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

Abstract

A thermal printhead that improves print characteristics on a print medium is provided. In addition, a manufacturing method of the thermal printhead is provided. Furthermore, a thermal printer including the thermal printhead is provided. The thermal printhead of the present invention includes a heat storage layer, a first electrode portion on the heat storage layer, a heat generating resistor on the first electrode portion, a second electrode portion on the heat generating resistor, and a protective film covering the second electrode portion and the heat generating resistor.

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 in 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] In the formation of common electrodes and independent electrodes, electrode patterns are formed by screen printing using pastes of metals such as gold or silver.

[0004] In recent years, traceability has been emphasized, and all information such as the manufacturer's unique mark, manufacturing date, and expiration date is recorded on printed media such as labels and receipts. Consequently, in the logistics field, such as the mandatory display of nutritional information and changes in allergy information, the amount of printed information and label printing has been increasing.

[0005] To enable high-volume printing, which tends to increase, thermal printheads need to print information onto the printing medium at high speed and with high precision. For high-speed and high-precision printing, it is important to distribute the heat generated by electricity evenly or to narrow the spacing between electrodes (equal to the spacing between the heating resistors). However, in the electrode formation process of thermal printheads capable of high-speed and high-precision printing, the higher density of electrode integration leads to more frequent short circuits or broken lines, potentially reducing printing characteristics such as printing efficiency on the printing medium.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent document 1: Japanese Patent Application Publication No. 2000-141729. Summary of the Invention

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

[0010] One embodiment of this invention provides a thermal printhead that improves printing characteristics for printing media. Another embodiment provides a method for manufacturing the thermal printhead. Furthermore, yet another embodiment provides a thermal printer including the thermal printhead.

[0011] Technical means for solving problems

[0012] This embodiment, by including electrodes above and below the heating resistor, enables the uniform distribution of generated heat or narrows the distance between the electrodes, thereby improving the printing characteristics for printing media. One aspect of this embodiment is described below.

[0013] One embodiment of this invention is a thermal printhead comprising: a heat storage layer; a first electrode portion on the heat storage layer; a heating resistor on the first electrode portion; a second electrode portion on the heating resistor; and a protective film covering the second electrode portion and the heating resistor.

[0014] Alternatively, another embodiment of this invention is a thermal printer that includes the thermal printhead described above.

[0015] Another embodiment of this invention is a method for manufacturing a thermal printhead, wherein a heat storage layer is formed, a plurality of first electrodes are formed on the heat storage layer, an insulating layer is formed covering a portion of each of the plurality of first electrodes, a heating resistor is formed covering the area of ​​the plurality of first electrodes not covered by the insulating layer, a plurality of second electrodes are formed on the heating resistor and the insulating layer, and a protective film is formed covering the plurality of second electrodes, the heating resistor and the insulating layer.

[0016] Another embodiment of this invention is a method for manufacturing a thermal printhead, wherein a heat storage layer is formed, a plurality of first electrodes are formed on the heat storage layer, a heating resistor is formed covering the plurality of first electrodes, a plurality of second electrodes and a plurality of third electrodes different from the second electrodes are formed on the heating resistor and the heat storage layer, and a protective film is formed covering the plurality of second electrodes, the plurality of third electrodes and the heating resistor, wherein the second electrodes and the third electrodes are alternately arranged.

[0017] Invention Effects

[0018] According to this embodiment, a thermal printhead with improved printing characteristics for printing media can be provided. Furthermore, a method for manufacturing this thermal printhead can be provided. Moreover, a thermal printer including this thermal printhead can be provided. Attached Figure Description

[0019] Figure 1 This is a partial perspective view illustrating the thermal printhead of Embodiment 1.

[0020] Figure 2 It is along the main scan direction X. Figure 1 A partial cross-sectional view of line A-A'.

[0021] Figure 3 It is along the Y direction of the sub-scanning direction Figure 1 A partial cross-sectional view of line B-B'.

[0022] Figure 4 This is a partial perspective view (1) illustrating the manufacturing method of the thermal printhead in Embodiment 1.

[0023] Figure 5 It is along the main scan direction X. Figure 4 A partial cross-sectional view of line A-A'.

[0024] Figure 6 It is along the Y direction of the sub-scanning direction Figure 4 A partial cross-sectional view of line B-B'.

[0025] Figure 7 This is a partial perspective view (2) illustrating the manufacturing method of the thermal printhead in Embodiment 1.

[0026] Figure 8 It is along the main scan direction X. Figure 7 A partial cross-sectional view of line A-A'.

[0027] Figure 9 It is along the Y direction of the sub-scanning direction Figure 7 A partial cross-sectional view of line B-B'.

[0028] Figure 10 This is a partial perspective view (3) illustrating the manufacturing method of the thermal printhead in Embodiment 1.

[0029] Figure 11 It is along the main scan direction X. Figure 10 A partial cross-sectional view of line A-A'.

[0030] Figure 12 It is along the Y direction of the sub-scanning direction Figure 10 A partial cross-sectional view of line B-B'.

[0031] Figure 13 This is a partial perspective view (4) illustrating the manufacturing method of the thermal printhead in Embodiment 1.

[0032] Figure 14 It is along the main scan direction X. Figure 13 A partial cross-sectional view of line A-A'.

[0033] Figure 15 It is along the Y direction of the sub-scanning direction Figure 13 A partial cross-sectional view of line B-B'.

