JPH06246913A - Ink jet head - Google Patents

Abstract

PURPOSE:To stably obtain an ink jet head enhanced in protective film characteristics and excellent in product quality, good in yield by prescribing the thickness of a protective film. CONSTITUTION:As a protective film 20, an inorg. film, for example, an SiNx(silicon nitride) film is formed to the interior ceramics plate 1 by a CVD method or a sputtering method. In this case, x takes various values but it is pref. 4/3. For example, when the CVD method is employed, a film forming device consists of a chamber 101, a raw material gas introducing pipe 102, an exhaust device 103 and an RF power supply 104. The piezoelectric ceramics plate 1 is held on a sample holder 106 so that the surface provided with the groove thereof is turned toward a power supply electrode and the chamber 101 is evacuated up to 2E-7Torr.

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 in which at least one wall forming an ink liquid chamber comprises a piezoelectric ceramic element.

[0002]

2. Description of the Related Art Conventionally, as an ink ejecting apparatus using a piezoelectric ceramic element, for example, a drop-on-demand type ink ejecting apparatus has been proposed. This is because the volume of the groove provided in the piezoelectric ceramics element is changed by the deformation of the piezoelectric ceramics, so that the ink in the groove is ejected as droplets from the nozzle when the volume decreases and the volume of the groove increases from the ink introduction path when the volume increases. The ink is introduced into. Then, a large number of such nozzles are arranged close to each other, and ink droplets are ejected from nozzles at required positions according to required print data,
A desired character or image is formed on a paper surface facing the nozzle.

Examples of this type of ink ejecting device include, for example, Japanese Patent Laid-Open Nos. 63-247051 and 63-252.
750 and JP-A-2-150355. 1 to 4 are schematic views of these conventional examples.

FIG. 1 showing a cross-sectional view of the ink ejecting apparatus will be described below.
The configuration of the conventional example will be specifically described with reference to FIG. A piezoelectric ceramic element 1 having a plurality of grooves 12 and polarized in the direction of arrow 4, a cover plate 2 made of a ceramic material or a resin material, and a bonding layer 3 made of an epoxy adhesive or the like. The plurality of grooves 12 are configured as a plurality of ink flow paths by joining via the above. The ink channel has an elongated shape with a rectangular cross section, and the side wall 11 extends over the entire length of the ink channel. A metal electrode 13 for applying a driving electric field is formed on both surfaces of the side wall 11 near the adhesive layer 3 on the zenith part from the side wall upper part to the side wall central part. A protective film 20 is formed so as to cover the electrode 13. Ink is filled in all the ink flow paths.

Next, FIG. 2 showing a sectional view of the ink ejecting apparatus.
The operation of the conventional example will be described with reference to FIG. In the ink ejecting apparatus, for example, the groove 12 is formed according to required print data.
When b is selected, a positive drive voltage is rapidly applied to the metal electrodes 13e and 13f, and the metal electrodes 13d and 13g are grounded. As a result, the driving electric field in the direction of arrow 14b acts on the side wall 11b, and the driving electric field in the direction of arrow 14c acts on the side wall 11c. At this time, the driving electric field directions 14b and 14c
And the polarization direction 4 are orthogonal to each other, the side walls 11b and 1
1c is rapidly deformed inward of the groove 12b due to the piezoelectric thickness sliding effect. Due to this deformation, the volume of the groove 12b decreases and the ink pressure rapidly increases, a pressure wave is generated, and ink droplets are ejected from the nozzle 32 (FIG. 3) communicating with the groove 12b. Further, when the application of the drive voltage is gradually stopped, the side walls 11b and 11c return to the positions before the deformation, so that the ink pressure in the groove 12b gradually decreases, and the ink is supplied from the ink supply port 21 (FIG. 3) to the manifold 22 (FIG. 3). ), The ink is supplied into the groove 12b.

As an actual product, ink is supplied first by applying a drive voltage in the opposite direction to the above before the ejection operation, and then the drive voltage is abruptly stopped so that the side walls 11b and 11c are removed. The ink may be ejected by returning to the original state.

