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

Abstract

This thermal print head comprises: an underglaze layer; a conductor layer disposed on the upper surface of the underglaze layer; an insulating layer disposed on the upper surface of the conductor layer in a manner allowing a first connection region and a second connection region of the conductor layer to be exposed; an electrode layer disposed on the upper layer of the insulating layer and including a common electrode and an individual electrode; connection wiring having a first wiring region connected to the first connection region and the common electrode, and a second wiring region connected to the second connection region; a common electrode terminal disposed in the second wiring region of the connection wiring; and a heating resistor which is in contact with the common electrode and the individual electrode.

Description

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

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

[0002] Printing using a thermal printhead (also simply referred to as a thermal head) is performed by selectively generating heat from multiple heat-generating resistors (also referred to as heat-generating elements) arranged in the main scanning direction and conducting the heat from the heat-generating resistors to the print medium. The heat-generating resistors are areas that generate heat when a current flows between a common electrode and an individual electrode of a heat-generating resistor arranged on a glaze layer, also known as a heat storage layer. The print medium can be thermal paper for creating barcode sheets or receipts.

[0003] JP 2022-12222 A JP 2017-1396 A

[0004] There is a demand for improved printing efficiency in printing using thermal printheads. This can be achieved by increasing the heat generated in the heating resistors. However, increasing the power consumption of the thermal printhead in order to increase the heat generated in the heating resistors runs counter to efforts to reduce the power consumption of the thermal printhead.

[0005] Furthermore, in conventional thermal printheads, the placement of the electrodes for supplying ground potential can cause differences in power consumption in the heat-generating resistors, which can result in differences in print density in the heat-generating resistors and make it difficult to achieve optimal printing.

[0006] An object of the present disclosure is to provide a thermal printhead, a thermal printer, and a method for manufacturing a thermal printhead that can improve printing efficiency and suppress increases in power consumption.

[0007] Another object of the present disclosure is to provide a thermal printhead that is capable of suitable printing with reduced differences in print density.

[0008] One aspect of the present disclosure is a thermal printhead comprising: an underglaze layer; a conductor layer disposed on the upper surface of the underglaze layer; an insulating layer disposed on the upper surface of the conductor layer with a first connection region and a second connection region of the conductor layer exposed in a planar view seen from the thickness direction of the underglaze layer; an electrode layer disposed on the upper surface of the insulating layer and including a common electrode and individual electrodes; connection wiring isolated from the individual electrodes and facing the conductor layer except for the first connection region and the second connection region via the insulating layer, the connection wiring having a first wiring region connected to the first connection region and the common electrode and a second wiring region connected to the second connection region; a common electrode terminal disposed in the second wiring region of the connection wiring; and a heating resistor disposed above the insulating layer and in contact with the common electrode and the individual electrodes.

[0009] Another aspect of the present disclosure is a thermal printer including the thermal printhead described above.

[0010] Yet another aspect of the present disclosure is a method for manufacturing a thermal printhead, comprising: forming a conductor layer on the upper surface of an underglaze layer; forming an insulating layer on the upper surface of the conductor layer in a state in which a first connection region and a second connection region of the conductor layer are exposed in a planar view seen from the thickness direction of the underglaze layer; forming an electrode layer including a common electrode and an individual electrode on the upper surface of the insulating layer; forming connection wiring having a first wiring region connected to the first connection region and the common electrode and a second wiring region connected to the second connection region so as to be isolated from the individual electrodes and to face the conductor layer excluding the first connection region and second connection region via the insulating layer; forming a common electrode terminal in the second wiring region of the connection wiring; and forming heating resistors in contact with the common electrode and the individual electrodes above the insulating layer.

[0011]

[0010] Yet another aspect of the present disclosure is a rectangular thermal printhead comprising: a substrate; a heating resistor portion arranged in the longitudinal direction of the substrate; a plurality of individual electrodes in contact with the heating resistor portion and arranged in the transverse direction of the substrate; a plurality of common electrodes arranged in the transverse direction of the substrate and electrically connected to the plurality of individual electrodes via the heating resistor portion; a plurality of driving ICs arranged in a line in the longitudinal direction of the thermal printhead and electrically connected to the plurality of individual electrodes; a ground electrode that supplies a ground potential to each of the plurality of driving ICs; a plurality of power supply electrodes that supply power to each of the plurality of driving ICs; a plurality of signal electrodes that supply signals to each of the plurality of driving ICs; and external terminals electrically connected to the ground electrode, the plurality of power supply electrodes, and the plurality of signal electrodes. The external terminals include a first external terminal and a second external terminal. The plurality of driving ICs include a first group of driving ICs electrically connected to the first external terminal and a second group of driving ICs electrically connected to the second external terminal. The ground electrodes include a first ground electrode electrically connected to each of the first group of drive ICs, a second ground electrode electrically connected to each of the second group of drive ICs, and a common ground electrode electrically connecting the first ground electrode and the second ground electrode. The first and second ground electrodes are arranged on a first electrode layer of a substrate on which the plurality of individual electrodes and the plurality of power supply electrodes are provided. The common ground electrode is arranged on a second electrode layer laminated on the first electrode layer via an insulating layer, and is connected to the second electrode layer so as to surround the periphery of the plurality of drive ICs. The first and second ground electrodes and the common ground electrode are electrically joined via joining members at both ends of the plurality of drive ICs.

[0012] According to the present disclosure, it is possible to provide a thermal printhead, a thermal printer, and a method for manufacturing a thermal printhead that can improve printing efficiency and suppress increases in power consumption.

[0013] Furthermore, according to the present disclosure, it is possible to provide a thermal printhead that is capable of suitable printing with reduced differences in print density.

[0014] FIG. 1 is a schematic cross-sectional view showing the configuration of a thermal printhead according to the first embodiment, including a common electrode. FIG. 2 is a schematic cross-sectional view showing the configuration of a thermal printhead according to the first embodiment, including individual electrodes. FIG. 3 is a schematic plan view showing the configuration of a thermal printhead according to the first embodiment. FIG. 4 is a schematic plan view showing the arrangement of conductive layers and insulating layers of the thermal printhead according to the first embodiment. FIG. 5 is a schematic plan view showing the arrangement of connection wiring of the thermal printhead according to the first embodiment. FIG. 6 is a schematic plan view showing the wiring of an individual wiring section of the thermal printhead according to the first embodiment. FIG. 7 is a schematic plan view showing the arrangement of the common electrode and individual electrodes of the thermal printhead according to the first embodiment. FIG. 8 is a schematic diagram showing the configuration of a thermal printer according to the first embodiment. FIG. 9A is a schematic cross-sectional view (part 1) for explaining a method for manufacturing a thermal printhead according to the first embodiment. FIG. 9B is a schematic plan view (part 1) for explaining a method for manufacturing a thermal printhead according to the first embodiment. FIG. 10A is a schematic cross-sectional view (part 2) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 10B is a schematic plan view (part 2) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 11A is a schematic cross-sectional view (part 3) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 11B is a schematic plan view (part 3) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 12A is a schematic cross-sectional view (part 4) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 12B is a schematic plan view (part 4) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 13A is a schematic cross-sectional view (part 5) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 13B is a schematic plan view (part 5) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 14A is a schematic cross-sectional view (part 6) illustrating a method for manufacturing a thermal printhead according to the first embodiment.FIG. 14B is a schematic plan view (part 6) illustrating a method for manufacturing a thermal printhead according to the first embodiment. FIG. 15 is a schematic cross-sectional view illustrating the configuration of a thermal printhead according to a modified example of the first embodiment. FIG. 16 is a schematic cross-sectional view illustrating the positional relationship between a common electrode and individual electrodes and a heating resistor in a thermal printhead according to the first embodiment. FIG. 17 is a schematic cross-sectional view illustrating the positional relationship between a common electrode and individual electrodes and a heating resistor in a thermal printhead according to another embodiment. FIG. 18 is a plan view illustrating a thermal printhead according to a second embodiment. FIG. 19 is a cross-sectional view taken along line II-II in FIG. 18. FIG. 20 is an enlarged view of a portion III-III in FIG. 19. FIG. 21 is a plan view illustrating a thermal printhead according to a third embodiment. FIG. 22 is a plan view illustrating a thermal printhead according to a fourth embodiment. FIG. 23 is a plan view illustrating a thermal printhead of a comparative example.

[0015] Next, an embodiment will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each part, etc. may differ from the actual ones. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships or ratios.

[0016] Furthermore, the embodiments described below are merely examples of devices or methods for embodying the technical ideas, and are not intended to limit the shape, structure, arrangement, etc. of the components to those described below. Various modifications can be made to these embodiments within the scope of the claims.

[0017] 1 to 3, a thermal printhead 1 according to the first embodiment includes a base 10, a conductive layer 20, an insulating layer 30, an electrode layer 40, connection wiring 50, a common electrode terminal 61, a control electrode terminal 62, and a heating resistor 70. The electrode layer 40 includes a common electrode 41, individual electrodes 42, individual wiring sections 43, a control wiring section 44, and a power supply wiring section 45. In the thermal printhead 1, the heating resistor 70 is provided with a plurality of heating resistor sections that generate heat due to a current flowing between the common electrode 41 and the individual electrodes 42.