[0034] Figure 16This is a partial perspective view (5) illustrating the manufacturing method of the thermal printhead in Embodiment 1.

[0035] Figure 17 It is along the main scan direction X. Figure 16 A partial cross-sectional view of line A-A'.

[0036] Figure 18 It is along the Y direction of the sub-scanning direction Figure 16 A partial cross-sectional view of line B-B'.

[0037] Figure 19 This is a partial perspective view illustrating the thermal printhead of Embodiment 2.

[0038] Figure 20 It is along the main scan direction X. Figure 19 A partial cross-sectional view of line A-A'.

[0039] Figure 21 It is along the Y direction of the sub-scanning direction Figure 19 A partial cross-sectional view of line B-B'.

[0040] Figure 22 This is a partial perspective view (1) illustrating the manufacturing method of the thermal printhead in Embodiment 2.

[0041] Figure 23 It is along the main scan direction X. Figure 22 A partial cross-sectional view of line A-A'.

[0042] Figure 24 It is along the Y direction of the sub-scanning direction Figure 22 A partial cross-sectional view of line B-B'.

[0043] Figure 25 This is a partial perspective view (2) illustrating the manufacturing method of the thermal printhead in Embodiment 2.

[0044] Figure 26 It is along the main scan direction X. Figure 25 A partial cross-sectional view of line A-A'.

[0045] Figure 27 It is along the Y direction of the sub-scanning direction Figure 25 A partial cross-sectional view of line B-B'.

[0046] Figure 28 This is a partial perspective view (3) illustrating the manufacturing method of the thermal printhead in Embodiment 2.

[0047] Figure 29 It is along the main scan direction X. Figure 28 A partial cross-sectional view of line A-A'.

[0048] Figure 30 It is along the Y direction of the sub-scanning direction Figure 28 A partial cross-sectional view of line B-B'.

[0049] Figure 31 This is a partial perspective view (4) illustrating the manufacturing method of the thermal printhead in Embodiment 2.

[0050] Figure 32 It is along the main scan direction X. Figure 31 A partial cross-sectional view of line A-A'.

[0051] Figure 33 It is along the Y direction of the sub-scanning direction Figure 31 A partial cross-sectional view of line B-B'.

[0052] Figure 34 This is a partial cross-sectional view of a modified example 1 of the thermal printhead of Embodiment 1 in the main scanning direction X.

[0053] Figure 35 This is a partial cross-sectional view of a modified example 2 of the thermal printhead of Embodiment 1 in the main scanning direction X.

[0054] Figure 36 This is a partial cross-sectional view of a modified example 3 of the thermal printhead of Embodiment 1 in the main scanning direction X.

[0055] Figure 37 This is a partial cross-sectional view of a modified example 1 of the thermal printhead in Embodiment 2 along the main scanning direction X.

[0056] Figure 38 This is a partial cross-sectional view of a modified example 2 of the thermal printhead in Embodiment 2 along the main scanning direction X.

[0057] Figure 39 This is a partial cross-sectional view of a modified example 3 of the thermal printhead of Embodiment 2 in the main scanning direction X.

[0058] Figure 40 This is a cross-sectional view illustrating the thermal printhead of this embodiment.

[0059] Explanation of reference numerals in the attached figures

[0060] 5 Connecting substrate

[0061] 7 Driver IC

[0062] 8 Heat dissipation components

[0063] 15 substrate

[0064] 30 Third electrode

[0065] 31 First Electrode

[0066] 32 Second electrode

[0067] 32A Comb teeth section

[0068] 32B Public Department

[0069] 33 Heat Storage Layer

[0070] 34 Protective film

[0071] 35 Insulation layer

[0072] 40 Heating resistor

[0073] 41 Heating resistor section

[0074] 59 Connector

[0075] 81 lead wire

[0076] 82 Resin Section

[0077] 91 Paper Press Roller

[0078] 92 Printing Media

[0079] 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H thermal printheads Detailed Implementation

[0080] 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.

[0081] Furthermore, the ordinal numbers such as "first," "second," and "third" used in this specification and other documents are used to avoid confusion of the constituent elements and are not limited to quantity.

[0082] 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.

[0083] One specific embodiment of this method is described below.

[0084] <1> A thermal printhead includes: a heat storage layer; a first electrode portion on the heat storage layer; a heating resistor on the first electrode portion; a second electrode portion on the heating resistor; and a protective film covering the second electrode portion and the heating resistor.

[0085] <2> The thermal printhead as described in <1>, wherein the first electrode portion has a plurality of first electrodes, the second electrode portion has a plurality of second electrodes, one of the plurality of first electrodes overlaps with one of the plurality of second electrodes, and also overlaps with another of the plurality of second electrodes.

[0086] <3> The thermal printhead as described in <2>, wherein, in the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.

[0087] <4> The thermal printhead as described in <2> or <3>, wherein, in the main scanning direction, the width of the region where one of the plurality of first electrodes overlaps with one of the plurality of second electrodes is the same as the width of the region where one of the plurality of first electrodes overlaps with another of the plurality of second electrodes.

