JPH09156098A - Ink jet print head and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet print head for which an inexpensive driving circuit can be used and which is highly reliable and has high quality and high density by changing the compsn. of a piezoelectric film in a wiring region from the compsn. in a deformation region. SOLUTION: A compsn. adding film 31 is removed by means of etching while a part to be a wiring region afterward is kept remained. Thereafter, in order to crystallize a precursor of a piezoelectric film, the whole base sheet is kept for min at 650 deg.C in oxygen atmosphere from both faces of the base sheet by using an infrared rays radiation source 29 and then, is heated for 1min at 900 deg.C and is left to cool by itself to perform crystallization of a piezoelectric film. By this process, the precursor 24 of the piezoelectric film in the deformation region is crystallized and sintered as an aimed compsn. to be a piezoelectric film 11 with the first compsn. On the other hand, in the wiring region, during this heating process, lead of the compsn. adding film diffuses and dissolved as a solid soln. into the precursor 24 to become a film with a different compsn. 30 being a piezoelectric film with the second compsn. Thereafter, a top driving electrode film 12 is formed on the piezoelectric film 11 and the film 30 with a different compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head used in an ink jet printer for obtaining a visible image by selectively flying and fixing ink droplets on a recording sheet according to input print data.

More specifically, the present invention relates to an on-demand type ink jet head in which a nozzle plate and an ink pressurizing chamber substrate are laminated, and a piezoelectric film formed on the surface of the ink pressurizing chamber substrate is pressed to deflect ink droplets to cause ink droplets to fly.

[0003]

2. Description of the Related Art As prior art relating to the present invention, there are JP-A-5-504740 and JP-A-5-267742.

In the former conventional example, a piezoelectric film is integrally formed on a substrate containing an ink pressurizing chamber by a so-called thin film manufacturing method such as sputtering or a sol-gel method, so that a high-performance on-demand type ink jet printing is realized. The head is realized. Further, in the latter, the structure of an inkjet head using flexural deformation by a thick film manufacturing method and its wiring method are described.

[0005]

In the structure of such an ink jet print head, a wiring region for connecting to a drive circuit for applying a voltage to the upper and lower electrodes of the piezoelectric film is required, and this piezoelectric film is required. Is used as an insulating film between the upper limit electrodes, the manufacturing process is simplified, and a large step is not formed in the piezoelectric film and the lower drive electrode, so that the reliability of the wiring on the upper part can be improved.

However, since the piezoelectric film has a high relative dielectric constant, a non-negligible capacitance is attached between the upper and lower electrodes in this wiring region. Actually, since the displacement area and the wiring area are about the same in area, about half of the total capacity of one element is an unnecessary capacity. This capacitance causes loss of heat in the drive circuit during driving, which causes a large load on the drive circuit. Further, a voltage is applied to the piezoelectric film in the wiring region to generate piezoelectric stress and heat generation, which causes problems such as disconnection and film peeling due to long-term use.

The present invention is intended to solve such a problem, and its object is to solve the problems of capacitance addition and reliability deterioration of the wiring region with a simple wiring structure, and to achieve high quality and high performance. A flexible inkjet printhead is provided.

[0008]

SUMMARY OF THE INVENTION An ink jet print head according to the present invention comprises a pressure chamber substrate having ink pressure chambers arranged in a row with a partition wall, and one side of the pressure chamber substrate is covered to cover the partition wall. A pressure-generating film composed of an elastic film, a lower drive electrode film, a piezoelectric film, and an upper drive electrode film, which are suspended and fixed by means of a wall surface of the pressurizing chamber, and ink which communicates with each pressurizing chamber. The displacement region including the discharge nozzle and the ink supply hole, and the wiring region in which the piezoelectric film and one end of the upper drive electrode are extended and wired on the pressurizing chamber substrate, the deflection region of the pressure generating film is formed. An ink jet print head which ejects ink by a pressure generated by deformation, wherein the wiring region is composed of a lower drive electrode film, a piezoelectric film having a second composition, and an upper drive electrode film.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

The structure and manufacturing method of the ink jet print head of the present invention will be described with reference to FIGS. 1, 2 and 3. FIG.
2 is a schematic perspective view of an ink jet print head in an embodiment of the present invention, FIG. 2 is a cross-sectional view in a plane indicated by a two-dot chain line A in FIG. 1, and FIG. 3 is a diagram showing a cross-section indicated by a chain line B in FIG.

