Thermal print head, thermal printer, and method for manufacturing thermal print head

Abstract

According to the present invention, a thermal print head comprises a base material, a glaze layer, an electrode layer, and a resistor layer. The base material has a main surface facing a first side and a rear surface facing a second side in the thickness direction, and contains ceramic. The glaze layer is disposed on the first side in the thickness direction of the base material. The electrode layer is formed on the glaze layer. The resistor layer is formed on the glaze layer and has a plurality of heat generating parts. The base material has protrusions protruding to the first side in the thickness direction from the main surface and extending in a main scanning direction orthogonal to the thickness direction. The glaze layer has a cover part covering the protrusions. The plurality of heat generating parts overlap with the protrusions as viewed in the thickness direction.

Description

Thermal printhead, thermal printer, and method for manufacturing thermal printhead

[0001] The present disclosure relates to a thermal printhead, a thermal printer including the thermal printhead, and a method for manufacturing the thermal printhead.

[0002] Thermal printheads have traditionally been used as devices that print by applying heat to thermal paper or thermal ink ribbons. For example, Patent Document 1 discloses a conventional thermal printhead. The thermal printhead described in Patent Document 1 includes a substrate, a glaze layer, an electrode layer, a resistor layer, a protective layer, a driver IC, and a sealing resin. In one aspect disclosed in Patent Document 1, the glaze layer includes a heat storage section. The heat storage section is shaped to bulge in the thickness direction of the substrate. Multiple heat-generating sections of the resistor layer are arranged on the heat storage section.

[0003] Japanese Patent Application Laid-Open No. 2018-103608

[0004] To apply stronger pressure to the portion of the protective layer covering the heat generating elements and the thermal paper, it is preferable to make the heat storage element protrude further from the substrate. However, it is not easy to finish a heat storage element made of glass or the like in a protruding shape. Furthermore, if the heat storage element is too thick, there is a risk that heat dissipation from the heat generating elements will be excessively hindered. As a result, there is a concern that problems such as coloring may occur in areas where printing is not intended.

[0005] An object of the present disclosure is to provide an improved thermal printhead. Another object of the present disclosure is to provide a thermal printer including the thermal printhead, and a method for manufacturing the thermal printhead. In particular, in view of the above-described circumstances, an object of the present disclosure is to provide a thermal printhead (and, by extension, a thermal printer including the thermal printhead, and a method for manufacturing the thermal printhead) that allows the glaze layer to have a more appropriately protruding shape.

[0006] A thermal printhead provided by a first aspect of the present disclosure includes a substrate including a ceramic and having a main surface facing a first side in a thickness direction and a back surface facing a second side, a glaze layer disposed on the first side in the thickness direction of the substrate, an electrode layer formed on the glaze layer, and a resistor layer formed on the glaze layer and having a plurality of heating elements. The substrate has protruding portions protruding from the main surface to the first side in the thickness direction and extending in a main scanning direction perpendicular to the thickness direction. The glaze layer has covering portions that cover the protruding portions. The plurality of heating elements overlap the protruding portions when viewed in the thickness direction.

[0007] A thermal printer provided by a second aspect of the present disclosure includes the thermal printhead provided by the first aspect of the present disclosure.

[0008] A third aspect of the present disclosure provides a method for manufacturing a thermal printhead, comprising the steps of: preparing a substrate having a main surface facing a first side in a thickness direction and a back surface facing a second side and containing ceramic; forming convex portions containing ceramic, the convex portions protruding from the main surface toward the first side in the thickness direction and extending in a main scanning direction perpendicular to the thickness direction; forming a glaze layer having covering portions that cover the convex portions; forming an electrode layer on the glaze layer; and forming a resistor layer on the glaze layer having a plurality of heating portions that overlap the convex portions when viewed in the thickness direction.

[0009] According to the above configuration, the glaze layer of the thermal printhead can be made to have a more appropriate protruding shape.

[0010] Other features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0011] FIG. 1 is a plan view showing a thermal printhead according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 , showing a printer according to the first embodiment of the present disclosure. FIG. 3 is an enlarged plan view showing a thermal printhead according to the first embodiment of the present disclosure. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is an enlarged cross-sectional view showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 6 is an enlarged cross-sectional view showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 7 is an enlarged cross-sectional view showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 8 is an enlarged cross-sectional view showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 9 is an enlarged cross-sectional view showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 10 is an enlarged cross-sectional view showing a method for manufacturing a thermal printhead according to the first embodiment of the present disclosure. FIG. 11 is an enlarged cross-sectional view showing a first modified example of a thermal printhead according to the first embodiment of the present disclosure. 12 and 13 are enlarged cross-sectional views of a main portion of a thermal printhead according to a second embodiment of the present disclosure, and a first modified example of the thermal printhead according to the second embodiment of the present disclosure.

[0012] Preferred embodiments of the present disclosure will now be described in detail with reference to the drawings.

[0013] The terms "first," "second," "third," etc. in this disclosure are used for identification purposes only and are not intended to impose any ranking on their objects.

