Thermal printhead and method for manufacturing the same

Abstract

To provide a thermal print head which can improve printing efficiency while reducing friction resistance between a recording medium and the thermal print head, and a method for manufacturing the same.SOLUTION: A thermal print head A10 includes a substrate 11, a resistor layer 30 which includes a plurality of heating parts arranged in a main scanning direction, and is arranged on the substrate 11, a wiring layer 20 which is conducted to the plurality of heating parts and is arranged so as to be brought into contact with the resistor layer 30, and a first protective layer 40 covering at least a part of the wiring layer 20. In the first protective layer 40, slits 41 that extend in the main scanning direction and to which the plurality of heating parts are exposed are formed. The thermal print head A10 includes a second protective layer 50 which is at least partially stored in the slits 41, and covers the plurality of heating parts. Thermal conductivity of the second protective layer 50 is higher than thermal conductivity of the first protective layer 40.SELECTED DRAWING: Figure 8

Description

[Technical Field]

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

[0002] A thermal printhead is a main component of a thermal printer that prints on a recording medium such as thermal paper. Patent Document 1 discloses an example of a thermal printhead. The thermal printhead includes a substrate, a common electrode and a plurality of individual electrodes arranged on the substrate, and a heating resistor connected to the common electrode and the plurality of individual electrodes. Electricity is passed through the common electrode and the plurality of individual electrodes to selectively heat the heating resistor, thereby printing dots on the recording medium.

[0003] The thermal printhead disclosed in Patent Document 1 further includes a protective layer that covers the heating resistor. This protects the heating resistor from external influences while reducing frictional resistance between the recording medium and the thermal printhead. However, when heat generated by the heating resistor is transmitted through the protective layer, heat loss occurs in the protective layer. Therefore, depending on the environment in which the thermal printhead is used, the protective layer may cause a decrease in printing efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-240641 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above circumstances, an object of the present disclosure is to provide a thermal printhead that can improve printing efficiency while reducing frictional resistance with a recording medium, and a method for manufacturing the same. [Means for solving the problem]

[0006] A thermal printhead provided by a first aspect of the present disclosure includes a substrate, a plurality of heat generating elements arranged in a main scanning direction, and a resistor layer disposed on the substrate, a wiring layer electrically connected to the plurality of heat generating elements and disposed in contact with the resistor layer, and a first protective layer covering at least a portion of the wiring layer, wherein the first protective layer has slits formed therein extending in the main scanning direction and exposing the plurality of heat generating elements, and further includes a second protective layer at least a portion of which is accommodated in the slits and covers the plurality of heat generating elements, and the thermal conductivity of the second protective layer is higher than that of the first protective layer.

[0007] A method for manufacturing a thermal printhead provided by a second aspect of the present disclosure includes the steps of: forming a resistor layer on a substrate, the resistor layer including a plurality of heat generating portions arranged in a main scanning direction; forming a wiring layer that is conductive to the plurality of heat generating portions and in contact with the resistor layer; and forming a first protective layer that covers at least a portion of the wiring layer, wherein in the step of forming the first protective layer, slits that extend in the main scanning direction and through which the plurality of heat generating portions are exposed are formed in the first protective layer; and after the step of forming the first protective layer, the method further includes the step of forming a second protective layer that covers the plurality of heat generating portions and has a thermal conductivity higher than that of the first protective layer, wherein in the step of forming the second protective layer, at least a portion of the second protective layer is accommodated in the slits. [Effects of the Invention]

[0008] The thermal printhead and method of manufacturing the same according to the present disclosure can improve printing efficiency while reducing frictional resistance with the recording medium.

[0009] Other features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a plan view of a thermal printhead according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a bottom view of the thermal printhead shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a partially enlarged plan view of the thermal printhead shown in FIG. 1, with the first and second protective layers not shown. [Figure 5] FIG. 5 is a partially enlarged view of FIG. 4, in which the second protective layer is not shown. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 8 is a partially enlarged view of FIG. [Figure 9] 9A to 9C are cross-sectional views illustrating the manufacturing process of the thermal printhead shown in FIG. [Figure 10] 10A to 10C are cross-sectional views illustrating the manufacturing process of the thermal printhead shown in FIG. [Figure 11] 11A to 11C are cross-sectional views illustrating the manufacturing process of the thermal printhead shown in FIG. [Figure 12] 12A to 12C are cross-sectional views illustrating the manufacturing process of the thermal printhead shown in FIG. [Figure 13] FIG. 13 is a partially enlarged view of FIG. [Figure 14] 14A to 14C are cross-sectional views illustrating the manufacturing process of the thermal printhead shown in FIG. [Figure 15] FIG. 15 is a cross-sectional view of a thermal printhead according to the second embodiment of the present disclosure. [Figure 16] FIG. 16 is a cross-sectional view of the thermal printhead shown in FIG. 15, but the cross-sectional position is different from that of FIG. [Figure 17] FIG. 17 is a partially enlarged view of FIG. [Figure 18]18A to 18C are cross-sectional views illustrating the manufacturing process of the thermal printhead shown in FIG. [Figure 19] 19A to 19C are cross-sectional views illustrating the manufacturing process of the thermal printhead shown in FIG. [Figure 20] FIG. 20 is a cross-sectional view of a thermal printhead according to a third embodiment of the present disclosure. [Figure 21] FIG. 21 is a cross-sectional view of the thermal printhead shown in FIG. 20, but the cross-sectional position is different from that of FIG. [Figure 22] FIG. 22 is a partially enlarged view of FIG. [Figure 23] FIG. 23 is a cross-sectional view of a thermal printhead according to a fourth embodiment of the present disclosure. [Figure 24] FIG. 24 is a cross-sectional view of the thermal printhead shown in FIG. 23, but the cross-sectional position is different from that of FIG. [Figure 25] FIG. 25 is a partially enlarged plan view of a thermal printhead according to a fifth embodiment of the present disclosure, with the second protective layer not shown. [Figure 26] FIG. 26 is a cross-sectional view taken along line XXVI-XXVI in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0012] [First embodiment] A thermal printhead A10 according to a first embodiment of the present disclosure will be described with reference to Figures 1 to 8. The thermal printhead A10 includes a substrate 11, a glaze layer 12, a wiring layer 20, a resistor layer 30, a first protective layer 40, and a second protective layer 50. The thermal printhead A10 also includes a driving IC 71, a sealing resin 72, a connector 73, and a heat dissipation member 74. For ease of understanding, the first protective layer 40 and the second protective layer 50 are omitted from Figure 4. For ease of understanding, the second protective layer 50 is omitted from Figure 5.

