Thermal heads and thermal printers

Abstract

This thermal head is provided with: a substrate; a thermal storage layer positioned on the substrate; and a heat generation unit positioned on the thermal storage layer. Further, when a conveyance direction of a recoding medium is a first direction and a direction opposite to the first direction is a second direction, the thickness of a portion positioned beneath the end on a second direction side of the heat generation unit is larger than the thickness of a portion positioned beneath the end on a first direction side of the heat generation unit in the thermal storage layer.

Description

Technical Field

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

Background Art

[0002] Conventionally, various thermal heads have been proposed as printing devices such as facsimiles or video printers (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The thermal head of the present disclosure includes a substrate, a heat storage layer located on the substrate, and a heat generating portion located on the heat storage layer. Further, when the conveyance direction of the recording medium is taken as the first direction and the direction opposite to the first direction is taken as the second direction, in the heat storage layer, the thickness of the portion located below the end portion on the second direction side of the heat generating portion is thicker than the thickness of the portion located below the end portion on the first direction side of the heat generating portion.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a diagram schematically showing the configuration of a thermal head according to an embodiment. [Figure 2] FIG. 2 is a plan view showing the schematic configuration of the thermal head shown in FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view taken along the line A-A shown in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view showing an example of a main part of a thermal head according to an embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing another example of a main part of a thermal head according to an embodiment. [Figure 6]Figure 6 is a cross-sectional view showing an example of the main part of a thermal head according to another embodiment 1. [Figure 7] Figure 7 is a cross-sectional view showing an example of the main part of a thermal head according to another embodiment 2. [Figure 8] Figure 8 is a cross-sectional view showing another example of the main part of a thermal head according to another embodiment 2. [Figure 9] Figure 9 is a cross-sectional view showing an example of the main part of a thermal head according to another embodiment 3. [Figure 10] Figure 10 is a cross-sectional view showing another example of the main part of a thermal head according to another embodiment 3. [Figure 11] Figure 11 is a cross-sectional view showing an example of the main part of a thermal head according to another embodiment 4. [Figure 12] Figure 12 is a schematic diagram showing the configuration of a thermal printer according to an embodiment. [Modes for carrying out the invention]

[0006] Conventionally, various thermal heads have been proposed for printing devices such as facsimile machines and video printers. However, conventional technology still had room for improvement in achieving both high-speed thermal head operation and good print quality.

[0007] Therefore, there is a need for a technology that can solve the above problems and achieve both high speed and good print quality in thermal heads.

[0008] The embodiments of the thermal head and thermal printer disclosed herein will be described below with reference to the attached drawings. However, this disclosure is not limited to the embodiments described below.

[0009] Furthermore, each embodiment can be combined as appropriate, provided that the processing content is not inconsistent. Also, the same parts are denoted by the same reference numerals in each of the following embodiments, and redundant explanations are omitted.

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

[0011] <Thermal head schematic configuration> First, the schematic configuration of the thermal head 1 according to the embodiment will be described with reference to Figures 1 to 3. Figure 1 is a schematic diagram showing the configuration of the thermal head 1 according to the embodiment.

[0012] In the following explanation, an XYZ Cartesian coordinate system will be established, and the positional relationships of each part will be described while referring to this XYZ Cartesian coordinate system. A predetermined direction in the horizontal plane is defined as the X-axis direction, a direction perpendicular to the X-axis direction in the horizontal plane is defined as the Y-axis direction, and a direction perpendicular to both the X-axis and Y-axis directions is defined as the Z-axis direction. The XY plane, which includes the X and Y axes, is parallel to the horizontal plane.

[0013] Furthermore, in the following description, the surface of the substrate 7 of the thermal head 1 that mates with the connector 5 may be parallel to the horizontal plane. The Z-axis direction, which is perpendicular to the XY plane, is the vertical direction. In the following description, the direction perpendicular to the surface of the substrate 7 of the thermal head 1 that mates with the connector 5 may be parallel to the Z-axis.

[0014] As shown in Figure 1, the thermal head 1 according to this embodiment comprises a head base 2, a heat sink 3, an adhesive member 4, a connector 5, and a sealing member 6.

[0015] The head base 2 is formed, for example, in a roughly rectangular parallelepiped shape and is placed on the heat sink 3 via an adhesive member 4. The components constituting the thermal head 1 are provided on the substrate 7 of the head base 2.

[0016] The head base 2 applies a voltage according to an electrical signal supplied from the outside via the connector 5 to heat the heating part 8, and performs printing on the recording medium P (see FIG. 12). Note that each member constituting the thermal head 1 will be described later with reference to FIGS. 2 and 3, and the recording medium P will be described with reference to FIG. 12.

[0017] The connector 5 is joined to the head base 2 by a sealing member 6 and electrically connects the outside and the head base 2. The adhesive member 4 adheres the head base 2 and the heat sink 3.

