Thermal printhead and method of manufacturing the same, and thermal printer

Abstract

A thermal head capable of inhibiting disconnection of a comb-tooth portion of a common electrode is provided. In addition, a manufacturing method of the thermal head and a thermal printer having the thermal head are provided. The thermal head of the present invention includes a heat accumulating layer, an individual electrode on the heat accumulating layer, a common electrode having a comb-tooth portion spaced apart from the individual electrode and opposed to the individual electrode, a heat generating resistor on the individual electrode and the comb-tooth portion, and a connecting electrode made of a different material from the common electrode and in contact with the common electrode, in which a slit exists between the comb-tooth portion and a region on the common electrode in contact with the connecting electrode.

Description

Technical Field

[0001] This embodiment relates to a thermal printhead and its manufacturing method, as well as a thermal printer. Background Technology

[0002] A thermal printhead, for example, has a large number of heating elements arranged along the main scanning direction on a printhead substrate. Each heating element is formed by stacking a common electrode and an individual electrode on a resistive layer formed on the printhead substrate with a glaze layer in between, such that a portion of the resistive layer is exposed, wherein the ends of the common electrode and the individual electrode face each other. When an electric current is applied between the common electrode and the individual electrode, the exposed portion of the resistive layer (the heating element) heats up due to Joule heating. This heat is transferred to a printing medium (such as thermal paper used to make barcode labels or receipts), thereby enabling printing on the printing medium.

[0003] Common electrodes and individual electrodes are formed by screen printing a paste containing metals such as gold to create electrode patterns.

[0004] In addition, the common electrode and the independent electrode are in contact with the connecting electrode and wiring, respectively, for supplying voltage to the common electrode and the independent electrode from the outside. The connecting electrode pattern is formed by screen printing using a paste of metals such as silver, while the wiring is formed by photolithography using metals such as gold and silver. Due to the high price of gold, from the perspective of reducing product costs, a technology using silver as a relatively inexpensive and highly conductive metal has been proposed.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent document 1: Japanese Patent Application Publication No. 2000-141729.

[0008] Patent document 2: Japanese Patent Application Publication No. 5-89716. Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, when the materials of the common electrode and the connecting electrode are dissimilar metals, the Kirkendall effect occurs, where the interface between the common electrode and the connecting electrode shifts due to heating. For example, when the common electrode is made of gold and the connecting electrode is made of silver, the silver, as the material of the connecting electrode, diffuses into the common electrode due to heating. This diffusion causes Kirkendall voids to form in the common electrode. If these Kirkendall voids form at the comb teeth of the common electrode, they may cause wire breakage because the comb teeth are relatively fine electrodes. In addition, the diffusion of silver reduces the ductility of the gold, which is the material of the common electrode, and the comb teeth may be subjected to tension due to heating, potentially leading to wire breakage.

[0011] One aspect of this embodiment provides a thermal printhead capable of suppressing wire breakage at the comb teeth of the common electrode. Another aspect of this embodiment provides a method for manufacturing the thermal printhead. Furthermore, yet another aspect of this embodiment provides a thermal printer having the thermal printhead.

[0012] Technical means to solve the problem

[0013] In this embodiment, in a common electrode that contacts the connecting electrode and is made of a different material than the connecting electrode, a slit is provided between the comb-tooth portion of the common electrode and the area on the common electrode that contacts the connecting electrode. This reduces the area where material from the connecting electrode diffuses into the common electrode and suppresses the diffusion area from reaching the comb-tooth portion. Therefore, wire breakage in the comb-tooth portion of the common electrode can be suppressed. One aspect of this embodiment is described below.

[0014] One aspect of this embodiment provides a thermal printhead, comprising: a heat storage layer; independent electrodes on the heat storage layer; a common electrode having comb teeth spaced apart from and opposite to the independent electrodes; heating resistors on the independent electrodes and the comb teeth; and a connecting electrode made of a different material from the common electrode and in contact with the common electrode, wherein a slit exists between the comb teeth and the area on the common electrode in contact with the connecting electrode.

[0015] Furthermore, another aspect of this embodiment provides a thermal printer having the aforementioned thermal printhead.

[0016] Furthermore, another aspect of this embodiment provides a method for manufacturing a thermal printhead, wherein a heat storage layer is formed, an independent electrode and a common electrode having comb teeth and a slit are formed on the heat storage layer, wiring is formed in contact with the independent electrode, a connecting electrode is formed in contact with the common electrode, a heating resistor is formed on the independent electrode and the common electrode, the independent electrode is spaced apart from and opposite to the comb teeth of the common electrode, the common electrode is made of a different material than the connecting electrode, and the slit is located between the comb teeth and the area on the common electrode in contact with the connecting electrode.

