Thermal printhead, thermal printer, and method for manufacturing a thermal printhead

Abstract

To provide a thermal print head which secures the excellent printing efficiency in the time of printing, a thermal printer which includes the thermal print head, and a manufacturing method of the thermal print head which secures the excellent printing efficiency in the time of printing.SOLUTION: A thermal print head 100 comprises: a heat accumulation layer 33; a heating resistor 40 which is arranged on the heat accumulation layer 33; a common electrode 32 which is arranged on the heat accumulation layer 33 and has a comb tooth part 32A; and an individual electrode 31 which is arranged on the heat accumulation layer 33, is apart from the comb tooth part 32A of the common electrode 32 and is opposed to the comb tooth part 32A. In the thickness direction Z of the heat accumulation layer 33, the individual electrode 31 and the comb tooth part 32A each include a first film thickness part, and a second film thickness part whose film thickness is smaller than the first film thickness part. The heating resistor 40 is in contact with the second film thickness part of the individual electrode 31 and the second film thickness part of the comb tooth part 32A.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] This embodiment relates to a thermal print head, a thermal printer, and a method for manufacturing a thermal print head.

Background Art

[0002] A thermal print head includes, for example, a number of heating elements arranged in the main scanning direction on a head substrate. Each heating element is formed by laminating a glaze layer (also referred to as a heat storage layer), a common electrode, an individual electrode, and a resistor layer on the head substrate. By applying electricity between the common electrode and the individual electrode, the exposed portion (heating element) of the resistor layer generates heat due to Joule heat. By transferring this heat to a printing medium (such as thermal paper for creating a barcode sheet or receipt), printing on the printing medium is performed.

[0003] The common electrode and the individual electrode, etc., are formed into an electrode pattern by screen printing a paste using a metal such as gold or silver (a lithography process may further be performed). Also, wirings for supplying voltage from the outside to the common electrode and the individual electrode are in contact with the common electrode and the individual electrode, respectively. The wirings are formed by a lithography process using a metal such as gold or silver. Since gold is expensive, a technique using silver as a relatively inexpensive and good electrically conductive metal has been proposed from the viewpoint of reducing the cost of the product.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] One aspect of this embodiment aims to provide a thermal print head that ensures good printing efficiency during printing. Another aspect of this embodiment aims to provide a thermal printer equipped with the thermal print head. Yet another aspect of this embodiment aims to provide a method for manufacturing a thermal print head that ensures good printing efficiency during printing. [Means for solving the problem]

[0007] One aspect of this embodiment comprises a heat storage layer, a heat-generating resistor disposed on the heat storage layer, a common electrode disposed on the heat storage layer and having a comb-shaped portion, and individual electrodes disposed on the heat storage layer, spaced apart from the comb-shaped portion of the common electrode and facing the comb-shaped portion, wherein in the thickness direction of the heat storage layer, the individual electrodes and the comb-shaped portion each have a first film thickness portion and a second film thickness portion having a smaller film thickness than the first film thickness portion, and the heat-generating resistor is in contact with the second film thickness portion of the individual electrodes and the second film thickness portion of the comb-shaped portion. Furthermore, at the contact points between the heating resistor, the individual electrodes, and the comb teeth, the heating resistor is positioned on the individual electrodes and the comb teeth. It is a thermal printhead.

[0008] Another aspect of this embodiment is a thermal printer equipped with the thermal print head described above.

[0009] Another embodiment of this model is a heat storage layer, on which a common electrode having comb teeth and individual electrodes spaced apart from and facing the comb teeth are formed, each having a first film thickness portion and a second film thickness portion, and a heating resistor is formed on the comb teeth and the individual electrodes, wherein in the thickness direction of the heat storage layer, the film thickness of the second film thickness portion is smaller than the film thickness of the first film thickness portion, and the heating resistor is in contact with the second film thickness portion of the individual electrodes and the second film thickness portion of the comb teeth. The formation of the individual electrodes and the common electrode comprises the steps of forming a first electrode layer on the heat storage layer and forming a second electrode layer on the first electrode layer in the thickness direction of the heat storage layer, excluding the region overlapping with the heat-generating resistor, wherein the thickness of the first film portion is the sum of the thickness of the first electrode layer and the thickness of the second electrode layer, and the thickness of the second film portion is the thickness of the first electrode layer. This is a method for manufacturing thermal printheads.

[0010] Another aspect of this embodiment is a method for manufacturing a thermal print head, comprising: forming a heat storage layer; forming a heat-generating resistor on the heat storage layer; forming a common electrode having comb teeth and individual electrodes spaced apart from and facing the comb teeth on the heat storage layer and the heat-generating resistor, each having a first film thickness portion and a second film thickness portion; in the thickness direction of the heat storage layer, the film thickness of the second film thickness portion is smaller than the film thickness of the first film thickness portion; and the heat-generating resistor is in contact with the second film thickness portion of the individual electrodes and the second film thickness portion of the comb teeth. [Effects of the Invention]

[0011] According to this embodiment, it is possible to provide a thermal print head that ensures good printing efficiency during printing. Furthermore, it is possible to provide a thermal printer equipped with a thermal print head. Furthermore, it is possible to provide a method for manufacturing a thermal print head that ensures good printing efficiency during printing. [Brief explanation of the drawing]

