Thermal printing head and manufacturing method of thermal printing head

Abstract

The disclosure relates to a thermal printhead and a method of manufacturing the thermal printhead. The present disclosure addresses the problem of providing a thermal print head capable of suppressing adhesion. The thermal print head of the present disclosure includes a substrate, an enamel layer, a wiring layer, a heating element, and a protective layer. The glaze layer is disposed on the substrate. The wiring layer is disposed on the glaze layer. The wiring layer has a common electrode and a plurality of individual electrodes. The common electrode has a plurality of protrusions which are arranged at intervals in a first direction in plan view, and which extend in a second direction orthogonal to the first direction in plan view. The individual electrode has a tip portion extending in the second direction. The protruding parts and the front end parts are alternately arranged at intervals in the first direction in a plan view. The heating element extends in the first direction in a plan view, and is disposed on the glaze layer so as to overlap the protruding portion and the tip portion. The protective layer is disposed on the glaze layer so as to cover the wiring layer and the heating element.

Description

Technical Field

[0001] The present disclosure relates to a thermal print head and a method for manufacturing the thermal print head. Background Art

[0002] Japanese Patent Application Laid-Open No. 2023-077118 (Patent Document 1) describes a thermal print head. The thermal print head described in Patent Document 1 includes a substrate, a glaze layer, a wiring layer, a heating element, and a protective layer.

[0003] The glaze layer is arranged on the substrate. The wiring layer is arranged on the glaze layer. The wiring layer has a common electrode and a plurality of individual electrodes. The common electrode has a plurality of protrusions, which are arranged at intervals in a first direction when viewed from above, and extend in a second direction orthogonal to the first direction when viewed from above. The individual electrodes have front ends extending in the second direction when viewed from above. The protrusions and the front ends are alternately arranged at intervals in the first direction when viewed from above. The heating element is arranged on the glaze layer so as to overlap with the protrusions and the front ends. The heating element extends in the first direction when viewed from above. The protective layer is arranged on the glaze layer so as to cover the wiring layer and the heating element.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-077118 Summary of the invention

[0007] The thermal print head described in Patent Document 1 may cause sticking (paper to be printed on may stick to the surface of the protective layer).

[0008] The thermal print head disclosed in the present invention comprises a substrate, a glaze layer, a wiring layer, a heating element and a protective layer. The glaze layer is arranged on the substrate. The wiring layer is arranged on the glaze layer. The wiring layer has a common electrode and a plurality of individual electrodes. The common electrode has a plurality of protrusions, which are arranged at intervals in a first direction when viewed from above, and extend in a second direction orthogonal to the first direction when viewed from above. The individual electrodes have front ends extending in the second direction. The protrusions and the front ends are alternately arranged at intervals in the first direction when viewed from above. The heating element extends in the first direction when viewed from above, and is arranged on the glaze layer so as to overlap with the protrusions and the front ends. The protective layer is arranged on the glaze layer so as to cover the wiring layer and the heating element. A recess extending in the first direction so as to overlap with the heating element when viewed from above is formed on the surface of the protective layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a top view of the thermal print head 100 .

[0010] Figure 2 yes Figure 1 Cross-sectional view along line II-II.

[0011] Figure 3 yes Figure 1 Cross-sectional view along III-III.

[0012] Figure 4 1 is a diagram showing the manufacturing steps of the thermal print head 100 .

[0013] Figure 5 It is a cross-sectional view for explaining the glaze layer forming step S2.

[0014] Figure 6 It is a cross-sectional view explaining the wiring layer forming step S3.

[0015] Figure 7 It is a cross-sectional view for explaining the heating element forming step S5.

[0016] Figure 8 It is a cross-sectional view for explaining the first step S71.

[0017] Fig. 9 It is a cross-sectional view for explaining the second step S72.

[0018] Fig.10 is a cross-sectional view of the thermal print head 100A.

[0019] Fig.11 1 is a top view of the thermal print head 100B.

[0020] Fig.12 yes Fig.11 Sectional view along XII-XII. DETAILED DESCRIPTION

[0021] [Details]

[0022] The details of the present disclosure will be described with reference to the accompanying drawings. In the following drawings, the same reference numerals are used for the same or corresponding parts, and repeated descriptions will not be repeated. A thermal print head 100 is used as a thermal print head of the embodiment.