Next, FIG. 3 showing a perspective view of the ink ejecting apparatus.
The configuration and manufacturing method of the conventional example will be described with reference to FIG. Grooves 12 are formed in the piezoelectric ceramic element 1 by cutting using a thin disk-shaped diamond blade or the like. The grooves 12 are parallel grooves having the same depth over almost the entire area of the piezoelectric ceramics element 1, but become gradually shallower as they approach the end face 15, and shallow shallow parallel groove portions 16 near the end face 15 are formed.
Is. The metal electrode 1 is formed on the inner surface and the side wall of the groove 12.
3 is formed by a well-known technique such as sputtering. Further, the protective film 2 is formed on the inner surface of the groove 12 so as to cover the electrode 13.
0 is formed into a dry or wet film.

On the other hand, as for the cover plate processing, the ink introducing port 21 and the manifold 22 are formed on the cover plate 2 made of a ceramic material or a resin material by grinding or cutting. Next, the surface of the piezoelectric ceramic element 1 on which the groove 12 is processed and the surface of the cover plate 2 on which the manifold is processed are bonded together with an epoxy adhesive or the like. Next, the grooves 12 are formed on the end faces of the piezoelectric ceramic element 1 and the cover plate 2.
The nozzle plate 31 provided with the nozzle 32 at the position corresponding to is bonded. Further, on the surface of the piezoelectric ceramic element 1 opposite to the surface on which the groove 12 is processed, a substrate 41 having a conductive layer pattern 42 provided at a position corresponding to each groove 12 is formed by an epoxy adhesive or the like. To glue. Then, the metal electrode 13 formed on the bottom surface of the shallow groove portion 16 of the groove 12 and the pattern 42 of the conductive layer are connected by the conductive wire 43 by wire bonding.

Next, referring to FIG. 4, which shows a block diagram of the control unit, the configuration of the conventional control unit will be described. The conductive layer patterns 42 provided on the substrate 41 are individually connected to the LSI chip 51, and the clock line 52, the data line 53, the voltage line 54, and the ground line 55 are also LSI.
It is connected to the chip 51. The LSI chip 51 determines from which nozzle the ink droplet should be ejected based on the data appearing on the data line 53 based on the continuous clock pulse supplied from the clock line 52, and the inside of the driven groove 12 is driven. The voltage V of the voltage line 54 is applied to the pattern 42 of the conductive layer that is electrically connected to the metal electrode 13. Further, the voltage 0v of the ground line 55 is applied to the pattern 42 of the conductive layer which is electrically connected to the metal electrode 13 other than the groove 12.

In an ink jet head having such a mechanism, a protective film 20 is provided for insulating and protecting the electrode 13 and for preventing corrosion of the electrode itself. As the protective film 20, an inert inorganic non-reactive material is used. A dynamic film, specifically an alternating film of silicon nitride (SiNx) and silicon oxynitride (SiON) was suitable.

[0011]

However, in such a protective film for insulating and protecting the electrodes of the ink jet head, the coating state of the film influences the protective properties such as withstand voltage characteristics, adhesion and acid resistance. Defective protective film is related to the product quality stability of the head, and in the conventional technology, there is no restriction on the coating state of the protective film.Therefore, the protective film characteristics vary among the heads, and the product quality stability becomes significantly poor and yield increases. There was a problem that it went down.

The present invention has been made in order to solve the above-mentioned problems, and by defining the film thickness of the protective film, the characteristics of the protective film are enhanced, and an ink jet head having excellent product quality is stably provided. The purpose is to provide a high yield.

[0013]

In order to achieve this object, in the ink jet print head of the present invention,
An inorganic passivation protective film for insulating and protecting the electrode is provided, and the protective film is characterized in that it is deposited at least on the electrode, preferably in the entire groove, as a covering state.

[0014]

In the ink jet head of the present invention having the above-mentioned constitution, by defining the coating state of the inorganic passivation type protective film, it becomes a protective film having excellent corrosion resistance against the stimulus from the environment.

[0015]

EXAMPLES An example of an ink jet head embodying the present invention will be described below with reference to FIGS.
The basic configuration of the inkjet head of this embodiment is as follows.
Since it is almost the same as the conventional head shown in FIGS. 1 to 4, description thereof will be omitted.

As the protective film 20, an inorganic film such as S is used.
An iNx (silicon nitride) film is formed in the groove 12 of the piezoelectric ceramic plate 1 by a well-known technique such as a CVD method or a sputtering method. In this case, x takes various values, but is preferably 4/3.