[0013] The thermal printhead A10 shown in these figures is an electronic device that prints on a recording medium 81 such as thermal paper by selectively generating heat in multiple heat generating elements 31 (described in detail below) contained in a resistor layer 30, as shown in FIG. 3. The resistor layer 30 is formed by printing and baking. Therefore, the thermal printhead A10 is known as a thick-film type.

[0014] For ease of explanation, the main scanning direction of the thermal printhead A10 is referred to as the "x direction." The sub-scanning direction of the thermal printhead A10 is referred to as the "y direction." The thickness direction of the substrate 11 is referred to as the "z direction." The z direction is perpendicular to both the x direction and the y direction. In the following explanation, "viewed along the z direction" means "viewed along the thickness direction."

[0015] As shown in FIGS. 1 and 2, the substrate 11 has a strip shape extending in the x-direction. The composition of the substrate 11 includes alumina (Al2O3). The substrate 11 is a ceramic made of a material including alumina and a resin binder. The material of the substrate 11 may also include a light-shielding material. The light-shielding material is, for example, carbon (C).

[0016] As shown in Figures 6 and 7, the glaze layer 12 is located between the substrate 11 and the wiring layer 20 in the z direction. The glaze layer 12 is made of a material containing amorphous glass. The amorphous glass is, for example, SiO2-BaO-Al2O3-SnO-ZnO-based glass. Therefore, the glaze layer 12 is transparent or white.

[0017] 6 and 7, the substrate 11 has a main surface 111. The main surface 111 faces the glaze layer 12. The glaze layer 12 is in contact with the main surface 111 and covers the entire main surface 111.

[0018] As shown in FIGS. 1 and 4, the wiring layer 20 is disposed on the substrate 11. The wiring layer 20 forms a conductive path for supplying electricity to the resistor layer 30. The wiring layer 20 is in contact with the glaze layer 12. The wiring layer 20 includes a common wiring 21 and a plurality of individual wirings 22. In the thermal printhead A10, current flows from the common wiring 21 to the plurality of individual wirings 22 via the resistor layer 30. Therefore, the common wiring 21 is a positive electrode, and the plurality of individual wirings 22 are a negative electrode. An example of a material for the wiring layer 20 is a resinate paste containing gold (Au) as a main component. An example of the thickness range of the wiring layer 20 is 0.6 μm or more and 1.2 μm or less.

[0019] 4 and 5, the common wiring 21 has a connecting portion 212 and a plurality of first strip portions 211. The connecting portion 212 is positioned apart from the resistor layer 30 in the y direction and has a strip shape extending in the x direction.

[0020] As shown in FIGS. 4 and 5, the multiple first strip portions 211 extend from the connecting portion 212 toward the resistor layer 30. The multiple first strip portions 211 are arranged at equal intervals in the x direction. The multiple first strip portions 211 have a base portion 211A and an extending portion 211B. The base portion 211A is rectangular. One side of the base portion 211A in the y direction is connected to the connecting portion 212. The extending portion 211B extends from the other side of the base portion 211A in the y direction toward the resistor layer 30. The width (dimension in the x direction) of the extending portion 211B is smaller than the width (dimension in the x direction) of the base portion 211A. The width of the extending portion 211B is 25 μm or less.

[0021] As shown in Figures 4 and 5, the multiple individual wires 22 extend in the y direction. The multiple individual wires 22 are arranged on the substrate 11 in bundles corresponding to the individual driving ICs 71. The multiple individual wires 22 apply voltage to individually selected portions of the resistor layer 30. The multiple individual wires 22 are arranged in the x direction. The multiple individual wires 22 have a second strip portion 221, an intermediate portion 222, and a connection portion 223.

[0022] As shown in FIGS. 4 and 5, the second strip portion 221 has a strip shape extending in the y direction. The second strip portion 221 is located between two first strip portions 211 adjacent to each other in the x direction among the multiple common wirings 21 of the common wiring 21. The second strip portion 221 has a base portion 221A and an extending portion 221B. The base portion 221A is rectangular. One side of the base portion 221A in the y direction is connected to the intermediate portion 222. The extending portion 221B extends from the other side of the base portion 221A in the y direction toward the resistor layer 30. The width (dimension in the x direction) of the extending portion 221B is smaller than the width (dimension in the x direction) of the base portion 221A. The width of the extending portion 221B is 25 μm or less.

