Thermal head and thermal printer

Abstract

This thermal head comprises a substrate, a heat-generating part, a plurality of drive ICs, a connection electrode, an insulating coating film, and a protective film. The heat-generating part is positioned on the substrate. The plurality of drive ICs are positioned on the substrate and arranged in the main scanning direction. The connection electrode is positioned on the substrate and connects adjacent drive ICs. The coating film is positioned on the heat-generating part and the connection electrode. The protective film is positioned on the coating film and faces a recording medium. The protective film has a specific resistance lower than that of the coating film. A contact part in contact with the connection electrode is provided at an end part of the protective film positioned between the heat-generating part and the drive ICs in a plan view.

Description

Thermal Head and Thermal Printer

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

[0002] Conventionally, various thermal heads have been proposed as printing devices such as facsimiles or video printers. For example, a structure is known in which a charge removal layer connected to a common electrode is provided to remove static electricity generated by the movement of a recording medium or the like.

[0003] International Publication No. 2016 / 68313 International Publication No. 2016 / 31740

[0004] The thermal head according to one aspect of the embodiment includes a substrate, a heating portion, a plurality of drive ICs, connection electrodes, an insulating coating film, and a protective film. The heating portion is located on the substrate. The plurality of drive ICs are located on the substrate and arranged in the main scanning direction. The connection electrodes are located on the substrate and connect adjacent drive ICs. The coating film is located on the heating portion and the connection electrodes. The protective film is located on the coating film and faces the recording medium. The protective film has a lower specific resistance than the coating film. The end portion of the protective film located between the heating portion and the drive IC in plan view has a contact portion that contacts the connection electrode.

[0005] FIG. 1 is a plan view showing an example of the thermal head according to the embodiment. FIG. 2 is a cross-sectional view taken along line A - A shown in FIG. 1. FIG. 3 is an enlarged plan view of the vicinity between drive ICs included in the thermal head according to the embodiment. FIG. 4 is a cross-sectional view taken along line B - B shown in FIG. 3. FIG. 5 is a schematic view showing an example of the thermal printer according to the embodiment.

[0006] Hereinafter, embodiments of the thermal head and the thermal printer disclosed in the present application will be described with reference to the accompanying drawings. Note that the present disclosure is not limited by the following embodiments.

[0007] [Embodiment] Figure 1 is a plan view showing an example of a thermal head according to this embodiment. The thermal head 10 according to this embodiment has a heater section 30 extending along the main scanning direction and a plurality of drive ICs 36 arranged along the main scanning direction. Here, the main scanning direction refers to the direction in which scanning in the line direction is performed when an image is divided into multiple lines and written (printed). In the thermal head 10, the heater section 30 writes (prints) an 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, so the direction in which this sub-scan is performed is called the sub-scan direction. For example, as shown in Figure 5, the transport direction S in which the recording medium P is moved is the sub-scan direction. Therefore, the main scanning direction and the sub-scan direction are usually orthogonal to each other.

[0008] In Figure 1, for the sake of clarity, a three-dimensional Cartesian coordinate system (right-handed system) including the Z-axis, with the vertically upward direction being positive, is shown. The primary scanning direction is along the X-axis, and the secondary scanning direction is along the Y-axis. This Cartesian coordinate system may also be shown in other figures described later.

[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, a common electrode 21, a coating film 22, a protective film 24, a protective layer 26, and a drive IC 36.

[0010] The substrate 12, when viewed from above, is rectangular in shape with a longer length along the main scanning direction. 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 explanation, the surface of the substrate 12 on the side where each component is arranged, i.e., the surface on the positive Z-axis side, may be referred to as the "top surface" of the substrate 12. Similarly, when using the components arranged on the top surface side of the substrate 12 as a reference, the positive Z-axis side may be referred to as "up" or "above".

[0011] The heat storage portion 14 is raised in the thickness direction of the substrate 12. In other words, the heat storage portion 14 protrudes from the upper surface of the substrate 12 in the positive Z-axis direction.

[0012] 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 5) to be printed on.

[0013] 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.

[0014] 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 surface of the substrate 12 by screen printing or the like, firing it, and then etching it as necessary.

