JPH0471711B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an ink jet recording head (liquid jet recording head) that performs recording using flying droplets formed by ejecting liquid from an ejection port, and in particular to an ink jet recording head that uses thermal energy. The present invention relates to an ink ejecting recording head that ejects liquid. [Prior Art] There are various types of ink jet recording devices (liquid jet recording devices), among which, for example, OLS No. 2843064, OLS No. 2944005,
The liquid jet recording apparatus of the type disclosed in USP 4,335,389 and the like can easily perform high-speed color recording. The ink ejecting recording head, which is the main part of the output section, has high resolution because it has a high density array of ejection ports (orifices) for ejecting recording liquid to form flying droplets. At the same time, the recording head can be made compact overall and suitable for mass production, and it takes advantage of the advantages of IC technology and micro-processing technology, where technological advances and reliability improvements have been remarkable in the semiconductor field. It has been attracting a lot of attention recently because it can be easily made into a longer length by using it in minutes. A typical recording head of the above-mentioned liquid jet recording apparatus is provided with an electrothermal transducer as means for generating thermal energy for ejecting liquid from an orifice to form flying droplets. The electrothermal converter is capable of efficiently applying the generated thermal energy to the liquid, and of reducing the thermal effect on the liquid.
In order to increase the ON-OFF response speed, it is considered desirable to have a structure in which the heat-acting part is connected to the orifice so as to be in direct contact with the liquid. However, since the electrothermal converter described above basically consists of a heating resistor that generates heat when energized and a pair of electrodes for energizing the heating resistor, If the heating resistor is in direct contact with the liquid, depending on the electrical resistance of the recording liquid, electricity may flow through the liquid, or the liquid itself may undergo electrolysis due to the flow of electricity through the liquid. Or, when the heating resistor is energized, the heating resistor and liquid react with each other, resulting in a change in resistance value due to corrosion of the heating resistor itself, and even damage or destruction of the heating resistor. Furthermore, the surface of the heating resistor may be damaged or heat may be generated due to mechanical shock due to a sudden change in the state of the liquid, preferably including the generation of bubbles, due to the action of heat generated from the heating resistor. A part of the resistor may crack or be destroyed. For this reason, in the past, alloys such as NiCr and
The heating resistor is made of an inorganic material that has relatively excellent properties as a heating resistor material, such as metal borides such as ZrB ₂ and HfB ₂ , and SiO ₂ etc. By providing a protective layer (upper layer) made of a material with excellent oxidation resistance, the heating resistor is prevented from coming into direct contact with the liquid, solving the above problems and improving reliability. It has been proposed to try to improve the durability against repeated use. [Problems to be Solved by the Invention] However, an ink jet recording head equipped with an electrothermal converter having the above-mentioned configuration uses a liquid with relatively low electrical conductivity ( For example, when using distilled water or alcohol as a liquid medium, it has excellent oxidation resistance and is reasonably satisfactory in terms of repeated use durability, but the content of Na ions etc. Therefore, when recording liquids or electrolyte liquids with high electrical conductivity are used, they are not necessarily sufficient in terms of durability for repeated use and resistance to changes over time. Therefore, there are restrictions on the selection of the recording liquid to be used.
In particular, this has been an obstacle when recording in multiple colors or in natural colors. Furthermore, even in the case where a protective layer is provided on the heating resistor as described above, it is possible to substantially completely prevent liquid from penetrating toward the heating resistor due to defects in the protective layer itself that occur during layer formation, for example. This is extremely difficult in terms of reproducibility and mass production. In particular, in the case of so-called high-density multi-orifice construction in which a liquid flow path is provided with a large number of heat-acting parts as part of its structure, it is necessary to provide at least as many electrothermal converters at once as there are liquid flow paths. Due to necessity, the impact on manufacturing yield of electrothermal converters that are defective due to defects in the previous protective layer is a major problem, including in terms of manufacturing costs.
