JP2000119575A - Ink for ink jet printing use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject ink by using ultra-microparticles each having a specific size as a color-developing material and capable of developing any of various colors through selecting the constitutive element and size, etc., of the ultra-microparticles to vary absorption wavelength and light emission wavelength. SOLUTION: This ink for ink jet printing use is obtained by including pref. 0.01-10 (more pref. 0.05-1) wt.% of at least one kind of ultra-microparticles each 0.1-100 nm in average size selected from pref. groups I-VII, II-VI, III-V compound semiconductors, and pref. a surfactant and a solvent for dispersing the ultra-microparticles therein. This ink is preferably used for water-based ink jet printing and water-based ink jet coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink-jet ink. More specifically, the present invention relates to an inkjet ink containing ultrafine particles having a specific particle diameter as a novel material suitable for use as an inkjet recording liquid or an inkjet coating liquid.

[0002]

2. Description of the Related Art Heretofore, as an ink jet ink, an ink basically comprising a dye or pigment and an aqueous medium has been generally used.

[0003]

SUMMARY OF THE INVENTION The present invention provides a novel ink-jet ink capable of characterizing its color development by using a novel material in place of the dye or pigment used in the above-mentioned conventional ink composition. It is intended to provide. In other words, ultrafine particles represented by compound semiconductors (hereinafter referred to as "nanoparticles")
Is a substance suitable for use as a pigment, since the absorption wavelength and emission wavelength vary depending on the constituent elements, particle size, and the like, and various colors can be expected. Also, if used in combination with conventional pigments such as carbon black, it is possible to characterize the reflection spectrum, etc., even when the nanoparticles do not develop color alone, which can be useful for preventing forgery of printed matter, for example. become.

[0004] On the other hand, conventionally, when nanoparticles are used for purposes other than the ink targeted in the present invention, the surface of the nanoparticles is often covered with a hydrophobic organic substance,
It could be dispersed only in organic solvents such as toluene and chloroform. However, when used as an inkjet ink, it is preferable that the ink is water-soluble in consideration of the influence on the environment, the influence on the human body, and safety.
Therefore, another object of the present invention is to provide a composition that enables the use of nanoparticles as an aqueous ink for inkjet.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, it has been found that the use of ultrafine particles having a specific particle size as an ink jet ink enables a characteristic color development. In addition, the present inventors have found that the ink can be used as an aqueous system by containing a specific coexisting substance in the ink together with the fine particles, and have reached the present invention.

That is, the gist of the present invention is that the average particle size is 0.1 to
An ink jet ink characterized by containing ultrafine particles of 100 nm. Another aspect of the invention resides in an inkjet ink containing ultrafine particles having an average particle diameter of 0.1 to 100 nm, a surfactant, and a solvent for dispersing the ultrafine particles.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The ink-jet ink of the present invention contains ultrafine particles having an average particle size of 0.1 to 100 nm. A more preferred range of the average particle size is 0.5 n
m to 100 nm, and more preferably 1 to 50 nm. If the particle size is too large, it becomes bulky, and if it is too small, it becomes atoms or molecules themselves.

The type of ultrafine particles used in the present invention is not particularly limited, and may be any fine particles having the above-mentioned predetermined size. Examples thereof include Group I-VII compound semiconductors such as CuCl and II-VI compounds such as CdS and CdSe. Group compound semiconductor, I
Semiconductor crystals such as III-V group compound semiconductors such as nAs and group IV semiconductors, metal oxides such as TiO ₂ , SiO and SiO ₂ , phosphors, inorganic compounds such as fullerenes and dendrimers, phthalocyanines and azo compounds etc. An organic compound, a composite material thereof, or the like can be given.

[0009] Incidentally, within a range not to impair the object of the present invention,
The surface of these nanoparticles may be chemically or physically modified, and additives such as a surfactant, a dispersion stabilizer and an antioxidant may be added. Such nanoparticles can be obtained by colloidal chemistry, such as the reverse micelle method (Lianos, P. et a).
l., Chem. Phys. Lett., 125, 299 (1986)) and the hot soap method (Peng, X. et al., J. Am. Chem. Soc., 119, 7).
019 (1997)), it is possible to synthesize particles that are approximately spherical and have a particle size of several nanometers.