[0015] The heat storage layer 16 is positioned to cover the substrate 12 and the heat storage section 14. The heat storage layer 16 may also be positioned to cover the portion of the substrate 12 where the heat storage section 14 is not located. 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.

[0016] The electrode 20 is located above the heat storage unit 14 and the heating resistor 18. The heating resistor 18 is located between the heat storage unit 14 and the individual electrodes 20a. The individual electrodes 20a are arranged 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 unit 14. The position of the heating resistor 18 between the heat storage unit 14 and the individual electrodes 20a creates exposed regions of the heating resistor 18 between the individual electrodes 20a aligned in the main scanning direction. The exposed regions of the heating resistor 18 are arranged along the main scanning direction, and each exposed region constitutes a heating element of the heating unit 28. The configuration of the heating elements is not limited to that shown in the figure. Furthermore, an insulating layer (not shown) may be interposed between the heating resistor 18 and the heat storage layer 16 as needed.

[0017] The heating resistor 18 is formed from a material with relatively high electrical resistance, such as a TaN-based, TaSiO-based, TaSiNO-based, TiSiO-based, TiSiCO-based, or NbSiO-based material. Therefore, when a voltage is applied to the heating resistor 18 via the individual electrodes 20a, the heating portion 28 generates heat through Joule heating. The heating resistor 18 may be etched as needed.

[0018] The electrode 20 includes individual electrodes 20a. One of a pair of individual electrodes 20a, which are located separately, is connected to the common electrode 21, and the other is connected to the drive IC 36. The individual electrodes 20a are formed of a conductive material. The material of the electrode 20 may be, for example, one of the metals Al, Au, Ag, and Cu, or an alloy thereof.

[0019] 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.

[0020] The coating film 22 covers, for example, the heating resistor 18 including the heating element 28 and the electrode 20. The coating film 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. The coating film 22 has insulating properties. Examples of the coating film 22 include SiN, SiO, and SiO. ２ SiO2, TiN, TiON, TiCrN, or TiAlON can be used.

[0021] The protective film 24 covers the heat storage layer 16, the heat-generating resistor 18 including the heat-generating section 28, the electrode 20, and the coating film 22. The protective film 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.

[0022] The protective film 24 has a lower resistivity than the coating film 22. The resistivity of the protective film 24 is, for example, 6.61 × 10⁻⁶. ３ Ω・m or more 4.30×10 ６ The density can be Ω·m or less. For example, SiC can be used as the protective film 24. The protective film 24 may also contain carbon (C). Details of the protective film 24 will be described later.

[0023] The protective layer 26 is provided to partially cover the electrode 20, the coating film 22, and the protective film 24. The protective layer 26 protects the covered areas of the electrode 20, the coating film 22, and the protective film 24 from oxidation due to contact with the atmosphere or corrosion due to the adhesion of moisture contained in the atmosphere. In addition, the protective layer 26, which is placed on the coating film 22 and the protective film 24, covers the edges of the coating film 22 and the protective film 24, making it difficult for the coating film 22 and the protective film 24 to peel off from the protected object, such as the heating element 28 or the electrode 20.

[0024] The protective layer 26 has openings (not shown) to expose individual electrodes 20a connected to the drive IC 36. The individual electrodes 20a are connected to the drive IC 36 through these openings. The drive IC 36 is sealed by the sealing material 34 while connected to the individual electrodes 20a.

[0025] The sealing material 34 seals the drive IC 36 while it is connected to the individual electrodes 20a. The sealing material 34 protects the drive IC 36 and the connection between the drive IC 36 and the individual electrodes 20a. As the sealing material 34, a resin material such as epoxy resin or silicone resin can be used.

[0026] Multiple drive ICs 36 are arranged in a line in the main scanning direction. The multiple drive ICs 36 are arranged along the arrangement direction of the heating unit 28 so as to correspond to each heating element of the heating unit 28 assigned to each drive IC 36. The drive ICs 36 are electrically connected to each heating element of the heating unit 28 via individual electrodes 20a, and supply power to the heating unit 28 to individually heat each heating element of the heating unit 28 according to an electrical signal supplied from the outside. As the drive IC 36, for example, a switching member having multiple switching elements inside can be used.

