Thermal print head and manufacturing method of the same

Abstract

To provide a thermal print head which inhibits occurrence of short-circuits in a wiring layer 30.SOLUTION: A thermal print head 100 has a substrate 1. The substrate 1 has a first surface 10a. The first surface 10a is formed with a plurality of first recessed parts h1. A width w1 of the first recessed part h1 is 50 μm or larger.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to thermal printheads and methods for manufacturing thermal printheads. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2021-115716 (Patent Document 1) discloses a thermal printhead in which a glaze layer is formed on the main surface of a substrate, and a wiring layer is formed on the glaze layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-115716 A [Summary] However, fine recesses may be formed on the surface of a substrate used as a thermal printhead. This is because, in order to manufacture many substrates at once, the substrates are manufactured by stacking and firing multiple sheet molded bodies. When firing these sheet molded bodies, fine powder is scattered between the multiple sheet molded bodies to prevent the overlapping substrates from adhering to each other. This fine powder causes fine recesses to be formed on the surface of the fired substrate. If a wiring layer is formed directly on the surface of a substrate with such fine recesses, defects such as short circuits may occur in the wiring layer.

[0004] A thermal printhead according to one embodiment of the present disclosure includes a substrate having a first surface on which a plurality of first recesses are formed, each having a width of 50 μm or greater.

[0005] A method for manufacturing a thermal printhead according to one embodiment of the present disclosure includes the steps of preparing a substrate having a first surface and smoothing the first surface, wherein the first surface has a plurality of recesses formed therein. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic plan view of a thermal printhead according to a first embodiment. [Figure 2] FIG. 2 is a schematic partial cross-sectional view of the thermal printhead taken along line II-II in FIG. [Figure 3] FIG. 3 is a flowchart showing a method for manufacturing the thermal printhead according to the first embodiment. [Figure 4] FIG. 4 is a schematic partial cross-sectional view showing a step in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 5] FIG. 5 is a schematic partial cross-sectional view showing a step subsequent to the step shown in FIG. 4 in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 6] FIG. 6 is a schematic partial cross-sectional view showing a step subsequent to the step shown in FIG. 5 in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 7] FIG. 7 is a schematic partial cross-sectional view showing a step subsequent to the step shown in FIG. 6 in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 8] FIG. 8 is a schematic partial cross-sectional view showing a step subsequent to the step shown in FIG. 7 in the method for manufacturing the thermal printhead according to the first embodiment. [Figure 9] 9 is a schematic partial cross-sectional view showing a step subsequent to the step shown in FIG. 8 in the method for manufacturing a thermal printhead according to the first embodiment. [Detailed Description] The details of the embodiments of the present disclosure will be described with reference to the drawings. Note that the same or corresponding parts in the following drawings are designated by the same reference numerals, and their description will not be repeated. At least some of the configurations of the embodiments described below may be combined in any manner.

[0007] Embodiment 1 (Thermal printhead configuration) Figure 1 is a schematic plan view of a thermal printhead 100 according to embodiment 1. Figure 2 is a schematic partial cross-sectional view of the thermal printhead 100 taken along line II-II in Figure 1. Note that the protective film 4 is omitted from Figure 1.

[0008] The thermal printhead 100 shown in FIGS. 1 and 2 comprises a substrate 1, a partial glaze layer 20, a wiring layer 30, a heat generating portion 5, and a protective film 4.

[0009] As shown in FIG. 2, the substrate 1 has a first surface 10a and a second surface 10b. The first surface 10a and the second surface 10b are end surfaces of the substrate 1 in the thickness direction. The second surface 10b is the surface opposite to the first surface 10a. The shape of the substrate 1 in a plan view of the first surface 10a is, for example, rectangular. The direction perpendicular to the first surface 10a is the z direction. The direction perpendicular to the z direction is the x direction. The direction perpendicular to the x direction and the z direction is the y direction. The plan view refers to the case where the substrate 1 is viewed from the first surface 10a side along the z direction of the first surface 10a. The x direction corresponds to the longitudinal direction of the substrate 1 in a plan view. As will be described later, the x direction is the direction in which the heat generating portion 5 extends. The y direction corresponds to the lateral direction of the substrate 1 in a plan view.