[0018] In the drawings referred to in the description of the first embodiment, the direction in which the common electrode 41 and the individual electrodes 42 are located as viewed from the base 10 is referred to as the upward direction, and the direction in which the base 10 is located as viewed from the common electrode 41 and the individual electrodes 42 is referred to as the downward direction. The upward surface is referred to as the upper surface, and the downward surface is referred to as the lower surface. The main scanning direction X is the direction in which the heating resistor 70 extends linearly. As will be described later, multiple heating resistor portions provided on the heating resistor 70 are arranged in the main scanning direction X. The sub-scanning direction Y is a direction perpendicular to the main scanning direction X and parallel to the top surface of the base 10. The thickness direction Z is a normal direction to the top surface of the base 10. In other words, the thickness direction Z is a direction perpendicular to both the main scanning direction X and the sub-scanning direction Y.

[0019] FIG. 1 is a cross-sectional view taken along the direction II-II in FIG. 3, including the common electrode 41. FIG. 2 is a cross-sectional view taken along the direction II-II in FIG. 3, including the individual electrodes 42. FIG. 3 is a plan view seen from the thickness direction of the base 10. In FIG. 3, the conductor layer 20 and the insulating layer 30 are shown by dashed lines through the electrode layer 40 and the connection wiring 50. Note that the protective film 80 shown in FIGS. 1 and 2 is omitted from FIG. 3. Also, the control IC 90 shown in FIG. 3 is omitted from FIGS. 1 and 2.

[0020] The base 10 has a rectangular shape when viewed from a plane in the thickness direction Z (hereinafter simply referred to as "plan view"). The base 10 has a structure in which a substrate 11 and an underglaze layer 12 are laminated. The material of the substrate 11 may be, for example, a ceramic substrate or a single-crystal semiconductor substrate. As a ceramic substrate, for example, an alumina substrate can be used for the substrate 11. As a single-crystal semiconductor substrate, for example, a silicon substrate can be used for the substrate 11. From the viewpoint of heat dissipation, it is preferable to use an alumina substrate, which has a relatively high thermal conductivity, for the substrate 11.

[0021] The underglaze layer 12 accumulates the heat generated by the heating resistor 70. For this reason, the underglaze layer 12 is also referred to as a heat storage layer. An insulating material can be used as the material for the underglaze layer 12. For example, silicon dioxide, which is the main component of glass, may be used for the underglaze layer 12. The size of the underglaze layer 12 in the thickness direction Z (hereinafter also simply referred to as "thickness") is not particularly limited, but is, for example, about 100 μm to 200 μm.

[0022] The conductor layer 20 is disposed on the upper surface of the underglaze layer 12. The unevenness of the upper surface of the substrate 11, which is made of a ceramic material or the like, is reduced on the upper surface of the underglaze layer 12, which also has the effect of flattening the upper surface of the substrate 10 on which the conductor layer 20 is disposed. A conductive material such as metal may be used as the material for the conductor layer 20. For example, silver (Ag), which is a relatively inexpensive and highly conductive material, is preferably used for the conductor layer 20. The thickness of the conductor layer 20 is, for example, approximately 3 μm to 20 μm.

[0023] The conductor layer 20 has a first connection region 201 and a second connection region 202. In a plan view, the first connection region 201 is arranged on one side of the rectangular base 10, and the second connection region 202 is arranged on the side opposite to the side on which the first connection region 201 is arranged. The first connection region 201 is arranged close to the common electrode 41. The second connection region 202 is arranged close to the common electrode terminal 61. The thermal printhead 1 has two second connection regions 202, a second connection region 202A and a second connection region 202B. When the second connection region 202A and the second connection region 202B are not limited, they are referred to as the second connection region 202.

[0024] The insulating layer 30 is disposed on the upper surface of the conductive layer 20, with the first connection region 201 and the second connection region 202 of the conductive layer 20 exposed in a planar view. In other words, as shown in FIG. 4 , the remaining region of the conductive layer 20, excluding the first connection region 201 and the second connection region 202, is covered by the insulating layer 30 in a planar view. In the thermal printhead 1, as shown in FIG. 4 , a portion of the outer edge of the conductive layer 20 is located outside the outer edge of the insulating layer 30 in a planar view, and the portions of the conductive layer 20 located outside the outer edge of the insulating layer 30 are the first connection region 201 and the second connection region 202. As shown in FIG. 4 , the outer edge of the insulating layer 30 is located outside the outer edge of the conductive layer 20, except for the first connection region 201 and the second connection region 202 of the conductive layer 20. The insulating layer 30 may be made of, for example, crystallized glass. The thickness of the insulating layer 30 is, for example, about 10 μm to 30 μm.

[0025] The electrode layer 40 is disposed on the upper surface of the insulating layer 30. The electrode layer 40 faces the conductor layer 20 via the insulating layer 30. The arrangement of the common electrode 41 and the individual electrodes 42 will be described in detail below. A heating resistor portion is provided between the common electrode 41 and the individual electrodes 42 in the heating resistor 70. The material of the electrode layer 40 (hereinafter also referred to as the "electrode material") is a conductor because the common electrode 41 and the individual electrodes 42 form a path for conducting electricity to the heating resistor 70. The electrode material may be, for example, a metal material such as copper (Cu), silver, palladium (Pd), iridium (Ir), platinum (Pt), or gold (Au). From the viewpoint of metal properties and ionization tendency, the electrode material is preferably copper, silver, platinum, or gold. For example, gold is preferably used as the electrode material. The thickness of the electrode layer 40 is, for example, approximately 0.2 μm to 5 μm.

[0026] The heating resistor 70 is disposed above the insulating layer 30 and is in contact with the common electrode 41 and the individual electrodes 42. A current flows between the common electrode 41 and the individual electrodes 42 in the heating resistor 70, causing the heating resistor portion of the heating resistor 70 to generate heat, thereby forming a print dot. A material having a higher resistivity than the materials of the common electrode 41 and the individual electrodes 42 is used for the heating resistor 70. For example, tantalum nitride or silicon dioxide containing tantalum may be used as the material for the heating resistor 70. Alternatively, ruthenium oxide may be used as the material for the heating resistor 70. The thickness of the heating resistor 70 is, for example, approximately 0.05 to 10 μm.

[0027] The connection wiring 50 is isolated from the individual electrodes 42 and is disposed above the underglaze layer 12 via the insulating layer 30, with the conductor layer 20 excluding the first connection region 201 and the second connection region 202. As shown in FIG. 3 , the connection wiring 50 is disposed along the outer edge of the base 10.

[0028] 5 , the first wiring region 501 of the connection wiring 50 covers the first connection region 201 of the conductor layer 20 and is electrically connected to the first connection region 201. In the first wiring region 501, the connection wiring 50 overlaps a part of the common electrode 41 in a plan view. As a result, the connection wiring 50 electrically connects the conductor layer 20 and the common electrode 41.

[0029] The second wiring regions 502A and 502B, which are ends of the connection wiring 50, cover at least a portion of the second connection region 202 of the conductor layer 20 in a planar view and are electrically connected to the second connection region 202. Specifically, the second wiring region 502A covers at least a portion of the second connection region 202A, and the second wiring region 502B covers at least a portion of the second connection region 202B. Hereinafter, when the second wiring region 502A and the second wiring region 502B are not limited, they will be referred to as the second wiring region 502. In the second wiring region 502, the connection wiring 50 overlaps with the common electrode terminal 61 in a planar view. As a result, the connection wiring 50 electrically connects the conductor layer 20 and the common electrode terminal 61.

[0030] As described above, the connection wiring 50 has a first wiring region 501 that connects to the first connection region 201 of the conductor layer 20 and the common electrode 41, and a second wiring region 502 that connects to the second connection region 202 of the conductor layer 20 and the common electrode terminal 61. Therefore, the common electrode 41 and the common electrode terminal 61 are electrically connected via the conductor layer 20 and the connection wiring 50. Silver is preferably used as the material for the connection wiring 50, as it is relatively inexpensive and has good metallic properties and ionization tendency.

[0031] A terminal group 60 in which common electrode terminals 61 and control electrode terminals 62 are arranged is disposed above the underglaze layer 12, close to the area in which the second connection area 202 of the conductor layer 20 is disposed. When a thermal printer incorporating the thermal printhead 1 is used, electrical signals (hereinafter also referred to as "print signals") for setting the potentials of the common electrode 41 and the individual electrodes 42 are transmitted from outside the thermal printhead 1 to the common electrode terminals 61 and the control electrode terminals 62. A suitable material for the terminal group 60 is, for example, a silver (Ag)-platinum (Pt) material.

[0032] In the thermal printhead 1, two terminals at each end of the terminal group 60 are common electrode terminals 61, and a plurality of control electrode terminals 62 are arranged between the common electrode terminals 61. The common electrode terminals 61 arranged at both ends of the terminal group 60 are connected to the second wiring region 502 of the connection wiring 50.

[0033] The control electrode terminals 62 are electrically connected to a control IC 90 that sets the potential of the individual electrodes 42. For example, the control IC 90 is a semiconductor integrated circuit having a logic circuit for setting the potential of the individual electrodes 42. The control wiring section 44 of the electrode layer 40 includes wiring that connects the control electrode terminals 62 and the control IC 90. The individual wiring section 43 of the electrode layer 40 includes wiring that electrically connects the control IC 90 and the individual electrodes 42. For example, as shown in FIG. 6 , each of the individual electrodes 42 is individually connected to the control IC 90 by an independent wiring of the individual wiring section 43.