[0012] [Figure 1A] Figure 1A is a partial perspective view illustrating the thermal print head according to this embodiment. [Figure 1B] Figure 1B is a partial cross-sectional view along the IB-IB line in Figure 1A. [Figure 1C] Figure 1C is a partial cross-sectional view along the IC-IC line in Figure 1A. [Figure 1D] FIG. 1D is a partial cross-sectional view taken along the ID-ID line of FIG. 1A. [Figure 2A] FIG. 2A is a partial perspective view (Part 1) for explaining a method of manufacturing a thermal print head according to the present embodiment. [Figure 2B] FIG. 2B is a partial cross-sectional view taken along the IIB-IIB line of FIG. 2A. [Figure 2C] FIG. 2C is a partial cross-sectional view taken along the IIC-IIC line of FIG. 2A. [Figure 2D] FIG. 2D is a partial cross-sectional view taken along the IID-IID line of FIG. 2A. [Figure 3A] FIG. 3A is a partial perspective view (Part 2) for explaining a method of manufacturing a thermal print head according to the present embodiment. [Figure 3B] FIG. 3B is a partial cross-sectional view taken along the IIIB-IIIB line of FIG. 3A. [Figure 3C] FIG. 3C is a partial cross-sectional view taken along the IIIC-IIIC line of FIG. 3A. [Figure 3D] FIG. 3D is a partial cross-sectional view taken along the IIID-IIID line of FIG. 3A. [Figure 4A] FIG. 4A is a partial perspective view (Part 3) for explaining a method of manufacturing a thermal print head according to the present embodiment. [Figure 4B] FIG. 4B is a partial cross-sectional view taken along the IVB-IVB line of FIG. 4A. [Figure 4C] FIG. 4C is a partial cross-sectional view taken along the IVC-IVC line of FIG. 4A. [[ID=D36]] [Figure 4D] FIG. 4D is a partial cross-sectional view taken along the IVD-IVD line of FIG. 4A. [Figure 5A] FIG. 5A is a partial perspective view (Part 4) for explaining a method of manufacturing a thermal print head according to the present embodiment. [Figure 5B] FIG. 5B is a partial cross-sectional view taken along the VB-VB line of FIG. 5A. [Figure 5C] FIG. 5C is a partial cross-sectional view taken along the VC-VC line of FIG. 5A. [Figure 5D] FIG. 5D is a partial cross-sectional view taken along the VD-VD line of FIG. 5A. [Figure 6A] FIG. 6A is a partial perspective view (part 5) for explaining a method of manufacturing a thermal print head according to the present embodiment. [Figure 6B] FIG. 6B is a partial cross-sectional view taken along line VIB-VIB of FIG. 6A. [Figure 6C] FIG. 6C is a partial cross-sectional view taken along line VIC-VIC of FIG. 6A. [Figure 6D] FIG. 6D is a partial cross-sectional view taken along line VID-VID of FIG. 6A. [Figure 7A] FIG. 7A is a partial perspective view for explaining a thermal print head according to a first modification. [Figure 7B] FIG. 7B is a partial cross-sectional view taken along line VIIB-VIIB of FIG. 7A. [Figure 7C] FIG. 7C is a partial cross-sectional view taken along line VIIC-VIIC of FIG. 7A. [Figure 7D] FIG. 7D is a partial cross-sectional view taken along line VIID-VIID of FIG. 7A. [Figure 8A] FIG. 8A is a partial perspective view for explaining a thermal print head according to a second modification. [Figure 8B] FIG. 8B is a partial cross-sectional view taken along line VIIIB-VIIIB of FIG. 8A. [Figure 8C] FIG. 8C is a partial cross-sectional view taken along line VIIIC-VIIIC of FIG. 8A. [Figure 8D] FIG. 8D is a partial cross-sectional view taken along line VIIID-VIIID of FIG. 8A. [Figure 9A] FIG. 9A is a partial perspective view (part 1) for explaining a method of manufacturing a thermal print head according to the second modification. [Figure 9B] FIG. 9B is a partial cross-sectional view taken along line IXB-IXB of FIG. 9A. [Figure 9C] FIG. 9C is a partial cross-sectional view taken along line IXC-IXC of FIG. 9A. [Figure 9D] FIG. 9D is a partial cross-sectional view taken along line IXD-IXD of FIG. 9A. [Figure 10A]Figure 10A is a partial perspective view illustrating a second modified example of a thermal printhead manufacturing method (part 2). [Figure 10B] Figure 10B is a partial cross-sectional view along the line XB-XB in Figure 10A. [Figure 10C] Figure 10C is a partial cross-sectional view along the line XC-XC in Figure 10A. [Figure 10D] Figure 10D is a partial cross-sectional view along the line XD-XD in Figure 10A. [Figure 11A] Figure 11A is a partial perspective view illustrating a method for manufacturing a thermal print head according to a second modified example (part 3). [Figure 11B] Figure 11B is a partial cross-sectional view along the line XIB-XIB in Figure 11A. [Figure 11C] Figure 11C is a partial cross-sectional view along the XIC-XIC line in Figure 11A. [Figure 11D] Figure 11D is a partial cross-sectional view along the XID-XID line in Figure 11A. [Figure 12A] Figure 12A is a partial perspective view illustrating a second modified example of a thermal printhead manufacturing method (part 4). [Figure 12B] Figure 12B is a partial cross-sectional view along the line XIIB-XIIB in Figure 12A. [Figure 12C] Figure 12C is a partial cross-sectional view along the XIIC-XIIC line in Figure 12A. [Figure 12D] Figure 12D is a partial cross-sectional view along the XIID-XIID line in Figure 12A. [Figure 13A] Figure 13A is a partial perspective view illustrating a thermal print head relating to a third modified example. [Figure 13B] Figure 13B is a partial cross-sectional view along the line XIIIB-XIIIB in Figure 13A. [Figure 13C] Figure 13C is a partial cross-sectional view along the line XIIIC-XIIIC in Figure 13A. [Figure 13D] Figure 13D is a partial cross-sectional view along the line XIIID-XIIID in Figure 13A. [Figure 14]Figure 14 is a cross-sectional view illustrating a thermal printhead. [Modes for carrying out the invention]

[0013] Next, this embodiment will be described with reference to the drawings. In the drawings described below, identical or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and planar dimensions of each component may differ from reality. Therefore, specific thicknesses and dimensions should be determined by referring to the following explanation. Furthermore, it goes without saying that there are parts in the drawings where the relationships and ratios of dimensions differ from those of other parts.

[0014] Furthermore, the embodiments described below are illustrative examples of devices and methods for realizing the technical concept, and do not specify the material, shape, structure, arrangement, etc., of each component. Various modifications can be made to these embodiments within the scope of the claims.

[0015] One specific embodiment of this model is as follows:

[0016] <1> A thermal print head comprising: a heat storage layer; a heat-generating resistor disposed on the heat storage layer; a common electrode disposed on the heat storage layer and having comb teeth; and individual electrodes disposed on the heat storage layer, spaced apart from the comb teeth of the common electrode and facing the comb teeth, wherein in the thickness direction of the heat storage layer, the individual electrodes and the comb teeth each have a first film thickness portion and a second film thickness portion having a smaller film thickness than the first film thickness portion, and the heat-generating resistor is in contact with the second film thickness portion of the individual electrodes and the second film thickness portion of the comb teeth.

[0017] <2> At the contact points between the heating resistor, the individual electrodes, and the comb teeth, the heating resistor is positioned on the individual electrodes and the comb teeth. <1> The thermal print head described above.

[0018] <3> At the contact points between the heating resistor, the individual electrodes, and the comb teeth, the individual electrodes and the common electrode are arranged on the heating resistor. <1> The thermal print head described above.

[0019] <1> ~ <3> According to this method, disconnection due to metal aggregation in the metal paste can be suppressed during the formation (firing) of individual and common electrodes. Furthermore, the resistance of the individual and common electrodes can be reduced. In addition, because the film thickness of the individual and common electrodes in the region overlapping with the heating resistor is small, heat conduction from the heating resistor to the individual and common electrodes can be reduced, thereby suppressing the increase in energy required to raise the heating resistor to a predetermined temperature. As a result, good printing efficiency can be ensured.

[0020] <4> The common electrode further has a common portion connected to the comb teeth portion, and the film thickness of the common portion is the same as the film thickness of the first film portion. <1> ~ <3> A thermal print head as described in any one of the following items.

[0021] <4> According to this method, the resistance of the common section can be reduced, and furthermore, wire breakage due to metal aggregation can be suppressed.

[0022] <5> The material of the individual electrodes and the material of the common electrode include silver or gold. <1> ~ <4> A thermal print head as described in any one of the following items.

[0023] <5> According to this method, individual electrodes and a common electrode with good metallic properties and ionization tendency can be obtained.

[0024] <6> The present invention further comprises a substrate on which the heat storage layer is disposed on the upper surface, and the substrate is made of ceramic. <1> ~ <5> A thermal print head as described in any one of the following items.

[0025] <6> According to this, a substrate with excellent heat dissipation properties can be used with the thermal print head.

[0026] <7> <1> ~ <6> A thermal printer equipped with a thermal print head as described in any one of the items.

[0027] <7> According to this, a thermal printer with good printing efficiency can be obtained.