[0027] The drive IC 36 is connected to the individual electrodes 20a via a conductive bonding material 37. The bonding material 37 may be bonded to a terminal portion 38 that is electrically connected to the individual electrodes 20a. The bonding material 37 and terminal portion 38 located between the drive IC 36 and the individual electrodes 20a may be sealed with an underfill material 32. As the underfill material 32, for example, an insulating resin such as epoxy resin can be used. Alternatively, a sealing material 34 may be used instead of the underfill material 32.

[0028] Next, the main parts of the thermal head 10 according to this embodiment will be further described with reference to Figures 2 to 4. Figure 3 is an enlarged plan view of the vicinity of the drive ICs in the thermal head according to this embodiment. Figure 4 is a cross-sectional view taken along the line B-B shown in Figure 3.

[0029] The electrode 20 has a connecting electrode 20b that electrically connects adjacent drive ICs 36 in the scanning direction (X-axis direction). The connecting electrode 20b includes a plurality of wires 20b1 to 20b5, each having a different function. Figure 3 illustrates a connecting electrode 20b having five wires 20b1 to 20b5, but there is no limit to the number of wires that the connecting electrode 20b may have.

[0030] The connecting electrode 20b is partially covered with a protective film 24. A protective layer 26 is located on the portion of the connecting electrode 20b that is not covered with the protective film 24. Note that the protective layer 26 is not shown in Figure 3.

[0031] As shown in Figure 4, the coating film 22 has an end portion 22a located between the heating element 28 and the drive IC 36 in a plan view. Similarly, the protective film 24 has an end portion 24a located between the heating element 28 and the drive IC 36 in a plan view. The end portion 24a has a portion closer to the drive IC 36 than the end portion 22a. In this case, the protective film 24 located between the end portion 22a and the end portion 24a has a contact portion 241 that contacts the connecting electrode 20b.

[0032] As described above, since the protective film 24 is positioned facing the recording medium P, it is prone to becoming charged, for example, due to the movement of the recording medium P. If the charged protective film 24 is left without being discharged, for example, discharge is more likely to occur, and the protective film 24 is more susceptible to damage.

[0033] The thermal head 10 according to this embodiment has a contact portion 241 at the end 24a of the protective film 24, which is located between the heating element 28 and the drive IC 36 in a plan view, and which contacts the connecting electrode 20b. In this way, by bringing the protective film 24, which has a lower resistivity than the coating film 22, into contact with the connecting electrode 20b, static electricity charged on the protective film 24 can be quickly discharged. Therefore, the static discharge performance is improved according to the thermal head 10 according to this embodiment.

[0034] In Figure 4, an example is shown where the contact portion 241 is in contact with the side surface of the wiring 20b3, but the contact portion 241 may be in contact with other parts, such as the top surface of the wiring 20b3. Also, in Figure 4, an example is shown where the contact portion 241 is in contact with the wiring 20b3, but the contact portion 241 may be in contact with other wirings of the connecting electrode 20b. The contact portion 241 may be in contact with multiple wirings of the connecting electrode 20b.

[0035] Furthermore, the contact portion 241 may be in contact with the individual electrode 20a. Also, the contact portion 241 may be in contact with an electrode 20 different from the individual electrode 20a and the connecting electrode 20b, such as an electrode 20 located at the end in the main scanning direction.

[0036] [Thermal Printer] Next, a thermal printer having a thermal head 10 will be described with reference to Figure 5. Figure 5 is a schematic diagram showing an example of a thermal printer according to the embodiment.

[0037] The thermal printer 100 according to this embodiment includes the thermal head 10, a transport mechanism 40, a platen roller 50, a power supply unit 60, and a control device 70. 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 unit 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.

[0038] The transport mechanism 40 includes a drive unit (not shown) and transport rollers 43, 45, 47, and 49. The transport mechanism 40 transports the 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 section 30 of the thermal head 10, which is protected by a protective film 24. 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. 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 protective film 24 of the thermal head 10. The transport mechanism 40 is an example of a moving part that moves the thermal head 10 and the recording medium P relative to each other. The moving part may also be one that moves the thermal head 10 relative to the recording medium P.