[0023] (Configuration of Thermal Print Head 100)

[0024] Next, the structure of the thermal print head 100 will be described.

[0025] Figure 1 is a top view of the thermal print head 100 . Figure 1 In the figure, the protective layer 50 is omitted. Figure 2 yes Figure 1 Cross-sectional view along line II-II. Figure 3 yes Figure 1The cross-sectional view along III-III. Figures 1 to 3 As shown, the thermal print head 100 includes a substrate 10 , a glaze layer 20 , a wiring layer 30 , a heating element 40 , and a protective layer 50 .

[0026] The substrate 10 has a main surface 10a and a main surface 10b. The main surface 10a and the main surface 10b are end surfaces in the thickness direction of the substrate 10. The main surface 10b is the opposite surface of the main surface 10a. The main component of the constituent material of the substrate 10 is, for example, a ceramic such as aluminum oxide (Al2O3). The main component refers to a component that accounts for more than 50% by mass in the constituent material.

[0027] The glaze layer 20 is disposed on the substrate 10. More specifically, the glaze layer 20 is disposed on the main surface 10a. The main component of the constituent material of the glaze layer 20 is glass.

[0028] The wiring layer 30 is disposed on the glaze layer 20. The wiring layer 30 includes a common electrode 31 and a plurality of individual electrodes 32. The main component of the constituent material of the wiring layer 30 is, for example, gold (Au).

[0029] The common electrode 31 includes a strip-shaped portion 31a and a plurality of protrusions 31b. The strip-shaped portion 31a extends in the first direction DR1 when viewed from above. The term "viewed from above" refers to the state of viewing from the main surface 10a side along the normal direction of the main surface 10a. The plurality of protrusions 31b are arranged in the first direction DR1 at intervals when viewed from above. The protrusions 31b extend in the second direction DR2 when viewed from above. The second direction DR2 is a direction orthogonal to the first direction DR1 when viewed from above. The protrusion 31b protrudes from one side of the strip-shaped portion 31a extending in the first direction DR1.

[0030] The plurality of individual electrodes 32 are arranged in the first direction DR1 in a plan view. The individual electrode 32 has a front end 32a at one end. The front end 32a extends in the second direction DR2 in a plan view. The front end 32a and the protrusion 31b are alternately arranged in the first direction DR1 at intervals in a plan view. The individual electrode 32 has a bonding pad 32b at the other end.

[0031] Although not shown, the thermal print head 100 also has a first wiring and a second wiring. The first wiring is arranged on the glaze layer 20 in a manner connected to the common electrode 31 (strip-shaped portion 31a). The second wiring is arranged on the first wiring. The main component of the material constituting the first wiring and the second wiring is, for example, silver (Ag). The first wiring and the second wiring are formed, for example, by a sintered body containing a plurality of silver particles.

[0032] The heating element 40 extends in the first direction DR1 in a plan view. The heating element 40 is arranged on the glaze layer 20 so as to overlap with the protrusion 31b and the front end portion 32a. That is, the adjacent protrusions 31b and the front end portion 32a are electrically connected through the heating element 40. The heating element 40 is formed of a sintered body containing ruthenium oxide (RuO2) particles, for example.

[0033] The protective layer 50 is disposed on the glaze layer 20 so as to cover the wiring layer 30, the heating element 40, the first wiring, and the second wiring. The bonding pad 32b is exposed from the protective layer 50. The main component of the material constituting the protective layer 50 is glass.

[0034] A recess 51 is formed on the surface of the protective layer 50. The recess 51 extends in the first direction DR1 when viewed from above. The recess 51 overlaps with the heating element 40 when viewed from above. The width of the heating element 40 in the second direction DR2 is set to width W1. The width of the recess 51 in the second direction DR2 is set to width W2. The width W2 is preferably within the range of ±50 μm relative to the width W1. In other words, the absolute value of the difference between the width W2 and the width W1 is preferably less than 50 μm. Preferably, in a cross-sectional view orthogonal to the first direction DR1, the bottom surface of the recess 51 is in the shape of a curved line that bulges upward. The upward bulge means bulging toward the side opposite to the substrate 10.

