JPS5849763A - Ink composition for ink-jet recording - Google Patents

Abstract

PURPOSE:To provide an ink composition for ink-jet recording, capable of giving clear printed letter at high speed without troubles in the spraying of ink, by using specific amounts of a polyhydric alcohol, water, and a dye, and adjusting the composition so as to give a specific kinetic viscosity at the working temperature. CONSTITUTION:An ink composition composed of a polyhydric alcohol (preferably a 2-6C polyhydric alcohol), water, and a dye (e.g. C.I. Direct Black 19) and having a kinetic viscosity of <=10cst at the working temperature (generally at 30-40 deg.C, preferably at 35 deg.C). The content of the polyhydric alcohol in the composition is >=80wt%. The control of the viscosity is carried out mainly by the selection of the polyhydric alcohol. A preferable example of the ink composition is the one containing 82(wt)% ethylene glycol, 16% distilled water, 1.8% dye (C. I. Direct Black 19) and 0.2% lithium hydroxide, and having a kinetic viscosity of 6.5cst at 35 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an ink composition for inkjet recording, particularly for nozzle O1! An inkjet recording method in which ink droplets are ejected from a nozzle by rapidly reducing the volume of the pressure chamber of a printer head using an inkjet recording ink composition modified to enable high-speed recording without clogging. are well known, and are described, for example, in Japanese Patent Publication No. 47-2006. Several ink compositions for use in such recording methods have also been proposed (for example, in Japanese Patent Publication No. 50-8361). , special public official 1839
6, etc.) These ink compositions improve clarity by providing characteristics such as no nozzle clogging, clear recorded fonts, and excellent storage stability of recorded fonts. The present invention has the same goal of achieving a satisfactory distribution.

In the prior art, it is said that the content of polyhydric alcohol in an ink composition should not exceed 80% by weight at the maximum (1-0), which means that the content of polyhydric alcohol is high.
If the viscosity exceeds the proper viscosity range of the ink, printing becomes impossible, speed decreases, and abnormalities occur.
In addition, such an ink composition certainly prevents nozzle clogging when the ambient temperature and the ink composition itself are at 11 degrees Celsius or 20 to 25 degrees Celsius. Stable ejection t4 -However, in the inkjet recording method, the temperature is usually adjusted to keep the ink composition at a temperature of about 35°C.
The reason for the + symbol is to prevent the ink composition from changing in temperature due to a change in ambient temperature, since this will increase or decrease the viscosity and cause ejection failure. .

In that case, if the temperature near the nozzle is locally high, the saturated vapor pressure of water there increases and the relative humidity decreases.For example, the humidity in a heated room at 20℃ in winter is about 20
Assuming that the humidity in six 25°C air-conditioned rooms in the summer is approximately ro%nH and the temperature is adjusted to approximately 35°C, the humidity near the nozzles of the print head is approximately 8°C. .356RH and about 395! RH decreases. In conventional ink compositions, when the humidity greatly decreases, the viscosity of the ink composition in the nozzle circle increases rapidly due to evaporation of water, making jetting impossible. In a multi-nozzle print head, depending on the printing conditions, there are nozzles that eject frequently and nozzles that eject frequently, and thickening of the ink composition can at least cause clogging in those nozzles that eject frequently. Make it easier.

On the other hand, in the prior art, the viscosity of the ink composition is, for example, 100 centipoise or less in the aforementioned Japanese Patent Publication No. 50-8361, and 4 to 20 centipoise in the Japanese Patent Publication No. 56-18396.
I think centipoise is appropriate. However, according to the inventors' experiments, when the force exceeds 10 mm, it is necessary to apply an excessive 3 mm force pulse during injection, which results in a long vibration time, which is inappropriate.Drop-on-demand In a printhead, if the next ink droplet is ejected while the next ink droplet is still in the zero vibration state where vibrations remain due to shaking after ink ejection, the flight speed of the particle may change compared to the previous particle, or the t The vibration resonates and becomes larger, sucking air from the nozzle into the pressure chamber.Therefore, the next particle cannot be ejected until the vibration is constant and damped by the bell platform.The reason is that the viscosity of the ink It shows the relationship between the damping time of vibration and the value of 0. K increases the printing speed, and the shorter the damping time, the longer the damping time.
-It can be seen that there is a viscosity range suitable for high-speed printing.It can be said that the viscosity needs to be 3 to 10c8t for 1 hour of mouth shaking (lO,sImm or less) (C injection number of 2000 pieces/cod or more). When it exceeds 1Oest, there was also the disadvantage that the recorded ink smeared on the paper and the quality of the recorded font deteriorated.Himi@ aims to overcome the above-mentioned disadvantages and deficiencies in the conventional technology. . In particular, the purpose is to reduce and eliminate printer jetting failures in temperature-controlled inkjet recording methods.
0 The present invention relates to an inkjet recording ink composition comprising a polyhydric alcohol, water and a dye, the ink composition containing a polyhydric alcohol exceeding 80% by weight and having a viscosity of 10 centipoise or less at about 35°C. By providing products, the above objectives are achieved.