Reference numeral 1 denotes an ink pressurizing chamber substrate, pressurizing chambers 2 arranged in a zigzag pattern in two rows, and ink (not shown) in each pressurizing chamber.
Has a common flow path 3 for supplying the pressure chamber 2 and a supply path 9 that connects the respective pressurizing chambers 2 with the common flow path 3. Array pitch is 180
The print head has a print density of 360 dots / inch in two rows, which is one-half inch, about 141 microns.

On the lower surface of the pressurizing chamber substrate 1, an elastic film 4 serving as a substantially rectangular pressure generating film 50, a lower drive electrode 10, a piezoelectric film 11, and an upper drive electrode 12 are sequentially laminated. The substrate 1 and the pressure generating film 50 are integrally formed. 8
Is a wiring board for supplying a signal to the displacement element.

Reference numeral 6 denotes a nozzle plate having a plurality of ink ejection nozzles 7 corresponding to the pressurizing chamber 2. After the pressure chamber substrate 1 and the nozzle plate 6 are bonded, they are fitted on the base body 90 to form an inkjet print head.

FIG. 3 is a sectional view in the direction of arrangement of the pressure chambers of FIG. 1, in which 7 is a nozzle in the nozzle plate 6, 13 is ink in the pressure chambers 2 arranged, 4 is an elastic film, and 10 is an elastic film. A lower drive electrode, 11 is a piezoelectric film, and 12 is an upper drive electrode. The piezoelectric film 11 corresponds to each pressure chamber and is formed by etching to have a width slightly narrower than the width of the pressure chamber. Reference numerals 14, 15, 16, and 17 are wiring circuits schematically shown, in which 14 is a driving voltage source, 15 is a wiring connecting the driving voltage source 14 and the lower driving electrode 10, 1
6 is a wiring connecting the drive voltage source 14 and the upper drive electrode 12,
Reference numeral 17 denotes a drive signal switch interposed between each piezoelectric film 11 and the wiring. In this way, one ink ejection element 19
Is a pressure chamber 2 partitioned by a nozzle 7 and a partition wall 18, a partition wall 18
It is composed of an elastic film 4, a lower drive electrode 10, a piezoelectric film 11, an upper drive electrode 12, and a switch 17, which are connected in series.

In this example, the pressurizing chamber pitch was 141 μm, the pressurizing chamber width was 80 μm, the length (depth direction in the drawing) was 3 mm, and the partition wall width was 61 μm.

Here, the principle of ink ejection will be briefly described. During standby, the switch 17a is opened to prepare for the next discharge. The ejection element at the left end of FIG. 3 shows the standby state. At the time of ejection, as shown in the ejection element diagram in the center of FIG. 3, the switch 17b is closed to have the same polarity as the polarization direction of the piezoelectric film 11 shown by the arrow A,
In other words, when a voltage is applied in the same manner as the applied voltage polarity during polarization, the piezoelectric film 11 expands in the thickness direction and contracts in the width direction (horizontal direction in FIG. 3). Due to this contraction, a compressive shear stress acts on the interface between the piezoelectric film 11 and the elastic film 4, and the elastic film 4 and the piezoelectric film 11 bend upward in the drawing. Due to this deflection, the volume of the pressurizing chamber 2b is reduced and the ink droplet 30 is ejected from the nozzle. When the switch 17c is opened again as shown in the right end of FIG.

