JPS6067161A - Liquid jet recording device - Google Patents

Abstract

PURPOSE:To prolong the life of a head significantly even if defective spots exist in a protective film as a heating means and improve the reliability of a finished product by providing an electrode giving an electric potential to liquid, thus controlling the electrode of liquid. CONSTITUTION:An electrode 16 is provided for giving an electric potential to liquid 12. As a result, it is possible to regulate the electric potential Vink of an electrode 16 through a power supply 17 and in turn, regulate the electric potential of liquid 12 so that a state where the electrochemical reaction of liquid 12 and a resistor 9 (or an electrode is controlled 10) may be created. That is, the electrochemical reactions won't advance significantly because of the electric potential of the resistor 9 (or the electrode 10) being higher than or not much different from that of the liquid 12 and the subsequent phenomenon to hamper a smooth flow of electric current. As a result, the life of the resistor 9 or the electrode 10 is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a liquid jet recording device that performs recording by forming flying droplets using heat generation.

[Prior Art] FIG. 1(a) is a plan sectional view showing an example of a conventional liquid jet recording head, and FIG. 1(b) is a sectional view taken along line AA in FIG. 1(a). In the same figure, a heat generating means, that is, an electric-thermal converting section (hereinafter referred to as 9 heat generating section) 2 and a conductive section 3 are formed on a substrate 1, and a protective film 9 (not shown) is formed thereon. Each of the zero heat generating parts 2 is partitioned by a grooved plate 4 to form a heat action chamber 5 and a liquid supply chamber 6. There is a discharge lower at one end of the heat action chamber 5,
The liquid is sprayed from here. The liquid to be injected is supplied through a liquid supply vibrator 8 provided on the opposite side from the discharge lower, and fills the liquid supply chamber 6 and the heat action chamber 5.

The ejection of liquid from the discharge lower is caused by heat generated by the heat generating section 2. The heat generating part 2 at the desired position is
When a predetermined pulse voltage is applied to the conductive part 3 to which the conductive part 3 is connected, heat is generated. When this voltage is applied, the liquid in the vicinity of the heat generating section 2 is instantaneously vaporized by the heat, and the bubbles thereof rapidly grow within the heat action chamber 5. Due to this pressure, the liquid on the ejection lower side is rapidly pushed out from the ejection lower, becoming flying droplets that adhere to the recording member and recording is performed.6Next, when the applied voltage is turned off, the bubbles rapidly disappear. Shrink and disappear.

In the liquid ejecting head that operates in this manner, a protective film is provided to prevent the nine heat generating means (heat generating section 2 and conductive section 3) from coming into contact with the liquid. FIG. 2 is an enlarged sectional view showing the vicinity of the heat generating section 2 of the liquid jet recording head shown in FIG. 1(b) in more detail. In the same figure, a resistor 9 and an electrode 10 are formed on a substrate 1, and the part where only the resistor 9 is located is the heat generating part 2 in FIG.
The overlapping portions of the electrodes 10 and 10 correspond to the conductive portions 3 in FIG. 1, respectively. The resistor 9 and electrode 10 serving as heat generating means are protected from the liquid 12 by an M retaining film 11.

When the resistor 9 and the electrode 10 come into contact with the liquid 12, they are altered by chemical reactions such as oxidation and electrolysis.
There is a risk of resistance value changing or wire breakage. For this purpose, a protective film 11 is provided. If this protective film 11 is complete, there is no problem, and the resistor 9 and electrode 10
is completely separated from the liquid 12, and a long life of the resistor 9 is guaranteed.

However, it is actually extremely difficult to form such an ideal protective film. In the normal manufacturing process, minute defect points 13 of several microns or less as shown in FIG. 2 inevitably occur in the protective film 11. Furthermore, it is known that the defective point 13 is caused in the protective IFJ t 1 due to thermal stress due to heat generated by the heat generating portion 2 of the resistor 9, as well as shock caused by the generation and disappearance of bubbles as described above. When the defective point 13 exists, the liquid 12 comes into contact with the resistor 9 and the electrode 10, and an electrochemical reaction occurs, but the reaction rate depends on the type of the resistor 9 and the electrode 10, the heat generation temperature of the resistor 9, And it varies greatly depending on the type of conductive ions in the liquid. However, if a defective point 13 occurs in the heat generating part 2 of the resistor 9, the heat generating part 2 of the resistor 9 will be destroyed and disconnected after only 105 to 106 voltages are applied, resulting in no practical durability. do not have. For practical use, it is necessary that the resistor 9 (particularly the heat generating part 2) and the electrode 10 be durable enough to not be damaged even if a pulse voltage is applied at least 108 times.