[0018] The heat sink 3 is formed, for example, in a substantially rectangular parallelepiped shape and is provided to dissipate the heat of the head base 2. The heat sink 3 is made of, for example, a metal material such as copper, iron, or aluminum, and has a function of dissipating the heat generated in the heating part 8 of the head base 2 that does not contribute to printing.

[0019] Next, each member constituting the thermal head 1 will be further described with reference to FIGS. 2 and 3. FIG. 2 is a plan view showing the schematic configuration of the thermal head 1 shown in FIG. 1. FIG. 3 is a cross-sectional view taken along the line A-A shown in FIG. 2.

[0020] As shown in FIGS. 2 and 3, the thermal head 1 further includes a substrate 7, a heat storage layer 21, a resistance layer 22, a common electrode 23, an individual electrode 24, a first connection electrode 25, a ground electrode 26, a connection terminal 27, a second connection electrode 28, a drive IC 30, a hard coat 31, a protective layer 32, a coating layer 33, and a joining member 34.

[0021] The substrate 7 is rectangular in a plan view and has a first long side 7a, a second long side 7b, a first short side 7c, a second short side 7d, a side surface 7e, a first surface 7f, and a second surface 7g. The substrate 7 is made of, for example, an electrically insulating material such as alumina ceramics or a semiconductor material such as single crystal silicon.

[0022] For the sake of clarity, the first surface 7f may be referred to as the "top surface" and the second surface 7g as the "bottom surface." Similarly, the side of the first surface 7f may be referred to as the "top" or "upper side" and the side of the second surface 7g as the "bottom" or "lower side," with respect to the side of the side 7e.

[0023] A connector 5 is provided on the side surface 7e of the substrate 7. The connector 5 is fixed to the side surface 7e by connector pins 9, a bonding member 34, and a sealing member 6. The bonding member 34 is conductive and is placed between the connection terminal 27 and the connector pins 9. Examples of the bonding member 34 include solder or anisotropic conductive paste.

[0024] A pad portion (not shown), which is a metal plating layer made of Ni, Au, or Pd, is provided between the joining member 34 and the connecting terminal 27. The joining member 34 is not necessarily required.

[0025] Furthermore, the connector 5 has a plurality of connector pins 9 and a housing 10 that houses the plurality of connector pins 9. The first ends of the plurality of connector pins 9 are exposed to the outside of the housing 10, and the second ends are housed inside the housing 10. The plurality of connector pins 9 are electrically connected to the connection terminals 27 of the head base 2 and are electrically connected to various electrodes of the head base 2.

[0026] The sealing member 6 comprises a first sealing member 6a and a second sealing member 6b. The first sealing member 6a is located on the first surface 7f side of the substrate 7, and the second sealing member 6b is located on the second surface 7g side of the substrate 7. The first sealing member 6a is provided to seal the connector pins 9 and the various electrodes, and the second sealing member 6b is provided to seal the contact portion between the connector pins 9 and the substrate 7.

[0027] The sealing member 6 is provided so that the connection terminals 27 and connector pins 9 are not exposed to the outside. The sealing member 6 can be made of, for example, an epoxy-based thermosetting resin, an ultraviolet-curable resin, or a visible-light-curable resin.

[0028] The adhesive member 4 is placed on the heat sink 3 and joins the second surface 7g of the substrate 7 to the heat sink 3. Examples of adhesive members 4 include double-sided tape or a resin-based adhesive.

[0029] The heat storage layer 21 is located on the first surface 7f of the substrate 7. The heat storage layer 21 has a base portion 21a and a raised portion 21b. The base portion 21a is located across the entire surface of the first surface 7f of the substrate 7. The raised portion 21b rises from the base portion 21a in the thickness direction of the substrate 7. In other words, the raised portion 21b protrudes in a direction away from the first surface 7f of the substrate 7.

[0030] The raised portion 21b is positioned adjacent to the first long side 7a of the substrate 7 and extends along the main scanning direction. The cross-section of the raised portion 21b is approximately semi-elliptical. As a result, the protective layer 32 located on the heat-generating portion 8 makes good contact with the recording medium P (see Figure 12) to be printed on.

[0031] The height of the heat storage layer 21 from the first surface 7f of the substrate 7, including the base portion 21a and the raised portion 21b, can be 15 to 90 μm.

[0032] The heat storage layer 21 is made of a material with low thermal conductivity, such as glass, and has the function of temporarily storing a portion of the heat generated in the heat-generating section 8. Therefore, the heat storage layer 21 can shorten the time required to raise the temperature of the heat-generating section 8. As a result, the heat storage layer 21 functions to improve the thermal response characteristics of the thermal head 1.

[0033] The heat storage layer 21 is formed, for example, by applying a predetermined glass paste obtained by mixing glass powder with a suitable organic solvent to the upper surface of the substrate 7 by screen printing or the like, and then firing it.

[0034] In this disclosure, the heat storage layer 21 is not limited to a glaze layer composed of glass material. The heat storage layer 21 may be composed of a dielectric material such as silicon oxide and may be formed by various vapor-phase synthesis methods (for example, PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition)).