[0010] The substrate 1 has a first side surface 10c and a second side surface 10d. Each of the first side surface 10c and the second side surface 10d connects the first surface 10a and the second surface 10b. The second side surface 10d is the surface opposite the first side surface 10c.

[0011] The material constituting the substrate 1 is, for example, ceramic, and may be, for example, a material containing ceramic such as alumina (Al2O3) as a main component.

[0012] A plurality of first recesses h1 are formed on the first surface 10a of the substrate 1. The first recesses h1 are recessed from the first surface 10a toward the second surface 10b. The openings of the first recesses h1 are located on the first surface 10a. As shown in FIG. 2, the surface forming the first recesses h1 (the inner peripheral surface of the first recesses h1) is located between the first surface 10a and the second surface 10b in the z direction. In other words, the openings of the first recesses h1 are the boundary between the surface forming the first recesses h1 and the first surface 10a. At the openings of the first recesses h1, the surface forming the first recesses h1 and the first surface 10a are smoothly connected.

[0013] In a plan view of the first surface 10a, the shape of the first recess h1 may be circular, elliptical, or rectangular.

[0014] A plurality of second recesses h2 are formed on the second surface 10b of the substrate 1. The second recesses h2 are recessed from the second surface 10b toward the first surface 10a. The openings of the second recesses h2 are located on the second surface 10b. As shown in FIG. 2, the surface forming the second recesses h2 is located between the second surface 10b and the first surface 10a in the z direction. That is, the openings of the second recesses h2 are the boundary between the surface forming the second recesses h2 and the second surface 10b. At the openings of the second recesses h2, the surface forming the second recesses h2 and the second surface 10b are not as smoothly connected as at the openings of the first recesses h1. That is, at the openings of the first recesses h1, the surface forming the first recesses h1 and the first surface 10a are more smoothly connected than at the openings of the second recesses h2. The width w2 of the second recesses h2 is smaller than the width w1 of the first recesses h1. The width w1 of the first recess h1 can be measured by a method such as white light interference using a laser microscope (model number: VK-X3000) manufactured by Keyence Corporation. The laser microscope is used to identify the outermost surface of the first surface 10a. The width w1 of the first recess h1 is measured based on the outermost surface. The width w2 of the second recess h2 can also be measured using the same method as the width w1 of the first recess h1.

[0015] As shown in FIG. 2, the partial glaze layer 20 is formed on the first surface 10a. Specifically, the partial glaze layer 20 is not formed over the entire first surface 10a, but is formed on a partial region of the first surface 10a. The partial glaze layer 20 extends in the x direction. As shown in FIG. 2, the outer edge of the cross-sectional shape of the partial glaze layer 20 in a cross section taken along a direction perpendicular to the direction in which the partial glaze layer 20 extends may be, for example, arc-shaped. The material that constitutes the partial glaze layer 20 is, for example, glass. The partial glaze layer 20 stores heat from the heat-generating portion 5. Such a glaze layer is formed as the partial glaze layer 20 on a partial region of the first surface 10a. This improves the printing sensitivity of the thermal printhead 100. Furthermore, compared to a thermal printhead 100 in which a glaze layer is formed over the entire first surface 10a, the amount of material required to make up the glaze layer, such as glass, can be reduced, thereby reducing the manufacturing cost of the thermal printhead 100 according to this embodiment 1.

[0016] As shown in FIG. 2, the wiring layer 30 is formed on the first surface 10a and the partial glaze layer 20. The wiring layer 30 may be disposed on the surface that forms the first recess h1. Therefore, the wiring layer 30 may have a shape that conforms to the surface that forms the first recess h1. In other words, a plurality of recesses may be formed on the surface of the wiring layer 30 (the surface opposite the surface on which the wiring layer 30 faces the first surface 10a). In a plan view of the first surface 10a, the recesses are disposed at positions that overlap the first recess h1.

[0017] As shown in FIG. 1, the wiring layer 30 has a main body portion 30a, multiple protrusions 30b, and multiple individual electrode portions 31. In a plan view of the first surface 10a, the main body portion 30a has, for example, a rectangular shape. The main body portion 30a extends along the x direction. The main body portion 30a is located on the first side surface 10c side in the y direction. That is, the distance between the main body portion 30a and the first side surface 10c in the y direction is smaller than the distance between the main body portion 30a and the second side surface 10d in the y direction. The protrusions 30b protrude along the y direction from the side of the main body portion 30a facing the second side surface 10d. Some of the protrusions 30b are located on the partial glaze layer 20. The multiple protrusions 30b are arranged at equal intervals along the x direction.

