JP2698418B2 - Liquid jet recording head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid jet recording head, and more particularly, to a structure of a heat storage layer in a heat generating portion of a bubble jet type ink jet recording head.

2. Description of the Related Art Non-impact recording methods have recently attracted attention in that the generation of noise during recording is extremely small to a negligible level. Among them, the so-called ink jet recording method, which can perform high-speed recording and can perform recording on so-called plain paper without requiring a special fixing process, is an extremely powerful recording method. Some have been proposed and commercialized with improvements, while others are still being put to practical use.

In such an ink jet recording method, droplets of a recording medium called so-called ink are made to fly and adhere to a recording member to perform recording. The control method for controlling the flying direction of the generated recording liquid droplet is roughly classified into several types.

First, the first method is disclosed in, for example, US Pat. No. 3,060,429 (Tele type method), in which droplets of a recording liquid are generated by electrostatic attraction, and the generated recording liquid droplets are removed. The electric field is controlled in accordance with a recording signal, and recording is performed by selectively adhering small droplets of a recording medium onto a recording member.

More specifically, in more detail, an electric field is applied between the nozzle and the accelerating electrode to discharge a uniformly charged droplet of the recording liquid from the nozzle, and the discharged droplet of the recording liquid is converted into a recording signal. In accordance with this, recording is performed by causing the droplets to fly between the xy-prone electrodes configured so as to be electrically controllable and selectively adhering small droplets onto the recording member by a change in the intensity of the electric field.

The second method is described, for example, in US Pat. No. 3,596,275, US Pat.
Method disclosed in the specification of 298030 (Sweet method)
Wherein a droplet of the recording liquid having a controlled charge amount is generated by a continuous vibration generation method, and the generated droplet having a controlled charge amount is applied between the deflection electrodes to which a uniform electric field is applied. Is recorded on the recording member by flying the recording medium.

More specifically, a charging electrode configured so that a recording signal is applied in front of an orifice (ejection port) of a nozzle, which is a part of a recording head provided with a piezoelectric vibrating element, is separated by a predetermined distance. The piezoelectric vibrating element is mechanically vibrated by applying an electric signal of a constant frequency to the piezoelectric vibrating element, and a droplet of the recording liquid is discharged from the discharge port. At this time, a charge is electrostatically induced in the recording liquid droplet discharged by the charging electrode, and the droplet is charged with a charge amount according to the recording signal. When the droplet of the recording liquid whose charge amount is controlled flies between the deflection electrodes to which a constant electric field is uniformly applied, the droplet is deflected according to the added charge amount and carries a recording signal. Only the recording material can be deposited on the recording member.

The third method is a method disclosed in, for example, US Pat. No. 3,416,153 (Hertz method), in which an electric field is applied between a nozzle and a ring-shaped charging electrode, and a continuous vibration generation method is used.
This is a system in which small droplets of the recording liquid are generated and atomized for recording.
That is, in this method, the atomization state of the small droplet is controlled by modulating the electric field intensity applied between the nozzle and the charging electrode in accordance with the recording signal, and the image is recorded with the gradation of the recorded image.

The fourth method is, for example, a method (Stemme method) disclosed in US Pat. No. 3,747,120, and this method is fundamentally different from the above three methods in principle.

That is, in each of the three methods, the droplet of the recording liquid discharged from the nozzle is electrically controlled during the flight, and the droplet carrying the recording signal is selectively attached to the recording member. On the other hand, according to the Stemme method, recording is performed by ejecting a small droplet of recording liquid from an ejection port in accordance with a recording signal.

That is, in the Stemme method, the piezoelectric vibrating element attached to the recording head having the ejection port for ejecting the recording medium includes:
Applying an electrical recording signal, converting the electrical recording signal into mechanical vibration of a piezo-vibrating element, and ejecting a droplet of the recording liquid from the ejection port in accordance with the mechanical vibration to cause the droplet to fly and adhere to the recording member. Is to record.

Each of these four conventional methods has its own features, but on the other hand, there are points that can be solved.

That is, in the first to third methods, the direct energy of the generation of the droplet of the recording liquid is electric energy,
Droplet deflection control is also electric field control. Therefore, the first method is simple in structure, but requires a high voltage to generate small droplets, and is not suitable for high-speed printing because it is difficult to use a multi-nozzle recording head.

The second method enables multi-nozzle recording heads and is suitable for high-speed recording. However, the method is complicated in structure, and the electrical control of small droplets of recording liquid is difficult and difficult. Are liable to occur.

