Thermal printhead and manufacturing method thereof

Abstract

A thermal print head comprising: a structure having a projecting part on a substrate, a granular heat storage layer on the substrate and the projecting part, a heat-emitting part on the heat storage layer, wiring that is formed from a metal layer and connected to the heat-emitting part, a protective film on the wiring and the heat storage layer, and an electroconductive layer that is connected to the metal layer via an opening provided in the protective film; and a hard film contacting the protective film, wherein the electroconductive layer of the structure is thicker than the protective film and contacts the inner surface of the protective film at the opening, and the electroconductive layer has a flat upper surface, whereby when a plurality of the structures are overlapped, contact between the protective film and the substrate is inhibited by the electroconductive layer, damage to the protective layer is inhibited, and it is possible to form the hard film simultaneously on the plurality of structures in the state in which the structures are overlapped.

Description

[Technical field]

[0001] The present embodiment relates to a thermal printhead and a method for manufacturing the same. [Background technology]

[0002] A thermal printhead, for example, has a large number of heat generating parts arranged in the main scanning direction on the main surface side of a head substrate. Each heat generating part is formed by laminating an upstream electrode layer and a downstream electrode layer with their ends facing each other so that a part of the heat generating part is exposed on a resistor layer formed on the head substrate via a glaze layer. By passing a current between the upstream electrode layer and the downstream electrode layer, the exposed part (heat generating part) of the resistor layer generates heat by Joule heat.

[0003] In order to efficiently transfer heat to the print medium and enable high-speed printing, the thermal printhead is provided with a convex glaze that extends in the main scanning direction as a heat storage section, and each heating section is located on the top of this convex glaze. This convex glaze also helps improve the contact of each heating section with the platen roller, thereby improving print quality.

[0004] Also disclosed is a technique for forming a protective film (protective layer) on a plurality of substrates in a state where the substrates are stacked on a support table with their positions shifted from one another. According to this technique, a protective film made of a hard film can be further formed on the main surface side of each of the substrates at the same time, thereby improving manufacturing efficiency. In this case, a protective film or the like is already provided on the substrate, and stacking the substrates may cause a problem in which the back surface (opposite surface to the main surface) of the upper substrate damages the protective film or conductive layer provided on the main surface side of the lower substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-269036 A [Patent Document 2] Japanese Patent Application Publication No. 5-92596 Summary of the Invention [Problem to be solved by the invention]

[0006] The thermal printhead of this embodiment is configured so that the back surface of the upper substrate and the protective film of the lower substrate do not come into direct contact with each other in order to prevent damage to the protective film, conductive layer, etc. provided on the main surface side of the substrate. With this configuration, it is possible to prevent the back surface of the upper substrate and the protective film of the main surface side of the lower substrate from rubbing against each other when multiple substrates are stacked. Therefore, it is possible to prevent damage to the protective film, conductive layer, etc. of the lower substrate.

[0007] One aspect of the present embodiment provides a thermal printhead that prevents damage to a protective film or the like provided on a main surface side of a substrate and ensures yield and reliability. Another aspect of the present embodiment provides a method for manufacturing the thermal printhead. [Means for solving the problem]

[0008] One aspect of this embodiment is a thermal print head comprising a structure having a convex portion on a substrate, a heat storage layer on the substrate and on the convex portion, a heat generating portion on the heat storage layer, wiring made of a metal layer and connected to the heat generating portion, a protective film on the wiring and on the heat storage layer, and a conductive layer connected to the metal layer through an opening provided in the protective film, and a hard film in contact with the protective film, wherein the conductive layer is thicker than the protective film and in contact with the inner surface of the protective film at the opening, and the conductive layer has a flat upper surface.

[0009] Another aspect of this embodiment is a thermal printhead comprising a substrate having a first convex portion and a second convex portion, a heat storage layer on the substrate, a heat generating portion on the heat storage layer, wiring connected to the heat generating portion, and a protective film on the wiring and on the heat storage layer, and a hard film in contact with the protective film, wherein the first convex portion is taller than the second convex portion, and on the second convex portion, the protective film has a protrusion, and the protrusion has a flat upper surface.

[0010] Another aspect of this embodiment is a method for manufacturing a thermal printhead, comprising the steps of: removing a portion of a substrate to form a convex portion; forming a heat storage film on a substrate having the convex portion; forming a resistor film on the heat storage film; forming a wiring film on the resistor film; removing a portion of the wiring film to form wiring; removing a portion of the resistor film to form a heating portion; forming a protective film on the substrate having the convex portion, on the heat storage film, on the heating portion, and on the wiring; forming an opening in the protective film that reaches the wiring; forming a conductive layer that is thicker than the protective film and has a flat upper surface on the wiring in the opening to manufacture a structure; preparing two or more of the structures; superimposing a portion of the structure and another portion of the structure on each other with a conductive layer of the structure sandwiched therebetween; and forming a hard film in contact with the protective film of the two or more structures by a vapor phase growth method while the two or more structures are superimposed on each other.

[0011] In another aspect of this embodiment, a part of a substrate is removed to form a first convex portion and a second convex portion, a heat storage film is formed on a substrate having the first convex portion and the second convex portion, a resistor film is formed on the heat storage film, a wiring film is formed on the resistor film, a part of the wiring film is removed to form wiring, a part of the resistor film is removed to form a heat generating portion, a protective film is formed on the substrate having the first convex portion and the second convex portion, on the heat storage film, on the heat generating portion, and on the wiring, an opening is formed in the protective film to reach the wiring, and the opening a conductive layer is formed on the first convex portion to produce a structure, the first convex portion being taller than the second convex portion, the protective film having a protrusion on the second convex portion, the protrusion having a flat upper surface, two or more of the structures are prepared, one part of the structures and another part of the structures are overlapped on each other with the one protrusion of the structure in between, and a hard film in contact with the protective film of the two or more structures is formed by a vapor phase growth method while the two or more structures are overlapped on each other. Effect of the Invention