[0035] The protective layer 50 includes, for example, a first layer 52 and a second layer 53. The first layer 52 covers the wiring layer 30 and the heating element 40. The second layer 53 covers the first layer 52 while avoiding the upper part of the heating element 40. The bottom surface of the recess 51 is formed by the surface of the first layer 52 exposed from the second layer 53. The thickness of the second layer 53 is set to thickness T. As the thickness T increases, paper adhesion is less likely to occur. On the other hand, if the thickness T is too large, the printing on the paper will become thinner. In consideration of these aspects, the thickness T is preferably less than 10 μm. In addition, the thickness of the first layer 52 may be Fig.10 The thickness of the protective layer 50 in the structure shown is less than that of the protective layer 50 in the structure shown. Fig.10 The heat generating elements 40 in the illustrated configuration have the same height.

[0036] The bonding pad 32b is electrically connected to the driver IC (Integrated Circuit) via a bonding wire (not shown). The driver IC selectively supplies voltage to the individual electrode 32 from the bonding pad 32b via the bonding wire. On the other hand, a common voltage is supplied to the common electrode 31 via the first wiring and the second wiring. The portion of the heating element 40 connected between the front end portion 32a of an individual electrode 32 to which voltage is selectively supplied and the protrusion 31b adjacent to the front end portion 32a of the individual electrode 32 is energized and generates heat. The paper is printed by transferring the heat to the paper in contact with the surface of the protective layer 50 covering the heating element 40.

[0037] <Example of Change>

[0038] The first layer 52 may be formed to cover the wiring layer 30 and not to cover the heat generating element 40 (to cover the wiring layer 30 while avoiding the heat generating element 40). The second layer 53 may be formed to cover the first layer 52 and the heat generating element 40.

[0039] (Method of Manufacturing Thermal Print Head 100)

[0040] Next, a method for manufacturing the thermal print head 100 will be described.

[0041] Figure 4 1 is a diagram of the manufacturing steps of the thermal print head 100. Figure 4 As shown, the manufacturing method of the thermal print head 100 includes a preparation step S1, a glaze layer forming step S2, a wiring layer forming step S3, a first wiring forming step S4, a heating element forming step S5, a second wiring forming step S6, a protection layer forming step S7 and a singulation step S8.

[0042] In the preparation step S1, the substrate 10 is prepared. After the preparation step S1, the glaze layer forming step S2 is performed. Figure 5 2 is a cross-sectional view illustrating the glaze layer forming step S2. Figure 5 As shown, in the glaze layer forming step S2, a paste containing glass is applied on the main surface 10a and the applied paste is fired to form the glaze layer 20. After the glaze layer forming step S2, the wiring layer forming step S3 is performed.

[0043] Figure 6 2 is a cross-sectional view illustrating the wiring layer forming step S3. Figure 6As shown, in the wiring layer forming step S3, the wiring layer 30 is formed. In the wiring layer forming step S3, first, a resinate slurry containing the constituent materials of the wiring layer 30 is applied on the glaze layer 20. Second, a metal layer is formed by firing the applied resinate slurry. Third, a resist pattern is formed on the metal layer. The resist pattern is formed by applying a photoresist on the metal layer and exposing and developing the applied photoresist. Fourth, the metal layer is etched using the resist pattern as a mask. Thus, the metal layer is patterned to become the wiring layer 30. After the wiring layer forming step S3 is performed, the first wiring forming step S4 is performed.

[0044] In the first wiring forming step S4, the first wiring is formed. The first wiring is formed by applying a conductive paste containing a plurality of silver particles and firing the applied conductive paste. After the first wiring forming step S4, the heating element forming step S5 is performed.

[0045] Figure 7 2 is a cross-sectional view illustrating the heating element forming step S5. Figure 7 As shown, in the heating element forming step S5, first, a slurry containing ruthenium oxide particles is applied to the glaze layer 20. The slurry is applied along the first direction DR1 in a plan view so as to overlap with the protrusion 31b and the front end portion 32a. Second, the heating element 40 is formed by firing the applied slurry. After the heating element forming step S5, the second wiring forming step S6 is performed.

[0046] In the second wiring forming step S6, the second wiring is formed. The first wiring is formed by applying a conductive paste containing a plurality of silver particles and firing the applied conductive paste. After the second wiring forming step S6, a protective layer forming step S7 is performed.