[0035] The resistive layer 22 is provided on the substrate 7 and the heat storage layer 21. Various electrodes constituting the head base 2 are provided on the resistive layer 22. The resistive layer 22 is patterned to be substantially the same shape as the various electrodes constituting the head base 2, and has an exposed region between the common electrode 23 and the individual electrodes 24 where the resistive layer 22 is exposed. Multiple heat-generating units 8 are arranged in this exposed region.

[0036] Multiple heat-generating units 8 are arranged on the heat storage layer 21 along the longitudinal direction of the substrate 7. Furthermore, the multiple heat-generating units 8 are positioned with a predetermined spacing between them and the first short side 7c and the second short side 7d of the first surface 7f of the substrate 7, which are aligned in the short direction.

[0037] The heating element 8 generates heat according to an electrical signal supplied from the outside and has the function of thermally transferring ink from an ink sheet (not shown) onto the recording medium P. Multiple heating elements 8 are arranged at a density such as 100 dpi to 2400 dpi (dots per inch).

[0038] Note that the arrangement of the resistive layer 22 constituting the heat-generating section 8 is not limited to that shown in the figure; for example, it may be provided only between the common electrode 23 and the individual electrodes 24.

[0039] The resistive layer 22 is composed of a material with relatively high electrical resistance, such as TaN-based, TaSiO-based, TaSiNO-based, TiSiO-based, TiSiCO-based, or NbSiO-based materials. The common electrode 23 and individual electrodes 24 are composed of metals such as Al or Cu.

[0040] When a voltage is applied to the resistive layer 22 positioned between the common electrode 23 and the individual electrodes 24, the resistive layer 22 generates heat through Joule heating and functions as a heat-generating section 8. In other words, the portion of the resistive layer 22 located between the common electrode 23 and the individual electrodes 24 functions as a heat-generating section 8.

[0041] The common electrode 23 has main wiring sections 23a and 23d, a sub-wiring section 23b, and a lead section 23c. The common electrode 23 electrically connects the multiple heating elements 8 and the connector 5. The main wiring section 23a extends along the first long side 7a of the substrate 7. The sub-wiring sections 23b extend along the first short side 7c and the second short side 7d of the substrate 7, respectively.

[0042] The lead portion 23c extends individually from the main wiring portion 23a toward each of the multiple heat-generating portions 8. The main wiring portion 23d extends along the second long side 7b of the substrate 7.

[0043] The individual electrodes 24 electrically connect the heating element 8 and the drive IC 30. Specifically, the multiple heating elements 8 are divided into multiple groups. The individual electrodes 24 electrically connect the multiple heating elements 8 constituting each group to the corresponding drive IC 30. The drive IC 30 will be described later.

[0044] The first connection electrode 25 electrically connects the drive IC 30 and the connector 5. Multiple first connection electrodes 25 are connected to each drive IC 30, and each of these first connection electrodes 25 consists of one or more wires having different functions.

[0045] The ground electrode 26 is surrounded by the individual electrodes 24, the first connecting electrode 25, and the main wiring portion 23d of the common electrode 23. The ground electrode 26 is maintained at a ground potential of 0 to 1V.

[0046] Furthermore, a pad portion (not shown), which is a metal plating layer for soldering the connector 5 to the substrate 7 (connection terminal 27), is provided on the upper part of each electrode layer, including the common electrode 23, individual electrodes 24, first connecting electrode 25, and ground electrode 26.

[0047] The pad portion is made of a metal material such as Au. The pad portion may also be made of Ni or Pd in ​​addition to Au. The solder joint between the connector 5 and the substrate 7 (connection terminal 27) is covered by a sealing member 6.

[0048] The connection terminal 27 is provided on the second long side 7b of the circuit board 7 and connects the common electrode 23, individual electrodes 24, first connection electrode 25, and ground electrode 26 to the connector 5. The connection terminal 27 is provided to correspond to the connector pins 9, and when connecting the connector 5, the connector pins 9 and the connection terminal 27 are connected so that they are electrically independent of each other.

[0049] Furthermore, a protective resin layer (not shown) is provided on the upper surface of the connection terminal 27 (the contact surface with the connector pin 9).

[0050] The second connecting electrodes 28 electrically connect adjacent drive ICs 30. Each second connecting electrode 28 is provided corresponding to the first connecting electrode 25 and transmits various signals between adjacent drive ICs 30.

[0051] The resistive layer 22 and various electrodes can be formed, for example, as shown below. The materials constituting each are sequentially laminated on the heat storage layer 21 by thin-film molding techniques such as sputtering.

[0052] Next, the laminate is processed into a predetermined pattern using conventional photoetching or the like to form the resistive layer 22 and various electrodes. In this way, the various electrodes are electrically connected to the heating element 8. Their thickness can be, for example, 0.1 to 1 μm.

[0053] The drive IC 30 is, for example, located on the first surface 7f side of the substrate 7. Furthermore, multiple drive ICs 30 are arranged along the direction of the arrangement of the heat-generating units 8 so as to correspond to the group of heat-generating units 8 assigned to each drive IC 30.

