Thermal print head and thermal printer

Abstract

A thermal printhead includes a substrate, an electrode layer, a resistor layer, a protective layer, a first driving IC, and a plurality of wires. The electrode layer contains Ag. The electrode layer has a first pad section to which a first wire is connected and a second pad section to which a second wire is connected. The protective layer has at least one of a first opening and a second opening. The first opening exposes only a portion of the electrode layer electrically connected to the first pad section. The second opening exposes a portion of the electrode layer electrically connected to the first pad portion and a portion electrically connected to the second pad portion. In the second opening, the shortest distance between the portion electrically connected to the first pad portion and the portion electrically connected to the second pad portion is 80 μm or more.

Description

Thermal printheads and thermal printers

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

[0002] Thermal printheads have been used as devices that print by applying heat to thermal paper or thermal ink ribbons. For example, Patent Document 1 discloses a conventional thermal printhead. The thermal printhead described in Patent Document 1 includes a substrate, an electrode layer, a resistor layer, a protective layer, a driver IC, and a sealing resin. The resistor layer is electrically connected to the driver IC via the electrode layer. In this document, the electrode layer contains Ag.

[0003] Japanese Patent Application Laid-Open No. 2018-103608

[0004] When a voltage is applied to an electrode layer containing Ag, ion migration may occur. If parts of the electrode layers come into contact with each other due to ion migration, an electrical short circuit may occur.

[0005] An object of the present disclosure is to provide an improved thermal printhead and, by extension, a thermal printer. In particular, in view of the above-mentioned circumstances, an object of the present disclosure is to provide a thermal printhead that can suppress the occurrence of ion migration in the electrode layer, and to provide a thermal printer equipped with such a thermal printhead.

[0006] A thermal printhead provided by a first aspect of the present disclosure includes a substrate having a main surface and a back surface facing opposite each other in a thickness direction, an electrode layer and a resistor layer supported on the main surface, a protective layer covering a portion of the electrode layer and at least a portion of the resistor layer, a first driving IC that controls current flow to the resistor layer, and a plurality of wires connected to the first driving IC. The electrode layer contains Ag. The first driving IC has a first electrode and a second electrode. The plurality of wires includes a first wire connected to the first electrode and a second wire connected to the second electrode. The electrode layer has a first pad portion connected to the first wire and a second pad portion connected to the second wire. The protective layer has at least one of a first opening that exposes only a portion of the electrode layer that is conductive to the first pad portion and a second opening that exposes a portion of the electrode layer that is conductive to the first pad portion and a portion of the electrode layer that is conductive to the second pad portion. In the second opening, the shortest distance between a portion that is electrically connected to the first pad portion and a portion that is electrically connected to the second pad portion is 80 μm or more.

[0007] A thermal printer provided by a second aspect of the present disclosure includes the thermal printhead provided by the first aspect of the present disclosure.

[0008] According to the above configuration, for example, in a thermal printhead, it is possible to suppress the occurrence of ion migration in the electrode layer.

[0009] Other features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0010] FIG. 1 is a plan view showing a thermal printhead according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 , showing a printer according to the first embodiment of the present disclosure. FIG. 3 is an enlarged plan view showing a thermal printhead according to the first embodiment of the present disclosure. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is an enlarged plan view showing a thermal printhead according to the first embodiment of the present disclosure. FIG. 6 is an enlarged plan view showing a thermal printhead according to the first embodiment of the present disclosure. FIG. 7 is an enlarged cross-sectional view taken along line VII-VII in FIG. 6. FIG. 8 is an enlarged cross-sectional view taken along line VIII-VIII in FIG. 6. FIG. 9 is an enlarged cross-sectional view taken along line IX-IX in FIG. 6. FIG. 10 is an enlarged plan view showing a first modified example of the thermal printhead according to the first embodiment of the present disclosure. FIG. 11 is a plan view showing a thermal printhead according to a second embodiment of the present disclosure. FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 11, showing the printer according to the first embodiment of the present disclosure.

[0011] Preferred embodiments of the present disclosure will now be described in detail with reference to the drawings.

[0012] The terms "first," "second," "third," etc. in this disclosure are used for identification purposes only and are not intended to impose any ranking on their objects.

[0013] In this disclosure, unless otherwise specified, "a certain object A is formed on a certain object B" and "a certain object A is formed on a certain object B" include "a certain object A is formed directly on a certain object B" and "a certain object A is formed on a certain object B with another object interposed between the certain object A and the certain object B." Similarly, "a certain object A is disposed on a certain object B" and "a certain object A is disposed on a certain object B" include "a certain object A is disposed directly on a certain object B" and "a certain object A is disposed on a certain object B with another object interposed between the certain object A and the certain object B" unless otherwise specified. Similarly, "a certain object A is located on a certain object B" includes "a certain object A is located on a certain object B with a certain object A in contact with the certain object B" and "a certain object A is located on a certain object B with another object interposed between the certain object A and the certain object B." Furthermore, unless otherwise specified, the phrase "an object A overlaps an object B when viewed in a certain direction" includes "an object A overlaps the entire object B" and "an object A overlaps a part of an object B." Furthermore, in the present disclosure, "a surface A faces in (one side or the other side of) direction B" is not limited to the case where the angle of surface A with respect to direction B is 90°, but also includes the case where surface A is tilted with respect to direction B.

[0014] 1 to 9 show a thermal printhead A1 and a thermal printer P1 according to a first embodiment of the present disclosure. The thermal printhead A1 includes a substrate 1, a protective layer 2, an electrode layer 3, a resistor layer 4, multiple wires 61, 62, and 63, multiple driving ICs 7, a protective resin 78, and a heat dissipation member 8. The thermal printhead A1 is incorporated into a thermal printer P1 that prints on a print medium C1 (see FIG. 2).