[0017] Invention Effects

[0018] This embodiment provides a thermal printhead capable of suppressing wire breakage at the comb teeth of the common electrode. Furthermore, a method for manufacturing this thermal printhead can be provided. Ultimately, a thermal printer having this thermal printhead can be provided. Attached Figure Description

[0019] Figure 1 This is a top view illustrating the thermal printhead 100A of this embodiment.

[0020] Figure 2 It is along Figure 1 A cross-sectional view along line AA.

[0021] Figure 3 It is along Figure 1 A cross-sectional view of the BB line.

[0022] Figure 4 This is a top view (1) illustrating the manufacturing method of the thermal printhead 100A according to this embodiment.

[0023] Figure 5 It is along Figure 4 A cross-sectional view along line AA.

[0024] Figure 6 It is along Figure 4 A cross-sectional view of the BB line.

[0025] Figure 7 This is a top view (2) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0026] Figure 8 It is along Figure 7 A cross-sectional view along line AA.

[0027] Figure 9 It is along Figure 7 A cross-sectional view of the BB line.

[0028] Figure 10 This is a top view (3) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0029] Figure 11 It is along Figure 10 A cross-sectional view along line AA.

[0030] Figure 12 It is along Figure 10 A cross-sectional view of the BB line.

[0031] Figure 13 This is a top view (4) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0032] Figure 14 It is along Figure 13 A cross-sectional view along line AA.

[0033] Figure 15 It is along Figure 13 A cross-sectional view of the BB line.

[0034] Figure 16 This is a top view (5) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0035] Figure 17 It is along Figure 16 A cross-sectional view along line AA.

[0036] Figure 18 It is along Figure 16 A cross-sectional view of the BB line.

[0037] Figure 19 This is a top view (6) illustrating the manufacturing method of the thermal printhead 100A of this embodiment.

[0038] Figure 20 It is along Figure 19 A cross-sectional view along line AA.

[0039] Figure 21 It is along Figure 19 A cross-sectional view of the BB line.

[0040] Figure 22 This is a top view illustrating the thermal printhead 100B of this embodiment.

[0041] Figure 23 This is a top view illustrating the thermal printhead 100C of this embodiment.

[0042] Figure 24 This is a top view illustrating the thermal printhead 100D of this embodiment.

[0043] Figure 25 This is a cross-sectional view illustrating the thermal printhead of this embodiment.

[0044] Figure 26 (A) is a top view illustrating the position of the slit 45 provided on the common electrode 32 in the thermal printhead 100A of this embodiment. Figure 26 (B) is Figure 26 (A) is a top view showing the case where distance D1 is shorter. Figure 26 (C) is Figure 26 (A) is a top view of the case where distance D2 is shorter.

[0045] Explanation of reference numerals in the attached figures

[0046] 5 Connecting substrate

[0047] 7 Driver IC

[0048] 8 Heat dissipation components

[0049] 15 substrate

[0050] 31 Independent Electrodes

[0051] 32 Common Electrode

[0052] 32A Comb teeth section

[0053] 32B Public Department

[0054] 33 Heat Storage Layer

[0055] 41 Wiring

[0056] 42 Connecting electrodes

[0057] 45, 45a slits

[0058] 50 Heating Resistor

[0059] 51 Heating resistor section

[0060] 52, 54 Protective film

[0061] 59 Connector

[0062] 81 lead wire

[0063] 82 Resin Section

[0064] 91 Paper Press Roller

[0065] 92 Printing Media

[0066] 100A, 100B, 100C, 100D thermal printheads Detailed Implementation

[0067] Next, this embodiment will be described with reference to the accompanying drawings. In the drawings described below, the same or similar parts are labeled with the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the thickness and planar dimensions of each component differ from those of a real product. Therefore, specific thicknesses and dimensions should be determined by referring to the following description. Furthermore, the drawings naturally include parts with different dimensional relationships and scales.

[0068] Furthermore, the embodiments shown below illustrate apparatus and methods for embodying the technical concept, but they do not limit the material, shape, structure, or arrangement of the constituent components. Various modifications can be made within the scope of the inventive concept.

[0069] One aspect of this specific embodiment is described below.

[0070] <1> A thermal printhead includes: a heat storage layer; an independent electrode on the heat storage layer; a common electrode having a comb portion spaced apart from and opposite to the independent electrode; a heating resistor on the independent electrode and the comb portion; and a connecting electrode made of a different material from the common electrode and in contact with the common electrode, wherein a slit exists between the comb portion and the area on the common electrode in contact with the connecting electrode.

[0071] <2> The thermal printhead as described in <1>, wherein the common electrode comprises gold and the connecting electrode comprises silver.

[0072] <3> The thermal printhead as described in <1> or <2>, wherein the width of the slit in the main scanning direction is greater than the width of the comb portion in the main scanning direction.

[0073] <4> The thermal printhead as described in any one of <1> to <3>, wherein the width of the slit in the sub-scanning direction is 5 μm or more.