[0047] The protective layer forming step S7 includes a first step S71 and a second step S72. The second step S72 is performed after the first step S71. Figure 8 1 is a cross-sectional view illustrating the first step S71. Figure 8 As shown, in the first step S71, the first layer 52 is formed so as to cover the wiring layer 30, the heating element 40, the first wiring and the second wiring. In the first step S71, first, a paste containing glass is applied. Second, the applied paste is fired. Thus, the first layer 52 is formed.

[0048] Fig. 9 2 is a cross-sectional view illustrating the second step S72. Fig. 9As shown, in the second step S72, the second layer 53 is formed in a manner covering the first layer 52. In the second step S72, first, a slurry containing glass is applied on the first layer 52. At this time, the slurry is applied while avoiding the top of the heating element 40. Second, the applied slurry is fired. Thus, the second layer 53 is formed on the first layer 52 while avoiding the top of the heating element 40. In addition, since the second layer 53 is not formed above the heating element 40, a recess 51 is formed on the protective layer 50 in a manner overlapping with the heating element 40 when viewed from above. After the protective layer forming step S7 (the second step S72), the singulation step S8 is performed.

[0049] In the singulation step S8, the substrate 10, the glaze layer 20, and the protective layer 50 are cut according to the positions that become the outer periphery of the thermal print head 100. Figures 1 to 3 The structure of the thermal print head 100 is shown.

[0050] <Example of Change>

[0051] In the first step S71, the first layer 52 may be formed so as to cover the wiring layer 30 but not the heating element 40. In this case, in the second step S72, the second layer 53 is formed so as to cover the first layer 52 and the heating element 40. By such a method, the protective layer 50 having the concave portion 51 on the surface can also be formed.

[0052] (Effect of thermal print head 100)

[0053] The effects of the thermal print head 100 will be described below in comparison with a comparative example. The thermal print head of the comparative example 1 is set to a thermal print head 100A, and the thermal print head of the comparative example 2 is set to a thermal print head 100B.

[0054] Fig.10 FIG. 1 is a cross-sectional view of the thermal print head 100A. Fig.10 As shown, the thermal print head 100A includes a substrate 10, a glaze layer 20, a wiring layer 30, a heating element 40, and a protective layer 50. In the thermal print head 100A, the recessed portion 51 is not formed on the surface of the protective layer 50 so as to overlap with the heating element 40.

[0055] Since the thermal print head 100A does not have the recessed portion 51, the contact area between the paper to be printed and the surface of the protective layer 50 is likely to increase. As a result, the thermal print head 100A may cause sticking (a phenomenon in which the paper adheres to the surface of the protective layer 50). On the other hand, since the thermal print head 100 has the recessed portion 51, the contact area between the paper to be printed and the surface of the protective layer 50 is unlikely to increase. Therefore, according to the thermal print head 100, it is possible to suppress the paper from sticking to the surface of the protective layer 50.

[0056] Fig.11 1 is a top view of the thermal print head 100B. Fig.12 yes Fig.11 The cross-sectional view along XII-XII. Fig.11 and Fig.12 As shown, the thermal print head 100B includes a substrate 10 , a glaze layer 21 , a wiring layer 30 (a common electrode 31 and a plurality of individual electrodes 32 ), a heating element 41 , and a protective layer 50 .

[0057] The glaze layer 21 is arranged on the main surface 10a in a manner extending in the first direction DR1 when viewed from above. In the thermal print head 100B, the wiring layer 30 is arranged on the main surface 10a except for the protrusion 31b and the front end 32a. The protrusion 31b and the front end 32a extend in the second direction DR2 when viewed from above so as to reach the glaze layer 21. The protrusion 31b and the front end 32a are opposed to each other at a distance in the second direction DR2. The heating element 41 is interposed between the substrate 10 or the glaze layer 21 and the wiring layer 30. Since the protrusion 31b and the front end 32a are opposed to each other at a distance, the heating element 41 is exposed from between the protrusion 31b and the front end 32a.

[0058] The protective layer 50 covers the glaze layer 21, the wiring layer 30, and the heating element 41 exposed between the protrusion 31b and the front end 32a. Because the wiring layer 30 is removed between the protrusion 31b and the front end 32a, there is a step difference in this part. The step difference causes a step difference to be formed on the surface of the protective layer 50. Therefore, in the thermal print head 100B, the contact area between the paper as the printing object and the surface of the protective layer 50 is not easy to increase, thereby suppressing the paper from adhering to the surface of the protective layer 50. However, because the heating element 41 exposed between the protrusion 31b and the front end 32a in the thermal print head 100B generates heat uniformly, the printing efficiency is reduced in view of the fact that the contact area between the paper as the printing object and the surface of the protective layer 50 is not easy to increase.