[0018] One end of the individual electrode portion 31 in the y direction is closer to the first side surface 10c than the other end of the individual electrode portion 31 in the y direction. The individual electrode portion 31 has a tip portion 31a at one end in the y direction. The tip portion 31a extends along the y direction. As shown in FIG. 2, a portion of the tip portion 31a is disposed on the partial glaze layer 20. The protrusions 30b and the tip portions 31a are alternately disposed at intervals in the x direction. The individual electrode portion 31 has a pad 31b at the other end in the y direction. The thermal printhead 100 is electrically connected to a driver IC (not shown) at the pad 31b.

[0019] The material forming the wiring layer 30 is, for example, a conductive material. Specifically, the material forming the wiring layer 30 is a metal material. The material forming the wiring layer 30 may be, for example, gold (Au).

[0020] The narrowest width in the wiring layer 30 is, for example, 10 μm or more. The narrowest width in the wiring layer 30 may be, for example, 15 μm or more. The narrowest width in the wiring layer 30 may be the width of the tip portion 31a in a direction perpendicular to the direction in which the tip portion 31a extends in a plan view of the first surface 10a. The narrowest width in the wiring layer 30 may be the width of the protrusion 30b in a direction perpendicular to the direction in which the protrusion 30b extends in a plan view of the first surface 10a.

[0021] 2, the heat generating portion 5 is formed so as to be connected to the individual electrode portion 31. The heat generating portion 5 extends along the x direction. A portion of the heat generating portion 5 overlaps with the protruding portion 30b and the tip portion 31a.

[0022] The heat generating portion 5 includes, for example, glass and a plurality of conductive particles mixed in the glass. The conductive particles are made of, for example, ruthenium oxide (RuO2).

[0023] The driver IC selectively applies a voltage to the individual electrode portion 31. This causes a current to flow through the portion of the heat generating portion 5 that electrically connects the tip portion 31a of the individual electrode portion 31 to which the voltage is applied and the adjacent protrusion 30b. As a result, the heat generating portion 5 generates heat. This heat causes printing on paper that is in contact with the heat generating portion 5.

[0024] 2, the protective film 4 is formed to cover the entire first surface 10a of the substrate 1. In other words, the protective film 4 covers the wiring layer 30 and the heat generating portion 5. A portion of the protective film 4 is connected to the first surface 10a of the substrate 1. The material that forms the protective film 4 is, for example, glass. The pad 31b may be exposed from the protective film 4.

[0025] In conventional thermal printheads, a glaze layer is formed over the entire surface of the first surface 10a to prevent short circuits in the wiring layer 30, resulting in the wiring layer 30 being formed on the flat surface of the glaze layer. On the other hand, when a glaze layer (partial glaze layer 20) called heater glaze or die-bond glaze that stores heat from the heat generating unit 5 is formed partially on the first surface 10a, a glass layer is formed in an area adjacent to the partial glaze layer 20 on the first surface 10a. The wiring layer 30 is formed on the glass layer. The glass layer is formed after the partial glaze layer 20 is formed. Therefore, to prevent the shape of the previously formed partial glaze layer 20 from changing when the glass layer is formed, a glass material with a melting point lower than that of the glass material constituting the partial glaze layer 20 is used for the glass layer. As a result, defective products may occur in thermal printheads that use glaze layers made of glass materials with different melting points.

[0026] A feature of the thermal printhead 100 according to the first embodiment is that a first recess h1 is formed in the first surface 10a. As described above, it is sufficient that the surface forming the first recess h1 and the first surface 10a are smoothly connected at the opening of the first recess h1. In this way, when the wiring layer 30 is formed directly on the first surface 10a, the occurrence of a short circuit in the wiring layer 30 due to the first recess h1 is suppressed.

[0027] The first recess h1 may be larger than the width w2 of a minute recess (second recess h2 shown in FIG. 4) found on the first surface 10a of the substrate 1 after the substrate 1 is manufactured and the width w2 of the second recess h2 formed on the second surface 10b, so that the surface forming the first recess h1 and the first surface 10a are smoothly connected. Specifically, the width w1 of the first recess h1 is larger than the width w2 of the second recess h2. The width w1 of the first recess h1 may be the maximum width of the opening of the first recess h1 in a plan view of the first surface 10a. The width w2 of the second recess h2 may be the maximum width of the opening of the second recess h2 in a plan view of the first surface 10a.

