JPH0526656B2 - - 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 ejected 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, 1c and 1d. FIG. 1a is a partial front view of the liquid jet recording head seen from the orifice side, and FIGS.
It is a cutaway partial view when cutting at a portion indicated by XY.

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 them in this manner, the structure has an orifice 104 and a liquid discharge part 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, and a first protective layer 111 provided on the heat generating resistor layer 110. be done. The heating resistance layer 110 includes a layer 11 for generating heat.
Electrodes 113 and 114 for energizing 0 are provided on its surface. The electrode 113 is a common electrode for the heat generating part of each liquid discharge part, and the electrode 114 is
This is a selection electrode for selectively generating heat in the heat generating section of each liquid discharge section, and is provided along the liquid flow path of the liquid discharge section.

In the heat generating section 107, the first protective layer 111 protects the heat generating resistor layer 110 from the liquid used by chemically and physically protecting the heat generating resistor layer 110 and the liquid flow path of the liquid discharge section 105. The electrodes 113, 11 are separated from the filling liquid, and the electrodes 113, 11 are connected through the liquid.
The heating resistance layer 110 prevents short circuit between
It has a protective function. 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 selection electrode, or to prevent electrical leakage caused by the electrode under each liquid flow path coming into contact with the liquid for some reason and energizing the electrode. It is important to prevent electrolytic corrosion, 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-mentioned properties as desired, and at present, materials are used with some of the properties of - being relaxed. That is, the heat generating section 107
In the case of , and, priority is given to material selection, and on the other hand, in areas other than the heat generating section 107, for example, the electrode section, material selection is performed with priority given to , and. Then, an upper layer is formed of each corresponding material on each corresponding 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. In the case of stairs where the formation of the upper layer is repeated and the removal of a portion of the formed layer is repeated, the surface on which the upper layer is formed becomes the step wedge part (step part).
Since the surface has a fine unevenness, the step coverage of the upper layer at this stepped portion is 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. Also,
If the upper layer to be formed has a high probability of having defects due to the manufacturing method, liquid will penetrate through the defects, which will significantly shorten the life of the electrothermal converter. There is.

For these reasons, the upper layer must have good coverage at the stepped portion, 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.

Therefore, in order to meet these requirements, the upper layer may be formed by stacking a first protective layer made of an inorganic insulating material and a second protective layer made of an organic material, or even The layer has a two-layer structure, with the lower layer made of an inorganic insulating material, and the upper layer is sticky and has relatively good mechanical strength, and has good adhesion and adhesiveness to the first and second protective layers. Some inventions have been proposed in which the protective layer is made of an inorganic material such as a metal, or a third protective layer is made of an inorganic material such as a metal on top of the second protective layer.

However, although the second protective layer made of an organic material has excellent covering properties, it has poor heat resistance, and therefore is not provided on the heat generating resistive layer of the heat generating portion. In view of this, the present inventor first proposed a first protective layer made of an inorganic insulating material and a second protective layer made of an organic material on at least a portion of the electrode below the liquid flow path. are laminated in this order, and an upper layer is provided in which a first protective layer and a third protective layer made of an inorganic material are laminated in this order at least on the heat generating part. We are proposing an invention to In such a structure of the protective layer, if the second protective layer 112 and the third protective layer 116 do not overlap as shown in FIG. cannot fulfill its protective function. Not only that, but the concentration of electric potential is biased in the area, and eventually the electrode layer dissolves. In other words, corrosion resistance deteriorates. Furthermore, even if the second protective layer and the third protective layer overlap, if the overlap width is small, the liquid will penetrate and the potential will concentrate as the liquid immersion time increases, which will cause the electrode part to become concentrated. Dissolution occurs. On the other hand, if the overlap width is too large, the following problems will occur. As shown in FIG. 1c, the third protective layer 116 made of an inorganic material such as metal is placed below the second protective layer 112 made of an organic material in the vicinity of the heat generating part. When the third protective layer 116 is disposed on the third protective layer 111, the probability of occurrence of shoots between the third protective layer 116 and the electrodes 113, 114 increases, and the product yield is extremely reduced, which is undesirable. Also, as shown in Figure 1d,
Contrary to FIG.
2. When the third protective layer 116 is laminated in this order, the stress of the inorganic material layer (third protective layer) causes the organic material layer (second protective layer) to be damaged by immersion in the liquid from the liquid flow path. Peeling progresses.

