JPS6153373A - Ink composition for ink jet recording - Google Patents

Abstract

PURPOSE:To provide the titled ink composition free from the tendency to cause the clogging at the tip of the nozzle, exhibiting excellent quick-drying property when recorded on a plain paper, and having excellent storage stability, by adding a specific amount of a water-soluble dye to an ink composition containing an oil-soluble dye. CONSTITUTION:A water-soluble dye (e.g. C.I. Direct Yellow 8, etc.) is added to an ink-jet recording ink composition composed of water, a water-miscible organic solvent [preferably having a vapor pressure of <=1mm.Hg (at 25 deg.C and 1atm) and a boiling point of >=150 deg.C, e.g. (di)ethylene glycol, etc.] and an oil-soluble dye (e.g. C.I. Solvent Yellow 8, etc.) at a ratio falling within the range defined by the formula (Do is weight of oil-soluble dye; Dw is weight of water-soluble dye).

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an ink composition for inkjet recording. More specifically, the present invention relates to an inkjet recording ink composition that does not cause clogging at the nozzle tip, exhibits excellent quick drying properties when recorded on plain paper, and has excellent storage stability.

[Prior art]

Conventionally, there has been an inkjet recording method in which information is recorded by controlling and ejecting ink liquid onto a recording carrier without bringing a recording head into contact with the recording carrier.

In recent years, it has been adopted in terminal printers because it is noiseless, capable of high-speed recording, and can record on plain paper.
It is rapidly becoming popular.

Conventionally known inkjet recording methods include an inkjet method in which the internal volume of the container is rapidly reduced, an inkjet method in which ejection is performed by extrusion or suction with a constant pressure, and a signal voltage between a nozzle and a counter electrode. An inkjet method is known in which ink is electrostatically accelerated and ejected from a nozzle by applying a current, and an ink mist method is known in which a mist is generated by ultrasonic vibrations.

The ink composition used in this type of inkjet recording method or ink mist recording method must: 1) have a sufficient dye concentration necessary for recording; 2) not evaporate and dry at the tip of the ejection nozzle (clogging) , 3) When ink droplets are attached and formed on paper, they dry immediately (showing drying properties), 4) The recorded ink does not smudge due to water or sweat, and the printed area does not disappear. (water resistance); and 5) characteristics such as not causing changes in physical properties or forming precipitates upon storage of the composition are required.

In general, water-based inks have the disadvantage that when the water content m in the ink is extremely large, the water evaporates at the nozzle tip, causing crystallization of the dye, which tends to cause clogging.

Further, since the surface tension of the ink composition is high, when this ink composition is printed on plain paper, the ink composition has poor permeability and cannot satisfy quick drying properties. For this reason, various organic solvents are used to prevent ink from clogging at the nozzle tip and to improve quick drying performance.

For example, it is well known that a wetting agent such as ethylene glycol is used to prevent clogging at the tip of the 2/zure. It has also been proposed to add penetrants such as diethylene glycol monobutyl ether to ink compositions to lower the surface tension and improve quick drying properties of the ink compositions.

However, the organic solvents used for these individual purposes have completely different properties; for example, ethylene glycol has properties similar to water and can dissolve water-soluble dyes well. However, the other diethylene glycol monobutyl ether is highly organic and does not dissolve water-soluble dyes at all. Therefore, in water-based ink, it is difficult to determine the appropriate concentration of dye, water, and 2N organic solvent with different properties so as to satisfy both clogging prevention and quick drying properties, and the range The disadvantage was that it was narrowly limited. 'Also, there is water! ! An ink composition using an oil dye in a mixed solvent consisting of a solvent is known, for example, as described in JP-A-58-21466. However, this ink composition uses a surfactant to dissolve the dye.
As a result, the ink composition develops foaming properties and bubbles are formed at the nozzle tip, resulting in a disadvantage that the ink ejection characteristics in response to the ejection frequency deteriorate.

As a result of various experiments regarding this problem, the present inventors found that among two types of organic solvents with different properties, namely, a wetting agent (or water retention) and a penetrating agent, one of the wetting agents (and water) is water-soluble. An ink composition consisting of at least two dyes having different water solubility and oil solubility, in which a dye is dissolved and an oil-soluble dye is dissolved in the other penetrating agent, has a certain relationship between the oil-based dye and the water-soluble dye. One day, he discovered that it satisfies both clogging prevention and quick drying properties, and also has excellent water resistance, which led him to complete the present invention.