[0023] As shown in FIGS. 4 and 5, the intermediate portion 222 connects the second strip portion 221 and the connecting portion 223. The intermediate portion 222 has a parallel portion 222A and an oblique portion 222B. The parallel portion 222A is connected to the connecting portion 223 on one side in the y direction and extends along the y direction. The width (dimension in the x direction) of the parallel portion 222A is 20 μm or less. The oblique portion 222B is inclined with respect to the y direction. The oblique portion 222B is connected to the base portion 221A of the second strip portion 221 on one side in the y direction and to the parallel portion 222A on the other side in the y direction. As shown in FIG. 4, in the multiple individual wirings 22 arranged in bundles corresponding to individual driving ICs 71, the boundary positions between the parallel portion 222A and the oblique portion 222B are shifted in the y direction by ΔL when compared at both ends in the x direction.

[0024] As shown in FIG. 4, the connection portion 223 is located on the opposite side of the intermediate portion 222 from the second strip portion 221 in the y direction. The connection portion 223 is connected to the parallel portion 222A of the intermediate portion 222. The connection portion 223 includes a first connection portion 223A and a second connection portion 223B. The second connection portion 223B is located further away from the first connection portion 223A in the y direction. As a result, the first connection portions 223A of the multiple individual wirings 22 and the second connection portions 223B of the multiple individual wirings 22 are staggered in the x direction. The width (dimension in the x direction) of the parallel portion 222A connected to the second connection portion 223B and located between two adjacent first connection portions 223A is 10 μm or less. A plurality of wires 75 are individually connected to the connection portions 223 of the multiple individual wirings 22. The composition of the plurality of wires 75 includes, for example, gold.

[0025] As shown in FIGS. 1 and 4, the resistor layer 30 has a strip shape extending in the x-direction. The resistor layer 30 is in contact with the glaze layer 12. The resistor layer 30 intersects with the multiple first strip portions 211 of the common wiring 21 and the multiple second strip portions 221 of the multiple individual wirings 22. The resistor layer 30 covers a portion of each of the multiple first strip portions 211 and the multiple second strip portions 221 of the multiple individual wirings 22. In the thermal printhead A10, the resistor layer 30 straddles the multiple first strip portions 211 and the multiple second strip portions 221.

[0026] The region of the resistor layer 30 sandwiched between a portion covering one of the plurality of first strip portions 211 and a portion covering one of the second strip portions 221 of the plurality of individual wirings 22 adjacent to the portion in the x direction is defined as a heat generating portion 31. This results in the resistor layer 30 including a plurality of heat generating portions 31 arranged in the x direction and electrically connected to the wiring layer 20. The plurality of heat generating portions 31 selectively generate heat when selectively energized by the wiring layer 20. This results in dot printing on the recording medium 81 shown in FIG. 3. The material of the resistor layer 30 is selected to have a higher electrical resistivity than the wiring layer 20. One example of the material of the resistor layer 30 is a conductive paste containing ruthenium oxide (RuO2) particles and glass frit. The maximum thickness of the resistor layer 30 is 6 μm or more and 10 μm or less.

[0027] 6 and 7, the first protective layer 40 is in contact with the glaze layer 12. The first protective layer 40 covers at least a portion of the wiring layer 20. In the thermal printhead A10, the first protective layer 40 covers the wiring layer 20 except for a portion of the multiple individual wires 22 including the connection portions 223. The first protective layer 40 is made of a material containing amorphous glass, like the glaze layer 12.

[0028] As shown in FIGS. 5 to 7, slits 41 are formed in the first protective layer 40. The slits 41 penetrate the first protective layer 40 in the z direction and extend in the x direction. A plurality of heat generating portions 31 of the resistor layer 30 are exposed through the slits 41. The dimension b2 of the slits 41 in the y direction is greater than the dimension b2 of each of the heat generating portions 31 in the y direction. As shown in FIGS. 5 and 8, the slits 41 have a pair of inner surfaces 411. The pair of inner surfaces 411 are spaced apart from each other in the y direction. As shown in FIGS. 6 and 7, the first protective layer 40 has a first surface 42. The first surface 42 faces the opposite side of the resistor layer 30 from the side on which the substrate 11 is located in the z direction, i.e., faces the same side as the main surface 111 of the substrate 11 in the z direction. The pair of inner surfaces 411 are connected to the first surface 42.

[0029] As shown in FIGS. 6 and 7, the second protective layer 50 covers the multiple heat generating portions 31 of the resistor layer 30. At least a portion of the second protective layer 50 is accommodated in the slits 41 of the first protective layer 40. The second protective layer 50 is made of a material containing amorphous glass, similar to the glaze layer 12. As shown in FIG. 8, the second protective layer 50 contains a first substrate 501 and a second substrate 502. The first substrate 501 is composed of silicon dioxide (SiO2). The first substrate 501 forms part of the amorphous glass that constitutes the second protective layer 50.

[0030] The thermal conductivity of the second substrate 502 is higher than that of the first substrate 501. The weight percentage (wt%) of the second substrate 502 relative to the second protective layer 50 is higher than that of the first substrate 501. The composition of the second substrate 502 having such properties is, for example, silicon (Si). The weight percentage of the second substrate 502 relative to the second protective layer 50 is 50% or more and 98% or less. The second substrate 502 is in a state of being melted into the amorphous glass. Therefore, in FIG. 8, the second substrate 502 is conceptually shown by an imaginary line. As a result, the thermal conductivity of the second protective layer 50 is higher than that of the first protective layer 40.