[0015] The thermal printer P1 includes a thermal printhead A1 and a platen roller B1. The platen roller B1 faces the thermal printhead A1. A print medium C1 is sandwiched between the thermal printhead A1 and the platen roller B1 and transported in the y direction by the platen roller B1. Examples of such print media C1 include thermal paper for creating barcode sheets or receipts. A flat rubber platen may be used instead of the platen roller B1. This platen includes a cylindrical rubber portion with a large radius of curvature that is arch-shaped in cross section.

[0016] FIG. 1 is a plan view showing a thermal printhead A1. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, showing a printer according to a first embodiment of the present disclosure. FIG. 3 is an enlarged plan view of a main portion of the thermal printhead A1. FIG. 4 is an enlarged cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is an enlarged plan view of a main portion of the thermal printhead A1. FIG. 6 is an enlarged cross-sectional view of a main portion of the thermal printhead A1. FIG. 7 is an enlarged cross-sectional view taken along line VII-VII in FIG. 6. FIG. 8 is an enlarged cross-sectional view taken along line VIII-VIII in FIG. 6. FIG. 9 is an enlarged cross-sectional view taken along line IX-IX in FIG. 6. In FIG. 1, the protective layer 2 and the multiple wires 61, 62, and 63 are omitted. In FIG. 3, the protective layer 2 is omitted, and the electrode layer 3 is hatched. In FIGS. 5 and 6, the protective resin 78 is omitted. In Figure 5, the protective layer 2 is hatched. In Figure 6, the protective layer 2 is shown by imaginary lines. In these figures, the thickness direction of the substrate 1 (base material 11 described below) is the z direction. The x direction is the main scanning direction, and the y direction is the sub-scanning direction. Both the x direction and the y direction are directions perpendicular to the z direction. During printing, the printing medium C1 is fed from the y2 side to the y1 side in the y direction. In the y direction, the y1 side may be referred to as the downstream side, and the y2 side as the upstream side.

[0017] 1 , the substrate 1 is a plate-like member extending elongately in the x-direction. The substrate 1 is a support member that supports a protective layer 2, an electrode layer 3, a resistor layer 4, and a plurality of driving ICs 7. The substrate 1 has a base material 11 and a glaze layer 12.

[0018] The substrate 11 includes a ceramic such as AlN (aluminum nitride), Al2O3 (alumina), or zirconia, and has these ceramics as its main component. The substrate 11 has a thickness of 0.6 mm or more and 1.0 mm or less. As shown in FIG. 1 , the substrate 11 has a rectangular shape extending elongately in the x-direction in a plan view. The substrate 11 has a first main surface 11a and a first back surface 11b. The first main surface 11a and the first back surface 11b are spaced apart in the z-direction. The first main surface 11a faces the z1 side in the z-direction. The first back surface 11b faces the z2 side in the z-direction. The first main surface 11a is an example of a "main surface," and the first back surface 11b is an example of a "back surface."

[0019] The glaze layer 12 is formed on the first main surface 11a of the substrate 11. The glaze layer 12 covers the first main surface 11a. The glaze layer 12 is made of a glass material such as amorphous glass. The glaze layer 12 in this example includes a bulging portion 122 and a flat portion 121. Note that the glaze layer 12 may also include the flat portion 121 but not the bulging portion 122.

[0020] The bulging portion 122 extends elongatedly in the x direction. When viewed in the x direction, the bulging portion 122 bulges in the z direction. As shown in FIG. 4 , the bulging portion 122 has an arc-shaped cross section (y-z cross section) taken along a plane perpendicular to the x direction. The bulging portion 122 is provided to make it easier to press the heat-generating portion of the resistor layer 4 (the heat-generating portion 41 described below) against the print medium C1. The bulging portion 122 is also provided as a heat storage layer that accumulates heat from the heat-generating portion 41. The dimension (maximum dimension) of the bulging portion 122 in the z direction is larger than that of the flat portion 121.

[0021] The flat portion 121 is formed adjacent to the bulging portion 122, and has a flat surface on the z1 side in the z direction. The thickness of the flat portion 121 is, for example, about 2.0 μm. The flat portion 121 covers the first main surface 11 a of the base material 11, which is a relatively rough surface, to form a smooth surface suitable for forming the electrode layer 3.

[0022] There are no limitations on the softening point of the glaze layer 12. The softening point of the flat portion 121 and the softening point of the bulging portion 122 may be the same or different from each other. The softening points of the flat portion 121 and the bulging portion 122 are, for example, 800°C or higher and 850°C or lower, or, for example, approximately 680°C.

[0023] The substrate 1 of this embodiment is also provided with a plurality of terminals 19. The plurality of terminals 19 are arranged in the x direction, for example, along the edge of the substrate 1 on the y2 side in the y direction.

[0024] A plurality of driver ICs 7 are mounted on the substrate 1. In this embodiment, the plurality of driver ICs 7 are used to individually energize a plurality of heat generating portions 41. As shown in FIG. 7 , the plurality of driver ICs 7 are mounted on the protective layer 2 by a bonding layer 79.

[0025] The driving IC 7 has a plurality of first electrodes 71, second electrodes 72, and third electrodes 73. The plurality of third electrodes 73 are connected to the plurality of individual electrodes 34 (a plurality of third pad portions 37) by a plurality of wires 63. The plurality of first electrodes 71 and second electrodes 72 are also electrically connected to appropriate locations on the electrode layer 3 via a plurality of wires 61 and 62.

[0026] The control of the energization of the heat generating elements 41 by the drive ICs 7 is in accordance with command signals input from outside the thermal printhead A1, for example, via the terminals 19. The drive ICs 7 are provided as needed according to the number of heat generating elements 41.