[0028] <8> A method for manufacturing a thermal print head, comprising: forming a heat storage layer; forming a common electrode having comb teeth and individual electrodes spaced apart from and facing the comb teeth, each having a first film thickness portion and a second film thickness portion; forming a heating resistor on the comb teeth and on the individual electrodes; in the thickness direction of the heat storage layer, the film thickness of the second film thickness portion is smaller than the film thickness of the first film thickness portion; and the heating resistor is in contact with the second film thickness portion of the individual electrodes and the second film thickness portion of the comb teeth.

[0029] <9> The formation of the individual electrodes and the common electrode comprises the steps of forming a first electrode layer on the heat storage layer and forming a second electrode layer on the first electrode layer in the thickness direction of the heat storage layer, excluding the region overlapping with the heat-generating resistor, wherein the thickness of the first film portion is the sum of the thickness of the first electrode layer and the thickness of the second electrode layer, and the thickness of the second film portion is the thickness of the first electrode layer. <8> A method for manufacturing a thermal printhead as described above.

[0030] <10> The formation of the individual electrodes and the common electrode comprises the steps of forming a first electrode layer on the heat storage layer in the thickness direction of the heat storage layer, excluding the region overlapping with the heat-generating resistor, and forming a second electrode layer on the first electrode layer and on the region of the heat storage layer overlapping with the heat-generating resistor, wherein the thickness of the first thickness portion is the sum of the thickness of the first electrode layer and the thickness of the second electrode layer, and the thickness of the second thickness portion is the thickness of the second electrode layer. <8> A method for manufacturing a thermal printhead as described above.

[0031] <11> A method for manufacturing a thermal print head, comprising: forming a heat storage layer; forming a heat-generating resistor on the heat storage layer; forming a common electrode having comb teeth and individual electrodes spaced apart from and facing the comb teeth on the heat storage layer and the heat-generating resistor, each having a first film thickness portion and a second film thickness portion; in the thickness direction of the heat storage layer, the film thickness of the second film thickness portion is smaller than the film thickness of the first film thickness portion; and the heat-generating resistor is in contact with the second film thickness portion of the individual electrodes and the second film thickness portion of the comb teeth.

[0032] <12> The formation of the individual electrodes and the common electrode comprises the steps of forming a first electrode layer on the heat storage layer in the thickness direction of the heat storage layer, excluding the region overlapping with the heat-generating resistor, and forming a second electrode layer on the first electrode layer and on the heat-generating resistor, wherein the thickness of the first thickened portion is the sum of the thickness of the first electrode layer and the thickness of the second electrode layer, and the thickness of the second thickened portion is the thickness of the second electrode layer. <11> A method for manufacturing a thermal printhead as described above.

[0033] <13> The formation of the individual electrodes and the common electrode comprises the steps of forming a first electrode layer on the heat storage layer and the heat-generating resistor, and forming a second electrode layer on the first electrode layer in the thickness direction of the heat storage layer, excluding the region overlapping with the heat-generating resistor, wherein the thickness of the first film portion is the sum of the thickness of the first electrode layer and the thickness of the second electrode layer, and the thickness of the second film portion is the thickness of the first electrode layer. <11> A method for manufacturing a thermal printhead as described above.

[0034] <8> ~ <13> According to this method, disconnection due to metal aggregation in the metal paste can be suppressed during the formation (firing) of individual and common electrodes. Furthermore, the resistance of the individual and common electrodes can be reduced. In addition, because the film thickness of the individual and common electrodes in the region overlapping with the heating resistor is small, heat conduction from the heating resistor to the individual and common electrodes can be reduced, thereby suppressing the increase in energy required to raise the heating resistor to a predetermined temperature. As a result, good printing efficiency can be ensured.

[0035] <Thermal Print Head> A thermal print head 100 according to this embodiment will be described with reference to the drawings.

[0036] Figure 1A is a partial perspective view showing the thermal print head 100. Figure 1B is a partial cross-sectional view along the IB-IB line in Figure 1A. Figure 1C is a partial cross-sectional view along the IC-IC line in Figure 1A. Figure 1D is a partial cross-sectional view along the ID-ID line in Figure 1A. Figures 1A to 1D show a part of a thermal printer equipped with multiple thermal print heads (corresponding to one thermal print head), and in this embodiment, this one thermal print head is a piece-shaped thermal print head 100. The thermal print head 100 comprises an insulating substrate 15, a heat storage layer 33 on the substrate 15, a common electrode 32 disposed on the heat storage layer 33 and having a comb-toothed portion 32A, individual electrodes 31 disposed on the heat storage layer 33, spaced apart from the comb-toothed portion 32A of the common electrode 32 and facing the comb-toothed portion 32A, a heating resistor 40 on the heat storage layer 33, the individual electrodes 31, and the common electrode 32, and a protective film 34 covering the individual electrodes 31, the common electrode 32, and the heating resistor 40. Figure 1A omits the illustration of the protective film 34 for ease of understanding.

[0037] Each individual electrode 31 has a first electrode layer 31a and a second electrode layer 31b on the first electrode layer 31a in the thickness direction Z (described later), excluding the region that overlaps with the heat-generating resistor 40. The common electrode 32 has a first electrode layer 32a and a second electrode layer 32b on the first electrode layer 32a in the thickness direction Z, excluding the region that overlaps with the heat-generating resistor 40. In this embodiment, the portion of the heat storage layer 33 in the thickness direction Z where the first electrode layer 31a and the second electrode layer 31b are stacked is defined as the first thickness portion of the individual electrode 31, and the portion consisting only of the first electrode layer 31a is defined as the second thickness portion of the individual electrode 31. Furthermore, in this embodiment, the portion of the heat storage layer 33 in the thickness direction Z where the first electrode layer 32a and the second electrode layer 32b are stacked is defined as the first thickness portion of the common electrode 32 (including the comb-tooth portion 32A, etc.), and the portion consisting only of the first electrode layer 32a is defined as the second thickness portion of the common electrode 32. In other words, in the individual electrode 31, the thickness of the second thickness portion is smaller than that of the first thickness portion, and in the common electrode 32, the thickness of the second thickness portion is smaller than that of the first thickness portion. The heating resistor 40 is in contact with the second thickness portion of the individual electrode 31 and the second thickness portion of the comb-tooth portion 32A, which is part of the common electrode 32.

[0038] The heating resistor 40 includes a plurality of heating resistors 41 that generate heat due to the current flowing through the individual electrodes 31 and the common electrode 32. Each heating resistor 41 is formed independently between the individual electrodes 31 and the common electrode 32. Figure 1A omits the illustration of the plurality of heating resistors 41. The plurality of heating resistors 41 are arranged linearly on the heat storage layer 33.

[0039] The heating resistor 40 is electrically connected to the individual electrodes 31 and the common electrode 32, and heat is generated in the portion through which current flows from the individual electrodes 31 and the common electrode 32. Specifically, the heating resistor 40 (heating resistor section 41) is selectively heated by individually applying a heating voltage according to a printing signal transmitted from an external drive IC or the like. The heating resistor section 41 is selectively heated by being individually energized according to the printing signal. Printed dots are formed by this heating. At the contact points between the heating resistor 40 and the individual electrodes 31 and the common electrode 32 (comb tooth section 32A), the heating resistor 40 is positioned on the individual electrodes 31 and the common electrode 32 (comb tooth section 32A). The heating resistor 40 can be made of a material with a higher resistivity than the materials constituting the individual electrodes 31 and the common electrode 32, such as ruthenium oxide.

