JPH0811302A - Application of liquid ink to paper piece - Google Patents

Abstract

PURPOSE:To enhance heat generating efficiency and to extend the life of a product by applying voltage to liquid ink and generating Joule heat by a current flowing through conductive particles and ejecting or raising the liquid ink from an orifice by the volumetric expansion of the liquid ink or the pressure due to the generation of an air bubble. CONSTITUTION:When voltage is applied across electrodes 41, 42, a current selects a place low in resistance to flow into liquid ink containing conductive particles. Since the electrodes 41, 42 and the conductive particles as well as mutual conductive particles become a contact state in an extremely small area and the resistance of a solvent is high, the concn. of a current is generated in the contact parts and large Joule heat is generated per a unit area. A temp. rise is generated by this Joule heat and the temp. of the liquid ink exceeds the b.p. of the solvent to generate small air bubbles and some air bubbles gather to become a large air bubble 9'' and a current passage 8'' larger in the concn. of a current is formed and the growth of the air bubble is generated with increasing speed by the mutual action of the generation and formation of the air bubble and the temp. rise due to the concn. of a current and the liquid ink rises from the leading end of an orifice 1 to be ejected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying liquid ink to a paper piece or the like for printing characters or image information on the paper piece or the like.

[0002]

2. Description of the Related Art As a conventional method for applying liquid ink to a piece of paper or the like, there is an ink jet method, and as this ink jet method, there is a method called bubble jet. In this method, as disclosed in JP-A-55-27281, a resistor is provided in the vicinity of the orifice, and heat generated by energizing the resistor is applied to the liquid ink in the flow path by heat conduction. The method is a method in which the liquid ink is instantly boiled into a gas to be extruded from the orifice by the pressure of bubbles generated.

Further, a method is also known in which an electrode is directly provided in the liquid ink of the flow path, and the liquid ink is ejected by discharge by applying a high voltage. For example, JP-A-46-47
As disclosed in Japanese Laid-Open Patent Publication No. 07-2007, this is a method in which electrodes are provided in the rear part of the flow path and the nozzle part, and a high voltage is applied to discharge in the liquid.

[0004]

However, in the recording method called the bubble jet, the heat generated from the resistor is transmitted to the flow path wall in addition to the liquid ink, and the heat transfer efficiency to the liquid ink is very good. It has the drawback of not having it. In addition, the method of ejecting the liquid ink by the above-mentioned discharge has the drawbacks that a high voltage drive circuit is required and thus the cost becomes high, and the electrode is rapidly deteriorated and the product life is short because of the discharge.

In view of the above circumstances, it is an object of the present invention to provide a method for applying liquid ink to a piece of paper or the like which has a high heat generation efficiency of liquid ink, and which makes it difficult for electrode deterioration to occur and prolongs product life. To do.

[0006]

In order to solve the above-mentioned problems, a method of applying liquid ink to a piece of paper or the like according to the present invention applies a voltage to a liquid ink containing conductive particles to remove the conductive particles. An electric current flowing through the liquid ink causes Joule heat in the liquid ink to raise the temperature, and the liquid ink is ejected or raised from the orifice by utilizing the pressure caused by the volume expansion of the liquid ink or the generation of bubbles, so that the liquid ink is ejected to a paper piece or the like. It is characterized by being added to.

Oil-based ink may be used as the liquid ink.

[0008]

According to the above construction, the liquid ink containing the conductive particles is used, and an electric current is applied to the liquid ink, and the liquid ink itself generates Joule heat to raise the temperature. Compared with the case where heat is applied to the liquid ink by conduction, the heat is suppressed from being conducted to, for example, the flow path wall, and the heat generation effect of the liquid ink with respect to the energy application amount can be improved. Further, since the electrode is only energized to the liquid ink and does not discharge, the electrode hardly deteriorates and the life can be extended.

