Liquid ejection head substrate, liquid ejection head, and method of manufacturing liquid ejection head substrate

Abstract

To perform reliable and high quality recording by stabilizing the initial ejection characteristics of a liquid ejection head.SOLUTION: The substrate for the liquid discharge head includes a heating part 104H for generating heat energy for discharging a liquid, a first protection layer 106 covering the heating part 104H, a second protection layer 107 formed to overlap the first protection layer 106 by using a metal-containing material, and a third protection layer 110 formed to overlap the second protection layer 107 by using a material containing a material dissolved in the liquid.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a substrate for a liquid ejection head, a liquid ejection head, and a method for manufacturing a substrate for a liquid ejection head. [Background technology]

[0002] Inkjet recording devices are capable of high-speed, high-quality recording by using thermal energy to bubble a liquid such as ink. A liquid ejection head used in an inkjet recording device has, for example, multiple ejection orifices, liquid flow paths communicating with the ejection orifices, and multiple electrothermal conversion elements corresponding to the multiple ejection orifices. The electrothermal conversion elements generate thermal energy used to eject ink from the ejection orifices. The electrothermal conversion elements are configured with a heating resistor and electrodes for supplying power to the heating resistor. The electrothermal conversion elements are covered with an electrically insulating protective layer, ensuring insulation between the multiple electrothermal conversion elements. Ink is supplied to the liquid flow paths from an ink tank that stores ink. The ink supplied to the liquid flow paths is guided from the liquid flow paths to the ejection orifices and held there, forming a meniscus near the ejection orifices. When an electrothermal conversion element is selectively driven in this state, thermal energy is generated from the selectively driven electrothermal conversion element. The thermal energy generated by the electrothermal transducer rapidly heats the ink at the contact point (heat application area) near the electrothermal transducer, causing it to bubble. The pressure generated by this bubbling causes the ink to be ejected from the nozzle.

[0003] The thermal action portion of a liquid ejection head is exposed to high temperatures due to heating by the heating resistor, and is also subjected to a combination of physical effects such as impacts from cavitation caused by bubbling and contraction of the ink, and chemical effects from the ink. Hereinafter, the liquid ejection head may be simply referred to as the head. To protect the electrothermal conversion elements from the physical and chemical effects of the thermal action portion of the head, an upper protective layer is provided on the thermal action portion. Conventionally, an upper protective layer made of tantalum (Ta), which is relatively resistant to physical effects such as impacts from cavitation and chemical effects from the ink, was provided to a thickness of 0.2 to 0.5 μm, thereby achieving both a long head life and high reliability.

[0004] When heated to high temperatures, colorants and additives contained in ink decompose at the molecular level, converting them into hardly soluble substances, which then physically adsorb to the upper protective layer. This phenomenon is known as "kogation." When hardly soluble organic or inorganic substances are adsorbed to the upper protective layer, heat conduction to the ink becomes uneven, resulting in unstable bubbling. In response to this issue, Patent Document 1 proposes a method in which the upper protective layer is formed using a metal film that dissolves through an electrochemical reaction. The upper protective layer is then dissolved by the electrochemical reaction before the kogation affects the ink's ejection, thereby removing the kogation along with the upper protective layer. Examples of metal films that dissolve through an electrochemical reaction include iridium (Ir) and ruthenium (Ru). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-105364 Summary of the Invention [Problem to be solved by the invention]

[0006] During the multiple processes from the formation of the upper protective layer to the completion of the liquid ejection head, foreign matter may adhere to the surface of the upper protective layer. However, cleaning is performed during each process to keep the surface of the upper protective layer clean. However, there are cases where foreign matter adheres to the surface of the upper protective layer due to unforeseen circumstances, and the foreign matter cannot be removed by subsequent cleaning. For example, when photolithography is used in the process of forming the nozzles (ejection ports), there is a concern that foreign matter may adhere to the surface of the upper protective layer of some of the nozzles in the head. If the head is completed with foreign matter still adhering to the surface of the upper protective layer, the foreign matter will reduce the ink ejection speed, affecting the printed material.

[0007] An object of the present disclosure is to stabilize the initial ejection characteristics of a liquid ejection head, thereby enabling reliable, high-quality printing. [Means for solving the problem]

[0008] A substrate for a liquid ejection head according to one embodiment of the present disclosure includes a heat generating portion that generates thermal energy for ejecting liquid, a first protective layer that covers the heat generating portion, a second protective layer formed on top of the first protective layer using a material that contains metal, and a third protective layer formed on top of the second protective layer using a material that contains a substance that dissolves in liquid. [Effects of the Invention]

[0009] According to the present disclosure, the initial ejection characteristics of the liquid ejection head can be stabilized, and reliable, high-quality printing can be performed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of an inkjet recording apparatus. [Figure 2] FIG. 2 is a perspective view showing a liquid ejection head unit. [Figure 3] FIG. 1 is a perspective view schematically illustrating a liquid ejection head. [Figure 4]3 is a plan view schematically showing the vicinity of a heat application part in the element substrate according to the first embodiment. FIG. [Figure 5] 3 is a cross-sectional view schematically showing the vicinity of a heat application portion on an element substrate. FIG. [Figure 6] FIG. 1 is a potential-pH diagram of the metals used in the second and third protective layers. [Figure 7] 5A to 5C are schematic cross-sectional views illustrating a manufacturing process of an element substrate. [Figure 8] 5A to 5C are schematic cross-sectional views illustrating a manufacturing process of an element substrate. [Figure 9] 5A to 5C are schematic cross-sectional views illustrating a manufacturing process of the liquid ejection head. [Figure 10] FIG. 10 is a cross-sectional view schematically showing the vicinity of a heat application portion in an element substrate according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the present disclosure, and not all combinations of features described in the following embodiments are necessarily essential to the solutions of the present disclosure. Note that the same components will be described with the same reference numerals.