If the defective point 13 exists in the protective film 11 in this manner, the life of the heat generating portion 2 of the resistor 9 will be shortened, and as a result, the life of the head will also be shortened. This is because the time when one resistor is destroyed is also the end of the head's lifespan. However, as already mentioned, it is extremely difficult to completely eliminate the defect points 13. In addition, increasing the thickness of the protective films 7 and 11 must be avoided for reasons such as a decrease in thermal efficiency and a deterioration in thermal response to input signals. therefore,
In the production of conventional recording heads, it is inevitable that heads with short lifespans will be mixed in among the many heads, which has the problem of significantly reducing product reliability.

[Object of the Invention] The present invention has been made in view of the above-mentioned prior art, and its purpose is to make it practical even if the protective film of the heating means has the same level of defects as before. An object of the present invention is to provide a liquid jet recording device that has a long service life.

[Summary of the Invention] In order to achieve the above objects, a liquid jet recording device according to the present invention is provided with an electrode that applies an electric potential to the liquid.

It is characterized by controlling the liquid electrode to suppress conductive ions (anions, cations, H", OH-, etc.) in the liquid from causing electrochemical reactions with resistors and electrodes through defect points. .

[Embodiments of the invention] Hereinafter, two embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a schematic basic configuration diagram of an embodiment of a liquid jet recording apparatus according to the present invention, and FIG. 4 is a wiring diagram of this embodiment.

A voltage vh is applied to one end of the electrode 10 by a power source 14, and the other end of the electrode 10 is connected to a switching transistor 15 via the heat generating portion 2 of the resistor 9. The switching transistor 15 is turned on or off by a predetermined signal, and performs an operation of supplying a pulsed voltage to the heat generating portion 2 of the resistor 9. The configuration up to this point is the same as the conventional one, but in the present invention, the electrode 16 is in contact with the liquid 12.
A voltage (ink) is applied to the liquid 12 by a power source 17.

In a conventional liquid jet recording head that does not have an electrode 16 as shown, if a defective point 13 exists in the protective film 11, the potential of the liquid 12 becomes approximately the same level as the voltage vh supplied by the power source 14. For this purpose, the heating section 2 to which the voltage vh is applied
In part A, there was almost no potential difference between the liquid 12 and the electrochemical reaction between the liquid 12 and the resistor 9 or the electrode lo. When the switching transistor 15 is turned on, the potential of the portion B drops to near the ground voltage Vg, so that a potential difference of approximately Vh-Vg is generated between the portion and the liquid 12. Therefore, if the defective point 13 exists near part B, current will more easily flow through the defective point 13, and as a result, an electrochemical reaction will rapidly proceed between the resistor 9 and the liquid 12, and finally The resistor 9 is destroyed and the wire is disconnected.

However, the progress of electrochemical reactions due to defect points has not yet been fully elucidated. However, what is certain is that, as mentioned above, the potential of the liquid 12 is high and the resistor 9
(or the electrode 10), current easily flows from the liquid 12 to the resistor 9 (or the electrode 10),
In the opposite case, that is, when the potential of the resistor 9 (or the electrode 10) is higher than the potential of the liquid 12, it is difficult for current to flow.

Therefore, if the potential of the liquid 12 is higher, the resistor 9 (
Alternatively, the electrochemical reaction with the electrode 10) proceeds rapidly, and conversely, the potential of the resistor 9 (or electrode 10) increases with the liquid 1.
If the potential is higher than the potential of 2, or if there is not much difference, it is difficult for current to flow and the electrochemical reaction does not proceed much. As a result, the life of the resistor 9 (and the heat generating part 2) and the electrode 10 becomes longer. The present invention utilizes this phenomenon.

Electrodes 16 in FIGS. 3 and 4 are provided to apply an electric potential to liquid 12. Electrodes 16 in FIGS. For this purpose, by adjusting the potential Vink of the electrode 16 using the power supply 17, the liquid 1
It is possible to create a state in which the electrochemical reaction between the liquid 12 and the resistor 9 (or the electrode 10) is suppressed by adjusting the potential of the resistor 2.

Next, this will be demonstrated using specific experimental examples.

First, the relationship between the potential Vink and the life of the resistor will be investigated.

In Figure 3, a 5i02 thermal oxide film is placed on the St substrate at 5'
7zm is formed, and on top of that, tantalum Ta is formed as a resistor 9.
2,000 electrodes and 5,000 electrodes of gold (Au) were formed as the electrode 1o. Then, by photolithography process, 30pm x 100g
After forming a resistor pattern of T as a protective film 11,
I passed 5000 people on A205. However, in the two experimental examples, in order to create an S-retaining film with many defects, the diameter was approximately 3.
Dust on the order of micrometers was deliberately attached before forming the protective film.

