Thermal head and thermal printer

Abstract

A thermal head (X1) comprises a substrate, a heat storage layer (13), a heat generation unit, a common electrode 17, and a plurality of individual electrodes (19). The heat storage layer (13) is positioned on the substrate. The plurality of individual electrodes (19) are positioned on the heat storage layer (13) and extend along a first direction (D3) of the substrate. The common electrode has: a plurality of first electrodes (17c) that extend along the first direction (D3); and a second electrode that extends along a second direction and is connected to the plurality of first electrodes (17c). The first electrode (17c) and the individual electrode (19) are arranged alternately in the second direction that intersects the first direction (D3). In each of the plurality of first electrodes (17c), among both ends of the first direction (D3), an end that is positioned farther from the second electrode is defined as a first tip end. In each of the plurality of individual electrodes (19), among both ends of the first direction (D3), an end that is positioned closer to the second electrode is defined as a second tip end. The thickness of the first electrode (17c) is different from the thickness of the individual electrode (19).

Description

Thermal heads and thermal printers

[0001] The present disclosure relates to a thermal head and a thermal printer.

[0002] 2. Description of the Related Art Various thermal heads have been proposed as printing devices for facsimiles, video printers, and the like.

[0003] Japanese Unexamined Patent Publication No. 61-099443

[0004] A thermal head according to one aspect of the present disclosure includes a substrate, a heat storage layer, a heat generating portion, a common electrode, and a plurality of individual electrodes. The heat storage layer is located on the substrate. The heat generating portion is located on the heat storage layer and has a plurality of elements. The common electrode is located on the heat storage layer and is electrically connected to the plurality of elements. The plurality of individual electrodes are located on the heat storage layer and extend along a first direction of the substrate. The common electrode has a plurality of first electrodes extending along the first direction. The first electrodes and the individual electrodes are alternately arranged in a second direction intersecting the first direction. The common electrode has a second electrode extending along the second direction and connected to the plurality of first electrodes. Of the ends of each of the plurality of first electrodes in the first direction, the end located farther from the second electrode is defined as a first tip, and of the ends of each of the plurality of individual electrodes in the first direction, the end located closer to the second electrode is defined as a second tip. The thickness of the first electrode is different from the thickness of the individual electrode.

[0005] FIG. 1 is a perspective view showing an outline of a thermal head according to the first embodiment. FIG. 2 is a cross-sectional view showing an outline of the thermal head shown in FIG. 1. FIG. 3 is a plan view showing an outline of the head substrate shown in FIG. 1. FIG. 4 is a schematic enlarged view of region IV shown in FIG. 3. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 4. FIG. 6 is a cross-sectional view showing another example of a thermal head according to the first embodiment. FIG. 7 is a schematic diagram of a thermal printer according to the first embodiment. FIG. 8 is a schematic plan view showing the configuration of a thermal head according to the second embodiment. FIG. 9 is a schematic plan view showing the configuration of a thermal head according to the third embodiment. FIG. 10 is a schematic plan view showing the configuration of a thermal head according to the fourth embodiment. FIG. 11 is a schematic plan view showing the configuration of a thermal head according to the fifth embodiment. FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 11. FIG. 13 is a cross-sectional view showing another example of a thermal head according to the fifth embodiment.

[0006] Below, a detailed description will be given of a thermal head and a thermal printer according to the present disclosure (hereinafter referred to as an "embodiment") with reference to the drawings. Note that the present disclosure is not limited to the embodiment. Furthermore, the embodiments can be appropriately combined as long as the processing content is not contradictory. Furthermore, the same components in the following embodiments are designated by the same reference numerals, and redundant description will be omitted.

[0007] Furthermore, in the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in the strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision or installation precision.

[0008] The structure of a conventional thermal head leaves room for improvement, for example, in terms of improving printing characteristics. The present disclosure has been made in view of the above, and provides a thermal head and a thermal printer that can improve printing characteristics.

[0009] First Embodiment Fig. 1 is a perspective view showing an outline of a thermal head X1 according to a first embodiment. As shown in Fig. 1, the thermal head X1 according to the first embodiment includes a heat sink 1, a head substrate 3, and an FPC (flexible printed circuit board) 5. The head substrate 3 is located on the heat sink 1. The FPC 5 is electrically connected to the head substrate 3. The head substrate 3 includes a substrate 7, a heat generating portion 9, a plurality of driving ICs 11, and a covering member 29.

[0010] The heat sink 1 is plate-shaped. The heat sink 1 has a rectangular shape in a plan view. The heat sink 1 has a heat dissipation function. Specifically, the heat sink 1 dissipates heat generated in the heat generating portion 9 of the head substrate 3 that does not contribute to printing to the outside of the thermal head X1. The head substrate 3 is adhered to the top surface of the heat sink 1 with double-sided tape or adhesive (not shown). The heat sink 1 is made of a metal material such as copper, iron, or aluminum.

[0011] The head substrate 3 is plate-shaped. The head substrate 3 has a rectangular shape in a plan view. The head substrate 3 has each component that constitutes the thermal head X1 positioned on a substrate 7. The head substrate 3 prints on a recording medium P (see FIG. 7) in accordance with an electrical signal supplied from the outside.

[0012] The driving IC 11 is located on the substrate 7. The driving ICs 11 are arranged along the main scanning direction. The driving ICs 11 are electronic components that have the function of controlling the energization state of each heat generating portion 9. As an example, a switching member having a plurality of switching elements therein may be used as the driving IC 11.