[0012] According to the present embodiment, it is possible to provide a thermal printhead that can suppress damage to a protective film or the like provided on the main surface side of a substrate and ensures yield and reliability. Another aspect of the present embodiment is to provide a method for manufacturing the thermal printhead. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view of a thermal printhead according to a first embodiment. [Diagram 2] FIG. 2 is a simplified cross-sectional view taken along line II in FIG. [Diagram 3] FIG. 3 is a partially enlarged plan view (with some components omitted) of the thermal printhead of the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing a head substrate included in the thermal printhead of the first embodiment. [Diagram 5]FIG. 5 is a diagram illustrating the method for producing the thermal printhead of the first embodiment, and is a plan view of a step of forming a resist. [Figure 6] FIG. 6 is a cross-sectional view of FIG. [Figure 7] FIG. 7 is a diagram illustrating the method for manufacturing the thermal printhead of the first embodiment, and is a plan view showing a step of removing a part of the substrate. [Figure 8] FIG. 8 is a cross-sectional view of FIG. [Figure 9] FIG. 9 is a diagram illustrating the method for manufacturing the thermal printhead of the first embodiment, and is a plan view showing a step of removing a part of the substrate. [Figure 10] FIG. 10 is a cross-sectional view of FIG. [Figure 11] FIG. 11 is a diagram illustrating the method for manufacturing the thermal printhead of the first embodiment, and is a plan view showing a step of forming a heat storage layer. [Figure 12] FIG. 12 is a cross-sectional view of FIG. [Figure 13] FIG. 13 is a diagram illustrating the method for manufacturing the thermal printhead of the first embodiment, and is a plan view showing a step of forming a resistor film and a wiring film. [Figure 14] FIG. 14 is a cross-sectional view of FIG. [Figure 15] FIG. 15 is a diagram illustrating the method for manufacturing the thermal printhead of the first embodiment, and is a plan view showing a step of removing a part of the resistor film and the wiring film to form a resistor layer and wiring. [Figure 16] FIG. 16 is a cross-sectional view of FIG. [Figure 17] FIG. 17 is a diagram illustrating the method for manufacturing the thermal printhead of the first embodiment, and is a plan view showing a step of forming a protective film and a conductive layer. [Figure 18] FIG. 18 is a cross-sectional view of FIG. [Figure 19] FIG. 19 is a diagram illustrating the method for manufacturing the thermal printhead of the first embodiment, and is a plan view showing a step of forming a hard film. [Figure 20] FIG. 20 is a cross-sectional view of FIG. [Figure 21] FIG. 21 is a diagram illustrating the method for producing the thermal printhead of the first embodiment, and is a cross-sectional view of a plurality of stacked structures after a hard film has been formed. [Figure 22] FIG. 22 is a cross-sectional view of a thermal printhead according to the second embodiment. [Diagram 23] FIG. 23 is a cross-sectional view illustrating a step of forming a resist, illustrating the method for producing the thermal printhead of the second embodiment. [Figure 24] FIG. 24 is a cross-sectional view illustrating a step of forming the second convex portion, illustrating the method for manufacturing the thermal printhead of the second embodiment. [Diagram 25] FIG. 25 is a diagram illustrating the method for manufacturing the thermal printhead of the second embodiment, and is a cross-sectional view showing the steps of forming the heat storage layer, the resistor layer, and the wiring. [Figure 26] FIG. 26 is a diagram illustrating the method for manufacturing the thermal printhead of the second embodiment, and is a cross-sectional view showing the steps of forming the protective film, the conductive layer, and the hard film. [Figure 27] FIG. 27 is a diagram illustrating the method for producing a thermal printhead according to the second embodiment, and is a cross-sectional view of a plurality of stacked structures after a hard film has been formed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Next, the present embodiment will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are given the same or similar reference numerals. However, it should be noted that the drawings are simplified and schematic, and the relationship between the thickness and planar dimensions of each component is different from the actual relationship. Therefore, the specific thickness and dimensions should be determined with reference to the following description. In addition, it goes without saying that the drawings include parts with different dimensional relationships and ratios.

[0015] The following embodiments are merely examples of devices and methods for embodying the technical ideas, and do not specify the materials, shapes, structures, arrangements, etc. of the components. Various modifications can be made to the embodiments within the scope of the claims.

[0016] One aspect of this embodiment is as follows.

[0017] <1> A thermal printhead comprising a structure having a convex portion on a substrate, a heat storage layer on the substrate and on the convex portion, a heat generating portion on the heat storage layer, wiring made of a metal layer and connected to the heat generating portion, a protective film on the wiring and on the heat storage layer, and a conductive layer connected to the metal layer through an opening provided in the protective film, and a hard film in contact with the protective film, wherein the conductive layer is thicker than the protective film and in contact with the inner surface of the protective film at the opening, and the conductive layer has a flat upper surface.

[0018] <2> The conductive layer has a thickness of 1 to 10 μm. <1> 2. The thermal print head according to claim 1 .

[0019] <3> the substrate and the protrusion are integrally formed of a single crystal semiconductor; <1> or <2> 2. The thermal print head according to claim 1 .

[0020] <4> The single crystal semiconductor is made of silicon. <3> 2. The thermal print head according to claim 1 .

[0021] <5> The substrate is a ceramic substrate. <1> or <2> 2. The thermal print head according to claim 1 .

[0022] <6> A thermal printhead comprising: a substrate having a first convex portion and a second convex portion; a heat storage layer on the substrate; a heat generating portion on the heat storage layer; wiring connected to the heat generating portion; and a protective film on the wiring and on the heat storage layer; and a hard film in contact with the protective film, wherein the first convex portion is higher than the second convex portion, and on the second convex portion, the protective film has a protrusion, the protrusion having a flat upper surface.

[0023] <7> The height of the second convex portion is 1 to 10 μm. <6> 2. The thermal print head according to claim 1 .

[0024] <8> The height of the first projection is 20 to 300 μm. <6> or <7> 2. The thermal print head according to claim 1 .

[0025] <9> The substrate is made of a single crystal semiconductor. <6> ~ <8> 13. The thermal printhead according to claim 12 .

[0026] <10> The single crystal semiconductor is made of silicon. <9> 2. The thermal print head according to claim 1 .

[0027] <11> There are two or more structures, and a rear surface of the substrate of one of the structures has a contact surface that is in contact with a part of an upper surface of the conductive layer or an upper surface of the protective film of another of the structures. <1> ~ <10> 13. The thermal printhead according to claim 12 .

[0028] <12> The hard film of one of the structures is in contact with a part of a side surface and a part of a back surface of the substrate of one of the structures, and is spaced apart from the contact surface. <11> 2. The thermal print head according to claim 1 .

[0029] <13> a conductive layer that is thicker than the protective layer and has a flat upper surface, and is formed on the wiring in the opening; a method for manufacturing a thermal printhead, comprising the steps of: removing a portion of a substrate to form a convex portion; forming a heat storage film on a substrate having the convex portion; forming a resistor film on the heat storage film; forming a wiring film on the resistor film; removing a portion of the wiring film to form wiring; removing a portion of the resistor film to form a heating portion; forming a protective film on the substrate having the convex portion, on the heat storage film, on the heating portion, and on the wiring; forming an opening in the protective film reaching the wiring; forming a conductive layer that is thicker than the protective film and has a flat upper surface on the wiring in the opening to manufacture a structure; preparing two or more of the structures; superimposing a portion of the structures and another portion of the structures on each other with a conductive layer of the structures sandwiched therebetween; and forming a hard film in contact with the protective film of the two or more structures by a vapor deposition method while the two or more structures are superimposed on each other.