The third method has a feature that an image having excellent gradation can be recorded by atomizing a recording liquid droplet, but on the other hand, it is difficult to control the atomization state, and fogging occurs in the recorded image. In addition, there are problems such as the fact that it is difficult to use a multi-nozzle recording head, and it is not suitable for high-speed recording.

The fourth scheme has relatively many advantages over the first to third schemes. That is, in order to perform recording by discharging the recording liquid from the discharge port of the nozzle on demand (on-demand), it is simple in terms of the configuration. It is not necessary to collect small droplets that are not required for recording an image, and there is no need to use a conductive recording liquid as in the first and second methods, and the recording liquid material Has a great advantage such as a large degree of freedom. However, on the other hand, it is difficult to form a multi-nozzle recording head because there are problems in processing the recording head and it is extremely difficult to reduce the size of the piezoelectric vibrating element having a desired resonance number. However, since the recording liquid droplets are ejected and fly by the mechanical energy of mechanical vibration of the piezo-vibration element, it is not suitable for high-speed recording.

As described above, the conventional method has advantages and disadvantages in terms of configuration, high-speed recording, multi-nozzle recording head, generation of satellite dots and occurrence of fogging of a recorded image, etc. There was a restriction that only the application was possible.

Also, Japanese Patent Application Laid-Open No. 55-123478 proposes that a thermal energy generating means in a so-called bubble jet liquid jet recording apparatus be provided on a substrate having a thin film having low thermal conductivity.

FIG. 6 is a view for explaining the details of the thermal energy generating section disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 55-123478. The heat generating resistor 11 is provided on a substrate 12 having a large thermal conductivity. It is formed by coating a thin film 13 having a small degree, and further laminating a heating element layer 14 and an electrode layer 15 for applying a signal from the outside. In the figure, a portion H is a heating portion. Reference numeral 16 denotes a protective film, which is provided as necessary for the purpose of protecting the heating element layers and electrodes, insulating the recording medium liquid in direct contact with the heating resistor, and the like. As a material of the substrate 12, for example, Al, C
Metals such as u or ceramics such as Al ₂ O ₃ are mentioned.
As a material for the thin film laminated on the substrate, it is necessary to improve the responsiveness and energy efficiency, such as not being affected by heat, being able to form a uniform layer, and improving the responsiveness and energy efficiency within the temperature range near the heating element layer. It is required that a layer having a thickness of about 0.1 to 10 μm can be easily formed, and that the layer has sufficient adhesion to other layers (heating element layer, substrate, etc.) in a laminated state.
Also, at a temperature near normal temperature, its thermal conductivity value is 0.6 kcal / mh
Those having a temperature of r ° C or less, preferably 0.05 to 0.4 kcal / mhr ° C are used.

Further, a material satisfying the above condition is usually 0.1 to 10 μm, preferably 0.3 to 10 μm, and most preferably 1 to 10 μm in consideration of the amount of signal energy applied to the heating resistor, the interval between signal application times, and the like. It is desirable to form a layer with a thickness in the range of 6 μm.

The material to be used may be any type such as an inorganic or organic material, and depending on the case, a composite material composed of these materials or a plurality of laminated materials as long as these conditions are satisfied. . In particular, a heat-resistant organic polymer material having a softening point or melting point of 150 ° C. or more, and more preferably 200 ° C. or more, is suitably used.

In general, organic materials are effective as materials for low thermal conductivity thin films because they can be easily formed, easy to obtain a layer with high adhesion to other layers when laminated, It is mentioned that the degree value is sufficiently low.

Thus, in the invention described in JP-A-55-123478, the thermal energy generating means is provided on a substrate having a low thermal conductive thin film, and the low thermal conductivity of this thin film is important. However, JP-A-55-123478 does not disclose durability, which is another important quality requirement. Although there is no description of a heat storage layer made of SiOx in particular, in a bubble jet, the thermal energy action section is exposed to a severe heat cycle, so that its durability is an important issue. In particular, in a head that is continuously driven at a high speed (for example, higher than 4 kHz), the problem becomes serious.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in particular for the purpose of improving the durability of a bubble jet type ink jet recording head heat generating portion which is driven continuously at high speed.