[0013] The driving ICs 11 are covered with a covering member 29 made of a resin such as epoxy resin or silicone resin. The covering member 29 is positioned over the plurality of driving ICs 11. The covering member 29 is an example of a sealing material.

[0014] The FPC 5 has, for example, a pair of first and second ends in the short direction. The first end of the FPC 5 is electrically connected to the head base 3. The second end of the FPC 5 is electrically connected to the connector 31. Note that a connector may be used instead of the FPC 5 to connect the thermal head X1 to the outside.

[0015] The FPC 5 is electrically connected to the head substrate 3 by a conductive bonding material 23 (see FIG. 2). As an example, the conductive bonding material 23 may be a solder material or an anisotropic conductive film (ACF) in which conductive particles are mixed into an electrically insulating resin.

[0016] Each member constituting the head substrate 3 will be described below with reference to Figures 1 to 4. Figure 2 is a cross-sectional view showing an outline of the thermal head X1 shown in Figure 1. Figure 3 is a plan view showing an outline of the head substrate 3 shown in Figure 1. Figure 4 is a schematic enlarged view of region IV shown in Figure 3.

[0017] The head substrate 3 further includes a substrate 7, a common electrode 17, a plurality of individual electrodes 19, a third electrode 12, a fourth electrode 14, a terminal 2, a resistor layer 15, a protective layer 25, and a covering layer 27. Note that the protective layer 25 and the covering layer 27 are omitted from Fig. 1. Fig. 3 also shows a simplified view of the wiring of the head substrate 3. The driving IC 11, the protective layer 25, and the covering layer 27 are omitted from Fig. 3. The configuration of the fourth electrode 14 is also simplified in Fig. 3.

[0018] The substrate 7 has a rectangular shape in a plan view. The substrate 7 has a first surface 7e, which is its upper surface and the surface with the largest area. The first surface 7e has a first long side 7a, which is one of the long sides, a second long side 7b, which is the other long side, a first short side 7c, and a second short side 7d. The substrate 7 is made of an electrically insulating material such as alumina ceramics, or a semiconductor material such as single crystal silicon.

[0019] The substrate 7 may also have a heat storage layer 13. The heat storage layer 13 is located on the first surface 7e of the substrate 7. The heat storage layer 13 is a portion that protrudes from the first surface 7e in the thickness direction of the substrate 7 and extends in a band shape along the second direction D2 (main scanning direction). The heat storage layer 13 has the function of effectively pressing the recording medium P to be printed (see FIG. 7 ) against the protective layer 25 located on the heat generating portion 9.

[0020] The heat storage layer 13 may have a base portion (not shown). In this case, the base portion is a portion located over the entire area of ​​the first surface 7e side of the substrate 7.

[0021] The heat storage layer 13 contains, for example, a glass component. The heat storage layer 13 temporarily stores a portion of the heat generated by the heat generating unit 9. This allows the heat storage layer 13 to shorten the time required to increase the temperature of the heat generating unit 9. In other words, the heat storage layer 13 has the function of improving the thermal response characteristics of the thermal head X1.

[0022] The heat storage layer 13 is produced, for example, by applying a predetermined glass paste obtained by mixing glass powder with an appropriate organic solvent to the first surface 7e of the substrate 7 by conventionally known screen printing or the like, and then firing the paste. Note that the substrate 7 may have only a base portion as the heat storage layer 13.

[0023] 3, the common electrode 17 is located on the first surface 7e of the substrate 7. The common electrode 17 is made of a conductive material. For example, the common electrode 17 may be made of any one of aluminum, gold, silver, and copper, or an alloy thereof.

[0024] The common electrode 17 has a first common electrode 17a, a plurality of second common electrodes 17b, a plurality of third common electrodes 17c, and a plurality of terminals 2. The common electrode 17 is electrically connected in common to the plurality of elements 9a of the heat generating portion 9.

[0025] The first common electrode 17a is located between the first long side 7a of the substrate 7 and the heat generating portion 9. The first common electrode 17a extends in the second direction D2 (main scanning direction). The multiple second common electrodes 17b extend in the first direction D1 (sub-scanning direction). One of the multiple (here, two) second common electrodes 17b is located on the first short side 7c side of the substrate 7, and the other is located on the second short side 7d side. The second common electrode 17b connects the terminal 2 to the first common electrode 17a. The multiple third common electrodes 17c extend along the first direction D1 (sub-scanning direction). Each of the multiple third common electrodes 17c extends from the first common electrode 17a toward each element 9a of the heat generating portion 9 and further extends past the heat generating portion 9. The multiple third common electrodes 17c extend in a comb-like shape from the first common electrode 17a toward each element 9a of the heat generating portion 9. At least a portion of the third common electrode 17c is located on the heat storage layer 13. The third common electrodes 17c are located at intervals from one another in the second direction D2 (main scanning direction). The third common electrode 17c is an example of a first electrode, and the first common electrode 17a is an example of a second electrode.