[0074] <5> A thermal printhead as described in any one of <1> to <4>, wherein there are multiple slits, and the spacing between adjacent slits is greater than the width of the comb portion in the main scanning direction.

[0075] <6> The thermal printhead as described in <5>, wherein the spacing between adjacent slits is more than 100 μm.

[0076] <7> A thermal printhead as described in any one of <1> to <4>, wherein there are multiple slits, and one of the multiple slits is a slit whose width in the main scanning direction is greater than the spacing between adjacent slits.

[0077] <8> The thermal printhead as described in <7>, wherein one end of a slit whose width in the main scanning direction is greater than the spacing between adjacent slits is located between the end of one of the adjacent slits and the area on the common electrode that contacts the connecting electrode, and the other end of a slit whose width in the main scanning direction is greater than the spacing between adjacent slits is located between the end of the other of the adjacent slits and the area on the common electrode that contacts the connecting electrode.

[0078] <9> A thermal printhead as described in any one of <1> to <8>, wherein it further includes wiring in contact with the independent electrode, the connecting electrode being thicker than the wiring.

[0079] <10> A thermal printhead as described in any one of <1> to <9>, wherein the independent electrode is spaced apart from the comb portion in the main scanning direction.

[0080] <11> A thermal printer having a thermal printhead as described in any one of <1> to <10>.

[0081] <12> A method for manufacturing a thermal printhead, wherein a heat storage layer is formed, an independent electrode and a common electrode having comb teeth and a slit are formed on the heat storage layer, a wiring in contact with the independent electrode is formed, a connecting electrode in contact with the common electrode is formed, a heating resistor is formed on the independent electrode and the common electrode, the independent electrode is spaced apart from and opposite to the comb teeth of the common electrode, the common electrode is made of a different material than the connecting electrode, and the slit is located between the comb teeth and the area on the common electrode in contact with the connecting electrode.

[0082] <13> The method for manufacturing a thermal printhead as described in <12>, wherein the common electrode comprises gold and the connecting electrode comprises silver.

[0083] <14> A method for manufacturing a thermal printhead as described in <12> or <13>, wherein the width of the slit in the main scanning direction is greater than the width of the comb portion in the main scanning direction.

[0084] <15> A method for manufacturing a thermal printhead as described in any one of <12> to <14>, wherein the width of the slit in the sub-scanning direction is 5 μm or more.

[0085] <16> A method for manufacturing a thermal printhead as described in any one of <12> to <15>, wherein there are multiple slits, and the spacing between adjacent slits is greater than the width of the comb portion in the main scanning direction.

[0086] <17> The method for manufacturing a thermal printhead as described in <16>, wherein the spacing between adjacent slits is 100 μm or more.

[0087] <18> A method for manufacturing a thermal printhead as described in any one of <12> to <15>, wherein there are multiple slits, and one of the multiple slits is a slit whose width in the main scanning direction is greater than the spacing between adjacent slits.

[0088] <19> A method for manufacturing a thermal printhead as described in <18>, wherein one end of a slit whose width in the main scanning direction is greater than the spacing between adjacent slits is located between the end of one of the adjacent slits and the area on the common electrode that contacts the connecting electrode, and the other end of a slit whose width in the main scanning direction is greater than the spacing between adjacent slits is located between the end of the other of the adjacent slits and the area on the common electrode that contacts the connecting electrode.

[0089] <20> A method for manufacturing a thermal printhead as described in any one of <12> to <19>, wherein the connecting electrode is thicker than the wiring.

[0090] <21> A method for manufacturing a thermal printhead as described in any one of <12> to <20>, wherein the connecting electrode is formed by screen printing a metal paste, and the wiring is formed by a photolithography process.

[0091] <Thermal Printhead>

[0092] The thermal printhead of this embodiment will be described using the accompanying drawings.

[0093] Figure 1 This is a top view of the thermal printhead. Figure 2 It is along Figure 1 A cross-sectional view along line AA. Figure 3 It is along Figure 1 A cross-sectional view of the BB line. Figures 1-3 This represents a portion of a thermal printhead (equivalent to one thermal printhead), and in this embodiment, this single thermal printhead is referred to as a monolithic thermal printhead 100A. The thermal printhead 100A includes: a substrate 15; a heat storage layer 33 on the substrate 15; a plurality of independent electrodes 31 on the heat storage layer 33 and a common electrode 32 having comb-like portions 32A; heating resistors 50 on the independent electrodes 31 and on the comb-like portions 32A of the common electrode 32; wiring 41 in contact with the independent electrodes 31; a connecting electrode 42 in contact with the common electrode 32; and protective films 52 and 54 covering the heat storage layer 33, the independent electrodes 31, the common electrode 32, the heating resistors 50, the wiring 41, and the connecting electrode 42. Furthermore, the independent electrodes 31 are spaced apart from the comb-like portions 32A of the common electrode 32 in the main scanning direction X, and are opposite to the comb-like portions 32A. The common electrode 32 is made of a different material than the connecting electrode 42. In the common electrode 32, there are multiple slits 45 between the comb portion 32A and the common portion 32B of the common electrode 32 in the area that contacts the connecting electrode 42.