As shown in FIG. 2, the present ink jet head has a piezoelectric film 11 and its driving electrodes 10 and 1 on the substrate surface.
2, a displacement region 32 including the elastic film 4, the pressure chamber 2, and the like, which pressurizes the ink 13 by piezoelectric displacement, and the displacement region 3
The drive electrodes 10 and 12 are extended from 2 and have a wiring region 33 for connecting to a drive circuit.

A method of manufacturing the ink jet print head of the present invention will be described with reference to FIG. A silicon single crystal substrate 20, which is a pressurizing chamber substrate having a (110) plane with a thickness suitable for forming a pressurizing chamber, for example, 220 μm, is formed on the entire surface of the silicon single crystal substrate 20 by a thermal oxidation method by etching protection made of silicon dioxide. Form the layer 21.

On the surface of the etching protection layer 21 on one surface of the silicon single crystal substrate 20, platinum to be the lower drive electrode 10 is formed to a thickness of 800 nm by a thin film forming method such as a sputtering film forming method. At this time, ultrathin titanium, chromium or the like may be interposed as an intermediate layer in order to increase the adhesion between the platinum layer and the upper and lower layers thereof. The lower drive electrode 10 also serves as an elastic film.

A piezoelectric film precursor 24, which is a first piezoelectric film precursor, is laminated thereon. In this example, lead titanate and lead zirconate PZT-based piezoelectric film precursors having a molar composition ratio of 55% and 45% were applied 6 times by the sol-gel method until the final thickness was 1 μm. The film formation was repeated by repeating drying / degreasing. As a result of various trial experiments, the chemical formula of this piezoelectric film is represented by Pb CTi AZr BO3 [A + B = 1], and A and C in the chemical formula are 0.5≤A≤0.
6. If selected within the range of 0.85 ≦ C ≦ 1.10, it was possible to obtain a piezoelectric property that can withstand practical use. Needless to say, the film forming method is not limited to this method, and high frequency sputter film forming or CVD may be used. Further, a composition addition film 31, which is a second piezoelectric film precursor, is formed thereon. In this example, a lead oxide film having a thickness of 50 nm was formed by the same sol-gel method.
(Fig. 4 (I)).

Next, the composition addition film 31 formed in the previous step
Is removed by etching, leaving a portion to be the wiring region 33 later. After that, the entire substrate is heated to crystallize the piezoelectric film precursor. In this example, by using an infrared radiant light source 29 from both sides of the substrate, holding in an oxygen atmosphere at 650 ° C. for 3 minutes and then heating at 900 ° C. for 1 minute to naturally lower the temperature,
The piezoelectric film was crystallized. By this step, the piezoelectric film precursor 24 in the displacement region was crystallized and sintered with the composition as intended, and the piezoelectric film 11 having the first composition was obtained. On the other hand, in the wiring region 33, the lead of the composition-added film 31 is diffused and solid-dissolved in the precursor 24 during this heating process, and becomes the different composition film 30 which is the piezoelectric film having the second composition (FIG. 4 (II)). And Figure 5). After that, when the composition of the different composition film 30 was analyzed, lead was 1.12 times the total molar amount of zirconia and titanium.

Thereafter, the upper drive electrode film 12 is formed on the piezoelectric film 11 and the different composition film 30. In this example, the upper drive electrode 12 is formed by sputtering platinum with a thickness of 200 nm.
(Fig. 4 (III)).

Next, an appropriate etching mask (not shown) is applied to the upper drive electrode 12, the piezoelectric film 11, and the lower drive electrode 10 in accordance with the position where the pressure chamber 2 is formed, and then a predetermined separation shape is formed. Was formed using ion milling (Fig. 4 (IV)
6 and 7, but the upper drive electrode is not shown in FIGS.

On the opposite surface of the substrate 20, the etching protection layer 21 is etched with hydrogen fluoride so as to match the shape of the pressure chamber 2 to form a window 22 (FIG. 4 (V)).

