JP2007276151A - Inkjet printer head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer head of high density nozzle arrangement in which the problems of decreasing in delivering efficiency, crosstalk and the like are improved, and to provide an inkjet head having no problem of durability such as occurrence of crack even when delivering is repeated. <P>SOLUTION: In the inkjet head having a plurality of compression chambers 3, nozzles 10 and a piezoelectric/electrostrictive actuator 7, a wall forming a vibration region 8 out of the walls of the compression chamber 3 is located on a first surface 9 side of a substrate forming the compression chamber, a groove 12 is formed in parallel with the longitudinal direction of the compression chamber 3 in the boundary region of the vibration region 8 of adjoining piezoelectric/electrostrictive actuators 7, and the angle made by a surface formed by the sidewall 13 of the groove 12 in the longitudinal direction and the first surface 9 side of a substrate forming the compression chamber is set in the range of 100-145°. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet printer head having a plurality of nozzles provided with a bending / mode piezoelectric / electrostrictive actuator.

  Inkjet printers have excellent features such as low noise, easy maintenance, high printing quality, and low price, and in recent years are rapidly spreading as output devices for personal computers. Ink jet printers generate pressure waves in ink and use them to eject ink. As pressure wave generation methods, there are mainly known ones that utilize foaming by heat-generating elements in ink, and those that utilize vibrations of displacement elements such as piezoelectric / electrostrictive actuators and electrostatic actuators. In the method using a displacement element, normally, ink is supplied from a common ink tank to each pressurizing chamber, and the vibration region of the vibration plate provided in the pressurizing chamber is driven by the displaceable element to generate discharge pressure. Ink is ejected from nozzles communicating with the nozzle.

  In recent years, ink jet printer heads equipped with piezoelectric / electrostrictive actuators according to the present invention have been actively developed with a high density nozzle array for the purpose of increasing the resolution of printed images and improving the printing speed. ing. Along with this, several problems occur, and the solution is eagerly desired.

  For one thing, the width of the pressurizing chamber is narrowed by increasing the density, so that the width of the vibration region for each pressurizing chamber of the diaphragm is also narrowed. Compared to conventional inkjet printer heads, the piezoelectric / electrostrictive actuator The displacement amount, that is, the volume change amount of the pressurizing chamber decreased, making it difficult to obtain a large discharge pressure. As a result, the ejection efficiency of the ink droplets is lowered, and the control of the ink droplet diameter becomes difficult.

  Next, the thickness of the partition wall that separates the adjacent pressurizing chambers is also reduced, and as a detrimental effect, the problem of unnecessary pressure waves propagating from the adjacent ink chambers through the partition walls, the so-called crosstalk problem, is aggravated. As a result, there is a problem that ink overflows from an adjacent nozzle that should not be ejected and remains in the vicinity of the nozzle opening, preventing subsequent ink ejection or disturbing the ejection direction.

  Furthermore, when the adjacent piezoelectric / electrostrictive actuators are driven at the same time and when driven independently, the deformation state of the pressurization chamber side wall is greatly different. As a result, the displacement of the diaphragm during simultaneous driving is different. However, the ink droplets are not stabilized and the ink droplet ejection speed and the droplet diameter vary.

  The following proposals can be found as a method for improving such a problem.

  Patent Document 1 discloses a substrate on which an ink flow path having a plurality of nozzles and a pressure chamber communicating with each nozzle is formed, a vibration plate bonded on the substrate, and a piezoelectric element bonded on the vibration plate. In the inkjet head comprising: a groove within the thickness of the diaphragm is provided at a position where the diaphragm is slightly escaped from the boundary between the pressurizing chambers to the inside of the pressurizing chamber. An ink jet head is disclosed. However, although the ink jet head disclosed in Patent Document 1 is effective in reducing crosstalk between adjacent pressurizing chambers and improving ink ejection efficiency as compared with a head without a groove, the degree is small. It was insufficient.