[Object of the Invention] Accordingly, the first object of the present invention is to provide an ink composition for inkjet recording that is less likely to be clogged at the tip of a nozzle due to dye crystals and has excellent storage stability.

A second object of the present invention is to provide an inkjet recording ink composition in which the ink ejected onto recording paper, particularly plain paper, has sufficient permeability and satisfies quick drying properties. be.

A third object of the present invention is to provide an ink composition for inkjet recording that has excellent water resistance, and the recorded ink does not bleed due to water or sweat, and the printed area does not disappear.

[Structure of the Invention] The above object of the present invention is to provide an inkjet recording ink composition comprising water, a water-miscible solvent, and an oil-based dye, which further contains a water-soluble dye in the following ratio. This is achieved by an ink composition for inkjet recording.

0.15≦Dw / (Do +0w) <0.50
However, DO represents the weight of the oil-based dye, and Dw represents the weight of the water-soluble dye.

In the present invention, the organic solvents used in addition to water are two types of organic solvents: a wetting agent (or water retention agent) and a penetrating agent. All of these organic solvents are miscible with water, and preferably have a vapor pressure of 1ff1 mHa or less (25°C 1 mHa or less).
atom), more preferably one having a boiling point of 150°C or higher.

In this specification, the term "wetting agent" refers to the transpiration rate of a solution obtained by mixing a specific solvent used in an ink composition with water, which is the same as that of water when exposed to the atmosphere under the same conditions. For example, the transpiration rate of a mixed solvent of ethylene glycol and water at room temperature is extremely slow compared to that of water, and has properties as a wetting agent. Organic solvents (hereinafter referred to as wettable organic solvents) used as such wetting agents include aliphatic polyhydric alcohols, such as 1. Ethylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, tetraethylene glycol, etc.; oxycarboxylic acid intramolecular esters, such as valerolactone,
Specific examples include caprolactone, γ-butyrolactone, and the like; and cyclic ethers, such as tetrahydrofuran and dioxane.

Such a wettable organic solvent is preferably present in an amount of 10 to 4 wt % based on the ink composition. Further, such a wettable organic solvent can be used together with water, and the mixing ratio of water and wettable organic solvent is 8:1 to 1:2, more preferably 6:1 to 1: It is 1. The wettable organic solvents can be used alone or in combination of two or more.

The organic solvent used as a penetrant in the present invention (hereinafter referred to as a penetrant organic solvent) can be miscible with water. The term "penetrating agent" as used herein refers to an organic solvent that has the property of allowing ink droplets attached to the surface of the paper to penetrate into the interior through the gaps between the m fibers of the paper, and it controls the degree of quick drying. It is also related to the surface tension of the droplet. Normally, the surface tension of a droplet attached to the surface of paper is 30 to 40 dVn/
The substance that converts it into cm is called a penetrant.

Examples of the permeable organic solvent used in the present invention include alkyl ethers of aliphatic polyhydric alcohols, such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Diethylene glycol monobutyl ether, etc.; Pyrrolidones, such as pyrrolidones, N-vinylpyrrolidone, N-methylpyrrolidone, β-hydroxyethylpyrrolidone, N-methyl-2-pyrrolidone, etc.; N-alkylimidazolidinones, such as 1° Specific examples include 3-dimethylimidazolidine and the like.

Among these, preferred are alkyl ethers of aliphatic polyhydric alcohols represented by the following general formula [I].

The following is the blank general formula CI) CnHtn-)-1-÷0CH2CH2→770H However, 2≦m≦6 p m + 1≦n≦m+3 A specific example of such a water-miscible permeable organic solvent is 'C: I can list the following.