[0031] As shown in FIGS. 6 and 7, the second protective layer 50 has a first portion 51 and a second portion 52. The first portion 51 is housed in the slit 41 of the first protective layer 40. As shown in FIG. 8, the first portion 51 contacts the glaze layer 12, the resistor layer 30, and a pair of inner surfaces 411 of the slit 41. The second portion 52 is connected to the first portion 51 and protrudes from the slit 41. The second portion 52 contacts the first surface 42 of the first protective layer 40. In the thermal printhead A10, the second portion 52 covers the first surface 42. The second portion 52 has a second surface 521. The second surface 521 faces the same side as the first surface 42 of the first protective layer 40 in the z direction. The thickness t2 of the second portion 52 is thinner than the thickness t1 of the first protective layer 40. The thickness t2 is the maximum value of the dimension from the second surface 521 to the first surface 42 in the z direction.

[0032] In the thermal printhead A10, the thermal conductivity of the glaze layer 12 is set to be lower than the thermal conductivity of the second substrate 502.

[0033] As shown in FIGS. 1 and 3 , the driving IC 71 is located on the other side of the resistor layer 30 in the y direction. The driving IC 71 is mounted on the substrate 11. A plurality of pads (not shown) are provided on the upper surface of the driving IC 71. Some of the pads are connected to a plurality of wires 75 connected to the connection portions 223 of the plurality of individual wirings 22 corresponding to the driving IC 71. This allows the driving IC 71 to be electrically connected to the corresponding plurality of individual wirings 22. Other pads are connected to a plurality of wires 75 connected to wiring arranged on the substrate 11. The driving IC 71 selectively energizes the plurality of individual wirings 22 via the plurality of wires 75. This causes the plurality of heat generating portions 31 included in the resistor layer 30 to selectively generate heat. Alternatively, the driving IC 71 may be mounted on a wiring substrate that is separated from the substrate 11 in the y direction and supported by a heat dissipation member 74. The wiring substrate is, for example, a flexible substrate.

[0034] 3, the sealing resin 72 covers the driving IC 71 and the plurality of wires 75. In addition to these, the sealing resin 72 also covers some areas (such as the plurality of connection portions 223) of the plurality of individual wirings 22 that are not covered by the first protective layer 40. The sealing resin 72 is a black, soft resin that is used, for example, for underfill.

[0035] As shown in FIGS. 1 to 3, the connector 73 is disposed at an end of the substrate 11 located on the opposite side of the resistor layer 30 from the driving IC 71 in the y direction. The connector 73 is used to connect the thermal printhead A10 to a thermal printer. The connector 73 is connected to wiring disposed on the substrate 11. This establishes electrical continuity between the connector 73 and the individual wirings 22 via the wiring, the driving IC 71, and the plurality of wires 75. The connector 73 is also electrically connected to the connecting portion 212 of the common wiring 21 via the wiring.

[0036] 3, the heat dissipation member 74 is located on the opposite side of the substrate 11 from the resistor layer 30 in the z direction. The substrate 11 is bonded to the heat dissipation member 74 via a bonding material (not shown). The composition of the heat dissipation member 74 includes, for example, aluminum (Al).

[0037] Next, the operation of the thermal printhead A10 will be described.

[0038] As shown in FIG. 3 , the multiple heat-generating elements 31 of the thermal printhead A10 face a platen roller 82 incorporated in the thermal printer via the first protective layer 40. A recording medium 81 is sandwiched between the platen roller 82 and the area of ​​the first protective layer 40 that covers the multiple heat-generating elements 31. When the thermal printer is operating, the platen roller 82 rotates, feeding the recording medium 81 at a constant speed. When this occurs, the multiple heat-generating elements 31 selectively generate heat, and the heat is transferred to the recording medium 81 via the first protective layer 40, thereby printing on the recording medium 81. At the same time, the heat generated by the multiple heat-generating elements 31 is also transferred to the glaze layer 12. Some of this heat is stored in the glaze layer 12. The remainder of the heat is released to the outside of the thermal printhead A10 via the substrate 11 and the heat dissipation member 74.

[0039] Next, an example of a method for manufacturing the thermal printhead A10 will be described with reference to Figures 9 to 14. The cross-sectional positions of Figures 9 to 12 and Figure 14 are the same as those of Figure 7.

[0040] First, as shown in Fig. 9, a glaze layer 12 is formed on a substrate 11. The glaze layer 12 is formed by thick-printing an amorphous glass paste and then firing it. As a result, the main surface 111 of the substrate 11 is covered with the glaze layer 12.

[0041] 10, the wiring layer 20 is formed on the glaze layer 12. To form the wiring layer 20, first, a resinate paste containing gold as a main component is thick-film printed and then fired to form a conductor layer. The conductor layer is then patterned by etching to form the wiring layer 20.

[0042] Next, as shown in FIG. 11 , a resistor layer 30 including a plurality of heating elements 31 electrically connected to the wiring layer 20 is formed. To form the resistor layer 30, a paste containing a metal element is first thick-film printed in a strip shape extending in the x direction. The paste contains ruthenium oxide particles and glass frit. The paste is thick-film printed so that it contacts the glaze layer 12 and the wiring layer 20. The paste is then fired. Finally, the fired paste is appropriately trimmed to adjust its resistance, thereby forming the resistor layer 30.

[0043] Next, as shown in FIG. 12, a first protective layer 40 is formed in contact with the glaze layer 12 and covering a portion of the wiring layer 20. The first protective layer 40 is formed by thick-film printing of an amorphous glass paste and then firing the thick-film printing. During the thick-film printing, slits 41 extending in the y direction are formed in the first protective layer 40. As shown in FIG. 13, a plurality of heat generating portions 31 of the resistor layer 30 are exposed through the slits 41.

