Thermal head and recorder

Abstract

This thermal head comprises: a substrate; a heat storage layer; a heat generation part; and a covering layer. The heat storage layer is positioned above the substrate. The heat generation part is positioned above the heat storage layer. The covering layer is positioned above the heat storage layer and the heat generation part and faces a recording medium. The covering layer has: a first region positioned above the heat generation part; a second region adjacent to the first region in a sub-scanning direction; and a third region positioned on the opposite side of the second region from the first region. The surface roughness of the second region is greater than that of the first region. The surface roughness of the third region is greater than that of the second region.

Description

Thermal Head and Recording Device

[0001] The disclosed embodiments relate to a thermal head and a recording device.

[0002] Conventionally, various thermal heads have been proposed as printing devices such as facsimiles or video printers. For example, a substrate structure of a thermal head in which a glaze layer is provided on the surface of a substrate and smoothed is known.

[0003] Japanese Patent Laid-Open No. 2-106357, Japanese Patent Laid-Open No. 2-125757

[0004] A thermal head according to one aspect of the embodiment includes a substrate, a heat storage layer, a heat generating portion, and a coating layer. The heat storage layer is located on the substrate. The heat generating portion is located on the heat storage layer. The coating layer is located on the heat storage layer and the heat generating portion and faces the recording medium. The coating layer has a first region located on the heat generating portion, a second region adjacent to the first region in the sub-scanning direction, and a third region located on the opposite side of the first region across the second region. The surface roughness of the second region is greater than that of the first region. The surface roughness of the third region is greater than that of the second region.

[0005] FIG. 1 is a plan view showing an example of a thermal head according to the first embodiment. FIG. 2 is a cross-sectional view taken along line A-A shown in FIG. 1. FIG. 3 is a cross-sectional view showing another example of the thermal head according to the first embodiment. FIG. 4 is a cross-sectional view showing another example of the thermal head according to the first embodiment. FIG. 5 is a plan view showing an example of a thermal head according to the second embodiment. FIG. 6 is a cross-sectional view taken along line B-B shown in FIG. 5. FIG. 7 is a cross-sectional view showing another example of the thermal head according to the second embodiment. FIG. 8 is a schematic view showing an example of a thermal printer according to the embodiment.

[0006] In the above-described substrate structure, for example, there is room for improvement in the durability of the coating layer that protects the surface of the thermal head. Therefore, there is an expectation for providing a thermal head and a recording device that can improve the durability of the coating layer.

[0007] The embodiments of the thermal head and recording device disclosed herein will be described below with reference to the attached drawings. However, this disclosure is not limited to the embodiments described below.

[0008] [First Embodiment] Figure 1 is a plan view showing an example of a thermal head according to the first embodiment. The thermal head 10 according to this embodiment has a heater section 30 that extends along the main scanning direction. Here, when an image is divided into multiple lines and written (printed), scanning in the line direction is called the main scan. The main scanning direction refers to this main scanning direction. In the thermal head 10, the heater section 30 writes (prints) the image for each line, so the heater section 30 extends along the main scanning direction. Also, after writing one line, the recording medium is moved to write the next line, and this movement to the next line is called a sub-scan. The sub-scan direction refers to this sub-scan direction. The sub-scan direction is, for example, the direction along the transport direction S in which the recording medium P is moved, as shown in Figure 8. Therefore, the main scanning direction and the sub-scan direction may be orthogonal to each other.

[0009] Figure 2 is a cross-sectional view taken along line A-A in Figure 1. The thermal head 10 according to this embodiment includes a substrate 12, a heat storage section 14, a heat storage layer 16, a heating resistor 18, an electrode 20, and a coating layer 24. The thermal head 10 may also include a protective layer 22 located between the electrode 20 and the coating layer 24.

[0010] The substrate 12 is plate-shaped. The substrate 12 may also be rectangular in shape, with a longer length along the main scanning direction when viewed from above. The substrate 12 has a first surface 12a and a second surface 12b located on the opposite side of the first surface 12a. In the thermal head 10 according to this embodiment, each component is arranged on the first surface 12a.