Exemplary compound 1) C3Ht (OCHI CHI)! OH2
') C, He (ocHt CHt), OH3)
CI HIS (OCHt CHt )t OH4)
C4He (0CHt CH,)m OH5) Cm
Hat (0CHt CHI )s OH6) C,H
, (0CHt CHt )s OH7) CI Hll
(0CHt CHt )40H8) C・HIs (
OCHz CHt )40 He)CtH or (OCH,
CHI )40H10) Ca Hxs (0CHt
CHI )s 0H11) c, )(ts (OCH
! CHI ) S 0H12) Ca Hn (0CH
t CHI )s 0H13) Ct Hu+ (0C
Ht CHI )110H14) Cs Hat (O
CH* CHI )s 0H15) Co HIo (
0CHt CHt )s OH The water-miscible penetrating organic solvent used in the present invention is preferably 10 to 40 wt%, more preferably 20 to 40 wt%, based on the ink composition.
It can be used within a range of 40 wt%, and such permeable organic solvents can be used alone or in combination of two or more kinds. Furthermore, between the wettable organic solvent and the permeable organic solvent, it is preferable to use less of the former than the latter, specifically 1:1 to 1:4, preferably 1:2 to 1:
It is 3.

Preferred combinations of wettable organic solvents and permeable organic solvents include, for example, ethylene glycol and diethylene glycol monobutyl ether (1:1.3), diethylene glycol, triethylene glycol, and N-methylpyrrolidone (1:1:3), etc. are specifically mentioned.

Examples of oil-based dyes used in the present invention include:
The following can be used:

C, 1,5olvent Yellow, 2.3.
13.19.22.29.36.31.38.39.4
0.43.44.45.47.82.133.71.7
6.81.85.86 C, 1,5olvent Red 8 (V, F, R#3304), 27.35.36.
37.38.39.40.58.60.65.67.8
9.81 (V, F, R#1306), 86.89
．． 91.92.97.99, 100 (V, F, R#33
06) , 109, 118, 119, 122 C, I , 5OIVent 91ue14.2
4.26.34.37.38.39.42.43.45
．． 48.52.53.55.59.67.70 (V,
F, B#2606) C, 1,5olvent Black8.14,17
．． 19.20. 22 (V, F, 81ack# 3804
), 24.26.27 (V, F, BIack#38
20), 2B.

29 (V, F, BIack #3806) Such an oil-based dye may be dissolved in advance in a penetrating organic solvent to form the ink composition of the present invention, or it may be composed of water, a wettable organic solvent, and a penetrating organic solvent. There is no problem even if it is appropriately dissolved in Mixture i*.

Various water-soluble dyes can be used in the present invention. For example, as a yellow dye, C
, 1, Direct Yellow 8.12.26.
24, 50, 85, 98, and 142: Also, as red dyes, C, 1, Direct Red 4.
9.13.23.31.79.81.83, 240 and 242 etc.: As blue dyes, C, I, D
Irect B Iuel, 2.15.22.25.7
1.86.81.90.98 and 192; and black dyes include C and I;

Direct Black 17.19.32.51
, 108 and 154.

Such water-soluble dyes can be predissolved in water or water and a wettable organic solvent before forming the ink composition of the present invention.

The amount of these oil-based dyes and water-soluble dyes to be added depends on the desired recording surface aS degree, the recording method of the device used for recording, the types of other components to be added, the required liquid physical properties, etc. Although determined as appropriate, it is usually 0.5 to 10% by weight, preferably 0.5% by weight, based on the ink composition to be prepared.
It is sufficient if it is 7% by weight.

Further, it is necessary that the amounts of both the oil dye and the water-soluble dye used have the following relationship.

0.15≦Dv/(Do+0w)<0.5
0 However, DO represents the weight of the oil-based dye, and [)W represents the weight of the water-soluble dye, respectively.

Dw/(Do +0w) is less than 0.15 and 0.
If it exceeds 50, sufficient clogging prevention effect cannot be achieved.

The ratio of [)w / (Do +0w) is more preferably 0.20≦Dw / (Do +0w)≦0.3
It is 5.

The respective weight percentages of water, organic solvent, and dye in the inkjet ink composition of the present invention are 20 to 80:20 to 8.
0: 0.5-10, preferably water: wetting organic solvent: penetrating organic solvent: dye each weight % from 20 to a
o:io to 40:10 to 40:1 to 7, more preferably 30 to 60:10 to 30:20 to 40:1 to 7.

The ink composition of the present invention has water, an oil dye, a water-soluble dye, and a water-miscible organic solvent as basic components, and various other additives can be optionally added as necessary. For example, if long-term storage is expected, preservatives and antifungal agents can be added to the ink of the present invention to prevent or reduce the growth of bacteria and mold in the ink.