[0026] The individual electrodes 19 are located on the first surface 7e of the substrate 7. At least a portion of the individual electrodes 19 is located on the heat storage layer 13 (see FIG. 2). The individual electrodes 19 contain a metal component and are conductive. The individual electrodes 19 are formed of metals such as aluminum, nickel, gold, silver, platinum, palladium, and copper, or alloys thereof. The individual electrodes 19 extend in the first direction D1 (sub-scanning direction). The individual electrodes 19 are located along the second direction D2 (main scanning direction). The individual electrodes 19 are located between two adjacent third common electrodes 17c. Therefore, in the thermal head X1, the third common electrodes 17c and the individual electrodes 19 are alternately arranged at a predetermined interval in the second direction D2 (main scanning direction). In other words, the third common electrodes 17c and the individual electrodes 19 are alternately arranged in the second direction D2 (main scanning direction) while being spaced apart. The individual electrodes 19 are connected to electrode pads 10 on the second long side 7b side of the substrate 7. The third common electrode 17c and the individual electrodes 19 do not necessarily need to be arranged at a predetermined interval (constant interval).

[0027] The third electrodes 12 are connected to the electrode pads 10. The third electrodes 12 extend in a first direction D1 (sub-scanning direction). A driving IC 11 is mounted on the electrode pads 10.

[0028] The fourth electrode 14 extends in the second direction D2 (main scanning direction) and is located across the plurality of third electrodes 12. The fourth electrode 14 is connected to the outside via a terminal 2.

[0029] The terminal 2 is located on the second long side 7b of the substrate 7. The terminal 2 is connected to the FPC 5 by a conductive bonding material 23 (see FIG. 2), thereby electrically connecting the head base 3 to the outside.

[0030] The individual electrodes 19, the third common electrode 17c, and the third electrode 12 can be made of, for example, a conductive paste containing a metal component and a glass component in an organic solvent. The individual electrodes 19, the third common electrode 17c, and the third electrode 12 can be formed by printing the material layers constituting each of them on the substrate 7 using, for example, screen printing, flexographic printing, gravure printing, or gravure offset printing. The thickness of the individual electrodes 19 and the third common electrode 17c is, for example, about 0.5 to 1.5 μm.

[0031] Furthermore, the material layers constituting the first common electrode 17a, the second common electrode 17b, the fourth electrode 14, and the terminal 2 can be formed on the substrate 7 by, for example, screen printing. The thicknesses of the first common electrode 17a, the second common electrode 17b, the fourth electrode 14, and the terminal 2 are, for example, approximately 5 to 20 μm. The first common electrode 17a, the second common electrode 17b, the fourth electrode 14, and the terminal 2 are indicated by dots in FIG. 3 and the same applies to the following drawings. The individual electrodes 19, the third common electrode 17c, the third electrode 12, the first common electrode 17a, the second common electrode 17b, the fourth electrode 14, and the terminal 2 may be formed to the same thickness and by the same manufacturing method, or may be formed to different thicknesses and by different manufacturing methods.

[0032] The resistor layer 15 is positioned across the third common electrode 17c and the individual electrodes 19, spaced apart from the first long side 7a of the substrate 7. Portions of the resistor layer 15 located between the third common electrode 17c and the individual electrodes 19 function as the elements 9a of the heat generating section 9. In other words, the elements 9a of the heat generating section 9 are located on the heat storage layer 13 and are arranged at predetermined intervals in the second direction D2. Although the elements 9a of the heat generating section 9 are depicted in a simplified manner in FIG. 3, they may be positioned at a density of 100 dpi (dots per inch) or more. Furthermore, the elements 9a of the heat generating section 9 may be positioned at a density of 200 to 2400 dpi.

[0033] The thickness of the resistor layer 15 is, for example, about 3 to 6 μm. The sheet resistance of the resistor layer 15 is, for example, about 500 to 8000 Ω / □. The thermal expansion coefficient of the resistor layer 15 is, for example, about 5 to 10 ppm / °C. The thermal conductivity of the resistor layer 15 is, for example, about 0.5 to 2 W / (m·K).

[0034] The resistor layer 15 may be formed, for example, by applying a material paste containing a conductive component and a glass component in a long strip shape in the main scanning direction to the substrate 7 on which various electrodes have been patterned, using a screen printing method or a dispensing device. The conductive component may include, for example, ruthenium oxide. The glass component may include, for example, lead borosilicate glass.

[0035] The protective layer 25 is located on the heat storage layer 13 formed on the first surface 7e (see FIG. 1) of the substrate 7. The protective layer 25 covers the heat generating portion 9. The protective layer 25 is located from the first long side 7a of the substrate 7 across the main scanning direction of the substrate 7 so as to be spaced apart from the electrode pads 10.

[0036] The protective layer 25 has insulating properties. This protects the covered area from corrosion due to adhesion of moisture contained in the atmosphere or abrasion due to contact with the recording medium P (see FIG. 7 ) to be printed. The protective layer 25 can be made of, for example, glass. The protective layer 25 can be made using a thick film formation technique such as printing. The protective layer 25 may contain, for example, lead borosilicate glass. The protective layer 25 may also further contain, for example, one or both of alumina and zirconia.

[0037] The protective layer 25 is made of SiN, SiON, SiO ２ , SiC, C-SiC, TiN, TiAlN, TiC, TiCN, TiSiN, CrN, DLC (Diamond-Like Carbon), or the like. Such protective layer 25 can be formed using a thin film formation technique such as a sputtering method. Although a single-layer protective layer 25 is shown in FIG. 2, the protective layer 25 may be composed of two or more layers of different materials, such as a glass layer and the above-mentioned thin film layer of SiN or the like.

[0038] Furthermore, the protective layer 25 may have a surface roughness Ra of, for example, 0.3 μm or less.

