JP2009233927A - Manufacturing method for inkjet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head which attains compatibility between high print quality and durability even in use of electricity conductive ink. <P>SOLUTION: This invention relates to a manufacturing method is provided for the inkjet head including: a nozzle plate in which a plurality of nozzles for emitting ink are formed; a plurality of pressure chambers communicating with the nozzles; an electrode for supplying a drive pulse to a pressure generating means for emitting the ink; a first protective film formed on the pressure chamber side face of the electrode and formed from an inorganic insulating material; and a second protective film formed on the pressure chamber side face of the first protective film and formed from an organic insulating material. The manufacturing method includes a laser processing step in which after the first protective film is formed, the nozzle plate before the nozzles are formed is stuck to a face of the pressure chamber, the second protective film is formed, and subsequently the nozzle are formed in the nozzle plate. In the laser processing step, the thickness of the first protective film in the area to which a laser beam is emitted after the nozzles are opened is equal to or greater than 1 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an inkjet head having a protective film on an electrode and a nozzle formed by laser processing.

  Patent Document 1 describes a so-called shear mode type ink jet head in which ink droplets are ejected from nozzles by utilizing shear mode deformation of a piezoelectric member. FIG. 7 is an exploded perspective view of this conventional ink jet head. FIG. 8 is a cross-sectional view of the main part of the conventional ink jet head.

  The inkjet head 111 includes a piezoelectric ceramic plate 116 having a plurality of grooves 117 formed by cutting in a piezoelectric member, an ink chamber plate 123 having an ink supply port 125, and a nozzle plate 126 in which a plurality of nozzles 127 are formed. It consists of and. It is exemplified that the nozzle 127 is formed by performing laser processing using an excimer laser on a polyimide nozzle plate 126. A space surrounded by the groove 117, the ink chamber plate 123, and the nozzle plate 126 forms a pressure chamber that generates ink ejection pressure. An electrode 119 is provided on the side wall 118 of the piezoelectric member shared between adjacent pressure chambers. When a drive pulse is applied to the electrode 119, the side wall 118 operates as a pressure generating means for generating ink discharge pressure. The nozzle plate 126 is bonded to the end surface of the bonded body 150 after the protective layer 120 is formed on the bonded body 150 of the piezoelectric ceramic plate 116 and the ink chamber plate 123.

On the electrode 119, a protective layer 120 is formed in which an inorganic insulating film 121 made of an inorganic material and an organic insulating film 122 made of an organic material are sequentially provided. Silicon dioxide (SiO ₂ ) is used as the material of the inorganic insulating film 121, and the film thickness is 0.5 μm or more. Monochloroparaxylene is used as the material of the organic insulating film 122, and the film thickness is 5 μm or more.

In this ink jet head, since the inorganic insulating film 121 is resistant to organic solvents and the organic insulating film 122 is resistant to inorganic chemicals, a wide variety of electrically conductive liquids are used as inks. Further, it is described that the insulation between the ink and the electrode 119 can be maintained, and the dissolution of the electrode 119 can be prevented.
JP 2002-160364 A

  In Patent Document 1, in the process of manufacturing an inkjet head, the nozzle plate 126 on which the nozzle 127 is formed is bonded to the bonded body 150, or the nozzle plate 126 on which the nozzle 127 is not formed is bonded to the bonded body 150. It is not disclosed whether the nozzle 127 was formed later. The inkjet head by this different nozzle formation method has the following problems. Hereinafter, a description will be given with reference to FIGS. 9 and 10.

  FIG. 9 is a cross-sectional view of an ink jet head manufactured by joining a nozzle plate 126 having nozzles 127 already formed to a joined body 150. The nozzle plate 126 is joined to the joined body 150 of the piezoelectric ceramic plate 116 and the ink chamber plate 123 using an adhesive 151. When the nozzle plate 126 and the bonded body 150 are bonded, the adhesive 151 protrudes from the gap between the bonded body 150 and the nozzle plate 126, and part of the opening on the groove 117 side of the nozzle 127 is blocked. When a part of the nozzle 127 is blocked, the ink flow in the nozzle 127 is disturbed during ink ejection, the ink ejection speed and direction are varied, and the print quality is deteriorated.

  FIG. 10 is a cross-sectional view of the ink jet head in which the nozzle 127 is formed by an excimer laser after the nozzle plate 126 in which the nozzle 127 is not formed is bonded to the bonded body 150. The adhesive 151 leaked when the joined body 150 is joined to the nozzle plate 126 in which the nozzle 127 is not formed is removed when the nozzle 127 is processed by the excimer laser. Therefore, it is possible to prevent a decrease in print quality that occurs because a part of the nozzle 127 on the groove 117 side is blocked.