[0094] The heating resistor 50 includes a plurality of heating resistor sections 51 that are heated by an electric current flowing in the individual electrode 31 and the common electrode 32. Each heating resistor section 51 is independently formed between the individual electrode 31 and the common electrode 32. Figure 1 Multiple heating resistor sections 51 are omitted. The multiple heating resistor sections 51 are arranged in a straight line on the heat storage layer 33. Furthermore, for ease of understanding, Figure 1 Protective film 52 and protective film 54 are omitted.

[0095] In this embodiment, the main scanning direction X is the direction in which the plurality of heating resistors 51 extend in a straight line; the secondary scanning direction Y is the direction perpendicular to the main scanning direction X and parallel to the upper surface of the substrate 15; and the thickness direction Z is the direction corresponding to the thickness of the substrate 15. In other words, the thickness direction Z is a direction perpendicular to both the main scanning direction X and the secondary scanning direction Y.

[0096] The substrate 15 is made of ceramic or single-crystal semiconductor. For example, alumina can be used as a ceramic. For example, silicon can be used as a single-crystal semiconductor. From a heat dissipation perspective, alumina, which has a high thermal conductivity, is preferred for the substrate 15.

[0097] A heat storage layer 33 (also called a glaze layer) with heat storage function is laminated on a substrate 15 made of alumina or the like. The heat storage layer 33 stores the heat generated from the heating resistor 51, which will be described later. The heat storage layer 33 can be made of an insulating material, such as silicon oxide or silicon nitride, which are the main components of glass. The dimension of the heat storage layer 33 in the thickness direction Z is not particularly limited, for example, it is 30 to 80 μm, preferably 40 to 60 μm.

[0098] Individual electrodes 31 and common electrodes 32 formed of metal paste are disposed on the heat storage layer 33. The individual electrodes 31 and common electrodes 32 are obtained by forming electrode patterns by coating metal paste using methods such as screen printing.

[0099] As a metal paste, a paste containing metal particles such as copper, silver, palladium, iridium, platinum, and gold can be used. From the viewpoint of the properties and ionization tendency of metals, copper, silver, platinum, and gold are preferred, and gold is more preferred. In addition, the solvent contained in the metal paste has the function of uniformly dispersing the metal particles. Examples of solvents include one or a mixture of two or more of the following: ester solvents, ketone solvents, ethylene glycol ether solvents, aliphatic solvents, alicyclic solvents, aromatic solvents, alcohol solvents, and water, but are not limited to these.

[0100] Examples of ester-based solvents include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and dimethyl carbonate. Examples of ketone-based solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone benzene, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Examples of glycol ether-based solvents include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, and other monoether acetates, as well as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether.

[0101] Examples of aliphatic solvents include n-heptane, n-hexane, cyclohexane, methylcyclohexane, and ethylcyclohexane. Examples of alicyclic solvents include methylcyclohexane, ethylcyclohexane, and cyclohexane. Examples of aromatic solvents include toluene, xylene, and tetrahydronaphthalene. Examples of alcohol solvents (excluding the ethylene glycol ether solvents mentioned above) include ethanol, propanol, and butanol.

[0102] Metal pastes can contain dispersants, surface treatment agents, abrasion modifiers, infrared absorbers, ultraviolet absorbers, fragrances, antioxidants, organic pigments, inorganic pigments, defoamers, silane coupling agents, titanate coupling agents, plasticizers, flame retardants, humectants, ion scavengers, etc., as needed.

[0103] Each individual electrode 31 is a strip extending approximately along the sub-scanning direction Y, and they are not electrically connected to each other. Therefore, when a printer equipped with a thermal printhead is used, each individual electrode 31 can be applied with a different potential. Each individual electrode 31 has an individual pad connected to its end. The individual pad is configured to be located away from the heating resistor 50 and in contact with the wiring 41.

[0104] The common electrode 32 is the portion whose polarity is opposite to that of the multiple individual electrodes 31 when the printer with the thermal printhead is used. The common electrode 32 includes comb teeth 32A and a common portion 32B that connects the comb teeth 32A together. The common portion 32B is formed along the upper edge of the substrate 15 in the main scanning direction X. In the sub-scanning direction Y, the direction in which the common electrode 32 is located when viewed from the individual electrodes 31 is defined as the upper side of the sub-scanning direction Y. Each comb tooth 32A is a strip extending in the sub-scanning direction Y. The front end of each comb tooth 32A is located in the region between the front ends of two adjacent individual electrodes 31 and is spaced apart from these two individual electrodes 31 along the main scanning direction X by a predetermined interval.

