JPH06157958A - Ink jet recording ink - Google Patents

Abstract

PURPOSE:To provide the subject ink capable of stable ink jet recording by adding a small amount of a surfactant thereto. CONSTITUTION:This ink jet recording ink incorporated with an ionic surfactant and a salt bearing counterion common to that of the surfactant; or, incorporated with a nonionic surfactant and a salt with a large salting-out constant for the surfactant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drop-on-demand ink jet printer head ink.

[0002]

2. Description of the Related Art The largest factor that hinders high frequency driving of ink jets is the drawing of bubbles from the nozzle surface. When air bubbles are trapped, it becomes impossible to eject droplets from the head.

A specific description will be given with reference to FIG.
Is a part of the cross section of the liquid chamber parallel to the droplet discharge direction. There is no liquid film on the surface of the nozzle 1, and the meniscus 3 is largely drawn depending on the driving voltage and the driving frequency, and at that time, a phenomenon occurs in which bubbles are entrained in the flow chamber.

In order to prevent this, it has been proposed to improve the liquid contact property between the ink and the nozzle plate. In order to improve the liquid contact property between the ink and the nozzle plate, a surfactant is added to the ink. Although it is effective to add them, there is a limitation in the type and concentration of the activator due to the problem of image quality. In order to ensure stability, some activators require a considerable concentration, but adding a large amount of activator causes problems such as peeling of the adhesive that bonds the nozzle plate and head. Occurs, which is not preferable.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to provide an ink capable of stable ink jet recording with a small amount of a surfactant added.

[0006]

The constitution of the present invention for solving the above-mentioned problems is an ink for ink jet recording as set forth in the claims. That is, when an ionic surfactant is used as a surfactant, a salt having a common counter ion with the surfactant is used together, and when a nonionic surfactant is used, a salt having a large salting-out constant is used together. It is a recording ink.

Experiments have shown that the added activator concentration is effective when it is above the critical micelle concentration of the activator. This is because a liquid film is formed on the surface of the nozzle plate as described above, air bubble entrainment is reduced, and a large amount of activator (micelle) is present inside the ink, so that the free surface increases rapidly when forming a liquid column. It is expected that at this time, the activator migrates to the surface of the liquid column and the partial unevenness of the surface tension is eliminated.

However, from the viewpoint of image quality on paper, there are restrictions on the type of activator to be added, and the concentration of activator is also limited due to problems such as bleeding. Further, when a large amount of the activator is added, it penetrates into the adhesive and causes a problem such as separation of the nozzle plate.

As a result of several attempts to reduce the concentration of the added activator while ensuring the stability, the addition of a certain salt to the ink resulted in the formation of a large amount of micelles with a small amount of the activator added. It became possible, and it turned out that the same stability can be secured. It is presumed that this is because the addition of salt weakens the repulsive force due to the charge on the surface of the micelle, or the dehydration occurs around the activator, thereby lowering the critical micelle concentration.

When the activator is an ionic activator, a salt having a counter ion common to the activator is preferable, and when the activator is a nonionic activator, a salt having a large salting out constant is most suitable.

When Co is the critical micelle concentration of the activator and Cs is the salt concentration, in the case of an ionic activator, LOG (Co) = k.LOG (Co + Cs) + L k, L is a constant nonionic constant peculiar to the activator. In the activator, LOG (Co) =-Ks.Cs + L 'Ks is the salting-out constant and L'is the constant specific to the activator, and the critical micelle concentration decreases according to it, and the activator concentration necessary for ensuring stability decreases accordingly. To do. The type of activator, the type of salt, and the concentration depend on other substances contained in the ink (for example, dyes,
This cannot be generally stated because it is affected by the thickener), the quality of paper used, the head structure, the driving method, and the like.

The operation when the ink of the present invention is used will be described with reference to the drawings. FIG. 1 is a part of a liquid chamber cross section parallel to the droplet discharge direction. The material of the liquid chamber nozzle plate 1 is made of a material that has good liquid contact with the ink so that the meniscus can be easily moved between the nozzle surface and the inside of the nozzle. The member having good liquid contact property here means a material that has a small contact angle with ink and is easily wetted. Further, in order to improve the liquid contact property, a surfactant is added to the ink, and when not driven, a liquid film 2 having a thickness of several μm is formed on the nozzle surface.
To form. The presence of this liquid film 2 plays an important role in stability. Meniscus 3 depending on drive voltage and drive frequency
The entrainment of air bubbles is large, and at that time, a phenomenon occurs in which air bubbles are trapped inside the liquid chamber. For example, when a liquid film exists on the nozzle surface, the amount of the meniscus 3 drawn in is reduced by drawing ink from the liquid film 2, and the probability of entraining air bubbles inside the liquid chamber is greatly reduced. According to the present invention, even if the concentration of the activator is smaller than in the conventional case, the same effect as the above effect can be obtained.

For example, in the case of an activator called CTAB, in order to ensure stability, it was necessary to add 0.04 g / dl or more without salt, but by adding 0.05M NaBr, the amount of activator added was increased. It can be reduced to 1/3.

[0014]

As described above, according to the present invention, when a surfactant is added to the ink of an ink jet printer, stable ink jet recording is possible even if the concentration of the surfactant is small.

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section of a nozzle when an ink containing an activator is used,

FIG. 2 is a schematic view of a cross section of a nozzle when using an ink to which an activator is not added,

[Explanation of symbols]

 1 nozzle 2 liquid film 3 meniscus

Claims (2)

[Claims] 1. An ink-jet recording ink in which a surfactant is added to the ink, wherein the surfactant is an ionic surfactant, and a salt having a counter ion common to the surfactant is added. Ink for inkjet recording. 2. An ink-jet recording ink in which a surfactant is added to the ink, wherein the surfactant is a nonionic surfactant and a salt having a large salting-out constant is added. .