[0088] <5> A thermal printhead as described in any one of <2> to <4>, wherein one of the first electrode and the second electrode is an independent electrode, and the other of the first electrode and the second electrode is a common electrode, wherein the plurality of first electrodes or the plurality of second electrodes serving as the common electrode each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

[0089] <6> A thermal printhead as described in any one of <2> to <5>, wherein it further comprises an insulating layer located between a portion of the first electrode portion and a portion of the second electrode portion, and at least one of the insulating layer and the heating resistor is disposed between the first electrode portion and the second electrode portion.

[0090] <7> The thermal printhead as described in <1>, wherein the first electrode portion has a plurality of first electrodes, the second electrode portion has a plurality of second electrodes and a plurality of third electrodes different from the second electrodes, and the second electrodes and the third electrodes are alternately arranged.

[0091] <8> The thermal printhead as described in <7>, wherein one of the plurality of first electrodes overlaps with one of the plurality of second electrodes and with one of the plurality of third electrodes.

[0092] <9> A thermal printhead as described in <7> or <8>, wherein, in the main scanning direction, the width of the first electrode is greater than the width of the second electrode and the width of the third electrode.

[0093] <10> A thermal printhead as described in any one of <7> to <9>, wherein one of the second electrode and the third electrode is an independent electrode, and the other of the second electrode and the third electrode is a common electrode, and the plurality of second electrodes or the plurality of third electrodes serving as the common electrode each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

[0094] <11> A thermal printer comprising any one of <1> to <10> thermal printheads.

[0095] <12> A method for manufacturing a thermal printhead, characterized in that a heat storage layer is formed, a plurality of first electrodes are formed on the heat storage layer, an insulating layer is formed covering a portion of each of the plurality of first electrodes, a heating resistor is formed covering the area of ​​the plurality of first electrodes not covered by the insulating layer, a plurality of second electrodes are formed on the heating resistor and the insulating layer, and a protective film is formed covering the plurality of second electrodes, the heating resistor and the insulating layer.

[0096] <13> The method for manufacturing a thermal printhead as described in <12>, wherein one of the first electrode and the second electrode is an independent electrode, and the other of the first electrode and the second electrode is a common electrode, wherein the plurality of first electrodes or the plurality of second electrodes serving as the common electrode each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

[0097] <14> A method for manufacturing a thermal printhead, wherein a heat storage layer is formed, a plurality of first electrodes are formed on the heat storage layer, a heating resistor is formed covering the plurality of first electrodes, a plurality of second electrodes and a plurality of third electrodes different from the second electrodes are formed on the heating resistor and the heat storage layer, and a protective film is formed covering the plurality of second electrodes, the plurality of third electrodes and the heating resistor, wherein the second electrodes and the third electrodes are alternately arranged.

[0098] <15> The method for manufacturing a thermal printhead as described in <14>, wherein one of the second electrode and the third electrode is an independent electrode, and the other of the second electrode and the third electrode is a common electrode, and the plurality of second electrodes or the plurality of third electrodes serving as the common electrode each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

[0099] <16> A method for manufacturing a thermal printhead as described in <12> or <13>, wherein one of the plurality of first electrodes overlaps with one of the plurality of second electrodes and with another of the plurality of second electrodes.

[0100] <17> A method for manufacturing a thermal printhead as described in any one of <12>, <13> and <16>, wherein, in the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.

[0101] <18> A method of manufacturing a thermal printhead as described in any one of <12>, <13>, <16> and <17>, wherein, in the main scanning direction, the width of the region where one of the plurality of first electrodes overlaps with one of the plurality of second electrodes and the width of the region where one of the plurality of first electrodes overlaps with another of the plurality of second electrodes are the same.

[0102] <19> A method for manufacturing a thermal printhead as described in <14> or <15>, wherein one of the plurality of first electrodes overlaps with one of the plurality of second electrodes and with one of the plurality of third electrodes.

[0103] <20> A method for manufacturing a thermal printhead as described in any one of <14>, <15> and <19>, wherein, in the main scanning direction, the width of the first electrode is greater than the width of the second electrode and the width of the third electrode.

[0104] <Thermal Printhead>

[0105] (Implementation Method 1)

[0106] The thermal printhead of this embodiment will be described using the accompanying drawings.

[0107] Figure 1 This is a partial 3D view of the thermal printhead. Figure 2 It is along the main scan direction X. Figure 1 A partial cross-sectional view of line A-A'. Figure 3 Along the Y direction of the sub-scan Figure 1 A partial cross-sectional view of line B-B'. Figures 1-3This refers to a portion of a thermal printhead (equivalent to one thermal printhead). In this embodiment, the single thermal printhead is defined as a monolithic thermal printhead 100A. The thermal printhead 100A includes at least a heat storage layer 33, a first electrode portion on the heat storage layer 33, a heating resistor 40 on the first electrode portion, a second electrode portion on the heating resistor 40, and a protective film 34 covering the second electrode portion and the heating resistor 40. Specifically, the thermal printhead 100A includes: a substrate 15; a heat storage layer 33 on the substrate 15; a plurality of first electrodes 31 included in the first electrode portion on the heat storage layer 33; an insulating layer 35 covering a portion of each of the plurality of first electrodes 31; a heating resistor 40 covering the area of ​​the plurality of first electrodes 31 not covered by the insulating layer 35; a plurality of second electrodes 32 included in the second electrode portion on the heating resistor 40 and the insulating layer 35; and a protective film 34 covering the plurality of second electrodes 32, the heating resistor 40, and the insulating layer 35. Furthermore, one of the first electrode 31 and the second electrode 32 is an independent electrode, and the other of the first electrode 31 and the second electrode 32 is a common electrode. For example, in this embodiment, the first electrode 31 is an independent electrode, and the other of the second electrodes 32 is a common electrode. The heating resistor 40 includes a plurality of heating resistor portions 41 that are heated by current flowing in the independent electrode and the common electrode. Each of the plurality of heating resistor portions 41 is independently formed between the first electrode 31 and the second electrode 32. Figure 1 Multiple heating resistor sections 41 are omitted. The multiple heating resistor sections 41 are arranged in a straight line on the heat storage layer 33. Furthermore, for ease of understanding, Figure 1 The protective film 34 was omitted.

