Thermal printhead, method of manufacturing a thermal printhead, and thermal printer

Abstract

To provide a thermal head capable of suppressing a decrease in manufacturing efficiency and improving abrasion resistance to a recording medium, a manufacturing method of the thermal head, and a thermal printer provided with the thermal head. The thermal head of the present invention includes: a substrate 1 having a main surface 10 facing a thickness direction; a resistance layer 3 including a plurality of heat generating portions 31 arranged in a main scanning direction and formed on the main surface 10; a wiring layer 4 formed on the resistance layer 3 and in conduction with the plurality of heat generating portions 31; and a protective layer 5 covering a portion of the main surface 10, the plurality of heat generating portions 31, and the wiring layer 4; and further includes: a coating layer covering at least a portion of the protective layer 5; and when viewed along the thickness direction, the coating layer 6 overlaps the plurality of heat generating portions 31, the coating layer 6 has a base layer 61 in contact with the protective layer 5 and a body layer 62 laminated on the base layer 61, and the base layer 61 and the body layer 62 each include a metal element.

Description

Technical Field

[0001] This invention relates to a thermal printhead and its manufacturing method, and a thermal printer equipped with the thermal printhead. Background Technology

[0002] Patent document 1 discloses an example of a thermal printhead. The thermal printhead includes: a heating resistor disposed on a support substrate; and multiple electrodes disposed on the heating resistor. When current flows through the multiple electrodes, the heating resistor heats up. Thus, text is printed on a recording medium such as thermal paper.

[0003] The thermal printhead also includes a protective film covering the heating resistor and multiple electrodes. This protective film exhibits a unique characteristic: the distribution of film stress within the protective film varies along its thickness direction relative to the supporting substrate. Specifically, the film stress gradually increases as the distance from the heating resistor along the thickness direction increases. Consequently, the surface hardness of the protective film becomes greater, resulting in superior wear resistance of the thermal printhead to the recording medium. Furthermore, the film stress within the protective film gradually decreases from its surface towards the heating resistor along the thickness direction, thus suppressing thermal stress concentration caused by the heating resistor. Therefore, even with relatively high hardness, the protective film is less prone to cracking.

[0004] However, the protective film is formed by sputtering. During the formation of this protective film, the gas pressure needs to be adjusted each time, and a relatively large number of deposition cycles are required to accumulate the silicide film. Therefore, since the formation of this protective film is a significant cause of low manufacturing efficiency in the thermal printhead, improvements in this area are desired.

[0005] [Background Technical Documents]

[0006] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2018-34407 Summary of the Invention

[0008] [The problem the invention aims to solve]

[0009] In view of the above circumstances, the present invention aims to provide a thermal printhead that can suppress low manufacturing efficiency and improve abrasion resistance to recording media, a method for manufacturing the same, and a thermal printer having said thermal printhead.

[0010] [Technical means to solve the problem]

[0011] The thermal printhead provided by the first aspect of the present invention is characterized by comprising: a substrate having a main surface facing the thickness direction; a resistive layer containing a plurality of heating elements arranged in the main scanning direction and formed on the main surface; a wiring layer formed on the resistive layer and communicating with the plurality of heating elements; and a protective layer covering a portion of the main surface, the plurality of heating elements, and the wiring layer; and the thermal printhead further comprising: a coating layer covering at least a portion of the protective layer; and when viewed along the thickness direction, the coating layer overlaps with the plurality of heating elements, the coating layer having a base layer in contact with the protective layer and a body layer stacked on the base layer, the base layer and the body layer each comprising a metal element.

[0012] Preferably, in implementing this invention, the metal elements are bonded to each other through metallic bonds.

[0013] In implementing this invention, it is preferable that the Vickers hardness of the body layer is greater than that of the protective layer.

[0014] Preferably, when implementing the present invention, the protective layer contains silicon in its composition.

[0015] Preferably, when implementing the present invention, the main surface includes a base surface and a convex surface protruding from the base surface toward the thickness direction, the convex surface extending along the main scanning direction, and the plurality of heating elements formed on the convex surface.

[0016] Preferably, when the present invention is implemented, the coating layer overlaps with the convex surface when viewed along the thickness direction.

[0017] Preferably, when implementing the present invention, the convex surface comprises: a top surface, parallel to the base surface; and a pair of inclined surfaces, connected to the top surface and the base surface, and located at positions away from each other in the sub-scanning direction; the plurality of heating elements are formed on at least one of the top surface and the pair of inclined surfaces.

[0018] Preferably, when implementing the present invention, the wiring layer includes a common wiring and multiple independent wirings, the common wiring being located on one side of the sub-scanning direction relative to the multiple heating elements, and the multiple independent wirings being located on the other side of the sub-scanning direction relative to the multiple heating elements, and a portion of the common wiring and a portion of each of the multiple independent wirings being formed on either of the pair of inclined surfaces.

[0019] Preferably, when implementing the present invention, the pair of inclined surfaces are inclined relative to the base surface in such a way that they approach each other from the base surface toward the top surface.

[0020] Preferably, in implementing the present invention, each of the pair of inclined surfaces includes a first region connected to the base surface and a second region connected to the top surface and the first region, wherein the inclination angle of the second region relative to the base surface is smaller than the inclination angle of the first region relative to the base surface.

[0021] Preferably, when implementing the present invention, the substrate comprises a semiconductor material, wherein the semiconductor material comprises a single crystal material composed of silicon.

[0022] Preferably, when implementing the present invention, it further includes an insulating layer covering the main surface, wherein the resistive layer is in contact with the insulating layer.

[0023] Preferably, when implementing the present invention, a heat sink is also provided, and the substrate has a back side facing the opposite side to the main surface in the thickness direction, the back side being joined to the heat sink.

