JP2000290551A - Ink jet printing ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printing ink which prevents clogging in ink passages such as a nozzle of high speed ink jet printers. SOLUTION: The titled ink contains a water-soluble polymer compound and a water-soluble organic solvent, wherein the water-soluble organic solvent comprises at least two solvents and accounts for 30% or more of the ink in total. Preferably, the water-soluble organic solvents account for 40% or less of the ink in total and comprises two or three solvents. Furthermore, at least two of the water-soluble organic solvents have a vapor pressure at 20 deg.C of 1 hPa. A water-soluble polymer compound which is in a solid state at 25 deg.C may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording ink used for an ink jet printer, and more particularly to an ink composition capable of forming ink droplets stably without clogging.

[0002]

2. Description of the Related Art An ink jet printer has advantages such as low noise, low running cost, and easy color printing. 2. Description of the Related Art In recent years, as an ink jet printer has spread as a digital signal output device such as a computer, high-speed printing has been desired more than an electrophotographic printer. Recording inks used in this high-speed printing inkjet printer include inks mainly composed of water-based dyes, pigments and the like.

[0003] Inks mainly containing water-based dyes are widely used because of their color developing properties during color printing and the effect of the solvent in the ink on the human body and the environment is small.

[0004] Such water-based inks can stably form uniform ink droplets during high-speed printing, and do not cause clogging of head nozzles due to deposition of solid components such as dyes due to long-term suspension of the printer. Is required.

In a conventional ink jet recording apparatus, it is desirable that the viscosity is somewhat high in order to discharge uniform ink droplets at high speed. Therefore, it is necessary to optimize physical properties such as viscosity and surface tension. Has been done. For example, the viscosity is adjusted by adding a water-soluble polymer compound to the ink, and the precipitation of solid components is reduced by adding a water-soluble high-boiling organic solvent as a wetting agent.

[0006]

However, among the water-soluble high-molecular compounds used as viscosity modifiers, low-molecular-weight substances must be added in large amounts to obtain the desired viscosity. Such an ink containing a large amount of a substance having a high water retention rate causes the printing portion to dry slowly, and in multicolor printing, bleeding occurs at the boundary portion, resulting in deterioration of image quality. For this reason, it is necessary to use a polymer compound as a viscosity modifier. However, while the high molecular weight substance can reach the target viscosity with a small amount, there are many solid substances at normal temperature and solid components precipitate out when stored as ink for a long period of time, which causes a problem of ejection failure.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an ink jet recording ink for preventing clogging in an ink flow path such as a nozzle of a high-speed ink jet printer.

[0008]

In order to achieve the above-mentioned object, an ink jet recording ink according to the present invention contains a water-soluble polymer compound and a water-soluble organic solvent, and the water-soluble organic solvent contains at least 2 30% or more in total and in total. At this time, the total content of the water-soluble organic solvent was 40
% Is desirable. Further, it is desirable to contain two or three of the water-soluble organic solvents.

In addition, the ink for ink jet recording according to the present invention is preferably such that at least two of the water-soluble organic solvents
1 hour at 20 ° C with a water-soluble organic solvent
Pa or less.

Further, the ink for ink jet recording according to the present invention may contain 25 ° C. as the water-soluble polymer compound.
Can be used.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) The ink composition of the present invention will be described below.

In the ink of the present invention, various water-soluble dyes are used as a coloring agent. Examples thereof include C.I.
I. direct. Yellow 86, 132, 144, C.I.
I. direct. Red 227, C.I. I. direct.
Blue 199, C.I. I. direct. Direct dyes such as black 154, C.I. I. Acid. Yellow 23, C.I.
I. Acid. Red 52, C.I. I. Acid. There are acid dyes such as Blue 9, basic dyes, and reactive dyes, each of which is used alone or in combination. The preferred addition amount of these coloring agents is 0.1 to 5% by weight.

The water-soluble polymer compound used as a viscosity modifier includes polyvinyl alcohol, polyethylene glycol, carboxymethyl cellulose, polyvinyl pyrrolidone and the like. The preferred addition amount of these viscosity modifiers is 0.1 to 20% by weight.

A water-soluble organic solvent used as a wetting agent is compatible with water, and is used to improve the solubility of solvents or dyes having low solubility in water such as a viscosity modifier, or to prevent nozzle clogging due to drying of ink. , Ethylene glycol, diethylene glycol, glycerin,
Propylene glycol, 1,3-propanediol,
1,4-butanediol, glycols such as 1,5-pentanediol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, Triethylene glycol monomethyl ether,
Glycol ethers such as triethylene glycol monobutyl ether, 2-pyrrolidone, N-methyl-2-
It can be appropriately selected from pyrrolidone, diethanolamine, triethanolamine and the like, and the amount used is preferably 1 to 40% by weight based on the total amount of the ink.