Thereafter, an anisotropic etching solution, for example 80
Anisotropic etching is performed on the silicon single crystal substrate 20 using a potassium hydroxide aqueous solution having a concentration of about 17% kept at 0 ° C. until it reaches the protective layer on the facing side (lower side in the figure). In addition to this, the pressure chamber may be formed by an anisotropic etching method using an active gas such as parallel plate type reactive ion etching.

After that, the silicon oxide film 21 immediately below the separated piezoelectric film precursor is removed by etching with hydrogen fluoride (FIG. 4 (VI)).

As described above with reference to FIGS. 1 and 2, the substrate and the nozzle plate are bonded and fixed to the pressure unit 5 thus formed to complete the ink jet print head.

The capacity per element of the ink jet print head formed as described above is about 10 in the conventional case.
While it was nF, it decreased to 7 nF. Further, when reliability was evaluated by long-term printing, it was found in the present example that 10% of the printing elements were defective due to disconnection and film peeling in this wiring area after ink ejection of 50 million times.
It was possible to reduce the amount to 1% or less by ejecting ink 100 million times. This is because the lead composition of the piezoelectric film having the second composition in the wiring region increased and deviated from the optimum composition of its dielectric constant and piezoelectric characteristics. When the dielectric constant and the piezoelectric characteristic of the piezoelectric films having the first composition and the second composition were measured by another experiment, the dielectric constant was 18 for the first composition.
The second composition was 900, while the piezoelectric characteristic d31 was 150 pC / N for the first composition, and 80 pC / N for the second composition. Therefore, it is considered that the capacitance of the entire device is reduced and the piezoelectric displacement itself caused by the voltage application in the wiring region is reduced, and the reliability can be improved.

Generally, in a piezoelectric material using a multi-element metal oxide, its piezoelectric characteristics greatly depend on the composition ratio.
Therefore, as described above, the composition of the displacement region area is set to the optimum value in terms of characteristics, and in the wiring area, at least one composition of the constituent elements is greatly increased or decreased with respect to this optimum value.
The object of the present invention can be achieved. Alternatively, a new element that can significantly change the characteristics may be added by the above manufacturing method.

The present inventor first measured the characteristics of the piezoelectric film in the wiring region by using lead oxide as a composition-added film based on the above PZT-based composition and changing its thickness. As a result, when the lead content of the piezoelectric film after firing was 0.85 or less or 1.10 or more with respect to the stoichiometric composition, the characteristics were significantly deteriorated.

Similarly, the same evaluation was performed using titanium oxide or zirconium oxide as the composition-added film.
When the ratio of Ti to the total amount of Ti and Zr in the piezoelectric film after firing was 0.5 or less or 0.6 or more, the characteristics were significantly deteriorated.

By positively shifting the composition of the piezoelectric film in the wiring region from the optimum point in this way, it was possible to realize the reduction in the dielectric constant and the piezoelectric characteristic in the wiring region, which is the object of the present invention.

In this example, the composition-added film was formed in the wiring region, but the composition of the displacement region after firing has an optimum value in terms of characteristics,
The piezoelectric film precursor 24 and the composition-added film may be adjusted so that the electrical characteristics of the wiring region may be lower than that, and the composition-added film may be selectively attached to the displacement region and baked.

The composition-added film deteriorates in characteristics due to the addition of the element, and any film may be used as long as good adhesion and film quality can be obtained, regardless of the element forming the piezoelectric film. However, the elements constituting the piezoelectric film are easier to control in manufacturing and often have better film quality / adhesion.

In this example, the PZT-based material was used as the piezoelectric film, but niobate, nickel oxide,
The present invention is also effective for materials to which other metal oxides such as magnesium oxide are added or materials other than PZT-based materials.

[0036]

According to the present invention, by changing the composition of the piezoelectric film in the wiring region from the composition in the displacement region, an inexpensive drive circuit can be used, and a highly reliable, high-quality and high-density ink jet system can be used. A printhead can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of an inkjet printhead according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an inkjet printhead according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of an ink jet print head according to an exemplary embodiment of the present invention in a pressure chamber array direction.