[0024] The method for manufacturing a thermal printhead provided by the second aspect of the present invention is characterized by comprising the following steps: forming a resistive layer on the main surface, the resistive layer including a plurality of heating elements arranged in a main scanning direction relative to a substrate having a main surface having a thickness direction; forming a wiring layer connected to the plurality of heating elements on the resistive layer; forming a protective layer covering a portion of the main surface, the plurality of heating elements, and the wiring layer; and the manufacturing method further comprising: after the step of forming the protective layer, forming a cover layer covering at least a portion of the protective layer; the step of forming the cover layer including: forming a base layer in contact with the protective layer and comprising a metal element; and forming a body layer deposited on the base layer and comprising a metal element; the body layer being formed by plating.

[0025] In implementing the present invention, it is preferable that, in the step of forming the coating layer, the substrate layer is formed by sputtering, and in the step of forming the coating layer, the body layer is formed by electroplating with the substrate layer as a conductive path.

[0026] Preferably, when implementing the present invention, the main surface includes a base surface and a convex surface protruding from the base surface in the thickness direction. Before the step of forming the resistive layer, a step of forming a protrusion on the substrate is further included. The protrusion protrudes from the base surface in the thickness direction and extends along the main scanning direction, and includes the convex surface. In the step of forming the resistive layer, the plurality of heating elements are formed on the convex surface.

[0027] Preferably, when implementing the present invention, the substrate comprises a semiconductor material, and the semiconductor material comprises a single crystal material composed of silicon.

[0028] In implementing the present invention, it is preferable that the protrusion is formed by anisotropic etching in the step of forming the protrusion.

[0029] The thermal printer provided by the third embodiment of the present invention includes: a thermal printhead as provided by the first embodiment of the present invention; and a pressure plate arranged opposite to the plurality of heating elements.

[0030] [The effects of the invention]

[0031] The thermal printhead and its manufacturing method according to the present invention can suppress low manufacturing efficiency and improve abrasion resistance to recording media.

[0032] Other features and advantages of the present invention will become clearer from the following detailed description based on the accompanying drawings. Attached Figure Description

[0033] Figure 1 This is a top view of the thermal printhead according to the first embodiment of the present invention.

[0034] Figure 2 yes Figure 1 The top view of the main part of the thermal printhead is shown.

[0035] Figure 3 yes Figure 2 A magnified view of a portion of the image.

[0036] Figure 4 It is along Figure 1 A cross-sectional view along line IV-IV.

[0037] Figure 5 yes Figure 1 The image shows a cross-sectional view of the main part of the thermal printhead.

[0038] Figure 6 yes Figure 5 A magnified view of a portion of the image.

[0039] Figure 7 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0040] Figure 8 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0041] Figure 9 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0042] Figure 10 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0043] Figure 11 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0044] Figure 12 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0045] Figure 13 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0046] Figure 14 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0047] Figure 15 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0048] Figure 16 This is an explanation Figure 1 A partially enlarged view of the manufacturing steps of the key parts of the thermal printhead.

[0049] Figure 17 This is an explanation Figure 1 A partially enlarged view of the manufacturing steps of the key parts of the thermal printhead.

[0050] Figure 18 This is an explanation Figure 1 A cross-sectional view showing the manufacturing process of the main part of the thermal printhead.

[0051] Figure 19 This is a cross-sectional view of the main part of the thermal printhead according to the second embodiment of the present invention.

[0052] Figure 20 yes Figure 19 A magnified view of a portion of the image. Detailed Implementation

[0053] The embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

[0054] [First Implementation]

[0055] based on Figures 1-6The thermal printhead A10 of the first embodiment of the present invention will be described below. The thermal printhead A10 forms the main part of the thermal printer B10, which will be described later. The thermal printhead A10 consists of a main part and auxiliary parts. The main part of the thermal printhead A10 includes a substrate 1, an insulating layer 2, a resistive layer 3, a wiring layer 4, a protective layer 5, and a coating layer 6. The auxiliary parts of the thermal printhead A10 include a wiring substrate 71, a heat sink 72, a plurality of driving elements 73, a plurality of first wires 74, a plurality of second wires 75, a sealing resin 76, and a connector 77. Here, in... Figure 1 The illustrations of the protective layer 5, the coating layer 6, the multiple first conductors 74, the multiple second conductors 75, and the sealing resin 76 are omitted. Figure 2 and Figure 3 In the middle, protective layer 5 is omitted. Figure 6 The illustration.

[0056] For ease of explanation, the main scanning direction of the thermal printhead A10 is referred to as the "x-direction". The secondary scanning direction of the thermal printhead A10 is referred to as the "y-direction". The thickness direction of the substrate 1 is referred to as the "z-direction". The z-direction is orthogonal to both the x-direction and the y-direction. In the following description, "observing along the z-direction" means "observing along the thickness direction".

[0057] In the thermal printhead A10, such as Figure 4 As shown, the substrate 1, which forms the core of the thermal printhead A10, is bonded to the heat sink 72. Furthermore, a wiring substrate 71 is located near the substrate 1 in the y-direction. The wiring substrate 71, like the substrate 1, is fixed to the heat sink 72. A portion of the resistive layer 3 is formed on the substrate 1, and a plurality of heat-generating elements 31 (details will be described later) are formed therein, arranged in the x-direction. The plurality of heat-generating elements 31 are selectively heated by a plurality of driving elements 73 mounted on the wiring substrate 71. The plurality of driving elements 73 are driven according to a printing signal transmitted from the outside via a connector 77.

[0058] Furthermore, the thermal printer B10 of the present invention, as Figure 4 As shown, the thermal printer B10 includes a thermal printhead A10 and a pressure roller 79. In the thermal printer B10, the pressure roller 79 is a roller-shaped mechanism that feeds recording media such as thermal paper. The pressure roller 79 presses the recording media onto a plurality of heating elements 31, thereby printing text onto the recording media. In the thermal printer B10, a non-roller-shaped mechanism may be used instead of the pressure roller 79. This mechanism has a flat surface. Here, the flat surface includes a curved surface with a small curvature. In the thermal printer B10, the roller-shaped mechanism, including the pressure roller 79, and together with the aforementioned mechanism, are referred to as a "pressure plate". Here, for ease of explanation, Figure 4 The supply source side of the recording medium ( Figure 4 The right side of the middle (in the middle) is called the "upstream side". Figure 4 The discharge end of the recording medium ( Figure 4 The left side of the middle is called the "downstream side".