[0014] In this disclosure, unless otherwise specified, "a certain object A is formed on a certain object B" and "a certain object A is formed on a certain object B" include "a certain object A is formed directly on a certain object B" and "a certain object A is formed on a certain object B with another object interposed between the certain object A and the certain object B." Similarly, "a certain object A is disposed on a certain object B" and "a certain object A is disposed on a certain object B" include "a certain object A is disposed directly on a certain object B" and "a certain object A is disposed on a certain object B with another object interposed between the certain object A and the certain object B" unless otherwise specified. Similarly, "a certain object A is located on a certain object B" includes "a certain object A is located on a certain object B with a certain object A in contact with the certain object B" and "a certain object A is located on a certain object B with another object interposed between the certain object A and the certain object B." Furthermore, unless otherwise specified, the phrase "an object A overlaps an object B when viewed in a certain direction" includes "an object A overlaps the entire object B" and "an object A overlaps a part of an object B." Furthermore, in the present disclosure, "a surface A faces in (one side or the other side of) direction B" is not limited to the case where the angle of surface A with respect to direction B is 90°, but also includes the case where surface A is tilted with respect to direction B.

[0015] 1 to 4 show a thermal printhead A1 and a thermal printer P1 according to a first embodiment of the present disclosure. The thermal printhead A1 includes a substrate 1, a protective layer 2, an electrode layer 3, a resistor layer 4, a connection substrate 5, multiple wires 61 and 62, multiple driver ICs 7, a protective resin 78, and a heat dissipation member 8. The thermal printhead A1 is incorporated into a thermal printer P1 that prints on a print medium C1 (see FIG. 2).

[0016] The thermal printer P1 includes a thermal printhead A1 and a platen roller B1. The platen roller B1 faces the thermal printhead A1. A print medium C1 is sandwiched between the thermal printhead A1 and the platen roller B1 and transported in the sub-scanning direction y by the platen roller B1. Examples of such print media C1 include thermal paper for creating barcode sheets or receipts. A flat rubber platen may be used instead of the platen roller B1. This platen includes a cylindrical rubber portion with a large radius of curvature that is arch-shaped in cross section.

[0017] FIG. 1 is a plan view showing a thermal printhead A1. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, showing a printer according to a first embodiment of the present disclosure. FIG. 3 is an enlarged plan view showing a main portion of the thermal printhead A1. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. 3. The protective layer 2 and the multiple wires 61 and 62 are omitted in FIG. 1. The protective layer 2 is omitted in FIG. 3, and the electrode layer 3 is hatched.

[0018] In these figures, the thickness direction of the substrate 1 (base material 11 described below) is referred to as the thickness direction z. The z1 side of the thickness direction z is an example of the "first side," and the z2 side is an example of the "second side." The main scanning direction x and the sub-scanning direction y are both perpendicular to the thickness direction z and are perpendicular to each other. During printing, the printing medium C1 is fed from the y2 side to the y1 side of the sub-scanning direction y. In the sub-scanning direction y, the y1 side may be referred to as the downstream side, and the y2 side as the upstream side.

[0019] 1, the substrate 1 is a plate-like member extending in the main scanning direction x. The substrate 1 is a support member that supports a protective layer 2, an electrode layer 3, a resistor layer 4, and a plurality of driver ICs 7. The substrate 1 has a base material 11 and a glaze layer 12.

[0020] The substrate 11 includes a ceramic such as AlN (aluminum nitride), Al2O3 (alumina), or zirconia, and has these ceramics as its main component. The substrate 11 has a thickness of 0.6 mm or more and 1.0 mm or less. As shown in FIG. 1 , the substrate 11 has a rectangular shape extending in the main scanning direction x in a plan view. The substrate 11 has a first main surface 11a, a first back surface 11b, and a convex portion 111.

[0021] The first major surface 11a and the first back surface 11b are spaced apart in the thickness direction z. The first major surface 11a faces the z1 side in the thickness direction z. The first back surface 11b faces the z2 side in the thickness direction z. The first major surface 11a is an example of a "major surface," and the first back surface 11b is an example of a "back surface."

[0022] As shown in Fig. 4, the convex portion 111 protrudes from the first main surface 11a toward the z1 side in the thickness direction z. As shown in Fig. 3, the convex portion 111 extends in the main scanning direction x. The shape and size of the convex portion 111 are not limited in any way. As shown in Fig. 4, the convex portion 111 in this example includes a first portion 1111 and a second portion 1112.

[0023] The first portion 1111 is a portion that protrudes from the first main surface 11a. The second portion 1112 is a portion that is located on the z1 side in the thickness direction z with respect to the first portion 1111. A first dimension W1, which is the size of the first portion 1111 in the sub-scanning direction y, is larger than a second dimension W2, which is the size of the second portion 1112 in the sub-scanning direction y. The relationship between the first dimension W1 and the second dimension W2 is not limited in any way, and for example, the second dimension W2 is 50% or more and 95% or less of the first dimension W1.