[0034] In plan view, the first wiring region 501 of the connection wiring 50 and a portion of the common electrode 41 overlap, and the first connection region 201 of the conductor layer 20 overlaps the first wiring region 501. That is, the portion of the first wiring region 501 that overlaps the upper surface of the insulating layer 30 overlaps with a portion of the common electrode 41 in plan view. The overlapping portion of the first wiring region 501 creeps up the side surface of the insulating layer 30 above the first connection region 201.

[0035] Furthermore, the power supply wiring portion 45 of the electrode layer 40 and the second wiring region 502 of the connection wiring 50 overlap with each other. That is, the common electrode terminal 61 is disposed on the laminated structure of the electrode layer 40 and the portion of the second wiring region 502 that overlaps with the upper surface of the insulating layer 30. The overlapping portion of the second wiring region 502 creeps up the side surface of the insulating layer 30 above the second connection region 202.

[0036] As described above, in the thermal printhead 1, a conductive material is laminated on the common electrode 41 and the common electrode terminal 61. Therefore, the electrical resistance between the common electrode 41 and the common electrode terminal 61 can be reduced.

[0037] 1 and 2, the thermal printhead 1 further includes a protective film 80 that covers the heating resistor 70, the electrode layer 40, and the like. The protective film 80 protects the heating resistor 70 and the like from wear, corrosion, oxidation, and the like. For example, the protective film 80 may be made of an insulating material such as amorphous glass. The thickness of the protective film 80 is, for example, approximately 2 μm to 10 μm. A protective film 80 with a thickness within this range can suppress voltage resistance defects and provide a thermal printhead 1 that can maintain good print quality.

[0038] In order for the terminal group 60 to receive print signals transmitted from outside the thermal printhead 1, the protective film 80 does not cover at least a portion of the upper surface of the terminal group 60. In other words, the common electrode terminal 61 and the control electrode terminal 62 are exposed to the outside of the protective film 80.

[0039] Printing is performed using the thermal printhead 1 by causing the heating resistor portion of the heating resistor 70 to heat up due to a current flowing between the common electrode 41 and the individual electrodes 42, and then conducting the heat from the heating resistor portion to the print medium. Figure 7 shows an example of the thermal printhead 1 with an enlarged view of the periphery of the heating resistor portion 71. Figure 7 is a plan view showing an example of the arrangement of the common electrode 41 and the individual electrodes 42 around the heating resistor portion 71. The cross-sectional view taken along line II in Figure 7 is included in the cross-sectional view of Figure 1, and the cross-sectional view taken along line II-II in Figure 7 is included in the cross-sectional view of Figure 2.

[0040] 7 includes a comb-shaped common electrode 41, a plurality of comb-tooth portions 411 of the common electrode 41 and a plurality of individual electrodes 42 arranged alternately along the main scanning direction X, and a heating resistor 70 in contact with the comb-tooth portions 411 and the individual electrodes 42. The heating resistor portion 71 is a region of the heating resistor 70 through which a current flows between the comb-tooth portions 411 and the individual electrodes 42.

[0041] Each of the comb tooth portions 411 extends from the common portion 412 in the sub-scanning direction Y. Adjacent comb tooth portions 411 are arranged at a predetermined interval along the main scanning direction X. A thermal printhead 1 having a comb-shaped common electrode 41 can narrow the interval between the comb tooth portions 411 and the individual electrodes 42, thereby narrowing the pitch of the heating resistor portions 71. A thermal printhead 1 with a narrow pitch of the heating resistor portions 71 is capable of high-resolution printing.

[0042] The individual electrodes 42 are not electrically connected to each other. Therefore, when a thermal printer incorporating the thermal printhead 1 is used, a potential can be set independently for each individual electrode 42. A potential of the opposite polarity to that of the individual electrodes 42 is set for the common electrode 41.

[0043] The first connection region 201, the first wiring region 501, and the common portion 412 of the common electrode 41 extend in the main scanning direction X in parallel with the heating resistor 70. The common electrode 41 is disposed between the first connection region 201 and the first wiring region 501 and the heating resistor 70 in a plan view.

[0044] As described above, in the thermal printhead 1 according to the first embodiment, the common electrode 41 and the common electrode terminal 61 are electrically connected by both the conductor layer 20 and the connection wiring 50. Therefore, with the thermal printhead 1, the electrical resistance of the wiring from the common electrode terminal 61 to the common electrode 41 can be reduced compared to a thermal printhead in which the common electrode 41 and the common electrode terminal 61 are connected only by wiring arranged above the insulating layer 30. As a result, it is possible to increase the power consumption in the heating resistor portion 71 while suppressing an increase in the power consumption of the entire thermal printhead 1. Therefore, with the thermal printhead 1, it is possible to suppress an increase in power consumption and improve printing efficiency.

[0045] 1 , in the thermal printhead 1, the outer edge of the common electrode 41 that overlaps with the connection wiring 50 overlaps with the outer edge of the insulating layer 30 in a plan view. A current path is formed in the thickness direction Z by the first wiring region 501 that connects the conductor layer 20 and the common electrode 41 along the outer edges of the common electrode 41 and the insulating layer 30. This allows the formation of a current path by the connection wiring 50 that connects the conductor layer 20 and the common electrode 41. Alternatively, the outer edge of the common electrode 41 that overlaps with the connection wiring 50 may be located inside the outer edge of the insulating layer 30.

[0046] In a printing operation of a thermal printer having the thermal printhead 1, a print signal is sent from outside the thermal printhead 1 to the control IC 90 via the control electrode terminals 62. The control IC 90 selectively sets the potential of the individual electrodes 42 in response to the print signal, thereby selectively generating heat in the plurality of heat generating resistor portions 71 arranged along the main scanning direction X in the heat generating resistor 70. As a result, printing is performed on a print medium such as thermal paper pressed against the heat generating resistor 70.

[0047] An example of the printing operation of a thermal printer having a thermal printhead 1 will be described with reference to Figure 8. The thermal printer shown in Figure 8 has a platen roller 101 facing the thermal printhead 1. The print medium 100 is transported in the sub-scanning direction Y as shown by the arrow in Figure 8. Typically, the print medium 100 is transported from the side of the terminal group 60 toward the side of the heating resistor 70. The print medium 100 is pressed against the heating resistor 71 by the platen roller 101.

[0048] In the printing operation of the thermal printer, the control IC 90 receives a print signal and sets any individual electrode 42 to a predetermined potential, causing any of the plurality of heating resistor portions 71 provided on the heating resistor 70 to selectively generate heat. The heat from the generated heating resistor portion 71 is transferred to the print medium 100, thereby printing on the print medium 100.

[0049] The thermal printer may further include a measurement circuit (not shown). The measurement circuit measures the resistance value of each of the plurality of heating resistors 71. For example, the measurement circuit measures the resistance value of the heating resistors 71 when no printing is being performed on the print medium. By measuring the resistance value of the heating resistors 71, it is possible to estimate the lifespan of the heating resistors 71 and to check whether any heating resistors 71 are faulty.

[0050] A method for manufacturing a thermal printhead 1 according to embodiment 1 will now be described with reference to the drawings. Note that the method for manufacturing a thermal printhead 1 described below is just one example, and it goes without saying that various other manufacturing methods, including variations thereof, are possible. In the following Figures 9A, 9B to 14A, and 14B, figures with an A at the end are cross-sectional views taken along the II direction in Figure 1, and figures with a B at the end are plan views.

[0051] First, a base 10 is prepared, in which a substrate 11 and an underglaze layer 12 are laminated. For example, an underglaze layer 12 made of a glass material is formed on the upper surface of a ceramic substrate 11. The underglaze layer 12 is formed by firing at a temperature of, for example, about 1200°C.

[0052] 9A and 9B, a conductor layer 20 is formed on the upper surface of the underglaze layer 12. For example, a metal paste such as silver paste is applied by screen printing or the like, and the applied metal paste is fired to form the conductor layer 20. Note that the conductor layer 20 may be formed into a predetermined shape by using a combination of screen printing and photolithography.

[0053] 10A and 10B , an insulating layer 30 is formed on the upper surface of the conductor layer 20 so that the first connection region 201 and the second connection region 202 are exposed in a planar view. The insulating layer 30 may be made of, for example, crystallized glass. In this case, the insulating layer 30 and the conductor layer 20 may be formed so that a portion of the outer edge of the conductor layer 20 is located outside the outer edge of the insulating layer 30 in a planar view. The outer edge of the conductor layer 20 located outside the outer edge of the insulating layer 30 is the first connection region 201 and the second connection region 202. After the entire surface of the conductor layer 20 is covered with the insulating layer 30, openings that expose a portion of the conductor layer 20 may be formed in the insulating layer 30 to provide the first connection region 201 and the second connection region 202. However, by arranging the first connection region 201 and the second connection region 202 outside the insulating layer 30, the first connection region 201 and the second connection region 202 can be formed more easily than by forming openings in the insulating layer 30 that expose the first connection region 201 and the second connection region 202. The first connection region 201 is formed to extend in the main scanning direction X.

