Thermal print head and recording device

Abstract

A thermal print head according to the present disclosure comprises a plurality of individual electrodes, a common electrode, and a resistor layer. The plurality of individual electrodes extend along a first direction and are arrayed in a second direction intersecting the first direction. The common electrode has a first electrode and a plurality of second electrodes. The first electrode extends along the second direction. The plurality of second electrodes are connected to the first electrode, extend along the first direction, and are arrayed in the second direction. The resistor layer extends along the second direction and, in a plan view viewed from a third direction orthogonal to the first direction and the second direction, has a portion overlapping the plurality of individual electrodes and the plurality of second electrodes. The common electrode further has a third electrode. The third electrode is connected to the first electrode, extends along the first direction, and does not overlap the resistor layer in plan view. The plurality of second electrodes and the third electrode are arrayed at intervals in the second direction.

Description

Thermal head and recording apparatus

[0001] The present disclosure relates to a thermal head and a recording apparatus including the thermal head.

[0002] Conventionally, various thermal heads have been proposed as printing devices for facsimiles, video printers, and the like. For example, a thermal head includes a plurality of heating units arranged in a main scanning direction on a substrate. Each heating unit is formed by alternately arranging comb-teeth portions of a common electrode extending in the main scanning direction and individual electrodes in the sub-scanning direction on a substrate, and covering a part of these alternately arranged portions with a resistor layer. In the thermal head, when electricity is passed between the common electrode and the individual electrodes, a portion (heating unit) of the resistor layer located between the common electrode and the individual electrode generates heat. The thermal head performs printing on a print medium by transferring the heat to the print medium.

[0003] Electrode patterns of the common electrode and the individual electrodes are formed by screen-printing a paste using a metal such as gold.

[0004] Furthermore, connection electrodes for supplying voltage from the outside to the common electrode and the individual electrodes are respectively in contact with the common electrode and the individual electrodes. Electrode patterns of the connection electrodes are formed by screen-printing a paste using a metal such as silver. Since gold is expensive, from the viewpoint of reducing product cost, a technology using silver as a relatively inexpensive metal with good electrical conductivity has been proposed.

[0005] Japanese Patent Application Laid-Open No. 2022-59865

[0006] The thermal head according to this disclosure comprises a plurality of individual electrodes, a common electrode, and a resistive layer. The plurality of individual electrodes have portions extending along a first direction and are aligned in a second direction intersecting the first direction. The common electrode has a first electrode and a plurality of second electrodes. The first electrode extends along a second direction. The plurality of second electrodes are connected to the first electrode and extend along the first direction and are aligned in the second direction. The resistive layer extends along a second direction and has portions that overlap with the plurality of individual electrodes and the plurality of second electrodes in a plan view from a third direction perpendicular to the first and second directions. The common electrode further has a third electrode. The third electrode is connected to the first electrode and extends along the first direction and does not overlap with the resistive layer in a plan view. The plurality of second electrodes and the third electrode are spaced apart in the second direction.

[0007] The recording device according to this disclosure includes the thermal head and a moving unit that moves the thermal head and the recording medium relative to each other.

[0008] Figure 1 is an exploded perspective view showing a schematic of a thermal head according to the first embodiment. Figure 2 is a plan view showing a schematic of the thermal head shown in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Figure 4 is a schematic enlarged view of region IV shown in Figure 2. Figure 5 is a schematic plan view showing the configuration of the first electrode according to the first embodiment. Figure 6 is a schematic plan view showing the configuration of a thermal head according to the second embodiment. Figure 7 is a schematic plan view showing another example of the configuration of a thermal head according to the second embodiment. Figure 8 is a schematic diagram of a thermal printer according to the first or second embodiment.

[0009] The embodiments for implementing the thermal head and recording device according to this disclosure (hereinafter referred to as "Embodiments") will be described in detail below with reference to the drawings. However, this disclosure is not limited by these embodiments. Furthermore, each embodiment can be combined as appropriate, provided that the processing content is not inconsistent. Also, the same parts are denoted by the same reference numerals in each of the following embodiments, and redundant descriptions are omitted.

[0010] Furthermore, in the embodiments described below, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not require strict adherence to "constant," "orthogonal," "perpendicular," or "parallel" conditions. In other words, each of the above expressions allows for deviations such as manufacturing accuracy or installation accuracy.

[0011] Furthermore, in the drawings referenced below, a Cartesian coordinate system with mutually orthogonal X, Y, and Z axes may be shown for the sake of clarity.

[0012] When the materials of the common electrode and the connecting electrode are dissimilar metals, heating causes mass transfer at the interface between the common electrode and the connecting electrode due to the interdiffusion of atoms. As a result, the Kirkendall effect occurs due to the difference in the diffusion rates of the respective metals.