[0030] <14> The convex portion is formed by performing anisotropic etching using potassium hydroxide. <13> A method for manufacturing a thermal printhead.

[0031] <15> The conductive layer has a thickness of 1 to 10 μm. <13> or <14> A method for producing the thermal printhead according to claim 1.

[0032] <16> a conductive layer is formed in the opening to manufacture a structure, the first convex portion is higher than the second convex portion, and on the second convex portion, the protective film has a protrusion, the protrusion has a flat upper surface, and two or more of the structures are prepared, a part of the structure and another part of the structure are overlapped with each other with the protrusion of the structure sandwiched therebetween, and a hard film in contact with the protective film of the two or more structures is formed by a vapor deposition method while the two or more structures are overlapped with each other.

[0033] <17> the second convex portion is formed by forming a resist on the substrate other than the first convex portion after forming the first convex portion, and removing a part of the substrate having the first convex portion by using the resist as a mask. <16> A method for producing the thermal printhead according to claim 1.

[0034] <18> The first convex portion and the second convex portion are formed by performing anisotropic etching using potassium hydroxide. <16> or <17> A method for manufacturing a thermal printhead.

[0035] <19> The height of the second convex portion is 1 to 10 μm. <16> ~ <18> 13. A method for producing the thermal printhead according to any one of claims 1 to 12.

[0036] <20> The height of the first projection is 20 to 300 μm. <16> ~ <19> 13. A method for producing the thermal printhead according to any one of claims 1 to 12.

[0037] <21> The substrate is made of a single crystal semiconductor. <13> ~ <20> 13. A method for producing the thermal printhead according to any one of claims 1 to 12.

[0038] <22> The single crystal semiconductor is made of silicon. <21> A method for producing the thermal printhead according to claim 1.

[0039] <23> a back surface of the substrate of one of the structures has a contact surface in contact with a part of an upper surface of the conductive layer or an upper surface of the protective film of another of the structures; <13> ~ <22> 13. A method for producing the thermal printhead according to any one of claims 1 to 12.

[0040] <24> The hard film of one of the structures is in contact with a part of a side surface and a part of a back surface of the one of the substrates of the structure and is spaced apart from the contact surface. <23> A method for producing the thermal printhead according to claim 1.

[0041] (Embodiment 1) A thermal printhead and a method for manufacturing the same according to the present embodiment will be described with reference to the drawings.

[0042] Fig. 1 is a simplified plan view of a thermal printhead, Fig. 2 is a cross-sectional view taken along line II in Fig. 1, Fig. 3 is a partially enlarged plan view of the thermal printhead, and Fig. 4 is a cross-sectional view showing a head substrate included in the thermal printhead.

[0043] The thermal printhead 10 of this embodiment includes a substrate 11, a wiring substrate 12, a heat sink 13, a heat storage section 21, wiring 3, a resistor layer 4, a conductive layer 5, a protective film 6, a driving IC 7, a plurality of wires 81, a resin section 82, and a connector 83. For ease of understanding, some components may be omitted in FIGS. 1 to 3. As shown in FIG. 2, the thermal printhead 10 is incorporated into a printer that performs printing on a print medium 801. The print medium 801 is pressed against the resistor layer 4 (heat generating section 41) of the thermal printhead 10 by a platen roller 802. Examples of the print medium 801 include a barcode sheet, a two-dimensional code sheet, and thermal paper for producing receipts. The sub-scanning direction X (more precisely, the −X direction) shown in FIGS. 1 to 3 is the direction in which the print medium 801 is transported (paper feed direction).

[0044] The substrate 11 is made of a single crystal semiconductor or ceramic. For example, silicon can be used as the single crystal semiconductor. For example, alumina or aluminum nitride can be used as the ceramic. From the viewpoint of easily forming a convex portion (first convex portion) described later, it is preferable to use a single crystal semiconductor for the substrate 11. In addition, the first convex portion P1 described later may be formed on the substrate 11 using a material other than the substrate, and for example, an insulating film such as a silicon oxide film or a silicon nitride film can be used. For example, a silicon oxide film (TEOS oxide film) formed using TEOS (tetraethyl orthosilicate) as a raw material gas can be used as the silicon oxide film. The thickness of the substrate 11 is, for example, about 0.5 to 1.0 mm. As shown in FIG. 2, the substrate 11 is a flat plate extending long in the main scanning direction Y.

[0045] A conductive layer 111, which is a convex portion used in the manufacturing process, is formed on the main surface 15 side of the substrate 11. The conductive layer 111 is preferably formed on the upstream side of the substrate 11, which is the side of the supply source of the printing medium 801 (the +X side close to the resin part 82 in FIG. 2), at a position some distance away from the resistor layer 4. The conductive layer 111 may be covered by the resin part 82.

[0046] 2 and 3, the substrate 11 has a main surface 15 which is the substrate surface. The main surface 15 is flat and extends in the sub-scanning direction X and the main scanning direction Y. The main surface 15 extends longitudinally along the main scanning direction Y. The main surface 15 faces one side in the thickness direction Z of the substrate 11 (upward (i.e., the +Z direction) in FIG. 4).

[0047] The wiring board 12 may be, for example, a printed wiring board. The wiring board 12 has a structure in which a base layer and a wiring layer (not shown) are laminated. The base layer may be, for example, a glass epoxy resin. The wiring layer may be, for example, copper. The wiring board 12 may be a flexible printed wiring board.

[0048] Heat sink 13 has a function of dissipating heat from substrate 11. Substrate 11 and wiring board 12 are attached to heat sink 13. Heat sink 13 may be made of a metal such as aluminum.

[0049] The heat storage section 21 is formed on the main surface 15 of the substrate 11. The heat storage section 21 may also be referred to as a glaze layer. The heat storage section 21 extends in a band shape along the main scanning direction Y. In FIG. 3, the boundary of the formation region of the heat storage section 21 is indicated by a broken line. In this embodiment, the heat storage section 21 has a shape with a part protruding. This allows the heat storage section 21 to appropriately abut the part of the protective film 6 covering the heat generating section 41 against the printing medium 801. It is preferable that the heat storage section 21 has insulating properties. The heat storage section 21 can be formed on the first convex portion P1 by processing a substrate made of a single crystal semiconductor. In this case, it is preferable to form an insulating film on the main surface 15 including the heat storage section 21.