[0028] Furthermore, in order to suppress the occurrence of short circuits in the wiring layer 30 due to the first recess h1, the width w1 of the first recess h1 may be relatively larger than the width of the wiring layer 30 in a direction perpendicular to the direction in which the wiring layer 30 extends. The width w1 of the first recess h1 may be 50 μm or more. The width w1 of the first recess h1 may be 70 μm or more, or may be 100 μm or more. The value obtained by dividing the width w1 of the first recess h1 by the width of the wiring layer 30 may be 3 or more. The value obtained by dividing the width w1 of the first recess h1 by the width of the wiring layer 30 may be 4 or more, or may be 5 or more.

[0029] The depth d1 of the first recess h1 may be 30 μm or less so that the surface forming the first recess h1 and the first surface 10a are smoothly connected. The depth d1 of the first recess h1 may be 15 μm or less, or may be 10 μm or less. As shown in FIG. 2, the depth d1 of the first recess h1 is the distance from the point on the surface forming the first recess h1 that is farthest from the first surface 10a in the z direction to the first surface 10a. The depth d1 of the first recess h1 can be measured by a method such as white light interference using a laser microscope (model number: VK-X3000) manufactured by Keyence Corporation. The outermost surface of the first surface 10a is identified using the laser microscope. The depth d1 of the first recess h1 is measured using the outermost surface as a reference.

[0030] The value obtained by dividing the width w1 of the first recess h1 by the depth d1 of the first recess h1 may be 1.6 or greater. The value obtained by dividing the width w1 of the first recess h1 by the depth d1 of the first recess h1 may be 2 or greater, or may be 3 or greater. In this way, the width w1 of the first recess h1 is larger than the depth d1 of the first recess h1, so that the surface forming the first recess h1 and the first surface 10a are smoothly continuous.

[0031] (Thermal printhead manufacturing method) The following describes a method for manufacturing the thermal printhead 100. Figure 3 is a flowchart of the method for manufacturing the thermal printhead 100 of the first embodiment. Figures 4 to 9 are schematic partial cross-sectional views showing a step in the method for manufacturing the thermal printhead 100 of the first embodiment.

[0032] 4, the method for manufacturing the thermal printhead 100 first performs the step (S1) of preparing the substrate 1. In this step (S1), the substrate 1 is prepared as shown in Fig. 4. The substrate 1 is, for example, an insulating substrate made of ceramic.

[0033] In order to manufacture multiple substrates 1 by a single firing, the substrates 1 are manufactured by stacking and firing multiple sheet bodies. When firing these sheet bodies, fine powder is scattered between the multiple sheet bodies to prevent the stacked substrates 1 from sticking together. The presence of this fine powder results in the formation of minute recesses (second recesses h2) as shown in FIG. 4 on the first surface 10a and second surface 10b of the substrate 1 manufactured by firing. If the wiring layer 30 is formed directly on the first surface 10a of the substrate 1 on which such second recesses h2 are formed in the step (S4) of forming the wiring layer 30, which will be described later, a short circuit may occur in the wiring layer 30.

[0034] A plurality of second recesses h2 are formed on the first surface 10a and the second surface 10b of the substrate 1. As shown in FIG. 4, the width w2 of the second recesses h2 is, for example, 30 μm or less. The width w2 of the second recesses h2 may be, for example, 20 μm or less, or may be 10 μm or less. The depth d2 of the second recesses h2 may be 30 μm or less. The depth d2 of the second recesses h2 may be 15 μm or less, or may be 10 μm or less.

[0035] Next, a step (S2) of smoothing the first surface 10a is performed. In this step (S2), the first surface 10a is smoothed using wet blasting so that the width w2 of the second recess h2 is 50 μm or more. By doing so, the width w2 of the second recess h2 formed on the first surface 10a is expanded, and the first recess h1 is formed as shown in FIG. 5. In other words, the first surface 10a and the second recess h2 formed on the first surface 10a are polished so that the surface forming the recess and the first surface 10a are smoothly connected. Note that the second surface 10b does not need to be smoothed in this step (S2).