[0013] For example, if the common electrode is made of gold and the connecting electrode is made of silver, heating causes the gold material of the common electrode and the silver material of the connecting electrode to diffuse with each other. This diffusion generates Kirkendal voids. If these Kirkendal voids form in the common electrode, especially in the comb-shaped sections where the common electrode and individual electrodes are arranged alternately, it may lead to a break in the connection because the comb-shaped sections are thin electrodes. Also, if the silver from the connecting electrode diffuses through the common electrode to the resistor, the resistance value may fluctuate.

[0014] In this regard, Patent Document 1 discloses a thermal print head in which a common electrode, which is in contact with a connecting electrode and made of a different material from the connecting electrode, has a slit provided between the contact point with the connecting electrode and the comb-tooth portion of the common electrode. It is stated that this makes it possible to reduce the area in which the material of the connecting electrode diffuses into the common electrode, and reduces the extent to which the diffusion area reaches the comb-tooth portion.

[0015] However, in the technology described in Patent Document 1, the presence of a slit in the current path from the connecting electrode to the comb teeth of the common electrode may obstruct the flow of current. If the flow of current is obstructed, the print quality may deteriorate.

[0016] (First Embodiment) Figure 1 is an exploded perspective view showing a schematic of a thermal head X1 according to the first embodiment. As shown in Figure 1, the thermal head X1 according to the first embodiment includes a heat sink 1, an adhesive member 2, a head base 3, and a connector 4. Note that the heat sink 1, adhesive member 2, and connector 4 are not necessarily required.

[0017] The heat sink 1 dissipates excess heat from the head base 3. The adhesive member 2 adheres the heat sink 1 and the head base 3 together. The head base 3 is placed on the heat sink 1 via the adhesive member 2. The head base 3 prints onto the recording medium P (see Figure 8) when an external voltage is applied. The connector 4 electrically connects the head base 3 to the outside.

[0018] The heat sink 1 has a rectangular parallelepiped shape. The heat sink 1 is made of a metal material such as copper, iron, or aluminum, and dissipates the heat generated in the heat-generating part 9a of the head base 3 that does not contribute to printing.

[0019] The adhesive member 2 is located on the heat sink 1. The adhesive member 2 joins the head base 3 and the heat sink 1. Examples of adhesive members 2 include double-sided tape or a resin-based adhesive.

[0020] The head base 3 has a substrate 5. The components constituting the thermal head X1 are arranged on the substrate 5. The head base 3 prints on the recording medium P (see Figure 8) according to electrical signals supplied from the outside.

[0021] Next, we will further explain each component constituting the thermal head X1 using Figures 2 to 4. Figure 2 is a schematic plan view of the thermal head X1 shown in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Figure 4 is a schematic enlarged view of region IV shown in Figure 2. Note that in Figure 2, the covering member 10 is shown by a dashed line, and the protective layer 11 and the covering layer 12 are not shown.

[0022] The head base 3 includes a substrate 5, a plurality of electrodes 6, a plurality of connection terminals 7, a plurality of drive ICs (Integrated Circuits) 8, a resistive layer 9, a covering member 10, a protective layer 11, and a covering layer 12. Note that not all of these components are necessarily included. Furthermore, the head base 3 may also include other components.

[0023] The substrate 5 is placed on the heat sink 1. When viewed from above in the thickness direction of the substrate 5 (the Z-axis direction in Figure 4), the substrate 5 is rectangular in shape. As shown in Figure 3, the substrate 5 has a first surface 5a, a second surface 5b, and a side surface 5c.

[0024] As shown in Figure 2, the first surface 5a has a first long side 5d, a second long side 5e, a first short side 5f, and a second short side 5g. The components constituting the head base 3 are arranged on the first surface 5a.

[0025] The second surface 5b is located on the opposite side from the first surface 5a. The second surface 5b is located on the side of the heat sink 1 and is joined to the heat sink 1 via the adhesive member 2. The side surface 5c connects the first surface 5a and the second surface 5b and is located on the side of the second long side 5e.

[0026] The substrate 5 is formed from, for example, an electrically insulating material such as alumina ceramics or a semiconductor material such as single-crystal silicon.

[0027] The substrate 5 may have a first heat storage layer 13. The first heat storage layer 13 is located on the first surface 5a of the substrate 5. The first heat storage layer 13 is located away from the first long side 5d of the substrate 5. The first heat storage layer 13 protrudes from the first surface 5a in the thickness direction of the substrate 5 (here, the Z-axis direction) and extends in a strip shape along a second direction (here, the Y-axis direction) that intersects the first direction (here, the X-axis direction). As shown in Figure 4, in a plan view from a third direction (here, the Z-axis direction) perpendicular to the first and second directions, the first heat storage layer 13 has a portion that overlaps with the resistor layer 9. The first heat storage layer 13 has the function of pressing the recording medium P (see Figure 8) to be printed on against the protective layer 11 located on the heat-generating portion 9a.

[0028] The first heat storage layer 13 may also have a base portion (not shown) that extends over the entire area of ​​the first surface 5a side of the substrate 5.