[0024] There are no limitations on the thickness Z1 of the first portion 1111 and the thickness Z2 of the second portion 1112. Thickness Z1 may be greater than, smaller than, or the same as thickness Z2. A specific example of thickness Z1 and thickness Z2 is, for example, 30 μm or more and 200 μm or less.

[0025] The cross-sectional shape of the first portion 1111 perpendicular to the main scanning direction x is not limited in any way, and in the illustrated example, it is rectangular. The cross-sectional shape of the second portion 1112 perpendicular to the main scanning direction x is not limited in any way, and in the illustrated example, it is rectangular.

[0026] The glaze layer 12 is disposed on the z1 side of the substrate 11 in the thickness direction z. The glaze layer 12 covers at least a portion of the first main surface 11a and the protrusions 111. The glaze layer 12 is made of a glass material such as amorphous glass. The glaze layer 12 in this example includes a covering portion 122 and a flat portion 121.

[0027] The covering portion 122 covers at least a portion of the protrusion 111. In the illustrated example, the covering portion 122 covers the entire protrusion 111. Note that the covering portion 122 may be configured to cover only a portion of the protrusion 111. For example, a region of the protrusion 111 where the electrode layer 3 and the resistor layer 4 described below are not formed may be exposed from the covering portion 122. Alternatively, if the surface properties of the protrusion 111 are such that the electrode layer 3 and the resistor layer 4 can be formed thereon, a portion of the electrode layer 3 and the resistor layer 4 may be in contact with the protrusion 111.

[0028] The covering portion 122 extends elongatedly in the main scanning direction x. When viewed in the main scanning direction x, the covering portion 122 bulges in the thickness direction z. The surface of the covering portion 122 has a curved cross-sectional shape perpendicular to the main scanning direction x that bulges toward the z1 side in the thickness direction z. The covering portion 122 is provided to make it easier to press the heat-generating portion of the resistor layer 4 (the heat-generating portion 41 described below) against the printing medium C1. There are no limitations on the thickness of the covering portion 122, and it is, for example, 5 μm or more and 15 μm or less.

[0029] The flat portion 121 is formed adjacent to the covering portion 122, and has a flat surface on the z1 side in the thickness direction z. The thickness of the flat portion 121 is, for example, about 2.0 μm. The flat portion 121 covers the first main surface 11 a of the base material 11, which is a relatively rough surface, to form a smooth surface suitable for forming the electrode layer 3.

[0030] There is no limitation on the softening point of the glaze layer 12. The softening point of the flat portion 121 and the softening point of the covering portion 122 may be different from each other or may be the same. The softening points of the flat portion 121 and the covering portion 122 are, for example, 800°C or higher and 850°C or lower, or, for example, approximately 680°C.

[0031] The electrode layer 3 forms a conductive path for supplying electricity to the resistor layer 4. The electrode layer 3 is made of a conductive material. The electrode layer 3 is, for example, a metal containing Au (gold). The electrode layer 3 is formed on the glaze layer 12 of the substrate 1. The thickness of the electrode layer 3 is, for example, 1 μm or more and 7.5 μm or less (preferably approximately 5.0 μm). As shown in FIGS. 3 and 4 , the electrode layer 3 has a common electrode 31 and a plurality of individual electrodes 34. Note that the shape and arrangement of each part of the electrode layer 3 are not limited to the examples shown in FIGS. 3 and 4 , and various configurations are possible. Furthermore, the material of each part of the electrode layer 3 is not limited in any way.

[0032] As shown in FIG. 3 , the common electrode 31 has a plurality of strip-shaped portions 32 and connecting portions 33. The connecting portions 33 are arranged near the edge of the substrate 1 on the y1 side in the sub-scanning direction y and are strip-shaped extending in the main scanning direction x. The plurality of strip-shaped portions 32 each extend from the connecting portion 33 in the sub-scanning direction y and are arranged at equal intervals in the main scanning direction x. In the example shown in FIG. 3 , an auxiliary layer 331 is laminated on the connecting portion 33 to reduce the resistance value of the connecting portion 33, but the auxiliary layer 331 does not have to be laminated. The auxiliary layer 331 is formed, for example, by printing and firing a paste containing an organic Ag (silver) compound or a paste containing Ag (silver) particles, glass frit, Pd (palladium), and a resin.

[0033] The individual electrodes 34 are used to partially apply current to the resistor layer 4. Each individual electrode 34 has an opposite polarity to the common electrode 31. Each individual electrode 34 extends from the resistor layer 4 toward the driver IC 7. The individual electrodes 34 are arranged in the main scanning direction x. Each of the individual electrodes 34 has a strip portion 35, a connecting portion 36, and a bonding portion 37.

[0034] 3, the strip portions 35 extend in the sub-scanning direction y and are strip-shaped when viewed in the thickness direction z. Each strip portion 35 is located between two adjacent strip portions 32 of the common electrode 31. The distance between the strip portions 35 of adjacent individual electrodes 34 and the strip portions 32 of the common electrode 31 is, for example, 50 μm or less.