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 a heat generating resistive layer and a pair of electrodes connected to the heat generating resistive layer,
The electrothermal converter includes an electrothermal converter in which a heat generating portion is formed between the pair of electrodes, and a protective layer provided to cover at least the electrothermal converter, and the heat generating portion generates heat. In a liquid jet recording head that ejects ink from an orifice using energy, the protective layer includes a first protective layer made of at least an inorganic insulating material on at least the electrothermal converter, and at least one of the electrodes. a second protective layer made of an organic material that is laminated on the first protective layer on a portion below the liquid flow path; a third protective layer made of an inorganic material laminated thereon, the second protective layer and the third protective layer overlap on the electrode, and the width of the overlapping portion is 10 to 10 cm. It is characterized by being 500 μm.

The overlapping order of the second protective layer and the third protective layer is
As long as the width of the overlapping part is within this range, it does not matter which layer is the upper layer. Moreover, the overlap width does not have to be the same in all the peripheral parts of the electrothermal converter, but may be different as long as it is within this range.

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 third protective layer 116 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 third 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. metal oxides and their composites, high-resistance nitrides such as silicon nitride, aluminum nitride, boron nitride, tantalum nitride, their oxides, nitride composites, and semiconductors such as amorphous silicon and amorphous selenium. Examples include thin film materials that have low resistance in bulk but can be made high in resistance through manufacturing processes such as sputtering, CVD, vapor deposition, gas phase reaction, and liquid coating.

The material for forming the third protective layer 116 is as follows:
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, Ci-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 third 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 third protective layer may be made of the above-mentioned materials alone, but of course some of these materials may also be combined.

The second protective layer is composed of an organic insulating material that has excellent liquid penetration prevention and liquid resistance properties, and also has good film formability, a dense structure with few pinholes, and swells with the ink used. It is desirable that the material has physical properties such as not melting, good insulation properties when formed into a film, and high heat resistance. Examples of such organic materials include the following resins, such as silicone resins, fluororesins, aromatic polyamides, addition polymerization 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). In addition to this, the second 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-nitrosodiphenylamine, acetylene, 1,2,4-tri The second 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 second 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.), Photonice (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 their layer thicknesses are designed so that they flow 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, tundsten, 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, and these are used to provide a predetermined size, shape, and thickness at a predetermined position 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 A liquid jet recording head of the present invention 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 3000 Å as a heating resistance layer by sputtering, and then a Ti layer of 50 Å and an Al layer of 10000 Å were successively deposited by electron beam evaporation.

The electrode portions were patterned by a photolithography process to form electrodes 113 and 114. The size of the heat acting surface is 50 μm wide and 150 μm long.

Next, as the first protective layer 111, a 2.8 μm thick SiO ₂ layer was deposited by high-rate sputtering.

Next, the third protective layer 116 was formed as follows.

Polyimide resin was used as a Ta lift-off resist in the window area around the heat-active surface (400 x 300 μm)
After that, a Ta film was formed to a thickness of 0.5 μm by magnetron sputtering. Ta
After film formation, lift-off patterning was performed by removing the polyimide resin with a stripping solution so that the Ta film remained in the window portion.

Next, Photonyce (manufactured by Toray Industries, Ltd.) was applied by spinner coating, and patterned and developed so that a window portion (300×200 μm) was formed around the heat-active surface, thereby creating the second protective layer 112. The width of the overlapped part of the second protective layer and the third protective layer is all 50μ
It is m. Further baking was performed to prepare a substrate for a liquid jet recording head.

When a pulsed voltage of 23 V was applied at 800 Hz for 10 μs to the electrothermal transducer of the recording head created in this way, the liquid was ejected as droplets in response to the applied signal, and flying droplets were stably formed. .