[0027] 5 to 9 show a portion of the thermal printhead A1. Figures 5 to 7 show a first driver IC 7A and a second driver IC 7B included in the multiple driver ICs 7. Which of the multiple driver ICs 7 is the first driver IC 7A and which is the second driver IC 7B is determined by the relationship with the protective layer 2, electrode layer 3, and multiple wires 61, 62, and 63, which will be described later. Therefore, if a certain driver IC 7 is designated as the first driver IC 7A, the driver IC 7 corresponding to the second driver IC 7B may also correspond to the first driver IC 7A.

[0028] The protective layer 2 is intended to protect the electrode layer 3, the resistor layer 4, and the like. The protective layer 2 may be composed of a single layer or a laminate of multiple layers. The material of the protective layer 2 is not limited in any way. One example of the protective layer 2 is one that is primarily composed of amorphous glass. Another example of the protective layer 2 is one in which a first layer made of amorphous glass is laminated with a second layer made of SiAlON. SiAlON is a silicon nitride-based engineering ceramic obtained by combining SiN (silicon nitride) with AlO (alumina) and SiO (silica). The second layer is formed, for example, by sputtering. SiC (silicon carbide) may be used for the second layer instead of SiAlON.

[0029] 5 to 9 , the protective layer 2 has a first opening 21, a second opening 22, and a third opening 23. The first opening 21, the second opening 22, and the third opening 23 are formed by through holes that penetrate the protective layer 2 in the z direction. The shapes, sizes, and locations of the first opening 21, the second opening 22, and the third opening 23 are not limited in any way and are set appropriately depending on the configuration of the multiple driving ICs 7, the electrode layer 3, the multiple wires 61, 62, and 63, etc. For example, the first opening 21, the second opening 22, and the third opening 23 are provided around the driving ICs 7 and are arranged on the y2 side in the y direction relative to the multiple strip portions 32, the multiple strip portions 35, the resistor layer 4, etc.

[0030] The electrode layer 3 forms a conductive path for supplying electricity to the resistor layer 4. The electrode layer 3 is made of a conductive material. At least a portion of the electrode layer 3 contains Ag (silver). Another portion of the electrode layer 3 may contain a material other than Ag (silver), such as Au (gold).

[0031] The electrode layer 3 containing Ag (silver) may be formed by printing and firing, for example, a paste containing an organic Ag compound or a paste containing Ag particles, glass frit, Pd, and a resin. In this embodiment, the portions of the electrode layer 3 shown in FIGS. 5 and 6 are primarily composed of Ag (silver). The plurality of strip portions 32 and the plurality of strip portions 35 of the electrode layer 3 that contact the resistor layer 4 may be primarily composed of Au (gold). The thickness of the electrode layer 3 is not particularly limited and is, for example, 1 μm or more and 10 μm or less.

[0032] The electrode layer 3 is formed on the glaze layer 12 of the substrate 1. As shown in Figures 3 and 4, the electrode layer 3 has a common electrode 31 and a plurality of individual electrodes 34. Note that the shape and arrangement of each part of the electrode layer 3 are not limited to the examples shown in Figures 3 and 4, and various configurations are possible.

[0033] As shown in FIG. 3 , the common electrode 31 has a plurality of strip-shaped portions 32 and a connecting portion 33. The connecting portion 33 is disposed near the edge of the substrate 1 on the y1 side in the y direction and has a strip shape extending in the x direction. The plurality of strip-shaped portions 32 each extend from the connecting portion 33 to the y2 side in the y direction and are disposed at equal intervals in the x direction. In the example shown in FIG. 3 , an auxiliary layer 331 is laminated on the connecting portion 33 to reduce the resistance value of the connecting portion 33, but the auxiliary layer 331 does not have to be laminated. The auxiliary layer 331 is formed, for example, by printing and firing a paste containing an organic Ag (silver) compound or a paste containing Ag (silver) particles, glass frit, Pd (palladium), and a resin.

[0034] The individual electrodes 34 are used to partially apply current to the resistor layer 4. Each individual electrode 34 has an opposite polarity to the common electrode 31. Each individual electrode 34 extends from the resistor layer 4 toward the driving IC 7. The individual electrodes 34 are arranged in the x direction. Each of the individual electrodes 34 has a strip portion 35, a connecting portion 36, and a third pad portion 37.

[0035] 3, the strip portions 35 extend in the y direction and are strip-shaped when viewed in the z direction. Each strip portion 35 is located between two adjacent strip portions 32 of the common electrode 31. The distance between the strip portions 35 of adjacent individual electrodes 34 and the strip portions 32 of the common electrode 31 is, for example, 50 μm or less.

[0036] The connecting portion 36 is a portion that extends from the strip portion 35 toward the driving IC 7. The connecting portion 36 includes a parallel portion 361 and an inclined portion 362. One end of the parallel portion 361 is connected to the third pad portion 37 and extends along the y direction. The inclined portion 362 is inclined with respect to the y direction. The inclined portion 362 is sandwiched between the parallel portion 361 and the strip portion 35 in the y direction. The multiple individual electrodes 34 are also concentrated on the driving IC 7.

[0037] 3, the plurality of third pad portions 37 are formed on the end portions of the individual electrodes 34 on the y2 side in the y direction, and each is connected to each parallel portion 361. Each third pad portion 37 is bonded to a wire 63 (third wire 63). This establishes electrical continuity between each individual electrode 34 and the driving IC 7 via each wire 63 (third wire 63).