[0039] The covering layer 27 is located on the substrate 7 so as to partially cover the common electrode 17, the individual electrodes 19, the third electrode 12, and the fourth electrode 14. The covering layer 27 protects the covered area from oxidation due to contact with the atmosphere or corrosion due to adhesion of moisture contained in the atmosphere. The covering layer 27 can be made of a resin material such as an epoxy resin, a polyimide resin, or a silicone resin.

[0040] Next, the main parts of the thermal head X1 according to the first embodiment will be described in detail with reference to Figures 5 and 6. Figure 5 is a cross-sectional view taken along line VV in Figure 4. Figure 6 is a cross-sectional view showing another example of the thermal head X1 according to the first embodiment.

[0041] As shown in FIG. 5, the thermal head X1 according to the first embodiment includes a heat storage layer 13, a third common electrode 17c, individual electrodes 19, a resistor layer 15, and a protective layer 25.

[0042] The third common electrode 17c and the individual electrodes 19 are located on the heat storage layer 13. The upper surface 17ca of the third common electrode 17c has a central portion in the second direction D2 that protrudes further in the third direction D3 than the ends in the second direction D2. The third direction D3 is a direction that intersects the first direction D1 (see FIG. 3 ) and the second direction D2. Similarly, the upper surface 19a of the individual electrode 19 has a central portion in the second direction D2 that protrudes further in the third direction D3 than the ends in the second direction D2. Note that another layer (not shown) may be located between the third common electrode 17c and the individual electrodes 19 and the heat storage layer 13.

[0043] The resistor layer 15 is located on the third common electrode 17c and the individual electrodes 19, and on the heat storage layer 13 that does not have the third common electrode 17c or the individual electrodes 19. As a result, the third common electrode 17c and the individual electrodes 19 are located sandwiched between the heat storage layer 13 and the resistor layer 15. In addition, the protective layer 25 is located so as to cover the resistor layer 15.

[0044] Here, the thicknesses of the third common electrode 17c and the individual electrodes 19 will be described. The thickness t1 of the individual electrode 19 is different from the thickness t2 of the third common electrode 17c. In the example of FIG. 5, the thickness t1 of the individual electrode 19 is thicker than the thickness t2 of the third common electrode 17c. Specifically, the central portion of the upper surface 19a of the individual electrode 19 in the second direction D2 protrudes further in the third direction D3 than the central portion of the upper surface 17ca of the third common electrode 17c in the second direction D2. On the other hand, in the example of FIG. 6, the thickness t4 of the third common electrode 17c is thicker than the thickness t3 of the individual electrode 19. Specifically, the central portion of the upper surface 17ca of the third common electrode 17c in the second direction D2 protrudes further in the third direction D3 than the central portion of the upper surface 19a of the individual electrode 19 in the second direction D2.

[0045] In this way, the thickness t1 of the individual electrodes 19 is different from the thickness t2 of the third common electrode 17c. As a result, the thermal head X1 according to the first embodiment has improved printing characteristics compared to when the thickness t1 of the individual electrodes 19 and the thickness t2 of the third common electrode 17c are the same. This point will be further explained using FIGS. 4 to 6.

[0046] As shown in Fig. 4, the thermal head X1 prints one dot using a heat generating portion 9 corresponding to a predetermined individual electrode 19X and the third common electrodes 17cL and 17cR that are adjacent to the predetermined individual electrode 19X in the second direction D2 (main scanning direction). In other words, as shown by the two-dot chain line in Fig. 4, the printing area Tr of one dot in plan view extends from the third common electrode 17cL to the third common electrode 17cR in the second direction D2 (main scanning direction). In other words, the individual electrode 19X is close to the center of one dot, and the third common electrodes 17cL and 17cR are close to the outline of one dot.

[0047] When the thermal head X1 prints one dot on the recording medium P (see FIG. 7), for example, current flows from the third common electrodes 17cL, 17cR of the common electrode 17 to the individual electrode 19X, causing the elements 9aL, 9aR of the heat generating unit 9 to generate heat. As a result, printing is performed on the recording medium P by the heat of the two elements 9aL, 9aR aligned in the second direction D2 (main scanning direction). Furthermore, the region of the element 9a closer to the individual electrode 19 has a higher temperature during heating than the region closer to the third common electrode 17c.

[0048] 5, when the thickness t1 of the individual electrode 19 is thicker than the thickness t2 of the third common electrode 17c, the temperature of the resistor layer 15 located on the individual electrode 19 can be increased appropriately compared to when the thickness t1 of the individual electrode 19 and the thickness t2 of the third common electrode 17c are the same. Furthermore, when the thermal head X1 prints one dot on the recording medium P, the pressure applied to the recording medium P by the resistor layer 15 located on the individual electrode 19 increases. This makes the center of one dot clearer in the printed matter printed by the thermal head X1, improving the printing characteristics of the thermal head X1.

[0049] On the other hand, as shown in FIG. 6 , the thickness t4 of the third common electrode 17c can be made thicker than the thickness t3 of the individual electrode 19. In this case, the temperature of the resistor layer 15 located above the third common electrode 17c can be increased more appropriately compared to when the thickness t3 of the individual electrode 19 and the thickness t4 of the third common electrode 17c are the same. Furthermore, when the thermal head X1 prints one dot on the recording medium P, the resistor layer 15 located above the third common electrode 17c exerts a higher pressure on the recording medium P. This results in a clearer outline of one dot on the printed matter printed by the thermal head X1, improving the printing characteristics of the thermal head X1. Furthermore, because the pressure on the recording medium P is reduced from the region of the element 9a near the individual electrode 19, where the temperature during heating is relatively high, the heat-generating portion 9 is less susceptible to deterioration due to wear.