[0040] In this embodiment, the direction in which the heating resistor 40 extends linearly is defined 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 defined as the sub-scanning direction Y, and the direction corresponding to the thickness of the substrate 15 is defined as the thickness direction Z. In other words, the thickness direction Z is perpendicular to both the main scanning direction X and the sub-scanning direction Y. Furthermore, the direction in which the heat storage layer 33 is located relative to the substrate 15 is defined as the upward direction, and the direction in which the substrate 15 is located relative to the heat storage layer 33 is defined as the downward direction.

[0041] Furthermore, in this specification, "electrically connected" includes cases where connections are made via "something that has some kind of electrical function." Here, "something that has some kind of electrical function" is not particularly limited as long as it enables the exchange of electrical signals between the connected objects. For example, "something that has some kind of electrical function" includes electrodes, wiring, switching elements, resistive elements, inductors, capacitive elements, and other elements with various functions.

[0042] The substrate 15 is an insulator and is made of, for example, ceramic or single-crystal semiconductor. As a ceramic, alumina can be used, for example. As a single-crystal semiconductor substrate, a silicon substrate can be used, for example. From the viewpoint of heat dissipation, it is preferable to use alumina, which has a relatively high thermal conductivity, for the substrate 15.

[0043] A heat storage layer 33 (also called a glaze layer) having the function of accumulating heat is laminated on the substrate 15. The heat storage layer 33 stores the heat generated from the heat-generating resistance section 41, which will be described later. The heat storage layer 33 can be made of an insulating material, for example, silicon oxide or silicon nitride, which are the main components of glass, can be used for the heat storage layer 33. The dimensions of the heat storage layer 33 in the thickness direction Z are not particularly limited, and are, for example, 5 to 200 μm, preferably 10 to 30 μm.

[0044] Individual electrodes 31 and a common electrode 32, formed from metal paste, are provided on the heat storage layer 33. The individual electrodes 31 and the common electrode 32 are obtained by applying the metal paste, which is the material for the individual electrodes 31 and the common electrode 32, to the heat storage layer 33 by screen printing or the like, and then firing it to form an electrode pattern. Alternatively, the individual electrodes 31 and the common electrode 32 may be formed by performing a lithography process in addition to screen printing.

[0045] As the metal paste, for example, a paste containing metal particles such as copper, silver, palladium, iridium, platinum, and gold can be used. Organometallic compounds can also be used as the metal paste. From the viewpoint of metal properties and ionization tendency, silver and gold are preferred, and from the viewpoint of metal properties, ionization tendency, and cost reduction, silver is more preferred. The solvent contained in the metal paste has the function of uniformly dispersing the metal particles, and examples include, but are not limited to, ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, alicyclic solvents, aromatic solvents, alcohol solvents, and mixtures of one or more of these.

[0046] 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 ketonebenzene, diisobutyl ketone, diacetone alcohol, isophorone, and cyclohexanenone. Examples of glycol ether solvents include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, acetate esters of these monoethers, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and acetate esters of these monoethers.

[0047] 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 tetralin. Examples of alcoholic solvents (excluding the glycol ether solvents mentioned above) include ethanol, propanol, and butanol.

[0048] The metal paste may contain, as needed, dispersants, surface treatment agents, friction enhancers, infrared absorbers, ultraviolet absorbers, fragrances, antioxidants, organic pigments, inorganic pigments, defoamers, silane coupling agents, titanate coupling agents, plasticizers, flame retardants, humectants, ion scavengers, etc.

[0049] Each individual electrode 31 has a first electrode layer 31a and a second electrode layer 31b. The common electrode 32 has a first electrode layer 32a and a second electrode layer 32b. The first electrode layers 31a and 32a are preferably formed using a paste containing metal particles with smaller particle sizes than the second electrode layers 31b and 32b, for example, preferably from a silver-containing resinate paste. The dimensions of the first electrode layers 31a and 32a in the thickness direction Z are not particularly limited, for example, 1 to 3 μm, and preferably 1.5 to 2.5 μm.

[0050] The second electrode layer 31b is positioned on a portion of the first electrode layer 31a, specifically on the portion of the first electrode layer 31a that does not overlap with the heat-generating resistor 40 described later, in the thickness direction Z. The second electrode layer 32b is positioned on a portion of the first electrode layer 32a, specifically on the portion of the first electrode layer 32a that does not overlap with the heat-generating resistor 40 described later, in the thickness direction Z. The second electrode layers 31b and 32b are preferably formed using a paste containing metal particles with a particle size larger than the metal particles contained in the paste used to form the first electrode layers 31a and 32a, for example, preferably formed from a resinate paste containing silver particles. The dimensions of the second electrode layers 31b and 32b in the thickness direction Z are not particularly limited, and are, for example, 1 to 5 μm, preferably 2 to 4 μm.

[0051] The metal particles contained in the paste used to form the first electrode layer 31a and the first electrode layer 32a have a smaller particle size than the metal particles contained in the paste used to form the second electrode layer 31b and the second electrode layer 32b. Therefore, the average surface roughness of the first electrode layer 31a and the first electrode layer 32a is smaller than the average surface roughness of the second electrode layer 31b and the second electrode layer 32b. The average surface roughness can be determined, for example, in accordance with JIS B 0601:2013 or ISO 25178.

[0052] It is preferable to place the electrode layer with a large average surface roughness on the upper side that comes into contact with the wire, etc., because this improves bonding characteristics such as adhesion. Specifically, by placing the second electrode layer 31b and the second electrode layer 32b, which have relatively large average surface roughness, on the first electrode layer 31a and the first electrode layer 32a, respectively, on the first electrode layer 31a and the first electrode layer 32a, which have relatively small average surface roughness, the contact between the wire and the second electrode layer 31b or the second electrode layer 32b in the individual pad portions (not shown) becomes wider, resulting in improved bonding characteristics.

[0053] In the individual electrode 31, the thickness of the first film layer is the sum of the thickness of the first electrode layer 31a and the thickness of the second electrode layer 31b, and the thickness of the second film layer is the thickness of the first electrode layer 31a. In the common electrode 32, the thickness of the first film layer is the sum of the thickness of the first electrode layer 32a and the thickness of the second electrode layer 32b, and the thickness of the second film layer is the thickness of the first electrode layer 32a. If the first electrode layer 31a (or first electrode layer 32a) and the second electrode layer 31b (or second electrode layer 32b) are made of the same material and it is difficult to distinguish the boundary between them, the interface between the first electrode layer 31a (or first electrode layer 32a) and the second electrode layer 31b (or second electrode layer 32b) is defined as the portion of the first electrode layer 31a (or first electrode layer 32a) that is separated from the upper surface of the second electrode layer 31b (or second electrode layer 32b) by the thickness of the first electrode layer 31a (or first electrode layer 32a).