According to, for example, the CVD method, the film forming apparatus is shown in FIG.
As shown in FIG.
02, an exhaust device 103, and an RF power source 104. Then, the film formation is performed as follows. In the chamber, the power supply electrode 105 and the sample holder 106 are arranged so as to face each other with a distance of several cm. First, the piezoelectric ceramic plate 1 is held on the sample holder 106 with the grooved surface facing the power supply electrode, and the chamber 101 is evacuated to 2E-7 Torr.

Next, as source gases, SiH ₄ / N ₂ and NH
₃ and N ₂ are 60 sccm, 180 sccm, 9 respectively
The gas was introduced into the chamber through the raw material gas introduction pipe 102 at a flow rate of 00 sccm (sccm is a nitrogen-converted flow rate per minute), and the gas flowed inside the chamber 10
1 is maintained at 1.2 Torr, and the power supply electrode 105 receives 0.
Applying 8kW, high frequency discharge occurs. Then, the raw material gas becomes a chemically active species, which causes difficult decomposition and chemical reaction by ordinary thermal excitation. This chemical reaction is a non-equilibrium reaction, for example, as shown in equation (1), and 1000 angstroms of SiNx is deposited on the substrate by discharging for about 3 minutes. The film thickness can be controlled by the discharge time.

3SiH ₄ + 4NH ₃ → Si ₃ N ₄ + 12H ₂ (1) In order to grasp the minimum film thickness of the protective film 20, a dielectric breakdown test was conducted by changing the SiNx film thickness. Specifically, first, a conductive aluminum film is previously formed on a glass substrate by a well-known sputtering technique, then a SiNx film is formed on aluminum by the above-described CVD method, and an aluminum film is again formed on them. Form. Further, a resist is spin-coated with a spin coater, and a predetermined resist pattern is formed by contact exposure and dipping development using a mask having a predetermined pattern. In this case, the predetermined pattern is to use the outermost aluminum as a tester electrode, and 20 circles having a diameter of about 2 mm are arranged in a line at regular intervals. Then, immersing it in an aluminum etching solution, etching the aluminum in the non-resist part and finally removing the resist, processing the surface aluminum into a shape in which 20 circles with a diameter of about 2 mm are lined up at a fixed distance To do.

In the test sample as described above, the film thickness of the SiNx film as the protective film was 0.02, 0.04, 0.
Those having different thicknesses of 06, 0.08, 0.10, 0.12 and 0.14 μm were prepared and the dielectric strength was measured as follows. The tester terminals are brought into contact with the aluminum films on both sides of the SiNx film, and a voltage of 100 V is applied and held for 1 minute, which is the minimum scale of the ammeter of 1 μA.
Dielectric breakdown was when the above current flowed. Incidentally, 100
The voltage value V is a value that is several times higher than the withstand voltage required for the protective film of the inkjet head of the present invention.

In 20 points of electrode per sample,
As a result of examining the number of dielectric breakdown, as shown in FIG.
It was found that when the thickness of the protective film 20 is less than 0.1 μm, dielectric breakdown easily occurs. To make matters worse, when a dielectric breakdown occurs, a crack is generated at that portion, and the electrode 13
It is highly possible that the base material of PZT and PZT itself will be damaged by the ink.

On the other hand, when the SiNx film thickness is increased, the deformation state of the groove wall which causes ink ejection of this ink jet head was examined. As a test sample substrate, a piezoelectric ceramic having a side wall thickness of 80 μm, a height of 500 μm and a groove width of 90 μm, and an aluminum electrode film having a thickness of 2 μm formed on both side wall surfaces by a dry method such as vacuum deposition was prepared. A film is formed in the groove 12 of the substrate by the above-described CVD method so that the ratio of the thickness of the SiNx film as the protective film and the width of the groove wall is 1/100, 1/25, 1/12, 1/8, respectively. A film was formed. After adhering the cover plate to these samples, a pulse voltage of 50 V was applied and the deformation state of the side wall was measured using a laser displacement meter. Since the thickness of the electrode film is smaller than the thickness of the groove wall, the influence of the electrode film will be ignored when considering the deformation of the groove wall.

FIG. 7 shows the relationship between the film thickness of each sample and the normalized deformation efficiency when the measurement results are arranged by the volume change of the adjacent groove volumes and the volume change in the case of 1/100 sample is set to 1. . As is clear from FIG. 7, the deformation efficiency is remarkably reduced in the sample in which the ratio of the thickness of the protective film and the dimension of the groove wall of the piezoelectric material is 1/8. This is because the piezoelectric material and the protective film material SiNx have different Young's moduli, and the thicker protective film affects the deformation.