  In Patent Document 2, in order to obtain a greater improvement effect, a groove along the longitudinal direction of the pressurizing chamber is provided in the side wall separating the pressurizing chambers at a depth reaching the side wall from the diaphragm. An ink jet head is disclosed, and a head having a deeper groove is proposed as compared with Patent Document 1. Also in Patent Document 3, a piezoelectric / electrostrictive operation unit composed of an electrode film and a piezoelectric / electrostrictive film is baked and integrated on a ceramic substrate provided with a pressure chamber or a laminated ceramic substrate, or the electrode film and piezoelectric / In a piezoelectric / electrostrictive film type element provided by laminating each of the electrostrictive films while being sequentially fired and integrated, an appropriate length deeper than the thickness of the diaphragm from the surface of the pressurizing chamber side wall of the ceramic substrate or the laminated ceramic substrate A piezoelectric / electrostrictive film type element is disclosed in which at least one groove is formed along the side wall of the pressurizing chamber and at an appropriate interval from the inner wall surface of the side wall. . In these inkjet heads, by providing a deep groove on the side wall, each pressurizing chamber is separated from the adjacent pressurizing chamber, thereby causing problems such as a drop in ink droplet ejection efficiency, crosstalk problems, and adjacent pressurizing. The problem of variation in ejected ink droplets when the chamber actuators were driven simultaneously could be further improved. However, when the side wall is deformed, stress is easily concentrated on the bottom of the groove, and when repeated discharge is performed, there is a problem that a crack starts from the bottom of the groove due to endurance fatigue.

Further, in Patent Document 4, an ink chamber forming substrate on which partition walls for partitioning a plurality of ink chambers are formed, and one surface of the ink chamber forming substrate is sealed, and a piezoelectric element is formed corresponding to the ink chamber. And a sealing substrate that seals the other surface of the ink chamber forming substrate, and the piezoelectric element, the vibration plate, the ink chamber forming substrate, and the sealing substrate are integrated by firing of ceramics. An ink jet head is disclosed in which a groove is provided at a depth reaching the sealing substrate through the diaphragm and the partition wall of the ink chamber. In this ink jet head, deformation near the bottom of the side wall when the actuator is driven is small, and the occurrence of cracks during durability is considerably improved. However, since the thickness of the pressurizing chamber side wall is less than half over the entire surface, the rigidity of the pressurizing chamber is greatly reduced. As a result, the absorption of the discharge pressure generated by driving the actuator to the pressurizing chamber wall surface is increased, and the ink discharge efficiency is significantly reduced. Therefore, it has been difficult to realize an ink jet printer head having a high density nozzle array.
JP-A-2-187352 Japanese Patent Laid-Open No. 6-1515070 JP-A-6-350155 JP-A-7-156398

  The problems with the inkjet printer head of the present invention are that, in realizing an inkjet printer head with a high-density nozzle arrangement, there are problems such as a decrease in discharge efficiency, a crosstalk problem, a discharge speed when the actuators in adjacent pressurizing chambers are driven simultaneously, In addition to further improving the problem of variation in droplet diameter, by giving sufficient pressure chamber rigidity, there is little loss of discharge pressure due to absorption of the pressure chamber wall surface, and even when repeated discharge is performed, It is an object of the present invention to provide an ink jet head free from problems related to durability such as crack generation.

  In order to solve the above-described problems, an inkjet printer head according to the present invention includes a plurality of elongated pressurizing chambers, at least a part of which is provided in a pressurizing chamber forming substrate, and regularly arranged, and each of the pressurizing chambers. In an inkjet head having a plurality of communicating nozzles and a plurality of piezoelectric / electrostrictive actuators that act independently on each of the pressurizing chambers, a wall that forms a vibration region among the pressurizing chamber walls forms a pressurizing chamber Located on the first surface side of the substrate, the piezoelectric / electrostrictive actuator is composed of at least the vibration region, the piezoelectric / electrostrictive film, and a plurality of electrodes, and further in the longitudinal direction of the pressurizing chamber at the boundary region between adjacent vibration regions The angle between the surface formed by the longitudinal side wall of the groove and the first surface of the pressurizing chamber forming substrate is 100 degrees or more and 145 degrees or less.