[0108] In this embodiment, the direction in which the plurality of heating resistors 41 extend in a straight line is designated as the main scanning direction X, the direction perpendicular to the main scanning direction X and parallel to the upper surface of the substrate 15 is designated as the sub-scanning direction Y, and the direction corresponding to the thickness of the substrate 15 is designated as the thickness direction Z. In other words, the thickness direction Z is a direction perpendicular to both the main scanning direction X and the sub-scanning direction Y.

[0109] 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 relatively high thermal conductivity, is preferred for the substrate 15.

[0110] 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 41 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.

[0111] Multiple first electrodes 31, formed of metal paste, are disposed on the heat storage layer 33 as independent electrodes. The first electrodes 31 are obtained by coating the metal paste and forming an electrode pattern using a screen printing method or the like.

[0112] 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 metal properties and ionization tendency, copper, silver, platinum, and gold are preferred, and from the viewpoint of metal properties, ionization tendency, and cost reduction, copper and silver are 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 more of the following: ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, alicyclic solvents, aromatic solvents, alcohol solvents, and water, but are not limited to these.

[0113] Examples of ester solvents include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, and dimethyl carbonate. Examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanone. Examples of diol ether solvents include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, and acetate esters of these monoethers, 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.

[0114] 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 glycol ether solvents mentioned above) include ethanol, propanol, and butanol.

[0115] Metal pastes can contain dispersants, surface treatment agents, friction improvers, 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.

[0116] Each first electrode 31 is a strip extending approximately in the sub-scanning direction Y, and they are not electrically connected to each other. Therefore, when using a printer equipped with a thermal printhead, different potentials can be applied to each first electrode 31. A separate solder pad (not shown) is connected to the end of each first electrode 31. The separate solder pad is disposed separately from the heating resistor 40 and is not covered by the insulating layer 35.

[0117] The insulating layer 35 is provided in such a way that the first electrode 31 and the second electrode 32 do not directly contact each other. Furthermore, the insulating layer 35 does not completely cover each of the first electrodes 31, having a portion of each first electrode 31 that is not covered by the insulating layer 35. Each first electrode 31 contacts the heating resistor 40 through the portion not covered by the insulating layer 35. The insulating layer 35 is, for example, made of amorphous glass. The insulating layer 35 is formed by thick-film printing of a glass paste followed by firing.

[0118] The heating resistor 40 is partially heated by the current flowing through the individual electrodes and the common electrode. Specifically, the heating resistor 40 is selectively heated by applying a heating voltage individually according to a printing signal sent from the outside to the driver IC, etc. The heating resistor section 41 is selectively heated by being energized individually according to the printing signal. Print dots are formed by heating in this way. The heating resistor 40 uses a material with a higher resistivity than the material constituting the wiring, such as ruthenium oxide. The heating resistor 40 can be formed by screen printing or by firing a resistor paste supplied by a dispenser. In this embodiment, the dimension in the thickness direction Z of the heating resistor 40 is, for example, about 1 to 10 μm.

[0119] A plurality of second electrodes 32, formed of metal paste, serving as common electrodes, are provided on the heating resistor section 41 and the insulating layer 35. The second electrodes 32 are obtained by coating the metal paste and forming an electrode pattern using a method such as screen printing. The second electrodes 32 can be made of the same material as or different from the material described in the first electrode 31. For example, the first electrode 31 and the second electrode 32 can each be copper, the first electrode 31 can be copper, and the second electrode can be gold.

[0120] The second electrode 32, serving as a common electrode, is the portion whose polarity is opposite to that of the plurality of first electrodes 31 when the printer with the thermal printhead is used. The common electrode has a comb-tooth portion 32A and a common portion 32B that connects the comb-tooth portions 32A together. In this embodiment, the comb-tooth portion 32A and the common portion 32B are sometimes collectively referred to as the second electrode 32. The common portion 32B is formed along the upper edge of the substrate 15 in the main scanning direction X. Furthermore, in the sub-scanning direction Y, the direction in which the second electrode 32 is located when viewed from the first electrode 31 is set to the upper side of the sub-scanning direction Y. Each comb-tooth portion 32A is a strip extending in the sub-scanning direction Y. The front end of each comb-tooth portion 32A is located in the region between the front ends of two adjacent first electrodes 31, and is spaced apart from these two first electrodes 31 by a predetermined interval along the main scanning direction X.

[0121] The front end of each comb tooth portion 32A may also be spaced apart from the front end of each first electrode 31 along the sub-scanning direction Y. In this case, it is preferable to form the heating resistor portion 41 only in the region where the front end of the comb tooth portion 32A is opposite to the front end of the first electrode 31. In other words, it is preferable not to arrange the heating resistor portion 41 in the main scanning direction X, except in the region where the front end of the comb tooth portion 32A is opposite to the front end of the first electrode 31.