[0038] The arrangement of the multiple third pad portions 37 is not limited in any way. In this embodiment, the multiple third pad portions 37 include a third pad portion 37A and a third pad portion 37B. The width (length in the x direction) of the parallel portion 361 sandwiched between two adjacent third pad portions 37A is, for example, 10 μm or less. The third pad portion 37B is located on the y2 side of the third pad portion 37A in the y direction. The third pad portion 37B is connected to the parallel portion 361 sandwiched between two adjacent third pad portions 37A. With this configuration, the multiple third pad portions 37 are prevented from interfering with each other despite being wider than most portions of the connecting portion 36. The portion of the connecting portion 36 sandwiched between adjacent third pad portions 37A has the smallest width in the individual electrode 34.

[0039] 5 to 7 show all of the third pads 37 that are electrically connected to the first driver IC 7A. These third pads 37 are exposed from the third opening 23 of the protective layer 2. The third opening 23 has a shape and size that allows all of the third pads 37 to be accommodated therein, and in the illustrated example, has a shape with its longitudinal direction aligned in the x direction.

[0040] As shown in FIGS. 5 to 9, the electrode layer 3 of this embodiment further includes a plurality of first pad portions 381 , a plurality of second pad portions 382 and a fourth pad portion 384 .

[0041] The first pad portion 381 is connected to the first electrode 71 of the first driver IC 7A via the first wire 61. The shape and size of the first pad portion 381 are not limited in any way. The first pad portion 381 may have a shape and size suitable for bonding the first wire 61, for example. In the illustrated example, the multiple first pad portions 381 include first pad portions 381a, 381b, 381c, 381d, 381e, 381f, and 381g. The electrical function of the first pad portion 381 is not limited in any way. In this embodiment, the time period during which a voltage is applied to the first pad portion 381 during operation of the thermal printhead A1 (thermal printer P1) is longer than the time period during which a voltage is applied to the third pad portion 37, which is part of the individual electrode 34. In other words, because a voltage is applied to the third pad portion 37 of each individual electrode 34 when printing dots, the time period is extremely short. On the other hand, there are cases where a voltage is applied to the first pad section 381 for most of the time period from when the thermal printer P1 is turned on until it is turned off, and the time rate is significantly large.

[0042] The first pad portion 381a is disposed on the x1 side in the x direction relative to the plurality of third pad portions 37. The shape of the first pad portion 381a is not limited in any way, and in the illustrated example, it is rectangular. The first pad portion 381a is housed in the first opening 21a and is exposed from the first opening 21a. A first wire 61a is connected to the first pad portion 381a. The first wire 61a connects the first pad portion 381a to the first electrode 71a of the first driver IC 7A. The first pad portion 381a is a portion to which, for example, a serial data signal of a print pattern by the thermal printhead A1 is input.

[0043] The first pad portion 381b is disposed on the x1 side of the first driver IC 7A in the x direction. The shape of the first pad portion 381b is not limited in any way, and in the illustrated example, it is rectangular. The first pad portion 381b is housed in the first opening 21b and is exposed from the first opening 21b. A plurality of first wires 61b are connected to the first pad portion 381b. The first wires 61b connect the first pad portion 381b to the first electrode 71b of the first driver IC 7A. The first pad portion 381b is, for example, part of a power supply line for enabling printing by the thermal printhead A1.

[0044] In the illustrated example, the electrode layer 3 includes a coated wiring portion 391. The coated wiring portion 391 is a wiring portion that overlaps with the first driving IC 7A when viewed in the z direction. As shown in FIG. 7 , a portion of the protective layer 2 is interposed between the first driving IC 7A and the coated wiring portion 391. The coated wiring portion 391 is connected to the first pad portion 381b. In other words, the first opening 21b exposes only the first pad portion 381b and a portion of the coated wiring portion 391 that is electrically connected to the first pad portion 381b.

[0045] The first pad portion 381c is disposed on the y2 side of the first driver IC 7A in the y direction. The shape of the first pad portion 381c is not limited, and in the illustrated example, it is rectangular or polygonal. The first pad portion 381c is housed in the first opening 21c and exposed through the first opening 21c. Multiple first wires 61c are connected to the first pad portion 381c. The first wires 61c connect the first pad portion 381c to the first electrodes 71c of the first driver IC 7A. The first pad portion 381c is a portion to which a signal (strobe signal) for passing a current through the heating portion 41 corresponding to a print signal input to the thermal printhead A1 is input.

[0046] In the illustrated example, the electrode layer 3 includes an interconnection portion 399c. The interconnection portion 399c is disposed in a region extending in the x-direction, and as shown in FIG. 7 , at least a portion of the interconnection portion 399c is covered by the protective layer 2. The interconnection portion 399c is connected to the first pad portion 381c. In other words, the first opening 21c exposes only the first pad portion 381c and a portion of the interconnection portion 399c that is electrically connected to the first pad portion 381c.

[0047] The first pad portion 381d is located on the y2 side of the first driver IC 7A in the y direction and on the x2 side of the first pad portion 381c in the x direction. The shape of the first pad portion 381d is not limited, and in the illustrated example, it is rectangular or polygonal. The first pad portion 381d is housed in the first opening 21d and exposed through the first opening 21d. A first wire 61d is connected to the first pad portion 381d. The first wire 61d connects the first pad portion 381d to the first electrode 71d of the first driver IC 7A. The first pad portion 381d is a portion through which a signal (strobe signal) flows to apply current to the heating portion 41 in response to a print signal input to the thermal printhead A1.

[0048] In the illustrated example, the electrode layer 3 includes an interconnection portion 399d. The interconnection portion 399d is arranged in a region extending in the x direction, and is arranged on the y1 side in the y direction with respect to a portion of the interconnection portion 399c. At least a portion of the interconnection portion 399c is covered with the protective layer 2. The interconnection portion 399d is connected to the first pad portion 381d. In other words, the first opening 21d exposes only the first pad portion 381d and a portion of the interconnection portion 399d that is electrically connected to the first pad portion 381d.