[0050] The difference in thickness between the individual electrodes 19 and the third common electrode 17c is, for example, about 0.01 to 0.35 μm.

[0051] The individual electrodes 19 and the third common electrode 17c having different thicknesses as described above can be produced, for example, by pouring the materials constituting each electrode into recesses of different depths in a plate and printing them.

[0052] As shown in FIGS. 4 to 6 , the thickness of the tip portion of the third common electrode 17c may be different from the thickness of the tip portion of the individual electrode 19. The tip portion of the third common electrode 17c may be defined, for example, as follows: First, the position where the third common electrode 17c contacts the first common electrode 17a is defined as the base end of the third common electrode 17c, and the end opposite the base end is defined as the tip 17T of the third common electrode 17c. The range from the base end to the tip 17T of the third common electrode 17c is divided into three equal regions, and the region including the tip 17T may be defined as the tip portion of the third common electrode 17c. Similarly, the tip portion of the individual electrode 19 may be defined, for example, as follows: First, the position where the third common electrode 17c contacts the electrode pad 10 is defined as the base end of the individual electrode 19, and the end opposite the base end is defined as the tip 19T of the individual electrode 19. The range from the base end of the individual electrode 19 to the tip 19T may be divided into three equal parts, and the region including the tip 19T may be defined as the tip of the individual electrode 19. In other words, the tip of the third common electrode 17c may be a region extending 0.3 mm from the tip 17T. The same applies to the tip of the individual electrode 19. The tip 17T of the third common electrode 17c is an example of a first tip, and the tip of the third common electrode 17c is an example of the first tip. The tip 19T of the individual electrode 19 is an example of a second tip, and the tip of the individual electrode 19 is an example of the second tip.

[0053] The thickness of the portion of the third common electrode 17c facing the individual electrode 19 may be different from the thickness of the portion of the individual electrode 19 facing the third common electrode 17c. In addition, in a plan view of the thermal head X1, the thickness of the portion of the third common electrode 17c overlapping with the heat storage layer 13 may be different from the thickness of the portion of the individual electrode 19 overlapping with the heat storage layer 13.

[0054] It should be noted that the thickness of all the third common electrodes 17c constituting the thermal head X1 does not need to be different from the thickness of the individual electrodes 19. For example, in the thermal head X1, the thickness of the third common electrodes 17c at any four points is measured to calculate the first average thickness, and the thickness of the individual electrodes 19 at any four points is measured to calculate the second average thickness. In this case, it is sufficient that the first average thickness and the second average thickness are different.

[0055] Next, a thermal printer Z1 having a thermal head X1 will be described with reference to Fig. 7. Fig. 7 is a schematic diagram of the thermal printer Z1 according to the first embodiment.

[0056] The thermal printer Z1 according to the first embodiment includes the thermal head X1, a transport mechanism 40, a platen roller 50, a power supply unit 60, and a control unit 70. The thermal head X1 is attached to a mounting surface 80a of a mounting member 80 disposed in a housing (not shown) of the thermal printer Z1. The thermal head X1 is attached to the mounting member 80 so as to be aligned in the main scanning direction, which is perpendicular to the transport direction S.

[0057] 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 the protective layer 25 located above the multiple heat generating elements 9 of the thermal head X1. The drive unit functions to drive 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 each have a cylindrical shaft 43a, 45a, 47a, or 49a made of a metal such as stainless steel, covered with an elastic member 43b, 45b, 47b, or 49b made of a material such as butadiene rubber. When the recording medium P is an image receiving paper onto which ink is transferred, an ink film (not shown) is transported between the recording medium P and the heat generating elements 9 of the thermal head X1 along with the recording medium P.

[0058] The platen roller 50 has the function of pressing the recording medium P onto the protective layer 25 located above the heat generating portion 9 of the thermal head X1. The platen roller 50 is disposed so as 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 heat generating portion 9. The platen roller 50 may be configured, for example, by covering a cylindrical shaft 50a made of a metal such as stainless steel with an elastic member 50b made of butadiene rubber or the like.

[0059] As described above, the power supply device 60 has a function of supplying a current for generating heat from the heat generating portion 9 of the thermal head X1 and a current for operating the driving IC 11. The control device 70 has a function of supplying a control signal to the driving IC 11 for controlling the operation of the driving IC 11 in order to selectively generate heat from the heat generating portion 9 of the thermal head X1.

[0060] The thermal printer Z1 presses the recording medium P onto the heat generating portion 9 of the thermal head X1 with the platen roller 50, transports the recording medium P onto the heat generating portion 9 with the transport mechanism 40, and selectively causes the heat generating portion 9 to heat with the power supply unit 60 and the control unit 70. In this way, the thermal printer Z1 performs a predetermined print on the recording medium P. Note that if the recording medium P is receiver paper or the like, printing on the recording medium P is performed by thermally transferring ink from an ink film (not shown) transported together with the recording medium P to the recording medium P.