[0054] The drive IC 30 is connected to the drive IC 30 side end of the individual electrode 24 and the drive IC 30 side end of the first connecting electrode 25, and supplies power to the heating elements 8 to individually generate heat in accordance with an electrical signal supplied from the outside. As the drive IC 30, for example, a switching member having multiple switching elements inside can be used.

[0055] The protective layer 32 is placed on the heat storage layer 21 formed on the upper surface 7h1 of the substrate 7 and is a component that covers the heat-generating part 8, the common electrode 23, and the individual electrodes 24. More specifically, the protective layer 32 is provided so as to cover a portion of the individual electrodes 24 from the edges of the substrate 7, i.e., the first long side 7a, the first short side 7c, and the second short side 7d of the substrate 7.

[0056] The protective layer 32 protects the heating element 8, the common electrode 23, and the individual electrodes 24 in the area covered by the protective layer from corrosion caused by the adhesion of moisture contained in the atmosphere, or from abrasion caused by contact with the recording medium P on which the image is printed.

[0057] The protective layer 32 can be formed using, for example, SiN, SiO2, SiON, SiC, or diamond-like carbon. The protective layer 32 may consist of a single layer or multiple layers.

[0058] The coating layer 33 is provided on the substrate 7 to partially cover the common electrode 23, individual electrodes 24, first connecting electrode 25, and protective layer 32. The coating layer 33 protects the covered area from oxidation due to contact with the atmosphere or corrosion due to the adhesion of moisture contained in the atmosphere.

[0059] Furthermore, the coating layer 33 makes close contact with the protective layer 32 and covers the edges of the protective layer 32, thereby reducing the occurrence of defects in which the protective layer 32 peels off from the protected object, such as the heat-generating part 8 or various electrodes.

[0060] The coating layer 33 is composed of a resin material such as an epoxy resin, a polyimide resin, or a silicone resin. All of these resin materials are fluid before they harden and form the coating layer 33.

[0061] The coating layer 33 has openings (not shown) to expose the individual electrodes 24 and the first connecting electrode 25 that are connected to the drive IC 30. These wires are connected to the drive IC 30 through these openings.

[0062] Furthermore, the drive IC 30 is sealed with a hard coat 31 while connected to the individual electrodes 24 and the first connecting electrode 25. This protects the drive IC 30, or the connections between the drive IC 30 and these electrodes. The hard coat 31 is formed from a resin, such as epoxy resin or silicone resin.

[0063] <Details of the thermal head> Next, the detailed configuration of the thermal head 1 according to the embodiment will be described with reference to Figure 4. Figure 4 is a cross-sectional view showing an example of the main part of the thermal head 1 according to the embodiment.

[0064] As shown in Figure 4, a heat-generating portion 8 is provided at the top 21b1 and its vicinity on the raised portion 21b of the heat storage layer 21. This heat-generating portion 8 is located in the resistive layer 22 between the individual electrodes 24 located upstream of the top 21b1 in the transport direction S of the recording medium P (see Figure 12) and the lead portion 23c of the common electrode 23 located downstream of the top 21b1.

[0065] Specifically, between the tip 24a of the individual electrode 24 and the tip 23c1 of the lead portion 23c of the common electrode 23, current flows through the resistive layer 22, which has relatively high electrical resistance, causing the resistive layer 22 to heat up. As a result, the aforementioned portion of the resistive layer 22 functions as a heat-generating part 8.

[0066] Furthermore, the heating element 8 has a first portion 8a and a second portion 8b. The first portion 8a is the end of the heating element 8 on the second direction side (hereinafter also referred to as the upstream side), when the transport direction S is considered the first direction and the direction opposite to the first direction is considered the second direction. In other words, the first portion 8a is the portion that contacts the tip portion 24a of the individual electrode 24 located on the upstream side of the transport direction S relative to the heating element 8.

[0067] Furthermore, the second portion 8b is the end of the heating element 8 on the first direction side (hereinafter also referred to as the downstream side) in the transport direction S. That is, the second portion 8b is the portion that contacts the tip portion 23c1 of the lead portion 23c, which is located downstream of the heating element 8 in the transport direction S.

[0068] In this embodiment, the thickness T1 of the portion of the heat storage layer 21 located below the first portion 8a is greater than the thickness T2 of the portion located below the second portion 8b. In this disclosure, "below the first portion 8a (or second portion 8b)" refers to the direction perpendicular to the first surface 7f of the substrate 7 from the first portion 8a (or second portion 8b).

[0069] As a result, the heat retention capacity around the first part 8a is improved compared to the area around the second part 8b, allowing the temperature of the first part 8a to be higher than the temperature of the second part 8b.

[0070] Furthermore, by increasing the temperature of the first part 8a, when a recording medium P at a low temperature (for example, around room temperature) is transported to the heating part 8, the recording medium P can be quickly heated up in the first part 8a.