[0035] The connecting portion 36 is a portion that extends from the strip portion 35 toward the driver IC 7. The connecting portion 36 includes a parallel portion 361 and an oblique portion 362. One end of the parallel portion 361 is connected to the bonding portion 37 and extends along the sub-scanning direction y. The oblique portion 362 is inclined with respect to the sub-scanning direction y. The oblique portion 362 is sandwiched between the parallel portion 361 and the strip portion 35 in the sub-scanning direction y. Furthermore, the multiple individual electrodes 34 are concentrated on the driver IC 7.

[0036] As shown in FIG. 3 , the bonding portions 37 are formed on the end of the individual electrodes 34 on the y2 side in the sub-scanning direction y, and each is connected to a corresponding parallel portion 361. A wire 61 is bonded to each bonding portion 37. This establishes electrical continuity between each individual electrode 34 and the driver IC 7 via the wire 61. The bonding portions 37 include a first bonding portion 37A and a second bonding portion 37B. The width (length in the main scanning direction x) of the parallel portion 361 sandwiched between two adjacent first bonding portions 37A is, for example, 10 μm or less. The second bonding portion 37B is located farther from the resistor layer 4 than the first bonding portion 37A in the sub-scanning direction y. The second bonding portion 37B is connected to the parallel portion 361 sandwiched between two adjacent first bonding portions 37A. This configuration prevents the multiple bonding portions 37 from interfering with each other, even though they are wider than most of the connecting portion 36. The portion of the connecting portion 36 that is sandwiched between adjacent first bonding portions 37A has the smallest width on the individual electrode 34.

[0037] The resistor layer 4 is formed using a material having a higher resistivity than the material constituting the electrode layer 3. The resistor layer 4 includes, for example, ruthenium oxide. In this example, the resistor layer 4 is formed on the covering portion 122 as shown in FIGS. 3 and 4 . The shape of the resistor layer 4 as viewed in the thickness direction z is not limited in any way. In this embodiment, the resistor layer 4 has a strip shape extending in the main scanning direction x as shown in FIGS. 1 and 3 . The resistor layer 4 straddles each strip portion 32 (common electrode 31) and each strip portion 35 (individual electrode 34). In the thickness direction z, the resistor layer 4 is stacked on the z1 side of the multiple strip portions 32 and the multiple strip portions 35.

[0038] The portions of the resistor layer 4 sandwiched between the strip portions 32 and 35 are defined as heat generating portions 41. The heat generating portions 41 generate heat when partially energized by the electrode layer 3. Print dots are formed by the heat generated by each heat generating portion 41. The heat generating portions 41 are arranged in the main scanning direction x. The greater the number of heat generating portions 41 arranged in the main scanning direction x per unit length (e.g., 1 mm) of the main scanning direction x of the substrate 1, the greater the dot density of the thermal printhead A1. The heat generating portions 41 overlap with the protrusions 111 when viewed in the thickness direction z. In this example, the heat generating portions 41 overlap with the first portions 1111 when viewed in the thickness direction z.

[0039] The thickness of the resistor layer 4 is, for example, 3 μm to 6 μm The material and thickness of the resistor layer 4 are not limited.

[0040] The protective layer 2 is intended to protect the electrode layer 3, the resistor layer 4, and the like. The protective layer 2 may be composed of a single layer or a laminate of multiple layers. The material of the protective layer 2 is not limited in any way. One example of the protective layer 2 is one that is primarily composed of amorphous glass. Another example of the protective layer 2 is one in which a first layer made of amorphous glass is laminated with a second layer made of SiAlON. SiAlON is a silicon nitride-based engineering ceramic obtained by combining SiN (silicon nitride) with AlO (alumina) and SiO (silica). The second layer is formed, for example, by sputtering. SiC (silicon carbide) may be used for the second layer instead of SiAlON.

[0041] As shown in Figures 1 and 2, the connection board 5 is disposed upstream of the substrate 1 in the sub-scanning direction y. The connection board 5 is, for example, a printed circuit board, and has a wiring pattern (not shown) formed thereon. A connector 59 (described below) is mounted on the connection board 5. The shape of the connection board 5 is not particularly limited, but in this embodiment, it is rectangular with the main scanning direction x as its longitudinal direction. The connection board 5 has a second main surface 5a and a second back surface 5b. The second main surface 5a faces the same side as the first main surface 11a of the substrate 11, and the second back surface 5b faces the same side as the first back surface 11b of the substrate 11.

[0042] Each of the multiple driver ICs 7 is mounted on, for example, the substrate 1 and serves to individually energize the multiple heat generating portions 41. Each driver IC 7 may be mounted across the substrate 1 and the connection substrate 5, or may be mounted on the connection substrate 5. The multiple driver ICs 7 are connected to the multiple individual electrodes 34 (multiple bonding portions 37) by multiple wires 61. The multiple driver ICs 7 control the energization of the multiple heat generating portions 41 in accordance with a command signal input from outside the thermal printhead A1 via the connection substrate 5. The multiple driver ICs 7 are connected to a wiring pattern (not shown) on the connection substrate 5 by multiple wires 62. The multiple driver ICs 7 are provided as needed according to the number of the multiple heat generating portions 41.

