with organic acids which are decomposed
while being decarboxylated, amine releasing compounds which are
decomposed by intramolecular nucleophilic displacement reaction,
Lossen rearrangement, or Beckmann rearrangement, and compounds
which are subjected to any thermal reaction to release bases.
Listed as specific compounds are salts of trichloroacetic acid,
salts of (.alpha.-sulfonylacetic acid, salts of propionic acid,
2-carboxycarboxyamide derivatives, compounds compromised of alkali
metals as base components other than organic bases, salts with
thermally decomposable acids employing alkaline earth metals,
hydroxamcarbamates, and aldoximcarbamates which generate nitrile
upon being heated. Other than those, various thermal base
generating agents are useful. Specific examples further include
guanidinotrichloroacetic acid, methylguanidinotrichloroacetic acid,
potassium trichloroacetate, guanidinophenylsulfonylacetic acid,
guanidino-p-chlorophenylsulfonylaceti- c acid,
guanidino-p-methanesulfonylphenylsulfinylacetic acid, potassium
phenylpropiolate, guanidinophenylpropiolic acid, cesium
phenylpropiolate, guanidino-p-chlorophenylpropiolic acid,
guanidine-p-phenylene-bis-phenylp- ropiolic acid,
tetramethylammonium phenylsulfonylacetate, and tetramethylammonium
phenylpropiolate. The aforesaid thermal base generating agents may
be employed in a wide range.
[0084] Other than these, if desired, it is possible to add surface
active agents, leveling additives, matting agents, as well as
polyester based resins, vinyl based resins, acryl based resins,
rubber based resins, and waxes to adjust physical properties of the
resultant layer. In order to improve tight adhesion properties onto
recording media, comprised of compounds such as olefin and PET, it
is preferable to incorporate tackifiers which do not adversely
affect polymerization. Specific compounds include high molecular
weight adhesive polymers (being copolymers comprised of esters of
acrylic acid or methacrylic acid with alcohol having an alkyl group
having from 1 to 20 carbon atoms, esters of acrylic acid or
methacrylic acid with alicyclic alcohol having from 6 to 14 carbon
atoms, or esters of acrylic acid or methacrylic acid with aromatic
alcohol having from 6 to 14 carbon atoms) and low molecular weight
adhesion providing resins having a polymerizable unsaturated
bond.
[0085] In order to improve adhesion properties onto recording
media, an extremely minute amount of organic solvents, which
results in no adverse effects for drying, may be incorporated. In
such cases, said addition is effective in a range which does not
cause problems with solvent resistance as well as VOC. The amount
is commonly from 0.1 to 5 percent, and is preferably from 0.1 to 3
percent.
[0086] Further, as a means to minimize a decrease in sensitivity
due to light shielding effects, it is possible to prepare a
radical-cationic hybrid type curable ink by combining cationically
polymerizable monomers which extend the functional life of an
initiation agent with polymerizable monomers.
[0087] In the ink jet recording method, one of the embodiments is
the method which comprises the steps of heating an ink in an
ink-jet head to be not less than 40.degree. C. and jetting the ink
onto an ink-jet recording medium.
[0088] The ink to be used includes colored ink and a white ink. It
is preferable that the ink having a viscosity of 10 to 500
Pa.multidot.s at 30.degree. C. and more preferably its viscosity is
from 7 to 30 mPa.multidot.s when heated to at least 40.degree. C.
Furthermore, at least using the white ink is preferable.
[0089] Other one of embodiments of the present invention includes
that method for providing a material such as documents or
photographic employing an ink jet apparatus comprising the step of
jetting an ink onto a recording material, wherein the viscosity of
the ink composition has the viscosity of 7 to 30 mPa.multidot.s at
the temperature which is same or vicinity of temperature of the ink
jet head when jetting ink is carried out. It is preferable that the
viscosity of the ink composition has the viscosity of 7 to 30
mPa.multidot.s at any one point of the temperature of the ink jet
head nozzle.+-.2.degree. C. when jetting ink is carried out.