It is also possible to add a surfactant to the ink as a surface tension modifier, such as an anionic surfactant, an amphoteric surfactant, a cationic surfactant, a nonionic surfactant, and the like. There is.

Further, inorganic salts such as lithium hydroxide, sodium hydroxide and potassium hydroxide and amines such as morpholine may be added as a pH adjuster.

Next, examples and comparative examples in the first embodiment will be described. The present invention is based on the types and combinations of the wetting agents, viscosity modifiers, dyes and the like shown in these examples and comparative examples. It is not limited.

Example 1 An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 10.0 parts by weight 1,5-pentanediol 10.0 parts by weight Polyethylene glycol (20,000) 1.0 weight part ion-exchanged water remaining part (Example 2) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 10.0 parts by weight 1,5-pentanediol 15.0 parts by weight Polyethylene glycol (20,000) 1.0 part by weight ion-exchanged water remaining part (Example 3) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight 1,5-pentanediol 15.0 parts by weight Glycerin 15.0 parts by weight Polyethylene glycol (20,000) 1.0 part by weight Ion-exchanged water remaining part ( 0.2 ml of each of the inks of Examples 1) to (Example 3) was weighed into a 7 cm diameter petri dish, spread evenly, and allowed to stand for one week in the open to the atmosphere to precipitate solid components of the dye and the viscosity modifier. The presence or absence was checked.

A test using this petri dish will be described. Usually, the printer has a mechanism for sealing the head by covering the head with a cap or the like, but it is not always possible to seal the head. Therefore, there is a possibility that the ink droplets adhere to the orifice surface such as the head nozzle and solidify. In such a case, the reliability of stable ejection of the ink is deteriorated due to bending of the ink ejection. In this case, a petri dish is regarded as an orifice surface, and the state of ink droplets is confirmed.

Comparative Example 1 An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Ion-exchanged water The remainder (Comparative Example 2) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 10.0 parts by weight Deionized water The remainder (Comparative Example 3) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Polyethylene glycol (20000) 1.0 parts by weight Ion-exchanged water Remainder (Comparative Example 4) It was adjusted. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 10.0 parts by weight Polyethylene glycol (20,000) 1.0 part by weight Ion-exchanged water remaining part (comparative) Example 5) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 10.0 parts by weight 1,5-pentanediol 5.0 parts by weight Polyethylene glycol (20,000) 1.0 part by weight ion-exchanged water remaining part (Comparative Example 6) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 15.0 parts by weight Polyethylene glycol (20,000) 1.0 part by weight Ion-exchanged water remaining Example 7) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Diethylene glycol 30.0 parts by weight Polyethylene glycol (20000) 1.0 part by weight Ion-exchanged water Remaining Ink of Comparative Examples 1 to 7 For each of them, a test using a petri dish was performed in the same manner as in (Example 1) to (Example 3). Table 1 shows the test results of (Example 1) to (Example 3) and (Comparative Example 1) to (Comparative Example 7).

[0021]

[Table 1]

From the results in Table 1, the following can be understood. In the case of one type of wetting agent: solid components are precipitated regardless of the presence or absence of the viscosity modifier and the total amount of the wetting agent (Comparative Example 1,
3, 7). When the viscosity adjusting agent is not added in a mixed system of two types of the wetting agent: Even if the total amount of the wetting agent is less than 30%, no solid component is precipitated (Comparative Example 2). When the viscosity modifier is added in a mixture of two types of wetting agents:
When the total amount of the wetting agent is 30% or more, no solid component precipitates (Example 3). When the viscosity modifier is added in a mixture of two types of wetting agents:
If the total amount of the wetting agent is less than 30%, solid components are precipitated (Comparative Examples 4 and 6). When the viscosity modifier is added in a mixture of three types of wetting agents:
When the total amount of the wetting agent is 30% or more, no solid component is precipitated (Examples 1 and 2). When the viscosity modifier is added in a mixture of three types of wetting agents:
When the total amount of the wetting agent is less than 30%, solid components are precipitated (Comparative Example 5).