[0043] The driver ICs 7, the wires 61, and the wires 62 are covered with a protective resin 78. The protective resin 78 is made of, for example, an insulating resin and is, for example, black. The protective resin 78 is formed so as to straddle the substrate 1 and the connection substrate 5.

[0044] The connector 59 is used to connect the thermal printhead A1 to a thermal printer. The connector 59 is attached to the connection board 5 and connected to the wiring pattern (not shown) of the connection board 5.

[0045] As shown in FIG. 2 , the heat dissipation member 8 supports the substrate 1 and the connection substrate 5. The heat dissipation member 8 is intended to dissipate some of the heat generated by the multiple heat-generating portions 41 to the outside via the substrate 1. The heat dissipation member 8 is a block-shaped member made of a metal such as Al. As shown in FIG. 2 , the heat dissipation member 8 has support surfaces 81. Each of the support surfaces 81 faces upward in the thickness direction z. A first back surface 11 b of the base material 11 and a second back surface 5 b of the connection substrate 5 are joined to the support surface 81.

[0046] Next, a method for manufacturing the thermal printhead A1 will be described below with reference to FIGS.

[0047] First, as shown in FIG. 5 , a substrate 11 is prepared. At this stage, the substrate 11 has a first main surface 11 a and a first back surface 11 b, but does not yet have any protrusions 111. At this stage, the substrate 11 may be a hardened ceramic, or a green body that will harden into a ceramic by firing. For ease of understanding, the following description will be given of an example in which components for forming one thermal printhead A1 are formed sequentially. However, this is not limiting. For example, components for forming multiple thermal printheads A1 may be formed simultaneously. In this case, a process of dividing the substrate 11 is appropriately performed. In the process of dividing the substrate 11, the glaze layer 12 may be divided simultaneously, or the glaze layer 12 may be formed in an area of ​​the substrate 11 that avoids the divided areas.

[0048] Next, as shown in FIG. 6 , a first portion 1111 is formed. The method for forming the first portion 1111 is not limited in any way. For example, a 3D printing method using ceramic stereolithography technology can be used to form the first portion 1111. The 3D printing method is a method for selectively subjecting a ceramic filler to photopolymerization processing to layer-by-layer manufacturing of a three-dimensional structure. An example of an apparatus that can realize such a 3D printing method is an apparatus manufactured by Lithoz.

[0049] For example, a slurry containing a photocurable resin binder and ceramic powder is applied to a transparent container. The first main surface 11a of the substrate 11 is brought into contact with this slurry from above. In this state, the slurry is exposed to visible light through the transparent container, corresponding to the shape of the first portion 1111 as viewed in the thickness direction z (a strip shape with a first dimension W1 extending in the sub-scanning direction y in the main scanning direction x). The exposed slurry becomes a ceramic green body that will become the first portion 1111, and adheres to the first main surface 11a. At this time, the thickness Z1 is, for example, 30 μm or more and 200 μm or less.

[0050] Next, new slurry is applied to the container, and the green body that will become the first portion 1111 is brought into contact with the slurry. In this state, the slurry is exposed to visible light through the transparent container, corresponding to the shape of the second portion 1112 as viewed in the thickness direction z (a strip extending in the main scanning direction x and having a second dimension W2 in the sub-scanning direction y). As a result, as shown in FIG. 7 , the exposed slurry becomes a ceramic green body that will become the second portion 1112, and adheres to the first portion 1111. In this case, the thickness Z2 is, for example, 30 μm or more and 200 μm or less.

[0051] Next, the substrate 11 on which the green bodies to become the first portion 1111 and the second portion 1112 have been formed is subjected to a firing process or the like. This results in the substrate 11 having the convex portion 111. The convex portion 111 includes the first portion 1111 and the second portion 1112.

[0052] Next, as shown in Fig. 8, the glaze layer 12 is formed. The glaze layer 12 is formed, for example, by applying a paste containing glass so as to cover the first main surface 11a and the protrusions 111. Next, the glass paste is fired. As a result, the glaze layer 12 including the flat portions 121 and the covering portions 122 is obtained.

[0053] Next, as shown in Fig. 9, the electrode layer 3 is formed. The electrode layer 3 is formed, for example, by applying a paste containing Au (gold) resinate onto the glaze layer 12 and firing it to form a metal layer containing Au (gold). The metal layer is then patterned, for example by etching, to obtain the electrode layer 3. Alternatively, the auxiliary layer 331 may be formed by printing and firing a paste containing Ag (silver).

[0054] 10, the resistor layer 4 is formed. The resistor layer 4 is formed, for example, by applying a paste containing ruthenium oxide in a strip shape extending in the main scanning direction x and then firing the applied paste. After this, the thermal printhead A1 is obtained by forming the protective layer 2, mounting the driver IC 7, bonding the wires 61 and 62, and attaching the substrate 1 and the connection substrate 5 to the heat dissipation member 8.

[0055] Next, the operation of the thermal printhead A1 and the thermal printer P1 will be described.