[0049] The first pad portion 381e is disposed on the x2 side in the x direction relative to the plurality of third pad portions 37. The shape of the first pad portion 381e is not limited in any way, and in the illustrated example, it is rectangular. The first pad portion 381e is housed in the first opening 21e and is exposed through the first opening 21e. A first wire 61e is connected to the first pad portion 381e. The first wire 61e connects the first pad portion 381e to a first electrode 71e of the first driving IC 7A. The first pad portion 381e is a portion where, for example, a serial data signal of a print pattern by the thermal printhead A1 is output from the first driving IC 7A.

[0050] In the illustrated example, the electrode layer 3 includes a connecting wiring portion 399e. The connecting wiring portion 399e extends in the x-direction. The connecting wiring portion 399c is housed in the first opening 21e. The connecting wiring portion 399e is connected to the first pad portion 381e. In other words, the first opening 21e exposes only the first pad portion 381e and the portion of the connecting wiring portion 399e that is electrically connected to the first pad portion 381e. The portion of the connecting wiring portion 399e connected to the x2 side in the x-direction is used, for example, as a portion through which a serial data signal of a print pattern by the thermal printhead A1 is input to the second drive IC 7B.

[0051] The first pad portion 381f and the second pad portion 382a are disposed on the y2 side in the y direction relative to the first driver IC 7A and the interconnection wiring portion 399c, and are disposed between the first pad portion 381c and the first pad portion 381d in the x direction. The shapes of the first pad portion 381f and the second pad portion 382a are not limited in any way, and in the illustrated example, they are rectangular. The first pad portion 381f and the second pad portion 382a are housed in the second opening 22a and exposed from the second opening 22a. The shortest distance d1 between the first pad portion 381f and the second pad portion 382a is 80 μm or more.

[0052] A plurality of first wires 61f are connected to the first pad portion 381f. The first wires 61f connect the first pad portion 381f and a first electrode 71f of the driving IC 7. The first pad portion 381f is connected to, for example, a ground terminal, and in this example, two first wires 61f are connected to allow more current to flow. A second wire 62a is connected to the second pad portion 382a. The second wire 62a connects the second pad portion 382a and a second electrode 72a of the first driving IC 7A. The second pad portion 382a is connected to, for example, a ground terminal.

[0053] The first pad portion 381g, the second pad portion 382b, and the fourth pad portion 384 are disposed between the first driver IC 7A and the second driver IC 7B in the x direction. The shapes of the first pad portion 381g, the second pad portion 382b, and the fourth pad portion 384 are not limited in any way and are rectangular or polygonal in the illustrated example. The first pad portion 381g, the second pad portion 382b, and the fourth pad portion 384 are housed in the second opening 22b and exposed from the second opening 22b. The shape of the second opening 22b is not limited in any way and is a combination of three rectangles with rounded corners in the illustrated example.

[0054] The shortest distance d2 between the first pad portion 381g and the second pad portion 382b is 80 μm or more. The shortest distance d3 between the first pad portion 381g and the fourth pad portion 384 is 80 μm or more.

[0055] A plurality of first wires 61g are connected to the first pad 381g. The first wires 61g connect the first pad 381g to a first electrode 71g of the driving IC 7. The first pad 381g is a portion through which a signal (clock signal) for inputting a serial signal to the first driving IC 7A flows. The first pad 381g is connected to a covered wiring portion 392.

[0056] A second wire 62b is connected to the second pad 382b. The second wire 62b connects the second pad 382b to the second electrode 72b of the first driver IC 7A. The second pad 382b is a portion through which a control signal (latch signal) flows to transfer print data provided from an external device, for example, from a shift register (not shown) to a register that temporarily holds the data.

[0057] A plurality of fourth wires 64 are connected to the fourth pad 384. The fourth wires 64 connect the fourth pad 384 to the fourth electrode 74a of the second driver IC 7B. The fourth pad 384 is, for example, part of a power supply line for enabling printing by the thermal printhead A1, and is electrically connected to the first pad 381b via the coated wiring portion 391.

[0058] The resistor layer 4 is formed using a material having a higher resistivity than the material constituting the electrode layer 3. The resistor layer 4 includes, for example, ruthenium oxide. In this example, the resistor layer 4 is formed on the bulge portion 122 as shown in FIGS. 3 and 4 . The shape of the resistor layer 4 as viewed in the z direction is not limited in any way. In this embodiment, the resistor layer 4 has a strip shape extending in the x direction as shown in FIGS. 1 and 3 . The resistor layer 4 intersects with each strip portion 32 (common electrode 31) and each strip portion 35 (individual electrode 34). In the z direction, the resistor layer 4 is stacked on the z1 side of the multiple strip portions 32 and the multiple strip portions 35.

[0059] The portions of the resistor layer 4 sandwiched between the strip portions 32 and 35 are heat generating portions 41. The heat generating portions 41 generate heat when partially energized by the electrode layer 3. Printed dots are formed by the heat generated by each heat generating portion 41. The heat generating portions 41 are arranged in the x direction. The greater the number of heat generating portions 41 arranged in the x direction per unit length (e.g., 1 mm) of the substrate 1 in the x direction, the greater the dot density of the thermal printhead A1.

[0060] The thickness of the resistor layer 4 is, for example, 3 μm or more and 6 μm or less. There are no limitations on the material and thickness of the resistor layer 4. In the example shown in FIG. 4 , the resistor layer 4 is formed on the top of the bulge portion 122, but it does not have to be formed on the top of the bulge portion 122.