[0029] The first heat storage layer 13 contains, for example, a glass component. The first heat storage layer 13 temporarily stores a portion of the heat generated in the heat-generating section 9a. This allows the first heat storage layer 13 to shorten the time required to raise the temperature of the heat-generating section 9a. In other words, the first heat storage layer 13 has the function of improving the thermal response characteristics of the thermal head X1.

[0030] The first heat storage layer 13 is manufactured, for example, by applying a predetermined glass paste obtained by mixing glass powder with a suitable organic solvent to the first surface 5a of the substrate 5 by conventionally known screen printing or the like, and then firing it. The substrate 5 may have only a base portion as the first heat storage layer 13.

[0031] Multiple electrodes 6 are located on the first surface 5a of the substrate 5. Multiple electrodes 6 constitute a conductive path for energizing the heating element 9a and the drive IC 8. Multiple electrodes 6 include a common electrode 61, multiple individual electrodes 62, multiple first connecting electrodes 63, and multiple second connecting electrodes 64.

[0032] The common electrode 61 is located on the first surface 5a of the substrate 5. The common electrode 61 electrically connects the plurality of heating elements 9a and the connector 4. The common electrode 61 has a first electrode 611, a plurality of second electrodes 612, a plurality of third electrodes 613, a plurality of fourth electrodes 614, and a plurality of fifth electrodes 615. The first electrode 611 extends along a second direction (here, the Y-axis direction) that intersects the first direction. The plurality of second electrodes 612 are arranged at predetermined intervals in the second direction (here, the Y-axis direction). Each second electrode 612 is connected to the first electrode 611 and extends along the first direction (here, the X-axis direction). A portion of each second electrode 612 is inserted through to the opposite side of the heating element 9a. The plurality of fourth electrodes 614 extend along the first short side 5f and the second short side 5g of the substrate 5, respectively. Multiple fifth electrodes 615 extend along the second long side 5e of the substrate 5. Each fifth electrode 615 is connected to each fourth electrode 614.

[0033] The individual electrodes 62 are located on the first surface 5a of the substrate 5. The individual electrodes 62 electrically connect the heating element 9a and the drive IC 8. The multiple heating elements 9a are divided into multiple groups. The individual electrodes 62 electrically connect the heating elements 9a constituting each group to the corresponding drive IC 8.

[0034] The individual electrodes 62 are electrically connected to the drive IC 8 by a bonding material 24. The bonding material 24 is conductive. The bonding material 24 may contain gold (Au) or tin (Sn). The material of the bonding material 24 may be, for example, AuSn, SnAg, SnAgCu, SnAgCuNi, Sn, or Au. Such a bonding material 24 has high mechanical strength, such as shear stress resistance, and is less likely to peel off from the individual electrodes 62, thus providing high durability.

[0035] Multiple individual electrodes 62 are arranged at predetermined intervals in the second direction (here, the Y-axis direction). Each individual electrode 62 extends along the first direction (here, the X-axis direction). The individual electrodes 62 are located between two adjacent second electrodes 612. Therefore, in the thermal head X1, the second electrodes 612 and individual electrodes 62 are arranged alternately at predetermined intervals in the second direction (here, the Y-axis direction).

[0036] Multiple first connection electrodes 63 electrically connect the drive IC 8 and the connector 4.

[0037] Multiple second connecting electrodes 64 electrically connect adjacent drive ICs 8.

[0038] The common electrode 61, individual electrodes 62, first connecting electrode 63, and second connecting electrode 64 are formed of a conductive material. The material of the common electrode 61, individual electrodes 62, first connecting electrode 63, and second connecting electrode 64 may be, for example, one of the metals Al, Au, Cu, or Ag, or an alloy containing these metallic elements.

[0039] The thickness of the individual electrodes 62 is, for example, 3.0 μm or less, and may be, for example, 0.1 μm to 3.0 μm. This makes it less likely for heat generated in the heat-generating section 9a to dissipate through the individual electrodes 62. In addition, by reducing the step difference with the substrate 5, for example, the protective layer 11 covering the heat-generating section 9a becomes less likely to peel off, improving the reliability of the thermal head X1.

[0040] Furthermore, the thickness of the various electrodes other than the individual electrode 62 is, for example, about 0.1 μm to 15 μm, or for example, about 0.3 μm to 10 μm. Note that the thickness of the various electrodes other than the individual electrode 62 may be the same as the thickness of the individual electrode 62.

[0041] Multiple electrodes 6 can be formed, for example, by gravure offset printing. The method for forming electrodes 6 by gravure offset printing is as follows: First, printing paste is filled into the recesses of the gravure plate with a doctor blade. Next, the printing paste is transferred to a blanket. Then, the printing paste transferred to the blanket is transferred to the object to be printed, such as a substrate. Finally, the electrodes 6 are formed by firing the printing paste.

[0042] Furthermore, the multiple electrodes 6 may be formed by, for example, screen printing, flexographic printing, or gravure printing. The common electrode 61, individual electrodes 62, first connecting electrode 63, and second connecting electrode 64 may be formed with the same thickness and the same manufacturing method, or they may be formed with different thicknesses and different manufacturing methods.