[0011] The substrate 12 is formed of, for example, an electrically insulating material such as alumina ceramics or a semiconductor material such as single-crystal silicon. For the sake of convenience in this explanation, the first surface 12a may be referred to as the "top surface" and the second surface 12b as the "bottom surface." Similarly, the direction away from the substrate 12 with respect to the first surface 12a may be referred to as "up" or "above."

[0012] The heat storage portion 14 is raised in the thickness direction of the substrate 12. In other words, the heat storage portion 14 protrudes upward from the first surface 12a of the substrate 12.

[0013] The heat storage unit 14 extends along the main scanning direction. The heat storage unit 14 may have a roughly semi-elliptical cross-section. This makes it easier for the heater unit 30 located on the surface of the thermal head 10 to come into contact with the recording medium P (see Figure 8) to be printed on.

[0014] The heat storage section 14 is made of, for example, glass with low thermal conductivity, and temporarily stores a portion of the heat generated by the heat-generating section 28, which will be described later. As a result, the time required to raise the temperature of the heat-generating section 28 can be shortened, and the thermal response characteristics of the thermal head 10 can be improved.

[0015] The heat storage section 14 may be formed, for example, by applying a predetermined glass paste obtained by mixing glass powder with a suitable organic solvent to the first surface 12a by screen printing or the like, firing it, and then etching it as necessary.

[0016] The heat storage layer 16 is positioned to cover the first surface 12a of the substrate 12 and the heat storage section 14. The material of the heat storage layer 16 may be the same as or different from the material of the heat storage section 14. The heat storage layer 16 may be formed by thin-film deposition techniques such as sputtering or CVD (Chemical Vapor Deposition). Alternatively, it may be formed by thick-film deposition techniques, such as screen printing, which involves forming a coating film of material paste and then firing it. In any case, it may also be formed by etching as needed.

[0017] The heating resistor 18 is located on the upper surface of the heat storage layer 16. The heating resistor 18 may also be located from the upper surface of the heat storage layer 16 covering the heat storage section 14 to its periphery. Electrodes 20 are located on the heating resistor 18. The electrodes 20 are arranged side by side in the main scanning direction according to the resolution of the print, and are located apart in the sub-scanning direction above the heat storage section 14. Because the pairs of electrodes 20 are located apart, an exposed region of the heating resistor 18 is formed between these pairs of electrodes 20. The exposed regions of the heating resistor 18 are arranged side by side along the main scanning direction, and each exposed region constitutes one of the heating elements of the heating section 28. An insulating layer (not shown) may be interposed between the heating resistor 18 and the heat storage layer 16 as needed.

[0018] The heating resistor 18 is formed from a material with relatively high electrical resistance, such as TaN, TaSiO, TaSiNO, TiSiO, TiSiCO, or NbSiO. Therefore, when a voltage is applied to the heating section 28 via the electrode 20, the heating section 28 generates heat through Joule heating. The heating resistor 18 may be etched as needed.

[0019] The electrodes 20 may consist of a pair of electrodes located separately, one of which is a common electrode and the other is an individual electrode. The electrodes 20 are made of a conductive material. The material of the electrodes 20 may be, for example, one of the metals Al, Au, Ag, and Cu, or an alloy thereof.

[0020] The electrodes 20 can be formed, for example, by laminating the material layers constituting each electrode onto the heating resistor 18 using a thin-film molding technique such as sputtering, and then processing them into a predetermined pattern using photoetching or the like. Alternatively, the electrodes 20 may be manufactured by methods such as screen printing, flexographic printing, gravure printing, or gravure offset printing.

[0021] The protective layer 22 covers, for example, the heat-generating resistor 18, which includes the heat-generating part 28, and the electrode 20. The protective layer 22 protects the covered portion from corrosion due to the adhesion of moisture contained in the atmosphere, or from abrasion due to contact with the recording medium P on which the image is printed. Examples of materials for the protective layer 22 include SiN, SiO, and SiO. ２ SiAlON, TiN, TiON, TiCrN, TiAlON, etc. can be used.