  By forming the groove in this way, and the angle formed by the surface formed by the side wall in the longitudinal direction of the groove and the first surface of the pressure chamber forming substrate is in the range of 100 degrees to 145 degrees, Adjacent pressurization chambers caused by crosstalk at the same time as increasing the amount of displacement of the piezoelectric / electrostrictive actuators provided in the respective pressurization chambers without causing a significant decrease in rigidity and improving ink droplet ejection efficiency. This can solve the problems of inability to eject the nozzles and the disorder of the ejection direction, and the problem that the ejection speed and droplet diameter of the ink enemy vary when adjacent piezoelectric / electrostrictive actuators are driven simultaneously.

  If the angle formed between the surface formed by the side wall in the longitudinal direction of the groove and the first surface of the pressure chamber forming substrate is less than 100 degrees, the rigidity of the side wall decreases in a wide region from the vicinity of the bottom of the groove to the vicinity of the groove opening. When the ink is discharged, the loss of discharge pressure becomes large, a sufficient discharge speed cannot be obtained, and it becomes difficult to control the discharged ink droplets. If the angle is greater than 145 degrees, the opening width becomes larger than the groove depth, and it becomes difficult to design an ink jet head in which nozzles are arranged at high density. More preferably, it is 105 degrees or more and 130 degrees or less.

  In the ink jet printer head of the present invention, it is preferable that a thin film constituting at least a part of the vibration region is formed on the first surface of the pressurizing chamber forming substrate, and further, the thin film extends inside the groove. It is preferable to be formed.

  Thus, the efficiency of the piezoelectric / electrostrictive actuator can be further improved by forming the thin film with a material more suitable for the vibration region other than the pressurizing chamber forming substrate. Further, the durability of the piezoelectric / electrostrictive actuator is improved by forming the thin film not only in the vibration region but also in the groove located at the boundary of the vibration region.

  As described above, according to the present invention, there is a problem of a decrease in discharge efficiency, a problem of crosstalk, a decrease in discharge efficiency when the actuators in the adjacent pressurizing chamber are simultaneously driven, a droplet discharge speed, a droplet diameter. Can be improved, and the pressure chamber side wall has sufficient rigidity to reduce the loss of generated pressure waves and to prevent cracking even when repeated discharges are performed. can get. Thereby, it is possible to realize an inkjet printer head having a high-density nozzle arrangement.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of the first embodiment of the present invention. Reference numeral 1 denotes a pressurizing chamber forming substrate on which the pressurizing chamber 3 is formed. The pressurizing chambers are formed so as to be arranged in the horizontal direction in the figure, and each pressurizing chamber has an elongated shape in a direction perpendicular to the paper surface. The width of the pressurizing chamber is preferably 200 μm to 15 μm, more preferably 150 μm to 25 μm. The pitch in which the pressurizing chambers are formed adjacent to each other is preferably 300 μm to 30 μm, more preferably 200 μm to 50 μm. The length of the pressurizing chamber is preferably 50 mm to 200 μm. On the upper surface, which is the first surface 9 of the pressurizing chamber forming substrate, a piezoelectric region comprising a vibration region 8, a lower electrode 4, a piezoelectric / electrostrictive film 5, and an upper electrode 6 that are part of the pressurizing chamber forming substrate. / An electrostrictive actuator element 7 is formed. The piezoelectric / electrostrictive actuator may be of a bending mode such as unimorph or bimorph, and the configuration of the electrodes and the direction of spontaneous polarization of the piezoelectric / electrostrictive film are not particularly limited. The piezoelectric / electrostrictive film is formed by a vapor phase method such as a sputtering method or a chemical vapor deposition method, a liquid layer method such as a sol-gel method or a hydrothermal method, or screen printing of a piezoelectric / electrostrictive paste.