The maximum allowable thickness of the protective film can also be defined by the increase of internal stress. CV described above on Si wafer
SiNx film is 2, 4, 6, 8, 10, 12μ by D method
A sample having a thickness of m was prepared and the internal stress was measured. As a measuring method, the warp of the Si wafer before film formation is measured in advance by a surface shape measuring instrument, the warp at the same place after film formation is measured, and based on the difference between the warp before and after film formation (2) It was calculated from the dynamic formula shown in.

Σ = (h ² / 6d) · {E / (1−m)} · {2 (Δy) / R ² } ... (2) h: Wafer thickness (525 μm; 4 inches) d: Film thickness of SiNx film (2 to 12 μm) m: Poisson's ratio of wafer (0.3) R: Half of chord length of warpage measurement (25 mm; 4 inches) Δy: Maximum warpage change of wafer center E: Wafer Young's modulus (1.60E12 dyne / cm
² ; crystal orientation (111)) The values in parentheses at the end of the symbol explanation are the numerical values of the 4-inch wafer used in the experiment.

As shown in FIG. 8, the measurement result shows that as the thickness increases, the absolute value of the internal stress (stress) of the film tends to increase, and particularly the stress increases when the SiNx film thickness is 10 μm or more. . The film thickness of 10 μm corresponds to the sample in which the ratio of the thickness of the protective film to the dimension of the groove wall of the piezoelectric material is 1/8, but cracks were generated in this film and peeling from the base was partially caused. The cracks and peeling were observed with an optical microscope.

Further, making the film thickness thick causes the film formation to take a long time, resulting in a marked decrease in productivity. The deposition speed of the SiNx film by the above-mentioned CVD method is about 0.01 to 0.05 μm / min, though it depends on the conditions, and a minimum of 200 minutes is required to form a 10 μm film.

Therefore, the maximum thickness of the SiNx protective film is
Considering the deformation efficiency of the groove wall and the adhesion and stability of the film, it is desirable that the thickness of the protective film does not exceed ⅛ of the groove wall size of the piezoelectric material. Further, this leads to a reduction in production time, that is, a low cost, which is more desirable.

For the above reasons, the thickness of the protective film is 0.1 μm.
Thus, the ratio of the thickness of the protective film to the width of the groove wall is 1 / maximum.
By setting the value not to exceed 8, it is possible to form the protective film 20 that is excellent in the insulating film, the resistance, the adhesion, and the like, and has a good ink jetting property, at a low cost. Therefore, with the configuration of this embodiment, a high quality ink jet head having stable ink ejection characteristics was obtained.

In the present embodiment, the SiNx film has been described as an example of the inorganic passivation protective film.
Oxides such as iO ₂ , SiON that is a mixed film of a nitride and an oxide, and alternate films thereof showed almost the same tendency as the above-mentioned measurement results. Therefore, by setting the film thickness of these films within the above range, it is possible to obtain a high-quality inkjet head having stable ink ejection characteristics.

The quality of the protective film of the present invention can be maintained in other modes. When a SiNx film is formed as the protective film 20 in the groove 12 of the piezoelectric ceramic plate 1 by the above-described CVD method, the film density is 1.8 g / cm.
Set to ³ or more. This value is a pinhole test performed on SiNx films having different film densities, measurement of buffered hydrofluoric acid (B · HF) resistance, and FT-IR as shown below.
(Fourier transform infrared spectroscopy) Derived from measurement.

Specifically, the pinhole test is performed by forming a nickel (Ni) film as a conductive film on a glass substrate in advance by a well-known sputtering technique, and then forming SiNx on the Ni film.
The film is formed into a 1 μm SiNx film by the above-described CVD method, and the density of the SiNx film is 1.5 by changing the forming conditions such as gas pressure and substrate temperature at this time.
The films of 1.8 and 2.5 were prepared. After these samples were washed with alkali and water, they were washed with 40 g / l of copper sulfate and 30
Immerse in a plating bath composed of cc / l sulfuric acid, use this as a cathode, and place electrolytic Cu as an anode at a position separated by several cm, and apply a current at a current density of ² A / dm ² between the electrodes to form Cu. Electrolytic plating was performed for 30 minutes. Cu does not originally deposit on the SiNx film, which is an insulating film, but if there are pinholes in the film, conduction is ensured and Cu is formed by a chemical reaction.
Is deposited.