[0061] As described above, the thickness t1 of the individual electrodes 19 of the thermal head X1 according to the first embodiment is different from the thickness t2 of the third common electrode 17c, which improves the printing characteristics of the thermal head X1 according to the first embodiment compared to when the thickness t1 of the individual electrodes 19 and the thickness t2 of the third common electrode 17c are the same.

[0062] 5 and 6 show examples in which the central portion of the third common electrode 17c or the individual electrode 19 in the second direction D2 protrudes further in the third direction D3 than the end portions in the second direction D2, but this is not necessarily the case. The thickness of the third common electrode 17c or the individual electrode 19 in the second direction D2 may be constant. In other words, the cross-sectional shape of the third common electrode 17c or the individual electrode 19 may be rectangular.

[0063] Second Embodiment Fig. 8 is a schematic plan view showing the configuration of a thermal head X1 according to a second embodiment. As shown in Fig. 8, the thermal head X1 may have a gap S1 between the heat generating portion 9 and the tip 19T of the individual electrode 19. The gap S1 may be provided so as to penetrate the individual electrode 19. In this case, the substrate 7 is exposed from the gap S1.

[0064] With this configuration, compared to when there is no gap S1 between the heat generating portion 9 and the tip 19T of the individual electrode 19, the heat from the heat generating portion 9 is less likely to move to the tip 19T of the individual electrode 19, and the heat from the heat generating portion 9 is less likely to dissipate through the individual electrode 19. This improves the heat storage capacity of the heat storage layer 13, and stabilizes color development when the thermal head X1 prints on the recording medium P (see FIG. 7).

[0065] Note that, although an example in which the gap S1 is located between the heat generating portion 9 and the tip 19T of the individual electrode 19 has been described here, the location of the gap S1 is not limited to this. For example, the thermal head X1 may have a gap S1 between the heat generating portion 9 or the heat storage layer 13 and the tip 17T of the third common electrode 17c. In this case as well, it becomes difficult for heat from the heat generating portion 9 to move to the tip 17T of the third common electrode 17c, and it becomes difficult for the heat from the heat generating portion 9 to dissipate via the third common electrode 17c. This improves the heat storage capacity of the heat storage layer 13, and stabilizes color development when the thermal head X1 prints on the recording medium P.

[0066] The thermal head X1 may have a gap S1 both between the heat generating portion 9 and the tip 19T of the individual electrode 19 and between the heat generating portion 9 and the tip 17T of the third common electrode 17c.

[0067] Furthermore, the thermal head X1 may have a gap S1 between the tip 19T of at least one of the multiple individual electrodes 19 and the heat generating portion 9. Similarly, a gap S1 may be formed between the tip 17T of at least one of the multiple third common electrodes 17c and the heat generating portion 9. Furthermore, the gap S1 does not necessarily need to penetrate the individual electrode 19. For example, the gap S1 may be provided between the substrate 7 and the individual electrode 19 when viewed in cross section. In other words, the upper surface of the gap S1 may be covered by the individual electrode 19. With this configuration, the presence of the gap S1 can reduce the contact area between the substrate 7 and the individual electrode 19. As a result, heat from the heat generating portion 9 is less likely to be dissipated to the substrate 7 through the individual electrode 19.

[0068] 9 is a schematic plan view showing the configuration of a thermal head X1 according to a third embodiment. In the first embodiment, an example was shown in which the size of the heat generating portion 9 in the first direction D1 and the size of the heat storage layer 13 in the first direction D1 were approximately the same, but the size of the heat generating portion 9 in the first direction D1 and the size of the heat storage layer 13 in the first direction D1 may be different. For example, as shown in FIG. 9, the size of the heat storage layer 13 in the first direction D1 may be larger than the size of the heat generating portion 9 in the first direction D1.

[0069] As shown in FIG. 9 , the tip 17T of the third common electrode 17c or the tip 19T of the individual electrode 19 may be located on the heat storage layer 13. With this configuration, heat from the heat generating portion 9 is transferred to the heat storage layer 13 via the third common electrode 17c or the individual electrode 19, improving the heat storage capacity of the heat storage layer 13. The improved heat storage capacity of the heat storage layer 13 enhances the thermal response, enabling the thermal head X1 to print at a higher speed and with improved printing characteristics. In particular, when the thickness t1 of the individual electrode 19 is thicker than the thickness t2 of the third common electrode 17c (see FIG. 5 ), the pressure applied to the recording medium P (see FIG. 7 ) from the region of the element 9a near the individual electrode 19, where the temperature during heating is relatively high, is increased, improving heat transfer, and achieving a greater effect.

[0070] In addition, Figure 9 shows an example in which both the tip 17T of the third common electrode 17c and the tip 19T of the individual electrode 19 are located on the heat storage layer 13, but either the tip 17T of the third common electrode 17c or the tip 19T of the individual electrode 19 may be located on the heat storage layer 13.

[0071] Furthermore, a tip 19T of at least one of the multiple individual electrodes 19 may be located on the heat storage layer 13. Similarly, a tip 17T of at least one of the multiple third common electrodes 17c may be located on the heat storage layer 13. Note that, when there is a gap S1 (see FIG. 8 ) as in the thermal head X1 according to the second embodiment, the gap S1 penetrates the individual electrodes 19, and the heat storage layer 13 is exposed from the gap S1.

[0072] 10 is a schematic plan view showing the configuration of a thermal head X1 according to a fourth embodiment. As shown in FIG. 10, the tip 17T of the third common electrode 17c or the tip 19T of the individual electrode 19 may be located on the substrate 7.