[0043] Multiple connection terminals 7 are located on the second long side 5e of the substrate 5. Each connection terminal 7 connects the common electrode 61 or the first connection electrode 63 to the connector 4. Each connection terminal 7 may be located corresponding to the connector pins (not shown) of the connector 4. When connecting the connector 4, the connector pins and connection terminals 7 may be connected so that they are electrically independent of each other.

[0044] The plurality of driving ICs 8 are located on the first surface 5a side of the substrate 5. The plurality of driving ICs 8 are arranged along the arrangement direction of the heat generating portions 9a (the Y-axis direction in the present description). Each driving IC 8 is positioned corresponding to the plurality of heat generating portions 9a assigned to the respective driving IC 8. Each driving IC 8 is connected to the plurality of individual electrodes 62, the plurality of first connection electrodes 63, and the second connection electrodes 64. The driving IC 8 controls the energization state of the heat generating portions 9a. The driving IC 8 supplies electric power for individually causing each heat generating portion 9a to generate heat to the heat generating portions 9a in accordance with an electric signal supplied from the outside. As the driving IC 8, for example, a switching IC having a plurality of switching elements therein can be used.

[0045] The resistor layer 9 extends along the second direction (the Y-axis direction in the present description). As shown in FIG. 2 and FIG. 4, the resistor layer 9 has portions overlapping the plurality of second electrodes 612 of the common electrode 61 and the plurality of individual electrodes 62 in a plan view seen from the third direction (the Z-axis direction in the present description). In the resistor layer 9, portions located between the second electrodes 612 and the individual electrodes 62 each function as the heat generating portion 9a. As shown in FIG. 4, the plurality of heat generating portions 9a are arranged at predetermined intervals in the second direction (the Y-axis direction in the present description). Each heat generating portion 9a may be located at a density of, for example, 100 dpi (dots per inch) or more. Further, each heat generating portion 9a may be located at a density of 200 to 2400 dpi.

[0046] The thickness of the resistor layer 9 is, for example, approximately 3 to 6 μm. The sheet resistance of the resistor layer 9 is, for example, approximately 500 to 8000Ω / □. Further, the coefficient of thermal expansion of the resistor layer 9 is, for example, approximately 5 to 10 ppm / °C. Further, the thermal conductivity of the resistor layer 9 is, for example, approximately 0.5 to 2 W / (m·K).

[0047] The resistor layer 9 may be formed, for example, by placing a material paste containing a conductive component and a glass component into a long strip shape in the main scanning direction by a screen printing method or a dispensing device or the like on the substrate 5 on which various electrodes have been patterned. The conductive component may contain ruthenium oxide, for example. The glass component may contain lead borosilicate glass, for example.

[0048] The covering member 10 is a member that seals the drive IC 8, the individual electrodes 62, the first connecting electrode 63, and the second connecting electrode 64 while they are connected. The covering member 10 is arranged to extend in the second direction (here, the Y-axis direction) and integrally seals multiple drive ICs 8. The covering member 10 covers a portion of the covering layer 12. For example, a resin material such as epoxy resin or silicone resin can be used as the covering member 10.

[0049] The protective layer 11 is located on the first surface 5a side of the substrate 5. The protective layer 11 covers the heat-generating portion 9a. The protective layer 11 is located across the substrate 5 in a second direction (in this case, the Y-axis direction).

[0050] The protective layer 11 protects the covered area from corrosion caused by the adhesion of moisture contained in the atmosphere, or from abrasion caused by contact with the recording medium P (see Figure 8) to be printed on. Examples of materials for the protective layer 11 include SiN, SiON, and SiO ２ SiO2, TiN, TiON, TiCrN, or TiAlON can be used.

[0051] The coating layer 12 is located on the first surface 5a side of the substrate 5. The coating layer 12 partially covers the common electrode 61, individual electrodes 62, first connecting electrode 63, and second connecting electrode 64. The coating layer 12 protects the covered area from oxidation due to contact with the atmosphere or corrosion due to the adhesion of moisture contained in the atmosphere. For example, a resin material such as epoxy resin, polyimide resin, or silicone resin can be used as the coating layer 12.

[0052] In the thermal head X1 described above, if the material of the first electrode 611 and the material of the second electrode 612 of the common electrode 61 are dissimilar metals, heating causes mass transfer based on the mutual diffusion of atoms at the interface between the first electrode 611 and the second electrode 612. As a result, the Kirkendal effect occurs due to the difference in the diffusion rates of the respective metals. For example, if the first electrode 611 is made of silver and the second electrode 612 is made of gold, heating causes the silver, which is the material of the first electrode 611, and the gold, which is the material of the second electrode 612, to diffuse with each other. This diffusion generates Kirkendal voids. If these Kirkendal voids occur in the second electrode 612, it may lead to a break in the wire because the second electrode 612 is a thin electrode. Also, if the silver, which is the material of the first electrode 611, diffuses through the second electrode 612 to the resistor layer 9, the resistance value may fluctuate.