The ink-jet ink of the present invention usually contains the ultrafine particles and a dispersion medium, preferably an aqueous dispersion medium. Although the aqueous dispersion medium is mainly composed of water,
A water-soluble organic solvent may be added to water for use. Examples of the water-soluble organic solvent include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol (# 2).
00, # 400), glycerin, alkyl ethers of the above glycols, N-methylpyrrolidone, 1,3-dimethylimidazolinone, thiodiglycol, 2-pyrrolidone, sulfolane, dimethylsulfoxide, diethanolamine, triethanolamine, ethanol, Isopropanol and the like. The amount of the water-soluble organic solvent used in the aqueous dispersion medium is usually preferably 30% by weight or less, and more preferably 20% by weight.

The ultrafine particles are usually contained in an amount of 0.0
It is used in the range of 1 to 10% by weight, but is more preferably in the range of 0.05 to 1% by weight. If the content of the ultrafine particles is too small, the effect at the time of printing is small, and if it is too large, the ejection stability is impaired. In addition, as the inkjet ink of the present invention, it is preferable that a surfactant and a solvent for dispersing the ultrafine particles coexist in addition to the ultrafine particles and the dispersion medium.

Examples of the surfactant include known surfactants such as anionic surfactants (sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate,
Sodium laurate, ammonium salts of polyoxyethylene alkyl ether sulfate), nonionic surfactants (polyoxyethylene alkyl ether,
Polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, etc., and these may be used alone or in combination of two or more. it can. The amount of surfactant is based on the total weight of the ink.
Usually, it is used in a range of 0.1 to 30% by weight.
More preferably, it is in the range of 20% by weight. When the amount of the surfactant is less than this range, oil-water separation occurs in the aqueous dispersion, and uniform printing may not be performed. Conversely, if it is more than this range, the viscosity of the aqueous dispersion medium tends to be too high.

The solvent for dispersing the ultrafine particles is usually a liquid such as toluene, hexane, pyridine or chloroform, and is preferably volatile. The amount of the dispersing solvent is usually used in the range of about 0.1 to 20% by weight, but is more preferably in the range of 1 to 10% by weight. If the amount of the dispersing solvent is less than this range, the amount of ultrafine particles that can be contained in the aqueous medium becomes small. Conversely, if the amount is more than this range, oil-water separation occurs in the aqueous dispersion medium, and uniform printing may not be performed.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

Example 1 (Synthesis of CdSe nanoparticles) Preparation of high-concentration stock solution In a glove box kept at room temperature in a nitrogen atmosphere, 0.8 g of selenium powder (purity: 99.999%) manufactured by Aldrich was used.
The mixture was placed in a ml vial, and 8.0 g of tri-n-butylphosphine (purity: 99%) manufactured by Strem Chemicals was added and shaken for several minutes to obtain a uniform transparent solution. To this, 2.16 g of dimethyl cadmium (purity 99 +%) manufactured by Strem Chemicals, which was stored in a freezer in a glove box after purification by a vacuum transfer method, was added, and the mixture was shaken for several minutes. A clear solution was obtained.

Preparation of Diluted Stock Solution At room temperature, in a glove box kept in a nitrogen atmosphere, 1.0 g of the above high-concentration stock solution was placed in a 20 ml vial, and tri-n-butylphosphine manufactured by Strem Chemicals was added to the vial. (Purity 99%) 4.0 g was added and shaken for several minutes to obtain a uniform transparent solution. The vial was capped with a septum cap and stored in a glove box.

Synthesis of CdSe Nanoparticles A 25 ml three-necked round bottom flask was charged with 2 g of trioctyl phosphine oxide (purity 90%) and a magnetic stirrer manufactured by Aldrich, and Ar gas was allowed to flow for 30 minutes. The atmosphere was replaced. After the stirring was started, the internal temperature was raised to 350 ° C. by a mantle heater. Take out the diluted stock solution from the glove box, and under Ar atmosphere, 5 ml
1.0 ml was dispensed with a syringe and injected into the flask in about 0.1 second. The liquid inside the flask became dark purple, confirming that the reaction had started. Internal temperature from 270 to 290
C., and after 60 minutes from the injection, the reaction was stopped by cooling to room temperature.