Here, in order to clarify the relationship between the overlap width and the defective rate of the recording head, we inserted the recording head electrode into the ink liquid at +40V, and inserted a Pt electrode so that the ink potential was GND, and the temperature of the ink liquid was adjusted. Defects were investigated after being left at 80°C for 200 hours.

Figure 2 shows the overlap width b as shown in Figure 1b.
This is the result of investigating disconnection due to electrode melting that occurs when the value is from negative to near zero. When the overlap width b is negative (no overlap), defects in the inorganic insulating layer (poor step coverage, pinholes),
The electrode will melt, leading to disconnection. Further, the liquid penetrates the overlapping boundary part up to about 10 μm, which also leads to wire breakage.

If the overlap width b is positive (overlapping) as shown in Figure 1c and d, the third protective layer made of an inorganic material is the second protective layer as shown in Figure 1c. When lower, as shown in Figure 3a,
Shorts (defects in the inorganic insulating layer) between the third protective layer and the electrode pose a problem. In particular, b
If the ink is determined, the yield of the product will be extremely reduced, and furthermore, if a heating potential immersion test is performed in the ink as described above, the surface of the inorganic layer will be oxidized and stable ejection will not be obtained.

If the third protective layer is above the second protective layer composed of an organic material, as shown in FIG. 1d, the third protective layer, as shown in FIG. 3b,
That is, film peeling becomes a problem due to the stress of the upper inorganic layer, the swelling of the second protective layer, that is, the lower organic layer, and the stress caused by the difference in coefficient of thermal expansion between both layers. This film peeling occurs when there is a step in the organic layer or a defect in the inorganic layer, so it will occur to some extent even if the overlap width is small, but especially when the overlap width is 50μ
If it exceeds m, the entire surface of the inorganic layer will peel off from the tip, which becomes a serious problem.

Therefore, by setting the overlap width to 10 to 500 μm, it is possible to provide a liquid jet recording head with high reliability, high yield, and excellent ink resistance.

[Brief explanation of the drawing]

Figures 1a, b, c, and d are for explaining the configuration of a conventional liquid jet recording head, respectively.
Figure a is a schematic front partial view, Figures b, c, and d are
FIG. 1 is a partial cross-sectional view taken along the dashed-dotted line XY in FIG. 1a; Figure 1b shows that the second protective layer and the third protective layer do not overlap, and Figure 1c shows that the second protective layer overlaps the second protective layer and the third protective layer. Figure 1 d is above the second protective layer.
In the overlapping part of the protective layer and the third protective layer,
The case where the second protective layer is below the third protective layer is shown. FIG. 2 is a graph showing the relationship between the overlap width b of the second protective layer and the third protective layer and the disconnection rate. FIG. 3a is a graph showing the relationship between the overlap width b and the shoot rate in a liquid jet recording head in which the second protective layer is above the third protective layer in the overlapped portion. FIG. 3b is a graph showing the overlap b and the film peeling rate in a liquid jet recording head in which the second protective layer is below the third protective layer in the overlapped portion. 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 (inorganic insulating material layer), 112...Second protective layer (organic material layer), 113...Common electrode, 114...Selection electrode, 115... Support, 116... Third protective layer (inorganic material layer), b... Overlapping width of the second protective layer and the third protective layer.

Claims (1)

[Scope of Claims] 1. An electrothermal transducer comprising a heat generating resistor layer and a pair of electrodes connected to the heat generating resistor layer, and a heat generating portion is formed between the pair of electrodes; a protective layer provided to cover an electrothermal converter; and a liquid jet recording head that ejects ink from an orifice using thermal energy generated by the heat generating section, the protective layer comprising: a first protective layer made of at least an inorganic insulating material on at least the electrothermal converter; and laminated on the first protective layer on at least a portion of the electrode below the liquid flow path. a second protective layer made of an organic material; and a third protective layer made of an inorganic material laminated on at least the first protective layer on the heat generating part, The second protective layer and the third protective layer overlap on the electrode, and the width of the overlapping portion is 10
A liquid jet recording head characterized in that the thickness is ~500 μm.