If oil-based ink is used as the liquid ink, electrolysis due to application of electric current can be prevented.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

FIG. 1 is a block diagram of the vicinity of an orifice of a recording head in which the method of applying liquid ink to a piece of paper or the like according to this embodiment is carried out. The liquid ink 3 is stored in the flow path 2 near the orifice 1. Then, the electrodes 41,
42 is formed. An external power source 5 is connected to the electrodes 41 and 42 so that the liquid ink 3 can be energized.

FIG. 2 is a schematic diagram showing the flow of current and the generation of bubbles in the liquid ink 3 when a voltage is applied between the electrodes 41 and 42 from the external power source 5. The liquid ink 3 is a solvent 6 in which a large number of conductive particles 7 ... Are dispersed. As the solvent 6, for example, a non-electrolytic oil ink in which a colorant is dissolved is used.

When a voltage is applied between the electrodes 41 and 42, a current flows in the liquid ink 3, but this current tends to flow in a place having a small resistance. For example, the electrode 41
To the conductive particles 7 (71) in the vicinity thereof, and further through the conductive particles 7 (71) to the electrode 4 in the vicinity thereof.
By flowing into the other conductive particles 7 (72) on the second side, current paths 8 ... Are formed to the electrodes 42 that are arranged to face each other with the flow path 2 in between. Here, the electrodes 41, 42, the conductive particles 7, ..., And the conductive particles 7, 7 are in contact with each other in an extremely small area, and since the resistance of the solvent 6 is large, the concentration of the current at the contact portion is caused. Happens. Therefore,
Large Joule heat is generated per unit area.

Due to the Joule heat, the temperature rises, the solvent 6 eventually exceeds its boiling point, and small bubbles 9 are generated. For example, bubbles 9 (91) are generated between the electrode 41 and the conductive particles 7 (72), and bubbles 9 (92) are generated between the conductive particles 7 (71) and the conductive particles 7 (72). In this stage of FIG. 2, there is no single current path. That is, the electrode 4
The current paths 8 (81, 82, ...) Exist in a wide range between the conductive particles 7 ... Similarly, many small bubbles 9 are generated in a wide range.

FIG. 3 shows a state in which some of these small bubbles 9 are gathered to form a larger bubble 9 '. At this stage, the bubble 9'is smaller than the electrodes 41 and 42, so that there are still many current paths 8 '. However, FIG.
Since the volume occupied by the bubble 9'is larger than that in the step (3), the degree of concentration of the electric current is large.

When several bubbles 9'are gathered, a larger bubble 9 "is formed as shown in FIG. 4, and a current path 8" having a greater degree of current concentration is formed. Such bubble generation and growth, and temperature rise due to concentration of electric current interact with each other, and bubble growth occurs at an accelerated rate, the liquid ink 3 rises from the tip of the orifice 1, and finally FIG.
As shown in FIG. Then, the bubbles burst due to this jet, and the electrodes 41,
The temperature falls due to the inflow of air outside the orifice 1 and the supply of the liquid ink 3 from the rear of the flow path 2 between 42, and the bubbles contract or disappear, returning to the state of FIG.

As described above, when the liquid ink 3 containing the conductive particles 7 is used and an electric current is applied to the liquid ink 3, the liquid ink 3 itself generates Joule heat and its temperature rises. As compared with the case where the heat from the resistor is applied to the liquid ink by conduction as described above, the conduction of the heat to, for example, the wall of the flow path 2 is suppressed, and the heat generation effect of the liquid ink 3 with respect to the energy application amount is improved. You can Further, since the electrodes 41 and 42 only energize the liquid ink 3 and do not discharge it, the electrodes are less likely to deteriorate and the life can be extended.

Next, an example of the composition of the liquid ink 3 containing the conductive particles 7 ... And its ejection conditions will be described.

The liquid ink is composed of conductive particles (conductive filler), a resin binder, a solvent and an additive. Iron or carbon powder (average particle size of 0.1 to 2 μm) can be used as the conductive filler. As the solvent, diethylene glycol (boiling point 197 ° C., specific heat C _P = 0.56 cal / (g · ° C.), specific gravity ρ = 1.1 g
/ Cm ³ ) can be used.