Separation of CdSe nanoparticles Absolute methanol (purity 99.8, manufactured by Aldrich) was added to the flask.
%) Was added and stirred for 5 minutes to obtain a turbid dark purple suspension. Transfer some or all of this suspension to several 5 ml vials and
Centrifuged at rpm for 15 min. After centrifugation, the supernatant was discarded, and the remaining precipitate was blown with nitrogen gas and dried.
In this way, about 90 mg of CdSe nanoparticles having an average particle size of 34 Å were obtained.

(Preparation of recording liquid) 11.1 mg of CdSe nanoparticles having an average particle diameter of 34 ° obtained by the above method were dispersed in 0.5130 g of chloroform. 1.5025 g of sodium dodecyl sulfonate and 9.5300 g of ion-exchanged water were added to the solution, and the mixture was shaken for about 5 minutes.
An aqueous pigment dispersion was prepared.

[0020]

Table 1 Composition of recording liquid Amount (parts by weight) CdSe nanoparticles having an average particle size of 34 ° C. 0.1 Sodium dodecylsulfonate 13.0 Chloroform 4.4 Ion-exchanged water 82.5 Total 100.0

(Printing Test) An ink jet printer (a product of Hewlett-Packard Company, trade name Desk) was prepared by using the aqueous dispersion obtained by the method described in the above example.
Writer 660C) 12.6cm × on Recycled PPC paper Green100 manufactured by FUJI XEROX
As a result of performing inkjet recording with solid printing of 6.1 cm, stable and good ejection properties were exhibited without clogging or the like, and the printed portion was lightly colored pink and a printed matter having good print quality was obtained.

Example 2 (Printing on OHP) The aqueous dispersion used in Example 1 was applied to the OHP film Model Number MC701 for an inkjet printer manufactured by Mitsubishi Chemical Corporation using the ink jet printer used in Example 1.
As a result of performing ink jet recording by solid printing of 2.6 cm × 6.1 cm, a stable and good printed matter without clogging or the like was obtained.

(Measurement of Photoluminescence) The OHP sheet produced by the above method was stored at room temperature in a dark place for 24 hours and dried. 3cm for solid printed area
Four pieces of 3 cm were cut out and superimposed photoluminescence (hereinafter abbreviated as PL) was measured. The superposition is performed to emphasize the PL peak. FIG. 1 shows the profile of this PL. FIG. 1 shows a baseline correction. Light emission by the CdSe ultrafine particles was confirmed at around 555 nm, which indicates that good printing was achieved. 535
The peaks at nm and 600 nm are the molecular vibrations of the capping agent trioctylphosphine oxide used in synthesizing CdSe by a colloid chemistry technique.

[0024]

The ink-jet ink of the present invention uses ultrafine particles having a specific particle size as a color-forming material.
By selecting the constituent elements and the particle size of the ultrafine particles, it is possible to change the absorption wavelength and the emission wavelength to produce various colors. In addition, it is possible to give a characteristic to a reflection spectrum or the like by mixing and using a conventional pigment.

[Brief description of the drawings]

FIG. 1 is an emission spectrum of a semiconductor ultrafine particle thin film formed on an OHP film by an inkjet method.

Continued on front page F-term (reference) 2C056 FC01 2H086 BA53 BA55 BA59 BA60 BA62 4J039 BA10 BA13 BA18 BA20 BA21 BA29 BA31 BA35 BC02 BC03 BC05 BC09 BC12 BC20 BC33 BC36 BC39 BC50 BC54 BC60 BE12 BE22 CA06 EA21 EA29 EA48 GA13 GA24

Claims (7)

[Claims] 1. An ink-jet ink comprising ultrafine particles having an average particle size of 0.1 to 100 nm. 2. The ink-jet ink according to claim 1, wherein the ultrafine particles are semiconductors. 3. The method according to claim 1, wherein the ultrafine particles are of groups I-VII, II-VI and II.
The ink-jet ink according to claim 1, wherein the ink is at least one selected from the group consisting of an IV group compound semiconductor and a group IV semiconductor. 4. The inkjet ink according to claim 1, wherein the content of the ultrafine particles is in the range of 0.01 to 10% by weight. 5. The inkjet ink according to claim 1, further comprising a surfactant and a solvent for dispersing the ultrafine particles. 6. The inkjet ink according to claim 1, which is used for aqueous inkjet recording. 7. The inkjet ink according to claim 1, which is used for aqueous inkjet coating.