Inkjet head, method for manufacturing for inkjet head, and inkjet recording device

Abstract

Provided is an inkjet head having a service life that is prolonged by improving the heat resistance of a protective film.　The inkjet head comprises a base material and a protective film that protects the base material. The protective film has, from the base material side, at least a first layer and a second layer. The first layer contains: polyparaxylylene having a structure represented by general formula (1); or a derivative thereof. The second layer contains a derivative of polyparaxylylene having a structure represented by general formula (2).

Description

Inkjet head, method for manufacturing an inkjet head, and inkjet recording apparatus

[0001] This invention relates to an inkjet head, a method for manufacturing an inkjet head, and an inkjet recording apparatus.

[0002] In an inkjet head, providing a protective film on the surface that comes into contact with the ink can suppress corrosion of the substrate or other components (Patent Document 1).

[0003] Japanese Patent Publication No. 2008-201026

[0004] Generally, inkjet head chips are manufactured by joining their various components with adhesive. In recent years, adhesives with high resistance to the solvents contained in ink have been used to extend the product's lifespan. Such adhesives generally have high curing temperatures, and each component is exposed to high temperatures during joining. Therefore, the protective film applied to the surface that comes into contact with the ink requires further improvement in heat resistance.

[0005] The problem to be solved by this invention is to provide an inkjet head with a longer lifespan by improving the heat resistance of the protective film.

[0006] The inventors investigated the causes of the above problems in order to solve them. The inkjet head comprises a substrate and a protective film, and the protective film has at least a first layer and a second layer in order from the substrate side. The first layer and the second layer each contain a predetermined polyparaxylylene or a derivative thereof. The inventors found that this improves the heat resistance of the protective film and provides an inkjet head with a longer lifespan, leading to the present invention. That is, the above problems according to the present invention are solved by the following means.

[0007] 1. An inkjet head comprising a substrate and a protective film for protecting the substrate, wherein the protective film has at least a first layer and a second layer in order from the substrate side, the first layer contains polyparaxylylene or a derivative thereof having a structure represented by the following general formula (1), and the second layer contains a derivative of polyparaxylylene having a structure represented by the following general formula (2).

[0008]

[0009] In general formula (1), each of the a X1 atoms independently represents an alkyl group having 1 to 5 carbon atoms, or a halogen atom. a represents an integer from 0 to 4. n1 represents the polymerization number.

[0010]

[0011] In general formula (2), each of the b X2 atoms independently represents an alkyl group having 1 to 5 carbon atoms, or a halogen atom. b is an integer from 0 to 4. n2 represents the number of polymerization units. Each of the c X3 atoms independently represents an alkyl group having 1 to 5 carbon atoms. c is an integer from 0 to 3. d is an integer from 1 to 4. n3 represents the number of polymerization units.

[0012] 2. The inkjet head according to paragraph 1, wherein the protective film, in which the second layer is the outermost layer, is in contact with the ink.

[0013] 3. The inkjet head according to paragraph 1 or 2, wherein the thickness of the protective film is in the range of 0.2 to 20 μm.

[0014] 4. The inkjet head according to paragraph 1 or 2, wherein the thickness of the first layer is in the range of 0.1 to 10 μm.

[0015] 5. The inkjet head according to paragraph 1 or 2, wherein the thickness of the second layer is in the range of 0.1 to 10 μm.

[0016] 6. The inkjet head according to paragraph 1 or 2, wherein the substrate contains nickel.

[0017] 7. The inkjet head according to paragraph 1 or 2, wherein the inkjet head has an adhesive layer, and the adhesive layer contains an epoxy resin or a fluororesin.

[0018] 8. A method for manufacturing an inkjet head as described in paragraph 1 or 2, comprising a protection step of protecting the substrate with a protective film, the method comprising: a first layer formation step of forming the first layer on the substrate; a second layer formation step of forming the second layer on the formed first layer; and a second layer heating step of heating the formed first and second layers, wherein the first and second layers are formed continuously without opening to the atmosphere from the start of the first layer formation step to the end of the second layer heating step.

[0019] 9. A method for manufacturing an inkjet head according to paragraph 8, comprising a first layer heating step of heating the formed first layer between the first layer forming step and the second layer forming step.

[0020] 10. The method for manufacturing an inkjet head according to paragraph 8, wherein the substrate contains nickel, and the substrate is formed by sputtering or plating.

[0021] 11. The method for manufacturing an inkjet head according to paragraph 8, wherein the inkjet head comprises a nozzle substrate, a flow channel substrate, and an actuator having the substrate protected by the protective film, and the method for manufacturing an inkjet head is to join the nozzle substrate and the flow channel substrate, and then join the flow channel substrate and the actuator.

[0022] 12. An inkjet recording device comprising the inkjet head described in paragraph 1 or 2.

[0023] According to the present invention, the lifespan of an inkjet head can be extended.

[0024] The mechanism by which the effects of this invention manifest or the mechanism of action are presumed to be as follows.

[0025] Conventional protective films, especially those containing polymers, are prone to cracks and other defects within the protective film due to the breakdown of polymer molecule bonds caused by reactive oxygen species generated in high-temperature environments. Ink can then penetrate the substrate through these cracks and other defects, leading to corrosion of the substrate and other components.

[0026] In this embodiment, the polymer contained in the protective film is a derivative of polyparaxylylene (PPX-NH) into which an amino group has been introduced. ２ ) is used. The mechanism is not clear, but PPX-NH ２ It is less prone to cracking and other defects even in high-temperature environments, and has high heat resistance. Therefore, the substrate and other materials are less likely to corrode over long periods, extending the lifespan of the inkjet head.

[0027] However, PPX-NH ２ It was found that, depending on the underlying layer that forms the base for the film, growth can occur as islands rather than as layers. In other words, depending on the underlying layer, it may not be possible to form a protective film with uniform thickness and without inconsistencies, making the protective film prone to defects.