[0073] With this configuration, heat from the heat generating portion 9 is dissipated to the substrate 7 via the third common electrode 17c or the individual electrode 19, improving the heat dissipation of the thermal head X1 and reducing trailing during printing. In particular, when the thickness t1 of the individual electrode 19 is thicker than the thickness t2 of the third common electrode 17c (see FIG. 5), the heat dissipation is improved in the region of the element 9a close to the individual electrode 19, where the temperature during heat generation is relatively high, and a greater effect can be obtained.

[0074] In addition, Figure 10 shows an example in which both the tip 17T of the third common electrode 17c and the tip 19T of the individual electrode 19 are located on the substrate 7, but either the tip 17T of the third common electrode 17c or the tip 19T of the individual electrode 19 may be located on the substrate 7.

[0075] Furthermore, the tip 19T of at least one of the plurality of individual electrodes 19 may be located on the substrate 7. Similarly, the tip 17T of at least one of the plurality of third common electrodes 17c may be located on the substrate 7.

[0076] Fifth Embodiment Fig. 11 is a schematic plan view showing the configuration of a thermal head X1 according to a fifth embodiment. Fig. 12 is a cross-sectional view taken along line XII-XII in Fig. 11. Fig. 13 is a cross-sectional view showing another example of a thermal head X1 according to the fifth embodiment. In the first embodiment, an example was shown in which the thickness of the individual electrodes 19 in the first direction D1 was constant, but the thickness of the individual electrodes 19 in the first direction D1 may vary.

[0077] 12, the thickness t5 of the tip 19T of the individual electrode 19 may be thicker than the thickness t6 of the portion of the individual electrode 19 other than the tip 19T. In the examples of Figures 11 and 12, the tip 19T of the individual electrode 19 is located on the substrate 7 and is not in contact with the heat storage layer 13 or the resistor layer 15. Therefore, compared to when the thickness of the individual electrode 19 in the first direction D1 is constant, the pressure from the resistor layer 15 located on the individual electrode 19 to the recording medium P (see Figure 7) is lower, and the heat generating portion 9 is less likely to deteriorate due to wear.

[0078] On the other hand, when the tip 19T of the individual electrode 19 is located above the heat storage layer 13, particularly when the tip 19T of the individual electrode 19 is located between the heat generating portion 9 and the heat storage layer 13, the printing characteristics of the thermal head X1 are improved. The reason for this effect is that, compared to when the thickness of the individual electrode 19 in the first direction D1 is constant, the pressure from the heat generating portion 9 to the recording medium P is higher, improving heat transfer. In particular, when the thickness t1 of the individual electrode 19 is thicker than the thickness t2 of the third common electrode 17c (see FIG. 5), the pressure from the region of the element 9a close to the individual electrode 19, where the temperature during heat generation is relatively high, to the recording medium P is higher, improving heat transfer, and a greater effect is obtained.

[0079] As shown in FIG. 13 , the thickness t7 of the portion of the individual electrode 19 located under the heat generating portion 9 may be thicker than the thickness t8 of the portion of the individual electrode 19 other than the portion located under the heat generating portion 9. With this configuration, compared to when the thickness of the individual electrode 19 in the first direction D1 is constant, the pressure from the resistor layer 15 located above the individual electrode 19 to the recording medium P is increased, improving heat transfer. This results in a clearer center of each dot on the printed matter printed by the thermal head X1, improving the printing characteristics of the thermal head X1. In particular, when the thickness t1 of the individual electrode 19 is thicker than the thickness t2 of the third common electrode 17c (see FIG. 5 ), the pressure from the region of the element 9a close to the individual electrode 19, where the temperature during heating is relatively high, to the recording medium P is increased, improving heat transfer, resulting in a greater effect.

[0080] While the example in which the individual electrodes 19 have different thicknesses in the first direction D1 has been described above, the thickness of the third common electrode 17c in the first direction D1 may also be different. Specifically, the thickness of the tip 17T of the third common electrode 17c may be thicker than the thickness of the portion of the third common electrode 17c other than the tip 17T. With this configuration, when the tip 17T of the third common electrode 17c is located on the substrate 7, the pressure from the resistor layer 15 located on the third common electrode 17c to the recording medium P is lower than when the thickness of the third common electrode 17c in the first direction D1 is constant. This reduces the risk of deterioration of the heat generating portion 9 due to wear. On the other hand, when the tip 17T of the third common electrode 17c is located on the heat storage layer 13, the printing characteristics of the thermal head X1 are improved compared to when the thickness of the third common electrode 17c in the first direction D1 is constant. This effect is achieved because the pressure from the heat generating portion 9 to the recording medium P is increased, improving heat transfer.

[0081] Furthermore, the thickness of the portion of the third common electrode 17c located below the heat generating portion 9 may be thicker than the thickness of the remaining portion of the third common electrode 17c located below the heat generating portion 9. With this configuration, compared to when the thickness of the third common electrode 17c in the first direction D1 is constant, the pressure from the resistor layer 15 located above the third common electrode 17c to the recording medium P is increased, improving heat transfer. As a result, the outline of each dot on the printed material printed by the thermal head X1 becomes clearer, improving the printing characteristics of the thermal head X1.