[0059] Substrate 1 as Figure 1 As shown, when viewed along the z-direction, it appears as a band extending in the x-direction. Substrate 1 contains a semiconductor material. The semiconductor material comprises a single-crystal material composed of silicon (Si).

[0060] like Figure 5 As shown, substrate 1 has a main surface 10 and a back surface 13. The orientation of both the main surface 10 and the back surface 13, based on the crystal structure of substrate 1, is (100) plane. The main surface 10 and the back surface 13 face opposite sides in the z-direction. Figure 4 As shown, in the thermal printhead A10, the main surface 10 faces the pressure roller 79, and the back surface 13 faces the wiring substrate 71. The main surface 10 also includes a base surface 11 and a convex surface 12. The base surface 11 is parallel to the back surface 13. The convex surface 12 protrudes from the base surface 11 in the z-direction. The convex surface 12 extends along the x-direction.

[0061] like Figure 6 As shown, the convex surface 12 has a top surface 121 and a pair of inclined surfaces 122. The top surface 121 is located away from the base surface 11 in the z-direction and is parallel to the base surface 11. The pair of inclined surfaces 122 are located away from each other in the y-direction. The pair of inclined surfaces 122 are connected to the top surface 121 and the base surface 11. The pair of inclined surfaces 122 are inclined relative to the base surface 11 in a manner that they approach each other from the base surface 11 toward the top surface 121. The inclination angle α of each of the pair of inclined surfaces 122 relative to the base surface 11 is the same.

[0062] like Figure 6 As shown, a protrusion 17 is formed on the substrate 1. The protrusion 17 protrudes from the base surface 11 in the z-direction and extends along the x-direction. The convex surface 12 is the surface of the protrusion 17. Therefore, the convex surface 12 is configured to follow the shape of the protrusion 17.

[0063] Insulating layer 2 as Figure 6 As shown, the main surface 10 of the substrate 1 is covered. The substrate 1 is electrically insulated from the resistive layer 3 and the wiring layer 4 by an insulating layer 2. The insulating layer 2, for example, contains silicon dioxide (SiO2) made from tetraethyl orthosilicate (TEOS). The thickness of the insulating layer 2 is, for example, 1 μm or more and 15 μm or less.

[0064] Resistor layer 3 Figure 5 and Figure 6As shown, the resistive layer 3 is formed on the main surface 10 of the substrate 1. The resistive layer 3 is in contact with the insulating layer 2. Thus, in the thermal printhead A10, the insulating layer 2 is sandwiched between the substrate 1 and the resistive layer 3. The resistive layer 3, for example, contains tantalum nitride (TaN). The thickness of the resistive layer 3 is, for example, 0.02 μm or more and 0.1 μm or less.

[0065] like Figure 2 , Figure 3 and Figure 6 As shown, the resistive layer 3 includes a plurality of heating elements 31. In the resistive layer 3, the plurality of heating elements 31 are portions exposed from the wiring layer 4. By selectively energizing the plurality of heating elements 31 from the wiring layer 4, the plurality of heating elements 31 locally heat the recording medium. The plurality of heating elements 31 are arranged in the x-direction. Two adjacent heating elements 31 in the x-direction are located at a distance from each other. The plurality of heating elements 31 are formed on the top surface 121 of the convex surface 12 of the substrate 1. Figure 4 As shown, in the thermal printer B10, multiple heating elements 31 face the pressure roller 79. In the convex surface 12, multiple heating elements 31 can be formed across either the top surface 121 or a pair of inclined surfaces 122.

[0066] Wiring layer 4 as Figure 5 and Figure 6 As shown, a wiring layer 4 is formed on the resistive layer 3. A wiring layer 4 forms conductive paths for energizing the plurality of heat-generating portions 31 of the resistive layer 3. The resistivity of the wiring layer 4 is less than that of the resistive layer 3. The wiring layer 4 is, for example, a metal layer containing copper (Cu). The thickness of the wiring layer 4 is, for example, 0.3 μm or more and 2.0 μm or less. Furthermore, the wiring layer 4 may be composed of two metal layers: a titanium (Ti) layer deposited on the resistive layer 3 and a copper layer deposited on the titanium layer. In this case, the thickness of the titanium layer is, for example, 0.1 μm or more and 0.2 μm or less.

[0067] like Figure 2 As shown, wiring layer 4 includes a common wiring 41 and multiple independent wirings 42. The common wiring 41 is located on one side of the y-direction relative to the multiple heat-generating parts 31 of resistive layer 3. The multiple independent wirings 42 are located on the other side of the y-direction relative to the multiple heat-generating parts 31. Figure 3 As shown, when viewed along the z-direction, multiple regions in the resistive layer 3 sandwiched between the common wiring 41 and multiple independent wirings 42 are multiple heat-generating parts 31.

[0068] like Figure 2 and Figure 3As shown, the common wiring 41 has a base 411 and a plurality of extensions 412. In the y-direction, the base 411 is located furthest from the plurality of heat-generating portions 31 of the resistive layer 3. When viewed along the z-direction, the base 411 is a strip extending in the x-direction. The plurality of extensions 412 are strips extending from the ends of the base 411 opposite to the protrusions 17 of the substrate 1 in the y-direction toward the plurality of heat-generating portions 31. The plurality of extensions 412 are arranged along the x-direction. A portion of each of the plurality of extensions 412 is formed on one of a pair of inclined surfaces 122 of the substrate 1 opposite to the base 411. Therefore, a portion of the common wiring 41 is formed on either of the pair of inclined surfaces 122. In the common wiring 41, current flows from the base 411 through the plurality of extensions 412 to the plurality of heat-generating portions 31.