[0039] The platen roller 50 presses the recording medium P onto the protective film 24 positioned on the heater portion 30 of the thermal head 10. The platen roller 50 is arranged to extend along a direction orthogonal to the conveyance direction S, that is, the main scanning direction, and both ends thereof are supported and fixed so as to be rotatable while pressing the recording medium P onto the heater portion 30. The platen roller 50 can be configured by covering, for example, a columnar shaft body 50a mainly composed of a metal such as stainless steel with an elastic member 50b mainly composed of butadiene rubber or the like.

[0040] The power supply device 60 supplies a current for causing the heat generating portion 28 (see FIG. 2) of the thermal head 10 to generate heat and a current for operating the drive IC 36 included in the thermal head 10 as described above. The control device 70 supplies a control signal for controlling the operation of the drive IC 36 to the drive IC 36 in order to selectively generate heat in the heat generating portion 28 of the thermal head 10 as described above.

[0041] The thermal printer 100 conveys the recording medium P onto the heater portion 30 by the conveyance mechanism 40 while pressing the recording medium P onto the heater portion 30 of the thermal head 10 by the platen roller 50. Then, the thermal printer 100 performs predetermined printing on the recording medium P by selectively generating heat in the heat generating portion 28 by the power supply device 60 and the control device 70 while conveying the recording medium P onto the heater portion 30. When the recording medium P is a receiving paper or the like, printing on the recording medium P is performed by thermally transferring the ink of an ink film (not shown) conveyed together with the recording medium P onto the recording medium P.

[0042] In FIG. 5, as an example, a thermal printer 100 having the thermal head 10 according to the embodiment is illustrated, but the thermal printer 100 may have a thermal head 10 according to other embodiments. For example, an end face head in which the heater portion 30 is provided on the end face of the substrate 12 may be used as the thermal head 10.

[0043] As described above, the embodiments of the present disclosure have been described, but the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof.

[0044] In one embodiment, (1) the thermal head includes a substrate, a heat generating portion located on the substrate, a plurality of drive ICs located on the substrate and arranged in the main scanning direction, connection electrodes located on the substrate and connecting adjacent drive ICs, an insulating coating film located on the heat generating portion and the connection electrodes, and a protective film located on the coating film and facing the recording medium. The protective film has a lower specific resistance than the coating film, and an end portion of the protective film located between the heat generating portion and the drive IC in a plan view has a contact portion that contacts the connection electrode.

[0045] (2) In the thermal head of (1) above, an individual electrode connecting the heat generating portion and the drive IC may be provided, and the end portion of the protective film may have the contact portion that contacts the individual electrode.

[0046] (3) In the thermal head of (1) or (2) above, the protective film may contain SiC.

[0047] (4) In the thermal head of (3) above, the protective film may contain carbon.

[0048] (5) The thermal printer has the thermal head according to any one of (1) to (4) above and a moving portion that relatively moves the thermal head and the recording medium.

[0049] Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present disclosure are not limited to the specific details and representative embodiments represented and described as above. Accordingly, various changes can be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

[0050] 10 Thermal head 12 Substrate 14 Heat storage portion 16 Heat storage layer 18 Heating resistor 20 Electrode 20a Individual electrode 20b Connection electrode 21 Common electrode 22 Coating film 24 Protective film 26 Protective layer 28 Heat generating portion 30 Heater portion 36 Drive IC 100 Thermal printer 241 Contact portion

Claims

1. A thermal head comprising: a substrate; a heating element located on the substrate; a plurality of drive ICs located on the substrate and arranged in the main scanning direction; connecting electrodes located on the substrate and connecting adjacent drive ICs; an insulating coating film located on the heating element and the connecting electrodes; and a protective film located on the coating film and facing a recording medium, wherein the protective film has a lower resistivity than the coating film, and the edge of the protective film located between the heating element and the drive ICs in a plan view has a contact portion that contacts the connecting electrodes.

2. The thermal head according to claim 1, comprising individual electrodes connecting the heating element and the drive IC, wherein the end of the protective film has a contact portion that contacts the individual electrodes.

3. The thermal head according to claim 1 or 2, wherein the protective film comprises SiC.

4. The thermal head according to claim 3, wherein the protective film comprises carbon.

5. A thermal printer having a thermal head according to any one of claims 1 to 4, and a moving unit for moving the thermal head and a recording medium relative to each other.

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