[0071] In other words, in this embodiment, by increasing the temperature of the first part 8a, printing can be done quickly on a specified location on the recording medium P.

[0072] Furthermore, by lowering the temperature of the second section 8b, it is possible to reduce the occurrence of the so-called trailing effect, in which, after printing at a designated location upstream, the downstream side is also unexpectedly over-printed at a high temperature.

[0073] In other words, in this embodiment, by lowering the temperature of the second part 8b, it is possible to print with good quality on a specified location on the recording medium P.

[0074] Furthermore, in this embodiment, as shown in Figure 5, the base portion 21a located downstream of the raised portion 21b may be omitted. If the base portion 21a is omitted, the temperature of the second portion 8b tends to be lower, so that printing can be performed with better quality on the specified location on the recording medium P.

[0075] As explained above, according to the embodiment, by making the thickness T1 of the portion located below the first portion 8a in the heat storage layer 21 thicker than the thickness T2 of the portion located below the second portion 8b, it is possible to achieve both high speed of the thermal head 1 and good print quality.

[0076] Furthermore, in this embodiment, a stepped portion 21c is provided near the top portion 21b1 of the heat storage layer 21. This stepped portion 21c is formed near the top portion 21b1 by a rapid decrease in the thickness of the heat storage layer 21 as it moves in the transport direction S.

[0077] In this way, by providing a stepped portion 21c between the first portion 8a and the second portion 8b, the thickness T1 of the portion located below the first portion 8a in the heat storage layer 21 can be made thicker than the thickness T2 of the portion located below the second portion 8b.

[0078] Furthermore, in this embodiment, the stepped portion 21c may not be provided rising perpendicularly to the first surface 7f of the substrate 7, but rather the stepped portion 21c may be provided such that the thickness of the heat storage layer 21 changes along the curved surface at the stepped portion 21c.

[0079] This reduces the formation of sharp corners in the protective layer 32 provided on the stepped portion 21c. Therefore, according to this embodiment, when the recording medium P is pressed against the heating portion 8 by the platen roller 50 (see Figure 12), the problem of the recording medium P being torn due to sharp corners in the protective layer 32 can be reduced.

[0080] Furthermore, the method for forming the stepped portion 21c may be to remove the downstream side of the raised portion 21b by etching using photolithography or the like, or the printing process of the heat storage layer 21 may be carried out in multiple stages to form a thicker upstream side of the raised portion 21b.

[0081] <Another Embodiment 1> Next, we will describe the thermal head 1 according to various other embodiments with reference to Figures 6 to 11. Figure 6 is a cross-sectional view showing an example of the main part of the thermal head 1 according to another embodiment 1.

[0082] As shown in Figure 6, in another embodiment 1, the configuration of the heat storage layer 21 differs from that of the embodiment described above. Specifically, in another embodiment 1, the heat storage layer 21 has a first heat storage layer 21A and a second heat storage layer 21B. The second heat storage layer 21B is made of a material with a lower thermal conductivity than the first heat storage layer 21A.

[0083] In another embodiment 1, the second heat storage layer 21B is positioned between the first portion 8a of the heat-generating section 8 and the substrate 7, but not between the second portion 8b of the heat-generating section 8 and the substrate 7. This allows the heat generated by the heat-generating section 8 to be stored more effectively in the heat storage layer 21 near the first portion 8a.

[0084] Therefore, according to another embodiment 1, the recording medium P (see Figure 12) can be heated up even more quickly at the first part 8a, thereby further increasing the speed of the thermal head 1.

[0085] In another embodiment 1, the second heat storage layer 21B is located between the substrate 7 and the first heat storage layer 21A. This allows the heat storage layer 21 of another embodiment 1 to be formed by forming the second heat storage layer 21B in the printing process and then forming the first heat storage layer 21A in the printing process, thereby simplifying the manufacturing process of the thermal head 1.

[0086] <Another Embodiment 2> Figure 7 is a cross-sectional view showing an example of the main part of the thermal head 1 according to another embodiment 2. As shown in Figure 7, in another embodiment 2, the arrangement of the heat storage layer 21 differs from that of another embodiment 1 described above. Specifically, in another embodiment 2, the second heat storage layer 21B is located between the first heat storage layer 21A and the heat-generating part 8 (i.e., between the first heat storage layer 21A and the resistance layer 22).

[0087] This allows the heat generated in the heat-generating section 8 to be stored at a location close to the heat-generating section 8, thereby enabling even better heat storage.

[0088] Therefore, according to another embodiment 2, the recording medium P (see Figure 12) can be heated even more quickly at the first part 8a, thereby further increasing the speed of the thermal head 1.

[0089] Furthermore, in another embodiment 2, as shown in Figure 8, the second heat storage layer 21B may be extended below the flat portion of the individual electrodes 24. This allows for better storage of the heat generated in the heat-generating section 8, which is more advantageous for increasing speed.