Further it is preferable that the ink has a viscosity at 30.degree.
C. of 10 to 500 mpa.multidot.s. Although the ink includes either or
both colored and white ink, it is preferable to use at least white
ink which has the property as described.
[0090] Another one embodiment of the recording method includes that
recording is carried out employing at least a tone reproduction
means, a colored ink and white ink, and a recording medium so that
a color image is formed on a white image when said image is viewed
perpendicular to the surface or through said recording medium.
[0091] <Tone Reproduction Means>
[0092] In the present invention, in order to produce high quality
images with conventional photographic tone, a tone reproduction
means is employed.
[0093] Employed as said means is a pseudo-halftone processing
method in which image data are subjected to binarization
processing. Listed as said methods are a dither method, an error
diffusion method, and an average density retention method.
[0094] In the dither method, each segment of data is binarized
employing the threshold value of each pixel, based on the dither
matrix. The dither method is disclosed by for example JP-A 9-39274
and U.S. Pat. No. 5,917,510.
[0095] In the error diffusion method, as described, for example, in
R. Floyd & L. Stenberg, "An Adaptive Algorithm for Spatial Gray
Scale", SID'75 Digest, pages 36 and 37, multilevel image data of
noted pixel is binarized and the difference between the resultant
binary level and the multilevel data prior to said binarization is
distribution-diffused near the noted pixel, and is added.
[0096] Further, in the average density retention method, as
described, for example, in JP-A No. 2-210962, U.S. Pat. No.
5,121,446A(A1) or U.S. Pat. No. 6,134,355A(A1) based on values
including values in which a noted pixel is binarized into black or
white, a threshold value is determined and pixel data of the noted
pixel is binarized based on the resultant threshold value.
[0097] These tone reproduction methods are excellent representation
methods when the resolution capability of printers is sufficiently
high.
[0098] Further, when the resolution of printers is not sufficiently
high, a method is useful in which recording dots are subjected to
multilevel value processing.
[0099] Such methods include a method in which tone reproduction is
carried out by varying the diameter of droplets at a plurality of
levels while controlling voltage applied to the printing head, or
the pulse width, a method in which by employing a plurality of inks
at different densities, tone reproduction is carried out employing
the same or similar color droplets of at least two different
densities, and a combined method thereof.
[0100] <Recording Method>
[0101] In the recording method, when images are viewed from the
image side of a recording medium, a white image is formed on the
recording medium employing a white ink and subsequently, a
right-reading gradation color image is formed on the white image
employing colored inks, while employing an ink jet printer fitted
with a tone reproduction means. On the other hand, when images are
viewed through the recording medium, initially a reverse gradation
color image is formed on a recording medium employing colored inks,
and subsequently a white image is formed thereon employing a white
ink.
[0102] In order to obtain excellent color formation as well as
excellent gradation of color images, a white ink layer is preferred
which has a transmission density of at least 0.15 as well as the L
value of at least 70. When the resultant values are less than the
lower limit, or the white ink layer is not provided, the resultant
color image does not result in desired contrast against the
recording medium. As a result, visibility is degraded.
Specifically, in the low density area, image quality is degraded
due to insufficient contrast. Even though there are no upper
limits, as the obtainable level of high density from ink
production, the transmission density is at most 0.5 and the L value
is at most 100.
[0103] The transmission density in the present invention refers to
the transmission density determined by optical transmission
densitometers such as a Macbeth Densitometer and an X-Rite
Densitometer. Generally, depending on the color being measured,
density is determined through various filters such as a red filter,
a blue filter, or a green filter. Herein, the transmission density
refers to the transmission density through a blue filter which
makes it possible to efficiently determine white based transmission
density.
[0104] The L value in the present invention refers to lightness
index L* described in JIS Z 8729 (corresponding to Publication CIE
No. 15.2 (1986) COLORIMETRY, SECOND EDITION-4), which is measured
by, for example, a Spextrolino manufactured by Macbeth Co. As the L
value approaches 100, lightness increases (whitens), while, when it
approaches 0, the lightness decreases (darkens).