Therefore, there is a strong desire to develop an ink jet recording head equipped with an electrothermal converter that is comprehensively superior in liquid resistance, repeatability of use, mechanical shock resistance, electrochemical reaction resistance, etc. The present invention has been made in view of the above points, and its main object is to provide an excellent ink ejecting recording head that solves all of the conventional problems mentioned above. Another object of the present invention is to provide an ink jet recording head that is comprehensively superior in liquid resistance, mechanical impact resistance, repeated use, electrochemical reaction resistance, and the like. [Means for Solving the Problems] The ink jet recording head of the present invention includes a plurality of heat action chambers that apply thermal energy to the ink, and a heat action chamber that is provided in each of the plurality of heat action chambers and provides heat energy directly to the ink. an electrothermal transducer having a heating resistance layer forming a working surface and generating thermal energy for forming bubbles in the ink on the heat working surface when energized; In an ink ejection recording head that ejects ink to form flying droplets, the heating resistance layer of the electrothermal transducer is made of Ta or Ta.
Consisting of Ta-Al alloy containing 35 mol% or more of
The heat acting surface is formed on the heat generating resistance layer.
The present invention is characterized in that a protective layer including a Ta layer and a Si insulating layer between the Ta layer and the heating resistance layer is provided. [Function] The layer of Ta or Ta-Al alloy (containing Ta: 35 mol % or more) forming the heating resistance layer has relatively low reactivity to ions in the ink and is stable.
Moreover, this stability is maintained even in high temperature ink. Therefore, the heat generating resistance layer of the present invention is particularly excellent in electrochemical reactivity resistance. The Ta layer that forms the protective layer (upper protective layer) that forms the heat-active surface is
Since it has high toughness, it also has high mechanical strength, and therefore has excellent mechanical impact resistance (cavitation resistance) and usability for drying. The Si insulating layer forming the lower protective layer maintains insulation between the heating resistance layer and the upper protective layer. The ink jet recording head of the present invention is mainly made of Ta or Ta-Al alloy (Ta: 35 mol) in order to provide electrochemical strength.
Due to the synergistic effect of the heat generating resistive layer formed from Ta (containing more than %) and the upper protective layer formed mainly from Ta to provide physical strength, it is extremely excellent, especially when ejecting ink using thermal energy. Shows durability. [Embodiment Examples] The present invention will be described in more detail below with reference to the drawings. FIG. 1a is a front partial view of the main part of the ink jet recording head of the present invention as seen from the orifice side;
FIG. 1B is a partial cross-sectional view of FIG. 1A taken along the dashed line XY. The recording head 1 shown in the figure includes a substrate 3 having an electrothermal transducer 2 on its surface, and a grooved plate 4 having a predetermined number of grooves of a predetermined width and depth at a predetermined linear density. It has a structure in which an orifice 5 and a liquid discharge part 6 are formed by joining so as to cover each other. In the case of the ink jet recording head shown in the figure,
Although shown as having a plurality of orifices 5, the present invention is of course not limited to this, and the present invention also falls within the scope of the present invention when applied to a head with a single orifice. The liquid discharge part 6 has an orifice 5 at its terminal end for discharging liquid to form flying droplets, and thermal energy generated by the electrothermal converter 2 acting on the liquid to generate bubbles. It has a heat acting part 7 which causes a rapid state change due to expansion and contraction of volume. The heat acting part 7 is located above the heat generating part 8 of the electrothermal converter 2, and has a heat acting surface 9 that contacts the liquid of the heat generating part 8 as its bottom surface. The heat generating section 8 is a lower layer 1 provided on the substrate 3.
0, a heat generating resistor layer (heat generating resistor) 11 provided on the lower layer 10, and an upper layer 12 provided on the heat generating resistor layer 11 as necessary. The heating resistor layer 11 is provided with electrodes 13 and 14 on its surface for supplying electricity to the layer 11 in order to generate heat. The electrode 13 is an electrode common to the heat generating section of each liquid discharging section, and the electrode 14 is a selection electrode for selectively generating heat in the heat generating section of each liquid discharging section. It is located along the road. The upper layer 12 isolates the heating resistance layer 11 from the liquid in the liquid discharge part 6 in order to chemically and physically protect the heating resistance layer 11 from the liquid used, and also connects the electrodes 13 and 14 through the liquid. The heating resistance layer 11 has a protective function of preventing shortening of the heat generating resistance layer 11. The lower layer 10 mainly has a heat flow control function.