[0090] <Another Embodiment 3> Figure 9 is a cross-sectional view showing an example of the main part of the thermal head 1 according to another embodiment 3. As shown in Figure 9, in another embodiment 3, the configuration of the substrate 7 differs from that of the embodiment described above. Specifically, in another embodiment 3, a projection 7h is located on the first surface 7f of the substrate 7, and a heating element 8 is provided on this projection 7h.

[0091] The projection 7h has, for example, a trapezoidal shape in cross-section. The projection 7h is provided with an upper surface 7h1 and a side surface 7h2, which are part of the first surface 7f. The side surface 7h2 is the downstream side of the projection 7h in the transport direction S.

[0092] In another embodiment 3, a raised portion 21b of the heat storage layer 21 is provided so as to cover the protrusion 7h, and a heat-generating portion 8 is provided in the region from near the top to the downstream portion of the raised portion 21b.

[0093] In another embodiment 3, similar to the embodiment described above, the thickness T1 of the portion of the heat storage layer 21 located below the first portion 8a is greater than the thickness T2 of the portion located below the second portion 8b. In another embodiment 3, the thickness T1 of the portion of the heat storage layer 21 located below the first portion 8a corresponds to the distance between the first portion 8a and the upper surface 7h1 of the projection 7h, and the thickness T2 of the portion located below the second portion 8b corresponds to the distance between the second portion 8b and the side surface 7h2 of the projection 7h.

[0094] As a result, in another embodiment 3, similar to the embodiment, it is possible to achieve both high speed of the thermal head 1 and good print quality.

[0095] In another embodiment 3, the heat storage layer 21 and the heat generating section 8 are located across multiple surfaces of the substrate 7 (in this case, the top surface 7h1 and the side surface 7h2). The angle between the top surface 7h1 facing the first portion 8a and the printed surface of the recording medium P is smaller than the angle between the side surface 7h2 facing the second portion 8b and the printed surface of the recording medium P.

[0096] As a result, on the upstream side of the transport direction S, the recording medium P (see Figure 12) and the upper surface 7h1 are nearly parallel and face each other at a relatively small angle, which allows for stronger pressing pressure on the recording medium P.

[0097] On the other hand, downstream of the transport direction S, the recording medium P and the side surface 7h2 are tilted relative to each other and face each other at a relatively large angle, which allows the pressing force on the recording medium P to be reduced.

[0098] In other words, in another embodiment 3, the heat transfer efficiency from the heat-generating unit 8 to the recording medium P can be improved on the upstream side, and the excessive heat transfer from the heat-generating unit 8 to the recording medium P can be reduced on the downstream side.

[0099] Therefore, according to another embodiment 3, it is possible to achieve both high speed of the thermal head 1 and good print quality at a high level.

[0100] Furthermore, in another embodiment 3, as shown in Figure 10, the upper surface 7h1 of the projection 7h and the first surface 7f are the same surface, and the first surface 7f and the side surface 7h2 may have a so-called stepped shape. In this other embodiment 3 as well, the heat transfer efficiency from the heat-generating part 8 to the recording medium P can be improved on the upstream side, and the excessive heat transfer from the heat-generating part 8 to the recording medium P can be reduced on the downstream side. Therefore, it is possible to achieve both high speed of the thermal head 1 and good print quality at a high level.

[0101] <Another Embodiment 4> Figure 11 is a cross-sectional view showing an example of the main part of the thermal head 1 according to another embodiment 4. As shown in Figure 11, in another embodiment 4, the configuration of the heat storage layer 21 differs from that of another embodiment 3 described above. Specifically, in another embodiment 4, in the heat storage layer 21, the thickness T3 of the portion located on the ridge 7h3 provided between the upper surface 7h1 and the side surface 7h2 of the projection 7h is thicker than the thicknesses T1 and T2.

[0102] In other words, in this alternative embodiment 4, the thickness of the heat storage layer 21 is T3 > T1 > T2.

[0103] As a result, the protective layer 32 has a convex shape between the first portion 8a and the second portion 8b of the heating element 8, making it easier to bring the recording medium P (see Figure 12) into contact with the protective layer 32 located on the heating element 8 of the thermal head 1.

[0104] Therefore, according to another embodiment 4, the tolerance for the head mounting angle in the thermal printer 100 (see Figure 12) can be increased.

[0105] <Thermal Printer> Next, the thermal printer 100 according to the embodiment will be described with reference to Figure 12. Figure 12 is a schematic diagram showing the configuration of the thermal printer 100 according to the embodiment.

[0106] As shown in Figure 12, the thermal printer 100 according to this embodiment includes the thermal head 1 described above, a transport mechanism 40, a platen roller 50, a power supply unit 60, and a control device 70.

[0107] The thermal head 1 is mounted on the mounting surface 80a of a mounting member 80 provided on the housing (not shown) of the thermal printer 100. The thermal head 1 is mounted on the mounting member 80 so as to be aligned with the main scanning direction which is perpendicular to the transport direction S.

[0108] 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 to which ink is transferred, onto the protective layer 32 located on the heating element 8 of the thermal head 1, along the transport direction S indicated by the arrow.