[0105] <Recording Media>
[0106] Recording media employed in the present invention is not
particularly limited, as long as they are printable. Listed as
those are conventional printing paper known in the arts, packaging
film, plastic film, glass, cloth, board, metal plates, card base
materials, and tacky label paper. The present invention is
effective when recording media are transparent or exhibit low
lightness.
[0107] Preferred as materials of transparent recording media are
polyester, polyolefin, polyamide, polyesteramide, polyether,
polyimide, polyamidimide, polystyrene, polycarbonate,
poly-p-phenylene sulfide, polyether esters, polyvinyl chloride,
(meth)acrylic acid esters, polyethylene, polypropylene, and nylon.
Further, copolymers and blends thereof, and crosslinked products
thereof may be employed. Of these, stretched polyethylene
terephthalate, polystyrene, polypropylene and nylon are preferred
from the aspect of transparency, dimensional stability, rigidity,
environmental load, and cost.
[0108] For the purpose of adjusting adhesion strength with a
forming layer and obtaining excellent printability, it is
preferable that the surface of supports is subjected to a corona
discharge treatment, and an adhesion enhancing treatment.
[0109] <Ink Compositions>
[0110] Employed as colored ink compositions may be ink compositions
known in the art which are employed in ink jet printing, such as a
type employing high-boiling point solvents which make ejection
stable, and a type which is solid at room temperature and is soften
liquidified when heated.
[0111] Specifically, when recording media are transparent, almost
all of them are non-ink absorptive. When recording is carried out
employing such recording media, from the viewpoint of adhesion
properties, layer strength, and image quality, it is preferable to
use curable ink compositions. Said curable ink compositions are
comprised of at least a coloring agent and a polymerizable
compound.
[0112] Further, better gradation is obtained by employing a
plurality of ink compositions having different densities in each
color.
EXAMPLES
[0113] The embodiments of the present invention will be shown
hereinafter. Incidentally, "parts" in the following description is
"parts by weight".
[0114] White Pigment Dispersions 1 through 3 were prepared
employing White Pigments 1 through 3, described below.
Example 1
[0115] (White Pigments)
[0116] White Pigment 1: titanium oxide (having an average particle
diameter of 0.15 .mu.m and a refractive index of 2.52)
[0117] White Pigment 2: white organic pigment (Shigenox OWP having
a particle diameter of 0.3 .mu.m, manufactured by Hakko Chemical
Co.)
[0118] White Pigment 3: fine hollow polymer particles (Ropague
OP-62 having an outer diameter of 0.5 .mu.m, Rohm and Haas Co.)
1 (White Pigment Despersions 1 through 3) Any of said White
Pigments 1 through 3 25 parts Polymer dispersing agent 5 parts
Tetraethylene glycol diacrylate 70 parts Employing any of said
White Pigment Dispersions 1 through 3, white ink compositions
having the formula described below were prepared. White Ink
Composition 1 White Pigment Dispersion 1 (comprising 20 parts White
Pigment 1) Lauryl acrylate 15 parts Stearyl acrylate 10 parts
Tetraethylene glycol diacrylate 25 parts Ethylene oxide modified
24.5 parts trimethylolpropane triacrylate TMP-3EO-A, manufactured
by Kyoeisha Chemical Co., Ltd.) Initiator 1 (Irugacure 907,
2-methyl-l[4- 5 parts (methylthio)phenyl]-2-
morpholinopropane-1-one, manufactured by Ciba-Geigy Corp.)