[0054] 11A and 11B , an electrode layer 40 including a common electrode 41 and individual electrodes 42 is formed on the upper surface of the insulating layer 30. At this time, the electrode layer 40 is formed so that the common electrode 41 is close to the first connection region 201. For example, a metal paste applied to the upper surface of the insulating layer 30 by screen printing or the like is fired. Then, the metal paste may be patterned using photolithography to form the common electrode 41, the individual electrodes 42, the individual wiring portion 43, the control wiring portion 44, and the power supply wiring portion 45. The electrode layer 40 may be made of a material such as gold.

[0055] In addition, the insulating layer 30 and the electrode layer 40 are formed so that, in a plan view, the outer edge of the common electrode 41 that overlaps with the connection wiring 50 overlaps with the outer edge of the insulating layer 30 or is located inside the outer edge of the insulating layer 30. In addition, the common portion 412 of the common electrode 41 is formed to extend in the main scanning direction X.

[0056] 12A and 12B , connection wiring 50 is formed above underglaze layer 12, isolated from individual electrodes 42 and with insulating layer 30 interposed between conductor layer 20 and the first connection region 201 and the second connection region 202. At this time, connection wiring 50 is formed so that first wiring region 501 connects to first connection region 201 and common electrode 41, and second wiring region 502 connects to second connection region 202. Like electrode layer 40, connection wiring 50 may be formed using screen printing, photolithography, or the like. Silver is preferably used as the material for connection wiring 50.

[0057] The connection wiring 50 is formed so as to overlap a portion of the common electrode 41 in a planar view. That is, the connection wiring 50 is formed so that a portion of the first wiring region 501 that overlaps the upper surface of the insulating layer 30 and a portion of the common electrode 41 overlap in a planar view. For example, the first wiring region 501 overlaps the common portion 412 of the common electrode 41. Furthermore, the connection wiring 50 is formed so that a portion of the second wiring region 502 that overlaps the upper surface of the insulating layer 30 and the power supply wiring portion 45 overlap in a planar view.

[0058] 13A and 13B , a common electrode terminal 61 and a control electrode terminal 62 are formed. The common electrode terminal 61 is formed in the second wiring region 502 of the connection wiring 50 so as to be electrically connected to the common electrode 41 via the conductor layer 20 and the connection wiring 50. For example, the common electrode terminal 61 is formed on a laminated structure of a portion of the second wiring region 502 of the connection wiring 50 that overlaps the upper surface of the insulating layer 30 and the power supply wiring portion 45 of the electrode layer 40. The control electrode terminal 62 is formed so as to be connected to the wiring of the control wiring portion 44 that connects to the control IC 90. The common electrode terminal 61 and the control electrode terminal 62 may be formed using screen printing, photolithography, or the like.

[0059] 14A and 14B , the heating resistor 70 in contact with the common electrode 41 and the individual electrodes 42 is formed above the insulating layer 30. For example, the heating resistor 70 may be formed using screen printing, photolithography, or the like. The heating resistor 70 extends in the main scanning direction X while intersecting the comb tooth portions 411 and the individual electrodes 42 in a plan view.

[0060] Thereafter, the control IC 90 is mounted at a predetermined position on the control wiring section 44, and the wiring of the individual wiring section 43 and the control wiring section 44 is connected to the control IC 90. When mounting the control IC 90, the electrode layer 40 and the control IC 90 may be connected using solder. For example, solder bumps are provided between the electrode layer 40 and the control IC 90, and the solder bumps are melted by heat treatment in an inert gas atmosphere such as nitrogen in a reflow furnace, thereby electrically connecting the electrode layer 40 and the control IC 90.

[0061] Furthermore, a protective film 80 is formed above the insulating layer 30 so as to cover the heating resistor 70 and the electrode layer 40. For example, the material of the protective film 80 may be glass. However, the protective film 80 does not cover at least a portion of the upper surfaces of the common electrode terminal 61 and the control electrode terminal 62. With the above steps, the thermal printhead 1 is completed.

[0062] The material used for underglaze layer 12 has a higher firing temperature than the electrode layer 40, connection wiring 50, terminal group 60, and heating resistor 70. For example, the firing temperature for underglaze layer 12 made of silicon dioxide, the main component of glass, is approximately 1200°C, while the firing temperature for other conductive materials is approximately 810°C. For this reason, the manufacturing process, including firing after the formation of underglaze layer 12, can be simplified by performing it at a relatively low firing temperature.

[0063] According to the manufacturing method of the thermal printhead 1 of the first embodiment described above, the common electrode 41 and the common electrode terminal 61 are electrically connected by both the conductor layer 20 and the connection wiring 50. This reduces the electrical resistance of the wiring from the common electrode terminal 61 to the common electrode 41. As a result, it is possible to suppress an increase in power consumption of the entire thermal printhead 1 and increase power consumption in the heating resistor section 71. Therefore, according to the manufacturing method of the thermal printhead 1 described above, it is possible to manufacture a thermal printhead 1 that suppresses an increase in power consumption and improves printing efficiency.

[0064] <Modification> Fig. 15 shows a thermal printhead 1A according to a modification of the first embodiment. The thermal printhead 1A shown in Fig. 15 has a groove 200 that penetrates the conductive layer 20 in the thickness direction in a region of the conductive layer 20 that overlaps the heating resistor 70 in a plan view. The groove 200 is surrounded by the conductive layer 20. The groove 200 may be formed, for example, by photolithography and anisotropic etching. That is, a photoresist film or the like formed on the upper surface of the conductive layer 20 may be patterned into a predetermined shape by photolithography to form an etching mask, and then a portion of the conductive layer 20 may be selectively etched by anisotropic etching to form the groove 200.

[0065] The underglaze layer 12 functions as a heat storage layer that accumulates heat generated by the heating resistor 70. By providing grooves 200 that penetrate the conductive layer 20 in the thickness direction, heat generated by the heating resistor 70 is more easily transferred to the underglaze layer 12. In other words, the thermal printhead 1A shown in FIG. 15 can prevent a decrease in the heat storage function of the underglaze layer 12. While FIG. 15 shows an example in which the grooves 200 are filled with the insulating layer 30, the interior of the grooves 200 may be empty, or may be filled with a material with good thermal conductivity. Furthermore, the grooves 200 may be formed over the entire area below the heating resistor 70, or may be formed only partially below the heating resistor 70.

[0066] (Other Embodiments) As described above, the first embodiment has been described, but the descriptions and drawings that form part of this disclosure should not be understood to limit this embodiment. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

[0067] For example, in the above description, the comb-tooth portion 411 of the common electrode 41 and the individual electrode 42 are disposed between the heating resistor 70 and the insulating layer 30 as shown in Fig. 16. However, as shown in Fig. 17, the heating resistor 70 may be disposed between the comb-tooth portion 411 and the individual electrode 42 and the insulating layer 30. Even in the configuration shown in Fig. 17, the heating resistor portion 71 in the heating resistor 70 generates heat due to the current flowing between the comb-tooth portion 411 of the common electrode 41 and the individual electrode 42.

[0068] Thus, the first embodiment includes various embodiments not described here.

[0069] 18 to 20 show a thermal printhead according to a second embodiment of the present disclosure. The thermal printhead 1B is incorporated into a printer that prints on a print medium 8 that is conveyed between the thermal printhead 1B and a platen roller (not shown). Examples of such print media 8 include thermal paper for producing barcode sheets, receipts, and the like.

[0070] 18 is a plan view showing a thermal printhead 1B according to embodiment 2. The thermal printhead 1B includes a substrate 11A, a heat generating resistor 4, a plurality of individual electrodes 32, a plurality of common electrodes 31, an auxiliary electrode 35, a common ground electrode 14, a plurality of driving ICs 5, a first wiring group 21, a second wiring group 22, external terminals 9, and a bonding member 16.

[0071] As shown in Fig. 18, the substrate 11A has a rectangular flat plate shape in a plan view and is made of, for example, alumina ceramic. The main scanning direction X shown in Fig. 18 is the longitudinal direction of the substrate 11A, and the sub-scanning direction Y is the lateral direction of the substrate 11A. The thickness direction Z shown in Figs. 19 and 20 is the thickness direction of the substrate 11A. The thickness of the substrate 11A is, for example, 1 mm.

[0072] The heating resistor section 4 is a heat source for the thermal printhead 1B. The heating resistor section 4 is in the form of a strip extending in the main scanning direction X and is sandwiched between a plurality of individual electrodes 32 and a plurality of common electrodes 31. The heating resistor section 4 generates heat by generating a potential difference between the plurality of individual electrodes 32 and the plurality of common electrodes 31. The plurality of individual electrodes 32 and the plurality of common electrodes 31 are connected by numerous wires spaced apart, which are shown in black in the figure.

[0073] The multiple individual electrodes 32 are arranged side by side with gaps between them in the main scanning direction X. The multiple individual electrodes 32 are electrically connected to the multiple driving ICs and are arranged in bundles corresponding to each driving IC 5. The multiple individual electrodes 32 are arranged at equal intervals with gaps between them in the main scanning direction X like the teeth of a comb. Each of the multiple individual electrodes 32 extends in the sub-scanning direction Y from the driving IC 5 toward the heating resistor portion 4 so as to widen outward.