Configuration In order to achieve the above object, the present invention provides a thermal energy operating section that accommodates a recording liquid to be introduced, generates bubbles in the recording liquid by heat, and generates an action force accompanying an increase in the volume of the bubbles. And an orifice communicating with the flow path to discharge the recording liquid as droplets by the action force, and an orifice communicating with the flow path to introduce the recording liquid into the flow path. A liquid chamber and a liquid jet recording head comprising means for introducing the recording liquid into the liquid chamber, wherein the thermal energy action section is formed by sputtering, at least a heating layer, an electrode layer,
A thermal energy acting portion comprising a protective layer, wherein the protective layer is a layer of SiO ₂ formed by sputtering, and the thermal energy acting portion is a Si having a thermal storage layer of SiO ₂ grown by thermal oxidation. It is formed on a substrate and is continuously driven at a frequency higher than 4 kHz.
The heat storage layer is characterized by being SiO ₂ grown on a Si substrate by high-pressure thermal oxidation. Less than,
A description will be given based on an embodiment of the present invention.

FIG. 1 is a sectional view of an essential part for explaining one embodiment of the present invention, that is, an enlarged sectional view of a heat energy acting part, FIG.
FIG. 3 is a diagram for explaining the operation of a bubble jet head as an example of an ink jet head to which the present invention is applied, FIG. 3 is a perspective view showing an example of a bubble jet head, and FIG. FIG. 4 (a) is a perspective view when the cover substrate (FIG. 4 (a)) and the heating element substrate (FIG. 4 (b)) constituting the head shown in FIG. In the figure, 21 is a lid substrate, 22 is a heating element substrate, 23 is a recording liquid inlet, 24 is an orifice, 25 is a flow path, and 26 is a liquid chamber in the drawing. , 27 is an individual (independent) electrode, 28 is a common electrode, 29 is a heating element (heater), 30 is ink, 31 is a bubble, 32 is a flying ink droplet, 33 is a heat storage layer, 34
Is a heating resistor protection layer, and 35 is an electrode protection layer.

First, the ink ejection by bubble jet will be described with reference to FIG. 2. (a) is a steady state, and the surface tension of the ink 30 and the external pressure are in an equilibrium state at the orifice surface.

3B shows a state in which the heater 29 is heated until the surface temperature of the heater 29 sharply rises and boiling development occurs in the adjacent ink layer, and minute bubbles 31 are scattered.

(C) shows a state in which the adjacent ink layer, which is rapidly heated on the entire surface of the heater 29, is instantaneously vaporized to form a boiling film, and the bubbles 31 grow. At this time, the pressure in the nozzle rises by an amount corresponding to the growth of the bubble, the balance with the external pressure on the orifice surface is lost, and the ink column starts to grow from the orifice.

(D) is a state in which the bubble has grown to the maximum, and the ink 30 corresponding to the volume of the bubble is pushed out from the orifice surface. At this time, no current is flowing through the heater 29, and the surface temperature of the heater 29 is decreasing. The maximum value of the volume of the bubble 31 is slightly delayed from the timing of applying the electric pulse.

(E) shows a state where the bubble 31 is cooled by ink or the like and starts to contract. At the front end of the ink column, the ink moves forward while maintaining the pushed speed, and at the rear end, the ink flows backward from the orifice surface into the nozzle due to a decrease in the nozzle internal pressure due to the contraction of the bubble, and the ink column is constricted. .

(F) is a state in which the bubble 31 further contracts, the ink comes into contact with the heater surface, and the heater surface is cooled more rapidly. At the orifice surface, the external pressure is higher than the internal pressure of the nozzle, so that the meniscus largely enters the nozzle. The tip of the ink column becomes a droplet and moves in the direction of the recording paper.
Flying at a speed of 10m / sec.

(G) is a process in which the ink is supplied (refilled) to the orifice again by capillary action and returns to the state of (a).
The bubbles have completely disappeared.

The present invention protects the thermal energy action portion of the ink jet head for bubble jet as described above from a heat cycle, and through many experiments and many prototypes of materials for a heat storage layer for improving the life time thereof,
The purpose of the present invention is to provide a configuration that can be truly put to practical use by carefully selecting and limiting the composition thereof.

FIG. 1 is a sectional view of an essential part for explaining an embodiment of a liquid jet recording head according to the present invention, in other words, an enlarged sectional view of a heat energy acting portion. In the present invention, a heating resistor 29 is formed. It is selected so that silicon oxide (SiOx) is used as the material of the portion to be heat-treated, that is, the heat storage layer 33. The reason for this is that silicon oxide has a low thermal conductivity and also exhibits excellent performance as an insulating material, so that the thermal energy generated by the heating element 29 does not escape to the substrate side 22 while bubbles are generated. Because. This heat storage layer 33 is formed by a sputtering method.
Although it can be easily manufactured by a CVD method or the like, the most preferable method is to use silicon as the substrate 22 and grow silicon or silicon oxide (SiOx) by thermal oxidation. Those manufactured under easy conditions, even though they are silicon compounds, may not be able to maintain durability due to a severe heat cycle, and may cause destruction of the heat energy action portion. This problem,
This problem becomes more serious as the number of repeated heat cycles increases, and is particularly important for a head that may be driven continuously at a speed higher than 4 kHz for high-speed recording.