[0061] The protective resin 78 covers the multiple driver ICs 7, the multiple wires 61, 62, and 63, and a portion of the protective layer 2. The protective resin 78 is made of, for example, an insulating resin and is, for example, black. The protective resin 78 may also be configured with multiple layers made of different materials (resin, glass, etc.) stacked one on top of the other. In FIG. 2 , the cross-sectional shape of the protective resin 78 gently bulges toward the z1 side in the z direction, but this is not limited to this and may be configured in various other shapes. The protective resin 78 may also be configured to include a portion forming a ring-shaped dam surrounding the multiple driver ICs when viewed in the z direction and a portion filling the dam portion.

[0062] As shown in Figures 1 and 2, the heat dissipation member 8 supports the substrate 1. The heat dissipation member 8 is intended to dissipate some of the heat generated by the multiple heat-generating portions 41 to the outside via the substrate 1. The heat dissipation member 8 is a block-shaped member made of a metal such as Al (aluminum). As shown in Figure 2, the heat dissipation member 8 has a support surface 81. The support surface 81 faces the z1 side in the z direction. A first back surface 11b of the base material 11 is joined to the support surface 81.

[0063] There is no limitation on the material and wire diameter of the first wire 61, the second wire 62, the third wire 63, and the fourth wire 64. The first wire 61, the second wire 62, the third wire 63, and the fourth wire 64 may contain a metal such as Au (gold) or Ag (silver), or may have any of these as a main component.

[0064] Next, the operation of the thermal printhead A1 and the thermal printer P1 will be described.

[0065] According to this embodiment, the first opening 21 (e.g., first opening 21a) exposes only the first pad portion 381 (e.g., first pad portion 381a). Alternatively, the first opening 21 (e.g., first opening 21b) exposes only the first pad portion 381 (e.g., first pad portion 381b) and a portion (e.g., covered wiring portion 391) conductive to the first pad portion 381. As a result, although a voltage is applied to the first pad portion 381 for a longer period of time than to the third pad portion 383, a portion of the electrode layer 3 adjacent to the first pad portion 381 is covered with the protective layer 2. Therefore, when a voltage is applied between the first pad portion 381 and the portion of the electrode layer 3 adjacent to the first pad portion 381, migration can be suppressed.

[0066] Furthermore, the second opening 22 (for example) exposes the first pad portion 381 (for example, the first pad portion 381f) and the second pad portion 382 (for example, the second pad portion 382a). The shortest distance d1 between the first pad portion 381f and the second pad portion 382a is 80 μm or more. According to the inventors' research, even when not covered with the protective layer 2, as long as the shortest distance is 80 μm or more, migration can be suppressed when the time rate at which a voltage is applied between portions of the electrode layer 3 containing Ag (silver) is longer than that of, for example, the third pad portion 383. Furthermore, by accommodating the first pad portion 381 and the second pad portion 382 in a single second opening 22, the planar layout of the thermal printhead A1 can be made more compact.

[0067] In addition to the first pads 381g and 382b, the second opening 22b also accommodates a fourth pad 384. The fourth pad 384 is electrically connected to the second driving IC 7B, which is a different driving IC 7 from the first driving IC 7A. Thus, portions of the electrode layer 3 electrically connected to different driving ICs 7 often have different potentials. Even between portions to which a voltage strong enough to cause migration is applied, migration can be suppressed by, for example, setting the shortest distance d3 to 80 μm or greater. Furthermore, by accommodating the first pad 381, the second pad 382, ​​and the fourth pad 384 in a single second opening 22, the planar layout of the thermal printhead A1 can be made more compact.

[0068] The multiple third pad portions 37 are housed together in the third opening 23. The shortest distance between adjacent third pad portions 37 may be less than the aforementioned 80 μm. However, because voltage is applied to the multiple third pad portions 37 only when print dots are formed by each heating portion 41, the time ratio during which voltage is applied is smaller than that of the first pad portion 381, the second pad portion 382, ​​the fourth pad portion 384, etc. This reduces the risk of migration occurring, allowing the thermal printhead A1 to operate properly.

[0069] 10 to 12 show modified examples and other embodiments of the present disclosure. In these figures, elements that are the same as or similar to those in the above-described embodiment are given the same reference numerals. Furthermore, the configurations of the various parts in each modified example and each embodiment can be combined with each other as appropriate within the scope of not causing technical contradictions.

[0070] 10 shows a first modified example of the thermal printhead A1. In this example, the second opening 22a accommodates the first pad 381c in addition to the first pad 381f and the second pad 382a. That is, the first pad 381f, the second pad 382a, and the first pad 381c are exposed from the second opening 22a.

[0071] The second opening 22a has a shape that is, for example, a combination of the first opening 21c and the second opening 22a in the thermal printhead A1. The shortest distance d4 between the first pad portion 381c and the first pad portion 381f is 80 μm or more.

[0072] Furthermore, the second opening 22b accommodates the first pad portion 381e and the interconnection portion 399e in addition to the first pad portion 381g, the second pad portion 382b, and the fourth pad portion 384. That is, the first pad portion 381g, the second pad portion 382b, the fourth pad portion 384, the first pad portion 381e, and the interconnection portion 399e are exposed from the second opening 22b.

[0073] The second opening 22b has a shape that is, for example, a combination of the first opening 21e and the second opening 22a in the thermal printhead A1. The shortest distance d5 between the first pad portion 381e and the second pad portion 382b is 80 μm or more.

[0074] This modification also makes it possible to suppress the occurrence of ion migration in the electrode layer 3. As can be seen from this modification, the structural relationship between the second opening 22 and the electrode layer 3 can be set in various ways.

[0075] 11 and 12 show a thermal printhead and a thermal printer according to a second embodiment of the present disclosure. The thermal printer P2 of this embodiment includes a thermal printhead A2 and a platen roller B1. The thermal printhead A2 includes a connection board 5.