That is, when forming flying droplets, the heating resistance layer 11
Rather than the heat generated in is conducted toward the board 3 side,
The rate of conduction toward the heat acting part 7 side is increased as much as possible, and after the flying droplets are formed and the power to the clogging heat generating resistor layer 11 is turned off, the heat that becomes the heat acting part 7 and the heat generating part 8 is increased. This is provided so that the liquid in the heat acting section 7 and the generated air bubbles are rapidly cooled by being quickly discharged to the substrate 3 side. The ink jet recording head of the present invention can be made more excellent by designing the lower layer 10 such that it can fully exhibit the above-mentioned functions in relation to the heat generating resistor layer 11 and the substrate 3. That is, when forming flying droplets, the heat acting part 7
When the heat flow rate to the side is as large as possible, and the power to the heat generating resistor layer 11 is turned off, the substrate 3
By increasing the ratio of heat flow to the side as much as possible, we can improve the efficiency of droplet ejection energy, high thermal response, and continuous repeatable droplet ejection, improve the droplet formation frequency, and increase the amount of droplets. uniformity, stabilization of droplet flight direction, uniformity of droplet initial flight speed,
Furthermore, it is possible to more effectively improve the fidelity and reliability of responses to recorded signals. As mentioned above, the heat generating resistance layer 11 in the ink jet recording head of the present invention is made of Ta (tantalum) or
It is provided as a thin layer of Ta-Al alloy containing 35 mol% or more of Ta. In the present invention, the layer thickness of the heat generating resistor layer 11 is determined based on the characteristics, type and content of the constituent materials, the flying droplet formation characteristics required for the device itself, etc. so that appropriate thermal energy is effectively generated. It can be determined as appropriate, but preferably 50 Å to 5 μ, more preferably 100
It is desirable that the thickness be Å to 2μ, optimally 300Å to 1μ. In the present invention, when the heating resistance layer 11 is formed from a Ta-Al alloy, it is a mating metal of Ta, and when the layer 11 is formed, it is a mating metal of Ta, i.e.
Place a piece of Al with the desired area on the Ta target,
Preferably, it is formed by co-sputtering. Next, an overview of the manufacturing method and form of ink jet recording heads manufactured in Examples and Comparative Examples of the present invention to be described hereinafter will be explained. First, heating resistor installed substrates corresponding to the following Examples and Comparative Examples were prepared in the following manner. Lower layer 1 of alumina substrate 3 that also serves as lower layer 10
After forming the heating resistance layer 11 and the aluminum electrode layer on the
Heat generating resistor 11-1 to 11 with a length of 40 μm and a length of 200 μm
-3... was formed. Further, the selection electrode 14 and the common electrode 13 were formed by etching. Furthermore, a protective layer (upper layer) 12 was laminated on the surface of each electrode and each heating resistor, if necessary. In addition, apart from these, a grooved glass plate is formed by cutting a glass plate with multiple grooves (for example, width 40 μm, depth 40 μm) and a groove that becomes a common ink chamber (not shown) using a micro cutter. Plate 4 was also created. The heating resistor installed substrate and the grooved plate created in this way are bonded after aligning the heating resistor and the groove, and liquid ink is supplied from an ink supply unit (not shown) to the common ink chamber. An ink introduction tube (not shown) for introducing the ink was also connected to complete the recording head. Further, this recording head was attached with a lead substrate having lead electrodes (common lead electrode and selection lead electrode) connected to the aforementioned selection electrode and common electrode. In the ink jet recording head having the above structure, the upper layer 12 is a 1.0 μ thick layer of SiO ₂ and a thin layer of Ta 0.5 μ thick, which are laminated on each heating resistor layer 11.
A driving voltage margin of 1.5 to 1.9 times the foaming threshold voltage was obtained. This shows that heat resistance is further improved by providing the upper layer 12 compared to a system in which the heating resistance layer 11 is exposed to the liquid. At this time, the system without the upper layer 12 has a driving voltage margin of about 1.3 times the foaming threshold voltage, which is shown to be superior to the conventional system. As the substrate 3, a silicon wafer is used in addition to the alumina substrate, and as the lower layer 10, layers 2 to 2 formed by thermally oxidizing the surface of the silicon wafer are used.