[0044] 14, a second protective layer 50 is formed to cover the heat generating portions 31 of the resistor layer 30 and to have a higher thermal conductivity than the first protective layer 40. In manufacturing the thermal printhead A10, the second protective layer 50 is formed by thick-film printing a paste containing amorphous glass including a first base material 501 and a powdery second base material 502, followed by firing the paste. As a result, at least a portion of the second protective layer 50 is accommodated in the slits 41 of the first protective layer 40. In manufacturing the thermal printhead A10, the second protective layer 50 is configured to cover the first surface 42 of the first protective layer 40.

[0045] After forming the second protective layer 50, a driving IC 71 is mounted on the glaze layer 12 by die bonding. Next, multiple wires 75 are formed by wire bonding, and then a sealing resin 72 is formed. Next, the substrate 11 is cut along the y direction. Finally, a connector 73 and a heat dissipation member 74 are attached to the substrate 11, thereby obtaining the thermal printhead A10.

[0046] Next, the effects of the thermal printhead A10 will be described.

[0047] The first protective layer 40 of the thermal printhead A10 covers at least a portion of the wiring layer 20. The first protective layer 40 has slits 41 through which the multiple heat generating elements 31 of the resistor layer 30 are exposed. The thermal printhead A10 further includes a second protective layer 50, at least a portion of which is accommodated in the slits 41 and which covers the multiple heat generating elements 31. The thermal conductivity of the second protective layer 50 is higher than that of the first protective layer 40. This configuration reduces the frictional resistance of the thermal printhead A10 to the recording medium 81 (see FIG. 3 ), and allows heat to be conducted more quickly from the multiple heat generating elements 31 to the recording medium 81. Therefore, the thermal printhead A10 can improve printing efficiency while reducing frictional resistance with the recording medium 81.

[0048] The first protective layer 40 covers at least a portion of the wiring layer 20. This reduces the frictional resistance of the recording medium 81 against the thermal printhead A10, while suppressing an increase in the thermal resistance of the wiring layer 20 due to current.

[0049] In the thermal printhead A10, the second protective layer 50 has a first portion 51 accommodated in the slit 41 of the first protective layer 40, and a second portion 52 connected to the first portion 51 and covering the first surface 42 of the first protective layer 40. The thickness t2 of the second portion 52 is thinner than the thickness t1 of the first protective layer 40. This makes it possible to suppress a decrease in the rate of heat conduction from the multiple heat generating portions 31 of the resistor layer 30 to the recording medium 81.

[0050] The glaze layer 12 has the function of storing a portion of the heat generated by the plurality of heat generating portions 31 of the resistor layer 30. For example, when the thermal printhead A10 is used in a cold climate, the heat storage function of the glaze layer 12 can suppress a sudden drop in temperature of the plurality of resistor layers 30. This prevents deterioration of print quality. In this configuration, it is preferable that the glaze layer 12 covers the entire main surface 111 of the substrate 11.

[0051] Furthermore, in order for the glaze layer 12 to exert the above-mentioned effects, it is preferable that the thermal conductivity of the glaze layer 12 be lower than the thermal conductivity of the second protective layer 50 .

[0052] Second Embodiment A thermal printhead A20 according to a second embodiment of the present disclosure will be described with reference to Figures 15 to 17. In these figures, elements that are the same as or similar to those in the thermal printhead A10 described above are designated by the same reference numerals, and duplicate explanations will be omitted. The cross-sectional position in Figure 15 is the same as the cross-sectional position in Figure 6, which shows the thermal printhead A10. The cross-sectional position in Figure 16 is the same as the cross-sectional position in Figure 7, which shows the thermal printhead A10.

[0053] The thermal printhead A20 differs from the thermal printhead A10 in the configuration of the second protective layer 50. The thermal printhead A20 further comprises a third protective layer 60 in addition to the thermal printhead A10.

[0054] 15 to 17, in the thermal printhead A20, the second protective layer 50 is made up of a first portion 51. Therefore, the second protective layer 50 is exposed from the slit 41 of the first protective layer 40.

[0055] As shown in FIGS. 15 to 17, the third protective layer 60 covers the second protective layer 50 and the first surface 42 of the first protective layer 40. The thermal conductivity of the third protective layer 60 is higher than that of the first protective layer 40. In the thermal printhead A20, the thermal conductivity of the third protective layer 60 is higher than that of the second protective layer 50. Furthermore, the Vickers hardness of the third protective layer 60 is higher than that of the first protective layer 40. The composition of the third protective layer 60 includes silicon carbide (SiC).

[0056] Next, an example of a method for manufacturing the thermal printhead A20 will be described with reference to Figures 18 and 19. The cross-sectional positions of Figures 18 and 19 are the same as those of Figure 16.

[0057] The manufacturing process of the thermal printhead A20 is the same as that of the thermal printhead A10 from the step of forming the glaze layer 12 to the step of forming the first protective layer 40. Therefore, in the description of the manufacturing method of the thermal printhead A20, the description of the steps up to the step of forming the first protective layer 40 will be omitted.

[0058] After forming the first protective layer 40, the second protective layer 50 is formed as shown in Fig. 18. The second protective layer 50 is formed by filling the slits 41 of the first protective layer 40 with the same material as the second protective layer 50 of the thermal printhead A10 using a dispenser, and then baking it.

[0059] 19, a third protective layer 60 is formed to cover the first protective layer 40 and the second protective layer 50 and to have a higher thermal conductivity and Vickers hardness than the first protective layer 40. The third protective layer 60 is formed by depositing a thin film of silicon carbide on the first protective layer 40 and the second protective layer 50 by sputtering.