[0082] The present technology may also be configured as follows. (1) A thermal head (for example, thermal head X1) includes a substrate (for example, substrate 7), a heat storage layer (for example, heat storage layer 13), a heat generating portion (for example, heat generating portion 9), a common electrode (for example, common electrode 17), and a plurality of individual electrodes (for example, individual electrodes 19). The heat storage layer is located on the substrate. The heat generating portion is located on the heat storage layer and has a plurality of elements (for example, elements 9a). The common electrode is located on the heat storage layer and is electrically connected in common to the plurality of elements. The plurality of individual electrodes are located on the heat storage layer and extend along a first direction of the substrate. The common electrode has a plurality of first electrodes (for example, third common electrode 17c) extending along the first direction. The first electrodes and the individual electrodes are alternately arranged in a second direction intersecting the first direction. The common electrode has a second electrode extending along the second direction and connected to the plurality of first electrodes. In each of the plurality of first electrodes, the end located farther from the second electrode in the first direction is designated as a first tip (e.g., tip 17T), and in each of the plurality of individual electrodes, the end located closer to the second electrode in the first direction is designated as a second tip (e.g., tip 19T). The thickness of the first electrode is different from the thickness of the individual electrode. (2) In the thermal head described in (1) above, when a predetermined portion including the first tip of each of the plurality of first electrodes is designated as a first tip portion and a predetermined portion including the second tip of each of the plurality of individual electrodes is designated as a second tip portion, the thickness of the first tip portion may be different from the thickness of the second tip portion. (3) In the thermal head described in (1) or (2) above, the thickness of the individual electrode may be thicker than the thickness of the first electrode. (4) In the thermal head described in (1) or (2) above, the thickness of the first electrode may be thicker than the thickness of the individual electrode. (5) The thermal head according to any one of (1) to (4) above may have a gap between the heat generating portion and the first tip or the second tip in a plan view. (6) In the thermal head according to any one of (1) to (5) above, the first tip or the second tip may be located on the heat storage layer.(7) In the thermal head described in any one of (1) to (5) above, the first tip or the second tip may be located on the substrate. (8) In the thermal head described in any one of (1) to (7) above, the thickness of the first tip or the second tip of either the first electrode or the individual electrode may be thicker than the thickness of a portion other than the first tip or the second tip. (9) In the thermal head described in any one of (1) to (7) above, the thickness of a portion of either the first electrode or the individual electrode located under the heat generating unit may be thicker than the thickness of a portion other than the portion located under the heat generating unit. (10) A thermal printer (for example, the thermal printer Z1) may include the thermal head described in any one of (1) to (9) above, a transport mechanism (for example, the transport mechanism 40) that transports a recording medium over the heat generating unit, and a platen roller (for example, the platen roller 50) that presses the recording medium against the heat generating unit.

[0083] The disclosed embodiments should be considered in all respects as illustrative and not restrictive. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0084] X1 Thermal head Z1 Thermal printer 1 Heat sink 3 Head base 7 Substrate 9 Heat generating portion 10 Electrode pad 11 Driving IC 15 Resistive layer 17 Common electrode 17c Third common electrode 19 Individual electrode 25 Protective layer 27 Covering layer 29 Covering member 40 Transport mechanism 50 Platen roller

Claims

1. A thermal head comprising: a substrate; a heat storage layer located on the substrate; a heat generating portion located on the heat storage layer and having a plurality of elements; a common electrode located on the heat storage layer and electrically connected to the plurality of elements; and a plurality of individual electrodes located on the heat storage layer and extending along a first direction of the substrate, wherein the common electrode has a plurality of first electrodes extending along the first direction, the first electrodes and the individual electrodes being alternately arranged in a second direction intersecting the first direction, and the common electrode has a second electrode extending along the second direction and connected to the plurality of first electrodes, wherein, of both ends of each of the plurality of first electrodes, an end located farther from the second electrode is defined as a first tip, and, of both ends of each of the plurality of individual electrodes, an end located closer to the second electrode is defined as a second tip, and the thickness of the first electrode is different from the thickness of the individual electrodes.

2. A thermal head as described in claim 1, wherein, in each of the plurality of first electrodes, a predetermined portion including the first tip is defined as a first tip portion, and in each of the plurality of individual electrodes, a predetermined portion including the second tip is defined as a second tip portion, and the thickness of the first tip portion is different from the thickness of the second tip portion.

3. A thermal head according to claim 1 or 2, wherein the thickness of the individual electrodes is greater than the thickness of the first electrodes.

4. A thermal head according to claim 1 or 2, wherein the thickness of the first electrode is greater than the thickness of the individual electrodes.

5. A thermal head according to any one of claims 1 to 4, wherein, in plan view, there is a gap between the heat generating portion and the first tip or the second tip.

6. A thermal head according to any one of claims 1 to 5, wherein the first tip or the second tip is located above the heat storage layer.

7. A thermal head according to any one of claims 1 to 5, wherein the first tip or the second tip is located above the substrate.

8. A thermal head according to any one of claims 1 to 7, wherein the thickness of the first tip or the second tip of either the first electrode or the individual electrode is greater than the thickness of the portion other than the first tip or the second tip.

9. A thermal head according to any one of claims 1 to 7, wherein the thickness of the portion of either the first electrode or the individual electrode located below the heat generating portion is thicker than the thickness of the portion other than the portion located below the heat generating portion.

10. A thermal printer comprising: a thermal head according to any one of claims 1 to 9; a transport mechanism for transporting a recording medium onto the heat generating portion; and a platen roller for pressing the recording medium onto the heat generating portion.

Images