[0053] Therefore, the common electrode 61 of the thermal head X1 according to the first embodiment further has a third electrode 613. The third electrode 613 is connected to the first electrode 611 and extends along the first direction (here, the X-axis direction). As shown in Figure 4, the third electrode 613 does not overlap with the resistive layer 9 in a plan view from the third direction (here, the Z-axis direction). The multiple second electrodes 612 and the third electrode 613 are arranged with a gap between them in the second direction (here, the Y-axis direction). Also, the material of the third electrode 613 may be the same as the material of the second electrode 612.

[0054] Thus, because the common electrode 61 has a third electrode 613, even if the material of the first electrode 611 and the materials of the second electrode 612 and third electrode 613 are dissimilar metals, Kirkendal voids are less likely to occur in the second electrode 612. For example, if the first electrode 611 is made of silver and the second electrode 612 and third electrode 613 are made of gold, heating causes the silver, which is the material of the first electrode 611, to diffuse into the third electrode 613 and the second electrode 612, thereby reducing the amount of silver that diffuses into the second electrode 612. As a result, Kirkendal voids are less likely to occur in the second electrode 612. In addition, the diffusion of the silver, which is the material of the first electrode 611, to the resistive layer 9 via the second electrode 612 can be reduced. As a result, fluctuations in the resistance value due to the diffusion of silver into the resistive layer 9 are less likely to occur. Furthermore, compared to the case where there is a slit in the first electrode 611, the flow of current is less likely to be obstructed. Therefore, the thermal head X1 according to the first embodiment has excellent print quality.

[0055] As shown in Figure 4, the common electrode 61 may have multiple third electrodes 613. The second electrode 612 and the third electrode 613 may be arranged alternately at a predetermined interval in the second direction (here, the Y-axis direction).

[0056] As shown in Figure 4, each of the multiple second electrodes 612 may have a first portion 612a connected to the first electrode 611 and a second portion 612b connected to the first portion 612a. In this case, the width W2 of the second portion 612b may be smaller than the width W1 of the first portion 612a.

[0057] As a result, even if the material of the first electrode 611 and the materials of the second electrode 612 and the third electrode 613 are dissimilar metals, heating causes a large amount of the metal material of the first electrode 611 to diffuse into the third electrode 613 and the first portion 612a of the second electrode 612. This reduces the amount of metal diffusion into the second portion 612b of the second electrode 612.

[0058] The distance S1 between the multiple second electrodes 612 and the third electrode 613 in the second direction (here, the Y-axis direction) may be smaller than the width W3 of the third electrode 613.

[0059] This allows the area of ​​the third electrode 613 to be increased. Therefore, even if the material of the first electrode 611 and the materials of the second electrode 612 and the third electrode 613 are dissimilar metals, heating allows a large amount of the metal material of the first electrode 611 to diffuse into the third electrode 613, and the amount of metal diffusion to the second electrode 612 can be further reduced.

[0060] As shown in Figure 4, in a plan view from the third direction (in this case, the Z-axis direction), the first heat storage layer 13 does not overlap with the third electrode 613.

[0061] This reduces the diffusion of the metal material of the first electrode 611 into the resistor layer 9 via the third electrode 613 and the first heat storage layer 13 due to heating. Therefore, fluctuations in the resistance value due to the diffusion of metal into the resistor layer 9 become less likely.

[0062] As shown in Figure 4, in a plan view from a third direction (here, the Z-axis direction), the ends 613a of the third electrode 613 that are not connected to the first electrode 611 in the first direction (here, the X-axis direction) may have an arc shape.

[0063] In gravure offset printing, the doctor blade frequently wears down. This can result in uneven ink removal, causing electrodes to form in an island-like shape in areas where there should be no pattern. Through these island-like electrodes, the metal of the third electrode 613 or metal diffused onto the third electrode 613 can cause ion migration between the end 613a of the third electrode 613 and the tip of the individual electrode 62, potentially leading to a short circuit. At this time, if there is a corner at the end 613a of the third electrode 613, electric field concentration occurs, accelerating ion migration. On the other hand, the third electrode 613 according to the first embodiment has an arc shape at the end 613a, which mitigates electric field concentration and reduces ion migration.

[0064] Next, the configuration of the first electrode 611 according to the first embodiment will be described using Figure 5. Figure 5 is a schematic plan view showing the configuration of the first electrode 611 according to the first embodiment. For ease of understanding, in Figure 5, the second metal layer 6112 covering the first metal layer 6111 of the first electrode 611 is shown by a dashed line.

[0065] As shown in Figure 5, the first electrode 611 may have a first metal layer 6111 and a second metal layer 6112. The first metal layer 6111 may have a plurality of third portions 6111a and a fourth portion 6111b.