[0074] The plurality of common electrodes 31 are disposed between the plurality of individual electrodes 32. The plurality of common electrodes 31 are disposed on the opposite side of the heating resistor portion 4 from the plurality of driving ICs 5. The plurality of common electrodes 31 are arranged at equal intervals along the main scanning direction X, like the teeth of a comb. Each of the plurality of common electrodes 31 is disposed so as to alternate with each of the plurality of individual electrodes 32 adjacent to it in the main scanning direction X. The base portions of the plurality of common electrodes 31 are connected in a strip shape. The auxiliary electrode 35 is provided so as to cover the base portions of the plurality of common electrodes 31. The auxiliary electrode 35 is preferably made of a material such as silver, and is provided to reduce electrical resistance.

[0075] The plurality of driver ICs 5 apply current to the heating resistor portion 4 via the plurality of individual electrodes 32 and the plurality of common electrodes 31, thereby performing drive control to cause the heating resistor portion 4 to generate heat in a specific portion. The plurality of driver ICs 5 generate heat at a specific position of the heating resistor portion 4 by selectively applying current to the plurality of individual electrodes 32 based on a control signal received from an external device, for example. The plurality of driver ICs 5 are covered with a sealing resin (not shown) for protection.

[0076] The multiple driver ICs 5 include a first group of driver ICs 111 and a second group of driver ICs 112. The external terminals 9 include a first external terminal 9X and a second external terminal 9Y. The first group of driver ICs 111 and the first external terminal 9X are electrically connected via a first wiring group 21. The second group of driver ICs 112 and the second external terminal 9Y are electrically connected via a second wiring group 22. The multiple driver ICs 5 are divided into two systems, the first group of driver ICs 111 and the second group of driver ICs 112, due to design requirements such as ensuring space for components (e.g., thermistors) to be placed in the header and routing of wiring. Note that the multiple driver ICs 5 may be divided into three or more systems. The term "system" refers to the same type of driver ICs; for example, each system may have a different wiring group but the drive control of the multiple driver ICs 5 is the same.

[0077] The first wiring group 21 and the second wiring group 22 are each composed of a collection of multiple wires. The wires are not shown in the drawings. The first wiring group 21 includes multiple power electrodes 21 a, first ground electrodes 21 b, and multiple signal electrodes 21 c. The second wiring group 22 includes multiple power electrodes 22 a, second ground electrodes 22 b, and multiple signal electrodes 22 c.

[0078] The power supply electrode 21a is an electrode for supplying power to each of the first group of driver ICs 111 among the plurality of driver ICs 5. The first ground electrode 21b is an electrode for supplying a ground potential to each of the first group of driver ICs 111 among the plurality of driver ICs 5. The signal electrode 21c is an electrode for supplying a signal to each of the first group of driver ICs 111 among the plurality of driver ICs 5.

[0079] The power supply electrode 22a is an electrode for supplying power to each of the second group of driving ICs 112 among the multiple driving ICs 5. The second ground electrode 22b is an electrode for supplying a ground potential to each of the second group of driving ICs 112 among the multiple driving ICs 5. The signal electrode 22c is an electrode for supplying a signal to each of the second group of driving ICs 112 among the multiple driving ICs 5.

[0080] In the thermal printhead 1B, the common ground electrode 14 is provided above the first ground electrode 21b and the second ground electrode 22b in the thickness direction Z. The common ground electrode 14 is electrically connected to the first ground electrode 21b and the second ground electrode 22b via a bonding member 16. The bonding member 16 is made of a conductive material.

[0081] The first external terminals 9X include a power terminal 90A for connection to the multiple power electrodes 21a, a ground terminal 91 for connection to the first ground electrode 21b, a ground terminal 92 for connection to the common ground electrode 14, and a signal terminal 93 for connection to the multiple signal electrodes 21c. The second external terminals 9Y include a power terminal 90A for connection to the multiple power electrodes 22a, a ground terminal 91 for connection to the second ground electrode 22b, a ground terminal 92 for connection to the common ground electrode 14, and a signal terminal 93 for connection to the multiple signal electrodes 22c. A bonding member 16 is disposed on each of the external terminals 9 to adjust the thickness in the thickness direction Z. Note that the bonding member 16 for adjusting the thickness may be disposed on only some of the external terminals 9, rather than on all of the external terminals 9.

[0082] The electrodes, wiring, terminals, and bonding members 16 in this embodiment may be made of materials containing particles of metal such as copper, silver, platinum, and gold.

[0083] A comparative example of a thermal printhead 1E will now be described. FIG. 23 is a plan view of the comparative example of a thermal printhead 1E. As shown in FIG. 23 , in the thermal printhead 1E, the multiple driver ICs 5 may be divided into two groups: a first group of driver ICs 111 and a second group of driver ICs 112, depending on design requirements such as ensuring space for components (e.g., thermistors) to be placed in the header and routing of wiring. A plurality of individual electrodes 32 are connected to one side of the multiple driver ICs 5, contacting the heat generating resistors 4 arranged in the longitudinal direction of the substrate 11A and arranged in the lateral direction of the substrate 11A. A plurality of common electrodes 31 are provided on the opposite side of the multiple individual electrodes 32 across the heat generating resistors 4, electrically connected to the multiple individual electrodes 32.

[0084] On the other side of the multiple driver ICs 5, a first wiring group 21 and a second wiring group 22 are arranged, which are connected to external terminals 9 provided at the end of the thermal printhead 1E. The first wiring group 21 includes multiple power supply electrodes 21a that supply power to each of the multiple driver ICs 5, a first ground electrode 21b that supply a ground potential to each of the multiple driver ICs 5, and multiple signal electrodes 21c that supply signals to each of the multiple driver ICs. The second wiring group 22 includes multiple power supply electrodes 22a that supply power to each of the multiple driver ICs 5, a second ground electrode 22b that supply a ground potential to each of the multiple driver ICs 5, and multiple signal electrodes 22c that supply signals to each of the multiple driver ICs.

[0085] The external terminals 9 include a first external terminal 9X and a second external terminal 9Y. The first external terminal 9X includes a power terminal 90A for connection with the multiple power electrodes 21a, a ground terminal 91C for connection with the first ground electrode 21b, and a signal terminal 93 for connection with the multiple signal electrodes 21c. The second external terminal 9Y includes a power terminal 90A for connection with the multiple power electrodes 22a, a ground terminal 91C for connection with the second ground electrode 22b, and a signal terminal 93 for connection with the multiple signal electrodes 22c.

[0086] In the thermal printhead 1E, the first ground electrode 21b of the first group of driver ICs 111 and the second ground electrode 22b of the second group of driver ICs 112 are provided as separate ground electrodes that are not electrically connected. This can result in a difference in the amount of voltage drop between the first ground electrode 21b of the first group of driver ICs 111 and the second ground electrode 22b of the second group of driver ICs 112. This can result in a difference in power consumption between the heat generating resistor units 4 corresponding to the first group of driver ICs 111 and the heat generating resistor units 4 corresponding to the second group of driver ICs 112, which can cause a difference in print density and prevent desirable printing.

[0087] The thermal printhead 1B of the second embodiment can solve the problem of the thermal printhead 1E of the comparative example, where a difference in print density occurs and suitable printing cannot be performed.

[0088] First, the layering relationship in the thickness direction Z, which is the thickness direction of the thermal printhead 1B, will be described in detail. Figure 19 is a cross-sectional view taken along line II-II in Figure 18. Figure 20 is an enlarged view of the III-III portion of Figure 19. As shown in Figure 19, a heating resistor unit 4 is provided at the end of the thermal printhead 1B in the sub-scanning direction Y, and a bonding member 16 is disposed at the center of the thermal printhead 1B in the sub-scanning direction Y, where multiple driver ICs 5 are disposed.

[0089] The portion where the heating resistor 4 is provided will be described. As shown in Figure 19, a glaze layer 2, an electrode layer 3, a heating resistor 4, and a protective layer 7 are stacked in this order from the substrate 11A. The glaze layer 2 is made of glass and is formed to cover the surface of the substrate 11A. The glaze layer 2 serves to provide a smooth surface suitable for mounting the electrode layer 3, the heating resistor 4, and a plurality of driver ICs 5. As shown in Figure 19, a portion of the surface of the glaze layer 2 bulges in the thickness direction Z. This bulging portion is referred to as a bulging portion 23.

[0090] The electrode layer 3 includes a plurality of individual electrodes 32 and a plurality of common electrodes 31. Ends of the plurality of common electrodes 31 are electrically connected to auxiliary electrodes 35. The heating resistor 4 is disposed above the bulging portion 23 via the electrode layer 3. The protective layer 7 covers the electrodes and the heating resistor 4 to protect them from foreign matter and the like. The protective layer 7 is made of an appropriate material selected from the group consisting of glass, sialon, tantalum nitride, and silicon carbide.

[0091] 19 and 20 , a cross section of a position where multiple driving ICs 5 are arranged in the sub-scanning direction Y shows a glaze layer 2, a first wiring group 21, an insulating layer 6 and a bonding member 16, a common ground electrode 14, and a protective layer 7 stacked in this order from the substrate 11A. The first ground electrode 21b included in the first wiring group 21 is electrically connected to the common ground electrode 14 via the bonding member 16. The insulating layer 6 is formed of a non-conductive material to prevent electrical connection between the upper and lower layers at positions other than the bonding member 16. The stacking relationship between the second ground electrode 22b included in the second wiring group 22 and the common ground electrode 14 is the same as the stacking relationship shown in FIGS. 19 and 20 .