[0109] The drive unit has the function of driving the conveyor rollers 43, 45, 47, and 49, and can use a motor, for example. The conveyor rollers 43, 45, 47, and 49 can be made of cylindrical shafts 43a, 45a, 47a, and 49a made of metal such as stainless steel, covered with elastic members 43b, 45b, 47b, and 49b made of butadiene rubber or the like.

[0110] Furthermore, if the recording medium P is, for example, a receiving paper onto which ink is transferred, it is preferable to transport the ink film (not shown) together with the recording medium P between the recording medium P and the heating element 8 of the thermal head 1.

[0111] The platen roller 50 has the function of pressing the recording medium P onto the protective layer 32 located on the heating element 8 of the thermal head 1. The platen roller 50 is arranged to extend along the main scanning direction, and both ends are supported and fixed so that it can rotate in accordance with the transport of the recording medium P while pressing the recording medium P onto the heating element 8.

[0112] The platen roller 50 can be, for example, a cylindrical shaft 50a made of a metal such as stainless steel, covered with an elastic member 50b made of butadiene rubber or the like.

[0113] The power supply unit 60 has the function of supplying current to generate heat in the heat-generating part 8 of the thermal head 1 and current to operate the drive IC 30, as described above. The control device 70 has the function of supplying a control signal to the drive IC 30 to control the operation of the drive IC 30 in order to selectively generate heat in the heat-generating part 8 of the thermal head 1, as described above.

[0114] The thermal printer 100 presses the recording medium P onto the heating element 8 of the thermal head 1 with the platen roller 50, and transports the recording medium P onto the heating element 8 with the transport mechanism 40, while selectively heating the heating element 8 with the power supply unit 60 and the control unit 70 to print a predetermined image on the recording medium P.

[0115] Furthermore, if the recording medium P is such as image receiving paper, printing is performed on the recording medium P by thermally transferring the ink from an ink film (not shown) that is transported together with the recording medium P to the recording medium P.

[0116] The thermal head 1 according to this embodiment includes a substrate 7, a heat storage layer 21 located on the substrate 7, and a heat-generating section 8 located on the heat storage layer 21. Furthermore, if the transport direction S of the recording medium P is considered the first direction, and the direction opposite to this first direction is considered the second direction, then in the heat storage layer 21, the thickness T1 of the portion located below the end of the heat-generating section 8 on the second direction side (first portion 8a) is greater than the thickness T2 of the portion located below the end of the heat-generating section 8 on the first direction side (second portion 8b). This makes it possible to achieve both high speed for the thermal head 1 and good print quality.

[0117] Furthermore, in the thermal head 1 according to this embodiment, the heat storage layer 21 has a first heat storage layer 21A and a second heat storage layer 21B. The first heat storage layer 21A is located between the end of the heat-generating part 8 on the second direction side (first portion 8a) and the substrate 7, and between the end of the heat-generating part 8 on the first direction side (second portion 8b) and the substrate 7. The second heat storage layer 21B has a lower thermal conductivity than the first heat storage layer 21A and is located between the end of the heat-generating part 8 on the second direction side (first portion 8a) and the substrate 7. This makes it possible to further increase the speed of the thermal head 1.

[0118] Furthermore, in the thermal head 1 according to this embodiment, the second heat storage layer 21B is located between the substrate 7 and the first heat storage layer 21A. This simplifies the manufacturing process of the thermal head 1.

[0119] Furthermore, in the thermal head 1 according to this embodiment, the second heat storage layer 21B is located between the first heat storage layer 21A and the heat generating section 8. This allows the thermal head 1 to operate at an even higher speed.

[0120] Furthermore, in the thermal head 1 according to this embodiment, the heat storage layer 21 and the heating element 8 are positioned across multiple surfaces (top surface 7h1, side surface 7h2) of the substrate 7. Also, the angle between the surface of the substrate 7 (top surface 7h1) facing the end of the heating element 8 on the second direction side (first portion 8a) and the printing surface of the recording medium P is smaller than the angle between the surface of the substrate 7 (side surface 7h2) facing the end of the heating element 8 on the first direction side (second portion 8b) and the printing surface of the recording medium P. This makes it possible to achieve both high speed and good print quality for the thermal head 1 at a high level.

[0121] Furthermore, in the thermal head 1 according to the embodiment, the thickness T3 of the portion of the heat storage layer 21 located on the edge 7h3 between multiple surfaces of the substrate 7 is greater than the thickness T1 of the portion located below the end of the heating element 8 on the second direction side (first portion 8a) and the thickness T2 of the portion located below the end of the heating element 8 on the first direction side (second portion 8b). This makes it possible to increase the tolerance of the head mounting angle in the thermal printer 100.

[0122] Furthermore, in the thermal head 1 according to the embodiment, the heat storage layer 21 has a stepped portion 21c between the portion located below the end (first portion 8a) on the second direction side of the heat-generating portion 8 and the portion located below the end (first portion 8a) on the first direction side of the heat-generating portion 8. In addition, the thickness of the heat storage layer 21 changes along the curved surface at the stepped portion 21c. This reduces the problem of the recording medium P being torn due to the presence of sharp corners in the protective layer 32 when the recording medium P is pressed against the heat-generating portion 8 by the platen roller 50.