[0069] like Figure 2 and Figure 3 As shown, each of the multiple independent wirings 42 has a base 421 and an extension 422. In the y-direction, the base 421 is located furthest from the multiple heat-generating portions 31 of the resistive layer 3. The bases 421 of the multiple independent wirings 42 are arranged in an alternating configuration in the x-direction. The extension 422 is a strip extending from the end of the base 421 facing the protrusion 17 of the substrate 1 in the y-direction toward the multiple heat-generating portions 31. The extensions 422 of the multiple independent wirings 42 are arranged along the x-direction. Each extension 422 of the multiple independent wirings 42 is formed on one of a pair of inclined surfaces 122 of the substrate 1 opposite the base 421 of the multiple independent wirings 42. Therefore, a portion of each of the multiple independent wirings 42 is formed on either of the pair of inclined surfaces 122. In the multiple independent wirings 42, current flows from any one of the multiple heat-generating portions 31 to the base 422 via the extension 422. When viewed along the z-direction, each of the multiple heating elements 31 is sandwiched between any one of the extensions 422 of the multiple independent wiring 42 and any one of the multiple extensions 412 of the shared wiring 41.

[0070] Protective layer 5 Figure 5 As shown, a portion of the main surface 10 of the substrate 1, multiple heating elements 31 of the resistive layer 3, and the wiring layer 4 are covered. The protective layer 5 is electrically insulating. The protective layer 5 contains silicon in its composition. For example, the protective layer 5 contains any one of silicon dioxide, silicon nitride (Si3N4), and silicon carbide (SiC). Alternatively, the protective layer 5 may be a laminate containing multiple substances of the aforementioned materials. The thickness of the protective layer 5 is, for example, 1.0 μm or more and 10 μm or less. In the thermal printer B10, the recording medium is pressed by the pressure roller 79 as shown in 4 onto the area of ​​the protective layer 5 covering the multiple heating elements 31.

[0071] like Figure 6As shown, a wiring opening 51 is provided on the protective layer 5. The wiring opening 51 penetrates the protective layer 5 in the z direction. A portion of the base 421 of the plurality of independent wirings 42 and a portion of the extension 422 of the plurality of independent wirings 42 are exposed from the wiring opening 51.

[0072] Covering layer 6 Figure 5 As shown, at least a portion of the protective layer 5 is covered. When viewed along the z-direction, the coating layer 6 overlaps with a plurality of heat-generating portions 31 of the resistive layer 3. Furthermore, when viewed along the z-direction, the coating layer 6 overlaps with the convex surface 12 of the substrate 1. Figure 6 As shown, the coating layer 6 has a base layer 61 and a body layer 62. Each of the base layer 61 and the body layer 62 contains a metallic element. The metallic elements contained in the base layer 61 and the body layer 62 are bonded to each other through metallic bonds. Therefore, the coating layer 6 is a conductor that allows current to flow relatively easily. The base layer 61 is in contact with the protective layer 5. The base layer 61 consists of a barrier layer connected to the protective layer 5 and a seed layer deposited on the barrier layer. The metallic element contained in the barrier layer is, for example, titanium. The metallic element contained in the seed layer is, for example, copper. The body layer 62 is deposited on the base layer 61. The thickness of the body layer 62 is greater than the thickness of the base layer 61. The Vickers hardness (HV) of the body layer 62 is greater than the Vickers hardness of the protective layer 5. The metallic element contained in the body layer 62 is, for example, copper. Alternatively, the element contained in the body layer 62 may also be nickel (Ni).

[0073] Wiring substrate 71, as Figure 4 As shown, it is located near substrate 1 in the y-direction. Figure 1 As shown, when viewed along the z-direction, multiple independent wirings 42 are located in the y-direction between the multiple heat-generating parts 31 of the resistive layer 3 and the wiring substrate 71. When viewed along the z-direction, the area of ​​the wiring substrate 71 is larger than the area of ​​the substrate 1. Furthermore, when viewed along the z-direction, the wiring substrate 71 is rectangular with the x-direction as its length. The wiring substrate 71 is, for example, a PCB (Printed Circuit Board) substrate. Multiple driving elements 73 and connectors 77 are mounted on the wiring substrate 71.

[0074] Heatsink 72 Figure 4 As shown, it faces the back surface 13 of the substrate 1. The back surface 13 is bonded to the heat sink 72. The wiring substrate 71 is fixed to the heat sink 72 by fasteners such as screws. When the thermal printhead A10 is used, a portion of the heat generated from the multiple heat-generating parts 31 of the resistive layer 3 is transferred to the heat sink 72 via the substrate 1. The heat transferred to the heat sink 72 is dissipated to the outside. The heat sink 72 contains, for example, aluminum (Al).

[0075] Multiple drive elements 73 such Figure 1 and Figure 4As shown, the chip bonding material (not shown) with electrical insulation is mounted on the wiring substrate 71. Each of the plurality of driving elements 73 is a semiconductor element constituting various circuits. One end of each of the plurality of driving elements 73 and one end of each of the plurality of first wires 74 are bonded to each of the plurality of driving elements 73. The other end of each of the plurality of first wires 74 is independently bonded to the base 421 of a plurality of independent wirings 42. The other end of each of the plurality of second wires 75 is bonded to wiring (not shown) disposed on the wiring substrate 71 and connected to the connector 77. Thus, printing signals, control signals, and voltages supplied to the plurality of heating elements 31 of the resistive layer 3 are input from the outside to the plurality of driving elements 73 via the connector 77. Based on the electrical signals, the plurality of driving elements 73 selectively apply voltages to the plurality of independent wirings 42. Thus, the plurality of heating elements 31 selectively heat up.