A similar evaluation was performed using a 5μ SiO ₂ layer, and similar good results were obtained. Further, as the substrate 3, in addition to those used in the embodiments, glass, ceramics, heat-resistant plastic, etc. can also be used. In addition to Al, electrode materials include Al-Cu, Al-
Si, etc. can be used, but when using these materials, in order to isolate the electrode and the liquid, for example, a coating made of hardened photosensitive heat-resistant resin is used, excluding the heat-active surface. It is preferred to cover the electrode and the area around the electrode. Since the ink jet recording head of the present invention has a wide range of recording liquids to choose from, it can easily perform color recording in desired multi-colors and natural colors. Examples and Comparative Examples For the ink jet recording heads (sample Nos. 1-1 to 3-5) having the configuration described above (100 liquid channels, per one liquid channel - electrothermal converter), one Reliability was measured by counting the number of failed heating resistors when pulse driving was performed 5×10 ⁸ times per electrothermal converter. The results are shown in the table below. In addition, in the table, the "Ink" column of "Number of failed heating resistors" mainly shows electrochemical strength (ion resistance), and the "Distilled water" column mainly shows physical strength (cavitation resistance). ) is considered to be indicated. Further, "μυ/cm" in the "Ink" column of "Number of failed heating resistors" is a unit of electrical conductivity (specific conductivity).

【table】

[Table] Example: Sample number 2-1, 3-1,
3-2, 3-3
Comparative example: Sample number 1-1, 1-2,
2-2, 3-4, 3-5
[Effects of the Invention] The layer of Ta or Ta-Al alloy (containing Ta: 35 mol % or more) forming the heating resistance layer has relatively low reactivity with ions in the ink and is stable.
Moreover, this stability is maintained even in high temperature ink. Therefore, the heat generating resistance layer of the present invention is particularly excellent in electrochemical reactivity resistance. The Ta layer that forms the protective layer (upper protective layer) that forms the heat-active surface is
Since it has high toughness, it also has high mechanical strength, and therefore has excellent mechanical impact resistance (cavitation resistance) and repeated usability. The Si insulating layer forming the lower protective layer maintains insulation between the heating resistance layer and the upper protective layer. The ink jet recording head of the present invention is mainly made of Ta or Ta-Al alloy (Ta: 35 mol) in order to provide electrochemical strength.
Due to the synergistic effect of the heat generating resistive layer formed from Ta (containing more than %) and the upper protective layer formed mainly from Ta to provide physical strength, it is extremely excellent, especially when ejecting ink using thermal energy. Shows durability. Therefore, according to the present invention, it is possible to provide an ink jet recording head that is comprehensively superior in liquid resistance, mechanical impact resistance, repeated use property, electrochemical reaction resistance, and the like. This ink jet recording head has excellent response fidelity and reliability to recording signals, and is capable of recording high-resolution, high-quality images at high speed.

[Brief explanation of drawings]

FIG. 1a is a partial front view from the orifice side of a preferred embodiment of an ink jet recording head to which the present invention is applied. Figure 1b is the same as Figure 1a.
FIG. 3 is a partial cross-sectional view taken along the dashed-dotted line XY. DESCRIPTION OF SYMBOLS 1... Ink jet recording head, 2... Electrothermal converter, 3... Substrate, 4... Grooved plate, 5... Orifice, 6... Liquid ejection part, 7... Heat acting part, 8...
Heat generating part, 9...Heat action surface, 10...Lower layer, 1
DESCRIPTION OF SYMBOLS 1...Heating resistance layer, 12...Upper layer, 13...Common electrode, 14...Selection electrode.

Claims (1)

[Scope of Claims] 1. A plurality of heat action chambers that apply thermal energy to the ink, and a heat action surface that is provided in each of the plurality of heat action chambers and that directly applies thermal energy to the ink, and that generates the heat by energization. an electrothermal converter having a heating resistance layer that generates thermal energy to form bubbles in the ink on the working surface; and a common ink chamber that communicates with the plurality of heat action chambers and supplies ink. In an ink jet recording head that ejects ink to form flying droplets, the heating resistance layer of the electrothermal transducer is made of Ta or Ta.
Consisting of Ta-Al alloy containing 35 mol% or more of
The heat acting surface is formed on the heat generating resistance layer.
An ink jet recording head comprising a protective layer comprising a Ta layer and a Si insulating layer between the Ta layer and the heating resistance layer.