[0076] The connection board 5 is disposed on the y2 side of the substrate 1 in the y direction. The connection board 5 is, for example, a printed circuit board, and has a wiring pattern (not shown) formed thereon. A connector 59 is mounted on the connection board 5. The shape of the connection board 5 is not particularly limited, but in this embodiment, it is rectangular with the x direction as its longitudinal direction. The connection board 5 has a second main surface 5a and a second back surface 5b. The second main surface 5a faces the same side as the first main surface 11a of the base material 11, and the second back surface 5b faces the same side as the first back surface 11b of the base material 11. The second back surface 5b is joined to the support surface 81 of the heat dissipation member 8.

[0077] The connector 59 is used to connect the thermal printhead A2 to the thermal printer P2. The connector 59 is attached to the connection board 5 and connected to the wiring pattern (not shown) of the connection board 5.

[0078] In this embodiment, the driving IC 7 and the connection substrate 5 are connected via a fifth wire 65. The fifth wire 65 is connected to one of the electrodes (not shown) of the driving IC 7 and an appropriate position of the wiring pattern (not shown) of the connection substrate 5.

[0079] The protective resin of this embodiment covers the driving IC 7 and all wires such as the third wire 63 connected to the driving IC 7, including the fifth wire 65. The protective resin 78 is formed so as to straddle the substrate 1 and the connection substrate 5.

[0080] In this embodiment, the configurations of the above-mentioned first opening 21, second opening 22, third opening 23, first pad portion 381, second pad portion 382, ​​third pad portion 383, fourth pad portion 384, first wire 61, second wire 62, third wire 63 and fourth wire 64 are also appropriately adopted.

[0081] This embodiment also makes it possible to suppress the occurrence of ion migration in the electrode layer 3. Furthermore, as can be understood from this embodiment, the thermal printhead of the present disclosure may be configured to include a connection substrate 5 in addition to the base material 11 (substrate 1).

[0082] The thermal printhead and thermal printer according to the present disclosure are not limited to the above-described embodiments. The specific configurations of the components of the thermal printhead and thermal printer according to the present disclosure can be freely modified in various ways. For example, the present disclosure includes the embodiments described in the following appendices.

[0083] Supplementary Note 1. A substrate comprising: a substrate having a main surface and a back surface facing opposite each other in a thickness direction; an electrode layer and a resistor layer supported on the main surface; a protective layer covering a portion of the electrode layer and at least a portion of the resistor layer; a first driving IC that controls current flow to the resistor layer; and a plurality of wires connected to the first driving IC, wherein the electrode layer contains Ag, the first driving IC has a first electrode and a second electrode, the plurality of wires including a first wire connected to the first electrode and a second wire connected to the second electrode, the electrode layer having a first pad portion connected to the first wire and a second pad portion connected to the second wire, and the protective layer has at least one of a first opening that exposes only a portion of the electrode layer that is conductive to the first pad portion and a second opening that exposes a portion of the electrode layer that is conductive to the first pad portion and a portion that is conductive to the second pad portion, A thermal printhead, wherein in the second opening, the shortest distance between a portion that conducts to the first pad portion and a portion that conducts to the second pad portion is 80 μm or more. Appendix 2. A thermal printhead according to Appendix 1, wherein the resistor layer includes a plurality of heat generating portions arranged in the main scanning direction. Appendix 3. A thermal printhead according to Appendix 2, wherein the resistor layer includes a plurality of individual wirings that are individually connected to the plurality of heat generating portions. Appendix 4. A thermal printhead according to Appendix 3, wherein the first driving IC has a plurality of third electrodes, the plurality of wires include a plurality of third wires individually connected to the plurality of third electrodes and the plurality of individual wirings, each of the plurality of individual wirings has a third pad portion to which the third wire is connected, and the protective layer further has a third opening that collectively exposes the third pad portions of all of the plurality of individual wirings that are electrically connected to one of the first driving ICs. Appendix 5. The thermal printhead of claim 4, wherein a time ratio during which a voltage is applied to the first pad portion and the second pad portion is longer than a time ratio during which a voltage is applied to the third pad portion. The thermal printhead of claim 1, wherein the substrate includes a ceramic.Appendix 7. The thermal printhead of Appendix 1, further comprising a glaze layer interposed between the substrate and the electrode layer. Appendix 8. The thermal printhead of Appendix 7, wherein the first driving IC is disposed on the glaze layer. Appendix 9. The thermal printhead of Appendix 8, wherein the electrode layer includes a covered wiring portion that overlaps with the first driving IC when viewed in the thickness direction of the substrate. Appendix 10. The thermal printhead of Appendix 9, wherein the first pad portion is electrically connected to the covered wiring portion. Appendix 11. The thermal printhead of Appendix 9, wherein the second pad portion is electrically connected to the covered wiring portion. Appendix 12. The thermal printhead according to any one of Supplementary Notes 1 to 11, further comprising: a second driving IC having a fourth electrode; and a fourth wire connected to the fourth electrode; the electrode layer further having a fourth pad portion to which the fourth wire is connected; the second opening exposes a portion of the electrode layer that is conductive to the first pad portion, a portion that is conductive to the second pad portion, and a portion that is conductive to the fourth pad portion; and in the second opening, the shortest distance between the portion that is conductive to the first pad portion, the portion that is conductive to the second pad portion, and the portion that is conductive to the fourth pad portion is 80 μm or more.Supplementary Note 13. The thermal printhead according to Supplementary Note 1, wherein the first driving IC has two of the first electrodes, the plurality of wires includes two of the first wires, and the two first wires are connected to one of the first pad portions.Supplementary Note 14. The thermal printhead according to Supplementary Note 1, wherein all of the plurality of wires are connected to the electrode layer.Supplementary Note 15. Appendix 1: A thermal printhead according to Appendix 1, further comprising a wiring board arranged in the sub-scanning direction relative to the base material, and any of the plurality of wires being connected to the wiring board. Appendix 16: A thermal printhead according to Appendix 1, further comprising a protective resin that covers the first driver IC, the plurality of wires, and all of at least either the first opening or the second opening. Appendix 17: A thermal printer comprising the thermal printhead according to Appendix 1.