Useful materials for the heating resistor layer 29 include, for example, tantalum nitride, nichrome, silver-palladium alloy, silicon semiconductor or hafnium, lanthanum, zirconium, titanium, tantalum, tungsten,
Boride of a metal such as molybdenum, niobium, chromium, and vanadium.

Among these materials constituting the heating resistor layer, metal borides can be particularly excellent, and among them, hafnium boride has the most excellent characteristics.
Next are zirconium boride, lanthanum boride, tantalum boride, vanadium boride, and niobium boride.

The heating resistor layer can be formed using the above-mentioned materials by a technique such as electron beam evaporation or sputtering. The thickness of the heating resistor layer is determined according to the area, the material, the shape and size of the heat acting portion, the actual power consumption, etc. so that the amount of heat generated per unit time is as desired. But usually 0.001-5μ
m, preferably 0.01 to 1 μm.

As the material constituting the electrodes 27 and 28, many commonly used electrode materials are effectively used.Specifically, for example, Al, Ag, Au, Pt, Cu and the like are mentioned. Use, a predetermined size in a predetermined position by a method such as evaporation,
Provided in shape and thickness.

The characteristics required for the protective layer 34 are that the heat generated by the heating resistor is not effectively transmitted to the recording liquid (ink) and that the heating resistor is protected from the ink. . Useful materials for the protective layer include, for example, silicon oxide, silicon nitride, magnesium oxide, aluminum oxide, tantalum oxide, zirconium oxide, and the like. Can be formed. The thickness of the protective layer is usually 0.01 to 10 μm, preferably 0.1 to 5 μm.
m, optimally 0.1 to 3 μm.

Comparative Example A film was formed on a silicon substrate by sputtering using SiO ₂ and Ta as targets, and the ratio between the two was approximately 8: 2. The thickness is 2.5 μm. Then, with the structure shown in FIG. 1, 0.3 μm of tantalum nitride (heating element), 0.8 μm of gold (electrode), and 1 μm of SiO ₂ as a protective film of the heating element
μm. The effective size of the heating element is 25μm ×
The thickness was 100 μm, and the array density was 16 lines / mm. When this was driven in ink, there was no problem with continuous driving at 2 kHz, but when driven at 5 kHz,
Damaged after a few minutes.

Example An SiO ₂ film was grown on a silicon substrate by thermal oxidation. At this time, the thickness of the SiO ₂ film was set to 2 μm by using a high-pressure thermal oxidation technique so as to form a denser SiO ₂ film.

The subsequent pattern formation is the same as in the first embodiment. Such a heating element substrate could do was driven in the ink, no abnormality was observed even when driven at 5 kHz, 10 ⁹ times or more repeated cycles were obtained.

Effects As is clear from the above description, according to the present invention, there is an advantage that the durability of the heat storage layer is improved and the life of the entire heat energy action section is significantly prolonged.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram for explaining an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of a bubble jet head as an example of an ink jet head to which the present invention is applied, FIG. 3 is a perspective view showing an example of a bubble jet head, FIG. 4 is an exploded perspective view, FIG. 5 is a view of a lid substrate viewed from the back side, and FIG. FIG. 22 ... heating element substrate, 27, 28 ... electrode, 29 ... heating resistor, 33 ... heat storage layer, 34 ... heating resistor protection layer, 35 ... electrode protection layer.

Claims (2)

(57) [Claims] 1. A storage device for accommodating a recording liquid to be introduced,
A flow path provided with a thermal energy action portion for generating bubbles in the recording liquid by heat and generating an action force in accordance with an increase in the volume of the bubbles; and connecting the recording liquid by the action force to communicate with the flow path. A liquid jet recording head comprising: an orifice for discharging droplets; a liquid chamber for communicating with the flow path to introduce the recording liquid into the flow path; and a means for introducing the recording liquid into the liquid chamber. The heat energy action section is a heat energy action section formed by sputtering, at least a heating layer, an electrode layer, and a protection layer, wherein the protection layer is a layer of SiO ₂ formed by sputtering, Si thermal energy acting portion having a heat storage layer of SiO ₂ grown by thermal oxidation
A liquid jet recording head formed on a substrate and continuously driven at a frequency higher than 4 kHz. 2. The liquid jet recording head according to claim 1, wherein said heat storage layer is made of SiO ₂ grown on a Si substrate by high-pressure thermal oxidation.