Initiator 2 (diethylthioxanthone) 0.5 part White Ink Composition 2
White Pigment Dispersion 2 (comprising 30 parts White Pigment 2)
Lauryl acrylate 13 parts Stearyl acrylate 8 parts Tetraethylene
glycol diacrylate 22 parts Ethylene oxide modified 21.5 parts
trimethylolpropane triacrylate, TMP-3EO-A, manufactured by Kyoeisha
Chemical Co., Ltd.) Initiator 1 (Irugacure 907, 2-methyl-1[4- 5
parts (methylthio)phenyl]-2- morpholinopropane-1-one, manufactured
by Ciba-Geigy Corp.) Initiator 2 (diethylthioxanthone) 0.5 part
White Ink Composition 3 White Pigment Dispersion 3 (comprising 30
parts White Pigment 3) Lauryl acrylate (monofunctional) 13 parts
Ethoxydiethylene glycol acrylate 8 parts (monofunctional)
Tetraethylene glycol diacrylate 22 parts (bifunctional) Caprolactam
modified dipentaerythritol 21.5 parts hexaacrylate (hexafunctional)
Initiator 1 (Irugacure 907, 2-methyl-1[4- 5 parts
(methylthio)phenyl]-2- morpholinopropane-1-one, manufactured by
Ciba-Geigy Corp.) Initiator 2 (diethylthioxanthone) 0.5 part White
Ink Composition 4 White Pigment Dispersion 1 (comprising 10 parts
White Pigment 1) White Pigment Dispersion 3 (comprising 20 parts
White Pigment 3) Lauryl acrylate (monofunctional) 13 parts
Ethoxydiethylene glycol acrylate 8 parts (monofunctional)
Tetraethylene glycol diacrylate 22 parts (bifunctional) Caprolactam
modified dipentaerithritol 21.5 parts hexaacrylate (hexafunctional)
(TMP-3EO-A, manufactured by Kyoeisha Chemical Co., Ltd.) Initiator
1 (Irugacure 907, 2-methyl-l[4- 5 parts (methylthio)phenyl]-2-
morpholinopropane-1-one, manufactured by Ciba-Geigy Corp.)
Initiator 2 (diethylthioxanthone) 0.5 part White Ink Composition 5
White Pigment Dispersion 1 (comprising 30 parts White Pigment 1)
Isobornyl acrylate (monofunctional) 13 parts Ethoxydiethylene
glycol acrylate 8 parts (monofunctional) Tetraethylene glycol
diacrylate 22 parts (bifunctional) Glycerin propoxytriacrylate 22
parts (trifunctional) (OTA 480, manufactured by Daicel UCB)
Initiator 3 (Irugacure 819 2-methyl-1[4- 1 part
methylthio]phenyl)-2-morpholinopropane- 1-one, manufactured by
Ciba-Geigy Corp.) Initiator 4 (Irugacure-184, 1-hydroxy- 1 part
cyclohexyl phenyl ketone, manufactured by Ciba-Geigy Corp.) White
Ink Composition 6 White Pigment Dispersion 1 (comprising 30 parts
White Pigment 1) Isobornyl acrylate (monofunctional) 13 parts
Ethoxydiethylene glycol acrylate 8 parts (monofunctional)
Tetraethylene glycol diacrylate 22 parts (bifunctional) Glycerin
propoxytriacrylate 22 parts (trifunctional) (OTA 480, manufactured
by Daicel UCB) Initiator 3 (Irugacure 819 2-methyl-1[4- 1 part
methylthio]phenyl)-2-morpholinopropane- 1-one, manufactured by
Ciba-Geigy Corp.) Initiator 4 (Irugacure-184, 1-hydroxy- 1 part
cyclohexyl phenyl ketone, manufactured by Ciba-Geigy Corp.) White
Ink Composition 7 White Pigment Dispersion 1 (comprising 10 parts
White Pigment 1) White Pigment Dispersion 2 (comprising 20 parts
White Pigment 2) Lauryl acrylate (monofunctional) 13 parts
Ethoxydiethylene glycol acrylate 8 parts (monofunctional)
Tetraethylene glycol diacrylate 22 parts (bifunctional) Caprolactam
modified dipentaerythritol 21.5 parts hexaacrylate (hexafunctional)
(TMP-3EO-A, manufactured by Kyoeisha Chemical Co., Ltd.) Initiator
1 (Irugacure 907, 2-methyl-1[4- 5 parts (methylthio)phenyl}-2-
morpholinopropane-1-one, manufactured by Ciba-Geigy Corp.)