[0092] As shown in Figures 18 to 20, the first ground electrode 21b included in the first wiring group 21 and the second ground electrode 22b included in the second wiring group 22 are arranged on the electrode layer 3, which serves as the first electrode layer of the substrate 11A on which a plurality of individual electrodes 32, a plurality of common electrodes 31, a plurality of power electrodes 21a, 22a, and a plurality of signal electrodes 21c, 22c are provided.

[0093] The common ground electrode 14 is disposed on a second electrode layer stacked on the electrode layer 3 via an insulating layer 6. Therefore, the common ground electrode 14 can be freely positioned without considering the positions of the first wiring group 21 and the second wiring group 22 provided on the first electrode layer. The common ground electrode 14 is disposed on the second electrode layer so as to be connected to each of the first group of driving ICs 111 and the second group of driving ICs 112, surrounding the periphery of each of the first group of driving ICs 111 and the second group of driving ICs 112. By arranging the common ground electrode 14 so as to surround the periphery of each of the first group of driving ICs 111 and the second group of driving ICs 112, wiring resistance can be reduced compared to when the first ground electrode 21b and the second ground electrode 22b are simply connected by wiring. The first ground electrode 21b and the second ground electrode 22b are electrically connected to the common ground electrode 14 via bonding members 16 at both ends of each of the first group of driving ICs 111 and the second group of driving ICs 112.

[0094] In the thermal printhead 1B, the first and second ground electrodes 21b and 22b are electrically connected to the common ground electrode 14 via the bonding members 16 at both ends of each of the first and second drive ICs 111 and 112. This allows the thermal printhead 1B to reduce the difference in voltage drop between the first and second ground electrodes 21b and 22b via the common ground electrode 14. This allows the thermal printhead 1B to equalize the power consumption of the heat generating resistor units 4 driven by the first and second drive ICs 111 and 112, preventing differences in print density and enabling favorable printing.

[0095] In the thermal printhead 1B, the common ground electrode 14 is disposed on a second electrode layer above the first electrode layer. This allows the wiring widths of the power electrodes 21a and signal electrodes 21c included in the first wiring group 21 and the power electrodes 22a and signal electrodes 22c included in the second wiring group 22 to be wider than when the common ground electrode 14 is disposed on the first electrode layer. This reduces the wiring resistance of the first electrode layer and the power loss in the first wiring group 21 and the second wiring group 22.

[0096] Furthermore, since the thermal printhead 1B has the common ground electrode 14 wired to the second electrode layer where no other wiring is provided, the wiring width of the common ground electrode 14 can be secured wide without being restricted by other wiring, thereby reducing wiring resistance.

[0097] In the thermal printhead 1B, the joining member 16 is also disposed at the position of the external terminals 9. This prevents unevenness in the thickness direction Z, making it possible to make the thickness uniform.

[0098] The thermal printhead 1B is configured such that the distance from the external terminals 9 to the plurality of driver ICs 5 in the short direction of the thermal printhead 1B is shorter than the distance from the plurality of driver ICs 5 to the heat generating resistor portions 4. This makes it possible to reduce the wiring resistance from the external terminals 9 for connecting to external devices to the plurality of driver ICs 5.

[0099] [Embodiment 3] In the second embodiment, a bonding member 16 is disposed on both ends of each of the multiple driving ICs 5, and the bonding member 16 is connected to the common ground electrode 14. The shape of the common ground electrode 14 and the arrangement of the bonding member 16 may be other configurations. Figure 21 is a plan view showing a thermal printhead 1C according to the third embodiment. Note that in Figure 21, the same components as those described in the second embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0100] In the thermal printhead 1C of the third embodiment, a common ground electrode 14A is arranged in the second electrode layer so as to connect and surround the first group of driving ICs 111 and the second group of driving ICs 112. The first ground electrode 21b and the second ground electrode 22b are electrically joined to the common ground electrode 14A via joining members 16 at both ends of the first group of driving ICs 111 and the second group of driving ICs 112.

[0101] In the thermal printhead 1C, the first and second ground electrodes 21b and 22b are electrically connected to the common ground electrode 14 via the bonding members 16 at both ends of the first and second drive ICs 111 and 112. This allows the thermal printhead 1C to reduce the difference in voltage drop between the first and second ground electrodes 21b and 22b via the common ground electrode 14. This allows the thermal printhead 1C to equalize the power consumption of the heat generating resistor units 4 driven by the first and second drive ICs 111 and 112, preventing differences in print density and enabling favorable printing.

[0102] In the thermal printhead 1C, the common ground electrode 14 is disposed on a second electrode layer above the first electrode layer. This allows the wiring widths of the power electrodes 21a and signal electrodes 21c included in the first wiring group 21 and the power electrodes 22a and signal electrodes 22c included in the second wiring group 22 to be wider than when the common ground electrode 14 is disposed on the first electrode layer. This reduces the wiring resistance of the first electrode layer and the power loss in the first wiring group 21 and the second wiring group 22.

[0103] Furthermore, since the thermal printhead 1C has the common ground electrode 14 wired to the second electrode layer where no other wiring is provided, the wiring width of the common ground electrode 14 can be secured wide without being restricted by other wiring, thereby reducing wiring resistance.

[0104] [Embodiment 4] In embodiment 2, a case was described in which a bonding member 16 was disposed on both ends of each of the multiple driving ICs 5 and connected to the common ground electrode 14. The shape of the common ground electrode 14 and the arrangement of the bonding member 16 may be other configurations. Figure 22 is a plan view showing a thermal printhead 1D according to embodiment 3. Note that in Figure 22, the same components as those described in embodiment 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0105] In the thermal printhead 1D of the fourth embodiment, the common ground electrode 14B is arranged in the second electrode layer so as to connect and surround the periphery of the plurality of driving ICs 5. The first ground electrode 21b and the second ground electrode 22b are electrically joined to the common ground electrode 14B via the joining members 16 at both ends of the plurality of driving ICs 5.

[0106] In the thermal printhead 1D, the first and second ground electrodes 21b and 22b are electrically connected to the common ground electrode 14 via the bonding members 16 at both ends of the plurality of drive ICs 5. This allows the thermal printhead 1D to reduce the difference in voltage drop between the first and second ground electrodes 21b and 22b via the common ground electrode 14. This allows the thermal printhead 1D to equalize the power consumption of the heat generating resistor units 4 driven by the first group of drive ICs 111 and the second group of drive ICs 112, preventing differences in print density and enabling favorable printing.

[0107] In the thermal printhead 1D, the common ground electrode 14 is disposed on a second electrode layer above the first electrode layer. This allows the wiring widths of the power electrodes 21a and signal electrodes 21c included in the first wiring group 21 and the power electrodes 22a and signal electrodes 22c included in the second wiring group 22 to be wider than when the common ground electrode 14 is disposed on the first electrode layer. This reduces the wiring resistance of the first electrode layer and the power loss in the first wiring group 21 and the second wiring group 22.

[0108] Furthermore, since the thermal printhead 1D has the common ground electrode 14 wired to the second electrode layer where no other wiring is provided, the wiring width of the common ground electrode 14 can be secured wide without being restricted by other wiring, thereby reducing wiring resistance.

[0109] As described above, the present invention has been described with reference to Embodiments 2 to 4. However, the descriptions and drawings that form part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

[0110] For example, in the thermal printheads 1B, 1C, and 1D, the bonding members 16 are described as being disposed below each of the portions of the common ground electrode 14 that extend in the sub-scanning direction Y, but the bonding members 16 may not be disposed at all positions of the portions that extend in the sub-scanning direction Y. For example, it is sufficient that the bonding members 16 electrically connect the first ground electrode 21b and the second ground electrode 22b at at least one location among the multiple portions of the common ground electrode 14 that extend in the sub-scanning direction Y.

[0111] As such, embodiments 2 to 4 include various embodiments not described here.

[0112] Furthermore, a configuration may be adopted in which the first embodiment is appropriately combined with the second to fourth embodiments. For example, in the thermal printhead 1 of the first embodiment, as described in the second to fourth embodiments, the first and second ground electrodes 21b and 22b may be electrically connected to the common ground electrode 14 via the bonding members 16 at both ends of each of the first group of driving ICs 111 and the second group of driving ICs 112. This configuration can suppress increases in power consumption, improve printing efficiency, and prevent differences in print density.

[0113] The present disclosure includes configurations relating to the following notes.