[0076] Sealing resin 76 Figure 4 As shown, a portion of each of the following is covered: multiple drive elements 73, multiple first wires 74, multiple second wires 75, substrate 1, and wiring substrate 71. The sealing resin 76 is electrically insulating. The sealing resin 76 is, for example, a black and soft synthetic resin used for underfilling.

[0077] Connector 77 Figure 1 and Figure 4 As shown, it is mounted on one end of the wiring substrate 71 in the y-direction. Connector 77 is connected to the thermal printer B10. Connector 77 has multiple pins (not shown). A portion of these pins is on the wiring substrate 71 and is connected to wiring (not shown) engaging multiple second conductors 75. Furthermore, a portion of these pins is on the wiring substrate 71 and is connected to wiring (not shown) connected to the base 411 of the common wiring 41.

[0078] Next, based on Figures 7-18 An example of the manufacturing method for the thermal printhead A10 will be described here. Figures 7-18 (among which, excluding) Figure 16 and Figure 17 The cross-sectional position of the thermal printhead A10 is shown in the figure. Figure 5 The cross-sectional positions are the same.

[0079] Initially, as Figure 7 and Figure 8 As shown, a protrusion 17 is formed on the substrate 81.

[0080] First, such as Figure 7As shown, a first mask layer 891 covering a substrate 81 and a second mask layer 892 covering a portion of the first mask layer 891 are formed. The substrate 81 contains a semiconductor material. The semiconductor material contains a single-crystal material composed of silicon. The substrate 81 is a silicon wafer. In a direction orthogonal to the z-direction, a plurality of regions, each corresponding to a plurality of substrates 1, are connected to form the substrate 81. The substrate 81 has a first surface 81A and a second surface 81B. The first surface 81A and the second surface 81B face opposite sides to each other in the z-direction. The orientation of the first surface 81A and the second surface 81B, based on the crystal structure of the substrate 81, is the (100) plane. The first mask layer 891 is formed to cover the first surface 81A and the second surface 81B. The first mask layer 891 contains silicon dioxide. The second mask layer 892 is formed to cover the region of the first mask layer 891 covering the first surface 81A. The second mask layer 892 contains silicon nitride. A mask opening 893 extending in the z-direction is formed in the region of the first mask layer 891 covering the first surface 81A and the region of the second mask layer 892 covering the same region.

[0081] When forming the first mask layer 891 and the second mask layer 892, firstly, a silicon dioxide thin film covering the first surface 81A and the second surface 81B is formed by thermal oxidation. Next, a silicon nitride thin film covering the area of ​​the first mask layer 891 covering the first surface 81A is formed by thermal CVD (Chemical Vapor Deposition). Finally, a portion of the silicon dioxide thin film covering the first surface 81A and a portion of the silicon nitride thin film covering the area are removed by etching patterning and reactive ion etching (RIE). Thus, the first mask layer 891 and the second mask layer 892 are formed, and mask openings 893 are formed in the area of ​​the first mask layer 891 covering the first surface 81A and in the area of ​​the second mask layer 892 covering the area.

[0082] Next, as Figure 8 As shown, a main surface 10 and a protrusion 17 are formed on a substrate 81. The main surface 10 and the protrusion 17 are formed by... Figure 7The area of ​​the first surface 81A exposed by the mask opening 893 shown is formed by wet etching using an aqueous solution of potassium hydroxide (KOH). The etching is anisotropic. Finally, the first mask layer 891 and the second mask layer 892 are removed by wet etching using hydrofluoric acid (HF). Through the above, a main surface 10 including a base surface 11 and a convex surface 12, and a protrusion 17 are formed on the substrate 82. Furthermore, the second surface 81B of the substrate 81 becomes the back surface 13. The convex surface 12 protrudes from the base surface 11 in the z-direction. The protrusion 17 protrudes from the base surface 11 in the z-direction and extends along the x-direction. The protrusion 17 includes the convex surface 12. The area of ​​the first surface 81A covered by the first mask layer 891 and the second mask layer 892 becomes the top surface 121 of the convex surface 12. Furthermore, the inclination angle α of each of the pair of inclined surfaces 122 of the convex surface 12 relative to the base surface 11 is the same. This is because the protrusion 17 is formed by anisotropic etching.

[0083] Next, as Figure 9 As shown, an insulating layer 2 is formed covering the main surface 10 of the substrate 81. The insulating layer 2 is formed by multiple layers of silicon dioxide thin film, which is formed by plasma CVD (Chemical Vapor Deposition) using tetraethyl orthosilicate (TEOS) as the raw material gas.

[0084] Next, as Figures 10-13 As shown, a resistive layer 3 and a wiring layer 4 are formed. The resistive layer 3 includes a plurality of heat-generating elements 31 arranged in the x-direction. The wiring layer 41 is electrically connected to the plurality of heat-generating elements 31. Furthermore, the step of forming the wiring layer 4 includes the step of forming a common wiring 41 and a plurality of independent wirings 42. On the substrate 81, the common wiring 41 is relative to... Figure 13 The multiple heating elements 31 of the resistive layer 3 shown are located on one side in the y-direction. On the substrate 81, multiple independent wirings 42 are positioned relative to... Figure 13 The multiple heating elements 31 shown are located on the other side in the y direction.

[0085] First, such as Figure 10 As shown, a resistive film 82 is formed on the main surface 10 of the substrate 81. The resistive film 82 is formed in such a way that it covers the entire surface of the insulating layer 2. The resistive film 82 is formed by depositing a tantalum nitride thin film onto the insulating layer 2 by sputtering.

[0086] Next, as Figure 11 As shown, a conductive layer 83 is formed covering the entire surface of the resistive film 82. The conductive layer 83 is formed by repeatedly depositing a copper thin film onto the resistive film 82 using a sputtering method. Alternatively, the conductive layer 83 can be formed by depositing a titanium thin film onto the resistive film 82 using a sputtering method, followed by repeatedly depositing a copper thin film onto the titanium thin film using a sputtering method.