[0122] In this embodiment, one end of the first electrode 31 in the main scanning direction X overlaps with one of the two adjacent second electrodes 32, and the other end of the first electrode 31 overlaps with the other of the two adjacent second electrodes 32. By adopting such a structure, the spacing between the electrodes (equal to the spacing between the heating resistors) can be narrowed, thereby improving the printing characteristics for the printing medium.

[0123] Furthermore, in the main scanning direction X, if the width of the region overlapping with one of the two second electrodes 32 adjacent to the first electrode 31 and the width of the region overlapping with the other of the two second electrodes 32 adjacent to the first electrode 31 are the same, then the generated heat can be evenly distributed, which is preferable. Here, "same width" also includes the case where the difference between the two widths is less than 5% based on the larger of the two widths.

[0124] Multiple second electrodes 32, heating resistors 40, and insulating layers 35 are covered by a protective film 34, protecting them from wear, corrosion, oxidation, etc. The protective film 34 can be made of an insulating material, such as amorphous glass. The protective film 34 is formed by thick-film printing of a glass paste followed by firing. The thickness dimension of the protective film 34 in the Z-direction is, for example, approximately 3 to 8 μm.

[0125] Here, the manufacturing method of the thermal printhead 100A of this embodiment will be described.

[0126] like Figures 4-6 As shown, firstly, a substrate 15 is prepared, and a glass paste is applied to the substrate 15 by screen printing or the like. After the glass paste is dried, a heat treatment is performed to form a heat storage layer 33 on the substrate 15. The firing process is performed, for example, at 850 to 1200°C for 1 to 5 hours.

[0127] Next, as Figures 7-9 As shown, a plurality of first electrodes 31 are formed on the heat storage layer 33. The plurality of first electrodes 31 can be obtained by coating the metal paste using screen printing or the like and forming an electrode pattern.

[0128] Next, as Figures 10-12 As shown, an insulating layer 35 is formed covering a portion of each of the plurality of first electrodes 31. The insulating layer 35 does not completely cover each of the first electrodes 31, and there are areas of each of the first electrodes 31 that are not covered by the insulating layer 35. In this embodiment, the insulating layer 35 is in the shape of a strip extending generally in the main scanning direction X, and the central portion of each of the first electrodes 31 is the area that contacts the heating resistor 40 described later, and therefore is not covered by the insulating layer 35.

[0129] Next, as Figures 13-15 As shown, among the plurality of first electrodes 31, a heating resistor 40 (heating resistor section 41) is formed by a thick film forming technique to cover the area not covered by the insulating layer 35. The heating resistor 40 is formed by screen printing or firing a resistor paste supplied by a dispenser. The resistor paste contains, for example, ruthenium oxide.

[0130] By forming the insulating layer 35 and the heating resistor 40, the plurality of first electrodes 31 are completely covered. Additionally, individual solder pads (not shown) connected to the ends of each first electrode 31 are separately disposed from the heating resistor 40 and are not covered by the insulating layer 35. In this embodiment, the heating resistor 40 is formed to cover the areas not covered by the insulating layer 35 after the insulating layer 35 is formed. However, this is not a limitation; the insulating layer 35 covering the areas not covered by the heating resistor 40 may also be formed after the heating resistor 40 is formed at the central portion of each first electrode 31.

[0131] Next, as Figures 16-18 As shown, a plurality of second electrodes 32 are formed on the heating resistor 40 and the insulating layer 35. The second electrodes 32 are common electrodes, and the common electrodes have second electrodes 32 that serve as comb teeth 32A and a common portion 32B that connects the comb teeth 32A together. The second electrodes 32 can be obtained by coating the aforementioned metal paste and forming an electrode pattern using screen printing or the like.

[0132] In this embodiment, one end of the first electrode 31 in the main scanning direction X overlaps with one of the two adjacent second electrodes 32, and the other end of the first electrode 31 overlaps with the other of the two adjacent second electrodes 32. By adopting such a structure, the spacing between the electrodes (equal to the spacing between the heating resistors) can be narrowed, thereby improving the printing characteristics for the printing medium.

[0133] Next, as Figures 1 to 3 As shown, a protective film 34 is formed. The protective film 34 is, for example, made of amorphous glass. The protective film 34 is formed by printing a glass paste into a thick film and then firing it.

[0134] The thermal printhead of this embodiment can be manufactured through the above processes.

[0135] According to this embodiment, by making one end of the first electrode 31 overlap with one of the two adjacent second electrodes 32, and making the other end of the first electrode 31 overlap with the other of the two adjacent second electrodes 32, the spacing between the electrodes can be reduced, and the printing characteristics of the printing medium can be improved.

[0136] (Implementation Method 2)

[0137] The thermal printhead of this embodiment will be described using the accompanying drawings.