[0114] (Note 1) An underglaze layer 12; a conductor layer 20 disposed on the upper surface of the underglaze layer 12; an insulating layer 30 disposed on the upper surface of the conductor layer 20, with a first connection region 201 and a second connection region 202 of the conductor layer 20 exposed in a plan view seen from the thickness direction of the underglaze layer 12; an electrode layer 40 disposed on the upper surface of the insulating layer 30 and including a common electrode 41 and an individual electrode 42; a connection wiring 50 isolated from the individual electrode 42 and facing the conductor layer 20 except for the first connection region 201 and the second connection region 202 via the insulating layer 30, the connection wiring 50 having a first wiring region 501 connected to the first connection region 201 and the common electrode 41 and a second wiring region 502 connected to the second connection region 202; a common electrode terminal 61 disposed in the second wiring region 502 of the connection wiring 50; a heating resistor 70 disposed above the insulating layer 30 and in contact with the common electrode 41 and the individual electrode 42. The thermal printhead 1, 1A includes:

[0115] In the thermal printhead 1, 1A described in Appendix 1, the common electrode 41 and the common electrode terminal 61 are electrically connected by both the conductor layer 20 and the connection wiring 50. Therefore, the thermal printhead 1, 1A described in Appendix 1 can reduce the electrical resistance between the common electrode 41 and the common electrode terminal 61. As a result, it is possible to suppress an increase in the overall power consumption of the thermal printhead 1, 1A and increase the heat generated in the heat-generating resistor portion. Therefore, the thermal printhead 1, 1A described in Appendix 1 can suppress an increase in power consumption and improve printing efficiency.

[0116] (Supplementary Note 2) The thermal printhead 1, 1A according to Supplementary Note 1, wherein the portion of the first wiring region 501 that overlaps the upper surface of the insulating layer 30 and a part of the common electrode 41 overlap in plan view.

[0117] (Appendix 3) The thermal printhead 1, 1A described in Appendix 1 or 2, wherein the common electrode terminal 61 is arranged on a laminated structure of the electrode layer 40 and a portion of the second wiring region 502 that overlaps the upper surface of the insulating layer 30.

[0118] According to the thermal printhead 1, 1A described in Supplementary Note 2 or 3, a conductive material is laminated on the common electrode 41 and the common electrode terminal 61. This makes it possible to reduce the electrical resistance between the common electrode 41 and the common electrode terminal 61.

[0119] (Appendix 4) A thermal printhead 1A according to any one of Appendices 1 to 3, wherein a groove 200 penetrating the conductive layer 20 in the thickness direction is provided in the area of ​​the conductive layer 20 that overlaps with the heating resistor 70 in a planar view.

[0120] According to the thermal printhead 1A described in Appendix 4, by providing a groove 200 that penetrates the conductive layer 20 in the thickness direction, the heat generated by the heating resistor 70 is more easily transferred to the underglaze layer 12, which is a heat storage layer.

[0121] (Appendix 5) The thermal printhead 1, 1A according to any one of Appendices 1 to 4, wherein the material of the underglaze layer 12 is a material having a higher firing temperature than the electrode layer 40, the connection wiring 50, the common electrode terminal 61 and the heating resistor 70.

[0122] According to the thermal printhead 1, 1A described in Appendix 5, the manufacturing process including the firing after the formation of the underglaze layer 12 can be simplified by performing the firing at a relatively low temperature.

[0123] (Appendix 6) The thermal printhead 1, 1A described in any one of Appendices 1 to 5, wherein, in a planar view, the outer edge of the common electrode 41 that overlaps with the connection wiring 50 overlaps with the outer edge of the insulating layer 30 or is located inside the outer edge of the insulating layer 30.

[0124] According to the thermal printhead 1, 1A described in Supplementary Note 6, a current path can be formed by the connection wiring 50 that connects the conductive layer 20 and the common electrode 41.

[0125] (Supplementary Note 7) The thermal printhead 1, 1A according to any one of Supplementary Notes 1 to 6, wherein the first connection region 201, the first wiring region 501 and the common portion 412 of the common electrode 41 extend in the main scanning direction X.

[0126] (Appendix 8) The thermal printhead 1, 1A according to any one of Appendices 1 to 7, wherein a part of the outer edge of the conductive layer 20 located outside the outer edge of the insulating layer 30 in a planar view is the first connection region 201 and the second connection region 202.

[0127] (Appendix 9) The thermal printhead 1, 1A according to any one of appendices 1 to 8, wherein the material of the connection wiring 50 is silver.

[0128] According to the thermal printhead 1, 1A described in Appendix 9, the connection wiring 50 can be obtained at low cost and has good metallic properties and ionization tendency.

[0129] (Supplementary Note 10) A thermal printer comprising the thermal printhead 1, 1A according to any one of Supplementary Notes 1 to 9.

[0130] In the thermal printer described in Supplementary Note 10, the common electrode 41 and the common electrode terminal 61 are electrically connected by both the conductive layer 20 and the connection wiring 50. Therefore, the thermal printer described in Supplementary Note 10 can reduce the electrical resistance between the common electrode 41 and the common electrode terminal 61. As a result, it is possible to suppress an increase in the overall power consumption of the thermal printer and increase the heat generated in the heat generating resistor portion. Therefore, the thermal printer described in Supplementary Note 10 can suppress an increase in power consumption and improve printing efficiency.

[0131] a common electrode terminal 61 formed in the second wiring region 502 of the connection wiring 50; and a heating resistor 70 in contact with the common electrode 41 and the individual electrode 42 formed above the insulating layer 30. (Appendix 11) A method for manufacturing a thermal printhead (1, 1A) comprising: forming a conductor layer 20 on the upper surface of the underglaze layer 12; forming an insulating layer 30 on the upper surface of the conductor layer 20 with a first connection region 201 and a second connection region 202 of the conductor layer 20 exposed in a plan view seen from the thickness direction of the underglaze layer 12; forming an electrode layer 40 including a common electrode 41 and an individual electrode 42 on the upper surface of the insulating layer 30;

[0132] In the method for manufacturing the thermal printhead 1, 1A described in Appendix 11, the common electrode 41 and the common electrode terminal 61 are electrically connected by both the conductor layer 20 and the connection wiring 50. Therefore, the method for manufacturing the thermal printhead 1, 1A described in Appendix 11 can reduce the electrical resistance between the common electrode 41 and the common electrode terminal 61. As a result, it is possible to suppress an increase in the overall power consumption of the thermal printhead 1, 1A and increase the heat generated in the heat-generating resistor portion. Therefore, the method for manufacturing the thermal printhead 1, 1A described in Appendix 11 can manufacture a thermal printhead 1, 1A that suppresses an increase in power consumption and improves printing efficiency.

[0133] (Appendix 12) A method for manufacturing the thermal printhead 1, 1A described in Appendix 11, in which the connection wiring 50 is formed so that the portion of the first wiring region 501 that overlaps the upper surface of the insulating layer 30 and a portion of the common electrode 41 overlap in a planar view.

[0134] (Appendix 13) A method for manufacturing the thermal printhead 1, 1A described in Appendix 11 or 12, in which the common electrode terminal 61 is formed on a laminated structure of the electrode layer 40 and a portion of the second wiring region 502 that overlaps the upper surface of the insulating layer 30.

[0135] According to the manufacturing method of the thermal printhead 1, 1A described in Supplementary Note 12 or 13, a conductive material is laminated on the common electrode 41 and the common electrode terminal 61. Therefore, the electrical resistance between the common electrode 41 and the common electrode terminal 61 can be reduced.

[0136] (Appendix 14) A method for manufacturing a thermal printhead 1A according to any one of Appendices 11 to 13, wherein a groove 200 is provided penetrating the conductive layer 20 in the thickness direction in a region of the conductive layer 20 that overlaps with the heating resistor 70 in a plan view.

[0137] According to the manufacturing method of the thermal printhead 1A described in Appendix 14, by providing a groove 200 that penetrates the conductive layer 20 in the thickness direction, the heat generated by the heating resistor 70 is more easily transferred to the underglaze layer 12, which is a heat storage layer.

[0138] (Appendix 15) A method for manufacturing the thermal printhead 1, 1A according to any one of Appendices 11 to 14, wherein the electrode layer 40, the connection wiring 50, the common electrode terminal 61, and the heating resistor 70 are fired at a temperature lower than the firing temperature of the underglaze layer 12.

[0139] According to the method for manufacturing the thermal printheads 1 and 1A described in Appendix 15, the manufacturing process including the firing after the formation of the underglaze layer 12 can be simplified by performing the firing at a relatively low temperature.

[0140] (Appendix 16) A method for manufacturing a thermal printhead 1, 1A described in any of Appendices 11 to 15, in which the electrode layer 40 is formed so that, in a planar view, the outer edge of the common electrode 41 that overlaps with the connection wiring 50 overlaps with the outer edge of the insulating layer 30 or is located inside the outer edge of the insulating layer 30.

[0141] According to the method for manufacturing the thermal printheads 1 and 1A described in Appendix 16, a current path can be formed by the connection wiring 50 that connects the conductive layer 20 and the common electrode 41.

[0142] (Supplementary Note 17) A method for manufacturing the thermal printhead 1, 1A according to any one of Supplementary Notes 11 to 16, wherein the first connection region 201, the first wiring region 501, and the common portion 412 of the common electrode 41 are formed to extend in the main scanning direction X.

[0143] (Appendix 18) A method for manufacturing a thermal printhead 1, 1A described in any of Appendices 11 to 17, in which the insulating layer 30 and the conductive layer 20 are formed so that a portion of the outer edge of the conductive layer 20 is located outside the outer edge of the insulating layer 30 in a planar view, and these portions are designated as the first connection region 201 and the second connection region 202.

[0144] (Appendix 19) The method for manufacturing the thermal printhead 1, 1A according to any one of Appendices 11 to 18, wherein the material of the connection wiring 50 is silver.

[0145] According to the method for manufacturing the thermal printhead 1, 1A described in Appendix 19, it is possible to form the connection wiring 50 at low cost, with good metallic properties and ionization tendency.