[0022] The coating layer 24 covers the heat storage layer 16, the heat-generating resistor 18 including the heat-generating part 28, and the electrode 20. The coating layer 24 may also cover the protective layer 22. The coating layer 24 protects the covered portion from oxidation due to contact with the atmosphere, corrosion due to the adhesion of moisture contained in the atmosphere, or abrasion due to contact with the recording medium P to be printed on. As for the coating layer 24, for example, like the protective layer 22, SiN, SiO ２ SiAlON, TiN, TiON, TiCrN, TiAlON, etc. can be used.

[0023] Next, the main parts of the thermal head 10 according to this embodiment will be described further.

[0024] The coating layer 24 has a first region 24a, two second regions 24b, and two third regions 24c. The first region 24a is located above the heating element 28. The two second regions 24b are located on either side of the first region 24a in the sub-scanning direction of the thermal head 10. The two second regions 24b are also located adjacent to the first region 24a. The two third regions 24c are located on the opposite side of the first region 24a from each of the two second regions 24b. The two third regions 24c are also located adjacent to each of the two second regions 24b. That is, the two second regions 24b are positioned to sandwich the first region 24a in the sub-scanning direction. The two third regions 24c are also positioned to sandwich the first region 24a and the second regions 24b in the sub-scanning direction. Therefore, when viewed in the sub-scanning direction from one of the two third regions 24c to the other third region 24c, the third region 24c, second region 24b, first region 24a, second region 24b, and third region 24c are arranged in that order.

[0025] The second region 24b has a rougher surface than the first region 24a. The third region 24c has a rougher surface than the second region 24b. In this way, the surface roughness of the coating layer 24 covering the heater section 30 may be made different in the order of the first region 24a, the second region 24b, and the third region 24c, increasing outward in the sub-scanning direction when viewed from the first region 24a. With such a configuration, for example, the coating layer 24 becomes less likely to peel off, and the durability of the thermal head 10 is improved.

[0026] Furthermore, by sequentially varying the surface roughness of the coating layer 24 along the transport direction S of the recording medium P, the recording medium P becomes easier to peel off from the coating layer 24 after printing. Therefore, according to the thermal head 10 of this embodiment, printing performance is improved.

[0027] The first region 24a may have an arithmetic mean height Sa of less than 10 nm. This improves, for example, the heat transfer from the heating element 28 to the coating layer 24, thereby improving the thermal efficiency of the thermal head 10. It also improves the wear resistance of the first region 24a, thereby improving the durability of the thermal head 10.

[0028] Furthermore, the third region 24c may have an arithmetic mean height Sa of 100 nm or more and 300 nm or less, and may also be 150 nm or more and 300 nm or less. This improves the durability of the thermal head 10, for example, by making it more difficult for the coating layer 24 to peel off. It also makes it easier for the recording medium P (see Figure 8) to peel off from the coating layer 24, improving the printing performance of the thermal head 10.

[0029] Furthermore, the arithmetic mean height Sa of the second region 24b may be 50 nm or more and 200 nm or less, and may also be 50 nm or more and 100 nm or less. This makes it more difficult for the coating layer 24 to peel off, improving the durability of the thermal head 10. Also, after printing, the recording medium P becomes easier to peel off from the coating layer 24, improving the printing performance of the thermal head 10.

[0030] The heat storage layer 16 facing the first region 24a may have a smoother surface facing the coating layer 24 compared to the heat storage layer 16 facing the third region 24c. This improves the pulse resistance of the heat-generating section 28 and improves the printing performance of the thermal head 10. Note that the portion of the heat storage layer 16 having a smoother surface facing the coating layer 24 compared to the heat storage layer 16 facing the third region 24c is not limited to the portion facing the first region 24a. The portion of the heat storage layer 16 having a smoother surface facing the coating layer 24 compared to the heat storage layer 16 facing the third region 24c may also be the portion facing the first region 24a and the second region 24b adjacent to the first region 24a.

[0031] The second region 24b may include, for example, the portion of the coating layer 24 located on the heat storage unit 14 and the electrode 20, excluding the first region 24a. The third region 24c may include, for example, the portion of the coating layer 24 that protrudes away from the first surface 12a, where the heat storage unit 14 is not located.