  A groove 12 extending in a direction perpendicular to the paper surface is formed in a boundary region between adjacent vibration regions of the pressurizing chamber forming substrate. As described above, the present invention is characterized in that the angle formed by the surface formed by the side wall 13 in the longitudinal direction of the groove and the pressure chamber forming substrate first surface 9 is not less than 100 degrees and not more than 145 degrees. More preferably, it is 105 degrees or more and 130 degrees or less.

  Reference numeral 2 denotes a nozzle plate, and nozzles 10 are provided so as to correspond to the pressurizing chambers 3 of the pressurizing chamber forming substrate. In FIG. 1, the nozzle plate is bonded to the second surface 11 which is the lower surface of the pressurization chamber forming substrate, but the nozzle plate is bonded to the end surface of the pressurization chamber forming substrate so that the nozzle and the pressurization chamber correspond. It may be formed so as to. The pressure chamber forming substrate or the nozzle plate is formed with a common ink chamber and an ink path communicating from the common ink chamber to each pressure chamber.

  Structural materials such as a pressure chamber substrate and nozzle plate used in the present invention are not particularly limited, but metals such as single crystal silicon, polycrystalline silicon, stainless steel, aluminum, alumina, mullite, zirconia, sialon, beryllia, cordierite, magnesia, Ceramics (metal oxides, metal nitrides, metal carbides) such as steatite, quartz, partially stabilized zirconia, silicon nitride, silicon carbide, aluminum nitride, etc. (polyoxide, polyaramide, polyphenylphenylene) , Organic polymer compounds such as polyoxymethylene and epoxy resin, glass, glass ceramics, and photosensitive glass. In particular, a silicon single crystal substrate is preferable as the pressurizing chamber forming substrate. When a silicon substrate is used, a piezoelectric actuator drive circuit can be formed using a semiconductor process.

  The processing method for the pressure chamber, flow path, common ink chamber, nozzle, etc. is not particularly limited, but sand blasting, anisotropic, anisotropic wet etching or dry etching, specifically reactive ion etching, ICP plasma Etching, so-called Bosch process, advanced silicon etching process (TM), isotropic etching of silicon using xenon difluoride, laser-assisted etching, stereolithography using photosensitive resin, and ceramic structures using stereolithography LIGA process, electric discharge machining, YAG laser machining, laser ablation, ion milling, dicing blade machining, and the like.

  As shown in FIG. 4 or FIG. 5, a diaphragm for forming a vibration region is formed on the first surface of the pressurizing chamber forming substrate by a vapor phase method such as sputtering or chemical vapor deposition, a liquid layer method such as sol-gel method, ceramic, etc. You may form using screen printing of paste, electroforming, etc. The thickness of the diaphragm is preferably 10 μ to 0.1 μm, and the material of the diaphragm is a metal such as YSZ, metal, nickel, chromium, aluminum, titanium, alloy, plastic, ceramic, zirconia, silicon nitride, sialon, silicon carbide, Examples include diamond.

  The discharge liquid is not limited to ink, and may be, for example, a dispersion of a functional substance or a DNA solution.

Example 1
A 100-oriented silicon single crystal substrate having a thickness of 200 microns was used as the pressure chamber forming substrate. In order to form a groove at a position to be a partition between the pressurizing chambers, wet etching was performed using an aqueous potassium hydroxide solution by patterning the oxide film as a mask. A plurality of grooves are formed on the first surface of the substrate at a pitch of 85 microns, the groove depth is about 20 microns, the opening is about 28 microns wide, and the angle between the first surface of the substrate and the side wall of the groove is 125 degrees. there were.

  Further, a platinum film having a thickness of 0.1 μm is formed on the first surface of the substrate by sputtering as a common electrode, and a single crystal film of lead zirconate titanate having a thickness of 3 μm is formed by sputtering. An individual electrode corresponding to each pressure chamber having a thickness of 1 micron was formed.