[0138] Figure 19 This is a partial 3D view of the thermal printhead. Figure 20 It is along the main scan direction X. Figure 19 A partial cross-sectional view of line A-A'. Figure 21 It is along the Y direction of the sub-scanning direction Figure 19 A partial cross-sectional view of line B-B'. Figures 19-21This refers to a portion of a thermal printhead (equivalent to one thermal printhead). In this embodiment, the single thermal printhead is designated as a monolithic thermal printhead 100B. The thermal printhead 100B includes at least a heat storage layer 33, a first electrode portion on the heat storage layer 33, a heating resistor 40 on the first electrode portion, a second electrode portion on the heating resistor 40, and a protective film 34 covering the second electrode portion and the heating resistor 40. Specifically, the thermal printhead 100B includes: a substrate 15; a heat storage layer 33 on the substrate 15; a plurality of third electrodes 30 included in the first electrode portion on the heat storage layer 33; heating resistors 40 respectively covering the plurality of third electrodes 30; a plurality of first electrodes 31 and a plurality of second electrodes 32 included in the second electrode portion on the heating resistor 40 and the heat storage layer 33; and a protective film 34 covering the plurality of first electrodes 31, the plurality of second electrodes 32, and the heating resistor 40. The first electrodes 31 and the second electrodes 32 are alternately arranged. In this embodiment, ordinal numbers such as "first," "second," and "third" are used to avoid confusion of the constituent elements, and there are cases where the ordinal numbers differ from those in the claims.

[0139] Furthermore, one of the first electrode 31 and the second electrode 32 is an independent electrode, and the other of the first electrode 31 and the second electrode 32 is a common electrode. In this embodiment, the first electrode 31 is an independent electrode, and the second electrode 32 is a common electrode. For example, in this embodiment, the first electrode 31 is an independent electrode, and the second electrode 32 is a common electrode. The heating resistor 40 includes a plurality of heating resistor portions 41 that are heated by current flowing in the independent electrode and the common electrode. Each of the plurality of heating resistor portions 41 is independently formed between the first electrode 31 and the second electrode 32. Figure 1 Multiple heating resistor sections 41 are omitted. The multiple heating resistor sections 41 are arranged in a straight line on the heat storage layer 33. Furthermore, for ease of understanding, Figure 19 The protective film 34 was omitted.

[0140] The substrate 15, the heating resistor 40 (heating resistor part 41) and the protective film 34 can be described using the description of Embodiment 1.

[0141] A plurality of third electrodes 30 formed of metal paste are disposed on the heat storage layer 33. The third electrodes 30 are obtained by coating the metal paste and forming an electrode pattern using a method such as screen printing. Alternatively, the third electrodes 30 can also be formed by a photolithography process. The third electrodes 30 can be made of the same material as the first electrode 31 described in Embodiment 1 or a different material.

[0142] In the third electrode 30, current flows from the common electrode through the heating resistor 40, and then from the third electrode 30 through the heating resistor 40 to the individual electrodes. By forming such a current path, the generated heat can be evenly distributed, thereby improving the printing characteristics of the printing medium.

[0143] A plurality of first electrodes 31 and a plurality of second electrodes 32 are provided on the heating resistor 40 and the heat storage layer 33. Except for the positions of the plurality of first electrodes 31 and the plurality of second electrodes 32, the description of Embodiment 1 can be referred to.

[0144] Here, the manufacturing method of the thermal printhead 100B of this embodiment will be described.

[0145] like Figures 22-24 As shown, first, a substrate 15 is prepared, and a glass paste is applied to the substrate 15 by screen printing or the like. After the glass paste is dried, a heat treatment is performed to form a heat storage layer 33 on the substrate 15. The firing process is, for example, performed at 1250°C for 4.5 hours.

[0146] Next, as Figures 25-27 As shown, a plurality of third electrodes 30 are formed on the heat storage layer 33. The plurality of third electrodes 30 can be obtained, for example, by forming an electrode pattern using a photolithography process.

[0147] Next, as Figures 28-30 As shown, heating resistors 40 (heating resistor sections 41) covering multiple third electrodes 30 are formed using a thick film forming technique. By forming the heating resistors 40, the multiple third electrodes 30 are completely covered. The heating resistors 40 are formed by firing a resistor paste supplied by screen printing or a dispenser. The resistor paste may contain, for example, ruthenium oxide.

[0148] Next, as Figures 31-33 As shown, a plurality of first electrodes 31 and a plurality of second electrodes 32 are formed on the heating resistor 40 and the heat storage layer 33. The second electrodes 32 are common electrodes, and the common electrodes have comb-tooth portions 32A and common portions 32B that connect the comb-tooth portions 32A together. In addition, the first electrodes 31 and the second electrodes 32 are arranged alternately. Furthermore, a third electrode 30 is disposed in the region between the first electrodes 31 and the second electrodes 32. The plurality of first electrodes 31 and the plurality of second electrodes 32 can be obtained by coating the aforementioned metal paste using screen printing or the like to form an electrode pattern.

[0149] In this embodiment, by forming a current path from the common electrode through the heating resistor 40 to the third electrode 30, and then from the third electrode 30 through the heating resistor 40 to the independent electrode, the generated heat can be evenly distributed, thereby improving the printing characteristics of the printing medium.

[0150] Next, as Figures 19 to 21 As shown, a protective film 34 is formed. The protective film 34 is, for example, made of amorphous glass. The protective film is formed by printing a glass paste into a thick film and then firing it.

[0151] The thermal printhead of this embodiment can be manufactured through the above processes.

[0152] According to this embodiment, by placing the third electrode 30 in a portion of the current path from the common electrode to the independent electrode, the generated heat can be evenly distributed, thereby improving the printing characteristics of the printing medium.