[0032] Here, the arithmetic mean height Sa of each region in the coating layer 24 can be measured in accordance with ISO 25178, the international standard for three-dimensional surface properties. Specifically, it can be measured using a stylus-type roughness meter (Dektak, manufactured by BRUKER). Furthermore, the arithmetic mean height Sa of each region in the coating layer 24 can be measured under the following conditions.

[0033] Cutoff wavelength: 0.02 mm or greater; Radius (stylus tip radius): 50 nm; Stylus Force: 4 mg; Length: 350 μm; Duration: 60 sec; Resolution (horizontal resolution of measurement): 0.019 μm / pt

[0034] Figures 3 and 4 are cross-sectional views showing another example of a thermal head according to the first embodiment.

[0035] As shown in Figure 3, the width of the second region 24b along the transport direction S of the recording medium P may be smaller on the downstream side of the transport direction S (the leftward side in Figure 3) than on the upstream side of the transport direction S (the rightward side in Figure 3). This makes it easier for the recording medium P to begin contact with the coating layer 24 at a position upstream of the heat-generating section 28, so that the temperature of the recording medium P rises more gradually. Therefore, according to the thermal head 10 of this embodiment, heat can be efficiently transferred to the recording medium P, improving print quality.

[0036] Furthermore, as shown in Figure 4, the width of the second region 24b along the transport direction S of the recording medium P may be smaller on the upstream side of the transport direction S (the side moving to the right in Figure 4) than on the downstream side of the transport direction S (the side moving to the left in Figure 4). This makes it easier for the recording medium P to peel off from the coating layer 24 after printing. Therefore, according to the thermal head 10 of this embodiment, the recording medium P peels off smoothly from the coating layer 24 after printing, improving the printing performance of the thermal head 10.

[0037] In all of the thermal heads 10 described above, the first region 24a and the third region 24c of the coating layer 24 are located on the first surface 12a of the substrate 12, i.e., on the same surface. However, the thermal head 10 of this disclosure is not limited to the above configuration, and the first region 24a and the third region 24c of the coating layer 24 may be located on different surfaces of the substrate 12.

[0038] [Second Embodiment] Figure 5 is a plan view showing an example of a thermal head according to the second embodiment. Figure 6 is a cross-sectional view taken along the line B-B shown in Figure 5.

[0039] As shown in Figure 6, the thermal head 10 according to this embodiment comprises a substrate 12, a heat storage section 14, a heat storage layer 16, a heat-generating resistor 18, an electrode 20, an optional protective layer 22, and a coating layer 24.

[0040] The substrate 12 has a third surface 121 and a fourth surface 122 that are orthogonal to each other, and a fifth surface 123 located between the third surface 121 and the fourth surface 122. The angle between the third surface 121 and the fifth surface 123 may be the same as or different from the angle between the fourth surface 122 and the fifth surface 123. For the sake of explanation, the direction away from the substrate 12 with respect to the fifth surface 123 may be referred to as "up" or "above".

[0041] The heat storage section 14 protrudes upward from the fifth surface 123 of the substrate 12. The width of the heat storage section 14 along the sub-scanning direction may be the same as the fifth surface 123, or it may be smaller than the fifth surface 123.

[0042] The heat storage layer 16 is positioned to cover the third surface 121, the fourth surface 122, and the fifth surface 123 of the substrate 12 and the heat storage portion 14. The heating resistor 18 is positioned on the upper surface of the heat storage layer 16. The heating resistor 18 may be positioned from the upper surface of the heat storage layer 16 covering the heat storage portion 14 to the portions covering the third surface 121 and the fourth surface 122 around it. Above the heating resistor 18, electrodes 20 are arranged side by side in the main scanning direction according to the resolution of the printing and are positioned apart in the sub-scanning direction above the heat storage portion 14. The exposed region of the heating resistor 18 formed by the paired electrodes 20 being positioned apart constitutes each heating element of the heating portion 28.

[0043] The protective layer 22 covers, for example, the heat storage layer 16, the heating resistor 18 including the heating portion 28, and the electrodes 20. The coating layer 24 covers the heat storage layer 16, the heating resistor 18 including the heating portion 28, and the electrodes 20. The coating layer 24 may cover the protective layer 22.