[0087] Next, as Figure 12As shown, after etching and patterning the conductive layer 83, a portion of the conductive layer 83 is removed. This removal is performed by wet etching using a mixed solution of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2). This forms a common wiring 41 and multiple individual wirings 42 on the resistive film 82. Therefore, the wiring layer 4 is formed through this step. Furthermore, the area of ​​the resistive film 82 formed on the top surface 121 (convex surface 12) of the substrate 81 is exposed from the wiring layer 4.

[0088] Next, as Figure 13 As shown, after etching and patterning the resistive film 82 and the wiring layer 4, a portion of the resistive film 82 is removed. This removal is performed by reactive ion etching. As a result, the resistive layer 3 is formed on the main surface 10 of the substrate 81. Multiple heat-generating portions 31 appear on the top surface 121 of the substrate 81.

[0089] Next, as Figure 14 As shown, a protective layer 5 is formed covering a portion of the main surface 10 of the substrate 81, multiple heating elements 31 of the resistive layer 3, and the wiring layer 4. The protective layer 5 is formed by laminating a silicon nitride thin film using plasma CVD.

[0090] Next, as Figure 15 As shown, a through wiring opening 51 in the z-direction is formed on the protective layer 5. The wiring opening 51 is formed by removing a portion of the protective layer 5 after etching patterning. The removal is performed by reactive ion etching. As a result, a portion of a plurality of individual wirings 42 (such as a portion of the base 421 of the plurality of individual wirings 42 shown in 5, and a portion of each of the extensions 422 of the plurality of individual wirings 42) is exposed from the wiring opening 51.

[0091] Next, as Figures 16-18 As shown, a cover layer 6 is formed covering at least a portion of the protective layer 5. The step of forming the cover layer 6 includes the step of forming a base layer 61 that is in contact with the protective layer 5 and contains a metal element, and the step of depositing a body layer 62 that contains a metal element on the base layer 61.

[0092] First, such as Figure 16 As shown, a base layer 61 is formed covering a portion of the protective layer 5 and the portion of the multiple independent wirings 42 exposed in the wiring opening 51 of the protective layer 5. The base layer 61 is formed by sputtering a titanium thin film onto the protective layer 5 and the portion of the multiple independent wirings 42 exposed in the wiring opening 51, and then sputtering a copper thin film onto the titanium thin film.

[0093] Next, as Figure 17As shown, a body layer 62 is formed on a substrate layer 61. The body layer 62 comprises copper. The body layer 62 is formed by plating after etching and patterning the substrate layer 61. The plating can be either electroplating or electroless plating. In the case of electroplating, the body layer 62 is formed by using the substrate layer 61 as a conductive path.

[0094] Next, as Figure 18 As shown, the areas of the base layer 61 not covered by the body layer 62 are removed. This removal is performed by wet etching using a mixed solution of sulfuric acid and hydrogen peroxide. This forms the coating layer 6.

[0095] Next, the substrate 81 is divided into individual pieces by cutting along the x and y directions. This yields the main portion of the thermal printhead A10, which includes the substrate 1. Next, multiple drive elements 73 and connectors 77 are mounted on the wiring substrate 71. Next, the back surface 13 of the substrate 1 and the wiring substrate 71 are bonded to the heat sink 72. Next, multiple first wires 74 and multiple second wires 75 are bonded to the wiring substrate 71. Finally, a sealing resin 76 is formed on the substrate 1 and the wiring substrate 71, covering the drive elements 73, the multiple first wires 74, and the multiple second wires 75. Through these steps, the thermal printhead A10 is obtained.

[0096] Next, the function and effect of the thermal printhead A10 will be explained.

[0097] The thermal printhead A10 includes: a protective layer 5 covering a portion of the main surface 10 of the substrate 1, a plurality of heating elements 31 of the resistive layer 3, and a wiring layer 4; and a cover layer 6 covering at least a portion of the protective layer 5. When viewed along the z-direction, the cover layer 6 overlaps with the plurality of heating elements 31. The cover layer 6 has a base layer 61 connected to the protective layer 5 and a body layer 62 deposited on a body layer 62. Both the base layer 61 and the body layer 62 contain metallic elements. Thus, when the thermal printhead A10 is used, the recording medium comes into contact with the cover layer 6. Therefore, since the recording medium does not come into contact with the protective layer 5, the abrasion resistance of the thermal printhead A10 to the recording medium can be improved.

[0098] The base layer 61 of the coating layer 6 contains metallic elements. Therefore, the base layer 61 can be formed by sputtering. Furthermore, the body layer 62 of the coating layer 6 also contains metallic elements. Therefore, the body layer 62 can be formed by depositing metallic elements onto the base layer 61. Thus, according to this configuration, the coating layer 6 can be formed relatively easily and efficiently. As described above, according to the thermal printhead A10, manufacturing inefficiency can be suppressed, and the abrasion resistance of the thermal printhead A10 to the recording medium can be improved.

[0099] The metal elements contained in the base layer 61 and the body layer 62 of the coating layer 6 are bonded to each other through metallic bonds. Thus, the base layer 61 and the body layer 62 each become conductors through which current flows relatively easily. Therefore, the body layer 62 can be formed by electroplating with the base layer 61 as the current path. This further reduces the low manufacturing efficiency of the thermal printhead A10.

[0100] The Vickers hardness of the body layer 62 of the coating layer 6 is greater than that of the protective layer 5. This property is preferred for improving the abrasion resistance of the thermal printhead A10 to the recording medium. Furthermore, the coefficient of kinetic friction of the body layer 62 is preferably lower. As a result, when using the thermal printhead A10, the adhesion of paper scraps caused by the recording medium to the coating layer 6 can be suppressed.