For this reason, an average of 2 to 5 pieces of dust was observed on the formed resistor.

The thus-formed substrate was heated in an aqueous solution of Na (10.2 mol) with a pulse width of 10 g5ec, a frequency of 3KH2, and a voltage of Vh.
It was driven under the condition that =20V.

Gold (Au) was used as the electrode 16, and as shown in FIG. 3, it was used as an electrode opposite to the resistor 9. In this way, power supply 1
7 to change Vink and apply a pulse voltage to the resistor 9. Table 1 shows how many times the pulse voltage was applied to damage the heat generating part 2 (that is, the life span of the heat generating part 2).

Table 1 Table 1 D13, V i n k = 20V (7)
Since vh=Vink, the case of the conventional example is shown. Looking at the table, it can be seen that the lifespan tends to be longer when Vink is lower than 20V. This tendency was the same even when NiCr, ZrB2, HfB2, tantalum nitride, or the like was used for the resistor.

Next, a liquid jet recording head was actually produced, and the number of defective nozzles was measured when pulse voltage was applied 108 times. However, the protective film is made to have a thickness of 1JLm so as to reduce defects as much as possible. Other than these conditions, the conditions are the same as those in the previous experimental example. Also, the nozzle width of the created head is 40 g m
, 40 JLm high and 500 JLm long.

Looking at the change in defective rate in Table 2, it can be seen that the value of Vink is preferably in the range of -10 [V] to +10 [V]. In particular, in the range -10 [V] to OrV], the defective rate was zero, and Table 1 also shows a long life.

The above results will be explained using FIG. 5. In the same figure,
The vertical axis represents voltage, the horizontal axis represents time, and the rectangular curve represents the voltage change at the heat generating portion 2 of the resistor 9. A dotted line 18 represents the voltage at part A when current flows through the heat generating part 2, and a broken line 19 represents the voltage at part B. As already stated, the potential difference between portion B and vh is greater than that between portion B and vh.

The electrochemical reaction is suppressed when the potential V i n k of the liquid 12 is lower than the potential of the heat generating part 2, but as shown in previous experimental examples, favorable results cannot be obtained even if the potential difference is too low or the potential difference becomes large. I understand. Therefore, the range of Vink can be generalized and expressed as approximately the following equation.

Vg-A, (Vh-Vg)<Vink<Vg+A
(V h - V g) where Vg is the ground voltage and vh is the voltage applied to the heat generating part of the resistor. A is a coefficient, and it is desirable that A=0.5. That is, as shown in FIG. 5, VL・n
The range of k is ±0.5 around Vg (Vh-Vg)
The range is . In particular, the following equation, Vg-0,5(Vh-'Vg
)<Wink<'Vg, the most preferable result is selected.

FIG. 6 is a schematic diagram of an embodiment of a liquid jet recording apparatus according to the present invention. In this embodiment, an electrode 16 is inserted into a liquid tank 20 in order to apply an electric potential to the liquid.

[Effects of the Invention] As described above in detail, the liquid jet recording device according to the present invention controls the potential of the liquid, so there is no need to pay much attention to defects when creating the protective film, and it is more effective than the conventional method. This has the great effect of greatly extending the life of the head and improving the reliability of the product even if the same level of defects exists.

[Brief explanation of drawings]

FIG. 1(a) is a plan view of a -S fracture of a conventional example of a liquid jet recording head, and FIG. 1(b) is an A-A in FIG. 1(a).
2 is an enlarged partial sectional view of the vicinity of the heat generating part in FIG. The wiring diagram of this embodiment, FIG. 5 is a curve diagram showing the time change of voltage in the heat generating portion of the resistor, and FIG. 6 is a schematic configuration diagram of this embodiment. 9... fist resistor, 10 fist/meeting electrode, 11-... protective film
12. Fist liquid, 13. Defect point, 16. Life electrode. Figure 1 (Q) Figure 1 (b) Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) A liquid jet recording device that has a heat generating means and ejects liquid by the thermal action of the heat generating means, characterized in that an electrode in contact with the liquid is provided to apply a potential to the liquid. (2) The potential applied to the liquid is vg-o, where vh is the potential applied to the heating means and Vg is the ground voltage.
, 5 (vh-Vg), and Vg+0.5
The liquid jet recording device according to claim 1, wherein the liquid jet recording device is smaller than (Vh-Vg).