The ink composition for inkjet recording contains a polyhydric alcohol, water, and a dye. The dye used in Himi@ is a water-soluble dye that dissolves in a medium of polyhydric alcohol and water, and is selected from known or conventional dyes, such as blue dyes such as C, I.

DI r@et B1ue86. c.1. Ac1
d B1ts*182°C, 1, Ac1d Blue
12+s' C, 1, Ac1d Blue 90.

C, 1, Reactive 49, as a red dye, C
,I.

Direct Red 89. C,1,Direct
Red 225°C, 1, Aell R@(13
7,C,1,Aeld R*d265°C,In R
@aet lve Red 2'Jh As a black dye,
C,1,D1r@t Blaekl 9,
C,1,D1r@etBlack38 e C@
Z-AI id Black 2', C as yellow dye
,1,Direct Yellow 8LC,1,Di
rectY'*11@w 87 e C,1,Dlre
et Yellow 50*C,1,muell Yel
low 17. C,1,R@aotiveY@llow
81 can be used. You can also use these alone or in combination. ◎Selection is from the list of fonts〇-
Due to the composition of Ichihimi@O, which has been designed with storage stability in mind, the dye content is usually about 1 to 6 weight - 11! The polyhydric alcohol used is hygroscopic, has low vapor pressure, and has thickening properties.
However, in the present invention, especially low
The most important feature that keeps the composition of the ink composition unchanged in the atmosphere! ! It is something. Attached *1mK shows the relationship between typical glycol equilibrium moisture content and relative humidity. Under normal office conditions, the area near the nozzle should be less than about 4011RH. *I
According to the II'l' diagram, below 41GRH, the difference is 0.
The equilibrium water content does not exceed 20% by weight. Therefore, during operation of the printer, K is set so that the viscosity of the ink in the nozzle does not increase even if no ejection signal is applied for a while.
It is understood that the glycol concentration must exceed at least 80% by weight vIt. Polyhydric alcohols are, for example, ethylene glycol.

Glycerin, diethylene glycol, propylene glycol, triethylene glycol, hexylene glycol, triethanolamine, etc.] with 2 to 6 carbon atoms
-1L of polyhydric alcohol is preferred.