[0123] Furthermore, the thermal printer 100 according to this embodiment includes the thermal head 1, a transport mechanism 40 for transporting the recording medium P onto the heating element 8, and a platen roller 50 for pressing the recording medium P onto the heating element 8. This makes it possible to realize a thermal printer 100 that can achieve both high speed and good print quality.

[0124] While embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. For example, the above embodiments show the case where the heating element 8 is located on the first surface 7f of the substrate 7, but the present disclosure is not limited to such examples.

[0125] For example, in this disclosure, the heat-generating portion 8 may be located on the side surface of the substrate 7 on the first long side 7a side, or the heat-generating portion 8 may be formed on a slope separately formed along the first long side 7a of the substrate 7 from the top surface to the side surface.

[0126] Furthermore, although the above embodiment shows a case where the projection 7h has a trapezoidal shape in cross-section, this disclosure is not limited to such examples, and may have a polygonal shape in cross-section, for example.

[0127] Further effects and other embodiments can be readily derived by those skilled in the art. Therefore, broader embodiments of this disclosure are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents. [Explanation of Symbols]

[0128] 1 Thermal Head 7 circuit boards 7h Protrusion 7h1 Top 7h2 side 7h3 Ridge 8. Heat-generating part 8a Part 1 8b 2nd part 21 Heat storage layer 21A 1st heat storage layer 21B 2nd heat storage layer 21c Step section 22 Resistance layer 23 Common electrode 24 individual electrodes 40 Conveying mechanism 50 Platen Rollers 100 Thermal Printers P recording medium S Conveying direction T1~T3 Thickness

Claims

1. circuit board and A heat storage layer located on the substrate, A heat-generating element located on the heat storage layer, Equipped with, If we define the transport direction of the recording medium as the first direction, and the direction opposite to the first direction as the second direction, Of the surfaces of the substrate, the surface in contact with the heat storage layer is a single plane from the portion located below the end on the first direction side of the heat generating portion to the portion located below the end on the second direction side. In the heat storage layer, the first thickness of the first portion located below the end of the heating element on the second direction side is greater than the second thickness of the second portion located below the end of the heating element on the first direction side. The heat storage layer has a portion between the first portion and the second portion that is thicker than the first thickness. Thermal head.

2. A substrate having multiple surfaces, A heat storage layer located on the substrate having the aforementioned multiple surfaces, A heat-generating element located on the heat storage layer, Equipped with, The heat storage layer and the heat generating section are located across the multiple surfaces, If we define the transport direction of the recording medium as the first direction, and the direction opposite to the first direction as the second direction, In the heat storage layer, the thickness of the portion located below the end of the heating element in the second direction is greater than the thickness of the portion located below the end of the heating element in the first direction. The angle between the surface of the substrate facing the end of the heating element in the second direction and the printed surface of the recording medium is smaller than the angle between the surface of the substrate facing the end of the heating element in the first direction and the printed surface of the recording medium. Thermal head.

3. The substrate has single-crystal silicon The thermal head according to claim 1 or 2.

4. The aforementioned heat storage layer is A first heat storage layer is located between the end of the heating element on the second direction side and the substrate, and between the end of the heating element on the first direction side and the substrate. The present invention comprises a second heat storage layer having a lower thermal conductivity than the first heat storage layer and located between the end of the heating element on the second direction side and the substrate. The thermal head according to claim 1.

5. The second heat storage layer is located between the substrate and the first heat storage layer. The thermal head according to claim 4.

6. The second heat storage layer is located between the first heat storage layer and the heat generating section. The thermal head according to claim 4.

7. In the heat storage layer, the thickness of the portion located on the edge between the multiple surfaces of the substrate is greater than the thickness of the portion located below the end of the heating element in the second direction and the thickness of the portion located below the end of the heating element in the first direction. The thermal head according to claim 2.

8. The heat storage layer has a stepped portion between the portion located below the end of the heating element on the second direction side and the portion located below the end of the heating element on the first direction side. In the stepped portion, the thickness of the heat storage layer changes along the curved surface. A thermal head according to any one of claims 1, 2, 4 to 7.

9. A thermal head according to any one of claims 1, 2, 4 to 7, A transport mechanism for transporting the recording medium onto the heat-generating section, A platen roller presses the recording medium onto the heating element, A thermal printer equipped with [a specific feature / feature].

10. The thermal head described in claim 3, A transport mechanism for transporting the recording medium onto the heat-generating section, A platen roller presses the recording medium onto the heating element, A thermal printer equipped with [a specific feature / feature].

11. The thermal head according to claim 8, A transport mechanism for transporting the recording medium onto the heat-generating section, A platen roller presses the recording medium onto the heating element, A thermal printer equipped with [a specific feature / feature].

Images