[0036] The first surface 10a is polished by spraying a liquid containing an abrasive toward the first surface 10a using wet blasting.

[0037] Next, a step (S3) of forming a partial glaze layer 20 is performed. In this step (S3), as shown in FIG. 6, the partial glaze layer 20 is formed in a partial region on the first surface 10a. Specifically, a paste containing glass is applied to the first surface 10a. The applied paste is then heated. This evaporates the solvent in the paste and bonds the glass particles in the paste together, thereby forming the partial glaze layer 20.

[0038] Next, a step (S4) of forming the wiring layer 30 is performed. In this step (S4), as shown in FIG. 7, the wiring layer 30 is formed on the first surface 10a and the partial glaze layer 20. The wiring layer 30 is formed by applying a resinate paste containing the material that constitutes the wiring layer 30 onto the first surface 10a and the partial glaze layer 20 and then firing the resinate paste. However, the method of forming the wiring layer 30 is not limited to this.

[0039] Next, a step (S5) of patterning the wiring layer 30 is performed. In this step (S5), as shown in FIG. 8, the wiring layer 30 is patterned to form a main body portion 30a, a plurality of protrusions 30b, and a plurality of individual electrode portions 31. First, a resist is applied to the wiring layer 30 (not shown). The resist is applied using, for example, a roll coater. Next, the resist applied to the wiring layer 30 is exposed to light. The exposure is performed, for example, by partially irradiating the resist with UV (Ultra Violet) light using a glass mask. The resist in the irradiated UV light portion is altered. Next, the portions of the resist altered by exposure are dissolved and removed to form a resist pattern. Next, the wiring layer 30 is etched using the resist pattern as a mask to form a main body portion 30a, a plurality of protrusions 30b, and a plurality of individual electrode portions 31 (see FIG. 1). Note that the resist pattern is removed after etching the wiring layer 30.

[0040] Next, a step (S6) of forming heat generating portion 5 is performed. In this step (S6), heat generating portion 5 is formed as shown in FIG. 9. In a plan view of first surface 10a, heat generating portion 5 is formed on wiring layer 30 so as to overlap partial glaze layer 20. First, a conductive paste containing glass and ruthenium oxide particles is applied onto wiring layer 30. Next, the applied conductive paste is fired.

[0041] Next, a step (S7) of forming a protective film 4 is performed. In this step (S7), as shown in FIG. 2, the protective film 4 is formed to cover the first surface 10a, the partial glaze layer 20, the wiring layer 30, and the heat generating portion 5.

[0042] In this way, the thermal printhead 100 shown in FIGS. 1 and 2 can be obtained in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0043] (Action and effect) A thermal printhead 100 according to the present disclosure has a substrate 1. The substrate 1 has a first surface 10a. A plurality of first recesses h1 are formed on the first surface 10a. The width w1 of each first recess h1 is 50 μm or greater.

[0044] In this way, by forming the wiring layer 30 directly on the first surface 10a, it is possible to obtain a thermal printhead 100 in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0045] In the thermal printhead 100, the depth d1 of the first recess h1 is 30 μm or less.

[0046] In this way, by forming the wiring layer 30 directly on the first surface 10a, it is possible to obtain a thermal printhead 100 in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0047] The thermal printhead 100 includes a wiring layer 30. The wiring layer 30 is formed directly on the first surface 10a.

[0048] In this way, it is not necessary to form a glaze layer over the entire first surface 10a, and the wiring layer 30 may be formed directly on the first surface 10a. As a result, it is possible to reduce the manufacturing cost of the thermal printhead 100. Furthermore, it is possible to obtain a thermal printhead 100 in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0049] In the thermal printhead 100, the substrate 1 has a second surface 10b. The second surface 10b is the surface opposite to the first surface 10a. A plurality of second recesses h2 are formed on the second surface 10b.

[0050] In this way, by forming the wiring layer 30 directly on the first surface 10a, which is the surface opposite to the second surface 10b, it is possible to obtain a thermal printhead 100 in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0051] In the thermal printhead 100, the width w2 of the second recess h2 is smaller than the width w1 of the first recess h1.