The above results show that when no viscosity modifier is added, solid components do not precipitate even if the total amount is less than 30% when two types of wetting agents are used, but when the viscosity modifier is added, the wetting agent is not precipitated. Unless two or more types and the total amount is 30% or more, it indicates that solid components are precipitated. That is, by using two types of wetting agents, the solubility of the solid component increases due to compatibility, but if the total amount of the wetting agents is less than 30%, sufficient solubility cannot be obtained. The same applies to the case where the type is used.

The reason why the humectant is required to be 30% or more will be described. Evaporation of water is the largest under the atmosphere. The polymer compound (high-molecular-weight polyethylene glycol) used as a viscosity modifier is easily soluble in water, but is a solid at 25 ° C., so that when water evaporates, a solid component precipitates. Therefore, evaporation of moisture is suppressed by adding a wetting agent. Further, the wetting agent that hardly evaporates has an affinity with polyethylene glycol, and suppresses precipitation when the water content is reduced. If the total amount of the wetting agent is less than 30%, these effects are not sufficient.

Although not shown in Table 1, when the total amount of the wetting agent exceeds 40%, the bleeding of the printing result becomes large and the water resistance is remarkably reduced, so that it is not practical.

Further, although no tests have been conducted, it is expected that no solid component will precipitate if the total amount is 30% or more even when four or more types of wetting agents are used. Not a target.

Therefore, when two or more types of wetting agents are used and the total amount is 30 to 40%, even if a high-molecular-weight viscosity modifier is used, the precipitation of solid components is suppressed for a long time, and the printing result is good and water resistance is high. Excellent ink can be obtained. At this time, if two or three types of wetting agents are used, a desirable ink can be obtained from the viewpoint of manufacturing cost and the like.

When the ink for ink-jet recording obtained in the first embodiment is used in a high-speed ink-jet printer, clogging of the ink in an ink flow path such as a head nozzle is prevented, and ejection conditions of ink droplets (surface tension) etc)
Can be widened, and the reliability in stable ejection can be improved.

(Second Embodiment) The first embodiment has shown that the precipitation of solid components can be suppressed by using two or more water-soluble organic solvents as the wetting agent.
However, when the organic solvent used has a high vapor pressure, for example, in a high-temperature environment, the solvent itself is easily evaporated, which causes a solid component to precipitate. The use environment of the ink jet printer is not always at room temperature, and for example, use in an environment near 40 ° C. is also conceivable. Therefore, under such conditions, the evaporation of the ink used for this becomes remarkable. In particular, as shown in the first embodiment, in the case of a high-viscosity type ink using a viscosity modifier that is solid at ordinary temperature, the solubility of the solid component may be reduced due to evaporation of the solvent and may be precipitated. The same problem occurs if the device is left open to the atmosphere for a long time even at room temperature. Therefore, the second embodiment focuses on the vapor pressure of the organic solvent,
A more effective method for selecting an organic solvent will be described.

Examples and comparative examples according to the second embodiment will be described below, but the present invention is limited to the types and combinations of the wetting agents, viscosity modifiers, dyes and the like shown in these examples and comparative examples. It is not something to be done.

Example 4 An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 10.0 parts by weight Glycerin 10.0 parts by weight Polyethylene glycol (20,000) 1.0 part by weight Ion-exchanged water: balance (Comparative Example 8) An ink was prepared according to the following formulation. C. I. Food Black 2 2.0 parts by weight Ethylene glycol monoethyl ether 10.0 parts by weight Diethylene glycol 10.0 parts by weight Cyclohexanol 10.0 parts by weight Polyethylene glycol (20,000) 1.0 part by weight Part Ion-exchanged water Remaining part Table 2 shows the vapor pressure of the wetting agent used in each of the inks of (Example 1), (Example 4) and (Comparative Example 8).

[0032]

[Table 2]

Considering that the vapor pressure increases at high temperatures, the following can be seen from Table 2. Diethylene glycol, glycerin and 1,5-pentanediol all have a vapor pressure of 1 hour at 20 ° C.
It is less than Pa (low vapor pressure). Cyclohexanol and ethylene glycol monoethyl ether have a vapor pressure of 1 hPa or more at 20 ° C. (high vapor pressure).

The above ink was applied to a petri dish having a diameter of 7 cm.
2 ml was weighed, spread uniformly, and allowed to stand for 10 days in the open to the atmosphere, and the presence or absence of solid components of the dye and the viscosity modifier was examined. Table 3 shows the test results of (Example 1), (Example 4) and (Comparative Example 8). Although not shown in Table 3, no precipitation was observed in any of the examples when left for one week.

[0035]

[Table 3]

Tables 2 and 3 show the following. When two of the three types of humectants used had a low vapor pressure, no solid component was precipitated (Examples 1 and 2).
4). When two of the three wetting agents have a high vapor pressure, solid components are precipitated (Comparative Example 8).