[0044] The coating layer 24 has a first region 24a, a second region 24b, and a third region 24c. The first region 24a is positioned above the heating portion 28. The second regions 24b are respectively adjacent to both sides of the first region 24a in the sub-scanning direction. The third regions 24c are positioned on the opposite side of the first region 24a in the sub-scanning direction with the second regions 24b sandwiched therebetween for each of the second regions 24b. In an example of this embodiment as well, the second regions 24b are positioned so as to sandwich the first region 24a in the sub-scanning direction, and the third regions 24c are positioned so as to sandwich the first region 24a and the second regions 24b in the sub-scanning direction. When these regions are viewed in the sub-scanning direction from one of the two third regions 24c to the other third region 24c, they are arranged in the order of the third region 24c, the second region 24b, the first region 24a, the second region 24b, and the third region 24c.

[0045] The surface roughness of the second region 24b is greater than that of the first region 24a. The surface roughness of the third region 24c is greater than that of the second region 24b. Thus, if the surface roughness of the coating layer 24 covering the heater unit 30 is made different so as to increase in the order of the first region 24a, the second region 24b, and the third region 24c toward the outside in the sub-scanning direction as viewed from the first region 24a, for example, the coating layer 24 becomes difficult to peel off. Thereby, the durability of the thermal head 10 is improved.

[0046] Also, by making the surface roughness of the coating layer 24 different in order along the conveyance direction S of the recording medium P, for example, after printing, the recording medium P becomes easy to peel off from the coating layer 24, and the printing performance of the thermal head 10 is improved.

[0047] The third region 24c may include, for example, a portion where the surface of the coating layer 24 is substantially parallel to the third surface 121. Also, the third region 24c may include, for example, a portion where the surface of the coating layer 24 is substantially parallel to the fourth surface 122. In such a case, the second region 24b can be provided between the first region 24a and the third region 24c.

[0048] Also, the second region 24b may include, for example, a portion of the coating layer 24 located above the heat storage portion 14 and the electrodes 20, excluding the first region 24a. The third region 24c may include, for example, a portion of the coating layer 24 protruding away from the fifth surface 123, where the heat storage portion 14 is not located.

[0049] FIG. 7 is a cross-sectional view showing another example of the thermal head according to the second embodiment. As shown in FIG. 7, the thermal head 10 according to the present embodiment includes a substrate 12, a heat storage layer 16, a heat generating resistor 18, electrodes 20, an optional protective layer 22, and a coating layer 24. That is, the thermal head 10 according to the present embodiment may not have the heat storage portion 14.

[0050] In this case, the heat storage layer 16 is positioned to cover the third surface 121, the fourth surface 122, and the fifth surface 123 of the substrate 12. The heating resistor 18 is located on the upper surface of the heat storage layer 16. The heating resistor 18 may also be positioned from the surface of the heat storage layer 16 covering the fifth surface 123 to its periphery, that is, on the upper surface of the heat storage layer 16 covering the third surface 121 and the fourth surface 122. On the heating resistor 18, electrodes 20 are arranged in a line in the main scanning direction according to the resolution of the print, and are positioned apart in the sub-scanning direction above the fifth surface 123. The exposed region of the heating resistor 18 formed between these pairs of electrodes 20, which are positioned apart from each other, constitutes each heating element of the heating unit 28.

[0051] The protective layer 22 covers, for example, the heat storage layer 16, the heat-generating resistor 18 including the heat-generating part 28, and the electrode 20. The coating layer 24 covers the heat storage layer 16, the heat-generating resistor 18 including the heat-generating part 28, and the electrode 20. The coating layer 24 may also cover the protective layer 22.

[0052] The coating layer 24 has a first region 24a, a second region 24b, and a third region 24c. The first region 24a is located above the heating element 28. The second region 24b is located adjacent to the first region 24a on both sides in the sub-scanning direction. The third region 24c is located on the opposite side of the first region 24a in the sub-scanning direction from each of the second regions 24b, with the second region 24b in between. In other examples of this second embodiment, the second region 24b is located so as to sandwich the first region 24a in the sub-scanning direction, and the third region 24c is located so as to sandwich the first region 24a and the second region 24b in the sub-scanning direction. These regions, when viewed in the sub-scanning direction from one of the two third regions 24c to the other, are arranged in the order of third region 24c, second region 24b, first region 24a, second region 24b, and third region 24c.