Various preservatives are known to be useful for this purpose, but desirable ones include, for example, 1°3.5
-/\xahydrotriazine derivative II (Batilard 3
5; manufactured by Hoechst).

In addition, a surfactant can be added to adjust the surface tension that governs the wetting of the ink of the present invention on recording paper. The surfactant is not particularly limited as long as it has extremely low solubility or does not interact with dyes, but polyoxyalkylene and its alkyl ethers, siloxane-oxyalkylene copolymers, fluorine-based Surfactants and the like are preferred. These surfactants are not commercially available.

The amount of these surfactants added is generally 1% or less based on the amount of ink, but especially 0.05 to 0.0%.
A range of 5 weight percent is desirable.

Further, various inorganic or organic buffers can be added to the ink for the purpose of preventing IIH change mainly due to carbon dioxide absorption in the air while the ink is stored in a container or retained in a nozzle. desirable! Examples of the liI agent include carbonates such as sodium carbonate and potassium carbonate, and the amount of these added is practically appropriate from 0.1 to 5% by weight based on the total amount of the ink, and preferably, 0.1 to 2 weight percent is suitable.

Additionally, chelating agents can be added for the purpose of masking the metals and metal inks in the inks of the present invention. Typical examples include sodium gluconate, ethylenediaminetetraacetic acid 1 (EDTA), EDTA disodium salt, Oka trisodium salt, EDTA sodium salt, and sodium salt of diethylenetriaminopentaacetic acid. Practically speaking, the appropriate amount is 0.1 to 5% by weight based on the total amount of ink, preferably 0.
．． 1-2 weight percent is suitable.

The present invention will be illustrated below with reference to Examples, but the embodiments of the present invention are not limited thereto.

[Examples] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Example 6 Examples 1 to 5, Comparative Examples 1 to US Pat. No. 4,18, in which the ink composition obtained in 6 was prepared with the parameters shown in Table 1.
No. 9,734, the inkjet recording device described in Figures 1 to 3 was filled, and the nozzle tip was heated at a relative humidity of 10% and a temperature of 40°C for 24 hours, 6 hours, 8 hours, 12 hours, 18 hours, and 24 hours. (Nozzle diameter: 50 μmφ) After leaving the cap removed, the ink composition was injected from the nozzle, and 2
A clogging test was conducted with the clogging occurrence time defined as the time when at least one of the four nozzles could not eject.

The presence or absence of clogging was determined by irradiating the ink ejecting path with light synchronized with the ejection frequency and observing the ejected ink droplets at a magnification of about 40 times WAmll. In addition to this clogging test, the quick drying properties and water resistance of the ink printed on the recording paper were also investigated. These results are shown in Table 2.

Below are the margins: Table 1 Table 2 Table 2 (R) *(1) Quick drying evaluation: ROJ is defined as ink droplets that dry within 3 seconds after drying. Items that required the following were marked with an “×”.

*2) Water resistance is evaluated by soaking ink-recorded paper in water for 12 hours, drying it, and determining if the reflection density of the ink decreases by 10%.
If it is within 15%, it is ``0'', and if it exceeds 15%, it is r.
It was set as xJ.

As is clear from Table 2, the samples of the present invention are less prone to clogging than the comparative samples.

Example 7 Each of the samples of Examples 1 to 5 and Comparative Examples 1 to 6 was
After being stored for 1 month at °C and for 3 months at room temperature, these samples were filtered through a membrane filter with a pore size of 0.65μ to examine the filterability of each sample. 3rd result
Shown in the table.

LET Hatakemukai Table 3 *(3) Evaluation of filterability O; Good 80 or more Δ; Slightly poor 15-80 ×; Poor 15 or less ) Flow 50 cc through the membrane filter and measure the time (T) when all of it has passed. Next, 50 cc of the ink composition of each sample was passed through the membrane filter, and the time (1) for each sample to finish passing was measured and calculated using the following equation.

As is clear from Table 3, the samples of the present invention have better storage stability than the comparative samples.

Claims (1)

[Scope of Claims] An inkjet recording ink composition comprising water, an organic solvent miscible with water, and an oil dye, characterized in that the ink composition further contains a water-soluble dye in the following ratio: Recording ink composition. 0.15≦Dw/(Do+Dw)<0.50 Do: Oil-based dye weight Dw: Water-soluble dye weight