[0054] Since the first film thickness of the individual electrode 31 is greater than the second film thickness of the individual electrode 31, and the first film thickness of the common electrode 32 is greater than the second film thickness of the common electrode 32, wire breakage due to aggregation of metal contained in the metal paste can be suppressed during the formation (firing) of the individual electrode 31 and the common electrode 32. Furthermore, the resistance of the individual electrode 31 and the common electrode 32 can be reduced. The second film thickness of the individual electrode 31 and the second film thickness of the common electrode 32, which are regions that overlap with the heat-generating resistor 40 described later, are thinner than the first film thickness of the individual electrode 31 and the first film thickness of the common electrode 32, respectively. Therefore, heat conduction from the heat-generating resistor 40 to the individual electrode 31 and the common electrode 32 can be reduced, and the increase in energy required to raise the heat-generating resistor 40 to a predetermined temperature can be suppressed. As a result, good printing efficiency can be ensured.

[0055] Each individual electrode 31 is generally strip-shaped and extends in the sub-scanning direction Y, and they are not electrically connected to each other. Therefore, when a printer with a thermal print head is used, each individual electrode 31 may be individually assigned a different potential to it. Individual pad portions (not shown) are connected to the ends of each individual electrode 31.

[0056] The common electrode 32 is a portion that has the opposite electrical polarity to the multiple individual electrodes 31 when a printer incorporating a thermal print head is used. The common electrode 32 has a comb-tooth portion 32A and a common portion 32B connected to the comb-tooth portion 32A. 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 portion 32B of the common electrode 32 is located, as viewed from the individual electrodes 31, is defined as the upper side of the sub-scanning direction Y. Each comb-tooth portion 32A is strip-shaped and extends in the sub-scanning direction Y. The tip of each comb-tooth portion 32A is positioned opposite the tip of each individual electrode 31 at a predetermined distance along the sub-scanning direction Y. This configuration allows the pitch of the heating resistor 40 to be narrowed, enabling high-resolution printing.

[0057] The heat-generating resistor 40 can be formed by firing a resistor paste. In this embodiment, the dimension of the heat-generating resistor 40 in the thickness direction Z is, for example, about 1 to 10 μm.

[0058] The heat-generating resistor 40 and the like are covered with a protective film 34, which protects the heat-generating resistor 40 and the like from wear, corrosion, oxidation, etc. The protective film 34 can be made of an insulating material, for example, amorphous glass. The protective film 34 is formed by printing a glass paste in a thick film and then firing it. The dimension of the protective film 34 in the thickness direction Z is, for example, about 2 to 8 μm. A thickness within this range is preferable because it can suppress pressure resistance failure and maintain good print quality, thus providing a thermal print head 100.

[0059] Here, we will describe the manufacturing method of the thermal print head 100 of this embodiment.

[0060] As shown in Figures 2A to 2D, first, a substrate 15 is prepared, and a heat storage layer 33 is formed on the substrate 15.

[0061] The heat storage layer 33 can be formed, for example, by applying glass paste to the substrate 15 by screen printing or the like, drying the applied glass paste, and then performing a firing process. The firing process is performed, for example, at 800 to 1200°C for 10 minutes to 1 hour. The dimension of the heat storage layer 33 in the thickness direction Z is, for example, 25 μm.

[0062] Next, as shown in Figures 3A to 3D, the first electrode layer 31a of the individual electrodes 31 and the first electrode layer 32a of the common electrode 32 are formed on the heat storage layer 33. The first electrode layers 31a and 32a are obtained by applying the aforementioned relatively small particle size metal paste to the heat storage layer 33 by screen printing or the like, then firing it, and performing a lithography process. The dimensions of the first electrode layers 31a and 32a in the thickness direction Z are, for example, 1 to 3 μm.

[0063] Next, as shown in Figures 4A to 4D, a second electrode layer 31b is formed on the first electrode layer 31a, excluding the region that will overlap with the later-formed heat-generating resistor 40, and a second electrode layer 32b is formed on the first electrode layer 32a, excluding the region that will overlap with the heat-generating resistor 40. The second electrode layers 31b and 32b are obtained by applying a paste containing metal particles with a larger particle size than the metal particles contained in the paste used to form the first electrode layers 31a and 32a to the first electrode layers 31a and 32a by screen printing or the like, followed by firing and a lithography process. The dimensions of the second electrode layers 31b and 32b in the thickness direction Z are, for example, 1 to 5 μm.

[0064] Through the above process, an individual electrode 31 can be formed having a first film thickness portion in which the first electrode layer 31a and the second electrode layer 31b are laminated, and a second film thickness portion in which only the first electrode layer 31a is present. In addition, a common electrode 32 can be formed having a first film thickness portion in which the first electrode layer 32a and the second electrode layer 32b are laminated, and a second film thickness portion in which only the first electrode layer 32a is present.

[0065] The method for forming the individual electrodes 31 and the common electrode 32 is not limited to this. For example, a metal paste that will become the first electrode layer 31a and the first electrode layer 32a may be applied to the substrate 15 by screen printing or the like, and then a metal paste that will become the second electrode layer 31b and the second electrode layer 32b may be applied to the metal paste that will become the first electrode layer 31a and the first electrode layer 32a by screen printing or the like, and then these metal pastes may be fired together and formed by a lithography process. Alternatively, a portion of the single electrode layer (the portion that will overlap with the later formed heating resistor 40) may be removed by etching or the like to form the individual electrodes 31 and the common electrode 32 having the first and second film thickness portions described above.

[0066] Next, as shown in Figures 5A to 5D, a resistor paste is formed to become the heat-generating resistor 40 (heat-generating resistor portion 41). The resistor paste contains, for example, ruthenium oxide. Next, the heat-generating resistor 40 (heat-generating resistor portion 41) is formed by firing the resistor paste described above.

[0067] Next, a protective film 34 is formed as shown in Figures 6A to 6D. The protective film 34 is made of, for example, amorphous glass. The protective film 34 is formed by printing a glass paste in a thick film and then firing it.

[0068] By following the above steps, the thermal print head 100 of this embodiment can be manufactured.

[0069] According to this embodiment, it is possible to suppress wire breakage due to the aggregation of metal contained in the metal paste during the formation (firing) of the individual electrodes 31 and the common electrode 32. Furthermore, the resistance of the individual electrodes 31 and the common electrode 32 can be reduced. In addition, because the film thickness of the individual electrodes 31 and the common electrode 32 in the region overlapping with the heating resistor 40 is small, heat conduction from the heating resistor 40 to the individual electrodes 31 and the common electrode 32 can be reduced, and the increase in energy required to raise the heating resistor 40 to a predetermined temperature can be suppressed. As a result, good printing efficiency can be ensured.

[0070] <First variation> The configuration of the thermal print head 100A in this modified example will be explained.

[0071] Figure 7A is a partial perspective view showing the thermal print head 100A. Figure 7B is a partial cross-sectional view along the line VIIB-VIIB in Figure 7A. Figure 7C is a partial cross-sectional view along the line VIIC-VIIC in Figure 7A. Figure 7D is a partial cross-sectional view along the line VIID-VIID in Figure 7A. The thermal print head 100A comprises an insulating substrate 15, a heat storage layer 33 on the substrate 15, a common electrode 32 disposed on the heat storage layer 33 and having a comb-tooth portion 32A, individual electrodes 31 disposed on the heat storage layer 33, spaced apart from the comb-tooth portion 32A of the common electrode 32 and facing the comb-tooth portion 32A, a heating resistor 40 on the heat storage layer 33, on the individual electrodes 31, and on the common electrode 32, and a protective film 34 covering the individual electrodes 31, the common electrode 32, and the heating resistor 40. For ease of understanding, the protective film 34 is not shown in Figure 7A.