The ink composition of the present invention has a kinematic viscosity of 10 m in length when used.
: One of the characteristics is that it is less than centistokes, but this viscosity is mainly adjusted by selecting the polyhydric alcohol. This K ensures more stable injection. There is no particular limit to the operating temperature (temperature control temperature), but it is easier to control the temperature by heating, and generally 3.
The temperature is 0 to 40°C, preferably 35°C. Here, as stated in the claims, "1O-4 at about 38°C
The term "lower than lθ sec stokes" is used in the sense of 1 degree to include "lower than lθ sec stokes at 40 °C" for ordinary liquids whose viscosity decreases as the temperature increases in the vicinity of 30 to 40 °C. /'h - In other words, 35°C is suitable as the temperature control temperature, but it is within the idea oIis of the Zero-HatsufI to obtain the same effect by controlling the temperature at 40°C. In the case of other temperatures, the usual interpretation of the composition should be followed♂ Himi＠Oiν It is also possible to add polyhydric alcohols, water, dyes, etc. to the composition. -1 For example, a preservative agent, a vJ mold agent, a surfactant, &6 The ink composition of the present invention is produced by stirring and mixing each component,
Good 11. ＜Haso011Fat is commonly used in the production of inkjet recording ink compositions, %A,!・However, since the O ink composition of the present invention has high heat absorbing property, it is preferable to stir and mix it in a closed container and store it in a closed container.◎Himi@Oin! The composition makes it possible to reduce evaporation under high temperature and low humidity to a greater extent than conventional O ink compositions, thereby significantly reducing clogging in printers using temperature-controlled inkjet recording methods. Prevented. In particular, clogging is largely prevented even in nozzles that eject ink infrequently when the printer is used. Furthermore, when using a printer, it is possible to easily prevent clogging by capping the nozzle.Furthermore, the ink composition according to the present invention makes it possible to print clear fonts at high speed. Is Narou a different body? The invention will be described with reference to II below f.
) At IFII, various prototype inks were tested under O conditions.The printer head used a drop-on-demand head using a cylindrical piezo vibrator. The ambient conditions of the printer are 20℃,
The humidity was set to 2011 RHK, the temperature of the printer head was adjusted to 135 ± 3 °C using a tape heater, and the ink droplet of 60 ± 3 voices - φ was heated at a speed of 3,0 ± 0.1
It seems to be injected at gm/sec.

t o % Place a paper in front of the nozzle and emit a single pulse t10 for a few seconds.
By applying an electric current and observing whether there were dots on the paper, it was determined whether the nozzle was clogged or not, and the time until the nozzle became incapable of jetting was determined by varying the ejection pause time.

a Printing test Same ambient conditions, controlled temperature and injection conditions as the clogging test C Droplet diameter and speed JI! ') A printing test was conducted by placing a high-quality coded paper without supercalender treatment at a distance of 2 cm from the nozzle and recording at a recording density of 8 dots/cm under o.

The ink compositions described in the prior art were tested in a comparative manner, and the ink compositions described in Example IK of Japanese Patent Publication No. 56-18396 were prepared and tested. Its composition and properties are as follows:9 Composition: Ethylene glycol 64.0ωt% Distilled water
31.9ωtts Nigrosine 4,0ω1*Dioxine
0.1ω is one viscosity:
7. Oc, p, 5 (25C) surface tension crab 4
F, F dine/am (25° C.) The content of polyvalent arbul in this case is 68.1ωtS. Injection t5~7
If it stopped for a minute, injection became impossible.

Example 2 An ink composition having the following composition and characteristics was prepared.

Composition: Ethylene glycol 8λ0ω monodistilled water
16.0ωtqb hydroxide f') J-(LIQH11 horse 01 0.2
(kl t flb kinematic viscosity = 6.5 centistokes (35°C), polyhydric aluminum content is 8.2.0 ωt. The injection suspension time until injection becomes impossible is approximately 30 minutes. The diameter of the ink dot on the recording paper is 150.
~200μ votes φ, and high-resolution recording was possible.

S An ink composition having the following composition and characteristics was prepared.

composition: Ethylene glycol 50. “0ωt%.

Diethylene glycol 35.0ωtS dye (C,
1, Reativ*176) 3. Oa+tt
s Distilled water 12.0 ωt Kinematic viscosity: 9.3 centistokes (35°C) Polyhydric alcohol content 85.0 ωt % 0 The injection suspension time before injection became impossible was about 1 hour. The results of the printing test were the same as in Example 2. An ink composition with the following composition and characteristics was prepared: Ethi, Rangelicol 63.0ω, Glycerin 19. ．． 0ωt% dye (e, 1.Re
actlveRed13) 2.5*t% distilled water
15.5ωt% Physical viscosity: 9.8 centistokes (35°C) Polyhydric alcohol content is 82.0ωtS. The results of the clogging test and printing test obtained were the same as in Example 2.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between relative water content and relative humidity at 70-80 degrees Fahrenheit for various glycols. Figure 2 is a graph showing the relationship between the kinematic viscosity of the ink composition and the meniscus vibration reduction time.

Claims (1)

[Claims] 1. An inkjet recording ink composition comprising a polyhydric alcohol, water and a dye. Ink composition 0 characterized by having a viscosity t- below Stokes