FIG. 4 is a diagram showing a manufacturing process of the ink jet print head in the embodiment of the present invention.

FIG. 5 is a diagram showing a step in the manufacturing process of the inkjet print head according to the embodiment of the present invention.

FIG. 6 is a diagram showing one step in the manufacturing process of the inkjet print head in the embodiment of the present invention.

FIG. 7 is a diagram showing one step in the manufacturing process of the inkjet print head in the embodiment of the present invention.

[Explanation of symbols]

 1 Pressurizing Chamber Substrate 2 Pressurizing Chamber 3 Common Channel 4 Elastic Film 5 Pressurizing Unit 6 Nozzle Plate 7 Ink Discharging Nozzle 8 Wiring Board 9 Supply Channel 10 Lower Driving Electrode 11 Piezoelectric Film 12 Upper Driving Electrode 13 Ink 14 Driving Voltage source 15 Wiring 16 Wiring 17 Switch 18 Pressure chamber partition 19 Ink ejection element 20 Silicon single crystal substrate 21 Etching protection layer 24 Piezoelectric film precursor 30 Different composition film 31 Composition addition film 32 Displacement region 33 Wiring region 34 Step

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 41/187 H01L 41/22 A 41/24

Claims (8)

[Claims] 1. A pressurizing chamber substrate having ink pressurizing chambers arranged in rows via partition walls, one side of the pressurizing chamber substrate being covered and fixed and suspended by the partition walls, and one wall surface of the pressurizing chambers. A pressure-generating film composed of an elastic film, a lower drive electrode film, a piezoelectric film of the first composition, and an upper drive electrode film, which are arranged so as to form an ink discharge nozzle and an ink communicating with each of the pressure chambers. A displacement region including a supply hole; and a wiring region in which the piezoelectric film and one end of the upper drive electrode are extended and wired on the pressure chamber substrate, and the wiring region is the lower drive electrode. An inkjet printhead comprising a film, a piezoelectric film having a second composition, and an upper drive electrode film. 2. The ink jet print head according to claim 1, wherein the first composition and the second composition of the piezoelectric film are composed of the same element and have different composition ratios. 3. The chemical formula of the piezoelectric film having the first composition in the displacement region is represented by Pb CTiAZr BO3 [A + B = 1], and A and C in the chemical formula are 0.5 ≦ A ≦ 0. .6, 0.
The inkjet printhead according to claim 1, wherein the range is 85 ≦ C ≦ 1.10. 4. The chemical formula of the piezoelectric film having the second composition in the wiring region is represented by Pb CTiAZr BO3 [A + B = 1], and at least A in the chemical formula is A <0.5 or 0. The ink jet print head according to claim 3, wherein 6 <A. 5. The chemical formula of the piezoelectric film having the second composition in the wiring region is represented by Pb CTiAZr BO3 [A + B = 1], and at least C in the chemical formula is C <0.85 or 1. 4. It is within the range of 10 <C.
An inkjet printhead as described. 6. The ink jet print head according to claim 3, wherein Pb (Mg1 / 3Nb2 / 3O3) is added to the piezoelectric film having the first composition in the displacement region. 7. A film is formed on the displacement region with a first piezoelectric film precursor, and a film is formed on the wiring region with a stack of the first piezoelectric film precursor and a second piezoelectric film precursor. A method for manufacturing an ink jet print head, characterized in that the piezoelectric film having the first and second compositions is simultaneously formed by forming the piezoelectric film and then firing the first and second piezoelectric film precursors. 8. The wiring region is formed by film-forming with a first piezoelectric film precursor, and the displacement region is formed by laminating the first piezoelectric film precursor and a second piezoelectric film precursor. A method for manufacturing an ink jet print head, characterized in that the piezoelectric film having the first and second compositions is simultaneously formed by forming the piezoelectric film and then firing the first and second piezoelectric film precursors.