[0052] In this way, by smoothing only the first surface 10a, the width of the second recess h2 formed on the first surface 10a can be increased. As a result, by forming the wiring layer 30 directly on the first surface 10a, it is possible to obtain a thermal printhead 100 in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0053] In the thermal printhead 100, the width w2 of the second recess h2 is 30 μm or less.

[0054] In this way, by smoothing only the first surface 10a, the width of the second recess h2 formed on the first surface 10a can be increased. As a result, by forming the wiring layer 30 directly on the first surface 10a, it is possible to obtain a thermal printhead 100 in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0055] In the thermal printhead 100, the material that constitutes the substrate 1 is ceramic.

[0056] If the substrate 1 is an insulating substrate such as one made of ceramic, minute recesses may be formed on the first surface 10a of the substrate 1 during firing to manufacture the substrate 1. By smoothing the first surface 10a of such a substrate 1 using shot blasting, it is possible to obtain a thermal printhead 100 in which short circuits in the wiring layer 30 are suppressed, even when the wiring layer 30 is formed directly on the first surface 10a.

[0057] A method for manufacturing a thermal printhead 100 according to the present disclosure includes a step (S1) of preparing a substrate 1 having a first surface 10a, and a step (S2) of smoothing the first surface 10a. In the preparation step (S1), a plurality of second recesses h2 are formed in the first surface 10a.

[0058] By smoothing the first surface 10a on which such fine recesses are formed, a thermal printhead 100 can be obtained in which short circuits in the wiring layer 30 are suppressed, even if the wiring layer 30 is formed directly on the first surface 10a.

[0059] According to the method for manufacturing the thermal printhead 100, in the smoothing step (S2), the first surface 10a is smoothed by wet blasting.

[0060] By smoothing the first surface 10a on which such fine recesses are formed, a thermal printhead 100 can be obtained in which short circuits in the wiring layer 30 are suppressed, even if the wiring layer 30 is formed directly on the first surface 10a.

[0061] According to the method for manufacturing the thermal printhead 100, in the smoothing step (S2), the first surface 10a is smoothed so that the width w2 of the second recesses h2 as recesses is 50 μm or more.

[0062] By smoothing the first surface 10a on which such fine recesses are formed, a thermal printhead 100 can be obtained in which short circuits in the wiring layer 30 are suppressed, even if the wiring layer 30 is formed directly on the first surface 10a.

[0063] The method for manufacturing the thermal printhead 100 further includes, after the smoothing step (S2), a step (S4) of forming the wiring layer 30 on the first surface 10a.

[0064] In this way, the wiring layer 30 can be formed directly on the smoothed first surface 10a, resulting in a thermal printhead 100 in which short circuits in the wiring layer 30 are suppressed.

[0065] According to the manufacturing method of the thermal printhead 100, in the preparation step (S1), the substrate 1 has a second surface 10b. The second surface 10b is the surface opposite to the first surface 10a. A plurality of second recesses h2 are formed on the second surface 10b.

[0066] In this way, by forming the wiring layer 30 directly on the first surface 10a, which is the surface opposite to the second surface 10b, it is possible to obtain a thermal printhead 100 in which the occurrence of short circuits in the wiring layer 30 is suppressed.

[0067] According to the method for manufacturing the thermal printhead 100, in the preparation step (S1), the width w2 of the second recess h2 as a recess is 30 μm or less.

[0068] By smoothing the first surface 10a on which such fine recesses are formed, a thermal printhead 100 can be obtained in which short circuits in the wiring layer 30 are suppressed, even if the wiring layer 30 is formed directly on the first surface 10a.

[0069] In the method for manufacturing the thermal printhead 100, the material that constitutes the substrate 1 is ceramic.

[0070] If the substrate 1 is an insulating substrate such as one made of ceramic, minute recesses may be formed on the first surface 10a of the substrate 1 during firing to manufacture the substrate 1. By smoothing the first surface 10a of such a substrate 1 using shot blasting, it is possible to obtain a thermal printhead 100 in which short circuits in the wiring layer 30 are suppressed, even when the wiring layer 30 is formed directly on the first surface 10a.