[0066] The multiple third portions 6111a may be arranged at predetermined intervals in the second direction (here, the Y-axis direction). The multiple third portions 6111a may be connected one-to-one with the multiple second electrodes 612 and may extend in the first direction (here, the X-axis direction).

[0067] The fourth part 6111b may connect two adjacent third parts 6111a.

[0068] The second metal layer 6112 may extend along a second direction (in this case, the Y-axis direction). The second metal layer 6112 may have a portion that covers the first metal layer 6111.

[0069] The second metal layer 6112 may contain a different metal element than the one contained in the first metal layer 6111. Alternatively, the first metal layer 6111 may contain the same metal element as the one contained in the third electrode 613.

[0070] In this way, when the second metal layer 6112, which contains a different metal element than the first metal layer 6111, covers the first metal layer 6111, the metal material of the second metal layer 6112 diffuses into the first metal layer 6111 upon heating. This reduces the amount of metal that diffuses into the second electrode 612.

[0071] As shown in Figure 5, the thermal head X1 may have multiple fourth portions 6111b. In this case, two adjacent fourth portions 6111b may be in different positions in the first direction (here, the X-axis direction).

[0072] As a result, in the process of forming the first electrode 611 by gravure offset printing, if the second direction is perpendicular to the direction of travel of the doctor blade or blanket, the number of adjacent recesses (corresponding to the fourth portion 6111b) in the second direction is reduced. Therefore, the phenomenon of the doctor blade or blanket sinking deeply into recesses can be reduced. Consequently, the possibility of defects in the first electrode 611 or the printing width of the printed pattern becoming wider than the design value can be reduced, and the quality of printing can be improved.

[0073] As shown in Figure 5, the first metal layer 6111 may further have a fifth portion 6111c. The fifth portion 6111c is connected to the third electrode 613 and may extend in the first direction (in this case, the X-axis direction).

[0074] The fifth portion 6111c does not need to be in contact with the multiple third portions 6111a and fourth portions 6111b. This reduces the diffusion of the metal material of the first metal layer 6111 from the third electrode 613 to the second electrode 612 via the third portions 6111a and fourth portions 6111b due to heating.

[0075] As described above, the common electrode 61 of the thermal head X1 according to the first embodiment further has a third electrode 613. The third electrode 613 is connected to the first electrode 611 and extends along the first direction (here, the X-axis direction). As shown in Figure 4, the third electrode 613 does not overlap with the resistive layer 9 in a plan view from the third direction (here, the Z-axis direction). The multiple second electrodes 612 and the third electrode 613 are arranged with a gap between them in the second direction (here, the Y-axis direction). As a result, when heated, the metal material of the first electrode 611 diffuses into the third electrode 613, thus reducing the diffusion of metal to the second electrode 612. Therefore, Kirkendal voids are less likely to occur in the second electrode 612. In addition, fluctuations in resistance due to the diffusion of metal into the resistive layer 9 are less likely to occur. Accordingly, the thermal head X1 according to the first embodiment has excellent print quality.

[0076] Figure 4 shows an example where the third electrode 613 extends from the first electrode 611 toward the resistor layer 9. However, the third electrode 613 does not necessarily have to extend from the first electrode 611. For example, the third electrode 613 may have a portion that overlaps with the first electrode 611 in a plan view from a third direction (here, the Z-axis direction). This allows the amount of metal diffusion to the second electrode 612 to be reduced because heating causes the metal material of the first electrode 611 to diffuse into the third electrode 613, even if the materials of the first electrode 611 and the third electrode 613 are dissimilar metals.

[0077] Although Figures 4 and 5 show an example in which the end portion 613a of the third electrode 613 has an arc shape, the design is not limited to this, and the end portion of the second electrode 612 or the end portion of the individual electrodes 62 may also have an arc shape.

[0078] (Second Embodiment) Figure 6 is a schematic plan view showing the configuration of the thermal head X1 according to the second embodiment. Figure 7 is a schematic plan view showing another example of the configuration of the thermal head X1 according to the second embodiment.

[0079] As shown in Figures 6 and 7, the thermal head X1 according to the second embodiment may further have a second heat storage layer 14.

[0080] The second heat storage layer 14 has a portion that overlaps with the first electrode 611. The second heat storage layer 14 does not necessarily have to overlap with the first heat storage layer 13 in a plan view from the third direction (in this case, the Z-axis direction).

[0081] This induces the diffusion of the metal from the first electrode 611 into the second heat storage layer 14, while reducing the diffusion of the metal from the second heat storage layer 14 to the first heat storage layer 13, thereby reducing the diffusion of the metal from the second heat storage layer 14 to the resistor layer 9 via the first heat storage layer 13.

[0082] The second metal layer 6112 of the common electrode 61 may have a portion that is in contact with the second heat storage layer 14. In the example of Figure 6, a portion of the second metal layer 6112 is in contact with a portion of the second heat storage layer 14. In the example of Figure 7, the entire second metal layer 6112 is in contact with a portion of the second heat storage layer 14.