Initiator 2 (diethylthioxanthone) 0.5 part
[0119] Said White Ink Compositions 1 through 7 were filtered by a
filter having an absolute filtration accuracy of 2 .mu.m.
[0120] the viscosity of the resultant White Ink Compositions 1
through 7 was in the range of 30 to 100 Pa.multidot.s at 30.degree.
C. and was in the range of 10 to 20 Pa.multidot.s at 70.degree.
C.
[0121] (Image Recording)
[0122] Each of the aforesaid White Ink Compositions 1 through 7 was
placed in an ink jet recording apparatus, employing piezoelectric
type ink jet nozzles, and subsequently recording onto recording
media was carried out. The ink supply system was comprised of ink
tanks, supply pipes, pre-ink tanks positioned just before the head,
piping fitted with a filter and a piezoelectric head. During the
test run, the portion from said pre-chamber ink tank to said head
was not heated and heated. A thermal sensor was provided near said
pre-chamber ink tank as well as the nozzles of said head. The
temperature at the nozzle portion was continuously maintained at
70.+-.2.degree. C. Said piezoelectric head was driven so that 8 to
30 pl multi-size dots were ejected under a resolution of
720.times.720 dpi. Incidentally, as described herein, the term
"dpi" is used to refer to the number of dots per inch, i.e., per
2.540 cm.
[0123] As recording media, 50 .mu.m transparent shrink PET film was
used. After placement of ink droplets, UV exposure was carried out
at a total exposure energy of 160 mJ/cm.sup.2.
[0124] (Evaluation)
[0125] As a result, by employing White Ink Compositions 1 through
7, it was possible to produce white images as well as white text
which resulted in excellent adhesion properties onto base materials
as well as excellent durability. Further, when color images were
provided on the resultant images, it was possible to produce images
which exhibited excellent color formation properties as well as
excellent visibility, even on transparent base materials. Further,
by employing the aforesaid white ink compositions, printing was
carried out in the same manner on OPS base materials with a large
surface tension, printed circuit substrates, and black plastic base
materials.
Example 2 (Comparative)
[0126] The white ink compositions described below were prepared and
were evaluated in the same manner as Example 1.
2 White Ink Composition 8 (Comparative Example) Titanium dioxide
14.1 parts Water based acrylic resin 10.5 parts Methanol 7 parts
Ethanol 49.2 parts Water 17.6 parts Sodium thiocyanate 2 parts
White Ink Composition 9 (Comparative Example) Titanium oxide 15
parts Rosin modified xylene resin 40 parts Cyclohexanone 60 parts
Ethanol 20 parts Ethyl acetate 5 parts White Ink Composition 10
(Comparative Example) White organic pigment 25 parts Rosin modified
maleic acid resin 10 parts Ethylene glycol 5 parts Ethanol 5 parts
Water 55 parts White Ink Composition 11 (Comparative Example) Water
based titanium oxide dispersion 33 parts (30 parts of the pigment)
Water based urethane oligomer dispersion 34 parts
Dipentaneerythritol polyacrylate 1.5 parts Photopolymerization
initiator 1.5 parts Water 35 parts White Ink Composition 12
(Comparative Example) White Pigment Dispersion 1(comprising 20
parts White Pigment 1) Stearyl acrylate 75 parts Initiator
(Irugacure 184, manufactured 5 parts by Ciba-Geigy Corp.)
[0127] The ink viscosity of white Ink Compositions 8 through 12 was
8 mpa.multidot.s at 30.degree. C., and 6 mPa.multidot.s at
70.degree. C.
[0128] The resultant White Ink Compositions 8 through 12 were
subjected to image recording and evaluation in the same manner as
Example 1. White Ink Compositions 8 through 10 were not capable of
forming high quality images due to image bleeding on non-absorptive
PET base materials. After carrying out printing employing White Ink
Composition 11, in order to remove residual solvents, drying was
carried out at 50.degree. C. for 10 minutes. Thereafter, curing was
carried out exposing UV radiation, which resulted in wavy
deformation of the PET base material. Further, White Ink
Composition 12 resulted in fluctuation of image quality on PET base
materials as well as on OPS base materials due to differences in
dot diameter.