[0056] According to this embodiment, the substrate 11 has convex portions 111 that protrude from the first major surface 11a toward the z1 side in the thickness direction z. The covering portions 122 of the glaze layer 12 cover the convex portions 111. This allows the glaze layer 12 (covering portions 122) to have a more protruding shape than when the glaze layer 12 is formed only from glass or the like on the flat first major surface 11a. Furthermore, the covering portions 122 only need to have a thickness that covers the convex portions 111. This prevents problems such as the glaze layer 12 (covering portions 122) becoming excessively thick, excessively hindering heat dissipation from the multiple heat-generating portions 41 and causing color development in areas that should not be printed.

[0057] The protrusion 111 includes a first portion 1111 and a second portion 1112. The second dimension W2 of the second portion 1112 is smaller than the first dimension W1 of the first portion 1111. This gives the protrusion 111 a stepped shape. This allows the covering portion 122 to have a shape that bulges out more toward the z1 side in the thickness direction z.

[0058] The cross-sectional shapes of the first portion 1111 and the second portion 1112 are rectangular. For example, when forming the convex portion 111 using the above-described 3D printing method, two exposures are required: one to form the green body that will become the first portion 1111, and the other to form the green body that will become the second portion 1112. This improves the manufacturing efficiency of the thermal printhead A1 compared to shapes that require multiple exposures.

[0059] 11 to 13 show modified examples and other embodiments of the present disclosure. In these figures, elements that are the same as or similar to those in the above-described embodiment are given the same reference numerals. Furthermore, the configurations of the various parts in each modified example and each embodiment can be combined with each other as appropriate within the scope of not causing technical contradictions.

[0060] 11 shows a first modified example of the thermal printhead A1. In the thermal printhead A11 of this example, the cross-sectional shapes of the first portion 1111 and the second portion 1112 perpendicular to the main scanning direction x are different from those of the above-described example.

[0061] In this modified example, the cross-sectional shape of the first portion 1111 and the second portion 1112 perpendicular to the main scanning direction x is trapezoidal. The first dimension W1 and thickness Z1 of the first portion 1111 and the second dimension W2 and thickness Z2 of the second portion 1112 are not limited in any way and may be the same as the dimensions of the thermal printhead A1, for example.

[0062] The first portion 1111 and the second portion 1112 in this example can be formed by the 3D printing method exemplified in the manufacturing method of the thermal printhead A1 described above. To form each of the first portion 1111 and the second portion 1112, the above-described slurry application and exposure are repeated multiple times. The thickness of the applied slurry is significantly thinner than the thickness applied in the manufacturing method of the thermal printhead A1. Furthermore, with each application and exposure, the size of the exposed region in the sub-scanning direction y is gradually reduced. This results in trapezoidal first portion 1111 and second portion 1112. Depending on the applied slurry thickness, exposure conditions, and the like, the side surfaces of the first portion 1111 and the second portion 1112 on both sides in the sub-scanning direction y may have a stepped shape microscopically.

[0063] This modification also allows the glaze layer 12 to have a more appropriate protruding shape. Furthermore, as can be understood from this modification, there is no limitation on the specific shapes of the first portion 1111 and the second portion 1112. By making the first portion 1111 and the second portion 1112 trapezoidal, the covering portion 122 can be finished into a more gently bulging shape.

[0064] 12 shows a thermal printhead according to a second embodiment of the present disclosure. A thermal printhead A2 of this embodiment differs from the above-described embodiment in the configuration of the convex portion 111.

[0065] In this embodiment, the convex portion 111 includes a first portion 1111, a second portion 1112, and a third portion 1113. The third portion 1113 is disposed on the z1 side of the second portion 1112 in the thickness direction z. The size and shape of the third portion 1113 are not limited. In the illustrated example, the third dimension W3, which is the size of the third portion 1113 in the sub-scanning direction y, is smaller than the second dimension W2. For example, the third dimension W3 is 50% to 95% of the second dimension W2. The thickness Z3 of the third portion 1113 is not limited and may be different from or the same as the thickness Z1 and the thickness Z2, for example, 30 μm to 200 μm. The cross-sectional shape of the third portion 1113 is not limited and is rectangular in the illustrated example.

[0066] The formation of the convex portion 111 including the third portion 1113 can be achieved, for example, by forming a green body to become the second portion 1112 in the above-described 3D printing method, and then forming a green body to become the third portion 1113 by a similar process. Then, by performing the above-described firing process or the like, the substrate 11 having the convex portion 111 including the first portion 1111, the second portion 1112, and the third portion 1113 can be formed.

[0067] This embodiment also allows the glaze layer 12 to have a more appropriate protruding shape. Furthermore, by including the third portion 1113 in addition to the first portion 1111 and the second portion 1112 in the protruding portion 111, the shape of the covering portion 122 can be finished into a shape that protrudes further toward the z1 side in the thickness direction z. Furthermore, as can be understood from this embodiment, the protruding portion 111 is not limited to a configuration including the first portion 1111 and the second portion 1112, or a configuration including the first portion 1111, the second portion 1112, and the third portion 1113. For example, the protruding portion 111 may be a configuration including only the first portion 1111, or a configuration including a portion that forms an additional step on the z1 side of the third portion 1113 in the thickness direction z.