[0105] The front end of each comb tooth portion 32A may also be spaced apart from the front end of each individual electrode 31 along the sub-scanning direction Y. In this case, it is preferable to form the heating resistor portion 51 only in the region where the front end of the comb tooth portion 32A is opposite to the front end of the individual electrode 31. In other words, it is preferable that, in the main scanning direction X, the heating resistor portion 51 is not arranged in the region other than the region where the front end of the comb tooth portion 32A is opposite to the front end of the individual electrode 31.

[0106] A plurality of slits 45 are provided on the common part 32B. The slits 45 are located between the comb part 32A and the area on the common electrode 32 that contacts the connecting electrode 42 (described later). By providing the slits 45, as... Figure 26 As shown in (A), the diffusion region (the slanted part in the figure) that allows the material of the connecting electrode 42 to diffuse towards the common electrode 32 can be reduced, and the diffusion region can be suppressed so that it does not reach the comb tooth part 32A.

[0107] In such Figure 26 As shown in (A), when the distance between the front end of the connecting electrode 42 and the slit 45 is D1, and the distance between the connecting surface between the comb portion 32A and the common portion 32B and the slit 45 is D2, if the distance D1 is too short, then as shown in (A), the following will occur. Figure 26 As shown in (B), because the diffusion area on the side of slit 45 closer to the connecting electrode 42 is smaller, the diffusion cannot remain only in the area between the front end of the connecting electrode 42 and the slit 45. The diffusion area extends broadly to the side of slit 45 closer to the comb tooth portion 32A, thus potentially spreading to the comb tooth portion 32A. Conversely, if the distance D2 is too short, then... Figure 26 As shown in (C), the diffusion area extends from the slit 45 to the comb tooth section 32A.

[0108] Therefore, the position of slit 45 is preferably set as D1∶D2=1∶3~3∶1.

[0109] Furthermore, if the width of the slit 45 in the main scanning direction X is larger than the width of the comb portion 32A, the slit 45 can further suppress the spread of the diffusion region, which is therefore preferred. One side of the slit 45 in the main scanning direction X is preferably parallel to the connection surface between the comb portion 32A and the common portion 32B. In this embodiment, "parallel" means that two straight lines are arranged to form an angle of -5° or more and 5° or less. Furthermore, regarding the spacing between adjacent slits 45, when it is greater than the width of the comb portion 32A in the main scanning direction X, it can further suppress the breakage between adjacent slits 45, which is therefore preferred, for example, preferably 100 μm or more.

[0110] Furthermore, in the sub-scanning direction Y, the width of the slit 45 is preferably 5 μm or more, and more preferably 30 μm. Using this range can further reduce the diffusion region.

[0111] In this embodiment, by providing a slit 45 between the comb tooth portion 32A of the common electrode 32 and the area on the common electrode 32 that contacts the connecting electrode 42, the area where material from the connecting electrode 42 diffuses into the common electrode 32 can be reduced, and the diffusion area can be suppressed so that it does not reach the comb tooth portion 32A. Therefore, wire breakage in the comb tooth portion 32A of the common electrode 32 can be suppressed.

[0112] In the heating resistor 50, the portion through which current flows from the individual electrode 31 and the common electrode 32 heats up. Specifically, the heating resistor 50 is independently energized with a heating voltage according to a print signal sent from an external source such as a driver IC, enabling selective heating. The heating resistor section 51 is independently energized according to the print signal, thereby selectively heating. Printed dots are formed by heating in this way. The heating resistor 50 uses a material with a higher resistivity than the material constituting the wiring, such as ruthenium oxide. The heating resistor 50 can be formed by supplying resistor paste using screen printing or a distributor and then sintering it. In this embodiment, the dimension in the thickness direction Z of the heating resistor 50 is, for example, about 1 to 10 μm.

[0113] Wiring 41 is in contact with independent electrode 31. Wiring 41 has the function of supplying voltage to independent electrode 31 from the outside, for example, by using a photolithography process using metals such as gold or silver.

[0114] The connecting electrode 42 is in contact with the common electrode 32. The connecting electrode 42 has the function of supplying voltage to the common electrode 32 from the outside, for example, by coating a metal paste such as silver using a screen printing method to form an electrode pattern.

[0115] The connecting electrode 42 formed by screen printing is thicker than the wiring 41 formed by photolithography. Since the amount of material diffusion varies with thickness, when the materials of the connecting electrode 42 and wiring 41 are the same, and the materials of the common electrode 32 and independent electrode 31 are the same but different from the materials of the connecting electrode 42 and wiring 41, the amount of material from the connecting electrode 42 diffusing into the common electrode 32 is greater than the amount of material from the wiring 41 diffusing into the independent electrode 31. Therefore, it is necessary to provide a slit 45 located in the common electrode 32 as described above, thereby reducing the diffusion area.