  A path communicating from the second surface, which is the back surface of the first surface of the pressurizing chamber base, to the pressurizing chamber from the pressurizing chamber, the common ink chamber, and the common ink chamber was formed by dry etching. The width of the pressurizing chamber was 50 μm, and a 3 μm silicon wall was left as a vibration region above the pressurizing chamber. A silicon substrate having a nozzle of 25 microns in a position corresponding to each pressurizing chamber was used as a nozzle substrate, and this was bonded to the second surface of the pressurizing chamber substrate as a gold vapor deposition film as an intermediate layer.

(Example 2)
A 100-oriented silicon single crystal substrate having a thickness of 200 microns was used as the pressure chamber forming substrate. The first surface of the pressure chamber forming substrate is patterned with a resist, and a groove having an opening width of 30 microns at an 85 micron pitch is formed by anisotropic dry etching so that the angle formed with the first surface of the substrate is 100 degrees. It formed so that it might become. Hereinafter, an inkjet head was prepared in the same manner as in Example 1.

(Example 3 to Example 5)
In the same manner as in Example 2, the ink jet heads of Examples 3 to 5 were formed so that the angles formed by the groove sidewall and the first surface of the pressure chamber substrate were 105 degrees, 130 degrees, and 145 degrees, respectively. .

(Example 6)
A 200 micron thick 100-oriented silicon single crystal substrate is used as the pressurizing chamber substrate, a 5 micron zirconia thin film is formed on the first surface of the pressurizing chamber forming substrate, and then patterned using a resist. Then, the grooves having an opening width of 30 microns at an 85 micron pitch were formed by anisotropic dry etching so that the angle formed with the first surface of the substrate was 120 degrees. Next, a piezoelectric / electrostrictive actuator was formed on the zirconia thin film in the same manner as in Example 1. Furthermore, a path communicating with the pressure chamber, the common ink chamber, and the common ink chamber was formed from the second surface of the pressure chamber forming substrate by dry etching. The width of the pressurizing chamber was 50 microns, and the wall of the zirconia thin film 5 microns was left as a vibration region in the upper portion of the pressurizing chamber. Thereafter, a nozzle substrate was prepared in the same manner as in Example 1, and an ink jet head of Example 6 was prepared by bonding to a pressure chamber substrate. FIG. 4 is a schematic cross-sectional view of the head of Example 6.

(Example 7)
A 200-micron-thick 100-oriented silicon single crystal substrate was used as the pressure chamber substrate, a resist was patterned on the first surface of the substrate, and a plurality of grooves were formed at 85-micron pitch by anisotropic dry etching. At this time, the width of the opening of the groove was 30 microns, and the angle formed between the side wall of the groove and the first surface of the pressurizing chamber forming substrate was 120 degrees. A zirconia thin film was formed by sputtering in the region where the pressurizing chamber on the first surface of the pressurizing chamber forming substrate provided with the groove was formed so as to extend also into the groove. Next, a piezoelectric / electrostrictive actuator was formed in the same manner as in Example 6, a flow path, a common ink chamber, and a pressurizing chamber forming substrate were formed, and a nozzle substrate was joined to produce an inkjet head of Example 7. FIG. 5 is a schematic cross-sectional view of the head of Example 7.

(Comparative Examples 1 to 2)
In the same manner as in Example 2, the angle formed between the groove sidewall and the first surface of the pressurizing chamber substrate was 95 degrees and 150 degrees, respectively, and ink jet heads of Comparative Examples 1 and 2 were prepared.

(Comparative Example 3 to Comparative Example 4)
A groove having a depth of about 20 microns and a width of about 20 microns was formed on the first surface of the pressurizing chamber forming substrate at an angle formed between the side wall of the groove and the first surface of the pressurizing chamber substrate. Other than that was carried out similarly to Example 2, and created the inkjet head of the comparative example 3. FIG. FIG. 2 is a schematic cross-sectional view of the head of Comparative Example 3. Next, an inkjet head of Comparative Example 4 was prepared in the same manner as Comparative Example 3 except that the groove width was 10 microns. FIG. 3 shows a schematic cross-sectional view of the head of Comparative Example 4.