Example 3
[0129] <Colored ink and White Ink Compositions>
[0130] Employed as ink compositions were UV curable ink
compositions capable of resulting in excellent printability even on
transparent non-ink absorptive media.
[0131] Pigment dispersions were prepared based on the compositions
described below. Dispersion was carried out so as to obtain an
average particle diameter of 0.2 to 0.3 .mu.m.
3 (Yellow Pigment Dispersion) Pigment Yellow 12 10 parts by weight
Polymer dispersing agent 5 parts by weight Stearyl acrylate 85
parts by weight (Magenta Pigment Dispersion) Pigment Red 57:1 15
parts by weight Polymer dispersing agent 5 parts by weight Stearyl
acrylate 80 parts by weight (Cyan Pigment Dispersion) Pigment Blue
15:3 20 parts by weight Polymer dispersing agent 5 parts by weight
Stearyl acrylate 75 parts by weight (Black Pigment Dispersion)
Pigment Black 7 20 parts by weight Polymer dispersing agent 5 parts
by weight Stearyl acrylate 75 parts by weight (White Pigment
Dispersion) Titanium oxide (anatase type 20 parts by weight having
a particle diameter of 0.2 .mu.m) Polymer dispersing agent 5 parts
by weight Stearyl acrylate 85 parts by weight Inks having the
formula described below were prepared, employing the aforesaid
dispersions. (Yellow Ink (Yd Ink)) Yellow Pigment Dispersion 20
parts by weight Stearyl acrylate 60 parts by weight Bifunctional
aromatic urethane 10 parts by weight acrylate (having a molecular
weight of 1,500) Hexafunctional aliphatic urethane 5 parts by
weight acrylate (having a molecular weight of 1,000) Initiator
(Irugacure 184, 5 parts by weight manufactured by Ciba-Geigy Corp.)
(Magenta Ink (Md Ink)) Magenta Pigment Dispersion 20 parts by
weight Stearyl acrylate 60 parts by weight Bifunctional aromatic
urethane 10 parts by weight acrylate (having a molecular weight of
1,500) Hexafunctional aliphatic urethane 5 parts by weight acrylate
(having a molecular weight of 1,000) Initiator (Irugacure 184, 5
parts by weight manufactured by Ciba-Geigy Corp.) (Cyan Ink (Cd
Ink)) Cyan Pigment Dispersion 15 parts by weight Stearyl acrylate
65 parts by weight Bifunctional aromatic urethane 10 parts by
weight acrylate (having a molecular weight of 1,500) Hexafunctional
aliphatic urethane 5 parts by weight acrylate (having a molecular
weight of 1,000) Initiator (Irugacure 184, 5 parts by weight
manufactured by Ciba-Geigy Corp.) (Black Ink (Kd Ink)) Black
Pigment Dispersion 15 parts by weight Stearyl acrylate 65 parts by
weight Bifunctional aromatic urethane 10 parts by weight acrylate
(having a molecular weight of 1,500) Hexafunctional aliphatic
urethane 5 parts by weight acrylate (having a molecular weight of
1,000) Initiator (Irugacure 184, 5 parts by weight manufactured by
Ciba-Geigy 5 parts by weight Corp.) Corp.) (White Ink (W Ink))
White Pigment Dispersion 15 parts by weight Stearyl acrylate 65
parts by weight Bifunctional aromatic urethane 10 parts by weight
acrylate (having a molecular weight of 1,500) Hexafunctional
aliphatic urethane 5 parts by weight acrylate (having a molecular
weight of 1,000) Initiator (Irugacure 184, 5 parts by weight
manufactured by Ciba-Geigy Corp.)
[0132] Each of the aforesaid inks was filtered employing a filter
having an absolute filtration accuracy of 2 .mu.m, whereby said ink
was prepared.
[0133] Further, each ink was diluted so that the resultant
concentration was from 1/4 to 1/6, whereby a pale ink (Y1 Ink, M1
Ink, C1 Ink, or K1 ink) was prepared.