[0050] A resistor layer 4 is formed on the heat storage section 21. The resistor layer 4 generates heat in a portion where a current flows from the wiring 3. This generation of heat forms print dots on thermal paper or the like. The resistor layer 4 is made of a material having a higher resistivity than the material constituting the wiring 3, and may be made of, for example, tantalum nitride or silicon oxide containing tantalum. In this embodiment, the resistor layer 4 has a thickness of, for example, about 0.05 to 0.2 μm. In this embodiment, the resistor layer 4 is interposed between the wiring 3 and the heat storage section 21. A part of the heat generated by the resistor layer 4 is stored in the heat storage section 21.

[0051] As shown in Fig. 3, the resistor layer 4 includes a plurality of heat generating portions 41. For ease of understanding, the heat generating portions 41 in Fig. 3 are shaded.

[0052] The wiring 3 is formed on the resistor layer 4. The wiring 3 constitutes a path for passing electricity through the resistor layer 4. The wiring 3 is made of a conductor. As the conductor, for example, a metal layer such as aluminum, copper, titanium, or gold can be used. In this embodiment, the thickness of the wiring 3 is, for example, about 0.2 to 0.8 μm. The wiring 3 may have a multi-layer structure. The wiring 3 may have two layers, for example, a titanium layer mainly composed of titanium formed on the resistor layer 4, and a copper layer mainly composed of copper formed on the titanium layer.

[0053] In this embodiment, the wiring 3 includes a plurality of individual electrodes 31, a plurality of common electrodes 32, and a plurality of relay electrodes 33, as shown in FIG.

[0054] The individual electrodes 31 are not electrically connected to one another. Therefore, when a printer incorporating the thermal printhead 10 is used, different potentials can be applied to the individual electrodes 31 individually. Each individual electrode 31 has an individual electrode strip portion 311, a wide portion 312, and a bonding portion 313 (bonding pad). Each individual electrode strip portion 311 is strip-shaped and extends along the sub-scanning direction X. The individual electrode strip portion 311 is laminated on the resistor layer 4. The wide portion 312 is connected to the individual electrode strip portion 311 and extends along the sub-scanning direction X. The width dimension (dimension in the main scanning direction Y) of the wide portion 312 is larger than the width dimension (dimension in the main scanning direction Y) of the individual electrode strip portion 311. The bonding portion 313 is a portion to which the wire 81 is bonded. In this embodiment, the width of the individual electrode strip portion 311 is, for example, about 45 to 50 μm, the width of the wide portion 312 is, for example, about 50 to 70 μm, and the width of the bonding portion 313 is, for example, about 50 to 75 μm.

[0055] The common electrode 32 is a portion that has an electrically opposite polarity to the individual electrodes 31 when a printer incorporating the thermal printhead 10 is used. The common electrode 32 has a plurality of common electrode strip portions 321, a plurality of branch portions 322, a plurality of perpendicular portions 323, and one main portion 324. Each common electrode strip portion 321 is strip-shaped extending in the sub-scanning direction X. As shown in FIG. 3, in each common electrode 32, the common electrode strip portions 321 are spaced apart from one another in the main scanning direction Y and are conductive to one another. Each common electrode strip portion 321 is laminated on the resistor layer 4. Each common electrode strip portion 321 is spaced apart from the individual electrode strip portions 311 in the main scanning direction Y. In this embodiment, two adjacent common electrode strip portions 321 are sandwiched between two individual electrode strip portions 311. The common electrode strip portions 321 and the individual electrode strip portions 311 are arranged along the primary scanning direction Y. The branch portion 322 is a portion that connects two common electrode strip portions 321 and one straight portion 323, and is Y-shaped. The straight portion 323 extends along the secondary scanning direction X. The main portion 324 is a strip-shaped pattern that extends in the primary scanning direction Y, and each of the straight portions 323 that extend along the secondary scanning direction X is connected to the main portion 324. In this embodiment, the width of the common electrode strip portion 321 is, for example, about 45 to 50 μm, and the width of the straight portion 323 is, for example, about 50 to 70 μm. The width of the main portion 324 is, for example, about 300 to 550 μm.

[0056] As shown in FIG. 3, the relay electrodes 33 are arranged along the primary scanning direction Y. The relay electrodes 33 are located on the opposite side of the heat generating portions 41 from the common electrode 32 and the individual electrodes 31 in the secondary scanning direction X. In FIG. 3, two adjacent individual heating elements (represented by a rectangle elongated in the X direction in the resistor layer 4) form one heat generating portion 41. Each relay electrode 33 is in contact with two adjacent individual heating elements (a pair) among the individual heating elements. Each of the relay electrodes 33 is electrically interposed between one of the individual electrodes 31 and the common electrode 32. Each relay electrode 33 has two (a pair) relay electrode strip portions 331, a connecting portion 332, and an extending portion 333. Two adjacent individual heating elements (a pair) connected by one relay electrode 33 form one heat generating portion 41. One heat generating portion 41 corresponds to one print dot formed on thermal paper.

[0057] Each relay electrode strip portion 331 is strip-shaped extending in the sub-scanning direction X. The multiple relay electrode strip portions 331 are spaced apart from each other in the main scanning direction Y. Each relay electrode strip portion 331 is laminated on the resistor layer 4. The multiple relay electrode strip portions 331 are arranged on the resistor layer 4 on the opposite side in the sub-scanning direction X to the multiple individual electrode strip portions 311 and the multiple common electrode strip portions 321. Each pair of relay electrode strip portions 331 constituting each relay electrode 33 is in contact with an adjacent pair of individual heating elements. One of the pair of relay electrode strip portions 331 in each relay electrode 33 is arranged to face one of the multiple common electrode strip portions 321 across one individual heating element in the sub-scanning direction X. The other of the pair of relay electrode strip portions 331 in each relay electrode 33 is arranged to face one of the multiple individual electrode strip portions 311 across one individual heating element adjacent to the above-mentioned one individual heating element in the sub-scanning direction X. Each relay electrode strip portion 331 is located on the heat storage portion 21 .

[0058] Each of the multiple connecting portions 332 extends along the primary scanning direction Y. Each connecting portion 332 is connected to a pair of relay electrode strip portions 331 in each relay electrode 33. This allows the pair of relay electrode strip portions 331 in each relay electrode 33 to be electrically connected to each other. Each connecting portion 332 is located on the heat storage portion 21.

[0059] Each of the multiple extension portions 333 extends along the sub-scanning direction X. Each extension portion 333 is connected to a connecting portion 332 of each relay electrode 33. In Fig. 3, the boundary between the connecting portion 332 and the extension portion 333 is represented by an upper imaginary line.