[0072] Each individual electrode 31 has a first electrode layer 31a and a second electrode layer 31b on the first electrode layer 31a. The common electrode 32 has a first electrode layer 32a and a second electrode layer 32b on the first electrode layer 32a. In this modified example, the portion of the heat storage layer 33 in the thickness direction Z where the first electrode layer 31a and the second electrode layer 31b are stacked is defined as the first thickness portion of the individual electrode 31, and the portion consisting only of the second electrode layer 31b is defined as the second thickness portion of the individual electrode 31. Furthermore, in this modified example, the portion of the heat storage layer 33 in the thickness direction Z where the first electrode layer 32a and the second electrode layer 32b are stacked is defined as the first thickness portion of the common electrode 32 (including the comb-tooth portion 32A, etc.), and the portion consisting only of the second electrode layer 32b is defined as the second thickness portion of the common electrode 32. The heating resistor 40 is in contact with the second film thickness portion of the individual electrode 31 and the second film thickness portion of the comb-tooth portion 32A, which is part of the common electrode 32. The difference between the thermal print head 100A according to this modified example and the thermal print head 100 shown in Figures 1A to 1D above is that the second film thickness portion of the individual electrode 31 consists only of the second electrode layer 31b, and the second film thickness portion of the common electrode 32 consists only of the second electrode layer 32b. The points in common with the thermal print head 100 shown in Figures 1A to 1D in this modified example will be explained by referring to the above explanation, and the points of difference will be explained below.

[0073] Each individual electrode 31 has a first electrode layer 31a and a second electrode layer 31b. The common electrode 32 has a first electrode layer 32a and a second electrode layer 32b. The first electrode layers 31a and 32a are arranged on at least a portion of the heat storage layer 33, excluding the region overlapping with the heat-generating resistor 40. The second electrode layer 31b is arranged on the first electrode layer 31a and on the region of the heat storage layer 33 overlapping with the heat-generating resistor 40. The second electrode layer 32b is arranged on the first electrode layer 32a and on the region of the heat storage layer 33 overlapping with the heat-generating resistor 40. Since the heat-generating resistor 40 is in contact with the second electrode layers 31b and 32b, which have a large average surface roughness, the contact between the heat-generating resistor 40 and the second electrode layer 31b or 32b is widespread, and good adhesion can be obtained at these contacts.

[0074] In the individual electrode 31 in this modified example, the thickness of the first film portion is the sum of the thickness of the first electrode layer 31a and the thickness of the second electrode layer 31b, and the thickness of the second film portion is the thickness of the second electrode layer 31b. In the common electrode 32 in this modified example, the thickness of the first film portion is the sum of the thickness of the first electrode layer 32a and the thickness of the second electrode layer 32b, and the thickness of the second film portion is the thickness of the second electrode layer 32b.

[0075] According to this modified example, it is possible to suppress wire breakage due to the aggregation of metal contained in the metal paste during the formation (firing) of the individual electrodes 31 and the common electrode 32. Furthermore, the resistance of the individual electrodes 31 and the common electrode 32 can be reduced. In addition, because the film thickness of the individual electrodes 31 and the common electrode 32 in the region overlapping with the heating resistor 40 is small, heat conduction from the heating resistor 40 to the individual electrodes 31 and the common electrode 32 can be reduced, and the increase in energy required to raise the heating resistor 40 to a predetermined temperature can be suppressed. As a result, good printing efficiency can be ensured.

[0076] <Second variation> The configuration of the thermal print head 100B related to this modified example will be explained.

[0077] Figure 8A is a partial perspective view showing the thermal print head 100B. Figure 8B is a partial cross-sectional view along the line VIIIB-VIIIB in Figure 8A. Figure 8C is a partial cross-sectional view along the line VIIIC-VIIIC in Figure 8A. Figure 8D is a partial cross-sectional view along the line VIIID-VIIID in Figure 8A. The thermal print head 100B comprises an insulating substrate 15, a heat storage layer 33 on the substrate 15, a heat-generating resistor 40 on the heat storage layer 33, a common electrode 32 having comb-toothed portions 32A on the heat storage layer 33 and the heat-generating resistor 40, individual electrodes 31 on the heat storage layer 33 and the heat-generating resistor 40 that are spaced apart from the comb-toothed portions 32A of the common electrode 32 and facing the comb-toothed portions 32A, and a protective film 34 covering the heat storage layer 33, the heat-generating resistor 40, the individual electrodes 31, and the common electrode 32. Figure 8A omits the illustration of the protective film 34 for ease of understanding. The difference between the thermal print head 100B in this modified example and the thermal print head 100 shown in Figures 1A to 1D above is that some of the individual electrodes 31 and some of the common electrodes 32 are arranged on the heating resistor 40. The points in common with the thermal print head 100 shown in Figures 1A to 1D in this modified example will be explained using the above explanation, and the differences will be explained below.

[0078] The individual electrodes 31 are arranged on the heat storage layer 33 and the heat-generating resistor 40, and have a first electrode layer 31a and a second electrode layer 31b. The common electrode 32 is arranged on the heat storage layer 33 and the heat-generating resistor 40, and has a first electrode layer 32a and a second electrode layer 32b. The first electrode layers 31a and 32a are arranged on the heat storage layer 33 and the heat-generating resistor 40. The second electrode layer 31b is arranged on the first electrode layer 31a except for the region that overlaps with the heat-generating resistor 40. The second electrode layer 32b is arranged on the first electrode layer 32a except for the region that overlaps with the heat-generating resistor 40.

[0079] In the individual electrode 31 in this modified example, the thickness of the first film portion is the sum of the thickness of the first electrode layer 31a and the thickness of the second electrode layer 31b, and the thickness of the second film portion is the thickness of the first electrode layer 31a. In the common electrode 32 in this modified example, the thickness of the first film portion is the sum of the thickness of the first electrode layer 32a and the thickness of the second electrode layer 32b, and the thickness of the second film portion is the thickness of the first electrode layer 32a.

[0080] Here, we will describe the manufacturing method of the thermal print head 100B of this embodiment.

[0081] First, as shown in Figures 2A to 2D, a substrate 15 is prepared, and a heat storage layer 33 is formed on the substrate 15. Next, as shown in Figures 9A to 9D, a resistor paste that will become the heat-generating resistor 40 (heat-generating resistor portion 41) is formed on the heat storage layer 33. The resistor paste contains, for example, ruthenium oxide. Next, the heat-generating resistor 40 (heat-generating resistor portion 41) is formed by firing the resistor paste described above.

[0082] Next, as shown in Figures 10A to 10D, the first electrode layer 31a of the individual electrodes 31 and the first electrode layer 32a of the common electrode 32 are formed on the heat storage layer 33 and the heat generating resistor 40. The first electrode layers 31a and 32a are obtained by applying the aforementioned small-particle metal paste to the heat storage layer 33 and the heat generating resistor 40 by screen printing or the like, followed by firing and lithography processes. The dimensions of the first electrode layers 31a and 32a in the thickness direction Z are, for example, 1 to 3 μm.