[0116] The protective film 52 covers the independent electrode 31, common electrode 32, wiring 41, connecting electrode 42, and heating resistor 50, protecting them from wear, corrosion, oxidation, etc. The protective film 52 can be made of an insulating material, such as amorphous glass. The protective film 52 is formed by thick-film printing using glass paste, followed by sintering. The thickness dimension of the protective film 52 in the Z-direction is, for example, about 3 to 8 μm.

[0117] Additionally, a protective film 54 may be provided to cover the protective film 52 as needed. The protective film 54 is the outermost protective film that directly rubs against the printing medium; for example, a protective film with a hardness of approximately 1000–2000 HK, primarily composed of amorphous glass, sialon, silicon carbide, or silicon nitride, can be used. The thickness dimension of the protective film 54 in the Z-direction is, for example, 5–8 μm.

[0118] Here, the manufacturing method of the thermal printhead 100A of this embodiment will be described.

[0119] like Figures 4-6 As shown, a substrate 15 is first prepared, and a glass paste is applied to the substrate 15 by screen printing or the like. The applied glass paste is then dried, and a heat storage layer 33 is formed on the substrate 15 by heat treatment. The sintering process is performed, for example, at 850 to 1200°C for 1 to 5 hours.

[0120] Next, as Figures 7-9 As shown, multiple individual electrodes 31 and a common electrode 32 are formed on the heat storage layer 33. The common electrode 32 includes a comb-tooth portion 32A and a common portion 32B that connects the comb-tooth portions 32A together. Multiple slits 45 are provided on the common portion 32B. The individual electrodes 31 and the common electrode 32 can be obtained by forming an electrode pattern by coating the aforementioned metal paste using methods such as screen printing.

[0121] Next, as Figures 10-12 As shown, multiple wirings 41 are formed that contact multiple independent electrodes 31. The wirings 41 can be formed, for example, by using a photolithography process using metals such as gold or silver.

[0122] Next, as Figures 13-15 As shown, a connecting electrode 42 is formed that contacts the common electrode 32. The connecting electrode 42 is formed such that the slit 45 is located between the comb tooth portion 32A and the area on the common electrode 32 that contacts the connecting electrode 42. The connecting electrode 42 is obtained, for example, by forming an electrode pattern by coating a metal paste such as silver using a screen printing method.

[0123] Next, as Figures 16-18 As shown, a heating resistor 50 (heating resistor portion 51) is formed on the individual electrode 31 and the comb portion 32A of the common electrode 32 using a thick film forming technique. The heating resistor 50 is formed by supplying a resistor paste using screen printing or a dispenser and then sintering it. The resistor paste may contain, for example, ruthenium oxide.

[0124] Next, as Figures 19-21Protective films 52 and 54 are shown. Protective film 52 is made of, for example, amorphous glass. Protective film 52 is formed by thick-film printing using glass paste, followed by sintering. Protective film 54 can be made of, for example, the same amorphous glass as protective film 52, or silicon carbide formed by CVD (chemical vapor deposition).

[0125] The thermal printhead of this embodiment can be manufactured through the above steps.

[0126] In this embodiment, in the common electrode 32, which is in contact with the connecting electrode 42 and is made of a different material than the connecting electrode 42, a slit 45 is provided between the comb-tooth portion 32A of the common electrode 32 and the area on the common electrode 32 in contact with the connecting electrode 42. This reduces the area where the material of the connecting electrode 42 diffuses into the common electrode 32, and suppresses the diffusion area from reaching the comb-tooth portion 32A. Therefore, wire breakage in the comb-tooth portion 32A of the common electrode 32 can be suppressed.

[0127] (Other implementation methods)

[0128] The foregoing description of one embodiment is exemplary, but the description and drawings that form part of this disclosure are exemplary and should not be construed as limiting. Those skilled in the art will be able to identify various alternative embodiments, examples, and applications based on this disclosure. Therefore, this embodiment includes various embodiments not described herein.

[0129] For example, in thermal printhead 100B, which is a modified example 1 of thermal printhead 100A, such as Figure 22 As shown, in addition to the plurality of slits 45, a plurality of slits 45a are provided in the common portion 32B of the common electrode 32. Preferably, the width of each slit 45a is larger than the spacing between adjacent slits 45 in the main scanning direction X. Furthermore, it is preferable that one end of each slit 45a is located between the end of one of the adjacent slits 45 and the area on the common electrode 32 that contacts the connecting electrode 42, and the other end of each slit 45a is located between the end of another of the adjacent slits 45 and the area on the common electrode 32 that contacts the connecting electrode 42. By employing such a structure, even if the material of the connecting electrode 42 diffuses between adjacent slits 45a, the diffusion area can be reduced using the slits 45.

[0130] Furthermore, in the thermal printhead 100C, which is a modified example 2 of the thermal printhead 100A, such as Figure 23 As shown, the width of the slit 45 in the main scanning direction X can be increased.

