JPS60115450A - Inkjet printer - Google Patents

Abstract

PURPOSE:To provide an ink jet printer which can almost uniformize the reflective concentration even in a printing medium with a different water absorptivity by adjusting the liquid temperature of ink stored in an inkjet printing head according to the water absorptivity of the printing medium. CONSTITUTION:For example, a Peltier element 15 is attached to an on-demand type inkjet print head 1 equipped with a piezo-electric vibration plate 2 and cooled or heated depending on the direction of current flowing through the element 15. Then, the setting point of the Peltier element 15 is adjusted according to the absorptivity of a printing medium for printing with ink drops 11 injected from the head 1 to regulate the liquid temperature of ink in the head.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an inkjet printing device that prints an arbitrary image on the surface of a printing medium using minute ink droplets.

(B) Prior art In an inkjet printing device that prints an arbitrary image on the surface of a printing medium by depositing minute ink droplets, one of the factors that determines the printing quality of such printing device is: Printing is performed while maintaining a predetermined relationship between the ink droplets of the adjacent pixels without causing the ink droplets of adjacent pixels to greatly overlap each other on the surface of the printing medium, or conversely, to avoid wide separation between the ink droplets of the adjacent pixels. It is adhesion to the surface of the medium.

However, the size of adhering ink droplets on the surface of the printing medium is greatly affected by the water absorption of the printing medium even when driven under the same driving conditions, and as a result, pixels adjacent to the surface of the printing medium with different water absorption It is difficult to make ink droplets of a size that maintain a predetermined relationship with each other.
Since the reflection density becomes uneven, printing quality inevitably deteriorates.

9. Purpose of the invention The present invention has been made in view of this point.

The purpose is to provide improved image printing with substantially uniform reflection density on printing media of different water absorption properties.

(B) Structure of the Invention The inkjet printing apparatus of the present invention, which ejects minute ink droplets from the ink hole toward the printing medium, adjusts the liquid temperature of the ink contained in the ink hole to the ink. The configuration is such that control is performed based on the water absorbency of the printing medium to which the droplets are attached.

(E) Embodiment FIG. 1 shows the inkjet printing device of the present invention during printing operation, and (1) shows the horn-shaped displacement amplification of on-demand minute vibration displacement of the piezoelectric diaphragm (2). Through chamber (3) °C
A small ink chamber (5) located 11 in front of the passive vibrating plate (4) and having a thickness of less than 1'ILm and containing the ink to be ejected. The ink column (7) is entirely protruded from the first orifice (61) by applying an amplified minute vibration displacement of the ink≦2, and the ink column (7) protruding from the first orifice (6) is The kinetic energy and surface tension acting on the ink column (7) and the air added toward the center from the air pump (9) to the front chamber (8) provided in front of the first orifice (6) Together with the flow aO1, the ink droplet (11) becomes an ink droplet (11), and finally the first orifice (
The liquid is discharged from the second orifice (12), which is coaxially drilled with the opening diameter of the second orifice (12) and has a diameter approximately twice that of the second orifice (12).

(13) is a printing medium to which the ink droplets (11) adhere after flying.

(14) A cylindrical drum that winds the printing medium (131) and main scans the medium in the rotational direction is used to apply the ink (11
is sub-scanned in a direction (axial direction of the cylindrical drum) perpendicular to the main scanning direction of the drum (141) by a carriage (not shown).

(In L9, one end surface (15a) is reversed from a heating state to a cooling state by switching the current direction.

This is a Vertier element that utilizes the Peltier effect in which the other end surface (zsb) changes from cooling to heat generation state, and the one end surface (15a) of the Vertier element (151) has an inverted-shaped heat generating state as shown in FIG. The conductor 1 is fixed to the bottom surface (16a) of a support (10) made of aluminum, for example, and has a U-shaped notch (
By screwing the planted surface (16c) provided with ISb) to the back surface of the helitopody αη, the Bertier element (19) and the helitopody aη are coupled with each other with good thermal conductivity.On the other hand, the Bertier element αS The other end surface (15b) has a radiation fin a9 for promoting heat dissipation from the other end surface (15b) when the other end surface generates heat, that is, when the one end surface (15a) cools down.
is bonded to the integrally formed good heat conductive plate gloss in a good heat conductive manner. Therefore, the Bertier element (151) generates heat and cools, and therefore acts as a heating and cooling element that heats and cools the ink in the ink head (1).