  However, when the nozzle 127 is formed by laser processing, the protective layer 120 is irradiated with laser light immediately after the laser light penetrates the nozzle plate 126. Therefore, the protective layer 120 is damaged at the portion 152 where the laser beam is irradiated. The protective layer 120 is composed of two layers of an organic insulating film 122 and an inorganic insulating film 121. However, when the organic insulating film 122 receives laser light, it evaporates and has a hole. If the inorganic insulating film 121 has a film thickness of about 0.5 μm, the resistance to laser light is insufficient, and the insulation between the ink and the electrode 119 cannot be maintained. For this reason, when ink having electrical conductivity is used, it is impossible to prevent dissolution of the electrode 119 in the portion 152 irradiated with the laser beam, and the durability of the ink jet head cannot be maintained.

  As described above, the inkjet head disclosed in Patent Document 1 has a problem that the print quality deteriorates when the nozzle is formed before the nozzle plate is joined, and the nozzle is formed after the nozzle plate is joined. In this case, there is a problem that the durability of the inkjet head cannot be maintained. An object of the present invention is to solve this problem and to provide an ink jet head that achieves both printing quality and durability even when an electrically conductive ink is used.

  In order to solve the above problems, the present invention provides a nozzle plate in which a plurality of nozzles for ejecting ink are formed, a plurality of pressure chambers communicating with the nozzles, and ejects ink in the pressure chambers from the nozzles. Pressure generating means, ink supply means for supplying ink to the pressure chamber, an electrode formed on the pressure chamber side surface of the pressure generating means, for supplying a driving pulse to the pressure generating means, and pressure of the electrode A first protective film formed on the chamber side surface and made of an insulating inorganic material; and a first protective film made of an insulating organic material formed on the pressure chamber side surface of the first protective film. In the method of manufacturing an ink jet head having two protective films, after forming the first protective film, a nozzle plate before nozzle formation is adhered to one surface of the pressure chamber to form the second protective film. After filming Including a laser processing step of forming the nozzle on a nozzle plate before the nozzle formation by laser processing, and the film thickness of the first protective film in a portion irradiated with laser light after the nozzle is opened in the laser processing step Was 1 μm or more.

  According to the present invention, since the nozzle is formed by laser processing after the nozzle plate is bonded, the adhesive that protrudes when the nozzle plate is bonded is removed by the laser beam at the time of nozzle processing. Therefore, it is possible to prevent deterioration of print quality due to the adhesive protruding into the nozzle hole. Further, immediately after the nozzle is opened in laser processing, the protective film is irradiated with laser light, and the second protective film made of an organic material evaporates at the irradiated portion, but the first protective film made of an inorganic material is 1 μm. Since the film thickness is as described above, the insulation between the ink and the electrode can be maintained. Since the first protective film is made of an inorganic material, it is difficult to completely prevent the generation of pinholes. However, the first protective film is protected by the second protective film except for the portion irradiated with the laser beam. It is unlikely that the insulation will be damaged by the pinhole. For this reason, even when a liquid having electrical conductivity is used as the ink, dissolution of the electrode 119 and the like can be prevented, and durability of the inkjet head can be maintained. That is, according to the present invention, in an inkjet head having a structure in which a nozzle is formed by laser processing and has an insulating protective layer on the inner surface of the pressure chamber, the inkjet head having both printing quality and durability against electrically conductive ink is provided. Can be provided.

  The structure and operation of the inkjet head according to the embodiment of the present invention will be described. 1 and 2 are cross-sectional views of the ink jet head 1.

  The inkjet head 1 includes a substrate 12, a top plate frame 13, a top plate lid 17, and a nozzle plate 16. A plurality of long grooves 11 are formed in the substrate 12 in parallel. Electrodes 4 are formed electrically independently on the inner surface of each long groove 11 and connected to the flexible cable 7 via the upper surface of the substrate 12. The flexible cable 7 is connected to a drive circuit 20 that generates drive pulses for driving the inkjet head. A first protective film 5 made of an insulating inorganic material and a second protective film 6 made of an insulating organic material are sequentially formed on the surface of the electrode 4. Each long groove 11 is sealed with a top plate frame 13, and a portion surrounded by the long groove 11 and the top plate frame 13 forms a pressure chamber 3. Adjacent pressure chambers 3 are separated via a side wall 10 composed of piezoelectric members 8 and 9. The side wall 10 is composed of piezoelectric members 8 and 9 polarized in opposite directions, and operates as an actuator that is deformed in a shear mode by a drive pulse applied to the electrode 4. A nozzle plate 16 is provided at the end of the pressure chamber 3, and each pressure chamber 3 communicates with the outside through a nozzle 2 formed on the nozzle plate 16. Ink is supplied in the order of the common pressure chamber 15, the long groove 11, the pressure chamber 3, and the nozzle 2 from the ink supply port 14 formed in the top plate lid 17. When a driving pulse is supplied from the driving circuit 20, a potential difference is generated between the electrodes 4a and 4c and the electrode 4b, and an electric field is generated on the side walls 10a and 10b. By this electric field, the side walls 10a and 10b are deformed in the shear mode, and pressure fluctuation occurs in the ink in the pressure chamber 3b, and ink is ejected from the nozzle 2b. Even when ink having electrical conductivity is used, the ink and the electrode 4 are electrically insulated by the first protective film and the second protective film. Therefore, corrosion of the electrode 4 due to current flowing through the ink, electrolysis of the ink, aggregation of the dispersion in the ink such as pigment, and the like are prevented.

For the substrate 12, alumina (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), aluminum nitride (AlN), lead zirconate titanate (PZT), or the like can be used. In consideration of the difference in expansion coefficient from the piezoelectric members 8 and 9 and the dielectric constant, PZT having a low dielectric constant is used as the substrate 12. The piezoelectric members 8 and 9 are lead zirconate titanate (PZT: Pb (Zr, Ti) O ₃ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like. In this embodiment, PZT having a high piezoelectric constant is used.

  The electrode 4 has a two-layer structure of nickel (Ni) and gold (Au). The electrode 4 was formed by a plating method in order to form a uniform film inside the long groove. Masking necessary for forming electrodes individually in each long groove is performed, and plating is performed. As a method of forming the electrode 4, a sputtering method or a vapor deposition method can also be used. The long grooves 11 have a depth of 300 μm and a width of 80 μm, and are arranged in parallel at a pitch of 169 μm.

  The nozzle plate 16 is a polyimide film having a thickness of 50 μm, and the nozzles 2 corresponding to the number of long grooves are formed by an excimer laser device. The shape of the nozzle 2 is 30 μm on the discharge side and 50 μm on the pressure chamber side, and has a reverse taper narrowed to the discharge side.

  A method for manufacturing the inkjet head 1 will be described. FIG. 3 is a cross-sectional view showing a manufacturing process of the inkjet head 1 of the embodiment.

[First Embodiment]
As shown in FIG. 3 (a), two piezoelectric members 8 and 9 (PZT) polarized so that their directions are opposite to each other in the thickness direction are bonded, embedded in the substrate 12, and bonded. . As described above, PZT having a dielectric constant lower than that of the piezoelectric members 2 and 3 is used as the material of the substrate 1. Next, as shown in FIG. 3B, a plurality of long grooves 11 with a constant interval are formed in a direction parallel to the end face of the substrate 12 and across the piezoelectric members 8 and 9 by cutting with a diamond cutter. Next, as shown in FIG. 3C, an electrode pattern is formed by electroless Ni plating on the surface of the substrate and the inner surface of the long groove, and gold plating is further performed on the electrode. Next, SiO ₂ is formed in a long groove with a film thickness of 1 μm or more as a first protective film made of an inorganic insulating material.

The SiO ₂ film is formed to a thickness of 1 μm or more by high frequency sputtering. During film formation, a part of the electrode 4 drawn out on the upper surface of the substrate 12 is masked so that the SiO ₂ film is not formed at the connection portion between the flexible cable 7 and the electrode 4.

Examples of the inorganic insulating material include Al ₂ O ₃ , SiO ₂ , ZnO, MgO, ZrO ₂ , Ta ₂ O ₅ , Cr ₂ O ₃ , TiO ₂ , Y ₂ O ₃ , YBCO, mullite (Al ₂ O ₃ .SiO ₂ ), SrTiO ₃ , Si ₃ N ₄ , ZrN, AlN, or the like.

As the film forming method, the above-described sputtering method, CVD (chemical vapor deposition) method, vapor deposition method, sol-gel method, plating method, coating method, printing method, or the like can be used. In other words, the inorganic insulating material is deposited by chemical reaction or condensation on the gold-plated electrode in a vacuum or in the atmosphere. Any method may be used as long as the above-described inorganic insulating material containing SiO ₂ can be formed on the gold-plated electrode.

  Next, as shown in FIG. 3D, the top plate frame 13 is bonded to the upper surface of the substrate 12. Next, as shown in FIG. 3E, the substrate 12 is divided into two inkjet heads 1 by cutting. Next, as shown in FIG. 3F, a polyimide film that becomes the nozzle plate 16 is bonded to the side surface of the pressure chamber 3. When the polyimide film is bonded to the side surface of the pressure chamber 3, the adhesive between the side wall 10 and the polyimide film protrudes into the pressure chamber 3. The protruding adhesive is cured as a thin film on the pressure chamber side of the polyimide film.

  Next, as shown in FIG. 3G, parylene (polyparaxylylene), which is an organic insulating material, is formed as a second protective film with a film thickness of 3 μm or more in the long groove. A method for forming a parylene film will be described.

  After vaporizing the raw material diparaxylylene, it is thermally decomposed at a high temperature to form a highly reactive radical monomer (diradical paraxylylene). When the monomer is adsorbed on the first protective film or the gold plating electrode, it polymerizes there to form a polymer film (parylene film).

  In addition, as an organic insulating material other than parylene, polyimide, DLC (diamond-like carbon), or the like can be used.

  In this embodiment, the ink jet head 1 is divided into two ink jet heads 1 shown in FIGS. 3E and 3F, and after a polyimide film and a top plate frame 13 are bonded to the substrate 12, a parylene film shown in FIG. ing. When cut into the two inkjet heads shown in FIG. 3E, a rough surface may be formed in the vicinity of the cut portion of the side wall 11. Even in this case, since the parylene film is formed after bonding the polyimide film, the organic insulating film is sufficiently formed also in the vicinity of the boundary between the long groove 11 and the polyimide film as shown in FIG.

  Next, as shown in FIG. 3H, a reverse-tapered nozzle is formed on the nozzle plate 16 of polyimide film by an excimer laser. Excimer laser is irradiated to the polyimide film from the side opposite to the pressure chamber 3 with the polyimide film interposed therebetween, and the polyimide is chemically decomposed to form a nozzle. By shifting the focal position of the excimer laser from the polyimide film, the laser beam spreads, so that an inversely tapered shape is formed in which the discharge port side is narrow and the pressure chamber side is wide.

  FIG. 4 shows a detailed cross-sectional view around the nozzle 2 after the reverse taper processing is performed on the nozzle plate 16 of the polyimide film by the excimer laser. The adhesive 18 protruding when the nozzle plate 16 is bonded to the side surface of the pressure chamber 3 is removed when the nozzle 2 is formed by the excimer laser. At the same time, a part of the organic insulating film, which is the second protective film, is also removed by the laser light irradiated on the side wall 10 to form a laser damage hole 19. However, since the thickness of the first protective film 5 is 1 μm or more at the site of the laser damage hole 19, no hole is formed in the first protective film 5 even when the laser light is irradiated. Therefore, even when conductive ink is injected into the pressure chamber 3, the electrode 4 and the ink are kept electrically insulated. Therefore, it is possible to prevent corrosion of the electrode 4 and electrolysis of the ink. Since the first protective film 5 is made of an inorganic material, it is difficult to completely prevent the generation of pinholes. However, the first protective film is protected by the second protective film at portions other than the laser damage hole 19. The possibility of impairing insulation by pinholes is small.

In order to confirm the resistance of the first protective film 5, which is an inorganic insulating film, to laser processing, the following test was performed. After irradiating excimer laser light with an intensity of 10 mJ on four types of test pieces in which SiO ₂ films were formed on gold electrodes with thicknesses of 0.5 μm, 1 μm, 3 μm, and 5 μm, the insulation properties of these test pieces were examined. It was. As a result, it was confirmed that insulation was not maintained in the test piece having a film thickness of 0.5 μm, but insulation was maintained in the test piece having a film thickness of 1 μm or more. For the investigation of insulation, the apparatus shown in FIG. 5 was used, and conduction was confirmed by the red reaction of the phenol rain solution. The reason why the excimer laser beam has an intensity of 10 mJ is to set the same conditions as the energy required for processing the nozzle holes of the polyimide film. From this test result, it was confirmed that the insulating property can be maintained even if the laser beam is irradiated if the inorganic insulating film has a thickness of 1 μm or more.

[Second Embodiment]
A second embodiment will be described. As shown in FIG. 6A, two piezoelectric members 8 and 9 (PZT) polarized so as to be opposite to each other in the plate thickness direction are bonded, embedded in the substrate 12, and bonded. . As described above, PZT having a lower dielectric constant than that of the piezoelectric members 8 and 9 is used as the material of the substrate 12. Next, as shown in FIG. 6B, a plurality of long grooves 11 with a constant interval are formed in a direction parallel to the end face of the substrate 12 and across the piezoelectric members 8 and 9 by cutting with a diamond cutter. Next, as shown in FIG. 6C, an electrode pattern is formed by electroless Ni plating on the surface of the substrate and the inner surface of the long groove, and electrolytic gold plating is further performed on the electrode. Next, SiO ₂ is formed in a long groove with a film thickness of 1 μm or more as a first protective film made of an inorganic insulating material. Subsequently, parylene (polyparaxylylene), which is an organic insulating material, is formed as a second protective film with a film thickness of 3 μm or more in the long groove. SiO ₂ and parylene were formed in the same manner as in the first embodiment.

  Next, as shown in FIG. 6 (d), the top plate frame 13 is bonded to the upper surface of the substrate 12, and as shown in FIG. 6 (e), the substrate 12 is divided into two inkjet heads by cutting, As shown in FIG. 6 (f), a polyimide film that becomes the nozzle plate 16 is bonded to the side surface of the pressure chamber 3.

  Next, as shown in FIG. 6G, an inversely tapered nozzle is formed on the nozzle plate 16 of polyimide film by an excimer laser. The nozzle processing was performed under the same conditions as the processing described in the first embodiment.

  Also in the second embodiment, since the thickness of the first protective film 5 is 1 μm or more at the site of the laser damage hole 19 shown in FIG. 4, the first protective film 5 has a hole even when irradiated with laser light. Is not formed. Therefore, even when conductive ink is injected into the pressure chamber 3, the electrode 4 and the ink are kept electrically insulated. Therefore, it is possible to prevent corrosion of the electrode 4 and electrolysis of the ink.

FIG. 3 is a longitudinal sectional view of an ink jet head according to the manufacturing method of the present invention. FIG. 3 is a cross-sectional view of an inkjet head manufactured by the manufacturing method of the present invention. The longitudinal cross-sectional view which shows the process of the manufacturing method of 1st Embodiment. FIG. 3 is a cross-sectional view of a main part of the inkjet head according to the manufacturing method of the first embodiment. The figure which shows the principle of the test apparatus of an insulating film. The longitudinal cross-sectional view which shows the process of the manufacturing method in 2nd Embodiment. The disassembled perspective view of the inkjet head of a prior art. Sectional drawing of the principal part of the inkjet head of a prior art. Sectional drawing which shows the subject of the inkjet head of a prior art. Sectional drawing which shows the other subject of the inkjet head of a prior art.

Explanation of symbols

1 Inkjet head
2 nozzles
3 Pressure chamber
4 electrodes
5 First protective film
6 Second protective film
7 Flexible cable
8, 9 Piezoelectric member
10 Side wall
11 Long groove
12 Substrate
13 Top plate frame
14 Ink supply port
15 Common pressure chamber
16 Nozzle plate
17 Top cover
18 Adhesive
19 Laser damage hole

Claims (2)

A nozzle plate having a plurality of nozzles for discharging ink, a plurality of pressure chambers communicating with the nozzles, pressure generating means for discharging ink in the pressure chambers from the nozzles, and supplying ink to the pressure chambers Formed on the pressure chamber side surface of the pressure generating means, and formed on the pressure chamber side surface of the electrode, and formed from an inorganic insulating material. In the method of manufacturing an ink jet head, comprising: a first protective film comprising: a second protective film made of an organic insulating material and formed on the pressure chamber side surface of the first protective film;
After forming the first protective film, the nozzle plate before forming the nozzle is adhered to one surface of the pressure chamber, and after forming the second protective film, the nozzle plate before forming the nozzle by laser processing Including a laser processing step for forming the nozzle, wherein the thickness of the first protective film in the portion irradiated with laser light after the nozzle is opened in the laser processing step is 1 μm or more. A method for manufacturing an inkjet head. A nozzle plate having a plurality of nozzles for discharging ink, a plurality of pressure chambers communicating with the nozzles, pressure generating means for discharging ink in the pressure chambers from the nozzles, and supplying ink to the pressure chambers Formed on the pressure chamber side surface of the pressure generating means, and formed on the pressure chamber side surface of the electrode, and formed from an inorganic insulating material. In the method of manufacturing an ink jet head, comprising: a first protective film comprising: a second protective film made of an organic insulating material and formed on the pressure chamber side surface of the first protective film;
After forming the first and second protective films, a laser processing step of adhering a nozzle plate before forming the nozzle to one surface of the pressure chamber and forming the nozzle on the nozzle plate before forming the nozzle by laser processing And a film thickness of the first protective film at a portion irradiated with laser light after the nozzle is opened in the laser processing step is 1 μm or more.

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