[0084] A1, A11, A2: thermal print head P1, P2: thermal printer 1: substrate 2: protective layer 3: electrode layer 4: resistor layer 5: connection substrate 5a: second main surface 5b: second back surface 8: heat dissipation member 11: base material 11a: first main surface 11b: first back surface 12: glaze layer 19: terminal 21, 21a, 21b, 21c, 21d, 21e: first opening 22, 22a, 22b: second opening 23: third opening 31: common electrode 32: strip-shaped portion 33: connecting portion 34: individual electrode 35: strip-shaped portion 36: connecting portion 37, 37A, 37B: third pad portion 41: heat-generating portion 59: connector 61, 61a, 61b, 61c, 61d, 61e, 61f, 61g: First wire 62, 62a, 62b: Second wire 63: Third wire 64: Fourth wire 65: Fifth wire 71, 71a, 71b, 71c, 71d, 71e, 71f, 71g: First electrode 72, 72a, 72b: Second electrode 73: Third electrode 74a: Fourth electrode 78: Protective resin 79: Bonding layer 81: Support surface 121: Flat portion 122: Bulging portion 331: Auxiliary layer 361: Parallel portion 362: Oblique portion 381 (381a to 381g): First pad portion 382, ​​382a, 382b: Second pad portion 383: Third pad portion 384: Fourth pad portion 391, 392: Covered wiring portion 399c, 399d, 399e: Interconnect wiring portion B1: Platen roller C1: Printing medium 7: Driving IC 7A: First driving IC 7B: Second driving IC d1, d2, d3, d4, d5: Shortest distance

Claims

1. A substrate having a main surface and a back surface facing opposite each other in a thickness direction; an electrode layer and a resistor layer supported on the main surface; a protective layer covering a portion of the electrode layer and at least a portion of the resistor layer; a first driving IC for controlling current flow to the resistor layer; a plurality of wires connected to the first driving IC; The electrode layer contains Ag, the first driving IC has a first electrode and a second electrode; the plurality of wires includes a first wire connected to the first electrode and a second wire connected to the second electrode; the electrode layer has a first pad portion to which the first wire is connected and a second pad portion to which the second wire is connected, the protective layer has at least one of a first opening exposing only a portion of the electrode layer that is conductive to the first pad portion and a second opening exposing a portion of the electrode layer that is conductive to the first pad portion and a portion that is conductive to the second pad portion, A thermal printhead, wherein in the second opening, the shortest distance between a portion that is electrically connected to the first pad portion and a portion that is electrically connected to the second pad portion is 80 μm or more.

2. 2. The thermal printhead according to claim 1, wherein the resistor layer includes a plurality of heat generating portions arranged in a main scanning direction.

3. The thermal printhead according to claim 2 , wherein the resistor layer includes a plurality of individual wirings each connected to one of the plurality of heat generating portions.

4. the first driving IC has a plurality of third electrodes; the plurality of wires include a plurality of third wires individually connected to the plurality of third electrodes and the plurality of individual wirings, each of the plurality of individual wirings has a third pad portion to which the third wire is connected; 4. The thermal printhead according to claim 3, wherein the protective layer further has a third opening for collectively exposing the third pad portions of all the plurality of individual wirings that are electrically connected to one of the first driving ICs.

5. The thermal printhead of claim 4 , wherein a time ratio during which a voltage is applied to the first pad portion and the second pad portion is longer than a time ratio during which a voltage is applied to the third pad portion.

6. 6. The thermal printhead according to claim 1, wherein the substrate comprises a ceramic.

7. The thermal printhead of claim 1 , further comprising a glaze layer interposed between the substrate and the electrode layer.

8. The thermal printhead of claim 7 , wherein the first driver IC is disposed on the glaze layer.

9. The thermal printhead according to claim 8 , wherein the electrode layer includes a covered wiring portion that overlaps with the first driving IC when viewed in a thickness direction of the base material.

10. The thermal printhead according to claim 9 , wherein the first pad portion is electrically connected to the coated wiring portion.

11. The thermal printhead according to claim 9 , wherein the second pad portion is electrically connected to the coated wiring portion.

12. a second driving IC having a fourth electrode; a fourth wire connected to the fourth electrode, the electrode layer further includes a fourth pad portion to which the fourth wire is connected, the second opening exposes a portion of the electrode layer that is electrically connected to the first pad portion, a portion that is electrically connected to the second pad portion, and a portion that is electrically connected to the fourth pad portion; 2. A thermal printhead as described in claim 1, wherein in the second opening, the shortest distance between the portion that is conductive to the first pad portion, the portion that is conductive to the second pad portion, and the portion that is conductive to the fourth pad portion is 80 μm or more.

13. the first driving IC has two of the first electrodes, the plurality of wires includes two of the first wires, The thermal printhead according to claim 1 , wherein the two first wires are connected to one of the first pad portions.

14. The thermal printhead of claim 1 , wherein the plurality of wires are all connected to the electrode layer.

15. A wiring board is further provided, the wiring board being arranged in a sub-scanning direction with respect to the base material. The thermal printhead according to claim 1 , wherein any one of the plurality of wires is connected to the wiring board.

16. The thermal printhead of claim 1 , further comprising a protective resin that covers the first driving IC, the plurality of wires, and all of at least either the first opening or the second opening.

17. A thermal printer comprising the thermal printhead according to claim 1.