[0153] (Other implementation methods)

[0154] As described above, several embodiments have been described, but the discussions and drawings that form part of this disclosure are illustrative and should not be construed as limiting. Based on this disclosure, those skilled in the art will be able to identify various alternative embodiments, examples, and applications. Thus, this disclosure includes various embodiments not described herein.

[0155] For example, the thermal printhead 100C of variation 1 of embodiment 1 is as follows: Figure 34 As shown, in the main scanning direction X, the width of the first electrode 31 is smaller than the width of the second electrode 32. By employing this structure, when the first electrode 31 is an independent electrode, the smaller width of the independent electrode allows for a more concentrated current path from the common electrode to the independent electrode. This enables control over the distribution of generated heat, further improving the printing characteristics for the printing medium.

[0156] Furthermore, as a variation of the thermal printhead 100A in Embodiment 1, the thermal printhead 100D in Embodiment 2 is as follows: Figure 35 As shown, the first electrode 31 and the second electrode 32 can also be arranged so that they do not overlap.

[0157] In addition, such as Figure 36 As shown, the thermal printhead 100E, a variation of the thermal printhead 100A in Embodiment 1, can also be configured such that the second electrode 32 and the first electrode 31 completely overlap.

[0158] The thermal printhead 100F of Embodiment 2, a variation of the thermal printhead 100B, is as follows: Figure 37As shown, one end of the third electrode 30 in the main scanning direction X overlaps with one of the adjacent first electrode 31 and second electrode 32, and the other end of the third electrode 30 overlaps with the other of the adjacent first electrode 31 and second electrode 32. By adopting this structure, the distance between the third electrode 30 and the first electrode 31, and the distance between the third electrode 30 and the second electrode 32, can be shortened, thus shortening the current path in the heating resistor 40 and enabling control over the distribution of generated heat. This control further improves the printing characteristics for the printing medium.

[0159] Furthermore, as a variation of the thermal printhead 100B in Embodiment 2, the thermal printhead 100G is as follows: Figure 38 As shown, with Figure 37 In contrast, the third electrode 30 is finely segmented. This structure forms a current path from the common electrode through the heating resistor 40 to the third electrode 30, then from the third electrode 30 through the heating resistor 40 to other adjacent third electrodes 30, and further from the other adjacent third electrodes 30 through the heating resistor 40 to the individual electrodes. The current flowing from one third electrode 30 to the other adjacent third electrodes 30 through the heating resistor 40 also generates heat along this path, thus enabling a more uniform distribution of the generated heat and further improving the printing characteristics for the printing medium.

[0160] Furthermore, in variation 3 of embodiment 2, the thermal printhead 100H is as follows: Figure 39 As shown, in the main scanning direction, if the width of the third electrode 30 is greater than the width of the first electrode 31 and the width of the second electrode 32, the distance between the two ends of the third electrode 30 becomes larger, so the heat distribution near the two ends of the third electrode 30 can be more evenly dispersed, which can further improve the printing characteristics of the printing medium.

[0161] <Thermal Printer>

[0162] like Figure 40 As shown, the thermal printhead of this embodiment (e.g., thermal printhead 100A) also includes a substrate 15 (the heat storage layer 33, the first electrode layer, and the first electrode layer on the substrate 15 are not shown), a connecting substrate 5, a heat dissipation component 8, a driver IC 7, a plurality of leads 81, a resin portion 82, and a connector 59. The substrate 15 and the connecting substrate 5 are mounted on the heat dissipation component 8 adjacent to each other in the sub-scanning direction Y. A plurality of heating resistor portions 41 arranged in the main scanning direction X are formed on the substrate 15. The heating resistor portions 41 are selectively heated by the driver IC 7 mounted on the connecting substrate 5. The heating resistor portions 41 print on the printing medium 92, such as thermal paper, which is pressed against the heating resistor portions 41 by the paper pressure roller 91, according to the printing signal sent from the outside via the connector 59.

[0163] The connection substrate 5 can be, for example, a printed wiring substrate. The connection substrate 5 has a structure formed by stacking 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.

[0164] The heat dissipation component 8 has the function of dissipating 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 metal such as aluminum.

[0165] The leads 81 can be made of conductors such as gold. There are multiple leads 81, some of which are soldered to make the driver IC7 conductive to each individual electrode. In addition, some of the other leads 81 are soldered to make the driver IC7 conductive to the connector 59 via the wiring layer in the connecting substrate 5.

[0166] 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 and protects the driver IC7 and the multiple leads 81. The connector 59 is fixed to the connection substrate 5. The connector 59 is connected to wiring for supplying power to the thermal printhead from the outside of the thermal printhead and controlling the driver IC7.

[0167] The thermal printer of this embodiment can include the aforementioned thermal printhead. The thermal printer prints onto a printing medium conveyed along the sub-scanning direction Y. Typically, the printing medium is conveyed from the connector 59 side to the heating resistor 41 side. Examples of printing media include barcode sheets and thermal paper used for making receipts.

[0168] 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.

[0169] The main power supply circuit supplies power to the multiple heating resistors 41 in the thermal printhead 100A. A measuring circuit measures the resistance value of each of the multiple heating resistors 41. For example, the measuring circuit measures the resistance value of each of the multiple heating resistors 41 when no printing is being performed on the printing medium. This allows the lifespan of the heating resistors 41 to be determined and whether any heating resistors 41 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 41. Sometimes the measuring circuit is omitted.