[0131] Furthermore, in the thermal printhead 100D, which is a variation of the thermal printhead 100A, such as Figure 24As shown, one side of the slit 45 may not be parallel to the connecting surface between the comb tooth portion 32A and the common portion 32B. For example, a portion of the slit 45 may be configured such that the angle formed between one side of the slit 45 and the aforementioned connecting surface is 30° or more and 60° or less.

[0132] <Thermal Printer>

[0133] The thermal printhead of this embodiment (e.g., thermal printhead 100A) also... Figure 25 As shown, the system includes a substrate 15 (with a heat storage layer 33, individual electrodes 31, and a common electrode 32 on the substrate 15, etc., not shown), a connecting substrate 5, a heat dissipation component 8, a driver IC 7, multiple leads 81, a resin section 82, and a connector 59. The substrate 15 and the connecting substrate 5 are mounted adjacent to each other on the heat dissipation component 8 in the sub-scanning direction Y. Multiple heating resistor sections 51 arranged along the main scanning direction X are formed on the substrate 15. These heating resistor sections 51 are selectively heated by the driver IC 7 mounted on the connecting substrate 5. The heating resistor sections 51 are printed on a printing medium 92, such as thermal paper, pressed onto the heating resistor sections 51 by a paper pressure roller 91, according to a printing signal sent from the outside via the connector 59.

[0134] The connection substrate 5 can be, for example, a printed wiring board. The connection substrate 5 has a structure formed by laminating a substrate layer and a wiring layer (not shown). The substrate layer can be, for example, glass epoxy resin. The wiring layer can be, for example, metals such as copper, silver, palladium, iridium, platinum, and gold.

[0135] The heat dissipation component 8 has the function of releasing heat from the substrate 15. The substrate 15 and the connecting substrate 5 are mounted on the heat dissipation component 8. The heat dissipation component 8 can be made of a metal such as aluminum.

[0136] The leads 81 can be made of conductors such as gold. Multiple leads 81 are present, some of which are soldered to connect the driver IC7 to individual electrodes. Additionally, a portion of the other leads 81 are soldered to connect the driver IC7 to the connector 59 via a wiring layer in the connecting substrate 5.

[0137] The resin section 82 can be made of, for example, black resin. Epoxy resin, silicone resin, etc., can be used as the resin section 82. The resin section 82 covers the driver IC7 and the multiple leads 81, protecting the driver IC7 and the multiple leads 81. The connector 59 is fixed to the connection substrate 5. Wiring for supplying power to the thermal printhead from the outside and for controlling the driver IC7 are connected to the connector 59.

[0138] The thermal printer of this embodiment can have the aforementioned thermal printhead. The thermal printer prints on a printing medium that is conveyed along the sub-scanning direction Y. Typically, the printing medium is conveyed from the connector 59 side to the heating resistor 51 side. Examples of printing media include thermal paper used for making barcode labels or receipts.

[0139] A thermal printer includes, for example, a thermal printhead 100A, a paper pressure roller 91, a main power supply circuit, a measurement circuit, and a control unit. The paper pressure roller 91 is directly opposite the thermal printhead 100A.

[0140] The main power supply circuit supplies power to the multiple heating resistors 51 in the thermal printhead 100A. A measuring circuit measures the resistance value of each of the multiple heating resistors 51. The measuring circuit measures the resistance value of each of the multiple heating resistors 51, for example, when no printing is being performed on the printing media. This allows the lifespan of the heating resistors 51 to be determined and whether any heating resistors 51 have failed. A control unit controls the drive state of the main power supply circuit and the measuring circuit. The control unit controls the energizing state of each of the multiple heating resistors 51. The measuring circuit may sometimes be omitted.

[0141] Connector 59 is used for communication with devices other than the thermal printhead 100A. The thermal printhead 100A is electrically connected to the main power supply circuit and the measurement circuit via connector 59. The thermal printhead 100A is also electrically connected to the control unit via connector 59.

[0142] The driver IC7 receives a signal from the control unit via connector 59. Based on the signal received from the control unit, the driver IC7 controls the energizing state of each of the plurality of heating resistors 51. Specifically, the driver IC7 heats up any one of the plurality of heating resistors 51 by selectively energizing multiple independent electrodes.

[0143] Next, the usage of the thermal printer will be explained.

[0144] When printing on the printing medium, a potential v11 is applied from the main power circuit to the connector 59 as potential V1. In this case, the plurality of heating resistors 51 are selectively energized and heated. By transferring this heat to the printing medium, printing can be performed on the printing medium. As described above, when a potential v11 is applied from the main power circuit to the connector 59 as potential V1, a power supply path for each of the plurality of heating resistors 51 can be ensured.