[0146] (Appendix A1) The present disclosure relates to rectangular thermal printheads 1B, 1C, and 1D. Each of the thermal printheads 1B, 1C, and 1D includes a substrate 11A, a heat generating resistor 4 arranged in the longitudinal direction of the substrate 11A, a plurality of individual electrodes 32 in contact with the heat generating resistor 4 and arranged in the lateral direction of the substrate 11A, a plurality of common electrodes 31 arranged in the lateral direction of the substrate 11A and electrically connected to the plurality of individual electrodes 32 via the heat generating resistor 4, a plurality of driving ICs 5 arranged in a line in the longitudinal direction of the thermal printheads 1B, 1C, and 1D and electrically connected to the plurality of individual electrodes 32, a ground electrode supplying a ground potential to each of the driving ICs 5, a plurality of power supply electrodes 21 a, 22 a supplying power to each of the driving ICs 5, a plurality of signal electrodes 21 c, 22 c supplying signals to each of the driving ICs 5, and external terminals 9 electrically connected to the ground electrode, the plurality of power supply electrodes 21 a, 22 a, and the plurality of signal electrodes 21 c, 22 c. The external terminals 9 include first external terminals 9X and second external terminals 9Y. The multiple driving ICs 5 include a first group of driving ICs 111 electrically connected to the first external terminals 9X and a second group of driving ICs 112 electrically connected to the second external terminals 9Y. The ground electrodes include a first ground electrode 21b electrically connected to each of the first group of driving ICs 111, a second ground electrode 22b electrically connected to each of the second group of driving ICs 112, and a common ground electrode 14 electrically connecting the first ground electrode 21b and the second ground electrode 22b. The first ground electrode 21b and the second ground electrode 22b are disposed on a first electrode layer of the substrate 11A, on which the multiple individual electrodes 32 and the multiple power electrodes 21a, 22a are provided. The common ground electrode 14 is disposed on a second electrode layer, which is stacked on the first electrode layer via an insulating layer 6, and is connected to the second electrode layer so as to surround the multiple driving ICs 5. The first ground electrode 21 b and the second ground electrode 22 b are electrically connected to the common ground electrode 14 via the connecting members 16 at both ends of the plurality of driving ICs 5 .

[0147] (Appendix A2) In the thermal printhead 1C described in (Appendix A1), the common ground electrode 14 is arranged on the second electrode layer and connected to surround the peripheries of the first group of driver ICs 111 and the second group of driver ICs 112. The first ground electrode 21b and the second ground electrode 22b are electrically joined to the common ground electrode 14 via joining members 16 at both ends of the first group of driver ICs 111 and the second group of driver ICs 112.

[0148] (Appendix A3) In the thermal printhead 1B described in (Appendix A1), the common ground electrode 14 is arranged on the second electrode layer and connected to surround each of the first group of driving ICs 111 and each of the second group of driving ICs 112. The first ground electrode 21 b and the second ground electrode 22 b are electrically joined to the common ground electrode 14 via joining members 16 at both ends of each of the first group of driving ICs 111 and each of the second group of driving ICs 112.

[0149] (Appendix A4) In the thermal printhead 1B, 1C, or 1D according to any one of (Appendix A1) to (Appendix A3), the bonding member 16 is also provided on the external terminal 9.

[0150] (Appendix A5) A thermal printhead 1B, 1C, or 1D described in any one of (Appendix A1) to (Appendix A4), wherein the distance from the external terminal 9 to the plurality of driving ICs 5 in the short direction of the thermal printhead 1B, 1C, or 1D is shorter than the distance from the plurality of driving ICs 5 to the heat generating resistor portion 4.

[0151] According to the thermal printheads 1B, 1C, and 1D disclosed herein, it is possible to equalize the power consumption of the heat generating resistor section 4 driven by the first group of drive ICs 111 and the heat generating resistor section 4 driven by the second group of drive ICs 112, thereby preventing differences in print density and enabling suitable printing.

[0152] Although the embodiments of the present disclosure have been described above, the above-described embodiments can be modified in various ways. Furthermore, the scope of the present disclosure is not limited to the above-described embodiments. The scope of the present disclosure is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0153] REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D...thermal print head 4...heat generating resistor portion 5, 111, 112...driver IC 6, 30...insulating layer 9...external terminal 9X...first external terminal 9Y...second external terminal 10...base 11, 11A...substrate 12...underglaze layer 14...common ground electrode 16...bonding member 20...conductor layer 21a...power supply electrode 21b...first ground electrode 21c...signal electrode 22a...power supply electrode 22b...second ground electrode 22c...signal electrode 31, 41...common electrode 32, 42...individual electrode 40...electrode layer 50...connection wiring 61...common electrode terminal 70...heat generating resistor 200...groove 201...first connection region 202...second connection region 412...common portion 501...first wiring region 502...Second wiring area

Claims

1. An underglaze layer; a conductive layer disposed on an upper surface of the underglaze layer; an insulating layer disposed on an upper surface of the conductor layer in a state in which a first connection region and a second connection region of the conductor layer are exposed in a plan view seen from a thickness direction of the underglaze layer; an electrode layer disposed on an upper surface of the insulating layer, the electrode layer including a common electrode and individual electrodes; a connection wiring that is isolated from the individual electrode and faces the conductor layer except for the first connection region and the second connection region via the insulating layer, the connection wiring having a first wiring region connected to the first connection region and the common electrode, and a second wiring region connected to the second connection region; a common electrode terminal disposed in the second wiring region of the connection wiring; a heating resistor disposed above the insulating layer and in contact with the common electrode and the individual electrodes; A thermal print head comprising:

2. The thermal printhead according to claim 1 , wherein a portion of the first wiring region that overlaps the upper surface of the insulating layer and a portion of the common electrode overlap in the plan view.

3. The thermal printhead according to claim 1 , wherein the common electrode terminal is disposed on a laminated structure including a portion of the second wiring region overlapping the upper surface of the insulating layer and the electrode layer.

4. 4. The thermal printhead according to claim 1, wherein a groove penetrating said conductive layer in a thickness direction is provided in a region of said conductive layer overlapping said heating resistor in the plan view.

5. 2. The thermal printhead according to claim 1, wherein the material of the underglaze layer is a material having a higher firing temperature than the electrode layer, the connection wiring, the common electrode terminal and the heating resistor.

6. The thermal printhead according to claim 1 , wherein, in the plan view, an outer edge of the common electrode that overlaps with the connection wiring overlaps with an outer edge of the insulating layer or is located inside the outer edge of the insulating layer.

7. The thermal printhead according to claim 1 , wherein the first connection region, the first wiring region and the common portion of the common electrode extend in a main scanning direction.

8. The thermal printhead according to claim 1 , wherein a part of an outer edge of the conductive layer located outside an outer edge of the insulating layer in the plan view is the first connection region and the second connection region.

9. 2. The thermal printhead of claim 1, wherein the material of the connecting wires is silver.

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

11. forming a conductive layer on the upper surface of the underglaze layer; forming an insulating layer on an upper surface of the conductor layer in a state in which a first connection region and a second connection region of the conductor layer are exposed in a plan view seen from a thickness direction of the underglaze layer; forming an electrode layer including a common electrode and individual electrodes on an upper surface of the insulating layer; a connection wiring having a first wiring region connected to the first connection region and the common electrode and a second wiring region connected to the second connection region is formed so as to be isolated from the individual electrodes and to face the conductor layer except for the first connection region and the second connection region via the insulating layer; forming a common electrode terminal in the second wiring region of the connection wiring; A heating resistor in contact with the common electrode and the individual electrodes is formed above the insulating layer. A method for manufacturing a thermal printhead.

12. The method for manufacturing a thermal printhead according to claim 11 , wherein the connection wiring is formed such that a portion of the first wiring region that overlaps the upper surface of the insulating layer and a portion of the common electrode overlap in the plan view.

13. The method for manufacturing a thermal printhead according to claim 11 , wherein the common electrode terminal is formed on a laminated structure of the electrode layer and a portion of the second wiring region that overlaps the upper surface of the insulating layer.

14. The method for manufacturing a thermal printhead according to claim 11 , further comprising providing a groove penetrating the conductive layer in a thickness direction in a region of the conductive layer overlapping the heating resistor in the plan view.

15. The method for manufacturing a thermal printhead according to claim 11 , wherein the electrode layer, the connection wiring, the common electrode terminal, and the heating resistor are fired at a temperature lower than a firing temperature of the underglaze layer.

16. The method for manufacturing a thermal printhead according to claim 11 , wherein the electrode layer is formed such that, in the planar view, an outer edge of the common electrode that overlaps with the connection wiring overlaps with an outer edge of the insulating layer or is located inside the outer edge of the insulating layer.

17. The method for manufacturing a thermal printhead according to claim 11 , wherein the first connection region, the first wiring region and the common portion of the common electrode are formed to extend in a main scanning direction.

18. The method for manufacturing a thermal printhead according to claim 11, wherein the insulating layer and the conductive layer are formed so that a portion of an outer edge of the conductive layer is positioned outside an outer edge of the insulating layer in the planar view, and the portion is made to be the first connection region and the second connection region.

19. The method for manufacturing a thermal printhead according to claim 11 , wherein the material of the connection wiring is silver.