[0060] After forming the third protective layer 60, a driving IC 71 is mounted on the glaze layer 12 by die bonding. Next, multiple wires 75 are formed by wire bonding, and then a sealing resin 72 is formed. Next, the substrate 11 is cut along the y direction. Finally, a connector 73 and a heat dissipation member 74 are attached to the substrate 11, thereby obtaining the thermal printhead A20.

[0061] Next, the effects of the thermal printhead A20 will be described.

[0062] The first protective layer 40 of the thermal printhead A20 covers at least a portion of the wiring layer 20. The first protective layer 40 has slits 41 formed therein, through which the plurality of heat generating elements 31 of the resistor layer 30 are exposed. The thermal printhead A20 further includes a second protective layer 50, at least a portion of which is accommodated in the slits 41 and which covers the plurality of heat generating elements 31. The thermal conductivity of the second protective layer 50 is higher than that of the first protective layer 40. Therefore, the thermal printhead A20 can also improve printing efficiency while reducing frictional resistance with the recording medium 81. Furthermore, by sharing a configuration in common with the thermal printhead A10, the thermal printhead A20 achieves the same effects as the thermal printhead A10.

[0063] The thermal printhead A20 further includes a third protective layer 60 that covers the second protective layer 50 and the first surface 42 of the first protective layer 40. The third protective layer 60 has a higher thermal conductivity and Vickers hardness than the first protective layer 40. This makes it possible to suppress heat loss from the multiple heat generating portions 31 of the resistor layer 30 to the recording medium 81, while also preventing wear on the first protective layer 40 and the second protective layer 50 due to repeated contact with the recording medium 81.

[0064] Third Embodiment A thermal printhead A30 according to a third embodiment of the present disclosure will be described with reference to Figures 20 to 22. In these figures, elements that are the same as or similar to those in the thermal printhead A10 described above are designated by the same reference numerals, and redundant explanations will be omitted. The cross-sectional position in Figure 20 is the same as the cross-sectional position in Figure 6, which shows the thermal printhead A10. The cross-sectional position in Figure 21 is the same as the cross-sectional position in Figure 7, which shows the thermal printhead A10.

[0065] In the thermal printhead A30, the configuration of the second protective layer 50 differs from that of the thermal printhead A10 described above.

[0066] 20 to 22, in the thermal printhead A30, the second portion 52 of the second protective layer 50 covers part of the slit 41 of the first protective layer 40. The second surface 521 of the second portion 52 is curved convexly in the z direction. Therefore, the second portion 52 bulges in the z direction. The thickness t2 of the second portion 52 is greater than the thickness t1 of the first protective layer 40.

[0067] Next, the effects of the thermal printhead A30 will be described.

[0068] The first protective layer 40 of the thermal printhead A30 covers at least a portion of the wiring layer 20. The first protective layer 40 has slits 41 formed therein, through which the plurality of heat generating elements 31 of the resistor layer 30 are exposed. The thermal printhead A30 further includes a second protective layer 50, at least a portion of which is accommodated in the slits 41 and which covers the plurality of heat generating elements 31. The thermal conductivity of the second protective layer 50 is higher than that of the first protective layer 40. Therefore, the thermal printhead A30 can also improve printing efficiency while reducing frictional resistance with the recording medium 81. Furthermore, by sharing a configuration common to the thermal printhead A10, the thermal printhead A30 achieves the same effects as the thermal printhead A10.

[0069] In the thermal printhead A30, the second portion 52 of the second protective layer 50 bulges in the z direction. This reduces the contact area between the recording medium 81 and the second protective layer 50 compared to the thermal printhead A10. This improves printing efficiency and print quality.

[0070] [Fourth embodiment] A thermal printhead A40 according to a fourth embodiment of the present disclosure will be described with reference to Figures 23 and 24. In these figures, elements that are the same as or similar to those in the thermal printhead A10 described above are designated by the same reference numerals, and duplicate explanations will be omitted. The cross-sectional position in Figure 23 is the same as the cross-sectional position in Figure 6, which shows the thermal printhead A10. The cross-sectional position in Figure 24 is the same as the cross-sectional position in Figure 7, which shows the thermal printhead A10.

[0071] The thermal printhead A40 further comprises a third protective layer 60 in addition to the thermal printhead A30 described above.

[0072] 23 and 24, the third protective layer 60 covers the second portion 52 of the second protective layer 50 and the first surface 42 of the first protective layer 40. The rest of the configuration of the third protective layer 60 is the same as the configuration of the third protective layer 60 of the thermal printhead A20 described above.

[0073] Next, the effects of the thermal printhead A40 will be described.

[0074] The first protective layer 40 of the thermal printhead A40 covers at least a portion of the wiring layer 20. The first protective layer 40 has slits 41 formed therein, through which the plurality of heat generating elements 31 of the resistor layer 30 are exposed. The thermal printhead A40 further includes a second protective layer 50, at least a portion of which is accommodated in the slits 41 and which covers the plurality of heat generating elements 31. The thermal conductivity of the second protective layer 50 is higher than that of the first protective layer 40. Therefore, the thermal printhead A40 can also improve printing efficiency while reducing frictional resistance with the recording medium 81. Furthermore, by sharing a configuration common to the thermal printhead A10, the thermal printhead A40 achieves the same effects as the thermal printhead A10.

[0075] The thermal printhead A40 further includes a third protective layer 60 that covers the second portion 52 of the second protective layer 50 and the first surface 42 of the first protective layer 40. The third protective layer 60 has a higher thermal conductivity and Vickers hardness than the first protective layer 40. This reduces heat loss from the multiple heat generating portions 31 of the resistor layer 30 to the recording medium 81, while preventing wear on the second portion 52 due to repeated contact with the recording medium 81. This therefore prolongs the effect of improving print quality achieved by the second portion 52, which has the same configuration as the thermal printhead A30.