[0060] The conductive layer 5 is laminated on the main surface 15 side of the substrate 11. The conductive layer 5 is provided, for example, so as to surround at least a part of the wiring 3. The conductive layer 5 is formed at a position spaced from the extension portion 333 on one side in the sub-scanning direction X (the -X direction side). The conductive layer 5 shown in FIG. 3 has a predetermined width in the sub-scanning direction X and extends along the main scanning direction Y. The conductive layer 5 is made of, for example, the same material as the wiring 3. Note that the conductive layer 5 is not necessarily required. Unlike this embodiment, the conductive layer 5 may not be provided.

[0061] The protective film 6 has a function of protecting the wiring 3, the resistor layer 4, and the conductive layer 5, and may be made of an insulating material such as silicon nitride. The thickness of the protective film 6 is, for example, about 1 to 8 μm.

[0062] The driving IC 7 applies a potential to each individual electrode 31, and controls a current flowing through each heat generating portion 41. By applying a potential to each individual electrode 31, a voltage is applied between each individual electrode 31 and the common electrode 32, and a current flows selectively through each heat generating portion 41. The driving IC 7 is disposed on the wiring board 12. As shown in FIG. 3, the driving IC 7 includes a plurality of pads 71. The plurality of pads 71 ​​are formed in, for example, two rows. Unlike this embodiment, the driving IC 7 may be disposed on the board 11.

[0063] The wires 81 may be made of a conductor such as gold. There are a plurality of wires 81, some of which (in FIG. 3, the wires on the upper side of the driving IC 7) are bonded to the pads 71 ​​of the driving IC 7 and are also bonded to the bonding portions 313. The driving IC 7 and each individual electrode 31 are electrically connected by bonding. Some of the other wires 81 (in FIG. 3, the wires on the lower side of the driving IC 7) are bonded to the pads 71 ​​of the driving IC 7 and are also bonded to a wiring layer in the wiring board 12. The driving IC 7 and the connector 83 are electrically connected by bonding through the wiring layer. The remaining wires 81 are bonded to the backbone 324 connected to the common electrode 32 and are also bonded to the wiring layer for the common electrode in the wiring board 12. The common electrode 32 and the wiring layer are electrically connected by bonding.

[0064] 2 may be made of, for example, a black resin. For example, epoxy resin, silicone resin, or the like may be used as the resin portion 82. The resin portion 82 covers the driving IC 7, the multiple wires 81, and the protective film 6, and protects the driving IC 7 and the multiple wires 81. The connector 83 is fixed to the wiring board 12. Wiring for supplying power to the thermal printhead 10 from outside the thermal printhead 10 and for controlling the driving IC 7 is connected to the connector 83.

[0065] FIG. 4 shows a cross-sectional view of an example of a head substrate included in a thermal printhead including the above-mentioned components. The head substrate 150 shown in FIG. 4 includes a substrate 11 having a first convex portion P1, a heat storage layer 102, a resistor layer 109 having a heat generating portion, wiring 107, a protective film 110, a structure having a conductive layer 111 (second convex portion) connected to the wiring 107 through an opening provided in the protective film 110, and a hard film 112. The conductive layer 111 is thicker than the protective film 110 and is in contact with the side surface of the protective film 110. The conductive layer 111 has a flat upper surface. In this specification, the term "flat" includes an average surface roughness of 5 μm or less. The average surface roughness can be determined, for example, in accordance with JIS B 0601:2013 or ISO 25178. As will be described later, the thermal printhead includes one head substrate 150 manufactured from the above-mentioned structure.

[0066] The heat storage layer 102 corresponds to the heat storage layer including the heat storage portion 21 described above, the resistor layer 109 corresponds to the resistor layer 4 described above, the wiring 107 corresponds to the wiring 3 described above, and the protective film 110 corresponds to the protective film 6 described above.

[0067] The heat storage layer 102 covers the substrate 11. The heat storage layer 102 may be made of an insulating material, such as silicon oxide, silicon nitride, or a TEOS oxide film, and is preferably made of a TEOS oxide film. The thickness of the heat storage layer 102 is not particularly limited and is, for example, 5 to 15 μm, and preferably 5 to 10 μm.

[0068] The conductive layer 111 may be made of, for example, copper, silver, gold, nickel, or palladium, and may have a single-layer structure or a multilayer structure. For example, a layer containing nickel, a layer containing palladium, and a layer containing gold may be formed in this order. In this case, the thickness of the layer containing nickel in contact with the wiring 107 is preferably about 4 μm, and the thickness of the conductive layer 111 is preferably 3 to 10 μm, and more preferably 4 to 7 μm. By setting the thickness of the conductive layer 111 within the above range, the height of the upper surface of the conductive layer 111 can be made higher than the upper surface of the protective film 110 around the conductive layer 111. In other words, the conductive layer 111 is formed to be thicker than usual.

[0069] In the process of manufacturing two or more of the above-mentioned structures and forming the hard film 112 shown in FIG. 4 (see FIG. 21), a part of the structure A and a part of the structure B are overlapped with each other, sandwiching a conductive layer 111 formed thicker than usual (here, the upper structure A overlaps the lower structure B in a part of its area). In FIGS. 21 and 27, for convenience, the head substrate after the hard film 112 is formed is explained using structures A and B. In this process, as shown in FIGS. 21 and 27, the thickness of the conductive layer 111 of the structure B can suppress contact between the protective film 110 of the structure B and the back surface of the substrate 11 of the structure A. Therefore, it is possible to suppress damage (e.g., cracks, disconnections, etc.) to the protective film 110 of the lower structure B caused by the back surface of the substrate 11 of the upper structure A.

[0070] In this embodiment, the conductive layer 111 is formed by plating. Either electrolytic plating or electroless plating may be used as the plating. The conductive layer 111 has a function of a spacer in the process of forming the hard film 112 (see FIG. 21) and a function of a bonding portion 313 to which the wire 81 (see FIG. 2) is connected. By using plating, the conductive layer 111 can be formed at a desired position in the Y direction shown in FIG. 2, such as between the driving ICs 7 or further outside the driving ICs 7 at both ends. The conductive layer 111 can also be formed at a desired position in the X direction. In addition, by performing electroless plating or by appropriately providing plating leads when performing electrolytic plating, it is possible to form a conductive layer 111 that is not electrically connected to any signal, a conductive layer 111 that is connected to a ground potential, and the like.

[0071] The hard film 112 is the outermost protective film that directly rubs against the print medium, and may be made of, for example, sialon, silicon carbide, or silicon nitride as a main component and have a hardness of about 1000 to 2000 HK. The thickness of the hard film is, for example, 5 to 8 μm.