[0059] On the other hand, in the thermal print head 100, the current flows concentratedly in the center of the heating element 40 in the second direction DR2, so the center of the heating element 40 in the second direction DR2 generates heat intensively. Therefore, even if the contact area between the paper and the surface of the protective layer 50 is not easily increased due to the formation of the recessed portion 51, the printing efficiency can be maintained.

[0060] If the width W2 is too small relative to the width W1, it is difficult to make the paper to be printed contact with the surface of the protective layer 50 covering the heating element 40 (that is, the bottom surface of the recess 51), and printing may be hindered. On the other hand, if the width W2 is too large relative to the width W1, the effect of suppressing the increase in the contact area between the paper and the surface of the protective layer 50 is insufficient. Therefore, in the case where the width W2 is within a range of ±50μm or more relative to the width W1, more appropriate printing can be performed while suppressing the adhesion of the paper. When the bottom surface of the recess 51 is an upwardly convex curved shape in the cross-section in the first direction DR1, it is easy to further suppress the increase in the contact area between the paper and the surface of the protective layer 50.

[0061] (Note)

[0062] The embodiments of the present disclosure include the following configurations.

[0063] <Note 1>

[0064] A thermal print head having:

[0065] Substrate,

[0066] Glaze layer,

[0067] Wiring layer,

[0068] Heater, and

[0069] Protective layer,

[0070] The glaze layer is disposed on the substrate,

[0071] The wiring layer is arranged on the glaze layer,

[0072] The wiring layer has a common electrode and a plurality of individual electrodes.

[0073] The common electrode has a plurality of protrusions, which are arranged at intervals in a first direction in a plan view and extend in a second direction orthogonal to the first direction in a plan view.

[0074] The individual electrode has a front end portion extending in the second direction,

[0075] The protrusions and the front end portions are alternately arranged at intervals in the first direction in a plan view,

[0076] The heating element extends in the first direction in a plan view and is arranged on the glaze layer so as to overlap with the protruding portion and the front end portion.

[0077] The protective layer is arranged on the glaze layer in a manner covering the wiring layer and the heating element.

[0078] A recessed portion extending in the first direction so as to overlap with the heat generating element in a plan view is formed on the surface of the protective layer.

[0079] <Note 2>

[0080] The thermal print head according to Supplementary Note 1, wherein a width of the recessed portion in the second direction is within a range of ±50 μm with respect to a width of the heating element in the second direction.

[0081] <Note 3>

[0082] The thermal print head according to Supplementary Note 1 or Supplementary Note 2, wherein the bottom surface of the recessed portion is in a curved shape that is convex upward in a cross-sectional view orthogonal to the first direction.

[0083] <Note 4>

[0084] A method for manufacturing a thermal print head comprises the following steps:

[0085] preparing a substrate;

[0086] forming a glaze layer on the substrate;

[0087] forming a wiring layer on the glaze layer;

[0088] forming a heating element on the glaze layer; and

[0089] forming a protective layer on the glaze layer in a manner covering the wiring layer and the heating element;

[0090] The wiring layer has a common electrode and a plurality of individual electrodes.

[0091] The common electrode has a plurality of protrusions, which are arranged at intervals in a first direction in a plan view and extend in a second direction orthogonal to the first direction in a plan view.

[0092] The individual electrode has a front end portion extending in the second direction,

[0093] The protrusions and the front end portions are alternately arranged at intervals in the first direction in a plan view,

[0094] The heating element extends in the first direction in a plan view and is arranged on the glaze layer so as to overlap with the protruding portion and the front end portion.

[0095] A recessed portion extending in the first direction so as to overlap with the heat generating element in a plan view is formed on the surface of the protective layer.

[0096] <Note 5>

[0097] The method for manufacturing a thermal print head according to Supplement 4, wherein the protective layer comprises a first layer and a second layer,

[0098] In the step of forming the protective layer, the second layer is formed after the first layer is formed.

[0099] The first layer covers the wiring layer and the heating element.

[0100] The second layer covers the first layer while avoiding an upper portion of the heat generating element.