[0076] Fifth Embodiment A thermal printhead A50 according to a fifth embodiment of the present disclosure will be described with reference to Figures 25 and 26. In these figures, elements that are the same as or similar to those in the thermal printhead A10 described above are designated by the same reference numerals, and duplicate explanations will be omitted. For ease of understanding, the second protective layer 50 is not shown in Figure 25.

[0077] In the thermal printhead A50, the configurations of the wiring layer 20 and resistor layer 30 differ from those of the thermal printhead A10 described above.

[0078] 25 and 26, in the thermal printhead A50, the second strip portions 221 of the individual wires 22 are arranged to individually face the first strip portions 211 of the common wire 21 in the y direction. Gaps are provided between the second strip portions 221 of the individual wires 22 and the first strip portions 211. The heat generating portions 31 of the resistor layers 30 are located in these gaps in the y direction. Therefore, the heat generating portions 31 are sandwiched between the second strip portions 221 of the individual wires 22 and the first strip portions 211 in the y direction.

[0079] Next, the effects of the thermal printhead A50 will be described.

[0080] The first protective layer 40 of the thermal printhead A50 covers at least a portion of the wiring layer 20. The first protective layer 40 has slits 41 formed therein, through which the plurality of heat generating elements 31 of the resistor layer 30 are exposed. The thermal printhead A50 further includes a second protective layer 50, at least a portion of which is accommodated in the slits 41 and which covers the plurality of heat generating elements 31. The thermal conductivity of the second protective layer 50 is higher than that of the first protective layer 40. Therefore, the thermal printhead A50 can also improve printing efficiency while reducing frictional resistance with the recording medium 81. Furthermore, by sharing a configuration in common with the thermal printhead A10, the thermal printhead A50 achieves the same effects as the thermal printhead A10.

[0081] In the thermal printhead A50, the configurations of the first protective layer 40 and the second protective layer are the same as those of the thermal printhead A10. However, the configurations of the first protective layer 40, second protective layer 50, and third protective layer 60 provided in each of the thermal printheads A20 to A40 can also be selectively applied to the thermal printhead A50.

[0082] The present disclosure is not limited to the above-described embodiment, and the specific configuration of each part of the present disclosure can be freely modified in various ways.

[0083] The technical configuration of the thermal printhead and the manufacturing method thereof provided by the present disclosure will be described below. [Appendix 1] A substrate; a resistor layer including a plurality of heat generating portions arranged in a main scanning direction and disposed on the substrate; a wiring layer that is electrically connected to the plurality of heat generating portions and is disposed in contact with the resistor layer; a first protective layer that covers at least a portion of the wiring layer; the first protective layer has slits formed therein, the slits extending in the main scanning direction and exposing the plurality of heat generating portions; a second protective layer at least partially accommodated in the slit and covering the plurality of heat generating portions; A thermal printhead, wherein the second protective layer has a higher thermal conductivity than the first protective layer. [Appendix 2] the second protective layer includes a first substrate and a second substrate, The composition of the first substrate is silicon dioxide; the thermal conductivity of the second substrate is higher than the thermal conductivity of the first substrate; 2. A thermal printhead as described in Appendix 1, wherein the weight percentage of the second protective layer is higher in the second substrate than in the first substrate. [Appendix 3] 3. A thermal printhead as described in Appendix 2, wherein the second substrate is composed of silicon. [Appendix 4] 4. The thermal printhead according to claim 1, wherein the dimension of the slit in the sub-scanning direction is larger than the dimension of each of the plurality of heat generating elements in the sub-scanning direction. [Appendix 5] the slit includes a pair of inner surfaces spaced apart from each other in the sub-scanning direction, 5. The thermal printhead according to claim 1, wherein the second protective layer is in contact with the pair of inner surfaces. [Appendix 6] the first protective layer has a first surface facing a side opposite to a side on which the substrate is located with respect to the resistor layer in a thickness direction of the substrate, 6. A thermal printhead as described in Appendix 5, wherein the pair of inner surfaces are connected to the first surface. [Appendix 7] 7. The thermal printhead of claim 6, wherein the second protective layer covers the first surface. [Appendix 8] 7. The thermal printhead of claim 6, wherein the second protective layer is exposed from the first surface. [Appendix 9] a third protective layer covering the second protective layer and the first surface; 9. The thermal printhead of claim 8, wherein the third protective layer has a higher thermal conductivity than the first protective layer. [Appendix 10] 10. The thermal printhead of claim 9, wherein the third protective layer has a higher Vickers hardness than the first protective layer. [Appendix 11] 11. A thermal printhead as described in claim 10, wherein the composition of the third protective layer includes silicon carbide. [Appendix 12] a glaze layer positioned between the substrate and the wiring layer in a thickness direction of the substrate, 12. The thermal printhead according to any one of claims 1 to 11, wherein the wiring layer is in contact with the glaze layer. [Appendix 13] the substrate has a main surface facing the glaze layer, 13. The thermal printhead of claim 12, wherein the main surface is in contact with the glaze layer. [Appendix 14] 14. The thermal printhead of claim 13, wherein the glaze layer covers the entire main surface. [Appendix 15] 15. A thermal printhead according to any one of claims 12 to 14, wherein the thermal conductivity of the glaze layer is lower than the thermal conductivity of the second protective layer. [Appendix 16] forming a resistor layer on a substrate, the resistor layer including a plurality of heat generating portions arranged in a main scanning direction; forming a wiring layer that is electrically connected to the plurality of heat generating portions and that is in contact with the resistor layer; forming a first protective layer that covers at least a portion of the wiring layer; In the step of forming the first protective layer, slits extending in the main scanning direction and exposing the plurality of heat generating portions are formed in the first protective layer; the step of forming a second protective layer that covers the plurality of heat generating portions and has a thermal conductivity higher than that of the first protective layer is further included after the step of forming the first protective layer; In the step of forming the second protective layer, at least a portion of the second protective layer is accommodated in the slit. [Appendix 17] 17. The method for manufacturing a thermal printhead according to claim 16, wherein the first protective layer and the second protective layer are formed by firing. [Appendix 18] the step of forming the second protective layer further includes a step of forming a third protective layer that covers the first protective layer and the second protective layer and has a thermal conductivity and a Vickers hardness higher than those of the first protective layer, 18. The method for manufacturing a thermal printhead according to claim 16 or 17, wherein the third protective layer is formed by sputtering. [Explanation of symbols]