The jetting conditions are as follows, assuming a 360 dpi specification. That is, the flow path is 50 μm × 50 μ
m. In this case, the dot diameter after printing is about 100 μm. The electrode shape is also 50 μm × 50 μm. Then, the energy E for raising the temperature of the volume (ν) of the solvent by the temperature (ΔT) is represented by the following Expression 1.

[0021]

[Equation 1] E = k × _CP × ρ × ν × ΔT (1)

Here, taking diethylene glycol as an example, its volume (ν) is set to 50 × 50 × 50 μm ^3, and the energy for raising the temperature by 200 ° C. is calculated by the formula 1
If k of k = 4.2 J / cal is calculated as follows.

[0023]

[Equation 2] E = 4.2 J / cal × 0.56 cal / (g · ° C.) × 1.1 g / cm ³ × (50 × 10 ⁻⁴ cm) ³ × 2 × 10 ² ° C. = 6.5 × 10 ⁻⁵ J

On the other hand, the condition for electrically obtaining the energy E is expressed by the following equation 2, where the applied voltage is V, the ink resistance is R, and the pulse width is t.

[0025]

[Equation 2] E = V ² / R × t (2)

Here, assuming that the applied voltage V is 26 V, the ink resistance R is 10 kΩ, and the pulse width t is 0.96 ms, the calculation is performed as follows, and the above-mentioned volume (ν) is 50 × 50 ×.
Energy to raise the temperature of 50 μm ³ of diethylene glycol by 200 ° C. is obtained.

[0027]

E = (26V) ² / (10 ⁴ Ω) × (0.96 × 10 ⁻³ s) = 6.5 × 10 ⁻⁵ J

In the above embodiments, the case of a single nozzle has been described, but a multi-structure having a plurality of nozzles arranged in the main scanning direction (a cross section perpendicular to the main scanning direction corresponds to FIG. 1) is used. It can also be applied to nozzles. Further, it is needless to say that the present invention can be applied to a case where printing is performed only by raising the liquid ink from the tip of the orifice without ejecting the liquid ink.

[0029]

As described above, according to the present invention, as compared with the conventional case where the heat from the resistor is applied to the liquid ink by conduction, the conduction of the heat to the flow path wall is suppressed. Therefore, the heat generation effect of the liquid ink with respect to the energy application amount can be improved. Further, since the electrode is only energized to the liquid ink and does not discharge, the electrode hardly deteriorates and the life can be extended. Further, if oil-based ink is used as the liquid ink, it is possible to avoid electrolysis during energization.

[Brief description of drawings]

FIG. 1 is a configuration diagram in the vicinity of an orifice of a recording head in which a method of applying liquid ink to a piece of paper or the like according to the present invention is carried out.

FIG. 2 is a schematic diagram showing the flow of current and the generation of bubbles in the ink when a voltage is applied between the electrodes in FIG.

FIG. 3 is a schematic diagram showing an initial stage in which some small bubbles that have been generated are collected and bubbles grow.

FIG. 4 is a schematic diagram showing how the degree of concentration of current increases as bubbles further grow.

FIG. 5 is a schematic diagram showing how liquid ink is ejected as ink droplets from the tip of an orifice.

[Explanation of symbols] 1 orifice 2 flow path 3 liquid ink 41, 42 electrode 5 power supply 6 solvent 7 conductive particles 8, 8 ', 8 "current path 9, 9', 9" bubble

Claims (2)

[Claims] 1. A volume expansion of the liquid ink by applying a voltage to the liquid ink containing the conductive particles and generating Joule heat in the liquid ink by the current flowing through the conductive particles to raise the temperature. Alternatively, a method of applying liquid ink to a paper piece or the like is characterized in that the liquid ink is applied to the paper piece or the like by ejecting or raising the liquid ink from an orifice by using the pressure generated by the generation of bubbles. 2. The method of applying liquid ink to a piece of paper or the like according to claim 1, wherein the liquid ink is an oil-based ink.