It is known that the viscosity of aqueous ink generally decreases in inverse proportion to temperature rise, as shown in FIG.

The main feature of the present invention is that it utilizes the temperature characteristics of ink viscosity. Specifically, in the inkjet printing apparatus of the present invention, in order to cause ink droplets of a predetermined size to adhere to the surface of the printing medium (131), the ink is Controls the temperature of the ink contained in the head (1).

Specific examples are described below.

Coated paper (hereinafter referred to as coated paper) whose surface is coated with white clay or the like and uncoated paper (hereinafter referred to as plain paper) are prepared as printing media having different water absorption properties.

In order to investigate the water absorption properties of these two types of printing media aJ.

An ink whose viscosity change has temperature characteristics as shown in Fig. 3 1 above is supplied to the ink by the operation of the Bertier element aQ in a state where the liquid temperature of the ink is maintained at 25°C. When ink droplets ai were ejected from the first orifice (61) with an opening diameter of 40 μm under the same driving conditions, 100 ink droplets were ejected on the coated paper and plain paper surfaces respectively.
The deposition of ink droplets of ~120 μm and 153-200 μm was obtained. In other words, even though ink droplets (111) of the same diameter are ejected from 9 dots (1) to the ink, on coated paper, ink droplets with a minute diameter of 100 to 120 μm adhere to the surface of the paper. Ink droplets of 150 to 200 μm adhere to plain paper.

On the other hand, the cross section of the ink droplet adhering to the surface of the printing medium (131) is as shown in Figure 4 (M). On the other hand, it penetrates deeply in the thickness direction, as shown in Figure 4 (B
The ink droplet (11b) on the plain paper (1, b) of 1 spreads in the surface direction along with the coated paper and does not reach deeply in the thickness direction.

Therefore, even if ink droplets a11 of the same size are attached to one surface, the coated paper (13a) has a large penetration in the thickness direction, so the reflection density will be higher than that of the plain paper (13b). need to be considered.

This is because the reflection density of ink droplets ejected under the same driving conditions on the printing medium αλ differs between coated paper (13a) and plain paper (13b).

The Bertier element αω is operated to generate heat or cool, and the liquid temperature of the ink contained in the ink head (1) is set to a predetermined value. Specifically, the viscosity change of the ink used exhibits the temperature characteristics shown in FIG.

The attached diameters of ink droplets (11a) and (11b) at a liquid temperature of 25°C are 100 to 120 μm and 150 to 2 [10 μm, respectively.
When using coated paper (13a) or plain paper (13b) as the printing medium (131), when using the coated paper (13a), the liquid temperature of the ink is reduced to about 25% by the heating or cooling operation of the Beltier element (151). Keep it at °C and keep it on plain paper (
13b) is set at approximately 14°C.

As a result of ejecting ink droplets Ut under the same conditions except that the liquid temperature of the ink was about 25°C and about 14°C, an ink droplet (11B) of about 100 to 120 μm was formed on the surface of about 2500 coated paper (13a). Plain paper (131: +
) On surface C, slightly larger ink droplets (11b) of approximately 100 to 140 μm were deposited. That is, the printing medium (L
Considering not only the adhesion diameter of the ink droplets (11a) and (11b) on 31 but also the difference in the penetration depth in the ink thickness direction, the adhesion diameter of the plain paper (13b) is slightly thicker (as much as possible, the ink droplets are slightly thicker). (Setting the temperature of the ink in step 11 by the Bertier element (151)) Effects of the Invention As is clear from the above description, the inkjet printing device of the present invention adjusts the temperature of the ink stored in the ink heave to the ink droplets. is controlled based on the water absorbency (-) of the printing medium to which it should adhere, so even if printing media with different water absorption properties are used, variations in the size of the attached ink droplets are prevented and the reflection density is almost uniform. It is possible to provide a copy of the image.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is a sectional view of the main part, Fig. 2 is an exploded perspective view, Fig. 3 is a temperature characteristic diagram of ink viscosity,
Figure 4(B) shows a cross-sectional view showing the state of ink adhesion on coated paper, and Figure 4(B) shows a cross-sectional view showing the state of ink adhesion on plain paper. +11... Ink head , (111...ink droplet,
0...printing medium, <151...Bertier element.

Claims (1)

[Claims] (1) In an inkjet printing device that ejects minute ink droplets from one ink droplet to another toward a printing medium, the liquid temperature of the ink contained in the ink droplet is An inkjet printing device characterized by control based on the water absorption of the printing medium to which it is attached.