As a result of conducting a pinhole test by a Cu decoration method for observing Cu precipitation caused by such pinholes, as shown in FIG. 9, the horizontal axis of the graph is the film density and the vertical axis is a constant area. , The number of Cu deposits confirmed by an optical microscope in 400 μm ² . As is apparent from FIG. 9, the film density is about 1.5, about 1.8, about 2.5 g / cm.
Compared with the ones in ³ , there are many Cu deposits in 1.5,
The amounts of 1.8 and 2.5 were small enough to be attributed to dust during film formation.

Next, regarding the B / HF resistance, a sample similar to that used in the pinhole test was used, and a B content of 1% and 24 ° C. was used.
The sample was dipped in the HF solution and the etching rate per minute was measured and evaluated. The amount of film loss was obtained by measuring the level difference with the resist cover portion using a surface roughness meter. Results, Figure 1
As shown in 0, when the film density is lower than 1.8, the etching rate is large, and for 1.5, the etching rate is 10 times or more that of the thermal nitride film. Furthermore, regarding FT-IR (Fourier transform infrared spectroscopy) measurement, 400 to 4000 cm ⁻¹ (Kaiser; wave number) measurement was performed using a sample similar to the pinhole test. The results for 1.5 and 1.8 are as shown in FIG. 11, where the horizontal axis is the wave number and the vertical axis is the transmittance. According to FIG. 11, the Si—H bond absorption peak (3340 cm ⁻¹ ) in the film having a density of 1.5 was observed significantly more significantly than that in the film having a density of 1.8, and the hydrogen content in the film was high. I understand.
A large amount of hydrogen means deterioration of acid resistance, and this result is consistent with the above-mentioned B · HF resistance measurement.

From the above test and measurement, the density was 1.8.
It was found that if it is lower than g / cm ³ , the SiNx film has many pinholes and the film is not densely deposited, the content of hydrogen impurities is large and the acid resistance is poor, and the film quality is deteriorated.

Therefore, the density of the protective SiNx film is 1.8.
By setting it to g / cm ³ or more, it is possible to form a dense protective film 14 having few pinholes and impurities and excellent in acid resistance, and an inkjet printer head having stable product quality can be obtained.

In this embodiment, the SiNx film has been described as an example of the inorganic passivation protective film.
Oxides such as iO ₂ , SiON that is a mixed film of a nitride and an oxide, and alternate films thereof showed almost the same tendency as the above-mentioned measurement results. Therefore, for these films as well, by setting the film density within the above range,
A high quality inkjet head can be obtained.

The quality of the protective film of the present invention can be maintained in other modes. As shown in FIG. 12, when the protective film 20, for example, the SiNx film is formed in the groove 12 of the piezoelectric ceramic plate 1 by the well-known technique, the CVD method, in order to prevent the corrosion of the electrode film and to provide a good ejection characteristic. As shown in FIG. 12, at least the SiNx film needs to be deposited on the electrode, and it is preferable to cover the entire region of the groove 12 without interruption. This is confirmed by the experiments and measurements described below.

To evaluate the protective properties of the protective film, the degree of corrosion of the electrode in a corrosive environment was measured, and the change in the specific resistance of the electrode film in an accelerated environment was also measured. Specifically, the procedure was as follows. First, a corrosion test was performed by a polarization characteristic measuring method using a generally known potentiostat. The sample has a sidewall thickness of 80 μm, height of 500 μm, and groove width of 90.
For a ceramics substrate in which 10 μm grooves are formed and aluminum (Al) is vapor-deposited on the side wall as an electrode film, the conditions relating to the deposition pressure of the above-mentioned CVD method production conditions are mainly controlled, The protective film covers only half of the groove wall in the groove 12, that is, the electrode only (electrode covering), and the step coverage is improved to continuously cover the entire area of the groove 12 (continuous covering) with an average film thickness of 0. 0.2 μm was manufactured. These two kinds of samples were placed in 0.1N (N) saline solution, and platinum (Pt) was used as a counter electrode and silver / silver chloride (Ag / AgCl) was placed at a position several cm away as a reference electrode. Then, a voltage was gradually applied to the electrode film below the protective film, and the current flow at the sample electrode was measured.