[0134] Subsequently, recording was carried out onto recording
media, employing an ink jet recording apparatus fitted with
piezoelectric type ink jet nozzles. The ink supply system was
comprised of ink tanks, supply pipes, pre-ink tanks positioned just
before the head, piping fitted with a filter and a piezoelectric
head. During the test runs, the portion from said pre-chamber ink
tank to said head was not heated and also heated. A thermal sensor
was provided near said pre-chamber ink tank as well as the nozzles
of said head. The temperature at the nozzle portion was
continuously maintained at 60.+-.2.degree. C. Said piezoelectric
head having a nozzle diameter of 24 .mu.m was driven so as to eject
under a resolution of 720.times.720 dpi (which represents the
number of dots per inch, i.e., per 2.54 cm). The exposure system,
the primary scanning rate, and the ejection frequency were adjusted
so that UV-A radiation was focused so as to result in illumination
intensity of 100 mW/cm.sup.2 on the exposure surface, and exposure
was initiated 0.1 second after the placement of ink. Exposure was
carried out while varying the exposure time.
[0135] Printing was carried out onto 50 .mu.m thick transparent
shrunk PET, employing W Ink based on the dither method, as well as
image data prepared utilizing a liquid droplet diameter variable
control. Thereafter, employing Yd Ink, Md Ink, Cd Ink, and Kd Ink,
a color image was printed thereon, and UV radiation was exposed
onto the resultant image, whereby an image having photographic
gradation was produced. During this operation, the solid image area
of the white ink layer exhibited a transmission density of 0.3 and
an L value of 75. Images prepared as above exhibited high contrast,
smooth gradation and excellent graininess especially in highlight
areas, irrespective of images on a transparent base material.
[0136] Further, the dither method was only applied to image data
with low resolution. As a result, excellent images, which exhibited
desired gradation, were obtained.
Example 4
[0137] Employing Yd Ink, Md Ink, Cd Ink, Kd Ink, Y1 Ink, M1 Ink, C1
Ink, and K1 Ink as shown in Example 3, a color image was printed
onto a surface-treated OPP (biaxially stretched polypropylene)
film, which had been subjected to print adaptability, based on
image data processed by the error diffusion method. Thereafter,
printing was carried out employing W Ink, whereby an image was
produced. During this operation, the solid image area of the white
ink layer exhibited a transmission density of 0.25 and an L value
of 70. When the image produced as above was viewed through an OPP
film, it exhibited smooth gradation and excellent graininess,
especially at highlight areas.
[0138] Further, in order to decrease the size of the apparatus as
well as to cut cost, printing was carried out without employing Y1
Ink as well as K1 Ink. However, by employing the present invention,
desired images were obtained.
Example 5 (Comparative)
[0139] In Examples 3 and 4, images were formed directly on a
transparent film without employing W Ink. The obtained images
resulted in poor color formation and did not result in desired
gradation, especially not in the highlight areas. In addition, the
resultant image neither exhibited desired visibility nor desired
resolution.
[0140] The white ink composition of the present invention exhibited
at least markedly excellent effects resulting in excellent
visibility for transparent non-ink absorptive recording media, low
lightness recording media, and metal surfaces, as well as resulting
in excellent printability in regard to image quality, drying
properties, adhesion properties onto base materials, and
durability.
[0141] Also, the image or material producing method employing ink
jet recording method of the present invention makes it possible to
prepare images having excellent visibility as well as excellent
tone reproduction, even though transparent recording media as well
as recording media having low lightness are employed.
[0142] The embodiments illustrated and discussed in this
specification are intended only to teach those skilled in the art
the best way known to the inventors to make and use the invention.
Nothing in this specification should be considered as limiting the
scope of the present invention. Modifications and variations of the
above-described embodiments of the invention are possible without
departing from the invention, as appreciated by those skilled in
the art in light of the above teachings. It is therefore to be
understood that, within the scope of the claims and their
equivalents, the invention may be practiced otherwise than as
specifically described.
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