[0145] When no printing is being performed on the printing medium, the resistance value of each heating resistor 51 is measured. During this measurement, no potential is applied from the main power circuit to the connector 59. When measuring the resistance value of each heating resistor 51, a potential v12 is applied from the measuring circuit to the connector 59 as potential V1. In this case, the multiple heating resistors 51 are energized sequentially (for example, starting from the heating resistor 51 located at the end in the main scanning direction X). The measuring circuit measures the resistance value of each heating resistor 51 based on the value of the current flowing in the heating resistor 51 and the potential v12. As described above, when a potential v11 is applied from the main power circuit to the connector 59 as potential V1, the power supply path to each of the multiple heating resistors 51 is essentially cut off. Therefore, the resistance value of each heating resistor 51 can be measured more accurately using the measuring circuit, and the lifespan of the heating resistor 51 and whether any heating resistor 51 has failed can be confirmed.

[0146] By employing this embodiment, a thermal printer with improved printing characteristics on the printing medium can be obtained.

[0147] This invention relates to the subject matter of Japanese Patent Application 2020-167733, filed on October 2, 2020, the entire disclosure of which is incorporated herein by reference.

Claims

1. A thermal printhead, characterized in that, include: Heat storage layer; The independent electrodes on the heat storage layer; A common electrode having comb-like teeth spaced apart from and opposite to the individual electrodes; The independent electrode and the heating resistor on the comb teeth; and A connecting electrode, which is made of a different material than the common electrode, and is in contact with the common electrode. In the common electrode, there is a slit between the comb teeth and the area on the common electrode that contacts the connecting electrode. The connecting electrode is positioned at a distance from the slit. There are multiple slits. One of the plurality of slits is a slit whose width in the main scanning direction is greater than the spacing between adjacent slits. One end of the slit, whose width in the main scanning direction is greater than the spacing between adjacent slits, is located between the end of one of the adjacent slits and the area on the common electrode that contacts the connecting electrode. The other end of the slit, whose width in the main scanning direction is greater than the spacing between adjacent slits, is located between the end of another slit in the adjacent slits and the area on the common electrode that contacts the connecting electrode.

2. The thermal printhead as described in claim 1, characterized in that: The common electrode contains gold. The connecting electrode contains silver.

3. The thermal printhead as described in claim 1 or 2, characterized in that: The width of the slit in the main scanning direction is greater than the width of the comb teeth in the main scanning direction.

4. The thermal printhead as described in claim 1 or 2, characterized in that: The width of the slit in the sub-scanning direction is 5 μm or more.

5. The thermal printhead as described in claim 1 or 2, characterized in that: The spacing between adjacent slits is greater than the width of the comb teeth in the main scanning direction.

6. The thermal printhead as described in claim 5, characterized in that: The adjacent slits are spaced at least 100 μm apart.

7. The thermal printhead as described in claim 1 or 2, characterized in that: It also includes wiring that contacts the individual electrodes. The connecting electrode is thicker than the wiring.

8. The thermal printhead as described in claim 1 or 2, characterized in that: The independent electrode is spaced apart from the comb portion in the main scanning direction.

9. A thermal printer, characterized in that, It has the thermal printhead as described in claim 1 or 2.

10. A method for manufacturing a thermal printhead, characterized in that: Forming a heat storage layer, Individual electrodes and a common electrode with comb-like teeth and slits are formed on the heat storage layer. Forming wiring that contacts the individual electrodes. A connection electrode is formed that contacts the common electrode. A heating resistor is formed on the individual electrode and the common electrode. The independent electrode is spaced apart from the comb teeth of the common electrode and is opposite to the comb teeth. The common electrode is made of a different material than the connecting electrode. The slit is located between the comb teeth and the area on the common electrode that contacts the connecting electrode. The connecting electrode is positioned at a distance from the slit. There are multiple slits. One of the plurality of slits is a slit whose width in the main scanning direction is greater than the spacing between adjacent slits. One end of the slit, whose width in the main scanning direction is greater than the spacing between adjacent slits, is located between the end of one of the adjacent slits and the area on the common electrode that contacts the connecting electrode. The other end of the slit, whose width in the main scanning direction is greater than the spacing between adjacent slits, is located between the end of another slit in the adjacent slits and the area on the common electrode that contacts the connecting electrode.

11. The method for manufacturing a thermal printhead as described in claim 10, characterized in that: The common electrode contains gold. The connecting electrode contains silver.

12. The method for manufacturing a thermal printhead as described in claim 10 or 11, characterized in that: The width of the slit in the main scanning direction is greater than the width of the comb teeth in the main scanning direction.

13. The method for manufacturing a thermal printhead as described in claim 10 or 11, characterized in that: The width of the slit in the sub-scanning direction is 5 μm or more.

14. The method for manufacturing a thermal printhead as described in claim 10 or 11, characterized in that: The spacing between adjacent slits is greater than the width of the comb teeth in the main scanning direction.

15. The method for manufacturing a thermal printhead as described in claim 14, characterized in that: The adjacent slits are spaced at least 100 μm apart.

16. The method for manufacturing a thermal printhead as described in claim 10 or 11, characterized in that: The connecting electrode is thicker than the wiring.

Images