[0170] 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.

[0171] 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 41. Specifically, the driver IC7 selectively energizes multiple independent electrodes, causing any one of the plurality of heating resistors 41 to heat up.

[0172] Next, the usage of the thermal printer will be explained.

[0173] 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 41 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 41 can be ensured.

[0174] When no printing is being performed on the printing medium, the resistance value of each heating resistor 41 is measured. During this measurement, no potential is applied from the main power supply circuit to the connector 59. When measuring the resistance value of each heating resistor 41, a potential v12 is applied from the measuring circuit to the connector 59 as potential V1. In this case, the multiple heating resistors 41 are energized sequentially (for example, starting from the heating resistor 41 located at the end in the main scanning direction X). The measuring circuit measures the resistance value of each heating resistor 41 based on the value of the current flowing through the heating resistor 41 and the potential v12. As described above, when a potential v11 is applied from the main power supply circuit to the connector 59 as potential V1, the power supply path to each of the multiple heating resistors 41 is essentially cut off. Therefore, the resistance value of each heating resistor 41 can be measured more accurately using the measuring circuit, and the lifespan of the heating resistor 41 and whether any heating resistor 41 has failed can be confirmed.

[0175] According to this embodiment, a thermal printer with improved printing characteristics for printing media can be obtained.

[0176] This invention relates to the subject matter of Japanese Patent Application No. 2020-167615, 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 first electrode portion on the heat storage layer; Heating resistor on the first electrode portion; The second electrode portion on the heating resistor; and A protective film covering the second electrode and the heating resistor. The first electrode section has a plurality of first electrodes. The second electrode section has a plurality of second electrodes. One of the plurality of first electrodes overlaps with one of the plurality of second electrodes, and also overlaps with another of the plurality of second electrodes. In the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.

2. The thermal printhead as described in claim 1, characterized in that: In the main scanning direction, the width of the region where one of the plurality of first electrodes overlaps with one of the plurality of second electrodes is the same as the width of the region where one of the plurality of first electrodes overlaps with another of the plurality of second electrodes.

3. The thermal printhead as described in claim 1 or 2, characterized in that: One of the first electrode and the second electrode is an independent electrode. The other of the first and second electrodes is a common electrode. The plurality of first electrodes or the plurality of second electrodes, which serve as the common electrode, each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

4. The thermal printhead as described in claim 1 or 2, characterized in that: It also has an insulating layer located between a portion of the first electrode portion and a portion of the second electrode portion. At least one of the insulating layer and the heating resistor is disposed between the first electrode portion and the second electrode portion.

5. A thermal printhead, characterized in that, include: Heat storage layer; The first electrode portion on the heat storage layer; Heating resistor on the first electrode portion; The second electrode portion on the heating resistor; and A protective film covering the second electrode and the heating resistor. The first electrode section has a plurality of first electrodes. The second electrode portion has a plurality of second electrodes and a plurality of third electrodes that are different from the second electrodes. The second electrode and the third electrode are arranged alternately. One of the second electrode and the third electrode is an independent electrode. The other of the second and third electrodes is a common electrode. The plurality of second electrodes or the plurality of third electrodes, which serve as the common electrode, each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

6. The thermal printhead as described in claim 5, characterized in that: One of the plurality of first electrodes overlaps with one of the plurality of second electrodes and with one of the plurality of third electrodes.

7. The thermal printhead as described in claim 5 or 6, characterized in that: In the main scanning direction, the width of the first electrode is greater than the width of the second electrode and the width of the third electrode.

8. A thermal printer, characterized in that: Includes the thermal printhead as described in claim 1 or 5.

9. A method for manufacturing a thermal printhead, characterized in that: Forming a heat storage layer, Multiple first electrodes are formed on the heat storage layer. An insulating layer is formed covering a portion of each of the plurality of first electrodes. A heating resistor is formed to cover the area of ​​the plurality of first electrodes that is not covered by the insulating layer. A plurality of second electrodes are formed on the heating resistor and the insulating layer. A protective film is formed covering the plurality of second electrodes, the heating resistor, and the insulating layer. One of the plurality of first electrodes overlaps with one of the plurality of second electrodes, and also overlaps with another of the plurality of second electrodes. In the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.

10. The method for manufacturing a thermal printhead as described in claim 9, characterized in that: One of the first electrode and the second electrode is an independent electrode. The other of the first and second electrodes is a common electrode. The plurality of first electrodes or the plurality of second electrodes, which serve as the common electrode, each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

11. A method for manufacturing a thermal printhead, characterized in that: Forming a heat storage layer, Multiple first electrodes are formed on the heat storage layer. A heating resistor is formed covering the plurality of first electrodes. A plurality of second electrodes and a plurality of third electrodes, different from the second electrodes, are formed on the heating resistor and the heat storage layer. A protective film is formed covering the plurality of second electrodes, the plurality of third electrodes, and the heating resistor. The second electrode and the third electrode are arranged alternately. One of the second electrode and the third electrode is an independent electrode. The other of the second and third electrodes is a common electrode. The plurality of second electrodes or the plurality of third electrodes, which serve as the common electrode, each have a comb-tooth portion and a common portion connected to the comb-tooth portion.

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