[0101] The main surface 10 of the substrate 1 includes a base surface 11 and a convex surface 12 protruding from the base surface 11 in the z-direction. The convex surface 12 extends along the x-direction. A plurality of heating elements 31 are formed on the convex surface 12. Therefore, when using the thermal printhead A10, the contact area between the recording medium and the thermal printhead A10 can be further reduced. Thus, the printing quality on the recording medium caused by the plurality of heating elements 31 can be improved.

[0102] Furthermore, the convex surface 12 includes: a top surface 121 parallel to the base surface 11 of the substrate 1; and a pair of inclined surfaces 122 connected to the top surface 121 and the base surface 11, and located apart from each other in the y-direction. A plurality of heating elements 31 are formed on the top surface 121. A portion of the common wiring 41 and a portion of each of the plurality of independent wirings 42 are formed on either of the pair of inclined surfaces 122. Therefore, when viewed along the z-direction, the size of each of the plurality of heating elements 31 in the y-direction can be further reduced, and when using the thermal printhead A10, the contact area between the recording medium and the thermal printhead A10 can be further reduced. Thus, heat generation in the thermal printhead A10 can be suppressed, and the print quality on the recording medium can be further improved.

[0103] In substrate 1, a pair of inclined surfaces 122 are inclined relative to base surface 11 in a manner that they approach each other from base surface 11 toward top surface 121. In the manufacturing method of thermal printhead A10, the shape of this convex surface 12 is revealed by forming a protrusion 17 in substrate 81 using anisotropic etching. This is because substrate 81 contains a semiconductor material, and the semiconductor material contains a single crystal material composed of silicon.

[0104] The thermal printhead A10 also includes a heat sink 72. The back side 13 of the substrate 1 is bonded to the heat sink 72. Thus, when using the thermal printhead A10, a portion of the heat emitted from the multiple heat-generating parts 31 can be quickly released to the outside via the substrate 1 and the heat sink 72.

[0105] [Second Implementation]

[0106] based on Figure 19 and Figure 20 The thermal printhead A20 of the second embodiment of the present invention will be described below. In the accompanying drawings, elements that are the same as or similar to the thermal printhead A10 described above are labeled with the same symbols, and repeated descriptions are omitted. Figure 19 The cross-sectional position is similar to that of the thermal printhead A10 described above. Figure 5 The cross-sectional positions are the same.

[0107] In the thermal printhead A20, the configuration of the convex surface 12 of the substrate 1 and the configuration of the plurality of heating elements 31 of the resistive layer 3 are different from those of the thermal printhead A10 described above.

[0108] like Figure 19 and Figure 20 As shown, the convex surface 12 has a pair of inclined surfaces 122, each comprising a first region 122A and a second region 122B. The first region 122A is connected to the base surface 11 of the substrate 1. The second region 122B is connected to the top surface 121 of the convex surface 12 and the first region 122A. The inclination angle α2 of the second region 122B of each of the pair of inclined surfaces 122 relative to the base surface 11 is smaller than the inclination angle α1 of the first region 122A relative to the base surface 11. This pair of inclined surfaces 122 is achieved by... Figure 8 The steps shown, and Figure 9 Between the steps shown, the boundary between the top surface 121 and the pair of inclined surfaces 122 and the vicinity of the boundary are formed by wet etching using an aqueous solution of tetramethylammonium hydroxide (TMAH).

[0109] like Figure 20 As shown, the plurality of heating elements 31 of the resistive layer 3 are formed in the following manner: First, the plurality of heating elements 31 are formed on the top surface 121 of the convex surface 12. Second, the plurality of heating elements 31 are formed across the top surface 121 and the second region 122B of the inclined surface 122 located downstream of the pair of inclined surfaces 122 of the convex surface 12. Third, the plurality of heating elements 31 are formed across the top surface 121, the second region 122B of the inclined surface 122 located downstream of the pair of inclined surfaces 122, and the first region 122A of the inclined surface 122. Fourth, the plurality of heating elements 31 are formed across the second region 122B of the inclined surface 122 located downstream of the pair of inclined surfaces 122 and the first region 122A of the inclined surface 122. If these manners are summarized, then the plurality of heating elements 31 are formed on at least one of the top surface 121 and the pair of inclined surfaces 122.

[0110] Next, the function and effect of the thermal printhead A20 will be explained.

[0111] The thermal printhead A20 includes: a protective layer 5 covering a portion of the main surface 10 of the substrate 1, a plurality of heating elements 31 of the resistive layer 3, and a wiring layer 4; and a cover layer 6 covering at least a portion of the protective layer 5. When viewed along the z-direction, the cover layer 6 overlaps with the plurality of heating elements 31. The cover layer 6 has a base layer 61 connected to the protective layer 5 and a body layer 62 deposited on a body layer 62. The base layer 61 and the body layer 62 each contain a metallic element. Therefore, according to the thermal printhead A20, manufacturing inefficiencies can be suppressed, and the abrasion resistance of the thermal printhead A20 to the recording medium can be improved.

[0112] In the thermal printhead A20, a pair of inclined surfaces 122 (convex surfaces 12) of the substrate 1 each include a first region 122A and a second region 122B. The first region 122A is connected to the base surface 11 of the substrate 1. The second region 122B is connected to the top surface 121 of the convex surface 12 and the first region 122A. The inclination angle α2 of the second region 122B of each pair of inclined surfaces 122 relative to the base surface 11 is smaller than the inclination angle α1 of the first region 122A relative to the base surface 11. By adopting this configuration, the surface of the protective layer 5 formed along the convex surface 12 is smoother. Furthermore, since the coating layer 6 follows the shape of the surface of the protective layer 5, the surface of the coating layer 6 is also smoother. Therefore, when using the thermal printhead A20, the dynamic friction force of the recording medium on the coating layer 6 can be reduced when the recording medium comes into contact with the coating layer 6, thus suppressing paper dust caused by the recording medium from adhering to the coating layer 6.