[0053] The second region 24b has a rougher surface than the first region 24a. The third region 24c has a rougher surface than the second region 24b. By making the surface roughness of the coating layer 24 covering the heater section 30 different in the order of the first region 24a, the second region 24b, and the third region 24c, increasing outward in the sub-scanning direction when viewed from the first region 24a, the coating layer 24 becomes less likely to peel off. This improves the durability of the thermal head 10.

[0054] Furthermore, by making the surface roughness of the coating layer 24 different in order from the first region 24a to the second region 24b and the third region 24c along the transport direction S of the recording medium P described later, the recording medium P becomes easier to peel off from the coating layer 24 after printing. This improves the printing performance of the thermal head 10.

[0055] The third region 24c may include, for example, a portion where the surface of the coating layer 24 is substantially parallel to the third surface 121. Alternatively, the third region 24c may also include, for example, a portion where the surface of the coating layer 24 is substantially parallel to the fourth surface 122. In this case, the area between the first region 24a and the third region 24c can be designated as the second region 24b.

[0056] Furthermore, the second region 24b may include, for example, the portion of the coating layer 24 located on the fifth surface 123 and the electrode 20, excluding the first region 24a. The third region 24c may include, for example, the portion of the coating layer 24 located on the opposite side of the first region 24a, with the second region 24b in between, that may come into contact with the recording medium P, which will be described later.

[0057] [Thermal Printer] Next, a thermal printer having a thermal head 10 will be described with reference to Figure 8. Figure 8 is a schematic diagram showing an example of a thermal printer according to the embodiment.

[0058] The thermal printer 100 according to this embodiment includes the thermal head 10, a transport mechanism 40, a platen roller 50, a power supply 60, and a control device 70. The thermal printer 100 is an example of a recording device. The thermal head 10 is mounted on the mounting surface 80a of a mounting member 80 located on the housing (not shown) of the thermal printer 100. The thermal head 10 is mounted on the mounting member 80 such that the longitudinal direction of the substrate 12 and the direction in which the heater portion 30 extends are aligned with the main scanning direction, which is perpendicular to the transport direction S. A heat sink (not shown) may also be placed between the thermal head 10 and the mounting member 80.

[0059] 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 heater portion 30 of the thermal head 10, which is protected by a coating layer 24. The transport mechanism 40 is an example of a moving unit that moves the thermal head 10 and the recording medium P relative to each other. The drive unit includes, for example, a motor (not shown) and drives the transport rollers 43, 45, 47, and 49. The transport rollers 43, 45, 47, and 49 may be cylindrical shafts 43a, 45a, 47a, and 49a made of a metal such as stainless steel, covered with elastic members 43b, 45b, 47b, and 49b made of butadiene rubber or the like. Furthermore, if the recording medium P is an image-receiving paper or the like to which ink is transferred, an ink film (not shown) is transported together with the recording medium P between the recording medium P and the coating layer 24 of the thermal head 10.

[0060] The platen roller 50 presses the recording medium P onto the coating layer 24 located on the heater portion 30 of the thermal head 10. The platen roller 50 is arranged to extend in a direction perpendicular to the transport direction S, i.e., along the main scanning direction, and both ends are supported and fixed so that it can rotate while pressing the recording medium P onto the heater portion 30. The platen roller 50 can 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.

[0061] As described above, the power supply unit 60 supplies current to generate heat in the heat-generating part 28 (see Figure 2) of the thermal head 10 and current to operate the drive IC (not shown) of the thermal head 10. As described above, the control device 70 supplies a control signal to the drive IC to control the operation of the drive IC in order to selectively generate heat in the heat-generating part 28 of the thermal head 10.

[0062] The thermal printer 100 presses the recording medium P against the heater section 30 of the thermal head 10 using the platen roller 50, while transporting the recording medium P onto the heater section 30 using the transport mechanism 40. As the recording medium P is transported over the heater section 30, the power supply unit 60 and the control device 70 selectively heat the heating section 28 to perform a predetermined print on the recording medium P. 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 print.