The results, as shown in FIG. 13, showed that in the sample in which the protective film was coated only on the electrodes, the current suddenly flowed out at a certain potential, the protective film was deteriorated, and the electrode metal film was corroded. On the other hand, the sample of the continuous coating film does not have the rise of current as in the former case. In the corrosive environment, the protective film is only on the electrode. In the sample, since the boundary end face of the protective film exists, it is considered that the corrosive solution entered from the end face and corroded the metal electrode film. That is, the sample whose protective film is only on the electrode is
It can be seen that the protective film function against the environmental stimulus is inferior, the corrosion of the electrode film is likely to proceed, and the continuous coating having no end face has the excellent protective film function against the corrosive environment. In addition, it was shown that when there was no protective film, a current flowed out immediately after the voltage was applied, and the corrosion started immediately.

Next, as an environment acceleration test, a sample similar to that used in the corrosion test was used and exposed to an environment of a temperature of 60 ° C. and a humidity of 90% for 30 days, and then the resistivity change of the metal electrode film under the protective film was changed. As a result, the sample having the protective film only on the electrode increased the specific resistance by about 1.5 times, and the continuous film sample showed almost no increase in the specific resistance by about 1.1 times. The reason for the 1.5-fold increase seems to be that excess water entered from the end surface of the protective film and oxidized a part of the electrode film. Generally, in an ink jet printer, ink ejection is caused by deformation of a wall. When electrically viewed, it is a charge / discharge phenomenon of a capacitor, and τ = cR (τ: time constant, c: side wall capacitance, R: The specific resistance of the electrode) is established. Ink ejection requires rapid deformation, that is, τ equal to or less than a certain value. An increase in R results in an increase in τ, which is disadvantageous to ink ejection. As with the results of the corrosion test, it can be seen that the continuous protective film is superior to the protective film only on the electrode. From the above experiment, it is necessary to deposit the protective film on at least the electrode, and it is desirable to cover the entire area of the groove 12 continuously without interruption, which is strong against external stimuli and excellent in corrosion resistance.
It has been found that the protective film 20 provides good jetting characteristics.

Therefore, an ink jet printer head having excellent durability and stable ejection characteristics was obtained in the continuous coating protective film of this example.

In the present embodiment, the SiNx film has been described as an example of the inorganic passivation protective film.
Oxides such as iO ₂ , SiON that is a mixed film of a nitride and an oxide, and alternate films thereof showed almost the same tendency as the above-mentioned measurement results. Therefore, also for these films, a high-quality inkjet head can be obtained by setting the film coating state within the above range.

[0044]

As is apparent from the above description, according to the present invention, an inorganic passivation type film is used as a protective film in an ink jet head, and at least the electrode, preferably the entire groove is covered. As a result, it becomes a protective film with excellent durability against environmental stimuli, and an inkjet head with excellent product quality can be stably supplied.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a conventional ink jet head and an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a conventional inkjet head and an inkjet head according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a configuration of a conventional inkjet head and an inkjet head according to an embodiment of the present invention.

FIG. 4 is a block diagram of a control unit of a conventional ink jet head and an embodiment of the present invention.

FIG. 5 is a schematic view of a CVD apparatus used for forming a protective film in the present invention.

FIG. 6 is a graph of the thickness of a protective film and the number of dielectric breakdowns in the present invention.

FIG. 7 is a graph of the film thickness of the protective film and the normalized deformation efficiency in the present invention.

FIG. 8 is a graph showing the film thickness of the protective film and the internal stress in the present invention.

FIG. 9 is a graph of the density of the protective film and the number of Cu deposits in the present invention.

FIG. 10 is a graph of the density of the protective film and the etching rate with respect to B · HF in the present invention.

FIG. 11 is an FT-IR measurement chart of the protective film of the present invention.

FIG. 12 is a cross-sectional view showing the configuration of an inkjet printer head according to the present invention.

FIG. 13 is a graph showing polarization characteristics of an electrode film when a protective film according to the present invention is used.

[Explanation of symbols]

 1 Ceramics Element 11 Side Wall 12 Groove 13 Metal Electrode 20 Protective Film

Claims (1)

[Claims] 1. In an ink jet head in which at least one wall forming the ink liquid chamber is made of a piezoelectric ceramic element, and an electrode for driving the piezoelectric ceramic element is provided in the ink liquid chamber, in order to protect the electrode from insulation. 2. An inkjet head, comprising the inorganic passivation protective film, and being deposited as a covering state of the protective film on at least an electrode, preferably the entire ink chamber.