JPS6067163A - Liquid jet recording device - Google Patents

Abstract

PURPOSE:To reduce the breakdown rate of a resistor significantly and improve the reliability of the device even if defective spots exist in a protective film by providing an electrode giving an electric potential to liquid and also a resistor containing a specific amount of tantalum. CONSTITUTION:An electrode 10 for giving an electric potential to liquid 12 is provided and also a resistor 9 containing more than 30atom% of tantalum Ta is prepared. If the voltage Vink is set within a prearranged range, the surface of the resistor 9 is subjected to anodic oxidation through defective spots 13 in a protective film. Thus said surface is covered with an inert tantalum oxide with satisfactory results.

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, from which the liquid is injected. The liquid to be injected is supplied through a liquid supply pipe 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.Next, 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 9 heat generating means (heat generating section 2 and conductive section 3) from coming into contact with the liquid. Figure 2 is Figure 1(b)
FIG. 3 is an enlarged cross-sectional view showing in more detail the vicinity of the heat generating section 2 of the liquid jet recording head shown in FIG. In the same figure,
A resistor 9 and an electrode 1o are formed on the substrate 1,
The portion where only the resistor 9 corresponds to the heat generating portion 2 in FIG. 1, and the portion where the resistor 9 and the electrode 10 overlap corresponds to the conductive portion 3 in FIG. 1, respectively. The resistor 9 and electrode 10 serving as heat generating means are protected from the liquid 12 by a protective film 11 .

When the resistor 9 and the electrode 1o come into contact with the liquid 12, there is a risk that the resistance value may change or the wire may be disconnected as a result of deterioration due to chemical reactions such as oxidation or electrolysis. For this purpose, a protective film 11 is provided. If this protective film 11 is perfect, there is no problem, and the resistor 9 and electrode 1
o 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. Also,
It is known that defective points 13 are generated in the protective film 11 due to thermal stress due to heat generated by the heat generating portion 2 of the resistor 9, shocks caused by the generation and disappearance of bubbles as described above, and the like. 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.
The reaction speed depends on the type of resistor 9 and electrode lO,
It varies greatly depending on the heat generation temperature of the liquid, the type of conductive ions in the liquid, etc. However, if a defect point 13 occurs in the heat generating part 2, the heat generating part 2 of the resistor 9 will be destroyed and disconnected after only about 105 to 106 pulse voltages are applied, resulting in practical durability. does not have For practical use, it is necessary to have such durability that the resistor 9 (particularly the heat generating part 2) and the electrode 1O are not 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 way, 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. Furthermore, increasing the thickness of the protective film 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.

Furthermore, it is known that the life of a resistor also depends on the voltage applied to the heat generating part 2 of the resistor.

In fact, a liquid jet recording head is provided with a large number of nozzles, for example, 100 or more.

As described above, each nozzle has a built-in resistor, and in order to generate bubbles due to heat generation, it is necessary to apply a voltage equal to or higher than a predetermined value (threshold value) to the resistor. However, as the number of nozzles increases, it is inevitable that the characteristics of each resistor will vary. Therefore, in order to reliably generate bubbles in all nozzles, it is desirable to apply a voltage approximately 1.3 times the threshold voltage vh.

However, when the applied voltage is increased by 1.3 times, there is a problem in that the failure rate of the resistor increases much more than when applying an applied voltage of about a threshold value. For example, when the applied voltage is 1.3Vth, the applied voltage is l,
The failure rate is one order of magnitude higher than in the case of lVth. For this reason, with conventional heads, sufficient reliability can be ensured by driving the nozzles with an applied voltage of 1.3 Vth to ensure that the energy to eject the liquid is generated in all nozzles. The problem was that it was difficult.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional drawbacks, and its purpose is to solve the problem even if the protective film of the heating means has the same level of defects as the conventional one. It is an object of the present invention to provide a liquid jet recording device that has a long service life that can be put to practical use even when a sufficiently high voltage is applied to a resistor to ensure that liquid is jetted from a nozzle.

[Summary of the Invention] In order to achieve the above object, a liquid jet recording device according to the present invention is provided with an electrode for applying a potential to the liquid, and
The resistor is characterized in that it contains tantalum Ta at 30 atomic % or more.

[Embodiments of the invention] Hereinafter, nine embodiments of the present invention will be described in detail using the drawings.