[0083] Thus, because the second metal layer 6112 has a portion in contact with the second heat storage layer 14, diffusion of the metal from the second metal layer 6112 into the second heat storage layer 14 is induced, thereby reducing the amount of metal diffusion to the second electrode 612. Furthermore, diffusion of the metal from the first electrode 611 to the resistor layer 9 via the second electrode 612 can be reduced, thereby improving the stability and reliability of the resistance value.

[0084] (Thermal Printer Configuration) Next, a thermal printer Z1 having a thermal head X1 according to the first or second embodiment will be described with reference to Figure 8. Figure 8 is a schematic diagram of the thermal printer Z1 according to the first or second embodiment.

[0085] The thermal printer Z1 comprises a thermal head X1 according to the first or second embodiment, a transport mechanism 40, a platen roller 50, a power supply unit 60, and a control device 70. The thermal head X1 is mounted on the mounting surface 80a of a mounting member 80 located on the housing (not shown) of the thermal printer Z1. The thermal head X1 is mounted on the mounting member 80 so as to be aligned with the main scanning direction, which is perpendicular to the transport direction S.

[0086] The transport mechanism 40 includes a drive unit (not shown) and transport rollers 43, 45, 47, and 49. The transport mechanism 40 transports a recording medium P, such as thermal paper or image receiving paper onto which ink is transferred, along the transport direction S indicated by the arrow onto a protective layer 11 located on a plurality of heating elements 9a of the thermal head X1. The drive unit has the function of driving the transport rollers 43, 45, 47, and 49. For example, a motor may be used as the drive unit. The transport rollers 43, 45, 47, and 49 may be constructed by covering cylindrical shafts 43a, 45a, 47a, and 49a made of a metal such as stainless steel with elastic members 43b, 45b, 47b, and 49b made of a material such as butadiene rubber. When the recording medium P is image receiving paper onto which ink is transferred, an ink film (not shown) is transported together with the recording medium P between the recording medium P and the heating elements 9a of the thermal head X1.

[0087] The platen roller 50 has the function of pressing the recording medium P onto the protective layer 11 located on the heating element 9a of the thermal head X1. The platen roller 50 is arranged to extend in a direction perpendicular to the transport direction S, and both ends are supported and fixed so that it can rotate while pressing the recording medium P onto the heating element 9a. The platen roller 50 may be constructed, for example, by covering a cylindrical shaft 50a made of metal such as stainless steel with an elastic member 50b made of butadiene rubber or the like.

[0088] The power supply unit 60 has the function of supplying current to generate heat in the heat-generating part 9a of the thermal head X1 and current to operate the drive IC 8, as described above. The control device 70 has the function of supplying a control signal to the drive IC 8 to control the operation of the drive IC 8 in order to selectively generate heat in the heat-generating part 9a of the thermal head X1, as described above.

[0089] The thermal printer Z1 presses the recording medium P onto the heating element 9a of the thermal head X1 using the platen roller 50, and transports the recording medium P onto the heating element 9a using the transport mechanism 40, while selectively heating the heating element 9a using the power supply unit 60 and the control unit 70. As a result, the thermal printer Z1 prints a predetermined image onto the recording medium P. The transport mechanism 40 is an example of a moving part that moves the thermal head X1 and the recording medium P relative to each other. The thermal printer Z1 is also an example of a recording device that records various types of information onto the recording medium P. Furthermore, if the recording medium P is image-receiving paper or the like, the ink from an ink film (not shown) transported together with the recording medium P is thermally transferred to the recording medium P to perform the printing.