[0084] A10, A20, A30, A40, A50: Thermal printhead 11: Circuit board 111: Main surface 12: Glaze layer 20: Wiring layer 21: Common wiring 211: First belt 211A: Base 211B: Extension part 212: Connection part 22: Individual wiring 221: Second belt 221A: Base 221B: Extension part 222: Middle section 222A: Parallel part 222B: Diagonal section 223: Connection 223A: First connection part 223B: Second connection part 30: Resistor layer 31: Heat generating part 40: 1st protective layer 41: Slit 411: Inner surface 42: 1st page 50:Second protective layer 501: 1st base material 502:Second base material 51: Part 1 52: Part 2 521:Second side 60: 3rd protective layer 401: 1st base material 402:Second base material 75: Wire 71: Driver IC 72: Sealing resin 73: Connector 74: Heat sink 75: Wire 81: Recording media 82: Platen roller

Claims

1. A substrate; a resistor layer including a plurality of heat generating portions arranged in a main scanning direction and disposed on the substrate; a wiring layer that is electrically connected to the plurality of heat generating portions and is disposed in contact with the resistor layer; a first protective layer that covers at least a portion of the wiring layer; the first protective layer has slits formed therein, the slits extending in the main scanning direction and exposing the plurality of heat generating portions; a second protective layer at least a portion of which is accommodated in the slit and which covers the plurality of heat generating portions; A thermal printhead, wherein the second protective layer has a higher thermal conductivity than the first protective layer.

2. the second protective layer contains a first substrate and a second substrate, The composition of the first substrate is silicon dioxide; the thermal conductivity of the second substrate is higher than the thermal conductivity of the first substrate; The thermal printhead of claim 1 , wherein the weight percentage of the second protective layer is higher in the second substrate than in the first substrate.

3. The thermal printhead of claim 2 , wherein the second substrate is made of silicon.

4. 4. A thermal printhead according to claim 1, wherein the dimension of said slit in the sub-scanning direction is larger than the dimension of each of said plurality of heat generating portions in the sub-scanning direction.

5. the slit includes a pair of inner surfaces spaced apart from each other in the sub-scanning direction, 5. The thermal printhead according to claim 1, wherein the second protective layer is in contact with the pair of inner surfaces.

6. the first protective layer has a first surface facing a side opposite to a side on which the substrate is located with respect to the resistor layer in a thickness direction of the substrate, The thermal printhead according to claim 5 , wherein the pair of inner surfaces are connected to the first surface.

7. The thermal printhead of claim 6 , wherein the second protective layer covers the first surface.

8. The thermal printhead of claim 6 , wherein the second protective layer is exposed from the first surface.

9. a third protective layer covering the second protective layer and the first surface; The thermal printhead of claim 8 , wherein the thermal conductivity of the third protective layer is higher than the thermal conductivity of the first protective layer.

10. The thermal printhead according to claim 9 , wherein the third protective layer has a Vickers hardness higher than that of the first protective layer.

11. The thermal printhead of claim 10 , wherein the composition of the third protective layer includes silicon carbide.

12. a glaze layer positioned between the substrate and the wiring layer in a thickness direction of the substrate, 12. The thermal printhead according to claim 1, wherein the wiring layer is in contact with the glaze layer.

13. the substrate has a main surface facing the glaze layer, The thermal printhead of claim 12 , wherein the major surface is in contact with the glaze layer.

14. 14. The thermal printhead of claim 13, wherein the glaze layer covers the entire main surface.

15. 15. The thermal printhead according to claim 12, wherein the thermal conductivity of the glaze layer is lower than the thermal conductivity of the second protective layer.

16. forming a resistor layer on a substrate, the resistor layer including a plurality of heat generating portions arranged in a main scanning direction; forming a wiring layer that is electrically connected to the plurality of heat generating portions and that is in contact with the resistor layer; forming a first protective layer that covers at least a portion of the wiring layer; In the step of forming the first protective layer, slits extending in the main scanning direction and exposing the plurality of heat generating portions are formed in the first protective layer; the step of forming the first protective layer further includes a step of forming a second protective layer that covers the plurality of heat generating portions and has a thermal conductivity higher than that of the first protective layer, In the step of forming the second protective layer, at least a portion of the second protective layer is accommodated in the slit.

17. The method for manufacturing a thermal printhead according to claim 16 , wherein the first protective layer and the second protective layer are formed by firing.

18. the method further includes, after the step of forming the second protective layer, a step of forming a third protective layer that covers the first protective layer and the second protective layer and has a thermal conductivity and a Vickers hardness higher than those of the first protective layer; The method for manufacturing a thermal printhead according to claim 16 or 17, wherein the third protective layer is formed by sputtering.

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