[0072] Next, a method for manufacturing the thermal printhead of this embodiment will be described with reference to the drawings.

[0073] First, a substrate 100 is prepared. Next, a resist 101 is formed as shown in FIGS.

[0074] 7 and 8, a portion of the substrate 100 is removed using the resist 101 as a mask to form a substrate 100a. For example, the portion of the substrate 100 can be removed by anisotropic etching using potassium hydroxide. Thereafter, the resist 101 is peeled off. For example, hydrofluoric acid can be used for the peeling.

[0075] 9 and 10, a portion of the substrate 100a is removed to form the substrate 11 having the main surface 15 and the first convex portion P1. For example, the portion of the substrate 100a can be removed by anisotropic etching using tetramethylammonium hydroxide (TMAH). This process forms the first convex portion P1. For example, the dimension (width dimension) of the first convex portion P1 in the sub-scanning direction X is about 300 to 700 μm, and the dimension (thickness dimension) in the thickness direction Z is about 100 to 170 μm.

[0076] 11 and 12, the heat storage layer 102 is formed on the main surface 15 of the substrate 11. The heat storage layer 102 may be made of, for example, TEOS using CVD (Chemical Vapor Deposition).

[0077] 13 and 14, a resistor film 103 which becomes a heating portion and a wiring film 104 which becomes wiring are formed in this order. For example, tantalum nitride or the like formed by sputtering can be used for the resistor film 103. For example, copper, titanium or the like formed by sputtering can be used for the wiring film 104.

[0078] Next, as shown in Fig. 15 and Fig. 16, a part of the resistor film 103 and the wiring film 104 are removed to form the resistor layer 109 and the wiring 107. The resistor layer 109 and the wiring 107 can be formed, for example, by forming a resist and performing wet etching or the like using the resist as a mask. The resistor layer 109 has a heat generating portion. This process forms a resistor layer pattern and a wiring pattern in order from the bottom up. The "wiring 107" includes, in addition to the wiring that transmits a signal, a conductive layer pattern that is not electrically connected to any signal, a conductive layer pattern that is connected to a ground potential, and the like.

[0079] 17 and 18, a protective film 110 is formed, an opening reaching the wiring 107 is formed in the protective film 110, and a conductive layer 111 is formed in the opening. The protective film 110 can be made of silicon nitride using CVD, for example. The opening can be formed, for example, by forming a resist and performing reactive ion etching using the resist as a mask. The conductive layer 111 can be made of a structure in which a layer containing nickel, a layer containing palladium, and a layer containing gold are formed in this order by plating, for example.

[0080] The conductive layer 111 is formed so as to fill the opening formed in the protective film 110, and is therefore in contact with the inner surface of the protective film 110. Moreover, the conductive layer 111 is thicker than the protective film 110, and the height of the upper surface of the conductive layer 111 is higher than the upper surface of the protective film 110 around the conductive layer 111. Furthermore, the conductive layer 111 has a flat upper surface.

[0081] By the above steps, the structure included in the thermal printhead of this embodiment can be manufactured.

[0082] Next, as shown in Fig. 19 and Fig. 20, a hard film 112 is formed. The hard film 112 may be in contact with the side surface of the substrate 11. The hard film 112 may also be in contact with a part of the rear surface of the substrate 11. The hard film 112 is separated from a contact surface to be described later. The hard film 112 may be made of silicon carbide or the like formed by a vapor phase growth method (for example, by a CVD (chemical vapor deposition) method). The hard film 112 may also be formed by a physical vapor deposition method.

[0083] 21, the hard film 112 is formed in a lump by stacking a plurality of the above-mentioned structures with the conductive layer 111 sandwiched therebetween. In this process, the lower surface of the upper structure A and the surfaces of the protective film 110 and the hard film 112 on the upper surface of the lower structure B are spaced apart from each other.

[0084] Each of the structures A and B shown in FIG. 21 may be in a state where a plurality of head substrates 150 used for one thermal printhead are connected (a state where a plurality of head substrates are connected along the Y direction in FIG. 1). In this case, a single structure on which the hard film 112 is formed is diced to produce a plurality of head substrates. For dicing, for example, a dicer may be used, or a cutting device using laser light may be used. It is also possible to form blind holes discretely using a laser light along the planned cutting line in one structure (head substrate) on which the hard film 112 is formed, and then to fracture the head substrate.

[0085] By configuring the conductive layer 111 as described above, when stacking a plurality of the above-described structures, the thickness of the conductive layer 111 of the lower structure B can prevent contact between the protective film 110 of the structure B and the substrate 11 of the upper structure A. This can prevent the protective film 110 of the lower structure B from being damaged (e.g., cracked, disconnected, etc.) by the rear surface of the substrate 11 of the upper structure A.

[0086] Furthermore, the back surface of the substrate 11 of the upper structure A has a contact surface that comes into contact with the top surface of the conductive layer 111 of the lower structure B. If a hard film 112 were formed on the back surface of the substrate 11 of the upper structure A in the state shown in FIG. 21, the contact surface and the hard film 112 would be spaced apart. Therefore, the hard film 112 would not be formed on the surface of the conductive layer 111 of the lower structure B. Since the surface of the conductive layer 111 of the lower structure B is exposed, the conductive layer 111 functions as a bonding part. As a result, a thermal printhead with ensured yield and reliability can be obtained.

[0087] The thermal printhead of this embodiment can be manufactured by the above steps. The thermal printhead of this embodiment has a conductive layer 111 that functions as a spacer in the step of forming the hard film 112. According to this embodiment, the thermal printhead can be manufactured without adding a manufacturing step for forming the conductive layer 111 that functions as a spacer.

[0088] (Embodiment 2) A thermal printhead and a manufacturing method thereof according to this embodiment, which is different from the above-described embodiment 1, will be described with reference to the drawings. Note that the parts not described below are the same as those in the above-described embodiment 1. In Figures 22 to 27, the left end portion of the substrate including the main part 324 shown in Figure 4 is omitted.

[0089] 22, the thermal printhead of this embodiment includes a substrate 11a having a first protrusion P1 and a second protrusion P2, a heat storage layer 102, a resistor layer 109 having a heat generating portion, wiring 107, a protective film 110, a structure including a conductive layer 111 connected to the wiring 107 through an opening provided in the protective film 110, and a hard film 112. The first protrusion P1 is higher than the second protrusion P2, and the protective film 110 has a protrusion on the second protrusion P2, and the protrusion has a flat upper surface. Furthermore, as will be described later, the thermal printhead includes one head substrate 150a manufactured from the structure described above.