[0028] In this embodiment, the protective film has a two-layer structure, and PPX-NH ２ A first layer containing polyparaxylylene or a derivative of polyparaxylylene (PPX) without amino groups is provided between the second layer containing the substrate and the substrate. The PPX-containing layer protects the substrate, and PPX grows relatively easily regardless of the underlying layer, making it easy to form a uniform film with consistent thickness. By using such a two-layer protective film, heat resistance can be improved, and the lifespan of the protected inkjet head can be extended.

[0029] This is a perspective view showing an example of an inkjet head. This is a cross-sectional view of an inkjet head. This is a partial cross-sectional view of an inkjet head. This is a cross-sectional view along line IV-IV in Figure 3. This is a schematic cross-sectional view showing an example of a laminate. This is a schematic cross-sectional view showing an example of a laminate. This is a flowchart explaining the manufacturing method of an inkjet head. This is a flowchart explaining the actuator manufacturing process. This is a flowchart explaining the protection process. This is a schematic diagram showing the general configuration of an inkjet recording device. This is a schematic diagram of the line head as seen from the conveyor belt side.

[0030] The inkjet head of the present invention includes a base material and a protective film for protecting the base material. The protective film has at least a first layer and a second layer in this order from the base material side. The first layer contains poly(p-xylylene) having a structure represented by the above general formula (1) or a derivative thereof. The second layer contains a derivative of poly(p-xylylene) having a structure represented by the above general formula (2). The inkjet head of the present invention is characterized by the above. This feature is a technical feature common to or corresponding to the following embodiments.

[0031] As this embodiment, in the protective film, it is preferable that the second layer is the outermost layer and comes into contact with the ink. Thereby, since the second layer coming into contact with the liquid has heat resistance, the life of the inkjet head can be extended.

[0032] As this embodiment, the thickness of the protective film is preferably within the range of 0.2 to 20 μm. Thereby, the function as a protective film can be sufficiently exhibited, and the life of the inkjet head can be extended.

[0033] As this embodiment, the thickness of the first layer is preferably within the range of 0.1 to 10 μm. Thereby, the function as a protective film can be sufficiently exhibited, and the life of the inkjet head can be extended.

[0034] As this embodiment, the thickness of the second layer is preferably within the range of 0.1 to 10 μm. Thereby, the function as a protective film can be sufficiently exhibited, and the life of the inkjet head can be extended.

[0035] As this embodiment, the base material preferably contains nickel. Thereby, the easily corroded nickel base material can be sufficiently protected, and the life of the inkjet head can be extended.

[0036] As this embodiment, the inkjet head has an adhesive layer, and the adhesive layer preferably contains an epoxy resin or a fluororesin. Thereby, the adhesive layer has high durability to the solvent contained in the ink, and the life of the inkjet head can be extended.

[0037] The present invention relates to a method for manufacturing an inkjet head, which is a method for manufacturing the above-mentioned inkjet head. The method includes a protection step in which a substrate is protected with a protective film, a first layer formation step in which a first layer is formed on the substrate, a second layer formation step in which a second layer is formed on the formed first layer, and a second layer heating step in which the formed first and second layers are heated. The first and second layers are formed continuously without opening to the atmosphere from the start of the first layer formation step until the end of the second layer heating step. This makes it possible to suppress the mixing of impurities originating from atmospheric components at the interface between the first and second layers.

[0038] In this embodiment, it is preferable to have a first layer heating step between the first layer formation step and the second layer formation step, in which the formed first layer is heated. This improves the adhesion between the substrate and the protective film, and extends the lifespan of the inkjet head.

[0039] In this embodiment, the base material preferably contains nickel, and the base material is formed by sputtering or plating. This allows for the formation of a base material with uniform thickness and no unevenness.

[0040] In this embodiment, the inkjet head comprises a nozzle substrate, a flow channel substrate, and an actuator having a substrate protected by a protective film. It is preferable to join the nozzle substrate and the flow channel substrate first, and then join the flow channel substrate and the actuator. This reduces the time the protective film is exposed to high temperatures, thereby extending the lifespan of the inkjet head.

[0041] The inkjet recording device of the present invention is equipped with the above-described inkjet head. This makes it possible to extend the lifespan of the inkjet recording device.

[0042] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the disclosed embodiments.

[0043] [Inkjet Head] Figure 1 is a perspective view showing an example of an inkjet head 1 of this embodiment. Figure 2 is a partial cross-sectional view of the inkjet head 1. When recording on a recording medium, the bottom surface of the inkjet head and the recording surface of the recording medium are positioned opposite each other. Specifically, the recording medium is positioned so that its recording surface is located below the inkjet head and perpendicular to the direction in which the ink is ejected. Inkjet recording is performed as the recording medium is transported.

[0044] For convenience, in the following explanation, the direction in which ink is ejected from the inkjet head will be considered downwards, and the opposite direction will be considered upwards. Furthermore, the direction in which the recording medium is transported will be considered the front-to-back direction, and the direction perpendicular to the direction in which the recording medium is transported on the recording surface will be considered the left-to-right direction.

[0045] The inkjet head 1 comprises an actuator 30, a manifold (not shown), a flow path substrate 40, and a nozzle substrate 50, which are housed in a housing 6. A flexible substrate, a drive circuit board, etc. (not shown) are located above these, and these are covered by a cover member 7 attached to the housing 6.

[0046] The housing 6 is formed by die-casting using, for example, aluminum as the material. The housing 6 is, for example, elongated in the left-right direction. The bottom surface of the housing 6 has an opening so that the nozzle substrate 50 is exposed to the outside. The housing 6 has mounting holes 68 at both ends in the left-right direction for attaching the housing 6 to the printer body.

[0047] In the example shown in Figure 2, the actuator 30 is of the bend mode type. The nozzle substrate 50 has a nozzle 51 for ejecting ink to the outside of the inkjet head 1. The actuator 30, the flow path substrate 40, and the nozzle substrate 50 are each joined together via an adhesive layer 2.

[0048] In this embodiment, the "flow channel substrate" refers to a substrate that forms a flow channel through which ink flows, and is located between the actuator 30 and the nozzle substrate 50. The flow channel substrate 40 is provided with a supply channel 21, a supply-side communication channel 23, and a nozzle-side communication channel 24. The supply-side communication channel 23 extends from the top of the supply channel 21 and is connected to the pressure chamber 22. The nozzle-side communication channel 24 penetrates the flow channel substrate 40 to connect the pressure chamber 22 and the nozzle 51 of the nozzle substrate 50.

[0049] The material of the flow channel substrate 40 is not particularly limited, but examples include glass, ceramic, silicon, plastic, stainless steel, etc.

[0050] The nozzle substrate 50 has a nozzle 51 that penetrates the nozzle substrate 50 at a position corresponding to the nozzle-side communication channel 24 extending from the lower part of the pressure chamber 22. The nozzle 51 has a shape in which the diameter gradually decreases as it extends downward, and the diameter is uniform near the outlet. The material of the nozzle substrate 50 is not particularly limited, but examples include silicon, polyimide, stainless steel, etc.

[0051] The actuator 30 is provided with a protective film 4 on the side that joins the flow channel substrate 40. The protective film 4 may be provided on the entire side of the actuator 30 that joins the flow channel substrate 40, or only on the part that comes into contact with the ink. Although not shown in Figure 2, the flow channel substrate 40 and the nozzle substrate 50 may also be provided with a protective film 4 on the parts that come into contact with the ink.

[0052] The actuator 30 has a pressure chamber layer 31 that forms a pressure chamber 22, and a diaphragm 32, an insulating layer 33, a piezoelectric layer 34, and an electrode layer 35 are laminated on top of the pressure chamber layer 31. The diaphragm 32, insulating layer 33, piezoelectric layer 34, and electrode layer 35 can be formed by a vacuum deposition method such as sputtering. These layers may also be formed by other deposition methods such as coating.

[0053] The pressure chamber layer 31 can be formed by a thick film formation method such as plating or by an etching method for a metal plate. The pressure chamber 22 is formed when the flow channel substrate 40 is joined to the lower surface of the pressure chamber layer 31. Examples of known metal materials for the pressure chamber layer 31 include nickel (Ni).

[0054] The diaphragm 32 contains a conductive metallic material and also serves as the lower electrode (common electrode) of the piezoelectric layer 34. Examples of known metallic materials for the diaphragm 32 include nickel (Ni).

[0055] The insulating layer 33 insulates the diaphragm 32 from the piezoelectric layer 34. In other words, the insulating layer 33 shields the application of voltage to the piezoelectric layer 34 outside the piezoelectric functional region R1.

[0056] The piezoelectric layer 34 preferably contains a perovskite-type compound. Examples of perovskite-type compounds include barium titanate (BaTiO2). ３ ), lead zirconate titanate (PZT: Pb(Zr・Ti)O ３ Examples include the above, and among them, it is preferable that it contains PZT as the main component. The molar ratio of Zr and Ti in PZT is preferably in the range of Zr / Ti = 30 / 70 to 70 / 30. Here, "main component" means that it is contained in an amount of 85% by mass or more of the total mass of the piezoelectric material.

[0057] To improve the performance of the piezoelectric material, donor ions may be added to the PZT. Examples of donor ions include metal ions such as lanthanum (La), niobium (Nb), tantalum (Ta), tungsten (W), aluminum (Al), and strontium (Sr). In particular, it is preferable that the donor ion be one or more metal ions selected from the group including La, Nb, Ta, and W. Furthermore, it is preferable that the thickness of the piezoelectric layer 34 be about a few μm.

[0058] The electrode layer 35 contains a conductive material. For example, the electrode layer 35 contains titanium, which is a precious metal. The thickness of the electrode layer 35 is approximately 0.2 μm.

[0059] When a voltage is applied to the electrode layer 35, the piezoelectric layer 34 deforms in the Z-axis direction in the piezoelectric functional region R1, and consequently, the diaphragm 32 deforms. When the diaphragm 32 deforms downward in the piezoelectric functional region R1, the volume of the pressure chamber 22 decreases, and the pressure of the ink 60 filled in the pressure chamber 22 increases. Conversely, when the diaphragm 32 deforms upward in the piezoelectric functional region R1, the volume of the pressure chamber 22 increases, and the pressure of the ink 60 filled in the pressure chamber 22 decreases. By varying the pressure of the ink 60 in a predetermined sequence, for example, by reducing the pressure and then increasing it, droplets 61 of ink 60 are ejected from the nozzle 51, which communicates with the pressure chamber 22 via the nozzle-side communication channel 24.

[0060] The pressure chamber layer 31, diaphragm 32, insulating layer 33, piezoelectric layer 34, and electrode layer 35 do not necessarily have to be single layers, but may each be multiple layers. Furthermore, other layers may be positioned between each layer.

[0061] The thickness of the adhesive layer 2 is preferably in the range of 0.1 to 5 μm.

[0062] The adhesive used to form the adhesive layer 2 is not particularly limited as long as it is an adhesive that can bond the actuator 30, the flow channel substrate 40, and the nozzle substrate 50, respectively. Examples of adhesives include room-temperature curing adhesives that cure at room temperature, thermosetting adhesives that cure by accelerating polymerization through heating, and active energy ray curing adhesives that cure by accelerating polymerization through irradiation with active energy rays such as ultraviolet rays.

[0063] In particular, a thermosetting adhesive is preferred. Thermosetting adhesives generally have strong resistance to solvents contained in inks and do not deteriorate easily even when in contact with ink. Furthermore, when a thermosetting adhesive is heated to a predetermined temperature for curing after bonding, the viscosity of the adhesive temporarily decreases, making it more fluid and easier to obtain a uniform thickness of the bonded layer. Examples of thermosetting adhesives include epoxy adhesives containing epoxy resin and fluororesin adhesives containing fluororesin. In addition, a conductive adhesive may be used from the viewpoint of good electrical connection. Examples of conductive adhesives include adhesives in which conductive particles are dispersed.

[0064] Figure 3 is a partial cross-sectional view of the inkjet head 1. In the example shown in Figure 3, the actuator 30 is of the shear mode type. The actuator 30 and the nozzle substrate 50 are joined via an adhesive layer 2. Although not shown in Figure 3, a flow channel substrate 40 may be provided between the actuator 30 and the nozzle substrate 50.

[0065] The actuator 30 has a pressure chamber layer 31 that forms a drive channel (pressure chamber) 11 and a dummy channel 12. The partition wall between the drive channel 11 and the dummy channel 12 is a drive wall 13 containing a piezoelectric material. Preferably, the piezoelectric material contains the same compound as that used in the bend-mode type.

[0066] The drive channel 11 and the dummy channel 12 penetrate the pressure chamber layer 31, and the drive channel 11 is connected to the nozzle 51 of the nozzle substrate 50. The nozzle substrate 50 has a nozzle 51 at a position corresponding to the drive channel 11. The nozzle substrate 50 does not have a nozzle 51 at a position corresponding to the dummy channel 12, and therefore the lower opening of the dummy channel 12 is blocked by the nozzle substrate 50. During ink ejection, ink flows through the drive channel 11 in the direction of the arrow, but no ink flows through the dummy channel 12. The dummy channel 12 is usually filled with a gas such as air.

[0067] Figure 4 is a cross-sectional view taken along the line IV-IV in Figure 3. As shown in Figure 4, the drive electrodes 14 are located on the surfaces of the four walls facing into the drive channel 11 and the dummy channel 12. The actuator 30 is provided with protective films 4 on the four walls of the drive electrodes 14 that come into contact with the ink. In Figures 3 and 4, the drive electrodes 14 in the drive channel 11 are provided with protective films 4 on the four walls that come into contact with the ink, but the drive electrodes 14 in the dummy channel 12 may also be provided with protective films 4. In the dummy channel 12, the protective films 4 protect the drive electrodes 14 from moisture contained in gases such as air.

[0068] On the upper surface of the pressure chamber layer 31, connecting electrodes 15 are positioned so as to correspond one-to-one with the drive channels 11 and dummy channels 12. One end of each connecting electrode 15 is electrically connected to the drive electrode 14 in the corresponding drive channel 11 or dummy channel 12.

[0069] The actuator 30 shown in Figures 3 and 4 is an independently driven actuator in which drive channels 11 and dummy channels 12 are alternately positioned in each channel row of the pressure chamber layer 31. The actuator 30 deforms the drive wall 13 by shearing it by applying a drive signal of a predetermined voltage to the drive electrode 14. As a result, the pressure in the ink supplied into the drive channel 11 changes, and ink droplets are ejected from the nozzle 51 of the nozzle substrate 50.

[0070] The driving electrode 14 and the connecting electrode 15 contain a conductive material. Examples of conductive materials include platinum (Pt), gold (Au), copper (Cu), palladium (Pd), ruthenium (Ru), titanium (Ti), nickel (Ni), aluminum (Al), chromium (Cr), tungsten (W), and iridium (Ir). These may be included individually or in combination of two or more. The conductive material may be a mixture of metals or an alloy. In that case, it may be a mixture or alloy of at least one of the above metals with other metals.

[0071] The thickness of the adhesive layer 2 is preferably in the range of 0.1 to 5 μm. The adhesive used to form the adhesive layer 2 is not particularly limited, and the same adhesive as that used for the bend-mode type can be used.

[0072] (Protective Film) Figures 5 and 6 are schematic cross-sectional views showing an example of a laminate 70. The laminate 70 has a protective film 4 on a substrate 71. The protective film 4 mainly protects the substrate 71 from ink, but may also protect the substrate 71 from other sources such as the outside air. The protective film 4 comprises at least a first layer 41 and a second layer 42 from the substrate 71 side. The protective film 4 may have layers other than the first layer 41 and the second layer 42. For example, as shown in Figure 6, there may be a third layer 43 between the substrate 71 and the first layer 41, or a fourth layer 44 on the surface side of the second layer. Although not shown, there may also be other layers between the first layer and the second layer.

[0073] As layers other than the first layer 41 and the second layer 42 in the protective film 4, there are no particular restrictions, but examples include a layer for improving the adhesion between layers, a layer for improving the durability against the solvent contained in the ink, and the like. As a layer for improving the durability against the solvent contained in the ink, there are inorganic oxide layers such as a silicon dioxide (SiO ２ ) layer and an aluminum oxide (Al ２ O ３ ) layer.

[0074] As described above, in the bend mode, the protective film 4 is provided on the pressure chamber layer 31 and on the diaphragm 32. In this case, the pressure chamber layer 31 and the diaphragm 32 correspond to the base material 71 in the laminate 70. Also, in the shear mode, the drive electrode 14 is provided on the pressure chamber layer 31, and further, the protective film 4 is provided on the drive electrode 14. In this case, the drive electrode 14 corresponds to the base material 71 in the laminate 70.

[0075] The actuator 30 includes the protective film 4 on the surface that comes into contact with the ink. The flow path substrate 40 and the nozzle substrate 50 may or may not include the protective film 4 on the surface that comes into contact with the ink. When the flow path substrate 40 and the nozzle substrate 50 are made of a material that is less likely to be corroded by the ink, they do not necessarily need to include the protective film 4.

[0076] In the production of the inkjet head, after the actuator 30, the flow path substrate 40, and the nozzle substrate 50 are each produced, it is preferable that they are joined with an adhesive. Thereby, suitable materials can be used for each part, and the manufacturing process can be simplified. However, in this method, after forming the protective film 4 on the actuator 30, each part is joined with a thermosetting adhesive. That is, the protective film 4 is exposed to a high-temperature (the curing temperature of the adhesive) environment. Therefore, the protective film 4 requires heat resistance such that no microcracks or the like occur even when exposed to a high-temperature environment of about 80°C, for example.

[0077] The overall thickness of the protective film 4 is not particularly limited, but is preferably in the range of 0.2 to 20 μm, more preferably in the range of 0.5 to 15 μm, and even more preferably in the range of 1 to 10 μm. Having a certain thickness allows the protective film to fully perform its function. Also, not being too thick does not hinder the deformation of the diaphragm 32 in the bend mode or the deformation of the drive wall 13 in the shear mode. The thickness can be controlled by adjusting the film formation conditions and the amount of raw material added in each layer.

[0078] The first layer 41 and the second layer 42 that constitute the protective film 4 will be described in order below.

[0079] (1) The first layer contains polyparaxylylene or a derivative thereof having a structure represented by the following general formula (1). In this specification, polyparaxylylene or a derivative thereof having a structure represented by the following general formula (1) is also referred to as "PPX". In this embodiment, "PPX" is referred to as "PPX-NH" as described later. ２ " is not included.

[0080]

[0081] In general formula (1), each of the a X1 atoms independently represents an alkyl group having 1 to 5 carbon atoms, or a halogen atom. a represents an integer from 0 to 4. n1 represents the polymerization number.

[0082] Alkyl groups may be linear or branched. Examples of C1-C5 alkyl groups include methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl, secondary butyl, tert-butyl, isopentyl, neopentyl, and tert-pentyl groups. Examples of halogen atoms include fluorine, chlorine, and bromine.

[0083] In this embodiment, PPX is synthesized using 99 parts by mass or more of a paraxylylene compound that does not have an amino group, when the total amount of raw materials is 100 parts by mass.

[0084] A specific example of PPX is shown. n1 represents the polymerization number.

[0085]

[0086] The first layer may contain any resin or other material in addition to PPX.

[0087] Thin films containing PPX can be formed by a vapor-phase synthesis method, also known as CVD (Chemical Vapor Deposition), using polyparaxylylene or its derivative dimer (solid) as the deposition source. In vapor-phase synthesis, when the dimer is heated under vacuum, it sublimes into a dimer gas. This gas decomposes thermally, causing the dimer to cleave and become monomers. In a deposition chamber at room temperature, this monomer gas polymerizes on all surfaces, forming a transparent thin film. In vapor-phase synthesis, the monomer gas can penetrate and polymerize even in narrow areas, making it easy to form a uniform thin film without unevenness.

[0088] Specifically, a thin film is formed according to the following chemical reaction equation. Formula (I) below shows the chemical structure of dimer (I) of paraxylylene or its derivative. Hereinafter, paraxylylene or its derivative will also be referred to as "paraxylylene compound (A)".

[0089] The following formula (II) shows the diradical of the stable paraxylylene compound (A) generated by sublimation and thermal decomposition of the dimer (I), and the chemical structure of the paraxylylene compound (A). Formula (II) shows the state in which the diradical of the paraxylylene compound (A) and the paraxylylene compound (A) coexist reversibly.

[0090] Formula (III) below shows the chemical structure of polymer (III) of paraxylylene compound (A), which is obtained by adsorption and polymerization of the diradicals of paraxylylene compound (A) onto a substrate. Polymer (III) is formed on the substrate, i.e., on the side of actuator 30 that comes into contact with the ink.

[0091] In the CVD process, diradicals of stable paraxylylene compound (A) are generated by sublimation and thermal decomposition of dimer (I). The diradicals of paraxylylene compound (A) are preferable because they have excellent penetration into fine structures and penetrate sufficiently and uniformly deep into the fine structure of the surface of the actuator 30 that comes into contact with the ink.

[0092]

[0093] In the above formulas (I), (II), and (III), X1 and a are the same as X1 and a in the above general formula (1).

[0094] The surface of the first layer, i.e., the side that has the second layer, may be oxidized. Methods of oxidation treatment include laser irradiation, UV / ozone treatment, and plasma irradiation. Among these, plasma irradiation is preferred as the oxidation treatment method. Oxidation treatment introduces hydrophilic groups such as carboxyl groups and hydroxyl groups to the surface of the first layer, making it possible to uniformly increase the critical surface tension of the film. In addition, minute irregularities can be given to the surface of the first layer. This improves the adhesion between the first layer and the second layer, which can improve the durability of the actuator and the yield during manufacturing.

[0095] The thickness of the first layer is preferably in the range of 0.1 to 10 μm. Having a certain thickness allows it to fully function as a protective film. Also, not being too thick does not hinder the deformation of the diaphragm in the bend mode or the deformation of the drive wall in the shear mode. The thickness can be controlled by adjusting the film formation conditions and the amount of raw material added.

[0096] When microcracks occur in the protective film under high-temperature conditions, the substrate is exposed at the cracks, and the substrate and ink come into contact. If the substrate contains metals such as nickel, the ink is likely to corrode the substrate. Furthermore, the ink seeps into the interior of the substrate and comes into contact with other components, resulting in corrosion of components even in areas not in contact with the ink. However, PPX-NH can be used on substrates containing metals such as nickel. ２ If you try to deposit a film directly, PPX-NH ２ It was found that this material is prone to island formation and does not easily form uniform layers of consistent thickness.

[0097] On the other hand, PPX is easily grown on substrates containing metals such as nickel, and it is easy to form a uniform, even layer. Therefore, by directly applying the first layer to the substrate, a uniform, even protective film can be formed on substrates containing metals such as nickel, and the thickness of the protective film can be reduced.

[0098] (2) Second layer The second layer contains a polyparaxylylene derivative having the structure represented by the following general formula (2). In this specification, a polyparaxylylene derivative having the structure represented by the following general formula (2) is referred to as "PPX-NH ２ It is also said as "."

[0099]

[0100] In general formula (2), each of the b X2 atoms independently represents an alkyl group having 1 to 5 carbon atoms, or a halogen atom. b is an integer from 0 to 4. n2 represents the number of polymerization units. Each of the c X3 atoms independently represents an alkyl group having 1 to 5 carbon atoms. c is an integer from 0 to 3. d is an integer from 1 to 4. n3 represents the number of polymerization units.

[0101] Alkyl groups may be linear or branched. Examples of C1-C5 alkyl groups include methyl, ethyl, propyl, butyl, pentyl, isopropyl, isobutyl, secondary butyl, tert-butyl, isopentyl, neopentyl, and tert-pentyl groups. Examples of halogen atoms include fluorine, chlorine, and bromine.

[0102] The arrangement of the repeating structure without an amino group and the repeating structure with an amino group is not particularly limited. PPX-NH ２ This may be any of the following: random copolymer, alternating copolymer, block copolymer, or Kraft copolymer.

[0103] In this embodiment, PPX-NH ２ In this case, when the total amount of raw materials is 100 parts by mass, it is synthesized using 1 part by mass or more of a paraxylylene compound having an amino group. For example, in a certain polymer, if the amount of a paraxylylene compound without an amino group is more than 99 parts by mass and the amount of a paraxylylene compound having an amino group is less than 1 part by mass, then the polymer is PPX-NH ２ It does not fall under the above category and is considered to fall under PPX.

[0104] PPX-NH ２In this process, when the total amount of raw materials is 100 parts by mass, the amount of paraxylylene compound having an amino group used is preferably in the range of 1 to 20 parts by mass, and more preferably in the range of 2 to 10 parts by mass. The film formed by synthesis in this ratio has good heat resistance. In other words, in terms of polymerization number, n2 / n3 is preferably in the range of 80 / 20 to 99 / 1, and more preferably in the range of 90 / 10 to 98 / 2.

[0105] PPX-NH ２ Specific examples are shown below. n21, n22, and n3 represent the polymerization number. Note that in the repeating structure without an amino group, the specific examples show both a structure in which the hydrogen atoms of the benzene ring are substituted with chlorine atoms and a structure in which the hydrogen atoms are not substituted, but the structure in which the hydrogen atoms of the benzene ring are not substituted is not necessarily required.

[0106]

[0107] The second layer is PPX-NH ２ In addition, any resin or other material may be included. The second layer can be formed using the same method as the first layer, and may also be subjected to oxidation treatment.

[0108] The thickness of the second layer is preferably in the range of 0.1 to 10 μm. Having a certain thickness allows it to fully function as a protective film. Also, by not being too thick, it does not hinder the deformation of the diaphragm 32 in the bend mode or the deformation of the drive wall 13 in the shear mode. The thickness can be controlled by adjusting the film formation conditions and the amount of raw material input.

[0109] [Method for Manufacturing an Inkjet Head] Figure 7 is a flowchart illustrating the method for manufacturing an inkjet head. First, the actuator, nozzle substrate, and flow channel substrate are manufactured (steps S1 to S3). Next, the nozzle substrate and the flow channel substrate are joined together (step S4). Finally, the flow channel substrate and the actuator are joined together (step S5).

[0110] In the joining process, after bonding the parts together with the aforementioned adhesive, the parts are heated to approximately 80°C. It is preferable to avoid exposing the protective film on the actuator to high temperatures as much as possible. Therefore, it is preferable to join the nozzle substrate and the flow path substrate first, and then join the flow path substrate and the actuator last, that is, to perform step S4 followed by step S5. However, in this embodiment, the protective film has sufficient heat resistance, so it is less likely to deteriorate even if exposed to high temperatures for a long time. In other words, the order of steps S4 and S5 may be reversed.

[0111] Figure 8 is a flowchart illustrating the actuator manufacturing process. First, the actuator base material is formed (step S11). Next, the formed base material is protected with a protective film (step S12). Here, "base material" refers to the components of the actuator that come into contact with the ink. Specifically, in the bend mode, the pressure chamber layer 31 and the diaphragm 32 correspond to the base material, and in the shear mode, the drive electrode 14 corresponds to the base material.

[0112] When the base material contains nickel, it is preferable to form the base material by sputtering or plating. This allows for the formation of a uniform layer with consistent thickness.

[0113] Figure 9 is a flowchart illustrating the protection process. Each layer of the protective film is formed sequentially from the substrate side using the CVD method described above. Details of the CVD method are as described above. In the flowchart shown in Figure 9, the protective film is configured to have only the first and second layers, but the protective film may have other layers, and each of the other layers can be formed using conventionally known methods.

[0114] First, a first layer is formed on the substrate by CVD (Step S121), and the formed first layer is heated (Step S122). Next, a second layer is formed on the heated first layer by CVD (Step S123), and the formed second layer is heated (Step S124).

[0115] It is preferable to form the first and second layers continuously without opening to the atmosphere from the start of the first layer formation step S121 until the end of the second layer heating step S124. By forming them continuously, it is possible to suppress the incorporation of impurities originating from atmospheric components at the interface between the first and second layers.

[0116] The layer formation by the CVD method is preferably carried out at room temperature (25°C) ± 10°C, i.e., within the range of 15 to 35°C, and more preferably at room temperature (25°C) ± 5°C, i.e., within the range of 20 to 30°C. The heat treatment after layer formation is preferably carried out at a range of 60 to 150°C, and more preferably at a range of 80 to 120°C. Heating within the above range makes the layer less prone to deformation even in subsequent high-temperature environments.

[0117] In the second layer heating step S124, both the first and second layers are essentially heated. Therefore, the first layer heating step S122 may be omitted, but it is preferable to perform the first layer heating step S122. By shrinking the first layer once to change its crystal structure before forming the second layer, deformation of the first layer during the second layer heating step S124 can be suppressed, and a decrease in adhesion between the substrate and the first layer, and between the first and second layers, can be suppressed.

[0118] [Inkjet Recording Device] Figure 10 is a schematic diagram showing the general configuration of the inkjet recording device 100 of this embodiment. The inkjet recording device 100 includes a transport unit 110 and a recording unit 120 having a plurality of line heads 121, etc.

[0119] The transport unit 110 (moving means) comprises a first transport roller 111, a second transport roller 112, and a transport belt 113. The first transport roller 111 and the second transport roller 112 rotate around a rotation axis extending to the left in Figure 10. The transport belt 113 is a ring-shaped belt whose inner side is supported by the first transport roller 111 and the second transport roller 112. The transport belt 113 moves in a circular motion around the first transport roller 111 and the second transport roller 112 as the first transport roller 111 rotates in response to the operation of a transport motor (not shown). The transport unit 110 transports the recording medium M in the direction of movement of the transport belt 113 (forward direction in Figure 10) by having the transport belt 113 move in a circular motion with the recording medium M placed on the transport surface of the transport belt 113. In other words, the transport unit 110 moves the line head 121 of the recording unit 120 and the recording medium M relative to each other in the forward direction.

[0120] The recording medium M may be, for example, a sheet of paper cut to a certain size. The recording medium M is supplied onto the conveyor belt 113 by a paper feeder (not shown), and ink is ejected from the line head 121 to record an image. After that, the recording medium M is discharged from the conveyor belt 113 to a predetermined paper discharge section. A long medium such as roll paper may be used as the recording medium M. Examples of recording medium M include plain paper, coated paper, cloth, or sheet-like resin.

[0121] The recording unit 120 is equipped with four line heads 121, each corresponding to one of four ink colors: yellow (Y), magenta (M), cyan (C), and black (K). The line heads 121 eject ink at appropriate timings based on image data onto the recording medium M transported by the transport unit 110 to record an image. The four line heads 121 are arranged at predetermined intervals from the upstream side in the transport direction (forward direction) of the recording medium M, for example, in the order of colors Y, M, C, and K. The number of line heads 121 can be changed depending on the number of colors used, and may be three or fewer, or five or more.

[0122] Figure 11 is a schematic diagram of the line head 121 as viewed from the conveyor belt 113 side. The line head 121 has a plurality of inkjet heads 1, each provided with a plurality of nozzles 51 for ejecting ink. In each inkjet head 1, the plurality of nozzles 51 are arranged in the left-right direction to form a nozzle row. Alternatively, as shown in Figure 11, two inkjet heads 1 may be combined to form a single head module 101.

[0123] Furthermore, the detailed configuration of each device constituting the inkjet head can also be modified as appropriate without departing from the spirit of the present invention.

[0124] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, the units "parts" or "%" are used, and unless otherwise specified, they represent "parts by mass" or "mass%". In addition, in the following examples, the operations were carried out at room temperature (25°C) unless otherwise specified.

[0125] For the bend mode actuator of the inkjet head "KM800" (manufactured by Konica Minolta, Inc.), the protective film on the surface in contact with the ink was replaced with a protective film with the configuration shown in Table I to obtain actuators (ACTs) for each comparative example or example. The substrate material of the actuator was nickel. Note that PPX and PPX-NH ２ The following compounds were used. n1, n21, n22, and n3 represent the polymerization number.

[0126]

[0127] (Example 1) In Example 1 (ACT1 and ACT2), a 1 μm thick layer of PPX[P-1] was formed as the first layer of the protective film on the surface of the actuator that comes into contact with the ink, using a vapor deposition apparatus (manufactured by SCS). Specifically, a monochloroparaxylylene dimer was used as the film-forming material, and the dimer was sublimated in a sublimation furnace and then decomposed in a pyrolysis furnace. The surface of the actuator that comes into contact with the ink (the surface on which the protective film is to be formed) was exposed to the resulting vapor at a film-forming pressure of 40 mTorr and room temperature (25°C) to form the first layer.

[0128] Next, as the second protective layer, a 1 μm thick PPX-NH layer was applied to the formed first layer using a vapor deposition apparatus (manufactured by SCS Corporation). ２ Layer [N-1] was formed. Specifically, dimers of dichloroparacyclophane and aminoparacyclophane were used as film-forming materials, and these dimers were sublimated. The resulting vapor was used to form the second layer by exposing the surface of the actuator that comes into contact with the ink (the surface forming the protective film) to the vapor at a film-forming pressure of 40 mTorr and room temperature (25°C).

[0129] Next, no heat treatment was performed on ACT1, while heat treatment was performed on ACT2. For the heat treatment, the actuator was heated at 140°C for 1 hour. This heat treatment was intended to bond the actuator, the flow path substrate, and the nozzle substrate using a thermosetting adhesive.

[0130] (Comparative Example 1) In Comparative Example 1, actuators (ACT3 and ACT4) were manufactured using the same procedure as in Example 1, except that the first layer was not formed.

[0131] (Comparative Example 2) In Comparative Example 2, actuators (ACT5 and ACT6) were fabricated using the same procedure as in Example 1, except that a layer of PPX (compound P-1) was formed in the second layer.

[0132] The obtained actuators were subjected to ink immersion evaluation. The ink used was a reactive dye ink, specifically pure ink (cyan, manufactured by Konica Minolta, Inc.) for the "Nassenger" inkjet textile printer. It should be noted that this reactive dye ink is an acidic, water-based ink, and corrosion is particularly likely to occur if the actuator's substrate is made of metal such as nickel.

[0133] As part of the immersion treatment, the actuator was immersed in the reactive dye ink and left at 60°C for one week or five weeks. This immersion treatment was intended for use in a printer where the ink is heated to 60°C for extended periods. A one-week immersion period corresponds to a two-month printer usage period, and a five-week immersion period corresponds to a one-year printer usage period.

[0134] The condition of the protective film and the corrosion state of the base material (nickel) in the actuator were evaluated according to the following criteria. Grade A was deemed acceptable, indicating no practical problems. A: No peeling of the protective film and no corrosion of the base material. B: Peeling of the protective film and corrosion of the base material.

[0135] Table I below shows the composition of the protective film, the heat treatment conditions, and the results of the ink immersion evaluation. A "-" in the table indicates that the corresponding layer is not present or that the corresponding treatment was not performed.

[0136]

[0137] From the comparative examples and examples, by adopting the protective film according to this embodiment, that is, the protective film consists of a PPX layer as the first layer and a PPX-NH as the second layer. ２ It can be seen that the heat resistance of the inkjet head is improved by having this layer. In Comparative Example 1, because the first layer is not present, the second layer cannot be formed as a uniform and even layer of thickness, so the protective film cannot adequately protect the substrate and the ink immersion evaluation is considered to be unsuccessful. In Comparative Example 2, the second layer is made of PPX-NH ２ Because it is not a protective layer, the protective film cracks when heated, and the ink immersion evaluation is considered to have failed.

[0138] Furthermore, in the ink immersion evaluation, a reactive dye ink prone to corrosion was used, but Example 1 passed the test. This indicates that the inkjet head of this embodiment can suppress substrate corrosion regardless of the type of ink used.

[0139] By using the present invention, the lifespan of an inkjet head and an inkjet recording device (printer) equipped with the inkjet head can be extended.

[0140] 1 Inkjet head 2 Adhesive layer 4 Protective film 6 Housing 7 Cover member 11 Drive channel 12 Dummy channel 13 Drive wall 14 Drive electrode 15 Connecting electrode 21 Supply channel 22 Pressure chamber 23 Supply side communication channel 24 Nozzle side communication channel 30 Actuator 31 Pressure chamber layer 32 Diaphragm 33 Insulating layer 34 Piezoelectric layer 35 Electrode layer 40 Channel substrate 41 First layer 42 Second layer 43 Third layer 44 Fourth layer 50 Nozzle substrate 51 Nozzle 60 Ink 61 Droplet 68 Mounting hole 70 Laminate 71 Substrate 100 Inkjet recording device 101 Head module 110 Transport section 111 First transport roller 112 Second transport roller 113 Transport belt 120 Recording section 121 Line head

Claims

1. An inkjet head comprising a substrate and a protective film for protecting the substrate, wherein the protective film has at least a first layer and a second layer in order from the substrate side, the first layer contains polyparaxylylene or a derivative thereof having a structure represented by the following general formula (1), and the second layer contains a derivative of polyparaxylylene having a structure represented by the following general formula (2). In general formula (1), each of the a X1 atoms independently represents an alkyl group having 1 to 5 carbon atoms, or a halogen atom. a represents an integer from 0 to 4. n1 represents the polymerization number. In general formula (2), each of the b X2 atoms independently represents an alkyl group having 1 to 5 carbon atoms, or a halogen atom. b is an integer from 0 to 4. n2 represents the number of polymerization units. Each of the c X3 atoms independently represents an alkyl group having 1 to 5 carbon atoms. c is an integer from 0 to 3. d is an integer from 1 to 4. n3 represents the number of polymerization units.

2. The inkjet head according to claim 1, wherein the protective film, the second layer is the outermost layer and is in contact with the ink.

3. The inkjet head according to claim 1 or claim 2, wherein the thickness of the protective film is in the range of 0.2 to 20 μm.

4. The inkjet head according to claim 1 or claim 2, wherein the thickness of the first layer is in the range of 0.1 to 10 μm.

5. The inkjet head according to claim 1 or claim 2, wherein the thickness of the second layer is in the range of 0.1 to 10 μm.

6. The inkjet head according to claim 1 or claim 2, wherein the substrate contains nickel.

7. The inkjet head according to claim 1 or claim 2, wherein the inkjet head has an adhesive layer, and the adhesive layer contains an epoxy resin or a fluororesin.

8. A method for manufacturing an inkjet head according to claim 1 or claim 2, comprising a protection step of protecting the substrate with a protective film, the method comprising: a first layer forming step of forming the first layer on the substrate; a second layer forming step of forming the second layer on the formed first layer; and a second layer heating step of heating the formed first and second layers, wherein the first and second layers are formed continuously without opening to the atmosphere from the start of the first layer forming step to the end of the second layer heating step.

9. The method for manufacturing an inkjet head according to claim 8, further comprising a first layer heating step of heating the formed first layer between the first layer forming step and the second layer forming step.

10. The method for manufacturing an inkjet head according to claim 8, wherein the substrate contains nickel, and the substrate is formed by sputtering or plating.

11. The method for manufacturing an inkjet head according to claim 8, wherein the inkjet head comprises a nozzle substrate, a flow channel substrate, and an actuator having the substrate protected by the protective film, and the method for manufacturing an inkjet head is to join the nozzle substrate and the flow channel substrate, and then join the flow channel substrate and the actuator.

12. An inkjet recording apparatus comprising the inkjet head described in claim 1 or claim 2.

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