[0068] 13 shows a first modified example of the thermal printhead A2. In the thermal printhead A21 of this example, the cross-sectional shapes of the first portion 1111, the second portion 1112, and the third portion 1113 perpendicular to the main scanning direction x are different from those of the above-described example.

[0069] In this modified example, the cross-sectional shape perpendicular to the main scanning direction x of the first portion 1111, the second portion 1112, and the third portion 1113 is trapezoidal. The first dimension W1 and thickness Z1 of the first portion 1111, the second dimension W2 and thickness Z2 of the second portion 1112, and the third dimension W3 and thickness Z3 of the third portion 1113 are not limited in any way and may be the same as the dimensions of the thermal printhead A2, for example.

[0070] This modification also allows the glaze layer 12 to have a more appropriate protruding shape. The cross-sectional shapes of the first portion 1111, the second portion 1112, and the third portion 1113 may all be rectangular or trapezoidal, or one may be rectangular and the others may be trapezoidal, or a combination thereof may be used.

[0071] The thermal printhead, thermal printer, and method of manufacturing a thermal printhead according to the present disclosure are not limited to the above-described embodiments. The specific configurations of the thermal printhead, thermal printer, and method of manufacturing a thermal printhead according to the present disclosure can be freely modified in various ways. The present disclosure includes the embodiments described in the following appendices.

[0072] Supplementary Note 1. A thermal printhead comprising: a substrate having a main surface facing a first side in a thickness direction and a back surface facing a second side and including ceramic; a glaze layer disposed on the first side in the thickness direction of the substrate; an electrode layer formed on the glaze layer; and a resistor layer formed on the glaze layer and having a plurality of heat generating portions, wherein the substrate has convex portions that protrude from the main surface to the first side in the thickness direction and extend in a main scanning direction perpendicular to the thickness direction, the glaze layer has a covering portion that covers the convex portions, and the plurality of heat generating portions overlap with the convex portions when viewed in the thickness direction. Supplementary Note 2. The thermal printhead according to Supplementary Note 1, wherein the convex portions include a first portion and a second portion located on the first side in the thickness direction relative to the first portion, and a first dimension that is a size of the first portion in the thickness direction and in a sub-scanning direction perpendicular to the main scanning direction is larger than a second dimension that is a size of the second portion in the sub-scanning direction. Supplementary Note 3. The thermal printhead according to Appendix 2, wherein the second dimension is 50% to 95% of the first dimension. Appendix 4. The thermal printhead according to Appendix 2 or 3, wherein the first portion has a rectangular cross-sectional shape perpendicular to the main scanning direction. Appendix 5. The thermal printhead according to Appendix 4, wherein the second portion has a rectangular cross-sectional shape perpendicular to the main scanning direction. Appendix 6. The thermal printhead according to Appendix 2 or 3, wherein the first portion has a trapezoidal cross-sectional shape perpendicular to the main scanning direction. Appendix 7. The thermal printhead according to Appendix 6, wherein the second portion has a trapezoidal cross-sectional shape perpendicular to the main scanning direction. Appendix 8. The thermal printhead according to any of Appendixes 2 to 7, wherein the thickness in the thickness direction of the first portion is 30 μm to 200 μm. Appendix 9. The thermal printhead according to claim 8, wherein the second portion has a thickness in the thickness direction of 30 μm or more and 200 μm or less. The thermal printhead according to claim 10, wherein the convex portion further includes a third portion located on the first side in the thickness direction relative to the second portion, and a third dimension, which is the size of the third portion in the sub-scanning direction, is smaller than the second dimension.Appendix 11. The thermal printhead of Appendix 10, wherein the third portion has a rectangular cross-sectional shape perpendicular to the main scanning direction. Appendix 12. The thermal printhead of Appendix 10, wherein the third portion has a trapezoidal cross-sectional shape perpendicular to the main scanning direction. Appendix 13. The thermal printhead of any of Appendixes 10 to 12, wherein the third portion has a thickness in the thickness direction of 30 μm to 200 μm. Appendix 14. The thermal printhead of any of Appendixes 1 to 13, wherein the surface of the covering portion of the glaze layer has a cross-sectional shape perpendicular to the main scanning direction that is curved and bulges out toward the first side in the thickness direction. Appendix 15. The thermal printhead of any of Appendixes 1 to 14, wherein the electrode layer includes a common electrode having a plurality of strip-shaped portions and a plurality of individual electrodes, and the plurality of strip-shaped portions and the plurality of individual electrodes are arranged alternately in the main scanning direction. Appendix 16. a thermal printhead according to claim 15, wherein the resistor layer is in a band shape extending in the main scanning direction and spanning the plurality of band-shaped portions and the plurality of individual electrodes; a thermal printer comprising the thermal printhead according to any one of claims 1 to 16; and a method for manufacturing a thermal printhead, comprising the steps of: preparing a substrate having a main surface facing a first side in a thickness direction and a back surface facing a second side, and comprising ceramic; forming convex portions including ceramic, protruding from the main surface to the first side in the thickness direction and extending in a main scanning direction perpendicular to the thickness direction; forming a glaze layer having covering portions that cover the convex portions; forming an electrode layer on the glaze layer; and forming a resistor layer on the glaze layer having a plurality of heating portions that overlap with the convex portions as viewed in the thickness direction.