[0090] Furthermore, this technology can also take the following configuration: (1) A thermal head comprising: a plurality of individual electrodes having a portion extending along a first direction and arranged in a second direction intersecting the first direction; a common electrode having a first electrode extending along the second direction and a plurality of second electrodes connected to the first electrode and extending along the first direction and arranged in the second direction; and a resistive layer extending along the second direction and having a portion that overlaps with the plurality of individual electrodes and the plurality of second electrodes in a plan view from a third direction perpendicular to the first and second directions, wherein the common electrode further has a third electrode, the third electrode is connected to the first electrode and extends along the first direction and does not overlap with the resistive layer in the plan view, and the plurality of second electrodes and the third electrode are arranged with a gap between them in the second direction. (2) The thermal head according to (1), wherein each of the plurality of second electrodes has a first portion connected to the first electrode and a second portion connected to the first portion, and the width of the second portion is smaller than the width of the first portion. (3) The thermal head according to (1) or (2), wherein the spacing between the plurality of second electrodes and the third electrode in the second direction is smaller than the width of the third electrode. (4) The thermal head according to any one of (1) to (3), wherein it has a first heat storage layer having a portion that overlaps with the resistor layer in the plan view, and the first heat storage layer does not overlap with the third electrode in the plan view. (5) The thermal head according to any one of (1) to (4), wherein the ends of the third electrode in the first direction that are not connected to the first electrode have an arc shape in the plan view.(6) The thermal head according to any one of (1) to (5), wherein the first electrode has a first metal layer and a second metal layer, the first metal layer has a plurality of third portions and a fourth portion, the plurality of third portions are arranged in the second direction and are connected one-to-one with the plurality of second electrodes and extend along the first direction, the fourth portion connects two adjacent third portions to each other, the second metal layer extends along the second direction and has a portion that covers the first metal layer, and the second metal layer contains a metal element different from the metal element contained in the first metal layer. (7) The thermal head according to (6), wherein the first electrode has a plurality of fourth portions, and two adjacent fourth portions are in different positions in the first direction. (8) The thermal head according to (6) or (7), wherein the first metal layer has a fifth portion connected to the third electrode and extending in the first direction, the fifth portion not in contact with the plurality of third portions and the fourth portion. (9) The thermal head according to (4), wherein in plan view, it has a second heat storage layer having a portion that overlaps with the first electrode and does not overlap with the first heat storage layer. (10) The thermal head according to (9), wherein the first electrode has a first metal layer and a second metal layer, the first metal layer has a plurality of third portions and a fourth portion, the plurality of third portions are arranged in the second direction and are connected one-to-one with the plurality of second electrodes and extend along the first direction, the fourth portions connect two adjacent third portions to each other, the second metal layer extends along the second direction and has a portion that covers the first metal layer, and the second metal layer has a portion that contacts the second heat storage layer. (11) A recording device having the thermal head according to any one of (1) to (10), and a moving part that moves the thermal head and a recording medium relative to each other.

[0091] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. Indeed, the embodiments described above can be embodied in a variety of forms. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0092] 9 Resistor layer 13 First heat storage layer 14 Second heat storage layer 61 Common electrode 62 Individual electrodes 611 First electrode 612 Second electrode 612a First part 612b Second part 613 Third electrode 613a End 6111 First metal layer 6111a Third part 6111b Fourth part 6111c Fifth part 6112 Second metal layer X1 Thermal head

Claims

1. A thermal head comprising: a plurality of individual electrodes having a portion extending along a first direction and arranged in a second direction intersecting the first direction; a common electrode having a first electrode extending along the second direction and a plurality of second electrodes connected to the first electrode and extending along the first direction and arranged in the second direction; and a resistive layer extending along the second direction and having a portion that overlaps with the plurality of individual electrodes and the plurality of second electrodes in a plan view from a third direction perpendicular to the first and second directions, wherein the common electrode further has a third electrode, the third electrode is connected to the first electrode and extends along the first direction and does not overlap with the resistive layer in the plan view, and the plurality of second electrodes and the third electrode are spaced apart in the second direction.

2. The thermal head according to claim 1, wherein each of the plurality of second electrodes has a first portion connected to the first electrode and a second portion connected to the first portion, and the width of the second portion is smaller than the width of the first portion.

3. The thermal head according to claim 1 or 2, wherein the distance between the plurality of second electrodes and the third electrode in the second direction is smaller than the width of the third electrode.

4. A thermal head according to any one of claims 1 to 3, having a first heat storage layer that overlaps with the resistor layer in a plan view, wherein the first heat storage layer does not overlap with the third electrode in a plan view.

5. The thermal head according to any one of claims 1 to 4, wherein the ends of the third electrode in the first direction that are not connected to the first electrode have an arc shape in plan view.

6. The thermal head according to any one of claims 1 to 5, wherein the first electrode has a first metal layer and a second metal layer, the first metal layer has a plurality of third portions and a fourth portion, the plurality of third portions are arranged in the second direction and connected one-to-one with the plurality of second electrodes and extend along the first direction, the fourth portion connects two adjacent third portions, the second metal layer extends along the second direction and has a portion that covers the first metal layer, and the second metal layer contains a metal element different from the metal element contained in the first metal layer.

7. The thermal head according to claim 6, having a plurality of the fourth parts, wherein two adjacent fourth parts are in different positions in the first direction.

8. The thermal head according to claim 6 or 7, wherein the first metal layer has a fifth portion connected to the third electrode and extending in the first direction, the fifth portion not in contact with the plurality of third portions and the fourth portion.

9. The thermal head according to claim 4, wherein, in a plan view, it has a second heat storage layer that overlaps with the first electrode and does not overlap with the first heat storage layer.

10. The thermal head according to claim 9, wherein the first electrode has a first metal layer and a second metal layer, the first metal layer has a plurality of third portions and a fourth portion, the plurality of third portions are arranged in the second direction and are connected one-to-one with the plurality of second electrodes and extend along the first direction, the fourth portions connect two adjacent third portions, the second metal layer extends along the second direction and has a portion that covers the first metal layer, and the second metal layer has a portion that is in contact with the second heat storage layer.

11. A recording device comprising: a thermal head according to any one of claims 1 to 10; and a moving unit for moving the thermal head and a recording medium relative to each other.

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