[0090] The difference between the thermal printhead of this embodiment and the thermal printhead of the previously described embodiment 1 is that in this embodiment, a substrate 11a having a first convex portion P1 and a second convex portion P2 is provided, and the thickness of the conductive layer 111 that functions as a bonding pad is approximately the same as that of a normal thermal printhead.

[0091] The substrate 11a is made of a single crystal semiconductor. For example, silicon can be used as the single crystal semiconductor. In the substrate 11a, the first convex portion P1 is higher than the second convex portion P2, for example, 20 to 170 μm or less, and the second convex portion P2 is, for example, 1 to 10 μm. In addition, the first convex portion P1 and the second convex portion P2 each have a flat upper surface. By forming the second convex portion P2, the protective film 110 on the second convex portion P2 has a protruding portion, and the protruding portion has a flat upper surface according to the shape of the second convex portion P2. In the step of manufacturing two or more of the above-mentioned structures and forming the hard film 112 (see FIG. 27), a part of the structure A and a part of the structure B are overlapped with each other with the protruding portion sandwiched therebetween (here, the upper structure A overlaps the lower structure B in a partial area). 27, the protruding portion of the protective film 110 of the structure B can prevent contact between the protective film 110 and the back surface of the substrate 11a of the structure A at a portion other than the second protruding portion of the structure B. This can prevent the protective film 110 of the lower structure B from being damaged (e.g., cracked, broken, etc.) by the back surface of the substrate 11a of the upper structure A.

[0092] Next, a method for manufacturing the thermal printhead of this embodiment will be described with reference to the drawings.

[0093] A substrate 11 is formed as in the above-described embodiment 1. Next, a resist 101a is formed as shown in FIG.

[0094] Next, as shown in FIG. 24, using the resist 101a as a mask, a portion of the substrate 11 is removed to form the substrate 11a having the main surface 15, the first convex portion P1, and the second convex portion P2. For example, the portion of the substrate 11 can be removed by anisotropic etching using potassium hydroxide. Thereafter, the resist 101a is peeled off. For example, hydrofluoric acid can be used for the peeling. Through this process, the first convex portion P1 and the second convex portion P2 each having a final shape are formed.

[0095] 25, the heat storage layer 102, the resistor layer 109, and the wiring 107 are formed. For the formation of the heat storage layer 102, the resistor layer 109, and the wiring 107, the description of the first embodiment can be applied.

[0096] 26, a protective film 110 and a conductive layer 111 are formed. For the formation of the protective film 110 and the conductive layer 111, the description of the first embodiment can be applied.

[0097] By the above steps, the structure included in the thermal printhead of this embodiment can be manufactured.

[0098] 26, a hard film 112 is formed. The hard film 112 may be in contact with a side surface of the substrate 11a. The hard film 112 may be in contact with a part of the back surface of the substrate 11a. The hard film 112 is spaced apart from a contact surface to be described later.

[0099] The hard film 112 is formed by stacking a plurality of the above-mentioned structures at once, as shown in Fig. 27. In this process, the lower surface of the upper structure A and the surfaces of the protective film 110 and the hard film 112 on the upper surface of the lower structure B are spaced apart from each other.

[0100] By providing the substrate 11a having the first protrusion P1 and the second protrusion P2, when a plurality of the above-mentioned structures are stacked, the protruding portion of the protective film 110 of the lower structure B can prevent the protective film 110 from contacting the back surface of the substrate 11a of the structure A except on the second protrusion P2 of the structure B. Therefore, it is possible to prevent the protective film 110 of the lower structure B from being damaged (for example, cracked, broken, etc.) by the back surface of the substrate 11a of the upper structure A.

[0101] Also, the back surface of the substrate 11a of the upper structure A has a contact surface that contacts the upper surface of the protective film 110 on the second protrusion P2 of the lower structure B. If a hard film 112 is formed on the back surface of the substrate 11 in the state shown in FIG. 27, the contact surface and the hard film 112 are spaced apart. The conductive layer 111 of the lower structure B is located on the opposite side to the side on which the hard film 112 is formed on the back surface of the substrate 11a of the upper structure A, sandwiching the second protrusion P2 of the structure B. Therefore, the hard film 112 is not formed on the surface of the conductive layer 111 of the lower structure B. Since the surface of the conductive layer 111 of the lower structure B is exposed, the conductive layer 111 functions as a bonding part. As a result, a thermal printhead with high yield and reliability can be obtained.

[0102] The thermal printhead of this embodiment can be manufactured by the above steps. According to this embodiment, a thermal printhead having an insulating protective film 110 on the second protrusion P2 can be manufactured. The protective film 110 on the second protrusion P2 functions as an insulating spacer in the step of forming the hard film 112.

[0103] In each embodiment, an example has been described in which the first protrusions P1 are formed by processing a substrate made of a single crystal semiconductor. For example, a glass material such as amorphous glass can be used as the first protrusions P1. The softening point of this glass material is, for example, 800 to 850°C. The dimension of the first protrusions P1 in the sub-scanning direction X is, for example, about 500 to 600 μm. The dimension of the first protrusions P1 in the thickness direction Z is, for example, about 20 to 100 μm. By using screen printing, the first protrusions P1 can be easily formed and the cost of the manufacturing equipment can be reduced.

[0104] (How to use a thermal print head) An example of how to use a thermal printhead will now be briefly described.

[0105] The thermal printhead is used in a state where it is incorporated in a printer. As shown in FIG. 2, in the printer, each heat generating portion 41 of the thermal printhead 10 faces a platen roller 802. When the printer is in use, the platen roller 802 rotates to feed a print medium 801 between the platen roller 802 and each heat generating portion 41 at a constant speed along the sub-scanning direction X (more precisely, the −X direction). The print medium 801 is pressed against the portion of the protective film 6 that covers each heat generating portion 41 by the platen roller 802. Meanwhile, a potential is selectively applied to each individual electrode 31 shown in FIG. 3 by the driving IC 7. As a result, a voltage is applied between the common electrode 32 and each of the multiple individual electrodes 31. Then, a current selectively flows through the multiple heat generating portions 41, generating heat. Then, the heat generated in each heat generating portion 41 is transferred to the print medium 801 via the protective film 6. Then, a plurality of dots are printed in a first line region that extends linearly in the main scanning direction Y on the print medium 801. The heat generated in each heat generating portion 41 is also transmitted to the heat storage portion 21 and stored therein.