[0113] The thermal printheads A10 and A20 of the present invention have a coating layer 6 comprising a base layer 61 and a body layer 62. In addition to being applied to thermal printheads A10 and A20 manufactured from a substrate 81 containing semiconductor materials, the coating layer 6 can also be applied to the following thermal printheads: First, a thick-film type thermal printhead, wherein a plurality of heating elements 31, a wiring layer 4, and a protective layer 5 are formed on a ceramic substrate such as an aluminum substrate or an aluminum nitride (ALN) substrate, or a glass substrate using thick-film technology. The material of the plurality of heating elements 31 in this case can be ruthenium dioxide (RuO2), TaSiO2, TaN (tantalum nitride), TaSiN, etc. Second, a thin-film type thermal printhead, wherein a plurality of heating elements 31, a wiring layer 4, and a protective layer 5 are formed on a ceramic substrate or a glass substrate, etc., using thin-film technology. The material of the plurality of heating elements 31 in this case can be TaSiO2, TaN, TaSiN, etc.

[0114] This invention is not limited to the described embodiments. The specific configuration of each part of this invention can be freely modified in various ways.

[0115] [Symbol Explanation]

[0116] A10, A20: Thermal printheads

[0117] 1: Substrate

[0118] 10: Main side

[0119] 11: Base plane

[0120] 12: Convex surface

[0121] 121: Top surface

[0122] 122: Inclined surface

[0123] 122A: Area 1

[0124] 122B: Area 2

[0125] 13: Back

[0126] 17:convex part

[0127] 2: Insulation layer

[0128] 3: Resistive layer

[0129] 31: Heating section

[0130] 4: Wiring layer

[0131] 41: Shared cabling

[0132] 411: Base

[0133] 412: Extension

[0134] 42: Independent cabling

[0135] 421: Base

[0136] 422: Extension

[0137] 5: Protective layer

[0138] 51: Wiring opening

[0139] 6: Basal layer

[0140] 61: Basal layer

[0141] 62: Body Layer

[0142] 71: Wiring substrate

[0143] 72: Heatsink

[0144] 73: Driving element

[0145] 74: First conductor

[0146] 75: Second conductor

[0147] 76: Sealing resin

[0148] 77: Connector

[0149] 79: Paper Press Roller

[0150] 81: Substrate

[0151] 81A:Side 1

[0152] 81B: Page 2

[0153] 82: Resistive film

[0154] 83: Conductive layer

[0155] 84: Basal layer

[0156] 85: Body Layer

[0157] 891: First mask layer

[0158] 892: Second mask layer

[0159] 893: Mask opening

[0160] α, α1, α2: Inclination angles.

Claims

1. A thermal printhead, comprising: The substrate has a main surface facing the thickness direction; A resistive layer, comprising a plurality of heating elements arranged in the main scanning direction, is formed on the main surface; A wiring layer is formed on the resistive layer and is connected to the plurality of heat-generating components; A protective layer covers a portion of the main surface, the plurality of heating elements, and the wiring layer; and A covering layer that covers at least a portion of the protective layer; and When viewed along the thickness direction, the coating layer includes: a portion overlapping the plurality of heating elements, and a portion located further outward than the plurality of heating elements. The coating layer has: a base layer in contact with the protective layer, and a body layer laminated on the base layer. The base layer and the body layer each contain a metallic element. The main surface includes a first base surface and a first convex surface protruding from the first base surface in the thickness direction. The first convex surface extends along the main scanning direction. The plurality of heating elements are formed on the first convex surface. The protective layer has: a second base surface on the same side as the first base surface in the thickness direction, and a second convex surface protruding from the second base surface. When viewed along the thickness direction, the entirety of the first convex surface and the coating layer overlaps with the second convex surface. The coating layer has a pair of end faces located on both sides in the sub-scanning direction and rising from the interface with the second convex surface. Each of the pair of end faces is inclined relative to the thickness direction on the side facing the second convex face.

2. The thermal printhead according to claim 1, wherein the metal elements are bonded to each other by metallic bonds.

3. The thermal printhead according to claim 2, wherein the Vickers hardness of the body layer is greater than the Vickers hardness of the protective layer.

4. The thermal printhead of claim 3, wherein the protective layer comprises silicon in its composition.

5. The thermal printhead according to claim 1, wherein the first convex surface comprises: a top surface parallel to the first base surface; and a pair of inclined surfaces, each connected to the top surface and the first base surface, and separated from each other in the sub-scanning direction; The plurality of heating elements are formed on the top surface and at least one of the pair of inclined surfaces.

6. The thermal printhead according to claim 5, wherein the wiring layer comprises common wiring and multiple independent wirings. The common wiring is located on one side of the sub-scanning direction relative to the plurality of heating elements. The multiple independent wirings are located on the opposite side of the sub-scanning direction relative to the multiple heating elements. A portion of the shared wiring and a portion of each of the multiple independent wirings are formed on either of the pair of inclined surfaces.

7. The thermal printhead of claim 6, wherein the pair of inclined surfaces are inclined relative to the first base surface in such a manner that they approach each other from the first base surface toward the top surface.

8. The thermal printhead of claim 7, wherein each of the pair of inclined surfaces comprises a first region connected to the first base surface and a second region connected to the top surface and the first region. The tilt angle of the second region relative to the first base plane is smaller than the tilt angle of the first region relative to the first base plane.

9. The thermal printhead according to any one of claims 1 to 8, wherein the substrate comprises a semiconductor material. The semiconductor material comprises a single-crystal material composed of silicon.

10. The thermal printhead according to any one of claims 1 to 8, further comprising an insulating layer covering the main surface, The resistive layer is in contact with the insulating layer.

11. The thermal printhead according to any one of claims 1 to 8, further comprising a heat sink, The substrate has a back side facing the opposite side to the main surface in the thickness direction. The back side is joined to the heat sink.

12. A thermal printer, comprising: The thermal printhead according to any one of claims 1 to 11; and The pressure plate is arranged opposite to the plurality of heating elements.

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