[0101] <Note 6>

[0102] The method for manufacturing a thermal print head according to Supplement 4, wherein the protective layer comprises a first layer and a second layer,

[0103] In the step of forming the protective layer, the second layer is formed after the first layer is formed.

[0104] The first layer covers the wiring layer,

[0105] The second layer covers the heat generating element and the first layer.

[0106] The embodiments of the present disclosure are described as above, but various changes may be made to the above embodiments. In addition, the scope of the present invention is not limited to the above embodiments. The scope of the present invention is shown by the claims, and is intended to include all changes within the meaning and scope equivalent to the claims.

[0107] [Explanation of Symbols]

[0108] 100: Thermal print head

[0109] 10: Substrate

[0110] 10a, 10b: Main surface

[0111] 20,21: Glaze layer

[0112] 30: Wiring layer

[0113] 31: Common electrode

[0114] 31a: Strip

[0115] 31b: protrusion

[0116] 32: Single electrode

[0117] 32a: front end

[0118] 32b: Bonding pad

[0119] 40,41: Heating element

[0120] 50: Protective layer

[0121] 51: concave part

[0122] 52: Layer 1

[0123] 53: Layer 2

[0124] 100A,100B: Thermal print head

[0125] DR1: Direction 1

[0126] DR2: Direction 2

[0127] S1: Preparation Steps

[0128] S2: Glaze layer forming step

[0129] S3: Wiring layer formation step

[0130] S4: 1st wiring forming step

[0131] S5: Heat generating element forming step

[0132] S6: Second wiring forming step

[0133] S7: Protective layer forming step

[0134] S71: Step 1

[0135] S72: Step 2

[0136] S8: Singulation step

[0137] W1,W2: Width

[0138] T: thickness.

Claims

1. A thermal print head having: Substrate, Glaze layer, Wiring layer, Heater, and Protective layer, The glaze layer is disposed on the substrate, The wiring layer is arranged on the glaze layer, The wiring layer has a common electrode and a plurality of individual electrodes. The common electrode has a plurality of protrusions which are arranged at intervals in a first direction in a plan view and extend in a second direction orthogonal to the first direction in a plan view. The individual electrode has a front end portion extending in the second direction, The protrusions and the front end portions are alternately arranged at intervals in the first direction in a plan view, and the heating element extends in the first direction in a plan view and is arranged on the glaze layer to overlap with the protrusions and the front end portions. The protective layer is arranged on the glaze layer in a manner covering the wiring layer and the heating element. A recessed portion extending in the first direction so as to overlap with the heat generating element in a plan view is formed on the surface of the protective layer. 2 . The thermal print head according to claim 1 , wherein a width of the concave portion in the second direction is within a range of ±50 μm with respect to a width of the heating element in the second direction. 3 . The thermal print head according to claim 1 , wherein the bottom surface of the recessed portion is in a curved shape that is convex upward in a cross-sectional view perpendicular to the first direction.

4. A method for manufacturing a thermal print head, comprising the following steps: preparing a substrate; forming a glaze layer on the substrate; forming a wiring layer on the glaze layer; forming a heating element on the glaze layer; as well as forming a protective layer on the glaze layer in a manner covering the wiring layer and the heating element; The wiring layer has a common electrode and a plurality of individual electrodes. The common electrode has a plurality of protrusions which are arranged at intervals in a first direction in a plan view and extend in a second direction orthogonal to the first direction in a plan view. The individual electrode has a front end portion extending in the second direction, The protrusions and the front end portions are alternately arranged at intervals in the first direction in a plan view, The heating element extends in the first direction in a plan view and is arranged on the glaze layer so as to overlap with the protruding portion and the front end portion. A recessed portion extending in the first direction so as to overlap with the heat generating element in a plan view is formed on the surface of the protective layer.

5. The method for manufacturing a thermal print head according to claim 4, wherein the protective layer comprises a first layer and a second layer, In the step of forming the protective layer, the second layer is formed after the first layer is formed. The first layer covers the wiring layer and the heating element. The second layer covers the first layer while avoiding an upper portion of the heat generating element.

6. The method for manufacturing a thermal print head according to claim 4, wherein the protective layer comprises a first layer and a second layer, In the step of forming the protective layer, the second layer is formed after the first layer is formed. The first layer covers the wiring layer, The second layer covers the heat generating element and the first layer.

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