[0083] Next, as shown in Figures 11A to 11D, a second electrode layer 31b is formed on the first electrode layer 31a, excluding the region overlapping with the heat-generating resistor 40, and a second electrode layer 32b is formed on the first electrode layer 32a, excluding the region overlapping with the heat-generating resistor 40. The second electrode layers 31b and 32b are obtained by applying a paste containing metal particles with a larger particle size than the metal particles contained in the paste used to form the first electrode layers 31a and 32a to the first electrode layers 31a and 32a by screen printing or the like, followed by firing and lithography processes. The dimensions of the second electrode layers 31b and 32b in the thickness direction Z are, for example, 1 to 5 μm.

[0084] Through the above process, an individual electrode 31 can be formed having a first film thickness portion in which the first electrode layer 31a and the second electrode layer 31b are laminated, and a second film thickness portion in which only the first electrode layer 31a is present. In addition, a common electrode 32 can be formed having a first film thickness portion in which the first electrode layer 32a and the second electrode layer 32b are laminated, and a second film thickness portion in which only the first electrode layer 32a is present.

[0085] Next, a protective film 34 is formed as shown in Figures 12A to 12D. The protective film 34 is made of, for example, amorphous glass. The protective film 34 is formed by printing a glass paste in a thick film and then firing it.

[0086] By following the above steps, the thermal print head 100B of this embodiment can be manufactured.

[0087] According to this modified example, it is possible to suppress wire breakage due to the aggregation of metal contained in the metal paste during the formation (firing) of the individual electrodes 31 and the common electrode 32. Furthermore, the resistance of the individual electrodes 31 and the common electrode 32 can be reduced. In addition, because the film thickness of the individual electrodes 31 and the common electrode 32 in the region overlapping with the heating resistor 40 is small, heat conduction from the heating resistor 40 to the individual electrodes 31 and the common electrode 32 can be reduced, and the increase in energy required to raise the heating resistor 40 to a predetermined temperature can be suppressed. As a result, good printing efficiency can be ensured.

[0088] <Third variation> The configuration of the thermal print head 100C related to this modified example will be explained.

[0089] Figure 13A is a partial perspective view showing the thermal print head 100C. Figure 13B is a partial cross-sectional view along the line XIIIB-XIIIB in Figure 13A. Figure 13C is a partial cross-sectional view along the line XIIIC-XIIIC in Figure 13A. Figure 13D is a partial cross-sectional view along the line XIIID-XIIID in Figure 13A. The thermal print head 100C comprises an insulating substrate 15, a heat storage layer 33 on the substrate 15, a heat-generating resistor 40 on the heat storage layer 33, a common electrode 32 having comb-toothed portions 32A on the heat storage layer 33 and the heat-generating resistor 40, individual electrodes 31 on the heat storage layer 33 and the heat-generating resistor 40 that are spaced apart from the comb-toothed portions 32A of the common electrode 32 and facing the comb-toothed portions 32A, and a protective film 34 covering the heat storage layer 33, the heat-generating resistor 40, the individual electrodes 31, and the common electrode 32. Figure 13A omits the illustration of the protective film 34 for ease of understanding. The difference between the thermal print head 100C according to this modified example and the thermal print head 100A shown in Figures 7A to 7D above is that some of the individual electrodes 31 and some of the common electrodes 32 are arranged on the heating resistor 40. The points that are common to the thermal print head 100A shown in Figures 7A to 7D in this modified example will be explained by referring to the above explanation, and the differences will be explained below.

[0090] The individual electrodes 31 are arranged on the heat storage layer 33 and the heat-generating resistor 40, and have a first electrode layer 31a and a second electrode layer 31b. The common electrode 32 is arranged on the heat storage layer 33 and the heat-generating resistor 40, and has a first electrode layer 32a and a second electrode layer 32b. In this modified example, the portion of the heat storage layer 33 in the thickness direction Z where the first electrode layer 31a and the second electrode layer 31b are stacked is defined as the first thickness portion of the individual electrode 31, and the portion consisting only of the second electrode layer 31b is defined as the second thickness portion of the individual electrode 31. Furthermore, in this modified example, the portion of the heat storage layer 33 in the thickness direction Z where the first electrode layer 32a and the second electrode layer 32b are stacked is defined as the first thickness portion of the common electrode 32 (including the comb-tooth portion 32A, etc.), and the portion consisting only of the second electrode layer 32b is defined as the second thickness portion of the common electrode 32. The heat-generating resistor 40 is in contact with the second film thickness portion of the individual electrode 31 and the second film thickness portion of the comb-tooth portion 32A, which is part of the common electrode 32. Since the heat-generating resistor 40 is in contact with the second electrode layers 31b and 32b, which have a large average surface roughness, the contact between the heat-generating resistor 40 and the second electrode layers 31b or 32b is wide, and good adhesion can be obtained at these contacts.

[0091] In the individual electrode 31 in this modified example, the thickness of the first film portion is the sum of the thickness of the first electrode layer 31a and the thickness of the second electrode layer 31b, and the thickness of the second film portion is the thickness of the second electrode layer 31b. In the common electrode 32 in this modified example, the thickness of the first film portion is the sum of the thickness of the first electrode layer 32a and the thickness of the second electrode layer 32b, and the thickness of the second film portion is the thickness of the second electrode layer 32b.

[0092] According to this modified example, it is possible to suppress wire breakage due to the aggregation of metal contained in the metal paste during the formation (firing) of the individual electrodes 31 and the common electrode 32. Furthermore, the resistance of the individual electrodes 31 and the common electrode 32 can be reduced. In addition, because the film thickness of the individual electrodes 31 and the common electrode 32 in the region overlapping with the heating resistor 40 is small, heat conduction from the heating resistor 40 to the individual electrodes 31 and the common electrode 32 can be reduced, and the increase in energy required to raise the heating resistor 40 to a predetermined temperature can be suppressed. As a result, good printing efficiency can be ensured.

[0093] (Other embodiments) As described above, one embodiment has been described, but the descriptions and drawings that constitute part of the disclosure are illustrative and should not be understood as limiting. Various alternative embodiments, examples, and operational techniques will become apparent to those skilled in the art from this disclosure. Thus, this embodiment includes various embodiments and the like that are not described herein.

[0094] <Thermal Printer> The thermal print head (for example, thermal print head 100) further comprises a substrate 15 (heat storage layer 33 etc. on the substrate 15 are not shown), a connecting substrate 5, a heat dissipation member 8, a drive IC 7, a plurality of wires 81, a resin part 82, and a connector 59, as shown in Figure 14. The substrate 15 and the connecting substrate 5 are mounted adjacent to each other in the sub-scanning direction Y on the heat dissipation member 8. The substrate 15 has a plurality of heat-generating resistance parts 41 arranged in the main scanning direction X. These heat-generating resistance parts 41 are driven to generate heat selectively by the drive IC 7 mounted on the connecting substrate 5. The heat-generating resistance parts 41 print on a printing medium 92 such as thermal paper, which is pressed against the heat-generating resistance parts 41 by a platen roller 91, according to a printing signal transmitted from the outside via the connector 59.