[0063] In Figure 8, a thermal printer 100 having a thermal head 10 according to the first embodiment is shown as an example, but the thermal printer 100 may have a thermal head 10 according to other embodiments.

[0064] While embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from its spirit.

[0065] In one embodiment, (1) the thermal head comprises a substrate, a heat storage layer located on the substrate, a heating element located on the heat storage layer, and a coating layer located on the heat storage layer and the heating element and facing the recording medium, wherein the coating layer has a first region located on the heating element, a second region adjacent to the first region in the sub-scanning direction and having a larger surface roughness than the first region, and a third region located on the opposite side of the first region with the second region in between and having a larger surface roughness than the second region.

[0066] (2) In the thermal head described in (1) above, the first region may have an arithmetic mean height Sa of less than 10 nm.

[0067] (3) In the thermal head described in (1) or (2) above, the third region may have an arithmetic mean height Sa of 100 nm or more and 300 nm or less.

[0068] (4) In any one of the thermal heads described in (1) to (3) above, the second region may have an arithmetic mean height Sa of 50 nm or more and 200 nm or less.

[0069] (5) In any one of the thermal heads described in (1) to (4) above, the width of the second region along the transport direction of the recording medium may be smaller on the downstream side in the transport direction than on the upstream side in the transport direction.

[0070] (6) In any one of the thermal heads described in (1) to (4) above, the width of the second region along the transport direction of the recording medium may be smaller on the upstream side in the transport direction than on the downstream side in the transport direction.

[0071] (7) In any one of the thermal heads described in (1) to (6) above, the first region and the third region may be located on the same plane of the substrate.

[0072] (8) In any one of the thermal heads described in (1) to (6) above, the first region and the third region may be located on different surfaces of the substrate.

[0073] (9) In any one of the thermal heads described in (1) to (8) above, the heat storage layer facing the first region may have a smoother surface facing the coating layer than the heat storage layer facing the third region.

[0074] In one embodiment, the recording device (10) has one of the thermal heads described in (1) to (9) above, and a moving unit that moves the thermal head and the recording medium relative to each other.

[0075] 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.

[0076] 10 Thermal head 12 Substrate 14 Heat storage section 16 Heat storage layer 18 Heating resistor 20 Electrode 22 Protective layer 24 Coating layer 24a First region 24b Second region 24c Third region 28 Heating section 30 Heater section 100 Thermal printer

Claims

1. A thermal head comprising: a substrate; a heat storage layer located on the substrate; a heat generating section located on the heat storage layer; and a coating layer located on the heat storage layer and the heat generating section and facing the recording medium, wherein the coating layer has a first region located on the heat generating section; a second region adjacent to the first region in the sub-scanning direction and having a surface roughness greater than that of the first region; and a third region located on the opposite side of the first region, with the second region in between, and having a surface roughness greater than that of the second region.

2. The thermal head according to claim 1, wherein the first region has an arithmetic mean height Sa of less than 10 nm.

3. The thermal head according to claim 1 or 2, wherein the third region has an arithmetic mean height Sa of 100 nm or more and 300 nm or less.

4. The thermal head according to any one of claims 1 to 3, wherein the second region has an arithmetic mean height Sa of 50 nm or more and 200 nm or less.

5. The thermal head according to any one of claims 1 to 4, wherein the width of the second region along the transport direction of the recording medium is smaller on the downstream side in the transport direction than on the upstream side in the transport direction.

6. The thermal head according to any one of claims 1 to 4, wherein the width of the second region along the transport direction of the recording medium is smaller on the upstream side in the transport direction than on the downstream side in the transport direction.

7. The thermal head according to any one of claims 1 to 6, wherein the first region and the third region are located on the same plane of the substrate.

8. The thermal head according to any one of claims 1 to 6, wherein the first region and the third region are located on different surfaces of the substrate.

9. The thermal head according to any one of claims 1 to 8, wherein the heat storage layer facing the first region has a smoother surface facing the coating layer compared to the heat storage layer facing the third region.

10. A recording device having a thermal head according to any one of claims 1 to 9, and a moving unit for moving the thermal head and a recording medium relative to each other.

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