[0012] <<First Embodiment>> <Configuration of Inkjet Recording Apparatus> The liquid ejection head according to this embodiment can be installed in inkjet recording devices such as printers, copiers, facsimiles with communication systems, and word processors with printer units. The liquid ejection head can also be installed in systems that combine various processing devices with an inkjet recording device. By using this liquid ejection head, recording can be performed on a variety of recording media, including paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramics. In this specification, "recording" refers not only to the application of meaningful images, such as characters and figures, to a recording medium, but also to the application of meaningless images, such as patterns.

[0013] Here, we will explain a cartridge-type liquid ejection head unit in which a liquid ejection head is integrated with an ink tank, and an inkjet recording apparatus that performs recording using the liquid ejection head unit. The liquid ejection head is also called an inkjet head. The liquid ejection head unit is also called an inkjet head unit. FIG. 1 is a perspective view showing a schematic configuration of an inkjet recording apparatus 500. In FIG. 1, the Z direction indicates the vertical direction and intersects (orthogonal in this embodiment) the XY plane defined by the X and Y directions.

[0014] As shown in FIG. 1, the inkjet recording apparatus 500 includes a liquid ejection head unit 1, a carriage 510, and a linear encoder 520. The inkjet recording apparatus 500 further includes a pair of upper and lower upstream roller units 531, a pair of upper and lower downstream roller units 532, and a cap member 540. The carriage 510 is fixed to an endless belt 511 and is capable of moving along a guide shaft 512. The endless belt 511 is wound around two pulleys 513. A drive shaft of a carriage motor 514 is connected to one of the two pulleys 513. Therefore, the carriage 510 moves back and forth in the main scanning direction (X direction) along the guide shaft 512 by the rotational drive of the carriage motor 514.

[0015] A cartridge-type liquid ejection head unit 1 is mounted on the upper side of the carriage 510. The liquid ejection head unit 1 is mounted on the carriage 510 so that the ejection ports 121 (see FIG. 3) of the liquid ejection head 10 face the recording medium, i.e., the recording paper P. The liquid ejection head unit 1 is also mounted on the carriage 510 so that the arrangement direction of the ejection ports 121 coincides with a direction different from the main scanning direction (X direction) (for example, the sub-scanning direction (Y direction) which is the transport direction of the recording paper P). The number of liquid ejection head units 1 mounted on the upper side of the carriage 510 corresponds to the type of ink to be used. In the example shown in FIG. 1, four liquid ejection head units 1 corresponding to four colors of ink (for example, black ink, yellow ink, magenta ink, and cyan ink) are mounted on the upper side of the carriage 510. In this embodiment, four colors of ink are used, which are produced by dissolving dyes or pigments in a solvent. However, a liquid such as a primer that does not contain coloring materials such as dyes or pigments and has a specific function may also be used.

[0016] The linear encoder 520 detects the movement position of the carriage 510 in the main scanning direction. The linear encoder 520 includes a linear scale 521, a detection system 522, and a signal processing circuit (not shown) for the detection system 522. The linear scale 521 is provided along the movement direction of the carriage 510. Slits are formed in the linear scale 521 at equal intervals and at a predetermined density. The detection system 522 and the signal processing circuit are attached to the carriage 510. The detection system 522 has, for example, a light-emitting unit and a light-receiving sensor (not shown), and detects the slits formed in the linear scale 521. The signal processing circuit outputs a position detection signal for the carriage 510 and an ejection timing signal for defining the timing of ejecting ink based on the detection result of the slits by the detection system 522.

[0017] The recording paper P is transported intermittently in a sub-scanning direction (Y direction) that is perpendicular to the main scanning direction (X direction). The recording paper P is supported by an upstream roller unit 531 and a downstream roller unit 532. A constant tension is applied to the recording paper P by the upstream roller unit 531 and the downstream roller unit 532, and the recording paper P is transported while ensuring flatness relative to the liquid ejection head 10. The driving force to each roller unit is transmitted from a transport motor (not shown).

[0018] Recording is performed on the entire recording paper P by alternately moving the liquid ejection head unit 1 together with the carriage 510 in the main scanning direction (X direction) and transporting the recording paper P in the sub-scanning direction (Y direction). The carriage 510 stops at a home position as needed when starting or during recording. A cap member 540 is provided at this home position. The cap member 540 caps the surface (ejection port surface) of each liquid ejection head unit 1 on which the ejection ports 121 (see FIG. 3) are provided. A suction recovery mechanism (not shown) is connected to the cap member 540. The suction recovery mechanism generates negative pressure inside the cap member 540, forcibly sucks ink from the ejection ports 121, and discharges the ink from the liquid flow path. The operation of discharging ink by the suction recovery mechanism is also referred to as a suction recovery operation. The suction recovery operation of the suction recovery mechanism prevents clogging of the ejection ports 121.

[0019] <Configuration of liquid ejection head unit> FIG. 2 is a perspective view showing an example of a liquid ejection head unit 1. As shown in FIG. 2, the liquid ejection head unit 1 includes a liquid ejection head 10, an ink tank 20, and a tape member 30. As described above, the liquid ejection head unit 1 has a cartridge configuration in which the liquid ejection head 10 is integrated with the ink tank 20. The ink tank 20 stores ink to be supplied to the liquid ejection head 10. The tape member 30 is a tape member for TAB (Tape Automated Bonding) that has terminals for supplying power to the liquid ejection head 10. The tape member 30 supplies power to the liquid ejection head 10 from a main body (not shown) of the inkjet recording apparatus 500 via contacts 40.

[0020] The liquid ejection head unit 1 is not limited to a cartridge form. For example, the ink tank 20 may be removably attached to the liquid ejection head unit 1. This allows the ink tank 20 to be removed and a new ink tank 20 to be attached when the ink inside it runs out. Also, the ink tank may be attached to the main body of the inkjet recording apparatus 500 separately from the liquid ejection head, and the ink stored in the ink tank may be supplied to the liquid ejection head via a tube or the like.

[0021] <Configuration of liquid ejection head> Next, a liquid ejection head using a liquid ejection head substrate according to this embodiment will be described. FIG. 3 is a perspective view schematically showing a liquid ejection head 10. In the following description, the liquid ejection head substrate will be referred to as an element substrate 100. The liquid ejection head 10 includes the element substrate 100 and a flow path forming member 120. The element substrate 100 has two element rows in which heat generating portions 104H serving as electrothermal conversion elements are arranged in parallel in the Y direction at a predetermined pitch. Details of the element substrate 100 will be described later. A flow path forming member 120 is bonded to one surface (the +Z direction side) of the element substrate 100. The flow path forming member 120 is formed in a box shape that covers one surface of the element substrate 100 and extends in the Y direction. The flow path forming member 120 has ejection ports 121 formed at positions corresponding to the heat generating portions 104H. The flow path forming member 120 forms, between itself and the element substrate 100, a liquid flow path 125 (see FIG. 5(a)) that communicates with the ink supply port 116 and the ejection port 121 that are formed through the element substrate 100.

[0022] 2 and 3 is a so-called serial type liquid ejection head that ejects ink while moving in the main scanning direction, but is not limited to this. The liquid ejection head may also be a so-called full-line type liquid ejection head that is capable of ejecting ink across the entire width of the recording paper P without moving in the main scanning direction.

[0023] <Configuration of Liquid Ejection Head Substrate> Next, the element substrate 100 (liquid ejection head substrate) will be described. Fig. 4 is a plan view schematically showing the vicinity of the heat application portion in the element substrate 100 according to the first embodiment. Fig. 5 is a cross-sectional view schematically showing the vicinity of the heat application portion in the element substrate 100. Fig. 5(a) is a cross-sectional view taken along line Va-Va in Fig. 4. In this embodiment, a configuration will be described that can stabilize the initial ejection characteristics of the liquid ejection head 10 and perform reliable, high-quality printing.

[0024] As shown in FIGS. 4 and 5(a), the element substrate 100 includes a base 101, a heat storage layer 102, a heating resistor layer 104, an electrode wiring layer 105, a first protective layer 106, a second protective layer 107, an adhesive layer 109, and a third protective layer 110. The base 101 is formed in a plate shape using silicon (Si) or the like. The heat storage layer 102 is formed on one side (+Z direction side) of the base 101 using a thermal oxide film, a SiO film, a SiN film, or the like. The heating resistor layer 104 is formed on one side of the heat storage layer 102 using a conductive material with a higher resistivity than the electrode wiring layer 105. The electrode wiring layer 105 is formed on one side of the heating resistor layer 104 using a material containing a metal such as aluminum (Al), an Al-Si alloy, or an Al-Cu alloy. The electrode wiring layer 105 forms wiring electrically connected to the heating resistor layer 104. A gap is formed by removing a portion of the electrode wiring layer 105, and the heating resistor layer 104 located in the gap is exposed to form a heating portion 104H as an electrothermal conversion element. The heating portion 104H generates thermal energy used to eject ink from the ejection ports 121. The electrode wiring layer 105 forms a power supply wiring 105a and a ground wiring 105b on either side of the heating portion 104H. The power supply wiring 105a and the ground wiring 105b are electrically connected to a drive element circuit or an external power supply terminal (not shown) and can receive power from an external source.

[0025] The first protective layer 106 is made of an insulating material such as a SiO film or a SiN film and is formed to overlap one surface of the heat storage layer 102, the heating resistor layer 104, and the electrode wiring layer 105. The first protective layer 106 covers and protects the heat generating portion 104H and also functions as an insulating layer that insulates the heating resistor layer 104 and the electrode wiring layer 105. The first protective layer 106 is inserted into through holes 113 formed in the heating resistor layer 104 and the electrode wiring layer 105 and is bonded to the heat storage layer 102. The second protective layer 107 is formed to overlap one surface of the first protective layer 106 via an adhesive layer 109. The second protective layer 107 protects the heat generating portion 104H, which serves as an electrothermal conversion element, from physical effects such as impacts caused by cavitation due to heat generation by the heat generating portion 104H and chemical effects caused by ink. Furthermore, the second protective layer 107 dissolves into ink due to an electrochemical reaction during a cleaning process to remove kogation. The second protective layer 107 is formed using a material containing a metal, such as iridium (Ir), that dissolves into ink due to an electrochemical reaction. A portion of the second protective layer 107 located above the heat generating portion 104H, where heat generated from the heat generating portion 104H acts on the ink, is referred to as a heat application portion 108. As described above, the flow path forming member 120 is bonded to one surface (the +Z direction side) of the element substrate 100. A liquid flow path 125 is formed between the element substrate 100 and the flow path forming member 120, communicating from the ink supply port 116 of the element substrate 100 through the heat application portion 108 to the ejection port 121 of the flow path forming member 120.

[0026] The adhesion layer 109 is formed between the first protective layer 106 and the second protective layer 107 using a conductive material such as tantalum (Ta). The adhesion layer 109 improves the adhesion of the second protective layer 107 to the first protective layer 106. The third protective layer 110 is formed on one side of the second protective layer 107 using a metal that dissolves in ink, such as a material containing magnesium (Mg). The metal that dissolves in ink is a metal that has a greater ionization tendency than the metal used for the second protective layer 107. For example, the metal that dissolves in ink is a metal that corrodes at least partially in the pH (hydrogen ion exponent) range of 6 to 9. As a result, when the third protective layer 110 comes into contact with neutral ink, it ionizes without forming a passivation layer such as an oxide film and dissolves into the ink.

[0027] The second protective layer 107 has a heat generating portion-side region 107a located near the heat generating portion 104H, a counter electrode-side region 107b spaced apart in the −X direction from the heat generating portion-side region 107a, and a covered region 107c covered by the flow path forming member 120. The third protective layer 110 covering the second protective layer 107 similarly has a heat generating portion-side region 110a, a counter electrode-side region 110b, and a covered region 110c. The covered regions 107c and 110c of the second protective layer 107 and the third protective layer 110 are inserted into wiring through holes 111 formed in the first protective layer 106 and are electrically connected to the electrode wiring layer 105 via the heat generating portion-side region 109a of the adhesive layer 109. The electrode wiring layer 105 electrically connected to the second protective layer 107 extends to the edge of the element substrate 100. At the tip of the electrode wiring layer 105 located at the edge of the element substrate 100, an external electrode 112 is formed for electrical connection to the outside.

[0028] Furthermore, a region 109b on the counter electrode side of the adhesion layer 109 is formed between a region 107b on the counter electrode side of the second protective layer 107 and the first protective layer 106. As shown in Fig. 4, the region 109b on the counter electrode side of the adhesion layer 109 extends to the edge of the element substrate 100. An external electrode 112 for electrical connection to the outside is formed at the tip of the region 109b on the counter electrode side of the adhesion layer 109.

[0029] FIG. 5B is a cross-sectional view schematically illustrating the element substrate 100 with the liquid flow path 125 filled with ink 130. As shown in FIG. 5B, when the liquid flow path 125 is filled with ink 130, the region 110a of the third protective layer 110 on the heat generating portion side and the region 110b on the counter electrode side dissolve in the ink 130 and disappear. The covered region 110c of the third protective layer 110 is covered by the flow path forming member 120 and therefore does not disappear even when the liquid flow path 125 is filled with ink 130. Deposits on the heating portion 108 generated during the process of manufacturing the liquid ejection head 10 from the element substrate 100 adhere to the region 110a of the third protective layer 110 on the heat generating portion side and are therefore removed by the ink 130 filling the liquid flow path 125. At this time, the region 107a of the second protective layer 107 on the heat generating portion side and the region 107b on the counter electrode side come into contact with the ink 130, but do not dissolve in the ink 130 under normal conditions. When a current flows between the region 107a on the heat generating part side of the second protective layer 107 and the region 107b on the counter electrode side via the ink 130, an electrochemical reaction occurs at the interface between the region 107a on the heat generating part side of the second protective layer 107 and the ink 130. Due to the electrochemical reaction occurring at the interface with the ink 130, a portion of the region 107a on the heat generating part side of the second protective layer 107 dissolves into the ink 130. This makes it possible to remove kogation that has adsorbed to the region 107a on the heat generating part side of the second protective layer 107. Note that the region 110a on the heat generating part side and the region 110b on the counter electrode side of the third protective layer 110 are not involved in this electrochemical reaction because they dissolve and disappear in the ink 130 when the liquid flow path 125 is filled with ink 130.

[0030] <Materials for the second and third protective layers> Next, the materials of the second protective layer 107 and the third protective layer 110 will be described. The material of the second protective layer 107 contains a metal that dissolves due to an electrochemical reaction and does not form an oxide film that prevents dissolution into ink when heated. Examples of materials for the second protective layer 107 include iridium (Ir), ruthenium (Ru), or a material containing iridium or ruthenium. In this embodiment, a material containing iridium is used as the material for the second protective layer 107.

[0031] The standard redox potential between a hydrated ion in aqueous solution and an elemental metal indicates its ionization tendency. For example, the standard redox potential between a hydrated ion in aqueous solution and iridium is 1.156 V. The standard redox potential between a hydrated ion in aqueous solution and silver (Ag) is 0.799 V. The standard redox potential between a hydrated ion in aqueous solution and platinum (Pt) is 1.188 V. The standard redox potential between a hydrated ion in aqueous solution and iron (Fe) is -0.44 V. The standard redox potential between a hydrated ion in aqueous solution and manganese (Mn) is -1.18 V. The standard redox potential between a hydrated ion in aqueous solution and magnesium (Mg) is -2.356 V. Iridium has a lower ionization tendency than silver and is comparable to that of platinum. Ruthenium (Ru), like iridium, is a stable precious metal with a low ionization tendency and is resistant to acid and alkali reactions. For this reason, many metals such as iron, manganese, and magnesium have a greater tendency to ionize than noble metals such as iridium and ruthenium.

[0032] The metals used in the second protective layer 107 and the third protective layer 110 preferably have a corrosion region in the pH (hydrogen ion exponent) range of 6 or more and 9 or less. FIG. 6 shows potential-pH diagrams of the metals used in the second protective layer 107 and the third protective layer 110. FIG. 6(a) shows a potential-pH diagram of iridium. FIG. 6(b) shows a potential-pH diagram of magnesium. FIG. 6(c) shows a potential-pH diagram of manganese. FIG. 6(d) shows a potential-pH diagram of iron. In FIGS. 6(a) to 6(d), the vertical axis of the graph represents potential E (electrode potential of a standard hydrogen electrode), and the horizontal axis of the graph represents pH. The small-pitched hatched areas indicate corrosion regions due to dissolution in solution. The large-pitched hatched areas indicate passivation regions due to a hydrated oxide film. The plain areas indicate insensitive regions.

[0033] As shown in FIG. 6( a), for iridium, the pH range of 6 to 9, which corresponds to the pH (hydrogen ion exponent) of ink, becomes an insensitive region when the potential E is low. If the potential E is not increased, no reaction occurs when the second protective layer 107 formed using iridium comes into contact with ink. As shown in FIG. 6( b), for magnesium, the pH range of 6 to 9 becomes a corrosion region regardless of the potential E. The third protective layer 110 formed using magnesium dissolves when it comes into contact with ink. As shown in FIG. 6( c), for manganese, the pH range of 6 to 9 becomes a corrosion region over a relatively wide range of potential E. The third protective layer 110 formed using manganese dissolves when it comes into contact with ink. As shown in FIG. 6( d), for iron, the pH range of 6 to 9 becomes a corrosion region when the potential E is low. The third protective layer 110 formed using iron dissolves when it comes into contact with ink if the potential E is lowered. Thus, for the second protective layer 107 formed using iridium, magnesium, manganese, or iron can be used as the material for the third protective layer 110.

[0034] As described above, the second protective layer 107 and the third protective layer 110 have covering regions 107c, 110c that are covered by the flow path forming member 120. As described above, the second protective layer 107 is formed using a material containing iridium, for example. The third protective layer 110 is formed using a material containing magnesium, for example. The adhesion layer 109 is formed using a conductive material such as tantalum, which has a relatively high resistivity. At a temperature of 0°C, the resistivity of tantalum is 12.3×10 -8 The resistivity of iridium is 4.7×10 -8 The resistivity of magnesium is 4.0×10 -8 The electrical resistance is [Ω·m]. By forming the covering regions 107c, 110c of the second protective layer 107 and the third protective layer 110 overlapping the region 109a of the adhesive layer 109 on the heat generating part side, it is possible to reduce the resistance of the wiring between the region 107a of the second protective layer 107 on the heat generating part side and the external electrode 112.

[0035] <Method of manufacturing a liquid ejection head substrate> Next, a method for manufacturing the element substrate 100 (liquid ejection head substrate) according to the first embodiment will be described with reference to FIGS. 7 and 8. FIGS. 7 and 8 are schematic cross-sectional views illustrating the manufacturing process of the element substrate 100. The manufacturing process of the element substrate 100 is shown in the order of FIGS. 7(a) to 7(d) and 8(a) to 8(d). In the manufacturing process described below, it is assumed that a drive circuit (not shown) for selectively driving the heat generating portions 104H is already built into the base 101. The drive circuit for selectively driving the heat generating portions 104H is configured using semiconductor elements such as switching transistors. FIGS. 7 and 8 show a simplified view of the base 101, and the drive circuit is not shown.

[0036] First, as shown in Fig. 7(a), the heat storage layer 102 is formed on one side (+Z direction side) of the base 101. In the process of forming the heat storage layer 102, the heat storage layer 102 made of a thermal oxide film using SiO2 is formed using a thermal oxidation method, a sputtering method, a CVD (Chemical Vapor Deposition) method, or the like. It is possible to form the heat storage layer 102 during the manufacturing process in which the above-mentioned drive circuit is built into the base 101.

[0037] Next, a heating resistor layer 104 made of TaSiN or the like is formed on one side of the heat storage layer 102, and an electrode wiring layer 105 made of aluminum is formed on one side of the heating resistor layer 104. In the process of forming the heating resistor layer 104 and the electrode wiring layer 105, the heating resistor layer 104 is formed to a thickness of approximately 50 nm using a reactive sputtering method. Subsequently, the electrode wiring layer 105 is formed to a thickness of approximately 300 nm using a sputtering method. Then, the heating resistor layer 104 and the electrode wiring layer 105 are simultaneously dry-etched using a photolithography technique to obtain a cross-sectional shape having a through-hole 113 as shown in FIG. 7(a). Note that reactive ion etching (RIE) can be used as the dry etching method.

[0038] 7(b), the heating portion 104H of the heating resistor layer 104 is formed. In the process of forming the heating portion 104H, a part of the electrode wiring layer 105 is removed by wet etching using photolithography to form a gap, and the heating resistor layer 104 located in the gap is exposed. Note that it is desirable to remove a part of the electrode wiring layer 105 by wet etching in order to improve the coverage of the first protective layer 106 with respect to the part of the electrode wiring layer 105 near the heating portion 104H.

[0039] 7(c), a first protective layer 106 is formed on one surface of the heat storage layer 102, the heating resistor layer 104, and the electrode wiring layer 105. In the step of forming the first protective layer 106, the first protective layer 106 is formed by using a plasma CVD method, and is made of a SiN film having a thickness of about 350 nm.

[0040] 7(d), wiring through-holes 111 are formed in the first protective layer 106. In the step of forming the wiring through-holes 111, photolithography is used to remove a part of the first protective layer 106 by wet etching to form the wiring through-holes 111, thereby exposing the electrode wiring layer 105 located in the part of the wiring through-holes 111.

[0041] 8(a), an adhesion layer 109 made of tantalum is formed on one surface (the +Z direction side) of the first protective layer 106. In the step of forming the adhesion layer 109, the adhesion layer 109 having a thickness of about 50 nm is formed by sputtering.

[0042] 8(a), a second protective layer 107 made of iridium is formed on one surface of the adhesive layer 109. In the step of forming the second protective layer 107, a sputtering method is used to form the second protective layer 107 having a thickness of approximately 200 nm.

[0043] Next, as shown in FIG. 8( a), a third protective layer 110 made of magnesium is formed on one surface of the second protective layer 107. In the step of forming the third protective layer 110, a sputtering method is used to form the third protective layer 110 having a thickness of approximately 200 nm. Note that if there is a region where only the third protective layer 110 needs to be removed and the second protective layer 107 needs to remain, if the third protective layer 110 is thick, there is a possibility that the second protective layer 107 will be excessively removed by over-etching. Therefore, it is preferable that the thickness of the third protective layer 110 is equal to or less than the thickness of the second protective layer 107. This makes it possible to prevent the second protective layer 107 from being excessively removed by over-etching.

[0044] 8(b), a region 110a on the heat generating part side, a region 110b on the counter electrode side, and a covered region 110c are formed in the third protective layer 110, and a region 107a on the heat generating part side, a region 107b on the counter electrode side, and a covered region 107c are formed in the second protective layer 107. In the process of forming the regions of the third protective layer 110 and the second protective layer 107, after the third protective layer 110 is formed, portions of the third protective layer 110 and the second protective layer 107 are removed by dry etching using a photolithography technique. By performing dry etching, regions 107a and 110a on the heat generating part side, regions 107b and 110b on the counter electrode side, and covered regions 107c and 110c are formed in the second protective layer 107 and the third protective layer 110.

[0045] 8(c), a region 109a on the heat generating part side and a region 109b on the counter electrode side are formed in the adhesion layer 109. In the process of forming each region of the adhesion layer 109, a part of the adhesion layer 109 is removed by dry etching using a photolithography technique. By performing dry etching, the region 109a on the heat generating part side and the region 109b on the counter electrode side are formed in the adhesion layer 109.

[0046] 8(d), an external electrode 112 is formed on a tip of the electrode wiring layer 105 located on an edge of the element substrate 100. At this time, the external electrode 112 is also formed on a tip of a region 109b of the adhesion layer 109 on the counter electrode side, which is located on the edge of the element substrate 100. In the process of forming the external electrode 112, a part of the first protective layer 106 is removed by dry etching using a photolithography technique, and the tip of the electrode wiring layer 105 is exposed as the external electrode 112. A part of the first protective layer 106 is also removed by dry etching using a photolithography technique, and the tip of the region 109b of the adhesion layer 109 on the counter electrode side is exposed as the external electrode 112.

[0047] <Method of manufacturing liquid ejection head> Next, a method for manufacturing a liquid ejection head 10 using an element substrate 100 (liquid ejection head substrate) will be described with reference to FIG. 9. FIG. 9 is a schematic cross-sectional view illustrating the manufacturing process of the liquid ejection head 10. The manufacturing process of the element substrate 100 is shown in the order of FIGS. 9(a) to 9(d). In the manufacturing process described below, the heat storage layer 102, heating resistor layer 104, electrode wiring layer 105, first protective layer 106, second protective layer 107, adhesion layer 109, third protective layer 110, and the like formed on the base 101 will be collectively referred to as a circuit section 115. FIG. 9 shows a simplified view of the element substrate 100 using the base 101 and the circuit section 115.

[0048] As shown in FIG. 9(a), a first resist layer 201 and a second resist layer 202 for forming the liquid flow path 125 (see FIG. 5(a)) are formed on one surface (the +Z direction side) of the element substrate 100. In the process of forming the first resist layer 201 and the second resist layer 202, the resist is applied using a spin coating method. Then, the first resist layer 201 and the second resist layer 202 are patterned into the desired shape of the liquid flow path using a photolithography technique. As a material for the resist, for example, a material that acts as a positive resist, such as polymethyl isopropenyl ketone (PMIK), is used.

[0049] 9(b), a coating resin layer 203 for forming flow path walls, discharge ports 121, and the like that constitute the flow path forming member 120 is formed on one surface of the element substrate 100, the first resist layer 201, and the second resist layer 202. In the step of forming the coating resin layer 203, a resin is applied using a conventionally known coating method. Note that, before forming the coating resin layer 203, a silane coupling treatment or the like may be appropriately performed to improve the adhesion of the coating resin layer 203.

[0050] 9(c), photolithography is used to pattern the coating resin layer 203 into the desired shapes of the flow path walls and discharge ports. At this time, parts of the first resist layer 201 and the second resist layer 202 are exposed through openings in the coating resin layer 203 (such as parts corresponding to the discharge ports 121).

[0051] 9(d), an ink supply port 116 is formed in a portion of the element substrate 100 that contacts the liquid flow path (first resist layer 201). In the process of forming the ink supply port 116, an anisotropic etching method, a sandblasting method, an anisotropic plasma etching method, or the like is used to form the ink supply port 116 penetrating from the back side of the element substrate 100. Note that it is preferable to form the ink supply port 116 using a chemical silicon anisotropic etching method using tetramethylhydroxyamine (TMAH), sodium hydroxide (NaOH), potassium hydroxide (KOH), or the like.

[0052] Then, as shown in FIG. 9(d), the first resist layer 201 and the second resist layer 202 are removed. In the process of removing the first resist layer 201 and the second resist layer 202, deep ultraviolet light (Deep-UV) is used to expose the entire surface of the coating resin layer 203, the first resist layer 201, and the second resist layer 202. Then, development and drying are performed to remove the first resist layer 201 and the second resist layer 202, which dissolve as positive resists. As a result, a flow path forming member 120 having ejection ports 121 is formed on one surface of the element substrate 100. Note that by integrating the liquid ejection head 10 manufactured as described above with an ink tank 20, a cartridge-type liquid ejection head unit 1 (see FIG. 2) can be manufactured. In this case, ink stored in the ink tank 20 is filled into the liquid flow path 125 through the ink supply port 116 of the liquid ejection head 10. When the liquid flow path 125 is filled with ink, the region 110a on the heat generating portion side and the region 110b on the counter electrode side of the third protective layer 110 dissolve in the ink and disappear.

[0053] As described above, according to the first embodiment, the initial ejection characteristics of the liquid ejection head 10 can be stabilized, enabling reliable, high-quality recording. Specifically, in this embodiment, a first protective layer 106 covering the heat generating portion 104H, a second protective layer 107 formed on the first protective layer 106, and a third protective layer 110 formed on the second protective layer 107 using a material containing a substance soluble in ink are provided. After the third protective layer 110 is formed, there is a concern that deposits may adhere to the third protective layer 110 before the liquid ejection head 10 is completed. The material of the third protective layer 110 contains a metal (e.g., magnesium) that has a greater ionization tendency than the metal (e.g., iridium) contained in the material of the second protective layer 107. Furthermore, the material of the third protective layer 110 contains a metal that corrodes at least partially in a pH (hydrogen ion exponent) range of 6 to 9. After the liquid ejection head 10 is completed, the liquid flow path 125 is filled with ink, and the third protective layer 110 dissolves in the ink. When the third protective layer 110 dissolves in the ink and disappears, any deposits on the third protective layer 110 are removed by the lift-off effect, and the second protective layer 107 that was covered by the third protective layer 110 appears clean. Therefore, even if deposits adhere to the third protective layer 110 during the manufacturing process of the liquid ejection head 10, the initial ejection characteristics of the liquid ejection head 10 can be stabilized. In this way, the initial ejection characteristics of the liquid ejection head 10 can be stabilized, allowing reliable, high-quality recording. The above-mentioned ink may be an ink for shipping inspection used during shipping inspection.

[0054] Furthermore, the thickness of the third protective layer 110 is equal to or less than the thickness of the second protective layer 107. This makes it possible to prevent the second protective layer 107 from being excessively removed by over-etching, as described above.

[0055] <<Second embodiment>> Next, a second embodiment will be described. Since the individual components in the second embodiment have the same configuration as those in the first embodiment, they will be described using the same reference numerals as those in the first embodiment.

[0056] <Configuration of Liquid Ejection Head Substrate> FIG. 10 is a cross-sectional view schematically illustrating the vicinity of a heat application portion in an element substrate 100 according to the second embodiment. As shown in FIG. 10, the second protective layer 107 according to the second embodiment has a region 107a on the heat generating portion side and a region 107b on the counter electrode side. The third protective layer 110 similarly has a region 110a on the heat generating portion side and a region 110b on the counter electrode side. As such, the second protective layer 107 and the third protective layer 110 according to the second embodiment do not have the covering regions 107c, 110c. The region 109a on the heat generating portion side of the adhesive layer 109 is inserted into a wiring through-hole 111 formed in the first protective layer 106 and electrically connected to the electrode wiring layer 105. As a result, the region 107a on the heat generating portion side of the second protective layer 107 is electrically connected to the electrode wiring layer 105 via the region 109a on the heat generating portion side of the adhesive layer 109.

[0057] As in the first embodiment, when the liquid flow path 125 is filled with ink, the region 110a on the heat generating portion side and the region 110b on the counter electrode side of the third protective layer 110 dissolve and disappear in the ink. Deposits on the heat application portion 108 generated during the process of manufacturing the liquid ejection head 10 from the element substrate 100 adhere to the region 110a on the heat generating portion side of the third protective layer 110 and are therefore removed by the ink filling the liquid flow path 125. At this time, the region 107a on the heat generating portion side and the region 107b on the counter electrode side of the second protective layer 107 come into contact with the ink, but do not dissolve into the ink under normal conditions. When a current flows between the region 107a on the heat generating portion side and the region 107b on the counter electrode side of the second protective layer 107 via ink, an electrochemical reaction occurs at the interface between the ink and the region 107a on the heat generating portion side of the second protective layer 107. The electrochemical reaction occurring at the interface with the ink causes a portion of the region 107a on the heat generating portion side of the second protective layer 107 to dissolve into the ink. This makes it possible to remove kogation adsorbed to the region 107a of the second protective layer 107 on the heat generating portion side.

[0058] The method for manufacturing the element substrate 100 according to the second embodiment is similar to that according to the first embodiment, and therefore a detailed description thereof will be omitted. In the second embodiment, a region 110a on the heat generating portion side and a region 110b on the counter electrode side are formed in the third protective layer 110, and a region 107a on the heat generating portion side and a region 107b on the counter electrode side are formed in the second protective layer 107. In the process of forming the regions of the third protective layer 110 and the second protective layer 107, after the third protective layer 110 is formed, portions of the third protective layer 110 and the second protective layer 107 are removed by dry etching using a photolithography technique. At this time, portions of the second protective layer 107 and the third protective layer 110 corresponding to the covered regions 107c and 110c are also removed. By performing dry etching, the regions 107a and 110a on the heat generating portion side and the regions 107b and 110b on the counter electrode side are formed in the second protective layer 107 and the third protective layer 110.

[0059] As described above, according to the second embodiment, similarly to the first embodiment, the initial ejection characteristics of the liquid ejection head 10 can be stabilized, and reliable, high-quality printing can be performed.

[0060] In the above-described embodiments, the second protective layer 107 is formed using a material containing, for example, iridium, but is not limited to this. For example, the second protective layer 107 may be formed using a material containing ruthenium.

[0061] In each of the above-described embodiments, the third protective layer 110 is formed using, for example, a material containing magnesium, but is not limited to this. For example, the third protective layer 110 may be formed using a material containing manganese or a material containing iron.

[0062] <<Other embodiments>> The disclosure of this embodiment includes configurations represented by the following examples of a substrate for a liquid ejection head, examples of a liquid ejection head, and examples of a method for manufacturing a substrate for a liquid ejection head.

[0063] <Configuration 1> a heat generating unit that generates thermal energy for discharging the liquid; a first protective layer covering the heat generating portion; a second protective layer formed on the first protective layer using a material containing metal; a third protective layer formed on the second protective layer using a material containing a substance that dissolves in a liquid; A substrate for a liquid ejection head, comprising:

[0064] <Configuration 2> 2. The liquid ejection head substrate according to configuration 1, wherein the third protective layer has a thickness equal to or smaller than that of the second protective layer.

[0065] <Configuration 3> 3. The liquid ejection head substrate according to configuration 1 or 2, wherein the substance is a metal having a higher ionization tendency than a metal contained in the material of the second protective layer.

[0066] <Configuration 4> 4. The liquid ejection head substrate according to configuration 3, wherein the metal contained in the substance is a metal that corrodes at least in part in the range of a hydrogen ion exponent of 6 or more and 9 or less.

[0067] <Configuration 5> 5. The liquid ejection head substrate according to any one of configurations 1 to 4, wherein the metal contained in the substance is magnesium, manganese, or iron.

[0068] <Configuration 6> 6. The liquid ejection head substrate according to any one of configurations 1 to 5, wherein the metal contained in the material of the second protective layer is iridium or ruthenium.

[0069] <Configuration 7> 7. The liquid ejection head substrate according to any one of configurations 1 to 6, wherein the third protective layer dissolves in a liquid having a hydrogen ion exponent of 6 or more and 9 or less and disappears.

[0070] <Configuration 8> 8. The liquid ejection head substrate according to any one of configurations 1 to 7, wherein the heat generating portion is formed by a gap in an electrode wiring layer and a heat generating resistor layer.

[0071] <Configuration 9> A liquid ejection head substrate according to any one of configurations 1 to 8, a flow path forming member having a discharge port for discharging a liquid, the flow path forming member forming a liquid flow path communicating with the discharge port between the liquid discharge head substrate and the flow path forming member; A liquid ejection head comprising:

[0072] <Configuration 10> the second protective layer and the third protective layer each have a heat generating portion side region located in the vicinity of the heat generating portion and a counter electrode side region spaced apart from the heat generating portion side region, A liquid ejection head according to configuration 9, wherein the region of the third protective layer on the heat generating portion side and the region on the counter electrode side dissolve and disappear in a liquid having a hydrogen ion exponent of 6 or more and 9 or less filled in the liquid flow path.

[0073] <Configuration 11> 11. The liquid ejection head according to configuration 10, wherein the second protective layer and the third protective layer have a covering region that is covered by the flow path forming member.

[0074] <Configuration 12> a step of forming a heat generating portion that generates thermal energy for ejecting liquid by using a gap in the electrode wiring layer and the heat generating resistor layer; forming a first protective layer that covers the heat generating portion; forming a second protective layer on the first protective layer using a material including a metal; forming a third protective layer on the second protective layer using a material containing a substance that dissolves in a liquid having a hydrogen ion concentration of 6 or more and 9 or less; 1. A method for manufacturing a substrate for a liquid ejection head, comprising:

[0075] <Configuration 13> 13. The method for manufacturing a liquid ejection head substrate according to Configuration 12, wherein the thickness of the third protective layer is equal to or less than the thickness of the second protective layer.

[0076] <Configuration 14> 14. The method of manufacturing a substrate for a liquid ejection head according to claim 12 or 13, wherein the substance is a metal having a higher ionization tendency than a metal contained in the material of the second protective layer.

[0077] <Configuration 15> 15. The method for manufacturing a substrate for a liquid ejection head according to Configuration 14, wherein the metal contained in the substance is a metal that corrodes at least in part in the range of a hydrogen ion exponent of 6 or more and 9 or less.

[0078] <Configuration 16> 16. The method for manufacturing a substrate for a liquid ejection head according to any one of configurations 12 to 15, wherein the metal contained in the substance is magnesium, manganese, or iron.

[0079] <Configuration 17> 17. The method for manufacturing a liquid ejection head substrate according to any one of Configurations 12 to 16, wherein the metal contained in the material of the second protective layer is iridium or ruthenium.

[0080] <Configuration 18> 18. The method for manufacturing a substrate for a liquid ejection head according to any one of Configurations 12 to 17, wherein the third protective layer dissolves in a liquid having a hydrogen ion exponent of 6 or more and 9 or less and disappears.

[0081] <Configuration 19> A method for manufacturing a substrate for a liquid ejection head, described in any one of configurations 12 to 18, wherein when forming the third protective layer, dry etching is performed to form an area on the heat generating part side located near the heat generating part and an area on the opposing electrode side spaced apart from the area on the heat generating part side in the third protective layer and the second protective layer. [Explanation of symbols]

[0082] 10 Liquid ejection head 100 Element substrate 104 Heating resistor layer 104H Heat generating part 105 Electrode wiring layer 106 1st protective layer 107 Second protective layer 110 Third protective layer

Claims

1. a heat generating unit that generates thermal energy for discharging the liquid; a first protective layer covering the heat generating portion; a second protective layer formed on the first protective layer using a material containing metal; a third protective layer formed on the second protective layer using a material containing a substance that dissolves in a liquid; A substrate for a liquid ejection head, comprising:

2. 2. The liquid ejection head substrate according to claim 1, wherein the thickness of the third protective layer is equal to or less than the thickness of the second protective layer.

3. 2. The liquid ejection head substrate according to claim 1, wherein the substance is a metal having a higher ionization tendency than a metal contained in the material of the second protective layer.

4. 4. The liquid ejection head substrate according to claim 3, wherein the metal contained in the substance is a metal that corrodes at least in a part of the range of a hydrogen ion exponent of 6 or more and 9 or less.

5. 2. The liquid ejection head substrate according to claim 1, wherein the metal contained in the substance is magnesium, manganese, or iron.

6. 2. The liquid ejection head substrate according to claim 1, wherein the metal contained in the material of the second protective layer is iridium or ruthenium.

7. 2. The liquid ejection head substrate according to claim 1, wherein the third protective layer dissolves in a liquid having a hydrogen ion exponent of 6 or more and 9 or less and disappears.

8. 2. The liquid ejection head substrate according to claim 1, wherein the heat generating portion is formed by a gap in an electrode wiring layer and a heat generating resistor layer.

9. A liquid ejection head substrate according to any one of claims 1 to 8, a flow path forming member having a discharge port for discharging a liquid, the flow path forming member forming a liquid flow path communicating with the discharge port between the liquid discharge head substrate and the flow path forming member; A liquid ejection head comprising:

10. the second protective layer and the third protective layer each have a heat generating portion side region located in the vicinity of the heat generating portion and a counter electrode side region spaced apart from the heat generating portion side region, The liquid ejection head according to claim 9 , wherein the region of the third protective layer on the heat generating portion side and the region on the counter electrode side dissolve and disappear in a liquid having a hydrogen ion exponent of 6 or more and 9 or less that fills the liquid flow path.

11. The liquid ejection head according to claim 10 , wherein the second protective layer and the third protective layer have a covering region that is covered by the flow path forming member.

12. a step of forming a heat generating portion that generates thermal energy for ejecting liquid by using a gap in the electrode wiring layer and the heat generating resistor layer; forming a first protective layer that covers the heat generating portion; forming a second protective layer over the first protective layer using a material including a metal; forming a third protective layer on the second protective layer using a material containing a substance that dissolves in a liquid having a hydrogen ion concentration of 6 or more and 9 or less; 10. A method for manufacturing a substrate for a liquid ejection head, comprising:

13. The method for manufacturing a liquid ejection head substrate according to claim 12, wherein the thickness of the third protective layer is equal to or less than the thickness of the second protective layer.

14. The method for manufacturing a substrate for a liquid ejection head according to claim 12, wherein the substance is a metal having a higher ionization tendency than a metal contained in the material of the second protective layer.

15. 15. The method for manufacturing a substrate for a liquid discharge head according to claim 14, wherein the metal contained in the substance is a metal that corrodes at least in a part of the range of a hydrogen ion exponent of 6 or more and 9 or less.

16. The method for manufacturing a substrate for a liquid ejection head according to claim 12, wherein the metal contained in the substance is magnesium, manganese, or iron.

17. The method for manufacturing a liquid ejection head substrate according to claim 12, wherein the metal contained in the material of the second protective layer is iridium or ruthenium.

18. The method for manufacturing a liquid ejection head substrate according to claim 12, wherein the third protective layer dissolves in a liquid having a hydrogen ion exponent of 6 or more and 9 or less and disappears.

19. 13. A method for manufacturing a substrate for a liquid ejection head as described in claim 12, wherein when forming the third protective layer, dry etching is performed to form an area on the heat generating portion side located near the heat generating portion and an area on the opposing electrode side spaced apart from the area on the heat generating portion side in the third protective layer and the second protective layer.

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