That is, no solid component was precipitated in any of the examples when left for one week, but the solid component was deposited in (Comparative Example 8) when left for 10 days. Considering the chemicals used and their vapor pressure, ethylene glycol monoethyl ether is (Example 1)
Although used in both (Example 4) and (Comparative Example 8), the vapor pressure at 20 ° C. was high and one of the three types was used.
It can be seen that even if a chemical having a high vapor pressure is used, no solid component is precipitated. Focusing on the other two types of wetting agents, cyclohexanol having a high vapor pressure was used for one of them (Comparative Example 8).
Because of the above, they are easily evaporated, and sufficient moisture retention cannot be secured.

Therefore, when two of the three wetting agents having low vapor pressure (less than 1 hPa at 20 ° C.) are used, no solid component is precipitated, but only one of the three wetting agents is used. When a material having a low vapor pressure is used, it can be said that a solid component is precipitated. That is, when a chemical having a high vapor pressure is used for two of the three types of wetting agents, solid components are precipitated. Therefore, it is necessary to use a chemical having a low vapor pressure for at least two types.

Polyethylene glycol used as a viscosity modifier is easily soluble in water but is solid at 25 ° C.
When the water evaporates in this manner, a solid component precipitates. Therefore, if a large amount of a wetting agent having a high vapor pressure is used in the mixed system,
When left for a long period of time, the humectant evaporates together with the water, and the solubility of the solid component is reduced to cause precipitation.

When the ink for ink-jet recording obtained in the second embodiment is used in a high-speed ink-jet printer, clogging of the ink in an ink flow path such as a head nozzle is prevented, and ejection conditions of ink droplets (surface tension) etc)
Can be widened, and the reliability in stable ejection can be improved.

[0041]

As described above, the invention according to claim 1 of the present application provides a water-soluble organic solvent used as a wetting agent in a total amount of 30% or more, so that a water-soluble organic solvent can be used as a viscosity modifier. Even when a polymer compound is used, there is the effect that solid components do not precipitate for a long period of time in the open to the atmosphere, and a highly viscous and highly reliable inkjet recording ink can be obtained. The invention according to claim 2 of the present application has an effect that water resistance can be maintained by setting the total amount of the water-soluble organic solvent used as the wetting agent to 40% or less. Further, the invention according to claim 3 of the present application has an effect that it is possible to prevent an increase in cost due to an increase in the number of types of the wetting agent by using two or three types of water-soluble organic solvents used as the wetting agent. .

The invention according to claim 4 of the present application is directed to claim 1 or 2 by using a water-soluble organic solvent having a vapor pressure of 1 hPa or less at 20 ° C. for at least two of the wetting agents. As compared with the present invention, precipitation of solid components due to evaporation of a water-soluble organic solvent can be suppressed for a longer period of time, and there is an effect that an inkjet recording ink with further improved reliability can be obtained.

Further, the invention according to claim 5 of the present application is characterized in that:
The use of a polymer compound that is solid at 5 ° C. (eg, high molecular weight polyethylene glycol) as a viscosity modifier has the effect of obtaining a desired viscosity with a small amount and maintaining water resistance.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuru Kishimoto 4-11-22 Shibaura, Minato-ku, Tokyo Inside the company offshore data (72) Inventor Hideyuki Kobayashi 4-11-22 Shibaura, Minato-ku, Tokyo Shares F term (reference) in company offshore data 2C056 FC01 2H086 BA51 BA53 BA59 BA60 BA62 4J039 AB02 AD06 AD23 AE07 BC07 BC09 BC13 BC35 BC36 BC50 BE12 BE22 BE23 CA03 EA10 EA38 EA41 EA44 EA47 GA24

Claims (5)

[Claims] 1. An ink jet recording ink containing a water-soluble polymer compound and a water-soluble organic solvent, and containing at least two kinds of the water-soluble organic solvents in a total amount of 30% or more. 2. The ink jet recording ink according to claim 1, wherein the ink contains 40% or less of the water-soluble organic solvent in total. 3. The ink jet recording ink according to claim 1, wherein the ink contains two or three types of the water-soluble organic solvent. 4. At least two of said water-soluble organic solvents
Vapor pressure of water-soluble organic solvents of 1 hP at 20 ° C
The inkjet recording ink according to any one of claims 1 to 3, wherein a is equal to or less than a. 5. The ink jet recording ink according to claim 1, wherein the water-soluble polymer compound is solid at 25 ° C.