[0106] Furthermore, as the platen roller 802 rotates, the printing medium 801 continues to be fed at a constant speed along the sub-scanning direction X (more precisely, the -X direction). Then, similar to the printing on the first line area, printing is performed on a second line area adjacent to the first line area, which extends linearly in the main scanning direction Y on the printing medium 801. When printing on the second line area, in addition to the heat generated in each heat generating portion 41, the heat stored in the heat storage portion 21 during printing on the first line area is transferred to the printing medium 801. In this manner, printing on the second line area is performed. As described above, printing on the printing medium 801 is performed by printing a plurality of dots for each line area extending linearly in the main scanning direction Y on the printing medium 801.

[0107] [Other embodiments] As described above, several embodiments have been described, but the descriptions and drawings forming part of the disclosure are illustrative and should not be understood as limiting. From this disclosure, various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art. Thus, the present embodiment includes various embodiments not described herein. [Explanation of symbols]

[0108] 3...wiring, 4...resistance layer, 5...conductive layer, 6...protective film, 7...driving IC, 10...thermal print head, 11...substrate, 11a...substrate, 12...wiring substrate, 13...heat sink, 15...main surface, 21...heat storage section, 31...individual electrode, 32...common electrode, 33...relay electrode, 41...heat generating section, 71...pad, 81...wire, 82...resin section, 83...connector, 100...substrate, 100a...substrate, 101...resist, 101a...resist, 102...heat storage layer, 10 3...resistor film, 104...wiring film, 107...wiring, 109...resistor layer, 110...protective film, 111...conductive layer, 112...hard film, 150...head substrate, 150a...head substrate, 311...individual electrode strip portion, 312...wide portion, 313...bonding portion, 321...common electrode strip portion, 322...branch portion, 323...straight portion, 324...main portion, 331...relay electrode strip portion, 332...connecting portion, 333...extending portion, 801...printing medium, 802...platen roller

Claims

1. A protrusion on a substrate; a heat storage layer on the substrate and on the protrusion; A heat generating portion on the heat storage layer; A wiring made of a metal layer and connected to the heat generating portion; a protective film on the wiring and the heat storage layer; a conductive layer connected to the metal layer through an opening provided in the protective film; A structure having a hard film in contact with the protective film; the conductive layer is thicker than the protective film and is in contact with an inner surface of the protective film at the opening; The conductive layer has a flat upper surface.

2. 2. The thermal printhead according to claim 1, wherein the conductive layer has a thickness of 1 to 10 μm.

3. 3. The thermal printhead according to claim 1, wherein the substrate and the protrusions are integrally formed from a single crystal semiconductor.

4. 4. The thermal printhead of claim 3, wherein the single crystal semiconductor is made of silicon.

5. The thermal printhead according to claim 1 or 2, wherein the substrate is a ceramic substrate.

6. a substrate having a first protrusion and a second protrusion; A heat storage layer on the substrate; A heat generating portion on the heat storage layer; Wiring connected to the heat generating portion; a protective film on the wiring and the heat storage layer; A structure having a hard film in contact with the protective film; The first protrusion is higher than the second protrusion, The protective film has a protruding portion on the second convex portion, The protrusion has a flat upper surface.

7. 7. The thermal printhead according to claim 6, wherein the height of the second convex portion is 1 to 10 μm.

8. 8. The thermal printhead according to claim 6, wherein the height of the first convex portion is 20 to 300 μm.

9. 9. The thermal printhead according to claim 6, wherein the substrate is made of a single crystal semiconductor.

10. The thermal printhead of claim 9 , wherein the single crystal semiconductor is made of silicon.

11. There are two or more of the structures, A thermal printhead according to any one of claims 1 to 5, wherein the back surface of the substrate of one of the structures has a contact surface in contact with a portion of the top surface of the conductive layer of the other of the structures.

12. There are two or more of the structures, A thermal printhead according to any one of claims 6 to 10, wherein the rear surface of one of the substrates of the structure has a contact surface that contacts a portion of the upper surface of the protective film of another of the structure.

13. The thermal printhead according to claim 11 or 12, wherein the hard film of one of the structures contacts a portion of a side surface and a portion of a back surface of the substrate of one of the structures and is spaced apart from the contact surface.

14. Removing a portion of the substrate to form a protrusion; forming a heat storage film on the substrate having the protrusions; forming a resistor film on the heat storage film; forming a wiring film on the resistor film; A part of the wiring film is removed to form a wiring; A part of the resistor film is removed to form a heating portion; forming a protective film on the substrate having the protrusions, on the heat storage film, on the heat generating portion, and on the wiring; forming an opening in the protective film that reaches the wiring; forming a conductive layer having a thickness greater than that of the protective film and a flat upper surface on the wiring in the opening to manufacture a structure; Preparing two or more of the structures; a part of the structure and another part of the structure are overlapped with each other with a conductive layer of the structure interposed therebetween; forming a hard film in contact with the protective film of the two or more structures by a vapor phase growth method while the two or more structures are superimposed on each other; A method for manufacturing a thermal printhead.

15. The method for manufacturing a thermal printhead according to claim 14, wherein the convex portion is formed by anisotropic etching using potassium hydroxide.

16. The method for manufacturing a thermal printhead according to claim 14 or 15, wherein the conductive layer has a thickness of 1 to 10 μm.

17. removing a portion of the substrate to form a first protrusion and a second protrusion; forming a heat storage film on a substrate having the first convex portion and the second convex portion; forming a resistor film on the heat storage film; forming a wiring film on the resistor film; A part of the wiring film is removed to form a wiring; A part of the resistor film is removed to form a heating portion; forming a protective film on a substrate having the first convex portion and the second convex portion, on the heat storage film, on the heat generating portion, and on the wiring; forming an opening in the protective film that reaches the wiring; forming a conductive layer in the opening to produce a structure; The first protrusion is higher than the second protrusion, The protective film has a protruding portion on the second convex portion, the protrusion has a flat upper surface; Preparing two or more of the structures; One part of the structure and another part of the structure are overlapped with each other with the one protruding portion of the structure sandwiched therebetween, forming a hard film in contact with the protective film of the two or more structures by a vapor phase growth method while the two or more structures are superimposed on each other; A method for manufacturing a thermal printhead.

18. 18. The method for manufacturing a thermal printhead according to claim 17, wherein the second convex portion is formed by forming a resist on the substrate other than the first convex portion after forming the first convex portion, and removing a portion of the substrate having the first convex portion using the resist as a mask.

19. The method for manufacturing a thermal printhead according to claim 17 or 18, wherein the first convex portion and the second convex portion are formed by performing anisotropic etching using potassium hydroxide.

20. The method for manufacturing a thermal printhead according to any one of claims 17 to 19, wherein the height of the second convex portion is 1 to 10 µm.

21. The method for manufacturing a thermal printhead according to any one of claims 17 to 20, wherein the height of the first convex portion is 20 to 300 µm.

Images