FIG. 3 is a schematic 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 IO is connected to a switching transistor 15 via the heat generating portion 2 of the resistor 9. switching,
The 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, an electrode 16 is provided in contact with the liquid 12, and a voltage Vink 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 electrode #i14. For this reason, there was almost no potential difference between the liquid 12 and the liquid 12 in the A part of the heat generating part 2 to which the voltage vh was applied, and as a result, the electrochemical reaction between the liquid 12 and the resistor 9 or electrode 10 did not proceed so rapidly. . However, when the switching transistor 15 is turned on, the potential of the B portion drops to near the ground voltage Vg, so that a potential difference of approximately vh-vg is generated between the B 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 This leads to a situation where 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 IO) 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 electrode io) proceeds rapidly, and conversely, the potential of resistor 9 (or electrode IO)
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 (particularly the heat generating part 2) and the electrode 1O 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 liquid 12 and the resistor 9 (or the electrode 10).

Next, the material of the resistor 9 will be explained using a specific experimental example.

In FIG. 3, a 5i02 thermal oxide film is formed for 5 m on the SL substrate, and a resistor 9 is placed on it at 200oA and an electrode lO2.
As a result, 5,000 gold Au members were formed. After forming a resistor pattern of 30 gm
0 people spattered.

However, in the 9th experimental example, in order to create a protective film with many defects, dust with a diameter of about 3 pm was intentionally attached before creating the protective film. For this reason, an average of 2 to 5 pieces of dust was observed on the formed resistor. The electrode 16 that applies a potential to the liquid was made of gold (Au), and served as an electrode opposite to the resistor 9.

As the liquid 12, a 10.2 mol Na aqueous solution was used.The threshold voltage vth varies depending on the material, shape, etc. of the resistor 9, but in the case of the resistor used in this example, the vth was 18V to 2.
It was 5V. In this embodiment, the threshold voltage vt
The voltage V in applied to the electrode 16 at a voltage 1.3 times h, a pulse width of 10 pLsec, and a driving frequency of 3 KHz.
The defective nozzle rate (destruction rate of the resistor) was measured after applying a pulse voltage to the resistor 108 times while changing k. The results are shown in Table 1.

Table 1 In Table 1, the higher the tantalum Ta content, the lower the destruction rate of the resistor 9 in the range of the master voltage V in k from -10 (V) to 0 (V). Especially tantalum T
The a content is 30 at% or more and Vink is -10 (V)
-O(V), very good results were obtained.

The higher the tantalum content of the resistor, the better the results obtained.The reason why the surface of the resistor 9 is anodized through the defect point 13 of the protective film 11 when vink is -1O(V) to 0(V) This is because it is coated with inert tantalum oxide. Utilizing this phenomenon, it is possible to significantly reduce the destruction of the resistor caused by the defect points 13. In other words, even if a defective point occurs during the manufacturing process of the protective film 11 and a new defective point occurs due to impact when the bubble disappears, Vink can be controlled within the range of -10 (V) to 0 (V) +7). Then, since the surface of the resistor 9 is anodized, the resistor 9 is covered with an inert film, making it difficult for electrochemical reactions to proceed as in the conventional case.

[Effects of the Invention] - As described in detail above, the liquid jet recording device according to the present invention uses a protective film to form an inert film by anodic oxidation on the surface of the resistor by applying a desired potential to the liquid. This has the great effect of significantly reducing the failure rate of the resistor and improving reliability even if the same level of defect points exists as in the conventional method.

[Brief explanation of the drawing]

FIG. 1(a) is a partially cutaway plan view 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. 1(b), FIG. 3 is a basic configuration diagram of an embodiment of the liquid jet recording device according to the present invention, and FIG. 4 is a diagram of the present embodiment. FIG. 3 is an example wiring diagram. 2・ψ・Heating part, 9Φ・Resistor, 10・Electrode, l
l...protective film, 12...liquid. 13φ・Fist defect point, 16・・Fist electrode. Figure 1 ((1) Figure 1 (b) Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) In a liquid jet recording device in which a resistor generates heat and ejects a liquid by the thermal action, an electrode is provided for applying a potential to the liquid, and the resistor contains tantalum Ta at 30 atomic % or more. A liquid jet recording device characterized by: