JPH0526657B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid jet recording head that performs recording by jetting liquid and forming flying droplets. The inkjet recording method (liquid jet recording method) is
It has recently attracted attention because it generates negligible noise during recording, is capable of high-speed recording, and can be recorded without the need for special processing such as fixing on plain paper. There is. Among them, for example, the liquid jet recording method described in Japanese Unexamined Patent Publication No. 54-51837 and German Publication of Publication (DOLS) No. 2843064 applies thermal energy to the liquid to obtain the motive force for ejecting droplets. In this respect, it has different characteristics from other liquid jet recording methods. That is, in the recording method disclosed in the above-mentioned publication, the liquid subjected to the action of thermal energy undergoes a state change accompanied by a sharp increase in volume, and the acting force based on the state change causes the tip of the recording head to Liquid is ejected from the orifice to form flying droplets, and the droplets adhere to the recording member to perform recording. In particular, the liquid jet recording method disclosed in DOLS No. 2843064 is not only very effectively applied to the so-called drop-on demand recording method, but also
Since the recording head section can be easily implemented as a full line type recording head with high density multi-orifice, it has the feature that high resolution and high quality images can be obtained at high speed. The recording head part of the apparatus applied to the above recording method is a part that communicates with an orifice provided for ejecting liquid and where thermal energy acts on the liquid in order to eject droplets. The apparatus includes a liquid discharge part having a liquid flow path in which a heat acting part is a part of the structure, and an electrothermal converter as a means for generating thermal energy. This electrothermal converter includes a pair of electrodes,
The heating resistor layer is connected to these electrodes and has a heat generating region (heat generating portion) between these electrodes. Typical examples of the structure of such a liquid jet recording head are shown in FIGS. 1a, 1b and 1c. FIG. 1a is a partial front view of the liquid jet recording head seen from the orifice side, and FIG.
1A is a cutaway view taken along the line XY shown in FIG. 1A, and FIG. 1C is a plan view of the substrate. The recording head 100 covers the surface of a substrate 102 on which an electrothermal converter 101 is provided with a grooved plate 103 having a predetermined number of grooves of a predetermined width and depth at a predetermined linear density. By joining in this manner, the structure has an orifice 104 and a liquid discharge portion 105 formed therein. In the case of the recording head shown in the figure, it is shown as having a plurality of orifices 104, but of course the present invention is not limited to this.
Single orifice recording heads are also within the scope of this invention. The liquid discharge part 105 has an orifice 104 for discharging liquid at its terminal end, and an electrothermal converter 10.
Thermal action part 106 is a part where the thermal energy generated from 1 acts on the liquid and generates bubbles, causing a sudden change in state due to expansion and contraction of the volume.
and has. The heat acting part 106 is located above the heat generating part 107 of the electrothermal converter 101, and has a heat acting surface 108, which is a surface of the heat generating part 107 that comes into contact with the liquid, as its bottom surface. The heat generating section 107 includes a lower layer 109 provided on the substrate 102, a heat generating resistor layer 110 provided on the lower layer 109, a first protective layer 111 provided on the heat generating resistor layer 110, and a second protective layer 111 provided on the heat generating resistor layer 110. It is composed of a protective layer 112. The heating resistance layer 110 includes an electrode 1 for supplying electricity to the layer 110 to generate heat.
13 and 114 are provided on its surface. The electrode 113 is a common electrode for the heat generating section of each liquid discharging section, and the electrode 114 is a selection electrode for selectively generating heat in the heat generating section of each liquid discharging section. It is provided along the flow path. First protective layer 111 and second protective layer 112
In the heat generating section 107, the heating resistance layer 110
In order to chemically and physically protect the liquid from the liquid to be used, the heating resistance layer 110 and the liquid filling the liquid flow path of the liquid discharge part 105 are separated from each other, and the electrodes 113 and 114 are short-circuited through the liquid. The heating resistance layer 110 has a protective function of preventing this. The first protective layer 111 also has the role of preventing electrical leakage between adjacent electrodes. In particular, it is necessary to prevent electrical leakage between each selected electrode, or to prevent electrical leakage that may occur when the electrode under each liquid flow path comes into contact with the liquid for some reason and is energized. Prevention of electrolytic corrosion is important, and for this purpose, the first protective layer 111 having the function of a protective layer is provided at least on the electrodes located below the liquid flow path. The upper layers including the first protective layer have different characteristics depending on where they are provided.
That is, for example, in the heat generating part 107, heat resistance, liquid resistance, liquid penetration prevention property, thermal conductivity,
It is required to have excellent oxidation prevention properties, insulation properties, and tear resistance, and in areas other than the heat generating part 107, it is relieved by thermal conditions, but it is required to have excellent liquid penetration prevention properties.
Sufficiently excellent liquid resistance and puncture resistance are required. However, at present, there is no material constituting the upper layer that fully satisfies all of the above characteristics as desired, and the current situation is that some of the characteristics of ~ are relaxed when used. That is, in the heat generating part 107, priority is given to and when selecting the material, while in other parts, such as electrode parts, priority is given to and. A selection of materials is made and a top layer is formed with each corresponding material on each relevant area surface. On the other hand, in the case of a multi-orifice type liquid jet recording head, in order to simultaneously form a large number of fine electrothermal transducers on the substrate, each layer is formed on the substrate during the manufacturing process. The formation of the upper layer and the removal of a portion of the formed layer are repeated, and at the stage where the upper layer is formed, the surface on which the upper layer is formed has a step wedge portion (stepped portion).
The step coverage of the upper layer at this stepped part is high because it has a certain fine unevenness.
is becoming important. In other words, if the coverage of this stepped portion is poor, liquid will penetrate into that portion, causing electrolytic corrosion or electrical breakdown. In addition, if the upper layer to be formed has a high probability of having defects due to the manufacturing method, liquid may penetrate through the defects, which can significantly shorten the life of the electrothermal converter. It's summery. For these reasons, the upper layer must have good coverage in the step part, and the probability that defects such as pinholes will occur in the formed layer is low, and even if they occur, they can be ignored in practical terms. Or even less is required. On the other hand, in the heat action section 106, the liquid is vaporized by heating, but because this is subcooled boiling and because the heating time is short, it is immediately cooled and condensed. Therefore, foaming and condensation are repeated at a high frequency of several thousand times per second in the vicinity of the heat-active surface, and the pressure changes (cavitation and corrosion) at this time often destroy the substrate. In recent years, there has been a strong demand for high image quality and high density printing quality, and more precise processing of minute parts such as electrodes, heating resistor layers, and accompanying protective layers is required than ever before. The present invention has been developed in view of the above points, and has excellent overall durability in frequent repeated use and long-term continuous use, and maintains good initial droplet formation characteristics over a long period of time. The main object of the present invention is to provide a liquid jet recording head that can be stably maintained. Another object of the present invention is to provide a liquid jet recording head that is highly reliable in manufacturing and processing. Another object of the present invention is to provide a liquid jet recording head that has a high manufacturing yield even when it is made into a multi-orifice head. The liquid jet recording head of the present invention has an orifice provided for ejecting liquid to form flying droplets, and is in communication with the orifice, so that thermal energy for forming the droplets acts on the liquid. A plurality of liquid flow paths each having a heat acting part as a part of the structure, and at least one pair of opposing electrodes in each liquid flow path are provided electrically connected to the heat generating resistor layer, and between these electrodes. In a liquid jet recording head comprising a plurality of electrothermal transducers each having a heat generating section formed therein, at least a portion of the heat generating section above the heat generating resistive layer is provided with a plurality of electrothermal transducers formed of at least an inorganic insulating material. The present invention is characterized in that it has one protective layer and a second protective layer formed of an inorganic material and continuously formed in a band shape in the arrangement direction of the liquid flow paths on the adjacent heat generating part. The liquid jet recording head of the present invention will be specifically explained below with reference to the drawings. FIG. 2 shows a preferred embodiment of the liquid jet recording head of the present invention corresponding to FIG. 1c. As shown in FIG. 2, in the present invention, the second protective layer is not provided individually on each heat generating portion, but is continuously provided in a bar shape on adjacent heat generating portions. As mentioned above, the upper layer mainly has the function of isolating the heating resistance layer from the liquid in the liquid flow path and the anti-cavitation function, but in the example shown in FIG. The second protective layer mainly has the former function, and the second protective layer mainly has the latter function. By providing the second protective layer in the shape shown in FIG. 2, patterning becomes easy. Therefore, even if the nozzle density is increased, the machining process will not become complicated and higher precision will not be required. By adopting this shape, the probability that the electrode, heating resistance layer, and first protective layer will be short-circuited is approximately twice that of the conventional example shown in Fig. 1, but the pinhole density is high enough to cause a short-circuit. is about 1-5
Considering that the short circuit probability is ^0.02 to 0.1% even in a high-density liquid jet recording head with 1000 ^nozzles , and a sufficiently high manufacturing yield can be ensured. Judging comprehensively from the viewpoints of processability, yield, etc., it is ultimately possible to provide a high-density liquid jet recording head of higher quality than the conventional one. In the illustrated example, the lower portions of the liquid flow paths of the electrodes 113 and 114 are mostly covered only by the first protective layer 111. A third protective layer may be formed on top of the first protective layer except for the heat acting surface, using an organic material or the like having excellent covering properties. The first protective layer 111 is made of an inorganic insulating material such as an inorganic oxide such as SiO ₂ or an inorganic nitride such as Si ₃ N ₄ , and the second protective layer 112 is sticky and relatively mechanical. For example, if the first protective layer is made of _SiO2 , it is preferable to use a metal material such as Ta, which has excellent physical strength and adhesion and adhesion to the first protective layer. preferable. The fact that the second protective layer is made of an inorganic material such as a metal that is relatively sticky and has mechanical strength is advantageous in that it protects the heat-active surface 108 from the cavitation effect that occurs when liquid is discharged. Shock can be sufficiently absorbed and the life of the electrothermal converter 101 can be significantly extended. The materials constituting the first protective layer 111 include:
Inorganic insulating materials with relatively excellent thermal conductivity and heat resistance are suitable. For example, inorganic oxides such as SiO ₂ , titanium oxide, vanadium oxide, niobium oxide,
Transition metal oxides such as molybdenum oxide, tantalum oxide, tungsten oxide, chromium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, yttrium oxide, manganese oxide, as well as aluminum oxide, calcium oxide, strontium oxide, barium oxide, silicon oxide, etc. Bulk metal oxides and their composites, high-resistance nitrides such as silicon nitride, aluminum nitride, boron nitride, tantalum nitride, and composites of these oxides and nitrides, and semiconductors such as amorphous silicon and amorphous selenium. Examples include thin film materials that have low resistance but can be made high in resistance through manufacturing processes such as sputtering, CVD, vapor deposition, gas phase reaction, and liquid coating. Materials for forming the second protective layer 112 include:
In addition to Ta mentioned above, periodic table a such as Sc, Y etc.
group elements, group a elements such as Ti, Zr, Hf,
Group A elements such as V and Nb; Group A elements such as Cr, Mo, and W; Group A elements such as Fe, Co, and Ni; Ti-Ni, Ta-W, Ta-Mo-Ni, Ni
-Cr, Fe-Co, Ti-W, Fe-Ti, Fe-Ni, Fe
- Alloys of the above metals such as Cr, Fe-Ni-Cr; Ti-
Borides of the above metals such as B, Ta-B, Hf-B, W-B; Ti-C, Zr-C, V-C, Ta-C,
Carbides of the above metals such as Mo-C and Cr-C; Mo
Examples include silicides of the above metals such as -Si, W-Si and Ta-Si; nitrides of the above metals such as Ti-N, Nb-N and Ta-N. The second protective layer can be formed using these materials by vapor deposition, sputtering, or CVD.
It can be formed by a method such as a method. The second protective layer may be made of the above-mentioned materials alone, but of course some of these materials may also be combined. The third protective layer described above is made of an organic insulating material that has excellent liquid penetration prevention and liquid resistance properties, and further includes:
It has good film forming properties, has a dense structure and few pinholes, does not swell or dissolve in the ink used, and has good insulation properties when formed into a film.
It is desirable that the material has physical properties such as high heat resistance. Examples of such organic materials include the following resins, such as silicone resins, fluororesins, aromatic polyamides, addition polymerized polyimides, polybenzimidazole, metal chelate polymers, titanate esters, epoxy resins, phthalate resins, and thermoplastic resins. Curable phenolic resin, P-vinylphenol resin,
Examples include Zyloc resin, triazine resin, BT resin (triazine resin and bismaleimide addition polymer resin), and the like. In addition to this, the third protective layer can also be formed by vapor depositing a polyxylylene resin or a derivative thereof. Furthermore, various organic compound monomers such as thiourea, thioacetamide, vinylferrocene,
1,3,5-trichlorobenzene, chlorobenzene, styrene, ferrocene, pyrroline, naphthalene, pentamethylbenzene, nitrotoluene, acrylonitrile, diphenylselenide, P-toluidine, P-xylene, N,N-dimethyl-P
-Toluidine, toluene, aniline, diphenylmercury, hexamethylbenzene, malononitrile, tetracyanoethylene, thiophene, benzeneselenol, tetrafluoroethylene, ethylene, N-nitrodiphenylamine, acetylene, 1,2,4-tri The third protective layer can also be formed by a plasma polymerization method using chlorobenzene, propane, or the like. However, if a high-density multi-orifice type recording head is to be manufactured, an organic material that is extremely easy to process using fine photolithography must be used as the material for forming the third protective layer, in addition to the above-mentioned organic materials. is desirable. Specifically, such organic materials include, for example, polyimide isoindoquinazolinedione (trade name: PIQ, manufactured by Hitachi Chemical), polyimide resin (trade name: PYRALIN, manufactured by DuPont), and cyclized polybutadiene (trade name: JSR−CBR, CBR−
Preferred examples include M901 (manufactured by Japan Synthetic Rubber Co., Ltd.), Photonis (trade name: manufactured by Toray Industries), and other photosensitive polyimide resins. The support 115 is made of silicon, glass, ceramics, or the like. The lower layer 109 is provided as a layer that mainly controls the flow of heat generated from the heat generating section 107 toward the support body 115, and when applying thermal energy to the liquid in the heat acting section 106, , the heat generated from the heat generating section 107 is made to flow more toward the heat acting section 106, and when the electricity to the electrothermal converter 101 is turned off, the heat remaining in the heat generating section 107 is transferred to the support. The constituent materials are selected and the layer thickness is designed so that the material flows quickly toward the body 115. Materials constituting the lower layer 109 include SiO ₂ , zirconium oxide, tantalum oxide,
Examples include inorganic materials typified by metal oxides such as magnesium oxide. As the material constituting the heat generating resistor layer 110, almost any material can be used as long as it generates desired heat when energized. Specific examples of such materials include tantalum nitride, nichrome, silver-palladium alloy, silicon semiconductor, hafnium, lanthanum,
Preferred examples include metals such as zirconium, titanium, tantalum, tungsten, molybdenum, niobium, chromium, and vanadium, alloys thereof, and borides thereof. Among these materials constituting the heating resistance layer 110, metal borides are particularly excellent, and among them, hafnium boride has the best properties, followed by zirconium boride, The order is lanthanum boride, tantalum boride, vanadium boride, and niobium boride. The heat generating resistor layer 110 can be formed using the above-mentioned materials using methods such as electron beam evaporation and sputtering. As the material constituting the electrodes 113 and 114, many commonly used electrode materials can be effectively used, and specifically, for example, Al, Ag,
Examples include metals such as Au, Pt, and Cu, which are used to provide a predetermined size, shape, and thickness at a predetermined location by a method such as vapor deposition. The materials constituting the grooved plate 103 and the components of the common liquid chamber provided on the upstream side of the heat acting section 106 are materials whose shape is not affected by thermal effects during the construction of the recording head or under the environment during use. It is possible to easily apply micro-precision machining to a material that does not receive or hardly receives it, and can easily obtain the desired surface accuracy, and furthermore, the flow path formed by such a material can be easily applied. Most materials are effective as long as they can be processed so that liquid can flow smoothly through them. Typical examples of such materials include ceramics, glass, metal, plastic, and silicon wafers. In particular, glass and silicon wafers are suitable materials because they are easy to process and have appropriate heat resistance, thermal expansion coefficient, and thermal conductivity. The outer surface around the orifice 104 is treated with a water-repellent treatment if the liquid is aqueous, or an oil-repellent treatment if the liquid is non-aqueous, to prevent liquid from leaking and getting around the outside of the orifice 104. It's better to do so. The liquid jet recording head of the present invention will be specifically explained below with reference to Examples. EXAMPLE The liquid jet recording head shown in FIG. 2 was manufactured as follows. A 5 μm thick SiO ₂ film was formed by thermal oxidation of a Si wafer and used as a substrate. HfB ₂ was formed on the substrate to a thickness of 1500 Å as a heating resistance layer by sputtering, and then a Ti layer of 50 Å and an Al layer of 5000 Å were successively deposited by electron beam evaporation. A pattern as shown in FIG. 2 was formed by a photolithography process, and electrodes 113 and 114 were formed. The size of the heat-active surface was 30 μm wide, 150 μm long, and 150 ohms including the resistance of the Al electrode. Next, as the first protective layer 111, a 2.5 μm thick SiO ₂ layer was deposited by high-rate sputtering. Next, the second protective layer 112 was created according to the following steps. A 3 μm polyimide film (PIQ manufactured by Hitachi Chemical) was patterned as a Ta lift-off resist, and then a 1.0 μm Ta film was formed by DC sputtering. After forming the Ta film, the PIQ film was peeled off to obtain the desired Ta film pattern, completing the substrate fabrication. Short-circuiting between the heating resistor and electrode of the substrate thus formed and the first protective layer Ta is prevented per substrate.
When I investigated 100 segments and 123 boards, I found that
None showed a resistance of less than 10 MΩ. Finally, a glass plate with grooves for forming a liquid flow path, a heat acting part, and an orifice was bonded in a predetermined manner so that the grooves were appropriately arranged with the heat generating part formed on the substrate. A liquid ejection experiment was conducted by applying a rectangular voltage of 30 V at 800 Hz for 10 μs to the electrothermal transducer of the recording head created in this way, and the reliability was equal to or better than that of the conventional method. Also, the nozzle density is 8/mm, 12/mm, 16/
A recording head of mm was prepared in the same manner. Ta at that time
Table 1 shows a comparison of the film patterning yield with the conventional method.

[Table] As described above, according to the present invention, a high-quality, high-density liquid jet recording head can be provided with a high manufacturing yield.

[Brief explanation of the drawing]

Figures 1a, b, and c are for explaining the configuration of a conventional liquid jet recording head, respectively.
is a schematic front partial view, FIG. 1b is a partial view cut along the dashed line XY in FIG. 1a, FIG. 1c is a schematic plan view of the substrate, and FIG. FIG. 2 is a schematic plan view of a substrate corresponding to FIG. 1c, for explaining the configuration. 100...liquid jet recording head, 101...electrothermal converter, 102...substrate, 103...grooved plate, 104...orifice, 105...liquid discharge section, 106...thermal action section, 107... heat generating part,
108...Heat action surface, 109...Lower layer, 110
...Heating resistance layer, 111...First protective layer, 11
2...Second protective layer, 113...Common electrode, 11
4...Selective electrode, 115...Support.

Claims (1)

[Scope of Claims] 1. An orifice provided for ejecting liquid to form flying droplets, and a portion communicating with the orifice where thermal energy acts on the liquid to form the droplets. A plurality of liquid channels each having a certain heat acting part as a part of the structure, and at least one pair of opposing electrodes in each liquid channel are electrically connected to a heat generating resistor layer, and heat is generated between these electrodes. In a liquid jet recording head comprising a plurality of electrothermal transducers in which a heat generation section is formed, at least a first portion made of an inorganic insulating material is provided on at least a portion of the heat generation section that is above the heating resistance layer. 1. A liquid jet recording head comprising: a protective layer; and a second protective layer formed of an inorganic material and continuously formed in a band shape in the arrangement direction of the liquid flow paths on an adjacent heat generating section.