[0073] A1, A11, A2, A21: thermal print head P1: thermal printer 1: substrate 2: protective layer 3: electrode layer 4: resistor layer 5: connection substrate 5a: second main surface 5b: second back surface 7: driver IC 8: heat dissipation member 11: base material 11a: first main surface (main surface) 11b: first back surface (back surface) 12: glaze layer 31: common electrode 32: strip-shaped portion 33: connecting portion 34: individual electrode 35: strip-shaped portion 36: connecting portion 37: bonding portion 37A: first bonding portion 37B: second bonding portion 41: heat-generating portion 59: connector 61, 62: wire 78: protective resin 81: support surface 111: convex portion 121: flat portion 122: covering portion 331: auxiliary layer 361: parallel portion 362: Oblique portion 1111: First part 1112: Second part 1113: Third part B1: Platen roller C1: Printing medium W1: First dimension W2: Second dimension W3: Third dimension Z1, Z2, Z3: Thickness x: Main scanning direction y: Sub-scanning direction z: Thickness direction

Claims

1. a substrate including a ceramic and having a main surface facing a first side and a back surface facing a second side in a thickness direction; A glaze layer disposed on the first side in the thickness direction of the base material; an electrode layer formed on the glaze layer; a resistor layer formed on the glaze layer and having a plurality of heating portions; the base material has a convex portion protruding from the main surface to the first side in the thickness direction and extending in a main scanning direction perpendicular to the thickness direction, The glaze layer has a covering portion that covers the protrusion, The plurality of heat generating portions overlap with the protrusions when viewed in the thickness direction.

2. The protrusion includes a first portion and a second portion located on the first side in the thickness direction with respect to the first portion, 2. The thermal printhead of claim 1, wherein a first dimension, which is a size of the first portion in the thickness direction and in a sub-scanning direction perpendicular to the main scanning direction, is larger than a second dimension, which is a size of the second portion in the sub-scanning direction.

3. The thermal printhead of claim 2 , wherein the second dimension is greater than or equal to 50% and less than or equal to 95% of the first dimension.

4. The thermal printhead according to claim 2 , wherein the first portion has a rectangular cross-sectional shape perpendicular to the main scanning direction.

5. The thermal printhead according to claim 4 , wherein the second portion has a rectangular cross-sectional shape perpendicular to the main scanning direction.

6. The thermal printhead according to claim 2 , wherein the first portion has a trapezoidal cross section perpendicular to the main scanning direction.

7. The thermal printhead according to claim 6 , wherein the second portion has a trapezoidal cross-sectional shape perpendicular to the main scanning direction.

8. The thermal printhead according to claim 2 , wherein the first portion has a thickness in the thickness direction of at least 30 μm and at most 200 μm.

9. The thermal printhead according to claim 8 , wherein the second portion has a thickness in the thickness direction of 30 μm or more and 200 μm or less.

10. the protruding portion further includes a third portion located on the first side in the thickness direction with respect to the second portion, The thermal printhead according to claim 2 , wherein a third dimension, which is a size of the third portion in the sub-scanning direction, is smaller than the second dimension.

11. The thermal printhead according to claim 10 , wherein the third portion has a rectangular cross-sectional shape perpendicular to the main scanning direction.

12. The thermal printhead according to claim 10 , wherein the third portion has a trapezoidal cross-sectional shape perpendicular to the main scanning direction.

13. The thermal printhead according to claim 10 , wherein the third portion has a thickness in the thickness direction of not less than 30 μm and not more than 200 μm.

14. The thermal printhead according to claim 1 , wherein a surface of the covering portion of the glaze layer has a cross-sectional shape perpendicular to the main scanning direction that is curved and bulges out toward the first side in the thickness direction.

15. the electrode layer includes a common electrode having a plurality of strip-shaped portions and a plurality of individual electrodes; 2. The thermal printhead according to claim 1, wherein the plurality of strip portions and the plurality of individual electrodes are arranged alternately in the main scanning direction.

16. The thermal printhead according to claim 15 , wherein the resistor layer is in a band shape extending in the main scanning direction and spanning the plurality of band-shaped portions and the plurality of individual electrodes.

17. A thermal printer comprising the thermal printhead according to claim 1.

18. A step of preparing a substrate including a ceramic and having a main surface facing a first side and a back surface facing a second side in a thickness direction; forming a protrusion including ceramic, the protrusion protruding from the main surface toward the first side in the thickness direction and extending in a main scanning direction perpendicular to the thickness direction; forming a glaze layer having a covering portion that covers the protrusions; forming an electrode layer on the glaze layer; forming a resistor layer on the glaze layer, the resistor layer having a plurality of heating portions that overlap the protrusions when viewed in the thickness direction.