[0071] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. Unless there is a contradiction, at least two of the embodiments disclosed herein may be combined. The basic scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0072] The present disclosure includes the following aspects. (Appendix 1) 1. A thermal printhead having a substrate, the substrate has a first surface having a plurality of first recesses formed therein; A thermal printhead, wherein the width of the first recess is 50 μm or more. (Appendix 2) 2. The thermal printhead of claim 1, wherein the first recess has a depth of 30 μm or less. (Appendix 3) Further comprising a wiring layer; 3. The thermal printhead according to claim 1, wherein the wiring layer is formed directly on the first surface. (Appendix 4) the substrate has a second surface opposite to the first surface, 4. The thermal printhead according to claim 1, wherein the second surface has a plurality of second recesses formed therein. (Appendix 5) 5. The thermal printhead of claim 4, wherein the width of the second recess is smaller than the width of the first recess. (Appendix 6) 6. The thermal printhead of claim 5, wherein the width of the second recess is 30 μm or less. (Appendix 7) 7. The thermal printhead according to any one of claims 1 to 6, wherein the material constituting the substrate is ceramic. (Appendix 8) providing a substrate having a first surface; smoothing the first surface; In the preparing step, A method for manufacturing a thermal printhead, wherein a plurality of recesses are formed in the first surface. (Appendix 9) 9. The method for manufacturing a thermal printhead according to claim 8, wherein the first surface is smoothed using wet blasting in the smoothing step. (Appendix 10) 10. The method for manufacturing a thermal printhead according to claim 8, wherein in the smoothing step, the first surface is smoothed so that the width of the recess is 50 μm or more. (Appendix 11) The method for manufacturing a thermal printhead according to any one of claims 8 to 10, further comprising the step of forming a wiring layer on the first surface after the smoothing step. (Appendix 12) In the preparing step, the substrate has a second surface opposite to the first surface, 12. The method for manufacturing a thermal printhead according to claim 8, wherein a plurality of the recesses are formed on the second surface. (Appendix 13) 13. The method for manufacturing a thermal printhead according to claim 8, wherein in the preparing step, the width of the recess is 30 μm or less. (Appendix 14) 14. The method for manufacturing a thermal printhead according to any one of claims 8 to 13, wherein the material constituting the substrate is ceramic. [Explanation of symbols]

[0073] 1 substrate, 4 protective film, 5 heating portion, 10a first surface, 10b second surface, 10c first side surface, 10d second side surface, 20 partial glaze layer, 30 wiring layer, 30a main body portion, 30b protrusion portion, 31 individual electrode portion, 31a tip portion, 31b pad, 100 thermal print head, h1 first recess, h2 second recess, w1, w2 width, d1, d2 depth.

Claims

1. 1. A thermal printhead having a substrate, the substrate has a first surface having a plurality of first recesses formed therein; A thermal printhead, wherein the width of the first recess is 50 μm or more.

2. 2. The thermal printhead according to claim 1, wherein the depth of the first recess is 30 [mu]m or less.

3. Further comprising a wiring layer; The thermal printhead according to claim 1 , wherein the wiring layer is formed directly on the first surface.

4. the substrate has a second surface opposite to the first surface, The thermal printhead according to claim 1 , wherein the second surface has a plurality of second recesses formed therein.

5. The thermal printhead of claim 4 , wherein the width of the second recess is smaller than the width of the first recess.

6. 6. The thermal printhead according to claim 5, wherein the width of the second recess is 30 [mu]m or less.

7. 7. The thermal printhead according to claim 1, wherein the material constituting the substrate is ceramic.

8. providing a substrate having a first surface; smoothing the first surface; In the preparing step, A method for manufacturing a thermal printhead, wherein a plurality of recesses are formed in the first surface.

9. The method for manufacturing a thermal printhead according to claim 8 , wherein the first surface is smoothed by wet blasting in the smoothing step.

10. The method for manufacturing a thermal printhead according to claim 8 , wherein in the smoothing step, the first surface is smoothed so that the width of the recess is 50 μm or more.

11. The method for manufacturing a thermal printhead according to claim 8 , further comprising the step of forming a wiring layer on the first surface after the smoothing step.

12. In the preparing step, the substrate has a second surface opposite to the first surface, The method for manufacturing a thermal printhead according to claim 8 , wherein a plurality of the recesses are formed in the second surface.

13. The method for manufacturing a thermal printhead according to claim 8 , wherein in the preparing step, the width of the recess is 30 μm or less.

14. The method for manufacturing a thermal printhead according to claim 8 , wherein the material constituting the substrate is ceramic.

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