(Comparative Example 5)
An inkjet head of Comparative Example 5 was prepared in the same manner as Example 1 without providing a groove.

(Comparative Example 6)
An ink jet printer head similar to that in Comparative Example 5 was prepared, and a groove having a depth reaching the nozzle plate using a YAG laser was provided in a boundary region between adjacent vibration regions on the first surface of the pressure chamber forming substrate. The angle formed between the side wall of the groove and the first surface of the pressure chamber substrate was 90 to 93 degrees. This was designated as the inkjet printer head of Comparative Example 6.

  Using the inkjet printer heads of Examples 1 to 7 and Comparative Examples 1 to 6, an ink ejection test was performed at a driving voltage of 30 V to measure the ejection speed of ink droplets. Furthermore, the rate at which the discharge speed decreased was measured as compared to the case where both adjacent nozzles were discharged simultaneously and discharged alone. In the ink jet printer head of the example, a high discharge speed was obtained. Particularly, the angle formed by the side wall of the groove and the first surface of the pressurizing chamber substrate was 105 degrees or more and 130 degrees or less, and was 17 m / s or more. Even when driven simultaneously with adjacent nozzles, the decrease in discharge speed was 7% or less and was small. Next, a continuous printing endurance test was performed, and the ejection speed was measured every predetermined number of sheets, and the number of printed sheets required to decrease by 3% from the initial state was examined. The printer head of the example was found to have sufficient durability. In particular, the durability of the head of Example 7 was excellent. These results are shown in Table 1.

It is sectional drawing which shows the structure of 1st embodiment of the inkjet printer head of this invention. It is sectional drawing which shows the structure of the conventional inkjet printer head. It is sectional drawing which shows the structure of the conventional inkjet printer head. It is sectional drawing which shows the structure of 2nd embodiment of the inkjet printer head of this invention. It is sectional drawing which shows the structure of 3rd embodiment of the inkjet printer head of invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressurization chamber forming substrate 2 Nozzle plate 3 Pressurizing chamber 4 Lower electrode 5 Piezoelectric / electrostrictive film 6 Upper electrode 7 Piezoelectric / electrostrictive actuator 8 Vibration region 9 First surface of pressurizing chamber forming substrate 10 Nozzle 11 Pressurizing chamber Second surface of forming substrate 12 groove 13 side wall in the longitudinal direction of the groove

Claims (4)

  A plurality of elongated pressurizing chambers, at least a part of which are provided in the pressurizing chamber forming substrate and regularly arranged, a plurality of nozzles communicating with each of the pressurizing chambers, and independent of each of the pressurizing chambers. In the inkjet head having a plurality of piezoelectric / electrostrictive actuators that act as described above, a wall that forms a vibration region among the walls of the pressurizing chamber is on the first surface side of the pressurizing chamber forming substrate, and the piezoelectric / electrostrictive actuator is It is composed of at least the vibration region, the piezoelectric / electrostrictive film, and a plurality of electrodes, and a groove parallel to the longitudinal direction of the pressurizing chamber is formed in a boundary region between adjacent vibration regions, and a side wall in the longitudinal direction of the groove An ink jet printer head in which an angle formed by the surface formed by the first chamber and the pressure chamber forming substrate first surface is not less than 100 degrees and not more than 145 degrees.   2. The ink jet printer head according to claim 1, wherein an angle formed by a surface formed by the side wall in the longitudinal direction of the groove and the first surface of the pressurizing chamber forming substrate is 105 degrees or more and 130 degrees or less.   The ink jet printer head according to claim 1 or 2, wherein a thin film constituting at least a part of the vibration region is formed on a first surface of the pressurizing chamber forming substrate.   The inkjet printer head according to claim 3, wherein the thin film is formed so as to extend inside the groove.

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