[0095] The connecting board 5 can be, for example, a printed circuit board. The connecting board 5 has a structure in which a base layer and a wiring layer (not shown) are laminated. The base layer can be, for example, a glass epoxy resin. The wiring layer can be, for example, a metal such as copper, silver, palladium, iridium, platinum, and gold.

[0096] The heat dissipation member 8 has the function of dissipating heat from the substrate 15. The substrate 15 and the connecting substrate 5 are attached to the heat dissipation member 8. The heat dissipation member 8 can be made of a metal such as aluminum.

[0097] The wire 81 can be made of a conductor such as gold. There are multiple wires 81, some of which are bonded to each individual electrode of the drive IC 7. Other wires 81 are bonded to each other to the drive IC 7 and the connector 59 via the wiring layer on the connection board 5.

[0098] The resin part 82 can be made of, for example, black resin. For the resin part 82, epoxy resin, silicone resin, etc., can be used. The resin part 82 covers the drive IC 7 and the multiple wires 81, protecting the drive IC 7 and the multiple wires 81. The connector 59 is fixed to the connection board 5. Wiring for supplying power to the thermal print head from outside the thermal print head and for controlling the drive IC 7 is connected to the connector 59.

[0099] A thermal printer may be equipped with the thermal print head described above. The thermal printer prints on a printing medium that is transported along the sub-scanning direction Y. Typically, the printing medium is transported from the connector 59 side toward the heating resistance unit 41 side. Examples of printing mediums include thermal paper for creating barcode sheets or receipts.

[0100] A thermal printer includes, for example, a thermal print head 100, a platen roller 91, a main power supply circuit, a measurement circuit, and a control unit. The platen roller 91 faces directly in front of the thermal print head 100.

[0101] The main power supply circuit supplies power to the multiple heat-generating resistors 41 in the thermal print head 100. The measurement circuit measures the resistance value of each of the multiple heat-generating resistors 41. The measurement circuit measures the resistance value of each of the multiple heat-generating resistors 41, for example, when no printing is being performed on the printing medium. This allows for confirmation of the lifespan of the heat-generating resistors 41 and the presence or absence of a faulty heat-generating resistor 41. The control unit controls the drive state of the main power supply circuit and the measurement circuit. The control unit controls the energized state of each of the multiple heat-generating resistors 41. The measurement circuit may be omitted.

[0102] Connector 59 is used to communicate with devices outside the thermal print head 100. Through connector 59, the thermal print head 100 is electrically connected to the main power supply circuit and the measurement circuit. Through connector 59, the thermal print head 100 is electrically connected to the control unit.

[0103] The drive IC 7 receives a signal from the control unit via the connector 59. Based on the signal received from the control unit, the drive IC 7 controls the energized state of each of the multiple heating resistors 41. Specifically, the drive IC 7 selectively energizes one of the multiple heating resistors 41 to generate heat as desired by selectively energizing multiple individual electrodes.

[0104] Furthermore, the thermal print head is not limited to the above configuration. For example, the drive IC 7 may be mounted directly on the substrate 15 without providing a connection substrate 5, or the wire 81 may be omitted by flip-chip mounting, or the heat dissipation member 8 may be omitted.

[0105] Next, we will explain how to use a thermal printer.

[0106] When printing on a printing medium, a first potential, which is an input signal, is applied to the connector 59 from the main power supply circuit. In this case, multiple heating resistors 41 are selectively energized and generate heat. Printing is performed on the printing medium by transferring this heat. As described above, when the first potential is applied to the connector 59 from the main power supply circuit, a power supply path is secured to each of the multiple heating resistors 41.

[0107] When printing is not being performed on the printing medium, the resistance value of each heat-generating resistor 41 is measured. During this measurement, no potential is applied to the connector 59 from the main power supply circuit. When measuring the resistance value of each heat-generating resistor 41, a second potential is applied to the connector 59 from the measurement circuit. In this case, multiple heat-generating resistors 41 are energized sequentially (for example, starting from the heat-generating resistor 41 located at the end of the main scanning direction X). Based on the value of the current flowing through the heat-generating resistor 41 and the second potential, the measurement circuit measures the resistance value of each heat-generating resistor 41. As described above, when the second potential is applied to the connector 59 from the main power supply circuit, the energization path to each of the multiple heat-generating resistors 41 is substantially blocked. This allows the measurement circuit to measure the resistance value of each heat-generating resistor 41 more accurately, and the lifespan of the heat-generating resistor 41 and the presence or absence of a faulty heat-generating resistor 41 can be confirmed.

[0108] According to the above, a thermal printer with good printing efficiency can be obtained. [Explanation of Symbols]

[0109] 5. Connection board 7. Drive IC 8 Heat dissipation components 15 circuit boards 31 Individual electrodes 31a, 32a First electrode layer 31b, 32b Second electrode layer 32 Common electrode 32A Comb teeth part 32B Common part 33 Heat storage layer 34 Protective film 40 Heat-generating resistor 41 Heat-generating resistance section 59 Connectors 81 Wire 82 Resin part 91 Platen Roller 92 Print media 100, 100A, 100B, 100C Thermal Printheads

Claims

1. A heat storage layer, A heat-generating resistor disposed on the heat storage layer, A common electrode, which is placed on the heat storage layer and has comb-like teeth, The device comprises individual electrodes arranged on the heat storage layer, separated from the comb-tooth portion of the common electrode, and facing the comb-tooth portion, In the thickness direction of the heat storage layer, the individual electrodes and the comb teeth each have a first film thickness portion and a second film thickness portion having a smaller film thickness than the first film thickness portion. The heating resistor is in contact with the second film thickness portion of the individual electrode and the second film thickness portion of the comb teeth, A thermal print head in which, at the contact points between the heating resistor and the individual electrodes and the comb teeth, the heating resistor is positioned on the individual electrodes and the comb teeth.

2. The common electrode further has a common portion connected to the comb teeth portion, The thermal print head according to claim 1, wherein the film thickness of the common portion is the same as the film thickness of the first film thickness portion.

3. The thermal print head according to claim 1 or 2, wherein the material of the individual electrodes and the material of the common electrode include silver or gold.

4. The substrate further comprises the aforementioned heat storage layer having an upper surface, The thermal print head according to any one of claims 1 to 3, wherein the substrate is made of ceramic.

5. A thermal printer comprising a thermal print head according to any one of claims 1 to 4.

6. Forms a heat storage layer, On the heat storage layer, a common electrode having comb teeth and individual electrodes spaced apart from and facing the comb teeth are formed, each having a first film thickness portion and a second film thickness portion. A heating resistor is formed on the comb teeth and on the individual electrodes. In the thickness direction of the heat storage layer, the thickness of the second thickness portion is smaller than the thickness of the first thickness portion. The heating resistor is in contact with the second film thickness portion of the individual electrode and the second film thickness portion of the comb teeth, The formation of the individual electrodes and the common electrode is as follows: The process involves forming a first electrode layer on the heat storage layer, The process includes the step of forming a second electrode layer on the first electrode layer in the thickness direction of the heat storage layer, excluding the region that overlaps with the heat-generating resistor, The thickness of the first film portion is the sum of the thickness of the first electrode layer and the thickness of the second electrode layer. A method for manufacturing a thermal print head, wherein the thickness of the second film thickness portion is the thickness of the first electrode layer.

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